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72,202,609 | https://en.wikipedia.org/wiki/Quantum%20natural%20language%20processing | Quantum natural language processing (QNLP) is the application of quantum computing to natural language processing (NLP). It computes word embeddings as parameterised quantum circuits that can solve NLP tasks faster than any classical computer. It is inspired by categorical quantum mechanics and the DisCoCat framework, making use of string diagrams to translate from grammatical structure to quantum processes.
Theory
The first quantum algorithm for natural language processing used the DisCoCat framework and Grover's algorithm to show a quadratic quantum speedup for a text classification task. It was later shown that quantum language processing is BQP-Complete, i.e. quantum language models are more expressive than their classical counterpart, unless quantum mechanics can be efficiently simulated by classical computers.
These two theoretical results assume fault-tolerant quantum computation and a QRAM, i.e. an efficient way to load classical data on a quantum computer. Thus, they are not applicable to the noisy intermediate-scale quantum (NISQ) computers available today.
Experiments
The algorithm of Zeng and Coecke was adapted to the constraints of NISQ computers and implemented on IBM quantum computers to solve binary classification tasks. Instead of loading classical word vectors onto a quantum memory, the word vectors are computed directly as the parameters of quantum circuits. These parameters are optimised using methods from quantum machine learning to solve data-driven tasks such as question answering, machine translation and even algorithmic music composition.
See also
Categorical quantum mechanics
Natural language processing
Quantum machine learning
Applied category theory
String diagram
References
External links
DisCoPy, a Python toolkit for computing with string diagrams
lambeq, a Python library for quantum natural language processing
Quantum computing
Natural language processing | Quantum natural language processing | [
"Technology"
] | 342 | [
"Natural language processing",
"Natural language and computing"
] |
72,202,706 | https://en.wikipedia.org/wiki/Mycophycobiosis | A mycophycobiosis (composed of myco-, from the Ancient Greek: (mukês , "mushroom"), phyco-, from Ancient Greek: , (phûkos, fucus, used for algae), and -biose, from ancient Greek: (bióô, "to spend one's life") is a symbiotic organism made up of a multicellular algae and an ascomycete fungus housed inside the algae (in the thallus for example). The algae and fungus involved in this association are called mycophycobionts.
The essential role of the algae is to carry out photosynthesis, while that of the fungus is less obvious, but it could be linked to the transfer of minerals within the thallus, to a repellent effect on herbivores and, above all, to resistance to desiccation of this living organism in the intertidal zone.
Such symbioses have been reported in a few green algae (Prasiola, Blidingia) and red algae (Apophlaea), both in seawater and in freshwater.
Definition elements
Although compared to lichens by certain authors, mycophycobioses carry out an association of the opposite type: the algal partner is multicellular and forms the external structure of the symbiotic organization. Moreover, the reproduction of the two partners is always disjoint (the algae and the fungus reproduce separately). To explain the nuances of this duality, the ecologists Chantal Delzenne-Van Haluwyn and Michel Lerond propose the analogy of the two symbionts with an "ideal couple". In a lichen, the host is compared to a "macho fungus"; in mycophycobiosis, the host is "the algae that wears the panties".
According to Hawksworth the physiology of this symbiosis could well be comparable to that of lichens, but it remains to be better explored. Unlike lichens, mycophycobioses look like an algal partner, which remains fertile. These associations appear to be less coevolved than lichens, as they exhibit neither joint asexual multiplication of partners nor do they contain the equivalent lichen products.
History
The term mycophycobiosis was introduced by Jan and Erika Kohlmeyer in 1972, based on the case of the brown algal species Ascophyllum nodosum, which regularly harbours the ascomycete Mycosphaerella ascophylli.
Another example of mycophycobiosis occurs in the genus Turgidosculum (synonym: Mastodia), which associates a green alga of the genus Prasiola with an ascomycete pyrenomycete of the genus Kohlmeyera. While the only alga of the genus Prasiola remains subservient to a certain at least temporary marine cover, the mycophycobiotic association allows a more terrestrial conquest outside the intertidal zone.
Some authors hypothesize that vascular plants may have evolved from such a type of association and that this symbiosis may have helped land plants to conquer continents (similar to the association that gave rise to lichens).
Major evolutionary role: exiting the waters
The major groups of carbon phototrophs, prokaryotes and eukaryotes, arose in the marine environment. The establishment of symbioses has made it possible to make a macroevolutionary leap to conquer the more hostile terrestrial environment. Various mutualistic associations (mycophycobioses, lichens, then mycorrhizae) have been simultaneously or successively used.
Examples
In fresh water, the fungus Phaeospora lemaneae grows inside Lemanea fluviatilis.
In the marine environment, the fungus Blodgettia confervoides can associate with several species of Cladophora. The fungus Mycophycias ascophylli associates with Ascophyllum nodosum (black seaweed) or another Fucaceae, Pelvetia canaliculata.
References
Symbiosis
Lichenology | Mycophycobiosis | [
"Biology"
] | 874 | [
"Biological interactions",
"Lichenology",
"Behavior",
"Symbiosis"
] |
72,203,153 | https://en.wikipedia.org/wiki/Phosphorus%20porphyrin | Phosphorus-centered (or P-centered) porphyrins are conjugated polycyclic ring systems consisting of either four pyrroles with inward-facing nitrogens and a phosphorus atom at their core or porphyrins with one of the four pyrroles substituted for a phosphole. Unmodified porphyrins are composed of pyrroles and linked by unsaturated hydrocarbon bridges often acting as multidentate ligands centered around a transition metal like Cu II, Zn II, Co II, Fe III. Being highly conjugated molecules with many accessible energy levels, porphyrins are used in biological systems to perform light-energy conversion and modified synthetically to perform similar functions as a photoswitch or catalytic electron carriers. Phosphorus III and V ions are much smaller than the typical metal centers and bestow distinct photochemical properties unto the porphyrin. Similar compounds with other pnictogen cores (As, Sb, Bi) or different polycyclic rings coordinated to phosphorus result in other changes to the porphyrin’s chemistry.
Synthesis
Phosphorus core
Early experiments with group 15 elements at the porphyrin core by Barbour et al. in 1992 included syntheses of P-centered porphyrin compounds from meso-Tetra-p-tolylporphyrin (TTP). Phosphorus oxychloride (POCl3) added to H2TTP forms the P-centered porphyrin molecule [P(TTP)Cl2]+Cl−. Several chemical variants were synthesized by refluxing in solutions of pyridine solvent and alcohols to produce [P(TTP)OCH2CH3]+Cl−, [P(TTP)(O-p-C6H4OH)2]+OH−, and other similar compounds. Other researchers including Poddutoori in 2015 and 2022 have used such synthetic methods to yield hypervalent phosphorus (V) bonded to porphyrin as well as axial alcohols substituents.
Later syntheses have been performed with other phosphorus precursors, including PhPCl2 and octaethylporphyrin (OEP) in DCM to yield [POEP(Cl)2]+Cl−. PCl3/POCl3 and KPF6 yield similar porphyrin products with a PF6− counterion. Other halogens like bromine have been used successfully in place of chlorine for this synthesis method of P-centered rings. More syntheses with complex alcohols have been reported. Porphyrins functionalized with axial carbazolylvinylnaphthalimides are synthesized using similar methods to the previously described process for binding alcohols to phosphorus cores. In a similar synthetic process, Susumu et al. linked several modified porphyrins in a center-to-edge bonding scheme. The chlorines on a P-centered porphyrin are first substituted by an external hydroxyphenyl group on another porphyrin. The substituent porphyrins are then refluxed with POCl3 to synthesize the final center-to-edge porphyrin array. The resulting P-centered complex consists of three porphyrins with phosphorus atoms bound at each core.
Phosphaporphyrins
Synthesis of a phosphole-substituted porphyrin or phosphaporphyrin involves a more complex chemical route. Phosphaporphyrins are not created using an unmodified porphyrin ring as a synthetic reagent. As reported by Matano and Imahori in 2008, a phosphaporphyrin is constructed with a phosphole linked to two pyrrole functional groups which is then bound to another pyrrole molecule. Specifically, addition of 2,5-bis(hydroxymethyl)-1-phenyl-1-thiophosphole to excess pyrrole in the presence of BF3·OEt2 results in the phosphatripyrrane precursor. A phosphaporphyrinogen ring is formed through dehydration condensation of the phosphatripyrrane with a 2,5-difunctionalized pyrrole. Dichloro-dicyanobenzoquinone (DDQ) oxidation of the product yields the highly conjugated 18π-system phosphaporphyrin product.
Metals can be coordinated in the core of the phosphaporphyrin by introducing metal salts. Rhodium metal is very easily inserted into the core of a phosphaporphyrin without the presence of a stabilizing thiophene-substituted pyrrole.
Properties
Several varieties of the P-centered porphyrin exist. The porphyrin with a core phosphorus (V) ion can be tuned with additional substituents added to either the outside of the polycyclic ring system or axially to the core phosphorus. Meso-substituted porphyrins like meso-tetra-p-tolylporphyrin (TTP) and octaethylporphyrin (OEP) are often used in synthesis of the core phosphorus porphyrin. Substituents on the hypervalent phosphorus also result in the existence of a diverse array of molecules with varying properties. Axial substituents on the phosphorus include a wide variety of alkyl (-CH3, -CH2CH3), alkoxy (-OCH3, -OCH2CH3), aryl (-C6H5), and halide functional groups. Crystallographic experiments reveal that substituents affect the structure properties of these complexes. The porphyrin P-N bond distances decrease as the electronegativity of the axial substituents increase.
Porphyrins bound to unnaturally small ions at the core result in ruffling, a deviation in position of the carbon atoms from the median plane of the aromatic conjugated system. This phenomenon, like saddling and doming, has been observed as well with small transition metal ions like nickel II. The ruffling effect of phosphorus (V) in a porphyrin is apparent because of the small size of the ion. More electronegative axial groups result in greater ruffling while large, sterically bulky groups have a similar effect. The degree to which various substituents cause ruffling was determined by Akiba et al. in 2001.
Phosphaporphyrins possess phospholes usually bound to a phenyl group resting above the porphyrin plane in a trigonal pyramidal molecular geometry as is typical of phosphorus centers. In addition to the bound phenyl group, these molecules may also possess a metal ion core that coordinates to the three pyrroles and phosphole and distorts the naturally planar molecule. Very negative nucleus independent chemical shift (NCIS) values used to quantify aromaticity indicate the aromatic character of the phosphaporphyrins. These values however are more positive than NICS values for the undistorted four-pyrrole structure, which is a result of the less planar π-system in phosphaporphyrins.
Photoelectrochemical properties
Unmodified porphyrins have been identified and used in spectroscopic studies because of their highly conjugated π-systems. Isolated monolayers of porphyrins with dicationic transition metals yield similar spectroscopic data to those suspended in dilute solution. Axial ligand substitution of the metal was proposed as a method of varying the electrochemical properties and has since been done extensively with phosphorus ions.
Phosphorus core porphyrins have been researched extensively to assess their photo and electrochemical properties. Axial groups bonded to the core phosphorus exert influence on the oxidation and reduction potentials of porphyrins. Like the electronegativity effects of the axial group on P-N bonding distance and plane ruffling, electronegativity effects the molecular redox potentials. Akiba et al. in 2002 were first to quantify the redox potentials of various porphyrin molecules with different axial groups. Generally, as the electronegativity of the groups increases, the oxidative and reductive potentials become more positive indicating the complex’s ability to accept an electron more easily. A 2022 study by Sharma et al. compounded the axial group electrochemical effects with the effects of outer porphyrin ring aryl substituents to determine their overall influence on P-centered porphyrin electrochemistry. More electron-withdrawing groups on the outside of the porphyrin like 3,4,5-trimethoxyphenyl resulted in a greater red-shift in the absorption spectra as opposed to less withdrawing groups like a simple phenyl. Additionally, the high oxidation potential of the modified porphyrins allows for their use in electrochemical applications. Artificial photosynthetic systems can be fine-tuned by the addition of different functional groups for catalysis and energy storage.
Poddutoori et al. in 2015 explored the electrochemical applications of the p-core porphyrins deposited with Ir(III)Cp on tin (II) oxide to form a pre-catalyst for water-splitting reactions. The ability to form an effective catalytic system is a result of the high redox potential (1.62-1.65V) of the phosphorus-modified porphyrin bound to tin (II) oxide. In 2016, he devised a similar application for p-centered porphyrins with tin (IV) oxide and Mn(II)typ. Photooxidation of the Mn complex allows the reduction of the tin(IV) ion to tin(III) through the porphyrin as an electron carrier in a similar fashion to the 2015 publication. The photoreduction applications mimic those of the natural porphyrin role in photosynthesis; however, the phosphorus (V) allows for tuning and more wide-ranging applications than transition metal ions.
Phosphaporphyrins have been studied to a lesser degree. UV-vis and cyclic voltammetry (CV) experiments with phosphaporphyrins reveal that the single pyrrole to phosphole substitution narrows the HOMO and LUMO gap in an 18 π-system, allowing for a more easily accessible excited state and unique electrochemical applications.
The phosphole component has been shown by Reau et al. in 2002 to be prone to hyperpolarizability. This characteristic is more true of phospholes when bound to a palladium II ion as is often the case in porphyrins. Nonlinear optical (NLO) properties like molecular hyperpolarizability in metal-phosphole hybrids yield unique electrochemical applications.
A variety of phosphole-metal complexes have been synthesized to bridge copper II and silver I metal ions through phosphorus-containing chelating ligands. The new electrochemically stabile complexes indicate the importance of the NLO properties that are unique to phosphaporphyrins by virtue of their phosphorus-integrated π-system.
Photochemical applications
As early as 2002, axial substituents on the phosphorus core have been utilized for photochemistry. Reddy and Maiya pioneered the use of a p-centered porphyrin with azobenzene substituents capable of reversible (E/Z) isomerization upon irradiation at a wavelength of 345 nm. The process of isomerization is made possible through quenching of the fluorescence by the highly conjugated porphyrin ring and the reversibility of the isomerization. The high yield of both isomers after several iterations of the reaction indicates that the photoswitching is a reliable, stable process.
Photovoltaic devices using NiO have also been made more efficient by hole injection of phosphorus porphyrins, yielding ground state reactants that are regenerated at a much faster rate than is typical for a TiO2 cell.
Biological applications
Photodynamic therapy (PDT) is used to target and destroy DNA in cases of extreme cell proliferation as is common in cancer. Porphyrins are used to generate radical oxygen species in the body to degrade nucleotides, stopping proliferation. Tetraphenylporphyrin phosphorus (V) complexes with DNA and possesses an oxidation potential larger than guanine(1.4-1.8V > 1.24V). Upon coupling to DNA fragments through electrostatic interaction, a p-centered porphyrin electron is excited with 365 nm radiation to the S2 state and proceeds down an energy cascade via two mechanisms to degrade guanine. The first mechanism involves electron transfer that degrades a sequence of consecutive guanine nucleotides while the second mechanism proceeds via oxygen radical formation that indiscriminately destroys guanine residues in DNA.
Reactivity
P-centered porphyrins typically react in redox reactions where they serve as tunable intermediate electron carriers in biological reactions for DNA degradation as well as other industrial catalytic reactions. Tn (II/IV) oxide is photoreduced by iridium and manganese complexes through p-centered porphyrin electron carriers in catalysis. Photovoltaic cells involving NiO complexes supplemented with high oxidation potential p-centered porphyrins improve cell efficiency as is the case in indium tin oxide cells with porphyrins containing axial carbazolylvinylnaphthalimides bound to a core phosphorus.
Phosphorus (V) porphyrins are particularly good electron carriers in redox reactions because of their adjustable reduction potential. Poddutoori et al. in 2021 investigated the electron transfer of naphthalene, a commonly excited molecule in photochemistry, to octaethylporphyrin and TEP. The relatively low potentials of the porphyrins yield highly energetic charge-separated states upon the transfer of the electron from naphthalene. The axial and peripheral substituent diversity is key to accessing the wide range of charge-separated states and electron transfer across electronically diverse reactants to form a great variety of redox products.
Phosphaporphyrins after synthesis can be complexed with metals like the unmodified porphyrin molecule. Nickel, palladium, and platinum can be coordinated as the metal center of a phosphaporphyrin by reacting the conjugated ring with metal salts like Ni(cod)2, Pd(dba)2, and Pt(dba)2 in DCM/dichlorobenzene respectively.
Derivatives and structural analogs
Other pnictogen ion cores
Phosphorus (V) is a prevalent ion center in modified porphyrin complexes but is not the only group 15 element that has been used in place of a transition metal ion. Antimony and bismuth have also been identified as suitable porphyrin cores as early as 1991 by Barbour et al.
Stronger electron donating from the less electronegative antimony results in a more positive reduction potential than in the phosphorus ion. Sterically speaking, arsenic (V), being a larger ion than phosphorus (V), possesses a more stable, planar coordinated porphyrin as opposed to the ruffled porphyrin coordinated to phosphorus. Oppositely, a pnictogen element too large to neatly coordinate into the porphyrin hole like bismuth causes a disruption of symmetry in the ring.
Calixphyrins
Calixphyrins are analogous to porphyrins with two of the hydrocarbon bridges between pyrroles fully saturated. Like phosphaporphyrin, a calixphyrin pyrrole can be substituted with a phosphole to form a P-centered calixphyrin. The results of increased saturation are mixed sp2 and sp3 hybridization of the ring carbons and the extension of the metal-nitrogen bond length.
Matano et al. in 2006 used the first ever P,S-hybridized calixphyrin coordinated to palladium to catalyze the Heck reaction to form substituted alkenes. Like porphyrins, electronic properties of this complex are also tunable through the influence of various functional groups. In 2009, these molecules were examined in comparison to porphyrins due to their more restricted π-systems and carefully characterized with a focus on the tunability of their electronic properties with different metals and substituents.
Calixpyrroles
Calixpyrroles have all four hydrocarbon bridges fully saturated, breaking the conjugation between heterocycles present in other porphyrinoids. A phosphole replacing a pyrrole allows for similar chemistry to other phosphaporphyrinoids with increased flexibility of the tetradentate ligand by virtue of sp3 hybridization.
Isophlorins
Isophlorins are less stable nonaromatic complexes that engage in similar chemistry to the porphyrinoids. The 20π systems are synthesized from 18π porphyrins via redox-coupled complexation. Although the 4πn conjugated system would suggest that the molecule exhibits antiaromatic character, geometric and magnetic criteria confirm that the complex is nonaromatic.
References
Phosphorus heterocycles
Porphyrins | Phosphorus porphyrin | [
"Chemistry"
] | 3,621 | [
"Porphyrins",
"Biomolecules"
] |
72,203,783 | https://en.wikipedia.org/wiki/Arnold%20conjecture | The Arnold conjecture, named after mathematician Vladimir Arnold, is a mathematical conjecture in the field of symplectic geometry, a branch of differential geometry.
Strong Arnold conjecture
Let be a closed (compact without boundary) symplectic manifold. For any smooth function , the symplectic form induces a Hamiltonian vector field on defined by the formula
The function is called a Hamiltonian function.
Suppose there is a smooth 1-parameter family of Hamiltonian functions , . This family induces a 1-parameter family of Hamiltonian vector fields on . The family of vector fields integrates to a 1-parameter family of diffeomorphisms . Each individual is a called a Hamiltonian diffeomorphism of .
The strong Arnold conjecture states that the number of fixed points of a Hamiltonian diffeomorphism of is greater than or equal to the number of critical points of a smooth function on .
Weak Arnold conjecture
Let be a closed symplectic manifold. A Hamiltonian diffeomorphism is called nondegenerate if its graph intersects the diagonal of transversely. For nondegenerate Hamiltonian diffeomorphisms, one variant of the Arnold conjecture says that the number of fixed points is at least equal to the minimal number of critical points of a Morse function on , called the Morse number of .
In view of the Morse inequality, the Morse number is greater than or equal to the sum of Betti numbers over a field , namely . The weak Arnold conjecture says that
for a nondegenerate Hamiltonian diffeomorphism.
Arnold–Givental conjecture
The Arnold–Givental conjecture, named after Vladimir Arnold and Alexander Givental, gives a lower bound on the number of intersection points of two Lagrangian submanifolds and in terms of the Betti numbers of , given that intersects transversally and is Hamiltonian isotopic to .
Let be a compact -dimensional symplectic manifold, let be a compact Lagrangian submanifold of , and let be an anti-symplectic involution, that is, a diffeomorphism such that and , whose fixed point set is .
Let , be a smooth family of Hamiltonian functions on . This family generates a 1-parameter family of diffeomorphisms by flowing along the Hamiltonian vector field associated to . The Arnold–Givental conjecture states that if intersects transversely with , then
.
Status
The Arnold–Givental conjecture has been proved for several special cases.
Givental proved it for .
Yong-Geun Oh proved it for real forms of compact Hermitian spaces with suitable assumptions on the Maslov indices.
Lazzarini proved it for negative monotone case under suitable assumptions on the minimal Maslov number.
Kenji Fukaya, Yong-Geun Oh, Hiroshi Ohta, and Kaoru Ono proved it for semi-positive.
Urs Frauenfelder proved it in the case when is a certain symplectic reduction, using gauged Floer theory.
See also
Symplectomorphism#Arnold conjecture
Floer homology
Spectral invariants
Conley–Zehnder theorem
References
Citations
Bibliography
.
.
Conjectures
Symplectic geometry
Hamiltonian mechanics
Unsolved problems in mathematics | Arnold conjecture | [
"Physics",
"Mathematics"
] | 660 | [
"Unsolved problems in mathematics",
"Theoretical physics",
"Classical mechanics",
"Hamiltonian mechanics",
"Conjectures",
"Mathematical problems",
"Dynamical systems"
] |
72,205,317 | https://en.wikipedia.org/wiki/N-Heterocyclic%20carbene%20boryl%20anion | An N-heterocyclic carbene boryl anion is an isoelectronic structure of an N-heterocyclic carbene (NHC), where the carbene carbon is replaced with a boron atom that has a -1 charge. NHC boryl anions have a planar geometry, and the boron atom is considered to be sp2-hybridized. They serve as extremely strong bases, as they are very nucleophilic. They also have a very strong trans influence, due to the σ-donation coming from the boron atom. NHC boryl anions have stronger electron-releasing character when compared to normal NHCs. These characteristics make NHC boryl anions key ligands in many applications, such as polycyclic aromatic hydrocarbons, and more commonly low oxidation state main group element bonding.
Synthesis
Ever since the first crystalline carbene structure was isolated by Arduengo ins 1990, tuning different properties of NHCs has been a popular area of study in main group chemistry. The first NHC boryl anion was synthesized by Segawa in 2006. The precursor to the complex was first synthesized by a diimine reduction by magnesium followed by a reaction with BBr3. The final complex was synthesized through cleavage on a boron-bromide bond in a bromo-diazaborole complex by lithium naphthalenide. This reaction made a boryllithium complex, where the boron atom shows strong structural similarity to a free boryl anion. These similarities show that boron has the anionic -1 charge and is recognized as an isoelectronic compound to a singlet carbene. The key to this synthesis was bulky R substituents on the nitrogen which prevented dimerization, something that is common in boron chemistry. These bulky substituents and low temperatures provided successful isolation of the species.
Differing Boryllithium Backbones
After the first synthesis of the NHC boryl anion, Segawa continued to synthesize other NHC boryl anions by switching the backbones of the complexes. In 2008, it was found that by using the same reducing conditions as the first boryl anions, many other NHC boryl anions could be synthesized.
The "Naked" Boryl Anion
A "naked" boryl anion, in which there is no cation near the -1 boron, can be synthesized through an amide metathesis reaction. What is formed is a borylpotassium dimer, in which the K+ ions interact weakly with both the carbons on the substituents on the nitrogens and also the boron centers. The K-B bond distances are >3.1 Å, which is much greater than the sum of the covalent radii. Additionally, the N-B-N bond angle is very close to the calculated gas-phase anion, leading to the conclusion that the boryl anion is as "free" as possible.
Reactivity
NHC boryl ligands tend to be strong σ donors but π acceptors.
Bonding with Group 1 and 2 Elements
When the NHC boryl anion is in the form of a boryllithium salt, it has displayed reactivity with CO, one of the most important building blocks in the industrial field. The complex goes through an insertion reaction, where the CO is inserted into the B-Li bond to make a short-lived intermediate species. This reaction shows promising applications in carbonylative coupling reactions, where CO insertion is necessary.
In 2007, the first B-Mg single bond was synthesized using an NHC boryl anion as the ligand. The B-Mg bonds are slightly longer than the sum of the covalent radii, but this has been attributed to weakened Coulombic interaction due to coordination of the solvent, which was THF in this experiment. This solvent interaction also affects the geometry of the molecule, as the crystal structure shows that the Mg atom has a distorted sp3-hybridized center. However, the results show that the Mg-B bond has ionic character and can be considered a single bond. Another Mg-B bond was synthesized by reacting the NHC boryl anion with a Mg compound in a 2:1 ratio. This Mg atom also had a distorted tetrahedral coordination, which was also attributed to the coordination of the solvent (THF).
The first Be-B bond was reported in 2014, however this bond showed more covalent character, rather than the ionic bond that was reported in the Mg analogue of this complex. This complex was formed by reacting two equivalents of the NHC boryl anion with BeCl2 using benzene as the solvent. In 2020, however, a very interesting reaction between the NHC boryl anion and Be was reported. In this case, the boryl anion was reacted with a Be complex, and rather than forming a bond to, and receiving σ-donation from the boron atom, it reacted with one of the carbons in the backbone of the anion. Although the mechanism of this reaction is unclear, it is believed that one of the backbone protons becomes deprotonated, allowing the Be to bind to the positively charged carbons. This compound is extremely stable even at room temperature, and more studies are being completed to further understand the mechanism of this reaction.
Bonding with Main Group Elements
The NHC boryl anion has also been used to achieve B=B double bonds, but in a tetraborane species rather than the diborane molecule. For this synthesis, an extra boron atom was added to the NHC boryl anion, and then was reduced, forcing dimerization between the molecules and allowing for a H-bridged tetraborane species to occur. Although the complex is H-bridged, the inner B-B bond distance lies between reported double and triple bond lengths. Additionally, the NPA charges on the central B-B moiety are negative, showing that the boryl anions donate electron density, leading to the conclusion that a B=B double bond is occurring.
With specific reaction conditions, a disilane single or double bond can be achieved using the NHC boryl anion. To make a Si-Si single bond, a NHC boryl silane compound is reduced by KC8 in DME solvent. To make a Si-Si double bond, a slightly different NHC boryl silane compound is reduced in KC8 in THF solvent.
Additionally, a dianionic disilyne (Si-Si triple bond) was reported in the form of a Mg complex. Two equivalents of a NHC boryl silane compound is reduced with Mg in THF, leading to a Mg-Si-Si three-membered ring. The boryl anion groups are arranged in a cis formation, and the Si atoms have planar geometry. Additionally, the Si-Si bond length is calculated to be the sum of the covalent radii for a double bond, and the NPA charges show dianionic character on the Si atoms.
Bonding with Transition Metals
NHC boryl anions have also been investigated for their ability to activate C-H bonds and hydroboration activity, two things that were previously thought to only be completed by transition metal systems. Anionic boryl ligands can covalently bond to transition metals, which is different than how it bonds to main group elements (ionically). These boryl ligands σ-bond but also are able to receive π-back donation into the vacant pz orbital that the boron has. It is said that boryl ligands, like NHC boryl anions, are the most effective ligand in controlling reactivity.
Many transition metal boryl complexes have been synthesized, including silver, gold, copper, and zinc. These complexes give insight into potential intermediates of transition metal catalyst reactions, and provide potential starting materials for both organic and inorganic synthetic chemistry.
Group 12 metal bonding has almost exclusively had the metals in the +1-oxidation state, but NHC boryl anions have helped synthesize group 12 M-M bonds in the 0-oxidation state. Group 12 metals take part in very weak bonding in the 0-oxidation state due to the filled valence d-orbitals, when the metals have NHC boryl anion ligands, they are able to bond in the 0-oxidation state because of the increase electron density that is donated by the ligand. These molecules are synthesized by first have m-terphenyls as the ligands on the metal, and then an isolobal exchange occurs, placing the boryl ligands onto the metal and allowing for the metal to be in the 0-oxidation state.
Polycyclic Aromatic Hydrocarbons
One of the most exciting applications for NHC boryl anions are their place in polycyclic aromatic hydrocarbons, or PAHs. PAHs are normally defined as a molecule that has two or more benzenoid rings and contain no other elements except hydrogen and carbon. They are highly fluorescent, and are naturally found in crude oil and other petrochemical products. It has been shown that replacing the end carbons with a B-N moiety expands the family of PAHs and can serve as functional materials.
Placing boron into PAHs is known to improve and diversity the optoelectronic properties by reducing the LUMO energy level. This lowering of the LUMO energy increases acceptor ability by lowering the energy needed for absorption and emission. The fused NHC boryl anion units add an element of bifunctionality and induce π-conjugation because of the empty pz orbital. The absorption and emission qualities of these molecules are very interesting. PAHs that have a pyrene core all fluoresce blue light under UV light, but their smaller and more planar counterparts had a variety of colors that are emitted. This change in color is attributed to the NHC boryl anion rings contributing more to the smaller PAHs, whereas in the pyrene core there is less effect coming from the boron ligand. These planar NHC boryl anion molecules are very promising in their application to functional materials because they emit light in the near-IR region.
References
Boron heterocycles
Anions
Nitrogen heterocycles
Pentacyclic compounds | N-Heterocyclic carbene boryl anion | [
"Physics",
"Chemistry"
] | 2,153 | [
"Ions",
"Matter",
"Anions"
] |
72,206,134 | https://en.wikipedia.org/wiki/HR%208526 | HR 8526, also known as HD 212168, is the primary of a triple star located in the southern circumpolar constellation Octans. The star and its companion have apparent magnitudes of 6.12 and 9.36 respectively. The system is located relatively close at a distance of 76 light years based on Gaia DR3 parallax measurements, but is receding with a heliocentric radial velocity of .
This is a Sun-like star with a stellar classification of G0 V. It has 105% the mass of the Sun and 117% its girth. It radiates 157% the luminosity of the Sun from its photosphere at an effective temperature of , giving it a whitish-yellow hue. HR 8526 has an iron abundance similar to the Sun's and spins modestly with a projected rotational velocity of . HD 212168 has a similar age to the Sun; the former is 4.7 billion years old while the latter is 4.6 billion years old.
The B subsystem is located away along a position angle of 78°. It has a combined mass 76% that of the Sun and take roughly 11 years to orbit each other. Spectral classifications for this star vary from G0-V to K2V. The G0 class has been used as an argument that the two visible components form a purely optical pair, but this has been dismissed as mis-identification or contamination and that the actual spectral class is early or mid K.
DENIS J222644.3-750342 is a cool M8 red dwarf located 264 arcseconds away from HR 8526. In 2012, J.A. Caballero identified it as a companion to the AB system, making it a quadruple star system.
References
G-type main-sequence stars
M-type main-sequence stars
Octans
Octantis, 72
8526
CD-75 01241
212168
110712 | HR 8526 | [
"Astronomy"
] | 402 | [
"Octans",
"Constellations"
] |
72,206,141 | https://en.wikipedia.org/wiki/Time%20in%20Dominica | Dominica observes Atlantic Standard Time (UTC−4) year-round.
IANA time zone database
In the IANA time zone database, Dominica is given one zone in the file zone.tab—America/Dominica. "DM" refers to the country's ISO 3166-1 alpha-2 country code. Data for Dominica directly from zone.tab of the IANA time zone database; columns marked with * are the columns from zone.tab itself:
References
External links
Current time in Dominica at Time.is
Time in Dominica at TimeAndDate
Time by country
Geography of Dominica | Time in Dominica | [
"Physics"
] | 126 | [
"Spacetime",
"Physical quantities",
"Time",
"Time by country"
] |
72,207,564 | https://en.wikipedia.org/wiki/Evolved%20wireless%20ad%20hoc%20network | An evolved wireless ad hoc network (EVAN) is a decentralized type of wireless network that compensates for the shortcomings of the existing wireless ad hoc network (WANET). An EVAN is ad hoc like a WANET because it does not rely on a pre-existing infrastructure, such as routers in wired networks or access points in wireless networks. Further advantages of WANETs over networks with a fixed topology include flexibility (an ad hoc network can be created anywhere with mobile devices), scalability (you can easily add more nodes to the network) and lower administration costs (no need to build an infrastructure first). These characteristics of WANETs are maintained in EVAN as well. However, an EVAN has a physically separate resource management channel called tone channel, unlike existing WANETs. In WANETs, the data channel performs two roles: resource management and data transfer, but in EVAN, the data channel is used only for data transfer.
Challenges
Several books and works have revealed the technical and research challenges facing wireless ad hoc networks or MANETs. UEs moving in WANET rapidly change network topology. Many resources are used for channel management. A resource collision occurs when a UE allocates a resource or moves while occupying the resource. The UE in the middle experiences collisions due to packets being received simultaneously.
In summary:
Dynamic network topology by mobile UEs
Limited channel bandwidth
Communication resource collision
Hidden node problem
Solution
To solve the problems, the tone channel is used. this channel is dedicated to resource management. The types of tones used in the tone channel include an allocation tone for allocating a resource, a clearing tone for occupying a resource, and a detection tone for detecting a collision of an occupied resource. These tones are transmitted in tone slots. A tone slot consists of multiple tone subslots where a tone is transmitted. A slot 'n' in a tone channel maps to a slot 'n+1' in a data channel. Therefore, a UE allocate tone slot 'n' to use data slot 'n+1'.
Dynamic network topology by mobile UEs
A UE occupying a resource in the data channel transmits a clearing tone in a tone slot related to the occupied resource. The UE occupying the data slot ‘n+1’ transmits a clearing tone in the tone slot ‘n-1’. By receiving one tone channel continueously, each UE can examine the resources occupied by other UEs in real time.
Limited channel bandwidth
In general, the bandwidth of the tone channel is much smaller than the bandwidth of the data channel. The larger the bandwidth of the data channel compared to the bandwidth of the tone channel, the closer the frequency efficiency is to 100%.
Communication resource collision
A resource collision occurs when a UE allocates a resource or when a UE moves while occupying a resource. The probability of collisions occurring when allocating resources is significantly improved compared to carrier-sense multiple access with collision avoidance (CSMA/CA). This improvement is due to the fact that an EVAN has two contention compared to CSMA/CA having one contention. The collision of occupied resources caused by movement is detected in real time by each UE transmitting and receiving multiple detection tones. Two UEs can transmit different detection tones than the other by randomly selecting the transmission detection tones. UEs sense the tones when they do not transmit a detection tone. Therefore, the detection tones sent by the other UE can be detected.
Hidden node problem
In general, the tone channel bandwidth is quite small compared to the data channel bandwidth. When the two channels have the same transmit power, the communication distance of the tone channel is more than twice that of the data channel. Thus, the tone channel collides before the data channel collides. Since tone channel collisions can be detected, the UE can prevent a data channel collision by selecting another channel resource without collision. This solves the hidden node problem.
Advantages
Existing WANETs must broadcast 1-hop channel information or receive signals from other UEs to notify collisions. In contrast, in EVAN, if the UE does not need to listen to broadcasts, the UE operates only in the data slot and tone slot it uses, and may be in sleep mode at other times. That is, in EVAN, a sleep mode is possible when UEs are not being used for routing. This makes an EVAN suitable for 1-hop-based services that do not require routing.
Disadvantages
RF hardware for data channel and RF hardware for tone channel are required separately. Since the tone channel only performs a simple operation of transmitting or sensing a tone signal, the RF hardware of the tone channel is very simple.
See also
Ad hoc network
Ad hoc wireless distribution service
Carrier-sense multiple access with collision avoidance
Wireless ad hoc network
Wireless mesh network
References
Networking standards | Evolved wireless ad hoc network | [
"Technology",
"Engineering"
] | 974 | [
"Networking standards",
"Computer standards",
"Computer networks engineering"
] |
72,207,575 | https://en.wikipedia.org/wiki/Metric%20fixation | Metric fixation refers to a tendency for decision-makers to place excessively large emphases on selected metrics.
In management (and many other social science fields), decision makers typically use metrics to measure how well a person or an organization attain desired goal(s). E.g., a company might use "the number of new customers gained" as a metric to evaluate the success of a marketing campaign. The issue of metric fixation is said to arise if the decision maker(s) focus excessively on the metrics, often to the point that they treat "attaining desired values on the metrics" as a core goal (instead of simply an indicator of successes). For example, a school may want to improve the number of students who pass a certain test (metric = "number of students who pass"). This is based on the assumption that the said test truly can evaluate students' ability to succeed in the real world (assuming there already is a good definition of what "success" means). If the said test fails to evaluate the students' ability to function in the working world, focusing solely on increasing their scores on this test might cause the school to ignore other learning goals also crucial for real world functioning. As a result, the students' developments might be impaired.
Although related to several similar, older concepts, the term "metric fixation" was first mentioned in the 2018 book The Tyranny of Metrics. and has since drawn the attention of some management researchers and data scientists.
See also
References
Management
Measurement | Metric fixation | [
"Physics",
"Mathematics"
] | 316 | [
"Quantity",
"Physical quantities",
"Measurement",
"Size"
] |
72,208,356 | https://en.wikipedia.org/wiki/Journal%20of%20Environmental%20Management | The Journal of Environmental Management is a semi-monthly peer-reviewed scientific journal covering research on environmental science and quality that was established in 1973. It is published by Elsevier and the editors-in-chief are Raf Dewil (KU Leuven), Jason Evans (Stetson University), and Lixiao Zhang (Beijing Normal University).
History
The journal absorbed Advances in Environmental Research which was published between 1997 and 2004. The open access journal Environmental Challenges, published since 2020, is a companion journal.
Abstracting and indexing
The journal is abstracted and indexed in:
According to the Journal Citation Reports, the journal has a 2021 impact factor of 8.910, ranking it 34th out of 279 journals in the category "Environmental Sciences".
References
External links
Elsevier academic journals
Academic journals established in 1973
English-language journals
Environmental science journals
Semi-monthly journals | Journal of Environmental Management | [
"Environmental_science"
] | 175 | [
"Environmental science journals"
] |
72,208,872 | https://en.wikipedia.org/wiki/L%C3%A9anord | Léanord (Laboratoire d'Electronique et d'Automatisme du Nord) was a French computer brand, founded in 1960 at Haubourdin, near Lille. It was a subsidiary of Creusot-Loire and started to develop computers in the late 1970s.
The first machines, called Picolog 8, Picolog 80 and Picodidac 80 were based on Intel 8008, 8080 and 8085 microprocessors and designed for automation and machine code learning.
Léanord's first microcomputer was the Silex, released in 1978. Based on a licensed Apple II motherboard with a MOS 6502 running at 1Mhz and 32Kb RAM, the machine was expensive for the time (costing 29,000 Francs) and came with SILBasic (a BASIC interpreter), SILPascal (a Pascal interpreter) and SILDOS (a disk operating system). It had an 8-inch floppy disc drive and came in a 54x35x59 cm box, that also included the keyboard and monitor.
In 1979 Léanord released the Sil'z, similar in appearance to the Silex but CP/M compatible. It was powered by a Zilog Z80 at 2.5 MHz, had 64 Kb of RAM, 80x24 character monochrome display, two 5'' 1/4 320Kb disc drives, two RS-232c ports (for printer and modem), and measured 54x33x57 cm.
It was followed by the Sil'z II in 1981 (adding a Western WD1795 controller for extra floppy disc drives) and Sil'z III in 1982. In 1983, the Sil'z IV was released, with a different design featuring a separate keyboard and monitor and adding a hard drive.
The Sil'z 16 was released in 1983 with relation to the Computing for All government program, featuring the Nanoréseau, a small network based on the RS422 standard, and developed in connection with Lille university. This machine came with a Intel 8088 CPU running at 4.77Mhz, 128 Kb of RAM, MS-DOS, CP/M-86 and Microsoft Basic.
Later machines were PC compatible. The Challenger Elan series, released in 1986, were 16-bit ISA backplane machines with 8086, 8088, 80286 and 80386 processors.
In 1989 Léanord merged with Intertechnique, being eventually absorbed by Siemens-Nixdorf.
Models
Picolog 8 - Intel 8008, 1977
Picolog 80 - Intel 8080, 1977
Picodidac 80 - Intel 8085, 1979
Silex - Licensed Apple II motherboard, MOS 6502 @ 1Mhz, 32Kb RAM, 1978
Sil’z - Zilog Z80 @ 2.5 MHz, 64 Kb RAM, CP/M, 1979–1980
Sil’z II - Zilog Z80 @ 2.5 MHz, 64 Kb RAM, CP/M 2.2, 1981
Sil’z III - Zilog Z80 @ 2.5 MHz, 64 Kb RAM, CP/M 2.2, 1982
Sil’z IV - Zilog Z80 @ 2.5 MHz, 64 Kb RAM, CP/M, Separate keyboard and monitor, hard drive, 1983
Sil’z 16 - Intel 8088 @ 4.77Mhz, 128 Kb RAM, MS-DOS, CP/M-86, Nanoréseau network machine, based on the ProtoPC from Future Computers, 1983
Challenger Elan - First backplane PCs, 8086, 8088, 80286 and 80386, 1986
See also
Computing for All, a French government plan to introduce computers to the country's pupils
References
Computer companies of France
History of computing in France
Defunct computer hardware companies
Defunct computer systems companies
Computer science education in France
Computing for All | Léanord | [
"Technology"
] | 819 | [
"History of computing",
"History of computing in France"
] |
72,209,765 | https://en.wikipedia.org/wiki/Organoberyllium%20chemistry | Organoberyllium chemistry involves the synthesis and properties of organometallic compounds featuring the group 2 alkaline earth metal beryllium (Be). The area remains less developed relative to the chemistry of other main-group elements, because Be compounds are toxic and few applications have been found.
Structure
Homoleptic compounds
The coordination number of Be in organoberyllium compounds ranges from two to four.
Dimethylberyllium and dimethylmagnesium adopts the same structure. Diethylberyllium, however, does not structurally resemble diethylmagnesium (which has the same structure as dimethylmagnesium). This contrast is attributed to the small size of Be relative to its heavier congener Mg: Be is one of the smallest atoms on the periodic table. Dineopentylberyllium and many other dialkyl derivatives has been reported.
The phenyl derivative is represented by trimeric Be3Ph6. A terphenyl derivative is known. With bulky aryl ligands three-coordination is observed, see .
Organoberyllium compounds are typically prepared by transmetallation or alkylation of beryllium chloride.
Beryllocene
Beryllocene features both pi- and sigma-bonded cyclopentadienyl ligands.
It is prepared from and potassium cyclopentadienide:
Mixed ligand compounds
Many mixed ligand complexes are simply formed by addition of Lewis bases to diaryl and dialkylberyllium compounds. Many derivatives are known of the type are known where L = thioether, pyridine, NHC, and 1,4-Diazabutadienes.
Beryllium forms a variety of complexes with N-hetereocyclic carbenes (NHCs).
Low oxidation beryllium chemistry
While the +2-oxidation state is by far the most common for Be, compounds containing Be(I) and Be(0) have been described. A number of beryllium complexes with cyclic alkyl amino carbene (CAAC) ligands have been proposed to feature low-oxidation state beryllium centres. However, these low-oxidation state formulations have been contested due to the redox non-innocence of CAAC ligands. Unambiguous low-oxidation state organo-beryllium complexes with Be–Be bonds have been synthesized by the group of Simon Aldridge.
History
Dimethylberyllium was reported in 1876. A. Atterberg produced this first organoberyllium compound by treatment of dimethylmercury with elemental beryllium.
The alkylation of beryllium halides was studied by H. Gilman. Early systematic work was conducted by G. E. Coates.
See also
Group 2 organometallic chemistry
Beryllium
References
Beryllium compounds
Organometallic chemistry | Organoberyllium chemistry | [
"Chemistry"
] | 594 | [
"Organometallic chemistry"
] |
72,211,161 | https://en.wikipedia.org/wiki/Pleurotus%20cystidiosus | Pleurotus cystidiosus, also known as abalone mushroom and maple oyster mushroom, is an edible species of fungus in the family Pleurotaceae, described as new to science by mycologist Orson K. Miller Jr. in 1969. It can be cultivated, with spores and growing kits being available commercially. Antromycopsis macrocarpa (or A. broussonetiae) is the anamorphic form of this species.
See also
List of Pleurotus species
References
External links
Fungi described in 1969
Pleurotaceae
Fungus species | Pleurotus cystidiosus | [
"Biology"
] | 117 | [
"Fungi",
"Fungus species"
] |
72,211,204 | https://en.wikipedia.org/wiki/Transformer%20ratio%20arm%20bridge | The transformer ratio arm bridge or TRA bridge is a type of bridge circuit for measuring electronic components, using a.c. It can be designed to work in terms of either impedance or admittance. It can be used on resistors, capacitors and inductors, measuring minor as well as major terms, e.g. series resistance in capacitors. It is probably the most accurate type of bridge available, being capable of the precision needed, for example, when checking secondary component standards against national standards.
Like all bridges, the TRA bridge involves comparing an unknown component against a standard. Like all a.c. bridges, it requires a signal source and a null detector. The accuracy of this class of bridge depends on the ratio of the turns on one or more transformers. A notable advantage is that normal stray capacitance across the transformer, including lead capacitance, may affect the sensitivity of the bridge but does not affect its measuring accuracy.
History
The invention of the TRA bridge is credited to Alan Blumlein in his UK patent 323037 (published 1929), and this class of bridge is sometimes known as a Blumlein bridge, although links to earlier types of bridge can be seen. Blumlein's first patent was for a capacitance-measuring bridge: Fig. 1 is redrawn from one of the diagrams in the patent.
Subsequently the ratio arm principle was applied more generally, to other classes of electronic components and at frequencies up to r.f., and with many variations in how the unknown component was connected to the transformer or transformers.
