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Regulatory elements that responds to other signals are known; examples include photomodulated conductances as well as "thermal switches" constructed by isomerization of the carbamate group. To date, no mechanosensitive synthetic ion channels have been reported. | 0 | Theoretical and Fundamental Chemistry |
Many biologically active molecules are chiral, including the naturally occurring amino acids (the building blocks of proteins) and sugars.
The origin of this homochirality in biology is the subject of much debate. Most scientists believe that Earth life's "choice" of chirality was purely random, and that if carbon-based life forms exist elsewhere in the universe, their chemistry could theoretically have opposite chirality. However, there is some suggestion that early amino acids could have formed in comet dust. In this case, circularly polarised radiation (which makes up 17% of stellar radiation) could have caused the selective destruction of one chirality of amino acids, leading to a selection bias which ultimately resulted in all life on Earth being homochiral.
Enzymes, which are chiral, often distinguish between the two enantiomers of a chiral substrate. One could imagine an enzyme as having a glove-like cavity that binds a substrate. If this glove is right-handed, then one enantiomer will fit inside and be bound, whereas the other enantiomer will have a poor fit and is unlikely to bind.
-forms of amino acids tend to be tasteless, whereas -forms tend to taste sweet. Spearmint leaves contain the -enantiomer of the chemical carvone or R-(−)-carvone and caraway seeds contain the -enantiomer or S-(+)-carvone. The two smell different to most people because our olfactory receptors are chiral.
Chirality is important in context of ordered phases as well, for example the addition of a small amount of an optically active molecule to a nematic phase (a phase that has long range orientational order of molecules) transforms that phase to a chiral nematic phase (or cholesteric phase). Chirality in context of such phases in polymeric fluids has also been studied in this context. | 0 | Theoretical and Fundamental Chemistry |
Coprostanol and its derivative epicoprostanol are used in archaeological and paleoenvironmental studies as indicators of past human activity due to their longevity in soils and strong association with production in the human gut. Researchers have used the presence of coprostanol to identify archaeological features such as cesspits or landscape activities like manuring. Variations in the concentration of coprostanol over time can be used to create human population reconstructions within a specific depositional environment. | 1 | Applied and Interdisciplinary Chemistry |
The coenzyme is a substrate for coenzyme F hydrogenase, 5,10-methylenetetrahydromethanopterin reductase and methylenetetrahydromethanopterin dehydrogenase.
A long list of other enzymes use F to oxidize (dehydrogenate) or F-H to reduce substrates. | 1 | Applied and Interdisciplinary Chemistry |
A sudden closure involves the rapid sealing of a tidal inlet or breach in a dike. This is typically prepared in such a manner that the gap can be entirely closed in one swift action during slack tide. The use of caissons or sluice caissons is common, though other unique methods, such as sandbags or ships, have also been employed. Caissons were initially utilized as an emergency response for sealing dike breaches post the Allied Battle of Walcheren in 1944 and subsequently after the 1953 North Sea flood. This technique has since been refined and applied in the Delta Works projects. | 1 | Applied and Interdisciplinary Chemistry |
Plane-wave topography can be made to extract an additional wealth of information from a sample by recording not just one image, but an entire sequence of topographs all along the sample's rocking curve. By following the diffracted intensity in one pixel across the entire sequence of images, local rocking curves from very small areas of sample surface can be reconstructed.
Although the required post-processing and numerical analysis is sometimes moderately demanding, the effort is often compensated by very comprehensive information on the sample's local properties. Quantities that become quantitatively measurable in this way include local scattering power, local lattice tilts (crystallite misorientation), and local lattice quality and perfection. Spatial resolution is, in many cases, essentially given by the detector pixel size.
The technique of sequential topography, in combination with appropriate data analysis methods also called rocking curve imaging, constitutes a method of microdiffraction imaging, i.e. a combination of X-ray imaging with X-ray diffractometry.
Literature: | 0 | Theoretical and Fundamental Chemistry |
In physical and analytical chemistry, colorimetry or colourimetry is a technique used to determine the concentration of colored compounds in solution.
A colorimeter is a device used to test the magnitude of a solution by measuring its absorbance of a specific wavelength of light (not to be confused with the tristimulus colorimeter used to measure colors in general).
To use the colorimeter, different solutions must be made, including a control or reference of known concentration. With a visual colorimeter, for example the Duboscq colorimeter illustrated, the length of the light path through the solutions can be varied while filtered light transmitted through them is compared for a visual match. The concentration times path length is taken to be equal when the colors match, so the concentration of the unknown can be determined by simple proportions. Nessler tubes work on the same principle.
There are also electronic automated colorimeters; before these machines are used, they must be calibrated with a cuvette containing the control solution. The concentration of a sample can be calculated from the intensity of light before and after it passes through the sample by using the Beer–Lambert law. Photoelectric analyzers came to dominate in the 1960s.
The color or wavelength of the filter chosen for the colorimeter is extremely important, as the wavelength of light that is transmitted by the colorimeter has to be the same as that absorbed by the substance being measured. For example, the filter on a colorimeter might be set to red if the liquid is blue. | 0 | Theoretical and Fundamental Chemistry |
A traditional version of the second law of thermodynamics states: Heat does not spontaneously flow from a colder body to a hotter body.
The second law refers to a system of matter and radiation, initially with inhomogeneities in temperature, pressure, chemical potential, and other intensive properties, that are due to internal constraints, or impermeable rigid walls, within it, or to externally imposed forces. The law observes that, when the system is isolated from the outside world and from those forces, there is a definite thermodynamic quantity, its entropy, that increases as the constraints are removed, eventually reaching a maximum value at thermodynamic equilibrium, when the inhomogeneities practically vanish. For systems that are initially far from thermodynamic equilibrium, though several have been proposed, there is known no general physical principle that determines the rates of approach to thermodynamic equilibrium, and thermodynamics does not deal with such rates. The many versions of the second law all express the general irreversibility of the transitions involved in systems approaching thermodynamic equilibrium.
In macroscopic thermodynamics, the second law is a basic observation applicable to any actual thermodynamic process; in statistical thermodynamics, the second law is postulated to be a consequence of molecular chaos. | 0 | Theoretical and Fundamental Chemistry |
[https://web.archive.org/web/20110720035915/http://metpetdb.rpi.edu/ MetPetDB] was built for the purpose of archiving published data and for storing new data for ready access to researchers and students in the petrologic community. This database facilitates the gathering of information for researchers beginning new projects and permits browsing and searching for data relating to anywhere on the globe. [https://web.archive.org/web/20110720035915/http://metpetdb.rpi.edu/ MetPetDB] provides a platform for collaborative studies among researchers anywhere on the planet, serves as a portal for students beginning their studies of metamorphic geology, and acts as a repository of vast quantities of data being collected by researchers globally. | 0 | Theoretical and Fundamental Chemistry |
Inorganic arsenic and its compounds, upon entering the food chain, are progressively metabolised (detoxified) through a process of methylation. The methylation occurs through alternating reductive and oxidative methylation reactions, that is, reduction of pentavalent to trivalent arsenic followed by addition of a methyl group (CH).
In mammals, methylation occurs in the liver by methyltransferases, the products being the (CH)AsOH (dimethylarsinous acid) and (CH)As(O)OH (dimethylarsinic acid), which have the oxidation states As(III) and As(V), respectively. Although the mechanism of methylation of arsenic in humans has not been elucidated, the source of methyl is methionine, which suggests a role of S-adenosyl methionine. Exposure to toxic doses begin when the liver's methylation capacity is exceeded or inhibited.
There are two major forms of arsenic that can enter the body, arsenic (III) and arsenic (V). Arsenic (III) enters the cells though aquaporins 7 and 9, which is a type of aquaglyceroporin. Arsenic (V) compounds use phosphate transporters to enter cells. The arsenic (V) can be converted to arsenic (III) by the enzyme purine nucleoside phosphorylase. This is classified as a bioactivation step, as although arsenic (III) is more toxic, it is more readily methylated.
There are two routes by which inorganic arsenic compounds are methylated. The first route uses Cyt19 arsenic methyltransferase to methylate arsenic (III) to a mono-methylated arsenic (V) compound. This compound is then converted to a mono-methylated arsenic (III) compound using Glutathione S-Transferase Omega-1 (GSTO1). The mono-methylated arsenic (V) compound can then be methylated again by Cyt19 arsenic methyltransferase, which forms a dimethyl arsenic (V) compound, which can be converted to a dimethyl arsenic (III) compound by Glutathione S-Transferase Omega-1 (GTSO1). The other route uses glutathione (GSH) to conjugate with arsenic (III) to form an arsenic (GS) complex. This complex can form a monomethylated arsenic (III) GS complex, using Cyt19 arsenic methyltransferase, and this monomethylated GS complex is in equilibrium with the monomethylated arsenic (III). Cyt19 arsenic methyltransferase can methylate the complex one more time, and this forms a dimethylated arsenic GS complex, which is in equilibrium with a dimethyl arsenic (III) complex. Both of the mono-methylated and di-methylated arsenic compounds can readily be excreted in urine. However, the monomethylated compound was shown to be more reactive and more toxic than the inorganic arsenic compounds to human hepatocytes (liver), keratinocytes in the skin, and bronchial epithelial cells (lungs).
Studies in experimental animals and humans show that both inorganic arsenic and methylated metabolites cross the placenta to the fetus, however, there is evidence that methylation is increased during pregnancy and that it could be highly protective for the developing organism.
Enzymatic methylation of arsenic is a detoxification process; it can be methylated to methylarsenite, dimethylarsenite or trimethylarsenite, all of which are trivalent. The methylation is catalyzed by arsenic methyltransferase (AS3MT) in mammals, which transfers a methyl group on the cofactor S-adenomethionine (SAM) to arsenic (III). An orthologue of AS3MT is found in bacteria and is called CmArsM. This enzyme was tested in three states (ligand free, arsenic (III) bound and SAM bound). Arsenic (III) binding sites usually use thiol groups of cysteine residues. The catalysis involves thiolates of Cys72, Cys174, and Cys224. In an SN2 reaction, the positive charge on the SAM sulfur atom pulls the bonding electron from the carbon of the methyl group, which interacts with the arsenic lone pair to form an As−C bond, leaving SAH. | 1 | Applied and Interdisciplinary Chemistry |
The Cori cycle (also known as the lactic acid cycle), named after its discoverers, Carl Ferdinand Cori and Gerty Cori, is a metabolic pathway in which lactate, produced by anaerobic glycolysis in muscles, is transported to the liver and converted to glucose, which then returns to the muscles and is cyclically metabolized back to lactate. | 1 | Applied and Interdisciplinary Chemistry |
The piezoelectrochemical transducer effect (PECT) is a coupling between the electrochemical potential and the mechanical strain in ion-insertion-based electrode materials. It is similar to the piezoelectric effect – with both exhibiting a voltage-strain coupling - although the PECT effect relies on movement of ions within a material microstructure, rather than charge accumulation from the polarization of electric dipole moments.
