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An action spectrum is a graph of the rate of biological effectiveness plotted against wavelength of light. It is related to absorption spectrum in many systems. Mathematically, it describes the inverse quantity of light required to evoke a constant response. It is very rare for an action spectrum to describe the level of biological activity, since biological responses are often nonlinear with intensity.
Action spectra are typically written as unit-less responses with peak response of one, and it is also important to distinguish if an action spectrum refers to quanta at each wavelength (mol or log-photons), or to spectral power (W).
It shows which wavelength of light is most effectively used in a specific chemical reaction. Some reactants are able to use specific wavelengths of light more effectively to complete their reactions. For example, chlorophyll is much more efficient at using the red and blue regions than the green region of the light spectrum to carry out photosynthesis. Therefore, the action spectrum graph would show spikes above the wavelengths representing the colours red and blue.
The first action spectrum was made by T. W. Engelmann, who split light into its components by the prism and then illuminated Cladophora placed in a suspension of aerobic bacteria. He found that bacteria accumulated in the region of blue and red light of the split spectrum. He thus discovered the effect of the different wavelengths of light on photosynthesis and plotted the first action spectrum of photosynthesis.
Action spectra have a wide variety of uses in biological and chemical research, particularly in understanding the effect of ultraviolet (UV) light on biological molecules and systems. UV light wavelengths range between 295 nm-400 nm and are known to induce skin and DNA damage. As a result, action spectra have been used to measure the efficiency of different light wavelengths in disinfecting water, the rate and mechanism of photodegradation of folic acid in the blood, and the chirality of molecules to determine secondary structure. Further examples include suppression of melatonin by wavelength and a variety of hazard functions, related to tissue damage from visible and near-visible light. | 0 | Theoretical and Fundamental Chemistry |
The IIR holds international conferences and congresses on key themes which include:
* natural refrigerants
* the cold chain
* magnetic refrigeration
* cryogenics
* compressors
* phase-change materials and slurries
* thermophysical properties and transfer processes of refrigerants
* new technologies | 0 | Theoretical and Fundamental Chemistry |
Physicochemical distance is a measure that assesses the difference between replaced amino acids. The value of distance is based on properties of amino acids. There are 134 physicochemical properties that can be used to estimate similarity between amino acids. Each physicochemical distance is based on different composition of properties. | 1 | Applied and Interdisciplinary Chemistry |
Ions of opposite charge are naturally attracted to each other by the electrostatic force. This is described by Coulomb's law:
where is the force of attraction, and are the magnitudes of the electrical charges, is the dielectric constant of the medium and is the distance between the ions. For ions in solution this is an approximation because the ions exert a polarizing effect on the solvent molecules that surround them, which attenuates the electric field somewhat. Nevertheless, some general conclusions can be inferred.
:Ion association will increase as:
:*the magnitude(s) of the electrical charge(s) and increase,
:*the magnitude of the dielectric constant decreases,
:*the size of the ions decreases so that the distance between cation and anion decreases.
The equilibrium constant for ion-pair formation, like all equilibrium constants, is related to the standard free-energy change:
where is the gas constant and is the temperature in kelvins. Free energy is made up of an enthalpy term and an entropy term:
The coulombic energy released when ions associate contributes to the enthalpy term, . In the case of contact ion pairs, the covalent interaction energy also contributes to the enthalpy, as does the energy of displacing a solvent molecule from the solvation shell of the cation or anion. The tendency to associate is opposed by the entropy term, which results from the fact that the solution containing unassociated ions is more disordered than a solution containing associates. The entropy term is similar for electrolytes of the same type, with minor differences due to solvation effects. Therefore, it is the magnitude of the enthalpy term that mostly determines the extent of ion association for a given electrolyte type. This explains the general rules given above. | 0 | Theoretical and Fundamental Chemistry |
Additive effects can occur with drugs with either equivalent or overlapping actions, or independent actions. | 1 | Applied and Interdisciplinary Chemistry |
Corrosive compounds, especially O and CO must be removed, usually by use of a deaerator. Residual amounts can be removed chemically, by use of oxygen scavengers. Additionally, feed water is typically alkalized to a pH of 9.0 or higher, to reduce oxidation and to support the formation of a stable layer of magnetite on the water-side surface of the boiler, protecting the material underneath from further corrosion. This is usually done by dosing alkaline agents into the feed water, such as sodium hydroxide (caustic soda) or ammonia. Corrosion in boilers is due to the presence of dissolved oxygen, dissolved carbon dioxide, or dissolved salts. | 1 | Applied and Interdisciplinary Chemistry |
Lamellar phase refers generally to packing of polar-headed long chain nonpolar-tail molecules in an environment of bulk polar liquid, as sheets of bilayers separated by bulk liquid. In biophysics, polar lipids (mostly, phospholipids, and rarely, glycolipids) pack as a liquid crystalline bilayer, with hydrophobic fatty acyl long chains directed inwardly and polar headgroups of lipids aligned on the outside in contact with water, as a 2-dimensional flat sheet surface. Under transmission electron microscope (TEM), after staining with polar headgroup reactive chemical osmium tetroxide, lamellar lipid phase appears as two thin parallel dark staining lines/sheets, constituted by aligned polar headgroups of lipids. Sandwiched between these two parallel lines, there exists one thicker line/sheet of non-staining closely packed layer of long lipid fatty acyl chains. This TEM-appearance became famous as Robertson's unit membrane - the basis of all biological membranes, and structure of lipid bilayer in unilamellar liposomes. In multilamellar liposomes, many such lipid bilayer sheets are layered concentrically with water layers in between.
In lamellar lipid bilayers, polar headgroups of lipids align together at the interface of water and hydrophobic fatty-acid acyl chains align parallel to one another hiding away from water. The lipid head groups are somewhat more tightly packed than relatively fluid hydrocarbon fatty acyl long chains. The lamellar lipid bilayer organization, thus reveals a flexibility gradient of increasing freedom of motions from near the head-groups towards the terminal fatty-acyl chain methyl groups. Existence of such a dynamic organization of lamellar phase in liposomes as well as biological membranes can be confirmed by spin label electron paramagnetic resonance and high resolution nuclear magnetic resonance spectroscopy studies of biological membranes and liposomes.
In soft matter science, where physics and chemistry meet biological science, a bilayer lamellar phase has been recently created from fluorinated silica, and it has been projected for use as a shear-thinning lubricant. | 0 | Theoretical and Fundamental Chemistry |
The school of metalwork in Mosul is believed to have been founded in the early 13th century under Zengid patronage. During this time, the Zengid region was operating as a vassal under the Ayyubid Sultanate. Control over Mosul as a city central to trade between China, the Mediterranean, Anatolia, and Mesopotamia was contested between the Zengids and the Ayyubid sultan, Saladin, throughout the early acquisitions of the Ayyubid Sultanate in Syria and Iraq after the decline of Fatimid rule. However, the Zengids remained in Mosul and were allowed some degree of authority under the Sultanate.
Around 1256, the Mongol occupation of Iraq began, and the region became a part of the Ilkhanate. Of the artifacts agreed to be "nabish al-Mawsili" (of Mosul), approximately 80% were produced after the commencement of Mongol rule in Mosul. However, it is unclear as to whether or not all of these artifacts were produced within Mosul and later exported as esteemed gifts, or created elsewhere by Mosulian artisans who relocated but maintained the "al-Mawsili" signature. | 1 | Applied and Interdisciplinary Chemistry |
Many vertebrate axons are surrounded by a myelin sheath, allowing rapid and efficient saltatory ("jumping") propagation of action potentials. The contacts between neurons and glial cells display a very high level of spatial and temporal organization in myelinated fibers. The myelinating glial cells - oligodendrocytes in the central nervous system (CNS), and Schwann cells in the peripheral nervous system (PNS) - are wrapped around the axon, leaving the axolemma relatively uncovered at the regularly spaced nodes of Ranvier.
The internodal glial membranes are fused to form compact myelin, whereas the cytoplasm-filled paranodal loops of myelinating cells are spirally wrapped around the axon at both sides of the nodes. This organization demands a tight developmental control and the formation of a variety of specialized zones of contact between different areas of the myelinating cell membrane. Each node of Ranvier is flanked by paranodal regions where helicoidally wrapped glial loops are attached to the axonal membrane by a septate-like junction.
The segment between nodes of Ranvier is termed as the internode, and its outermost part that is in contact with paranodes is referred to as the juxtaparanodal region. The nodes are encapsulated by microvilli stemming from the outer aspect of the Schwann cell membrane in the PNS, or by perinodal extensions from astrocytes in the CNS. | 1 | Applied and Interdisciplinary Chemistry |
The cyclol hypothesis is the now discredited first structural model of a folded, globular protein, formulated in the 1930s. It was based on the cyclol reaction of peptide bonds proposed by physicist Frederick Frank in 1936, in which two peptide groups are chemically crosslinked. These crosslinks are covalent analogs of the non-covalent hydrogen bonds between peptide groups and have been observed in rare cases, such as the ergopeptides.
Based on this reaction, mathematician Dorothy Wrinch hypothesized in a series of five papers in the late 1930s a structural model of globular proteins. She postulated that, under some conditions, amino acids will spontaneously make the maximum possible number of cyclol crosslinks, resulting in cyclol molecules and cyclol fabrics. She further proposed that globular proteins have a tertiary structure corresponding to Platonic solids and semiregular polyhedra formed of cyclol fabrics with no free edges. In contrast to the cyclol reaction itself, these hypothetical molecules, fabrics and polyhedra have not been observed experimentally. The model has several consequences that render it energetically implausible, such as steric clashes between the protein sidechains. In response to such criticisms J. D. Bernal proposed that hydrophobic interactions are chiefly responsible for protein folding, which was indeed borne out. | 1 | Applied and Interdisciplinary Chemistry |
A significant indentation on the middle section of the pillar, approximately from the current courtyard ground level, has been shown to be the result of a cannonball fired at close range. The impact caused horizontal fissuring of the column in the area diametrically opposite to the indentation site, but the column itself remained intact. While no contemporaneous records, inscriptions, or documents describing the event are known to exist, historians generally agree that Nadir Shah is likely to have ordered the pillar's destruction during his invasion of Delhi in 1739, as he would have considered a Hindu temple monument undesirable within an Islamic mosque complex. Alternatively, he may have sought to dislodge the decorative top portion of the pillar in search of hidden precious stones or other items of value.
