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Lignin The conventional method for lignin quantitation in the pulp industry is the Klason lignin and acid-soluble lignin test, which is standardized according to TAPPI or NREL procedure. The cellulose is first decrystallized and partially depolymerized into oligomers by keeping the sample in 72% sulfuric acid at 30 °C ... | https://en.wikipedia.org/wiki?curid=190996 |
Lignin The ratio of syringyl lignol (S) to vanillyl lignol (V) and cinnamyl lignol (C) to vanillyl lignol (V) is variable based on plant type and can therefore be used to trace plant sources in aquatic systems (woody vs. non-woody and angiosperm vs. gymnosperm). Ratios of carboxylic acid (Ad) to aldehyde (Al) forms of ... | https://en.wikipedia.org/wiki?curid=190996 |
Planck's law describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature "T", when there is no net flow of matter or energy between the body and its environment. At the end of the 19th century, physicists were unable to explain why the observed spect... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law The spectral radiance can also be expressed per unit wavelength instead of per unit frequency. By choosing an appropriate system of unit of measure (i.e. natural Planck units), the law can be simplified to become: Equating the integral of spectral radiance in per unit wavelength to that of per unit frequen... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law As an energy distribution, it is one of a family of thermal equilibrium distributions which include the Bose–Einstein distribution, the Fermi–Dirac distribution and the Maxwell–Boltzmann distribution. A black-body is an idealised object which absorbs and emits all radiation frequencies. Near thermodynamic ... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law The passage of radiation across an interface between media can be characterized by the emissivity of the interface (the ratio of the actual radiance to the theoretical Planck radiance), usually denoted by the symbol . It is in general dependent on chemical composition and physical structure, on temperature... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law If the photon gas is not Planckian, the second law of thermodynamics guarantees that interactions (between photons and other particles or even, at sufficiently high temperatures, between the photons themselves) will cause the photon energy distribution to change and approach the Planck distribution. In suc... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law The various forms of the law for spectral radiance are summarized in the table below. Forms on the left are most often encountered in experimental fields, while those on the right are most often encountered in theoretical fields. These distributions represent the spectral radiance of blackbodies—the power ... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law In order to convert the corresponding forms so that they express the same quantity in the same units we multiply by the spectral increment. Then, for a particular spectral increment, the particular physical energy increment may be written Also, , so that . Substitution gives the correspondence between the ... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law so that for "spectral radiant exitance" can be written as describes the unique and characteristic spectral distribution for electromagnetic radiation in thermodynamic equilibrium, when there is no net flow of matter or energy. Its physics is most easily understood by considering the radiation in a cavity w... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law If supplemented by the classically unjustifiable assumption that for some reason the radiation is finite, classical thermodynamics provides an account of some aspects of the Planck distribution, such as the Stefan–Boltzmann law, and the Wien displacement law. For the case of the presence of matter, quantum... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law This is unlike the case of thermodynamic equilibrium for material gases, for which the internal energy is determined not only by the temperature, but also, independently, by the respective numbers of the different molecules, and independently again, by the specific characteristics of the different molecule... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law The following is an introductory sketch of that situation, and is very far from being a rigorous physical argument. The purpose here is only to summarize the main physical factors in the situation, and the main conclusions. There is a difference between conductive heat transfer and radiative heat transfer.... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law This must hold for every frequency band. This became clear to Balfour Stewart and later to Kirchhoff. Balfour Stewart found experimentally that of all surfaces, one of lamp-black emitted the greatest amount of thermal radiation for every quality of radiation, judged by various filters. Thinking theoretical... