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In physics, circulation is the line integral of a vector field around a closed curve. In fluid dynamics, the field is the fluid velocity field. In electrodynamics, it can be the electric or the magnetic field.
Circulation was first used independently by Frederick Lanchester, Martin Kutta and Nikolay Zhukovsky. It is usually denoted (Greek uppercase gamma). | 1 | Applied and Interdisciplinary Chemistry |
Lithotrophic bacteria cannot use, of course, their inorganic energy source as a carbon source for the synthesis of their cells. They choose one of three options:
* Lithoheterotrophs do not have the ability to fix carbon dioxide and must consume additional organic compounds in order to break them apart and use their carbon. Only a few bacteria are fully lithoheterotrophic.
* Lithoautotrophs are able to use carbon dioxide from the air as a carbon source, the same way plants do.
* Mixotrophs will take up and use organic material to complement their carbon dioxide fixation source (mix between autotrophy and heterotrophy). Many lithotrophs are recognized as mixotrophic in regard to their C-metabolism. | 1 | Applied and Interdisciplinary Chemistry |
The reduced folate carrier protein (RFC) is a transmembrane protein responsible for the transport of folate, or vitamin B9, into cells. It uses the large gradient of organic phosphate to move folate into the cell against its concentration gradient. The RFC protein can transport folates, reduced folates, the derivatives of reduced folate, and the drug methotrexate. The transporter is encoded by the SLC19A1 gene and is ubiquitously expressed in human cells. Its peak activity occurs at pH 7.4, with no activity occurring below pH 6.4. The RFC protein is critical because folates take the form of hydrophilic anions at physiological pH, so they do not diffuse naturally across biological membranes. Folate is essential for processes such as DNA synthesis, repair,and methylation, and without entry into cells, these could not occur.
Because folates are essential for various life-sustaining processes, a deficiency in this molecule can lead to fetal abnormalities, neurological disorders, cardiovascular disease, and cancer. Folates cannot be synthesized in the body, so it must be taken in through diet and moved into cells. Without the RFC protein facilitating this movement, processes such as embryological development and DNA repair cannot occur.
Adequate folate levels are required for the development of the neural tube in the fetus. Folate deficiency during pregnancy increases the risk of defects such as spina bifida and anencephaly. In mouse models, inactivating both alleles of the FRC protein gene causes death of the embryo. Even if folate is supplemented during gestation, the mice died within two weeks of birth from the failure of hematopoietic tissues.
Altered function of the RFC protein can increase folate deficiency, enhancing cardiovascular disease, neurodegenerative diseases, and cancer. In terms of cardiovascular issues, folate contributes to homocysteine metabolism. Low folate levels result in elevated homocysteine levels, which is a risk factor for cardiovascular diseases. In terms of cancer, folate deficiency is related to an increased risk, especially that of colorectal cancers. In mouse models with altered RFC protein expression showed increased transcripts of genes related to colon cancer and increased proliferation of colonocytes. The cancer risk is likely related to the FRC protein's role in DNA synthesis because inadequate levels of folate can lead to DNA damage and aberrant DNA methylation. | 1 | Applied and Interdisciplinary Chemistry |
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. | 1 | Applied and Interdisciplinary Chemistry |
Ecology
Calanus spp. are abundantly distributed copepods, particularly in the polar and temperate North Atlantic. Studies attempting to quantify the lipid pump have primarily focused on the cousin species of C. finmarchicus, Calanus glacialis and Calanus helgolandicus, C. hyperboreus. C. hyperboreous, the largest of these species, uses an overwintering diapause (hibernation) strategy, and its life-history will be described in more detail as a representative Calanus spp. With a life cycle of two to six years on average, each C. hyperboreous individual can go through multiple overwintering periods. Positively buoyant eggs are spawned by females at depth and rise to the surface. Larvae (nauplii) first develop from these eggs, and complete their maturation into an early juvenile (copepodite) within one season, after which they undergo their first overwintering. Copepodite have three stages before maturing to the adult stages. While female Calanus spp. are generally expected to experience mortality after spawning, some may return to the surface to build up lipid stores before entering another overwintering and reproductive cycle.
Lipid accumulation and metabolism
Lipids are stored by all copepodite and adult Calanus spp. in an oil sac, which can account for up to 60% of an individuals dry weight. Calanus spp. accumulate these lipids while feeding closer to the ocean surface during the spring and summer months, aligning with phytoplankton blooms. Early in the growing season, Calanus spp. biogenergetics are allocated to reproduction, feeding and growth, but eventually shift to the production of lipids to provide energy during diapause. These lipids take the form of wax esters, energy-rich compounds like omega-3 fatty acids, and long-chain carbon molecules. At the end of the feeding/growing season, Calanus spp. migrate downward, with to depths varying from 600 to 3000m, but with the requirement that Calanus spp.' settle below the thermocline to prevent premature return to the surface waters. Stored lipids are metabolized at these depths, accounting for approximately 25% of the basal metabolic rate. A 6–8 month-long overwintering period can drain a substantial fraction (44–93%) of the stored lipids despite the decreased metabolism.
Physical characteristics
The physical characteristics of Calanus spp. (i.e., dry weight, prosome length, lipid content, and carbon content) are always changing, varying between different regions, temporally, and across life stages. Based on isomorphism, or the similarity in form or structure of organisms, Calanus spp. may deviate in size but their basic physical structure remains constant across different overwintering stages and between different copepod species. The only significant taxonomic difference is the number of segments on the tail across developmental stage CIII and older (CIV, CV). With an outcome of isomorphism, dry weight (d [mg]) and prosome length (p [mm]) can be scaled as they are related as d = cp, where c is a coefficient. Observations identify the relationship between dry weight and prosome length with a coefficient between 3.3 and 3.5 for C. hyperboreus. Although this relationship is not supported extensively by empirical evidence, it has been used for model frameworks to observe Calanus spp. carbon content.
Relationships between NAO and Calanus spp. populations
In the North Atlantic and Nordic Seas, a primary long-term forcing that affects Calanus spp. and its habitat is the North Atlantic Oscillation (NAO) index, defined as the normalized difference in sea surface pressure between the Azores High and the Icelandic Low. While high NAO index values indicate a net flow of Atlantic water to the northeast and into the Norwegian Sea, low NAO index values indicate a reduced Atlantic water inflow into the Nordic Seas. In the Northwestern Atlantic, positive trends in the abundances of Calanus spp. correspond with higher sea surface temperatures and positive NAO forcing with a lag of one or two years. However, the influence of the NAO in explaining Calanus spp. abundance was substantially diminished when temporal autocorrelation and detrending analyses were involved. | 0 | Theoretical and Fundamental Chemistry |
Berg-Barrett topography uses a narrow incident beam that is reflected from the surface of the sample under study under conditions of high asymmetry (grazing incidence, steep exit). To achieve sufficient spatial resolution, the detector (film) needs to be placed rather close to the sample surface. Berg-Barrett topography is another routine technique in many X-ray laboratories. | 0 | Theoretical and Fundamental Chemistry |
Particulate pollution is pollution of an environment that consists of particles suspended in some medium. There are three primary forms: atmospheric particulate matter, marine debris, and space debris. Some particles are released directly from a specific source, while others form in chemical reactions in the atmosphere. Particulate pollution can be derived from either natural sources or anthropogenic processes. | 1 | Applied and Interdisciplinary Chemistry |
Formulated drugs are stored in container closure systems for extended periods of time. These include blisters, bottles, vials, ampules, syringes, and cartridges. The containers can be made from a variety of materials including glass, plastic, and metal. The drug may be stored as a solid, liquid, or gas.
It's important to check whether there are any undesired interactions between the preparation and the container. For instance, if a plastic container is used, tests are carried out to see whether any of the ingredients become adsorbed on to the plastic, and whether any plasticizer, lubricants, pigments, or stabilizers leach out of the plastic into the preparation. Even the adhesives for the container label need to be tested, to ensure they do not leach through the plastic container into the preparation. | 1 | Applied and Interdisciplinary Chemistry |
An amperostat delivers a constant current of about 6—8 mA to the generator electrodes for the titration of the solution, and a digital timer is started. A second pair of silver electrodes are used as a detector to measure the conductance of the solution. The same constant current is known to titrate a given number of moles of a chloride standard solution in time . Titration of the assay solution will result in the generation of insoluble silver chloride until the chloride ions are consumed, after which time an increase in silver ions will be detected at the detector electrodes. This time, , is the titration time of the solution being measured. The concentration of chloride ions in this solution is then calculated as:
Although the absolute quantity of silver ions () required to react with the chloride ions can be determined using Faraday's laws of electrolysis, in practice calibration is required.
Silver ions are generated by oxidation at the anode when an electric potential is applied across the silver electrodes. This is the anodic reaction.
The silver ions enter the solution at a rate proportional to the electrical current. Because the current is constant, the rate of silver ion production is hence proportional to the time of current flow, and silver ions enter the solution at a constant rate from the silver wire anode. These ions react with the chloride ions in the titration reaction, resulting in insoluble silver chloride.
The end point, which occurs when there are no more chloride ions with which silver ions may react, is detected by a pair of silver microelectrodes in the solution, which is connected in series with a microammeter. The increasing concentration of silver ions creates a current between the microelectrodes, activating a switch that shuts off power to the main electrodes and the timer, terminating the measurement. The duration of the titration is the titration time , which is proportional to the amount of silver ions released, and hence to the amount of chloride in the assay solution. | 0 | Theoretical and Fundamental Chemistry |
Hani Abdulaziz Al Hussein is a Kuwaiti engineer and politician. He served as chief executive officer of the Kuwait Petroleum Corporation from 2004 to 2007 and oil minister from February 2012 to May 2013. | 1 | Applied and Interdisciplinary Chemistry |
When determining the stability constants of metal-ligand complexes, it is common practice to fix ligand protonation constants at values that have been determined using data obtained from metal-free solutions. Hydrolysis constants of metal ions are usually fixed at values which were obtained using ligand-free solutions. When determining the stability constants for ternary complexes, MAB it is common practice the fix the values for the corresponding binary complexes MA and MB, at values which have been determined in separate experiments. Use of such constraints reduces the number of parameters to be determined, but may result in the calculated errors on refined stability constant values being under-estimated. | 0 | Theoretical and Fundamental Chemistry |
The heterokontophytes, also known as the stramenopiles, are a very large and diverse group of eukaryotes. The photoautotrophic lineage, Ochrophyta, including the diatoms and the brown algae, golden algae, and yellow-green algae, also contains red algal derived chloroplasts.
