text
stringlengths 105
4.57k
| label
int64 0
1
| label_text
stringclasses 2
values |
|---|---|---|
The drag resistance to a moving sphere, also known as Stokes' solution is here summarised. Given a sphere of radius , travelling at velocity , in a Stokes fluid with dynamic viscosity , the drag force is given by:
The Stokes solution dissipates less energy than any other solenoidal vector field with the same boundary velocities: this is known as the Helmholtz minimum dissipation theorem. | 1 | Applied and Interdisciplinary Chemistry |
Dextromethorphan has been found to possess the following actions (<1 μM) using rat tissues:
* Uncompetitive antagonist of the NMDA receptor via the MK-801/ site
* and blocker (cf. serotonin–norepinephrine reuptake inhibitor)
* Sigma σ receptor agonist
* Negative allosteric modulator of nicotinic acetylcholine receptors
* Ligand of the serotonin 5-HT, histamine H, α-adrenergic, and muscarinic acetylcholine receptors
Dextromethorphan is a prodrug of dextrorphan, which is the actual mediator of most of its dissociative effects through acting as a more potent NMDA receptor antagonist than dextromethorphan itself. What role, if any, (+)-3-methoxymorphinan, dextromethorphan's other major metabolite, plays in its effects is not entirely clear. | 0 | Theoretical and Fundamental Chemistry |
Three linkage isomers are common for nitrite ligands, O-bonded, N-bonded, and bidentate O,O-bonded. The former two isomers have been characterized for the pentamminecobalt(III) system, i.e. and , referred to as N-nitrito and O-nitrito, respectively. These two forms are sometimes called nitro and nitrito. These isomers can be interconverted in some complexes.
An example of chelating nitrite is – "bipy" is the bidentate ligand 2,2′-bipyridyl. This bonding mode is sometimes described as κ-.
Focusing on electron-counting in monometallic complexes, O-bonded, N-bonded are viewed as 1-electron pseudohalides ("X-ligand"). The bidentate O,O-bonded is an "L-X ligand", akin to bidentate carboxylate.
With respect to HSAB theory, the N bonding mode is more common for softer metal centers. The O and O,O-bidentate modes are hard ligands, being found on Lewis-acidic metal centers.
The kinetically-favored O-bonded isomer converts to . In its reaction with ferric porphyrin complexes, nitrite gives the O-bonded isomer, . Addition of donor ligands to this complex induces the conversion to the octahedral low-spin isomer, which now is a soft Lewis acid. The nitrite isomerizes to the N-bonded isomer, .
The isomerization of to proceeds in an intramolecular manner. | 0 | Theoretical and Fundamental Chemistry |
Cloning is the process of producing individual organisms with identical genomes, either by natural or artificial means. In nature, some organisms produce clones through asexual reproduction; this reproduction of an organism by itself without a mate is known as parthenogenesis. In the field of biotechnology, cloning is the process of creating cloned organisms of cells and of DNA fragments.
The artificial cloning of organisms, sometimes known as reproductive cloning, is often accomplished via somatic-cell nuclear transfer (SCNT), a cloning method in which a viable embryo is created from a somatic cell and an egg cell. In 1996, Dolly the sheep achieved notoriety for being the first mammal cloned from a somatic cell. Another example of artificial cloning is molecular cloning, a technique in molecular biology in which a single living cell is used to clone a large population of cells that contain identical DNA molecules.
In bioethics, there are a variety of ethical positions regarding the practice and possibilities of cloning. The use of embryonic stem cells, which can be produced through SCNT, in some stem cell research has attracted controversy. Cloning has been proposed as a means of reviving extinct species. In popular culture, the concept of cloning—particularly human cloning—is often depicted in science fiction; depictions commonly involve themes related to identity, the recreation of historical figures or extinct species, or cloning for exploitation (i.e. cloning soldiers for warfare). | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, the Schmidt number (denoted ) of a fluid is a dimensionless number defined as the ratio of momentum diffusivity (kinematic viscosity) and mass diffusivity, and it is used to characterize fluid flows in which there are simultaneous momentum and mass diffusion convection processes. It was named after German engineer Ernst Heinrich Wilhelm Schmidt (1892–1975).
The Schmidt number is the ratio of the shear component for diffusivity (viscosity divided by density) to the diffusivity for mass transfer . It physically relates the relative thickness of the hydrodynamic layer and mass-transfer boundary layer.
It is defined as:
where (in SI units):
* is the kinematic viscosity (m/s)
* is the mass diffusivity (m/s).
* is the dynamic viscosity of the fluid (Pa·s = N·s/m = kg/m·s)
* is the density of the fluid (kg/m).
The heat transfer analog of the Schmidt number is the Prandtl number (). The ratio of thermal diffusivity to mass diffusivity is the Lewis number (). | 1 | Applied and Interdisciplinary Chemistry |
N-Fluoropyridinium triflate is an organofluorine compound with the formula [CHNF]OSCF. It is a white solid with low solubility in polar organic solvents. The compound is used as an electrophilic fluorinating agent. It is a salt, consisting of the N-fluoropyridinium cation ([CHNF]) and the triflate anion. Related reagents include Selectfluor, which is also an N-fluorinated salt.
N-Fluoropyridinium cations are not only electrophilic fluorinating agents (i.e., sources of "F"), they are also one-electron oxidants. | 0 | Theoretical and Fundamental Chemistry |
The F-T process attracted attention as a means of Nazi Germany to produce liquid hydrocarbons. The original process was developed by Franz Fischer and Hans Tropsch, working at the Kaiser-Wilhelm-Institut for Chemistry in 1926. They filed a number of patents, e.g., , applied 1926, published 1930. It was commercialized by Brabag in Germany in 1936. Being petroleum-poor but coal-rich, Germany used the process during World War II to produce ersatz (replacement) fuels. FT production accounted for an estimated 9% of German war production of fuels and 25% of the automobile fuel. Many refinements and adjustments have been made to the process since Fischer and Tropsch's time.
The United States Bureau of Mines, in a program initiated by the Synthetic Liquid Fuels Act, employed seven Operation Paperclip synthetic fuel scientists in a Fischer–Tropsch plant in Louisiana, Missouri in 1946.
In Britain, Alfred August Aicher obtained several patents for improvements to the process in the 1930s and 1940s. Aichers company was named Synthetic Oils Ltd' (not related to a company of the same name in Canada).
Around the 1930s and 1940s, Arthur Imhausen developed and implemented an industrial process for producing edible fats from these synthetic oils through oxidation. The products were fractionally distilled and the edible fats were obtained from the - fraction which were reacted with glycerol such as that synthesized from propylene. "Coal butter" margarine made from synthetic oils was found to be nutritious and of agreeable taste, and it was incorporated into diets contributing as much as 700 calories per day. The process required at least 60 kg of coal per kg of synthetic butter. | 0 | Theoretical and Fundamental Chemistry |
In biochemistry, the glutamate–glutamine cycle is a cyclic metabolic pathway which maintains an adequate supply of the neurotransmitter glutamate in the central nervous system. Neurons are unable to synthesize either the excitatory neurotransmitter glutamate, or the inhibitory GABA from glucose. Discoveries of glutamate and glutamine pools within intercellular compartments led to suggestions of the glutamate–glutamine cycle working between neurons and astrocytes. The glutamate/GABA–glutamine cycle is a metabolic pathway that describes the release of either glutamate or GABA from neurons which is then taken up into astrocytes (non-neuronal glial cells). In return, astrocytes release glutamine to be taken up into neurons for use as a precursor to the synthesis of either glutamate or GABA. | 1 | Applied and Interdisciplinary Chemistry |
A wealth of literature exists on the defensive chemistry of secondary metabolites produced by terrestrial plants and their antagonistic effects on pests and pathogens, likely owing to the fact that human society depends upon large-scale agricultural production to sustain global commerce. Since the 1950s, over 200,000 secondary metabolites have been documented in plants. These compounds serve a variety of physiological and allelochemical purposes, and provide a sufficient stock for the evolution of defensive chemicals. Examples of common secondary metabolites used as chemical defenses by plants include alkaloids, phenols, and terpenes. Defensive chemicals used to avoid consumption may be broadly characterized as either toxins or substances reducing the digestive capacity of herbivores. Although toxins are defined in a broad sense as any substance produced by an organism that reduces the fitness of another, in a more specific sense toxins are substances which directly affect and diminish the functioning of certain metabolic pathways. Toxins are minor constituents (<2% dry weight), active in small concentrations, and more present in flowers and young leaves. On the other hand, indigestible compounds make up to 60% dry weight of tissue and are predominately found in mature, woody species. Many alkaloids, pyrethrins, and phenols are toxins. Tannins are major inhibitors of digestion and are polyphenolic compounds with large molecular weights. Lignin and cellulose are important structural elements in plants and are also usually highly indigestible. Tannins are also toxic against pathogenic fungi at natural concentrations in a variety of woody tissues. Not only useful as deterrents to pathogens or consumers, some of the chemicals produced by plants are effective in inhibiting competitors as well. Two separate shrub communities in the California chaparral were found to produce phenolic compounds and volatile terpenes which accumulated in soil and prevented various herbs from growing near the shrubs. Other plants were only observed to grow when fire removed shrubs, but herbs subsequently died off after shrubs returned. Although the focus has been on broad-scale patterns in terrestrial plants, Paul and Fenical in 1986 demonstrated a variety of secondary metabolites in marine algae which prevented feeding or induced mortality in bacteria, fungi, echinoderms, fishes, and gastropods. In nature, pests are a severe problem to plant communities as well, leading to the co-evolution of plant chemical defenses and herbivore metabolic strategies to detoxify their plant food. A variety of invertebrates consume plants, but insects have received a majority of the attention. Insects are pervasive agricultural pests and sometimes occur in such high densities that they can strip fields of crops. | 1 | Applied and Interdisciplinary Chemistry |
Binding metal ions to protein and other components of biological material is one of the most popular uses of ITC, since ovotransferrin to ferric iron binding study published by Lin et al. from MicroCal Inc. This is due to some of the metal ions utilized in biological systems having d electron configuration which cannot be studied with other common techniques such as UV-vis spectrophotometry or electron paramagnetic resonance. It is also closely related to biochemical and medicinal studies due to the large abundance of metal binding enzymes in biological systems. | 0 | Theoretical and Fundamental Chemistry |
A pre-supposed guiding principle of thermodynamics is the conservation of energy. The total energy of a system is the sum of its internal energy, of its potential energy as a whole system in an external force field, such as gravity, and of its kinetic energy as a whole system in motion. Thermodynamics has special concern with transfers of energy, from a body of matter, such as, for example a cylinder of steam, to the surroundings of the body, by mechanisms through which the body exerts macroscopic forces on its surroundings so as to lift a weight there; such mechanisms are the ones that are said to mediate thermodynamic work.
