1.
Particle
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A particle is a minute fragment or quantity of matter. In the physical sciences, a particle is a small localized object to which can be ascribed several physical or chemical properties such as volume or mass. Particles can also be used to create models of even larger objects depending on their density. The term particle is rather general in meaning, and is refined as needed by various scientific fields, something that is composed of particles may be referred to as being particulate. However, the particulate is most frequently used to refer to pollutants in the Earths atmosphere. The concept of particles is particularly useful when modelling nature, as the treatment of many phenomena can be complex. It can be used to make simplifying assumptions concerning the processes involved, francis Sears and Mark Zemansky, in University Physics, give the example of calculating the landing location and speed of a baseball thrown in the air. The treatment of large numbers of particles is the realm of statistical physics, the term particle is usually applied differently to three classes of sizes. The term macroscopic particle, usually refers to particles much larger than atoms and these are usually abstracted as point-like particles, or even invisible. This is even though they have volumes, shapes, structures, examples of macroscopic particles would include powder, dust, sand, pieces of debris during a car accident, or even objects as big as the stars of a galaxy. Another type, microscopic particles usually refers to particles of sizes ranging from atoms to molecules, such as carbon dioxide, nanoparticles and these particles are studied in chemistry, as well as atomic and molecular physics. The smallest of particles are the particles, which refer to particles smaller than atoms. These particles are studied in particle physics, because of their extremely small size, the study of microscopic and subatomic particles fall in the realm of quantum mechanics. Particles can also be classified according to composition, composite particles refer to particles that have composition – that is particles which are made of other particles. For example, an atom is made of six protons, eight neutrons. By contrast, elementary particles refer to particles that are not made of other particles, according to our current understanding of the world, only a very small number of these exist, such as the leptons, quarks or gluons. However it is possible some of these might turn up to be composite particles after all. While composite particles can very often be considered point-like, elementary particles are truly punctual, both elementary and composite particles, are known to undergo particle decay
2.
Ion
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An ion is an atom or a molecule in which the total number of electrons is not equal to the total number of protons, giving the atom or molecule a net positive or negative electrical charge. Ions can be created, by chemical or physical means. In chemical terms, if an atom loses one or more electrons. If an atom gains electrons, it has a net charge and is known as an anion. Ions consisting of only a single atom are atomic or monatomic ions, because of their electric charges, cations and anions attract each other and readily form ionic compounds, such as salts. In the case of ionization of a medium, such as a gas, which are known as ion pairs are created by ion impact, and each pair consists of a free electron. The word ion comes from the Greek word ἰόν, ion, going and this term was introduced by English physicist and chemist Michael Faraday in 1834 for the then-unknown species that goes from one electrode to the other through an aqueous medium. Faraday also introduced the words anion for a charged ion. In Faradays nomenclature, cations were named because they were attracted to the cathode in a galvanic device, arrhenius explanation was that in forming a solution, the salt dissociates into Faradays ions. Arrhenius proposed that ions formed even in the absence of an electric current, ions in their gas-like state are highly reactive, and do not occur in large amounts on Earth, except in flames, lightning, electrical sparks, and other plasmas. These gas-like ions rapidly interact with ions of charge to give neutral molecules or ionic salts. These stabilized species are commonly found in the environment at low temperatures. A common example is the present in seawater, which are derived from the dissolved salts. Electrons, due to their mass and thus larger space-filling properties as matter waves, determine the size of atoms. Thus, anions are larger than the parent molecule or atom, as the excess electron repel each other, as such, in general, cations are smaller than the corresponding parent atom or molecule due to the smaller size of its electron cloud. One particular cation contains no electrons, and thus consists of a single proton - very much smaller than the parent hydrogen atom. Since the electric charge on a proton is equal in magnitude to the charge on an electron, an anion, from the Greek word ἄνω, meaning up, is an ion with more electrons than protons, giving it a net negative charge. A cation, from the Greek word κατά, meaning down, is an ion with fewer electrons than protons, there are additional names used for ions with multiple charges
3.
Inequality (mathematics)
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In mathematics, an inequality is a relation that holds between two values when they are different. The notation a ≠ b means that a is not equal to b and it does not say that one is greater than the other, or even that they can be compared in size. If the values in question are elements of a set, such as the integers or the real numbers. The notation a < b means that a is less than b, the notation a > b means that a is greater than b. In either case, a is not equal to b and these relations are known as strict inequalities. The notation a < b may also be read as a is less than b. The notation a ≥ b means that a is greater than or equal to b, not less than can also be represented by the symbol for less than bisected by a vertical line, not. In engineering sciences, a formal use of the notation is to state that one quantity is much greater than another. The notation a ≪ b means that a is less than b. The notation a ≫ b means that a is greater than b. Inequalities are governed by the following properties, all of these properties also hold if all of the non-strict inequalities are replaced by their corresponding strict inequalities and monotonic functions are limited to strictly monotonic functions. The transitive property of inequality states, For any real numbers a, b, c, If a ≥ b and b ≥ c, If a ≤ b and b ≤ c, then a ≤ c. If either of the premises is an inequality, then the conclusion is a strict inequality. E. g. if a ≥ b and b > c, then a > c An equality is of course a special case of a non-strict inequality. E. g. if a = b and b > c, then a > c The relations ≤ and ≥ are each others converse, For any real numbers a and b, If a ≤ b, then b ≥ a. If a ≥ b, then a + c ≥ b + c, If a ≤ b and c >0, then ac ≤ bc and a/c ≤ b/c. If c is negative, then multiplying or dividing by c inverts the inequality, If a ≥ b and c <0, then ac ≤ bc, If a ≤ b and c <0, then ac ≥ bc and a/c ≥ b/c. More generally, this applies for a field, see below
4.
Electronvolt
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In physics, the electronvolt is a unit of energy equal to approximately 1. 6×10−19 joules. By definition, it is the amount of energy gained by the charge of an electron moving across an electric potential difference of one volt. Thus it is 1 volt multiplied by the elementary charge, therefore, one electronvolt is equal to 6981160217662079999♠1. 6021766208×10−19 J. The electronvolt is not a SI unit, and its definition is empirical, like the elementary charge on which it is based, it is not an independent quantity but is equal to 1 J/C √2hα / μ0c0. It is a unit of energy within physics, widely used in solid state, atomic, nuclear. It is commonly used with the metric prefixes milli-, kilo-, in some older documents, and in the name Bevatron, the symbol BeV is used, which stands for billion electronvolts, it is equivalent to the GeV. By mass–energy equivalence, the electronvolt is also a unit of mass and it is common in particle physics, where units of mass and energy are often interchanged, to express mass in units of eV/c2, where c is the speed of light in vacuum. It is common to express mass in terms of eV as a unit of mass. The mass equivalent of 1 eV/c2 is 1 eV / c 2 = ⋅1 V2 =1.783 ×10 −36 kg. For example, an electron and a positron, each with a mass of 0.511 MeV/c2, the proton has a mass of 0.938 GeV/c2. In general, the masses of all hadrons are of the order of 1 GeV/c2, the unified atomic mass unit,1 gram divided by Avogadros number, is almost the mass of a hydrogen atom, which is mostly the mass of the proton. To convert to megaelectronvolts, use the formula,1 u =931.4941 MeV/c2 =0.9314941 GeV/c2, in high-energy physics, the electronvolt is often used as a unit of momentum. A potential difference of 1 volt causes an electron to gain an amount of energy and this gives rise to usage of eV as units of momentum, for the energy supplied results in acceleration of the particle. The dimensions of units are LMT−1. The dimensions of units are L2MT−2. Then, dividing the units of energy by a constant that has units of velocity. In the field of particle physics, the fundamental velocity unit is the speed of light in vacuum c. Thus, dividing energy in eV by the speed of light, the fundamental velocity constant c is often dropped from the units of momentum by way of defining units of length such that the value of c is unity
5.
