Quadrant Model of Reality: Quadrant Model of Reality Book 13 Science Physics Chemistry and Biology

The Quadrant Model Theory books are organized around the four fields of inquiry, which are science, religion, art, and philosophy. This book is a further expansion of examples of the quadrant model, elaborating on the extent of its comprehensivity, and cementing the reality that the quadrant model pattern is fundamental to existence.

The cross that Jesus is crucified on in the Bible is the shape of a quadrant. I argue that the reason why the crucified savior is such a powerful symbol is because the quadrant itself represents the Form of Being, or the Form of Existence.

Matrices in mathematics are quadrants. Graphs are made up of quadrant grids. I pointed out in my previous books the ubiquity of the quadrant. I also illustrated in my previous books the nature of the quadrant model, which I plan to expatiate in this book.

The quadrant model pattern is there are 16 squares and four quadrants. The first quadrant/square is weird and mental, but good and inspiring. The second quadrant/square is foundation and homeostasis and is good. The third quadrant/square is bad and destructive and action oriented. The fourth quadrant/square does not seem to belong and transcends the previous three, while simultaneously possessing qualities that contains or completely transcend the previous three. The fourth square seems to not exist. The fourth square always points to a fifth square and its nature indicates the nature of the fifth square. The fifth square can then become its own quadrant.

Science Chapter

Physics Chapter

QMR Four sons of PenroseIn this paper, we distill the arguments on both sides. Specifically, we reduce the bone of contention to a consideration only of the question, “Does X not respond to input X?”, and restrict ourselves to one entity versed in computer science, namely, “Roger”. In the process, we demonstrate that there are exactly four ways to resolve the conundrum raised by the above “diagonalization” argu- ment. Roger falls into one (or more) of the following categories:

I. An idealized human who is inherently more powerful than Turing’s machines.

II. A slipshod human who can err in judgement.

III. An impetuous human who sometimes errs, having resorted to a baseless hunch.

IV. A pedantic human who may decline to express an opinion when questioned

QMRThe Four Sons

The following facts are indisputable:

All human errors are impatience, a premature breaking off of methodical procedure. . . .

A(CA)=T ⇔ CA(CA)=T (4) A(CA) ̸= T ⇔ CA(CA) = ⊥ (5) A(CA)=T ⇒ G(CA)=F (6) A(CA)̸=T ⇒ G(CA)=T . (7)

The Four Sons

The following facts are indisputable:

All human errors are impatience, a premature breaking off of methodical procedure. . . .

A(CA)=T ⇔ CA(CA)=T (4) A(CA) ̸= T ⇔ CA(CA) = ⊥ (5) A(CA)=T ⇒ G(CA)=F (6) A(CA)̸=T ⇒ G(CA)=T . (7)

Facts (4,5) follow directly from the references to A in the definition (1) of C: CA calls A, answers T if A does, and loops, otherwise. Facts (6,7) follow directly from C’s behavior and the specification (2) of G: If A(CA) yields T, then CA does not diverge (4), and G knows it; if A(CA) doesn’t yield T, then CA does diverge (5), and again G knows it.

Now, G is infallible and total (G(CA) ̸= ⊥). Hence (by 6, 7), no A can always be right, whether the result of A, when asked question CA, is T, F, or ⊥. That is:

A(CA) ̸= G(CA) , (8)

—Franz Kafka (1917)

which is just a restatement (as in Sect. 3) of Turing’s undecidability result for the halting problem. That is, no program A(X) can answer infallibly—for any program X—whether X(X) diverges; specifically, it must trip up with regard to CA. So, if A happens to agree with R about CA, then R, too, must not give the textbook answer G.

The upshot of the above facts is that:

A(CA) = R(CA) ⇒ R(CA) ̸= G(CA) . (9)

In other words, if A simulates R (at least on CA), then R does not respond properly (T for F , F for T , or ⊥), while if R is averred to never err (precluding both Options II and III), then either A(CA) ̸= R(CA) (Option I) or else R(CA) = ⊥ (as dictated by Option IV). In the last case, R’s knowledge is incomplete:

A(CA) = R(CA) = ⊥ ⇒ ¬K[A(CA) ̸= T] , (10)

since, were K to have responded, so would have R.

The dichotomy at the heart of the debate is whether there in fact exists a

computer program A in Π that agrees with R on CA, or perhaps there can never be such a program. According to both the strong and weak AI points of view, there exists such a program A that, in particular, agrees with R when queried regarding CA. But, then, either neither answer, or else both give the same wrong answer. In the latter case, R’s error may result either from faulty “reasoning”, or from some other cause. It is much like an examinee who, presented with a difficult true/false question, cannot work out the correct answer within the time limit. In this situation, a person may “guess” (using heuristics, perhaps), or may give up and leave the answer blank.

To summarize, we have discerned four characteristics of the nature of R:3

I . R t h e W i s e : R ∈/ Π

(wise, in a super-Turing sense);

II. R the Wicked: K[A(CA) ̸= T] = T but in fact ¬[A(CA) ̸= T] (wicked, in that R internalizes an untruth);

III. R the Simpleton: K[A(CA) ̸= T] ̸= T and in reality R(CA) = ¬G(CA) (acting without thinking);

IV. R the Ignorant: R(CA) = ⊥ (expressing no opinion in the matter).

QMR The Toyota 4Runner is a mid-size sport utility vehicle (SUV) produced by the Japanese manufacturer Toyota and sold throughout the world from 1984 to present. In Japan it was known as the Toyota Hilux Surf (トヨタハイラックスサーフ). The original 4Runner was a compact SUV and little more than a Toyota pickup truck with a fiberglass shell over the bed, but the model has since undergone significant independent development into a cross between a compact and a mid-size SUV. All 4Runners have been built at Toyota's Tahara plant at Tahara, Aichi, Japan, or at Hino Motors' Hamura, Japan plant, and in Brazil. Its mid-size crossover SUV counterpart is the Toyota Highlander.

Hilux Surf models in Japan are widely exported as used vehicles to Somalia, Pakistan, Afghanistan, United Kingdom, Ireland, New Zealand, and Australia.

For Southeast Asia the Hilux Surf was replaced in 2005 by the similar Fortuner, which is based on the Hilux platform.

As of 2014, the Toyota 4Runner is sold in the U.S., Canada, Central America, Bahamas, Ecuador, Peru, and Chile.

QMRNASA's series of Great Observatories satellites are four large, powerful space-based telescopes. The four missions were designed to examine a specific region of the electromagnetic spectrum using very different technologies. Dr. Charles Pellerin, NASA's Director, Astrophysics invented and developed the program.

Contents [hide]

1 Great Observatories

2 History of the program

2.1 Hubble telescope program

2.2 Gamma ray program

2.3 Chandra X-ray history

2.4 Spitzer history

2.5 Great Observatory origin

3 Strengths

4 Impact

5 Synergies

6 Successors to GO instruments

7 Later programs

8 Gallery

9 See also

10 References

11 External links

Great Observatories[edit]

The Hubble Space Telescope (HST) primarily observes visible light and near-ultraviolet. It was launched in 1990 aboard Discovery during STS-31. A servicing mission in 1997 added capability in the near-infrared range and one last mission in 2009 was to fix and extend the life of Hubble which resulted in some of the best results to date.

The Compton Gamma Ray Observatory (CGRO) primarily observed gamma rays, though it extended into hard x-rays as well. It was launched in 1991 aboard Atlantis during STS-37 and was de-orbited in 2000 after failure of a gyroscope.

The Chandra X-ray Observatory (CXO) primarily observes soft x-rays. It was launched in 1999 aboard Columbia during STS-93 and was initially named the Advanced X-ray Astronomical Facility (AXAF).

The Spitzer Space Telescope (SST) observes the infrared spectrum. It was launched in 2003 aboard a Delta II rocket and was called the Space Infrared Telescope Facility (SIRTF) before launch.

Of these satellites, only the Compton Gamma Ray Observatory is not currently operating; one of its gyroscopes failed, and NASA ordered it to be de-orbited on June 4, 2000. Parts that survived reentry splashed into the Pacific Ocean. Hubble was originally intended to be retrieved and returned to Earth by the Space Shuttle, but the retrieval plan was later abandoned. On October 31, 2006 NASA Administrator Michael D. Griffin gave the go-ahead for a final refurbishment mission. The 11-day STS-125 mission by Atlantis, launched on 11 May 2009,[1] installed fresh batteries, replaced all gyroscopes, replaced a command computer, fixed several instruments and installed the Wide Field Camera 3 and the Cosmic Origins Spectrograph.[2]

Spitzer was the only one of the Great Observatories not launched by the Space Shuttle. It was originally intended to be so launched, but after the Challenger disaster, the Centaur LH2/LOX upper stage that would have been required to push it into a heliocentric orbit was banned from Shuttle use. Titan and Atlas rockets were canceled for cost reasons. After redesign and lightening, it was launched by a Delta II rocket instead.

History of the program[edit]

Hubble telescope program[edit]

The history of the Hubble Space Telescope can be traced back as far as 1946, when the astronomer Lyman Spitzer wrote the paper Astronomical advantages of an extraterrestrial observatory.[3] Spitzer devoted much of his career to pushing for a space telescope to be developed.

The 1966-72 Orbiting Astronomical Observatory missions demonstrated the important role space-based observations could play in astronomy, and 1968 saw the development by NASA of firm plans for a space-based reflecting telescope with a mirror 3 m in diameter, known provisionally as the Large Orbiting Telescope or Large Space Telescope (LST), with a launch slated for 1979.[4] Congress eventually approved funding of US$36,000,000 for 1978, and the design of the LST began in earnest, aiming for a launch date of 1983. During the early 1980s, the telescope was named after Edwin Hubble.

Gamma ray program[edit]

Gamma rays had been examined above the atmosphere by several early space missions. During its High Energy Astronomy Observatory Program in 1977, NASA announced plans to build a "great observatory" for gamma-ray astronomy. The Gamma Ray Observatory (GRO), renamed Compton Gamma-Ray Observatory (CGRO), was designed to take advantage of the major advances in detector technology during the 1980s. Following 14 years of effort, the CGRO was launched on 5 April 1991.[5]

Chandra X-ray history[edit]

In 1976 the Chandra X-ray Observatory (called AXAF at the time) was proposed to NASA by Riccardo Giacconi and Harvey Tananbaum. Preliminary work began the following year at Marshall Space Flight Center (MSFC) and the Smithsonian Astrophysical Observatory (SAO). In the meantime, in 1978, NASA launched the first imaging X-ray telescope, Einstein (HEAO-2), into orbit. Work continued on the Chandra project through the 1980s and 1990s. In 1992, to reduce costs, the spacecraft was redesigned. Four of the twelve planned mirrors were eliminated, as were two of the six scientific instruments. Chandra's planned orbit was changed to an elliptical one, reaching one third of the way to the Moon's at its farthest point. This eliminated the possibility of improvement or repair by the space shuttle but put the observatory above the Earth's radiation belts for most of its orbit.

Spitzer history[edit]

By the early 1970s, astronomers began to consider the possibility of placing an infrared telescope above the obscuring effects of Earth's atmosphere. Most of the early concepts, envisioned repeated flights aboard the NASA Space Shuttle. This approach was developed in an era when the Shuttle program was presumed to be capable of supporting weekly flights of up to 30 days duration. In 1979, a National Research Council of the National Academy of Sciences report, A Strategy for Space Astronomy and Astrophysics for the 1980s, identified a Shuttle Infrared Telescope Facility (SIRTF) as "one of two major astrophysics facilities [to be developed] for Spacelab," a Shuttle-borne platform.

The launch of the Infrared Astronomical Satellite, an Explorer-class satellite designed to conduct the first infrared survey of the sky led to anticipation of an instrument using new infrared detector technology. By September 1983 NASA was considering the "possibility of a long duration [free-flyer] SIRTF mission." The 1985 Spacelab-2 flight aboard STS-51-F confirmed the Shuttle environment was not well suited to an onboard infrared telescope, and a free-flying design was better. The first word of the name was changed from Shuttle so it would be called the Space Infrared Telescope Facility.[6][7]

Great Observatory origin[edit]

The concept of a Great Observatory program was first proposed in the 1979 NRC report "A Strategy for Space Astronomy and Astrophysics for the 1980's." This report laid the essential groundwork for the Great Observatories and was chaired by Peter Meyer (through June 1977) and then by Harlan J. Smith (through publication). In the mid-1980s it was further advanced by all of the astrophysics Division Directors at NASA headquarters, including Frank Martin and Charlie Pellerin. NASA's "Great Observatories" program used four separate satellites, each designed to cover a different part of the spectrum in ways which terrestrial systems could not. This perspective enabled the proposed X-ray and InfraRed observatories to be appropriately seen as a continuation of the astronomical program begun with Hubble and CGRO rather than competitors or replacements.[8][9]

QMROtto cycle: Otto cycle is the typical cycle for most of the cars internal combustion engines, that work using gasoline as a fuel. Otto cycle is exactly the same one that was described for the four-stroke engine. It consists of the same four major steps: Intake, compression, ignition and exhaust.

QMRThe idealized diagrams of a four-stroke Otto cycle Both diagrams:

the intake (A) stroke is performed by an isobaric expansion, followed by an adiabatic compression (B) stroke. Through the combustion of fuel, heat is added in an a constant volume (isochoric process) process, followed by an adiabatic expansion process power (C) stroke. The cycle is closed by the exhaust (D) stroke, characterized by isochoric cooling and isentropic compression processes.

The four-stroke engine was first patented by Alphonse Beau de Rochas in 1861.[3] Before, in about 1854–57, two Italians (Eugenio Barsanti and Felice Matteucci) invented an engine that was rumored to be very similar, but the patent was lost.

"The request bears the no. 700 of Volume VII of the Patent Office of the Reign of Piedmont. We do not have the text of the patent request, only a photo of the table which contains a drawing of the engine. We do not even know if it was a new patent or an extension of the patent granted three days earlier, on December 30, 1857, at Turin."

f. Eugenio Barsanti and Felice Matteucci, June 4, 1853 [4]

The first person to build a working four-stroke engine, a stationary engine using a coal gas-air mixture for fuel (a gas engine), was German engineer Nikolaus Otto.[5] This is why the four-stroke principle today is commonly known as the Otto cycle and four-stroke engines using spark plugs often are called Otto engines.

Cycle analysis[edit]

In processes 1–2 the piston does work on the gas and in process 3–4 the gas does work on the piston during those isentropic compression and expansion processes, respectively. Processes 2–3 and 4–1 are isochoric processes; heat transfer occurs but no work is done on the system or extracted from the system. No work is done during an isochoric (constant volume) process because addition or removal of work from a system as that requires movement of the boundaries of the system; hence, as the cylinder volume does not change, no shaft work is added or removed from the system.

Four different equations are used to describe those four processes. A simplification is made by assuming changes of the kinetic and potential energy that take place in the system (mass of gas) can be neglected and then applying the first law of thermodynamics (energy conservation) to the mass of gas as it changes state as characterized by the gas's temperature, pressure, and volume.[2][7]

During a complete cycle, the gas returns to its original state of temperature, pressure and volume, hence the net internal energy change of the system (gas) is zero. As a result, the energy (heat or work) added to the system must be offset by energy (heat or work) that leaves the system. In the analysis of thermodynamic systems, the convention is to account energy that enters the system as positive and energy that leaves the system is accounted as negative.

Equation 1a:

During a complete cycle, the change of energy of the system is zero:

\Delta E = E_\text{in} - E_\text{out} = 0

The above states that the system (the mass of gas) returns to the original thermodynamic state it was in at the start of the cycle.

Where E_\text{in}is energy added to the system from 1–2–3 and E_\text{out} is energy is removed from 3–4–1. In terms of work and heat added to the system

Equation 1b:

W_{1-2} + Q_{2-3} + W_{3-4} + Q_{4-1} = 0

Each term of the equation can be expressed in terms of the internal energy of the gas at each point in the process:

W_{1-2} = U_2 - U_1

Q_{2-3} = U_3 - U_2

W_{3-4} = U_4 - U_3

Q_{4-1} = U_1 - U_4

The energy balance Equation 1b becomes

W_{1-2} + Q_{2-3} + W_{3-4} + Q_{4-1} = \left(U_2 - U_1\right) + \left(U_3 - U_2\right) + \left(U_4 - U_3\right) + \left(U_1 - U_4\right) = 0

If the internal energies are assigned values for points 1,2,3, and 4 of 1,5,9, and 4 respectively (these values are arbitrarily but rationally selected for the sake of illustration), the work and heat terms can be calculated.

The energy added to the system as work during the compression from 1 to 2 is

\left(U_2 - U_1\right) = \left(5 - 1\right) = 4

The energy added to the system as heat from point 2 to 3 is

\left({U_3 - U_2}\right) = \left(9 - 5\right) = 4

The energy removed from the system as work during the expansion from 3 to 4 is

\left(U_4 - U_3\right) = \left(4 - 9\right) = -5

The energy removed from the system as heat from point 4 to 1 is

\left(U_1 - U_4\right) = \left(1 - 4\right) = -3

The energy balance is

\Delta E = + 4 + 4 - 5 - 3 = 0

Note that energy added to the system is counted as positive and energy leaving the system is counted as negative and the summation is zero as expected for a complete cycle that returns the system to its original state.

From the energy balance the work out of the system is:

\Sigma Work = W_{1-2} + W_{3-4} = \left(U_2 - U_1\right) + \left(U_4 - U_3\right) = 4 - 5 = -1

The net energy out of the system as work is -1, meaning the system has produced one net unit of energy that leaves the system in the form of work.

The net heat out of the system is:

\Sigma Heat = Q_{2-3} + Q_{4-1} = \left(U_3 - U_2\right) + \left(U_1 - U_4\right) = 4 -3 = 1

As energy added to the system as heat is positive. From the above it appears as if the system gained one unit of heat. This matches the energy produced by the system as work out of the system.

Thermal efficiency is the quotient of the net work from the system, to the heat added to system. Equation 2:

\eta = \frac{W_{1-2} + W_{3-4} }{Q_{2-3}} = \frac{\left(U_2 - U_1\right) + \left(U_4 - U_3\right)}{ \left(U_3 - U_2\right)}

\eta =1+\frac{U_1 - U_4 }{ \left(U_3 - U_2\right)} = 1+\frac{(1-4)}{ (9-5)} = 0.25

Alternatively, thermal efficiency can be derived by strictly heat added and heat rejected.

\eta=\frac{Q_{2-3} + Q_{4-1}}{Q_{2-3}}

=1+\frac{\left(U_1-U_4\right) }{ \left(U_3-U_2\right)}

Supplying the fictitious values

\eta=1+\frac{1-4}{9-5}=1+\frac{-3}{4}=0.25

In the Otto cycle, there is no heat transfer during the process 1–2 and 3–4 as they are isentropic processes. Heat is supplied only during the constant volume processes 2–3 and heat is rejected only during the constant volume processes 4–1.

The above values are absolute values that might, for instance, have units of joules (assuming the MKS system of units are to be used) and would be of use for a particular engine with particular dimensions. In the study of thermodynamic systems the extensive quantities such as energy, volume, or entropy (versus intensive quantities of temperature and pressure) are placed on a unit mass basis, and so too are the calculations, making those more general and therefore of more general use. Hence, each term involving an extensive quantity could be divided by the mass, giving the terms units of joules/kg (specific energy), meters3/kg (specific volume), or joules/(kelvin·kg) (specific entropy, heat capacity) etc. and would be represented using lower case letters, u, v, s, etc.

Equation 1 can now be related to the specific heat equation for constant volume. The specific heats are particularly useful for thermodynamic calculations involving the ideal gas model.

C_\text{v} = \left(\frac{\delta u}{\delta T}\right)_\text{v}

Rearranging yields:

\delta u = (C_\text{v})(\delta T)

Inserting the specific heat equation into the thermal efficiency equation (Equation 2) yields.

\eta = 1-\left(\frac{C_\text{v}(T_4 - T_1)}{ C_\text{v}(T_3 - T_2)}\right)

Upon rearrangement:

\eta = 1-\left(\frac{T_1}{T_2}\right)\left(\frac{T_4/T_1-1}{T_3/T_2-1}\right)

Next, noting from the diagrams T_4/T_1 = T_3/T_2 (see isentropic relations for an ideal gas), thus both of these can be omitted. The equation then reduces to:

Equation 2:

\eta = 1-\left(\frac{T_1}{T_2}\right)

Since the Otto cycle uses isentropic processes during the compression (process 1 to 2) and expansion (process 3 to 4) the isentropic equations of ideal gases and the constant pressure/volume relations can be used to yield Equations 3 & 4.[8]

Equation 3:

\left(\frac{T_2}{T_1}\right)=\left(\frac{p_2}{p_1}\right)^{(\gamma-1)/{\gamma}}

Equation 4:

\left(\frac{T_2}{T_1}\right)=\left(\frac{V_1}{V_2}\right)^{(\gamma-1)}

where

{\gamma} = \left(\frac{C_\text{p}}{C_\text{v}}\right)

{\gamma} is the specific heat ratio

The derivation of the previous equations are found by solving these four equations respectively (where R is the specific gas constant):

C_\text{p} \ln\left(\frac{V_1}{V_2}\right) - R \ln \left(\frac{p_2}{p_1}\right) = 0

C_\text{v} \ln\left(\frac{T_2}{T_1}\right) - R \ln \left(\frac{V_2}{V_1}\right) = 0

C_\text{p} = \left(\frac{\gamma R}{\gamma-1}\right)

C_\text{v} = \left(\frac{R}{\gamma-1}\right)

Further simplifying Equation 4, where r is the compression ratio (V_1/V_2):

Equation 5:

\left(\frac{T_2}{T_1}\right) = \left(\frac{V_1}{V_2}\right)^{(\gamma-1)} = r^{(\gamma-1)}

From inverting Equation 4 and inserting it into Equation 2 the final thermal efficiency can be expressed as:[7]

Equation 6:

\eta = 1 - \left(\frac{1}{r^{(\gamma-1)}}\right)

From analyzing equation 6 it is evident that the Otto cycle efficiency depends directly upon the compression ratio r. Since the \gamma for air is 1.4, an increase in r will produce an increase in \eta. However, the \gamma for combustion products of the fuel/air mixture is often taken at approximately 1.3. The foregoing discussion implies that it is more efficient to have a high compression ratio. The standard ratio is approximately 10:1 for typical automobiles. Usually this does not increase much because of the possibility of autoignition, or "knock", which places an upper limit on the compression ratio.[2] During the compression process 1–2 the temperature rises, therefore an increase in the compression ratio causes an increase in temperature. Autoignition occurs when the temperature of the fuel/air mixture becomes too high before it is ignited by the flame front. The compression stroke is intended to compress the products before the flame ignites the mixture. If the compression ratio is increased, the mixture may auto-ignite before the compression stroke is complete, leading to "engine knocking". This can damage engine components and will decrease the brake horsepower of the engine.

Power[edit]

The power produced by the Otto cycle is the energy developed per unit of time. The Otto engines are called four-stroke engines. The intake stroke and compression stroke require one rotation of the engine crankshaft. The power stroke and exhaust stroke require another rotation. For two rotations there is one work generating stroke.

From the above cycle analysis the net work produced by the system was:

\Sigma Work = W_{1-2} + W_{3-4} = \left(U_2 - U_1\right) + \left(U_4 - U_3\right) = +4 - 5 = -1

(again, using the sign convention, the minus sign implies energy is leaving the system as work)

If the units used were MKS the cycle would have produced one joule of energy in the form of work. For an engine of a particular displacement, such as one liter, the mass of gas of the system can be calculated assuming the engine is operating at standard temperature (20 °C) and pressure (1 atm). Using the Universal Gas Law the mass of one liter of gas is at room temperature and sea level pressure:

M=\frac{PV}{RT}

V=0.001 m3, R=0.286 kJ/(kg·K), T=293 K, P=101.3 kN/m2

M=0.00121 kg

At an engine speed of 2000 RPM there is 1000 work-strokes/minute or 16.7 work-strokes/second.

\Sigma Work = 1\,\text{J}(\text{kg}\cdot\text{stroke})\times 0.00121\,\text{kg}= 0.00121\,\text{J}/\text{stroke}

Power is 16.7 times that since there are 16.7 work-strokes/second

P = 16.7 \times 0.00121=0.0202\,\text{J}/\text{sec}\; \text{or} \;\text{watts}

If the engine is multi-cylinder, the result would be multiplied by that factor. If each cylinder is of a different liter displacement, the results would also be multiplied by that factor. These results are the product of the values of the internal energy that were assumed for the four states of the system at the end each of the four strokes (two rotations). They were selected only for the sake of illustration, and are obviously of low value. Substitution of actual values from an actual engine would produce results closer to that of the engine. Whose results would be higher than the actual engine as there are many simplifying assumptions made in the analysis that overlook inefficiencies. Such results would overestimate the power output.

thermodynamic cycle wiki

QMRThe Prizma Color system was a technique of color motion picture photography, invented in 1913 by William Van Doren Kelley and Charles Raleigh. Initially, it was a two-color additive color system, similar to its predecessor, Kinemacolor. However, Kelley eventually transformed Prizma into a bi-pack color system that itself became the predecessor for future color processes such as Multicolor and Cinecolor.

