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reservoir, from which it is materially and thermally insulated. Other thermometers (e.g. mercury thermometers, which display the volume of mercury to the observer), may now be constructed, and calibrated against the ideal gas thermometer. == References ==
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{
"page_id": 3281057,
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"title": "Thermodynamic instruments"
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The molecular formula C15H22O2 (molar mass : 234.33 g/mol) may refer to: Coprinol 3,5-Di-tert-butylsalicylaldehyde Polygodial, an active constituent of Dorrigo Pepper, Mountain Pepper, Horopito, Canelo, Paracress and Water-pepper Valerenic acid, a sesquiterpenoid constituent of the essential oil of the Valerian plant
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"page_id": 24187043,
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"title": "C15H22O2"
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Zero sound is the name given by Lev Landau in 1957 to the unique quantum vibrations in quantum Fermi liquids. The zero sound can no longer be thought of as a simple wave of compression and rarefaction, but rather a fluctuation in space and time of the quasiparticles' momentum distribution function. As the shape of Fermi distribution function changes slightly (or largely), zero sound propagates in the direction for the head of Fermi surface with no change of the density of the liquid. Predictions and subsequent experimental observations of zero sound was one of the key confirmation on the correctness of Landau's Fermi liquid theory. == Derivation from Boltzmann transport equation == The Boltzmann transport equation for general systems in the semiclassical limit gives, for a Fermi liquid, ∂ f ∂ t + ∂ E ∂ p → ⋅ ∂ f ∂ x → − ∂ E ∂ x → ⋅ ∂ f ∂ p → = St [ f ] {\displaystyle {\frac {\partial f}{\partial t}}+{\frac {\partial E}{\partial {\vec {p}}}}\cdot {\frac {\partial f}{\partial {\vec {x}}}}-{\frac {\partial E}{\partial {\vec {x}}}}\cdot {\frac {\partial f}{\partial {\vec {p}}}}={\text{St}}[f]} , where f ( p → , x → , t ) = f 0 ( p → ) + δ f ( p → , x → , t ) {\displaystyle f({\vec {p}},{\vec {x}},t)=f_{0}({\vec {p}})+\delta f({\vec {p}},{\vec {x}},t)} is the density of quasiparticles (here we ignore spin) with momentum p → {\displaystyle {\vec {p}}} and position x → {\displaystyle {\vec {x}}} at time t {\displaystyle t} , and E ( p → , x → , t ) = E 0 ( p → ) + δ E ( p → , x → , t ) {\displaystyle E({\vec {p}},{\vec {x}},t)=E_{0}({\vec {p}})+\delta E({\vec {p}},{\vec {x}},t)} is the energy of a quasiparticle of momentum p →
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{\displaystyle {\vec {p}}} ( f 0 {\displaystyle f_{0}} and E 0 {\displaystyle E_{0}} denote equilibrium distribution and energy in the equilibrium distribution). The semiclassical limit assumes that f {\displaystyle f} fluctuates with angular frequency ω {\displaystyle \omega } and wavelength λ = 2 π / k {\displaystyle \lambda =2\pi /k} , which are much lower than E F / ℏ {\displaystyle E_{\rm {F}}/\hbar } and much longer than ℏ / p F {\displaystyle \hbar /p_{\rm {F}}} respectively, where E F {\displaystyle E_{\rm {F}}} and p F {\displaystyle p_{\rm {F}}} are the Fermi energy and momentum respectively, around which f {\displaystyle f} is nontrivial. To first order in fluctuation from equilibrium, the equation becomes ∂ δ f ∂ t + ∂ E 0 ∂ p → ⋅ ∂ δ f ∂ x → − ∂ δ E ∂ x → ⋅ ∂ f 0 ∂ p → = St [ f ] {\displaystyle {\frac {\partial \delta f}{\partial t}}+{\frac {\partial E_{0}}{\partial {\vec {p}}}}\cdot {\frac {\partial \delta f}{\partial {\vec {x}}}}-{\frac {\partial \delta E}{\partial {\vec {x}}}}\cdot {\frac {\partial f_{0}}{\partial {\vec {p}}}}={\text{St}}[f]} . When the quasiparticle's mean free path ℓ ≪ λ {\displaystyle \ell \ll \lambda } (equivalently, relaxation time τ ≪ 1 / ω {\displaystyle \tau \ll 1/\omega } ), ordinary sound waves ("first sound") propagate with little absorption. But at low temperatures T {\displaystyle T} (where τ {\displaystyle \tau } and ℓ {\displaystyle \ell } scale as T − 2 {\displaystyle T^{-2}} ), the mean free path exceeds λ {\displaystyle \lambda } , and as a result the collision functional St [ f ] ≈ 0 {\displaystyle {\text{St}}[f]\approx 0} . Zero sound occurs in this collisionless limit. In the Fermi liquid theory, the energy of a quasiparticle of momentum p → {\displaystyle {\vec {p}}} is E F + v F ( | p
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→ | − p F ) + ∫ d 3 p → ′ 4 π p F m ∗ F ( p , p ′ ) δ f ( p ′ ) {\displaystyle E_{\rm {F}}+v_{\rm {F}}(|{\vec {p}}|-p_{\rm {F}})+\int {\frac {d^{3}{\vec {p}}'}{4\pi p_{\rm {F}}m^{*}}}F(p,p')\delta f(p')} , where F {\displaystyle F} is the appropriately normalized Landau parameter, and f 0 ( p → ) = Θ ( p F − | p → | ) {\displaystyle f_{0}({\vec {p}})=\Theta (p_{\rm {F}}-|{\vec {p}}|)} . The approximated transport equation then has plane wave solutions δ f ( p → , x → , t ) = δ ( E ( p → ) − E F ) e i ( k → ⋅ r → − ω t ) ν ( p ^ ) {\displaystyle \delta f({\vec {p}},{\vec {x}},t)=\delta (E({\vec {p}})-E_{\rm {F}})e^{i({\vec {k}}\cdot {\vec {r}}-\omega t)}\nu ({\hat {p}})} , with ν ( p ^ ) {\displaystyle \nu ({\hat {p}})} given by ( ω − v F p ^ ⋅ k ^ ) ν ( p ^ ) = v F p ^ ⋅ k ^ ∫ d 2 p ^ ′ 4 π F ( p ^ , p ^ ′ ) ν ( p ^ ′ ) {\displaystyle (\omega -v_{\rm {F}}{\hat {p}}\cdot {\hat {k}})\nu ({\hat {p}})=v_{\rm {F}}{\hat {p}}\cdot {\hat {k}}\int d^{2}{\frac {{\hat {p}}'}{4\pi }}F({\hat {p}},{\hat {p}}')\nu ({\hat {p}}')} . This functional operator equation gives the dispersion relation for the zero sound waves with frequency ω {\displaystyle \omega } and wave vector k → {\displaystyle {\vec {k}}} . The transport equation is valid in the regime where ℏ ω ≪ E F {\displaystyle \hbar \omega \ll E_{\rm {F}}} and ℏ | k → | ≪ p F {\displaystyle \hbar |{\vec {k}}|\ll p_{\rm {F}}} . In many systems, F ( p ^ , p ^ ′
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) {\displaystyle F({\hat {p}},{\hat {p}}')} only slowly depends on the angle between p ^ {\displaystyle {\hat {p}}} and p ^ ′ {\displaystyle {\hat {p}}'} . If F {\displaystyle F} is an angle-independent constant F 0 {\displaystyle F_{0}} with F 0 > 0 {\displaystyle F_{0}>0} (note that this constraint is stricter than the Pomeranchuk instability) then the wave has the form ν ( p ^ ) ∝ ( ω / ( v F p ^ ⋅ k → ) − 1 ) − 1 {\displaystyle \nu ({\hat {p}})\propto ({\omega }/({v_{\rm {F}}{\hat {p}}\cdot {\vec {k}}})-1)^{-1}} and dispersion relation s 2 log s + 1 s − 1 − 1 = 1 / F 0 {\displaystyle {\frac {s}{2}}\log {\frac {s+1}{s-1}}-1=1/F_{0}} where s = ω / k v F {\displaystyle s=\omega /{kv_{\rm {F}}}} is the ratio of zero sound phase velocity to Fermi velocity. If the first two Legendre components of the Landau parameter are significant, F ( p ^ , p ^ ′ ) = F 0 + F 1 p ^ ⋅ p ^ ′ {\displaystyle F({\hat {p}},{\hat {p}}')=F_{0}+F_{1}{\hat {p}}\cdot {\hat {p}}'} and F 1 > 6 {\displaystyle F_{1}>6} , the system also admits an asymmetric zero sound wave solution ν ( p ^ ) ∝ sin ( 2 θ ) / ( s − cos θ ) e i ϕ {\displaystyle \nu ({\hat {p}})\propto {\sin(2\theta )}/({s-\cos {\theta }})e^{i\phi }} (where ϕ {\displaystyle \phi } and θ {\displaystyle \theta } are the azimuthal and polar angle of p ^ {\displaystyle {\hat {p}}} about the propagation direction k ^ {\displaystyle {\hat {k}}} ) and dispersion relation ∫ 0 π sin 3 θ cos θ s − cos θ d θ = 4 F 1 {\displaystyle \int _{0}^{\pi }{\frac {\sin ^{3}\theta \cos \theta }{s-\cos \theta }}d\theta ={\frac {4}{F_{1}}}}
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. == See also == Second sound Third sound == References == == Further reading == Piers Coleman (2016). Introduction to Many-Body Physics (1st ed.). Cambridge University Press. ISBN 9780521864886.
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"page_id": 7344293,
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The Efimov effect is an effect in the quantum mechanics of few-body systems predicted by the Russian theoretical physicist V. N. Efimov in 1970. Efimov's effect is where three identical bosons interact, with the prediction of an infinite series of excited three-body energy levels when a two-body state is exactly at the dissociation threshold. One corollary is that there exist bound states (called Efimov states) of three bosons even if the two-particle attraction is too weak to allow two bosons to form a pair. A (three-particle) Efimov state, where the (two-body) sub-systems are unbound, is often depicted symbolically by the Borromean rings. This means that if one of the particles is removed, the remaining two fall apart. In this case, the Efimov state is also called a Borromean state. == Theory == Pair interactions among three identical bosons will approach "Resonance (particle physics)" as the binding energy of some two-body bound state approaches zero, or equivalently, the s-wave scattering length of the state becomes infinite. In this limit, Efimov predicted that the three-body spectrum exhibits an infinite sequence of bound states N = 0 , 1 , 2 , … {\displaystyle N=0,1,2,\ldots } whose scattering lengths a N {\displaystyle a_{N}} and binding energies E N {\displaystyle E_{N}} each form a geometric progression a N = a 0 λ N E N = E 0 λ − 2 N {\displaystyle {\begin{aligned}a_{N}&=a_{0}\lambda ^{N}\\E_{N}&=E_{0}\lambda ^{-2N}\end{aligned}}} where the common ratio λ = e π / s 0 = 22.69438 … {\displaystyle \lambda =\mathrm {e} ^{\mathrm {\pi } /s_{0}}=22.69438\ldots } is a universal constant (OEIS: A242978). Here s 0 = 1.0062378 … {\displaystyle s_{0}=1.0062378\ldots } is the order of the imaginary-order modified Bessel function of the second kind K ~ s 0 ( r / a ) {\displaystyle {\tilde {K}}_{s_{0}}(r/a)} that describes the radial dependence
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of the wavefunction. By virtue of the resonance-determined boundary conditions, this is the unique positive value of s {\displaystyle s} satisfying the transcendental equation − s cosh π s 2 + 8 3 sinh π s 6 = 0. {\displaystyle -s\cosh \left.{\tfrac {\mathrm {\pi } s}{2}}\right.+{\tfrac {8}{\sqrt {3}}}\sinh \left.{\tfrac {\mathrm {\pi } s}{6}}\right.=0.} The geometric progression of the energy levels of Efimov states is an example of a emergent discrete scaling symmetry. This phenomenon, exhibiting a renormalization group limit cycle, is closely related to the scale invariance of the 1 / r 2 {\displaystyle 1/r^{2}} form of the quantum mechanical potential of the system. == Experimental results == In 2005, the research group of Rudolf Grimm and Hanns-Christoph Nägerl at the Institute for Experimental Physics at the University of Innsbruck experimentally confirmed the existence of such a state for the first time in an ultracold gas of caesium atoms. In 2006, they published their findings in the scientific journal Nature. Further experimental support for the existence of the Efimov state has been given recently by independent groups. Almost 40 years after Efimov's purely theoretical prediction, the characteristic periodic behavior of the states has been confirmed. The most accurate experimental value of the scaling factor of the states has been determined by the experimental group of Rudolf Grimm at Innsbruck University as λ = 21.0 ± 1.3 {\displaystyle \lambda =21.0\pm 1.3} Interest in the "universal phenomena" of cold atomic gases is still growing. The discipline of universality in cold atomic gases near the Efimov states is sometimes referred to as "Efimov physics". The experimental groups of Cheng Chin of the University of Chicago and Matthias Weidemüller of the University of Heidelberg have observed Efimov states in an ultracold mixture of lithium and caesium atoms, extending Efimov's original picture of
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"page_id": 7606440,
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"title": "Efimov state"
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three identical bosons. An Efimov state existing as an excited state of a helium trimer was observed in an experiment in 2015. == Usage == The Efimov states are independent of the underlying physical interaction and can in principle be observed in all quantum mechanical systems (i.e. molecular, atomic, and nuclear). The states are very special because of their "non-classical" nature: The size of each three-particle Efimov state is much larger than the force-range between the individual particle pairs. This means that the state is purely quantum mechanical. Similar phenomena are observed in two-neutron halo-nuclei, such as lithium-11; these are called Borromean nuclei. (Halo nuclei could be seen as special Efimov states, depending on the subtle definitions.) == See also == Three-body force == References == == External links == Press release about the experimental confirmation (2006.03.16) Overwhelming proof for Efimov State that's become a hotbed for research some 40 years after it first appeared (2009.12.14) Observation of the Second Triatomic Resonance in Efimov’s Scenario (2014.05.15)
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Paul Breslin is a geneticist and biologist. He is most notable for his work in taste perception and oral irritation, in humans as well as in Drosophila melanogaster, the common fruit fly. He is a member of the faculty at the Monell Chemical Senses Center and acts as director of the Science Apprenticeship Program. He is a professor in the Department of Nutritional Sciences at Rutgers, the State University of New Jersey. Breslin and two colleagues discovered that Oleocanthal, a compound found in extra-virgin olive oil kills a variety of human cancer cells without harming healthy cells. == References ==
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"page_id": 18682025,
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The Stanton number (St), is a dimensionless number that measures the ratio of heat transferred into a fluid to the thermal capacity of fluid. The Stanton number is named after Thomas Stanton (engineer) (1865–1931).: 476 It is used to characterize heat transfer in forced convection flows. == Formula == S t = h G c p = h ρ u c p {\displaystyle \mathrm {St} ={\frac {h}{Gc_{p}}}={\frac {h}{\rho uc_{p}}}} where h = convection heat transfer coefficient G = mass flux of the fluid ρ = density of the fluid cp = specific heat of the fluid u = velocity of the fluid It can also be represented in terms of the fluid's Nusselt, Reynolds, and Prandtl numbers: S t = N u R e P r {\displaystyle \mathrm {St} ={\frac {\mathrm {Nu} }{\mathrm {Re} \,\mathrm {Pr} }}} where Nu is the Nusselt number; Re is the Reynolds number; Pr is the Prandtl number. The Stanton number arises in the consideration of the geometric similarity of the momentum boundary layer and the thermal boundary layer, where it can be used to express a relationship between the shear force at the wall (due to viscous drag) and the total heat transfer at the wall (due to thermal diffusivity). == Mass transfer == Using the heat-mass transfer analogy, a mass transfer St equivalent can be found using the Sherwood number and Schmidt number in place of the Nusselt number and Prandtl number, respectively. S t m = S h L R e L S c {\displaystyle \mathrm {St} _{m}={\frac {\mathrm {Sh_{L}} }{\mathrm {Re_{L}} \,\mathrm {Sc} }}} S t m = h m ρ u {\displaystyle \mathrm {St} _{m}={\frac {h_{m}}{\rho u}}} where S t m {\displaystyle St_{m}} is the mass Stanton number; S h L {\displaystyle Sh_{L}} is the Sherwood number based on length;
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"page_id": 3739824,
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"title": "Stanton number"
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R e L {\displaystyle Re_{L}} is the Reynolds number based on length; S c {\displaystyle Sc} is the Schmidt number; h m {\displaystyle h_{m}} is defined based on a concentration difference (kg s−1 m−2); u {\displaystyle u} is the velocity of the fluid == Boundary layer flow == The Stanton number is a useful measure of the rate of change of the thermal energy deficit (or excess) in the boundary layer due to heat transfer from a planar surface. If the enthalpy thickness is defined as: Δ 2 = ∫ 0 ∞ ρ u ρ ∞ u ∞ T − T ∞ T s − T ∞ d y {\displaystyle \Delta _{2}=\int _{0}^{\infty }{\frac {\rho u}{\rho _{\infty }u_{\infty }}}{\frac {T-T_{\infty }}{T_{s}-T_{\infty }}}dy} Then the Stanton number is equivalent to S t = d Δ 2 d x {\displaystyle \mathrm {St} ={\frac {d\Delta _{2}}{dx}}} for boundary layer flow over a flat plate with a constant surface temperature and properties. === Correlations using Reynolds-Colburn analogy === Using the Reynolds-Colburn analogy for turbulent flow with a thermal log and viscous sub layer model, the following correlation for turbulent heat transfer for is applicable S t = C f / 2 1 + 12.8 ( P r 0.68 − 1 ) C f / 2 {\displaystyle \mathrm {St} ={\frac {C_{f}/2}{1+12.8\left(\mathrm {Pr} ^{0.68}-1\right){\sqrt {C_{f}/2}}}}} where C f = 0.455 [ l n ( 0.06 R e x ) ] 2 {\displaystyle C_{f}={\frac {0.455}{\left[\mathrm {ln} \left(0.06\mathrm {Re} _{x}\right)\right]^{2}}}} == See also == Strouhal number, an unrelated number that is also often denoted as S t {\displaystyle \mathrm {St} } . == References ==
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Sir Frederick Spencer Lister (8 April 1876 – 6 September 1939) was an English-born South African doctor and bacteriologist. Lister was born in Norwell, Nottinghamshire. In 1897 he joined West Hertfordshire Football Club (later Watford Football Club) as an amateur association football player, making twelve appearances and scoring three goals for the team in all competitions. He trained as a doctor at St Bartholomew's Hospital Medical College in London, qualifying in 1905. He then went to the Transvaal, serving as medical officer to the Premier Diamond Mines from 1907 to 1912 and to the Rand Gold Mines near Johannesburg from 1912 to 1917. In 1917 he was appointed Research Bacteriologist at the South African Institute for Medical Research in Johannesburg. He later became Director of the Institute and Professor of Pathology and Bacteriology at the University of the Witwatersrand. From 1928 he served on the South African Medical Council. He wrote important papers on pneumonia and influenza and was also an expert on leprosy. He was knighted in the 1920 New Year Honours, for services to bacteriology. Lister died of a heart attack in the library of the Institute for Medical Research. == Footnotes == == References == Obituary, The Times, 8 September 1939
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Julian Huxley used the phrase "the eclipse of Darwinism" to describe the state of affairs prior to what he called the "modern synthesis". During the "eclipse", evolution was widely accepted in scientific circles but relatively few biologists believed that natural selection was its primary mechanism. Historians of science such as Peter J. Bowler have used the same phrase as a label for the period within the history of evolutionary thought from the 1880s to around 1920, when alternatives to natural selection were developed and explored—as many biologists considered natural selection to have been a wrong guess on Charles Darwin's part, or at least to be of relatively minor importance. Four major alternatives to natural selection were in play in the 19th century: Theistic evolution, the belief that God directly guided evolution Neo-Lamarckism, the idea that evolution was driven by the inheritance of characteristics acquired during the life of the organism Orthogenesis, the belief that organisms were affected by internal forces or laws of development that drove evolution in particular directions Mutationism, the idea that evolution was largely the product of mutations that created new forms or species in a single step. Theistic evolution had largely disappeared from the scientific literature by the end of the 19th century as direct appeals to supernatural causes came to be seen as unscientific. The other alternatives had significant followings well into the 20th century; mainstream biology largely abandoned them only when developments in genetics made them seem increasingly untenable, and when the development of population genetics and the modern synthesis demonstrated the explanatory power of natural selection. Ernst Mayr wrote that as late as 1930 most textbooks still emphasized such non-Darwinian mechanisms. == Context == Evolution was widely accepted in scientific circles within a few years after the publication of On the Origin of
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{
"page_id": 15732918,
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Species, but there was much less acceptance of natural selection as its driving mechanism. Six objections were raised to the theory in the 19th century: The fossil record was discontinuous, suggesting gaps in evolution. The physicist Lord Kelvin calculated in 1862 that the Earth would have cooled in 100 million years or less from its formation, too little time for evolution. It was argued that many structures were nonadaptive (functionless), so they could not have evolved under natural selection. Some structures seemed to have evolved on a regular pattern, like the eyes of unrelated animals such as the squid and mammals. Natural selection was argued not to be creative, while variation was admitted to be mostly not of value. The engineer Fleeming Jenkin correctly noted in 1868, reviewing The Origin of Species, that the blending inheritance favoured by Charles Darwin would oppose the action of natural selection. Both Darwin and his close supporter Thomas Henry Huxley freely admitted, too, that selection might not be the whole explanation; Darwin was prepared to accept a measure of Lamarckism, while Huxley was comfortable with both sudden (mutational) change and directed (orthogenetic) evolution. By the end of the 19th century, criticism of natural selection had reached the point that in 1903 the German botanist, Eberhard Dennert , edited a series of articles intended to show that "Darwinism will soon be a thing of the past, a matter of history; that we even now stand at its death-bed, while its friends are solicitous only to secure for it a decent burial." In 1907, the Stanford University entomologist Vernon Lyman Kellogg, who supported natural selection, asserted that "... the fair truth is that the Darwinian selection theory, considered with regard to its claimed capacity to be an independently sufficient mechanical explanation of descent, stands today seriously
