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Dialysis has a wide range of applications. These can be divided into two categories depending on the type of dialysis used. | 1 | Biochemistry |
Twin laws are symmetry operations that define the orientation between twin crystal segments. These are as characteristic of the mineral as are its crystal face angles. For example, crystals of staurolite show twinning at angles of almost precisely 90 degrees or 30 degrees. A twin law is not a symmetry operation of the full set of basis points.
Twin laws include reflection operations, rotation operations, and the inversion operation. Reflection twinning is described by the Miller indices of the twin plane (i.e. {hkl}) while rotational twinning is described by the direction of the twin axis (i.e. <hkl>). Inversion twinning is typically equivalent to a reflection or rotation symmetry.
Rotational twin laws are almost always 2-fold rotations, though any other permitted rotation symmetry (3-fold, 4-fold, 5-fold or 6-fold) is possible. The twin axis will be perpendicular to a lattice plane. It is possible for a rotational twin law to share the same axis as a rotational symmetry of the individual crystal if the twin law is a 2-fold rotation and the symmetry operation is a 3-fold rotation. This is the case for spinel law twinning on <111>: The spinel structure has a 3-fold rotational symmetry on <111> and spinel is commonly twinned by 2-fold rotation on <111>.
The boundary between crystal segments is called a composition surface or, if it is planar, a composition plane. The composition plane is often, though not always, parallel to the twin law plane of a reflection law. If this is the case, the twin plane is always parallel to a possible crystal face. | 3 | Analytical Chemistry |
A compressor map shows the operating range of a compressor and how well it works within its operating range. Two fundamental requirements for the gas flowing through a compressor explain why it works best at a design condition and not so well at other conditions, known as off-design. First, the exit area has to be smaller than the inlet area because the compressed gas has a higher density. The exit area is sized to pass the specific volume at the design condition. Second, all the rotor and stator blades in an axial compressor, and impeller inducer and diffuser vanes in a centrifugal compressor, are angled to meet approaching air head-on at the design condition to minimize incidence losses. Incidence losses reduce the efficiency of compression. Satisfactory operation of the compressor relies on controlling the angle at which the gas approaches rotating and stationary blades to within an acceptable range. Deviating from the optimum first results in increased losses/reduced efficiency then either stalling or sonic velocity/choking which occur in the blade passages at opposite ends of an axial compressor at the same time. They also occur in a centrifugal compressor at entry to the impeller and in the diffuser.
The compressor design point will be in an area of high efficiency whether the compressor is part of a gas turbine engine or whether it is used for pumping air into a blast furnace. However the compressor has to provide suitable performance at other operating conditions imposed on it which means a high efficiency is required over a wider range of operation. In the case of a gas turbine engine it must permit the engine to be started readily and accelerated rapidly to the design speed which means operating at lower speeds than the design speed. At speeds and flows away from the design point the compressor flow area reduction is not appropriate for the actual density rise. A NACA report illustrates pictorially the difference in contraction required at the design condition and at low speed. At lower speeds, for example, the gas hasn't been compressed enough to exit the compressor without adversely affecting the blade angles of attack through the compressor. Away from the design point the middle stages of an axial compressor continue to operate at about the optimum angle of attack but the front stages deviate one way, towards stall, and the rear stages in the opposite direction towards choke. The deviation was acceptable up to a design pressure ratio of about 5:1, producing only a loss in efficiency. At higher design pressure ratios prevention of rotating stall, which occurs at low corrected speeds, and choking was required with the introduction of inlet guide vanes which partially closed at low speeds, or by removing air part-way along the compressor at low speeds. Rows of variable stators or split compressors, which allowed the front stages to speed up and the rear to slow down relative to each other, would also be introduced for the same reason. When pressure ratios reached about 12:1 compressors would incorporate more than one of these features together. | 7 | Physical Chemistry |
In course of his research and scholastic endeavors, Achinewhu has visited many universities and has received a number of international as well as local awards. | 1 | Biochemistry |
Yuri Berlin received his master's degree in Physics from the Moscow Engineering Physics Institute in 1968, studying luminescence of aromatic molecules dissolved in organic liquids. During the period 1968-1974, Berlin worked as a research fellow at the Institute of Chemical Physics, the USSR Academy of Science, and in 1974 completed his PhD studies at the Moscow Institute for Physics and Technology under the supervision of Victor Talrose. His thesis was focused on the development of theory for the ion-pair mechanism of radiolysis of non-polar liquids. | 7 | Physical Chemistry |
Hundreds of metal artefacts were found from the Late Bronze Age (second half of 2nd millennium BCE): ca.
200 blade weapons, 140 metal vessels, some working tools, small arrowheads, and decorative objects. All
the blades analyzed were made of tin bronze and most of all the other copper-based objects are either tin bronze alloy or have tin in their metal as impurity.
At this stage, large quantities of copper and tin ingots (i.e., 10 tons of Cu and 3 tons of Sn ingots in one cargo of Uluburun shipwreck from the 14th century BCE) were found all over the coasts of the Mediterranean and in several shipwrecks under the sea, mainly off the southern coast of Turkey. In Canaan at that time, Cypriot, Egyptian, Syrian, and Mesopotamian types of bronze objects were found, besides the local Canaanite metal collection. These were all basically made of tin bronze. The “prestige” objects like sickle blade swords or cast-hilt daggers were alloyed with highquality (11–13% by weight) Sn, whereas the simpler and probably less expensive objects had lower levels of tin in the metal. | 8 | Metallurgy |
A metallacarboxylic acid is a metal complex with the ligand COH. These compounds are intermediates in reactions that involve carbon monoxide and carbon dioxide, these species are intermediates in the water gas shift reaction. Metallacarboxylic acids are also called hydroxycarbonyls. | 0 | Organic Chemistry |
In quantum mechanics, ionized impurity scattering is the scattering of charge carriers by ionization in the lattice. The most primitive models can be conceptually understood as a particle responding to unbalanced local charge that arises near a crystal impurity; similar to an electron encountering an electric field. This effect is the mechanism by which doping decreases mobility.
In the current quantum mechanical picture of conductivity the ease with which electrons traverse a crystal lattice is dependent on the near perfectly regular spacing of ions in that lattice. Only when a lattice contains perfectly regular spacing can the ion-lattice interaction (scattering) lead to almost transparent behavior of the lattice. Impurity atoms in a crystal have an effect similar to thermal vibrations where conductivity has a direct relationship with temperature.
A crystal with impurities is less regular than a pure crystal, and a reduction in electron mean free paths occurs. Impure crystals have lower conductivity than pure crystals with less temperature sensitivity in that lattice. | 7 | Physical Chemistry |
Kinesis, like a taxis or tropism, is a movement or activity of a cell or an organism in response to a stimulus (such as gas exposure, light intensity or ambient temperature).
Unlike taxis, the response to the stimulus provided is non-directional. The animal does not move toward or away from the stimulus but moves at either a slow or fast rate depending on its "comfort zone." In this case, a fast movement (non-random) means that the animal is searching for its comfort zone while a slow movement indicates that it has found it. | 1 | Biochemistry |
Separation processes are used to decrease the complexity of material mixtures. Chromatography and electrophoresis are representative of this field. | 3 | Analytical Chemistry |
Photochromic coordination complexes are relatively rare in comparison to the organic compounds listed above. There are two major classes of photochromic coordination compounds. Those based on sodium nitroprusside and the ruthenium sulfoxide compounds. The ruthenium sulfoxide complexes were created and developed by Rack and coworkers. The mode of action is an excited state isomerization of a sulfoxide ligand on a ruthenium polypyridine fragment from S to O or O to S. The difference in bonding from between Ru and S or O leads to the dramatic color change and change in Ru(III/II) reduction potential. The ground state is always S-bonded and the metastable state is always O-bonded. Typically, absorption maxima changes of nearly 100 nm are observed. The metastable states (O-bonded isomers) of this class often revert thermally to their respective ground states (S-bonded isomers), although a number of examples exhibit two-color reversible photochromism. Ultrafast spectroscopy of these compounds has revealed exceptionally fast isomerization lifetimes ranging from 1.5 nanoseconds to 48 picoseconds. | 5 | Photochemistry |
α-Halo carboxylic acids and esters are organic compounds with the respective formulas where R and R' are organic substituents. The X in these compounds is a halide, usually chloride and bromide. These compounds are often used as intermediates in the preparation of more elaborate derivatives. They are often potent alkylating agents. The mono halide derivatives are chiral. | 0 | Organic Chemistry |
Dexpramipexole is the (D)-enantiomer of pramipexole. Enantiopure dexpramipexole has essentially no dopamine agonist activity and shares no other pharmacologic similarity to pramipexole. In contrast, pramipexole the (S)-enantiomer is a dopamine agonist and is an approved drug (Mirapex) used in Parkinson’s disease.
Dexpramipexole is a low molecular weight, orally bioavailable, water-soluble small molecule with linear pharmacokinetics and linear dose proportionality. | 4 | Stereochemistry |
One criticism of the concept of the control coefficient as defined above is that it is dependent on being described relative to a change in enzyme activity. Instead, the Berlin school defined control coefficients in terms of changes to local rates brought about by any suitable parameter, which could include changes to enzyme levels or the action of drugs. Hence a more general definition is given by the following expressions:
and concentration control coefficients by
In the above expression, could be any convenient parameter. For example, a drug, changes in enzyme expression etc. The advantage is that the control coefficient becomes independent of the applied perturbation. For control coefficients defined in terms of changes in enzyme expression, it is often assumed that the effect on the local rate by changes to the enzyme activity is proportional so that: | 1 | Biochemistry |
The earliest estimated use of bitumen dates back 40,000 years to the paleolithic age in which Bitumen was used to adhere handles onto primitive stone tools.