Heterokont chloroplasts are very similar to haptophyte chloroplasts, containing a pyrenoid, triplet thylakoids, and with some exceptions, having four layer plastidic envelope, the outermost epiplastid membrane connected to the endoplasmic reticulum. Like haptophytes, heterokontophytes store sugar in chrysolaminarin granules in the cytoplasm. Heterokontophyte chloroplasts contain chlorophyll a and with a few exceptions chlorophyll c, but also have carotenoids which give them their many colors. | 0 | Theoretical and Fundamental Chemistry |
Enone–alkene cycloadditions can produce two isomers, depending on the orientation of substituents on the alkene and the enone carbonyl group. When the enone carbonyl and substituent of highest priority are proximal, the isomer is termed "head-to-head." When the enone carbonyl and substituent are distal, the isomer is called "head-to-tail." Selectivity for one of these isomers depends on both steric and electronic factors (see below).
The regiochemistry of the reaction is controlled primarily by two factors: steric interactions and electrostatic interactions between the excited enone and alkene. In their excited state, the polarity of enones is reversed so that the β carbon possesses a partial negative charge. In the transition state for the first bond formation, the alkene tends to align itself so that the negative end of its dipole points away from the β carbon of the enone.
Steric interactions encourage the placement of large substituents on opposite sides of the new
cyclobutane ring.
If the enone and alkene are contained in rings of five atoms or fewer, double-bond configuration
is preserved. However, when larger rings are used, double bond isomerization during the reaction becomes a
possibility. This energy-wasting process competes with cycloaddition and is evident in reactions that yield mixtures of cis- and trans-fused products.
Diastereofacial selectivity is highly predictable in most cases. The less hindered faces of the enone
and alkene react.
Intramolecular enone–alkene cycloaddition may give either "bent" or "straight" products depending on the reaction
regioselectivity. When the tether between the enone and alkene is two atoms long, bent products predominate
due to the rapid formation of five-membered rings. Longer tethers tend to give straight products.
The tether can also be attached at the 2 position of the enone. When the alkene is tethered here, bulky substituents at the 4 position of the enone enforce moderate diastereoselectivity.
Enone–alkene cycloaddition has been applied to the synthesis of a cubane. The Favorskii rearrangement established the carbon skeleton of cubane, and further synthetic manipulations provided the desired unfunctionalized target. | 0 | Theoretical and Fundamental Chemistry |
In computational biology, protein pK calculations are used to estimate the pK values of amino acids as they exist within proteins. These calculations complement the pK values reported for amino acids in their free state, and are used frequently within the fields of molecular modeling, structural bioinformatics, and computational biology. | 0 | Theoretical and Fundamental Chemistry |
The pan-ErbB inhibitor Neratinib was approved in the US in 2017 and in the EU in 2018 for the extended adjuvant treatment of adult patients with early-stage HER2-overexpressed/amplified breast cancer after trastuzumab-based therapy. | 1 | Applied and Interdisciplinary Chemistry |
In the Rawal synthesis (1994, racemic) amine 1 and enone 2 were combined in an amine-carbonyl condensation followed by methyl chloroformate quench to triene 3 which was then reacted in a Diels–Alder reaction (benzene 185 °C) to hexene 4. The three ester groups were hydrolyzed using iodotrimethylsilane forming pentacyclic lactam 5 after a methanol quench in a combination of 7 reaction steps (one of them a Dieckmann condensation). The C segment 6 was added in an amine alkylation and Heck reaction of 7 formed isostrychnine 8 after TBS deprotection.
The overall yield (10%) is to date the largest of any of the published methods | 0 | Theoretical and Fundamental Chemistry |
*Prastarika: metal trader
*Sulbhadhatusastra: science of metals
*panchaloha, sarva loha: the five base metals (tin, lead, iron, copper, silver) | 1 | Applied and Interdisciplinary Chemistry |
PubMeth is a database that contains information about DNA hypermethylation in cancer. It can be queried either by searching a list of genes, or cancer (sub)types.
It was created at the lab for bioinformatics and computational genomics in the Department of Molecular Biotechnology, Faculty of Bioscience Engineering at Ghent University, Belgium.
It was published in Nucleic Acids Research | 1 | Applied and Interdisciplinary Chemistry |
The United States Environmental Protection Agency (EPA) defined secondary treatment based on the performance observed at late 20th-century bioreactors treating typical United States municipal sewage. Secondary treated sewage is expected to produce effluent with a monthly average of less than 30 mg/L BOD and less than 30 mg/L suspended solids. Weekly averages may be up to 50 percent higher. A sewage treatment plant providing both primary and secondary treatment is expected to remove at least 85 percent of the BOD and suspended solids from domestic sewage. The EPA regulations describe stabilization ponds as providing treatment equivalent to secondary treatment removing 65 percent of the BOD and suspended solids from incoming sewage and discharging approximately 50 percent higher effluent concentrations than modern bioreactors. The regulations also recognize the difficulty of meeting the specified removal percentages from combined sewers, dilute industrial wastewater, or Infiltration/Inflow. | 1 | Applied and Interdisciplinary Chemistry |
Professor Mukherjee's first work was done independently, while he was a MSc student of the Presidency College, his work on colloids was published in the Journal
of the American Chemical Society in 1915. In 1919 he and Jnan Chandra Ghosh joined the University College, London to work in the Physical Chemistry Laboratory under the charge of Professor FG Donnan, FRS. Professor Mukherjee continued his research on colloids and his major line of work was to develop
his theory of the electrokinetic double layer and its ionic constitution. JN Mukherjee's work on the electrochemistry of colloids is considered highly significant. He is also well known for the boundary method he developed for determining the cataphoretic speed of colloid particles. | 0 | Theoretical and Fundamental Chemistry |
CCCTC-Binding factor or CTCF was initially discovered as a negative regulator of the chicken c-myc gene. This protein was found to be binding to three regularly spaced repeats of the core sequence CCCTC and thus was named CCCTC binding factor. | 1 | Applied and Interdisciplinary Chemistry |
* "Smiley" gels - this edge effect is caused when the voltage applied is too high for the gel concentration used.
* Overloading of DNA - overloading of DNA slows down the migration of DNA fragments.
* Contamination - presence of impurities, such as salts or proteins can affect the movement of the DNA. | 1 | Applied and Interdisciplinary Chemistry |
TPCK-treated trypsin is used to improve infection yield in laboratory tissue culture of some wild virus isolates that are not well-adapted to growth in vitro, such as some low-pathogenic avian influenza strains or fresh clinical isolates of SARS-CoV-2. The trypsin performs the maturation cleavage of the viral envelope proteins efficiently. | 1 | Applied and Interdisciplinary Chemistry |
Rieke metals are usually prepared by a reduction of an anhydrous metal chloride with an alkali metal, in a suitable solvent. For example, Rieke magnesium can be prepared from magnesium chloride with potassium as the reductant:
:MgCl + 2 K → Mg + 2 KCl
Rieke originally described three general procedures:
* Reaction with molten sodium or potassium in a solvent whose boiling point is higher than the metal's melting point, and which can dissolve some of the anhydrous salt, in an inert atmosphere. Suggested combinations were potassium in tetrahydrofuran (THF), sodium in 1,2-dimethoxyethane, and either metal with benzene or toluene. The exothermic reaction takes a few hours, and usually requires refluxing.
* Reaction with an alkali metal at temperatures below its melting point, with a catalytic amount (5-10% by mole) of an electron carrier such as naphthalene or biphenyl. This method can be used with lithium as the reducing agent, even at room temperature, and is therefore less hazardous than the previous method; and often results in more reactive powders.
* Reaction with previously prepared lithium naphthalide or lithium biphenylide instead of lithium. This process can be carried out at even lower temperatures, below ambient. Although slower, it was found to produce even smaller particles.
The alkali metal chloride coprecipitates with the finely divided metal, which can be used in situ or separated by washing away the alkali chloride with a suitable solvent. | 0 | Theoretical and Fundamental Chemistry |
The Patterson power cell is an electrolysis device invented by chemist James A. Patterson, which he said created 200 times more energy than it used, and neutralizes radioactivity without emitting any harmful radiation. It is one of several cells that some observers classified as cold fusion; cells which were the subject of an intense scientific controversy in 1989, before being discredited in the eyes of mainstream science.
The Patterson power cell is given little credence by scientists. Physicist Robert L. Park describes the device as fringe science in his book Voodoo Science. | 0 | Theoretical and Fundamental Chemistry |
The structure of P680 consists of a heterodimer of two distinct chlorophyll molecules,
referred to as P and P. This “special pair” forms an excitonic dimer that functions as a single unit, excited by light energy as if they were a single molecule. | 0 | Theoretical and Fundamental Chemistry |
In analytical chemistry, sub-sampling is a procedure by which a small, representative sample is taken from a larger sample. Good sub-sampling technique becomes important when the large sample is not homogeneous. | 0 | Theoretical and Fundamental Chemistry |
Using the convexity of the log function appearing in the exact perturbation analysis result, together with Jensen's inequality, gives an inequality in the linear level; combined with the analogous result for the B ensemble one gets the following version of the Gibbs-Bogoliubov inequality:
Note that the inequality agrees with the negative sign of the coefficient of the (positive) variance term in the second order result. | 0 | Theoretical and Fundamental Chemistry |
The diffusive theory of bainite's transformation process is based on the assumption that a bainitic ferrite plate grows with a similar mechanism as Widmanstätten ferrite at higher temperatures. Its growth rate thus depends on how rapidly carbon can diffuse from the growing ferrite into the austenite. A common misconception is that this mechanism excludes the possibility of coherent interfaces and a surface relief. In fact it is accepted by some that formation of Widmanstätten ferrite is controlled by carbon diffusion and do show a similar surface relief. | 1 | Applied and Interdisciplinary Chemistry |
Proper names of oxidoreductases are formed as "donor:acceptor oxidoreductase"; however, other names are much more common.
* The common name is "donor dehydrogenase" when possible, such as glyceraldehyde-3-phosphate dehydrogenase for the second reaction above.
* Common names are also sometimes formed as "acceptor reductase", such as NAD reductase.
