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Polymers with thermally induced shape-memory effect are those polymers that respond to external stimuli and because of this have the ability to change their shape. The thermally induced shape-memory effect results from a combination of proper processing and programming of the system.
This effect can be observed in polymers with very different chemical composition, which opens a great possibility of applications. | 7 | Physical Chemistry |
The ciliate, dasycladacean and Hexamita nuclear code (translation table 6) is a genetic code used by certain ciliate, dasycladacean and Hexamita species.
The ciliate macronuclear code has not been determined completely. The codon UAA is known to code for Gln only in the Oxytrichidae. | 1 | Biochemistry |
Just like the many uses of plasma, there are several means for its generation. However, one principle is common to all of them: there must be energy input to produce and sustain it. For this case, plasma is generated when an electric current is applied across a dielectric gas or fluid (an electrically non-conducting material) as can be seen in the adjacent image, which shows a discharge tube as a simple example (DC used for simplicity).
The potential difference and subsequent electric field pull the bound electrons (negative) toward the anode (positive electrode) while the cathode (negative electrode) pulls the nucleus. As the voltage increases, the current stresses the material (by electric polarization) beyond its dielectric limit (termed strength) into a stage of electrical breakdown, marked by an electric spark, where the material transforms from being an insulator into a conductor (as it becomes increasingly ionized). The underlying process is the Townsend avalanche, where collisions between electrons and neutral gas atoms create more ions and electrons (as can be seen in the figure on the right). The first impact of an electron on an atom results in one ion and two electrons. Therefore, the number of charged particles increases rapidly (in the millions) only "after about 20 successive sets of collisions", mainly due to a small mean free path (average distance travelled between collisions). | 7 | Physical Chemistry |
Tardigrade specific proteins are types of intrinsically disordered proteins specific to tardigrades. These proteins help tardigrades survive desiccation, one of the adaptations which contribute to tardigrade's extremotolerant nature. Tardigrade specific proteins are strongly influenced by their environment, leading to adaptive malleability across a variety of extreme abiotic environments. | 1 | Biochemistry |
As an ACE inhibitor, moexipril causes a decrease in ACE. This blocks the conversion of angiotensin I to angiotensin II. Blockage of angiotensin II limits hypertension within the vasculature. Additionally, moexipril has been found to possess cardioprotective properties. Rats given moexipril one week prior to induction of myocardial infarction, displayed decreased infarct size. The cardioprotective effects of ACE inhibitors are mediated through a combination of angiotensin II inhibition and bradykinin proliferation. Increased levels of bradykinin stimulate in the production of prostaglandin E and nitric oxide, which cause vasodilation and continue to exert antiproliferative effects. Inhibition of angiotensin II by moexipril decreases remodeling effects on the cardiovascular system. Indirectly, angiotensin II stimulates of the production of endothelin 1 and 3 (ET1, ET3) and the transforming growth factor beta-1 (TGF-β1), all of which have tissue proliferative effects that are blocked by the actions of moexipril. The antiproliferative effects of moexipril have also been demonstrated by in vitro studies where moexipril inhibits the estrogen-stimulated growth of neonatal cardiac fibroblasts in rats. Other ACE inhibitors have also been found to produce these actions, as well. | 4 | Stereochemistry |
N-heterocyclic carbene (NHC) supported Cu complexes catalyze carboxylation of organoboronic esters. The catalyst forms in situ from CuCl, an NHC ligand, and KOBu. Copper tert-butoxide can transmetallate with the organoboronic ester to generate the Cu-C bond, which intermediate can insert into CO smoothly to get the respective carboxylate. Salt metathesis with KOBu releases product and regenerates catalyst (Scheme 2).
Apart from transmetallation, there are other approaches forming Cu-C bond. C-H functionalization is a straightforward and atom economic method. Base can help deprotonate acidic C-H protons and form Cu-C bond. [(Phenanthroline)Cu(PR)] catalyst effect C-H carboxylation on terminal alkynes together with CsCO. NHC-Cu-H species to deprotonate acidic proton to effect carboxylation of terminal alkynes. Cu-H species were generated from Cu-F and organosilanes. The carboxylate product was trapped by silyl fluoride to get silyl ether. For non-acidic C-H bonds, directed metalation with BuAl(TMP)Li is adopted followed by transmetallation with copper to get Cu-C bond. Allylic C-H bonds and phenyl C-H bonds got carboxylated with this approach by Hou and co-workers:
Carbometallation to alkynes and allenes using organozinc and organoaluminum reagents followed by transmetallation to copper is also a strategy to initiate carboxylation. Trimethylaluminium is able to insert into unbiased aliphatic internal alkynes with syn fashion directed by ether directing group. Vinyl copper complexes are formed by transmetallation and carboxylation is realized with a similar pathway giving tetrasubstituted aliphatic vinyl carboxylic acids. In this case, regioslectivity is controlled by the favor of six-membered aluminum ring formation. Furthermore, carboxylation can be achieved on ynamides and allenamides using less reactive dimethyl zinc via similar approach. | 0 | Organic Chemistry |
The concentration of HCFC-141b in the atmosphere grew to near 25 parts per trillion by year 2016. It has an ozone depletion potential (ODP) of 0.12. This is low compared to the ODP=1 of trichlorofluoromethane (CFC-11, R-11), which also grew about ten times more abundant in the atmosphere prior to introduction of HFC-141b and subsequent adoption of the Montreal Protocol.
HFC-141b is also a minor but potent greenhouse gas. It has an estimated lifetime of about 10 years and a 100-year global warming potential ranging 725 to 2500. This compares to the GWP=1 of carbon dioxide, which had a much greater atmospheric concentration near 400 parts per million in year 2020. | 2 | Environmental Chemistry |
The temperature-based phase behavior of ELPs can be utilized to produce stiff networks that may be compatible with cellular regeneration applications. At high concentrations (weight percent exceeding 15%), the ELP transition from a linear state to a spherical aggregate state above the transition temperature is arrested, leading to the formation of brittle gels. These otherwise brittle networks can then be modified chemically, via oxidative coupling, to yield hydrogels which can sustain high levels of mechanical stress and strain. Also, the modified gel networks contain pores, through which important cell-sustaining compounds can easily be delivered. Such strong hydrogels, when bathed in minimal cell media, have been found to promote the growth of human mesencyhmal stem cell populations. The ability of these arrested ELP networks to promote cell growth may prove indispensable in the production of tissue scaffolds that promote cartilage production, for example. Such an intervention may prove useful in the treatment of bone disease and rheumatoid arthritis. | 7 | Physical Chemistry |
The concept of microstructure is observable in macrostructural features in commonplace objects. Galvanized steel, such as the casing of a lamp post or road divider, exhibits a non-uniformly colored patchwork of interlocking polygons of different shades of grey or silver. Each polygon is a single crystal of zinc adhering to the surface of the steel beneath. Zinc and lead are two common metals which form large crystals (grains) visible to the naked eye. The atoms in each grain are organized into one of seven 3d stacking arrangements or crystal lattices (cubic, tetrahedral, hexagonal, monoclinic, triclinic, rhombohedral and orthorhombic). The direction of alignment of the matrices differ between adjacent crystals, leading to variance in the reflectivity of each presented face of the interlocked grains on the galvanized surface. The average grain size can be controlled by processing conditions and composition, and most alloys consist of much smaller grains not visible to the naked eye. This is to increase the strength of the material (see Hall-Petch Strengthening). | 8 | Metallurgy |
In order to terminate the integrated stress response, dephosphorylation of eIF2α is required. The protein phosphatase 1 complex (PP1) aids in the dephosphorylation of eIF2α. This complex contains a PP1 catalytic subunit as well as two regulatory subunits. This complex is negatively regulated by two proteins: growth arrest and DNA damage‐inducible protein (GADD34), also known as PPP1R15A, or constitutive repressor of eIF2α phosphorylation (CReP), also known as PPP1R15B. CReP acts to keep levels of eIF2α phosphorylation low in cells under normal conditions. GADD34 is produced in response to ATF4 and works to increase dephosphorylation of eIF2α. The dephosphorylation of eIF2α results in the return of normal protein synthesis and cellular function. However, dephosphorylation of eIF2α can also facilitate the production of death-inducing proteins in cases where the cell is so severely damaged that normal functioning cannot be restored. | 1 | Biochemistry |
Kaminsky's discovery of well-defined, high activity homogeneous catalysts led to many innovations in the design of novel cyclopentadienyl ligands. These innovations include ansa-metallocenes, C-symmetric fluorenyl-Cp ligands, constrained geometry catalysts, Some Kaminsky-inspired catalysts use of chiral metallocenes that have bridged cyclopentadienyl rings. These innovations made possible highly stereoselective (or stereoregular) polymerization of α-olefins, some of which have been commercialized. | 7 | Physical Chemistry |
Spin states relate to chemical and biochemical reaction mechanisms because bonds can be formed only between two electrons of opposite spin (Hund's rules). Sometimes when a bond is broken in a particular manner, for example, when struck by photons, each electron in the bond relocates to each respective molecule, and a radical-pair is formed. Furthermore, the spin of each electron previously involved in the bond is conserved, which means that the radical-pair now formed is a singlet (each electron has opposite spin, as in the origin bond). As such, the reverse reaction, i.e. the reforming of a bond, called recombination, readily occurs. The radical-pair mechanism explains how external magnetic fields can prevent radical-pair recombination with Zeeman interactions, the interaction between spin and an external magnetic field, and shows how a higher occurrence of the triplet state accelerates radical reactions because triplets can proceed only to products, and singlets are in equilibrium with the reactants as well as with the products.
