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Macromolecular structures can be determined from protein crystal using a variety of methods, including X-Ray Diffraction/X-ray crystallography, Cryogenic Electron Microscopy (CryoEM) (including Electron Crystallography and Microcrystal Electron Diffraction (MicroED)), Small-angle X-ray scattering, and Neutron diffraction. See also Structural biology.
Crystallization of proteins can also be useful in the formulation of proteins for pharmaceutical purposes. | 0 | Theoretical and Fundamental Chemistry |
Red mud, now more frequently termed bauxite residue, is an industrial waste generated during the processing of bauxite into alumina using the Bayer process. It is composed of various oxide compounds, including the iron oxides which give its red colour. Over 95% of the alumina produced globally is through the Bayer process; for every tonne of alumina produced, approximately 1 to 1.5 tonnes of red mud are also produced. Annual production of alumina in 2020 was over 133 million tonnes resulting in the generation of over 175 million tonnes of red mud.
Due to this high level of production and the material's high alkalinity, if not stored properly, it can pose a significant environmental hazard. As a result, significant effort is being invested in finding better methods for safe storage and dealing with it such as waste valorization in order to create useful materials for cement and concrete.
Less commonly, this material is also known as bauxite tailings, red sludge, or alumina refinery residues. | 1 | Applied and Interdisciplinary Chemistry |
The Euler equations in a rotating frame of reference, rotating with an angular velocity is given by
where is the Levi-Civita symbol, is the centrifugal acceleration and is the Coriolis acceleration. | 1 | Applied and Interdisciplinary Chemistry |
The Eötvös rule, named after the Hungarian physicist Loránd (Roland) Eötvös (1848–1919) enables the prediction of the surface tension of an arbitrary liquid pure substance at all temperatures. The density, molar mass and the critical temperature of the liquid have to be known. At the critical point the surface tension is zero.
The first assumption of the Eötvös rule is:
1. The surface tension is a linear function of the temperature.
:This assumption is approximately fulfilled for most known liquids. When plotting the surface tension versus the temperature a fairly straight line can be seen which has a surface tension of zero at the critical temperature.
The Eötvös rule also gives a relation of the surface tension behaviour of different liquids in respect to each other:
2. The temperature dependence of the surface tension can be plotted for all liquids in a way that the data collapses to a single master curve. To do so either the molar mass, the density, or the molar volume of the corresponding liquid has to be known.
More accurate versions are found on the main page for surface tension. | 0 | Theoretical and Fundamental Chemistry |
The waste product was allowed to cool in the hearth and removed as a "mosser". In the Furness district they were often left as the capstone of a wall, particularly near Spark Bridge and Nibthwaite forges. | 1 | Applied and Interdisciplinary Chemistry |
Peptide computing is a form of computing which uses peptides, instead of traditional electronic components. The basis of this computational model is the affinity of antibodies towards peptide sequences. Similar to DNA computing, the parallel interactions of peptide sequences and antibodies have been used by this model to solve a few NP-complete problems. Specifically, the hamiltonian path problem (HPP) and some versions of the set cover problem are a few NP-complete problems which have been solved using this computational model so far. This model of computation has also been shown to be computationally universal (or Turing complete).
This model of computation has some critical advantages over DNA computing. For instance, while DNA is made of four building blocks, peptides are made of twenty building blocks. The peptide-antibody interactions are also more flexible with respect to recognition and affinity than an interaction between a DNA strand and its reverse complement. However, unlike DNA computing, this model is yet to be practically realized. The main limitation is the availability of specific monoclonal antibodies required by the model. | 1 | Applied and Interdisciplinary Chemistry |
In biological systems, phosphorus can be found as free phosphate anions in solution (inorganic phosphate) or bound to organic molecules as various organophosphates.
Inorganic phosphate is generally denoted P and at physiological (homeostatic) pH primarily consists of a mixture of and ions. At a neutral pH, as in the cytosol (pH = 7.0), the concentrations of the orthophoshoric acid and its three anions have the ratios
Thus, only and ions are present in significant amounts in the cytosol (62% , 38% ). In extracellular fluid (pH = 7.4), this proportion is inverted (61% , 39% ).
Inorganic phosphate can also be present as pyrophosphate anions , which give orthophosphate by hydrolysis:
: + HO 2
Organic phosphates are commonly found in the form of esters as nucleotides (e.g. AMP, ADP, and ATP) and in DNA and RNA. Free orthophosphate anions can be released by the hydrolysis of the phosphoanhydride bonds in ATP or ADP. These phosphorylation and dephosphorylation reactions are the immediate storage and source of energy for many metabolic processes. ATP and ADP are often referred to as high-energy phosphates, as are the phosphagens in muscle tissue. Similar reactions exist for the other nucleoside diphosphates and triphosphates. | 0 | Theoretical and Fundamental Chemistry |
When the pipe surfaces roughness height is significant (typically at high Reynolds number), the friction factor departs from the smooth pipe curve, ultimately approaching an asymptotic value ("rough pipe" regime). In this regime, the resistance to flow varies according to the square of the mean flow velocity and is insensitive to Reynolds number. Here, it is useful to employ yet another dimensionless parameter of the flow, the roughness Reynolds number'
where the roughness height is scaled to the pipe diameter .
It is illustrative to plot the roughness function :
Figure 3 shows versus for the rough pipe data of Nikuradse, Shockling, and Langelandsvik.
In this view, the data at different roughness ratio fall together when plotted against , demonstrating scaling in the variable . The following features are present:
* When , then is identically zero: flow is always in the smooth pipe regime. The data for these points lie to the left extreme of the abscissa and are not within the frame of the graph.
* When , the data lie on the line ; flow is in the smooth pipe regime.
* When , the data asymptotically approach a horizontal line; they are independent of , , and .
* The intermediate range of constitutes a transition from one behavior to the other. The data depart from the line very slowly, reach a maximum near , then fall to a constant value.
Afzal's fit to these data in the transition from smooth pipe flow to rough pipe flow employs an exponential expression in that ensures proper behavior for (the transition from the smooth pipe regime to the rough pipe regime):
and
This function shares the same values for its term in common with the Kármán–Prandtl resistance equation, plus one parameter 0.305 or 0.34 to fit the asymptotic behavior for along with one further parameter, 11, to govern the transition from smooth to rough flow. It is exhibited in Figure 3.
The friction factor for another analogous roughness becomes
and
This function shares the same values for its term in common with the Kármán–Prandtl resistance equation, plus one parameter 0.305 or 0.34 to fit the asymptotic behavior for along with one further parameter, 26, to govern the transition from smooth to rough flow.
The Colebrook–White relation fits the friction factor with a function of the form
This relation has the correct behavior at extreme values of , as shown by the labeled curve in Figure 3: when is small, it is consistent with smooth pipe flow, when large, it is consistent with rough pipe flow. However its performance in the transitional domain overestimates the friction factor by a substantial margin. Colebrook acknowledges the discrepancy with Nikuradze's data but argues that his relation is consistent with the measurements on commercial pipes. Indeed, such pipes are very different from those carefully prepared by Nikuradse: their surfaces are characterized by many different roughness heights and random spatial distribution of roughness points, while those of Nikuradse have surfaces with uniform roughness height, with the points extremely closely packed. | 1 | Applied and Interdisciplinary Chemistry |
One important consideration deriving from Kirkendall's work is the presence of pores formed during diffusion. These voids act as sinks for vacancies, and when enough accumulate they can become substantial and expand in an attempt to restore equilibrium. Porosity occurs due to the difference in diffusion rate of the two species.