No additional damage attributable to cannon fire has been found on the pillar, suggesting that no further shots were taken. Historians have speculated that ricocheting fragments of the cannonball may have damaged the nearby Quwwat-ul-Islam mosque, which suffered damage to its southwestern portion during the same period, and the assault on the pillar might have been abandoned as a result. | 1 | Applied and Interdisciplinary Chemistry |
This standard method is recognized by EPA, which is labeled Method 5210B in the Standard Methods for the Examination of Water and Wastewater. In order to obtain BOD, dissolved oxygen (DO) concentrations in a sample must be measured before and after the incubation period, and appropriately adjusted by the sample corresponding dilution factor. This analysis is performed using 300 mL incubation bottles in which buffered dilution water is dosed with seed microorganisms and stored for 5 days in the dark room at 20 °C to prevent DO production via photosynthesis. The bottles have traditionally been made of glass, which required cleaning and rinsing between samples. A SM 5210B approved, disposable, plastic BOD bottle is available which eliminates this step. In addition to the various dilutions of BOD samples, this procedure requires dilution water blanks, glucose glutamic acid (GGA) controls, and seed controls. The dilution water blank is used to confirm the quality of the dilution water that is used to dilute the other samples. This is necessary because impurities in the dilution water may cause significant alterations in the results. The GGA control is a standardized solution to determine the quality of the seed, where its recommended BOD concentration is 198 mg/L ± 30.5 mg/L. For measurement of carbonaceous BOD (cBOD), a nitrification inhibitor is added after the dilution water has been added to the sample. The inhibitor hinders the oxidation of ammonia nitrogen, which supplies the nitrogenous BOD (nBOD). When performing the BOD test, it is conventional practice to measure only cBOD because nitrogenous demand does not reflect the oxygen demand from organic matter. This is because nBOD is generated by the breakdown of proteins, whereas cBOD is produced by the breakdown of organic molecules.
BOD is calculated by:
*Unseeded :
*Seeded:
where:
: is the dissolved oxygen (DO) of the diluted solution after preparation (mg/L)
: is the DO of the diluted solution after 5 day incubation (mg/L)
: is the decimal dilution factor
: is the DO of diluted seed sample after preparation (mg/L)
: is the DO of diluted seed sample after 5 day incubation (mg/L)
: is the ratio of seed volume in dilution solution to seed volume in BOD test on seed | 0 | Theoretical and Fundamental Chemistry |
Pumps vary in pressure capacity, but their performance is measured on their ability to yield a consistent and reproducible volumetric flow rate. Pressure may reach as high as 60 MPa (6000 lbf/in), or about 600 atmospheres. Modern HPLC systems have been improved to work at much higher pressures, and therefore are able to use much smaller particle sizes in the columns (), or about 1200 atmospheres. The term "UPLC" is a trademark of the Waters Corporation, but is sometimes used to refer to the more general technique of UHPLC. | 0 | Theoretical and Fundamental Chemistry |
An oxygen diffusion-enhancing compound is any substance that increases the availability of oxygen in body tissues by influencing the molecular structure of water in blood plasma and thereby promoting the movement (diffusion) of oxygen through plasma. Oxygen diffusion-enhancing compounds have shown promise in the treatment of conditions associated with hypoxia (a lack of oxygen in tissues) and ischemia (a lack of oxygen in the circulating blood supply). Such conditions include hemorrhagic shock, myocardial infarction (heart attack), and stroke. | 1 | Applied and Interdisciplinary Chemistry |
In physics and chemistry, specifically in nuclear magnetic resonance (NMR), magnetic resonance imaging (MRI), and electron spin resonance (ESR), the Bloch equations are a set of macroscopic equations that are used to calculate the nuclear magnetization M = (M, M, M) as a function of time when relaxation times T and T are present. These are phenomenological equations that were introduced by Felix Bloch in 1946. Sometimes they are called the equations of motion of nuclear magnetization. They are analogous to the Maxwell–Bloch equations. | 0 | Theoretical and Fundamental Chemistry |
Chemolithotrophy is a type of metabolism where energy is obtained from the oxidation of inorganic compounds. Most chemolithotrophic organisms are also autotrophic. There are two major objectives to chemolithotrophy: the generation of energy (ATP) and the generation of reducing power (NADH). | 1 | Applied and Interdisciplinary Chemistry |
Synthetic polymers invariably consist of a mixture of macromolecular species with different degrees of polymerization and therefore of different molecular weights. There are different types of average polymer molecular weight, which can be measured in different experiments. The two most important are the number average (X) and the weight average (X).
The number-average degree of polymerization is a weighted mean of the degrees of polymerization of polymer species, weighted by the mole fractions (or the number of molecules) of the species. It is typically determined by measurements of the osmotic pressure of the polymer.
The weight-average degree of polymerization is a weighted mean of the degrees of polymerization, weighted by the weight fractions (or the overall weight of the molecules) of the species. It is typically determined by measurements of Rayleigh light scattering by the polymer. | 0 | Theoretical and Fundamental Chemistry |
Highly charged ions interact strongly with water, breaking hydrogen bonds and inducing electrostatic structuring of nearby water, and are thus called "structure-makers" or "kosmotropes". Conversely, weak ions can disrupt the structure of water, and are thus called "structure-breakers" or
"chaotropes". The order of the tendency of ions to make or break water structure is the basis of the Hofmeister series.
Hofmeister discovered a series of salts that have consistent effects on the solubility of proteins and (it was discovered later) on the stability of their secondary and tertiary structure. Anions appear to have a larger effect than cations, and are usually ordered
(kosmotropic) : (chaotropic)
(This is a partial listing; many more salts have been studied.)
The order of cations is usually given as
(chaotropic) : (kosmotropic)
When oppositely charged kosmotropic cations and anions are in solution together, they are attracted to each other, rather than to water, and the same can be said for chaotropic cations and anions. Thus, the preferential associations of oppositely charged ions can be ordered as:
kosmotrope-kosmotrope > kosmotrope-water > water-water > chaotrope-water > chaotrope-chaotrope
Combining kosmotropic anions with kosmotropic cations reduces the kosmotropic effect of these ions because they are pairing to each other too strongly to be structuring water. Kosmotropic anions do not readily pair with chaotropic cations. The combination of kosmotropic anions with chaotropic cations is the best ion combination to stabilize proteins. | 0 | Theoretical and Fundamental Chemistry |
Another form of the Colebrook-White equation exists for free surfaces. Such a condition may exist in a pipe that is flowing partially full of fluid. For free surface flow:
The above equation is valid only for turbulent flow. Another approach for estimating f in free surface flows, which is valid under all the flow regimes (laminar, transition and turbulent) is the following:
where a is:
and b is:
where Re is Reynolds number where h is the characteristic hydraulic length (hydraulic radius for 1D flows or water depth for 2D flows) and R is the hydraulic radius (for 1D flows) or the water depth (for 2D flows). The Lambert W function can be calculated as follows: | 1 | Applied and Interdisciplinary Chemistry |
In the US, more copper is recovered and put back into service from recycled material than is derived from newly mined ore. Copper's recycle value is so great that premium-grade scrap normally has at least 95% of the value of primary metal from newly mined ore. In Europe, about 50% of copper demand comes from recycling (as of 2016).
, recycled copper provided 35% of total worldwide copper usage. | 1 | Applied and Interdisciplinary Chemistry |
Autoinducer-2 (AI-2), a furanosyl borate diester or tetrahydroxy furan (species dependent), is a member of a family of signaling molecules used in quorum sensing. AI-2 is one of only a few known biomolecules incorporating boron. First identified in the marine bacterium Vibrio harveyi, AI-2 is produced and recognized by many Gram-negative and Gram-positive bacteria. AI-2 arises by the reaction of 4,5-dihydroxy-2,3-pentanedione, which is produced enzymatically, with boric acid and is recognized by the two-component sensor kinase LuxPQ in Vibrionaceae.
AI-2 is actively transported by the Lsr ABC-type transporter into the cell in Enterobacteriaceae and few other bacterial taxa such as Pasteurella, Photorhabdus, Haemophilus, and Bacillus, where it is phosphorylated by LsrK. Then, Phospho-AI-2 binds the transcriptional repressor protein, LsrR, which subsequently is released from the promoter/operator region of the lsr operon – and transcription of the lsr genes is initiated. AI-2 signalling is also regulated by glucose and cAMP/CRP via the lsr operon. In the presence of glucose, low levels of cAMP/CRP result in almost no lsr operon (lsrABCDFG) expression. Without glucose, cAMP-CRP is needed to stimulate the lsr expression, while LsrR represses its expression in the absence of the inducer, phospho-AI-2. As AI-2 accumulates, more AI-2 is taken in via LsrABCD, phosphorylated via LsrK, and the lsr transcription is de-repressed, enabling even more AI-2 uptake.
Doubts have been expressed regarding AI-2s status as a universal signal. Although the luxS gene, which encodes the protein responsible for AI-2 production is widespread, the latter has mainly a primary metabolic role in the recycling of S'-adenosyl--methionine, with AI-2 being a by-product of that process. An unequivocally AI-2 related behavior was found to be restricted primarily to organisms bearing known AI-2 receptor genes. Thus, while it is certainly true that some bacteria respond to AI-2, it is doubtful that it is always being produced for purposes of signaling. | 1 | Applied and Interdisciplinary Chemistry |
An ion-neutral complex in chemistry is an aggregate of an ion with one or more neutral molecules in which at least one of the partners has a rotational degree of freedom about an axis perpendicular to the intermolecular direction In chemistry, the dissociation of a molecule into two or more fragments can take place in the gas phase, provided there is sufficient internal energy for the requisite barriers to be overcome.
For many years, it was assumed that the fragments of a gas phase dissociation simply fly apart. In 1958, Allan Maccoll suggested that the decomposition of alkyl halides (RX) might take place via the intermediacy of ion pairs, [R X], in which the charged fragments were no longer covalently bonded but were held together by electrostatic attraction. Maccoll and coworkers subsequently examined chlorine isotope effects in the thermal decomposition of chloroethane and concluded that the data did not support that interpretation; however, he had provided the germ of an idea that came to fruition two decades later in the study of decompositions of electrically charged molecules.
In the late 1970s three research groups—in England, the United States, and France—independently provided evidence for the occurrence of ion-neutral complexes (sometimes called ion-dipole complexes or ion-molecule complexes) in the unimolecular dissociations of positive ions under the conditions associated with mass spectrometry (i.e. as isolated species in a vacuum). The general idea is that a charged species, RY, can give rise to dissociation fragments via a transient complex, [R Y], in which the electrically charged partner, R, can undergo molecular rearrangements at the same time as it rotates relative to the neutral partner, Y. Similarly, the neutral partner, Y, can also rotate relative to the charged partner, as well as having the ability to exchange Hydrogens and internal energy with it.
More recently several research groups have provided evidence that revives Maccoll's original hypothesis, but with the variation that the fragments that sojourn in the presence of one another are both electrically uncharged. In other words, dissociations of a neutral molecule RX can take place in the gas phase via the intermediacy of radical pairs [R· X·], where X· can be as small as a hydrogen atom. In the gas phase such intermediates are often called roaming radicals. | 0 | Theoretical and Fundamental Chemistry |
Surface runoff can cause erosion of the Earth's surface; eroded material may be deposited a considerable distance away. There are four main types of soil erosion by water: splash erosion, sheet erosion, rill erosion and gully erosion. Splash erosion is the result of mechanical collision of raindrops with the soil surface: soil particles which are dislodged by the impact then move with the surface runoff. Sheet erosion is the overland transport of sediment by runoff without a well defined channel. Soil surface roughness causes may cause runoff to become concentrated into narrower flow paths: as these incise, the small but well-defined channels which are formed are known as rills. These channels can be as small as one centimeter wide or as large as several meters. If runoff continue to incise and enlarge rills, they may eventually grow to become gullies. Gully erosion can transport large amounts of eroded material in a small time period.