* "Donor oxidase" is a special case where O is the acceptor. | 0 | Theoretical and Fundamental Chemistry |
MLST is highly unambiguous and portable. Materials required for ST determination can be exchanged between laboratories. Primer sequences and protocols can be accessed electronically. It is reproducible and scalable. MLST is automated, combines advances in high throughput sequencing and bioinformatics with established population genetics techniques. MLST data can be used to investigate evolutionary relationships among bacteria. MLST provides good discriminatory power to differentiate isolates.
The application of MLST is huge, and provides a resource for the scientific, public health, and veterinary communities as well as the food industry. The following are examples of MLST applications. | 1 | Applied and Interdisciplinary Chemistry |
The analogy applies to other shapes besides tetrahedral and octahedral geometries. The derivations used in octahedral geometry are valid for most other geometries. The exception is square-planar because square-planar complexes typically abide by the 16-electron rule. Assuming ligands act as two-electron donors the metal center in square-planar molecules is d. To relate an octahedral fragment, ML, where M has a d electron configuration to a square planar analogous fragment, the formula ML where M has a d electron configuration should be followed.
Further examples of the isolobal analogy in various shapes and forms are shown in figure 8. | 0 | Theoretical and Fundamental Chemistry |
Originally developed in the 1970s by French neuroscientist Michel Jouvet and Lafon Laboratories, modafinil has been prescribed in France since 1994, and was approved for medical use in the United States in 1998.
Concerns have been raised about the growing use of modafinil as a "smart drug" or cognitive enhancer among healthy individuals who use it with the aim to improve concentration and memory. In 2003, modafinil sales were skyrocketing, with some experts concerned that it had become a tempting pick-me-up for people looking for an extra edge in a productivity-obsessed society. The cost of modafinil varied depending on factors such as location and insurance coverage, still, in 2004, the price of modafinil in the US was around $120 or more per monthly supply. However, the availability of generic versions has increased since then and may have driven down prices.
In 2020, modafinil was the 302nd most commonly prescribed medication in the United States, with just over prescriptions.
the global sales figures for modafinil are not known. Still, modafinil sold under the brand name Provigil accounted for over 40% of Cephalon's global turnover for several years, according to the information published in 2020. | 0 | Theoretical and Fundamental Chemistry |
The Sieder–Tate correlation for turbulent flow is an implicit function, as it analyzes the system as a nonlinear boundary value problem. The Sieder–Tate result can be more accurate as it takes into account the change in viscosity ( and ) due to temperature change between the bulk fluid average temperature and the heat transfer surface temperature, respectively. The Sieder–Tate correlation is normally solved by an iterative process, as the viscosity factor will change as the Nusselt number changes.
where:
: is the fluid viscosity at the bulk fluid temperature
: is the fluid viscosity at the heat-transfer boundary surface temperature
The Sieder–Tate correlation is valid for | 1 | Applied and Interdisciplinary Chemistry |
The Skimwing ("Tsurak" in Navi) is a large Flying Fish like creature. They are primarily ridden by the Metkayina Clan in place of Banshee into battle. They do not form long-term bonds like the Mountain Banshee. They are first introduced in Avatar: The Way of Water', where Jake Sully tames one for battle. | 1 | Applied and Interdisciplinary Chemistry |
As with all gene therapies, a number of safety and toxicity issues need to be evaluated during the development of DDRNAI therapeutics.
Oncogene activation by viral insertion: Some gene therapy vectors integrate into the host genome, thereby acting as insertional mutagens. This was a particular issue with early retroviral vectors where insertions adjacent to oncogenes resulted in the development of lymphoid tumors. AAV vectors are considered low-risk for host-genome integration, as adeno-associated virus infection has not been associated with the induction of cancers in humans despite widespread prevalence across the general population. Moreover, extensive clinical use of AAV vectors has provided no evidence of carcinogenicity. While lentiviral vectors do integrate into the genome they do not appear to show a propensity to activate oncogene expression.
Immune response to gene therapy vectors: An immunological response to an adenoviral vector resulted in the death of a patient in an early human trial. Careful monitoring of potential toxicities in preclinical testing and analyses of pre-existing antibodies to gene therapy vectors in patients minimizes such risks.
Innate immune response: siRNAs have been shown to activate immune responses through interaction with Toll-like receptors leading to interferon responses. These receptors reside on the cell's surface and so DDRNAIconstructs – delivered directly into intracellular space – are not expected to induce this response.
Toxic effects due to over-expression of shRNAs: High-level expression of shRNAs has been shown to be toxic. Strategies to minimize levels of shRNA expression or promote precise processing of shRNAs can overcome this problem.
Off-target effects: Unintended silencing of genes that share sequence homology with expressed shRNAs can theoretically occur. Careful selection of shRNA sequences and thorough preclinical testing of constructs can circumvent this issue. | 1 | Applied and Interdisciplinary Chemistry |
Switzerland has one of Europes oldest green roofs, created in 1914 at the Moos lake water-treatment plant, Wollishofen, Zürich. Its filter tanks have of flat concrete roofs. To keep the interior cool and prevent bacterial growth in the filtration beds, a drainage layer of gravel and a layer of soil was spread over the roofs, which had been waterproofed with asphalt. A meadow developed from seeds already present in the soil; it is now a haven for many plant species, some of which are now otherwise extinct in the district, most notably 6,000 Orchis morio (green-winged orchid). More recent Swiss examples can be found at Klinikum 1 and Klinikum 2, the Cantonal Hospitals of Basel, and the Sihlpost platform at Zürichs main railway station. | 1 | Applied and Interdisciplinary Chemistry |
Using 2 drugs at the same time can sometimes affect each others fraction unbound. For example, assume that Drug A and Drug B are both protein-bound drugs. If Drug A is given, it will bind to the plasma proteins in the blood. If Drug B is also given, it can displace Drug A from the protein, thereby increasing Drug As fraction unbound. This may increase the effects of Drug A, since only the unbound fraction may exhibit activity.
Note that for Drug A, the % increase in unbound fraction is 100% – hence, Drug A's pharmacological effect can potentially double (depending on whether the free molecules get to their target before they are eliminated by metabolism or excretion). This change in pharmacologic effect could have adverse consequences.
However, this effect is really only noticeable in closed systems where the pool of available proteins could potentially be exceeded by the number of drug molecules. Biological systems, such as humans and animals, are open systems where molecules can be gained, lost or redistributed and where the protein pool capacity is almost never exceeded by the number of drug molecules. A drug that is 99% bound means that 99% of the drug molecules are bound to blood proteins not that 99% of the blood proteins are bound with drug. When two, highly protein-bound drugs (A and B) are added into the same biological system it will lead to an initial small increase in the concentration of free drug A (as drug B ejects some of the drug A from its proteins). However, this free drug A is now more available for redistribution into the body tissues and/or for excretion. This means the total amount of drug in the system will decrease quite rapidly, keeping the free drug fraction (the concentration of free drug divided by the total drug concentration) constant and yielding almost no change in clinical effect.
The effects of drugs displacing each other and changing the clinical effect (though important in some examples) is vastly overestimated usually and a common example incorrectly used to display the importance of this effect is the anticoagulant warfarin. Warfarin is highly protein-bound (>95%) and has a low therapeutic index. Since a low therapeutic index indicates that there is a high risk of toxicity when using the drug, any potential increases in warfarin concentration could be very dangerous and lead to hemorrhage. In horses, it is very true that if warfarin and phenylbutazone are administered concurrently, the horse can develop bleeding issues which can be fatal. This is often explained as being due to the effect of phenylbutazone ejecting warfarin from its plasma protein, thus increasing the concentration of free warfarin and increasing its anticoagulant effect. However, the real problem is that phenylbutazone interferes with the liver's ability to metabolize warfarin so free warfarin cannot be metabolized properly or excreted. This leads to an increase in free warfarin and the resulting bleeding problems. | 1 | Applied and Interdisciplinary Chemistry |
Combined with certain metallic species, amorphous films can crystallize in a process known as metal-induced crystallization (MIC). The effect was discovered in 1969, when amorphous germanium (a-Ge) films crystallized at surprisingly low temperatures when in contact with Al, Ag, Cu, or Sn. The effect was also verified in amorphous silicon (a-Si) films, as well as in amorphous carbon and various metal-oxide films.
Likewise, the MIC evolved from simple temperature-driven annealing approaches to others involving laser or microwave radiation, for example.
A very common variant of the MIC procedure is the metal-induced lateral crystallization (MILC). In this case, the metal is deposited (onto the top or at the bottom) of some selected areas of the desired amorphous film. Upon annealing, crystallization starts from the portion of the amorphous film that is in contact with the metal species, and the MIC proceeds laterally.
So far, lots of studies have been carried out to investigate the MIC phenomenon -- invariably by applying different sample production methods and characterization tools. According to them, the MIC process is highly susceptible to the type and amount of the metallic species, the sample history (production method, geometry and annealing details), as well as to the methodology to determine crystallization. Besides, the MIC process is well beyond the mere diffusion of species (as it is usually discussed in studies involving layered sample structures) and involves many complex atomic-thermodynamic processes at the microscopic level. | 0 | Theoretical and Fundamental Chemistry |
Products containing dexmethylphenidate have a side effect profile comparable to those containing methylphenidate. | 0 | Theoretical and Fundamental Chemistry |
He joined the faculty of University of Oviedo as Professor of Chemistry in 1975 and became Emeritus Professor in 2010 after 35 years of service at the university.
He has supervised 120 Ph.D. students of whom 18 have hold positions as Professors of Chemistry at different Spanish universities. His laboratory has been active in the field of organic chemistry with research interests in synthetic methodology development of transition-metal reagents, stoichiometric and catalytic processes.
