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Hexahydroxybenzene triscarbonate is a chemical compound, an oxide of carbon with formula . Its molecular structure consists of a benzene core with the six hydrogen atoms replaced by three carbonate groups. It can be seen as a sixfold ester of hexahydroxybenzene (benzenehexol) and carbonic acid.
The compound was obtained by C. Nallaiah in 1984, as a tetrahydrofuran solvate. | 0 | Theoretical and Fundamental Chemistry |
The Bunsen–Kirchhoff Award is a prize for "outstanding achievements" in the field of analytical spectroscopy. It has been awarded since 1990 by the German Working Group for Applied Spectroscopy, and is endowed with by PerkinElmer, Germany. The prize is named in honor of chemist Robert Bunsen and physicist Gustav Kirchhoff. | 0 | Theoretical and Fundamental Chemistry |
Consider a binary electrolyte AB which dissociates reversibly into A and B ions. Ostwald noted that the law of mass action can be applied to such systems as dissociating electrolytes. The equilibrium state is represented by the equation:
If is the fraction of dissociated electrolyte, then is the concentration of each ionic species. must, therefore be the fraction of undissociated electrolyte, and the concentration of same. The dissociation constant may therefore be given as
For very weak electrolytes (however, neglecting α for most weak electrolytes yields counterproductive result) , implying that .
This gives the following results;
Thus, the degree of dissociation of a weak electrolyte is proportional to the inverse square root of the concentration, or the square root of the dilution. The concentration of any one ionic species is given by the root of the product of the dissociation constant and the concentration of the electrolyte. | 0 | Theoretical and Fundamental Chemistry |
The cytochrome complex, or cyt c, is a small hemeprotein found loosely associated with the inner membrane of the mitochondrion where it plays a critical role in cellular respiration.
It transfers electrons between Complexes III (Coenzyme Q – Cyt c reductase) and IV (Cyt c oxidase). Cytochrome c is highly water-soluble, unlike other cytochromes. It is capable of undergoing oxidation and reduction as its iron atom converts between the ferrous and ferric forms, but does not bind oxygen. It also plays a major role in cell apoptosis. In humans, cytochrome c is encoded by the CYCS gene. | 1 | Applied and Interdisciplinary Chemistry |
Coal analysis techniques are specific analytical methods designed to measure the particular physical and chemical properties of coals. These methods are used primarily to determine the suitability of coal for coking, power generation or for iron ore smelting in the manufacture of steel. | 0 | Theoretical and Fundamental Chemistry |
The overall metallic behavior of UPdAl, e.g. as deduced from the dc resistivity, is typical for a heavy-fermion material and can be explained as follows: incoherent Kondo scattering above approximately 80 K and coherent heavy-fermion state (in a Kondo lattice) at lower temperatures. Upon cooling below 14 K, UPdAl orders antiferromagnetically in a commensurate fashion (ordering wave vector (0,0,1/2)) and with a sizable ordered magnetic moment of approximately 0.85 µ per uranium atom, as determined from neutron scattering.
The metallic heavy-fermion state is characterized by a strongly enhanced effective mass, which is connected to a reduced Fermi velocity, which in turn brings about a strongly suppressed transport scattering rate. Indeed, for UPdAl optical Drude behavior with an extremely low scattering rate was observed at microwave frequencies. This is the slowest Drude relaxation observed for any three-dimensional metallic system so far. | 1 | Applied and Interdisciplinary Chemistry |
He is credited with writing the following episodes:
*"Treehouse of Horror XV" (all three segments) (2004)
*"The Seven-Beer Snitch" (2005)
*"The Mook, the Chef, the Wife and Her Homer" (2006)
*"Crook and Ladder" (2007)
*"Double, Double, Boy in Trouble" (2008)
*"Million Dollar Maybe" (2010)
*"Love Is a Many Strangled Thing" (2011)
*"Adventures in Baby-Getting" (2012)
*"Pulpit Friction" (2013)
*"Super Franchise Me" (2014)
*"To Courier with Love" (2016)
*"The Last Traction Hero" (2016)
*"Grampy Can Ya Hear Me" (2017)
*"Forgive and Regret" (2018)
*"The Fat Blue Line” (2019) | 0 | Theoretical and Fundamental Chemistry |
In 1991, Yamamoto disclosed the first catalytic enantioselective method for carbonyl allylation, which employed a chiral boron Lewis acid-catalyst in combination with allyltrimethylsilane. Numerous other catalytic enantioselective methods for carbonyl allylation followed. Catalytic variants of the Nozaki-Hiyama-Kishi reaction represent an alternative method for asymmetric carbonyl allylation, but stoichiometric metallic reductants are required.
Whereas the aforementioned asymmetric carbonyl allylations rely on preformed allylmetal reagents, the Krische allylation exploits allyl acetate for enantioselective carbonyl allylation. Selected methods for asymmetric carbonyl allylation are summarized below. | 0 | Theoretical and Fundamental Chemistry |
Thermal desorption is described by the Polanyi–Wigner equation derived from the Arrhenius equation.
where
: the desorption rate [mol/(cm s)] as a function of ,
: order of desorption,
: surface coverage,
: pre-exponential factor [Hz] as a function of ,
: activation energy of desorption [kJ/mol] as a function of ,
: gas constant [J/(K mol)],
: temperature [K].
This equation is difficult in practice while several variables are a function of the coverage and influence each other. The “complete analysis method” calculates the pre-exponential factor and the activation energy at several coverages. This calculation can be simplified. First we assume the pre-exponential factor and the activation energy to be independent of the coverage.
We also assume a linear heating rate:
<br />
(equation 1)
where:
: the heating rate in [K/s],
: the start temperature in [K],
: the time in [s].
We assume that the pump rate of the system is indefinitely large, thus no gasses will absorb during the desorption. The change in pressure during desorption is described as:
<br />
(equation 2)
where:
: the pressure in the system,
: the time in [s].
: the sample surface [m],
: a constant,
: volume of the system [m],
: the desorption rate [mol/(cm s)],
: the pump rate,
: volume of the system [m],
We assume that is indefinitely large so molecules do not re-adsorp during desorption process and we assume that
where:
: the desorption rate[mol/(cm s)],
: order of desorption,
: surface coverage,
: pre-exponential factor [Hz],
: activation energy of desorption [kJ/mol],
: gas constant,
: temperature [K].
Using the before mentioned Redhead method (a method less precise as the "complete analysis" or the "leading edge" method) and the temperature maximum one can determine the activation energy:
<br />
(equation 5)
<br />
for n=1
<br />
(equation 6)
<br />
for n=2
M. Ehasi and K. Christmann described a simple method to determine the activation energy of the second order.
Equation 6 can be changed into:
<br />
(equation 6a)
where:
is the surface area of a TDS or TPD peak.
A graph of versus results in a straight line with a slope equal to .
Thus in a first-order reaction the is independent of the surface coverage. Changing the surface coverage one can determine . Usually a fixed value of the pre-exponential factor is used and is known, with these values one can derive the iteratively from . | 0 | Theoretical and Fundamental Chemistry |
For the special case where the incident radiation is normal (perpendicular) to a surface and the absorption is negligible, the intensity of the reflected and transmitted beams can be calculated from the refractive indices η and η of the two media, where is the fraction of the incident light reflected, and is the fraction of the transmitted light:
, , with the fraction absorbed taken as zero ( = 0 ). | 0 | Theoretical and Fundamental Chemistry |
Carboximidates are good electrophiles and undergo a range of addition reactions; with aliphatic imidates generally reacting faster than aromatic imidates. They can be hydrolyzed to give esters and by an analogous process react with amines (including ammonia) to form amidines. Aliphatic imidates react with an excess of alcohol under acid catalysis to form orthoesters RC(OR), aromatic imidates can also be converted but far less readily. | 0 | Theoretical and Fundamental Chemistry |
The Schlenk equilibrium, named after its discoverer Wilhelm Schlenk, is a chemical equilibrium taking place in solutions of Grignard reagents and Hauser bases
:2 RMgX MgX + MgR
The process described is an equilibrium between two equivalents of an alkyl or aryl magnesium halide on the left of the equation and on the right side, one equivalent of the dialkyl or diaryl magnesium compound and magnesium halide salt. Organomagnesium halides in solution also form dimers and higher oligomers, especially at high concentration. Alkyl magnesium chlorides in ether are present as dimers.
The position of the equilibrium is influenced by solvent, temperature, and the nature of the various substituents. It is known that magnesium center in Grignard reagents typically coordinates two molecules of ether such as diethyl ether or tetrahydrofuran (THF). Thus they are more precisely described as having the formula RMgXL where L = an ether. In the presence of monoethers, the equilibrium typically favors the alkyl- or arylmagnesium halide. Addition of dioxane to such solutions, however, leads to precipitation of the coordination polymers MgX(μ-dioxane)2, driving the equilibrium completely to the right. The dialkylmagnesium compounds are popular in the synthesis of organometallic compounds. | 0 | Theoretical and Fundamental Chemistry |
The relative static permittivity, ε, can be measured for static electric fields as follows: first the capacitance of a test capacitor, C, is measured with vacuum between its plates. Then, using the same capacitor and distance between its plates, the capacitance C with a dielectric between the plates is measured. The relative permittivity can be then calculated as
For time-variant electromagnetic fields, this quantity becomes frequency-dependent. An indirect technique to calculate ε is conversion of radio frequency S-parameter measurement results. A description of frequently used S-parameter conversions for determination of the frequency-dependent ε of dielectrics can be found in this bibliographic source. Alternatively, resonance based effects may be employed at fixed frequencies. | 0 | Theoretical and Fundamental Chemistry |
Many different nucleophiles have been reported to be effective for this reaction. Some of the most common nucleophiles include malonates, enolates, primary alkoxides, carboxylates, phenoxides, amines, azide, sulfonamides, imides, and sulfones. | 0 | Theoretical and Fundamental Chemistry |
More recently, numerous studies have identified the plausibility of sweat as an alternative to blood analysis. The potential substitution for sweat versus blood analysis has many potential benefits. For example, sweat can be: extracted in a non-invasive manner via iontophoresis; extracted with little-to-no pain; and monitored continuously. There are downfalls to the technology, however. For example, demonstration of successful and reliable sweat extraction and analysis on a cohesive device has yet to be demonstrated. Furthermore, although some biomarker partitioning mechanisms are well understood and well studied, partitioning of other useful biomarkers (cytokines, peptides, etc.) are less understood. | 1 | Applied and Interdisciplinary Chemistry |
A Bernoulli grip uses airflow to adhere to an object without physical contact. Such grippers rely on the Bernoulli airflow principle. While an accelerating, increasing speed, airstream has a low downstream static pressure, the sharp turn from linear to radial flow is the cause of a region of very low pressure around the blower exit hole. This is the cause of a net force on the object in the direction normal to the side with higher local pressure. A Bernoulli gripper takes advantage of this by maintaining this negative pressure at the gripper face compared to the ambient pressure below the sample, while maintaining an air gap between the gripper and the object being held. | 1 | Applied and Interdisciplinary Chemistry |
To prepare for an assay, the researcher fills each well of the plate with some biological entity that they wish to conduct the experiment upon, such as a protein, cells, or an animal embryo. After some incubation time has passed to allow the biological matter to absorb, bind to, or otherwise react (or fail to react) with the compounds in the wells, measurements are taken across all the plates wells, either manually or by a machine. Manual measurements are often necessary when the researcher is using microscopy to (for example) seek changes or defects in embryonic development caused by the wells compounds, looking for effects that a computer could not easily determine by itself. Otherwise, a specialized automated analysis machine can run a number of experiments on the wells (such as shining polarized light on them and measuring reflectivity, which can be an indication of protein binding). In this case, the machine outputs the result of each experiment as a grid of numeric values, with each number mapping to the value obtained from a single well. A high-capacity analysis machine can measure dozens of plates in the space of a few minutes like this, generating thousands of experimental datapoints very quickly.
