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Electron mobility In here, the following definition for the scattering cross section is used: number of particles scattered into solid angle dΩ per unit time divided by number of particles per area per time (incident intensity), which comes from classical mechanics. As Boltzmann statistics are valid for semiconductors ... | https://en.wikipedia.org/wiki?curid=760994 |
Electron mobility At lower temperatures, ionized impurity scattering dominates, while at higher temperatures, phonon scattering dominates, and the actual mobility reaches a maximum at an intermediate temperature. Carrier mobility is most commonly measured using the Hall effect. The result of the measurement is called t... | https://en.wikipedia.org/wiki?curid=760994 |
Electron mobility Sub "v" into the expression for "ξ", where "R" is the Hall coefficient for electron, and is defined as Since formula_32 Similarly, for holes From the Hall coefficient, we can obtain the carrier mobility as follows: Similarly, Here the value of "V (Hall voltage), t (sample thickness), I (current) and B... | https://en.wikipedia.org/wiki?curid=760994 |
Electron mobility In this technique, the transistor is operated in the linear region (or "ohmic mode"), where V is small and formula_40 with slope m. Then the mobility is: This equation comes from the approximate equation for a MOSFET in the linear region: In practice, this technique may overestimate the true mobility,... | https://en.wikipedia.org/wiki?curid=760994 |
Electron mobility formula_43 and up), the mobility in silicon is often characterized by the empirical relationship: where "N" is the doping concentration (either "N" or "N"), and "N" and α are fitting parameters. At room temperature, the above equation becomes: Majority carriers: Minority carriers: These equations appl... | https://en.wikipedia.org/wiki?curid=760994 |
Terne plate is a form of tinplate: a thin steel sheet coated with an alloy of lead and tin. The terne alloy was in the ratio of 10-20% tin and the remainder lead. The low tin content made it cheaper than other tinplates. plate was used for tinsmithed sheet metal goods, such as storage vessels, jugs and funnels, particu... | https://en.wikipedia.org/wiki?curid=761347 |
Terne If the paint is maintained, terne metal can last 90 years or more. coated stainless steel (TCS II or Roofinox) or copper is commonly used to replace terne metal roofs as either material will outlast terne metal. coated stainless steel roofing can last 100 years or more unpainted, copper roofing can last 50 years ... | https://en.wikipedia.org/wiki?curid=761347 |
Marshall Warren Nirenberg (April 10, 1927 – January 15, 2010) was an American biochemist and geneticist. He shared a Nobel Prize in Physiology or Medicine in 1968 with Har Gobind Khorana and Robert W. Holley for "breaking the genetic code" and describing how it operates in protein synthesis. In the same year, together ... | https://en.wikipedia.org/wiki?curid=762368 |
Marshall Warren Nirenberg Nirenberg's groundbreaking experiments advanced him to become the head of the Section of Biochemical Genetics in 1962 in the National Heart Institute (now the National Heart, Lung, and Blood Institute), where he remained a laboratory chief until his death. Fellow laboratory chiefs included Ern... | https://en.wikipedia.org/wiki?curid=762368 |
Marshall Warren Nirenberg By 1958, experiments and analysis such as the Avery–MacLeod–McCarty experiment, the Hershey–Chase experiment, the and the Meselson–Stahl experiment had shown DNA to be the molecule of genetic information. It was not known, however, how DNA directed the expression of proteins, or what role RNA ... | https://en.wikipedia.org/wiki?curid=762368 |
Marshall Warren Nirenberg In August 1961, at the International Congress of Biochemistry in Moscow, Nirenberg presented a paper to a small group of scientists. Francis Crick convinced the conference leaders to invite Nirenberg to repeat his performance the next day. Speaking before the assembled congress of more than a ... | https://en.wikipedia.org/wiki?curid=762368 |
Marshall Warren Nirenberg , director of the National Institute of Arthritis and Metabolic Diseases, called this period of collaboration "NIH's finest hour". Nirenberg's later research focused on neuroscience, neural development, and the homeobox genes. | https://en.wikipedia.org/wiki?curid=762368 |
Supercritical fluid A supercritical fluid (SCF) is any substance at a temperature and pressure above its critical point, where distinct liquid and gas phases do not exist. It can effuse through solids like a gas, and dissolve materials like a liquid. In addition, close to the critical point, small changes in pressure o... | https://en.wikipedia.org/wiki?curid=762691 |
Supercritical fluid By changing the pressure and temperature of the fluid, the properties can be "tuned" to be more liquid-like or more gas-like. One of the most important properties is the solubility of material in the fluid. Solubility in a supercritical fluid tends to increase with density of the fluid (at constant ... | https://en.wikipedia.org/wiki?curid=762691 |
