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An ideal hydrophobic surface would have a contact angle of 180 degrees to water. This means that the hydrocarbons lie flat against the surface creating a thin layer and preventing dampening water absorption. However, in practice it is fine or even preferred to have a low level of dampening water absorption because of a phenomenon that occurs when water settles at the surface of paper. This phenomenon is when ink is unable to transfer to the paper because of the water layer at the surface. The contact angle value for hydrocarbons on a rough pigment-coated paper can be found to be approximately 110° through a contact angle meter.
The Youngs equation can be used to calculate the surface energy of a liquid on paper. Youngs equation is:
where is the interfacial tension between the solid and the liquid, is the interfacial tension between the liquid and the vapor, and is the interfacial tension between the solid and the vapor.
An ideal oleophilic surface would have a contact angle of 0° with oil, therefore allowing the ink to transfer to the paper and be absorbed. The hydrocarbon plasma coating provides an oleophilic surface to the paper by lowering the contact angle of the paper with the oil in the ink.
The hydrocarbon plasma coating increases the non-polar interactions while decreasing polar interactions which allow paper to absorb ink while preventing dampening water absorption. | 7 | Physical Chemistry |
Biodegradation has been well investigated because of its relevance to sewage plants with specialized microorganisms. Two microorganisms that have been studied in depth are the white rot fungus and the bacterium Nocardia Corallina. | 3 | Analytical Chemistry |
Ultraviolet rays are usually invisible to most humans. The lens of the human eye blocks most radiation in the wavelength range of 300–400 nm; shorter wavelengths are blocked by the cornea. Humans also lack color receptor adaptations for ultraviolet rays. Nevertheless, the photoreceptors of the retina are sensitive to near-UV, and people lacking a lens (a condition known as aphakia) perceive near-UV as whitish-blue or whitish-violet. Under some conditions, children and young adults can see ultraviolet down to wavelengths around 310 nm. Near-UV radiation is visible to insects, some mammals, and some birds. Birds have a fourth color receptor for ultraviolet rays; this, coupled with eye structures that transmit more UV gives smaller birds "true" UV vision. | 5 | Photochemistry |
The anion is abbreviated PP, standing for inorganic pyrophosphate. It is formed by the hydrolysis of ATP into AMP in cells.
:ATP → AMP + PP
For example, when a nucleotide is incorporated into a growing DNA or RNA strand by a polymerase, pyrophosphate (PP) is released. Pyrophosphorolysis is the reverse of the polymerization reaction in which pyrophosphate reacts with the 3′-nucleosidemonophosphate (NMP or dNMP), which is removed from the oligonucleotide to release the corresponding triphosphate (dNTP from DNA, or NTP from RNA).
The pyrophosphate anion has the structure , and is an acid anhydride of phosphate. It is unstable in aqueous solution and hydrolyzes into inorganic phosphate:
or in biologists' shorthand notation:
In the absence of enzymic catalysis, hydrolysis reactions of simple polyphosphates such as pyrophosphate, linear triphosphate, ADP, and ATP normally proceed extremely slowly in all but highly acidic media.
(The reverse of this reaction is a method of preparing pyrophosphates by heating phosphates.)
This hydrolysis to inorganic phosphate effectively renders the cleavage of ATP to AMP and PP irreversible, and biochemical reactions coupled to this hydrolysis are irreversible as well.
PP occurs in synovial fluid, blood plasma, and urine at levels sufficient to block calcification and may be a natural inhibitor of hydroxyapatite formation in extracellular fluid (ECF). Cells may channel intracellular PP into ECF. ANK is a nonenzymatic plasma-membrane PP channel that supports extracellular PP levels. Defective function of the membrane PP channel ANK is associated with low extracellular PP and elevated intracellular PP. Ectonucleotide pyrophosphatase/phosphodiesterase (ENPP) may function to raise extracellular PP.
From the standpoint of high energy phosphate accounting, the hydrolysis of ATP to AMP and PP requires two high-energy phosphates, as to reconstitute AMP into ATP requires two phosphorylation reactions.
:AMP + ATP → 2 ADP
:2 ADP + 2 P → 2 ATP
The plasma concentration of inorganic pyrophosphate has a reference range of 0.58–3.78 µM (95% prediction interval). | 1 | Biochemistry |
Reductive elimination occurs more rapidly for complexes of three- or five-coordinate metal centers than for four- or six-coordinate metal centers. For even coordination number complexes, reductive elimination leads to an intermediate with a strongly metal-ligand antibonding orbital. When reductive elimination occurs from odd coordination number complexes, the resulting intermediate occupies a nonbonding molecular orbital. | 0 | Organic Chemistry |
Accelerated solvent extraction has found many applications in the food industry, including in:
* The testing of dietary seafoods for arsenic content
* Extraction of catechins from green tea samples
* Authentication of natural vanilla flavors
* The analysis of terpenoids and sterols in tobacco | 3 | Analytical Chemistry |
The heat of neutralization of a fully dissociated acid with a fully dissociated base is approximately –56kJ/mol. The reaction is thus strongly exothermic, and is an excellent basis for a wide range of analysis in industry. An advantage for the industrial analyst is that the use of stronger titrants (1 to 2 mol/L) permits a reduction in the amount of sample preparation, and samples can often be directly and accurately dispensed into the titration vessel prior to titration. | 3 | Analytical Chemistry |
eOn was a volunteer computing project running on the Berkeley Open Infrastructure for Network Computing (BOINC) platform, which uses theoretical chemistry techniques to solve problems in condensed matter physics and materials science. It was a project of the Institute for Computational Engineering and Sciences at the University of Texas.
Traditional molecular dynamics can accurately model events that occur within a fraction of a millisecond. In order to model events that take place on much longer timescales, Eon combines transition state theory with kinetic Monte Carlo. The result is a combination of classical mechanics and quantum methods like density functional theory.
Since the generation of new work units depended on the results of previous units, the project could only give each host a few units at a time.
On May 26, 2014, it was announced that eOn would be retiring from BOINC. | 7 | Physical Chemistry |
Lisinopril is contraindicated in people who have a history of angioedema (hereditary or idiopathic) or who have diabetes and are taking aliskiren. | 4 | Stereochemistry |
Roses metal, Rose metal or Roses alloy is a fusible alloy with a low melting point.
Rose's metal consists of 50% bismuth, 25–28% lead and 22–25% tin. Its melting point is between . The alloy does not appreciably contract or expand on solidification, this characteristic being a function of its bismuth percentage, but does slightly contract on cooling. | 8 | Metallurgy |
The existence of frigorific mixtures can be viewed as a consequence of the Gibbs phase rule, which describes the relationship at equilibrium between the number of components, the number of coexisting phases, and the number of degrees of freedom permitted by the conditions of heterogeneous equilibrium. Specifically, at constant atmospheric pressure, in a system containing linearly independent chemical components, if +1 phases are specified to be present in equilibrium, then the system is fully determined (there are no degrees of freedom). That is, the temperature and the compositions of all phases are determined. Thus, in for example the chemical system HO-NaCl, which has two components, the simultaneous presence of the three phases liquid, ice, and hydrohalite can exist only at atmospheric pressure at the unique temperature of –21.2 °C
. The approach to equilibrium of a frigorific mixture involves spontaneous temperature change driven by the conversion of latent heat into sensible heat as the phase proportions adjust to accommodate the decrease in thermodynamic potential associated with the approach to equilibrium. | 7 | Physical Chemistry |
The reaction is irreproducible in each run due to the initial inhomogeneity of the mixture which result from variation in stirring rate, overall volume as well as geometry of the reactors. Repeating the reaction in the statistically meaningful manners leads to the reproducible cumulative probability distribution curve. The example for this clock is iodate/arsenous acid reaction.
One reaction may fall into more than one classification above depending on the circumstance. For example, iodate−arsenous acid reaction can be substrate-depletive clock reaction, autocatalysis-driven clock reaction and crazy clock reaction. | 7 | Physical Chemistry |
Moiety conservation is the conservation of a subgroup in a chemical species, which is cyclically transferred from one molecule to another. In biochemistry, moiety conservation can have profound effects on the system's dynamics. | 1 | Biochemistry |
Economizers (US and Oxford spelling), or economisers (UK), are mechanical devices intended to reduce energy consumption, or to perform useful function such as preheating a fluid. The term economizer is used for other purposes as well. Boiler, power plant, heating, refrigeration, ventilating, and air conditioning (HVAC) uses are discussed in this article. In simple terms, an economizer is a heat exchanger. | 7 | Physical Chemistry |
The icosahedral charge-neutral closo-carboranes, 1,2-, 1,7-, and 1,12- (informally ortho-, meta-, and para-carborane) are particularly stable and are commercially available. The ortho-carborane forms first upon the reaction of decaborane and acetylene. It converts quantitatively to the meta-carborane upon heating in an inert atmosphere. Producing meta-carborane from ortho-carborane requires 700 °C, proceeding in ca. 25% yield.
is also well established. | 7 | Physical Chemistry |
The search for organic molecules at the surface of Mars is a top priority of Mars exploration space missions. Therefore, a key step in interpretation of future data collected by these missions is to understand the preservation of organic matter in the Martian environment. A 1.5-year exposure to Mars-like surface UV radiation conditions in space resulted in complete degradation of the organic compounds (glycine, serine, phthalic acid, phthalic acid in the presence of a mineral phase, and mellitic acid). Their half-lives were between 50 and 150 h for Martian surface conditions.