Prizma gave a demonstration of color motion pictures in 1917 that used an additive four-color process, using a disk of four filters acting on a single strip of panchromatic film in the camera. The colors were red, yellow, green, and blue, with overlapping wavelengths to prevent pulsating effects on the screen with vivid colors. The film was photographed at 26 to 32 frames per second, and projected at 32 frame/s. The disk used in projection consisted mainly of two colors, red-orange and blue-green, adapted to the four-color process by the superimposition of two small magenta filters over one of the red sectors and two similar blue filters over one of the blue-green sectors.[1][2] Motion Picture News reported,

The results by this process are characterized by extreme delicacy of color, and subdued shades are most admirably rendered.… The blue-green element of the projecting filter appears to favor the blue rather than the green, and as a result, skies and water are well reproduced. We have not noticed anything approaching a true green in any of the subjects so far exhibited, although this is probably by reason of the fact that no prominent greens existed in the subjects photographed. Yellow is not in evidence in the current Prizma films, although a wide variety of warm tones are apparent, ranging from chestnut-brown to a deep red-orange. Colors in full saturation are hardly within the scope of this process.[3]

QMR Otto cycle

Otto Cycle:

1→2: Isentropic Expansion: Constant entropy (s), Decrease in pressure (P), Increase in volume (v), Decrease in temperature (T)

2→3: Isochoric Cooling: Constant volume(v), Decrease in pressure (P), Decrease in entropy (S), Decrease in temperature (T)

3→4: Isentropic Compression: Constant entropy (s), Increase in pressure (P), Decrease in volume (v), Increase in temperature (T)

4→1: Isochoric Heating: Constant volume (v), Increase in pressure (P), Increase in entropy (S), Increase in temperature (T)

QMRthe pressure-volume mechanical work output from the heat engine cycle (net work out), consisting of 4 thermodynamic processes, is[citation needed][dubious – discuss]:

\text{(3)} \qquad W_{net} = W_{1\to 2} + W_{2\to 3} + W_{3\to 4} + W_{4\to 1}

W_{1\to 2} = \int_{V_1}^{V_2} P \, dV, \, \, \text{negative, work done on system}

W_{2\to 3} = \int_{V_2}^{V_3} P \, dV, \, \, \text{zero work if V2 equal V3}

W_{3\to 4} = \int_{V_3}^{V_4} P \, dV, \, \, \text{positive, work done by system}

W_{4\to 1} = \int_{V_4}^{V_1} P \, dV, \, \, \text{zero work if V4 equal V1}

If no volume change happens in process 4-1 and 2-3, equation (3) simplifies to:

\text{(4)} \qquad W_{net} = W_{1\to 2} + W_{3\to 4}

The clockwise thermodynamic cycle indicated by the arrows shows that the cycle represents a heat engine. The cycle consists of four states (the point shown by crosses) and four thermodynamic processes (lines).

QMRThe Idealized Diesel Cycle[edit]

p-V Diagram for the ideal Diesel cycle. The cycle follows the numbers 1-4 in clockwise direction.

The image on the left shows a p-V diagram for the ideal Diesel cycle; where p is pressure and V the volume or v the specific volume if the process is placed on a unit mass basis. The ideal Diesel cycle follows the following four distinct processes:

Process 1 to 2 is isentropic compression of the fluid (blue)

Process 2 to 3 is reversible constant pressure heating (red)

Process 3 to 4 is isentropic expansion (yellow)

Process 4 to 1 is reversible constant volume cooling (green)[1]

The Diesel cycle is a combustion process of a reciprocating internal combustion engine. In it, fuel is ignited by heat generated during the compression of air in the combustion chamber, into which fuel is then injected. This is in contrast to igniting the fuel-air mixture with a spark plug as in the Otto cycle (four-stroke/petrol) engine. Diesel engines are used in aircraft, automobiles, power generation, diesel-electric locomotives, and both surface ships and submarines.[dubious – discuss]

QMRThe Soviet World War II-era four-engine strategic bomber Petlyakov Pe-8 was built with Charomskiy ACh-30 diesel engines, but later in the production run diesels were replaced with radial gasoline engines because of efficiency concerns. The Yermolaev Yer-2 long-range medium bomber was also built with Charomskiy diesel engines.

The first manufacturer to produce a certified design for the general aviation market was Thielert, located in the small town of Lichtenstein in the German state of Saxony. They produce four-stroke, liquid-cooled, geared, turbo-diesel aircraft engines based on Mercedes automotive designs which will run on both diesel and jet aviation fuel (Jet A-1). Their first engine, a 1.7 litres (100 in3), 135 hp (101 kW) four-cylinder (based on the 1.7 turbo diesel Mercedes A-class power unit), was first certified in 2002. It is certified for retrofitting to Cessna 172s and Piper Cherokees which were originally equipped with the 160 hp (120 kW) Lycoming O-320 320 cubic inches (5.2 l) Avgas engine. Although the weight of the 135 hp (101 kW) Thielert Centurion 1.7 at around 136 kilograms (300 lb) is similar to that of the 160 hp (120 kW) Lycoming O-320, its displacement is less than a third of that of the Lycoming. It however achieves maximum power at 2300 prop rpm (3900 crank rpm) as opposed to 2700 for the petrol Lycoming.

Thielert users included Austrian aircraft firm Diamond Aircraft Industries, which offered its single-engine Diamond DA40-TDI Star with a Thielert Centurion 1.7' engine, and also the DA42 (formerly known as Twin Star) with two. The twin-Thielert engined DA42 offered low fuel consumption with a high fuel efficiency of 15.1 L/h (3.3 imp gal/h; 4.0 gal/h). Several hundred Thielert-powered airplanes are flying. There was also a certified a 4.0-litre (240 cu in), V8, 310 hp (230 kW) version available from 2005 although this engine has not been certified for installation in any airframes. Apex aircraft, formerly Robin, also offered an aircraft (Ecoflyer) with the Thielert engine.

In May 2008, Thielert went bankrupt. Although Bruno M. Kubler, Thielert's insolvency administrator, was able to announce in January 2009 that the company was "in the black and working to capacity," by then Cessna had dropped plans to install Thielert engines in some models, and Diamond Aircraft has now developed its own in-house diesel engine.

France[edit]

SMA Engines, located in Bourges, 150 km south of Paris have designed a four-stroke, air-cooled, turbo-diesel aircraft engine from the ground up, the SR305-230. SMA's engineering team came from Renault Sport (Formula 1). The 230 hp (170 kW), 305 cubic inch (5.0 liter) jet fuel engine first obtained European certification in April 2001, followed by US FAA certification in July 2002. It is now certified as retrofit on several Cessna 182 models in Europe and the USA, and Maule is working toward certification of the M-9-230.

France[edit]

Bourke engine, designed by Russell Bourke, of Petaluma, CA, is an opposed rigidly connected twin cylinder design using the detonation principle.[8]

Diesel Air Limited, a British company who are developing a 100 hp (75 kW) twin-cylinder (therefore four-piston), two-stroke opposed-piston engine inspired by the original Junkers design. Their engine has flown in test aircraft and airship installations. Unlike the Junkers, it is made for horizontal installation with a central output shaft for the geared cranks, the overall installed shape thereby approximately resembling a four-stroke flat-four engine.[9]

Wilksch Airmotive, a British company who are developing/producing a 120 hp (89 kW) three-cylinder (WAM-120) two-stroke diesel and are working on a four-cylinder 160 hp (120 kW) design (WAM-160). In 2007 Wilksch claimed that they had completed multiple tests on the WAM-100 LSA in accordance with ASTM F 2538 - the WAM-100 LSA is a derated WAM-120. Wilksch originally showed a two-cylinder prototype alongside the three- and four-cylinder models. By mid-2009, approximately 40 WAM-120 units had been sold, with around half currently flying. The British owner of a VANS RV-9A fitted with a WAM-120 reports getting 125 knots (232 km/h) TAS at 6,000 ft (1,800 m) on 15 litre/hr of jet A1 fuel. A Rutan LongEz canard-pusher (G-LEZE) has also flown with the WAM120 engine with test flights showing a TAS of 160 kn (300 km/h) at 11,000 ft (3,400 m) and 22ltrs per hour. At economy cruise of 125 knots (232 km/h) at 2,000 ft (610 m) the fuel consumption is 12 ltrs/hr giving a range of 1,890 nautical miles (3,500 km); see [1]

Raptor Turbo Diesel LLC, an American company currently developing the Raptor 105 diesel engine. It is a four-stroke inline turbo charged engine. Known as Vulcan Aircraft Engines until September 2007.[11]

QMRDirect-drive transmissions can become very complex, considering that a typical locomotive has four or more axles

QMRA four-stroke engine (also known as four cycle) is an internal combustion (IC) engine in which the piston completes four separate strokes while turning a crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either direction. The four separate strokes are termed:

Intake: This stroke of the piston begins at top dead center (T.D.C.) and ends at bottom dead center (B.D.C.). In this stroke the intake valve must be in the open position while the piston pulls an air-fuel mixture into the cylinder by producing vacuum pressure into the cylinder through its downward motion.

Compression: This stroke begins at B.D.C, or just at the end of the suction stroke, and ends at T.D.C. In this stroke the piston compresses the air-fuel mixture in preparation for ignition during the power stroke (below). Both the intake and exhaust valves are closed during this stage.

Power: This is the start of the second revolution of the four stroke cycle. At this point the crankshaft has completed a full 360 degree revolution. While the piston is at T.D.C. (the end of the compression stroke) the compressed air-fuel mixture is ignited by a spark plug (in a gasoline engine) or by heat generated by high compression (diesel engines), forcefully returning the piston to B.D.C. This stroke produces mechanical work from the engine to turn the crankshaft.

Exhaust: During the exhaust stroke, the piston once again returns from B.D.C. to T.D.C. while the exhaust valve is open. This action expels the spent air-fuel mixture through the exhaust valve.

Daimler and Maybach left their employ at Otto and Cie and developed the first high-speed Otto engine in 1883. In 1885, they produced the first automobile to be equipped with an Otto engine. The Daimler Reitwagen used a hot-tube ignition system and the fuel known as Ligroin to become the world's first vehicle powered by an internal combustion engine. It used a four-stroke engine based on Otto's design. The following year Karl Benz produced a four-stroke engined automobile that is regarded as the first car

QMRThe disadvantage of the four-stroke Atkinson-cycle engine versus the more common Otto-cycle engine is reduced power density. Due to a smaller portion of the compression stroke being devoted to compressing the intake air, an Atkinson-cycle engine does not take in as much air as would a similarly designed and sized Otto-cycle engine.

Four-stroke engines of this type that use the same type of intake valve motion but with a supercharger to make up for the loss of power density are known as Miller-cycle engines.

While a modified Otto-cycle piston engine using the Atkinson cycle provides good fuel efficiency, it is at the expense of a lower power-per-displacement as compared to a traditional four-stroke engine.[4] If demand for more power is intermittent, the power of the engine can be supplemented by an electric motor during times when more power is needed. This forms the basis of an Atkinson-cycle-based hybrid electric drivetrain. These electric motors can be used independently of, or in combination with, the Atkinson-cycle engine, to provide the most efficient means of producing the desired power. This drive-train first entered production in late 1997 in the Japanese-market Toyota Prius.

QMRWhile most production V8 engines use four crank throws spaced 90° apart, high-performance V8 engines often use a "flat" crankshaft with throws spaced 180° apart. The difference can be heard as the flat-plane crankshafts result in the engine having a smoother, higher-pitched sound than cross-plane (for example, IRL IndyCar Series compared to NASCAR Sprint Cup Series, or a Ferrari 355 compared to a Chevrolet Corvette). See the main article on crossplane crankshafts.

QMRIn engineering, the Miller cycle is a thermodynamic cycle used in a type of internal combustion engine. The Miller cycle was patented by Ralph Miller, an American engineer, US patent 2817322 dated Dec 24, 1957. The engine may be two-stroke or four stroke and may be run on diesel fuel, gas fuel or dual fuel.[1]

A traditional reciprocating internal combustion engine uses four strokes, of which two can be considered high-power: the compression stroke (high power flow from crankshaft to the charge) and power stroke (high power flow from the combustion gases to crankshaft).

The overview given above may describe a modern version of the Miller cycle but it differs in some respects from the 1957 patent. The patent describes "a new and improved method of operating a supercharged intercooled engine". The engine may be two-cycle or four-cycle and the fuel may be diesel, dual fuel or gas. It is clear from the context that "gas" means gaseous fuel and not gasoline. The pressure-charger shown in the diagrams is a turbocharger, not a positive-displacement supercharger. The engine (whether four-stroke or two-stroke) has a conventional valve or port layout but there is an additional "compression control valve" (CCV) in the cylinder head. There is a servo mechanism, operated by inlet manifold pressure, which controls the lift of the CCV during part of the compression stroke and releases air from the cylinder to the exhaust manifold. The CCV would have maximum lift at full load and minimum lift at no load. The effect is to produce an engine with a variable compression ratio. As inlet manifold pressure goes up (because of the action of the turbocharger) the effective compression ratio in the cylinder goes down (because of the increased lift of the CCV) and vice versa. This "will insure proper starting and ignition of the fuel at light loads".[2]

QMRFour-stroke internal combustion engine[edit]

Main article: Four-stroke engine

Most modern internal combustion engines work on a four-stroke cycle; that is, a complete cylinder cycle consists of four discrete strokes, as described below. Other types of engines can have very different stroke cycles.

Induction stroke[edit]

The induction stroke is the first stroke in a four-stroke internal combustion engine cycle. It involves the downward movement of the piston, creating a partial vacuum that draws (allows atmospheric pressure to push) a fuel/air mixture into the combustion chamber.

In a reciprocating engine, it is that portion of the cycle when the pistons move from TDC (top dead center) to BDC (bottom dead center) and the fuel-air mixture is drawn into the cylinders....

This is a cylinder for a 4-stroke Petrol/Gasoline engine. The first step is to get the air-fuel mixture into the chamber. Mixture enters through an inlet port that is opened and closed by an inlet valve. This is called Intake

Compression stroke[edit]

The compression stroke is the second of four stages in an otto cycle or diesel cycle internal combustion engine.

In this stage, the mixture (in the case of an Otto engine) or air (in the case of a Diesel engine) is compressed to the top of the cylinder by the piston until it is either ignited by a spark plug in an Otto engine or, in the case of a Diesel engine, reaches the point at which the injected fuel spontaneously combusts, forcing the piston back down. In a Diesel engine, the injection of fuel usually leads top dead center by about 4 mechanical degrees, this "lead" being intended to allow complete fuel ignition to occur slightly after top dead center.

Compression serves to increase the proportion of energy which can be extracted from the hot gas and should be optimised for a given application. Too high a compression can cause detonation, which is undesirable compared with a smooth, controlled burn. Too low a compression may result in the fuel/air mixture still burning when the piston reaches the bottom of the stroke and the exhaust valve opens.

Power stroke/expansion stroke[edit]

A power stroke is, in general, the stroke or movement of a cyclic motor while generating force and thus power. It is used in describing mechanical engines. This force is the result of the spark plug igniting the compressed fuel-air mixture.

Exhaust stroke[edit]

The exhaust stroke is the fourth of four stages in a |four stroke internal combustion engine cycle. In this stage gases remaining in the cylinder from the fuel ignited during the compression step are removed from the cylinder through an exhaust valve at the top of the cylinder. The gases are forced up to the top of the cylinder as the piston rises and are pushed through the opening, which then closes to allow a fresh air/fuel mixture into the cylinder so the process can repeat itself.

QMRTwo-and-four stroke engines are engines that combine elements from both two-stroke and four-stroke engines. They usually incorporate two pistons.

M4+2 engine[edit]

The M4+2 engine , also known as the double piston internal combustion engine, is a new type of internal combustion engine invented by a Polish patent holder Piotr Mężyk.[1]

The M4+2 engine took its name from a combination of the two working modes of the known engines, that is from the Two-stroke engine and Four-stroke engine. The two-stroke combustion engine is characterized by a simple construction and system of air load change as well as bigger index of power output. Unfortunately, its filling ratio is worse than in four-stroke engine. The ecological index of two-stroke engine is also unfavorable. The system of valves of the four-stroke engine is its disadvantage. The cylinders of both modules of double pistons engine have been joined along one axis with common cylinder head - in the form of the ring. The pistons are moved with different speed and with appropriate stage displacement. There are two crankshafts, which are connected with special transmission in shown solution. The four-stroke crankshaft is rotated with twice a speed of two-stroke crankshaft. The engine is named double pistons because of its construction - double pistons and crankshafts. In the M4+2 the advantages of both engines being connected are obvious; the pistons of the engine working in one combustion cylinder are set oppositely to each other, but in different modes. Although the projects of connecting two stroke modes in one cylinder were tried already a long time ago in the Opposed piston engine, the combination of the two different cycles had never been tried before. It turned out that the engine is not only able to work, but that the effects are very promising. The engine has a far greater efficiency over the break-even value known to combustion engines (ca 35%) and closer to the one associated with steam turbines or electric engines (ca 70%).[citation needed]

Ricardo 2x4 engine[edit]

The two cycle modes are currently being researched at Ricardo Consulting Engineers in the UK. The concept consists in switching from one mode to the other depending on rpm value. The four stroke engine is more efficient when running at full throttle, while the opposite is the case for the two stroke engine. When a small car under heavy load runs at half speed, the engine automatically switches to the two cycle mode which is then more efficient. The research on this showed a 27% reduction in fuel consumption.[8][9]

Since the shaft of the four stroke piston in the M4+2 engine always rotates twice as fast as the shaft of the two stroke piston, meaning the two stroke part always runs at half speed, both parts work in optimal conditions regarding fuel consumption at all times. The same principles are involved as with having distinct engines, but the design of the M4+2 is much simpler.

QMRThe six-stroke engine is a type of internal combustion engine based on the four-stroke engine, but with additional complexity intended to make it more efficient and reduce emissions. Two types of six-stroke engine have been developed since the 1890s:

In the first approach, called the single-piston design, the engine captures the heat lost from the four-stroke Otto cycle or Diesel cycle and uses it to power an additional power and exhaust stroke of the piston in the same cylinder. Designs use either steam or air as the working fluid for the additional power stroke.[1] The pistons in this type of six-stroke engine go up and down three times for each injection of fuel. There are two power strokes: one with fuel, the other with steam or air.

The

QMRBeare head[edit]

This design was developed by Malcolm Beare of Australia. The technology combines a four-stroke engine bottom end with an opposed piston in the cylinder head working at half the cyclical rate of the bottom piston. Functionally, the second piston replaces the valve mechanism of a conventional engine. Claimed benefits include a 9% increase in power, and improved thermodynamic efficiency through an increased compression ratio and expansion ratio similar to the Miller or Atkins cycle.[10]

M4+2[edit]

This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2014)

The M4+2 engine working cycle animation

The M4+2 engines have much in common with the Beare-head engines, combining two opposed pistons in the same cylinder. One piston works at half the cyclical rate of the other, but while the main function of the second piston in a Beare-head engine is to replace the valve mechanism of a conventional four-stroke engine, the M4+2 takes the principle one step further. The double-piston combustion engine's work is based on the cooperation of both modules. The air load change takes place in the two-stroke section of the engine. The piston of the four-stroke section is an air load exchange aiding system, working as a system of valves. The cylinder is filled with air or with an air-fuel mixture. The filling process takes place at overpressure by the slide inlet system. The exhaust gases are removed as in the classical two-stroke engine, by exhaust windows in the cylinder. The fuel is supplied into the cylinder by a fuel-injection system. Ignition is realized by two spark plugs. The effective power output of the double-piston engine is transferred by two crankshafts. The characteristic feature of this engine is an opportunity of continuous change of cylinder capacity and compression rate during engine work by changing the piston's location. The mechanical and thermodynamical models were meant for double-piston engines, which enable to draw up new theoretical thermodynamic cycle for internal combustion double-pistons engine.[11]

The working principle of the engine is explained in the two- and four-stroke engines article.

QMRSquare four engine[edit]

See also: Motorcycle engine

Ariel Square Four

A square four is a type of four-cylinder engine, a U engine with two cylinders on each side. This configuration was used on the Ariel Square Four motorcycle from 1931 to 1959. Although the engine was compact and had as narrow a frontal area as a 500 cc, parallel twin, the rear pair of cylinders on this air-cooled engine were prone to overheating.

This design was revived as a liquid-cooled two-stroke version on some racing Suzukis, and their subsequent road-going version the Suzuki RG500. Although some racing success was achieved, the road bikes did not sell well and the design was phased out in favour of inline four-stroke designs, as engineering and marketing resources were being applied to more common four-stroke designs at the time.[citation needed]

An experimental square four outboard motor was built for evaluation, but the design was not used due to the complexity of the drivetrain

QMRThe Square Four is a motorcycle produced by Ariel between 1931 and 1959, designed by Edward Turner, who devised the Square Four engine in 1928. At this time he was looking for work, showing drawings of his engine design to motorcycle manufacturers.[5] The early engine with "two transverse crankshafts"[2] was essentially a pair of 'across frame' OHC parallel twins joined by their geared central flywheels, with a four-cylinder block (or Monobloc) and single head.[6] The idea for the engine was rejected by BSA, but adopted by Ariel. Thus it became the Ariel Square Four.

In 1966 Phil Vincent wrote in Motor Cycle: "Alas, in 1959 the Square Four went out of production, a victim of the modern trend towards small, high-revving modern power units. The demand had tailed off a bit, and with reduced output, the price would have had to be hoisted excessively high. At the time it was approaching £350—out of reach of all but a few of the potential buyers."[2]

A further development was the Healey 1000/4 based on an updated Square Four, produced between 1971 and 1977.

4F (1931–1936)[edit]

Ariel Square Four 600 cc 1935 (at the National Motorcycle Museum (UK)

The first Ariel Square Four 4F was shown at the Olympia Motorcycle Show in 1930,[7] in chain driven overhead-camshaft 500 cc form.[8][dead link] Early Square Fours used a hand-change, four-speed Burman gearbox.[6]

In 1932, the cylinder bores were enlarged by 5 mm to give a capacity of 601 cc, specifically to accommodate owners who wanted a sidecar.[9] This model was used for the Maudes Trophy test, covering 700 miles (1,127 km) in 700 minutes, followed by a timed lap of 87.4 mph (140.7 km/h).[citation needed] (In 1923 a Mr George Pettyt, of Maudes Motor Mart, had donated a "challenge trophy" for the ACU to award each year for the most meritorious, observed endurance test for motorcycles, known as the Maudes Trophy).[10]

4G (1936–1949)[edit]

Ariel Square Four 4G 1938

The “Cammy” engine gained a reputation for overheating the rear cylinder heads, so in 1936 the engine was completely redesigned, emerging as the 1937 OHV 995 cc model 4G.[5][dead link] In 1939 Ariel's patented Anstey-link plunger rear suspension became an option.[8]

In 1946, the plunger rear was available again, and oil damped telescopic front forks replaced the previous girder type.[8]

Mark I (1949–1953)[edit]

Two-pipe alloy engine

In 1949, the Ariel Square Four Mark I saw the cast-iron cylinder head and barrel replaced by alloy head and barrel.[8] This saved about 30 pounds (14 kg) in weight. The 1949 machine weighed around 435 lb (197 kg) dry, produced 35 bhp (26 kW) at 5,500 rpm.[6] The Mark I was capable of 90 mph-plus.

Mark II (1953–1959)[edit]

MkII upper engine detail showing bolt-on cast aluminium exhaust manifolds, high-mounted carburettor with high inlet stub cast into the rocker box, and the rear-mounted distributor

In 1953, the ‘four pipe’ 997 cc Ariel Square Four Mk II was released, with separate barrels, a re-designed cylinder head with four separate exhaust pipes from two cast-aluminium manifolds and a rocker-box combined with the inlet manifold. A redesigned frame provided clearance for the high-mounted, tall, car-type, SU carburettor.[2][3][7] This 40 hp (30 kW) Square Four was capable of 100 mph (160 km/h).[8] It weighed425 lb (193 kg) and cost £336.16.6.[11]

In 1954, Ariel built prototypes of a Mk3 with Earles forks, but the model was never put into production.[6]

Mk2 1000cc Ariel Square Four

In 1959, Square Four production, along with that of all other Ariel four-stroke models, ceased.[8]

QMRTwo-stroke Four-stroke Six-stroke Two-and four-stroke

QMRAn X engine is a piston engine comprising twinned V-block engines horizontally opposed to each other. Thus, the cylinders are arranged in four banks, driving a common crankshaft. Viewed head-on, this would appear as an X. X engines were often coupled engines derived from existing powerplants.

This configuration is extremely uncommon, primarily due its weight and complexity as compared to a radial engine. It was more compact (per number of cylinders) than a V-engine, however. Shorter crankshafts relative to an inline or V design also appealed to early 20th-century engineers like Henry Ford, given the less developed metallurgical technology of the time.[2]

Most examples of X engines are from the World War II era, and were designed for large military aircraft. The majority of these are X-24s based on existing V-12s. The following are examples of this engine type:

Ford, as an X-8 prototype during the 1920s that led the way to the company's eventual Flathead V-8.[3][4]

Daimler-Benz DB 604, developed for the Luftwaffe’s Bomber B program. Development suspended.

Isotta-Fraschini Zeta R.C. 24/60, developed for the Caproni Vizzola F.6Z fighter, but never fully completed before Italy’s surrender in 1943.

Rolls-Royce Vulture, based on two Peregrines and the powerplant of the ill-fated Avro Manchester bomber and the Hawker Tornado fighter.

Rolls-Royce Exe, an air-cooled sleeve valve prototype engine.

Napier Cub, a water-cooled X-16 engine of the 1920s, which powered the prototype Blackburn Cubaroo torpedo bomber.

Honda is said to have experimented with an X-32 engine configuration in the 1960s for their Formula One racing efforts, but abandoned the design as being too complex and unreliable.