Many different materials have been shown to exhibit a PECT effect including: lithiated graphite.; carbon fibers inserted with lithium, sodium, and potassium; sodiated black phosphorus; lithiated aluminium; lithium cobalt oxide; vanadium oxide nanofibers inserted with lithium and sodium; and lithiated silicon.
These materials all exhibit a voltage-strain coupling, whereby the material expands when it is charged with ions, and contracts when it is discharged. The reverse is also true: when applying a mechanical strain the electrical potential changes.
This has led to various proposals of applications for the PECT effect with research focusing on actuators, strain-sensors, and energy harvesters. | 0 | Theoretical and Fundamental Chemistry |
In a study of 5000 oxides, only 13% of them satisfy all of the last 4 rules, indicating limited universality of Pauling's rules. | 0 | Theoretical and Fundamental Chemistry |
Saturated absorption spectroscopy measures the transition frequency of an atom or molecule between its ground state and an excited state. In saturated absorption spectroscopy, two counter-propagating, overlapped laser beams are sent through a sample of atomic gas. One of the beams stimulates photon emission in excited atoms or molecules when the laser's frequency matches the transition frequency. By changing the laser frequency until these extra photons appear, one can find the exact transition frequency. This method enables precise measurements at room temperature because it is insensitive to doppler broadening. Absorption spectroscopy measures the doppler-broadened transition, so the atoms must be cooled to millikelvin temperatures to achieve the same sensitivity as saturated absorption spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
The Société Française de Génie des Procédés (French Society of Process Engineers) or SFGP is a French organization for chemical engineers. It is a member of the European Federation of Chemical Engineering and acts as joint Secretariat, and of la Fédération Française pour les sciences de la Chimie (FFC). It publishes a technical journal "Récents progrès en Génie des Procédés", and news for members "Procédique" (first published April 1988), and organizes a congress every alternate year. As of 2014 its membership is in excess of 600.
Its history dates back to a congress in 1987, 1er Congrès Français de Génie des Procédés, and the formation the following year of a Groupe Français de Génie des Procédés (GFGP), which in 1989 had 340 members. and formally transformed into the present organization in 1997.
Its mission statement is to:
*promote Process Engineering.
*promote exchanges between academics, trainers and researchers, manufacturers developing and operating processes, engineering companies and suppliers at the national, European and global levels.
*build a network of experts to respond to societal challenges and the innovation needs of Process Industries.
*be a force for representations to political and institutional decision-makers. | 1 | Applied and Interdisciplinary Chemistry |
Flow rates through an orifice plate can be calculated without specifically calibrating the individual flowmeter so long as the construction and installation of the device complies with the stipulations of the relevant standard or handbook. The calculation takes account of the fluid and fluid conditions, the pipe size, the orifice size and the measured differential pressure; it also takes account of the coefficient of discharge of the orifice plate, which depends upon the orifice type and the positions of the pressure tappings. With local pressure tappings (corner, flange and D+D/2), sharp-edged orifices have coefficients around 0.6 to 0.63, while the coefficients for conical entrance plates are in the range 0.73 to 0.734 and for quarter-circle plates 0.77 to 0.85. The coefficients of sharp-edged orifices vary more with fluids and flow rates than the coefficients of conical-entrance and quarter-circle plates, especially at low flows and high viscosities.
For compressible flows such as flows of gases or steam, an expansibility factor or expansion factor is also calculated. This factor is primarily a function of the ratio of the measured differential pressure to the fluid pressure and so can vary significantly as the flow rate varies, especially at high differential pressures and low static pressures.
The equations provided in American and European national and industry standards and the various coefficients used to differ from each other even to the extent of using different combinations of correction factors, but many are now closely aligned and give identical results; in particular, they use the same Reader-Harris/Gallagher (1998) equation for the coefficient of discharge for sharp-edged orifice plates. The equations below largely follow the notation of the international standard ISO 5167 and use SI units.
Volume flow rate:<br />
Mass flow rate:<br /> | 1 | Applied and Interdisciplinary Chemistry |
Plasma ignition in the definition of Townsend (Townsend discharge) is a self-sustaining discharge, independent of an external source of free electrons. This means that electrons from the cathode can reach the anode in the distance and ionize at least one atom on their way. So according to the definition of this relation must be fulfilled:
If is used instead of () one gets for the breakdown voltage | 0 | Theoretical and Fundamental Chemistry |
Vixotrigine (, ), formerly known as raxatrigine (, ), is an analgesic which is under development by Convergence Pharmaceuticals for the treatment of lumbosacral radiculopathy (sciatica) and trigeminal neuralgia (TGN). Vixotrigine was originally claimed to be a selective central Na1.3 blocker, but was subsequently redefined as a selective peripheral Na1.7 blocker. Following this, vixotrigine was redefined once again, as a non-selective voltage-gated sodium channel blocker. As of January 2018, it is in phase III clinical trials for trigeminal neuralgia and is in phase II clinical studies for erythromelalgia and neuropathic pain. It was previously under investigation for the treatment of bipolar disorder, but development for this indication was discontinued. | 0 | Theoretical and Fundamental Chemistry |
In thermodynamics, the triple point of a substance is the temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium. It is that temperature and pressure at which the sublimation, fusion, and vaporisation curves meet. For example, the triple point of mercury occurs at a temperature of and a pressure of 0.165 mPa.
In addition to the triple point for solid, liquid, and gas phases, a triple point may involve more than one solid phase, for substances with multiple polymorphs. Helium-4 is unusual in that it has no sublimation/deposition curve and therefore no triple points where its solid phase meets its gas phase. Instead, it has a vapor-liquid-superfluid point, a solid-liquid-superfluid point, a solid-solid-liquid point, and a solid-solid-superfluid point. None of these should be confused with the Lambda Point, which is not any kind of triple point.
The triple point of water was used to define the kelvin, the base unit of thermodynamic temperature in the International System of Units (SI). The value of the triple point of water was fixed by definition, rather than by measurement, but that changed with the 2019 redefinition of SI base units. The triple points of several substances are used to define points in the ITS-90 international temperature scale, ranging from the triple point of hydrogen (13.8033 K) to the triple point of water (273.16 K, 0.01 °C, or 32.018 °F).
The term "triple point" was coined in 1873 by James Thomson, brother of Lord Kelvin. | 0 | Theoretical and Fundamental Chemistry |
Another family of carbonyl-based PPGs exists that is structurally like the phenacyl motif, but which reacts through a separate mechanism. As the name suggests, these PPGs react through abstraction of the carbonyl's γ-hydrogen. The compound is then able to undergo a photoenolization, which is mechanistically like a keto-enol tautomerization. From the enol form, the compound can finally undergo a ground-state transformation that releases the substrate. The quantum yield of this mechanism directly corresponds to the ability of the protected substrate to be a good leaving group. For good leaving groups, the rate-determining step is either hydrogen abstraction or isomerization; however, if the substrate is a poor leaving group, release is the rate-determining step. | 0 | Theoretical and Fundamental Chemistry |
Sitagliptin (Januvia) has a novel structure with β-amino amide derivatives (Figure 7). Since sitagliptin has shown excellent selectivity and in vivo efficacy it urged researchers to inspect the new structure of DPP-4 inhibitors with appended β-amino acid moiety. Further studies are being developed to optimize these compounds for the treatment of diabetes.
In October 2006 sitagliptin became the first DPP-4 inhibitor that got FDA approval for the treatment of type 2 diabetes. Crystallographic structure of sitagliptin along with molecular modeling has been used to continue the search for structurally diverse inhibitors. A new potent, selective and orally bioavailable DPP-4 inhibitor was discovered by replacing the central cyclohexylamine in sitagliptin with 3-aminopiperidine. A 2-pyridyl substitution was the initial SAR breakthrough since that group plays a significant role in potency and selectivity for DPP-4.
It has been shown with an X-ray crystallography how sitagliptin binds to the DPP-4 complex:
1. The trifluorophenyl group occupies the S1-pocket
2. The trifluoromethyl group interacts with the side chains of residues Arg358 and Ser209.
3. The amino group forms a salt bridge with Tyr662 and the carboxylated groups of the two glutamate residues, Glu205 and Glu206.
4. The triazolopiperazine group collides with the phenyl group of residue Phe357 | 1 | Applied and Interdisciplinary Chemistry |
Transition state theory explains the reaction dynamics of reactions. The theory is based on the idea that there is an equilibrium between the activated complex and reactant molecules. The theory incorporates concepts from collision theory, which states that for a reaction to occur, reacting molecules must collide with a minimum energy and correct orientation. The reactants are first transformed into the activated complex before breaking into the products. From the properties of the activated complex and reactants, the reaction rate constant iswhere K is the equilibrium constant, is the Boltzmann constant, T is the thermodynamic temperature, and h is Planck's constant. Transition state theory is based on classical mechanics, as it assumes that as the reaction proceeds, the molecules will never return to the transition state. | 0 | Theoretical and Fundamental Chemistry |
In retirement, the Corbetts lived in Tauranga. Enid Corbett died there in 2012, and Ted Corbett died on 3 February 2018, also in Tauranga. | 0 | Theoretical and Fundamental Chemistry |
For catalytic hydroboration, pinacolborane and catecholborane are widely used. They also exhibit higher reactivity toward alkynes. Pinacolborane is also widely used in a catalyst-free hydroborations. | 0 | Theoretical and Fundamental Chemistry |
The most common adverse effects of levetiracetam treatment include CNS effects such as somnolence, decreased energy, headache, dizziness, mood swings and coordination difficulties. These adverse effects are most pronounced in the first month of therapy. About 4% of patients dropped out of pre-approval clinical trials due to these side effects.
About 13% of people taking levetiracetam experience adverse neuropsychiatric symptoms, which are usually mild. These include agitation, hostility, apathy, anxiety, emotional lability, and depression. Serious psychiatric adverse side effects that are reversed by drug discontinuation occur in about 1%. These include hallucinations, suicidal thoughts, or psychosis. These occurred mostly within the first month of therapy, but they could develop at any time during treatment.
Although rare, Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), which appears as a painful spreading rash with redness and blistering and/or peeling skin, have been reported in patients treated with levetiracetam. The incidence of SJS following exposure to anti-epileptics such as levetiracetam is about 1 in 3,000.
Levetiracetam should not be used in people who have previously shown hypersensitivity to levetiracetam or any of the inactive ingredients in the tablet or oral solution. Such hypersensitivity reactions include, but are not limited to, unexplained rash with redness or blistered skin, difficulty breathing, and tightness in the chest or airways.
In a study, the incidence of decreased bone mineral density of patients on levetiracetam was significantly higher than those for other epileptic medications. | 0 | Theoretical and Fundamental Chemistry |
To begin, proteins of interest are prepared for the SDS-PAGE technique and subsequently loaded onto the gel for separation on the basis of molecular size. Large proteins will have difficulty navigating through the mesh-like structure of the gel as they can not fit through the pores with the ease that smaller proteins can. As a result, large proteins do not travel very far on the gel in comparison to smaller proteins that travel further. After enough time, this results in distinct bands that can be visualized from a number of post-gel electrophoresis staining procedures. The bands are at different positions on the gel relative to the well that they were loaded into.
