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Indirectly, it has been deduced that the origin of KREEP is contained in the origin of the Moon. This is now commonly thought to be the result of a rocky object the size of Mars that struck the Earth about 4.5 billion (4.5×10) years ago. This collision threw a large amount of broken rock into orbit around the Earth. This ultimately gathered together to form the Moon.
Given the high energy such a collision would involve, it has been deduced that a large portion of the Moon would have been liquified, and this
formed a lunar magma ocean. As the crystallization of this liquid rock proceeded, minerals such as olivine and pyroxene precipitated and sank to the bottom to form the lunar mantle.
After the solidification was about 75% complete, the material anorthositic plagioclase began to crystallize, and because of its low density, it floated, forming a solid crust. Hence, elements that are usually incompatible (i.e., those that usually partition in the liquid phase) would have been progressively concentrated into the magma. Thus a KREEP-rich magma was formed that was sandwiched at first between the crust and mantle. The evidence for these processes comes from the highly anorthositic composition of the crust of the lunar highlands, as well as the presence of the rocks rich in KREEP. | 9 | Geochemistry |
Different thermogalvanic cells have been constructed attending to their uses and properties. Usually they are classified according to the electrolyte employed in each specific type of cell. | 7 | Physical Chemistry |
Shell molding is similar to sand casting, but the molding cavity is formed by a hardened "shell" of sand instead of a flask filled with sand. The sand used is finer than sand casting sand and is mixed with a resin so that it can be heated by the pattern and hardened into a shell around the pattern. Because of the resin and finer sand, it gives a much finer surface finish. The process is easily automated and more precise than sand casting. Common metals that are cast include cast iron, aluminium, magnesium, and copper alloys. This process is ideal for complex items that are small to medium-sized. | 8 | Metallurgy |
Magnet-assisted transfection is a transfection method which uses magnetic interactions to deliver DNA into target cells. Nucleic acids are associated with magnetic nanoparticles, and magnetic fields drive the nucleic acid-particle complexes into target cells, where the nucleic acids are released. | 1 | Biochemistry |
The carboxyl radical, •COOH, only exists briefly. The acid dissociation constant of •COOH has been measured using electron paramagnetic resonance spectroscopy. The carboxyl group tends to dimerise to form oxalic acid. | 0 | Organic Chemistry |
Bravais lattices, also referred to as space lattices, describe the geometric arrangement of the lattice points, and therefore the translational symmetry of the crystal. The three dimensions of space afford 14 distinct Bravais lattices describing the translational symmetry. All crystalline materials recognized today, not including quasicrystals, fit in one of these arrangements. The fourteen three-dimensional lattices, classified by lattice system, are shown above.
The crystal structure consists of the same group of atoms, the basis, positioned around each and every lattice point. This group of atoms therefore repeats indefinitely in three dimensions according to the arrangement of one of the Bravais lattices. The characteristic rotation and mirror symmetries of the unit cell is described by its crystallographic point group. | 3 | Analytical Chemistry |
Trans-acting factors can be categorized by their interactions with the regulated genes, cis-acting elements of the genes, or the gene products. | 1 | Biochemistry |
This branch of spectroscopy deals with radiation related to atoms that are stripped of several electrons (multiply ionized atoms (MIA), multiply charged ions, highly charged ions). These are observed in very hot plasmas (laboratory or astrophysical) or in accelerator experiments (beam-foil, electron beam ion trap (EBIT)). The lowest exited electron shells of such ions decay into stable ground states producing photons in VUV, EUV and soft X-ray spectral regions (so-called resonance transitions). | 7 | Physical Chemistry |
The GLIC receptor is a bacterial (loeobacter) igand-gated on hannel, homolog to the nicotinic acetylcholine receptors. It is a proton-gated (the channel opens when it binds a proton, ion), cation-selective channel (it selectively lets the positive ions through). Like the nicotinic acetylcholine receptors is a functional pentameric oligomer (the channel normally works as an assembly of five subunits). However while its eukaryotic homologues are hetero-oligomeric (assembled from different subunits), all until now known bacteria known to express LICs encode a single monomeric unit, indicating the GLIC to be functionally homo-oligomeric (assembled from identical subunits).
The similarity of amino-acid sequence to the eukaryotic LGICs is not localized to any single or particular tertiary domain, indicating the similar function of the GLIC to its eukaryotic equivalents. Regardless, the purpose of regulating the threshold for action potential excitation in the nerve signal transmission of multicellular organisms cannot translate to single-cell organisms, thereby not making the purpose of bacterial LGICs immediately obvious. | 1 | Biochemistry |
Analysis of molecular variance (AMOVA), is a statistical model for the molecular algorithm in a single species, typically biological. The name and model are inspired by ANOVA. The method was developed by Laurent Excoffier, Peter Smouse and Joseph Quattro at Rutgers University in 1992.
Since developing AMOVA, Excoffier has written a program for running such analyses. This program, which runs on Windows, is called Arlequin and is freely available on Excoffier's website. There are also implementations in R language in the ade4 and the pegas packages, both available on CRAN (Comprehensive R Archive Network). Another implementation is in Info-Gen, which also runs on Windows. The student version is free and fully functional. Native language of the application is Spanish but an English version is also available.
An additional free statistical package, GenAlEx, is geared toward teaching as well as research and allows for complex genetic analyses to be employed and compared within the commonly used Microsoft Excel interface. This software allows for calculation of analyses such as AMOVA, as well as comparisons with other types of closely related statistics including F-statistics and Shannon's index, and more. | 1 | Biochemistry |
In organic chemistry, a dithiol is a type of organosulfur compound with two thiol () functional groups. Their properties are generally similar to those of monothiols in terms of solubility, odor, and volatility. They can be classified according to the relative location of the two thiol groups on the organic backbone. | 0 | Organic Chemistry |
From 1897-1898, she was granted a graduate scholarship to pursue her PhD. Upon completion of her PhD, she was granted one of Yales University Fellowships to continue work in Goochs laboratory until 1899. | 3 | Analytical Chemistry |
, GOSAT-GW, the successor of GOSAT-2 and GCOM-W "Shizuku", is under development for launch in JFY2024 on the last flight of the H-IIA launch vehicle. | 2 | Environmental Chemistry |
Hydrogenated starch hydrolysates are used commercially in the same way as other common sugar alcohols. They are often used as both a sweetener and as a humectant (moisture-retaining ingredient). As a crystallization modifier, they can prevent syrups from forming crystals of sugar. It is used to add bulk, body, texture, and viscosity to mixtures, and can protect against damage from freezing and drying. HSH products are generally blended with other sweeteners, both caloric and artificial. | 0 | Organic Chemistry |
The oral bioavailability of drospirenone is between 66 and 85%. Peak levels occur 1 to 6 hours after an oral dose. Levels are about 27 ng/mL after a single 4 mg dose. There is 1.5- to 2-fold accumulation in drospirenone levels with continuous administration, with steady-state levels of drospirenone achieved after 7 to 10 days of administration. Peak levels of drospirenone at steady state with 4 mg/day drospirenone are about 41 ng/mL. With the combination of 30 μg/day ethinylestradiol and 3 mg/day drospirenone, peak levels of drospirenone after a single dose are 35 ng/mL, and levels at steady state are 60 to 87 ng/mL at peak and 20 to 25 ng/mL at trough. The pharmacokinetics of oral drospirenone are linear with a single dose across a dose range of 1 to 10 mg. Intake of drospirenone with food does not influence the absorption of drospirenone. | 4 | Stereochemistry |
Because there is a difference in concentration of ions on either side of the membrane, the pH (defined using the relative activity) may also differ when protons are involved. In many instances, from ultrafiltration of proteins to ion exchange chromatography, the pH of the buffer adjacent to the charged groups of the membrane is different from the pH of the rest of the buffer solution. When the charged groups are negative (basic), then they will attract protons so that the pH will be lower than the surrounding buffer. When the charged groups are positive (acidic), then they will repel protons so that the pH will be higher than the surrounding buffer. | 7 | Physical Chemistry |
Oxaloacetate is an intermediate of the citric acid cycle, where it reacts with acetyl-CoA to form citrate, catalyzed by citrate synthase. It is also involved in gluconeogenesis, the urea cycle, the glyoxylate cycle, amino acid synthesis, and fatty acid synthesis. Oxaloacetate is also a potent inhibitor of complex II. | 1 | Biochemistry |
By determination of the interaction partners of unknown proteins, the possible functions of these new proteins may be inferred. This can be done using a single known protein against a library of unknown proteins or conversely, by selecting from a library of known proteins using a single protein of unknown function. | 1 | Biochemistry |
A reducing sugar is one that reduces another compound and is itself oxidized; that is, the carbonyl carbon of the sugar is oxidized to a carboxyl group.
A sugar is classified as a reducing sugar only if it has an open-chain form with an aldehyde group or a free hemiacetal group. | 0 | Organic Chemistry |
The kinetic isotope effect (KIE) of ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO) is the isotopic fractionation associated solely with the step in the Calvin-Benson cycle where a molecule of carbon dioxide () is attached to the 5-carbon sugar ribulose-1,5-bisphosphate (RuBP) to produce two 3-carbon sugars called 3-phosphoglycerate (3 PGA). This chemical reaction is catalyzed by the enzyme RuBisCO, and this enzyme-catalyzed reaction creates the primary kinetic isotope effect of photosynthesis. It is also largely responsible for the isotopic compositions of photosynthetic organisms and the heterotrophs that eat them. Understanding the intrinsic KIE of RuBisCO is of interest to earth scientists, botanists, and ecologists because this isotopic biosignature can be used to reconstruct the evolution of photosynthesis and the rise of oxygen in the geologic record, reconstruct past evolutionary relationships and environmental conditions, and infer plant relationships and productivity in modern environments. | 7 | Physical Chemistry |
Pharmaceutical manufacturers make amoxicillin in trihydrate form, for oral use available as capsules, regular, chewable and dispersible tablets, syrup and pediatric suspension for oral use, and as the sodium salt for intravenous administration.