Pores in metals have ramifications for mechanical, thermal, and electrical properties, and thus control over their formation is often desired. The equation
where is the distance moved by a marker, is a coefficient determined by intrinsic diffusivities of the materials, and is a concentration difference between components, has proven to be an effective model for mitigating Kirkendall porosity. Controlling annealing temperature is another method of reducing or eliminating porosity. Kirkendall porosity typically occurs at a set temperature in a system, so annealing can be performed at lower temperatures for longer times to avoid formation of pores. | 1 | Applied and Interdisciplinary Chemistry |
Leukotriene A4 hydrolase (LTA4H) acts primarily, if not exclusively, to hydrolyze leukotriene A4 (LTA4, i.e. 5S,6S-oxido-7E,9E,11Z,14Z-eicosatetetraenoic acid; IUPAC name 4-<nowiki/>{(2S,3S)-3-[(1E,3E,5Z,8Z)-1,3,5,8-Tetradecatetraen-1-yl]-2-oxiranyl}butanoic acid) to its diol metabolite, leukotriene B4 (LTB4, i.e. 5S,12R-dihydroxy-6Z,8E,10E,14Z-icosatetraenoic acid; IUPA name 5S,6Z,8E,10E,12R,14Z)-5,12-Dihydroxy-6,8,10,14-icosatetraenoic acid). LTB4 is an important recruiter and activator of leukocytes involved in mediation in inflammatory responses and diseases. The enzyme also possess aminopeptidase activity, degrading, for example, the leukocyte chemotactic factor tripeptide, Pro-Gly-Pro (PGP); the function of the aminopeptidase activity of LTA4AH is unknown but has been proposed to be involved in limiting inflammatory reactions caused by this or other aminopeptidase-susceptible peptides. | 1 | Applied and Interdisciplinary Chemistry |
While the JamesonCell continued to expand in base metals concentrate cleaning, SX–EW electrolyte cleaning and coal fines recovery applications, it also found new applications in cleaning potash slimes and was adopted by the Philex Mining Corporation as the sole flotation machine for its Benguet copper concentrator. This is not the normal application for the Cell. No other metals concentrator operates solely using Jameson Cells. | 1 | Applied and Interdisciplinary Chemistry |
Passive transport is a type of membrane transport that does not require energy to move substances across cell membranes. Instead of using cellular energy, like active transport, passive transport relies on the second law of thermodynamics to drive the movement of substances across cell membranes. Fundamentally, substances follow Fick's first law, and move from an area of high concentration to an area of low concentration because this movement increases the entropy of the overall system. The rate of passive transport depends on the permeability of the cell membrane, which, in turn, depends on the organization and characteristics of the membrane lipids and proteins. The four main kinds of passive transport are simple diffusion, facilitated diffusion, filtration, and/or osmosis.
Passive transport follows Fick's first law. | 1 | Applied and Interdisciplinary Chemistry |
It is uncertain whether the use of mechanical closure of the cervical canal following embryo transfer has any effect.
There is considerable evidence that prolonges bed rest (more than 20 minutes) after embryo transfer is associated with reduced chances of clinical pregnancy.
Using hyaluronic acid as an adherence medium for the embryo may increase live birth rates. There may be little or no benefit in having a full bladder, removal of cervical mucus, or flushing of the endometrial or endocervical cavity at the time of embryo transfer. Adjunctive antibiotics in the form of amoxicillin plus clavulanic acid probably does not increase the clinical pregnancy rate compared with no antibiotics. The use of Atosiban, G-CSF and hCG around the time of embryo transfer showed a trend towards increased clinical pregnancy rate.
For frozen-thawed embryo transfer or transfer of embryo from egg donation, no previous ovarian hyperstimulation is required for the recipient before transfer, which can be performed in spontaneous ovulatory cycles. Still, various protocols exist for frozen-thawed embryo transfers as well, such as protocols with ovarian hyperstimulation, protocols in which the endometrium is artificially prepared by estrogen and/or progesterone. There is some evidence that in cycles where the endometrium is artificially prepared by estrogen or progesterone, it may be beneficial to administer an additional drug that suppresses hormone production by the ovaries such as continuous administration of a gonadotropin releasing hormone agonist (GnRHa). For egg donation, there is evidence of a lower pregnancy rate and a higher cycle cancellation rate when the progesterone supplementation in the recipient is commenced prior to oocyte retrieval from the donor, as compared to commenced day of oocyte retrieval or the day after.
Seminal fluid contains several proteins that interact with epithelial cells of the cervix and uterus, inducing active gestational immune tolerance. There are significantly improved outcomes when women are exposed to seminal plasma around the time of embryo transfer, with statistical significance for clinical pregnancy, but not for ongoing pregnancy or live birth rates with the limited data available. | 1 | Applied and Interdisciplinary Chemistry |
Tre recombinase is an experimental enzyme that in lab tests has removed DNA inserted by HIV from infected cells. Through selective mutation, Cre recombinase which recognizes loxP sites are modified to identify HIV long terminal repeats (loxLTR) instead. As a result, instead of performing Cre-Lox recombination, the new enzyme performs recombination at HIV provirus sites.
The structure of Tre in complex with loxLTR has been resolved (), allowing for analyzing the roles of individual mutations. | 1 | Applied and Interdisciplinary Chemistry |
An orifice plate is a thin plate with a hole in it, which is usually placed in a pipe. When a fluid (whether liquid or gaseous) passes through the orifice, its pressure builds up slightly upstream of the orifice but as the fluid is forced to converge to pass through the hole, the velocity increases and the fluid pressure decreases. A little downstream of the orifice the flow reaches its point of maximum convergence, the vena contracta (see drawing to the right) where the velocity reaches its maximum and the pressure reaches its minimum. Beyond that, the flow expands, the velocity falls and the pressure increases. By measuring the difference in fluid pressure across tappings upstream and downstream of the plate, the flow rate can be obtained from Bernoulli's equation using coefficients established from extensive research.
In general, the mass flow rate measured in kg/s across an orifice can be described as
The volume flow rate measured in m/s is
The overall pressure loss in the pipe due to an orifice plate is lower than the measured differential pressure, typically by a factor of . | 1 | Applied and Interdisciplinary Chemistry |
*Chevalier of the Ordre national de la Légion d'Honneur
*Chevalier of the Ordre National du Mérite
*Officier of the Ordre des Palmes Académiques | 0 | Theoretical and Fundamental Chemistry |
Chloroplasts are considered endosymbiotic Cyanobacteria. Cyanobacteria are sometimes called blue-green algae even though they are prokaryotes. They are a diverse phylum of gram-negative bacteria capable of carrying out photosynthesis. Cyanobacteria also contain a peptidoglycan cell wall, which is thicker than in other gram-negative bacteria, and which is located between their two cell membranes. Like chloroplasts, they have thylakoids within them. On the thylakoid membranes are photosynthetic pigments, including chlorophyll a. Phycobilins are also common cyanobacterial pigments, usually organized into hemispherical phycobilisomes attached to the outside of the thylakoid membranes (phycobilins are not shared with all chloroplasts though). | 0 | Theoretical and Fundamental Chemistry |
Inverse geometry spectrometers at spallation sources include IRIS and OSIRIS at the ISIS neutron source at Rutherford-Appleton, BASIS at the Spallation Neutron Source, and MARS at the Paul Scherrer Institute | 0 | Theoretical and Fundamental Chemistry |
As an example of the usefulness of the first approach, suppose we wish to calculate the distance a cannonball travels when fired with a vertical velocity component and a horizontal velocity component , assuming it is fired on a flat surface. Assuming no use of directed lengths, the quantities of interest are then , the distance travelled, with dimension L, , , both dimensioned as TL, and the downward acceleration of gravity, with dimension TL.
