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Binding affinity data alone does not determine the overall potency of a drug or a naturally produced (biosynthesized) hormone.
Potency is a result of the complex interplay of both the binding affinity and the ligand efficacy. | 1 | Applied and Interdisciplinary Chemistry |
* Neighborhood: Similar genomic context in different species suggest a similar function of the proteins.
* Fusion-fission events: Proteins that are fused in some genomes are very likely to be functionally linked (as in other genomes where the genes are not fused).
* Occurrence: Proteins that have a similar function or an occurrence in the same metabolic pathway, must be expressed together and have similar phylogenetic profile.
* Coexpression: Predicted association between genes based on observed patterns of simultaneous expression of genes. | 1 | Applied and Interdisciplinary Chemistry |
Hydrogen embrittles a variety of metals including steel, aluminium (at high temperatures only), and titanium. Austempered iron is also susceptible, though austempered steel (and possibly other austempered metals) displays increased resistance to hydrogen embrittlement. NASA has reviewed which metals are susceptible to embrittlement and which only prone to hot hydrogen attack: nickel alloys, austenitic stainless steels, aluminium and alloys, copper (including alloys, e.g. beryllium copper). Sandia has also produced a comprehensive guide. | 0 | Theoretical and Fundamental Chemistry |
Proposed mechanisms:
*Reduced expression of penicillin binding proteins during stationary growth phase
*Induction of microbial resistance mechanisms (such as beta lactamases with short half-lives) by high drug concentrations
*Precipitation of antimicrobial drug in vitro, possibly also leading to the crystallized drug being mis-detected as colonies of the microbe.
*Self-antagonising the receptor with which it binds (penicillin binding proteins, for example, in the case of a penicillin).
Penicillin is a bactericidal antibiotic that works by inhibiting cell wall synthesis but this synthesis only occurs when bacteria are actively replicating (or in the log phase of growth). In cases of extremely high bacterial burden (such as with Group A Strep), bacteria may be in the stationary phase of growth. In this instance since no bacteria are actively replicating (presumably due to nutrient restriction) penicillin has no activity. This is why adding an antibiotic like clindamycin, which acts ribosomally, kills some of the bacteria and returns them to the log phase of growth. | 1 | Applied and Interdisciplinary Chemistry |
The term "cold fusion" was coined to refer to muon-catalyzed fusion in a 1956 New York Times article about Luis W. Alvarez's paper.
In 1957 Theodore Sturgeon wrote a novelette, "The Pod in the Barrier", in which humanity has ubiquitous cold fusion reactors that work with muons. The reaction is "When hydrogen one and hydrogen two are in the presence of Mu mesons, they fuse into helium three, with an energy yield in electron volts of 5.4 times ten to the fifth power". Unlike the thermonuclear bomb contained in the Pod (which is used to destroy the Barrier) they can become temporarily disabled by "concentrated disbelief" that muon fusion works.
In Sir Arthur C. Clarkes third novel in the Space Odyssey series, 2061: Odyssey Three', muon-catalyzed fusion is the technology that allows mankind to achieve easy interplanetary travel. The main character, Heywood Floyd, compares Luis Alvarez to Lord Rutherford for underestimating the future potential of their discoveries. | 0 | Theoretical and Fundamental Chemistry |
In the 19th century chemists found it puzzling that benzene could be so unreactive toward addition reactions, given its presumed high degree of unsaturation. The cyclohexatriene structure for benzene was first proposed by August Kekulé in 1865. Over the next few decades, most chemists readily accepted this structure, since it accounted for most of the known isomeric relationships of aromatic chemistry.
Between 1897 and 1906, J. J. Thomson, the discoverer of the electron, proposed three equivalent electrons between each carbon atom in benzene.
An explanation for the exceptional stability of benzene is conventionally attributed to Sir Robert Robinson, who was apparently the first (in 1925) to coin the term aromatic sextet as a group of six electrons that resists disruption.
In fact, this concept can be traced further back, via Ernest Crocker in 1922, to Henry Edward Armstrong, who in 1890 wrote "the (six) centric affinities act within a cycle...benzene may be represented by a double ring (sic) ... and when an additive compound is formed, the inner cycle of affinity suffers disruption, the contiguous carbon-atoms to which nothing has been attached of necessity acquire the ethylenic condition".
Here, Armstrong is describing at least four modern concepts. First, his "affinity" is better known nowadays as the electron, which was to be discovered only seven years later by J. J. Thomson. Second, he is describing electrophilic aromatic substitution, proceeding (third) through a Wheland intermediate, in which (fourth) the conjugation of the ring is broken. He introduced the symbol C centered on the ring as a shorthand for the inner cycle, thus anticipating Erich Clars notation. It is argued that he also anticipated the nature of wave mechanics, since he recognized that his affinities had direction, not merely being point particles, and collectively having a distribution that could be altered by introducing substituents onto the benzene ring (much as the distribution of the electric charge in a body is altered by bringing it near to another body').
The quantum mechanical origins of this stability, or aromaticity, were first modelled by Hückel in 1931. He was the first to separate the bonding electrons into sigma and pi electrons. | 0 | Theoretical and Fundamental Chemistry |
Novec 649/1230 does not deplete ozone (ODP 0) and has a global warming potential of 1 (over 100 years), equivalent to that of carbon dioxide. The Globally Harmonized System of Classification and Labeling of Chemicals (GHS) classifies this chemical as H412 - Harmful to aquatic life with long lasting effects. Photolysis in sunlight, hydrolysis and hydration may be a significant sink of Novec 649/1230 in the environment. It has very short estimated atmospheric lifetime of around 4 to 15 days.
Novec 649/1230 is classified as a PFAS substance. In December 2022, 3M announced that it would cease production of all PFAS products by 2025, including Novec 649/1230. It degrades to Trifluoroacetic acid (TFA) via photolytic degradation in sunlight. | 1 | Applied and Interdisciplinary Chemistry |
Pseudoknots are common structural motifs found in RNA. They are formed by two nested stem-loops such that the stem of one structure is formed from the loop of the other. There are multiple folding topologies among pseudoknots and great variation in loop lengths, making them a structurally diverse group.
Inverted repeats are a key component of pseudoknots as can be seen in the illustration of a naturally occurring pseudoknot found in the human telomerase RNA component. Four different sets of inverted repeats are involved in this structure. Sets 1 and 2 are the stem of stem-loop A and are part of the loop for stem-loop B. Similarly, sets 3 and 4 are the stem for stem-loop B and are part of the loop for stem-loop A.
Pseudoknots play a number of different roles in biology. The telomerase pseudoknot in the illustration is critical to that enzymes activity. The ribozyme for the hepatitis delta virus (HDV)' folds into a double-pseudoknot structure and self-cleaves its circular genome to produce a single-genome-length RNA. Pseudoknots also play a role in programmed ribosomal frameshifting found in some viruses and required in the replication of retroviruses. | 1 | Applied and Interdisciplinary Chemistry |
DESs are fluids generally composed of two or three cheap and safe components that are capable of self-association, often through hydrogen bond interactions, to form eutectic mixtures with a melting point lower than that of each individual component. DESs are generally liquid at temperatures lower than 100 °C, and they exhibit similar physico-chemical properties to traditional ILs, while being much cheaper and environmentally friendlier. Most of them are mixtures of choline chloride and a hydrogen-bond donor (e.g., urea, ethylene glycol, malonic acid) or mixtures of choline chloride with a hydrated metal salt. Other choline salts (e.g. acetate, citrate, nitrate) have a much higher costs or need to be synthesised, and the DES formulated from these anions are typically much more viscous and can have higher conductivities than for choline chloride. This results in lower plating rates and poorer throwing power and for this reason chloride-based DES systems are still favoured. For instance, Reline (a 1:2 mixture of choline chloride and urea) has been used to selectively recover Zn and Pb from a mixed metal oxide matrix. Similarly, Ethaline (a 1: 2 mixture of choline chloride and ethylene glycol) facilitates metal dissolution in electropolishing of steels. DESs have also demonstrated promising results to recover metals from complex mixtures such Cu/Zn and Ga/As, and precious metals from minerals. It has also been demonstrated that metals can be recovered from complex mixtures by electrocatalysis using a combination of DESs as lixiviants and an oxidising agent, while metal ions can be simultaneously separated from the solution by electrowinning. | 1 | Applied and Interdisciplinary Chemistry |
Professor Stork received a number of awards and honors including the following:
* 1957 Award in Pure Chemistry of the American Chemical Society
* 1959 Guggenheim Foundation Fellow
* 1961 Baekeland Medal, North Jersey ACS
* 1962 Harrison Howe Award
* 1966 Edward Curtis Franklin Memorial Award, Stanford University
* 1967 ACS Award for Creative Work in Synthetic Organic Chemistry
* 1971 Synthetic Organic Chemical Manufacturers Association Gold Medal
* 1973 Nebraska Award
* 1978 Roussel Prize, Paris
* 1980 Nichols Medal, New York ACS, Arthur C. Cope Award, ACS
* 1982 Edgar Fahs Smith Award, Philadelphia ACS
* 1982 Willard Gibbs Medal, Chicago ACS
* 1982 National Academy of Sciences Award in Chemical Sciences
* 1982 National Medal of Science from Ronald Reagan; Linus Pauling Award
* 1985 Tetrahedron Prize
* 1986 Remsen Award, Maryland ACS
* 1986 Cliff S. Hamilton Award
* 1987 Monie A Ferst Award and Medal, Georgia Tech.
* 1991 Roger Adams Award
* 1992 George Kenner Award, Liverpool
* 1992 Robert Robinson Lectureship, University of Manchester
* 1992 Chemical Pioneer Award, American Institute of Chemists
* 1993 Welch Award in Chemistry, Robert A. Welch Foundation
* 1994 Allan R. Day Award, Philadelphia Organic Chemists Club
* 1995 Wolf Prize, Israel
* 2002 Sir Derek Barton Gold medal, Royal Society of Chemistry
* 2005 Herbert C. Brown Award, American Chemical Society
Stork also held honorary doctorates from Lawrence University, the University of Wisconsin–Madison, the University of Paris, the University of Rochester, and Columbia University.
The inaugural Gilbert Stork Lecture was held in his honor in 2014 at his alma mater, the University of Wisconsin-Madison. Gilbert Stork named lecture series are also held at other institutions, including Columbia University and the University of Pennsylvania, as a result of his endowments.
He was fêted for his sense of humor and colorful personality by historian of chemistry Jeffrey I. Seeman who published a collection of "Storkisms". | 0 | Theoretical and Fundamental Chemistry |
In chromatography, resolution is a measure of the separation of two peaks of different retention time t in a chromatogram. | 0 | Theoretical and Fundamental Chemistry |
A separation in which the mobile phase composition remains constant throughout the procedure is termed isocratic (meaning constant composition). The word was coined by Csaba Horvath who was one of the pioneers of HPLC.
The mobile phase composition does not have to remain constant. A separation in which the mobile phase composition is changed during the separation process is described as a gradient elution. For example, a gradient can start at 10% methanol in water, and end at 90% methanol in water after 20 minutes. The two components of the mobile phase are typically termed "A" and "B"; A is the "weak" solvent which allows the solute to elute only slowly, while B is the "strong" solvent which rapidly elutes the solutes from the column. In reversed-phase chromatography, solvent A is often water or an aqueous buffer, while B is an organic solvent miscible with water, such as acetonitrile, methanol, THF, or isopropanol.
In isocratic elution, peak width increases with retention time linearly according to the equation for N, the number of theoretical plates. This can be a major disadvantage when analyzing a sample that contains analytes with a wide range of retention factors. Using a weaker mobile phase, the runtime is lengthened and results in slowly eluting peaks to be broad, leading to reduced sensitivity. A stronger mobile phase would improve issues of runtime and broadening of later peaks but results in diminished peak separation, especially for quickly eluting analytes which may have insufficient time to fully resolve. This issue is addressed through the changing mobile phase composition of gradient elution.
