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Intermolecular bonding

There are four basic types of bonds that can be formed between two or more (otherwise non-associated) molecules, ions or atoms. Intermolecular forces cause molecules to be attracted or repulsed by each other. Often, these define some of the physical characteristics (such as the melting point) of a substance.
A large difference in electronegativity between two bonded atoms will cause a permanent charge separation, or dipole, in a molecule or ion. Two or more molecules or ions with permanent dipoles can interact within dipole-dipole interactions. The bonding electrons in a molecule or ion will, on average, be closer to the more electronegative atom more frequently than the less electronegative one, giving rise to partial charges on each atom, and causing electrostatic forces between molecules or ions.
A hydrogen bond is effectively a strong example of an interaction between two permanent dipoles. The large difference in electronegativities between hydrogen and any of fluorine, nitrogen and oxygen, coupled with their lone pairs of electrons cause strong electrostatic forces between molecules. Hydrogen bonds are responsible for the high boiling points of water and ammonia with respect to their heavier analogues.
The London dispersion force arises due to instantaneous dipoles in neighbouring atoms. As the negative charge of the electron is not uniform around the whole atom, there is always a charge imbalance. This small charge will induce a corresponding dipole in a nearby molecule; causing an attraction between the two. The electron then moves to another part of the electron cloud and the attraction is broken.
A cation–pi interaction occurs between a pi bond and a cation.



The four common allotropes of phosphorus


White, red, violet, and black phosophorous


White phosophorous is tetrahedral. Tetra means four.

White phosphorus[edit]
This section is about the chemistry of white phosphorus. For military applications, see white phosphorus munitions.

White phosphorus sample
White phosphorus, yellow phosphorus or simply tetraphosphorus (P4) exists as molecules made up of four atoms in a tetrahedral structure. The tetrahedral arrangement results in ring strain and instability. The molecule is described as consisting of six single P–P bonds. Two different crystalline forms are known. The α form, which is stable under standard conditions, has a body-centered cubic crystal structure. It transforms reversibly into the β form at 195.2 K. The β form is believed to have a hexagonal crystal structure.[1]

White phosphorus is a translucent waxy solid that quickly becomes yellow when exposed to light. For this reason it is also called yellow phosphorus. It glows greenish in the dark (when exposed to oxygen), is highly flammable and pyrophoric (self-igniting) upon contact with air as well as toxic (causing severe liver damage on ingestion and phossy jaw from chronic ingestion or inhalation). The odour of combustion of this form has a characteristic garlic smell, and samples are commonly coated with white "diphosphorus pentoxide", which consists of P4O10 tetrahedral with oxygen inserted between the phosphorus atoms and at their vertices. White phosphorus is only slightly soluble in water and it can be stored under water. Indeed, white phosphorus is only safe from self-igniting when it is submerged in water. It is soluble in benzene, oils, carbon disulfide, and disulfur dichloride.

Natural lead consists of four stable isotopes, with mass numbers of 204, 206, 207, and 208, [26] and traces of five short-lived radioisotopes.[27] The high number of such isotopes is due to lead's atomic number of 82 being even,[e] as well as a magic number (meaning lead's protons form complete shells within its atomic nucleus).[f] With its high atomic number, lead is the second-heaviest element whose natural isotopes are regarded as stable: bismuth has atomic number 83, but its only primordial isotope was found in 2003 to decay at an extremely gradual rate.[g] The four stable isotopes of lead could theoretically undergo alpha decay to isotopes of mercury with a release of energy, but this has not been observed for any of them;[31] accordingly, their predicted half-lives are extremely long, ranging up to over 10100 years.[32][h]

Types of decay[edit]

This diagram illustrates the four decay chains discussed in the text: thorium (4n, in blue), neptunium (4n+1, in purple), radium (4n+2, in red) and actinium (4n+3, in green).
The four most common modes of radioactive decay are: alpha decay, beta decay, inverse beta decay (considered as both positron emission and electron capture), and isomeric transition. Of these decay processes, only alpha decay changes the atomic mass number (A) of the nucleus, and always decreases it by four. Because of this, almost any decay will result in a nucleus whose atomic mass number has the same residue mod 4, dividing all nuclides into four chains. The members of any possible decay chain must be drawn entirely from one of these classes. All four chains also produce helium-4 (alpha particles are helium-4 nuclei).

Three main decay chains (or families) are observed in nature, commonly called the thorium series, the radium or uranium series, and the actinium series, representing three of these four classes, and ending in three different, stable isotopes of lead. The mass number of every isotope in these chains can be represented as A = 4n, A = 4n + 2, and A = 4n + 3, respectively. The long-lived starting isotopes of these three isotopes, respectively thorium-232, uranium-238, and uranium-235, have existed since the formation of the earth, ignoring the artificial isotopes and their decays since the 1940s.

Due to the relatively short half-life of its starting isotope neptunium-237 (2.14 million years), the fourth chain, the neptunium series with A = 4n + 1, is already extinct in nature, except for the final rate-limiting step, decay of bismuth-209. The ending isotope of this chain is now known to be thallium-205. Some older sources give the final isotope as bismuth-209, but it was recently discovered that it is radioactive, with a half-life of 1.9×1019 years.


This diagram illustrates the four decay chains discussed in the text: thorium (4n, in blue), neptunium (4n+1, in purple), radium (4n+2, in red) and actinium (4n+3, in green).




A silicon–oxygen tetrahedron is the SiO4 anionic group, or a silicon atom with four surrounding oxygen atoms arranged to define the corners of a tetrahedron. This is a fundamental component of most silicates in the Earth's crust. A variety of silicate minerals can be identified by the way that the tetrahedra links differ, also by the cations present in the mineral.



Tetra is four. Silicon (called the miracle element by chemists along with carbon) has four valence electrons and looks like a quadrant.


Most of the Earth is made of silicon

I'm a paragraph. Click here to add your own text and edit me. It's easy.

Naturally occurring iron (Fe) consists of four stable isotopes: 5.845% of 54Fe, 91.754% of 56Fe, 2.119% of 57Fe and 0.282% of 58Fe.

Iron is a very important metal. There are at least four allotropic forms of iron, known as α, γ, δ, and ε; at very high pressures, some controversial experimental evidence exists for a phase β stable at very high pressures and temperatures.

The shells of the nucleus fill according to 2, 8, 20, 28, 50, 84, 126. Iron 58 appears to be a point where all four inner shells are completely full (2+8+20+28=58). Iron 56 appears to be a point where the second, third and fourth shells are completely full (8+20+28=56).

There is a trend for nuclides of nucleon numbers in multiples of 4 to be particularly stable (i.e. have a high binding energy).

· Fe is the most stable nuclide.

Iron is the most stable element in the Universe.



tetra is four
Arsenic is known for being toxic. The most toxic form is the tetrahedral form.
Gray arsenic is also the most stable form. Yellow arsenic is soft and waxy, and somewhat similar to tetraphosphorus (P
4). Both have four atoms arranged in a tetrahedral structure in which each atom is bound to each of the other three atoms by a single bond. This unstable allotrope, being molecular, is the most volatile, least dense, and most toxic. Solid yellow arsenic is produced by rapid cooling of arsenic vapor, As
4. It is rapidly transformed into gray arsenic by light. The yellow form has a density of 1.97 g/cm3.[10] Black arsenic is similar in structure to red phosphorus.[10] Black arsenic can also be formed by cooling vapor at around 100–220 °C. It is glassy and brittle. It is also a poor electrical conductor.[12]


I described that silicon and carbon are called "the miracle elements" by chemists. Most of the Earth is silicon. Most of life is carbon. Germanium (important in electrons), lead (bullets), tin (cans), and flerovium are also shaped as quadrants with four valence electrons

The carbon group is a periodic table group consisting of carbon (C), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), and flerovium (Fl).

In modern IUPAC notation, it is called Group 14. In the field of semiconductor physics, it is still universally called Group IV. The group was once also known as the tetrels (from the Greek word tetra, which means four), stemming from the Roman numeral IV in the group names, or (not coincidentally) from the fact that these elements have four valence electrons (see below). The group is sometimes also referred to as tetragens because it has four electrons in its outermost shell or the valence shell. This group is also called the crystallogens.

Lead has four valence electrons and thus is shaped as a quadrant.


Lead (/lɛd/) is a chemical element in the carbon group with symbol Pb (from Latin: plumbum) and atomic number 82. Lead is a soft, malleable and heavy post-transition metal. Lead is used in building construction, lead-acid batteries, bullets and shot, weights, as part of solders, pewters, fusible alloys, and as a radiation shield.




These carbon group elements have four valence electrons and look like quadrants. They are also known for being extremely important in relation to all of the other elements on the periodic table


Modern discoveries[edit]

Amorphous elemental silicon was first obtained pure in 1824 by the Swedish chemist Jöns Jacob Berzelius; impure silicon had already been obtained in 1811. Crystalline elemental silicon was not prepared until 1854, when it was obtained as a product of electrolysis.


Germanium is one of three elements the existence of which was predicted in 1869 by the Russian chemist Dmitri Mendeleev when he first devised his periodic table. However, the element was not actually discovered for some time. In September 1885, a miner discovered a mineral sample in a silver mine and gave it to the mine manager, who determined that it was a new mineral and sent the mineral to Clemens A. Winkler. Winkler realized that the sample was 75% silver, 18% sulfur, and 7% of an undiscovered element. After several months, Winkler isolated the element and determined that it was element 32.[13]


The first attempt to discover flerovium (then referred to as "element 114") was in 1969, at the Joint Institute for Nuclear Research, but it was unsuccessful. In 1977, researchers at the Joint Institute for Nuclear Research bombarded plutonium-244 atoms with calcium-48, but were again unsuccessful. This nuclear was repeated in 1998, this time successfully.[13]



Carbon is most commonly used in its amorphous form. In this form, carbon is used for steelmaking, as carbon black, as a filling in tires, in respirators, and as activated charcoal. Carbon is also used in the form of graphite is commonly used as the lead in pencils. Diamond, another form of carbon, is commonly used in jewelery.[13] Carbon fibers are used in numerous applications, such as satellite struts, because the fibers are highly strong yet elastic.[17]


Silicon dioxide has a wide variety of applications, including toothpaste, construction fillers, and silica is a major component of glass. 50% of pure silicon is devoted to the manufacture of metal alloys. 45% of silicon is devoted to the manufacture of silicones. Silicon is also commonly used in semiconductors since the 1950s.[12][17]


Germanium was used in semiconductors until the 1950s, when it was replaced by silicon.[12] Radiation detectors contain germanium. Germanium oxide is used in fiber optics and wide-angle camera lenses. A small amount of germanium mixed with silver can make silver tarnish-proof. The resulting alloy is known as argentium.[13]


Solder is the most important use of tin; 50% of all tin produced goes into this application. 20% of all tin produced is used in tin plate. 20% of tin is also used by the chemical industry. Tin is also a constituent of numerous alloys, including pewter. Tin (IV) oxide has been commonly used in ceramics for thousands of years. Cobalt stannate is a tin compound which is used as a cerulean blue pigment.[13]


80% of all lead produced goes into lead-acid batteries. Other applications for lead include weights, pigments, and shielding against radioactive materials. Lead was historically used in gasoline in the form of tetraethyl lead, but this application has been discontinued due to concerns of toxicity.[18]


Biological role[edit]

Carbon is a key element to all known life. It is in all organic compounds, for example, DNA, steroids, and proteins.[3] Carbon's importance to life is primarily due to its ability to form numerous bonds with other elements.[12] There are 16 kilograms of carbon in a typical 70-kilogram human.[13]


Silicon-based life's feasibility is commonly discussed. However, it is less able than carbon to form elaborate rings and chains.[3] Silicon in the form of silicon dioxide is used by diatoms and sea sponges to form their cell walls and skeletons. Silicon is essential for bone growth in chickens and rats and may also be essential in humans. Humans consume on average between 20 and 1200 milligrams of silicon per day, mostly from cereals. There is 1 gram of silicon in a typical 70-kilogram human.[13]


A biological role for germanium is not known, although it does stimulate metabolism. In 1980, germanium was reported by Kazuhiko Asai to benefit health, but the claim has not been proven. Some plants take up germanium from the soil in the form of germanium oxide. These plants, which include grains and vegetables contain roughly 0.05 parts per million of germanium. The estimated human intake of germanium is 1 milligram per day. There are 5 milligrams of germanium in a typical 70-kilogram human.[13]


Tin has been shown to be essential for proper growth in rats, but there is, as of 2013, no evidence to indicate that humans need tin in their diet. Plants do not require tin. However, plants do collect tin in their roots. Wheat and corn contain seven and three parts per million respectively. However, the level of tin in plants can reach 2000 parts per million if the plants are near a tin smelter. On average, humans consume 0.3 milligrams of tin per day. There are 30 milligrams of tin in a typical 70-kilogram human.[13]


Lead has no known biological role, and is in fact highly toxic, but some microbes are able to survive in lead-contaminated environments. Some plants, such as cucumbers contain up to tens of parts per million of lead. There are 120 milligrams of lead in a typical 70-kilogram human.[13]

Tetra is four


Germanium tetrachloride -Molecular shape

tetrahedral- is a colourless, fuming liquid with a peculiar, acidic odour. It is used as an intermediate in the production of purified germanium metal. In recent years, GeCl4 usage has increased substantially due to its use as a reagent for fiber optic production.


Germanium tetrachloride is used almost exclusively as an intermediate for several optical processes. GeCl4 can be directly hydrolyzed to GeO2, an oxide glass with several unique properties and applications, described below and in linked articles:


Fiber Optics[edit]

A notable derivative of GeCl4 is Germanium dioxide. In Fibre Optic manufacture, silicon tetrachloride, SiCl4 and germanium tetrachloride, GeCl4 are introduced with oxygen into a hollow glass preform, which is carefully heated to allow for oxidation of the reagents to their respective oxides and formation of a glass mixture. The GeO2 has a high index of refraction, so by varying the flowrate of germanium tetrachloride the overall index of refraction of the optical fiber can be specifically controlled. The GeO2 is about 4% by weight of the glass.[2]

tetra is four


Crystal structure




Silicon tetrachloride is the inorganic compound with the formula SiCl4. It is a colourless volatile liquid that fumes in air. It is used to produce high purity silicon and silica for commercial applications.