Supercritical fluid Other properties, such as density, can also be calculated using equations of state. Figures 1 and 2 show two-dimensional projections of a phase diagram. In the pressure-temperature phase diagram (Fig. 1) the boiling separates the gas and liquid region and ends in the critical point, where the liquid... | https://en.wikipedia.org/wiki?curid=762691 |
Supercritical fluid viscosity, the relative permittivity and the solvent strength, which are all closely related to the density. At higher temperatures, the fluid starts to behave like a gas, as can be seen in Figure 2. For carbon dioxide at 400 K, the density increases almost linearly with pressure. Many pressurized g... | https://en.wikipedia.org/wiki?curid=762691 |
Supercritical fluid More recently, supercritical fluids have found application in a variety of fields, ranging from the extraction of floral fragrance from flowers to applications in food science such as creating decaffeinated coffee, functional food ingredients, pharmaceuticals, cosmetics, polymers, powders, bio- and ... | https://en.wikipedia.org/wiki?curid=762691 |
Supercritical fluid The fluids appear like great black billowing clouds of smoke due to the precipitation of dissolved metals in the fluid. It is likely that at depth many of these vent sites reach supercritical conditions, but most cool sufficiently by the time they reach the sea floor to be subcritical. One particula... | https://en.wikipedia.org/wiki?curid=762691 |
Supercritical fluid The extraction can be selective to some extent by controlling the density of the medium, and the extracted material is easily recovered by simply depressurizing, allowing the supercritical fluid to return to gas phase and evaporate leaving little or no solvent residues. Carbon dioxide is the most co... | https://en.wikipedia.org/wiki?curid=762691 |
Supercritical fluid chromatography (SFC) can be used on an analytical scale, where it combines many of the advantages of high performance liquid chromatography (HPLC) and gas chromatography (GC). It can be used with non-volatile and thermally labile analytes (unlike GC) and can be used with the universal flame ionizati... | https://en.wikipedia.org/wiki?curid=762691 |
Supercritical fluid A substance is dissolved in the supercritical fluid, the solution flowed past a solid substrate, and is deposited on or dissolves in the substrate. Dyeing, which is readily carried out on polymer fibres such as polyester using disperse (non-ionic) dyes, is a special case of this. Carbon dioxide also... | https://en.wikipedia.org/wiki?curid=762691 |
Supercritical fluid The generation of pure and dried new cocrystals (crystalline molecular complexes comprising the API and one or more conformers in the crystal lattice) can be achieved due to unique properties of SCFs by using different supercritical fluid properties: supercritical CO solvent power, anti-solvent effe... | https://en.wikipedia.org/wiki?curid=762691 |
Supercritical fluid The supercritical water, acts as a solvent, a supplier of bond-breaking thermal energy, a heat transfer agent and as a source of hydrogen atoms. All polysaccharides are converted into simple sugars in near-quantitative yield in a second or less. The aliphatic inter-ring linkages of lignin are also r... | https://en.wikipedia.org/wiki?curid=762691 |
Supercritical fluid Carbon dioxide can also be used in supercritical cycle nuclear power plants, with similar efficiency gains. Many coal-fired supercritical steam generators are operational all over the world, and have enhanced the efficiency of traditional steam-power plants. Conversion of vegetable oil to biodiesel ... | https://en.wikipedia.org/wiki?curid=762691 |
Supercritical fluid There is also the possibility to reduce the amount of CO in the atmosphere by using biomass to generate power and sequestering the CO produced. The use of supercritical carbon dioxide, instead of water, has been examined as a geothermal working fluid. Supercritical carbon dioxide is also emerging as... | https://en.wikipedia.org/wiki?curid=762691 |
Supercritical fluid Additionally, due to the high rates of precursor transport in solution, it is possible to coat high surface area particles which under chemical vapour deposition would exhibit depletion near the outlet of the system and also be likely to result in unstable interfacial growth features such as dendrit... | https://en.wikipedia.org/wiki?curid=762691 |
Morse potential The Morse potential, named after physicist Philip M. Morse, is a convenient interatomic interaction model for the potential energy of a diatomic molecule. It is a better approximation for the vibrational structure of the molecule than the QHO (quantum harmonic oscillator) because it explicitly includes ... | https://en.wikipedia.org/wiki?curid=762970 |
Morse potential The force constant (stiffness) of the bond can be found by Taylor expansion of formula_8 around formula_9 to the second derivative of the potential energy function, from which it can be shown that the parameter, formula_5, is where formula_12 is the force constant at the minimum of the well. Since the z... | https://en.wikipedia.org/wiki?curid=762970 |