He discovered the bis(pyridine)iodonium tetrafluoroborate (IPyBF), an iodinating reagent now named after him which is available from numerous chemical suppliers worldwide. One of his papers on the use of the reagent is his most cited article, with 223 citations through September 2014 according to Google Scholar. Other papers of his on this topic have had as many as 170 and 172 citations. | 0 | Theoretical and Fundamental Chemistry |
The standard ISO 7 - Pipe threads where pressure-tight joints are made on the threads consists of the following parts:
* ISO 7-1:1994 Dimensions, tolerances and designation
* ISO 7-2:2000 Verification by means of limit gauges | 1 | Applied and Interdisciplinary Chemistry |
In addition to their main use in agriculture, pesticides have a number of other applications. Pesticides are used to control organisms that are considered to be harmful, or pernicious to their surroundings. For example, they are used to kill mosquitoes that can transmit potentially deadly diseases like West Nile virus, yellow fever, and malaria. They can also kill bees, wasps or ants that can cause allergic reactions. Insecticides can protect animals from illnesses that can be caused by parasites such as fleas. Pesticides can prevent sickness in humans that could be caused by moldy food or diseased produce. Herbicides can be used to clear roadside weeds, trees, and brush. They can also kill invasive weeds that may cause environmental damage. Herbicides are commonly applied in ponds and lakes to control algae and plants such as water grasses that can interfere with activities like swimming and fishing and cause the water to look or smell unpleasant. Uncontrolled pests such as termites and mold can damage structures such as houses. Pesticides are used in grocery stores and food storage facilities to manage rodents and insects that infest food such as grain. Pesticides are used on lawns and golf courses, partly for cosmetic reasons.
Integrated pest management, the use of multiple approaches to control pests, is becoming widespread and has been used with success in countries such as Indonesia, China, Bangladesh, the U.S., Australia, and Mexico. IPM attempts to recognize the more widespread impacts of an action on an ecosystem, so that natural balances are not upset.
Each use of a pesticide carries some associated risk. Proper pesticide use decreases these associated risks to a level deemed acceptable by pesticide regulatory agencies such as the United States Environmental Protection Agency (EPA) and the Pest Management Regulatory Agency (PMRA) of Canada.
DDT, sprayed on the walls of houses, is an organochlorine that has been used to fight malaria vectors (mosquitos) since the 1940s. The World Health Organization recommend this approach. It and other organochlorine pesticides have been banned in most countries worldwide because of their persistence in the environment and human toxicity. DDT has become less effective, as resistance was identified in Africa as early as 1955, and by 1972 nineteen species of mosquito worldwide were resistant to DDT. | 1 | Applied and Interdisciplinary Chemistry |
Due to the binding of metal ions being essential for various enzymes to maintain their enzymatic activity, thiomers are potent reversible enzyme inhibitors. Many non-invasively administered drugs such as therapeutic peptides or nucleic acids are degraded on the mucosa by membrane bound enzymes strongly reducing their bioavailability. In case of oral administration this ‘enzymatic barrier’ is even more pronounced as an additional degradation caused by luminally secreted enzymes takes place. Because of their capability to bind zinc ions via thiol groups, thiomers are potent inhibitors of most membrane bound and secreted zinc-dependent enzymes. Due to this enzyme inhibitory effect, thiolated polymers can significantly improve the bioavailability of non-invasively administered drugs | 0 | Theoretical and Fundamental Chemistry |
The first appearance of the term ‘safety pharmacology’ in the published literature dates back to 1980. The term was certainly in common usage in the 1980s within the pharmaceutical industry to describe nonclinical pharmacological evaluation of unintended effects of candidate drugs for regulatory submissions. Back then, it was part of a wider ‘general pharmacology’ assessment, which addressed actions of a drug candidate beyond the therapeutically intended effects. The only detailed guidelines indicating the requirements from drug regulatory authorities for general pharmacology studies were from the Ministry of Health, Labour, and Welfare. Nowadays, the term ‘general pharmacology’ is no longer used, and the ICH S7A guidelines distinguish between primary pharmacodynamics (“studies on the mode of action and/or effects of a substance in relation to its desired therapeutic target”), secondary pharmacodynamics (“studies on the mode of action and/or effects of a substance not related to its desired therapeutic target”) and safety pharmacology (“studies that investigate the potential undesirable pharmacodynamic effects of a substance on physiological functions in relation to exposure in the therapeutic range and above.”).
A major stimulus to the discipline of safety pharmacology was the release in 1996 of a draft ‘Points to Consider’ document on QT prolongation by the European Medicines Agency's Committee for Proprietary Medicinal Products (CPMP), issued in final form the following year. This initiative had been prompted by growing concern of sudden death caused by drug-induced torsade de pointes, a potentially lethal cardiac tachyarrhythmia. Later, in 2005, this concern was addressed by issue of the ICH S7B guidelines. | 1 | Applied and Interdisciplinary Chemistry |
The first total synthesis of torreyanic acid was reported by Porco an co-workers in 2000. This total synthesis aimed to employ and confirm the Diels–Alder genesis proposed by Lee et al. To synthesize the monomers required for Diels–Alder dimerization, 1,3-dioxane intermediate 4 was lithiated with BuLi, brominated with BrCFCFBr, and underwent acid hydrolysis to afford benzaldehyde 5. Upon selective methylation of 5 with sulfuric acid, phenol 6 was produced in 52% yield. Phenol 6 first underwent an allylation with allyl bromide, then a borohydride reduction, and finally a protection with a silyl group to furnish 7. Dimethoxyacetal 8 was furnished upon thermal Claisen rearrangement of 7, which afforded an unstable allyl phenol that directly underwent a hypervalent iodine oxidation with in methanol. 8 was then subjected to an acetal exchange with 1,3-propanediol to afford 1,3-dioxane 9, which was smoothly monoepoxidized with Ph3COOH, KHMDS, −78 °C to −20 °C over 6 hours to afford 10. A 2-methyl-2-butenoic acid moiety was installed to afford 11. Intermediate 11 underwent a Stille vinylation with (E)-tributyl-1-heptenyl stannane, subsequently subjected to TBAF/AcOH for silyl removal and acetal hydrolysis to afford quinone epoxide 12. Treatment of 12 with Dess-Martin periodinane initiated a tandem oxidation-6p-electrocyclization-dimerization to afford two dimeric products 13 and 14. Upon treatment of 13 and 14 with TFA to remove the tert-butyl ester, iso-torreyanic acid 15 and torreyanic acid 1 were afforded, respectively. | 0 | Theoretical and Fundamental Chemistry |
Often, the largest source of error in a study that depends on the natural abundance of carbon is the slight variation in natural C abundance itself. Such variations arise because the starting materials used in the reaction are themselves products of some other reactions that have kinetic isotope effects and corresponding isotopic enrichments in the products. To compensate for this error when NMR spectroscopy is used to determine the kinetic isotope effect, the following guidelines have been proposed:
* Choose a carbon that is remote from the reaction center that will serve as a reference and assume it does not have a kinetic isotope effect in the reaction.
* In the starting material that has not undergone any reaction, determine the ratios of the other carbon NMR peak integrals to that of the reference carbon.
* Obtain the same ratios for the carbons in a sample of the starting material after it has undergone some reaction.
* The ratios of the latter ratios to the former ratios yields R/R.
If these as well as some other precautions listed by Jankowski are followed, kinetic isotope effects with precisions of three decimal places can be achieved. | 0 | Theoretical and Fundamental Chemistry |
The ropB protein binding location lies adjacent to speB promoter 1 that is also located within the highly repetitive intergenic region, however the ropB gene and the speB gene are transcribed in opposite directions. The -10 and -35 regions of speB promoter 1 have poor consensus; in order to ameliorate this, the ropB aids the RNA polymerase bondage with the help of a polyU polypyrimidine tract inside the palindromic inverted repeat region in a fashion uncannily similar to intrinsic termination in E.coli. | 1 | Applied and Interdisciplinary Chemistry |
Recent research suggests that cAMP affects the function of higher-order thinking in the prefrontal cortex through its regulation of ion channels called hyperpolarization-activated cyclic nucleotide-gated channels (HCN). When cAMP stimulates the HCN, the channels open, This research, especially the cognitive deficits in age-related illnesses and ADHD, is of interest to researchers studying the brain.
cAMP is involved in activation of trigeminocervical system leading to neurogenic inflammation and causing migraine. | 1 | Applied and Interdisciplinary Chemistry |
We can define a long-time average of the expectation value of the operator according to the expression
If we use the explicit expression for the time evolution of this expectation value, we can write
The integration in this expression can be performed explicitly, and the result is
Each of the terms in the second sum will become smaller as the limit is taken to infinity. Assuming that the phase coherence between the different exponential terms in the second sum does not ever become large enough to rival this decay, the second sum will go to zero, and we find that the long-time average of the expectation value is given by
This prediction for the time-average of the observable is referred to as its predicted value in the diagonal ensemble, The most important aspect of the diagonal ensemble is that it depends explicitly on the initial state of the system, and so would appear to retain all of the information regarding the preparation of the system. In contrast, the predicted value in the microcanonical ensemble is given by the equally-weighted average over all energy eigenstates within some energy window centered around the mean energy of the system
where is the number of states in the appropriate energy window, and the prime on the sum indices indicates that the summation is restricted to this appropriate microcanonical window. This prediction makes absolutely no reference to the initial state of the system, unlike the diagonal ensemble. Because of this, it is not clear why the microcanonical ensemble should provide such an accurate description of the long-time averages of observables in such a wide variety of physical systems.
However, suppose that the matrix elements are effectively constant over the relevant energy window, with fluctuations that are sufficiently small. If this is true, this one constant value A can be effectively pulled out of the sum, and the prediction of the diagonal ensemble is simply equal to this value,
where we have assumed that the initial state is normalized appropriately. Likewise, the prediction of the microcanonical ensemble becomes
The two ensembles are therefore in agreement.