Next, proteins are to be renatured followed by the gel being subjected to pressed between two nitrocellulose filters which rely on diffusion to transfer the proteins from the gel to the membrane filters. At this point replicas of the gel have been created of which each serves a particular purpose. One membrane filter can be stained to see the protein bands that were created from gel electrophoresis and the other is used in the actual process of hybridizing with prepared P radioactively labeled specific oligonucleotide probes. To detect any protein-DNA interactions, autoradiography is commonly used. | 1 | Applied and Interdisciplinary Chemistry |
Organic photochemistry encompasses organic reactions that are induced by the action of light. The absorption of ultraviolet light by organic molecules often leads to reactions. In the earliest days, sunlight was employed, while in more modern times ultraviolet lamps are employed. Organic photochemistry has proven to be a very useful synthetic tool. Complex organic products can be obtained simply. | 0 | Theoretical and Fundamental Chemistry |
It has been shown that ATM phosphorylates KAP1 upon the discovery of damaged or broken DNA. Phosphorylated KAP1, along with many other DNA damage proteins, rapidly migrate to the site of the DNA damage. Its exact involvement in this pathway is somewhat unclear, but it has been implicated in triggering cell arrest, allowing for the damaged DNA to be repaired. | 1 | Applied and Interdisciplinary Chemistry |
To identify diverse post-transcriptional modifications of RNA molecules and determine the transcriptome-wide landscape of RNA modifications by means of next generation RNA sequencing, recently many studies have developed conventional or specialised sequencing methods. Examples of specialised methods are MeRIP-seq, m6A-seq, PA-mC-seq , methylation-iCLIP, m6A-CLIP, Pseudo-seq, Ψ-seq, CeU-seq, Aza-IP and RiboMeth-seq). Many of these methods are based on specific capture of the RNA species containing the specific modification, for example through antibody binding coupled with sequencing of the captured reads. After the sequencing these reads are mapped against the whole transcriptome to see where they originate from. Generally with this kind of approach it is possible to see the location of the modifications together with possible identification of some consensus sequences that might help identification and mapping further on. One example of the specialize methods is PA-mC-seq. This method was further developed from PA-mA-seq method to identify mC modifications on mRNA instead of the original target N6-methyladenosine. The easy switch between different modifications as target is made possible with a simple change of the capturing antibody form m6A specific to mC specific. Application of these methods have identified various modifications (e.g. pseudouridine, mA, m5C, 2′-O-Me) within coding genes and non-coding genes (e.g. tRNA, lncRNAs, microRNAs) at single nucleotide or very high resolution. | 1 | Applied and Interdisciplinary Chemistry |
* Cytochrome P450 monooxygenase system
* Flavin-containing monooxygenase system
* Alcohol dehydrogenase and aldehyde dehydrogenase
* Monoamine oxidase
* Co-oxidation by peroxidases | 1 | Applied and Interdisciplinary Chemistry |
In 2002, Schadler and Garde produced a seven-minute pilot show for the local planetarium called “Molecularium” for the Digistar II Planetarium system. It introduces children to the concepts of atoms and molecules from small molecules like water to larger molecules like polymers. | 1 | Applied and Interdisciplinary Chemistry |
Myogenin, is a transcriptional activator encoded by the MYOG gene.
Myogenin is a muscle-specific basic-helix-loop-helix (bHLH) transcription factor involved in the coordination of skeletal muscle development or myogenesis and repair. Myogenin is a member of the MyoD family of transcription factors, which also includes MyoD, Myf5, and MRF4.
In mice, myogenin is essential for the development of functional skeletal muscle. Myogenin is required for the proper differentiation of most myogenic precursor cells during the process of myogenesis. When the DNA coding for myogenin was knocked out of the mouse genome, severe skeletal muscle defects were observed. Mice lacking both copies of myogenin (homozygous-null) suffer from perinatal lethality due to the lack of mature secondary skeletal muscle fibers throughout the body.
In cell culture, myogenin can induce myogenesis in a variety of non-muscle cell types. | 1 | Applied and Interdisciplinary Chemistry |
One statement of the so-called zeroth law of thermodynamics is directly focused on the idea of conduction of heat. Bailyn (1994) writes that "the zeroth law may be stated: All diathermal walls are equivalent".
A diathermal wall is a physical connection between two bodies that allows the passage of heat between them. Bailyn is referring to diathermal walls that exclusively connect two bodies, especially conductive walls.
This statement of the "zeroth law" belongs to an idealized theoretical discourse, and actual physical walls may have peculiarities that do not conform to its generality.
For example, the material of the wall must not undergo a phase transition, such as evaporation or fusion, at the temperature at which it must conduct heat. But when only thermal equilibrium is considered and time is not urgent, so that the conductivity of the material does not matter too much, one suitable heat conductor is as good as another. Conversely, another aspect of the zeroth law is that, subject again to suitable restrictions, a given diathermal wall is indifferent to the nature of the heat bath to which it is connected. For example, the glass bulb of a thermometer acts as a diathermal wall whether exposed to a gas or a liquid, provided that they do not corrode or melt it.
These differences are among the defining characteristics of heat transfer. In a sense, they are symmetries of heat transfer. | 1 | Applied and Interdisciplinary Chemistry |
Immediately after his Ph.D, in 1980, René Roy joined the National Research Council (NRC) in Ottawa where he worked as researcher in the Institute for Biological Sciences. Then, in 1985, he began his career as professor in the department of chemistry of the University of Ottawa where he served until December 2002. In parallel, he held the positions of Associate Director of the Ottawa-Carleton Chemistry Institute from 1993 to 1996, Director from 1996 to 1999, and again Associate Director in 2000. From 2002 to 2004, he was chairman of the American Chemical Society (ACS) Division of Carbohydrate Chemistry and, in 2005, head of the ACS awards committee.
In 2008, he returned to Montreal to teach organic chemistry at the Université du Québec à Montréal. There, he also founded the PharmaQAM biopharmaceutical research center which gathers some 50 professors and 17 institutions with common interests in the molecular aspects of medicinal chemistry and drug discovery working on new bioactive molecules, their mechanism of action and the way they are vectorized in vivo. He served as director of PharmaQAM until December 2017.
During his career, René Roy has co-developed meningitis vaccines, for humans and animals, that led to commercial success. One of them, targeting the Haemophilus influenzae b (HIB) bacteria, has been designed jointly with the Cuban researcher Vincente Verez Bencomo to prevent lethal meningitis and pneumonia in developing countries. It is the first human semi-synthetic glycoconjugate vaccine approved and remains the only one. In use since 2004, more than 34 million doses have been distributed to children in several countries including Vietnam, Syria, Brazil, Venezuela and Angola, eradicating the infectious disease in Cuba.
Rene Roy is a cofounder of Glycovax Pharma, a biotech company operating in Montreal, developing glycochemistry-based treatments against cancer and other disease with unmet medical needs. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, the wave method (WM), or wave characteristic method (WCM), is a model describing unsteady flow of fluids in conduits (pipes). | 1 | Applied and Interdisciplinary Chemistry |
Saltatory conduction in myelinated axons requires organization of the nodes of Ranvier, whereas voltage-gated sodium channels are highly populated. Studies show that αII-Spectrin, a component of the cytoskeleton is enriched at the nodes and paranodes at early stages and as the nodes mature, the expression of this molecule disappears. It is also proven that αII-Spectrin in the axonal cytoskeleton is absolutely vital for stabilizing sodium channel clusters and organizing the mature node of Ranvier. | 1 | Applied and Interdisciplinary Chemistry |
Extrapolating site or depth specific measurements to the entire lake can be problematic as there can be significant metabolic variability both vertically and horizontally within a lake (see variability section). For example, many lake metabolism studies only have a single epilimnetic estimate of metabolism, however, this may overestimate metabolic characteristics about the lake such as NEP depending on the mixed layer depth to light extinction depth ratio. Averaging daily metabolism estimates over longer time periods may help overcome some of these single site extrapolation issues, but one must carefully consider the implications of the metabolic estimates and not over extrapolate measurements. | 1 | Applied and Interdisciplinary Chemistry |
The strength of the electronic coupling of the donor and acceptor decides whether the electron transfer reaction is adiabatic or non-adiabatic. In the non-adiabatic case the coupling is weak, i.e. H in Fig. 3 is small compared to the reorganization energy and donor and acceptor retain their identity. The system has a certain probability to jump from the initial to the final potential energy curves. In the adiabatic case the coupling is considerable, the gap of 2 H is larger and the system stays on the lower potential energy curve.
Marcus theory as laid out above, represents the non-adiabatic case. Consequently, the semi-classical Landau-Zener theory can be applied, which gives the probability of interconversion of donor and acceptor for a single passage of the system through the region of the intersection of the potential energy curves
where H is the interaction energy at the intersection, v the velocity of the system through the intersection region, s and s the slopes there.
Fig. 3 Energy diagram for Electron Transfer including inner and outer sphere reorganization and electronic coupling: The vertical axis is the free energy, and the horizontal axis is the "reaction coordinate" – a simplified axis representing the motion of all the atomic nuclei (inclusive solvent reorganization)
Working this out, one arrives at the basic equation of Marcus theory
where is the rate constant for electron transfer, is the electronic coupling between the initial and final states, is the reorganization energy (both inner and outer-sphere), and is the total Gibbs free energy change for the electron transfer reaction ( is the Boltzmann constant and is the absolute temperature).
Thus Marcus's theory builds on the traditional Arrhenius equation for the rates of chemical reactions in two ways:
1. It provides a formula for the activation energy, based on a parameter called the reorganization energy, as well as the Gibbs free energy. The reorganization energy is defined as the energy required to "reorganize" the system structure from initial to final coordinates, without making the charge transfer.
2. It provides a formula for the pre-exponential factor in the Arrhenius equation, based on the electronic coupling between the initial and final state of the electron transfer reaction (i.e., the overlap of the electronic wave functions of the two states). | 0 | Theoretical and Fundamental Chemistry |
Scientists and engineers are able to use liquid crystals in a variety of applications because external perturbation can cause significant changes in the macroscopic properties of the liquid crystal system. Both electric and magnetic fields can be used to induce these changes. The magnitude of the fields, as well as the speed at which the molecules align are important characteristics industry deals with. Special surface treatments can be used in liquid crystal devices to force specific orientations of the director. | 0 | Theoretical and Fundamental Chemistry |
The back-end of the nuclear fuel cycle, mostly spent fuel rods, contains fission products that emit beta and gamma radiation, and actinides that emit alpha particles, such as uranium-234 (half-life 245 thousand years), neptunium-237 (2.144 million years), plutonium-238 (87.7 years) and americium-241 (432 years), and even sometimes some neutron emitters such as californium (half-life of 898 years for californium-251). These isotopes are formed in nuclear reactors.