|
{
"page_id": 15732918,
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"title": "The eclipse of Darwinism"
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discredited in the biological world." He added, however, that there were problems preventing the widespread acceptance of any of the alternatives, as large mutations seemed too uncommon, and there was no experimental evidence of mechanisms that could support either Lamarckism or orthogenesis. Ernst Mayr wrote that a survey of evolutionary literature and biology textbooks showed that as late as 1930 the belief that natural selection was the most important factor in evolution was a minority viewpoint, with only a few population geneticists being strict selectionists. === Motivation for alternatives === A variety of different factors motivated people to propose other evolutionary mechanisms as alternatives to natural selection, some of them dating back before Darwin's Origin of Species. Natural selection, with its emphasis on death and competition, did not appeal to some naturalists because they felt it was immoral, and left little room for teleology or the concept of progress in the development of life. Some of these scientists and philosophers, like St. George Jackson Mivart and Charles Lyell, who came to accept evolution but disliked natural selection, raised religious objections. Others, such as Herbert Spencer, the botanist George Henslow (son of Darwin's mentor John Stevens Henslow, also a botanist), and Samuel Butler, felt that evolution was an inherently progressive process that natural selection alone was insufficient to explain. Still others, including the American paleontologists Edward Drinker Cope and Alpheus Hyatt, had an idealist perspective and felt that nature, including the development of life, followed orderly patterns that natural selection could not explain. Another factor was the rise of a new faction of biologists at the end of the 19th century, typified by the geneticists Hugo DeVries and Thomas Hunt Morgan, who wanted to recast biology as an experimental laboratory science. They distrusted the work of naturalists like Darwin and Alfred
|
{
"page_id": 15732918,
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"title": "The eclipse of Darwinism"
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Russel Wallace, dependent on field observations of variation, adaptation, and biogeography, considering these overly anecdotal. Instead they focused on topics like physiology, and genetics that could be easily investigated with controlled experiments in the laboratory, and discounted natural selection and the degree to which organisms were adapted to their environment, which could not easily be tested experimentally. == Anti-Darwinist theories during the eclipse == === Theistic evolution === British science developed in the early 19th century on a basis of natural theology which saw the adaptation of fixed species as evidence that they had been specially created to a purposeful divine design. The philosophical concepts of German idealism inspired concepts of an ordered plan of harmonious creation, which Richard Owen reconciled with natural theology as a pattern of homology showing evidence of design. Similarly, Louis Agassiz saw Ernest Haeckel's recapitulation theory, which held that the embryological development of an organism repeats its evolutionary history, as symbolising a pattern of the sequence of creations in which humanity was the goal of a divine plan. In 1844 Vestiges adapted Agassiz's concept into theistic evolutionism. Its anonymous author Robert Chambers proposed a "law" of divinely ordered progressive development, with transmutation of species as an extension of recapitulation theory. This popularised the idea, but it was strongly condemned by the scientific establishment. Agassiz remained forcefully opposed to evolution, and after he moved to America in 1846 his idealist argument from design of orderly development became very influential. In 1858 Owen cautiously proposed that this development could be a real expression of a continuing creative law, but distanced himself from transmutationists. Two years later, in his review of On the Origin of Species, Owen attacked Darwin while at the same time openly supporting evolution, expressing belief in a pattern of transmutation by law-like means. This
|
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"page_id": 15732918,
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idealist argument from design was taken up by other naturalists such as George Jackson Mivart, and the Duke of Argyll who rejected natural selection altogether in favor of laws of development that guided evolution down preordained paths. Many of Darwin's supporters accepted evolution on the basis that it could be reconciled with design. In particular, Asa Gray considered natural selection to be the main mechanism of evolution and sought to reconcile it with natural theology. He proposed that natural selection could be a mechanism in which the problem of evil of suffering produced the greater good of adaptation, but conceded that this had difficulties and suggested that God might influence the variations on which natural selection acted to guide evolution. For Darwin and Thomas Henry Huxley such pervasive supernatural influence was beyond scientific investigation, and George Frederick Wright, an ordained minister who was Gray's colleague in developing theistic evolution, emphasised the need to look for secondary or known causes rather than invoking supernatural explanations: "If we cease to observe this rule there is an end to all science and all sound science." A secular version of this methodological naturalism was welcomed by a younger generation of scientists who sought to investigate natural causes of organic change, and rejected theistic evolution in science. By 1872 Darwinism in its broader sense of the fact of evolution was accepted as a starting point. Around 1890 only a few older men held onto the idea of design in science, and it had completely disappeared from mainstream scientific discussions by 1900. There was still unease about the implications of natural selection, and those seeking a purpose or direction in evolution turned to neo-Lamarckism or orthogenesis as providing natural explanations. === Neo-Lamarckism === Jean-Baptiste Lamarck had originally proposed a theory on the transmutation of species that
|
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"page_id": 15732918,
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"title": "The eclipse of Darwinism"
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was largely based on a progressive drive toward greater complexity. Lamarck also believed, as did many others in the 19th century, that characteristics acquired during the course of an organism's life could be inherited by the next generation, and he saw this as a secondary evolutionary mechanism that produced adaptation to the environment. Typically, such characteristics included changes caused by the use or disuse of a particular organ. It was this mechanism of evolutionary adaptation through the inheritance of acquired characteristics that much later came to be known as Lamarckism. Although Alfred Russel Wallace completely rejected the concept in favor of natural selection, Darwin always included what he called Effects of the increased Use and Disuse of Parts, as controlled by Natural Selection in On the Origin of Species, giving examples such as large ground feeding birds getting stronger legs through exercise, and weaker wings from not flying until, like the ostrich, they could not fly at all. In the late 19th century the term neo-Lamarckism came to be associated with the position of naturalists who viewed the inheritance of acquired characteristics as the most important evolutionary mechanism. Advocates of this position included the British writer and Darwin critic Samuel Butler, the German biologist Ernst Haeckel, the American paleontologists Edward Drinker Cope and Alpheus Hyatt, and the American entomologist Alpheus Packard. They considered Lamarckism to be more progressive and thus philosophically superior to Darwin's idea of natural selection acting on random variation. Butler and Cope both believed that this allowed organisms to effectively drive their own evolution, since organisms that developed new behaviors would change the patterns of use of their organs and thus kick-start the evolutionary process. In addition, Cope and Haeckel both believed that evolution was a progressive process. The idea of linear progress was an important part
|
{
"page_id": 15732918,
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of Haeckel's recapitulation theory. Cope and Hyatt looked for, and thought they found, patterns of linear progression in the fossil record. Packard argued that the loss of vision in the blind cave insects he studied was best explained through a Lamarckian process of atrophy through disuse combined with inheritance of acquired characteristics. Many American proponents of neo-Lamarckism were strongly influenced by Louis Agassiz, and a number of them, including Hyatt and Packard, were his students. Agassiz had an idealistic view of nature, connected with natural theology, that emphasized the importance of order and pattern. Agassiz never accepted evolution; his followers did, but they continued his program of searching for orderly patterns in nature, which they considered to be consistent with divine providence, and preferred evolutionary mechanisms like neo-Lamarckism and orthogenesis that would be likely to produce them. In Britain the botanist George Henslow, the son of Darwin's mentor John Stevens Henslow, was an important advocate of neo-Lamarckism. He studied how environmental stress affected the development of plants, and he wrote that the variations induced by such environmental factors could largely explain evolution. The historian of science Peter J. Bowler writes that, as was typical of many 19th century Lamarckians, Henslow did not appear to understand the need to demonstrate that such environmentally induced variations would be inherited by descendants that developed in the absence of the environmental factors that produced them, but merely assumed that they would be. ==== Polarising the argument: Weismann's germ plasm ==== Critics of neo-Lamarckism pointed out that no one had ever produced solid evidence for the inheritance of acquired characteristics. The experimental work of the German biologist August Weismann resulted in the germ plasm theory of inheritance. This led him to declare that inheritance of acquired characteristics was impossible, since the Weismann barrier would prevent
|
{
"page_id": 15732918,
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"title": "The eclipse of Darwinism"
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any changes that occurred to the body after birth from being inherited by the next generation. This effectively polarised the argument between the Darwinians and the neo-Lamarckians, as it forced people to choose whether to agree or disagree with Weismann and hence with evolution by natural selection. Despite Weismann's criticism, neo-Lamarckism remained the most popular alternative to natural selection at the end of the 19th century, and would remain the position of some naturalists well into the 20th century. ==== Baldwin effect ==== As a consequence of the debate over the viability of neo-Lamarckism, in 1896 James Mark Baldwin, Henry Fairfield Osborne and C. Lloyd Morgan all independently proposed a mechanism where new learned behaviors could cause the evolution of new instincts and physical traits through natural selection without resort to the inheritance of acquired characteristics. They proposed that if individuals in a species benefited from learning a particular new behavior, the ability to learn that behavior could be favored by natural selection, and the result would be the evolution of new instincts and eventually new physical adaptations. This became known as the Baldwin effect and it has remained a topic of debate and research in evolutionary biology ever since. === Orthogenesis === Orthogenesis was the theory that life has an innate tendency to change, in a unilinear fashion in a particular direction. The term was popularized by Theodor Eimer, a German zoologist, in his 1898 book On Orthogenesis: And the Impotence of Natural Selection in Species Formation. He had studied the coloration of butterflies, and believed he had discovered non-adaptive features which could not be explained by natural selection. Eimer also believed in Lamarckian inheritance of acquired characteristics, but he felt that internal laws of growth determined which characteristics would be acquired and guided the long term direction of
|
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"page_id": 15732918,
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"title": "The eclipse of Darwinism"
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evolution down certain paths. Orthogenesis had a significant following in the late 19th and early 20th centuries, its proponents including the Russian biologist Leo S. Berg, and the American paleontologist Henry Fairfield Osborn. Orthogenesis was particularly popular among some paleontologists, who believed that the fossil record showed patterns of gradual and constant unidirectional change. Those who accepted this idea, however, did not necessarily accept that the mechanism driving orthogenesis was teleological (goal-directed). They did believe that orthogenetic trends were non-adaptive; in fact they felt that in some cases they led to developments that were detrimental to the organism, such as the large antlers of the Irish elk that they believed led to the animal's extinction. Support for orthogenesis began to decline during the modern synthesis in the 1940s, when it became apparent that orthogenesis could not explain the complex branching patterns of evolution revealed by statistical analysis of the fossil record by paleontologists. A few biologists however hung on to the idea of orthogenesis as late as the 1950s, claiming that the processes of macroevolution, the long term trends in evolution, were distinct from the processes of microevolution. === Mutationism === Mutationism was the idea that new forms and species arose in a single step as a result of large mutations. It was seen as a much faster alternative to the Darwinian concept of a gradual process of small random variations being acted on by natural selection. It was popular with early geneticists such as Hugo de Vries, who along with Carl Correns helped rediscover Gregor Mendel's laws of inheritance in 1900, William Bateson a British zoologist who switched to genetics, and early in his career, Thomas Hunt Morgan. The 1901 mutation theory of evolution held that species went through periods of rapid mutation, possibly as a result of environmental
|
{
"page_id": 15732918,
"source": null,
"title": "The eclipse of Darwinism"
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|
stress, that could produce multiple mutations, and in some cases completely new species, in a single generation. Its originator was the Dutch botanist Hugo de Vries. De Vries looked for evidence of mutation extensive enough to produce a new species in a single generation and thought he found it with his work breeding the evening primrose of the genus Oenothera, which he started in 1886. The plants that de Vries worked with seemed to be constantly producing new varieties with striking variations in form and color, some of which appeared to be new species because plants of the new generation could only be crossed with one another, not with their parents. DeVries himself allowed a role for natural selection in determining which new species would survive, but some geneticists influenced by his work, including Morgan, felt that natural selection was not necessary at all. De Vries's ideas were influential in the first two decades of the 20th century, as some biologists felt that mutation theory could explain the sudden emergence of new forms in the fossil record; research on Oenothera spread across the world. However, critics including many field naturalists wondered why no other organism seemed to show the same kind of rapid mutation. Morgan was a supporter of de Vries's mutation theory and was hoping to gather evidence in favor of it when he started working with the fruit fly Drosophila melanogaster in his lab in 1907. However, it was a researcher in that lab, Hermann Joseph Muller, who determined in 1918 that the new varieties de Vries had observed while breeding Oenothera were the result of polyploid hybrids rather than rapid genetic mutation. While they were doubtful of the importance of natural selection, the work of geneticists like Morgan, Bateson, de Vries and others from 1900 to 1915
|
{
"page_id": 15732918,
"source": null,
"title": "The eclipse of Darwinism"
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established Mendelian genetics linked to chromosomal inheritance, which validated August Weismann's criticism of neo-Lamarckian evolution by discounting the inheritance of acquired characteristics. The work in Morgan's lab with Drosophila also undermined the concept of orthogenesis by demonstrating the random nature of mutation. == End of the eclipse == During the period 1916–1932, the discipline of population genetics developed largely through the work of the geneticists Ronald Fisher, J.B.S. Haldane, and Sewall Wright. Their work recognized that the vast majority of mutations produced small effects that served to increase the genetic variability of a population rather than creating new species in a single step as the mutationists assumed. They were able to produce statistical models of population genetics that included Darwin's concept of natural selection as the driving force of evolution. Developments in genetics persuaded field naturalists such as Bernhard Rensch and Ernst Mayr to abandon neo-Lamarckian ideas about evolution in the early 1930s. By the late 1930s, Mayr and Theodosius Dobzhansky had synthesized the ideas of population genetics with the knowledge of field naturalists about the amount of genetic diversity in wild populations, and the importance of genetically distinct subpopulations (especially when isolated from one another by geographical barriers) to create the early 20th century modern synthesis. In 1944 George Gaylord Simpson integrated paleontology into the synthesis by statistically analyzing the fossil record to show that it was consistent with the branching non-directional form of evolution predicted by the synthesis, and in particular that the linear trends cited by earlier paleontologists in support of Lamarckism and orthogenesis did not stand up to careful analysis. Mayr wrote that by the end of the synthesis natural selection together with chance mechanisms like genetic drift had become the universal explanation for evolutionary change. == Historiography == The concept of eclipse suggests that Darwinian
|
{
"page_id": 15732918,
"source": null,
"title": "The eclipse of Darwinism"
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|
research paused, implying in turn that there had been a preceding period of vigorously Darwinian activity among biologists. However, historians of science such as Mark Largent have argued that while biologists broadly accepted the extensive evidence for evolution presented in The Origin of Species, there was less enthusiasm for natural selection as a mechanism. Biologists instead looked for alternative explanations more in keeping with their worldviews, which included the beliefs that evolution must be directed and that it constituted a form of progress. Further, the idea of a dark eclipse period was convenient to scientists such as Julian Huxley, who wished to paint the modern synthesis as a bright new achievement, and accordingly to depict the preceding period as dark and confused. Huxley's 1942 book Evolution: The Modern Synthesis therefore, argued Largent, suggested that the so-called modern synthesis began after a long period of eclipse lasting until the 1930s, in which Mendelians, neo-Lamarckians, mutationists, and Weismannians, not to mention experimental embryologists and Haeckelian recapitulationists fought running battles with each other. The idea of an eclipse also allowed Huxley to step aside from what was to him the inconvenient association of evolution with aspects such as social Darwinism, eugenics, imperialism, and militarism. Accounts such as Michael Ruse's very large book Monad to Man ignored, claimed Largent, almost all the early 20th century American evolutionary biologists. Largent has suggested as an alternative to eclipse a biological metaphor, the interphase of Darwinism, interphase being an apparently quiet period in the cycle of cell division and growth. == See also == Coloration evidence for natural selection Objections to evolution == Notes == == References == == Sources ==
|
{
"page_id": 15732918,
"source": null,
"title": "The eclipse of Darwinism"
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Heptynes are alkynes with one triple bond and the molecular formula C7H12. The isomers are: 1-Heptyne 2-Heptyne 3-Heptyne
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{
"page_id": 60887222,
"source": null,