With these four quantities, we may conclude that the equation for the range may be written:
Or dimensionally
from which we may deduce that and , which leaves one exponent undetermined. This is to be expected since we have two fundamental dimensions T and L, and four parameters, with one equation.
However, if we use directed length dimensions, then will be dimensioned as TL, as TL, as L and as TL. The dimensional equation becomes:
and we may solve completely as , and . The increase in deductive power gained by the use of directed length dimensions is apparent.
Huntley's concept of directed length dimensions however has some serious limitations:
* It does not deal well with vector equations involving the cross product,
* nor does it handle well the use of angles as physical variables.
It also is often quite difficult to assign the L, L, L, L, symbols to the physical variables involved in the problem of interest. He invokes a procedure that involves the "symmetry" of the physical problem. This is often very difficult to apply reliably: It is unclear as to what parts of the problem that the notion of "symmetry" is being invoked. Is it the symmetry of the physical body that forces are acting upon, or to the points, lines or areas at which forces are being applied? What if more than one body is involved with different symmetries?
Consider the spherical bubble attached to a cylindrical tube, where one wants the flow rate of air as a function of the pressure difference in the two parts. What are the Huntley extended dimensions of the viscosity of the air contained in the connected parts? What are the extended dimensions of the pressure of the two parts? Are they the same or different? These difficulties are responsible for the limited application of Huntley's directed length dimensions to real problems. | 1 | Applied and Interdisciplinary Chemistry |
The PMCA technology has been used by several groups to understand the molecular mechanism of prion replication, the nature of the infectious agent, the phenomenon of prion strains and species barrier, the effect of cellular components, to detect PrP in tissues and biological fluids and to screen for inhibitors against prion replication. Recent studies by the groups of Supattapone and Ma were able to produce prion replication in vitro by PMCA using purified PrP and recombinant PrP with the sole addition of synthetic polyanions and lipids. These studies have shown that infectious prions can be produced in the absence of any other cellular component and constitute some of the strongest evidence in favor of the prion hypothesis.
Research in 2020 concluded that protein misfolding cyclic amplification could be used to distinguish between two progressive neurodegenerative diseases, Parkinson's disease and multiple system atrophy, being the first process to give an objective diagnosis of Multiple System Atrophy instead of just a differential diagnosis. | 1 | Applied and Interdisciplinary Chemistry |
Order strengthening brought about from the interaction of dislocations with ordered precipitates, forming anti-phase boundaries as dislocations move throughout the crystal, can lead to significant increases in strength and creep resistance. For this reason, order strengthening is often exploited for high-temperature creep resistant superalloys used in turbine blades.
Antiphase domains carry with them a surface energy penalty when compared to the perfect lattice due to their chemical disorder, and the presence of these boundaries impedes dislocation motion throughout the crystal, leading to increased strength under shear stress. Figure 3 below shows the process of an edge dislocation propagating through an ordered particle. As the dislocation moves throughout the particle, lattice planes are displaced from their equilibrium configuration, and A-A bonds and B-B bonds are formed throughout the slip plane. This forms a higher energy state than when compared to the equilibrium A-B bonding configuration, and the change in energy is called the anti-phase boundary energy (APBE). This can increase the degree of strengthening created from precipitation hardening, making it more difficult for cutting to occur, and instead increasing the likelihood of Orowan bowing around the precipitate.
<br />
Figure 3: The process of an edge dislocation moving through an ordered precipitate. In (a), the perfectly ordered particle is shown. In (b), the dislocations has moved through part of the particle. In (c), the dislocation exits the precipitate, leading to an increase in surface energy from increased surface area and a higher-energy bonding configuration.
Order strengthening is often characterized by a ratio of the attractive anti-phase boundary energy (APBE) to the repulsive dislocation energy(Gb): . The degree of order strengthening depends on both this ratio and whether the alloy is in the early or late stages of precipitation. When is low, the trailing dislocation moves far behind the leading dislocations, leading to separate cutting of precipitates as seen in Figure 4a. Alternatively, when is high, the trailing dislocation follows close behind the leading dislocation, leading to common cutting as seen in Figure 4b. During the early stages of precipitation, the increase in shear stress can be expressed as:
for low or
for high where G is the shear modulus, f is the volume fraction of precipitates, r is the radius of the precipitate, and b is the burgers vector of the dislocation.
In the later stages of precipitation, the analogous expressions are:
for low or
for high .
<br />
Figure 4: Dislocation motion around precipitates. | 0 | Theoretical and Fundamental Chemistry |
The molecule has two electrophilic sites, the carbon and the S(VI) center.
CSI has been employed for the preparation of β-lactams, some of which are medicinally important. Thus, alkenes undergo a -cycloaddition to give the sulfonamide. The SOCl group can be removed simply by hydrolysis, leaving the secondary amide.
Other reactions of CSI:
*Cycloaddition to alkynes to give 1,2,3-oxathiazine-2,2-dioxide-6-chlorides.
*Conversion of primary alcohols to carbamates.
*Conversion of carboxylic acids and the acid chlorides into nitriles.
*Preparation of N,N-disubstituted sulfamides, RNSONH
*Preparation of Burgess reagent | 0 | Theoretical and Fundamental Chemistry |
Transcriptional gene regulation process depends on many spatial and temporal factors in the nucleus such as global or local chromatin states, nucleosome positioning, TF binding, enhancer/promoter activities. Variant that alter the function of any of these biological processes may alter the gene regulation and cause phenotypic abnormality. Genetic variants that located in distal regulatory region can affect the binding motif of TFs, chromatin regulators and other distal transcriptional factors, which disturb the interaction between enhancer/silencer and its target gene. | 1 | Applied and Interdisciplinary Chemistry |
Katherine Austin Lathrop (1915 – 2005) was an American nuclear medicine researcher, biochemist and member of the Manhattan Project.
Lathrop conducted pioneer work on the effects of radiation exposure on animals and humans. | 0 | Theoretical and Fundamental Chemistry |
One consequence of geometric strain on both the boron and the porphyrin moieties is unique reactivity. The Brothers group was able to demonstrate reductive coupling, wherein two BX units inside the porphyrin pocket become X-B-B-X, only occurs with X=Br and when the substrates are within the porphyrin pocket. DFT calculations show that for X=Cl or F, the reaction is endothermic and non-spontaneous. However, for X=Br, the reduction is spontaneous, which was consistent with experimental findings. Further, when the same reaction is simulated with two porphyrin halves ((dipyrromethene)BX), it is non-spontaneous even for X=Br, suggesting the steric strain of the porphyrin ring to be the driving force behind the reduction reaction. | 0 | Theoretical and Fundamental Chemistry |
The Mammalian Promoter Database (MPromDb) is a curated database of gene promoters identified from ChIP-seq. The proximal promoter region (upstream of the core-promoter region) contains the cis-regulatory elements of most of the transcription factors (TFs).