Morse potential where formula_28 and formula_29 is a generalized Laguerre polynomial: There also exists the following important analytical expression for matrix elements of the coordinate operator (here it is assumed that formula_31 and formula_32) The eigenenergies in the initial variables have form: where formula_35 ... | https://en.wikipedia.org/wiki?curid=762970 |
Morse potential As is clear from dimensional analysis, for historical reasons the last equation uses spectroscopic notation in which formula_51 represents a wavenumber obeying formula_54, and not an angular frequency given by formula_55. An important extension of the that made the Morse form very useful for modern spec... | https://en.wikipedia.org/wiki?curid=762970 |
Calcium peroxide or calcium dioxide is the inorganic compound with the formula CaO. It is the peroxide (O) salt of Ca. Commercial samples can be yellowish, but the pure compound is white. It is almost insoluble in water. As a solid, it is relatively stable against decomposition. In contact with water however it hydroly... | https://en.wikipedia.org/wiki?curid=763076 |
Wake In fluid dynamics, a wake may either be: The wake is the region of disturbed flow (often turbulent) downstream of a solid body moving through a fluid, caused by the flow of the fluid around the body. For a blunt body in subsonic external flow, for example the Apollo or Orion capsules during descent and landing, th... | https://en.wikipedia.org/wiki?curid=223993 |
Wake The non-dimensional parameter of interest is the Froude number. Waterfowl and boats moving across the surface of water produce a wake pattern, first explained mathematically by Lord Kelvin and known today as the Kelvin wake pattern. This pattern consists of two wake lines that form the arms of a chevron, V, with t... | https://en.wikipedia.org/wiki?curid=223993 |
Wake Airy wave theory. Parts of the pattern may be obscured by the effects of propeller wash, and tail eddies behind the boat's stern, and by the boat being a large object and not a point source. The water need not be stationary, but may be moving as in a large river, and the important consideration then is the velocit... | https://en.wikipedia.org/wiki?curid=223993 |
Wake These shock waves are at sharper angles than one would naively expect, because it is group velocity that dictates the area of constructive interference and, in deep water, the group velocity is half of the phase velocity. All shock waves, that each by itself would have had an angle between 33° and 72°, are compres... | https://en.wikipedia.org/wiki?curid=223993 |
Wake the boat assemble to the standard shock wedge tangent to all of them, cf. Fig.12.3. As indicated above, the openings of these chevrons vary with wavenumber, the angle between the phase shock wavefront and the path of the boat (the water) being = arcsin(/"v") ≡ . Evidently, increases with . However, these phase che... | https://en.wikipedia.org/wiki?curid=223993 |
Wake 3 shock pattern, the universal Kelvin wake pattern arises: the full visible chevron angle is twice that, 2arcsin(1/3) ≈ 39°. The wavefronts of the wavelets in the wake are at 53°, which is roughly the average of 33° and 72°. The wave components with would-be shock wave angles between 73° and 90° dominate the inter... | https://en.wikipedia.org/wiki?curid=223993 |
Wake Powered narrowboats on British canals are not permitted to create a breaking wash (a wake large enough to create a breaking wave) along the banks, as this erodes them. This rule normally restricts these vessels to 4 statute miles per hour or less. Wakes are occasionally used recreationally. Swimmers, people riding... | https://en.wikipedia.org/wiki?curid=223993 |
Bowen ratio The is used to describe the type of heat transfer for a surface that has moisture. Heat transfer can either occur as sensible heat (differences in temperature without evapotranspiration) or latent heat (the energy required during a change of state, without a change in temperature). The is generally used to ... | https://en.wikipedia.org/wiki?curid=224300 |
Bowen ratio The Bowen ratio, formula_10, is less than one over surfaces with abundant water supplies. | https://en.wikipedia.org/wiki?curid=224300 |
Silicon carbide (SiC), also known as carborundum , is a semiconductor containing silicon and carbon. It occurs in nature as the extremely rare mineral moissanite. Synthetic SiC powder has been mass-produced since 1893 for use as an abrasive. Grains of silicon carbide can be bonded together by sintering to form very har... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide Moissan also synthesized SiC by several routes, including dissolution of carbon in molten silicon, melting a mixture of calcium carbide and silica, and by reducing silica with carbon in an electric furnace. Acheson patented the method for making silicon carbide powder on February 28, 1893. Acheson also ... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide Naturally occurring moissanite is found in only minute quantities in certain types of meteorite and in corundum deposits and kimberlite. Virtually all the silicon carbide sold in the world, including moissanite jewels, is synthetic. Natural moissanite was first found in 1893 as a small component of the ... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide Fine SiO particles in plant material (e.g. rice husks) can be converted to SiC by heating in the excess carbon from the organic material. The silica fume, which is a byproduct of producing silicon metal and ferrosilicon alloys, can also be converted to SiC by heating with graphite at . The material form... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide Homoepitaxial and heteroepitaxial SiC layers can be grown employing both gas and liquid phase approaches. To form complex shaped SiC, preceramic polymers can be used as precursors which form the ceramic product through pyrolysis at temperatures in the range 1000–1100 °C . Precursor materials to obtain s... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide Alpha silicon carbide (α-SiC) is the most commonly encountered polymorph, and is formed at temperatures greater than 1700 °C and has a hexagonal crystal structure (similar to Wurtzite). The beta modification (β-SiC), with a zinc blende crystal structure (similar to diamond), is formed at temperatures be... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide Metallic conductivity has been achieved by heavy doping with boron, aluminium or nitrogen. Superconductivity has been detected in 3C-SiC:Al, 3C-SiC:B and 6H-SiC:B at the same temperature of 1.5 K. A crucial difference is however observed for the magnetic field behavior between aluminium and boron doping... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide In the 1980s and 1990s, silicon carbide was studied in several research programs for high-temperature gas turbines in Europe, Japan and the United States. The components were intended to replace nickel superalloy turbine blades or nozzle vanes. However, none of these projects resulted in a production qu... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide These brake disks are used on some road-going sports cars, supercars, as well as other performance cars including the Porsche Carrera GT, the Bugatti Veyron, the Chevrolet Corvette ZR1, the McLaren P1, Bentley, Ferrari, Lamborghini and some specific high-performance Audi cars. is also used in a sintered... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide This spark gap is ionized and rendered conductive when lightning raises the voltage of the power line conductor, thus effectively connecting the SiC column between the power conductor and the earth. Spark gaps used in lightning arresters are unreliable, either failing to strike an arc when needed or fai... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide As a result, devices made of SiC crystals initially displayed poor reverse blocking performance though researchers have been tentatively finding solutions to improve the breakdown performance. Apart from crystal quality, problems with the interface of SiC with silicon dioxide have hampered the developme... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide The production was soon stopped because gallium nitride showed 10–100 times brighter emission. This difference in efficiency is due to the unfavorable indirect bandgap of SiC, whereas GaN has a direct bandgap which favors light emission. However, SiC is still one of the important LED components – it is ... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide References to silicon carbide heating elements exist from the early 20th century when they were produced by Acheson's Carborundum Co. in the U.S. and EKL in Berlin. offered increased operating temperatures compared with metallic heaters. elements are used today in the melting of glass and non-ferrous me... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide Problems have been reported with the ability to join the pieces of the SiC composite. As a gemstone used in jewelry, silicon carbide is called "synthetic moissanite" or just "moissanite" after the mineral name. Moissanite is similar to diamond in several important respects: it is transparent and hard (9... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide Silicon carbide, dissolved in a basic oxygen furnace used for making steel, acts as a fuel. The additional energy liberated allows the furnace to process more scrap with the same charge of hot metal. It can also be used to raise tap temperatures and adjust the carbon and silicon content. is cheaper than... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide When it comes to its production, silicon is used primarily as a substrate to grow the graphene. But there are actually several methods that can be used to grow the graphene on the silicon carbide. The confinement controlled sublimation (CCS) growth method consists of a SiC chip that is heated under vacu... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide However, there have been certain procedures that have been performed and studied that could potentially yield methods that use lower temperatures to help manufacture graphene. More specifically this different approach to graphene growth has been observed to produce graphene within a temperature environm... | https://en.wikipedia.org/wiki?curid=225256 |
