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Tardigrade specific proteins are a type of intrinsically disordered proteins, which have no predetermined shape or task. These proteins use many different conformations, called an ensemble, to move through different structures. Because of this, intrinsically disordered proteins may react strongly to the environment they inhabit. There are three families of tardigrade specific proteins, each named after where the protein is localized within a cell. These proteins are similar to late embryogenesis abundant proteins but are specific to tardigrades. The three families do not resemble each other and are expressed or enriched during desiccation. Unlike traditional proteins, intrinsically disordered proteins do not precipitate out of solution or denature during high heat. Tardigrades rely on these proteins to help them survive extreme environments, where they put their bodies in a dehydrated state called a tun. In most organisms, dehydration causes problems for cells, which need a hydrated environment for their proteins to function. However, tardigrade specific proteins assist in preventing aggregation of cell contents upon dehydration, and maintain the integrity of the cell membrane upon rehydration. | 1 | Applied and Interdisciplinary Chemistry |
As many as 20% of human tumors are caused by viruses. Some such viruses that are commonly recognized include HPV, T-cell Leukemia virus type I, and hepatitis B.
Viral oncogenesis are most common with DNA and RNA tumor viruses, most frequently the retroviruses. There are two types of oncogenic retroviruses: acute transforming viruses and non-acute transforming viruses. Acute transforming viruses induce a rapid tumor growth since they carry viral oncogenes in their DNA/RNA to induce such growth. An example of an acute transforming virus is the Rous Sarcoma Virus (RSV) that carry the v-src oncogene. v-Src is part of the c-src, which is a cellular proto-oncogene that stimulates rapid cell growth and expansion. A non-acute transforming virus on the other hand induces a slow tumor growth, since it does not carry any viral oncogenes. It induces tumor growth by transcriptionally activating the proto-oncogenes particularly the long terminal repeat (LTR) in the proto-oncogenes.
Viral Oncogenesis through transformation can occur via 2 mechanisms:
# The tumor virus can introduce and express a "transforming" gene either through the integration of DNA or RNA into the host genome.
# The tumor virus can alter expression on preexisting genes of the host.
One or both of these mechanisms can occur in the same host cell. | 1 | Applied and Interdisciplinary Chemistry |
In pre-modern medicine, diasenna (medical Lat dia-, "composed of" + senna, from Arab. sanā) is a soft, purgative electuary containing the plant senna. The other ingredients are sugar candy, cinnamon, lapis lazuli, silk, cloves, galanga minor, black pepper, nardus indicus, seed of the basilica, leaves of cloves, cardamomum, saffron, ginger, zedoary, rosemary flowers, long pepper, lapis armenius, and honey. Diasenna was said to ease and comfort the melancholic, and splenetic, and was good against all diseases arising from an atrabilis. | 1 | Applied and Interdisciplinary Chemistry |
Mutagens are not necessarily carcinogens, and vice versa. Sodium azide for example may be mutagenic (and highly toxic), but it has not been shown to be carcinogenic. Meanwhile, compounds which are not directly mutagenic but stimulate cell growth which can reduce the effectiveness of DNA repair and indirectly increase the chance of mutations, and therefore that of cancer. One example of this would be anabolic steroids, which stimulate growth of the prostate gland and increase the risk of prostate cancer among others. Other carcinogens may cause cancer through a variety of mechanisms without producing mutations, such as tumour promotion, immunosuppression that reduces the ability to fight cancer cells or pathogens that can cause cancer, disruption of the endocrine system (e.g. in breast cancer), tissue-specific toxicity, and inflammation (e.g. in colorectal cancer). | 0 | Theoretical and Fundamental Chemistry |
Another area of controversy and uncertainty concerns the question of whether, and if so, to what extent, vancomycin increases the toxicity of other nephrotoxins. Clinical studies have yielded variable results, but animal models indicate some increased nephrotoxic effect probably occurs when vancomycin is added to nephrotoxins such as aminoglycosides. However, a dose- or serum level-effect relationship has not been established. | 0 | Theoretical and Fundamental Chemistry |
Since scientists produced the first cloned mammal Dolly the sheep in 1996 using the somatic cell nuclear transfer (SCNT) technique, 23 mammalian species have been successfully cloned, including cattle, cats, dogs, horses and rats. Using this technique for primates had never been successful and no pregnancy had lasted more than 80 days. The main difficulty was likely the proper programming of the transferred nuclei to support the growth of the embryo. Tetra (born October 1999), a female rhesus macaque, was created by a team led by Gerald Schatten of the Oregon National Primate Research Center using a different technique, called "embryo splitting". She is the first cloned primate by artificial twinning, which is a much less complex procedure than the DNA transfer used for the creation of Zhong Zhong and Hua Hua.
In January 2019, scientists in China reported the creation of five identical cloned gene-edited monkeys, using the same cloning technique that was used with Zhong Zhong and Hua Hua, and the same gene-editing CRISPR-Cas9 technique allegedly used by He Jiankui in creating the first ever gene-modified human babies Lulu and Nana. The monkey clones were made in order to study several medical diseases. | 1 | Applied and Interdisciplinary Chemistry |
Although anti-Jo-1 antibodies are often included with ANAs, they are actually antibodies to the cytoplasmic protein, Histidyl-tRNA synthetase – an aminoacyl-tRNA synthetase essential for the synthesis of histidine loaded tRNA. They are highly associated with polymyositis and dermatomyositis, and are rarely found in other connective tissue diseases. Around 20–40% of polymyositis is positive for Jo-1 antibodies and most will have interstitial lung disease, HLA-DR3 and HLA-DRw52 human leukocyte antigen (HLA) markers; collectively known as Jo-1 syndrome. | 1 | Applied and Interdisciplinary Chemistry |
The drug is contraindicated in premenopausal women, which of course includes pregnant and lactating women. | 0 | Theoretical and Fundamental Chemistry |
Diphosphorus is an old target of chemists since it is the heavy analogue of N. Its fleeting existence is inferred by the controlled degradation of certain niobium complexes in the presence of trapping agents. Again, a Diels-Alder strategy is employed in the trapping: | 0 | Theoretical and Fundamental Chemistry |
Recently, EDHF has been implicated in gender-related differences in blood pressure control. The generation of animals that lack both endothelial nitric oxide synthase (eNOS) and COX-1 (Cyclooxygenase-1, a protein that acts as an enzyme to speed up the production of certain chemical messengers), has allowed a direct assessment of the involvement of EDHF to endothelium-dependent relaxation in small arteries. In mice lacking both eNOS and COX-1, EDHF-mediated response appeared to compensate the absence of endothelial NO in females but not in males. In female mice, the deletion of eNOS and COX-1 did not affect mean arterial blood pressure, while males become hypertensive
In accordance with this study, EDHF has been suggested to be more important in female arteries to confer endothelium-dependent dilatation, while NO played a predominant role in arteries from males. The latter finding indeed concurs with previous reports in several vascular beds, including mesenteric and tail arteries from rats as well as genital arteries from rabbits. These findings together suggest that under pathological conditions EDHF could compensate for the loss of NO in female rather than in male arteries | 1 | Applied and Interdisciplinary Chemistry |
Cell culture techniques make it possible to produce epithelial sheets for the replacement of damaged oral mucosa. Partial-thickness tissue engineering uses one type of cell layer, this can be in monolayers or multilayers. Monolayer epithelial sheets suffice for the study of the basic biology of oral mucosa, for example its responses to stimuli such as mechanical stress, growth factor addition and radiation damage. Oral mucosa, however, is a complex multilayer structure with proliferating and differentiating cells and monolayer epithelial sheets have been shown to be fragile, difficult to handle and likely to contract without a supporting extracellular matrix. Monolayer epithelial sheets can be used to manufacture multilayer cultures. These multilayer epithelial sheets show signs of differentiation such as the formation of a basement membrane and keratinization. Fibroblasts are the most common cells in extracellular matrix and are important for epithelial morphogenesis. If fibroblasts are absent from the matrix, the epithelium stops proliferating but continues to differentiate. The structures obtained by partial-thickness oral mucosa engineering form the basis for full-thickness oral mucosa engineering. | 1 | Applied and Interdisciplinary Chemistry |
Metal carbene complexes are often classified into two types. The Fischer carbenes, named after Ernst Otto Fischer, feature strong π-acceptors at the metal and are electrophilic at the carbene carbon atom. Schrock carbenes, named after Richard R. Schrock, are characterized by more nucleophilic carbene carbon centers; these species typically feature higher oxidation state (valency) metals. N-Heterocyclic carbenes (NHCs) were popularized following Arduengo's isolation of a stable free carbene in 1991. Reflecting the growth of the area, carbene complexes are now known with a broad range of different reactivities and diverse substituents. Often it is not possible to classify a carbene complex solely with regards to its electrophilicity or nucleophilicity. | 0 | Theoretical and Fundamental Chemistry |
The "hard ionization" process of electron ionization can be softened by the cooling of the molecules before their ionization, resulting in mass spectra that are richer in information. In this method named cold electron ionization (cold-EI) the molecules exit the GC column, mixed with added helium make up gas and expand into vacuum through a specially designed supersonic nozzle, forming a supersonic molecular beam (SMB). Collisions with the make up gas at the expanding supersonic jet reduce the internal vibrational (and rotational) energy of the analyte molecules, hence reducing the degree of fragmentation caused by the electrons during the ionization process. Cold-EI mass spectra are characterized by an abundant molecular ion while the usual fragmentation pattern is retained, thus making cold-EI mass spectra compatible with library search identification techniques. The enhanced molecular ions increase the identification probabilities of both known and unknown compounds, amplify isomer mass spectral effects and enable the use of isotope abundance analysis for the elucidation of elemental formulas. | 0 | Theoretical and Fundamental Chemistry |
When a substance reacts simultaneously to give two different products, a parallel or competitive reaction is said to take place. | 0 | Theoretical and Fundamental Chemistry |
Bearing heaters typically range from 1 kVA to 25 kVA and are used to heat parts from , dependent upon the application. The power required is a function of the weight, target temperature and cycle time to aid selection many manufacturers publish graphs and charts. | 1 | Applied and Interdisciplinary Chemistry |
An oxaziridine is an organic molecule that features a three-membered heterocycle containing oxygen, nitrogen, and carbon. In their largest application, oxaziridines are intermediates in the industrial production of hydrazine. Oxaziridine derivatives are also used as specialized reagents in organic chemistry for a variety of oxidations, including alpha hydroxylation of enolates, epoxidation and aziridination of olefins, and other heteroatom transfer reactions. Oxaziridines also serve as precursors to nitrones and participate in [3+2] cycloadditions with various heterocumulenes to form substituted five-membered heterocycles. Chiral oxaziridine derivatives effect asymmetric oxygen transfer to prochiral enolates as well as other substrates. Some oxaziridines also have the property of a high barrier to inversion of the nitrogen, allowing for the possibility of chirality at the nitrogen center. | 0 | Theoretical and Fundamental Chemistry |
A sigma factor (σ factor or specificity factor) is a protein needed for initiation of transcription in bacteria. It is a bacterial transcription initiation factor that enables specific binding of RNA polymerase (RNAP) to gene promoters. It is homologous to archaeal transcription factor B and to eukaryotic factor TFIIB. The specific sigma factor used to initiate transcription of a given gene will vary, depending on the gene and on the environmental signals needed to initiate transcription of that gene. Selection of promoters by RNA polymerase is dependent on the sigma factor that associates with it. They are also found in plant chloroplasts as a part of the bacteria-like plastid-encoded polymerase (PEP).