Recently, a better approach to annotate active promoters has been demonstrated with a combination of ChIP-seq and computational technique. This technique has been used to find the target genes of TFs in mammalian systems. The MPromDb is based on this technology. Curated promoter sequences for eukaryotic organisms are provided by an EPD database; however, promoter activity information at tissue/ cell centric level is not offered.
The MPromDb data base added active RNAP-II promoters identified after analyzing ten different mouse cell/tissue ChIP-seq experiments performed with RNAP-II antibodies and six different human cell types. The data was acquired by a series of computational methods followed by manual correction to ensure its high level quality. In the newest version of MPromDb, about 507 million uniquely-aligned RNA Pol-II ChIP-seq reads have already been analyzed from 26 different databases, including six human cell-types and 10 distinct mouse cell/tissues. | 1 | Applied and Interdisciplinary Chemistry |
In a chain termination step, the active center disappears, resulting in the termination of chain propagation. This is different from chain transfer in which the active center only shifts to another molecule but does not disappear.
For radical polymerization, termination involves a reaction of two growing polymer chains to eliminate the unpaired electrons of both chains. There are two possibilities.
1. Recombination is the reaction of the unpaired electrons of two chains to form a covalent bond between them. The product is a single polymer molecule with the combined length of the two reactant chains:
* RM° + RM° → P
2. Disproportionation is the transfer of a hydrogen atom from one chain to the other, so that the two product chain molecules are unchanged in length but are no longer free radicals:
* RM° + RM° → P + P
Initiation, propagation and termination steps also occur in chain reactions of smaller molecules. This is not true of the chain transfer and branching steps considered next. | 0 | Theoretical and Fundamental Chemistry |
* Due to its reliance on the ability of the fluid or gas to displace the float, graduations on a given rotameter will only be accurate for a given substance at a given temperature. The main property of importance is the density of the fluid; however, viscosity may also be significant. Floats are ideally designed to be insensitive to viscosity; however, this is seldom verifiable from manufacturers' specifications. Either separate rotameters for different densities and viscosities may be used, or multiple scales on the same rotameter can be used.
*Because operation of a rotameter depends on the force of gravity for operation, a rotameter must be oriented vertically. Significant error can result if the orientation deviates significantly from the vertical.
* Due to the direct flow indication the resolution is relatively poor compared to other measurement principles. Readout uncertainty gets worse near the bottom of the scale. Oscillations of the float and parallax may further increase the uncertainty of the measurement.
* Since the float must be read through the flowing medium, some fluids may obscure the reading. A transducer may be required for electronically measuring the position of the float.
* Rotameters are not easily adapted for reading by machine; although magnetic floats that drive a follower outside the tube are available.
* Rotameters are not generally manufactured in sizes greater than 6 inches/150 mm, but bypass designs are sometimes used on very large pipes. | 1 | Applied and Interdisciplinary Chemistry |
Very small amount of carbon is sufficient to stabilize "ScBC". This compound has a broad composition range, namely ScBC with x ≤ 2.2 and y ≤ 0.44. ScBC has a hexagonal crystal structure with space group P6mmm (No. 199) and lattice constants a, b = 1.45501(15) nm and c = 0.84543(16) nm.
There are 19 atomic sites in the unit cell, which are assigned to one scandium site Sc, 14 boron sites B1–B14 having 100% occupancy, two boron-carbon mixed-occupancy sites B/C15 and B/C16, and two partial-occupancy boron sites B17 and B18. Atomic coordinates, site occupancies and isotropic displacement factors are listed in table VII. Although a very small amount of carbon (less than 2 wt%!) plays an important role in the phase stability, carbon does not have its own sites but shares with boron two interstitial sites B/C15 and B/C16.
There are two inequivalent B icosahedra, I1 and I2, which are constructed by the B1–B5 and B8–B12 sites, respectively. A "tube" is another characteristic structure unit of ScBC. It extends along the c-axis and consists of B13, B14, B17 and B18 sites where B13 and B14 form 6-membered rings. B17 and B18 sites also form 6-membered rings; however, their mutual distances (0.985 Å for B17 and 0.955 Å for B18) are too short for a simultaneous occupation of the neighboring sites. Therefore, boron atoms occupy 2nd neighbor site forming a triangle. The occupancies of B17 and B18 sites should be 50%, but the structure analysis suggests larger values. The crystal structure viewed along the a-axis is shown in figure 20, which suggests that the ScBC is a layered material. Two layers, respectively constructed by the icosahedra I1 and I2, alternatively stack along the c-axis. However, the ScBC crystal is not layered. For example, during arc-melting, ScBC needle crystals violently grow along the c-axis – this never happens in layered compounds. The crystal structure viewed along the c-axis is shown in figure 21a. The icosahedra I1 and I2 form a ring centered by the "tube" shown in figure 21b, which probably governs the properties of the ScBC crystal. B/C15 and B/C16 mixed-occupancy sites interconnect the rings. A structural similarity can be seen between ScBC and BeB.
Figures 22a and b present HRTEM lattice images and electron diffraction patterns taken along the [0001] and [110] crystalline directions, respectively. The HRTEM lattice image of figure 22a reproduces well the (a, b) plane of the crystal structure shown in figure 21a, with the clearly visible rings membered by icosahedra I1 and I2 and centered by the "tube". Figure 22b proves that ScBC does not have layered character but its c-axis direction is built up by the ring-like structure and tubular structures. | 0 | Theoretical and Fundamental Chemistry |
Cell types differentiated from pluripotent stem cells (PSCs) are being evaluated as preclinical in vitro models of Human diseases. Human cell types in a dish provide an alternative to traditional preclinical assays using animal, human immortalized cells or primary cultures from biopsies, which have their limitations. Clinically relevant cell types i.e. cell type affected in diseases are a major focus of research, this includes hepatocytes, Langerhans islet beta-cells, cardiomyocytes and neurons. Drug screen are performed on miniaturized cell culture in multiwell-plates or on a chip. | 1 | Applied and Interdisciplinary Chemistry |
Broaching is a machining operation used to cut keyways into shafts. Electron beam machining (EBM) is a machining process where high-velocity electrons are directed toward a work piece, creating heat and vaporizing the material. Ultrasonic machining uses ultrasonic vibrations to machine very hard or brittle materials. | 1 | Applied and Interdisciplinary Chemistry |
An initial estimate of the toxicity of CYN in 1985 was that an at 24 hours was 64±5 mg of freeze-dried culture/kg of mouse body weight on intraperitoneal injection. A further experiment in 1997 measured the LD as 52 mg/kg at 24 hours and 32 mg/kg at 7 days, however the data suggested that another toxic compound was present in the isolate of sonicated cells used; predictions made by Ohtani et al. about the 24‑hour toxicity were considerably higher, and it was proposed that another metabolite was present to account for the relatively low 24‑hour toxicity level measured.
Because the most likely human route of uptake of CYN is ingestion, oral toxicity experiments were conducted on mice. The oral LD was found to be 4.4-6.9 mg CYN/kg, and in addition to some ulceration of the oesophageal gastric mucosa, symptoms were consistent with that of intraperitoneal dosing. Stomach contents included culture material, which indicated that these LD figures might be overestimated.
Another means of exposure to CYN is related to alterations in the gut microbiome by artificial sweetners. A study including Aspartame conducted at Cedars-Sinai in Los Angeles by Ruchi Mathur, MD detected CYN in the duodenum at levels four times above baseline in Aspartame users, along with alterations in bacterial species. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, a non-covalent interaction differs from a covalent bond in that it does not involve the sharing of electrons, but rather involves more dispersed variations of electromagnetic interactions between molecules or within a molecule. The chemical energy released in the formation of non-covalent interactions is typically on the order of 1–5 kcal/mol (1000–5000 calories per 6.02 molecules). Non-covalent interactions can be classified into different categories, such as electrostatic, π-effects, van der Waals forces, and hydrophobic effects.
