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The WSSUS (Wide-Sense Stationary Uncorrelated Scattering) model provides a statistical description of the transmission behavior of wireless channels. "Wide-sense stationarity" means the second-order moments of the channel are stationary, which means that they depends only on the time difference, while "uncorrelated scattering" refers to the delay due to scatterers.
Modelling of mobile channels as WSSUS (wide sense stationary uncorrelated scattering) has become popular among specialists. The model was introduced by Phillip A. Bello in 1963.
A commonly used description of time variant channel applies the set of Bello functions and the theory of stochastic processes. | 0 | Theoretical and Fundamental Chemistry |
Basic sediment and water (BS&W) is a both a technical specification of certain impurities in crude oil and the method for measuring it. When extracted from an oil reservoir, the crude oil will contain some amount of water and suspended solids from the reservoir formation. The particulate matter is known as sediment or mud. The water content can vary greatly from field to field, and may be present in large quantities for older fields, or if oil extraction is enhanced using water injection technology. The bulk of the water and sediment is usually separated at the field to minimize the quantity that needs to be transported further. The residual content of these unwanted impurities is measured as BS&W. Oil refineries may either buy crude to a certain BS&W specification or may alternatively have initial crude oil dehydration and desalting process units that reduce the BS&W to acceptable limits, or a combination thereof. | 1 | Applied and Interdisciplinary Chemistry |
One of the drawbacks of using a separating funnel is emulsions can form easily, and can take a long time to separate once formed. They are often formed while liquids are being mixed in the separating funnel. This can occur when small droplets are suspended in an aqueous solution. If an emulsion is formed, one technique used to separate the liquids is to slowly swirl the solution in the separating funnel. If the emulsion is not separated by this process, a small amount of saturated saline solution is added ("salting out").
Research is being done on alternative, more efficient techniques, mostly utilizing stir bars (stirrer bars) to decrease or even eliminate the chance of emulsification, thus decreasing the amount of waiting time. | 0 | Theoretical and Fundamental Chemistry |
The NURF complex in Drosophila contains four subunits: NURF301, NURF140, NURF55, and NURF38. NURF140 is an ISWI ATPase, distinguishable by its HAND, SANT, and SLIDE domains (SANT-like but with several insertions). The NURF complex in Homo sapiens has three subunits, BPTF, SNF2L, and pRBAP46/48, homologous to NURF301, NURF140, and NURF55, respectively. There is no human homolog for NURF38. | 1 | Applied and Interdisciplinary Chemistry |
The symbol used to represent specific volume in equations is "v" with SI units of cubic meters per kilogram.
The symbol used to represent volume in equations is "V" with SI units of cubic meters.
When performing a thermodynamic analysis, it is typical to speak of intensive and extensive properties. Properties which depend on the amount of gas (either by mass or volume) are called extensive properties, while properties that do not depend on the amount of gas are called intensive properties. Specific volume is an example of an intensive property because it is the ratio of volume occupied by a unit of mass of a gas that is identical throughout a system at equilibrium. 1000 atoms a gas occupy the same space as any other 1000 atoms for any given temperature and pressure. This concept is easier to visualize for solids such as iron which are incompressible compared to gases. However, volume itself --- not specific --- is an extensive property. | 0 | Theoretical and Fundamental Chemistry |
A few other elements have been proposed as candidates for supporting biological systems and processes as fundamentally as carbon does, for example, processes such as metabolism. The most frequently suggested alternative is silicon. Silicon, atomic number of 14, more than twice the size of carbon, shares a group in the periodic table with carbon, can also form four valence bonds, and also bonds to itself readily, though generally in the form of crystal lattices rather than long chains. Despite these similarities, silicon is considerably more electropositive than carbon, and silicon compounds do not readily recombine into different permutations in a manner that would plausibly support lifelike processes. Silicon is abundant on Earth, but as it is more electropositive, it mainly forms Si–O bonds rather than Si–Si bonds. Boron does not react with acids and does not form chains naturally. Thus boron is not a candidate for life. Arsenic is toxic to life, and its possible candidacy has been rejected. In the past (1960s-1970s) other candidates for life were plausible, but with time and more research, only carbon as the complexity and stability for life, to make very large molecules, like polymers. Thus life must be carbon based. | 1 | Applied and Interdisciplinary Chemistry |
Inverted repeats play an important role in riboswitches, which are RNA regulatory elements that control the expression of genes that produce the mRNA, of which they are part. A simplified example of the flavin mononucleotide (FMN) riboswitch is shown in the illustration. This riboswitch exists in the mRNA transcript and has several stem-loop structures upstream from the coding region. However, only the key stem-loops are shown in the illustration, which has been greatly simplified to help show the role of the inverted repeats. There are multiple inverted repeats in this riboswitch as indicated in green (yellow background) and blue (orange background).
In the absence of FMN, the Anti-termination structure is the preferred conformation for the mRNA transcript. It is created by base-pairing of the inverted repeat region circled in red. When FMN is present, it may bind to the loop and prevent formation of the Anti-termination structure. This allows two different sets of inverted repeats to base-pair and form the Termination structure. The stem-loop on the 3 end is a transcriptional terminator because the sequence immediately following it is a string of uracils (U). If this stem-loop forms (due to the presence of FMN) as the growing RNA strand emerges from the RNA polymerase complex, it will create enough structural tension to cause the RNA strand to dissociate and thus terminate transcription. The dissociation occurs easily because the base-pairing between the Us in the RNA and the A's in the template strand are the weakest of all base-pairings. Thus, at higher concentration levels, FMN down-regulates its own transcription by increasing the formation of the termination structure. | 1 | Applied and Interdisciplinary Chemistry |
After a genomic library is constructed with a viral vector, such as lambda phage, the titer of the library can be determined. Calculating the titer allows researchers to approximate how many infectious viral particles were successfully created in the library. To do this, dilutions of the library are used to transform cultures of E. coli of known concentrations. The cultures are then plated on agar plates and incubated overnight. The number of viral plaques are counted and can be used to calculate the total number of infectious viral particles in the library. Most viral vectors also carry a marker that allows clones containing an insert to be distinguished from those that do not have an insert. This allows researchers to also determine the percentage of infectious viral particles actually carrying a fragment of the library.
A similar method can be used to titer genomic libraries made with non-viral vectors, such as plasmids and BACs. A test ligation of the library can be used to transform E. coli. The transformation is then spread on agar plates and incubated overnight. The titer of the transformation is determined by counting the number of colonies present on the plates. These vectors generally have a selectable marker allowing the differentiation of clones containing an insert from those that do not. By doing this test, researchers can also determine the efficiency of the ligation and make adjustments as needed to ensure they get the desired number of clones for the library. | 1 | Applied and Interdisciplinary Chemistry |
The Arrhenius equation is an elementary treatment that gives the quantitative basis of the relationship between the activation energy and the reaction rate at which a reaction proceeds. The rate constant as a function of thermodynamic temperature is then given by:
The reaction rate is given by:
where E is the activation energy, and R is the gas constant, and m and n are experimentally determined partial orders in [A] and [B], respectively. Since at temperature T the molecules have energies according to a Boltzmann distribution, one can expect the proportion of collisions with energy greater than E to vary with e. The constant of proportionality A is the pre-exponential factor, or frequency factor (not to be confused here with the reactant A) takes into consideration the frequency at which reactant molecules are colliding and the likelihood that a collision leads to a successful reaction. Here, A has the same dimensions as an (m + n)-order rate constant (see Units below).
Another popular model that is derived using more sophisticated statistical mechanical considerations is the Eyring equation from transition state theory:
where ΔG is the free energy of activation, a parameter that incorporates both the enthalpy and entropy change needed to reach the transition state. The temperature dependence of ΔG is used to compute these parameters, the enthalpy of activation ΔH and the entropy of activation ΔS, based on the defining formula ΔG = ΔH − TΔS. In effect, the free energy of activation takes into account both the activation energy and the likelihood of successful collision, while the factor kT/h gives the frequency of molecular collision.
The factor (c) ensures the dimensional correctness of the rate constant when the transition state in question is bimolecular or higher. Here, c is the standard concentration, generally chosen based on the unit of concentration used (usually c = 1 mol L = 1 M), and M is the molecularity of the transition state. Lastly, κ, usually set to unity, is known as the transmission coefficient, a parameter which essentially serves as a "fudge factor" for transition state theory.
The biggest difference between the two theories is that Arrhenius theory attempts to model the reaction (single- or multi-step) as a whole, while transition state theory models the individual elementary steps involved. Thus, they are not directly comparable, unless the reaction in question involves only a single elementary step.
Finally, in the past, collision theory, in which reactants are viewed as hard spheres with a particular cross-section, provided yet another common way to rationalize and model the temperature dependence of the rate constant, although this approach has gradually fallen into disuse. The equation for the rate constant is similar in functional form to both the Arrhenius and Eyring equations:
where P is the steric (or probability) factor and Z is the collision frequency, and ΔE is energy input required to overcome the activation barrier. Of note, , making the temperature dependence of k different from both the Arrhenius and Eyring models. | 0 | Theoretical and Fundamental Chemistry |
ECgene in computational biology is a database of genomic annotations taking alternative splicing events into consideration. | 1 | Applied and Interdisciplinary Chemistry |
Indirect calorimetry provides at least two pieces of information: a measure of energy expenditure or 24-hour caloric requirements as reflected by the Resting Energy Expenditure (REE) and a measure of substrate utilization as reflected in the Respiratory Quotient (RQ). Knowledge of the many factors that affect these values has led to a much broader range of applications. Studies of indirect calorimetry over the past 20 years have led to the characterization of the hypermetabolic stress response to injury and the design of nutritional regimens whose substrates are most efficiently assimilated in different disease processes and organ failure states. Indirect calorimetry has influenced everyday practices of medical and surgical care, such as the warming of burn unit and surgical suites and the weaning of patients from ventilators. | 1 | Applied and Interdisciplinary Chemistry |
The Brus equation or confinement energy equation can be used to describe the emission energy of quantum dot semiconductor nanocrystals in terms of the band gap energy E, Plancks constant h, the radius of the quantum dot r, as well as the effective mass of the excited electron m* and of the excited hole m'*. The equation was named after Louis E. Brus who independently discovered it a few years later.