By starting from a weaker mobile phase and strengthening it during the runtime, gradient elution decreases the retention of the later-eluting components so that they elute faster, giving narrower (and taller) peaks for most components, while also allowing for the adequate separation of earlier-eluting components. This also improves the peak shape for tailed peaks, as the increasing concentration of the organic eluent pushes the tailing part of a peak forward. This also increases the peak height (the peak looks "sharper"), which is important in trace analysis. The gradient program may include sudden "step" increases in the percentage of the organic component, or different slopes at different times – all according to the desire for optimum separation in minimum time.
In isocratic elution, the retention order does not change if the column dimensions (length and inner diameter) change – that is, the peaks elute in the same order. In gradient elution, however, the elution order may change as the dimensions or flow rate change. if they are no scaled down or up according to the change
The driving force in reversed phase chromatography originates in the high order of the water structure. The role of the organic component of the mobile phase is to reduce this high order and thus reduce the retarding strength of the aqueous component. | 0 | Theoretical and Fundamental Chemistry |
One of the primary causes of WECs is the passage of electrical current through the bearings. Both Alternating Current (AC) and Direct Current (DC) can lead to the formation of WECs, albeit through slightly different mechanisms. In general, hydrogen generation from lubricants can be accelerated by electric current, potentially accelerating WEC formation. Under certain conditions, when the current densities are low (less than 1 mA/mm2), electrical discharges can significantly shorten the lifespan of bearings by causing WECs. These WECs can develop in under 50 hours due to electrical discharges. Electrostatic sensors prove to be useful in detecting these critical discharges early on, which are associated with failures induced by WECs. The analysis revealed that different reaction layers form in the examined areas, depending on the electrical polarity.
In the case of AC, the rapid change in polarity involves the creation of a plasma channel through the lubricant film in the bearing, leading to a momentary, intense discharge of energy. The localised heating and rapid cooling associated with these discharges can cause changes in the microstructure of the steel, leading to the formation of WEAs and WECs.
On the other hand, DC can cause a steady flow of electrons through the bearing. This can lead to the electrochemical dissolution of the metal, a process known as fretting corrosion. The constant flow of current can also cause local heating, leading to thermal gradients within the bearing material. These gradients can cause stresses that lead to the formation of WECs. | 1 | Applied and Interdisciplinary Chemistry |
The Raman/AFM technique has two approaches: aperture and apertureless, and the apertureless mode is realized with SERS and TERS. Figure 5 is the example of an integrated TERS system. It shows that there are five main components for a whole integrated TERS (apertureless) system. These components are: microscope, one objective lens, one integrated AFM head, a Raman spectrometer and a CCD. The laser is focused on the sample, on piezo-stage and the AFM tip by the moving the laser beam along the tip. The movement of the laser beam is achieved by the mirror in the top left corner. The XYZ piezo-stage in the left bottom holds the sample. In this design, the laser beam is focused on the sample through an objective lens, and the scattered light is collected by the same lens.
This setup utilizes a low contact-pressure to reduce the damage to the AFM tip and sample. The laser power is typically below 1 mW. The notch filter can filter Rayleigh scattering from the excitation laser light from the back of the cantilever. The laser beam is focused on the apex of the gold-coated AFM tip and the sample. The laser scanning is completed by the moving the mirror across the approaching tip. A small enhance in background occurs when the laser spot focuses on the tip area. The movement of the XYZ piezo-stage finishes the sample scanning. The wide red signal is Raman signal which is collected through the objective lens. The same lens is also used for excitation of the sample and collecting the Raman signal. | 0 | Theoretical and Fundamental Chemistry |
The vortex lattice method is built on the theory of ideal flow, also known as Potential flow. Ideal flow is a simplification of the real flow experienced in nature, however for many engineering applications this simplified representation has all of the properties that are important from the engineering point of view. This method neglects all viscous effects. Turbulence, dissipation and boundary layers are not resolved at all. However, lift induced drag can be assessed and, taking special care, some stall phenomena can be modelled. | 1 | Applied and Interdisciplinary Chemistry |
In order to determine the fate of natural carbon containing substances deep in the Earth, experiments have been conducted to see what happens when high pressure, and or temperatures are applied. Such substances include carbon dioxide, carbon monoxide, graphite, methane, and other hydrocarbons such as benzene, carbon dioxide water mixtures and carbonate minerals such as calcite, magnesium carbonate, or ferrous carbonate. Under super high pressures carbon may take on a higher coordination number than the four found in sp compounds like diamond, or the three found in carbonates. Perhaps carbon can substitute into silicates, or form a silicon oxycarbide. Carbides may be possible. | 0 | Theoretical and Fundamental Chemistry |
BVS was first developed by C. P. Chen and R. S. Lakes in 1989 in order to address the shortcomings of existing laboratory techniques for studying viscoelastic materials. It was later refined by M. Brodt et al. to improve the rigidity and resolution of the apparatus, which were sources of error in the original design. First used to study poly(methyl methacrylate) (PMMA), it has since seen applications in determining the properties of bone, capacitor dielectrics, high damping metals, and other such viscoelastic materials. | 0 | Theoretical and Fundamental Chemistry |
Like many other unsaturated functional groups, nitrones activate the α and β carbons towards reaction. The α carbon is an electrophile and the β carbon a nucleophile; that is, nitrones polarize like carbonyls and nitriles but unlike nitro compounds and vinyl sulfur derivatives.
Nitrones hydrolyze extremely easily to the corresponding carbonyl and N-hydroxylamine. | 0 | Theoretical and Fundamental Chemistry |
Most production, use, and emissions of HFC-152a have occurred within Earths more industrialized and populated northern hemisphere following the substances introduction in the 1990s. Its concentration in the northern troposphere reached an annual average of about 10 parts per trillion by year 2011. The concentration of HFC-152a in the southern troposphere is about 50% lower due to its removal rate (i.e. lifetime) of about 1.5 years being similar in magnitude to the global atmospheric mixing time of one to two years. | 1 | Applied and Interdisciplinary Chemistry |
Proteins can also be cross-linked artificially using small-molecule crosslinkers. This approach has been used to elucidate protein–protein interactions. Crosslinkers bind only surface residues in relatively close proximity in the native state. Common crosslinkers include the imidoester crosslinker dimethyl suberimidate, the N-Hydroxysuccinimide-ester crosslinker BS3 and formaldehyde. Each of these crosslinkers induces nucleophilic attack of the amino group of lysine and subsequent covalent bonding via the crosslinker. The zero-length carbodiimide crosslinker EDC functions by converting carboxyls into amine-reactive isourea intermediates that bind to lysine residues or other available primary amines. SMCC or its water-soluble analog, Sulfo-SMCC, is commonly used to prepare antibody-hapten conjugates for antibody development. An in-vitro cross-linking method is PICUP (photo-induced cross-linking of unmodified proteins). Typical reagents are ammonium persulfate (APS), an electron acceptor, the photosensitizer tris-bipyridylruthenium (II) cation (). In in-vivo crosslinking of protein complexes, cells are grown with [[photoreactive diazirine analogs to leucine and methionine, which are incorporated into proteins. Upon exposure to ultraviolet light, the diazirines are activated and bind to interacting proteins that are within a few ångströms of the photo-reactive amino acid analog (UV cross-linking). | 0 | Theoretical and Fundamental Chemistry |
Cloxacillin was discovered and developed by Beecham (now GlaxoSmithKline).
It is sold under a number of trade names, including Cloxapen, Cloxacap, Tegopen and Orbenin. | 0 | Theoretical and Fundamental Chemistry |
Some of Naim's recent publications include (but are not limited to):
* Maalouf K, Jia J, Rizk S, Brogden G, Keiser M, Das A, Naim HY A modified lipid composition in Fabry disease leads to an intracellular block of the detergent-resistant membrane-associated dipeptidyl peptidase IV
* Sim L, Willemsma C, Mohan S, Naim HY, Pinto BM, Rose DR Structural basis for substrate selectivity in human maltase-glucoamylase and sucrase-isomaltase N-terminal domains
* Krahn MP, Rizk S, Alfalah M, Behrendt M, Naim HY Protocadherin of the liver, kidney and colon associates with detergent-resistant membranes during cellular differentiation
* Zimmer KP, Fischer I, Mothes T, Weissen-Plenz G, Schmitz M, Wieser H, Mendez E, Buening J, Lerch MM, Ciclitira PC, Weber P, Naim HY Endocytotic Segregation of Gliadin Peptide 31-49 in Enterocytes
* Behrendt M, Polaina J, Naim HY Structural hierarchy of regulatory elements in the folding and transport of an intestinal multi-domain protein | 1 | Applied and Interdisciplinary Chemistry |
In its pill form, selegiline is used to treat symptoms of Parkinson's disease. It is most often used as an adjunct to drugs such as levodopa (-DOPA), although it has been used off-label as a monotherapy. The rationale for adding selegiline to levodopa is to decrease the required dose of levodopa and thus reduce the motor complications of levodopa therapy. Selegiline delays the point when levodopa treatment becomes necessary from about 11 months to about 18 months after diagnosis. There is some evidence that selegiline acts as a neuroprotectant and reduces the rate of disease progression, though this is disputed.
Selegiline has also been used off-label as a palliative treatment for dementia in Alzheimer's disease. | 0 | Theoretical and Fundamental Chemistry |
Cryoablation of tumor induces necrosis of tumor cells. The immunotherapeutic effect of cryoablation of tumor is the result of the release of intracellular tumor antigens from within the necrotized tumor cells. The released tumor antigens help activate anti-tumor T cells, which destroy remaining malignant cells. Thus, cryoablation of tumor elicits a systemic anti-tumor immunologic response.
The resulting immunostimulation from cryoablation may not be sufficient to induce sustained, systemic regression of metastases, and can be synergised with the combination of immunotherapy treatment and vaccine adjuvants.
Various adjuvant immunotherapy and chemotherapy treatments can be combined with cryoablation to sustain systemic anti-tumor response with regression of metastases, including:
* Injection of immunomodulating drugs (i.e.: therapeutic antibodies) and vaccine adjuvants (saponins) directly into the cryoablated, necrotized tumor lysate, immediately after cryoablation
* Administration of autologous immune enhancement therapy, including: dendritic cell therapy, CIK cell therapy | 1 | Applied and Interdisciplinary Chemistry |
Apothecary businesses were typically family-run, and wives or other women of the family worked alongside their husbands in the shops, learning the trade themselves. Women were still not allowed to train and be educated in universities so this allowed them a chance to be trained in medical knowledge and healing. Previously, women had some influence in other women's healthcare, such as serving as midwives and other feminine care in a setting that was not considered appropriate for males. Though physicians gave medical advice, they did not make medicine, so they typically sent their patients to particular independent apothecaries, who did also provide some medical advice, in particular remedies and healing. | 1 | Applied and Interdisciplinary Chemistry |
Calcium sulfate (its α- and β-hemihydrates) is a well known biocompatible material that is widely used as a bone graft substitute in dentistry or as its binder. | 1 | Applied and Interdisciplinary Chemistry |
The ICBM cooperates closely with the Max Planck Institute for Marine Microbiology und MARUM, both located in Bremen; with the Alfred Wegener Institute in Bremerhaven, as well as with the Senckenberg Institute by the Sea and the Jade University of Applied Sciences, both located in Wilhelmshaven. The ICBM is a member of the German Marine Research Consortium (KDM) and of the Northwest Marine Research Association (NWMV). | 0 | Theoretical and Fundamental Chemistry |
Ružička married twice: to Anna Hausmann in 1912, and 1951 to Gertrud Acklin. From 1929, he lived at Freudenbergstrasse 101 until the last years of his life. He died in Mammern, Switzerland, a village on Lake Constance at the age of 89. | 0 | Theoretical and Fundamental Chemistry |
Upon heating, DAST converts to the highly explosive (NEt)SF with expulsion of sulfur tetrafluoride. To minimize accidents, samples are maintained below 50 °C. Bis-(2-methoxyethyl)aminosulfur trifluoride (trade name: Deoxo-Fluor) and difluoro(morpholino)sulfonium tetrafluoroborate (trade name: XtalFluor-M) are reagents related to DAST with less explosive potential.