Silicon tetrachloride is used as an intermediate in the manufacture of polysilicon, a hyper pure form of silicon,[2] since it has a boiling point convenient for purification by repeated fractional distillation. It is reduced to trichlorosilane (HSiCl3) by hydrogen gas in a hydrogenation reactor, and either directly used in the Siemens process or further reduced to silane (SiH4) and injected into a fluidized bed reactor. Silicon tetrachloride reappears in both these two processes as a by-product and is recycled in the hydrogenation reactor. Vapor phase epitaxy of reducing silicon tetrachloride with hydrogen at approximately 1250oC was done:



4(g) + 2 H

2(g) → Si(s) + 4 HCl

2(g) at 1250oC[6]

The produced polysilicon is used as wafers in large amounts by the photovoltaic industry for conventional solar cells made of crystalline silicon and also by the semiconductor industry.


Silicon tetrachloride can also be hydrolysed to fumed silica. High purity silicon tetrachloride is used in the manufacture of optical fibres. This grade should be free of hydrogen containing impurities like trichlorosilane. Optical fibres are made using processes like MCVD and OFD where silicon tetrachloride is oxidized to pure silica in the presence of oxygen.

It looks like a quadrant

Tetraethyl orthosilicate, formally named tetraethoxysilane, is the chemical compound with the formula Si(OC2H5)4. Often abbreviated TEOS, it is a colorless liquid that degrades in water. TEOS is the ethyl ester of orthosilicic acid, Si(OH)4. It is the most prevalent alkoxide of silicon.

TEOS is a tetrahedral molecule. Like its many analogues, it is prepared by alcoholysis of silicon tetrachloride:

SiCl4 + 4 EtOH → Si(OEt)4 + 4 HCl
where Et is the ethyl radical, C2H5, and thus EtOH is ethanol.


TEOS is mainly used as a crosslinking agent in silicone polymers and as a precursor to silicon dioxide in the semiconductor industry.[3] TEOS is also used as the silica source for synthesis of some zeolites.[4] Other applications include coatings for carpets and other objects. TEOS is used in the production of aerogel. These applications exploit the reactivity of the Si-OR bonds.[5]



Silicon has four valence electrons and is a quadrant


Silicon biochemistry[edit]


Structure of silane, analog of methane.


Structure of the silicone polydimethylsiloxane (PDMS).


Marine diatoms—carbon-based organisms that extract silicon from sea water and incorporate it into their cell walls

See also: Organosilicon

The silicon atom has been much discussed as the basis for an alternative biochemical system, because silicon has many chemical properties similar to those of carbon and is in the same group of the periodic table, the carbon group. Like carbon, silicon can create molecules that are sufficiently large to carry biological information.[10]


However, silicon has several drawbacks as an alternative to carbon. Silicon, unlike carbon, lacks the ability to form chemical bonds with diverse types of atoms as is necessary for the chemical versatility required for metabolism. Elements creating organic functional groups with carbon include hydrogen, oxygen, nitrogen, phosphorus, sulfur, and metals such as iron, magnesium, and zinc. Silicon, on the other hand, interacts with very few other types of atoms.[10] Moreover, where it does interact with other atoms, silicon creates molecules that have been described as "monotonous compared with the combinatorial universe of organic macromolecules".[10] This is because silicon atoms are much bigger, having a larger mass and atomic radius, and so have difficulty forming double bonds (the double bonded carbon is part of the carbonyl group, a fundamental motif of bio-organic chemistry).


Silanes, which are chemical compounds of hydrogen and silicon that are analogous to the alkane hydrocarbons, are highly reactive with water, and long-chain silanes spontaneously decompose. Molecules incorporating polymers of alternating silicon and oxygen atoms instead of direct bonds between silicon, known collectively as silicones, are much more stable. It has been suggested that silicone-based chemicals would be more stable than equivalent hydrocarbons in a sulfuric-acid-rich environment, as is found in some extraterrestrial locations.[11]


Of the varieties of molecules identified in the interstellar medium as of 1998, 84 are based on carbon while only 8 are based on silicon.[12] Moreover, of those 8 compounds, four also include carbon within them. The cosmic abundance of carbon to silicon is roughly 10 to 1. This may suggest a greater variety of complex carbon compounds throughout the cosmos, providing less of a foundation on which to build silicon-based biologies, at least under the conditions prevalent on the surface of planets. Also, even though Earth and other terrestrial planets are exceptionally silicon-rich and carbon-poor (the relative abundance of silicon to carbon in Earth's crust is roughly 925:1), terrestrial life is carbon-based. The fact that carbon is used instead of silicon, may be evidence that silicon is poorly suited for biochemistry on Earth-like planets. Reasons for which may be that silicon is less versatile than carbon in forming compounds, that the compounds formed by silicon are unstable, and that it blocks the flow of heat.[13]


Even so, biogenic silica is used by some Earth life, such as the silicate skeletal structure of diatoms. According to the clay hypothesis of A. G. Cairns-Smith, silicate minerals in water played a crucial role in abiogenesis: they replicated their crystal structures, interacted with carbon compounds, and were the precursors of carbon-based life.[14][15]


Although not observed in nature, carbon–silicon bonds have been added to biochemistry by using directed evolution (artificial selection). A heme containing cytochrome c protein from Rhodothermus marinus has been engineered using directed evolution to catalyze the formation of new carbon silicon bonds between hydrosilanes and diazo compounds.[16]


Silicon compounds may possibly be biologically useful under temperatures or pressures different from the surface of a terrestrial planet, either in conjunction with or in a role less directly analogous to carbon. Polysilanols, the silicon compounds corresponding to sugars, are soluble in liquid nitrogen, suggesting that they could play a role in very low temperature biochemistry.[17][18]


In cinematic and literary science fiction, at a moment when man-made machines cross from nonliving to living, it is often posited, this new form would be the first example of non-carbon-based life. Since the advent of the microprocessor in the late 1960s, these machines are often classed as computers (or computer-guided robots) and filed under "silicon-based life", even though the silicon backing matrix of these processors is not nearly as fundamental to their operation as carbon is for "wet life".


Organosilicons are made of carbon and silicon- both are quadrants

Organosilicon compounds are organometallic compounds containing carbon–silicon bonds. Organosilicon chemistry is the corresponding science of their preparation and properties. Most organosilicon compounds are similar to the ordinary organic compounds, being colourless, flammable, hydrophobic, and stable to air. Silicon carbide is an inorganic compound.

Occurrence and applications[edit]
Organosilicon compounds are widely encountered in commercial products. Most common are sealants, caulks, adhesives, and coatings made from silicones. Others important uses include agricultural and plant control adjuvants such as herbicides and fungicides.

Silicone caulk, commercial sealants, are mainly composed of organosilicon compounds.

Polydimethylsiloxane (PDMS) is the principal component of silicones.
Biology and medicine[edit]
Carbon–silicon bonds are absent in biology.[1][2] Silicates, on the other hand, have known existence in diatoms.[3] Silafluofen is an organosilicon compound that functions as a pyrethroid insecticide. Several organosilicon compounds have been investigated as pharmaceuticals.[4][5]

Properties of Si–C, Si–O, and Si–F bonds[edit]
In most organosilicon compounds, Si is tetravalent with tetrahedral molecular geometry. Carbon–silicon bonds compared to carbon–carbon bonds are longer (186 pm vs. 154 pm) and weaker with bond dissociation energy 451 kJ/mol vs. 607 kJ/mol.[6] The C–Si bond is somewhat polarised towards carbon due to carbon's greater electronegativity (C 2.55 vs Si 1.90). The Si–C bond can be broken more readily than typical C–C bonds. One manifestation of bond polarization in organosilanes is found in the Sakurai reaction.[7] Certain alkyl silanes can be oxidized to an alcohol in the Fleming–Tamao oxidation.

Another manifestation is the β-silicon effect describes the stabilizing effect of a β-silicon atom on a carbocation with many implications for reactivity.

Si–O bonds are much stronger (809 kJ/mol compared to 538 kJ/mol) than a typical C–O single bond. The favorable formation of Si–O bonds drives many organic reactions such as the Brook rearrangement and Peterson olefination. Compared to the strong Si–O bond, the Si–F bond is even stronger.

Carbon is a quadrant

The discoverers of the Buckminsterfullerene (C60) allotrope of carbon named it after Richard Buckminster Fuller, a noted architectural modeler who popularized the geodesic dome. Since buckminsterfullerenes have a similar shape to those of such domes, they thought the name appropriate.[18]
As the discovery of the fullerene family came after buckminsterfullerene, the shortened name 'fullerene' is used to refer to the family of fullerenes. The suffix "-ene" indicates that each C atom is covalently bonded to three others (instead of the maximum of four), a situation that classically would correspond to the existence of bonds involving two pairs of electrons ("double bonds").

Types of fullerene[edit]
Since the discovery of fullerenes in 1985, structural variations on fullerenes have evolved well beyond the individual clusters themselves. Examples include:[19]

Buckyball clusters: smallest member is C
20 (unsaturated version of dodecahedrane) and the most common is C
Nanotubes: hollow tubes of very small dimensions, having single or multiple walls; potential applications in electronics industry;
Megatubes: larger in diameter than nanotubes and prepared with walls of different thickness; potentially used for the transport of a variety of molecules of different sizes;[20]
polymers: chain, two-dimensional and three-dimensional polymers are formed under high-pressure high-temperature conditions; single-strand polymers are formed using the Atom Transfer Radical Addition Polymerization (ATRAP) route;[21]
nano"onions": spherical particles based on multiple carbon layers surrounding a buckyball core;[22] proposed for lubricants;[23]
linked "ball-and-chain" dimers: two buckyballs linked by a carbon chain;[24]
fullerene rings.[25]

Carbon nanotubes[edit]

This rotating model of a carbon nanotube shows its 3D structure.
Main article: Carbon nanotube
Nanotubes are cylindrical fullerenes. These tubes of carbon are usually only a few nanometres wide, but they can range from less than a micrometer to several millimeters in length. They often have closed ends, but can be open-ended as well. There are also cases in which the tube reduces in diameter before closing off. Their unique molecular structure results in extraordinary macroscopic properties, including high tensile strength, high electrical conductivity, high ductility, high heat conductivity, and relative chemical inactivity (as it is cylindrical and "planar" — that is, it has no "exposed" atoms that can be easily displaced). One proposed use of carbon nanotubes is in paper batteries, developed in 2007 by researchers at Rensselaer Polytechnic Institute.[37] Another highly speculative proposed use in the field of space technologies is to produce high-tensile carbon cables required by a space elevator.

For the past decade, the chemical and physical properties of fullerenes have been a hot topic in the field of research and development, and are likely to continue to be for a long time. Popular Science has discussed possible uses of fullerenes (graphene) in armor.[40] In April 2003, fullerenes were under study for potential medicinal use: binding specific antibiotics to the structure to target resistant bacteria and even target certain cancer cells such as melanoma. The October 2005 issue of Chemistry & Biology contains an article describing the use of fullerenes as light-activated antimicrobial agents.[41]

In the field of nanotechnology, heat resistance and superconductivity are some of the more heavily studied properties.

A common method used to produce fullerenes is to send a large current between two nearby graphite electrodes in an inert atmosphere. The resulting carbon plasma arc between the electrodes cools into sooty residue from which many fullerenes can be isolated.

There are many calculations that have been done using ab-initio quantum methods applied to fullerenes. By DFT and TD-DFT methods one can obtain IR, Raman and UV spectra. Results of such calculations can be compared with experimental results.

Quantum mechanics[edit]
In 1999, researchers from the University of Vienna demonstrated that wave-particle duality applied to molecules such as fullerene.[53]

Tumor research[edit]
While past cancer research has involved radiation therapy, photodynamic therapy is important to study because breakthroughs in treatments for tumor cells will give more options to patients with different conditions. Recent experiments using HeLa cells in cancer research involves the development of new photosensitizers with increased ability to be absorbed by cancer cells and still trigger cell death. It is also important that a new photosensitizer does not stay in the body for a long time to prevent unwanted cell damage.[59]

Fullerenes can be made to be absorbed by HeLa cells. The C60 derivatives can be delivered to the cells by using the functional groups L-phenylalanine, folic acid, and L-arginine among others.[60] Functionalizing the fullerenes aims to increase the solubility of the molecule by the cancer cells. Cancer cells take up these molecules at an increased rate because of an upregulation of transporters in the cancer cell, in this case amino acid transporters will bring in the L-arginine and L-phenylalanine functional groups of the fullerenes.[61]

Once absorbed by the cells, the C60 derivatives would react to light radiation by turning molecular oxygen into reactive oxygen which triggers apoptosis in the HeLa cells and other cancer cells that can absorb the fullerene molecule. This research shows that a reactive substance can target cancer cells and then be triggered by light radiation, minimizing damage to surrounding tissues while undergoing treatment.[62]

When absorbed by cancer cells and exposed to light radiation, the reaction that creates reactive oxygen damages the DNA, proteins, and lipids that make up the cancer cell. This cellular damage forces the cancerous cell to go through apoptosis, which can lead to the reduction in size of a tumor. Once the light radiation treatment is finished the fullerene will reabsorb the free radicals to prevent damage of other tissues.[63] Since this treatment focuses on cancer cells, it is a good option for patients whose cancer cells are within reach of light radiation. As this research continues, the treatment may penetrate deeper into the body and be absorbed by cancer cells more effectively.[59]

Popular culture[edit]
Main article: Fullerenes in popular culture
Examples of fullerenes in popular culture are numerous. Fullerenes appeared in fiction well before scientists took serious interest in them. In a humorously speculative 1966 column for New Scientist, David Jones suggested that it may be possible to create giant hollow carbon molecules by distorting a plane hexagonal net by the addition of impurity atoms.[64]

On 4 September 2010, Google used an interactively rotatable fullerene [65] C60 as the second 'o' in their logo to celebrate the 25th anniversary of the discovery of the fullerenes.[66][67]

In determining the Avogadro constant, the preferred method has been to use one of the high-precision spheres fabricated here at the ACPO. These come in the form of a highly polished 1 kg single crystal silicon sphere, fabricated with a roundness in range of 60 nm. Silicon is used because of its well known crystal structure, stability and its relative ease of use. The volume is determined from the measurement of the silicon sphere's diameter and roundness. Accurate measurement of the mass then allows the density to be derived. This is the most ambitious project in measurement history and will be used to be the standard for measuring a kilo. Again silicon is the quadrant pattern, with four valence electrons forming a quadrant image. The reason silicon is being used for the project is because of its ordered arrangement due to its quadrant formation.