Non-covalent interactions are critical in maintaining the three-dimensional structure of large molecules, such as proteins and nucleic acids. They are also involved in many biological processes in which large molecules bind specifically but transiently to one another (see the properties section of the DNA page). These interactions also heavily influence drug design, crystallinity and design of materials, particularly for self-assembly, and, in general, the synthesis of many organic molecules.
The non-covalent interactions may occur between different parts of the same molecule (e.g. during protein folding) or between different molecules and therefore are discussed also as intermolecular forces. | 0 | Theoretical and Fundamental Chemistry |
A single pit in a critical point can cause a great deal of damage. One example is the explosion in Guadalajara, Mexico on 22 April 1992, when gasoline fumes accumulated in sewers destroyed kilometers of streets. The vapors originated from a leak of gasoline through a single hole formed by corrosion between a steel gasoline pipe and a zinc-plated water pipe.
Firearms can also suffer from pitting, most notably in the bore of the barrel when corrosive ammunition is used and the barrel is not cleaned soon afterwards. Deformities in the bore caused by pitting can greatly reduce the firearm's accuracy. To reduce pitting in firearm bores, most modern firearms have a bore lined with chromium.
Pitting corrosion can also help initiate stress corrosion cracking, as happened when a single eyebar on the Silver Bridge in West Virginia, United States failed and killed 46 people on the bridge in December 1967.
In laboratories, pitting corrosion may damage equipment, reducing its performance or longevity. Fume hoods are of particular concern, as the material constitution of their ductwork must suit the primary effluent(s) intended for exhaust. If the chosen vent material is unsuitable for the primary effluent(s), consequent pitting corrosion will prevent the fume hood from effectively containing harmful airborne particles. | 1 | Applied and Interdisciplinary Chemistry |
Ladles can be "lip pour" design, "teapot spout" design, "lip-axis design" or "bottom pour" design:
*For lip pour design the ladle is tilted and the molten metal pours out of the ladle like water from a pitcher.
*The teapot spout design, like a teapot, takes liquid from the base of the ladle and pours it out via a lip-pour spout. Any impurities in the molten metal will form on the top of the metal so by taking the metal from the base of the ladle, the impurities are not poured into the mould. The same idea is behind the bottom pour process.
*Lip-axis ladles have the pivot point of the vessel as close to the tip of the pouring spout as can be practicable. Therefore as the ladle is rotated the actual pouring point has very little movement. Lip-axis pouring is often used on molten metal pouring systems where there is a need to automate the process as much as possible and the operator controls the pouring operation at a remote distance.
*For bottom pour ladles, a stopper rod is inserted into a tapping hole in the bottom of the ladle. To pour metal the stopper is raised vertically to allow the metal to flow out the bottom of the ladle. To stop pouring the stopper rod is inserted back into the drain hole. Large ladles in the steelmaking industry may use slide gates below the taphole.
Ladles can be either open-topped or covered. Covered ladles have a (sometimes removable) dome-shaped lid to contain radiant heat; they lose heat slower than open-topped ladles. Small ladles do not commonly have covers, although a ceramic blanket may be used instead (where available).
Medium and large ladles which are suspended from a crane have a bail which holds the ladle on shafts, called trunnions. To tilt the ladle a gearbox is used and this is typically a worm gear. The gear mechanism may be hand operated with a large wheel or may be operated by an electric motor or pneumatic motor. Powered rotation allows the ladle operator to be moved to a safe distance and control the rotation of the ladle via a pendant or radio remote control. Powered rotation also allows the ladle to have a number of rotation speeds which may be beneficial to the overall casting process. Powered rotation obviously also reduces the effort required by the ladle operator and allows high volumes of molten metal to be transferred and poured for long periods without operator fatigue. Where the ladle is fitted with a manually operated gearbox, the type of gearbox most commonly used is the worm and wheel design because in most practical circumstances, and when correctly maintained it can be considered as "self-locking" and does not need an internal friction brake to regulate the tilting speed of the ladle. Other types of gear system can also be used but they have to be fitted with an additional braking system that can hold the ladle if the operator takes his hand off the hand-wheel.
Lip-axis ladles may also use hydraulic rams to tilt the ladle. The largest ladles are un-geared and are typically poured using a special, two-winch crane, where the main winch carries the ladle while the second winch engages a lug at the bottom of the ladle. Raising the second winch then rotates the ladle on its trunnions.
Ladles are often designed for special purposes such as adding alloys to the molten metal. Ladles may also have porous plugs inserted into the base, so inert gases can be bubbled through the ladle to enhance alloying or metallic treatment practices. | 1 | Applied and Interdisciplinary Chemistry |
Precious metal refining is the separation of precious metals from noble-metalliferous materials. Examples of these materials include used catalysts, electronic assemblies, ores or metal alloys. | 1 | Applied and Interdisciplinary Chemistry |
Nomenclature of Inorganic Chemistry, commonly referred to by chemists as the Red Book, is a collection of recommendations on IUPAC nomenclature, published at irregular intervals by the IUPAC. The last full edition was published in 2005, in both paper and electronic versions. | 0 | Theoretical and Fundamental Chemistry |
Hardy has a considerable number of publications and patents under her name and in collaboration with other scientists.