Thin film
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A thin film is a layer of material ranging from fractions of a nanometer to several micrometers in thickness. The controlled synthesis of materials as thin films is a step in many applications. A familiar example is the mirror, which typically has a thin metal coating on the back of a sheet of glass to form a reflective interface. The process of silvering was once used to produce mirrors. It is also being applied to pharmaceuticals, via thin-film drug delivery, a stack of thin films is called a multilayer. In addition to their applied interest, thin films play an important role in the development and study of materials with new, examples include multiferroic materials, and superlattices that allow the study of quantum confinement by creating two-dimensional electron states. The act of applying a thin film to a surface is thin-film deposition – any technique for depositing a film of material onto a substrate or onto previously deposited layers. Thin is a term, but most deposition techniques control layer thickness within a few tens of nanometres. Molecular beam epitaxy and atomic layer deposition allow a single layer of atoms to be deposited at a time and it is useful in the manufacture of optics, electronics, packaging, and in contemporary art. Deposition techniques fall into two categories, depending on whether the process is primarily chemical or physical. Here, a fluid precursor undergoes a change at a solid surface. An everyday example is the formation of soot on an object when it is placed inside a flame. Chemical deposition is further categorized by the phase of the precursor, Plating relies on liquid precursors, some plating processes are driven entirely by reagents in the solution, but by far the most commercially important process is electroplating. It was not commonly used in processing for many years. Chemical solution deposition or chemical bath deposition uses a liquid precursor and this is a relatively inexpensive, simple thin film process that is able to produce stoichiometrically accurate crystalline phases. This technique is known as the sol-gel method because the sol gradually evolves towards the formation of a gel-like diphasic system. The speed at which the solution is spun and the viscosity of the sol determine the thickness of the deposited film. Repeated depositions can be carried out to increase the thickness of films as desired, thermal treatment is often carried out in order to crystallize the amorphous spin coated film
6.
Etching
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Etching is traditionally the process of using strong acid or mordant to cut into the unprotected parts of a metal surface to create a design in intaglio in the metal. In modern manufacturing, other chemicals may be used on other types of material, as a method of printmaking, it is, along with engraving, the most important technique for old master prints, and remains in wide use today. In a number of variants such as microfabrication etching and photochemical milling it is a crucial technique in much modern technology. In traditional pure etching, a plate is covered with a waxy ground which is resistant to acid. The artist then scratches off the ground with an etching needle where he or she wants a line to appear in the finished piece. The échoppe, a tool with an oval section, is also used for swelling lines. The plate is dipped in a bath of acid, technically called the mordant or etchant. The acid bites into the metal where it is exposed, leaving behind lines sunk into the plate, the remaining ground is then cleaned off the plate. The plate is inked all over, and then the ink wiped off the surface, the plate is then put through a high-pressure printing press together with a sheet of paper. The paper picks up the ink from the lines, making a print. The process can be repeated many times, typically several hundred impressions could be printed before the shows much sign of wear. The work on the plate can also be added to by repeating the whole process, Etching has often been combined with other intaglio techniques such as engraving or aquatint. The process as applied to printmaking is believed to have been invented by Daniel Hopfer of Augsburg, Hopfer was a craftsman who decorated armour in this way, and applied the method to printmaking, using iron plates. Apart from his prints, there are two examples of his work on armour, a shield from 1536 now in the Real Armeria of Madrid. The switch to copper plates was made in Italy. On the other hand, the handling of the ground and acid need skill and experience, prior to 1100 AD, the New World Hohokam independently utilized the technique of acid etching in marine shell designs. Jacques Callot from Nancy in Lorraine made important technical advances in etching technique and he developed the échoppe, a type of etching-needle with a slanting oval section at the end, which enabled etchers to create a swelling line, as engravers were able to do. Callot also appears to have responsible for an improved, harder, recipe for the etching ground
7.
Collision cascade
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A collision cascade is a set of nearby adjacent energetic collisions of atoms induced by an energetic particle in a solid or liquid. The initial energetic atom can be, e. g, the nature of collision cascades can vary strongly depending on the energy and mass of the recoil/incoming ion and density of the material. This kind of a cascade can be well treated using the binary collision approximation simulation approach. For instance, H and He ions with energies below 10 keV can be expected to lead to purely linear cascades in all materials. The most commonly used BCA code SRIM can be used to simulate linear collision cascades in disordered materials for all ion in all materials up to ion energies of 1 GeV. Note, however, that SRIM does not treat such as damage due to electronic energy deposition or damage produced by excited electrons. The nuclear and electronic stopping powers used are averaging fits to experiments, when the ion is heavy and energetic enough, and the material is dense, the collisions between the ions may occur so near to each other that they can not be considered independent of each other. Computer simulation-based animations of collision cascades in the heat spike regime are available on YouTube, typically, a heat spike is characterized by the formation of a transient underdense region in the center of the cascade, and an overdense region around it. After the cascade, the region becomes interstitial defects. If the kinetic energy of the atoms in the region of collisions is recalculated into temperature. Because of this, the region can be considered to be very hot, the heat spike cools down to the ambient temperature in 1–100 ps, so the temperature here does not correspond to thermodynamic equilibrium temperature. In many cases, the same condition is a combination of linear cascades. For example,10 MeV Cu ions bombarding Cu would initially move in the lattice in a linear cascade regime, but once the Cu ion would slow down enough, the nuclear stopping power would increase and a heat spike would be produced. Moreover, many of the primary and secondary recoils of the ions would likely have energies in the keV range. For instance, for copper irradiation of copper, recoil energies of around 5–20 keV are almost guaranteed to produce heat spikes, at lower energies, the cascade energy is too low to produce a liquid-like zone. At much higher energies, the Cu ions would most likely lead initially to a linear cascade, the concept subcascade breakdown threshold energy signifies the energy above which a recoil in a material is likely to produce several isolated heat spikes rather than a single dense one. Swift heavy ions, i. e. However, at least the stage of the damage might be better understood in terms of a Coulomb explosion mechanism. Regardless of what the mechanism is, it is well established that swift heavy ions in insulators typically produce ion tracks forming long cylindrical damage zones of reduced density
8.