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law At that frequency , the radiative power from the walls into that cross-section in the opposite sense in that direction may be denoted , for the wall temperature . For the material of , defining the absorptivity as the fraction of that incident radiation absorbed by , that incident energy is absorbed at a r... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law The equality of absorptivity and emissivity here demonstrated is specific for thermodynamic equilibrium at temperature and is in general not to be expected to hold when conditions of thermodynamic equilibrium do not hold. The emissivity and absorptivity are each separately properties of the molecules of th... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law According to Kirchhoff's law of thermal radiation, this entails that, for every frequency , at thermodynamic equilibrium at temperature , one has , so that the thermal radiation from a black body is always equal to the full amount specified by Planck's law. No physical body can emit thermal radiation that ... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law Radiation entering the hole has almost no possibility of escaping the cavity without being absorbed by multiple impacts with its walls. As explained by Planck, a radiating body has an interior consisting of matter, and an interface with its contiguous neighbouring material medium, which is usually the medi... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law Because of the isotropy of the radiation in the body's interior, the spectral radiance of radiation transmitted from its interior to its exterior through its surface is independent of direction. This is expressed by saying that radiation from the surface of a black body in thermodynamic equilibrium obeys L... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law The total power emitted per unit area at the surface of a black body () may be found by integrating the black body spectral flux found from Lambert's law over all frequencies, and over the solid angles corresponding to a hemisphere () above the surface. The infinitesimal solid angle can be expressed in sph... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law Stimulated emission is emission by the material body which is caused by and is proportional to the incoming radiation. It is included in the absorption term because, like absorption, it is proportional to the intensity of the incoming radiation. Since the amount of absorption will generally vary linearly a... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law The change in a light beam as it traverses a small distance will then be The equation of radiative transfer will then be the sum of these two contributions: If the radiation field is in equilibrium with the material medium, then the radiation will be homogeneous (independent of position) so that and: which... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law The three parameters , and , known as the Einstein coefficients, are associated with the photon frequency produced by the transition between two energy levels (states). As a result, each line in a spectra has its own set of associated coefficients. When the atoms and the radiation field are in equilibrium,... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law In addition, one must also multiply the result of the substitution by This factor shifts the peak of the distribution to higher energies. These peaks are the "mode" energy of a photon, when binned using equal-size bins of frequency or wavelength, respectively. Meanwhile, the "average" energy of a photon fr... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law 01% of the radiation is at a wavelength below µm, 20% below µm, etc. The wavelength and frequency peaks are in bold and occur at 25.0% and 64.6% respectively. The 41.8% point is the wavelength-frequency-neutral peak. These are the points at which the respective Planck-law functions , and divided by attai... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law For comparison a planet modeled as a black body radiating at a nominal 288 K (15 °C) as a representative value of the Earth's highly variable temperature has wavelengths more than twenty times that of the Sun, tabulated in the third row in micrometers (thousands of nanometers). That is, only 1% of the Sun'... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law Hence only 37% of the TOA insolation is visible to the human eye. The atmosphere shifts these percentages substantially in favor of visible light as it absorbs most of the ultraviolet and significant amounts of infrared. Consider a cube of side with conducting walls filled with electromagnetic radiation in... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law In the following we will calculate the internal energy of the box at absolute temperature . According to statistical mechanics, the equilibrium probability distribution over the energy levels of a particular mode is given by: Here The denominator , is the partition function of a single mode and makes prope... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law This means that the number of photon states in a certain region of -space is twice the volume of that region. An energy range of corresponds to shell of thickness in -space. Because the components of have to be positive, this shell spans an octant of a sphere. The number of photon states , in an energy ran... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law Since the radiation is the same in all directions, and propagates at the speed of light (), the spectral radiance of radiation exiting the small hole is which yields It can be converted to an expression for in wavelength units by substituting by and evaluating Dimensional analysis shows that the unit of st... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law He discussed the experiments in terms of rays which could be reflected and refracted, and which obeyed the Helmholtz reciprocity principle (though he did not use an eponym for it). He did not in this paper mention that the qualities of the rays might be described by their wavelengths, nor did he use spectr... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law He applied the Helmholtz reciprocity principle to account for the material interface processes as distinct from the processes in the interior material. He concluded that his experiments showed that, in the interior of an enclosure in thermal equilibrium, the radiant heat, reflected and emitted combined, le... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law (In contrast with Balfour Stewart's, Kirchhoff's definition of his absorption ratio did not refer in particular to a lamp-black surface as the source of the incident radiation.) Thus the ratio of emitting power to absorption ratio is a dimensioned quantity, with the dimensions of emitting power, because is... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law In 1860, still not knowing of Stewart's measurements for selected qualities of radiation, Kirchhoff pointed out that it was long established experimentally that for total heat radiation, of unselected quality, emitted and absorbed by a body in equilibrium, the dimensioned total radiation ratio , has one an... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law It required that the bodies be kept in a cavity in thermal equilibrium at temperature . His proof intended to show that the ratio was independent of the nature of the non-ideal body, however partly transparent or partly reflective it was. His proof first argued that for wavelength and at temperature , at t... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law (Geometrical factors, taken into detailed account by Kirchhoff, have been ignored in the foregoing.) Thus Kirchhoff's law of thermal radiation can be stated: "For any material at all, radiating and absorbing in thermodynamic equilibrium at any given temperature ', for every wavelength ', the ratio of emiss... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law In a more considered account in a book in 1862, Kirchhoff mentioned the connection of his law with "Carnot's principle", which is a form of the second law. According to Helge Kragh, "Quantum theory owes its origin to the study of thermal radiation, in particular to the "blackbody" radiation that Robert Kir... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law They had one peak at a spectral value characteristic for the temperature, and fell either side of it towards the horizontal axis. Such spectral sections are widely shown even today. In a series of papers from 1881 to 1886, Langley reported measurements of the spectrum of heat radiation, using diffraction g... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law In 1898, Otto Lummer and Ferdinand Kurlbaum published an account of their cavity radiation source. Their design has been used largely unchanged for radiation measurements to the present day. It was a platinum box, divided by diaphragms, with its interior blackened with iron oxide. It was an important ingre... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law For theoretical reasons, Planck at that time accepted this formulation, which has an effective cut-off of short wavelengths. Max Planck produced his law on 19 October 1900 as an improvement upon the Wien approximation, published in 1896 by Wilhelm Wien, which fit the experimental data at short wavelengths ... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law Planck perhaps patched together these two heuristic formulas, for long and for short wavelengths, to produce a formula This led Planck to the formula where Planck used the symbols and to denote empirical fitting constants. Planck sent this result to Rubens, who compared it with his and Kurlbaum's observati... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law The hypothetical oscillators were for Planck purely imaginary theoretical investigative probes, and he said of them that such oscillators do not need to "really exist somewhere in nature, provided their existence and their properties are consistent with the laws of thermodynamics and electrodynamics.". Pla... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law Heuristically, Boltzmann had distributed the energy in arbitrary merely mathematical quanta , which he had proceeded to make tend to zero in magnitude, because the finite magnitude had served only to allow definite counting for the sake of mathematical calculation of probabilities, and had no physical sign... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law Present-day physics explains the transduction between frequencies in the presence of atoms by their quantum excitability, following Einstein. Planck believed that in a cavity with perfectly reflecting walls and with no matter present, the electromagnetic field cannot exchange energy between frequency compo... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law Some recent proposals in the possible physical explanation of the Planck's constant suggests that, following de Broglie's spirit of wave-particle duality, if regarding the radiation as a wave packet, the Planck's constant is determined by the physical properties of the vacuum and a critical amount of distu... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law As an introduction to his reasoning, Einstein recapitulated Planck's model of hypothetical resonant material electric oscillators as sources and sinks of radiation, but then he offered a new argument, disconnected from that model, but partly based on a thermodynamic argument of Wien, in which Planck's form... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law " Kuhn pointed out that his study of Planck's papers of 1900 and 1901, and of his monograph of 1906, had led him to "heretical" conclusions, contrary to the widespread assumptions of others who saw Planck's writing only from the perspective of later, anachronistic, viewpoints. Kuhn's conclusions, finding a... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law It was first noted by Lord Rayleigh in 1900, and then in 1901 by Sir James Jeans; and later, in 1905, by Einstein when he wanted to support the idea that light propagates as discrete packets, later called 'photons', and by Rayleigh and by Jeans. In 1913, Bohr gave another formula with a further different p... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law In an electromagnetic field isolated in a vacuum in a vessel with perfectly reflective walls, such as was considered by Planck, indeed the photons would be conserved according to Einstein's 1905 model, but Lewis was referring to a field of photons considered as a system closed with respect to ponderable ma... | https://en.wikipedia.org/wiki?curid=191123 |
Planck's law At that time, Heisenberg knew nothing of matrix algebra, but Max Born read the manuscript of Heisenberg's paper and recognized the matrix character of Heisenberg's theory. Then Born and Jordan published an explicitly matrix theory of quantum mechanics, based on, but in form distinctly different from, Heise... | https://en.wikipedia.org/wiki?curid=191123 |
Congenital disorder of glycosylation A congenital disorder of glycosylation (previously called carbohydrate-deficient glycoprotein syndrome) is one of several rare inborn errors of metabolism in which glycosylation of a variety of tissue proteins and/or lipids is deficient or defective. Congenital disorders of glycosyl... | https://en.wikipedia.org/wiki?curid=191510 |
Congenital disorder of glycosylation A biologically very important group of carbohydrates is the asparagine (Asn)-linked, or N-linked, oligosaccharides. Their biosynthetic pathway is very complex and involves a hundred or more glycosyltransferases, glycosidases, transporters and synthases. This plethora allows for the ... | https://en.wikipedia.org/wiki?curid=191510 |
Congenital disorder of glycosylation Not all structures are fully modified, some remain as high-mannose structures, others as hybrids (one unmodified Man branch and one modified), but the majority become fully modified complex type oligosaccharides. In addition to glycosidase I, mutations have been found: However, the ... | https://en.wikipedia.org/wiki?curid=191510 |
Congenital disorder of glycosylation " POMT1/POMT2-CDG (Walker-Warburg syndrome and Muscle-Eye-Brain syndrome)) with deficiencies in "O"-mannosylation of proteins; "O"-xylosylglycan synthesis defects (EXT1/EXT2-CDG (hereditary multiple exostoses) and B4GALT7-CDG (Ehlers-Danlos syndrome, progeroid variant)); "O"-fucosyl... | https://en.wikipedia.org/wiki?curid=191510 |
Congenital disorder of glycosylation During the next 15 years the underlying defect remained unknown but since the plasmaprotein transferrin was underglycosylated (as shown by "e.g." "isoelectric focusing"), the new syndrome was named carbohydrate-deficient glycoprotein syndrome (CDGS) Its "classical" phenotype include... | https://en.wikipedia.org/wiki?curid=191510 |
OLED An organic light-emitting diode (or Organic LED), also known as an organic EL (organic electroluminescent) diode, is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound that emits light in response to an electric current. This organic layer is situated between ... | https://en.wikipedia.org/wiki?curid=191646 |
OLED In low ambient light conditions (such as a dark room), an screen can achieve a higher contrast ratio than an LCD, regardless of whether the LCD uses cold cathode fluorescent lamps or an LED backlight. displays are made in the same way as LCDs, but after TFT (for active matrix displays), addressable grid (for passi... | https://en.wikipedia.org/wiki?curid=191646 |
