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When hemoglobin is exposed to certain conditions, reversible or irreversible hemichromes are formed.
Reversible hemichrome formation occurs in the presence of:
* Fatty acids
* Aliphatic alcohol (n-butanol)
* Dehydration
* High concentration of glycerol
* Polyethylene glycol
Irreversible hemichrome formation occurs in the presence of:
* Phenylhydrazine
* Sodium dodecyl sulphate (SDS) | 1 | Biochemistry |
The duplication and transmission of genetic material from one generation of cells to the next is the basis for molecular inheritance and the link between the classical and molecular pictures of genes. Organisms inherit the characteristics of their parents because the cells of the offspring contain copies of the genes in their parents' cells. In asexually reproducing organisms, the offspring will be a genetic copy or clone of the parent organism. In sexually reproducing organisms, a specialized form of cell division called meiosis produces cells called gametes or germ cells that are haploid, or contain only one copy of each gene. The gametes produced by females are called eggs or ova, and those produced by males are called sperm. Two gametes fuse to form a diploid fertilized egg, a single cell that has two sets of genes, with one copy of each gene from the mother and one from the father.
During the process of meiotic cell division, an event called genetic recombination or crossing-over can sometimes occur, in which a length of DNA on one chromatid is swapped with a length of DNA on the corresponding homologous non-sister chromatid. This can result in reassortment of otherwise linked alleles. The Mendelian principle of independent assortment asserts that each of a parent's two genes for each trait will sort independently into gametes; which allele an organism inherits for one trait is unrelated to which allele it inherits for another trait. This is in fact only true for genes that do not reside on the same chromosome or are located very far from one another on the same chromosome. The closer two genes lie on the same chromosome, the more closely they will be associated in gametes and the more often they will appear together (known as genetic linkage). Genes that are very close are essentially never separated because it is extremely unlikely that a crossover point will occur between them. | 1 | Biochemistry |
The atmospheric abundance of CFC-115 rose from 8.4 parts per trillion (ppt) in year 2010 to 8.7 ppt in 2020 based on analysis of air samples gathered from sites around the world. | 2 | Environmental Chemistry |
* Guttmann, Y.M. (1999). The Concept of Probability in Statistical Physics, Cambridge University Press, Cambridge UK, . | 7 | Physical Chemistry |
From 1954 until 1971, the Fox River in Appleton, Wisconsin, had PCBs deposited into it from Appleton Paper/NCR, P.H. Gladfelter, Georgia-Pacific and other notable local paper manufacturing facilities. The Wisconsin DNR estimates that after wastewater treatment the PCB discharges to the Fox River due to production losses ranged from 81,000 kg to 138,000 kg. (178,572 lbs. to 304,235 lbs). The production of Carbon Copy Paper and its byproducts led to the discharge into the river. Fox River clean up is ongoing. | 2 | Environmental Chemistry |
In chemistry, fine chemicals are complex, single, pure chemical substances, produced in limited quantities in multipurpose plants by multistep batch chemical or biotechnological processes. They are described by exacting specifications, used for further processing within the chemical industry and sold for more than $10/kg (see the comparison of fine chemicals, commodities and specialties). The class of fine chemicals is subdivided either on the basis of the added value (building blocks, advanced intermediates or active ingredients), or the type of business transaction, namely standard or exclusive products.
Fine chemicals are produced in limited volumes (< 1000 tons/year) and at relatively high prices (> $10/kg) according to exacting specifications, mainly by traditional organic synthesis in multipurpose chemical plants. Biotechnical processes are gaining ground. Fine chemicals are used as starting materials for specialty chemicals, particularly pharmaceuticals, biopharmaceuticals and agrochemicals. Custom manufacturing for the life science industry plays a big role; however, a significant portion of the fine chemicals total production volume is manufactured in-house by large users. The industry is fragmented and extends from small, privately owned companies to divisions of big, diversified chemical enterprises. The term "fine chemicals" is used in distinction to "heavy chemicals", which are produced and handled in large lots and are often in a crude state.
Since the late 1970s, fine chemicals have become an important part of the chemical industry. Their global total production value of $85 billion is split about 60-40 between in-house production in the life-science industry—the products' main consumers—and companies producing them for sale. The latter pursue both a "supply push" strategy, whereby standard products are developed in-house and offered ubiquitously, and a "demand pull" strategy, whereby products or services determined by the customer are provided exclusively on a "one customer / one supplier" basis. The products are mainly used as building blocks for proprietary products. The hardware of the top tier fine chemical companies has become almost identical. The design, lay-out and equipment of the plants and laboratories have become practically the same globally. Most chemical reactions performed go back to the days of the dyestuff industry. Numerous regulations determine the way labs and plants must be operated, thereby contributing to the uniformity. | 0 | Organic Chemistry |
The CRFs in thin layer chromatography characterize the equal-spreading of the spots. The ideal case, when the RF of the spots are uniformly distributed in <0,1> range (for example 0.25,0.5 and 0.75 for three solutes) should be characterized as the best situation possible.
The simplest criteria are and product (Wang et al., 1996). They are the smallest difference between sorted RF values, or product of such differences.
Another function is the multispot response function (MRF) as developed by De Spiegeleer et al.{Analytical Chemistry (1987):59(1),62-64} It is based also of differences product. This function always lies between 0 and 1. When two RF values are equal, it is equal to 0, when all RF values are equal-spread, it is equal to 1. The L and U values – upper and lower limit of RF – give possibility to avoid the band region.
The last example of coefficient sensitive to minimal distance between spots is Retention distance (Komsta et al., 2007)
The second group are criteria insensitive for minimal difference between RF values (if two compounds are not separated, such CRF functions will not indicate it). They are equal to zero in equal-spread state increase when situation is getting worse.
There are:
Separation response (Bayne et al., 1987)
Performance index (Gocan et al., 1991)
Informational entropy (Gocan et al., 1991, second reference)
Retention uniformity (Komsta et al., 2007)
In all above formulas, n is the number of compounds separated, R are the Retention factor of the compounds sorted in non-descending order, R = 0 and R = 1. | 3 | Analytical Chemistry |
Cyclohexene derivatives, such as imines, epoxides, and halonium ions, react with nucleophiles in a stereoselective fashion, affording trans-diaxial addition products. The term “Trans-diaxial addition” describes the mechanism of the addition, however the products are likely to equilibrate by ring flip to the lower energy conformer, placing the new substituents in the equatorial position. | 4 | Stereochemistry |
CKLF-like MARVEL transmembrane domain-containing protein 3 (i.e. CMTM3), also termed chemokine-like factor superfamily 3 (i.e. CKLFSF3), is a member of the CKLF-like MARVEL transmembrane domain-containing family (i.e. CMTM) of proteins. In humans, CMTM2 protein is encoded by the CMTM3 gene located in band 22.1 on the long (i.e. "q") arm of chromosome 16. This protein is expressed in a wide range of tissues, including fetal tissues. It is highly expressed in the male reproductive system, particularly testicular tissues and may play a role in the development of this tissue. It is also highly expressed in the immune system including circulating blood cells, i.e. B lymphocytes, CD4+ T lymphocytes, and monocytes. However, CMTM3 protein is weakly expressed or unexpressed in the malignant tissues of several types of cancers. In many but not all of theses cancers, this decreased or lack of expression appears due to methylation of the GpC islands in the promoter region, and thereby the silencing, of the CMTM3 gene.
Studies of CMTM3 protein levels in normal versus malignant tissues found that the malignant tissue levels of several types of cancer were lower, in a variable percentage of cases, than the levels in the normal tissues as well as the cases with high CMTM2 levels in the same cancer type. These cancers included those of the stomach, breast, nasopharynx (e.g. oral squamous cell carcinoma), male larynx, esophagus, prostate gland, colon, and kidney (i.e. the kidney clear-cell type). Moreover, low cancer tissue levels of CTMT3 protein were found to be associated with poorer prognoses compared to cases with higher levels of this protein in cancers of the stomach, esophagus, nasopharynx (i.e. oral squamous cell carcinoma type), and prostate gland. These finding suggest that the CMTM3 protein may act to suppress the development and/or progression of these cancers. Further studies are needed to support this suggestion and determine if CMTM3 protein can be a useful clinical marker to predict the severity of these cancers and/or serve as a therapeutic target for treating them.
Contrastingly, other studies have reported that: 1) CMTM3 protein promoted the proliferation of cultured glioblastoma immortalized cells; 2) high levels of CMTM3 protein were associated with shorter survival times in individuals with glioblastomas and gastric cancer; 3) analyses of 178 patients with pancreatic cancer found that their tumor tissues had higher CMTM3 protein levels than normal nearby pancreas tissues; and 4) patients with high levels of CMTM3 protein in their pancreatic cancer tissues had poorer prognoses and overall survival rates compared to patients with lower CMTM3 levels in their pancreatic cancer tissues. These findings suggest that CMTM3 acts to promote the development and/or progression of these three cancer types. They support further studies to confirm this suggestion, to determine if CMTM3 can be use as a prognostic indicator and a clinical therapeutic target for these three cancer types. Further investigations into the mechanisms behind the apparent ability of CMTM3 to suppress or promote these cancers are also needed. | 1 | Biochemistry |
In order to access the nucleosomal DNA, the bonds between it and the histone octamer must be broken. This change takes place periodically in the cell as specific regions are transcribed, and it happens genome-wide during replication. Remodeling proteins work in three distinct ways: they can slide the DNA along the surface of the octamer, replace the one histone dimer with a variant, or remove the histone octamer entirely. No matter the method, in order to modify the nucleosomes, the remodeling complexes require energy from ATP hydrolysis to drive their actions.
Of the three techniques, sliding is the most common and least extreme. The basic premise of the technique is to free up a region of DNA that the histone octamer would normally tightly bind. While the technique is not well defined, the most prominent hypothesis is that the sliding is done in an “inchworm” fashion. In this method, using ATP as an energy source, the translocase domain of the nucleosome-remodeling complex detaches a small region of DNA from the histone octamer. This “wave” of DNA, spontaneously breaking and remaking the hydrogen bonds as it goes, then propagates down the nucleosomal DNA until it reaches the last binding site with the histone octamer. Once the wave reaches the end of the histone octamer the excess that was once at the edge is extended into the region of linker DNA. In total, one round of this method moves the histone octamer several base pairs in a particular direction—away from the direction the “wave” propagated. | 1 | Biochemistry |
The structure of a protein-coding gene consists of many elements of which the actual protein coding sequence is often only a small part. These include introns and untranslated regions of the mature mRNA. Noncoding genes can also contain introns that are removed during processing to produce the mature functional RNA.