Reduced crop productivity usually results from erosion, and these effects are studied in the field of soil conservation. The soil particles carried in runoff vary in size from about 0.001 millimeter to 1.0 millimeter in diameter. Larger particles settle over short transport distances, whereas small particles can be carried over long distances suspended in the water column. Erosion of silty soils that contain smaller particles generates turbidity and diminishes light transmission, which disrupts aquatic ecosystems.
Entire sections of countries have been rendered unproductive by erosion. On the high central plateau of Madagascar, approximately ten percent of that country's land area, virtually the entire landscape is devoid of vegetation, with erosive gully furrows typically in excess of 50 meters deep and one kilometer wide. Shifting cultivation is a farming system which sometimes incorporates the slash and burn method in some regions of the world. Erosion causes loss of the fertile top soil and reduces its fertility and quality of the agricultural produce.
Modern industrial farming is another major cause of erosion. Over a third of the U.S. Corn Belt has completely lost its topsoil. Switching to no-till practices would reduce soil erosion from U.S. agricultural fields by more than 70 percent. | 1 | Applied and Interdisciplinary Chemistry |
Podsolisation is an extreme form of leaching which causes the eluviation of iron and aluminium sesquioxides.
The process generally occurs in areas where precipitation is greater than evapotranspiration. The minerals are removed by a process known as leaching.
When organic material is broken down nutrients are released, but at the same time organic acids are released. These organic acids are known as chelating agents. Many podsol soils form underneath coniferous forests, the fact that pine trees are evergreen causes a very thin litter layer inhibiting the production of humus. As a result, an acidic (pH 4.5) mor humus is produced which provides a greater amount of chelating agents. | 0 | Theoretical and Fundamental Chemistry |
Further research with double layers on ruthenium dioxide films in 1971 by Sergio Trasatti and Giovanni Buzzanca demonstrated that the electrochemical behavior of these electrodes at low voltages with specific adsorbed ions was like that of capacitors. The specific adsorption of the ions in this region of potential could also involve a partial charge transfer between the ion and the electrode. It was the first step towards understanding pseudocapacitance. | 0 | Theoretical and Fundamental Chemistry |
Bencao Gangmu calls the concoction miren (蜜人), translated as "honey person" or "mellified man". Miziren (蜜漬人 "honey-saturated person") is a modern synonym. The place it comes from is Tianfangguo, an old name for Arabia or the Middle East. The Chinese munaiyi (木乃伊), along with "mummy" loanwords in many other languages, derives from Arabic mūmīya (mummy) or from Persian mūmiyâyī (, "mummy"), itself from mūm "wax".
Mellification is a mostly obsolete term for the production of honey, or the process of honeying something, from the Latin mellificāre (“to make honey”), or mel (“honey”). The Ancient Greek word mélissa (μέλισσα) means "bee; honeybee; (poetic) honey". | 1 | Applied and Interdisciplinary Chemistry |
In analytical chemistry, a calibration curve, also known as a standard curve, is a general method for determining the concentration of a substance in an unknown sample by comparing the unknown to a set of standard samples of known concentration. A calibration curve is one approach to the problem of instrument calibration; other standard approaches may mix the standard into the unknown, giving an internal standard. The calibration curve is a plot of how the instrumental response, the so-called analytical signal, changes with the concentration of the analyte (the substance to be measured). | 1 | Applied and Interdisciplinary Chemistry |
In some considerations, hydrology is thought of as starting at the land-atmosphere boundary and so it is important to have adequate knowledge of both precipitation and evaporation. Precipitation can be measured in various ways: disdrometer for precipitation characteristics at a fine time scale; radar for cloud properties, rain rate estimation, hail and snow detection; rain gauge for routine accurate measurements of rain and snowfall; satellite for rainy area identification, rain rate estimation, land-cover/land-use, and soil moisture, for example.
Evaporation is an important part of the water cycle. It is partly affected by humidity, which can be measured by a sling psychrometer. It is also affected by the presence of snow, hail, and ice and can relate to dew, mist and fog. Hydrology considers evaporation of various forms: from water surfaces; as transpiration
from plant surfaces in natural and agronomic ecosystems. Direct measurement of evaporation can be obtained using Simon's evaporation pan.
Detailed studies of evaporation involve boundary layer considerations as well as momentum, heat flux, and energy budgets. | 1 | Applied and Interdisciplinary Chemistry |
The set of all possible positions r and momenta p is called the phase space of the system; in other words a set of three coordinates for each position coordinate x, y, z, and three more for each momentum component , , . The entire space is 6-dimensional: a point in this space is , and each coordinate is parameterized by time t. The small volume ("differential volume element") is written
Since the probability of molecules, which all have and within , is in question, at the heart of the equation is a quantity which gives this probability per unit phase-space volume, or probability per unit length cubed per unit momentum cubed, at an instant of time . This is a probability density function: , defined so that,
is the number of molecules which all have positions lying within a volume element about and momenta lying within a momentum space element about , at time . Integrating over a region of position space and momentum space gives the total number of particles which have positions and momenta in that region:
which is a 6-fold integral. While is associated with a number of particles, the phase space is for one-particle (not all of them, which is usually the case with deterministic many-body systems), since only one and is in question. It is not part of the analysis to use , for particle 1, , for particle 2, etc. up to , for particle N.
It is assumed the particles in the system are identical (so each has an identical mass ). For a mixture of more than one chemical species, one distribution is needed for each, see below. | 1 | Applied and Interdisciplinary Chemistry |
In 2008, Acambis announced work on a universal flu vaccine (ACAM-FLU-ATM) based on the less variable M2 protein component of the flu virus shell. See also H5N1 vaccines.
In 2009, the Wistar Institute in Pennsylvania received a patent for using "a variety of peptides" in a flu vaccine, and announced it was seeking a corporate partner.
In 2010, the National Institute of Allergy and Infectious Diseases (NIAID) of the U.S. NIH announced a breakthrough; the effort targets the stem, which mutates less often than the head of the viral HA.
By 2010 some universal flu vaccines had started clinical trials.
* BiondVax identified 9 conserved epitopes of the influenza virus and combined them into a recombinant protein called Multimeric-001. All seven of Biondvax's completed phase 2 human trials demonstrated safety and significant levels of immunogenicity. More recently, Biondvax undertook a two-year, phase 3 study of Multimeric-001, its candidate universal influenza vaccine. In October 2020, results of the phase 3 study were published, indicating no apparent efficacy.
* ITS's fp01 includes 6 peptide antigens to highly conserved segments of the PA, PB1, PB2, NP & M1 proteins, and has started phase I trials.
DNA vaccines, such as VGX-3400X (aimed at multiple H5N1 strains), contain DNA fragments (plasmids). Inovio's SynCon DNA vaccines include H5N1 and H1N1 subtypes.
Other companies pursuing the vaccine as of 2009 and 2010 include Theraclone, VaxInnate, Crucell NV, Inovio Pharmaceuticals, Immune Targeting Systems (ITS) and iQur.
In 2019, Distributed Bio completed pre-clinical trials of a vaccine that consists of computationally selected distant evolutionary variants of hemagglutinin epitopes and is expected to begin human trials in 2021.
In recent years, research has concerned use of an antigen for the flu hemagglutinin (HA) stem.
Based on the results of animal studies, a universal flu vaccine may use a two-step vaccination strategy: priming with a DNA-based HA vaccine, followed by a second dose with an inactivated, attenuated, or adenovirus-vector-based vaccine.
Some people given a 2009 H1N1 flu vaccine have developed broadly protective antibodies, raising hopes for a universal flu vaccine.
A vaccine based on the hemagglutinin (HA) stem was the first to induce "broadly neutralizing" antibodies to both HA-group 1 and HA-group 2 influenza in mice.
In July 2011, researchers created an antibody, which targets a protein found on the surface of all influenza A viruses called haemagglutinin.
FI6 is the only known antibody that binds (its neutralizing activity is controversial) to all 16 subtypes of the influenza A virus hemagglutinin and might be the lynchpin for a universal influenza vaccine. The subdomain of the hemagglutinin that is targeted by FI6, namely the stalk domain, was actually successfully used earlier as universal influenza virus vaccine by Peter Palese's research group at Mount Sinai School of Medicine.
Other vaccines are polypeptide based. | 1 | Applied and Interdisciplinary Chemistry |
The adhesion of gas or liquid molecules to the surface is known as adsorption. This can be due to either chemisorption or physisorption, and the strength of molecular adsorption to a catalyst surface is critically important to the catalyst's performance (see Sabatier principle). However, it is difficult to study these phenomena in real catalyst particles, which have complex structures. Instead, well-defined single crystal surfaces of catalytically active materials such as platinum are often used as model catalysts. Multi-component materials systems are used to study interactions between catalytically active metal particles and supporting oxides; these are produced by growing ultra-thin films or particles on a single crystal surface.
Relationships between the composition, structure, and chemical behavior of these surfaces are studied using ultra-high vacuum techniques, including adsorption and temperature-programmed desorption of molecules, scanning tunneling microscopy, low energy electron diffraction, and Auger electron spectroscopy. Results can be fed into chemical models or used toward the rational design of new catalysts. Reaction mechanisms can also be clarified due to the atomic-scale precision of surface science measurements. | 0 | Theoretical and Fundamental Chemistry |
The curing process can be monitored by measuring changes in various parameters:
*the concentration of specific reactive resin species using spectroscopic methods such as FTIR & Raman;
*the refractive index or fluorescence of the resin (optical property);
*the internal resin strain (mechanical property) with the use of Fiber Bragg grating (FBG) sensors. | 0 | Theoretical and Fundamental Chemistry |
In operating batteries and fuel cells, charge transfer coefficient is the parameter that signifies the fraction of overpotential that affects the current density. This parameter has had a mysterious significance in electrochemical kinetics for over three quarters of the previous century. It can also be said that charge transfer coefficient is the heart of electrode kinetics. | 0 | Theoretical and Fundamental Chemistry |
Photofragment ion imaging or, more generally, Product Imaging is an experimental technique for making measurements of the velocity of product molecules or particles following a chemical reaction or the photodissociation of a parent molecule. The method uses a two-dimensional detector, usually a microchannel plate, to record the arrival positions of state-selected ions created by resonantly enhanced multi-photon ionization (REMPI). The first experiment using photofragment ion imaging was performed by David W Chandler and Paul L Houston in 1987 on the phototodissociation dynamics of methyl iodide (iodomethane, CHI). | 0 | Theoretical and Fundamental Chemistry |
In neuroscience, repolarization refers to the change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential which has changed the membrane potential to a positive value. The repolarization phase usually returns the membrane potential back to the resting membrane potential. The efflux of potassium (K) ions results in the falling phase of an action potential. The ions pass through the selectivity filter of the K channel pore.