The sigma factor, together with RNA polymerase, is known as the RNA polymerase holoenzyme. Every molecule of RNA polymerase holoenzyme contains exactly one sigma factor subunit, which in the model bacterium Escherichia coli is one of those listed below. The number of sigma factors varies between bacterial species. E. coli has seven sigma factors. Sigma factors are distinguished by their characteristic molecular weights. For example, σ is the sigma factor with a molecular weight of 70 kDa.
The sigma factor in the RNA polymerase holoenzyme complex is required for the initiation of transcription, although once that stage is finished, it is dissociated from the complex and the RNAP continues elongation on its own. | 1 | Applied and Interdisciplinary Chemistry |
The compound adopts a spinel structure. The oxidation states for the constituent metals are Cu(II) and Cr(III). A variety of compositions are recognized for the substance, including CuCrO·CuO·BaCrO (CAS# 99328-50-4) and CuCrO (CAS# 12053-18-8). Commercial samples often contain barium oxide and other components. | 0 | Theoretical and Fundamental Chemistry |
The 7 crystal systems consist of 32 crystal classes (corresponding to the 32 crystallographic point groups) as shown in the following table below:
The point symmetry of a structure can be further described as follows. Consider the points that make up the structure, and reflect them all through a single point, so that (x,y,z) becomes (−x,−y,−z). This is the inverted structure. If the original structure and inverted structure are identical, then the structure is centrosymmetric. Otherwise it is non-centrosymmetric. Still, even in the non-centrosymmetric case, the inverted structure can in some cases be rotated to align with the original structure. This is a non-centrosymmetric achiral structure. If the inverted structure cannot be rotated to align with the original structure, then the structure is chiral or enantiomorphic and its symmetry group is enantiomorphic.
A direction (meaning a line without an arrow) is called polar if its two-directional senses are geometrically or physically different. A symmetry direction of a crystal that is polar is called a polar axis. Groups containing a polar axis are called polar. A polar crystal possesses a unique polar axis (more precisely, all polar axes are parallel). Some geometrical or physical property is different at the two ends of this axis: for example, there might develop a dielectric polarization as in pyroelectric crystals. A polar axis can occur only in non-centrosymmetric structures. There cannot be a mirror plane or twofold axis perpendicular to the polar axis, because they would make the two directions of the axis equivalent.
The crystal structures of chiral biological molecules (such as protein structures) can only occur in the 65 enantiomorphic space groups (biological molecules are usually chiral). | 0 | Theoretical and Fundamental Chemistry |
Trichloroacetonitrile is an organic compound with the formula CClCN. It is a colourless liquid, although commercial samples often are brownish. It is used commercially as a precursor to the fungicide etridiazole. It is prepared by dehydration of trichloroacetamide. As a bifunctional compound, trichloroacetonitrile can react at both the trichloromethyl and the nitrile group. The electron-withdrawing effect of the trichloromethyl group activates the nitrile group for nucleophilic additions. The high reactivity makes trichloroacetonitrile a versatile reagent, but also causes its susceptibility towards hydrolysis. | 0 | Theoretical and Fundamental Chemistry |
Al-Kindi denied the possibility of transmuting base metals into precious metals such as gold and silver, a position that was later attacked by the Persian alchemist and physician Abu Bakr al-Razi ().
One work attributed to al-Kindi, variously known as the Kitāb al-Taraffuq fī l-ʿiṭr ("The Book of Gentleness on Perfume") or the Kitāb Kīmiyāʾ al-ʿiṭr wa-l-taṣʿīdāt ("The Book of the Chemistry of Perfume and Distillations"), contains one of the earliest known references to the distillation of wine. The work also describes the distillation process for extracting rose oils, and provides recipes for 107 different kinds of perfumes. | 1 | Applied and Interdisciplinary Chemistry |
The NMDA receptor (NMDAR) does not, in resting or near-resting membrane potential conditions, contribute significant current to the EPSP. Following the presynaptic release of the glutamate that binds to and opens the AMPAR, the NMDAR also binds this glutamate and opens. However, current does not flow through the NMDAR ion channel because it is instantaneously blocked by a magnesium ion (Mg) that binds to a site "inside" the open pore of the NMDAR channel. Magnesium has access to this binding site only when the NMDAR channel is opened by glutamate binding, a so-called open channel block. | 1 | Applied and Interdisciplinary Chemistry |
The separation of a racemate into its components, the individual enantiomers, is called a chiral resolution. Various methods exist for this separation, including crystallization, chromatography, and the use of various reagents. | 0 | Theoretical and Fundamental Chemistry |
The term "homoaromaticity" derives from the structural similarity between homoaromatic compounds and the analogous homo-conjugated alkenes previously observed in the literature. The IUPAC Gold Book requires that Bis-, Tris-, etc. prefixes be used to describe homoaromatic compounds in which two, three, etc. sp centers separately interrupt conjugation of the aromatic system. | 0 | Theoretical and Fundamental Chemistry |
* 2014 documentary Whats In My Baggie?' deals with adulterants and additives in recreational drugs.
* Largest public accessible database with reagent test results and their sources | 0 | Theoretical and Fundamental Chemistry |
Several groups of bacteria can conduct anoxygenic photosynthesis: green sulfur bacteria (GSB), red and green filamentous phototrophs (FAPs e.g. Chloroflexia), purple bacteria, acidobacteriota, and heliobacteria.
Some archaea (e.g. Halobacterium) capture light energy for metabolic function and are thus phototrophic but none are known to "fix" carbon (i.e. be photosynthetic). Instead of a chlorophyll-type receptor and electron transport chain, proteins such as halorhodopsin capture light energy with the aid of diterpenes to move ions against a gradient and produce ATP via chemiosmosis in the manner of mitochondria. | 0 | Theoretical and Fundamental Chemistry |
Past hydrological changes on our planet have had enormous effects on the environment. Over most of geologic time, the long-term mean sea level has been higher than today. Only at the Permian-Triassic boundary ~250 million years ago was the long-term mean sea level lower than today. Long term changes in the mean sea level are the result of changes in the oceanic crust, with a downward trend expected to continue in the very long term. Twenty thousand years ago, the sea level was lower than at present with vast amounts of water being locked up as ice; in the northern hemisphere, there was twenty times more ice than the present volume.
The climate of the Sahara, for example, has undergone enormous variations between wet and dry over the last few hundred thousand years, believed to be caused by long-term changes in the North African climate cycle that alters the path of the North African Monsoon. Paleohydrological studies of sediments in the Fazzan Basin in Libya show that humid conditions once prevailed there that were capable of creating a lake with a surface area of around . Before the abrupt desertification of North Africa about five thousand years ago, the Sahara was the home of Neolithic men and supported verdant vegetation and diverse wildlife. | 1 | Applied and Interdisciplinary Chemistry |
Commonly reported adverse effects associated with the use of oxacillin include skin rash, diarrhea, nausea, vomiting, hematuria, agranulocytosis, eosinophilia, leukopenia, neutropenia, thrombocytopenia, hepatotoxicity, acute interstitial nephritis, and fever. High doses of oxacillin have been reported to cause renal, hepatic, and nervous system toxicity. Common to all members of the penicillin class of drugs, oxacillin may cause acute or delayed hypersensitivity reactions. As an injection, oxacillin may cause injection site reactions, which may be characterized by redness, swelling, and itching. | 0 | Theoretical and Fundamental Chemistry |
Poly(ADP-ribose)polymerases (PARPs) can function in DNA repair of single strand breaks as well as double strand breaks. In single-strand break repair (base excision repair) the PARP can either facilitate removal of an oxidized sugar or strand cleavage. PARP1 binds the single-strand breaks and pulls any nearby base excision repair intermediates close. These intermediates include XRCC1 and APLF and they can be recruited directly or through the PBZ domain of the APLF. This leads to the synthesis of poly(ADP-ribose). The PBZ domain is present in many proteins involved in DNA repair and allows for the binding of the PARP and thus ADP-ribosylation which recruits repair factors to interact at the break site. PARP2 is a secondary responder to DNA damage but serves to provide functional redundancy in DNA repair.
There are many mechanisms for the repair of damaged double stranded DNA. PARP1 may function as a synapsis factor in alternative non-homologous end joining. Additionally, it has been proposed that PARP1 is required to slow replication forks following DNA damage and promotes homologous recombination at replication forks that may be dysfunctional. It is possible that PARP1 and PARP3 work together in repair of double-stranded DNA and it has been shown that PARP3 is critical for double-stranded break resolution. There are two hypotheses by which PARP1 and PARP3 coincide. The first hypothesis states that the two (ADP-ribosyl)transferases serve to function for each other's inactivity. If PARP3 is lost, this results in single-strand breaks, and thus the recruitment of PARP1. A second hypothesis suggests that the two enzyme work together; PARP3 catalyzes mono(ADP-ribosyl)ation and short poly(ADP-ribosyl)ation and serves to activate PARP1.