Binding energy
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Binding energy is the energy required to disassemble a whole system into separate parts. A bound system typically has a potential energy than the sum of its constituent parts. Often this means that energy is released upon the creation of a bound state and this definition corresponds to a positive binding energy. In bound systems, if the energy is removed from the system, it must be subtracted from the mass of the unbound system. Thus, if energy is removed from the system at the time it is bound, system mass is not conserved in this process because the system is open during the binding process. There are several types of binding energy, each operating over a different distance, the smaller the scale of a bound system, the higher its associated binding energy. In astrophysics, the binding energy of a celestial body is the energy required to expand the material to infinity.66 eV per atom. If a carbon-12 body had the mass and radius of the Sun, at the molecular level, bond energy and bond-dissociation energy are measures of the binding energy between the atoms in a chemical bond. It is the required to disassemble a molecule into its constituent atoms. This energy appears as chemical energy, such as that released in chemical explosions, bond energies and bond-dissociation energies are typically in the range of few eV per bond. For example, the energy of a carbon-carbon bond is about 3.6 eV. At the atomic level, the binding energy of the atom derives from electromagnetic interaction. It is the required to disassemble an atom into free electrons. Electron binding energy is a measure of the required to free electrons from their atomic orbits. This is more known as ionization energy. Among the chemical elements, the range of energies is from 3.8939 eV for the first electron in an atom of caesium to 11.567617 keV for the 29th electron in an atom of copper. At the nuclear level, nuclear binding energy is the required to disassemble a nucleus into the free. It is the equivalent of the mass defect, the difference between the mass number of a nucleus and its true measured mass
9.
Plasma (physics)
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Plasma is one of the four fundamental states of matter, the others being solid, liquid, and gas. Yet unlike these three states of matter, plasma does not naturally exist on the Earth under normal surface conditions, the term was first introduced by chemist Irving Langmuir in the 1920s. However, true plasma production is from the separation of these ions and electrons that produces an electric field. Based on the environmental temperature and density either partially ionised or fully ionised forms of plasma may be produced. The positive charge in ions is achieved by stripping away electrons from atomic nuclei, the number of electrons removed is related to either the increase in temperature or the local density of other ionised matter. Plasma may be the most abundant form of matter in the universe, although this is currently tentative based on the existence. Plasma is mostly associated with the Sun and stars, extending to the rarefied intracluster medium, Plasma was first identified in a Crookes tube, and so described by Sir William Crookes in 1879. The nature of the Crookes tube cathode ray matter was identified by British physicist Sir J. J. The term plasma was coined by Irving Langmuir in 1928, perhaps because the glowing discharge molds itself to the shape of the Crookes tube and we shall use the name plasma to describe this region containing balanced charges of ions and electrons. Plasma is a neutral medium of unbound positive and negative particles. Although these particles are unbound, they are not ‘free’ in the sense of not experiencing forces, in turn this governs collective behavior with many degrees of variation. The average number of particles in the Debye sphere is given by the plasma parameter, bulk interactions, The Debye screening length is short compared to the physical size of the plasma. This criterion means that interactions in the bulk of the plasma are more important than those at its edges, when this criterion is satisfied, the plasma is quasineutral. Plasma frequency, The electron plasma frequency is compared to the electron-neutral collision frequency. When this condition is valid, electrostatic interactions dominate over the processes of ordinary gas kinetics, for plasma to exist, ionization is necessary. The term plasma density by itself refers to the electron density, that is. The degree of ionization of a plasma is the proportion of atoms that have lost or gained electrons, even a partially ionized gas in which as little as 1% of the particles are ionized can have the characteristics of a plasma. The degree of ionization, α, is defined as α = n i n i + n n, where n i is the number density of ions and n n is the number density of neutral atoms
10.
Stopping power (particle radiation)
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Its application is important in areas such as radiation protection and nuclear medicine. Both charged and uncharged particles lose energy while passing through matter, positive ions are considered in most cases below. The stopping power depends on the type and energy of the radiation and on the properties of the material it passes, since the production of an ion pair requires a fixed amount of energy, the density of ionization is proportional to the stopping power. The stopping power of the material is numerically equal to the loss of energy E per unit path length, the force usually increases toward the end of range and reaches a maximum, the Bragg peak, shortly before the energy drops to zero. The curve that describes the force as function of the depth is called the Bragg curve. This is of practical importance for radiation therapy. The equation above defines the linear stopping power which in the system is expressed in N but is usually indicated in other units like MeV/mm or similar. If a substance is compared in gaseous and solid form, then the linear stopping powers of the two states are very different just because of the different density, the mass stopping power then depends only very little on the density of the material. The picture shows how the power of 5.49 MeV alpha particles increases while the particle traverses air. This particular energy corresponds to that of the alpha radiation from naturally radioactive gas radon which is present in the air in minute amounts. The deposited energy can be obtained by integrating the stopping power over the path length of the ion while it moves in the material. Electronic stopping refers to the slowing down of a projectile ion due to the collisions between bound electrons in the medium and the ion moving through it. The term inelastic is used to signify that energy is lost during the process, linear electronic stopping power is identical to unrestricted linear energy transfer. Instead of energy transfer, some consider the electronic stopping power as momentum transfer between electron gas and energetic ion. This is consistent with the result of Bethe in the energy range. Instead, the stopping power is often given as a simple function of energy F e which is an average taken over all energy loss processes for different charge states. It can be determined to an accuracy of a few % in the energy range above several hundred keV per nucleon from theoretical treatments. At energies lower than about 100 keV per nucleon, it more difficult to determine the electronic stopping theoretically
11.
Insulator (electricity)
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An electrical insulator is a material whose internal electric charges do not flow freely, very little electric current will flow through it under the influence of an electric field. This contrasts with other materials, semiconductors and conductors, which conduct electric current more easily, the property that distinguishes an insulator is its resistivity, insulators have higher resistivity than semiconductors or conductors. A perfect insulator does not exist, because even insulators contain small numbers of mobile charges which can carry current, in addition, all insulators become electrically conductive when a sufficiently large voltage is applied that the electric field tears electrons away from the atoms. This is known as the voltage of an insulator. Some materials such as glass, paper and Teflon, which have high resistivity, are good electrical insulators. Examples include rubber-like polymers and most plastics which can be thermoset or thermoplastic in nature, insulators are used in electrical equipment to support and separate electrical conductors without allowing current through themselves. An insulating material used in bulk to wrap electrical cables or other equipment is called insulation, the term insulator is also used more specifically to refer to insulating supports used to attach electric power distribution or transmission lines to utility poles and transmission towers. They support the weight of the suspended wires without allowing the current to flow through the tower to ground, electrical insulation is the absence of electrical conduction. Electronic band theory says that a charge flows if states are available into which electrons can be excited and this allows electrons to gain energy and thereby move through a conductor such as a metal. If no such states are available, the material is an insulator, most insulators have a large band gap. This occurs because the valence band containing the highest energy electrons is full, there is always some voltage that gives electrons enough energy to be excited into this band. Once this voltage is exceeded the material ceases being an insulator, however, it is usually accompanied by physical or chemical changes that permanently degrade the materials insulating properties. Materials that lack electron conduction are insulators if they lack other mobile charges as well, for example, if a liquid or gas contains ions, then the ions can be made to flow as an electric current, and the material is a conductor. Electrolytes and plasmas contain ions and act as conductors whether or not electron flow is involved, when subjected to a high enough voltage, insulators suffer from the phenomenon of electrical breakdown. These freed electrons and ions are in turn accelerated and strike other atoms, creating more charge carriers, rapidly the insulator becomes filled with mobile charge carriers, and its resistance drops to a low level. In a solid, the voltage is proportional to the band gap energy. The air in a region around a conductor can break down and ionise without a catastrophic increase in current. Even a vacuum can suffer a sort of breakdown, but in case the breakdown or vacuum arc involves charges ejected from the surface of metal electrodes rather than produced by the vacuum itself
12.