The radius of the quantum dot affects the wavelength of the emitted light due to quantum confinement, and this equation describes the effect of changing the radius of the quantum dot on the wavelength λ of the emitted light (and thereby on the emission energy ΔE = hc/λ, where c is the speed of light). This is useful for calculating the radius of a quantum dot from experimentally determined parameters.
The overall equation is
E, m*, and m* are unique for each nanocrystal composition.
For example, with cadmium selenide (CdSe) nanocrystals:
:E (CdSe) = 1.74 eV = 2.8·10 Joules,
:m* (CdSe) = 0.13 m = 1.18·10 kg,
:m* (CdSe) = 0.45 m = 4.09·10 kg. | 0 | Theoretical and Fundamental Chemistry |
The apothecaries system, or apothecaries weights and measures, is a historical system of mass and volume units that were used by physicians and apothecaries for medical prescriptions and also sometimes by scientists. The English version of the system is closely related to the English troy system of weights, the pound and grain being exactly the same in both. It divides a pound into 12 ounces, an ounce into 8 drachms, and a drachm into 3 scruples of 20 grains each. This exact form of the system was used in the United Kingdom; in some of its former colonies, it survived well into the 20th century. The apothecaries' system of measures is a similar system of volume units based on the fluid ounce. For a long time, medical recipes were written in Latin, often using special symbols to denote weights and measures.
The use of different measure and weight systems depending on the purpose was an almost universal phenomenon in Europe between the decline of the Roman Empire and metrication. This was connected with international commerce, especially with the need to use the standards of the target market and to compensate for a common weighing practice that caused a difference between actual and nominal weight. In the 19th century, most European countries or cities still had at least a "commercial" or "civil" system (such as the English avoirdupois system) for general trading, and a second system (such as the troy system) for precious metals such as gold and silver. The system for precious metals was usually divided in a different way from the commercial system, often using special units such as the carat. More significantly, it was often based on different weight standards.
The apothecaries system often used the same ounces as the precious metals system, although even then the number of ounces in a pound could be different. The apothecaries pound was divided into its own special units, which were inherited (via influential treatises of Greek physicians such as Dioscorides and Galen, 1st and 2nd century) from the general-purpose weight system of the Romans. Where the apothecaries weights and the normal commercial weights were different, it was not always clear which of the two systems was used in trade between merchants and apothecaries, or by which system apothecaries weighed medicine when they actually sold it. In old merchants handbooks, the former system is sometimes referred to as the pharmaceutical system and distinguished from the apothecaries' system.
__TOC__ | 1 | Applied and Interdisciplinary Chemistry |
The peritrich nuclear code (translation table 30) is a genetic code used by the nuclear genome of the peritrich ciliates Vorticella and Opisthonecta. | 1 | Applied and Interdisciplinary Chemistry |
The order of modules and domains of a complete nonribosomal peptide synthetase is as follows:
* Initiation or Starting module: [F/NMT]-A-PCP-
* Elongation or Extending modules: -(C/Cy)-[NMT]-A-PCP-[E]-
* Termination or Releasing module: -(TE/R)
(Order: N-terminus to C-terminus; []: optionally; (): alternatively) | 1 | Applied and Interdisciplinary Chemistry |
DNA condensation refers to the process of compacting DNA molecules in vitro or in vivo. Mechanistic details of DNA packing are essential for its functioning in the process of gene regulation in living systems. Condensed DNA often has surprising properties, which one would not predict from classical concepts of dilute solutions. Therefore, DNA condensation in vitro serves as a model system for many processes of physics, biochemistry and biology. In addition, DNA condensation has many potential applications in medicine and biotechnology.
DNA diameter is about 2 nm, while the length of a stretched single molecule may be up to several dozens of centimetres depending on the organism. Many features of the DNA double helix contribute to its large stiffness, including the mechanical properties of the sugar-phosphate backbone, electrostatic repulsion between phosphates (DNA bears on average one elementary negative charge per each 0.17 nm of the double helix), stacking interactions between the bases of each individual strand, and strand-strand interactions. DNA is one of the stiffest natural polymers, yet it is also one of the longest molecules. The persistence length of double-stranded DNA (dsDNA) is a measure of its stiffness or flexibility, which depends on the DNA sequence and the surrounding environment, including factors like salt concentration, pH, and temperature. Under physiological conditions (e.g., near-neutral pH and physiological salt concentrations), the persistence length of dsDNA is generally around 50 nm, which corresponds to approximately 150 base pairs. This means that at large distances DNA can be considered as a flexible rope, and on a short scale as a stiff rod. Like a garden hose, unpacked DNA would randomly occupy a much larger volume than when it is orderly packed. Mathematically, for a non-interacting flexible chain randomly diffusing in 3D, the end-to-end distance would scale as a square root of the polymer length. For real polymers such as DNA, this gives only a very rough estimate; what is important, is that the space available for the DNA in vivo is much smaller than the space that it would occupy in the case of a free diffusion in the solution. To cope with volume constraints, DNA can pack itself in the appropriate solution conditions with the help of ions and other molecules. Usually, DNA condensation is defined as "the collapse of extended DNA chains into compact, orderly particles containing only one or a few molecules". This definition applies to many situations in vitro and is also close to the definition of DNA condensation in bacteria as "adoption of relatively concentrated, compact state occupying a fraction of the volume available". In eukaryotes, the DNA size and the number of other participating players are much larger, and a DNA molecule forms millions of ordered nucleoprotein particles, the nucleosomes, which is just the first of many levels of DNA packing. | 1 | Applied and Interdisciplinary Chemistry |
Imidoyl chlorides are organic compounds that contain the functional group RC(NR)Cl. A double bond exist between the RN and the carbon centre. These compounds are analogues of acyl chloride. Imidoyl chlorides tend to be highly reactive and are more commonly found as intermediates in a wide variety of synthetic procedures. Such procedures include Gattermann aldehyde synthesis, Houben-Hoesch ketone synthesis, and the Beckmann rearrangement. Their chemistry is related to that of enamines and their tautomers when the α hydrogen is next to the C=N bond. Many chlorinated N-heterocycles are formally imidoyl chlorides, e.g. 2-chloropyridine, 2, 4, and 6-chloropyrimidines. | 0 | Theoretical and Fundamental Chemistry |
The Yolngu people of northeastern Arnhem Land in the Northern Territory of Australia identified a link between the Moon and the tides, which they mythically attributed to the Moon filling with water and emptying out again. | 1 | Applied and Interdisciplinary Chemistry |
Although the underlying equations governing plasmas are relatively simple, plasma behaviour is extraordinarily varied and subtle: the emergence of unexpected behaviour from a simple model is a typical feature of a complex system. Such systems lie in some sense on the boundary between ordered and disordered behaviour and cannot typically be described either by simple, smooth, mathematical functions, or by pure randomness. The spontaneous formation of interesting spatial features on a wide range of length scales is one manifestation of plasma complexity. The features are interesting, for example, because they are very sharp, spatially intermittent (the distance between features is much larger than the features themselves), or have a fractal form. Many of these features were first studied in the laboratory, and have subsequently been recognized throughout the universe. Examples of complexity and complex structures in plasmas include: | 0 | Theoretical and Fundamental Chemistry |
Nontrigonal pnictogen compounds refer to tricoordinate trivalent pnictogen (phosphorus, arsenic, antimony and bismuth: P, As, Sb and Bi) compounds that are not of typical trigonal pyramidal molecular geometry. By virtue of their geometric constraint, these compounds exhibit distinct electronic structures and reactivities, which bestow on them potential to provide unique nonmetal platforms for bond cleavage reactions. | 0 | Theoretical and Fundamental Chemistry |
Extraction thimbles are rod-shape filter paper often used in soxhlet extractors or atomized extractors. It is ideal for very sensitive detection, the performance depends on the thickness of inner diameter. Also, it is usually used in areas of food control and environmental monitoring. | 0 | Theoretical and Fundamental Chemistry |
Peptide-based self-healing hydrogels may be selectively grown onto nanofiber material which can then incorporated into the desired reconstructive tissue target. The hydrogel framework is then chemically modified to promote cell adhesion to the nanofiber peptide scaffold. Because the growth of the extracellular matrix scaffold is pH dependent, the materials selected must be factored for pH response when selecting the scaffolding material. | 0 | Theoretical and Fundamental Chemistry |
1 - Enzymatic hydrolysis - a single source of feedstock, switchgrass for example, is mixed with strong enzymes which convert a portion of cellulosic material into sugars which can then be fermented into ethanol. Genencor and Novozymes are two companies that have received United States government Department of Energy funding for research into reducing the cost of cellulase, a key enzyme in the production cellulosic ethanol by this process.
2 - Synthesis gas fermentation - a blend of feedstock, not exceeding 30% water, is gasified in a closed environment into a syngas containing mostly carbon monoxide and hydrogen. The cooled syngas is then converted into usable products through exposure to bacteria or other catalysts. BRI Energy, LLC is a company whose pilot plant in Fayetteville, Arkansas is currently using synthesis gas fermentation to convert a variety of waste into ethanol. After gasification, anaerobic bacteria (Clostridium ljungdahlii) are used to convert the syngas (CO, CO, and H) into ethanol. The heat generated by gasification is also used to co-generate excess electricity.
3 - C.O.R.S. and Grub Composting are sustainable technologies that employ organisms that feed on organic matter to reduce and convert organic waste in to high quality feedstuff and oil rich material for the biodiesel industry.
Organizations pioneering this novel approach to waste management are EAWAG, ESR International, Prota Culture and BIOCONVERSION that created the e-CORS® system to meet large scale organic waste management needs and environmental sustainability in both urban and livestock farming reality. This type of engineered system introduces a substantial innovation represented by the automatic modulation of the treatment, able to adapt conditions of the system to the biology of the scavenger used, improving their performances and the power of this technology. | 1 | Applied and Interdisciplinary Chemistry |
Clarkes father had been the European representative of US photographic pioneer company Kodak for several years, and was a personal friend of founder George Eastman. After Hans graduated in Chemistry, Eastman consulted with him a few times regarding chemistry-related processes. When World War I erupted, Eastman was forced to look for other sources of the chemicals that he had been obtaining from Germany, and he turned to Hans Clarke for assistance. At Eastmans request, Clarke moved to Rochester, New York in 1914 to assist what he assumed to be the company's considerable chemical engineering department. He was shocked to discover that he was the sole organic chemist there.