Blumlein himself was responsible for several further related patents. He made his first bridge while employed by the British company Standard Telephones and Cables, which did not manufacture test instruments. TRA bridges have since been made by many specialist manufacturers, including Boonton, ESI (formerly Brown Engineering and BECO), General Radio, Marconi Instruments, H. W. Sullivan (now part of Megger) and Wayne Kerr.
Principle
One possible configuration using two transformers is shown in Fig. 2. (The two transformers allow both the signal source and the null detector to be isolated from the measured component.) The unknown and the standard are both driven by T1, feeding currents to the primary of T2. Because of the winding sense of the two halves of the T2 primary, these currents are in antiphase.
If and have the same value and are fed from the same tap on T1, the antiphase currents cancel out perfectly and the null detector will show balance. When and are unequal, balance can be approached by connecting to a different tap on the T1 secondary. An exact balance may be achieved by using two or more standards connected to suitable taps.
Fig. 2 shows and as single components. Fig. 3 shows separate standards for conductance and susceptance , allowing minor as well as major terms of to be resolved. The standards are shown as variable components connected to fixed taps on the T1 secondary, but bridges can equally be made with fixed standards connected to variable taps.
The unknown component too may be connected to a tap part-way along the T1 secondary. Also the numbers of turns on the two arms of the T1 secondary are not necessarily equal, and likewise those on the T2 primary. Combinations of these various options offer great flexibility of construction, allowing measurements over a wide range of values while using only a small number of standards – essentially one per significant figure of the resistance or conductance value and one per significant figure of the reactance or susceptance value.
In Fig. 3, at balance
The bridge may be balanced (nulled) by manual switching of the standards, but "autobalance" bridges, in which the switching is wholly or partially automated, are also made.
Detailed example
The operation of a universal TRA bridge is best explained on the basis of an actual product, the Wayne Kerr B221 bridge, dating from the 1950s. It used valve (vacuum tube) technology. The following description is simplified.
The bridge is based on two transformers (Fig. 4): T1 is described as the voltage transformer, and is driven by the signal source in the usual way. T2, the "current transformer", compares the two arms of the circuit – for the unknown and the various standards – and drives the null detector, which takes the form of a phase-sensitive detector with adjustable sensitivity, feeding two magic eyes. (Later versions of the instrument, with transistorised circuitry, used a moving-coil meter as the display for the null detector.)
Taps at 1, 10, 100 and 1000 turns are shown on the T1 secondary and on T2 primary P2a. Four-way selector switches are shown, but the tap selections are actually combined on a single switch to give seven measuring ranges. Full-scale limits at full accuracy (specified as ±0.1%) are 100 MΩ, 11.1 pF and 10 kH for the least sensitive range, and 100 Ω, 11.1 μF and 10 mH for the most sensitive range. Each range can be extended in the direction of higher resistance, higher inductance or lower capacitance at reduced accuracy. The voltage applied by T1 to is about 30 V r.m.s. on the least sensitive range, 30 mV on the two most sensitive.
The most significant figures of the major and minor components of are obtained by switching the resistance standard Rs1 and the capacitance standard Cs1 to one of taps 0 to 10 on the secondary of T1. The second significant figures are obtained by switching Rs2 and Cs2 in the same way. Continuous ("vernier") fine adjustment to give third and fourth significant figures is provided by Rs3 and Cs3. Rs3 and Cs3 are shown connected to tap 10 on T1, but in practice these two standards may be connected to any convenient tap, as appropriate to their values.
Primary P2b on T2 provides 100-turn taps of both polarities. Switching the capacitance standards between the positive and negative taps selects between capacitance measurements and inductance measurements. Similarly the polarity of the resistance standard can be reversed, so that measurements can be made in all four quadrants.
Besides the main balance controls described above, the front panel of the instrument has zero adjustments for both resistance and capacitance. The inductive elements of the wire-wound resistance standards are compensated by trimming capacitors. All these and other trimming components are omitted in Fig. 4.
This bridge measures conductance and susceptance in parallel. The susceptance reading is displayed as capacitance, and inductance must be calculated as a reciprocal using
To simplify the arithmetic, the bridge operates at 1592 Hz so that ω2 is 108 s−2. The readings can be converted to resistance and capacitance in series. On the most sensitive ranges, readings must be adjusted to take account of lead resistance and inductance.
The external link allows two-, three- or four-terminal measurements to be made. Besides conventional component measurements, the bridge can also be used to measure attenuator performance, transformer turns ratio and the effectiveness of transformer screening. Subject to conditions, in-situ (in-circuit) measurement of a component is possible. With additional external components, capacitors with a polarising voltage or inductors with a standing direct current can be measured.
An optional low-impedance adaptor extends the measuring range downwards by another four orders of magnitude, giving full-scale readings down to 10 mΩ, 5 F and 1 μH at ±1% basic accuracy.
See also
Capacitance meter
LCR meter
References
Further reading
Henry P. Hall, A History of Impedance Measurements, based on a draft for an unpublished book.
Electrical meters
Bridge circuits
Measuring instruments
English inventions
Impedance measurements
Electronic test equipment | Transformer ratio arm bridge | [
"Physics",
"Technology",
"Engineering"
] | 1,645 | [
"Physical quantities",
"Electronic test equipment",
"Measuring instruments",
"Electrical meters",
"Impedance measurements",
"Electrical resistance and conductance"
] |
72,212,574 | https://en.wikipedia.org/wiki/HD%20206610 | HD 206610, also known as Bosona, is a star with an orbiting exoplanet in the constellation of Aquarius. Based on parallax measurements, it is located at a distance of approximately 482 light years from the Sun. The absolute magnitude of this star is 1.99, but at that distance it is too faint to view with the naked eye, having an apparent visual magnitude of 8.34. The system is drifting closer with a radial velocity of −18.6 km/s.
This is an aging K-type subgiant star with a stellar classification of K0III. Having exhausted the supply of hydrogen at its core, the star is cooling and expanding along the red giant branch. At the age of about three billion years, it has 1.5 times the Sun's mass and has grown to six times the radius of the Sun. It has a similar iron abundance to the Sun and is spinning with a projected rotational velocity of 1.77 km/s. The star is radiating 18 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,819 K.
The star HD 206610 and its exoplanet HD 206610 b are named Bosona and Naron respectively. The names were selected in the NameExoWorlds campaigns by Bosnia and Herzegovina during the 100th anniversary of the IAU. Bosona is the historic name for Bosnia, Horion Bosona, described in De Administrando Imperio by Porphyrogenitus in 10th century, and its namesake the river Bosna's ancient name Bosona (Bosina, Basina, Basante). Naron is one of the names given to the Neretva river in Herzegovina originating with the Romans (Naro, Narona, Narenta, Nerenta), while in local tradition the name is said to go back even earlier with the Celts who called it Nera Etwa, which means the Flowing Divinity.
Planetary system
HD 206610 has one known exoplanet, HD 206610 b named Naron, discovered in 2010 using the radial velocity method.
References
External links
Image HD 206610
Bosona eSky
K-type subgiants
Planetary systems with one confirmed planet
Aquarius (constellation)
BD-08 5719
206610
107251
Bosona | HD 206610 | [
"Astronomy"
] | 497 | [
"Constellations",
"Aquarius (constellation)"
] |
72,213,808 | https://en.wikipedia.org/wiki/Isotopocule | Isotopocules are isotopically substituted molecules, which differ only in their isotopic composition or their isotopes' intramolecular position. "Isotopocule" is also an umbrella term for the more specific terms "isotopologue" and "isotopomer", coined by Jan Kaiser and Thomas Röckmann in 2008.
References
Isotopes
Physical chemistry | Isotopocule | [
"Physics",
"Chemistry"
] | 79 | [
"Applied and interdisciplinary physics",
"Isotopes",
"nan",
"Nuclear physics",
"Physical chemistry",
"Physical chemistry stubs"
] |
72,214,602 | https://en.wikipedia.org/wiki/Magnesium%28I%29%20dimer | A magnesium(I) dimer is a molecular compound containing a magnesium to magnesium bond (Mg-Mg), giving the metal an apparent +1 oxidation state.
Alkaline earth metals are commonly found in the +2-oxidation state, such as magnesium. The M2+ are considered as redox-inert, meaning that the +2 state is significant. However, recent advancements in main group chemistry have yielded low-valent magnesium(I) dimers, also given as Mg(I), with the first compound being reported in 2007. They can be generally represented as LMg-MgL, with L being a monoanionic ligand. For example, β-diketiminate, commonly referred to as Nacnac, is a useful chelate regarding these complexes. By tuning the ligand, the thermodynamics of the complex change. For instance, the ability to add substituents onto Nacnac can contribute to the steric bulk, which can affect reactivity and stability. As their discovery has grown, so has their usefulness. They are employed in organic and inorganic reduction reactions. It is soluble in a hydrocarbon solvent, like toluene, stoichiometric, selective, and safe.
Discovery
Role of zinc
The first zinc(I) dimer was isolated in 2004, with more being synthesized in subsequent years. The chemical similarities between magnesium and zinc led researchers to believe that a Mg(I) dimer could then be achieved. With a calculated stability of Mg—Mg bonded dimers, a synthesis route was needed.
Initials calculations and techniques
S-block compounds with low oxidation states can be short lived. There are various techniques available for use. However, the generation and detection of these molecules rely on frozen inert gas matrices, low pressures, high temperatures in the gas phase, or a combination of these. This can then be combined with theoretical studies to gain more information regarding the complex. Matrix isolation techniques were carried out for gaining spectroscopic insight on how the Mg(I) dimer may behave.
By heating magnesium diboride, MgB2, at 700 Celsius (°C) with a pressure of 0.1 mbar, and passing HCl gas over it several products are formed, such as magnesium chloride, MgCl. The generation of •MgCl and subsequent compounds from the reaction then underwent further study. At 10 Kelvin (K), the solution was combined with an inert gas, undergoing IR and Raman spectroscopic techniques, combined with Density Functional Theory (DFT) calculations. This showed the monomeric and dimeric Mg(I) Halides, •MgCl and ClMgMgCl, a linear molecule. While these studies were useful in gaining more insight on the Mg-Mg bond characteristics, it failed to yield a stable Mg(I) dimer in ambient conditions.
Synthesis
Precursors
The stability of the Mg-Mg bond needed to be dealt with. Researchers began to investigate sterically demanding guanidinates and amidinates. Their stabilizing abilities in low-oxidation state chemistry was attractive since it allowed for other low-valent main group complexes to be achieved. This research also allowed for the first stable dimer Mg(I) dimer, [{(Priso)Mg}2]. Potassium reduction of heteroleptic Mg(II) iodide precursor complexes were then carried out. The ligands guanidinato and, β-diketiminato Mg(II) iodide etherate complexes can be prepared from free NH ligands and methyl magnesium iodide in diethyl ether. An example of the synthesis of the precursor synthesis can be shown below. An additional precursor synthesis is shown, needed for [{(tBuNacnac)Mg}2], which can be explained in the section below.
Mg(I) dimer species
Reducing the species and its related precursors with sodium or potassium have given dimeric magnesium(I) compounds such as [{(Priso)Mg}2] and other compounds with substituted versions of β-diketiminato. These compounds, with a general formula of [{(ArNacnac)Mg}2]. However, as the size of the substituent on Nacnac decreased, the difficulty to isolate a magnesium(I) dimer increased. This can be shown by phenol, where only a Mg(II) dimer was gained, given by [(PhNacnac)2Mg]. For a bulkier analogue such as [{(tBuNacnac)Mg}2] a different synthesis route was carried out. Dibutyl magnesium and iodine were chosen since the free β -diketimine, tBuNacnacH has a different reactivity.This is due to tBuNacnacH not reacting with the Grignard reagent shown above. Instead, it can be heated with dibutylmagnesium and become deprotonated.
For the reactant, the was stabilized by utilizing a bulkier, or more sterically demanding, N-ligand. This reaction is carried out through potassium reduction of the α-diimine, MeDipDAB and Mg(II) chloride in tetrahydrofuran (THF). It can be noted that MeDipDAB can be shown by the chemical formula as [(DipNCMe)2]). The shown Mg(I) complexes are all thermally stable. Some can even tolerate temperatures up to 300 °C. They also range in colors from colorless to orange. As these compounds are investigated further, the dimers have been found to be kinetically stabilized by multiple β-diketiminate derivatives, a guanidinate, a diiminophosphinate, an enediamide, and several diimine-enolates.,,,
Bond properties
The Mg(I) dimer formula, LMgMgL, has undergone multiple theoretical investigations regarding the bonds. Furthermore, L, a monoanionic ligand, can also include halides, hydrogen, small alkyl groups, aryl groups, cyclopentadienyl with respective derivatives and chelating monoanionic nitrogen ligands. Mg—Mg bonded molecules underwent the primary investigation, with the bond length found to be 2.76-2.89 Å. Additionally, the bond dissociation energy was found to be between 45 and 48 kcal mol−1. Specifically, for ClMgMgCl, it was found to be 47.1 kcal mol−1.
s and p-orbital overlap
The Mg-Mg bond for a neutral magnesium(I) dimer has shown to be significantly sigma-bonding. This arises from the s-orbital overlap of the two metals. The bonding interaction that occurs may be connected to the highest occupied molecular orbital (HOMO), giving the highest energy bond of the molecule. This can be reflected through the Wiberg Bond Index (WBI). The sigma single bond gives a WBI value of 0.9, having 90% s-character. Further theoretical investigations have proved that this does not hold for every complex. There can be notable p-orbital contribution to the Mg—Mg, with it being determined to be 55% in some complexes as the charge changes. There were also findings regarding the lowest unoccupied molecular orbital (LUMO). For example, bonding character was also discovered in nearly degenerate LUMO and LUMO+1, with a HOMO-LUMO gap of 93 kcal mol−1.
Potential Applications
Mg(I) dimer benefits
Reducing agents can also be considered in demand as the rapid rise of low oxidation state chemistry has been reliant on them. Common compounds include but are not limited to potassium graphite (KC8), sodium naphthalenide and its alkali derivatives, or s-block metals in their elemental form, such as lithium. However, these reducing agents can have drawbacks, especially concerning accessing low oxidation states. For instance, these complexes may not be soluble in certain solutions, may lack certain selectivity, or can have an over-reduction effect of the initial precursor. Additionally, other side reactions can occur. More importantly, corrosion can be considered. Pure magnesium can be employed as an example. As the humidity increases, the corrosion rate of pure magnesium increases. At 10% humidity, there is no corrosion; at 30% there is a small layer of surface oxide, with slight corrosion evident; at 80% an amorphous phase coats about 30% of the surface and shows significant corrosion. Instances like these concerning the disadvantages of reducing agents, can make the dimers more appealing to certain chemical synthesizes.
Mg(I) reagent potential for complexes
Mg(I) dimers have the potential to be reducing agents that can be utilized in organic and organometallic synthesis. The thermal stability, moderate air and water sensitivity, and wide range of solubility in organic solvents may make the dimer attractive to chemists. An example of this can be shown through low oxidation state germanium (Ge) chemistry. Using Mg(I) dimers led to a Ge double bond. It can also be noted that the product had low yield. Additionally, the ligand, DipNacnac has poor solubility in the reaction solvent of ether. This allows for easy separation too.
Additionally, hydrogen storage has been gained significant research attention as an alternative to fossil fuels.
Ammonia borane, NH3BH3, has a high H-content, at 19.6%, concerning hydrogen storage material. However, there are issues regarding the safety, kinetics, and practical characteristics of the compound. Alternatively, more s-block amidoboranes have been researched as an alternative, with some interest lying in magnesium amidoborane. Some studies have shown that using reductive dehydrogenation of ammonia borane can be achieved using Mg(I) dimers.
Grignard reagent potential
Grignard reagents, given by RMgX, with R being a monoanionic organic substituent and X being a halide, are thought to proceed through some magnesium(I) intermediates, such as RMgMgX. It is believed that some of the transformations that occur with Grignard reagents may proceed via single electron transfer. This proceeds from the RMg to the substrate. Organic one electron reductions are also believed to be in equilibrium with a univalent magnesium compounds such as XMgMgX. This reagent could have potential to be more selective when compared to other reducing agents, such as samarium(II) Iodide, SmI2, that also acts as a one electron reductant.
Carbon activation
Mg(I) dimers have also been researched for carbon monoxide, CO, activation. Further research regarding the synthesis of these complexes revealed that their behavior can be compared to low-valent f-blocks compounds concerning the reduction of CO2, socyanides, and nitriles.,
Computational studies carried out further reinforced this idea by showing parallels between CO activation with f-block metal hydride complexes. The researchers first started with Mg(I) dimers. These dimers were then hydrogenated in hopes of generating magnesium(II) dimers. Additionally, the hydrogenation of Mg(I) dimers in a CO atmosphere, led to Cross-Coupled alkoxy products. The mechanism in which this reaction proceeded was shown by the computational studies to proceed similarly to related reactions of f-block metal hydride complexes. More specifically, researchers drew a close analogy to the reactivity of [{(DippNacnac)Mg}2] towards CO2. After the reaction was carried out, the dimer was shown to have a similar reactivity towards CO2 that could also be shown in samarium(II) or uranium(III) complexes. This reaction could also illustrate the potential magnesium(I) dimers have for the conversion of H2/CO mixtures. By using more reactive dimers, it was hypothesized that uses for the stoichiometric or catalytic transformation of CO/H2 mixtures to value added oxygenate products. Finally, the similarity to low-valent f-block complexes can give rise to a more affordable, nontoxic, and nonradioactive practices. Comparatively, the diamagnetic dimer could also a difference in electronic properties when compared to paramagnetic nature of the lanthanides and actinides.
References
Organomagnesium compounds
Cluster chemistry | Magnesium(I) dimer | [
"Chemistry"
] | 2,594 | [
"Cluster chemistry",
"Organometallic chemistry",
"Organomagnesium compounds",
"Reagents for organic chemistry"
] |
73,622,656 | https://en.wikipedia.org/wiki/Laser-assisted%20drug%20delivery | Laser-assisted drug delivery (LADD) is a drug delivery technique commonly used in the dermatology field that involves lasers. As skin acts as a protective barrier to the environment, the absorption of topical products through the epidermis is limited; thus, different drug delivery modalities have been employed to improve the efficacy of these treatments. The use of lasers in LADD has been shown to enhance the penetration of drugs transdermal, leading to a higher absorption rate, limited systemic effects, and reduced duration of treatment. Although this technique has evolved in the past decade due to its efficacy through scientific research and clinical practice, there remain some limitations regarding the safety aspect that needs to be taken into consideration.
Transdermal drug delivery
The skin barrier
Skin is the largest organ in the human body that acts as the primary protective barrier against the external environment. It provides protection against ultraviolet light, trauma, pathogens, microorganisms, and toxins, sensory perception, temperature regulation, and immunity. There are primarily three layers of skin, which include the outer epidermis, followed by the dermis and subcutaneous tissue, or hypodermis. Skin is used as the target for drug delivery as it is a convenient route of drug administration, and the large area allows for different placements on the skin for transdermal delivery
Transdermal delivery
Transdermal delivery is a non-invasive method commonly assisted in transporting topical products into intact and healthy skin. The substances initially penetrate through the stratum corneum, which is the outermost layer of the epidermis, then diffuse into the deeper epidermis and dermis layers for a systemic effect. Although transdermal drug delivery presents several advantages as compared to other conventional modalities such as oral and parenteral routes, the complexity of the skin barrier limits the methodology to reach its full potential.
Improvement in transdermal delivery
Various technologies have been developed to enhance the permeability of transdermal drugs, which can be divided into passive or chemical and active or physical methods. The passive approach involves the optimization of drug and vehicle interaction that could modify the stratum corneum structure or the addition of penetration enhancers for better absorption rates. Some of the limitations of this approach include lag time in drug release, low efficiency, and skin irritation. The active approach involves ultrasound, electrical stimulation, thermal approach, and mechanical approach. These techniques facilitate the transportation of drugs by using energy as a driving force. Within the thermal approach, laser-assisted drug delivery is a common and effective method that has been used to increase the efficiency of transdermal drug delivery by selectively destroying the chromophores of interest using light waves.
Specifications for using LADD
Lasers
There are different types of lasers used in LADD, and they can be categorized into four main groups: (1) fully ablative lasers, (2) ablative fractional lasers (AFL), (3) non-ablative fractional lasers (NAFL), and (4) non-ablative dermal remodeling lasers. Common fully ablative lasers, including carbon dioxide (CO₂, wavelength peak 10,600 nm) and erbium-doped yttrium aluminum garnet (Er:YAG, wavelength peak 2940 nm), target water as their chromophore where all water-containing tissues within the epidermis are ablated. With its high wavelength peak, CO₂ laser has a high absorption rate of water and adipose tissues; whereas the wavelength of Er:YAG allows for the precise ablation of water and minimizes heat generation. The mechanism of AFL is similar to fully ablative lasers but when used fractionally, they create multiple vertical columns on the skin surface, which are also called microscopic treatment zones (MTZ) and allow for a more quantitatively controllable usage in LADD. NAFL are also fractionated lasers that produce MTZ, but as they are non-ablative, there is no ablation of the epidermis and instead, they use light energy to damage the dermis layer. Non-ablative dermal remodeling lasers include all types of lasers with a chromophore that is different from water as used in the previous groups. Common lasers within this group are neodymium-doped YAG laser (Nd: YAG, wavelength peak 1064 nm and 1320 nm), pulsed dye laser (wavelength ranges from 585 to 600 nm), and intense pulsed laser (IPL, wavelength ranges from 500 to 1200 nm). In general, with its high efficiency and rapid recovery time, AFL is the more common modality used for LADD, especially in the dermatology field.
Drugs
Lipophilic substances have shown to have a greater ability to cross the epidermis, thus, the efficiency of LADD is more remarkable when using hydrophilic substances. Liquid and gel formulations of drugs also are proven to cross the channels created from the fractional lasers more easily as compared to oily formulations such as creams or ointments. Common drugs used in LAPP include but are not limited to 5-aminolaevulinic (5-ALA), 5-aminolevulinate (MAL), methotrexate (MTX), imiquimod, 5-fluorouracil (5-FU), timolol, triamcinolone acetonide (TAC), bimatoprost, tretinoin, pimecrolimus, poly-L-lactic acid (PLLA), analgesics, minoxidil (MXD), diphencyprone (DPCP), vitamin C, small interfering RNA (siRNA), vaccine, and antibodies.
Patients
The efficiency of LADD with the selected laser settings is dependent upon the different characteristics associated with individual patients. The dermatological condition, the properties of the skin, and the surface area are taken into consideration to determine the eligibility of the patients for certain lasers and provide optimal treatments for each patient. For example, hydrated skin has a higher affinity for absorption of oily substances; skin atrophy that is associated with solar elastosis is more likely to produce pathological scarring under high laser intensity; hair areas have a higher absorption rate; older patients are more prone to adverse effects such as atrophy, erosion, ulceration, and will require longer recovery time. Not all patients are candidates for LADD as this method is intensified as compared to conventional topical treatment.
Pre-clinical application
A vast majority of pre-clinical work on LADD focuses on AFL based on its translational characteristics in clinical settings. These studies utilized mostly either porcine or murine skin as their disease model.
Porcine skin
Within the dermatology field, porcine skin has been used as a disease model for testing the efficacy of LADD in vivo. Haedersdal et al. pre-treated porcine skin with CO2-AFL before the application of MAL photodynamic therapy (PDT), creating single MTZs that increased porphyrin fluorescence uniformly up to 1.5 mm from the ablated channels. This demonstrated that for MAL, pre-treatment of AFL with MTZs spacing at 3-mm intervals, covering less than 1% surface of the area, was useful for the entire lesion. Similarly, Bachhav et al. showed that the increased numbers of MTZs from Er:YAG laser did not affect the absorption of lidocaine into either the epidermis or dermis, and thus, higher fluences of laser were not proportionally correlated to the absorption rate. AFL pre-treatment of porcine skin also has also shown to enhance the delivery of MAL at deeper layers of the skin, increase surface fluorescence from MAL as compared to non-AFL pre-treated skin, and induce higher fluorescence of 5-ALA as compared to MAL for deeper structure.
Murine skin
Besides porcine skin, murine skin has also been used for testing the efficacy of LADD. A study performed on murine skin has shown that the penetration of 5-FU through skin increased 36 to 133-fold after pre-treatment with fully ablative Q-switched ruby, CO2, or Er:YAG lasers. Likewise, delivery of imiquimod in both murine and porcine skin increased up to 65-fold and 127-fold, after one and four passes of low-fluence fractional Er:YAG laser, respectively. As a result, with LADD, a dose of 0.4% imiquimod was equivalent to a topically applied dose of 5% imiquimod, which implied that a lower dosage of drug could be used with similar clinical outcomes. Besides topical drugs, Chen et al. showed that the treatment of fractional CO2 on murine skin increased 8- to 15-fold the delivery of ovalbumin vaccine, along with an enhanced production of ovalbumin specific antibodies at 2 weeks.
Clinical application
LADD has been implemented in clinical practice to support the absorption of topical agents into the skin, representative drugs include 5-ALA, MAL, 5-FU, corticosteroid, vitamin, and lidocaine.
Photodynamic therapy
LADD has been used in adjunction to photodynamic therapy (PDT) as a pre-treatment, which has shown to enhance the absorption of these drugs into the skin. 5-ALA and MAL are common photosensitizers that are used in PDT to treat different skin diseases such as actinic keratoses (AK), Bowen’s disease, and superficial cell carcinoma.
5-ALA
Lim et al. (2014) utilized nonablative fractional laser Er:YAG to pre-treat twelve treatment areas on the back of 10 healthy males, followed by the incubation of 5-ALA. The results showed that pre-treated areas had higher level of porphyrin fluorescence as compared to non-pretreated areas, which indicated that LADD enhanced 5-ALA skin penetration. In another study, Jang et al. (2013) pre-treated 29 AK patients with an ablative CO2 fractional laser, followed by 5-ALA-PDT treatment with varying incubation times. The pre-treatment of laser showed improvement of clinical outcomes even with the short incubation time, with 70.6% of the AK lesions had a complete clinical response to PDT.
MAL
In a randomized study, Choi et al. used both conventional MAL-PDT and a combination of AFL (Er:YAG) and MAL-PDT to treat 93 AK patients. The group treated with a combination of LADD and PDT showed higher clinical response rate of 91.7% as compared to conventional MAL-PDT group with clinical response rate of 65.6% after three months, and results were persistent after a twelve-month follow-up. In another randomized study with 21 patients with Bowen’s disease, the clearance rate of the lesions after 3 months was higher with pre-treatment of one session of ablative fractional Er:YAG followed by MAL-PDT (93.8%) as compared to two sessions of conventional MAL-PDT (73.1%), and with lower recurrence rates (6.7% versus 31.6%).
5-FU
5-FU is a common drug which is used to treat cancer and certain skin diseases, such as AK and certain types of nonmelanoma skin cancers. In a case study of 28 patients, including 16 superficial basal cell carcinomas and 14 squamous cell carcinomas in situ, pre-treatment of a single pass of CO2-AFL followed by a single application of 5-FU showed histological clearance of 100% squamous cell carcinomas in situ and 71% of the superficial basal cell carcinomas. In a case report study, a patient with multiple Bowen’s disease lesions was selected for a half-side study, one was treated with Er:YAG laser followed by a topical treatment of 5-FU and the other was treated with only 5-FU cream. The legions treated with LADD showed accelerated clinical and histologic response as compared to conventional 5-FU, with no recurrences of lesions after 9 months. In another study, Wenande et al. (2021) showed that CO2-AFL enhanced the efficiency of cisplatin and 5-FU treatment for 20 patients with basal cell carcinoma, with 94.7% patients showed clinical clearance.
Corticosteroid
Triamcinolone acetonide (TAC) is a common corticosteroid used as a therapeutic strategy for hypertrophic scars and keloids. In a case study, Waibel et al. used CO2-AFL to assist topical TAC delivery to treat 15 patients with hypertrophic and restrictive cutaneous scars. The results showed that significant improvement of the scars was observed after 6 months, with the most impacts on texture. Similarly, in a pilot study, either CO2-AFL or radiofrequency was used in adjunction with ultrasound-assisted TAC to treat alopecia areata, a disease associated with hair loss. All patients showed complete response after the treatment and specifically, the use of LADD with CO2-AFL showed complete response of patients after a single session as compared to a required of three and six sessions for radiofrequency.
Vitamin
Vitamin C and E are important substances that show antioxidant effects against UV radiation. Transdermal delivery after topical application of these vitamins has been facilitated with LADD. Lee et al. (2003) showed that the application of either nonablative fractional Er:YAG or CO2 lasers improved the transdermal penetration of vitamin C significantly. In a split face comparison study regarding UV-induced skin aging, Trelles et al. treated 14 patients with conventional CO2-AFL on one side and CO2-AFL along with the application of vitamin C and E on the other side. As a result, the combination of LADD and vitamins demonstrated a 79% reduction in fine lines as compared to a 69% reduction for AFL-treated side without the delivery of vitamins.
Lidocaine
Local anesthesia is used widely for dermatological surgeries via topical products or injections. As topical agents have a long incubation time for drug penetration and injections are associated with pain, LADD has been applied to the field for advancing the efficacy of anesthesia. Lidocaine is a local anesthetic cream used to prevent and treat pain. Increase dermal absorption and transdermal bioavailability of lidocaine were seen when using in conjunction with LADD, specifically AFL. Yun et al. demonstrated that 5% lidocaine cream applied after Er:YAG-AFL for a full resurfacing procedure showed significant lower pain score after the first pass of resurfacing, but there were only half of the patients were able to tolerate the second pass. Nevertheless, this indicated that LADD showed an enhancement of lidocaine penetration through the stratum corneum. Similarly, in a double-blind randomized controlled trial with 320 healthy volunteers, the patients were either pre-treated with Er:YAG-AFL followed by 4% lidocaine or treated with topical 4% lidocaine alone before cannulation. The results showed a 62% reduction in pain with the use of LADD as compared to conventional topical lidocaine.
Safety and adverse events
When applying LADD in clinical settings, safety is an imperative factor that needs to be considered. As mentioned above, there are different lasers with distinct properties that could be implemented for patients. However, radiation of any type will damage human tissue to some extent. Some potential adverse events that are laser-induced include erythema, edema, scabbing, blistering, and pigmentary changes, especially at higher intensity and densities. Regarding intralesional therapies for scarring, telangiectasia, hypopigmentation, and skin atrophy have been observed in multiple studies as side effects of LADD. In LADD application for management of pigmentary condition, there are some pigment-related adverse effects such as worsening of melasma, and hyperpigmentation in vitiligo. While LADD improves the dermal infiltration of different medications, the skin also has heightened local reaction when exposed to the substances and external environment. In several studies about AFL-assisted delivery of MAL-photodynamic therapy, there are intensified local cutaneous responses, including burning sensation, pain, edema, pruritus, purpura, and transient pigmentary changes. Furthermore, exposing the underlying dermis and vasculature to the outside environment also increases the risk of infection. AFL-assisted delivery of 5-FU, steroids, and MAL have shown elevated bacterial infections. In general, most LADD safety concerns are related to local reactions similar to that of laser therapy, and are generally well-tolerated with some exceptions.
Future direction
Current studies support the use of LADD in adjunction with topical products in treating dermatological diseases, but these studies are limited in sample size and lack of long-term follow-up outcomes. Larger randomized controlled trials with a wide variety of topical drugs are required to validate the efficacy and side effects of LADD before this technique could be employed as a standard of treatment. Besides its application in drug delivery, the prospect of using LADD to improve the transdermal delivery of vaccines, promote wound healing, correct genetic sequence, and as a complement to inflammatory dermatoses and cosmetic indications is being investigated
References
Drug delivery devices | Laser-assisted drug delivery | [
"Chemistry"
] | 3,668 | [
"Pharmacology",
"Drug delivery devices"
] |
73,622,945 | https://en.wikipedia.org/wiki/Mariko%20Hasegawa | Mariko Hiraiwa Hasegawa (, born 1952) is a zoologist and anthropologist who studies behavioral ecology, evolutionary psychology, and physical anthropology. Hasegawa is president of the Graduate University for Advanced Studies (Sokendai) in Kanagawa Prefecture, Japan. She is "among the rare Japanese women primatologists to have gained international recognition."
Her mother Satsue Mito collected field data on Japanese macaque troupes beginning in the 1950s, ultimately documenting four decades worth of behavior. Mito documented the cultural transmission of sweet-potato-washing within a group of wild macaques. During Hasegawa's doctoral studies at the University of Tokyo, she also studied Japanese macaques, as well as Tanzanian chimpanzees. She won a British Council Scholarship and went to Cambridge for zoology. She was on the faculty of Senshu University from 1990 to 2000, at which time she joined the faculty of Waseda University.
References
External links
ResearchGate: Mariko-Hiraiwa-Hasegawa
Living people
1952 births
Primatologists
Japanese anthropologists
Ecologists
Japanese psychologists
University of Tokyo alumni | Mariko Hasegawa | [
"Environmental_science"
] | 232 | [
"Ecologists",
"Environmental scientists"
] |
73,623,750 | https://en.wikipedia.org/wiki/Mobility%20mat | A mobility mat (also mobi-mat) is an assistive device that allows wheelchair users access to sandy beaches, dirt trails, or other surfaces that may be challenging for people with limited mobility, like the wooden deck of an ocean pier, or a path covered in wood chips.
Mobi-mats used in Australia are "1.5 metres wide and can be up to 50 metres long." This inclusive technology is a non-slip mat, sometimes with ridges, that provides stability for anyone traveling with the help of wheels, including parents with strollers or wagons, and people using walkers. Most beach mobility mats do not reach the water's edge to prevent tide damage, but they make beaches significantly more wheelchair accessible than they were previously. Some seashore recreation systems may offer beach wheelchairs that users can borrow for the day.
The mats are portable and can be relocated. Increasing numbers of beaches in Florida and California have installed them; availability should be listed on beach websites or included in informational recordings available by phone.
References
Assistive technology | Mobility mat | [
"Engineering"
] | 212 | [
"Design stubs",
"Design"
] |
73,623,970 | https://en.wikipedia.org/wiki/MSPI%20%28nerve%20agent%29 | MSPI is an irreversible acetylcholinesterase inhibitor. MSPI reacts with the acetylcholinesterase to form an aged enzyme adduct that can't be reactivated by cholinesterase reactivators.
See also
EA-2192
Guanitoxin
References
Acetylcholinesterase inhibitors
Imidazolium compounds
Methyl esters
Phosphoramidothioates
Zwitterions
Nerve agents | MSPI (nerve agent) | [
"Physics",
"Chemistry"
] | 93 | [
"Matter",
"Chemical weapons",
"Functional groups",
"Phosphoramidothioates",
"Zwitterions",
"Nerve agents",
"Ions"
] |
73,624,176 | https://en.wikipedia.org/wiki/Europium%28III%29%20phosphate | Europium(III) phosphate is one of the phosphates of europium, with the chemical formula of EuPO4. Other phosphates include europium(II) phosphate (Eu3(PO4)2) and europium(II,III) phosphate (Eu3Eu(PO4)3).
Preparation
Europium phosphate can be produced by the sol-gel method of europium(III) oxide. First, europium(III) oxide was dissolved in an equimolar amount of nitric acid, and then an excess of 10% phosphoric acid was added. The process also requires the addition of ammonia to adjust the pH to 4 and form a gel, which is then washed with water and heated to 1200 °C for a day.
Properties
Europium(III) phosphate is isotypic to CePO4 and crystallizes in the monazite structure type, in the space group P21/n (no. 14, position 2) with the lattice parameters a = 668.13(10), b = 686.18(9), c = 634.91(8) pm and β = 103.96(1)° with four formula units per unit cell. Its heat capacity is 111.5 J·K−1·mol−1 at 298.15 K, and its bulk modulus is 159(2) GPa.
References
Europium(III) compounds
Phosphates | Europium(III) phosphate | [
"Chemistry"
] | 304 | [
"Phosphates",
"Salts"
] |
73,624,621 | https://en.wikipedia.org/wiki/Orphan%20device | An orphan device is a product or an equipment intended for the prevention, prediction, diagnosis, support, treatment or management of a life-threatening or chronically debilitating disease with a low prevalence/incidence, most notably for rare diseases. Orphan medical technology is then considered as both the medical device (tool or equipment) and the connectivity of the device. Many orphan devices provide essential functions for patients with rare diseases, their carers, and the healthcare professionals using them. Nevertheless, there are very few medical devices that are specifically developed for rare diseases (in contrast to orphan medicinal products). At the same time, many patients and carers express a substantial unmet need for new medical devices for their conditions.
Orphan devices constitute a very diverse group of products, reflecting the broad field of rare diseases. Device needs for rare diseases vary from noninvasive markers for monitoring disease activity, wearables and tests that allow home monitoring of disease by patients and treatment side effects, or imaging enhanced functional scans. Devices are also needed to support quality of life and activities ofdaily living as best as possible, helping, for example, with rehabilitation, muscle support, or nutrition support. As such, there is a high need to connect patients, carers, and healthcare professionals to technology that can address these requirements.
The development of medical technologies for rare diseases faces many of the same challenges as developing orphan medicinal products, including the small number of patients, the geographical spread of patients, the lack of expertise on specific diseases, and the fact that most diseases are paediatric-onset. Some geographies have developed supportive specific orphan-device legislation. However, there is no harmonization between different geographies, and joint applications between Europe, the United States and Japan do not exist. Examples of existing orphan device legislation are the United States Food and Drug Administration (FDA) Humanitarian use device program, which designates medical devices to benefit patients in treating or diagnosing rare diseases. In Japan, the PMD Act outlines regulations for reviewing medical device applications, except for medical software programs which are independently regulated. Europe has no legislation specifically for medical devices for rare diseases despite the implementation in 2021 of new regulations for in vitro diagnostics and medical devices.
The approval process provided by the FDA and the Japanese Pharmaceuticals and Medical Devices Agency allows a medical device to be marketed with several incentives and limited prove of effectiveness. Like orphan drugs, most orphan devices would not be profitable to develop and produce without government assistance and regulatory incentives due to the small number of patients affected by these conditions. The assignment of orphan status to a disease and to devices developed to diagnose and treat it is a matter of public policy that depends on the country's legislation if any exists.
Definitions
United States
The FDA currently does not have a definition of orphan devices or orphan medical technology. The closest resembling definition is that of a humanitarian use device, which is "a medical device intended to benefit patients in the treatment or diagnosis of a disease or condition that affects or is manifested in not more than 8,000 individuals in the United States per year".
Europe
In the EU no definition of orphan devices or orphan medical technology exists. Orphan devices follow the same procedure as devices for common diseases, and have to adhere to the Medical Device Regulation.
Japan
In Japan drugs and medical devices are given the designation as an orphan drug or device based on the Act of Securing Quality, Efficacy, Safety of Pharmaceuticals, Medical Devices, Regenerative or Cellular Therapy Products, Gene Therapy Products, and Cosmetics "if they are intended for use in less than 50,000 patients in Japan and for which there is a high medical need".
Support for orphan devices
Several initiatives are currently supporting both research and the development of policies and incentives for orphan devices. Most notably, the International Rare Diseases Research Consortium (IRDiRC) has set up a Working Group specifically for medical technologies for rare diseases. In the United States, the SHIP-MD consortium examining unmet needs of pediatric medical device development and develops solutions to address those needs. In Europe, the CORE-MD project, review methodologies for the clinical evaluation of high-risk medical devices, also specifically for rare diseases and recommend new designs to set an appropriate balance between innovation, safety, and clinical effectiveness.
References
Medical devices | Orphan device | [
"Biology"
] | 863 | [
"Medical devices",
"Medical technology"
] |
73,625,081 | https://en.wikipedia.org/wiki/Asian%20Association%20on%20Remote%20Sensing | Asian Association on Remote Sensing (AARS) is a non-governmental organization established in 1981 to promote remote sensing in the Asia-Pacific region; it currently has members from 29 countries.
Members
Its members include:
Indian Society of Remote Sensing
Surveying & Spatial Sciences Institute
Malaysian Remote Sensing Agency
Japan Society of Photogrammetry and Remote Sensing
SPARRSO
Institute of Remote Sensing and Digital Earth
Korean Society of Remote Sensing
References
External links
Remote sensing organizations
Remote sensing
Geodesy | Asian Association on Remote Sensing | [
"Mathematics"
] | 93 | [
"Applied mathematics",
"Geodesy"
] |
73,627,447 | https://en.wikipedia.org/wiki/Introduction%20to%20Elementary%20Particles%20%28book%29 | Introduction to Elementary Particles, by David Griffiths, is an introductory textbook that describes an accessible "coherent and unified theoretical structure" of particle physics, appropriate for advanced undergraduate physics students. It was originally published in 1987, and the second revised and enlarged edition was published 2008.
Content (2nd edition)
Table of contents
History and Overview
Chapter 1: Historical Introduction to the Elementary Particles
Chapter 2: Elementary Particle Dynamics
Chapter 3: Relative Kinematics
Chapter 4: Symmetries
Chapter 5: Bound States
Quantitative Formulation of Particle Dynamics
Chapter 6: The Feynman Calculus
Chapter 7: Quantum Electrodynamics
Chapter 8: Electrodynamics of Quarks and Hadrons
Chapter 9: Quantum Chromodynamics
Chapter 10: Weak Interactions
Chapter 11: Gauge Theories
Appendices
Appendix A: The Dirac Delta Function
Appendix B: Decay Rates and Cross Sections
Appendix C: Pauli and Dirac Matrices
Appendix D: Feynman Rules
New content in the second addition includes "neutrino oscillations and prospects for physics beyond the Standard Model".
Reception
The first edition, reviewed by Gerald Intermann, earned praise for its "good use of examples as a means of discussing in detail useful problem-solving techniques that other texts leave for the student to discover."
Acknowledging it as a "a well-established textbook", an IAEA review said the second edition "...strikes a balance between quantitative rigor and intuitive understanding, using a lively, informal style... The first chapter provides a detailed historical introduction to the subject, while subsequent chapters offer a quantitative presentation of the Standard Model. A simplified introduction to the Feynman rules, based on a 'toy' model, helps readers learn the calculational techniques without the complications of spin. It is followed by accessible treatments of quantum electrodynamics, the strong and weak interactions, and gauge theories."
The Times Higher Education review said, "The first edition of this textbook was notable for providing a clear and logical overview of particle physics that was at the right level for advanced undergraduates... The contents of this revised edition are largely similar to those contained in the first edition and changes reflect the development of the subject in the intervening 20 years. As a result, some discussions have now been tightened or removed, and chapters describing neutrino oscillations and contemporary theoretical developments have been added." The review concluded, "Reading any section will always yield insights, and you can't go wrong with Griffiths as a guide. Who is it for? Advanced undergraduates, postgraduates, lecturers and anyone in the field of experimental particle physics."
Publication history
References
External links
, Preface | Physics Audio Books, video (4:11 minutes)
Physics textbooks
Quantum mechanics
1987 non-fiction books
2005 non-fiction books
2004 non-fiction books
Undergraduate education
Wiley (publisher) | Introduction to Elementary Particles (book) | [
"Physics"
] | 575 | [
"Quantum mechanics",
"Works about quantum mechanics"
] |
73,627,835 | https://en.wikipedia.org/wiki/Neodymium%28II%29%20hydride | Neodymium dihydride is an inorganic compound, with the chemical formula of NdH2, although it is an electride, and it is actually composed of Nd3+(e−)(H−)2. It is ferromagnetic.
Chemical properties
Neodymium dihydride reacts with lithium borohydride to obtain neodymium tetraboride:
NdH2 + 4 LiBH4 → NdB4 + 4 LiH + 7 H2↑
See also
Europium hydride
Ytterbium hydride
References
External reading
Struss, Arthur W.; Corbett, John D. Reaction of hydrogen with metallic and reduced halides. The requirement of delocalized electrons for reaction. Inorganic Chemistry, 1978. 17(4): 965-9. DOI:10.1021/ic50182a034
Neodymium(II) compounds
Metal hydrides
Ferromagnetic materials | Neodymium(II) hydride | [
"Physics",
"Chemistry"
] | 204 | [
"Electron",
"Inorganic compounds",
"Electrides",
"Ferromagnetic materials",
"Salts",
"Reducing agents",
"Materials",
"Metal hydrides",
"Matter"
] |
73,630,369 | https://en.wikipedia.org/wiki/Allogeneic%20cultured%20keratinocytes%20and%20fibroblasts%20in%20bovine%20collagen | Allogeneic cultured keratinocytes and fibroblasts in bovine collagen, sold under the brand name Gintuit, is a cellular therapy used for the treatment of mucogingival (the oral mucosa and gingival (gum) tissues of the mouth) conditions.
Common adverse reactions observed during clinical trials include sinusitis (sinus inflammation), nasopharyngitis (inflammation of the upper throat, upper respiratory tract infection, aphthous stomatitis (canker sores), and local surgery site reactions such as pain and redness.
Allogeneic cultured keratinocytes and fibroblasts in bovine collagen is a cellular sheet that consists of two layers, an upper layer composed of living human keratinocytes (the primary cell type in the skin's outer layer) and a lower layer constructed of bovine-derived collagen, human extracellular matrix proteins (molecules that support and give structure to cells), and living human dermal fibroblasts (skin cells that generate connective tissues). It is the first cell-based product made from allogeneic (cells derived from a donor source that is unrelated to the intended recipient) human cells and bovine collagen approved by the US Food and Drug Administration (FDA). It was approved for medical use in the United States in March 2012.
Medical uses
Allogeneic cultured keratinocytes and fibroblasts in bovine collagen is indicated for topical (non-submerged) application to a surgically created vascular wound bed in the treatment of mucogingival conditions in adults.
History
The efficacy of allogeneic cultured keratinocytes and fibroblasts in bovine collagen (Gintuit) was evaluated in two clinical studies in adults with insufficient gingival tissue. In each of the two studies, Gintuit was associated with an increase of at least 2 mm of gingival tissue in at least 50% of the study subjects. The overall clinical trial safety data for Gintuit included 121 subjects from both studies.