A re-examination of artifacts uncovered in 1908 at Le Moustier rock shelters in France has identified Mousterian stone tools that were attached to grips made of ochre and bitumen. The grips were formulated with 55% ground goethite ochre and 45% cooked liquid bitumen to create a moldable putty that hardened into handles. Earlier excavations at Le Moustier prevent conclusive identification of the archaeological culture and age, but the European Mousterian style of these tools suggests they are associated with Neanderthals during the late Middle Paleolithic, between 60,000 and 35,000 years before present. It is the earliest evidence of compound adhesive use in Europe. | 7 | Physical Chemistry |
Following oral administration of lisinopril, peak serum concentrations of lisinopril occur within about seven hours, although there was a trend to a small delay in time taken to reach peak serum concentrations in acute myocardial infarction patients. The peak effect of lisinopril is about 6 hours after administration for most people. Declining serum concentrations exhibit a prolonged terminal phase, which does not contribute to drug accumulation. This terminal phase probably represents saturable binding to ACE and is not proportional to dose. Lisinopril does not undergo metabolism and absorbed drug is excreted unchanged entirely in the urine. Based on urinary recovery, the mean extent of absorption of lisinopril is approximately 25% (reduced to 16% in people with New York Heart Association Functional Classification (NYHA) Class II–IV heart failure), with large interpatient variability (6 to 60%) at all doses tested (5 to 80 mg). Lisinopril absorption is not affected by the presence of food in the gastrointestinal tract.
Studies in rats indicate that lisinopril crosses the blood-brain barrier poorly. Multiple doses of lisinopril in rats result in little or no accumulation in brain tissue. | 4 | Stereochemistry |
* Foreign DNA inserted
* Insertional mutagenesis (but not lethal for the plant cell – as the organism is diploid)
* Transformation DNA fed to rodents ends up in their phagocytes and rarely in other cells. Specifically, this refers to bacterial and M13 DNA. (This preferential accumulation in phagocytes is thought to be real and not a detection artefact since these DNA sequences are thought to provoke phagocytosis.) However, no gene expression is known to have resulted, and this is not thought to be possible. | 1 | Biochemistry |
Carbon–carbon bond-forming reactions are organic reactions in which a new carbon–carbon bond is formed. They are important in the production of many human-made chemicals such as pharmaceuticals and plastics. The reverse reaction, where a carbon-carbon bond is broken, is known as carbon-carbon bond activation.
Some examples of reactions which form carbon–carbon bonds are the aldol reaction, Diels–Alder reaction, Grignard reaction, cross-coupling reactions, the Michael reaction and the Wittig reaction.
The directed synthesis of desired three-dimensional structures for tertiary carbons was largely solved during the late 20th century, but the same ability to direct quaternary carbon synthesis did not start to emerge until the first decade of the 21st century. | 0 | Organic Chemistry |
Due to the similar aqueous chemistries of aluminium and iron, it has been long thought that an analogous iron polycation should be isolatable from water. Moreover, in 2007, the structure of ferrihydrite was determined and shown to be built of iron Keggin ions. This further captured scientists' imagination and drive to isolate the iron Keggin ion. In 2015, the iron Keggin ion was isolated from water, but as a polyanion with a −17 charge; and protecting chemistry was required. Iron-bound water is very acidic; so it is difficult to capture the intermediate Keggin ion form without bulky and nonprotic ligands instead of the water that is found in the aluminum Keggin ion. However, more important in this synthesis was the bismuth () counterions that provided high positive charge to stabilize the high negative charge of the heptadecavalent polyanion. | 7 | Physical Chemistry |
It also brings around the conversion of a hydrazone to a diazo compound, for example in the diazo-thioketone coupling. It also converts thioacetals to their parent carbonyl compounds. | 0 | Organic Chemistry |
Turning now to quantum mechanics an atom or a molecule can be thought of as a collection of point charges (electrons and nuclei), so that the second definition of the dipole applies. The interaction of atom or molecule with a uniform external field is described by the operator
This operator is used as a perturbation in first- and second-order perturbation theory to account for the first- and second-order Stark effect. | 7 | Physical Chemistry |
The diagnosis is generally based on symptoms and supported by a lithium level blood level. Blood levels are most useful six to twelve hours after the last dose. The normal blood serum lithium level in those on treatment is between 0.6-1.2 mEq/L. Some blood tubes contain lithium heparin which may result in falsely positive results.
When lithium toxicity is suspected tests may include:
*fingerstick glucose
* serum lithium concentration
*basic metabolic panel to assess renal function
* serum acetaminophen and salicylate concentrations to rule out other sources of acute ingestion
*urine pregnancy tests to ensure management does not cause abortion
Imaging tests are not helpful. | 1 | Biochemistry |
Immunofluorescence (IF) is a light microscopy-based technique that allows detection and localization of a wide variety of target biomolecules within a cell or tissue at a quantitative level. The technique utilizes the binding specificity of antibodies and antigens. The specific region an antibody recognizes on an antigen is called an epitope. Several antibodies can recognize the same epitope but differ in their binding affinity. The antibody with the higher affinity for a specific epitope will surpass antibodies with a lower affinity for the same epitope.
By conjugating the antibody to a fluorophore, the position of the target biomolecule is visualized by exciting the fluorophore and measuring the emission of light in a specific predefined wavelength using a fluorescence microscope. It is imperative that the binding of the fluorophore to the antibody itself, do not interfere with the immunological specificity of the antibody or the binding capacity of its antigen.
Immunofluorescence is a widely used example of immunostaining (using antibodies to stain proteins) and is a specific example of immunohistochemistry (the use of the antibody-antigen relationship in tissues). This technique primarily utilizes fluorophores to visualize the location of the antibodies, while others provoke a color change in the environment containing the antigen of interest or make use of a radioactive label. Immunofluorescent techniques that utilized labelled antibodies was conceptualized in the 1940’s by Albert H. Coons.
Immunofluorescence is employed in foundational scientific investigations and clinical diagnostic endeavors, showcasing its multifaceted utility across diverse substrates, including tissue sections, cultured cell lines, or individual cells. Its usage includes analysis of the distribution of proteins, glycans, small biological and non-biological molecules, and visualization of structures such as intermediate-sized filaments.
If the topology of a cell membrane is undetermined, epitope insertion into proteins can be used in conjunction with immunofluorescence to determine structures within the cell membrane. Immunofluorescence (IF) can also be used as a “semi-quantitative” method to gain insight into the levels and localization patterns of DNA methylation. IF can additionally be used in combination with other, non-antibody methods of fluorescent staining, e.g., the use of DAPI to label DNA.
Examination of immunofluorescence specimens can be conducted utilizing various microscope configurations, including the epifluorescence microscope, confocal microscope, and widefield microscope. | 1 | Biochemistry |
Large quantities of wood flour are frequently to be found in the waste from woodworking and furniture companies. An adaptive reuse to which this material can be directed is composting.
Wood flour can be subject to dust explosions if not cared for and disposed of properly. | 2 | Environmental Chemistry |
Chiral inversion is the process of conversion of one enantiomer of a chiral molecule to its mirror-image version with no other change in the molecule.
Chiral inversion happens depending on various factors (viz. biological-, solvent-, light-, temperature- induced, etc.) and the energy barrier associated with the stereogenic element present in the chiral molecule. 2-Arylpropionic acid nonsteroidal anti-inflammatory drugs (NSAIDs) provide one of the best pharmaceutical examples of chiral inversion. Chirality is attributed to a molecule due to the presence of a stereogenic element (viz. center, planar, helical, or axis). Many pharmaceutical drugs are chiral and have a labile (configurationally unstable) stereogenic element. Chiral compounds with stereogenic center are found to have high energy barriers for inversion and generally undergo biologically mediated chiral inversion. While compounds with helical or planar chirality have low energy barriers and chiral inversions are often caused by solvent, light, temperature. When this happens, the configuration of the chiral molecule may rapidly change reversibly or irreversibly depending on the conditions. The chiral inversion has been intensively studied in the context of the pharmacological and toxicological consequences. Other than NSAIDs, chiral drugs with different chemical structures can also show this effect.
Chiral drugs have different effects on the body depending on whether one enantiomer or both enantiomers act on different biological targets. As a result, chiral inversion can change how a pharmaceutical drug works in the body. From a pharmacological and toxicological point of view, it is very important to learn more about chiral inversion, the things that make it happen, and the tools used to figure out chiral inversion. | 4 | Stereochemistry |
Fumagillin and the related fumagillol (the hydrolysis product) have been a target in total synthesis, with several reported successful strategies, racemic, asymmetric, and formal. | 0 | Organic Chemistry |
The microscopic model and most optical properties of ensembles of the NV centers have been firmly established in the 1970s based on the optical measurements combined with uniaxial stress and on the electron paramagnetic resonance. However, a minor error in EPR results (it was assumed that illumination is required to observe NV EPR signals) resulted in the incorrect multiplicity assignments in the energy level structure. In 1991 it was shown that EPR can be observed without illumination, which established the energy level scheme shown above. The magnetic splitting in the excited state has been measured only recently.
The characterization of single NV centers has become a very competitive field nowadays, with many dozens of papers published in the most prestigious scientific journals. One of the first results was reported back in 1997. In that paper, it was demonstrated that the fluorescence of single NV centers can be detected by room-temperature fluorescence microscopy and that the defect shows perfect photostability. Also one of the outstanding properties of the NV center was demonstrated, namely room-temperature optically detected magnetic resonance. | 7 | Physical Chemistry |
Butyric acid is used in the preparation of various butyrate esters. It is used to produce cellulose acetate butyrate (CAB), which is used in a wide variety of tools, paints, and coatings, and is more resistant to degradation than cellulose acetate. CAB can degrade with exposure to heat and moisture, releasing butyric acid.
Low-molecular-weight esters of butyric acid, such as methyl butyrate, have mostly pleasant aromas or tastes. As a consequence, they are used as food and perfume additives. It is an approved food flavoring in the EU FLAVIS database (number 08.005).
Due to its powerful odor, it has also been used as a fishing bait additive. Many of the commercially available flavors used in carp (Cyprinus carpio) baits use butyric acid as their ester base. It is not clear whether fish are attracted by the butyric acid itself or the substances added to it. Butyric acid was one of the few organic acids shown to be palatable for both tench and bitterling. The substance has been used as a stink bomb by the Sea Shepherd Conservation Society to disrupt Japanese whaling crews. | 1 | Biochemistry |
Building on the reactivity of the triphenylphosphine ligand, the structure of ligands used for the Tsuji–Trost reaction quickly became more complex. Today, these ligands may contain phosphorus, sulfur, nitrogen or some combination of these elements, but most studies have concentrated on the mono- and diphosphine ligands. These ligands can be further classified based on the nature of their chirality, with some ligands containing central chirality on the phosphorus or carbon atoms, some containing biaryl axial chirality, and others containing planar chirality.