Chelyabinsk Tractor Plant T-14 X12 engine 12Н360[5]

X's are quadants

Symmetrical X-Engine (90°/90°/90°/90°)

It is a perfect quadrant

X's are quadrants

QMRThe first V-type engine, a 2-cylinder vee twin, was built in 1889 by Daimler, to a design by Wilhelm Maybach. By 1903 V8 engines were being produced for motor boat racing by the Société Antoinette to designs by Léon Levavasseur, building on experience gained with in-line four-cylinder engines. In 1904, the Putney Motor Works completed a new V12 marine racing engine – the first V12 engine produced for any purpose.[1]

The first V-type engine, a 2-cylinder vee twin, was built in 1889 by Daimler, to a design by Wilhelm Maybach. By 1903 V8 engines were being produced for motor boat racing by the Société Antoinette to designs by Léon Levavasseur, building on experience gained with in-line four-cylinder engines. In 1904, the Putney Motor Works completed a new V12 marine racing engine – the first V12 engine produced for any purpose.[1]

QMRThe original "four-bank" design[edit]

In 1937 Allison built the V-3420 by 'combining' two of their V-1710s on a common crankcase. Early in World War II, Daimler-Benz built the DB 606A/B "power system", weighing 1.5 tonnes apiece. Based on the Daimler-Benz DB 601 V12 aircraft engine. It was a pair of liquid-cooled inverted V12s coupled to work on a single gear shaft. Derided as "welded-together engines" by Reichsmarschall Hermann Göring in August 1942 from being given inadequately-designed engine nacelles as existed in the airframe design for the He 177A German heavy bomber, they were in essence W24 engines of the 4-bank arrangement of 6 cylinders each. The inboard rows of cylinders were oriented downward and almost parallel to each other.

The modern "four-bank" design[edit]

A W16 engine from the Bugatti Veyron

Volkswagen Group created the first successful automotive W engine, with the introduction of its W8 (as a testbed for the W12).[citation needed] The W12 combines two narrow-angle VR6 engine cylinder heads around a single crankshaft for a total of four banks of cylinders. For this reason, the four-bank configuration is sometimes, and more accurately, referred to as a "VV" ("vee-vee" or "double-vee") or "WR", to distinguish it from the traditional three-bank "W" design (the earlier W8 combined two VR4 engines.)

The W8 was used in the B5.5 Volkswagen Passat and the W12 is used in the Volkswagen Phaeton, the Volkswagen Touareg, the Audi A8, and the Bentley Continental GT — though in the latter application, the engine has been highly modified by Bentley, and fitted with twin turbochargers. As a result, it produces considerably more power than the original version. The narrow (15°) angle between bank pairs makes this resemble a V12 engine, in that it has just two cylinder heads and two sets of camshafts. The W12 engine has bore-stroke of 84.0 millimetres (3.31 in) and 90.2 millimetres (3.55 in).

Volkswagen Group went on to produce a W16 engine prototype which produced 465 kilowatts (632 PS; 624 bhp) for the Bentley Hunaudières concept car. A quad-turbocharged version of this engine went into production in 2005 powering the 736 kilowatts (1,001 PS; 987 bhp) Bugatti Veyron EB16.4. The major advantage of these engines is packaging; they contain high numbers of cylinders but are relatively compact in their external dimensions.

W engine

The W-engine in the Bugatti Veyron[edit]

In 2006, the Volkswagen Group-owned Bugatti produced the Bugatti Veyron EB16.4 with an 8.0 litre W16 engine. This has four turbochargers, and it produces DIN rated[citation needed] motive power output of 736 kilowatts (1,001 PS; 987 bhp) at 6,000 revolutions per minute (rpm). It uses four valves per cylinder, 64 valves total, with four overhead camshafts arranged in a double overhead camshaft (two overhead camshafts per cylinder bank) layout, and a bore-stroke ratio 1:1 (both bore and stroke are 86.0 millimetres (3.39 in)).

QMRA multi-valve design typically has three, four, or five valves per cylinder to achieve improved performance- sometimess they have six valves- those are the four options

Four-valve cylinder head

This is the most common type of multi-valve head, with two exhaust valves and two similar (or slightly larger) inlet valves. This design allows similar breathing as compared to a three-valve head, and as the small exhaust valves allow high RPM, this design is very suitable for high power outputs.

A cylinder head of a four valve engine.

( Nissan VQ engine )

- It looks like a quadrant

Three-valve cylinder head

This has a single large exhaust valve and two smaller intake valves. A three-valve layout allows better breathing than a two-valve head, but the large exhaust valve results in an RPM limit no higher than a two-valve head. The manufacturing cost for this design can be lower than for a four-valve design. The three-valve design was common in the late 1980s and early 1990s; and from 2004 the main valve arrangement used in Ford F-Series trucks, and Ford SUVs.

Four-valve cylinder head

Five-valve cylinder head

Less common is the five-valve head, with two exhaust valves and three inlet valves. All five valves are similar in size. This design allows excellent breathing, and, as every valve is small, high RPM and very high power outputs are theoretically available. Although, compared to a four-valve engine, a five-valve design should have a higher maximum RPM, and the three inlet ports should give efficient cylinder-filling and high gas turbulence (both desirable traits), it has been questioned whether a five-valve configuration gives a cost-effective benefit over four-valve designs.[1] After making five-valve Genesis engines for several years, Yamaha has reverted to the cheaper four-valve design.

Beyond five valves

For a cylindrical bore and equal-area sized valves, increasing the number of valves beyond five decreases the total valve area. The following table shows the effective areas of differing valve quantities as proportion of cylinder bore. These percentages are based on simple geometry and do not take into account orifices for spark plugs or injectors, but these voids will usually be sited in the "dead space" unavailable for valves. Also, in practice, intake valves are often larger than exhaust in heads with an even number of valves-per-cylinder.

2 = 50%

3 = 64%

4 = 68%

5 = 68%

6 = 66%

7 = 64%

8 = 61%

Cars and trucks[edit]

Before 1914[edit]

The first motorcar in the world to have an engine with two overhead camshafts and four valves per cylinder was the 1912 Peugeot L76 Grand Prix race car designed by Ernest Henry. Its 7.6-litre monobloc straight-4 with modern hemispherical combustion chambers produced 148 bhp (19.5 HP/Liter(0.32 bhp per cubic inch)). In April 1913, on the Brooklands racetrack in England, a specially built L76 called "la Torpille" (torpedo) beat the world speed record of 170 km/h.[2] Robert Peugeot also commissioned the young Ettore Bugatti to develop a GP racing car for the 1912 Grand Prix. This chain-driven Bugatti Type 18 had a 5-litre straight-4 with SOHC and three valves per cylinder (two inlet, one exhaust). It produced appr. 100 bhp at 2800 rpm (0.30 bhp per cubic inch) and could reach 99 mph. The three-valve head would later be used for some of Bugatti's most famous cars, including the 1922 Type 29 Grand Prix racer and the legendary Type 35 of 1924. Both Type 29 and Type 35 had a 100 bhp 2-liter SOHC 24-valve NA straight-8 that produced 0.82 bhp per cubic inch.

Between 1914 and 1945[edit]

A.L.F.A. 40/60 GP was a fully working early racing car prototype made by the company now called Alfa Romeo. Only one example was built in 1914, which was later modified in 1921. This design of Giuseppe Merosi was the first Alfa Romeo DOHC engine. It had four valves per cylinder, 90-degree valve angle and twin-spark ignition.[4] The GP engine had a displacement of 4.5-liter (4490 cc) and produced 88 bhp (66 kW) at 2950 rpm (14.7 kW/liter), and after modifications in 1921 102 bhp (76 kW) at 3000 rpm. The top speed of this car was 88-93 mph (140–149 km/h). It wasn't until the 1920s when these DOHC engines came to Alfa road cars like the Alfa Romeo 6C.

In 1916 US automotive magazine Automobile Topics described a four-cylinder, four-valve-per-cylinder car engine made by Linthwaite-Hussey Motor Co. of Los Angeles, CA, USA: "Firm offers two models of high-speed motor with twin intakes and exhausts.".[5]

Early multi-valve engines in T-head configuration were the 1917 Stutz straight-4 and 1919 Pierce-Arrow straight-6 engines. The standard flathead engines of that day were not very efficient and designers tried to improve engine performance by using multiple valves. The Stutz Motor Company used a modified T-head with 16 valves, twin-spark ignition and aluminium pistons to produce 80 bhp (59 kW) at 2400 rpm from a 360.8 cid (5.8-liter) straight-4 (0.22 bhp per cubic inch). Over 2300 of these powerful early multi-valve engines were built. Stutz not only used them in their famous Bearcat sportscar but in their standard touring cars as well.[6][7][8] In 1919 Pierce-Arrow introduced its 524.8 cid (8.6-liter) straight-6 with 24 valves. The engine produced 48.6 bhp (0.09 bhp per cubic inch) and ran very quietly, which was an asset to the bootleggers of that era.[9][10][11]

Multi-valve engines continued to be popular in racing and sports engines. Robert M. Roof, the chief engineer for Laurel Motors, designed his multi-valve Roof Racing Overheads early in the 20th century. Type A 16-valve heads were successful in the teens, Type B was offered in 1918 and Type C 16-valve in 1923. Frank Lockhart drove a Type C overhead cam car to victory in Indiana in 1926.[12][13]

Bugatti also had developed a 1.5-liter OHV straight-4 with four valves per cylinder as far back as 1914 but did not use this engine until after World War I. It produced appr. 30 bhp (22.4 kW) at 2700 rpm (15.4 kW/liter or 0.34 bhp/cid). In the 1920 Voiturettes Grand Prix at Le Mans driver Ernest Friderich finished first in a Bugatti Type 13 with the 16-valve engine, averaging 91.96 km/h. Even more successful was Bugattis clean sweep of the first four places at Brescia in 1921. In honour of this memorable victory all 16-valve-engined Bugattis were dubbed Brescia. From 1920 through 1926 about 2000 were built.

Peugeot had a triple overhead cam 5-valve Grand Prix car in 1921.[14]

Bentley used multi-valve engines from the beginning. The Bentley 3 Litre, introduced in 1921, used a monobloc straight-4 with aluminium pistons, pent-roof combustion chambers, twin spark ignition, SOHC, and four valves per cylinder. It produced appr. 70 bhp (0.38 bhp per cubic inch). The 1927 Bentley 4½ Litre was of similar engine design. The NA racing model offered 130 bhp (0.48 bhp per cubic inch) and the 1929 supercharged 4½ Litre (Blower Bentley) reached 240 bhp (0.89 bhp per cubic inch). The 1926 Bentley 6½ Litre added two cylinders to the monobloc straight-4. This multi-valve straight-6 offered 180-200 bhp (0.45-0.50 bhp per cubic inch). The 1930 Bentley 8 Litre multi-valve straight-6 produced appr. 220 bhp (0.45 bhp per cubic inch).

In 1931 the Stutz Motor Company introduced a 322 cid (5.3-liter) dual camshaft 32-valve straight-8 with 156 bhp (116 kW) at 3900 rpm, called DV-32. The engine offered 0.48 bhp per cubic inch. About 100 of these multi-valve engines were built. Stutz also used them in their top-of-the-line sportscar, the DV-32 Super Bearcat that could reach 100 mph (160 km/h).[15][16]

The 1935 Duesenberg SJ Mormon Meteor's engine was a 419.6 cid (6.9-liter) straight-8 with DOHC, 4 valves per cylinder and a supercharger. It achieved 400 bhp (298.3 kW) at 5,000 rpm and 0.95 bhp per cubic inch.[17][18]

The 1937 Mercedes-Benz W125 racing car used a supercharged 5.7-liter straight-8 with DOHC and four valves per cylinder. The engine produced 592-646 bhp (441.5-475 kW) at 5800 rpm and achieved 1.71-1.87 bhp per cubic inch (77.8-85.1 kW/liter). The W125 top speed was appr. 200 mph (322 km/h).

After 1945[edit]

Combustion chamber of a 2009 Ford Ecoboost 3.5-liter turbocharged V6 petrol engine (77.8 kW/liter) showing two intake valves (right), two exhaust valves (left), centrally placed spark plug, and direct fuel injector (right).

The 1967 Cosworth DFV F1 engine, a NA 3.0-liter V8 producing appr. 400 bhp (298 kW; 406 PS) at 9,000 rpm (101.9 kW/liter), featured four valves per cylinder. For many years it was the dominant engine in Formula One, and it was also used in other categories, including CART, Formula 3000 and Sportscar racing.

Debuting at the 1968 Japanese Grand Prix in the original 300 PS (221 kW; 296 hp) 3.0-liter version the Toyota 7 engine participated in endurance races as a 5.0-liter (4,968 cc) non-turbo V8 with DOHC and 32-valves. It produced 600 PS (441 kW; 592 hp) at 8,000 rpm (88.8 kW/liter) and 55.0 kg·m (539 N·m; 398 lb·ft) at 6,400 rpm.

The first mass-produced car using four valves per cylinder was the British Jensen Healey in 1972 which used a Lotus 907 belt-driven DOHC 16-valve 2-liter straight-4 producing 140 bhp (54.6 kW/liter, 1.20 bhp/cid).

The 1973 Triumph Dolomite Sprint used an in-house developed SOHC 16-valve 1,998 cc (122 ci) straight-4 that produced appr. 127 bhp (47.6 kW/liter, 1.10 bhp/cid).

The 1975 Chevrolet Cosworth Vega featured a DOHC multi-valve head designed by Cosworth Engineering in the UK. This 122-cubic-inch straight-4 produced 110 bhp (82 kW; 112 PS) at 5600 rpm (0.90 bhp/cid; 41.0 kW/liter) and 107 lb·ft (145 N·m) at 4800 rpm.[19]

The 1976 Fiat 131 Abarth (51.6 kW/liter), 1976 Lotus Esprit with Lotus 907 engine (54.6 kW/liter, 1.20 bhp/cid), and 1978 BMW M1 with BMW M88 engine (58.7 kW/liter, 1.29 bhp/cid) all used four valves per cylinder. The BMW M88/3 engine was used in the 1983 BMW M635CSi and in the 1985 BMW M5.

The 1978 Porsche 935/78 racer used a twin turbo 3.2-liter flat-6 (845 bhp/630 kW@8,200 rpm; 784 Nm/578 ft.lbs@6,600 rpm). The water-cooled engine featured four valves per cylinder and output a massive 196.2 kW/liter. Porsche had to abandon its traditional aircooling because the multi-valve DOHC hampered aircooling of the spark plugs. Only two cars were built.

Ferrari developed their Quattrovalvole (or QV) engines in the 80s. Four valves per cylinder were added for the 1982 308 and Mondial Quattrovalvole, bringing power back up to the pre-FI high of 245 hp (183 kW) . A very unusual Dino Quattrovalvole was used in the 1986 Lancia Thema 8.32. It was based on the 308 QV's engine, but used a split-plane crankshaft rather than the Ferrari-type flat-plane. The engine was constructed by Ducati rather than Ferrari, and was produced from 1986 through 1991. The Quattrovalvole was also used by Lancia for their attempt at the World Sportscar Championship with the LC2. The engine was twin-turbocharged and destroked to 2.65 litres, but produced 720 hp (537 kW) in qualifying trim. The engine was later increased to 3.0 litres and increased power output to 828 hp (617 kW). The 1984 Ferrari Testarossa had a 4.9-liter flat-12 with four valves per cylinder. Almost 7,200 Testarossa were produced between 1984 and 1991.

In 1985 Lamborghini released a Countach Quattrovalvole, producing 455 PS (335 kW; 449 hp) from a 5.2-liter (5167 cc) Lamborghini V12 engine (64.8 kW/liter).

16 is the squares of the quadrant model

The Mercedes-Benz 190E 2.3-16 with 16-valve engine debuted at the Frankfurt Auto Show in September 1983 after it set a world record at Nardo, Italy, recording a combined average speed of 154.06 mph (247.94 km/h) over the 50,000 km (31,000 mi) endurance test. The engine was based on the 2.3-liter 8-valve 136 hp (101 kW) unit already fitted to the 190- and E-Class series. Cosworth developed the DOHC light alloy cast cylinder head with four large valves per cylinder. In roadgoing trim, the 190 E 2.3-16 produced 49 hp (36 kW) and 41 ft•lbf (55 N•m) of torque more than the basic single overhead cam 2.3 straight-4 engine on which it was based offering 185 hp (138 kW) at 6,200 rpm (59.2 kW/liter) and 174 lb·ft (236 N·m) at 4,500 rpm. In 1988 an enlarged 2.5-liter engine replaced the 2.3-liter. It offered double valve timing chains to fix the easily snapping single chains on early 2.3 engines, and increased peak output by 17 bhp (12.5 kW) with a slight increase in torque. For homologation Evolution I (1989) and Evolution II (1990) models were produced that had a redesigned engine to allow for a higher rev limit and improved top-end power capabilities. The Evo II engine offered 235 PS (173 kW; 232 hp) from 2463 cc (70.2 kW/liter).

Saab introduced a 16-valve head to their 2.0-liter (1985 cc) straight-4 in 1984 and offered the engine with and without turbocharger (65.5 kW/liter and 47.9 kW/liter respectively) in the Saab 900 and Saab 9000.

The 1.6-liter (1,587 cc) 4A-GE Toyota engine was one of the earliest straight-4 engines to have both a DOHC 16-valve configuration (four valves per cylinder, two intake, two exhaust) and electronic fuel injection (EFI). The cylinder head was developed by Yamaha Motor Corporation and was built at Toyota's Shimayama plant. While originally conceived of as a two-valve design, in 1984 Toyota and Yamaha changed the 4A-GE to a four-valve after a year of evaluation. It produced 115-140 bhp/86-104 kW@6,600 rpm (54.2-65.5 kW/liter) and 148 Nm/109 lbft@5,800 rpm. To compensate for the reduced air speed of a multi-valve engine at low rpm, the first-generation engines included the T-VIS feature.

In 1986 Volkswagen introduced a multi-valved Golf GTI 16V. The 16-valve 1.8-liter straight-4 produced 139 PS (102 kW; 137 bhp) or 56.7 kW/liter, almost 25% up from the 45.6 kW/liter for the previous 8-valve Golf GTI engine.

The GM Quad 4 multi-valve engine family debuted early 1987. The Quad 4 was the first mainstream multi-valve engine to be produced by GM after the Chevrolet Cosworth Vega. The NA Quad 4 achieved 1.08 bhp (1 kW; 1 PS) per cubic inch (49.1 kW/liter).[3][20] Such engines soon became common as Japanese manufacturers adopted the multi-valve concept.

Four valves[edit]

Nissan SR20VE 2.0-liter straight-4-cylinder head with DOHC, Nissan's Neo VVL variable valve timing with lift control and four valves per cylinder.

Multi-valve train of Volvo's 2005 truck diesel engine D13A, a 12.8-liter turbocharged straight-6 (21.1-28.1 kW/liter) with SOHC and four valves per cylinder located around a central injector, and VEB engine brake that operates both exhaust valves.

Examples of SOHC four-valve engines include: the Honda F-series engines, D-series engines, all J-series engines, the R-series engines, the Mazda B8-ME, the Chrysler 3.5 L V6 engine.

The V12 engines of many World War II fighter aircraft also used a SOHC configuration with four valves for each cylinder.

The 1993 Mercedes-Benz C-Class (OM604 engine) was the first 4-valve diesel-engined car.

Pushrod[edit]

Although most multi-valve engines have overhead camshafts, either SOHC or DOHC, a multivalve engine may be a pushrod overhead valve engine (OHV) design. Chevrolet has revealed a three-valve version of its Generation IV V8 which uses pushrods to actuate forked rockers, and Cummins makes a four-valve OHV straight six diesel, the Cummins B Series (now known as ISB). Ford also uses pushrods in its 6.7L Power Stroke engine using four pushrods, four rockers and four valves per cylinder.

The V12 engines of many World War II fighter aircraft used a SOHC configuration with four valves for each cylinder.

An example of a modern multi-valve piston-engine for small aircraft is the Austro Engine AE300. This liquid-cooled turbocharged 2.0-liter (1,991 cc) DOHC 16-valve straight-4 diesel engine uses common rail direct fuel injection and delivers 168 bhp (125 kW; 170 PS) at 3,880 rpm (62.0 kW/liter). The propeller is driven by an integrated gearbox (ratio 1.69:1) with torsional vibration damper. Total power unit weight is 185 kg (408 lb).

QMRThe Audi Quattro is a road and rally car, produced by the German automobile manufacturer Audi, part of the Volkswagen Group. It was first shown at the 1980 Geneva Motor Show on 3 March.[1][3] Production of the original version continued through 1991.

It has four valves

The word quattro is derived from the Italian word for "four". The name has also been used by Audi to refer to the quattro four-wheel-drive system, or any four-wheel-drive version of an Audi model. The original Quattro model is also commonly referred to as the Ur-Quattro - the "Ur-" (German for "primordial", "original", or "first of its kind") is an augmentative prefix, in this case meaning "original", and is also applied to the first generation Audi S4 and Audi S6 models, as in "Ur-S4" and "Ur-S6".

The Audi Quattro was the first rally car to take advantage of the then-recently changed rules which allowed the use of four-wheel drive in competition racing. It won competition after competition for the next two years.[1] To commemorate the success of the original vehicle, all subsequent Audis with their trademark quattro four-wheel-drive system were badged "quattro" with a lower case "q" and in a distinct typeface which has remained nearly unchanged since its inception.

The Audi Quattro shared many parts and core body components with the Coupé version of the Audi 80 (B2) model range.[1] The Quattro was internally designated Typ 85, a production code it shared with the quattro versions of the Audi 80 coupé Audi 80. Its characteristic flared wheelarches were styled by Martin Smith. The Audi Quattro also had independent rear suspension and independent front suspension.[4][5]

QMR The logo for audi is four circles

The company name is based on the Latin translation of the surname of the founder, August Horch. "Horch", meaning "listen" in German, becomes "audi" in Latin. The four rings of the Audi logo each represent one of four car companies that banded together to create Audi's predecessor company, Auto Union. Audi's slogan is Vorsprung durch Technik, meaning "Advancement through Technology". However, since 2007 Audi USA has used the slogan "Truth in Engineering".[13] Audi is among the best-selling luxury automobiles in the world.[14]

The merger of the four companies under the logo of four rings

Main article: Auto Union

In August 1928, Jørgen Rasmussen, the owner of Dampf-Kraft-Wagen (DKW), acquired the majority of shares in Audiwerke AG.[24] In the same year, Rasmussen bought the remains of the U.S. automobile manufacturer Rickenbacker, including the manufacturing equipment for eight-cylinder engines. These engines were used in Audi Zwickau and Audi Dresden models that were launched in 1929. At the same time, six-cylinder and four-cylinder (the "four" with a Peugeot engine) models were manufactured. Audi cars of that era were luxurious cars equipped with special bodywork.

In 1932, Audi merged with Horch, DKW, and Wanderer, to form Auto Union AG, Chemnitz. It was during this period that the company offered the Audi Front that became the first European car to combine a six-cylinder engine with front-wheel drive. It used a powertrain shared with the Wanderer, but turned 180-degrees, so that the drive shaft faced the front.

Before World War II, Auto Union used the four interlinked rings that make up the Audi badge today, representing these four brands. This badge was used, however, only on Auto Union racing cars in that period while the member companies used their own names and emblems. The technological development became more and more concentrated and some Audi models were propelled by Horch or Wanderer built engines.

Reflecting the economic pressures of the time, Auto Union concentrated increasingly on smaller cars through the 1930s, so that by 1938 the company's DKW brand accounted for 17.9% of the German car market, while Audi held only 0.1%. After the final few Audis were delivered in 1939 the "Audi" name disappeared completely from the new car market for more than two decades.

QMRCountach 5000 Quattrovalvole[edit]

In 1985 the engine design evolved again, as it was bored and stroked to 5167 cc and given four valves per cylinder—quattrovalvole in Italian, hence the model's name, Countach 5000 Quattrovalvole or 5000 QV in short. The carburetors were moved from the sides to the top of the engine for better breathing—unfortunately this created a hump on the engine deck, reducing the already poor rear visibility to almost nothing. Some body panels were also replaced by Kevlar. In later versions of the engine, the carburetors were replaced with fuel injection.

Although this change was the most notable on the exterior, the most prominent change under the hood was the introduction of fuel injection, with the Bosch K-Jetronic fuel injection, providing 414 bhp (309 kW; 420 PS), rather than the six Weber carburetors providing 455 bhp (339 kW; 461 PS) used in the previous carbureted models. As for other markets, 1987 and 1988 model Quattrovalvoles received straked sideskirts. 610 cars were built.

QMRColor Graphics Adapter (CGA)[edit]

The first color capable video card for the IBM PC family was the Color Graphics Adapter (CGA), which includes two graphic modes: 320×200 pixels with four colors (two bits per pixel) and 640×200 pixels black-and-white (one bit per pixel). The card as a whole implemented the "digital RGBI" 16-color space (i.e. each primary color (red, green, and blue) could be either on or off for a given pixel, and an additional intensity bit would brighten all three primaries if it was turned on for a pixel.

The color mode uses two bits to store red and green 1-bit components for each pixel (that is, colors in the RG color space) while the blue and intensity components were fixed for the entire screen.

This gave four possibilities for each single pixel: background (any one of the 16 colors the system offered, black or blue was most used; however only one background color could be chosen for the entire screen), red, green and yellow, with two possibilities of intensity selectable for the entire screen (except the background): low (darker) and high (lighter). This was known as Fixed palette #2. The Fixed palette #1 adds the blue component to all colors except the background, giving background (usually black was chosen), magenta (red+blue), cyan (green+blue) and white (yellow+blue), with two possible intensities, too.

QMRIn offset printing, a spot color is any color generated by an ink (pure or mixed) that is printed using a single run.

The widespread offset-printing process is composed of four spot colors: Cyan, Magenta, Yellow, and Key (black) commonly referred to as CMYK.

QMRThe CMYK color model (process color, four color) is a subtractive color model, used in color printing, and is also used to describe the printing process itself. CMYK refers to the four inks used in some color printing: cyan, magenta, yellow, and key (black). Though it varies by print house, press operator, press manufacturer, and press run, ink is typically applied in the order of the abbreviation.

The "K" in CMYK stands for key because in four-color printing, cyan, magenta, and yellow printing plates are carefully keyed, or aligned, with the key of the black key plate. Some sources suggest that the "K" in CMYK comes from the last letter in "black" and was chosen because B already means blue.[1][2] However, this explanation, although useful as a mnemonic, is incorrect. K is used as "Key", which was possibly chosen because black is often used as outline.[3]

The CMYK model works by partially or entirely masking colors on a lighter, usually white, background. The ink reduces the light that would otherwise be reflected. Such a model is called subtractive because inks "subtract" brightness from white.