Europa (moon)
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Europa /jʊˈroʊpə/, is the smallest of the four Galilean moons orbiting Jupiter, and the sixth-closest to the planet. It is also the sixth-largest moon in the Solar System, Europa was discovered in 1610 by Galileo Galilei and was named after Europa, the legendary mother of King Minos of Crete and lover of Zeus. Slightly smaller than Earths Moon, Europa is primarily made of rock and has a water-ice crust. It has an atmosphere composed primarily of oxygen. Its surface is striated by cracks and streaks, whereas craters are relatively rare, in addition to Earth-bound telescope observations, Europa has been examined by a succession of space probe flybys, the first occurring in the early 1970s. Europa has the smoothest surface of any solid object in the Solar System. The apparent youth and smoothness of the surface have led to the hypothesis that a water ocean exists beneath it, sea salt from a subsurface ocean may be coating some geological features on Europa, suggesting that the ocean is interacting with the seafloor. This may be important in determining if Europa could be habitable, in addition, the Hubble Space Telescope detected water vapor plumes similar to those observed on Saturns moon Enceladus, which are thought to be caused by erupting cryogeysers. The Galileo mission, launched in 1989, provides the bulk of current data on Europa, no spacecraft has yet landed on Europa, although there have been several proposed exploration missions. The European Space Agencys Jupiter Icy Moon Explorer is a mission to Ganymede that is due to launch in 2022, NASAs planned Europa Multiple-Flyby Mission will be launched in the mid-2020s. Europa, along with Jupiters three other large moons, Io, Ganymede, and Callisto, was discovered by Galileo Galilei on 8 January 1610, and possibly independently by Simon Marius. The first reported observation of Io and Europa was made by Galileo Galilei on 7 January 1610 using a 20×-magnification refracting telescope at the University of Padua. However, in observation, Galileo could not separate Io and Europa due to the low magnification of his telescope. The following day,8 January 1610, Io and Europa were seen for the first time as separate bodies during Galileos observations of the Jupiter system, Europa is named after Europa, daughter of the king of Tyre, a Phoenician noblewoman in Greek mythology. Like all the Galilean satellites, Europa is named after a lover of Zeus, Europa was courted by Zeus and became the queen of Crete. The naming scheme was suggested by Simon Marius, who discovered the four satellites independently, Marius attributed the proposal to Johannes Kepler. The names fell out of favor for a time and were not revived in general use until the mid-20th century. In much of the astronomical literature, Europa is simply referred to by its Roman numeral designation as Jupiter II or as the second satellite of Jupiter
13.
Hollow atoms
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Hollow Atoms are short-lived multiply excited neutral atoms which carry a large part of their Z electrons in high-n levels while inner shells remain empty. This population inversion arises for typically 100 femtoseconds during the interaction of a highly charged ion with a solid surface. Short movie on hollow atom formation, EU Network ITS-LEIF MPI Heidelberg, Germany NIST, USA TU Wien, Austria
14.
Reactive-ion etching
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Reactive-ion etching is an etching technology used in microfabrication. RIE is a type of dry etching which has different characteristics than wet etching, RIE uses chemically reactive plasma to remove material deposited on wafers. The plasma is generated under low pressure by an electromagnetic field, high-energy ions from the plasma attack the wafer surface and react with it. A typical RIE system consists of a vacuum chamber, with a wafer platter situated in the bottom portion of the chamber. The wafer platter is electrically isolated from the rest of the chamber, gas enters through small inlets in the top of the chamber, and exits to the vacuum pump system through the bottom. The types and amount of gas used vary depending upon the process, for instance. Gas pressure is maintained in a range between a few millitorr and a few hundred millitorr by adjusting gas flow rates and/or adjusting an exhaust orifice. Other types of RIE systems exist, including inductively coupled plasma RIE, in this type of system, the plasma is generated with an RF powered magnetic field. Very high plasma densities can be achieved, though etch profiles tend to be more isotropic, a combination of parallel plate and inductively coupled plasma RIE is possible. Photolithography Irregular Shaped Dicing Plasma is initiated in the system by applying a strong RF electromagnetic field to the wafer platter, the field is typically set to a frequency of 13.56 Megahertz, applied at a few hundred watts. The oscillating electric field ionizes the gas molecules by stripping them of electrons, in each cycle of the field, the electrons are electrically accelerated up and down in the chamber, sometimes striking both the upper wall of the chamber and the wafer platter. At the same time, the more massive ions move relatively little in response to the RF electric field. When electrons are absorbed into the walls they are simply fed out to ground. However, electrons deposited on the wafer platter cause the platter to build up due to its DC isolation. This charge build up develops a negative voltage on the platter. The plasma itself develops a positive charge due to the higher concentration of positive ions compared to free electrons. Because of the voltage difference, the positive ions tend to drift toward the wafer platter. The ions react chemically with the materials on the surface of the samples, due to the mostly vertical delivery of reactive ions, reactive-ion etching can produce very anisotropic etch profiles, which contrast with the typically isotropic profiles of wet chemical etching
15.
Secondary ion mass spectrometry
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The mass/charge ratios of these secondary ions are measured with a mass spectrometer to determine the elemental, isotopic, or molecular composition of the surface to a depth of 1 to 2 nm. SIMS is the most sensitive surface analysis technique, with detection limits ranging from parts per million to parts per billion. In 1910 British physicist J. J. Thomson observed a release of positive ions, improved vacuum pump technology in the 1940s enabled the first prototype experiments on SIMS by Herzog and Viehböck in 1949, at the University of Vienna, Austria. In the mid-1950s Honig constructed a SIMS instrument at RCA Laboratories in Princeton, then in the early 1960s two SIMS instruments were developed independently. These first instruments were based on a double focusing sector field mass spectrometer. In the 1970s, K. Wittmaack and C, magee developed SIMS instruments equipped with quadrupole mass analyzers. The Castaing and Slodzian design was developed in the 1960s by the French company CAMECA S. A. S, recent developments are focusing on novel primary ion species like C60+, ionized clusters of gold and bismuth, or large gas cluster ion beams. SIMS requires a vacuum with pressures below 10−4 Pa. Three types of ion guns are employed, in one, ions of gaseous elements are usually generated with duoplasmatrons or by electron ionization, for instance noble gases, oxygen, or even ionized molecules such as SF5+ or C60+. This type of ion gun is easy to operate and generates roughly focused, a second source type, the surface ionization source, generates 133Cs+ primary ions. Cesium atoms vaporize through a porous tungsten plug and are ionized during evaporation, depending on the gun design, fine focus or high current can be obtained. A third source type, the metal ion gun, operates with metals or metallic alloys. The liquid metal covers a tungsten tip and emits ions under influence of an electric field. While a gallium source is able to operate with elemental gallium, recently developed sources for gold, indium, the LMIG provides a tightly focused ion beam with moderate intensity and is additionally able to generate short pulsed ion beams. It is therefore used in static SIMS devices. The choice of the ion species and ion gun respectively depends on the required current, depending on the SIMS type, there are three basic analyzers available, sector, quadrupole, and time-of-flight. A sector field mass spectrometer uses a combination of an electrostatic analyzer, a quadrupole mass analyzer separates the masses by resonant electric fields, which allow only the selected masses to pass through. The time of mass analyzer separates the ions in a field-free drift path according to their velocity
16.