An extended-release is available. The intravenous form of amoxicillin is not sold in the United States. When an intravenous aminopenicillin is required in the United States, ampicillin is typically used. When there is an adequate response to ampicillin, the course of antibiotic therapy may often be completed with oral amoxicillin.
Research with mice indicated successful delivery using intraperitoneally injected amoxicillin-bearing microparticles. | 4 | Stereochemistry |
The earliest habitation at the site dates back to the Chalcolithic period.
Arslantepe (VII) became important in this region in the Late Chalcolithic. A monumental area with a huge mudbrick building stood on top of a mound. This large building had wall decorations; its function is uncertain. | 8 | Metallurgy |
The ε-amino groups of the lysine residues in urease and phosphotriesterase also feature carbamate. The carbamate derived from aminoimidazole is an intermediate in the biosynthesis of inosine. Carbamoyl phosphate is generated from carboxyphosphate
rather than CO. | 0 | Organic Chemistry |
Halothane was first synthesized by C. W. Suckling of Imperial Chemical Industries in 1951 at the ICI Widnes Laboratory and was first used clinically by M. Johnstone in Manchester in 1956. Initially, many pharmacologists and anaesthesiologists had doubts about the safety and efficacy of the new drug. But halothane, which required specialist knowledge and technologies for safe administration, also afforded British anaesthesiologists the opportunity to remake their speciality as a profession during a period, when the newly established National Health Service needed more specialist consultants. In this context, halothane eventually became popular as a nonflammable general anesthetic replacing other volatile anesthetics such as trichloroethylene, diethyl ether and cyclopropane. In many parts of the world it has been largely replaced by newer agents since the 1980s but is still widely used in developing countries because of its lower cost.
Halothane was given to many millions of people worldwide from its introduction in 1956 through the 1980s. Its properties include cardiac depression at high levels, cardiac sensitization to catecholamines such as norepinephrine, and potent bronchial relaxation. Its lack of airway irritation made it a common inhalation induction agent in pediatric anesthesia.
Its use in developed countries has been mostly replaced by newer anesthetic agents such as sevoflurane. It is not commercially available in the United States. | 4 | Stereochemistry |
The functionality of a monomer molecule is the number of functional groups which participate in the polymerization. Monomers with functionality greater than two will introduce branching into a polymer, and the degree of polymerization will depend on the average functionality f per monomer unit. For a system containing N molecules initially and equivalent numbers of two functional groups A and B, the total number of functional groups is Nf.
And the modified Carothers equation is
: , where p equals to | 7 | Physical Chemistry |
Prehydrated electrons are free electrons that occur in water under irradiation. Usually they form complexes with water molecules and become hydrated electrons. They can also react with the bases of the nucleotides dGMP and dTMP in aqueous solution. This suggests they may also react with the bases of the DNA double helix, ultimately breaking molecular bonds and causing DNA damage. This mechanism is hypothesized to be a cause of radiation damage to DNA. | 5 | Photochemistry |
Ionic bonding is a kind of chemical bonding that arises from the mutual attraction of oppositely charged ions. Ions of like charge repel each other, and ions of opposite charge attract each other. Therefore, ions do not usually exist on their own, but will bind with ions of opposite charge to form a crystal lattice. The resulting compound is called an ionic compound, and is said to be held together by ionic bonding. In ionic compounds there arise characteristic distances between ion neighbours from which the spatial extension and the ionic radius of individual ions may be derived.
The most common type of ionic bonding is seen in compounds of metals and nonmetals (except noble gases, which rarely form chemical compounds). Metals are characterized by having a small number of electrons in excess of a stable, closed-shell electronic configuration. As such, they have the tendency to lose these extra electrons in order to attain a stable configuration. This property is known as electropositivity. Non-metals, on the other hand, are characterized by having an electron configuration just a few electrons short of a stable configuration. As such, they have the tendency to gain more electrons in order to achieve a stable configuration. This tendency is known as electronegativity. When a highly electropositive metal is combined with a highly electronegative nonmetal, the extra electrons from the metal atoms are transferred to the electron-deficient nonmetal atoms. This reaction produces metal cations and nonmetal anions, which are attracted to each other to form a salt. | 7 | Physical Chemistry |
TMAO reductase has an enzyme commission (EC) number of 1.7.2.3. EC numbers are a system of enzyme nomenclature, and each part of this nomenclature refers to a progressive classification of the enzyme with regards to its reaction. The first number defines the reaction type, the second number provides information on involved compounds, the third number specifies the type of reaction, and the fourth number completes the unique serial number for each enzyme.
Trimethylamine N-oxide reductase has the EC number 1.7.2.3, and these components refer to the following enzyme classifications:
* EC 1 enzymes are oxidoreductase enzymes, where an oxidation reduction reaction occurs, and the substrate being oxidized is either an oxygen or hydrogen donor
* EC 1.7 enzymes act on other nitrogenous compounds as donors
* EC 1.7.2 enzymes have a cytochrome as an acceptor
* EC 1.7.2.3 is the enzyme TMAO reductase, which reduces the cytochrome TorC | 1 | Biochemistry |
Without a chiral influence (for example a chiral catalyst, solvent or starting material), a chemical reaction that makes a chiral product will always yield a racemate. That can make the synthesis of a racemate cheaper and easier than making the pure enantiomer, because it does not require special conditions. This fact also leads to the question of how biological homochirality evolved on what is presumed to be a racemic primordial earth.
The reagents of, and the reactions that produce, racemic mixtures are said to be "not stereospecific" or "not stereoselective", for their indecision in a particular stereoisomerism. A frequent scenario is that of a planar species (such as an sp carbon atom or a carbocation intermediate) acting as an electrophile. The nucleophile will have a 50% probability of hitting either of the two sides of the planar grouping, thus producing a racemic mixture: | 4 | Stereochemistry |
Colloid solutions used in intravenous therapy belong to a major group of volume expanders, and can be used for intravenous fluid replacement. Colloids preserve a high colloid osmotic pressure in the blood, and therefore, they should theoretically preferentially increase the intravascular volume, whereas other types of volume expanders called crystalloids also increase the interstitial volume and intracellular volume. However, there is still controversy to the actual difference in efficacy by this difference, and much of the research related to this use of colloids is based on fraudulent research by Joachim Boldt. Another difference is that crystalloids generally are much cheaper than colloids. | 7 | Physical Chemistry |
In bioinformatics, a sequence alignment is a way of arranging the sequences of DNA, RNA, or protein to identify regions of similarity that may be due to functional, structural, or evolutionary relationships between the sequences. If two sequences in an alignment share a common ancestor, mismatches can be interpreted as point mutations and gaps as insertion or deletion mutations (indels) introduced in one or both lineages in the time since they diverged from one another. In sequence alignments of proteins, the degree of similarity between amino acids occupying a particular position in the sequence can be interpreted as a rough measure of how conserved a particular region or sequence motif is among lineages. The absence of substitutions, or the presence of only very conservative substitutions (that is, the substitution of amino acids whose side chains have similar biochemical properties) in a particular region of the sequence, suggest that this region has structural or functional importance. Although DNA and RNA nucleotide bases are more similar to each other than are amino acids, the conservation of base pairs can indicate a similar functional or structural role.
Computational phylogenetics makes extensive use of sequence alignments in the construction and interpretation of phylogenetic trees, which are used to classify the evolutionary relationships between homologous genes represented in the genomes of divergent species. The degree to which sequences in a query set differ is qualitatively related to the sequences' evolutionary distance from one another. Roughly speaking, high sequence identity suggests that the sequences in question have a comparatively young most recent common ancestor, while low identity suggests that the divergence is more ancient. This approximation, which reflects the "molecular clock" hypothesis that a roughly constant rate of evolutionary change can be used to extrapolate the elapsed time since two genes first diverged (that is, the coalescence time), assumes that the effects of mutation and selection are constant across sequence lineages. Therefore, it does not account for possible differences among organisms or species in the rates of DNA repair or the possible functional conservation of specific regions in a sequence. (In the case of nucleotide sequences, the molecular clock hypothesis in its most basic form also discounts the difference in acceptance rates between silent mutations that do not alter the meaning of a given codon and other mutations that result in a different amino acid being incorporated into the protein.) More statistically accurate methods allow the evolutionary rate on each branch of the phylogenetic tree to vary, thus producing better estimates of coalescence times for genes. | 1 | Biochemistry |
All measurements are reported with their standard uncertainty. Measurements of particular combinations of oxygen and hydrogen isotopes are unnecessary because water molecules constantly exchange atoms with each other. | 9 | Geochemistry |
In October 1921, Ostromislensky left Russia and moved to Latvia. There he assumed a position of assistant professor at the department of organic chemistry of University of Latvia in Riga. There he taught two major courses, on chemistry of rubber and on chemotherapeutic drugs. In May 1922, at the invitation of Dr. A. Hopkinson from the US "Rubber Company" Ostromislensky moved to New York. There he continued his work on chemistry and technology of rubber and pharmaceuticals in two companies, United States Rubber Company and Goodyear Tire and Rubber Company. In 1925, he opened his "Ostro Research Laboratory", where he studied the pharmaceutical properties of various compounds based on arsenic and vegetable oils which were used to treat leprosy. He also advocated commercial production of chemotherapeutic drugs pyridium and pyrazolone. In 1928 he received a US patent for production of polystyrene which was used by US Rubber for the first commercial production of polystyrene in the early 1930s. He also patented his early work on the synthesis of polyvinyl chloride in the US.