All genes are associated with regulatory sequences that are required for their expression. First, genes require a promoter sequence. The promoter is recognized and bound by transcription factors that recruit and help RNA polymerase bind to the region to initiate transcription. The recognition typically occurs as a consensus sequence like the TATA box. A gene can have more than one promoter, resulting in messenger RNAs (mRNA) that differ in how far they extend in the 5' end. Highly transcribed genes have "strong" promoter sequences that form strong associations with transcription factors, thereby initiating transcription at a high rate. Others genes have "weak" promoters that form weak associations with transcription factors and initiate transcription less frequently. Eukaryotic promoter regions are much more complex and difficult to identify than prokaryotic promoters.
Additionally, genes can have regulatory regions many kilobases upstream or downstream of the gene that alter expression. These act by binding to transcription factors which then cause the DNA to loop so that the regulatory sequence (and bound transcription factor) become close to the RNA polymerase binding site. For example, enhancers increase transcription by binding an activator protein which then helps to recruit the RNA polymerase to the promoter; conversely silencers bind repressor proteins and make the DNA less available for RNA polymerase.
The mature messenger RNA produced from protein-coding genes contains untranslated regions at both ends which contain binding sites for ribosomes, RNA-binding proteins, miRNA, as well as terminator, and start and stop codons. In addition, most eukaryotic open reading frames contain untranslated introns, which are removed and exons, which are connected together in a process known as RNA splicing. Finally, the ends of gene transcripts are defined by cleavage and polyadenylation (CPA) sites, where newly produced pre-mRNA gets cleaved and a string of ~200 adenosine monophosphates is added at the 3 end. The poly(A) tail protects mature mRNA from degradation and has other functions, affecting translation, localization, and transport of the transcript from the nucleus. Splicing, followed by CPA, generate the final mature mRNA, which encodes the protein or RNA product. Although the general mechanisms defining locations of human genes are known, identification of the exact factors regulating these cellular processes is an area of active research. For example, known sequence features in the 3-UTR can only explain half of all human gene ends.
Many noncoding genes in eukaryotes have different transcription termination mechanisms and they do not have poly(A) tails.
Many prokaryotic genes are organized into operons, with multiple protein-coding sequences that are transcribed as a unit. The genes in an operon are transcribed as a continuous messenger RNA, referred to as a polycistronic mRNA. The term cistron in this context is equivalent to gene. The transcription of an operon's mRNA is often controlled by a repressor that can occur in an active or inactive state depending on the presence of specific metabolites. When active, the repressor binds to a DNA sequence at the beginning of the operon, called the operator region, and represses transcription of the operon; when the repressor is inactive transcription of the operon can occur (see e.g. Lac operon). The products of operon genes typically have related functions and are involved in the same regulatory network. | 1 | Biochemistry |
Xi Zhenfeng (; born April 2, 1963, in Henan) is a Chinese organic chemist.
Xi received his B.S. degree from Xiamen University in 1983, and his M.S. degree from Nanjing University, Zhengzhou University and Henan Institute of Chemistry in 1989. He joined Professor Tamotsu Takahashi's group at the Institute for Molecular Sciences, Japan, as a Ph.D. course student in 1993 and obtained a Ph.D. degree in 1996.
He took an assistant professor position at Hokkaido University, Japan, in 1997, after he worked as a postdoctoral research fellow with Professor Takahashi at Catalyst Research Centre, Hokkaido University. In 1998, he joined the Department of Chemistry, Peking University, China, as an associate professor and was promoted to professor in 1999. He is a Chang Jiang Scholar Distinguished Professor (since 2001) of Peking University. In 2015, he became the academician of Chinese Academy of Sciences.
His research interests are focused on organometallic chemistry and organic synthesis, including development of synthetic methodologies based on selective cleavage of C–H, C–C and C–X bonds mediated by organometallic compounds, development of organometallic reagents, study on mechanisms of reactions involving reactive organometallic intermediates, and synthesis of functional structures.
He is now serving as editor or consultant for several international academic journals, including:
* Applied Organometallic Chemistry (John-Wiley), Associate Editor (since 2008).
* Tetrahedron and Tetrahedron Letters (Elsevier), Board of Consulting Editors (since 2008).
* Synlett and Synthesis (Thieme), Advisory Board (since 2009).
* Asian Journal of Organic Chemistry (John-Wiley), Editorial Board (since 2012).
* Organic Letters (ACS), Associate Editor (since 2013).
He has been visiting professors for several universities/institutes in the worlds, including:
*Hokkaido University, Japan, 2006
*University of Rennes 1, France, 2007
*RIKEN, Japan, 2010 | 0 | Organic Chemistry |
The European Congress on Molecular Spectroscopy (EUCMOS) is held every two years. The first Congress in this series was held in Basel (Switzerland) in 1951. It focuses on all aspects of spectroscopic methods and techniques (including applications), as well as computational and theoretical approaches for the investigation of structure, dynamics, and properties of molecular systems.
This Congress covers various scientific topics including vibrational, electronic and rotational spectroscopies, spectroscopy of surfaces and interfaces, spectroscopy of biological molecules, computational methods in spectroscopy, applied spectroscopies (archaeology, geology, mineralogy, arts, environmental analysis, food analysis, and processing), new materials, and time-resolved spectroscopy. | 7 | Physical Chemistry |
* Loading: Analogous to the starting stage, each module loads its specific amino acid onto its PCP-domain.
* Condensation: The C-domain catalyzes the amide bond formation between the thioester group of the growing peptide chain from the previous module with the amino group of the current module. The extended peptide is now attached to the current PCP-domain.
* Condensation-Cyclization: Sometimes the C-domain is replaced by a Cy-domain, which, in addition to the amide bond formation, catalyzes the reaction of the serine, threonine, or cysteine sidechain with the amide-N, thereby forming oxazolidines and thiazolidine, respectively.
* Epimerization: Sometimes an E-domain epimerizes the innermost amino acid of the peptide chain into the D-configuration.
* This cycle is repeated for each elongation module. | 1 | Biochemistry |
TEOS-10 is based on thermodynamic potentials. Fluids like humid air and liquid water in TEOS-10 are therefore described by the Helmholtz energy F(m,T,V)=F(m,T,m/ρ) or the specific Helmholtz-energy f(T,ρ)=F(m,T,m/ρ)/m. The Helmholtz energy has a unique value across phase boundaries. For the calculation of the thermodynamic properties of seawater and ice, TEOS-10 uses the specific Gibbs potential g(T,P)=G/m, G=F+pV, because the pressure is a more easily measurable property than density in a geophysical context. Gibbs energies are multivalued around phase boundaries and need to be defined for each phase separately.
The thermodynamic potential functions are determined by a set of adjustable parameters which are tuned to fit experimental data and theoretical laws of physics like the ideal gas equation. Since absolute energy and entropy cannot be directly measured, arbitrary reference states for liquid water, seawater and dry air in TEOS-10 are defined in a way that
* internal energy and entropy of liquid water at the solid-liquid-gas triple point are zero,
* entropy and enthalpy of seawater are zero at S (Absolute Salinity) = 35.16504 g/kg, T (Temperature) = 273.15 K, p (pressure) = 101325 Pa,
* entropy and enthalpy of dry air are zero at T (Temperature) = 273.15 K, p (pressure) = 101325 Pa. | 7 | Physical Chemistry |
A lattice arrangement (commonly called a regular arrangement) is one in which the centers of the spheres form a very symmetric pattern which needs only n vectors to be uniquely defined (in n-dimensional Euclidean space). Lattice arrangements are periodic. Arrangements in which the spheres do not form a lattice (often referred to as irregular) can still be periodic, but also aperiodic (properly speaking non-periodic) or random. Because of their high degree of symmetry, lattice packings are easier to classify than non-lattice ones. Periodic lattices always have well-defined densities. | 3 | Analytical Chemistry |
Galling is often found between metallic surfaces where direct contact and relative motion have occurred. Sheet metal forming, thread manufacturing, and other industrial operations may include moving parts, or contact surfaces made of stainless steel, aluminium, titanium, and other metals whose natural development of an external oxide layer through passivation increases their corrosion resistance but renders them particularly susceptible to galling.
In metalworking that involves cutting (primarily turning and milling), galling is often used to describe a wear phenomenon that occurs when cutting soft metal. The work material is transferred to the cutter and develops a "lump." The developed lump changes the contact behavior between the two surfaces, which usually increases adhesion, and resistance to further cutting, and, due to created vibrations, can be heard as a distinct sound.
Galling often occurs with aluminium compounds and is a common cause of tool breakdown. Aluminium is a ductile metal, which means it possesses the ability for plastic flow with relative ease, presupposing a relatively consistent and significant plastic zone.
High ductility and flowing material can be considered a general prerequisite for excessive material transfer and galling because frictional heating is closely linked to the structure of plastic zones around penetrating objects.
Galling can occur even at relatively low loads and velocities because it is the real energy density in the system that induces a phase transition, which often leads to an increase in material transfer and higher friction. | 7 | Physical Chemistry |
Oxide dispersion strengthening is based on incoherency of the oxide particles within the lattice of the material. Coherent particles have a continuous lattice plane from the matrix to the particles whereas incoherent particles do not have this continuity and therefore both lattice planes end at the interface. This mismatch in interfaces results in a high interfacial energy, which impedes dislocation. The oxide particles instead are stable in the matrix, which helps prevent creep. Particle stability implies little dimensional change, embrittlement, effects on properties, stable particle spacing, and general resistance to change at high temperatures.