Diphosphine ligands with central chirality emerged as an effective type of ligand (particularly for asymmetric allylic alkylation procedures) with the Trost Ligand being one such example.
Phosphinooxazolines (PHOX) ligands have been employed in the AAA, particularly with carbon-based nucleophiles. | 0 | Organic Chemistry |
The cell used in this process consists of an iron tank lined with carbon at the bottom.
A molten alloy of copper, crude aluminium and silicon is used as the anode. It forms the lowermost layer in the cell.
The middle layer consists of molten mixture of fluorides of sodium, aluminium and barium (cryolite + BaF).
The uppermost layer consists of molten aluminium.
A set of graphite rods dipped in molten aluminium serve as the cathode.
During electrolysis, Al ions from the middle layer migrate to the upper layer, where they are reduced to aluminum by gaining 3 electrons.
Equal numbers of Al ions are produced in the lower layer. These ions migrate to the middle layer. Pure aluminium is tapped off from time to time. The Hoopes process gives about 99.99% pure aluminium. | 8 | Metallurgy |
Sunflower trypsin inhibitor (SFTI) is a small, circular peptide produced in sunflower seeds, and is a potent inhibitor of trypsin. It is the smallest known member of the Bowman-Birk family of serine protease inhibitors.
One example of Sunflower trypsin inhibitor is Sunflower trypsin inhibitor-1 (SFTI-1). Sunflower trypsin inhibitor-1 is a potent Bowman-Birk inhibitor. Sunflower trypsin inhibitor-1 is the simplest cysteine-rich peptide scaffold because it is a bicyclic 14 amino acid peptide and only has one disulfide bond. The disulfide bond divides the peptide into two loops. One loop is a functional trypsin inhibitory and the second loop is a nonfunctional loop. The nonfunctional loop can be replaced by a bioactive loop. It is extracted from a seed of a sunflower called Helianthus annuus. The synthesis of SFTI is not known however, it can evolutionarily linked to a gene-coded product from classic Bowman-Birk inhibitors. STFI is used in radiopharmaceutical, antimicrobial, and pro-angiogenic peptides. | 1 | Biochemistry |
Chemists have demonstrated that many artificial supramolecular systems can be designed that exhibit molecular recognition. One of the earliest examples of such a system are crown ethers which are capable of selectively binding specific cations. However, a number of artificial systems have since been established. | 6 | Supramolecular Chemistry |
Whenever a water molecule leaves a surface and diffuses into a surrounding gas, it is said to have evaporated. Each individual water molecule which transitions between a more associated (liquid) and a less associated (vapor/gas) state does so through the absorption or release of kinetic energy. The aggregate measurement of this kinetic energy transfer is defined as thermal energy and occurs only when there is differential in the temperature of the water molecules. Liquid water that becomes water vapor takes a parcel of heat with it, in a process called evaporative cooling. The amount of water vapor in the air determines how frequently molecules will return to the surface. When a net evaporation occurs, the body of water will undergo a net cooling directly related to the loss of water.
In the US, the National Weather Service measures the actual rate of evaporation from a standardized "pan" open water surface outdoors, at various locations nationwide. Others do likewise around the world. The US data is collected and compiled into an annual evaporation map. The measurements range from under 30 to over 120 inches per year. Formulas can be used for calculating the rate of evaporation from a water surface such as a swimming pool. In some countries, the evaporation rate far exceeds the precipitation rate.
Evaporative cooling is restricted by atmospheric conditions. Humidity is the amount of water vapor in the air. The vapor content of air is measured with devices known as hygrometers. The measurements are usually expressed as specific humidity or percent relative humidity. The temperatures of the atmosphere and the water surface determine the equilibrium vapor pressure; 100% relative humidity occurs when the partial pressure of water vapor is equal to the equilibrium vapor pressure. This condition is often referred to as complete saturation. Humidity ranges from 0 grams per cubic metre in dry air to 30 grams per cubic metre (0.03 ounce per cubic foot) when the vapor is saturated at 30 °C. | 2 | Environmental Chemistry |
* 2Fe–2S: AOX1; FDX1; FDX2; NDUFS1; SDHB; XDH;
* 4Fe–4S: ABCE1; DPYD; NDUFS8; | 5 | Photochemistry |
Flow injection analysis (FIA) was first described by Ruzicka and Hansen in Denmark and Stewart and coworkers in United States in the middle of 1970. FIA is a popular, simple, rapid, and versatile technique which is a well-established position in modern analytical chemistry, and widespread application in quantitative chemical analysis. | 3 | Analytical Chemistry |
In addition to the qualities mentioned for Genetic engineering, a Genetic tool also:-
* Used for analysis of gene expression and protein functioning in signature-tagging mutagenesis.
** This analytical tool allows researchers the ability to determine phenotypic expression of gene sequences. Also, this analytic technique mutates the desired locus of interest so that the phenotypes of the original and the mutated gene can be compared. | 1 | Biochemistry |
Fluorescent labeling is known for its non-destructive nature and high sensitivity. This has made it one of the most widely used methods for labeling and tracking biomolecules. Several techniques of fluorescent labeling can be utilized depending on the nature of the target. | 1 | Biochemistry |
The salen anion forms complexes with most transition metals. These complexes are usually prepared by the reaction of Hsalen ("proligand") with metal precursors containing built-in bases, such as alkoxides, metal amides, or metal acetate. The proligand may also be treated with a metal halide, with or without an added base. Lastly, the proligand may be deprotonated by a nonnucleophilic base, such as sodium hydride, before treatment with the metal halide. For example, Jacobsen's catalyst is prepared from the salen ligand precursor with manganese acetate. | 0 | Organic Chemistry |
Barbas has a Ph.D. from Complutense University of Madrid. From 2005 until 2006 she was a Marie Curie fellow at King's College London. As of 2022 she is a professor of analytical chemistry at the Universidad CEU San Pablo and is the president of the Madrid section of the Spanish Royal Society of Chemistry. | 3 | Analytical Chemistry |
Friedel's salt discovery is relatively difficult to trace back from the recent literature, simply because it is an ancient finding of a poorly known and non-natural product. It has been synthesised and identified in 1897 by Georges Friedel, mineralogist and crystallographer, son of the famous French chemist Charles Friedel. Georges Friedel also synthesised calcium aluminate (1903) in the framework of his work on the macles theory (twin crystals). This point requires further verification. | 3 | Analytical Chemistry |
John Ulric Nef (Johann Ulrich Nef; June 14, 1862 – August 13, 1915) was a Swiss-born American chemist and the discoverer of the Nef reaction and Nef synthesis. He was a member of the American Academy of Arts and Sciences and the National Academy of Sciences. | 0 | Organic Chemistry |
* The Genesis Account: A theological, historical, and scientific commentary on Genesis 1-11, 2015, Creation Book Publishers
* Christianity for Skeptics, 2012, with Steve Kumar (first author), Creation Book Publishers
* The Greatest Hoax on Earth? Refuting Dawkins on Evolution, 2010, Creation Book Publishers
* By Design: Evidence for natures Intelligent Designer—the God of the Bible', 2008, Creation Book Publishers ABN: 978-0-949906-72-4
* Refuting Compromise: A Biblical and Scientific Refutation of Progressive Creationism, 2004, Creation Book Publishers
* The Revised & Expanded Answers Book, 2003, with Carl Wieland and David Catchpoole, edited by Don Batten,
* Refuting Evolution 2, 2002/2011, Creation Book Publishers
* Refuting Evolution, 1999–2010, Creation Book Publishers | 7 | Physical Chemistry |
X-ray diffraction shows that all six carbon-carbon bonds in benzene are of the same length, at 140 picometres (pm). The C–C bond lengths are greater than a double bond (135 pm) but shorter than a single bond (147 pm). This intermediate distance is caused by electron delocalization: the electrons for C=C bonding are distributed equally between each of the six carbon atoms. Benzene has 6 hydrogen atoms, fewer than the corresponding parent alkane, hexane, which has 14. Benzene and cyclohexane have a similar structure, only the ring of delocalized electrons and the loss of one hydrogen per carbon distinguishes it from cyclohexane. The molecule is planar. The molecular orbital description involves the formation of three delocalized π orbitals spanning all six carbon atoms, while the valence bond description involves a superposition of resonance structures. It is likely that this stability contributes to the peculiar molecular and chemical properties known as aromaticity. To reflect the delocalized nature of the bonding, benzene is often depicted with a circle inside a hexagonal arrangement of carbon atoms.
Derivatives of benzene occur sufficiently often as a component of organic molecules, so much so that the Unicode Consortium has allocated a symbol in the Miscellaneous Technical block with the code U+232C (⌬) to represent it with three double bonds, and U+23E3 (⏣) for a delocalized version. | 2 | Environmental Chemistry |
Bromophenol blue is also used as a dye. At neutral pH, the dye absorbs red light most strongly and transmits blue light. (Its peak absorbance is 590 nm at a basic pH of 12.) Solutions of the dye, therefore, are blue. At low pH, the dye absorbs ultraviolet and blue light most strongly and appears yellow in solution.
In solution at pH 3.6 (in the middle of the transition range of this pH indicator) obtained by dissolution in water without any pH adjustment, bromophenol blue has a characteristic green red colour, where the apparent colour shifts depending on the concentration and/or path length through which the solution is observed. This phenomenon is called dichromatic color. Bromophenol blue is the substance with the highest known value of Kreft's dichromaticity index. This means it has the largest change in colour hue, when the thickness or concentration of observed sample increases or decreases. | 3 | Analytical Chemistry |
* Bethea, R. M. 1978. Air Pollution Control Technology. New York: Van Nostrand Reinhold.
* National Asphalt Pavement Association. 1978. The Maintenance and Operation of Exhaust Systems in the Hot Mix Batch Plant. 2nd ed. Information Series 52.