Zeeman interactions can “flip” only one of the radicals electrons spin if the radical-pair is anisotropic, thereby converting singlet radical-pairs to triplets.
The Zeeman interaction is an interaction between spin and external magnetic field, and is given by the equation
where is the energy of the Zeeman interaction, is the Larmor frequency, is the external magnetic field, is the Bohr magneton, is Planck's constant, and is the g-factor of a free electron, 2.002319, which is slightly different in different radicals.
It is common to see the Zeeman interaction formulated in other ways. | 7 | Physical Chemistry |
In the early 1990s, technical personnel from the then Union Miniére worked with MIM Holdings personnel to develop an ISASMELT-based process to treat scrap materials and residues containing copper and lead. Union Miniére operated a smelter at Hoboken, near Antwerpen in Belgium, that specialised in recycling scrap non-ferrous materials. The test work program was undertaken using an ISASMELT test rig at MIM Holdings’ lead refinery, Britannia Refined Metals, at Northfleet in the United Kingdom.
A demonstration plant was designed by MIM Holdings personnel and operated for several months at the Hoboken smelter site. The new smelter was commissioned in the final quarter of 1997 and in 2007 was treating up to 300,000 t/y of secondary materials. The installation of the ISASMELT furnace replaced a roasting plant, a sinter plant, 1 of two sulfuric acid plants, a copper blast furnace and four Hoboken converters. It substantially reduced operating costs at the Hoboken smelter.
Umicore's Hoboken plant uses a two-step process in a single furnace. The first step involves the oxidation of the feed to form a copper matte and a lead-rich slag. The slag is then tapped and the remaining copper matte is then converted to blister copper. The lead-rich slag is subsequently reduced in a blast furnace to produce lead metal, while the copper is refined and the contained precious metals recovered. | 8 | Metallurgy |
The effect is named after the German physicist Johannes Stark, who discovered it in 1913. It was independently discovered in the same year by the Italian physicist Antonino Lo Surdo, and in Italy it is thus sometimes called the Stark–Lo Surdo effect. The discovery of this effect contributed importantly to the development of quantum theory and Stark was awarded with the Nobel Prize in Physics in the year 1919.
Inspired by the magnetic Zeeman effect, and especially by Hendrik Lorentz's explanation of it, Woldemar Voigt performed classical mechanical calculations of quasi-elastically bound electrons in an electric field. By using experimental indices of refraction he gave an estimate of the Stark splittings. This estimate was a few orders of magnitude too low. Not deterred by this prediction, Stark undertook measurements on excited states of the hydrogen atom and succeeded in observing splittings.
By the use of the Bohr–Sommerfeld ("old") quantum theory, Paul Epstein and Karl Schwarzschild were independently able to derive equations for the linear and quadratic Stark effect in hydrogen. Four years later, Hendrik Kramers derived formulas for intensities of spectral transitions. Kramers also included the effect of fine structure, with corrections for relativistic kinetic energy and coupling between electron spin and orbital motion. The first quantum mechanical treatment (in the framework of Werner Heisenberg's matrix mechanics) was by Wolfgang Pauli. Erwin Schrödinger discussed at length the Stark effect in his third paper on quantum theory (in which he introduced his perturbation theory), once in the manner of the 1916 work of Epstein (but generalized from the old to the new quantum theory) and once by his (first-order) perturbation approach.
Finally, Epstein reconsidered the linear and quadratic Stark effect from the point of view of the new quantum theory. He derived equations for the line intensities which were a decided improvement over Kramers's results obtained by the old quantum theory.
While the first-order-perturbation (linear) Stark effect in hydrogen is in agreement with both the old Bohr–Sommerfeld model and the quantum-mechanical theory of the atom, higher-order corrections are not. Measurements of the Stark effect under high field strengths confirmed the correctness of the new quantum theory. | 7 | Physical Chemistry |
Synthetic analogues of the naturally occurring Fe–S clusters were first reported by Holm and coworkers. Treatment of iron salts with a mixture of thiolates and sulfide affords derivatives such as (EtN)FeS(SCHPh)]. | 7 | Physical Chemistry |
L-amino-acid alpha-ligase - L-ornithine N5 monooxygenase - lambda - Lamprin - Laser capture microdissection - latarcin - leucine zipper - leukemia - leukotriene-B4 20-monooxygenase - library - licodione synthase - ligase - linear epitope - linkage - linker protein - linoleate diol synthase - lipofectin - lipopolysaccharide kinase (Kdo/WaaP) family - lipopolysaccharide-transporting ATPase - lithocholate 6beta-hydroxylase - locus - LOD score - Long intergenic non-protein coding rna 1157 - lymphocyte - lysine—tRNA(Pyl) ligase - | 1 | Biochemistry |
The reaction steps are:
* hydrogenation of -glucose to -sorbitol, an organic reaction with nickel as a catalyst under high temperature and high pressure.
* Microbial oxidation or fermentation of sorbitol to -sorbose with acetobacter at pH 4-6 and 30 °C.
* protection of the 4 hydroxyl groups in sorbose by formation of the acetal with acetone and an acid to Diacetone-L-sorbose (2,3:4,6−Diisopropyliden−α−L−sorbose)
* Organic oxidation with potassium permanganate (to Diprogulic acid) followed by heating with water gives the 2-Keto-L-gulonic acid
* The final step is a ring-closing step or gamma lactonization with removal of water.
* Intermediate 5 can also be prepared directly from 3 with oxygen and platinum
The microbial oxidation of sorbitol to sorbose is important because it provides the correct stereochemistry. | 0 | Organic Chemistry |
In 2011, Khalifa, Al-Omran, and Mohammed reported on a monitored study of a 2-ton capacity air conditioner unit while exchanging out a silica gel wheel and a wheel made of activated carbon to determine if it would reduce the relative humidity in a small room in Baghdad when compared to the unit without the Cromer cycle added. They found that the "Cromer cycle can reduce the indoor relative humidity from 80% to about 60% using active carbon of 5 cm wheel thickness." | 7 | Physical Chemistry |
; General
* Aitchison, Leslie. 1960. A History of Metals. London: Macdonald & Evans Ltd.
* Bayley, Justine; Butcher, Sarnia. 2004. Roman Brooches in Britain: A Technological and Typological Study based on the Richborough Collection. London: The Society of Antiquaries of London.
* Craddock, Paul T. 1995. Early Metal Mining and Production. Edinburgh: Edinburgh University Press.
* Craddock, Paul T. 1999. Paradigms of Metallurgical Innovation in Prehistoric Europe in Hauptmann, A., Ernst, P., Rehren, T., Yalcin, U. (eds). The Beginnings of Metallurgy: Proceedings of the International Conference “The Beginnings of Metallurgy”, Bochum 1995. Hamburg
* Davies, O. Roman Mines in Europe 1935., Oxford University Press
* Hughes, M. J. 1980 The Analysis of Roman Tin and Pewter Ingots in Ody, W. A. (ed) Aspects of Early Metallurgy. Occasional Paper No 17. British Museum Occasional Papers.
* Shepard, Robert. 1993. Ancient Mining. London: Elsevier Applied Science.
* Sim, David. 1998. Beyond the Bloom: Bloom Refining and Iron Artifact Production in the Roman World. Ridge, Isabel (ed). BAR International Series 725. Oxford: Archaeopress.
* Tylecote, R.F. 1962. Metallurgy in Archaeology: A Prehistory of Metallurgy in the British Isles. London: Edward Arnold (Publishers) Ltd.
* Zwicker, U., Greiner, H., Hofmann, K-H., Reithinger, M. 1985. Smelting, Refining and Alloying of Copper and Copper Alloys in Crucible Furnaces During Prehistoric up to Roman Times in Craddock, P.T., Hughes, M.J. (eds) Furnaces and Smelting Technology in Antiquity. Occasional Paper No 48. London: British Museum Occasional Papers.
* J. S., Hodgkinson. 2008. "The Wealden Iron Industry." (The History Press, Stroud).
* Cleere, Henry. 1981. The Iron Industry of Roman Britain. Wealden Iron Research Group.
; Output
* Callataÿ, François de (2005): "The Graeco-Roman Economy in the Super Long-Run: Lead, Copper, and Shipwrecks", Journal of Roman Archaeology, Vol. 18, pp. 361–372
* Cech, Brigitte (2010): Technik in der Antike, Wissenschaftliche Buchgesellschaft, Darmstadt,
* Cleere, H. & Crossley, D. (1995): The Iron industry of the Weald. 2nd edition, Merton Priory Press, Cardiff, : republishing the 1st edition (Leicester University Press 1985) with a supplement.