It is important to distinguish the processing of uranium to make fuel from the reprocessing of used fuel. Used fuel contains the highly radioactive products of fission (see high-level waste below). Many of these are neutron absorbers, called neutron poisons in this context. These eventually build up to a level where they absorb so many neutrons that the chain reaction stops, even with the control rods completely removed. At that point, the fuel has to be replaced in the reactor with fresh fuel, even though there is still a substantial quantity of uranium-235 and plutonium present. In the United States, this used fuel is usually "stored", while in other countries such as Russia, the United Kingdom, France, Japan, and India, the fuel is reprocessed to remove the fission products, and the fuel can then be re-used. The fission products removed from the fuel are a concentrated form of high-level waste as are the chemicals used in the process. While most countries reprocess the fuel carrying out single plutonium cycles, India is planning multiple plutonium recycling schemes and Russia pursues closed cycle. | 0 | Theoretical and Fundamental Chemistry |
Charge recombination reactions of PSII cause the production of triplet P and, as a consequence, singlet oxygen. Charge recombination is more probable under dim light than under higher light intensities. | 0 | Theoretical and Fundamental Chemistry |
“Synthesize a multi-component mixture of compounds in a single process and screen it also a single process”. This is the principle of combinatorial chemistry invented by Prof. Furka Á. (Eötvös Loránd University Budapest Hungary) in 1982, and described it including the method of synthesis of combinatorial libraries and that of a deconvolution strategy in a document notarized in the same year. Motivations that led to the invention had been published in 2002. DNA encoded chemical libraries (DECLs) are synthesized by the combinatorial chemistry principle and it clearly agrees with their application.
The concept of DNA-encoding was first described in a theoretical paper by Brenner and Lerner in 1992 in which was proposed to link each molecule of a chemically synthesized entity to a particular oligonucleotide sequence constructed in parallel and to use this encoding genetic tag to identify and enrich active compounds. In 1993 the first practical implementation of this approach was presented by S. Brenner and K. Janda and similarly by the group of M.A. Gallop. Brenner and Janda suggested to generate individual encoded library members by an alternating parallel combinatorial synthesis of the heteropolymeric chemical compound and the appropriate oligonucleotide sequence on the same bead in a “split-&-pool”-based fashion (see below).
Since unprotected DNA is restricted to a narrow window of conventional reaction conditions, until the end of the 1990s a number of alternative encoding strategies were envisaged (i.e. MS-based compound tagging, peptide encoding, haloaromatic tagging, encoding by secondary amines, semiconductor devices.), mainly to avoid inconvenient solid phase DNA synthesis and to create easily screenable combinatorial libraries in high-throughput fashion. However, the selective amplificability of DNA greatly facilitates library screening and it becomes indispensable for the encoding of organic compounds libraries of this unprecedented size. Consequently, at the beginning of the 2000s DNA-combinatorial chemistry experienced a revival.
The beginning of the millennium saw the introduction of several independent developments in DEL technology. These technologies can be classified under two general categories: non-evolution-based and evolution-based DEL technologies capable of molecular evolution. The first category benefits from the ability to use off the shelf reagents and therefore enables rather straightforward library generation. Hits can be identified by DNA sequencing, however DNA translation and therefore molecular evolution is not feasible by these methods. The split and pool approaches developed by researchers at Praecis Pharmaceuticals (now owned by GlaxoSmithKline), Nuevolution (Copenhagen, Denmark) and ESAC technology developed in the laboratory of Prof D. Neri (Institute of Pharmaceutical Science, Zurich, Switzerland) fall under this category. ESAC technology sets itself apart being a combinatorial self-assembling approach which resembles fragment based hit discovery (Fig 1b). Here DNA annealing enables discrete building block combinations to be sampled, but no chemical reaction takes place between them.
Examples of evolution-based DEL technologies are DNA-routing developed by Prof. D.R. Halpin and Prof. P.B. Harbury (Stanford University, Stanford, CA), DNA-templated synthesis developed by Prof. D. Liu (Harvard University, Cambridge, MA) and commercialized by Ensemble Therapeutics (Cambridge, MA) and YoctoReactor technology. developed and commercialized by Vipergen (Copenhagen, Denmark). These technologies are described in further detail below. DNA-templated synthesis and YoctoReactor technology require the prior conjugation of chemical building blocks (BB) to a DNA oligonucleotide tag before library assembly, therefore more upfront work is required before library assembly. Furthermore, the DNA tagged BBs enable the generation of a genetic code for synthesized compounds and artificial translation of the genetic code is possible: That is the BB's can be recalled by the PCR-amplified genetic code, and the library compounds can be regenerated. This, in turn, enables the principle of Darwinian natural selection and evolution to be applied to small molecule selection in direct analogy to biological display systems; through rounds of selection, amplification and translation. | 1 | Applied and Interdisciplinary Chemistry |
A metallodendrimer is a type of dendrimer with incorporated metal atoms. The development of this type of material is actively pursued in academia. | 0 | Theoretical and Fundamental Chemistry |
Rescue fusion hybridization is a process used to manufacture some therapeutic cancer vaccines in which individual tumor cells obtained through biopsy are fused with an antibody-secreting cell to form a heterohybridoma. This cell then secretes the unique idiotype, or immunoglobulin antigen characteristic of the individual tumor, which is purified for use as the vaccine. It is used to produce the BiovaxID vaccine for follicular lymphoma. | 1 | Applied and Interdisciplinary Chemistry |
Initially, pyruvate and thiamine pyrophosphate (TPP or vitamin B) are bound by pyruvate dehydrogenase subunits. The thiazolium ring of TPP is in a zwitterionic form, and the anionic C2 carbon performs a nucleophilic attack on the C2 (ketone) carbonyl of pyruvate. The resulting hemithioacetal undergoes decarboxylation to produce an acyl anion equivalent (see cyanohydrin or aldehyde-dithiane umpolung chemistry, as well as benzoin condensation). This anion attacks S1 of an oxidized lipoate species that is attached to a lysine residue. In a ring-opening S2-like mechanism, S2 is displaced as a sulfide or sulfhydryl moiety. Subsequent collapse of the tetrahedral hemithioacetal ejects thiazole, releasing the TPP cofactor and generating a thioacetate on S1 of lipoate. The E1-catalyzed process is the rate-limiting step of the whole pyruvate dehydrogenase complex. | 1 | Applied and Interdisciplinary Chemistry |
Although the terms direct and indirect bilirubin are used equivalently with conjugated and unconjugated bilirubin, this is not quantitatively correct, because the direct fraction includes both conjugated bilirubin and δ bilirubin.
Delta bilirubin is albumin-bound conjugated bilirubin. In the other words, delta bilirubin is the kind of bilirubin covalently bound to albumin, which appears in the serum when hepatic excretion of conjugated bilirubin is impaired in patients with hepatobiliary disease. Furthermore, direct bilirubin tends to overestimate conjugated bilirubin levels due to unconjugated bilirubin that has reacted with diazosulfanilic acid, leading to increased azobilirubin levels (and increased direct bilirubin).
δ bilirubin = total bilirubin – (unconjugated bilirubin + conjugated bilirubin) | 1 | Applied and Interdisciplinary Chemistry |
The Cahn–Ingold–Prelog priority rules (often abbreviated as the CIP system) were first published in 1966; allowing enantiomers to be more easily and accurately described.
The same year saw first successful enantiomeric separation by gas chromatography an important development as the technology was in common use at the time.
Metal-catalysed enantioselective synthesis was pioneered by William S. Knowles, Ryōji Noyori and K. Barry Sharpless; for which they would receive the 2001 Nobel Prize in Chemistry. Knowles and Noyori began with the development of asymmetric hydrogenation, which they developed independently in 1968. Knowles replaced the achiral triphenylphosphine ligands in Wilkinson's catalyst with chiral phosphine ligands. This experimental catalyst was employed in an asymmetric hydrogenation with a modest 15% enantiomeric excess. Knowles was also the first to apply enantioselective metal catalysis to industrial-scale synthesis; while working for the Monsanto Company he developed an enantioselective hydrogenation step for the production of L-DOPA, utilising the DIPAMP ligand.
Noyori devised a copper complex using a chiral Schiff base ligand, which he used for the metal–carbenoid cyclopropanation of styrene.
In common with Knowles findings, Noyoris results for the enantiomeric excess for this first-generation ligand were disappointingly low: 6%. However continued research eventually led to the development of the Noyori asymmetric hydrogenation reaction.
Sharpless complemented these reduction reactions by developing a range of asymmetric oxidations (Sharpless epoxidation, Sharpless asymmetric dihydroxylation, Sharpless oxyamination) during the 1970s and 1980s. With the asymmetric oxyamination reaction, using osmium tetroxide, being the earliest.
During the same period, methods were developed to allow the analysis of chiral compounds by NMR; either using chiral derivatizing agents, such as Mosher's acid,
or europium based shift reagents, of which Eu(DPM) was the earliest.
Chiral auxiliaries were introduced by E.J. Corey in 1978 and featured prominently in the work of Dieter Enders. Around the same time enantioselective organocatalysis was developed, with pioneering work including the Hajos–Parrish–Eder–Sauer–Wiechert reaction.
Enzyme-catalyzed enantioselective reactions became more and more common during the 1980s, particularly in industry, with their applications including asymmetric ester hydrolysis with pig-liver esterase. The emerging technology of genetic engineering has allowed the tailoring of enzymes to specific processes, permitting an increased range of selective transformations. For example, in the asymmetric hydrogenation of statin precursors. | 0 | Theoretical and Fundamental Chemistry |
Both methods of PG cooling surpass the Doppler limit and instead are limited by the one-photon recoil limit:
Where M is the atomic mass.
For a given detuning and Rabi frequency , dependent on the light intensity, both configurations display a similar scaling at low intensity () and large detuning ():
Where is a dimensionless constant dependent on the configuration and atomic species. See ref for a full derivation of these results. | 0 | Theoretical and Fundamental Chemistry |
An upper limit on of 4 is usually quoted, corresponding to the precision of the measurements, but it also depends on how intense the effect is. Spectra of contributing species should be clearly distinct from each other | 0 | Theoretical and Fundamental Chemistry |
James Murray worked at the University of Otago in Dunedin as a senior lecturer in chemistry.
Murray began research with lichens in the 1950s, applying his knowledge and skills in plant secondary compounds as well as morphology. This was the first systematic work on the lichens of New Zealand since the 1890s. He revised the New Zealand lichens within the Coniocarpineae, Peltigeraceae, Teloschistaceae among others, as well as lichens from the Antarctic and Subantarctic regions.
He spent 1959 on sabbatical working with the chemist Derek Barton at Imperial College, University of London. During this visit Murray also met with Peter James, a lichen specialist at the Natural History Museum, London. There were extensive nineteenth-century specimens of New Zealand lichens at both this museum and at Royal Botanic Gardens, Kew. Murray was able to work with these specimens and with James. They began to define the genus Sticta more precisely, distinguishing it from Pseudocyphellaria and also other groups such as Menegazzia, Nephroma, the Pannariaceae and the Parmeliaceae that contained more species in the Southern Hemisphere. Murray also visited several other lichenologists in France and Sweden including Henri Des Abbayes, Michael Mitchell, Greta Du Rietz, Adolf Hugo Magnusson, Gunnar Degelius, Rolf Santesson and Einar Timdall. He returned to New Zealand in February 1961.