References
Medical treatments | Allogeneic cultured keratinocytes and fibroblasts in bovine collagen | [
"Biology"
] | 450 | [
"Cell therapies"
] |
73,631,860 | https://en.wikipedia.org/wiki/Twin%20towers%20%28architecture%29 | Twin towers are a concept in architecture where 2 similar looking towers are built in close proximity to each other. They have been an architectural motif in human civilization for millennia.
Early examples include the use of twin gate towers in urban and palatial architecture in Chinese cities from the Warring States period, when they were viewed as "signifiers of the celestial realm". In the medieval period, examples include the Seljuk Kharraqan towers, twin towers wrought in decorative brickwork that represent a prominent work in the art and architecture of Islamic Iran.
In the contemporary era, the Petronas Twin Towers in Kuala Lumpur, Malaysia are a particularly celebrated example of twin tower architecture that, from 1998 to 2003, were the tallest structure in the world. The twin towers that were part of the original World Trade Center in New York City, New York until 2001 are also very iconic, although infamous due to the September 11 attacks. Twin towers also recur in Chinese construction, where, while the structures still representing a relative rarity, architects and engineers have developed novel interlinking twinned structures such as the CCTV Headquarters.
In contemporary architecture, structurally connected twin towers with unequal heights have found particular favor among architects for their earthquake-resistant properties, due to such couplings yielding two differing vibration frequencies, enabling the twinned towers to support their counterparts at their more vulnerable frequencies.
References
Towers | Twin towers (architecture) | [
"Engineering"
] | 280 | [
"Architecture stubs",
"Structural engineering",
"Towers",
"Architecture"
] |
73,632,444 | https://en.wikipedia.org/wiki/Neohygrocybe%20pseudoingrata | Neohygrocybe pseudoingrata is a species of agaric (gilled mushroom) in the family Hygrophoraceae.
Distribution
The species is found in agriculturally unimproved, mesic grassland on acidic, neutral, and calcareous soils. It has been recorded in Slovakia and the Czech Republic.
Description
The species is pale greyish in colour. It has robust sporocarps. It has a distinct nitrous smell. The surface of the pileus is smooth or somewhat fibrillose.
References
Hygrophoraceae
Fungus species | Neohygrocybe pseudoingrata | [
"Biology"
] | 121 | [
"Fungi",
"Fungus species"
] |
73,634,096 | https://en.wikipedia.org/wiki/HD%20186756 | HD 186756, also known as HR 7521 or rarely 68 G. Telescopii, is a solitary orange hued star located in the southern constellation Telescopium. It has an apparent magnitude of 6.25, placing it near the limit for naked eye visibility, even under ideal conditions. Gaia DR3 parallax measurements imply a distance of 743 light years; it is currently approaching with a heliocentric radial velocity of . At its current distance, HD 186756's brightness is diminished by 0.34 magnitudes due to extinction from interstellar dust and it has an absolute magnitude of −0.96.
This is an evolved red giant star with a stellar classification of K1 III. It has 123% the mass of the Sun but it has expanded to 21.01 times the radius of the Sun. The object radiates 177 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of . HD 186756 is slightly metal deficient with an iron abundance of [Fe/H] = −0.13 (74% solar) and it spins too slowly for its projected rotational velocity to be measured accurately.
References
K-type giants
Telescopium
Telescopii, 68
186756
097491
7521
CD-53 08294 | HD 186756 | [
"Astronomy"
] | 274 | [
"Telescopium",
"Constellations"
] |
73,634,732 | https://en.wikipedia.org/wiki/Tartarian%20Empire | Tartarian Empire refers to a group of pseudohistorical conspiracy theories, including ideas of a "hidden past" and "mud floods" which originated as pseudoscientific Russian nationalism.
Tartary or Tartaria is a historical name for Central Asia and Siberia. Conspiracy theories assert that Tartary or the Tartarian Empire was a lost civilization with advanced technology and culture. This ignores the well-documented history of Asia, which Tartary refers to. In the present day, the Tartary region covers a region spanning from central Afghanistan to northern Kazakhstan, as well as areas in present Mongolia, China, and the Russian Far East in "Chinese Tartary".
Background
The theory of Great Tartaria as a suppressed lost land or civilization originated in Russia, with aspects first appearing in Anatoly Fomenko's new chronology in the mid-1970s and early 1980s, and then popularized by the racial occult history of Nikolai Levashov. In Russian pseudoscience, known for its nationalism, Tartaria is presented as the "real" name for Russia, which was maliciously "ignored" in the West. The Russian Geographical Society has debunked the conspiracy theory as an extremist fantasy, and far from denying the existence of the term, has used the opportunity to share numerous maps of "Tartary" in its collection. Since about 2016, conspiracy theories about the supposed lost empire of "Tartaria" have gained popularity on the Internet, divorced from its original Russian nationalist frame.
Conspiracy theory
The globalized version of the conspiracy theory is based on an alternative view of architectural history. Adherents propose that demolished buildings such as the Singer Building, the original New York Penn Station, and the temporary grounds of the 1915 World's Fair were actually the buildings of a vast empire based in Tartary that has been suppressed from history. Sumptuously styled Gilded Age buildings are often held out as really having been built by the supposed Tartaria. Other buildings, such as the Great Pyramids and the White House, are further held out as Tartarian buildings. The conspiracy theory only vaguely describes how such a supposedly advanced civilization which had reputedly achieved world peace could have fallen and been hidden.
In the conspiracy theory, the idea that a "mud flood" wiped out much of the world via depopulation and thus old buildings is common, supported by the fact that many buildings across the world have architectural elements like doors, windows and archways submerged many feet below "ground level". Both World War I and II are cited as a way in which Tartaria was destroyed and hidden, reflecting the reality that the extensive bombing campaigns of World War II did destroy many historic buildings. The general evidence for the theory is that there are similar styles of building around the world, such as capitol buildings with domes, or star forts. Also many photographs from the turn of the 20th century appear to show deserted city streets in many capital cities across the world. When people do start to appear in the photographs there is a striking contrast between the horse and cart dwellers in the muddy streets and the elaborate, highly ornate stone mega-structures which tower above the inhabitants of the cities, which is seen even in modern cities where extreme poverty is contrasted with skyscrapers.
Zach Mortice, writing for Bloomberg, believes that the theory reflects a cultural discontent with modernism, and a supposition that traditional styles are inherently good and modern styles are bad. He describes the theory as "the QAnon of architecture". Moritz Maurer, a religious scholar, links Tartarian imagery to "giant trees" theory, in which colossal, flat buttes are envisioned as the stumps of primordial "mother trees" cut down at some point in the past by unknown nefarious agents. Maurer attributes the lack of a clear narrative for both conspiracies to the image-based social media on which they are presented, describing it as "meme culture" and also comparing it to QAnon.
See also
Ancient astronauts
Hyperborea, in Greek mythology, a mythical people in the far north of the world
New chronology (Fomenko), claim that historical timescales have been falsified to hide evidence of 'Russian Horde' empire
Mongol Empire, stretched across east and central Asia in the 12th–13th centuries
References
Sources
Conspiracy theories
Fictional empires
History of Central Asia
History of Siberia
Pseudohistory | Tartarian Empire | [
"Technology"
] | 887 | [
"Free energy conspiracy theories",
"Science and technology-related conspiracy theories"
] |
73,635,681 | https://en.wikipedia.org/wiki/Hyperchaos | A hyperchaotic system is a dynamical system with a bounded attractor set, on which there are at least two positive Lyapunov exponents.
Since on an attractor, the sum of Lyapunov exponents is non-positive, there must be at least one negative Lyapunov exponent. If the system has continuous time, then along the trajectory, the Lyapunov exponent is zero, and so the minimal number of dimensions in which continuous-time hyperchaos can occur is 4.
Similarly, a discrete-time hyperchaos requires at least 3 dimensions.
Mathematical examples
The first two hyperchaotic systems were proposed in 1979. One is a discrete-time system ("folded-towel map"):
Another is a continuous-time system:More examples are found in.
Experimental examples
Only few experimental hyperchaotic behaviors have been identified.
Examples include in an electronic circuit, in a NMR laser, in a semiconductor system, and in a chemical system.
References
Chaotic maps
Nonlinear systems
Articles containing video clips | Hyperchaos | [
"Mathematics"
] | 217 | [
"Functions and mappings",
"Mathematical objects",
"Nonlinear systems",
"Mathematical relations",
"Chaotic maps",
"Dynamical systems"
] |
73,635,724 | https://en.wikipedia.org/wiki/Open%20Connect | Open Connect is a content distribution network specifically developed by Netflix to deliver its TV shows and movies to avoid traffic and fees.
Netflix provides physical appliances to internet service providers that allow them to avoid traffic during peak hours of streaming or sustain the anticipated ones. By shipping copies of content to these appliances ahead of time, the devices can store duplicates of titles, thereby reducing the network burden. Also, Netflix places its servers in locations with the highest number of subscribers and forms partnerships with ISP networks or IXPs.
Furthermore, Netflix adapts its content to the quality of the network. This is achieved by sending three copies of each title, each at a different quality level, to its servers. For example, if a user's ISP is overwhelmed or the Internet connection is poor, the system can select a lower-bitrate version of the title.
History
Netflix launched Open Connect in 2012. Since then, Netflix has spent over $1 billion to develop and distribute more than 8,000 Open Connect Appliances (OCA). The service started working on the free-of-charge distribution of OCAs in cooperation with ISPs. So far, more than 1,000 ISPs have acquired and installed OCAs, which has allowed them to save $1.25 billion by 2021.
In the case of an OCA that is hosted at an IXP, Netflix maintains ownership of the OCA and is responsible for covering its own expenses such as power consumption, colocation fees, cross-connect fees, and other related costs. Netflix has installed OCAs in over 52 IXPs around the world, enabling a connection with any ISP.
Deployment
IX deployment
Netflix deploys OCAs within IXPs located in major Netflix markets around the world. These OCAs are interconnected with ISPs present at the same location through free public or private peering.
Embedded deployment
OCAs are directly installed within ISP networks. While Netflix supplies the server hardware at no cost, ISPs are responsible for providing space, power, and connectivity.
Requirements
Three primary factors that determine the number of appliances that need to be deployed are:
The network architecture requirements
The maximum amount of Netflix traffic to be delivered from a particular site
The availability and failover options that can be implemented at that site.
Hardware
Open Connect is a combination of local servers, referred to as OCAs, and additional infrastructure. Netflix has developed storage appliances that are used to store the content in many IX locations globally and are embedded at larger ISP partner locations. The storage holds up to 350 TB, therefore, if something from storage becomes popular, Netflix will move that title onto the other server called flash server which serves large traffic.
Software
These are used software for designing Open Connect Appliance Software:
Operating system – FreeBSD
Web server – NGINX
Routing Intelligence Proxy – BIRD internet routing daemon
IP support – IPv4 and IPv6
Other software handle content management and transmits information regarding the system's health and other statistics to the Open Connect supporting services at Netflix.
Benefits
Open Connect permits ISPs to circumvent the expenses associated with transit charge and costly international backhaul capacity by delivering the traffic directly to the ISP instead of through a transit link.
If an ISP has multiple OCAs in place, it is possible to transmit the traffic to the consumer from a server nearby, which reduces costs for the core network capacity.
Open Connect assists wideband networks in retaining their customers by preventing slow speed and instability. Moreover, if one element fails, it is possible to redirect the traffic to other servers, which minimizes the risk of downtime.
Netflix invests in delivery infrastructure, such as OCAs, as well as compression technology, to optimize the delivery of its content and support the growing global demand for video content and broadband internet access.
The OCAs report their health values and receive their configurations from the Open Connect supporting services (if it is reachable from the Network Operations Center). Netflix also automatically incorporates feedback on the health information into its content routing decisions.
References
External links
Netflix
Content delivery networks
Streaming media systems | Open Connect | [
"Technology"
] | 823 | [
"Streaming media systems",
"Telecommunications systems",
"Computer systems"
] |
73,636,178 | https://en.wikipedia.org/wiki/Modifiable%20temporal%20unit%20problem | The Modified Temporal Unit Problem (MTUP) is a source of statistical bias that occurs in time series and spatial analysis when using temporal data that has been aggregated into temporal units. In such cases, choosing a temporal unit (e.g., days, months, years) can affect the analysis results and lead to inconsistencies or errors in statistical hypothesis testing.
Background
The MTUP is closely related to the modifiable areal unit problem or MAUP, in that they both relate to the scale of analysis and the issue of choosing an appropriate analysis. While the MAUP refers to the choice of spatial enumeration units, the MTUP arises because different temporal units have different properties and characteristics, such as the number of periods they contain or the amount of detail they provide. For example, daily sales data for a product can be aggregated into weekly, monthly, or yearly sales data. In this case, using monthly data instead of daily data can result in losing important information about the timing of events, and using yearly data can obscure short-term trends and patterns. However, the daily data in the example may have too much noise, temporal autocorrelation, or be inconsistent with other datasets. With only daily data, conducting an analysis accurately at the hourly rate would not be possible. In addition, the Modifiable Temporal Unit Problem can also arise when the time units are irregular or when the data is missing for some periods. In such cases, the choice of the time unit can affect the amount of missing data, which can impact the accuracy of the analysis and forecasting.
Overall, the Modifiable Temporal Unit Problem highlights the importance of carefully considering the time unit when analyzing and forecasting time series data. It is often necessary to try different time units and evaluate the results to determine the most appropriate choice.
Temporal autocorrelation
Temporal autocorrelation refers to the degree of correlation or similarity between values of a variable at different time points. It examines how a variable's past values are related to its current values over a sequence of time intervals. High temporal autocorrelation implies that past observations influence future observations, while low autocorrelation suggests that current values are independent of past values. This concept is often used in time series analysis to understand patterns, trends, and dependencies within a time-ordered dataset, helping to make predictions and infer the underlying dynamics of a system over time. By adjusting the temporal unit used to bin the data in the analysis, temporal autocorrelation can be addressed.
Implications
Crime
The impact of MTUP on crime analysis can be significant, as it can affect the accuracy and reliability of crime data and its conclusions about crime patterns and trends. For example, suppose the temporal unit of analysis is changed from days to weeks. In that case, the number of reported crimes may decrease or increase, even if the underlying pattern remains constant. This can lead to incorrect conclusions about the effectiveness of crime prevention strategies or the overall level of crime in a given area.
Food accessibility
The MTUP can also have an impact on food accessibility. This issue arises when the temporal unit of analysis is changed, leading to changes in the patterns and trends observed in food accessibility data. For example, if food accessibility data is analyzed from different years or aggregated differently, then the results of a study are likely to be impacted. This can affect our understanding of the availability of food in different areas over time, and can result in incorrect or incomplete conclusions about food accessibility.
Epidemiology
The MTUP can affect our understanding of the incidence and prevalence of diseases or health outcomes in different populations over time, resulting in incorrect or incomplete conclusions about the public health situation. The timeframe chosen for collecting and analyzing public health data is something that needs to be considered by researchers.
Suggested solutions
To address the MTUP, it is important to consider the temporal resolution of the data and choose the most appropriate temporal unit based on the research question and the goals of the analysis. In some cases, it may be necessary to aggregate or interpolate the data to a consistent temporal unit. Additionally, it may be helpful to use multiple temporal units or to present results for different temporal units to demonstrate the sensitivity of the results to the choice of temporal unit.
See also
Arbia's law of geography
Boundary problem (spatial analysis)
Coastline paradox
Concepts and Techniques in Modern Geography
Chronology
Ecological fallacy
Facility location problem
Geographic information systems
Historical GIS
Neighborhood effect averaging problem
Torsten Hägerstrand
Spatial epidemiology
Technical geography
Time geography
Timestamp
Tobler's first law of geography
Tobler's second law of geography
Uncertain geographic context problem
References
Bias
Geographic information systems
Problems in spatial analysis | Modifiable temporal unit problem | [
"Technology"
] | 951 | [
"Information systems",
"Geographic information systems"
] |
73,636,853 | https://en.wikipedia.org/wiki/Boletus%20nobilis | Boletus nobilis, the noble bolete, is a species of edible basidiomycete mushroom of the genus Boletus found in eastern United States. Morphologically close to Boletus edulis, it is distinguished by an elongated stem, a beige skin and white pores, even when old.
Taxonomy
The species was described as Boletus nobilis by Peck in 1910. For many years Boletus nobilis was considered a subspecies or form of Boletus edulis. Phylogenetic analysis has shown that Boletus nobilis is a separate species and a member of a clade closely related to Boletus separans.
Morphology
Basidiocarp: as with other boletes, the size of the fruitbody is variable, but it does not reach the prominence of Boletus edulis. Flesh is "thin even in very large specimens"
Hymenium: pores white, even when old, without the "greenish tint" of B. edulis. Pores not depressed around the stipe.
Pileus:7-20cm wide, convex becoming plane with age, dry, with a yellowish to reddish brown skin, lighter in the center of the cap, becoming lighter with age to pale ochraceous.
Stipe: the stipe is elongated, sometimes bulbous, and its general color white, sometimes "with a lilaceous tinge". It is finely reticulated below the hymenium, the reticulation being shallow.
Spore print: dull ochre brown to dull rusty brown.
Distribution and habitat
Boletus nobilis is found under oak and beech trees on the East Coast of the United States: Appalachia, Pennsylvania, Ohio from summer to fall.
Edibility
Boletus nobilis is edible, but not as desirable as the lookalike boletes. It can be preserved and cooked or frozen.
See also
List of Boletus species
List of North American boletes
References
External links
Edible fungi
nobilis
Fungi described in 1910
Fungi of North America
Taxa named by Charles Horton Peck
Fungus species | Boletus nobilis | [
"Biology"
] | 428 | [
"Fungi",
"Fungus species"
] |
73,636,988 | https://en.wikipedia.org/wiki/Scott%20W.%20Nixon | Scott W. Nixon (1943 – May 21, 2012) was an ecosystem ecologist whose research primarily focused on nitrogen and eutrophication in coastal and estuarine ecosystems. He was the first to clearly define coastal eutrophication. Nixon was a faculty member of the University of Rhode Island’s Graduate School of Oceanography from 1969 until his death. Throughout his life, he also served important roles in many organizations and committees, including as the director of Rhode Island Sea Grant, editor-in-chief of Estuaries, and a member of the National Research Council's Ocean Studies Board.
Education
In 1965, Nixon obtained a Bachelor of Arts degree in biology from the University of Delaware. Under the mentorship of Howard T. Odum, he received a doctorate in Botany from the University of North Carolina in Chapel Hill in 1970. His dissertation discussed field and laboratory microcosm results from salinas in Puerto Rico.
Career
Identified by the dean John Knauss as having potential, Nixon was hired by the University of Rhode Island's Graduate School of Oceanography as a research associate a year prior to obtaining his doctorate and began working as an assistant professor in 1970. In his early days at the University of Rhode Island, Nixon worked with Candace Oviatt and Michael Pilson, eventually starting the Marine Ecosystem Research Lab together in 1976. MERL is home to several mesocosms, where long term experiments on Narragansett Bay are performed.
Nixon was an elected member of the board of Association for the Sciences of Limnology and Oceanography from 1984 – 1987. He was the coordinator, then director of the Rhode Island Sea Grant from 1986 – 2000. An active member of the Coastal and Estuarine Research Federation, he was editor-in-chief of their journal Estuaries from 1988 – 2005 and additionally an editor on the Journal of Sea Research from 1999 until his death. He additionally participated in the New England Estuarine Research Society. He was appointed the UNESCO/Cousteau Chair in Coastal Ecology and Global Assessment in 2004 and was a long time participant in committees for the National Research Council performing review and advisory for a variety of coastal scientific and restorative projects.
Nixon advised 37 graduate students during his career, while additionally working with 4 students at the time of his death.
Nixon was known to value performing research that could be applied to restoration efforts and met the needs of the affected communities, and was active in service activities with those who worked on coastal management, considering alternatives in a way that had him sometimes labeled contrarian. Nixon had a reputation for his skill in communicating difficult scientific concepts to a general audience and recontextualizing research to find where it fit in the bigger picture.
The University of Rhode Island's Coastal Institute holds the Scott W. Nixon Lecture on coastal research annually in his honor, choosing speakers whose research re-examines scientific consensus.
Research
Nixon's first research often collaborated with Oviatt and focused mainly on the ecology of estuaries and salt marshes near the University of Rhode Island campus, including field studies on the metabolisms of mussels, eelgrass, and fish. Bissel Cove and other locations throughout Narragansett Bay were frequent sites of interest. The collaboration between Nixon and Oviatt on a whole-ecosystem study of Bissel Cove was one of the first whole-ecosystem studies published.
In 1972, Nixon and Oviatt began to more closely study carbon and nitrogen in Bissel Cove. After this, Nixon began to depart from mostly studying metabolisms of specific coastal marine species to studying nutrient dynamics in coastal marine environments, especially their sediments.
In 1977, Nixon published a book with fellow field ecologist James Kremer of the University of Connecticut on using computers to create an ecosystem model for Narragansett Bay. The book, A Coastal Marine Ecosystem, was intended to help connect ecologists with numerical modeling.
In some of his earliest work on eutrophic systems, Nixon published a report for the Rhode Island Water Resources center on the Pettaquamscutt River’s Upper Pond in 1981. He delved further into the nitrogen cycle and eutrophication with several papers during the early 1980s, oftentimes second author to one of his graduate students, like Sybil Seitzinger and Veronica Berounsky.
In the later 1980s, Nixon began to broaden his scope. In his earlier career, Nixon rarely strayed from studies outside the Narragansett Bay area, but he began to perform a study on Chesapeake Bay, wrote a literature review on lakes, coasts, and oceans around the world, and contributed to a special edition of Ambio on marine eutrophication discussing its international significance.
Nixon published fewer papers in the 1990s, but published one of his most significant in 1995 defining the growing international problem of coastal eutrophication. This paper clearly identified and separated the causes of coastal eutrophication from its indicators.
Awards
Bostwick H. Ketchum Award for Coastal Excellence from Woods Hole Oceanographic Institute, 1992
Odum Lifetime Achievement Award from the Estuarine Research Federation, 2003
Posthumous Distinguished Naturalist from the Rhode Island Natural History Survey, 2013
Citation for Scientific Excellence from the Association for the Sciences of Limnology and Oceanography, 2013
References
1943 births
2012 deaths
Date of birth missing
American ecologists
Biogeochemists
Place of birth missing
Place of death missing
University of Delaware alumni
University of North Carolina at Chapel Hill alumni
University of Rhode Island faculty
Ecology journal editors | Scott W. Nixon | [
"Chemistry"
] | 1,107 | [
"Geochemists",
"Biogeochemistry",
"Biogeochemists"
] |
73,637,182 | https://en.wikipedia.org/wiki/Portillo%20C%C3%A1ceres%20v%20Paraguay | Portillo Cáceres v Paraguay (Communication No.2751/2016) was a case decided by the United Nations Human Rights Committee in 2019.
The case was initiated by a group of farmers in Paraguay who lived next to soybean plantations that had been using illegal agrochemicals. Contamination from negligent practices had resulted negative health effects, including the death of one farmer, Rubén Portillo Cáceres, and the poisoning of 22 others as well as negative impacts on the livelihoods of families living in the area. Despite an investigation by local and state officials finding evidence of wrongdoing, the state did not put environmental protection measures into effect and large amounts of chemicals continued to be released near the victims' homes.
In a resolution on 9 August 2019, the committee ruled in favor of the farmers, finding that their rights to life, privacy, family life, and residence were violated, and that Paraguay did not adequately demand compliance with environmental regulations or repair the damage caused.
Portillo Cáceres v Paraguay is a landmark court case in international toxics regulation. It marked the first instance of the United Nations Human Rights Committee recognizing that a state can violate its obligations under the International Covenant on Civil and Political Rights by failing to take action in cases of environmental harm. Paraguay was the first country in the world to be condemned by the Human Rights Committee for the death of a person from pesticide poisoning.
Background
94% of arable land in Paraguay is dedicated to the agricultural production of commodities such as soybeans, corn and cotton. Paraguay is the world's seventh-largest producer of transgenic soybeans, a crop frequently fumigated with pesticides such as bifenthrin, chlorpyrifos, paraquat and atrazine. Between 2011 and 2013, the import of pesticides to Paraguay nearly quadrupled, from 8.8 to 32.4 million liters.
Yerutí is a campesino colony founded by Paraguay in 1991 on land that an education minister of dictator Alfredo Stroessner surrendered in compensation for the embezzlement of public funds. While the colony has 223 lots, by 2019 there were only 34 registered properties, with industrial soybean fields occupying the untitled public land. Despite Agrarian Reforms meant to prevent the practice, much of the land is sold or leased to soybean plantations run by Brazilians and Brasiguayos. The widespread use of agrochemicals in Yerutí has impacted living conditions, domestic economies and the health of residents. Contamination of aquifers and water sources rendered the Yerutí and Kuairû streams unusable for fishing. Residents also experienced the deterioration of their crops, losing fruit trees, as well as the death of their livestock.
Pesticide poisoning incident
Rubén Portillo Cáceres, a farmer from the village of Colonia Yerutí in Canindeyú Department of eastern Paraguay, lived with his family on property adjacent to the transgenic soybean fields of Condor Agricola and Hermanos Galhera. During the soybean fumigation season at the beginning of 2011, the 26-year-old farmer fell ill, experiencing headaches, vomiting, and diarrhea. Three days later, on 6 January 2011, he died while on his way to the hospital in Curuguaty. His death was determined to be the result of toxic levels of pesticides in his system. Another 22 other residents of the village also became ill, including Portillo Cáceres's two-year-old son, all of whom were admitted to the hospital.
Investigation
Following Rubén's death and the mass poisoning incident, Curuguaty Hospital director Angie Duarte collected blood and urine samples from the victims and contacted the Prosecutor's Office, the National Service for Plant and Seed Quality and Health, and the Ministry of Environment. The Prosecutor's Office office began an investigation and government inspectors arrived on 13 January. They documented several violations of environmental laws, finding that the expansive soybean farming operations that bordered the family farm were not separated by required buffer zones. Soybeans had also been planted up to the edge of community walkways and there were no protective strips of vegetation to shield residents from pesticides. Inspectors conducted tests for chemicals and found evidence of restricted or banned agricultural insecticides in the Portillo Cáceres family's well water, including aldrin, lindane, and endosulfan. The concentration of lindane, a chemical related to the appearance of non-Hodgkin lymphoma, was three times the limit established for humans by the World Health Organization.
The two agribusinesses involved in the cultivation of soybeans around Yerutí, Condor SA/KLM SA (Condor Agricola) and Hermanos Galhera Agrovalle del Sol S.A/Emmerson Shinin (Hermanos Galhera), were owned by Brazilians and found to have engaged in negligent practices. Hermanos Galhera supplies soybeans to the multinational agribusinesses ADM, Cargill and Bunge Limited. The investigation determined that freshwater sources had been contaminated by chemical residues, finding chemical containers on the ground and citing poor management practices. The corporations did not possess environmental permits for their operations and were washing their spraying equipment in local streams. According to one of the inspectors, neither of the corporations met "the most basic standards of environmental control". The two firms were fined, but denied responsibility and their cases were later dropped following an appeal.
Legal history
District of Curuguaty
On 14 January 2011, the family of Portillo Cáceres and other farming families impacted by the poisoning filed an amparo, which is a legal action aimed at protecting constitutional rights. While prosecutor Miguel Ángel Rojas repeatedly requested an autopsy for Portillo Cáceres and the medical records of the victims, he did not receive them. Evidence that the well water contained agrochemicals was also excluded from the investigation. While seven Brazilian citizens were accused in the case, none of them were the managers or owners of the Condor Agricola or Hermanos Galhera farms. The District of Curuguaty court ruled on 15 April 2011 that both the National Plant and Seed Quality and Health Service as well as the Ministry of the Environment had failed in their duties and enabled the cause of serious physical harm to the complainants.
Despite the court's decision, the soybean agribusinesses continued using large amounts of pesticides without environmental protection measures or permits. Claims by the family of Portillo Cáceres were ignored by the State of Paraguay for three years. Rubén's sister Norma, along with the other victims of agrochemical poisoning, then submitted a petition to the Human Rights Committee of the United Nations.
United Nations Human Rights Committee
The Human Rights Committee addressed the case's admissibility before considering its merits. Paraguay argued that domestic remedies had not been exhausted by the complainants and that HRC did not possess ratione materiae jurisdiction as the right to a healthy environment is not recognized by the International Covenant on Civil and Political Rights. The HRC found the complaint admissible, citing the lack of progress in the case over eight years and noting that the claim pertained to the rights to life, the rights to private and family life, and the right to home.
The Human Rights Committee issued a resolution on 9 August 2019. The committee concluded that the response by the government of Paraguay to illegal fumigation was inadequate and had violated the human rights of the victims. The resolution found that the government had specifically violated the right to life, the right to family life, and the right to remedy from harm. The resolution found that no progress had been made in the eight years since the events were initially reported and emphasised that Paraguay did not conduct an autopsy for Ruben despite requests to do so on four separate occasions. The resolution also noted that the Paraguayan government had not published the results of urine and blood tests that were conducted on those who had been poisoned.
The resolution condemned the Paraguayan government for its failure to sanction the corporations involved and ordered the state to conduct an investigation into agrochemical fumigation and to levy administrative and criminal penalties against those responsible. Specifically, the committee recognized that the failure of a state to take action "against environmental harm can violate its obligations to protect the rights to life and to private and family life under Articles 6 and 17 of the International Covenant on Civil and Political Rights". Paraguay was the first country in the world to be condemned by the United Nations Human Rights Committee for the death of a person from pesticide poisoning. The resolution marked the first time that the United Nations Human Rights Committee recognized a connection between environmental protection and the right to life. The decision relied on General Comment No. 36 on the Right to Life, which includes language defining the relationship between the environment and human rights.
Aftermath
While Paraguay was sanctioned by the United Nations in the case, it was ultimately a formality. As of 2022, there has been no penalty issued for Rubén's death and industrial soybean farming continues to operate up to the border of the family farm. Both Condor Agricola and Hermanos Galhera continue agricultural operations in the Yerutí area.
Another opinion of the Human Rights Committee in 2021, in the case Benito Oliveira Pereira et al. v. Paraguay , found that extensive pesticide use by agricultural companies had violated the rights of the Campo Agua'ẽ indigenous community of the Ava Guaraní people to their lands and residence. The Pereira case was emblematic because the notion of "domicile" was applied to an indigenous community in regard to its relationship with its land and territory.
See also
Teitiota v Chief Executive Ministry of Business, Innovation and Employment
United Nations Declaration on the Rights of Peasants
Notes
References
External links
Text of full decision
Video including interviews with family members, Global Witness
2019 in case law
2019 in Paraguay
Toxic effects of pesticides
Pesticide regulation
Human rights abuses in Paraguay
Soybean industry
2019 in the United Nations
United Nations resolutions
United Nations Human Rights Committee case law | Portillo Cáceres v Paraguay | [
"Chemistry"
] | 2,055 | [
"Regulation of chemicals",
"Pesticide regulation"
] |
73,637,313 | https://en.wikipedia.org/wiki/Biphytane | Biphytane (or bisphytane) is a C40 isoprenoid produced from glycerol dialkyl glycerol tetraether (GDGT) degradation. As a common lipid membrane component, biphytane is widely used as a biomarker for archaea. In particular, given its association with sites of active anaerobic oxidation of methane (AOM), it is considered a biomarker of methanotrophic archaea. It has been found in both marine and terrestrial environments.
Chemical structure
Glycerol dialkyl glycerol tetraethers (GDGT) are major membrane lipids synthesized by archaea and some bacteria. In particular, isoprenoid GDGTs are characterized by isoprenoid carbon chains connected to the glycerol molecules by ether bonds. Biphytane is produced by the chemical cleavage of the ether bonds within isoprenoid GDGT (GDGT-0). It is composed of isoprene units bound by ether bonds with six isoprene units (or two phytanes) linked together by a head-to-head linkage.
Biphytane can be found in cyclic forms containing one to three pentacyclic rings when derived from isoprenoid GDGTs with such biosynthetically cyclized isoprenoid carbon skeletons. In most analyzed samples from the environment, the acyclic form with biphytane as the isoprenoid carbon chain is typically the most abundant form. Hence, in this article, biphytane is used to refer to the acyclic form unless stated otherwise.
Biological origin
As it occurs within GDGT, biphytane has been detected in the water column, marine sediments, hydrothermally-influenced sediments, cold seep sediments dominated by anaerobic oxidation of methane activity, and limestone. Though it had been primarily studied in aquatic settings, recent studies have also started investigating terrestrial environments, such as peat bogs where the source of biphytane was identified as methanogenic peat archaea. Studies have reported the detection of biphytane in petroleum as well.
While early studies had considered GDGTs (and hence biphytane) to be biomarkers of extremophilic archaea, both indirect and direct evidence of GDGT originating from archaea of mesophilic marine environments or lacustrine environments with non-extreme pH and salinity have been available since the late 1970s. Because biphytane in particular has been widely detected in sties of active AOM activity, it is considered a biomarker of methanotrophic archaea.
Analogous to sterols in eukaryotic membranes, GDGT plays a similar role in improving the rigidity of archaeal cell membranes. Supporting this, it has been reported that thermophiles increase the degree of cyclization with increasing growth temperatures to further improve membrane fluidity.
Measurement techniques
Typically, biphytane measurement is performed as an indirect analysis of GDGT. When chemically deriving biphytane from such ether lipids, the ether bonds are first cleaved using hydrogen iodide (HI), boron trichloride (BCl3), or boron tribromide (BBr3) that produces alkyl halides. Then, the alkyl halides are either reduced to saturated hydrocarbons using HI/NaSCH3 or LiAlH4 or converted to methylthioesthers with NaSCH3. The obtained saturated or derivatized hydrocarbons can subsequently be separated and measured using standard gas chromatography-mass spectrometry (GC-MS) procedures.
Alternatively, direct analysis of GDGT can be done with liquid chromatography but, when further structural characterization is required, MS fragments characteristic of biphytane can be obtained via high-performance liquid chromatography linked to tandem mass spectrometry (HPLC-MS/MS).
The diagnostic mass spectral fragment ions for biphytane are m/z 197, 259, 267, 323, 383, 393, and 463. Because the cyclic biphytanes yield different mass spectral fragment ions, the modified forms of biphytane present in a sample can be differentiated.
Application as a biomarker
Biphytane is considered to have a relatively high stability given its detection in high abundance within both recent and ancient sediments and petroleum, suggesting its ability to persist thermal maturation. Whether biphytane degrades to shorter isoprenoids over time remains unclear.
Biphytane is a well-established biomarker of archaea since it is found exclusively in archaea and all major groups except for halophilic Archaea. When combined with other analyses, it could be used to gain further insight into the analyzed sample. For instance, the abundance ratio of the biphytane (both acyclic and cyclic) to phytane has been used to distinguish between different groups of anaerobic methanotrophic archaea (ANME) from marine sediments given its higher abundance in ANME-1 than -2.
Alternatively, δ13C measurements could be combined to further confirm the origin. Because methanotrophs utilize isotopically light carbon sources, they are characterized by very negative carbon isotope values (i.e. depleted in 13C). For example, by comparing δ13C values of biphytanic diacids and GDGT-derived biphytane from the same seep limestones, a study inferred that, despite the chemical similarity of the compounds, they likely were derived from different sources; while the biphytanic diacids were mostly derived from methane-oxidizing euryarchea, the biphytanes were from mixed sources.
Case study: Late Archean sediments
In 2006, Ventura et al. measured solvent-extractable hydrocarbons with GC-MS from metasedimentary rocks sampled from the Tisdale and Porcupine Assemblage (2,707 to 2685 Ma) near Timmins, ON, Canada. From the extracted samples, the authors measured biphytane, cyclic biphytanes, and derivatives of biphytanes. Because post-Archaean deposition of the compounds could be ruled out given the reduced adsorptive capacity and restricted porosity of the sediments, the authors were able to conclude that the presence of biphytane, along with other molecular fossils, suggests the existence of archaea in the Late Archean sedimentary environments and in subsurface hydrothermal settings.
References
Terpenes and terpenoids | Biphytane | [
"Chemistry"
] | 1,413 | [
"Organic compounds",
"Biomolecules by chemical classification",
"Terpenes and terpenoids",
"Natural products"
] |
73,637,362 | https://en.wikipedia.org/wiki/Ash%20Creek%20State%20Wildlife%20Area | The Ash Creek State Wildlife Area is a protected region managed by the California Department of Fish and Wildlife (CDFW) in the heart of Big Valley. Spanning approximately 14,500 acres, it comprises various natural habitats and serves as a vital sanctuary for diverse plant and animal species.
Overview
Previously known as Ash Creek Wildlife Refuge, the area was renamed to Ash Creek State Wildlife Area after the California Department of Fish and Game licensed waterfowl hunting within its boundaries. It is one of the most remote, least improved, and pristine wildlife areas managed by the CDFW.
Habitat
The Ash Creek State Wildlife Area primarily consists of freshwater wetlands, which are formed by the seasonal flow of six streams, including Ash Creek. The region contains 3,000 acres of natural wetlands, vernal pools, and upland sagebrush. The wildlife area boasts the largest acreage of vernal pools in the watershed, providing a unique habitat for various plant and invertebrate species.
Flora and fauna
Various mammal and bird species inhabit the Ash Creek State Wildlife Area. Mammals include pronghorn antelope, beaver, and bobcat. Bird species range from waterfowl, sandhill cranes, falcons, sage grouse, short-eared owls, to bald eagles.
Recreational activities
The Ash Creek State Wildlife Area is popular among hunters, who travel from across California and neighboring states to hunt waterfowl during fall and winter. Other recreational activities available include fishing and bird watching. Ash Creek offers opportunities for catching local trout, and bird watching during fall and spring migration.
Historic sites
Two historic barns, remnants of a time when the area was a working ranch, can be accessed via a county road from the east.
Access and routes
Visitors can travel to via paved roads around the Ash Creek State Wildlife Area, beginning at the mill north of Bieber, California. The route offers views of the wetlands and a chance to explore the historic barns. Visitors can also find refreshments and a picnic spot at Adin Supply, a market located on the bank of Ash Creek in the town of Adin.
References
Wildlife
California Department of Fish and Wildlife areas
Nature reserves in California | Ash Creek State Wildlife Area | [
"Biology"
] | 433 | [
"Animals",
"Wildlife"
] |
59,910,872 | https://en.wikipedia.org/wiki/Moorella%20perchloratireducens | Moorella perchloratireducens is a thermophilic, anaerobic, Gram-positive and endospore-forming bacterium from the genus Moorella, which has been isolated from an underground gas storage tank in Russia. One of the main characteristics of this microorganism is that it is able to completely reduce chlorate and perchlorate to chloride and oxygen.
References
Thermoanaerobacterales
Bacteria described in 2008
Thermophiles
Anaerobes | Moorella perchloratireducens | [
"Biology"
] | 103 | [
"Bacteria",
"Anaerobes"
] |
59,911,014 | https://en.wikipedia.org/wiki/Systematic%20Reviews%20in%20Pharmacy | The Systematic Reviews in Pharmacy is a monthly peer-reviewed open-access medical journal covering pharmaceutics, biopharmaceutics, pharmaceutical chemistry, pharmacognosy, pharmacology, pharmaceutical analysis, pharmacy practice, clinical and Biomedical sciences.
Abstracting and indexing
The journal is abstracted and indexed in:
According to Scopus, the journal has a 2019 CiteScore of 3.9
References
External links
Open access journals
Monthly journals
English-language journals
Pharmacology journals
Academic journals established in 2009
2009 establishments in Malaysia
Medknow Publications academic journals
Biomedical engineering journals | Systematic Reviews in Pharmacy | [
"Engineering",
"Biology"
] | 122 | [
"Biological engineering",
"Bioengineering stubs",
"Biotechnology stubs",
"Medical technology stubs",
"Medical technology"
] |
59,912,350 | https://en.wikipedia.org/wiki/Polysuccinimide | Polysuccinimide (PSI), also known as polyanhydroaspartic acid or polyaspartimide, is formed during the thermal polycondensation of aspartic acid and is the simplest polyimide. Polysuccinimide is insoluble in water, but soluble in some aprotic dipolar solvents. Its reactive nature makes polysuccinimide a versatile starting material for functional polymers made from renewable resources.
The name is derived from the salt of succinic acid, the structurally related succinate.
Production
The production of polysuccinimide was reported by Hugo Schiff as early as 1897. When dry aspartic acid was heated for about 20 hours at 190 °C to 200 °C, a colorless product was obtained. Above 200 °C, a weak yellowing occurs, the yield was almost quantitative.
In the experiments by Hugo Schiff, oligomers and low-molecular polymers were formed in a solid state reaction by polycondensation upon water elimination. This is generally the case in the absence of strong acids, which suppress the thermal decomposition of free amino end groups and thus chain interruption reactions. The formation of the polyimide polysuccinimide can be followed by the intensive absorption band in the infrared spectrum at 1714 cm−1. Many process variants described in the patent literature yield besides a relatively low degree of polymerization often branched and yellow to brown discolored products.
Recent work has focused on increasing the molar mass and achieving a linear chain structure while avoiding decomposition reactions. With a simple "oven process" in which a mixture or paste of crystalline aspartic acid and concentrated phosphoric acid or polyphosphoric acid in a thin layer is heated to 200 °C for 2 to 4 hours, polysuccinimide is produced with molar masses in the range of 30,000 g/mol and cream white shade. The implementation of the polycondensation in several steps (precondensation, comminution, postcondensation), with other dehydrating substances (for example zeolites, triphenyl phosphite) or in the presence of solvents (for example propylene carbonate) provides higher molecular weight products with molar masses in the range of 10,000 to 200,000 g/mol. However, the patent literature does not address the polymer morphology, in particular the degree of branching.
A recent patent describes the simple preparation of high molecular weight, virtually colorless and linear, unbranched polysuccinimide. For this purpose, aspartic acid, which is present as crystalline zwitterion and practically water-insoluble, is firstly dissolved with an aqueous, volatile acid (preferably hydrochloric acid) and mixed with phosphoric acid as condensing agent. The resulting homogeneous solution is evaporated at 120 °C and the resulting glassy mass is then polycondensed at 180 °C to 200 °C for at least one hour. The phosphoric acid is washed out and the dried polysuccinimide is converted by mild alkaline hydrolysis into water-soluble polyaspartic acid; the molar mass of which can be determined by gel permeation chromatography. The process provides reproducible polysuccinimide with molar masses above 100,000 g/mol.
Synthetic routes for polysuccinimides based on maleic acid monoammonium salt, maleic anhydride and ammonia or based on the intermediately formed maleic acid monoamide achieved only low molar masses of a few 1,000 g/mol and yielded colored products. The same was the case for "green" process variants in supercritical carbon dioxide and while avoiding mineral acids as catalysts.
Due to the lower cost of maleic anhydride and ammonia, starting materials produced from fossil raw materials, no L-aspartic acid (of biogenic origin) is used in the production of the commercial product Baypure® polysuccinimide either.
Properties
Polysuccinimide is produced as an odourless, non-hygroscopic, cream-white to brown powder which is soluble in aprotic dipolar solvents such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, triethylene glycol or mesitylene/sulfolane mixtures. Polysuccinimide hydrolyses in water only very slowly. In diluted alkaline media (e.g. 1M sodium hydroxide solution), hydrolysis takes place in α- and β-position of the succinimide (2,5-pyrrolidinedione) ring structures and racemization follows at the chiral center of the aspartic acid, yielding the water-soluble sodium salt of the poly(α, β)-DL-aspartic acid. The α form is formed to approx. 30%, the β form to approx. 70% in random arrangement along the polymer chain.
In more basic solutions or with longer reaction times, the amide linkages in the polymer chain are attacked upon degradation of the molar mass. The presence of amide bonds makes the polyaspartic acid obtained in the hydrolysis relatively biodegradable (about 70% in wastewater), even of initially highly crosslinked polysuccinimides.
Use
The polysuccinimide developed by Bayer AG and marketed by Lanxess AG under the brand name Baypure® DSP with an average molecular weight of 4,400 g/mol is partially hydrolyzed even at slightly elevated pH values and is thus swellable in highly crosslinked form or water-soluble in linear form. The copoly-(succinimide-aspartic acid) formed by partial hydrolysis and especially polyaspartic acid (trade name Baypure® DS 100) produced by partial hydrolysis is suitable as a long-lasting inhibitor against limescale deposition in water treatment and applications in the oil and mining industries, and as a setting retarder for cement in the construction industry. Patent literature mentions polysuccinimide applications as chelating agents, inhibitors against scale formation, dispersant, humectants, and fertilizer additives.
The opening of the pyrrolidinedione ring structures in polysuccinimide via aminolysis with ammonia water (containgin NH4OH) produces poly-(α, β)-DL-asparagine, with hydrazine poly-(α, β)-DL-aspartylhydrazide (PAHy) and with functional amines, e.g. ethanolamine poly-(α), β)-DL-2-hydroxyethylaspartate (PHEA). PHEA can be used a plasma expander with good biocompatibility and biodegradability, high water solubility at low manufacturing costs and was investigated more intensive as a potential drug carrier) in medical applications.
Cross-linked poly(α, β)-DL aspartic acid sodium salt, which is the commercially most interesting polysuccinimide derivative, has been extensively tested for its suitability as a biodegradable superabsorbent compared to the non-biodegradable standard cross-linked sodium polyacrylate. The results obtained have not yet led to the use of crosslinked polyaspartic acid in large-volume applications for superabsorbents (e.g. baby diapers).
References
Polymers
Succinimides | Polysuccinimide | [
"Chemistry",
"Materials_science"
] | 1,594 | [
"Polymers",
"Polymer chemistry"
] |
59,913,404 | https://en.wikipedia.org/wiki/NGC%204086 | NGC 4086 is a lenticular galaxy located 330 million light-years away in the constellation Coma Berenices. NGC 4086 was discovered by astronomer Heinrich d'Arrest on May 2, 1864 and is a member of the NGC 4065 Group.