This constancy of the values of over small energy windows is the primary idea underlying the eigenstate thermalization hypothesis. Notice that in particular, it states that the expectation value of in a single energy eigenstate is equal to the value predicted by a microcanonical ensemble constructed at that energy scale. This constitutes a foundation for quantum statistical mechanics which is radically different from the one built upon the notions of dynamical ergodicity. | 0 | Theoretical and Fundamental Chemistry |
The dehydration of alcohols affords ethers:
: 2 R–OH → R–O–R + HO at high temperature
This direct nucleophilic substitution reaction requires elevated temperatures (about 125 °C). The reaction is catalyzed by acids, usually sulfuric acid. The method is effective for generating symmetrical ethers, but not unsymmetrical ethers, since either OH can be protonated, which would give a mixture of products. Diethyl ether is produced from ethanol by this method. Cyclic ethers are readily generated by this approach. Elimination reactions compete with dehydration of the alcohol:
: R–CH–CH(OH) → R–CH=CH + HO
The dehydration route often requires conditions incompatible with delicate molecules. Several milder methods exist to produce ethers. | 0 | Theoretical and Fundamental Chemistry |
The absorption of methyl orange on the UV/vis spectrum is between 350-550 nm, with its peak at 464 nm. This is in the green-purple visible light range and explains why methyl orange is, in fact, orange. | 0 | Theoretical and Fundamental Chemistry |
The Uhlenhuth test, or the antigen–antibody precipitin test for species, was invented by Paul Uhlenhuth in 1901 and could distinguish human blood from animal blood, based on the discovery that the blood of different species had one or more characteristic proteins. The test represented a major breakthrough and came to have tremendous importance in forensic science. The test was further refined for forensic use by the Swiss chemist Maurice Müller in the year 1960s. | 0 | Theoretical and Fundamental Chemistry |
The formation of a complex between a metal ion, M, and a ligand, L, is in fact usually a substitution reaction. For example, In aqueous solutions, metal ions will be present as aquo ions, so the reaction for the formation of the first complex could be written as
:[M(HO)] + L [M(HO)L] + HO
However, since water is in vast excess, the concentration of water is usually assumed to be constant and is omitted from equilibrium constant expressions. Often, the metal and the ligand are in competition for protons. For the equilibrium
:p M + q L + r H MLH
a stability constant can be defined as follows:
The definition can easily be extended to include any number of reagents. It includes hydroxide complexes because the concentration of the hydroxide ions is related to the concentration of hydrogen ions by the self-ionization of water
Stability constants defined in this way, are association constants. This can lead to some confusion as pK values are dissociation constants. In general purpose computer programs it is customary to define all constants as association constants. The relationship between the two types of constant is given in association and dissociation constants.
In biochemistry, an oxygen molecule can bind to an iron(II) atom in a heme prosthetic group in hemoglobin. The equilibrium is usually written, denoting hemoglobin by Hb, as
: Hb + O HbO
but this representation is incomplete as the Bohr effect shows that the equilibrium concentrations are pH-dependent. A better representation would be
: [HbH] + O HbO + H
as this shows that when hydrogen ion concentration increases the equilibrium is shifted to the left in accordance with Le Châtelier's principle. Hydrogen ion concentration can be increased by the presence of carbon dioxide, which behaves as a weak acid.
:HO + CO + H
The iron atom can also bind to other molecules such as carbon monoxide. Cigarette smoke contains some carbon monoxide so the equilibrium
:HbO + CO + O
is established in the blood of cigarette smokers.
Chelation therapy is based on the principle of using chelating ligands with a high binding selectivity for a particular metal to remove that metal from the human body.
Complexes with polyamino carboxylic acids find a wide range of applications. EDTA in particular is used extensively. | 0 | Theoretical and Fundamental Chemistry |
Self-assembly of nanoparticles is driven by either maximization of packing density or minimization of the contact area between particles according to hard or soft nanoparticles. Examples of hard nanoparticles are: silica, fullerenes; soft nanoparticles are often organic nanoparticles, block copolymer micelles, DNA nanoparticles. The ordered self-assembly structure of nanoparticles is called superlattice. | 0 | Theoretical and Fundamental Chemistry |
Topochemical polymerization is a polymerization method performed by monomers aligned in the crystal state. In this process, the monomers are crystallised and polymerised under external stimuli such as heat, light, or pressure. Compared to traditional polymerisation, the movement of monomers was confined by the crystal lattice in topochemical polymerisation, giving rise to polymers with high crystallinity, tacticity, and purity. Topochemical polymerisation can also be used to synthesise unique polymers such as polydiacetylene that are otherwise hard to prepare.
Various reactions have been adopted in the field of topochemical polymerisation, such as [2+2], [4+2], [4+4], and [3+2] cycloaddition, linear addition between dienes, trienes, diacetylenes. Other than linear polymers, they can also be applied to the synthesis of two dimensional covalent networks. | 0 | Theoretical and Fundamental Chemistry |
Fermented water contains a similar alcoholic content of wines as both beverages are fermented on yeast, however fermented water differs from wine and other fermented beverages in that it contains no fruit juice or residual sugar after manufacture.
Kilju can be produced by fermenting sugar, yeast, and water, but it was illegal in Finland before March 2018; therefore, grain, potatoes, fruits or berries were used during fermentation to avoid legal problems and to flavor the drink. Oranges and lemons are a popular choice for this purpose. | 1 | Applied and Interdisciplinary Chemistry |
Chloromethane was a widely used refrigerant, but its use has been discontinued. It was particularly dangerous among the common refrigerants of the 1930s due to its combination of toxicity, flammability and lack of odor as compared with other toxic refrigerants such as sulfur dioxide and ammonia. Chloromethane was also once used for producing lead-based gasoline additives (tetramethyllead). | 1 | Applied and Interdisciplinary Chemistry |
ERH has been used for over 15 years for treatment of unconsolidated soils in both the vadose and saturated zones. Recent advancements and results show that ERH can be an effective treatment method for bedrock. At an ERH site, the primary electrical current path is on the thin layer of water immediately adjacent to the soil or rock grains. Little current is carried by the water in the pore volume. It is not the pore fluid that dominates the electrical conductivity; it is the grain wetting fluid that dominates the electrical conductivity. Sedimentary rock will typically possess the thin layer of water required for current flow. This means ERH can effectively be used for treatment of sedimentary bedrock, which typically has significant primary porosity. | 1 | Applied and Interdisciplinary Chemistry |
In scientific literature, porous glass is a porous material containing approximately 96% silica, which is produced by an acidic extraction or a combined acidic and alkaline extraction respectively, of phase separated alkali borosilicate glasses, and features a three-dimensional interconnected porous microstructure. For commercially available porous glasses, the terms porous VYCOR-Glass (PVG) and Controlled Pore Glass (CPG) are used. The pore structure is formed by a syndetic channel system and has a specific surface from 10 to 300 m/g. Porous glasses can be generated by an acidic extraction of phase separated alkaliborosilica glasses, or by a sol-gel-process. By regulating the manufacturing parameters, it is possible to produce a porous glass with a pore size of between 0.4 and 1000 nm in a very narrow pore size distribution. You can generate various moulds, for example, irregular particles (powder, granulate), spheres, plates, sticks, fibers, ultra thin membranes, tubes and rings. | 0 | Theoretical and Fundamental Chemistry |
Synchrotron radiation circular dichroism spectroscopy, commonly referred to as SRCD and also known as VUV-circular dichroism or VUVCD spectroscopy, is a powerful extension to the technique of circular dichroism (CD) spectroscopy, often used to study structural properties of biological molecules such as proteins and nucleic acids. The physical principles of SRCD are essentially identical to those of CD, in that the technique measures the difference in absorption (ΔA) of left (A) and right (A) circularly polarized light (ΔA=A-A) by a sample in solution. To obtain a CD(SRCD) spectrum the sample must be innately optically active (chiral), or, in some way be induced to have chiral properties, as only then will there be an observable difference in absorption of the left and right circularly polarized light. The major advantages of SRCD over CD arise from the ability to measure data over an extended wavelength range into the vacuum ultra violet (VUV) end of the spectrum. As these measurements are utilizing a light source with a higher photon flux (quantity of light stricking a given surface area) than a bench-top CD machine it means data are more accurate at these extended wavelengths because there is a larger signal over the background noise (the signal-to-noise ratio) and, generally, less sample is needed when recording the spectra and there is more information content available in the data. Many beamlines now exist around the world to enable the measurement of SRCD data. | 0 | Theoretical and Fundamental Chemistry |
The Gouy-Stodola theorem is often applied to refrigeration cycles. These are thermodynamic cycles or mechanical systems where external work can be used to move heat from low temperature sources to high temperature sinks, or vice versa. Specifically, the theorem is useful in analyzing vapor compression and vapor absorption refrigeration cycles.
The theorem can help identify which components of a system have major irreversibilities, and how much exergy they destroy. It can be used to find at which temperatures the performance is optimal, or what size system should be constructed. Overall, that is, the Gouy-Stodola theorem is a tool to find and quantify inefficiencies in a system, and can point to how to minimize them - this is the goal of exergy analysis. When the theorem is used for these purposes, it is usually applied in its modified form. | 0 | Theoretical and Fundamental Chemistry |
Biodistribution is a method of tracking where compounds of interest travel in an experimental animal or human subject. For example, in the development of new compounds for PET (positron emission tomography) scanning, a radioactive isotope is chemically joined with a peptide (subunit of a protein). This particular class of isotopes emits positrons (which are antimatter particles, equal in mass to the electron, but with a positive charge). When ejected from the nucleus, positrons encounter an electron, and undergo annihilation which produces two gamma rays travelling in opposite directions. These gamma rays can be measured, and when compared to a standard, quantified. | 1 | Applied and Interdisciplinary Chemistry |
The first explanation of the attraction between noble gas atoms was given by Fritz London in 1930. He used a quantum-mechanical theory based on second-order perturbation theory. The perturbation is because of the Coulomb interaction between the electrons and nuclei of the two moieties (atoms or molecules). The second-order perturbation expression of the interaction energy contains a sum over states. The states appearing in this sum are simple products of the stimulated electronic states of the monomers. Thus, no intermolecular antisymmetrization of the electronic states is included, and the Pauli exclusion principle is only partially satisfied.
London wrote a Taylor series expansion of the perturbation in , where is the distance between the nuclear centers of mass of the moieties.
This expansion is known as the multipole expansion because the terms in this series can be regarded as energies of two interacting multipoles, one on each monomer. Substitution of the multipole-expanded form of V into the second-order energy yields an expression that resembles an expression describing the interaction between instantaneous multipoles (see the qualitative description above). Additionally, an approximation, named after Albrecht Unsöld, must be introduced in order to obtain a description of London dispersion in terms of polarizability volumes, , and ionization energies, , (ancient term: ionization potentials).
In this manner, the following approximation is obtained for the dispersion interaction between two atoms and . Here and are the polarizability volumes of the respective atoms. The quantities and are the first ionization energies of the atoms, and is the intermolecular distance.
Note that this final London equation does not contain instantaneous dipoles (see molecular dipoles). The "explanation" of the dispersion force as the interaction between two such dipoles was invented after London arrived at the proper quantum mechanical theory. The authoritative work contains a criticism of the instantaneous dipole model and a modern and thorough exposition of the theory of intermolecular forces.