After his death, his lichen specimens (over 10,000), notes and papers were donated to University of Otago and Peter James was seconded in 1962 to curate the collection. Murrays work on the natural products of lichens contributed to developments in this area and also became important to definition of genera in the Lobariaceae'. He developed keys to New Zealand lichen genera, some published posthumously. | 0 | Theoretical and Fundamental Chemistry |
Eutectic NaK (NaK-77, an alloy of 77% potassium and 23% sodium by mass) can be used as a hydraulic fluid in high-temperature and high-radiation environments, for temperature ranges of . Its bulk modulus at is 2.14 GPa, higher than of a hydraulic oil at room temperature. Its lubricity is poor, so positive-displacement pumps are unsuitable and centrifugal pumps have to be used. Addition of caesium shifts the useful temperature range to . NaK-77 was tested in hydraulic and fluidic systems for the Supersonic Low Altitude Missile. NaK may also be used to transmit forces inside high temperature pressure transducers as an alternative to mercury. | 1 | Applied and Interdisciplinary Chemistry |
*[http://tomcat.cs.rhul.ac.uk/home/mxba001/ Web-based Structural Analysis tool for any uploaded PDB file, producing Ramachandran plots, computing dihedral angles and extracting sequence from PDB]
*[https://web.archive.org/web/20090726062008/http://www.fos.su.se/~pdbdna/input_Raman.html Web-based tool showing Ramachandran plot of any PDB entry]
*[http://molprobity.biochem.duke.edu MolProbity web service that produces Ramachandran plots and other validation of any PDB-format file]
*[http://services.mbi.ucla.edu/SAVES SAVES] (Structure Analysis and Verification) — uses WHATCHECK, PROCHECK, and does its own internal Ramachandran Plot
*STING
*Pymol with the DynoPlot extension
*VMD, distributed with dynamic Ramachandran plot plugin
*WHAT CHECK, the stand-alone validation routines from the WHAT IF software
*UCSF Chimera, found under the Model Panel.
*Sirius
*[https://spdbv.vital-it.ch/ Swiss PDB Viewer]
*[http://spin.niddk.nih.gov/NMRPipe/talos/ TALOS]
*[http://www.al-nasir.com/www/Jamie/Zeus/ Zeus molecular viewer] — found under "Tools" menu, high quality plots with regional contours
*[http://www.ebi.ac.uk/thornton-srv/software/PROCHECK/ Procheck]
*[http://dunbrack.fccc.edu/ndrd Neighbor-Dependent and Neighbor-Independent Ramachandran Probability Distributions]
*See also PDB for a list of similar software. | 1 | Applied and Interdisciplinary Chemistry |
The friction loss in uniform, straight sections of pipe, known as "major loss", is caused by the effects of viscosity, the movement of fluid molecules against each other or against the (possibly rough) wall of the pipe. Here, it is greatly affected by whether the flow is laminar (Re < 2000) or turbulent (Re > 4000):
* In laminar flow, losses are proportional to fluid velocity, V; that velocity varies smoothly between the bulk of the fluid and the pipe surface, where it is zero. The roughness of the pipe surface influences neither the fluid flow nor the friction loss.
* In turbulent flow, losses are proportional to the square of the fluid velocity, V; here, a layer of chaotic eddies and vortices near the pipe surface, called the viscous sub-layer, forms the transition to the bulk flow. In this domain, the effects of the roughness of the pipe surface must be considered. It is useful to characterize that roughness as the ratio of the roughness height ε to the pipe diameter D, the "relative roughness". Three sub-domains pertain to turbulent flow:
** In the smooth pipe domain, friction loss is relatively insensitive to roughness.
** In the rough pipe domain, friction loss is dominated by the relative roughness and is insensitive to Reynolds number.
** In the transition domain, friction loss is sensitive to both.
* For Reynolds numbers 2000 < Re < 4000, the flow is unstable, varying with time as vortices within the flow form and vanish randomly. This domain of flow is not well modeled, nor are the details well understood. | 1 | Applied and Interdisciplinary Chemistry |
The Joback method is a group-contribution method. These kinds of methods use basic structural information of a chemical molecule, like a list of simple functional groups, add parameters to these functional groups, and calculate thermophysical and transport properties as a function of the sum of group parameters.
Joback assumes that there are no interactions between the groups, and therefore only uses additive contributions and no contributions for interactions between groups. Other group-contribution methods, especially methods like UNIFAC, which estimate mixture properties like activity coefficients, use both simple additive group parameters and group-interaction parameters. The big advantage of using only simple group parameters is the small number of needed parameters. The number of needed group-interaction parameters gets very high for an increasing number of groups (1 for two groups, 3 for three groups, 6 for four groups, 45 for ten groups and twice as much if the interactions are not symmetric).
Nine of the properties are single temperature-independent values, mostly estimated by a simple sum of group contribution plus an addend.
Two of the estimated properties are temperature-dependent: the ideal-gas heat capacity and the dynamic viscosity of liquids. The heat-capacity polynomial uses 4 parameters, and the viscosity equation only 2. In both cases the equation parameters are calculated by group contributions. | 0 | Theoretical and Fundamental Chemistry |
Combinatorial split-mix (split and pool) synthesis is based on the solid-phase synthesis developed by Merrifield. If a combinatorial peptide library is synthesized using 20 amino acids (or other kinds of building blocks) the bead form solid support is divided into 20 equal portions. This is followed by coupling a different amino acid to each portion. The third step is the mixing of all portions. These three steps comprise a cycle. Elongation of the peptide chains can be realized by simply repeating the steps of the cycle.
The procedure is illustrated by the synthesis of a dipeptide library using the same three amino acids as building blocks in both cycles. Each component of this library contains two amino acids arranged in different orders. The amino acids used in couplings are represented by yellow, blue and red circles in the figure. Divergent arrows show dividing solid support resin (green circles) into equal portions, vertical arrows mean coupling and convergent arrows represent mixing and homogenizing the portions of the support.
The figure shows that in the two synthetic cycles 9 dipeptides are formed. In the third and fourth cycles, 27 tripeptides and 81 tetrapeptides would form, respectively.
The "split-mix synthesis" has several outstanding features:
* It is highly efficient. As the figure demonstrates the number of peptides formed in the synthetic process (3, 9, 27, 81) increases exponentially with the number of executed cycles. Using 20 amino acids in each synthetic cycle the number of formed peptides are: 400, 8,000, 160,000 and 3,200,000, respectively. This means that the number of peptides increases exponentially with the number of the executed cycles.
* All peptide sequences are formed in the process that can be deduced by a combination of the amino acids used in the cycles.
* Portioning of the support into equal samples assures formation of the components of the library in nearly equal molar quantities.
* Only a single peptide forms on each bead of the support. This is the consequence of using only one amino acid in the coupling steps. It is completely unknown, however, which is the peptide that occupies a selected bead.
* The split-mix method can be used for the synthesis of organic or any other kind of library that can be prepared from its building blocks in a stepwise process.
In 1990 three groups described methods for preparing peptide libraries by biological methods and one year later Fodor et al. published a remarkable method for synthesis of peptide arrays on small glass slides.
A "parallel synthesis" method was developed by Mario Geysen and his colleagues for preparation of peptide arrays. They synthesized 96 peptides on plastic rods (pins) coated at their ends with the solid support. The pins were immersed into the solution of reagents placed in the wells of a microtiter plate. The method is widely applied particularly by using automatic parallel synthesizers. Although the parallel method is much slower than the real combinatorial one, its advantage is that it is exactly known which peptide or other compound forms on each pin.
Further procedures were developed to combine the advantages of both split-mix and parallel synthesis. In the method described by two groups the solid support was enclosed into permeable plastic capsules together with a radiofrequency tag that carried the code of the compound to be formed in the capsule. The procedure was carried out similar to the split-mix method. In the split step, however, the capsules were distributed among the reaction vessels according to the codes read from the radiofrequency tags of the capsules.
A different method for the same purpose was developed by Furka et al. is named "string synthesis". In this method, the capsules carried no code. They are strung like the pearls in a necklace and placed into the reaction vessels in stringed form. The identity of the capsules, as well as their contents, are stored by their position occupied on the strings. After each coupling step, the capsules are redistributed among new strings according to definite rules. | 1 | Applied and Interdisciplinary Chemistry |
User submission to the database is encouraged. To contribute to the database, one must submit: contact info, PubMed identifier and the two molecules that interact. The person who submits a record is the owner of it. All records are validated before being made public and BIND is curated for quality assurance. BIND curation has two tracks: high-throughput (HTP) and low-throughput (LTP). HTP records are from papers which have reported more than 40 interaction results from one experimental methodology. HTP curators typically have a bioinformatics backgrounds. The HTP curators are responsible for the collection of storage of experimental data and they also create scripts to update BIND based on new publications. LTP records are curated by individuals with either an MSc or PhD and laboratory experience in interaction research. LTP curators are given further training through the Canadian Bioinformatics Workshops. Information on small molecule chemistry is curated separately by chemists to ensure the curator is knowledgeable about the subject. The priority for BIND curation is to focus on LTP to collect information as it is published. Although, HTP studies provide more information at once, there are more LTP studies being reported and similar numbers of interactions are being reported by both tracks. In 2004, BIND collected data from 110 journals. | 1 | Applied and Interdisciplinary Chemistry |
The volumetric titration is based on the same principles as the coulometric titration, except that the anode solution above now is used as the titrant solution. The titrant consists of an alcohol (ROH), base (B), and a known concentration of . Pyridine has been used as the base in this case.
One mole of is consumed for each mole of . The titration reaction proceeds as above, and the end point may be detected by a bipotentiometric method as described above. | 0 | Theoretical and Fundamental Chemistry |
In nuclear physics, a nuclear chain reaction occurs when one single nuclear reaction causes an average of one or more subsequent nuclear reactions, thus leading to the possibility of a self-propagating series or "positive feedback loop" of these reactions. The specific nuclear reaction may be the fission of heavy isotopes (e.g., uranium-235, U). A nuclear chain reaction releases several million times more energy per reaction than any chemical reaction. | 0 | Theoretical and Fundamental Chemistry |
Radiofrequency (RF) induced evaporative cooling is the most common method for evaporatively cooling atoms in a magneto-optical trap (MOT). Consider trapped atoms laser cooled on a |F=0 |F=1 transition. The magnetic sublevels of the |F=1 state (|m= -1,0,1) are degenerate for zero external field. The confining magnetic quadrupole field, which is zero at the center of the trap and nonzero everywhere else, causes a Zeeman shift in atoms which stray from the trap center, lifting the degeneracy of the three magnetic sublevels. The interaction energy between the total spin angular momentum of the trapped atom and the external magnetic field depends on the projection of the spin angular momentum onto the z-axis, and is proportional toFrom this relation it can be seen that only the |m=-1 magnetic sublevel will have a positive interaction energy with the field, that is to say, the energy of atoms in this state increases as they migrate from the trap center, making the trap center a point of minimum energy, the definition of a trap. Conversely, the energy of the |m=0 state is unchanged by the field (no trapping), and the |m=1 state actually decreases in energy as it strays from the trap center, making the center a point of maximum energy. For this reason |m=-1 is referred to as the trapping state, and |m=0,1 the non-trapping states.