The PARPs have many protein targets at the site of DNA damage. KU protein and DNA-PKcs are both double-stranded break repair components with unknown sites of ADP-ribosylation. Histones are another protein target of the PARPs. All core histones and linker histone H1 are ADP-ribosylated following DNA damage. The function of these modifications is still unknown, but it has been proposed that ADP-ribosylation modulates higher-order chromatin structure in efforts to facilitate more accessible sites for repair factors to migrate to the DNA damage. | 1 | Applied and Interdisciplinary Chemistry |
Steroid 21-hydroxylase is a cytochrome P450 enzyme that is notable for its substrate specificity and relatively high catalytic efficiency.
Like other cytochrome P450 enzymes, steroid 21-hydroxylase participates in the cytochrome P450 catalytic cycle and engages in one-electron transfer with NADPH-P450 reductase. Steroid 21-hydroxylase is highly specific for hydroxylation of progesterone and 17-hydroxyprogesterone. This is in marked contrast to the evolutionarily and functionally related P450 enzyme 17-hydroxylase, which has a broad range of substrates.
The chemical reaction in which steroid 21-hydroxylase catalyzes the addition of hydroxyl (-OH) to the C21 position of progesterone, 17α-hydroxyprogesterone and 21-desoxycortisone was first described in 1952.
Studies of the human enzyme expressed in yeast initially classified 17-hydroxyprogesterone as the preferred substrate for steroid 21-hydroxylase, however, later analysis of the purified human enzyme found a lower K and greater catalytic efficiency for progesterone over 17-hydroxyprogesterone.
The catalytic efficiency of steroid 21-hydroxylase for conversion of progesterone in humans is approximately 1.3 x 10 Ms at 37 °C. This makes it the most catalytically efficient P450 enzyme of those reported to date, and catalytically more efficient than the closely related bovine steroid 21-hydroxylase enzyme. C-H bond breaking to create a primary carbon radical is thought to be the rate-limiting step in the hydroxylation. | 1 | Applied and Interdisciplinary Chemistry |
This compound is a diamine in which the two dimethylamino groups are attached on the same side (peri position) of a naphthalene ring. This molecule has several very interesting properties; one is its very high basicity; another is its spectroscopic properties.
With a pK of 12.34 for its conjugate acid in aqueous solution, 1,8-bis(dimethylamino)naphthalene is one of the strongest organic bases. However, it only absorbs protons slowly—hence the trade name. The high basicity is attributed to the relief of strain upon protonation and/or the strong interaction between the nitrogen lone pairs. Additionally, although many aromatic amines such as aniline show reduced basicity (due to nitrogen being sp hybridized; its lone pair occupying a 2p orbital and interacting and being withdrawn by the aromatic ring), this is not possible in this molecule, as the nitrogens' methyl groups prevent its substituents from adopting a planar geometry, as this would require forcing methyl groups from each nitrogen atom into one another—thus the basicity is not reduced by this factor which is found in other molecules. It is sterically hindered, making it a weak nucleophile. Because of this combination of properties, it has been used in organic synthesis as a highly selective non-nucleophilic base.
Proton sponge also exhibits a very high affinity for boron and is capable of displacing hydride from borane to form a boronium–borohydride ion pair. | 0 | Theoretical and Fundamental Chemistry |
Physisorption, also called physical adsorption, is a process in which the electronic structure of the atom or molecule is barely perturbed upon adsorption. | 0 | Theoretical and Fundamental Chemistry |
The Martian atmosphere contains high abundances of photochemically produced CO and H, which are reducing molecules. Mars' atmosphere is otherwise mostly oxidizing, leading to a source of untapped energy that life could exploit if it used by a metabolism compatible with one or both of these reducing molecules. Because these molecules can be observed, scientists use this as evidence for an antibiosignature. Scientists have used this concept as an argument against life on Mars. | 1 | Applied and Interdisciplinary Chemistry |
C-type lectin-like receptors (CLRs) contain one or more C-type lectin (Ca2+ dependent carbohydrate-binding lectin) domains. Example pairs include:
* CD94/NKG2, expressed in NK and some T cells and interacts with the ligand HLA-E.
* Dendritic cell immunoreceptor (DCIR)/dendritic cell immunoactivating receptor (DCAR), characterized as a pair in mice, though no human DCAR has been identified.
* NKR-P1 (CD161) is a member of a paired receptor group in rodents, but the human genome contains only one, inhibitory receptor, NKRP1A (KLRB1).
* The Ly49 family in mice has been extensively studied for its role in NK activation using laboratory mice as a model organism, but has no homologous gene cluster in the human genome. The KIR family is the functional equivalent. | 1 | Applied and Interdisciplinary Chemistry |
In the Cassie–Baxter model, the drop sits on top of the textured surface with trapped air underneath. During the wetting transition from the Cassie state to the Wenzel state, the air pockets are no longer thermodynamically stable and liquid begins to nucleate from the middle of the drop, creating a "mushroom state" as seen in Figure 10. The penetration condition is given by:
where
:* θ is the critical contact angle
:* Φ is the fraction of solid/liquid interface where drop is in contact with surface
:* r is solid roughness (for flat surface, r = 1)
The penetration front propagates to minimize the surface energy until it reaches the edges of the drop, thus arriving at the Wenzel state. Since the solid can be considered an absorptive material due to its surface roughness, this phenomenon of spreading and imbibition is called hemiwicking. The contact angles at which spreading/imbibition occurs are between 0 and π/2.
The Wenzel model is valid between θ and π/2. If the contact angle is less than Θ, the penetration front spreads beyond the drop and a liquid film forms over the surface. Figure 11 depicts the transition from the Wenzel state to the surface film state. The film smoothes the surface roughness and the Wenzel model no longer applies. In this state, the equilibrium condition and Young's relation yields:
By fine-tuning the surface roughness, it is possible to achieve a transition between both superhydrophobic and superhydrophilic regions. Generally, the rougher the surface, the more hydrophobic it is. | 0 | Theoretical and Fundamental Chemistry |
Some phenolic compounds produced from previous reactions worked as bactericides and the actinomycetales order of bacteria also produced antibiotic compounds (e.g., streptomycin). Thus the action of anaerobic bacteria ceased at about 10 m below the water or sediment. The mixture at this depth contained fulvic acids, unreacted and partially reacted fats and waxes, slightly modified lignin, resins and other hydrocarbons. As more layers of organic matter settled into the sea or lake bed, intense heat and pressure built up in the lower regions. As a consequence, compounds of this mixture began to combine in poorly understood ways to kerogen. Combination happened in a similar fashion as phenol and formaldehyde molecules react to urea-formaldehyde resins, but kerogen formation occurred in a more complex manner due to a bigger variety of reactants. The total process of kerogen formation from the beginning of anaerobic decay is called diagenesis, a word that means a transformation of materials by dissolution and recombination of their constituents. | 0 | Theoretical and Fundamental Chemistry |
The first potash application was in England in 1993, where Jameson Cells were used to treat potash slimes (see Potash flotation). It has subsequently been applied at Israel Chemicals Limited's Dead Sea Works and by an unnamed producer in the Saskatchewan province of Canada. | 1 | Applied and Interdisciplinary Chemistry |
Landfills are the oldest known method of waste disposal. Waste is buried in large dug out pits (unless naturally occurring locations are available) and covered. Bacteria and archaea decompose the waste over several decades producing several by-products of importance, including methane gas (natural gas), leachate, and volatile organic compounds (such as hydrogen sulfide (HS), NO, etc.).
Methane gas, a strong greenhouse gas, can build up inside the landfill leading to an explosion unless released from the cell. Leachate are fluid metabolic products from decomposition and contain various types of toxins and dissolved metallic ions. If leachate escapes into the ground water it can cause health problems in both animals and plants. The volatile organic compounds (VOCs) are associated with causing smog and acid rain. With the increasing amount of waste produced, appropriate places to safely store it have become difficult to find. | 1 | Applied and Interdisciplinary Chemistry |
Some chain-growth polymerizations include chain transfer steps, in which another atom (often hydrogen) is transferred from a molecule in the system to the polymer radical. The original polymer chain is terminated and a new one is initiated. The kinetic chain is not terminated if the new radical can add monomer. However the degree of polymerization is reduced without affecting the rate of polymerization (which depends on kinetic chain length), since two (or more) macromolecules are formed instead of one. For the case of termination by disproportionation, the degree of polymerization becomes:
where R is the rate of transfer. The greater R is, the shorter the final macromolecule. | 0 | Theoretical and Fundamental Chemistry |
Classical pinch-analysis primarily calculates the energy costs for the heating and cooling utility. At the pinch point, where the hot and cold streams are the most constrained, large heat exchangers are required to transfer heat between the hot and cold streams. Large heat exchangers entail high investment costs. In order to reduce capital cost, in practice a minimum temperature difference (Δ T) at the pinch point is demanded, e.g., 10 °F. It is possible to estimate the heat exchanger area and capital cost, and hence the optimal Δ T minimum value. However, the cost curve is quite flat and the optimum may be affected by "topology traps". The pinch method is not always appropriate for simple networks or where severe operating constraints exist. Kemp (2006) and Kemp and Lim (2019) discuss these aspects in detail. | 1 | Applied and Interdisciplinary Chemistry |
Small amounts of yttrium (0.1 to 0.2%) have been used to reduce the grain sizes of chromium, molybdenum, titanium, and zirconium. Yttrium is used to increase the strength of aluminium and magnesium alloys. The addition of yttrium to alloys generally improves workability, adds resistance to high-temperature recrystallization, and significantly enhances resistance to high-temperature oxidation (see graphite nodule discussion below).
Yttrium can be used to deoxidize vanadium and other non-ferrous metals. Yttria stabilizes the cubic form of zirconia in jewelry.
Yttrium has been studied as a nodulizer in ductile cast iron, forming the graphite into compact nodules instead of flakes to increase ductility and fatigue resistance. Having a high melting point, yttrium oxide is used in some ceramic and glass to impart shock resistance and low thermal expansion properties. Those same properties make such glass useful in camera lenses. | 1 | Applied and Interdisciplinary Chemistry |
One of the most important engineering applications of the hydraulic jump is to dissipate energy in channels, dam spillways, and similar structures so that the excess kinetic energy does not damage these structures. The rate of energy dissipation or head loss across a hydraulic jump is a function of the hydraulic jump inflow Froude number and the height of the jump.