XtalFluor-E has been jointly developed by OmegaChem Inc. and Manchester Organics Ltd. in 2009–2010. | 0 | Theoretical and Fundamental Chemistry |
The redox (reduction–oxidation) cell is a reversible cell in which redox-active species are in fluid (liquid or gas) media. Redox flow batteries are rechargeable (secondary) cells. Because they employ heterogeneous electron transfer rather than solid-state diffusion or intercalation they are more similar to fuel cells rather than to conventional batteries (such as lead–acid or lithium-ion). The main reason fuel cells are not considered to be batteries, is because originally (in the 1800s) fuel cells emerged as a means to produce electricity directly from fuels (and air) via a non-combustion electrochemical process. Later, particularly in the 1960s and 1990s, rechargeable fuel cells (i.e. /, such as unitized regenerative fuel cells in NASA's Helios Prototype) were developed.
Examples of redox flow batteries are the vanadium redox flow battery, polysulfide–bromide battery (Regenesys), iron redox flow battery (IRFB), and uranium redox flow battery. Redox fuel cells are less common commercially although many systems have been proposed.
Vanadium redox flow batteries are the most marketed flow batteries at present, due to the advantages they provide over other chemistries, despite limited energy and power densities. Since they use vanadium at both electrodes, they do not suffer cross-contamination. The limited solubility of vanadium salts, however, offsets this advantage in practice. More importantly for the commercial success of VRFBs is actually an almost perfect match of the voltage window of carbon/aqueous acid interface with the working voltage range of the vanadium redox-couples. This assures the durability of the low-cost carbon electrodes and low-impact of side reactions, such as H2 and O2 evolutions, resulting in record-long calendar (many years) and cycle(15,000–20,000 cycles) lives, which in turn results in a record low levelized cost of energy (LCOE, i.e. the system cost divided by the usable energy, the cycle life, and round-trip efficiency). The long lifetimes of flow batteries allow for the amortization of their relatively high capital cost (due to vanadium, carbon felts, bipolar plates, membranes). The levelized cost of energy for VRFBs is in the order of a few tens of $ cents or € cents per kWh, much lower than of solid-state batteries and not so far from the targets of $0.05 and €0.05, stated by US and EC government agencies. The major challenges for the broad implementation include: low abundance and high costs of VO (> $30 / Kg), the raw materials for VRFB; parasite reactions including hydrogen and oxygen evolution; and precipitation of VO during cycling. It is the major driving force to develop alternative flow battery technologies.
Traditional flow battery chemistries have both low specific energy (which makes them too heavy for fully electric vehicles) and low specific power (which makes them too expensive for stationary energy storage). However a high power of 1.4 W/cm was demonstrated for hydrogen–bromine flow batteries, and a high specific energy (530 Wh/kg at the tank level) was shown for hydrogen–bromate flow batteries | 0 | Theoretical and Fundamental Chemistry |
The helium dimer is a van der Waals molecule with formula He consisting of two helium atoms. This chemical is the largest diatomic molecule—a molecule consisting of two atoms bonded together. The bond that holds this dimer together is so weak that it will break if the molecule rotates, or vibrates too much. It can only exist at very low cryogenic temperatures.
Two excited helium atoms can also bond to each other in a form called an excimer. This was discovered from a spectrum of helium that contained bands first seen in 1912. Written as He with the * meaning an excited state, it is the first known Rydberg molecule.
Several dihelium ions also exist, having net charges of negative one, positive one, and positive two. Two helium atoms can be confined together without bonding in the cage of a fullerene. | 0 | Theoretical and Fundamental Chemistry |
It is possible to manufacture a complicated 3D shape from in-situ bonded AFS. In case of the second type, i.e. integral foam moulding, the desired geometry of the foamed part is achieved by designing the mould inside which the foam is cast.
In the case of the third type the three-layer composite precursor is reshaped prior to foaming. Heating of such part yields in a 3D shaped foam part. The three-layer composite AFS panels are also reshaped after foaming by forging. If an AFS is made of heat treatable alloys, the strength is further enhanced by age hardening. In order to join two AFS parts or to join an AFS part with a metallic part several joining technologies are employed, such as laser welding, TIG welding, MIG welding, riveting, etc. | 0 | Theoretical and Fundamental Chemistry |
From 1965 — Associate Research Fellow of the Kiev Institute of Hygiene and Occupational Diseases, where he received a PhD degree in medical sciences. Since 1971, research activities related to Romain Efimovicha connected with VNIIGINTOKS (now the Institute of ecological hygiene and toxicology behalf L. I. Medved). Over 26 years of work at the institute, he has gone from a research assistant to the deputy director for scientific work. The main focus of his activity was the methodology of integrated assessment of chemical risks to human health and the environment. He took an active part in the development of new directions in toxicology and health - a complex hygienic regulation of pesticides, hygienic regulation of pesticides in soil, application of mathematical methods to assess and predict the real risk of accumulation of pesticides in the environment and the human body. He is coauthor of environmental hygiene and classification of pesticides hazard. As a toxicologist Romen E. Sova has made a significant contribution to the development problems of biological standards of laboratory animals, the methodology and methods of studying the combined, integrated and combined effects of chemicals and other factors. Romain Yefimovich established the All-Union Center "Dioxin", commenced research on this problem, developed the first hygienic standards of the most dangerous environmental pollutants. He was an expert of WHO on the issue of dioxin, an expert from Ukraine on the issue of persistent organic pollutants in the United Nations Environment Programme, a member of the committee on the hygienic regulation of MH of Ukraine. Romen Yefimovich prepared 5 Candidates of Medical Sciences, published 6 monographs and more than 230 scientific papers. | 0 | Theoretical and Fundamental Chemistry |
Despite the fact that the solid-state community represented a major force in The Electrochemical Society, there was no form of recognition at the Society level of achievements in the field prior to the establishment of this award. Known as the Solid-State Science and Technology Award until 2005, the award was then renamed after Intel co-founder and author of Moore's Law, Gordon E. Moore, who is a long-time member of The Electrochemical Society. | 0 | Theoretical and Fundamental Chemistry |
Erik Lentz, a physicist at the University of Göttingen, has theorized that solitons could allow for the generation of Alcubierre warp bubbles in spacetime without the need for exotic matter, i.e., matter with negative mass. | 1 | Applied and Interdisciplinary Chemistry |
Calcineurin is a heterodimer of a 61-kD calmodulin-binding catalytic subunit, calcineurin A and a 19-kD Ca-binding regulatory subunit, calcineurin B. There are three isozymes of the catalytic subunit, each encoded by a separate gene (PPP3CA, PPP3CB, and PPP3CC) and two isoforms of the regulatory, also encoded by separate genes (PPP3R1, PPP3R2). | 1 | Applied and Interdisciplinary Chemistry |
Chlorine was discovered in 1774 by Swedish chemist Carl Wilhelm Scheele, who called it "dephlogisticated marine acid" (see phlogiston theory) and mistakenly thought it contained oxygen. Davy showed that the acid of Scheeles substance, called at the time oxymuriatic acid, contained no oxygen. This discovery overturned Lavoisiers definition of acids as compounds of oxygen. In 1810, chlorine was given its current name by Humphry Davy, who insisted that chlorine was in fact an element. The name chlorine, chosen by Davy for "one of [the substance's] obvious and characteristic properties – its colour", comes from the Greek χλωρος (chlōros), meaning green-yellow. | 1 | Applied and Interdisciplinary Chemistry |
When overheating, the temperature of the part rises above the operating temperature. Overheating can take place:
*if heat is produced in more than expected amount (such as in cases of short-circuits, or applying more voltage than rated), or
*if heat dissipation is poor, so that normally produced waste heat does not drain away properly.
Overheating may be caused from any accidental fault of the circuit (such as short-circuit or spark-gap), or may be caused from a wrong design or manufacture (such as the lack of a proper heat dissipation system).
Due to accumulation of heat, the system reaches an equilibrium of heat accumulation vs. dissipation at a much higher temperature than expected. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, momentum theory or disk actuator theory is a theory describing a mathematical model of an ideal actuator disk, such as a propeller or helicopter rotor, by W.J.M. Rankine (1865), Alfred George Greenhill (1888) and Robert Edmund Froude (1889).
The rotor is modeled as an infinitely thin disc, inducing a constant velocity along the axis of rotation. The basic state of a helicopter is hovering. This disc creates a flow around the rotor. Under certain mathematical premises of the fluid, there can be extracted a mathematical connection between power, radius of the rotor, torque and induced velocity. Friction is not included.
For a stationary open rotor with no outer duct, such as a helicopter in hover, the power required to produce a given thrust is:
where:
* T is the thrust
* is the density of air (or other medium)
* A is the area of the rotor disc
* P is power
A device which converts the translational energy of the fluid into rotational energy of the axis or vice versa is called a Rankine disk actuator. The real life implementations of such devices include marine and aviation propellers, windmills, helicopter rotors, centrifugal pumps, wind turbines, turbochargers and chemical agitators. | 1 | Applied and Interdisciplinary Chemistry |
The function of the active zone is to ensure that neurotransmitters can be reliably released in a specific location of a neuron and only released when the neuron fires an action potential.
As an action potential propagates down an axon it reaches the axon terminal called the presynaptic bouton. In the presynaptic bouton, the action potential activates calcium channels (VDCCs) that cause a local influx of calcium. The increase in calcium is detected by proteins in the active zone and forces vesicles containing neurotransmitter to fuse with the membrane. This fusion of the vesicles with the membrane releases the neurotransmitters into the synaptic cleft (space between the presynaptic bouton and the postsynaptic membrane). The neurotransmitters then diffuse across the cleft and bind to ligand gated ion channels and G-protein coupled receptors on the postsynaptic membrane. The binding of neurotransmitters to the postsynaptic receptors then induces a change in the postsynaptic neuron. The process of releasing neurotransmitters and binding to the postsynaptic receptors to cause a change in the postsynaptic neuron is called neurotransmission. | 1 | Applied and Interdisciplinary Chemistry |
The exact compounds an organism is exposed to will be largely unpredictable, and may differ widely over time; these are major characteristics of xenobiotic toxic stress. The major challenge faced by xenobiotic detoxification systems is that they must be able to remove the almost-limitless number of xenobiotic compounds from the complex mixture of chemicals involved in normal metabolism. The solution that has evolved to address this problem is an elegant combination of physical barriers and low-specificity enzymatic systems.
All organisms use cell membranes as hydrophobic permeability barriers to control access to their internal environment. Polar compounds cannot diffuse across these cell membranes, and the uptake of useful molecules is mediated through transport proteins that specifically select substrates from the extracellular mixture. This selective uptake means that most hydrophilic molecules cannot enter cells, since they are not recognised by any specific transporters. In contrast, the diffusion of hydrophobic compounds across these barriers cannot be controlled, and organisms, therefore, cannot exclude lipid-soluble xenobiotics using membrane barriers.
However, the existence of a permeability barrier means that organisms were able to evolve detoxification systems that exploit the hydrophobicity common to membrane-permeable xenobiotics. These systems therefore solve the specificity problem by possessing such broad substrate specificities that they metabolise almost any non-polar compound. Useful metabolites are excluded since they are polar, and in general contain one or more charged groups.
The detoxification of the reactive by-products of normal metabolism cannot be achieved by the systems outlined above, because these species are derived from normal cellular constituents and usually share their polar characteristics. However, since these compounds are few in number, specific enzymes can recognize and remove them. Examples of these specific detoxification systems are the glyoxalase system, which removes the reactive aldehyde methylglyoxal, and the various antioxidant systems that eliminate reactive oxygen species. | 1 | Applied and Interdisciplinary Chemistry |
Ampicillin is contraindicated in those with a hypersensitivity to penicillins, as they can cause fatal anaphylactic reactions. Hypersensitivity reactions can include frequent skin rashes and hives, exfoliative dermatitis, erythema multiforme, and a temporary decrease in both red and white blood cells.