In 1930, Ostromislensky received U.S. citizenship and was invited to work in the company Union Carbide to develop commercial production of butadiene from ethanol. The production ceased only after the World War II, because it could not compete with butylene-based technologies. In the US, Ostromislensky improved several industrial technologies of synthetic rubber production. He also developed a technology for producing safety glass for the automobile windshields.
In one of developed by him reactions, ethanol is oxidized to acetaldehyde, which reacts with additional ethanol over a tantalum-promoted porous silica catalyst at 325–350 °C to yield butadiene:
:CHCHOH + CHCHO → CH=CH-CH=CH + 2 HO
This process was used in the United States to produce government rubber during World War II, and remains in use today in China and India. | 0 | Organic Chemistry |
There are various expansions or additional techniques that can be applied in IVF, which are usually not necessary for the IVF procedure itself, but would be virtually impossible or technically difficult to perform without concomitantly performing methods of IVF. | 1 | Biochemistry |
The idea that life originated from non-living matter in slow stages appeared in Herbert Spencers 1864–1867 book Principles of Biology, and in William Turner Thiselton-Dyers 1879 paper "On spontaneous generation and evolution". On 1 February 1871 Charles Darwin wrote about these publications to Joseph Hooker, and set out his own speculation, suggesting that the original spark of life may have begun in a "warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity, , present, that a compound was chemically formed ready to undergo still more complex changes." Darwin went on to explain that "at the present day such matter would be instantly devoured or absorbed, which would not have been the case before living creatures were formed."
Alexander Oparin in 1924 and J. B. S. Haldane in 1929 proposed that the first molecules constituting the earliest cells slowly self-organized from a primordial soup, and this theory is called the Oparin–Haldane hypothesis. Haldane suggested that the Earth's prebiotic oceans consisted of a "hot dilute soup" in which organic compounds could have formed. J. D. Bernal showed that such mechanisms could form most of the necessary molecules for life from inorganic precursors. In 1967, he suggested three "stages": the origin of biological monomers; the origin of biological polymers; and the evolution from molecules to cells. | 9 | Geochemistry |
Many discoveries of precolonial gold artifacts go unreported because the gold is found or stolen by treasure hunters, who simply melt the gold down for profit. Among the most important gold artifact discoveries are the "Surigao Treasure" found by construction worker Berto Morales in 1991, the Agusan image found by Manobo woman Belay Campos in 1917, the Bolinao Skull discovered by the National Museum of the Philippines at the Balingasay Archaeological Site in Bolinao, Pangasinan,and the Oton Death Mask excavated rom San Antonio, Iloilo on Panay Island by a team from the National Museum of the Philippines and the University of the Philippines Diliman in the 1960s. | 8 | Metallurgy |
These rules are based on empirical evidence and numerous "exceptions" are known. Examples include:
* cyclisations of cations
* reactions involving third-row atoms, such as sulfur
* Transition metal catalysis | 4 | Stereochemistry |
The technique was developed in Wallonia in present-day Belgium during the Middle Ages. The Walloon method consisted of making pig iron in a blast furnace, followed by refining it in a finery forge. The process was devised in the Liège region, and spread into France and thence from the Pays de Bray to England before the end of the 15th century. Louis de Geer took it to Roslagen in Sweden in the early 17th century, where he employed Walloon ironmakers. Iron made there by this method was known in England as oregrounds iron. | 8 | Metallurgy |
The mechanism of a glycosynthase is similar to the hydrolysis reaction of retaining glycosidases except no covalent-enzyme intermediate is formed. Mutation of the active site nucleophile to a non-nucleophilic amino acid prevents the formation of a covalent intermediate. An activated glycosyl donor with a good anomeric-leaving group (often a fluorine) is required. The leaving group is displaced by an alcohol of the acceptor sugar aided by the active site general base amino acid of the enzyme. | 0 | Organic Chemistry |
Iron was not the only metal to be used in Africa; copper and brass were widely utilised too. However the steady spread of iron meant it must have had more favourable properties for many different uses. Its durability over copper meant that it was used to make many tools from farming pieces to weaponry. Iron was used for personal adornment in jewelry, impressive pieces of artwork and even instruments. It was used for coins and currencies of varying forms. For example, kisi pennies; a traditional form of iron currency used for trading in West Africa. They are twisted iron rods ranging from <30 cm to >2m in length. Suggestions for their uses vary from marital transactions, or simply that they were a convenient shape for transportation, melting down and reshaping into a desired object. There are many different forms of iron currency, often regionally differing in shape and value. Iron did not replace other materials, such as stone and wooden tools, but the quantity of production and variety of uses met were significantly high by comparison. | 8 | Metallurgy |
Oncoprotein 18/Stathmin has been shown to increase the frequency of catastrophe. Oncoprotein 18 (Op18) is a cytosolic protein that are found in abundance in either benign or malignant tumor site: through the complex timing of phosphorylation, this biomolecule regulates the depolymerization of microtubules. It has four sites of phosphorylation characterized by serine residues and are associated with cyclin-dependent protein kinases (CDKs): Ser16, Ser25, Ser38 and Ser63. There are two different models that are in contention regarding the destabilization of microtubules due to Op18: the inhibition of tubulin dimer formation or a catastrophe phenomena.
The Kinesin-related protein XKCM1 stimulates catastrophes in Xenopus microtubules.
The Kinesin-Related Protein 13 MCAK increases the frequency of catastrophe without affecting the promotion of microtubule growth. | 1 | Biochemistry |
In 1980, Joan J. Taylor published the first comprehensive study of the available evidence, entitled Bronze Age Goldwork of the British Isles. In 1994, the archaeologist George Eogan published an academic monograph on the subject, entitled The Accomplished Art: Gold and Gold-Working in Britain and Ireland during the Bronze Age, which was brought out through the U.K.-based Oxbow Books. In it, Eogan noted that his study was "not a corpus or catalogue" of artefacts, instead being "an evaluation and interpretation of the material in social terms". | 8 | Metallurgy |
Chelation therapy is a form of medical treatment in which a chelating ligand is used to selectively remove a metal from the body. When the metal exists as a divalent ion, such as with lead, Pb or mercury, Hg selectivity against calcium, Ca and magnesium, Mg, is essential in order that the treatment does not remove essential metals.
Selectivity is determined by various factors. In the case of iron overload, which may occur in individuals with β-thalessemia who have received blood transfusions, the target metal ion is in the +3 oxidation state and so forms stronger complexes than the divalent ions. It also forms stronger complexes with oxygen-donor ligands than with nitrogen-donor ligands. deferoxamine, a naturally occurring siderophore produced by the actinobacter Streptomyces pilosus and was used initially as a chelation therapy agent. Synthetic siderophores such as deferiprone and deferasirox have been developed, using the known structure of deferoxamine as a starting point. Chelation occurs with the two oxygen atoms.
Wilson's disease is caused by a defect in copper metabolism which results in accumulation of copper metal in various organs of the body. The target ion in this case is divalent, Cu. This ion is classified as borderline in the scheme of Ahrland, Chatt and Davies. This means that it forms roughly equally strong complexes with ligands whose donor atoms are N, O or F as with ligands whose donor atoms are P, S or Cl. Penicillamine, which contains nitrogen and sulphur donor atoms, is used as this type of ligand binds more strongly to copper ions than to calcium and magnesium ions.
Treatment of poisoning by heavy metals such as lead and mercury is more problematical, because the ligands used do not have high specificity relative to calcium. For example, EDTA may be administered as a calcium salt to reduce the removal of calcium from bone together with the heavy metal. Factors determining selectivity for lead against zinc, cadmium and calcium have been reviewed, | 7 | Physical Chemistry |
A molecule can have more than one acyl halide functional group. For example, "adipoyl dichloride", usually simply called adipoyl chloride, has two acyl chloride functional groups; see the structure at right. It is the dichloride (i.e., double chloride) of the 6-carbon dicarboxylic acid adipic acid. An important use of adipoyl chloride is polymerization with an organic di-amino compound to form a polyamide called nylon or polymerization with certain other organic compounds to form polyesters.
Phosgene (carbonyl dichloride, Cl–CO–Cl) is a very toxic gas that is the dichloride of carbonic acid (HO–CO–OH). Both chlorine atoms in phosgene can undergo reactions analogous to the preceding reactions of acyl halides. Phosgene is used a reactant in the production of polycarbonate polymers, among other industrial applications. | 0 | Organic Chemistry |
Asemota has undertaken outreach research with Jamaican farmers, experimenting with lab-derived yam planting materials in their fields, and reviving threatened Jamaican yam varieties. | 1 | Biochemistry |
Bronzing is a process by which a bronze-like surface is applied to other materials (metallic or non-metallic). Some bronzing processes are merely simulated finishes (patinas) applied to existing metal surfaces, or coatings of powdered metal that give the appearance of a solid metal surface. In other cases, an actual layer of heavy copper is electroplated onto an object to produce a bronze-like surface. This electroplating is the method traditionally used for "bronzing" of baby shoes, but to electroplate a non-conductive item like a baby shoe, a conductive material must first be applied, then the copper plating is done. | 7 | Physical Chemistry |
* Member of the Lithuanian Biochemical Society (since 2003)
* Member of the Royal Society of Chemistry (since 2016)
* Member of the International Chemical Biology Society (since 2017)
* Member of the American Chemical Society (since 2021)
* Member of the Sigma Xi (since 2023) | 1 | Biochemistry |
Ichnofacies are assemblages of individual trace fossils that occur repeatedly in time and space. Palaeontologist Adolf Seilacher pioneered the concept of ichnofacies, whereby geologists infer the state of a sedimentary system at its time of deposition by noting the fossils in association with one another. The principal ichnofacies recognized in the literature are Skolithos, Cruziana, Zoophycos, Nereites, Glossifungites, Scoyenia, Trypanites, Teredolites, and Psilonichus. These assemblages are not random. In fact, the assortment of fossils preserved are primarily constrained by the environmental conditions in which the trace-making organisms dwelt. Water depth, salinity, hardness of the substrate, dissolved oxygen, and many other environmental conditions control which organisms can inhabit particular areas. Therefore, by documenting and researching changes in ichnofacies, scientists can interpret changes in environment. For example, ichnological studies have been utilized across mass extinction boundaries, such as the Cretaceous–Paleogene mass extinction, to aid in understanding environmental factors involved in mass extinction events. | 2 | Environmental Chemistry |
In aqueous solutions (solutions of water), water gradually (over the course of hours) hydrolyzes polyphosphates into smaller phosphates and finally into ortho-phosphate, given enough water. Higher temperature or acidic conditions can speed up the hydrolysis reactions considerably.