In additive color models such as RGB, white is the "additive" combination of all primary colored lights, while black is the absence of light. In the CMYK model, it is the opposite: white is the natural color of the paper or other background, while black results from a full combination of colored inks. To save cost on ink, and to produce deeper black tones, unsaturated and dark colors are produced by using black ink instead of the combination of cyan, magenta and yellow.

QMRSpecifications for Web Offset Publications, invariably abbreviated to SWOP, is an organization and the name of a set of specifications that it produces, with the aim of improving the consistency and quality of professionally printed material in the United States, and of certain other products, programs and endorsements related to their work.

The SWOP specification covers many areas related to print production, complementing, extending and limiting those in other industry standards. The specification includes (but is not limited to) the following.

A specification for the colors of the cyan, magenta, yellow and key inks used in CMYK printing. Inks conforming to the specification can be called SWOP inks. The specifications make reference to, but are not identical to, the ISO standard ISO 2846-1:2006.

Jacob Christoph Le Blon, or Jakob Christoffel Le Blon, (2 May 1667 – 16 May 1741) was a painter and engraver from Frankfurt who invented the system of three- and four-colour printing, using an RYBK color model similar to the modern CMYK system.[2] He used the mezzotint method to engrave three or four metal plates (one each per printing ink) to make prints with a wide range of colours. His methods helped form the foundation for modern colour printing.

QMRWhile there are many techniques for reproducing images in color, specific graphic processes and industrial equipment are used for mass reproduction of color images on paper. In this sense, "color printing" involves reproduction techniques suited for printing presses capable of thousands or millions of impressions for publishing newspapers and magazines, brochures, cards, posters and similar mass-market items. In this type of industrial or commercial printing, the technique used to print full-color images, such as color photographs, is referred to as four-color-process or merely process printing. Four inks are used: three secondary colors plus black. These ink colors are cyan, magenta, yellow and key (black); abbreviated as CMYK. Cyan can be thought of as minus-red, magenta as minus-green, and yellow as minus-blue. These inks are semi-transparent or translucent. Where two such inks overlap on the paper due to sequential printing impressions, a primary color is perceived. For example, yellow (minus-blue) overprinted by magenta (minus green) yields red. Where all three inks may overlap, almost all incident light is absorbed or subtracted, yielding near black, but in practical terms it is better and cheaper to use a separate black ink instead of combining three colored inks. The secondary or subtractive colors cyan, magenta and yellow may be considered "primary" by printers and watercolorists (whose basic inks and paints are transparent).

Two graphic techniques are required to prepare images for four-color printing. In the "pre-press" stage, original images are translated into forms that can be used on a printing press, through "color separation," and "screening" or "halftoning." These steps make possible the creation of printing plates that can transfer color impressions to paper on printing presses based on the principles of lithography.

An emerging method of full-color printing is six-color process printing (for example, Pantone's Hexachrome system) which adds orange and green to the traditional CMYK inks for a larger and more vibrant gamut, or color range. However, such alternate color systems still rely on color separation, halftoning and lithography to produce printed images.

Color printing can also involve as few as one color ink, or multiple color inks which are not the primary colors. Using a limited number of color inks, or specific color inks in addition to the primary colors, is referred to as "spot color" printing. Generally, spot-color inks are specific formulations that are designed to print alone, rather than to blend with other inks on the paper to produce various hues and shades. The range of available spot color inks, much like paint, is nearly unlimited, and much more varied than the colors that can be produced by four-color-process printing. Spot-color inks range from subtle pastels to intense fluorescents to reflective metallics.

Color printing involves a series of steps, or transformations, to generate a quality color reproduction. The following sections focus on the steps used when reproducing a color image in CMYK printing, along with some historical perspective.

QMRPrint production[edit]

Carved woodblock for printing

Key block for ukiyo-e print, Utagawa Yoshiiku, 1862

Main articles: Relief printing and Woodblock printing in Japan

Ukiyo-e prints were the works of teams of artisans in several workshops;[173] it was rare for designers to cut their own woodblocks.[174] Labour was divided into four groups: the publisher, who commissioned, promoted, and distributed the prints; the artists, who provided the design image; the woodcarvers, who prepared the woodblocks for printing; and the printers, who made impressions of the woodblocks on paper.[175] Normally only the names of the artist and publisher were credited on the finished print.[

QMRThe initial ARPANET consisted of four IMPs:[24]

University of California, Los Angeles (UCLA), where Leonard Kleinrock had established a Network Measurement Center, with an SDS Sigma 7 being the first computer attached to it;

The Augmentation Research Center at Stanford Research Institute (now SRI International), where Douglas Engelbart had created the ground-breaking NLS system, a very important early hypertext system, and would run the Network Information Center (NIC), with the SDS 940 that ran NLS, named "Genie", being the first host attached;

University of California, Santa Barbara (UCSB), with the Culler-Fried Interactive Mathematics Center's IBM 360/75, running OS/MVT being the machine attached;

The University of Utah's Computer Science Department, where Ivan Sutherland had moved, running a DEC PDP-10 operating on TENEX.

By 5 December 1969, the entire four-node network was established

QMRIn the worldwide consumer market, four manufacturers account for the majority of inkjet printer sales: Canon, HP, Epson, and Lexmark, a 1991 spin-off from IBM.[3]

QMRSome recent TV and computer displays are starting to add a fourth "primary" of yellow, often in a four-point square pixel area, to get brighter pure yellows and larger color gamut.[16] Even the four-primary technology does not yet reach the range of colors the human eye is theoretically capable of perceiving (as defined by the sample-based estimate called the Pointer Gamut[17]), with 4-primary LED prototypes providing typically about 87% and 5-primary prototypes about 95%. Several firms, including Samsung and Mitsubishi, have demonstrated LED displays with five or six "primaries", or color LED point light sources per pixel.[18] A recent academic literature review claims a gamut of 99% can be achieved with 5-primary LED technology.[19] While technology for achieving a wider gamut appears to be within reach, other issues remain; for example, affordability, dynamic range, and brilliance. In addition, there exists hardly any source material recorded in this wider gamut, nor is it currently possible to recover this information from existing visual media. Regardless, industry is still exploring a wide variety of "primary" active light sources (per pixel) with the goal of matching the capability of human color perception within a broadly affordable price. One example of a potentially affordable but yet unproven active light hybrid places a LED screen over a plasma light screen, each with different "primaries". Because both LED and plasma technologies are many decades old (plasma pixels going back to the 1960s), both have become so affordable that they could be combined.

Painters have long used more than three "primary" colors in their palettes—and at one point considered red, yellow, blue, and green to be the four primaries.[25] Red, yellow, blue, and green are still widely considered the four psychological primary colors,[26] though red, yellow, and blue are sometimes listed as the three psychological primaries,[27] with black and white occasionally added as a fourth and fifth.[28]

QMRQuattron is the brand name of an LCD color display technology produced by Sharp Electronics. In addition to the standard RGB (Red, Green, and Blue) color subpixels, the technology utilizes a yellow fourth color subpixel (RGBY) which Sharp claims increases the range of displayable colors,[1][2] and which may mimic more closely the way the brain processes color information.[3][4] The screen is a form of multi-primary color display, other forms of which have been developed in parallel to Sharp's version.[5][6]

The technology is used in Sharp's Aquos LCD TV product line, particularly in models with screens 40 inches across and larger.[7] The technology, distinct from the product line, has been advertised featuring George Takei as the spokesperson in the debut commercial, in which he uses his catchphrase "Oh My".[8] Another commercial had Takei advertising the 3-D model with the Minions from the 2010 movie "Despicable Me".[9]

Criticism[edit]

According to an analysis published in MaximumPC Magazine by Raymond Soneira, president of DisplayMate Technologies, a video calibration equipment producer, Sharp's Quattron technology does not have the ability to show more colors than a standard RGB set. He argues that, due to industry-standard color spaces used by content providers, there is no existing source material that contains the fourth color channel. He further states that any "extra" colors displayed must simply be created in the television itself through video processing, resulting in exaggerated, less accurate color.[10]

Scientific analysis of Quattron[edit]

Spectral response of a common Quattron display. The white response was compared with each of the 4 primaries, given by the respective colored lines. It may be observed that yellow light produced by the display is simply the sum of the light that passes through the red pixel and the green pixel.

Color researchers at Queen Mary University of London investigated the Quattron technology and found that although Quattron does have 4 physical color sub-pixels it does not have a fourth primary in the backlight to drive it (yellow is approximately 575 nm). In other words, Quattron has a yellow sub-pixel to let light through, but the manufacturer has not made any provision to produce the yellow light needed to pass through it. (The yellow subpixel merely lets through more red and green light.) On that basis they conclude that it serves no useful function.[11]

QMREarly personal computers of the late 1970s and early 1980s, such as those from Apple, Atari and Commodore, did not use RGB as their main method to manage colors, but rather composite video. IBM introduced a 16-color scheme (four bits—one bit each for red, green, blue, and intensity) with the Color Graphics Adapter (CGA) for its first IBM PC (1981), later improved with the Enhanced Graphics Adapter (EGA) in 1984. The first manufacturer of a truecolor graphic card for PCs (the TARGA) was Truevision in 1987, but it was not until the arrival of the Video Graphics Array (VGA) in 1987 that RGB became popular, mainly due to the analog signals in the connection between the adapter and the monitor which allowed a very wide range of RGB colors. Actually, it had to wait a few more years because the original VGA cards were palette-driven just like EGA, although with more freedom than VGA, but because the VGA connectors were analogue, later variants of VGA (made by various manufacturers under the informal name Super VGA) eventually added truecolor. In 1992, magazines heavily advertised truecolor Super VGA hardware.

Modern storage, however, is far less costly, greatly reducing the need to minimize image file size. By using an appropriate combination of red, green, and blue intensities, many colors can be displayed. Current typical display adapters use up to 24-bits of information for each pixel: 8-bit per component multiplied by three components (see the Digital representations section below (24bits = 2563, each primary value of 8 bits with values of 0–255). With this system, 16,777,216 (2563 or 224) discrete combinations of R, G and B values are allowed, providing millions of different (though not necessarily distinguishable) hue, saturation, and lightness shades. Increased shading has been implemented in various ways, some formats such as .png and .tga files among others using a fourth greyscale color channel as a masking layer, often called RGB32

QMRA Bayer filter mosaic is a color filter array (CFA) for arranging RGB color filters on a square grid of photosensors. Its particular arrangement of color filters is used in most single-chip digital image sensors used in digital cameras, camcorders, and scanners to create a color image. The filter pattern is 50% green, 25% red and 25% blue, hence is also called RGBG,[1][2] GRGB,[3] or RGGB.[4]

It arranges them in a quadrant grid

The Bayer filter is almost universal on consumer digital cameras. Alternatives include the CYGM filter (cyan, yellow, green, magenta) and RGBE filter (red, green, blue, emerald), which require similar demosaicing. The Foveon X3 sensor (which layers red, green, and blue sensors vertically rather than using a mosaic) and arrangements of three separate CCDs (one for each color) don't need demosaicing.

Panchromatic" cells[edit]

On June 14, 2007, Eastman Kodak announced an alternative to the Bayer filter: a color-filter pattern that increases the sensitivity to light of the image sensor in a digital camera by using some "panchromatic" cells that are sensitive to all wavelengths of visible light and collect a larger amount of light striking the sensor.[7] They present several patterns, but none with a repeating unit as small as the Bayer pattern's 2×2 unit.

Earlier RGBW filter pattern

Another 2007 U.S. patent filing, by Edward T. Chang, claims a sensor where "the color filter has a pattern comprising 2×2 blocks of pixels composed of one red, one blue, one green and one transparent pixel," in a configuration intended to include infrared sensitivity for higher overall sensitivity.[8] The Kodak patent filing was earlier.[9]

Such cells have previously been used in "CMYW" (cyan, magenta, yellow, and white)[10] "RGBW" (red, green, blue, white)[11] sensors, but Kodak has not compared the new filter pattern to them yet.

Fujifilm "X-Trans" filter[edit]

The repeating 6×6 grid used in the x-trans sensor

The Fujifilm X-Trans CMOS sensor used in many Fujifilm X-series cameras is claimed[12] to provide better resistance to color moiré than the Bayer filter, and as such they can be made without an anti-aliasing filter. This in turn allows cameras using the sensor to achieve a higher resolution with the same megapixel count. Also, the new design is claimed to reduce the incidence of false colors, by having red, blue and green pixels in each line. The semi-random arrangement of these pixels is also said to provide grain more like film.

It is a 6 by 6 quadrant grid

QMRIn digital photography, the CYGM filter is an alternative color filter array to the Bayer filter (GRGB). It similarly uses a mosaic of pixel filters, of cyan, yellow, green and magenta, and so also requires demosaicing to produce a full-color image.

QMRIn digital photography, the RGBE filter is an alternative color filter array to the Bayer filter (GRGB). It similarly uses a mosaic of pixel filters, of red, green, blue and "emerald" ("like cyan" according to Sony), and so also requires demosaicing to produce a full-color image. It was developed by Sony and so far is used only in the ICX456 8-megapixel CCD and in the Sony Cyber-shot DSC-F828 camera.[1]

Sony states that the reason for adding the fourth filter color is "to reduce the color reproduction errors and to record natural images closer to the natural sight perception of the human eye."[2]

The RGBE array uses a fourth color, cyan, as well as red, green and blue

Compare to the earlier Bayer filter, with twice the number of pure green cells (while cyan colored light is a mix of green and blue, so sensors for that color also detects green and blue colors)

QMRThe Bayer arrangement of color filters on the pixel array of an image sensor. Each two-by-two cell contains two green, one blue, and one red filter.

Each two by two cell is a quadrant

QMRThe Bayer color filter mosaic. Each two-by-two submosaic contains 2 green, 1 blue and 1 red filter, each covering one pixel sensor.

Each 2 by 2 cell is a quadrant

QMRList of color filter arrays[edit]

Image Name Description Pattern size (pixels)

Bayer pattern Bayer filter Very common RGB filter. With one blue, one red, and two green. 2×2

RGBE pattern RGBE filter Bayer-like with one of the green filters modified to "emerald"; used in a few Sony cameras. 2×2

CYYM pattern CYYM filter One cyan, two yellow, and one magenta; used in a few cameras of Kodak. 2×2

CYGM pattern CYGM filter One cyan, one yellow, one green, and one magenta; used in a few cameras. 2×2

RGBW pattern RGBW Bayer Traditional RGBW similar to Bayer and RGBE patterns. 2×2

RGBW pattern RGBW #1 Three example RGBW filters from Kodak, with 50% white. (See Bayer filter#Modifications) 4×4

RGBW pattern RGBW #2

RGBW pattern RGBW #3 2×4

Bayer

QMRA CYYM filter is a color filter array. It has one cyan, two yellow, and one magenta element.[1] Developed by Kodak, it was used in the Kodak DCS 620x and DCS 720x DSLRs

A CYYM array, with 4 sub-arrays, each with one cyan, one magenta.

It is a quadrant grid

QMRCharge generation[edit]

Before the MOS capacitors are exposed to light, they are biased into the depletion region; in n-channel CCDs, the silicon under the bias gate is slightly p-doped or intrinsic. The gate is then biased at a positive potential, above the threshold for strong inversion, which will eventually result in the creation of a n channel below the gate as in a MOSFET. However, it takes time to reach this thermal equilibrium: up to hours in high-end scientific cameras cooled at low temperature.[14] Initially after biasing, the holes are pushed far into the substrate, and no mobile electrons are at or near the surface; the CCD thus operates in a non-equilibrium state called deep depletion.[15] Then, when electron–hole pairs are generated in the depletion region, they are separated by the electric field, the electrons move toward the surface, and the holes move toward the substrate. Four pair-generation processes can be identified:

photo-generation (up to 95% of quantum efficiency),

generation in the depletion region,

generation at the surface, and

generation in the neutral bulk.

QMRDigital color cameras generally use a Bayer mask over the CCD. Each square of four pixels has one filtered red, one blue, and two green (the human eye is more sensitive to green than either red or blue). The result of this is that luminance information is collected at every pixel, but the color resolution is lower than the luminance resolution.

The Bayers mask is a quadrant grid

QMRPenTile matrix is a family of patented subpixel matrix schemes used in electronic device displays. PenTile is a trademark of Samsung.

These subpixel layouts are specifically designed to operate with proprietary algorithms for subpixel rendering embedded in the display driver, allowing plug and play compatibility with conventional RGB (Red-Green-Blue) stripe panels.

Matrices are quadrant grids

The PenTile RGBW layout uses each red, green, blue and white subpixel to present high-resolution luminance information to the human eyes' red-sensing and green-sensing cone cells, while using the combined effect of all the color subpixels to present lower-resolution chroma (color) information to all three cone cell types. Combined, this optimizes the match of display technology to the biological mechanisms of human vision.[17] The layout uses one third fewer subpixels for the same resolution as the RGB stripe (RGB-RGB) layout, in spite of having four color primaries instead of the conventional three, using subpixel rendering combined with metamer rendering. Metamer rendering optimizes the energy distribution between the white subpixel and the combined red, green, and blue subpixels: W <> RGB, to improve image sharpness.

QMRRendering intent[edit]

When the gamut of source color space exceeds that of the destination, saturated colors are liable to become clipped (inaccurately represented), or more formally burned. The color management module can deal with this problem in several ways. The ICC specification includes four different rendering intents: absolute colorimetric, relative colorimetric, perceptual, and saturation.[4][5][6]

QMrTo see how this works in practice, suppose we have a particular RGB and CMYK color space, and want to convert from this RGB to that CMYK. The first step is to obtain the two ICC profiles concerned. To perform the conversion, each RGB triplet is first converted to the Profile connection space (PCS) using the RGB profile. If necessary the PCS is converted between CIELAB and CIEXYZ, a well defined transformation. Then the PCS is converted to the four values of C,M,Y,K required using the second profile.

QMrIT8.7/3 - 1993 (R2003) Graphic technology - Input data for characterization of 4-color process printing[edit]

The purpose of this standard is to specify an input data file, a measurement procedure and an output data format to characterize any four-color printing process. The output data (characterization) file should be transferred with any four-color (cyan, magenta, yellow and black) halftone image files to enable a color transformation to be undertaken when required. 29 pp.

IT8 is a set of American National Standards Institute (ANSI) standards for color communications and control specifications. Formerly governed by the IT8 Committee, IT8 activities were merged with those of the Committee for Graphics Arts Technologies Standards (CGATS) in 1994.

QMRColorChecker charts[edit]

Main article: ColorChecker

The ColorChecker—first produced as the “Macbeth ColorChecker” in 1976—a cardboard-framed arrangement of twenty-four squares of painted samples based on Munsell colors. Its previous maker Gretag–Macbeth was acquired in 2006 by X-Rite.

ColorChecker Color Rendition Chart

A ColorChecker chart can be used to manually adjust color parameters (e.g. color temperature) to achieve a desired color rendition. ColorChecker charts are available in different sizes and forms.

It is a quadrant grid

An IT8.7 Target by LaserSoft Imaging used for color management of digital cameras or scanners.

It is made up of color quadrants

QMRThe ColorChecker Color Rendition Chart (often referred to by its original name, the Macbeth ColorChecker[1] or simply Macbeth chart[2]) is a color calibration target consisting of a cardboard-framed arrangement of 24 squares of painted samples. The ColorChecker was introduced in a 1976 paper by McCamy, Marcus, and Davidson in the Journal of Applied Photographic Engineering.[3] The chart’s color patches have spectral reflectances intended to mimic those of natural objects such as human skin, foliage, and flowers, to have consistent color appearance under a variety of lighting conditions, especially as detected by typical color photographic film, and to be stable over time.

Design[edit]

The ColorChecker chart is a rectangular card measuring about 11 × 8.25 inches, or in its original incarnation about 13 × 9 in., an aspect ratio approximately the same as that of 35 mm film.[4] It includes 24 patches in a 4 × 6 grid, each slightly under 2 inches square, made of matte paint applied to smooth paper, and surrounded by a black border. Six of the patches form a uniform gray lightness scale, and another six are primary colors typical of chemical photographic processes – red, green, blue, cyan, magenta, and yellow. The remaining colors include approximations of medium light and medium dark human skin, blue sky, the front of a typical leaf, and a blue chicory flower. The rest were chosen arbitrarily to represent a gamut "of general interest and utility for test purposes", though the orange and yellow patches are similarly colored to typical oranges and lemons.[3]

QMRIn Ancient Greece, green and blue were sometimes considered the same color, and the same word sometimes described the color of the sea and the color of trees. The philosopher Democritus described two different greens; cloron, or pale green, and prasinon, or leek green. Aristotle considered that green was located midway between black, symbolizing the earth, and white, symbolizing water. However, green was not counted among of the four classic colors of Greek painting; red, yellow, black and white, and is rarely found in Greek art.

Chemistry Chapter

Chemistry Chapter Tetrahedral and other Four Shapes

Tetrahedron Letters is a weekly international journal for rapid publication of full original research papers in the field of organic chemistry. According to the Journal Citation Reports, the journal has a 2014 impact factor of 2.379 and it is ranked 22nd out of 57 journals in the "Organic Chemistry" category.[1]

QMRTetrapyrroles are a class of chemical compounds whose molecules contain four pyrrole rings held together by direct covalent bonds or by one-carbon bridges (=(CH)- or -CH

2- units), in either a linear or a cyclic fashion. A pyrrole ring in a molecule is a five-atom ring where four of the ring atoms are carbon and one is nitrogen. In cyclic tetrapyrroles, lone electron pairs on nitrogen atoms facing the center of the macrocycle ring can bond or chelate with a metal ion such as iron,cobalt, or magnesium.

Some tetrapyrroles are the active cores of some compounds with crucial biochemical roles in living systems, such as hemoglobin and chlorophyll. In these two molecules, in particular, the pyrrole macrocycle ring frames a metal atom, that forms a coordination compound with the pyrroles and plays a central role in the biochemical function of those molecules.

Structure[edit]

Linear tetrapyrroles (called bilanes) include:[1]

Heme breakdown products (e.g., bilirubin, biliverdin)

Phycobilins (found in cyanobacteria)

In organic chemistry, the term aromaticity is used to describe a cyclic, planar molecule that exhibits unusual stability as compared to linear molecules with the same number of atoms. As a result of this stability, these molecules are difficult to break and react

QMRHofmann was multilingual and published extensively, particularly about his work on coal tar and its derivatives. In 1865 Hofmann published An Introduction to Modern Chemistry, summarizing type theory and emerging ideas about chemical structure. Type theory modeled four inorganic molecules, hydrogen, hydrogen chloride, water, and ammonia, and used them as a basis for systematizing and categorizing both organic and inorganic compounds by exploring the substitution of one or more atoms of hydrogen for an equivalent atom or group. Hofman himself had focused on researching ammonia, but discussed all four models in his book. In it, he also first introduced the term valence, under its longer variant quantivalence, to describe the combining capacity of an atom. His textbook strongly influenced introductory textbooks in both Europe and the United States.[22]

In addition to his scientific works, Hofmann wrote biographical notices and essays on the history of chemistry, including a study of Liebig.[3]

QMRChemist Linus Pauling first developed the hybridisation theory in 1931 in order to explain the structure of simple molecules such as methane (CH4) using atomic orbitals.[2] Pauling pointed out that a carbon atom forms four bonds by using one s and three p orbitals, so that "it might be inferred" that a carbon atom would form three bonds at right angles (using p orbitals) and a fourth weaker bond using the s orbital in some arbitrary direction. In reality however, methane has four bonds of equivalent strength separated by the tetrahedral bond angle of 109.5°. Pauling explained this by supposing that in the presence of four hydrogen atoms, the s and p orbitals form four equivalent combinations or hybrid orbitals, each denoted by sp3 to indicate its composition, which are directed along the four C-H bonds.[3] This concept was developed for such simple chemical systems, but the approach was later applied more widely, and today it is considered an effective heuristic for rationalising the structures of organic compounds. It gives a simple orbital picture equivalent to Lewis structures. Hybridisation theory finds its use mainly in organic chemistry.

QMRsp3[edit]

Four sp3 orbitals.

Hybridisation describes the bonding atoms from an atom's point of view. For a tetrahedrally coordinated carbon (e.g., methane CH4), the carbon should have 4 orbitals with the correct symmetry to bond to the 4 hydrogen atoms.

Carbon's ground state configuration is 1s2 2s2 2p2 or more easily read:

C ↑↓ ↑↓ ↑ ↑

1s 2s 2p 2p 2p

The carbon atom can utilize its two singly occupied p-type orbitals, to form two covalent bonds with two hydrogen atoms, yielding the singlet methylene CH2, the simplest carbene. The carbon atom can also bond to four hydrogen atoms by an excitation of an electron from the doubly occupied 2s orbital to the empty 2p orbital, producing four singly occupied orbitals.

C* ↑↓ ↑ ↑ ↑ ↑

1s 2s 2p 2p 2p

The energy released by formation of two additional bonds more than compensates for the excitation energy required, energetically favouring the formation of four C-H bonds.

Quantum mechanically, the lowest energy is obtained if the four bonds are equivalent, which requires that they be formed from equivalent orbitals on the carbon. A set of four equivalent orbitals can be obtained that are linear combinations of the valence-shell (core orbitals are almost never involved in bonding) s and p wave functions,[5] which are the four sp3 hybrids.

C* ↑↓ ↑ ↑ ↑ ↑

1s sp3 sp3 sp3 sp3

In CH4, four sp3 hybrid orbitals are overlapped by hydrogen 1s orbitals, yielding four σ (sigma) bonds (that is, four single covalent bonds) of equal length and strength.