The energy loss at a hydraulic jump expressed as a head loss is: | 1 | Applied and Interdisciplinary Chemistry |
Born and raised in countryside China, Yu obtained his B.Sc. (Chemistry) from Shandong University in 1991 at an age of 20. He then received his joint M.Sc. from Shandong University and Dalian Institute of Chemical Physics (Chemical Physics) in 1994, and his Ph.D. from Peking University (Materials Chemistry, with Prof. Zhong-Fan Liu) in 1997. He did his postdoctoral research with Nobel Laureate Ahmed Zewail and electrochemist Fred Anson at the California Institute of Technology from 1997 to 1999. | 0 | Theoretical and Fundamental Chemistry |
In 1934 he was appointed as professor at the University of Oslo. He is well known in the Nordic countries for his textbook Lærebok i organisk kjemi. The first modern Norwegian textbook in organic chemistry, it was first released in 1942 and then re-released several times, the last in 1964. The 1958 edition became known for introducing new Norwegian-language names of several chemical elements: hydrogen, nitrogen, karbon (carbon) og oksygen (oxygen).
During the occupation of Norway by Nazi Germany, his academic career was interrupted. When the Nazi authorities were about to change the rules for admission to the university in autumn 1943, a protest ensued. In retaliation, the authorities arrested 11 staff, 60 male students and 10 female students. The staff Johannes Andenæs, Eiliv Skard, Johan Christian Schreiner, Harald Krabbe Schjelderup, Anatol Heintz, Odd Hassel, Ragnar Frisch, Carl Jacob Arnholm, Bjørn Føyn and Endre Berner were sent to Grini concentration camp. Berner was first incarcerated at Berg concentration camp from 22 November 1943, then at Grini until 24 December 1944.
After the war Berner continued as professor at the University of Oslo until 1962, except for a stay at the Imperial College London from 1954 to 1955. He was also active as a professor emeritus until his death. He was elected as a member of the Royal Norwegian Society of Sciences and Letters in 1927, of the Norwegian Academy of Science and Letters in 1933 and of the Society of Chemical Industry in 1951. In 1959, he earned the Nansen medal for Outstanding Research and in 1969 he was decorated with the Order of St. Olav. He was the president of the Norwegian Chemical Society from 1946 to 1950, having co-founded the Trondheim branch of the society, and ultimately received honorary membership. | 0 | Theoretical and Fundamental Chemistry |
Phosphorus chains (with organic substituents) have been prepared, although these tend to be quite fragile. Small rings or clusters are more common. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, the Natta projection (named for Italian chemist Giulio Natta) is a way to depict molecules with complete stereochemistry in two dimensions in a skeletal formula. In a hydrocarbon molecule with all carbon atoms making up the backbone in a tetrahedral molecular geometry, the zigzag backbone is in the paper plane (chemical bonds depicted as solid line segments) with the substituents either sticking out of the paper toward the viewer (chemical bonds depicted as solid wedges) or away from the viewer (chemical bonds depicted as dashed wedges). The Natta projection is useful for representing the tacticity of a polymer. | 0 | Theoretical and Fundamental Chemistry |
The storage of seeds in a temperature and moisture controlled environment. This technique is used for taxa with orthodox seeds that tolerate desiccation. Seed bank facilities vary from sealed boxes to climate controlled walk-in freezers or vaults. Taxa with recalcitrant seeds that do not tolerate desiccation are typically not held in seed banks for extended periods of time. | 1 | Applied and Interdisciplinary Chemistry |
Ratsimamanga was a pacifist and politically active, and during his years of study, he forged close relationships with French intellectual and political circles. While in France, he co-founded the association of Malagasy Students in France and the Democratic Movement for Malagasy Renovation (MDRM) in 1946 with Jacques Rabemananjara, Joseph Raseta and Joseph Ravoahangy Andrianavalona. MDRM led the protests against the bloody repression of the Malagasy Uprising of 1947. However, MDRM was known to be dominated by Hova elites, who had been politically prominent in the former Merina royal court and wanted to regain the political dominance of the Merina upon independence. Jacques Rabemananjara, Joseph Raseta and Joseph Ravoahangy Andrianavalona were later sentenced to life in prison but were granted amnesty in 1958. Ratsimamanga claimed that he was unaware of the uprising and, thus, was not involved. Later in 1949, Ratsimamanga created the Malagasy National Council, a Government in exile. It was a failure.
On 26 August 1948, Ratsimamanga represented Madagascar at the World Congress of Intellectuals in Defence of Peace, which took place between the 25 to 28 August 1948 of August at Wrocław University of Science and Technology, Poland, and played a role in the framing of the communist powers as supporters of peace, and on the opposite side, portraying the West as a threat to peace.
Ratsimamanga was a member of the delegation that negotiated Madagascars independence from France. 77% of Malagasy voted for independence in the 1958 referendum, and after the independence, Ratsimamanga was appointed the Malagasy Republic ambassador to France from 1960 to 1972. After the 1972 Coup détat, on 14 December 1972, he was appointed the first Ambassador of the Malagasy Republic to China and the Soviet Union. He later established embassies in West Germany, North Korea, and Sierra Leone.
Furthermore, Ratsimamanga represents the Malagasy Republic at the European Economic Community, UNESCO, and Food and Agriculture Organization. He also became UNESCO Vice-chairman of the Executive Council. | 1 | Applied and Interdisciplinary Chemistry |
After the single-stranded viral DNA enters the cytoplasm, it serves as a template for the synthesis of a complementary DNA strand. This synthesis is initiated in the intergenic region of the DNA sequence by host RNA polymerase, which synthesizes a short RNA primer on the infecting DNA as template. The host DNA polymerase III then uses this primer to synthesize the full complementary strand of DNA, yielding a double-stranded circle, sometimes called the replicative form (RF) DNA. The complementary strand of the RF is the transcription template for phage coded proteins, especially p2 and p10, which are necessary for further DNA replication.
The p2 protein cleaves the viral strand of the RF DNA, and host DNA polymerase III synthesizes a new viral strand. The old viral strand is displaced as the new one is synthesized. When a circle is complete, the covalently linked p2 cuts the displaced viral strand at the junction between the old and newly synthesized DNA and re-ligates the two ends and liberates p2. RF replicates by this rolling circle mechanism to generate dozens of copies of the RF.
When the concentration of phage proteins has increased, new viral strands are coated by the replication/assembly protein p5 rather than by the complementary DNA strands. The p5 also inhibits translation of p2, so that progeny viral ssDNA production and packaging are in synchrony. | 1 | Applied and Interdisciplinary Chemistry |
Huntington's disease is a disease characterized by minor coordination problems, jerking eye movements, and uncontrollable movement of peripheral limbs. Symptoms generally occur at the age of 40, and are often accompanied by depression and psychosis. The disease is caused by a mutation in the Huntingtin gene, on chromosome 4, which causes abnormally large numbers of glutamate residues in the protein. Via an unknown mechanism, this accumulation leads to neurodegeneration in the caudate nucleus and putamen, selectively destroying GABAergic neurons which project to the globus pallidus. There is also significant necrosis in the thalamus and cerebral cortex. Cholinergic interneurons and dopaminergic neurons in the midbrain are largely unaffected.
Treatment for Huntington's disease is extremely limited due to the lack of knowledge concerning the pathogenesis of protein accumulation, though drugs used include dopamine receptor antagonists to minimize tremors and antidepressants to ameliorate symptoms of psychosis and depression. | 1 | Applied and Interdisciplinary Chemistry |
Ligands of proteins can be characterized also by the number of protein chains they bind. "Monodesmic" ligands (μόνος: single, δεσμός: binding) are ligands that bind a single protein chain, while "polydesmic" ligands (πολοί: many) are frequent in protein complexes, and are ligands that bind more than one protein chain, typically in or near protein interfaces. Recent research shows that the type of ligands and binding site structure has profound consequences for the evolution, function, allostery and folding of protein compexes. | 1 | Applied and Interdisciplinary Chemistry |
The rate and outcome of chemical reactions taking place in water often depends on the acidity of the water, and it is therefore useful to know the acidity of the water, typically measured by means of a pH meter. Knowledge of pH is useful or critical in many situations, including chemical laboratory analyses. pH meters are used for soil measurements in agriculture, water quality for municipal water supplies, swimming pools, environmental remediation; brewing of wine or beer; manufacturing, healthcare and clinical applications such as blood chemistry; and many other applications.
Advances in the instrumentation and in detection have expanded the number of applications in which pH measurements can be conducted. The devices have been miniaturized, enabling direct measurement of pH inside of living cells. In addition to measuring the pH of liquids, specially designed electrodes are available to measure the pH of semi-solid substances, such as foods. These have tips suitable for piercing semi-solids, have electrode materials compatible with ingredients in food, and are resistant to clogging. | 0 | Theoretical and Fundamental Chemistry |
The Faraday Medal is awarded by the Electrochemistry Group of the Royal Society of Chemistry. Since 1977, it honours distinguished mid-career electrochemists working outside of the United Kingdom and the Republic of Ireland for their research advancements. | 0 | Theoretical and Fundamental Chemistry |
Regions of the short arm of chromosome 8 are frequently deleted in a range of solid tumors, indicating that tumor suppressor genes reside at these loci. Caldwell et al. have shown frequent interstitial deletions in a series of prostate cancers, squamous cell head and neck cancers and colorectal carcinomas. There was also an association between 8p11.2 deletion and local invasion.
The first coding exon contains the whole of the frizzled-related cysteine rich domain (CRD), while the third exon (COOH-terminal domain) contains the netrin-related domain. Netrin is a regulator of apoptosis; the SFRP1 netrin-related motif is also found in a range of other proteins that is thought to mediate protein-protein interactions. The middle exon most likely represents a spacer between the first and third exon. There are 2 introns present within the coding sequence of SFRP1. | 1 | Applied and Interdisciplinary Chemistry |
Uridine diphosphate N-acetylglucosamine or UDP-GlcNAc is a nucleotide sugar and a coenzyme in metabolism. It is used by glycosyltransferases to transfer N-acetylglucosamine residues to substrates. -Glucosamine is made naturally in the form of glucosamine-6-phosphate, and is the biochemical precursor of all nitrogen-containing sugars. To be specific, glucosamine-6-phosphate is synthesized from fructose 6-phosphate and glutamine as the first step of the hexosamine biosynthesis pathway. The end-product of this pathway is UDP-GlcNAc, which is then used for making glycosaminoglycans, proteoglycans, and glycolipids.