Moseley showed that there were four gaps in the atomic number sequence at numbers 43, 61, 72, and 75. These spaces are now known, respectively, to be the places of the radioactive synthetic elements technetium and promethium, and also the last two quite rare naturally occurring stable elements hafnium (discovered 1923) and rhenium (discovered 1925). Nothing about these four elements was known of in Moseley's lifetime, not even their very existence. Based on the intuition of a very experienced chemist, Dmitri Mendeleev had predicted the existence of a missing element in the Periodic Table, which was later found to be filled by technetium, and Bohuslav Brauner had predicted the existence of another missing element in this Table, which was later found to be filled by promethium. Henry Moseley's experiments confirmed these predictions, by showing exactly what the missing atomic numbers were, 43 and 61. In addition, Moseley predicted the two more undiscovered elements, those with the atomic numbers 72 and 75, and gave very strong evidence that there were no other gaps in the Periodic Table between the elements aluminium (atomic number 13) and gold (atomic number 79).

Moseley discovered atomic number determined the number of electrons and his findings were revolutionary in the periodic table.


The Fragrance Wheel is a fragrance classification chart first developed in 1983 by Michael Edwards, a consultant in the fragrance industry.[1] The wheel is a method for perfume classification which he first designed after being inspired by a fragrance seminar by Firmenich, and seeks to show the relationships between each individual fragrance family.[2] The fragrance wheel has been shown to be highly consistent with previous studies on odor descriptor and odor profile representations.[3]
The chart was first created in an attempt to develop a fragrance classification method and naming scheme without technical jargon that can be used in consumer settings by retailers.[4] The main purpose of the wheel is to allow a retailer to suggest different fragrances in a similar category to ones that their customers may prefer, which has been put into use by retailers such as Sephora and Nordstrom.
Since its creation, the wheel and the developed fragrance classification scheme has been modified several times through the addition of different groups to encompass different fragrance types.[1]
The four standard families are Floral, Oriental, Woody and Fresh.


The Fragrance wheel is a relatively new classification method that is widely used in retail and in the fragrance industry. The method was created in 1983 by Michael Edwards, a consultant in the perfume industry, who designed his own scheme of fragrance classification after being inspired by a fragrance seminar by Firmenich. The new scheme was created in order to simplify fragrance classification and naming, as well as to show the relationships between each individual classes. The five standard families consist of Floral, Oriental, Woody, Fougère, and Fresh, with the former four families being more "classic" while the latter consists of newer, bright and clean smelling citrus and oceanic fragrances that have arrived due to improvements in fragrance technology. With the exception of the Fougère family, each of the families are in turn divided into three sub-groups and arranged around a wheel:
1. Floral
Soft Floral
Floral Oriental
2. Oriental
Soft Oriental
Woody Oriental
3. Woody
Mossy Woods
Dry Woods
4. Fresh
5. Fougère
The Fougère family is placed at the center of this wheel since they are large family of scents that usually contain fragrance elements from each of the other four families. In this classification scheme, Chanel No.5, which is traditionally classified as a "Floral Aldehyde" would be located under Soft Floral sub-group, and "Amber" scents would be placed within the Oriental group. As a class, Chypres is more difficult to place since they would located under parts of the Oriental and Woody families. For instance, Guerlain Mitsouko, which is classically identified as a chypre will be placed under Mossy Woods, but Hermès Rouge, a chypre with more floral character, would be placed under Floral Oriental.
According to Osmoz, there are eight major families: Chypre, Citrus, Floral and Oriental (feminine), and Aromatic, Citrus, Oriental and Woody (masculine). Each one of those olfactive families is then split into several subfamilies.



Perfume is a billion dollar industry and has been very important throughout human history.

Perfume oils usually contain tens to hundreds of ingredients and these are typically organized in a perfume for the specific role they will play. These ingredients can be roughly grouped into four groups:

Primary scents (Heart): Can consist of one or a few main ingredients for a certain concept, such as "rose". Alternatively, multiple ingredients can be used together to create an "abstract" primary scent that does not bear a resemblance to a natural ingredient. For instance, jasmine and rose scents are commonly blends for abstract floral fragrances. Cola flavourant is a good example of an abstract primary scent.

Modifiers: These ingredients alter the primary scent to give the perfume a certain desired character: for instance, fruit esters may be included in a floral primary to create a fruity floral; calone and citrus scents can be added to create a "fresher" floral. The cherry scent in cherry cola can be considered a modifier.

Blenders: A large group of ingredients that smooth out the transitions of a perfume between different "layers" or bases. These themselves can be used as a major component of the primary scent. Common blending ingredients include linalool and hydroxycitronellal.

Fixatives: Used to support the primary scent by bolstering it. Many resins, wood scents, and amber bases are used as fixatives.

The top, middle, and base notes of a fragrance may have separate primary scents and supporting ingredients. The perfume's fragrance oils are then blended with ethyl alcohol and water, aged in tanks for several weeks and filtered through processing equipment to, respectively, allow the perfume ingredients in the mixture to stabilize and to remove any sediment and particles before the solution can be filled into the perfume bottles


The most common arrangement of liquid water (H2O) molecules is tetrahedral with two hydrogen atoms covalently attached to oxygen and two attached by hydrogen bonds. Since the hydrogen bonds vary in length many of these water molecules are not symmetrical and form transient irregular tetrahedra between their four associated hydrogen atoms. Water is what keeps organisms alive and its polar nature is also very important in chemistry. It is no coincidence that it is tetrahedrally arranged. Four is very important.



Steno, in his Dissertationis prodromus of 1669 is credited with four of the defining principles of the science of stratigraphy: the law of superposition: "... at the time when any given stratum was being formed, all the matter resting upon it was fluid, and, therefore, at the time when the lower stratum was being formed, none of the upper strata existed"; the principle of original horizontality: "Strata either perpendicular to the horizon or inclined to the horizon were at one time parallel to the horizon"; the principle of lateral continuity: "Material forming any stratum were continuous over the surface of the Earth unless some other solid bodies stood in the way"; and the principle of cross-cutting relationships: "If a body or discontinuity cuts across a stratum, it must have formed after that stratum."[32] These principles were applied and extended in 1772 by Jean-Baptiste L. Romé de l'Isle. Steno's ideas still form the basis of stratigraphy and were key in the development of James Hutton's theory of infinitely repeating cycles of seabed deposition, uplifting, erosion, and submersion

The first three Steno called principles and the last one he called a law. The fourth is always different.



The first serious attempts to formulate a geological time scale that could be applied anywhere on Earth were made in the late 18th century. The most influential of those early attempts (championed by Abraham Werner, among others) divided the rocks of Earth’s crust into four types: Primary, Secondary, Tertiary, and Quaternary. Each type of rock, according to the theory, formed during a specific period in Earth history. It was thus possible to speak of a "Tertiary Period" as well as of "Tertiary Rocks." Indeed, "Tertiary" (now Paleogene and Neogene) and "Quaternary" (now Pleistocene and Holocene) remained in use as names of geological periods well into the 20th century.

From the website Swastika Science

Chiral metamaterials is a well-established research topic in the group, who were the first to have demonstrated optical activity in planar chiral metamaterials. The metamaterials generally consist of arrays of planar metallic or dielectric gammadions on a substrate, where, if linearly polarized light is incident on the array, it becomes elliptically polarized upon interaction with the gammadions with the same handedness as the gammadion itself.
A chiral structure such as a gammadion is defined as a shape with a certain handedness (left or right), which cannot be brought into congruence with the opposite handedness unless they are removed from the plane. This has the effect that if light is shone from one direction onto the array, the resulting polarization is left or right elliptically polarized, and if light is shone from the opposite direction onto the array, the resulting polarization is the opposite handed elliptical polarization to the other direction.
this is what they look like
the swastika and all it implies is here to stay
in fact it appears that it was heaven sent to help guide us ...



Sir William Thomson’s Quadrant Electrometer #10560

J. White, Glasgow

Thomson invented the quadrant electrometer in 1853. As with the electrostatic voltmeter, the quadrant electrometer utilizes the electrical force between charged electrodes. A butterfly-shaped electrode composed of two quadrants of a circular disk is supported by a torsion fiber inside a stationary circular box composed of four quadrants, opposite pairs of which are electrically connected. The rotation of the suspended electrode depends on the potentials applied to the various electrodes. A beam of light reflected from a mirror attached to the fiber is shown on a scale and is deflected as the fiber is rotated. The serial number of this instrument is 152.

Substitution and elimination reactions (between Lewis-bases and alkyl-halides) are some of the first reactions taught in organic chemistry. The figure above, organizes the main factors that distinquish: SN1, SN2, E1 or E2 mechanisms into a single, 4-quadrant spectrum. We describe the heirarchy of these factors in more detail below.
Acidic/Cationic conditions or Basic/Anionic conditions distinquich “1” vs “2” mechanism, respectively.
Elimination requires alpha hydrogens and predominates with 2-3° alkyl-halides.
Elimination predominates with harder bases (due to stronger electrostatic interactions) while Substitution predominates with softer/nucleophilic bases(due to better orbital overlap). See post on Hard-Soft Acid-Base Theory for more details.
In addition the most general rules outlined above:
Under Acidic conditions: Substitution is favored with protic solvents (due to stabilization of the carbocation intermediate)
Under Basic condition: Elimination is favored with higher substitution of either halide or base



RICE chart, or RICE box is a tabular system of keeping track of changing concentrations in an equilibrium reaction. RICE stands for "Reaction, Initial, Change, Equilibrium".[1] It is used in chemistry to keep track of the changes in amount of substance of the reactants and also organize a set of conditions that one wants to solve with.

To illustrate the processes, consider the case of dissolving a weak acid, HA, in water. How can the pH be calculated? Note that in this example, we are assuming that the acid is not very weak, and that the concentration is not very dilute, so that the concentration of [OH−] ions can be neglected. This is equivalent to the assumption that the final pH will be below about 6 or so. See Calculations of pH for more details.

First write down the equilibrium expression. This is generally regarded as the 'R'.

HA\rightleftharpoons A^{-}+H^{+}

The columns of the table correspond to the three species in equilibrium.

R [HA] [A−] [H+]

I Ca 0 0

C -x +x +x

E Ca - x x x

RICE charts are fundamental in chemistry and the chart has four parts.



I watched a Hare Krishna video on ISKHON where they were talking about Krishna and they mentioned the 16 rivers (there are 16 squares in the quadrant model)


Known as Ganga-Satluj Ka Maidaan (गँगा सतलज का मैदान), this area is drained by 16 major rivers. The major Himalayan Rivers are the Indus, Ganges, and Brahmaputra. These rivers are long,and are joined by many large and important tributaries. Himalayan rivers have long courses from their source to sea.(in India Arabian sea and Bay of Bengal)

16 is the squares of the quadrant model


There are four main stages in the water cycle. They are evaporation, condensation, precipitation and collection. Let's look at each of these stages.
Evaporation: This is when warmth from the sun causes water from oceans, lakes, streams, ice and soils to rise into the air and turn into water vapour (gas). Water vapour droplets join together to make clouds!
Condensation: This is when water vapour in the air cools down and turns back into liquid water.
Precipitation: This is when water (in the form of rain, snow, hail or sleet) falls from clouds in the sky.
Collection: This is when water that falls from the clouds as rain, snow, hail or sleet, collects in the oceans, rivers, lakes, streams. Most will infiltrate (soak into) the ground and will collect as underground water.
The water cycle is powered by the sun's energy and by gravity. The sun kickstarts the whole cycle by heating all the Earth's water and making it evaporate. Gravity makes the moisture fall back to Earth.
The water cycle is one of the most important processes for life. It is no coincidence it reflects the quadrant model pattern


Testing for Quaternary Ammonium Compounds (K-1582)


It’s liberating and humbling to write a lesson-learnt blog. Last year’s lesson-learnt evolved from my high-density plantings in a raised bed.

I divided my four ft. by four ft. raised bed into four quadrants. In one quadrant I planted three types of kale; the next quadrant beans; the third quadrant, beets; and the fourth quadrant, cucumbers and zucchini.

In the sod-based crop rotation project at the North Florida Research and Education Center, in Marianna, Fla., a 160-acre field is divided into quadrants and rotated with two years of bahiagrass, followed by a year of peanuts and then a year of cotton. The system has shown long-term benefits in soil health, reduced pest pressure and increased crop yields.





How It Works (Legume <- Leaf <- Fruit <- Root)


I like this system that breaks the various garden plants into four groups based on their nutritional needs: leaf (nitrogen), fruit (phosphorus), root (potassium), and legume (fixes nitrogen). In this system, the leaf plants go where legumes were last year, because legumes fix nitrogen in the soil, and leaf plants need large amounts of nitrogen. The fruits follow the leaf plants because they need phosphorus, and too much nitrogen causes them not to have fruits. The roots follow the fruits because they need potassium and need nitrogen less than the fruits. Finally, the legumes follow the roots to put nitrogen back into the soil. Because this is a simple sequence, and it makes sense to me, I can remember how it goes each year. There’s a downloadable version of the graphic below here, if you’d like to keep it for your garden file.








Four basic types


Representation of four basic chemical reactions types: synthesis, decomposition, single replacement and double replacement.


Main article: Synthesis reaction

In a synthesis reaction, two or more simple substances combine to form a more complex substance. These reactions are in the general form:






{\displaystyle {\ce {{A}+{B}->AB}}}

Two or more reactants yielding one product is another way to identify a synthesis reaction. One example of a synthesis reaction is the combination of iron and sulfur to form iron(II) sulfide:









{\displaystyle {\ce {{8Fe}+S8->8FeS}}}

Another example is simple hydrogen gas combined with simple oxygen gas to produce a more complex substance, such as water.[18]



Main article: Decomposition reaction

A decomposition reaction is when a more complex substance breaks down into its more simple parts. It is thus the opposite of a synthesis reaction, and can be written as[18][19]






{\displaystyle {\ce {AB->{A}+{B}}}}

One example of a decomposition reaction is the electrolysis of water to make oxygen and hydrogen gas:












{\displaystyle {\ce {2H2O->{2H2}+{O2}}}}

Single replacement

In a single replacement reaction, a single uncombined element replaces another in a compound; in other words, one element trades places with another element in a compound[18] These reactions come in the general form of:








{\displaystyle {\ce {{A}+{BC}->{AC}+{B}}}}

One example of a single displacement reaction is when magnesium replaces hydrogen in water to make magnesium hydroxide and hydrogen gas:
















↑{\displaystyle {\ce {{Mg}+{2H2O}->{Mg(OH)2}+{H2\uparrow }}}}

Double replacement

In a double replacement reaction, the anions and cations of two compounds switch places and form two entirely different compounds.[18] These reactions are in the general form:[19]








{\displaystyle {\ce {{AB}+{CD}->{AD}+{CB}}}}

For example, when barium chloride (BaCl2) and magnesium sulfate (MgSO4) react, the SO42− anion switches places with the 2Cl− anion, giving the compounds BaSO4 and MgCl2.