QMRSilicon tetrafluoride or Tetrafluorosilane is the chemical compound with the formula SiF4. This tetrahedral molecule is notable for having a remarkably narrow liquid range (its boiling point is only 4 °C above its melting point). It was first synthesized by John Davy in 1812.[2]

Contents [hide]

1 Preparation

2 Uses

3 Occurrence

4 References

Preparation[edit]

SiF

4 is a by-product of the production of phosphate fertilizers, resulting from the attack of HF (derived from fluorapatite protonolysis) on silicates. In the laboratory, the compound is prepared by heating BaSiF

6 above 300 °C, whereupon the solid releases volatile SiF

4, leaving a residue of BaF

2. The required BaSiF

6 is prepared by treating aqueous hexafluorosilicic acid with barium chloride.[3] The corresponding GeF

4 is prepared analogously, except that the thermal "cracking" requires 700 °C.[4] SiF

4 can also be created by placing silicon dioxide in hydrofluoric acid using the following equation:

4HF + SiO2 → SiF4 + 2H2O

Uses[edit]

This volatile compound finds limited use in microelectronics and organic synthesis.[5]

Occurrence[edit]

Volcanic plumes contain significant amounts of silicon tetrafluoride. Production can reach several tonnes per day.[6] The silicon tetrafluoride is partly hydrolysed and forms hexafluorosilicic acid.

QMRXenon tetrafluoride is a chemical compound with chemical formula XeF

4. It was the first discovered binary compound of a noble gas.[3] It is produced by the chemical reaction of xenon with fluorine, F

2, according to the chemical equation:[4][5]

Xe + 2 F

2 → XeF

This reaction is exothermic, releasing an energy of 251 kJ/mol of xenon.[3]

Xenon tetrafluoride is a colorless crystalline substance under ordinary conditions. Its crystalline structure was determined by both NMR spectroscopy and X-ray crystallography in 1963.[6][7] The structure is square planar, as has been confirmed by neutron diffraction studies,[8] and is justified by VSEPR theory because xenon has two lone pairs of electrons above and below the plane of the molecule.

Xenon tetrafluoride sublimes at a temperature of 115.7 °C (240.26 °F).

The formation of xenon tetrafluoride, like the other xenon fluorides, is exergonic. They are stable at normal temperatures and pressures. All of them readily react with water, releasing pure xenon gas, hydrogen fluoride, and molecular oxygen. This reaction occurs in slightly moist air; hence, all xenon fluorides must be kept in anhydrous atmospheres.

It is the shape of a quadrant

Synthesis[edit]

Xenon tetrafluoride is produced by heating a mixture of xenon and fluorine in a 1:5 ratio in a nickel container to 400 °C. Some xenon hexafluoride, XeF

6, is also produced, and this production is increased with an increased fluorine concentration in the input mixture.[9] The nickel is not a catalyst for this reaction; nickel containers are used because they react with fluorine to form a protective, non-peeling layer of nickel fluoride NiF

2 on their interior surfaces.

Chemistry[edit]

Xenon tetrafluoride is hydrolyzed by water at low temperatures to form elemental xenon, oxygen, hydrofluoric acid, and aqueous xenon trioxide.[10]

Reaction with tetramethylammonium fluoride forms tetramethylammonium pentafluoroxenate, which contains the pentagonal XeF−

5 anion. The XeF−

5 anion is also formed by reaction with caesium fluoride:[11]

CsF + XeF

4 → CsXeF

Reaction with bismuth pentafluoride (BiF

5) forms the XeF+

3 cation:[12]

BiF

5 + XeF

4 → XeF3BiF6

The XeF+

3 cation has also been identified in the salt XeF3Sb2F11 by NMR spectroscopy.[13]

At 400 °C, XeF

4 reacts with xenon gas to form XeF

2:[9]

XeF4 + Xe → 2 XeF2

The reaction of xenon tetrafluoride with platinum yields platinum tetrafluoride (PtF

4) and xenon gas:[9]

XeF4 + Pt → PtF4 + Xe

Applications[edit]

Xenon tetrafluoride is used as a decomposition agent of silicone rubber for analysing trace metal impurities in the rubber. XeF

4 reacts with the silicone structure that makes up the backbone of silicone rubber to form simple gaseous products, leaving behind any content of metal impurities.[14]

QMRQuaternary ammonium cations, also known as quats, are positively charged polyatomic ions of the structure NR4+, R being an alkyl group or an aryl group.[1] Unlike the ammonium ion (NH4+) and the primary, secondary, or tertiary ammonium cations, the quaternary ammonium cations are permanently charged, independent of the pH of their solution. Quaternary ammonium salts or quaternary ammonium compounds (called quaternary amines in oilfield parlance) are salts of quaternary ammonium cations.

Synthesis[edit]

Quaternary ammonium compounds are prepared by the alkylation of tertiary amines with a halocarbon. In older literature this is often called a Menshutkin reaction, however modern chemists usually refer to it simply as quaternization.[2] The reaction can be used to produce a compound with unequal alkyl chain lengths; for example when making cationic surfactants one of the alkyl groups on the amine is typically longer than the others.[3] A typical synthesis is for benzalkonium chloride from a long-chain alkyldimethylamine and benzyl chloride:

CH3(CH2)nN(CH3)2 + ClCH2C6H5 → [CH3(CH2)nN(CH3)2CH2C6H5]+Cl−

Reactions[edit]

While not very reactive, quaternary ammonium salts undergo Sommelet–Hauser rearrangement[4] and Stevens rearrangement,[5] as well as dealkylation under harsh conditions. Quaternary ammonium cations can also undergo the Hofmann Elimination and Emde degradation if there are hydrogens beta to the nitrogen.

Applications[edit]

Quaternary ammonium salts are used as disinfectants, surfactants, fabric softeners, and as antistatic agents (e.g. in shampoos). In liquid fabric softeners, the chloride salts are often used. In dryer anticling strips, the sulfate salts are often used. Spermicidal jellies also contain quaternary ammonium salts.

As antimicrobials[edit]

Quaternary ammonium compounds have also been shown to have antimicrobial activity.[6] Certain quaternary ammonium compounds, especially those containing long alkyl chains, are used as antimicrobials and disinfectants. Examples are benzalkonium chloride, benzethonium chloride, methylbenzethonium chloride, cetalkonium chloride, cetylpyridinium chloride, cetrimonium, cetrimide, dofanium chloride, tetraethylammonium bromide, didecyldimethylammonium chloride and domiphen bromide. Also good against fungi, amoebas, and enveloped viruses,[7] quaternary ammonium compounds are believed to act by disrupting the cell membrane.[citation needed] Quaternary ammonium compounds are lethal to a wide variety of organisms except endospores, Mycobacterium tuberculosis and non-enveloped viruses.

Quaternary ammonium compounds are cationic detergents, as well as disinfectants, and as such can be used to remove organic material. They are very effective in combination with phenols. Quaternary ammonium compounds are deactivated by anionic detergents (including common soaps). Also, they work best in soft waters[citation needed]. Effective levels are at 200 ppm. They are effective at temperatures up to 212 °F (100 °C).

Quaternary ammonium salts are commonly used in the foodservice industry as sanitizing agents.

As phase transfer catalysts[edit]

In organic synthesis, quaternary ammonium salts are employed as phase transfer catalysts (PTCs). Such catalysts accelerate reactions between reagents dissolved in immiscible solvents. The highly reactive reagent dichlorocarbene is generated via PTC by reaction of chloroform and sodium hydroxide.

Fabric softeners[edit]

In the 1950s, distearyldimethylammonium chloride (DHTDMAC), was introduced as a fabric softener. This compound was discontinued because the cation biodegrades too slowly. Contemporary fabric softeners are based on salts of quaternary ammonium cations where the fatty acid is linked to the quaternary center via ester linkages; these are commonly referred to as betaine-esters or ester-quats and are susceptible to degradation, e.g., by hydrolysis.[8] Characteristically, the cations contain one or two long alkyl chains derived from fatty acids linked to an ethoxylated ammonium salt.[9] Other cationic compounds can be derived from imidazolium, guanidinium, substituted amine salts, or quaternary alkoxy ammonium salts.[10]

Osmolytes[edit]

Quaternary ammonium compounds are present in osmolytes, specifically glycine betaine, which stabilize osmotic pressure in cells.[11]

Plant growth retardants[edit]

Cycocel (chlormequat chloride) reduces plant height by inhibiting the production of gibberellins, the primary plant hormones responsible for cell elongation. Therefore, their effects are primarily on stem, petiole and flower stalk tissues. Lesser effects are seen in reductions of leaf expansion, resulting in thicker leaves with darker green color.[12]

Health effects[edit]

Quaternary ammonium compounds can display a range of health effects, amongst which are mild skin and respiratory irritation [13] up to severe caustic burns on skin and gastro-intestinal lining (depending on concentration), gastro-intestinal symptoms (e.g., nausea and vomiting), coma, convulsions, hypotension and death.[14]

They are thought to be the chemical group responsible for anaphylactic reactions that occur with use of neuromuscular blocking drugs during general anaesthesia in surgery.[15] Quaternium-15 is the single most often found cause of allergic contact dermatitis of the hands (16.5% in 959 cases)[16]

Possible reproductive effects in laboratory animals[edit]

Quaternary ammonium-based disinfectants (Virex and Quatricide) were tentatively identified as the most probable cause of jumps in birth defects and fertility problems in caged lab mice.[17] See also Hunt and Hrubek (Reproductive Toxicology, 50:163-70, 2014).

Quantification[edit]

The quantification of quaternary ammonium compounds in environmental and biological samples is problematic using conventional chromatography techniques because the compounds are highly soluble in water. While analyzing them by liquid chromatography coupled tandem mass spectrometry it has been found that they follow an exception rule. Under standard electrospray ionization (ESI) conditions, mono- and di-quaternary ammonium compounds form molecular ions with the formula of m^q / z^q rather than ( m + z )/ z.[clarification needed] Formation of m^q / 2 is observed for di-quaternary ammonium compounds (like diquat) as precursor ion and m^q / 1 as product ion due to the loss of one of the quaternary charge during CID. In di-quaternary ammonium compounds, this process can also result in the formation of fragment ions with higher mass as compared to their precursor ion. Hydrophilic interaction liquid chromatographic separation has been reported to demonstrate a successful separation of quaternary ammonium compounds for their quantification in ESI-MS/MS with higher precision.[18]

QMRPolyquaternium is the International Nomenclature for Cosmetic Ingredients designation for several polycationic polymers that are used in the personal care industry. Polyquaternium is a neologism used to emphasize the presence of quaternary ammonium centers in the polymer. INCI has approved at least 37 different polymers under the polyquaternium designation. Different polymers are distinguished by the numerical value that follows the word "polyquaternium". Polyquaternium-5, polyquaternium-7, and polyquaternium-47 are three examples, each a chemically different type of polymer. The numbers are assigned in the order in which they are registered rather than because of their chemical structure.

Polyquaterniums find particular application in conditioners, shampoo, hair mousse, hair spray, hair dye, and contact lens solutions. Because they are positively charged, they neutralize the negative charges of most shampoos and hair proteins and help hair lie flat. Their positive charges also ionically bond them to hair and skin. Some have antimicrobial properties.

QMrSilicone quaternary amine is a chemical antimicrobial agent used in some odor-repellent socks, including Burlington Bioguard Socks.

QMRQuaternary ammonium muscle relaxants are quaternary ammonium salts used as drugs for muscle relaxation, most commonly in anesthesia. It is necessary to prevent spontaneous movement of muscle during surgical operations. Muscle relaxants inhibit neuron transmission to muscle by blocking the nicotinic acetylcholine receptor. What they have in common, and is necessary for their effect, is the structural presence of quaternary ammonium groups, usually two. Some of them are found in nature and others are synthesized molecules

Quaternary muscle relaxants bind to the nicotinic acetylcholine receptor and inhibit or interfere with the binding and effect of ACh to the receptor. Each ACh-receptor has two receptive sites and activation of the receptor requires binding to both of them. Each receptor site is located at one of the two α-subunits of the receptor. Each receptive site has two subsites, an anionic site that binds to the cationic ammonium head and a site that binds to the blocking agent by donating a hydrogen bond.[3]

QMRDiquat is a contact herbicide that produces desiccation and defoliation most often available as the dibromide, diquat dibromide.[2] Brand names for this formulation include Aquacide, Dextrone, Preeglone, Deiquat, Spectracide, Detrone, Reglone, Reglon, Reglox, Tribune, Ortho-Diquat, Weedtrine-D,[3] Weedol 2 and, in combination with glyphosate, Resolva.[4]

Diquat is a non-selective herbicide that acts quickly to damage only those parts of the plant to which it is applied.[5] It has been used in pre-harvest crop desiccation.[6] It bonds strongly to mineral and organic particles in soil and water where it remains without significant degradation for years. However, bound to clays diquat is biologically inactive at concentrations typically observed in agricultural soils.[5]

Diquat dibromide is moderately toxic. It may be fatal to humans if swallowed, inhaled, or absorbed through the skin in large quantities.[5]

QMRParaquat (trivial name; /ˈpærəkwɑːt/) or N,N′-dimethyl-4,4′-bipyridinium dichloride (systematic name) is the organic compound with the chemical formula [(C6H7N)2]Cl2. It is classified as a viologen, a family of redox-active heterocycles of similar structure. This salt is one of the most widely used herbicides. It is quick-acting and non-selective, killing green plant tissue on contact. It is also toxic to human beings and animals. It is linked to development of Parkinson's disease.[5][6] The name is derived from the para positions of the quat ernary nitrogens. Quantities are sometimes expressed by cation mass alone (paraquat cation, paraquat ion); other salts (with other anions besides chloride) exist. In fact, its redox activity, which produces superoxide anions, is why it is toxic.

Production[edit]

Pyridine is coupled by treatment with sodium in ammonia followed by oxidation. The resulting 4,4'-bipyridine, which is then methylated with chloromethane to give the desired compound:[7]

Synthesis of paraquat.png

History[edit]

Although first synthesized in 1882, paraquat's herbicidal properties were not recognized until 1955.[8] Paraquat was first manufactured and sold by ICI in early 1962, and is today among the most commonly used herbicides.

The European Union approved the use of paraquat in 2004 but Sweden, supported by Denmark, Austria, and Finland, appealed this decision. In 2007, the court annulled the directive authorizing paraquat as an active plant protection substance stating that the 2004 decision was wrong in finding that there were no indications of neurotoxicity associated with paraquat and that the studies about the link between paraquat and Parkinson's disease should have been considered.[9]

Herbicide use[edit]

The key characteristics that distinguish the non-selective contact herbicide paraquat from other active ingredients used in plant protection products are:

It kills a wide range of annual grasses and broad-leaved weeds and the tops of established perennial weeds.

It is very fast-acting.

It is rain-fast within minutes of application.

It is partially inactivated upon contact with soil.[10][11]

These properties led to paraquat being used in the development of no-till farming.[12][13][14] Current research into no-till farming using mulching techniques as a substitute for herbicide application are producing good results[15]

In the United States, paraquat is available primarily as a solution in various strengths. It is classified as "restricted use," which means that it can be used by licensed applicators only. In the European Union, paraquat has been forbidden since 2007.[9]

Reactivity and mode of action[edit]

Paraquat interferes with electron transfer, a process that is common to all life. It is an electron acceptor in redox and radical reactions.

As an herbicide, paraquat acts by inhibiting photosynthesis. In light-exposed plants, it accepts electrons from photosystem I (more specifically Fd, which is presented with electrons from PS I) and transfers them to molecular oxygen. In this manner, destructive reactive oxygen species are produced. In forming these reactive oxygen species, the oxidized form of paraquat is regenerated, and is again available to shunt electrons from photosystem I to start the cycle again.[16]

Paraquat is often used in science to catalyze the formation of reactive oxygen species (ROS), more specifically, the superoxide free radical. Paraquat will undergo redox cycling in vivo, being reduced by an electron donor such as NADPH, before being oxidized by an electron receptor such as dioxygen to produce superoxide, a major ROS.[17]

Weed resistance management[edit]

Problems with herbicide resistant weeds may be addressed by applying herbicides with different modes of action, along with cultural methods such as crop rotation, in integrated weed management (IWM) systems. Paraquat, with its distinctive mode of action, is one of few chemical options that can be used to prevent and mitigate problems with weeds that have become resistant to the very widely used non-selective herbicide glyphosate.[18][19]

One example is the "Double Knock" system used in Australia.[20] Before planting a crop, weeds are sprayed with glyphosate first, then followed seven to ten days later by a paraquat herbicide. Although twice as expensive as using a single glyphosate spray, the "Double Knock" system is an important resistance management strategy widely relied upon by farmers.[21] Nevertheless, herbicide resistance has been seen for both herbicides in Western Australia.[22]

A computer simulation showed that with alternating annual use between glyphosate and paraquat, only one field in five would be expected to have glyphosate-resistant annual ryegrass (Lolium rigidum) after 30 years, compared to nearly 90% of fields sprayed only with glyphosate.[23] A "Double Knock" regime with paraquat cleaning-up after glyphosate was predicted to keep all fields free of glyphosate resistant ryegrass for at least 30 years

Weed resistance management[edit]

Use in suicide and murder[edit]

A large majority (93 percent) of fatalities from paraquat poisoning are suicides, which occur mostly in developing countries.[32] For instance, in Samoa from 1979–2001, 70 percent of suicides were by paraquat poisoning. Trinidad and Tobago is particularly well known for its incidence of suicides involving the use of Gramoxone (commercial name of paraquat). In southern Trinidad, particularly in Penal, Debe from 1996–1997, 76 percent of suicides were by paraquat, 96 percent of which involved the over-consumption of alcohol such as rum.[33] Fashion celebrity Isabella Blow committed suicide using paraquat in 2007. Paraquat is widely used as a suicide agent in third-world countries because it is widely available at low cost. Further, the toxic dose is low (10 mL or 2 teaspoons is enough to kill). Campaigns exist to control or even ban paraquat, and there are moves to restrict its availability by requiring user education and the locking up of paraquat stores.

The indiscriminate paraquat murders, which occurred in Japan in 1985, were carried out using paraquat as a poison.

Paraquat, as the weedkiller Gramoxone, was used in the UK in 1981 by Susan Barber to poison the gravy of her husband Michael's pie. She was convicted of murder in November 1982, maintaining throughout that she had not intended to kill him.[34]

Parkinson's disease[edit]

In 2011, a US National Institutes of Health study showed a link between paraquat use and Parkinson's disease in farm workers.[35] A co-author of the paper said that paraquat increases production of certain oxygen derivatives that may harm cellular structures, and that people who used paraquat, or other pesticides with a similar mechanism of action, were more likely to develop Parkinson's.[5] Paraquat-induced toxicity in rats has also been linked to Parkinson's-like neurological degenerative mechanisms.[36] A study by the Buck Institute for Research on Aging showed a connection between exposure to paraquat and iron in infancy and mid-life Parkinson's in laboratory mice.[37]

Paraquat is structurally similar to MPP+, a known fast-acting inducer of Parkinson's disease in primate brains. The chloride of MPP+ was sold under the trade name Cyperquat.

Paraquat also induces oxidative stress in invertebrates such as Drosophila melanogaster. Paraquat-fed flies suffer early-onset mortality and significant increases in superoxide dismutase activity.[38]

QMRThe term parkinsonism is used for a motor syndrome whose main symptoms are tremor at rest, stiffness, slowing of movement and postural instability. Parkinsonian syndromes can be divided into four subtypes according to their origin:

primary or idiopathic

secondary or acquired

hereditary parkinsonism, and

Parkinson plus syndromes or multiple system degeneration

Four motor symptoms are considered cardinal in PD: tremor, rigidity, slowness of movement, and postural instability.[4]

QMRSteroids are characterized by four fused rings of carbon atoms (three six-membered rings and one five-membered ring). Many steroids also have a "side chain" of carbon atoms, usually attached to the five-membered ring.

The fourth is always different.

QMRThe endomorphins are a group of endogenous opioid peptides consisting of endomorphin-1 (Tyr-Pro-Trp-Phe-NH2) and endomorphin-2 (Tyr-Pro-Phe-Phe-NH2). They are tetrapeptides with the highest known affinity and selectivity for the μ-opioid receptor. Endomorphin-1 is found in the nucleus of the solitary tract, the periventricular hypothalamus, and the dorsomedial hypothalamus, where it is found within histaminergic neurons and may regulate sedative and arousal behaviors.[1] It is assumed that endomorphins are the cleavage products of a larger precursor, but this polypeptide or protein has not yet been identified.

QMRTetracyclic antidepressants (TeCAs) are a class of antidepressants that were first introduced in the 1970s. They are named after their chemical structure, which contains four rings of atoms, and are closely related to the tricyclic antidepressants (TCAs), which contain three rings of atoms.

Skeletal formula of tetracyclic antidepressant mirtazapine. Note its four fused "rings".

QMRTetrazoles are a class of synthetic organic heterocyclic compound, consisting of a 5-member ring of four nitrogen and one carbon atom (plus hydrogens). The simplest is tetrazole itself, CH2N4. They are unknown in nature.

There are several pharmaceutical agents which are tetrazoles. The tetrazole ring can act as a bioisostere for the carboxylate group. Angiotensin II receptor blockers - such as losartan and candesartan, often are tetrazoles. A well-known tetrazole is dimethyl thiazolyl diphenyl tetrazolium bromide (MTT). This tetrazole is used in the MTT assay to quantify the respiratory activity of live cells culture, although it generally kills the cells in the process. Some tetrazoles can also be used in DNA assays.[4]

Some tetrazole derivatives with high energy have been investigated as high performance explosives as a replacement for TNT and also for use in high performance solid rocket propellant formulations.[5][6]

Other tetrazoles are used for their explosive or combustive properties, such as tetrazole itself and 5-aminotetrazole, which are sometimes used as a component of gas generators in automobile airbags. Tetrazole based energetic materials produce high-temperature, non-toxic reaction products such as water and nitrogen gas,[7] and have a high burn rate and relative stability,[8] all of which are desirable properties. The delocalization energy in tetrazole is 209 kJ/mol.

QMRThe square planar molecular geometry in chemistry describes the stereochemistry (spatial arrangement of atoms) that is adopted by certain chemical compounds. As the name suggests, molecules of this geometry have their atoms positioned at the corners of a square on the same plane about a central atom.

It looks like a quadrant

QMRZeise's salt, potassium trichloro(ethene)platinate(II), is the chemical compound with the formula K[PtCl3(C2H4)]·H2O. The anion of this air-stable, yellow, coordination complex contains an η2-ethylene ligand. The anion features a platinum atom with a square planar geometry. The salt is of historical importance in the area of organometallic chemistry as one of the first examples of a transition metal alkene complex. Square planar looks like a quadrant

History[edit]

Zeise's salt was one of the first organometallic compounds to be reported.[5] It was discovered by William Christopher Zeise, a professor at the University of Copenhagen, who prepared this compound in 1830 while investigating the reaction of PtCl4 with boiling ethanol. Following careful analysis he proposed that the resulting compound contained ethylene. Justus von Liebig, a highly influential chemist of that era, often criticised Zeise's proposal, but Zeise's proposal was decisively supported in 1868 when Birnbaum prepared the complex using ethylene.[6] Zeise's salt received a great deal of attention during the second half of the 19th century because chemists could not explain its molecular structure. This question remained unanswered until the determination of x-ray crystal structure in the 20th century. Zeise's salt stimulated much scientific research in the field of organometallic chemistry and would be key in defining new concepts in chemistry the Dewar-Chatt-Duncanson model explains how the metal is coordinated to the C=C double bond.

QMRn-Butyllithium, an organometallic compound. Four lithium atoms (in purple) form a tetrahedron, with four butyl groups attached to the faces (carbon is black, hydrogen is white)

n-Butyllithium (abbreviated n-BuLi) is an organolithium reagent. It is widely used as a polymerization initiator in the production of elastomers such as polybutadiene or styrene-butadiene-styrene (SBS). Also, it is broadly employed as a strong base (superbase) in the synthesis of organic compounds as in the pharmaceutical industry.

Butyllithium is commercially available as solutions (15%, 25%, 2 M, 2.5 M, 10 M, etc.) in alkanes such as pentane, hexanes, and heptanes. Solutions in diethyl ether and THF can be prepared, but are not stable enough for storage. Annual worldwide production and consumption of butyllithium and other organolithium compounds is estimated at 1800 tonnes.[citation needed]

Although butyllithium is colorless, n-butyllithium is usually encountered as a pale yellow solution in alkanes. Such solutions are stable indefinitely if properly stored,[1] but in practice, they degrade upon aging. Fine white precipitate (lithium hydride) is deposited and the color changes to orange.[2][1]

QMRNickel carbonyl (IUPAC name: tetracarbonylnickel) is the organonickel compound with the formula Ni(CO)4. This pale-yellow liquid is the principal carbonyl of nickel. It is an intermediate in the Mond process for the purification of nickel and a reagent in organometallic chemistry. Nickel carbonyl is one of the most toxic substances encountered in industrial processes.[3]

QMRTetraethyllead (commonly styled tetraethyl lead), abbreviated TEL, is an organolead compound with the formula (CH3CH2)4Pb.

TEL was mixed with gasoline (petrol) beginning in the 1920s as a patented octane rating booster that allowed engine compression to be raised substantially, which in turn increased vehicle performance or fuel economy.[3][4] TEL in automotive fuel was phased out starting in the U.S. in the mid-1970s because of its cumulative neurotoxicity and its damaging effect on catalytic converters. When present in fuel, TEL is also the main cause of spark plug fouling.[5] TEL is still used as an additive in some grades of aviation gasoline, and in some developing countries.

Innospec has claimed to be the last firm still making TEL, but as of 2013 TEL is apparently being produced illegally by several companies in China

QMRTetramethylethylenediamine (TMEDA or TEMED) is a chemical compound with the formula (CH3)2NCH2CH2N(CH3)2. This species is derived from ethylenediamine by replacement of the four N-H groups with four N-methyl groups. It is a colourless liquid, although old samples often appear yellow. Its odor is remarkably similar to that of rotting fish.[3]

As a reagent in organic and inorganic synthesis[edit]

TMEDA is widely employed as a ligand for metal ions. It forms stable complexes with many metal halides, e.g. zinc chloride and copper(I) iodide, giving complexes that are soluble in organic solvents. In such complexes, TMEDA serves as a bidentate ligand.