Besides transfer of energy as work, thermodynamics admits transfer of energy as heat. For a process in a closed (no transfer of matter) thermodynamic system, the first law of thermodynamics relates changes in the internal energy (or other cardinal energy function, depending on the conditions of the transfer) of the system to those two modes of energy transfer, as work, and as heat. Adiabatic work is done without matter transfer and without heat transfer. In principle, in thermodynamics, for a process in a closed system, the quantity of heat transferred is defined by the amount of adiabatic work that would be needed to effect the change in the system that is occasioned by the heat transfer. In experimental practice, heat transfer is often estimated calorimetrically, through change of temperature of a known quantity of calorimetric material substance.
Energy can also be transferred to or from a system through transfer of matter. The possibility of such transfer defines the system as an open system, as opposed to a closed system. By definition, such transfer is neither as work nor as heat.
Changes in the potential energy of a body as a whole with respect to forces in its surroundings, and in the kinetic energy of the body moving as a whole with respect to its surroundings, are by definition excluded from the body's cardinal energy (examples are internal energy and enthalpy). | 0 | Theoretical and Fundamental Chemistry |
During the Renaissance, Leonardo da Vinci was well known for his experimental skills. His notes provide precise depictions of various phenomena, including vessels, jets, hydraulic jumps, eddy formation, tides, as well as designs for both low drag (streamlined) and high drag (parachute) configurations. Da Vinci is also credited for formulating the conservation of mass in one-dimensional steady flow. | 1 | Applied and Interdisciplinary Chemistry |
The role of inflammation in cancer is not well understood. Some organs of the body show greater risk of cancer when they are chronically inflamed. While there is an association between increased levels of C-reactive protein and risk of developing cancer, there is no association between genetic polymorphisms influencing circulating levels of CRP and cancer risk.
In a 2004 prospective cohort study on colon cancer risk associated with CRP levels, people with colon cancer had higher average CRP concentrations than people without colon cancer. It can be noted that the average CRP levels in both groups were well within the range of CRP levels usually found in healthy people. However, these findings may suggest that low inflammation level can be associated with a lower risk of colon cancer, concurring with previous studies that indicate anti-inflammatory drugs could lower colon cancer risk. | 1 | Applied and Interdisciplinary Chemistry |
The Flood Estimation Handbook was published in 1999 and replaces the FSR. It is based on the percentage runoff equation:
where PR is percentage runoff, PIMP is percentage imperviousness of the catchment, SOIL is the soil index and UCWI is urban catchment wetness index. | 1 | Applied and Interdisciplinary Chemistry |
Buffering Mechanisms such as molecular titration can generate ultrasensitivity. In vitro, this can be observed for the simple mechanism:
Where the monomeric form of A is active and it can be inactivated by binding B to form the heterodimer AB. When the concentration of ( = [B] + [AB]) is much greater than the , this system exhibits a threshold determined by the concentration of . At concentrations of ( = [A] +[AB]), lower than , B acts as a buffer to free A and nearly all A will be found as AB. However, at the equivalence point, when ≈ , can no longer buffer the increase in , so a small increase in causes a large increase in A. The strength of the ultrasensitivity of [A] to changes in is determined by /. Ultrasensitivity occurs when this ratio is greater than one and is increased as the ratio increases. Above the equivalence point, and A are again linearly related.
In vivo, the synthesis of A and B as well as the degradation of all three components complicates generation of ultrasensitivity. If the synthesis rates of A and B are equal this system still exhibits ultrasensitivity at the equivalence point.
One example of a buffering mechanism is protein sequestration, which is a common mechanism found in signalling and regulatory networks. In 2009, Buchler and Cross constructed a synthetic genetic network that was regulated by protein sequestration of a transcriptional activator by a dominant-negative inhibitor. They showed that this system results in a flexibile ultrasensitive response in gene expression. It is flexible in that the degree of ultrasensitivity can be altered by changing expression levels of the dominant-negative inhibitor. Figure 1 in their article illustrates how an active transcription factor can be sequestered by an inhibitor into the inactive complex AB that is unable to bind DNA. This type of mechanism results in an "all-or-none" response, or ultransensitivy, when the concentration of the regulatory protein increases to the point of depleting the inhibitor. Robust buffering against a response exists below this concentration threshold, and when it is reached any small increase in input is amplified into a large change in output. | 1 | Applied and Interdisciplinary Chemistry |
;Grahams law: This law states that the rate at which gas molecules diffuse is inversely proportional to the square root of the gas density at a constant temperature. Combined with Avogadros law (i.e. since equal volumes have an equal number of molecules) this is the same as being inversely proportional to the root of the molecular weight.
;Daltons law of partial pressures: This law states that the pressure of a mixture of gases simply is the sum of the partial pressures of the individual components. Daltons law is as follows:
:and all component gases and the mixture are at the same temperature and volume
:where P is the total pressure of the gas mixture
:P is the partial pressure or pressure of the component gas at the given volume and temperature.
;Amagats law of partial volumes: This law states that the volume of a mixture of gases (or the volume of the container) simply is the sum of the partial volumes of the individual components. Amagats law is as follows:
:and all component gases and the mixture are at the same temperature and pressure
:where V is the total volume of the gas mixture or the volume of the container,
:V is the partial volume, or volume of the component gas at the given pressure and temperature.
;Henry's law: This states that at constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid. The equation is as follows:
;Real gas law: This was formulated by Johannes Diderik van der Waals in 1873. | 0 | Theoretical and Fundamental Chemistry |
In waters of the U.S., Canada and other countries, water quality is monitored to protect the health of the general public. Bacteria contamination is one monitored pollutant. In the U.S., fecal coliform testing is one of the nine tests of water quality that form the overall water-quality rating in a process used by U.S. EPA. The fecal coliform assay should only be used to assess the presence of fecal matter in situations where fecal coliforms of non-fecal origin are not commonly encountered. EPA has approved a number of different methods to analyze samples for bacteria. | 0 | Theoretical and Fundamental Chemistry |
Orange peel contains a compound called limonene which is a hydrocarbon compound similar to the rubber that can be used to make balloons. Based on "like dissolves like" principle, rubber balloons can be dissolved by limonene, popping the balloon. If the balloon is vulcanized (hardened with sulfur), the balloon will not pop. | 1 | Applied and Interdisciplinary Chemistry |
Lavoisier urged the establishment of a Royal Commission on Agriculture. He then served as its Secretary and spent considerable sums of his own money in order to improve the agricultural yields in the Sologne, an area where farmland was of poor quality. The humidity of the region often led to a blight of the rye harvest, causing outbreaks of ergotism among the population. In 1788 Lavoisier presented a report to the Commission detailing ten years of efforts on his experimental farm to introduce new crops and types of livestock. His conclusion was that despite the possibilities of agricultural reforms, the tax system left tenant farmers with so little that it was unrealistic to expect them to change their traditional practices. | 1 | Applied and Interdisciplinary Chemistry |
Reinforced lipids are lipid molecules in which some of the fatty acids contain deuterium instead of hydrogen. They can be used for the protection of living cells by slowing the chain reaction due to isotope effect on lipid peroxidation. The lipid bilayer of the cell and organelle membranes contain polyunsaturated fatty acids (PUFA) are key components of cell and organelle membranes. Any process that either increases oxidation of PUFAs or hinders their ability to be replaced can lead to serious disease. Correspondingly, use of reinforced lipids that stop the chain reaction of lipid peroxidation has preventive and therapeutic potential. | 1 | Applied and Interdisciplinary Chemistry |
O concentrations in the ocean have decreased since the 1980s. Part of this decrease is due to increased ocean heat content (OHC) from global warming decreasing O solubility. As solubility in surface oceans decreases, O out gasses to the atmosphere. Increased AOU is likely also contributing to declining ocean O concentrations. Changes in AOU in the ocean could be caused by multiple forcings, such as changes in subduction rates, changes in water mass boundaries, initial O from water mass formation, biochemical consumption of O, or changes in eddy mixing. Based on observations, global AOU increase seems to be linked to increasing OHC. | 0 | Theoretical and Fundamental Chemistry |
The concept of DNA computing came about as a way to address storage density issues because of the exploding volumes of data information. Theoretically, a gram of single-stranded DNA is capable of storing over 400 exabytes (order of 10 bytes) of data at a density of two bits per nucleotide. Leonard Adleman is credited with having established the field in 1994. Recently, molecular logic gate systems have been utilized in DNA computing models.
Massey and coworkers constructed photonic DNA molecular logic circuits using cascades of AND, OR, NAND, and NOR molecular logic gates. They used lanthanide complexes as fluorescent markers, and their luminescent outputs were detected by FRET-based devices at the terminals of DNA strands. Works by Campbell et al. on demonstrating NOT, AND, OR, and XNOR logic systems based on DNA crossover tiles, Bader and co. on manipulating the DNA G-quadruplex structure to realize YES, AND, and OR logic operations, and Chatterjee and coworkers on constructing logic gates using reactive DNA hairpins on DNA origami surfaces are some examples that mark the progress in the field of logic gate-based DNA computing. | 0 | Theoretical and Fundamental Chemistry |
Trichloroethyl chloroformate is used in organic synthesis for the introduction of the trichloroethyl chloroformate (Troc) protecting group for amines, thiols and alcohols. It readily cleaves vs other carbamates and can be used in an overall protecting group strategy.