To understand the chemical behavior of organic molecules in the space environment, amino acids and a dipeptide in pure form and embedded in meteorite powder were exposed to space conditions for 18 months; the samples were returned to Earth and analyzed in the laboratory for reactions caused by solar UV and cosmic radiation. The results show that resistance to irradiation is a function of the chemical nature of the exposed molecules and the wavelengths of the UV light. The most altered compounds were the dipeptide, aspartic acid, and aminobutyric acid. The most resistant were alanine, valine, glycine, and aminoisobutyric acid. The results also demonstrate the protective effect of meteorite powder, which reemphasizes the importance of exogenic contribution to the inventory of prebiotic organics on early Earth. | 1 | Biochemistry |
The earliest hominid remains found around the Caspian Sea are from Dmanisi dating back to around 1.8 Ma and yielded a number of skeletal remains of Homo erectus or Homo ergaster. More later evidence for human occupation of the region came from a number of caves in Georgia and Azerbaijan such as Kudaro and Azykh Caves. There is evidence for Lower Palaeolithic human occupation south of the Caspian from western Alburz. These are Ganj Par and Darband Cave sites.
Neanderthal remains also have been discovered at a cave in Georgia. Discoveries in the Hotu cave and the adjacent Kamarband cave, near the town of Behshahr, Mazandaran south of the Caspian in Iran, suggest human habitation of the area as early as 11,000 years ago. Ancient Greeks focused on the civilization on the south shore – they call it the (H)yr(c/k)anian Sea (, with sources noting the latter word was evolving then to todays Thelessa': late ).
Hafiz-i Abru, a fourteenth century Timurid Empire geographer, has recorded that the destruction of Oxus river dam and irrigation works which diverting the river flow towards Caspian sea, has caused Aral sea to nearly disappeared. | 2 | Environmental Chemistry |
The integral of thus yields the logarithm of the ratio of the upper and lower cut-offs. This number is known as the Coulomb logarithm and is designated by either or . It is the factor by which small-angle collisions are more effective than large-angle collisions. The Coulomb logarithm was introduced independently by Lev Landau in 1936 and Subrahmanyan Chandrasekhar in 1943. For many plasmas of interest it takes on values between and . (For convenient formulas, see pages 34 and 35 of the [https://www.nrl.navy.mil/ppd/content/nrl-plasma-formulary NRL Plasma formulary].) The limits of the impact parameter integral are not sharp, but are uncertain by factors on the order of unity, leading to theoretical uncertainties on the order of . For this reason it is often justified to simply take the convenient choice . The analysis here yields the scalings and orders of magnitude. | 7 | Physical Chemistry |
Isotopes in the decay chains of actinides are unique amongst radiogenic isotopes because they are both radiogenic and radioactive. Because their abundances are normally quoted as activity ratios rather than atomic ratios, they are best considered separately from the other radiogenic isotope systems. | 9 | Geochemistry |
In addition to water and ammonia, the clouds in the atmospheres of the gas giant planets contain ammonium sulfides. The reddish-brownish clouds are attributed to polysulfides, arising from the exposure of the ammonium sulfides to light. | 8 | Metallurgy |
These glycosides contain an aglycone group that is a derivative of anthraquinone. They have a laxative effect. They are mainly found in dicot plants except the family Liliaceae which are monocots. They are present in senna, rhubarb and Aloe species. Anthron and anthranol are reduced forms of anthraquinone. | 0 | Organic Chemistry |
Three prime untranslated regions (3UTRs) of messenger RNAs (mRNAs) often contain regulatory sequences that post-transcriptionally cause RNA interference. Such 3-UTRs often contain both binding sites for microRNAs (miRNAs) as well as for regulatory proteins. By binding to specific sites within the 3-UTR, miRNAs can decrease gene expression of various mRNAs by either inhibiting translation or directly causing degradation of the transcript. The 3-UTR also may have silencer regions that bind repressor proteins that inhibit the expression of a mRNA.
The 3-UTR often contains microRNA response elements (MREs). MREs are sequences to which miRNAs bind. These are prevalent motifs within 3-UTRs. Among all regulatory motifs within the 3'-UTRs (e.g. including silencer regions), MREs make up about half of the motifs.
As of 2014, the miRBase web site, an archive of miRNA sequences and annotations, listed 28,645 entries in 233 biologic species. Of these, 1,881 miRNAs were in annotated human miRNA loci. miRNAs were predicted to have an average of about four hundred target mRNAs (affecting expression of several hundred genes). Freidman et al. estimate that >45,000 miRNA target sites within human mRNA 3'UTRs are conserved above background levels, and >60% of human protein-coding genes have been under selective pressure to maintain pairing to miRNAs.
Direct experiments show that a single miRNA can reduce the stability of hundreds of unique mRNAs. Other experiments show that a single miRNA may repress the production of hundreds of proteins, but that this repression often is relatively mild (less than 2-fold).
The effects of miRNA dysregulation of gene expression seem to be important in cancer. For instance, in gastrointestinal cancers, nine miRNAs have been identified as epigenetically altered and effective in down regulating DNA repair enzymes.
The effects of miRNA dysregulation of gene expression also seem to be important in neuropsychiatric disorders, such as schizophrenia, bipolar disorder, major depression, Parkinsons disease, Alzheimers disease and autism spectrum disorders. | 1 | Biochemistry |
The desired enantiomer from resolution, allylic alcohol 5.1 (Scheme 5) was acetylated with acetic anhydride and 4-(dimethylamino)pyridine in methylene chloride to yield monoacetate 5.2. It is noteworthy that this reaction was exclusive for the allylic alcohol, and the adjacent hydroxyl group was not acetylated. Alcohol 5.2 was oxidized with tetrapropylammonium perruthenate and N-methylmorpholine N-oxide to give ketone 5.3. Alkene 5.3 underwent hydroboration in tetrahydrofuran. Oxidation with basic hydrogen peroxide and sodium bicarbonate gave alcohol 5.4 in 35% yield, with 15% yield of a regioisomer. The acetonide was removed, giving triol 5.5. This alcohol was monoacetylated, to give acetate 5.6. The benzyl group was removed and replaced with a triethylsilyl group. Diol 5.7 was selectively activated using methanesulfonyl chloride and 4-(dimethylamino)pyridine to give mesylate 5.8, in 78% yield.
The acetyl group in 6.1 (Scheme 6) was removed to give primary alcohol 6.2. The Taxol ring (D) was added by an intramolecular nucleophilic substitution involving this hydroxyl group to give oxetane 6.3. After acetylation, phenyllithium was used to open the carbonate ester ring to give alcohol 6.5. Allylic oxidation with pyridinium chlorochromate, sodium acetate, and celite gave ketone 6.6, which was subsequently reduced using sodium borohydride to give secondary alcohol 6.7. This was the last compound before the addition of the amide tail. | 0 | Organic Chemistry |
T790M, also known as Thr790Met, is a gatekeeper mutation of the epidermal growth factor receptor (EGFR). The mutation substitutes a threonine (T) with a methionine (M) at position 790 of exon 20, affecting the ATP binding pocket of the EGFR kinase domain. Threonine is a small polar amino acid; methionine is a larger nonpolar amino acid. Rather than directly blocking inhibitor binding to the active site, T790M increases the affinity for ATP so that the inhibitors are outcompeted; irreversible covalent inhibitors such as osimertinib can overcome this resistance. | 1 | Biochemistry |
The first evidence of presence of a neutralizing substance in the blood that could counter infections came when Emil von Behring along with Kitasato Shibasaburō in 1890 developed effective serum against diphtheria. This they did by transferring serum produced from animals immunized against diphtheria to animals suffering from it. Transferring the serum thus could cure the infected animals. Behring was awarded the Nobel Prize for this work in 1901.
At this time though the chemical nature of what exactly in the blood conferred this protection was not known. In a few decades to follow, it was shown that the protective serum could neutralize and precipitate toxins, and clump bacteria. All these functions were attributed to different substances in the serum, and named accordingly as antitoxin, precipitin and agglutinin. That all the three substances were one entity (gamma globulins) was demonstrated by Elvin A. Kabat in 1939. In the preceding year Kabat had demonstrated the heterogeneity of antibodies through ultracentrifugation studies of horses' sera.
Until this time, cell-mediated immunity and humoral immunity were considered to be contending theories to explain effective immune response, but the former lagged behind owing to lack of advanced techniques. Cell-mediated immunity got an impetus in its recognition and study when in 1942, Merrill Chase successfully transferred immunity against tuberculosis between pigs by transferring white blood cells.
It was later shown in 1948 by Astrid Fagraeus in her doctoral thesis that the plasma B cells are specifically involved in antibody production. The role of lymphocytes in mediating both cell-mediated and humoral responses was demonstrated by James Gowans in 1959.
In order to account for the wide range of antigens the immune system can recognize, Paul Ehrlich in 1900 had hypothesized that preexisting "side chain receptors" bind a given pathogen, and that this interaction induces the cell exhibiting the receptor to multiply and produce more copies of the same receptor. This theory, called the selective theory was not proven for next five decades, and had been challenged by several instructional theories which were based on the notion that an antibody would assume its effective structure by folding around the antigen. In the late 1950s however, the works of three scientists—Jerne, Talmage and Burnet (who largely modified the theory)—gave rise to the clonal selection theory, which proved all the elements of Ehrlich's hypothesis except that the specific receptors that could neutralize the agent were soluble and not membrane-bound.