Another example of a double displacement reaction is the reaction of lead(II) nitrate with potassium iodide to form lead(II) iodide and potassium nitrate:

















{\displaystyle {\ce {{Pb(NO3)2}+2KI->PbI2(v)+2KNO3}}}


In the Pali literature, the mahabhuta ("great elements") or catudhatu ("four elements") are earth, water, fire and air. In early Buddhism, the four elements are a basis for understanding suffering and for liberating oneself from suffering. The earliest Buddhist texts explain that the four primary material elements are the sensory qualities solidity, fluidity, temperature, and mobility; their characterization as earth, water, fire, and air, respectively, is declared an abstraction – instead of concentrating on the fact of material existence, one observes how a physical thing is sensed, felt, perceived.[12]


The Buddha's teaching regarding the four elements is to be understood as the base of all observation of real sensations rather than as a philosophy. The four properties are cohesion (water), solidity or inertia (earth), expansion or vibration (air) and heat or energy content (fire). He promulgated a categorization of mind and matter as composed of eight types of "kalapas" of which the four elements are primary and a secondary group of four are color, smell, taste, and nutriment which are derivative from the four primaries.[citation needed]


Thanissaro Bhikkhu (1997) renders an extract of Shakyamuni Buddha's from Pali into English thus:


Just as a skilled butcher or his apprentice, having killed a cow, would sit at a crossroads cutting it up into pieces, the monk contemplates this very body – however it stands, however it is disposed – in terms of properties: 'In this body there is the earth property, the liquid property, the fire property, & the wind property.'[13]


Tibetan Buddhist medical literature speaks of the Panch Mahābhūta (five elements).[14]



Ancient times[edit]

In classical thought, the four elements earth, water, air, and fire as proposed by Empedocles frequently occur; Aristotle added a fifth element, aether; it has been called akasha in India and quintessence in Europe.


The concept of the five elements formed a basis of analysis in both Hinduism and Buddhism. In Hinduism, particularly in an esoteric context, the four states-of-matter describe matter, and a fifth element describes that which was beyond the material world. Similar lists existed in ancient China and Japan. In Buddhism the four great elements, to which two others are sometimes added, are not viewed as substances, but as categories of sensory experience.




A Greek text called the Kore Kosmou ("Virgin of the World") ascribed to Hermes Trismegistus (associated with the Egyptian god Thoth), names the four elements fire, water, air, and earth. As described in this book:


And Isis answer made: Of living things, my son, some are made friends with fire, and some with water, some with air, and some with earth, and some with two or three of these, and some with all. And, on the contrary, again some are made enemies of fire, and some of water, some of earth, and some of air, and some of two of them, and some of three, and some of all. For instance, son, the locust and all flies flee fire; the eagle and the hawk and all high-flying birds flee water; fish, air and earth; the snake avoids the open air. Whereas snakes and all creeping things love earth; all swimming things love water; winged things, air, of which they are the citizens; while those that fly still higher love the fire and have the habitat near it. Not that some of the animals as well do not love fire; for instance salamanders, for they even have their homes in it. It is because one or another of the elements doth form their bodies' outer envelope. Each soul, accordingly, while it is in its body is weighted and constricted by these four.


According to Galen, these elements were used by Hippocrates in describing the human body with an association with the four humours: yellow bile (fire), black bile (earth), blood (air), and phlegm (water). Medical care was flexible and primarily about helping the patient stay in or return to his/her own personal natural balanced state.[4][citation needed]



Cosmic elements in Babylonia[edit]

In Babylonian mythology, the cosmogony called Enûma Eliš, a text written between the 18th and 16th centuries BC, involves four gods that we might see as personified cosmic elements: sea, earth, sky, wind. In other Babylonian texts these phenomena are considered independent of their association with deities,[5] though they are not treated as the component elements of the universe, as later in Empedocles.


From this important work Aristotle gives us two of his most remembered contributions. First, the Four Causes and also the Four Elements (earth, wind, fire and water). He uses these four elements to provide an explanation for the theories of other Greeks concerning atoms, an idea Aristotle considered absurd.




The following epigram is engraved on the tomb which houses Proclus and his master Syrianus:


"I am Proclus,

Lycian whom Syrianus brought up to teach his doctrine after him.

This tomb reunites both our bodies.

May an identical sojourn be reserved to our both souls!"


The Neoplatonic philosopher, Proclus, rejected Aristotle's theory relating the elements to the sensible qualities hot, cold, wet, and dry. He maintained that each of the elements has three properties. Fire is sharp, subtle, and mobile while its opposite, earth, is blunt, dense, and immobile; they are joined by the intermediate elements, air and water, in the following fashion:[25]


Fire Sharp Subtle Mobile

Air Blunt Subtle Mobile

Water Blunt Dense Mobile

Earth Blunt Dense Immobile




In Bön or ancient Tibetan philosophy, the five elemental processes of earth, water, fire, air and space are the essential materials of all existent phenomena or aggregates. The elemental processes form the basis of the calendar, astrology, medicine, psychology and are the foundation of the spiritual traditions of shamanism, tantra and Dzogchen.


Tenzin Wangyal Rinpoche states that


physical properties are assigned to the elements: earth is solidity; water is cohesion; fire is temperature; air is motion; and space is the spatial dimension that accommodates the other four active elements. In addition, the elements are correlated to different emotions, temperaments, directions, colors, tastes, body types, illnesses, thinking styles, and character. From the five elements arise the five senses and the five fields of sensory experience; the five negative emotions and the five wisdoms; and the five extensions of the body. They are the five primary pranas or vital energies. They are the constituents of every physical, sensual, mental, and spiritual phenomenon.[26]


The names of the elements are analogous to categorised experiential sensations of the natural world. The names are symbolic and key to their inherent qualities and/or modes of action by analogy. In Bön the elemental processes are fundamental metaphors for working with external, internal and secret energetic forces. All five elemental processes in their essential purity are inherent in the mindstream and link the trikaya and are aspects of primordial energy. As Herbert V. Günther states:


Thus, bearing in mind that thought struggles incessantly against the treachery of language and that what we observe and describe is the observer himself, we may nonetheless proceed to investigate the successive phases in our becoming human beings. Throughout these phases, the experience (das Erlebnis) of ourselves as an intensity (imaged and felt as a "god", lha) setting up its own spatiality (imaged and felt as a "house" khang) is present in various intensities of illumination that occur within ourselves as a "temple." A corollary of this Erlebnis is its light character manifesting itself in various "frequencies" or colors. This is to say, since we are beings of light we display this light in a multiplicity of nuances.[27]


In the above block quote the trikaya is encoded as: dharmakaya "god"; sambhogakaya "temple" and nirmanakaya "house".





Seventeenth century alchemical emblem showing the four Classical elements in the corners of the image, alongside the tria prima on the central triangle

The elemental system used in Medieval alchemy was developed primarily by the Persian alchemist Jābir ibn Hayyān (Geber).[28] His system consisted of the four classical elements of air, earth, fire, and water, in addition to two philosophical elements: sulphur, characterizing the principle of combustibility, "the stone which burns"; and mercury, characterizing the principle of metallic properties. They were seen by early alchemists as idealized expressions of irreducibile components of the universe[29] and are of larger consideration within philosophical alchemy.


The three metallic principles—sulphur to flammability or combustion, mercury to volatility and stability, and salt to solidity—became the tria prima of the Swiss alchemist Paracelsus. He reasoned that Aristotle’s four element theory appeared in bodies as three principles. Paracelsus saw these principles as fundamental and justified them by recourse to the description of how wood burns in fire. Mercury included the cohesive principle, so that when it left in smoke the wood fell apart. Smoke described the volatility (the mercurial principle), the heat-giving flames described flammability (sulphur), and the remnant ash described solidity (salt).[30]



[icon] This section needs expansion. You can help by adding to it. (December 2016)

The Islamic philosophers al-Kindi, Avicenna and Fakhr al-Din al-Razi connected the four elements with the four natures heat and cold (the active force), and dryness and moisture (the recipients).[31]




Main article: Five elements (Japanese philosophy)

Japanese traditions use a set of elements called the 五大 (godai, literally "five great"). These five are earth, water, fire, wind/air, and void. These came from Indian Vastu shastra philosophy and Buddhist beliefs; in addition, the classical Chinese elements (五行, wu xing) are also prominent in Japanese culture, especially to the influential Neo-Confucianists during the medieval Edo period.


Earth represented things that were solid.

Water represented things that were liquid.

Fire represented things that destroy.

Air represented things that moved.

Void or Sky/Heaven represented things not of our everyday life.

Western astrology[edit]


Main article: Astrology and the classical elements

Western astrology uses the four classical elements in connection with astrological charts and horoscopes. The twelve signs of the zodiac are divided into the four elements: Fire signs are Aries, Leo and Sagittarius, Earth signs are Taurus, Virgo and Capricorn, Air signs are Gemini, Libra and Aquarius, and Water signs are Cancer, Scorpio, and Pisces.[32]


Modern [edit]

See also: Chemical element § History

The Aristotelian tradition and medieval Alchemy eventually gave rise to modern scientific theories and new taxonomies. By the time of Antoine Lavoisier, for example, a list of elements would no longer refer to classical elements.[33] Some modern scientists see a parallel between the classical elements and the four states of matter: solid, liquid, gas and weakly ionized plasma.[34]


Modern science recognizes classes of elementary particles which have no substructure (or rather, particles that are not made of other particles) and composite particles having substructure (particles made of other particles).


Astrology and the classical elements

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New millennium astrological chart


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Astrology has used the concept of classical elements from antiquity up until the present. In Western astrology and Indian astrology four elements are used, namely Fire, Earth, Air and Water.


Contents [hide]

1 Western astrology

1.1 Elements in classical astrology

1.1.1 Triplicity rulerships

1.1.2 Triplicities by season

1.2 Elements in modern astrology

2 Indian astrology

3 Chinese astrology

4 Notes

5 References

Western astrology[edit]

Main article: Triplicity


Four Classical Elements; this classic diagram has two squares on top of each other, with the corners of one being the classical elements, and the corners of the other being the properties

In Western tropical astrology, there are always 12 astrological signs. Each of the four elements is associated with 3 signs of the Zodiac which are always located exactly 120 degrees away from each other along the ecliptic and said to be in trine with one another. Most modern astrologers use the four classical elements extensively, (also known as triplicities) and indeed it is still viewed as a critical part of interpreting the astrological chart.


Beginning with the first sign Aries which is a Fire sign, the next in line Taurus is Earth, then to Gemini which is Air, and finally to Cancer which is Water. This cycle continues on twice more and ends with the twelfth and final astrological sign, Pisces. The elemental rulerships for the twelve astrological signs of the zodiac (according to Marcus Manilius) are summarised as follows:


Fire — 1 - Aries; 5 - Leo; 9 - Sagittarius - hot, dry, ardent

Earth — 2 - Taurus; 6 - Virgo; 10 - Capricorn - heavy, cold, dry

Air — 3 - Gemini; 7 - Libra; 11 - Aquarius - light, hot, wet

Water — 4 - Cancer; 8 - Scorpio; 12 - Pisces - cold, wet, soft

Elements in classical astrology[edit]

Triplicity rulerships[edit]

In traditional astrology, each triplicity has several planetary rulers, which change with conditions of sect – that is, whether the chart is a day chart or a night chart. Triplicity rulerships are an important essential dignity – one of the several factors used by traditional astrologers to weigh the strength, effectiveness and integrity of each planet in a chart.


Triplicity rulerships (using the "Dorothean system") are as follows:[1]


Triplicity Rulerships

Triplicity Day Ruler Night Ruler Participating Ruler

Fire (Aries, Leo, Sagittarius) Sun Mars Mars

Earth (Taurus, Virgo, Capricorn) Venus Moon Venus

Air (Gemini, Libra, Aquarius) Saturn Mercury Jupiter

Water (Cancer, Scorpio, Pisces) Venus Jupiter Moon

"Participating" rulers were not used by Ptolemy, as well as some subsequent astrologers in later traditions who followed his approach.


Triplicities by season[edit]

In ancient astrology, triplicities were more of a seasonal nature, so a season was given the qualities of an element, which means the signs associated with that season would be allocated to that element. The seasonal elements of ancient astrology are as follows:


Spring (wet becoming hot) - Air - Aries, Taurus, Gemini

Summer (hot becoming dry) - Fire - Cancer, Leo, Virgo

Autumn (dry becoming cold) - Earth - Libra, Scorpio, Sagittarius

Winter (cold becoming wet) - Water - Capricorn, Aquarius, Pisces

Using the seasonal qualities accounts for the differences in expression between signs of the same element. All the fire signs are by their nature hot and dry. However, the addition of the elemental qualities of the seasons results in differences between the fire signs. Leo being the midsummer sign gets a double dose of hot and dry and is the pure fire sign, but Aries being a Spring sign is wetter (hot & dry, hot & wet), and Sagittarius being an Autumnal sign is colder (hot & dry, cold & dry).


In the Southern Hemisphere the seasonal cycle is reversed.[2]


This yields secondary and tertiary elements for each sign.