NGC 4086 is classified as a LINER galaxy.
See also
List of NGC objects (4001–5000)
References
External links
4086
038290
Coma Berenices
Astronomical objects discovered in 1864
Lenticular galaxies
NGC 4065 Group
LINER galaxies
07076
Discoveries by Heinrich Louis d'Arrest | NGC 4086 | [
"Astronomy"
] | 112 | [
"Coma Berenices",
"Constellations"
] |
59,913,462 | https://en.wikipedia.org/wiki/NGC%20680 | NGC 680 is an elliptical galaxy located in the constellation Aries. It is located at a distance of circa 120 million light years from Earth, which, given its apparent dimensions, means that NGC 680 is about 100,000 light years across. It was discovered by William Herschel on September 15, 1784.
Characteristics
NGC 680 appears asymmetrical, probably due to interactions with other galaxies. The tidal forces have disturbed the shape of the galaxy and have created arcs, shells and an asymmetric envelope. It also features a patchy dusty feature. The hydrogen gas of the galaxy forms two large diffuse stellar plumes that may be associated with tidal tails. One plume extends to the south-east and the other to the north-west and have projected lengths of 75 and 60 kpc accordingly. However, the galaxy does not have a kinematically decoupled nucleus.
All these characteristics indicate that the current galaxy was created by the merger of two galaxies, maybe two gas rich galaxies, maybe spirals, based on the amount of gas located around the galaxy. The lack of detection of molecular gas indicated that the merger took place 1-2 billion years ago. The merger remnant is characterised as a "fast rotator" that indicates either that the galaxy retained the angular momentum of the original galaxy or that the two galaxies merged in a way that they attained angular momentum.
The mean age of the stellar population of the central 0.3 kpc of NGC 680 is 7.8 billion years, while for the central 2.6 kpc the mean age is 6.5 billion years. Ionised gas has been detected in the nucleus of the galaxy, it is probably created by the gas emitted by stars at the end of their life. An arc of bluer and younger stars has been detected east of the galaxy.
Nearby galaxies
NGC 680 is a member of a galaxy group known as the NGC 691 group. Other members of the group include IC 163, NGC 678, NGC 691, NGC 694, IC 167, and NGC 697. NGC 680 forms a pair with NGC 678, located 5.5 arcminutes to the northwest, and IC 1730 lies 3.7 arcminutes northwards.
Hydrogen emission surrounds both NGC 680 and the nearby NGC 678 and an HI tail has been found to extend towards NGC 691, with the total of this cloud HI mass estimated to by about . This gas was probably stripped by NGC 678 after a close encounter with NGC 680. However, with the use of deep photography, a stellar bridge between the two galaxies has not been detected, nor between NGC 680 and IC 1730.
References
External links
NGC 680 on SIMBAD
Elliptical galaxies
Peculiar galaxies
Aries (constellation)
0680
01286
06719
Astronomical objects discovered in 1784
Discoveries by William Herschel | NGC 680 | [
"Astronomy"
] | 569 | [
"Aries (constellation)",
"Constellations"
] |
59,913,760 | https://en.wikipedia.org/wiki/NGC%204089 | NGC 4089 is an elliptical galaxy located 340 million light-years away in the constellation Coma Berenices. NGC 4089 was discovered by astronomer Heinrich d'Arrest on May 4, 1864 and is a member of the NGC 4065 Group.
The galaxy hosts an AGN.
References
External links
4089
038298
Coma Berenices
Astronomical objects discovered in 1864
Elliptical galaxies
NGC 4065 Group
Active galaxies
Discoveries by Heinrich Louis d'Arrest | NGC 4089 | [
"Astronomy"
] | 94 | [
"Coma Berenices",
"Constellations"
] |
59,914,793 | https://en.wikipedia.org/wiki/NGC%204090 | NGC 4090 is a spiral galaxy located 340 million light-years away in the constellation Coma Berenices. The galaxy was discovered by astronomer Heinrich d'Arrest on May 2, 1864 and is a member of the NGC 4065 Group.
NGC 4090 hosts an AGN.
On April 5, 2018 a type Ia supernova designated as SN 2018aqh was discovered in NGC 4090.
See also
List of NGC objects (4001–5000)
References
External links
4090
038288
Coma Berenices
Astronomical objects discovered in 1864
Spiral galaxies
NGC 4065 Group
Active galaxies
07077
Discoveries by Heinrich Louis d'Arrest | NGC 4090 | [
"Astronomy"
] | 131 | [
"Coma Berenices",
"Constellations"
] |
59,915,725 | https://en.wikipedia.org/wiki/Behrend%20sequence | In number theory, a Behrend sequence is an integer sequence whose multiples include almost all integers. The sequences are named after Felix Behrend.
Definition
If is a sequence of integers greater than one, and if denotes the set of positive integer multiples of members of , then is a Behrend sequence if has natural density one. This means that the proportion of the integers from 1 to that belong to converges, in the limit of large , to one.
Examples
The prime numbers form a Behrend sequence, because every integer greater than one is a multiple of a prime number. More generally, a subsequence of the prime numbers forms a Behrend sequence if and only if the sum of reciprocals of diverges.
The semiprimes, the products of two prime numbers, also form a Behrend sequence. The only integers that are not multiples of a semiprime are the prime powers. But as the prime powers have density zero, their complement, the multiples of the semiprimes, have density one.
History
The problem of characterizing these sequence was described as "very difficult" by Paul Erdős in 1979.
These sequences were named "Behrend sequences" in 1990 by Richard R. Hall, with a definition using logarithmic density in place of natural density. Hall chose their name in honor of Felix Behrend, who proved that for a Behrend sequence , the sum of reciprocals of must diverge. Later, Hall and Gérald Tenenbaum used natural density to define Behrend sequences in place of logarithmic density. This variation in definitions makes no difference in which sequences are Behrend sequences, because the Davenport–Erdős theorem shows that, for sets of multiples, having natural density one and having logarithmic density one are equivalent.
Derived sequences
When is a Behrend sequence, one may derive another Behrend sequence by omitting from any finite number of elements.
Every Behrend sequence may be decomposed into the disjoint union of infinitely many Behrend sequences.
References
Integer sequences | Behrend sequence | [
"Mathematics"
] | 435 | [
"Sequences and series",
"Integer sequences",
"Mathematical structures",
"Recreational mathematics",
"Mathematical objects",
"Combinatorics",
"Numbers",
"Number theory"
] |
59,915,731 | https://en.wikipedia.org/wiki/Davenport%E2%80%93Erd%C5%91s%20theorem | In number theory, the Davenport–Erdős theorem states that, for sets of multiples of integers, several different notions of density are equivalent.
Let be a sequence of positive integers. Then the multiples of are another set that can be defined as the set of numbers formed by multiplying members of by arbitrary positive integers.
According to the Davenport–Erdős theorem, for a set , the following notions of density are equivalent, in the sense that they all produce the same number as each other for the density of :
The lower natural density, the inferior limit as goes to infinity of the proportion of members of in the interval .
The logarithmic density or multiplicative density, the weighted proportion of members of in the interval , again in the limit, where the weight of an element is .
The sequential density, defined as the limit (as goes to infinity) of the densities of the sets of multiples of the first elements of . As these sets can be decomposed into finitely many disjoint arithmetic progressions, their densities are well defined without resort to limits.
However, there exist sequences and their sets of multiples for which the upper natural density (taken using the superior limit in place of the inferior limit) differs from the lower density, and for which the natural density itself (the limit of the same sequence of values) does not exist.
The theorem is named after Harold Davenport and Paul Erdős, who published it in 1936. Their original proof used the Hardy–Littlewood tauberian theorem; later, they published another, elementary proof.
See also
Behrend sequence, a sequence for which the density described by this theorem is one
References
Theorems in number theory | Davenport–Erdős theorem | [
"Mathematics"
] | 348 | [
"Mathematical theorems",
"Theorems in number theory",
"Mathematical problems",
"Number theory"
] |
59,915,858 | https://en.wikipedia.org/wiki/NGC%204091 | NGC 4091 is a spiral galaxy located 360 million light-years away in the constellation Coma Berenices. The galaxy was discovered by astronomer Heinrich d'Arrest on May 2, 1864. NGC 4091 is a member of the NGC 4065 Group and is a LINER galaxy.
See also
List of NGC objects (4001–5000)
References
External links
4091
038308
Coma Berenices
Astronomical objects discovered in 1864
Spiral galaxies
NGC 4065 Group
LINER galaxies
07083
Discoveries by Heinrich Louis d'Arrest | NGC 4091 | [
"Astronomy"
] | 110 | [
"Coma Berenices",
"Constellations"
] |
59,916,033 | https://en.wikipedia.org/wiki/Cost%20of%20reproduction%20hypothesis | In life history theory, the cost of reproduction hypothesis is the idea that reproduction is costly in terms of future survival and reproduction. This is mediated by various mechanisms, with the two most prominent being hormonal regulation and differential allocation of internal resources.
Definition and predictions
The cost of reproduction hypothesis posits that reproduction (and increased reproductive effort) is costly in terms of future survival and reproduction. These costs may be exacerbated in certain organisms, such as first--time breeders. Along with the idea that organisms are selected to maximize lifetime reproductive success, this hypothesis results in a trade-off between current reproduction and future fitness that is pivotal in life history theory. This trade-off can be analyzed on three levels: the genetic (which analyzes the genetic basis of covariation between traits), the phenotypic (which assess how traits directly connected to fitness covary), and the intermediate level (which involves the analysis of the mechanisms connecting the genetic and phenotypic levels, like physiological mechanisms).
A major prediction of the cost of reproduction hypothesis is that the importance of the cost declines as an organism ages, resulting in increased reproductive effort in older organisms (this prediction is the terminal investment hypothesis). The cost of reproduction hypothesis also predicts that the optimal reproductive effort in a season is less than the effort that would maximize the number of offspring produced that season. This is especially true in organisms with a long lifespan, as their residual reproductive value (measured as the total reproductive value minus the current reproductive investment) would be higher compared to those with a shorter life.
Trade-offs and causes
Costs of reproduction arise from multiple factors, including physiological, ecological, and behavioural factors. The two most prominent physiological factors are hormones and differential allocation of internal resources. Hormones influence the trade-off between current reproductive and future fitness through their multiple effects. For example, in Drosophila melanogaster, females with a mutation in the insulin receptor gene (DInR) released less ecdysteroids and produced less juvenile hormone; the reduction of the latter results in reduced egg production and a longer lifespan. In another insect, Gryllus firmus, short-winged females are more fecund at an early age and have elevated levels of ecdysteroids and juvenile hormones in their hemolymph (a fluid in invertebrates similar to blood), but are less able to disperse than their long-winged counterparts. This shows how hormones can mediate the cost of reproduction: by linking increased reproduction with decreased somatic function (decreased function in the rest of the body). Additionally, the amount of time the juvenile hormone titer (concentration) is above a certain level likely affects the cost of reproduction, as evidenced by the juvenile hormone titer's circadian rhythm in long-winged morphs and constant level in short-winged morphs.
The traditional view of the cost of reproduction says that a cost is caused by differential allocation of limited internal resources. This view is seen in the Y model of the cost of reproduction, where resources may be allocated to either reproduction or soma. Evidence for this can be seen in G. firmus, where short-winged females have as much as a 400% increase in ovarian growth and a 30% to 40% reduction in somatic triglyceride reserves (used for movement) compared to long-winged females. Short-winged females also divert less resources (in the form of fatty acids and amino acids) to synthesizing triglycerides and more resources to the production of ovarian proteins. Differential allocation of resources may be hormonally mediated; a juvenile hormone analog given to long-winged females reduced triglyceride synthesis and increased egg production, indicating how hormones and differential allocation of resources may work in tandem. Reduced immune function and a decreased defense against environment stress are also important factors in the cost of reproduction. The former has been especially well studied in male birds. Reduced immune function may take the form of increased susceptibility to diseases and parasites or a decreased immune response. This reduced function may be regulated by hormones; in Tenebrio molitor, for example, immunosuppression was caused by increased juvenile hormone as a result of mating. A decreased defense against environmental stress could operate through either somatic damage as a result of reproduction or a rerouting of the resources needed to protect against such damage.
Ecological factors, such as predation, also impact the cost of reproduction. Predation disproportionately affects breeding organisms because of multiple factors. These include increased exposure to predators due to mate searching, predators being attracted to conspicuous mating displays, and decreased mobility during copulation and pregnancy. Predation risk during reproduction can induce many evolutionary responses. In guppies, males in locations with high predation pressure generally are less colourful and perform courtship displays less frequently. When they do display, it is more often during darker periods of the day. Males also tend to rely more on non-visual copulation. Females in similar locations generally prefer less colourful males. They also dedicate more resources to offspring development, and the resulting young are smaller and more numerous. Coevolution may occur between the predators and their prey. Fireflies of the genus Photuris, for example, lure other fireflies through various means, including mimicking the female of the prey species. Some species may respond to this by emitting a nonsense signal that only predators would respond to.
See also
Life history theory
Terminal investment hypothesis
References
Evolutionary biology
Reproduction | Cost of reproduction hypothesis | [
"Biology"
] | 1,121 | [
"Biological interactions",
"Behavior",
"Evolutionary biology",
"Reproduction"
] |
59,916,746 | https://en.wikipedia.org/wiki/Stephen%20Drury%20%28mathematician%29 | Stephen William Drury is an Anglo-Canadian mathematician and professor of mathematics at McGill University. He specializes in mathematical analysis, harmonic analysis and linear algebra. He received his doctorate from the University of Cambridge in 1970 under the supervision of Nicholas Varopoulos and completed his postdoctoral training at the Faculté des sciences d'Orsay, France. He was recruited to McGill by Professor Carl Herz in 1972.
Among other contributions, he solved the Sidon set union problem, worked on restrictions of Fourier and Radon transforms to curves, and generalized von Neumann's inequality. In operator theory, the Drury–Arveson space is named after William Arveson and him.
His research now pertains to the interplay between matrix theory and harmonic analysis and their applications to graph theory.
References
Year of birth missing (living people)
Living people
20th-century Canadian mathematicians
21st-century Canadian mathematicians
Academic staff of McGill University
Mathematical analysts
Alumni of the University of Cambridge
20th-century British mathematicians
British emigrants to Canada
21st-century British mathematicians | Stephen Drury (mathematician) | [
"Mathematics"
] | 209 | [
"Mathematical analysis",
"Mathematical analysts"
] |
59,917,885 | https://en.wikipedia.org/wiki/Nick%20Patterson%20%28scientist%29 | Nicholas James Patterson (born 9 June 1947)
is a mathematician working as a staff scientist at the Broad Institute with notable contributions to the area of computational genomics.
His work has appeared in scientific journals such as Nature, Science and Nature Genetics.
His research has brought a better understanding of early human migrations.
He is among the group of scientists who have sequenced the Neanderthal genome in 2010.
This was followed by the sequencing of a much higher quality Neanderthal genome, where the subject was from the Altai Mountains, in 2014.
These studies have uncovered some unexpected facts about the interbreeding between archaic and modern humans.
Biography
Patterson was an only child who grew up in the Bayswater section of central London. Patterson received his B.A. and Ph.D. in mathematics at Cambridge University. His doctoral advisor was John G. Thompson. He initially worked for the British code-breaking agency GCHQ and the Center for Communications Research in Princeton.
Following this cryptology work, Patterson worked at the quantitative trading firm Renaissance Technologies.
In 2001, Patterson joined the Center for Genome Research at MIT, the Whitehead Institute. He briefly worked on gene expression data applied to cancer before switching to the study of human genetics.
In 2012, Patterson developed ADMIXTOOLS, a software package written in C that is currently widely used by population geneticists.
Chess
Nick Patterson was a child chess prodigy. He won the Irish Chess Championship in 1969. In a long game in the Chess Olympiad of Siegen in 1970, where he played top board for Ireland, he met the Danish grandmaster Bent Larsen, who was one of the top 10 players in the world at the time, and managed to make a draw after 93 moves.
References
External links
Living people
1947 births
American geneticists
Broad Institute people
Alumni of the University of Cambridge
Chess Olympiad competitors
Irish chess players
People from Bayswater
Phylogenetics researchers | Nick Patterson (scientist) | [
"Biology"
] | 380 | [
"Phylogenetics",
"Phylogenetics researchers"
] |
59,919,683 | https://en.wikipedia.org/wiki/List%20of%20astrometric%20solvers | Programs capable of Astrometric solving:
The solvers Elbrus and Charon are obsolete and no longer developed.
External links
Astrometry.net webpage
All sky solver webpage
ANSVR webpage
Astrometry.net API lite
Astrotortilla webpage
CloudMakers webpage
Stellar Solver
ASTAP webpage
Regim webpage
Siril webpage
SIPS webpage
Tetra3 webpage
XParallax viu webpage
Astrometrica webpage
Observatory webpage
PinPoint webpage
PixInsight webpage
PlaneWave Instruments webpage
TheSky Astronomy Software webpage
Logiciel PRISM
PlateSolve3 info
Astronomical imaging
Astronomy software
astrometric solvers | List of astrometric solvers | [
"Astronomy",
"Technology"
] | 137 | [
"Lists of software",
"Computing-related lists",
"Works about astronomy",
"Astrometry",
"Astronomy software",
"Astronomical sub-disciplines"
] |
59,919,751 | https://en.wikipedia.org/wiki/Hayward%20metric | The Hayward metric is the simplest description of a black hole which is non-singular. The metric was written down by Sean Hayward as the minimal model which is regular, static, spherically symmetric and asymptotically flat. The metric is not derived from any particular alternative theory of gravity, but provides a framework to test the formation and evaporation of non-singular black holes both within general relativity and beyond. Hayward first published his metric in 2005 and numerous papers have studied it since.
References
Theories of gravity
General relativity | Hayward metric | [
"Physics"
] | 107 | [
"Theoretical physics",
"Theory of relativity",
"General relativity",
"Relativity stubs",
"Theories of gravity"
] |
59,920,113 | https://en.wikipedia.org/wiki/Conjugated%20estriol | Conjugated estriol, sold under the brand names Progynon and Emmenin, is an estrogen medication which was previously used for estrogen-type indications such as the treatment of menopausal symptoms in women. The term specifically refers to formulations of estriol conjugates which were manufactured from the estrogen-rich urine of pregnant women and were used as medications in the 1920s and 1930s. Conjugated estriol is analogous to and was superseded by conjugated estrogens (brand name Premarin), which is manufactured from the urine of pregnant mares. Conjugated estriol was among the first forms of pharmaceutical estrogen to be used in medicine. It was taken by mouth.
The main components of conjugated estriol are estriol glucuronides and to a lesser extent estriol sulfates. Estrogen glucuronides can be deglucuronidated into the corresponding free estrogens by β-glucuronidase in tissues that express this enzyme, such as the mammary gland, liver, and kidney, among others. Likewise, estrogen sulfates can be desulfated into the corresponding free estrogens by steroid sulfatase in tissues that express this enzyme. Consequently, estrogen conjugates have estrogenic activity via conversion into unconjugated estrogens.
Progynon
Progynon was an orally active formulation of estrogen that was developed by Adolf Butenandt at Schering and introduced in Germany in 1928. It was reportedly the first sex hormone product and hence also the first estrogen product to be introduced for medical use. Progynon was originally an ovarian or placental extract, but Schering soon switched for economic reasons to using the urine of women who were in late pregnancy. This form of Progynon was essentially the same product as Emmenin, which was developed by James Collip at Ayerst and introduced in Canada in 1930 (and in the in 1934).
To further reduce the costs of manufacturing Progynon, Schering eventually switched to using the urine of pregnant mares and called its new product Progynon 2. Ayerst followed suit, with the introduction of Premarin (conjugated equine estrogens) in 1941. Premarin soon superseded Emmenin and has since become not only a very widely used estrogen, but one of the most widely prescribed drugs in North America.
Both Progynon and Emmenin contained a mixture of water-soluble estrogens, which was determined later to be mostly estriol glucuronide. Conjugates of estriol like estriol glucuronide and estriol sulfate constitute more than 90% of the estrogens in the urine of pregnant women. Of these conjugates, 35 to 46% are estriol glucuronides and 15 to 22% are estriol 3-sulfate in late pregnancy; the double conjugate estriol sulfate glucuronide (probably estriol 3-sulfate 16α-glucuronide) also occurs.
Progynon was also the name that Butenandt originally gave estrone (which he had isolated in 1929) in his first publication on the substance (and later referred to as folliculine, with the name estrone not finally being adopted until 1935). Aside from Progynon and Progynon 2, the Progynon name has also been used in a variety of other estrogenic products marketed by Schering, including Progynon-B (estradiol benzoate), Progynon-DH (estradiol; "dihydroxyestrin"), Progynon-DP (estradiol dipropionate), Progynon-C (ethinylestradiol), Progynova (estradiol valerate), and Progynon Depot (estradiol valerate, estradiol undecylate).
Emmenin
Emmenin was an orally active formulation of estrogen that was developed by James Collip at Ayerst and introduced in Canada in 1930 and the United States in 1934. It was originally an extract obtained from human placenta. At some point, it seems to have been changed to an extract of the urine of women who were in late pregnancy, which was equivalent in composition but was less expensive to source, and was essentially the same product as Progynon, a related estrogen developed by Adolf Butenandt at Schering and introduced in Germany. These estrogen products were the first orally active estrogens to be marketed for medical use.
To reduce the costs of manufacturing Emmenin and Progynon, Ayerst and Schering eventually switched to using the urine of pregnant mares (which contains conjugated equine estrogens, primarily estrone sulfate) and called their new products Premarin and Progynon 2, respectively. Premarin was introduced by Ayerst in 1941 and has become not only a very widely used estrogen, but one of the most widely prescribed drugs in North America.
Both Emmenin and Progynon contained a mixture of water-soluble conjugated estrogens, later determined to be mostly estriol glucuronide. Conjugates of estriol like estriol glucuronide and estriol sulfate constitute more than 90% of the estrogens in the urine of pregnant women. Of these conjugates, 35 to 46% are estriol glucuronides and 15 to 22% are estriol 3-sulfate in late pregnancy; the double conjugate estriol sulfate glucuronide (probably estriol 3-sulfate 16α-glucuronide) also occurs. Unlike unconjugated estrogens like estradiol and estrone, these estrogens were orally active.
See also
Estrogenic substances
Conjugated estrogens
Esterified estrogens
Estrogen conjugate
List of combined sex-hormonal preparations
References
Abandoned drugs
Estranes
Estriol esters
Estrogens
Glucuronide esters
Sex hormone esters and conjugates
Sulfate esters | Conjugated estriol | [
"Chemistry"
] | 1,310 | [
"Drug safety",
"Abandoned drugs"
] |
59,920,864 | https://en.wikipedia.org/wiki/Women%20in%20the%20yellow%20vests%20movement | Women have been involved in the yellow vests movement since its inception. This is a result of women on the whole being more affected by poverty in France than their male counterparts, in part because many are heads-of-household and need to take time off from paid employment to give birth to children. Their role is greater than most past social movements in France because of the economically precarious position that many women in the country find themselves in.
Two women played critical roles in starting the movement. Priscillia Ludosky was one of the first people involved, after launching it inadvertently on 29 May 2018 by posting an online petition about the need for lower taxes, reducing salaries and pensions of public officials and creating an implementation of the citizens' initiative referendum. After she had heavily promoting it in September, it began to really gain traction in October 2018. Jacline Mouraud played another critical role that month in creating the movement, when she posted a Facebook video that went viral about France's proposed eco-tax to which she was opposed.
Act I saw women like Laëtitia Dewalle and Marine Charrette-Labadie organize local marches. Both would become key local spokespeople for their regions. Act II saw continued involvement of women, along with gender specific violence targeting women of color who were stuck in traffic as a result of the protests. An 80-year-old woman was killed in Marseille during Act III. During the same time period, research was published that said poor working women in France as a percentage of the population grew by around 2% from two years prior. Act IV saw the creation of a Facebook group "Femmes gilets jaunes" by Karen, a 42-year-old from Marseille. It also saw President Emmanuel Macron mention the presence of women in yellow vest protests, though he failed to address any specific needs of poor women. Act VI saw Eric Drouet arrested and key female figures in the movement condemn his arrest. It also saw an anti-Semitic act committed by men on the Paris metro against a female Holocaust survivor. Act VII saw the first of the yellow vest women's march taking place on 6 January, the Sunday after the main events of the Act. Act X saw social justice around women's needs begin to feature as an issue that needed to be addressed. Act XII saw women presenting female specific demands for the first time.
The yellow vest movement has birthed several political parties, two of which are being led by women. Citizen-Led Rally was created in January 2019 by Ingrid Levavasseur to try to effect political change. The Risen was founded by Jacline Mouraud with the intention of running candidates in France's local elections in 2020, sitting out the 2019 European Parliament elections. It was positioning itself as neither left wing, nor right wing.
Background
Of the class of people represented by the yellow vest movement, 45% are women. 52.1% of poor adults in France are women. Women on the whole are more affected by poverty in France than their male counterparts, in part because many are heads-of-household. Many women have to spend time out of the workforce to give birth to children, and are unable to make up the salary loss and the consequent government contribution towards retirement payments. Government models for social payments have largely been based around the needs of men, with the assumption that a head-of-household is a man married to a woman who has children. At the same time, women across France are subject to daily sexual harassment and insults, with men on the street calling them whores and sluts.
Women's role in the yellow vest movement is greater than in most past social movements in France because of the economically precarious position that many women in the country find themselves in.
As a group, poor women in France have never been specifically targeted by campaigners. At the same time, most poor women have not self-mobilized prior to the yellow vest movement to articulate the needs of their gender-based class. Some of this has been attributed to the feminist movement in France being led by liberals, who prioritize issues like anti-racism, multiculturalism, and the needs of women in other countries ahead of French women.
Origin
Women have been involved with the yellow vest movement from the start, serving through their acts as catalysts for the movement and as spokespeople even before the movement took to the street.
Priscillia Ludosky was one of the first people involved in the yellow vest movement, launching it inadvertently on 29 May 2018 by posting an online petition about the need for "lower taxes on essential goods, the implementation of the citizens' initiative referendum, lower pensions and salaries of senior officials and elected officials". Initially, no one gave any attention to the petition, and went about life as usual from June to September 2018. In mid-September she tried to get more attention for her petition. She started reaching out on more social networks and to local media. Eventually, her petition was picked up nationally by Le Parisien. Because of her surname, some journalists initially assumed she was of Polish descent or married to a Polish man.
Seeking to gain more support for the grievances listed in the petition and to combat rising fuel prices, Eric Drouet reached out to Ludosky in October 2018. Drouet was interested in organizing action to protest fuel prices, and their concerns became joined. The pair together called for the first protest on 17 November 2018. While the biggest protest was in Paris, Ludosky participated in a 17 November protest near her home. Meanwhile, her petition had 938,325 signatories by 20 November 2018. On November 27, the pair met for the first time at the Ministry for the Ecological and Solidary Transition to share their message from Ludosky's petition with the government.
According to The Guardian and other news sources, Jacline Mouraud has "been widely credited with starting the yellow vests movement" (). Mouraud's visibility in the movement came as a surprise to her and others. At the time, she was earning less than €1,000 a month and her most valuable possession was her car, a black diesel SUV that she had bought ten years earlier for €11,000. Some months, she was earning only €800 per month.
Mouraud's involvement in the movement began in October 2018 when she posted a Facebook video that went viral about France's proposed eco-tax to which she was opposed. The video was 4 minutes and 38 seconds in length, and attracted over 6 million views. In it, she asked President Macron, “What are you doing with the money apart from buying new dishes at the Élysée Palace and building yourself swimming pools?” The video was not her first of its kind, as Mouraud had made a similar one in April 2017.
Technology
Women have been enabled during these protests because of an ability to harness Facebook as an organizing tool. Both Facebook and Twitter have also served a key role in letting marginalized voices be heard by others in their class and the media establishment.
Timeline regarding female participation
17 November 2018: "Act I"
Women were among the organizers and participants in Act I.
Laëtitia Dewalle organized the first yellow vest protest in the Val-d'Oise. She organized local action on a Facebook page titled "représentante du Val d'Oise". Following Act I, she was part of a group demanding a referendum on the legitimacy on the presidency of Emmanuel Macron.
Marine Charrette-Labadie's involvement predated the 17 November 2018 protests, when she served as a local organizer in advance for Act I. She got involved because she felt as if she could not sit idly by and do nothing. Most of Charrette-Labadie's activity took place on Facebook. As a local organizer, she was part of a group of protesters who lifted toll gates in Brives on 17 November 2018. Earlier that week, Charrette-Labadie had participated in protests in front of the tax office in the city.
24 November 2018: "Act II"
Act II took place on the same day as international protest violence against women day. French organizers of local events were nervous that the yellow vest protests would eclipse their march's message. Organizers took to social media to ask yellow vest marchers not to impede their own events. They were seeking to capitalize on the #NousToutes movement, which had seen 4,000 women in France come out to protest violence against women in September, with 600 of those protests being in Paris. Concern about yellow vest interference came after one local organizer in Bourg-en-Bresse canceled because she feared women would not be able to get to it because of yellow vest imposed road blockages.
Women were again among the participants of this act. Some traveled for hours via bus to Paris, bringing with them their male companions. By the end of Act II, women had met, networked and begun discussing the particular needs of women in the yellow vest movement.
Women were also subjected to racist abuse during Act II on the part of activists in general. A black woman, after being stopped by protesters at a roundabout in Cognac, got out of her car, where her children were sitting. She was confronted by protesters, who told her to go home and no one wants to hear about the problems of black people in France. At another roundabout in Auchan-Fayet, a Muslim woman in a veil had been stuck in traffic for an hour as a result of yellow vest related road closures. They would not let her pass until she removed her veil. Yellow vest protesters also made monkey noises at her.
Ahead of Act II on 24 November 2017, while acting as a yellow vest spokesperson, Dewalle said protesters had no intention to march on Champ-de-Mars. Rather, they were holding a street protest. She made clear to the media following Act II that the yellow vest movement was apolitical, and not aligned with any French unions. She also recognized that during Act II, the protest was infiltrated by extremists from both the left and right, expressing regret that the police did not take any steps to stop them.
Shortly after Act II, the yellow vests put forward a list of their desires. One specifically mentioned women, demanding, "Respect male / female parity: alignment of the qualification and the position held at equal pay."
Act II saw Drouet talk openly about his intention to "enter the Elysee". It also saw another yellow vest activist, Maxime Nicolle, question the timing of the 2018 Strasbourg attack and imply it was a false flag. These two developments caused Ludosky to largely disappear from the yellow vest movement.
Marine Charrette-Labadie, then a 22-year-old, emerged as one of the early spokesperson in the "yellow vests" () movement. She was one of eight official spokespeople. This group was announced on 26 November 2018. During her time as a spokesperson, Charrette-Labadie was contacted constantly by people in the movement asking for updates as to what had been accomplished and by members of the media seeking comment. She was also being contacted by members of many political parties who were seeking to align themselves with the yellow vest leadership.
Charrette-Labadie was in Paris around 25 November 2019 for a meeting with the government, where she served as one of the representatives of the movement. After consulting people on Facebook, she and other representatives said they had two things they wanted the government to do: create a citizen's assembly and lower all taxes on people. Her participation was criticized by others in the movement, including local Cana leader Christian Lapauze who said they were not consulted about any demands and the representatives had no legitimacy. On 27 November 2018, she was one of six yellow vests activists to participate in a LCI program called "The Great Explanation" ().
Charrette-Labadie announced she was retiring from the movement at a national level on 28 November 2018 at a press conference in Brives, saying, "I was tired of it, I was tired and I did not want to fight for people who do not deserve it." By the time she made the announcement, five of the original eight spokespeople had also resigned. On 29 November 2018, she was invited by France's Prime Minister's office to participate in a meeting with other spokespeople at Matignon. She also participated in a meeting at the Ministry of Ecological Transition with other representatives. The group emerged disappointed.
1 December 2018: "Act III"
A report by Oxfam published in December found that the percentage of poor women workers in France rose from 5.6% of the population in 2016 to 7.3% of the population by 2018.
Women were again amongst the marchers present during this Act. They came from such places as a rural village in Ile-de-France. Women involved in this Act viewed a car as essential to their lives, necessary to drive to work and take care of their children. Some women who had traveled to Paris for Act II wanted to participate once again at the march in the city, but financial considerations meant they were unable to do so or were forced to participate in marches much closer to home. Elodie Renault was one of the participants in this act, having been involved in all previous acts. Renault would leave her four children with her parents before heading to the protests. The beautician on family leave said of her participation, "There are so many things that are not going away that it does not change anything. We are so completely fed up that we expect to see much more." Not all women involved in Act III liked the violence found in the yellow vest movement, but some saw it as a necessary part of accomplishing their goals.
An 80-year-old woman was killed in Marseille during Act III after being hit by a tear gas canister while closing the shutters in her fourth floor apartment. She had been in poor health.
In early December, Mouraud was part of a delegation of yellow vest protesters who met with France's Prime Minister Edouard Philippe.
8 December 2018: "Act IV"
Women were part of a protest mobilization camp at the Monsanto factory in Trèbes. Coming from a wide age range, they included Ariège educator Esther who was quoted as saying, "We live in a world where humans are more and more victims of slavery. I see disabled adults working for 50 euros a day and sometimes on call at weekends." Another participant was 35-year-old Clarise, who said, "With the Facebook of Carcassonne in anger, we put back the ideas, the lists of demands, and the decisions are subjected to the vote: is it we block, do we continue?"
During Act IV on 8 December, Dewalle told the media, “We’re continuing – always in a peaceful spirit. [...] This movement itself is not violent. That’s not our way of doing things.” Following Act IV of the movement, Dewalle signed a letter condemning police violence aimed at demonstrators that was published on 26 December.
The Facebook group "Femmes gilets jaunes" was created by Karen, a 42-year-old nurse from Marseille. Organizers started using imagery for their protest featuring a woman wearing Phrygian cap and crying blue, white and red tears. Private Facebook discussions at this time among women were asking if they should put forth their demands as women separate from the main part of the yellow vest movement. There was also discussion about if and how marchers should identify themselves as women, including some participants suggesting women wear skirts. Others suggested bringing children, pregnant women or stuffing their shirts so they appeared pregnant. Not only would this serve to highlight needs specific to women, but it might make it more difficult for police to be openly violent towards them as clearly defined feminine figures.
Women involved in the discussion also discussed whether their marches should be women only, or mixed gender spaces. A compromise arose, with women wearing yellow vests leading their processions, with men allowed at the back and without yellow vests. Organization discussions also focused on finding accommodation for women offered by other women, finding childcare for women marchers who did not want to bring their children with them, and seeking ways to allow women with disabilities to participate fully in their marches.
Despite the French government having talked to many yellow vest activists and the large number of women involved in the protests, no one in government had specifically addressed the particular needs of women protesters. In a 10 December 2018 speech about the movement, Emmanuel Macron did acknowledge the specific issues facing many types of women, even if he offered no specific support for this group.
15 December 2018: "Act V"
On the Champs Elysees during Act V, women organized a silent, artistic, topless performance protest while dressed as Marianne, a woman who represents the French Republic. The event was organized by the nude performance artist Deborah de Robertis. It was attended by members of Femen. Police officers were nearby during the protest.
Following Act V, Dewalle said she had little faith that Emmanuel Macron would announce any measures that would satisfy yellow vest protesters. She told the media of her expectations of Macron, "It will take strong and concrete measures right now, but we have little hope. [...] What is essential to satisfy us is the RIC, the citizens' initiative referendum, restore the ISF, increase the Smic (minimum wage) and low wages by a reduction in social contributions. [...] And if he could talk about lowering the salaries of MPs and ministers, then we would really start talking."
22 December 2018: "Act VI"
During Act VI, Eric Drouet was one of 64 people arrested in Paris. While he was being arrested, Dewalle was on television talking to RT France. Following his arrest, Maxime Nicolle, Priscillia Ludosky and other activists signed a petition requesting the police to release Eric Drouet after they had accused him of holding an unregistered protest. The petition called his detention a "brutal aggression, the arbitrary arrest and unjustified victimization of Eric Drouet."
Three male yellow vest protesters returning home on the Paris metro from Act VI engaged in anti-Semitic behavior. A female Jewish Auschwitz holocaust survivor asked them to stop. The men laughed at her, and told her the holocaust was a hoax. They then told the woman to get off the metro and return to her home country. No one else on the metro car said anything at the time, and the lady got off at the next stop. The government later investigated the incident as an anti-Semitic act.
Ludosky traveled throughout France to witness her movement, including visiting a border crossing in Boulou on 22 December 2018. Her goal in these trips was to draw media attention to the fact that the issues raised in the petition impacted more than just the people living in Paris.
29 December 2018: "Act VII"
Act VII saw fewer protests than the week before. 22-year-old Monica Piazza de Valencia, attending the Act VII Paris protest said, "We are not against deductions and taxes ... But it's just not reasonable, time and time again, that we're always the ones who have to pay and our contributions keep going up and up."
Ludosky continued to travel around France to witness her movement, visiting Marseille on 29 December 2018, and going to Bourges on 12 January 2019. Dewalle planned to have a New Year's Eve yellow vest demonstration.
5 January 2019: "Act VIII"
The general march on 5 January was marked by high levels of violence on a Saturday that saw 50,000 people take to the streets across France.
The first of the yellow vest women's marches took place on 6 January. As a group, they disliked the use of the word feminist because "of a old-fashioned and worn-out mistrust of feminism that tends to describe as extremists as those seeking to abolish male dominance over women." While stating their intentions were not feminist in nature, their mobilization mirrored historical feminist movements. They also sit at an intersection of many past feminist critiques of problems facing women. The image of a woman wearing Phrygian cap and crying blue, white and red tears was present on signs by protesters across the country. Many women also carried yellow balloons. The women denounced police violence that occurred during previous Acts. They also wanted to stress that their concerns mattered, and they were less violent than men during protests. Among the chants, one was, "Macron, you're screwed, chicks are in the street." () Prior to the start of the rally, 11,000 people indicated on Facebook an interest in participating. Organizers were not keen to talk to the media ahead of the march.
There were around 100 women at the march in Metz, 200 in Douai, and around 300 in Saint-Brieuc. Another 20 women accompanied by around a dozen men marched in Le Mans. In Paris, where several hundred women participated, marchers met on the steps of Opera Bastille, before marching to Place de la République. One participant in Paris was 40-year-old Sophie Tissier. Around 300 women marched in Toulouse, their march starting at Place Arnaud-Bernard with a heavy police escort. They marched behind a banner that read, "Subverted, discriminated against, rebellious, Women on the front line". () Around one hundred women participated at the Caen march. Women brought their children with them, despite heavy violence in the yellow vest march the day before. 28-year-old riding instructor Chloé Tessier said at the Caen march, "The government wants to make us look like thugs, but today we are mothers, grandmothers, we are the daughters, the sisters of all citizens, and we want to say that (...) our anger is legitimate. It is during social crises that women's rights are most at risk." Another roughly one hundred women participated in a march in Saône-et-Loire.
12 January 2019: "Act IX"
Among yellow vest protests in general, far-right extremism had creeped into the movement along with overt sexism, racism and homophobia. Threats and acts of violence against members of the media had also become a regular feature of the movement by Act IX. During this act, a female journalist from La Dépêche du midi covering the protests in Toulouse was threatened with rape. Minister for Gender Equality Marlène Schiappa had been depicted by some protesters online and at protests as half naked and as an inflatable doll. After criticizing a jailed member of the movement, she had also been subject to many threats online, including death threats and threats that she would be raped.
Ludosky continued her travels through France to witness her movement, going to Bourges on 12 January 2019. On 14 January 2019, Ludosky announced on Facebook that she was distancing herself from Drouet. The pair had been feuding for a while, with the instigator of the January fight being the name of the Facebook page used to organize the movement. Ludosky also claimed Drouet had been making threats against her. Ludosky said the split meant she was finally able to freely criticize his behavior. Around 16 January 2019, Ludosky went to the French Economic, Social and Environmental Council for a meeting. She said the meeting was productive, and many issues of concern were addressed.
Dewalle was involved with local protests in Val-d'Oise for Act IX on 12 January 2019.
Women marched for a second consecutive Sunday in women's only marches on 13 January. Marches took place in Toulouse, Perpignan, Le Mans, Pau and Bordeaux. Ninety women participated in Pau, around 300 women in Le Mans and a few hundred in Paris. Bordeaux organizers estimated 200 participants, while local police estimated 150 participants in their local march. They were accompanied by a few men. 42-year-old Christelle, who had participated in all the main protests since November, said of the Bordeaux march, "There are only women because some are afraid to come on Saturday after everything we see in the news. Many do not see themselves as yellow vests, there is a march of women angry against the government, some wore yellow vests, others not." The Perpignan march was the first women's yellow vest march in that city. It was also the first women's only protest ever in the city's history. At the Toulouse protest, a man wore a yellow vest with the word "President" on it, offering himself as a spokesperson for the women's march. Unlike some other cities, there were more men participating in this women's march.
Signs again featured imagery of a woman wearing Phrygian cap and crying blue, white and red tears.
19 January 2019: "Act X"
On 18 January 2019, Ludosky announced the launch of an Android app for yellow vest protesters. It offered carpooling information, help in finding hosts when traveling to yellow vest protests and events, and information on potentially dangerous situations for protesters.
A women's yellow vest mobilization took place on 20 January. It was the third Sunday in a row where women protested in the streets. The purpose was to show women's involvement in the movement. Another goal was to give more legitimacy to the movement by highlighting women's participation. Specific social injustices facing women were a major part of this Act, having been less central in Acts VIII and IX.
Several hundred women took part in marches in Paris, Bordeaux, and Toulouse. Around 120 people took part in Bordeaux, with Genevieve Deyres one of the activists participating. Around 130 people, mostly women but also a few men, participated in the Toulouse march. Around 100 women marched in Metz, and nearly three hundred women marched in Saint-Brieuc with their faces covered in makeup to make them look wounded. Around 120 men and women participated in the Bordeaux march. Another roughly thirty women marched in Creac'h Gwen. Another rally took place in Quimper. Around 200 women participated in the Paris march. Another took place in Val d'Oise.
The Paris women's march started near the Eiffel Tower and then finished near the Place de la Bastille. Yellow vest founder Ludosky participated in the women's march in Paris. She said of the march, "It is a beautiful message to say that women also have the right to express themselves on social issues." Chris, a woman participating in Creac'h Gwen said, "It's hard when you're a woman, quite simply, it's a patriarchal society, the government wants to fight violence against women, but is violent against them in protests. [...] This is not a feminist claim, our goal is to give voice to women." Dewalle said of her local march, "It is much more difficult to stigmatize a women's movement, to stigmatize it as racist, extremist, xenophobic, homophobic. It just doesn't work. So we also want to overturn the picture the government is trying to make of us." Dewalle went on to say, "We are here to remind ourselves that there are these conditions, without being a feminist movement, but a movement that shows the social injustice of women."
2 February 2019: "Act XII"
Women were again marching on Sunday. One march occurred in Toulon, the second Sunday yellow vest women marched in the city. They had a specific set of demands for the government about the needs of women. Their demands included "Equal pay for men and women, a retirement age that will unfairly penalize women who have stopped working to raise their children, the terrible lack of emergency accommodation, violence to women ... " Their march started at Place Liberté and ended at Boulevard Général Leclerc. Another march took place in Avignon with around 70 participants.
16 February 2019: "Act XIV"
During Acts XIII and XIV, Levavasseur faced continual harassment and threats from other activists for her attempts to politicize the movement and draw attention to herself as an individual. Levavasseur found this difficult to deal with, especially given her employment situation.
During Act XIV around 16 February 2019, Ludosky gave an interview in which she said that yellow vest Saturday protests must not stop, even as participation numbers were declining week by week. She said the violence during marches had overshadowed the marchers' message. In the interview, she went on, "We must not block to block. I remain supportive of the Saturday demonstrations, but we must not be limited to that. Other initiatives can take place. For example, we need to put more pressure on large companies that do not pay enough tax, which would fund the reduction of VAT on essential goods, one of our demands." Ludosky and Etienne Chouard attended a 2,000 person strong march in Castres during Saturday Act XIV events. Following Act XIV an open letter was addressed to Priscillia Ludosky, Jacline Mouraud, Ingrid Levavasseur, Eric Drouet, Maxime Nicolle and other yellow vest spokespeople asking them "to condemn the aggression committed against Alain Finkielkraut and the anti-Semitic remarks of which he was the victim."
8 March 2019 "International Women's Day"
Secretary of State for Gender Equality Marlène Schiappa announced that on International Women's Day, she would do a reverse-conference, giving poor and elderly women a chance to make their voices heard. She said she was inspired to do this after seeing how difficult it was for women's voices and women's concerns to be heard in the yellow vest movement.
General assemblies
Val-d'Oise
In mid-January 2019, Dewalle's local area was having general assemblies to be more coherently present their demands. At the first of these meetings, Dewalle was elected as a spokesperson alongside Largo Farouk. Dewalle hoped they could have a new general assembly every six weeks, but cost was an issue with the hall costing €800.
Political parties
The major political parties had been trying to harness the potential political energy of participants in the movement since its inception. By February 2019, they still had not made any major inroads towards using them for their own parties's purposes.
Citizen-Led Rally
In January 2019, Ingrid Levavasseur created a new political party for both men and women called Citizen-Led Rally (RIC), capitalizing on her involvement in the yellow vest movement in order to try to effect political change. Her party was one of several to emerge from the movement. She felt it was important to create a party because many of the people involved did not feel they had been represented by politicians in the past. Christophe Chalençon helped her in creating the RIC. The party intended to put forward a list for the 2019 European Parliament elections. Levavasseur would be at the head of the party's list. She went into the elections a political novice, never having run for office or been involved in party politics before. She had been voting in elections. Brigitte Lapeyronie was number five on the original list, before withdrawing to be more active with trade unions. Hayk Shahinyan, also named to the original list, withdrew from it. Marc Doyer, one of the ten people on the original list, also withdrew after people expressed concern about his connections to the previous campaign of Emmanuel Macron. All the withdrawals meant the party was left with only nine candidates of the 79 required to be on the ballot.