Conversely, polyphosphoric acids or polyphosphates are often formed by dehydrating a phosphoric acid solution; in other words, removing water from it often by heating and evaporating the water off. | 0 | Organic Chemistry |
In crystallography, the dyakis dodecahedron only exists in one crystal, which is pyrite. Pyrite has other forms other than the dyakis dodecahedron, including tetrahedra, octahedra, cubes and pyritohedra. Though the cube and octahedron are in the cubic crystal system, the dyakis dodecahedron and the pyritohedon are in the isometric crystal system and the tetrahedron is in the tetrahedral crystal system. Though the dyakis dodecahedron has 3-fold axes like the pyritohedron and cube, it doesn't have 4-fold axes but it does have order-4 vertices, as when the dyakis dodecahedron is rotated 90 or 270° along an order-4 vertex, it is not the same as before, because the order-4 vertices act as 2-fold axes, as when they are rotated a full turn or 180°, the polyhedron looks the same as before. | 3 | Analytical Chemistry |
Redox titrations are based on a reduction-oxidation reaction between an oxidizing agent and a reducing agent. A potentiometer or a redox indicator is usually used to determine the endpoint of the titration, as when one of the constituents is the oxidizing agent potassium dichromate. The color change of the solution from orange to green is not definite, therefore an indicator such as sodium diphenylamine is used. Analysis of wines for sulfur dioxide requires iodine as an oxidizing agent. In this case, starch is used as an indicator; a blue starch-iodine complex is formed in the presence of excess iodine, signalling the endpoint.
Some redox titrations do not require an indicator, due to the intense color of the constituents. For instance, in permanganometry a slight persisting pink color signals the endpoint of the titration because of the color of the excess oxidizing agent potassium permanganate. In iodometry, at sufficiently large concentrations, the disappearance of the deep red-brown triiodide ion can itself be used as an endpoint, though at lower concentrations sensitivity is improved by adding starch indicator, which forms an intensely blue complex with triiodide. | 3 | Analytical Chemistry |
In a reaction much similar to the enamine alkylation, enamines can be acylated to form a final dicarbonyl product. The enamine starting material undergoes a nucleophilic addition to acyl halides forming the iminium salt intermediate which can hydrolyze in the presence of acid. | 0 | Organic Chemistry |
In a classical ideal gas with massive particles, the energy of the particles is distributed according to a Maxwell–Boltzmann distribution. This distribution is established as the particles collide with each other, exchanging energy (and momentum) in the process. In a photon gas, there will also be an equilibrium distribution, but photons do not collide with each other (except under very extreme conditions, see two-photon physics), so the equilibrium distribution must be established by other means. The most common way that an equilibrium distribution is established is by the interaction of the photons with matter. If the photons are absorbed and emitted by the walls of the system containing the photon gas, and the walls are at a particular temperature, then the equilibrium distribution for the photons will be a black-body distribution at that temperature.
A very important difference between a generic Bose gas (gas of massive bosons) and a photon gas with a black-body distribution is that the number of photons in the photon gas is not conserved. A photon may collide with an electron in the wall, exciting it to a higher energy state, removing a photon from the photon gas. This electron may drop back to its lower level in a series of steps, each one of which releases an individual photon back into the photon gas. Although the sum of the photon energies of the emitted photons are the same as the absorbed photon, the number of emitted photons will vary. It can be shown that, as a result of this lack of constraint on the number of photons in the system, the chemical potential of the photons must be zero for black-body radiation.
The thermodynamics of a black-body photon gas may be derived using quantum mechanical arguments. The derivation yields the spectral energy density u which is the energy per unit volume per unit frequency interval, given by Planck's law:
where h is Plancks constant, c is the speed of light, ν is the frequency, k is the Boltzmann constant, and T' is temperature.
Integrating over frequency and multiplying by the volume, V, gives the internal energy of a black-body photon gas:
The derivation also yields the (expected) number of photons N:
where is the Riemann zeta function. Note that for a particular temperature, the particle number N varies with the volume in a fixed manner, adjusting itself to have a constant density of photons.
If we note that the equation of state for an ultra-relativistic quantum gas (which inherently describes photons) is given by
then we can combine the above formulas to produce an equation of state that looks much like that of an ideal gas:
The following table summarizes the thermodynamic state functions for a black-body photon gas. Notice that the pressure can be written in the form , which is independent of volume (b is a constant). | 7 | Physical Chemistry |
In biochemistry, Michaelis–Menten kinetics, named after Leonor Michaelis and Maud Menten, is the simplest case of enzyme kinetics, applied to enzyme-catalysed reactions of one substrate and one product. It takes the form of a differential equation describing the reaction rate (rate of formation of product P, with concentration ) to , the concentration of the substrate A (using the symbols recommended by the IUBMB). Its formula is given by the Michaelis–Menten equation:
, which is often written as , represents the limiting rate approached by the system at saturating substrate concentration for a given enzyme concentration. The Michaelis constant is defined as the concentration of substrate at which the reaction rate is half of . Biochemical reactions involving a single substrate are often assumed to follow Michaelis–Menten kinetics, without regard to the model's underlying assumptions. Only a small proportion of enzyme-catalysed reactions have just one substrate, but the equation still often applies if only one substrate concentration is varied. | 7 | Physical Chemistry |
The [4+4] Photocycloaddition is a cycloaddition reaction in which two unsaturated molecules connect via four atoms from each molecule (hence "4 + 4") to create an eight-membered ring. As a photochemical reaction, it is promoted by some form of light, as opposed to a thermal process. | 5 | Photochemistry |
Several simple methods for encoding text have been proposed. Most of these involve translating each letter into a corresponding "codon", consisting of a unique small sequence of nucleotides in a lookup table. Some examples of these encoding schemes include Huffman codes, comma codes, and alternating codes. | 1 | Biochemistry |
Intramolecular aglycon delivery is a synthetic strategy for the construction of glycans. This approach is generally used for the formation of difficult glycosidic linkages. | 0 | Organic Chemistry |
In 1553, Pierre Belon described in his work Observations that pissasphalto, a mixture of pitch and bitumen, was used in the Republic of Ragusa (now Dubrovnik, Croatia) for tarring of ships.
An 1838 edition of Mechanics Magazine cites an early use of asphalt in France. A pamphlet dated 1621, by "a certain Monsieur d'Eyrinys, states that he had discovered the existence (of asphaltum) in large quantities in the vicinity of Neufchatel", and that he proposed to use it in a variety of ways – "principally in the construction of air-proof granaries, and in protecting, by means of the arches, the water-courses in the city of Paris from the intrusion of dirt and filth", which at that time made the water unusable. "He expatiates also on the excellence of this material for forming level and durable terraces" in palaces, "the notion of forming such terraces in the streets not one likely to cross the brain of a Parisian of that generation".
But the substance was generally neglected in France until the revolution of 1830. In the 1830s there was a surge of interest, and asphalt became widely used "for pavements, flat roofs, and the lining of cisterns, and in England, some use of it had been made of it for similar purposes". Its rise in Europe was "a sudden phenomenon", after natural deposits were found "in France at Osbann (Bas-Rhin), the Parc (Ain) and the Puy-de-la-Poix (Puy-de-Dôme)", although it could also be made artificially. One of the earliest uses in France was the laying of about 24,000 square yards of Seyssel asphalt at the Place de la Concorde in 1835. | 7 | Physical Chemistry |
Ubiquinol oxidases () are enzymes in the bacterial electron transport chain that oxidise ubiquinol into ubiquinone and reduce oxygen to water. These enzymes are one set of the many alternative terminal oxidases in the branched prokaryotic electron transport chain. The overall structure of the E. coli ubiquinol oxidase is similar to that of the mammalian Cytochrome c oxidase, with the addition of a polar ubiquinol-binding site embedded in the membrane. | 1 | Biochemistry |
James Clerk Maxwell in his 1871 Theory of Heat outlines four stipulations for the definition of heat:
* It is something which may be transferred from one body to another, according to the second law of thermodynamics.
* It is a measurable quantity, and so can be treated mathematically.
* It cannot be treated as a material substance, because it may be transformed into something that is not a material substance, e.g., mechanical work.
* Heat is one of the forms of energy. | 7 | Physical Chemistry |
Esmirtazapine (ORG-50,081) is a tetracyclic antidepressant drug that was under development by Organon for the treatment of insomnia and vasomotor symptoms (e.g., hot flashes) associated with menopause. Esmirtazapine is the (S)-(+)-enantiomer of mirtazapine and possesses similar overall pharmacology, including inverse agonist actions at H and 5-HT receptors and antagonist actions at α-adrenergic receptors.