* Cleere, Henry. 1981. The Iron Industry of Roman Britain. Wealden Iron Research Group. p. 74-75
* Craddock, Paul T. (2008): "Mining and Metallurgy", in: Oleson, John Peter (ed.): The Oxford Handbook of Engineering and Technology in the Classical World, Oxford University Press, , pp. 93–120
* Healy, John F. (1978): Mining and Metallurgy in the Greek and Roman World, Thames and Hudson, London,
* Hong, Sungmin; Candelone, Jean-Pierre; Patterson, Clair C.; Boutron, Claude F. (1994): "Greenland Ice Evidence of Hemispheric Lead Pollution Two Millennia Ago by Greek and Roman Civilizations", Science, Vol. 265, No. 5180, pp. 1841–1843
* Hong, Sungmin; Candelone, Jean-Pierre; Patterson, Clair C.; Boutron, Claude F. (1996): "History of Ancient Copper Smelting Pollution During Roman and Medieval Times Recorded in Greenland Ice", Science, Vol. 272, No. 5259, pp. 246–249
* Patterson, Clair C. (1972): "Silver Stocks and Losses in Ancient and Medieval Times", The Economic History Review, Vol. 25, No. 2, pp. 205–235
* Lewis, P. R. and G. D. B. Jones, The Dolaucothi gold mines, I: the surface evidence, The Antiquaries Journal, 49, no. 2 (1969): 244-72.
* Lewis, P. R. and G. D. B. Jones, Roman gold-mining in north-west Spain, Journal of Roman Studies 60 (1970): 169-85.
* Lewis, P. R., The Ogofau Roman gold mines at Dolaucothi, The National Trust Year Book 1976-77 (1977).
* Settle, Dorothy M.; Patterson, Clair C. (1980): "Lead in Albacore: Guide to Lead Pollution in Americans", Science, Vol. 207, No. 4436, pp. 1167–1176
* Sim, David; Ridge, Isabel (2002): Iron for the Eagles. The Iron Industry of Roman Britain, Tempus, Stroud, Gloucestershire,
* Smith, A. H. V. (1997): "Provenance of Coals from Roman Sites in England and Wales", Britannia, Vol. 28, pp. 297–324
* Wilson, Andrew (2002): "Machines, Power and the Ancient Economy", The Journal of Roman Studies, Vol. 92, pp. 1–32 | 8 | Metallurgy |
The Hertz–Knudsen equation describes the non-dissociative adsorption of a gas molecule on a surface by expressing the variation of the number of molecules impacting on the surfaces per unit of time as a function of the pressure of the gas and other parameters which characterise both the gas phase molecule and the surface:
where:
Since the equation result has the units of s it can be assimilated to a rate constant for the adsorption process. | 7 | Physical Chemistry |
*Agnes Fay Morgan Research Award, Iota Sigma Pi, 2019
*Marshall University College of Science Distinguished Alumni Award, 2019
*Eli Lilly Young Investigator Award in Analytical Chemistry, 2018
*US HUPO Robert J. Cotter New Investigator Award, 2018
* NSF CAREER Award, 2015
* Arthur C. Neish Young Investigator Award, 2014
* NSF Graduate Research Fellowship, 2002-2005 | 3 | Analytical Chemistry |
TTFB (4,5,6,7-Tetrachloro-2-trifluoromethylbenzimidazole) is a halogenated benzimidazole derivative that acts as an uncoupling agent. | 1 | Biochemistry |
In simple terms, phosphorescence is a process in which energy absorbed by a substance is released relatively slowly in the form of light. This is in some cases the mechanism used for glow-in-the-dark materials which are "charged" by exposure to light. Unlike the relatively swift reactions in fluorescence, such as those seen in laser mediums like the common ruby, phosphorescent materials "store" absorbed energy for a longer time, as the processes required to reemit energy occur less often. However, timescale is still only a general distinction, as there are slow-emitting fluorescent materials, for example uranyl salts, and, likewise, some phosphorescent materials like zinc sulfide (in violet) are very fast. Scientifically, the phenomena are classified by the different mechanisms that produce the light, as materials that phosphoresce may be suitable for some purposes such as lighting, but may be completely unsuitable for others that require fluorescence, like lasers. Further blurring the lines, a substance may emit light by one, two, or all three mechanisms depending on the material and excitation conditions.
When the stored energy becomes locked in by the spin of the atomic electrons, a triplet state can occur, slowing the emission of light, sometimes by several orders of magnitude. Because the atoms usually begin in a singlet state of spin, favoring fluorescence, these types of phosphors typically produce both types of emission during illumination, and then a dimmer afterglow of strictly phosphorescent light typically lasting less than a second after the illumination is switched off.
Conversely, when the stored energy is due to persistent phosphorescence, an entirely different process occurs without a fluorescence precursor. When electrons become trapped within a defect in the atomic or molecular lattice, light is prevented from reemitting until the electron can escape. To escape, the electron needs a boost of thermal energy to help spring it out of the trap and back into orbit around the atom. Only then can the atom emit a photon. Thus, persistent phosphorescence is highly dependent on the temperature of the material. | 7 | Physical Chemistry |
In biochemistry and metabolism, beta oxidation (also β-oxidation) is the catabolic process by which fatty acid molecules are broken down in the cytosol in prokaryotes and in the mitochondria in eukaryotes to generate acetyl-CoA. Acetyl-CoA enters the citric acid cycle, generating NADH and FADH, which are electron carriers used in the electron transport chain. It is named as such because the beta carbon of the fatty acid chain undergoes oxidation and is converted to a carbonyl group to start the cycle all over again. Beta-oxidation is primarily facilitated by the mitochondrial trifunctional protein, an enzyme complex associated with the inner mitochondrial membrane, although very long chain fatty acids are oxidized in peroxisomes.
The overall reaction for one cycle of beta oxidation is:
:C-acyl-CoA + FAD + NAD + HO + CoA → C-acyl-CoA + FADH + NADH + H + acetyl-CoA | 1 | Biochemistry |
The removal of the inhibitory RuBP, CA1P, and the other inhibitory substrate analogs by activase requires the consumption of ATP. This reaction is inhibited by the presence of ADP, and, thus, activase activity depends on the ratio of these compounds in the chloroplast stroma. Furthermore, in most plants, the sensitivity of activase to the ratio of ATP/ADP is modified by the stromal reduction/oxidation (redox) state through another small regulatory protein, thioredoxin. In this manner, the activity of activase and the activation state of RuBisCO can be modulated in response to light intensity and, thus, the rate of formation of the ribulose 1,5-bisphosphate substrate. | 5 | Photochemistry |
Brigitte Zanda (born July 29, 1958) is a French meteoriticist, astrophysicist, and cosmochemist. She is an associate professor at the National Museum of Natural History (MNHN) in Paris, affiliated with the Institut de minéralogie, de physique des matériaux et de cosmochimie.
As a teacher-researcher, she specializes in primitive meteorites: chondrites. In 2019–2020, she served as the vice president of the Meteoritical Society. Additionally, she is the co-director of the observation network and the coordinator-manager of the participatory science project Vigie-Ciel. | 9 | Geochemistry |
In ionic bonding, the atoms are bound by attraction of oppositely charged ions, whereas, in covalent bonding, atoms are bound by sharing electrons to attain stable electron configurations. In covalent bonding, the molecular geometry around each atom is determined by valence shell electron pair repulsion VSEPR rules, whereas, in ionic materials, the geometry follows maximum packing rules. One could say that covalent bonding is more directional in the sense that the energy penalty for not adhering to the optimum bond angles is large, whereas ionic bonding has no such penalty. There are no shared electron pairs to repel each other, the ions should simply be packed as efficiently as possible. This often leads to much higher coordination numbers. In NaCl, each ion has 6 bonds and all bond angles are 90°. In CsCl the coordination number is 8. By comparison carbon typically has a maximum of four bonds.
Purely ionic bonding cannot exist, as the proximity of the entities involved in the bonding allows some degree of sharing electron density between them. Therefore, all ionic bonding has some covalent character. Thus, bonding is considered ionic where the ionic character is greater than the covalent character. The larger the difference in electronegativity between the two types of atoms involved in the bonding, the more ionic (polar) it is. Bonds with partially ionic and partially covalent character are called polar covalent bonds. For example, Na–Cl and Mg–O interactions have a few percent covalency, while Si–O bonds are usually ~50% ionic and ~50% covalent. Pauling estimated that an electronegativity difference of 1.7 (on the Pauling scale) corresponds to 50% ionic character, so that a difference greater than 1.7 corresponds to a bond which is predominantly ionic.
Ionic character in covalent bonds can be directly measured for atoms having quadrupolar nuclei (H, N, Br, Cl or I). These nuclei are generally objects of NQR nuclear quadrupole resonance and NMR nuclear magnetic resonance studies. Interactions between the nuclear quadrupole moments Q and the electric field gradients (EFG) are characterized via the nuclear quadrupole coupling constants
:QCC =
where the eq term corresponds to the principal component of the EFG tensor and e is the elementary charge. In turn, the electric field gradient opens the way to description of bonding modes in molecules when the QCC values are accurately determined by NMR or NQR methods.
In general, when ionic bonding occurs in the solid (or liquid) state, it is not possible to talk about a single "ionic bond" between two individual atoms, because the cohesive forces that keep the lattice together are of a more collective nature. This is quite different in the case of covalent bonding, where we can often speak of a distinct bond localized between two particular atoms. However, even if ionic bonding is combined with some covalency, the result is not necessarily discrete bonds of a localized character. In such cases, the resulting bonding often requires description in terms of a band structure consisting of gigantic molecular orbitals spanning the entire crystal. Thus, the bonding in the solid often retains its collective rather than localized nature. When the difference in electronegativity is decreased, the bonding may then lead to a semiconductor, a semimetal or eventually a metallic conductor with metallic bonding. | 6 | Supramolecular Chemistry |
Dithiocarbamates are readily S-alkylated. Thus, methyl dimethyldithiocarbamate can be prepared by methylation of the dithiocarbamate:
:(CH)NCSNa + (CHO)SO → (CH)NC(S)SCH + Na[CHOSO]
Oxidation of dithiocarbamates gives the thiuram disulfide:
:2 RNCS → [RNC(S)S] + 2e
Thiuram disulfides react with Grignard reagents to give esters of dithiocarbamic acid:
:[RNC(S)S] + RMgX → RNC(S)SR + RNCSMgX
Dithiocarbamates react with transition metal salts to give a wide variety of transition metal dithiocarbamate complexes. | 0 | Organic Chemistry |
The Greenhouse Gases Observing Satellite-2 was launched from Tanegashima Space Center by a H-IIA rocket on October 29, 2018. | 2 | Environmental Chemistry |
Cefalexin is rapidly and almost completely absorbed from the gastrointestinal tract with oral administration. Absorption is slightly reduced when it is taken with food and the medication can be taken without regard for meals. Peak levels of cefalexin occur about 1 hour after administration. Maximal levels of cefalexin increase approximately linearly over a dose range of 250 to 1,000 mg.