UDP-GlcNAc is extensively involved in intracellular signaling as a substrate for O-linked N-acetylglucosamine transferases (OGTs) to install the O-GlcNAc post-translational modification in a wide range of species. It is also involved in nuclear pore formation and nuclear signalling. OGTs and OG-ases play an important role in the structure of the cytoskeleton. In mammals, there is enrichment of OGT transcripts in the pancreas beta-cells, and UDP-GlcNAc is thought to be part of the glucose sensing mechanism. There is also evidence that it plays a part in insulin sensitivity in other cells. In plants, it is involved in the control of gibberellin production.
Clostridium novyi type A alpha-toxin is an O-linked N-actetylglucosamine transferase acting on Rho proteins and causing the collapse of the cytoskeleton. | 1 | Applied and Interdisciplinary Chemistry |
The internal states of each ion can be treated as a two level system, with eigenstates denoted and . One of the ion's normal modes is chosen to be the transfer mode used for state mapping. This motional mode must be shared by both ions, which requires both ions be similar in mass. The normal mode has harmonic oscillator states denoted as , where n is the nth level of mode m. The wave function
denotes both ions and the transfer mode in the ground state. S and L represent the spectroscopy and logic ion. The spectroscopy ion's spectroscopy transition is then excited with a laser, producing the state:
A red sideband pi-pulse is then driven on the spectroscopy ion, resulting in the state:
At this stage, the spectroscopy ions internal state has been mapped on to the transfer mode. The internal state of the ion has been coupled to its motional mode. The state is unaffected by the pulse of light carrying out this operation because the state does not exist. QLS takes advantage of this in order to map the spectroscopy ions state onto the transfer mode. A final red sideband pi-pulse is applied to the logic ion, resulting in the state:
The spectroscopy ion's initial state has been mapped onto the logic ion, which can then be detected. | 0 | Theoretical and Fundamental Chemistry |
Total triiodothyronine (Total T) is rarely measured, having been largely superseded by free T3 tests. Total T3 is generally elevated in hyperthyroidism and decreased in hypothyroidism.
Reference ranges depend on the method of analysis. Results should always be interpreted using the range from the laboratory that performed the test. Example values are: | 1 | Applied and Interdisciplinary Chemistry |
After graduating, she returned to China and taught at Yanjing University, where she went to the University of Berlin, Germany in 1933 to conduct research on rayon and invented the first rayon made from grass fibres, returning to China in 1936 to serve as a commissioner of the Central Economic Commission. In 1938 she moved to Chongqing to set up the Southwest Chemical Industry Manufacturing Factory, where she conducted research on ramie processing and eventually spun out the "Cloud Silk", known as Yunsi fiber. In 1949, she attended the First Plenary Session of the Chinese People's Political Consultative Conference.
After the founding of the Peoples Republic of China, Feng Yunhe became an advisor to the Ministry of Textile Industry and Deputy Director of the Guangdong Chemical Research Institute, and in 1951, she began researching the chemical denaturation of ramie fibres, which was successful after five years of experiments. During the Cultural Revolution, she was branded as a "reactionary academic authority". After the end of the Cultural Revolution, she became a consultant to the Shanghai Textile Industry Bureaus Wool and Hemp Textile Industry Company and joined the Communist Party of China in 1979. She was awarded the invention prize by the State Science and Technology Commission in 1981 for the development of a large number of ramie fibre sulphonation denaturation products in Shanghai, and was a technical advisor to Hubei Province on textile technology from 1984. | 1 | Applied and Interdisciplinary Chemistry |
When measuring the irradiance of PAR, values are expressed using units of energy (W/m), which is relevant in energy-balance considerations for photosynthetic organisms.
However, photosynthesis is a quantum process and the chemical reactions of photosynthesis are more dependent on the number of photons than the energy contained in the photons. Therefore, plant biologists often quantify PAR using the number of photons in the 400-700 nm range received by a surface for a specified amount of time, or the Photosynthetic Photon Flux Density (PPFD). Values of PPFD are normally expressed using units of mol⋅m⋅s. In relation to plant growth and morphology, it is better to characterise the light availability for plants by means of the Daily Light Integral (DLI), which is the daily flux of photons per ground area, and includes both diurnal variation as well as variation in day length.
PPFD used to sometimes be expressed using einstein units, i.e., μE⋅m⋅s, although this usage is nonstandard and is no longer used. | 0 | Theoretical and Fundamental Chemistry |
If one considers a flow which is inviscid, this is where the viscous forces are small and can therefore be neglected in the calculations, then one arrives at Euler's equations:
Although in this case we have assumed an inviscid fluid this assumption does not hold for flows where there is a boundary. The presence of a boundary causes some viscosity at the boundary layer which cannot be neglected and one arrives back at the Navier–Stokes equation. Finding the solutions to these governing equations under different circumstances and determining their stability is the fundamental principle in determining the stability of the fluid flow itself. | 1 | Applied and Interdisciplinary Chemistry |
In chemical kinetics, a reaction rate constant or reaction rate coefficient () is a proportionality constant which quantifies the rate and direction of a chemical reaction by relating it with the concentration of reactants.
For a reaction between reactants A and B to form a product C,
where
:A and B are reactants
:C is a product
:a, b, and c are stoichiometric coefficients,
the reaction rate is often found to have the form:
Here is the reaction rate constant that depends on temperature, and [A] and [B] are the molar concentrations of substances A and B in moles per unit volume of solution, assuming the reaction is taking place throughout the volume of the solution. (For a reaction taking place at a boundary, one would use moles of A or B per unit area instead.)
The exponents m and n are called partial orders of reaction and are not generally equal to the stoichiometric coefficients a and b. Instead they depend on the reaction mechanism and can be determined experimentally.
Sum of m and n, that is, (m + n) is called the overall order of reaction. | 0 | Theoretical and Fundamental Chemistry |
The compatibility of two different metals may be predicted by consideration of their anodic index. This parameter is a measure of the electrochemical voltage that will be developed between the metal and gold. To find the relative voltage of a pair of metals it is only required to subtract their anodic indices.
To reduce galvanic corrosion for metals stored in normal environments such as storage in warehouses or non-temperature and humidity controlled environments, there should not be more than 0.25V difference in the anodic index of the two metals in contact. For controlled environments in which temperature and humidity are controlled, 0.50V can be tolerated. For harsh environments such as outdoors, high humidity, and salty environments, there should be not more than 0.15V difference in the anodic index. For example: gold and silver have a difference of 0.15V, therefore the two metals will not experience significant corrosion even in a harsh environment.
When design considerations require that dissimilar metals come in contact, the difference in anodic index is often managed by finishes and plating. The finishing and plating selected allow the dissimilar materials to be in contact, while protecting the more base materials from corrosion by the more noble. It will always be the metal with the most negative anodic index which will ultimately suffer from corrosion when galvanic incompatibility is in play. This is why sterling silver and stainless steel tableware should never be placed together in a dishwasher at the same time, as the steel items will likely experience corrosion by the end of the cycle (soap and water having served as the chemical electrolyte, and heat having accelerated the process). | 1 | Applied and Interdisciplinary Chemistry |
Soy-derived lecithin is considered by some to be kitniyot and prohibited on Passover for Ashkenazi Jews when many grain-based foods are forbidden, but not at other times. This does not necessarily affect Sephardi Jews, who do not have the same restrictions on rice and kitniyot during Passover.
Muslims are not forbidden to eat lecithin per se; however, since it may be derived from animal as well as plant sources, care must be taken to ensure this source is halal. Lecithin derived from plants and egg yolks is permissible, as is that derived from animals slaughtered according to the rules of dhabihah.
Sunflower lecithin, sourced from the seeds of sunflowers, is entirely plant-based and may be an option for those with religious or cultural concerns regarding food intake. | 0 | Theoretical and Fundamental Chemistry |
The fuel is injected part-way up the shaft, producing maximum temperature at this point. The fresh feed fed in at the top is first dried then heated to 800 °C, where de-carbonation begins, and proceeds progressively faster as the temperature rises. Below the burner, the hot lime transfers heat to, and is cooled by, the combustion air. A mechanical grate withdraws the lime at the bottom. A fan draws the gases through the kiln, and the level in the kiln is kept constant by adding feed through an airlock. As with batch kilns, only large, graded stone can be used, in order to ensure uniform gas-flows through the charge. The degree of burning can be adjusted by changing the rate of withdrawal of lime. Heat consumption as low as 4 MJ/kg is possible, but 4.5 to 5 MJ/kg is more typical. Due to temperature peak at the burners up to 1200 °C in a shaft kiln conditions are ideal to produce medium and hard burned lime. | 1 | Applied and Interdisciplinary Chemistry |
Protein kinase A, more precisely known as adenosine 3,5-monophosphate (cyclic AMP)-dependent protein kinase, abbreviated to PKA, was discovered by chemists Edmond H. Fischer and Edwin G. Krebs in 1968. They won the Nobel Prize in Physiology or Medicine in 1992 for their work on phosphorylation and dephosphorylation and how it relates to PKA activity.
PKA is one of the most widely researched protein kinases, in part because of its uniqueness; out of 540 different protein kinase genes that make up the human kinome, only one other protein kinase, casein kinase 2, is known to exist in a physiological tetrameric complex, meaning it consists of four subunits.