Clarke stayed with Kodak until 1928, when he was invited to become the Professor of Biological Chemistry in the Columbia University College of Physicians and Surgeons. His administrative skills and ability to recognize talent contributed to the growth of Columbia's biochemistry department, which by the 1940s had become one of the largest and most influential in the United States.
As the dark events foreshadowing World War II pushed eminent Jewish scientists out of Europe, Clarke opened his laboratory to refugee biochemists, among them E. Brand, Erwin Chargaff, Zacharias Dische, K. Meyer, David Nachmansohn, Rudolph Schoenheimer, and Heinrich Waelsch.
As head of Columbia's Biochemistry Department, Clarke took a personal interest in graduate students, of whom he demanded rigorous qualifications prior to admission. As time went on he devoted less time to his own research, becoming inundated with departmental and professional responsibilities.
Clarke's time at Kodak resulted in few publications in the chemical literature, but he aided the preparation of 26 substances to the Organic Syntheses series, and checked some 65 others. He stayed associated with Kodak for the rest of his life, only retiring as a consultant in 1969. Among other researches, he was involved in the production of penicillin in the United States.
Clarke retired from Columbia in 1956 due to its mandatory retirement policy, but was able to move to Yale University, where he spent eight years in full-time research. When Yale required the space that he was occupying he moved again, and did another seven years work at the Childrens Cancer Relief Foundation in Boston, Massachusetts. | 0 | Theoretical and Fundamental Chemistry |
In geometry, the dyakis dodecahedron /ˈdʌɪəkɪsˌdəʊdɪkəˈhiːdrən/ or diploid is a variant of the deltoidal icositetrahedron with pyritohedral symmetry, transforming the kite faces into chiral quadrilaterals. It is the dual of the cantic snub octahedron. It can be constructed by enlarging 24 of the 48 faces of the disdyakis dodecahedron, and is inscribed in the dyakis dodecahedron, thus it exists as a hemihedral form of it with indices {hkl}. It can be constructed into two non regular pentagonal dodecahedra, the pyritohedron and the tetartoid. The transformation to the pyritohedron can be made by combining two adjacent trapezoids that share a long edge together into one hexagon face, which is a pyritohedral pentagon with an extra vertex added. The edges that bend at it can be combined and the vertex removed to finally get the pentagon. The transformation to the tetartoid can be made by enlarging 12 of the dyakis dodecahedron's 24 faces.
Since the quadrilaterals are chiral and non-regular, the dyakis dodecahedron is a non-uniform polyhedron, a type of polyhedron that isnt vertex transitive and doesnt have regular polygon faces. Since it is face-transitive, it is an isohedron. The name diploid derives from the Greek word διπλάσιος (diplásios), meaning twofold since it has 2-fold symmetry along its 6 octahedral vertices. It has the same number of faces, edges and vertices as the deltoidal icositetrahedron as they are topologically identical. | 0 | Theoretical and Fundamental Chemistry |
Through anthropogenic impact the material flux of rivers has changed, which enters the sea and has a strong effect on coastal and shelf environments. | 1 | Applied and Interdisciplinary Chemistry |
Because of its ability to cause chemical reactions and excite fluorescence in materials, ultraviolet radiation has a number of applications. The following table gives some uses of specific wavelength bands in the UV spectrum.
* 13.5 nm: Extreme ultraviolet lithography
* 30–200 nm: Photoionization, ultraviolet photoelectron spectroscopy, standard integrated circuit manufacture by photolithography
* 230–365 nm: UV-ID, label tracking, barcodes
* 230–400 nm: Optical sensors, various instrumentation
* 240–280 nm: Disinfection, decontamination of surfaces and water (DNA absorption has a peak at 260 nm), germicidal lamps
* 200–400 nm: Forensic analysis, drug detection
* 270–360 nm: Protein analysis, DNA sequencing, drug discovery
* 280–400 nm: Medical imaging of cells
* 300–320 nm: Light therapy in medicine
* 300–365 nm: Curing of polymers and printer inks
* 350–370 nm: Bug zappers (flies are most attracted to light at 365 nm) | 0 | Theoretical and Fundamental Chemistry |
Terminal alkynes are weak acids:
: RC≡CH + R″M R″H + RC≡CM
To generate acetylides from acetylene and alkynes relies on the use of organometallic or inorganic superbases in solvents which are less acidic than the terminal alkyne. In early studies liquid ammonia was employed, but ethereal solvents are more common.
Lithium amide, LiHMDS, or organolithium reagents, such as butyllithium, are frequently used to form lithium acetylides:
Monopotassium and monosodium acetylide can be prepared from various inorganic reagents (such as sodium amide) or from their elemental metals, often at room temperature and atmospheric pressure.
Copper(I) acetylide can be prepared by passing acetylene through an aqueous solution of copper(I) chloride because of a low solubility equilibrium. Similarly, silver acetylides can be obtained from silver nitrate.
Calcium carbide is prepared by heating carbon with lime (calcium oxide) at approximately 2,000 °C. A similar process is used to produce lithium carbide. | 0 | Theoretical and Fundamental Chemistry |
Valerie has two daughters, and her father is the honorary president of the Johannesburg Sephardic Hebrew Congregation. She grew up speaking Judeo-Spanish at home. | 1 | Applied and Interdisciplinary Chemistry |
Some common per- and polyfluoroalkyl substances include:
* Polytetrafluoroethylene (aka PTFE or Teflon)
* Perfluoroalkyl carboxylic acids (PFCAs)
* Perfluorosulfonic acids (PFSAs)
* Fluorotelomers (FTOHs) | 0 | Theoretical and Fundamental Chemistry |
A dispersant or a dispersing agent is a substance, typically a surfactant, that is added to a suspension of solid or liquid particles in a liquid (such as a colloid or emulsion) to improve the separation of the particles and to prevent their settling or clumping.
Dispersants are widely used to stabilize various industrial and artisanal products, such as paints, ferrofluids, and salad dressings. The plasticizers or superplasticizers, used to improve the workability of pastes like concrete and clay, are typically dispersants. The concept also largely overlaps with that of detergent, used to bring oily contamination into water suspension, and of emulsifier, used to create homogeneous mixtures of immiscible liquids like water and oil. Natural suspensions like milk and latex contain substances that act as dispersants. | 0 | Theoretical and Fundamental Chemistry |
The amount of alcohol on the breath can be measured, without requiring drawing blood, by blowing into a breathalyzer, resulting in a breath alcohol content (BrAC). The BrAC specifically correlates with the concentration of alcohol in arterial blood, satisfying the equation . Its correlation with the standard BAC found by drawing venous blood is less strong. Jurisdictions vary in the statutory conversion factor from BrAC to BAC, from 2000 to 2400. Many factors may affect the accuracy of a breathalyzer test, but they are the most common method for measuring alcohol concentrations in most jurisdictions. | 1 | Applied and Interdisciplinary Chemistry |
In Chinese alchemy, elixir poisoning refers to the toxic effects from elixirs of immortality that contained metals and minerals such as mercury and arsenic. The official Twenty-Four Histories record numerous Chinese emperors, nobles, and officials who died from taking elixirs to prolong their lifespans. The first emperor to die from elixir poisoning was likely Qin Shi Huang (d. 210 BCE) and the last was the Yongzheng Emperor (d. 1735 CE). Despite common knowledge that immortality potions could be deadly, fangshi and Daoist alchemists continued the elixir-making practice for two millennia. | 1 | Applied and Interdisciplinary Chemistry |
Stress corrosion cracking (SCC) is the growth of a crack in a corrosive environment. It requires three conditions to take place: 1)corrosive environment 2)stress 3)susceptible material. SCC can lead to unexpected sudden and hence catastrophic failure of normally ductile metals under tensile stress. This is usually exacerbated at elevated temperature. SCC is highly chemically specific in that certain alloys are likely to undergo SCC only when exposed to a small number of chemical environments. It is common for SCC to go undetected prior to failure. SCC usually quite progresses rapidly after initial crack initiation, and is seen more often in alloys as opposed to pure metals. The corrosion engineer thus must be aware of this phenomenon. | 1 | Applied and Interdisciplinary Chemistry |
* Folch, Albert. Hidden in Plain Sight: The History, Science, and Engineering of Microfluidic Technology (MIT Press, 2022) [http://www.h-net.org/reviews/showrev.php?id=57939 online review] | 1 | Applied and Interdisciplinary Chemistry |
Disrupted functioning of cAMP has been noted as one of the mechanisms of several bacterial exotoxins.
They can be subgrouped into two distinct categories:
* Toxins that interfere with enzymes ADP-ribosyl-transferases, and
* invasive adenylate cyclases. | 1 | Applied and Interdisciplinary Chemistry |
The fermentation processes used in alcohol production is commonly maintained in low oxygen conditions, under a blanket of carbon dioxide, while growing yeast for biomass involves aerating the broth for maximized energy production. Despite the bactericidal effects of ethanol, acidifying effects of fermentation, and low oxygen conditions of industrial alcohol production, bacteria that undergo lactic acid fermentation can contaminate such facilities because lactic acid has a low pKa of 3.86 to avoid decoupling the pH membrane gradient that supports regulated transport. | 1 | Applied and Interdisciplinary Chemistry |
AAV is capable of transducing multiple cell types within the retina. AAV serotype 2, the most well-studied type of AAV, is commonly administered in one of two routes: intravitreal or subretinal. Using the intravitreal route, AAV is injected in the vitreous humor of the eye. Using the subretinal route, AAV is injected underneath the retina, taking advantage of the potential space between the photoreceptors and RPE layer, in a short surgical procedure. Although this is more invasive than the intravitreal route, the fluid is absorbed by the RPE and the retina flattens in less than 14 hours without complications. Intravitreal AAV targets retinal ganglion cells and a few Muller glial cells. Subretinal AAV efficiently targets photoreceptors and RPE cells.