The troc group is traditionally removed via Zn insertion in the presence of acetic acid, resulting in elimination and decarboxylation. | 0 | Theoretical and Fundamental Chemistry |
VUV detectors are compatible with most gas chromatography (GC) manufacturers. The detectors can be connected through a heated transfer line inserted through a punch-out in the GC oven casing. A makeup flow of carrier gas is introduced at the end of the transfer line. Analytes arrive in the flow cell and are exposed to VUV light from a deuterium lamp. Specially coated reflective optics paired with a back-thinned charged coupled device (CCD) enable the collection of high quality VUV absorption data. Figure 1 shows a schematic of the analyte path from GC to VUV detector. | 0 | Theoretical and Fundamental Chemistry |
The elementary example operates under quasi equilibrium conditions. Its main quantum feature is the discrete energy level structure.
More realistic devices operate out of equilibrium possessing friction heat leaks and finite heat flow.
Quantum thermodynamics supplies a dynamical theory required for systems out of equilibrium such as heat engines, thus,
inserting dynamics into thermodynamics.
The theory of open quantum systems constitutes the basic theory. For heat engines a reduced description of the dynamics
of the working substance is sought, tracing out the hot and cold baths.
The starting point is the general Hamiltonian of the combined systems:
and the system Hamiltonian is time dependent.
A reduced description leads to the equation of motion of the system:
where is the density operator describing the state of the working medium and is the generator of dissipative dynamics
which includes the heat transport terms from the baths.
Using this construction, the total change in energy of the sub-system becomes:
leading to the dynamical version of the first law of thermodynamics:
* The power
* Heat currents and .
The rate of entropy production becomes:
The global structure of quantum mechanics is reflected in the derivation of the reduced description.
A derivation which is consistent with the laws of thermodynamics is based on
the weak coupling limit.
A thermodynamical idealization assumes that the system and the baths are uncorrelated, meaning that the total state
of the combined system becomes a tensor product at all times:
Under these conditions the dynamical equations of motion become:
where is the Liouville superoperator described in terms of the system's Hilbert space,
where the reservoirs are described implicitly.
Within the formalism of quantum open system, can take the form of the
Gorini-Kossakowski-Sudarshan-Lindblad (GKS-L) Markovian generator or also known just as Lindblad equation
. Theories beyond the weak coupling regime have been proposed. | 0 | Theoretical and Fundamental Chemistry |
As a liquid is supercooled, the difference in entropy between the liquid and solid phase decreases. By extrapolating the heat capacity of the supercooled liquid below its glass transition temperature, it is possible to calculate the temperature at which the difference in entropies becomes zero. This temperature has been named the Kauzmann temperature.
If a liquid could be supercooled below its Kauzmann temperature, and it did indeed display a lower entropy than the crystal phase, the consequences would be paradoxical. This Kauzmann paradox has been the subject of much debate and many publications since it was first put forward by Walter Kauzmann in 1948.
One resolution of the Kauzmann paradox is to say that there must be a phase transition before the entropy of the liquid decreases. In this scenario, the transition temperature is known as the calorimetric ideal glass transition temperature T. In this view, the glass transition is not merely a kinetic effect, i.e. merely the result of fast cooling of a melt, but there is an underlying thermodynamic basis for glass formation. The glass transition temperature: | 0 | Theoretical and Fundamental Chemistry |
#The genomes of higher eukaryotes contain many ncRNA-derived pseudogenes and repeats. Distinguishing these non-functional copies from functional ncRNA is a formidable challenge.
#Introns are not modeled by covariance models. | 1 | Applied and Interdisciplinary Chemistry |
Thrust-producing flow which passes through an engines thermal cycle is called primary airflow. Using only cycle flow was relatively short-lived as the turbojet engine. Airflow through a propeller or a turbomachine fan is called secondary flow and is not part of the thermal cycle. This use of secondary flow reduces losses and increases the overall efficiency of the propulsion system. The secondary flow may be many times that through the engine. | 1 | Applied and Interdisciplinary Chemistry |
Operons occur primarily in prokaryotes but also rarely in some eukaryotes, including nematodes such as C. elegans and the fruit fly, Drosophila melanogaster. rRNA genes often exist in operons that have been found in a range of eukaryotes including chordates. An operon is made up of several structural genes arranged under a common promoter and regulated by a common operator. It is defined as a set of adjacent structural genes, plus the adjacent regulatory signals that affect transcription of the structural genes. The regulators of a given operon, including repressors, corepressors, and activators, are not necessarily coded for by that operon. The location and condition of the regulators, promoter, operator and structural DNA sequences can determine the effects of common mutations.
Operons are related to regulons, stimulons and modulons; whereas operons contain a set of genes regulated by the same operator, regulons contain a set of genes under regulation by a single regulatory protein, and stimulons contain a set of genes under regulation by a single cell stimulus. According to its authors, the term "operon" is derived from the verb "to operate". | 1 | Applied and Interdisciplinary Chemistry |
The phase diagram of quark matter is not well known, either experimentally or theoretically. A commonly conjectured form of the
phase diagram is shown in the figure to the right. It is applicable to matter in a compact star, where the only relevant thermodynamic potentials are quark chemical potential μ and temperature T.
For guidance it also shows the typical values of μ and T in heavy-ion collisions and in the early universe. For readers who are not familiar with the concept of a chemical potential, it is helpful to think of μ as a measure of the imbalance between quarks and antiquarks in the system. Higher μ means a stronger bias favoring quarks over antiquarks. At low temperatures there are no antiquarks, and then higher μ generally means a higher density of quarks.
Ordinary atomic matter as we know it is really a mixed phase, droplets of nuclear matter (nuclei) surrounded by vacuum, which exists at the low-temperature phase boundary between vacuum and nuclear matter, at μ = 310 MeV and T close to zero. If we increase the quark density (i.e. increase μ) keeping the temperature low, we move into a phase of more and more compressed nuclear matter. Following this path corresponds to burrowing more and more deeply into a neutron star.
Eventually, at an unknown critical value of μ, there is a transition to quark matter. At ultra-high densities we expect to find the color-flavor-locked (CFL) phase of color-superconducting quark matter. At intermediate densities we expect some other phases (labelled "non-CFL quark liquid" in the figure) whose nature is presently unknown. They might be other forms of color-superconducting quark matter, or something different.
Now, imagine starting at the bottom left corner of the phase diagram, in the vacuum where μ = T = 0. If we heat up the system without introducing any preference for quarks over antiquarks, this corresponds to moving vertically upwards along the T axis. At first, quarks are still confined and we create a gas of hadrons (pions, mostly). Then around T = 150 MeV there is a crossover to the quark gluon plasma: thermal fluctuations break up the pions, and we find a gas of quarks, antiquarks, and gluons, as well as lighter particles such as photons, electrons, positrons, etc. Following this path corresponds to travelling far back in time (so to say), to the state of the universe shortly after the big bang (where there was a very tiny preference for quarks over antiquarks).
The line that rises up from the nuclear/quark matter transition and then bends back towards the T axis, with its end marked by a star, is the conjectured boundary between confined and unconfined phases. Until recently it was also believed to be a boundary between phases where chiral symmetry is broken (low temperature and density) and phases where it is unbroken (high temperature and density). It is now known that the CFL phase exhibits chiral symmetry breaking, and other quark matter phases may also break chiral symmetry, so it is not clear whether this is really a chiral transition line. The line ends at the "chiral critical point", marked by a star in this figure, which is a special temperature and density at which striking physical phenomena, analogous to critical opalescence, are expected. (Reference for this section:).
For a complete description of phase diagram it is required that one must have complete understanding of dense, strongly interacting hadronic matter and strongly interacting quark matter from some underlying theory e.g. quantum chromodynamics (QCD). However, because such a description requires the proper understanding of QCD in its non-perturbative regime, which is still far from being completely understood, any theoretical advance remains very challenging. | 0 | Theoretical and Fundamental Chemistry |
Depending on whether an assay just looks at a single time point or timed readings taken at multiple time points, an assay may be:
#An end point assay, in which a single measurement is performed after a fixed incubation period; or
#A kinetic assay, in which measurements are performed multiple times over a fixed time interval. Kinetic assay results may be visualized numerically (for example, as a slope parameter representing the rate of signal change over time), or graphically (for example, as a plot of the signal measured at each time point). For kinetic assays, both the magnitude and shape of the measured response over time provide important information.
#A high throughput assay can be either an endpoint or a kinetic assay usually done on an automated platform in 96-, 384- or 1536-well microplate formats (High Throughput Screening). Such assays are able to test large number of compounds or analytes or make functional biological readouts in response to a stimuli and/or compounds being tested. | 1 | Applied and Interdisciplinary Chemistry |
Figure 4 shows the difference between relative wind stress and resting ocean wind stress. Data for relative wind stress is obtained from scatterometers. These accurately represent the relative wind stress as they measure backscatter from small-scale structures on the ocean surface, which respond to the sea surface-air interface and not to wind speed.
Overestimations of power input into the ocean in models have been identified when using wind stress calculated from zonal mean wind instead of relative wind stress, ranging between 20-35%. In regions where wind speeds are relatively low and current speeds relatively high this effect is the greatest. An example is the tropical Pacific ocean where trade winds blow with 5-9m/s and the ocean current velocities can exceed 1m/s. In this region, depending on if it is an El Niño or La Niña state, the wind stress difference (resting ocean wind stress minus relative wind stress) can vary between negative and positive, respectively. | 1 | Applied and Interdisciplinary Chemistry |
If the drip rate is quicker than one drop per minute, most of the CaCO will be carried to the ground, still in solution. The leachate solution then has a chance to absorb CO from the atmosphere (or degas CO depending on reaction) and deposit the CaCO on the ground as a stalagmite.
In most locations within manmade concrete structures, calthemite stalagmites only grow to a maximum of a few centimetres high, and look like low rounded lumps. This is because of the limited supply of CaCO from the leachate seepage path through the concrete and the amount which reaches the ground. Their location may also inhibit their growth due to abrasion from vehicle tires and pedestrian traffic. | 1 | Applied and Interdisciplinary Chemistry |
Sodium nitrate is used to remove air bubbles from molten glass and some ceramics. Mixtures of the molten salt are used to harden some metals. | 0 | Theoretical and Fundamental Chemistry |
The above describes an ideal wake, where the bodys means of propulsion has no other effect on the water. In practice the wave pattern between the V-shaped wavefronts is usually mixed with the effects of propeller backwash and eddying behind the boats (usually square-ended) stern.