The diversity of mammalian PKA subunits was realized after Dr. Stan McKnight and others identified four possible catalytic subunit genes and four regulatory subunit genes. In 1991, Susan Taylor and colleagues crystallized the PKA Cα subunit, which revealed the bi-lobe structure of the protein kinase core for the very first time, providing a blueprint for all the other protein kinases in a genome (the kinome). | 1 | Applied and Interdisciplinary Chemistry |
Ferrous iron is a soluble form of iron that is stable at extremely low pHs or under anaerobic conditions. Under aerobic, moderate pH conditions ferrous iron is oxidized spontaneously to the ferric () form and is hydrolyzed abiotically to insoluble ferric hydroxide (). There are three distinct types of ferrous iron-oxidizing microbes. The first are acidophiles, such as the bacteria Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans, as well as the archaeon Ferroplasma. These microbes oxidize iron in environments that have a very low pH and are important in acid mine drainage. The second type of microbes oxidize ferrous iron at near-neutral pH. These micro-organisms (for example Gallionella ferruginea, Leptothrix ochracea, or Mariprofundus ferrooxydans) live at the oxic-anoxic interfaces and are microaerophiles. The third type of iron-oxidizing microbes are anaerobic photosynthetic bacteria such as Rhodopseudomonas, which use ferrous iron to produce NADH for autotrophic carbon dioxide fixation. Biochemically, aerobic iron oxidation is a very energetically poor process which therefore requires large amounts of iron to be oxidized by the enzyme rusticyanin to facilitate the formation of proton motive force. Like sulfur oxidation, reverse electron flow must be used to form the NADH used for carbon dioxide fixation via the Calvin cycle. | 1 | Applied and Interdisciplinary Chemistry |
Waste containing biocide concentrations exceeding the secondary treatment ecosystem tolerance level may kill a major fraction of one or more important ecosystem species. BOD reduction normally accomplished by that species temporarily ceases until other species reach a suitable population to utilize that food source, or the original population recovers as biocide concentrations decline. | 1 | Applied and Interdisciplinary Chemistry |
For insulating materials (both solid and liquid), probing charge dynamics with microwaves is a part of dielectric spectroscopy.
Amongst the conductive materials, superconductors are a material class that is often studied with microwave spectroscopy, giving information about penetration depth (governed by the superconducting condensate), energy gap (single-particle excitation of Cooper pairs), and quasiparticle dynamics.
Another material class that has been studied using microwave spectroscopy at low temperatures are heavy fermion metals with Drude relaxation rates at GHz frequencies. | 0 | Theoretical and Fundamental Chemistry |
Between these two limits is a point at which the dispersion caused by gravity cancels out the dispersion due to the capillary effect. At a certain wavelength, the group velocity equals the phase velocity, and there is no dispersion. At precisely this same wavelength, the phase velocity of gravity–capillary waves as a function of wavelength (or wave number) has a minimum. Waves with wavelengths much smaller than this critical wavelength are dominated by surface tension, and much above by gravity. The value of this wavelength and the associated minimum phase speed are:
For the air–water interface, is found to be , and is .
If one drops a small stone or droplet into liquid, the waves then propagate outside an expanding circle of fluid at rest; this circle is a caustic which corresponds to the minimal group velocity. | 1 | Applied and Interdisciplinary Chemistry |
The following references are for critical reviews of published stability constants for various classes of ligands. All these reviews are published by IUPAC and the full text is available, free of charge, in pdf format.
*ethylenediamine (en)
*Nitrilotriacetic acid (NTA)
*aminopolycarboxylic acids (complexones)
*Alpha hydroxy acids and other hydroxycarboxylic acids
*crown ethers
*phosphonic acids
*imidazoles and histamines
*amino acids with polar side-chains
*nucleotides
*acetylacetone
*general
*Chemical speciation of environmentally significant heavy metals with inorganic ligands. Part 1: The Hg–Cl, OH, , , and systems.
*Chemical speciation of environmentally significant metals with inorganic ligands Part 2: The Cu–OH, Cl</sup>, , , and aqueous systems
*Chemical speciation of environmentally significant metals with inorganic ligands Part 3: The Pb–OH, Cl</sup>, , , and systems
*Chemical speciation of environmentally significant metals with inorganic ligands. Part 4: The Cd–OH, Cl, , , and systems | 0 | Theoretical and Fundamental Chemistry |
In organometallic chemistry, a transition metal alkyne complex is a coordination compound containing one or more alkyne ligands. Such compounds are intermediates in many catalytic reactions that convert alkynes to other organic products, e.g. hydrogenation and trimerization. | 0 | Theoretical and Fundamental Chemistry |
Gestonorone caproate has been available widely in Europe, including in the United Kingdom, and has also been marketed in Japan, China, Mexico, and certain other countries. However, it has been discontinued in most countries and its availability is more limited today; it appears to remain marketed only in the Czech Republic, Japan, Mexico, and Russia. It has not been marketed in the United States, Canada, and many other countries. | 0 | Theoretical and Fundamental Chemistry |
Turbulence and radiative transfer are the most important physical processes that have to be parameterized in a prognostic mesoscale model. In the MEMO model, radiative transfer is calculated with an efficient scheme based on the emissivity method for longwave radiation and an implicit multilayer method for shortwave radiation (Moussiopoulos 1987).
The diffusion terms may be represented as the divergence of the corresponding fluxes. For turbulence parameterizations, K-theory is applied. In case of MEMO turbulence can be treated either with a zero-, one- or two-equation turbulence model. For most applications a one-equation model is used, where a conservation equation for the turbulent kinetic energy is solved. | 1 | Applied and Interdisciplinary Chemistry |
DNA ends refer to the properties of the ends of linear DNA molecules, which in molecular biology are described as "sticky" or "blunt" based on the shape of the complementary strands at the terminus. In sticky ends, one strand is longer than the other (typically by at least a few nucleotides), such that the longer strand has bases which are left unpaired. In blunt ends, both strands are of equal length – i.e. they end at the same base position, leaving no unpaired bases on either strand.
The concept is used in molecular biology, in cloning, or when subcloning insert DNA into vector DNA. Such ends may be generated by restriction enzymes that break the molecule's phosphodiester backbone at specific locations, which themselves belong to a larger class of enzymes called exonucleases and endonucleases. A restriction enzyme that cuts the backbones of both strands at non-adjacent locations leaves a staggered cut, generating two overlapping sticky ends, while an enzyme that makes a straight cut (at locations directly across from each other on both strands) generates two blunt ends. | 1 | Applied and Interdisciplinary Chemistry |
Recent research indicates that hyperspectral imaging may be useful to detect the development of cracks in pavements which are hard to detect from images taken with visible spectrum cameras. | 0 | Theoretical and Fundamental Chemistry |
To understand the photoreceptor's behavior to light intensities, it is necessary to understand the roles of different currents.
There is an ongoing outward potassium current through nongated K-selective channels. This outward current tends to hyperpolarize the photoreceptor at around −70 mV (the equilibrium potential for K).
There is also an inward sodium current carried by cGMP-gated sodium channels. This "dark current" depolarizes the cell to around −40 mV. This is significantly more depolarized than most other neurons.
A high density of Na-K pumps enables the photoreceptor to maintain a steady intracellular concentration of Na and K.
When light intensity increases, the potential of the membrane decreases (hyperpolarization). Because as the intensity increases, the release of the stimulating neurotransmitter glutamate of the photoreceptors is reduced. When light intensity decreases, that is, in the dark environment, glutamate release by photoreceptors increases. This increases the membrane potential and produces membrane depolarization. | 1 | Applied and Interdisciplinary Chemistry |
Using PICUP on protein complexes is useful in providing catalytic and kinetic information about these proteins, as catalytic mechanisms are rapid and PICUP allows for fast and highly efficient cross-linking of proteins. Some epitope and affinity tags were shown to be unaffected by the PICUP reaction, enabling visualization of the cross-linked proteins.
Furthermore, PICUP allows for visualization of quantitative bands of protein oligomer distribution when it is coupled with protein fractionation techniques. This combination is especially useful when examining the oligomers of neurodegenerative diseases, such as Alzheimers disease, Parkinsons disease, and Huntington's disease, that result from protein aggregation. PICUP is extremely important when possible prevention and treatment procedures for these diseases are explored, as it is necessary to investigate the aggregation propensity of the respective amyloidogenic proteins. | 1 | Applied and Interdisciplinary Chemistry |
Since a proton-transferred geometry is usually the minimum-energy tautomer only in the excited state and relatively unstable in the ground state, molecules that have ESIPT character may show extraordinarily larger Stokes shift than common fluorescent molecules, or exhibit dual fluorescence that shorter-wavelength one comes from the original tautomer and longer-wavelength one from proton-transferred tautomer. However, there are some exceptional cases where ESIPT molecules have no dual luminescence or significantly red-shifted emission from proton-transferred tautomer, from various reasons.
Rate of ESIPT process may slow down by deuterium substitution of hydrogen that is transferred in ESIPT, because the deuteration increases only mass of the transferred significantly while do not change electrostatic potential in the molecule substantially. However the amount of rate change may lie in the range of 1~50, depending on the shape and size of potential energy surfaces of the molecule. | 0 | Theoretical and Fundamental Chemistry |
The structure of chitin was determined by Albert Hofmann in 1929. Hofmann hydrolyzed chitin using a crude preparation of the enzyme chitinase, which he obtained from the snail Helix pomatia.
Chitin is a modified polysaccharide that contains nitrogen; it is synthesized from units of N-acetyl--glucosamine (to be precise, 2-(acetylamino)-2-deoxy--glucose). These units form covalent β-(1→4)-linkages (like the linkages between glucose units forming cellulose). Therefore, chitin may be described as cellulose with one hydroxyl group on each monomer replaced with an acetyl amine group. This allows for increased hydrogen bonding between adjacent polymers, giving the chitin-polymer matrix increased strength.
In its pure, unmodified form, chitin is translucent, pliable, resilient, and quite tough. In most arthropods, however, it is often modified, occurring largely as a component of composite materials, such as in sclerotin, a tanned proteinaceous matrix, which forms much of the exoskeleton of insects. Combined with calcium carbonate, as in the shells of crustaceans and molluscs, chitin produces a much stronger composite. This composite material is much harder and stiffer than pure chitin, and is tougher and less brittle than pure calcium carbonate. Another difference between pure and composite forms can be seen by comparing the flexible body wall of a caterpillar (mainly chitin) to the stiff, light elytron of a beetle (containing a large proportion of sclerotin).
In butterfly wing scales, chitin is organized into stacks of gyroids constructed of chitin photonic crystals that produce various iridescent colors serving phenotypic signaling and communication for mating and foraging. The elaborate chitin gyroid construction in butterfly wings creates a model of optical devices having potential for innovations in biomimicry. Scarab beetles in the genus Cyphochilus also utilize chitin to form extremely thin scales (five to fifteen micrometres thick) that diffusely reflect white light. These scales are networks of randomly ordered filaments of chitin with diameters on the scale of hundreds of nanometres, which serve to scatter light. The multiple scattering of light is thought to play a role in the unusual whiteness of the scales. In addition, some social wasps, such as Protopolybia chartergoides, orally secrete material containing predominantly chitin to reinforce the outer nest envelopes, composed of paper.