The reason that different routes of administration lead to different cell types being transfected (e.g., different tropism) is that the inner limiting membrane (ILM) and the various retinal layers act as physical barriers for the delivery of drugs and vectors to the deeper retinal layers. Thus overall, subretinal AAV is 5-10 times more efficient than delivery using the intravitreal route. | 1 | Applied and Interdisciplinary Chemistry |
Photoactuation in microelectromechanical systems (MEMS) has been demonstrated in proof-of-concept experiments. Instead of a typical substrate, a specialized cantilever is placed on top of the liquid-insulator-photoconductor stack. As light is shined on the photoconductor, the capillary force from the drop on the cantilever changes with the contact angle, and deflects the beam. This wireless actuation can be used as a substitute for complex circuit-based systems currently used for optical addressing and control of autonomous wireless sensors | 1 | Applied and Interdisciplinary Chemistry |
Cleaning is the preparatory process of ensuring that the surface to be etched is free of contaminants which could negatively impact the quality of the finished part. An improperly cleaned surface could result in poor adhesion of the maskant, causing areas to be etched erroneously, or a non-uniform etch rate which could result in inaccurate final dimensions. The surface must be kept free from oils, grease, primer coatings, markings and other residue from the marking out process, scale (oxidation), and any other foreign contaminants. For most metals, this step can be performed by applying a solvent substance to the surface to be etched, washing away foreign contaminants. The material may also be immersed in alkaline cleaners or specialized de-oxidizing solutions. It is common practice in modern industrial chemical etching facilities that the workpiece never be directly handled after this process, as oils from human skin could easily contaminate the surface. | 1 | Applied and Interdisciplinary Chemistry |
Isotopocule is a shorthand for an isotopically substituted molecule. Isotopocules are molecules that differ only in their isotopic composition or the intramolecular position of the isotopes. It is an umbrella term for the more specific terms isotopologue and isotopomer, coined by Jan Kaiser and Thomas Röckmann in 2008. | 0 | Theoretical and Fundamental Chemistry |
Usually, plastocyanin can be found in organisms that contain chlorophyll b and cyanobacteria, as well as algae that contain chlorophyll c. Plastocyanin has also been found in the diatom, Thalassiosira oceanica, which can be found in oceanic environments. It was surprising to find these organisms containing the protein plastocyanin because the concentration of copper dissolved in the ocean is usually low (between 0.4 – 50 nM). However, the concentration of copper in the oceans is comparatively higher compared to the concentrations of other metals such as zinc and iron. Other organisms that live in the ocean, such as phytoplankton, have adapted to where they do not need these low concentration metals (Fe and Zn) to facilitate photosynthesis and grow. | 0 | Theoretical and Fundamental Chemistry |
* Citalopram: steps were taken to separate the more potent enantiomer, escitalopram.
* Thalidomide is a drug whose two enantiomers cause distinctly different effects from one another. The unforeseen teratogenicity of the (R)-(+)-isomer caused it to become an important case study of stereochemistry in medicine. Although it is possible to chemically isolate just the desired (S)-(−)-isomer from the racemic mixture, the two enantiomers rapidly interconvert in vivo; thus rendering their separation to be of little use.
* Methorphan is another drug whose two enantiomers possess very different binding profiles, with the L enantiomer being a potent opioid analgesic, and the D enantiomer being a commonly used over-the-counter cough suppressant which acts as an NMDA-antagonist but possesses nearly no opioid activity. In the case of morphinan, the eudysmic ratio is preserved after metabolism as the D and L metabolites possess the same pharmacological targets as the corresponding methorphan enantiomers, but are considerably more potent than their parent compounds.
* Amino acids are also an example of eudysmic ratio. Nearly all of the amino acids in the human body are called "L" amino acids; despite being chiral, the body almost exclusively creates and uses amino acids in this one configuration. D amino acids, the enantiomers — or "mirror images" — of the amino acids in the human body cannot be incorporated into proteins. D-aspartate and D-serine are two notable counterexamples, since they do not appear to ever be incorporated into proteins, but instead act individually as signalling molecules. However, mammals can metabolize significant amount of D amino acids by oxidizing them to alpha-ketoacids (most of which are non-chiral) and then transaminases can create L amino acids. There are no reasons to believe that humans are exceptional, they have all required enzymes (DDO, DAO). Some common foods contain near-racemic mixtures of amino acids. | 0 | Theoretical and Fundamental Chemistry |
Molds excrete toxic compounds called mycotoxins, secondary metabolites produced by fungi under certain environmental conditions. These environmental conditions affect the production of mycotoxins at the transcription level. Temperature, water activity and pH, strongly influence mycotoxin biosynthesis by increasing the level of transcription within the fungal spore. It has also been found that low levels of fungicides can boost mycotoxin synthesis. Certain mycotoxins can be harmful or lethal to humans and animals when exposure is high enough.
Extreme exposure to very high levels of mycotoxins can lead to neurological problems and, in some cases, death; fortunately, such exposures rarely to never occur in normal exposure scenarios, even in residences with serious mold problems. Prolonged exposure, such as daily workplace exposure, can be particularly harmful.
It is thought that all molds may produce mycotoxins, and thus all molds may be potentially toxic if large enough quantities are ingested, or the human becomes exposed to extreme quantities of mold. Mycotoxins are not produced all the time, but only under specific growing conditions. Mycotoxins are harmful or lethal to humans and animals only when exposure is high enough.
Mycotoxins can be found on the mold spore and mold fragments, and therefore they can also be found on the substrate upon which the mold grows. Routes of entry for these insults can include ingestion, dermal exposure, and inhalation.
Aflatoxin is an example of a mycotoxin. It is a cancer-causing poison produced by certain fungi in or on foods and feeds, especially in field corn and peanuts.
Toxic effects from mold were thought to be the result of exposure to the mycotoxins of some mold species, such as Stachybotrys chartarum. In 1927, Ismailson, a Soviet scientist, noted a form of mycotoxicosis in employees in a binder twine factory. In the 1940s, "Stachybotryotoxicosis" was identified in Ukraine as a new disease in humans in close contact with moldy hay, including inhalation of the associated dust, which caused, among other symptoms, a "haemorrhagic exúdate". Following cases of pulmonary hemorrhage in infants in Cleveland, Ohio in 1993–94, several related studies suggested a causal relationship between exposure to S. chartarum and the disease. An anonymous panel from within the CDC revisited the cases and argued that the link was not proven. Subsequent studies with mice and rats exposed to S. chartarum and associated mycotoxins showed that pulmonary hemorrhage could occur, suggesting the link is plausible. The American Academy of Pediatrics also found the link plausible, and subsequent analysis and case studies with humans have further noted the association. As well, a 1987 report by the United States Army Medical Research Institute of Infectious Diseases suggested that the effects of "trichothecene mycotoxins are more than 10 times greater via inhalation than via intravenous exposure." The presumed mechanism of action is that Stachybotrys produces a compound, stachylysin, which is a hemolysin that disintegrates (lyses) red blood cells. | 1 | Applied and Interdisciplinary Chemistry |
Interpretation of carbon isotope effects are usually complicated by simultaneously forming and breaking bonds to carbon. Even reactions that involve only bond cleavage from the carbon, such as S1 reactions, involve strengthening of the remaining bonds to carbon. In many such reactions, leaving group isotope effects tend to be easier to interpret. For example, substitution and elimination reactions in which chlorine act as a leaving group are convenient to interpret, especially since chlorine acts as a monatomic species with no internal bonding to complicate the reaction coordinate, and it has two stable isotopes, Cl and Cl, both with high abundance. The major challenge to the interpretation of such isotope affects is the solvation of the leaving group.
Owing to experimental uncertainties, measurement of isotope effect may entail significant uncertainty. Often isotope effects are determined through complementary studies on a series of isotopomers. Accordingly, it is quite useful to combine hydrogen isotope effects with heavy-atom isotope effects. For instance, determining nitrogen isotope effect along with hydrogen isotope effect was used to show that the reaction of 2-phenylethyltrimethylammonium ion with ethoxide in ethanol at 40 °C follows an E2 mechanism, as opposed to alternative non-concerted mechanisms. This conclusion was reached upon showing that this reaction yields a nitrogen isotope effect, k/k, of 1.0133±0.0002 along with a hydrogen kinetic isotope effect of 3.2 at the leaving hydrogen.
Similarly, combining nitrogen and hydrogen isotope effects was used to show that syn eliminations of simple ammonium salts also follow a concerted mechanism, which was a question of debate before. In the following two reactions of 2-phenylcyclopentyltrimethylammonium ion with ethoxide, both of which yield 1-phenylcyclopentene, both isomers exhibited a nitrogen isotope effect k/k at 60 °C. Although the reaction of the trans isomer, which follows syn elimination, has a smaller nitrogen kinetic isotope effect (1.0064) compared to the cis isomer which undergoes anti elimination (1.0108), both results are large enough to be indicative of weakening of the C-N bond in the transition state that would occur in a concerted process. | 0 | Theoretical and Fundamental Chemistry |
Johannes Sibertus Kuffler (1595–1677) was a German inventor and chemist, from Cologne.
He had a 1618 doctorate from the University of Padua. After he married Catherina, daughter of Cornelius Drebbel, he started in a successful dyeing business in Leiden, with his brother Abraham. Supposedly he used a procedure invented by his father-in-law, using stannic chloride as a fixative.
He was an associate of Johann Glauber, and went into an alchemical venture with Johann Moriaen and Benjamin Worsley.
In 1656 the alchemist Israel Tonge provided a loan of 100 pounds to have the Kuffler family moved from Arnhem in the Netherlands to England so that "his abilities in his profession, his relation to Cornelius Dribellius his life & conversation & concerning the reality & certaintie of the Experiments, hereafter mentioned in these præsents, shall vnto wise & indiferent men be of satisfaction.".
He later moved it to Bow, London. The new colour was called "Color Kufflerianus" or "Bow dye". During the Protectorate they also spent much effort promoting a secret weapon (torpedo or submarine) for naval warfare, petitioning Richard Cromwell.
Like his father-in-law, he contributed to technology, in the matter of ovens that were self-regulating. He demonstrated a use as incubator to the Royal Society. | 1 | Applied and Interdisciplinary Chemistry |
Niobium-germanium (NbGe) is an intermetallic chemical compound of niobium (Nb) and germanium (Ge). It has A15 phase structure.
It is a superconductor with a critical temperature of 23.2 K.