OLED They further described the necessary energetic requirements (work functions) for hole and electron injecting electrode contacts. These contacts are the basis of charge injection in all modern devices. Pope's group also first observed direct current (DC) electroluminescence under vacuum on a single pure crystal of ... | https://en.wikipedia.org/wiki?curid=191646 |
OLED Their proposed mechanism involved electronic excitation at the contacts between the graphite particles and the anthracene molecules. Roger Partridge made the first observation of electroluminescence from polymer films at the National Physical Laboratory in the United Kingdom. The device consisted of a film of poly... | https://en.wikipedia.org/wiki?curid=191646 |
OLED In 1999, Kodak and Sanyo had entered into a partnership to jointly research, develop, and produce displays. They announced the world's first 2.4-inch active-matrix, full-color display in September the same year. In September 2002, they presented a prototype of 15-inch HDTV format display based on white with color ... | https://en.wikipedia.org/wiki?curid=191646 |
OLED These materials have conductivity levels ranging from insulators to conductors, and are therefore considered organic semiconductors. The highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of organic semiconductors are analogous to the valence and conduction bands of inorganic semiconductors.... | https://en.wikipedia.org/wiki?curid=191646 |
OLED During operation, a voltage is applied across the such that the anode is positive with respect to the cathode. Anodes are picked based upon the quality of their optical transparency, electrical conductivity, and chemical stability. A current of electrons flows through the device from cathode to anode, as electrons... | https://en.wikipedia.org/wiki?curid=191646 |
OLED Decay from triplet states (phosphorescence) is spin forbidden, increasing the timescale of the transition and limiting the internal efficiency of fluorescent devices. Phosphorescent organic light-emitting diodes make use of spin–orbit interactions to facilitate intersystem crossing between singlet and triplet stat... | https://en.wikipedia.org/wiki?curid=191646 |
OLED Experimental research has proven that the properties of the anode, specifically the anode/hole transport layer (HTL) interface topography plays a major role in the efficiency, performance, and lifetime of organic light-emitting diodes. Imperfections in the surface of the anode decrease anode-organic film interface... | https://en.wikipedia.org/wiki?curid=191646 |
OLED Similarly, hole only devices can be made by using a cathode made solely of aluminium, resulting in an energy barrier too large for efficient electron injection. Balanced charge injection and transfer are required to get high internal efficiency, pure emission of luminance layer without contaminated emission from c... | https://en.wikipedia.org/wiki?curid=191646 |
OLED Fluorescent dyes can be chosen to obtain light emission at different wavelengths, and compounds such as perylene, rubrene and quinacridone derivatives are often used. Alq has been used as a green emitter, electron transport material and as a host for yellow and red emitting dyes. The production of small molecule d... | https://en.wikipedia.org/wiki?curid=191646 |
OLED Polymer light-emitting diodes (PLED, P-OLED), also light-emitting polymers (LEP), involve an electroluminescent conductive polymer that emits light when connected to an external voltage. They are used as a thin film for full-spectrum colour displays. Polymer OLEDs are quite efficient and require a relatively small... | https://en.wikipedia.org/wiki?curid=191646 |
OLED While unsubstituted poly(p-phenylene vinylene) (PPV) is typically insoluble, a number of PPVs and related poly(naphthalene vinylene)s (PNVs) that are soluble in organic solvents or water have been prepared via ring opening metathesis polymerization. These water-soluble polymers or conjugated poly electrolytes (CPE... | https://en.wikipedia.org/wiki?curid=191646 |
OLED The use of macromolecular species like polyhedral oligomeric silsesquioxanes (POSS) in conjunction with the use of phosphorescent species such as Ir for printed OLEDs have exhibited brightnesses as high as 10,000cd/m. All displays (passive and active matrix) use a driver IC, often mounted using Chip-on-glass (COG)... | https://en.wikipedia.org/wiki?curid=191646 |
OLED An oxygen meter ensures that no oxygen enters the chamber as it could damage (through oxidation) the electroluminescent material, which is in powder form. The mask is aligned with the mother substrate before every use, and it is placed just below the substrate. The substrate and mask assembly are placed at the top... | https://en.wikipedia.org/wiki?curid=191646 |
OLED This is done by using an emission spectrum with high human-eye sensitivity, special color filters with a low spectrum overlap, and performance tuning with color statistics into consideration. This approach is also called the "Color-by-white" method. There are other types of emerging patterning technologies to incr... | https://en.wikipedia.org/wiki?curid=191646 |