The London theory has much similarity to the quantum mechanical theory of light dispersion, which is why London coined the phrase "dispersion effect". In physics, the term "dispersion" describes the variation of a quantity with frequency, which is the fluctuation of the electrons in the case of the London dispersion. | 0 | Theoretical and Fundamental Chemistry |
Neurophysins are carrier proteins which transport the hormones oxytocin and vasopressin to the posterior pituitary from the paraventricular and supraoptic nucleus of the hypothalamus, respectively. Inside the neurosecretory granules, the analogous neurophysin I and II form stabilizing complexes via covalent interactions. Stabilizing neurophysin-hormone complexes that are formed within neurosecretory granules located in the posterior pituitary gland aid in intra-axonal transport. During intra-axonal transport, the neurophysin's are believed to prevent the bound hormone from leaking into the cytoplasmic space and proteolytic digestion via enzymes. However, due to the low concentration of neurophysin in the blood, it is likely the protein-hormone complex dissociates, indicating the neurophysin does not aid in transporting the hormone through the circulatory system.
Neurophysins are also secreted out of the posterior pituitary hypothalamus, each carrying their respective associated passenger hormone. When the posterior pituitary hypothalamus secretes vasopressin and its neurophysin carrier, it also secretes a glycopeptide.
There are two types:
* Neurophysin I - Oxytocin
* Neurophysin II - Vasopressin (Also known as "antidiuretic hormone" or ADH) | 1 | Applied and Interdisciplinary Chemistry |
*G are involved in Rho family GTPase signaling (see Rho family of GTPases). This is through the RhoGEF superfamily involving the RhoGEF domain of the proteins' structures). These are involved in control of cell cytoskeleton remodeling, and thus in regulating cell migration. | 1 | Applied and Interdisciplinary Chemistry |
All the lifting surfaces of an aircraft are divided into some number of quadrilateral panels, and a horseshoe vortex and a collocation point (or control point) are placed on each panel. The transverse segment of the vortex is at the 1/4 chord position of the panel, while the collocation point is at the 3/4 chord position. The vortex strength is to be determined. A normal vector is also placed at each collocation point, set normal to the camber surface of the actual lifting surface.
For a problem with panels, the perturbation velocity at collocation point is given by summing the contributions of all the horseshoe vortices in terms of an Aerodynamic Influence Coefficient (AIC) matrix .
The freestream velocity vector is given in terms of the freestream speed and the angles of attack and sideslip, .
A Neumann boundary condition is applied at each collocation point, which prescribes that the normal velocity across the camber surface is zero. Alternate implementations may also use the Dirichlet boundary condition directly on the velocity potential.
This is also known as the flow tangency condition. By evaluating the dot products above the following system of equations results. The new normalwash AIC matrix is , and the right hand side is formed by the freestream speed and the two aerodynamic angles
This system of equations is solved for all the vortex strengths . The total force vector and total moment vector about the origin are then computed by summing the contributions of all the forces on all the individual horseshoe vortices, with being the fluid density.
Here, is the vortexs transverse segment vector, and is the perturbation velocity at this segments center location (not at the collocation point).
The lift and induced drag are obtained from the components of the total force vector . For the case of zero sideslip these are given by | 1 | Applied and Interdisciplinary Chemistry |
The first observations of a different behavior of water molecules, close to the walls of its container, date back to late 1960s and early 1970s, when Drost-Hansen, upon reviewing many experimental articles, came to the conclusion that interfacial water shows structural difference.
In 1986 Deryagin and his colleagues observed an exclusion zone next to the walls of cells.
In 2006 the group of Gerald Pollack reported their observation of what they called an exclusion zone. They observed that the particles of colloidal and molecular solutes suspended in aqueous solution are profoundly and extensively excluded from the vicinity of various hydrophilic surfaces. The exclusion zone has been observed and characterized by several independent groups since those early observations. | 1 | Applied and Interdisciplinary Chemistry |
(-)-C-demethyl arteannuin B is a structural analog of the antimalarial artemisinin. It exhibits potent antimalarial activity even against a drug-resistant strain. Little and coworkers obtained the alkylated hydrazone in diastereomerically pure form (de > 95%) through the Enders' alkylation reaction. This intermediate was then elaborated into (-)-C-demethyl arteannuin B. | 0 | Theoretical and Fundamental Chemistry |
Wire arc spray is a form of thermal spraying where two consumable metal wires are fed independently into the spray gun. These wires are then charged and an arc is generated between them. The heat from this arc melts the incoming wire, which is then entrained in an air jet from the gun. This entrained molten feedstock is then deposited onto a substrate with the help of compressed air. This process is commonly used for metallic, heavy coatings. | 1 | Applied and Interdisciplinary Chemistry |
Crevice corrosion refers to corrosion occurring in occluded spaces such as interstices in which a stagnant solution is trapped and not renewed. These spaces are generally called crevices. Examples of crevices are gaps and contact areas between parts, under gaskets or seals, inside cracks and seams, spaces filled with deposits and under sludge piles. | 1 | Applied and Interdisciplinary Chemistry |
Recalescence is an increase in temperature that occurs while cooling metal when a change in structure with an increase in entropy occurs. The heat responsible for the change in temperature is due to the change in entropy. When a structure transformation occurs the Gibbs free energy of both structures are more or less the same. Therefore, the process will be exothermic. The heat provided is the latent heat.
Recalescence also occurs after supercooling, when the supercooled liquid suddenly crystallizes, forming a solid but releasing heat in the process. | 1 | Applied and Interdisciplinary Chemistry |
Methane has a very light δC signature: biogenic methane of −60‰, thermogenic methane −40‰. The release of large amounts of methane clathrate can impact on global δC values, as at the Paleocene–Eocene Thermal Maximum.
More commonly, the ratio is affected by variations in primary productivity and organic burial. Organisms preferentially take up light C, and have a δC signature of about −25‰, depending on their metabolic pathway. Therefore, an increase in δC in marine fossils is indicative of an increase in the abundance of vegetation.
An increase in primary productivity causes a corresponding rise in δC values as more C is locked up in plants. This signal is also a function of the amount of carbon burial; when organic carbon is buried, more C is locked out of the system in sediments than the background ratio. | 0 | Theoretical and Fundamental Chemistry |
Ethenium has been observed in rarefied gases subjected to radiation. Another preparation method is to react certain proton donors such as trihydrogen cation|, helium hydride ion|, diazenylium|, and with ethane at ambient temperature and pressures below 1 mmHg. (Other donors such as methanium| and form ethanium preferably to ethenium.)
At room temperature and in a rarefied methane atmosphere, ethanium slowly dissociates to ethenium and . The reaction is much faster at 90 °C. | 0 | Theoretical and Fundamental Chemistry |
Other flow-type batteries include the zinc–cerium battery, the zinc–bromine battery, and the hydrogen–bromine battery. | 0 | Theoretical and Fundamental Chemistry |
Processing of mRNA differs greatly among eukaryotes, bacteria, and archaea. Non-eukaryotic mRNA is, in essence, mature upon transcription and requires no processing, except in rare cases. Eukaryotic pre-mRNA, however, requires several processing steps before its transport to the cytoplasm and its translation by the ribosome. | 1 | Applied and Interdisciplinary Chemistry |
Studies have reported that: 1) the levels of CMTM5-v1 in the malignant tissues of patients with prostate cancer are lower than the levels in their nearby normal prostate gland tissues as well as in the tissues of patients with benign prostate hyperplasia; 2) patients with lower prostate cancer tissue levels of CMTM5-v1 have higher prostate cancer Gleason scores and therefore poorer prognoses than patients with higher prostate cancer tissue levels of CMTM5-v1; and 3) the forced overexpression of CMTM5-v1 in cultured DU145 cells (a human prostate cancer cell line) reduces, while the forced higher expression of the CMTM5-v1 levels increases, their proliferation and migration. Similar findings for an unspecified CMTM5 isoform are reported in ovarian cancer, hepatocellular carcinoma, pancreatic cancer, non-small-cell lung carcinoma, renal cell carcinoma, and breast cancer. The forced over expression of CMTM5-v1 in Huh7 human hepatic cells also inhibited the ability of these cells to grow in a mouse model of cancer. Finally, various cancer human cell lines including those of the liver, breast, prostate, colon, stomach, nasopharynx, laryngopharynx, esophagus, lung, and cervix express low levels of, or no, CMTM5-v1 and concurrently have highly methylated CpG sites near to the CMTM5 gene. These findings suggest that the CMTM5 gene may act as a tumor suppressor gene, i.e. a normal gene whose product(s) inhibit the development and/or progression of various cancers. The findings also support further studies to confirm and expand these relationships and determine if the expression of CMTM5 isoforms can be used as tumor markers for these cancers severities/prognoses and/or targets as for treating them. | 1 | Applied and Interdisciplinary Chemistry |
In genetics and cell biology, repression is a mechanism often used to decrease or inhibit the expression of a gene. Removal of repression is called derepression. This mechanism may occur at different stages in the expression of a gene, with the result of increasing the overall RNA or protein products. Dysregulation of derepression mechanisms can result in altered gene expression patterns, which may lead to negative phenotypic consequences such as disease. | 1 | Applied and Interdisciplinary Chemistry |
Fluorapatite (Ca(PO)F) is mined along with other apatites for its phosphate content and is used mostly for production of fertilizers. Most of the Earth's fluorine is bound in this mineral, but because the percentage within the mineral is low (3.5%), the fluorine is discarded as waste. Only in the United States is there significant recovery. There, the hexafluorosilicates produced as byproducts are used to supply water fluoridation. | 0 | Theoretical and Fundamental Chemistry |
In a rat model of premature aging, oxidative stress induced DNA damage in the neocortex and hippocampus was substantially higher than in normally aging control rats. Numerous studies have shown that the level of 8-oxo-2-deoxyguanosine, a product of oxidative stress, increases with age in the brain and muscle DNA of the mouse, rat, gerbil and human. Further information on the association of oxidative DNA damage with aging is presented in the article DNA damage theory of aging. However, it was recently shown that the fluoroquinolone antibiotic Enoxacin can diminish aging signals and promote lifespan extension in nematodes C. elegans 'by inducing oxidative stress. | 1 | Applied and Interdisciplinary Chemistry |
The reflection operation is carried out with respect to symmetry elements known as planes of symmetry or mirror planes. Each such plane is denoted as (sigma). Its orientation relative to the principal axis of the molecule is indicated by a subscript. The plane must pass through the molecule and cannot be completely outside it.