From the equation for the magnetic field interaction energy, it can also be seen that the energies of the |m=1,-1 states shift in opposite directions, changing the total energy difference between these two states. The |m=-1|m=1 transition frequency therefore experiences a Zeeman shift. With this in mind, the RF evaporative cooling scheme works as follows: the size of the Zeeman shift of the -1+1 transition depends on the strength of the magnetic field, which increases radially outward from the trap center. Those atoms which are coldest move within a small region around the trap center, where they experience only a small Zeeman shift in the -1+1 transition frequency. Warm atoms, however, spend time in regions of the trap much further from the center, where the magnetic field is stronger and the Zeeman shift therefore larger. The shift induced by magnetic fields on the scale used in typical MOTs is on the order of MHz, so that a radiofrequency source can be used to drive the -1+1 transition. The choice of frequency for the RF source corresponds to a point on the trapping potential curve at which atoms experience a Zeeman shift equal to the frequency of the RF source, which then drives the atoms to the anti-trapping |m=1 magnetic sublevel and immediately exits the trap. Lowering the RF frequency is therefore equivalent to lowering the dashed line in the figure, effectively reducing the depth of the potential well. For this reason the RF source used to remove these energetic atoms is often referred to as an "RF knife," as it effectively lowers the height of the trapping potential to remove the most energetic atoms from the trap, "cutting" away the high energy tail of the trap's energy distribution. This method was famously used to cool a cloud of rubidium atoms below the condensation critical temperature to form the first experimentally observed Bose-Einstein condensate (BEC) | 0 | Theoretical and Fundamental Chemistry |
Calcination is thermal decomposition of a material. Examples include decomposition of hydrates such as ferric hydroxide to ferric oxide and water vapor, the decomposition of calcium carbonate to calcium oxide and carbon dioxide as well as iron carbonate to iron oxide:
:CaCO → CaO + CO
Calcination processes are carried out in a variety of furnaces, including shaft furnaces, rotary kilns, and fluidized bed reactors. | 1 | Applied and Interdisciplinary Chemistry |
Iodic acid is a relatively strong acid with a pK of 0.75. It is strongly oxidizing in acidic solution, less so in basic solution. When iodic acid acts as oxidizer, then the product of the reaction is either iodine, or iodide ion. Under some special conditions (very low pH and high concentration of chloride ions, such as in concentrated hydrochloric acid), iodic acid is reduced to iodine trichloride, a golden yellow compound in solution and no further reduction occurs. In the absence of chloride ions, when there is an excess amount of reductant, then all iodate is converted to iodide ion. When there is an excess amount of iodate, then part of the iodate is converted to iodine. It may be used in preparation of ionization to form alkyl halides. | 0 | Theoretical and Fundamental Chemistry |
The above-ground nuclear tests that occurred in several countries between 1955 and 1980 (see nuclear test list) dramatically increased the amount of carbon-14 in the atmosphere and subsequently in the biosphere; after the tests ended, the atmospheric concentration of the isotope began to decrease, as radioactive was fixed into plant and animal tissue, and dissolved in the oceans.
One side-effect of the change in atmospheric carbon-14 is that this has enabled some options (e.g., bomb-pulse dating) for determining the birth year of an individual, in particular, the amount of carbon-14 in tooth enamel, or the carbon-14 concentration in the lens of the eye.
In 2019, Scientific American reported that carbon-14 from nuclear bomb testing has been found in the bodies of aquatic animals found in one of the most inaccessible regions of the earth, the Mariana Trench in the Pacific Ocean.
The concentration of carbon-14 in atmospheric CO, reported as the ratio of carbon-14 to carbon-12 with respect to a standard, has now (approximately since the year 2022) declined to levels similar to those prior to the above-ground nuclear tests of the 1950s and 1960s. Although the extra carbon-14 atoms generated during those nuclear tests have not disappeared from the atmosphere, oceans and biosphere, they are diluted because of the Suess effect. | 0 | Theoretical and Fundamental Chemistry |
The precipitation of calcium carbonate is important as it results in a loss of alkalinity as well as a release of CO (Equation 4), and therefore a change in the rate of preservation of calcium carbonate can alter the partial pressure of CO in Earths atmosphere. CaCO is supersatured in the great majority of ocean surface waters and undersaturated at depth, meaning the shells are more likely to dissolve as they sink to ocean depths. CaCO can also be dissolved through metabolic dissolution (i.e. can be used as food and excreted) and thus deep ocean sediments have very little calcium carbonate. The precipitation and burial of calcium carbonate in the ocean removes particulate inorganic carbon from the ocean and ultimately forms limestone. On time scales greater than 500,000 years Earths climate is moderated by the flux of carbon in and out of the lithosphere. Rocks formed in the ocean seafloor are recycled through plate tectonics back to the surface and weathered or subducted into the mantle, the carbon outgassed by volcanoes. | 0 | Theoretical and Fundamental Chemistry |
Gemperline came to the notice of a larger scientific community in 1984 with the publication of a paper describing DISNET in the Journal of Automated Methods and Management in Chemistry. (The journal title was changed to Journal of Analytical Methods in Chemistry in 2013.) Gemperline and his colleagues provided methodologies which underlay the improvements in calibration accuracy, computer-based data acquisition and mathematical analysis in chemometrics. The qualitative advances helped open new scientific fields such as molecular modeling and QSAR, cheminformatics, the ‘-omics’ fields of genomics, proteomics, metabonomics and metabolomics, process modeling and process analytical technology.
Gemperline is a self-taught chemometrician, and he has been most influential by dispersing knowledge of his chemometric methodologies through his publications. Perhaps the best example of this is his book, Practical Guide to Chemometrics, for which he served as both editor and as a contributor. Better process methods can create inflection points that became the foundation for radical improvements and transitions in the scientific enterprise. It can be decades before the implications of particular advances are intuited, especially those related to the basic training of the next generations of chemists. His research in chemometrics has been "focused on development of new algorithms and software tools for analysis of multivariate spectroscopic measurements using pattern recognition methods, artificial neural networks, multivariate statistical methods, multivariate calibration, and non-linear model estimation." Sandia National Laboratories researcher, David Haaland, called Gemperline a "chemometrician extraordinaire," with a "deep understanding of chemometrics" and "wide-ranging" contributions to the research literature, and said after his first meeting with Gemperline he "always read his publications and attended his talks at conferences knowing that I would learn something new every time."
According to former graduate student, Patrick Cutler, another important aspect of Gemperlines research and teaching career has been his ability to collaborate with industry, which allowed "opportunities for students to gain invaluable experience." Cutler mentions pharmaceutical company Burroughs Wellcome in particular which at one time operated a production plant in Greenville, North Carolina, in close proximity to East Carolina University. Gemperline collaborated with Burroughs Wellcome in the 1980s to develop software for multivariate pattern recognition analysis of near-infrared reflectance spectra for rapid, non-destructive testing of pharmaceutical ingredients and products. His research and publications in this area furthered his international recognition. Cutler notes that Gemperline, "built his career and has produced world-renowned chemometrics research with the limited resources of mostly undergraduates and masters level students."
Gemperline also has had research collaborations with Pfizer, Inc. and GlaxoSmithKline and he has received "significant" funding for his research from the National Science Foundation (NSF) and the Measurement and Control Engineering Center (MCEC) at University of Tennessee, Knoxville, an NSF-sponsored Industry-University Cooperative Research Center (IUCRC). He collaborated with David Haaland at Sandia National Laboratories to develop chemometric tools to study kinetics in cells using hyperspectral fluorescence imaging. Their efforts were judged successful, and led to the 2010 Meggers Award for them and coauthors Patrick Cutler and Erik Andres for their two 2009 publications in Applied Spectroscopy about their research.
Gemperline served as the editor-in-chief of Journal of Chemometrics for ten years, from 2007 to 2017, and before that as the North American editor for five years, from 1996 to 2001. The journal honored him with a special issue in July 2020. He joined the editorial advisory board of Spectroscopy Magazine in 2020. | 0 | Theoretical and Fundamental Chemistry |
The DrugWipe is a test used to wipe surfaces for traces of drug residue. It may also be used for sweat or saliva testing of individuals. DrugWipe was named a finalist in the 2011 Cygnus Law Enforcement Group Innovation Awards competition. The DrugWipe 6s (saliva only) test was entered under the category of Traffic Enforcement. | 0 | Theoretical and Fundamental Chemistry |
Cation exchange sorbents are derivatized with functional groups that interact and retain positively charged cations, such as bases. Strong cation exchange sorbents contain aliphatic sulfonic acid groups that are always negatively charged in aqueous solution, and weak cation exchange sorbents contain aliphatic carboxylic acids, which are charged when the pH is above about 5. Strong cation exchange sorbents are useful because any strongly basic impurities in the sample will bind to the sorbent and usually will not be eluted with the analyte of interest; to recover a strong base a weak cation exchange cartridge should be used. To elute the analyte from either the strong or weak sorbent, the stationary phase is washed with a solvent that neutralizes ionic interaction between the analyte and the stationary phase. | 0 | Theoretical and Fundamental Chemistry |
Incongruent melting occurs when a solid substance being partially melted does not melt uniformly, so that the chemical composition of neither the resulting liquid nor the resulting solid is the same as that of the original solid. For example, melting of orthoclase (KAlSiO) produces leucite (KAlSiO) in addition to a melt. The melt produced is richer in silica (SiO). The proportions of leucite and melt formed can be recombined to yield the bulk composition of the starting feldspar. Another mineral that can melt incongruently is enstatite (MgSiO), which produces forsterite (MgSiO) in addition to a melt richer in SiO when melting at low pressure. Enstatite melts congruently at higher pressures between 2.5 and 5.5 kilobars. | 0 | Theoretical and Fundamental Chemistry |
The presence of color in water does not necessarily indicate that the water is not drinkable. Water with high water clarity is generally more cyan in color due to low concentrations of particles and/or dissolved substances. Color-causing particulate substances can be easily removed by filtration. Color-causing dissolved substances such as tannins are only toxic to animals in large concentration.
Color from dissolved substances is not removed by typical water filters; however the use of coagulants may succeed in trapping the color-causing compounds within the resulting precipitate.
Other factors can affect the color seen:
*Particles and solutes can absorb light, as in tea or coffee. Green algae in rivers and streams often lend a blue-green color. The Red Sea has occasional blooms of red Trichodesmium erythraeum algae.