Sputter deposition
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Sputter deposition is a physical vapor deposition method of thin film deposition by sputtering. This involves ejecting material from a target that is a source onto a substrate such as a silicon wafer, resputtering is re-emission of the deposited material during the deposition process by ion or atom bombardment. Sputtered atoms ejected from the target have an energy distribution. The sputtered ions can ballistically fly from the target in straight lines, the entire range from high-energy ballistic impact to low-energy thermalized motion is accessible by changing the background gas pressure. The sputtering gas is often an inert gas such as argon, reactive gases can also be used to sputter compounds. The compound can be formed on the surface, in-flight or on the substrate depending on the process parameters. The availability of many parameters that control sputter deposition make it a complex process, one of the earliest widespread commercial applications of sputter deposition, which is still one of its most important applications, is in the production of computer hard disks. Sputtering is used extensively in the industry to deposit thin films of various materials in integrated circuit processing. Thin antireflection coatings on glass for optical applications are deposited by sputtering. Because of the low temperatures used, sputtering is an ideal method to deposit contact metals for thin-film transistors. Another familiar application of sputtering is low-emissivity coatings on glass, used in double-pane window assemblies, the coating is a multilayer containing silver and metal oxides such as zinc oxide, tin oxide, or titanium dioxide. A large industry has developed around tool bit coating using sputtered nitrides, such as titanium nitride, Sputtering is also used as the process to deposit the metal layer during the fabrication of CDs and DVDs. Hard disk surfaces use sputtered CrOx and other sputtered materials, Sputtering is one of the main processes of manufacturing optical waveguides and is another way for making efficient photovoltaic solar cells. Sputter coating in scanning electron microscopy is a deposition process to cover a specimen with a thin layer of conducting material, typically a metal. A conductive coating is needed to prevent charging of a specimen with a beam in conventional SEM mode. While metal coatings are useful for increasing signal to noise ratio. For this reason when using X-ray spectroscopy a carbon coating is preferred, Sputter deposited films have a composition close to that of the source material. The difference is due to different elements spreading differently because of their different mass, sputtered films typically have a better adhesion on the substrate than evaporated films
17.
Wafer (semiconductor)
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Finally the individual microcircuits are separated and packaged. By 1960, silicon wafers were being manufactured in the U. S. by companies such as MEMC/SunEdison. In 1965, American engineers Eric O. Ernst, Donald J. Hurd, Wafers are formed of highly pure, nearly defect-free single crystalline material. One process for forming crystalline wafers is known as Czochralski growth invented by the Polish chemist Jan Czochralski. In this process, an ingot of high purity mono crystalline semiconductor, such as silicon or germanium. The boule is then sliced with a saw and polished to form wafers. The size of wafers for photovoltaics is 100–200 mm square and the thickness is 200–300 μm, in the future,160 μm will be the standard. Electronics use wafer sizes from 100–450 mm diameter, Wafers are cleaned with weak acids to remove unwanted particles, or repair damage caused during the sawing process. When used for cells, the wafers are textured to create a rough surface to increase their efficiency. The generated PSG is removed from the edge of the wafer in the etching, silicon wafers are available in a variety of diameters from 25.4 mm to 300 mm. Semiconductor fabrication plants are defined by the diameter of wafers that they are tooled to produce, Wafers grown using materials other than silicon will have different thicknesses than a silicon wafer of the same diameter. Wafer thickness is determined by the strength of the material used. This was the cost basis for increasing wafer size, conversion to 300 mm wafers from 200 mm wafers began in earnest in 2000, and reduced the price per die about 30-40%. However, this was not without significant problems for the industry, there is considerable resistance to the 450 mm transition despite the possible productivity improvement, because of concern about insufficient return on investment. Higher cost semiconductor fabrication equipment for larger wafers increases the cost of 450 mm fabs, converting to larger 450 mm wafers would reduce price per die only for process operations such as etch where cost is related to wafer count, not wafer area. Cost for processes such as lithography is proportional to wafer area, nikon plans to deliver 450-mm lithography equipment in 2015, with volume production in 2017. In November 2013 ASML paused development of 450-mm lithography equipment, citing uncertain timing of chipmaker demand, the time-line for 450 mm has not been fixed. Mark Durcan, CEO of Micron Technology, said in February 2014 that he expects 450 mm adoption to be delayed indefinitely or discontinued, “I am not convinced that 450mm will ever happen but, to the extent that it does, it’s a long way out in the future
18.
Argon
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Argon is a chemical element with symbol Ar and atomic number 18. It is in group 18 of the table and is a noble gas. Argon is the third-most abundant gas in the Earths atmosphere, at 0. 934% and it is more than twice as abundant as water vapor,23 times as abundant as carbon dioxide, and more than 500 times as abundant as neon. Argon is the most abundant noble gas in Earths crust, comprising 0. 00015% of the crust, nearly all of the argon in Earths atmosphere is radiogenic argon-40, derived from the decay of potassium-40 in the Earths crust. In the universe, argon-36 is by far the most common argon isotope, the name argon is derived from the Greek word ἀργόν, neuter singular form of ἀργός meaning lazy or inactive, as a reference to the fact that the element undergoes almost no chemical reactions. The complete octet in the atomic shell makes argon stable. Its triple point temperature of 83.8058 K is a fixed point in the International Temperature Scale of 1990. Argon is produced industrially by the distillation of liquid air. Argon is also used in incandescent, fluorescent lighting, and other gas-discharge tubes, Argon makes a distinctive blue-green gas laser. Argon is also used in fluorescent glow starters, Argon has approximately the same solubility in water as oxygen and is 2.5 times more soluble in water than nitrogen. Argon is colorless, odorless, nonflammable and nontoxic as a solid, liquid or gas, Argon is chemically inert under most conditions and forms no confirmed stable compounds at room temperature. Although argon is a gas, it can form some compounds under extreme conditions. Argon fluorohydride, a compound of argon with fluorine and hydrogen that is stable below 17 K, has been demonstrated. Although the neutral ground-state chemical compounds of argon are presently limited to HArF, ions, such as ArH+, and excited-state complexes, such as ArF, have been demonstrated. Theoretical calculation predicts several more argon compounds that should be stable but have not yet been synthesized, Argon was suspected to be a component of air by Henry Cavendish in 1785. Argon was first isolated from air in 1894 by Lord Rayleigh and Sir William Ramsay at University College London by removing oxygen, carbon dioxide, water and they had determined that nitrogen produced from chemical compounds was 0. 5% lighter than nitrogen from the atmosphere. The difference was slight, but it was important enough to attract their attention for many months and they concluded that there was another gas in the air mixed in with the nitrogen. Argon was also encountered in 1882 through independent research of H. F. Newall, each observed new lines in the color spectrum of air that did not match known elements
19.