Since the oxide particles are incoherent, dislocations can only overcome the particles by climb. If instead the particles are semi-coherent or coherent with the lattice, dislocations can simply cut the particles by a more favourable process that requires less energy called dislocation glide or by Orowan bowing between particles, both of which are athermal mechanisms. Dislocation climb is a diffusional process, which is less energetically favourable, and mostly occurs at higher temperatures that provide enough energy to advance via the addition and removal of atoms. Because the particles are incoherent, glide mechanisms alone are not enough and the more energetically exhausting climb process is dominant, meaning that dislocations are stopped more effectively. Climb can occur either at the particle-dislocation interface (local climb) or by overcoming multiple particles at once (general climb). In local climb, the part of the dislocation that is between two particles stays in the glide plane while the rest of the dislocation is climbing along the surface of the particle. For general climb, the dislocations all come out the glide plane. General climb requires less energy because the mechanism decreases the dislocation line length which reduces the elastic strain energy and therefore is the common climb mechanism. For γ’ volume fractions of 0.4 to 0.6 in nickel-based alloys, the threshold stress for local climb is only about 1.25 to 1.40 times higher than general climb.
Dislocations are not limited to either all local or all general climb as the path that requires less energy is taken. Cooperative climb is an example of a more nuanced mechanism where a dislocation travels around a group of particles rather than climbing past each particle individually. McLean stated that the dislocation is most relaxed when climbing over multiple particles because of the skipping of some of the abrupt interfaces between segments in the glide plane to segments that travel along the particle surface.
The presence of incoherent particles introduces a threshold stress (σ), since an additional stress will have to be applied for the dislocations to move past the oxides by climb. After overcoming a particle by climb, dislocations can remain pinned at the particle-matrix interface with an attractive phenomenon called interfacial pinning, which requires additional threshold stress to free a dislocation out of this pinning, which must be overcome for plastic deformation to occur. This detachment phenomenon is a result of the interaction between the particle and the dislocation where total elastic strain energy is reduced. Schroder and Arzt explain that the additional stress required is due to the relaxation caused by the reduction in the stress field as the dislocation climbs and accommodates the shear traction. The following equations represent the strain rate and stress as a result of oxide introduction.
Strain Rate:
Threshold Shear Stress: | 8 | Metallurgy |
In addition to anchoring artificial metal center on a protein, researchers like Frances Arnold also focused on changing the native environment of natural metal cofactor. Due to the protein context in which the metal catalytic center located, ArMs have a large sequence space to evolve to meet different demands on substance specificity and regio- and enantioselectivity. Directed evolution was used to tailor the catalytic capacity and repurpose the enzyme function. Mostly based on native porphyrin-metal cofactor, Arnold's lab has developed many ArMs has unique ArMs to catalyze regioselective and/or enantioselective Carbon-Boron bond formation, carbene insertion, and aminohydroxylation by evolving the sequence context of the corresponding ArMs. | 0 | Organic Chemistry |
Flickering analysis of cellular or membranous structures is a widespread technique for measuring the bending modulus and other properties from the power spectrum of thermal fluctuations.
First demonstrated theoretically by Brochard and Lennon in 1975, flickering spectroscopy has become a widespread technique due to its simplicity and lack of specialised equipment beyond a brightfield microscope. It is used in structures such as red blood cells, giant unilamellar vesicles and other cell-like structures. | 7 | Physical Chemistry |
A quantity of sample is weighed, placed in a crucible, and subjected to destructive distillation. During a fixed period of severe heating, the residue undergoes cracking and coking reactions . At the termination of the heating period, the crucible containing the carbonaceous residue is cooled in a desiccator and weighed. The residue remaining is calculated as a percentage of the original sample, and reported as Conradson carbon residue. | 9 | Geochemistry |
The fractional population distribution of different conformers follows a Boltzmann distribution:
The left hand side is the proportion of conformer i in an equilibrating mixture of M conformers in thermodynamic equilibrium. On the right side, E (k = 1, 2, ..., M) is the energy of conformer k, R is the molar ideal gas constant (approximately equal to 8.314 J/(mol·K) or 1.987 cal/(mol·K)), and T is the absolute temperature. The denominator of the right side is the partition function. | 4 | Stereochemistry |
Human iron metabolism is the set of chemical reactions that maintain human homeostasis of iron at the systemic and cellular level. Iron is both necessary to the body and potentially toxic. Controlling iron levels in the body is a critically important part of many aspects of human health and disease. Hematologists have been especially interested in systemic iron metabolism, because iron is essential for red blood cells, where most of the human body's iron is contained. Understanding iron metabolism is also important for understanding diseases of iron overload, such as hereditary hemochromatosis, and iron deficiency, such as iron-deficiency anemia. | 1 | Biochemistry |
Generally, nucleophilic epoxidations are carried out under inert atmosphere in anhydrous conditions. For zinc-mediated epoxidations, diethylzinc and ligand are first mixed and oxidized, then the enone is introduced. Lanthanide-mediated epoxidations typically require an additive to stabilize the catalyst; this is most commonly triphenylphosphine oxide or triphenylarsine oxide.
Phase-transfer catalyzed epoxidations may be carried out using one of three possible sets of reaction conditions: (1) sodium hypochlorite at room temperature, (2) freshly prepared 8 M potassium hypochlorite, or (3) trichloroisocyanuric acid in aqueous or non-aqueous conditions.
Among polypeptide-based methods, employing a phase transfer catalyst and triphasic media permits lower catalyst loadings. Biphasic conditions using an organic base in conjunction with urea/HO may also be used. | 0 | Organic Chemistry |
The American Brass Superfund site is a former industrial site, located in Henry County, Alabama. American Brass Inc. (ABI) operated a brass smelter and foundry facility on the site between 1978 and 1992. Prior to its closure in December 1992, the company had been cited by the United States Environmental Protection Agency (EPA), and the Alabama Department of Environmental Management, (ADEM), on several occasions for Resource Conservation and Recovery Act (RCRA) violations, arising from its waste and hazardous waste disposal processes. Site surveys, conducted by ADEM after ABI ceased operations, revealed stockpiles of 150,000 tons of contaminated waste, and extensive soil and groundwater contamination.
After assessment by the EPA, it was added to the National Priorities List, in May 1999, for long-term remedial action. | 2 | Environmental Chemistry |
The first committed step of purine biosynthesis starts from 5-phosphoribosyl 1 pyrophosphate. This undergoes a series of reactions to form IMP, an important branch point in the pathway. The pathway then branches to form adenylosuccinate and then adenylate (AMP) in one branch and xanthylate (XMP) and then guanylate (GMP) in the other branch. IMP dehydrogenase catalyses the conversion of IMP to XMP and GMP synthetase catalyses the conversion of XMP to GMP. | 1 | Biochemistry |
In subsequent phase II reactions, these activated xenobiotic metabolites are conjugated with charged species such as glutathione (GSH), sulfate, glycine, or glucuronic acid. Sites on drugs where conjugation reactions occur include carboxy (-COOH), hydroxy (-OH), amino (NH), and thiol (-SH) groups. Products of conjugation reactions have increased molecular weight and tend to be less active than their substrates, unlike Phase I reactions which often produce active metabolites. The addition of large anionic groups (such as GSH) detoxifies reactive electrophiles and produces more polar metabolites that cannot diffuse across membranes, and may, therefore, be actively transported.
These reactions are catalysed by a large group of broad-specificity transferases, which in combination can metabolise almost any hydrophobic compound that contains nucleophilic or electrophilic groups. One of the most important classes of this group is that of the glutathione S-transferases (GSTs). | 1 | Biochemistry |
In organic chemistry, Eschenmoser's salt (named for Albert Eschenmoser) is the ionic, organic compound . It is the iodide salt of the dimethylaminomethylene cation .
The dimethylaminomethylene cation is a strong dimethylaminomethylating agent, used to prepare derivatives of the type . Enolates, silyl enol ethers, and even more acidic ketones undergo efficient dimethylaminomethylation. Once prepared, such tertiary amines can be further methylated and then subjected to base-induced elimination to afford methylidenated ketones. The salt was first prepared by the group of Albert Eschenmoser after whom the reagent is named. | 0 | Organic Chemistry |
* Relative entropy is always non-negative, a result known as Gibbs' inequality, with equals zero if and only if as measures.
In particular, if and , then -almost everywhere. The entropy thus sets a minimum value for the cross-entropy , the expected number of bits required when using a code based on rather than ; and the Kullback–Leibler divergence therefore represents the expected number of extra bits that must be transmitted to identify a value drawn from , if a code is used corresponding to the probability distribution , rather than the "true" distribution .
* No upper-bound exists for the general case. However, it is shown that if and are two discrete probability distributions built by distributing the same discrete quantity, then the maximum value of can be calculated.
* Relative entropy remains well-defined for continuous distributions, and furthermore is invariant under parameter transformations. For example, if a transformation is made from variable to variable , then, since and where is the absolute value of the derivative or more generally of the Jacobian, the relative entropy may be rewritten:
* The Taylor expansion is . | 7 | Physical Chemistry |
Generally pyridinium photoinitiators are N-substituted pyridine derivatives, with a positive charge placed on the nitrogen. The counter ion is in most cases a non-nucleophilic anion. Upon radiation, homolytic bond cleavage takes place generating a pyridinium cationic radical and a neutral free radical. In most cases, a hydrogen atom is abstracted from the oligomer by the pyridinium radical. The free radical generated from the hydrogen abstraction is then terminated by the free radical in solution. This results in a strong pyridinium acid that can initiate polymerization. | 5 | Photochemistry |
Schlögl was one of the pioneers of the research into the geometric structure of organic compounds and the resulting mechanisms of their chemical reactions. He has been very successful with his work on new pharmaceutical substances.
Schlögl authored and co-authored over 200 scientific publications and was an inventor on four patents. He supervised 51 dissertations of his doctoral students.
Schlögl's main field of research since about 1963 was stereochemistry, and in 1970 he began to shift his focus specifically on the chirality of organic compounds. | 0 | Organic Chemistry |
In two dimensions, any lattice can be specified by the length of its two primitive translation vectors and the angle between them. There are an infinite number of possible lattices one can describe in this way. Some way to categorize different types of lattices is desired. One way to do so is to recognize that some lattices have inherent symmetry. One can impose conditions on the length of the primitive translation vectors and on the angle between them to produce various symmetric lattices. These symmetries themselves are categorized into different types, such as point groups (which includes mirror symmetries, inversion symmetries and rotation symmetries) and translational symmetries. Thus, lattices can be categorized based on what point group or translational symmetry applies to them.