Sputtered films have been reported to have an upper critical field of 37 teslas at 4.2 K. | 1 | Applied and Interdisciplinary Chemistry |
In August 2018, scientists announced new observations regarding the rapid transformation of fluid deuterium from an insulating to a metallic form below 2000 K. Remarkable agreement is found between the experimental data and the predictions based on quantum Monte Carlo simulations, which is expected to be the most accurate method to date. This may help researchers better understand giant gas planets, such as Jupiter, Saturn and related exoplanets, since such planets are thought to contain a lot of liquid metallic hydrogen, which may be responsible for their observed powerful magnetic fields. | 0 | Theoretical and Fundamental Chemistry |
Thermocells in which the electrolyte connecting the electrodes is an ionic material have been considered and constructed too. The temperature range is also elevated as compared to liquid electrolytes. Studied systems fall in the 400–900 K. Some solid ionic materials that have been employed to construct thermogalvanic cells are AgI, PbCl and PbBr. | 0 | Theoretical and Fundamental Chemistry |
Adhesive strength depends also on the size and macroscopic shape of adhesive contact. When a rigid punch with a flat but oddly shaped face is carefully pulled off its soft counterpart, the detachment does not occur instantaneously. Instead, detachment fronts start at pointed corners and travel inwards until the final configuration is reached. The main parameter determining the adhesive strength of flat contacts appears to be the maximum linear size of the contact. The process of detachment can as observed experimentally can be seen in the film. | 0 | Theoretical and Fundamental Chemistry |
All commonly used cloning vectors in molecular biology have key features necessary for their function, such as a suitable cloning site and selectable marker. Others may have additional features specific to their use. For reason of ease and convenience, cloning is often performed using E. coli. Thus, the cloning vectors used often have elements necessary for their propagation and maintenance in E. coli, such as a functional origin of replication (ori). The ColE1 origin of replication is found in many plasmids. Some vectors also include elements that allow them to be maintained in another organism in addition to E. coli, and these vectors are called shuttle vector. | 1 | Applied and Interdisciplinary Chemistry |
Sulfoxides feature relatively short S–O distances. In DMSO, the S–O distance is 1.531 Å. The sulfur center is pyramidal; the sum of the angles at sulfur is about 306°.
Sulfoxides are generally represented with the structural formula R−S(=O)−R, where R and R are organic groups. The bond between the sulfur and oxygen atoms is intermediate of a dative bond and a polarized double bond. The double-bond resonance form implies 10 electrons around sulfur (10-S-3 in N-X-L notation). The double-bond character of the S−O bond may be accounted for by donation of electron density into C−S antibonding orbitals ("no-bond" resonance forms in valence-bond language). Nevertheless, due to its simplicity and lack of ambiguity, the IUPAC recommends use of the expanded octet double-bond structure to depict sulfoxides, rather than the dipolar structure or structures that invoke "no-bond" resonance contributors. The S–O interaction has an electrostatic aspect, resulting in significant dipolar character, with negative charge centered on oxygen. | 0 | Theoretical and Fundamental Chemistry |
In 1987 antistasin was tested as the first direct Xa inhibitor. Antistasin is a protein made up of 119 amino acid residues, of which 20 are cysteines involved in 10 disulfide bonds. It acts as a slow, tight-binding inhibitor of factor Xa with a Ki value of 0.3–0.6 nM but it also inhibits trypsin. Recombinant Antistasin can be produced by genetically modified yeast, saccharomyces cerevisiae. Another natural occurring direct Xa-inhibitor, the tick anticoagulant peptide (TAP), was discovered in 1990. It is a single-chain, 60 amino acid peptide and like antistasin it is a slow, tight-binding inhibitor with a similar Ki value (~0.6 nM).
These two proteins were mostly used to validate factor Xa as a drug target. Animal studies suggested direct Xa-inhibition to be a more efficient approach to anticoagulation compared to direct thrombin inhibitors, especially offering a wider therapeutic window and reducing the risk of rebound thrombosis, (increase in thromboembolic events occurring shortly after the withdrawal of an antithrombotic medication) compared to direct and indirect thrombin inhibitors.
During the 1990s several low-molecular-weight substances were developed, such as DX-9065a and YM-60828.
DX-9065a was the first synthetic compound that inhibited FXa without inhibiting thrombin. That was attained by inserting a carboxyl group which seemed to be the most important moiety for a selective binding to FXa. Those early developed small molecules yet had amidine-groups or even higher-basic functions, which were thought to be necessary as mimics for an arginine residue in prothrombin, the natural substrate of factor Xa. Nevertheless, these basic functions are also related to a very poor oral bioavailability (e.g. 2–3% for DX-9065a).
In 1998 Bayer Healthcare, a pharmaceutical company started searching for low-molecular-weight direct factor Xa inhibitors with higher oral bioavailability. High-throughput screening and further optimisation at first lead to several substances from the class of isoindolinones demonstrating that much less basic substances can also act as potent Xa inhibitors to an IC value of up to 2 nM. Although isoindolinones have a better oral bioavailability than the original compounds it wasn't sufficient enough. However, the project later lead to the class of n-aryloxazolidinones that provides substances with both high potency of inhibiting factor Xa and high bioavailability. One compound of this class, Rivaroxaban (IC = 0.7 nM, bioavailability: 60%), was granted marketing authorization for the prevention of venous thromboembolism in Europe and Canada in September 2008. | 1 | Applied and Interdisciplinary Chemistry |
Kovacs reagent is a biochemical reagent consisting of isoamyl alcohol, para-dimethylaminobenzaldehyde (DMAB), and concentrated hydrochloric acid. It is used for the diagnostical indole test, to determine the ability of the organism to split indole from the amino acid tryptophan. The indole produced yields a red complex with para-dimethylaminobenzaldehyde under the given conditions. This was invented by the Hungarian physician Nicholas Kovacs and was published in 1928. This reagent is used in the confirmation of E. coli and many other pathogenic microorganisms. | 1 | Applied and Interdisciplinary Chemistry |
Using electroreflectance in surface physics studies gives some major advantages over techniques used before its discovery. Before, the determination of the surface potential was the hard to do since you need electrical measurements at the surface and it was difficult to probe the surface region without involving the bulk underneath. Electroreflectance does not need to make electrical measurements on the surface, but only uses optical measurements. Furthermore, due to direct functional relationships between surface potential and reflectivity we can get rid of a lot assumptions about mobility, scattering, or trapping of added carriers needed in the older methods. The electric field of the surface is probed by the modulation of the beam reflected by the surface. The incoming beam does not penetrate the material deep, so you only probe the surface without interacting with the bulk underneath. | 0 | Theoretical and Fundamental Chemistry |
EOS-80 (Equation of State of Seawater -1980) uses Practical Salinity measured on the PSS-78 (Practical Salinity Scale of 1978) scale that itself is based on measurements of temperature, pressure and electrical conductivity. Thus, EOS-80 did not account for different chemical compositions of seawater.
EOS-80 consisted of separate equations for density, sound speed, freezing temperature and heat capacity but did not provide expressions for entropy or chemical potentials. Therefore, it was not a complete and consistent description of the thermodynamic properties of seawater. Inconsistencies in EOS-80 appear for example in the heat content at high pressure, depending on which equation is used for the calculation. Furthermore, EOS-80 was not consistent with meteorological equations while TEOS-10 is valid for humid air as well as for seawater.
EOS-80 provided expressions for potential temperature, which removes the effect of pressure on temperature but not for Conservative Temperature, which is a direct measure for potential enthalpy and therefore heat content.
In TEOS-10 the current standard for temperature scales, ITS-90 (International Temperature Scale of 1990) is used, while EOS-80 used the IPTS-68 (International Practical Temperature of 1968). In the SIA-Library of TEOS-10 implementations to convert outdated into current scales are included.
TEOS-10 was derived using absolute pressure P while EOS-80 used the pressure relative to the sea surface 𝑝. They can be converted by: P/Pa = 101325 + 10000 ∙ 𝑝/dbar (see Atmospheric Pressure). | 0 | Theoretical and Fundamental Chemistry |
In a top load washing machine the agitator projects from the bottom of the wash basket and creates the wash action by rotating back and forth, rolling garments from the top of the load, down to the bottom, then back up again.
There are several types of agitators with the most common being the "straight-vane" and "dual-action" agitators. The "straight-vane" is a one-part agitator with bottom and side fins that usually turns back and forth. The Dual-action is a two-part agitator that has bottom washer fins that move back and forth and a spiral top that rotates clockwise to help guide the clothes to the bottom washer fins.
The modern agitator, which is dual-action, was first made in Kenmore Appliances washing machines in the 1980s to present. These agitators are known by the company as dual-rollover and triple-rollover action agitators. | 1 | Applied and Interdisciplinary Chemistry |
Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U).
Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), Valine (Val, V) | 1 | Applied and Interdisciplinary Chemistry |
Those who use lithium should receive regular serum level tests and should monitor thyroid and kidney function for abnormalities, as it interferes with the regulation of sodium and water levels in the body, and can cause dehydration. Dehydration, which is compounded by heat, can result in increasing lithium levels. The dehydration is due to lithium inhibition of the action of antidiuretic hormone, which normally enables the kidney to reabsorb water from urine. This causes an inability to concentrate urine, leading to consequent loss of body water and thirst.
Lithium concentrations in whole blood, plasma, serum or urine may be measured using instrumental techniques as a guide to therapy, to confirm the diagnosis in potential poisoning victims or to assist in the forensic investigation in a case of fatal overdosage. Serum lithium concentrations are usually in the range of 0.5–1.3 mmol/L (0.5–1.3 mEq/L) in well-controlled people, but may increase to 1.8–2.5 mmol/L in those who accumulate the drug over time and to 3–10 mmol/L in acute overdose.
Lithium salts have a narrow therapeutic/toxic ratio, so should not be prescribed unless facilities for monitoring plasma concentrations are available. Doses are adjusted to achieve plasma concentrations of 0.4 to 1.2 mmol /L on samples taken 12 hours after the preceding dose.
Given the rates of thyroid dysfunction, thyroid parameters should be checked before lithium is instituted and monitored after 3–6 months and then every 6–12 months.
Given the risks of kidney malfunction, serum creatinine and eGFR should be checked before lithium is instituted and monitored after 3–6 months at regular interval. Patients who have a rise in creatinine on three or more occasions, even if their eGFR is > 60 ml/min/
1.73m2 require further evaluation, including a urinalysis for haematuria, proteinuria, a review of their medical history with attention paid to cardiovascular, urological and medication history, and blood pressure control and management. Overt proteinuria should be further quantified with a urine protein to creatinine ratio. | 1 | Applied and Interdisciplinary Chemistry |
Stereographic projection plots can be carried out by a computer using the explicit formulas given above. However, for graphing by hand these formulas are unwieldy. Instead, it is common to use graph paper designed specifically for the task. This special graph paper is called a stereonet or Wulff net, after the Russian mineralogist George (Yuri Viktorovich) Wulff.