Anisotropy
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Anisotropy /ˌænaɪˈsɒtrəpi/ is the property of being directionally dependent, which implies different properties in different directions, as opposed to isotropy. It can be defined as a difference, when measured along different axes, another is wood, which is easier to split along its grain than against it. In the field of graphics, an anisotropic surface changes in appearance as it rotates about its geometric normal. Anisotropic filtering is a method of enhancing the quality of textures on surfaces that are far away. Older techniques, such as bilinear and trilinear filtering, do not take account the angle a surface is viewed from. By reducing detail in one more than another, these effects can be reduced. In NMR spectroscopy, the orientation of nuclei with respect to the magnetic field determines their chemical shift. In this context, anisotropic systems refer to the distribution of molecules with abnormally high electron density. This abnormal electron density affects the magnetic field and causes the observed chemical shift to change. Anisotropy measurements reveal the average displacement of the fluorophore that occurs between absorption and subsequent emission of a photon. Physicists from University of California, Berkeley reported about their detection of the anisotropy in cosmic microwave background radiation in 1977. Their experiment demonstrated the Doppler shift caused by the movement of the earth with respect to the early Universe matter, cosmic anisotropy has also been seen in the alignment of galaxies rotation axes and polarisation angles of quasars. Physicists use the term anisotropy to describe direction-dependent properties of materials, magnetic anisotropy, for example, may occur in a plasma, so that its magnetic field is oriented in a preferred direction. Plasmas may also show filamentation that is directional, liquid crystals are examples of anisotropic liquids. Some materials conduct heat in a way that is isotropic, that is independent of spatial orientation around the heat source, heat conduction is more commonly anisotropic, which implies that detailed geometric modeling of typically diverse materials being thermally managed is required. The materials used to transfer and reject heat from the source in electronics are often anisotropic. Many crystals are anisotropic to light, and exhibit such as birefringence. Crystal optics describes light propagation in these media, an axis of anisotropy is defined as the axis along which isotropy is broken
20.
Mass spectrometry
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Mass spectrometry is an analytical technique that ionizes chemical species and sorts the ions based on their mass-to-charge ratio. In simpler terms, a mass spectrum measures the masses within a sample, mass spectrometry is used in many different fields and is applied to pure samples as well as complex mixtures. A mass spectrum is a plot of the ion signal as a function of the mass-to-charge ratio, in a typical MS procedure, a sample, which may be solid, liquid, or gas, is ionized, for example by bombarding it with electrons. This may cause some of the molecules to break into charged fragments. The ions are detected by a capable of detecting charged particles. Results are displayed as spectra of the abundance of detected ions as a function of the mass-to-charge ratio. The atoms or molecules in the sample can be identified by correlating known masses to the masses or through a characteristic fragmentation pattern. Goldstein called these positively charged anode rays Kanalstrahlen, the translation of this term into English is canal rays. Wien found that the charge-to-mass ratio depended on the nature of the gas in the discharge tube, thomson later improved on the work of Wien by reducing the pressure to create the mass spectrograph. The word spectrograph had become part of the international scientific vocabulary by 1884, a mass spectroscope is similar to a mass spectrograph except that the beam of ions is directed onto a phosphor screen. A mass spectroscope configuration was used in early instruments when it was desired that the effects of adjustments be quickly observed, once the instrument was properly adjusted, a photographic plate was inserted and exposed. The term mass spectroscope continued to be used though the direct illumination of a phosphor screen was replaced by indirect measurements with an oscilloscope. The use of the mass spectroscopy is now discouraged due to the possibility of confusion with light spectroscopy. Mass spectrometry is often abbreviated as mass-spec or simply as MS, modern techniques of mass spectrometry were devised by Arthur Jeffrey Dempster and F. W. Aston in 1918 and 1919 respectively. Sector mass spectrometers known as calutrons were used for separating the isotopes of uranium developed by Ernest O. Lawrence during the Manhattan Project, calutron mass spectrometers were used for uranium enrichment at the Oak Ridge, Tennessee Y-12 plant established during World War II. In 1989, half of the Nobel Prize in Physics was awarded to Hans Dehmelt, a mass spectrometer consists of three components, an ion source, a mass analyzer, and a detector. The ionizer converts a portion of the sample into ions, there is a wide variety of ionization techniques, depending on the phase of the sample and the efficiency of various ionization mechanisms for the unknown species. An extraction system removes ions from the sample, which are then targeted through the mass analyzer, the differences in masses of the fragments allows the mass analyzer to sort the ions by their mass-to-charge ratio
21.
Moon
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The Moon is an astronomical body that orbits planet Earth, being Earths only permanent natural satellite. It is the fifth-largest natural satellite in the Solar System, following Jupiters satellite Io, the Moon is second-densest satellite among those whose densities are known. The average distance of the Moon from the Earth is 384,400 km, the Moon is thought to have formed about 4.51 billion years ago, not long after Earth. It is the second-brightest regularly visible celestial object in Earths sky, after the Sun and its surface is actually dark, although compared to the night sky it appears very bright, with a reflectance just slightly higher than that of worn asphalt. Its prominence in the sky and its cycle of phases have made the Moon an important cultural influence since ancient times on language, calendars, art. The Moons gravitational influence produces the ocean tides, body tides, and this matching of apparent visual size will not continue in the far future. The Moons linear distance from Earth is currently increasing at a rate of 3.82 ±0.07 centimetres per year, since the Apollo 17 mission in 1972, the Moon has been visited only by uncrewed spacecraft. The usual English proper name for Earths natural satellite is the Moon, the noun moon is derived from moone, which developed from mone, which is derived from Old English mōna, which ultimately stems from Proto-Germanic *mǣnōn, like all Germanic language cognates. Occasionally, the name Luna is used, in literature, especially science fiction, Luna is used to distinguish it from other moons, while in poetry, the name has been used to denote personification of our moon. The principal modern English adjective pertaining to the Moon is lunar, a less common adjective is selenic, derived from the Ancient Greek Selene, from which is derived the prefix seleno-. Both the Greek Selene and the Roman goddess Diana were alternatively called Cynthia, the names Luna, Cynthia, and Selene are reflected in terminology for lunar orbits in words such as apolune, pericynthion, and selenocentric. The name Diana is connected to dies meaning day, several mechanisms have been proposed for the Moons formation 4.51 billion years ago, and some 60 million years after the origin of the Solar System. These hypotheses also cannot account for the angular momentum of the Earth–Moon system. This hypothesis, although not perfect, perhaps best explains the evidence, eighteen months prior to an October 1984 conference on lunar origins, Bill Hartmann, Roger Phillips, and Jeff Taylor challenged fellow lunar scientists, You have eighteen months. Go back to your Apollo data, go back to computer, do whatever you have to. Dont come to our conference unless you have something to say about the Moons birth, at the 1984 conference at Kona, Hawaii, the giant impact hypothesis emerged as the most popular. Afterward there were only two groups, the giant impact camp and the agnostics. Giant impacts are thought to have been common in the early Solar System, computer simulations of a giant impact have produced results that are consistent with the mass of the lunar core and the present angular momentum of the Earth–Moon system
22.
Mars
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Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, after Mercury. Named after the Roman god of war, it is referred to as the Red Planet because the iron oxide prevalent on its surface gives it a reddish appearance. Mars is a planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the valleys, deserts, and polar ice caps of Earth. The rotational period and seasonal cycles of Mars are likewise similar to those of Earth, Mars is the site of Olympus Mons, the largest volcano and second-highest known mountain in the Solar System, and of Valles Marineris, one of the largest canyons in the Solar System. The smooth Borealis basin in the northern hemisphere covers 40% of the planet, Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Mars trojan, there are ongoing investigations assessing the past habitability potential of Mars, as well as the possibility of extant life. Future astrobiology missions are planned, including the Mars 2020 and ExoMars rovers, liquid water cannot exist on the surface of Mars due to low atmospheric pressure, which is about 6⁄1000 that of the Earths, except at the lowest elevations for short periods. The two polar ice caps appear to be largely of water. The volume of ice in the south polar ice cap, if melted. On November 22,2016, NASA reported finding a large amount of ice in the Utopia Planitia region of Mars. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior, Mars can easily be seen from Earth with the naked eye, as can its reddish coloring. Its apparent magnitude reaches −2.91, which is surpassed only by Jupiter, Venus, the Moon, optical ground-based telescopes are typically limited to resolving features about 300 kilometers across when Earth and Mars are closest because of Earths atmosphere. Mars is approximately half the diameter of Earth with an area only slightly less than the total area of Earths dry land. Mars is less dense than Earth, having about 15% of Earths volume and 11% of Earths mass, the red-orange appearance of the Martian surface is caused by iron oxide, or rust. It can look like butterscotch, other common colors include golden, brown, tan. Like Earth, Mars has differentiated into a metallic core overlaid by less dense materials. Current models of its interior imply a core with a radius of about 1,794 ±65 kilometers, consisting primarily of iron and this iron sulfide core is thought to be twice as rich in lighter elements than Earths. The core is surrounded by a mantle that formed many of the tectonic and volcanic features on the planet
23.