Chitosan is produced commercially by deacetylation of chitin by treatment with sodium hydroxide. Chitosan has a wide range of biomedical applications including wound healing, drug delivery and tissue engineering. Due to its specific intermolecular hydrogen bonding network, dissolving chitin in water is very difficult.Chitosan (with a degree of deacetylation of more than ~28%), on the other hand, can be dissolved in dilute acidic aqueous solutions below a pH of 6.0 such as acetic, formic and lactic acids. Chitosan with a degree of deacetylation greater than ~49% is soluble in water | 1 | Applied and Interdisciplinary Chemistry |
The HILIC mode of separation is used extensively for separation of some biomolecules, organic and some inorganic molecules by differences in polarity. Its utility has increased due to the simplified sample preparation for biological samples, when analyzing for metabolites, since the metabolic process generally results in the addition of polar groups to enhance elimination from the cellular tissue. This separation technique is also particularly suitable for glycosylation analysis and quality assurance of glycoproteins and glycoforms in biologic medical products. For the detection of polar compounds with the use of electrospray-ionization mass spectrometry as a chromatographic detector, HILIC can offer a ten fold increase in sensitivity over reversed-phase chromatography because the organic solvent is much more volatile. | 1 | Applied and Interdisciplinary Chemistry |
The three atoms in a cyanate ion lie on a straight line, giving the ion a linear structure. The electronic structure is described most simply as
: :Ö̤−C≡N:
with a single C−O bond and a triple C≡N bond. (Or more completely as :Ö̤−C≡N: ↔ Ö̤=C=N̤̈ ↔ :O≡C−N̤̈:) The infrared spectrum of a cyanate salt has a band at ca. 2096 cm; such a high frequency is characteristic of a triple bond.
The cyanate ion is a Lewis base. Both the oxygen and nitrogen atoms carry a lone pair of electrons and either one, the other, or both can be donated to Lewis acid acceptors. It can be described as an ambidentate ligand. | 0 | Theoretical and Fundamental Chemistry |
The triazine family of herbicides, which includes atrazine, was introduced in the 1950s; they have the current distinction of being the herbicide family of greatest concern regarding groundwater contamination. Atrazine does not break down readily (within a few weeks) after being applied to soils of above-neutral pH. Under alkaline soil conditions, atrazine may be carried into the soil profile as far as the water table by soil water following rainfall causing the aforementioned contamination. Atrazine is thus said to have "carryover", a generally undesirable property for herbicides.
Glyphosate had been first prepared in the 1950s but its herbicidal activity was only recognized in the 1960s. It was marketed as Roundup in 1971. The development of glyphosate-resistant crop plants, it is now used very extensively for selective weed control in growing crops. The pairing of the herbicide with the resistant seed contributed to the consolidation of the seed and chemistry industry in the late 1990s.
Many modern herbicides used in agriculture and gardening are specifically formulated to degrade within a short period after application. | 1 | Applied and Interdisciplinary Chemistry |
The Davisson–Germer Prize in Atomic or Surface Physics is an annual prize that has been awarded by the American Physical Society since 1965. The recipient is chosen for "outstanding work in atomic physics or surface physics". The prize is named after Clinton Davisson and Lester Germer, who first measured electron diffraction, and as of 2007 it is valued at $5,000. | 0 | Theoretical and Fundamental Chemistry |
Since FFT based analyzers are only capable of considering narrow bands, one technique is to combine swept and FFT analysis for consideration of wide and narrow spans. This technique allows for faster sweep time.
This method is made possible by first down converting the signal, then digitizing the intermediate frequency and using superheterodyne or FFT techniques to acquire the spectrum.
One benefit of digitizing the intermediate frequency is the ability to use digital filters, which have a range of advantages over analog filters such as near perfect shape factors and improved filter settling time. Also, for consideration of narrow spans, the FFT can be used to increase sweep time without distorting the displayed spectrum. | 0 | Theoretical and Fundamental Chemistry |
Captopril, sold under the brand name Capoten among others, is an angiotensin-converting enzyme (ACE) inhibitor used for the treatment of hypertension and some types of congestive heart failure. Captopril was the first oral ACE inhibitor found for the treatment of hypertension. It does not cause fatigue as associated with beta-blockers. Due to the adverse drug event of causing hyperkalemia, as seen with most ACE Inhibitors, the medication is usually paired with a diuretic.
Captopril was patented in 1976 and approved for medical use in 1980. | 0 | Theoretical and Fundamental Chemistry |
In the Kroll process, the TiCl is reduced by liquid magnesium to give titanium metal:
The reduction is conducted at 800–850 °C in a stainless steel retort. Complications result from partial reduction of the TiCl, giving to the lower chlorides TiCl and TiCl. The MgCl can be further refined back to magnesium. The resulting porous metallic titanium sponge is purified by leaching or vacuum distillation. The sponge is crushed, and pressed before it is melted in a consumable carbon electrode vacuum arc furnace. The melted ingot is allowed to solidify under vacuum. It is often remelted to remove inclusions and ensure uniformity. These melting steps add to the cost of the product. Titanium is about six times as expensive as stainless steel.
In the earlier Hunter process, which ceased to be commercial in the 1990s, the TiCl from the chloride process is reduced to the metal by sodium. | 1 | Applied and Interdisciplinary Chemistry |
#Isolate the fly genome.
#Undergo a light digest (using an enzyme [enzyme 1] known NOT to cut in the reporter gene), giving fragments of a few kilobases, a few with the insertion and its flanking DNA.
#Self ligate the digest (low DNA concentration to ensure self ligation) giving a selection of circular DNA fragments, a few with the insertion and its flanking DNA.
#Cut the plasmids at some point in the reporter gene (with an enzyme [enzyme 2] known to cut very rarely in genomic DNA, but is known to in the reporter gene).
#Using primers for the reporter gene sections, the DNA can be amplified for sequencing.
The process of cutting, self ligation and re cutting allows the amplification of the flanking regions of DNA without knowing the sequence. The point at which the ligation occurred can be seen by identifying the cut site of [enzyme 1]. | 1 | Applied and Interdisciplinary Chemistry |
Surface diffusion kinetics can be thought of in terms of adatoms residing at adsorption sites on a 2D lattice, moving between adjacent (nearest-neighbor) adsorption sites by a jumping process. The jump rate is characterized by an attempt frequency and a thermodynamic factor that dictates the probability of an attempt resulting in a successful jump. The attempt frequency ν is typically taken to be simply the vibrational frequency of the adatom, while the thermodynamic factor is a Boltzmann factor dependent on temperature and E, the potential energy barrier to diffusion. Equation 1 describes the relationship:
Where ν and E are as described above, Γ is the jump or hopping rate, T is temperature, and k is the Boltzmann constant. E must be smaller than the energy of desorption for diffusion to occur, otherwise desorption processes would dominate. Importantly, equation 1 tells us how strongly the jump rate varies with temperature. The manner in which diffusion takes place is dependent on the relationship between E and kT as is given in the thermodynamic factor: when E T the thermodynamic factor approaches unity and E ceases to be a meaningful barrier to diffusion. This case, known as mobile diffusion, is relatively uncommon and has only been observed in a few systems. For the phenomena described throughout this article, it is assumed that E >> kT and therefore Γ from an Arrhenius plot of the logarithm of the diffusion coefficient, D, versus 1/T. For cases where more than one diffusion mechanism is present (see below), there may be more than one E such that the relative distribution between the different processes would change with temperature.
Random walk statistics describe the mean squared displacement of diffusing species in terms of the number of jumps N and the distance per jump a. The number of successful jumps is simply Γ multiplied by the time allowed for diffusion, t. In the most basic model only nearest-neighbor jumps are considered and a corresponds to the spacing between nearest-neighbor adsorption sites. The root mean squared displacement goes as:
The diffusion coefficient is given as:
where for 1D diffusion as would be the case for in-channel diffusion, for 2D diffusion, and for 3D diffusion. | 0 | Theoretical and Fundamental Chemistry |
Physalaemin (PHY) is known to take on both a linear and helical three dimensional structure. Grace et al. (2010) have shown that in aqueous environments, PHY preferentially takes on the linear conformation whereas in an environment that simulates a cellular membrane, PHY takes on a helical confirmation from the Pro residue to the C-Terminus. This helical conformation is essential to allow the binding of PHY to neurokinin-1 (NK1) receptors. Consensus sequences between Substance P (a mammalian tachykinin and agonist of NK1) and PHY have been used to confirm that the helical confirmation is necessary for PHY to bind to NK1. | 1 | Applied and Interdisciplinary Chemistry |
The Dulong–Petit law, a thermodynamic law proposed by French physicists Pierre Louis Dulong and Alexis Thérèse Petit, states that the classical expression for the molar specific heat capacity of certain chemical elements is constant for temperatures far from the absolute zero.
In modern terms, Dulong and Petit found that the heat capacity of a mole of many solid elements is about 3R, where R is the universal gas constant. The modern theory of the heat capacity of solids states that it is due to lattice vibrations in the solid. | 0 | Theoretical and Fundamental Chemistry |
The types of gel most typically used are agarose and polyacrylamide gels. Each type of gel is well-suited to different types and sizes of the analyte. Polyacrylamide gels are usually used for proteins and have very high resolving power for small fragments of DNA (5-500 bp). Agarose gels, on the other hand, have lower resolving power for DNA but have a greater range of separation, and are therefore used for DNA fragments of usually 50–20,000 bp in size, but the resolution of over 6 Mb is possible with pulsed field gel electrophoresis (PFGE). Polyacrylamide gels are run in a vertical configuration while agarose gels are typically run horizontally in a submarine mode. They also differ in their casting methodology, as agarose sets thermally, while polyacrylamide forms in a chemical polymerization reaction. | 1 | Applied and Interdisciplinary Chemistry |
Until recent years, the US Agency for Toxic Substances and Disease Registry (ATSDR) contended that trichloroethylene had little-to-no carcinogenic potential and was probably a co-carcinogen—that is, it acted in concert with other substances to promote the formation of tumors.
State, federal, and international agencies classify trichloroethylene as a known or probable carcinogen. In 2014, the International Agency for Research on Cancer updated its classification of trichloroethylene to Group 1, indicating that sufficient evidence exists that it causes cancer of the kidney in humans as well as some evidence of cancer of the liver and non-Hodgkin's lymphoma.