"title": "Heptyne"
}
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Garbhanga Wildlife Sanctuary (formerly Garbhanga and Rani Reserve Forest) is a wildlife sanctuary on the southwestern side of Guwahati City, bordering the state of Meghalaya, India. The forested area is the key urban wildlife site and catchment area near Guwahati City. Located approximately 15 km (10 miles) away from Guwahati, Garbhanga Wildlife Sanctuary is situated in the southern part of Assam, bordering the foothills of Meghalaya. It is located very close to the Deepor Bill, and because of its location in an urban area it is considered a key wildlife area of Guwahati City. Garbhanga Wildlife Sanctuary has a total land area of 117 km2 and lies between the Garbhanga and Rani ranges. == Etymology == The origin of wildlife sanctuary's name is unclear. However, some believe that the name comes from the Karbi people, who came from the Markang area of Sonapur and eventually entered the hilly forest for Jhum cultivation. Garbhanga was declared a wildlife sanctuary by the second secretary to the government of Assam, Mr G.T. Lloyd. He was under the supervision of Major Briggs, who surveyed the forest in 1862. == Brief boundary description == The Garbhanga Wildlife Sanctuary is surrounded by Guwahati City and Dipor Bill in the South, the Meghalayan ranges on the east and north, and Rani Range on the west. === North === The northern boundary starts at BSF headquarters near the VIP Road, then runs along the foothills of Matia, Chakradeo, Dipor Bil, Mahua Para, Pamohi, and Mainakhurung up to Paschdhora River, which is the common boundary between Garbhanga Reserve Forest and Rani Reserve Forest. From there, the boundary runs along Phalbama, Nawagaon, and Nalapara, up to Lokhara Village and to the Siva Temple, which is situated in the northeast corner. === East === On the east side, the boundary runs
|
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"page_id": 71307448,
"source": null,
"title": "Garbhanga Wildlife Sanctuary"
}
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along the Basistha river, up to the front side of the Government Art School and then follows the stream. Permanent boundary pillars are situated near the Basistha River, then the eastern boundary runs up to Umthana Forest Camp. The name of the river changes in different locations, such as Umsing, Umpani, Umrit etc. This entire stretch is the interstate boundary with Meghalaya. === South === The southern boundary starts at Doomati village, which is the joining point of Umrit and Umsopari rivers. From there, the boundary runs up to Pathar Khama, then up to Rangang River that runs out from Meghalaya. === West === The western boundary starts at Pathar Khama, then goes up Jeepable Fair Weather Road along the Umsang River. From this point the boundary runs along Naharpaham, Bhadiakhowa, where it meets Umtru River, and then the boundary follows the stream to where it meets Kapili river. The boundary then runs along Ganapati, Rani, Bahupara, Andherijuli, Rani Tea estate, Sajanpara, Patgaon, to where it meets at the starting point at the corner of BSF Headquarters. == Landscape and biodiversity == In earlier days, various NGOs and researchers witnessed rare animals such as serow, clouded leopard, and bison and wanted to study Garbhanga. Therefore, when the Working Plan of the Kamrup East Division was prepared, an attempt was made to document the faunal and flora diversity of Garbhanga and Rani Reserve Forest. === Flora === The wildlife sanctuary has diverse flora. A study has found 139 species of trees, 122 herbs and shrubs, 52 species of climbers, 11 species of orchids, and five species of bamboo and rattan were documented. === Fauna === The wildlife sanctuary is rich in fauna. A total of 36 species of mammals, 219 species of birds, 38 species of reptiles, 15 species of amphibians,
|
{
"page_id": 71307448,
"source": null,
"title": "Garbhanga Wildlife Sanctuary"
}
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168 species of butterflies, and 15 species of spiders have been documented. == Disturbance and threats == In May 2005, at the 15th Annual Meeting of Early Bird, a local NGO warned the Assam government about the danger of losing the wildlife sanctuary in the future. The main threats to wildlife are encroachment, dumping of garbage, and deforestation. The NGO requested that the government prevent the encroachment on wild animals and also called for a ban on the dumping of garbage in the wetlands. == Present status == Groups have been constantly demanding the upgrading of Garbhanga-Rani Reserved Forests into a wildlife sanctuary for its better protection and care. Hydrological considerations - Protection of the watershed areas of Guwahati city and its adjacent areas would regulate water flow, maintain water quality and nutrient cycles, and prevent soil erosion and sedimentation. Genetic and species considerations - Protection of wild gene pools of flora and diverse avian, mammalian, reptilian, and other fauna. Ethnobotanical considerations - Protection of medicinal plants traditionally used by tribal communities residing in and around the forested areas. Economic considerations - Protection and maintenance of the areas with high scenic value for eco-tourism, which would provide economic opportunity to ethnic tribal inhabitants. === Declared a wildlife sanctuary === On 7 April 2022, in the Assam Gazette, the governor of Assam proposed that Garbangha Reserved Forest should be declared a wildlife sanctuary, which made it the 25th wildlife sanctuary in Assam. == References ==
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{
"page_id": 71307448,
"source": null,
"title": "Garbhanga Wildlife Sanctuary"
}
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The Fondation du patrimoine, created by the law of July 2, 1996, is a French private, independent, non-profit organization whose mission is to safeguard and promote local French heritage. Organized into regional delegations staffed mainly by volunteers, it supports heritage restoration projects by promoting their financing. To this end, it has been delegated by the State to grant a label that enables owners carrying out work to benefit from significant tax deductions, it organizes participative financing and corporate sponsorship operations, and receives part of the proceeds from the heritage lottery. == History == === Origin === In January 1994, the senator and mayor of Saumur, Jean-Paul Hugot, submitted a report to Jacques Toubon, Minister of Culture and Francophonie, entitled Conditions de création d'une fondation du patrimoine français, in which he advocated the creation of a structure that could mobilize private-sector players (companies and individuals) in support of heritage. The report was inspired by the British National Trust model. The Fondation du patrimoine was created by the law of July 2, 1996. At the time, it was chaired by Édouard de Royère, former head of the Air Liquide group. It was recognized as a public utility organization by decree on April 18, 1997. === Presidents === 1996-2005: Édouard de Royère 2005-2017: Charles de Croisset Since 2017: Guillaume Poitrinal == Mission == The French government has entrusted the Fondation du patrimoine with the mission of promoting the preservation and enhancement of local heritage, i.e. rural heritage (typical houses, mills, washhouses, etc.), religious heritage (churches, chapels, etc.) and industrial heritage (emblematic old factories, etc.). In most cases, the latter is neither classified (national interest) nor listed (regional interest), and is therefore not protected. It identifies buildings and sites threatened by deterioration or disappearance, raises awareness of the need for restoration among local players,
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"source": null,
"title": "Fondation du patrimoine"
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and helps finance projects (mobilizing the various players, granting the label, raising funds through sponsorship, public collection, or direct financing). == Action == === Methods of action === ==== Label ==== Under the law of July 2, 1996, the Fondation du patrimoine is authorized to award a label to work carried out by private owners on buildings not protected as historic monuments (i.e. neither listed nor registered). The label entitles the owner to significant tax deductions, ranging from half to the full cost of the work. The work must concern the exterior parts of buildings visible from the public highway. The application for the label is examined by the Foundation's project managers, then validated by the Foundation's regional delegate, and must be approved by the departmental architecture and heritage unit headed by the architects of the buildings of France. The aim of the “Fondation du patrimoine” label is to encourage private owners of unprotected heritage to carry out restoration work. This mechanism has two advantages: it encourages restoration work to be carried out using period techniques and materials, which is generally more expensive for the owner, and it promotes the preservation of non-inhabitable properties for which a private owner has little interest in spending money. ==== Participative financing or public fundraising ==== The Fondation du patrimoine launches public fundraising campaigns, calling for donations to finance projects to safeguard public and associative heritage. Donations collected through these crowdfunding campaigns are earmarked for a specific project. Donations are eligible for tax deductions. ==== Mobilizing corporate sponsorship ==== National and local sponsorship agreements are signed with companies to finance projects to safeguard and enhance local heritage. Since 2006, the leading corporate sponsor has been the Total Foundation. Corporate philanthropy can take the form of financial, in-kind or skills sponsorship, and is eligible for
|
{
"page_id": 78909628,
"source": null,
"title": "Fondation du patrimoine"
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tax benefits. Patrons' clubs have been launched to unite companies around local projects. Today, some 30 clubs bring together 250 companies throughout France, who collectively represent the Fondation du patrimoine's second-largest sponsor. The first patron club was founded in 2010, bringing together a number of companies committed to safeguarding the heritage of the Royal Logis of the Château d'Angers in Maine-et-Loire. ==== Open letter ==== In 2016, these eleven leading associations dedicated to safeguarding France's heritage are sharing their experience and forward-looking analysis with the French people and their elected representatives. In an open letter published in 1996 in the form of a book, they put forward twenty-two proposals for improved governance, simplified transmission and economic and sustainable management of heritage. ==== Mission Stéphane Bern ==== The Fondation du patrimoine is the operator of the heritage preservation mission entrusted to Stéphane Bern by the President of the Republic in September 2017. In particular, it provides support in identifying endangered monuments and finding financing solutions. In the first phase of the operation, more than 2,000 monuments were flagged by participatory approach on the digital platform of the Fondation du patrimoine and the Ministry of Culture. On May 31, 2018, the second phase was presented at the Élysée Palace, during which 269 priority projects, including 18 emblematic ones, were unveiled, spread throughout France (metropolitan and overseas). To mark the occasion, a heritage lottery was launched, with part of the proceeds going to the Fondation du patrimoine. The proceeds of the lottery enabled the Foundation to rapidly finance the first stage of restoration work on 18 emblematic projects. Priority projects are financed by a variable amount of the proceeds from the games, using participatory financing and corporate sponsorship. ==== Portail du patrimoine ==== In 2021, the Fondation du patrimoine launched the Portail du
|
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"page_id": 78909628,
"source": null,
"title": "Fondation du patrimoine"
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patrimoine. This information site, dedicated to heritage and the challenges of restoring it, provides owners with a variety of content to help them carry out their restoration projects. The site deals with various themes related to heritage: Help and Financing Culture and Heritage Heritage actors Communication and Mobilization Promoting heritage Heritage projects === Fondation du patrimoine's emblematic projects === Among the emblematic sites supported by the Fondation du patrimoine are the Charles-de-Gaulle memorial at Colombey-les-Deux-Églises, Reims Cathedral, the Château de Lunéville, the new church at Oradour-sur-Glane and the sets of the Théâtre national de Chaillot. Considering the extent of the damage caused to Notre-Dame Cathedral in Paris by the fire on April 15, 2019, which destroyed its roof, 13th-century framework and spire, the Fondation du patrimoine has opened an exceptional fund-raising campaign for the restoration of this edifice. === Specific programs === ==== Patrimoine Naturel et Biodiversité program ==== As part of its mission, the Fondation du patrimoine develops actions in favor of natural heritage to enhance biodiversity and rehabilitate sensitive natural areas. These actions give priority to projects that integrate built heritage as a complementary element of an environment, landscape, or biotope. Through the Natural Heritage program, the Fondation provides financial assistance for projects located in sensitive natural areas and remarkable coastal areas governed by the French urban planning code, areas protected or recognized under the French environmental code (national parks, nature reserves, regional nature parks, sites classified under the law of May 1930, areas classified for biotope protection, “Nature 2000” areas and conservatory land), and type I and II natural areas of ecological, faunistic and floristic interest. ==== Patrimoine Emploi program ==== Through its Patrimoine Emploi program, the Fondation contributes to training in heritage professions and to the social and professional integration of people in difficulty. It provides
|
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"page_id": 78909628,
"source": null,
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financial support for projects to preserve or enhance built heritage, carried out as part of integration projects for disadvantaged groups (unemployed young people, people in prison, the long-term unemployed, etc.), and for heritage training programs organized by schools, training centers, “chantiers écoles”, approved structures or specialized associations such as Union Rempart, Acta Vista or the Medieval History and Architecture Workshop (Chantiers Histoire et Architecture Médiévales - CHAM) association. == Organization == === A decentralized organization === The Foundation's activities were supported, in 2023, by a network of 977 volunteers and 89 employees. This local network is made up of 22 regional delegations in metropolitan and overseas France. The national head office is located in Neuilly-sur-Seine and employs 45 people. The Fondation du patrimoine is a decentralized organization whose driving force in the regions is the regional delegate. This volunteer guides the departmental teams, negotiates with the political and economic environment, and brings with them a network of contacts and stakeholders. The Fondation du patrimoine's Board of Directors is made up of representatives of the founding private organizations, national and local public institutions, the French government and its members. === A distinctive legal structure === The Fondation du patrimoine is both an allocation of assets and a group of individuals. Built on the model of foundations recognized as being of public utility under the decree of April 18, 1997, its statutes were laid down by Parliament. The French State is represented on the Board of Directors by three non-voting government commissioners. Nevertheless, the law provides for statutes that partly depart from the standard statutes for organizations recognized as being in the public interest, approved by decree by the Conseil d'Etat. The founding companies have the majority of votes on the Board of Directors of the Fondation du patrimoine. In addition, the
|
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"source": null,
"title": "Fondation du patrimoine"
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Foundation's articles of association provide for membership by individuals or legal entities in the same way as for an association. These specific features are designed to involve the founding companies closely in the running and financing of the foundation, and to attract widespread support from the general public. Influenced by the British National Trust, this status is intended to provide the foundation with substantial resources in the form of contributions, as well as a high profile in public opinion. 18% of French local authorities are members of the Fondation du patrimoine. The Fondation du patrimoine has the legal capacity to shelter foundations whose purpose is compatible with its missions, such as the VMF Foundation. By law, the Fondation du patrimoine receives the majority of unclaimed estates (75%), i.e. those without heirs. This amounted to 5.1 million euros in 2017. === Personalities associated with the Fondation du patrimoine === Stéphane Bern, radio and TV presenter, and writer, is a collaborator of the Fondation du patrimoine, notably through the Mission Patrimoine. Bernard Belloc, economist, university professor, former president of Toulouse Capitole University, advisor to French President Nicolas Sarkozy, is the Fondation du patrimoine's departmental delegate in Tarn-et-Garonne. Alain Schmitz, politician, former president of the Yvelines departmental council, was the Fondation du patrimoine's regional delegate for the Île-de-France region from 2016 to 2020. Michel Roquejeoffre, French army general, commander of French forces during the Gulf War, was the Fondation du patrimoine's departmental delegate for Ariège until 2014. Jean-Paul Hugot, politician, senator from 1992 to 2001, was behind the creation of the Fondation du patrimoine with the report he submitted in 1994 to Culture Minister Jacques Toubon. Charles de Croisset, businessman, Vice- President of Goldman Sachs Europe, member of the Inspection générale des finances, was President of the Fondation du patrimoine from 2005 to
|
{
"page_id": 78909628,
"source": null,
"title": "Fondation du patrimoine"
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2017. Dominique Vérien, politician, senator for the Yonne department, in 2019 tabled a bill to modernize the tools and governance of the Fondation du patrimoine. == Key figures == In 2021, the Fondation du patrimoine supported 3189 projects and awarded 1806 labels; it obtained 117.7 million euros, of which 12.6% was from collections, 43.6% from patronage and bequests, 26.6% from the heritage lottery, 6.3% from escheated estates, and the remainder from subsidies from local authorities, subscriptions and financial income. The heritage lottery, launched in September 2018, has made it possible to distribute 31 million euros in 2021 for heritage preservation. == Impact study == To mark its 25th anniversary (1996-2021), the Fondation du patrimoine has carried out a qualitative and quantitative socio-economic impact study of the projects it supports, in conjunction with a specialist consultancy firm. The analysis is based on two components: a macro-economic assessment of the economic activity and jobs created, through the study of 2,500 projects supported by the Fondation du patrimoine, an analysis of 7 case studies and 300 interviews. === Impact study results === The Fondation du patrimoine, through its means of intervention, in particular sponsorship and the collection of donations, creates civic commitment and a participative dynamic that stimulates the mobilization of public and private financiers. 1 € donated by the Foundation to a heritage restoration project generates €21 in economic spin-offs (economic spin-offs include direct, indirect or induced spin-offs generated during the construction period and, more sustainably, with the operation of the sites). Indeed, the expenditure injected into the local economy helps generate immediate and lasting economic benefits. This economic activity supported the creation or maintenance of 15,834 full-time equivalent jobs in 2019. == Visual identity == == Gallery == == Notes == == References == == Bibliography == Dinkel, René (1997). "Chapitre
|
{
"page_id": 78909628,
"source": null,
"title": "Fondation du patrimoine"
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XII-4 L'affaire de tous, Le mécénat culturel d'entreprise La Fondation du patrimoine" [Chapter XII-4 Everyone's business, Corporate cultural sponsorship The Fondation du patrimoine]. L'Encyclopédie du patrimoine (Monuments historiques, Patrimoine bâti et naturel - Protection, restauration, réglementation. Doctrines - Techniques : Pratiques) [The Heritage Encyclopedia (“Historic monuments”, “Built and natural heritage” - Protection, restoration, regulations. Doctrines - Techniques : Practices)] (in French). Les Encyclopédies du Patrimoine. pp. 334–345. Hugot, Jean-Paul (1994). Conditions de création d'une fondation du patrimoine français : rapport au ministre de la culture et de la francophonie [Conditions for the creation of a French heritage foundation: report to the Minister of Culture and Francophonie] (Report) (in French). Paris. Sallavuard, Guy (2016). Le patrimoine, une passion, des hommes: Voyage au cœur de nos régions [Heritage, a passion, people: Journey to the heart of our regions.] (in French). Éditions Autrement. ISBN 978-2-7467-4427-1.