*Particles in water can scatter light. The Colorado River is often muddy red because of suspended reddish silt in the water—this gives the river its name, from Spanish , . Some mountain lakes and streams with finely ground rock, such as glacial flour, are turquoise. Light scattering by suspended matter is required in order that the blue light produced by water's absorption can return to the surface and be observed. Such scattering can also shift the spectrum of the emerging photons toward the green, a color often seen when water laden with suspended particles is observed. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, dynamic pressure (denoted by or and sometimes called velocity pressure) is the quantity defined by:
where (in SI units):
* is the dynamic pressure in pascals (i.e., kg/(m*s),
* (Greek letter rho) is the fluid mass density (e.g. in kg/m), and
* is the flow speed in m/s.
It can be thought of as the fluid's kinetic energy per unit volume.
For incompressible flow, the dynamic pressure of a fluid is the difference between its total pressure and static pressure. From Bernoulli's law, dynamic pressure is given by
where and are the total and static pressures, respectively. | 1 | Applied and Interdisciplinary Chemistry |
*Yao, B., Kuznetsov, V. L., Xiao, T., Jie, X., Gonzalez-Cortes, S., Dilworth, J. R., Al-Megren, H.A., Alshihri, S.M. & Edwards, P. P. (2020). Fuels, power and chemical periodicity. Phil. Trans. R. Soc. A., 378(2180), 20190308. doi:10.1098/rsta.2019.0308.
*Yao, B., Kuznetsov, V. L., Xiao, T., Slocombe, D. R., Rao, C. N. R., Hensel, F., & Edwards, P. P. (2020). Metals and non-metals in the periodic table. Phil. Trans. R. Soc. A., 378(2180), 20200213. doi:10.1098/rsta.2020.0213.
*Jie, X., Li, W., Slocombe, D., Gao, Y., Banerjee, I., Gonzalez-Cortes, S., Yao, B., AlMegren, H., Alshihri, S., Dilworth, J. Thomas, J. Xiao, T., & Edwards, P. P. (2020). Microwave-initiated catalytic deconstruction of plastic waste into hydrogen and high-value carbons. Nature Catalysis, 3(11), 902-912. doi:10.1038/s41929-020-00518-5.
*Yao, B., Xiao, T., Makgae, O. A., Jie, X., Gonzalez-Cortes, S., Guan, S., Kirkland, A.I., Dilworth, J.R., Al-Megren, H.A., Alshihri, S.M., Dobson, P. J., Owen, G. P., Thomas J. M., & Edwards, P. P. (2020). Transforming carbon dioxide into jet fuel using an organic combustion-synthesized Fe-Mn-K catalyst. Nature Communications, 11(1), 1-12. doi:10.1038/s41467-020-20214-z. | 0 | Theoretical and Fundamental Chemistry |
acid is a monocarboxylic β-hydroxy acid and natural product with the molecular formula . At room temperature, pure acid occurs as a transparent, colorless to light yellow liquid which is soluble in water. acid is a weak acid with a pK of 4.4. Its refractive index () is 1.42. | 1 | Applied and Interdisciplinary Chemistry |
Due to anabaseine’s fairly non-specific binding to nicotinic acetylcholine receptors, the molecule was largely discarded as a useful tool in research or medicine. However, anabaseine derivatives have been identified with a more selective α7 binding profile. One such derivative (GTS-21, 3-(2,4-dimethoxybenzylidene)-anabaseine) has been studied as a drug candidate for cognitive and memory deficits, particularly associated with schizophrenia; it has been studied in phase II clinical trials without progression to phase III. Moreover, the modification of the anabaseine pyridine nucleus led to the obtainment of new derivatives endowed with binding and functional selectivity for the α3β4 nicotinic acetylcholine receptor subtype. | 1 | Applied and Interdisciplinary Chemistry |
Here is a list of radioisotopes formed by the action of cosmic rays on the atmosphere; the list also contains the production mode of the isotope. These data were obtained from the SCOPE50 report, see table 1.9 of chapter 1. | 0 | Theoretical and Fundamental Chemistry |
Growing understanding of small RNA gene-silencing mechanisms involving dsRNA-mediated sequence-specific mRNA degradation has directly impacted the fields of functional genomics, biomedicine, and experimental biology. The following section describes various applications involving the effects of RNA silencing. These include uses in biotechnology, therapeutics, and laboratory research. Bioinformatics techniques are also being applied to identify and characterize large numbers of small RNAs and their targets. | 1 | Applied and Interdisciplinary Chemistry |
Tissue clearing has been applied to the nervous system, bones (including teeth), skeletal muscles, hearts and vasculature, gastrointestinal organs, urogenital organs, skin, lymph nodes, mammary glands, lungs, eyes, tumors, and adipose tissues. Whole-body clearing is less common, but has been done in smaller animals, including rodents. Tissue clearing has also been applied to human cancer tissues | 1 | Applied and Interdisciplinary Chemistry |
It is important to be able to predict the onset of gelation, since it is an irreversible process that dramatically changes the properties of the system. | 0 | Theoretical and Fundamental Chemistry |
15-Crown-5 can be synthesized using a modified Williamson ether synthesis:
:(CHOCHCHCl) + O(CHCHOH) + 2 NaOH → (CHCHO) + 2 NaCl + 2 HO
It also forms from the cyclic oligomerization of ethylene oxide in the presence of gaseous boron trifluoride. | 0 | Theoretical and Fundamental Chemistry |
There are at least three other possible resolutions to the Kauzmann paradox. It could be that the heat capacity of the supercooled liquid near the Kauzmann temperature smoothly decreases to a smaller value. It could also be that a first order phase transition to another liquid state occurs before the Kauzmann temperature with the heat capacity of this new state being less than that obtained by extrapolation from higher temperature. Finally, Kauzmann himself resolved the entropy paradox by postulating that all supercooled liquids must crystallize before the Kauzmann temperature is reached. | 0 | Theoretical and Fundamental Chemistry |
A lift-producing airfoil either has camber or operates at a positive angle of attack, the angle between the chord line and the fluid flow far upstream of the airfoil. Moreover, the airfoil must have a sharp trailing edge.
Any real fluid is viscous, which implies that the fluid velocity vanishes on the airfoil. Prandtl showed that for large Reynolds number, defined as , and small angle of attack, the flow around a thin airfoil is composed of a narrow viscous region called the boundary layer near the body and an inviscid flow region outside. In applying the Kutta-Joukowski theorem, the loop must be chosen outside this boundary layer. (For example, the circulation calculated using the loop corresponding to the surface of the airfoil would be zero for a viscous fluid.)
The sharp trailing edge requirement corresponds physically to a flow in which the fluid moving along the lower and upper surfaces of the airfoil meet smoothly, with no fluid moving around the trailing edge of the airfoil. This is known as the Kutta condition.
Kutta and Joukowski showed that for computing the pressure and lift of a thin airfoil for flow at large Reynolds number and small angle of attack, the flow can be assumed inviscid in the entire region outside the airfoil provided the Kutta condition is imposed. This is known as the potential flow theory and works remarkably well in practice. | 1 | Applied and Interdisciplinary Chemistry |
Enteric fermentation occurs in the gut of some animals, especially ruminants. In the rumen, anaerobic organisms, including methanogens, digest cellulose into forms nutritious to the animal. Without these microorganisms, animals such as cattle would not be able to consume grasses. The useful products of methanogenesis are absorbed by the gut, but methane is released from the animal mainly by belching (eructation). The average cow emits around 250 liters of methane per day. In this way, ruminants contribute about 25% of anthropogenic methane emissions. One method of methane production control in ruminants is by feeding them 3-nitrooxypropanol. | 1 | Applied and Interdisciplinary Chemistry |
After synthesising the potassium salt of the phosphaethynolate anion in 2013, Goicoechea et al. began to look into the potential of PCO towards cycloadditions. They found that the anion could react in a [2+2] fashion with a diphenyl ketene to produce the first isolatable example of a four-membered monoanionic phosphorus containing heterocycle. They employed the same method to test other unsaturated substrates such as carbodiimides and found that the likelihood of cyclisation heavily relies on the nature of the substituents on the unsaturated substrate.
Cycloaddition reactions involving the phosphaethynolate anion have also been shown by Grutzmacher and co-workers to be a viable synthetic route to other heterocycles. One simple example is the reaction between the NaPCO and an α-pyrone. This reaction yields the sodium phosphinin-2-olate salt which is stable to both air and moisture. | 0 | Theoretical and Fundamental Chemistry |
The development of stable red color in the surface of the medium indicates sufficient acid production to lower the pH to 4.4 and constitute a positive test. Since other organism may produce lesser quantities of acid from the test substrate, an intermediate orange color between yellow and red may develop. This does not indicate positive test. | 0 | Theoretical and Fundamental Chemistry |
The IL 1-butyl-3-methylimidazolium chloride has been investigated for the recovery of uranium and other metals from spent nuclear fuel and other sources. | 0 | Theoretical and Fundamental Chemistry |
A 12" x 12" x 0.6" thick 316L steel CMF panel with a weight of 3.545 kg was tested in a torch-fire test. In this test, the panel was exposed to over 1204 °C temperatures for 30 minutes. Upon reaching the 30 minutes' time of exposure, the maximum temperature on the unexposed surface of the steel was 400 °C (752 °F) at the center of the plate directly above the jet burner. This temperature was well below the required temperature rise limit of 427 °C; therefore, this sample met the torch fire test requirements. For reference, a solid piece of equal volume steel used for calibration failed this test in about 4 minutes.
It is worth mentioning that the same CMF panel prior to the above-mentioned jet fire testing was subjected to a pool-fire test. In this test, the panel was exposed to 827 °C temperatures for 100 minutes. The panel withstood the extreme temperature for 100 minutes with ease, reaching a maximum backface temperature of 379 °C, far below the 427 °C failure temperature. For reference, the test was calibrated using an equal-sized piece of solid steel that failed the test in approximately 13 minutes. These studies indicate the extraordinary performance of CMF against fire and extreme heat.
Composite metal foam has a very low rate of heat transfer and has proven to isolate an extreme temperature of 1,100 °C (2,000 °F) within only a few inches, leaving the material at room temperature just about two inches away from a region of white-hot material. In addition, the steel CMF managed to retain most of its steel-like strength at this temperature while remaining as lightweight as aluminium, a material that would melt instantly at this extreme temperature. | 0 | Theoretical and Fundamental Chemistry |
Ambergris is formed from a secretion of the bile duct in the intestines of the sperm whale, and can be found floating on the sea or washed up on coastlines. It is sometimes found in the abdomens of dead sperm whales. Because the beaks of giant squids have been discovered within lumps of ambergris, scientists have theorized that the substance is produced by the whale's gastrointestinal tract to ease the passage of hard, sharp objects that it may have eaten.
Ambergris is passed like fecal matter. It is speculated that an ambergris mass too large to be passed through the intestines is expelled via the mouth, but this remains under debate. Another theory states that an ambergris mass is formed when the colon of a whale is enlarged by a blockage from intestinal worms and cephalopod parts resulting in the death of the whale and the mass being excreted into the sea. Ambergris takes years to form. Christopher Kemp, the author of Floating Gold: A Natural (and Unnatural) History of Ambergris, says that it is only produced by sperm whales, and only by an estimated one percent of them. Ambergris is rare; once expelled by a whale, it often floats for years before making landfall. The slim chances of finding ambergris and the legal ambiguity involved led perfume makers away from ambergris, and led chemists on a quest to find viable alternatives.