The clonal selection theory was proved correct when Sir Gustav Nossal showed that each B cell always produces only one antibody.
In 1974, the role of MHC in antigen presentation was demonstrated by Rolf Zinkernagel and Peter C. Doherty. | 1 | Biochemistry |
At temperatures below the lambda point, helium shows the unique property of superfluidity. The fraction of the liquid that forms the superfluid component is a macroscopic quantum fluid. The helium atom is a neutral particle, so . Furthermore, when considering helium-4, the relevant particle mass is , so Eq. () reduces to
For an arbitrary loop in the liquid, this gives
Due to the single-valued nature of the wave function
with integer, we have
The quantity
is the quantum of circulation. For a circular motion with radius r
In case of a single quantum ()
When superfluid helium is put in rotation, Eq. () will not be satisfied for all loops inside the liquid unless the rotation is organized around vortex lines (as depicted in Fig. 2). These lines have a vacuum core with a diameter of about 1 Å (which is smaller than the average particle distance). The superfluid helium rotates around the core with very high speeds. Just outside the core (r = 1 Å), the velocity is as large as 160 m/s. The cores of the vortex lines and the container rotate as a solid body around the rotation axes with the same angular velocity. The number of vortex lines increases with the angular velocity (as shown in the upper half of the figure). Note that the two right figures both contain six vortex lines, but the lines are organized in different stable patterns. | 7 | Physical Chemistry |
Nayak advocates that more people should be taught to perform the so-called miracles of godmen. He also advocates that people should be trained to recognize pseudoscience and demand scientific evidence. He holds the opinion that well-known scientists should be convinced to join the cause and form pressure groups against pseudoscience. He is also lobbying for a bill for the separation of state and religion to be introduced in the Indian parliament. After the murder of anti-superstition activist Narendra Dabholkar and enactment of the anti-superstition ordinance in Maharashtra state, Nayak expressed the need of a similar law in Karnataka. Regarding fellow Mangalorean George Fernandes, Nayak said the "You can hate George Fernandes, You can love Fernandes, but you cannot ignore him". Nayak was the guest of honour during the launch event of the book Bandh Samrat - Tales of Eternal Rebel written on George Fernandes's early trade union activities in Mangalore and Bombay | 1 | Biochemistry |
The boiling point elevation is a colligative property, which means that it is dependent on the presence of dissolved particles and their number, but not their identity. It is an effect of the dilution of the solvent in the presence of a solute. It is a phenomenon that happens for all solutes in all solutions, even in ideal solutions, and does not depend on any specific solute–solvent interactions. The boiling point elevation happens both when the solute is an electrolyte, such as various salts, and a nonelectrolyte. In thermodynamic terms, the origin of the boiling point elevation is entropic and can be explained in terms of the vapor pressure or chemical potential of the solvent. In both cases, the explanation depends on the fact that many solutes are only present in the liquid phase and do not enter into the gas phase (except at extremely high temperatures).
Put in vapor pressure terms, a liquid boils at the temperature when its vapor pressure equals the surrounding pressure. For the solvent, the presence of the solute decreases its vapor pressure by dilution. A nonvolatile solute has a vapor pressure of zero, so the vapor pressure of the solution is less than the vapor pressure of the solvent. Thus, a higher temperature is needed for the vapor pressure to reach the surrounding pressure, and the boiling point is elevated.
Put in chemical potential terms, at the boiling point, the liquid phase and the gas (or vapor) phase have the same chemical potential (or vapor pressure) meaning that they are energetically equivalent. The chemical potential is dependent on the temperature, and at other temperatures either the liquid or the gas phase has a lower chemical potential and is more energetically favorable than the other phase. This means that when a nonvolatile solute is added, the chemical potential of the solvent in the liquid phase is decreased by dilution, but the chemical potential of the solvent in the gas phase is not affected. This means in turn that the equilibrium between the liquid and gas phase is established at another temperature for a solution than a pure liquid, i.e., the boiling point is elevated.
The phenomenon of freezing-point depression is analogous to boiling point elevation. However, the magnitude of the freezing point depression is larger than the boiling point elevation for the same solvent and the same concentration of a solute. Because of these two phenomena, the liquid range of a solvent is increased in the presence of a solute. | 7 | Physical Chemistry |
For a one-dimensional crystal of size
where the factor in parentheses comes from the fact the sum is over nearest-neighbour pairs (), next nearest-neighbours (), ... and for a crystal of planes, there are pairs of nearest neighbours, pairs of next-nearest neighbours, etc. | 3 | Analytical Chemistry |
#Motilin
#Neurotensin
#Substance P
#Somatostatin
#Bombesin
#Serotonin
#Angiotensin
#Nitric Oxide
#Kinins
#Histamine | 1 | Biochemistry |
A quench press is a machine that uses concentrated forces to hold an object as it is quenched. These types of quench facilities are used to quench large gears and other circular parts so that they remain circular. They are also used to quench saw blades and other flat or plate-shaped objects so that they remain flat.
Quench presses are able to quench the part while it is being held because of the unique structure of the clamps holding the part. Clamps are slotted so that oil or water can flow through each slot and cool the part and the ribs of the clamps can hold the part in place. | 8 | Metallurgy |
Human chorionic gonadotropin (hCG) is a hormone for the maternal recognition of pregnancy produced by trophoblast cells that are surrounding a growing embryo (syncytiotrophoblast initially), which eventually forms the placenta after implantation. The presence of hCG is detected in some pregnancy tests (HCG pregnancy strip tests). Some cancerous tumors produce this hormone; therefore, elevated levels measured when the patient is not pregnant may lead to a cancer diagnosis and, if high enough, paraneoplastic syndromes, however, it is not known whether this production is a contributing cause, or an effect of carcinogenesis. The pituitary analog of hCG, known as luteinizing hormone (LH), is produced in the pituitary gland of males and females of all ages.
Various endogenous forms of hCG exist. The measurement of these diverse forms is used in the diagnosis of pregnancy and a variety of disease states. Preparations of hCG from various sources have also been used therapeutically, by both medicine and quackery. , the United States Food and Drug Administration has prohibited the sale of "homeopathic" and over-the-counter hCG diet products and declared them fraudulent and illegal.
Beta-hCG is initially secreted by the syncytiotrophoblast. | 1 | Biochemistry |
In liquid water there is some self-ionization giving hydronium ions and hydroxide ions.
The equilibrium constant for this reaction, known as the ionic product of water, , has a value of about at 25 °C. At neutral pH, the concentration of the hydroxide ion () equals that of the (solvated) hydrogen ion (), with a value close to 10 mol L at 25 °C. See data page for values at other temperatures.
The thermodynamic equilibrium constant is a quotient of thermodynamic activities of all products and reactants including water:
However, for dilute solutions, the activity of a solute such as HO or OH is approximated by its concentration, and the activity of the solvent HO is approximated by 1, so that we obtain the simple ionic product | 2 | Environmental Chemistry |
The goals of using semiochemicals in pest control are
# to monitor pest populations to determine if control is warranted and
# to alter the behavior of the pest or its enemies to the detriment of the pest. In general, the advantages of using semiochemicals are
## they have adverse effects only on target pests,
## they are relatively nontoxic and required in low amounts,
## they are nonpersistent and environmentally safe
## they appear difficult for insects to develop resistance against. Monitoring of pest populations with pheromones is often integrated in management programs. | 1 | Biochemistry |
The DNA template labeled at the 3 or 5 end, depending on the location of the binding site(s). Labels that can be used are: radioactivity and fluorescence. Radioactivity has been traditionally used to label DNA fragments for footprinting analysis, as the method was originally developed from the Maxam-Gilbert chemical sequencing technique. Radioactive labeling is very sensitive and is optimal for visualizing small amounts of DNA. Fluorescence is a desirable advancement due to the hazards of using radio-chemicals. However, it has been more difficult to optimize because it is not always sensitive enough to detect the low concentrations of the target DNA strands used in DNA footprinting experiments. Electrophoretic sequencing gels or capillary electrophoresis have been successful in analyzing footprinting of fluorescent tagged fragments. | 1 | Biochemistry |
We start with a three-state Λ-type system, where and are dipole-allowed transitions and is forbidden. In the rotating wave approximation, the semi-classical Hamiltonian is given by
with
where and are the Rabi frequencies of the probe field (of frequency ) and the coupling field (of frequency ) in resonance with the transition frequencies and , respectively, and H.c. stands for the Hermitian conjugate of the entire expression. We will write the atomic wave function as
Solving the Schrödinger equation , we obtain the solutions
Using the initial condition
we can solve these equations to obtain
with . We observe that we can choose the initial conditions
which gives a time-independent solution to these equations with no probability of the system being in state . This state can also be expressed in terms of a mixing angle as
with
This means that when the atoms are in this state, they will stay in this state indefinitely. This is a dark state, because it can not absorb or emit any photons from the applied fields. It is, therefore, effectively transparent to the probe laser, even when the laser is exactly resonant with the transition. Spontaneous emission from can result in an atom being in this dark state or another coherent state, known as a bright state. Therefore, in a collection of atoms, over time, decay into the dark state will inevitably result in the system being "trapped" coherently in that state, a phenomenon known as coherent population trapping. | 7 | Physical Chemistry |
Anthocyanins fluoresce, enabling a tool for plant cell research to allow live cell imaging without a requirement for other fluorophores. Anthocyanin production may be engineered into genetically modified materials to enable their identification visually. | 3 | Analytical Chemistry |
There are many different ways to prepare PBS solutions, common ones are Dulbecco's phosphate-buffered saline (DPBS) and the Cold Spring Harbor protocol. Some formulations of DPBS do not contain potassium and magnesium, while other ones contain calcium and/or magnesium (depending on whether or not the buffer is used on live or fixed tissue: the latter does not require CaCl or MgCl ).