Repolarization typically results from the movement of positively charged K ions out of the cell. The repolarization phase of an action potential initially results in hyperpolarization, attainment of a membrane potential, termed the afterhyperpolarization, that is more negative than the resting potential. Repolarization usually takes several milliseconds.
Repolarization is a stage of an action potential in which the cell experiences a decrease of voltage due to the efflux of potassium (K) ions along its electrochemical gradient. This phase occurs after the cell reaches its highest voltage from depolarization. After repolarization, the cell hyperpolarizes as it reaches resting membrane potential (−70 mV in neuron). Sodium (Na) and potassium ions inside and outside the cell are moved by a sodium potassium pump, ensuring that electrochemical equilibrium remains unreached to allow the cell to maintain a state of resting membrane potential. In the graph of an action potential, the hyper-polarization section looks like a downward dip that goes lower than the line of resting membrane potential. In this afterhyperpolarization (the downward dip), the cell sits at more negative potential than rest (about −80 mV) due to the slow inactivation of voltage gated K delayed rectifier channels, which are the primary K channels associated with repolarization. At these low voltages, all of the voltage gated K channels close, and the cell returns to resting potential within a few milliseconds. A cell which is experiencing repolarization is said to be in its absolute refractory period. Other voltage gated K channels which contribute to repolarization include A-type channels and Ca-activated K channels. Protein transport molecules are responsible for Na out of the cell and K into the cell to restore the original resting ion concentrations. | 0 | Theoretical and Fundamental Chemistry |
During springtime in the polar regions of Earth, unique photochemistry converts inert halide salt ions (e.g. Br) into reactive halogen species (e.g. Br atoms and BrO) that episodically deplete ozone in the atmospheric boundary layer to near zero levels. These processes are favored by light and low temperature conditions. Since their discovery in the late 1980s, research on these ozone depletion events has shown the central role of
bromine photochemistry. The exact sourcs and mechanisms that release bromine are still not fully understood, but the combination of concentrated sea salt in a condensed phase substrate appears to be a pre-requisite. Shallow boundary layers are also likely to be beneficial since they enhance the speed of autocatalytic bromine release by confining the released bromine to a smaller space. Under these conditions, and with sufficient acidity, gaseous hypobromous acid (HOBr) can react with condensed sea salt bromide and produce bromine that is then released to the atmosphere. Subsequent photolysis of this bromine generates bromine radicals that can react with and destroy ozone. Due to the autocatalytic nature of the reaction mechanism, it has been called bromine explosion. | 1 | Applied and Interdisciplinary Chemistry |
Oxidative deamination is the first step to breaking down the amino acids so that they can be converted to sugars. The process begins by removing the amino group of the amino acids. The amino group becomes ammonium as it is lost and later undergoes the urea cycle to become urea, in the liver. It is then released into the blood stream, where it is transferred to the kidneys, which will secrete the urea as urine. The remaining portion of the amino acid becomes oxidized, resulting in an α-keto acid. The alpha-keto acid will then proceed into the TCA cycle, in order to produce energy. The acid can also enter glycolysis, where it will be eventually converted into pyruvate. The pyruvate is then converted into acetyl-CoA so that it can enter the TCA cycle and convert the original pyruvate molecules into ATP, or usable energy for the organism.
Transamination leads to the same result as deamination: the remaining acid will undergo either glycolysis or the TCA cycle to produce energy that the organism's body will use for various purposes. This process transfers the amino group instead of losing the amino group to be converted into ammonium. The amino group is transferred to α-ketoglutarate, so that it can be converted to glutamate. Then glutamate transfers the amino group to oxaloacetate. This transfer is so that the oxaloacetate can be converted to aspartate or other amino acids. Eventually, this product will also proceed into oxidative deamination to once again produce alpha-ketoglutarate, an alpha-keto acid that will undergo the TCA cycle, and ammonium, which will eventually undergo the urea cycle.
Transaminases are enzymes that help catalyze the reactions that take place in transamination. They help catalyze the reaction at the point when the amino group is transferred from the original amino acid, like glutamate to α-ketoglutarate, and hold onto it to transfer it to another α-ketoacid. | 1 | Applied and Interdisciplinary Chemistry |
Short interspersed nuclear elements (SINEs) are non-autonomous, non-coding transposable elements (TEs) that are about 100 to 700 base pairs in length. They are a class of retrotransposons, DNA elements that amplify themselves throughout eukaryotic genomes, often through RNA intermediates. SINEs compose about 13% of the mammalian genome.
The internal regions of SINEs originate from tRNA and remain highly conserved, suggesting positive pressure to preserve structure and function of SINEs. While SINEs are present in many species of vertebrates and invertebrates, SINEs are often lineage specific, making them useful markers of divergent evolution between species. Copy number variation and mutations in the SINE sequence make it possible to construct phylogenies based on differences in SINEs between species. SINEs are also implicated in certain types of genetic disease in humans and other eukaryotes.
In essence, short interspersed nuclear elements are genetic parasites which have evolved very early in the history of eukaryotes to utilize protein machinery within the organism as well as to co-opt the machinery from similarly parasitic genomic elements. The simplicity of these elements make them remarkably successful at persisting and amplifying (through retrotransposition) within the genomes of eukaryotes. These "parasites" which have become ubiquitous in genomes can be very deleterious to organisms as discussed below. However, eukaryotes have been able to integrate short-interspersed nuclear elements into different signaling, metabolic and regulatory pathways and SINEs have become a great source of genetic variability. They seem to play a particularly important role in the regulation of gene expression and the creation of RNA genes. This regulation extends to chromatin re-organization and the regulation of genomic architecture. The different lineages, mutations, and activities among eukaryotes make short-interspersed nuclear elements a useful tool in phylogenetic analysis. | 1 | Applied and Interdisciplinary Chemistry |
A large group of bacterial exotoxins are referred to as "A/B toxins", in essence because they are formed from two subunits. The "A" subunit possesses enzyme activity, and is transferred to the host cell following a conformational change in the membrane-bound transport "B" subunit. Pertussis toxin is an exotoxin with six subunits (named S1 through S5—each complex contains two copies of S4). The subunits are arranged in A-B structure: the A component is enzymatically active and is formed from the S1 subunit, while the B component is the receptor-binding portion and is made up of subunits S2–S5. The subunits are encoded by ptx genes encoded on a large PT operon that also includes additional genes that encode Ptl proteins. Together, these proteins form the PT secretion complex. | 1 | Applied and Interdisciplinary Chemistry |
Coriolis meter shown in fig.(8) is very accurate in single-phase conditions but inaccurate to measure two-phase flows. It poses a complex fluid structure interaction problem in case of two-phase operation. There is a scarcity of theoretical models available to predict the errors reported by Coriolis meter in aforementioned conditions. Flow conditioners make no effect on meter accuracy while using wet gas due to the annular flow regime, which is not highly affected by flow conditioners. In single-phase conditions, Coriolis meter gives accurate measurement even in presence of severe flow disturbances. There is no need for flow conditioning before the meter to obtain accurate readings from it, which would be the case in other metering technologies like orifice and turbine. On the other hand, in two-phase flows, the meter consistently gives negative errors. The use of flow conditioners clearly affects the reading of the meter in aerated liquids. This phenomenon can be used to get fairly accurate estimate of flow rate in low gas volume fraction liquid flows. | 1 | Applied and Interdisciplinary Chemistry |
HDAC8 has been found to be most similar to HDAC3. Its major feature is its catalytic domain which contains an NLS region in the center. Two transcripts of this HDAC have been found which include a 2.0kb transcript and a 2.4kb transcript. Unlike the other HDAC molecules, when purified, this HDAC showed to be enzymatically active. At this point, due to its recent discovery, it is not yet known if it is regulated by co-repressor protein complexes. Northern blots have revealed that different tissue types show varying degrees of HDAC8 expression but has been observed in smooth muscles and is thought to contribute to contractility. | 0 | Theoretical and Fundamental Chemistry |
Manganese is an essential biological element in all organisms. It is used in many enzymes and proteins. It is essential in plants. | 1 | Applied and Interdisciplinary Chemistry |
Upon heating to 420 °C, it rearranges to form the meta isomer. The para isomer is produced by heating to temperatures above 600 °C. | 0 | Theoretical and Fundamental Chemistry |
Also known as a "bonderizer" bonding agents (spelled dentin bonding agents in American English) are resin materials used to make a dental composite filling material adhere to both dentin and enamel.
Bonding agents are often methacrylates with some volatile carrier and solvent like acetone. They may also contain diluent monomers. For proper bonding of resin composite restorations, dentin should be conditioned with polyacrylic acids to remove the smear layer, created during mechanical treatment with dental bore, and expose some of the collagen network or organic matrix of dentin. Adhesive resin should create the so-called hybrid layer (consisting of a collagen network exposed by etching and embedded in adhesive resin). This layer is an interface between dentin and adhesive resin and the final quality of dental restoration depends greatly on its properties.
Modern dental bonding systems come as a “three-step system”, where the etchant, primer, and adhesive are applied sequentially; as a “two-step system”, where the etchant and the primer are combined for simultaneous application; and as a “one-step system”, where all the components should be premixed and applied in a single application (so-called sixth generation of bonding agents). | 0 | Theoretical and Fundamental Chemistry |
Early Naiyyayikas wrote very little about Ishvara (literally, the Supreme Soul). Evidence available so far suggests that early Nyāya scholars were non-theistic or atheists. Later, and over time, Nyāya scholars tried to apply some of their epistemological insights and methodology to the question: does God exist? Some offered arguments against and some in favor. | 1 | Applied and Interdisciplinary Chemistry |
The rpoB gene encodes the β subunit of bacterial RNA polymerase and the homologous plastid-encoded RNA polymerase (PEP). It codes for 1342 amino acids in E. coli, making it the second-largest polypeptide in the bacterial cell. It is targeted by the rifamycin family of antibacterials, such as rifampin. Mutations in rpoB that confer resistance to rifamycins do so by altering the protein's drug-binding residues, thereby reducing affinity for these antibiotics.
Some bacteria contain multiple copies of the 16S rRNA gene, which is commonly used as the molecular marker to study phylogeny. In these cases, the single-copy rpoB gene can be used to study microbial diversity.