* Perry, J. H. (Ed.). 1973. Chemical Engineers’ Handbook. 5th ed. New York: McGraw-Hill.
* Richards, J. R. 1995. Control of Particulate Emissions (APTI Course 413). U.S. Environmental Protection Agency.
* Richards, J. R. 1995. Control of Gaseous Emissions. (APTI Course 415). U.S. Environmental Protection Agency.
* Schifftner, K. C. 1979, April. Venturi scrubber operation and maintenance. Paper presented at the U.S. EPA Environmental Research Information Center. Atlanta, GA.
* Semrau, K. T. 1977. Practical process design of particulate scrubbers. Chemical Engineering. 84:87-91.
* U.S. Environmental Protection Agency. 1982, September. Control Techniques for Particulate Emissions from Stationary Sources. Vol. 1. EPA 450/3-81-005a.
* Wechselblatt, P. M. 1975. Wet scrubbers (particulates). In F. L. Cross and H. E. Hesketh (Eds.), Handbook for the Operation and Maintenance of Air Pollution Control Equipment. Westport: Technomic Publishing. | 3 | Analytical Chemistry |
Woodward was born in Boston, Massachusetts, on April 10, 1917. He was the son of Margaret Burns (an immigrant from Scotland who claimed to be a descendant of the poet, Robert Burns) and her husband, Arthur Chester Woodward, himself the son of Roxbury apothecary, Harlow Elliot Woodward.
His father was one of the many victims of the 1918 influenza pandemic.
From a very early age, Woodward was attracted to and engaged in private study of chemistry while he attended a public primary school, and then Quincy High School, in Quincy, Massachusetts. By the time he entered high school, he had already managed to perform most of the experiments in Ludwig Gattermanns then widely used textbook of experimental organic chemistry. In 1928, Woodward contacted the Consul-General of the German consulate in Boston (Baron von Tippelskirch ), and through him, managed to obtain copies of a few original papers published in German journals. Later, in his Cope lecture, he recalled how he had been fascinated when, among these papers, he chanced upon Diels and Alders original communication about the Diels–Alder reaction. Throughout his career, Woodward was to repeatedly and powerfully use and investigate this reaction, both in theoretical and experimental ways. In 1933, he entered the Massachusetts Institute of Technology (MIT), but neglected his formal studies badly enough to be excluded at the end of the 1934 fall term. MIT readmitted him in the 1935 fall term, and by 1936 he had received the Bachelor of Science degree. Only one year later, MIT awarded him the doctorate, when his classmates were still graduating with their bachelors degrees. Woodwards doctoral work involved investigations related to the synthesis of the female sex hormone estrone. MIT required that graduate students have research advisors. Woodward's advisors were James Flack Norris and Avery Adrian Morton, although it is not clear whether he actually took any of their advice. After a short postdoctoral stint at the University of Illinois, he took a Junior Fellowship at Harvard University from 1937 to 1938, and remained at Harvard in various capacities for the rest of his life. In the 1960s, Woodward was named Donner Professor of Science, a title that freed him from teaching formal courses so that he could devote his entire time to research. | 4 | Stereochemistry |
Hydrophobic forces are the attractive entropic forces between any two hydrophobic groups in aqueous media, e.g. the forces between two long hydrocarbon chains in aqueous solutions. The magnitude of these forces depends on the hydrophobicity of the interacting groups as well as the distance separating them (they are found to decrease roughly exponentially with the distance). The physical origin of these forces is a debated issue but they have been found to be long-ranged and are the strongest among all the physical interaction forces operating between biological surfaces and molecules. Due to their long range nature, they are responsible for rapid coagulation of hydrophobic particles in water and play important roles in various biological phenomena including folding and stabilization of macromolecules such as proteins and fusion of cell membranes.
The potential V is given by
where C ( is a characteristic length scale of hydrophobic attraction and z is the distance of separation. | 6 | Supramolecular Chemistry |
*Tenofovir alafenamide: A pro-drug of the nucleotide analogue tenofovir, critical for HIV treatment.
*AMPA: Aminomethylphosphonic acid, degradation product of glyphosate
*Vinylphosphonic acid: monomer
*Dimethyl methylphosphonate (DMMP), one of the simplest phosphonate diesters
*Etidronic acid (HEDP): 1-hydroxyethylidene-1,1-diphosphonic acid, used in detergents, water treatment, cosmetics and pharmaceuticals
*ATMP: Aminotris(methylenephosphonic acid), chelating agent
*EDTMP: Ethylenediaminetetra(methylenephosphonic acid), chelating agent
*TDTMP: Tetramethylenediaminetetra(methylenephosphonic acid), chelating agent
*HDTMP: Hexamethylenediaminetetra(methylenephosphonic acid), chelating agent
*DTPMP: Diethylenetriaminepenta(methylenephosphonic acid), chelating agent
*PBTC: Phosphonobutanetricarboxylic acid
*PMIDA: N-(phosphonomethyl)iminodiacetic acid
*CEPA: 2-carboxyethyl phosphonic acid
*HPAA: 2-Hydroxyphosphonocarboxylic acid
*AMP: Aminotris(methylenephosphonic acid)
*BPMG: N,N-Bis(phosphonomethyl)glycine
*Glyphosate: a common agricultural herbicide
*Foscarnet: for treatment of herpes
*Perzinfotel: for treatment of stroke
*SF2312: a natural product phosphonate antibiotic inhibitor of enolase
*Selfotel: an abandoned experimental drug for stroke | 0 | Organic Chemistry |
In chemistry, a concerted reaction is a chemical reaction in which all bond breaking and bond making occurs in a single step. Reactive intermediates or other unstable high energy intermediates are not involved. Concerted reaction rates tend not to depend on solvent polarity ruling out large buildup of charge in the transition state. The reaction is said to progress through a concerted mechanism as all bonds are formed and broken in concert. Pericyclic reactions, the S2 reaction, and some rearrangements - such as the Claisen rearrangement - are concerted reactions.
The rate of the S2 reaction is second order overall due to the reaction being bimolecular (i.e. there are two molecular species involved in the rate-determining step). The reaction does not have any intermediate steps, only a transition state. This means that all the bond making and bond breaking takes place in a single step. In order for the reaction to occur both molecules must be situated correctly. | 0 | Organic Chemistry |
Carotenoids are produced by all photosynthetic organisms and are primarily used as accessory pigments to chlorophyll in the light-harvesting part of photosynthesis.
They are highly unsaturated with conjugated double bonds, which enables carotenoids to absorb light of various wavelengths. At the same time, the terminal groups regulate the polarity and properties within lipid membranes.
Most carotenoids are tetraterpenoids, regular isoprenoids. Several modifications to these structures exist: including cyclization, varying degrees of saturation or unsaturation, and other functional groups. Carotenes typically contain only carbon and hydrogen, i.e., they are hydrocarbons. Prominent members include α-carotene, β-carotene, and lycopene, are known as carotenes. Carotenoids containing oxygen include lutein and zeaxanthin. They are known as xanthophylls. Their color, ranging from pale yellow through bright orange to deep red, is directly related to their structure, especially the length of the conjugation. Xanthophylls are often yellow, giving their class name.
Carotenoids also participate in different types of cell signaling. They are able to signal the production of abscisic acid, which regulates plant growth, seed dormancy, embryo maturation and germination, cell division and elongation, floral growth, and stress responses. | 5 | Photochemistry |
The ability of a soapy solution to act as a detergent has been recognized for centuries. However, it was only at the beginning of the twentieth century that the constitution of such solutions was scientifically studied. Pioneering work in this area was carried out by James William McBain at the University of Bristol. As early as 1913, he postulated the existence of "colloidal ions" to explain the good electrolytic conductivity of sodium palmitate solutions. These highly mobile, spontaneously formed clusters came to be called micelles, a term borrowed from biology and popularized by G.S. Hartley in his classic book Paraffin Chain Salts: A Study in Micelle Formation. The term micelle was coined in nineteenth century scientific literature as the elle diminutive of the Latin word (particle), conveying a new word for "tiny particle". | 6 | Supramolecular Chemistry |
In humans, excessive exposure to UV radiation can result in acute and chronic harmful effects on the eye's dioptric system and retina. The risk is elevated at high altitudes and people living in high latitude areas where snow covers the ground right into early summer and sun positions even at zenith are low, are particularly at risk. Skin, the circadian system, and the immune system can also be affected.
The differential effects of various wavelengths of light on the human cornea and skin are sometimes called the "erythemal action spectrum". The action spectrum shows that UVA does not cause immediate reaction, but rather UV begins to cause photokeratitis and skin redness (with lighter skinned individuals being more sensitive) at wavelengths starting near the beginning of the UVB band at 315 nm, and rapidly increasing to 300 nm. The skin and eyes are most sensitive to damage by UV at 265–275 nm, which is in the lower UV‑C band. At still shorter wavelengths of UV, damage continues to happen, but the overt effects are not as great with so little penetrating the atmosphere. The WHO-standard ultraviolet index is a widely publicized measurement of total strength of UV wavelengths that cause sunburn on human skin, by weighting UV exposure for action spectrum effects at a given time and location. This standard shows that most sunburn happens due to UV at wavelengths near the boundary of the UV‑A and UV‑B bands. | 5 | Photochemistry |
In humans, about 70% of promoters located near the transcription start site of a gene (proximal promoters) contain a CpG island. CpG islands are generally 200 to 2000 base pairs long, have a C:G base pair content >50%, and have regions of DNA where a cytosine nucleotide is followed by a guanine nucleotide and this occurs frequently in the linear sequence of bases along its 5 → 3 direction.