Ambergris is found primarily in the Atlantic Ocean and on the coasts of South Africa; Brazil; Madagascar; the East Indies; The Maldives; China; Japan; India; Australia; New Zealand; and the Molucca Islands. Most commercially collected ambergris comes from the Bahamas in the Atlantic, particularly New Providence. In 2021, fishermen found a 127 kg (280-pound) piece of ambergris off the coast of Yemen, valued at US$1.5 million. Fossilised ambergris from 1.75 million years ago has also been found. | 1 | Applied and Interdisciplinary Chemistry |
As a fertile material thorium is similar to , the major part of natural and depleted uranium. The thermal neutron absorption cross section (σ) and resonance integral (average of neutron cross sections over intermediate neutron energies) for are about three and one third times those of the respective values for . | 0 | Theoretical and Fundamental Chemistry |
MFGM lipid components such as sphingolipids are involved in the intestinal uptake of cholesterol. Studies in adult rodents have shown that milk sphingomyelin could lower the intestinal absorption of cholesterol in a dose-dependent manner. Intestinal cholesterol absorption in adult rodents consuming a high fat diet was limited by sphingomyelin supplementation. Milk sphingomyelin and other phospholipids with high affinity for cholesterol could limit the micellar solubility of intestinal cholesterol, thereby limiting the cholesterol uptake by the enterocyte. Dietary sphingolipids have been shown to dose-dependently lower plasma cholesterol and triacylglycerol in adult rodents fed with Western-type diet and protect the liver from fat- and cholesterol-induced steatosis. Dietary sphingolipids also lowers hepatic cholesterol and triglyceride levels in adult rodents partly by modulating hepatic gene expression. | 1 | Applied and Interdisciplinary Chemistry |
Jacob Nissim Israelachvili, (19 August 1944 – 20 September 2018) was an Israeli physicist who was a professor at the University of California, Santa Barbara (UCSB). | 0 | Theoretical and Fundamental Chemistry |
*Anthroposophy
*Astrology
*Ayurveda
*Homeopathy
*Kayaku-Jutsu
*Magic, magick
*Moxibustion
*Tay al-Ard
*Yoga Nidra | 1 | Applied and Interdisciplinary Chemistry |
A single-molecule experiment is an experiment that investigates the properties of individual molecules. Single-molecule studies may be contrasted with measurements on an ensemble or bulk collection of molecules, where the individual behavior of molecules cannot be distinguished, and only average characteristics can be measured. Since many measurement techniques in biology, chemistry, and physics are not sensitive enough to observe single molecules, single-molecule fluorescence techniques (that have emerged since the 1990s for probing various processes on the level of individual molecules) caused a lot of excitement, since these supplied many new details on the measured processes that were not accessible in the past. Indeed, since the 1990s, many techniques for probing individual molecules have been developed.
The first single-molecule experiments were patch clamp experiments performed in the 1970s, but these were limited to studying ion channels. Today, systems investigated using single-molecule techniques include the movement of myosin on actin filaments in muscle tissue and the spectroscopic details of individual local environments in solids. Biological polymers' conformations have been measured using atomic force microscopy (AFM). Using force spectroscopy, single molecules (or pairs of interacting molecules), usually polymers, can be mechanically stretched, and their elastic response recorded in real time. | 0 | Theoretical and Fundamental Chemistry |
In the 1660s English physician Thomas Sydenham (1624–1689) popularized a proprietary opium tincture that he also named laudanum, although it differed substantially from the laudanum of Paracelsus. In 1676 Sydenham published a seminal work, Medical Observations Concerning the History and Cure of Acute Diseases, in which he promoted his brand of opium tincture, and advocated its use for a range of medical conditions. | 1 | Applied and Interdisciplinary Chemistry |
The company Pyrosequencing AB in Uppsala, Sweden was founded with venture capital provided by HealthCap in order to commercialize machinery and reagents for sequencing short stretches of DNA using the pyrosequencing technique. Pyrosequencing AB was listed on the Stockholm Stock Exchange in 1999. It was renamed to Biotage in 2003. The pyrosequencing business line was acquired by Qiagen in 2008. Pyrosequencing technology was further licensed to 454 Life Sciences. 454 developed an array-based pyrosequencing technology which emerged as a platform for large-scale DNA sequencing, including genome sequencing and metagenomics.
Roche announced the discontinuation of the 454 sequencing platform in 2013. | 1 | Applied and Interdisciplinary Chemistry |
Allyl boronic esters engage in electrophilic allyl shifts very much like silicon pendant in the Sakurai reaction. In one study a diallylation reagent combines both: | 0 | Theoretical and Fundamental Chemistry |
The absorbance of a material, denoted , is given by
where
* is the radiant flux by that material,
* is the radiant flux by that material, and
* is the transmittance of that material.
Absorbance is a dimensionless quantity. Nevertheless, the absorbance unit or AU is commonly used in ultraviolet–visible spectroscopy and its high-performance liquid chromatography applications, often in derived units such as the milli-absorbance unit (mAU) or milli-absorbance unit-minutes (mAU×min), a unit of absorbance integrated over time.
Absorbance is related to optical depth by
where is the optical depth. | 0 | Theoretical and Fundamental Chemistry |
Secondary (indirect) immunofluorescence (SIF) is similar to direct immunofluorescence, however the technique utilizes two types of antibodies whereas only one of them have a conjugated fluorophore. The antibody with the conjugated fluorophore is referred to as the secondary antibody, while the unconjugated is referred to as the primary antibody.
The principle of this technique is that the primary antibody specifically binds to the epitope on the target molecule, whereas the secondary antibody, with the conjugated fluorophore, recognizes and binds to the primary antibody.
This technique is considered to be more sensitive than primary immunofluorescence, because multiple secondary antibodies can bind to the same primary antibody. The increased number of fluorophore molecules per antigen increases the amount of emitted light, and thus amplifies the signal. There are different methods for attaining a higher fluorophore-antigen ratio such as the Avidin-Biotin Complex (ABC method) and Labeled Streptavidin-Biotin (LSAB method). | 1 | Applied and Interdisciplinary Chemistry |
BAC contigs are constructed by aligning BAC regions of known overlap via a variety of methods. One common strategy is to use sequence-tagged site (STS) content mapping to detect unique DNA sites in common between BACs. The degree of overlap is roughly estimated by the number of STS markers in common between two clones, with more markers in common signifying a greater overlap. Because this strategy provides only a very rough estimate of overlap, restriction digest fragment analysis, which provides a more precise measurement of clone overlap, is often used. In this strategy, clones are treated with one or two restriction enzymes and the resulting fragments separated by gel electrophoresis. If two clones, they will likely have restriction sites in common, and will thus share several fragments. Because the number of fragments in common and the length of these fragments is known (the length is judged by comparison to a size standard), the degree of overlap can be deduced to a high degree of precision. | 1 | Applied and Interdisciplinary Chemistry |
Since EPIC-seq contains certain computational parts after the wet-lab portion for further processing, the following steps are summarized based on the developers' steps provided in the original paper. | 1 | Applied and Interdisciplinary Chemistry |
The first human immunodeficiency virus (HIV) case was reported in the United States in the early 1980s. Many drugs have been discovered to treat the disease but mutations in the virus and resistance to the drugs make development difficult. Integrase is a viral enzyme that integrates retroviral DNA into the host cell genome. Integrase inhibitors are a new class of drugs used in the treatment of HIV. The first integrase inhibitor, raltegravir, was approved in 2007 and other drugs were in clinical trials in 2011. | 1 | Applied and Interdisciplinary Chemistry |
The coliform index is a rating of the purity of water based on a count of fecal bacteria. It is one of many tests done to assure sufficient water quality. Coliform bacteria are microorganisms that primarily originate in the intestines of warm-blooded animals. By testing for coliforms, especially the well known Escherichia coli (E. coli), which is a thermotolerant coliform, one can determine if the water has possibly been exposed to fecal contamination; that is, whether it has come in contact with human or animal feces. It is important to know this because many disease-causing organisms are transferred from human and animal feces to water, from where they can be ingested by people and infect them. Water that has been contaminated by feces usually contains pathogenic bacteria, which can cause disease. Some types of coliforms cause disease, but the coliform index is primarily used to judge if other types of pathogenic bacteria are likely to be present in the water.
The coliform index is used because it is difficult to test for pathogenic bacteria directly. There are many different types of disease-causing bacteria, and they are usually present in low numbers which do not always show up in tests. Thermotolerant coliforms are present in higher numbers than individual types of pathogenic bacteria and they can be tested relatively easily.
However, the coliform index is far from perfect. Thermotolerant coliforms can survive in water on their own, especially in tropical regions, so they do not always indicate fecal contamination. Furthermore, they do not give a good indication of how many pathogenic bacteria are present in the water, and they give no idea at all of whether there are pathogenic viruses or protozoa which also cause diseases and are rarely tested for. Therefore, it does not always give accurate or useful results regarding the purity of water. | 0 | Theoretical and Fundamental Chemistry |
Supercritical water oxidation (SCWO) is a process that occurs in water at temperatures and pressures above a mixture's thermodynamic critical point. Under these conditions water becomes a fluid with unique properties that can be used to advantage in the destruction of recalcitrant and hazardous wastes such as polychlorinated biphenyls (PCB) or per- and polyfluoroalkyl substances (PFAS). Supercritical water has a density between that of water vapor and liquid at standard conditions, and exhibits high gas-like diffusion rates along with high liquid-like collision rates. In addition, the behavior of water as a solvent is altered (in comparison to that of subcritical liquid water) - it behaves much less like a polar solvent. As a result, the solubility behavior is "reversed" so that oxygen, and organics such as chlorinated hydrocarbons become soluble in the water, allowing single-phase reaction of aqueous waste with a dissolved oxidizer. The reversed solubility also causes salts to precipitate out of solution, meaning they can be treated using conventional methods for solid-waste residuals. Efficient oxidation reactions occur at low temperature (400-650 °C) with reduced NOx production.
SCWO can be classified as green chemistry or as a clean technology. The elevated pressures and temperatures required for SCWO are routinely encountered in industrial applications such as petroleum refining and chemical synthesis.
A unique addition (mostly of academic interest) to the world of supercritical water (SCW) oxidation is generating high-pressure flames inside the SCW medium. The pioneer works on high-pressure supercritical water flames were carried out by professor EU Franck at the German University of Karlsruhe in the late 80s. The works were mainly aimed at anticipating conditions which would cause spontaneous generation of non-desirable flames in the flameless SCW oxidation process. These flames would cause instabilities to the system and its components. ETH Zurich pursued the investigation of hydrothermal flames in continuously operated reactors. The rising needs for waste treatment and destruction methods motivated a Japanese Group in the Ebara Corporation to explore SCW flames as an environmental tool. Research on hydrothermal flames has also begun at NASA Glenn Research Center in Cleveland, Ohio. | 0 | Theoretical and Fundamental Chemistry |
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