Sign Element Qualities Season: North Season: South

Aries Fire Hot & Dry Hot & Wet (Spring/Air) Cold & Dry (Autumn/Earth)

Taurus Earth Cold & Dry Hot & Wet (Spring/Air) Cold & Dry (Autumn/Earth)

Gemini Air Hot & Wet Hot & Wet (Spring/Air) Cold & Dry (Autumn/Earth)

Cancer Water Cold & Wet Hot & Dry (Summer/Fire) Cold & Wet (Winter/Water)

Leo Fire Hot & Dry Hot & Dry (Summer/Fire) Cold & Wet (Winter/Water)

Virgo Earth Cold & Dry Hot & Dry (Summer/Fire) Cold & Wet (Winter/Water)

Libra Air Hot & Wet Cold & Dry (Autumn/Earth) Hot & Wet (Spring/Air)

Scorpio Water Cold & Wet Cold & Dry (Autumn/Earth) Hot & Wet (Spring/Air)

Sagittarius Fire Hot & Dry Cold & Dry (Autumn/Earth) Hot & Wet (Spring/Air)

Capricorn Earth Cold & Dry Cold & Wet (Winter/Water) Hot & Dry (Summer/Fire)

Aquarius Air Hot & Wet Cold & Wet (Winter/Water) Hot & Dry (Summer/Fire)

Pisces Water Cold & Wet Cold & Wet (Winter/Water) Hot & Dry (Summer/Fire)

These associations are not given any great importance in modern astrology, although they are prominent in modern Western neopaganism, druidism and wicca


Elements in modern astrology[edit]

In modern astrology each of the elements are associated with different astrological signs.[3]


Element Signs

Fire Aries, Leo, Sagittarius

Earth Taurus, Virgo, Capricorn

Air Gemini, Libra, Aquarius

Water Cancer, Scorpio, Pisces

Indian astrology[edit]

Further information: Hindu astrology


Zodiac symbols (Indian astrology) on the terrace of a temple in Kanipakam, Andhra Pradesh

Indian astrology shares the same system as Western astrology of linking zodiac signs to elements.


In addition, in Vedic thought each of the five planets are linked to an element (with ether as the fifth). It was said in the Veda that everything emanated from the one basic vibration of "Om" or "Aum." From "Om" the five elemental vibrations emerged representing the five different tattwas (or elements). The five planets represent these five vibrations – Jupiter for Ether, Saturn for Air, Mars for Fire, Mercury for Earth, and Venus for Water.


Chinese astrology[edit]

Main article: Wu Xing

In many traditional Chinese theory field, matters and its developmental movement stage can be classified into the Wu Xing. They are Wood ruler Jupiter, Green, East and Spring, Fire ruler Mars, Red, South and Summer, Earth ruler Saturn, Yellow, Center and Last Summer, Metal ruler Venus, White, West and Autumn and Water ruler Mercury, Black, North and Winter. Note that the Wu Xing are chiefly an ancient mnemonic device for systems with 5 stages, rather than the notion of different kinds of material. For further information, see Wu Xing.



aPtolemy[4] later modified the rulerships of Water triplicity, making Mars the ruler of the water triplicity for both day and night charts—and William Lilly concurred.[5]

The universe's 94 naturally occurring chemical elements are thought to have been produced by four cosmic processes. Most of the hydrogen and helium in the universe was produced primordially in the first few minutes of the Big Bang. Three recurrently occurring later processes are thought to have produced the remaining elements. Stellar nucleosynthesis, an ongoing process, produces all elements from carbon through iron in atomic number, but little lithium, beryllium, or boron. Elements heavier in atomic number than iron, as heavy as uranium and plutonium, are produced by explosive nucleosynthesis in supernovas and other cataclysmic cosmic events. Cosmic ray spallation (fragmentation) of carbon, nitrogen, and oxygen is important to the production of lithium, beryllium and boron.




Nuclear fuel cycle begins when uranium is mined, enriched and manufactured to nuclear fuel (1) which is delivered to a nuclear power plant. After usage in the power plant the spent fuel is delivered to a reprocessing plant (if fuel is recycled) (2) or to a final repository (if no recycling is done) (3) for geological disposition. In reprocessing 95% of spent fuel can be recycled to be returned to usage in a nuclear power plant (4).



A thorium atom has 90 protons and therefore 90 electrons, of which four are valence electrons.






Tor's Fight with the Giants (1872) by Mårten Eskil Winge, depicting an artist's perception of Thor, the Norse god of thunder, raising his hammer in a battle against the giants.[70]



There are four commonly recognized tidal “zones” based on exposure during tidal periods, wave action and shoreline features. The presence or absence of water, temperature, wave action, variation in salinity (saltiness), exposure to light, and other factors determine what organisms are able to live happily in each zone. In general, physical factors, especially exposure to drying, limit how far up on shore an organism can live. An organism’s lower limit is often determined by competition or predators living in the lower zone.

Because a tidepool may hold water even during a low tide, a pool may provide suitable habitat for organisms that would normally be found in a lower zone. Giant green anemones and hermit crabs, for example, are generally found in the mid and low intertidal, but may be found in tidepools higher up.

Some organisms have a narrow range of tolerance for environmental factors and are found only in one zone, while others have a greater tolerance and are found in several zones.

intertidal zones

Spray or Splash Zone: This area extends from the highest reach of spray and storm waves to the average height of the high tides. It is usually dry, and relatively few types of organisms can live here. Species found in the splash zone might include: small barnacles, periwinkles and ribbed limpets.

Upper or High Intertidal Zone: This zone includes the area from the average high tide to just below the average sea level (i.e., covered only by the highest tides). Species found in the high intertidal zone might include: acorn barnacles, hermit crabs, shore crabs, black turban snails,aggregating anemones, sea lettuce, and rockweeds.

Mid Intertidal Zone: This zone extends from just below average sea level to the upper limit of the average lowest tides (i.e., it is exposed at low tides-usually twice a day). In a healthy intertidal area, this zone is rich both in diversity and numbers of organisms. There is generally a dense cover of algae, providing food and shelter for many animals. Species found in the middle intertidal zone might include: California mussels, giant green anemone, ochre sea star, black leather chitons, gooseneck barnacles, coralline algae, sea palms, and sponges.

Low Intertidal Zone: This zone is exposed to the air only at the lowest tides. Species found in the lower intertidal zone might include: gumboot chiton, ochre sea star, kelp crabs, blue top snail, purple sea urchin, feather boa kelp, nudibranchs and sponges.

Subtidal: Subtidal organisms that you are likely to encounter (sometimes washed up on the beach) include bull kelp, many bottom-dwelling invertebrates, and various fish. Sunflower sea stars tend to occur subtidally but occasionally will come up higher into the low tide zone.


I discussed there are four camps on Mt Everest


This articel has been adapted from our classroom textbook, GEOGRAPHY ALIVE! Regions and People by Diane Hart.

We have learned that the Andes Mountains of South America are divided into four different altitudinal zones, which are shown in the diagram below:

Life in each zone is very different. Whether you are looking at human life, or plant life, or even how the air is different. The zones are all unique. Each article below highlights one of the four zones, providing details on physical characteristics, human adaptations, and overall, the unique differences between each zone.


Imagine you are a worker picking bananas on a plantation in Ecuador. The temperature is very high, so you must stop very frequently to wipe the sweat from your brow. You also must watch out for spiders, because tarantulas often hide within the banana stalks. A tarantula bite may not be deadly, but it is EXTREMELY painful.

This banana plantation is located in the tierra caliente. Consisting mostly of the tropical lowlands, its elevation zone lies at the bottom of the Andes Mountains on both the eastern and western sides. People who live in tierra caliente must adapt to a hot year-round climate.

PHYSICAL CHARACTERISTICS: The tierra caliente is the lowest of the four elevation zones in the Andes Mountains, extending from sea level to about 3,000 feet. The climate of this zone is generally hot and humid, with the average temperature ranging around 75 to 80 degrees.

Broadleaf evergreen forests cover the eastern slopes of the Andes Mountains heading into the Amazon River basin. On the western side of the Andes, the natural vegetation ranges from lush rainforests to tropical grasslands.

HUMAN ADAPTATIONS: The tropical heat of the tierra caliente can make it a very difficult place to live. As a result, the area is less populated than cooler, higher elevation zones. Some inhabitants are descended from the Africans who were brought by the Spanish to labor on large plantations as slaves. Indigenous peoples also live in some parts of the tropical rainforest.

People in this elevation zone have adapted to life within the tropics. Farmers plant crops that can do well in the heat, with some of the most common crops being bananas, rice, and sugarcane. People dress in light clothing, and they live in houses that are open to the cooling breezes. Their houses are often made of bamboo or wood, with palm-thatch roofs. Some homes are raised on stilts to provide protection against flooding.


In the rolling hills of Ecuador's tierra templada, gardeners raise flowers, tending to long rows of carnations, daisies and roses. The flowers they grow will eventually be shipped to buyers thousands of miles away. In fact, many of the roses enjoyed by Americans on Valentine's Day come from Ecuador because the mild weather of Ecuador provides the perfect climate for cultivating and growing flowers.

PHYSICAL CHARACTERISTICS: The tierra templada is the second elevation zones of the Andes Mountains. It lies between 3,000 and 6,000 feet above sea level. At these elevations, the climate is temperate, with temperatures at around 65 to 75 degrees. There is rarely any frost. This pleasant weather lasts throughout the year, which is why people often call the tierra templada "The Land of Eternal Spring."

Vegetation changes with the elevation in this zone. At the lower elevations, tropical plants such as bamboo, palms, and jungle vines are quite common. At the higher elevations, broadleaf evergreen forests are typical.

HUMAN ADAPTATIONS: The mild climate in the tierra templada makes it a great place to live. Because of this, the tierra templada zone is more populated than the tierra caliente. Many of the people who live here are called MESTIZOS- which are a mixture of indigenous and European peoples. Europeans influences are common in the tierra templada.

Farmers in this zone choose their crops based on elevation. At lower levels, they grow heat-loving crops like bananas and oranges. The main crop of this zone is coffee, because the conditions of the tierra templada make it excellent for growing high-quality coffee beans. Most coffee beans are grown on small farms or plantations.

People who live in the tierra templada adapt their housing and their clothing to the comfortable climate. They live in solid homes made of concrete brick and are covered with tiled roofs. More wealthy residents may live in large homes called HACIENDAS.

TIERRA FRIA: "Cold Country"

A woman rises early in the highland city of Cuzco, Peru. This is tierra fria, and the morning air is very cold. The woman puts on a warm sweater and shawl and heads off to the market to buy food, walking down ancient stone streets that were built by her ancestors, the Incas. A light frost ont he stones makes them slippery, so she is careful. She is used to living life this way in the highlands.

PHYSICAL CHARACTERISTICS: Tierra fria covers most of the Central Andes Mountains, with an elevation of about 6,000 to 12,000 feet above sea level. Average temperatures here vary from about 55 degrees to 65 degrees. Nights are always colder. The temperatures can often reach below freezing at higher elevations.

Mountains and valleys are the main characteristics of the tierra fria zone. The mountains are steep and rugged, but plateaus are also very common.

A high plateau called the Altiplano lies at an average elevation of 11,000 feet between Peru and Bolivia. This Plateau contains Lake Titicaca, one of the world's highest navigable lakes. This is lake that is large and deep enough for bigger boats.

Elevation also affects what can grow where: the tree line in this zone lies between 10,000 and 12,000 feet. The tree line is important because it marks the highest elevation at which trees will grow.

HUMAN ADAPTATIONS: Half of the population that lives here are indigenous peoples. The two main groups are the Quechua and the Aymara. Both of these groups were once a main part of the Incan Empire.


Over the centuries, native peoples have adapted to life at higher elevations. They wear warm woolen clothing to protect themselves from the cold. They also build thick-walled homes out of ADOBE brick. Their bodies have even adapted to high elevations, as they develop larger lungs that can draw more oxygen from the thin mountain air.

Farmers grow crops that do well at high elevations, including potatoes, wheat, barley, corn, apples and pears.

Another common practice within the Andes Mountains is vertical trade, which is the trading of farm products between higher and lower elevations. Since not all crops can be grown in both, this helps the different elevation zones receive necessary items that grow within the different zones. Through veritcal trade, people who live in one elevation zone have access to foods grown in other elevation zones.

TIERRA HELADA: "Frost Country"

Every year, Quechua Indians hike to a shrine in the mountains that is high above the city of Cuzco. They travel there to worship the APUS, which are "mountain gods." "We make offerings to the mountains," says one pilgrim, "asking them to send water for our crops and livestock."

The shrine above Cuzco is in the tierra helada, the highest elevation zone of the Andes Mountains. The pilgrims who make this journey have to be careful to walk slowly because the air is very thin. If people move too quickly at this high elevation, they may experience altitude sickness from a lack of oxygen. Altitude sickness can cause headaches, fatigue, shortness of breath, and nausea.

PHYSICAL CHARACTERISTICS: The tierra helada lies between 12,000 and 15,000 feet. Average temperatures vary between 20 degrees and 55 degrees. The tierra helada region is a very extreme environment. Climate is very cold and windy, it often freezes at night, and snow falls at higher elevations regularly. At the upper edge of this zone is the snow line, which is the elevation where permanent snow and ice begin. Above the snow line, snow remains on the ground year round.

HUMAN ADAPTATIONS: It is very challenging to live in the tierra helada region. This is why very few people live at these extreme elevations. Most of the people who live here are indigenous people, like the Quechua and Aymara. People have adapted to life in the tierra helada through various ways. Like in the tierra fria, they dress in warm clothing mostly year round. They plant the few crops that will grow at high elevations, which include a native grain called QUINOA and certain types of potatoes. They also reaise llamas and alpacas, two types of animals related to the camel. Llamas and alpacas produce thick wool for blankets, bags, and clothing. Llamas also make good pack animals for transporting heavly loads across the mountains.

Some people who live in this elevation zone work in mines because the high Andes have several large mineral deposits like lead, copper and silver. Working conditions in the mine are quite dangerous, but it does provide one of the few sources of income for residents of the tierra helada.

People generally do not live above the snow line, but it is an important area because of glaciers. Glaciers are large ice fields that store large amounts of fresh water. in the summer, water melts from the glaciers and eventually flows down to the people living at lower elevations. Streams that are fed by these glaciers form a crucial part of the water supply.


The four zones are quite different and unique due to elevation, and depending on personal preference, each zone can and does provide a way of life for individuals seeking opportunity in the Andes Mountains. As time goes on and human adaptations continue, we may expect to see many changes taking place within this region of South America, as humans continually learn to adapt to this way of life and this territory of the earth. 


All of this stuff is in my books

The United States was divided into four time zones on November 18, 1883, and jurisdiction for the zones was given to the Interstate Commerce Commission (ICC). All places keep the same time within each time zone. The zones in the United States were intended to represent the mean times of four different meridians (not including daylight saving time):

Eastern Standard Time (EST).

Central Standard Time (CST).

Mountain Standard Time (MST).

Pacific Standard Time (PST).