Depending on the results of this first assay, the researcher can perform follow up assays within the same screen by "cherrypicking" liquid from the source wells that gave interesting results (known as "hits") into new assay plates, and then re-running the experiment to collect further data on this narrowed set, confirming and refining observations. | 1 | Applied and Interdisciplinary Chemistry |
Naturally occurring sea foam is not inherently toxic; however, it can be exposed to high concentrations of contaminants in the surface microlayer derived from the breakdown of algal blooms, fossil fuel production and transport, and stormwater runoff. These contaminants contribute to the formation of noxious sea foam through adsorption onto bubbles. Bubbles may burst and release toxins into the atmosphere in the form of sea spray or aerosol, or they may persist in foams. Toxins released through aerosols and breaking bubbles can be inhaled by humans. The microorganisms that occupy sea foams as habitat have increased susceptibility for contaminant exposure. Consequently, these toxic substances can be integrated into the trophic food web. | 0 | Theoretical and Fundamental Chemistry |
Dye-ligand affinity chromatography is one of the Affinity chromatography techniques used for protein purification of a complex mixture. Like general chromatography, but using dyes to apply on a support matrix of a column as the stationary phase that will allow a range of proteins with similar active sites to bind to, refers to as pseudo-affinity. Synthetic dyes are used to mimic substrates or cofactors binding to the active sites of proteins which can be further enhanced to target more specific proteins. Follow with washing, the process of removing other non-target molecules, then eluting out target proteins out by changing pH or manipulate the salt concentration. The column can be reused many times due to the stability of immobilized dyes. It can carry out in a conventional way by using as a packed column, or in high-performance liquid chromatography (HPLC) column. | 0 | Theoretical and Fundamental Chemistry |
G-RAST isnt just a powerhouse for metagenome analysis, its also a treasure trove for data exploration. Dive into a diverse toolbox for visualizing and comparing metagenome profiles across various datasets. Filter based on specifics like composition, quality, functionality, or sample type to tailor your search. Delve deeper with statistical inferences and ecological analyses – all within the user-friendly web interface. | 1 | Applied and Interdisciplinary Chemistry |
Most cell types take up iron primarily through receptor-mediated endocytosis via transferrin receptor 1 (TFR1), transferrin receptor 2 (TFR2) and GAPDH. TFR1 has a 30-fold higher affinity for transferrin-bound iron than TFR2 and thus is the main player in this process. The higher order multifunctional glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) also acts as a transferrin receptor. Transferrin-bound ferric iron is recognized by these transferrin receptors, triggering a conformational change that causes endocytosis. Iron then enters the cytoplasm from the endosome via importer DMT1 after being reduced to its ferrous state by a STEAP family reductase.
Alternatively, iron can enter the cell directly via plasma membrane divalent cation importers such as DMT1 and ZIP14 (Zrt-Irt-like protein 14). Again, iron enters the cytoplasm in the ferrous state after being reduced in the extracellular space by a reductase such as STEAP2, STEAP3 (in red blood cells), Dcytb (in enterocytes) and SDR2. | 1 | Applied and Interdisciplinary Chemistry |
The general equation in conservative form is
where
* is the variable of interest (species concentration for mass transfer, temperature for heat transfer),
* is the diffusivity (also called diffusion coefficient), such as mass diffusivity for particle motion or thermal diffusivity for heat transport,
* is the velocity field that the quantity is moving with. It is a function of time and space. For example, in advection, might be the concentration of salt in a river, and then would be the velocity of the water flow as a function of time and location. Another example, might be the concentration of small bubbles in a calm lake, and then would be the velocity of bubbles rising towards the surface by buoyancy (see below) depending on time and location of the bubble. For multiphase flows and flows in porous media, is the (hypothetical) superficial velocity.
* describes sources or sinks of the quantity , i.e. the creation or destruction of the quantity. For example, for a chemical species, means that a chemical reaction is creating more of the species, and means that a chemical reaction is destroying the species. For heat transport, might occur if thermal energy is being generated by friction.
For example, if is the concentration of a molecule, then describes how the molecule can be created or destroyed by chemical reactions. may be a function of and of other parameters. Often there are several quantities, each with its own convection–diffusion equation, where the destruction of one quantity entails the creation of another. For example, when methane burns, it involves not only the destruction of methane and oxygen but also the creation of carbon dioxide and water vapor. Therefore, while each of these chemicals has its own convection–diffusion equation, they are coupled together and must be solved as a system of simultaneous differential equations.
* represents gradient and represents divergence. In this equation, represents concentration gradient. | 1 | Applied and Interdisciplinary Chemistry |
LISICONs can be used as the solid electrolyte in lithium-based solid-state batteries, such as solid state nickel–lithium battery. For this application, solid lithium electrolytes require ionic conductivities greater than 10 S/cm, negligible electronic conductivity, and a wide range of electrochemcial stability. | 0 | Theoretical and Fundamental Chemistry |
Basically, Flow in pipes can be classified as follows –
* Fully developed flow (found in world-class flow laboratories)
* Pseudo-fully developed flow
* Non-swirling, non-symmetrical flow
* Moderate swirling, non-symmetrical flow
* High swirling, symmetrical flow | 1 | Applied and Interdisciplinary Chemistry |
* American Chemical Society Analytical Division
* AES Electrophoresis Society
* American Society for Mass Spectrometry
* Anachem
* Coblentz Society
* Council for Near-Infrared Spectroscopy
* Infrared Raman and Discussion Group
* International Society of Automation Analysis Division
* The North American Society for Laser-Induced Breakdown Spectroscopy
* Royal Society of Chemistry Analytical Division
* Society for Applied Spectroscopy
* The Spectroscopical Society of Japan | 0 | Theoretical and Fundamental Chemistry |
Since the molecule has a hydroxyl (-OH) group, it is frequently bound to other lipids including fatty acids; most analytical methods, therefore, utilise a strong alkali (KOH or NaOH) to saponify the ester linkages. Typical extraction solvents include 6% KOH in methanol. The free sterols and stanols (saturated sterols) are then separated from the polar lipids by partitioning into a less polar solvent such as hexane. Prior to analysis, the hydroxyl group is frequently derivatised with BSTFA (bis-trimethyl silyl trifluoroacetamide) to replace the hydrogen with the less exchangeable trimethylsilyl (TMS) group. Instrumental analysis is frequently conducted on gas chromatograph (GC) with either a flame ionisation detector (FID) or mass spectrometer (MS). The mass spectrum for 5β-coprostanol - TMS ether can be seen in the figure. Alternatively, liquid-chromatography mass spectrometry (LC-MS) techniques that employ atmospheric pressure chemical ionization (APCI) may also be employed to detect coprostanol under positive mode.<br /> | 1 | Applied and Interdisciplinary Chemistry |
Homovanillic acid (HVA) is a major catecholamine metabolite that is produced by a consecutive action of monoamine oxidase and catechol-O-methyltransferase on dopamine. Homovanillic acid is used as a reagent to detect oxidative enzymes, and is associated with dopamine levels in the brain.
In psychiatry and neuroscience, brain and cerebrospinal fluid levels of HVA are measured as a marker of metabolic stress caused by 2-deoxy--glucose. HVA presence supports a diagnosis of neuroblastoma and malignant pheochromocytoma.
Fasting plasma levels of HVA are known to be higher in females than in males. This does not seem to be influenced by adult hormonal changes, as the pattern is retained in the elderly and post-menopausal as well as transgender people according to their genetic sex, both before and during cross-sex hormone administration. Differences in HVA have also been correlated to tobacco usage, with smokers showing significantly lower amounts of plasma HVA. | 1 | Applied and Interdisciplinary Chemistry |
The chelating properties of aminopolycarboxylates can be engineered by varying the groups linking the nitrogen atoms so as to increase selectivity for a particular metal ion. The number of carbon atoms between the nitrogen and carboxyl group can also be varied and substituents can be placed on these carbon atoms. Altogether this allows for a vast range of possibilities. Fura-2 is noteworthy as it combines two functionalities: it has high selectivity for calcium over magnesium and it has a substituent which makes the complex fluorescent when it binds calcium. This reagent provides a means of determining the calcium content in intra-cellular fluid. Details concerning applications of the following examples can be found in the individual articles and/or reference. The aminopolycarboxylate nicotianamine is widespread in plants, where it is used to transport iron. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, a stagnation point is a point in a flow field where the local velocity of the fluid is zero. A plentiful, albeit surprising, example of such points seem to appear in all but the most extreme cases of fluid dynamics in the form of the "no-slip condition"; the assumption that any portion of a flow field lying along some boundary consists of nothing but stagnation points (the question as to whether this assumption reflects reality or is simply a mathematical convenience has been a continuous subject of debate since the principle was first established). The Bernoulli equation shows that the static pressure is highest when the velocity is zero and hence static pressure is at its maximum value at stagnation points: in this case static pressure equals stagnation pressure.
The Bernoulli equation applicable to incompressible flow shows that the stagnation pressure is equal to the dynamic pressure plus static pressure. Total pressure is also equal to dynamic pressure plus static pressure so, in incompressible flows, stagnation pressure is equal to total pressure. (In compressible flows, stagnation pressure is also equal to total pressure providing the fluid entering the stagnation point is brought to rest isentropically.) | 1 | Applied and Interdisciplinary Chemistry |
Knockouts are primarily used to understand the role of a specific gene or DNA region by comparing the knockout organism to a wildtype with a similar genetic background.