Start with 800 mL of distilled water to dissolve all salts. Add distilled water to a total volume of 1 liter. The resultant 1× PBS will have a final concentration of 157 mM Na, 140mM Cl, 4.45mM K, 10.1 mM HPO, 1.76 mM HPO and a pH of 7.96. Add 2.84 mM of HCl to shift the buffer to 7.3 mM HPO and 4.6 mM HPO for a final pH of 7.4 and a Cl concentration of 142 mM.
The pH of PBS is ~7.4. When making buffer solutions, it is good practice to always measure the pH directly using a pH meter. If necessary, pH can be adjusted using hydrochloric acid or sodium hydroxide.
PBS can also be prepared by using commercially made PBS buffer tablets or pouches.
If used in cell culturing, the solution can be dispensed into aliquots and sterilized by autoclaving or filtration. Sterilization may not be necessary depending on its use. PBS can be stored at room temperature or in the refrigerator. However, concentrated stock solutions may precipitate when cooled and should be kept at room temperature until precipitate has completely dissolved before use. | 1 | Biochemistry |
The Collaborative Computational Project Number 4 in Protein Crystallography (CCP4) was set up in 1979 in the United Kingdom to support collaboration between researchers working in software development and assemble a comprehensive collection of software for structural biology. The CCP4 core team is located at the Research Complex at Harwell (RCaH) at Rutherford Appleton Laboratory (RAL) in Didcot, near Oxford, UK.
CCP4 was originally supported by the UK Science and Engineering Research Council (SERC), and is now supported by the Biotechnology and Biological Sciences Research Council (BBSRC). The project is coordinated at CCLRC Daresbury Laboratory. The results of this effort gave rise to the CCP4 program suite, which is now distributed to academic and commercial users worldwide. | 3 | Analytical Chemistry |
* Jayko, A.S., et al. (2013). [https://purl.fdlp.gov/GPO/gpo45331 Methods and Spatial Extent of Geophysical Investigations, Mono Lake, California, 2009 to 2011.] Reston, Va.: U.S. Department of the Interior, U.S. Geological Survey. | 2 | Environmental Chemistry |
These are the Bravais lattice types in three dimensions:
* P – Primitive
* I – Body centered (from the German "Innenzentriert")
* F – Face centered (from the German "Flächenzentriert")
* A – Base centered on A faces only
* B – Base centered on B faces only
* C – Base centered on C faces only
* R – Rhombohedral | 3 | Analytical Chemistry |
Chromatography separates the analyte from the rest of the sample so that it may be measured without interference from other compounds. There are different types of chromatography that differ from the media they use to separate the analyte and the sample. In Thin-layer chromatography, the analyte mixture moves up and separates along the coated sheet under the volatile mobile phase. In Gas chromatography, gas separates the volatile analytes. A common method for chromatography using liquid as a mobile phase is High-performance liquid chromatography. | 3 | Analytical Chemistry |
In thermodynamics, the Massieu function (sometimes called Massieu–Gibbs function, Massieu potential, or Gibbs function, or characteristic (state) function in its original terminology), symbol (Psi), is defined by the following relation:
where for every system with degree of freedom one may choose variables, e.g. to define a coordinate system, where and are extensive and intensive variables, respectively, and where at least one extensive variable must be within this set in order to define the size of the system. The -th variable, , is then called the Massieu function.
The Massieu function was introduced in the 1869 paper "On the Characteristic Functions of Various Fluids" by French engineer François Massieu (1832-1896). The name "Gibbs function" is the eponym of American physicist Willard Gibbs (1839-1903), who cited Massieu in his 1876 On the Equilibrium of Heterogeneous Substances. Massieu, as discussed in the first footnote to the abstract of Gibbs Equilibrium, “appears to have been the first to solve the problem of representing all the properties of a body of invariable composition which are concerned in reversible processes by means of a single function.” Massieus 1869 paper seems to be the source for the generalized mathematical conception of the energy of a system being equal to summations of the products of pairs of conjugate variables. | 7 | Physical Chemistry |
Seliwanoff’s test is a chemical test which distinguishes between aldose and ketose sugars. If the sugar contains a ketone group, it is a ketose. If a sugar contains an aldehyde group, it is an aldose. This test relies on the principle that, when heated, ketoses are more rapidly dehydrated than aldoses. It is named after Theodor Seliwanoff, the chemist who devised the test. When added to a solution containing ketoses, a red color is formed rapidly indicating a positive test. When added to a solution containing aldoses, a slower forming light pink is observed instead.
The reagents consist of resorcinol and concentrated hydrochloric acid:
* The acid hydrolysis of polysaccharide and oligosaccharide ketoses yields simpler sugars followed by furfural.
* The dehydrated ketose then reacts with two equivalents of resorcinol in a series of condensation reactions to produce a molecule with a deep cherry red color.
* Aldoses may react slightly to produce a faint pink color.
Fructose and sucrose are two common sugars which give a positive test. Sucrose gives a positive test as it is a disaccharide consisting of fructose and glucose.
Generally, 6M HCl is used to run this test. Ketoses are dehydrated faster and give stronger colors. Aldoses react very slowly and give faint colors. | 0 | Organic Chemistry |
The basis for using corrected parameters on the map is mach number kinematic similarity. Corrected flow and speed define mach numbers through the compressor and flow angles onto the blades using velocity triangles. Velocity triangles allow flows to be transferred between different reference frames. In this case gas velocity and circumferential blade velocity in a stationary frame is converted to velocity in a rotating frame (rotor) passage. Losses in blade and vane rows depend primarily on incidence angles and mach number. A particular operating point on the map determines the mach numbers and flow angles everywhere in the compressor. | 7 | Physical Chemistry |
The isolobal analogy has applications beyond simple octahedral complexes. It can be used with a variety of ligands, charged species and non-octahedral complexes. | 0 | Organic Chemistry |
Oxidation of pyridine occurs at nitrogen to give pyridine N-oxide. The oxidation can be achieved with peracids:
:CHN + RCOH → CHNO + RCOH
Some electrophilic substitutions on the pyridine are usefully effected using pyridine N-oxide followed by deoxygenation. Addition of oxygen suppresses further reactions at nitrogen atom and promotes substitution at the 2- and 4-carbons. The oxygen atom can then be removed, e.g., using zinc dust. | 0 | Organic Chemistry |
Glutaminolysis (glutamine + -lysis) is a series of biochemical reactions by which the amino acid glutamine is lysed to glutamate, aspartate, CO, pyruvate, lactate, alanine and citrate. | 1 | Biochemistry |
Significant ERH technological advancements have occurred over the last five years. Three areas of focus have been: bedrock remediation, 1,4-dioxane and other emerging contaminants, and controlled low temperature heat to enhance other remedial or natural processes. | 2 | Environmental Chemistry |
BIND has grown significantly since its conception; in fact, the database saw a 10 fold increase in entries between 2003 and 2004. By September 2004, there were over 100,000 interaction records by 2004 (including 58,266 protein-protein, 4,225 genetic, 874 protein-small molecule, 25,857 protein-DNA, and 19,348 biopolymer interactions). The database also contains sequence information for 31,972 proteins, 4560 DNA samples and 759 RNA samples. These entries have been collected from 11,649 publications; therefore, the database represents an important amalgamation of data. The organisms with entries in the database include: Saccharomyces cerevisiae, Drosophila melanogaster, Homo sapiens, Mus musculus, Caenorhabditis elegans, Helicobacter pylori, Bos taurus, HIV-1, Gallus gallus, Arabidopsis thaliana, as well as others. In total, 901 taxa were included by September 2004 and BIND has been split up into BIND-Metazoa, BIND-Fungi, and BIND-Taxroot.
Not only is the information contained within the database continually updated, the software itself has gone through several revisions. Version 1.0 of BIND was released in 1999 and based on user feedback it was modified to include additional detail on experimental conditions required for binding and a hierarchical description of cellular location of the interaction. Version 2.0 was released in 2001 and included the capability to link to information available in other databases. Version 3.0 (2002) expanded the database from physical/biochemical interactions to also include genetic interactions. Version 3.5 (2004) included a refined user-interface that aimed to simplify information retrieval. In 2006, BIND was incorporated into the Biomolecular Object Network Database (BOND) where it continues to be updated and improved. | 1 | Biochemistry |
Of interest in chemical biology is the Staudinger ligation, which has been called one of the most important bioconjugation methods. Two versions of the Staudinger ligation have been developed. Both begin with the classic iminophosphorane reaction.