RIC believes in the importance of the European Union, considering France is stronger in dealing with China or the United States when it has EU backing. Alone, France is less powerful. In February 2019, Levavasseur made clear that the party does not have the financial backing of Bernard Tapie. Instead, the party would seek funding through small citizen donations, with a goal of raising €700,000.
Levavasseur posted a public letter to fellow yellow vest activist Karine during Act XIV after she faced a barrage of criticism on social media platforms like Facebook. In the letter, she also announced that she is abandoning her intention to have RIC run a list for the 2019 European Elections. She cited part of the reason as a lack of money and of being unemployed. She was still committed to going forward with the party and future elections, but she needed more time to build a team around her that she trusted.
The Risen
Early on, as part of Mouraud's involvement in what eventually became the yellow vest movement, she claimed to be apolitical. In October 2018, she claimed this because of her belief that all politicians were corrupt.
In January 2019, Mouraud created Les Émergents (English: The Risen), a political party that grew out of the yellow vest movement, with the intention of running candidates to run in France's local elections in 2020, sitting out the 2019 European Parliament elections. She stated that the party “won’t be rightwing or leftwing." Her platform for the party includes making a stronger parliament by weakening the powers of the executive, and to bring pay equity between men and women. Her platform is also concerned with climate change and the "cut of consumerism." She announced the creation of the party at a press conference in Orléans. She delayed naming the location of the press conference out of fear that it would be disrupted by others in the officially leaderless yellow vest movement.
Mouraud's proposed list for 2020 is to be headed by Ingrid Levavasseur, another well-known yellow vest activist. The list emerged from the group Citizen Initiative Rally (). Mouraud did not necessarily see herself as being part of that list.
International movement
Women have been inspired by the movement in other places around the world. Women marched as part of a yellow vest protest in London, alongside their male peers. Their demands are sometimes different than their French counterparts. Tracy Blackwell was marching to support suicide prevention and prevent child abuse.
The yellow vests inspired a similar protest in the Canadian city of Sarnia, with the creation of a Facebook page titled Yellow Vests Canada. Brittany Studzinsky was a representative of the Sarnia-Lambton County Chapter. Men and women in the city protested in front of the Sarnia City Hall in early February 2019 about the lack of government accountability, Justin Trudeau's leadership, the government's support of the UN immigration pact, and the carbon tax. They also supported a new oil pipeline in western Canada that would go to the coast.
In Switzerland, the union's activist Chloé Frammery participated in the movement in France and Switzerland.
References
November 2018 events in France
December 2018 events in France
January 2019 events in France
Protests in France
Protests in the European Union
Tax resistance in France
2018 protests
Petroleum politics
2018 in French politics
2019 in France
Social movements in Europe
History of women in France
Yellow vests protests | Women in the yellow vests movement | [
"Chemistry"
] | 7,235 | [
"Petroleum",
"Petroleum politics"
] |
59,921,575 | https://en.wikipedia.org/wiki/Fluorescence%20imaging | Fluorescence imaging is a type of non-invasive imaging technique that can help visualize biological processes taking place in a living organism. Images can be produced from a variety of methods including: microscopy, imaging probes, and spectroscopy.
Fluorescence itself, is a form of luminescence that results from matter emitting light of a certain wavelength after absorbing electromagnetic radiation. Molecules that re-emit light upon absorption of light are called fluorophores.
Fluorescence imaging photographs fluorescent dyes and fluorescent proteins to mark molecular mechanisms and structures. It allows one to experimentally observe the dynamics of gene expression, protein expression, and molecular interactions in a living cell. It essentially serves as a precise, quantitative tool regarding biochemical applications.
A common misconception, fluorescence differs from bioluminescence by how the proteins from each process produce light. Bioluminescence is a chemical process that involves enzymes breaking down a substrate to produce light. Fluorescence is the physical excitation of an electron, and subsequent return to emit light.
Attributes
Fluorescence mechanism
When a certain molecule absorbs light, the energy of the molecule is briefly raised to a higher excited state. The subsequent return to ground state results in emission of fluorescent light that can be detected and measured. The emitted light, resulting from the absorbed photon of energy hv, has a specific wavelength. It is important to know this wavelength beforehand so that when an experiment is running, the measuring device knows what wavelength to be set at to detect light production. This wavelength is determined by the equation:
where h = the Planck constant, and c = the speed of light. Typically a large scanning device or CCD is used here to measure the intensity and digitally photograph an image.
Fluorescent dyes versus proteins
Fluorescent dyes, with no maturation time, offer higher photo stability and brightness in comparison to fluorescent proteins. In terms of brightness, luminosity is dependent on the fluorophores’ extinction coefficient or ability to absorb light, and its quantum efficiency or effectiveness at transforming absorbed light into fluorescently emitting luminescence. The dyes themselves are not very fluorescent, but when they bind to proteins, they become more easily detectable. One example, NanoOrange, binds to the coating and hydrophobic regions of a protein while being immune to reducing agents. Regarding proteins, these molecules themselves will fluorescence when they absorb a specific incident light wavelength. One example of this, green fluorescent protein (GFP), fluoresces green when exposed to light in the blue to UV range. Fluorescent proteins are excellent reporter molecules that can aid in localizing proteins, observing protein binding, and quantifying gene expression.
Imaging range
Since some wavelengths of fluorescence are beyond the range of the human eye, charged-coupled devices (CCD) are used to accurately detect light and image the emission. This typically occurs in the 300–800 nm range. One of the advantages of fluorescent signaling is that intensity of emitted light behaves rather linearly in regards to the quantity of fluorescent molecules provided. This is obviously contingent that the absorbed light intensity and wavelength are constant. In terms of the actual image itself, it is usually in a 12-bit or 16-bit data format.
Imaging systems
The main components of fluorescence imaging systems are:
Excitation source: a device that produces either a broad-wavelength source like UV light, or a narrow wavelength source like a laser.
Light display optics: the mechanism of which light illuminates the sample. This is typically done through direct illumination of the sample.
Light assortment optics: the collection method of the light itself. This typically constitutes lenses, mirrors, and filters.
Filtration of emitted light: optical filters ensure that reflected and scattered light are not included with the fluorescence. The three classes of emission filters are long-pass, short-pass, and band-pass.
Detection, amplification, and visualization: either photomultiplier (PMT) or charge-couple device (CCD) is used to detect and quantify emitted photons
Applications
In PCR (agarose gel electrophoresis): SYBR Green is a very common dye that binds to DNA and is used to visualize DNA bands in an agarose gel. The dye absorbs blue light and fluoresces green for an imaging system to capture.
Blotting (Western, Northern, and Southern): fluorochromes can bind to antibodies, RNA, and DNA to fluoresce and quantify data
DNA Sequencing: Sanger Sequencing is a common form of nucleic acid detection that may use fluorescently labeled ddNTPs to image fluorescence peaks
Fluorescence image guided surgery: is a medical imaging approach that fluorescently labels a mass to aid in navigation. For example, indocyanine green can be used to detect lymph nodes in cancer patients.
Fluorescence imaging with one nanometer accuracy (FIONA): utilizes total internal reflection illumination to reduce noise and increase brightness of fluorophores
Calcium imaging: technique that utilizes fluorescent molecules called calcium indicators that change in fluorescence when bound to Ca2+ ions. This is a key part in seeing when cells are active in the nervous system.
Pegulicianine (Lumisight) is indicated for fluorescence imaging in adults with breast cancer as an adjunct for the intraoperative detection of cancerous tissue within the resection cavity following removal of the primary specimen during lumpectomy surgery.
Photoactivated localization microscopy.
Types of microscopy
A different array of microscope techniques can be employed to change the visualization and contrast of an image. Each method comes with pros and cons, but all utilize the same mechanism of fluorescence to observe a biological process.
Total internal reflection fluorescence microscopy: A microscopy technique that uses evanescent waves to selectively observe the fluorescence of a single molecule.
Light sheet fluorescence microscopy: A fluorescence microscopy technique that illuminates a thin slice of a sample at a perpendicular angle of examination.
Fluorescence-lifetime imaging microscopy: An imaging technique that records changes in fluorescence over time
Advantages
Non-invasive: imaging in vivo can take place without having to puncture the skin
Sensitive: probes are designed to be extremely sensitive to detecting biological molecules like DNA, RNA, and proteins.
Multi-labeling: multiple fluorochromes can be detected within the samples allowing for an easy way to integrate standards and a control.
Stability of labeled molecules: fluorescently labeled molecules used in imaging can be stored for months while other molecules like ones that are radiolabeled, will decay over a few days.
Relatively safe to handle: most fluorophores can be safely and sufficiently handled with gloves, while for example, radioisotopes may require lead shields or other radiation protection.
Simple disposal: many fluorophores require minimal disposal methods while radioactive wastes require regulated disposal and long-term handling. This also aids in lowering the cost needed to utilize these products.
Disadvantages
Photobleaching: A prevalent issue with fluorophores where the constant cycling between ground state and excited state damages the molecule and reduces its intensity.
Environmental susceptibility: environmental factors like temperature, ion concentration, and pH can affect the efficiency and emission of fluorochromes
Toxicity: Aome fluorochromes can be toxic to cells, to tissues, in vivo, or by producing mutations.
Limited resolving power: Fluorescence microscopes are limited in their ability to distinguish close objects at the macroscopic level. In comparison, electron microscopes for example, have the capacity to resolve at a much smaller range.
Limited initial luminosity range: the incidence light source intensity has a limit and beyond this point can result in photodestruction of molecules.
Overall, this form of imaging is extremely useful in cutting-edge research, with its ability to monitor biological processes. The progression from 2D fluorescent images to 3D ones has allowed scientists to better study spatial precision and resolution. In addition, with concentrated efforts towards 4D analysis, scientists are now able to monitor a cell in real time, enabling them to monitor fast acting processes.
Future directions
Developing more effective fluorescent proteins is a task that many scientists have taken up in order to improve imaging probe capabilities. Often, mutations in certain residues can significantly change the protein's fluorescent properties. For example, by mutating the F64L gene in jellyfish GFP, the protein is able to more efficiently fluoresce at 37 °C, an important attribute to have when growing cultures in a laboratory. In addition to this, genetic engineering can produce a protein that emits light at a better wavelength or frequency. In addition, the environment itself can play a crucial role. Fluorescence lifetime can be stabilized in a polar environment.
Mechanisms that have been well described but not necessarily incorporated into practical applications hold promising potential for fluorescence imaging. Fluorescence resonance energy transfer (FRET) is an extremely sensitive mechanism that produce signaling molecules in the range of 1–10 nm.
Improvements in the techniques that constitute fluorescence processes is also crucial towards more efficient designs. Fluorescence correlation spectroscopy (FCS) is an analysis technique that observes the fluctuation of fluorescence intensity. This analysis is a component of many fluorescence imaging machines and improvements in spatial resolution could improve the sensitivity and range.
Development of more sensitive probes and analytical techniques for laser induced fluorescence can allow for more accurate, up-to-date experimental data.
See also
Fluorescence in the life sciences
Fluorescence microscope
References
Further reading
Cell imaging
Fluorescence techniques | Fluorescence imaging | [
"Chemistry",
"Biology"
] | 1,933 | [
"Cell imaging",
"Fluorescence techniques",
"Microscopy"
] |
59,921,578 | https://en.wikipedia.org/wiki/Amplitwist | In mathematics, the amplitwist is a concept created by Tristan Needham in the book Visual Complex Analysis (1997) to represent the derivative of a complex function visually.
Definition
The amplitwist associated with a given function is its derivative in the complex plane. More formally, it is a complex number such that in an infinitesimally small neighborhood of a point in the complex plane, for an infinitesimally small vector . The complex number is defined to be the derivative of at .
Uses
The concept of an amplitwist is used primarily in complex analysis to offer a way of visualizing the derivative of a complex-valued function as a local amplification and twist of vectors at a point in the complex plane.
Examples
Define the function . Consider the derivative of the function at the point . Since the derivative of is , we can say that for an infinitesimal vector at , .
References
Functions and mappings
Complex analysis | Amplitwist | [
"Mathematics"
] | 192 | [
"Mathematical analysis",
"Functions and mappings",
"Mathematical relations",
"Mathematical objects"
] |
59,921,609 | https://en.wikipedia.org/wiki/NGC%201549 | NGC 1549 is an elliptical galaxy located in the constellation Dorado. It is located at a distance of about 50 million light years from Earth, which, given its apparent dimensions, means that NGC 1549 is about 75,000 light years across. NGC 1549 was discovered by John Herschel on 6 December 1835 and may have been observed by James Dunlop in 1826. It is a member of the Dorado Group.
In the centre of NGC 1549 is expected to lie a supermassive black hole, whose mass is estimated to be between 390 and 810 million (10) based on the Sérsic index of the galaxy. No polycyclic aromatic hydrocarbons (PAHs) emission, an indicator for the presence of interstellar dust, was detected by the Infrared Spectrograph onboard Spitzer Space Telescope. NGC 1549 has been found to emit X-rays, with its total flux exceeding ergs s–1 for the 0.3–5 keV band. A total number of 150 globular clusters are estimated to exist in NGC 1549, a number low compared to similar size galaxies. The outer isophotes of the galaxy appear twisted and feature faint shells.
NGC 1549 forms an interacting pair with the lenticular galaxy NGC 1553, which lies 12 arcminutes to the south. It is the largest elliptical galaxy in a moderate size galaxy group known as the Dorado Group.
References
External links
NGC 1549 on SIMBAD
Elliptical galaxies
Dorado
Dorado Group
1549
14757
Astronomical objects discovered in 1826
Discoveries by James Dunlop
Discoveries by John Herschel | NGC 1549 | [
"Astronomy"
] | 325 | [
"Dorado",
"Constellations"
] |
59,921,762 | https://en.wikipedia.org/wiki/Botryosphaeran | Botryosphaeran is an exopolysaccharide (EPS) produced by the ascomyceteous fungus Botryosphaeria rhodina. Characterization of the chemical structure of botryosphaeran showed this EPS to be a (1→3)(1→6)-β-D-glucan. This particular β-glucan can be produced by several strains of Botryosphaeria rhodina that include: MAMB-05, DABAC-P82, and RCYU 30101. Botryosphaeran exhibits interesting rheological properties and novel biological functions including hypoglycaemia, hypocholesterolaemia, anti-atheroslerosis and anti-cancer activity, with potential commercial applications. Three cosmetic products formulated with botryosphaeran have been developed to promote skin health and treat skin conditions for future intended commercialization purposes.
History
The ascomycete and filamentous fungus, Botryosphaeria rhodina (strain MAMB-05), was isolated from a canker on the trunk of a eucalypt tree, and was molecularly characterized by sequencing the Internal Transcribed Spacer (ITS) region of rDNA.
The β-glucan, botryosphaeran, was discovered accidentally in 1994 while cultivating Botryosphaeria rhodina MAMB-05 on nutrient media containing glucose to produce the enzyme, laccase. This fungal isolate produces a constitutive laccase that could be induced to higher enzyme titers by various lignin-like aromatic compounds, and especially veratryl alcohol. The fungus was found to be ligninolytic.
Botryosphaeran is secreted by the fungus during growth and appears in the fermentation broth where its presence causes an increase in the broth's viscosity. It can easily be extracted from the broth by precipitation methods. Veratryl alcohol, however, suppresses the formation of botryosphaeran.
Production and isolation
Botryosphaeran is produced under submerged fermentation conditions when Botryosphaeria rhodina MAMB-05 is grown on nutrient media containing glucose and mineral salts. Extracting the fermentation broth with alcohol causes the EPS (botryosphaeran) to precipitate from solution, and this can be separated by centrifugation or filtration.
The precipitate recovered can be lyophilized to a white fibrous material that is sparingly soluble in water. Alternatively, the recovered precipitate is resolubilized in water (gentle heating with stirring) to form a viscous solution that forms a firm gel when cooled to 5 °C. Solubilization of botryosphaeran can be enhanced through chemical derivatization with various functional groups.
The influence of the composition of the nutrient medium, including nitrogen, phosphate, minerals, supplements (soybean oil, Tween 80), and the carbon source (carbohydrates), is important in enhancing the production of botryosphaeran and biomass during fermentation by Botryosphaeria rhodina MAMB-05.
Catabolite repression, and the presence of β-glucan-hydrolyzing enzymes that attack botryosphaeran during the fermentation process are critical and limit the production of botryosphaeran.
Statistical factorial design methods, such as the response surface methodology (RSM), are effective in investigating complex fermentation parameters and their interactions to optimize metabolite production by microorganisms. RSM assists in defining the effects and interactions of the physiological factors playing a role in biotechnological processes in the production of microbial metabolites including exopolysaccharides such as β-glucans. Statistical methodologies reduce the number of experiments to provide sufficient information for statistically acceptable results.
The validation of the fermentation parameters by statistical factorial design improved botryosphaeran production by Botryosphaeria rhodina MAMB-05 over unoptimized conditions.
Botryosphaeria rhodina MAMB-05 when grown on nutrient media containing different carbohydrate substrates produces a family of botryosphaerans. These β-glucans differ only in the extent and frequency of side-chain substituents.
Botryosphaeran production can be enhanced when Botryosphaeria rhodina MAMB-05 is cultivated on glucose media containing soybean oil and the surfactant, Tween 80.
The most attractive feature for the commercialization of botryosphaeran is the ease by which it can be produced by simple fermentation processes on low-cost nutrient media, and its subsequent isolation through precipitation with ethanol, which all takes place on a time-scale of days compared to other commercial β-glucans available on the market. The latter are extracted from fungal fruiting bodies (mushrooms, fungal brackets), spent Brewers yeast, and cereal grains (barley, oat) that can take weeks-to-months to prepare.
The mycelium of Botryosphaeria rhodina MAMB-05 is a rich source of β-glucans.
Chemical structure
The chemical structure of botryosphaeran was first described in 2003, and was determined using the methods: methylation analysis, Smith degradation, Gas Chromatography-Mass Spectroscopy (GC-MS) and 13C NMR.
Hydrolysis
Total acid hydrolysis of botryosphaeran produces only D-glucose, while partial acid hydrolysis and enzymatic hydrolysis produces a series of homologous gluco-oligosaccharides of different degrees of polymerization, which can be analyzed by High Performance Liquid Chromatography (HPLC).
Enzymatic digestion of botryosphaeran under controlled conditions employing the enzymes: β-(1→3)-glucanases and β-(1→6)-glucanases from Botryosphaeria rhodina MAMB-05,Trichoderma harzianum Rifai, and Aureobasidium pullulans 1WA1, produces a mixed series of β-(1→3)- and β-(1→6)- linked gluco-oligosaccharides that can serve as prebiotics.
Enzymes hydrolyzing botryosphaeran can be obtained by cultivating Botryosphaeria rhodina MAMB-05, Trichoderma harzianum Rifai and Aureobasidium pullulans 1WA1 on nutrient media containing either botryosphaeran, or the biomass derived from Botryosphaeria rhodina MAMB-05, which is a rich source of β-glucans.
Prebiotics such as the (1→3)-linked gluco-oligosaccharides are emerging as nutraceuticals for inclusion in foods. Botryosphaeran can serve as a source of conveniently generating these oligosaccharides through enzymatic hydrolysis.
Chemical structure characterization
Methylation and Smith degradation analysis revealed that botryosphaeran constituted a backbone chain made up of (1→3)-β-linked glucose residues (i.e., it is a (1→3)-β-D-glucan) with β-(1→6)-linked glucose and di-glucose (gentiobiose) side-branches located at the C-6 position of glucose along the (1→3)-linked backbone chain. The chemical structure of botryosphaeran is a (1→3)(1→6)-β-D-glucan. 13C NMR spectroscopy confirmed its structure.
The degree of branching of the family of botryosphaerans varies from 21 to 31%. depending upon the carbohydrate source in the nutrient media during fermentation by the fungus, and this also affects the molecular weight (MW) of the botryosphaerans produced, which can be large (order of >1 x 106 daltons)
Botryosphaeran exists in a triple helix conformation, an important structural feature in manifesting biological response modifying activities.
Derivatization of botryosphaeran by carboxymethylation and sulfonylation results in improved solubility in water, and diminishes its viscous nature in solution.
In the case of sulfonated botryosphaeran, the chemically modified polysaccharide containing sulfonate groups exhibited new biological functions: anticoagulation, and antiviral activity against enveloped viruses such as human herpes simplex and Dengue, The latter is a mosquito-borne virus.
Related exopolysaccharides (β-glucans) from several strains of Botryosphaeria rhodina (the teleomorph Lasiodiplodia theobromae) isolated from rotting tropical fruits have been described, The chemical structures of three β-glucans produced were characterized; a (1→3)(1→6)-β-D-glucan with a single glucose repeat substituent (frequency of 20%), an unbranched (1→6)-β-glucan named lasiodiplodan, and a new (1→3)(1→6)-β-glucan with unique branches comprising gentiobiose and gentiotriose residues, but not glucose.
Structural characterization of the cell wall (mycelium) of Botryosphaeria rhodina MAMB-05 revealed the presence of three different D-glucans; a linear (1→6)-β-glucan, a branched (1→3)(1→6)-β-glucan with single glucose repeat branches (frequency of 18%), and a glycogen-like (1→4)(1→6)-α-glucan.
Biosafety
Botryosphaeran was demonstrated in extensive studies on mice and mammalian cell-lines (hamster, rat, human) that it was not mutagenic (assessed by the micronucleus test), nor was it genotoxic as assessed by the Ames test and Comet assay.
When administered orally to mice by gavage, botryosphaeran reduced the clastogenic effect of cyclophosphamide-induced micronucleus formation in bone marrow (polychromatic erythrocytes) and peripheral blood (reticulocytes) cells.
Using mammalian cell lines: lung fibroblasts (Chinese hamster) and hepatocarcinoma cells (rat), botryosphaeran was confirmed not to be mutagenic nor genotoxic by the micronucleus test and Comet assay procedures. Botryosphaeran exhibited no mutagenicity, and protected cultured human whole blood lymphocytes against DNA damage and cell death induced by bleomycin throughout the cell cycle stage. Botryosphaeran exhibited antigenotoxic activity against damage induced by methyl methanesulfonate, in normal and tumorigenic (Jurkat) human lymphocytes.
The absence of mutagenicity and genotoxicity assessed by the micronucleus, Ames and MTT tests, and the Comet assay, established that botryosphaeran has GRAS status (Generally Recommended As Safe), and is safe for use by humans and animals.
Rheological properties
The rheological properties of botryosphaeran has been described.
Botryosphaeran forms a viscous solution when dissolved in water that is stable to heat as occurs during autoclaving (steam sterilization). When an aqueous solution of botryosphaeran is cooled to 5 °C, it forms a strong gel that is firm and transparent.
Biological functions
Botryosphaeran possesses in-vitro free-radical scavenging properties and antioxidant activities.
Botryosphaeran exhibits an in-vivo antioxidant role in the β-cell line INS-1E derived from rat insulinoma (tumor of the pancreas derived from β-cells). Oxidative stress was induced by hydrogen peroxide (H2O2) in the INS-1E cells under high glucose, and botryosphaeran decreased this condition by reducing the production of reactive oxygen species (ROS). Apoptosis increased in the INS-1E cells treated with H2O2 in high glucose conditions, and treatment with botryosphaeran attenuated apoptosis.
Botryosphaeran exerts a chemoprotective effect exhibiting strong antimutagenic (anticlastogenic) activity against the in-vivo DNA-damaging effect of cyclophosphamide in mice., and genotoxic damage by doxorubicin in fibroblasts and hepatocarcinoma cells, bleomycin in human lymphocytes, and methyl methanesulfonate in Jurkat cells.
Botryosphaeran exhibits hypoglycaemic activity (lowering of blood glucose levels) in rats in which diabetes was induced by intramuscular injection of streptozotocin, which selectively damages the pancreatic insulin-secreting β-cells resulting in type-1 diabetes condition.
The cholesterol-lowering effect (hypocholesterolaemia) of β-glucans derived from oat and barley (β-(1→3)(1→4)-linked D-glucans) is well established. Botryosphaeran exhibits hypocholesterolaemic activity lowering total cholesterol and Low Density Lipoprotein (LDL)-cholesterol blood levels in rats preconditioned on hyperlipidaemic diets.
In experiments with elderly male knockout LDLr-/-mice (LDLreceptor-deficient mice that show elevated plasma cholesterol levels and develop atherosclerosis), botryosphaeran reduced the plasma glucose levels, improved the lipidic profiles, reduced LDL-cholesterol, and decreased aortic lipid deposition that lowers cardiovascular risks of atherosclerosis.
Treatment of obese rats with botryosphaeran by gavage was effective in ameliorating the comorbidities (diabetes, dyslipidaemia, hepatic steatosis) associated with obesity. Botryosphaeran reduces hepatic steatosis and dyslipidaemia, and glucose intolerance in diet-induced obese rats through activation of AMP-activated protein-kinase (AMPK) and the expression of the Forkhead transcription factor, FOXO3a, in adipose tissue.
Obese rats showed significant increases in weight gain, adipose tissue mass, and adiposity and atherogenic indices, and presented glucose intolerance, insulin resistance, dyslipidaemia, and hepatic steatosis. Botryosphaeran significantly reduces feed intake, weight gains, periepididymal and mesenteric fat, and improves glucose tolerance in obese rats. Botryosphaeran, furthermore, reduces the serum levels of triglyceride and VLDL-cholesterol, and increased HDL-cholesterol and glycogen in liver, and reduces the atherogenic index.
The above data demonstrated the beneficial effects of botryosphaeran in reducing the stimulatory effect of obesity on dyslipidaemia and hepatic steatosis, and can play a potential role in the management of obesity comorbidities.
Studies on human carcinoma cell-lines: Jurkat (lymphocytes) and breast (MCF-7) demonstrated that botryosphaeran manifests anti-cancer activity.
The action by which anticancer activity occurs is still not well understood, but a mechanistic insight on how this may occur in breast cancer MCF-7 cells was advanced in 2015, and involves cell-signaling pathways that suppress tumourigenesis (cell antiproliferation) through apoptosis, necrosis and oxidative stress. Botryosphaeran-induced apoptosis was mediated by AMPK and FOXO3a.
In tumorigenic human lymphocytes (Jurkat cells), botryosphaeran modulates gene expression and regulates cell cycle and the cell cycle checkpoint.
Encapsulation of probiotic bacteria (Lactobacillus casei) in alginate microspheres together with botryosphaeran and mucilages from linseed and okra increases the encapsulation efficiency, and improves the stability of the encapsulated probiotic bacteria during prolonged storage at 5 °C. Gastrointestinal simulation of the microencapsulated Lactobacillus casei cells demonstrated preservation of the viability of the probiotic bacteria against low pH and bile salts. The use of botryosphaeran in microencapsulating probiotic bacteria appears to be another promising application for this β-glucan.
New applications for botryosphaeran have included: biological response modifying activities of derivatized botryosphaerans; treatment of skin conditions (eczema, psoriasis, wound healing); antimicrobial activities; antinociceptive activity; as a matrix for enzyme (laccase) immobilization; as a platform for electrochemical sensors; and as a food additive (nutraceutical).
The biomass resulting from Botryosphaeria rhodina MAMB-05 on producing botryosphaeran by submerged fermentation has been successfully used as a biosorbent to extract metallic species; rare earth elements (lanthanides; La, Sm), and heavy metals (lead; Pb) from industrial effluents.
References
Biomolecules
Rheology
Probiotics
Carbohydrates
Fermentation
Biomass
Polysaccharides
Prebiotic chemistry
Botryosphaeriales | Botryosphaeran | [
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"Biology"
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59,921,988 | https://en.wikipedia.org/wiki/Metallurgy%20in%20Azerbaijan | The metallurgical production of the Republic of Azerbaijan is considered high due to the large deposits of alunite, polymetallic ores, deposits of iron ore, etc. The metallurgy industry of Azerbaijan encompasses both ferrous and non-ferrous branches.
Ferrous metallurgy
Ferrous metallurgy includes extraction of iron, smelting and refining of iron ore, rolling and ferroalloys production. The ferrous metallurgy production of the country started to meet the demand of oil and gas industry (due to pipe production) and grew further in order to improve other branches of the industry. Dashkasan iron ore in 4 deposits (Dashkesen, South Dashkasan, Hamanchay, Demiroglu) in the valley of Goshagarchay plays a key role in the development of ferrous metallurgy. The cities of Baku, Sumgait and Dashkesan are major centers of metallurgy in terms of extraction and processing of iron ore. The Sumgait Pipe-Rolling Plant produces drill pipes, casing, tubing, oil and gas pipes, etc. Bentonite clay deposits in the village of Dash Salakhly, Gazakh district, is used in steel smelting. Baku Steel Company, the largest metallurgical enterprise in Azerbaijan, was opened in 2001 on the initiative of Heydar Aliyev. With two electric arc furnaces and three rolling lines, the annual steel production capacity of the company increased to 1,000,000 tons.
Non-ferrous metallurgy
Aluminum, copper, molybdenum, cobalt, mercury reserves and most importantly electricity for the smelting process has led to the development of non-ferrous metallurgy. The Zeylik mine in Daskasan district is the main provider of the alunite for aluminum production. The extracted ore here transported through Guschu-Alabashli railway to the aluminum plant located in Ganja city. The obtained aluminum oxide is brought to Sumgayit aluminum plant in order to produce aluminum. Ganja Aluminum Plant produces sulfuric acid, aluminum oxide, and potassium fertilizer through extracted ore from Zalik deposit in Dashkesen. Aluminum oxide is also produced in Sumgait. AzerGold CJSC (created by the Presidential Decree No. 1047 on February 11, 2015) implements exploration, management, and also extraction, processing and sale of precious and non-ferrous metal ore deposits located within the borders of the country. In 2017, the volume of exports of precious metals carried out by this company amounted to 77340 million dollars.
Gold mining
Gold mining began in Gedebey in 2009. In 2016, Azer Gold CJSC began gold mining in the Chovdar deposit. In 2017, 6,390.8 kg of gold was mined (which exceeded the 2016 production by 3.4 times. Gold production in January–May 2018 amounted to 2,081.7 kg, which exceeds last year's data by 19.5%. In the first quarter of 2018, the company's exports amounted to $30 million. In 2017, 59,617 ounces of gold produces by Anglo Asian Mining PLC (the main gold producer in Azerbaijan) from Gadir Ugur and Gosha deposits.
Large metallurgical enterprises
Sumgait Aluminum Plant
Ganja Aluminum Plant
Bakı Poladtökmə
Bakusteelcompany
Sumgait Pipe Plant
AzerGold
CJSC Global Construction
CJSC Atahan Dirmir Sənaye
Daşkəsən Filizsaflaşdırma
Azərboru
Azərqızıl
Azertexnolayn LLC
http://www.azertexnolayn.com/en/
See also
Natural Resources of Azerbaijan
Environment of Azerbaijan
References
Metallurgy
Economy of Azerbaijan
Metallurgical industry of Azerbaijan | Metallurgy in Azerbaijan | [
"Chemistry",
"Materials_science",
"Engineering"
] | 815 | [
"Metallurgical industry of Azerbaijan",
"Metallurgy",
"Materials science",
"nan",
"Metallurgical industry by country"
] |
59,923,022 | https://en.wikipedia.org/wiki/Adams%20Plating | Adams Plating, also known as Adam's Plating, is a Superfund site in Lansing Charter Township near Lansing, Michigan.
Prior to 1964, a dry cleaning business was located at the site, and stored dry cleaning fluid there in an underground storage tank, which was removed in the 1950s. Electroplating operations involving the use of chrome and various metals began in 1964, following a change in ownership. Prior to 1980, these operations contaminated the soil and groundwater at the site, most notably with chromium, along with copper, nickel, and zinc (in both soil and groundwater) and arsenic (in the soil alone). In July 1980, green-colored chromium-tainted water was found to be leaking into the basement of a residence near the site.
Following investigations at the site from 1980 to 1993, an initial cleanup was completed in 1994. The cleanup began upon completion of a remedial investigation report in March 1993 and was substantially complete by September 1994, an expedited time frame made possible in part by the absence of lead at the site, and by the absence of potentially responsible parties as designated by the Superfund law. Five-year reviews of the site have since been undertaken by the Environmental Protection Agency (EPA).
The Adams Plating building was destroyed by a fire on December 27, 2010, after which the EPA and the Michigan Department of Environmental Quality undertook an emergency cleanup that included moving hazardous chemicals from the site. EPA demolished the building and conducted additional soil cleanup at the site in 2011. The incident prompted Ingham County and Lansing Township emergency response agencies to reassess their preparedness for emergencies at contaminated sites.
The EPA recorded elevated levels of benzene in residences near the site in 2016.
See also
List of Superfund sites in Michigan
References
Superfund sites in Michigan
Geography of Ingham County, Michigan
Chromium
Metal plating | Adams Plating | [
"Chemistry"
] | 382 | [
"Metallurgical processes",
"Coatings",
"Metal plating"
] |
59,923,373 | https://en.wikipedia.org/wiki/Web%20data%20integration | Web data integration (WDI) is the process of aggregating and managing data from different websites into a single, homogeneous workflow. This process includes data access, transformation, mapping, quality assurance and fusion of data. Data that is sourced and structured from websites is referred to as "web data". WDI is an extension and specialization of data integration that views the web as a collection of heterogeneous databases.
Data integration techniques in the context of the web, forms the foundation for businesses taking advantage of data available on the ever-increasing number of publicly-accessible websites. Corporate spending on this area amounted to about USD 2.5bn in 2017, and it is expected that by 2020 the market will reach almost USD 7bn.
Sources
Web data integration extends and specializes data integration to see the web as a collection of views of databases accessible over the web protocols, including, but not limited to:
Open data catalogs
Government data catalogs
Web applications and sites
UI (web scraping)
API
The semantic web (SPARQL)
HTML embedded structured data
HTML data tables
Spreadsheets
PDFs
Online encyclopedias
Data access and transformation
WDI has technical challenges different from data integration due to the data access and transformation required for the web data sources being often unstructured or semi-structured data without a standard query mechanism.
Data quality
Understanding the quality and veracity of data is even more important in WDI than in data integration, as the data is generally less implicitly trusted and of lower quality than that which is collected from a trusted source. There are attempts to try to automate a trust rating for web data.
Data quality in data integration can generally happen after data access and transformation, but in WDI quality may need to be monitored as data is collected, due to both the time and the cost of re-collecting the data.
Applications
WDI has application in many fields, including bioinformatics, search engines, price comparison, and forensic search data analysis, business intelligence, ecommerce, healthcare, pharmaceutical and product development.
Most price comparison engines and recommendation systems use user generated data to create recommendations for their users. Similarly, healthcare systems use results of competitions conducted on websites like Kaggle to see the accuracy of data and to create user-focused products. In fact, IBM estimates that poor quality WDI is costing companies over $3 trillion in revenue each year.
References
Data management
Data integration | Web data integration | [
"Technology"
] | 487 | [
"Data management",
"Data"
] |
59,923,476 | https://en.wikipedia.org/wiki/Unihertz%20Jelly | The Unihertz Jelly (also the enhanced model, Unihertz Jelly Pro) is an Android smartphone developed by Unihertz, which billed it as "the smallest 4G smartphone" upon its release in 2017. It was initially developed with a successful Kickstarter project which reached its $30,000 goal in just 57 minutes, and eventually raised over $1.25 million. The Unihertz Jelly Pro is still currently available for sale in over 60 countries, including major retailers.
Specifications
Unihertz Jelly and Jelly Pro are both marketed as a phone with the full features of Android 7.0 Nougat and support for a 4G network, but are much more lightweight and compact than other phones with this same functionality. They feature a 2.45-inch display and weigh in at 60 grams.
In 2020, its successor, Unihertz Jelly 2, was released, which features a slightly larger display.
Software
Hardware
Reception
Unihertz was associated with a previous very small 3G smartphone, the Posh Micro X, which launched in 2015.
Reviews of Jelly and Jelly Pro, the "world's smallest 4G smartphone" have been mixed,
but it drew international attention.
There have been accusations of poor battery performance, and network traffic possibly sending personal data to China. Responses claim the network traffic is to speed up apps, and the company has been updating the phone software to improve performance. However, others have disputed this claim. It has received mixed reviews, with some critics calling it "innovative", praising it for its capabilities at such a small size.
References
Smart devices
Android (operating system) devices | Unihertz Jelly | [
"Technology"
] | 337 | [
"Home automation",
"Smart devices"
] |
58,265,319 | https://en.wikipedia.org/wiki/Heok%20Hui%20Tan | Heok Hui Tan is a Singaporean ichthyologist at the Lee Kong Chian Natural History Museum of the National University of Singapore. Dr. Tan's main interest lies in the systematics of Southeast Asian freshwater fishes, encompassing taxonomy, ecology and biogeography. His primary areas of research focus on neglected and de novo habitats such as peat swamp forests, swamp forests, and rapids.
As of 2018, Tan has authored two species of Osphronemidae (Luciocephalus aura and Betta pi).
Publications (selection)
The Borneo Suckers: Revision of the Torrent Loaches of Borneo (Balitoridae, Gastromyzon, Neogastromyzon) (Natural History Publications (Borneo): 2006)
Britz, R., Kottelat. M, & Tan, H.H. 2011. Fangfangia spinicleithralis, a new genus and species of miniature cyprinid fish from the peat swamp forests of Borneo (Teleostei: Cyprinidae). Ichthyological Exploration of Freshwaters 22(4): 327–335. (PDF)
Tan has (co-)authored many publications. Also see the list of publications in the external links.
See also
:Category:Taxa named by Heok Hui Tan
References
External links
Hui Tan on Freshwater and Invasion Biology Laboratory (FIB Lab)
Living people
Taxon authorities
Singaporean ichthyologists
Year of birth missing (living people) | Heok Hui Tan | [
"Biology"
] | 299 | [
"Taxon authorities",
"Taxonomy (biology)"
] |
58,265,682 | https://en.wikipedia.org/wiki/Carboryne | In organoboron chemistry, a carboryne is an unstable derivative of ortho-carborane with the formula B10C2H10. They are also called 1,2-dehydro-o-carboranes. The hydrogen atoms on the C2 unit in the parent o-carborane are missing. The compound resembles and is isolobal with benzyne. A carboryne compound was first generated in 1990 starting from o-carborane. The hydrogen atoms connected to carbon are removed by n-butyllithium in tetrahydrofuran and the resulting lithium dianion is reacted with bromine at 0 °C to form the bromo monoanion.
Heating the reaction mixture to 35 °C releases carboryne, which can subsequently be trapped with suitable dienes:
such as anthracene (to afford a triptycene-like molecule) and furan in 10 to 25% chemical yield.
Carborynes react with alkynes to benzocarboranes in an adaptation of the above described procedure. O-carborane is deprotonated with n-butyllithium as before and then reacted with dichloro-di(triphenylphosphino) nickel to a nickel coordinated carboryne. This compound reacts with 3-hexyne in an alkyne trimerization to the benzocarborane.
Single crystal X-ray diffraction analysis of this compound shows considerable bond length alternation in the benzene ring (164.8 pm to 133.8 pm) ruling out aromaticity.
See also
Heteroborane
Organoboron chemistry
References
Organoboron compounds
Cluster chemistry | Carboryne | [
"Chemistry"
] | 353 | [
"Cluster chemistry",
"Organometallic chemistry"
] |
58,267,469 | https://en.wikipedia.org/wiki/Teresa%20Head-Gordon | Teresa Lyn Head-Gordon (née Teresa Lyn Gordon) is an American chemist and the Chancellor's Professor of Chemistry, Bioengineering, and Chemical and Biomolecular Engineering at the University of California, Berkeley. She is also a faculty scientist in the Chemical Sciences Division at the Lawrence Berkeley National Laboratory and a fellow of both the American Institute for Medical and Biological Engineering (AIMBE ) and the American Chemical Society (ACS).
Early life and education
Head-Gordon was born in Akron, Ohio. She completed her bachelor's degree in chemistry at Case Western Reserve University in 1983. She worked as a waitress for a year before starting a PhD in 1984, and in 1989 she earned her doctorate degree in Theoretical Chemistry from Carnegie Mellon University under the supervision of Charles L. Brooks III.
Research and career
From 1990 to 1992 Head-Gordon worked as a postdoctoral member of technical staff at Bell Labs, studying protein folding and the perturbation theories of water with Frank Stillinger. She joined Lawrence Berkeley National Laboratory in 1992, where she worked as a staff scientist until 2001. In 2001 Head-Gordon was awarded the IBM-SUR Award. That year she became a faculty member of Bioengineering at University of California, Berkeley. She was the 2005 Schlumberger Fellow at the University of Cambridge. In 2011 she became a member of Chemical and Biomolecular Engineering department; in 2012 she joined the chemistry department at University of California, Berkeley., and joined the chemical sciences division as a faculty scientist at Lawrence Berkeley National Laboratory. In 2012 she was made the Chancellor’s Professor at the University of California, Berkeley. She is a member of the Pitzer Center for Theoretical Chemistry.
Head-Gordon develops theoretical models that are used in chemical physics and biophysics. The Head-Gordon group studies condensed phase systems ranging from biomolecular systems, molecular liquids, and complex interfaces. Her group develops software packages for molecular simulations.
She is on the Board of Directors of the Molecular Sciences Software Institute. She became co-director of CalSov in 2016. In 2016 she was elected a fellow of the American Institute for Medical and Biological Engineering for her contributions to the computational methodologies for macromolecular assemblies. In 2018 she was elected a Fellow of the American Chemical Society.
References
Living people
21st-century American chemists
Carnegie Mellon University alumni
Case Western Reserve University alumni
Academics from Ohio
Year of birth missing (living people)
Computational chemists
Theoretical chemists
UC Berkeley College of Chemistry faculty | Teresa Head-Gordon | [
"Chemistry"
] | 505 | [
"Quantum chemistry",
"Physical chemists",
"Computational chemists",
"Theoretical chemistry",
"Computational chemistry",
"Theoretical chemists"
] |
58,268,288 | https://en.wikipedia.org/wiki/Maki%20Kawai | is a Japanese chemist who developed spatially selective single-molecule spectroscopy. In 2018, she became the first woman to become president of the Chemical Society of Japan.
Early life and education
Kawai earned her bachelor's degree at the University of Tokyo in 1975. She completed her doctoral studies at the University of Tokyo in 1980. Her PhD was supervised by Kenji Tamaru.
Research and career
Kawai was a postdoctoral researcher at Riken between 1980 and 1982. She joined the University of Tokyo as a Japan Society for the Promotion of Science fellow in 1982. Her research considers the vibrational dynamics of single-molecules at surfaces. Her group use STM to monitor molecules and atoms on top of surfaces. She uses this to understand the chemical and physical phenomena of nanowires, nanodots and biomolecules. She was awarded fellowships from the Surface Science Society of Japan and American Physical Society to develop single molecule spectroscopy. Her group monitor the vibrational and relaxation energies of single molecules using scanning tunneling microscopy and inelastically tunnelled electrons. She has contributed to several books and hundreds of peer-reviewed publications. Kawai continued to be supported by the Japan Society for the Promotion of Science, investigating nanoscale electron transport through molecular layers. By combining single molecule spectroscopy (using scanning tunneling spectroscopy) with inelastic electron tunneling spectroscopy to identify electron transfer channels. She discovered a new reaction pathway on the surface of titanium dioxide.
Kawai became Chief Scientist and Director of Surface Chemistry Laboratory at Riken in 1991 and an executive director in 2010. She was made a professor at the University of Tokyo in 2004. Kawai joined the Institute of Molecular Science as Director General in 2016. She was appointed President of the Chemical Society of Japan in 2018.
Awards and honours
2021 Person of Cultural Merit
2019 L'Oréal-UNESCO For Women in Science Awards
2018 Honorary Fellow of the Royal Society of Chemistry (UK)
2018 Kiel University Diels-Planck Lecture
2017 Medal of Honor with Purple Ribbon from the Japanese government
2016 American Vacuum Society Medard W. Welch Award
2015 IUPAC Distinguished Women in Chemistry / Chemical Engineering
2015 Max Planck Society Gerhard Ertl Lecture Award
2012 Mukai Award, Japan
2008 Commendation for Science and Technology by the Minister of Education, Culture, Sports, Science and Technology, Prize for Science and Technology
2009 Chemical Society of Japan Award
References
Living people
Japanese chemists
Japanese women chemists
University of Tokyo alumni
Academic staff of the University of Tokyo
Riken personnel
Recipients of the Medal of Honor (Japan)
Chemical Society of Japan
L'Oréal-UNESCO Awards for Women in Science laureates
Persons of Cultural Merit
Year of birth missing (living people)
Fellows of the American Physical Society | Maki Kawai | [
"Chemistry"
] | 541 | [
"Chemical Society of Japan"
] |
58,269,179 | https://en.wikipedia.org/wiki/Galactomyces%20reessii | Galactomyces reessii is a yeast, belonging to the genus Galactomyces. G. reessii that lives in soil and dissolves pectin.
Natural Occurrence and Reproduction
Galactomyces reessii lives naturally in soil and on decaying vegetable matter.
G. reessii does not consume D-mannitol. It cannot ferment glucose. Both D-mannitol and glucose are present in plant matter which impacts G. reessii's ability to digest decaying vegetation.
There are two reproductive states for G. reessii: an asexual and a sexual form. The asexual form is called arthroconidia; and the sexual form is called ascomycetous. Ascomycetous for G. reessii involves the creation of ascospores, which come from a fruit called ascocarp. These fruits are known to have hyphae with pores that include Woronin bodies. These bodies act as plugs when a trauma happens to the hyphal segments. In the asci, there are usually around eight ascospores. The ascospores could be single cellular or multicellular.