Knockout organisms are also used as screening tools in the development of drugs, to target specific biological processes or deficiencies by using a specific knockout, or to understand the mechanism of action of a drug by using a library of knockout organisms spanning the entire genome, such as in Saccharomyces cerevisiae. | 1 | Applied and Interdisciplinary Chemistry |
The behaviour of the coals ash residue at high temperature is a critical factor in selecting coals for steam power generation. Most furnaces are designed to remove ash as a powdery residue. Coal which has ash that fuses into a hard glassy slag known as clinker' is usually unsatisfactory in furnaces as it requires cleaning. However, furnaces can be designed to handle the clinker, generally by removing it as a molten liquid.
Ash fusion temperatures are determined by viewing a moulded specimen of the coal ash through an observation window in a high-temperature furnace. The ash, in the form of a cone, pyramid or cube, is heated steadily past 1000 °C to as high a temperature as possible, preferably . The following temperatures are recorded;
* Deformation temperature: This is reached when the corners of the mould first become rounded.
* Softening (sphere) temperature: This is reached when the top of the mould takes on a spherical shape.
* Hemisphere temperature: This is reached when the entire mould takes on a hemisphere shape.
* Flow (fluid) temperature: This is reached when the molten ash collapses to a flattened button on the furnace floor. | 0 | Theoretical and Fundamental Chemistry |
Haemozoin is a disposal product formed from the digestion of blood by some blood-feeding parasites. These hematophagous organisms such as malaria parasites (Plasmodium spp.), Rhodnius and Schistosoma digest haemoglobin and release high quantities of free heme, which is the non-protein component of haemoglobin. Heme is a prosthetic group consisting of an iron atom contained in the center of a heterocyclic porphyrin ring. Free heme is toxic to cells, so the parasites convert it into an insoluble crystalline form called hemozoin. In malaria parasites, hemozoin is often called malaria pigment.
Since the formation of hemozoin is essential to the survival of these parasites, it is an attractive target for developing drugs and is much-studied in Plasmodium as a way to find drugs to treat malaria (malarias Achilles heel). Several currently used antimalarial drugs, such as chloroquine and mefloquine, are thought to kill malaria parasites by inhibiting haemozoin biocrystallization. | 1 | Applied and Interdisciplinary Chemistry |
There are a number of problems that can be encountered during the casting process. The main types are: gas porosity, shrinkage defects, mold material defects, pouring metal defects, and metallurgical defects. | 1 | Applied and Interdisciplinary Chemistry |
Lipids comprise a diverse range of molecules and to some extent is a catchall for relatively water-insoluble or nonpolar compounds of biological origin, including waxes, fatty acids, fatty-acid derived phospholipids, sphingolipids, glycolipids, and terpenoids (e.g., retinoids and steroids). Some lipids are linear, open-chain aliphatic molecules, while others have ring structures. Some are aromatic (with a cyclic [ring] and planar [flat] structure) while others are not. Some are flexible, while others are rigid.
Lipids are usually made from one molecule of glycerol combined with other molecules. In triglycerides, the main group of bulk lipids, there is one molecule of glycerol and three fatty acids. Fatty acids are considered the monomer in that case, and maybe saturated (no double bonds in the carbon chain) or unsaturated (one or more double bonds in the carbon chain).
Most lipids have some polar character and are largely nonpolar. In general, the bulk of their structure is nonpolar or hydrophobic ("water-fearing"), meaning that it does not interact well with polar solvents like water. Another part of their structure is polar or hydrophilic ("water-loving") and will tend to associate with polar solvents like water. This makes them amphiphilic molecules (having both hydrophobic and hydrophilic portions). In the case of cholesterol, the polar group is a mere –OH (hydroxyl or alcohol).
In the case of phospholipids, the polar groups are considerably larger and more polar, as described below.
Lipids are an integral part of our daily diet. Most oils and milk products that we use for cooking and eating like butter, cheese, ghee etc. are composed of fats. Vegetable oils are rich in various polyunsaturated fatty acids (PUFA). Lipid-containing foods undergo digestion within the body and are broken into fatty acids and glycerol, the final degradation products of fats and lipids. Lipids, especially phospholipids, are also used in various pharmaceutical products, either as co-solubilizers (e.g. in parenteral infusions) or else as drug carrier components (e.g. in a liposome or transfersome). | 1 | Applied and Interdisciplinary Chemistry |
Formula for effective permeability of mixtures has a form
Here is effective relative complex permeability of the mixture, is relative complex permeability of the background medium containing small spherical inclusions of relative permeability with volume fraction of . This formula was derived in dipole approximation. Magnetic octupole mode and all other magnetic oscillation modes of odd orders were neglected here. When and this formula has a simple form | 0 | Theoretical and Fundamental Chemistry |
Piperacillin is a broad-spectrum β-lactam antibiotic of the ureidopenicillin class. The chemical structure of piperacillin and other ureidopenicillins incorporates a polar side chain that enhances penetration into Gram-negative bacteria and reduces susceptibility to cleavage by Gram-negative beta lactamase enzymes. These properties confer activity against the important hospital pathogen Pseudomonas aeruginosa. Thus piperacillin is sometimes referred to as an "anti-pseudomonal penicillin".
When used alone, piperacillin lacks strong activity against the Gram-positive pathogens such as Staphylococcus aureus, as the beta-lactam ring is hydrolyzed by the bacteria's beta-lactamase.
It was patented in 1974 and approved for medical use in 1981. Piperacillin is most commonly used in combination with the beta-lactamase inhibitor tazobactam (piperacillin/tazobactam), which enhances piperacillin's effectiveness by inhibiting many beta lactamases to which it is susceptible. However, the co-administration of tazobactam does not confer activity against MRSA, as penicillin (and most other beta lactams) do not avidly bind to the penicillin-binding proteins of this pathogen. The World Health Organization classifies piperacillin as critically important for human medicine. | 0 | Theoretical and Fundamental Chemistry |
A classic route to carbodiimides involves dehydrosulfurization of thioureas. A typical reagent for this process is mercuric oxide:
:(R(H)N)CS + HgO → (RN)C + HgS + HO
This reaction can often be conducted as stated, even though carbodiimides react with water. In some cases, a dehydrating agent is added to the reaction mixture.
The dehydration of N,N'-dialkylureas gives carbodiimides:
:(R(H)N)CO → (RN)C + HO
Phosphorus pentoxide and p-Toluenesulfonyl chloride have been used as a dehydrating agents. | 0 | Theoretical and Fundamental Chemistry |
The Godwin Laboratory is a research facility at the University of Cambridge. It was originally set up to investigate radiocarbon dating and its applications, and was one of the first laboratories to determine a radiocarbon calibration curve. The lab is named after the English scientist Harry Godwin. | 0 | Theoretical and Fundamental Chemistry |
Biochemical CCMs concentrate carbon dioxide in one temporal or spatial region, through metabolite exchange. C and CAM photosynthesis both use the enzyme Phosphoenolpyruvate carboxylase (PEPC) to add to a 4-Carbon sugar. PEPC is faster than RuBisCO, and more selective for . | 0 | Theoretical and Fundamental Chemistry |
The reciprocal lattice is easily constructed in one dimension: for particles on a line with a period , the reciprocal lattice is an infinite array of points with spacing . In two dimensions, there are only five Bravais lattices. The corresponding reciprocal lattices have the same symmetry as the direct lattice. 2-D lattices are excellent for demonstrating simple diffraction geometry on a flat screen, as below.
Equations (1)–(7) for structure factor apply with a scattering vector of limited dimensionality and a crystallographic structure factor can be defined in 2-D as .
However, recall that real 2-D crystals such as graphene exist in 3-D. The reciprocal lattice of a 2-D hexagonal sheet that exists in 3-D space in the plane is a hexagonal array of lines parallel to the or axis that extend to and intersect any plane of constant in a hexagonal array of points.
The Figure shows the construction of one vector of a 2-D reciprocal lattice and its relation to a scattering experiment.
A parallel beam, with wave vector is incident on a square lattice of parameter . The scattered wave is detected at a certain angle, which defines the wave vector of the outgoing beam, (under the assumption of elastic scattering, ). One can equally define the scattering vector and construct the harmonic pattern . In the depicted example, the spacing of this pattern coincides to the distance between particle rows: , so that contributions to the scattering from all particles are in phase (constructive interference). Thus, the total signal in direction is strong, and belongs to the reciprocal lattice. It is easily shown that this configuration fulfills Bragg's law. | 0 | Theoretical and Fundamental Chemistry |
The journal is abstracted and indexed in:
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According to the Journal Citation Reports, the journal has a 2020 impact factor of 4.105. | 0 | Theoretical and Fundamental Chemistry |
Penetration depth is a measure of how deep light or any electromagnetic radiation can penetrate into a material. It is defined as the depth at which the intensity of the radiation inside the material falls to 1/e (about 37%) of its original value at (or more properly, just beneath) the surface.
When electromagnetic radiation is incident on the surface of a material, it may be (partly) reflected from that surface and there will be a field containing energy transmitted into the material. This electromagnetic field interacts with the atoms and electrons inside the material. Depending on the nature of the material, the electromagnetic field might travel very far into the material, or may die out very quickly. For a given material, penetration depth will generally be a function of wavelength. | 0 | Theoretical and Fundamental Chemistry |
Serial analysis of gene expression (SAGE) was a development of EST methodology to increase the throughput of the tags generated and allow some quantitation of transcript abundance. cDNA is generated from the RNA but is then digested into 11 bp "tag" fragments using restriction enzymes that cut DNA at a specific sequence, and 11 base pairs along from that sequence. These cDNA tags are then joined head-to-tail into long strands (>500 bp) and sequenced using low-throughput, but long read-length methods such as Sanger sequencing. The sequences are then divided back into their original 11 bp tags using computer software in a process called deconvolution. If a high-quality reference genome is available, these tags may be matched to their corresponding gene in the genome. If a reference genome is unavailable, the tags can be directly used as diagnostic markers if found to be differentially expressed in a disease state.
The cap analysis gene expression (CAGE) method is a variant of SAGE that sequences tags from the 5’ end of an mRNA transcript only. Therefore, the transcriptional start site of genes can be identified when the tags are aligned to a reference genome. Identifying gene start sites is of use for promoter analysis and for the cloning of full-length cDNAs.
SAGE and CAGE methods produce information on more genes than was possible when sequencing single ESTs, but sample preparation and data analysis are typically more labour-intensive. | 1 | Applied and Interdisciplinary Chemistry |
Returning to the cost objective function, it cannot violate any of the operational constraints. Generally this cost is dominated by the energy cost for pumping. “The operational constraints include the standards of customer service, such as: the minimum delivered pressure, in addition to the physical constraints such as the maximum and the minimum water levels in storage tanks to prevent overtopping and emptying respectively.”
In order to optimize the operational performance of the water supply network, at the same time as minimizing the energy costs, it is necessary to predict the consequences of different pump and valve settings on the behavior of the network.