The Kelvin angle is also derived for the case of deep water in which the fluid is not flowing in different speed or directions as a function of depth ("shear"). In cases where the water (or fluid) has shear, the results may be more complicated. Also, the deep water model neglects surface tension, which implies that the wave source is large compared to capillary length. | 1 | Applied and Interdisciplinary Chemistry |
The cause of Tay–Sachs disease is a genetic defect that is passed from parent to child. This genetic defect is located in the HEXA gene, which is found on chromosome 15.
The HEXA gene makes part of an enzyme called beta-hexosaminidase A, which plays a critical role in the nervous system. This enzyme helps break down a fatty substance called GM2 ganglioside in nerve cells.
Mutations in the HEXA gene disrupt the activity of beta-hexosaminidase A, preventing the breakdown of the fatty substances. As a result, the fatty substances accumulate to deadly levels in the brain and spinal cord. The buildup of GM2 ganglioside causes progressive damage to the nerve cells. This is the cause of the signs and symptoms of Tay-Sachs disease. | 1 | Applied and Interdisciplinary Chemistry |
Plasma processing provides interfacial energies and injected monomer fragments larger than comparable processes. However, limited fluxes prevent high process rates. In addition, plasmas are thermodynamically unfavorable and therefore plasma-processed surfaces lack uniformity, consistency, and permanence. These obstacles with plasma processing preclude it from being a competitive surface modification method within industry.
The process begins with production of plasma via ionization either by deposition on monomer mixtures or gaseous carrier ions. The power required to produce the necessary plasma flux can be derived from the active volume mass/energy balance:
where
is the active volume
is the ionization rate
is the neutral density
is the electron density
is the ion loss by diffusion, convection, attachment, and recombination
Dissipation is generally initiated via direct current (DC), radio frequency (RF), or microwave power. Gas ionization efficiency can decrease the power efficiency more than tenfold depending on the carrier plasma and substrate. | 0 | Theoretical and Fundamental Chemistry |
An interstitial defect refers to additional atoms occupying some interstitial sites at random as crystallographic defects in a crystal which normally has empty interstitial sites by default. | 0 | Theoretical and Fundamental Chemistry |
The lipocalins that have been identified as biliproteins have been found in a wide variety of insects, but mainly in the order Lepidoptera. Scientists have discovered them in the large white butterfly and a number of moth and silkmoth species, including the ailanthus and domestic silkmoths, giant silkworm moth, tobacco hawk moth, honeycomb moth, and the puss moth. The biliproteins associated with these insect species are the bilin-binding proteins, biliverdin-binding proteins, bombyrin, lipocalins 1 and 4, insecticyanin, gallerin and CV-bilin respectively. The biliproteins found in the tobacco hawk moth and pussmoth make up a major part of the insects’ haemolymph fluids.
The biliproteins that have been found in other insect orders apart from Lepidoptera still have unknown sequences, and so their lipocalin nature is still open. | 1 | Applied and Interdisciplinary Chemistry |
Samuel Van Leer was a well-known ironmaster and a United States Army officer during the American Revolutionary War. He started a military career with enthusiasm with his neighbor General Anthony Wayne in 1775. His furnace, Reading Furnace in Pennsylvania, supplied cannon and cannonballs for the Continental Army. Van Leers furnace was a center of colonial ironmaking and is associated with the introduction of the Franklin Stove, and the retreat of George Washingtons army following its defeat at the Battle of Brandywine, where they came for musket repairs. The location is listed as a temporary George Washington Headquarter.W Van Leer's children all joined the iron business as well. | 1 | Applied and Interdisciplinary Chemistry |
Radical Polymerization is used in the curing of acrylic resins in the presence of UV in the industry. Light energy from UV breaks apart photoinitiaters, forming radicals. The radical then react with the polymers, forming polymers with radical groups that then react with additional monomers. The monomer chain extends until it reaches another polymer and reacts with the polymer. Polymers will form with monomer bridges between them, thus leading to a cross-linked network. | 0 | Theoretical and Fundamental Chemistry |
TGFB1I1 has been shown to interact with:
* Androgen receptor,
* Dopamine transporter
* Hsp27,
* PTK2B,
* PTK2, and
* PTPN12. | 1 | Applied and Interdisciplinary Chemistry |
Construction is underway for Velocys commercial reference plant incorporating its microchannel Fischer–Tropsch technology; ENVIA Energys Oklahoma City GTL project being built adjacent to Waste Management's East Oak landfill site. The project is being financed by a joint venture between Waste Management, NRG Energy, Ventech and Velocys. The feedstock for this plant will be a combination of landfill gas and pipeline natural gas. | 0 | Theoretical and Fundamental Chemistry |
Jean-Claude Bradley was a chemist who actively promoted Open Science in chemistry, including at the White House, for which he was awarded the Blue Obelisk award in 2007. He coined the term "Open Notebook science". He died in May 2014. A memorial symposium was held July 14, 2014 at Cambridge University, UK.
One outcome of his Open Notebook work is the collection of physicochemical properties of organic compounds he was studying. All of this data he made available as Open data under the CCZero license. For example, in 2009 Bradley et al. published their work on making solubility data of organic compounds available as Open data. Later, the melting point data set he collaborated on with Andrew Lang and Antony Williams was published with Figshare. Both data sets were also made available as books via the Lulu.com self-publishing platform.
He blogged extensively and contributed to at least 25 individual blogs. In an interview in 2008 with Bora Zivkovic titled "Doing Science Publicly", he spoke of his work and online presence. In 2010, he gave an extensive interview about the impact of Open Notebook science with Richard Poynder. | 0 | Theoretical and Fundamental Chemistry |
Peramivir is the cyclopentane derivative designed with a guanidino group replacing the C-4 hydroxyl group of Neu5Ac2en in the active site, with negatively charged carboxylate group and a n-butyl side chain. 1-ethylpropylamide, diethylamide, dipropylamide and 4-morpholinylamide groups all showed excellent inhibitory activity. Changing the cyclopentane ring to a pyrrolidine ring showed high inhibitory activity as well. | 1 | Applied and Interdisciplinary Chemistry |
An aromatic (or aryl) compound contains a set of covalently bound atoms with specific characteristics:
# A delocalized conjugated π system, most commonly an arrangement of alternating single and double bonds
# Coplanar structure, with all the contributing atoms in the same plane
# Contributing atoms arranged in one or more rings
# A number of π delocalized electrons that is even, but not a multiple of 4. That is, 4n + 2 number of π electrons, where n=0, 1, 2, 3, and so on. This is known as Hückel's Rule.
Whereas benzene is aromatic (6 electrons, from 3 double bonds), cyclobutadiene is not, since the number of π delocalized electrons is 4, which of course is a multiple of 4. The cyclobutadienide (2−) ion, however, is aromatic (6 electrons). An atom in an aromatic system can have other electrons that are not part of the system, and are therefore ignored for the 4n + 2 rule. In furan, the oxygen atom is sp² hybridized. One lone pair is in the π system and the other in the plane of the ring (analogous to C-H bond on the other positions). There are 6 π electrons, so furan is aromatic.
Aromatic molecules typically display enhanced chemical stability, compared to similar non-aromatic molecules. A molecule that can be aromatic will tend to alter its electronic or conformational structure to be in this situation. This extra stability changes the chemistry of the molecule. Aromatic compounds undergo electrophilic aromatic substitution and nucleophilic aromatic substitution reactions, but not electrophilic addition reactions as happens with carbon-carbon double bonds.
Many of the earliest-known examples of aromatic compounds, such as benzene and toluene, have distinctive pleasant smells. This property led to the term "aromatic" for this class of compounds, and hence the term "aromaticity" for the eventually discovered electronic property.
The circulating π electrons in an aromatic molecule produce ring currents that oppose the applied magnetic field in NMR. The NMR signal of protons in the plane of an aromatic ring are shifted substantially further down-field than those on non-aromatic sp² carbons. This is an important way of detecting aromaticity. By the same mechanism, the signals of protons located near the ring axis are shifted up-field.
Aromatic molecules are able to interact with each other in so-called π-π stacking: The π systems form two parallel rings overlap in a "face-to-face" orientation. Aromatic molecules are also able to interact with each other in an "edge-to-face" orientation: The slight positive charge of the substituents on the ring atoms of one molecule are attracted to the slight negative charge of the aromatic system on another molecule.
Planar monocyclic molecules containing 4n π electrons are called antiaromatic and are, in general, destabilized. Molecules that could be antiaromatic will tend to alter their electronic or conformational structure to avoid this situation, thereby becoming non-aromatic. For example, cyclooctatetraene (COT) distorts itself out of planarity, breaking π overlap between adjacent double bonds. Relatively recently, cyclobutadiene was discovered to adopt an asymmetric, rectangular configuration in which single and double bonds indeed alternate; there is no resonance and the single bonds are markedly longer than the double bonds, reducing unfavorable p-orbital overlap. This reduction of symmetry lifts the degeneracy of the two formerly non-bonding molecular orbitals, which by Hund's rule forces the two unpaired electrons into a new, weakly bonding orbital (and also creates a weakly antibonding orbital). Hence, cyclobutadiene is non-aromatic; the strain of the asymmetric configuration outweighs the anti-aromatic destabilization that would afflict the symmetric, square configuration. | 0 | Theoretical and Fundamental Chemistry |
Lipid microdomains are formed when lipids undergo lateral phase separations yielding stable coexisting lamellar domains. These phase separations can be induced by changes in temperature, pressure, ionic strength or by the addition of divalent cations or proteins. The question of whether such lipid microdomains observed in model lipid systems also exist in biomembranes had motivated considerable research efforts. Lipid domains are not readily isolated and examined as unique species, in contrast to the examples of lateral heterogeneity.
One can disrupt the membrane and demonstrate a heterogeneous range of composition in the population of the resulting vesicles or fragments. Electron microscopy can also be used to demonstrate lateral inhomogeneities in biomembranes.