OLED In OLEDs, light produced from the emissive layers of the is partially transmitted out of the device and partially trapped inside the device by total internal reflection (TIR). This trapped light is wave-guided along the interior of the device until it reaches an edge where it is dissipated by either absorption or ... | https://en.wikipedia.org/wiki?curid=191646 |
OLED Afterwards, the anode layer is applied to the device backplane to form bottom electrode. layers are applied to the anode layer with conventional vapor deposition, and covered with a conductive metal electrode layer. transfer-printing was capable to print onto target substrates up to 500mm X 400mm. This size limit ... | https://en.wikipedia.org/wiki?curid=191646 |
OLED One 2008 technical report on an TV panel found that after 1,000hours, the blue luminance degraded by 12%, the red by 7% and the green by 8%. In particular, blue OLEDs historically have had a lifetime of around 14,000hours to half original brightness (five years at eight hours per day) when used for flat-panel disp... | https://en.wikipedia.org/wiki?curid=191646 |
OLED It is said that the chemical breakdown in the semiconductors occurs in four steps: However, some manufacturers' displays aim to increase the lifespan of displays, pushing their expected life past that of LCD displays by improving light outcoupling, thus achieving the same brightness at a lower drive current. In 20... | https://en.wikipedia.org/wiki?curid=191646 |
OLED The organic layers are applied using inkjet printing, and the inorganic layers are applied using Atomic Layer Deposition (ALD). The encapsulation process is carried out under a nitrogen environment, using UV-curable LOCA glue and the electroluminescent and electrode material deposition processes are carried out un... | https://en.wikipedia.org/wiki?curid=191646 |
OLED Improvements to the efficiency and lifetime of blue OLEDs is vital to the success of OLEDs as replacements for LCD technology. Considerable research has been invested in developing blue OLEDs with high external quantum efficiency, as well as a deeper blue color. External quantum efficiency values of 20% and 19% ha... | https://en.wikipedia.org/wiki?curid=191646 |
Antoine Jérôme Balard (1802–1876) was a French chemist and one of the discoverers of bromine. Born at Montpellier, France, on 30 September 1802, he started as an apothecary, but taking up teaching he acted as chemical assistant at the faculty of sciences of his native town, and then became professor of chemistry at the... | https://en.wikipedia.org/wiki?curid=191838 |
Antoine Jérôme Balard In his researches on the bleaching compounds of chlorine he was the first to advance the view that bleaching-powder is a double compound of calcium chloride and hypochlorite; and he devoted much time to the problem of economically obtaining soda and potash from seawater, though here his efforts we... | https://en.wikipedia.org/wiki?curid=191838 |
Louis Nicolas Vauquelin Prof FRS(For) HFRSE (16 May 1763 – 14 November 1829) was a French pharmacist and chemist. He was the discoverer of both chromium and beryllium. Vauquelin was born at Saint-André-d'Hébertot in Normandy, France, the son of Nicolas Vauquelin, an estate manager, and his wife, Catherine Le Charterier... | https://en.wikipedia.org/wiki?curid=191850 |
Louis Nicolas Vauquelin He also managed to get liquid ammonia at atmospheric pressure. Later with Fourcroy, he identified a metal in a platinum residue they called ‘"ptène"’, This name ‘ptene’ or ‘ptène’ was reported as an early synonym for osmium. Either together or successively he held the offices of inspector of min... | https://en.wikipedia.org/wiki?curid=191850 |
Louis Nicolas Vauquelin He also discovered pectin and malic acid in apples, and isolated camphoric acid and quinic acid. His death occurred while he was on a visit to his birthplace. Among his best known works is ""Manuel de l'essayeur"" (Manual of the assayer). The plant genus "Vauquelinia" is named in his honor, as i... | https://en.wikipedia.org/wiki?curid=191850 |
Electric-field screening In physics, screening is the damping of electric fields caused by the presence of mobile charge carriers. It is an important part of the behavior of charge-carrying fluids, such as ionized gases (classical plasmas), electrolytes, and charge carriers in electronic conductors (semiconductors, met... | https://en.wikipedia.org/wiki?curid=191897 |
Electric-field screening In solid-state physics, especially for metals and semiconductors, the screening effect describes the electrostatic field and Coulomb potential of an ion inside the solid. Like the electric field of the nucleus is reduced inside an atom or ion due to the shielding effect, the electric fields of ... | https://en.wikipedia.org/wiki?curid=191897 |
Electric-field screening It manifests itself on macroscopic scales by a sheath (Debye sheath) next to a material with which the plasma is in contact. The screened potential determines the inter atomic force and the phonon dispersion relation in metals. The screened potential is used to calculate the electronic band str... | https://en.wikipedia.org/wiki?curid=191897 |
Electric-field screening The associated charge density is "Qδ"("r"), where "δ"("r") is the Dirac delta function. After the system has returned to equilibrium, let the change in the electron density and electric potential be "Δρ"("r") and "Δφ"("r") respectively. The charge density and electric potential are related by P... | https://en.wikipedia.org/wiki?curid=191897 |