The Wulff net shown here is the stereographic projection of the grid of parallels and meridians of a hemisphere centred at a point on the equator (such as the Eastern or Western hemisphere of a planet).
In the figure, the area-distorting property of the stereographic projection can be seen by comparing a grid sector near the center of the net with one at the far right or left. The two sectors have equal areas on the sphere. On the disk, the latter has nearly four times the area of the former. If the grid is made finer, this ratio approaches exactly 4.
On the Wulff net, the images of the parallels and meridians intersect at right angles. This orthogonality property is a consequence of the angle-preserving property of the stereographic projection. (However, the angle-preserving property is stronger than this property. Not all projections that preserve the orthogonality of parallels and meridians are angle-preserving.)
For an example of the use of the Wulff net, imagine two copies of it on thin paper, one atop the other, aligned and tacked at their mutual center. Let be the point on the lower unit hemisphere whose spherical coordinates are (140°, 60°) and whose Cartesian coordinates are (0.321, 0.557, −0.766). This point lies on a line oriented 60° counterclockwise from the positive -axis (or 30° clockwise from the positive -axis) and 50° below the horizontal plane . Once these angles are known, there are four steps to plotting :
#Using the grid lines, which are spaced 10° apart in the figures here, mark the point on the edge of the net that is 60° counterclockwise from the point (1, 0) (or 30° clockwise from the point (0, 1)).
#Rotate the top net until this point is aligned with (1, 0) on the bottom net.
#Using the grid lines on the bottom net, mark the point that is 50° toward the center from that point.
#Rotate the top net oppositely to how it was oriented before, to bring it back into alignment with the bottom net. The point marked in step 3 is then the projection that we wanted.
To plot other points, whose angles are not such round numbers as 60° and 50°, one must visually interpolate between the nearest grid lines. It is helpful to have a net with finer spacing than 10°. Spacings of 2° are common.
To find the central angle between two points on the sphere based on their stereographic plot, overlay the plot on a Wulff net and rotate the plot about the center until the two points lie on or near a meridian. Then measure the angle between them by counting grid lines along that meridian. | 0 | Theoretical and Fundamental Chemistry |
Plastic deformation involves using heat or pressure to make a workpiece more conductive to mechanical force. Historically, this and casting were done by blacksmiths, though today the process has been industrialized. In bulk metal forming, the workpiece is generally heated up.
* Cold sizing
* Extrusion
* Drawing
* Forging
* Powder metallurgy
* Friction drilling
* Rolling
* Burnishing | 1 | Applied and Interdisciplinary Chemistry |
Ammonia borane has been suggested as a storage medium for hydrogen, e.g. for when the gas is used to fuel motor vehicles. It can be made to release hydrogen on heating, being polymerized first to , then to , which ultimately decomposes to boron nitride (BN) at temperatures above 1000 °C. It is more hydrogen-dense than liquid hydrogen and also able to exist at normal temperatures and pressures.
Ammonia borane finds some use in organic synthesis as an air-stable derivative of diborane. It can be used as a reducing agent in transfer hydrogenation reactions, often in the presence of a transition metal catalyst. | 0 | Theoretical and Fundamental Chemistry |
Although much of the literature on the subject is concerned with just one mechanism, there are actually several different mechanisms that produce the photoacoustic effect. The primary universal mechanism is photothermal, based on the heating effect of the light and the consequent expansion of the light-absorbing material. In detail, the photothermal mechanism consists of the following stages:
# conversion of the absorbed pulsed or modulated radiation into heat energy.
# temporal changes of the temperatures at the loci where radiation is absorbed – rising as radiation is absorbed and falling when radiation stops and the system cools.
# expansion and contraction following these temperature changes, which are "translated" to pressure changes. The pressure changes, which occur in the region where light was absorbed, propagate within the sample body and can be sensed by a sensor coupled directly to it. Commonly, for the case of a condensed phase sample (liquid, solid), pressure changes are rather measured in the surrounding gaseous phase (commonly air), formed there by the diffusion of the thermal pulsations.
The main physical picture, in this case, envisions the original temperature pulsations as origins of propagating temperature waves ("thermal waves"), which travel in the condensed phase, ultimately reaching the surrounding gaseous phase. The resulting temperature pulsations in the gaseous phase are the prime cause of the pressure changes there. The amplitude of the traveling thermal wave decreases strongly (exponentially) along its propagation direction, but if its propagation distance in the condensed phase is not too long, its amplitude near the gaseous phase is sufficient to create detectable pressure changes. This property of the thermal wave confers unique features to the detection of light absorption by the photoacoustic method. The temperature and pressure changes involved are minute, compared to everyday scale – typical order of magnitude for the temperature changes, using ordinary light intensities, is about micro- to millidegrees and for the resulting pressure changes is about nano- to microbars.
The photothermal mechanism manifests itself, besides the photoacoustic effect, also by other physical changes, notably emission of infra-red radiation and changes in the refraction index. Correspondingly, it may be detected by various other means, described by terms such as "photothermal radiometry", "thermal lens" and "thermal beam deflection" (popularly also known as "mirage" effect, see Photothermal spectroscopy). These methods parallel the photoacoustic detection. However, each method has its special range of application. | 0 | Theoretical and Fundamental Chemistry |
Southeastern Los Angeles County installed thousands of stainless steel, full-capture trash devices on their road drains in 2011. | 1 | Applied and Interdisciplinary Chemistry |
The reactions are most usually carried out in test tubes into which a gel is formed that contains a dilute solution of one of the reactants.
If a hot solution of agar gel also containing a dilute solution of potassium dichromate is poured in a test tube, and after the gel solidifies a more concentrated solution of silver nitrate is poured on top of the gel, the silver nitrate will begin to diffuse into the gel. It will then encounter the potassium dichromate and will form a continuous region of precipitate at the top of the tube.
After some hours, the continuous region of precipitation is followed by a clear region with no sensible precipitate, followed by a short region of precipitate further down the tube. This process continues down the tube forming several, up to perhaps a couple dozen, alternating regions of clear gel and precipitate rings. | 0 | Theoretical and Fundamental Chemistry |
Nucleotide sugars are the activated forms of monosaccharides. Nucleotide sugars act as glycosyl donors in glycosylation reactions. Those reactions are catalyzed by a group of enzymes called glycosyltransferases. | 0 | Theoretical and Fundamental Chemistry |
Chan King-ming is a Hong Kong politician and academic. He served as the vice-chairman of the Democratic Party of Hong Kong from 2004 to 2006. He is also an associate professor in the department of biochemistry and Environmental Science Program of the Chinese University of Hong Kong. | 1 | Applied and Interdisciplinary Chemistry |
The second step of nitrification is the oxidation of nitrite into nitrate. This process is sometimes known as nitratation. Nitrite oxidation is conducted by nitrite-oxidizing bacteria (NOB) from the taxa Nitrospirota, Nitrospinota, Pseudomonadota and Chloroflexota. NOB are typically present in soil, geothermal springs, freshwater and marine ecosystems. | 1 | Applied and Interdisciplinary Chemistry |
Nanofluidic circuitry is a nanotechnology aiming for control of fluids in nanometer scale. Due to the effect of an electrical double layer within the fluid channel, the behavior of nanofluid is observed to be significantly different compared with its microfluidic counterparts. Its typical characteristic dimensions fall within the range of 1–100 nm. At least one dimension of the structure is in nanoscopic scale. Phenomena of fluids in nano-scale structure are discovered to be of different properties in electrochemistry and fluid dynamics. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, an adverse pressure gradient is a pressure gradient in which the static pressure increases in the direction of the flow. Mathematically this is expressed as for a flow in the positive -direction.
This is important for boundary layers. Increasing the fluid pressure is akin to increasing the potential energy of the fluid, leading to a reduced kinetic energy and a deceleration of the fluid. Since the fluid in the inner part of the boundary layer is slower, it is more greatly affected by the increasing pressure gradient. For a large enough pressure increase, this fluid may slow to zero velocity or even become reversed causing a flow separation. This has very significant consequences in aerodynamics since flow separation significantly modifies the pressure distribution along the surface and hence the lift and drag characteristics.
Turbulent boundary layers tend to be able to sustain an adverse pressure gradient better than an equivalent laminar boundary layer. The more efficient mixing which occurs in a turbulent boundary layer transports kinetic energy from the edge of the boundary layer to the low-momentum flow at the solid surface, often preventing the separation that would occur for a laminar boundary layer under the same conditions. This physical fact has led to a variety of schemes to actually produce turbulent boundary layers when boundary layer separation is dominant at high Reynolds numbers; the dimples on a golf ball, the fuzz on a tennis ball, or the seams on a baseball are good examples. Aeroplane wings are often engineered with vortex generators on the upper surface to produce a turbulent boundary layer. | 1 | Applied and Interdisciplinary Chemistry |
DNA printing can thus be used to produce DNA parts, which are defined as sequences of DNA that encode a specific biological function (for example, promoters, transcription regulatory sequences or open reading frames). However, because oligonucleotide synthesis typically cannot accurately produce oligonucleotides sequences longer than a few hundred base pairs, DNA assembly methods have to be employed to assemble these parts together to create functional genes, multi-gene circuits or even entire synthetic chromosomes or genomes. Some DNA assembly techniques only define protocols for joining DNA parts, while other techniques also define the rules for the format of DNA parts that are compatible with them. These processes can be scaled up to enable the assembly of entire chromosomes or genomes. In recent years, there has been proliferation in the number of different DNA assembly standards with 14 different assembly standards developed as of 2015, each with their pros and cons. Overall, the development of DNA assembly standards has greatly facilitated the workflow of synthetic biology, aided the exchange of material between research groups and also allowed for the creation of modular and reusable DNA parts.