Like most other cephalosporins, cefalexin is not metabolized or otherwise inactivated in the body.
The elimination half-life of cefalexin is approximately 30 to 60 minutes in people with normal renal function. Therapeutic levels of cefalexin with oral administration are maintained for 6 to 8 hours. For this reason, cefalexin is typically administered once every 6 to 12 hours depending on the indication. More than 90% of cefalexin is excreted unchanged in the urine within 8 hours. | 4 | Stereochemistry |
The energy of the bulk component of a solid substrate is determined by the types of interactions that hold the substrate together. High-energy substrates are held together by bonds, while low-energy substrates are held together by forces. Covalent, ionic, and metallic bonds are much stronger than forces such as van der Waals and hydrogen bonding. High-energy substrates are more easily wetted than low-energy substrates. In addition, more complete wetting will occur if the substrate has a much higher surface energy than the liquid. | 7 | Physical Chemistry |
Antibodies can also be used to purify their target compounds from mixtures, using the method of immunoprecipitation. | 1 | Biochemistry |
Le Bail analysis is a whole diffraction pattern profile fitting technique used to characterize the properties of crystalline materials, such as structure. It was invented by Armel Le Bail around 1988. | 3 | Analytical Chemistry |
Photosensitizers are light absorbers that alter the course of a photochemical reaction. They usually are catalysts. They can function by many mechanisms, sometimes they donate an electron to the substrate, sometimes they abstract a hydrogen atom from the substrate. At the end of this process, the photosensitizer returns to its ground state, where it remains chemically intact, poised to absorb more light. One branch of chemistry which frequently utilizes photosensitizers is polymer chemistry, using photosensitizers in reactions such as photopolymerization, photocrosslinking, and photodegradation. Photosensitizers are also used to generate prolonged excited electronic states in organic molecules with uses in photocatalysis, photon upconversion and photodynamic therapy. Generally, photosensitizers absorb electromagnetic radiation consisting of infrared radiation, visible light radiation, and ultraviolet radiation and transfer absorbed energy into neighboring molecules. This absorption of light is made possible by photosensitizers' large de-localized π-systems, which lowers the energy of HOMO and LUMO orbitals to promote photoexcitation. While many photosensitizers are organic or organometallic compounds, there are also examples of using semiconductor quantum dots as photosensitizers. | 5 | Photochemistry |
Globo-Hs TACA character allows for its utilization as an anticancer vaccine, inducing antibody response against the epitope. The resulting humoral immunity could enable the selective eradication of Globo H-presenting tumors. The Taiwanese biopharma company OBI Pharma, Inc., was first to develop Adagloxad Simolenin (OBI-822), a Globo H hexasaccharide conjugated with the immunostimulatory carrier protein KLH. The Phase III GLORIA study is underway evaluating the carbohydrate-based immunogens effects in high risk triple-negative breast cancer (TNBC) patients with an estimated completion date in 2027.
Alternative vaccine conjugates have been developed which avoid issues associated with the protein carrier KLH by substituting it with a lipid or carbohydrate-based carrier. Examples include the use of lipid A derivatives or entirely carbohydrate vaccine conjugates such as Globo H-PS A1 | 1 | Biochemistry |
Bryostatin 1 is a potent modulator of protein kinase C (PKC).
It showed activity in laboratory tests in cells and model animals, so it was brought into clinical trials. As of 2014 over thirty clinical trials had been conducted, using bryostatin alone and in combination with other agents, in both solid tumors and blood tumors; it did not show a good enough risk:benefit ratio to be advanced further.
It showed enough promise in animal models of Alzheimers disease that a Phase II trial was started by 2010; the trial was sponsored by the Blanchette Rockefeller Neurosciences Institute. Scientists from that institute started a company called Neurotrope, and launched another clinical trial in Alzheimers disease, preliminary results of which were released in 2017.
Bryostatin has also been studied in people with HIV. | 0 | Organic Chemistry |
A colorimeter is a device used to test the concentration of a solution by measuring its absorbance of a specific wavelength of light. To use this device, different solutions must be made, and a control (usually a mixture of distilled water and another solution) is first filled into a cuvette and placed inside a colorimeter to calibrate the machine. Only after the device has been calibrated you can use it to find the densities and/or concentrations of the other solutions. You do this by repeating the calibration, except with cuvettes filled with the other solutions.
The filter on a colorimeter must be set to red if the liquid is blue. The size of the filter initially chosen for the colorimeter is extremely important, as the wavelength of light that is transmitted by the colorimeter has to be same as that absorbed by the substance. | 3 | Analytical Chemistry |
* 1.F.1 The Synaptosomal Vesicle Fusion Pore (SVF-Pore) Family
* 1.F.2 The Octameric Exocyst (Exocyst) Family | 1 | Biochemistry |
Enhancer-FACS-seq (eFS), developed by the Bulyk lab at Brigham and Women’s Hospital and Harvard Medical School, is a highly parallel enhancer assay that aims for the identification of active, tissue-specific transcriptional enhancers, in the context of whole Drosophila melanogaster embryos. This technology replaces the use of microscopy to screen for tissue-specific enhancers with fluorescence activated cell sorting (FACS) of dissociated cells from whole embryos, combined with identification by high-throughput Illumina sequencing. | 1 | Biochemistry |
The paper used for fuel filters is a crêped paper with controlled porosity, which is pleated and wound to cartridges. The raw material for filter paper used in fuel filters are made of a mixture of hardwood and softwood fibres. The basis weight of the paper is 50–80 g/m. | 3 | Analytical Chemistry |
The area of temporary hypoxic bottom water that occurs most summers off the coast of Louisiana in the Gulf of Mexico is the largest recurring hypoxic zone in the United States. It occurs only during the summer months of the year due to summer warming, regional circulation, wind mixing and high freshwater discharge. The Mississippi River, which is the drainage area for 41% of the continental United States, dumps high-nutrient runoff such as nitrates and phosphorus into the Gulf of Mexico. According to a 2009 fact sheet created by NOAA, "seventy percent of nutrient loads that cause hypoxia are a result of this vast drainage basin". which includes the heart of U.S. agribusiness, the Midwest. The discharge of treated sewage from urban areas (pop. c 12 million in 2009) combined with agricultural runoff deliver c. 1.7 million tons of phosphorus and nitrogen into the Gulf of Mexico every year. Nitrogen is indeed needed to increase crop yields, but plants are inefficient at taking it up, and often more fertilizers are used than plants actually need. Therefore, only a percentage of applied nitrogen ends up in the crops; and in some areas that number is less than 20%. Even though Iowa occupies less than 5% of the Mississippi River drainage basin, average annual nitrate discharge from surface water in Iowa is about 204,000 to 222,000 metric tonnes, or 25% of all the nitrate which the Mississippi River delivers to the Gulf of Mexico. Export from the Raccoon River Watershed is among the highest in the United States with annual yields at 26.1 kg/ha/year which ranked as the highest loss of nitrate out of 42 Mississippi subwatersheds evaluated for a Gulf of Mexico hypoxia report. In 2012, Iowa introduced the Iowa Nutrient Reduction Strategy, which "is a science and technology-based framework to assess and reduce nutrients to Iowa waters and the Gulf of Mexico. It is designed to direct efforts to reduce nutrients in surface water from both point and nonpoint sources in a scientific, reasonable and cost effective manner." The strategy continues to evolve, using voluntary methods to reduce Iowas negative contributions through outreach, research, and implementation of nutrient holding practices. In order to help reduce agricultural runoff into the Mississippi Basin, Minnesota passed [https://www.revisor.mn.gov/statutes/cite/103F.48 MN Statute 103F.48] in 2015, also known as the "Buffer Law", which was designed to implement mandatory riparian buffers between farmland and public waterways across the State of Minnesota. The [http://bwsr.state.mn.us Minnesota Board of Water and Soil Resources] (BWSR) issued a January 2019 report stating that compliance with the Buffer Law' has reached 99%. | 9 | Geochemistry |
Neothiobinupharidine is a dimeric thiaspirane alkaloid isolated from the dwarf water lily Nuphar pumila. It exhibits weak immunosuppressive and cytotoxic bioactivity in cell line experiments. | 0 | Organic Chemistry |
During the last two decades, eco-evolutionary studies have investigated the relevance of life-history traits and environmental conditions on telomeres of wildlife. Most of these studies have been conducted in endotherms, i.e. birds and mammals. They have provided evidence for the inheritance of telomere length; however, heritability estimates vary greatly within and among species. Age and telomere length often negatively correlate in vertebrates, but this decline is variable among taxa and linked to the method used for estimating telomere length. In contrast, the available information shows no sex differences in telomere length across vertebrates. Phylogeny and life history traits such as body size or the pace of life can also affect telomere dynamics. For example, it has been described across species of birds and mammals. In 2019, a meta-analysis confirmed that the exposure to stressors (e.g. pathogen infection, competition, reproductive effort and high activity level) was associated with shorter telomeres across different animal taxa.