Notably, esmirtazapine has a shorter half life of around 10 hours, compared to R-mirtazapine and racemic mixture, which has a half-life of 18–40 hours. Merck has run several studies on low dose (3–4.5 mg) esmirtazapine for the treatment of insomnia. It is attractive for treating insomnia since it is a potent H-inhibitor and a 5-HT antagonist. Unlike low-dose mirtazapine, the half life (10 hours) is short enough that next-day sedation may be manageable, however, for people with CYP2D6 polymorphisms, which constitute a sizable fraction of the population, the half-life is expected to be quite a bit longer. Merck researchers claimed that the incidence of next-day sedation was not a problem in one of their studies, but this claim has been challenged (15% of patients complained of daytime sleepiness vs 3.5% in the placebo group).
In March 2010, Merck terminated its internal clinical development program for esmirtazapine for hot flashes and insomnia, "for strategic reasons". | 4 | Stereochemistry |
Research into solar power for terrestrial applications became prominent with the U.S. National Science Foundation's Advanced Solar Energy Research and Development Division within the "Research Applied to National Needs" program, which ran from 1969 to 1977, and funded research on developing solar power for ground electrical power systems. A 1973 conference, the "Cherry Hill Conference", set forth the technology goals required to achieve this goal and outlined an ambitious project for achieving them, kicking off an applied research program that would be ongoing for several decades. The program was eventually taken over by the Energy Research and Development Administration (ERDA), which was later merged into the U.S. Department of Energy.
Following the 1973 oil crisis, oil companies used their higher profits to start (or buy) solar firms, and were for decades the largest producers. Exxon, ARCO, Shell, Amoco (later purchased by BP) and Mobil all had major solar divisions during the 1970s and 1980s. Technology companies also participated, including General Electric, Motorola, IBM, Tyco and RCA. | 7 | Physical Chemistry |
Mustafa Babanlı (; born February 21, 1968), is an Azerbaijani scientist, Rector of the Azerbaijan State Oil and Industry University.
On September 3, 2015, Mustafa Babanli was appointed Rector of the Azerbaijan State University of Oil and Industry. He is a member of the International Association of University Presidents, serving as Regional Chair for Middle East, Caucasus & Central Asia. | 8 | Metallurgy |
Health Canada has investigated the risks and benefits of pseudoephedrine and ephedrine/Ephedra. Near the end of the study, Health Canada issued a warning on their website stating that those who are under the age of 12, or who have heart disease and may have strokes, should avoid taking pseudoephedrine and ephedrine. Also, they warned that everyone should avoid taking ephedrine or pseudoephrine with other stimulants like caffeine. They also banned all products that contain both ephedrine (or pseudoephedrine) and caffeine.
Products whose only medicinal ingredient is pseudoephedrine must be kept behind the pharmacy counter. Products containing pseudoephedrine along with other medicinal ingredients may be displayed on store shelves but may be sold only in a pharmacy when a pharmacist is present. | 4 | Stereochemistry |
One study in mice demonstrated dose-related carcinogenic potential at several different organ sites. The Food and Drug Administration in the US (FDA) has determined that gentian violet has not been shown by adequate scientific data to be safe for use in animal feed. Use of gentian violet in animal feed causes the feed to be adulterated and is a violation of the Federal Food, Drug, and Cosmetic Act in the US. On June 28, 2007, the FDA issued an "import alert" on farm raised seafood from China because unapproved antimicrobials, including gentian violet, had been consistently found in the products. The FDA report states:
"Like MG (malachite green), CV (crystal violet) is readily absorbed into fish tissue from water exposure and is reduced metabolically by fish to the leuco moiety, leucocrystal violet (LCV). Several studies by the National Toxicology Program reported the carcinogenic and mutagenic effects of crystal violet in rodents. The leuco form induces renal, hepatic and lung tumor in mice."
Health Canada recently found medical devices that use gentian violet to be safe for use but recommended to stop using all drug products that contain gentian violet, including on animals, causing Canadian engineering schools to revisit the usage of this dye during orientation. | 3 | Analytical Chemistry |
There are a large number of proteins yet to be identified that transport Mg. Even in the best studied eukaryote, yeast, Borrelly has reported a Mg/H exchanger without an associated protein, which is probably localised to the Golgi. At least one other major Mg transporter in yeast is still unaccounted for, the one affecting Mg transport in and out of the yeast vacuole. In higher, multicellular organisms, it seems that many Mg transporting proteins await discovery.
The CorA-domain-containing Mg transporters (CorA, Alr-like and Mrs2-like) have a similar but not identical array of affinities for divalent cations. In fact, this observation can be extended to all of the Mg transporters identified so far. This similarity suggests that the basic properties of Mg strongly influence the possible mechanisms of recognition and transport. However, this observation also suggests that using other metal ions as tracers for Mg uptake will not necessarily produce results comparable to the transporter's ability to transport Mg. Ideally, Mg should be measured directly.
Since Mg is practically unobtainable, much of the old data will need to be reinterpreted with new tools for measuring Mg transport, if different transporters are to be compared directly. The pioneering work of Kolisek and Froschauer using mag-fura 2 has shown that free Mg can be reliably measured in vivo in some systems. By returning to the analysis of CorA with this new tool, we have gained an important baseline for the analysis of new Mg transport systems as they are discovered. However, it is important that the amount of transporter present in the membrane is accurately determined if comparisons of transport capability are to be made. This bacterial system might also be able to provide some utility for the analysis of eukaryotic Mg transport proteins, but differences in biological systems of prokaryotes and eukaryotes will have to be considered in any experiment. | 1 | Biochemistry |
Woven wire cloth, typically produced from stainless steel, is commonly employed as a filtration medium for sieving in a wide range of industries. Most often woven with a plain weave, or a twill weave for the lightest of meshes, apertures can be produced from a few microns upwards (e.g. 25 microns), employing wires with diameters from as little as 25 microns. A twill weave allows a mesh to be woven when the wire diameter is too thick in proportion to the aperture. Other, less commonplace, weaves, such as Dutch/Hollander, allow the production of meshes that are stronger and/or having smaller apertures.
Today wire cloth is woven to strict international standards, e.g. ISO1944:1999, which dictates acceptable tolerance regarding nominal mesh count and blemishes. The nominal mesh count, to which mesh is generally defined is a measure of the number of openings per lineal inch, determined by counting the number of openings from the centre of one wire to the centre of another wire one lineal inch away. For example, a 2 mesh woven with a wire of 1.6mm wire diameter has an aperture of 11.1mm (see picture below of a 2 mesh with an intermediate crimp). The formula for calculating the aperture of a mesh, with a known mesh count and wire diameter, is as follows:
where a = aperture, b = mesh count and c = wire diameter.
Other calculations regarding woven wire cloth/mesh can be made including weight and open area determination. Of note, wire diameters are often referred to by their standard wire gauge (swg); e.g. a 1.6mm wire is a 16 swg.
Traditionally, screen cloth was made with metal wires woven with a loom. Today, woven cloth is still widely used primarily because they are less expensive than other types of screen media. Over the years, different weaving techniques have been developed; either to increase the open area percentage or add wear-life. Slotted opening woven cloth is used where product shape is not a priority and where users need a higher open area percentage. Flat-top woven cloth is used when the consumer wants to increase wear-life. On regular woven wire, the crimps (knuckles on woven wires) wear out faster than the rest of the cloth resulting in premature breakage. On flat-top woven wire, the cloth wears out equally until half of the wire diameter is worn, resulting in a longer wear life. Unfortunately flat-top woven wire cloth is not widely used because of the lack of crimps that causes a pronounced reduction of passing fines resulting in premature wear of con crushers. | 8 | Metallurgy |
The analyte of interest may be biological or chemical in nature, and by way of example, only may include chemical moieties (toxins, metabolites, drugs and drug residues), peptides, proteins, cellular components, viruses, and combinations thereof. The analyte of interest may be in either a fluid or a supporting medium, such as a gel.
SOFIA has demonstrated its potential as a device with a wide range of applications. These include clinical applications, such as detecting diseases, discovering predispositions to pathologies, establishing a diagnosis and tracking the effectiveness of prescribed treatments, and nonclinical applications, such as preventing the entry of toxins and other pathogenic agents into products intended for human consumption:
* Clinical applications – SOFIA may be used to conduct both qualitative tests (either positive or negative results) to detect or identify bacteria or viruses, and quantitative tests (measuring substances) to detect or quantify biological constants or markers, which are substances produced by the body in the presence of, for example, an infectious disease (to allow determination of viral load, for instance, in AIDS therapy, or the level of toxicity in drugs of abuse detection).
* Nonclinical applications - As an immunoassay, SOFIA can potentially be used on a wider scale to monitor the quality of food, pharmaceuticals, cosmetics, or water, as well as general environmental parameters and agricultural products. The ability to detect and screen bacteria and toxins for a wide range of products is a growing and more complex requirement as may be evidenced by the increase incidence of food- and animal-borne diseases, such as E. coli, Salmonella, BSE, avian influenza, etc. | 1 | Biochemistry |
Using antibody microarray in different medical diagnostic areas has attracted researchers attention. Digital bioassay is an example of such research domains. In this technology, an array of microwells on a glass/polymer chip are seeded with magnetic beads (coated with fluorescent tagged antibodies), subjected to targeted antigens and then characterised by a microscope through counting fluorescing wells. A cost-effective fabrication platform (using OSTE polymers) for such microwell arrays has been recently demonstrated and the bio-assay model system has been successfully characterised. Furthermore, immunoassays on thiol-ene "synthetic paper" micropillar scaffolds have shown to generate a superior fluorescence signal. | 1 | Biochemistry |
The database houses a wide range of information available for samples from all over the globe to be grouped into two categories: (a) observations and measurements (e.g. mineral data, images, chemical analyses), for which robust data models already exist, and (b) interpretative results (e.g. P-T conditions, crystallization ages, cooling rates, etc.), which are conclusions based on the observational data. Development of a robust data model for interpretative data is currently underway as of December 2010. The database system is beginning to incorporate a number of tools for data analysis and calculation that adds considerable power to the researcher.