Ampicillin is not recommended in people with concurrent mononucleosis, as over 40% of patients develop a skin rash. | 0 | Theoretical and Fundamental Chemistry |
Amoxicillin is effective for treatment of early cutaneous Lyme borreliosis; the effectiveness and safety of oral amoxicillin is neither better nor worse than common alternatively-used antibiotics. | 0 | Theoretical and Fundamental Chemistry |
A Taylor–Couette system can create laminar flows in which concentric cylinders of fluid move past each other in an apparent spiral. A fluid such as corn syrup with high viscosity fills the gap between two cylinders, with colored regions of the fluid visible through the transparent outer cylinder.
The cylinders are rotated relative to one another at a low speed, which together with the high viscosity of the fluid and thinness of the gap gives a low Reynolds number, so that the apparent mixing of colors is actually laminar and can then be reversed to approximately the initial state. This creates a dramatic demonstration of seemingly mixing a fluid and then unmixing it by reversing the direction of the mixer. | 1 | Applied and Interdisciplinary Chemistry |
Kevin Cherry and Lulu Qian at Caltech developed a DNA-based artificial neural network that can recognize 100-bit hand-written digits. They achieve this by programming on computer in advance with appropriate set of weights represented by varying concentrations weight molecules which will later be added to the test tube that holds the input DNA strands. | 1 | Applied and Interdisciplinary Chemistry |
In biology, a probe is a single strand of DNA or RNA that is complementary to a nucleotide sequence of interest.
RNA probes can be designed for any gene or any sequence within a gene for visualization of mRNA, lncRNA and miRNA in tissues and cells. FISH is used by examining the cellular reproduction cycle, specifically interphase of the nuclei for any chromosomal abnormalities. FISH allows the analysis of a large series of archival cases much easier to identify the pinpointed chromosome by creating a probe with an artificial chromosomal foundation that will attract similar chromosomes. The hybridization signals for each probe when a nucleic abnormality is detected. Each probe for the detection of mRNA and lncRNA is composed of ~20-50 oligonucleotide pairs, each pair covering a space of 40–50 bp. The specifics depend on the specific FISH technique used. For miRNA detection, the probes use proprietary chemistry for specific detection of miRNA and cover the entire miRNA sequence.
Probes are often derived from fragments of DNA that were isolated, purified, and amplified for use in the Human Genome Project. The size of the human genome is so large, compared to the length that could be sequenced directly, that it was necessary to divide the genome into fragments. (In the eventual analysis, these fragments were put into order by digesting a copy of each fragment into still smaller fragments using sequence-specific endonucleases, measuring the size of each small fragment using size-exclusion chromatography, and using that information to determine where the large fragments overlapped one another.) To preserve the fragments with their individual DNA sequences, the fragments were added into a system of continually replicating bacteria populations. Clonal populations of bacteria, each population maintaining a single artificial chromosome, are stored in various laboratories around the world. The artificial chromosomes (BAC) can be grown, extracted, and labeled, in any lab containing a library. Genomic libraries are often named after the institution in which they were developed. An example being the RPCI-11 library, which is named after Roswell Park Comprehensive Cancer Center (formerly known as Roswell Park Cancer Institute) in Buffalo, New York. These fragments are on the order of 100 thousand base-pairs, and are the basis for most FISH probes. | 1 | Applied and Interdisciplinary Chemistry |
Chromatography methods changed little after Tsvets work until the explosion of mid-20th century research in new techniques, particularly thanks to the work of Archer John Porter Martin and Richard Laurence Millington Synge. By "the marrying of two techniques, that of chromatography and that of countercurrent solvent extraction", Martin and Synge developed partition chromatography to separate chemicals with only slight differences in partition coefficients between two liquid solvents. Martin, who had previously been working in vitamin chemistry (including attempts to purify vitamin E), began collaborating with Synge in 1938, brought his experience with equipment design to Synges project of separating amino acids. After unsuccessful experiments with complex countercurrent extraction machines and liquid-liquid chromatography methods where the liquids move in opposite directions, Martin hit on the idea of using silica gel in columns to hold water stationary while an organic solvent flows through the column. Martin and Synge demonstrated the potential of the methods by separating amino acids marked in the column by the addition of methyl red. In a series of publications beginning in 1941, they described increasingly powerful methods of separating amino acids and other organic chemicals.
In pursuit of better and easier methods of identifying the amino acid constituents of peptides, Martin and Synge turned to other chromatography media as well. A short abstract in 1943 followed by a detailed article in 1944 described the use of filter paper as the stationary phase for performing chromatography on amino acids: paper chromatography. By 1947, Martin, Synge and their collaborators had applied this method (along with Fred Sangers reagent for identifying N-terminal residues) to determine the pentapeptide sequence of Gramicidin S. These and related paper chromatography methods were also foundational to Fred Sangers effort to determine the amino acid sequence of insulin. | 1 | Applied and Interdisciplinary Chemistry |
Several single nucleotide polymorphisms within the TCF7L2 gene have been associated with type 2 diabetes. Studies conducted by Ravindranath Duggirala and Michael Stern at The University of Texas Health Science Center at San Antonio were the first to identify strong linkage for type 2 diabetes at a region on Chromosome 10 in Mexican Americans This signal was later refined by Struan Grant and colleagues at DeCODE genetics and isolated to the TCF7L2 gene. The molecular and physiological mechanisms underlying the association of TCF7L2 with type 2 diabetes are under active investigation, but it is likely that TCF7L2 has important biological roles in multiple metabolic tissues, including the pancreas, liver and adipose tissue. TCF7L2 polymorphisms can increase susceptibility to type 2 diabetes by decreasing the production of glucagon-like peptide-1 (GLP-1). | 1 | Applied and Interdisciplinary Chemistry |
The heterometallic copper-aluminum superatom is a Mackay‐Type Cluster with formula [CuAl](Cp*). It is an open‐shell 67‐electron superatom.
At the time of its synthesis, it was the largest superatom to be synthesized. Its two distinct features are its large electron count compared to other heterometallic superatoms and its unprecedented electron structure of an open-shell configuration.
This is the very first example of a ligated heterometallic Mackay-type cluster, which is an extremely complex crystal structure whose surface is composed of two-shell 20 equilateral triangles composed of 55 copper and aluminum atoms. This shape is also called an icosahedron. The 43 copper and 12 aluminum atoms form a superatom by the metals forming a shared electron shell that resembles a single metal atom. Through magnetic data and analysis at the DFT level it shows that this superatom has a very unique electronic structure of the cluster which is a 67-electron open jellium shell [CuAl] core, protected by twelve Cp* ligands. These crystals have the chemical properties of individual copper atoms. They are attracted by a magnetic field, or paramagnetic due to three valence electrons in the outermost shell whose spin align themselves in a magnetic field. Another property of this compound is that it is pyrophoric, or can ignite spontaneously when exposed to air, so it is highly sensitive to the air and moisture. Also, this compound cannot be re-dissolved in any solvent without decomposition, which means extensive characterization of the compound cannot be obtained with high-resolution mass spectrometry or solution NMR spectroscopy. Thus X-ray diffraction structural analysis of the data obtained does not meet the accepted high-quality requirements, due to the compound forming relatively small, weakly diffracting cubes when using single crystals. | 0 | Theoretical and Fundamental Chemistry |
Catalysts that promote chain walking were discovered in the 1980-1990s. Nickel(II) and palladium(II) complexes of α-diimine ligands were known to efficiently catalyze polymerization of alkenes. They are also referred as Brookhart's catalysts after being used for making of high molar mass polyolefins for the first time at University of North Carolina at Chapel Hill in 1995. Currently nickel and palladium complexes bearing α-diimine ligands, such as the two examples shown, are the most thoroughly described chain walking catalysts in scientific literature. Ligand design influences not only CW extent but also regio- and stereoselectivity and also the sensitivity of the catalyst to undergo chain-breaking reactions, mainly β-H elimination, influencing achievable molar mass and also the possibility to achieve living polymerization behaviour. Thus stereo block copolymers could be made by combination of living and stereospecific CW polymerization catalysts. Continuous research effort led to design of other ligands which provide CW polymerization catalysts upon complexation to late transition metals. Examples are β-diimine, α-keto-β-diimine, amine-imine and most recently diamine ligands. As the vast majority of CW polymerization catalysts is based on late-transition metal complexes, having generally lower oxophilicity, these complexes were demonstrated also to provide copolymerisation of olefins with polar monomers like acrylates, alkylvinylketones, ω-alken-1-ols, ω-alken-1-carboxylic acids etc., which was the main initial intention of development of this class of catalysts. These random copolymers could further be utilized in the construction of sophisticated amphiphilic grafted copolymers with hydrophobic polyolefin core and shell based on hydrophilic arms, in some cases made of stimuli-responsive polymers. | 0 | Theoretical and Fundamental Chemistry |
Monochromators are often calibrated in units of wavelength. Uniform rotation of a grating produces a sinusoidal change in wavelength, which is approximately linear for small grating angles, so such an instrument is easy to build. Many of the underlying physical phenomena being studied are linear in energy though, and since wavelength and photon energy have a reciprocal relationship, spectral patterns that are simple and predictable when plotted as a function of energy are distorted when plotted as a function of wavelength. Some monochromators are calibrated in units of reciprocal centimeters or some other energy units, but the scale may not be linear. | 0 | Theoretical and Fundamental Chemistry |
The 1963 Nobel Prize in Chemistry was awarded to German Karl Ziegler, for his discovery of first titanium-based catalysts, and Italian Giulio Natta, for using them to prepare stereoregular polymers from propylene. Ziegler–Natta catalysts have been used in the commercial manufacture of various polyolefins since 1956. As of 2010, the total volume of plastics, elastomers, and rubbers produced from alkenes with these and related (especially Phillips) catalysts worldwide exceeds 100 million tonnes. Together, these polymers represent the largest-volume commodity plastics as well as the largest-volume commodity chemicals in the world.
In the early 1950s workers at Phillips Petroleum discovered that chromium catalysts are highly effective for the low-temperature polymerization of ethylene, which launched major industrial technologies culminating in the Phillips catalyst. A few years later, Ziegler discovered that a combination of titanium tetrachloride (TiCl) and diethylaluminium chloride (Al(CH)Cl) gave comparable activities for the production of polyethylene. Natta used crystalline α-TiCl in combination with Al(CH) to produce first isotactic polypropylene. Usually Ziegler catalysts refer to titanium-based systems for conversions of ethylene and Ziegler–Natta catalysts refer to systems for conversions of propylene.
Also, in the 1960s, BASF developed a gas-phase, mechanically-stirred polymerization process for making polypropylene. In that process, the particle bed in the reactor was either not fluidized or not fully fluidized. In 1968, the first gas-phase fluidized-bed polymerization process, the Unipol process, was commercialized by Union Carbide to produce polyethylene. In the mid-1980s, the Unipol process was further extended to produce polypropylene.
In the 1970s, magnesium chloride (MgCl) was discovered to greatly enhance the activity of the titanium-based catalysts. These catalysts were so active that the removal of unwanted amorphous polymer and residual titanium from the product (so-called deashing) was no longer necessary, enabling the commercialization of linear low-density polyethylene (LLDPE) resins and allowed the development of fully amorphous copolymers.
The fluidized-bed process remains one of the two most widely used processes for producing polypropylene. | 0 | Theoretical and Fundamental Chemistry |
The Fenna–Matthews–Olson (FMO) complex is a water-soluble complex and was the first pigment-protein complex (PPC) to be structure analyzed by x-ray spectroscopy. It appears in green sulfur bacteria and mediates the excitation energy transfer from light-harvesting chlorosomes to the membrane-embedded bacterial reaction center (bRC). Its structure is trimeric (C3-symmetry). Each of the three monomers contains eight bacteriochlorophyll a (BChl a) molecules. They are bound to the protein scaffold via chelation of their central magnesium atom either to amino acids of the protein (mostly histidine) or water-bridged oxygen atoms (only one BChl a of each monomer).