Atmosphere
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An atmosphere is a layer of gases surrounding a planet or other material body, that is held in place by the gravity of that body. An atmosphere is likely to be retained if the gravity it is subject to is high. The atmosphere of Earth is mostly composed of nitrogen, oxygen, argon with carbon dioxide, the atmosphere helps protect living organisms from genetic damage by solar ultraviolet radiation, solar wind and cosmic rays. Its current composition is the product of billions of years of modification of the paleoatmosphere by living organisms. The term stellar atmosphere describes the region of a star. Stars with sufficiently low temperatures may form compound molecules in their outer atmosphere, Atmospheric pressure is the force per unit area that is applied perpendicularly to a surface by the surrounding gas. It is determined by a gravitational force in combination with the total mass of a column of gas above a location. On Earth, units of air pressure are based on the recognized standard atmosphere. It is measured with a barometer, the pressure of an atmospheric gas decreases with altitude due to the diminishing mass of gas above. The height at which the pressure from an atmosphere declines by a factor of e is called the height and is denoted by H. For such an atmosphere, the pressure declines exponentially with increasing altitude. However, atmospheres are not uniform in temperature, so the determination of the atmospheric pressure at any particular altitude is more complex. Surface gravity, the force that holds down an atmosphere, differs significantly among the planets, for example, the large gravitational force of the giant planet Jupiter is able to retain light gases such as hydrogen and helium that escape from objects with lower gravity. Thus, the distant and cold Titan, Triton, and Pluto are able to retain their atmospheres despite their relatively low gravities, rogue planets, theoretically, may also retain thick atmospheres. Since a collection of gas molecules may be moving at a range of velocities. Lighter molecules move faster than ones with the same thermal kinetic energy. It is thought that Venus and Mars may have lost much of their water when, after being photo dissociated into hydrogen and oxygen by solar ultraviolet, Earths magnetic field helps to prevent this, as, normally, the solar wind would greatly enhance the escape of hydrogen. However, over the past 3 billion years Earth may have lost gases through the polar regions due to auroral activity
24.
Mercury (planet)
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Mercury is the smallest and innermost planet in the Solar System. Its orbital period around the Sun of 88 days is the shortest of all the planets in the Solar System and it is named after the Roman deity Mercury, the messenger to the gods. Like Venus, Mercury orbits the Sun within Earths orbit as a planet, so it can only be seen visually in the morning or the evening sky. Also, like Venus and the Moon, the displays the complete range of phases as it moves around its orbit relative to Earth. Seen from Earth, this cycle of phases reoccurs approximately every 116 days, although Mercury can appear as a bright star-like object when viewed from Earth, its proximity to the Sun often makes it more difficult to see than Venus. Mercury is tidally or gravitationally locked with the Sun in a 3,2 resonance, as seen relative to the fixed stars, it rotates on its axis exactly three times for every two revolutions it makes around the Sun. As seen from the Sun, in a frame of reference that rotates with the orbital motion, an observer on Mercury would therefore see only one day every two years. Mercurys axis has the smallest tilt of any of the Solar Systems planets, at aphelion, Mercury is about 1.5 times as far from the Sun as it is at perihelion. Mercurys surface appears heavily cratered and is similar in appearance to the Moons, the polar regions are constantly below 180 K. The planet has no natural satellites. Mercury is one of four planets in the Solar System. It is the smallest planet in the Solar System, with a radius of 2,439.7 kilometres. Mercury is also smaller—albeit more massive—than the largest natural satellites in the Solar System, Ganymede, Mercury consists of approximately 70% metallic and 30% silicate material. Mercurys density is the second highest in the Solar System at 5.427 g/cm3, Mercurys density can be used to infer details of its inner structure. Although Earths high density results appreciably from gravitational compression, particularly at the core, Mercury is much smaller, therefore, for it to have such a high density, its core must be large and rich in iron. Geologists estimate that Mercurys core occupies about 55% of its volume, Research published in 2007 suggests that Mercury has a molten core. Surrounding the core is a 500–700 km mantle consisting of silicates, based on data from the Mariner 10 mission and Earth-based observation, Mercurys crust is estimated to be 35 km thick. One distinctive feature of Mercurys surface is the presence of narrow ridges
25.
Exosphere
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In the case of bodies with substantial atmospheres, such as Earths atmosphere, the exosphere is the uppermost layer, where the atmosphere thins out and merges with interplanetary space. It is located directly above the thermosphere, mercury and several large moons, such as the Moon and the Galilean satellites of Jupiter, have exospheres without a denser atmosphere underneath, referred to as a surface boundary exosphere. Here, molecules are ejected on elliptic trajectories until they collide with the surface, smaller bodies such as asteroids, in which the molecules emitted from the surface escape to space, are not considered to have exospheres. The most common molecules within Earths exosphere are those of the lightest atmospheric gasses, hydrogen is present throughout the exosphere, with some helium, carbon dioxide, and atomic oxygen near its base. Because it can be difficult to define the boundary between the exosphere and outer space, the exosphere may be considered a part of interplanetary or outer space, the lower boundary of the exosphere is called the exobase. It is also called exopause and critical altitude as this is the altitude where barometric conditions no longer apply, atmospheric temperature becomes nearly a constant above this altitude. On Earth, the altitude of the ranges from about 500 to 1,000 kilometres depending on solar activity. This is shown in the following, consider a volume of air, with horizontal area A and height equal to the mean free path l, at pressure p and temperature T. For an ideal gas, the number of molecules contained in it is, from the requirement that each molecule traveling upward undergoes on average one collision, the pressure is, p = m A n g A where m A is the mean molecular mass of the gas. Solving these two equations gives, l = R T m A g which is the equation for the scale height. The fluctuation in the height of the exobase is important because this provides atmospheric drag on satellites, in principle, the exosphere covers distances where particles are still gravitationally bound to Earth, i. e. particles still have ballistic orbits that will take them back towards Earth. The upper boundary of the exosphere can be defined as the distance at which the influence of radiation pressure on atomic hydrogen exceeds that of Earths gravitational pull. This happens at half the distance to the Moon, the exosphere, observable from space as the geocorona, is seen to extend to at least 10,000 kilometres from Earths surface. The exosphere is a zone between Earths atmosphere and space. On 17 August 2015, based on studies with the Lunar Atmosphere and Dust Environment Explorer spacecraft, gerd W. Prolss, Physics of the Earths Space Environment, An Introduction
26.