Silicon carbide In 4H-SiC, the divacancy has four different configurations which correspond to four zero-phonon lines (ZPL). These ZPL values are written using the notation V-V and the unit eV: hh(1.095), kk(1.096), kh(1.119), and hk(1.150). | https://en.wikipedia.org/wiki?curid=225256 |
Caloric theory The caloric theory is an obsolete scientific theory that heat consists of a self-repellent fluid called caloric that flows from hotter bodies to colder bodies. Caloric was also thought of as a weightless gas that could pass in and out of pores in solids and liquids. The "caloric theory" was superseded by... | https://en.wikipedia.org/wiki?curid=226412 |
Caloric theory Pierre Prévost argued that cold was simply a lack of caloric. Since heat was a material substance in caloric theory, and therefore could neither be created nor destroyed, conservation of heat was a central assumption. The introduction of the caloric theory was influenced by the experiments of Joseph Blac... | https://en.wikipedia.org/wiki?curid=226412 |
Caloric theory However, one of the greatest apparent confirmations of the caloric theory was Pierre-Simon Laplace's theoretical correction of Sir Isaac Newton’s calculation of the speed of sound. Newton had assumed an isothermal process, while Laplace, a calorist, treated it as adiabatic. This addition not only substan... | https://en.wikipedia.org/wiki?curid=226412 |
Caloric theory In 1850, Rudolf Clausius published a paper showing that the two theories were indeed compatible, as long as the calorists' principle of the conservation of heat was replaced by a principle of conservation of energy. In this way, the caloric theory was absorbed into the annals of physics, and evolved into... | https://en.wikipedia.org/wiki?curid=226412 |
Silver nitrate is an inorganic compound with chemical formula . This compound is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides. It was once called "lunar caustic" because silver was called "luna" by the ancient alchemists, who... | https://en.wikipedia.org/wiki?curid=227100 |
Silver nitrate Most metal nitrates thermally decompose to the respective oxides, but silver oxide decomposes at a lower temperature than silver nitrate, so the decomposition of silver nitrate yields elemental silver instead. is the least expensive salt of silver; it offers several other advantages as well. It is non-hy... | https://en.wikipedia.org/wiki?curid=227100 |
Silver nitrate Similarly, this reaction is used in analytical chemistry to confirm the presence of chloride, bromide, or iodide ions. Samples are typically acidified with dilute nitric acid to remove interfering ions, e.g. carbonate ions and sulfide ions. This step avoids confusion of silver sulfide or silver carbonate... | https://en.wikipedia.org/wiki?curid=227100 |
Silver nitrate Silver salts have antiseptic properties. In 1881 Credé introduced the use of dilute solutions of AgNO in newborn babies' eyes at birth to prevent contraction of gonorrhea from the mother, which could cause blindness. (Modern antibiotics are now used instead.) Fused silver nitrate, shaped into sticks, was... | https://en.wikipedia.org/wiki?curid=227100 |
Silver nitrate Silver's antimicrobial activity saw many applications prior to the discovery of modern antibiotics, when it fell into near disuse. Its association with argyria made consumers wary and led them to turn away from it when given an alternative. Repeated daily application of silver nitrate can induce adequate... | https://en.wikipedia.org/wiki?curid=227100 |
Silver nitrate Argyria is a permanent cosmetic condition in which the skin and internal organs turn a blue-gray color. The United States Environmental Protection Agency used to have a maximum contaminant limit for silver in water until 1990, when it was determined that argyria did not impact the function of any affecte... | https://en.wikipedia.org/wiki?curid=227100 |
John Lennard-Jones Sir John Edward Lennard-Jones KBE, FRS (27 October 1894 – 1 November 1954) was a British mathematician and professor of theoretical physics at the University of Bristol, and then of theoretical science at the University of Cambridge. He may be regarded as the initiator of modern computational chemist... | https://en.wikipedia.org/wiki?curid=227618 |
John Lennard-Jones Atoms of a noble gas interact via a potential in which an attracting van der Waals force balances a repelling force which results from overlapping electron orbits. A well known approximation to this potential is the so-called Lennard-Jones potential, a description of the potential energy as a functio... | https://en.wikipedia.org/wiki?curid=227618 |
Lennard-Jones potential The (also termed the L-J potential, 6-12 potential, or 12-6 potential) is a mathematically simple model that approximates the interaction between a pair of neutral atoms or molecules. A form of this interatomic potential was first proposed in 1924 by John Lennard-Jones. The most common expressio... | https://en.wikipedia.org/wiki?curid=227686 |