Since the structure is available, calculating structure-based optical spectra is possible for comparison with experimental optical spectra. In the simplest case only the excitonic coupling of the BChls is taken into account. More realistic theories consider pigment-protein coupling. An important property is the local transition energy (site energy) of the BChls, different for each, due to their individual local protein environment. The site energies of the BChls determine the direction of the energy flow.
Some structural information on the FMO-RC super complex is available, which was obtained by electron microscopy and linear dichroism spectra measured on FMO trimers and FMO-RC complexes. From these measurements, two orientations of the FMO complex relative to the RC are possible. The orientation with BChl 3 and 4 close to the RC and BChl 1 and 6 (following Fenna and Matthews' original numbering) oriented towards the chlorosomes is useful for efficient energy transfer. | 0 | Theoretical and Fundamental Chemistry |
* On Fate, translated by D.P. Curtin (Philadelphia, PA: Dalcassian Publishing Company: 2023) [translation of De fato]
* On Resurrection, translated by Irven M. Resnick and Franklin T. Harkins (Washington, D.C.: Catholic University of America Press: 2020) [translation of De resurrectione]
* On the Body of the Lord, translated by Sr. Albert Marie Surmanski, OP (Washington, D.C.: Catholic University of America Press: 2017) [translation of De corpore Domini]
* On the Causes of the Properties of the Elements, translated by Irven M. Resnick (Milwaukee: Marquette University Press, 2010) [translation of Liber de causis proprietatum elementorum]
* Questions concerning Aristotles on Animals, translated by Irven M. Resnick and Kenneth F. Kitchell Jr. (Washington, D.C.: Catholic University of America Press, 2008) [translation of Quaestiones super De animalibus']
* The Cardinal Virtues: Aquinas, Albert, and Philip the Chancellor, translated by R. E. Houser (Toronto: Pontifical Institute of Mediæval Studies, 2004) [contains the translations of Parisian Summa, part six: On the good and Commentary on the Sentences of Peter Lombard, book 3, dist. 33 & 36]
* The Commentary of Albertus Magnus on Book 1 of Euclids Elements of Geometry, edited by Anthony Lo Bello (Boston: Brill Academic Publishers, 2003) [translation of Priumus Euclidis cum commento Alberti']
* On Animals: A Medieval Summa Zoologica, translated by Kenneth F. Kitchell Jr. and Irven Michael Resnick (Baltimore; London: Johns Hopkins University Press, 1999) [translation of De animalibus]
* Paola Zambelli, The Speculum Astronomiae and Its Enigma: Astrology, Theology, and Science in Albertus Magnus and His Contemporaries (Dordrecht; Boston: Kluwer Academic Publishers, 1992) [includes Latin text and English translation of Speculum astronomiae]
* Albert & Thomas: Selected Writings, translated by Simon Tugwell, Classics of Western Spirituality (New York: Paulist Press, 1988) [contains translation of Super Dionysii Mysticam theologiam]
* On Union with God, translated by a Benedictine of Princethorpe Priory (London: Burns Oates & Washbourne, 1911) [reprinted as (Felinfach: Llanerch Enterprises, 1991) and (London: Continuum, 2000)] [translation of De adherendo Deo] | 1 | Applied and Interdisciplinary Chemistry |
Many gels display thixotropy – they become fluid when agitated, but resolidify when resting.
In general, gels are apparently solid, jelly-like materials. It is a type of non-Newtonian fluid.
By replacing the liquid with gas it is possible to prepare aerogels, materials with exceptional properties including very low density, high specific surface areas, and excellent thermal insulation properties. | 0 | Theoretical and Fundamental Chemistry |
Most I production is from neutron irradiation of a natural tellurium target in a nuclear reactor. Irradiation of natural tellurium produces almost entirely I as the only radionuclide with a half-life longer than hours, since most lighter isotopes of tellurium become heavier stable isotopes, or else stable iodine or xenon. However, the heaviest naturally occurring tellurium nuclide, Te (34% of natural tellurium) absorbs a neutron to become tellurium-131, which beta decays with a half-life of 25 minutes to I.
A tellurium compound can be irradiated while bound as an oxide to an ion exchange column, with evolved I then eluted into an alkaline solution. More commonly, powdered elemental tellurium is irradiated and then I separated from it by dry distillation of the iodine, which has a far higher vapor pressure. The element is then dissolved in a mildly alkaline solution in the standard manner, to produce I as iodide and hypoiodate (which is soon reduced to iodide).
I is a fission product with a yield of 2.878% from uranium-235, and can be released in nuclear weapons tests and nuclear accidents. However, the short half-life means it is not present in significant quantities in cooled spent nuclear fuel, unlike iodine-129 whose half-life is nearly a billion times that of I.
It is discharged to the atmosphere in small quantities by some nuclear power plants. | 0 | Theoretical and Fundamental Chemistry |
Cryptophane cages are formed by two cup-shaped orthocyclophane units (see cyclotriveratrylene), connected by three bridges (denoted Y). There are also choices of the peripheral substitutes R1 and R2 attached to the aromatic rings of the units. Most cryptophanes exhibit two diastereomeric forms (syn and anti), distinguished by their symmetry type. This general scheme offers a variety of choices (Y, R1, R2, and symmetry type) by which the shape, volume and chemical properties of the generally hydrophobic pocket inside the cage can be modified, making cryptophanes suitable for encapsulating many types of small molecules and even chemical reactions. | 0 | Theoretical and Fundamental Chemistry |
Gaian hypotheses suggest that organisms co-evolve with their environment: that is, they "influence their abiotic environment, and that environment in turn influences the biota by Darwinian process". Lovelock (1995) gave evidence of this in his second book, Ages of Gaia, showing the evolution from the world of the early thermo-acido-philic and methanogenic bacteria towards the oxygen-enriched atmosphere today that supports more complex life.
A reduced version of the hypothesis has been called "influential Gaia" in "Directed Evolution of the Biosphere: Biogeochemical Selection or Gaia?" by Andrei G. Lapenis, which states the biota influence certain aspects of the abiotic world, e.g. temperature and atmosphere. This is not the work of an individual but a collective of Russian scientific research that was combined into this peer-reviewed publication. It states the coevolution of life and the environment through "micro-forces" and biogeochemical processes. An example is how the activity of photosynthetic bacteria during Precambrian times completely modified the Earth atmosphere to turn it aerobic, and thus supports the evolution of life (in particular eukaryotic life).
Since barriers existed throughout the twentieth century between Russia and the rest of the world, it is only relatively recently that the early Russian scientists who introduced concepts overlapping the Gaia paradigm have become better known to the Western scientific community. These scientists include Piotr Alekseevich Kropotkin (1842–1921) (although he spent much of his professional life outside Russia), Rafail Vasil’evich Rizpolozhensky (1862 – c. 1922), Vladimir Ivanovich Vernadsky (1863–1945), and Vladimir Alexandrovich Kostitzin (1886–1963).
Biologists and Earth scientists usually view the factors that stabilize the characteristics of a period as an undirected emergent property or entelechy of the system; as each individual species pursues its own self-interest, for example, their combined actions may have counterbalancing effects on environmental change. Opponents of this view sometimes reference examples of events that resulted in dramatic change rather than stable equilibrium, such as the conversion of the Earth's atmosphere from a reducing environment to an oxygen-rich one at the end of the Archaean and the beginning of the Proterozoic periods.
Less accepted versions of the hypothesis claim that changes in the biosphere are brought about through the coordination of living organisms and maintain those conditions through homeostasis. In some versions of Gaia philosophy, all lifeforms are considered part of one single living planetary being called Gaia. In this view, the atmosphere, the seas and the terrestrial crust would be results of interventions carried out by Gaia through the coevolving diversity of living organisms.
The Gaia paradigm was an influence on the deep ecology movement. | 0 | Theoretical and Fundamental Chemistry |
*Albert Lasker Award for Clinical Medical Research, 1984
*General Motors Cancer Research Foundation Kettering Prize, 1985
*Gairdner Foundation International Award, 1985
*The Harvey Prize, 1986
*National Medal of Science, 1987
*Pittsburgh Spectroscopy Award, 1987
*National Medal of Technology, 1988, (with Raymond Damadian)
*Bower Award, Franklin Institute of Philadelphia, 1990 (first recipient)
*Carnegie Mellon Dickson Prize in Science in 1993.
*NAS Award for Chemistry in Service to Society of the National Academy of Sciences, 2001
*Charter member, Phi Kappa Tau Hall of Fame in 2006.
*National Inventors Hall of Fame, class of 2007
*Asteroid 255598 Paullauterbur, discovered by Italian amateur astronomer Silvano Casulli in 2006, was named in his honor. The official was published by the Minor Planet Center on January 12, 2017 ().
*Stony Brook University named a student residence after Lauterbur in 2010. | 0 | Theoretical and Fundamental Chemistry |
*Alloway B.V., Larsen G., Lowe D.J., Shane P.A.R., Westgate J.A. (2007). "Tephrochronology", Encyclopedia of Quaternary Science (editor—Elias S.A.) 2869–2869 (Elsevier).
*Þórarinsson S. (1970). "Tephrochronology in medieval Iceland", Scientific Methods in Medieval Archaeology (ed. R. Berger) 295–328 (Berkeley: University of California Press). | 0 | Theoretical and Fundamental Chemistry |
The first stereographic projection defined in the preceding section sends the "south pole" (0, 0, −1) of the unit sphere to (0, 0), the equator to the unit circle, the southern hemisphere to the region inside the circle, and the northern hemisphere to the region outside the circle.
The projection is not defined at the projection point = (0, 0, 1). Small neighborhoods of this point are sent to subsets of the plane far away from (0, 0). The closer is to (0, 0, 1), the more distant its image is from (0, 0) in the plane. For this reason it is common to speak of (0, 0, 1) as mapping to "infinity" in the plane, and of the sphere as completing the plane by adding a point at infinity. This notion finds utility in projective geometry and complex analysis. On a merely topological level, it illustrates how the sphere is homeomorphic to the one-point compactification of the plane.
In Cartesian coordinates a point on the sphere and its image on the plane either both are rational points or none of them:
Stereographic projection is conformal, meaning that it preserves the angles at which curves cross each other (see figures). On the other hand, stereographic projection does not preserve area; in general, the area of a region of the sphere does not equal the area of its projection onto the plane. The area element is given in coordinates by
Along the unit circle, where , there is no inflation of area in the limit, giving a scale factor of 1. Near (0, 0) areas are inflated by a factor of 4, and near infinity areas are inflated by arbitrarily small factors.
The metric is given in coordinates by
and is the unique formula found in Bernhard Riemanns Habilitationsschrift on the foundations of geometry, delivered at Göttingen in 1854, and entitled Über die Hypothesen welche der Geometrie zu Grunde liegen'.
No map from the sphere to the plane can be both conformal and area-preserving. If it were, then it would be a local isometry and would preserve Gaussian curvature. The sphere and the plane have different Gaussian curvatures, so this is impossible.
Circles on the sphere that do not pass through the point of projection are projected to circles on the plane. Circles on the sphere that do pass through the point of projection are projected to straight lines on the plane. These lines are sometimes thought of as circles through the point at infinity, or circles of infinite radius. These properties can be verified by using the expressions of in terms of given in : using these expressions for a substitution in the equation of the plane containing a circle on the sphere, and clearing denominators, one gets the equation of a circle, that is, a second-degree equation with as its quadratic part. The equation becomes linear if that is, if the plane passes through the point of projection.