* The Introduction of Substituted Vinyl Groups. V. A Rearrangement Involving the Migration of an Allyl Group in a Three-Carbon System. Arthur C. Cope and Elizabeth M. Hardy. Publication date: February 1, 1940
* The Introduction of Substituted Vinyl Groups. VI. The Regeneration of Substituted Vinyl Malonic Esters from their Sodium Enolates. Arthur C. Cope and Elizabeth M. Hardy. Publication date: December 1, 1940
* The Rearrangement of Allyl Groups in Three-Carbon Systems. Arthur C. Cope, Corris M. Hofmann and Elizabeth M. Hardy. Publication date: July 1, 1941
* Aminoalcohols and their Esters. Evelyn M. Hancock, Elizabeth M. Hardy, Dorothea Heyl, Mary Elizabeth Wright and Arthur C. Cope. Publication date: October 1, 1944
* Study of the Aqueous Esterification of Anthrahydroquinones. Mario Scalera, William B. Hardy, Elizabeth M. Hardy and Asa W. Joyce. Publication Date:July 1, 1951
* Some new methods for preparing bunte salts. Hans Z. Lecher and Elizabeth M. Hardy. Publication date: April 1, 1955
* Manufacture of sulphuric ester salts of phenols. Hans Z. Lecher, Plainfleld, Mario Scalera, Somerville , Elizabeth M. Hardy, Bound Brook. Patented: June 25, 1946
* Preparation of pentaalkylguanidines. Hans Z. Lecher, Plainfleld, Elizabeth M. Hardy, Bound Brook, Clement L. Kosloski, North Easton. Patented: July 29, 1958
* Trichloromethyl benzenethio-sulfonates. Elizabeth M. Hardy and John F. Hosler, Bound Brook, Glentworth Lamb, Stamford. Patented: March 24, 1959
* Trichloromethyl 2-methoxy-5-phosphono-benzenethiolsulfonate pesticides. Elizabeth M. Hardy, Hohokus Patented: January 16, 1962
* Preparation of s-aryl-thiosulfuric acids. Hans Z. Lecher, Plainfleld, Elizabeth M. Hardy, Bound Brook. Patented: April 12, 1955
* Preparation of s-aryl-thiosulfuric acids. Hans Z. Lecher, Plainfleld, Elizabeth M. Hardy, Bound Brook. Patented: July 5, 1955
* 4-alkylmorpholine sulfur trioxide compounds. Mario Scalera, Somerville, Charles T. Lester, De Kalb, Elizabeth M. Hardy, Bound Brook. Patented: November 30, 1948
* Soluble vat dyes of the acridone series. William B. Hardy and Elizabeth M. Hardy, Bound Brook. Patented: August 18, 1953 | 0 | Theoretical and Fundamental Chemistry |
Phycobilisomes are protein complexes (up to 600 polypeptides) anchored to thylakoid membranes. They are made of stacks of chromophorylated proteins, the phycobiliproteins, and their associated linker polypeptides. Each phycobilisome consists of a core made of allophycocyanin, from which several outwardly oriented rods made of stacked disks of phycocyanin and (if present) phycoerythrin(s) or phycoerythrocyanin. The spectral property of phycobiliproteins are mainly dictated by their prosthetic groups, which are linear tetrapyrroles known as phycobilins including phycocyanobilin, phycoerythrobilin, phycourobilin and phycobiliviolin. The spectral properties of a given phycobilin are influenced by its protein environment. | 0 | Theoretical and Fundamental Chemistry |
It may be used in generic labels and store brands, Benylin DM, Mucinex DM, Camydex-20 tablets, Robitussin, NyQuil, Dimetapp, Vicks, Coricidin, Delsym, TheraFlu, Charcoal D, Cinfatós and others. It has been used in counterfeit medications. | 0 | Theoretical and Fundamental Chemistry |
In polymer science, the side chain of an oligomeric or polymeric offshoot extends from the backbone chain of a polymer. Side chains have noteworthy influence on a polymer's properties, mainly its crystallinity and density. An oligomeric branch may be termed a short-chain branch, and a polymeric branch may be termed a long-chain branch. Side groups are different from side chains; they are neither oligomeric nor polymeric. | 0 | Theoretical and Fundamental Chemistry |
The Laplace pressure is the pressure difference between the inside and the outside of a curved surface that forms the boundary between two fluid regions. The pressure difference is caused by the surface tension of the interface between liquid and gas, or between two immiscible liquids.
The Laplace pressure is determined from the Young–Laplace equation given as
where and are the principal radii of curvature and (also denoted as ) is the surface tension. Although signs for these values vary, sign convention usually dictates positive curvature when convex and negative when concave.
The Laplace pressure is commonly used to determine the pressure difference in spherical shapes such as bubbles or droplets. In this case, = :
For a gas bubble within a liquid, there is only one surface. For a gas bubble with a liquid wall, beyond which is again gas, there are two surfaces, each contributing to the total pressure difference.
If the bubble is spherical and the outer radius differs from the inner radius by a small distance, , we find | 1 | Applied and Interdisciplinary Chemistry |
Managing populations based on minimizing mean kinship values is often an effective way to increase genetic diversity and to avoid inbreeding within captive populations. Kinship is the probability that two alleles will be identical by descent when one allele is taken randomly from each mating individual. The mean kinship value is the average kinship value between a given individual and every other member of the population. Mean kinship values can help determine which individuals should be mated. In choosing individuals for breeding, it is important to choose individuals with the lowest mean kinship values because these individuals are least related to the rest of the population and have the least common alleles. This ensures that rarer alleles are passed on, which helps to increase genetic diversity. It is also important to avoid mating two individuals with very different mean kinship values because such pairings propagate both the rare alleles that are present in the individual with the low mean kinship value as well as the common alleles that are present in the individual with the high mean kinship value. This genetic management technique requires that ancestry is known, so in circumstances where ancestry is unknown, it might be necessary to use molecular genetics such as microsatellite data to help resolve unknowns. | 1 | Applied and Interdisciplinary Chemistry |
Note that the B shot which begins the Schilling test is enough to go a considerable way toward treating B deficiency, so the test is also a partial treatment for B deficiency. Also, the classic Schilling test can be performed at any time, even after full B repletion and correction of the anemia, and it will still show if the cause of the B deficiency was intrinsic-factor related. In fact, some clinicians have suggested that folate and B replacement for several weeks be normally performed before a Schilling test is done, since folate and B deficiencies are both known to interfere with intestinal cell function, and thus cause malabsorption of B on their own, even if intrinsic factor is being made. This state would then tend to cause a false-positive test for both simple B and intrinsic factor-related B malabsorption. Several weeks of vitamin replacement are necessary, before epithelial damage to the G.I. tract from B deficiency is corrected.
Many labs have stopped performing the Schilling test, due to lack of production of the cobalt radioisotopes and labeled-B test substances. Also, injection replacement of B has become relatively inexpensive, and can be self-administered by patients, as well as megadose oral B. Since these are the same treatments which would be administered for most causes of B malabsorption even if the exact cause were identified, the diagnostic test may be omitted without damage to the patient (so long as follow-up treatment and occasional serum B testing is not allowed to lapse).
It is possible for use of other radiopharmaceuticals to interfere with interpretation of the test. | 1 | Applied and Interdisciplinary Chemistry |
The most widely described RNA modification in mammalian viruses is mA, which was first identified in Influenza virus mRNAs, in 1976. The epitranscriptomic analysis of viral transcripts has revealed that mA levels in viral and cellular transcripts are similar. Nevertheless, in some viruses such as adenovirus-2, mA levels are higher in viral mRNAs. As with cellular RNAs, mA is predominantly added in the nucleus by METTL3, with the assistance of several cofactors such as METTL14, WTAP, KIAA1429 and RBM15/RMB15B. A recent study demonstrates the presence of mA in the small T antigen of Merkel cell polyomavirus (MCPyV) in Merkel cell carcinoma, a fatal skin cancer.
Studies of the viral mA mark have mostly been conducted with HIV. Despite the high mutagenic rate of this virus, mA sites have been evolutionarily conserved. This is due to the fact that mA is involved in regulating multiple stages in the HIV life-cycle. In addition to the normal functions mA has in pre-mRNA splicing, nuclear export, mRNA stability and translation; this mark also inhibits the recognition of viral transcripts by Toll-like receptors and RIG-1 receptors. As a result, mA positively influences viral replication. On the other hand, HIV also regulates the addition of the mA mark in a number of cellular mRNAs. For instance, 56 cellular transcripts that only contain mA during HIV infection have been identified. The effect this mark has on cellular transcripts during the course of the viral infection remains unknown.
Even if mA-marked viral transcripts are involved in regulating gene expression of a number of different viruses, the mechanisms by which this happens have not been identified. To date, three possible models have been proposed.
Although METTL3 and METTL14 are mostly localized in the nucleus, they can also be found in the cytoplasm, where they methylate the genomes and transcripts of cytoplasmic RNA viruses. As opposed to nuclear viruses, loss of mA on hepatitis C virus (HCV, a cytoplasmic RNA virus) increases the production of infectious HCV virions, which indicates that in this particular virus the mA mark has a negative effect on virus production. Nevertheless, in other cytoplasmic RNA viruses such as dengue virus and yellow fever virus, mA sites have been selected for during evolution, suggesting that the mA mark is beneficial for these viruses.