Studies on ectotherms, and other non-mammalian organisms, show that there is no single universal model of telomere erosion; rather, there is wide variation in relevant dynamics across Metazoa, and even within smaller taxonomic groups these patterns appear diverse. | 1 | Biochemistry |
* 1946 Harvard University: Instructor; 1948 Assistant Professor
* 1953 Columbia University: Associate Professor; 1955 Professor; 1967–1993 Eugene Higgins Professor; *1993 Professor Emeritus | 0 | Organic Chemistry |
Monocarboranes are clusters with cages. The 12-vertex derivative is best studied, but several are known.
Typically they are prepared by the addition of one-carbon reagents to boron hydride clusters. One-carbon reagents include cyanide, isocyanides, and formaldehyde. For example, monocarbadodecaborate () is produced from decaborane and formaldehyde, followed by addition of borane dimethylsulfide.
Monocarboranes are precursors to weakly coordinating anions. | 7 | Physical Chemistry |
Immunosequencing, sometimes referred to as repertoire sequencing or Rep-Seq, is a method for analyzing the genetic makeup of an individual's immune system. | 1 | Biochemistry |
In addition to this division, lithotrophs differ in the initial energy source which initiates ATP production:
* Chemolithotrophs use the above-mentioned inorganic compounds for aerobic or anaerobic respiration. The energy produced by the oxidation of these compounds is enough for ATP production. Some of the electrons derived from the inorganic donors also need to be channeled into biosynthesis. Mostly, additional energy has to be invested to transform these reducing equivalents to the forms and redox potentials needed (mostly NADH or NADPH), which occurs by reverse electron transfer reactions.
* Photolithotrophs use light as their energy source. These organisms are photosynthetic; examples of photolithotrophic bacteria are purple bacteria (e. g., Chromatiaceae), green bacteria (Chlorobiaceae and Chloroflexota), and "Cyanobacteria". Purple and green bacteria oxidize sulfide, sulfur, sulfite, iron or hydrogen. Cyanobacteria and plants extract reducing equivalents from water, i.e., they oxidize water to oxygen. The electrons obtained from the electron donors are not used for ATP production (as long as there is light); they are used in biosynthetic reactions. Some photolithotrophs shift over to chemolithotrophic metabolism in the dark. | 1 | Biochemistry |
In molecular biology, a termination factor is a protein that mediates the termination of RNA transcription by recognizing a transcription terminator and causing the release of the newly made mRNA. This is part of the process that regulates the transcription of RNA to preserve gene expression integrity and are present in both eukaryotes and prokaryotes, although the process in bacteria is more widely understood. The most extensively studied and detailed transcriptional termination factor is the Rho (ρ) protein of E. coli. | 1 | Biochemistry |
Gene regulation by miRNA is widespread across many genomes – by some estimates more than 60% of human protein-coding genes are likely to be regulated by miRNA, though the quality of experimental evidence for miRNA-target interactions is often weak. Because processing by microprocessor is a major determinant of miRNA abundance, microprocessor itself is then an important target of regulation.
Both Drosha and DGCR8 are subject to regulation by post-translational modifications modulating stability, intracellular localization, and activity levels. Activity against particular substrates may be regulated by additional protein cofactors interacting with the microprocessor complex. The loop region of the pri-miRNA stem-loop is also a recognition element for regulatory proteins, which may up- or down-regulate microprocessor processing of the specific miRNAs they target.
Microprocessor itself is auto-regulated by negative feedback through association with a pri-miRNA-like hairpin structure found in the DGCR8 mRNA, which when cleaved reduces DGCR8 expression. The structure in this case is located in an exon and is unlikely to itself function as miRNA in its own right. | 1 | Biochemistry |
Recent advances in technology have allowed for the use of argon gas to drive ice formation using a principle known as the Joule-Thomson effect. This gives physicians excellent control of the ice and minimizes complications using ultra-thin 17 gauge cryoneedles. | 1 | Biochemistry |
Classically acyl cyanides are produced by the salt metathesis reaction of acyl chlorides with sodium cyanide:
Alternatively, they can be produced by dehydration of acyl aldoximes:
Acetyl cyanide is also prepared by hydrocyanation of ketene: | 0 | Organic Chemistry |
Reduction of the anode by the photosynthetic material can be achieved by a direct electron transfer, or via a soluble redox mediator. Redox mediators may be lipid-soluble (e.g. vitamin K2), allowing them to pass through cell membranes, and can either be added to the system or produced by the biological material. | 7 | Physical Chemistry |
The growth-differentiation balance hypothesis states that plant defenses are a result of a tradeoff between "growth-related processes" and "differentiation-related processes" in different environments. Differentiation-related processes are defined as "processes that enhance the structure or function of existing cells (i.e. maturation and specialization)." A plant will produce chemical defenses only when energy is available from photosynthesis, and plants with the highest concentrations of secondary metabolites are the ones with an intermediate level of available resources.
The GDBH also accounts for tradeoffs between growth and defense over a resource availability gradient. In situations where resources (e.g. water and nutrients) limit photosynthesis, carbon supply is predicted to limit both growth and defense. As resource availability increases, the requirements needed to support photosynthesis are met, allowing for accumulation of carbohydrate in tissues. As resources are not sufficient to meet the large demands of growth, these carbon compounds can instead be partitioned into the synthesis of carbon based secondary metabolites (phenolics, tannins, etc.). In environments where the resource demands for growth are met, carbon is allocated to rapidly dividing meristems (high sink strength) at the expense of secondary metabolism. Thus rapidly growing plants are predicted to contain lower levels of secondary metabolites and vice versa. In addition, the tradeoff predicted by the GDBH may change over time, as evidenced by a recent study on Salix spp. Much support for this hypothesis is present in the literature, and some scientists consider the GDBH the most mature of the plant defense hypotheses. | 1 | Biochemistry |
Because the coiled shells of gastropods are asymmetric, they possess a quality called chirality–the "handedness" of an asymmetric structure.
Over 90% of gastropod species have shells in which the direction of the coil is dextral (right-handed). A small minority of species and genera have shells in which the coils are almost always sinistral (left-handed). Very few species show an even mixture of dextral and sinistral individuals (for example, Amphidromus perversus). | 4 | Stereochemistry |
The rate of sequencing or imaging is dependent on the mechanical movement speed of the magnetic beads, which is limited by drag force. Currently, it is possible to measure 10 hairpin open-close cycle per second. Additional complications include the existence of a secondary hairpin structure in the DNA of interest. In such a case the DNA loop to be ligated must be designed such that it its closing is favored over the closing of the endogenous loop in the DNA of interest. | 1 | Biochemistry |
Most self-healing hydrogels rely on electrostatic attraction to spontaneously create new bonds. The electrostatic attraction can be masked using protonation of the polar functional groups. When the pH is raised the polar functional groups become deprotonated, freeing the polar functional group to react.
Since the hydrogels rely on electrostatic attraction for self-healing, the process can be affected by electrostatic screening. The effects of a change in salinity can be modeled using the Gouy-Chapman-Stern theory Double Layer .
* : Zeta Potential
*: Salinity of solution
*: Distance between molecules, if the polar functional group is one molecule and an ion in solution is the other.
To calculate the Gouy-Chapmanm potential, the salinity factor must be calculated. The expression given for the salinity factor is as follows:
*: Charge of ion
*: 1.6 * 10^{-19} C
*: Number of ions per cubic meter
*: Dielectric constant of solvent
*: 8.85 * 10^{-12} C^2/(J*m), the permittivity of free space
*: 1.38 * 10^{-23} m^2 kg/(s^2), Boltzmann Constant
*: Temperature in kelvins
These effects become important when considering the application of self-healing hydrogels to the medical field. They will be affected by the pH and salinity of blood.
These effects also come into play during synthesis when trying to add large hydrophobes to a hydrophilic polymer backbone. A research group from the Istanbul Technical University has shown that large hydrophobes can be added by adding an electrolyte in a sufficient amount. During synthesis, the hydrophobes were held in micelles before attaching to the polymer backbone. By increasing the salinity of the solution, the micelles were able to grow and encompass more hydrophobes. If there are more hydrophobes in a micelle, then the solubility of the hydrophobe increases. The increase in the solubility lead to an increase in the formation of hydrogels with large hydrophobes. | 7 | Physical Chemistry |
All monosaccharides are reducing sugars because they either have an aldehyde group (if they are aldoses) or can tautomerize in solution to form an aldehyde group (if they are ketoses). This includes common monosaccharides like galactose, glucose, glyceraldehyde, fructose, ribose, and xylose.
Many disaccharides, like cellobiose, lactose, and maltose, also have a reducing form, as one of the two units may have an open-chain form with an aldehyde group. However, sucrose and trehalose, in which the anomeric carbon atoms of the two units are linked together, are nonreducing disaccharides since neither of the rings is capable of opening.