Lennard-Jones potential Whereas the functional form of the attractive term has a clear physical justification, the repulsive term has no theoretical justification. It is used because it approximates the Pauli repulsion well and is more convenient due to the relative computing efficiency of calculating "r" as the square... | https://en.wikipedia.org/wiki?curid=227686 |
Lennard-Jones potential There are many different ways to formulate the Lennard-Jones potential. Some common forms follow. This form is a simplified formulation that is used by some simulation software: where, formula_4 and formula_5. Conversely, formula_6 and formula_7. This is the form in which Lennard-Jones wrote the... | https://en.wikipedia.org/wiki?curid=227686 |
Lennard-Jones potential , Then the truncated formula_21 is defined as follows It can be easily verified that "V"("r") = 0, thus eliminating the jump discontinuity at "r" = "r". Although the value of the (unshifted) Lennard Jones potential at "r" = "r" = 2.5"σ" is rather small, the effect of the truncation can be signif... | https://en.wikipedia.org/wiki?curid=227686 |
Oleum (Latin "oleum", meaning oil), or fuming sulfuric acid, is a term referring to solutions of various compositions of sulfur trioxide in sulfuric acid, or sometimes more specifically to disulfuric acid (also known as pyrosulfuric acid). is identified by the CAS number 8014-95-7 (EC/List number: 616-954-1 ; ECHA Info... | https://en.wikipedia.org/wiki?curid=227914 |
Oleum The lead chamber process for sulfuric acid production was abandoned partly because it could not produce sulfur trioxide or concentrated sulfuric acid directly due to corrosion of the lead, and absorption of NO gas. Until this process was made obsolete by the contact process, oleum had to be obtained through indir... | https://en.wikipedia.org/wiki?curid=227914 |
Oleum Great care must be taken to avoid overheating, as this can increase the pressure in the tank car beyond the tank's safety valve limit. In addition, oleum is less corrosive to metals than sulfuric acid, because there is no free water to attack surfaces. Because of that, sulfuric acid is sometimes concentrated to o... | https://en.wikipedia.org/wiki?curid=227914 |
Oleum Mixtures of ordinary nitric acid in sulfuric acid therefore contain substantial amounts of water and are unsuitable for processes such as those that occur in the manufacture of trinitrotoluene. The synthesis of RDX and certain other explosives does not require oleum. Anhydrous nitric acid, referred to as white fu... | https://en.wikipedia.org/wiki?curid=227914 |
Atomic force microscopy (AFM) or scanning force microscopy (SFM) is a very-high-resolution type of scanning probe microscopy (SPM), with demonstrated resolution on the order of fractions of a nanometer, more than 1000 times better than the optical diffraction limit. (AFM) is a type of scanning probe microscopy (SPM), w... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy The surface topography is commonly displayed as a pseudocolor plot. Although the initial publication about the atomic force microscopy by Binnig, Quate and Gerber in 1986 speculated about the possibility of achieving atomic resolution, profound experimental challenges needed to be overcome befor... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy The major difference between atomic force microscopy and competing technologies such as optical microscopy and electron microscopy is that AFM does not use lenses or beam irradiation. Therefore, it does not suffer from a limitation in spatial resolution due to diffraction and aberration, and pre... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy An xyz drive (7) permits to displace the sample (6) and the sample stage (8) in x, y, and z directions with respect to the tip apex (4). Although Fig. 3 shows the drive attached to the sample, the drive can also be attached to the tip, or independent drives can be attached to both, since it is t... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy For other imaging modes, the process is similar, except that 'deflection' should be replaced by the appropriate feedback variable." When using the AFM to image a sample, the tip is brought into contact with the sample, and the sample is raster scanned along an x-y grid (fig 4). Most commonly, an... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy As long as the tip is in contact with the sample, the deflection then corresponds to surface topography. The main reason this method is not very popular anymore, is that the forces between tip and sample are not controlled, which can lead to forces high enough to damage the tip or the sample. It... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy The AFM has been applied to problems in a wide range of disciplines of the natural sciences, including solid-state physics, semiconductor science and technology, molecular engineering, polymer chemistry and physics, surface chemistry, molecular biology, cell biology, and medicine. Applications i... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy The AFM consists of a cantilever with a sharp tip (probe) at its end that is used to scan the specimen surface. The cantilever is typically silicon or silicon nitride with a tip radius of curvature on the order of nanometers. When the tip is brought into proximity of a sample surface, forces bet... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy AFM operation is usually described as one of three modes, according to the nature of the tip motion: contact mode, also called static mode (as opposed to the other two modes, which are called dynamic modes); tapping mode, also called intermittent contact, AC mode, or vibrating mode, or, after th... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy Because of this, keeping the probe tip close enough to the sample for short-range forces to become detectable while preventing the tip from sticking to the surface presents a major problem for contact mode in ambient conditions. Dynamic contact mode (also called intermittent contact, AC mode or ... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy The servo adjusts the height to maintain a set cantilever oscillation amplitude as the cantilever is scanned over the sample. A "tapping AFM" image is therefore produced by imaging the force of the intermittent contacts of the tip with the sample surface. Although the peak forces applied during ... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy Extracting the sample's material properties in a quantitative manner from phase images, however, is often not feasible. In non-contact atomic force microscopy mode, the tip of the cantilever does not contact the sample surface. The cantilever is instead oscillated at either its resonant frequenc... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy An AFM operating in contact mode will penetrate the liquid layer to image the underlying surface, whereas in non-contact mode an AFM will oscillate above the adsorbed fluid layer to image both the liquid and surface. Schemes for dynamic mode operation include frequency modulation where a phase-l... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy Amplitude modulation has also been used in the non-contact regime to image with atomic resolution by using very stiff cantilevers and small amplitudes in an ultra-high vacuum environment. Image formation is a plotting method that produces a color mapping through changing the x-y position of the ... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy Details will be explained in the case that especially "constant df mode"(FM-AFM) among AFM as an instance in next section. When the distance between the probe and the sample is brought to the range where atomic force may be detected, while a cantilever is excited in its natural eigen frequency (... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy The image in which the amounts of the negative feedback (the moving distance of the probe upward and downward in z-direction) are plotted against the x-y coordination of each measurement point is a topographic image. In other words, the topographic image is a trace of the tip of the probe regula... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy Forces of the order of a few piconewtons can now be routinely measured with a vertical distance resolution of better than 0.1 nanometers. Force spectroscopy can be performed with either static or dynamic modes. In dynamic modes, information about the cantilever vibration is monitored in addition... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy The AFM can be used to image and manipulate atoms and structures on a variety of surfaces. The atom at the apex of the tip "senses" individual atoms on the underlying surface when it forms incipient chemical bonds with each atom. Because these chemical interactions subtly alter the tip's vibrati... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy 4 mm in size – allows the operator to hold the AFM cantilever/probe assembly with tweezers and fit it into the corresponding holder clips on the scanning head of the atomic force microscope. This device is most commonly called an "AFM probe", but other names include "AFM tip" and "cantilever" (e... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy Among the coatings used are gold – for covalent bonding of biological molecules and the detection of their interaction with a surface, diamond for increased wear resistance and magnetic coatings for detecting the magnetic properties of the investigated surface. Another solution exists to achieve... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy In fact, the adhesion force measured between tip and sample in ambient air of finite humidity is usually dominated by capillary forces. As a consequence, it is difficult to pull the tip away from the surface. For soft samples including many polymers and in particular biological materials, the st... | https://en.wikipedia.org/wiki?curid=227982 |
Atomic force microscopy When these forces are calculated, a difference must be made between the wet on dry situation and the wet on wet situation. For a spherical tip, the force is: formula_4 for dry on wet formula_5for wet on wet where θ is the contact angle of the dry sphere and φ is the immersed angle, as shown in t... | https://en.wikipedia.org/wiki?curid=227982 |
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