International Standard Book Number
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The International Standard Book Number is a unique numeric commercial book identifier. An ISBN is assigned to each edition and variation of a book, for example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, the method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country. The initial ISBN configuration of recognition was generated in 1967 based upon the 9-digit Standard Book Numbering created in 1966, the 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108. Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure, however, this can be rectified later. Another identifier, the International Standard Serial Number, identifies periodical publications such as magazines, the ISBN configuration of recognition was generated in 1967 in the United Kingdom by David Whitaker and in 1968 in the US by Emery Koltay. The 10-digit ISBN format was developed by the International Organization for Standardization and was published in 1970 as international standard ISO2108, the United Kingdom continued to use the 9-digit SBN code until 1974. The ISO on-line facility only refers back to 1978, an SBN may be converted to an ISBN by prefixing the digit 0. For example, the edition of Mr. J. G. Reeder Returns, published by Hodder in 1965, has SBN340013818 -340 indicating the publisher,01381 their serial number. This can be converted to ISBN 0-340-01381-8, the check digit does not need to be re-calculated, since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with Bookland European Article Number EAN-13s. An ISBN is assigned to each edition and variation of a book, for example, an ebook, a paperback, and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, a 13-digit ISBN can be separated into its parts, and when this is done it is customary to separate the parts with hyphens or spaces. Separating the parts of a 10-digit ISBN is also done with either hyphens or spaces, figuring out how to correctly separate a given ISBN number is complicated, because most of the parts do not use a fixed number of digits. ISBN issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for country or territory regardless of the publication language. Some ISBN registration agencies are based in national libraries or within ministries of culture, in other cases, the ISBN registration service is provided by organisations such as bibliographic data providers that are not government funded. In Canada, ISBNs are issued at no cost with the purpose of encouraging Canadian culture. In the United Kingdom, United States, and some countries, where the service is provided by non-government-funded organisations. Australia, ISBNs are issued by the library services agency Thorpe-Bowker
27.
PubMed Identifier
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PubMed is a free search engine accessing primarily the MEDLINE database of references and abstracts on life sciences and biomedical topics. The United States National Library of Medicine at the National Institutes of Health maintains the database as part of the Entrez system of information retrieval, from 1971 to 1997, MEDLINE online access to the MEDLARS Online computerized database primarily had been through institutional facilities, such as university libraries. PubMed, first released in January 1996, ushered in the era of private, free, home-, the PubMed system was offered free to the public in June 1997, when MEDLINE searches via the Web were demonstrated, in a ceremony, by Vice President Al Gore. Information about the journals indexed in MEDLINE, and available through PubMed, is found in the NLM Catalog. As of 5 January 2017, PubMed has more than 26.8 million records going back to 1966, selectively to the year 1865, and very selectively to 1809, about 500,000 new records are added each year. As of the date,13.1 million of PubMeds records are listed with their abstracts. In 2016, NLM changed the system so that publishers will be able to directly correct typos. Simple searches on PubMed can be carried out by entering key aspects of a subject into PubMeds search window, when a journal article is indexed, numerous article parameters are extracted and stored as structured information. Such parameters are, Article Type, Secondary identifiers, Language, publication type parameter enables many special features. As these clinical girish can generate small sets of robust studies with considerable precision, since July 2005, the MEDLINE article indexing process extracts important identifiers from the article abstract and puts those in a field called Secondary Identifier. The secondary identifier field is to store numbers to various databases of molecular sequence data, gene expression or chemical compounds. For clinical trials, PubMed extracts trial IDs for the two largest trial registries, ClinicalTrials. gov and the International Standard Randomized Controlled Trial Number Register, a reference which is judged particularly relevant can be marked and related articles can be identified. If relevant, several studies can be selected and related articles to all of them can be generated using the Find related data option, the related articles are then listed in order of relatedness. To create these lists of related articles, PubMed compares words from the title and abstract of each citation, as well as the MeSH headings assigned, using a powerful word-weighted algorithm. The related articles function has been judged to be so precise that some researchers suggest it can be used instead of a full search, a strong feature of PubMed is its ability to automatically link to MeSH terms and subheadings. Examples would be, bad breath links to halitosis, heart attack to myocardial infarction, where appropriate, these MeSH terms are automatically expanded, that is, include more specific terms. Terms like nursing are automatically linked to Nursing or Nursing and this important feature makes PubMed searches automatically more sensitive and avoids false-negative hits by compensating for the diversity of medical terminology. The My NCBI area can be accessed from any computer with web-access, an earlier version of My NCBI was called PubMed Cubby
28.
Integrated Authority File
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The Integrated Authority File or GND is an international authority file for the organisation of personal names, subject headings and corporate bodies from catalogues. It is used mainly for documentation in libraries and increasingly also by archives, the GND is managed by the German National Library in cooperation with various regional library networks in German-speaking Europe and other partners. The GND falls under the Creative Commons Zero license, the GND specification provides a hierarchy of high-level entities and sub-classes, useful in library classification, and an approach to unambiguous identification of single elements. It also comprises an ontology intended for knowledge representation in the semantic web, available in the RDF format
29.
National Diet Library
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The National Diet Library is the only national library in Japan. It was established in 1948 for the purpose of assisting members of the National Diet of Japan in researching matters of public policy, the library is similar in purpose and scope to the United States Library of Congress. The National Diet Library consists of two facilities in Tokyo and Kyoto, and several other branch libraries throughout Japan. The Diets power in prewar Japan was limited, and its need for information was correspondingly small, the original Diet libraries never developed either the collections or the services which might have made them vital adjuncts of genuinely responsible legislative activity. Until Japans defeat, moreover, the executive had controlled all political documents, depriving the people and the Diet of access to vital information. The U. S. occupation forces under General Douglas MacArthur deemed reform of the Diet library system to be an important part of the democratization of Japan after its defeat in World War II. In 1946, each house of the Diet formed its own National Diet Library Standing Committee, hani Gorō, a Marxist historian who had been imprisoned during the war for thought crimes and had been elected to the House of Councillors after the war, spearheaded the reform efforts. Hani envisioned the new body as both a citadel of popular sovereignty, and the means of realizing a peaceful revolution, the National Diet Library opened in June 1948 in the present-day State Guest-House with an initial collection of 100,000 volumes. The first Librarian of the Diet Library was the politician Tokujirō Kanamori, the philosopher Masakazu Nakai served as the first Vice Librarian. In 1949, the NDL merged with the National Library and became the national library in Japan. At this time the collection gained a million volumes previously housed in the former National Library in Ueno. In 1961, the NDL opened at its present location in Nagatachō, in 1986, the NDLs Annex was completed to accommodate a combined total of 12 million books and periodicals. The Kansai-kan, which opened in October 2002 in the Kansai Science City, has a collection of 6 million items, in May 2002, the NDL opened a new branch, the International Library of Childrens Literature, in the former building of the Imperial Library in Ueno. This branch contains some 400,000 items of literature from around the world. Though the NDLs original mandate was to be a library for the National Diet. In the fiscal year ending March 2004, for example, the library reported more than 250,000 reference inquiries, in contrast, as Japans national library, the NDL collects copies of all publications published in Japan. The NDL has an extensive collection of some 30 million pages of documents relating to the Occupation of Japan after World War II. This collection include the documents prepared by General Headquarters and the Supreme Commander of the Allied Powers, the Far Eastern Commission, the NDL maintains a collection of some 530,000 books and booklets and 2 million microform titles relating to the sciences