MetPetDB differs from other Geochemistry relational databases (e.g. [https://web.archive.org/web/20070610152747/http://georoc.mpch-mainz.gwdg.de/georoc/ GEOROC], [http://www.navdat.org NAVDAT], PetDB) in that it incorporates unpublished data in addition to data published in peer-reviewed journals. The vast majority of data collected by metamorphic geologists is not presented in publication, and therefore a forum for sharing this data with the public is an objective of MetPetDB. Contributors to MetPetDB also have the ability to store private data and create projects, or collections of private, public, and published data for sharing and organization. A comprehensive list of the publications and their published samples are located at [http://metpetdb.rpi.edu/MetPetRest/parse_publications.html MetPetDB Published Samples] | 9 | Geochemistry |
During the day, the stomata close to conserve water, and the -storing organic acids are released from the vacuoles of the mesophyll cells. An enzyme in the stroma of chloroplasts releases the , which enters into the Calvin cycle so that photosynthesis may take place. | 5 | Photochemistry |
This process consists of depositing a solid culture substrate, such as rice or wheat bran, on flatbeds after seeding it with microorganisms; the substrate is then left in a temperature-controlled room for several days.
Liquid state fermentation is performed in tanks, which can reach at an industrial scale. Liquid culture is ideal for the growing of unicellular organisms such as bacteria or yeasts.
To achieve liquid aerobic fermentation, it is necessary to constantly supply the microorganism with oxygen, which is generally done via stirring the fermentation media. Accurately managing the synthesis of the desired metabolites requires regulating temperature, soluble oxygen, ionic strength, pH and control nutrients.
Applying this growing technique to filamentous fungi leads to difficulties. The fungus develops in its vegetative form, generating hyphae or multicellular ramous filaments, while a septum separates the cells. As this mycelium develops in a liquid environment, it generates abundant viscosity in the growing medium, reducing oxygen solubility, while stirring disrupts the cell network increasing cell mortality.
In nature, filamentous fungi grow on the ground, decomposing vegetal compounds under naturally ventilated conditions. Therefore, solid state fermentation enables the optimal development of filamentous fungi, allowing the mycelium to spread on the surface of solid compounds among which air can flow.
Solid state fermentation uses culture substrates with low water levels (reduced water activity), which is particularly appropriate for mould. The methods used to grow filamentous fungi using solid state fermentation allow the best reproduction of their natural environment. The medium is saturated with water but little of it is free-flowing. The solid medium comprises both the substrate and the solid support on which the fermentation takes place. The substrate used is generally composed of vegetal byproducts such as beet pulp or wheat bran.
At the beginning of the growth process, the substrates and solid culture compounds are non-soluble compounds composed of very large, biochemically complex molecules that the fungus will cut off to get essential C and N nutrients. To develop its natural substrate, the fungal organism sets forth its entire genetic potential to produce the metabolites necessary for its growth. The composition of the growth medium guides the microorganism's metabolism towards the production of enzymes that release bio-available single molecules such as sugars or amino acids by carving out macromolecules. Therefore, when selecting the components of the growth medium it is possible to guide the cells towards the production of the desired metabolite(s), mainly enzymes that transform polymers (cellulose, hemicellulose, pectins, proteins) into single moieties in a very efficient and cost-effective manner.
Compared to submerged fermentation processes, solid state fermentation is more cost-effective: smaller vessels, lower water consumption, reduced wastewater treatment costs and lower energy consumption (no need to heat up water, poor mechanical energy input due to smooth stirring).
Cultivating on heterogeneous substrates requires expertise to maintain optimal growth conditions. Air flow monitoring is key because it impacts temperature, oxygen supply and moisture. In order to maintain sufficient moisture content for the growth of filamentous fungus, waterlogged air is used and may require further addition of water. In most cases, solid state fermentation does not require a completely sterile environment as the initial sterilization of the fermentation substrate associated with the rapid colonization of the substrate by the fungous microorganism limits the development of the autochthonous flora. | 1 | Biochemistry |
A leukocidin is a type of cytotoxin created by some types of bacteria (Staphylococcus). It is a type of pore-forming toxin. The model for pore formation is step-wise. First, the cytotoxin’s “S” subunit recognizes specific protein-containing receptors, or an integrin on the host cell’s surface. The S subunit then recruits a second, “F” subunit, and the two subunits dimerize on the surface of the host’s cell. After dimerization, oligomerization occurs. Finally, the oligomers, consisting of alternating S and F subunits, undergo a significant structural change and form a beta-barrel, that pierces through the host cell’s lipid bilayer.
Leukocidins get their names by killing ("-cide") leukocytes. Leukocidins target phagocytes, natural killer cells, dendritic cells, and T lymphocytes and therefore targets both, innate and adaptive immune responses. Leukocidins fall into the category of bacterial invasin. Invasins are enzymatic secretions that help bacteria invade the host tissue to which they are attached. Although similar to exotoxins, invasins are different in two respects: they work through much less specific mechanisms than exotoxins, and their actions are generally more localized.
One type is Panton-Valentine leukocidin. | 1 | Biochemistry |
Figure 1 to the right explains the basic principle, in which the organic extractant E is contained inside the pores of a porous particle. The solute S, which is initially dissolved in the aqueous phase surrounding the SIR particle, physically dissolves in the organic extractant phase during the extraction process. Furthermore, the solute S can react with the extractant to form a complex ES. This complexation of the solute with the extractant shifts the overall extraction equilibrium further towards the organic phase. This way, the extraction of the solute is enhanced.
While during conventional liquid-liquid extraction the solvent and the extractant have to be dispersed, in a SIR setup the dispersion is already achieved by the impregnated particles. This also prevents an additional phase separation step, which would be necessary after the emulsification occurring in liquid-liquid extraction. In order to elucidate the effect of emulsification, Figure 2 (to the left) compares the two systems of an extractant in liquid-liquid equilibrium with water, left, and SIR particles in equilibrium with water, right. The figure shows that no emulsification occurs in the SIR system, whereas the liquid-liquid system shows turbidity implying emulsification. Also, the impregnation step decreases the solvent loss into the aqueous phase compared to liquid-liquid extraction. This decrease of extractant loss is contributed to physical sorption of the extractant on the particle surface, which means that the extractant inside the pores does not entirely behave as a bulk liquid. Depending on the pore size of the used particles, capillary forces may also play a role in retaining the extractant. Otherwise, van-der-Waals forces, pi-pi-interactions or hydrophobic interactions might stabilize the extractant inside the particle pores. However, the possible decrease of extractant loss depends largely on the pore size and the water solubility of the extractant. Nonetheless, SIRs have a significant advantage over e.g. custom made ion-exchange resins with chemically bonded ligands. SIRs can be reused for different separation tasks by just rinsing one complexing agent out and re-impregnating them with another more suitable extractant. This way, potentially expensive design and production steps of e.g. affinity resins can be avoided. Finally, by filling the whole volume of the particle pores with an extractant (complexing agent), a higher capacity for solutes can be achieved than with ordinary adsorption or ion exchange resins, where only the surface area is available.
However, there are possible drawbacks of SIR technology, such as leaching of the extractant or clogging of a fixed bed by attrition of the particles. These might be remedied by choosing the proper particle-extractant-system. This implies selecting a suitable extractant with low water solubility, which is sufficiently retained inside the pores, and selecting mechanically stable particles as a solid support for the extractant. Additionally, SIRs can be stabilized by coating them, as shown by D. Muraviev et al. As coating material, A. W. Trochimczuk et al. used polyvinyl alcohol.
In order to remove or recover the extracted solute, SIR particles can be regenerated using low pressure steam stripping, which is particularly effective for the recovery of volatile hydrocarbons. However, if the vapor pressure of the extracted solute is too low, or if the complexation between solute and extractant is too strong, other techniques need to be applied, e.g. pH swing. | 3 | Analytical Chemistry |
Leishmania tarentolae (cannot infect mammals) expression systems allow stable and lasting production of proteins at high yield, in chemically defined media. Produced proteins exhibit fully eukaryotic post-translational modifications, including glycosylation and disulfide bond formation. | 1 | Biochemistry |
Most humans have multiple copies of the regulatory gene sequence for prodynorphin, which is virtually identical among all primates, whereas other primates have only a single copy. In addition, most Asian populations have two copies of the gene sequence for prodynorphin, whereas East Africas, Middle Easterners, and Europeans tend to have three repetitions.
The extent of regulatory gene disparities for prodynorphin, between human and primates, has gained the attention of scientists. There are very few genes known to be directly related to mankind's speciation from other great apes. According to computational biologist researcher Matthew W. Hahn of Indiana University, "this is the first documented instance of a neural gene that has had its regulation shaped by natural selection during human origins."