Apart from Linear and Non-linear Programming, there are other methods and approaches to design, to manage and operate a water supply network to achieve sustainability—for instance, the adoption of appropriate technology coupled with effective strategies for operation and maintenance. These strategies must include effective management models, technical support to the householders and industries, sustainable financing mechanisms, and development of reliable supply chains. All these measures must ensure the following: system working lifespan; maintenance cycle; continuity of functioning; down time for repairs; water yield and water quality. | 1 | Applied and Interdisciplinary Chemistry |
* Cocaine, for example, blocks the reuptake of dopamine, leaving these neurotransmitters in the synaptic gap for longer.
* AMPT prevents the conversion of tyrosine to L-DOPA, the precursor to dopamine; reserpine prevents dopamine storage within vesicles; and deprenyl inhibits monoamine oxidase (MAO)-B and thus increases dopamine levels. | 1 | Applied and Interdisciplinary Chemistry |
Similar to chirality planes, chirality axes arise from an axis about which the spatial arrangement of substituents creates chirality. This can be seen in helical molecules (see section 3a) as well as some alkenes. | 0 | Theoretical and Fundamental Chemistry |
The triclinic form of boric acid consists of layers of molecules held together by hydrogen bonds with an O...O separation of 272 pm. The distance between two adjacent layers is 318 pm. | 0 | Theoretical and Fundamental Chemistry |
No single compound will prove life once existed. Rather, it will be distinctive patterns present in any organic compounds showing a process of selection. For example, membrane lipids left behind by degraded cells will be concentrated, have a limited size range, and comprise an even number of carbons. Similarly, life only uses left-handed amino acids. Biosignatures need not be chemical, however, and can also be suggested by a distinctive magnetic biosignature.
Chemical biosignatures include any suite of complex organic compounds composed of carbon, hydrogen, and other elements or heteroatoms such as oxygen, nitrogen, and sulfur, which are found in crude oils, bitumen, petroleum source rock and eventually show simplification in molecular structure from the parent organic molecules found in all living organisms. They are complex carbon-based molecules derived from formerly living organisms. Each biomarker is quite distinctive when compared to its counterparts, as the time required for organic matter to convert to crude oil is characteristic. Most biomarkers also usually have high molecular mass.
Some examples of biomarkers found in petroleum are pristane, triterpanes, steranes, phytane and porphyrin. Such petroleum biomarkers are produced via chemical synthesis using biochemical compounds as their main constituents. For instance, triterpenes are derived from biochemical compounds found on land angiosperm plants. The abundance of petroleum biomarkers in small amounts in its reservoir or source rock make it necessary to use sensitive and differential approaches to analyze the presence of those compounds. The techniques typically used include gas chromatography and mass spectrometry.
Petroleum biomarkers are highly important in petroleum inspection as they help indicate the depositional territories and determine the geological properties of oils. For instance, they provide more details concerning their maturity and the source material. In addition to that they can also be good parameters of age, hence they are technically referred to as "chemical fossils". The ratio of pristane to phytane (pr:ph) is the geochemical factor that allows petroleum biomarkers to be successful indicators of their depositional environments.
Geologists and geochemists use biomarker traces found in crude oils and their related source rock to unravel the stratigraphic origin and migration patterns of presently existing petroleum deposits. The dispersion of biomarker molecules is also quite distinctive for each type of oil and its source; hence, they display unique fingerprints. Another factor that makes petroleum biomarkers more preferable than their counterparts is that they have a high tolerance to environmental weathering and corrosion. Such biomarkers are very advantageous and often used in the detection of oil spillage in the major waterways. The same biomarkers can also be used to identify contamination in lubricant oils. However, biomarker analysis of untreated rock cuttings can be expected to produce misleading results. This is due to potential hydrocarbon contamination and biodegradation in the rock samples. | 1 | Applied and Interdisciplinary Chemistry |
Osama Kamal (; born 5 April 1959) was the Egyptian minister of petroleum and mineral resources. He was sworn into President Mohamad Morsi's cabinet, the Qandil Cabinet, on 2 August 2012, following the 2011–2012 Egyptian uprising that deposed President Hosni Mubarak. He was in office until 6 May 2013. | 1 | Applied and Interdisciplinary Chemistry |
Triglycerides of butyric acid compose 3–4% of butter. When butter goes rancid, butyric acid is liberated from the glyceride by hydrolysis. It is one of the fatty acid subgroup called short-chain fatty acids. Butyric acid is a typical carboxylic acid that reacts with bases and affects many metals.
It is found in animal fat and plant oils, bovine milk, breast milk, butter, parmesan cheese, body odor, vomit and as a product of anaerobic fermentation (including in the colon). It has a taste somewhat like butter and an unpleasant odor. Mammals with good scent detection abilities, such as dogs, can detect it at 10 parts per billion, whereas humans can detect it only in concentrations above 10 parts per million. In food manufacturing, it is used as a flavoring agent.
In humans, butyric acid is one of two primary endogenous agonists of human hydroxycarboxylic acid receptor 2 (), a G protein-coupled receptor.
Butyric acid is present as its octyl ester in parsnip (Pastinaca sativa) and in the seed of the ginkgo tree. | 1 | Applied and Interdisciplinary Chemistry |
There are two distinctive features of ion channels that differentiate them from other types of ion transporter proteins:
#The rate of ion transport through the channel is very high (often 10 ions per second or greater).
#Ions pass through channels down their electrochemical gradient, which is a function of ion concentration and membrane potential, "downhill", without the input (or help) of metabolic energy (e.g. ATP, co-transport mechanisms, or active transport mechanisms).
Ion channels are located within the membrane of all excitable cells, and of many intracellular organelles. They are often described as narrow, water-filled tunnels that allow only ions of a certain size and/or charge to pass through. This characteristic is called selective permeability. The archetypal channel pore is just one or two atoms wide at its narrowest point and is selective for specific species of ion, such as sodium or potassium. However, some channels may be permeable to the passage of more than one type of ion, typically sharing a common charge: positive (cations) or negative (anions). Ions often move through the segments of the channel pore in a single file nearly as quickly as the ions move through the free solution. In many ion channels, passage through the pore is governed by a "gate", which may be opened or closed in response to chemical or electrical signals, temperature, or mechanical force.
Ion channels are integral membrane proteins, typically formed as assemblies of several individual proteins. Such "multi-subunit" assemblies usually involve a circular arrangement of identical or homologous proteins closely packed around a water-filled pore through the plane of the membrane or lipid bilayer. For most voltage-gated ion channels, the pore-forming subunit(s) are called the α subunit, while the auxiliary subunits are denoted β, γ, and so on. | 1 | Applied and Interdisciplinary Chemistry |
Nature produces massive amounts of chloromethane and bromomethane. Most concern focuses on anthropogenic sources, which are potential toxins, even carcinogens. Similarly, great interest has been shown in remediation of man made halocarbons such as those produced on large scale, such as dry cleaning fluids. Volatile halocarbons degrade photochemically because the carbon-halogen bond can be labile. Some microorganisms dehalogenate halocarbons. While this behavior is intriguing, the rates of remediation are generally very slow. | 0 | Theoretical and Fundamental Chemistry |
Cyanobacteria are challenged by environmental stresses and internally generated reactive oxygen species that cause DNA damage. Cyanobacteria possess numerous E. coli-like DNA repair genes. Several DNA repair genes are highly conserved in cyanobacteria, even in small genomes, suggesting that core DNA repair processes such as recombinational repair, nucleotide excision repair and methyl-directed DNA mismatch repair are common among cyanobacteria. | 0 | Theoretical and Fundamental Chemistry |
* Switzerland: Swiss Nano Dragster, University of Basel
* France: Toulouse nanomobile club, Paul Sabatier University
* Austria/United States: NanoPrix Team University of Graz / Rice University
* Germany: Nano-windmill Company Technical University of Dresden (TU Dresden)
* Japan: Nano-Vehicle NIMS-MANA National Institute for Materials Science
* United States: Ohio Bobcat Nano-Wagon, Ohio University | 0 | Theoretical and Fundamental Chemistry |
Having worked for some time from the age of fourteen in the local Rylands linoleum factory managed by his father, he studied for and successfully passed the entrance examination to the University of Manchester in 1903 to study chemistry. He made this pursuit in spite of active discouragement by his parents. He gained his first-class honours degree in 1906. After gaining his masters degree under William Henry Perkin Jr., he was awarded an 1851 Research Fellowship from the Royal Commission for the Exhibition of 1851 and studied at the University of Göttingen earning his PhD in Otto Wallach's laboratory after only one year of study. A DSc from the University of Manchester followed in 1911, after which he served a short time at the Imperial College of Science and Technology as Senior Demonstrator in Chemistry.
In 1912 Haworth became a lecturer at United College of University of St Andrews in Scotland and became interested in carbohydrate chemistry, which was being investigated at St Andrews by Thomas Purdie (1843–1916) and James Irvine (1877–1952). Haworth began his work on simple sugars in 1915 and developed a new method for the preparation of the methyl ethers of sugars using methyl sulfate and alkali (now called Haworth methylation). He then began studies on the structural features of the disaccharides. Haworth organised the laboratories at St Andrews University for the production of chemicals and drugs for the British government during World War I (1914–1918).
He was appointed Professor of Organic Chemistry at the Armstrong College (Newcastle upon Tyne) of Durham University in 1920. The next year Haworth was appointed Head of the Chemistry Department at the college. It was during his time in the North East of England that he married Violet Chilton Dobbie.
In 1925 he was appointed Mason Professor of Chemistry at the University of Birmingham (a position he held until 1948). Among his lasting contributions to science was the confirmation of a number of structures of optically active sugars: by 1928, he had deduced and confirmed, among others, the structures of maltose, cellobiose, lactose, gentiobiose, melibiose, gentianose, raffinose, as well as the glucoside ring tautomeric structure of aldose sugars. He published a classic text in 1929, The Constitution of Sugars.