DESCRIPTION: It appears to have been the grammarian Crates of Mallos, a contemporary of Hipparchus, and a member of the Stoic School of Philosophers, who made the first attempt to construct a terrestrial globe, and that he exhibited the same in Pergamum, not far from the year 150 B.C. It seems to have been Crates’ idea that the earth’s surface, when represented on a sphere, should appear as divided into four island-like habitable regions. On the one hemisphere, which is formed by a meridional plane cutting the sphere, lies our own oikumene, or habitable world, and that of the Antoecians in corresponding longitude and in opposite latitude; on the other hemisphere lies the oikumene of the Perioecians in our latitude and in opposite longitude, and that of the Antipodes in latitude and longitude opposite to us. Through the formulation and expression of such a theory the idea of the existence of an antipodal people was put forth as a speculative problem, an idea frequently discussed in the Middle Ages (see #207 in Book IIA), and settled only by the actual discovery of antipodal regions and antipodal peoples in the day of great transoceanic discoveries.

The illustrations contained herein show modern reconstructions of the globe of Crates of Mallos. The various measurements of the earth’s size by Eratosthenes raised a curious problem. The known dimensions of the oikumene [inhabited world] were too small relative to the estimated size of the earth sphere, the oikumene occupied only one quadrant of the sphere. Such an imbalance in a spherical object was contrary to the Greek sense of symmetry. Crates, therefore, solved the problem on his globe by drawing three other “continents” (an anticipation/prediction of the existence of the Americas, all of Africa, Antarctica and Australia) to provide the necessary “balance” and symmetry. Here was born the concept of the Antipodes, or the great southern continent, the Terra Australis, that would be conjured up in medieval and renaissance period maps.

Crates, who wrote among other things on Homer and the wanderings of Odysseus, visited Rome. He was professionally interested in the city’s drainage system, but while exploring the Cloaca Maxima broke his leg. He used the period of recovery to give lectures in Rome, which are said to have created a great impression. His view of terrestrial mapping was that the shape could only be right if it was drawn on a globe, and eventually that the scale could only be effective if the globe was at least ten feet in diameter. In designing his ‘orb’, if indeed he put his theory into practice, Crates favored an unusual form of symmetry. There were, he said, separated by two intersecting belts of ocean, four symmetrical landmasses: (a) the known oikoumene, including its three continents Europe, Asia and the part of Africa known at that time; (b) the land of the Antoikoi [those who live opposite], parallel to the oikoumene in the southern hemisphere south of them; (c) west of them, the Perioikoi, [those who live around], parallel to the oikoumene on the western part of the globe; (d) south of the Perioikoi, the Antipodes [opposite feet], parallel to the Perioikoi in the southern hemisphere. The break between the landmass known at that time and that of the Antoikoi came, according to him, at a belt on each side of the equator, and there were Ethiopians (Aethiopes, ‘black-faces’) on each side of this water divide. Homer had written of the Ethiopians, split in two, some in the East, some by the setting sun. Later Greek writers interpreted this passage in various ways. No doubt, as a Homeric scholar, Crates was more concerned to give a plausible account of Homeric descriptions than to investigate explanations which suggested the existence of a continuous African landmass stretching across the equator. The idea however, was taken up by Cicero in the Somnium Scipionis [Dream of Scipio], which he incorporated in his De republica. When Macrobius wrote a commentary on the Somnium Scipionis about AD 390, he defended and amplified Crates’ theory, aspects of which thus found their way into medieval cartography; the Perioikoi and Antipodes were then omitted, although discussed by Cicero and Macrobius (see monograph #201 in Book IIA).

Pliny the Elder promoted this idea and suggested that the entire sphere was inhabited, including the Antipodes, although this raised a new problem:

Human beings are distributed all round the earth and stand with their feet pointing toward each other, and the top of the sky is alike for them all and the earth trodden under foot at the center in the same way from any direction, while ordinary people enquire why the persons on the opposite side do not fall off - just as if it were not reasonable that the people on the other side wonder that w do not fall off. (Plin. HN 2.161)

Such ideas remained purely academic, and were produced by intellectuals exploring scientific premises and conclusions. At the same time, however they inflamed the popular imagination.

It seems to have been Crates’ idea that the earth’s surface, when represented on a sphere, should appear as divided into four island-like habitable regions. On the one hemisphere, which is formed by a meridional plane cutting the sphere, lies our own oikumene, and that of the Antoecians in corresponding longitude and in opposite latitude; on the other hemisphere lies the oikumene of the Perioecians in our latitude and in opposite longitude, and that of the Antipodes in latitude and longitude opposite to us. Through the formulation and expression of such a theory the existence of an antipodal people was put forth as a speculative problem, an idea frequently discussed in the Middle Ages, and settled only by the actual discovery of antipodal regions and antipodal peoples in the day of great transoceanic discoveries of the 17th and 18th centuries.

A belief in the existence of antipodal peoples, very clearly was also accepted by Pythagoras, Eratosthenes, Posidonius, Aristotle, Strabo, and later Capella. Numerous others presupposed the earth to be globular in shape. [see Kretschmer, K., Die physische Erdkunde im christlichen Mittelalter, Wien, 1889, pp. 54-59, wherein the author gives consideration to the doctrine of the Antipodes as held in the Middle Ages]. Berger, Geschichte, pt. 3, p. 129, notes that the idea of the earth’s division into four parts or quarters persisted for centuries after Crates’ day, if not among scientific geographers, at least among those who could be said to have possessed general culture. Cleomedes, Ampelius, Nonnus, and Eumenius mention the idea as one to be accepted.

Narrowing our focus, we now consider the geographical divisions within the oikoumene. The Greeks recognized three continents within the inhabited world: Europe and Asia first, and then Lybia [Africa]. Hypotheses about other continents beyond the Ocean, for example Plato’s lost Atlantis — were mere fantasies. How did the concept of a continent deve1op? The basic distinction that emerges from the earliest Greek sources is between land and sea. This distinction was then refined to include a differentiation between mainland and islands, reflecting a mental opposition between territorial connectivity and isolation. Giving specific names to larger landmasses eventually yielded the three individual continents as the ancients knew them. There was thus nothing essentially unique about a continent in comparison to any other topographical unit, and in particular to large islands such as Sicily, Crete and Euboca. As islands had names, so too did continents, which were defined geographically by topographic features marking their limits, even if there were occasional arguments about the exact location of these limits. A continent’s precise borders were not always agreed, particularly as some authors were aware of earlier geological situations. For example, C. Acilius (fl. 155 BCE), a Roman historian writing in Greek, explained that Sicily was part of the mainland in prehistoric times, but that a flood had made it separate. Even when the division was permanent, there were different methods for defining borders between continents.

It was thought that Africa did not extend to the equator, or at least was not habitable to the equator. Below the equator there was thought to be water but beyond the uninhabitable and impassable torrid zone, a habitable region existed. The map of Lambertus (see monograph #217 in Book IIB) well represents this early theory. Pomponius Mela (#116) called the inhabitants of this southern region Antichthoni, their country being unknown to us because of the torrid zone intervening. Pliny, and after him Solinus, says that for a long time the island of Taprobana [Ceylon/Sri Lanka] was thought to be the region occupied by the Antichthoni.

That Strabo (#115), at a later date, had this Pergamenian example in mind when stating certain rules to be observed in the construction of globes seems probable, since he makes mention of Crates’ globe. Strabo alone among ancient writers, so far as we at presently know, treats terrestrial globes practically. He thought that a globe to be serviceable should be of large size, and his reasoning can readily be understood, for what at that time was really known of the earth’s surface was small indeed in comparison with what was unknown. Should one not make use of a sphere of large dimensions, the habitable regions in comparison with the earth’s entire surface, would occupy but small space. What Strabo states in his geography is interesting and may here well be cited.

Whoever would represent the real earth as near as possible by artificial means, should make a sphere like that of Crates, and upon this draw the quadrilateral within which his chart of geography is to be placed. For this purpose however a large globe is necessary since the section mentioned, though but a very small portion of the entire sphere, must be capable of containing properly all the regions of the habitable earth and of presenting an accurate view of them to those who wish to consult it. Anyone who is able will certainly do well to obtain such a globe. But it should have a diameter of not less than ten feet; those who cannot obtain a globe of this size, or one nearly as large, had better draw their charts on a plane surface of not less than seven feet. Draw straight lines for the parallels, and others at right angles to these. We can easily imagine how the eye can transfer the figure and extent (of these lines) from a plane surface to one that is spherical. The meridians of each country on the globe have a tendency to unite in a single point at the poles; nevertheless on the surface of a plane map there would be no advantage if the right lines alone which should represent the meridians were drawn slightly to converge.

Crates’ motive for his cartography was partly literary, interpreting Ulysses’ wanderings, and partly historical, rather than purely scientific. As a Stoic, he proclaimed Homer the founder of geography, crediting him with belief in a spherical earth and commenting on his poems accordingly. To explain Homer’s line, “The Ethiopians who dwell sundered in twain, the farthermost of men”, Crates argued that on each side of an equatorial ocean there lived the Ethiopians, divided by the ocean, one group in the Northern Hemisphere, the other group in the Southern, without any interchange between them. Again Strabo reports:

Crates, following the mere form of mathematical demonstration, says that the torrid zone is “occupied” by Oceanus, and that on both sides of this zone are the temperate zones, the one being on our side, while the other is on the opposite side of it. Now, just as these Ethiopians on our side of Oceanus, who face the south throughout the whole length of the inhabited world, are called the most remote of the one group of peoples, since they dwell on the shores of Oceanus, so too, Crates thinks, we must conceive that on the other side of Oceanus also there are Ethiopians, the most remote of the other group of peoples in the temperate zone, since they dwell on the shores of this same Oceanus.

The scientific thinking behind the geography of Crates’ globe was derived directly from the teaching of Eratosthenes about the relative size of the known world. By combining the geometric approach of his predecessor with his own interpretation of Homer (#105), he represented four inhabited worlds on the surface of his terrestrial globe. Two were in the Northern Hemisphere, the one where the Greeks lived, occupying far less than half of the Northern Hemisphere, and another symmetrically situated in the other half. Two other inhabited worlds are found in the Southern Hemisphere, symmetrical with the two north of the equator. These four worlds were separated by oceans along the equator (occupying the torrid zone made uninhabitable by heat) and along a meridian. The inhabited areas were thus islands, with no communication between them.

It is clear that this concept of four symmetrical land areas was a direct consequence of the geometry of the sphere and the size Eratosthenes attributed to the inhabited world in relation to the total globe. Crates demonstrated this by drawing the four areas on the surface of his globe and suggesting that the three unknown lands could be similar to the known one. To give it further credibility, he also drew in the main parallel circles, emphasizing those defining the zones: these were the tropics (at 24° distance from the equator), between which flowed the Ocean as envisaged by Homer, and the two polar circles (at 66° distance from the equator).

Crates’ globe was thus a product of theoretical mathematical cartography, communicating an image of the world that was very far from reality. Our understanding of the globe’s physical characteristics is meager, and there is no evidence to suggest how or of what material it was made, but its influence on the history of cartographic thought has been considerable. The concept of the equatorial ocean was transmitted to medieval Europe through Macrobius’ commentary on Cicero’s Dream of Scipio (#201). Scholars of later times also vied eagerly to give adequate names to these unknown worlds, but on the whole they did not doubt their existence.

The Yellowstone Plateau volcanic field is composed of four adjacent calderas.



Ascraeus Mons was discovered by the Mariner 9 spacecraft in 1971. The volcano was originally called North Spot[2] because it was the northernmost of only four spots visible on the surface due to a global dust storm that was then enshrouding the planet. As the dust cleared, the spots were revealed to be extremely tall volcanoes whose summits had projected above the dust-laden, lower atmosphere.[3] The volcano's name officially became Ascraeus Mons in 1973.[1]

Excerpt from book QMR
The four seasons fit the quadrant model.
*Square one: Spring; the first square is birth
*Square two: Summer, associated with being a very pleasant, social time--the second quadrant is about relationships and life; it is the normal square.
*Square three: Fall; connoting destruction, causing leaves to fall, and life to hibernate; it is often seen as very different and unpleasant and destructive.
*Square four: Winter. The fourth square, represents death.



Scientists divided the atmosphere into four layers according to temperature: troposphere, stratosphere, mesosphere, and thermosphere. The temperature drops as we go up through the troposphere, but it rises as we move through the next layer, the stratosphere. The farther away from earth, the thinner the atmosphere gets.




This is the layer of the atmosphere closest to the Earth's surface, extending up to about 10-15 km above the Earth's surface. It contains 75% of the atmosphere's mass. The troposphere is wider at the equator than at the poles. Temperature and pressure drops as you go higher up the troposphere.


Q: Why is the troposphere wider at the equator than at the poles?


The Tropopause: At the very top of the troposphere is the tropopause where the temperature reaches a (stable) minimum. Some scientists call the tropopause a "thermal layer" or "cold trap" because this is a point where rising water vapour cannot go higher because it changes into ice and is trapped. If there is no cold trap, Earth would loose all its water!


Most of what we call weather occurs in the troposphere. The uneven heating of the regions of the troposphere by the Sun causes convection currents and winds. Warm air from Earth's surface rises and cold air above it rushes in to replace it. When warm air reaches the tropopause, it cannot go higher as the air above it (in the stratosphere) is warmer and lighter ... preventing much air convection beyond the tropopause. The tropopause acts like an invisible barrier and is the reason why most clouds form and weather phenomena occur within the troposphere.


greenhouse effect The Greenhouse Effect: Heat from the Sun warms the Earth's surface but most of it is radiated and sent back into space. Water vapour and carbon dioxide in the troposphere trap some of this heat, preventing it from escaping thus keep the Earth warm. This trapping of heat is called the "greenhouse effect".


However, if there is too much carbon dioxide in the troposphere then it will trap too much heat. Scientists are afraid that the increasing amounts of carbon dioxide would raise the Earth's surface temperature, bringing significant changes to worldwide weather patterns ... shifting in climatic zones and the melting of the polar ice caps, which could raise the level of the world's oceans.


Q: Why is the amount of carbon dioxide in the troposphere increasing?





ozone layer This layer lies directly above the troposphere and is about 35 km deep. It extends from about 15 to 50 km above the Earth's surface.


The stratosphere is warmer at the top than the bottom. The lower portion has a nearly constant temperature with height but in the upper portion the temperature increases with altitude because of absorption of sunlight by ozone. This temperature increase with altitude is the opposite of the situation in the troposphere.


14 October 2012: Austrian daredevil Felix Baumgartner made an extreme skydive from the edge of space, leaping off a capsule more than 24 miles (39 km) above the Earth ... that's in the stratosphere. At this extreme altitude and low air pressure, a tear or crack in his pressurized suit or helmet would cause instant depressurization and his blood to "boil". The latter is a condition called "ebullism" that could cause gas bubbles to form in bodily fluids; and blood literally boils.