All lines in the plane, when transformed to circles on the sphere by the inverse of stereographic projection, meet at the projection point. Parallel lines, which do not intersect in the plane, are transformed to circles tangent at projection point. Intersecting lines are transformed to circles that intersect transversally at two points in the sphere, one of which is the projection point. (Similar remarks hold about the real projective plane, but the intersection relationships are different there.)
The loxodromes of the sphere map to curves on the plane of the form
where the parameter measures the "tightness" of the loxodrome. Thus loxodromes correspond to logarithmic spirals. These spirals intersect radial lines in the plane at equal angles, just as the loxodromes intersect meridians on the sphere at equal angles.
The stereographic projection relates to the plane inversion in a simple way. Let and be two points on the sphere with projections and on the plane. Then and are inversive images of each other in the image of the equatorial circle if and only if and are reflections of each other in the equatorial plane.
In other words, if:
* is a point on the sphere, but not a north pole and not its antipode, the south pole ,
* is the image of in a stereographic projection with the projection point and
* is the image of in a stereographic projection with the projection point ,
then and are inversive images of each other in the unit circle. | 0 | Theoretical and Fundamental Chemistry |
Lithotrophs are a diverse group of organisms using an inorganic substrate (usually of mineral origin) to obtain reducing equivalents for use in biosynthesis (e.g., carbon dioxide fixation) or energy conservation (i.e., ATP production) via aerobic or anaerobic respiration. While lithotrophs in the broader sense include photolithotrophs like plants, chemolithotrophs are exclusively microorganisms; no known macrofauna possesses the ability to use inorganic compounds as electron sources. Macrofauna and lithotrophs can form symbiotic relationships, in which case the lithotrophs are called "prokaryotic symbionts". An example of this is chemolithotrophic bacteria in giant tube worms or plastids, which are organelles within plant cells that may have evolved from photolithotrophic cyanobacteria-like organisms. Chemolithotrophs belong to the domains Bacteria and Archaea. The term "lithotroph" was created from the Greek terms lithos (rock) and troph (consumer), meaning "eaters of rock". Many but not all lithoautotrophs are extremophiles.
The last universal common ancestor of life is thought to be a chemolithotroph (due to its presence in the prokaryotes). Different from a lithotroph is an organotroph, an organism which obtains its reducing agents from the catabolism of organic compounds. | 1 | Applied and Interdisciplinary Chemistry |
Hydroxamic acids are used extensively in flotation of rare earth minerals during the concentration and extraction of ores to be subjected to further processing.
Some hydroxamic acids (e.g. vorinostat, belinostat, panobinostat, and trichostatin A) are HDAC inhibitors with anti-cancer properties. Fosmidomycin is a natural hydroxamic acid inhibitor of 1-deoxy--xylulose-5-phosphate reductoisomerase (DXP reductoisomerase). Hydroxamic acids have also been investigated for reprocessing of irradiated fuel. | 0 | Theoretical and Fundamental Chemistry |
The system can be adapted for situations where environmental or clinical pathogens require monitoring. For example, APDS could test for mold or fungal spores in buildings or for the airborne spread of contagious materials in hospitals. It also could identify disease outbreaks in livestock transport centers or feedlots. In water, APDS can detect pathogens in wastewater, agricultural irrigation lines, food processors, fish farms, and beaches. | 0 | Theoretical and Fundamental Chemistry |
Campbell was born in Waimate on 27 May 1925, the son of Mona Sevicke Campbell (née Jones) and David Brown Campbell. He was educated at Waimate High School, and then proceeded to study chemistry at the University of Otago, graduating Master of Science with second-class honours in 1948, and PhD in 1953. His doctoral thesis was titled Some applications of acrylonitrile.
In 1950, Campbell married Ruth Florence Smith, and the couple went on to have three children. | 0 | Theoretical and Fundamental Chemistry |
Sulfides, formerly known as thioethers, are characterized by C−S−C bonds Relative to C−C bonds, C−S bonds are both longer, because sulfur atoms are larger than carbon atoms, and about 10% weaker. Representative bond lengths in sulfur compounds are 183 pm for the S−C single bond in methanethiol and 173 pm in thiophene. The C−S bond dissociation energy for thiomethane is 89 kcal/mol (370 kJ/mol) compared to methane's 100 kcal/mol (420 kJ/mol) and when hydrogen is replaced by a methyl group the energy decreases to 73 kcal/mol (305 kJ/mol). The single carbon to oxygen bond is shorter than that of the C−C bond. The bond dissociation energies for dimethyl sulfide and dimethyl ether are respectively 73 and 77 kcal/mol (305 and 322 kJ/mol).
Sulfides are typically prepared by alkylation of thiols. Alkylating agents include not only alkyl halides, but also epoxides, aziridines, and Michael acceptors.
They can also be prepared via the Pummerer rearrangement.
In the Ferrario reaction, phenyl ether is converted to phenoxathiin by action of elemental sulfur and aluminium chloride.
Thioacetals and thioketals feature C−S−C−S−C bond sequence. They represent a subclass of sulfides. The thioacetals are useful in "umpolung" of carbonyl groups. Thioacetals and thioketals can also be used to protect a carbonyl group in organic syntheses.
The above classes of sulfur compounds also exist in saturated and unsaturated heterocyclic structures, often in combination with other heteroatoms, as illustrated by thiiranes, thiirenes, thietanes, thietes, dithietanes, thiolanes, thianes, dithianes, thiepanes, thiepines, thiazoles, isothiazoles, and thiophenes, among others. The latter three compounds represent a special class of sulfur-containing heterocycles that are aromatic. The resonance stabilization of thiophene is 29 kcal/mol (121 kJ/mol) compared to 20 kcal/mol (84 kJ/mol) for the oxygen analogue furan. The reason for this difference is the higher electronegativity for oxygen drawing away electrons to itself at the expense of the aromatic ring current. Yet as an aromatic substituent the thio group is less electron-releasing than the alkoxy group. Dibenzothiophenes (see drawing), tricyclic heterocycles consisting of two benzene rings fused to a central thiophene ring, occurs widely in heavier fractions of petroleum. | 0 | Theoretical and Fundamental Chemistry |
Nucleation is the formation and growth of a new phase with or without the presence of external surface. The presence of this surface results in heterogeneous nucleation whereas in its absence homogeneous nucleation occurs. Heterogeneous nucleation occurs in cases where there are pre-existing nuclei present, such as tiny dust particles suspended in a liquid or gas or reacting with a glass surface containing . For the process of Hoffman nucleation and its progression to Lauritzen–Hoffman growth theory, homogeneous nucleation is the main focus. Homogeneous nucleation occurs where no such contaminants are present and is less commonly seen. Homogeneous nucleation begins with small clusters of molecules forming from one phase to the next. As the clusters grow, they aggregate through the condensation of other molecules. The size continues to increase and ultimately form macroscopic droplets (or bubbles depending on the system).
Nucleation is often described mathematically through the change in Gibbs free energy of n moles of vapor at vapor pressure P that condenses into a drop. Also the nucleation barrier, in polymer crystallization, consists of both enthalpic and entropic components that must be over come. This barrier consists of selection processes taking place in different length and time scales which relates to the multiple regimes later on. This barrier is the free energy required to overcome in order to form nuclei. It is the formation of the nuclei from the bulk to a surface that is the interfacial free energy. The interfacial free energy is always a positive term and acts to destabilize the nucleus allowing the continuation of the growing polymer chain. The nucleation continues as a favorable reaction. | 0 | Theoretical and Fundamental Chemistry |
Bromine is present naturally as bromide salts in evaporite deposits. Bromine is also present in soils and in marine algae that synthesize organic bromine compounds. Other natural sources of bromine come from polar regions, salt lakes, and volcanoes.
The primary natural source of bromine to the atmosphere is sea spray aerosols. Smaller fluxes originate from volcanic emissions and biomass burning. The primary atmospheric sinks are sea spray deposition and photochemical reactions, which release gaseous bromine. | 0 | Theoretical and Fundamental Chemistry |
If analytes are too small to generate a readable signal for determining concentration, the assay matrix can be modified. CD/DVD based assays utilize the optical properties of gold. Gold nanoparticle bioconjugates are tracers used to increase the sensitivity of the assay. The gold nanoparticles can be identified with photometric or plasmonic detectors. The smaller the nanoparticles are, the more sensitive the assay becomes.
Silver enhancer solution is also used to increase the reflective properties of samples. Gold nanoparticles have catalytic properties which cause them to reduce silver ions to silver metal. The silver metal deposits on the analytes and causes signals to be amplified. Silver metal is more easily detectable by cameras, scanners, or other drives than is the analyte alone. Still, this enhancement procedure requires many additional reaction and washing steps which could lead to analytical errors. | 1 | Applied and Interdisciplinary Chemistry |
In molecular genetics, the three prime untranslated region (3′-UTR) is the section of messenger RNA (mRNA) that immediately follows the translation termination codon. The 3′-UTR often contains regulatory regions that post-transcriptionally influence gene expression.
During gene expression, an mRNA molecule is transcribed from the DNA sequence and is later translated into a protein. Several regions of the mRNA molecule are not translated into a protein including the 5 cap, 5 untranslated region, 3′ untranslated region and poly(A) tail. Regulatory regions within the 3′-untranslated region can influence polyadenylation, translation efficiency, localization, and stability of the mRNA. The 3′-UTR contains binding sites for both regulatory proteins and microRNAs (miRNAs). By binding to specific sites within the 3′-UTR, miRNAs can decrease gene expression of various mRNAs by either inhibiting translation or directly causing degradation of the transcript. The 3′-UTR also has silencer regions which bind to repressor proteins and will inhibit the expression of the mRNA.
Many 3′-UTRs also contain AU-rich elements (AREs). Proteins bind AREs to affect the stability or decay rate of transcripts in a localized manner or affect translation initiation. Furthermore, the 3′-UTR contains the sequence AAUAAA that directs addition of several hundred adenine residues called the poly(A) tail to the end of the mRNA transcript. Poly(A) binding protein (PABP) binds to this tail, contributing to regulation of mRNA translation, stability, and export. For example, poly(A) tail bound PABP interacts with proteins associated with the 5' end of the transcript, causing a circularization of the mRNA that promotes translation.
The 3′-UTR can also contain sequences that attract proteins to associate the mRNA with the cytoskeleton, transport it to or from the cell nucleus, or perform other types of localization. In addition to sequences within the 3′-UTR, the physical characteristics of the region, including its length and secondary structure, contribute to translation regulation. These diverse mechanisms of gene regulation ensure that the correct genes are expressed in the correct cells at the appropriate times. | 1 | Applied and Interdisciplinary Chemistry |
A significant amount of the energy released by fusion reactions is composed of electromagnetic radiation, essentially X-rays due to Bremsstrahlung. Those X-rays can not be converted into electric power with the various electrostatic and magnetic direct energy converters listed above, and their energy is lost.