In 1933, working with the then Assistant Director of Research (later Sir) Edmund Hirst and a team led by post-doctoral student Maurice Stacey (who in 1956 rose to the same Mason Chair), having properly deduced the correct structure and optical-isomeric nature of vitamin C, Haworth reported the synthesis of the vitamin. Haworth had been given his initial reference sample of "water-soluble vitamin C" or "hexuronic acid" (the previous name for the compound as extracted from natural products) by Hungarian physiologist Albert Szent-Györgyi, who had codiscovered its vitamin properties along with Charles Glen King, and had more recently discovered that it could be extracted in bulk from Hungarian paprika. In honour of the compound's antiscorbutic properties, Haworth and Szent-Györgyi now proposed the new name of "a-scorbic acid" for the molecule, with L-ascorbic acid as its formal chemical name. During World War II, he was a member of the MAUD Committee which oversaw research on the British atomic bomb project. | 0 | Theoretical and Fundamental Chemistry |
Colloidal quantum dots are nanoscale semiconductor materials with highly tunable optical and electronic properties. Quantum dots photosensitize via the same mechanism as organometallic photosensitizers and organic photosensitizers, but their nanoscale properties allow for greater control in distinctive aspects. Some key advantages to the use of quantum dots as photosensitizers includes their small, tunable band gap which allows for efficient transitions to the triplet state, and their insolubility in many solvents which allows for easy retrieval from a synthetic reaction mixture. | 0 | Theoretical and Fundamental Chemistry |
The archaeon Sulfolobus solfataricus RadA recombinase catalyzes DNA pairing and strand exchange, central steps in recombinational repair. The RadA recombinase has greater similarity to the eukaryotic Rad51 recombinase than to the bacterial RecA recombinase. | 1 | Applied and Interdisciplinary Chemistry |
o-Cresolphthalein is not produced industrially, rather, it is commercially available. To be produced, the method generally used to synthesize phthalein dyes is effective. This method is used to synthesize phenolphthalein and thymolphthalein. To begin, a 2M equivalent of a phenol or a substituted phenol should be combined with a 1M equivalent of a phthalic anhydride. | 0 | Theoretical and Fundamental Chemistry |
An alternative variation of four-wave-mixing-based frequency combs is known as Kerr frequency comb. Here, a single laser is coupled into a microresonator (such as a microscopic glass disk that has whispering-gallery modes). This kind of structure naturally has a series of resonant modes with approximately equally spaced frequencies (similar to a Fabry–Pérot interferometer). Unfortunately the resonant modes are not exactly equally spaced due to dispersion. Nevertheless, the four-wave mixing effect above can create and stabilize a perfect frequency comb in such a structure. Basically, the system generates a perfect comb that overlaps the resonant modes as much as possible. In fact, nonlinear effects can shift the resonant modes to improve the overlap with the perfect comb even more. (The resonant mode frequencies depend on refractive index, which is altered by the optical Kerr effect.)
In the time domain, while mode-locked lasers almost always emit a series of short pulses, Kerr frequency combs generally do not. However, a special sub-type of Kerr frequency comb, in which a "cavity soliton" forms in the microresonator, does emit a series of pulses. | 0 | Theoretical and Fundamental Chemistry |
Anabaseine causes paralysis in crustaceans and insects, but not in vertebrates, presumably by acting as an agonist on peripheral neuromuscular nicotinic acetylcholine receptors. | 1 | Applied and Interdisciplinary Chemistry |
Organic compounds such as amino acids, carbohydrates, fatty acids, and phenols are highly enriched in the SML interface. Most of these come from biota in the sub-surface waters, which decay and become transported to the surface, though other sources exist also such as atmospheric deposition, coastal runoff, and anthropogenic nutrification. The relative concentration of these compounds is dependent on the nutrient sources as well as climate conditions such as wind speed and precipitation. These organic compounds on the surface create a "film," referred to as a "slick" when visible, which affects the physical and optical properties of the interface. These films occur because of the hydrophobic tendencies of many organic compounds, which causes them to protrude into the air-interface. The existence of organic surfactants on the ocean surface impedes wave formation for low wind speeds. For increasing concentrations of surfactant there is an increasing critical wind speed necessary to create ocean waves. Increased levels of organic compounds at the surface also hinders air-sea gas exchange at low wind speeds. One way in which particulates and organic compounds on the surface are transported into the atmosphere is the process called "bubble bursting". Bubbles generate the major portion of marine aerosols. They can be dispersed to heights of several meters, picking up whatever particles latch on to their surface. However, the major supplier of materials comes from the SML. | 0 | Theoretical and Fundamental Chemistry |
Scavenger resins are polymers (resins) with bound functional groups that react with specific by-products, impurities, or excess reagents produced in a reaction. Polymer-bound functional groups permit the use of many different scavengers, as the functional groups are confined within a resin or are simply bound to the solid support of a bead. Simply, the functional groups of one scavenger will react minimally with the functional groups of another. | 0 | Theoretical and Fundamental Chemistry |
A real-time polymerase chain reaction (real-time PCR, or qPCR when used quantitatively) is a laboratory technique of molecular biology based on the polymerase chain reaction (PCR). It monitors the amplification of a targeted DNA molecule during the PCR (i.e., in real time), not at its end, as in conventional PCR. Real-time PCR can be used quantitatively and semi-quantitatively (i.e., above/below a certain amount of DNA molecules).
Two common methods for the detection of PCR products in real-time PCR are (1) non-specific fluorescent dyes that intercalate with any double-stranded DNA and (2) sequence-specific DNA probes consisting of oligonucleotides that are labelled with a fluorescent reporter, which permits detection only after hybridization of the probe with its complementary sequence.
The Minimum Information for Publication of Quantitative Real-Time PCR Experiments (MIQE) guidelines propose that the abbreviation qPCR be used for quantitative real-time PCR and that RT-qPCR be used for reverse transcription–qPCR. The acronym "RT-PCR" commonly denotes reverse transcription polymerase chain reaction and not real-time PCR, but not all authors adhere to this convention. | 1 | Applied and Interdisciplinary Chemistry |
The phosphate ion has a molar mass of 94.97 g/mol, and consists of a central phosphorus atom surrounded by four oxygen atoms in a tetrahedral arrangement. It is the conjugate base of the hydrogen phosphate ion , which in turn is the conjugate base of the dihydrogen phosphate ion , which in turn is the conjugate base of orthophosphoric acid, .
Many phosphates are soluble in water at standard temperature and pressure. The sodium, potassium, rubidium, caesium, and ammonium phosphates are all water-soluble. Most other phosphates are only slightly soluble or are insoluble in water. As a rule, the hydrogen and dihydrogen phosphates are slightly more soluble than the corresponding phosphates. | 0 | Theoretical and Fundamental Chemistry |
Basilicon, or basilicum, is the name given to various ointments that were believed to have sovereign virtues. One such example was an unguent composed of rosin, wax, pitch, and oil, which pre-modern surgeons used as a suppurative.
The German physician Wilhelm Fabry described the use of basilicon ointments in the treatment of burns. English physicians in the early nineteenth century reported their use in the prevention of gangrene. | 1 | Applied and Interdisciplinary Chemistry |
The integration of knowledge concerning the molecular and cellular actions of a drug within the brain circuitry leads to an overall understanding of a neurological drug's action mechanisms. This understanding of drug action in turn can be extrapolated to account for system-wide or clinical manifestations which are observed as symptoms. The clinical effects of a neural drug are due to both immediate changes in homeostasis and long-term neural adaptations characterized by the phenomena neural plasticity.
The most basic and fundamental neurological phenomena in neuropharmacology is the binding of a drug or neurologically active substance to a cellular target. One assay to determine the extent at which a ligand binds to its receptor is the radioligand binding assay (RBA), in which specific binding of a radioactively-labeled ligand is denoted by the difference between saturated and non-saturated tissue samples. While the RBA assay assumes that the tissue prepared has just one molecular target per ligand, in actuality this may not be the case. For example, serotonin binds to many diverse serotonin receptors which makes the RIA assay quite difficult to interpret. Because many receptors are essentially enzymes, the field of pharmakinetics utilizes the Michaelis–Menten equation to describe drug affinity (dissociation constant K) and total binding (B). Although K and B can be determined pictorially in a normal or logarithmic plot of ligand binding vs drug concentration, Scatchard plots allow for mathematical representation of several ligand binding sites, each with its own K.
Drug potency is the measure of binding strength between a drug and a specific molecular target, whereas drug efficacy describes the biological effect exerted by the drug itself, at either a cellular or organismal level. Because drugs range widely in their potency and efficacy, drugs have been categorized on the spectrum of agonists and antagonists. Agonists bind to receptors and elicit the same effects as an endogenous neurotransmitter. For example, morphine is an agonist of the opioid receptor family. Conversely, antagonists bind to a receptor and elicit no cellular change. Naloxone, an antagonist of the opioid receptors, exerts a biological effect only be interfering with endogenous neurotransmitter (morphine) binding. Inverse agonists bind to receptors and elicit the opposite effect that an agonist would. The spectrum of drug continuum also includes partial agonists and partial inverse agonists, which comprise the wide majority of neurological clinical treatments. The ultimate clinical effect of a drug can be analyzed with a dose-response curve. | 1 | Applied and Interdisciplinary Chemistry |
The G3P is converted to 1,3-bisphosphoglycerate in the presence of enzyme glyceraldehyde-3-phosphate dehydrogenase (an oxido-reductase).
The aldehyde groups of the triose sugars are oxidised, and inorganic phosphate is added to them, forming 1,3-bisphosphoglycerate.
The hydrogen is used to reduce two molecules of NAD, a hydrogen carrier, to give NADH + H for each triose.
Hydrogen atom balance and charge balance are both maintained because the phosphate (P) group actually exists in the form of a hydrogen phosphate anion (HPO), which dissociates to contribute the extra H ion and gives a net charge of -3 on both sides. | 1 | Applied and Interdisciplinary Chemistry |
While in the stratosphere (post-test period), the tritium interacted with and oxidized to water molecules and was present in much of the rapidly produced rainfall, making tritium a prognostic tool for studying the evolution and structure of the hydrologic cycle as well as the ventilation and formation of water masses in the North Atlantic Ocean.
Bomb-tritium data were used from the Transient Tracers in the Ocean (TTO) program in order to quantify the replenishment and overturning rates for deep water located in the North Atlantic.
Bomb-tritium also enters the deep ocean around the Antarctic. Most of the bomb tritiated water (HTO) throughout the atmosphere can enter the ocean through the following processes:
:(a) precipitation
:(b) vapor exchange
:(c) river runoff
These processes make HTO a great tracer for time-scales of up to a few decades.
Using the data from these processes for 1981, the 1 TU isosurface lies between 500 and 1,000 meters deep in the subtropical regions and then extends to 1,500–2,000 meters south of the Gulf Stream due to recirculation and ventilation in the upper portion of the Atlantic Ocean. To the north, the isosurface deepens and reaches the floor of the abyssal plain which is directly related to the ventilation of the ocean floor over 10–20 year time-scales.
Also evident in the Atlantic Ocean is the tritium profile near Bermuda between the late 1960s and late 1980s. There is a downward propagation of the tritium maximum from the surface (1960s) to 400 meters (1980s), which corresponds to a deepening rate of approximately 18 meters per year. There are also tritium increases at 1,500 meters depth in the late 1970s and 2,500 meters in the middle of the 1980s, both of which correspond to cooling events in the deep water and associated deep water ventilation.