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Duplodnaviria is a realm of viruses that includes all double-stranded DNA viruses that encode the HK97 fold major capsid protein. The HK97 fold major capsid protein (HK97 MCP) is the primary component of the viral capsid, which stores the viral deoxyribonucleic acid (DNA). Viruses in the realm also share a number of other characteristics, such as an icosahedral capsid, an opening in the capsid called a portal, a protease enzyme that empties the inside of the capsid prior to DNA packaging, and a terminase enzyme that packages viral DNA into the capsid. There are three groups of viruses in the realm: caudoviruses, herpesviruses, and the putative group mirusviruses. Caudoviruses are one of the most abundant group of viruses on Earth and are ubiquitous worldwide. They infect prokaryotes and are a major cause of death in them, which contributes to the recycling of organic material in a process called viral shunt. Caudoviruses have been used as model organisms to study biological processes and as a form of therapy to treat bacterial infections. Herpesviruses infect animals and are commonly associated with diseases such as herpes and chickenpox. Mirusviruses infect microscopic eukaryotes and are among the most common eukaryotic viruses in sunlit oceans. Many duplodnavirians are able to enter a latent state in which they persist in cells without forming virions. This is called the lysogenic cycle and contrasts with the lytic cycle, which produces virions. Duplodnaviria likely predates the last universal common ancestor (LUCA) of cellular life and was present in the LUCA. Caudoviruses in particular were likely already diverse by the time the LUCA emerged. Mirusviruses are related to viruses in the phylum Nucleocytoviricota in the realm Varidnaviria because they encode the core replication- and transcription-related proteins found in nucleocytoviruses. It is unclear, however, which realm these genes originate from. In
|
{
"page_id": 63770815,
"source": null,
"title": "Duplodnaviria"
}
|
any case, herpesviruses appear to have lost most of these genes through reductive evolution. Outside of the realm, an HK97-like fold is only found in encapsulins, which form nanocompartments in prokaryotes and are likely derived from duplodnaviruses. == Classification == Duplodnaviria contains one kingdom, which is divided into two phyla that contain two lineages of viruses in the realm: caudoviruses and herpesviruses. This taxonomy can be visualized as follows: Realm: Duplodnaviria Kingdom: Heunggongvirae Phylum: Peploviricota Class: Herviviricetes Order: Herpesvirales – herpesviruses, which infect animals (eukaryotes) Phylum: Uroviricota Class: Caudoviricetes – caudoviruses, also called head-tail viruses and tailed viruses, which infect archaea and bacteria (prokaryotes) The realm also contains mirusviruses, which have not been assigned to any taxon officially but which constitute the putative phylum Mirusviricota. As all viruses in the realm are double-stranded DNA (dsDNA) viruses, the realm belongs to Group I: dsDNA viruses of Baltimore classification, a classification system based on a virus's manner of messenger RNA (mRNA) production that is often used alongside standard virus taxonomy, which is based on evolutionary history. Realms are the highest level of taxonomy used for viruses and Duplodnaviria is one of seven. The others are Adnaviria, Monodnaviria, Riboviria, Ribozyviria, Singelaviria, and Varidnaviria. == Core characteristics == All viruses in Duplodnaviria contain an icosahedral capsid that is composed of a major capsid protein (MCP) that contains a unique folded structure, called the HK97 fold, named after the folded structure of the MCP of the bacterial virus HK97. The conserved elements of the HK97 fold, found in all duplodnavirians, are the axial (A) domain, the peripheral (P) domain, the extended (E) loop, and the N-terminal (N) arm. Many MCPs contain additional elements, such as the insertion (I) domain, which is grafted onto the A-domain, and the glycine-rich (G) loop, found in bacteriophage HK97's MCP.
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{
"page_id": 63770815,
"source": null,
"title": "Duplodnaviria"
}
|
Other hallmark traits among viruses in the realm involve the structure and assembly of capsids and include a portal protein that forms the opening of the capsid, a protease that empties the capsid before viral DNA is packaged, and a terminase enzyme that packages viral DNA into the capsid. In herpesviruses, their proteases are often referred to as assemblins. After HK97 MCPs have been synthesized by the host cell's ribosomes, the viral capsid is assembled from them with the proteins bonding to each other. The first product of capsid assembly is a procapsid, also called prohead for caudoviruses. Procapsids are roughly spherical, lumpy, and thick. Assembly of procapsids is driven by scaffold proteins that guide the geometric construction of the procapsid. In the absence of such proteins, the delta domain of the MCP, which faces toward the inside of the capsid, acts as a scaffold protein. A cylindrical opening the capsid, the portal, that serves as the entrance and exit for viral DNA is created with portal proteins at one of the 12 vertices of the capsid. After capsid assembly, scaffold proteins are removed from the inside of the capsid by the capsid maturation protease, which may be part of the scaffolding. Scaffold proteins may be removed intact or after the protease breaks them down in a process called proteolysis, either of which leaves the inside of the procapsid empty. At the same time as capsid assembly, replication of viral DNA occurs, and long molecules of DNA containing numerous copies of the viral genome, called concatemers, are created. The enzyme terminase, made of two subunits (large and small), finds the viral DNA inside of the cell via the small subunit, cuts the concatemers, and creates the endings (termini) of the genomes. Terminase recognizes a packaging signal in the genome and
|
{
"page_id": 63770815,
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"title": "Duplodnaviria"
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cuts the nucleic acid, creating a free end that it binds to. The terminase, now bound to the concatemer, attaches itself to the capsid portal and begins translocating the DNA from outside the capsid to the inside, using energy generated from ATP hydrolysis by its large subunit. As more DNA is inserted into the capsid, the capsid expands in size, becomes thinner, and its surface becomes flatter and more angular. Once the genome is completely inside, terminase cuts the concatemer again, completing packaging. Terminase then detaches itself from the portal and proceeds to repeat this process until all genomes in the concatemer have been packaged into capsids. For caudoviruses, the capsid is called the "head" of the complete virus particle and the rest of the virion is called the "tail". Caudoviruses sometimes have decoration proteins that attach to the capsid's surface to reinforance its structure. The tail, which is used for attaching to cells and injecting viral DNA into them, is assembled separately from the capsid and attached at the portal after DNA packaging. Caudoviruses have three types of tails and are informally referred to by which type of tail they have: short, non-contractile tails (podoviruses), long, contractile tails (myoviruses), and long, non-contractile, flexible tails (siphoviruses). After the virion is fully assembled, it leaves the cell. Caudoviruses leave the cell via rupturing of the cell membrane (lysis), which causes cell death. Herpesviruses leave via exocytosis after obtaining an envelope that covers the capsid from cellular vesicles from the Golgi apparatus. == Distribution == Caudoviruses are one of the most abundant groups of viruses on Earth and are the most numerous viruses in prokaryotes. They can be found in a wide variety of environments, including geothermal, hypersaline, soil, marine, and moderate ecosystems, as well as in the human body. In certain
|
{
"page_id": 63770815,
"source": null,
"title": "Duplodnaviria"
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environments, however, they may be outnumbered by other viruses, such as tectiliviricetes in marine environments and ssDNA viruses in offshore sediments. Archaeal caudoviruses transfer biomes recurrently via host-switching, including transfering between anoxic, hypersaline, and marine environments. Archaeal caudoviruses adapted to hypersaline environments become inactivated when removed from the environment but reactivate when reintroduced, indicating that they depend on high salinity. Mirusviruses have been identified in most major lineages of eukaryotes, both unicellular and multicellular, including eukaryotes in saltwater, freshwater, soil, as well as in parasites of animals and plants. They commonly infect marine eukaryotic plankton and are among the most abundant eukaryotic viruses in sunlit oceans. They are especially common in the euphotic subsurface layer where chlorophyll concentrations are high. Different mirusviruses are found in different regions; for example, some are found exclusively in the Arctic Ocean. At Lake Biwa in Japan, a freshwater lake, they are among the most abundant viruses in the epilimnion zone of the lake during seasonal algal blooms and are also present in the hypolimnion zone. Most can be described as specific to either the epilimnion, where their presence tended to be transient, or the hypolimnion, where their presence was more persistent. == Phylogenetics == The main scaffold of the HK97 fold MCP appears to have been created from a DUF1884 protein family domain that was inserted into a strand-helix-strand-strand (SHS2) fold protein related to the dodecin protein family. The emergence of duplodnavirians likely came before the last universal common ancestor (LUCA) of cellular life existed, and viruses in the realm likely infected the LUCA. Caudoviruses in particular likely had already diversified and obtained their three morphological types by the time the LUCA emerged. Outside of Duplodnaviria, an HK97-like fold is only found in encapsulins, proteins that form a type of prokaryotic nanocompartment that encapsulates
|
{
"page_id": 63770815,
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"title": "Duplodnaviria"
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a variety of cargo proteins related to the oxidative stress response. Encapsulins assemble into icosahedrons like the capsids of duplodnaviruses, but the HK97 MCP in viruses is much more divergent and widespread than encapsulins, which form a narrow monophyletic clade. As such, it is more likely that encapsulins are derived from viruses than vice versa. Archaea of the phylum Thermoproteota (formerly Crenarchaeota), however, contain encapsulins but are not known to be infected by caudoviruses, so the relation between encapsulins and Duplodnaviria remains unresolved. The ATPase subunit of Duplodnaviria terminases that generates energy for packaging viral DNA has the same general structural design of the P-loop fold as the packaging ATPases of viruses in the realm Varidnaviria but are otherwise not directly related to each other. While viruses in Duplodnaviria make use of the HK97 fold for their major capsid proteins, the major capsid proteins of viruses in Varidnaviria instead are marked by double vertical jelly roll folds. The duplodnavirian ATPase likely represents an ancient acquisition shortly after the ancestors of duplodnavirians obtained capsids. The ATPase is distantly related to superfamily 2 helicases and contains an additional RNAse H-fold nuclease domain. Exaptation of this protein involved significant change to the protein, including fusion of the ATPase and nuclease domains. Mirusviruses contain the hallmark structural genes of Duplodnaviria but also encode the replication and transcription (i.e. "informational") proteins of the Varidnaviria phylum Nucleocytoviricota, indicative of some form of evolutionary relationship between the two groups of viruses. Three possible scenarios have been proposed: a nucleocytovirus had its structural genes replaced with those of Duplodnaviria, the ancestors of mirusviruses inherited their informational proteins the ancestors of nucleocytoviruses, or vice versa. In the third scenario, the ancestors of caudoviruses may have had the informational genes, but they may have been replaced with another group of
|
{
"page_id": 63770815,
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genes in the caudovirus lineage. The transfer of such genes to varidnavirians may explain the evolutionary leap from "simple" varidnavirians to highly complex nucleocytoviruses. In any case, herpesviruses are thought to have lost most of the informational genes through reductive evolution. Mirusviruses have been found to integrate their genomes in their hosts and form episomes. Their episomal and integrate forms resemble the episomal and endogenous latent forms of herpesviruses. Furthermore, mirusviruses and herpesviruses have a tower domain inserted in the A subdomain of the HK97 fold that projects away from the surface of assembled capsids. The tower domain of mirusviruses is smaller than the tower domain of herpesviruses. Additionally, animals emerged after unicellular eukaryotes. For these reasons, mirusviruses may more closely resemble the ancestral state of eukaryotic duplodnavirians than herpesviruses, which would have underone reductive evolution and specialized to infecting animal cells. Although mirusviruses likely emerged before herpesviruses, their exact point of origin is unknown. == Interactions with hosts == === Latency === Viruses in Duplodnaviria have two different types of replication cycles: the lytic cycle, whereby infection leads directly to virion formation and exit from the host cell, and the lysogenic cycle, whereby a latent infection retains the viral DNA inside of the host cell without virion formation, either as an episome or via integration into the host cell's DNA, with the possibility of converting to the lytic cycle in the future. Viruses that can replicate through the lysogenic cycle are called temperate or lysogenic viruses. Caudoviruses vary in their temperateness, whereas all herpesviruses are temperate and able to avoid detection by the host's immune system and cause lifelong infections. Mirusviruses also appear to be capable of a lysogenic life cycle as they, like herpesviruses, are able to integrate their genome into the host cell's genome and form extra-chromosomal
|
{
"page_id": 63770815,
"source": null,
"title": "Duplodnaviria"
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episomes. === Disease === Herpesviruses are associated with a wide range of diseases in their hosts, including a respiratory tract illness in chickens, a respiratory and reproductive illness in cattle, and tumors in sea turtles. In humans, herpesviruses usually cause various epithelial diseases such as herpes simplex, chickenpox, shingles, and Kaposi's sarcoma. Initial infection causes acute symptoms and leads to lifelong infection via latency. Herpesviruses may emerge from their latency to cause illnesses, which may have severe symptoms such as encephalitis and pneumonia. === Viral shunt === Caudoviruses are ubiquitous worldwide and are a major cause of death among prokaryotes. Infection may lead to cell death via lysis, the rupturing of the cell membrane. As a result of lysis, organic material from the killed prokaryotes is released into the environment, contributing to a process called viral shunt. Caudoviruses shunt nutrients from organic material away from higher trophic levels so that they can be consumed by organisms in lower trophic levels, which has the effects of recycling nutrients and promoting increased diversity among marine life. == History == Caudoviruses were discovered independently by Frederick Twort in 1915 and Félix d'Hérelle in 1917, and they have been the focus of much research since then. Some have been used as model organisms to study various biological processes. For example, bacteriophage lambda has been used to study gene regulation and the lytic and lysogenic cycles. d'Hérelle envisioned bacteriophages as a way to treat bacterial infections and he first used caudoviruses to treat bacterial infections in 1919. Phage therapy was subsequently used extensively to treat bacterial infections in animals and humans. In the 1940s, phage therapy fell out of use due to the invention of penicillin and other antibiotics, but the emergence of drug-resistant bacteria and a decline in the number of novel antibiotics being
|
{
"page_id": 63770815,
"source": null,
"title": "Duplodnaviria"
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invented has sparked renewed interest in using lytic caudoviruses to treat bacterial infections. In the late 1990s, HK97 became the first bacteriophage to have its capsid structure solved. Diseases in humans caused by herpesviruses have been recognized for much of recorded history, and person-to-person transmission of the herpes simplex virus, the first herpesvirus discovered, was first recognized in 1893 by Émile Vidal. Over time, caudoviruses and herpesviruses were increasingly found to share many characteristics, and their genetic relation was formalized with the establishment of Duplodnaviria in 2019. Caudoviruses were originally classified into three families based on their morphology: Podoviridae, which have short, non-contractile tails; Myoviridae, which have long, contractile tails; and Siphoviridae, which have long, non-contractile, flexible tails. Since the early 2000s, genetic analysis has revealed a high level of diversity among caudoviruses, and the traditional system of morphology-based classification has been replaced with genetics-based classification starting in the late 2010s. The first possible identification of a mirusvirus was made in thraustochytrids in 1972, but they couldn't be studied further due to the limitations of the methods used at that time. They were officially discovered in 2023 via metagenomic analysis of saltwater biome samples taken from Tara expedition sampling locations throughout the world. A year later, a genetically distinct group of mirusviruses were found in Lake Biwa in Japan, a freshwater lake, and metagenomic testing identified them in most major lineages of eukaryotes. Mirusvirus virions have not been isolated yet, but based on the proteins encoded by them, they are predicted to form capsids resembling those of caudoviruses and herpesviruses. === Etymology === The name Duplodnaviria is a portmanteau of duplo, the Latin word for double, dna, from deoxyribonucleic acid (DNA), which refers to all members of the realm having double-stranded DNA genomes, and -viria, which is the suffix used
|
{
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for virus realms. Duplodnaviria is monotypic with only one kingdom, Heunggongvirae, so both the realm and kingdom have the same definition. Heunggongvirae takes the first part of its name from Cantonese 香港 [Hēunggóng], meaning and approximately pronounced "Hong Kong", which is a reference to bacteriophage HK97 (Hong Kong 97), the namesake of the HK97 fold, and the suffix -virae, which is the suffix used for virus kingdoms. == See also == List of higher virus taxa == References == == Further reading == Ward CW (1993). "Progress towards a higher taxonomy of viruses". Research in Virology. 144 (6): 419–53. doi:10.1016/S0923-2516(06)80059-2. PMC 7135741. PMID 8140287.