Q: What is the relationship between atmospheric pressure and boiling point of a liquid?


The Ozone Layer: The stratosphere contains a thin layer of ozone molecules (with three oxygen atoms) which forms a protective layer shielding life on Earth from the Sun’s harmful ultraviolet radiation. But this ozone layer is being depleted, and is getting thinner over Europe, Asia, North American and Antarctica. "Holes" are appearing in the ozone layer.


Q: Why are there "ozone holes" in the stratosphere?








Directly above the stratosphere, extending from 50 to 80 km above the Earth's surface, the mesosphere is a cold layer where the temperature generally decreases with increasing altitude. Here in the mesosphere, the atmosphere is very rarefied nevertheless thick enough to slow down meteors hurtling into the atmosphere, where they burn up, leaving fiery trails in the night sky.





The thermosphere extends from 80 km above the Earth's surface to outer space. The temperature is hot and may be as high as thousands of degrees as the few molecules that are present in the thermosphere receive extraordinary large amounts of energy from the Sun. However, the thermosphere would actually feel very cold to us because of the probability that these few molecules will hit our skin and transfer enough energy to cause appreciable heat is extremely low.


The thermosphere corresponds to the heterosphere, a zone where there is no uniform distribution of gases. In other words, the gases are not well-mixed; instead they are stratified that is layered, in accordance to their molecular masses. In contrast, the gases in the homosphere (consisting of the troposphere, stratosphere and mesosphere) are uniformly distributed.


Q: Why are the gases in the thermosphere stratified?




Earth has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere.

I'm a paragraph. Click here to add your own text and edit me. It's easy.

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Powerade is a sports drink manufactured and marketed by The Coca-Cola Company. Its primary competitor is PepsiCo's Gatorade brands.

In 2008, Powerade was relaunched as Powerade ION4, a formulation that contains four key electrolytes in the same ratio that is typically lost in sweat.[1] PepsiCo sued The Coca-Cola Company, after ads were released claiming that Gatorade was an incomplete sports drink, since it only contained two of the four key electrolytes. The presiding judge ruled in favor of Coca-Cola, for a number of reasons: the ads were no longer running, Gatorade had made similar claims about their Endurance line, and Pepsi failed to show any harm or damage caused by the ads, which were only designed to run for sixty days.



The Earth consists of FOUR concentric layers: inner core, outer core, mantle and crust. The crust is made up of tectonic plates, which are in constant motion. Earthquakes and volcanoes are most likely to occur at plate boundaries.

The structure of the Earth

The Earth is made up of four distinct layers:

The inner core is in the centre and is the hottest part of the Earth. It is solid and made up of iron and nickel with temperatures of up to 5,500°C. With its immense heat energy, the inner core is like the engine room of the Earth.

The outer core is the layer surrounding the inner core. It is a liquid layer, also made up of iron and nickel. It is still extremely hot, with temperatures similar to the inner core.

The mantle is the widest section of the Earth. It has a thickness of approximately 2,900 km. The mantle is made up of semi-molten rock called magma. In the upper parts of the mantle the rock is hard, but lower down the rock is soft and beginning to melt.

The crust is the outer layer of the earth. It is a thin layer between 0-60 km thick. The crust is the solid rock layer upon which we live.



I was asked if there were any swastika shaped molecules in the cell. Sure.



That’s a potassium channel. Your brains are full of them.




Also depressing: google for laminin, and aside from the Wikipedia entry, the top references right now are all to Christian kooks babbling about this trivial shape story. What a sad fate for a developmentally and evolutionarily significant molecule that has roots right down at the base of the metazoan family tree. I cringe to see these loons abusing molecular biology to cheerlead for superstition.


I was asked if there were any swastika shaped molecules in the cell. Sure.



That’s a potassium channel. Your brains are full of them.




Rather chillingly, when you look at the PETN molecule in three dimensions, as is shown above, at a certain orientation of the central tetrahedral carbon, the molecule takes on the shape of a swastika.



PETN, or PentaErythritol TetraNitrate, crops up in the news from time to time as a high explosive, often used by terrorists.


PETN's molecular structure is shown above. A central carbon atom supports four identical chains, each of which ends in a nitrate group. The resulting structure has the formula C(CH2NO3)4. This form of the formula emphasizes the four identical chains which the molecule contains. You can also write the formula at C(CO2)4(N2)24(H2O)4, which emphasizes the fact the PETN molecule contains just the right ratios of carbon, nitrogen, and oxygen to form many gas molecules from each molecule of explosive.


Not only do PETN's constuents contain a host of small stable combustion products ready to be released by the appropriate detonator, the molecule is also somewhat strained, with four identical large side chains terminating at the central carbon atom.


So when suitably triggered, PETN rearranges rapidly, releasing CO2, H2O, and N2, and plenty of heat, as these products are more stable than the PETN molecule itself. The result can be a devastating explosion.


Hence, PETN has been emplolyed by several terrorists, including Abdulfarouk Umar Muttalab.


Rather chillingly, when you look at the PETN molecule in three dimensions, as is shown above, at a certain orientation of the central tetrahedral carbon, the molecule takes on the shape of a swastika.



The derivatives of ethylenediamine-N,N,N‘,N‘-tetraamides were prepared, and their crystal structures were analyzed in order to understand the variations in their molecular and supramolecular geometries with respect to the substituents. The crystal structures of these compounds indicated that these moieties can exhibit four types of molecular geometries. These geometries contain a minimum of two intramolecular N−H···N hydrogen bonds between the amine N-atom and N−H group of the amide. The p-bromophenyl, p-chlorophenyl, 3-pyridyl, and 4-pyridyl derivatives exhibit H-shape geometry, p-iodophenyl, p-toloyl, and 4-pyridyl derivatives exhibit similar geometrical shape, the 4-pyridyl derivative exhibited the geometry of the Greek character π, and the benzyl derivative exhibited the geometry of a SWASTIKA. Among the halogen derivatives, the iodo derivative was found to behave differently from bromo and chloro derivatives. The amide-to-amide hydrogen bonds between the iodo-substituted molecules were sacrificed in favor of inclusion of DMF.



Effect of Substituents on Molecular Geometry and Self-Aggregation in the Crystal Structures of Ethylenediamine-N,N,N‘,N‘-tetraamides (PDF Download Available). Available from: https://www.researchgate.net/publication/231230886_Effect_of_Substituents_on_Molecular_Geometry_and_Self-Aggregation_in_the_Crystal_Structures_of_Ethylenediamine-NNN%27N%27-tetraamides [accessed Mar 24, 2017].


TIL that Orthocarbonic Acid is called "Hitler's Acid" because its molecular geometry resembles a swastika (en.wikipedia.org)



Orthocarbonic acid (methanetetrol) is the name given to a hypothetical compound with the chemical formula H4CO4 or C(OH)4. Its molecular structure consists of a single carbon atom bonded to four hydroxyl groups. It would be therefore a fourfold alcohol. In theory it could lose four protons to give the hypothetical oxocarbon anion CO4−

4 (orthocarbonate), and is therefore considered an oxoacid of carbon.


Orthocarbonic acid is highly unstable, decomposing spontaneously into carbonic acid monohydrate:[2][3]


H4CO4 → H2CO3 + H2O.

Orthocarbonic acid is one of the group of carboxylic ortho acids that have the general structure of RC(OH)3.The term ortho acid is also used to refer to the most hydroxylated acid in a set of oxoacids. Its molecular geometry resembles a swastika, and is therefore called "Hitler's acid".[4]


Researchers at the Moscow Institute of Physics and Technology predict that orthocarbonic acid may occur in the interiors of Neptune and Uranus.[4]


TIL that Carlsberg beer used to have a Swastika (as a symbol of purity) in its logo. They removed it in 1940 after the Nazi’s appropriated it. via /r/todayilearned



TIL that Carlsberg beer used to have a Swastika (as a symbol of purity) in its logo. They removed it in 1940 after the Nazi’s appropriated it.



Four of the amphibole minerals are among the minerals commonly called asbestos. These are: anthophyllite, riebeckite, cummingtonite/grunerite series, and actinolite/tremolite series. The cummingtonite/grunerite series is often termed amosite or brown asbestos; riebeckite is known as crocidolite or blue asbestos. These are generally called amphibole asbestos.[3]

This guest blog features four of our favorite Oregon "QPR" (Quality-Price-Relationship) from the winter of 2009-2010. We have rated the wines on a hybrid system consisting of a standard 100-point rating as well as a rating relative to price. For example, if we felt a wine was a "90", and it cost $10 less than it tastes, we gave it a "90/+10", which is a great QPR score and ranks in the top right of the QPR chart:





Tetra Pak is a multinational food packaging and processing company of Swedish origin with head offices in Lund, Sweden, and Lausanne, Switzerland. The company offers packaging, filling machines and processing for dairy, beverages, cheese, ice-cream and prepared food, including distribution tools like accumulators, cap applicators, conveyors, crate packers, film wrappers, line controllers and straw applicators.[1]


Tetra Pak was founded by Ruben Rausing and built on Erik Wallenberg's innovation, a tetrahedron-shaped plastic-coated paper carton, from which the company name was derived.[2] In the 1960s and 1970s, the development of the Tetra Brik package and the aseptic packaging technology made possible a cold chain supply, substantially facilitating distribution and storage. From the beginning of the 1950s to the mid-1990s, the company was headed by the two sons of Ruben Rausing, Hans and Gad, who took the company from a family business of six employees, in 1954, to a multinational corporation.[3] Tetra Pak is currently the largest food packaging company in the world by sales, operating in more than 170 countries and with over 23,000 employees (2012).[4][5] The company is privately owned by the family of Gad Rausing through the Swiss-based holding company Tetra Laval, which also includes the dairy farming equipment producer DeLaval and the PET bottle manufacturer Sidel.[6] In November 2011, the Tetra Brik carton package was represented at the exhibition Hidden Heroes – The Genius of Everyday Things at the London Science Museum/Vitra Design Museum, celebrating "the miniature marvels we couldn’t live without".[7][8][9] The aseptic packaging technology has been called the most important food packaging innovation of the 20th Century by the Institute of Food Technologists and the Royal Swedish Academy of Engineering Sciences called the Tetra Pak packaging system one of Sweden’s most successful inventions of all time.[10][11]


Traditional Chinese medicine is a style of traditional Asian medicine building on a foundation of more than 2500 years of Chinese medical practice, which includes various forms of herbal medicine, acupuncture, massage, exercise, and dietary therapy. Astragali Radix is the most common herbal medicine on the market. Four major flavonoids, derived from Astragali Radix, formononetin, ononin, calycosin, and calycosin-7-O-β-d-glucoside, have been shown to be effective in regulating EPO expression, which in turn might improve hematopoietic functions [18, 19]. The low levels of these flavonoids being used here could not fully account for the induction activity of EPO, suggesting a possible synergistic interaction among the four flavonoids. Different experimental approaches have been used for the optimization of combinatorial therapies. But these methods require numerous experiments, additional cost, and are time consuming. FSC scheme has been introduced to search for optimized drug combinations using iterative stochastic search in terms of iterations out of a hundred thousand possible trials [21, 22]. By using cell culture as a model, we have adopted this novel methodology in optimizing the four flavonoids in combination, which shows strong activation on transcriptional activity of hypoxia responsive element [20].


Four characteristics known informally as the four Cs are now commonly used as the basic descriptors of diamonds: carat, cut, color, and clarity. This system was developed by Gemological Institute of America in 1953 as internationally recognized standard to evaluate diamonds characteristics.


Most gem diamonds are traded on the wholesale market based on single values for each of the four Cs; for example knowing that a diamond is rated as 1.5 carats (300 mg), VS2 clarity, F color, excellent cut round brilliant, is enough to reasonably establish an expected price range. More detailed information from within each characteristic is used to determine actual market value for individual stones. Consumers who purchase individual diamonds are often advised to use the four Cs to pick the diamond that is "right" for them.



Germanium dioxide, also called germanium oxide and germania, is an inorganic compound with the chemical formula GeO2. It is the main commercial source of germanium. It also forms as a passivation layer on pure germanium in contact with atmospheric oxygen.

it is a tetragonal rutile form- IT IS TETRAHEDRAL


The two predominant polymorphs of GeO2 are hexagonal and tetragonal. Hexagonal GeO2 has the same structure as β-quartz, with germanium having coordination number 4. Tetragonal GeO2 (the mineral argutite) has the rutile-like structure seen in stishovite. In this motif, germanium has the coordination number 6. An amorphous (glassy) form of GeO2 is similar to fused silica.[1]


Germanium dioxide can be prepared in both crystalline and amorphous forms. At ambient pressure the amorphous structure is formed by a network of GeO4 tetrahedra. At elevated pressure up to approximately 9 GPa the germanium average coordination number steadily increases from 4 to around 5 with a corresponding increase in the Ge-O bond distance.[2] At higher pressures, up to approximately 15 GPa, the germanium coordination number increases to 6 and the dense network structure is composed of GeO6 octahedra.[3] When the pressure is subsequently reduced, the structure reverts to the tetrahedral form.[2][3] At high pressure, the rutile form converts to an orthorhombic CaCl2 form.[4]


Tetrapeptide Rapastinel (TETRA IS FOUR) (INN) (former developmental code names GLYX-13, BV-102) is a novel antidepressant that is under development by Allergan (previously Naurex) as an adjunctive therapy for the treatment of treatment-resistant major depressive disorder.[1][2] It is a centrally active, intravenously administered (non-orally active) amidated tetrapeptide (Thr-Pro-Pro-Thr-NH2) that acts as a selective, weak partial agonist (mixed antagonist/agonist) of an allosteric site of the glycine site of the NMDA receptor complex (Emax ≈ 25%).[1][2] The drug is a rapid-acting and long-lasting antidepressant as well as robust cognitive enhancer by virtue of its ability to both inhibit and enhance NMDA receptor-mediated signal transduction.[1][2]




Four quantities called "thermodynamic potentials" are useful in the chemical thermodynamics of reactions and non-cyclic processes. They are internal energy, the enthalpy, the Helmholtz free energy and the Gibbs free energy.


This is an active graphic. Click on any part for further details.


The four thermodynamic potentials are related by offsets of the "energy from the environment" term TS and the "expansion work" term PV. A mnemonic diagram suggested by Schroeder can help you keep track of the relationships between the four thermodynamic potentials.