The various DNA assembly methods can be classified into three main categories – endonuclease-mediated assembly, site-specific recombination, and long-overlap-based assembly. Each group of methods has its distinct characteristics and their own advantages and limitations. | 1 | Applied and Interdisciplinary Chemistry |
While semiconductors have been studied using microwave radiation since the 1950s, it was not until the late 1970s and early 1980s that John Warman at the Delft University of Technology exploited microwaves for time-resolved measurements of photoconductivity. The first reports used electrons then photons to generate charges in fluids. The technique was later refined to study semiconductors by Kunst and Beck at the Hahn Meitner Institute in Berlin.
Delft remains a significant center for TRMC, however the technique is now used at a number of institutions around the world, notably the National Renewable Energy Laboratory and Kyoto University. | 0 | Theoretical and Fundamental Chemistry |
The TET proteins also have activities that are independent of DNA demethylation. These include, for instance, TET2 interaction with O-linked N-acetylglucosamine (O-GlcNAc) transferase to promote histone O-GlcN acylation to affect transcription of target genes. | 1 | Applied and Interdisciplinary Chemistry |
The units of the rate constant depend on the overall order of reaction.
If concentration is measured in units of mol·L (sometimes abbreviated as M), then
* For order (m + n), the rate constant has units of mol·L·s (or M·s)
* For order zero, the rate constant has units of mol·L·s (or M·s)
* For order one, the rate constant has units of s
* For order two, the rate constant has units of L·mol·s (or M·s)
* For order three, the rate constant has units of L·mol·s (or M·s)
* For order four, the rate constant has units of L·mol·s (or M·s) | 0 | Theoretical and Fundamental Chemistry |
Dangling type side chain self-healing hydrogels are activated by changes in the relative acidity of solution they are in. Depending on user specified application, side chains may be selectively used in self-healing hydrogels as pH indicators. If a specified functional group chain end with a low pKa, such as a carboxylic acid, is subject to a neutral pH conditions, water will deprotonate the acidic chain end, activating the chain ends. Crosslinking or what is known as self-healing will begin, causing two or more separated hydrogels to fuse into one. | 0 | Theoretical and Fundamental Chemistry |
Pyrohydrolysis of hydrochloric spent pickle liquor from carbon steel pickling lines is a hydrometallurgical reaction which takes place according to the following chemical formulae:
4 FeCl + 4 HO + O = 8 HCl + 2 FeO
2 FeCl + 3 HO = 6 HCl + FeO
The process is an inversion of the chemical descaling (pickling) process. | 0 | Theoretical and Fundamental Chemistry |
In 2019, Rostami and Zeitlin reported a discovery of steady, long-living, slowly eastward-moving large-scale coherent twin cyclones, so-called “equatorial modon,” by means of a moist-convective rotating shallow water model. Crudest barotropic features of MJO such as eastward propagation along the equator, slow phase speed, hydro-dynamical coherent structure, the convergent zone of moist-convection, are captured by Rostami and Zeitlin's modon. Having an exact solution of streamlines for internal and external regions of equatorial asymptotic modon is another feature of this structure. It is shown that such eastward-moving coherent dipolar structures can be produced during geostrophic adjustment of localized large-scale pressure anomalies in the diabatic moist-convective environment on the equator. | 1 | Applied and Interdisciplinary Chemistry |
A methylene group is any part of a molecule that consists of two hydrogen atoms bound to a carbon atom, which is connected to the remainder of the molecule by two single bonds. The group may be represented as or , where the > denotes the two bonds.
This stands in contrast to a situation where the carbon atom is bound to the rest of the molecule by a double bond, which is preferably called a methylidene group, represented . Formerly the methylene name was used for both isomers. The name “methylene bridge“ can be used for the single-bonded isomer, to emphatically exclude methylidene. The distinction is often important, because the double bond is chemically different from two single bonds.
The methylene group should be distinguished from the molecule called carbene. This was also formerly called methylene. | 0 | Theoretical and Fundamental Chemistry |
In 2010, exometabolomics analysis of the cyanobacterium, Synechococcus sp. PCC 7002 by Baran, et al. revealed that this photoautotroph could deplete a diverse pool of exogenous metabolites. A follow-up exometabolomics study on sympatric microbial isolates from biological soil crust, which exist in communities with cyanobacteria in the desert soils of the Colorado Plateau, suggested that metabolite niche partitioning exists in these communities, where each isolate only utilizes 13-26% of metabolites from the soil | 1 | Applied and Interdisciplinary Chemistry |
Eugène-Anatole Demarçay (1 January 1852 – 5 March 1903) was a French chemist who designed an apparatus to produce a spark using an induction coil and used it to generate the spectra of rare earth elements which he examined using spectroscopy, thus detecting the element europium in 1896, and isolated it as the oxide europia in 1901. He helped Marie Curie to confirm the existence of another new element, radium, in 1898. | 1 | Applied and Interdisciplinary Chemistry |
* St. Elmo Brady, the First African-American Ph.D. in Chemistry
* Steroid Medicines and Upjohn Innovation
* Gas Chromatography-Mass Spectrometry, Midland, Michigan | 1 | Applied and Interdisciplinary Chemistry |
The last stage of transcription is termination, which leads to the dissociation of the complete transcript and the release of RNA polymerase from the template DNA.The process differs for each of the three RNA polymerases.
The mechanism of termination is the least understood of the three transcription stages. | 1 | Applied and Interdisciplinary Chemistry |
Malachite green is an organic compound that is used as a dyestuff and controversially as an antimicrobial in aquaculture. Malachite green is traditionally used as a dye for materials such as silk, leather, and paper. Despite its name the dye is not prepared from the mineral malachite; the name just comes from the similarity of color. | 0 | Theoretical and Fundamental Chemistry |
A coactivator is a type of transcriptional coregulator that binds to an activator (a transcription factor) to increase the rate of transcription of a gene or set of genes. The activator contains a DNA binding domain that binds either to a DNA promoter site or a specific DNA regulatory sequence called an enhancer. Binding of the activator-coactivator complex increases the speed of transcription by recruiting general transcription machinery to the promoter, therefore increasing gene expression. The use of activators and coactivators allows for highly specific expression of certain genes depending on cell type and developmental stage.
Some coactivators also have histone acetyltransferase (HAT) activity. HATs form large multiprotein complexes that weaken the association of histones to DNA by acetylating the N-terminal histone tail. This provides more space for the transcription machinery to bind to the promoter, therefore increasing gene expression.
Activators are found in all living organisms, but coactivator proteins are typically only found in eukaryotes because they are more complex and require a more intricate mechanism for gene regulation. In eukaryotes, coactivators are usually proteins that are localized in the nucleus. | 1 | Applied and Interdisciplinary Chemistry |
Consider an axisymmetric jet emerging from an orifice, located at the origin of a cylindrical polar coordinates , with being the jet axis and being the radial distance from the axis of symmetry. Since the jet is in constant pressure, the momentum flux in the direction is constant and equal to the momentum flux at the origin,
where is the constant density, are the velocity components in and direction, respectively and is the known momentum flux at the origin. The quantity is called as the kinematic momentum flux. The boundary layer equations are
where is the kinematic viscosity. The boundary conditions are
The Reynolds number of the jet,
is a large number for the Schlichting jet. | 1 | Applied and Interdisciplinary Chemistry |
Infectious bursal disease virus (IBDV) is the best-characterized member of the family Birnaviridae. These viruses have bipartite dsRNA genomes enclosed in single layered icosahedral capsids with T = 13l geometry. IBDV shares functional strategies and structural features with many other icosahedral dsRNA viruses, except that it lacks the T = 1 (or pseudo T = 2) core common to the Reoviridae, Cystoviridae, and Totiviridae. The IBDV capsid protein exhibits structural domains that show homology to those of the capsid proteins of some positive-sense single-stranded RNA viruses, such as the nodaviruses and tetraviruses, as well as the T = 13 capsid shell protein of the Reoviridae. The T = 13 shell of the IBDV capsid is formed by trimers of VP2, a protein generated by removal of the C-terminal domain from its precursor, pVP2. The trimming of pVP2 is performed on immature particles as part of the maturation process. The other major structural protein, VP3, is a multifunctional component lying under the T = 13 shell that influences the inherent structural polymorphism of pVP2. The virus-encoded RNA-dependent RNA polymerase, VP1, is incorporated into the capsid through its association with VP3. VP3 also interacts extensively with the viral dsRNA genome. | 1 | Applied and Interdisciplinary Chemistry |
When food is cooked, some of its proteins become denatured. This is why boiled eggs become hard and cooked meat becomes firm.
A classic example of denaturing in proteins comes from egg whites, which are typically largely egg albumins in water. Fresh from the eggs, egg whites are transparent and liquid. Cooking the thermally unstable whites turns them opaque, forming an interconnected solid mass. The same transformation can be effected with a denaturing chemical. Pouring egg whites into a beaker of acetone will also turn egg whites translucent and solid. The skin that forms on curdled milk is another common example of denatured protein. The cold appetizer known as ceviche is prepared by chemically "cooking" raw fish and shellfish in an acidic citrus marinade, without heat. | 1 | Applied and Interdisciplinary Chemistry |
Black Drop was a 19th-century dark medicine made of opium, vinegar, spices, often with sugar, sometimes called Black drops, and known in Great Britain and North America.
One recipe for Black Drop began, "Macerate the opium and nutmeg in... the diluted acetic acid, for seven days, stirring frequently".
As well as Kendal Black Drop, there were versions called Lancaster and Armstrongs Black Drop. Other names given in a 19th-century Cyclopædia of Several Thousand Practical Receipts were Quakers or Toustall's Black Drop, after a Dr. Toustall of the Society of Friends in County Durham who is said to have invented the recipe.
In 1823, Byron referred to it in his poem Don Juan:
At first Coleridge welcomed the relief from pain provided by Kendal Black Drop, but was later to say that his "eyes had been opened to the true nature of the habit into which I had been ignorantly deluded by the seeming magic effects of opium". | 1 | Applied and Interdisciplinary Chemistry |
When implanted on a surface, gold clusters catalyze oxidation of at ambient temperatures. Similarly gold clusters implanted on can oxidize at temperatures as low as 40K. Catalytic activity correlated with the structure of gold nanoclusters. A strong relationship between energetic and electronic properties with size and structure of gold nanoclusters. | 0 | Theoretical and Fundamental Chemistry |
Steroid 21-hydroxylase is a protein that in humans is encoded by the CYP21A2 gene. The protein is an enzyme that hydroxylates steroids at the C21 position on the molecule. Naming conventions for enzymes are based on the substrate acted upon and the chemical process performed. Biochemically, this enzyme is involved in the biosynthesis of the adrenal gland hormones aldosterone and cortisol, which are important in blood pressure regulation, sodium homeostasis and blood sugar control. The enzyme converts progesterone and 17α-hydroxyprogesterone into 11-deoxycorticosterone and 11-deoxycortisol, respectively, within metabolic pathways which in humans ultimately lead to aldosterone and cortisol creation—deficiency in the enzyme may cause congenital adrenal hyperplasia.