Enzymes and Uses
G. reessii contains enzymes that have diverse capabilities including the abilities to dissolve pectin,and remove phenol. G. reessii contains an enzyme that converts 3-methylcrotonic acid to 3-hydroxy-3-methylbutyric acid aka β-hydroxy β-methylbutyric acid. β-hydroxy β-methylbutyric acid (HMB) produced from Galactomyces reessii, was discovered to be beneficial to people engaging in resistance training.
It can also have an enzyme that dissolves pectin. G. reesii was used in a study for its "propectin-solubilizing enzyme-producing". Its enzyme was purified using chromotography and isolated as a crystalline form. The enzyme is a glycoprotein and catalyzes the highly polymerized pectin release from protopectins. The enzyme also works as a catalyst for the depolymerization of pectic acid oligomers.
Galactomyces reesii was studied as a treatment to remove phenolic contamination from palm oil extraction. G. reessii was isolated from subterranean termites. In this study, it was found that the enzymes, laccase and manganese peroxidase worked to depolymerize lignin, which is rich in phenol. During palm oil extraction, large amounts of water are used and contaminated with phenol. Phenol is dangerous because it's toxic to humans and can work as a corrosive. The results from this study indicated G. reessii could work as a phenol removal strain. This study concluded that this information could be used to make more efficient wastewater treatment systems for the removal of phenol.
References
Saccharomycetes
Fungus species | Galactomyces reessii | [
"Biology"
] | 627 | [
"Fungi",
"Fungus species"
] |
58,269,370 | https://en.wikipedia.org/wiki/Ortho-Carborane | ortho-Carborane is the organoboron compound with the formula C2B10H12. The prefix ortho is derived from ortho. It is the most prominent carborane. This derivative has been considered for a wide range of applications from heat-resistant polymers to medical applications. It is a colorless solid that melts, without decomposition, at 320 °C
Structure
The cluster has C2v symmetry.
Preparation
Ortho-carborane is prepared by the addition of acetylenes to decaborane(14). Modern syntheses involve two stages, the first involving generation of an adduct of decaborane:
B10H14 + 2 SEt2 → B10H12(SEt2)2 + H2
In the second stage, the alkyne is installed as the source of two carbon vertices:
B10H12(SEt2)2 + C2H2 → C2B10H12 + 2 SEt2 + H2
Substituted acetylenes can be employed more conveniently than acetylene gas. For example bis(acetoxymethyl)acetylene adds to the decarborane readily.
B10H12(SEt2)2 + C2(CH2O2CCH3)2 → C2B10H10(CH2O2CCH3)2 + 2 SEt2 + H2
The organic substituents are removed by ester hydrolysis followed by oxidation:
3 C2B10H10(CH2O2CH3)2 + 10 KOH + + 8 KMnO4 → 3 C2B10H12 + 6 CH3CO2K + 8 MnO2 + 6 K2CO3 + 8 H2O
Reactions
Thermal rearrangement
Upon heating to 420 °C, it rearranges to form the meta isomer. The para isomer is produced by heating to temperatures above 600 °C.
Reduction and "reverse isomerization"
ortho-Carborane undergoes 2e- reduction when treated with a solution of lithium in ammonia. The result is the nido cluster 7,9-[C2B10H12]2-. In the dianion, the carbon vertices are not adjacent. The same cluster is produced by reduction of meta-carborane. Oxidation of the resulting 7,9-[C2B10H12]2- gives ortho-carborane.
Deprotonation
Treatment with organolithium reagents gives the dilithio derivative.
C2B10H12 + 2 BuLi → Li2C2B10H10 + 2 BuH
This dilithiated compound reacts with a variety of electrophiles, e.g. chlorophosphines, chlorosilanes, and sulfur.
Base-degradation to dicarbollide
Base degradation of ortho carborane gives the anionic 11-vertex derivative, precursor to dicarbollide complexes:
C2B10H12 + NaOEt + 2 EtOH → Na+C2B9H12− + H2 + B(OEt)3
Na+C2B9H12− + NaH → Na2C2B8H11 + H2
Dicarbollides (C2B8H112-) function as ligands for transition metals and f-elements. The dianion forms sandwich compounds, bis(dicarbollides). Dicarbollides, being strong electron donors, stabilize higher oxidation states, e.g. Ni(IV).
Deprotonation of carborane
The CH vertices of closo-dicarbadodecaboranes undergo deprotonation upon treatment with organolithium reagents:
C2B10H12 + 2 BuLi → Li2C2B10H10 + 2 BuH
These dilithiated compounds react with a variety of electrophiles, e.g. chlorophosphines, chlorosilanes, and sulfur. Many of the same compounds can be produced by hydroboration of alkynes:
Li2C2B10H10 + 2 RX → R2C2B10H10 + 2LiX
L2B10H10 + RC2R → R2C2B10H10 + 2L (L = MeCN, etc.)
ortho-Carborane can be converted to highly reactive carborynes with the formula B10C2H10.
Substitution at the boron vertices
Unlike the hydrogens on the carbon vertices, the hydrogens on the boron vertices are not acidic and do not react with strong bases. This is because boron is not as electronegative as carbon and thus the polarity of the B—H bonds is relatively low. Substitution at the boron vertices is still possible using halogenating agents through electrophilic substitution or photochemical reactions.
For example, the boron vertices at the 9 and 12 positions opposite to the carbon vertices can be iodinated using iodine and a catalytic amount of AlCl3 while in refluxing dichloromethane.
Exohedral halogenation leads to an increase in the electron withdrawing effect of the carborane which increases the acidity of the C—H bonds especially when the halogens are located at the 9, and 12 positions. Per-halogenation is also possible and when increasing the number of halide atoms, the π backdonation ability of the halide decreases allowing for the formation of intramolecular halide-halide noncovalent bonds.
Iodinated derivatives of carborane can be further modified to access boron alkylated products via a cross coupling reaction. This can be done by treating the halogenated carborane with a Grignard reagent in the presence of a phosphine palladium complex. The bromo and chloro compounds do not react under the same conditions.
Dimerization of carborane
Upon treatment of ortho-carboranes with organolithium reagents such as n-Butyllithium, the CH vertices of the carborane cage can be deprotonated, affording the dilithiated ortho-carborane cage. Taking advantage of this more active carbon-lithium bond, the metalated carborane cages can then be treated with copper(I) chloride while in organic solvents, resulting in a copper-mediated carbon-carbon coupling reaction of the carborane cages. The copper salt is needed to avoid unwanted carbon-boron and boron-boron coupling reactions. The reaction mixture is allowed to stir at room temperature for two days, forming a copper-metalated carborane cage. Finally, the mixture is treated with 3M hydrochloric acid to quench the reaction process. The crude product is then purified via column chromatography and affords one half-equivalent of the carbon-carbon linked dimer of the original ortho-carborane in high yields. Worth noting is the effect of donating solvents on the yields of the reactions, as yields in solvents such as tetrahydrofuran and diethyl ether afford product in greatly decreased yields.
History
The preparation of closo-dicarbadodecaboranes was reported independently by groups at Olin Corporation and the Reaction Motors Division of Thiokol Chemical Corporation working under the U.S. Air Force and published in 1963. These groups demonstrated the high stability in air of 1,2-closo-dodecaborane and related compounds, presented a general synthesis, described the transformation of substituents without destroying the carborane cluster, and demonstrated the ortho to meta isomerization.
See also
Heteroborane
Organoboron chemistry
Platonic hydrocarbon
References
Organoboron compounds
Cluster chemistry | Ortho-Carborane | [
"Chemistry"
] | 1,628 | [
"Cluster chemistry",
"Organometallic chemistry"
] |
58,269,468 | https://en.wikipedia.org/wiki/Asus%20ZenFone%205 | Asus Zenfone 5 is a line of Android smartphones made by Asus. It is part of the Asus Zenfone series. The ZenFone 5 was unveiled on 27 February 2018 at the Mobile World Congress and went on sale on 6 August 2018, while the higher-end ZenFone 5Z was unveiled on 16 May 2018, and went on retail sale on 6 August 2018. The smartphone line also includes the lower-end ZenFone 5 Lite.
Variants
References
Mobile phones introduced in 2018
Mobile phones with multiple rear cameras
Mobile phones with 4K video recording
Discontinued flagship smartphones
Asus ZenFone | Asus ZenFone 5 | [
"Technology"
] | 129 | [
"Mobile technology stubs",
"Discontinued flagship smartphones",
"Flagship smartphones",
"Mobile phone stubs"
] |
58,269,490 | https://en.wikipedia.org/wiki/Nicholas%20Young%20%28mathematician%29 | Nicholas John Young is a British mathematician working in operator theory, functional analysis and several complex variables. He is a research professor at the University of Leeds. Much of his work has been about the interaction of operator theory and function theory.
Publications
Young has written more than a hundred papers, over 30 of them in collaboration with Jim Agler. He is the author of the book An Introduction to Hilbert Space.
His Ph.D. adviser was Vlastimil Pták, and he has had 5 Ph.D. students.
References
1943 births
Living people
Academics of the University of Leeds
Hilbert spaces
Operator theorists
20th-century British mathematicians
Alumni of the University of Oxford | Nicholas Young (mathematician) | [
"Physics"
] | 134 | [
"Hilbert spaces",
"Quantum mechanics"
] |
58,272,296 | https://en.wikipedia.org/wiki/DARVO | DARVO (an acronym for "deny, attack, and reverse victim & offender") is a reaction that perpetrators of wrongdoing, such as sexual offenders, may display in response to being held accountable for their behavior. Some researchers indicate that it is a common manipulation strategy of psychological abusers.
Process
As the acronym suggests, the common steps involved are:
The abuser the abuse ever took place
When confronted with evidence, the abuser then the person that was/is being abused (and/or the person's family and/or friends) for attempting to hold the abuser accountable for their actions, and finally
The abuser claims that they were/are actually the victim in the situation, thus the positions of and . It often involves not just playing the victim but also victim blaming.
Origins
The acronym and the analysis it is based on come from the work of the psychologist Jennifer Freyd, who wrote about it in 1997. The first stage of DARVO, denial, involves gaslighting. Freyd writes:
Usage and effectiveness
Freyd stated that DARVO is frequently used and effective, although the number of people who are inclined to believe a DARVO response decreases once they understand the tactic. However, the examination and determination of who is using DARVO proves to be difficult until the abuser and the victim in a case are clearly established.
DARVO tactics are more successful when abusers can take advantage of societal beliefs and stereotypes to convince their audience of their new narrative. In the case of sexual violence, assailants sometimes victim-blame by appealing to societal opinions on gender roles and power dynamics. Stereotypes can help perpetrators: if an assailant is a white wealthy man, he may be perceived as authoritative and sincere, whereas if an accusation against him was made by a journalist, they might be seen as predatory and thus less trustworthy. Stereotypes also can limit the effectiveness or opportunity for DARVO tactics: one example is how the ethnic stereotype of Black men as dangerous predators makes it harder for assailants who are Black men to employ DARVO.
Setting
DARVO is a particular concern in legal contexts and institutional reporting systems, because perpetrators engaging in DARVO tactics frequently use these systems against their victims. Judicial systems often treat alleged perpetrators and victims neutrally during investigations, so an alleged perpetrator and victim have similar legal processes and may have the same access to supportive or protective measures. In American universities, where Title IX offices often handle investigations of sexual assault and harassment, limited protective measures are available before a full investigation is completed. Assailants engaging in DARVO use these protective measures against their victims, taking advantage of the neutral policies of the office and the attempts of administrators to support the rights of both the accuser and accused. DARVO manifests in the legal system when assailants file lawsuits against their victims, and these commonly take the form of defamation or libel cases where assailants accuse their accusers of trying to hurt their reputations. Legal DARVO tactics had been growing more common as of 2022. After this rise, many U.S. states passed anti-SLAPP laws to help victims dismiss certain DARVO-based defamation lawsuits. Anti-SLAPP measures help in cases where a perpetrator's lawsuit would obviously fail and was just brought forward to increase public and financial pressure on the victim.
Although DARVO is often discussed in cases where the perpetrator had committed sexual violence, it has been studied and documented in many other situations where the perpetrator had committed some sort of harm. DARVO has been labeled in some cases of medical malpractice, where victim blaming is already common since doctors and hospitals generally refuse to admit their mistakes due to legal risk. DARVO has also been cited as common in workplace bullying and toxic workplace culture. In the case of academia, when professors try to report bullying, DARVO tactics often compel them to stop speaking up, adding to their trauma and contributing to a culture of silence.
In this vein, DARVO has been theorized as acting on groups of people and not just individuals. One case under study was the intense backlash to the MeToo movement, where men's rights activists cast MeToo allegations as false and claimed the assailants were the real victims via a reactionary hashtag, #HimToo. Other researchers say DARVO can happen at even wider societal levels, labeling it as DARVO when media organizations promote rape myths in efforts to discredit sexual assault victims. Researchers have also drawn parallels between individual DARVO tactics and the tendency for dominant cultural groups to stigmatize and blame groups who are speaking up about their trauma.
Internal beliefs
Researchers have examined how the beliefs of abusive partners match what is claimed in DARVO tactics, where perpetrators deny abuse happened and blame the victim for being the aggressor. In one study concerning intimate partner violence among college students, researchers asked students to fill out private surveys that measured internalized beliefs about their relationships and allowed students to self-report intimate partner violence they had committed. Researchers found a strong correlation between students of all genders who had previously abused their partners and the belief that relationship difficulties were their partner's fault, and not their own. For male respondents, avoiding the discussion of relationship difficulties was also strongly correlated with the likelihood of past abuse. Other research has found that violent men are more likely than nonviolent men to believe their partners are critical and intentionally malicious. Studies of abusive men have also found that they frequently minimize or fully deny that incidents of abuse happened, and that this behavior is most common when the abusers fear legal issues or other situational consequences.
DARVO tactics are also associated with victims blaming themselves more for their abuse, with one explanation being that perpetrators' victim blaming gets internalized by the victims over time.
See also
Crocodile tears
Gaslighting
Psychological projection
Tu quoque
Victim blaming
References
Abuse
Psychological abuse
Psychological manipulation
1997 neologisms | DARVO | [
"Biology"
] | 1,196 | [
"Abuse",
"Behavior",
"Aggression",
"Human behavior"
] |
58,272,448 | https://en.wikipedia.org/wiki/2N696 | The 2N696 and 2N697 were the first silicon transistors manufactured in Silicon Valley, in 1958, by Fairchild Semiconductor. Fairchild introduced itself to the world via its advertisements for these transistors, which were identical except for a post-manufacturing binning on current gain.
The 2N696/2N697 NPN mesa transistor was developed by a team led by Gordon Moore. The first batch of 100 was sold to IBM for $150 each () in order to build the computer for the B-70 bomber. More transistors were sold to Autonetics to build the guidance system for the Minuteman ballistic missile.
The 2N696 and 2N697 were popular devices, quickly copied by several other semiconductor companies, including Texas Instruments, Rheem Semiconductor, and others including Hoffman Electronics Corp. and Industro Transistor Corp. In a 1960 advertisement, Fairchild bragged, "The Fairchild 2N696 and 2N697 are the world's most copied transistors. We have now copied them ourselves in scaled down versions. The 2N717 and 2N718 are exactly the same as these popular types but packaged in the TO-18 case. They occupy 1/3 the volume of the standard TO-5, making them ideal for high-density equipment designs."
References
External links
The Transistor Museum – photo of an original Fairchild 2N697
History of computing hardware
Commercial transistors
1958 introductions | 2N696 | [
"Technology"
] | 315 | [
"History of computing hardware",
"History of computing"
] |
58,278,053 | https://en.wikipedia.org/wiki/Schwarz%20lantern | In mathematics, the Schwarz lantern is a polyhedral approximation to a cylinder, used as a pathological example of the difficulty of defining the area of a smooth (curved) surface as the limit of the areas of polyhedra. It is formed by stacked rings of isosceles triangles, arranged within each ring in the same pattern as an antiprism. The resulting shape can be folded from paper, and is named after mathematician Hermann Schwarz and for its resemblance to a cylindrical paper lantern. It is also known as Schwarz's boot, Schwarz's polyhedron, or the Chinese lantern.
As Schwarz showed, for the surface area of a polyhedron to converge to the surface area of a curved surface, it is not sufficient to simply increase the number of rings and the number of isosceles triangles per ring. Depending on the relation of the number of rings to the number of triangles per ring, the area of the lantern can converge to the area of the cylinder, to a limit arbitrarily larger than the area of the cylinder, or to infinity—in other words, the area can diverge. The Schwarz lantern demonstrates that sampling a curved surface by close-together points and connecting them by small triangles is inadequate to ensure an accurate approximation of area, in contrast to the accurate approximation of arc length by inscribed polygonal chains.
The phenomenon that closely sampled points can lead to inaccurate approximations of area has been called the Schwarz paradox. The Schwarz lantern is an instructive example in calculus and highlights the need for care when choosing a triangulation for applications in computer graphics and the finite element method.
History and motivation
Archimedes approximated the circumference of circles by the lengths of inscribed or circumscribed regular polygons. More generally, the length of any smooth or rectifiable curve can be defined as the supremum of the lengths of polygonal chains inscribed in them. However, for this to work correctly, the vertices of the polygonal chains must lie on the given curve, rather than merely near it. Otherwise, in a counterexample sometimes known as the staircase paradox, polygonal chains of vertical and horizontal line segments of total length can lie arbitrarily close to a diagonal line segment of length , converging in distance to the diagonal segment but not converging to the same length. The Schwarz lantern provides a counterexample for surface area rather than length, and shows that for area, requiring vertices to lie on the approximated surface is not enough to ensure an accurate approximation.
German mathematician Hermann Schwarz (1843–1921) devised his construction in the late 19th century as a counterexample to the erroneous definition in J. A. Serret's 1868 book , which incorrectly states that:
Independently of Schwarz, Giuseppe Peano found the same counterexample. At the time, Peano was a student of Angelo Genocchi, who, from communication with Schwarz, already knew about the difficulty of defining surface area. Genocchi informed Charles Hermite, who had been using Serret's erroneous definition in his course. Hermite asked Schwarz for details, revised his course, and published the example in the second edition of his lecture notes (1883). The original note from Schwarz to Hermite was not published until the second edition of Schwarz's collected works in 1890.
An instructive example of the value of careful definitions in calculus, the Schwarz lantern also highlights the need for care in choosing a triangulation for applications in computer graphics and for the finite element method for scientific and engineering simulations. In computer graphics, scenes are often described by triangulated surfaces, and accurate rendering of the illumination of those surfaces depends on the direction of the surface normals. A poor choice of triangulation, as in the Schwarz lantern, can produce an accordion-like surface whose normals are far from the normals of the approximated surface, and the closely-spaced sharp folds of this surface can also cause problems with aliasing.
The failure of Schwarz lanterns to converge to the cylinder's area only happens when they include highly obtuse triangles, with angles close to 180°. In restricted classes of Schwarz lanterns using angles bounded away from 180°, the area converges to the same area as the cylinder as the number of triangles grows to infinity. The finite element method, in its most basic form, approximates a smooth function (often, the solution to a physical simulation problem in science or engineering) by a piecewise-linear function on a triangulation. The Schwarz lantern's example shows that, even for simple functions such as the height of a cylinder above a plane through its axis, and even when the function values are calculated accurately at the triangulation vertices, a triangulation with angles close to 180° can produce highly inaccurate simulation results. This motivates mesh generation methods for which all angles are bounded away from 180°, such as nonobtuse meshes.
Construction
The discrete polyhedral approximation considered by Schwarz can be described by two parameters: , the number of rings of triangles in the Schwarz lantern; and , half of the number of triangles per For a single ring (), the resulting surface consists of the triangular faces of an antiprism of For larger values of , the Schwarz lantern is formed by stacking of these antiprisms. To construct a Schwarz lantern that approximates a given right circular cylinder, the cylinder is sliced by parallel planes into congruent cylindrical rings. These rings have circular boundaries—two at the ends of the given cylinder, and more where it was sliced. In each circle, vertices of the Schwarz lantern are spaced equally, forming a regular polygon. These polygons are rotated by an angle of from one circle to the next, so that each edge from a regular polygon and the nearest vertex on the next circle form the base and apex of an isosceles triangle. These triangles meet edge-to-edge to form the Schwarz lantern, a polyhedral surface that is topologically equivalent to the cylinder.
Ignoring top and bottom vertices, each vertex touches two apex angles and four base angles of congruent isosceles triangles, just as it would in a tessellation of the plane by triangles of the same shape. As a consequence, the Schwarz lantern can be folded from a flat piece of paper, with this tessellation as its crease pattern. This crease pattern has been called the Yoshimura pattern, after the work of Y. Yoshimura on the Yoshimura buckling pattern of cylindrical surfaces under axial compression, which can be similar in shape to the Schwarz lantern.
Area
The area of the Schwarz lantern, for any cylinder and any particular choice of the parameters can be calculated by a straightforward application of trigonometry. A cylinder of radius and length has For a Schwarz lantern with parameters and , each band is a shorter cylinder of approximated by isosceles triangles. The length of the base of each triangle can be found from the formula for the edge length of a regular -gon, namely
The of each triangle can be found by applying the Pythagorean theorem to a right triangle formed by the apex of the triangle, the midpoint of the base, and the midpoint of the arc of the circle bounded by the endpoints of the base. The two sides of this right triangle are the of the cylindrical band, and the sagitta of the arc, giving the formula
Combining the formula for the area of each triangle from its base and height, and the total number of the triangles, gives the Schwarz lantern a total area of
Limits
The Schwarz lanterns, for large values of both parameters, converge uniformly to the cylinder that they approximate. However, because there are two free parameters and , the limiting area of the Schwarz lantern, as both and become arbitrarily large, can be evaluated in different orders, with different results. If is fixed while grows, and the resulting limit is then evaluated for arbitrarily large choices one obtains
the correct area for the cylinder. In this case, the inner limit already converges to the same value, and the outer limit is superfluous. Geometrically, substituting each cylindrical band by a band of very sharp isosceles triangles accurately approximates its area.
On the other hand, reversing the ordering of the limits gives
In this case, for a fixed choice as grows and the of each cylindrical band becomes arbitrarily small, each corresponding band of isosceles triangles becomes nearly planar. Each triangle approaches the triangle formed by two consecutive edges of a regular and the area of the whole band of triangles approaches times the area of one of these planar triangles, a finite number. However, the of these bands grows arbitrarily large; because the lantern's area grows in approximate proportion it also becomes arbitrarily large.
It is also possible to fix a functional relation between and to examine the limit as both parameters grow large simultaneously, maintaining this relation. Different choices of this relation can lead to either of the two behaviors described above, convergence to the correct area or divergence to infinity. For instance, setting (for an arbitrary and taking the limit for large leads to convergence to the correct area, while setting leads to divergence. A third type of limiting behavior is obtained by setting . For this choice,
In this case, the area of the Schwarz lantern, parameterized in this way, converges, but to a larger value than the area of the cylinder. Any desired larger area can be obtained by making an appropriate choice of the
See also
Kaleidocycle, a chain of tetrahedra linked edge-to-edge like a degenerate Schwarz lantern with
Runge's phenomenon, another example of failure of convergence
Notes
References
External links
Area
Paper folding
Polyhedra
Mathematical paradoxes | Schwarz lantern | [
"Physics",
"Mathematics"
] | 2,008 | [
"Scalar physical quantities",
"Physical quantities",
"Recreational mathematics",
"Quantity",
"Size",
"Mathematical paradoxes",
"Wikipedia categories named after physical quantities",
"Mathematical problems",
"Paper folding",
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] |
58,278,093 | https://en.wikipedia.org/wiki/Seminars%20in%20Cell%20and%20Developmental%20Biology | Seminars in Cell and Developmental Biology is a bimonthly peer-reviewed scientific review journal covering cell and developmental biology. It was established in 1990 as Seminars in Cell Biology, obtaining its current name in 1996, when it incorporated Seminars in Developmental Biology (which was also established in 1990). It is published by Elsevier and the editor-in-chief is John Davey (University of Warwick). According to the Journal Citation Reports, the journal has a 2017 impact factor of 6.138.
References
External links
Developmental biology journals
Molecular and cellular biology journals
Review journals
Academic journals established in 1990
Bimonthly journals
Elsevier academic journals
English-language journals | Seminars in Cell and Developmental Biology | [
"Chemistry"
] | 130 | [
"Molecular and cellular biology journals",
"Molecular biology"
] |
58,278,312 | https://en.wikipedia.org/wiki/Aspect%27s%20experiment | Aspect's experiment was the first quantum mechanics experiment to demonstrate the violation of Bell's inequalities with photons using distant detectors. Its 1982 result allowed for further validation of the quantum entanglement and locality principles. It also offered an experimental answer to Albert Einstein, Boris Podolsky, and Nathan Rosen's paradox which had been proposed about fifty years earlier.
It was the first experiment to remove the locality loophole, as it was able to modify the angle of the polarizers while the photons were in flight, faster than what light would take to reach the other polarizer, removing the possibility of communications between detectors.
The experiment was led by French physicist Alain Aspect at the Institut d'optique théorique et appliquée in Orsay between 1980 and 1982. Its importance was immediately recognized by the scientific community. Although the methodology carried out by Aspect presents a potential flaw, the detection loophole, his result is considered decisive and led to numerous other experiments (the so-called Bell tests) which confirmed Aspect's original experiment.
For his work on this topic, Aspect was awarded part of the 2022 Nobel Prize in Physics.
History
Entanglement and the EPR paradox
The Einstein–Podolsky–Rosen (EPR) paradox is a thought experiment proposed by physicists Albert Einstein, Boris Podolsky and Nathan Rosen which argues that the description of physical reality provided by quantum mechanics is incomplete. In the 1935 EPR paper titled "Can Quantum-Mechanical Description of Physical Reality be Considered Complete?", they argued for the existence of "elements of reality" that were not part of quantum theory, and speculated that it should be possible to construct a theory containing these hidden variables. Resolutions of the paradox have important implications for the interpretation of quantum mechanics.
The thought experiment involves a pair of particles prepared in what would later become known as an entangled state. Einstein, Podolsky, and Rosen pointed out that, in this state, if the position of the first particle were measured, the result of measuring the position of the second particle could be predicted. If instead the momentum of the first particle were measured, then the result of measuring the momentum of the second particle could be predicted. They argued that no action taken on the first particle could instantaneously affect the other, since this would involve information being transmitted faster than light, which is forbidden by the theory of relativity. They invoked a principle, later known as the "EPR criterion of reality", positing that: "If, without in any way disturbing a system, we can predict with certainty (i.e., with probability equal to unity) the value of a physical quantity, then there exists an element of reality corresponding to that quantity." From this, they inferred that the second particle must have a definite value of both position and of momentum prior to either quantity being measured. But quantum mechanics considers these two observables incompatible and thus does not associate simultaneous values for both to any system. Einstein, Podolsky, and Rosen therefore concluded that quantum theory does not provide a complete description of reality.
Bell's inequalities
In 1964, Irish physicist John Stewart Bell carried the analysis of quantum entanglement much further. He deduced that if measurements are performed independently on the two separated particles of an entangled pair, then the assumption that the outcomes depend upon hidden variables within each half implies a mathematical constraint on how the outcomes on the two measurements are correlated. This constraint would later be named the Bell inequalities. Bell then showed that quantum physics predicts correlations that violate this inequality. Consequently, the only way that hidden variables could explain the predictions of quantum physics is if they are "nonlocal", which is to say that somehow the two particles are able to influence one another instantaneously no matter how widely they ever become separated.
In 1969, John Clauser and Michael Horne, along with Horne's doctoral student Abner Shimony, and Francis Pinki's doctoral student Richard Holt, came up with the CHSH inequality, a reformulation of Bell inequality that could be better tested with experiments.
Early experiments in the United States
The first rudimentary experiment designed to test Bell's theorem was performed in 1972 by Clauser and Stuart Freedman at University of California, Berkeley. In 1973, at Harvard University, Pipkin and Holt's experiments suggested the opposite conclusion, negating that quantum mechanics violates the Bell inequalities. Edward S. Fry and Randall C. Thompson of Texas A&M University reattempted the experiment in 1973 and agreed with Clauser. These experiments were only a limited test, because the choice of detector settings was made before the photons had left the source.
Advised by John Bell, Alain Aspect worked to develop an experiment to remove this limitation.
In France
Alain Aspect completed his doctoral thesis in 1971 working on holography and then went abroad to teach in the École Normale in Cameroon. He returned to France in 1974 and joined the Institut d'optique in Orsay working for his habilitation thesis. Physicist handled him various papers from Bell and Aspect worked for five year in the construction and preliminary tests for his experiment. He published his first experimental results in 1981, and completed his habilitation in 1983 with the final results of his experiment. The referees included André Maréchal and Christian Imbert from the Institut d'optique, Franck Laloë, Bernard d'Espagnat, Claude Cohen-Tannoudji, and John Bell.
Theoretical scheme
The illustration above represents the principle scheme from which John Bell demonstrated his inequalities: a source S of entangled photons simultaneously emits two photons, and , whose polarization is prepared so that both photons' state vector is:
This formula simply means that the photons are in a superposed state: they are in a linear combination of both photons vertically polarized plus both photons horizontally polarized, with an equal probability. These two photons are then measured using two polarizers P1 and P2, each with a configurable measuring angle: α and β. The result of each polarizer's measurement can be (+) or (−) according to whether the measured polarization is parallel or perpendicular to the polarizer's angle of measurement.
One noteworthy aspect is that the polarizers imagined for this ideal experiment give a measurable result both in the (−) and (+) situations. Not all real polarizers are able to do this: some detect the (+) situation for example, but are unable to detect anything in the (−) situation (the photon never leaves the polarizer). Early experiments used the latter sort of polarizer. Alain Aspect's polarizers were better able to detect both scenarios and therefore much closer to the ideal experiment.
Given the apparatus and the initial state of polarization given to the photons, quantum mechanics is able to predict the probabilities of measuring (+,+), (−,−), (+,−) and (−,+) on the polarizers (P1,P2), oriented on the (α,β) angles:
;
.
The quantity of interest is a correlation function given by
with
where (α',β') are a set of different angles. According to the CHSH inequality,
,
a type of Bell inequality. Quantum mechanics predicts a maximal violation of this inequality for |α−β| = |α'−β| = |α'−β'| = 22.5° and |α−β''' | = 67.5°.
Proposal
In 1975, since a decisive experiment based on the violation of Bell's inequalities and verifying the veracity of quantum entanglement was still missing, Alain Aspect proposed in an article, an experiment meticulous enough to be irrefutable.
Alain Aspect specified his experiment so that it would be as decisive as possible. Namely:
Its source of entangled particles must be excellent to shorten the duration of the experiment and to provide as clear a violation of Bell's inequalities as possible.
It must show correlations in measurements, but also demonstrate that these correlations are indeed the result of a quantum effect (and consequently of an instantaneous influence) and not of a classical slower-than-light effect between the two particles.
The experimental scheme must match John Bell's as closely as possible to demonstrate his inequalities so that the agreement between the measured and predicted results be as significant as possible.
Experiments
Alain Aspect carried out a three-round series of increasingly complex experiments from 1980 to 1981. The first round of experiments reproduced the experimental tests of Clauser, Holt and Fry. In the second round of experiments, Aspect added two-channel polarizers, which improved the efficiency of the detections. These two rounds of experiments were conducted with the help of research engineer Gérard Roger and physicist , an undergraduate student at the time.
The third round of experiments took place in 1982 and were carried out in collaboration with Roger and physicist Jean Dalibard, a young student at the time. This last round, the closest to the initial specifications, will be described here.
Photon source
The first experiments testing Bell's inequalities possessed low-intensity photon sources and necessitated a continuous week to complete. One of Aspect's first improvements consisted in using a photon source several orders of magnitude more efficient. This source allowed a detection rate of 100 photons per second, thus shortening the length of the experiment to 100 seconds.
The source used is a calcium radiative cascade, excited with a krypton laser.
Polarizers with an adjustable orientation variable and on a remote position
One of the main points of this experiment was to make sure that the correlation between the measurements P1 and P2 had not been the result of "classical" effects, especially experimental artefacts.
As an example, when P1 and P2 are prepared with fixed angles α and β, it can be surmised that this state generates parasitic correlations through current or mass loops, or some other effects. As a matter of fact, both polarizers belong to the same setup and could influence one another through the various circuits of the experimental device, and generate correlations upon measurement.
One can then imagine that the fixed orientation of the polarizers somehow impacts the state the photon couple is emitted with. In such a case, the correlations between the measurement results could be explained by local hidden variables within the photons, upon their emission. Alain Aspect had mentioned these observations to John Bell himself.
One way of ruling out these kinds of effects is to determine the (α,β) orientation of the polarizers at the last moment—after the photons have been emitted, and before their detection—and to keep them far enough from each other to prevent any signal from reaching any one of them.
This method assures that the orientation of the polarizers during the emission has no bearing on the result (since the orientation is yet undetermined during emission). It also assures that the polarizers do not influence each other, being too distant from one another.
As a consequence, Aspect's experimental setup has polarizers P1 and P2 set 6 metres apart from the source, and 12 metres apart from one another. With this setup, only 20 nanoseconds elapse between the emission of the photons and their detection. During this extremely short period of time, the experimenter has to decide on the polarizers' orientation and to then orient them.
Since it is physically impossible to modify a polarizer's orientation within such a time span, two polarizers—one for each side—were used and pre-oriented in different directions. A high-frequency shunting randomly oriented towards one polarizer or the other. The setup corresponded to one polarizer with a randomly tilting polarization angle.
Since it was not possible either to have the emitted photons provoke the tilting, the polarizers shunted periodically every 10 nanoseconds (asynchronously with the photon's emission) thus assuring the referral device would tilt at least once between the emission of the photon and its detection.
Two-channel polarizers
Another important characteristic of the 1982 experiment was the use of two-channel polarizers which allowed a measurable result in situations (+) and (−). The polarizers used until Aspect's experiment could detect situation (+), but not situation (−). These single-channel polarizers had two major inconveniences:
Situation (−) was difficult to discriminate from an experimentation mistake.
They had to be scrupulously calibrated.
The two-channel polarizers Aspect used in his experiment avoided these two inconveniences and allowed him to use Bell's formulas directly to calculate the inequalities.
Technically, the polarizers he used were polarizing cubes which transmitted one polarity and reflected the other one, emulating a Stern-Gerlach device.
Results
Bell's inequalities establish a theoretical curve of the number of correlations (++ or −−) between the two detectors in relation to the relative angle of the detectors . The shape of the curve is characteristic of the violation of Bell's inequalities. The measures' matching the shape of the curve establishes, quantitatively and qualitatively, that Bell's inequalities have been violated.
All three of Aspect's experiments unambiguously confirmed the violation, as predicted by quantum mechanics, thus undermining Einstein's local realistic outlook on quantum mechanics and local hidden variable scenarios. In addition to being confirmed, the violation was confirmed in the exact way predicted by quantum mechanics, with a statistical agreement of up to 242 standard deviations.
Given the technical quality of the experiment, the scrupulous avoidance of experimental artefacts, and the quasi-perfect statistical agreement, this experiment convinced the scientific community at large that quantum physics violates Bell's inequalities.
Reception and limitations
After the results, some physicists legitimately tried to look for flaws in Aspect's experiment and to find out how to improve it to resist criticism.
Some theoretical objections can be raised against the setup:
the quasi-periodical aspect of the shunting oscillations hinders the validity of the experiment because it can induce correlations through quasi-synchronization resulting from two referrals;
the correlations (+,+), (−,−) etc. were counted in real time, at the moment of detection. Each polarizer's two (+) and (−) channels were therefore linked by physical circuits. Once more, correlations may be induced.
The ideal experiment, which would negate any imaginable possibility of induced correlations should:
use purely random shunting;
record the (+) or (−) results on each side of the device, without any physical link between the two sides. The correlations would be calculated after the experiment, by comparing the recorded results of both sides.
The conditions of the experiment also suffered from a detection loophole.
After 1982, physicists began to look for applications of entanglement, leading to the development of quantum computing and quantum cryptography.
For his work on this topic, Aspect received several awards including the 2010 Wolf Prize in Physics and the 2022 Nobel Prize in Physics, both shared with John Clauser and Anton Zeilinger for their Bell tests.
Later experiments
The loopholes mentioned could only be solved starting in 1998. In the meantime, Aspect's experiment was reproduced, and the violation of Bell's inequalities was systematically confirmed, with a statistical certainty of up to 100 standard deviations.
Other experiments were conducted to test the violations of Bell's inequalities with observables other than polarization, in order to approach the original spirit of the EPR paradox, in which Einstein imagined measuring two combined variables (such as position and movement quantity) on an EPR pair. An experiment introduced the combined variables (time and energy) which, once again, confirmed quantum mechanics.
In 1998, the Geneva experiment tested the correlation between two detectors set 30 kilometres apart using the Swiss optical fibre telecommunication network. The distance gave more time to commute the angles of the polarizers. It was therefore possible to have a completely random shunting. Additionally, the two distant polarizers were entirely independent. The measurements were recorded on each side, and compared after the experiment by dating each measurement using an atomic clock. The violation of Bell's inequalities was once again verified under strict and practically ideal conditions. If Aspect's experiment implied that a hypothetical coordination signal must travel twice as fast as the speed of light c, Geneva's reached 10 million times c.
An experiment took place at the National Institute of Standards and Technology (NIST) in 2000 on trapped-ion entanglement using a very efficient correlation-based detection method. The reliability of detection proved to be sufficient for the experiment to violate Bell's inequalities on the whole, even though all detected correlations did not violate them.
In 2001, Antoine Suarez's team, which included Nicolas Gisin who had participated in the Geneva experiment, reproduced the experiment using mirrors or detectors in motion, allowing them to reverse the order of events across the frames of reference, in accordance with special relativity (this inversion is only possible for events without any causal relationship). The speeds are chosen so that when a photon is reflected or crosses the semi-transparent mirror, the other photon has already crossed or been reflected from the point of view of the frame of reference attached to the mirror. This is an "after-after" configuration, in which sound waves play the role of semi-transparent mirrors.
In 2015 the first three significant-loophole-free Bell-tests were published within three months by independent groups in Delft University of Technology, University of Vienna and NIST. All three tests simultaneously addressed the detection loophole, the locality loophole, and the memory loophole.
Implications
Prior to the Aspect experiments, Bell's theorem was mostly a niche topic. The publications by Aspect and collaborators prompted wider discussion of the subject.
The fact that nature is found to violate Bell's inequality implies that one or more of the assumptions underlying that inequality must not hold true. Different interpretations of quantum mechanics provide different views on which assumptions ought to be rejected. Copenhagen-type interpretations generally take the violation of Bell inequalities as grounds to reject the assumption often called counterfactual definiteness. This is also the route taken by interpretations that descend from the Copenhagen tradition, such as consistent histories (often advertised as "Copenhagen done right"), as well as QBism. In contrast, the versions of the many-worlds interpretation all violate an implicit assumption by Bell that measurements have a single outcome. Unlike all of these, the Bohmian or "pilot wave" interpretation abandons the assumption of locality: instantaneous communication can exist at the level of the hidden variables, but it cannot be used to send signals.
See also
Superdeterminism
References
Bibliography
Bernard d'Espagnat, Traité de physique et de philosophie, Fayard (in French). See chapter 3. Non-separability and Bell theorem.
Bernard d'Espagnat, À la recherche du réel, Bordas (in French).
Bernard d'Espagnat, Étienne Klein, Regards sur la matière'' (in French). See chapter VIII. Non-separability of correlating couples.
External links
Video conference on quantum optics (17 min), by Alain Aspect, head of research at the Institut d'Optique in Orsay (in French).
Centre for Quantum Philosophy
Physics experiments
Quantum measurement | Aspect's experiment | [
"Physics"
] | 4,083 | [
"Quantum mechanics",
"Quantum measurement",
"Experimental physics",
"Physics experiments"
] |
58,278,355 | https://en.wikipedia.org/wiki/J%C3%B3zsef%20Solymosi | József Solymosi is a Hungarian-Canadian mathematician and a professor of mathematics at the University of British Columbia. His main research interests are arithmetic combinatorics, discrete geometry, graph theory, and combinatorial number theory.
Education and career
Solymosi earned his master's degree in 1999 under the supervision of László Székely from the Eötvös Loránd University and his Ph.D. in 2001 at ETH Zürich under the supervision of Emo Welzl. His doctoral dissertation was Ramsey-Type Results on Planar Geometric Objects.
From 2001 to 2003 he was S. E. Warschawski Assistant Professor of Mathematics at the University of California, San Diego. He joined the faculty of the University of British Columbia in 2002.
He was editor in chief of the Electronic Journal of Combinatorics from 2013 to 2015.
Contributions
Solymosi was the first online contributor to the first Polymath Project, set by Timothy Gowers to find improvements to the Hales–Jewett theorem.
One of his theorems states that if a finite set of points in the Euclidean plane has every pair of points at an integer distance from each other, then
the set must have a diameter (largest distance) that is linear in the number of points. This result is connected to the Erdős–Anning theorem, according to which an infinite set of points with integer distances must lie on one line. In connection with the related Erdős–Ulam problem, on the existence of dense subsets of the plane for which all distances are rational numbers, Solymosi and de Zeeuw proved that every infinite rational-distance set must either be dense in the Zariski topology or it must have all but finitely many of its points on a single line or circle.
With Terence Tao, Solymosi proved a bound of on the number of incidences between points and affine subspaces of any finite-dimensional Euclidean space, whenever each pair of subspaces has at most one point of intersection. This generalizes the Szemerédi–Trotter theorem on points and lines in the Euclidean plane, and because of this the exponent of cannot be improved. Their theorem solves (up to the in the exponent) a conjecture of Toth, and was inspired by an analogue of the Szemerédi–Trotter theorem for lines in the complex plane.
He has also contributed improved bounds for the Erdős–Szemerédi theorem, showing that every set of real numbers has either a large set of pairwise sums or a large set of pairwise products, and for the Erdős distinct distances problem, showing that every set of points in the plane has many different pairwise distances.
Recognition
In 2006, Solymosi received a Sloan Research Fellowship and in 2008 he was awarded the André Aisenstadt Mathematics Prize. In 2012 he was named a doctor of the Hungarian Academy of Science.
Selected publications
References
External links
Home page
Year of birth missing (living people)
Living people
Canadian mathematicians
20th-century Hungarian mathematicians
21st-century Hungarian mathematicians
Eötvös Loránd University alumni
ETH Zurich alumni
Academic staff of the University of British Columbia
Combinatorialists
Graph theorists | József Solymosi | [
"Mathematics"
] | 647 | [
"Graph theory",
"Combinatorics",
"Combinatorialists",
"Mathematical relations",
"Graph theorists"
] |
64,963,121 | https://en.wikipedia.org/wiki/List%20of%20oil%20spills%20impacting%20penguins | Penguins are vulnerable to exposure to oil spills due to their site fidelity, aquatic lifestyle and near-surface foraging habits. Across their range, penguins have been impacted by chronic and acute oil pollution at sea. The following list includes examples of events where impacts to penguins were documented. It is not exhaustive.
References
Oil spills
Penguins
Environmental disasters | List of oil spills impacting penguins | [
"Chemistry",
"Environmental_science"
] | 70 | [
"Oil spills",
"Water pollution"
] |
64,964,188 | https://en.wikipedia.org/wiki/Jani%20Ingram | Jani Ingram is a professor of chemistry and biochemistry at Northern Arizona University. Ingram researches the chemistry and health impacts of environmental pollutants, especially uranium and arsenic. Ingram is a member of the Navajo tribe, and the Naneesht’ezhi clan. She leads the Bridging Arizona Native American Students to Bachelor's Degrees (NIH Bridges to Baccalaureate) program and the Native American Cancer Prevention Program. She promotes educational and professional opportunities for Native American students in chemistry through a number of initiatives and for this work was awarded the 2018 American Chemical Society Award for Encouraging Disadvantaged Students into Careers in the Chemical Sciences.
Education
Ingram began her academic studies at Yavapai Community College in Arizona where she earned an associate's degree. She subsequently studied at New Mexico State University and earned a bachelor's degree in chemistry. Her Ph.D. is in chemistry from the University of Arizona.
Career and research
Ingram's research areas are analytical chemistry and environmental chemistry. She specializes on environmental uranium and arsenic contamination and how they effect the food chain and water supplies of the Navajo nation. She also researches traditional Navajo food ingredients and their health benefits, for example juniper ash as a calcium source. In light of the COVID-19 pandemic, her research laboratory repurposed their facilities to produce hand sanitizer which was donated to the Navajo Nation.
References
Northern Arizona University faculty
Navajo scientists
Yavapai College alumni
New Mexico State University alumni
University of Arizona alumni
Analytical chemists
American women biochemists
21st-century American women scientists
Native American women scientists
21st-century Native American scientists
21st-century Native American women
Living people
Year of birth missing (living people)
Chemists from Arizona | Jani Ingram | [
"Chemistry"
] | 340 | [
"Analytical chemists"
] |
64,964,610 | https://en.wikipedia.org/wiki/K2-24 | K2-24 (also known as EPIC 203771098) is a metal-rich G3-type main sequence star larger and more massive than the Sun, located away in the constellation Scorpius. Two confirmed transiting exoplanets are known to orbit this star. An attempt to detect stellar companions using adaptive optics imaging at the Keck telescope was negative however later observations using lucky imaging at the Danish 1.54 m telescope at La Silla Observatory detected a possible companion at 3.8 arcseconds distance from K2-24. This candidate companion being over 8 magnitudes fainter than K2-24 and with a color temperature of , is inconsistent with a bound main sequence companion.
Planetary system
Discovery
Erik A. Petigura and team analyzed data obtained from the Kepler space telescope during its observation of the K2 Campaign 2 field. They reported the discovery and confirmation of both planets b and c. The Planetary signals were independently detected by Andrew Vanderburg and collaborators.