In two dimensions, the most basic point group corresponds to rotational invariance under 2π and π, or 1- and 2-fold rotational symmetry. This actually applies automatically to all 2D lattices, and is the most general point group. Lattices contained in this group (technically all lattices, but conventionally all lattices that don't fall into any of the other point groups) are called oblique lattices. From there, there are 4 further combinations of point groups with translational elements (or equivalently, 4 types of restriction on the lengths/angles of the primitive translation vectors) that correspond to the 4 remaining lattice categories: square, hexagonal, rectangular, and centered rectangular. Thus altogether there are 5 Bravais lattices in 2 dimensions.
Likewise, in 3 dimensions, there are 14 Bravais lattices: 1 general "wastebasket" category (triclinic) and 13 more categories. These 14 lattice types are classified by their point groups into 7 lattice systems (triclinic, monoclinic, orthorhombic, tetragonal, cubic, rhombohedral, and hexagonal). | 3 | Analytical Chemistry |
The cleanup process started when there was a survey of Manhattan Project sites. The plant was inspected in 1976 and found low levels of radiation. Westinghouse filed an application in 1988 with the Nuclear Regulatory Commission (NRC) to decommission those buildings. The demolition of the buildings was done from 1993 through 2004. During that period, certain radioactive contamination was removed from the site. However, some contaminated areas were covered with asphalt and concrete. The license on the site was terminated by NRC in 2003 so that the site can be released for unrestricted use, although New Jersey Department of Environmental Protection (NJDEP) disagreed with that decision. In 2006, NJDEP sued Viacom (successor of Westinghouse) and others for the continuation of ground water contamination at the site. | 8 | Metallurgy |
Bacteriorhodopsin is a light-driven proton pump. It is the retinal molecule that changes its isomerization state from all-trans to 13-cis when it absorbs a photon. The surrounding protein responds to the change in the chromophore shape, by undergoing an ordered sequence of conformational changes (collectively known as the photocycle). The conformational changes alter the pK values of conserved amino acids in the core of the protein, including Asp85, Asp96 and the Schiff base N atom (Lys216). These sequential changes in acid dissociation constant, result in the transfer of one proton from the intracellular side to the extracellular side of the membrane for each photon absorbed by the chromophore.
The bacteriorhodopsin photocycle consists of nine distinct stages, starting from the ground or resting state, which is denoted bR. The intermediates are identified by single letters and may be distinguished by their absorption spectra. The nine stages are:
: bR + photon → K L M M M N N O bR | 5 | Photochemistry |
EAB sensors possess the potential to significantly advance our comprehension of metabolism, endocrinology, pharmacokinetics, and neurochemistry as valuable research tools. Specifically, these sensors offer improved resolution and more quantitative measurements of phenomena such as drug delivery, clearance, and the maintenance of metabolic homeostasis. With their capability for feedback control, EAB sensors also present unprecedented opportunities to elucidate the correlation between, for instance, plasma drug levels and subsequent clinical or behavioral responses. The simultaneous measurements performed by EAB sensors in multiple body locations can enhance our understanding of drug and metabolite transport within and between bodily compartments. Beyond in-body measurements, EAB sensors could be beneficial for real-time monitoring in cell culture applications, ranging from small-scale (e.g., "organ on a chip") to industrial scale (e.g., monitoring industrial bioreactors). They have already demonstrated utility in applications such as monitoring ATP release in astrocytes and detecting serotonin in cell culture using glass nanopipettes.
Aptamers, referred to as "chemical antibodies," are used in therapeutics and biosensing due to their specific recognition and binding capabilities toward target molecules. They offer advantages over classical antibodies as they are significantly lighter, easily penetrate intracellular targets, can be synthetically produced, are non-immunogenic, and exhibit stability. Aptamers excel in discerning proteins, demonstrating precision in diagnostics and therapeutics, and have applications in laboratory assays and separations, particularly in biomolecule purification, chiral separation, and biochemical assays. The ability of aptamers to undergo conformational changes makes them ideal for developing quenching-based biosensors, showcasing flexibility that antibodies lack. Unlike antibodies, which are prone to cross-reactivity and batch variations, aptamers offer customizable selectivity and stability. This is particularly evident in biosensor applications targeting low-molecular-weight entities like small molecules | 7 | Physical Chemistry |
For virus-associated tumors, such as cervical cancer and a subset of head and neck cancers, epitopes derived from viral open reading frames contribute to the pool of neoantigens. | 1 | Biochemistry |
In a variation, the Ruff–Fenton degradation (Otto Ruff 1898, H.J.H. Fenton 1893) converts the aldose first to the alpha-hydroxy-carboxylic acid with bromine and calcium hydroxide and then to the shortened aldose by reaction with Iron(III) sulfate and hydrogen peroxide. | 0 | Organic Chemistry |
Chiral inversion is a very important part of designing and making drugs. Because this process can change how chiral drugs work in the body and can cause side effects that can be serious or even fatal. Traditionally, chiral inversions have been studied with NMR spectroscopy at different temperatures and chiroptical methods like polarimetry. But strong, complementary methods based on dynamic chromatography (GC, HPLC, SFC, CEC, and MEKC) and electrophoresis have been made and used to figure out how the enantiomeric composition of stereo-labile chiral compounds changes over time. Most of the time, liquid chromatographic methods are used to do enantioselective analysis of chiral drugs. When an analyte with one stereogenic center or axis is separated well, the chromatogram will show two peaks. But if the analyte is stereo-labile, the peaks tend to merge. How much coalescence there is will depend on how fast chiral inversion and enantioresolution happen. Over time, the peaks will merge into a flat area. Dynamic chromatography shows how the elution profile changes over time. This makes it useful for figuring out how pH, temperature, and solvents affect chiral inversion, which can happen on the stationary phase, in the injector, or in the detector.
Multidimensional approaches have been used to improve separation and detection. Table below shows a list of common methods and experiments used to figure out chiral inversion. Any of these methods can then be used to determine chiral inversion. Which instrument is used to analyze a chiral compound depends on its physical and chemical properties (i.e., the solubility, vapor pressure, thermal and solvent stability, and detection).
For example, capillary electrophoresis or liquid chromatography could be used if the analyte can be ionized and has a high vapor pressure, but it is also soluble in polar solvents. On the other hand, gas chromatography is the best way to test a substance that is stable at high temperatures but has a low vapor pressure. When compared to gas or liquid chromatography, supercritical fluid chromatography is a better way to measure chiral inversion because it uses mass spectrometers and a green method. | 4 | Stereochemistry |
TopFIND is a resource for comprehensive coverage of protein N- and C-termini discovered by all available in silico, in vitro as well as in vivo methodologies. It makes use of existing knowledge by seamless integration of data from UniProt and MEROPS and provides access to new data from community submission and manual literature curating. It renders modifications of protein termini, such as acetylation and citrullination, easily accessible and searchable and provides the means to identify and analyse extend and distribution of terminal modifications across a protein. Since its inception TopFIND has been expanded to further species. | 1 | Biochemistry |
Theodore Cohen (May 11, 1929 – December 13, 2017) was an American organic chemist and chemistry professor at University of Pittsburgh. He is known for his research on organic chemistry, and particularly on organosulfur compounds, on organometallic chemistry, and on the synthesis of phenols. | 0 | Organic Chemistry |
Nutrition polysaccharides are common sources of energy. Many organisms can easily break down starches into glucose; however, most organisms cannot metabolize cellulose or other polysaccharides like cellulose, chitin, and arabinoxylans. Some bacteria and protists can metabolize these carbohydrate types. Ruminants and termites, for example, use microorganisms to process cellulose.
Even though these complex polysaccharides are not very digestible, they provide important dietary elements for humans. Called dietary fiber, these carbohydrates enhance digestion. The main action of dietary fiber is to change the nature of the contents of the gastrointestinal tract and how other nutrients and chemicals are absorbed. Soluble fiber binds to bile acids in the small intestine, making them less likely to enter the body; this, in turn, lowers cholesterol levels in the blood. Soluble fiber also attenuates the absorption of sugar, reduces sugar response after eating, normalizes blood lipid levels and, once fermented in the colon, produces short-chain fatty acids as byproducts with wide-ranging physiological activities (discussion below). Although insoluble fiber is associated with reduced diabetes risk, the mechanism by which this occurs is unknown.
Not yet formally proposed as an essential macronutrient (as of 2005), dietary fiber is nevertheless regarded as important for the diet, with regulatory authorities in many developed countries recommending increases in fiber intake. | 0 | Organic Chemistry |
Marine carbonate ooids are formed in warm, supersaturated, shallow, highly agitated marine water intertidal environments, and their presence in geological records provides a key role in paleoclimatic and paleogeographic reconstructions. Huang et al. (2017), for example, based on the distribution of Permian ooids and glaciomarine diamictites, have repositioned the Baoshan Block in southwestern China, with respect to other Gondwana continents. | 9 | Geochemistry |
Endoglin (ENG) is a type I membrane glycoprotein located on cell surfaces and is part of the TGF beta receptor complex. It is also commonly referred to as CD105, END, FLJ41744, HHT1, ORW and ORW1. It has a crucial role in angiogenesis, therefore, making it an important protein for tumor growth, survival and metastasis of cancer cells to other locations in the body. | 1 | Biochemistry |
Sex pheromones are pheromones released by an organism to attract an individual of the same species, encourage them to mate with them, or perform some other function closely related with sexual reproduction.
Sex pheromones specifically focus on indicating females for breeding, attracting the opposite sex, and conveying information on species, age, sex and genotype. Non-volatile pheromones, or cuticular contact pheromones, are more closely related to social insects as they are usually detected by direct contact with chemoreceptors on the antennae or feet of insects.
Insect sex pheromones have found uses in monitoring and trapping of pest insects. | 1 | Biochemistry |
Restriction digest is most commonly used as part of the process of the molecular cloning of DNA fragment into a vector (such as a cloning vector or an expression vector). The vector typically contains a multiple cloning site where many restriction site may be found, and a foreign piece of DNA may be inserted into the vector by first cutting the restriction sites in the vector as well the DNA fragment, followed by ligation of the DNA fragment into the vector.