In classical Staudinger ligation, the organophosphorus compound becomes incorporated into the peptide. Typically, appended to the organophosphorus component are reporter groups such as fluorophores. In traceless Staudinger ligation, the organophosphorus group dissociates giving a phosphorus-free bioconjugate. | 0 | Organic Chemistry |
It has also been seen that metabolic phenotype of tumor cells changes to adapt to the prevailing local conditions. A convergence between phenotypic and metabolic state transitions that confers a survival advantage to cancer cells against clinically used drug combinations like taxanes and anthracyclines have also been reported while drug resistant cancer cells had increased activity of both the glycolytic and oxidative pathways and glucose flux through the pentose phosphate pathway (PPP). Some of the fatty acids have been linked to acquire resistance against some of the cancer drugs. Fatty acid synthase (FASN), a key complex catalyzing fatty acid synthesis has been found to be linked to acquired docetaxel, trastuzumab and adriamycin resistance in breast cancer. Similar resistance have been found with intrinsic gemcitabine and radiation resistance in pancreatic cancer. Glutaminolysis is linked to cisplatin resistance via the activation of mTORC1 signaling in gastric cancer. | 1 | Biochemistry |
The Cegelski Lab investigates the structure and function of bacterial cell walls and extracellular structures, including amyloid fibers and biofilms. | 7 | Physical Chemistry |
Nitriles are precursors to transition metal nitrile complexes, which are reagents and catalysts. Examples include tetrakis(acetonitrile)copper(I) hexafluorophosphate () and bis(benzonitrile)palladium dichloride (). | 0 | Organic Chemistry |
Researchers at Utah State University compared measurements for PPF and YPF using different types of equipment. They measured the PPF and YPF of seven common radiation sources with a spectroradiometer, then compared with measurements from six quantum sensors designed to measure PPF, and three quantum sensors designed to measure YPF.
They found that the PPF and YPF sensors were the least accurate for narrow-band sources (narrow spectrum of light) and most accurate for broad-band sources (fuller spectra of light). They found that PPF sensors were significantly more accurate under metal halide, low-pressure sodium and high-pressure sodium lamps than YPF sensors (>9% difference). Both YPF and PPF sensors were very inaccurate (>18% error) when used to measure light from red-light-emitting diodes. | 5 | Photochemistry |
Plasmids may also be used for gene transfer as a potential treatment in gene therapy so that it may express the protein that is lacking in the cells. Some forms of gene therapy require the insertion of therapeutic genes at pre-selected chromosomal target sites within the human genome. Plasmid vectors are one of many approaches that could be used for this purpose. Zinc finger nucleases (ZFNs) offer a way to cause a site-specific double-strand break to the DNA genome and cause homologous recombination. Plasmids encoding ZFN could help deliver a therapeutic gene to a specific site so that cell damage, cancer-causing mutations, or an immune response is avoided. | 1 | Biochemistry |
The Scatchard method is less used nowadays because of the availability of computer programs that directly fit parameters to binding data. Mathematically, the Scatchard equation is related to Eadie-Hofstee method, which is used to infer kinetic properties from enzyme reaction data. Many modern methods for measuring binding such as surface plasmon resonance and isothermal titration calorimetry provide additional binding parameters that are globally fit by computer-based iterative methods. | 1 | Biochemistry |
The annealing temperature has a dramatic influence on the rate of recrystallization which is reflected in the above equations. However, for a given temperature there are several additional factors that will influence the rate.
The rate of recrystallization is heavily influenced by the amount of deformation and, to a lesser extent, the manner in which it is applied. Heavily deformed materials will recrystallize more rapidly than those deformed to a lesser extent. Indeed, below a certain deformation recrystallization may never occur. Deformation at higher temperatures will allow concurrent recovery and so such materials will recrystallize more slowly than those deformed at room temperature e.g. contrast hot and cold rolling. In certain cases deformation may be unusually homogeneous or occur only on specific crystallographic planes. The absence of orientation gradients and other heterogeneities may prevent the formation of viable nuclei. Experiments in the 1970s found that molybdenum deformed to a true strain of 0.3, recrystallized most rapidly when tensioned and at decreasing rates for wire drawing, rolling and compression (Barto & Ebert 1971).
The orientation of a grain and how the orientation changes during deformation influence the accumulation of stored energy and hence the rate of recrystallization. The mobility of the grain boundaries is influenced by their orientation and so some crystallographic textures will result in faster growth than others.
Solute atoms, both deliberate additions and impurities, have a profound influence on the recrystallization kinetics. Even minor concentrations may have a substantial influence e.g. 0.004% Fe increases the recrystallization temperature by around 100 °C (Humphreys and Hatherly 2004). It is currently unknown whether this effect is primarily due to the retardation of nucleation or the reduction in the mobility of grain boundaries i.e. growth. | 8 | Metallurgy |
Organic semiconductor photocatalysts, in particular porous organic polymers (POPs), attracted attention due to their low cost, low toxicity, and tunable light absorption vs inorganic counterparts. They display high porosity, low density, diverse composition, facile functionalization, high chemical/thermal stability, as well as high surface areas. Efficient conversion of hydrophobic polymers into hydrophilic polymer nano-dots (Pdots) increased polymer-water interfacial contact, which significantly improved performance. | 5 | Photochemistry |
Several hundred metals, compounds, alloys and ceramics possess the property of superconductivity at low temperatures. The SU(2) color quark matter adjoins the list of superconducting systems. Although it is a mathematical abstraction, its properties are believed to be closely related to the SU(3)
color quark matter, which exists in nature when ordinary matter is compressed at supranuclear densities above ~ 0.5 10 nucleon/cm. | 7 | Physical Chemistry |
Sealing is the final step in the anodizing process. Acidic anodizing solutions produce pores in the anodized coating. These pores can absorb dyes and retain lubricants but are also an avenue for corrosion. When lubrication properties are not critical, they are usually sealed after dyeing to increase corrosion resistance and dye retention. There are three most common types of sealing.
# Long immersion in boiling-hot——deionized water or steam is the simplest sealing process, although it is not completely effective and reduces abrasion resistance by 20%. The oxide is converted into its hydrated form and the resulting swelling reduces the porosity of the surface.
# Mid-temperature sealing process which works at in solutions containing organic additives and metal salts. However, this process will likely leach the colors.
# Cold sealing process, where the pores are closed by impregnation of a sealant in a room-temperature bath, is more popular due to energy savings. Coatings sealed in this method are not suitable for adhesive bonding. Teflon, nickel acetate, cobalt acetate, and hot sodium or potassium dichromate seals are commonly used. MIL-A-8625 requires sealing for thin coatings (Types I and II) and allows it as an option for thick ones (Type III). | 8 | Metallurgy |
Coherent microwave scattering is a diagnostic technique used in the characterization of classical microplasmas. In this technique, the plasma to be studied is irradiated with a long-wavelength microwave field relative to the characteristic spatial dimensions of the plasma. For plasmas with sufficiently low skin-depths, the target is periodically polarized in a uniform fashion, and the scattered field can be measured and analyzed. In this case, the emitted radiation resembles that of a short-dipole predominantly determined by electron contributions rather than ions. The scattering is correspondingly referred to as constructive elastic. Various properties can be derived from the measured radiation such as total electron numbers, electron number densities (if the plasma volume is known), local magnetic fields through magnetically-induced depolarization, and electron collision frequencies for momentum transfer through the scattered phase. Notable advantages of the technique include a high sensitivity, ease of calibration using a dielectric scattering sample, good temporal resolution, low shot noise, non-intrusive probing, species-selectivity when coupled with resonance-enhanced multiphoton ionization (REMPI), single-shot acquisition, and the capability of time-gating due to continuous scanning. | 7 | Physical Chemistry |
Once the precursor oligosaccharide is formed, the completed glycan is then transferred to the nascent polypeptide in the lumen of the ER membrane. This reaction is driven by the energy released from the cleavage of the pyrophosphate bond between the dolichol-glycan molecule.
There are three conditions to fulfill before a glycan is transferred to a nascent polypeptide:
*Asparagine must be located in a specific consensus sequence in the primary structure (Asn–X–Ser or Asn–X–Thr or in rare instances Asn–X–Cys).
*Asparagine must be located appropriately in the three-dimensional structure of the protein (Sugars are polar molecules and thus need to be attached to asparagine located on the surface of the protein and not buried within the protein)
*Asparagine must be found in the luminal side of the endoplasmic reticulum for N-linked glycosylation to be initiated. Target residues are either found in secretory proteins or in the regions of transmembrane protein that face the lumen.
Oligosaccharyltransferase is the enzyme responsible for the recognition of the consensus sequence and the transfer of the precursor glycan to a polypeptide acceptor which is being translated in the endoplasmic reticulum lumen. N-linked glycosylation is, therefore, a co-translational event | 0 | Organic Chemistry |
Evaporation and condensation can give rise to both kinetic and equilibrium isotope effects. While equilibrium mass fractionation is present evaporation and condensation, it is negligible compared to kinetic effects. During condensation, the condensate is enriched in the light isotope, whereas in evaporation, the gas phase is enriched in the light isotope. Using the kinetic theory of gases, for Fe/Fe, a fractionation factor of α = 1.01835 for the evaporation of a pool containing equimolar amounts of Fe and Fe. In evaporation experiments, the evaporation of FeO at 1,823 K gave a fractionation factor of α = 1.01877. Presently, there have been no experimental attempts to determine the Fe/Fe fractionation factor of condensation. | 9 | Geochemistry |
The Duquenois reagent used in the Rapid Modified Duquenois–Levine test (also known as the simple Rapid Duquenois Test), is an established screening test for the presence of cannabis. The test was initially developed in the 1930s by the French Medical Biochemist, Pierre Duquénois (1904–1986), and was adopted in the 1950s by the United Nations as the preferred test for cannabis, and originally claimed to be specific to cannabis.