Often, lateral heterogeneity has been inferred from biophysical techniques where the observed signal indicates multiple populations rather than the expected homogeneous population. An example of this is the measurement of the diffusion coefficient of a fluorescent lipid analog in soybean protoplasts. Membrane microheterogeneity is sometimes inferred from the behavior of enzymes, where the enzymatic activity does not appear to be correlated with the average lipid physical state exhibited by the bulk of the membrane. Often, the methods suggest regions with different lipid fluidity, as would be expected of coexisting gel and liquid crystalline phases within the biomembrane. This is also the conclusion of a series of studies where differential effects of perturbation caused by cis and trans fatty acids are interpreted in terms of preferential partitioning of the two liquid crystalline and gel-like domains. | 1 | Applied and Interdisciplinary Chemistry |
An evaporative light scattering detector (ELSD) is a destructive chromatography detector, used in conjunction with high-performance liquid chromatography (HPLC), ultra high-performance liquid chromatography (UHPLC), purification liquid chromatography such as flash or preparative chromatography (using a splitter), countercurrent or centrifugal partition chromatography and supercritical fluid chromatography (SFC). It is commonly used for analysis of compounds that do not absorb UV-VIS radiation significantly, such as sugars, antiviral drugs, antibiotics, fatty acids, lipids, oils, phospholipids, polymers, surfactants, terpenoids and triglycerides.
ELSDs works by nebulizing the column's effluents into a fine aerosol mist, which then passes through a heated drift tube, where the solvent evaporates. Thus, it can be easily used in gradient method of LC and SFC. The remaining non-volatile analyte particles are carried further by a carrier gas to a light scattering cell, where a beam of light illuminates them and they scatter it. The scattered light proceeds to a photodiode which converts it to a signal, which is proportional to the mass of the analyte particles. This is why it is considered as a sort of "universal detector" as it is able to detect all compound which are less volatile than the mobile phase, i.e. non volatile and semi-volatile compounds.
ELSD is related to the charged aerosol detector (CAD), in which the aerosol is charged. Like the CAD, it falls under the category of destructive detectors. | 0 | Theoretical and Fundamental Chemistry |
Combustibility is a measure of how easily a substance bursts into flame, through fire or combustion. This is an important property to consider when a substance is used for construction or is being stored. It is also important in processes that produce combustible substances as a by-product. Special precautions are usually required for substances that are easily combustible. These measures may include installation of fire sprinklers or storage remote from possible sources of ignition.
Substances with low combustibility may be selected for construction where the fire risk must be reduced, such as apartment buildings, houses, or offices. If combustible resources are used there is greater chance of fire accidents and deaths. Fire resistant substances are preferred for building materials and furnishings. | 0 | Theoretical and Fundamental Chemistry |
When phospholipids or simple lipids like fatty acids are placed in water, the molecules spontaneously arrange such that the hydrophobic tails are shielded from the water, resulting in the formation of membrane structures such as bilayers, vesicles, and micelles. In modern cells, vesicles are involved in metabolism, transport, buoyancy control, and enzyme storage. They can also act as natural chemical reaction chambers. A typical vesicle or micelle in aqueous solution forms an aggregate with the hydrophilic "head" regions in contact with surrounding solvent, sequestering the hydrophobic single-tail regions in the micelle center. This phase is caused by the packing behavior of single-tail lipids in a bilayer. Although the spontaneous self-assembly process that form lipid monolayer vesicles and micelles in nature resemble the kinds of primordial vesicles or protocells that might have existed at the beginning of evolution, they are not as sophisticated as the bilayer membranes of today's living organisms. However, in a prebiotic context, electrostatic interactions induced by short, positively charged, hydrophobic peptides containing seven amino acids in length or fewer, can attach RNA to a vesicle membrane, the basic cell membrane.
Rather than being made up of phospholipids, early membranes may have formed from monolayers or bilayers of simple fatty acids, which may have formed more readily in a prebiotic environment. Fatty acids have been synthesized in laboratories under a variety of prebiotic conditions and have been found on meteorites, suggesting their natural synthesis in nature. Oleic acid vesicles represent good models of membrane protocells
Cohen et al. (2022) suggest that plausible prebiotic production of fatty acids — leading to the development of early protocell membranes — is enriched on metal-rich mineral surfaces, possibly from impact craters, increasing the prebiotic environmental mass of lipids by 10 times. They evaluate three different possible synthesis pathways of fatty acids in the Hadean, and found that these metal surfaces could produce 10 - 10 kg of 6-18 carbon fatty acids. Of these products, the 8-18C fatty acids are compatible with membrane formation. They also propose that alternative amphiphiles like alcohols are co-synthesized with fatty acid, and can help improve membrane stability. However, despite this production, the authors state that net fatty acid synthesis would not yield sufficient concentrations for spontaneous membrane formation without significant evaporation of Earth's aqueous environments. | 0 | Theoretical and Fundamental Chemistry |
In the determination of hypochlorite (for example in commercial bleach formulations), a direct titration with thiosulfate can be employed without recourse to an iodometric finish.
: ClO + HO + 2e ↔ Cl + 2OH
: O ↔ SO + 2e </u>
: 2SO +ClO +HO ↔ SO +Cl +2OH
Thermometric iodometric titrations employing thiosulfate as a titrant are also practical, for example in the determination of Cu(II). In this instance, it has been found advantageous to incorporate the potassium iodide reagent with the thiosulfate titrant in such proportions that iodine is released into solution just prior to its reduction by thiosulfate. This minimizes iodine losses during the course of the titration. | 0 | Theoretical and Fundamental Chemistry |
Hydrogen probes are used to monitor the penetration of hydrogen into steels, which can cause brittleness, porosity or decarbonization. | 1 | Applied and Interdisciplinary Chemistry |
Since 2019, the energy landscape in the United States has undergone a significant transformation with renewable energy consumption surpassing coal for the first time in more than a century. This shift is indicative of a broader global trend towards renewable energy sources as a result of their decreasing costs and increasing efficiency. | 1 | Applied and Interdisciplinary Chemistry |
The convection–diffusion equation is a combination of the diffusion and convection (advection) equations, and describes physical phenomena where particles, energy, or other physical quantities are transferred inside a physical system due to two processes: diffusion and convection. Depending on context, the same equation can be called the advection–diffusion equation, drift–diffusion equation, or (generic) scalar transport equation. | 1 | Applied and Interdisciplinary Chemistry |
Vitamins that are reducing agents can be pro-oxidants. Vitamin C has antioxidant activity when it reduces oxidizing substances such as hydrogen peroxide, however, it can also reduce metal ions which leads to the generation of free radicals through the Fenton reaction.
::2 Fe + 2 HO → 2 Fe + 2 OH· + 2 OH
:2 Fe + Ascorbate → 2 Fe + Dehydroascorbate
The metal ion in this reaction can be reduced, oxidized, and then re-reduced, in a process called redox cycling that can generate reactive oxygen species.
The relative importance of the antioxidant and pro-oxidant activities of antioxidant vitamins is an area of current research, but vitamin C, for example, appears to have a mostly antioxidant action in the body. However, less data is available for other dietary antioxidants, such as polyphenol antioxidants, zinc, and vitamin E. | 1 | Applied and Interdisciplinary Chemistry |
The ciliate, dasycladacean and Hexamita nuclear code (translation table 6) is a genetic code used by certain ciliate, dasycladacean and Hexamita species.
The ciliate macronuclear code has not been determined completely. The codon UAA is known to code for Gln only in the Oxytrichidae. | 1 | Applied and Interdisciplinary Chemistry |
, there are two different theories on the information processing that occurs on enhancers:
* Enhanceosomes – rely on highly cooperative, coordinated action and can be disabled by single point mutations that move or remove the binding sites of individual proteins.
* Flexible billboards – less integrative, multiple proteins independently regulate gene expression and their sum is read in by the basal transcriptional machinery. | 1 | Applied and Interdisciplinary Chemistry |
The compounds are generally prepared by salt metathesis reactions of alkali-metal cyclopentadienyl compounds with transition metal chlorides. Sodium cyclopentadienide (NaCp) and lithium cyclopentadienide are commonly used. Trimethylsilylcyclopentadiene cyclopentadienylthallium (CpTl) are alternative sources. For the preparation of some particularly robust complexes, e.g. nickelocene, cyclopentadiene is employed in the presence of a conventional base such as KOH. When only a single Cp ligand is installed, the other ligands typically carbonyl, halogen, alkyl, and hydride.
Most Cp complexes are prepared by substitution of preformed Cp complexes by replacement of halide, CO, and other simple ligands. | 0 | Theoretical and Fundamental Chemistry |
In continuum mechanics, an Arruda–Boyce model is a hyperelastic constitutive model used to describe the mechanical behavior of rubber and other polymeric substances. This model is based on the statistical mechanics of a material with a cubic representative volume element containing eight chains along the diagonal directions. The material is assumed to be incompressible. The model is named after Ellen Arruda and Mary Cunningham Boyce, who published it in 1993.
The strain energy density function for the incompressible Arruda–Boyce model is given by
where is the number of chain segments, is the Boltzmann constant, is the temperature in kelvins, is the number of chains in the network of a cross-linked polymer,
where is the first invariant of the left Cauchy–Green deformation tensor, and is the inverse Langevin function which can be approximated by
For small deformations the Arruda–Boyce model reduces to the Gaussian network based neo-Hookean solid model. It can be shown that the Gent model is a simple and accurate approximation of the Arruda–Boyce model. | 0 | Theoretical and Fundamental Chemistry |
Alkyl nitriles are sufficiently acidic to undergo deprotonation of the C-H bond adjacent to the CN group. Strong bases are required, such as lithium diisopropylamide and butyl lithium. The product is referred to as a nitrile anion. These carbanions alkylate a wide variety of electrophiles. Key to the exceptional nucleophilicity is the small steric demand of the CN unit combined with its inductive stabilization. These features make nitriles ideal for creating new carbon-carbon bonds in sterically demanding environments. | 0 | Theoretical and Fundamental Chemistry |
RAFT is one of the most versatile and convenient techniques in this context. The most common RAFT-processes are carried out in the presence of thiocarbonylthio compounds that act as radical buffers.
While in ATRP and NMP reversible deactivation of propagating radical-radical reactions takes place and the dormant structures are a halo-compound in ATRP and the alkoxyamine in NMP, both being a sink for radicals and source at the same time and described by the corresponding equilibria. RAFT on the contrary, is controlled by chain-transfer reactions that are in a deactivation-activation equilibrium. Since no radicals are generated or destroyed an external source of radicals is necessary for initiation and maintenance of the propagation reaction.