Since mA enhances viral replication, mA can be used as a target for antiviral therapy. The major challenge is to target this mark in viral transcripts without causing major effects to the host cells, as normally occurring cellular mA marks will also be depleted. The S-adenosylhomocysteine (SAC) hydrolase inhibitor 3-dezaadenosine (DAA) can be used as an antiviral drug, because it inhibits the addition of mA. However, it is yet to be determined whether this drug has any off-target effects. | 1 | Applied and Interdisciplinary Chemistry |
A xenobiotic-sensing receptor is a receptor that binds xenobiotics. They include the following nuclear receptors:
* Constitutive androstane receptor (CAR)
* Pregnane X receptor (PXR)
CAR and PXR are xenobiotic receptors and they both are members of NR1I nuclear receptor family. The regulate the metabolic pathway for the elimination of cholesterol. However, there is no physiological ligands was identified. Xenobiotic receptors recognize the foreign chemicals and trigger detoxification and metabolism pathways in different host tissues. | 1 | Applied and Interdisciplinary Chemistry |
Peters four-step chemistry is a systematically reduced mechanism for methane combustion, named after Norbert Peters, who derived it in 1985. The mechanism reads as
The mechanism predicted four different regimes where each reaction takes place. The third reaction, known as radical consumption layer, where most of the heat is released, and the first reaction, also known as fuel consumption layer, occur in a narrow region at the flame. The fourth reaction is the hydrogen oxidation layer, whose thickness is much larger than the former two layers. Finally, the carbon monoxide oxidation layer is the largest of them all, corresponding to the second reaction, and oxidizes very slowly. | 0 | Theoretical and Fundamental Chemistry |
A recent study based on molecular simulations and compliance constants describes molecular recognition as a phenomenon of organisation. Even for small molecules like carbohydrates, the recognition process can not be predicted or designed even assuming that each individual hydrogen bond's strength is exactly known. However, as Mobley et al. concluded, the accurate prediction of the molecular recognition events needs to go beyond the static snapshot of a single frame between the guest and the host. Entropies are key contributors to binding thermodynamics and need to be accounted for in order to predict more accurately the recognition process. Entropies are rarely observable in single bound structures (static snapshot). In proteins, highly-specific recognition can be achieved by evolutionary fine-tuning of chemical interactions, conformational changes, and entropy contributions. | 0 | Theoretical and Fundamental Chemistry |
This method is related to the downdraft, but uses a pump to power a spray nozzle, fixed a few inches above the water level. The spray action entraps and shreds the air in the base of the unit, similar to holding your thumb over a garden hose, which then rises to the collection chamber. In the United States, one company has patented the spray induction technology and the commercial product offerings are limited to that single company. | 0 | Theoretical and Fundamental Chemistry |
Besides education, CrysTBox is mainly used in research with fields of application spanning from nuclear research to archaeology and paleontology. Among others, the suite was employed in development of additive manufacturing (including 3D printed biodegradable alloys, metallic glass or high-entropy alloys), resistant coatings, laser shock peening, water cleaning technologies or characterization of 50 million years old flint.
Institutions whose research was supported by CrysTBox include educational facilities such as ETH Zurich, University of California, Uppsala University, Oxford University, University of Waterloo, Indian Institute of Technology, Nanyang Technological University or University of Tokyo as well as research institutes like Max Planck Institutes, Chinese Academy of Sciences, Fraunhofer Institutes or US national laboratories (NL) such as Oak Ridge NL, Lawrence Berkeley NL, Idaho NL and Lawrence Livermoore NL. | 0 | Theoretical and Fundamental Chemistry |
The ability to fix nitrogen in nodules is present in actinorhizal plants such as alder and bayberry, with the help of Frankia bacteria. They are found in 25 genera in the orders Cucurbitales, Fagales and Rosales, which together with the Fabales form a nitrogen-fixing clade of eurosids. The ability to fix nitrogen is not universally present in these families. For example, of 122 Rosaceae genera, only four fix nitrogen. Fabales were the first lineage to branch off this nitrogen-fixing clade; thus, the ability to fix nitrogen may be plesiomorphic and subsequently lost in most descendants of the original nitrogen-fixing plant; however, it may be that the basic genetic and physiological requirements were present in an incipient state in the most recent common ancestors of all these plants, but only evolved to full function in some of them.
In addition, Trema (Parasponia), a tropical genus in the family Cannabaceae, is unusually able to interact with rhizobia and form nitrogen-fixing nodules. | 1 | Applied and Interdisciplinary Chemistry |
The EI-MS spectra were measured in a JEOL JMS-01SG or a JEOL JMS-700 spectrometers, by the electron ionization method, with an electronic accelerating voltage of 75 eV and an ion accelerating voltage of 8 – 10 kV. The direct or reservoir inlet systems were used. The accuracy of the mass number is 0.5. This collection contains ca. 25,000 EI-MS spectra and is being updated. | 0 | Theoretical and Fundamental Chemistry |
The construct-specific detection methods can either be DNA or protein based. DNA based detection looks for a part of the foreign DNA inserted in a GMO. For technical reasons, certain DNA sequences are shared by several GMOs. Protein-based methods detect the product of the transgene, for example the Bt toxin. Since different GMOs may produce the same protein, construct-specific detection can test a sample for several GMOs in one step, but is unable to tell precisely which of the similar GMOs are present. Especially in the USA, protein-based detection is used for the construct-specific approach. | 1 | Applied and Interdisciplinary Chemistry |
PSII is extremely complex, a highly organized transmembrane structure that contains a water splitting complex, chlorophylls and carotenoid pigments, a reaction center (P680), pheophytin (a pigment similar to chlorophyll), and two quinones. It uses the energy of sunlight to transfer electrons from water to a mobile electron carrier in the membrane called plastoquinone:
Plastoquinol, in turn, transfers electrons to cyt bf, which feeds them into PSI. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, the Froude–Krylov force—sometimes also called the Froude–Kriloff force—is a hydrodynamical force named after William Froude and Alexei Krylov. The Froude–Krylov force is the force introduced by the unsteady pressure field generated by undisturbed waves. The Froude–Krylov force does, together with the diffraction force, make up the total non-viscous forces acting on a floating body in regular waves. The diffraction force is due to the floating body disturbing the waves. | 1 | Applied and Interdisciplinary Chemistry |
In the middle of 1960s, DuPont created and patented an industrial process for making fine ferromagnetic particles of chromium dioxide (CrO). The first CrO tapes for data and video appeared in 1968. In 1970, BASF, who would become the main proponent of CrO, launched its chrome cassette production; in the same year Advent introduced the first cassette deck with chrome capability and Dolby noise reduction. The combination of low noise CrO tape with companding noise reduction brought a revolutionary improvement to compact-cassette sound reproduction, almost reaching the high fidelity level. However, CrO tape required redesign of the bias and replay equalization circuitry. This problem was resolved during the 1970s, but three unsolved issues remained: the cost of making CrO powder, the cost of royalties charged by DuPont, and the pollution effects of hexavalent chromium waste.