Characteristics
The two known planets in this system have radii equal to 5.4 and 7.5 times that of the Earth. This places both planets radii between that of Uranus and Saturn, a range not present within the Solar System. With orbital periods of 20.9 days and 42.4 days, the planets are within 1% of the 2:1 mean-motion resonance. The low observed eccentricities and near orbital resonance provide evidence regarding the formation and evolution of the system, suggesting that they could possibly have resulted from gravitational interactions with a protoplanetary disk. K2-24c at 15.4 earth masses is significantly lighter than K2-24b's 19 Earth masses despite being a larger planet. It is estimated that K2-24b's atmosphere makes up 26% of its mass while K2-24c's atmosphere makes up 52%. The current model of core-nucleated accretion predicts that runaway accretion should occur when a planet reaches approximately 50% atmosphere by mass, this makes K2-24c a potential challenge to the model.
There is also a candidate planet, K2-24d, with a mass of and an orbital period of 470 days. While the radial velocity
signal of planet was confirmed, no validation tests were run to confirm its existence, rendering it as unconfirmed.
A transit observation of K2-24b with the Hubble Space Telescope's Wide Field Camera 3 suggested the presence of ammonia, in a high abundance, but did not find evidence for water.
References
External links
The Extrasolar Planets Encyclopaedia entry for K2-24b
The Extrasolar Planets Encyclopaedia entry for K2-24c
G-type main-sequence stars
Scorpius
Planetary systems with two confirmed planets
Planetary transit variables | K2-24 | [
"Astronomy"
] | 583 | [
"Scorpius",
"Constellations"
] |
64,965,378 | https://en.wikipedia.org/wiki/Calculus%20on%20Euclidean%20space | In mathematics, calculus on Euclidean space is a generalization of calculus of functions in one or several variables to calculus of functions on Euclidean space as well as a finite-dimensional real vector space. This calculus is also known as advanced calculus, especially in the United States. It is similar to multivariable calculus but is somewhat more sophisticated in that it uses linear algebra (or some functional analysis) more extensively and covers some concepts from differential geometry such as differential forms and Stokes' formula in terms of differential forms. This extensive use of linear algebra also allows a natural generalization of multivariable calculus to calculus on Banach spaces or topological vector spaces.
Calculus on Euclidean space is also a local model of calculus on manifolds, a theory of functions on manifolds.
Basic notions
Functions in one real variable
This section is a brief review of function theory in one-variable calculus.
A real-valued function is continuous at if it is approximately constant near ; i.e.,
In contrast, the function is differentiable at if it is approximately linear near ; i.e., there is some real number such that
(For simplicity, suppose . Then the above means that where goes to 0 faster than h going to 0 and, in that sense, behaves like .)
The number depends on and thus is denoted as . If is differentiable on an open interval and if is a continuous function on , then is called a C1 function. More generally, is called a Ck function if its derivative is Ck-1 function. Taylor's theorem states that a Ck function is precisely a function that can be approximated by a polynomial of degree k.
If is a C1 function and for some , then either or ; i.e., either is strictly increasing or strictly decreasing in some open interval containing a. In particular, is bijective for some open interval containing . The inverse function theorem then says that the inverse function is differentiable on U with the derivatives: for
Derivative of a map and chain rule
For functions defined in the plane or more generally on an Euclidean space , it is necessary to consider functions that are vector-valued or matrix-valued. It is also conceptually helpful to do this in an invariant manner (i.e., a coordinate-free way). Derivatives of such maps at a point are then vectors or linear maps, not real numbers.
Let be a map from an open subset of to an open subset of . Then the map is said to be differentiable at a point in if there exists a (necessarily unique) linear transformation , called the derivative of at , such that
where is the application of the linear transformation to . If is differentiable at , then it is continuous at since
as .
As in the one-variable case, there is
This is proved exactly as for functions in one variable. Indeed, with the notation , we have:
Here, since is differentiable at , the second term on the right goes to zero as . As for the first term, it can be written as:
Now, by the argument showing the continuity of at , we see is bounded. Also, as since is continuous at . Hence, the first term also goes to zero as by the differentiability of at .
The map as above is called continuously differentiable or if it is differentiable on the domain and also the derivatives vary continuously; i.e., is continuous.
As a linear transformation, is represented by an -matrix, called the Jacobian matrix of at and we write it as:
Taking to be , a real number and the j-th standard basis element, we see that the differentiability of at implies:
where denotes the i-th component of . That is, each component of is differentiable at in each variable with the derivative . In terms of Jacobian matrices, the chain rule says ; i.e., as ,
which is the form of the chain rule that is often stated.
A partial converse to the above holds. Namely, if the partial derivatives are all defined and continuous, then is continuously differentiable. This is a consequence of the mean value inequality:
(This version of mean value inequality follows from mean value inequality in applied to the function , where the proof on mean value inequality is given.)
Indeed, let . We note that, if , then
For simplicity, assume (the argument for the general case is similar). Then, by mean value inequality, with the operator norm ,
which implies as required.
Example: Let be the set of all invertible real square matrices of size n. Note can be identified as an open subset of with coordinates . Consider the function = the inverse matrix of defined on . To guess its derivatives, assume is differentiable and consider the curve where means the matrix exponential of . By the chain rule applied to , we have:
.
Taking , we get:
.
Now, we then have:
Since the operator norm is equivalent to the Euclidean norm on (any norms are equivalent to each other), this implies is differentiable. Finally, from the formula for , we see the partial derivatives of are smooth (infinitely differentiable); whence, is smooth too.
Higher derivatives and Taylor formula
If is differentiable where is an open subset, then the derivatives determine the map , where stands for homomorphisms between vector spaces; i.e., linear maps. If is differentiable, then . Here, the codomain of can be identified with the space of bilinear maps by:
where and is bijective with the inverse given by . In general, is a map from to the space of -multilinear maps .
Just as is represented by a matrix (Jacobian matrix), when (a bilinear map is a bilinear form), the bilinear form is represented by a matrix called the Hessian matrix of at ; namely, the square matrix of size such that , where the paring refers to an inner product of , and is none other than the Jacobian matrix of . The -th entry of is thus given explicitly as .
Moreover, if exists and is continuous, then the matrix is symmetric, the fact known as the symmetry of second derivatives. This is seen using the mean value inequality. For vectors in , using mean value inequality twice, we have:
which says
Since the right-hand side is symmetric in , so is the left-hand side: . By induction, if is , then the k-multilinear map is symmetric; i.e., the order of taking partial derivatives does not matter.
As in the case of one variable, the Taylor series expansion can then be proved by integration by parts:
Taylor's formula has an effect of dividing a function by variables, which can be illustrated by the next typical theoretical use of the formula.
Example: Let be a linear map between the vector space of smooth functions on with rapidly decreasing derivatives; i.e., for any multi-index . (The space is called a Schwartz space.) For each in , Taylor's formula implies we can write:
with , where is a smooth function with compact support and . Now, assume commutes with coordinates; i.e., . Then
.
Evaluating the above at , we get In other words, is a multiplication by some function ; i.e., . Now, assume further that commutes with partial differentiations. We then easily see that is a constant; is a multiplication by a constant.
(Aside: the above discussion almost proves the Fourier inversion formula. Indeed, let be the Fourier transform and the reflection; i.e., . Then, dealing directly with the integral that is involved, one can see commutes with coordinates and partial differentiations; hence, is a multiplication by a constant. This is almost a proof since one still has to compute this constant.)
A partial converse to the Taylor formula also holds; see Borel's lemma and Whitney extension theorem.
Inverse function theorem and submersion theorem
A -map with the -inverse is called a -diffeomorphism. Thus, the theorem says that, for a map satisfying the hypothesis at a point , is a diffeomorphism near For a proof, see .
The implicit function theorem says: given a map , if , is in a neighborhood of and the derivative of at is invertible, then there exists a differentiable map for some neighborhoods of such that . The theorem follows from the inverse function theorem; see .
Another consequence is the submersion theorem.
Integrable functions on Euclidean spaces
A partition of an interval is a finite sequence . A partition of a rectangle (product of intervals) in then consists of partitions of the sides of ; i.e., if , then consists of such that is a partition of .
Given a function on , we then define the upper Riemann sum of it as:
where
is a partition element of ; i.e., when is a partition of .
The volume of is the usual Euclidean volume; i.e., .
The lower Riemann sum of is then defined by replacing by . Finally, the function is called integrable if it is bounded and . In that case, the common value is denoted as .
A subset of is said to have measure zero if for each , there are some possibly infinitely many rectangles whose union contains the set and
A key theorem is
The next theorem allows us to compute the integral of a function as the iteration of the integrals of the function in one-variables:
In particular, the order of integrations can be changed.
Finally, if is a bounded open subset and a function on , then we define where is a closed rectangle containing and is the characteristic function on ; i.e., if and if provided is integrable.
Surface integral
If a bounded surface in is parametrized by with domain , then the surface integral of a measurable function on is defined and denoted as:
If is vector-valued, then we define
where is an outward unit normal vector to . Since , we have:
Vector analysis
Tangent vectors and vector fields
Let be a differentiable curve. Then the tangent vector to the curve at is a vector at the point whose components are given as:
.
For example, if is a helix, then the tangent vector at t is:
It corresponds to the intuition that the a point on the helix moves up in a constant speed.
If is a differentiable curve or surface, then the tangent space to at a point p is the set of all tangent vectors to the differentiable curves with .
A vector field X is an assignment to each point p in M a tangent vector to M at p such that the assignment varies smoothly.
Differential forms
The dual notion of a vector field is a differential form. Given an open subset in , by definition, a differential 1-form (often just 1-form) is an assignment to a point in a linear functional on the tangent space to at such that the assignment varies smoothly. For a (real or complex-valued) smooth function , define the 1-form by: for a tangent vector at ,
where denotes the directional derivative of in the direction at . For example, if is the -th coordinate function, then ; i.e., are the dual basis to the standard basis on . Then every differential 1-form can be written uniquely as
for some smooth functions on (since, for every point , the linear functional is a unique linear combination of over real numbers). More generally, a differential k-form is an assignment to a point in a vector in the -th exterior power of the dual space of such that the assignment varies smoothly. In particular, a 0-form is the same as a smooth function. Also, any -form can be written uniquely as:
for some smooth functions .
Like a smooth function, we can differentiate and integrate differential forms. If is a smooth function, then can be written as:
since, for , we have: . Note that, in the above expression, the left-hand side (whence the right-hand side) is independent of coordinates ; this property is called the invariance of differential.
The operation is called the exterior derivative and it extends to any differential forms inductively by the requirement (Leibniz rule)
where are a p-form and a q-form.
The exterior derivative has the important property that ; that is, the exterior derivative of a differential form is zero. This property is a consequence of the symmetry of second derivatives (mixed partials are equal).
Boundary and orientation
A circle can be oriented clockwise or counterclockwise. Mathematically, we say that a subset of is oriented if there is a consistent choice of normal vectors to that varies continuously. For example, a circle or, more generally, an n-sphere can be oriented; i.e., orientable. On the other hand, a Möbius strip (a surface obtained by identified by two opposite sides of the rectangle in a twisted way) cannot oriented: if we start with a normal vector and travel around the strip, the normal vector at end will point to the opposite direction.
The proposition is useful because it allows us to give an orientation by giving a volume form.
Integration of differential forms
If is a differential n-form on an open subset M in (any n-form is that form), then the integration of it over with the standard orientation is defined as:
If M is given the orientation opposite to the standard one, then is defined as the negative of the right-hand side.
Then we have the fundamental formula relating exterior derivative and integration:
Here is a sketch of proof of the formula. If is a smooth function on with compact support, then we have:
(since, by the fundamental theorem of calculus, the above can be evaluated on boundaries of the set containing the support.) On the other hand,
Let approach the characteristic function on . Then the second term on the right goes to while the first goes to , by the argument similar to proving the fundamental theorem of calculus.
The formula generalizes the fundamental theorem of calculus as well as Stokes' theorem in multivariable calculus. Indeed, if is an interval and , then and the formula says:
.
Similarly, if is an oriented bounded surface in and , then and similarly for and . Collecting the terms, we thus get:
Then, from the definition of the integration of , we have
where is the vector-valued function and . Hence, Stokes’ formula becomes
which is the usual form of the Stokes' theorem on surfaces. Green’s theorem is also a special case of Stokes’ formula.
Stokes' formula also yields a general version of Cauchy's integral formula. To state and prove it, for the complex variable and the conjugate , let us introduce the operators
In these notations, a function is holomorphic (complex-analytic) if and only if (the Cauchy–Riemann equations).
Also, we have:
Let be a punctured disk with center .
Since is holomorphic on , We have:
.
By Stokes’ formula,
Letting we then get:
Winding numbers and Poincaré lemma
A differential form is called closed if and is called exact if for some differential form (often called a potential). Since , an exact form is closed. But the converse does not hold in general; there might be a non-exact closed form. A classic example of such a form is:
,
which is a differential form on . Suppose we switch to polar coordinates: where . Then
This does not show that is exact: the trouble is that is not a well-defined continuous function on . Since any function on with differ from by constant, this means that is not exact. The calculation, however, shows that is exact, for example, on since we can take there.
There is a result (Poincaré lemma) that gives a condition that guarantees closed forms are exact. To state it, we need some notions from topology. Given two continuous maps between subsets of (or more generally topological spaces), a homotopy from to is a continuous function such that and . Intuitively, a homotopy is a continuous variation of one function to another. A loop in a set is a curve whose starting point coincides with the end point; i.e., such that . Then a subset of is called simply connected if every loop is homotopic to a constant function. A typical example of a simply connected set is a disk . Indeed, given a loop , we have the homotopy from to the constant function . A punctured disk, on the other hand, is not simply connected.
Geometry of curves and surfaces
Moving frame
Vector fields on are called a frame field if they are orthogonal to each other at each point; i.e., at each point. The basic example is the standard frame ; i.e., is a standard basis for each point in . Another example is the cylindrical frame
For the study of the geometry of a curve, the important frame to use is a Frenet frame on a unit-speed curve given as:
The Gauss–Bonnet theorem
The Gauss–Bonnet theorem relates the topology of a surface and its geometry.
Calculus of variations
Method of Lagrange multiplier
The set is usually called a constraint.
Example: Suppose we want to find the minimum distance between the circle and the line . That means that we want to minimize the function , the square distance between a point on the circle and a point on the line, under the constraint . We have:
Since the Jacobian matrix of has rank 2 everywhere on , the Lagrange multiplier gives:
If , then , not possible. Thus, and
From this, it easily follows that and . Hence, the minimum distance is (as a minimum distance clearly exists).
Here is an application to linear algebra. Let be a finite-dimensional real vector space and a self-adjoint operator. We shall show has a basis consisting of eigenvectors of (i.e., is diagonalizable) by induction on the dimension of . Choosing a basis on we can identify and is represented by the matrix . Consider the function , where the bracket means the inner product. Then . On the other hand, for , since is compact, attains a maximum or minimum at a point in . Since , by Lagrange multiplier, we find a real number such that But that means . By inductive hypothesis, the self-adjoint operator , the orthogonal complement to , has a basis consisting of eigenvectors. Hence, we are done. .
Weak derivatives
Up to measure-zero sets, two functions can be determined to be equal or not by means of integration against other functions (called test functions). Namely, the following sometimes called the fundamental lemma of calculus of variations:
Given a continuous function , by the lemma, a continuously differentiable function is such that if and only if
for every . But, by integration by parts, the partial derivative on the left-hand side of can be moved to that of ; i.e.,
where there is no boundary term since has compact support. Now the key point is that this expression makes sense even if is not necessarily differentiable and thus can be used to give sense to a derivative of such a function.
Note each locally integrable function defines the linear functional on and, moreover, each locally integrable function can be identified with such linear functional, because of the early lemma. Hence, quite generally, if is a linear functional on , then we define to be the linear functional where the bracket means . It is then called the weak derivative of with respect to . If is continuously differentiable, then the weak derivate of it coincides with the usual one; i.e., the linear functional is the same as the linear functional determined by the usual partial derivative of with respect to . A usual derivative is often then called a classical derivative. When a linear functional on is continuous with respect to a certain topology on , such a linear functional is called a distribution, an example of a generalized function.
A classic example of a weak derivative is that of the Heaviside function , the characteristic function on the interval . For every test function , we have:
Let denote the linear functional , called the Dirac delta function (although not exactly a function). Then the above can be written as:
Cauchy's integral formula has a similar interpretation in terms of weak derivatives. For the complex variable , let . For a test function , if the disk contains the support of , by Cauchy's integral formula, we have:
Since , this means:
or
In general, a generalized function is called a fundamental solution for a linear partial differential operator if the application of the operator to it is the Dirac delta. Hence, the above says is the fundamental solution for the differential operator .
Hamilton–Jacobi theory
Calculus on manifolds
Definition of a manifold
This section requires some background in general topology.
A manifold is a Hausdorff topological space that is locally modeled by an Euclidean space. By definition, an atlas of a topological space is a set of maps , called charts, such that
are an open cover of ; i.e., each is open and ,
is a homeomorphism and
is smooth; thus a diffeomorphism.
By definition, a manifold is a second-countable Hausdorff topological space with a maximal atlas (called a differentiable structure); "maximal" means that it is not contained in strictly larger atlas. The dimension of the manifold is the dimension of the model Euclidean space ; namely, and a manifold is called an n-manifold when it has dimension n. A function on a manifold is said to be smooth if is smooth on for each chart in the differentiable structure.
A manifold is paracompact; this has an implication that it admits a partition of unity subordinate to a given open cover.
If is replaced by an upper half-space , then we get the notion of a manifold-with-boundary. The set of points that map to the boundary of under charts is denoted by and is called the boundary of . This boundary may not be the topological boundary of . Since the interior of is diffeomorphic to , a manifold is a manifold-with-boundary with empty boundary.
The next theorem furnishes many examples of manifolds.
For example, for , the derivative has rank one at every point in . Hence, the n-sphere is an n-manifold.
The theorem is proved as a corollary of the inverse function theorem.
Many familiar manifolds are subsets of . The next theoretically important result says that there is no other kind of manifolds. An immersion is a smooth map whose differential is injective. An embedding is an immersion that is homeomorphic (thus diffeomorphic) to the image.
The proof that a manifold can be embedded into for some N is considerably easier and can be readily given here. It is known that a manifold has a finite atlas . Let be smooth functions such that and cover (e.g., a partition of unity). Consider the map
It is easy to see that is an injective immersion. It may not be an embedding. To fix that, we shall use:
where is a smooth proper map. The existence of a smooth proper map is a consequence of a partition of unity. See for the rest of the proof in the case of an immersion.
Nash's embedding theorem says that, if is equipped with a Riemannian metric, then the embedding can be taken to be isometric with an expense of increasing ; for this, see this T. Tao's blog.
Tubular neighborhood and transversality
A technically important result is:
This can be proved by putting a Riemannian metric on the manifold . Indeed, the choice of metric makes the normal bundle a complementary bundle to ; i.e., is the direct sum of and . Then, using the metric, we have the exponential map for some neighborhood of in the normal bundle to some neighborhood of in . The exponential map here may not be injective but it is possible to make it injective (thus diffeomorphic) by shrinking (for now, see ).
Integration on manifolds and distribution densities
The starting point for the topic of integration on manifolds is that there is no invariant way to integrate functions on manifolds. This may be obvious if we asked: what is an integration of functions on a finite-dimensional real vector space? (In contrast, there is an invariant way to do differentiation since, by definition, a manifold comes with a differentiable structure). There are several ways to introduce integration theory to manifolds:
Integrate differential forms.
Do integration against some measure.
Equip a manifold with a Riemannian metric and do integration against such a metric.
For example, if a manifold is embedded into an Euclidean space , then it acquires the Lebesgue measure restricting from the ambient Euclidean space and then the second approach works. The first approach is fine in many situations but it requires the manifold to be oriented (and there is a non-orientable manifold that is not pathological). The third approach generalizes and that gives rise to the notion of a density.
Generalizations
Extensions to infinite-dimensional normed spaces
The notions like differentiability extend to normed spaces.
See also
Differential geometry of surfaces
Integration along fibers
Lusin's theorem
Density on a manifold
Notes
Citations
References
(revised 1990, Jones and Bartlett; reprinted 2014, World Scientific) [this text in particular discusses density]
Calculus | Calculus on Euclidean space | [
"Mathematics"
] | 5,226 | [
"Calculus"
] |
64,965,758 | https://en.wikipedia.org/wiki/WASP-45 | WASP-45 is a K-type main-sequence star about away. The star's age cannot be well constrained, but it is probably older than the Sun. Yet, WASP-45 is enriched in heavy elements compared to the Sun, having 240% of the solar abundance.
The star has low ultraviolet emission, therefore it is suspected to have a low starspot activity, although chromospheric activity was reported elsewhere.
There is a companion star at a separation of 4.4 arcseconds, corresponding to 929 AU.
Planetary system
In 2011 a transiting hot Jupiter planet, WASP-45b, was detected. The planet equilibrium temperature is . No Rayleigh scattering was detected in the planetary atmosphere, implying the existence of hazes or a high cloud deck.
References
Sculptor (constellation)
K-type main-sequence stars
Planetary systems with one confirmed planet
Planetary transit variables
Binary stars
J00205699-3559537
229
120610833
45 | WASP-45 | [
"Astronomy"
] | 201 | [
"Astronomy organizations",
"Wide Angle Search for Planets",
"Constellations",
"Sculptor (constellation)"
] |
64,966,775 | https://en.wikipedia.org/wiki/European%20respirator%20standards | The European respirator standards refer to the filtering classification by EN 149, EN 14683, and EN 143, all European standards of testing and marking requirements for respirators. FFP standard masks (where FFP stands for filtering facepiece) cover the nose, mouth and chin and may have inhalation and/or exhalation valves.
EN 149 defines three classes of such particle half masks, called FFP1, FFP2 and FFP3, according to their filtering efficiency. It also classifies masks into "single shift use only" (not re-usable, marked NR) or "re-usable (more than one shift)" (marked R), while an additional marking letter D indicates that a mask has passed an optional clogging test using dolomite dust. Such mechanical filter respirators protect against the inhalation of particulates such as dust particles, droplets, and aerosols. EN 14683 defines respirators for use in medical settings, while European standard EN 143 defines the 'P' classes of particle filters that can be attached to a face mask, which are P1, P2, and P3. The EN 143 filters are typically used on reusable respirators, like elastomeric respirators.
EN 14387 is the chemical cartridge standard in Europe.
Almost identical tests (but different markings) are used in Australia, New Zealand, Korea and Brazil. Similar standards are used in the United States, China and Japan. For example, EN 149 FFP2 masks have similar performance requirements to N95 masks in the United States and KN95 filters of China, and EN 149 FFP3 masks have similar performance requirements to N99 masks in the United States. However EN 149 test requirements differ somewhat from the U.S./Chinese/Japanese standards: EN 149 requires an additional paraffin oil (paraffinum perliquidum) aerosol test and it tests at a range of different flow rates and defines several associated and permissible pressure drop levels.
Classification
EN 149
The EN 149 standard defines performance requirements for three classes of particle-filtering half masks: FFP1, FFP2 and FFP3. The protection provided by an FFP2 (or FFP3) mask includes the protection provided by a mask of the lower-numbered classes.
A mask conforming to the standard must have its class written on it, along with the name of the standard and its year of publication, as well as any applicable option codes, e.g. “EN 149:2001 FFP1 NR D”. Some manufacturers use in addition the colour of the elastic band to identify the mask class, however, the EN 149 standard does not specify any such colour coding and different manufacturers have used different colour schemes.
EN 14683 and EN 143
European standard EN 143 defines the 'P' classes of particle filters that can be attached to a face mask. These filters are typically used on reusable respirators, like elastomeric respirators.
Both European standard EN 143 and EN 149 test filter penetration with dry sodium chloride and paraffin oil aerosols after storing the filters at and for 24 h each. The standards include testing mechanical strength, breathing resistance and clogging. EN 149 tests the inward leakage between the mask and face, where 10 human subjects perform 5 exercises each. The truncated mean of average leakage from 8 individuals must not exceed the aforementioned values.
FFP1 mask
It is the least filtering mask of the three.
Aerosol filtration percentage: 80% minimum
Internal leak rate: maximum 22%
It is mainly used as a dust mask (for example for DIY jobs). Dust can cause lung diseases, such as silicosis, anthracosis, siderosis and asbestosis (in particular dust from silica, coal, iron ore, zinc, aluminium or cement are common particulate risks).
FFP2 mask
Aerosol filtration percentage: 94% minimum
Internal leak rate: maximum 8%
This mask offers protection in various areas such as the glass industry, foundry, construction, pharmaceutical industry and agriculture. It effectively stops powdered chemicals. This mask can also serve as protection against respiratory viruses such as avian influenza or severe acute respiratory syndrome associated with the coronavirus (SARS), as well as against the bacteria of pneumonic plague and tuberculosis. It is similar to the US-standard N95 respirator.
FFP3 mask
Aerosol filtration percentage: 99% minimum
Internal leak rate: maximum 2%
The FFP3 mask is the most filtering of the FFP masks. It protects against very fine particles such as asbestos and ceramic. It does not protect against gases and in particular oxides of nitrogen.
Requirements
EN 149 defines laboratory tests, field tests and certain requirements to ensure the conformity of the masks. The following points are analyzed:
Packaging
Materials: resistance to manipulation
Practical performance test
Leakage: total leakage inwards and penetration of the filter material
There are some European organizations that issue an examination certificate confirming conformity and specifying the characteristics of the products:
INRS then APAVE in France
INSPEC in Great Britain
Institute for Occupational Safety and Health of the German Social Accident Insurance in Germany
CIOP-PIB in Poland
2009 version
With the publication of the 2009 version of the standard, the designation of the respiratory protection mask is now "particulate filtering half mask". The abbreviation NR or R is added after FFP1, FFP2, FFP3:
NR (not reusable): if the use of the filtering half-face mask is limited to one working day. It is not reusable.
R (reusable): if the filtering half-face mask can be used for more than one working day, so it is reusable.
Additional suffixes include:
Anti-clogging NR masks (D). When the half mask has passed the dolomite dust test, a letter D can be added to indicate that the service life may exceed 8 h. Example: FFP3 NR D.
Valve. The presence of a valve can be indicated by the letter V.
Particulate type. The letters S or L respectively specify the filtration of solid dust (NaCl-only) or liquid mist (paraffin oil). Example: FFP3 SLV.
Masks manufactured before the new standard was taken into account may still have the old marking.
Marking
FFP respirators are a type of personal protective equipment (PPE). Here is the notice that should appear on every mask :
Manufacturer's name
Mask
CE number of the certification body (only FFP3) + EN 149: 2009 + the mask class (FFP1, FFP2 or FFP3) + acronym (NR or R) (Note: in case of FFP1 the conformity assessment procedures are done by the manufacturer itself as per Annex IV (Module A)
The marking must comply with European Union Directive 89/686 / EEC on PPE. If any of these entries are missing, the mask will be considered non-compliant.
Medical use
EN 149 tests the ability of masks to protect the wearers against inhaling liquid and dry aerosols. It makes no statement about, and does not specifically test the suitability of such masks for, infection control against airborne transmission of pathogens through respiratory droplets. Nevertheless, FFP2 and FFP3 masks are commonly used for this purpose in medical practice. A researcher at the MRC Biostatistics Unit at Cambridge University claimed in 2021 that switching to FFP3 in Addenbrooke hospital in Cambridge may have cut ward-based Covid infection of staff to zero.
EN 14387 chemical cartridge classifications
EN 14387 is the European chemical cartridge standard. It is similar in scope to ANSI K13.1-1973.
Similar standards
Several regions use standards based on nearly identical tests and thresholds as those in EN 149, but with different markings:
Russia (GOST R 12.4.191-2011): identical.
South Korea (KMOEL - 2017–64): considered identical to pre-2009 version. FFP1 is called "2nd grade" or KF80, FFP2 "1st grade" or KF94, and FFP3 "special grade" or KF99.
Australia and New Zealand (AS/NZ 1716:2012): similar grades with a different test agent. Grades are written simply "P".
Brazil (ABNT/NBR 13698:2011): identical to pre-2009 version. Grades are written as "PFF".
Other regions use similar tests that (in parts) resemble more closely the 42 CFR 84 requirements in the United States:
Japan (JMHLW-Notification 214, 2018): similar grades with a different coding scheme for NR/R and S/L types. Written with a two-letter prefix D/R and S/L that maps to NR/R and S/L respectively. Leakage requirement not present.
Taiwan (CNS 14755): D1/D2/D3 grades for 80/95/99 efficiency. No requirements for inward leakage.
See also
Gas mask
NIOSH air filtration rating
Respirator
Surgical mask
Face masks during the COVID-19 pandemic
Notes and references
European Union
Mechanical standards
Respirators
Medical masks | European respirator standards | [
"Engineering"
] | 1,945 | [
"Mechanical standards",
"Mechanical engineering"
] |
64,967,602 | https://en.wikipedia.org/wiki/IPod%20Touch%20%281st%20generation%29 | The first-generation iPod Touch, (colloquially known as the iPod Touch 1G, iPod Touch 1, or original iPod Touch) is a multi-touch mobile device designed and marketed by Apple Inc. with a touchscreen-based user interface. The first device of the iPod Touch series, it was unveiled and released at Apple's media event on September 5, 2007. It is compatible with up to iPhone OS 3.1.3 which was released on February 2, 2010.
Unlike the iPhone, the iPod Touch does not have a speaker or a camera. A speaker was added in the second generation, while a front and rear camera were added in the fourth generation.
History
The first-generation iPod touch was released after the first-generation iPhone as a companion device. It had similar features, but a thinner design with an all-metal back except for a small corner cut out for WiFi 802.11 b/g, allowing it to use Safari to browse websites. It used the same 30-pin connector as the first-generation iPhone and previous iPods, allowing most iPod accessories to work with the iPod touch.
Features
Software
It fully supports iPhone OS 1 to iPhone OS 3, though it received different features at different times from the first-generation iPhone. It also did not have the iPod app as it was an iPod, and instead had the Music app for playing music and podcasts, with a separate Videos app to watch videos. It also received the iTunes Store app before the iPhone did - the first-generation iPod touch received the iTunes Store app on launch with iPhone OS 1.1 on September 14, 2007, while the first-generation iPhone received the iTunes Store app on September 27, 2007, with the release of iPhone OS 1.1.1. It also had Calendar, Clock, Calculator, and Photos apps preinstalled.
The iPhone OS 2.0 update introduced the App Store, but unlike the iPhone, it was not available for free. Free iOS updates were not available on the iPod touch until iOS 4, which is not supported on this model.
An unofficial port of Android 2.3 Gingerbread called iDroid supports the first-generation iPod touch.
Emulation
In December 2022, Internet user Martijn de Vos, also known as devos50 has reverse engineered this device to successfully create a QEMU emulation of this device, running iPhone OS 1.0.
References
IPod
Apple Inc.
Touchscreens | IPod Touch (1st generation) | [
"Technology"
] | 500 | [
"Mobile computer stubs",
"Mobile technology stubs"
] |
64,969,095 | https://en.wikipedia.org/wiki/Kahausibware | Kahausibware is a serpentine female spirit and primeval creator goddess revered in the Solomon Islands. She was a Hi'ona—a powerful supernatural being who created the world.
According to myth, Kahausibware created pigs, cocoa-nut trees, and fruit trees. Having created food, she then created animals and humans to use it.
References
Creation myths
Creator goddesses
Mother goddesses
Snake goddesses
Solomon Islands mythology | Kahausibware | [
"Astronomy"
] | 89 | [
"Cosmogony",
"Creation myths"
] |
64,970,624 | https://en.wikipedia.org/wiki/Multidrug-resistant%20bacteria | Multidrug-resistant bacteria (MDR bacteria) are bacteria that are resistant to three or more classes of antimicrobial drugs. MDR bacteria have seen an increase in prevalence in recent years and pose serious risks to public health. MDR bacteria can be broken into 3 main categories: Gram-positive, Gram-negative, and other (acid-stain). These bacteria employ various adaptations to avoid or mitigate the damage done by antimicrobials. With increased access to modern medicine there has been a sharp increase in the amount of antibiotics consumed. Given the abundant use of antibiotics there has been a considerable increase in the evolution of antimicrobial resistance factors, now outpacing the development of new antibiotics.
Examples identified as serious threats to public health
Examples of MDR bacteria identified as serious threats to public health include:
Gram-positive MDR bacteria
Clostridioides difficile
Staphylococcus aureus
Streptococcus pneumoniae
Gram-negative MDR bacteria
Carbapenem-resistant Acinetobacter
Escherichia coli
Klebsiella pneumoniae
Neisseria gonorrhoeae
Campylobacter
Pseudomonas aeruginosa
Salmonella
Shigella
Other MDR bacteria
Mycobacterium tuberculosis
Microbial adaptations
MDR bacteria employ a plurality of adaptations to overcome the environmental insults caused by antibiotics. Bacteria are capable of sharing these resistance factors in a process called horizontal gene transfer where resistant bacteria share genetic information that encodes resistance to the naive population.
Antibiotic inactivation: bacteria create proteins that can prevent damage caused by antibiotics, they can do this in two ways. First, inactivating or modifying the antibiotic so that it can no longer interact with its target. Second, degrading the antibiotic directly.
Multidrug efflux pumps: The use of transporter proteins to expel the antibiotic.
Modification of target sites: mutating or modifying elements of the bacteria structure to prevent interaction with the antibiotic.
Structural modifications: mutating or modifying global elements of cell to adapt to Antibiotic (Such as increased acid tolerance to an acidic antimicrobial)
Alternative antimicrobial methods
Phage therapy
Bacteriophage therapy, commonly known as 'phage therapy,' uses bacteria-specific viruses to kill antibiotic resistant bacteria. Phage therapy offers considerably higher specificity as the phage can be engineered to only infect a certain bacteria species. Phage therapy also allows for the possibility of biofilm penetration in cases where antibiotics are ineffective due to the increased resistance of biofilm-forming pathogens. One major drawback to phage therapy is the evolution of phage-resistant microbes which was seen in a majority of phage therapy experiments aimed to treat sepsis and intestinal infection. Recent studies suggest that development of phage resistance comes as a trade-off for antibiotic resistance and can be used to create antibiotic-sensitive populations.
References
Microbiology
Public health
Symbiosis
Antibiotics
Antibiotic-resistant bacteria | Multidrug-resistant bacteria | [
"Chemistry",
"Biology"
] | 622 | [
"Behavior",
"Symbiosis",
"Biotechnology products",
"Biological interactions",
"Microbiology",
"Antibiotic-resistant bacteria",
"Antibiotics",
"Bacteria",
"Microscopy",
"Biocides"
] |
64,971,289 | https://en.wikipedia.org/wiki/Katja%20Loos | Katja Loos is professor at the Zernike Institute for Advanced Materials of the University of Groningen, The Netherlands holding the chair of Macromolecular Chemistry and New Polymeric Materials.
She currently serves as the President of the European Polymer Federation (EPF).
Biography
Katja Loos studied chemistry at the Johannes Gutenberg Universität in Mainz, Germany and graduated in 1996. During her graduate studies she focused her studies on Organic Chemistry and Polymer Chemistry. In 1992 and 1993 she was an international exchange student at the University of Massachusetts in Amherst, USA.
In 2001, she received her PhD in Macromolecular Chemistry from the University of Bayreuth, Germany. Her thesis was focused on hybrid materials bearing amylose using enzymatic polymerizations. During her PhD research she worked in 1997 as an international exchange researcher at the Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
In 2001, she received a Feodor Lynen research fellowship of the Alexander von Humboldt Foundation to conduct postdoctoral research at the Polytechnic University in Brooklyn, NY, USA, where she worked on fundamentals of self-assembled monolayers and immobilization supports for biocatalysts.
In 2003, she started an independent research group at the University of Groningen, the Netherlands.
Katja Loos worked as guest professor at the Technical University of Catalonia, Barcelona, Spain in 2006 and at the Technical University Dresden, Germany in 2016.
Research
The research of Loos is focused on enzymatic polymerization, especially the biocatalytic synthesis of saccharides, polyamides and furan based polymers, as well as the synthesis and self-assembly of block copolymers using supramolecular motifs and containing ferroelectric blocks.
Loos published over 270 scholarly peer-reviewed publications, various patents and book chapters. Her publications frequently get included in special themed collections of scientific journals like “Women in Polymer Science” from Wiley en “Women at the Forefront of Chemistry” of the American Chemical Society
She is the editor of the only currently available textbook in the field of Enzymatic Polymerizations.
She is editor of the scientific journal Polymer and guest-edited special issues of various scientific journals.
Since 2017 she is a member of the board of the Zernike Institute for Advanced Materials of the University of Groningen. She serves as the vice-chair of the program council Chemistry of Advanced Materials of ChemistryNL, a member of the board of the MaterialenNL Platform and is a member of the board of the Dutch national postgraduate research school Polymer Technology Netherlands (PTN).
Katja Loos is the national representative of the Netherlands to the European Polymer Federation (EPF).
In addition to her research, Katja Loos advocates for diversity in science and open access publishing
Awards and honours
Katja Loos was awarded two travel scholarships of the German Academic Exchange Service (DAAD) for research stays at the University of Massachusetts in Amherst, USA, in 1992 and 1993 and at Universidade Federal do Rio Grande do Sul, Porto Alegre, Brasil, in 1997.
In 2001, she received a Feodor Lynen Fellowship award of the Alexander von Humboldt Foundation to conduct her postdoctoral research.
The Netherlands Organisation for Scientific Research (NWO) awarded her a VIDI innovational research grant in 2009 and a VICI innovational research grant in 2014
In 2016 the Technical University Dresden and the German Research Council (DFG) within the scope of its excellency initiative awarded her the Eleonore Trefftz guest professorship.
The Alexander von Humboldt Foundation awarded Katja Loos in 2019 the Friedrich Wilhelm Bessel Research Award.
In 2019, she was named "Topper of the year" by Science Guide.
She is one of the recipients of the IUPAC 2021 Distinguished Women in Chemistry or Chemical Engineering award.
In 2022 she won the Team Science Award of the Dutch Research Council (NWO) with her research group HyBRit.
In 2023 she received the title of Knight of the Order of the Netherlands Lion, the prestigious Dutch order of chivalry founded by King William I in 1815.
Katja Loos is a Fellow of the Dutch Polymer Institute (DPI) and the Royal Society of Chemistry (FRSC)
References
External links
Website research group
Information on university website
Profile on NARCIS
Profile on AcademiaNet
External links
1971 births
Living people
Academic staff of the University of Groningen
21st-century Dutch chemists
21st-century German chemists
Johannes Gutenberg University Mainz alumni
University of Bayreuth alumni
21st-century Dutch inventors
Women inventors
Scientists from Frankfurt
Polymer scientists and engineers
Polytechnic Institute of New York University alumni
21st-century Dutch women scientists | Katja Loos | [
"Chemistry",
"Materials_science"
] | 952 | [
"Polymer scientists and engineers",
"Physical chemists",
"Polymer chemistry"
] |
64,971,320 | https://en.wikipedia.org/wiki/Justice%20Duel | Justice Duel is a platform game developed and published by Mega Cat Studios. It was released on the Nintendo Entertainment System in 2017. Players battle one another while riding cybernetically enhanced eagles. The game plays similarly to Joust.
Gameplay
The player controls a cyborg version of a past President of the United States riding a cybernetically enhanced eagle to duel either against other human players or the game's AI. The player duels by firing projectiles at their opponents; a level is completed once there are no remaining opponents. Players can pick up power-ups in the form of mines and traps to use against opponents. Justice Duel supports multiplayer for up to four players through the NES Four Score.
Development
Besides Joust, the game's developers cite TowerFall and Balloon Fight as having inspired elements of the game's design.
Evercade release
Mega Cat Studios released Justice Duel in a compilation cartridge for the Evercade, along with several other titles from the studio, including Little Medusa, Log Jammers, and Coffee Crisis.
Child's Play edition
In 2018, Mega Cat Studios released a special edition of Justice Duel to raise money for the charity Child's Play; it debuted at PAX East and was part of the Omegathon tournament. This special edition of the game features two additional playable characters: Della and Rod, who ride a duck and a quail, respectively.
Reception
Justice Duel has received a generally positive reception from the press, being praised for its aesthetic and fast paced gameplay.
References
External links
2017 video games
Eagles in popular culture
Fiction about cyborgs
Fictional presidents of the United States
Indie games
Mega Cat Studios games
Multiplayer and single-player video games
Nintendo Entertainment System games
Nintendo Entertainment System homebrew games
Nintendo Entertainment System-only games
Platformers
Unauthorized video games
Video games developed in the United States
Video games about birds | Justice Duel | [
"Biology"
] | 370 | [
"Fiction about cyborgs",
"Cyborgs"
] |
64,972,399 | https://en.wikipedia.org/wiki/Galina%20Khitrova | Galina Khitrova (1959 – June 4, 2016) was a Russian-American physicist and optical scientist known for her research on cavity quantum electrodynamics, excitons, nonlinear optics, quantum dots, and vacuum Rabi oscillations. She was a professor of optical sciences at the University of Arizona.
Education and career
Khitrova was born in Saint Petersburg, and has degrees in physics from Yerevan State University, Brooklyn College, and New York University, where she completed her Ph.D. She came to the University of Arizona as a researcher in 1986, married Arizona professor Professor Hyatt M. Gibbs in 1986, was given tenure as an associate professor in 1997, and became full professor in 2002.
Recognition
Khitrova was named a Fellow of The Optical Society in 2007, "for leadership in research in fundamental optical phenomena in semiconductor nanostructures". She was named a Fellow of the American Physical Society (APS) in 2012, after a nomination by the APS Division of Laser Science, "for fundamental studies of pump probe spectroscopy of atomic vapors and light-matter coupling of cavity fields with quantum wells and dots. In particular, for demonstrating the quantum regime of semiconductor cavity quantum electrodynamics via the vacuum Rabi splitting between a single quantum dot and the field in a photonic crystal nanocavity."
References
External links
1959 births
2016 deaths
American physicists
American women physicists
Russian physicists
Russian women physicists
Yerevan State University alumni
Brooklyn College alumni
New York University alumni
University of Arizona faculty
Fellows of the American Physical Society
Fellows of Optica (society)
Spectroscopists
American women academics
21st-century American women | Galina Khitrova | [
"Physics",
"Chemistry"
] | 342 | [
"Physical chemists",
"Spectrum (physical sciences)",
"Analytical chemists",
"Spectroscopists",
"Spectroscopy"
] |
61,330,792 | https://en.wikipedia.org/wiki/King%20Salman%20Award%20for%20Disability%20Research | The King Salman Award for Disability Research is an internationally recognized prize that is awarded to notable individuals who contributed to knowledge and scientific research in the field of disability. The prize was established by King Salman Center for Disability Research.
Areas and Nominations
There are three main areas of the award in which nominations are accepted. These areas are Health and Medical Sciences, Pedagogical and Educational Sciences, and Rehabilitative and Social Sciences. The Nominations are accepted from local and international research and scientific organizations as well as academic departments and universities.
Award Value
The laureates are given the following rewards:
A certificate with their names and works.
An honorary medal.
500,000 Saudi Riyals (US$133,450).
List of laureates
References
Saudi Arabian awards
Medicine awards | King Salman Award for Disability Research | [
"Technology"
] | 154 | [
"Science and technology awards",
"Medicine awards"
] |
61,330,798 | https://en.wikipedia.org/wiki/Solanesol | Solanesol is the organic compound with the formula Me2C=CHCH2(CH2C(Me)=CHCH2)8OH. It is an all trans stereoisomer. This white, waxy solid is classified as an nonaisoprenoid. Solanesol is a non-cyclic terpene alcohol that consists of nine isoprene units and mainly accumulates in solanaceous plants such as tobacco, potato, and tomato. It is extractable from the stems and leaves of solanaceous species. It is notable as the biosynthetic precursor to coenzyme Q10.
Occurrence
Solanesol is a non-cyclic terpene alcohol that consists of nine isoprene units and mainly accumulates in solanaceous plants such as tobacco, potato, and tomato. It is also accumulates in eggplant and pepper plants. It is notable as the biosynthetic precursor to coenzyme Q10. The leaf tobacco contains the tobacco-specific compound solanesol. It is found in tobacco smoke and in the emissions of heat-not-burn tobacco products. Tobacco has the highest solanesol content amongst all solanaceous plants. It is extractable from tobacco waste.
Functions
Solanesol is a secondary metabolite. Various plants produce numerous highly-specific terpenoids that play important roles in plant–environment interactions. In tobacco, solanesol might participate in the immune response towards pathogens: in a 2017 study by Bajda et al., the solanesol content in resistant tobacco varieties increased by more than 7 times one week after infection by the tobacco mosaic virus (TMV), while it did not increase significantly after infection in susceptible varieties. In potato, as compared to normal temperatures (22 °C during the day, 16 °C at night), moderately high temperatures (30 °C during the day, 20 °C at night) caused a more than six-fold increase in the solanesol content after one week, indicating that solanesol might play an important role in the response of potato to moderately high temperatures. Hence, solanesol plays important roles in the interactions of solanaceous plants with environmental factors.
Activities
Solanesol possesses antimicrobial, anti-tumor, anti-inflammatory, and anti-ulcer activities, and it serves as an important pharmaceutical intermediate for the synthesis of coenzyme Q10, vitamin K2, and N-solanesyl-N,N′-bis(3,4-dimethoxybenzyl) ethylenediamine (SDB). The physiological functions of coenzyme Q10 include anti-oxidation, anti-aging, immune-function enhancement, cardiovascular enhancement, brain-function enhancement, and the regulation of blood lipids; it may be used for treating migraines, neurodegenerative diseases, hypertension, and cardiovascular diseases, and as a dietary supplement for patients with type 2 diabetes. Vitamin K2 promotes bone growth, inhibits bone resorption, stimulates bone mineralization, has preventive and therapeutic effects on osteoporosis, diminishes blood clotting, and reduces the progression of arteriosclerosis. The anti-cancer agent synergizer SDB allows P-glycoprotein-mediated multidrug resistance in cancer cells to be overcome, and has synergistic effects with certain anti-tumor drugs. Recently as of 2017, it was found that solanesol induces the expression of HO-1 and Hsp70, which in turn alleviates alcohol-induced liver cell damage. Additionally, it inhibits the generation of inflammatory cytokines through the p38 and Akt signalling pathways, implying an anti-inflammatory effect. Therefore, solanesol and its derivatives are highly valuable from a pharmaceutical perspective.