After several modifications, it became known as the Duquenois–Levine test. However, in the 1960s and 70s various studies showed that the test was not specific to cannabis. In 1973, the Supreme Court of Wisconsin ruled the D–L test insufficient evidence for demonstrating that a substance was cannabis, specifically noting that the D–L tests used "are not exclusive or specific for marijuana."
The test is one of several forms of modern cannabis drug testing. | 3 | Analytical Chemistry |
There are other methods that are sometimes used to shed light on QCD, but for various reasons have not yet yielded useful results in studying quark matter. | 7 | Physical Chemistry |
Side effects include irregular heartbeat, respiratory depression, and hepatotoxicity. It appears to be safe in porphyria. It is unclear whether use during pregnancy is harmful to the baby, and it is not generally recommended for use during a C-section.
In rare cases, repeated exposure to halothane in adults was noted to result in severe liver injury. This occurred in about one in 10,000 exposures. The resulting syndrome was referred to as halothane hepatitis, immunoallergic in origin, and is thought to result from the metabolism of halothane to trifluoroacetic acid via oxidative reactions in the liver. About 20% of inhaled halothane is metabolized by the liver and these products are excreted in the urine. The hepatitis syndrome had a mortality rate of 30% to 70%. Concern for hepatitis resulted in a dramatic reduction in the use of halothane for adults and it was replaced in the 1980s by enflurane and isoflurane. By 2005, the most common volatile anesthetics used were isoflurane, sevoflurane, and desflurane. Since the risk of halothane hepatitis in children was substantially lower than in adults, halothane continued to be used in pediatrics in the 1990s as it was especially useful for inhalation induction of anesthesia. However, by 2000, sevoflurane, excellent for inhalation induction, had largely replaced the use of halothane in children.
Halothane sensitises the heart to catecholamines, so it is liable to cause cardiac arrhythmia, occasionally fatal, particularly if hypercapnia has been allowed to develop. This seems to be especially problematic in dental anesthesia.
Like all the potent inhalational anaesthetic agents, it is a potent trigger for malignant hyperthermia. Similarly, in common with the other potent inhalational agents, it relaxes uterine smooth muscle and this may increase blood loss during delivery or termination of pregnancy. | 4 | Stereochemistry |
The rotational direction of E. coli is controlled by the flagellar motor switch. A ring of 34 FliM proteins around the rotor bind CheY, whose phosphorylation state determines whether the motor rotates in a clockwise or counterclockwise manner. The rapid switching mechanism is attributed to an ultrasensitive response, which has a Hill coefficient of ~10. This system has been proposed to follow a dissipative allosteric model, in which rotational switching is a result of both CheY binding and energy consumption from the proton motive force, which also powers the flagellar rotation. | 1 | Biochemistry |
Diphosphines are a class of chelating ligands that contain two phosphine groups connected by a bridge (also referred to as a backbone). The bridge, for instance, might consist of one or more methylene groups or multiple aromatic rings with heteroatoms attached. Examples of common diphosphines are dppe, dcpm (Figure 1), and DPEphos (Figure 2). The structure of the backbone and the substituents attached to the phosphorus atoms influence the chemical reactivity of the diphosphine ligand in metal complexes through steric and electronic effects. | 0 | Organic Chemistry |
Both the term and concept of hypervalency still fall under criticism. In 1984, in response to this general controversy, Paul von Ragué Schleyer proposed the replacement of hypervalency with use of the term hypercoordination because this term does not imply any mode of chemical bonding and the question could thus be avoided altogether.
The concept itself has been criticized by Ronald Gillespie who, based on an analysis of electron localization functions, wrote in 2002 that "as there is no fundamental difference between the bonds in hypervalent and non-hypervalent (Lewis octet) molecules there is no reason to continue to use the term hypervalent."
For hypercoordinated molecules with electronegative ligands such as PF, it has been demonstrated that the ligands can pull away enough electron density from the central atom so that its net content is again 8 electrons or fewer. Consistent with this alternative view is the finding that hypercoordinated molecules based on fluorine ligands, for example PF do not have hydride counterparts, e.g. phosphorane (PH) which is unknown.
The ionic model holds up well in thermochemical calculations. It predicts favorable exothermic formation of from phosphorus trifluoride PF and fluorine F whereas a similar reaction forming is not favorable. | 4 | Stereochemistry |
When abscisic acid signals the guard cells, free Ca ions enter the cytosol from both outside the cell and internal stores, reversing the concentration gradient so the K+ ions begin exiting the cell. The loss of solutes makes the cell flaccid and closes the stomatal pores. | 1 | Biochemistry |
The molecule displays P(═O)H to P–OH tautomerism similar to that of phosphorous acid; the P(═O) form is strongly favoured.
HPA is usually supplied as a 50% aqueous solution and heating at low temperatures (up to about 90°C) prompts it to react with water to form phosphorous acid and hydrogen gas.
: HPO + HO → HPO + H
Heating above 110°C causes hypophosphorous acid to undergo disproportionation to give phosphorous acid and phosphine.
: 3 HPO → 2 HPO + PH | 0 | Organic Chemistry |
The most stable lactones are the 5-membered γ-lactones and 6-membered δ-lactones because, as in most organic cycles, 5 and 6 membered rings minimize the strain of bond angles. β-lactones appear in a number of natural products, but are only stable in artificial conditions (i.e. a test tube). αLactones can be detected as transient species in mass spectrometry experiments. The reactions of lactones are similar to those of esters.
Many naturally-occurring lactones are γ- and δ-lactones, both saturated and unsaturated. They contribute to the aroma of fruits, butter, cheese, and other foods.
Macrocyclic lactones are also important natural products. Cyclopentadecanolide is responsible for the musklike odor of angelica root oil. Of the naturally occurring bicyclic lactones, phthalides are responsible for the odors of celery and lovage oils, and coumarin for woodruff. Lactones are present in oak wood, and they contribute to the flavour profile of barrel-aged beers.
Lactone rings occur widely as building blocks in nature, such as in ascorbic acid, kavain, nepetalactone, gluconolactone, hormones (spironolactone, mevalonolactone), enzymes (lactonase), neurotransmitters (butyrolactone, avermectins), antibiotics (macrolides like erythromycin; amphotericin B), anticancer drugs (vernolepin, epothilones), phytoestrogens (resorcylic acid lactones, cardiac glycosides). | 0 | Organic Chemistry |
For his scientific achievements Choi received the New Technology Development Award from the Ministry of Science & Technology (1992), the Special Award from Korean Society for Molecular & Cell Biology from the Korean Society of Molecular and Cellular Biology (1999), the 11th Sangrok Agriculture & Life Science Award from Seoul National University College of Agriculture (2002), the Excellent Monograph Award from the Korean Federation for Science & Technology Societies (2003), the 11th Hwanong Award from Hwanong Academy & Research Foundation (2004), the KSABC Award from the Korean Society for Applied Biology and Chemistry (2006), the 52nd NAS Award from the National Academy of Sciences, and the Top Scientist and Technologist Award of Korea from the Korean Federation of Science and Technology Societies () (2008). | 1 | Biochemistry |
Delbrück scattering, the deflection of high-energy photons in the Coulomb field of nuclei as a consequence of vacuum polarization, was observed in 1975. The related process of the scattering of light by light, also a consequence of vacuum polarization, was not observed until 1998. In both cases, it is a process described by quantum electrodynamics. | 7 | Physical Chemistry |
In the Bosch synthesis of (1999, chiral) the olefin group in dione 1 was converted to an aldehyde by ozonolysis and chiral amine 2 was formed in a double reductive amination with (S)-1-phenethylamine. The phenylethyl substituent was removed using ClCOCHClCH and the enone group was introduced in a Grieco elimination using TMSI, HMDS then PhSeCl then ozone and then diisopropylamine forming carbamate 3. The amino group was deprotected by refluxing in methanol and then alkylated using (Z)-BrCHCICH=CHOTBDMS, to tertiary amine 4. A reductive Heck reaction took place next followed by methoxycarbonylation (LiHMDS, NCCOMe) to tricycle 5. Reaction with zinc dust in 10% sulfuric acid removed the TBDMS protective group, reduced the nitro group and brought about a reductive amino-carbonyl cyclization in a single step to tetracyclic 6 (epimeric mixture). In the final step to the Wieland-Gumlich aldehyde 7 reaction with NaH in MeOH afforded the correct epimer was followed by DIBAH reduction of the methyl ester. | 0 | Organic Chemistry |
The "twin prime editing" (twinPE) mechanism reported in 2021 allows editing large sequences of DNA – sequences as large as genes – which addresses the method's key drawback. It uses a prime editor protein and two prime editing guide RNAs. | 1 | Biochemistry |
There are various classification schemes. A commonly used scheme is based on the number of carbons and was devised by Jeffrey Harborne and Simmonds in 1964 and published in 1980: | 0 | Organic Chemistry |
Today most methanol is produced from methane through syngas. Trinidad and Tobago is the world's largest methanol producer, with exports mainly to the United States. The feedstock for the production of methanol comes natural gas.