;Initiation step of a RAFT polymerization
;Reversible chain transfer
;Reinitiation step
;Chain equilibration step
;Termination step | 0 | Theoretical and Fundamental Chemistry |
Advanced sewage treatment generally involves three main stages, called primary, secondary and tertiary treatment but may also include intermediate stages and final polishing processes. The purpose of tertiary treatment (also called advanced treatment) is to provide a final treatment stage to further improve the effluent quality before it is discharged to the receiving water body or reused. More than one tertiary treatment process may be used at any treatment plant. If disinfection is practiced, it is always the final process. It is also called effluent polishing. Tertiary treatment may include biological nutrient removal (alternatively, this can be classified as secondary treatment), disinfection and removal of micropollutants, such as environmental persistent pharmaceutical pollutants.
Tertiary treatment is sometimes defined as anything more than primary and secondary treatment in order to allow discharge into a highly sensitive or fragile ecosystem such as estuaries, low-flow rivers or coral reefs. Treated water is sometimes disinfected chemically or physically (for example, by lagoons and microfiltration) prior to discharge into a stream, river, bay, lagoon or wetland, or it can be used for the irrigation of a golf course, greenway or park. If it is sufficiently clean, it can also be used for groundwater recharge or agricultural purposes.
Sand filtration removes much of the residual suspended matter. Filtration over activated carbon, also called carbon adsorption, removes residual toxins. Micro filtration or synthetic membranes are used in membrane bioreactors and can also remove pathogens.
Settlement and further biological improvement of treated sewage may be achieved through storage in large human-made ponds or lagoons. These lagoons are highly aerobic, and colonization by native macrophytes, especially reeds, is often encouraged. | 1 | Applied and Interdisciplinary Chemistry |
The complexity of interactions in the human immune system has prompted the generation of a wealth of immunology-related multi-scale omic data. Multi-omic data analysis has been employed to gather novel insights about the immune response to infectious diseases, such as pediatric chikungunya, as well as noncommunicable autoimmune diseases. Integrative omics has also been employed strongly to understand effectiveness and side effects of vaccines, a field called systems vaccinology. For example, multiomics was essential to uncover the association of changes in plasma metabolites and immune system transcriptome on response to vaccination against herpes zoster. | 1 | Applied and Interdisciplinary Chemistry |
A lone pair of electrons resides on the sulfur atom, giving it tetrahedral electron-pair geometry and trigonal pyramidal shape (steric number 4 with one lone pair; see VSEPR theory). When the two organic residues are dissimilar, the sulfur atom is a chiral center, for example, in methyl phenyl sulfoxide. The energy barrier required to invert this stereocenter is sufficiently high that sulfoxides are optically stable near room temperature. That is, the rate of racemization is slow at room temperature. The enthalpy of activation for racemization is in the range 35 - 42 kcal/mol and the corresponding entropy of activation is -8 - +4 cal/mol-K. The barriers are lower for allylic and benzylic substituents. | 0 | Theoretical and Fundamental Chemistry |
Syntrophy, in the context of microbial metabolism, refers to the pairing of multiple species to achieve a chemical reaction that, on its own, would be energetically unfavorable. The best studied example of this process is the oxidation of fermentative end products (such as acetate, ethanol and butyrate) by organisms such as Syntrophomonas. Alone, the oxidation of butyrate to acetate and hydrogen gas is energetically unfavorable. However, when a hydrogenotrophic (hydrogen-using) methanogen is present the use of the hydrogen gas will significantly lower the concentration of hydrogen (down to 10 atm) and thereby shift the equilibrium of the butyrate oxidation reaction under standard conditions (ΔGº’) to non-standard conditions (ΔG’). Because the concentration of one product is lowered, the reaction is "pulled" towards the products and shifted towards net energetically favorable conditions (for butyrate oxidation: ΔGº’= +48.2 kJ/mol, but ΔG = -8.9 kJ/mol at 10 atm hydrogen and even lower if also the initially produced acetate is further metabolized by methanogens). Conversely, the available free energy from methanogenesis is lowered from ΔGº’= -131 kJ/mol under standard conditions to ΔG = -17 kJ/mol at 10 atm hydrogen. This is an example of intraspecies hydrogen transfer. In this way, low energy-yielding carbon sources can be used by a consortium of organisms to achieve further degradation and eventual mineralization of these compounds. These reactions help prevent the excess sequestration of carbon over geologic time scales, releasing it back to the biosphere in usable forms such as methane and . | 1 | Applied and Interdisciplinary Chemistry |
The WGS reaction is used in combination with the solid adsorption of CO in the sorption enhanced water gas shift (SEWGS) in order to produce a high pressure hydrogen stream from syngas. | 0 | Theoretical and Fundamental Chemistry |
Levan is a naturally occurring fructan present in many plants and microorganisms. This polymer is made up of fructose, a monosaccharide sugar, connected by 2,6 beta glycosidic linkages. Levan can have both branched and linear structures of relatively low molecular weight. Branched levan forms a very small, sphere-like structure with basal chains 9 units long. The 2,1 branching allows methyl ethers to form and create a spherical shape. The ends of levan also tend to contain a glucosyl residue. Branched levan tends to be more stable than linear polysaccharides. However, the amount of branching and length of polymerization tends to vary among different species. The shortest levan is 6-kestose, a chain of two fructose molecules and a terminal glucose molecule. | 1 | Applied and Interdisciplinary Chemistry |
In an arrayed screen, each well contains a specific and known sgRNA targeting a specific gene. Arrayed screens therefore allow for detailed profiling of a single cell, but are limited by high costs and the labour required to isolate and culture the high number of individual cell populations. Conventional pooled CRISPR screens are relatively simple and cost effective to perform, but are limited to the study of the entire cell population. This means that rare phenotypes may be more difficult to identify, and only crude phenotypes can be selected for e.g. cell survival, proliferation, or reporter gene expression. | 1 | Applied and Interdisciplinary Chemistry |
Traditionally, SSF has been used in Asian countries to produce Koji using rice to manufacture alcoholic beverages such as Sake or Koji using soybean seeds. The latter produces sauces such as soy sauce or other foods. In Western countries, the traditional manufacturing process of many foods uses SSF. Examples include fermented bakery products such as bread or for the maturing of cheese. SSF is also widely used to prepare raw materials such as chocolate and coffee; typically cacao bean fermentation and coffee bean skin removal are SSF processes carried out under natural tropical conditions. | 1 | Applied and Interdisciplinary Chemistry |
A major mechanism of resistance against piperacillin-tazobactam is Gram-negative bacteria producing β-lactamases. Other currently known mechanisms include mutations in the active site of penicillin-binding proteins, changes in membrane efflux, or bacteria permeability. Some enzymes, such as extended-spectrum β-lactamase (ESBL) have evolved from narrow-spectrum β-lactamases due to genetic mutations, increasing their capabilities to hydrolyze much broader spectrum penicillin. Due to prior conflicting reports on the drug's affinity with ESBL-producing bacteria, piperacillin-tazobactam treatment for such is not recommended. Antibiotic resistance occurs sporadically, conferred by the continuous use of piperacillin-tazobactam in situations where it may prove to be ineffective, leading to cases where plasmid-mediated β-lactamases are being produced in bacteria that do not naturally produce it.
Some Gram-positive bacteria penicillin-binding proteins such as Enterococcus faecium (PBP-5) or Staphylococcus aureus (PBP-2a) are intrinsically antibiotic resistant, consisting of relatively low affinity with piperacillin and therefore high resistance to piperacillin-tazobactam. Furthermore, mutations in penicillin-binding proteins cause fluctuations in piperacillin affinity, whereas Streptococcus pneumoniae (PBP-2b) autolytic response is significantly reduced due to decreased affinity with piperacillin. Although membrane permeability changes are less common as a mechanism of resistance, studies investigating Klebsiella pneumoniae have reported a correlation between decreased permeability of piperacillin and increased SHV-1 β-lactamase production. | 0 | Theoretical and Fundamental Chemistry |
The insertion of alkenes into metal-hydrogen bonds is a key step in hydrogenation and hydroformylation reactions. The reaction involves the alkene and the hydride ligands combining within the coordination sphere of a catalyst. In hydrogenation, the resulting alkyl ligand combines with a second hydride to give the alkane. Analogous reactions apply to the hydrogenation of alkynes: an alkenyl ligand combines with a hydride to eliminate an alkene. | 0 | Theoretical and Fundamental Chemistry |
All methods for assessing druggability are highly dependent on the training sets used to develop them. This highlights an important caveat in all the methods discussed above: which is that they have learned from the successes so far. The training sets are typically either databases of curated drug targets; screened targets databases (ChEMBL, BindingDB, PubChem etc.); or on manually compiled sets of 3D structure known by the developers to be druggable. As training sets improve and expand, the boundaries of druggability may also be expanded. | 1 | Applied and Interdisciplinary Chemistry |
In genetics, an enhancer is a short (50–1500 bp) region of DNA that can be bound by proteins (activators) to increase the likelihood that transcription of a particular gene will occur. These proteins are usually referred to as transcription factors. Enhancers are cis-acting. They can be located up to 1 Mbp (1,000,000 bp) away from the gene, upstream or downstream from the start site. There are hundreds of thousands of enhancers in the human genome. They are found in both prokaryotes and eukaryotes.
The first discovery of a eukaryotic enhancer was in the immunoglobulin heavy chain gene in 1983. This enhancer, located in the large intron, provided an explanation for the transcriptional activation of rearranged Vh gene promoters while unrearranged Vh promoters remained inactive. Lately, enhancers have been shown to be involved in certain medical conditions, for example, myelosuppression. Since 2022, scientists have used artificial intelligence to design synthetic enhancers and applied them in animal systems, first in a cell line, and one year later also in vivo. | 1 | Applied and Interdisciplinary Chemistry |
* L.I. Mandelstam, Zh. Russ. Fiz-Khim., Ova. 58, 381 (1926).