Restriction digests are also necessary for performing any of the following analytical techniques:
*RFLP – Restriction fragment length polymorphism
*AFLP – Amplified fragment length polymorphism
*STRP – Short tandem repeat polymorphism | 1 | Biochemistry |
Progesterone is produced in high amounts in the ovaries (by the corpus luteum) from the onset of puberty to menopause, and is also produced in smaller amounts by the adrenal glands after the onset of adrenarche in both males and females. To a lesser extent, progesterone is produced in nervous tissue, especially in the brain, and in adipose (fat) tissue, as well.
During human pregnancy, progesterone is produced in increasingly high amounts by the ovaries and placenta. At first, the source is the corpus luteum that has been "rescued" by the presence of human chorionic gonadotropin (hCG) from the conceptus. However, after the 8th week, production of progesterone shifts to the placenta. The placenta utilizes maternal cholesterol as the initial substrate, and most of the produced progesterone enters the maternal circulation, but some is picked up by the fetal circulation and used as substrate for fetal corticosteroids. At term the placenta produces about 250 mg progesterone per day.
An additional animal source of progesterone is milk products. After consumption of milk products the level of bioavailable progesterone goes up. | 0 | Organic Chemistry |
Several pyridine derivatives play important roles in biological systems. While its biosynthesis is not fully understood, nicotinic acid (vitamin B) occurs in some bacteria, fungi, and mammals. Mammals synthesize nicotinic acid through oxidation of the amino acid tryptophan, where an intermediate product, the aniline derivative kynurenine, creates a pyridine derivative, quinolinate and then nicotinic acid. On the contrary, the bacteria Mycobacterium tuberculosis and Escherichia coli produce nicotinic acid by condensation of glyceraldehyde 3-phosphate and aspartic acid. | 0 | Organic Chemistry |
Zofenopril (INN) is a medication that protects the heart and helps reduce high blood pressure. It is an angiotensin-converting enzyme (ACE) inhibitor.
In small studies, zofenopril appeared significantly more effective in reducing hypertension than two older antihypertensive drugs, atenolol and enalapril, and was associated with fewer adverse effects.
Zofenopril is a prodrug with zofenoprilat as the active metabolite.
It was patented in 1978 and approved for medical use in 2000. | 4 | Stereochemistry |
Chemical mimicry can also have benefits on the reproductive success of the operator. This form is used primarily by flowers in order to deceive pollinators. There are two main types, the first being pseudocopulation which involves attracting male pollinators by mimicking the pheromones of females of the species. The second type involves female plants mimicking the chemical signals of males of the same species. By doing this the female plant is able to draw more pollinators despite not producing the pollen that the animal is looking for. | 1 | Biochemistry |
Texture can be determined by various methods. Some methods allow a quantitative analysis of the texture, while others are only qualitative. Among the quantitative techniques, the most widely used is X-ray diffraction using texture goniometers, followed by the electron backscatter diffraction (EBSD) method in scanning electron microscopes. Qualitative analysis can be done by Laue photography, simple X-ray diffraction or with a polarized microscope. Neutron and synchrotron high-energy X-ray diffraction are suitable for determining textures of bulk materials and in situ analysis, whereas laboratory x-ray diffraction instruments are more appropriate for analyzing textures of thin films.
Texture is often represented using a pole figure, in which a specified crystallographic axis (or pole) from each of a representative number of crystallites is plotted in a stereographic projection, along with directions relevant to the materials processing history. These directions define the so-called sample reference frame and are, because the investigation of textures started from the cold working of metals, usually referred to as the rolling direction RD, the transverse direction TD and the normal direction ND'. For drawn metal wires the cylindrical fiber axis turned out as the sample direction around which preferred orientation is typically observed (see below). | 8 | Metallurgy |
Besides chemical bonds, compliance constants are also useful for determining non-covalent bonds, such as H-bonds in Watson-Crick base pairs. Grunenberg calculated the compliance constant for each of the donor-H⋯acceptor linkages in AT and CG base pairs and found that the central N-H⋯N bond in CG base pair is the strongest one with the compliance constant value of 2.284 Å/mdyn. (Note that the unit is reported in a reverse unit.) In addition, one of the three hydrogen bonding interactions in a AT base pair shows an extremely large compliance value of >20 Å/mdyn indicative of a weak interaction. | 6 | Supramolecular Chemistry |
C5a is an anaphylatoxin, causing increased expression of adhesion molecules on endothelium, contraction of smooth muscle, and increased vascular permeability. C5a des-Arg is a much less potent anaphylatoxin. Both C5a and C5a des-Arg can trigger mast cell degranulation, releasing proinflammatory molecules histamine and TNF-α. C5a is also an effective chemoattractant, initiating accumulation of complement and phagocytic cells at sites of infection or recruitment of antigen-presenting cells to lymph nodes.
C5a plays a key role in increasing migration and adherence of neutrophils and monocytes to vessel walls. White blood cells are activated by upregulation of integrin avidity, the lipoxygenase pathway and arachidonic acid metabolism.
C5a also modulates the balance between activating versus inhibitory IgG Fc receptors on leukocytes, thereby enhancing the autoimmune response. | 1 | Biochemistry |
Favipiravir has been approved to treat influenza in Japan. It is, however, only indicated for novel influenza (strains that cause more severe disease) rather than seasonal influenza. As of 2020, the probability of resistance developing appears low. | 4 | Stereochemistry |
Despite current understanding of 3′-UTRs, they are still relative mysteries. Since mRNAs usually contain several overlapping control elements, it is often difficult to specify the identity and function of each 3′-UTR element, let alone the regulatory factors that may bind at these sites. Additionally, each 3′-UTR contains many alternative AU-rich elements and polyadenylation signals. These cis- and trans-acting elements, along with miRNAs, offer a virtually limitless range of control possibilities within a single mRNA. Future research through the increased use of deep-sequencing based ribosome profiling will reveal more regulatory subtleties as well as new control elements and AUBPs. | 1 | Biochemistry |
Guanylin is a 15 amino acid peptide that is secreted by goblet cells in the colon. Guanylin acts as an agonist of the guanylyl cyclase receptor GC-C and regulates electrolyte and water transport in intestinal and renal epithelia. Upon receptor binding, guanylin increases the intracellular concentration of cGMP, induces chloride secretion and decreases intestinal fluid absorption, ultimately causing diarrhoea. The peptide stimulates the enzyme through the same receptor binding
region as the heat-stable enterotoxins.
Researches have found that a loss in guanylin expression can lead to colorectal cancer due to guanylyl cyclase Cs function as an intestinal tumor suppressor. When guanylin expression was measured on over 250 colon cancer patients, more than 85% of patients had a loss of guanylin expression in cancerous tissue samples by 100-1000 times when compared to the same patientss nearby healthy colon tissue. Another study done on genetically engineered mice found that mice on a high calorie diet had reduced guanylin expression in the colon. This loss of expression then resulted in guanylyl cyclase C inhibition and the formation of tumors, therefore linking diet-induced obesity with colorectal cancer. | 1 | Biochemistry |
Signal peptides are usually located at the N-terminus of proteins. Some have C-terminal or internal signal peptides (examples: peroxisomal targeting signal and nuclear localisation signal). The structure of these nonclassical signal peptides differs vastly from the N-terminal signal peptides. | 1 | Biochemistry |
Xing Qiyi () was a Chinese organic chemist who contributed to the total synthesis of bovine insulin, Xing is still well-known nowadays in China as the main editor of a highly-influential organic chemistry textbook. He was a member of China Democratic League since 1952. | 0 | Organic Chemistry |
Non ideal compressible fluid dynamics (NICFD), or non ideal gas dynamics, is a branch of fluid mechanics studying the dynamic behavior of fluids not obeying ideal-gas thermodynamics. It is for example the case of dense vapors, supercritical flows and compressible two-phase flows. With the term dense vapors, we indicate all fluids in the gaseous state characterized by thermodynamic conditions close to saturation and the critical point. Supercritical fluids feature instead values of pressure and temperature larger than their critical values, whereas two-phase flows are characterized by the simultaneous presence of both liquid and gas phases.
In all these cases, the fluid requires to be modelled as a real gas, since its thermodynamic behavior considerably differs from that of an ideal gas, which by contrast appears for dilute thermodynamic conditions. The ideal-gas law can be employed in general as a reasonable approximation of the fluid thermodynamics for low pressures and high temperatures. Otherwise, intermolecular forces and dimension of fluid particles, which are neglected in the ideal-gas approximation, become relevant and can significantly affect the fluid behavior. This is extremely valid for gases made of complex and heavy molecules, which tend to deviate more from the ideal model.
While the fluid dynamics of compressible flows in ideal conditions is well-established and is characterized by several analytical results, when non-ideal thermodynamic conditions are considered, peculiar phenomena possibly occur. This is particularly valid in supersonic conditions, namely for flow velocities larger than the speed of sound in the fluid considered. All typical features of supersonic flows are affected by non-ideal thermodynamics, resulting in both quantitative and qualitative differences with respect to the ideal gas dynamics. | 7 | Physical Chemistry |
The idea of interstitial compounds was started in the late 1930s and they are often called Hagg phases after Hägg. Transition metals generally crystallise in either the hexagonal close packed or face centered cubic structures, both of which can be considered to be made up of layers of hexagonally close packed atoms. In both of these very similar lattices there are two sorts of interstice, or hole:
*Two tetrahedral holes per metal atom, i.e. the hole is between four metal atoms
*One octahedral hole per metal atom, i.e. the hole is between six metal atoms
It was suggested by early workers that:
*the metal lattice was relatively unaffected by the interstitial atom
*the electrical conductivity was comparable to that of the pure metal
*there was a range of composition
*the type of interstice occupied was determined by the size of the atom
These were not viewed as compounds, but rather as solutions, of say carbon, in the metal lattice, with a limiting upper “concentration” of the smaller atom that was determined by the number of interstices available. | 8 | Metallurgy |
Sauvagine is a neuropeptide from the corticotropin-releasing factor (CRF) family of peptides and is orthologous to the mammalian hormone, urocortin 1, and the teleost fish hormone, urotensin 1. It is 40 amino acids in length, and has the sequence XGPPISIDLSLELLRKMIEIEKQEKEKQQAANNRLLLDTI-NH2, with a pyrrolidone carboxylic acid modification at the N-terminal and amidation of the C-terminal isoleucine residue. It was originally isolated from the skin of the frog Phyllomedusa sauvagii. Given its relation to other CRF-related peptides, it exerts similar physiological effects as corticotropin-releasing hormone.