*If the plane of symmetry contains the principal axis of the molecule (i.e., the molecular -axis), it is designated as a vertical mirror plane, which is indicated by a subscript ().
*If the plane of symmetry is perpendicular to the principal axis, it is designated as a horizontal mirror plane, which is indicated by a subscript ().
*If the plane of symmetry bisects the angle between two 2-fold axes perpendicular to the principal axis, it is designated as a dihedral mirror plane, which is indicated by a subscript ().
Through the reflection of each mirror plane, the molecule must be able to produce an identical image of itself. | 0 | Theoretical and Fundamental Chemistry |
Deflocculation is the exact opposite of flocculation, also sometimes known as peptization. Sodium silicate (NaSiO) is a typical example. Usually in higher pH ranges in addition to low ionic strength of solutions and domination of monovalent metal cations the colloidal particles can be dispersed.
The additive that prevents the colloids from forming flocs is called a deflocculant. For deflocculation imparted through electrostatic barriers, the efficacy of a deflocculant can be gauged in terms of zeta potential. According to the Encyclopedic Dictionary of Polymers deflocculation is "a state or condition of a dispersion of a solid in a liquid in which each solid particle remains independent and unassociated with adjacent particles (much like emulsifier). A deflocculated suspension shows zero or very low yield value".
Deflocculation can be a problem in wastewater treatment plants as it commonly causes sludge settling problems and deterioration of the effluent quality. | 1 | Applied and Interdisciplinary Chemistry |
Battens – the horizontal elements on "board and batten" shutters. Strap hinges usually mount centered on the battens. This is the standard construction approach for most barn doors.
Butt mounted – hinges that mortise into the sides of the hinges – only the barrel of the hinge is visible when the shutter is in the closed position.
Casement – the wood surrounding the window upon which the pintle is typically mounted.
Hinges – mate with the Pintles and are mounted on the shutter.
Pintles – the "pins" on which hinges swing. The pintles are, by definition, mounted to the structure. Pintles are offered in various configurations to match different installation situations.
Rails – with louvered or raised panel shutters, the rails are the horizontal elements of wood that frame the shutter. The width of the rails is an important consideration when choosing surface mounted hardware.
Show hinges – hinges arranged to mount so as to be visible when the shutter is in the open position.
Stiles – when a shutter is louvered or of the raised panel style, the stiles are the vertical elements of the frame. Knowing the width of the stiles allows positioning of the first fastener on strap hinges on their mid-line.
Surface mounted – hinges that mount to the face of the shutter – strap hinges and the "New York Style" hinges are examples. The hinges are visible when the shutter is in the closed position. | 1 | Applied and Interdisciplinary Chemistry |
By the time of his retirement in 1906 he had published some 65 chemical papers, most of them in the Spanish language, on such diverse topics as the chemical compositions of Argentine rivers, the medicinal plants of Córdoba Province, Argentina, the incrustation of locomotive boilers, the presence of organic matter in drinking water, the caffeine content of yerba mate, the adulteration of saffron, the wines of the Argentine Republic, compositions of meteorites fallen in Buenos Aires Province, Patagonian guano, the petroleum of Jujuy Province, a new alkaloid he isolated from Ruprechtia salicifolia, Cape Virgins gold, Tierra del Fuego platinum, well water, the cement of a failed dam, the destruction of masonry by cloacal gases, and a silver-yielding manganese ore from Mendoza Province.
According to Rapela and Depetris, Kyle was the first Argentine geochemist. Of his papers,
On a vanadiferous lignite found in the Argentine Republic with analysis of the ash was read before the British Association Edinburgh meeting in 1892. His last work, published in Ambrosetti, El bronce en la region calchaquí established that the Calchaquí Amerindians were a Bronze Age people. He died in Buenos Aires on 23 February 1922. | 0 | Theoretical and Fundamental Chemistry |
Apamin is an 18 amino acid globular peptide neurotoxin found in apitoxin (bee venom). Dry bee venom consists of 2–3% of apamin. Apamin selectively blocks SK channels, a type of Ca-activated K channel expressed in the central nervous system. Toxicity is caused by only a few amino acids, in particular cysteine, lysine, arginine, arginine and histidine. These amino acids are involved in the binding of apamin to the Ca-activated K channel. Due to its specificity for SK channels, apamin is used as a drug in biomedical research to study the electrical properties of SK channels and their role in the afterhyperpolarizations occurring immediately following an action potential. | 1 | Applied and Interdisciplinary Chemistry |
Because the coiled shells of gastropods are asymmetric, they possess a quality called chirality–the "handedness" of an asymmetric structure.
Over 90% of gastropod species have shells in which the direction of the coil is dextral (right-handed). A small minority of species and genera have shells in which the coils are almost always sinistral (left-handed). Very few species show an even mixture of dextral and sinistral individuals (for example, Amphidromus perversus). | 0 | Theoretical and Fundamental Chemistry |
Fumaric acid was developed as a medicine to treat the autoimmune condition psoriasis in the 1950s in Germany as a tablet containing 3 esters, primarily dimethyl fumarate, and marketed as Fumaderm by Biogen Idec in Europe. Biogen would later go on to develop the main ester, dimethyl fumarate, as a treatment for multiple sclerosis.
In patients with relapsing-remitting multiple sclerosis, the ester dimethyl fumarate (BG-12, Biogen) significantly reduced relapse and disability progression in a phase 3 trial. It activates the Nrf2 antioxidant response pathway, the primary cellular defense against the cytotoxic effects of oxidative stress. | 1 | Applied and Interdisciplinary Chemistry |
Direct reduced iron is highly susceptible to oxidation and rusting if left unprotected, and is normally quickly processed further to steel. The bulk iron can also catch fire since it is pyrophoric. Unlike blast furnace pig iron, which is almost pure metal, DRI contains some siliceous gangue (if made from scrap, not from new iron from direct reduced iron with natural gas), which needs to be removed in the steel-making process. | 1 | Applied and Interdisciplinary Chemistry |
In nuclear physics, resonance escape probability is the probability that a neutron will slow down from fission energy to thermal energies without being captured by a nuclear resonance. A resonance absorption of a neutron in a nucleus does not produce nuclear fission. The probability of resonance absorption is called the resonance factor , and the sum of the two factors is .
Generally, the higher the neutron energy, the lower the probability of absorption, but for some energies, called resonance energies, the resonance factor is very high. These energies depend on the properties of heavy nuclei. Resonance escape probability is highly determined by the heterogeneous geometry of a reactor, because fast neutrons resulting from fission can leave the fuel and slow to thermal energies in a moderator, skipping over resonance energies before reentering the fuel.
Resonance escape probability appears in the four factor formula and the six factor formula. To compute it, neutron transport theory is used. | 0 | Theoretical and Fundamental Chemistry |
At sawmills, unless reprocessed into particleboard, burned in a sawdust burner, or used to make heat for other milling operations, sawdust may collect in piles and add harmful leachates into local water systems, creating an environmental hazard. This has placed small sawyers and environmental agencies in a deadlock.
Questions about the science behind the determination of sawdust being an environmental hazard remain for sawmill operators (though this is mainly with finer particles), who compare wood residuals to dead trees in a forest. Technical advisors have reviewed some of the environmental studies, but say most lack standardized methodology or evidence of a direct impact on wildlife. They do not take into account large drainage areas, so the amount of material that is getting into the water from the site in relation to the total drainage area is minuscule.
Other scientists have a different view, saying the "dilution is the solution to pollution" argument is no longer accepted in environmental science. The decomposition of a tree in a forest is similar to the impact of sawdust, but the difference is of scale. Sawmills may be storing thousands of cubic metres of wood residues in one place, so the issue becomes one of concentration.
Of larger concern are substances such as lignins and fatty acids that protect trees from predators while they are alive, but can leach into water and poison wildlife. Those types of things remain in the tree and, as the tree decays, they slowly are broken down. But when sawyers are processing a large volume of wood and large concentrations of these materials permeate into the runoff, the toxicity they cause is harmful to a broad range of organisms. | 1 | Applied and Interdisciplinary Chemistry |
Ocean dynamics are governed by Newtons equations of motion expressed as the Navier-Stokes equations for a fluid element located at (x,y,z') on the surface of our rotating planet and moving at velocity (u,v,w) relative to that surface:
* the zonal momentum equation:
* the meridional momentum equation:
* the vertical momentum equation (assumes the ocean is in hydrostatic balance):
* the continuity equation (assumes the ocean is incompressible):
* the temperature equation:
* the salinity equation:
Here "u" is zonal velocity, "v" is meridional velocity, "w" is vertical velocity, "p" is pressure, "ρ" is density, "T" is temperature, "S" is salinity, "g" is acceleration due to gravity, "τ" is wind stress, and "f" is the Coriolis parameter. "Q" is the heat input to the ocean, while "P-E" is the freshwater input to the ocean. | 1 | Applied and Interdisciplinary Chemistry |
Serine is the first amino acid in this family to be produced; it is then modified to produce both glycine and cysteine (and many other biologically important molecules). Serine is formed from 3-phosphoglycerate in the following pathway:
3-phosphoglycerate → phosphohydroxyl-pyruvate → phosphoserine → serine
The conversion from 3-phosphoglycerate to phosphohydroxyl-pyruvate is achieved by the enzyme phosphoglycerate dehydrogenase. This enzyme is the key regulatory step in this pathway. Phosphoglycerate dehydrogenase is regulated by the concentration of serine in the cell. At high concentrations this enzyme will be inactive and serine will not be produced. At low concentrations of serine the enzyme will be fully active and serine will be produced by the bacterium. Since serine is the first amino acid produced in this family both glycine and cysteine will be regulated by the available concentration of serine in the cell. | 1 | Applied and Interdisciplinary Chemistry |
In the history of thermodynamics, the initial explanations of heat were thoroughly confused with explanations of combustion. After J. J. Becher and Georg Ernst Stahl introduced the phlogiston theory of combustion in the 17th century, phlogiston was thought to be the substance of heat.