*B.Ya. Zel’dovich, V.I.Popovichev, V.V.Ragulskii and F.S.Faisullov, "Connection between the wavefronts of the reflected and exciting light in stimulated Mandel’shtam Brillouin scattering," Sov. Phys. JETP, 15, 109 (1972) | 0 | Theoretical and Fundamental Chemistry |
Another family of carbenes is based on a cyclopropenylidene core, a three-carbon ring with a double bond between the two atoms adjacent to the carbenic one. This family is exemplified by bis(diisopropylamino)cyclopropenylidene. | 0 | Theoretical and Fundamental Chemistry |
Maltose, cellobiose, and chitobiose are hydrolysis products of the polysaccharides starch, cellulose, and chitin, respectively.
Less common disaccharides include: | 0 | Theoretical and Fundamental Chemistry |
For superalloys operating at high temperatures and exposed to corrosive environments, oxidation behavior is a concern. Oxidation involves chemical reactions of the alloying elements with oxygen to form new oxide phases, generally at the alloy surface. If unmitigated, oxidation can degrade the alloy over time in a variety of ways, including:
* sequential surface oxidation, cracking, and spalling, eroding the alloy over time
* surface embrittlement through the introduction of oxide phases, promoting crack formation and fatigue failure
* depletion of key alloying elements, affecting mechanical properties and possibly compromising performance
Selective oxidation is the primary strategy used to limit these deleterious processes. The ratio of alloying elements promotes formation of a specific oxide phase that then acts as a barrier to further oxidation. Most commonly, aluminum and chromium are used in this role, because they form relatively thin and continuous oxide layers of alumina (AlO) and chromia (CrO), respectively. They offer low oxygen diffusivities, effectively halting further oxidation beneath this layer. In the ideal case, oxidation proceeds through two stages. First, transient oxidation involves the conversion of various elements, especially the majority elements (e.g. nickel or cobalt). Transient oxidation proceeds until the selective oxidation of the sacrificial element forms a complete barrier layer.
The protective effect of selective oxidation can be undermined. The continuity of the oxide layer can be compromised by mechanical disruption due to stress or may be disrupted as a result of oxidation kinetics (e.g. if oxygen diffuses too quickly). If the layer is not continuous, its effectiveness as a diffusion barrier to oxygen is compromised. The stability of the oxide layer is strongly influenced by the presence of other minority elements. For example, the addition of boron, silicon, and yttrium to superalloys promotes oxide layer adhesion, reducing spalling and maintaining continuity.
Oxidation is the most basic form of chemical degradation superalloys may experience. More complex corrosion processes are common when operating environments include salts and sulfur compounds, or under chemical conditions that change dramatically over time. These issues are also often addressed through comparable coatings. | 1 | Applied and Interdisciplinary Chemistry |
The genes and receptor ligands are as follows:
(Hökfelt et al., 2001; Page, 2004; Pennefather et al., 2004; Maggi, 2000) | 1 | Applied and Interdisciplinary Chemistry |
If absorption is a physical process not accompanied by any other physical or chemical process, it usually follows the Nernst distribution law:
:"the ratio of concentrations of some solute species in two bulk phases when it is equilibrium and in contact is constant for a given solute and bulk phases":
The value of constant K depends on temperature and is called partition coefficient. This equation is valid if concentrations are not too large and if the species "x" does not change its form in any of the two phases "1" or "2". If such molecule undergoes association or dissociation then this equation still describes the equilibrium between "x" in both phases, but only for the same form – concentrations of all remaining forms must be calculated by taking into account all the other equilibria.
In the case of gas absorption, one may calculate its concentration by using, e.g., the Ideal gas law, c = p/RT. In alternative fashion, one may use partial pressures instead of concentrations. | 0 | Theoretical and Fundamental Chemistry |
Adding dense material to treatment helps stop sound waves from exiting a source wall, ceiling or floor. Materials include mass-loaded vinyl, drywall, soundproof sheetrock, plywood, fibreboard, concrete or rubber. Different widths and densities in soundproofing material reduce sound within a variable frequency range. | 1 | Applied and Interdisciplinary Chemistry |
In February 1862, Lord Kelvin used the existence of the Sun and the stars as an empirical proof that the universe has not achieved thermodynamic equilibrium, as entropy production and free work are still possible, and there are temperature differences between objects. Helmholtz and Rankine expanded Kelvin's work soon after.
Since there are stars and colder objects, the universe is not in thermodynamic equilibrium, so it cannot be infinitely old. | 0 | Theoretical and Fundamental Chemistry |
Process analytical chemistry (PAC) is the application of analytical chemistry with specialized techniques, algorithms, and sampling equipment for solving problems related to chemical processes. It is a specialized form of analytical chemistry used for process manufacturing similar to process analytical technology (PAT) used in the pharmaceutical industry.
The chemical processes are for production and quality control of manufactured products, and process analytical technology is used to determine the physical and chemical composition of the desired products during a manufacturing process. It is first mentioned in the chemical literature in 1946(1,2). | 0 | Theoretical and Fundamental Chemistry |
Applications of phage display technology include determination of interaction partners of a protein (which would be used as the immobilised phage "bait" with a DNA library consisting of all coding sequences of a cell, tissue or organism) so that the function or the mechanism of the function of that protein may be determined. Phage display is also a widely used method for in vitro protein evolution (also called protein engineering). As such, phage display is a useful tool in drug discovery. It is used for finding new ligands (enzyme inhibitors, receptor agonists and antagonists) to target proteins. The technique is also used to determine tumour antigens (for use in diagnosis and therapeutic targeting) and in searching for protein-DNA interactions using specially-constructed DNA libraries with randomised segments. Recently, phage display has also been used in the context of cancer treatments - such as the adoptive cell transfer approach. In these cases, phage display is used to create and select synthetic antibodies that target tumour surface proteins. These are made into synthetic receptors for T-Cells collected from the patient that are used to combat the disease.
Competing methods for in vitro protein evolution include yeast display, bacterial display, ribosome display, and mRNA display. | 1 | Applied and Interdisciplinary Chemistry |
Long-term storage of radioactive waste requires the stabilization of the waste into a form that will neither react nor degrade for extended periods. It is theorized that one way to do this might be through vitrification. Currently at Sellafield the high-level waste (PUREX first cycle raffinate) is mixed with sugar and then calcined. Calcination involves passing the waste through a heated, rotating tube. The purposes of calcination are to evaporate the water from the waste and de-nitrate the fission products to assist the stability of the glass produced.
The calcine generated is fed continuously into an induction heated furnace with fragmented glass. The resulting glass is a new substance in which the waste products are bonded into the glass matrix when it solidifies. As a melt, this product is poured into stainless steel cylindrical containers ("cylinders") in a batch process. When cooled, the fluid solidifies ("vitrifies") into the glass. After being formed, the glass is highly resistant to water.
After filling a cylinder, a seal is welded onto the cylinder head. The cylinder is then washed. After being inspected for external contamination, the steel cylinder is stored, usually in an underground repository. In this form, the waste products are expected to be immobilized for thousands of years.
The glass inside a cylinder is usually a black glossy substance. All this work (in the United Kingdom) is done using hot cell systems. Sugar is added to control the ruthenium chemistry and to stop the formation of the volatile RuO containing radioactive ruthenium isotopes. In the West, the glass is normally a borosilicate glass (similar to Pyrex), while in the former Soviet Union it is normal to use a phosphate glass. The amount of fission products in the glass must be limited because some (palladium, the other Pt group metals, and tellurium) tend to form metallic phases which separate from the glass. Bulk vitrification uses electrodes to melt soil and wastes, which are then buried underground. In Germany a vitrification plant is in use; this is treating the waste from a small demonstration reprocessing plant which has since been closed down. | 0 | Theoretical and Fundamental Chemistry |
The first recorded attempt to make copper clad steel wire took place in the early 1860s. Although for over 100 years people had been suggesting various ways of uniting copper and steel, it was not until the period mentioned that Farmer and Milliken tried wrapping a strip of copper about a steel wire. American engineers in 1883 and again in the 1890s made attempts to produce a copper-steel wire, in one instance at least, by electroplating copper on steel.
The Duplex Metals Co. traces its beginning to John Ferreol Monnot between 1900 and 1905. He had been very interested in the work of Mr. Martin in Paris.
:"After several years devoted to experimenting, [he] organized the Duplex Metals Company. Prior to his discovery of the process under which this company operates in producing its copper clad, probably almost every other possible way of welding copper and steel together had been tried by Mr. Monnot, but found useless for the purpose." | 1 | Applied and Interdisciplinary Chemistry |
Argentation chromatography is chromatography using a stationary phase that contains silver salts. Silver-containing stationary phases are well suited for separating organic compounds on the basis of the number and type of alkene groups. The technique is employed for gas chromatography and various types of liquid chromatography, including thin layer chromatography. Analytes containing alkene groups elute more slowly than the analogous compounds lacking alkenes. Separations are also sensitive to the type of alkene. The technique is especially useful in the analysis of fats and fatty acids, which are well known to exist in both saturated and unsaturated (alkene-containing) forms. For example, trans fats, undesirable contaminants in ultra-processed foods, are quantified by argentation chromatography. | 0 | Theoretical and Fundamental Chemistry |
Water has a very high specific heat capacity of 4184 J/(kg·K) at 20 °C (4182 J/(kg·K) at 25 °C) —the second-highest among all the heteroatomic species (after ammonia), as well as a high heat of vaporization (40.65 kJ/mol or 2257 kJ/kg at the normal boiling point), both of which are a result of the extensive hydrogen bonding between its molecules. These two unusual properties allow water to moderate Earth's climate by buffering large fluctuations in temperature. Most of the additional energy stored in the climate system since 1970 has accumulated in the oceans.
The specific enthalpy of fusion (more commonly known as latent heat) of water is 333.55 kJ/kg at 0 °C: the same amount of energy is required to melt ice as to warm ice from −160 °C up to its melting point or to heat the same amount of water by about 80 °C. Of common substances, only that of ammonia is higher. This property confers resistance to melting on the ice of glaciers and drift ice. Before and since the advent of mechanical refrigeration, ice was and still is in common use for retarding food spoilage.