In glucose polymers such as starch and starch-derivatives like glucose syrup, maltodextrin and dextrin the macromolecule begins with a reducing sugar, a free aldehyde. When starch has been partially hydrolyzed the chains have been split and hence it contains more reducing sugars per gram. The percentage of reducing sugars present in these starch derivatives is called dextrose equivalent (DE).
Glycogen is a highly branched polymer of glucose that serves as the main form of carbohydrate storage in animals. It is a reducing sugar with only one reducing end, no matter how large the glycogen molecule is or how many branches it has (note, however, that the unique reducing end is usually covalently linked to glycogenin and will therefore not be reducing). Each branch ends in a nonreducing sugar residue. When glycogen is broken down to be used as an energy source, glucose units are removed one at a time from the nonreducing ends by enzymes. | 0 | Organic Chemistry |
The structure of the open channel structure was solved by two independent research teams in 2009 at low pH values of 4-4.6 (GLIC being proton-gated). | 1 | Biochemistry |
As a strong base, lithium tert-butoxide is easily protonated.
Lithium tert-butoxide is used to prepare other tert-butoxide compounds such as copper(I) t-butoxide and hexa(tert-butoxy)dimolybdenum(III):
:2 MoCl(thf) + 6 LiOBu-t → Mo(OBu-t) + 6 LiCl + 6 thf | 0 | Organic Chemistry |
The BOP clade (sometimes BEP clade) is one of two major lineages (or clades) of undefined taxonomic rank in the grasses (Poaceae), containing more than 5,400 species, about half of all grasses. Its sister group is the PACMAD clade; in contrast with many species of that group who have evolved C photosynthesis, the BOP grasses all use the C photosynthetic pathway.
The clade contains three subfamilies from whose initials its name derives: the bamboos (Bambusoideae); Oryzoideae (syn. Ehrhartoideae), including rice; and Pooideae, mainly distributed in temperate regions, with the largest diversity and important cereal crops such as wheat and barley. Oryzoideae is the earliest-diverging lineage, sister to the bamboos and Pooideae: | 5 | Photochemistry |
Bioplastics can be made from proteins from different sources. For example, wheat gluten and casein show promising properties as a raw material for different biodegradable polymers.
Additionally, soy protein is being considered as another source of bioplastic. Soy proteins have been used in plastic production for over one hundred years. For example, body panels of an original Ford automobile were made of soy-based plastic.
There are difficulties with using soy protein-based plastics due to their water sensitivity and relatively high cost. Therefore, producing blends of soy protein with some already-available biodegradable polyesters improves the water sensitivity and cost. | 7 | Physical Chemistry |
Usually, a thin intermembrane space about 10–20 nanometers thick exists between the outer and inner chloroplast membranes.
Glaucophyte algal chloroplasts have a peptidoglycan layer between the chloroplast membranes. It corresponds to the peptidoglycan cell wall of their cyanobacterial ancestors, which is located between their two cell membranes. These chloroplasts are called muroplasts (from Latin "mura", meaning "wall"). Other chloroplasts were assumed to have lost the cyanobacterial wall, leaving an intermembrane space between the two chloroplast envelope membranes, but has since been found also in moss, lycophytes and ferns. | 5 | Photochemistry |
Jonas Asevicius-Acus-Acukas (July 29, 1885 in Jieznas – July 11, 1976 in Kaunas) was a Lithuanian army officer and chemist. From 1909 to 1918, he served in the Imperial Russian Army at Kaunas Fortress. He fought in the First World War and the Russian Civil War. In 1921 he returned to Lithuania and was mobilized into the Lithuanian Armed Forces, where he attained the rank of colonel (1927) and served until 1940. Acus graduated from Vytautas Magnus University in 1930. He lectured on chemistry and commodity science at Vytautas Magnus University (1934–1940), Vilnius University (1940–1950), and Lithuanian University of Agriculture (1951–1957). He wrote textbooks on foundations of commodity science (1949) and a short course in physical chemistry (1957). Acus was awarded the Commander's Crosses of the Order of Vytautas the Great (1938) and the Order of the Lithuanian Grand Duke Gediminas (1928). | 7 | Physical Chemistry |
Organocerium reagents are used almost exclusively for addition reactions in the same vein as organolithium and Grignard reagents.They are highly nucleophilic, allowing additions to imines in the absence of additional Lewis acid catalysts, making them useful for substrates in which typical conditions fail.
Despite this high reactivity, organocerium reagents are almost entirely non-basic, tolerating the presence of free alcohols and amines as well as enolizable α-protons.
They undergo 1,2-addition in reactions with conjugated electrophiles. At the same time, organocerium reagents can be used to synthesize ketones from acyl compounds without over-addition, as seen with organocuprates.
Organocerium reagents have been employed in a number of total syntheses. Shown below is a key coupling step in the total synthesis of roseophilin, a potent antitumor antibiotic. | 0 | Organic Chemistry |
From left to right the peaks are due to Po, Pu, Po and Am. The fact that isotopes such as Pu and Am have more than one alpha line indicates that the (daughter) nucleus can be in different discrete energy levels.
Calibration:
MCA does not work on energy, it works on voltage. To relate the energy to voltage one must calibrate the detection system. Here different alpha emitting sources of known energy were placed under the detector and the full energy peak is recorded.
Measurement of thickness of thin foils:
Energies of alpha particles from radioactive sources are measured before and after passing through the thin films. By measuring difference and using SRIM we can measure the thickness of thin foils. | 7 | Physical Chemistry |
Section B on Thermodynamics, Equipment and Systems of the IIR focuses on the technological and scientific fundamentals of classical refrigeration, excluding cryogenic temperatures. The fundamentals are represented by its Commission B1 Thermodynamics and Transfer Processes whereas Commission B2 Refrigerating Equipment covers all kinds of refrigeration technology. Section B is a key player in most of the IIR international conferences; except for the International Conference of Refrigeration (ICR) organised every four years for all 10 IIR Commissions, where approximately 50% of all presentations are related to Section B topics.
Independently, and together with other Sections, Section B hosts a multitude of conferences such as the Gustav Lorentzen Conference on Natural Working Fluids and the Ohrid Conference on Ammonia and Refrigeration Technologies; or conferences on Thermodynamic Properties and Transfer Processes of Refrigerants, on Magnetic Refrigeration at Room Temperature, on Compressors and Coolants, and on Phase Change Materials and Slurries for Refrigeration and Air Conditioning.
A number of Working Groups, where emerging topics in refrigeration are discussed by IIR experts with the aim of publishing results in handbooks or other forms publications, are organised within the scope of Section B. Main topics include mitigation of direct emissions of greenhouse gases in refrigeration, refrigerant charge reduction in refrigerating systems, magnetic cooling, life cycle climate performance evaluation, and refrigerant system safety.
* Commission B1: Thermodynamics and Transfer Processes
The objectives of Commission B1 on Thermodynamics and Transfer Processes are to provide academic and industrial information and data, and to propose any solutions on thermodynamics and transfer processes. The Commission B1 has been extremely active in IIR Working Groups, sub-commissions, IIR conferences and co-sponsored conferences and commission business meetings.
As well as being involved in IIR Working Groups on the mitigation of direct emissions of greenhouse gases in refrigeration, the commission is equally involved in the Working Group on Life Cycle Climate Performance (LCCP) Evaluation.
Active in IIR conferences and congresses, Commission B1 similarly organises workshops in various fields such as refrigerant charge reduction in refrigerating systems. Initiatives and opportunities, such as the phase-down of high-GWP refrigerants, energy-efficient buildings and cars, transport refrigeration, food preservation, the economic importance of the refrigeration sector, the involvement of the younger generation and identifying industrial needs are all at the heart of Commission B1.
* Commission B2: Refrigerating Equipment
Commission B2 Refrigerating Equipment participates in many IIR activities aimed at promoting knowledge of refrigeration technologies and their applications worldwide. It is a key Commission for most IIR activities synergizing with other Commissions. The Commission is very active in various IIR Working Groups on Magnetic Cooling and Refrigeration Safety. | 7 | Physical Chemistry |
In topochemical polymerization, little room is provided for the monomer to adjust their position. Thus, the reacting sites of the monomer should be pre-packed in a suitable manner. If [2+2] cycloaddition is involved in the polymerization, then the alignment of double bonds within the crystal should fulfill the aforementioned Schmidt's criteria. Sometimes multiple parameters should be considered. As shown in the figure, for example, the 1,4-polymerization of diacetylene requires the fine adjustment of angle as well as the monomer packing distance to achieve a satisfying reaction site distance d (distance between C1 and C4).
The method invented by Schmidt is still the most promising way to investigate the structural criteria of polymerization. In this approach, a series of monomers with different substituents are crystallized and characterized by single-crystal X-ray diffractometer. By comparing their polymerization reactivity and slightly different structure, the suitable range of lattice parameters can be derived.
Though Schmidts criteria are generally useful for predicting the topochemical reactivity, there are many instances of violation of these criteria. Many examples of smooth reaction of crystals that are not expected to be reactive based on Schmidts criteria are reported. | 7 | Physical Chemistry |
One group of ferredoxins, originally found in chloroplast membranes, has been termed "chloroplast-type" or "plant-type" (). Its active center is a [FeS] cluster, where the iron atoms are tetrahedrally coordinated both by inorganic sulfur atoms and by sulfurs of four conserved cysteine (Cys) residues.