The conventional route to methanol from methane passes through syngas generation by steam reforming combined (or not) with partial oxidation. Alternative ways to convert methane into methanol have also been investigated. These include:
* Methane oxidation with homogeneous catalysts in sulfuric acid media
* Methane bromination followed by hydrolysis of the obtained bromomethane
* Direct partial oxidation of methane with oxygen, including trapping of the partially oxidized product and subsequent extraction on copper and iron exchanged Zeolite (e.g. Alpha-Oxygen)
* Microbial conversion of methane
* Photochemical conversion of methane
All these synthetic routes emit the greenhouse gas carbon dioxide CO. To mitigate this, methanol can be made through ways minimizing the emission of CO. One solution is to produce it from syngas obtained by biomass gasification. For this purpose any biomass can be used including wood, wood wastes, grass, agricultural crops and their by-products, animal waste, aquatic plants and municipal waste. There is no need to use food crops as in the case of ethanol from corn, sugar cane and wheat.
:Biomass → Syngas (CO, CO, H) → CHOH
Methanol can be synthesized from carbon and hydrogen from any source, including fossil fuels and biomass. CO emitted from fossil fuel burning power plants and other industries and eventually even the CO contained in the air, can be a source of carbon. It can also be made from chemical recycling of carbon dioxide, which Carbon Recycling International has demonstrated with its first commercial scale plant. Initially the major source will be the CO rich flue gases of fossil-fuel-burning power plants or exhaust from cement and other factories. In the longer range however, considering diminishing fossil fuel resources and the effect of their utilization on Earths atmosphere, even the low concentration of atmospheric CO itself could be captured and recycled via methanol, thus supplementing natures own photosynthetic cycle. Efficient new absorbents to capture atmospheric CO are being developed, mimicking plants' ability. Chemical recycling of CO to new fuels and materials could thus become feasible, making them renewable on the human timescale.
Methanol can also be produced from CO by catalytic hydrogenation of CO with H where the hydrogen has been obtained from water electrolysis. This is the process used by Carbon Recycling International of Iceland. Methanol may also be produced through CO electrochemical reduction, if electrical power is available. The energy needed for these reactions in order to be carbon neutral would come from renewable energy sources such as wind, hydroelectricity and solar as well as nuclear power. In effect, all of them allow free energy to be stored in easily transportable methanol, which is made immediately from hydrogen and carbon dioxide, rather than attempting to store energy in free hydrogen.
:CO + 3H → CHOH + HO
or with electric energy
:CO +5HO + 6 e → CHOH + 6 HO
:6 HO → 3HO + 3/2 O + 6 e
:Total:
:CO +2HO + electric energy → CHOH + 3/2 O
The necessary CO would be captured from fossil fuel burning power plants and other industrial flue gases including cement factories. With diminishing fossil fuel resources and therefore CO emissions, the CO content in the air could also be used. Considering the low concentration of CO in air (0.04%) improved and economically viable technologies to absorb CO will have to be developed. For this reason, extraction of CO from water could be more feasible due to its higher concentrations in dissolved form. This would allow the chemical recycling of CO, thus mimicking nature's photosynthesis.
In large-scale renewable methanol is mainly produced of fermented biomass as well as municipal solid waste (bio-methanol) and of renewable electricity (e-Methanol). Production costs for renewable methanol currently are about 300 to US$1000/t for bio-methanol, about 800 to US$1600/t for e-Methanol of carbon dioxide of renewable sources and about 1100 to US$2400/t for e-Methanol of carbon dioxide of Direct Air Capture. | 2 | Environmental Chemistry |
Xerophthalmia, caused by a severe vitamin A deficiency, is described by pathologic dryness of the conjunctival epithelium and cornea. The conjunctiva becomes dry, thick, and wrinkled. Indicative is the appearance of Bitots spots, which are clumps of keratin debris that build up inside the conjunctiva. If untreated, xerophthalmia can lead to dry eye syndrome, corneal ulceration and ultimately to blindness as a result of cornea and retina damage. Although xerophthalmia is an eye-related issue, prevention (and reversal) are functions of retinoic acid having been synthesized from retinal rather than the 11-cis'-retinal to rhodopsin cycle.
Throughout southeast Asia, estimates are that more than half of children under the age of six years have subclinical vitamin A deficiency and night blindness, with progression to xerophthalmia being the leading cause of preventable childhood blindness. Estimates are that each year there are 350,000 cases of childhood blindness due to vitamin A deficiency. The causes are vitamin A deficiency during pregnancy, followed by low transfer of vitamin A during lactation and infant/child diets low in vitamin A or beta-carotene. The prevalence of pre-school age children who are blind due to vitamin A deficiency is lower than expected from incidence of new cases only because childhood vitamin A deficiency significantly increases all-cause mortality.
According to a 2017 Cochrane review, vitamin A deficiency, using serum retinol less than 0.70 µmol/L as a criterion, is a major public health problem affecting an estimated 190 million children under five years of age in low- and middle-income countries, primarily in Sub-Saharan Africa and Southeast Asia. In lieu of or in combination with food fortification programs, many countries have implemented public health programs in which children are periodically given very large oral doses of synthetic vitamin A, usually retinyl palmitate, as a means of preventing and treating VAD. Doses were 50,000 to 100,000 IU (International units) for children aged 6 to 11 months and 100,000 to 200,000 IU for children aged 12 months to five years, the latter typically every four to six months. In addition to a 24% reduction in all-cause mortality, eye-related results were reported. Prevalence of Bitot's spots at follow-up were reduced by 58%, night blindness by 68%, xerophthalmia by 69%. | 1 | Biochemistry |
As of 2012, Johnson and Johnson was facing around 3400 state and federal lawsuits filed by people who claimed tendon damage from levofloxacin; about 1900 pending in a class action at the United States District Court in Minnesota and about 1500 pending at a district court in New Jersey.
In October 2012, J&J settled 845 cases in the Minnesota action, after Johnson and Johnson prevailed in three of the first four cases to go to trial. By May 2014, all but 363 cases had been settled or adjudicated. | 4 | Stereochemistry |
Researchers could analyze individual epigenomes and transcriptomes to study the reactivation of dormant transposable elements through epigenetic release and their potential associations with human disease and exploring the specifics of gene regulatory networks. | 1 | Biochemistry |
The BIOPAN program started in the early nineties with an ESA contract for the a joint development by Kayser-Threde and Kayser Italia. It was based on the heritage of a low-tech Russian exposure container called KNA (Kontejner Nauchnoj Apparatury). The BIOPAN facilities are installed on the external surface of Foton descent capsules. It has a motor-driven hinged lid, which opens 180° in Earth orbit to expose the experiment samples to the harsh space environment. For re-entry, the closed facility is protected with an Ablative heat shield.
The BIOPAN facilities are equipped with thermometers, UV sensors, a radiometer, a pressure sensor and an active radiation dosimeter. Data acquired by the sensors is stored by BIOPAN throughout each mission and can be accessed after flight. The possibility of overheating during atmospheric re-entry was acknowledged early during the development, therefore, a quite massive heat shield was designed for it. While the total weight of BIOPAN is close to 27 kg, including the experiments, the heat shield is responsible for 12 kg of that figure.
The BIOPAN electronics consists of the following units: signal acquisition board, microcontroller board with its flight software, memory board and EGSE. | 1 | Biochemistry |
In 2007 and 2008, a man (Timothy Ray Brown) was cured of HIV by repeated hematopoietic stem cell transplantation (see also allogeneic stem cell transplantation, allogeneic bone marrow transplantation, allotransplantation) with double-delta-32 mutation which disables the CCR5 receptor. This cure was accepted by the medical community in 2011. It required complete ablation of existing bone marrow, which is very debilitating.
In August two of three subjects of a pilot study were confirmed to have been cured from chronic lymphocytic leukemia (CLL). The therapy used genetically modified T cells to attack cells that expressed the CD19 protein to fight the disease. In 2013, the researchers announced that 26 of 59 patients had achieved complete remission and the original patient had remained tumor-free.
Human HGF plasmid DNA therapy of cardiomyocytes is being examined as a potential treatment for coronary artery disease as well as treatment for the damage that occurs to the heart after myocardial infarction.