There is one version of the caloric theory that was introduced by Antoine Lavoisier. Prior to Lavoisiers caloric theory, published references concerning heat and its existence, outside of being an agent for chemical reactions, were sparse only having been offered by Joseph Black in Roziers Journal (1772) citing the melting temperature of ice. In response to Black, Lavoisiers private manuscripts revealed that he had encountered the same phenomena of a fixed melting point for ice and mentioned that he had already formulated an explanation which he had not published as of yet. Lavoisier developed the explanation of combustion in terms of oxygen in the 1770s. In his paper "Réflexions sur le phlogistique" (1783), Lavoisier argued that phlogiston theory was inconsistent with his experimental results, and proposed a subtle fluid called caloric as the substance of heat. According to this theory, the quantity of this substance is constant throughout the universe, and it flows from warmer to colder bodies. Indeed, Lavoisier was one of the first to use a calorimeter to measure the heat released during chemical reaction. Lavoisier presented the idea that caloric was a subtle fluid, obeying the common laws of matter, but attenuated to such a degree that it is capable of passing through dense matter without restraint; calorics own material nature is evident when it is in abundance such as in the case of an explosion.
In the 1780s, Count Rumford believed that cold was a fluid, "frigoric" after the results of Pictet's experiment. Pierre Prévost argued that cold was simply a lack of caloric.
Since heat was a material substance in caloric theory, and therefore could neither be created nor destroyed, conservation of heat was a central assumption. Heat conduction was believed to have occurred as a result of the affinity between caloric and matter thus the less caloric a substance possessed, thereby being colder, attracted excess caloric from nearby atoms until a caloric, and temperature, equilibrium was reached.
Chemists of the time believed in the self-repulsion of heat particles as a fundamental force thereby making the great fluid elasticity of caloric, which does not create a repulsive force, an anomalous property which Lavoisier could not explain to his detractors.
Radiation of heat was explained by Lavoisier to be concerned with the condition of the surface of a physical body rather than the material of which it was composed. Lavoisier described a poor radiator to be a substance with a polished or smooth surface as it possessed its molecules lying in a plane closely bound together thus creating a surface layer of caloric which insulated the release of the rest within. He described a great radiator to be a substance with a rough surface as only a small amount of molecules held caloric in within a given plane allowing for greater escape from within. Count Rumford would later cite this explanation of caloric movement as insufficient to explain the radiation of cold becoming a point of contention for the theory as a whole.
The introduction of the caloric theory was influenced by the experiments of Joseph Black related to the thermal properties of materials. Besides the caloric theory, another theory existed in the late eighteenth century that could explain the phenomenon of heat: the kinetic theory. The two theories were considered to be equivalent at the time, but kinetic theory was the more modern one, as it used a few ideas from atomic theory and could explain both combustion and calorimetry. Caloric theorys inability to explain evaporation and sublimation further led to the rise of kinetic theory through the work of Count Rumford. Count Rumford observed solid mercurys tendency to melt under atmospheric conditions and thus proposed that the intensity of heat itself must stem from particle motion for such an event to occur where great heat was not expected to be. | 1 | Applied and Interdisciplinary Chemistry |
White phosphorus, yellow phosphorus or simply tetraphosphorus () exists as molecules of four phosphorus atoms in a tetrahedral structure, joined by six phosphorus—phosphorus single bonds. The tetrahedral arrangement results in ring strain and instability. Although both are called "white phosphorus", in fact two different crystal allotropes are known, interchanging reversibly at 195.2 K. The element's standard state is the body-centered cubic α form, which is actually metastable under standard conditions. The β form is believed to have a hexagonal crystal structure.
Molten and gaseous white phosphorus also retains the tetrahedral molecules, until when it starts decomposing to molecules. The molecule in the gas phase has a P-P bond length of r = 2.1994(3) Å as was determined by gas electron diffraction. The β form of white phosphorus contains three slightly different molecules, i.e. 18 different P-P bond lengths — between 2.1768(5) and 2.1920(5) Å. The average P-P bond length is 2.183(5) Å.
White phosphorus is a translucent waxy solid that quickly yellows in light, and impure white phosphorus is for this reason called yellow phosphorus. It glows greenish in the dark (when exposed to oxygen) and is highly flammable and pyrophoric (self-igniting) upon contact with air. It is toxic, causing severe liver damage on ingestion and phossy jaw from chronic ingestion or inhalation. The odour of combustion of this form has a characteristic garlic smell, and samples are commonly coated with white "diphosphorus pentoxide", which consists of tetrahedral with oxygen inserted between the phosphorus atoms and at their vertices. White phosphorus is only slightly soluble in water and can be stored under water. Indeed, white phosphorus is safe from self-igniting when it is submerged in water; due to this, unreacted white phosphorus can prove hazardous to beachcombers who may collect washed-up samples while unaware of their true nature. is soluble in benzene, oils, carbon disulfide, and disulfur dichloride. | 0 | Theoretical and Fundamental Chemistry |
Comparing the two contributing structures of benzene, all single and double bonds are interchanged. Bond lengths can be measured, for example using X-ray diffraction. The average length of a C–C single bond is 154 pm; that of a C=C double bond is 133 pm. In localized cyclohexatriene, the carbon–carbon bonds should be alternating 154 and 133 pm. Instead, all carbon–carbon bonds in benzene are found to be about 139 pm, a bond length intermediate between single and double bond. This mixed single and double bond (or triple bond) character is typical for all molecules in which bonds have a different bond order in different contributing structures. Bond lengths can be compared using bond orders. For example, in cyclohexane the bond order is 1 while that in benzene is 1 + (3 ÷ 6) = . Consequently, benzene has more double bond character and hence has a shorter bond length than cyclohexane. | 0 | Theoretical and Fundamental Chemistry |
Beta-carotene, found in pumpkins, sweet potato, carrots and winter squash, is responsible for their orange-yellow colors. Dried carrots have the highest amount of carotene of any food per 100-gram serving, measured in retinol activity equivalents (provitamin A equivalents). Vietnamese gac fruit contains the highest known concentration of the carotenoid lycopene. Although green, kale, spinach, collard greens, and turnip greens contain substantial amounts of beta-carotene. The diet of flamingos is rich in carotenoids, imparting the orange-colored feathers of these birds.
Reviews of preliminary research in 2015 indicated that foods high in carotenoids may reduce the risk of head and neck cancers and prostate cancer. There is no correlation between consumption of foods high in carotenoids and vitamin A and the risk of Parkinson's disease.
Humans and other animals are mostly incapable of synthesizing carotenoids, and must obtain them through their diet. Carotenoids are a common and often ornamental feature in animals. For example, the pink color of salmon, and the red coloring of cooked lobsters and scales of the yellow morph of common wall lizards are due to carotenoids. It has been proposed that carotenoids are used in ornamental traits (for extreme examples see puffin birds) because, given their physiological and chemical properties, they can be used as visible indicators of individual health, and hence are used by animals when selecting potential mates.
Carotenoids from the diet are stored in the fatty tissues of animals, and exclusively carnivorous animals obtain the compounds from animal fat. In the human diet, absorption of carotenoids is improved when consumed with fat in a meal. Cooking carotenoid-containing vegetables in oil and shredding the vegetable both increase carotenoid bioavailability. | 0 | Theoretical and Fundamental Chemistry |
Ellipsometry has a number of advantages compared to standard reflection intensity measurements:
* Ellipsometry measures at least two parameters at each wavelength of the spectrum. If generalized ellipsometry is applied up to 16 parameters can be measured at each wavelength.
* Ellipsometry measures an intensity ratio instead of pure intensities. Therefore, ellipsometry is less affected by intensity instabilities of the light source or atmospheric absorption.
* By using polarized light, normal ambient unpolarized stray light does not significantly influence the measurement, no dark box is necessary.
* No reference measurement is necessary.
Ellipsometry is especially superior to reflectivity measurements when studying anisotropic samples. | 0 | Theoretical and Fundamental Chemistry |
Euler momentum equation is a Cauchy momentum equation with the Pascal law being the stress constitutive relation:
in nondimensional Lagrangian form is:
Free Euler equations are conservative. The limit of high Froude numbers (low external field) is thus notable and can be studied with perturbation theory. | 1 | Applied and Interdisciplinary Chemistry |
A number of these anions known. Some have attracted interest as components in fast ion conductors for use in solid state batteries. The binary thiophosphates do not exhibit the extensive diversity of the analogous oxyanions but contain similar structural features, for example P is 4 coordinate, P−S−P links form and there are P−P bonds. One difference is that ions may include polysulfide fragments of 2 or more S atoms whereas in the P−O anions there is only the reactive −O−O−, peroxo, unit.
* is the analogue of the nitrate ion, (there is no analogue); it was isolated as the yellow tetraphenylarsonium salt
* is the sulfur analogue of , and like is tetrahedral.
* the pyrothiophosphate ion consisting of two corner sharing PS tetrahedra, analogous to the pyrophosphates.
* An ion which can be visualised either as two PS tetrahedra joined by a disulfide link or a pyrothiophosphate where the bridging −S− is replaced by −S−.
* edge-shared bitetrahedral structure. The structure is therefore similar to the isoelectronic AlCl dimer. The oxygen analogue, dimetaphosphate , in contrast, is not known, the metaphosphates favour polymeric structures of chains or rings.
* and are related to but their two bridging −S− atoms are replaced by −S−S− in and by an −S−S−S− bridge in .
*PS These form water-stable salts. The anion has an ethane-like structure and contains a P−P bond. The formal oxidation state of phosphorus is +4. The oxygen analogue is the hypodiphosphate anion, hypophosphoric acid|.
* contains a six-membered PS ring. The ammonium salt is produced by reaction of PS in liquid ammonia. Another way of visualising the structure is that it is the PS adamantane (PO) structure with a PS vertex removed.
* contains a square P ring, contains a P ring and a P ring. These cyclic anions contain P with an oxidation state +3. Note they are not trigonal as arsenic(III) is in arsenites, but are tetrahedral with two bonds to other phosphorus atoms and two to sulfur. The anion is analogous to the ring anion.
* An unusual butterfly-shaped ion, SP(P)PS, which can be visualised as a P molecule where two P−S bonds replace one P−P bond.
* is a sulfido heptaphosphane cluster anion. | 0 | Theoretical and Fundamental Chemistry |
Cyclopropyl cyanide is prepared by the reaction of 4-chlorobutyronitrile with a strong base, such as sodium amide in liquid ammonia. | 0 | Theoretical and Fundamental Chemistry |
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