Four tetrahalides are known. Under normal conditions GeI4 is a solid, GeF4 a gas and the others volatile liquids. For example, germanium tetrachloride, GeCl4, is obtained as a colorless fuming liquid boiling at 83.1 °C by heating the metal with chlorine.[28] All the tetrahalides are readily hydrolyzed to hydrated germanium dioxide.[28] GeCl4 is used in the production of organogermanium compounds.[33] All four dihalides are known and in contrast to the tetrahalides are polymeric solids.[33] Additionally Ge2Cl6 and some higher compounds of formula GenCl2n+2 are known.[28] The unusual compound Ge6Cl16 has been prepared that contains the Ge5Cl12 unit with a neopentane structure.[41]



Each carbon atom in a diamond is covalently bonded to four other carbons in a tetrahedron. These tetrahedrons together form a 3-dimensional network of six-membered carbon rings (similar to cyclohexane), in the chair conformation, allowing for zero bond angle strain. This stable network of covalent bonds and hexagonal rings, is the reason that diamond is so strong. Although graphite is the most stable allotrope of carbon under standard laboratory conditions (273 or 298 K, 1 atm), a recent computational study indicated that under idealized conditions (T = 0, p = 0), diamond is the most stable allotrope by 1.1 kJ/mol compared to graphite.[2]



There are four main categories of photovoltaic cells: conventional mono and multi crystalline silicon (c-Si) cells, thin film solar cells (a-Si, CIGS and CdTe), and multi-junction (MJ) solar cells. The fourth category, emerging photovoltaics, contains technologies that are still in the research or development phase and are not listed in the table below.



The four most common modes of radioactive decay are: alpha decay, beta decay, inverse beta decay (considered as both positron emission and electron capture), and isomeric transition. Of these decay processes, only alpha decay changes the atomic mass number (A) of the nucleus, and always decreases it by four. Because of this, almost any decay will result in a nucleus whose atomic mass number has the same residue mod 4, dividing all nuclides into four chains. The members of any possible decay chain must be drawn entirely from one of these classes. All four chains also produce helium-4 (alpha particles are helium-4 nuclei).


Three main decay chains (or families) are observed in nature, commonly called the thorium series, the radium or uranium series, and the actinium series, representing three of these four classes, and ending in three different, stable isotopes of lead. The mass number of every isotope in these chains can be represented as A = 4n, A = 4n + 2, and A = 4n + 3, respectively. The long-lived starting isotopes of these three isotopes, respectively thorium-232, uranium-238, and uranium-235, have existed since the formation of the earth, ignoring the artificial isotopes and their decays since the 1940s.


Due to the relatively short half-life of its starting isotope neptunium-237 (2.14 million years), the fourth chain, the neptunium series with A = 4n + 1, is already extinct in nature, except for the final rate-limiting step, decay of bismuth-209. The ending isotope of this chain is now known to be thallium-205. Some older sources give the final isotope as bismuth-209, but it was recently discovered that it is radioactive, with a half-life of 1.9×1019 years.



A priority encoder is a circuit or algorithm that compresses multiple binary inputs into a smaller number of outputs. The output of a priority encoder is the binary representation of the original number starting from zero of the most significant input bit. They are often used to control interrupt requests by acting on the highest priority encoder.


If two or more inputs are given at the same time, the input having the highest priority will take precedence.[1] An example of a single bit 4 to 2 encoder is shown, where highest-priority inputs are to the left and "x" indicates an irrelevant value - i.e. any input value there yields the same output since it is superseded by higher-priority input. The output V indicates if the input is valid.


4 to 2 Priority Encoder

I3 I2 I1 I0 O1 O0 V

0 0 0 0 x x 0

0 0 0 1 0 0 1

0 0 1 x 0 1 1

0 1 x x 1 0 1

1 x x x 1 1 1

Priority encoders can be easily connected in arrays to make larger encoders, such as one 16-to-4 encoder made from six 4-to-2 priority encoders - four 4-to-2 encoders having the signal source connected to their inputs, and the two remaining encoders take the output of the first four as input.The priority encoder is an improvement on a simple encoder circuit, in terms of handling all possible input configurations.


Simple encoder[edit]

A simple encoder circuit is a one-hot to binary converter. That is, if there are 2n input lines, and at most only one of them will ever be high, the binary code of this 'hot' line is produced on the n-bit output lines.


For example, a 4-to-2 simple encoder takes 4 input bits and produces 2 output bits. The illustrated gate level example implements the simple encoder defined by the truth table, but it must be understood that for all the non-explicitly defined input combinations (i.e., inputs containing 0, 2, 3, or 4 high bits) the outputs are treated as don't cares.

Gate level circuit diagram of a single bit 4-to-2 line encoder




Four-port valves
Main article: four-way valve
A 4-port valve is a valve whose body has four ports equally spaced round the body and the disc has two passages to connect adjacent ports. It is operated with two positions.

It can be used to isolate and to simultaneously bypass a sampling cylinder installed on a pressurized water line. It is useful to take a fluid sample without affecting the pressure of a hydraulic system and to avoid degassing (no leak, no gas loss or air entry, no external contamination)....

Four-way valve

From Wikipedia, the free encyclopedia


See also: valve and ball valve

The four-way valve or four-way cock is a fluid control valve whose body has four ports equally spaced round the valve chamber and the plug has two passages to connect adjacent ports. The plug may be cylindrical or tapered, or a ball.

It has two flow positions as shown, and usually a central position where all ports are closed.

It can be used to isolate and to simultaneously bypass a sampling cylinder installed on a pressurized water line. It is useful to take a fluid sample without affecting the pressure of a hydraulic system and to avoid degassing (no leak, no gas loss or air entry, no external contamination).

It was used to control the flow of steam to the cylinder of early double-acting steam engines, such as those designed by Richard Trevithick. This use of the valve is possibly attributable to Denis Papin.

Because the two "L"-shaped ports in the plug do not interconnect, the four-way valve is sometimes referred to as an "×" port.



In the 1920s and 1930s, four-valved sousaphones were often used by professional players, especially E♭ sousaphones; today, however, four-valved B♭ sousaphones are uncommon and are prized by collectors, especially those made by Conn, King (H.N. White), and Holton. Jupiter Company started production of four-valve BB♭ sousaphones in the late 2000s, and Dynasty USA makes a four-valve BBb sousaphone as well. Criticisms of the fourth valve on a sousaphone center around additional weight, although the fourth valve improves intonation and facilitates playing of the lower register.


Due to the large size of most sousaphones, the sub-contra register (for which the fourth valve is largely intended) is already covered by alternate resonances, known as "false tones" (see Tuba article). Many beginners are not aware of the false-tone resonances on their sousaphones because these notes reside in the sub-contra register, which is nearly impossible for most beginners to access. Some professionals develop a "raised embouchure" to securely play these notes. This is where either the upper or lower lip (depending on the player) takes up most of the mouthpiece area. The embouchure provides almost twice the room for vibration of the single lip (compared to the 50–50 embouchure).



Formerly one of the four largest lakes in the world with an area of 68,000 km2 (26,300 sq mi), the Aral Sea has been steadily shrinking since the 1960s after the rivers that fed it were diverted by Soviet irrigation projects. By 2007, it had declined to 10% of its original size, splitting into four lakes – the North Aral Sea, the eastern and western basins of the once far larger South Aral Sea, and one smaller lake between the North and South Aral Seas.[4] By 2009, the southeastern lake had disappeared and the southwestern lake had retreated to a thin strip at the western edge of the former southern sea; in subsequent years, occasional water flows have led to the southeastern lake sometimes being replenished to a small degree.[5] Satellite images taken by NASA in August 2014 revealed that for the first time in modern history the eastern basin of the Aral Sea had completely dried up.[6] The eastern basin is now called the Aralkum Desert.



Madagascar was formerly located in the central part of the supercontinent Gondwana. It contains part of the East African Orogen, which formed in the Neoproterozoic to Cambrian assembly of the Gondwana. This heavily influenced the geology of central and northern Madagascar.[4]


The entire island can be divided into four tectonic and geologic units:[5] the Antongil block, the Antananarivo block, the Bekily Belt in the south, and the Bemarivo Belt in the far north.


The Antongil Block is characterized by a 3.2 Ga gneiss intruded by granite that has undergone greenschist facies metamorphism.

The Antananarivo Block contains 2.5 Ga gneiss layered with younger granitoids and gabbros. It has metamorphosed to granulite facies conditions.

The Bemarivo Belt contains two regions, metasedimentary gneisses in the southern part and granitic domes in the north.

The Bekily Belt is made up of mostly sedimentary protoliths and granulite and upper amphibolite grade gneisses.



7 large “plates” (16 major plates)



Synthetic fibers account for about half of all fiber usage, with applications in every field of fiber and textile technology. Although many classes of fiber based on synthetic polymers have been evaluated as potentially valuable commercial products, four of them - nylon, polyester, acrylic and polyolefin - dominate the market. These four account for approximately 98 percent by volume of synthetic fiber production, with polyester alone accounting for around 60 per cent.[11]



There are four commercially grown species of cotton, all domesticated in antiquity:


Gossypium hirsutum – upland cotton, native to Central America, Mexico, the Caribbean and southern Florida (90% of world production)

Gossypium barbadense – known as extra-long staple cotton, native to tropical South America (8% of world production)

Gossypium arboreum – tree cotton, native to India and Pakistan (less than 2%)

Gossypium herbaceum – Levant cotton, native to southern Africa and the Arabian Peninsula (less than 2%)



The basis of textile-grade glass fibers is silica, SiO2. In its pure form it exists as a polymer, (SiO2)n. It has no true melting point but softens up to 1200 °C, where it starts to degrade. At 1713 °C, most of the molecules can move about freely. If the glass is extruded and cooled quickly at this temperature, it will be unable to form an ordered structure.[6] In the polymer it forms SiO4 groups which are configured as a tetrahedron with the silicon atom at the center, and four oxygen atoms at the corners. These atoms then form a network bonded at the corners by sharing the oxygen atoms.



Although cannabis as a drug and industrial hemp are both members of the species Cannabis sativa and contain the psychoactive component tetrahydrocannabinol (THC), they are distinct strains with unique biochemical compositions and uses.[6] Hemp has lower concentrations of THC and higher concentrations of cannabidiol (CBD), which decreases or eliminates its psychoactive effects.[6] The legality of industrial hemp varies widely between countries. Some governments regulate the concentration of THC and permit only hemp that is bred with an especially low THC content.[7][8]

16 CORES- 16 SQUARES QMR- 128 is 16 times 8


SPARC T5 is the fifth generation multicore microprocessor of Oracle's SPARC T-Series family.[1] It was first presented at Hot Chips 24 in August 2012,[2] and was officially introduced with the Oracle SPARC T5 servers in March 2013.[3] The processor is designed to offer high multithreaded performance (16 cores per chip, with 8 threads per core), as well as high single threaded performance from the same chip.[4]


The processor uses the same SPARC S3 core design as its predecessor, the SPARC T4 processor, but is implemented in a 28 nm process and runs at 3.6 GHz.[5] The S3 core is a dual-issue core that uses dynamic threading and out-of-order execution,[6] incorporates one floating point unit, one dedicated cryptographic unit per core.[7]


The 64-bit SPARC Version 9 based processor has 16 cores supporting up to 128 threads per processor, and scales up to 1,024 threads in an 8 socket system.[4] Other changes include the support of PCIe version 3.0 and a new cache coherence protocol.[5]





Giovanni Arduino (October 16, 1714 – March 21, 1795) was an Italian geologist who is known as the "Father of Italian Geology".


Arduino was born at Caprino Veronese, Veneto. He was a mining specialist who developed possibly the first classification of geological time, based on study of the geology of northern Italy. He divided the history of the Earth into four periods: Primitive, Secondary, Tertiary and Volcanic, or Quaternary.


Arduino's stratigraphic section in Tuscany, (pen and ink) 1758

The scheme proposed by Arduino in 1759,[1] which was based on much study of rocks of the southern Alps, grouped the rocks into four series. These were (in addition to the Volcanic or Quaternary) as follows: the Primary series, which consisted of schists from the core of the mountains; the Secondary, which consisted of the hard sedimentary rocks on the mountain flanks; and the Tertiary, which consisted of the less hardened sedimentary rocks of the foothills. Because this arrangement did not always hold true for mountain ranges other than the Alps, the Primary and the Secondary were dropped in the general case. However the term 'Tertiary' has persisted in geological literature until its recent replacement by the Palaeogene and Neogene periods. The last period of the Cenozoic Era, known as the Pleistocene Epoch, is sometimes not included in the notion of the Tertiary. The Cenozoic was studied and further determined by, among others, the English geologist (and mentor of Charles Darwin) Charles Lyell.[1]



The Cambrian Period followed the Ediacaran Period and was followed by the Ordovician Period. The Cambrian is divided into four epochs (series) and ten ages (stages). Currently only two series and five stages are named and have a GSSP.



In common practice (e.g. MLK 1952, Weller 1960) the Canadian has been viewed as the Early, or Lower Ordovician. Flower however (1957, 1964) separated the Canadian from the rest of the Ordovician and defined it as a four-part system, divided in ascending order into the Gasconadian, Demingian, Jeffersonian, and Cassinian which stands today. The remaining Ordovician was also divided (Flower 1964, fig 3 p. 23) into four parts, the Whiterockian, Chazyan, Mohawkian, and Cincinnatian.


Divisions, Stages[edit]

Starting at the bottom:


The Gasconadian, named for the Gasconade Formation in the Ozarks in Missouri is the Lower Canadian. The base of the Gasconade is a dolomitic sand, the Gunter Sandstone which is deposited on an erosional surface on the underlying Cambrian. The North American Gasconadian and the Tremedocian of the standard section are equivalent.

The Demingian, named for the town of Deming in southern New Mexico which lies near localities where outcrops of this age are found is Middle Canadian and roughly equivalent to the Lower Arenigian.

The Jeffersonian which is the Lower Upper Canadian is based on the dolomitic Jefferson City Formation of Missouri, roughly the Middle Arenigian

The Cassinian, named for the Fort Cassin limestone of western Vermont, named for Fort Cassin which stood on the shore of Lake Champlain, is Upper Upper Canadian, equivalent in part to the Upper Arenigian.

The El Paso Group[edit]

All four stages of the Canadian, except for the uppermost Cassinian, are represented in the El Paso Group in New Mexico and West Texas. The name comes from the City of El Paso, Texas, which is next to the Franklin Mountains were the type section is found.