From a study in 1991, the tritium profile was used as a tool for studying the mixing and spreading of newly formed North Atlantic Deep Water (NADW), corresponding to tritium increases to 4 TU. This NADW tends to spill over sills that divide the Norwegian Sea from the North Atlantic Ocean and then flows to the west and equatorward in deep boundary currents. This process was explained via the large-scale tritium distribution in the deep North Atlantic between 1981 and 1983. The sub-polar gyre tends to be freshened (ventilated) by the NADW and is directly related to the high tritium values (> 1.5 TU). Also evident was the decrease in tritium in the deep western boundary current by a factor of 10 from the Labrador Sea to the Tropics, which is indicative of loss to ocean interior due to turbulent mixing and recirculation. | 0 | Theoretical and Fundamental Chemistry |
ISF compounds can be quantified either indirectly from merely diluted ISF samples by using OFM and additional calibration techniques, or directly from undiluted ISF samples which can be collected with additional OFM methods. Quantification of compounds from diluted ISF samples requires additional application of calibration methods, such as Zero Flow Rate, No Net Flux or Ionic Reference. Zero Flow Rate has been used in combination with dOFM by Schaupp et al. to quantify potassium, sodium and glucose in adipose ISF samples. No Net Flux has been applied to quantify several analytes in OFM studies in subcutaneous adipose, muscle and dermal ISF: the absolute lactate concentrations and the absolute glucose concentrations in adipose ISF, the absolute albumin concentration in muscle ISF and the absolute insulin concentration in adipose and muscle ISF have been successfully determined. Dragatin et al. used No Net Flux in combination with dOFM to assess the absolute ISF concentration of a fully human therapeutic antibody. Ionic Reference has been used in combination with OFM to assess the absolute glucose concentration and the absolute lactate concentration in adipose ISF. Dermal OFM has also been used to quantify the concentrations of human insulin and an insulin analogue in the ISF with inulin as exogenous marker.
Additional OFM methods, such as OFM recirculation and OFM suction can collect undiluted ISF samples from which direct and absolute quantification of compounds is feasible. OFM recirculation to collect undiluted ISF samples recirculates the perfusate in a closed loop until equilibrium concentrations between perfusate and ISF are established. Using albumin as analyte, 20 recirculation cycles have been enough to reach equilibrium ISF concentrations. OFM suction is performed by applying a mild vacuum, which pulls ISF from the tissue into the OFM probe. | 1 | Applied and Interdisciplinary Chemistry |
The Pearson symbol, or Pearson notation, is used in crystallography as a means of describing a crystal structure, and was originated by W. B. Pearson. The symbol is made up of two letters followed by a number. For example:
* Diamond structure, cF8
* Rutile structure, tP6
The two (italicised) letters specify the Bravais lattice. The lower-case letter specifies the crystal family, and the upper-case letter the centering type. The number at the end of the Pearson symbol gives the number of the atoms in the conventional unit cell.
The letters A, B and C were formerly used instead of S. When the centred face cuts the X axis, the Bravais lattice is called A-centred. In analogy, when the centred face cuts the Y or Z axis, we have B- or C-centring respectively.
The fourteen possible Bravais lattices are identified by the first two letters: | 0 | Theoretical and Fundamental Chemistry |
The increase in use of Terfenol-D in transducers required new production techniques that increased production rates and quality because the original methods were unreliable and small scale. There are four methods that are used to produce Terfenol-D, which are free stand zone melting, modified Bridgman, sintered powder compact, and polymer matrix composites.
The first two methods, free stand zone melting (FSZM) and modified Bridgman (MB), are capable of producing Terfenol-D that has high magnetostrictive properties and energy densities. However, FSZM cannot produce a rod larger than 8 mm in diameter due to the surface tension of the Terfenol-D and how the FSZM process has no container to restrict the material. The MB process offers a minimum of 10 mm diameter size and is only restricted due to the wall interfering with the crystal growth. Both methods create solid crystals that require later manufacturing if a geometry other than a right-angle cylinder is needed. The solid crystals produced have a fine lamellar structure.
The other two techniques, sintered powder compact and polymer matrix composites, are powder based. These techniques allow for intricate geometry and detail. However, the size is limited to 10mm in diameter and 100mm in length due to the molds used. The resulting microstructures of these powder based methods differ from the solid crystal ones because they do not have a lamellar structure and have a lower density. However, all methods have similar magnetostrictive properties.
Due to size restriction, MB is the best process to produce Terfenol-D, however it is a labor-intensive method. A newer process like MB is ET-Ryma crystal growth (ECG) that results in larger diameter Terfenol-D crystals and increased magnetostrictive performance. The reliability of magnetostrictive properties of the Terfenol-D throughout the life of the material is increased by using ET-Ryma.
Terfenol-D has some minor drawbacks which stem from its material properties. Terfenol-D has low ductility and low fracture resistance. To solve this, Terfenol-D has been added to polymers and other metals to create composites. When added to polymers, the stiffness of the resulting composite is low. When composites of Terfenol-D with ductile metal binders are created, the resulting material has increased stiffness and ductility with reduced magnetostrictive properties. These metal composites may be formed by explosion compaction. In a study done on processing Terfenol-D alloys, the resulting alloys created using copper and Terfenol-D had increased strength and hardness values, which supports the theory that the composites of ductile metal binders and Terfenol-D result in a stronger and more ductile material. | 1 | Applied and Interdisciplinary Chemistry |
Genetic markers can be used to study the relationship between an inherited disease and its genetic cause (for example, a particular mutation of a gene that results in a defective protein). It is known that pieces of DNA that lie near each other on a chromosome tend to be inherited together. This property enables the use of a marker, which can then be used to determine the precise inheritance pattern of the gene that has not yet been exactly localized.
Genetic markers are employed in genealogical DNA testing for genetic genealogy to determine genetic distance between individuals or populations. Uniparental markers (on mitochondrial or Y chromosomal DNA) are studied for assessing maternal or paternal lineages. Autosomal markers are used for all ancestry.
Genetic markers have to be easily identifiable, associated with a specific locus, and highly polymorphic, because homozygotes do not provide any information. Detection of the marker can be direct by RNA sequencing, or indirect using allozymes.
Some of the methods used to study the genome or phylogenetics are RFLP, AFLP, RAPD, SSR. They can be used to create genetic maps of whatever organism is being studied.
There was a debate over what the transmissible agent of CTVT (canine transmissible venereal tumor) was. Many researchers hypothesized that virus like particles were responsible for transforming the cell, while others thought that the cell itself was able to infect other canines as an allograft. With the aid of genetic markers, researchers were able to provide conclusive evidence that the cancerous tumor cell evolved into a transmissible parasite. Furthermore, molecular genetic markers were used to resolve the issue of natural transmission, the breed of origin (phylogenetics), and the age of the canine tumor.
Genetic markers have also been used to measure the genomic response to selection in livestock. Natural and artificial selection leads to a change in the genetic makeup of the cell. The presence of different alleles due to a distorted segregation at the genetic markers is indicative of the difference between selected and non-selected livestock. | 1 | Applied and Interdisciplinary Chemistry |
Response regulator proteins typically consist of a receiver domain and one or more effector domains, although in some cases they possess only a receiver domain and exert their effects through protein-protein interactions. In two-component signaling, a histidine kinase responds to environmental changes by autophosphorylation on a histidine residue, following which the response regulator receiver domain catalyzes transfer of the phosphate group to its own recipient aspartate residue. This induces a conformational change that alters the function of the effector domains, usually resulting in increased transcription of target genes. The mechanisms by which this occurs are diverse and include allosteric activation of the effector domain or oligomerization of phosphorylated response regulators. In a common variation on this theme, called a phosphorelay, a hybrid histidine kinase possesses its own receiver domain, and a histidine phosphotransfer protein performs the final transfer to a response regulator.
In many cases, histidine kinases are bifunctional and also serve as phosphatases, catalyzing the removal of phosphate from response regulator aspartate residues, such that the signal transduced by the response regulator reflects the balance between kinase and phosphatase activity. Many response regulators are also capable of autodephosphorylation, which occurs on a wide range of time scales. In addition, phosphoaspartate is relatively chemically unstable and may be hydrolyzed non-enzymatically.
Histidine kinases are highly specific for their cognate response regulators; there is very little cross-talk between different two-component signaling systems in the same cell. | 1 | Applied and Interdisciplinary Chemistry |
Ceramic solids are composed of inorganic compounds, usually oxides of chemical elements. They are chemically inert, and often are capable of withstanding chemical erosion that occurs in an acidic or caustic environment. Ceramics generally can withstand high temperatures ranging from 1000 to 1600 °C (1800 to 3000 °F). Exceptions include non-oxide inorganic materials, such as nitrides, borides and carbides.
Traditional ceramic raw materials include clay minerals such as kaolinite, more recent materials include aluminium oxide (alumina). The modern ceramic materials, which are classified as advanced ceramics, include silicon carbide and tungsten carbide. Both are valued for their abrasion resistance, and hence find use in such applications as the wear plates of crushing equipment in mining operations.
Most ceramic materials, such as alumina and its compounds, are formed from fine powders, yielding a fine grained polycrystalline microstructure that is filled with light-scattering centers comparable to the wavelength of visible light. Thus, they are generally opaque materials, as opposed to transparent materials. Recent nanoscale (e.g. sol-gel) technology has, however, made possible the production of polycrystalline transparent ceramics such as transparent alumina and alumina compounds for such applications as high-power lasers. Advanced ceramics are also used in the medicine, electrical and electronics industries.
Ceramic engineering is the science and technology of creating solid-state ceramic materials, parts and devices. This is done either by the action of heat, or, at lower temperatures, using precipitation reactions from chemical solutions. The term includes the purification of raw materials, the study and production of the chemical compounds concerned, their formation into components, and the study of their structure, composition and properties.
Mechanically speaking, ceramic materials are brittle, hard, strong in compression and weak in shearing and tension. Brittle materials may exhibit significant tensile strength by supporting a static load. Toughness indicates how much energy a material can absorb before mechanical failure, while fracture toughness (denoted K) describes the ability of a material with inherent microstructural flaws to resist fracture via crack growth and propagation. If a material has a large value of fracture toughness, the basic principles of fracture mechanics suggest that it will most likely undergo ductile fracture. Brittle fracture is very characteristic of most ceramic and glass-ceramic materials that typically exhibit low (and inconsistent) values of K.
For an example of applications of ceramics, the extreme hardness of zirconia is utilized in the manufacture of knife blades, as well as other industrial cutting tools. Ceramics such as alumina, boron carbide and silicon carbide have been used in bulletproof vests to repel large-caliber rifle fire. Silicon nitride parts are used in ceramic ball bearings, where their high hardness makes them wear resistant. In general, ceramics are also chemically resistant and can be used in wet environments where steel bearings would be susceptible to oxidation (or rust).