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Identity preservation is the practice of tracking the details of agricultural shipments so that the specific characteristics of each shipment is known. Identity preserved (IP) is the designation given to such bulk commodities marketed in a manner that isolates and preserves the identity of a shipment, presumably because of unique characteristics that have value otherwise lost through commingling during normal storage, handling and shipping procedures. The concept of IP has been accorded greater importance with the introduction of genetically modified organisms into agriculture. Technical and managerial techniques are used to track and document the paths that agricultural products move in the production process. A fully integrated IP system might track and document a commodity's seed characteristics, initial planting, growing conditions, harvesting, shipping, storage, processing, packaging, and ultimate sale to the consumer. Separating organic products from conventionally raised ones is one type of IP system. IP systems are a central component of value chains. == References == This article incorporates public domain material from Jasper Womach. Report for Congress: Agriculture: A Glossary of Terms, Programs, and Laws, 2005 Edition (PDF). Congressional Research Service.
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{
"page_id": 23662784,
"source": null,
"title": "Identity preservation"
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A pantropical ("all tropics") distribution is one which covers tropical regions of both the Eastern and Western hemispheres. Examples of species include caecilians, modern sirenians and the plant genera Acacia and Bacopa. Neotropical is a zoogeographic term that covers a large part of the Americas, roughly from Mexico and the Caribbean southwards (including cold regions in southernmost South America). Palaeotropical refers to geographical occurrence. For a distribution to be palaeotropical a taxon must occur in tropical regions in the Old World. According to Takhtajan (1978), the following families have a pantropical distribution: Annonaceae, Hernandiaceae, Lauraceae, Piperaceae, Urticaceae, Dilleniaceae, Tetrameristaceae, Passifloraceae, Bombacaceae, Euphorbiaceae, Rhizophoraceae, Myrtaceae, Anacardiaceae, Sapindaceae, Malpighiaceae, Proteaceae, Bignoniaceae, Orchidaceae and Arecaceae. == See also == Afrotropical realm Tropical Africa Tropical Asia == References ==
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{
"page_id": 2756802,
"source": null,
"title": "Pantropical"
}
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Difluorides are chemical compounds with two fluorine atoms per molecule (or per formula unit). Metal difluorides are all ionic. Despite being highly ionic, the alkaline earth metal difluorides generally have extremely high lattice stability and are thus insoluble in water. The exception is beryllium difluoride. In addition, many transition metal difluorides are water-soluble. Calcium difluoride is a notable compound. In the form of the mineral fluorite it is the major source of commercial fluorine. It also has an eponymic crystal structure, which is an end member of the spectrum starting from bixbyite and progressing through pyrochlore. == List of the difluorides == Examples of the difluorides include: === Alkaline earth metal difluorides === The alkaline earth metals all exhibit the oxidation state +2, and form difluorides. The difluoride of radium is however not well established due to the element's high radioactivity. Beryllium difluoride Magnesium fluoride Calcium fluoride Strontium difluoride Barium fluoride Radium fluoride === Lanthanide difluorides === Neodymium difluoride Samarium difluoride Europium difluoride Dysprosium difluoride Thulium difluoride Ytterbium difluoride === Transition metal difluorides === Compounds of the form MF2: Cadmium difluoride Chromium(II) fluoride Cobalt difluoride Copper(II) fluoride Iron(II) fluoride Manganese(II) fluoride Mercury difluoride Nickel difluoride Palladium difluoride Platinum difluoride Silver difluoride Vanadium difluoride Zinc difluoride === Post-transition metal difluorides === Lead difluoride Tin(II) fluoride === Nonmetal and metalloid difluorides === Dinitrogen difluoride Oxygen difluoride Dioxygen difluoride Selenoyl difluoride Sulfur difluoride Disulfur difluoride Thionyl difluoride Germanium difluoride === Noble gas difluorides === Helium difluoride (hypothetical) Argon difluoride (predicted) Krypton difluoride Xenon difluoride Radon difluoride === Bifluorides === The bifluorides contain the two fluorine atoms in a covalently bound HF2− polyatomic ion rather than as F− anions. Ammonium bifluoride Potassium bifluoride Sodium bifluoride === Organic difluorides === Ethanedioyl difluoride Ethylidene difluoride Carbonyl difluoride Carbon dibromide difluoride (dibromodifluoromethane) Carbon dichloride difluoride (dichlorodifluormethane) Methyl
|
{
"page_id": 34148547,
"source": null,
"title": "Difluoride"
}
|
difluoride Methylphosphonyl difluoride Polyvinylidene difluoride == References == == Bibliography == Greenwood, N. N.; Earnshaw, A. (1998). Chemistry of the Elements (second ed.). Butterworth Heinemann. ISBN 0-7506-3365-4. Lide, David R. (2004). Handbook of chemistry and physics (84th ed.). CRC Press. ISBN 0-8493-0566-7. Wiberg, Egon; Wiberg, Nils; Holleman, Arnold Frederick (2001). Inorganic chemistry. Academic Press. ISBN 978-0-12-352651-9. Retrieved 3 March 2011.
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{
"page_id": 34148547,
"source": null,
"title": "Difluoride"
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|
The Russian Journal of Physical Chemistry B (Russian: Химическая физика, romanized: Khimicheskaya fizika) is an English-language translation of the eponymous Russian-language peer-reviewed scientific journal published by MAIK Nauka/Interperiodica and Springer Science+Business Media. The journal covers all aspects of chemical physics and combustion. The editor-in-chief is Anatoly L. Buchachenko (Russian Academy of Sciences). == Abstracting and indexing == Current Contents/Physical, Chemical and Earth Sciences Reaction Citation Index Science Citation Index Expanded Journal Citation Reports/Science Edition Chemical Abstracts Service Scopus Inspec == See also == Russian Journal of Physical Chemistry A == References == == External links == Official website
|
{
"page_id": 40440002,
"source": null,
"title": "Russian Journal of Physical Chemistry B"
}
|
The molecular formula C17H13ClN4 (molar mass: 308.76 g/mol, exact mass: 308.0829 u) may refer to: Alprazolam 4'-Chlorodeschloroalprazolam Liarozole
|
{
"page_id": 24187079,
"source": null,
"title": "C17H13ClN4"
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The ascidian mitochondrial code (translation table 13) is a genetic code found in the mitochondria of Ascidia. == Code == AAs = FFLLSSSSYY**CCWWLLLLPPPPHHQQRRRRIIMMTTTTNNKKSSGGVVVVAAAADDEEGGGG Starts = ---M------------------------------MM---------------M------------ Base1 = TTTTTTTTTTTTTTTTCCCCCCCCCCCCCCCCAAAAAAAAAAAAAAAAGGGGGGGGGGGGGGGG Base2 = TTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGG Base3 = TCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAG Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U). Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), Valine (Val, V) == Differences from the standard code == == Systematic range and comments == There is evidence from a phylogenetically diverse sample of tunicates (Urochordata) that AGA and AGG code for glycine. In other organisms, AGA/AGG code for either arginine or serine and in vertebrate mitochondria they code a STOP. Evidence for glycine translation of AGA/AGG was first found in 1993 in Pyura stolonifera and Halocynthia roretzi. It was then confirmed by tRNA sequencing and sequencing whole mitochondrial genomes. == Alternative initiation codons == ATA, GTG and TTG ATT is the start codon for the CytB gene in Halocynthia roretzi. == See also == List of genetic codes == References == This article incorporates text from the United States National Library of Medicine, which is in the public domain.
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{
"page_id": 50729160,
"source": null,
"title": "Ascidian mitochondrial code"
}
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John David Hunt FRS (12 December 1936 – 8 December 2012) was a British metallurgist. His research career was mainly based at the University of Oxford, from 1966 to 2002. His legacy includes the Institute of Materials, Minerals and Mining's John Hunt Medal, awarded for 'outstanding contribution to the science and/or technology of casting and solidification of metals'. He was elected Fellow of the Royal Society in 2001. == References ==
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{
"page_id": 73732297,
"source": null,
"title": "John David Hunt"
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Metalworking is the process of shaping and reshaping metals in order to create useful objects, parts, assemblies, and large scale structures. As a term, it covers a wide and diverse range of processes, skills, and tools for producing objects on every scale: from huge ships, buildings, and bridges, down to precise engine parts and delicate jewelry. The historical roots of metalworking predate recorded history; its use spans cultures, civilizations and millennia. It has evolved from shaping soft, native metals like gold with simple hand tools, through the smelting of ores and hot forging of harder metals like iron, up to and including highly technical modern processes such as machining and welding. It has been used as an industry, a driver of trade, individual hobbies, and in the creation of art; it can be regarded as both a science and a craft. Modern metalworking processes, though diverse and specialized, can be categorized into one of three broad areas known as forming, cutting, or joining processes. Modern metalworking workshops, typically known as machine shops, hold a wide variety of specialized or general-use machine tools capable of creating highly precise, useful products. Many simpler metalworking techniques, such as blacksmithing, are no longer economically competitive on a large scale in developed countries; some of them are still in use in less developed countries, for artisanal or hobby work, or for historical reenactment. == Prehistory == The oldest archaeological evidence of copper mining and working was the discovery of a copper pendant in northern Iraq from 8,700 BCE. The earliest substantiated and dated evidence of metalworking in the Americas was the processing of copper in Wisconsin, near Lake Michigan. Copper was hammered until it became brittle, then heated so it could be worked further. In America, this technology is dated to about 4000–5000 BCE. The
|
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"page_id": 266443,
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"title": "Metalworking"
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oldest gold artifacts in the world come from the Bulgarian Varna Necropolis and date from 4450 BCE. Not all metal required fire to obtain it or work it. Isaac Asimov speculated that gold was the "first metal". His reasoning being, that, by its chemistry, it is found in nature as nuggets of pure gold. In other words, gold, as rare as it is, is sometimes found in nature as a native metal. Some metals can also be found in meteors. Almost all other metals are found in ores, a mineral-bearing rock, that require heat or some other process to liberate the metal. Another feature of gold is that it is workable as it is found, meaning that no technology beyond a stone hammer and anvil is needed to work the metal. This is a result of gold's properties of malleability and ductility. The earliest tools were stone, bone, wood, and sinew, all of which sufficed to work gold. At some unknown time, the process of liberating metals from rock by heat became known, and rocks rich in copper, tin, and lead came into demand. These ores were mined wherever they were recognized. Remnants of such ancient mines have been found all over Southwestern Asia. Metalworking was being carried out by the South Asian inhabitants of Mehrgarh between 7000 and 3300 BCE. The end of the beginning of metalworking occurs sometime around 6000 BCE when copper smelting became common in Southwestern Asia. Ancient civilisations knew of seven metals. Here they are arranged in order of their oxidation potential (in volts): Iron +0.44 V, Tin +0.14 V Lead +0.13 V Copper −0.34 V Mercury −0.79 V Silver −0.80 V Gold −1.50 V. The oxidation potential is important because it is one indicator of how tightly bound to the ore the metal is
|
{
"page_id": 266443,
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likely to be. As can be seen, iron is significantly higher than the other six metals while gold is dramatically lower than the six above it. Gold's low oxidation is one of the main reasons that gold is found in nuggets. These nuggets are relatively pure gold and are workable as they are found. Copper ore, being relatively abundant, and tin ore became the next important substances in the story of metalworking. Using heat to smelt copper from ore, a great deal of copper was produced. It was used for both jewelry and simple tools. However, copper by itself was too soft for tools requiring edges and stiffness. At some point tin was added into the molten copper and bronze was developed thereby. Bronze is an alloy of copper and tin. Bronze was an important advance because it had the edge-durability and stiffness that pure copper lacked. Until the advent of iron, bronze was the most advanced metal for tools and weapons in common use (see Bronze Age for more detail). Outside Southwestern Asia, these same advances and materials were being discovered and used around the world. People in China and Great Britain began using bronze with little time being devoted to copper. Japanese began the use of bronze and iron almost simultaneously. In the Americas it was different. Although the peoples of the Americas knew of metals, it was not until the European colonisation that metalworking for tools and weapons became common. Jewelry and art were the principal uses of metals in the Americas prior to European influence. About 2700 BCE, production of bronze was common in locales where the necessary materials could be assembled for smelting, heating, and working the metal. Iron was beginning to be smelted and began its emergence as an important metal for tools and
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weapons. The period that followed became known as the Iron Age. == History == By the historical periods of the Pharaohs in Egypt, the Vedic Kings in India, the Tribes of Israel, and the Maya civilization in North America, among other ancient populations, precious metals began to have value attached to them. In some cases rules for ownership, distribution, and trade were created, enforced, and agreed upon by the respective peoples. By the above periods metalworkers were very skilled at creating objects of adornment, religious artifacts, and trade instruments of precious metals (non-ferrous), as well as weaponry usually of ferrous metals and/or alloys. These skills were well executed. The techniques were practiced by artisans, blacksmiths, atharvavedic practitioners, alchemists, and other categories of metalworkers around the globe. For example, the granulation technique was employed by numerous ancient cultures before the historic record shows people traveled to far regions to share this process. Metalsmiths today still use this and many other ancient techniques. As time progressed, metal objects became more common, and ever more complex. The need to further acquire and work metals grew in importance. Skills related to extracting metal ores from the earth began to evolve, and metalsmiths became more knowledgeable. Metalsmiths became important members of society. Fates and economies of entire civilizations were greatly affected by the availability of metals and metalsmiths. The metalworker depends on the extraction of precious metals to make jewelry, build more efficient electronics, and for industrial and technological applications from construction to shipping containers to rail, and air transport. Without metals, goods and services would cease to move around the globe on the scale we know today. == General processes == Metalworking generally is divided into three categories: forming, cutting, and joining. Most metal cutting is done by high speed steel tools or carbide
|
{
"page_id": 266443,
"source": null,
"title": "Metalworking"
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tools. Each of these categories contains various processes. Prior to most operations, the metal must be marked out and/or measured, depending on the desired finished product. Marking out (also known as layout) is the process of transferring a design or pattern to a workpiece and is the first step in the handcraft of metalworking. It is performed in many industries or hobbies, although in industry, the repetition eliminates the need to mark out every individual piece. In the metal trades area, marking out consists of transferring the engineer's plan to the workpiece in preparation for the next step, machining or manufacture. Calipers are hand tools designed to precisely measure the distance between two points. Most calipers have two sets of flat, parallel edges used for inner or outer diameter measurements. These calipers can be accurate to within one-thousandth of an inch (25.4 μm). Different types of calipers have different mechanisms for displaying the distance measured. Where larger objects need to be measured with less precision, a tape measure is often used. == Casting == Casting achieves a specific form by pouring molten metal into a mold and allowing it to cool, with no mechanical force. Forms of casting include: Investment casting (called lost wax casting in art) Centrifugal casting Die casting Sand casting Shell casting Spin casting == Forming processes == These forming processes modify metal or workpiece by deforming the object, that is, without removing any material. Forming is done with a system of mechanical forces and, especially for bulk metal forming, with heat. === Bulk forming processes === Plastic deformation involves using heat or pressure to make a workpiece more conductive to mechanical force. Historically, this and casting were done by blacksmiths, though today the process has been industrialized. In bulk metal forming, the workpiece is generally heated
|
{
"page_id": 266443,
"source": null,
"title": "Metalworking"
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up. Cold sizing Extrusion Drawing Forging Powder metallurgy Friction drilling Rolling Burnishing === Sheet (and tube) forming processes === These types of forming process involve the application of mechanical force at room temperature. However, some recent developments involve the heating of dies and/or parts. Advancements in automated metalworking technology have made progressive die stamping possible which is a method that can encompass punching, coining, bending and several other ways below that modify metal at less cost while resulting in less scrap. Bending Coining Decambering Deep drawing (DD) Foldforming Hydroforming (HF) Hot metal gas forming Hot press hardening Incremental forming (IF) Spinning, Shear forming or Flowforming Planishing Raising Roll forming Roll bending Repoussé and chasing Rubber pad forming Shearing Stamping Superplastic forming (SPF) Wheeling using an English wheel (wheeling machine) == Cutting processes == Cutting is a collection of processes wherein material is brought to a specified geometry by removing excess material using various kinds of tooling to leave a finished part that meets specifications. The net result of cutting is two products, the waste or excess material, and the finished part. In woodworking, the waste would be sawdust and excess wood. In cutting metals the waste is chips or swarf and excess metal. Cutting processes fall into one of three major categories: Chip producing processes most commonly known as machining Burning, a set of processes wherein the metal is cut by oxidizing a kerf to separate pieces of metal Miscellaneous specialty process, not falling easily into either of the above categories Drilling a hole in a metal part is the most common example of a chip producing process. Using an oxy-fuel cutting torch to separate a plate of steel into smaller pieces is an example of burning. Chemical milling is an example of a specialty process that removes excess material