Whereas more classical thermal conversion has been considered with the use of a radiation/boiler/energy exchanger where the X-ray energy is absorbed by a working fluid at temperatures of several thousand degrees, more recent research done by companies developing nuclear aneutronic fusion reactors, like Lawrenceville Plasma Physics (LPP) with the Dense Plasma Focus, and Tri Alpha Energy, Inc. with the Colliding Beam Fusion Reactor (CBFR), plan to harness the photoelectric and Auger effects to recover energy carried by X-rays and other high-energy photons. Those photoelectric converters are composed of X-ray absorber and electron collector sheets nested concentrically in an onion-like array. Indeed, since X-rays can go through far greater thickness of material than electrons can, many layers are needed to absorb most of the X-rays. LPP announces an overall efficiency of 81% for the photoelectric conversion scheme. | 0 | Theoretical and Fundamental Chemistry |
In order to derive the properties of an Ekman spiral a look is taken at a uniform, horizontal geostrophic interior flow in a homogeneous fluid. This flow will be denoted by , where the two components are constant because of uniformity. Another result of this property is that the horizontal gradients will equal zero. As a result, the continuity equation will yield, . Note that the concerning interior flow is horizontal, so at all depths, even in the boundary layers. In this case, the Navier-Stokes momentum equations, governing geophysical motion can now be reduced to:
Where is the Coriolis parameter, the fluid density and the eddy viscosity, which are all taken as a constant here for simplicity. These parameters have a small variance on the scale of an Ekman spiral, thus this approximation will hold. A uniform flow requires a uniformly varying pressure gradient. When substituting the flow components of the interior flow, and , in the equations above, the following is obtained:
Using the last of the three equations at the top of this section, yields that the pressure is independent of depth.
and will suffice as a solution to the differential equations above. After substitution of these possible solutions in the same equations, will follow. Now, has the following possible outcomes:
Because of the no-slip condition at the bottom and the constant interior flow for , coefficients and can be determined. In the end, this will lead to the following solution for :
Here, . Note that the velocity vector will approach the values of the interior flow, when the takes the order of . This is the reason why is defined as the thickness of the Ekman layer. A number of important properties of the Ekman spiral will follow from this solution:
*When , it appears that the flow has a transverse component with respect to the interior flow, which differs 45 degrees to the left on the northern hemisphere, , and 45 degrees to the right on the southern hemisphere, . Note that, in this case, the angle between this flow and the interior flow is at its maximum. It will decrease for increasing .
*When takes the value of , the resulting flow is in line with the interior flow, but will be increased with , with respect to the interior flow.
*For higher values of , there will be a minimal transverse component in the other direction as before. The exponential term will go to zero for , resulting in . Because of these properties, the velocity vector of the flow as a function of depth will look like a spiral. | 1 | Applied and Interdisciplinary Chemistry |
Organophosphines, like phosphine itself, are pyramidal molecules with approximate C symmetry. The C–P–C bond angles are approximately 98.6°. The C–P–C bond angles are consistent with the notion that phosphorus predominantly uses the 3p orbitals for forming bonds and that there is little sp hybridization of the phosphorus atom. The latter is a common feature of the chemistry of phosphorus. As a result, the lone pair of trimethylphosphine has predominantly s-character as is the case for phosphine, PH.
Tertiary phosphines are pyramidal. When the organic substituents all differ, the phosphine is chiral and configurationally stable (in contrast to NRR'R"). Complexes derived from the chiral phosphines can catalyse reactions to give chiral, enantioenriched products. | 0 | Theoretical and Fundamental Chemistry |
Soil acidification can cause damage to plants and organisms in the soil. In plants, soil acidification results in smaller, less durable roots. Acidic soils sometimes damage the root tips reducing further growth. Plant height is impaired and seed germination also decreases. Soil acidification impacts plant health, resulting in reduced cover and lower plant density. Overall, stunted growth is seen in plants. Soil acidification is directly linked to a decline in endangered species of plants.
In the soil, acidification reduces microbial and macrofaunal diversity. This can reduce soil structure decline which makes it more sensitive to erosion. There are less nutrients available in the soil, larger impact of toxic elements to plants, and consequences to soil biological functions (such as nitrogen fixation). A recent study showed that sugarcane monoculture induces soil acidity, reduces soil fertility, shifts microbial structure, and reduces its activity. Furthermore, most beneficial bacterial genera decreased significantly due to sugarcane monoculture, while beneficial fungal genera showed a reverse trend. Therefore, mitigating soil acidity, improving soil fertility, and soil enzymatic activities, including improved microbial structure with beneficial service to plants and soil, can be an effective measure to develop a sustainable sugarcane cropping system.
At a larger scale, soil acidification is linked to losses in agricultural productivity due to these effects.
Impacts of acidic water and Soil acidification on plants could be minor or in most cases major. In minor cases which do not result in fatality of plant life include; less-sensitive plants to acidic conditions and or less potent acid rain. Also in minor cases the plant will eventually die due to the acidic water lowering the plants natural pH. Acidic water enters the plant and causes important plant minerals to dissolve and get carried away; which ultimately causes the plant to die of lack of minerals for nutrition. In major cases which are more extreme; the same process of damage occurs as in minor cases, which is removal of essential minerals, but at a much quicker rate. Likewise, acid rain that falls on soil and on plant leaves causes drying of the waxy leaf cuticle; which ultimately causes rapid water loss from the plant to the outside atmosphere and results in death of the plant. To see if a plant is being affected by soil acidification, one can closely observe the plant leaves. If the leaves are green and look healthy, the soil pH is normal and acceptable for plant life. But if the plant leaves have yellowing between the veins on their leaves, that means the plant is suffering from acidification and is unhealthy. Moreover, a plant suffering from soil acidification cannot photosynthesize. Drying out of the plant due to acidic water destroy chloroplast organelles. Without being able to photosynthesize a plant cannot create nutrients for its own survival or oxygen for the survival of aerobic organisms; which affects most species of Earth and ultimately end the purpose of the plants existence. | 0 | Theoretical and Fundamental Chemistry |
Ferrosilicon is an alloy of iron and silicon with a typical silicon content by weight of 15–90%. It contains a high proportion of iron silicides. | 1 | Applied and Interdisciplinary Chemistry |
In non-photosynthetic eukaryotes such as animals, fungi, and protozoa, as well as the class Alphaproteobacteria of bacteria, it is produced by the enzyme ALA synthase, from glycine and succinyl-CoA. This reaction is known as the Shemin pathway, which occurs in mitochondria.
In plants, algae, bacteria (except for the class Alphaproteobacteria) and archaea, it is produced from glutamic acid via glutamyl-tRNA and glutamate-1-semialdehyde. The enzymes involved in this pathway are glutamyl-tRNA synthetase, glutamyl-tRNA reductase, and glutamate-1-semialdehyde 2,1-aminomutase. This pathway is known as the C5 or Beale pathway. In most plastid-containing species, glutamyl-tRNA is encoded by a plastid gene, and the transcription, as well as the following steps of C5 pathway, take place in plastids. | 1 | Applied and Interdisciplinary Chemistry |
Stainless steel alloys remain a research target because of lower production costs, as well as the need for an austenitic stainless steel with high-temperature corrosion resistance in environments with water vapor. Research focuses on increasing high-temperature tensile strength, toughness, and creep resistance to compete with Ni-based superalloys.
Oak Ridge National Laboratory is researching austenitic alloys, achieving similar creep and corrosion resistance at 800 °C to that of other austenitic alloys, including Ni-based superalloys. | 1 | Applied and Interdisciplinary Chemistry |
One route to thioesters involves the reaction of an acid chloride with an alkali metal salt of a thiol:
Another common route entails the displacement of halides by the alkali metal salt of a thiocarboxylic acid. For example, thioacetate esters are commonly prepared by alkylation of potassium thioacetate:
The analogous alkylation of an acetate salt is rarely practiced. The alkylation can be conducted using Mannich bases and the thiocarboxylic acid:
Thioesters can be prepared by condensation of thiols and carboxylic acids in the presence of dehydrating agents:
A typical dehydration agent is DCC. Efforts to improve the sustainability of thioester synthesis have also been reported utilising safer coupling reagent T3P and greener solvent cyclopentanone. Acid anhydrides and some lactones also give thioesters upon treatment with thiols in the presence of a base.
Thioesters can be conveniently prepared from alcohols by the Mitsunobu reaction, using thioacetic acid.
They also arise via carbonylation of alkynes and alkenes in the presence of thiols. | 0 | Theoretical and Fundamental Chemistry |
Abrasive blasting also known as sandblasting, involves using compressed air to fire a steam of clean, sharp, crushed steel grit or aluminum oxide onto the surface of the component. Aluminum is a good option as it is relatively cheap. The fired grit breaks off small chucks of the substrate surface creating an evenly rough surface for good mechanical bonds to form. The substrate needs to be cleaned of any debris and residual grit from blasting prior to spraying. | 1 | Applied and Interdisciplinary Chemistry |
Functional genomics is a field of molecular biology that attempts to describe gene (and protein) functions and interactions. Functional genomics make use of the vast data generated by genomic and transcriptomic projects (such as genome sequencing projects and RNA sequencing). Functional genomics focuses on the dynamic aspects such as gene transcription, translation, regulation of gene expression and protein–protein interactions, as opposed to the static aspects of the genomic information such as DNA sequence or structures. A key characteristic of functional genomics studies is their genome-wide approach to these questions, generally involving high-throughput methods rather than a more traditional "candidate-gene" approach. | 1 | Applied and Interdisciplinary Chemistry |
Because Phlorizin is a nonselective inhibitor with poor oral bioavailability, a phlorizin derivative was synthesised and called T-1095. T-1095 is a methyl carbonate prodrug that is absorbed into the circulation when given orally, and is rapidly converted in the liver to the active metabolite T-1095A. By inhibiting SGLT-1 and SGLT-2, urinary glucose excretion increased in diabetic animals. T-1095 did not proceed in clinical development, probably because of the inhibition of SGLT-1 but non-selective SGLT inhibitors may also block glucose transporter 1 (GLUT-1). Because 90% of filtered glucose is reabsorbed through SGLT-2, research has focused specifically on SGLT-2. Inhibition of SGLT-1 may also lead to the genetic disease glucose-galactose malabsorption, which is characterized by severe diarrhea. | 1 | Applied and Interdisciplinary Chemistry |
Wells is known to his friends and family as Jumbo. He is an accomplished pianist. He married Ada Squires, then a widow, in 1939. During World War II, Wells worked on developing phosphors to be used in cathode-ray tubes and in helping service people move about in the dark. | 0 | Theoretical and Fundamental Chemistry |
Added space-time noise , where is an Wiener process, forms a stochastic Burgers' equation
This stochastic PDE is the one-dimensional version of Kardar–Parisi–Zhang equation in a field upon substituting . | 1 | Applied and Interdisciplinary Chemistry |
In methyl thiocyanate, and distances are 116 and 176 pm. By contrast, and distances are 117 and 158 pm in isothiocyanate]s.
Typical bond angles for are 100°. By contrast in aryl isothiocyanates is 165°. Again, the thiocyanate isomers are quite different with angle near 100°.
In both organic thiocyanate and isothiocyanate isomers the angle approaches 180°. | 0 | Theoretical and Fundamental Chemistry |
The IIR has over 200 publications available on refrigeration technologies and applications: reference documents, guides, technical books, conference and congress papers and proceedings, tables and diagrams comprising the thermophysical properties of refrigerants.
Books in the refrigeration field published by other publishers are also available for purchase. | 0 | Theoretical and Fundamental Chemistry |
If the nature of the neutrinos is Majorana, then they can be emitted and absorbed in the same process without showing up in the corresponding final state. As Dirac particles, both the neutrinos produced by the decay of the W bosons would be emitted, and not absorbed after.
Neutrinoless double beta decay can only occur if
* the neutrino particle is Majorana, and
* there exists a right-handed component of the weak leptonic current or the neutrino can change its handedness between emission and absorption (between the two W vertices), which is possible for a non-zero neutrino mass (for at least one of the neutrino species).
The simplest decay process is known as the light neutrino exchange. It features one neutrino emitted by one nucleon and absorbed by another nucleon (see figure to the right). In the final state, the only remaining parts are the nucleus (with its changed proton number ) and two electrons:
The two electrons are emitted quasi-simultaneously.
The two resulting electrons are then the only emitted particles in the final state and must carry approximately the difference of the sums of the binding energies of the two nuclei before and after the process as their kinetic energy. The heavy nuclei do not carry significant kinetic energy.
In that case, the decay rate can be calculated with
where denotes the phase space factor, the (squared) matrix element of this nuclear decay process (according to the Feynman diagram), and the square of the effective Majorana mass.
First, the effective Majorana mass can be obtained by
where are the Majorana neutrino masses (three neutrinos ) and the elements of the neutrino mixing matrix (see PMNS matrix). Contemporary experiments to find neutrinoless double beta decays (see section on experiments) aim at both the proof of the Majorana nature of neutrinos and the measurement of this effective Majorana mass (can only be done if the decay is actually generated by the neutrino masses).