Electric-field screening The former condition corresponds, in a real experiment, to keeping the metal/fluid in electrical contact with a fixed potential difference with ground. The chemical potential "μ" is, by definition, the energy of adding an extra electron to the fluid. This energy may be decomposed into a kinetic... | https://en.wikipedia.org/wiki?curid=191897 |
Electric-field screening It is a Coulomb potential multiplied by an exponential damping term, with the strength of the damping factor given by the magnitude of "k", the Debye or Fermi-Thomas wave vector. Note that this potential has the same form as the Yukawa potential. This screening yields a dielectric function form... | https://en.wikipedia.org/wiki?curid=191897 |
Electric-field screening One corresponds to the excitation of Langmuir waves by the particle, and the other one is its screened potential, as classically obtained by a linearized Vlasovian calculation involving a test particle (section 9.2 of). The screened potential is the above screened Coulomb potential for a therma... | https://en.wikipedia.org/wiki?curid=191897 |
Structural formula The structural formula of a chemical compound is a graphic representation of the molecular structure (determined by structural chemistry methods), showing how the atoms are possibly arranged in the real three-dimensional space. The chemical bonding within the molecule is also shown, either explicitly... | https://en.wikipedia.org/wiki?curid=191985 |
Structural formula Two or three parallel lines between pairs of atoms represent double or triple bonds, respectively. Alternatively, pairs of dots may be used to represent bonding pairs. In addition, all non-bonded electrons (paired or unpaired) and any formal charges on atoms are indicated. In early organic-chemistry ... | https://en.wikipedia.org/wiki?curid=191985 |
Structural formula Hydrogen atoms attached to atoms other than carbon must be written explicitly. Several methods exist to picture the three-dimensional arrangement of atoms in a molecule (stereochemistry). Chirality in skeletal formulas is indicated by the Natta projection method. Solid wedged or dashed wedged bonds r... | https://en.wikipedia.org/wiki?curid=191985 |
Structural formula The only difference is a slightly different perspective: the Newman projection looking straight down the bond of interest, the sawhorse projection looking at the same bond but from a somewhat oblique vantage point. In the Newman projection, a circle is used to represent a plane perpendicular to the b... | https://en.wikipedia.org/wiki?curid=191985 |
Structural formula The projection is unrealistic, as a saccharide would never adopt this multiply eclipsed conformation. Nonetheless, the Fischer projection is a simple way of depicting multiple sequential stereocenters that does not require or imply any knowledge of actual conformation: Fischer projection of -Glucose ... | https://en.wikipedia.org/wiki?curid=191985 |
Green roof A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage and irrigation systems. Container gardens on roofs, where plants a... | https://en.wikipedia.org/wiki?curid=192025 |
Green roof There are two types of green roof: intensive roofs, which are thicker, with a minimum depth of , and can support a wider variety of plants but are heavier and require more maintenance, and extensive roofs, which are shallow, ranging in depth from to , lighter than intensive green roofs, and require minimal m... | https://en.wikipedia.org/wiki?curid=192025 |
Green roof Traditional building materials soak up the sun's radiation and re-emit it as heat, making cities at least hotter than surrounding areas. On Chicago's City Hall, by contrast, which features a green roof, roof temperatures on a hot day are typically cooler than they are on traditionally roofed buildings nearby... | https://en.wikipedia.org/wiki?curid=192025 |
Green roof Water is stored by the roof's substrate and then taken up by the plants, from which it is returned to the atmosphere through transpiration and evaporation. Green roofs decrease the total amount of runoff and slow the rate of runoff from the roof. It has been found that they can retain up to 75% of rainwater,... | https://en.wikipedia.org/wiki?curid=192025 |
Green roof Even in high-rise urban settings as tall as 19 stories, it has been found that green roofs can attract beneficial insects, birds, bees and butterflies. A recent list of the bee species recorded from green roofs (worldwide) highlights both the diversity of species, but also the (expected) bias towards small g... | https://en.wikipedia.org/wiki?curid=192025 |
Green roof In a study done in Michigan above ground sequestration ranged from 64 g C m to 239 g C m for S. acre and S album. Also, by increasing the substrate depth would allow for more area of carbon storage and diversify the types of plants with greater potential of carbon storage. The direct carbon sequestration tec... | https://en.wikipedia.org/wiki?curid=192025 |
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