An inhibitor of transcription in bacteria, tagetitoxin, also inhibits PEP, showing that the complex found in plants is very similar to the homologous enzyme in bacteria. | 1 | Applied and Interdisciplinary Chemistry |
Thus it was noted that along the reaction coordinate of pericyclic processes one could have either a Möbius or a Hückel array of basis orbitals. With 4n or 4n + 2 electrons, one is then led to a prediction of allowedness or forbiddenness. Additionally, the M–H mnemonics give the MOs at part reaction. At each degeneracy there is a crossing of MOs. Thus one can determine if the highest occupied MO becomes antibonding with a forbidden reaction resulting. Finally, the M–H parity of sign inversions was utilized in the 1970 W–H treatment of allowedness and forbiddenness. The parity of sign inversions between bonds and atoms was used in place of the M–H use of atoms; the two approaches are equivalent. | 0 | Theoretical and Fundamental Chemistry |
The Nyāya theory of error is similar to that of Kumarilas Viparita-khyati (see Mimamsa). The Naiyyayikas also believe like Kumarila that error is due to a wrong synthesis of the presented and the represented objects. The represented object is confused with the presented one. The word anyatha<nowiki/> means elsewise and elsewhere and both these meanings are brought out in error. The presented object is perceived elsewise and the represented object exists elsewhere. They further maintain that knowledge is not intrinsically valid but becomes so on account of extraneous conditions (paratah pramana' during both validity and invalidity). | 1 | Applied and Interdisciplinary Chemistry |
There have been very few commercial uses for blue billy, either as a by-product of production or as a means of disposal when unintended deposits are discovered.
It has been offered for sale as an ingredient in sulfuric acid production, although with little commercial acceptance.
In the past, blue billy has been sold as a weedkiller. | 1 | Applied and Interdisciplinary Chemistry |
Hybridization is a basic property of nucleotide sequences and is taken advantage of in numerous molecular biology techniques. Overall, genetic relatedness of two species can be determined by hybridizing segments of their DNA (DNA-DNA hybridization). Due to sequence similarity between closely related organisms, higher temperatures are required to melt such DNA hybrids when compared to more distantly related organisms. A variety of different methods use hybridization to pinpoint the origin of a DNA sample, including the polymerase chain reaction (PCR). In another technique, short DNA sequences are hybridized to cellular mRNAs to identify expressed genes. Pharmaceutical drug companies are exploring the use of antisense RNA to bind to undesired mRNA, preventing the ribosome from translating the mRNA into protein. | 1 | Applied and Interdisciplinary Chemistry |
Muscleblind Like Splicing Regulator 1 (MBNL1) is an RNA splicing protein that in humans is encoded by the MBNL1 gene. It has a well characterized role in Myotonic dystrophy where impaired splicing disrupts muscle development and function. In addition to regulating mRNA maturation of hundreds of genes MBNL1 (along with its paralogs MBNL2 & MBNL3) autoregulate alternative splicing of the MBNL1 pre-mRNA transcript. The founding member of the human MBNL family of proteins was the Drosophila Muscleblind protein (PMID 9334280).
Human MBNL1 is an alternative splicing regulator that harbors dual function as both a repressor and activator for terminal muscle differentiation. The repressive function of Human MBNL1 by sequestering at normal splice sites has been shown to lead to RNA-splicing defects that lead to muscular diseases. The gene can be alternatively spliced into multiple functionally distinct isoforms, some of which linked to be involved in cancer biology.
Human MBNL1 is a 370 amino acid protein composed of four Zinc Finger protein domains of the CCCH type linked in tandem. The MBNL1 protein specifically binds to double stranded CUG RNA expansions. The Zinc Finger domains play a role in both protein:protein contacts as well as RNA:protein contacts when bound to an oligonucleotide. | 1 | Applied and Interdisciplinary Chemistry |
The sulfide ion, S, does not exist in aqueous alkaline solutions of NaS. Instead sulfide converts to hydrosulfide:
:S + HO → SH + OH
Upon treatment with an acid, sulfide salts convert to hydrogen sulfide:
:S + H → SH
:SH + H → HS
Oxidation of sulfide is a complicated process. Depending on the conditions, the oxidation can produce elemental sulfur, polysulfides, polythionates, sulfite, or sulfate. Metal sulfides react with halogens, forming sulfur and metal salts.
:8 MgS + 8 I → S + 8 MgI | 0 | Theoretical and Fundamental Chemistry |
Many types of substances are known to interact with amphetamine, resulting in altered drug action or metabolism of amphetamine, the interacting substance, or both. Inhibitors of the enzymes that metabolize amphetamine (e.g., CYP2D6 and FMO3) will prolong its elimination half-life, meaning that its effects will last longer. Amphetamine also interacts with , particularly monoamine oxidase A inhibitors, since both MAOIs and amphetamine increase plasma catecholamines (i.e., norepinephrine and dopamine); therefore, concurrent use of both is dangerous. Amphetamine modulates the activity of most psychoactive drugs. In particular, amphetamine may decrease the effects of sedatives and depressants and increase the effects of stimulants and antidepressants. Amphetamine may also decrease the effects of antihypertensives and antipsychotics due to its effects on blood pressure and dopamine respectively. Zinc supplementation may reduce the minimum effective dose of amphetamine when it is used for the treatment of ADHD. | 0 | Theoretical and Fundamental Chemistry |
Aluminium chloride finds a wide variety of other applications in organic chemistry. For example, it can catalyse the ene reaction, such as the addition of 3-buten-2-one (methyl vinyl ketone) to carvone:
It is used to induce a variety of hydrocarbon couplings and rearrangements.
Aluminium chloride combined with aluminium in the presence of an arene can be used to synthesize bis(arene) metal complexes, e.g. bis(benzene)chromium, from certain metal halides via the Fischer–Hafner synthesis. Dichlorophenylphosphine is prepared by reaction of benzene and phosphorus trichloride catalyzed by aluminium chloride. | 0 | Theoretical and Fundamental Chemistry |
Concentration of rNTPs within the cell is 10 to 10 times higher than the concentration of dNTP. Thus, during DNA replication the higher concentration of rNTP poses a problem as it can be erroneously incorporated into the developing DNA strand by DNA polymerases. The usage of RNA primers during DNA replication is an example of a correct incorporation of rNTPs during the process. Although, overly long RNA primers can decrease the effectiveness of T7 DNA polymerase in incorporating dNTP into the growing strand and weaken the binding between T7 and the template DNA strand. Essentially as the RNA primer grows, these rNMP residues inhibit RNA synthesis, decrease dNTP incorporation efficiency, decrease affinity between the helicase, DNA polymerase and template DNA strand overall decreases productivity of the DNA-protein complex. rNMPs are rNTPs without a pyrophosphate group attached, 2 P. However, DNA polymerases have a method to prevent rNTP incorporation centered around the major distinguishing feature between ribose and deoxyribose sugar bases, that feature being the absence of a 2-OH on the deoxyribose. The use of a steric gate residue present on the DNA polymerase prevents incorporation of rNTP by creating a steric clash between an active site amino acid residue on the DNA polymerase and the 2-OH on the sugar base of the rNTP. This steric clash is absent when incorporating dNTP since the sugar base on dNTPs have a 2-H instead of a 2-OH. Specifically the amino acid tyrosine positioned at residue 416 in DNA polymerase serves as the steric residue gate to prevent rNTP incorporation while in RNA polymerase the presence of a stabilizing electrostatic interaction between the 2-OH on the ribose allows for correct incorporation into a growing RNA strand as opposed to dNTP incorporation. The results obtained from using changes in the free energy of the transition state of T7 DNA polymerase and RNA polymerase when binding to either dNTP or rNTP substrates support the above method of discriminating between rNTP and dNTP during their respective biological procedures. The presence of correct water binding during dNTP or rNTP incorporation is also necessary. However, a specific human DNA polymerase known as DNA polymerase η incorporates rNTPs into the developing DNA strand at points in which the template strand has lesions or is damaged. DNA polymerase η ensures that the rNTP being incorporated is complementary to the DNA residue of the template strand based on Watson and Crick base pairing rules. It overcomes the steric interference with the steric gate residue via propeller twist of to allow enough space for the 2-OH. Incorporation of the appropriate rNTP into the developing DNA strand allows for corrections to be done on segments of the DNA that are damaged or have lesions. | 1 | Applied and Interdisciplinary Chemistry |
tert-butyl hydroperoxide is potentially dangerous, but explosions are rare.
A solution of tert-butyl hydroperoxide and water with a concentration of greater than 90% is forbidden to be shipped according to US Department of Transportation Hazardous Materials Table 49 CFR 172.101.
In some sources it also has an NFPA 704 rating of 4 for health, 4 for flammability, 4 for reactivity and is a potent oxidant, however other sources claim lower ratings of 3-2-2 or 1-4-4. | 0 | Theoretical and Fundamental Chemistry |
The mechanism of the above reaction has not been resolved, but it has been suggested that is found in its ionic form and the reaction proceeds via nucleophilic attack of by (from dissociation). Elimination of HCl (the major side product) creates a reactive nucleophilic intermediate
which through further attack of and subsequent HCl elimination, creates a growing acyclic intermediate
:, etc.
until an eventual intramolecular attack leads to the formation of one of the cyclic oligomers. | 0 | Theoretical and Fundamental Chemistry |
Gray arsenic, also called grey arsenic or metallic arsenic, is the most stable allotrope of the element at room temperature, and as such is its most common form. This soft, brittle allotrope of arsenic has a steel gray, metallic color, and is a good conductor. The rhombohedral form of this allotrope is analogous to the phosphorus allotrope black phosphorus. In its α-form, As rings in chair confirmations are condensed into packed layers lying perpendicular to the crystallographic c axis. Within each layer, the vicinal As-As bond distances are 2.517 Å, while the layer-to-layer As-As bond distances are 3.120 Å. The overall structure displays a distorted octahedral geometry, resulting in the largely metallic properties of this allotrope. Upon sublimation at 616 °C, the gas phase arsenic molecules lose this packing arrangement and form small clusters of As, As, and As, though As is by far the most abundant in this phase. If these vapors are condensed swiftly onto a cold surface () results due to the lack of energy required to form the rhombohedral gray arsenic lattice. Conversely, condensation of arsenic vapors onto a heated surface generates amorphous black arsenic. The crystalline form of black arsenic can also be isolated, and the amorphous form can be annealed to return to the metallic gray arsenic form. Yellow arsenic can also be returned to the gray allotrope in a facile manner through application of light or by returning the molecule to room temperature. | 0 | Theoretical and Fundamental Chemistry |
In solution, the acid and the hydrogen rhodizonate ion are mostly hydrated, with some of the carbonyl groups >C=O replaced by geminal hydroxyls, . | 0 | Theoretical and Fundamental Chemistry |
On September 27, 2012, NASA scientists announced that the Curiosity rover found evidence for an ancient streambed suggesting a "vigorous flow" of water on Mars.