As another example of ceramic applications, in the early 1980s, Toyota researched production of an adiabatic ceramic engine with an operating temperature of over 6000 °F (3300 °C). Ceramic engines do not require a cooling system and hence allow a major weight reduction and therefore greater fuel efficiency. In a conventional metallic engine, much of the energy released from the fuel must be dissipated as waste heat in order to prevent a meltdown of the metallic parts. Work is also being done in developing ceramic parts for gas turbine engines. Turbine engines made with ceramics could operate more efficiently, giving aircraft greater range and payload for a set amount of fuel. Such engines are not in production, however, because the manufacturing of ceramic parts in the sufficient precision and durability is difficult and costly. Processing methods often result in a wide distribution of microscopic flaws that frequently play a detrimental role in the sintering process, resulting in the proliferation of cracks, and ultimate mechanical failure. | 0 | Theoretical and Fundamental Chemistry |
More than 90% of world industrial production of urea is destined for use as a nitrogen-release fertilizer. Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use. Therefore, it has a low transportation cost per unit of nitrogen nutrient. The most common impurity of synthetic urea is biuret, which impairs plant growth. Urea breaks down in the soil to give ammonium ions (). The ammonium is taken up by the plant through its roots. In some soils, the ammonium is oxidized by bacteria to give nitrate (), which is also a nitrogen-rich plant nutrient. The loss of nitrogenous compounds to the atmosphere and runoff is wasteful and environmentally damaging so urea is sometimes modified to enhance the efficiency of its agricultural use. Techniques to make controlled-release fertilizers that slow the release of nitrogen include the encapsulation of urea in an inert sealant, and conversion of urea into derivatives such as urea-formaldehyde compounds, which degrade into ammonia at a pace matching plants' nutritional requirements. | 0 | Theoretical and Fundamental Chemistry |
Changes in the homeostatic levels of many neurologically active chemicals elicit clinical disorders and symptoms. | 1 | Applied and Interdisciplinary Chemistry |
Glutamate levels are observed to be elevated during mania. Lithium is thought to provide long-term mood stabilization and have anti-manic properties by modulating glutamate levels. It is proposed that lithium competes with magnesium for binding to NMDA glutamate receptor, increasing the availability of glutamate in post-synaptic neurons, leading to a homeostatic increase in glutamate re-uptake which reduces glutamatergic transmission.
The NMDA receptor is also affected by other neurotransmitters such as serotonin and dopamine. Effects observed appear exclusive to lithium and have not been observed by other monovalent ions such as rubidium and caesium. | 1 | Applied and Interdisciplinary Chemistry |
Hydrogel fiber is a hydrogel made into a fibrous state, where its width is significantly smaller than its length. The hydrogel's specific surface area at fibrous form is larger than that of the bulk hydrogel, and its mechanical properties also changed accordingly. As a result of these changes, hydrogel fiber has a faster matter exchange rate and can be woven into different structures.
As a water swollen network with usually low toxicity, hydrogel fiber can be used in a variety of biomedical applications such as drug carrier, optical sensor, and actuator.
But the production of hydrogel fiber can be challenging as the hydrogel is crosslinked and can not be shaped into a fibrous state after polymerization. To make hydrogel into a fibrous state, the pregel solution must be made into fibrous form and then crosslinked while maintaining this shape. | 0 | Theoretical and Fundamental Chemistry |
Modern ammonia plants produce more than 3000 tons per day in one production line. The following diagram shows the set-up of a Haber–Bosch plant:
Depending on its origin, the synthesis gas must first be freed from impurities such as hydrogen sulfide or organic sulphur compounds, which act as a catalyst poison. High concentrations of hydrogen sulfide, which occur in synthesis gas from carbonization coke, are removed in a wet cleaning stage such as the sulfosolvan process, while low concentrations are removed by adsorption on activated carbon. Organosulfur compounds are separated by pressure swing adsorption together with carbon dioxide after CO conversion.
To produce hydrogen by steam reforming, methane reacts with water vapor using a nickel oxide-alumina catalyst in the primary reformer to form carbon monoxide and hydrogen. The energy required for this, the enthalpy ΔH, is 206 kJ/mol.
The methane gas reacts in the primary reformer only partially. To increase the hydrogen yield and keep the content of inert components (i. e. methane) as low as possible, the remaining methane gas is converted in a second step with oxygen to hydrogen and carbon monoxide in the secondary reformer. The secondary reformer is supplied with air as the oxygen source. Also, the required nitrogen for the subsequent ammonia synthesis is added to the gas mixture.
In the third step, the carbon monoxide is oxidized to carbon dioxide, which is called CO conversion or water-gas shift reaction.
Carbon monoxide and carbon dioxide would form carbamates with ammonia, which would clog (as solids) pipelines and apparatus within a short time. In the following process step, the carbon dioxide must therefore be removed from the gas mixture. In contrast to carbon monoxide, carbon dioxide can easily be removed from the gas mixture by gas scrubbing with triethanolamine. The gas mixture then still contains methane and noble gases such as argon, which, however, behave inertly.
The gas mixture is then compressed to operating pressure by turbo compressors. The resulting compression heat is dissipated by heat exchangers; it is used to preheat raw gases.
The actual production of ammonia takes place in the ammonia reactor. The first reactors were bursting under high pressure because the atomic hydrogen in the carbonaceous steel partially recombined into methane and produced cracks in the steel. Bosch, therefore, developed tube reactors consisting of a pressure-bearing steel tube in which a low-carbon iron lining tube was inserted and filled with the catalyst. Hydrogen that diffused through the inner steel pipe escaped to the outside via thin holes in the outer steel jacket, the so-called Bosch holes. A disadvantage of the tubular reactors was the relatively high-pressure loss, which had to be applied again by compression. The development of hydrogen-resistant chromium-molybdenum steels made it possible to construct single-walled pipes.
Modern ammonia reactors are designed as multi-storey reactors with a low-pressure drop, in which the catalysts are distributed as fills over about ten storeys one above the other. The gas mixture flows through them one after the other from top to bottom. Cold gas is injected from the side for cooling. A disadvantage of this reactor type is the incomplete conversion of the cold gas mixture in the last catalyst bed.
Alternatively, the reaction mixture between the catalyst layers is cooled using heat exchangers, whereby the hydrogen-nitrogen mixture is preheated to the reaction temperature. Reactors of this type have three catalyst beds. In addition to good temperature control, this reactor type has the advantage of better conversion of the raw material gases compared to reactors with cold gas injection.
Uhde has developed and is using an ammonia converter with three radial flow catalyst beds and two internal heat exchangers instead of axial flow catalyst beds. This further reduces the pressure drop in the converter.
The reaction product is continuously removed for maximum yield. The gas mixture is cooled to 450 °C in a heat exchanger using water, freshly supplied gases, and other process streams. The ammonia also condenses and is separated in a pressure separator. Unreacted nitrogen and hydrogen are then compressed back to the process by a circulating gas compressor, supplemented with fresh gas, and fed to the reactor. In a subsequent distillation, the product ammonia is purified. | 0 | Theoretical and Fundamental Chemistry |
In 2005 a two hybrid system in plants was developed. Using protoplasts of A. thaliana protein-protein interactions can be studied in plants. This way the interactions can be studied in their native context. In this system the GAL4 AD and BD are under the control of the strong 35S promoter. Interaction is measured using a GUS reporter. In order to enable a high-throughput screening the vectors were made gateway compatible.
The system is known as the protoplast two hybrid (P2H) system. | 1 | Applied and Interdisciplinary Chemistry |
Prof. Blum began her independent research career in 2006 at the University of California, Irvine (UCI). Blum’s research focuses on the development and mechanistic study of reactions in organic, organometallic, catalytic, and materials chemistry, and on monitoring reaction intermediates by a combination of traditional spectroscopy and fluorescence microscopy methods. While many of her initial independent research publications were based on activated complexes of gold or palladium catalysts, she has more recently focused on borylation reactions to make advanced oxygen-, nitrogen-, or sulfur-containing heterocycles, amenable to pharmaceutical and agricultural derivation. Since starting her independent career, Blum developed single-molecule and single-particle techniques, often borrowed from biological or physical contexts, to study chemical processes, including to observe intermediates in "classical" reactions. Blum was elected Fellow of the American Association for the Advancement of Science (AAAS) in 2017 for distinguished contributions to molecular chemistry, particularly for the development of synthetic methods and of fluorescence microscopy tools to study chemical processes. | 0 | Theoretical and Fundamental Chemistry |
The three-dimensional protein structure of OCP (in the OCP form) was solved in 2003, before its photoprotective role had been defined. The 35 kDa protein contains two structural domains: an all-α-helical N-terminal domain (NTD) consisting of two interleaved 4-helix bundles, and a mixed α/β C-terminal domain (CTD). The two domains are connected by an extended linker. In OCP, the carotenoid spans both domains, which are tightly associated in this form of protein. In 2013 Kerfeld and co-workers showed that the NTD is the effector (quencher) domain of the protein while the CTD plays a regulatory role. | 0 | Theoretical and Fundamental Chemistry |
At the age of six, Davy was sent to the grammar school at Penzance. Three years later, his family moved to Varfell, near Ludgvan, and subsequently, in term-time, Davy boarded with John Tonkin, his godfather and later his guardian. Upon Davys leaving grammar school in 1793, Tonkin paid for him to attend Truro Grammar School to finish his education under the Rev Dr Cardew, who, in a letter to the engineer and Fellow of the Royal Society Davies Giddy (from 1817 called Davies Gilbert), said dryly, "I could not discern the faculties by which he was afterwards so much distinguished." Davy entertained his school friends by writing poetry, composing Valentines, and telling stories from One Thousand and One Nights'. Reflecting on his school days in a letter to his mother, Davy wrote, "Learning naturally is a true pleasure; how unfortunate then it is that in most schools it is made a pain." "I consider it fortunate", he continued, "I was left much to myself as a child, and put upon no particular plan of study ... What I am I made myself." His brother said Davy possessed a "native vigour" and "the genuine quality of genius, or of that power of intellect which exalts its possessor above the crowd." | 1 | Applied and Interdisciplinary Chemistry |
The p-hydroxyphenylpyruvate is synthesized from tyrosine, while the solanesyl diphosphate is synthesized through the MEP/DOXP pathway. Homogentisate is formed from p-hydroxyphenylpyruvate and is then combined with solanesyl diphosphate through a condensation reaction. The resulting intermediate, 2-methyl-6-solanesyl-1,4-benzoquinol is then methylated to form the final product, plastoquinol-9. This pathway is used in most photosynthetic organisms, like algae and plants. However, cyanobacteria appear to not use homogentisate for synthesizing plastoquinol, possibly resulting in a pathway different from the one shown below. | 0 | Theoretical and Fundamental Chemistry |
The dual fluid reactor (DFR) has a variant DFR/m which works with eutectic liquid metal alloys, e.g. U-Cr or U-Fe. | 0 | Theoretical and Fundamental Chemistry |
A preform is a pre-made shape of solder specially designed for the application where it is to be used. Many methods are used to manufacture the solder preform, stamping being the most common. The solder preform may include the solder flux needed for the soldering process. This can be an internal flux, inside the solder preform, or external, with the solder preform coated. | 1 | Applied and Interdisciplinary Chemistry |
Most protein pharmaceuticals are now produced through recombinant DNA technology using expression vectors. These peptide and protein pharmaceuticals may be hormones, vaccines, antibiotics, antibodies, and enzymes. The first human recombinant protein used for disease management, insulin, was introduced in 1982. Biotechnology allows these peptide and protein pharmaceuticals, some of which were previously rare or difficult to obtain, to be produced in large quantity. It also reduces the risks of contaminants such as host viruses, toxins and prions. Examples from the past include prion contamination in growth hormone extracted from pituitary glands harvested from human cadavers, which caused Creutzfeldt–Jakob disease in patients receiving treatment for dwarfism, and viral contaminants in clotting factor VIII isolated from human blood that resulted in the transmission of viral diseases such as hepatitis and AIDS. Such risk is reduced or removed completely when the proteins are produced in non-human host cells. | 1 | Applied and Interdisciplinary Chemistry |
Although many authors implicitly envisaged a traditional Sanger sequencing-based decoding, the number of codes to sequence simply according to the complexity of the library is definitely an unrealistic task for a traditional Sanger sequencing approach. Nevertheless, the implementation of Sanger sequencing for decoding DNA-encoded chemical libraries in high-throughput fashion was the first to be described. After selection and PCR amplification of the DNA-tags of the library compounds, concatamers containing multiple coding sequences were generated and ligated into a vector. Following Sanger sequencing of a representative number of the resulting colonies revealed the frequencies of the codes present in the DNA-encoded library sample before and after selection. | 1 | Applied and Interdisciplinary Chemistry |
* Contemporary Academic Research, page 24, Jan. 2008, written by Tingjun Wang, "Study of the Secret of Golden Flower internal alchemy practise". [https://archive.today/20130125223513/www.hktmc.com/ChineseMedia/Magazine/Education/62xdxsyj/15contents/2008/200801di17qi.aspx in Chinese] [http://www.daoism.ro/studiu-asupra-practicii-cultivarii-de-sine-a-misterului-florii-de-aur-a-marelui-unu-part-1/ Romanian Translation ] | 1 | Applied and Interdisciplinary Chemistry |
Regiospecific formation is the controlled enolate formation by the specific deprotonation at one of the α-carbons of the ketone starting molecule. This provides one of the best understood synthetic strategies to introduce chemical complexity in natural product and total syntheses. A prominent example of its use is in the total synthesis of progesterone illustrated in Figure "Regiospecific enolate formation in the total synthesis of progesterone".