Sauvagine belongs to the corticotropin-releasing factor (CRF) family that also includes CRF, urocortin l/urotensin l, urocortin II and urocortin III. | 1 | Biochemistry |
Using correlation diagrams one can derive selection rules for the following generalized classes of pericyclic reactions. Each of these particular classes is further generalized in the generalized Woodward–Hoffmann rules. The more inclusive bond topology descriptors antarafacial and suprafacial subsume the terms conrotatory and disrotatory, respectively. Antarafacial refers to bond making or breaking through the opposite face of a π system, p orbital, or σ bond, while suprafacial refers to the process occurring through the same face. A suprafacial transformation at a chiral center preserves stereochemistry, whereas an antarafacial transformation reverses stereochemistry. | 7 | Physical Chemistry |
The active component, eslicarbazepine, has the same mechanism of action as oxcarbazepine (which is a prodrug for licarbazepine, the racemate of eslicarbazepine) and most likely the closely related carbamazepine. It stabilises the inactive state of voltage-gated sodium channels, allowing for less sodium to enter neural cells, which leaves them less excitable. According to some sources, it has not been shown conclusively that this is the actual mechanism. | 4 | Stereochemistry |
The alloy has the highest magnetostriction of any alloy, up to 0.002 m/m at saturation; it expands and contracts in a magnetic field. Terfenol-D has a large magnetostriction force, high energy density, low sound velocity, and a low Youngs modulus. At its most pure form, it also has low ductility and a low fracture resistance. Terfenol-D is a gray alloy that has different possible ratios of its elemental components that always follow a formula of . The addition of dysprosium made it easier to induce magnetostrictive responses by making the alloy require a lower level of magnetic fields. When the ratio of Tb and Dy is increased, the resulting alloys magnetostrictive properties will operate at temperatures as low as −200 °C, and when decreased, it may operate at a maximum of 200 °C. The composition of Terfenol-D allows it to have a large magnetostriction and magnetic flux when a magnetic field is applied to it. This case exists for a large range of compressive stresses, with a trend of decreasing magnetostriction as the compressive stress increases. There is also a relationship between the magnetic flux and compression in which when the compressive stress increases, the magnetic flux changes less drastically. Terfenol-D is mostly used for its magnetostrictive properties, in which it changes shape when exposed to magnetic fields in a process called magnetization. Magnetic heat treatment is shown to improve the magnetostrictive properties of Terfenol-D at low compressive stress for certain ratios of Tb and Dy. | 8 | Metallurgy |
Thioglycosides were first reported in 1909 by Fischer and since then have been explored constantly allowing for the development of numerous protocols for their preparation.
The advantage of using thioglycosides is their stability under a wide range of reaction conditions allowing for protecting group manipulations. Additionally thioglycosides act as temporary protecting groups at the anomeric position allowing for thioglycosides to be useful as both glycosyl donors as well as glycosyl acceptors.
Thioglycosides are usually prepared by reacting per-acetylated sugars with and the appropriate thiol.
Thioglycosides used in glycosylation reactions as donors can be activated under a wide range of conditions, most notably using NIS/AgOTf. | 0 | Organic Chemistry |
Broadband high-resolution spectrometers were developed in 2000 and commercialized in 2003. Designed for material analysis, the spectrometer allowed the LIBS system to be sensitive to chemical elements in low concentration.
ARL LIBS applications studied from 2000 to 2010 included:
* Tested for detection of Halon alternative agents
* Tested a field-portable LIBS system for the detection of lead in soil and paint
* Studied the spectral emission of aluminum and aluminum oxides from bulk aluminum in different bath gases
* Performed kinetic modeling of LIBS plumes
* Demonstrated the detection and discrimination of geological materials, plastic landmines, explosives, and chemical and biological warfare agent surrogates
ARL LIBS prototypes studied during this period included:
* Laboratory LIBS setup
* Commercial LIBS system
* Man-portable LIBS device
* Standoff LIBS system developed for 100+ m detection and discriminate on of explosive residues. | 7 | Physical Chemistry |
The interplay of molecular scale mechanisms and hierarchical surface structures is known to result in high levels of static friction and bonding between pairs of surfaces. Technologically advanced adhesive devices sometimes make use of microstructures on surfaces, such as tightly packed periodic posts. These are biomimetic technologies inspired by the adhesive abilities of the feet of various arthropods and vertebrates (most notably, geckos). By intermixing periodic breaks into smooth, adhesive surfaces, the interface acquires valuable crack-arresting properties. Because crack initiation requires much greater stress than does crack propagation, surfaces like these are much harder to separate, as a new crack has to be restarted every time the next individual microstructure is reached. | 6 | Supramolecular Chemistry |
Several indices to measure bioavailability have been suggested: Respiration Index, Oxygen Supply Index, and the Metabolic Index. The Respiration Index describes oxygen availability based on the free energy available in the reactants and products of the stoichiometric equation for respiration. However, organisms have ways of altering their oxygen intake and carbon dioxide release, so the strict stoichiometric equation is not necessarily accurate. The Oxygen Supply Index accounts for oxygen solubility and partial pressure, along with the Q of the organism, but does not account for behavioral or physiological changes in organisms to compensate for reduced oxygen availability. The Metabolic Index accounts for the supply of oxygen in terms of solubility, partial pressure, and diffusivity of oxygen in water, and the organism's metabolic rate. The metabolic index is generally viewed as a closer approximation of oxygen bioavailability than the other indices.
There are two thresholds of oxygen required by organisms:
* P (critical partial pressure)- the oxygen level below which an organism cannot support a normal respiration rate
* P (lethal partial pressure)- the oxygen level below which an organism cannot support the minimum respiration rate necessary for survival.
Since bioavailability is specific to each organism and temperature, calculation of these thresholds is done experimentally by measuring activity and respiration rates under different temperature and oxygen conditions, or by collecting data from separate studies. | 9 | Geochemistry |
* Novosil is a stimulant of plant immunity and growth. It is also used in the fight against plant viruses. The product was developed by the Institute together with the Institute of Cytology and Genetics in 1992. It is used in various regions of Russia, as well as in Kazakhstan, Belarus, Ukraine and Georgia.
* Acrylate-siloxane hybrid monomer is a material with the addition of silicon. It can be used to create microcircuits. | 0 | Organic Chemistry |
Among the proteins recruited to polymerase are elongation factors, thus called because they stimulate transcription elongation. There are different classes of elongation factors. Some factors can increase the overall rate of transcribing, some can help the polymerase through transient pausing sites, and some can assist the polymerase to transcribe through chromatin. One of the elongation factors, P-TEFb, is particularly important. P-TEFb phosphorylates the second residue (Ser-2) of the CTD repeats (YSPTSPS) of the bound Pol II. P-TEFb also phosphorylates and activates SPT5 and TAT-SF1. SPT5 is a universal transcription factor that helps recruit 5'-capping enzyme to Pol II with a CTD phosphorylated at Ser-5. TAF-SF1 recruits components of the RNA splicing machinery to the Ser-2 phosphorylated CTD. P-TEFb also helps suppress transient pausing of polymerase when it encounters certain sequences immediately following initiation. | 1 | Biochemistry |
Plumbides can be formed when lead forms a Zintl phase compound with a more metallic element. One salt that can be formed this way is when cryptand reacts with sodium and lead in ethylenediamine (en) to produce [Pb], which is red in solution.
Lead can also create anions with tin, in a series of anions with the formula [SnPb].
Lead can also form the [Pb] anion, which is emerald green in solution. | 7 | Physical Chemistry |
NPP catalyses the nucleophilic substitution of one ester bond on a phosphodiester substrate. It has a nucleoside binding pocket that excludes phospholipid substrates from the active site. A threonine nucleophile has been identified through site-directed mutagenesis, and the reaction inverts the stereochemistry of the phosphorus center. The sequence of bond breakage and formation has yet to be resolved. | 1 | Biochemistry |
In addition to using TNP-ATP to determine whether a protein binds ATP, its binding affinity and dissociation constants, and number of binding sites, TNP-ATP can also be used in ligand binding studies. To do this, titrations of the protein are added to TNP-ATP. Then, ligand is added to displace the bound analog. This is measured by decreases in fluorescence. One can also do this by titrating protein with TNP-ATP in the presence and absence of varying concentrations of the ligand of interest. Using either experiment will allow the binding affinity of the ligand to protein to be measured.
TNP-ATP is also valuable fluorescence acceptor. This is because, as with any good acceptor, TNP-ATP absorbs over a wide wavelength range that corresponds to the range of emission of common FRET donors. Thus, TNP-ATP can be used to look at the conformational changes that proteins undergo. For example, Na+/K+ ATPase, the distance between the active site and Cys457 was shown to change from 25 Angstroms to 28 Angstroms in changing from the Na+ conformation to the K+ conformation.
In addition to fluorescent spectroscopy, TNP-ATP is very useful in fluorescent microscopy. This is because it greatly increases the sensitivity of the observations when bound to proteins—the enhanced fluorescence greatly reduces the problem of background fluorescence. This is especially true under epifluorescent illumation (illumination and light are both on the same side of the specimen).
TNP-ATP has also been used in X-ray crystallography because it can be used to determine binding constants of crystallized substrates. This technique also demonstrates the structure of proteins in the presence or absence of TNP-ATP, which may or may not correspond to the structure of proteins when they bind ATP. | 7 | Physical Chemistry |
The Journal of Physical Chemistry Letters publishes letters, perspectives on emerging topics, editorials and viewpoints. Specific materials of interest will include, but are not limited to:
* Physical Insights into Quantum Phenomena and Function
* Physical Insights into Materials and Molecular Properties
* Physical Insights into Light Interacting with Matter
* Physical Insights into the Biosphere, Atmosphere, and Space
* Physical Insights into Chemistry, Catalysis, and Interfaces
* Physical Insights into Energy Science | 7 | Physical Chemistry |
NAD+ 5’ capped RNA have been found in yeast, humans, and Arabidopsis thaliana. In eukaryotes, the NAD+ cap is removed by non-canonical decapping enzymes from the DXO family. DeNADing by DXO results in a 5’ end monophosphate RNA distinct from NudC which results in NMN plus 5′ monophosphate RNA. Importantly, DXO is ~6 fold more efficient at decapping NAD+ compared to m7G, suggesting that it selectively degrades NAD-capped RNA rather than the more common m7G cap, similar to NudC.