TMEDA has an affinity for lithium ions.[3] When mixed with n-butyllithium, TMEDA's nitrogen atoms coordinate to the lithium, forming a cluster of higher reactivity than the tetramer or hexamer that n-butyllithium normally adopts. BuLi/TMEDA is able to metallate or even doubly metallate many substrates including benzene, furan, thiophene, N-alkylpyrroles, and ferrocene.[3] Many anionic organometallic complexes have been isolated as their [Li(tmeda)2]+ complexes.[4] In such complexes [Li(tmeda)2]+ behaves like a quaternary ammonium salt, such as [NEt4]+.

TMEDA adduct of lithium bis(trimethylsilyl)amide. Notice that the diamine is a bidentate ligand.[5]

It is also worth noting that sBuLi/TMEDA is also a useful combination in organic synthesis. Utilization of this is useful in cases where the n-butyl anion is able to add into the starting material due to its weak nucleophilic nature. TMEDA is still capable of forming a metal complex with Li in this case as mentioned above.

Other uses[edit]

TEMED is used with ammonium persulfate to catalyze the polymerization of acrylamide when making polyacrylamide gels, used in gel electrophoresis, for the separation of proteins or nucleic acids. Although the amounts used in this technique may vary from method to method, 0.1-0.2% v/v TEMED is a "traditional" range. TEMED can also be a component of Hypergolic propellants.

Biology Chapter

QMRThe Systeme of the World: in Four Dialogues is the original 1661 English translation, by Thomas Salusbury, of Galileo Galilei's DIALOGO sopra i due MASSI SISTEMI DEL MONDO (1632). Galileo's publication is more generally recognized under the title of Stilman Drake's English translation, Dialogue Concerning the Two Chief World Systems, published in 1953. A revised and annotated edition of the Salusbury translation was also introduced in 1953 by Giorgio de Santillana under the title Dialogue on the Great World Systems.

The complete title of the Salusbury translation is "THE SYSTEME OF THE WORLD: IN FOUR DIALOGUES. Wherein the Two GRAND SYSTEMES Of PTOLOMY and COPERNICUS are largely discoursed of: And the REASONS, both Phylosophical and Physical, as well on the one side as the other, impartially and indefinitely propounded: By GALILEUS GALILEUS LINCEUS, A Gentleman of FLORENCE: Extraordinary Professor of the Mathematicks in the UNIVERSITY of PISA; and Chief Mathematician to the GRAND DUKE of TUSCANY."

QMRGalileo Galilei (Italian pronunciation: [ɡaliˈlɛːo ɡaliˈlɛi]; 15 February 1564[3] – 8 January 1642), was an Italian astronomer, physicist, engineer, philosopher, and mathematician who played a major role in the scientific revolution during the Renaissance. Galileo has been called the "father of observational astronomy",[4] the "father of modern physics",[5][6] and the "father of science".[7] His contributions to observational astronomy include the telescopic confirmation of the phases of Venus, the discovery of the four largest satellites of Jupiter (named the Galilean moons in his honour), and the observation and analysis of sunspots. Galileo also worked in applied science and technology, inventing an improved military compass and other instruments.

QMRFrancesco Ingoli

In addition to Bellarmine, Monsignor Francesco Ingoli initiated a debate with Galileo, sending him in January 1616 an essay disputing the Copernican system. Galileo later stated that he believed this essay to have been instrumental in the action against Copernicanism that followed in February. [31] According to Maurice Finocchiaro, Ingoli had probably been commissioned by the Inquisition to write an expert opinion on the controversy, and the essay provided the "chief direct basis" for the ban.[32] The essay focused on eighteen physical and mathematical arguments against heliocentrism. It borrowed primarily from the arguments of Tycho Brahe, and it notedly mentioned Brahe's argument that heliocentrism required the stars to be much larger than the sun. Ingoli wrote that the great distance to the stars in the heliocentric theory "clearly proves ... the fixed stars to be of such size, as they may surpass or equal the size of the orbit circle of the Earth itself."[33] Ingoli included four theological arguments in the essay, but suggested to Galileo that he focus on the physical and mathematical arguments. Galileo did not write a response to Ingoli until 1624, in which, among other arguments and evidence, he listed the results of experiments such as dropping a rock from the mast of a moving ship.[34]

QMRThe field of Marxist hermeneutics has been developed by the work of, primarily, Walter Benjamin and Fredric Jameson. Benjamin outlines his theory of the allegory in his monumental Ursprung des deutschen Trauerspiel ("Trauerspiel" literally means "Mourning Play" but is often translated as "Tragic Drama").[8] Fredric Jameson draws on Biblical hermeneutics, and the work of Northrop Frye, to advance his theory of Marxist hermeneutics in his influential The Political Unconscious. Jameson's Marxist hermeneutics is outlined in the first chapter of the book, titled "On Interpretation"[9] Jameson re-interprets (and secularizes) the fourfold system (or four levels) of Biblical exegesis (literal; moral; allegorical; anagogical) to relate interpretation to the Mode of Production, and eventually, history.

QMRThere are four different types of biblical hermeneutics, literal, moral, allegorical (spiritual) and anagogical.[according to whom?]

Literal[edit]

Encyclopædia Britannica states that literal analysis means “a biblical text is to be deciphered according to the ‘plain meaning’ expressed by its linguistic construction and historical context.” The intention of the authors is believed to correspond to the literal meaning. Literal hermeneutics is often associated with the verbal inspiration of the Bible.[19]

Moral[edit]

Moral interpretation searches for moral lessons which can be understood from writings within the Bible. Allegories are often placed in this category. This can be seen in the Epistle of Barnabas, which explains the dietary laws by stating which meats are forbidden but is interpreted as forbidding immorality with animals.[19]

Allegorical[edit]

Allegorical interpretation states that biblical narratives have a second level of reference that is more than the people, events and things that are explicitly mentioned. One type of allegorical interpretation is known as typological, where the key figures, events, and establishments of the Old Testament are viewed as “types”. In the New Testament this can also include foreshadowing of people, objects, and events. According to this theory readings like Noah’s Ark could be understood by using the Ark as a “type” of Christian church that God expected from the start.[19]

Anagogical[edit]

This type of interpretation is more often known as mystical interpretation. It purports to explain the events of the Bible and how they relate to or predict what the future holds. This is evident in the Jewish Kabbalah, which attempts to reveal the mystical significance of the numerical values of Hebrew words and letters.

In Judaism, anagogical interpretation is also evident in the medieval Zohar. In Christianity, it can be seen in Mariology

QMRExpression can be deduced via RNA-seq to the extent at which a sequence is retrieved. Transcriptome studies in yeast [28] show that in this experimental setting, a fourfold coverage is required for amplicons to be classified and characterized as an expressed gene. When the transcriptome is fragmented prior to cDNA synthesis, the number of reads corresponding to the particular exon normalized by its length in vivo yields gene expression levels which correlate with those obtained through qPCR.[26] This is frequently further normalized by the total number of mapped reads so that expression levels are expressed as Fragments Per Kilobase of transcript per Million mapped reads (FPKM).[21]

The only way to be absolutely sure of the individual's mutations is to compare the transcriptome sequences to the germline DNA sequence. This enables the distinction of homozygous genes versus skewed expression of one of the alleles and it can also provide information about genes that were not expressed in the transcriptomic experiment. An R-based statistical package known as CummeRbund[29] can be used to generate expression comparison charts for visual analysis.

QMRC. elegans is unsegmented, vermiform, and bilaterally symmetrical. It has a cuticle (a tough outer covering), four main epidermal cords, and a fluid-filled pseudocoelom (body cavity). It also has some of the same organ systems as larger animals. Almost all individuals of C. elegans are hermaphrodites, and a small minority, around one in a thousand, are males.[9] The basic anatomy of C. elegans includes a mouth, pharynx, intestine, gonad, and collagenous cuticle. Like all nematodes, they have neither a circulatory nor a respiratory system. The four bands of muscles that run the length of the body are connected to a neural system that allows the muscles to move the animal's body only as dorsal bending or ventral bending, but not left or right, except for the head, where the four muscle quadrants are wired independently from one another. When a wave of dorsal/ventral muscle contractions proceeds from the back to the front of the animal, the animal is propelled backwards. When wave of contractions is initiated at the front and proceeds posteriorly along the body, the animal is propelled forwards. Because of this dorsal/ventral bias in body bends, any normal living, moving individual will tend to lie on either its left side or its right side when observed crossing a horizontal surface. A set of ridges on the lateral sides of the body cuticle, the alae, are believed to give the animal added traction during these bending motions.

All cells of the germline arise from a single primordial germ cell, called the P4 cell established early in embryogenesis.[11][12] This germ cell divides to generate two further germ cells and these do not divide further until after hatching.[12] The hermaphrodite, which is considered to be a specialized form of self-fertile female because its soma is female whereas its germline produces male gametes first, lays eggs through its uterus after internal fertilization. Under environmental conditions which are favourable for reproduction, hatched larvae develop through four stages or molts, designated as L1 to L4.

QMRTranslation proceeds in four phases: activation, initiation, elongation, and termination (all describing the growth of the amino acid chain, or polypeptide that is the product of translation).

QMR Traditional Chinese Medicine, as described in the Yellow Emperor's Inner Canon or Huangdi Neijing, specified four diagnostic methods: inspection, auscultation-olfaction, interrogation, and palpation.[4] Hippocrates was known to make diagnoses by tasting his patients' urine and smelling their sweat.[5]

QMRSignal flag "Lima" called the "Yellow Jack" which when flown in harbor means ship is under quarantine. A simple yellow flag (also called the "Yellow Jack") had historically been used to signal quarantine (it stands for Q among signal flags), but now indicates the opposite, as a signal of a ship free of disease that requests boarding and inspection. It is a black and yellow quadrant

QMRThe ACL is one of the four major ligaments in the knee.

QMRThe anterior cruciate ligament is one of the four main ligaments of the knee, and the ACL provides 85% of the restraining force to anterior tibial displacement at 30 degrees and 90 degrees of knee flexion. [2]

QMRThe ligaments in the knee connect the femur (thighbone) to the tibia (shin bone), and include the following:

Anterior cruciate ligament (ACL). ...

Posterior cruciate ligament (PCL). ...

Medial collateral ligament (MCL). ...

Lateral collateral ligament (LCL).

QMRThere are 4 major ligaments in the knee. The ligaments in the knee connect the femur (thighbone) to the tibia (shin bone), and include the following:

Anterior cruciate ligament (ACL). The ligament, located in the center of the knee, that controls rotation and forward movement of the tibia (shin bone).

Posterior cruciate ligament (PCL). The ligament, located in the center of the knee, that controls backward movement of the tibia (shin bone).

Medial collateral ligament (MCL). The ligament that gives stability to the inner knee.

Lateral collateral ligament (LCL). The ligament that gives stability to the outer knee.

QMrRecovery Progression[edit]

Recovery is a four phase progression.

Phase 1 (0-2 weeks)[edit]

The goals of this phase are to:

Eliminate swelling due to inactivity

Progress from partial weight bearing to full weight bearing exercises

Regain normal range of motion

Increase quadriceps strength

Increase hamstring strength

Some equipment that can be used and exercises that can be performed are:

Use of Cryo-cuff

- provides cold compression

Isometric Contraction of Quads

Quad Sets

- stand against wall, push extended knee against rolled towel

- progress to straight leg raised to 30deg.

Wall Slides

- To increase knee flexion

Assisted Knee Flexion

Towel Squeeze

- Sit in chair, squeeze rolled towel between knees for 5 seconds. Relax & repeat.

VMO Strengthening Exercise

Supported Bilateral Calf-Raises

walk without crutches

Phase 2 (2-12 weeks)[edit]

The goals of this phase are to:

Regain full knee extension

Restore knee flexion to +130°

Perform a full squat properly

Regain good balance and control

Reestablish proper gait

Some exercises that can be performed are:

Mini squats

- Progress to full squats → single-leg half squat

Mini Lunges

- Progress to full lunges

Leg Press

- Double-leg → single

Step-ups

- lateral & forward

Bridges

- Double-leg → single

- Floor → Swiss ball

Hip Abduction w/ Theraband

Hip Extension w/ Theraband

Wobble board

- Assisted → un-assisted → eyes closed (assisted → unassisted)

Stork Stand

- Assisted → un-assisted → eyes closed (assisted → unassisted) → unstable surface

Static Proprioceptive hold/ball throwing

Functional Exercises that can be performed at this time include:

- Walking

- Bike

- Roman Chair

Phase 3 (3-6 months)[edit]

The goals of this phase are to:

Regain full range of motion

Regain full strength and power

Increase agility

allows for adaption to direction change, acceleration and deceleration

Be able to perform restricted sports-specific drills

Begin plyometric drills

Some exercises that can be performed are:

Continue exercises from Phase 2, progress as necessary

Jump & Land drills

- Jump from block & stick landing

- Double-leg landing → single-leg

Plyometric Drills

- Jumping over blocks, sideways & forward

- Hopping up & down steps/stairs

Phase 4 (6-15 months)[edit]

The goal of this phase is a return to activity, however it requires an ability to perform some functional performance tests such as:

Agility Tests

Illinois Agility Test

Zig Zag Agility Test

These tests are used to test the ability of the knee to withstand cutting and planting maneuvers

Standing Vertical Jump

Here you jump straight in the air from a standing start and land on two feet as stable as possible.

Heiden Hop Test

Here you essentially jump as far as possible with the uninjured leg and land on the injured leg. Your ability to stick the landing is indicative of good knee function.

Isokinetic Testing

This is used to evaluate muscle strength.

The individual should have at least 90% quadricep strength of the uninjured leg

They should also have equal hamstring strength to their uninjured leg as well

QMRThe three muscles of the posterior thigh (semitendinosus, semimembranosus, biceps femoris long & short head) flex (bend) the knee, while all but the short head of biceps femoris extend (straighten) the hip. The three 'true' hamstrings cross both the hip and the knee joint and are therefore involved in knee flexion and hip extension. The short head of the biceps femoris crosses only one joint (knee) and is therefore not involved in hip extension. With its divergent origin and innervation it is sometimes excluded from the 'hamstring' characterization.[3]

Muscle Origin Insertion Nerve

semitendinosus ischial tuberosity medial surface of tibia sciatic

semimembranosus ischial tuberosity medial tibial condyle sciatic

biceps femoris - long head ischial tuberosity lateral side of the head of the fibula sciatic

biceps femoris - short head linea aspera and lateral supracondylar line of femur lateral side of the head of the fibula (common tendon with the long head) common peroneal

A portion of the adductor magnus is sometimes considered a part of the hamstrings.[3]

The fourth part is always different

QMRThe upper three-quarters of the patella articulates with the femur and is subdivided into a medial and a lateral facet by a vertical ledge which varies in shape. Four main types of articular surface can be distinguished:

Most commonly the medial articular surface is smaller than the lateral.

Sometimes both articular surfaces are virtually equal in size.

Occasionally, the medial surface is hypoplastic or

the central ledge is only indicated.

QMRThe medial collateral ligament (MCL or tibial collateral ligament) is one of the four major ligaments of the knee. It is on the medial (inner) side of the knee joint in humans and other primates. Its primary function is to resist valgus forces on the knee.

QMRFour super radiations of insects have occurred: beetles (evolved about 300 million years ago), flies (evolved about 250 million years ago), and moths and wasps (evolved about 150 million years ago).[17] These four groups account for the majority of described species. The flies and moths along with the fleas evolved from the Mecoptera.

Traditional morphology-based or appearance-based systematics have usually given the Hexapoda the rank of superclass,[25]:180 and identified four groups within it: insects (Ectognatha), springtails (Collembola), Protura, and Diplura, the latter three being grouped together as the Entognatha on the basis of internalized mouth parts.

QMRThough the true dimensions of species diversity remain uncertain, estimates range from 2.6–7.8 million species with a mean of 5.5 million.[34] This probably represents less than 20% of all species on Earth[citation needed], and with only about 20,000 new species of all organisms being described each year, most species likely will remain undescribed for many years unless species descriptions increase in rate. About 850,000–1,000,000 of all described species are insects. Of the 24 orders of insects, four dominate in terms of numbers of described species, with at least 3 million species included in Coleoptera, Diptera, Hymenoptera and Lepidoptera. A recent study estimated the number of beetles at 0.9–2.1 million with a mean of 1.5 million.[34]

Comparison of the estimated number of species in the four most speciose insect orders[citation needed]

Described species Average description rate

(species per year) Publication effort

Coleoptera 300,000–400,000 2308 0.01

Lepidoptera 110,000–120,000 642 0.03

Diptera 90,000–150,000 1048 0.04

Hymenoptera 100,000–125,000 1196 0.02

QMRPolymorphism is where a species may have different morphs or forms, as in the oblong winged katydid, which has four different varieties: green, pink and yellow or tan

QMRGod is viewed as the creator, whose nature combines both masculinity and femininity, and is the source of all truth, beauty, and goodness. Human beings and the universe reflect God's personality, nature, and purpose.[48] "Give-and-take action" (reciprocal interaction) and "subject and object position" (initiator and responder) are "key interpretive concepts",[49] and the self is designed to be God's object.[49] The purpose of human existence is to return joy to God. The "four-position foundation" is "another important and interpretive concept", and explains in part the emphasis on the family.

QMRIn the horse, 84%, 15%, and 3% of the total triceps muscle weight correspond to the long, lateral and medial heads, respectively.[7]

Many mammals, such as dogs, cattle, and pigs, have a fourth head, the accessory head. It lies between the lateral and medial heads.[2] In humans, the anconeus is sometimes loosely called "the fourth head of the triceps brachii".

QMRevery movement at the wrist is the work of a group of muscles; because the four primary wrist muscles (FCR, FCU, ECR, and ECU) are attached to the four corners of the wrist, they also produce a secondary movement (i.e. ulnar or radial deviation). To produce pure flexion or extension at the wrist, these muscle therefore must act in pairs to cancel out each other's secondary action. On the other hand, finger movements without the corresponding wrist movements require the wrist muscles to cancel out the contribution from the extrinsic hand muscles at the wrist. [9]

QMRThe epidermis is the top layer of skin made up of epithelial cells. It does not contain blood vessels. Its main function is protection, absorption of nutrients, and homeostasis. In structure, it consists of a keratinized stratified squamous epithelium comprising four types of cells: keratinocytes, melanocytes, Merkel cells, and Langerhans' cells. The major cell of the epidermis is the keratinocyte, which produces keratin. Keratin is a fibrous protein that aids in protection. Keratin is also a waterproofing protein. Millions of dead keratinocytes rub off daily. The majority of the skin on the body is keratinized, meaning waterproofed. The only skin on the body that is non-keratinized is the lining of skin on the inside of the mouth. Non-keratinized cells allow water to "stay" atop the structure.

The protein keratin stiffens epidermal tissue to form fingernails. Nails grow from a thin area called the nail matrix; growth of nails is 1 mm per week on average. The lunula is the crescent-shape area at the base of the nail, this is a lighter color as it mixes with the matrix cells.

QMRLevel Muscle Extrinsic/Intrinsic Nerve

superficial flexor carpi radialis extrinsic median

superficial palmaris longus extrinsic median

superficial flexor carpi ulnaris extrinsic ulnar

superficial pronator teres intrinsic median

superficial (or intermediate) flexor digitorum superficialis extrinsic median

deep flexor digitorum profundus extrinsic ulnar + median (as anterior interosseous nerve)

deep flexor pollicis longus extrinsic median (as anterior interosseous nerve)

deep pronator quadratus intrinsic median (as anterior interosseous nerve)

QMRManubrium[edit]

Shape of manubrium

The manubrium, (Latin: handle), is the broad upper part of the sternum. It has a quadrangular shape, narrowing from the top, which gives it four borders.

QMRIn early life, the sternum's body is divided into four segments, not three, called sternebrae (singular: sternebra).

QMRThe concept of the chord zither is different from that of the concert and alpine zithers. These instruments may have from 12 to 50 (or more) strings, depending on design. All the strings are played open, in the manner of a harp. The strings on the left are arranged in groups of three or four, which form various chords to be played by the left hand.

QMRThe primary (parts of the cortex that receive sensory inputs from the thalamus) visual cortex is also known as V1, Visual area one, and the striate cortex. The extrastriate areas consist of visual areas two (V2), three (V3), four (V4), and five (V5)

These five regions fit the quadrant model pattern

In terms of anatomy, V2 is split into four quadrants, a dorsal and ventral representation in the left and the right hemispheres. Together, these four regions provide a complete map of the visual world. V2 has many properties in common with V1: Cells are tuned to simple properties such as orientation, spatial frequency, and color. The responses of many V2 neurons are also modulated by more complex properties, such as the orientation of illusory contours, binocular disparity,[15] and whether the stimulus is part of the figure or the ground (Qiu and von der Heydt, 2005). Recent research has shown that V2 cells show a small amount of attentional modulation (more than V1, less than V4), are tuned for moderately complex patterns, and may be driven by multiple orientations at different subregions within a single receptive field.

Visual area V4 is one of the visual areas in the extrastriate visual cortex. In macaques, it is located anterior to V2 and posterior to posterior inferotemporal area (PIT). It comprises at least four regions (left and right V4d, left and right V4v), and some groups report that it contains rostral and caudal subdivisions as well. It is unknown what the human homologue of V4 is, and this issue is currently the subject of much scrutiny.[26]

QMRThe thalamus is part of a nuclear complex structured of four parts, the hypothalamus, epithalamus, prethalamus (formerly called ventral thalamus), and dorsal thalamus.[6]

QMRIn terms of anatomy, the basal ganglia are divided by anatomists into four distinct structures, depending on how superior or rostral they are (in other words depending on how close to the top of the head they are): Two of them, the striatum and the pallidum, are relatively large; the other two, the substantia nigra and the subthalamic nucleus, are smaller. In the illustration to the right, two coronal sections of the human brain show the location of the basal ganglia components. Of note, and not seen in this section, the subthalamic nucleus and substantia nigra lie farther back (posteriorly) in the brain than the striatum and pallidum.

QMRThere are four classical muscles of mastication. During mastication, three muscles of mastication (musculi masticatorii) are responsible for adduction of the jaw, and one (the lateral pterygoid) helps to abduct it. All four move the jaw laterally. Other muscles, usually associated with the hyoid such as the sternohyomastoid, are responsible for opening the jaw in addition to the lateral pterygoid.

The muscles are:

The masseter (composed of the superficial and deep head)

The temporalis (the sphenomandibularis is considered a part of the temporalis by some sources, and a distinct muscle by others)

The medial pterygoid

The lateral pterygoid

In humans, the mandible, or lower jaw, is connected to the temporal bone of the skull via the temporomandibular joint, an extremely complex joint which permits movement in all planes. The muscles of mastication originate on the skull and insert into the mandible, thereby allowing for jaw movements during contraction.

Each of these primary muscles of mastication is paired, with each side of the mandible possessing one of the four.

QMRThe tongue's two sets of muscles, are four intrinsic muscles that originate in the tongue and are involved with its shaping, and four extrinsic muscles originating in bone that are involved with its movement.

QMRMuscles[edit]

The eight muscles of the human tongue are classified as either intrinsic or extrinsic. The four intrinsic muscles act to change the shape of the tongue, and are not attached to any bone. The four extrinsic muscles act to change the position of the tongue, and are anchored to bone.

Extrinsic[edit]

The extrinsic muscles originate from bone and extend to the tongue. Their main functions are altering the tongue's position allowing for protrusion, retraction, and side-to-side movement.[4]:991

Genioglossus, which arises from the mandible and protrudes the tongue. It is also known as the "safety muscle" of the tongue since it is the only muscle having the forward action.

Hyoglossus, which arises from the hyoid bone and depresses the tongue

Styloglossus, which arises from the styloid process of the temporal bone and elevates and retracts the tongue

Palatoglossus, which arises from the palatine aponeurosis, and depresses the soft palate, moves the palatoglossal fold towards the midline, and elevates the back of the tongue.

Intrinsic[edit]

Four paired intrinsic muscles of the tongue originate and insert within the tongue, running along its length. These muscles alter the shape of the tongue by: lengthening and shortening it, curling and uncurling its apex and edges, and flattening and rounding its surface. This provides shape, and helps facilitate speech, swallowing, and eating.[4]:991

The superior longitudinal muscle runs along the superior surface of the tongue under the mucous membrane, and elevates, assists in retraction of, or deviates the tip of the tongue. It originates near the epiglottis, the hyoid bone, from the median fibrous septum.

The inferior longitudinal muscle lines the sides of the tongue, and is joined to the styloglossus muscle.

The vertical muscle is located in the middle of the tongue, and joins the superior and inferior longitudinal muscles.

The transverse muscle divides the tongue at the middle, and is attached to the mucous membranes that run along the sides.

QMRDuring gastrulation the cells of the blastula undergo coordinated processes of cell division, invasion, and/or migration to form two (diploblastic) or three (triploblastic) tissue layers. In triploblastic organisms, the three germ layers are called endoderm, ectoderm, and mesoderm. The position and arrangement of the germ layers are highly species-specific, however, depending on the type of embryo produced. In vertebrates, a special population of embryonic cells called the neural crest has been proposed as a "fourth germ layer", and is thought to have been an important novelty in the evolution of head structures.

QMrJoints[edit]

The tibia is a part of four joints; the knee, ankle, superior and inferior tibiofibular joint.