The prodynorphin polypeptide is identical in humans and chimpanzees, but the regulatory promoter sequences have been shown to exhibit marked differences. According to Hahn, "humans have the ability to turn on this gene more easily and more intensely than other primates", a reason why regulation of this gene may have been important in the evolution of modern humans' mental capacity. | 1 | Biochemistry |
Bromothymol blue acts as a weak acid in a solution. It can thus be in protonated or deprotonated form, appearing yellow or blue, respectively. It is bright aquamarine by itself, and greenish-blue in a neutral solution. The deprotonation of the neutral form results in a highly conjugated structure, accounting for the difference in color. An intermediate of the deprotonation mechanism is responsible for the greenish color in neutral solution.
The protonated form of bromothymol blue has its peak absorption at 427 nm thus transmitting yellow light in acidic solutions, and the deprotonated form has its peak absorption at 602 nm thus transmitting blue light in more basic solutions. Highly acidic Bromothymol blue is magenta in color.
The general carbon skeleton of bromothymol blue is common to many indicators including chlorophenol red, thymol blue, and bromocresol green.
The presence of one moderate electron-withdrawing group (bromine atom) and two moderate donating groups (alkyl substituents) are responsible for bromothymol blues active indication range from a pH of 6.0 to 7.6. While the conjugation is responsible for the length and nature of the color change range, these substituent groups are ultimately responsible for the indicators active range.
Bromothymol blue is sparingly soluble in oil, but soluble in water, ether, and aqueous solutions of alkalis. It is less soluble in nonpolar solvents such as benzene, toluene, and xylene, and practically insoluble in petroleum ether. | 3 | Analytical Chemistry |
In plants, ATP synthase is also present in chloroplasts (CFF-ATP synthase). The enzyme is integrated into thylakoid membrane; the CF-part sticks into stroma, where dark reactions of photosynthesis (also called the light-independent reactions or the Calvin cycle) and ATP synthesis take place. The overall structure and the catalytic mechanism of the chloroplast ATP synthase are almost the same as those of the bacterial enzyme. However, in chloroplasts, the proton motive force is generated not by respiratory electron transport chain but by primary photosynthetic proteins. The synthase has a 40-aa insert in the gamma-subunit to inhibit wasteful activity when dark. | 5 | Photochemistry |
Diphosphene compounds usually exhibit a symmetry-allowed () (intense) and symmetry-forbidden electronic transitions () (weak). In Raman, there is significant enhancement of P=P stretch in the resonance with allowed electron transition than with the forbidden transition due to different geometries of excited states and enhancement mechanism. Also the observed strong Raman shifts for and suggest stronger dipnictenes feature of diphosphene compared with P-P single bond. | 0 | Organic Chemistry |
The term Reststrahlen was coined following the observation by Heinrich Rubens in 1898 that repeated reflection of an infrared beam at the surface of a given material suppresses radiation at all wavelengths except for certain spectral intervals, and Rubens detected wavelengths of sizes around 60 μm. The measured intensity for these special intervals (the Reststrahlen range) indicates a reflectance of up to 80% or even more, while the maximum reflectance due to infrared bands of dielectric materials are usually compared to the intensity of the incident radiation, while the light in the Reststrahlen range can maintain 40% of its original intensity by the time it reaches the detector. Obviously, this contrast increases with the number of reflections and explains the observation made by Rubens and the term Reststrahlen (residual rays) used to describe this spectral selection.
Reststrahlen bands manifest in diffuse reflectance infrared absorption spectra as complete band reversal, or in infrared emission spectra as a minimum in emissivity. | 7 | Physical Chemistry |
A glucuronide, also known as glucuronoside, is any substance produced by linking glucuronic acid to another substance via a glycosidic bond. The glucuronides belong to the glycosides.
Glucuronidation, the conversion of chemical compounds to glucuronides, is a method that animals use to assist in the excretion of toxic substances, drugs or other substances that cannot be used as an energy source. Glucuronic acid is attached via a glycosidic bond to the substance, and the resulting glucuronide, which has a much higher water solubility than the original substance, is eventually excreted by the kidneys.
Enzymes that cleave the glycosidic bond of a glucuronide are called glucuronidases. | 1 | Biochemistry |
To describe the geometry of graphical surfaces that illustrate equilibrium relations between thermodynamic functions of state, no one can fictively think of so-called "reversible processes". They are convenient theoretical objects that trace paths across graphical surfaces. They are called "processes" but do not describe naturally occurring processes, which are always irreversible. Because the points on the paths are points of thermodynamic equilibrium, it is customary to think of the "processes" described by the paths as fictively "reversible". Reversible processes are always quasistatic processes, but the converse is not always true. | 7 | Physical Chemistry |
The term Dallol was coined by the Afar people and means dissolution or disintegration, describing a landscape of green acid ponds and geysers (pH-values less than 1) and iron oxide, sulfur and salt desert plains. | 9 | Geochemistry |
The first version of HMDB was released on January 1, 2007, followed by two subsequent versions on January 1, 2009 (version 2.0), August 1, 2009 (version 2.5), September 18, 2012 (version 3.0) and Jan. 1, 2013 (version 3.5), 2017 (version 4.0)., 2022 (version 5.0). Details for each of the major HMDB versions (up to version 5.0) is provided in Table 1. | 1 | Biochemistry |
Progesterone and its neurosteroid active metabolite allopregnanolone appear to be importantly involved in libido in females. | 0 | Organic Chemistry |
Drug metabolism is the metabolic breakdown of drugs by living organisms, usually through specialized enzymatic systems. More generally, xenobiotic metabolism (from the Greek xenos "stranger" and biotic "related to living beings") is the set of metabolic pathways that modify the chemical structure of xenobiotics, which are compounds foreign to an organism's normal biochemistry, such as any drug or poison. These pathways are a form of biotransformation present in all major groups of organisms and are considered to be of ancient origin. These reactions often act to detoxify poisonous compounds (although in some cases the intermediates in xenobiotic metabolism can themselves cause toxic effects). The study of drug metabolism is called pharmacokinetics.
The metabolism of pharmaceutical drugs is an important aspect of pharmacology and medicine. For example, the rate of metabolism determines the duration and intensity of a drug's pharmacologic action. Drug metabolism also affects multidrug resistance in infectious diseases and in chemotherapy for cancer, and the actions of some drugs as substrates or inhibitors of enzymes involved in xenobiotic metabolism are a common reason for hazardous drug interactions. These pathways are also important in environmental science, with the xenobiotic metabolism of microorganisms determining whether a pollutant will be broken down during bioremediation, or persist in the environment. The enzymes of xenobiotic metabolism, particularly the glutathione S-transferases are also important in agriculture, since they may produce resistance to pesticides and herbicides.
Drug metabolism is divided into three phases. In phase I, enzymes such as cytochrome P450 oxidases introduce reactive or polar groups into xenobiotics. These modified compounds are then conjugated to polar compounds in phase II reactions. These reactions are catalysed by transferase enzymes such as glutathione S-transferases. Finally, in phase III, the conjugated xenobiotics may be further processed, before being recognised by efflux transporters and pumped out of cells. Drug metabolism often converts lipophilic compounds into hydrophilic products that are more readily excreted. | 1 | Biochemistry |
Herpesviruses are ubiquitous pathogens infecting a variety of animals, including humans. Hosts include many economically important species such as abalone, oysters, salmon, poultry (avian infectious laryngotracheitis, Marek's disease), cattle (bovine malignant catarrhal fever), dogs, goats, horses, cats (feline viral rhinotracheitis), and pigs (pseudorabies). Infections may be severe and may result in fatalities or reduced productivity. Therefore, outbreaks of herpesviruses in livestock cause significant financial losses and are an important area of study in veterinary virology. | 1 | Biochemistry |
Mutations that prevent the expression of Rab27 (knock out mutations) cause the hypopigmentation and immunodeficiency disorder known as type II Griscelli syndrome, while a decrease in Rab27 prenylation is thought to be involved in choroideremia.
The symptoms of type II Griscelli syndrome have shown that Rab27 is involved in melanosome transport in melanocytes and in cytotoxic killing activity in cytotoxic T lymphoblasts. In melanocytes Rab27 binds the melanosome. The melanosome is transported along the microtubule. Rab27 then recruits Slac2A and myosin Va, these enzymes are essential for the transfer of the melanosomes from the microtubules to actin filaments. The melanosomes can now continue on their path towards the cell periphery. If either Rab27, Slac2A or myosin Va are absent then the melanosomes remain in the perinuclear region of the cell. This disruption in pigmentation results in the hypopigmentation seen in the silvery hair colour of patients with Griscelli syndrome. | 1 | Biochemistry |
In recent years Raman-SEC has become an important tool in the study of electrochemical processes and in the characterization of many molecules, providing specific in situ information about them. Some applications are:
* Materials: Raman-SEC is widely used in the study and characterization of new materials, such as graphene, carbon nanotubes or conductive polymers, among others. It is also applied in the study of dyes, organic molecules capable of forming monolayers on the electrode, and in the study of proteins.
* Qualitative and quantitative analysis: Raman-SEC can be applied to highly complex samples, such as the detection of melamine in milk, the identification of bacteria, the detection of DNA biomarkers and/or uric acid in urine, among others. In addition, very low concentrations can be detected.
* Energy. Raman-SEC were used in the study of solar cells, batteries and catalysts for fuel cells.
* Transfer processes at the liquid/liquid interfaces: Raman-SEC is used to monitor ion or electron transfer processes at polarizable interfaces between immiscible electrolyte solutions. | 7 | Physical Chemistry |
There are three main classes of biopolymers: polysaccharides, polypeptides, and polynucleotides.