In 2011, Neovasculgen was registered in Russia as the first-in-class gene-therapy drug for treatment of peripheral artery disease, including critical limb ischemia; it delivers the gene encoding for VEGF. Neovasculogen is a plasmid encoding the CMV promoter and the 165 amino acid form of VEGF. | 1 | Biochemistry |
Dew harvesting yields may be improved with passive daytime radiative cooling application. Selective PDRC emitters that have a high emissivity only at the atmospheric window (8–13 μm) and broadband emitters may produce varying results. In one study using a broadband PDRC, the research condensed "~8.5 mL day of water for 800 W m2 of peak solar intensity." Whereas selective emitters may be less advantageous in other contexts, they may be more advantageous for dew harvesting applications. PDRCs could improve atmospheric water harvesting by being combined with solar vapor generation systems to improve water collection rates. | 7 | Physical Chemistry |
Research into the use self-healing hydrogels has revealed an effective method for mitigating acid spills through the ability to selectively crosslink under acidic conditions. In a testing done by the University of California San Diego, various surfaces were coated with self healing hydrogels and then mechanically damaged with 300 micrometer wide cracks with the coatings healing the crack within seconds upon exposure of low pH buffers. The hydrogels also can adhere to various plastics due to hydrophobic interactions. Both findings suggest the use of these hydrogels as a sealant for vessels containing corrosive acids. No commercial applications currently exist for implementation of this technology. | 7 | Physical Chemistry |
Mollapour holds a BSc (Hons) in Microbiology and Biochemistry from the University of East London, MSc in Applied Molecular Biology of Infectious Diseases and Diploma in Tropical Medicine & Infectious Diseases from the London School of Hygiene & Tropical Medicine. In 2001 he received his PhD in [https://www.ucl.ac.uk/biosciences/departments/structural-and-molecular-biology%29 Biochemistry] from the University College London. | 1 | Biochemistry |
Solutions of simple aldehydes in alcohols mainly consist of the hemiacetal. The equilibrium is easily reversed and dynamic. The equilibrium is sensitive to steric effects. | 0 | Organic Chemistry |
When looking at data related to individual molecules, one usually can construct propagators, and jumping time probability density functions, of the first order, the second order and so on, whereas from bulk experiments, one usually obtains the decay of a correlation function. From the information contained in these unique functions (obtained from individual molecules), one can extract a relatively clear picture on the way the system behaves; e.g. its kinetic scheme, or its potential of activity, or its reduced dimensions form. In particular, one can construct (many properties of) the reaction pathway of an enzyme when monitoring the activity of an individual enzyme. Additionally, significant aspects regarding the analysis of single molecule data—such as fitting methods and tests for homogeneous populations—have been described by several authors. On the other hand, there are several issues with the analysis of single molecule data including construction of a low noise environment and insulated pipet tips, filtering some of the remaining unwanted components (noise) found in recordings, and the length of time required for data analysis (pre-processing, unambiguous event detection, plotting data, fitting kinetic schemes, etc.). | 7 | Physical Chemistry |
All these analyses pointed out even that there are some elephant families friendlier than others and showed how there are dominant families that settle down in the best places, where there is plenty of food and water. | 9 | Geochemistry |
Nanoscale allows for the preparation of quantum systems in physical states without classical analogs. There, complex out-of-equilibrium scenarios may be produced by the initial preparation of either the working substance or the reservoirs of quantum particles, the latter dubbed as "engineered reservoirs". There are different forms of engineered reservoirs. Some of them involve subtle quantum coherence or correlation effects, while others rely solely on nonthermal classical probability distribution functions.
Interesting phenomena may emerge from the use of engineered reservoirs such as efficiencies greater than the Otto limit,
violations of Clausius inequalities, or simultaneous extraction of heat and work from the reservoirs. | 7 | Physical Chemistry |
PUVA (psoralen and UVA) is an ultraviolet light therapy treatment for skin diseases: vitiligo, eczema, psoriasis, graft-versus-host disease, mycosis fungoides, large plaque parapsoriasis, and cutaneous T-cell lymphoma, using the sensitizing effects of the drug psoralen. The psoralen is applied or taken orally to sensitize the skin, then the skin is exposed to UVA.
Photodynamic therapy is the general use of nontoxic light-sensitive compounds that are exposed selectively to light, whereupon they become toxic to targeted malignant and other diseased cells. Still, PUVA therapy is often classified as a separate technique from photodynamic therapy. | 5 | Photochemistry |
In chemical analysis, capillary electrochromatography (CEC) is a chromatographic technique in which the mobile phase is driven through the chromatographic bed by electro-osmosis. Capillary electrochromatography is a combination of two analytical techniques, high-performance liquid chromatography and capillary electrophoresis. Capillary electrophoresis aims to separate analytes on the basis of their mass-to-charge ratio by passing a high voltage across ends of a capillary tube, which is filled with the analyte. High-performance liquid chromatography separates analytes by passing them, under high pressure, through a column filled with stationary phase. The interactions between the analytes and the stationary phase and mobile phase lead to the separation of the analytes. In capillary electrochromatography capillaries, packed with HPLC stationary phase, are subjected to a high voltage. Separation is achieved by electrophoretic migration of solutes and differential partitioning. | 1 | Biochemistry |
Omar M. Yaghi and William A. Goddard III also reported COFs as exceptional methane storage materials. The best COF in terms of total volume of CH per unit volume COF adsorbent is COF-1, which can store 195 v/v at 298 K and 30 bar, exceeding the U.S. Department of Energy target for CH storage of 180 v/v at 298 K and 35 bar. The best COFs on a delivery amount basis (volume adsorbed from 5 to 100 bar) are COF-102 and COF-103 with values of 230 and 234 v(STP: 298 K, 1.01 bar)/v, respectively, making these promising materials for practical methane storage. More recently, new COFs with better delivery amount have been designed in the lab of William A. Goddard III, and they have been shown to be stable and overcome the DOE target in delivery basis. COF-103-Eth-trans and COF-102-Ant, are found to exceed the DOE target of 180 v(STP)/v at 35 bar for methane storage. They reported that using thin vinyl bridging groups aids performance by minimizing the interaction methane-COF at low pressure. | 6 | Supramolecular Chemistry |
Physical metallurgy is one of the two main branches of the scientific approach to metallurgy, which considers in a systematic way the physical properties of metals and alloys. It is basically the fundamentals and applications of the theory of phase transformations in metal and alloys, as the title of classic, challenging monograph on the subject with this title [http://www.sciencedirect.com/science/book/9780080440194 ]. While chemical metallurgy involves the domain of reduction/oxidation of metals, physical metallurgy deals mainly with mechanical and magnetic/electric/thermal properties of metals – treated by the discipline of solid state physics. Calphad methodology, able to produce Phase diagrams which is the basis for evaluating or estimating physical properties of metals, relies on Computational thermodynamics i.e. on Chemical thermodynamics and could be considered a common and useful field for both the two sub-disciplines. | 8 | Metallurgy |
No commercial applications of organoniobium compounds have been reported. They have found limited use in organic synthesis. | 0 | Organic Chemistry |
Advances in massively parallel sequencing has led to the development of RNA-Seq technology, that enables a whole transcriptome shotgun approach to characterize and quantify gene expression. Unlike microarrays, which need a reference genome and transcriptome to be available before the microarray itself can be designed, RNA-Seq can also be used for new model organisms whose genome has not been sequenced yet. | 1 | Biochemistry |
Vladimir Prelog (23 July 1906 – 7 January 1998) was a Croatian-Swiss organic chemist who received the 1975 Nobel Prize in chemistry for his research into the stereochemistry of organic molecules and reactions. Prelog was born and grew up in Sarajevo. He lived and worked in Prague, Zagreb and Zürich during his lifetime. | 4 | Stereochemistry |
In the bacterium Escherichia coli the reaction is catalyzed in two steps carried out by two separate enzymes, PurK and PurE.
PurK, N5-carboxyaminoimidazole ribonucleotide synthetase, catalyzes the conversion of 5-aminoimidazole ribonucleotide ("AIR"), ATP, and bicarbonate to N5-carboxyaminoimidazole ribonucleotide ("N5-CAIR"), ADP, and phosphate.
PurE, N5-carboxyaminoimidazole ribonucleotide mutase, converts N5-CAIR to CAIR, the sixth step of de novo purine biosynthesis. In the presence of high concentrations of bicarbonate, PurE is reported able to convert AIR to CAIR directly and without ATP. Some members of this family contain two copies of this domain. | 1 | Biochemistry |
An isolated system is more restrictive than a closed system as it does not interact with its surroundings in any way. Mass and energy remains constant within the system, and no energy or mass transfer takes place across the boundary. As time passes in an isolated system, internal differences in the system tend to even out and pressures and temperatures tend to equalize, as do density differences. A system in which all equalizing processes have gone practically to completion is in a state of thermodynamic equilibrium.
Truly isolated physical systems do not exist in reality (except perhaps for the universe as a whole), because, for example, there is always gravity between a system with mass and masses elsewhere. However, real systems may behave nearly as an isolated system for finite (possibly very long) times. The concept of an isolated system can serve as a useful model approximating many real-world situations. It is an acceptable idealization used in constructing mathematical models of certain natural phenomena.
In the attempt to justify the postulate of entropy increase in the second law of thermodynamics, Boltzmanns H-theorem used equations, which assumed that a system (for example, a gas) was isolated. That is all the mechanical degrees of freedom could be specified, treating the walls simply as mirror boundary conditions. This inevitably led to Loschmidts paradox. However, if the stochastic behavior of the molecules in actual walls is considered, along with the randomizing effect of the ambient, background thermal radiation, Boltzmann's assumption of molecular chaos can be justified.
The second law of thermodynamics for isolated systems states that the entropy of an isolated system not in equilibrium tends to increase over time, approaching maximum value at equilibrium. Overall, in an isolated system, the internal energy is constant and the entropy can never decrease. A closed system's entropy can decrease e.g. when heat is extracted from the system.
Isolated systems are not equivalent to closed systems. Closed systems cannot exchange matter with the surroundings, but can exchange energy. Isolated systems can exchange neither matter nor energy with their surroundings, and as such are only theoretical and do not exist in reality (except, possibly, the entire universe).
Closed system is often used in thermodynamics discussions when isolated system would be correct – i.e. there is an assumption that energy does not enter or leave the system. | 7 | Physical Chemistry |
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