Overview
Solanesol is a non-cyclic terpene alcohol that consists of nine isoprene units. Solanesol serves an important role in the interactions between plants and their environment, and it is a key intermediate for the pharmaceutical synthesis of ubiquinone-based supplements and drugs. Notably, although solanesol and its derivatives are highly valuable from a pharmaceutical perspective, solanesol as a C45 compound may act as a tumorigenic precursor in tobacco smoke. While in recent years as of 2017, studies on the identification of key enzymatic genes in solanesol biosynthesis and gene function have achieved significant progress, a number of questions on the regulatory mechanisms of solanesol synthesis remain unanswered. Genome sequencing of solanaceous plants such as tobacco, potato, and tomato has paved the way for deeper studies on the metabolic regulation of solanesol biosynthesis.
Transcriptomics and metabolomics studies may aid in resolving the metabolic flux distribution of solanesol and the mechanisms through which it interacts with other metabolic pathways. The creation of NtSPS1-overexpressing tobacco plants has been accomplished in a laboratory setting, which makes it possible to evaluate the effects of SPS1 overexpression on solanesol and related metabolites, photosynthesis, and the expression levels of key solanesol biosynthetic and related genes in tobacco. Moreover, overexpression of key enzymatic genes will allow tobacco plants with high solanesol content to be obtained, with significant importance for medical applications. Microbial heterologous expression of key tobacco enzymatic genes may be used to identify their function and to generate solanesol derivatives of medicinal value.
References
Terpenes and terpenoids
Primary alcohols | Solanesol | [
"Chemistry"
] | 1,156 | [
"Organic compounds",
"Biomolecules by chemical classification",
"Terpenes and terpenoids",
"Natural products"
] |
61,330,828 | https://en.wikipedia.org/wiki/Decrease%20in%20DNA%20Methylation%20I | Decreased DNA Methylation I (DDM1), is a plant gene that encodes a nucleosome remodeler which facilitates DNA methylation. The DDM1 gene has been described extensively in Arabidopsis thaliana and also in maize. The protein has been described to be similar to the SWI2/SNF2 chromatin remodeling proteins.
Since DNA methylation occurs mostly in transposable elements (TE), DDM1 is thought to be a crucial function in silencing TEs.
Arabidopsis thaliana (A. thaliana)
DDM1 is required for DNA methylation in highly heterochromatin transposable elements. DDM1, therefore, often silences transposable elements but the mutation in Arabidopsis thaliana is not embryo lethal. DDM1 mutants have also
Maize
DDM1 is being further explored in maize. Unlike A. thaliana, maize has two copies of the gene: CHR101 and CHR106. In maize, the double mutant of DDM1 is embryo lethal. However, other studies are using the heterozygote mutant. The maize genome is 80% transposons so DDM1 function is quite important.
See also
DNA methylation
DNA demethylation
References
Plant genes
Arabidopsis thaliana genes
DNA
Methylation
Epigenetics | Decrease in DNA Methylation I | [
"Chemistry"
] | 292 | [
"Methylation"
] |
61,334,503 | https://en.wikipedia.org/wiki/I.%20I.%20Rabi%20Prize | The I. I. Rabi Prize in Atomic, Molecular, and Optical Physics is given by the American Physical Society to recognize outstanding work by mid-career researchers in the field of atomic, molecular, and optical physics. The award was endowed in 1989 in honor of the physicist I. I. Rabi and has been awarded biannually since 1991.
The prize citation reads:
Recipients
Source:
1991 Chris H. Greene: "For his many contributions to atomic and molecular theory including studies of resonance vibronic processes, multiple electron excitations, photo-absorption in external fields, and threshold effects of long range forces."
1993 Timothy E. Chupp: "For his contributions to the development of high density polarized noble gases by spin exchange with optically pumped alkali atoms and in particular for his leadership and use of polarized 3He as a target for fundamental experiments in nuclear physics."
1995 Randall G. Hulet: "For his contributions to a broad range of important problems in atomic and optical physics including cavity quantum electrodynamics, quantum jumps, ion storage, and laser cooling of atoms. In the latter field, in particular for his demonstration of multiphoton cooling involving Doppleron resonances in neutral Lithium and his collision experiments with cooled Lithium vapor."
1997 Eric Allin Cornell and Wolfgang Ketterle: "For achieving Bose-Einstein condensation of an atomic gas, for creating techniques for studying the Bose condensate, and for measuring the physical properties of the weakly interacting atomic Bose gas."
1999 Mark G. Raizen: "For his pioneering advances in the experimental study of atom optics, and especially for the insightful connections he has developed between this discipline and studies of chaotic dynamics, condensed matter physics, and dissipative quantum systems."
2001 Christopher Monroe: "For his pivotal experiments that implemented quantum logic using trapped atomic ions, and for his fundamental studies of coherence and decoherence in entangled quantum systems."
2003 Mark A. Kasevich: "For developing atom interferometer inertial sensors with unprecedented precision, and for pioneering studies of Bose-Einstein condensates, especially the achievement of non-classical spin states and the demonstration of a mode-locked atom laser."
2005 Deborah Jin:
2007 Jun Ye: "For advances in precision measurement, including techniques for stabilizing and measuring optical frequencies, controlling the phase of femtosecond laser pulses, and measuring molecular transitions."
2009 Mikhail Lukin: "For pioneering theoretical and experimental work at the interface between quantum optics, quantum information processing, and the quantum many body problem."
2011 Cheng Chin: "For pioneering work in strongly interacting Fermi gas and few body physics including the discovery of the Effimov effect."
2013 Markus Greiner: "For seminal contributions to the field of ultracold atoms, including the observation of the superfluid-to-Mott-insulator transition, the study of the BEC-BCS cross over for fermions, and the development of imaging techniques for atoms in optical lattices with single-atom resolution"
2015 Ian Spielman: "For the development of quantum simulations using ultra-cold atoms, creation of synthetic electromagnetic fields, demonstration of synthetic spinorbit coupling, and applications to studying new physical systems."
2017 Martin Zwierlein: "For seminal studies of ultracold Fermi gases, including precision measurements of the equation of state, the observation of superfluidity, solitons, vortices, and polarons, the realization of a microscope for fermions in a lattice; and the production of chemically stable polar molecules."
2019 Kang-Kuen Ni: "For seminal work on ultracold molecules, including original contributions to the understanding of chemical reactions in the quantum regime, deterministic creation of individual molecules with optical tweezers, and development of novel, high-precision techniques to interrogate and control the complete set of internal molecular resources."
2021 Monika Schleier-Smith: "For seminal work in quantum optics and for discoveries at the intersection of AMO, condensed matter, and quantum information, including original contributions to spin squeezing in optical cavities, engineering long-range interactions for quantum simulations, and metrology, and for theoretical development of a measurement protocol related to the scrambling of quantum information."
2023 Adam M. Kaufman: "For seminal developments in optical tweezer arrays and clocks based on alkaline earth atoms, with applications to metrology and quantum information processing."
See also
List of physics awards
Arthur L. Schawlow Prize in Laser Science
Norman F. Ramsey Prize in Atomic, Molecular and Optical Physics, and in Precision Tests of Fundamental Laws and Symmetries
References
External links
I.I. Rabi Prize in Atomic, Molecular, and Optical Physics (official site)
Awards of the American Physical Society
Atomic physics
Atomic, molecular, and optical physics | I. I. Rabi Prize | [
"Physics",
"Chemistry"
] | 1,006 | [
"Quantum mechanics",
"Atomic physics",
" molecular",
"Atomic",
" and optical physics"
] |
61,335,100 | https://en.wikipedia.org/wiki/Amazon%20Rekognition | Amazon Rekognition is a cloud-based software as a service (SaaS) computer vision platform that was launched in 2016. It has been sold to, and used by, a number of United States government agencies, including U.S. Immigration and Customs Enforcement (ICE) and Orlando, Florida police, as well as private entities.
Capabilities
Rekognition provides a number of computer vision capabilities, which can be divided into two categories: Algorithms that are pre-trained on data collected by Amazon or its partners, and algorithms that a user can train on a custom dataset.
As of July 2019, Rekognition provides the following computer vision capabilities.
Pre-trained algorithms
Celebrity recognition in images
Facial attribute detection in images, including gender, age range, emotions (e.g. happy, calm, disgusted), whether the face has a beard or mustache, whether the face has eyeglasses or sunglasses, whether the eyes are open, whether the mouth is open, whether the person is smiling, and the location of several markers such as the pupils and jaw line.
People Pathing enables tracking of people through a video. An advertised use-case of this capability is to track sports players for post-game analysis.
Text detection and classification in images
Unsafe visual content detection
Algorithms that a user can train on a custom dataset
SearchFaces enables users to import a database of images with pre-labeled faces, to train a machine learning model on this database, and to expose the model as a cloud service with an API. Then, the user can post new images to the API and receive information about the faces in the image. The API can be used to expose a number of capabilities, including identifying faces of known people, comparing faces, and finding similar faces in a database.
Face-based user verification
History and use
2017
In late 2017, the Washington County, Oregon Sheriff's Office began using Rekognition to identify suspects' faces. Rekognition was marketed as a general-purpose computer vision tool, and an engineer working for Washington County decided to use the tool for facial analysis of suspects. Rekognition was offered to the department for free, and Washington County became the first US law enforcement agency known to use Rekognition. In 2018, the agency logged over 1,000 facial searches. The county, according to the Washington Post, by 2019 was paying about $7 a month for all of its searches. The relationship was unknown to the public until May 2018. In 2018, Rekognition was also used to help identify celebrities during a royal wedding telecast.
2018
In April 2018, it was reported that FamilySearch was using Rekognition to enable their users to "see which of their ancestors they most resemble based on family photographs". In early 2018, the FBI also began using it as a pilot program for analyzing video surveillance.
In May 2018, it was reported by the ACLU that Orlando, Florida was running a pilot using Rekognition for facial analysis in law enforcement, with that pilot ending in July 2019. After the report, on June 22, 2018, Gizmodo reported that Amazon workers had written a letter to CEO Jeff Bezos requesting he cease selling Rekognition to US law enforcement, particularly ICE and Homeland Security. A letter was also sent to Bezos by the ACLU. On June 26, 2018, it was reported that the Orlando police force had ceased using Rekognition after their trial contract expired, reserving the right to use it in the future. The Orlando Police Department said that they had "never gotten to the point to test images" due to old infrastructure and low bandwidth.
In July 2018, the ACLU released a test showing that Rekognition had falsely matched 28 members of Congress with mugshot photos, particularly Congresspeople of color. 25 House members afterwards sent a letter to Bezos, expressing concern about Rekognition. Amazon responded saying the Rekognition test had generated 80 percent confidence, while it recommended law enforcement only use matches rated at 99 percent confidence. The Washington Post states that Oregon instead has officers pick a "best of five" result, instead of adhering to the recommendation.
In September 2018, it was reported that Mapillary was using Rekognition to read the text on parking signs (e.g. no stopping, no parking, or specific parking hours) in cities.
In October 2018, it was reported that Amazon had earlier that year pitched Rekognition to U.S. Immigration and Customs Enforcement agency. Amazon defended government use of Rekognition.
On December 1, 2018, it was reported that 8 Democratic lawmakers had said in a letter that Amazon had "failed to provide sufficient answers" about Rekognition, writing that they had "serious concerns that this type of product has significant accuracy issues, places disproportionate burdens on communities of color, and could stifle Americans' willingness to exercise their First Amendment rights in public."
2019
In January 2019, MIT researchers published a peer-reviewed study asserting that Rekognition had more difficulty in identifying dark-skinned females than competitors such as IBM and Microsoft. In the study, Rekognition misidentified darker-skinned women as men 31% of the time, but made no mistakes for light-skinned men. Amazon called the report "misinterpreted results" of the research with an improper "default confidence threshold."
In January 2019, Amazon's shareholders "urged Amazon to stop selling Rekognition software to law enforcement agencies." Amazon in response defended its use of Rekognition, but supported new federal oversight and guidelines to "make sure facial recognition technology cannot be used to discriminate." In February 2019, it was reported that Amazon was collaborating with the National Institute of Standards and Technology (NIST) on developing standardized tests to improve accuracy and remove bias with facial recognition.
In March 2019, an open letter regarding Rekognition was sent by a group of prominent AI researchers to Amazon, criticizing its sale to law enforcement with around 50 signatures.
In April 2019, Amazon was told by the Securities and Exchange Commission that they had to vote on two shareholder proposals seeking to limit Rekognition. Amazon argued that the proposals were an "insignificant public policy issue for the Company" not related to Amazon's ordinary business, but their appeal was denied. The vote was set for May. The first proposal was tabled by shareholders. On May 24, 2019, 2.4% of shareholders voted to stop selling Rekognition to government agencies, while a second proposal calling for a study into Rekognition and civil rights had 27.5% support.
In August 2019, the ACLU again used Rekognition on members of government, with 26 of 120 lawmakers in California flagged as matches to mugshots. Amazon stated the ACLU was "misusing" the software in the tests, by not dismissing results that did not meet Amazon's recommended accuracy threshold of 99%. By August 2019, there had been protests against ICE's use of Rekognition to surveil immigrants.
In March 2019, Amazon announced a Rekognition update that would improve emotional detection, and in August 2019, "fear" was added to emotions that Rekognition could detect.
2020
In June 2020, Amazon announced it was implementing a one-year moratorium on police use of Rekognition, in response to the George Floyd protests.
2024
The Department of Justice disclosed that the FBI is initiating the use of Amazon Rekognition. The DOJ's AI inventory revealed the FBI's "Project Tyr" aims to customize Rekognition to identify nudity, weapons, explosives, and other information from lawfully acquired media.
Controversy regarding facial analysis
Racial and gender bias
In 2018, MIT researchers Joy Buolamwini and Timnit Gebru published a study called Gender Shades. In this study, a set of images was collected, and faces in the images were labeled with face position, gender, and skin tone information. The images were run through SaaS facial recognition platforms from Face++, IBM, and Microsoft. In all three of these platforms, the classifiers performed best on male faces (with error rates on female faces being 8.1% to 20.6% higher than error rates on male faces), and they performed worst on dark female faces (with error rates ranging from 20.8% to 30.4%). The authors hypothesized that this discrepancy is due principally to Megvii, IBM, and Microsoft having more light males than dark females in their training data, i.e. dataset bias.
In January 2019, researchers Inioluwa Deborah Raji and Joy Buolamwini published a follow-up paper that ran the experiment again a year later, on the latest versions same three SaaS facial recognition platforms, plus two additional platforms: Kairos, and Amazon Rekognition. While the systems' overall error-rates improved over the previous year, all five of the systems again performed better on male faces than on dark female faces.
See also
Amazon Lex
Amazon Mechanical Turk
Amazon Polly
Amazon SageMaker
Amazon Web Services
Facial recognition system
Timeline of Amazon Web Services
References
2016 software
Amazon Web Services
Cloud infrastructure
Criticism of Amazon
Computer vision software
Data mining and machine learning software
Facial recognition software
Object recognition and categorization | Amazon Rekognition | [
"Technology"
] | 1,936 | [
"Cloud infrastructure",
"IT infrastructure"
] |
61,337,148 | https://en.wikipedia.org/wiki/Apteronotus%20rostratus | Apteronotus rostratus is a species of apteronotid electric fish. These fish typically exhibit a wide diversity of skull shapes, ranging from highly elongate skulls to highly foreshortened ones, with both types evolving independently multiple times. In Apteronotus rostratus and some others, such as Compsaraia samueli, mature males grow extremely elongated snouts and oral jaws which are used in agonistic interactions with other males. This is an example of sexual weaponry. A study comparing skull shape and jaw-closing performance in males and females of Apteronotus rostratus suggested that males with elongated faces for use in fights did not have lower mechanical advantages, in contrast to the similar species Compsaraia samueli in which males exhibit a trade-off between sexual weaponry and jaw leverage.
References
Apteronotidae
Freshwater fish of Colombia
Fish of Panama
Freshwater fish of Venezuela
Fish described in 1913
Taxa named by Seth Eugene Meek
Taxa named by Samuel Frederick Hildebrand | Apteronotus rostratus | [
"Biology"
] | 205 | [] |
61,338,219 | https://en.wikipedia.org/wiki/Sisteplant | Sisteplant is a Spanish multinational company specializing in the automation and digitalization of industrial processes. It was founded in Bisay in 1984. It is headquartered in Madrid, with offices in Bilbao, Barcelona, Seville, Pontevedra, Valencia, Brazil, and Mexico.
History
The company was created in 1984 by Javier Borda, an industrial engineer. From its beginnings until the mid-1990s, the company was involved in the technological transformation and optimization of the Basque automotive, steel, and shipbuilding industries. It introduced information technologies and computerized maintenance systems. It has also spread to other regions of Spain, and to other sectors of the economy, such as energy, agri-food, aerospace and public administration. The company promoted productivity improvements through the implementation of lean manufacturing.
In the mid-1990s, they moved from mass production to high-tech sectors with small series or one-off production, such as aeronautics; and began their international expansion with the help of Spanish Ibex companies, opening offices in Mexico (Santiago de Querétaro), Brazil (São Paulo)) and China (Xuhui, Shanghai district).
The company has developed projects in the automotive, aerospace, energy, food, pharmaceutical, public administration, logistics and infrastructure sectors, both nationally and internationally.
Since 2007, it has developed the Tecnoiplant model, a technological, digital and organizational roadmap for the factory of the future, using its own software systems (Prisma, Captor, Promind, and Itracker). The company has also incorporated artificial intelligence tools to its digital platform, which is called Manufacturing Intelligence.
Sisteplant is a family company. Its capital is in the hands of its president, Javier Borda. Its shareholders included the venture capital fund Talde, the IBV group and other managing partners who later withdrew.
Innovation and development
Since its inception, the company has dedicated 20% of its turnover to the development of R&D&I projects in collaboration with the Basque Government, universities and research centres.
Together with Tecnalia, it has participated in innovative technological developments for the production of continuous CNT (carbon nanotube) sheets for the aeronautical and marine industries. It has also participated in the design of the facilities for the integration and assembly of the HyperloopTT ultra-fast train capsules.
Since (1988) Sisteplant recognises professional and organisational merit through the Excellence Awards. The thirty-fourth edition was held in 2022.
Awards and recognition
National Industrial Engineering Award for the most innovative company by the General Council of Official Associations of Industrial Engineers (CGCOII) - 2019.
Recognised by Actualidad Económica with the award for the 100 best ideas in 2018, 2019, and 2020.
Recognised by Actualidad Económica as one of the 100 best companies to work for in Spain: 2018, 2022, and 2023.
References
Related links
Official site
Service industries
Basque companies
Maintenance
Aerospace companies
Automotive industry | Sisteplant | [
"Engineering"
] | 601 | [
"Maintenance",
"Mechanical engineering"
] |
61,338,715 | https://en.wikipedia.org/wiki/International%20Organization%20for%20Plant%20Information | The International Organization for Plant Information (IOPI) is an international organization founded on September 20, 1991. It runs a series of collaborative international projects aimed at establishing databases of plant classification information and is a committee of the International Union of Biological Sciences.
The Global Plant Checklist was its first objective is to provide a list of all plants by merging data from existing sources. This required development of data standards as well as international co-operation, starting in 1993.
Later aims included the Species Plantarum Project to record taxonomic information about all the vascular plants in the world.
Its dataset was later incorporated into the Catalogue of Life.
References
Organizations established in 1991
Plant taxonomy | International Organization for Plant Information | [
"Biology"
] | 134 | [
"Plant taxonomy",
"Plants"
] |
61,338,800 | https://en.wikipedia.org/wiki/JCO%20Clinical%20Cancer%20Informatics | JCO Clinical Cancer Informatics is an online peer-reviewed medical journal of oncology and medical informatics published by Lippincott Williams & Wilkins. The journal was established in 2017 and the editor-in-chief is Jeremy L. Warner (Brown University). Articles are published upon acceptance and after 12 months become freely available. All ASCO special articles (e.g. clinical guidelines and policy statements), editorials, comments and controversies articles, and correspondence are freely available immediately upon publication.
Abstracting and indexing
This journal is abstracted and indexed in:
Emerging Sources Citation Index
Index Medicus/MEDLINE/PubMed
Scopus
See also
Journal of Clinical Oncology
Journal of Oncology Practice
JCO Global Oncology
References
External links
Oncology journals
Biomedical informatics journals
Delayed open access journals
English-language journals
Academic journals established in 2017
Continuous journals
Hybrid open access journals
Lippincott Williams & Wilkins academic journals | JCO Clinical Cancer Informatics | [
"Biology"
] | 185 | [
"Bioinformatics",
"Biomedical informatics journals"
] |
61,340,431 | https://en.wikipedia.org/wiki/Lunar%20resources | The Moon bears substantial natural resources which could be exploited in the future. Potential lunar resources may encompass processable materials such as volatiles and minerals, along with geologic structures such as lava tubes that, together, might enable lunar habitation. The use of resources on the Moon may provide a means of reducing the cost and risk of lunar exploration and beyond.
Insights about lunar resources gained from orbit and sample-return missions have greatly enhanced the understanding of the potential for in situ resource utilization (ISRU) at the Moon, but that knowledge is not yet sufficient to fully justify the commitment of large financial resources to implement an ISRU-based campaign. The determination of resource availability will drive the selection of sites for human settlement.
Overview
Lunar materials could facilitate continued exploration of the Moon, facilitate scientific and economic activity in the vicinity of both Earth and Moon (so-called cislunar space), or they could be imported to the Earth's surface where they would contribute directly to the global economy. Regolith (lunar soil) is the easiest product to obtain; it can provide radiation and micrometeoroid protection as well as construction and paving material by melting. Oxygen from lunar regolith oxides can be a source for metabolic oxygen and rocket propellant oxidizer. Water ice can provide water for radiation shielding, life-support, oxygen and rocket propellant feedstock. Volatiles from permanently shadowed craters may provide methane (), ammonia (), carbon dioxide () and carbon monoxide (CO). Metals and other elements for local industry may be obtained from the various minerals found in regolith.
The Moon is known to be poor in carbon and nitrogen, and rich in metals and in atomic oxygen, but their distribution and concentrations are still unknown. Further lunar exploration will reveal additional concentrations of economically useful materials, and whether or not these will be economically exploitable will depend on the value placed on them and on the energy and infrastructure available to support their extraction. For in situ resource utilization (ISRU) to be applied successfully on the Moon, landing site selection is imperative, as well as identifying suitable surface operations and technologies.
Scouting from lunar orbit by a few space agencies is ongoing, and landers and rovers are scouting resources and concentrations in situ (see: List of missions to the Moon).
Resources
Solar power, oxygen, and metals are abundant resources on the Moon. Elements known to be present on the lunar surface include, among others, hydrogen (H), oxygen (O), silicon (Si), iron (Fe), magnesium (Mg), calcium (Ca), aluminium (Al), manganese (Mn) and titanium (Ti). Among the more abundant are oxygen, iron and silicon. The atomic oxygen content in the regolith is estimated at 45% by weight.
Studies from Apollo 17's Lunar Atmospheric Composition Experiment (LACE) show that the lunar exosphere contains trace amounts of hydrogen (H2), helium (He), argon (Ar), and possibly ammonia (NH3), carbon dioxide (CO2), and methane (CH4). Several processes can explain the presence of trace gases on the Moon: high energy photons or solar winds reacting with materials on the lunar surface, evaporation of lunar regolith, material deposits from comets and meteoroids, and out-gassing from inside the Moon. However, these are trace gases in very low concentration. The total mass of the Moon's exosphere is roughly with a surface pressure of 3×10−15 bar (2×10−12 torr). Trace gas amounts are unlikely to be useful for in situ resource utilization.
Solar power
Daylight on the Moon lasts approximately two weeks, followed by approximately two weeks of night, while both lunar poles are illuminated almost constantly. The lunar south pole features a region with crater rims exposed to near constant solar illumination, yet the interior of the craters are permanently shaded from sunlight.
Solar cells could be fabricated directly on the lunar soil by a medium-size (~200 kg) rover with the capabilities for heating the regolith, evaporation of the appropriate semiconductor materials for the solar cell structure directly on the regolith substrate, and deposition of metallic contacts and interconnects to finish off a complete solar cell array directly on the ground. This process however requires the importation of potassium fluoride from Earth to purify the necessary materials from regolith.
Nuclear power
The Kilopower nuclear fission system is being developed for reliable electric power generation that could enable long-duration crewed bases on the Moon, Mars and destinations beyond. This system is ideal for locations on the Moon and Mars where power generation from sunlight is intermittent. Uranium and thorium are both present on the Moon, but due to the high energy density of nuclear fuels, it could be more economical to import suitable fuels from Earth rather than producing them in situ.
Radioisotope thermoelectric generators (RTGs) are another form of nuclear power which use the natural decay of radioisotopes rather than their induced fission. They have been used in space—including on the Moon—for decades. The usual process is to source the suitable substances from Earth, but plutonium-238 or strontium-90 could be produced on the Moon if feedstocks such as spent nuclear fuel are present (either delivered from Earth for processing or produced by local fission reactors). RTGs could be used to deliver power independent of available sunlight, for both lunar and non-lunar applications. RTGs do contain harmful toxic and radioactive materials, which leads to concerns of unintentional distribution of those materials in the event of an accident. Protests by the general public therefore often focus on the phaseout of RTGs (instead recommending alternative power sources), due to an overestimation of the dangers of radiation.
A more theoretical lunar resource are potential fuels for nuclear fusion. Helium-3 has received particular media attention as its abundance in lunar regolith is higher than on Earth. However, thus far nuclear fusion has not been employed by humans in a controlled fashion releasing net usable energy (devices like the fusor are net energy consumers while the hydrogen bomb is not a controlled fusion reaction). Furthermore, while helium-3 is required for one possible pathway of nuclear fusion, others instead rely on nuclides which are more easily obtained on Earth, such as tritium, lithium or deuterium.
Oxygen
The elemental oxygen content in the regolith is estimated at 45% by weight. Oxygen is often found in iron-rich lunar minerals and glasses as iron oxide. Such lunar minerals and glass include ilmenite, olivine, pyroxene, impact glass, and volcanic glass. Various isotopes of oxygen are present on the Moon in the form of 16O, 17O, and 18O.
At least twenty different possible processes for extracting oxygen from lunar regolith have been described, and all require high energy input: between 2–4 megawatt-years of energy (i.e. ) to produce 1,000 tons of oxygen. While oxygen extraction from metal oxides also produces useful metals, using water as a feedstock does not. One possible method of producing oxygen from lunar soil requires two steps. The first step involves the reduction of iron oxide with hydrogen gas (H2) to form elemental iron (Fe) and water (H2O). Water can then be electrolyzed to produce oxygen which can be liquified at low temperatures and stored. The amount of oxygen released depends on the iron oxide abundance in lunar minerals and glass. Oxygen production from lunar soil is a relatively fast process, occurring in a few tens of minutes. In contrast, oxygen extraction from lunar glass requires several hours.
Water
Cumulative evidence from several orbiters strongly indicate that water ice is present on the surface at the Moon poles, but mostly on the south pole region. However, results from these datasets are not always correlated. It has been determined that the cumulative area of permanently shadowed lunar surface is 13,361 km2 in the northern hemisphere and 17,698 km2 in the southern hemisphere, giving a total area of 31,059 km2. The extent to which any or all of these permanently shadowed areas contain water ice and other volatiles is not currently known, so more data is needed about lunar ice deposits, its distribution, concentration, quantity, disposition, depth, geotechnical properties and any other characteristics necessary to design and develop extraction and processing systems. The intentional impact of the LCROSS orbiter into the crater Cabeus was monitored to analyze the resulting debris plume, and it was concluded that the water ice must be in the form of small (< ~10 cm), discrete pieces of ice distributed throughout the regolith, or as a thin coating on ice grains. This, coupled with monostatic radar observations, suggest that the water ice present in the permanently shadowed regions of lunar polar craters is unlikely to be present in the form of thick, pure ice deposits.
Water may have been delivered to the Moon over geological timescales by the regular bombardment of water-bearing comets, asteroids and meteoroids or continuously produced in situ by the hydrogen ions (protons) of the solar wind impacting oxygen-bearing minerals.
The lunar south pole features a region with crater rims exposed to near constant solar illumination, where the craters' interior are permanently shaded from sunlight, allowing for natural trapping and collection of water ice that could be mined in the future.
Water molecules () can be broken down to form molecular hydrogen () and molecular oxygen () to be used as rocket bi-propellant or produce compounds for metallurgic and chemical production processes. Just the production of propellant, was estimated by a joint panel of industry, government and academic experts, identified a near-term annual demand of 450 metric tons of lunar-derived propellant equating to 2,450 metric tons of processed lunar water, generating US$2.4 billion of revenue annually.
Hydrogen
Slopes on the lunar surface that face the Moon's poles show a higher concentration of hydrogen. This is because pole facing slopes have less exposure to sunlight that will cause vaporization of hydrogen. Additionally, slopes closer to the Moon's poles show a higher concentration of hydrogen of about 45 ppmw. There are various theories to explain the presence of hydrogen on the Moon. Water, which contains hydrogen, could have been deposited on the Moon by comets and asteroids. Additionally, solar winds interacting with compounds on the lunar surface may have led to the formation of hydrogen-bearing compounds such as hydroxyl and water. The solar wind implants protons on the regolith, forming a protonated atom, which is a chemical compound of hydrogen (H). Although bound hydrogen is plentiful, questions remain about how much of it diffuses into the subsurface, escapes into space or diffuses into cold traps. Hydrogen would be needed for propellant production, and it has a multitude of industrial uses. For example, hydrogen can be used for the production of oxygen by hydrogen reduction of ilmenite.
Metals
Iron
Iron (Fe) is abundant in all mare basalts (~14–17% per weight) but is mostly locked into silicate minerals (i.e. pyroxene and olivine) and into the oxide mineral ilmenite in the lowlands. Extraction would be quite energy-demanding, but some prominent lunar magnetic anomalies are suspected as being due to surviving Fe-rich meteoritic debris. Only further exploration in situ will determine whether or not this interpretation is correct, and how exploitable such meteoritic debris may be. Hematite, a mineral composed of ferric oxide (Fe2O3), has been found on the Moon. This mineral is a product of a reaction between iron, oxygen, and liquid water. Oxygen from the Earth's atmosphere may cause this reaction as indicated by there being more hematite on the side of the Moon facing the Earth.
Free iron also exists in the regolith (0.5% by weight) naturally alloyed with nickel and cobalt and it can easily be extracted by simple magnets after grinding. This iron dust can be processed to make parts using powder metallurgy techniques, such as additive manufacturing, 3D printing, selective laser sintering (SLS), selective laser melting (SLM), and electron beam melting (EBM).
Titanium
Titanium (Ti) can be alloyed with iron, aluminium, vanadium, and molybdenum, among other elements, to produce strong, lightweight alloys for aerospace use. It exists almost exclusively in the mineral ilmenite (FeTiO3) in the range of 5–8% by weight. Ilmenite minerals also trap hydrogen (protons) from the solar wind, so that processing of ilmenite will also produce hydrogen, a valuable element on the Moon. The vast flood basalts on the northwest nearside (Mare Tranquillitatis) possess some of the highest titanium contents on the Moon, with 10 times as much titanium as rocks on Earth.
Aluminum
Aluminum (Al) is found with a concentration in the range of 10–18% by weight, present in the mineral anorthite (), the calcium endmember of the plagioclase feldspar mineral series. Aluminum is a good electrical conductor, and atomized aluminum powder also makes a good solid rocket fuel when burned with oxygen. Extraction of aluminum would also require breaking down plagioclase (CaAl2Si2O8).
Silicon
Silicon (Si) is an abundant metalloid in all lunar material, with a concentration of about 20% by weight. It is of enormous importance to produce solar panel arrays for the conversion of sunlight into electricity, as well as glass, fiber glass, and a variety of useful ceramics. Achieving a very high purity for use as semi-conductor would be challenging, especially in the lunar environment. Converting silica into silicon is an energy-intensive process. On earth this is usually done via carbothermic reduction, a process that requires carbon, an element in comparatively short supply on the moon.
Calcium
Calcium (Ca) is the fourth most abundant element in the lunar highlands, present in anorthite minerals (formula ). Calcium oxides and calcium silicates are not only useful for ceramics, but pure calcium metal is flexible and an excellent electrical conductor in the absence of oxygen. Anorthite is rare on the Earth but abundant on the Moon.
Calcium can also be used to fabricate silicon-based solar cells, requiring lunar silicon, iron, titanium oxide, calcium and aluminum.
When combined with water, lime (calcium oxide) produces significant amounts of heat. hydrated lime (calcium hydroxide) meanwhile absorbs carbon dioxide which can be used as a (non-replenishing) filter. The resulting material, calcium carbonate is commonly used as a building material on earth.
Magnesium
Magnesium (Mg) is present in magmas and in the lunar minerals pyroxene and olivine, so it is suspected that magnesium is more abundant in the lower lunar crust. Magnesium has multiple uses as alloys for aerospace, automotive and electronics.
Thorium
The Compton–Belkovich Thorium Anomaly is a volcanic complex on the far side of the Moon. It was found by a gamma-ray spectrometer in 1998 and is an area of concentrated thorium, a 'fertile' element.
Rare-earth elements
Rare-earth elements are used to manufacture everything from electric or hybrid vehicles, wind turbines, electronic devices and clean energy technologies. Despite their name, rare-earth elements are – with the exception of promethium – relatively plentiful in Earth's crust. However, because of their geochemical properties, rare-earth elements are typically dispersed and not often found concentrated in rare-earth minerals; as a result, economically exploitable ore deposits are less common. Major reserves exist in China, California, India, Brazil, Australia, South Africa, and Malaysia, but China accounts for over 95% of the world's production of rare-earths. (See: Rare earth industry in China.)
Although current evidence suggests rare-earth elements are less abundant on the Moon than on Earth, NASA views the mining of rare-earth minerals as a viable lunar resource because they exhibit a wide range of industrially important optical, electrical, magnetic and catalytic properties. KREEP are parts of the lunar surface richer in potassium (the "K" stands for the element symbol) rare earth elements and Phosphorus. Potassium and phosphorus are two of the three essential plant nutrients, the third being fixed nitrogen (hence NPK fertilizer) any agricultural activity on the moon would need a supply of those elements — whether sourced in situ or brought from elsewhere e.g. earth.
Helium-3
By one estimate, the solar wind has deposited more than 1 million tons of helium-3 (3He) on the Moon's surface. Materials on the Moon's surface contain helium-3 at concentrations estimated between 1.4 and 15 parts per billion (ppb) in sunlit areas, and may contain concentrations as much as 50 ppb in permanently shadowed regions. For comparison, helium-3 in the Earth's atmosphere occurs at 7.2 parts per trillion (ppt).
A number of people since 1986 have proposed to exploit the lunar regolith and use the helium-3 for nuclear fusion. Although as of 2020, functioning experimental nuclear fusion reactors have existed for decades – none of them has yet provided electricity commercially. Because of the low concentrations of helium-3, any mining equipment would need to process large amounts of regolith. By one estimate, over 150 tons of regolith must be processed to obtain of helium 3. China has begun the Chinese Lunar Exploration Program for exploring the Moon and is investigating the prospect of lunar mining, specifically looking for the isotope helium-3 for use as an energy source on Earth. Not all authors think the extraterrestrial extraction of helium-3 is feasible, and even if it was possible to extract helium-3 from the Moon, no useful fusion reactor design has produced more fusion power output than the electrical power input, defeating the purpose. However, on 13 December 2022, the United States Department of Energy announced that "...Monday, December 5, 2022, was a historic day in science thanks to the incredible people at Livermore Lab and the National Ignition Facility" and that the National Ignition Facility, "conducted the first controlled fusion experiment in history to reach this milestone, also known as scientific energy breakeven, meaning it produced more energy from fusion than the laser energy used to drive it." The downside remains that Helium-3 is a limited lunar resource that can be exhausted once mined.
Carbon and nitrogen
Carbon (C) would be required for the production of lunar steel, but it is present in lunar regolith in trace amounts (82 ppm), contributed by the solar wind and micrometeorite impacts. Due to extremely low temperatures, permanently shadowed regions of the Moon's poles have cold traps which possibly contain solid carbon dioxide. The presence of carbon is mostly due to solar wind carbon implanted in bulk regolith. Carbon is present in carbon-bearing ices at the lunar poles in concentrations as high as 20% by weight. However, most carbon-bearing ices have a 0–3% by weight carbon concentration. Carbon-bearing compounds that could exist include carbon monoxide (CO), ethylene (C2H4), carbon dioxide (CO2), methanol (CH3OH), methane (CH4), carbonyl sulfide (OCS), hydrogen cyanide (HCN), and toluene (C7H8). These compounds form roughly 5000 ppm of elemental carbon in soil samples brought back from the Moon. These polar regions contain C, H, and O which can serve as propellant sources for methalox spacecraft.
Nitrogen (N) was measured from soil samples brought back to Earth, and it exists as trace amounts at less than 5 ppm. It was found as isotopes 14N, 15N, and 16N. As much as 87% of nitrogen found in lunar regolith may come from non-solar sources (not from the Sun) or from other planets. Comets and meteorites contribute less than ~10% of nitrogen from non-solar sources. Carbon and fixed nitrogen would be required for farming activities within a sealed biosphere.
Changesite–(Y)
Regolith for construction
Developing a lunar economy will require a significant amount of infrastructure on the lunar surface, which will rely heavily on In situ resource utilization (ISRU) technologies to develop. One of the primary requirements will be to provide construction materials to build habitats, storage bins, landing pads, roads and other infrastructure. Unprocessed lunar soil, also called regolith, may be turned into usable structural components, through techniques such as sintering, hot-pressing, liquification, the cast basalt method, and 3D printing. Glass and glass fiber are straightforward to process on the Moon, and it was found regolith material strengths can be improved by using glass fiber, such as 70% basalt glass fiber and 30% PETG mixture. Successful tests have been performed on Earth using some lunar regolith simulants, including MLS-1 and MLS-2.
The lunar soil, although it poses a problem for any mechanical moving parts, can be mixed with carbon nanotubes and epoxies in the construction of telescope mirrors up to 50 meters in diameter. Several craters near the poles are permanently dark and cold, a favorable environment for infrared telescopes.
Some proposals suggest to build a lunar base on the surface using modules brought from Earth, and covering them with lunar soil. The lunar soil is composed of a blend of silica and iron-containing compounds that may be fused into a glass-like solid using microwave radiation.
The European Space Agency working in 2013 with an independent architectural firm, tested a 3D-printed structure that could be constructed of lunar regolith for use as a Moon base. 3D-printed lunar soil would provide both "radiation and temperature insulation. Inside, a lightweight pressurized inflatable with the same dome shape would be the living environment for the first human Moon settlers."
In early 2014, NASA funded a small study at the University of Southern California to further develop the Contour Crafting 3D printing technique. Potential applications of this technology include constructing lunar structures of a material that could consist of up to 90-percent lunar material with only ten percent of the material requiring transport from Earth. NASA is also looking at a different technique that would involve the sintering of lunar dust using low-power (1500 watt) microwave radiation. The lunar material would be bound by heating to , somewhat below the melting point, in order to fuse the nanoparticle dust into a solid block that is ceramic-like, and would not require the transport of a binder material from Earth.
Mining
There are several models and proposals on how to exploit lunar resources, yet few of them consider sustainability. Long-term planning is required to achieve sustainability and ensure that future generations are not faced with a barren lunar wasteland by wanton practices. To be truly sustainable, lunar mining would have to adopt processes that do not use nor yield toxic material, and would minimize waste through recycling loops.
Scouting
Numerous orbiters have mapped the lunar surface composition, including Clementine, Lunar Reconnaissance Orbiter (LRO), Lunar Crater Observation and Sensing Satellite (LCROSS), Artemis orbiter, SELENE, Lunar Prospector, Chandrayaan, and Chang'e, to name a few, while the Soviet Luna programme and Apollo Program brought lunar samples back to Earth for extensive analyses. As of 2019, a new "Moon race" is ongoing that features prospecting for lunar resources to support crewed bases.
In the 21st century, China's Chinese Lunar Exploration Program, is executing a step-wise approach to incremental technology development and scouting for resources for a crewed base, projected for the 2030s, according to Chinese state media Xinhua News Agency. India's Chandrayaan programme is focused in understanding the lunar water cycle first, and on mapping mineral location and concentrations from orbit and in situ. Russia's Luna-Glob programme is planning and developing a series of landers, rovers and orbiters for prospecting and science exploration, and to eventually employ in situ resource utilization (ISRU) methods with the intent to construct and operate their own crewed lunar base in the 2030s.
The US has been studying the Moon for decades and in 2019 it started to implement the Commercial Lunar Payload Services (CLPS) program to support the crewed Artemis program, both aimed at scouting and exploiting lunar resources to facilitate a long-term crewed base on the Moon, and depending on the lessons learned, then move on to a crewed mission to Mars. NASA's lunar Resource Prospector rover was planned to prospect for resources on a polar region of the Moon, and it was to be launched in 2022. The mission concept was in its pre-formulation stage, and a prototype rover was being tested when it was cancelled in April 2018. Its science instruments will be flown instead on several commercial lander missions contracted by NASA's CLPS program, that aims to focus on testing various lunar ISRU processes by landing several payloads on multiple commercial robotic landers and rovers. The first payload contracts were awarded on February 21, 2019, and will fly on separate missions. The CLPS will inform and support NASA's Artemis program, leading to a crewed lunar outpost for extended stays.
A European non-profit organization has called for a global synergistic collaboration between all space agencies and nations instead of a "Moon race"; this proposed collaborative concept is called the Moon Village. Moon Village seeks to create a vision where both international cooperation and the commercialization of space can thrive.
Some early private companies like Shackleton Energy Company, Deep Space Industries, Planetoid Mines, Golden Spike Company, Planetary Resources, Astrobotic Technology, and Moon Express are planning private commercial scouting and mining ventures on the Moon.
In 2024, an American startup called Interlune announced plans to mine Helium on the Moon for export back on Earth. The first mission plans to use NASA's Commercial Lunar Payload Services program to arrive on the Moon.
Extraction methods
The extensive lunar maria are composed of basaltic lava flows. Their mineralogy is dominated by a combination of five minerals: anorthites (CaAl2Si2O8), orthopyroxenes (), clinopyroxenes (), olivines (), and ilmenite (), all abundant on the Moon. It has been proposed that smelters could process the basaltic lava to break it down into pure calcium, aluminium, oxygen, iron, titanium, magnesium, and silica glass. The European Space Agency has awarded funding to Metalysis in 2020 to further develop the FFC Cambridge process to extract titanium from regolith while generating oxygen as a byproduct. Raw lunar anorthite could also be used for making fiberglass and other ceramic products. Another proposal envisions the use of fluorine brought from Earth as potassium fluoride to separate the raw materials from the lunar rocks.
Legal status of mining
Although Luna landers scattered pennants of the Soviet Union on the Moon, and United States flags were symbolically planted at their landing sites by the Apollo astronauts, no nation claims ownership of any part of the Moon's surface, and the international legal status of mining space resources is unclear and controversial.
The five treaties and agreements of international space law cover "non-appropriation of outer space by any one country, arms control, the freedom of exploration, liability for damage caused by space objects, the safety and rescue of spacecraft and astronauts, the prevention of harmful interference with space activities and the environment, the notification and registration of space activities, scientific investigation and the exploitation of natural resources in outer space and the settlement of disputes."
Russia, China, and the United States are party to the 1967 Outer Space Treaty (OST), which is the most widely adopted treaty, with 104 parties. The OST treaty offers imprecise guidelines to newer space activities such as lunar and asteroid mining, and it therefore remains under contention whether the extraction of resources falls within the prohibitive language of appropriation or whether the use encompasses the commercial use and exploitation. Although its applicability on exploiting natural resources remains in contention, leading experts generally agree with the position issued in 2015 by the International Institute of Space Law (ISSL) stating that, "in view of the absence of a clear prohibition of the taking of resources in the Outer Space Treaty, one can conclude that the use of space resources is permitted."
The 1979 Moon Treaty is a proposed framework of laws to develop a regime of detailed rules and procedures for orderly resource exploitation. This treaty would regulate exploitation of resources if it is "governed by an international regime" of rules (Article 11.5), but there has been no consensus and the precise rules for commercial mining have not been established. The Moon Treaty was ratified by very few nations, and thus suggested to have little to no relevancy in international law. The last attempt to define acceptable detailed rules for exploitation, ended in June 2018, after S. Neil Hosenball, who was the NASA General Counsel and chief US negotiator for the Moon Treaty, decided that negotiation of the mining rules in the Moon Treaty should be delayed until the feasibility of exploitation of lunar resources had been established.
Seeking clearer regulatory guidelines, private companies in the US prompted the US government, and legalized space mining in 2015 by introducing the US Commercial Space Launch Competitiveness Act of 2015. Similar national legislations legalizing extraterrestrial appropriation of resources are now being replicated by other nations, including Luxembourg, Japan, China, India and Russia. This has created an international legal controversy on mining rights for profit. A legal expert stated in 2011 that the international issues "would probably be settled during the normal course of space exploration." In April 2020, U.S. President Donald Trump signed an executive order to support moon mining.
See also
In situ resource utilization
References
Mining in space
Natural resources
Exploration of the Moon
Space colonization
Industry in space
Self-sustainability
Space manufacturing | Lunar resources | [
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