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by the use of etching chemicals and masking chemicals. There are many technologies available to cut metal, including: Manual technologies: saw, chisel, shear or snips Machine technologies: turning, milling, drilling, grinding, sawing Welding/burning technologies: burning by laser, oxy-fuel burning, and plasma Erosion technologies: by water jet, electric discharge, or abrasive flow machining. Chemical technologies: Photochemical machining Cutting fluid or coolant is used where there is significant friction and heat at the cutting interface between a cutter such as a drill or an end mill and the workpiece. Coolant is generally introduced by a spray across the face of the tool and workpiece to decrease friction and temperature at the cutting tool/workpiece interface to prevent excessive tool wear. In practice there are many methods of delivering coolant. === Health effects === The use of an angle grinder in cutting is not preferred as large amounts of harmful sparks and fumes (and particulates) are generated when compared with using reciprocating saw or band saw. Angle grinders produce sparks when cutting ferrous metals. They also produce shards cutting other materials. === Milling === Milling is the complex shaping of metal or other materials by removing material to form the final shape. It is generally done on a milling machine, a power-driven machine that in its basic form consists of a milling cutter that rotates about the spindle axis (like a drill), and a worktable that can move in multiple directions (usually two dimensions [x and y axis] relative to the workpiece). The spindle usually moves in the z axis. It is possible to raise the table (where the workpiece rests). Milling machines may be operated manually or under computer numerical control (CNC), and can perform a vast number of complex operations, such as slot cutting, planing, drilling and threading, rabbeting, routing, etc. Two
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common types of mills are the horizontal mill and vertical mill. The pieces produced are usually complex 3D objects that are converted into x, y, and z coordinates that are then fed into the CNC machine and allow it to complete the tasks required. The milling machine can produce most parts in 3D, but some require the objects to be rotated around the x, y, or z coordinate axis (depending on the need). Tolerances come in a variety of standards, depending on the locale. In countries still using the imperial system, this is usually in the thousandths of an inch (unit known as thou), depending on the specific machine. In many other European countries, standards following the ISO are used instead. In order to keep both the bit and material cool, a high temperature coolant is used. In most cases the coolant is sprayed from a hose directly onto the bit and material. This coolant can either be machine or user controlled, depending on the machine. Materials that can be milled range from aluminum to stainless steel and almost everything in between. Each material requires a different speed on the milling tool and varies in the amount of material that can be removed in one pass of the tool. Harder materials are usually milled at slower speeds with small amounts of material removed. Softer materials vary, but usually are milled with a high bit speed. The use of a milling machine adds costs that are factored into the manufacturing process. Each time the machine is used coolant is also used, which must be periodically added in order to prevent breaking bits. A milling bit must also be changed as needed in order to prevent damage to the material. Time is the biggest factor for costs. Complex parts can require hours
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to complete, while very simple parts take only minutes. This in turn varies the production time as well, as each part will require different amounts of time. Safety is key with these machines. The bits are traveling at high speeds and removing pieces of usually scalding hot metal. The advantage of having a CNC milling machine is that it protects the machine operator. === Turning === Turning is a metal cutting process for producing a cylindrical surface with a single point tool. The workpiece is rotated on a spindle and the cutting tool is fed into it radially, axially or both. Producing surfaces perpendicular to the workpiece axis is called facing. Producing surfaces using both radial and axial feeds is called profiling. A lathe is a machine tool which spins a block or cylinder of material so that when abrasive, cutting, or deformation tools are applied to the workpiece, it can be shaped to produce an object which has rotational symmetry about an axis of rotation. Examples of objects that can be produced on a lathe include candlestick holders, crankshafts, camshafts, and bearing mounts. Lathes have four main components: the bed, the headstock, the carriage, and the tailstock. The bed is a precise & very strong base which all of the other components rest upon for alignment. The headstock's spindle secures the workpiece with a chuck, whose jaws (usually three or four) are tightened around the piece. The spindle rotates at high speed, providing the energy to cut the material. While historically lathes were powered by belts from a line shaft, modern examples uses electric motors. The workpiece extends out of the spindle along the axis of rotation above the flat bed. The carriage is a platform that can be moved, precisely and independently parallel and perpendicular to the axis
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of rotation. A hardened cutting tool is held at the desired height (usually the middle of the workpiece) by the toolpost. The carriage is then moved around the rotating workpiece, and the cutting tool gradually removes material from the workpiece. The tailstock can be slid along the axis of rotation and then locked in place as necessary. It may hold centers to further secure the workpiece, or cutting tools driven into the end of the workpiece. Other operations that can be performed with a single point tool on a lathe are: Chamfering: Cutting an angle on the corner of a cylinder. Parting: The tool is fed radially into the workpiece to cut off the end of a part. Threading: A tool is fed along and across the outside or inside surface of rotating parts to produce external or internal threads. Boring: A single-point tool is fed linearly and parallel to the axis of rotation to create a round hole. Drilling: Feeding the drill into the workpiece axially. Knurling: Uses a tool to produce a rough surface texture on the work piece. Frequently used to allow grip by hand on a metal part. Modern computer numerical control (CNC) lathes and (CNC) machining centres can do secondary operations like milling by using driven tools. When driven tools are used the work piece stops rotating and the driven tool executes the machining operation with a rotating cutting tool. The CNC machines use x, y, and z coordinates in order to control the turning tools and produce the product. Most modern day CNC lathes are able to produce most turned objects in 3D. Nearly all types of metal can be turned, although more time & specialist cutting tools are needed for harder workpieces. === Threading === There are many threading processes including: cutting threads
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with a tap or die, thread milling, single-point thread cutting, thread rolling, cold root rolling and forming, and thread grinding. A tap is used to cut a female thread on the inside surface of a pre-drilled hole, while a die cuts a male thread on a preformed cylindrical rod. === Grinding === Grinding uses an abrasive process to remove material from the workpiece. A grinding machine is a machine tool used for producing very fine finishes, making very light cuts, or high precision forms using an abrasive wheel as the cutting device. This wheel can be made up of various sizes and types of stones, diamonds or inorganic materials. The simplest grinder is a bench grinder or a hand-held angle grinder, for deburring parts or cutting metal with a zip-disc. Grinders have increased in size and complexity with advances in time and technology. From the old days of a manual toolroom grinder sharpening endmills for a production shop, to today's 30000 RPM CNC auto-loading manufacturing cell producing jet turbines, grinding processes vary greatly. Grinders need to be very rigid machines to produce the required finish. Some grinders are even used to produce glass scales for positioning CNC machine axis. The common rule is the machines used to produce scales be 10 times more accurate than the machines the parts are produced for. In the past grinders were used for finishing operations only because of limitations of tooling. Modern grinding wheel materials and the use of industrial diamonds or other man-made coatings (cubic boron nitride) on wheel forms have allowed grinders to achieve excellent results in production environments instead of being relegated to the back of the shop. Modern technology has advanced grinding operations to include CNC controls, high material removal rates with high precision, lending itself well to aerospace applications
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and high volume production runs of precision components. === Filing === Filing is combination of grinding and saw tooth cutting using a file. Prior to the development of modern machining equipment it provided a relatively accurate means for the production of small parts, especially those with flat surfaces. The skilled use of a file allowed a machinist to work to fine tolerances and was the hallmark of the craft. Today filing is rarely used as a production technique in industry, though it remains as a common method of deburring. === Other === Broaching is a machining operation used to cut keyways into shafts. Electron beam machining (EBM) is a machining process where high-velocity electrons are directed toward a work piece, creating heat and vaporizing the material. Ultrasonic machining uses ultrasonic vibrations to machine very hard or brittle materials. == Joining processes == === Welding === Welding is a fabrication process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, but sometimes pressure is used in conjunction with heat, or by itself, to produce the weld. Many different energy sources can be used for welding, including a gas flame, an electric arc, a laser, an electron beam, friction, and ultrasound. While often an industrial process, welding can be done in many different environments, including open air, underwater and in space. Regardless of location, however, welding remains dangerous, and precautions must be taken to avoid burns, electric shock, poisonous fumes, and overexposure to ultraviolet light. === Brazing === Brazing is a joining process in which a filler metal is melted and drawn into a capillary formed by the assembly of two or more work
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pieces. The filler metal reacts metallurgically with the workpieces and solidifies in the capillary, forming a strong joint. Unlike welding, the work piece is not melted. Brazing is similar to soldering, but occurs at temperatures in excess of 450 °C (842 °F). Brazing has the advantage of producing less thermal stresses than welding, and brazed assemblies tend to be more ductile than weldments because alloying elements can not segregate and precipitate. Brazing techniques include, flame brazing, resistance brazing, furnace brazing, diffusion brazing, inductive brazing and vacuum brazing. === Soldering === Soldering is a joining process that occurs at temperatures below 450 °C (842 °F). It is similar to brazing in the way that a filler is melted and drawn into a capillary to form a joint, although at a lower temperature. Because of this lower temperature and different alloys used as fillers, the metallurgical reaction between filler and work piece is minimal, resulting in a weaker joint. === Riveting === Riveting is one of the most ancient metalwork joining processes. Its use declined markedly during the second half of the 20th century, but it still retains important uses in industry and construction, and in artisan crafts such as jewellery, medieval armouring and metal couture in the early 21st century. The earlier use of rivets is being superseded by improvements in welding and component fabrication techniques. A rivet is essentially a two-headed and unthreaded bolt which holds two other pieces of metal together. Holes are drilled or punched through the two pieces of metal to be joined. The holes being aligned, a rivet is passed through the holes and permanent heads are formed onto the ends of the rivet utilizing hammers and forming dies (by either cold working or hot working). Rivets are commonly purchased with one head already formed. When
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it is necessary to remove rivets, one of the rivet's heads is sheared off with a cold chisel. The rivet is then driven out with a hammer and punch. === Mechanical fixings === This includes screws, as well as bolts. This is often used as it requires relatively little specialist equipment, and are therefore often used in flat-pack furniture. It can also be used when a metal is joined to another material (such as wood) or a particular metal does not weld well (such as aluminum). This can be done to directly join metals, or with an intermediate material such as nylon. While often weaker than other methods such as welding or brazing, the metal can easily be removed and therefore reused or recycled. It can also be done in conjunction with an epoxy or glue, reverting its ecological benefits. == Associated processes == While these processes are not primary metalworking processes, they are often performed before or after metalworking processes. === Heat treatment === Metals can be heat treated to alter the properties of strength, ductility, toughness, hardness or resistance to corrosion. Common heat treatment processes include annealing, precipitation hardening, quenching, and tempering: annealing softens the metal by allowing recovery of cold work and grain growth. quenching can be used to harden alloy steels, or in precipitation hardenable alloys, to trap dissolved solute atoms in solution. tempering will cause the dissolved alloying elements to precipitate, or in the case of quenched steels, improve impact strength and ductile properties. Often, mechanical and thermal treatments are combined in what is known as thermo-mechanical treatments for better properties and more efficient processing of materials. These processes are common to high alloy special steels, super alloys and titanium alloys. === Plating === Electroplating is a common surface-treatment technique. It involves bonding a thin
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layer of another metal such as gold, silver, chromium or zinc to the surface of the product by hydrolysis. It is used to reduce corrosion, create abrasion resistance and improve the product's aesthetic appearance. Plating can even change the properties of the original part including conductivity, heat dissipation or structural integrity. There are four main electroplating methods to ensure proper coating and cost effectiveness per product: mass plating, rack plating, continuous plating and line plating. === Thermal spraying === Thermal spraying techniques are another popular finishing option, and often have better high temperature properties than electroplated coatings due to the thicker coating. The four main thermal spray processes include electric wire arc spray, flame (oxy acetylene combustion) spray, plasma spray and high velocity oxy fuel (HVOF) spray. == See also == Bronze and brass ornamental work Chip formation Heavy metals Lead poisoning List of metalworking occupations Metal swarf Metal testing Metalworking hand tool Occupational dust exposure Particulates Power tool Stone mould General: List of manufacturing processes Timeline of materials technology == References == == External links == What's the Best Way to Cut Thick Steel? Schneider, George. "Chapter 1: Cutting Tool Materials", American Machinist, October, 2009 Schneider, George. "Cutting Tool Applications: Chapter 2 Metal Removal Methods", American Machinist, November, 2009 Videos about metalworking published by Institut für den Wissenschaftlichen Film. Available in the AV-Portal of the German National Library of Science and Technology. Evidences of Metalworking History Reference Horner, Joseph Gregory (1911). "Metal-Work" . Encyclopædia Britannica. Vol. 18 (11th ed.). pp. 205–215.
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Solar air conditioning, or "solar-powered air conditioning", refers to any air conditioning (cooling) system that uses solar power. This can be done through passive solar design, solar thermal energy conversion, and photovoltaic conversion (sunlight to electricity). The U.S. Energy Independence and Security Act of 2007 created 2008 through 2012 funding for a new solar air conditioning research and development program, which should develop and demonstrate multiple new technology innovations and mass production economies of scale. == History == In the late 19th century, the most common fluid for absorption cooling was a solution of ammonia and water. Today, the combination of lithium bromide and water is also in common use. One end of the system of expansion/condensation pipes is heated, and the other end gets cold enough to make ice. Originally, natural gas was used as a heat source in the late 19th century. Today, propane is used in recreational vehicle absorption chiller refrigerators. Hot water solar thermal energy collectors can also be used as the modern "free energy" heat source. A National Aeronautics and Space Administration (NASA) sponsored report in 1976 surveyed solar energy system applications of air conditioning. Techniques discussed included both solar powered (absorption cycle and heat engine / Rankine cycle) and solar related (heat pump) along with an extensive bibliography of related literature. == Photovoltaic (PV) solar cooling == Photovoltaics can provide either indirect solar air conditioning power or, now, directly power to air conditioners. Indirect photovoltaic power for air conditioners consists of whole-house or whole-building solar which, traditionally for most users, has also meant net metering to the grid. Solar in this case is inverted to alternating current (AC) to run the appliances in the house or building, including the air conditioner(s). The advantage of this is the air conditioners don’t need any special electronics
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to accommodate solar, so it’s a simple implementation. The disadvantage is that these air conditioners usually have a SEER value of 14 or less, and the supplied solar has some loss from the power conversion of DC (direct current) solar to AC even before it reaches the air conditioners. Another disadvantage is that these air conditioners cannot run when the grid is down, since, in effect, the net-metered home or building is a node on the grid, and utilities need to prevent backfeeding power into a dead grid when the grid’s down. And, now, air conditioners, like many home appliances (e.g., TVs, computers) are beginning to run on DC power. So, whole-building solar for such units needs to be inverted to alternating current, and then rectified back to direct current, further increasing inefficiencies. Off-grid solar arrays instead use batteries to supply whole-house or whole-building solar. Such systems employ a voltage controller to manage battery charging, and then the battery power is inverted to provide alternating current for the home or building. Since they’re not grid tied or net metered, they can operate after a storm or other event brings down grid power. However, the power, once again, must be converted from DC from the solar panels and batteries to AC by inversion to run power remotely to the appliances. More recently, true solar-powered photovoltaic air conditioners heat pumps have been developed. Such units run using DC power, and, as such, they can and do make use of the inherent DC power generated by photovoltaic solar panels. One mini split version of this units employs a 48v DC power bus and a 48v battery array, usually 4 x 12v batteries in series (e.g., Hotspot Energy). Unlike the whole-house battery system, though, these batteries only run the air conditioner. The advantage of
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these systems is that, with enough solar and battery capacity, they can run at night or when it’s cloudy. Another mini split version allows the solar panels to be plugged directly to the outside part of the unit, uses a 310v DC power bus, and offers optional 120v plug-in backup grid power (Airspool) to be leveraged to fill in any lack of solar power available. The advantage of these inverter DC air conditioners is the lower cost, while the disadvantage is that they have no way to run without solar unless they're plugged in. Both of these systems make use variable refrigerant flow technology, with high-efficiency variable-speed DC motors and compressors to require very little run power, and both also offer heat in addition to air conditioning. A third type of unit is available for larger, usually commercial, buildings and offers both grid and battery backup as well as optional net metering. Like the two smaller units, these units are VRF, but unlike them, there’s an option to run heating in one part of the building and air conditioning in another part, making use of one outside/condensing unit and multiple inside/evaporative units located in different areas of the building to condition that areas based on specific user needs. Photovoltaic can be combined with geothermal technology, too. An efficient geothermal air conditioning system would require a smaller, less-expensive photovoltaic system. A high-quality geothermal heat pump installation can have a SEER in the range of 20 (±). A 29 kW (100,000 BTU/h) SEER 20 air conditioner would require less than 5 kW while operating. There are also new non-compressor-based electrical air conditioning systems with a SEER above 20 coming on the market. New versions of phase-change indirect evaporative coolers use nothing but a fan and a supply of water to cool buildings