On December 3, 2012, NASA reported that Curiosity performed its first extensive soil analysis, revealing the presence of water molecules, sulfur and chlorine in the Martian soil. On December 9, 2013, NASA reported that, based on evidence from Curiosity rover studying Aeolis Palus, Gale Crater contained an ancient freshwater lake which could have been a hospitable environment for microbial life. | 0 | Theoretical and Fundamental Chemistry |
Marie-Louise von Franz describes in her introduction to Ibn Umails "Book of the Explanation of the Symbols — Kitāb Ḥall ar-Rumūz" the contributions of Islamic alchemy as follows: In the 7th to 8th century, Islamic scholars were mainly concerned with translating ancient Hermetic-Gnostic texts without changing them. Gradually they began "confronting their content with the Islamic religion" and began "to think independently and experiment themselves in the realm of alchemy". Thus they added "an emphasis on the monotheistic outlook" (tawḥīd) and more and more creating a synopsis of the diverse antique traditions. Thus unifying their meaning, the Islamic scholars arrived at the idea, that the secret and aim of alchemy were the achievement of "one inner psychic experience, namely the God-image" and that stone, water, prima materia etc. were "all aspects of the inner mystery through which the alchemist unites with the transcendent God". Secondly, they added "a passionate feeling tone" by using much more a poetic language than the antique Hermetists did, also giving "a greater emphasis on the coniunctio motif", i.e. images of the union of male and female, sun and moon, king and queen etc. "The mystical masters of Islam understood alchemy as a transformative process of the alchemists psyche. The fire which promoted this transformation was the love of God." | 1 | Applied and Interdisciplinary Chemistry |
The similarities to graphite also include the possibility of scotch-tape delamination (exfoliation), resulting in phosphorene, a graphene-like 2D material with excellent charge transport properties, thermal transport properties and optical properties. Distinguishing features of scientific interest include a thickness dependent band-gap, which is not found in graphene. This, combined with a high on/off ratio of ~10 makes phosphorene a promising candidate for field-effect transistors (FETs). The tunable bandgap also suggests promising applications in mid-infrared photodetectors and LEDs. Exfoliated black phosphorus sublimes at 400 °C in vacuum. It gradually oxidizes when exposed to water in the presence of oxygen, which is a concern when contemplating it as a material for the manufacture of transistors, for example. Exfoliated black phosphorus is an emerging anode material in the battery community, showing high stability and lithium storage. | 0 | Theoretical and Fundamental Chemistry |
An outron is a nucleotide sequence at the 5' end of the primary transcript of a gene that is removed by a special form of RNA splicing during maturation of the final RNA product. Whereas intron sequences are located inside the gene, outron sequences lie outside the gene. | 1 | Applied and Interdisciplinary Chemistry |
3-phosphoglycerate can be separated and measured using paper chromatography as well as with column chromatography and other chromatographic separation methods. It can be identified using both gas-chromatography and liquid-chromatography mass spectrometry and has been optimized for evaluation using tandem MS techniques. | 0 | Theoretical and Fundamental Chemistry |
Magnesium is the eighth most abundant element on earth. It is the fourth most abundant element in vertebrates and the most abundant divalent cation within cells. The most available form of magnesium (Mg) for living organisms can be found in the hydrosphere. The concentration of Mg in seawater is around 55 mM. Mg is readily available to cells during early evolution due to its high solubility in water. Other transition metals like calcium precipitate from aqueous solutions at much lower concentrations than the corresponding Mg salts.
Since magnesium was readily available in early evolution, it can be found in every cell type living organism. Magnesium in anaerobic prokaryotes can be found in MgATP. Magnesium also has many functions in prokaryotes such as glycolysis, all kinases, NTP reaction, signalling, DNA/RNA structures and light capture. In aerobic eukaryotes, magnesium can be found in cytoplasm and chloroplasts. The reactions in these cell compartments are glycolysis, photophosphorylation and carbon assimilation.
ATP, the main source of energy in almost all living organisms, must bind with metal ions such as Mg or Ca to function. Examination of cells with limited magnesium supply has shown that a lack of magnesium can cause a decrease in ATP. Magnesium in ATP hydrolysis acts as a co-factor to stabilize the high negative charge transition state. MgATP can be found in both prokaryotes and eukaryotes cells. However, most of the ATP in cells is MgATP. Following the Irving–Williams series, magnesium has a higher binding constant than the Ca. Therefore, the dominant ATP in living organisms is MgATP. A greater binding constant also gives magnesium the advantage as a better catalyst over other competing transition metals. | 0 | Theoretical and Fundamental Chemistry |
Subfractions of LDL cholesterol that are implicated in causing atherosclerosis have reduced levels of sialic acid. These include small high density LDL particles and electronegative LDL. Reduced levels of sialic acid in small high density LDL particles increases the affinity of those particles for the proteoglycans in arterial walls. | 0 | Theoretical and Fundamental Chemistry |
In more common usage, an oxidizing agent transfers oxygen atoms to a substrate. In this context, the oxidizing agent can be called an oxygenation reagent or oxygen-atom transfer (OAT) agent. Examples include (permanganate), (chromate), OsO (osmium tetroxide), and especially (perchlorate). Notice that these species are all oxides.
In some cases, these oxides can also serve as electron acceptors, as illustrated by the conversion of to ,ie permanganate to manganate. | 0 | Theoretical and Fundamental Chemistry |
The insert is created by PCR using Taq polymerase. This polymerase lacks 3 to 5 proofreading activity and, with a high probability, adds a single, 3-adenine overhang to each end of the PCR product. It is best if the PCR primers have guanines at the 5 end as this maximizes probability of Taq DNA polymerase adding the terminal adenosine overhang. Thermostable polymerases containing extensive 3´ to 5´ exonuclease activity should not be used as they do not leave the 3´ adenine-overhangs. | 1 | Applied and Interdisciplinary Chemistry |
The report commissioned from Atkins Global by Rochdale council, at a cost of £80,000, was published in July 2006 and claimed that previous tests on the land, carried out on behalf of the developers, were not thorough enough, and that extensive work would be required before councillors should even consider the controversial planning application. Atkins Global also claimed that the majority of the developers tests did not detect the true levels of asbestos in the soil. The report concluded that "the presence of asbestos cannot be ruled out across much of the site." In June 2007, Countryside Properties withdrew from the joint planning application. MMC released a statement saying: "Countryside Properties Ltd has withdrawn from the planning application for a mixed use scheme on the former Turner Brothers site because they became disillusioned with the apparent unwillingness of the town planning department to deal with the application as a result of the ill-founded and negative publicity generated by Jason Addys campaign. The people of Rochdale should keep in mind that the site owners have not caused the contamination problems on the site. This was inherited from Federal Mogul... If we were to cave in to Jason Addys uninformed scaremongering and let him have his way, which we most certainly wont, the site would remain a contaminated eyesore on the face of Rochdale in eternity, and all the surrounding houses and properties will be devalued by his badly thought out obsession."
As of 2010, the site remains undeveloped and no significant remediation or decontamination work has been undertaken. | 1 | Applied and Interdisciplinary Chemistry |
* 1881, Jecker Prix, Section de Chimie de L' Academie des Sciences for contributions to organic chemistry | 1 | Applied and Interdisciplinary Chemistry |
Gene deserts are regions of the genome that are devoid of protein-coding genes. Gene deserts constitute an estimated 25% of the entire genome, leading to the recent interest in their true functions. Originally believed to contain inessential and “junk” DNA due to their inability to create proteins, gene deserts have since been linked to several vital regulatory functions, including distal enhancing and conservatory inheritance. Thus, an increasing number of risks that lead to several major diseases, including a handful of cancers, have been attributed to irregularities found in gene deserts. One of the most notable examples is the 8q24 gene region, which, when affected by certain single nucleotide polymorphisms, lead to a myriad of diseases. The major identifying factors of gene deserts lay in their low GpC content and their relatively high levels of repeats, which are not observed in coding regions. Recent studies have even further categorized gene deserts into variable and stable forms; regions are categorized based on their behavior through recombination and their genetic contents. Although current knowledge of gene deserts is rather limited, ongoing research and improved techniques are beginning to open the doors for exploration on the various important effects of these noncoding regions. | 1 | Applied and Interdisciplinary Chemistry |
Pharmacologic down-regulation of (mTOR) pathway during chemotherapy in a mouse model prevents activation of primordial follicles, preserves ovarian function, and maintains normal fertility using clinically available inhibitors INK and RAD. In that way, it helps to maintain fertility while undergoing chemotherapy treatments. These mTOR inhibitors, when administered as pretreatment or co-treatment with standard gonadotoxic chemotherapy, helps to maintain ovarian follicles in their primordial state. | 1 | Applied and Interdisciplinary Chemistry |
In small capillary hemodynamics, the cell-free layer is a near-wall layer of plasma absent of red blood cells since they are subject to migration to the capillary center in Poiseuille flow. Cell-free marginal layer model is a mathematical model which tries to explain Fåhræus–Lindqvist effect mathematically. | 1 | Applied and Interdisciplinary Chemistry |
William C. Brown demonstrated in 1964, during Walter Cronkite's CBS News program, a microwave-powered model helicopter that received all the power it needed for flight from a microwave beam. Between 1969 and 1975, Bill Brown was technical director of a JPL Raytheon program that beamed 30 kW of power over a distance of at 9.6% efficiency.
Microwave power transmission of tens of kilowatts has been well proven by existing tests at Goldstone in California (1975) and Grand Bassin on Reunion Island (1997).
More recently, microwave power transmission has been demonstrated, in conjunction with solar energy capture, between a mountaintop in Maui and the island of Hawaii (92 miles away), by a team under John C. Mankins.
Technological challenges in terms of array layout, single radiation element design, and overall efficiency, as well as the associated theoretical limits are presently a subject of research, as it was demonstrated by the Special Session on "Analysis of Electromagnetic Wireless Systems for Solar Power Transmission" held during the 2010 IEEE Symposium on Antennas and Propagation. In 2013, a useful overview was published, covering technologies and issues associated with microwave power transmission from space to ground. It includes an introduction to SPS, current research and future prospects.
Moreover, a review of current methodologies and technologies for the design of antenna arrays for microwave power transmission appeared in the Proceedings of the IEEE. | 0 | Theoretical and Fundamental Chemistry |
Lingual organoids are organoids that recapitulate, at least partly, aspects of the tongue physiology. Epithelial lingual organoids have been generated using BMI1 expressing epithelial stem cells in three-dimensional culture conditions through the manipulation of EGF, WNT, and TGF-β. This organoid culture, however, lacks taste receptors, as these cells do not arise from Bmi1 expressing epithelial stem cells. Lingual taste bud organoids containing taste cells, however, have been created using the LGR5+ or CD44+ stem/progenitor cells of circumvallate (CV) papilla tissue. These taste bud organoids have been successfully created both directly from isolated Lgr5- or LGR6-expressing taste stem/progenitor cells. and indirectly, through the isolation, digestion, and subsequent culturing of CV tissue containing Lgr5+ or CD44+ stem/progenitor cells. | 1 | Applied and Interdisciplinary Chemistry |
The ocean's chemistry is changing due to the uptake of anthropogenic carbon dioxide (CO). Ocean pH, carbonate ion concentrations ([CO]), and calcium carbonate mineral saturation states (Ω) have been declining as a result of the uptake of approximately 30% of the anthropogenic carbon dioxide emissions over the past 270 years (since around 1750). This process, commonly referred to as "ocean acidification", is making it harder for marine calcifiers to build a shell or skeletal structure, endangering coral reefs and the broader marine ecosystems.