In chloroplasts, FeS ferredoxins function as electron carriers in the photosynthetic electron transport chain and as electron donors to various cellular proteins, such as glutamate synthase, nitrite reductase, sulfite reductase, and the cyclase of chlorophyll biosynthesis. Since the cyclase is a ferredoxin dependent enzyme this may provide a mechanism for coordination between photosynthesis and the chloroplasts need for chlorophyll by linking chlorophyll biosynthesis to the photosynthetic electron transport chain. In hydroxylating bacterial dioxygenase systems, they serve as intermediate electron-transfer carriers between reductase flavoproteins and oxygenase. | 5 | Photochemistry |
Chemokinesis is chemically prompted kinesis, a motile response of unicellular prokaryotic or eukaryotic organisms to chemicals that cause the cell to make some kind of change in their migratory/swimming behaviour. Changes involve an increase or decrease of speed, alterations of amplitude or frequency of motile character, or direction of migration. However, in contrast to chemotaxis, chemokinesis has a random, non-vectorial moiety, in general.
<br />
Due to the random character, techniques dedicated to evaluate chemokinesis are partly different from methods used in chemotaxis research. One of the most valuable ways to measure chemokinesis is computer-assisted (see, e.g., Image J) checker-board analysis, which provides data about migration of identical cells, whereas, in Protozoa (e.g., Tetrahymena), techniques based on measurement of opalescence were also developed. | 1 | Biochemistry |
β-Catenin has been shown to interact with:
* APC,
* AXIN1,
* Androgen receptor,
* CBY1,
* CDH1,
* CDH2,
* CDH3,
* CDK5R1,
* CHUK,
* CTNND1,
* CTNNA1,
* EGFR,
* Emerin
* ESR1
* FHL2,
* GSK3B,
* HER2/neu,
* HNF4A,
* IKK2,
* LEF1 including transgenically,
* MAGI1,
* MUC1,
* NR5A1,
* PCAF,
* PHF17,
* Plakoglobin,
* PTPN14,
* PTPRF,
* PTPRK (PTPkappa),
*PTPRT (PTPrho),
*PTPRU (PCP-2),
* PSEN1,
* PTK7
* RuvB-like 1,
* SMAD7,
* SMARCA4
* SLC9A3R1,
* USP9X, and
* VE-cadherin.
* XIRP1 | 1 | Biochemistry |
Sulfamoyl fluorides can be made by treating secondary amines with sulfuryl fluoride (SOF) or sulfuryl chloride fluoride (SOClF). Cyclic secondary amines work as well, provided they are not aromatic.
Sulfamoyl fluorides can also be made from sulfamoyl chlorides, by reacting with a substance that can supply the fluoride ion, such as NaF, KF, HF, or SbF.
Sulfonamides can undergo a Hofmann rearrangement when treated with a difluoro-λ-bromane to yield a singly substituted N-sulfamoyl fluoride. | 0 | Organic Chemistry |
In small amounts, lactic acid is good for the human body by providing energy and substrates while it moves through the cycle. In lactose intolerant people, the fermentation of lactose to lactic acid has been shown in small studies to help lactose intolerant people. The process of fermentation limits the amount of lactose available. With the amount of lactose lowered, there is less build up inside of the body, reducing bloating. Success of lactic fermentation was most evident in yogurt cultures. Further studies are being conducted on other milk products like acidophilus milk. | 1 | Biochemistry |
Iodine and thyroxine have also been shown to stimulate the spectacular apoptosis of the cells of the larval gills, tail and fins during metamorphosis in amphibians, as well as the transformation of their nervous system from that of the aquatic, herbivorous tadpole into that of the terrestrial, carnivorous adult. The frog species Xenopus laevis has proven to be an ideal model organism for experimental study of the mechanisms of apoptosis and the role of iodine in developmental biology. | 1 | Biochemistry |
* Europium tetrakis (dibenzoylmethide)triethylammonium emits particularly bright red flashes upon the destruction of its crystals.
* Triphenylphosphinebis(pyridine)thiocyanatocopper(I) emits a reasonably strong blue light when crystals of it are fractured. This luminescence is not as extreme as the red luminescence; however, it is still very clearly visible to the naked eye in standard settings.
* N-acetylanthranilic acid emits a deep blue light when its crystals are fractured. | 5 | Photochemistry |
The Norman Hackerman Young Author Award was established in 1982 by The Electrochemical Society (ECS). The award is presented annually for the best paper published in the Journal of the Electrochemical Society for a topic in the field of electrochemical science and technology by a young author or authors. (This award incorporates the Turner Book Prize.)
Recipients of the award are presented with a scroll, cash prize (divided equally among eligible authors), and travel assistance to enable winner(s) to attend the ECS meeting where the award is presented.
This award is named after the chemist Norman Hackerman. | 7 | Physical Chemistry |
Complex molecules, in particular those containing carbon can be in the form of stereoisomers. With abiotic processes they would be expected to be equally likely, but in carbonaceous chondrites this is not the case. The reasons for this are unknown. | 9 | Geochemistry |
As of 2022, there have been five Nobel Prizes in Physics for superconductivity related subjects:
* Heike Kamerlingh Onnes (1913), "for his investigations on the properties of matter at low temperatures which led, inter alia, to the production of liquid helium".
* John Bardeen, Leon N. Cooper, and J. Robert Schrieffer (1972), "for their jointly developed theory of superconductivity, usually called the BCS-theory".
* Leo Esaki, Ivar Giaever, and Brian D. Josephson (1973), "for their experimental discoveries regarding tunneling phenomena in semiconductors and superconductors, respectively" and "for his theoretical predictions of the properties of a supercurrent through a tunnel barrier, in particular those phenomena which are generally known as the Josephson effects".
* Georg Bednorz and K. Alex Müller (1987), "for their important break-through in the discovery of superconductivity in ceramic materials".
* Alexei A. Abrikosov, Vitaly L. Ginzburg, and Anthony J. Leggett (2003), "for pioneering contributions to the theory of superconductors and superfluids". | 7 | Physical Chemistry |
PPR3, PRR5, PRR7, and PRR9 are all paralogs of each other. They have similar structure, and all repress the transcription of CCA1 and LHY. Additionally, they are all characterized by their lack of a phospho-accepting aspartate site. These genes are also paralogs to TOC1, which is alternatively called PRR1. | 1 | Biochemistry |
In mathematics, especially in geometry, a double lattice in is a discrete subgroup of the group of Euclidean motions that consists only of translations and point reflections and such that the subgroup of translations is a lattice. The orbit of any point under the action of a double lattice is a union of two Bravais lattices, related to each other by a point reflection. A double lattice in two dimensions is a p2 wallpaper group. In three dimensions, a double lattice is a space group of the type , as denoted by international notation. | 3 | Analytical Chemistry |
The Tsuji–Wilkinson decarbonylation reaction is a method for the decarbonylation of aldehydes and some acyl chlorides. The reaction name recognizes Jirō Tsuji, whose team first reported the use of Wilkinson's catalyst (RhCl(PPh)) for these reactions:
:RC(O)X + RhCl(PPh) → RX + RhCl(CO)(PPh) + PPh
Although decarbonylation can be effected by several transition metal complexes, Wilkinson's catalyst has proven the most effective. | 0 | Organic Chemistry |
The first step should always be an investigation to determine the cause of the deterioration. The general principles of repair include arresting and preventing further degradation; treating exposed steel reinforcement; and filling fissures or holes caused by cracking or left after the loss of spalled or damaged concrete.
Various techniques are available for the repair, protection and rehabilitation of concrete structures, and specifications for repair principals have been defined systematically. The selection of the appropriate approach will depend on the cause of the initial damage (e.g. impact, excessive loading, movement, corrosion of the reinforcement, chemical attack, or fire) and whether the repair is to be fully load bearing or simply cosmetic.
Repair principles which do not improve the strength or performance of concrete beyond its original (undamaged) condition include replacement and restoration of concrete after spalling and delamination; strengthening to restore structural load-bearing capacity; and increasing resistance to physical or mechanical attack.
Repair principles for arresting and preventing further degradation include control of anodic areas; cathodic protection, cathodic control; increasing resistivity; preserving or restoring passivity; increasing resistance to chemical attack; protection against ingress of adverse agents; and moisture control.
Techniques for filling holes left by the removal of spalled or damaged concrete include mortar repairs; flowing concrete repairs and sprayed concrete repairs. The filling of cracks, fissures or voids in concrete for structural purposes (restoration of strength and load-bearing capability), or non-structural reasons (flexible repairs where further movement is expected, or alternately to resist water and gas permeation) typically involves the injection of low viscosity resins or grouts based on epoxy, PU or acrylic resins, or micronised cement slurries.