The m7G cap has been shown to promote translation through recruitment of the initiation complex onto the mRNA. However, the NAD+-cap does not provide a similar function as NAD+-capped and polyadenylated mRNA displayed similar levels of translation in vitro to uncapped mRNA. Additionally, the 5’ NAD+ cap further promotes decay of the RNA it is attached to, NAD+-capped and polyadenylated mRNA were demonstrated in vitro to be less stable than mRNAs lacking a 5’ cap, suggesting that the NAD+ modification is actively facilitating DXO-mediated RNA decay.
While the relationship between RNA-binding proteins, such as glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and NAD+ concentration is established, the NAD+ cap has been hypothesized to represent a direct link between RNA expression levels and cellular metabolism. It is known that energy stresses such as glucose deprivation and caloric restriction influence NAD+ concentrations and can possibly impact NAD+ capping. Additionally, as low-nutrient conditions can affect mRNA stability, and seeing as NAD+ caps promote mRNA decay, it is possible that the energetic state of a cell could affect NAD+-capping and thus mRNA turnover. Certain findings, such as the higher abundance of NAD+-capped transcripts in stationary-phase bacteria as well as yeast grown on synthetic media, point toward this possibility. | 1 | Biochemistry |
International commerce of sulfuric acid is controlled under the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances, 1988, which lists sulfuric acid under Table II of the convention as a chemical frequently used in the illicit manufacture of narcotic drugs or psychotropic substances. | 7 | Physical Chemistry |
An Interest Group Macromolecules (EBF-IGM) was founded in 2008 to provide a platform for scientific exchange and harmonization of specific aspects for the bioanalysis of macromolecules: drugs and biomarkers as well as immunogenicity testing. | 3 | Analytical Chemistry |
Palladacycle, as a class of metallacycles, refers to complexes containing at least one carbon-palladium bond. Palladacycles are invoked as intermediates in catalytic or palladium mediated reactions. They have been investigated as pre-catalysts for homogeneous catalysis and synthesis. | 0 | Organic Chemistry |
Freshwater environmental quality parameters are those chemical, physical or biological parameters that can be used to characterise a freshwater body. Because almost all water bodies are dynamic in their composition, the relevant quality parameters are typically expressed as a range of expected concentrations.
They include the natural and man-made chemical, biological and microbiological characteristics of rivers, lakes and ground-waters, the ways they are measured and the ways that they change. The values or concentrations attributed to such parameters can be used to describe the pollution status of an environment, its biotic status or to predict the likelihood or otherwise of a particular organisms being present. Monitoring of environmental quality parameters is a key activity in managing the environment, restoring polluted environments and anticipating the effects of man-made changes on the environment. | 2 | Environmental Chemistry |
The high-frequency impact treatment or HiFIT – Method is the treatment of welded steel constructions at the weld transition to increase the fatigue strength. | 8 | Metallurgy |
The semiconductor is a collective term for a series of devices. It mainly includes three categories：two-terminal devices, three-terminal devices, and four-terminal devices. The combination of the semiconductors is called an integrated circuit.
The relationship between Ficks law and semiconductors: the principle of the semiconductor is transferring chemicals or dopants from a layer to a layer. Ficks law can be used to control and predict the diffusion by knowing how much the concentration of the dopants or chemicals move per meter and second through mathematics.
Therefore, different types and levels of semiconductors can be fabricated.
Integrated circuit fabrication technologies, model processes like CVD, thermal oxidation, wet oxidation, doping, etc. use diffusion equations obtained from Fick's law. | 7 | Physical Chemistry |
*O'Callaghan, Amy; van Sinderen, Douwe (2016). Bifidobacteria and Their Role as Members of the Human Gut Microbiota. Frontiers in Microbiology, 7,
*Paul György; Robert F. Norris; Catharine S. Rose (1954). Bifidus factor. I. A variant of Lactobacillus bifidus requiring a special growth factor, 48 (1), 193–201. | 1 | Biochemistry |
Translational control is critical for the development and survival of cancer. Cancer cells must frequently regulate the translation phase of gene expression, though it is not fully understood why translation is targeted over steps like transcription. While cancer cells often have genetically altered translation factors, it is much more common for cancer cells to modify the levels of existing translation factors. Several major oncogenic signaling pathways, including the RAS–MAPK, PI3K/AKT/mTOR, MYC, and WNT–β-catenin pathways, ultimately reprogram the genome via translation. Cancer cells also control translation to adapt to cellular stress. During stress, the cell translates mRNAs that can mitigate the stress and promote survival. An example of this is the expression of AMPK in various cancers; its activation triggers a cascade that can ultimately allow the cancer to escape apoptosis (programmed cell death) triggered by nutrition deprivation. Future cancer therapies may involve disrupting the translation machinery of the cell to counter the downstream effects of cancer. | 1 | Biochemistry |
Blue carbon is a concept within climate change mitigation that refers to "biologically driven carbon fluxes and storage in marine systems that are amenable to management." Most commonly, it refers to the role that tidal marshes, mangroves and seagrasses can play in carbon sequestration. These ecosystems can play an important role for climate change mitigation and ecosystem-based adaptation. However, when blue carbon ecosystems are degraded or lost they release carbon back to the atmosphere, thereby adding to greenhouse gas emissions.
The methods for blue carbon management fall into the category of "ocean-based biological carbon dioxide removal (CDR) methods". They are a type of biological carbon fixation.
Scientists are looking for ways to further develop the blue carbon potential of ecosystems. However, the long-term effectiveness of blue carbon as a carbon dioxide removal solution is under debate.
The term deep blue carbon is also in use and refers to storing carbon in the deep ocean waters. | 9 | Geochemistry |
One modification of the Hiyama coupling utilizes a silacyclobutane ring and a fluoride source that is hydrated as shown below. This mimics the use of an alkoxysilane/organosilanol rather than the use of alkylsilane. The mechanism of this reaction, using a fluoride source, allowed for the design of future reactions that can avoid the use of the fluoride source. | 0 | Organic Chemistry |
In Swedish Uppland north of Stockholm and certain adjacent provinces, another kind known as the Walloon forge was used, mainly for the production of a particularly pure kind of iron known as oregrounds iron, which was exported to England to make blister steel. Its purity depended on the use of ore from the Dannemora mine. The Walloon forge was virtually the only kind used in Great Britain.
The forge had two kinds of hearths, the finery to finish the product and the chafery to reheat the bloom that was the raw material of the process. | 8 | Metallurgy |
tert-Butyldimethylsilyl chloride is an organosilicon compound with the formula (MeC)MeSiCl (Me = CH). It is commonly abbreviated as TBSCl or TBDMSCl. It is a chlorosilane containing two methyl groups and a tert-butyl group. As such it is more bulky that trimethylsilyl chloride. It is a colorless or white solid that is soluble in many organic solvents but reacts with water and alcohols. The compound is used to protect alcohols in organic synthesis.
tert-Butyldimethylsilyl chloride reacts with alcohols in the presence of base to give tert-butyldimethylsilyl ethers:
:(MeC)MeSiCl + ROH → (MeC)MeSiOR + HCl
These silyl ethers hydrolyze much more slowly than the trimethylsilyl ethers.
It also can silylate terminal alkynes. | 0 | Organic Chemistry |
Crystallographic Information File (CIF) is a standard text file format for representing crystallographic information, promulgated by the International Union of Crystallography (IUCr). CIF was developed by the IUCr Working Party on Crystallographic Information in an effort sponsored by the IUCr Commission on Crystallographic Data and the IUCr Commission on Journals. The file format was initially published by Hall, Allen, and Brown and has since been revised, most recently versions 1.1 and 2.0. Full specifications for the format are available at the IUCr website. Many computer programs for molecular viewing are compatible with this format, including Jmol. | 3 | Analytical Chemistry |
Jay Quade was born and grew up in Nevada. As a teenager, he set two all-time Nevada State high school track and field records. At the University of New Mexico, he had a track scholarship, for four years. He was twice an NCAA All-American in track and once an NCAA champion in track (relay race). In 1977 he became a geologist employed by
the Mineral Exploration Division of Utah International, Inc. In 1978 he graduated with B.S. in geology from the University of New Mexico. In 1982 he graduated with an M.S. in geology from the University of Arizona. From 1982 to 1989 he worked as a geologist in Nevada — from 1982 to 1984 for Noranda Exploration, Inc., from 1984 to 1986 for the Desert Research Institute, and from 1986 to 1989 for Mifflin & Associates (a mining consulting firm founded in 1986 by the geologist Martin David Mifflin). From 1989 to 1990 Quade was a graduate student at the University of Utah, where he received his Ph.D. in 1990. In 1991 he was a postdoc at the Australian National University. At the University of Arizona, he was appointed to an assistant professorship in 1992, an associate professorship in 1998, and a full professorship in 2003.
Quade's research is remarkably varied, including low-temperature geochemistry, radiometric dating using a variety of isotopes, and theoretical reconstructions of paleoenvironments, mostly from the Cenozoic. Some of his projects have involved archaeologists and anthropologists. Quade with Thure E. Cerling and other colleagues did important research on stable isotope composition of soil carbonate in the Great Basin. In 2001, Quade with Nathan B. English, Julio L. Betancourt, and Jeffrey S. Dean published an important paper on the deforestation of Chaco Canyon. As a geological team member, Quade has done fieldwork on stratigraphy and paleohydrologic reconstruction in the western USA, gold deposits in Oregon, Alaska, and Nevada, and paleo-lake hydrology in Mongolia, Tibet, Chile, Argentina, and the western USA. From 1985 to 2015 his fieldwork on low temperature geochemistry has been done all over the world: parts of the US, Asia, Australia, and South America, as well as Greece and Ethiopia.