The nuclear matrix element (NME) cannot be measured independently; it must, but also can, be calculated. The calculation itself relies on sophisticated nuclear many-body theories and there exist different methods to do this. The NME differs also from nucleus to nucleus (i.e. chemical element to chemical element). Today, the calculation of the NME is a significant problem and it has been treated by different authors in different ways. One question is whether to treat the range of obtained values for as the theoretical uncertainty and whether this is then to be understood as a statistical uncertainty. Different approaches are being chosen here. The obtained values for often vary by factors of 2 up to about 5. Typical values lie in the range of from about 0.9 to 14, depending on the decaying nucleus/element.
Lastly, the phase-space factor must also be calculated. It depends on the total released kinetic energy (, i.e. "-value") and the atomic number . Methods use Dirac wave functions, finite nuclear sizes and electron screening. There exist high-precision results for for various nuclei, ranging from about 0.23 (for ), and 0.90 () to about 24.14 ().
It is believed that, if neutrinoless double beta decay is found under certain conditions (decay rate compatible with predictions based on experimental knowledge about neutrino masses and mixing), this would indeed "likely" point at Majorana neutrinos as the main mediator (and not other sources of new physics). There are 35 nuclei that can undergo neutrinoless double beta decay (according to the aforementioned decay conditions). | 0 | Theoretical and Fundamental Chemistry |
In proteins, crosslinks are important in generating mechanically stable structures such as hair and wool, skin, and cartilage. Disulfide bonds are common crosslinks. Isopeptide bond formation is another type of protein crosslink.
The process of applying a permanent wave to hair involves the breaking and reformation disulfide bonds. Typically a mercaptan such as ammonium thioglycolate is used for the breaking. Following this, the hair is curled and then "neutralized". The neutralizer is typically an acidic solution of hydrogen peroxide, which causes new disulfide bonds to form, thus permanently fixing the hair into its new configuration.
Compromised collagen in the cornea, a condition known as keratoconus, can be treated with clinical crosslinking.
In biological context crosslinking could play a role in atherosclerosis through advanced glycation end-products (AGEs), which have been implicated to induce crosslinking of collagen, which may lead to vascular stiffening. | 0 | Theoretical and Fundamental Chemistry |
Ocean alkalinity enhancement (OAE) is a proposed "carbon dioxide removal (CDR) method that involves deposition of alkaline minerals or their dissociation products at the ocean surface". The process would increase surface total alkalinity. It would work to increase ocean absorption of . The process involves increasing the amount of bicarbonate (HCO-) through accelerated weathering (enhanced weathering) of rocks (silicate, limestone and quicklime). This process mimics the silicate-carbonate cycle. The either becomes bicarbonate, remaining in that form for more than 100 years, or may precipitate into calcium carbonate (CaCO). When calcium carbonate is buried in the deep ocean, it can hold the carbon indefinitely when utilizing silicate rocks.
Enhanced weathering is one type of ocean alkalinity enhancement. Enhanced weathering increases alkalinity by scattering fine rock particles. This can happen on land and in the ocean (even though the outcome eventually affects the ocean).
In addition to sequestering , alkalinity addition buffers the pH of the ocean therefore reducing ocean acidification. However, little is known about how organisms respond to added alkalinity, even from natural sources. For example, weathering of some silicate rocks could release a large amount of trace metals at the weathering site.
Cost and energy consumed by ocean alkalinity enhancement (mining, pulverizing, transport) is high compared to other CDR techniques. The cost is estimated to be 20–50 USD per ton of CO (for "direct addition of alkaline minerals to the ocean").
Carbon sequestered as bicarbonate in the ocean amounts to about 30% of carbon emissions since the Industrial Revolution.
Experimental materials include limestone, brucite, olivine and alkaline solutions. Another approach is to use electricity to raise alkalinity during desalination to capture waterborne CO2. | 0 | Theoretical and Fundamental Chemistry |
In the nomenclature of organic chemistry, a locant is a term to indicate the position of a functional group or substituent within a molecule. | 0 | Theoretical and Fundamental Chemistry |
A class II gene is a type of gene that codes for a protein. Class II genes are transcribed by RNAP II .
Class II genes have a promoter that may contain a TATA box.
Basal transcription of class II genes requires the formation of a preinitiation complex.
They are transcribed by RNA polymerase II, include both intron and exon, and code for polypeptide.
Major histocompatibility complex (MHC) class II genes are important in the immune response.
Major histocompatibility complex (MHC) II is found on antigen-presenting cells (APCs) and functions to present exogenous proteins to CD4+ T cells. MHC II thus plays an important role in activating the immune system in response to extracellular pathogens via activation of CD4+ T cells. MHC class II molecules are differentially expressed across multiple cell-types. For example, MHC II molecules are constitutively expressed in thymic epithelial cells and antigen-presenting cells (APC's), whereas they undergo interferon-γ-mediated expression in other cell types. Central to the regulation of the complex gene-expression profile exhibited by MHC class II molecules is a single master regulatory factor known as the class II transactivator (CIITA). CIITA is a non-DNA-binding co-activator whose expression is tightly controlled by a regulatory region containing three independent promoters (pI, pIII and pIV). | 1 | Applied and Interdisciplinary Chemistry |
Davy was a pioneer in the field of electrolysis using the voltaic pile to split common compounds and thus prepare many new elements. He went on to electrolyse molten salts and discovered several new metals, including sodium and potassium, highly reactive elements known as the alkali metals. Davy discovered potassium in 1807, deriving it from caustic potash (KOH). Before the 19th century, no distinction had been made between potassium and sodium. Potassium was the first metal that was isolated by electrolysis. Davy isolated sodium in the same year by passing an electric current through molten sodium hydroxide. | 1 | Applied and Interdisciplinary Chemistry |
In 1874 Nilson became professor of general and agricultural chemistry at Uppsala.
From then on he could devote more time to research. He began working on rare earths such as euxenite and gadolinite, using methods of successive fractionation introduced by Nils Johan Berlin. One of his goals was to better understand the relationship of the newly discovered elements to the proposed periodic system.
In 1879 Nilson separated out the oxide scandia. By doing so he discovered a new element, scandium, which he named for Scandinavia. The discovery was of particular importance because the existence of an element with such properties, "ekaboron", had been predicted by Mendeleev, based on his organization of the periodic system.
Nilsons spectral analysis indicated a previously unreported pattern of lines. Per Theodor Cleve demonstrated the equivalence of Nilsons scandium and Mendeleev's hypothetical ekaboron.
Nilson and Sven Otto Pettersson were the first to isolate titanium metal in a relatively pure form, extracting a 95% pure sample in 1887. Jöns Jacob Berzelius had extracted titanium metal in 1825, but only in a very impure form.
In 1910 Matthew Hunter was finally able to produce 99.9% pure titanium metal, through his new Hunter process.
Nilson also studied the gas density of metals which made it possible to determine the valence of various metals. | 1 | Applied and Interdisciplinary Chemistry |
Cereals & Grains Association has nine active [https://www.cerealsgrains.org/membership/sections/Pages/default.aspx sections]. Four of the nine active sections are located outside of the United States and they are located in western Canada, Australia, Japan, and Europe. | 1 | Applied and Interdisciplinary Chemistry |
Early results from Dan Nocera, a researcher at Harvard University, gave insight on how his newly created bionic leaf can be used for fertilizer production. This new bionic leaf uses photovoltaic cells in conjunction with Xanthobacter autotrophicus bacteria to create a plastic called polyhydroxybutyrate (PHB). PHB supplies energy to the bacterias natural enzymes which then converts nitrogen gas from the air into ammonia. The bionic leaf, can perform this process using renewable electricity, allowing for the sustainable production of ammonia and bio-fertilizers. Currently, the main industrial production of ammonia is performed by what is known as the Haber-Bosch Process, which uses natural gas as the main energy source. The bacteria within the bionic leaf also help to remove carbon dioxide from the environment. The bionic leaf must still pass an environmental impact study in order to determine if this bacteria is safe to release into the wild. Although the bionic leaf currently operates at a mere 25% efficiency, research and development is still with the hopes of improving the process. X. autotrophicus cells act as a living bio-fertilizer due to their ability to directly promote plant growth when applied to organic material. A study was conducted by comparing plants treated with no fertilizer to the same treated with increasing amounts of X. autotrophicus' culture. The treated plants root mass and total mass increased by approximately 130% and 100% respectively, compared to that of the untreated control group. | 0 | Theoretical and Fundamental Chemistry |
Electro sinter forging (ESF) is an industrial single electromagnetic pulse sintering technique to rapidly produce a wide range of small components in metals, alloys, intermetallics, semiconductors, and composites. ESF was invented by Alessandro Fais, an Italian metallurgical engineer and scientist.
ESF is obtained by inserting loose, binder-less powders into the automatic dosing system, or manually inserted in the mold. The automatic procedure applies a pre-pressure onto the powders to ensure electrical contact; hence, it superimposes an intense electromagnetic pulse with a mechanical pulse. The two pulses last 30 to 100 ms. After a brief holding time, the sintered component is extracted by the lower plunger and pushed out by the extractor to leave room for the next sintering. Each sintering round lasts less than one second, and is carried out entirely in air (even with pyrophoric materials). | 1 | Applied and Interdisciplinary Chemistry |
The equivalent carbon content concept is used on ferrous materials, typically steel and cast iron, to determine various properties of the alloy when more than just carbon is used as an alloyant, which is typical. The idea is to convert the percentage of alloying elements other than carbon to the equivalent carbon percentage, because the iron-carbon phases are better understood than other iron-alloy phases. Most commonly this concept is used in welding, but it is also used when heat treating and casting cast iron. | 1 | Applied and Interdisciplinary Chemistry |
First studies of the interaction of plasmas with hypersonic flows around vehicles date back to the late 1950s, with the concept of a new kind of thermal protection system for space capsules during high-speed reentry. As low-pressure air is naturally ionized at such very high velocities and altitude, it was thought to use the effect of a magnetic field produced by an electromagnet to replace thermal ablative shields by a "magnetic shield". Hypersonic ionized flow interacts with the magnetic field, inducing eddy currents in the plasma. The current combines with the magnetic field to give Lorentz forces that oppose the flow and detach the bow shock wave further ahead of the vehicle, lowering the heat flux which is due to the brutal recompression of air behind the stagnation point. Such passive flow control studies are still ongoing, but a large-scale demonstrator has yet to be built. | 1 | Applied and Interdisciplinary Chemistry |
The history of pharmacy as a modern and independent science dates back to the first third of the 19th century. Before then, pharmacy evolved from antiquity as part of medicine. The history of pharmacy coincides well with the history of medicine, but it's important that there is a distinction between the two topics. Pharmaceuticals is one of the most-researched fields in the academic industry, but the history surrounding that particular topic is sparse compared to the impact its made world-wide. Before the advent of pharmacists, there existed apothecaries that worked alongside priests and physicians in regard to patient care. | 1 | Applied and Interdisciplinary Chemistry |
In such studies multiple experimental treatments are tested in a single trial. Genetic testing enables researchers to group patients according to their genetic profile, deliver drugs based on that profile to that group and compare the results. Multiple companies can participate, each bringing a different drug. The first such approach targets squamous cell cancer, which includes varying genetic disruptions from patient to patient. Amgen, AstraZeneca and Pfizer are involved, the first time they have worked together in a late-stage trial. Patients whose genomic profiles do not match any of the trial drugs receive a drug designed to stimulate the immune system to attack cancer. | 1 | Applied and Interdisciplinary Chemistry |
* C: Frank Wigglesworth Clarke of USGS and Henry Stephens Washington
</references>
* U: United States Geological Survey (USGS)
</references>
* B:
</references>
* F: Alexander Fersman
</references>
* G: Victor Goldschmidt
</references>
* M: Brian Mason
</references>
* K:
</references>
* H: Research on the history of chemistry
</references> | 0 | Theoretical and Fundamental Chemistry |
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