One novel proposal for the repair of cracks is to use bacteria. BacillaFilla is a genetically engineered bacterium designed to repair damaged concrete, filling in the cracks, and making them whole again. | 8 | Metallurgy |
This term has become very popular and commonly used in practice. But the appropriate expression is "enantioselective chromatography". Chiral chromatography has advanced to turn into the most preferred technique for the determination of enantiomeric purity as well as separation of pure enantiomers both on analytical and preparative scale. Chiral chromatographic assay is the first step in any study pertaining to enantioselective synthesis or separation. This includes the use of techniques viz. gas chromatography (GC), high performance liquid chromatography (HPLC), chiral supercritical fluid chromatography (SFC), capillary electrophoresis (CE) and thin-layer chromatography (TLC). The result of a literature survey done identifies HPLC-based chiral assays as the most dominating technology in use. An overview of various analytical methods engaged for chiral separation and analysis are listed in the table. | 4 | Stereochemistry |
The concept of human-equivalent energy (H-e) assists in understanding of energy flows in physical and biological systems by expressing energy units in human terms: it provides a “feel” for the use of a given amount of energy by expressing it in terms of the relative quantity of energy needed for human metabolism, assuming an average human energy expenditure of 12,500 kJ per day and a basal metabolic rate of 80 watts. A light bulb running at 100 watts is running at 1.25 human equivalents (100/80), i.e. 1.25 H-e. On the other hand, a human may generate as much as 1,000 watts for a task lasting a few minutes, or even more for a task of a few seconds' duration, while climbing a flight of stairs may represent work at a rate of about 200 watts. | 1 | Biochemistry |
TPV cells have been proposed as auxiliary power conversion devices for capture of otherwise lost heat in other power generation systems, such as steam turbine systems or solar cells. | 7 | Physical Chemistry |
Recent work demonstrates MTTF prediction using a machine learning model. The work uses a neural network-based supervised learning approach with current density, interconnect length, interconnect temperature as input features to the model. | 7 | Physical Chemistry |
Symmetries are of prime importance in physics and are closely related to the hypothesis that certain physical quantities are only relative and unobservable. Symmetries apply to the equations that govern the physical laws (e.g. to a Hamiltonian or Lagrangian) rather than the initial conditions, values or magnitudes of the equations themselves and state that the laws remain unchanged under a transformation. If a symmetry is preserved under a transformation it is said to be invariant. Symmetries in nature lead directly to conservation laws, something which is precisely formulated by Noether's theorem. | 7 | Physical Chemistry |
Capillary electrochromatography (CEC) is an electrochromatography technique in which the liquid mobile phase is driven through a capillary containing the chromatographic stationary phase by electroosmosis. It is a combination of high-performance liquid chromatography and capillary electrophoresis. The capillaries is packed with HPLC stationary phase and a high voltage is applied to achieve separation is achieved by electrophoretic migration of the analyte and differential partitioning in the stationary phase. | 1 | Biochemistry |
The compound is prepared by treatment of solid tetra-n-butylammonium bromide with bromine vapor:
:[N(CH)]Br + Br → [N(CH)]Br
Instead of bromine, tetra-n-butylammonium bromide can also be reacted with vanadium pentoxide and aqueous hydrogen peroxide, or alternatively with ceric ammonium nitrate. This molecule is commonly used as a catalyst in reactions involving the Fischer–Speier esterification mechanism and was heavily tested on by Dr Divyam Shard and Dr Arnav Mohammed, co-workers at Hustlers' University while working with Mr Atul Gowande. | 0 | Organic Chemistry |
There is varying impact on local corrosion noted from biofilms formed of diverse microbial communities. For instance, when isolating a sample of biofilm from a pipe within the first week of growth, the corrosion of the pipe accelerated, yet by the end of a month, the same biofilm began to act as a protective layer for the pipe. Variation between corrosion in similar environments might be attributed to the local bacterial communities. Biofilms further mediate corrosion by altering the electrochemical processes at the interface of the underlying substrate. | 8 | Metallurgy |
In organic chemistry, spherical aromaticity is formally used to describe an unusually stable nature of some spherical compounds such as fullerenes and polyhedral boranes.
In 2000, Andreas Hirsch and coworkers in Erlangen, Germany, formulated a rule to determine when a fullerene would be aromatic. They found that if there were 2(n+1) π-electrons, then the fullerene would display aromatic properties. This follows from the fact that an aromatic fullerene must have full icosahedral (or other appropriate) symmetry, so the molecular orbitals must be entirely filled. This is possible only if there are exactly 2(n+1) electrons, where n is a nonnegative integer. In particular, for example, buckminsterfullerene, with 60 π-electrons, is non-aromatic, since 60/2 = 30, which is not a perfect square.
In 2011, Jordi Poater and Miquel Solà, expanded the rule to determine when an open-shell fullerene species would be aromatic. They found that if there were 2n+2n+1 π-electrons, then the fullerene would display aromatic properties. This follows from the fact that a spherical species having a same-spin half-filled last energy level with the whole inner levels being fully filled is also aromatic. It is similar to Baird's rule. | 6 | Supramolecular Chemistry |
Bacterial luciferin is two-component system consisting of flavin mononucleotide and a fatty aldehyde found in bioluminescent bacteria. | 1 | Biochemistry |
A number of chemical reactions have water as a product. If the reactions take place at temperatures higher than the dew point of the surrounding air the water will be formed as vapor and increase the local humidity, if below the dew point local condensation will occur. Typical reactions that result in water formation are the burning of hydrogen or hydrocarbons in air or other oxygen containing gas mixtures, or as a result of reactions with oxidizers.
In a similar fashion other chemical or physical reactions can take place in the presence of water vapor resulting in new chemicals forming such as rust on iron or steel, polymerization occurring (certain polyurethane foams and cyanoacrylate glues cure with exposure to atmospheric humidity) or forms changing such as where anhydrous chemicals may absorb enough vapor to form a crystalline structure or alter an existing one, sometimes resulting in characteristic color changes that can be used for measurement. | 2 | Environmental Chemistry |
Flow boiling is boiling at a flowing fluid. Compared with pool boiling, flow boiling heat transfer depends on many factors including flow pressure, mass flow rate, fluid type, upstream condition, wall materials, system geometry, and applied heat flux. Characterization of flow boiling requires comprehensive consideration of operating condition. In 2021 a prototype electric vehicle charging cable using flow boiling was able to remove 24.22 kW of heat, allowing the charging current to reach 2,400 amps, far higher than state of the art charging cables that top out at 520 amps. | 7 | Physical Chemistry |
In 2021, SLR14 was reported to prevent infection in the lower respiratory tract and severe disease in an interferon type I (IFN-I)–dependent manner in mice. Immunodeficient mice with chronic SARS-CoV-2 infection experienced near-sterilizing innate immunity with no help from the adaptive immune system. | 1 | Biochemistry |
Peptide computing is a form of computing which uses peptides, instead of traditional electronic components. The basis of this computational model is the affinity of antibodies towards peptide sequences. Similar to DNA computing, the parallel interactions of peptide sequences and antibodies have been used by this model to solve a few NP-complete problems. Specifically, the hamiltonian path problem (HPP) and some versions of the set cover problem are a few NP-complete problems which have been solved using this computational model so far. This model of computation has also been shown to be computationally universal (or Turing complete).
This model of computation has some critical advantages over DNA computing. For instance, while DNA is made of four building blocks, peptides are made of twenty building blocks. The peptide-antibody interactions are also more flexible with respect to recognition and affinity than an interaction between a DNA strand and its reverse complement. However, unlike DNA computing, this model is yet to be practically realized. The main limitation is the availability of specific monoclonal antibodies required by the model. | 1 | Biochemistry |
The α-CH groups of alkyl sulfoxides are susceptible to deprotonation by strong bases, such as sodium hydride:
:CHS(O)CH + NaH → CHS(O)CHNa + H
In the Pummerer rearrangement, alkyl sulfoxides react with acetic anhydride to give migration of the oxygen from sulfur to the adjacent carbon as an acetate ester. The first step of the reaction sequence involves the sulfoxide oxygen acting as a nucleophile: | 0 | Organic Chemistry |
The enzyme ribulose-1,5-bisphosphate carboxylase-oxygenase (rubisco) catalyzes the reaction between RuBP and carbon dioxide. The product is the highly unstable six-carbon intermediate known as 3-keto-2-carboxyarabinitol 1,5-bisphosphate, or 2'-carboxy-3-keto-D-arabinitol 1,5-bisphosphate (CKABP). This six-carbon β-ketoacid intermediate hydrates into another six-carbon intermediate in the form of a gem-diol. This intermediate then cleaves into two molecules of 3-phosphoglycerate (3-PGA) which is used in a number of metabolic pathways and is converted into glucose.
In the Calvin-Benson cycle, RuBP is a product of the phosphorylation of ribulose-5-phosphate (produced by glyceraldehyde 3-phosphate) by ATP. | 5 | Photochemistry |
Uridine diphosphate, abbreviated UDP, is a nucleotide diphosphate. It is an ester of pyrophosphoric acid with the nucleoside uridine. UDP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase uracil.
UDP is an important factor in glycogenesis. Before glucose can be stored as glycogen in the liver and muscles, the enzyme UDP-glucose pyrophosphorylase forms a UDP-glucose unit by combining glucose 1-phosphate with uridine triphosphate, cleaving a pyrophosphate ion in the process. Then, the enzyme glycogen synthase combines UDP-glucose units to form a glycogen chain. The UDP molecule is cleaved from the glucose ring during this process and can be reused by UDP-glucose pyrophosphorylase. | 1 | Biochemistry |
In order to reduce humidity levels and spoiling due to bacterial growth, refrigeration is used for meat, produce, and dairy processing in farming today. Refrigeration systems are used the heaviest in the warmer months for farming produce, which must be cooled as soon as possible in order to meet quality standards and increase the shelf life. Meanwhile, dairy farms refrigerate milk year round to avoid spoiling. | 7 | Physical Chemistry |
AGEs are biochemicals formed continuously under normal circumstances, but more rapidly under a variety of stresses, especially oxidative stress and hyperglycemia. They serve as markers of stress and act as toxins themselves. Pentosidine is typical of the class, except that it fluoresces, which allows it to be seen and measured easily. Because it is well characterized, it is often studied to provide new insight into the biochemistry of AGE compounds in general. | 1 | Biochemistry |
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