Steroid 21-hydroxylase is a member of the cytochrome P450 family of monooxygenase enzymes that use an iron-containing heme cofactor to oxidize substrates.
In humans, the enzyme is localized in endoplasmic reticulum membranes of cells in adrenal cortex, and is encoded by the gene which is located near the CYP21A1P pseudogene that has high degree of sequence similarity. This similarity makes it difficult to analyze the gene at the molecular level, and sometimes leads to loss-of-function mutations of the gene due to intergenic exchange of DNA. | 1 | Applied and Interdisciplinary Chemistry |
Use of cyclooctanone is almost nonexistent drug chemistry with only 2 known exceptions:
#Blonanserin
#Iprindole | 0 | Theoretical and Fundamental Chemistry |
As observed through the literature, survivin is found to be over-expressed across many tumour types. Scientists are not sure of the mechanism that causes this abnormal over-expression of survivin; however, p53 is downregulated in almost all cancers, so it is tempting to suggest that survivin over-expression is due to p53 inactivity. Wagner et al. investigated the possible molecular mechanism involved with the over expression of survivin in acute myeloid leukemia (AML). In their experiments, they did both an epigenetic and a genetic analysis of the survivin gene promoter region in AML patients and compared the observations to what was seen in peripheral blood mononuclear cells (PBMCs) that have been shown to express no survivin. Assuming that the molecular mechanism of survivin re-expression in cancerous cells is at the transcriptional level, the authors decided to look at particular parts of the promoter region of survivin in order to see what happens in cancer cells that does not happen in normal cells that causes such a high level of survivin to be expressed. With regards to an epigenetic mechanism of survivin gene regulation, the authors measured the methylation status of the survivin promoter, since it is accepted that methylation of genes plays an important role in carcinogenesis by silencing of certain genes or vice versa. The authors used methylation specific polymerase chain reaction with bisulfite sequencing methods to measure the promoter methylation status in AML and PBMCs and found unmethylated survivin promoters in both groups. This result shows that DNA methylation status is not an important regulator of survivin re-expression during leukemogenesis. However, De Carvalho et al. performed a DNA methylation screening and identified that DNA methylation of IRAK3 plays a key role in survivin up-regulation in different types of Cancer, suggesting that epigenetic mechanisms plays an indirect role on abnormal over-expression of survivin. With regard to genetic analysis of the survivin promoter region, the isolated DNA of AML and PBMCs were treated with bisulfite, and the survivin promoter region sequence was amplified out with PCR and sequenced to look for any particular genetic changes in the DNA sequence between the two groups. Three single-nucleotide polymorphisms (SNPs) were identified and were all present both in AML patients and in healthy donors. This result suggests that the occurrence of these SNPs in the promoter region of the survivin gene also appears to be of no importance to survivin expression. However, it has not been ruled out yet that there may be other possible epigenetic mechanisms that may be responsible for a high level of survivin expression observed in cancer cells and not in normal cells. For example, the acetylation profile of the survivin promoter region can also be looked at. Different cancer and tissue types may have slight or significant differences in the way survivin expression is regulated in the cell, and, thus, the methylation status or genetic differences in the survivin promoter may be observed to be different in different tissues. Thus, further experiments assessing the epigenetic and genetic profile of different tumour types must be investigated. | 1 | Applied and Interdisciplinary Chemistry |
There are at least three distinct mechanisms in which pRb can repress transcription of E2F-regulated promoters. Though these mechanisms are known, it is unclear which are the most important for the control of the cell cycle.
E2Fs are a family of proteins whose binding sites are often found in the promoter regions of genes for cell proliferation or progression of the cell cycle. E2F1 to E2F5 are known to associate with proteins in the pRb-family of proteins while E2F6 and E2F7 are independent of pRb. Broadly, the E2Fs are split into activator E2Fs and repressor E2Fs though their role is more flexible than that on occasion. The activator E2Fs are E2F1, E2F2 and E2F3 while the repressor E2Fs are E2F4, E2F5 and E2F6. Activator E2Fs along with E2F4 bind exclusively to pRb. pRb is able to bind to the activation domain of the activator E2Fs which blocks their activity, repressing transcription of the genes controlled by that E2F-promoter. | 1 | Applied and Interdisciplinary Chemistry |
Magnetofection is a transfection method that uses magnetic fields to concentrate particles containing vectors to target cells in the body. Magnetofection has been adapted to a variety of vectors, including nucleic acids, non-viral transfection systems, and viruses. This method offers advantages such as high transfection efficiency and biocompatibility which are balanced with limitations. | 1 | Applied and Interdisciplinary Chemistry |
The sigma-2 receptor takes part in a number of normal-function roles, including cell proliferation, autophagy, cholesterol homeostasis, and both non-neuronal and neuronal signaling. Much of sigma-2 receptor function relies on signaling cascades. The receptor's interaction with EGFR and PGRMC1 proteins allow for sigma-2 receptors to play diverse roles within cell through Ras, PLC, and PI3K signaling. | 1 | Applied and Interdisciplinary Chemistry |
Neuromodulation also refers to an emerging class of medical therapies that target the nervous system for restoration of function (such as in cochlear implants), relief of pain, or control of symptoms, such as tremor seen in movement disorders like Parkinson's disease. The therapies consist primarily of targeted electrical stimulation, or infusion of medications into the cerebrospinal fluid using intrathecal drug delivery, such as baclofen for spasticity. Electrical stimulation devices include deep brain stimulation systems (DBS), colloquially referred to as "brain pacemakers", spinal cord stimulators (SCS) and vagus nerve stimulators (VNS), which are implanted using minimally invasive procedures, or transcutaneous electrical nerve stimulation and scrambler therapy devices, which are fully external, among others. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, transition state theory (TST) explains the reaction rates of elementary chemical reactions. The theory assumes a special type of chemical equilibrium (quasi-equilibrium) between reactants and activated transition state complexes.
TST is used primarily to understand qualitatively how chemical reactions take place. TST has been less successful in its original goal of calculating absolute reaction rate constants because the calculation of absolute reaction rates requires precise knowledge of potential energy surfaces, but it has been successful in calculating the standard enthalpy of activation (ΔH, also written ΔH), the standard entropy of activation (ΔS or ΔS), and the standard Gibbs energy of activation (ΔG or ΔG) for a particular reaction if its rate constant has been experimentally determined. (The notation refers to the value of interest at the transition state; ΔH is the difference between the enthalpy of the transition state and that of the reactants.)
This theory was developed simultaneously in 1935 by Henry Eyring, then at Princeton University, and by Meredith Gwynne Evans and Michael Polanyi of the University of Manchester. TST is also referred to as "activated-complex theory", "absolute-rate theory", and "theory of absolute reaction rates".
Before the development of TST, the Arrhenius rate law was widely used to determine energies for the reaction barrier. The Arrhenius equation derives from empirical observations and ignores any mechanistic considerations, such as whether one or more reactive intermediates are involved in the conversion of a reactant to a product. Therefore, further development was necessary to understand the two parameters associated with this law, the pre-exponential factor (A) and the activation energy (E). TST, which led to the Eyring equation, successfully addresses these two issues; however, 46 years elapsed between the publication of the Arrhenius rate law, in 1889, and the Eyring equation derived from TST, in 1935. During that period, many scientists and researchers contributed significantly to the development of the theory. | 0 | Theoretical and Fundamental Chemistry |
Photothermal microspectroscopy (PTMS), alternatively known as photothermal temperature fluctuation (PTTF), is derived from two parent instrumental techniques: infrared spectroscopy and atomic force microscopy (AFM). In one particular type of AFM, known as scanning thermal microscopy (SThM), the imaging probe is a sub-miniature temperature sensor, which may be a thermocouple or a resistance thermometer. This same type of detector is employed in a PTMS instrument, enabling it to provide AFM/SThM images: However, the chief additional use of PTMS is to yield infrared spectra from sample regions below a micrometer, as outlined below. | 0 | Theoretical and Fundamental Chemistry |
In 2014 the technique was used to produce the HIV drug didanosine: a simpler molecule was identified that can be converted into didanosine when subjected to a specific chemical transformation in the presence of a specific enzyme. The gene that creates the enzyme was then "copied", adding random mutations to each copy using ribokinase engineering. The mutant genes were inserted into Escherichia coli bacteria and used to produce (now-mutant) enzymes. The enzymes were then mixed with the precursor and the mutant enzymes that produced the greatest amount of didanosine were retained and replicated. One mutant stimulated a 50x increase in didanosine production. The first step was repeated, using the first precursor in place of didanosine, finding a yet simpler precursor and an enzyme to produce it. One mutated enzyme produced a 9,500x increase in nucleoside production. A third retrogression allowed them to start with the simple and inexpensive sugar named dideoxyribose and produce didanosine in a three-step sequence. | 0 | Theoretical and Fundamental Chemistry |
Beta particles can be used to treat health conditions such as eye and bone cancer and are also used as tracers. Strontium-90 is the material most commonly used to produce beta particles.
Beta particles are also used in quality control to test the thickness of an item, such as paper, coming through a system of rollers. Some of the beta radiation is absorbed while passing through the product. If the product is made too thick or thin, a correspondingly different amount of radiation will be absorbed. A computer program monitoring the quality of the manufactured paper will then move the rollers to change the thickness of the final product.
An illumination device called a betalight contains tritium and a phosphor. As tritium decays, it emits beta particles; these strike the phosphor, causing the phosphor to give off photons, much like the cathode-ray tube in a television. The illumination requires no external power, and will continue as long as the tritium exists (and the phosphors do not themselves chemically change); the amount of light produced will drop to half its original value in 12.32 years, the half-life of tritium.
Beta-plus (or positron) decay of a radioactive tracer isotope is the source of the positrons used in positron emission tomography (PET scan). | 0 | Theoretical and Fundamental Chemistry |
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