Ocean acidification has been called the "evil twin of global warming" and "the other CO problem". Increased ocean temperatures and oxygen loss act concurrently with ocean acidification and constitute the "deadly trio" of climate change pressures on the marine environment. The impacts of this will be most severe for coral reefs and other shelled marine organisms, as well as those populations that depend on the ecosystem services they provide. | 0 | Theoretical and Fundamental Chemistry |
Replication timing domains have been shown to be associated with TADs as their boundary is co localized with the boundaries of TADs that are located at either sides of compartments. Insulated neighborhoods, DNA loops formed by CTCF/cohesin-bound regions, are proposed to functionally underlie TADs. | 1 | Applied and Interdisciplinary Chemistry |
For double bonded molecules, Cahn–Ingold–Prelog priority rules (CIP rules) are followed to determine the priority of substituents of the double bond. If both of the high priority groups are on the same side of the double bond (cis configuration), then the stereoisomer is assigned the configuration Z (zusammen, German word meaning "together"). If the high priority groups are on opposite sides of the double bond ( trans configuration ), then the stereoisomer is assigned the configuration E (entgegen, German word meaning "opposed") | 0 | Theoretical and Fundamental Chemistry |
The manufacture and installation of pressure piping is tightly regulated by the ASME "B31" code series such as B31.1 or B31.3 which have their basis in the ASME Boiler and Pressure Vessel Code (BPVC). This code has the force of law in Canada and the US. Europe and the rest of the world has an equivalent system of codes. Pressure piping is generally pipe that must carry pressures greater than 10 to 25 atmospheres, although definitions vary. To ensure safe operation of the system, the manufacture, storage, welding, testing, etc. of pressure piping must meet stringent quality standards.
Manufacturing standards for pipes commonly require a test of chemical composition and a series of mechanical strength tests for each heat of pipe. A heat of pipe is all forged from the same cast ingot, and therefore had the same chemical composition. Mechanical tests may be associated to a lot of pipe, which would be all from the same heat and have been through the same heat treatment processes. The manufacturer performs these tests and reports the composition in a mill traceability report and the mechanical tests in a material test report, both of which are referred to by the acronym MTR. Material with these associated test reports is called traceable. For critical applications, third party verification of these tests may be required; in this case an independent lab will produce a certified material test report(CMTR), and the material will be called certified.
Some widely used pipe standards or piping classes are:
* The API range – now ISO 3183. E.g.: API 5L Grade B – now ISO L245 where the number indicates yield strength in MPa
* ASME SA106 Grade B (Seamless carbon steel pipe for high temperature service)
* ASTM A312 (Seamless and welded austenitic stainless steel pipe)
* ASTM C76 (Concrete Pipe)
* ASTM D3033/3034 (PVC Pipe)
* ASTM D2239 (Polyethylene Pipe)
* ISO 14692 (Petroleum and natural gas industries. Glass-reinforced plastics (GRP) piping. Qualification and manufacture)
* ASTM A36 (Carbon steel pipe for structural or low pressure use)
* ASTM A795 (Steel pipe specifically for fire sprinkler systems)
API 5L was changed in the second half of 2008 to edition 44 from edition 43 to make it identical to ISO 3183. It is important to note that the change has created the requirement that sour service, ERW pipe, pass a hydrogen induced cracking (HIC) test per NACE TM0284 in order to be used for sour service.
* ACPA [American Concrete Pipe Association]
* AWWA [American Water Works Association]
* AWWA M45 | 1 | Applied and Interdisciplinary Chemistry |
There is evidence for multiple euxinic events during the Phanerozoic. It is most likely that euxinia was periodic during the Paleozoic and Mesozoic, but geologic data is too sparse to draw any large scale conclusions. In this eon, there is some evidence that euxinic events are potentially linked with mass extinction events including the Late Devonian and Permian–Triassic. | 0 | Theoretical and Fundamental Chemistry |
Anoxic conditions result from a combination of environmental conditions including density stratification, inputs of organic material or other reducing agents, and physical barriers to water circulation. In fjords, shallow sills at the entrance may prevent circulation, while at continental boundaries, circulation may be especially low while organic material input from production at upper levels is exceptionally high. In wastewater treatment, the absence of oxygen alone is indicated anoxic while the term anaerobic is used to indicate the absence of any common electron acceptor such as nitrate, sulfate or oxygen.
When oxygen is depleted in a basin, bacteria first turn to the second-best electron acceptor, which in sea water, is nitrate. Denitrification occurs, and the nitrate will be consumed rather rapidly. After reducing some other minor elements, the bacteria will turn to reducing sulfate. This results in the byproduct of hydrogen sulfide (HS), a chemical toxic to most biota and responsible for the characteristic "rotten egg" smell and dark black sediment color:
:2 CHO + → 2 + HS + chemical energy
These sulfides will mostly be oxidized to either sulfates (~90%) in more oxygen-rich water or precipitated and converted into pyrite (~10%), according to the following chemical equations:
Some chemolithotrophs can also facilitate the oxidation of hydrogen sulfide into elemental sulfur, according to the following chemical equation:
:HS + O → S + HO
Anoxia is quite common in muddy ocean bottoms where there are both high amounts of organic matter and low levels of inflow of oxygenated water through the sediment. Below a few centimeters from the surface the interstitial water (water between sediment) is oxygen free.
Anoxia is further influenced by biochemical oxygen demand (BOD), which is the amount of oxygen used by marine organisms in the process of breaking down organic matter. BOD is influenced by the type of organisms present, the pH of the water, temperature, and the type of organic matter present in the area. BOD is directly related to the amount of dissolved oxygen available, especially in smaller bodies of water such as rivers and streams. As BOD increases, available oxygen decreases. This causes stress on larger organisms. BOD comes from natural and anthropogenic sources, including: dead organisms, manure, wastewater, and urban runoff. | 0 | Theoretical and Fundamental Chemistry |
Since the computation of a LIC image is expensive but inherently parallel, it has also been parallelized and, with availability of GPU-based implementations, it has become interactive on PCs. Also for UFLIC an interactive GPU-based implementation has been presented. | 1 | Applied and Interdisciplinary Chemistry |
Permeable paving systems, especially those with porous surfaces, require maintenance in order to keep the pores clear of fine aggregates as to not hinder the systems ability to infiltrate stormwater. The frequency of cleaning is again dependent on many site specific factors, such as runoff volume, neighboring sites and climate. Often, cleaning of permeable paving systems is done by suction excavators, which are alternatively used for excavation in sensitive areas and therefore are becoming increasingly common. If maintenance is not carried out on a regular basis, the porous pavements can begin to function more like impervious surfaces. With more advanced paving systems the levels of maintenance needed can be greatly decreased, elastomerically bound glass pavements requires less maintenance than regular concrete paving as the glass bound pavement has 50% more void space.
Plastic grid systems, if selected and installed correctly, are becoming more and more popular with local government maintenance personnel owing to the reduction in maintenance efforts: reduced gravel migration and weed suppression in public park settings.
Some permeable paving products are prone to damage from misuse, such as drivers who tear up patches of plastic & gravel grid systems by "joy riding" on remote parking lots at night. The damage is not difficult to repair but can look unsightly in the meantime. Grass pavers require supplemental watering in the first year to establish the vegetation, otherwise they may need to be re-seeded. Regional climate also means that most grass applications will go dormant during the dry season. While brown vegetation is only a matter of aesthetics, it can influence public support for this type of permeable paving.
Traditional permeable concrete paving bricks tend to lose their color in relatively short time which can be costly to replace or clean and is mainly due to the problem of efflorescence. | 1 | Applied and Interdisciplinary Chemistry |
Selenols are structurally similar to thiols, but the bond is about 8% longer at 196 pm. The angle approaches 90°. The bonding involves almost pure p-orbitals on Se, hence the near 90 angles. The bond energy is weaker than the bond, consequently selenols are easily oxidized and serve as H-atom donors. The Se-H bond is much weaker than the bond as reflected in their respective bond dissociation energy (BDE). For Benzeneselenol|, the BDE is 326 kJ/mol, while for Benzenethiol|, the BDE is 368 kJ/mol.
Selenols are about 1000 times stronger acids than thiols: the pK of Methaneselenol| is 5.2 vs 8.3 for Methanethiol|. Deprotonation affords the selenolate anion, , most examples of which are highly nucleophilic and rapidly oxidized by air.
The boiling points of selenols tend to be slightly greater than for thiols. This difference can be attributed to the increased importance of stronger van der Waals bonding for larger atoms. Volatile selenols have highly offensive odors. | 0 | Theoretical and Fundamental Chemistry |
The Chandrasekhar number is usually denoted by the letter , and is motivated by a dimensionless form of the Navier-Stokes equation in the presence of a magnetic force in the equations of magnetohydrodynamics:
where is the Prandtl number, and is the magnetic Prandtl number.
The Chandrasekhar number is thus defined as:
where is the magnetic permeability, is the density of the fluid, is the kinematic viscosity, and is the magnetic diffusivity. and are a characteristic magnetic field and a length scale of the system respectively.
It is related to the Hartmann number, , by the relation: | 1 | Applied and Interdisciplinary Chemistry |
There are three standard positions for pressure tappings (also called taps), commonly named as follows:
* placed immediately upstream and downstream of the plate; convenient when the plate is provided with an orifice carrier incorporating tappings
* or placed one pipe diameter upstream and half a pipe diameter downstream of the plate; these can be installed by welding bosses to the pipe
* placed 25.4 mm (1 inch) upstream and downstream of the plate, normally within specialised pipe flanges.
These types are covered by ISO 5167 and other major standards. Other types include
* or placed 2.5 pipe diameters upstream and 8 diameters downstream, at which point the measured differential is equal to the unrecoverable pressure loss caused by the orifice
* placed one pipe diameter upstream and at a position 0.3 to 0.9 diameters downstream, depending on the orifice type and size relative to the pipe, in the plane of minimum fluid pressure.
The measured differential pressure differs for each combination and so the coefficient of discharge used in flow calculations depends partly on the tapping positions.
The simplest installations use single tappings upstream and downstream, but in some circumstances these may be unreliable; they might be blocked by solids or gas-bubbles, or the flow profile might be uneven so that the pressures at the tappings are higher or lower than the average in those planes. In these situations multiple tappings can be used, arranged circumferentially around the pipe and joined by a piezometer ring, or (in the case of corner taps) annular slots running completely round the internal circumference of the orifice carrier. | 1 | Applied and Interdisciplinary Chemistry |
A more accurate approach as claimed by Grunenberg is to exploit compliance constants as means for describing chemical bonds as shown below.