When ketones are treated with base, enolates can be formed by deprotonation at either α-carbon. The selectivity is determined by both the steric and electronic effects on the α-carbons as well as the precise base used (see figure ""Masked functionality" for regiospecific enolate formation" for an example of this). Enolate formation will be thermodynamically favoured at the most acidic proton which depends on the electronic stabilization of the resulting anion. However, the selectivity can be reversed by sterically hindering the thermodynamic product and therefore kinetically favouring deprotonation at the other α-carbon centre. Traditional methods for regioselective enolate formation use either electronic activating groups (e.g. aldehydes) or steric blocking groups (e.g. 1,2-ethanedithiol protected ketone).
An enone can also serve as a precursor for regiospecific formation of an enolate, here the enone is a "masked functionality" for the enolate. This process is first described by Gilbert Stork who is best known for his contributions to the study of selective enolate formation methods in organic synthesis. Reacting an enone with lithium metal generates the enolate at the α-carbon of the enone. The enolate product can either be trapped or alkylated. By using "masked functionality", it is possible to produce enolates that are not accessible by traditional methods.
The "masked functionality" approach to regiospecific enolate formation has been widely used in the total synthesis of natural products. For example, in the total synthesis of the steroid hormone progesterone, Stork and co-workers used the "masked functionality" to stereospecifically construct one of the quaternary carbons in the molecule. | 0 | Theoretical and Fundamental Chemistry |
Allylic strain (also known as A strain, 1,3-allylic strain, or A-strain) in organic chemistry is a type of strain energy resulting from the interaction between a substituent on one end of an olefin (a synonym for an alkene) with an allylic substituent on the other end. If the substituents (R and R') are large enough in size, they can sterically interfere with each other such that one conformer is greatly favored over the other. Allylic strain was first recognized in the literature in 1965 by Johnson and Malhotra. The authors were investigating cyclohexane conformations including endocyclic and exocylic double bonds when they noticed certain conformations were disfavored due to the geometry constraints caused by the double bond. Organic chemists capitalize on the rigidity resulting from allylic strain for use in asymmetric reactions. | 0 | Theoretical and Fundamental Chemistry |
Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and propane.
The most common example is dichlorodifluoromethane (R-12). R-12 is also commonly called Freon and was used as a refrigerant. Many CFCs have been widely used as refrigerants, propellants (in aerosol applications), gaseous fire suppression systems, and solvents. As a result of CFCs contributing to ozone depletion in the upper atmosphere, the manufacture of such compounds has been phased out under the Montreal Protocol, and they are being replaced with other products such as hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs) including R-410A,R-134a and R-1234yf. | 1 | Applied and Interdisciplinary Chemistry |
Initially, the chemical reactions that normally occur in the cement paste, generate an alkaline environment, bringing the solution in the cement paste pores to pH values around 13. In these conditions, passivation of steel rebar occurs, due to a spontaneous generation of a thin film of oxides able to protect the steel from corrosion. Over time, the thin film can be damaged, and corrosion of steel rebar starts. The corrosion of steel rebar is one of the main causes of premature failure of reinforced concrete structures worldwide, mainly as a consequence of two degradation processes, carbonation and penetration of chlorides. With regard to the corrosion degradation process, a simple and accredited model for the assessment of the service life is the one proposed by Tuutti, in 1982. According to this model, the service life of a reinforced concrete structure can be divided into two distinct phases.
* , initiation time: from the moment the structure is built, to the moment corrosion initiates on steel rebar. More in particular, it is the time required for aggressive agents (carbon dioxide and chlorides) to penetrate the concrete cover thickness, reach the embedded steel rebar, alter the initial passivation condition on steel surface and cause corrosion initiation.
* , propagation time: which is defined as the time from the onset of active corrosion until an ultimate limit state is reached, i.e. corrosion propagation reaches a limit value corresponding to unacceptable structural damage, such as cracking and detachment of the concrete cover thickness.
The identification of initiation time and propagation time is useful to further identify the main variables and processes influencing the service life of the structure which are specific of each service life phase and of the degradation process considered. | 1 | Applied and Interdisciplinary Chemistry |
The releasable pool is located in the active zone and is bound directly to the presynaptic membrane. It is stabilized by proteins within the active zone and bound to the presynaptic membrane by SNARE proteins. These vesicles are ready to release by a single action potential and are replenished by vesicles from the reserve pool. The releasable pool is sometimes subdivided into the readily releasable pool and the releasable pool. | 1 | Applied and Interdisciplinary Chemistry |
The Köhler curve is the visual representation of the Köhler equation. It shows the supersaturation at which the cloud drop is in equilibrium with the environment over a range of droplet diameters. The exact shape of the curve is dependent upon the amount and composition of the solutes present in the atmosphere. The Köhler curves where the solute is sodium chloride are different from when the solute is sodium nitrate or ammonium sulfate.
The figure above shows three Köhler curves of sodium chloride. Consider (for droplets containing solute with diameter equal to 0.05 micrometers) a point on the graph where the wet diameter is 0.1 micrometers and the supersaturation is 0.35%. Since the relative humidity is above 100%, the droplet will grow until it is in thermodynamic equilibrium. As the droplet grows, it never encounters equilibrium, and thus grows without bound. However, if the supersaturation is only 0.3%, the drop will only grow until about 0.5 micrometers. The supersaturation at which the drop will grow without bound is called the critical supersaturation. The diameter at which the curve peaks is called the critical diameter. | 0 | Theoretical and Fundamental Chemistry |
The general methodology of TAP data analysis, developed in a series of papers by Grigoriy (Gregory) Yablonsky
is based on comparing an inert gas response which is controlled only by Knudsen diffusion
with a reactive gas response which is controlled by diffusion as well as adsorption and chemical reactions on the catalyst sample.
TAP pulse-response experiments can be effectively modeled by a one-dimensional (1D) diffusion equation with uniquely simple combination of boundary conditions. | 0 | Theoretical and Fundamental Chemistry |
The efficiency of the blast furnace was improved by the change to hot blast, patented by James Beaumont Neilson in Scotland in 1828. This further reduced production costs. Within a few decades, the practice was to have a stove as large as the furnace next to it into which the waste gas (containing CO) from the furnace was directed and burnt. The resultant heat was used to preheat the air blown into the furnace. | 1 | Applied and Interdisciplinary Chemistry |
2,3-Butanediol fermentation is anaerobic fermentation of glucose with 2,3-butanediol as one of the end products. The overall stoichiometry of the reaction is
:2 pyruvate + NADH --> 2CO + 2,3-butanediol.
Butanediol fermentation is typical for the facultative anaerobes Klebsiella and Enterobacter and is tested for using the Voges–Proskauer (VP) test. There are other alternative strains that can be used, talked about in details in the Alternative Bacteria Strains section below.
The metabolic function of 2,3-butanediol is not known, although some have speculated that it was an evolutionary advantage for these microorganisms to produce a neutral product thats less inhibitory than other partial oxidation products and doesnt reduce the pH as much as mixed acids.
There are many important industrial applications that butanediol can be used for, including antifreeze, food additives, antiseptic, and pharmaceuticals. It also is produced naturally in various places of the environment. | 1 | Applied and Interdisciplinary Chemistry |
Nanocar Race is an international scientific competition with the aim of testing the performance of getting a large molecule suspended over a solid surface to cover the largest distance with the use of a scanning tunneling microscope.
The first race consisted of overcoming a distance of 100 nanometer and was held for the first time in Toulouse on 28 and 29 April 2017. A second race was held in 2022 with the winners covering multiple hundreds of nanometers. | 0 | Theoretical and Fundamental Chemistry |
One of the primary functions of carbaminohemoglobin is to enable the transport of carbon dioxide in the bloodstream. When carbon dioxide is produced as a waste product of cellular metabolism in tissues, the compound is diffused into the bloodstream and it works to react with hemoglobin.
When the binding of molecules occurs to form carbaminohemoglobin, it allows for the transport of carbon dioxide from the tissues to the lungs. One it is in the lungs, carbon dioxide is released from carbaminohemoglobin and can be let out from the body during the exhalation process. This complete process is very important for maintaining the balance of gases in the blood and to ensure that gas exchange is being transported between tissues and organs. | 1 | Applied and Interdisciplinary Chemistry |
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