The specific heat capacity of ice at −10 °C is 2030 J/(kg·K) and the heat capacity of steam at 100 °C is 2080 J/(kg·K). | 1 | Applied and Interdisciplinary Chemistry |
There are a number of different dielectric mechanisms, connected to the way a studied medium reacts to the applied field (see the figure illustration). Each dielectric mechanism is centered around its characteristic frequency, which is the reciprocal of the characteristic time of the process. In general, dielectric mechanisms can be divided into relaxation and resonance processes. The most common, starting from high frequencies, are: | 0 | Theoretical and Fundamental Chemistry |
The applications of RNA-Seq are growing day by day. Other new application of RNA-Seq includes detection of microbial contaminants, determining cell type abundance (cell type deconvolution), measuring the expression of TEs and Neoantigen prediction etc. | 1 | Applied and Interdisciplinary Chemistry |
Dexmedetomidine is a highly selective α-adrenergic agonist. It possesses an α:α selectivity ratio of 1620:1, making it eight times more selective for the α-receptor than clonidine. Unlike opioids and other sedatives such as propofol, dexmedetomidine is able to achieve its effects without causing respiratory depression. Dexmedetomidine induces sedation by decreasing activity of noradrenergic neurons in the locus ceruleus in the brain stem, thereby increasing the downstream activity of inhibitory gamma-aminobutyric acid (GABA) neurons in the ventrolateral preoptic nucleus. In contrast, other sedatives like propofol and benzodiazepines directly increase activity of gamma-aminobutyric acid neurons. Through action on this endogenous sleep-promoting pathway the sedation produced by dexmedetomidine more closely mirrors natural sleep (specifically stage 2 non-rapid eye movement sleep), as demonstrated by EEG studies. As such, dexmedetomidine provides less amnesia than benzodiazepines. Dexmedetomidine also has analgesic effects at the spinal cord level and other supraspinal sites. | 0 | Theoretical and Fundamental Chemistry |
Ribozymes (ribonucleic acid enzymes) are RNA molecules that have the ability to catalyze specific biochemical reactions, including RNA splicing in gene expression, similar to the action of protein enzymes. The 1982 discovery of ribozymes demonstrated that RNA can be both genetic material (like DNA) and a biological catalyst (like protein enzymes), and contributed to the RNA world hypothesis, which suggests that RNA may have been important in the evolution of prebiotic self-replicating systems.
The most common activities of natural or in vitro evolved ribozymes are the cleavage (or ligation) of RNA and DNA and peptide bond formation. For example, the smallest ribozyme known (GUGGC-3) can aminoacylate a GCCU-3 sequence in the presence of PheAMP. Within the ribosome, ribozymes function as part of the large subunit ribosomal RNA to link amino acids during protein synthesis. They also participate in a variety of RNA processing reactions, including RNA splicing, viral replication, and transfer RNA biosynthesis. Examples of ribozymes include the hammerhead ribozyme, the VS ribozyme, leadzyme, and the hairpin ribozyme.
Researchers who are investigating the origins of life through the RNA world hypothesis have been working on discovering a ribozyme with the capacity to self-replicate, which would require it to have the ability to catalytically synthesize polymers of RNA. This should be able to happen in prebiotically plausible conditions with high rates of copying accuracy to prevent degradation of information but also allowing for the occurrence of occasional errors during the copying process to allow for Darwinian evolution to proceed.
Attempts have been made to develop ribozymes as therapeutic agents, as enzymes which target defined RNA sequences for cleavage, as biosensors, and for applications in functional genomics and gene discovery. | 0 | Theoretical and Fundamental Chemistry |
Transition metal nitrates form a variety of hydrates. The nitrate anion often binds to the metal, especially for those salts with fewer than six aquo ligands. Nitrates are uncommon in nature, so few minerals are represented here. Hydrated ferrous nitrate has not been characterized crystallographically. | 0 | Theoretical and Fundamental Chemistry |
Oxygen cycle refers to the movement of oxygen through the atmosphere (air), biosphere (plants and animals) and the lithosphere (the Earth’s crust). The oxygen cycle demonstrates how free oxygen is made available in each of these regions, as well as how it is used. The oxygen cycle is the biogeochemical cycle of oxygen atoms between different oxidation states in ions, oxides, and molecules through redox reactions within and between the spheres/reservoirs of the planet Earth. The word oxygen in the literature typically refers to the most common oxygen allotrope, elemental/diatomic oxygen (O), as it is a common product or reactant of many biogeochemical redox reactions within the cycle. Processes within the oxygen cycle are considered to be biological or geological and are evaluated as either a source (O production) or sink (O consumption).
Oxygen is one of the most common elements on Earth and represents a large portion of each main reservoir. By far the largest reservoir of Earths oxygen is within the silicate and oxide minerals of the crust and mantle (99.5% by weight). The Earths atmosphere, hydrosphere, and biosphere together hold less than 0.05% of the Earth's total mass of oxygen. Besides O, additional oxygen atoms are present in various forms spread throughout the surface reservoirs in the molecules of biomass, HO, CO, HNO, NO, NO, CO, HO, O, SO, HSO, MgO, CaO, Al2O3, SiO, and PO. | 0 | Theoretical and Fundamental Chemistry |
Lees father was a painter in Taiwan. His mother was an elementary school teacher, and his elder brother, Yuan-Chuan Lee, has been a professor in at Johns Hopkins University for 40 years, awarded the honor Special Chair Lectureship in Academia Sinica in Taiwan. Besides, his younger brother, Yuan-Pern Lee, also awarded this honor. Lees sister, Chi-Mei Lee has served as a professor in National Chung Hsing University.
In 2003, he was one of 22 Nobel Laureates who signed the Humanist Manifesto. | 0 | Theoretical and Fundamental Chemistry |
Levamlodipine (INN), also known as levoamlodipine or S-amlodipine is a pharmacologically active enantiomer of amlodipine. Amlodipine belongs to the dihydropyridine group of calcium channel blocker used as an antihypertensive and antianginal agent. It was approved by the U.S. FDA in December 2019 and is currently marketed under the brand name Conjupri. | 0 | Theoretical and Fundamental Chemistry |
* "Disintegration of the Radioactive Elements" Harpers Monthly Magazine,' January 1904, pages 279 to 284. | 1 | Applied and Interdisciplinary Chemistry |
Capillary flow porometry, also known as porometry, is a characterization technique based on the displacement of a wetting liquid from the sample pores by applying a gas at increasing pressure. It is widely used to measure minimum, maximum (or first bubble point) and mean flow pore sizes, and pore size distribution of the through pores in membranes nonwovens, paper, filtration and ultrafiltration media, hollow fibers, ceramics, etc.
In capillary flow porometry an inert gas is used to displace a liquid, which is in the pores. The pressure required to empty the pore corresponds to the pressure necessary to evacuate the liquid from the most constricted part of the pore. This most constricted part is the most challenging one and it offers the highest resistance to remove the wetting liquid. This parameter is very relevant in filtration and similar applications since it is important to know the smallest diameter of the through pores. | 1 | Applied and Interdisciplinary Chemistry |
Organoberyllium structures can consist of an aryl, dineopentylberyllium, beryllocene, phenyl, or terphenyl. | 0 | Theoretical and Fundamental Chemistry |
The fluorescent particles used in FCS are small and thus experience thermal motions in solution. The simplest FCS experiment is thus normal 3D diffusion, for which the autocorrelation is:
where is the ratio of axial to radial radii of the measurement volume, and is the characteristic residence time. This form was derived assuming a Gaussian measurement volume. Typically, the fit would have three free parameters—G(0), , and —from which the diffusion coefficient and fluorophore concentration can be obtained.
With the normalization used in the previous section, G(0) gives the mean number of diffusers in the volume <N>, or equivalently—with knowledge of the observation volume size—the mean concentration:
where the effective volume is found from integrating the Gaussian form of the measurement volume and is given by:
: D gives the diffusion coefficient: | 0 | Theoretical and Fundamental Chemistry |
Elongation of the polypeptide chain involves addition of amino acids to the carboxyl end of the growing chain. The growing protein exits the ribosome through the polypeptide exit tunnel in the large subunit.
Elongation starts when the fMet-tRNA enters the P site, causing a conformational change which opens the A site for the new aminoacyl-tRNA to bind. This binding is facilitated by elongation factor-Tu (EF-Tu), a small GTPase. For fast and accurate recognition of the appropriate tRNA, the ribosome utilizes large conformational changes (conformational proofreading).
Now the P site contains the beginning of the peptide chain of the protein to be encoded and the A site has the next amino acid to be added to the peptide chain. The growing polypeptide connected to the tRNA in the P site is detached from the tRNA in the P site and a peptide bond is formed between the last amino acids of the polypeptide and the amino acid still attached to the tRNA in the A site. This process, known as peptide bond formation, is catalyzed by a ribozyme (the 23S ribosomal RNA in the 50S ribosomal subunit). Now, the A site has the newly formed peptide, while the P site has an uncharged tRNA (tRNA with no amino acids). The newly formed peptide in the A site tRNA is known as dipeptide and the whole assembly is called dipeptidyl-tRNA. The tRNA in the P site minus the amino acid is known to be deacylated. In the final stage of elongation, called translocation, the deacylated tRNA (in the P site) and the dipeptidyl-tRNA (in the A site) along with its corresponding codons move to the E and P sites, respectively, and a new codon moves into the A site. This process is catalyzed by elongation factor G (EF-G). The deacylated tRNA at the E site is released from the ribosome during the next A-site occupation by an aminoacyl-tRNA again facilitated by EF-Tu.
The ribosome continues to translate the remaining codons on the mRNA as more aminoacyl-tRNA bind to the A site, until the ribosome reaches a stop codon on mRNA(UAA, UGA, or UAG).
The translation machinery works relatively slowly compared to the enzyme systems that catalyze DNA replication. Proteins in bacteria are synthesized at a rate of only 18 amino acid residues per second, whereas bacterial replisomes synthesize DNA at a rate of 1000 nucleotides per second. This difference in rate reflects, in part, the difference between polymerizing four types of nucleotides to make nucleic acids and polymerizing 20 types of amino acids to make proteins. Testing and rejecting incorrect aminoacyl-tRNA molecules takes time and slows protein synthesis. In bacteria, translation initiation occurs as soon as the 5' end of an mRNA is synthesized, and translation and transcription are coupled. This is not possible in eukaryotes because transcription and translation are carried out in separate compartments of the cell (the nucleus and cytoplasm). | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.