In the European Union, the Scientific Committee on Occupational Exposure Limit Values (SCOEL) recommends an exposure limit for workers exposed to trichloroethylene of 10 ppm (54.7 mg/m) for 8-hour TWA and of 30 ppm (164.1 mg/m) for STEL (15 minutes).
Existing EU legislation aimed at protection of workers against risks to their health (including Chemical Agents Directive 98/24/EC and Carcinogens Directive 2004/37/EC) currently do not impose binding minimum requirements for controlling risks to workers' health during the use phase or throughout the life cycle of trichloroethylene.
In 2023, the United States EPA determined that trichloroethylene presents an unreasonable risk of injury to human health under 52 out of 54 conditions of use, including during manufacturing, processing, mixing, recycling, vapor degreasing, as a lubricant, adhesive, sealant, cleaning product, and spray. It is dangerous from both inhalation and dermal exposure and was most strongly associated with immunosuppressive effects for acute exposure, as well as autoimmune effects for chronic exposures. As of June 1, 2023, two U.S. states (Minnesota and New York) have acted on the EPA's findings and banned trichloroethylene in all cases but research and development. According to the US EPA, in October 2023 it "proposed to ban the manufacture (including import), processing, and distribution in commerce of TCE for all uses, with longer compliance time frames and workplace controls (including an exposure limit) for some processing and industrial and commercial uses until the prohibitions come into effect" to protect everyone including bystanders from the harmful health effects of TCE. | 1 | Applied and Interdisciplinary Chemistry |
Porous carbons (PCs) are versatile materials with a wide range of applications, including sensors, actuators, thermal insulation, and energy conversion. Some examples of PCs are graphene and carbon nanotube-based aerogel. Physical properties that make PCs unique are their low density, high conductivity, mechanical flexibility, and stability in extreme environments. | 0 | Theoretical and Fundamental Chemistry |
Kirsch and co-workers were able to hydroxylate keto compounds with IBX in α-position under mild conditions. This method could be extended to β-keto esters. | 0 | Theoretical and Fundamental Chemistry |
Metallic glasses based on the Mg-Zn-Ca ternary alloy system only consist of the elements which already exist inside the human body. As such, it is being explored as a potential bioresorbable biomaterial for use in orthopaedic applications. | 1 | Applied and Interdisciplinary Chemistry |
A plants leaves and stem may be covered with sharp prickles, spines, thorns or trichomes- hairs on the leaf often with barbs, sometimes containing irritants or poisons. Plant structural features like spines, thorns and awns reduce feeding by large ungulate herbivores (e.g. kudu, impala, and goats) by restricting the herbivores feeding rate, or by wearing down the molars. Trichomes are frequently associated with lower rates of plant tissue digestion by insect herbivores. Raphides are sharp needles of calcium oxalate or calcium carbonate in plant tissues, making ingestion painful, damaging a herbivores mouth and gullet and causing more efficient delivery of the plants toxins. The structure of a plant, its branching and leaf arrangement may also be evolved to reduce herbivore impact. The shrubs of New Zealand have evolved special wide branching adaptations believed to be a response to browsing birds such as the moas. Similarly, African Acacias have long spines low in the canopy, but very short spines high in the canopy, which is comparatively safe from herbivores such as giraffes.
Trees such as palms protect their fruit by multiple layers of armor, needing efficient tools to break through to the seed contents. Some plants, notably the grasses, use indigestible silica (and many plants use other relatively indigestible materials such as lignin) to defend themselves against vertebrate and invertebrate herbivores. Plants take up silicon from the soil and deposit it in their tissues in the form of solid silica phytoliths. These mechanically reduce the digestibility of plant tissue, causing rapid wear to vertebrate teeth and to insect mandibles, and are effective against herbivores above and below ground. The mechanism may offer future sustainable pest-control strategies. | 1 | Applied and Interdisciplinary Chemistry |
Supramolecular catalysts can accelerate reactions not only by placing the two reactants in close proximity but also by stabilizing the transition state of the reaction and reducing activation energy. While this fundamental principle of catalysis is common in small molecule or heterogeneous catalysts, supramolecular catalysts however has a difficult time utilizing the concept due to their often rigid structures. Unlike enzymes that can change shape to accommodate the substrates, supramolecules do not have that kind of flexibility and so rarely achieve sub-angstrom adjustment required for perfect transition state stabilization.
An example of catalysts of this type is Sander's porphyrin trimer. A Diels Alder reaction between two pyridine functionalized substrates normally yield a mixture of endo and exo products. In the presence of the two catalysts, however, complete endo selectivity or exo selectivity could be obtained. The underlying cause of the selectivity is the coordination interaction between pyridine and the zinc ion on porphyrin. Depending on the shape of the catalysts, one product is preferred over the other. | 0 | Theoretical and Fundamental Chemistry |
Electrical resistance heating is used by the environmental restoration industry for remediation of contaminated soil and groundwater. ERH consists of constructing electrodes in the ground, applying alternating current (AC) electricity to the electrodes and heating the subsurface to temperatures that promote the evaporation of contaminants. Volatilized contaminants are captured by a subsurface vapor recovery system and conveyed to the surface along with recovered air and steam. Similar to Soil vapor extraction, the air, steam and volatilized contaminants are then treated at the surface to separate water, air and the contaminants. Treatment of the various streams depends on local regulations and the amount of contaminant.
Some low volatility organic contaminants have a short hydrolysis half-life For contaminants like these, i.e. 1,1,2,2-Tetrachloroethane and 1,1,1-trichloroethane, hydrolysis can be the primary form of remediation. As the subsurface is heated the hydrolysis half-life of the contaminant will decrease as described by the Arrhenius equation. This results in a rapid degradation of the contaminant. The hydrolysis by-product may be remediated by conventional ERH, however the majority of the mass of the primary contaminant will not be recovered but rather will degrade to a by-product.
There are predominantly two electrical load arrangements for ERH: three-phase and six-phase. Three-phase heating consists of electrodes in a repeating triangular or delta pattern. Adjacent electrodes are of a different electrical phase so electricity conducts between them as shown in Figure 1. The contaminated area is depicted by the green shape while the electrodes are depicted by the numbered circles.
Six-phase heating consists of six electrodes in a hexagonal pattern with a neutral electrode in the center of the array. The six-phase arrays are outlined in blue in Figure 2 below. Once again the contaminated area is depicted by the green shape while the electrodes are depicted by the numbered circles. In a six-phase heating pattern there can be hot spots and cold spots depending on the phases that are next to each other. For this reason, six-phase heating typically works best on small circular areas that are less than 65 feet in diameter.
ERH is typically most effective on volatile organic compounds (VOCs). The chlorinated compounds perchloroethylene, trichloroethylene, and cis- or trans- 1,2-dichloroethylene are contaminants that are easily remediated with ERH. The table shows contaminants that can be remediated with ERH along with their respective boiling points. Less volatile contaminants like xylene or diesel can also be remediated with ERH but energy requirements increase as the volatility decreases.
Electrode spacing and operating time can be adjusted to balance the overall remediation cost with the desired cleanup time. A typical remediation may consist of electrodes spaced 15 to 20 feet apart with operating times usually less than a year. The design and cost of an ERH remediation system depends on a number of factors, primarily the volume of soil/groundwater to be treated, the type of contamination, and the treatment goals. The physical and chemical properties of the target compounds are governed by laws that make heated remediations advantageous over most conventional methods. The electrical energy usage required for heating the subsurface and volatilizing the contaminants can account for 5 to 40% of the overall remediation cost.
There are several laws that govern an ERH remediation. Dalton’s law governs the boiling point of a relatively insoluble contaminant. Raoult’s law governs the boiling point of mutually soluble co-contaminants and Henry’s law governs the ratio of the contaminant in the vapor phase to the contaminant in the liquid phase. | 1 | Applied and Interdisciplinary Chemistry |
Unlike LPB, traditional burnishing tools consist of a hard wheel or fixed lubricated ball pressed into the surface of an asymmetrical work piece with sufficient force to deform the surface layers, usually in a lathe. The process does multiple passes over the work pieces, usually under increasing load, to improve surface finish and deliberately cold work the surface. Roller and ball burnishing have been studied in Russia and Japan, and were applied most extensively in the USSR in the 1970s. Various burnishing methods are used, particularly in Eastern Europe, to improve fatigue life. Improvements in HCF, corrosion fatigue and SCC are documented, with fatigue strength enhancement attributed to improved finish, the development of a compressive surface layer, and the increased yield strength of the cold worked surface.
LPB was developed and patented by Lambda Technologies in Cincinnati, Ohio in 1996. Since then, LPB has been developed to produce compression in a wide array of materials to mitigate surface damage, including fretting, corrosion pitting, stress corrosion cracking (SCC), and foreign object damage (FOD), and is being employed to aid in daily MRO operations. To this day, LPB is the only metal improvement method applied under continuous closed-loop process control and has been successfully applied to turbine engines, piston engines, propellers, aging aircraft structures, landing gear, nuclear waste material containers, biomedical implants, armaments, fitness equipment and welded joints. The applications involved titanium, iron, nickel and steel-based components and showed improved damage tolerance as well as high and low cycle fatigue performance by an order of magnitude. | 1 | Applied and Interdisciplinary Chemistry |
GTPases function as molecular switches or timers in many fundamental cellular processes.
Examples of these roles include:
* Signal transduction in response to activation of cell surface receptors, including transmembrane receptors such as those mediating taste, smell and vision.
* Protein biosynthesis (a.k.a. translation) at the ribosome.
* Regulation of cell differentiation, proliferation, division and movement.
* Translocation of proteins through membranes.
* Transport of vesicles within the cell, and vesicle-mediated secretion and uptake, through GTPase control of vesicle coat assembly.
GTPases are active when bound to GTP and inactive when bound to GDP. In the generalized receptor-transducer-effector signaling model of Martin Rodbell, signaling GTPases act as transducers to regulate the activity of effector proteins. This inactive-active switch is due to conformational changes in the protein distinguishing these two forms, particularly of the "switch" regions that in the active state are able to make protein-protein contacts with partner proteins that alter the function of these effectors. | 1 | Applied and Interdisciplinary Chemistry |
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