In the knee the tibia forms one of the two articulations with the femur, often referred to as the tibiofemoral components of the knee joint.[4][5] This is the weightbearing part of the knee joint.[2] The tibiofibular joints are the articulations between the tibia and fibula which allows very little movement.[citation needed] The proximal tibiofibular joint is a small plane joint. The joint is formed between the undersurface of the lateral tibial condyle and the head of fibula. The joint capsule is reinforced by anterior and posterior ligament of the head of the fibula.[2] The distal tibiofibular joint (tibiofibular syndesmosis) is formed by the rough, convex surface of the medial side of the distal end of the fibula, and a rough concave surface on the lateral side of the tibia.[2] The part of the ankle joint known as the talocrural joint, is a synovial hinge joint that connects the distal ends of the tibia and fibula in the lower limb with the proximal end of the talus. The articulation between the tibia and the talus bears more weight than between the smaller fibula and the talus.[citation needed]

QMRProteins are very large molecules – macro-biopolymers – made from monomers called amino acids. An amino acid consists of a carbon atom bound to four groups. One is an amino group, —NH2, and one is a carboxylic acid group, —COOH (although these exist as —NH3+ and —COO− under physiologic conditions). The third is a simple hydrogen atom. The fourth is commonly denoted "—R" and is different for each amino acid. There are 20 standard amino acids, each containing a carboxyl group, an amino group, and a side-chain (known as an "R" group). The "R" group is what makes each amino acid different, and the properties of the side-chains greatly influence the overall three-dimensional conformation of a protein. Some amino acids have functions by themselves or in a modified form; for instance, glutamate functions as an important neurotransmitter. Amino acids can be joined via a peptide bond. In this dehydration synthesis, a water molecule is removed and the peptide bond connects the nitrogen of one amino acid's amino group to the carbon of the other's carboxylic acid group. The resulting molecule is called a dipeptide, and short stretches of amino acids (usually, fewer than thirty) are called peptides or polypeptides. Longer stretches merit the title proteins. As an example, the important blood serum protein albumin contains 585 amino acid residues.[42]

QMRIn 1901, Karl Landsteiner published his discovery of the three main blood groups—A, B, and C (which he later renamed to O). Landsteiner described the regular patterns in which reactions occurred when serum was mixed with red blood cells, thus identifying compatible and conflicting combinations between these blood groups. A year later Alfred von Decastello and Adriano Sturli, two colleagues of Landsteiner, identified a fourth blood group—AB.

QMRThe blood's red color is due to the spectral properties of the hemic iron ions in hemoglobin. Each human red blood cell contains approximately 270 million of these hemoglobin biomolecules, each carrying four heme groups; hemoglobin comprises about a third of the total cell volume. This protein is responsible for the transport of more than 98% of the oxygen (the remaining oxygen is carried dissolved in the blood plasma). The red blood cells of an average adult human male store collectively about 2.5 grams of iron, representing about 65% of the total iron contained in the body.[33][34] (See Human iron metabolism.)

QMRIn mammals, the protein makes up about 96% of the red blood cells' dry content (by weight), and around 35% of the total content (including water).[6] Hemoglobin has an oxygen-binding capacity of 1.34 mL O2 per gram,[7] which increases the total blood oxygen capacity seventy-fold compared to dissolved oxygen in blood. The mammalian hemoglobin molecule can bind (carry) up to four oxygen molecules

QMRHemoglobin has a quaternary structure characteristic of many multi-subunit globular proteins.[32] Most of the amino acids in hemoglobin form alpha helices, connected by short non-helical segments. Hydrogen bonds stabilize the helical sections inside this protein, causing attractions within the molecule, folding each polypeptide chain into a specific shape.[33] Hemoglobin's quaternary structure comes from its four subunits in roughly a tetrahedral arrangement.[32]

In most vertebrates, the hemoglobin molecule is an assembly of four globular protein subunits. Each subunit is composed of a protein chain tightly associated with a non-protein heme group. Each protein chain arranges into a set of alpha-helix structural segments connected together in a globin fold arrangement, so called because this arrangement is the same folding motif used in other heme/globin proteins such as myoglobin.[34][35] This folding pattern contains a pocket that strongly binds the heme group.

A heme group consists of an iron (Fe) ion (charged atom) held in a heterocyclic ring, known as a porphyrin. This porphyrin ring consists of four pyrrole molecules cyclically linked together (by methine bridges) with the iron ion bound in the center.[36] The iron ion, which is the site of oxygen binding, coordinates with the four nitrogen atoms in the center of the ring, which all lie in one plane. The iron is bound strongly (covalently) to the globular protein via the N atoms of the imidazole ring of F8 histidine residue (also known as the proximal histidine) below the porphyrin ring. A sixth position can reversibly bind oxygen by a coordinate covalent bond,[37] completing the octahedral group of six ligands. Oxygen binds in an "end-on bent" geometry where one oxygen atom binds to Fe and the other protrudes at an angle. When oxygen is not bound, a very weakly bonded water molecule fills the site, forming a distorted octahedron.

Even though carbon dioxide is carried by hemoglobin, it does not compete with oxygen for the iron-binding positions but is bound to the protein chains of the structure.

The iron ion may be either in the Fe2+ or in the Fe3+ state, but ferrihemoglobin (methemoglobin) (Fe3+) cannot bind oxygen.[38] In binding, oxygen temporarily and reversibly oxidizes (Fe2+) to (Fe3+) while oxygen temporarily turns into the superoxide ion, thus iron must exist in the +2 oxidation state to bind oxygen. If superoxide ion associated to Fe3+ is protonated, the hemoglobin iron will remain oxidized and incapable of binding oxygen. In such cases, the enzyme methemoglobin reductase will be able to eventually reactivate methemoglobin by reducing the iron center.

In adult humans, the most common hemoglobin type is a tetramer (which contains four subunit proteins) called hemoglobin A, consisting of two α and two β subunits non-covalently bound, each made of 141 and 146 amino acid residues, respectively. This is denoted as α2β2. The subunits are structurally similar and about the same size. Each subunit has a molecular weight of about 16,000 daltons,[39] for a total molecular weight of the tetramer of about 64,000 daltons (64,458 g/mol).[40] Thus, 1 g/dL = 0.1551 mmol/L. Hemoglobin A is the most intensively studied of the hemoglobin molecules.

In human infants, the hemoglobin molecule is made up of 2 α chains and 2 γ chains. The gamma chains are gradually replaced by β chains as the infant grows.[41]

The four polypeptide chains are bound to each other by salt bridges, hydrogen bonds, and the hydrophobic effect.

QMRA tetramer is a protein with a quaternary structure of four subunits (tetrameric). Homotetramers have four identical subunits (such as glutathione S-transferase), dimers of dimers contain two heterodimer subunits (such as hemoglobin), and heterotetramers are complexes of four different subunits.

The interactions between subunits forming a tetramer is primarily determined by non covalent interaction.[1] Hydrophobic effects, hydrogen bonds and electrostatic interactions are the primary sources for this binding process between subunits. For homotetrameric proteins such as Sorbitol dehydrogenase (SDH), the structure is believed to have evolved going from a monomeric to a dimeric and finally a tetrameric structure in evolution. The binding process in SDH and many other tetrameric enzymes can be described by the gain in free energy which can be determined from the rate of association and dissociation.[1] The following image shows the assembly of the four subunits (A,B,C and D) in SDH.

Hydrogen bonds between subunits[edit]

Hydrogen bonding networks between subunits has been shown to be important for the stability of the tetrameric quaternary protein structure. For example a study of SDH which used diverse methods such as protein sequence alignments, structural comparisons, energy calculations, gel filtration experiments and enzyme kinetics experiments, could reveal an important hydrogen bonding network which stabilizes the tetrameric quaternary structure in mammalian SDH.[1]

Tetramers in immunology[edit]

In immunology, MHC tetramers can be used to quantify numbers of antigen-specific T cells (especially CD8+ T cells). MHC tetramers are based on recombinant class I molecules that, through the action of bacterial BirA, have been biotinylated. These molecules are folded with the peptide of interest and β2M and tetramerized by a fluorescently labeled streptavidin. (Streptavidin binds to four biotins per molecule.) This tetramer reagent will specifically label T cells that express T cell receptors that are specific for a given peptide-MHC complex. For example, a Kb/FAPGNYPAL tetramer will specifically bind to Sendai virus specific cytotoxic T cell in a C57BL/6 mouse. Antigen specific responses can be measured as CD8+, tetramer+ T cells as a fraction of all CD8+ lymphocytes.

The reason for using a tetramer, as opposed to a single labeled MHC class I molecule is that the tetrahedral tetramers can bind to three TCRs at once, allowing specific binding in spite of the low (10-6 molar) affinity of the typical class I-peptide-TCR interaction. MHC class II tetramers can also be made although these are more difficult to work with practically.[citation needed]

QMRA homotetramer is a protein complex made up of four identical subunits which are associated but not covalently bound.[1] A heterotetramer is a 4-subunit complex where one or more subunits differ.[2]

Examples of homotetramers include:

enzymes like beta-glucuronidase (pictured)

export factors such as SecB from Escherichia coli[3]

magnesium ion transporters such as CorA.[4]

lectins such as Concanavalin A

QMRA heterotetramer is protein containing four non-covalently bound subunits, wherein the subunits are not all identical.[1] A homotetramer contains four identical subunits.[2]

Examples include haemoglobin (pictured), the NMDA receptor, some aquaporins,[3] some AMPA receptors, as well as some enzymes.[4]

Purification of heterotetramers[edit]

Ion-exchange chromatography is useful for isolating specific heterotetrameric protein assemblies, allowing purification of specific complexes according to both the number and the position of charged peptide tags.[5][6] Nickel affinity chromatography may also be employed for heterotetramer purification.[7]

QMRAquaporins form tetramers in the cell membrane, with each monomer acting as a water channel.[8] The different aquaporins contain differences in their peptide sequence, which allows for the size of the pore in the protein to differ between aquaporins. The resultant size of the pore directly affects what molecules are able to pass through the pore, with small pore sizes only allowing small molecules like water to pass through the pore.

X-ray profiles show that aquaporins have two conical entrances. This hourglass shape could be the result of a natural selection process toward optimal permeability. It has been shown that conical entrances with suitable opening angle can indeed provide a large increase of the hydrodynamic channel permeability.

QMRMerosity is the number of component parts in each whorl of a plant structure. It is most commonly used in the context of flowers, in which case it refers to the number of sepals in the calyx, the number of petals in the corolla, and the number of stamens in each whorl of the androecium. The term may also be used to refer to the number of leaves in leaf whorls.

Types of merosity include:

2: dimery, dimerous, 2-merous

3: trimery, trimerous, 3-merous

4: tetramery, tetramerous, 4-merous

5: pentamery, pentamerous, 5-merous

high number: polymery, polymerous, n-merous

QMR Tetramerium is a genus of plants belonging to the family Acanthaceae. It is found mainly in the Americas,[1] especially in tropical dry forests.[2] Christian Gottfried Daniel Nees von Esenbeck first described the genus in 1846, after collecting two species (T. polystachyum and T. nervosum) on the journey of the HMS Sulphur.[2][3]

There are approximately 60 species in the genus :

Tetramerium abditum

Tetramerium angustius

Tetramerium aureum

Tetramerium butterwickianum

Tetramerium calderonii

Tetramerium coeruleum

Tetramerium costatum

Tetramerium crenatum

Tetramerium denudatum

Tetramerium diffusum

Tetramerium emilyanum

Tetramerium flavum

Tetramerium fruticosum

Tetramerium geniculatum

Tetramerium glandulosum

Tetramerium glutinosum

Tetramerium gualanense

Tetramerium guerrerense

Tetramerium hillii

Tetramerium hintonii

Tetramerium hispidum

Tetramerium jasminoides

Tetramerium langlassei

Tetramerium latifolium

Tetramerium leptocaule

Tetramerium macrostachyum

Tetramerium macvaughii

Tetramerium mcvaughii

Tetramerium montevidense

Tetramerium multiflorum

Tetramerium nemorum

Tetramerium nervosum

Tetramerium oaxacanum

Tetramerium obovatum

Tetramerium ochoterenae

Tetramerium occidentale

Tetramerium odoratissimum

Tetramerium oleaefolium

Tetramerium ovalifolium

Tetramerium ovatum

Tetramerium paniculatum

Tetramerium peruvianum

Tetramerium platystegium

Tetramerium polystachyum

Tetramerium racemulosum

Tetramerium rubrum

Tetramerium rzedowskii

Tetramerium sagasteguianum

Tetramerium scabrum

Tetramerium scorpioides

Tetramerium sessilifolium

Tetramerium standleyi

Tetramerium stipulaceum

Tetramerium surcubambense

Tetramerium tenuissimum

Tetramerium tetramerioides

Tetramerium torreyella

Tetramerium wasshausenii

Tetramerium yaquianum

Tetramerium zeta

QMrThe genus Rosa is subdivided into four subgenera:

Hulthemia (formerly Simplicifoliae, meaning "with single leaves") containing one or two species from southwest Asia, R. persica and Rosa berberifolia which are the only roses without compound leaves or stipules.

Hesperrhodos (from the Greek for "western rose") contains Rosa minutifolia and Rosa stellata, from North America.

Platyrhodon (from the Greek for "flaky rose", referring to flaky bark) with one species from east Asia, Rosa roxburghii (also known as the chestnut rose).

Rosa (the type subgenus, incorrectly called Eurosa) containing all the other roses. This subgenus is subdivided into 11 sections.

Banksianae – white and yellow flowered roses from China.

Bracteatae – three species, two from China and one from India.

Caninae – pink and white flowered species from Asia, Europe and North Africa.

Carolinae – white, pink, and bright pink flowered species all from North America.

Chinensis – white, pink, yellow, red and mixed-color roses from China and Burma.

Gallicanae – pink to crimson and striped flowered roses from western Asia and Europe.

Gymnocarpae – one species in western North America (Rosa gymnocarpa), others in east Asia.

Laevigatae – a single white flowered species from China

Pimpinellifoliae – white, pink, bright yellow, mauve and striped roses from Asia and Europe.

Rosa (syn. sect. Cinnamomeae) – white, pink, lilac, mulberry and red roses from everywhere but North Africa.

Synstylae – white, pink, and crimson flowered roses from all areas.

QMRKobophenol A is a stilbenoid. It is a tetramer of resveratrol. It can be isolated from Caragana chamlagu,[1] from Caragana sinica[2] and from Carex folliculata seeds.[3]

The molecule shows a 2,3,4,5-tetraaryltetrahydrofuran skeleton.[3]

It has been shown to inhibit acetylcholinesterase.[1]

Acid-catalyzed epimerization of kobophenol A to carasinol B can be performed in vitro.[4]

QMrConcanavalin A (ConA) is a lectin (carbohydrate-binding protein) originally extracted from the jack-bean, Canavalia ensiformis. It is a member of the legume lectin family. It binds specifically to certain structures found in various sugars, glycoproteins, and glycolipids, mainly internal and nonreducing terminal α-D-mannosyl and α-D-glucosyl groups.[2][3] ConA is a plant mitogen, and is known for its ability to stimulate mouse T-cell subsets giving rise to four functionally distinct T cell populations, including precursors to suppressor T-cell;[4] one subset of human suppressor T-cells as well is sensitive to ConA.[4] ConA was the first lectin to be available on a commercial basis, and is widely used in biology and biochemistry to characterize glycoproteins and other sugar-containing entities on the surface of various cells.[5] It is also used to purify glycosylated macromolecules in lectin affinity chromatography,[6] as well as to study immune regulation by various immune cells.[4]

It is a tetrameter

Like most lectins, ConA is a homotetramer: each sub-unit (26.5KDa, 235 amino-acids, heavily glycated) binds a metallic atom (usually Mn2+ and a Ca2+). It has the D2 symmetry.[1] Its tertiary structure has been elucidated,[7] and the molecular basis of its interactions with metals as well as its affinity for the sugars mannose and glucose[8] are well known.

ConA binds specifically α-D-mannosyl and α-D-glucosyl residues (two hexoses differing only by the alcohol on carbon 2) in terminal position of ramified structures from B-Glycans (reach in α-mannose, or hybrid and bi-antennary glycanes complexes). It has 4 binding sites, corresponding to the 4 sub-units.[3] The molecular weight is 104-112KDa and the isoelectric point (pI) is in the range of 4.5-5.5.

Concanavalin A has a low-frequency wave number of 20 cm−1 in its Raman spectra.[9] This emission has been assigned to the breathing motion of the beta barrel consisting of 14 beta-strands in the concanavalin A molecule.[10]

ConA can also initiate cell division (mitogenesis) principally acting on T-lymphocytes, by stimulating the energy metabolism of thymocytes within seconds of exposure.[11]

For biotechnological uses, see Fluorescent glucose biosensors.

Biological activity[edit]

Canavalin crystals grown on Earth (left) and in outer space (right).[12]

Concanavalin A interacts with diverse receptors containing mannose carbohydrates, notably rhodopsin, blood group markers, insulin-receptor[13] the Immunoglobulins and the carcino-embryonary antigen (CEA). It also interacts with lipoproteins.[14]

ConA strongly agglutinates erythrocytes irrespective of blood-group, and various cancerous cells.[15][16][17] It was demonstrated that transformed cells and trypsin-treated normal cells do not agglutinate at 4 °C, thereby initiate suggesting that there is a temperature-sensitive step involved in ConA-mediated agglutination.[18][19]

ConA-mediated agglutination of other cell types has been reported, including muscle cells (myocytes),[20] B-lymphocytes (through surface Immunoglobulins),[21] fibroblasts,[22] rat thymocytes,[23] human fetal (but not adult) intestinal epithelial cells,[24] and adipocytes.[25]

ConA is a lymphocyte mitogen. Similar to phytohemagglutinin (PHA), it is a selective T cell mitogen relative to its effects on B cells. PHA and ConA bind and cross-link components of the T cell receptor, and their ability to activate T cells is dependent on expression of the T cell receptor.[26][27]

ConA interacts with the surface mannose residues of many microbes, like the bacteria E. coli,[28] and Bacillus subtilis[29] and the protist Dictyostelium discoideum.[30]

It has also been shown as a stimulator of several matrix metalloproteinases (MMPs).[31]

ConA has proven useful in applications requiring solid-phase immobilization of glycoenzymes, especially those that have proved difficult to immobilize by traditional covalent coupling. Using ConA-couple matrices, such enzymes may be immobilized in high quantities without a concurrent loss of activity and/or stability. Such noncovalent ConA-glycoenzyme couplings may be relatively easily reversed by competition with sugars or at acidic pH. If necessary for certain applications, these couplings can be converted to covalent bindings by chemical manipulation.[32]

A recent (2009) report from Taiwan demonstrated potent therapeutic effect of ConA against experimental hepatoma (liver cancer); in the study by Lei and Chang,[33] ConA was found to be sequestered more by hepatic tumor cells, in preference to surrounding normal hepatocytes. Internalization of ConA occurs preferentially to the mitochondria after binding to cell membrane glycoproteins, which triggers an autophagic cell death. ConA was found to partially inhibit tumor nodule growth independent of its lymphocyte activation; the eradication of the tumor in the murine in-situ hepatoma model in this study was additionally attributed to the mitogenic/lymphoproliferative action of ConA that may have activated a CD8+ T-cell-mediated, as well as NK- and NK-T cell-mediated, immune response in the liver.[33]

ConA intravitreal injection can be used in the modeling of proliferative vitreoretinopathy in rats.

QMRImmunoglobulin domains[edit]

The Ig monomer is a "Y"-shaped molecule that consists of four polypeptide chains; two identical heavy chains and two identical light chains connected by disulfide bonds.[13] Each chain is composed of structural domains called immunoglobulin domains. These domains contain about 70–110 amino acids and are classified into different categories (for example, variable or IgV, and constant or IgC) according to their size and function.[21] They have a characteristic immunoglobulin fold in which two beta sheets create a "sandwich" shape, held together by interactions between conserved cysteines and other charged amino acids.

QMrA tetrapeptide has four amino acids

QMrA tetrapeptide is a peptide, classified as an oligopeptide, since it only consists of four amino acids joined by peptide bonds. Many tetrapeptides are pharmacologically active, often showing affinity and specificity for a variety of receptors in protein-protein signaling. Present in nature are both linear and cyclic tetrapeptides, tetrapeptides may be cyclized by a fourth peptide bond or other covalent bonds.

Examples of tetrapeptides are:

Tuftsin (L-threonyl-L-lysyl-L-prolyl-L-arginine) is a peptide related primarily to the immune system function.

Rigin (glycyl-L-glutaminyl-L-prolyl-L-arginine) is a tetrapeptide with functions similar to those of tuftsin.

Postin (Lys-Pro-Pro-Arg) is the N-terminal tetrapeptide of cystatin C and an antagonist of tuftsin.

Endomorphin-1 (H-Tyr-Pro-Trp-Phe-NH2) and endomorphin-2 (H-Tyr-Pro-Phe-Phe-NH2) are peptide amides with the highest known affinity and specificity for the μ opioid receptor.

Morphiceptin (H-Tyr-Pro-Phe-Pro-NH2) is a casomorphin peptide isolated from β-casein.

Gluten exorphines A4 (H-Gly-Tyr-Tyr-Pro-OH) and B4 (H-Tyr-Gly-Gly-Trp-OH) are peptides isolated from gluten.

Tyrosine-MIF-1 (H-Tyr-Pro-Leu-Gly-NH2) is an endogenous opioid modulator.

Tetragastrin (N-((phenylmethoxy)carbonyl)-L-tryptophyl-L-methionyl-L-aspartyl-L-phenylalaninamide) is the C-terminal tetrapeptide of gastrin. It is the smallest peptide fragment of gastrin which has the same physiological and pharmacological activity as gastrin.

Kentsin (H-Thr-Pro-Arg-Lys-OH) is a contraceptive peptide first isolated from female hamsters.

Achatin-I (glycyl-phenylalanyl-alanyl-aspartic acid) is a neuroexcitatory tetrapeptide from giant African snail (Achatina fulica).

Tentoxin (cyclo(N-methyl-L-alanyl-L-leucyl-N-methyl-trans-dehydrophenyl-alanyl-glycyl)) is a natural cyclic tetrapeptide produced by phytopathogenic fungi from genus Alternaria.

Rapastinel (H-Thr-Pro-Pro-Thr-NH2) is a partial agonist of the NMDA receptor.

HC-toxin, cyclo(D-Pro-L-Ala-D-Ala-L-Aeo), where Aeo is 2-amino-8-oxo-9,10-epoxy decanoic acid,, is a virulence factor for the fungus Cochliobolus carbonum on its host, maize.

QMRTuftsin is a tetrapeptide (Thr-Lys-Pro-Arg) produced by enzymatic cleavage of the Fc-domain of the heavy chain of immunoglobulin G. It is produced primarily in the spleen.

Contents [hide]

1 Function

2 Pathology

3 Clinical significance

4 History

5 References

6 See also

Function[edit]

Its biological activity is related primarily to the immune system function.

Tuftsin binds to specific receptors on the surface of macrophages and polymorphonuclear leukocytes, stimulating their migration, phagocytic, bactericidal, and tumoricidal activity. It also influences antibody formation.

Pathology[edit]

Tuftsin deficiency, either hereditary or following splenectomy, results in increased susceptibility to certain infections e.g.: caused by capsulated organisms as: H. influenza, pneumococci, meningococci and salmonella.[1]

Clinical significance[edit]

Tuftsin has been chemically synthesized and it is considered for use in immunotherapy.

History[edit]

Tuftsin was first identified in 1970 by scientists Najjar and Nishioka.[2] It was named after Tufts University where the peptide was discovered.

QMRChemical structure[edit]

In general, corticosteroids are grouped into four classes, based on chemical structure. Allergic reactions to one member of a class typically indicate an intolerance of all members of the class. This is known as the "Coopmanclassification",[24] after S. Coopman, who defined this classification in 1989.[25]

The highlighted steroids are often used in the screening of allergies to topical steroids.[26]

Group A — Hydrocortisone type[edit]

Hydrocortisone, hydrocortisone acetate, cortisone acetate, tixocortol pivalate, prednisolone, methylprednisolone, and prednisone (Short- to medium-acting glucocorticoids).

Group B — Acetonides (and related substances)[edit]

Triamcinolone acetonide, triamcinolone alcohol, mometasone, amcinonide, budesonide, desonide, fluocinonide, fluocinolone acetonide, and halcinonide.

Group C — Betamethasone type[edit]

Betamethasone, betamethasone sodium phosphate, dexamethasone, dexamethasone sodium phosphate, and fluocortolone.

Group D — Esters[edit]

Group D1 — Halogenated (less labile)[edit]

Hydrocortisone-17-valerate, halometasone, alclometasone dipropionate, betamethasone valerate, betamethasone dipropionate, prednicarbate, clobetasone-17-butyrate, clobetasol-17-propionate, fluocortolone caproate, fluocortolone pivalate, and fluprednidene acetate.

Group D2 — Labile prodrug esters[edit]

Hydrocortisone-17-butyrate, hydrocortisone-17-

QMRCorticosteroids have been used as drug treatment for some time. Lewis Sarett of Merck & Co. was the first to synthesize cortisone, using a complicated 36-step process that started with deoxycholic acid, which was extracted from ox bile.[32] The low efficiency of converting deoxycholic acid into cortisone led to a cost of US $200 per gram. Russell Marker, at Syntex, discovered a much cheaper and more convenient starting material, diosgenin from wild Mexican yams. His conversion of diosgenin into progesterone by a four-step process now known as Marker degradation was an important step in mass production of all steroidal hormones, including cortisone and chemicals used in hormonal contraception.