In living cells, they may be synthesized by enzyme-mediated processes, such as the formation of DNA catalyzed by DNA polymerase. The synthesis of proteins involves multiple enzyme-mediated processes to transcribe genetic information from the DNA to RNA and subsequently translate that information to synthesize the specified protein from amino acids. The protein may be modified further following translation in order to provide appropriate structure and functioning. There are other biopolymers such as rubber, suberin, melanin, and lignin. | 7 | Physical Chemistry |
Adenosine triphosphate (ATP) is a nucleotide that provides energy to drive and support many processes in living cells, such as muscle contraction, nerve impulse propagation, condensate dissolution, and chemical synthesis. Found in all known forms of life, it is often referred to as the "molecular unit of currency" of intracellular energy transfer.
When consumed in a metabolic processes, ATP converts either to adenosine diphosphate (ADP) or to adenosine monophosphate (AMP). Other processes regenerate ATP. It is also a precursor to DNA and RNA, and is used as a coenzyme. An average human adult processes around 50 kilograms daily.
From the perspective of biochemistry, ATP is classified as a nucleoside triphosphate, which indicates that it consists of three components: a nitrogenous base (adenine), the sugar ribose, and the triphosphate. | 1 | Biochemistry |
In biochemistry, naturally occurring phenols are natural products containing at least one phenol functional group. Phenolic compounds are produced by plants and microorganisms. Organisms sometimes synthesize phenolic compounds in response to ecological pressures such as pathogen and insect attack, UV radiation and wounding. As they are present in food consumed in human diets and in plants used in traditional medicine of several cultures, their role in human health and disease is a subject of research. Some phenols are germicidal and are used in formulating disinfectants. | 0 | Organic Chemistry |
IgA - IgE receptor - IGF type 1 receptor - IGF type 2 receptor - IgG - IgM - immediate-early protein - immune cell - immune system - immunoglobulin - immunoglobulin joining region - immunoglobulin variable region - immunologic receptor - immunology - In vivo - infrared spectroscopy - inhibin - inhibitor - inhibitory gi G-protein - Inorganic chemistry - insect protein - Insulin - insulin receptor - insulin-like growth factor I - Integral membrane protein - intein - intercellular adhesion molecule-1 - interferon receptor - interferon type I - interferon type II - interferon-alpha - interferon-beta - interleukin receptor - interleukin-1 receptor - interleukin-2 receptor - interleukin-3 - interleukin-3 receptor - intermediate filament - intermediate filament protein - intermembrane space - Intermolecular force - International Union of Pure and Applied Chemistry (IUPAC) - interphase - intracisternal A-particle gene - Intramolecular force - intron - Inverse agonist - invertebrate peptide receptor - invertebrate photoreceptor - Ion channel - ion channel gating - Ionic bond - ionization potential - iron–sulfur protein - isoenzyme - isoleucine - Isomer - Isothermal titration calorimeter - Isotopic tracer | 1 | Biochemistry |
LHASA (Logic and Heuristics Applied to Synthetic Analysis) is a computer program developed in 1971 by the research group of Elias James Corey at the Harvard University Department of Chemistry. The program uses artificial intelligence techniques to discover sequences of reactions which may be used to synthesize a molecule. This program was one of the first to use a graphical interface to input and display chemical structures. | 0 | Organic Chemistry |
The first α-Keggin anion, ammonium phosphomolybdate (), was first reported by Berzelius in 1826. In 1892, Blomstrand proposed the structure of phosphomolybdic acid and other poly-acids as a chain or ring configuration. Alfred Werner, using the coordination compounds ideas of Copaux, attempted to explain the structure of silicotungstic acid. He assumed a central group, ion, enclosed by four , where R is a unipositive ion. The are linked to the central group by primary valences. Two more groups were linked to the central group by secondary valences. This proposal accounted for the characteristics of most poly-acids, but not all.
In 1928, Linus Pauling proposed a structure for α-Keggin anions consisting of a tetrahedral central ion, , caged by twelve octahedra. In this proposed structure, three of the oxygen on each of the octahedra shared electrons with three neighboring octahedra. As a result, 18 oxygen atoms were used as bridging atoms between the metal atoms. The remaining oxygen atoms bonded to a proton. This structure explained many characteristics that were observed such as basicities of alkali metal salts and the hydrated form of some of the salts. However the structure could not explain the structure of dehydrated acids.
James Fargher Keggin with the use of X-ray diffraction experimentally determined the structure of α-Keggin anions in 1934. The Keggin structure accounts for both the hydrated and dehydrated α-Keggin anions without the need for significant structural change. The Keggin structure is the widely accepted structure for the α-Keggin anions. | 7 | Physical Chemistry |
Within atomic, molecular, and optical physics, there are numerous studies using molecules to verify fundamental constants and probe for physics beyond the Standard Model. Certain molecular structures are predicted to be sensitive to new physics phenomena, such as parity and time-reversal violation. Molecules are also considered a potential future platform for trapped ion quantum computing, as their more complex energy level structure could facilitate higher efficiency encoding of quantum information than individual atoms. From a chemical physics perspective, intramolecular vibrational energy redistribution experiments use vibrational spectra to determine how energy is redistributed between different quantum states of a vibrationally excited molecule. | 7 | Physical Chemistry |
Acoustic resonance spectroscopy (ARS) is a method of spectroscopy in the acoustic region, primarily the sonic and ultrasonic regions. ARS is typically much more rapid than HPLC and NIR. It is non destructive and requires no sample preparation as the sampling waveguide can simply be pushed into a sample powder/liquid or in contact with a solid sample.
To date, the AR spectrometer has successfully differentiated and quantified sample analytes in various forms; (tablets, powders, and liquids). It has been used to measure and monitor the progression of chemical reactions, such as the setting and hardening of concrete from cement paste to solid. Acoustic spectrometry has also been used to measure the volume fraction of colloids in a dispersion medium, as well as for the investigation of physical properties of colloidal dispersions, such as aggregation and particle size distribution. Typically, these experiments are carried out with sinusoidal excitation signals and the experimental observation of signal attenuation. From a comparison of theoretical attenuation to experimental observation, the particle size distribution and aggregation phenomena are inferred. | 7 | Physical Chemistry |
Reversible-deactivation polymerization is defined as a chain polymerization propagated by chain carriers that are deactivated reversibly, bringing them into one or more active-dormant equilibria. An example of a reversible-deactivation polymerization is group-transfer polymerization. | 7 | Physical Chemistry |
Resonance (or delocalization) energy is the amount of energy needed to convert the true delocalized structure into that of the most stable contributing structure. The empirical resonance energy can be estimated by comparing the enthalpy change of hydrogenation of the real substance with that estimated for the contributing structure.
The complete hydrogenation of benzene to cyclohexane via 1,3-cyclohexadiene and cyclohexene is exothermic; 1 mole of benzene delivers 208.4 kJ (49.8 kcal).
Hydrogenation of one mole of double bonds delivers 119.7 kJ (28.6 kcal), as can be deduced from the last step, the hydrogenation of cyclohexene. In benzene, however, 23.4 kJ (5.6 kcal) are needed to hydrogenate one mole of double bonds. The difference, being 143.1 kJ (34.2 kcal), is the empirical resonance energy of benzene. Because 1,3-cyclohexadiene also has a small delocalization energy (7.6 kJ or 1.8 kcal/mol) the net resonance energy, relative to the localized cyclohexatriene, is a bit higher: 151 kJ or 36 kcal/mol.
This measured resonance energy is also the difference between the hydrogenation energy of three non-resonance double bonds and the measured hydrogenation energy:
:(3 × 119.7) − 208.4 = 150.7 kJ/mol (36 kcal).
Regardless of their exact values, resonance energies of various related compounds provide insights into their bonding. The resonance energies for pyrrole, thiophene, and furan are, respectively, 88, 121, and
67 kJ/mol (21, 29, and 16 kcal/mol). Thus, these heterocycles are far less aromatic than benzene, as is manifested in the lability of these rings. | 7 | Physical Chemistry |
The Fick principle relies on the observation that the total uptake of (or release of) a substance by the peripheral tissues is equal to the product of the blood flow to the peripheral tissues and the arterial-venous concentration difference (gradient) of the substance. In the determination of cardiac output, the substance most commonly measured is the oxygen content of blood thus giving the arteriovenous oxygen difference, and the flow calculated is the flow across the pulmonary system. This gives a simple way to calculate the cardiac output:
Assuming there is no intracardiac shunt, the pulmonary blood flow equals the systemic blood flow. Measurement of the arterial and venous oxygen content of blood involves the sampling of blood from the pulmonary artery (low oxygen content) and from the pulmonary vein (high oxygen content). In practice, sampling of peripheral arterial blood is a surrogate for pulmonary venous blood. Determination of the oxygen consumption of the peripheral tissues is more complex.
The calculation of the arterial and venous oxygen concentration of the blood is a straightforward process. Almost all oxygen in the blood is bound to hemoglobin molecules in the red blood cells. Measuring the content of hemoglobin in the blood and the percentage of saturation of hemoglobin (the oxygen saturation of the blood) is a simple process and is readily available to physicians. Using the fact that each gram of hemoglobin can carry of O, the oxygen content of the blood (either arterial or venous) can be estimated by the following formula:
Assuming a hemoglobin concentration of and an oxygen saturation of 99%, the oxygen concentration of arterial blood is approximately of O per L.
The saturation of mixed venous blood is approximately 75% in health. Using this value in the above equation, the oxygen concentration of mixed venous blood is approximately of O per L.
Therefore, using the assumed Fick determination, the approximated cardiac output for an average man (1.9 m3) is:
:Cardiac Output = ( O/minute × 1.9) / ( O/L − O/L) =
Cardiac output may also be estimated with the Fick principle using production of carbon dioxide as a marker substance. | 1 | Biochemistry |
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