Distal promoters also frequently contain CpG islands, such as the promoter of the DNA repair gene ERCC1, where the CpG island-containing promoter is located about 5,400 nucleotides upstream of the coding region of the ERCC1 gene. CpG islands also occur frequently in promoters for functional noncoding RNAs such as microRNAs. | 1 | Biochemistry |
Compounds containing thiol groups on adjacent carbon centers are common. Ethane-1,2-dithiol reacts with aldehydes () and ketones () to give 1,3-dithiolanes:
Some dithiols are used in chelation therapy, i.e. the removal of heavy metal poisons. Examples include dimercaptopropanesulfate (DMPS), dimercaprol ("BAL"), and meso-2,3-dimercaptosuccinic acid. | 0 | Organic Chemistry |
It is possible to express the critical constants T and P as functions of a and b by reversing the following system of 2 equations a(T, P) and b(T, P) with 2 variables T, P:
Because of the definition of compressibility factor at critical condition, it is possible to reverse it to find the critical molar volume V, by knowing previous found P, T and Z=1/3. | 7 | Physical Chemistry |
Inorganic scintillators are usually crystals grown in high temperature furnaces, for example, alkali metal halides, often with a small amount of activator impurity. The most widely used is (thallium-doped sodium iodide); its scintillation light is blue. Other inorganic alkali halide crystals are: , , Caesium iodide|(pure), Caesium fluoride|, potassium iodide|, lithium iodide|. Some non-alkali crystals include: BGO, barium fluoride|, calcium fluoride|, zinc sulfide|, calcium tungstate|, Cadmium tungstate|, Yttrium aluminium garnet| (), gadolinium oxyorthosilicate|, lutetium orthosilicate|. (For more examples, see also phosphors).
Newly developed products include , lanthanum chloride doped with cerium, as well as a cerium-doped lanthanum bromide, . They are both very hygroscopic (i.e., damaged when exposed to moisture in the air) but offer excellent light output and energy resolution (63 photons/keV γ for versus 38 photons/keV γ for ), a fast response (16 ns for versus 230 ns for ), excellent linearity, and a very stable light output over a wide range of temperatures. In addition LaBr(Ce) offers a higher stopping power for γ rays (density of 5.08 g/cm versus 3.67 g/cm for ). LYSO () has an even higher density (7.1 g/cm, comparable to bismuth germanate|), is non-hygroscopic, and has a higher light output than (32 photons/keV γ), in addition to being rather fast (41 ns decay time versus 300 ns for ).
A disadvantage of some inorganic crystals, e.g., NaI, is their hygroscopicity, a property which requires them to be housed in an airtight container to protect them from moisture. and BaF are only slightly hygroscopic and do not usually need protection. CsF, , , are hygroscopic, while , , , and are not.
Inorganic crystals can be cut to small sizes and arranged in an array configuration so as to provide position sensitivity. Such arrays are often used in medical physics or security applications to detect X-rays or γ rays: high-Z, high density materials (e.g. LYSO, BGO) are typically preferred for this type of applications.
Scintillation in inorganic crystals is typically slower than in organic ones, ranging typically from 1.48 ns for to 9000 ns for . Exceptions are (~5 ns), fast (0.7 ns; the slow component is at 630 ns), as well as the newer products (, 28 ns; , 16 ns; , 41 ns).
For the imaging application, one of the advantage of inorganic crystals is very high light yield. Some high light yield scintillators above 100,000 photons/MeV at 662 keV are very recently reported for , , and .
Many semiconductor scintillator phosphors are known, such as ZnS(Ag) (mentioned in the history section), CdS(Ag), ZnO(Zn), ZnO(Ga), CdS(In), ZnSe(O), and ZnTe(O), but none of these are available as single crystals. CdS(Te) and ZnSe(Te) have been commercially available in single crystal form, but their luminosity is partially quenched at room temperature.
GaAs(Si,B) is a recently discovered cryogenic semiconductor scintillator with high light output in the infra-red and apparently no afterglow. In combination with ultra-low noise cryogenic photodetectors it is the target in experiments to detect rare, low-energy electronic excitations from interacting dark matter. | 5 | Photochemistry |
Different mRNAs within the same cell have distinct lifetimes (stabilities). In bacterial cells, individual mRNAs can survive from seconds to more than an hour. However, the lifetime averages between 1 and 3 minutes, making bacterial mRNA much less stable than eukaryotic mRNA. In mammalian cells, mRNA lifetimes range from several minutes to days. The greater the stability of an mRNA the more protein may be produced from that mRNA. The limited lifetime of mRNA enables a cell to alter protein synthesis rapidly in response to its changing needs. There are many mechanisms that lead to the destruction of an mRNA, some of which are described below. | 1 | Biochemistry |
KhAB-500s were typically filled with yperite (R-5) or phosgene (R-10). It was in diameter and about long. Its loaded weight was about including roughly of chemical agent and a impact-fused burst charge.
Upon detonation, the KhAB-500 R-10 would create a hemispherical cloud of gas with a radius of . In ideal weather conditions, the phosgene cloud could produce serious medical effects up to downwind.
The KhAB-500 was carried by Soviet Union era aircraft.
The bomb was removed from service as a result of the Chemical Weapons Convention in the early 1990s. | 1 | Biochemistry |
The exchange between bulk and coordinated water is of fundamental interest as a measure of the intrinsic kinetic lability of metal ions. This rate is relevant to toxicity, catalysis, magnetic resonance imaging, and other effects. For octahedral mono- and dicationic aquo complexes, these exchange processes occur via an interchange pathway that has more or less dissociative character. Rates vary by a factor of 10, being the slowest and being one of the fastest for octahedral complexes. Charge has a significant influence on these rates but non-electrostatic effects are also important. | 0 | Organic Chemistry |
Vectors and planes in a crystal lattice are described by the three-value Miller index notation. This syntax uses the indices h, k, and ℓ as directional parameters.
By definition, the syntax (hkℓ) denotes a plane that intercepts the three points a/h, a/k, and a/ℓ, or some multiple thereof. That is, the Miller indices are proportional to the inverses of the intercepts of the plane with the unit cell (in the basis of the lattice vectors). If one or more of the indices is zero, it means that the planes do not intersect that axis (i.e., the intercept is "at infinity"). A plane containing a coordinate axis is translated so that it no longer contains that axis before its Miller indices are determined. The Miller indices for a plane are integers with no common factors. Negative indices are indicated with horizontal bars, as in (13). In an orthogonal coordinate system for a cubic cell, the Miller indices of a plane are the Cartesian components of a vector normal to the plane.
Considering only (hkℓ) planes intersecting one or more lattice points (the lattice planes), the distance d between adjacent lattice planes is related to the (shortest) reciprocal lattice vector orthogonal to the planes by the formula | 3 | Analytical Chemistry |
A negative-calorie food is food that supposedly requires more food energy to be digested than the food provides. Its thermic effect or specific dynamic action—the caloric "cost" of digesting the food—would be greater than its food energy content. Despite its recurring popularity in dieting guides, there is no evidence supporting the idea that any food is calorically negative. While some chilled beverages are calorically negative, the effect is minimal and requires drinking very large amounts of water, which can be dangerous, as it can cause water intoxication. | 1 | Biochemistry |
The most common type of implementation of ISCR is the installation of permeable reactive barriers (PRBs), but there are instances when the reductant can be directly injected into the subsurface to treat source areas. | 2 | Environmental Chemistry |
The absorption of electromagnetic radiation by water depends on the state of the water.
The absorption in the gas phase occurs in three regions of the spectrum. Rotational transitions are responsible for absorption in the microwave and far-infrared, vibrational transitions in the mid-infrared and near-infrared. Vibrational bands have rotational fine structure. Electronic transitions occur in the vacuum ultraviolet regions.
Liquid water has no rotational spectrum but does absorb in the microwave region. Its weak absorption in the visible spectrum results in the pale blue color of water. | 7 | Physical Chemistry |
Natural rainwater, snow and other forms of precipitation typically have low concentrations of divalent cations such as calcium and magnesium. They may have small concentrations of ions such as sodium, chloride and sulfate derived from wind action over the sea. Where precipitation falls in drainage basins formed of hard, impervious and calcium-poor rocks, only very low concentrations of divalent cations are found and the water is termed soft water. Examples include Snowdonia in Wales and the Western Highlands in Scotland.
Areas with complex geology can produce varying degrees of hardness of water over short distances. | 3 | Analytical Chemistry |
Unlike the other assimilatory pathways, bacteria using the RuBP pathway derive all of their organic carbon from assimilation. This pathway was first elucidated in photosynthetic autotrophs and is better known as the Calvin Cycle. Shortly thereafter, methylotrophic bacteria who could grow on reduced compounds were found using this pathway.
First, 3 molecules of ribulose 5-phosphate are phosphorylated to ribulose 1,5-bisphosphate (RuBP). The enzyme ribulose bisphosphate carboxylase (RuBisCO) carboxylates these RuBP molecules which produces 6 molecules of 3-phosphoglycerate (PGA). The enzyme phosphoglycerate kinase phosphorylates PGA into 1,3-diphosphoglycerate (DPGA). Reduction of 6 DPGA by the enzyme glyceraldehyde phosphate dehydrogenase generates 6 molecules of the compound glyceraldehyde-3-phosphate (GAP). One GAP molecule is diverted towards biomass while the other 5 molecules regenerate the 3 molecules of ribulose 5-phosphate. | 0 | Organic Chemistry |
The Entner-Doudoroff pathway is a glycolytic pathway that is considered the second pathway used for carbohydrates used by certain microbes. In this process, glucose-6-phosphate is oxidized through 6-phosphogluconate to pyruvate and glyceraldehyde 3-phosphate, with the concomitant reduction of NADP. By conventional glyceraldehyde-3-phosphate oxidation to pyruvate, one NAD is reduced and a net one ATP is formed. In that pathway, for every glucose molecule there is an "investment" of one ATP molecule and a yield of two ATP and two pyruvate molecules and one NADH. The difference between the glycolytic used by humans and this pathway is that the latter requires one ATP to yield two ATP and two pyruvates as a net of only one NADPH produced and one ATP result (from substrate-level phosphorylation), and the former requires two ATP molecules to yield four ATP and two pyruvate molecules per glucose as a net of two ATP molecules. | 1 | Biochemistry |
Understanding and measuring the absorption of electromagnetic radiation has a variety of applications.
* In radio propagation, it is represented in non-line-of-sight propagation. For example, see computation of radio wave attenuation in the atmosphere used in satellite link design.
* In meteorology and climatology, global and local temperatures depend in part on the absorption of radiation by atmospheric gases (such as in the greenhouse effect) and land and ocean surfaces (see albedo).
* In medicine, X-rays are absorbed to different extents by different tissues (bone in particular), which is the basis for X-ray imaging.