QMRMorphiceptin is a tetrapeptide (Tyr-Pro-Phe-Pro-NH2) that is a selective μ-opioid receptor agonist. It is derived from β-casomorphin and has over 1,000 times selectivity for μ- over δ-opioid receptors. When injected intracerebroventricularly (into the ventricular system of the brain), morphiceptin had an analgesic ED50 of 1.7 nmol per animal. The analgesic effects of morphiceptin were reversed by naloxone, meaning that the analgesic effect is mediated by the μ-opioid receptor.[2]

QMRGluten exorphins are a group of opioid peptides formed during digestion of the gluten protein. It has been hypothesized that people with autism and schizophrenia have abnormal leakage from the gut of these compounds, which then pass into the brain and disrupt brain function[1] known as the opioid excess theory or a part of leaky gut syndrome. This is partly the basis for the gluten-free, casein-free diet. Two clinical studies of autism patients who followed this diet have found no evidence of benefit.[2][3] Another found evidence of benefit.[4] Another study suggested the diet may present a greater risk to brain development.[5]

There are four known gluten exorphins with known structure:

They are tetrapeptides

Gluten exorphin A5[edit]

Structure: H-Gly-Tyr-Tyr-Pro-Thr-OH

Chemical formula: C29H37N5O9

Molecular weight: 599.64 g/mol

Gluten exorphin B4[edit]

Structure: H-Tyr-Gly-Gly-Trp-OH

Chemical formula: C24H27N5O6

Molecular weight: 481.50 g/mol

Gluten exorphin B5[edit]

Structure: H-Tyr-Gly-Gly-Trp-Leu-OH

Chemical formula: C30H38N6O7

Molecular weight: 594.66 g/mol

Gluten exorphin C[edit]

Structure: H-Tyr-Pro-Ile-Ser-Leu-OH

Chemical formula: C29H45N5O8

Molecular weight: 591.70 g/mol

QMRCholecystokinin tetrapeptide (CCK-4, Trp-Met-Asp-Phe-NH2) is a peptide fragment derived from the larger peptide hormone cholecystokinin. Unlike cholecystokin which has a variety of roles in the gastrointenstinal system as well as central nervous system effects, CCK-4 acts primarily in the brain as an anxiogenic, although it does retain some GI effects, but not as much as CCK-8 or the full length polypeptide CCK-58.

CCK-4 reliably causes severe anxiety symptoms when administered to humans in a dose of as little as 50μg,[1] and is commonly used in scientific research to induce panic attacks for the purpose of testing new anxiolytic drugs.[2][3][4][5] Since it is a peptide, CCK-4 must be administered by injection, and is rapidly broken down once inside the body so has only a short duration of action,[6] although numerous synthetic analogues with modified properties are known.[7][8][9][10][11][12][13][14][15][16][17]

QMrThere are four types of cells in the stomach:

Parietal cells: Produce hydrochloric acid and intrinsic factor.

Gastric chief cells: Produce pepsinogen. Chief cells are mainly found in the body of stomach, which is the middle or superior anatomic portion of the stomach.

Mucous neck and pit cells: Produce mucin and bicarbonate to create a "neutral zone" to protect the stomach lining from the acid or irritants in the stomach chyme.

G cells: Produce the hormone gastrin in response to distention of the stomach mucosa or protein, and stimulate parietal cells production of their secretion. G cells are located in the antrum of the stomach, which is the most inferior region of the stomach.

QMRNuclei[edit]

The vagus nerve includes axons which emerge from or converge onto four nuclei of the medulla:

The dorsal nucleus of vagus nerve — which sends parasympathetic output to the viscera, especially the intestines

The nucleus ambiguus — which gives rise to the branchial efferent motor fibers of the vagus nerve and preganglionic parasympathetic neurons that innervate the heart

The solitary nucleus — which receives afferent taste information and primary afferents from visceral organs

The spinal trigeminal nucleus — which receives information about deep/crude touch, pain, and temperature of the outer ear, the dura of the posterior cranial fossa and the mucosa of the larynx

QMrMotor and sensory[edit]

In general, motor nuclei are closer to the front (ventral), and sensory nuclei and neurons are closer to the back (dorsal). This arrangement mirrors the arrangement of tracts in the spinal cord.

Close to the midline are the motor efferent nuclei, such as the oculomotor nucleus, which control skeletal muscle. Just lateral to this are the autonomic (or visceral) efferent nuclei.

There is a separation, called the sulcus limitans, and lateral to this are the sensory nuclei. Near the sulcus limitans are the visceral afferent nuclei, namely the solitary tract nucleus.

More lateral, but also less posterior, are the general somatic afferent nuclei. This is the trigeminal nucleus. Back at the dorsal surface of the brainstem, and more lateral are the special somatic afferents, this handles sensation such as balance.

Another area, not on the dorsum of the brainstem, is where the branchial efferent nuclei reside. These formed from the branchial arches, in the embryo. This area is a bit below the autonomic motor nuclei, and includes the nucleus ambiguus, facial nerve nucleus, as well as the motor part of the trigeminal nerve nucleus.

QMRTetrapoda includes four classes: amphibians, reptiles, mammals, and birds.

QMREarly tetrapods probably relied on four methods of respiration: with lungs, with gills, cutaneous respiration (skin breathing), and breathing through the lining of the digestive tract, especially the mouth.

Gills[edit]

The early tetrapod Acanthostega had at least three and probably four pairs of gill bars, each containing deep grooves in the place where one would expect to find the afferent branchial artery. This strongly suggests that functional gills were present.[77] Some aquatic temnospondyls retained internal gills at least into the early Jurassic.

QMRFour cone opsins were present in the first vertebrate, inherited from invertebrate ancestors:

LWS/MWS (long- to medium-wave sensitive) - green, yellow, or red

SWS1 (short-wave sensitive) - ultraviolet or violet - lost in monotremes (platypus, echidna)

SWS2 (short-wave sensitive) - violet or blue - lost in therians (placental mammals and marsupials)

RH2 (rhodopsin-like cone opsin) - green - lost separately in amphibians and mammals, retained in reptiles and birds

QMRTentoxin is a natural cyclic tetrapeptide produced by phytopathogenic fungus Alternaria alternata. It selectively induces chlorosis in several germinating seedling plants. Therefore, tentoxin may be used as a potential natural herbicide.

Tentoxin was first isolated from Alternaria alternata (syn. tenuis) and characterized by George Templeton et al. in 1967.[1]

Tentoxin has also been used in recent research to eliminate the polyphenol oxidase (PPO) activity from seedlings of higher plants.[2]

QMRAll the RNA-directed RNA polymerases, and many DNA-directed polymerases, employ a fold whose organization has been likened to the shape of a right hand with three subdomains termed fingers, palm, and thumb.[8] Only the palm subdomain, composed of a four-stranded antiparallel beta-sheet with two alpha-helices, is well conserved among all of these enzymes. In RdRp, the palm subdomain comprises three well-conserved motifs (A, B, and C). Motif A (D-x(4,5)-D) and motif C (GDD) are spatially juxtaposed; the Asp residues of these motifs are implied in the binding of Mg2+ and/or Mn2+. The Asn residue of motif B is involved in selection of ribonucleoside triphosphates over dNTPs and, thus, determines whether RNA rather than DNA is synthesized.[9] The domain organization[10] and the 3D structure of the catalytic centre of a wide range of RdPps, even those with a low overall sequence homology, are conserved. The catalytic centre is formed by several motifs containing a number of conserved amino acid residues.

QMRThere are 4 superfamilies of viruses that cover all RNA-containing viruses with no DNA stage:

Viruses containing positive-strand RNA or double-strand RNA, except retroviruses and Birnaviridae: viral RNA-directed RNA polymerases including all positive-strand RNA viruses with no DNA stage, double-strand RNA viruses, and the Cystoviridae, Reoviridae, Hypoviridae, Partitiviridae, Totiviridae families

Mononegavirales (negative-strand RNA viruses with non-segmented genomes)

Negative-strand RNA viruses with segmented genomes, i.e., Orthomyxoviruses (including influenza A, B, and C viruses, Thogotoviruses, and the infectious salmon anemia virus), Arenaviruses, Bunyaviruses, Hantaviruses, Nairoviruses, Phleboviruses, Tenuiviruses and Tospoviruses

Birnaviridae family of dsRNA viruses.

QMRThere are four stages in a flea's life. The first stage is the egg stage. Microscopic white eggs fall easily from the female to the ground or from the animal she lays on. If they are laid on an animal, they soon fall off in the dust or in the animals bedding. If the eggs do fall immediately on the ground, then they fall into crevices on the floor where they will be safe until they hatch one to ten days later (depending on the environment that they live in, it may take longer to hatch). They hatch into a larva that looks very similar to a worm and is about two millimeters long. It only has a small body and a mouth part. At this stage, the flea does not drink blood; instead it eats dead skin cells, flea droppings, and other smaller parasites lying around them in the dust. When the larva is mature it makes a silken cocoon around itself and pupates. The flea remains a pupa from one week to six months changing in a process called metamorphosis. When the flea emerges, it begins the final cycle, called the adult stage. A flea can now suck blood from host and mate with other fleas. A single female flea can mate once and lay eggs every day with up to 50 eggs per day.

Experimentally, it has been shown that the fleas flourish in dry climatic conditions with temperatures of 20–25 °C (68–77 °F).[2] They can live up to a year and can stay in the cocoon stage for up to a year if the conditions are not favourable.

QMRProposed modulators of LTP[25]

Modulator Target

β-Adrenergic receptor cAMP, MAPK amplification

Nitric oxide synthase Guanylyl cyclase, PKG, NMDAR

Dopamine receptor cAMP, MAPK amplification

Metabotropic glutamate receptor PKC, MAPK amplification

Tetra means fourRapastinel (INN) (code name GLYX-13) is an intravenously-administered, selective, weak partial agonist of the glycine site of the NMDA receptor (IA ≈ 25%) which is under development by Naurex as an adjunctive therapy for treatment-resistant depression.[1] It is an amidated tetrapeptide (Thr-Pro-Pro-Thr-NH2) which rapidly crosses the blood-brain-barrier, but is not active orally.[2] On March 3, 2014 the FDA granted Fast Track designation to the development of rapastinel as an adjunctive therapy in treatment-resistant major depressive disorder.[3] As of 2015, the drug has completed phase II clinical development for this indication.[4] Phase III clinical trials will be starting in 2015.[4]

In addition to its antidepressant effects, rapastinel has been shown to enhance memory and learning in both young adult and learning-impaired, aging rat models.[5] It has been shown to increase Schaffer collateral-CA1 long-term potentiation in vitro. In concert with a learning task, rapastinel has also been shown to elevate gene expression of hippocampal NR1, a subunit of the NMDA receptor, in 3-month-old rats.[6] Neuroprotective effects have also been demonstrated in Mongolian Gerbils by delaying the death of CA1, CA3, and dentate gyrus pyramidal neurons under glucose and oxygen-deprived conditions.[7] Additionally, rapastinel has demonstrated antinociceptive activity, which is of particular interest, as both competitive and noncompetitive NMDA receptor antagonists are ataxic at analgesic doses, while rapastinel and other glycine subunit ligands are able to elicit analgesia at sub-ataxic doses.[8]

QMRAromatic compounds play key roles in the biochemistry of all living things. The four aromatic amino acids histidine, phenylalanine, tryptophan, and tyrosine each serve as one of the 20 basic building-blocks of proteins. Further, all 5 nucleotides (adenine, thymine, cytosine, guanine, and uracil) that make up the sequence of the genetic code in DNA and RNA are aromatic purines or pyrimidines. The molecule heme contains an aromatic system with 22 π electrons. Chlorophyll also has a similar aromatic system.

QMRTetrahedron is a weekly peer-reviewed scientific journal covering the field of organic chemistry. According to the Journal Citation Reports, the journal has a 2014 impact factor of 2.641.[1] Tetrahedron and Elsevier, its publisher, support an annual symposium.[2]

QMRMelatonin biosynthesis in humans and some other organisms involves four enzymatic steps from the essential dietary amino acid tryptophan, which follows a serotonin pathway. In other organisms through the shikimic acid pathway.[75][76]

QMRThe allocortex has just three or four layers of neuronal cell bodies in contrast to the six layers of the neocortex. There are three subtypes of allocortex, the paleocortex, archicortex and periallocortex.[3]

Paleocortex is a type of thin, primitive cortical tissue that consists of three to five cortical laminae (layers of neuronal cell bodies).[4] In comparison, the neocortex has six layers and the archicortex has three or four layers.[5]

Archicortex is a type of cortical tissue that consists of three laminae (layers of neuronal cell bodies).[6] It has fewer layers than both neocortex, which has six, and paleocortex, which has either four or five. Because the number of laminae that compose a type of cortical tissue seems to be directly proportional to both the information-processing capabilities of that tissue and its phylogenetic age, paleocortex is thought to be an intermediate between neocortex and archicortex in both aspects, and archicortex is thought to be the oldest and most basic type of cortical tissue.

The ordering of these layers fits the quadrant pattern

QMRIn Nigeria, the Tiv ethnic group cut four lines into the abdomen of their girls during menarche. The lines are supposed to represent fertility

QMRThe ventricular system is a set of four interconnected cavities (ventricles) in the brain, where the cerebrospinal fluid (CSF) is produced. Within each ventricle is a region of choroid plexus, a network of ependymal cells involved in the production of CSF. The ventricular system is continuous with the central canal of the spinal cord (from the fourth ventricle) allowing for the flow of CSF to circulate. All of the ventricular system and the central canal of the spinal cord is lined with ependyma, a specialised form of epithelium.

The system comprises four ventricles:

lateral ventricles right and left (one for each hemisphere)

third ventricle

fourth ventricle

There are several foramina, openings acting as channels, that connect the ventricles. The interventricular foramina (also called the foramina of Monro) connect the lateral ventricles to the third ventricle through which the cerebrospinal fluid can flow.

Name From To

interventricular foramina (Monro) lateral ventricles third ventricle

cerebral aqueduct (Sylvius) third ventricle fourth ventricle

median aperture (Magendie) fourth ventricle subarachnoid space via the cisterna magna

right and left lateral aperture (Luschka) fourth ventricle subarachnoid space via the cistern of great cerebral vein

Ventricles[edit]

3D rendering of ventricles (lateral and anterior views).

The four cavities of the human brain are called ventricles.[1] The two largest are the lateral ventricles in the cerebrum; the third ventricle is in the diencephalon of the forebrain between the right and left thalamus; and the fourth ventricle is located at the back of the pons and upper half of the medulla oblongata of the hindbrain. The ventricles are concerned with the production and circulation of cerebrospinal fluid[2]

QMRThe spinal cord is made from part of the neural tube during development.There are four stages of the spinal cord that arises from the nueral tube: The nueral plate, neural fold, neural tube, and the spinal cord

QMRThe midbrain nuclei include four motor tracts that send upper motor neuronal axons down the spinal cord to lower motor neurons. These are the rubrospinal tract, the vestibulospinal tract, the tectospinal tract and the reticulospinal tract. The rubrospinal tract descends with the lateral corticospinal tract, and the remaining three descend with the anterior corticospinal tract.

QMRCorpora quadrigemina[edit]

Main article: Corpora quadrigemina

The corpora quadrigemina ("quadruplet bodies") are four solid lobes on the dorsal side of the cerebral aqueduct, where the superior posterior pair are called the superior colliculi and the inferior posterior pair are called the inferior colliculi.

The four solid lobes help to decussate several fibres of the optic nerve. However, some fibers also show ipsilateral arrangement (i.e., they run parallel on the same side without decussating.)

The superior colliculus is involved with saccadic eye movements; while the inferior is a synapsing point for sound information. The trochlear nerve comes out of the posterior surface of the midbrain, below the inferior colliculus.

In the brain, the corpora quadrigemina (Latin for "quadruplet bodies") are the four colliculi—two inferior, two superior—located on the tectum of the dorsal aspect of the midbrain. They are respectively named the inferior and superior colliculus.

The corpora quadrigemina are reflex centers involving vision and hearing.[1

QMRJan Janský is credited with the first classification of blood into four types (A, B, AB, and O)

QMRThe vestibular nuclei are the cranial nuclei for the vestibular nerve.

In Terminologia Anatomica they are grouped in both the pons and the medulla in the brainstem.

Subnuclei[edit]

There are 4 subnuclei; they are situated at the floor of the fourth ventricle.

Name Location Notes

medial vestibular nucleus (dorsal or chief vestibular nucleus) medulla (floor of fourth ventricle) corresponding to the lower part of the area acustica in the rhomboid fossa;[citation needed] the caudal end of this nucleus is sometimes termed the descending or spinal vestibular nucleus.

lateral vestibular nucleus or nucleus of Deiters medulla (upper) consisting of large cells and situated in the lateral angle of the rhomboid fossa; the dorso-lateral part of this nucleus is sometimes termed the nucleus of Bechterew.

inferior vestibular nucleus medulla (lower)

superior vestibular nucleus pons

QMRAt the level of gross anatomy, the cerebellum consists of a tightly folded layer of cortex, with white matter underneath and a fluid-filled ventricle at the base. At the microscopic level, there are four deep nuclei embedded in the white matter. Each part of the cortex consists of the same small set of neuronal elements, laid out in a highly stereotyped geometry. At an intermediate level, the cerebellum and its auxiliary structures can be separated into several hundred or thousand independently functioning modules called "microzones" or "microcompartments".

QMRThe cerebellum has four deep cerebellar nuclei embedded in the white matter in its center

Inputs[edit]

These nuclei receive inhibitory (GABAergic) inputs from Purkinje cells in the cerebellar cortex and excitatory (glutamatergic) inputs from mossy fiber and climbing fiber pathways. Most output fibers of the cerebellum originate from these nuclei. One exception is that fibers from the flocculonodular lobe synapse directly on vestibular nuclei without first passing through the deep cerebellar nuclei. The vestibular nuclei in the brainstem are analogous structures to the deep nuclei, since they receive both mossy fiber and Purkinje cell inputs.[citation needed]

Specific nuclei[edit]

From lateral to medial, the four deep cerebellar nuclei are the dentate, emboliform, globose, and fastigii. Some animals, including humans, do not have distinct emboliform and globose nuclei, instead having a single, fused interposed nucleus. In animals with distinct emboliform and globose nuclei, the term interposed nucleus is often used to refer collectively to these two nuclei.

QMRPrinciples[edit]

The comparative simplicity and regularity of the cerebellar anatomy led to an early hope that it might imply a similar simplicity of computational function, as expressed in one of the first books on cerebellar electrophysiology, TheCerebellum as a Neuronal Machine by John C. Eccles, Masao Ito, and János Szentágothai.[28] Although a full understanding of cerebellar function has remained elusive, at least four principles have been identified as important: (1) feedforward processing, (2) divergence and convergence, (3) modularity, and (4) plasticity.

Feedforward processing: The cerebellum differs from most other parts of the brain (especially the cerebral cortex) in that the signal processing is almost entirely feedforward—that is, signals move unidirectionally through the system from input to output, with very little recurrent internal transmission. The small amount of recurrence that does exist consists of mutual inhibition; there are no mutually excitatory circuits. This feedforward mode of operation means that the cerebellum, in contrast to the cerebral cortex, cannot generate self-sustaining patterns of neural activity. Signals enter the circuit, are processed by each stage in sequential order, and then leave. As Eccles, Ito, and Szentágothai wrote, "This elimination in the design of all possibility of reverberatory chains of neuronal excitation is undoubtedly a great advantage in the performance of the cerebellum as a computer, because what the rest of the nervous system requires from the cerebellum is presumably not some output expressing the operation of complex reverberatory circuits in the cerebellum but rather a quick and clear response to the input of any particular set of information."[29]

Divergence and convergence: In the human cerebellum, information from 200 million mossy fiber inputs is expanded to 40 billion granule cells, whose parallel fiber outputs then converge onto 15 million Purkinje cells.[4] Because of the way that they are lined up longitudinally, the 1000 or so Purkinje cells belonging to a microzone may receive input from as many as 100 million parallel fibers, and focus their own output down to a group of less than 50 deep nuclear cells.[17] Thus, the cerebellar network receives a modest number of inputs, processes them very extensively through its rigorously structured internal network, and sends out the results via a very limited number of output cells.

Modularity: The cerebellar system is functionally divided into more or less independent modules, which probably number in the hundreds to thousands. All modules have a similar internal structure, but different inputs and outputs. A module (a multizonal microcompartment in the terminology of Apps and Garwicz) consists of a small cluster of neurons in the inferior olivary nucleus, a set of long narrow strips of Purkinje cells in the cerebellar cortex (microzones), and a small cluster of neurons in one of the deep cerebellar nuclei. Different modules share input from mossy fibers and parallel fibers, but in other respects they appear to function independently—the output of one module does not appear to significantly influence the activity of other modules.[17]

Plasticity: The synapses between parallel fibers and Purkinje cells, and the synapses between mossy fibers and deep nuclear cells, are both susceptible to modification of their strength. In a single cerebellar module, input from as many as a billion parallel fibers converges onto a group of less than 50 deep nuclear cells, and the influence of each parallel fiber on those nuclear cells is adjustable. This arrangement gives tremendous flexibility for fine-tuning the relationship between the cerebellar inputs and outputs.[30]

QMRToday, the structure is called the hippocampus rather than hippocampus major, with pes hippocampi often being regarded as synonymous with De Garengeot's "cornu Ammonis",[3] a term that survives in the names of the four main histological divisions of the hippocampus: CA1, CA2, CA3, and CA4.[

QMR The ventromedial nucleus of the hypothalamus (VMN, also sometimes referred to as the ventromedial hypothalamus, VMH) is a nucleus of the hypothalamus. "The ventromedial hypothalamus (VMH) is a distinct morphological nucleus involved in feeding, fear, thermoregulation, and sexual activity."[1] This nuclear region is involved with the recognition of the feeling of fullness.It has four subdivisions:

anterior (VMHa)

dorsomedial (VMHdm)

ventrolateral (VMHvl)

central (VMHc).

These subdivisions differ anatomically, neurochemically, and behaviorally.

QMRTristimulus timbre model[edit]

The concept of tristimulus originates in the world of color, describing the way three primary colors can be mixed together to create a given color. By analogy, the musical tristimulus measures the mixture of harmonics in a given sound, grouped into three sections. The first tristimulus measures the relative weight of the first harmonic; the second tristimulus measures the relative weight of the second, third, and fourth harmonics taken together; and the third tristimulus measures the relative weight of all the remaining harmonics (Peeters 2003; Pollard and Jansson 1982,[page needed]):

T1 = \frac{a_1}{\sum_{h=1}^{H}{a_h}}

T2 = \frac{a_2 + a_3 + a_4}{\sum_{h=1}^{H}{a_h}}

T3 = \frac{\sum_{h=5}^{H}{a_h}}{\sum_{h=1}^{H}{a_h}}

QMRClassical Greek medicine[edit]

Fåhræus (a Swedish physician who devised the erythrocyte sedimentation rate) suggested that the Ancient Greek system of humorism, wherein the body was thought to contain four distinct bodily fluids (associated with different temperaments), were based upon the observation of blood clotting in a transparent container. When blood is drawn in a glass container and left undisturbed for about an hour, four different layers can be seen. A dark clot forms at the bottom (the "black bile"). Above the clot is a layer of red blood cells (the "blood"). Above this is a whitish layer of white blood cells (the "phlegm"). The top layer is clear yellow serum (the "yellow bile").[30][not in citation given]

Human blood[edit]

The ABO blood group system was discovered in the year 1900 by Karl Landsteiner. Jan Janský is credited with the first classification of blood into the four types (A, B, AB, and O) in 1907, which remains in use today. In 1907 the first blood transfusion was performed that used the ABO system to predict compatibility.[31] The first non-direct transfusion was performed on March 27, 1914. The Rhesus factor was discovered in 1937.

QMRTetradentate ligands bind with four atoms, an example being triethylenetetramine (abbreviated trien). Tetradentate ligands bind via three connectivities depending on their topology and the geometry of the metal center. For octahedral metals, the linear tetradentate trien can bind via three geometries. Tripodal tetradentate ligands, e.g. tris(2-aminoethyl)amine, are more constrained, and on octahedra leave two cis sites. Many naturally occurring macrocyclic ligands are tetradentative, an example being the porphyrin in heme.

QMRTetrahedral or square planar for four-coordination

QMRStructural isomerism[edit]

Structural isomerism occurs when the bonds are themselves different. There are four types of structural isomerism: ionisation isomerism, solvate or hydrate isomerism, linkage isomerism and coordination isomerism.

Ionisation isomerism – the isomers give different ions in solution although they have the same composition. This type of isomerism occurs when the counter ion of the complex is also a potential ligand. For example pentaamminebromidocobalt(III)sulfate [CoBr(NH3)5]SO4 is red violet and in solution gives a precipitate with barium chloride, confirming the presence of sulfate ion, while pentaamminesulfatecobalt(III)bromide [CoSO4(NH3)5]Br is red and tests negative for sulfate ion in solution, but instead gives a precipitate of AgBr with silver nitrate.

Solvate or hydrate isomerism – the isomers have the same composition but differ with respect to the number of solvent ligand molecules as well as the counter ion in the crystal lattice. For example [Cr(H2O)6]Cl3 is violet colored, [CrCl(H2O)5]Cl2·H2O is blue-green, and [CrCl2(H2O)4]Cl·2H2O is dark green

Linkage isomerism occurs with ambidentate ligands that can bind in more than one place. For example, NO2 is an ambidentate ligand: It can bind to a metal at either the N atom or an O atom.

Coordination isomerism – this occurs when both positive and negative ions of a salt are complex ions and the two isomers differ in the distribution of ligands between the cation and the anion. For example [Co(NH3)6][Cr(CN)6] and [Cr(NH3)6][Co(CN)6]

QMRligands with 2, 3, 4 or even 6 bonds to the central atom are common.

QMRThe sperm whale is one of the species originally described by Linnaeus in 1758 in his eighteenth century work, Systema Naturae. He recognised four species in the genus Physeter.[26] Experts soon realised that just one such species exists, although there has been debate about whether this should be named P. catodon or P. macrocephalus, two of the names used by Linnaeus. Both names are still used, although most recent authors now accept macrocephalus as the valid name, limiting catodon's status to a lesser synonym

Quadrant Model of Reality

Monday, February 22, 2016

Quadrant Model of Reality Book 13 Science Physics Chemistry and Biology

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