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without adding extra interior humidity (such as at McCarran Airport Las Vegas Nevada). In dry arid climates with relative humidity below 45% (about 40% of the continental U.S.) indirect evaporative coolers can achieve a SEER above 20, and up to SEER 40. A 29 kW (100,000 BTU/h) indirect evaporative cooler would only need enough photovoltaic power for the circulation fan (plus a water supply). A less-expensive partial-power photovoltaic system can reduce (but not eliminate) the monthly amount of electricity purchased from the power grid for air conditioning (and other uses). With American state government subsidies of $2.50 to US$5.00 per photovoltaic watt, the amortized cost of PV-generated electricity can be below $0.15 per kWh. This is currently cost effective in some areas where power company electricity is now $0.15 or more. Excess PV power generated when air conditioning is not required can be sold to the power grid in many locations, which can reduce or eliminate annual net electricity purchase requirement. (See Zero-energy building) Superior energy efficiency can be designed into new construction (or retrofitted to existing buildings). Since the U.S. Department of Energy was created in 1977, their Weatherization Assistance Program has reduced heating-and-cooling load on 5.5 million low-income affordable homes an average of 31%. A hundred million American buildings still need improved weatherization. Careless conventional construction practices are still producing inefficient new buildings that need weatherization when they are first occupied. == Geothermal cooling == Earth sheltering or earth cooling tubes can take advantage of the ambient temperature of the earth to reduce or eliminate conventional air conditioning requirements. In many climates where the majority of humans live, they can greatly reduce the buildup of undesirable summer heat, and also help remove heat from the interior of the building. They increase construction cost, but reduce or eliminate the
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cost of conventional air conditioning equipment. Earth cooling tubes are not cost effective in hot humid tropical environments where the ambient Earth temperature approaches human temperature comfort zone. A solar chimney or photovoltaic-powered fan can be used to exhaust undesired heat and draw in cooler, dehumidified air that has passed by ambient Earth temperature surfaces. Control of humidity and condensation are important design issues. A geothermal heat pump uses ambient earth temperature to improve SEER for heat and cooling. A deep well recirculates water to extract ambient earth temperature, typically at 8 litres (2 US gal) of water per metric ton per minute. These "open loop" systems were the most common in early systems, however water quality could cause damage to the coils in the heat pump and shorten the life of the equipment. Another method is a closed loop system, in which a loop of tubing is run down a well or wells, or in trenches in the lawn, to cool an intermediate fluid. When wells are used, they are back-filled with bentonite grout or another grout material to ensure good thermal conductivity to the earth. In the past the fluid of choice was a 50/50 mixture of propylene glycol because it is non-toxic unlike ethylene glycol (which is used in car radiators). Propylene glycol is viscous, and would eventually gum up some parts in the loop(s), so it has fallen out of favor. Today , the most common transfer agent is a mixture of water and ethyl alcohol (ethanol). Ambient earth temperature is much lower than peak summer air temperature, and much higher than the lowest extreme winter air temperature. Water is 25 times more thermally conductive than air, so it is much more efficient than an outside air heat pump, (which becomes less effective when the outside
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temperature drops in winter). The same type of geothermal well can be used without a heat pump but with greatly diminished results. Ambient earth temperature water is pumped through a shrouded radiator (like an automobile radiator). Air is blown across the radiator, which cools without a compressor-based air conditioner. Photovoltaic solar electric panels produce electricity for the water pump and fan, eliminating conventional air-conditioning utility bills. This concept is cost-effective, as long as the location has ambient earth temperature below the human thermal comfort zone (not the tropics). == Solar open-loop air conditioning using desiccants == Air can be passed over common, solid desiccants (like silica gel or zeolite) or liquid desiccants (like lithium bromide/chloride) to draw moisture from the air to allow an efficient mechanical or evaporative cooling cycle. The desiccant is then regenerated by using solar thermal energy to dehumidify, in a cost-effective, low-energy-consumption, continuously repeating cycle. A photovoltaic system can power a low-energy air circulation fan, and a motor to slowly rotate a large disk filled with desiccant. Energy recovery ventilation systems provide a controlled way of ventilating a home while minimizing energy loss. Air is passed through an "enthalpy wheel" (often using silica gel) to reduce the cost of heating ventilated air in the winter by transferring heat from the warm inside air being exhausted to the fresh (but cold) supply air. In the summer, the inside air cools the warmer incoming supply air to reduce ventilation cooling costs. This low-energy fan-and-motor ventilation system can be cost-effectively powered by photovoltaics, with enhanced natural convection exhaust up a solar chimney - the downward incoming air flow would be forced convection (advection). A desiccant like calcium chloride can be mixed with water to create a recirculating waterfall that dehumidifies a room using solar thermal energy to regenerate the
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liquid, and a PV-powered low-rate water pump to circulate liquid. Active solar cooling wherein solar thermal collectors provide input energy for a desiccant cooling system. There are several commercially available systems that blow air through a desiccant impregnated medium for both the dehumidification and the regeneration cycle. The solar heat is one way that the regeneration cycle is powered. In theory packed towers can be used to form a counter-current flow of the air and the liquid desiccant but are not normally employed in commercially available machines. Preheating of the air is shown to greatly enhance desiccant regeneration. The packed column yields good results as a dehumidifier/regenerator, provided pressure drop can be reduced with the use of suitable packing. == Passive solar cooling == In this type of cooling solar thermal energy is not used directly to create a cold environment or drive any direct cooling processes. Instead, solar building design aims at slowing the rate of heat transfer into a building in the summer, and improving the removal of unwanted heat. It involves a good understanding of the mechanisms of heat transfer: heat conduction, convective heat transfer, and thermal radiation, the latter primarily from the sun. For example, a sign of poor thermal design is an attic that gets hotter in summer than the peak outside air temperature. This can be significantly reduced or eliminated with a cool roof or a green roof, which can reduce the roof surface temperature by 70 °F (40 °C) in summer. A radiant barrier and an air gap below the roof will block about 97% of downward radiation from roof cladding heated by the sun. Passive solar cooling is much easier to achieve in new construction than by adapting existing buildings. There are many design specifics involved in passive solar cooling. It is
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a primary element of designing a zero energy building in a hot climate. == Solar closed-loop absorption cooling == Closed-loop air conditioning commonly uses the following materials for water-based absorption: Ammonia Lithium Bromide Lithium Chloride Silica Gel Zeolite An alternative to water-based systems is to use methanol with activated carbon. Active solar cooling uses solar thermal collectors to provide solar energy to thermally driven chillers (usually adsorption or absorption chillers). Solar energy heats a fluid that provides heat to the generator of an absorption chiller and is recirculated back to the collectors. The heat provided to the generator drives a cooling cycle that produces chilled water. The chilled water produced is used for large commercial and industrial cooling. Solar thermal energy can be used to efficiently cool in the summer, and also heat domestic hot water and buildings in the winter. Single, double or triple iterative absorption cooling cycles are used in different solar-thermal-cooling system designs. The more cycles, the more efficient they are. Absorption chillers operate with less noise and vibration than compressor-based chillers, but their capital costs are relatively high. Efficient absorption chillers nominally require water of at least 190 °F (88 °C). Common, inexpensive flat-plate solar thermal collectors only produce about 160 °F (71 °C) water. High temperature flat plate, concentrating (CSP) or evacuated tube collectors are needed to produce the higher temperature transfer fluids required. In large scale installations there are several projects successful both technical and economical in operation worldwide including, for example, at the headquarters of Caixa Geral de Depósitos in Lisbon with 1,579 square metres (17,000 sq ft) solar collectors and 545 kW cooling power or on the Olympic Sailing Village in Qingdao/China. In 2011 the most powerful plant at Singapore's new constructed United World College will be commissioned (1500 kW). These projects
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have shown that flat plate solar collectors specially developed for temperatures over 200 °F (93 °C) (featuring double glazing, increased backside insulation, etc.) can be effective and cost-efficient. Where water can be heated well above 190 °F (88 °C), it can be stored and used when the sun is not shining. The Audubon Environmental Center at the Ernest E. Debs Regional Park in Los Angeles has an example solar air conditioning installation, which failed fairly soon after commissioning and is no longer being maintained. The Southern California Gas Co. (The Gas Company) is also testing the practicality of solar thermal cooling systems at their Energy Resource Center (ERC) in Downey, California. Solar Collectors from Sopogy and Cogenra were installed on the rooftop at the ERC and are producing cooling for the building's air conditioning system. Masdar City in the United Arab Emirates is also testing a double-effect absorption cooling plant using Sopogy parabolic trough collectors, Mirroxx Fresnel array and TVP Solar high-vacuum solar thermal panels. A FedEx Ground sorting facility in Davenport, Florida uses a solar thermal air conditioning system to feed cool air into truck trailers parked at loading doors. For 150 years, absorption chillers have been used to make ice (before the electric light bulbs were invented). This ice can be stored and used as an "ice battery" for cooling when the sun is not shining, as it was in the 1995 Hotel New Otani Tokyo in Japan. Mathematical models are available in the public domain for ice-based thermal energy storage performance calculations. The ISAAC Solar Icemaker is an intermittent solar ammonia-water absorption cycle. The ISAAC uses a parabolic trough solar collector with a compact and efficient design to produce ice with no fuel or electric input, as well as with no moving parts. == Solar cooling systems
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}
|
utilizing concentrating collectors == The main reasons for employing concentrating collectors in solar cooling systems are: high efficient air-conditioning through coupling with double/triple effect chillers; and solar refrigeration serving industrial end-users, possibly in combination with process heat and steam. Concerning industrial applications, several studies in the recent years highlighted that there is a high potential for refrigeration (temperatures below 0 °C) in different areas of the globe (e.g., the Mediterranean, Central America). However, this can be achieved by ammonia/ water absorption chillers requiring high temperature heat input at the generator, in a range (120 ÷ 180 °C) which can only be satisfied by concentrating solar collectors. Moreover, several industrial applications require both cooling and steam for processes, and concentrating solar collectors can be very advantageous in the sense that their use is maximized. == Zero-energy buildings == Goals of zero-energy buildings include sustainable, green building technologies that can significantly reduce, or eliminate, net annual energy bills. The supreme achievement is the totally off-the-grid autonomous building that does not have to be connected to utility companies. In hot climates with significant degree days of cooling requirement, leading-edge solar air conditioning will be an increasingly important critical success factor. == See also == Passive house Passive solar building design Solar powered refrigerator == Notes == == References == == External links == Cooling with Solar Heat: Growing Interest in Solar Air Conditioning Archived 7 April 2010 at the Wayback Machine.
|
{
"page_id": 5837003,
"source": null,
"title": "Solar air conditioning"
}
|
In pure and applied mathematics, particularly quantum mechanics and computer graphics and their applications, a spherical basis is the basis used to express spherical tensors. The spherical basis closely relates to the description of angular momentum in quantum mechanics and spherical harmonic functions. While spherical polar coordinates are one orthogonal coordinate system for expressing vectors and tensors using polar and azimuthal angles and radial distance, the spherical basis are constructed from the standard basis and use complex numbers. == In three dimensions == A vector A in 3D Euclidean space R3 can be expressed in the familiar Cartesian coordinate system in the standard basis ex, ey, ez, and coordinates Ax, Ay, Az: or any other coordinate system with associated basis set of vectors. From this extend the scalars to allow multiplication by complex numbers, so that we are now working in C 3 {\displaystyle \mathbb {C} ^{3}} rather than R 3 {\displaystyle \mathbb {R} ^{3}} . === Basis definition === In the spherical bases denoted e+, e−, e0, and associated coordinates with respect to this basis, denoted A+, A−, A0, the vector A is: where the spherical basis vectors can be defined in terms of the Cartesian basis using complex-valued coefficients in the xy plane: in which i {\displaystyle i} denotes the imaginary unit, and one normal to the plane in the z direction: e 0 = e z {\displaystyle \mathbf {e} _{0}=\mathbf {e} _{z}} The inverse relations are: === Commutator definition === While giving a basis in a 3-dimensional space is a valid definition for a spherical tensor, it only covers the case for when the rank k {\displaystyle k} is 1. For higher ranks, one may use either the commutator, or rotation definition of a spherical tensor. The commutator definition is given below, any operator T q (
|
{
"page_id": 39653582,
"source": null,
"title": "Spherical basis"
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|
k ) {\displaystyle T_{q}^{(k)}} that satisfies the following relations is a spherical tensor: [ J ± , T q ( k ) ] = ℏ ( k ∓ q ) ( k ± q + 1 ) T q ± 1 ( k ) {\displaystyle [J_{\pm },T_{q}^{(k)}]=\hbar {\sqrt {(k\mp q)(k\pm q+1)}}T_{q\pm 1}^{(k)}} [ J z , T q ( k ) ] = ℏ q T q ( k ) {\displaystyle [J_{z},T_{q}^{(k)}]=\hbar qT_{q}^{(k)}} === Rotation definition === Analogously to how the spherical harmonics transform under a rotation, a general spherical tensor transforms as follows, when the states transform under the unitary Wigner D-matrix D ( R ) {\displaystyle {\mathcal {D}}(R)} , where R is a (3×3 rotation) group element in SO(3). That is, these matrices represent the rotation group elements. With the help of its Lie algebra, one can show these two definitions are equivalent. D ( R ) T q ( k ) D † ( R ) = ∑ q ′ = − k k T q ′ ( k ) D q ′ q ( k ) {\displaystyle {\mathcal {D}}(R)T_{q}^{(k)}{\mathcal {D}}^{\dagger }(R)=\sum _{q'=-k}^{k}T_{q'}^{(k)}{\mathcal {D}}_{q'q}^{(k)}} === Coordinate vectors === For the spherical basis, the coordinates are complex-valued numbers A+, A0, A−, and can be found by substitution of (3B) into (1), or directly calculated from the inner product ⟨, ⟩ (5): A 0 = ⟨ e 0 , A ⟩ = ⟨ e z , A ⟩ = A z {\displaystyle A_{0}=\left\langle \mathbf {e} _{0},\mathbf {A} \right\rangle =\left\langle \mathbf {e} _{z},\mathbf {A} \right\rangle =A_{z}} with inverse relations: In general, for two vectors with complex coefficients in the same real-valued orthonormal basis ei, with the property ei·ej = δij, the inner product is: where · is the usual dot product and the complex conjugate * must be used to
|
{
"page_id": 39653582,
"source": null,
"title": "Spherical basis"
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|
keep the magnitude (or "norm") of the vector positive definite. == Properties (three dimensions) == === Orthonormality === The spherical basis is an orthonormal basis, since the inner product ⟨, ⟩ (5) of every pair vanishes meaning the basis vectors are all mutually orthogonal: ⟨ e + , e − ⟩ = ⟨ e − , e 0 ⟩ = ⟨ e 0 , e + ⟩ = 0 {\displaystyle \left\langle \mathbf {e} _{+},\mathbf {e} _{-}\right\rangle =\left\langle \mathbf {e} _{-},\mathbf {e} _{0}\right\rangle =\left\langle \mathbf {e} _{0},\mathbf {e} _{+}\right\rangle =0} and each basis vector is a unit vector: ⟨ e + , e + ⟩ = ⟨ e − , e − ⟩ = ⟨ e 0 , e 0 ⟩ = 1 {\displaystyle \left\langle \mathbf {e} _{+},\mathbf {e} _{+}\right\rangle =\left\langle \mathbf {e} _{-},\mathbf {e} _{-}\right\rangle =\left\langle \mathbf {e} _{0},\mathbf {e} _{0}\right\rangle =1} hence the need for the normalizing factors of 1 / 2 {\displaystyle 1/\!{\sqrt {2}}} . === Change of basis matrix === The defining relations (3A) can be summarized by a transformation matrix U: ( e + e − e 0 ) = U ( e x e y e z ) , U = ( − 1 2 − i 2 0 + 1 2 − i 2 0 0 0 1 ) , {\displaystyle {\begin{pmatrix}\mathbf {e} _{+}\\\mathbf {e} _{-}\\\mathbf {e} _{0}\end{pmatrix}}=\mathbf {U} {\begin{pmatrix}\mathbf {e} _{x}\\\mathbf {e} _{y}\\\mathbf {e} _{z}\end{pmatrix}}\,,\quad \mathbf {U} ={\begin{pmatrix}-{\frac {1}{\sqrt {2}}}&-{\frac {i}{\sqrt {2}}}&0\\+{\frac {1}{\sqrt {2}}}&-{\frac {i}{\sqrt {2}}}&0\\0&0&1\end{pmatrix}}\,,} with inverse: ( e x e y e z ) = U − 1 ( e + e − e 0 ) , U − 1 = ( − 1 2 + 1 2 0 + i 2 + i 2 0 0 0 1 ) . {\displaystyle {\begin{pmatrix}\mathbf {e} _{x}\\\mathbf {e} _{y}\\\mathbf {e} _{z}\end{pmatrix}}=\mathbf {U} ^{-1}{\begin{pmatrix}\mathbf
|
{
"page_id": 39653582,
"source": null,
"title": "Spherical basis"
}
|
{e} _{+}\\\mathbf {e} _{-}\\\mathbf {e} _{0}\end{pmatrix}}\,,\quad \mathbf {U} ^{-1}={\begin{pmatrix}-{\frac {1}{\sqrt {2}}}&+{\frac {1}{\sqrt {2}}}&0\\+{\frac {i}{\sqrt {2}}}&+{\frac {i}{\sqrt {2}}}&0\\0&0&1\end{pmatrix}}\,.} It can be seen that U is a unitary matrix, in other words its Hermitian conjugate U† (complex conjugate and matrix transpose) is also the inverse matrix U−1. For the coordinates: ( A + A − A 0 ) = U ∗ ( A x A y A z ) , U ∗ = ( − 1 2 + i 2 0 + 1 2 + i 2 0 0 0 1 ) , {\displaystyle {\begin{pmatrix}A_{+}\\A_{-}\\A_{0}\end{pmatrix}}=\mathbf {U} ^{\mathrm {*} }{\begin{pmatrix}A_{x}\\A_{y}\\A_{z}\end{pmatrix}}\,,\quad \mathbf {U} ^{\mathrm {*} }={\begin{pmatrix}-{\frac {1}{\sqrt {2}}}&+{\frac {i}{\sqrt {2}}}&0\\+{\frac {1}{\sqrt {2}}}&+{\frac {i}{\sqrt {2}}}&0\\0&0&1\end{pmatrix}}\,,} and inverse: ( A x A y A z ) = ( U ∗ ) − 1 ( A + A − A 0 ) , ( U ∗ ) − 1 = ( − 1 2 + 1 2 0 − i 2 − i 2 0 0 0 1 ) . {\displaystyle {\begin{pmatrix}A_{x}\\A_{y}\\A_{z}\end{pmatrix}}=(\mathbf {U} ^{\mathrm {*} })^{-1}{\begin{pmatrix}A_{+}\\A_{-}\\A_{0}\end{pmatrix}}\,,\quad (\mathbf {U} ^{\mathrm {*} })^{-1}={\begin{pmatrix}-{\frac {1}{\sqrt {2}}}&+{\frac {1}{\sqrt {2}}}&0\\-{\frac {i}{\sqrt {2}}}&-{\frac {i}{\sqrt {2}}}&0\\0&0&1\end{pmatrix}}\,.} === Cross products === Taking cross products of the spherical basis vectors, we find an obvious relation: e q × e q = 0 {\displaystyle \mathbf {e} _{q}\times \mathbf {e} _{q}={\boldsymbol {0}}} where q is a placeholder for +, −, 0, and two less obvious relations: e ± × e ∓ = ± i e 0 {\displaystyle \mathbf {e} _{\pm }\times \mathbf {e} _{\mp }=\pm i\mathbf {e} _{0}} e ± × e 0 = ± i e ± {\displaystyle \mathbf {e} _{\pm }\times \mathbf {e} _{0}=\pm i\mathbf {e} _{\pm }} === Inner product in the spherical basis === The inner product between two vectors A and B in the spherical basis follows from the above definition of the
|
{
"page_id": 39653582,
"source": null,
"title": "Spherical basis"
}
|
inner product: ⟨ A , B ⟩ = A + B + ⋆ + A − B − ⋆ + A 0 B 0 ⋆ {\displaystyle \left\langle \mathbf {A} ,\mathbf {B} \right\rangle =A_{+}B_{+}^{\star }+A_{-}B_{-}^{\star }+A_{0}B_{0}^{\star }} == See also == Wigner–Eckart theorem Wigner D matrix 3D rotation group == References == === General === S. S. M. Wong (2008). Introductory Nuclear Physics (2nd ed.). John Wiley & Sons. ISBN 978-35-276-179-13. == External links ==
|
{
"page_id": 39653582,
"source": null,
"title": "Spherical basis"
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|