* In chemistry and materials science, different materials and molecules absorb radiation to different extents at different frequencies, which allows for material identification.
* In optics, sunglasses, colored filters, dyes, and other such materials are designed specifically with respect to which visible wavelengths they absorb, and in what proportions they are in.
* In biology, photosynthetic organisms require that light of the appropriate wavelengths be absorbed within the active area of chloroplasts, so that the light energy can be converted into chemical energy within sugars and other molecules.
* In physics, the D-region of Earth's ionosphere is known to significantly absorb radio signals that fall within the high-frequency electromagnetic spectrum.
* In nuclear physics, absorption of nuclear radiations can be used for measuring the fluid levels, densitometry or thickness measurements.
In scientific literature is known a system of mirrors and lenses that with a laser "can enable any material to absorb all light from a wide range of angles." | 7 | Physical Chemistry |
The ferric chloride test can be used to detect metabolites in urine in case of inborn error of metabolism such as phenylketonuria. Compounds such as phenylpyruvate increase in plasma and are excreted out via urine. Also, it can be used to detect salicylates in urine, quick diagnostic test for aspirin overdose. | 3 | Analytical Chemistry |
Large numbers of samples can be automatically injected onto an HPLC system, by the use of HPLC autosamplers. In addition, HPLC autosamplers have an injection volume and technique which is exactly the same for each injection, consequently they provide a high degree of injection volume precision.
It is possible to enable sample stirring within the sampling-chamber, thus promoting homogeneity. | 3 | Analytical Chemistry |
The absorbance of an object quantifies how much of the incident light is absorbed by it (instead of being reflected or refracted). This may be related to other properties of the object through the Beer–Lambert law.
Precise measurements of the absorbance at many wavelengths allow the identification of a substance via absorption spectroscopy, where a sample is illuminated from one side, and the intensity of the light that exits from the sample in every direction is measured. A few examples of absorption are ultraviolet–visible spectroscopy, infrared spectroscopy, and X-ray absorption spectroscopy. | 7 | Physical Chemistry |
Leng grew up in Scarborough, North Yorkshire. She spent her childhood on the cliffs and beaches of the Lower Jurassic. Leng studied geology for GCSE and A Level. At Sixth Form College she took a field trip to Ravenscar and described finding an ammonite which hooked her into geology. She studied for a BSc in Earth Science at Oxford Polytechnic, gained her PhD at Aberystwyth University in 1990, then moved to the British Geological Survey to work in the isotope laboratory. | 9 | Geochemistry |
Persistent triplet state carbenes have been prepared by photochemical decomposition of a diazomethane product via the expulsion of nitrogen gas, at a wavelength of 300 nm in benzene. | 0 | Organic Chemistry |
NPP1 helps scavenge extracellular nucleotides in order to meet the high purine and pyrimidine requirements of dividing cells. In T-cells, it may scavenge NAD from nearby dead cells as a source of adenosine.
The pyrophosphate produced by NPP1 in bone cells is thought to serve as both a phosphate source for calcium phosphate deposition and as an inhibitory modulator of calcification. NPP1 appears to be important for maintaining pyrophosphate/phosphate balance. Overactivity of the enzyme is associated with chondrocalcinosis, while deficiency correlates to pathological calcification.
NPP1 inhibits the insulin receptor in vitro. In 2005, overexpression of the isoform was implicated in insulin resistance in mice. It has been linked to insulin resistance and Type 2 diabetes in humans. | 1 | Biochemistry |
EQCM can be used to ideally modify polymer membranes together with other electrochemical measurements or surface characterization methods. A team has used CV, UV-Vis, IR and EQCM studied irreversible changes of some polythiophenes in the electrochemical reduction process in acetonitrile. Later on they used AFM and EQCM investigated growth of polypyrrole film in anionic surfactant micellar solution. Then combing with CV, UV-Vis, FTIR, ESR, they used EQCM to study conductivity and magnetic properties of 3,4-dimethoxy and 3,4-ethylenedioxy-terminated polypyrrole and polythiophene. | 7 | Physical Chemistry |
Bioluminescence imaging (BLI) is a technology developed over the past decades (1990's and onward). that allows for the noninvasive study of ongoing biological processes Recently, bioluminescence tomography (BLT) has become possible and several systems have become commercially available. In 2011, PerkinElmer acquired one of the most popular lines of optical imaging systems with bioluminescence from Caliper Life Sciences. | 1 | Biochemistry |
When simultaneous EDS/EBSD collection can be achieved, the capabilities of both techniques can be enhanced. There are applications where sample chemistry or phase cannot be differentiated via EDS alone because of similar composition, and structure cannot be solved with EBSD alone because of ambiguous structure solutions. To accomplish integrated mapping, the analysis area is scanned, and at each point, Hough peaks and EDS region-of-interest counts are stored. Positions of phases are determined in X-ray maps, and each element's measured EDS intensities are given in charts. The chemical intensity ranges are set for each phase to select the grains. All patterns are then re-indexed off-line. The recorded chemistry determines which phase/crystal-structure file is used to index each point. Each pattern is indexed by only one phase, and maps displaying distinguished phases are generated. The interaction volumes for EDS and EBSD are significantly different (on the order of micrometres compared to tens of nanometres), and the shape of these volumes using a highly tilted sample may have implications on algorithms for phase discrimination.
EBSD, when used together with other in-SEM techniques such as cathodoluminescence (CL), wavelength dispersive X-ray spectroscopy (WDS) and/or EDS can provide a deeper insight into the specimen's properties and enhance phase identification. For example, the minerals calcite (limestone) and aragonite (shell) have the same chemical composition – calcium carbonate (CaCO) therefore EDS/WDS cannot tell them apart, but they have different microcrystalline structures so EBSD can differentiate between them. | 7 | Physical Chemistry |
The first crystalline sponges developed by Makoto Fujita is [(Co(NCS))(TPT)], which is an infinitely extensive framework of Co octahedral complex. Each octahedral complex is composed of six Co(NCS) vertexes and four 2,4,6-tris(4-pyridyl)-1,3,5-triazine (TPT) ligands. Besides the basic octahedral cavity (ML), there are also two different cuboctahedral cavities (ML and ML) which can accommodate larger molecules, such as C, C.
In 2013, the Fujita and his team discovered that the [(ZnI)(TPT)] organometallic network can also act as a crystalline sponge. Because Zn crystalline sponges are less symmetrical (C) than Co crystalline sponges, the X-ray diffraction analysis of its guest molecules is easier to be elucidated.
The Zn-based sponges also have following advantages: (1) Pores sizes are suitable for accommodating general organic compounds (5 × 8Å), (2) The distribution of TPT ligand is flat, providing better stacking opportunity of aromatic guest compounds or C—H π interaction opportunity with aliphatic guest compounds, (3) The iodine atoms and the pyridinium protons can be hydrogen bond acceptors or donors, respectively. They would enhance the interaction between the substrate and the crystalline sponges, (4) The framework of Zn-based crystalline sponge is flexible to some extent. The molecule which is a little bit larger than the sponge cavity can still be accommodated via framework expansion to adjust the pore size. | 0 | Organic Chemistry |
As the functional group of the amino acid cysteine, the thiol group plays a very important role in biology. When the thiol groups of two cysteine residues (as in monomers or constituent units) are brought near each other in the course of protein folding, an oxidation reaction can generate a cystine unit with a disulfide bond (−S−S−). Disulfide bonds can contribute to a protein's tertiary structure if the cysteines are part of the same peptide chain, or contribute to the quaternary structure of multi-unit proteins by forming fairly strong covalent bonds between different peptide chains. A physical manifestation of cysteine-cystine equilibrium is provided by hair straightening technologies.
Sulfhydryl groups in the active site of an enzyme can form noncovalent bonds with the enzyme's substrate as well, contributing to covalent catalytic activity in catalytic triads. Active site cysteine residues are the functional unit in cysteine protease catalytic triads. Cysteine residues may also react with heavy metal ions (Zn, Cd, Pb, Hg, Ag) because of the high affinity between the soft sulfide and the soft metal (see hard and soft acids and bases). This can deform and inactivate the protein, and is one mechanism of heavy metal poisoning.
Drugs containing thiol group
6-Mercaptopurine (anticancer)
Captopril (antihypertensive)
D-penicillamine (antiarthritic)
Sodium aurothiolate (antiarthritic) | 0 | Organic Chemistry |
The mined ore is usually crushed into small chunks and heaped on an impermeable plastic or clay lined leach pad where it can be irrigated with a leach solution to dissolve the valuable metals. While sprinklers are occasionally used for irrigation, more often operations use drip irrigation to minimize evaporation, provide more uniform distribution of the leach solution, and avoid damaging the exposed mineral. The solution then percolates through the heap and leaches both the target and other minerals. This process, called the "leach cycle," generally takes from one or two months for simple oxide ores (e.g. most gold ores) to two years for nickel laterite ores. The leach solution containing the dissolved minerals is then collected, treated in a process plant to recover the target mineral and in some cases precipitate other minerals, and recycled to the heap after reagent levels are adjusted. Ultimate recovery of the target mineral can range from 30% of contained run-of-mine dump leaching sulfide copper ores to over 90% for the ores that are easiest to leach, some oxide gold ores.
The essential questions to address during the process of the heap leaching are:
* Can the investment of crushing the ore be justified by the potential increase in recovery and rate of recovery?
* How should the concentration of acid be altered over time in order to produce a solution that can be economically treated?
* How does the form of a heap affect the recovery and solution grade?
* Under any given set of circumstances, what type of recovery can be expected before the leach solution quality drops below a critical limit?
* What recovery (quantifiable measure) can be expected?
In recent years, the addition of an agglomeration drum has improved on the heap leaching process by allowing for a more efficient leach. The rotary drum agglomerator works by taking the crushed ore fines and agglomerating them into more uniform particles. This makes it much easier for the leaching solution to percolate through the pile, making its way through the channels between particles.
The addition of an agglomeration drum also has the added benefit of being able to pre-mix the leaching solution with the ore fines to achieve a more concentrated, homogeneous mixture and allow the leach to begin prior to the heap.