In 2001 Quade won the Farouk El-Baz Award of the Geological Society of America (GSA). In 2015 he was elected a Fellow of the Geological Society of American and also a Fellow of the American Geophysical Union (AGU). In 2017 he was elected a Fellow of the Geochemical Society. He received in 2016 a Lady Davis Fellowship from the Hebrew University and in 2017 a Japan Society for the Promotion of Science Fellowship from the University of Tokyo. In 2018 he was awarded the Arthur L. Day Medal.
In Nevada on December 21, 1984, Jay Quade married Barbra A. Valdez. They have three children. | 9 | Geochemistry |
In chemistry, a leaving group is defined by the IUPAC as an atom or group of atoms that detaches from the main or residual part of a substrate during a reaction or elementary step of a reaction. However, in common usage, the term is often limited to a fragment that departs with a pair of electrons in heterolytic bond cleavage. In this usage, a leaving group is a less formal but more commonly used synonym of the term nucleofuge. In this context, leaving groups are generally anions or neutral species, departing from neutral or cationic substrates, respectively, though in rare cases, cations leaving from a dicationic substrate are also known.
A species' ability to serve as a leaving group depends on its ability to stabilize the additional electron density that results from bond heterolysis. Common anionic leaving groups are halides such as and , and sulfonate esters such as tosylate (), while water (), alcohols (), and amines () are common neutral leaving groups.
In the broader IUPAC definition, the term also includes groups that depart without an electron pair in a heterolytic cleavage (groups specifically known as an electrofuges), like or , which commonly depart in electrophilic aromatic substitution reactions. Similarly, species of high thermodynamic stability like nitrogen () or carbon dioxide () commonly act as leaving groups in homolytic bond cleavage reactions of radical species. A relatively uncommon term that serves as the antonym of leaving group is entering group (i.e., a species that reacts with and forms a bond with a substrate or a substrate-derived intermediate).
In this article, the discussions below mainly pertain to leaving groups that act as nucleofuges. | 0 | Organic Chemistry |
The heat evolved when an aliquot of host solution is added to a solution containing the guest is the sum of contributions from each reaction
where is a measured heat change value (corrected for all extraneous heat contributions) at data point j, is the amount of heat absorbed or emitted when 1 mole of the ith reaction product is formed and is the actual change in the number of moles of that product at that data point. is calculated by solving the equations of mass-balance with given values of the equilibrium constants. If the equilibrium constant values are known, the standard enthalpy change may be calculated by a linear least-squares process, otherwise a non-linear method of data-fitting must be used.
Isothermal titration calorimetry is commonly used to determine the values of both an equilibrium constant and the corresponding standard reaction enthalpy. The manufactures of ITC instruments supply some software with which these quantities may be obtained from experimental data values. | 6 | Supramolecular Chemistry |
A simple substance (like water) may exist in equilibrium with its thermal decomposition products, effectively halting the decomposition. The equilibrium fraction of decomposed molecules increases with the temperature.
Since thermal decomposition is a kinetic process, the observed temperature of its beginning in most instances will be a function of the experimental conditions and sensitivity of the experimental setup. For a rigorous depiction of the process, the use of thermokinetic modeling is recommended.
main definition: Thermal decomposition is the breakdown of a compound into two or more different substances using heat, and it is an endothermic reaction | 7 | Physical Chemistry |
UIT was originally developed in 1972 and has since been perfected by a team of Russian scientists under the leadership of Dr. Efim Statnikov. Originally developed and utilized to enhance the fatigue and corrosion attributes of ship and submarine structures, UIT has been utilized in aerospace, mining, offshore drilling, shipbuilding, infrastructure, automotive, energy production and other industries.
Different industrial solutions exist nowadays and are commercialized by a limited number of Original Equipment Manufacturers worldwide. | 8 | Metallurgy |
Light crude oils have higher API gravity figures, due to having fewer impurities. It is more commonly used to produce diesel and gasoline than heavier oils are. Due to its lower viscosity, it is easier to extract and to transport. | 9 | Geochemistry |
As other species of sulfur at intermediate oxidation state, such as thiosulfate, tetrathionate can be responsible for the pitting corrosion of carbon steel and stainless steel.
Tetrathionate has also been found to serve as a terminal electron acceptor for Salmonella enterica serotype Typhimurium, whereas existing thiosulfate in the small intestines of mammals is oxidized by reactive oxygen species released by the immune system (mainly NADPH oxidase produced superoxide) to form tetrathionate. This aids in the growth of the bacterium, helped by the inflammatory response. | 8 | Metallurgy |
The story addresses a lot of recent scientific breakthroughs, and uses them as plot devices. For instance, The Human Genome Project, which documents all the genes and DNA in the human genetic makeup, is talked about when Dr. Wyatt explains his genetic testing to Eli for the first time. Scientific American recently published an article detailing the possible uses for the information gathered from the Human Genome Project. Modern advancements in gene studies currently can detect and, in some cases, even predict the presence of a genetic abnormality. In Double Helix, this ability to detect flaws before birth was used to genetically engineer a “more perfect son, devoid of flaws and with a proper chance to live free of Huntington’s.”
For some people, the biggest issue with genetic engineering is whether or not to seek out and act on knowledge about genetic flaws. Double Helix attempts to explore the life saving and life destroying aspects of genetic engineering. The book proposes that, while Elis life was saved by avoiding the Huntingtons disease gene, his concept of life and self were destroyed when he found out he was genetically engineered to be a certain way. | 1 | Biochemistry |
From 2001 to 2007, nickel prices rose from an average of US$5945 to US$37,216. Nickel is a key constituent of 316L stainless steel. This, combined with increases in some of the other constituents of the 316L alloy, prompted Xstrata Technology (by then the marketing organisation for the Isa Process technology) to seek an alternative material for the cathode plates.
Xstrata Technology personnel investigated the use of a new low-alloyed duplex stainless steel, LDX 2101 and 304L stainless steel. The LDX 2101 contains 1.5% nickel compared to 10–14% in 316L stainless steel.
LDX 2101 has superior mechanical strength to the 316L stainless steel, allowing thinner sheets to be used for the cathode plates. However, the flatness tolerance of commercially available LDX 2101 steel did not meet the required specifications. Xstrata Technology worked with a manufacturer to produce sheets that did meet the required flatness tolerance.
Xstrata Technology also had to develop a finish that allowed the surface to function in the same way as 316L.
Cathode plates using LDX 2010 have equivalent corrosion resistance to 316L plates.
The LDX 2101 alloy provides an alternative to the 316L stainless steel, with the selection depending on relatively prices of the various steels. | 8 | Metallurgy |
The refrigeration capacity of a refrigeration system is the product of the evaporators enthalpy rise and the evaporators mass flow rate. The measured capacity of refrigeration is often dimensioned in the unit of kW or BTU/h. Domestic and commercial refrigerators may be rated in kJ/s, or Btu/h of cooling. For commercial and industrial refrigeration systems, the kilowatt (kW) is the basic unit of refrigeration, except in North America, where both ton of refrigeration and BTU/h are used.
A refrigeration systems coefficient of performance (CoP) is very important in determining a systems overall efficiency. It is defined as refrigeration capacity in kW divided by the energy input in kW. While CoP is a very simple measure of performance, it is typically not used for industrial refrigeration in North America. Owners and manufacturers of these systems typically use performance factor (PF). A systems PF is defined as a systems energy input in horsepower divided by its refrigeration capacity in TR. Both CoP and PF can be applied to either the entire system or to system components. For example, an individual compressor can be rated by comparing the energy needed to run the compressor versus the expected refrigeration capacity based on inlet volume flow rate. It is important to note that both CoP and PF for a refrigeration system are only defined at specific operating conditions, including temperatures and thermal loads. Moving away from the specified operating conditions can dramatically change a system's performance.
Air conditioning systems used in residential application typically use SEER (Seasonal Energy Efficiency Ratio)for the energy performance rating. Air conditioning systems for commercial application often use EER (Energy Efficiency Ratio) and IEER (Integrated Energy Efficiency Ratio) for the energy efficiency performance rating. | 7 | Physical Chemistry |
In medicine, phosphonates and bisphosphonates are commonly used as inhibitors of enzymes which utilize phosphates and diphosphates as substrates. Most notably, these enzymes include those that produce the intermediates of cholesterol biosynthesis.
Phosphonate nucleotide analogues such as tenofovir, cidofovir and adefovir are critical antiviral medications, which in various pro-drug forms are used for the treatment of HIV, hepatitis B and others. | 0 | Organic Chemistry |
The dependence of the water ionization on temperature and pressure has been investigated thoroughly. The value of pK decreases as temperature increases from the melting point of ice to a minimum at c. 250 °C, after which it increases up to the critical point of water c. 374 °C. It decreases with increasing pressure.
With electrolyte solutions, the value of pK is dependent on ionic strength of the electrolyte. Values for sodium chloride are typical for a 1:1 electrolyte. With 1:2 electrolytes, MX, pK decreases with increasing ionic strength.
The value of K is usually of interest in the liquid phase. Example values for superheated steam (gas) and supercritical water fluid are given in the table.
:Notes to the table. The values are for supercritical fluid except those marked: at saturation pressure corresponding to 350 °C. superheated steam. compressed or subcooled liquid. | 7 | Physical Chemistry |
In mass spectrometry, matrix-assisted laser desorption/ionization (MALDI) is an ionization technique that uses a laser energy-absorbing matrix to create ions from large molecules with minimal fragmentation. It has been applied to the analysis of biomolecules (biopolymers such as DNA, proteins, peptides and carbohydrates) and various organic molecules (such as polymers, dendrimers and other macromolecules), which tend to be fragile and fragment when ionized by more conventional ionization methods. It is similar in character to electrospray ionization (ESI) in that both techniques are relatively soft (low fragmentation) ways of obtaining ions of large molecules in the gas phase, though MALDI typically produces far fewer multi-charged ions.
MALDI methodology is a three-step process. First, the sample is mixed with a suitable matrix material and applied to a metal plate. Second, a pulsed laser irradiates the sample, triggering ablation and desorption of the sample and matrix material. Finally, the analyte molecules are ionized by being protonated or deprotonated in the hot plume of ablated gases, and then they can be accelerated into whichever mass spectrometer is used to analyse them. | 1 | Biochemistry |
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