Abeba Birhane is an Ethiopian-born cognitive scientist who works at the intersection of complex adaptive systems, machine learning, algorithmic bias, and critical race studies. Birhane's work with Vinay Prabhu uncovered that large-scale image datasets commonly used to develop AI systems, including ImageNet and 80 Million Tiny Images, carried racist and misogynistic labels and offensive images. She has been recognized by VentureBeat as a top innovator in computer vision and named as one of the 100 most influential persons in AI 2023 by TIME magazine. == Early life and education == Birhane was born in Ethiopia. She received her Bachelors of Science in Psychology and a Bachelors of Arts in Philosophy from The Open University. In 2015, she completed her Master of Science in Cognitive Science and, in 2021, her Ph.D. at the Complex Software Lab in the School of Computer Science at University College Dublin. == Career and research == Birhane studied the impacts of emerging AI technologies and how they shape individuals and local communities. She found that AI algorithms tend to disproportionately impact vulnerable groups such as older workers, trans people, immigrants, and children. Her research on relational ethics won the best paper award at NeurIPS’s Black in AI workshop in 2019. She has also studied and written about algorithmic colonization driven by corporate agendas. Her work in decolonizing computational sciences addressed the inherited oppressions in current systems especially towards women of color. In 2020, Birhane and Vinay Prabhu, principal machine learning scientist at UnifyID, published a paper examining the problematic data collection, labelling, classification, and consequences of large image datasets. These datasets, including ImageNet and MIT's 80 Million Tiny Images, have been used to develop thousands of AI algorithms and systems. Birhane and Prabhu found that they contained many racist and misogynistic labels and slurs as well
|
{
"page_id": 67047637,
"source": null,
"title": "Abeba Birhane"
}
|
as offensive images. This resulted in MIT voluntarily and formally taking down the 80 Million Tiny Images dataset. More recently, Birhane has worked with Rediet Abebe, George Obaido, and Sekou Remy on researching the barriers to data sharing in Africa. They found that power imbalances are significant in the data sharing process, even when the data comes from Africa. Their research was published at the ACM Conference on Fairness, Accountability, and Transparency. In 2024, Birhane established the AI Accountability Lab research group at Trinity College Dublin. == Selected awards == 2019 NeurIPS Black in AI Workshop Best Paper Award 2020 Venture Beat AI Innovations Award in the category Computer Vision Innovation (received with Vinay Prabhu) 2021 100 Brilliant Women in AI Ethics Hall of Fame Honoree 2022 Lero Director’s Prize for PhD/PostDoctoral Contribution. 2023 100 Most Influential People in AI by TIME magazine == References ==
|
{
"page_id": 67047637,
"source": null,
"title": "Abeba Birhane"
}
|
Asparagine synthetase (or aspartate-ammonia ligase) is a chiefly cytoplasmic enzyme that generates asparagine from aspartate. This amidation reaction is similar to that promoted by glutamine synthetase. The enzyme is ubiquitous in its distribution in mammalian organs, but basal expression is relatively low in tissues other than the exocrine pancreas. Above average presence of asparagine synthetase in certain leukemia strains has been linked to be a significant contributing factor of chemotherapy resistance, particularly to the chemotherapy drug, L-asparaginase. == Structure == Escherichia coli derived asparagine synthetase is a dimeric protein with each subunit folding into two distinct domains. The N-terminal region consists of two layers of six-stranded antiparallel β-sheets between which is the active site responsible for the hydrolysis of glutamine. The C-terminal domain consists of a five-stranded parallel β-sheet flanked on either side by α-helices. This domain is responsible for the binding of both Mg2+ATP and aspartate. These two active sites are connected by a tunnel lined primarily with backbone atoms and hydrophobic, nonpolar amino acid residues. Structural characterization of asparagine synthetase from mammalian sources have been difficult due to the low abundance and instability of the enzyme during purification procedures. == Mechanism == Using information from Escherichia coli derived asparagine synthetase, some basic mechanisms of the enzyme have been understood. The N-terminal active site catalyzes glutamine hydrolysis to yield glutamate and ammonia. The C-terminal active site catalyzes activation of the side-chain carboxylate of aspartate to form an electrophilic intermediate, β-aspartyl-AMP (βAspAMP) 1, and inorganic pyrophosphate (PPi). The tunnel that links the two active sites allows for the passage of an ammonia molecule to act as a common intermediate to couple the two half-reactions carried out in the independent active sites of the enzyme. Thus, after being released in, and channeled from, the glutaminase site, the ammonia molecule attacks the
|
{
"page_id": 11473111,
"source": null,
"title": "Asparagine synthetase"
}
|
bound βAspAMP 1 to give asparagine and AMP via a tetrahedral intermediate. == Function == In plants, inorganic nitrogen is taken up from the environment in forms of nitrate or ammonium. Assimilation of this nitrogen into asparagine for use in nitrogen recycling, transport, and storage is an essential process for plant development, making asparagine synthetase vital to maintaining these asparagine reserves. Specific events in development which depend on asparagine synthetase are nitrogen mobilization in germinating seeds, nitrogen recycling and flow in vegetative cells in response to biotic and abiotic stresses, and nitrogen remobilization from source to sink organs. In mammals, asparagine synthetase expression has been found to be linked to cell growth, and its mRNA content is linked to changes in the cell cycle. Hamster BHK ts11 cells produce an inactive asparagine synthetase enzyme, and this loss of asparagine synthetase activity directly led to cell cycle arrest in the cells as a consequence of a depletion of cellular asparagine. Upregulation of asparagine synthetase mRNA was observed as well in these hamster cells. Other experiments demonstrated that quiescent rat thyroid cells entering S phase as a result of thyroid-stimulating hormone treatment was matched with a concurrent increase in asparagine synthetase mRNA content. == Classes == There seem to be two major groups of asparagine synthetase: Majority of prokaryotic isolated enzymes (asnA) utilize ammonia as the sole nitrogen source. Eukaryotic isolated and some prokaryotic isolated enzymes (asnB) utilize glutamine as the preferred nitrogen source, although these enzymes can also employ ammonia as an alternate substrate. The human glutamine-dependent AS is encoded by a single gene located in region q21.3 on chromosome 7. The lack of ammonia-dependent asparagine synthetase in eukaryotes is presumably because of the need to maintain cellular concentrations of ammonia at very low levels. == Clinical significance == === Cancer
|
{
"page_id": 11473111,
"source": null,
"title": "Asparagine synthetase"
}
|
=== ==== Leukemia ==== Cancerous cells exhibit rapid growth and cell division and subsequently have an increased nutritional need. The particularly low-level expression of asparagine synthetase in primary acute lymphoblastic leukemia (ALL) and numerous ALL cell lines, as compared to that of normal cells, makes asparagine depletion an effective method of treatment due to the cells' unusual dependency on circulating serum asparagine as a necessary nutrition for growth. As a result, L-asparaginase is a common chemotherapy drug utilized in the treatment of ALL and may have applications in other asparagine synthetase negative cancers, such as lymphomas, due to its aspariginase activity to deplete serum asparagine. This depletion of serum asparagine leads to a subsequent rapid efflux of cellular asparagine, which is immediately acted upon and destroyed by the L-asparaginase as well. Due to the transient response from these susceptible cancers in reaction to the asparagine depletion, tumor growth is significantly inhibited due to nutritional deficiency. Most somatic cells express sufficient basal amounts of asparagine synthetase to counteract this asparagine starvation and survive the effects of L-asparaginase. In addition, these normal cells are able to upregulate their expression of asparagine synthetase in response to the asparagine depletion, further countering some of the toxic effects of the medication on normal cell activity, a desirable trait for chemotherapy drugs. However, the opposite effect is visible in cases of asparaginase resistant cancers. In these resistant cancers, the effect of blood asparagine depletion through L-asparaginase instead leads to significant asparagine synthetase overexpression to compensate, effectively nullifying the effect of the chemotherapy drug. For example, in mouse models, 24 hours after exposure to L-asparaginase, tumors resistant to the depletion responded with 5- to 19-fold increases in asparagine synthetase expression. These resistant tumors also inherently express higher levels of asparagine synthetase activity, even without the application of
|
{
"page_id": 11473111,
"source": null,
"title": "Asparagine synthetase"
}
|
L-asparaginase to drive further expression. Similar trends are often seen in human studies as well, with high levels of asparagine synthetase activity being detected in asparaginase-resistant cases of treatment as compared with the negligible activity of susceptible cases. As seen in in vitro studies of resistant human leukemia cell lines, even six weeks after the removal of asparagine depleting factors, the increased level of expression of asparagine synthetase failed to return to a basal state, instead remaining elevated and retaining continued drug resistance. While the mechanisms underlying the sustained over-expression of ASNS have not been reported in these studies, transcriptome profiling of two T-ALL patients that have relapsed after L-asparaginase treatment revealed a recurrent promoter swap with KMT2E leading to ASNS over-expression and L-asparaginase resistance. It has been further demonstrated in mouse model systems that repeated subculturing of L-asparaginase sensitive tumor cells in sublethal concentrations of L-asparaginase could eventually make them resistant, a potential worry of lower dose chemotherapy treatments effectively encouraging resistant cell development. ==== Potential biomarker for ovarian cancer ==== A correlation between L-asparaginase efficacy and asparagine synthetase protein levels in a number of human ovarian cell lines has been observed. As mentioned above, this result confirmed similar observations in human leukemia cell lines. Hence asparagine synthetase might be used as a biomarker in ovarian cancer screening and potential treatment. ==== Potential role in solid tumor metastasis ==== An epithelial to mesenchymal transition was mimicked in metastatic cells by adapting PC-3 prostate cancer cells from adherent to suspension culture and then examined to investigate changes in gene expression concurrent with this adaption to suspension. It was found that the asparagine synthetase expression was sixfold greater in the suspension cells than in the adherent cells. In xenografts from a human breast cancer cell line in an established metastatic mouse
|
{
"page_id": 11473111,
"source": null,
"title": "Asparagine synthetase"
}
|
model, asparagine synthetase was elevated in circulating tumor cells isolated from the mouse blood compared with the parental cell line. When these circulating tumor cells were returned to an in vitro culture and exposed to hypoxia, they showed higher basal expression and greater induction of asparagine synthetase than their parental cell line. These circulating tumor cells were also found to have an increased capacity for colony formation in soft agar assays under hypoxic conditions and grew faster when reimplanted as xenografts. The increased prevalence of asparaginase synthetase in the metastatic cells suggests that its activity may be beneficial for circulating tumor cell survival. == Trivia == Guinea pigs have some of the highest levels of naturally expressing asparagine synthetase due to the fact that their serum inherently containing detectable levels of L-asparaginase. == References == == External links == Asparagine+synthetase at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
|
{
"page_id": 11473111,
"source": null,
"title": "Asparagine synthetase"
}
|
The American Society for Mass Spectrometry (ASMS) is a professional association based in the United States that supports the scientific field of mass spectrometry. As of 2018, the society had approximately 10,000 members primarily from the US, but also from around the world. The society holds a large annual meeting, typically in late May or early June as well as other topical conferences and workshops. The society publishes the Journal of the American Society for Mass Spectrometry. == Awards == The Society recognizes achievements and promotes academic research through four annual awards. The Biemann Medal and the John B. Fenn Award for a Distinguished Contribution in Mass Spectrometry both are awarded in recognition of singular achievements or contributions in fundamental or applied mass spectrometry, with the Biemann Medal being focused on individuals who are early in their careers. The Ronald A. Hites Award is awarded for outstanding original research demonstrated in papers published in the Journal of the American Society for Mass Spectrometry. The Research Awards are given to young scientists in mass spectrometry, based on the evaluation of their proposed research. The Fellows of ASMS are awarded to individuals in recognition for their scientific contribution to mass spectrometry and for their contribution to the ASMS community. == Publications == Journal of the American Society for Mass Spectrometry Measuring Mass: From Positive Rays to Proteins == Past presidents == The past presidents of ASMS are: == Conferences == The Society holds an annual conference in late May or early June as well as topical conferences (at Asilomar State Beach in California and Sanibel Island, Florida) and a fall workshop, which is also focused on a single topic. Conferences on Mass Spectrometry and Allied Topics have been held yearly since 1953. == See also == International Mass Spectrometry Foundation List of
|
{
"page_id": 11014361,
"source": null,
"title": "American Society for Mass Spectrometry"
}
|
female mass spectrometrists == References == == External links == ASMS website
|
{
"page_id": 11014361,
"source": null,
"title": "American Society for Mass Spectrometry"
}
|
A skin equivalent is an in vitro skin model using to conduct experiments on processes involving the skin, such as wound healing and keratinocyte migration. It is a more complex form of the dermal equivalent. == References ==
|
{
"page_id": 25432283,
"source": null,
"title": "Skin equivalent"
}
|
The superkingdom Metakaryota was defined by Thomas Cavalier-Smith as advanced eukaryotes resulting from the endosymbiosis of a proteobacterium, giving rise to the mitochondrion, by an archezoan eukaryote. However, with the collapse of the Archezoa hypothesis (that amitochondriate eukaryotes were basal), this grouping was abandoned in later schemes. In 2023, using molecular phylogenetic analysis of 186 taxa, Al Jewari and Baldauf proposed a phylogenetic tree with the metamonad Parabasalia as basal Eukaryotes. Discoba and the rest of the Eukaryota appear to have emerged as sister taxon to the Preaxostyla, incorporating a single alphaproteobacterium as mitochondria by endosymbiosis. Thus the Fornicata are more closely related to e.g. animals than to Parabasalia. The rest of the Eukaryotes emerged within the Excavata as sister of the Discoba. Caesar al Jewari and Sandra Baldauf argue instead that the Eukaryotes possibly started with an endosymbiosis event of a deltaproteobacterium or gammaproteobacterium, accounting for the otherwise unexplained presence of anaerobic bacterial enzymes in metamonada in this scenario. The sister of the Preaxostyla within Metamonada represents the rest of the Eukaryotes which acquired an alphaproteobacterium. == References ==
|
{
"page_id": 37294302,
"source": null,
"title": "Metakaryota"
}
|
Cultural materialism is an anthropological research orientation first introduced by Marvin Harris in his 1968 book The Rise of Anthropological Theory, as a theoretical paradigm and research strategy. It is said to be the most enduring achievement of that work. Harris subsequently developed a full elaboration and defense of the paradigm in his 1979 book Cultural Materialism. To Harris social change is dependent of three factors: a society's infrastructure, structure, and superstructure. Harris's concept of cultural materialism was influenced by the writings of Karl Marx and Friedrich Engels, as well as their theories as modified by Karl August Wittfogel and his 1957 book, Oriental Despotism: A Comparative Study of Total Power. Yet this materialism is distinct from Marxist dialectical materialism, as well as from philosophical materialism. Thomas Malthus's work encouraged Harris to consider reproduction of equal importance to production. The research strategy was also influenced by the work of earlier anthropologists including Herbert Spencer, Edward Tylor and Lewis Henry Morgan who, in the 19th century, first proposed that cultures evolved from the less complex to the more complex over time. Leslie White and Julian Steward and their theories of cultural evolution and cultural ecology were instrumental in the reemergence of evolutionist theories of culture in the 20th century and Harris took inspiration from them in formulating cultural materialism. == Epistemological principles == Cultural materialism is a scientific research strategy and as such utilizes the scientific method. Other important principles include operational definitions, Karl Popper's falsifiability, Thomas Kuhn's paradigms, and the positivism first proposed by Auguste Comte and popularized by the Vienna Circle. The primary question that arises in applying the techniques of science to understand the differences and similarities between cultures is how the research strategy "treats the relationship between what people say and think as subjects and what they
|
{
"page_id": 13963489,
"source": null,
"title": "Cultural materialism (anthropology)"
}
|
say and think and do as objects of scientific inquiry". In response to this cultural materialism makes a distinction between behavioral events and ideas, values, and other mental events. It also makes the distinction between emic and etic operations. Emic operations, within cultural materialism, are ones in which the descriptions and analyses are acceptable by the native as real, meaningful, and appropriate. Etic operations are ones in which the categories and concepts used are those of the observer and are able to generate scientific theories. The research strategy prioritizes etic behavior phenomena. == Theoretical principles == Etic and behavioral infrastructure, comprising a society's relations to the environment, which includes their ethics and behavioral modes of production and reproduction (material relations). Etic and behavioral Structure, the ethics and behavioral domestic and political economies of a society (social relations). Etic and behavioral Superstructure, the ethics and behavioral symbolic and ideational aspects of a society, e.g. the arts, rituals, sports and games, and science (symbolic and ideational relations). Emic and mental Superstructure, including "conscious and unconscious cognitive goals, categories, rules, plans, values, philosophies, and beliefs" (meaningful or ideological relations). Within this division of culture, cultural materialism argues for what is referred to as the principle of probabilistic infrastructural determinism. The essence of its materialist approach is that the infrastructure is in almost all circumstances the most significant force behind the evolution of a culture. Structure and superstructure are not considered "insignificant, epiphenomenal reflexes of infrastructural forces". The structure and symbolic/ideational aspects act as regulating mechanisms within the system as a whole. The research strategy predicts that it is more likely that in the long term infrastructure probabilistically determines structure, which probabilistically determines the superstructures, than otherwise. Thus, much as in earlier Marxist thought, material changes (such as in technology or environment) are seen
|
{
"page_id": 13963489,
"source": null,
"title": "Cultural materialism (anthropology)"
}
|
as largely determining patterns of social organization and ideology in turn. === Disagreement with Marxism === In spite of the debt owed to the economic theories of Marx and Engels, cultural materialism rejects the Marxist dialectic which in turn was based on the theories of the philosopher Georg Wilhelm Friedrich Hegel. == Research == During the 1980s, Marvin Harris had a productive interchange with behavioral psychologists, most notably Sigrid Glenn, regarding interdisciplinary work. Very recently, behavioral psychologists have produced a set of basic exploratory experiments in an effort toward this end. More recently young anthropologists have re-approached the work of Marvin Harris as part of a new anthropology of infrastructures. == See also == Marvin Harris Maxine Margolis Jerald T. Milanich == References ==
|
{
"page_id": 13963489,
"source": null,
"title": "Cultural materialism (anthropology)"
}
|
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