Although heap leach design has made significant progress over the last few years through the use of new materials and improved analytical tools, industrial experience shows that there are significant benefits from extending the design process beyond the liner and into the rock pile itself. Characterization of the physical and hydraulic (hydrodynamic) properties of ore-for-leach focuses on the direct measurement of the key properties of the ore, namely:
* The relationship between heap height and ore bulk density (density profile)
* The relationship between bulk density and percolation capacity (conductivity profile)
* The relationship between the bulk density, porosity and its components (micro and macro)
* The relationship between the moisture content and percolation capacity (conductivity curve)
* The relationship between the aforementioned parameters and the ore preparation practices (mining, crushing, agglomeration, curing, and method of placement)
Theoretical and numerical analysis, and operational data show that these fundamental mechanisms are controlled by scale, dimensionality, and heterogeneity, all of which adversely affect the scalability of metallurgical and hydrodynamic properties from the lab to the field. The dismissal of these mechanisms can result in a number of practical and financial problems that will resonate throughout the life of the heap impacting the financial return of the operation. Through procedures that go beyond the commonly employed metallurgical testing and the integration of data gleaned through real time 3D monitoring, a more complete representative characterization of the physicochemical properties of the heap environment is obtained. This improved understanding results in a significantly higher degree of accuracy in terms of creating a truly representative sample of the environment within the heap.
By adhering to the characterization identified above, a more comprehensive view of heap leach environments can be realized, allowing the industry to move away from the de facto black-box approach to a physicochemically inclusive industrial reactor model. | 8 | Metallurgy |
RATs are immunochromatographic assays which give results that can be seen with the naked eye (with or without special illumination, such as a UV lamp). They are qualitative in nature, although within a certain range it is possible to make rough order of magnitude estimates of viral load from the results. RATs are generally screening tests, with relatively low sensitivity and specificity, thus results should be evaluated on the basis of confirmatory tests like PCR testing or western blot.
One inherent advantage of an antigen test over an antibody test (such as antibody-detecting rapid HIV tests) is that it can take time for the immune system to develop antibodies after infection begins, but the foreign antigen is present right away. Although any diagnostic test may have false negatives, this latency period can open an especially wide avenue for false negatives in antibody tests, although the particulars depend on which disease and which test are involved. A rapid antigen test typically costs around US$5 to manufacture. | 1 | Biochemistry |
Ion channels are also classified according to their subcellular localization. The plasma membrane accounts for around 2% of the total membrane in the cell, whereas intracellular organelles contain 98% of the cell's membrane. The major intracellular compartments are endoplasmic reticulum, Golgi apparatus, and mitochondria. On the basis of localization, ion channels are classified as:
* Plasma membrane channels
**Examples: Voltage-gated potassium channels (Kv), Sodium channels (Nav), Calcium channels (Cav) and Chloride channels (ClC)
* Intracellular channels, which are further classified into different organelles
**Endoplasmic reticulum channels: RyR, SERCA, ORAi
**Mitochondrial channels: mPTP, KATP, BK, IK, CLIC5, Kv7.4 at the inner membrane and VDAC and CLIC4 as outer membrane channels. | 1 | Biochemistry |
Internal heat is the heat source from the interior of celestial objects, such as stars, brown dwarfs, planets, moons, dwarf planets, and (in the early history of the Solar System) even asteroids such as Vesta, resulting from contraction caused by gravity (the Kelvin–Helmholtz mechanism), nuclear fusion, tidal heating, core solidification (heat of fusion released as molten core material solidifies), and radioactive decay. The amount of internal heating depends on mass; the more massive the object, the more internal heat it has; also, for a given density, the more massive the object, the greater the ratio of mass to surface area, and thus the greater the retention of internal heat. The internal heating keeps celestial objects warm and active. | 7 | Physical Chemistry |
Sensor-based ore sorting is in comparison to other coarse particle separation technologies relatively cheap. While the costs for the equipment itself are relatively high in capital expenditure and operating costs, the absence of extensive infrastructure in a system results in operating costs that are to be compared to jigging. The specific costs are very much depending on the average particle size of the feed and on the ease of the separation. Coarser particles imply higher capacity and thus less costs. Detailed costing can be conducted after the mini-bulk stage in the technical feasibility evaluation.
Prejudice against waste rejection with sensor-based sorting widely spread, that the loss of valuables, thus the recovery penalty of this process, supersedes the potential downstream cost savings and is therefore economically not viable. It must be noted that for waste rejection the aim for the separation with sensor-based ore sorting must be put onto maximum recovery, which means that only low grade or barren waste is rejected because the financial feasibility is very much sensitive to that factor. Nevertheless, through the rejection of waste before comminution and concentration steps, recovery can be often increased in the downstream process, meaning that the overall recovery is equal or even higher than the one in the base case, meaning that instead of losing product, additional product can be produced, which adds the additional revenue to the cost savings on the positive side in the cash flow.
If the rejected material is replaced with additional higher grade material, the main economic benefit unfolds through the additional production. It implies, that in conjunction with sensor-based ore sorting, the capacity of the crushing station is increased, to allow for the additional mass-flow that is subsequently taken out by the sensor-based ore sorters as waste. | 3 | Analytical Chemistry |
FMRFamide (H-Phe-Met-Arg-Phe-NH2) is a neuropeptide from a broad family of FMRFamide-related peptides (FaRPs) all sharing an -RFamide sequence at their C-terminus. First identified in Hard clam (Mercenaria mercenaria), it is thought to play an important role in cardiac activity regulation. Several FMRFamide related peptides are known, regulating various cellular functions and possessing pharmacological actions, such as anti-opiate effects. In Mercenaria mercenaria, FMRFamide has been isolated and demonstrated to increase both the force and frequency of the heartbeat through a biochemical pathway that is thought to involve the increase of cytoplasmic cAMP in the ventricular region.
FMRFamide is an important neuropeptide in several phyla such as Insecta, Nematoda, Mollusca, and Annelida.
It is the most abundant neuropeptide in endocrine cells of insect alimentary tracts along with allatostatin and tachykinin families, however the neuropeptide’s function is not known. Generally, the neuropeptide is encoded by several genes such as flp-1 through flp-22 in C. elegans. The common precursor of the FaRPs is modified to yield many different neuropeptides all having the same FMRFamide sequence. Moreover, these peptides are not functionally redundant.
In invertebrates, the FMRFamide-related peptides are known to affect heart rate, blood pressure, gut motility, feeding behaviour and reproduction. In vertebrates such as mice, they are known to affect opioid receptors resulting in elicitation of naloxone-sensitive antinociception and reduction of morphine-induced antinociception.
Detection of this neuropeptide is important because its expression lays down the foundation of the CNS in the early stages of development in invertebrates. In recent years, neuromodulatory actions of FMRFamide in invertebrates have become more apparent. This is, in part, due to the extensive studies done on the Planorbid and Lymnaeid families of pond snails. | 1 | Biochemistry |
Addition of molecular oxygen to ribulose-1,5-bisphosphate produces 3-phosphoglycerate (PGA) and 2-phosphoglycolate (2PG, or PG). PGA is the normal product of carboxylation, and productively enters the Calvin cycle. Phosphoglycolate, however, inhibits certain enzymes involved in photosynthetic carbon fixation (hence is often said to be an inhibitor of photosynthesis). It is also relatively difficult to recycle: in higher plants it is salvaged by a series of reactions in the peroxisome, mitochondria, and again in the peroxisome where it is converted into glycerate. Glycerate reenters the chloroplast and by the same transporter that exports glycolate. A cost of 1 ATP is associated with conversion to 3-phosphoglycerate (PGA) (Phosphorylation), within the chloroplast, which is then free to re-enter the Calvin cycle.
Several costs are associated with this metabolic pathway; the production of hydrogen peroxide in the peroxisome (associated with the conversion of glycolate to glyoxylate). Hydrogen peroxide is a dangerously strong oxidant which must be immediately split into water and oxygen by the enzyme catalase. The conversion of 2× 2Carbon glycine to 1× serine in the mitochondria by the enzyme glycine-decarboxylase is a key step, which releases , NH, and reduces NAD to NADH. Thus, one molecule is produced for every two molecules of (two deriving from RuBisCO and one from peroxisomal oxidations). The assimilation of NH occurs via the GS-GOGAT cycle, at a cost of one ATP and one NADPH.
Cyanobacteria have three possible pathways through which they can metabolise 2-phosphoglycolate. They are unable to grow if all three pathways are knocked out, despite having a carbon concentrating mechanism that should dramatically lower the rate of photorespiration (see below). | 5 | Photochemistry |
Hydrolysis constants (log values) in critical compilations at infinite dilution and T = 298.15 K:
() 0.5 M HClO | 7 | Physical Chemistry |
Because the only form of known life is that on Earth, the search for biosignatures is heavily influenced by the products that life produces on Earth. However, life that is different than life on Earth may still produce biosignatures that are detectable by humans, even though nothing is known about their specific biology. This form of biosignature is called an "agnostic biosignature" because it is independent of the form of life that produces it. It is widely agreed that all life–no matter how different it is from life on Earth–needs a source of energy to thrive. This must involve some sort of chemical disequilibrium, which can be exploited for metabolism. Geological processes are independent of life, and if scientists can constrain the geology well enough on another planet, then they know what the particular geologic equilibrium for that planet should be. A deviation from geological equilibrium can be interpreted as an atmospheric disequilibrium and agnostic biosignature. | 2 | Environmental Chemistry |
The gabT gene encodes for GABA transaminase, an enzyme that catalyzes the conversion of GABA and 2-oxoglutarate into succinate semialdehyde and glutamate. Succinate semialdehyde is then oxidized into succinate by succinate semialdehyde dehydrogenase which is encoded by the gabP gene, thereby entering the TCA cycle as a usable source of energy. The gab operon contributes to homeostasis of polyamines such as putrescine, during nitrogen-limited growth. It is also known to maintain high internal glutamate concentrations under stress conditions. | 1 | Biochemistry |
GPCRs are integral membrane proteins that possess seven membrane-spanning domains or transmembrane helices. The extracellular parts of the receptor can be glycosylated. These extracellular loops also contain two highly conserved cysteine residues that form disulfide bonds to stabilize the receptor structure. Some seven-transmembrane helix proteins (channelrhodopsin) that resemble GPCRs may contain ion channels, within their protein.