All the calculated compliance constants above are given in N unit. For both n-butane and cyclobutane, the results are the same regardless of the choice of the coordinate systems. One aspect of compliance constants that proves more powerful than force constants in cyclobutane is because of less coupling. This compliance coupling constants are the off-diagonal elements in the inverted Hessian matrix and altogether with the compliance constants, they physically describe the relaxed distortion of a molecule closely through a minimum energy path. Moreover, the values of the compliance constants yield the same results for all the C-C bonds and the values are less compared to those obtained for n-butane. Compliance constants, thus, give results that are in accordance to what are generally known about the ring strain of cyclobutane. | 0 | Theoretical and Fundamental Chemistry |
At the nanoscale, size effects and different dimensional constraints, like grain boundaries, dislocations, and distribution of voids, can tremendously change the properties of a material. Nanolattices possess unparalleled mechanical properties. Nanolattices are the strongest existing cellular materials despite being extremely light-weight. Though consisting of 50%-99% air, nanolattice can be as strong as steel. Its effective strength can reach up to 1 GPa. On the order of 50nm, the extremely small volume of their individual members, such as walls, nodes, and trusses, thereby statistically nearly eliminates the material flaw population and the base material of nanolattices can reach mechanical strengths on the order of the theoretical strength of an ideal, perfect crystal. While such effects are typically limited to individual, geometrically primitive structures like nanowires, the specific architecture allows nanolattices to exploit them in complex, three-dimensional structures of notably larger overall size. Nanolattices can be designed highly deformable and recoverable, even with ceramic base materials. Nanolattices are able to undergo 80% compressive strain without catastrophic failure and then still recover to 100% original shape. Nanolattices can possess mechanical metamaterial properties like auxetic (negative Poisson's ratio) or meta-fluidic behavior (large Bulk modulus). Nanolattices can combine mechanical resilience and ultra-low thermal conductivity and can have electromagnetic metamaterial characteristics like optical cloaking. However, one of the challenges in nanolattices research is figure how to retain the robust properties while scaling up. It is inherently difficult to keep nanoscale size effects in bulk structure. The straightforward workaround to overcome this challenge is to combine bulk processes with thin film deposition techniques to retain the frame space hollow structure. | 0 | Theoretical and Fundamental Chemistry |
By the Late Bronze Age, the copper bun ingot, either in a simple form or with a hole in its center, had become the main form of copper ingot, replacing the earlier ‘bar ingot’ or rippenbarre. Weights of complete examples average ~4 kg, but examples of up to about 7 kg are known. Many early finds of British LBA bun ingots were unstratified but recently bun-shaped ingots and ingot fragments have been found in hoards alongside bronze artifacts and scrap metal. Several offshore finds of probable LBA date suggest that copper bun ingots may have been traded by sea during this period. | 1 | Applied and Interdisciplinary Chemistry |
In aerobic cells with sufficient oxygen, as in most human cells, the pyruvate is further metabolized. It is irreversibly converted to acetyl-CoA, giving off one carbon atom as the waste product carbon dioxide, generating another reducing equivalent as NADH. The two molecules acetyl-CoA (from one molecule of glucose) then enter the citric acid cycle, producing two molecules of ATP, six more NADH molecules and two reduced (ubi)quinones (via FADH as enzyme-bound cofactor), and releasing the remaining carbon atoms as carbon dioxide. The produced NADH and quinol molecules then feed into the enzyme complexes of the respiratory chain, an electron transport system transferring the electrons ultimately to oxygen and conserving the released energy in the form of a proton gradient over a membrane (inner mitochondrial membrane in eukaryotes). Thus, oxygen is reduced to water and the original electron acceptors NAD and quinone are regenerated. This is why humans breathe in oxygen and breathe out carbon dioxide. The energy released from transferring the electrons from high-energy states in NADH and quinol is conserved first as proton gradient and converted to ATP via ATP synthase. This generates an additional 28 molecules of ATP (24 from the 8 NADH + 4 from the 2 quinols), totaling to 32 molecules of ATP conserved per degraded glucose (two from glycolysis + two from the citrate cycle). It is clear that using oxygen to completely oxidize glucose provides an organism with far more energy than any oxygen-independent metabolic feature, and this is thought to be the reason why complex life appeared only after Earth's atmosphere accumulated large amounts of oxygen. | 1 | Applied and Interdisciplinary Chemistry |
The Knudsen number can be related to the Mach number and the Reynolds number.
Using the dynamic viscosity
with the average molecule speed (from Maxwell–Boltzmann distribution)
the mean free path is determined as follows:
Dividing through by L (some characteristic length), the Knudsen number is obtained:
where
: is the average molecular speed from the Maxwell–Boltzmann distribution [L T],
: T is the thermodynamic temperature [θ],
: μ is the dynamic viscosity [M L T],
: m is the molecular mass [M],
: k is the Boltzmann constant [M L T θ],
: is the density [M L].
The dimensionless Mach number can be written as
where the speed of sound is given by
where
: U is the freestream speed [L T],
: R is the Universal gas constant (in SI, 8.314 47215 J K mol) [M L T θ mol],
: M is the molar mass [M mol],
: is the ratio of specific heats [1].
The dimensionless Reynolds number can be written as
Dividing the Mach number by the Reynolds number:
and by multiplying by yields the Knudsen number:
The Mach, Reynolds and Knudsen numbers are therefore related by | 1 | Applied and Interdisciplinary Chemistry |
Cumulative effects from this process should not be confused with long-term effects – when short-term effects have disappeared and long-term effects are subclinical, reirradiation can still be problematic. These doses are calculated by the radiation oncologist and many factors are taken into account before the subsequent radiation takes place. | 0 | Theoretical and Fundamental Chemistry |
In the first step the polymers are processed by means of common techniques, such as injection or extrusion, thermoforming, at a temperature (T) at which the polymer melts, obtaining a final shape which is called "permanent" shape.
The next step is called system programming and involves heating the sample to a transition temperature (T). At that temperature the polymer is deformed, reaching a shape called "temporary". Immediately afterwards the temperature of the sample is lowered.
The final step of the effect involves the recovery of the permanent shape. The sample is heated to the transition temperature (T) and within a short time the recovery of the permanent shape is observed.
This effect is not a natural property of the polymer, but results from proper programming of the system with the appropriate chemistry.
For a polymer to exhibit this effect, it must have two components at the molecular level: bonds (chemical or physical) to determine the permanent shape and "trigger" segments with a T to fix the temporary shape. | 0 | Theoretical and Fundamental Chemistry |
The theoretically predicted maximum of the melting curve (the prerequisite for the liquid metallic hydrogen) was discovered by Shanti Deemyad and Isaac F. Silvera by using pulsed laser heating. Hydrogen-rich molecular silane () was claimed to be metallized and become superconducting by M.I. Eremets et al.. This claim is disputed, and their results have not been repeated. | 0 | Theoretical and Fundamental Chemistry |
The American Federation of Labor (AFL) tried and failed to organize the steelworkers in 1919. Although the strike gained widespread middle-class support because of its demand and the 12-hour day, the strike failed and unionization was postponed until the late 1930s. The mills ended the 12-hour day in the early 1920s.
The second surge of unionization came under the auspices of the militant Congress of Industrial Organizations in the late 1930s, when it set up the Steel Workers Organizing Committee. The SWOC focused almost exclusively on the achievement of a signed contract, with "Little Steel" (the major producers except for US Steel). At the grassroots however, women of the steel auxiliaries, workers on the picket line, and middle-class liberals from across Chicago sought to transform the strike into something larger than a showdown over union recognition. In Chicago, the Little Steel strike raised the possibility that steelworkers might embrace the ‘civic unionism’ that animated the left-led unions of the era. The effort failed, and while the strike was won, the resulting powerful United Steelworkers of America union suppressed grassroots opinions. | 1 | Applied and Interdisciplinary Chemistry |
During operation, Mount Polley runs four shifts. There is a day shift and a night shift each running twelve hours. Around 370 workers work these shifts seven days on and then get seven days off. About 50 staff include administrators, supervisors, warehouse operators, engineers, geologists, assayers, technical personnel, and human resources. | 1 | Applied and Interdisciplinary Chemistry |
18-Crown-6 binds to a variety of small cations, using all six oxygens as donor atoms. Crown ethers can be used in the laboratory as phase transfer catalysts. Salts which are normally insoluble in organic solvents are made soluble by crown ether. For example, potassium permanganate dissolves in benzene in the presence of 18-crown-6, giving the so-called "purple benzene", which can be used to oxidize diverse organic compounds.
Various substitution reactions are also accelerated in the presence of 18-crown-6, which suppresses ion-pairing. The anions thereby become naked nucleophiles. For example, using 18-crown-6, potassium acetate is a more powerful nucleophile in organic solvents:
:[K(18-crown-6)]OAc + CHCHCl → CHCHOAc + [K(18-crown-6)]Cl
The first electride salt to be examined with X-ray crystallography, [Cs(18-crown-6)]·e, was synthesized in 1983. This highly air- and moisture-sensitive solid has a sandwich molecular structure, where the electron is trapped within nearly spherical lattice cavities. However, the shortest electron-electron distance is too long (8.68 Å) to make this material a conductor of electricity. | 0 | Theoretical and Fundamental Chemistry |
Monocyclic cycloalkenes are cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, and so on. Bicyclic alkenes include norbornene and norbornadiene.
Two more examples are shown below, methylenecyclohexane on the left and 1-methylcyclohexene on the right:
An exocyclic group is always shown outside the ring structure, take for instance the exocyclic double bond of the former molecule. Isotoluenes are a prominent class of compounds with exocyclic double bonds.
The placement of double bonds in many alicyclic compounds can be predicted with Bredt's rule. | 0 | Theoretical and Fundamental Chemistry |
The Debye length has become increasingly significant in the modeling of solid state devices as improvements in lithographic technologies have enabled smaller geometries.
The Debye length of semiconductors is given:
where
* ε is the dielectric constant,
* k is the Boltzmann constant,
* T is the absolute temperature in kelvins,
* q is the elementary charge, and
* N is the net density of dopants (either donors or acceptors).
When doping profiles exceed the Debye length, majority carriers no longer behave according to the distribution of the dopants. Instead, a measure of the profile of the doping gradients provides an "effective" profile that better matches the profile of the majority carrier density.
In the context of solids, Thomas–Fermi screening length may be required instead of Debye length. | 0 | Theoretical and Fundamental Chemistry |
Cytochrome c is a highly conserved protein across the spectrum of eukaryotic species, found in plants, animals, fungi, and many unicellular organisms. This, along with its small size (molecular weight about 12,000 daltons), makes it useful in studies of cladistics. Cytochrome c has been studied for the glimpse it gives into evolutionary biology.
Cytochrome c has a primary structure consisting of a chain of about 100 amino acids. Many higher-order organisms possess a chain of 104 amino acids. The sequence of cytochrome c in humans is identical to that of chimpanzees (our closest relatives), but differs from that of horses.
Cytochrome c has an amino acid sequence that is highly conserved in eukaryotes, varying by only a few residues. In more than thirty species tested in one study, 34 of the 104 amino acids were conserved (identical at their characteristic position). For example, human cytochrome oxidase reacted with wheat cytochrome c, in vitro; which held true for all pairs of species tested. In addition, the redox potential of +0.25 volts is the same in all cytochrome c molecules studied. | 1 | Applied and Interdisciplinary Chemistry |