In 2000, the first crystal structure of a mammalian GPCR, that of bovine rhodopsin (), was solved. In 2007, the first structure of a human GPCR was solved This human β-adrenergic receptor GPCR structure proved highly similar to the bovine rhodopsin. The structures of activated or agonist-bound GPCRs have also been determined. These structures indicate how ligand binding at the extracellular side of a receptor leads to conformational changes in the cytoplasmic side of the receptor. The biggest change is an outward movement of the cytoplasmic part of the 5th and 6th transmembrane helix (TM5 and TM6). The structure of activated beta-2 adrenergic receptor in complex with G confirmed that the Gα binds to a cavity created by this movement.
GPCRs exhibit a similar structure to some other proteins with seven transmembrane domains, such as microbial rhodopsins and adiponectin receptors 1 and 2 (ADIPOR1 and ADIPOR2). However, these 7TMH (7-transmembrane helices) receptors and channels do not associate with G proteins. In addition, ADIPOR1 and ADIPOR2 are oriented oppositely to GPCRs in the membrane (i.e. GPCRs usually have an extracellular N-terminus, cytoplasmic C-terminus, whereas ADIPORs are inverted). | 1 | Biochemistry |
E. coli is one of the most widely used expression hosts, and DNA is normally introduced in a plasmid expression vector. The techniques for overexpression in E. coli are well developed and work by increasing the number of copies of the gene or increasing the binding strength of the promoter region so assisting transcription.
For example, a DNA sequence for a protein of interest could be cloned or subcloned into a high copy-number plasmid containing the lac (often LacUV5) promoter, which is then transformed into the bacterium E. coli. Addition of IPTG (a lactose analog) activates the lac promoter and causes the bacteria to express the protein of interest.
E. coli strain BL21 and BL21(DE3) are two strains commonly used for protein production. As members of the B lineage, they lack lon and OmpT proteases, protecting the produced proteins from degradation. The DE3 prophage found in BL21(DE3) provides T7 RNA polymerase (driven by the LacUV5 promoter), allowing for vectors with the T7 promoter to be used instead. | 1 | Biochemistry |
There are causes for deficiency other than low dietary intake of vitamin A as retinol or carotenes. Adequate dietary protein and caloric energy are needed for a normal rate of synthesis of RBP, without which, retinol cannot be mobilized to leave the liver. Systemic infections can cause transient decreases in RBP synthesis even if protein-calorie malnutrition is absent. Chronic alcohol consumption reduces liver vitamin A storage. Non-alcoholic fatty liver disease (NAFLD), characterized by the accumulation of fat in the liver, is the hepatic manifestation of metabolic syndrome. Liver damage from NAFLD reduces liver storage capacity for retinol and reduces the ability to mobilize liver stores to maintain normal circulating concentration.
Vitamin A appears is involved in the pathogenesis of anemia by diverse biological mechanisms, such as the enhancement of growth and differentiation of erythrocyte progenitor cells, potentiation of immunity to infection , and mobilization of iron stores from tissues. | 1 | Biochemistry |
Biofilms are a mixture of microorganisms, layered together and usually adhered to a surface. The advantages of a biofilm include resistance to environmental stresses, antibiotics, and the ability to more easily obtain nutrients. PhoB is used to enhance biofilm formation in environments where Pi is not in sufficient supply. This has been shown in multiple microbes including Pseudomonas, V. cholera, and E. coli. This is not always the effect of the Pho regulon as for other species in different environments it is more advantageous to not be in biofilm when Pi is low. In these cases PhoB represses biofilm formation. | 1 | Biochemistry |
The DLVO theory (named after Boris erjaguin and Lev andau, Evert erwey and Theodoor verbeek) explains the aggregation and kinetic stability of aqueous dispersions quantitatively and describes the force between charged surfaces interacting through a liquid medium.
It combines the effects of the van der Waals attraction and the electrostatic repulsion due to the so-called double layer of counterions.
The electrostatic part of the DLVO interaction is computed in the mean field approximation in the limit of low surface potentials - that is when the potential energy of an elementary charge on the surface is much smaller than the thermal energy scale, . For two spheres of radius each having a charge (expressed in units of the elementary charge) separated by a center-to-center distance in a fluid of dielectric constant containing a concentration of monovalent ions, the electrostatic potential takes the form of a screened-Coulomb or Yukawa potential,
where
* is the Bjerrum length,
* is the potential energy,
* ≈ 2.71828 is Euler's number,
* is the inverse of the Debye–Hückel screening length (); is given by , and
* is the thermal energy scale at absolute temperature | 7 | Physical Chemistry |
The rearrangements of heavy-chains are different from the light chains because DNA undergoes rearrangements of V-D-J gene segments in the heavy chains. These reorganizations of gene segments produce gene sequence from 5 prime to 3 prime ends such as a short leader exon, an intron, a joined VDJ segment, a second intron and several gene segments. The final product of the rearrangement is transcribed when RNA polymerase | 1 | Biochemistry |
The mass ratio is defined as the mass of a constituent divided by the total mass of all other constituents in a mixture:
If is much smaller than , the mass ratio is almost identical to the mass fraction.
The SI unit is kg/kg. However, the deprecated parts-per notation is often used to describe small mass ratios. | 3 | Analytical Chemistry |
There are many references to ayas in the early Indian texts.
The Atharvaveda and the Shatapatha Brahmana refer to kṛṣṇa-ayas (), which could be iron (but possibly also iron ore and iron items not made of smelted iron). There is also some controversy if the term śyāma-ayas (), refers to iron or not. In later texts the term refers to iron. In earlier texts, it could possibly also refer to darker-than-copper bronze, an alloy of copper and tin. Copper can also become black by heating it. Oxidation with the use of sulphides can produce the same effect.
The Yajurveda seems to know iron. In the Taittiriya Samhita are references to ayas and at least one reference to smiths. The Satapatha Brahmana 6.1.3.5 refers to the smelting of metallic ore. In the Manu Smriti (6.71), the following analogy is found: "For as the impurities of metallic ores, melted in the blast (of a furnace), are consumed, even so the taints of the organs are destroyed through the suppression of the breath." Metal was also used in agriculture, and the Buddhist text Suttanipata has the following analogy: "for as a ploughshare that has got hot during the day when thrown into the water splashes, hisses and smokes in volumes..."
In the Charaka Samhita an analogy occurs that probably refers to the lost wax technique. The Silpasastras (the Manasara, the Manasollasa (Abhilashitartha Chintamani) and the Uttarabhaga of Silparatna) describe the lost wax technique in detail.
The Silappadikaram says that copper-smiths were in Puhar and in Madura. According to the History of the Han Dynasty by Ban Gu, Kashmir and "Tien-chu" were rich in metals.
An influential Indian metallurgist and alchemist was Nagarjuna (born 931). He wrote the treatise Rasaratnakara that deals with preparations of rasa (mercury) compounds. It gives a survey of the status of metallurgy and alchemy in the land. Extraction of metals such as silver, gold, tin and copper from their ores and their purification were also mentioned in the treatise. The Rasa Ratnasamuccaya describes the extraction and use of copper. | 8 | Metallurgy |
Amorphous silicon (a-Si) is a popular solar cell material owing to its low cost and ease of production. Owing to disordered structure (Urbach tail), its absorption extends to the energies below the band gap resulting in a wide-range spectral response; however, it has a relatively low solar cell efficiency. Protocrystalline Si (pc-Si:H) also has a relatively low absorption near the band gap, owing to its more ordered crystalline structure. Thus, protocrystalline and amorphous silicon can be combined in a tandem solar cell, where the top thin layer of a-Si:H absorbs short-wavelength light whereas the longer wavelengths are absorbed by the underlying protocrystalline silicon layer. | 3 | Analytical Chemistry |
The Eyring equation (occasionally also known as Eyring–Polanyi equation) is an equation used in chemical kinetics to describe changes in the rate of a chemical reaction against temperature. It was developed almost simultaneously in 1935 by Henry Eyring, Meredith Gwynne Evans and Michael Polanyi. The equation follows from the transition state theory, also known as activated-complex theory. If one assumes a constant enthalpy of activation and constant entropy of activation, the Eyring equation is similar to the empirical Arrhenius equation, despite the Arrhenius equation being empirical and the Eyring equation based on statistical mechanical justification. | 7 | Physical Chemistry |
Glyoxalase I (GLO1), glyoxalase II (GLO2), and reduced glutathione (GSH). In bacteria, there is an additional enzyme that functions if there is no GSH, it is called the third glyoxalase protein, glyoxalase 3 (GLO3). GLO3 has not been found in humans yet.
The pathway begins with methylglyoxal (MG), which is produced from non-enzymatic reactions with DHAP or G3P produced in glycolysis. Methylglyoxal is then converted into S-d-lactoylglutathione by enzyme GLO1 with a catalytic amount of GSH, of which is hydrolyzed into non-toxic D-lactate via GLO2, during which GSH is reformed to be consumed again by GLO1 with a new molecule of MG. D-lactate ultimately goes on to be metabolized into pyruvate. | 1 | Biochemistry |
When a voltage is applied to an electrolysis cell, immediately following this an Electric Double Layer (EDL), or a diffusion layer, is theoretically formed. This can create a capacitance, or can cause the electrolyser to act as a capacitor. When this is present, excess voltage must be supplied by the direct current to compensate for the loss in the capacitor, which rises the required voltage supplied to what is called the thermo-neutral voltage. One of the aims of PDC electrolysis is to overcome this, and theoretically, when the PMW switches the current on, a capacitance will be stored, and when the duty cycle is over, it will be released, continuing the flow of current whilst reducing the EDL that is formed.
Poláčik and Pospíšil believe that by manipulating the dependent variables, such as the duty cycle, can increase or decrease the effectiveness of pulse electrolysis at reducing this layer. A theoretical equation, the Sand equation, is used to calculate the amount of time required to allow the EDL to fall to zero, and allow PDC electrolysis to achieve its highest efficiencies. | 7 | Physical Chemistry |
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