The reference CrO tape, approved by the IEC in 1981, is characterized by coercivity of (high bias) and remanence of . Retail CrO cassettes had coercivity in the range from 400 to . Owing to the very clean, uniform shape of the particles, chrome tapes easily attain an almost perfect squareness ratio of 0.90. True chromes, not modified by the addition of ferric additives or coatings, have very low and euphonic hiss (bias noise), and very low modulation noise at high frequencies. Double-layer CrO cassettes have the lowest absolute noise among all the audio formulations; these cassettes generate less noise at than a ferric tape at . Their sensitivity is usually also very high, but MOL is low, on par with basic Type I tapes. CrO tape does not tolerate overload very well: the onset of distortion is sharp and dissonant, so recording levels should be set conservatively, well below MOL. At low frequencies, the MOL of CrO tapes rolls off faster than in ferric or metal tapes, hence the reputation of bass shyness. CrO cassettes are best fit for recording dynamic music with rich harmonic content and relatively low bass levels; their dynamic range is a good fit for recording from uncompressed digital sources and for music with extended quiet passages. Good ferric tapes may have the same or higher treble SOL, but CrO tapes still sound subjectively better owing to lower hiss and modulation noise. | 0 | Theoretical and Fundamental Chemistry |
Even greater in scope than metalloboranes are metallacarboranes. These cages have carbon vertices, often CH, in addition to BH and M vertices. A well-developed class of metallacarboranes are prepared from dicarbollides, anions of the formula [CBH]. These anions function as ligands for a variety of metals, often forming sandwich complexes.
Some metalloboranes are derived by the metalation of neutral carboranes. Illustrative are the six-and seven-vertex cages prepared from closo-. Reaction of this carborane with iron carbonyl sources gives closo Fe- and Fe2-containing products, according to these idealized equations:
A further example of insertion into a closo carborane is the synthesis of the yellow-orange solid closo-1,2,3-:
A closely related reaction involves the capping of an anionic nido carborane
The last reaction is worked up with acid and air. | 0 | Theoretical and Fundamental Chemistry |
A vacuum Rabi oscillation is a damped oscillation of an initially excited atom coupled to an electromagnetic resonator or cavity in which the atom alternately emits photon(s) into a single-mode electromagnetic cavity and reabsorbs them. The atom interacts with a single-mode field confined to a limited volume V in an optical cavity. Spontaneous emission is a consequence of coupling between the atom and the vacuum fluctuations of the cavity field. | 0 | Theoretical and Fundamental Chemistry |
Together with [F]sodium floride, PET for bone imaging has been in use for 60 years for measuring regional bone metabolism and blood flow using static and dynamic scans. Researchers have recently started using [F]sodium floride to study bone metastasis as well. | 1 | Applied and Interdisciplinary Chemistry |
In printing, organic pigments are mainly used in the inks, so the shifting or bleaching of the color of a printing product due to the presence of UV light is usually just a matter of time. The use of organic pigments is justified primarily by their inexpensive cost compared to inorganic pigments. The particle size of the inorganic pigments is often larger than that of organic pigments, thus inorganic pigments are often not suitable to be used in offset printing.
In screen printing, the particle size of the pigment is not the limiting factor. Thus it is the preferred printing method for printing jobs requiring extreme lightfastness. The thickness of the ink layer affects the lightfastness by the amount of pigment laid on the substrate. The ink layer printed by screen printing is thicker than that printed by offset printing. In other words, it contains more pigment per area. This leads to better lightfastness even though the printing ink used in both methods would be based on the same pigment.
When mixing printing inks, the ink with the weaker lightfastness defines the lightfastness of the whole mixed color. The fading of one of the pigments leads to a tone shift towards the component with better lightfastness. If it is required that there will be something visible from the printing, even though its dominant pigment would fade, then a small amount of pigment with excellent lightfastness can be mixed with it. | 0 | Theoretical and Fundamental Chemistry |
Following a similar logic as above, one can derive the kinetic model for thermal conductivity of a dilute gas:
Consider two parallel plates separated by a gas layer. Both plates have uniform temperatures, and are so massive compared to the gas layer that they can be treated as thermal reservoirs. The upper plate has a higher temperature than the lower plate. The molecules in the gas layer have a molecular kinetic energy which increases uniformly with distance above the lower plate. The non-equilibrium energy flow is superimposed on a Maxwell-Boltzmann equilibrium distribution of molecular motions.
Let be the molecular kinetic energy of the gas at an imaginary horizontal surface inside the gas layer. The number of molecules arriving at an area on one side of the gas layer, with speed at angle from the normal, in time interval is
These molecules made their last collision at a distance above and below the gas layer, and each will contribute a molecular kinetic energy of
where is the specific heat capacity. Again, plus sign applies to molecules from above, and minus sign below. Note that the temperature gradient can be considered to be constant over a distance of mean free path.
Integrating over all appropriate velocities within the constraint
yields the energy transfer per unit time per unit area (also known as heat flux):
Note that the energy transfer from above is in the direction, and therefore the overall minus sign in the equation. The net heat flux across the imaginary surface is thus
Combining the above kinetic equation with Fourier's law
gives the equation for thermal conductivity, which is usually denoted when it is a dilute gas:
Similarly to viscosity, Revised Enskog Theory yields an expression for thermal conductivity that reduces to the above expression in the limit of infinite dilution, and which can be written as
where is a term that tends to unity in the limit of infinite dilution, accounting for excluded volume, and is a term accounting for the transfer of energy across a non-zero distance between particles during a collision. | 0 | Theoretical and Fundamental Chemistry |
Certain parent materials also contribute to soil acidification. Granites and their allied igneous rocks are called "acidic" because they have a lot of free quartz, which produces silicic acid on weathering. Also, they have relatively low amounts of calcium and magnesium. Some sedimentary rocks such as shale and coal are rich in sulfides, which, when hydrated and oxidized, produce sulfuric acid which is much stronger than silicic acid. Many coal soils are too acidic to support vigorous plant growth, and coal gives off strong precursors to acid rain when it is burned. Marine clays are also sulfide-rich in many cases, and such clays become very acidic if they are drained to an oxidizing state. | 0 | Theoretical and Fundamental Chemistry |
This test consisted of 85 questions. The first 23 questions numbered 1-23 were classification questions. The next 15 questions, numbered 101-115, were called relationship analysis questions. The SAT Subject Test in Chemistry was currently the only SAT that incorporates the relationship analysis questions. Relationship Analysis Questions required the student to identify the truth value of two statements. If both statements were true, the student would then have to analyze the relationship between the two statements to see if the second statement correctly explained the first statement. The last 47 questions numbered 24-70 were standard multiple choice questions. The metric system of measurement was used, rather than United States customary units. This was widely because students across the world would take SAT Subject Tests, not just Americans. Additionally, many chemists and scientists use the Metric System, considering the entire world uses it as well. | 1 | Applied and Interdisciplinary Chemistry |
While Muslim intellectuals were already acquainted with Greek philosophy (especially logic), al-Kindi is credited with being the first real Muslim philosopher. His own thought was largely influenced by the Neo-Platonic philosophy of Proclus, Plotinus and John Philoponus, amongst others, although he does appear to have borrowed ideas from other Hellenistic schools as well. He makes many references to Aristotle in his writings, but these are often unwittingly re-interpreted in a Neo-Platonic framework. This trend is most obvious in areas such as metaphysics and the nature of God as a causal entity. Experts have suggested that he was influenced by the Mutazilite school of theology, because of the mutual concern both he and they demonstrated for maintaining the singularity (tawhid) of God. A minority view however holds that such agreements are considered incidental. | 1 | Applied and Interdisciplinary Chemistry |
Often parents of children with a developmental disability want to know more about their childs conditions before choosing to have another child. These concerns can be addressed by analysis of the parents and childs DNA. In cases where the childs developmental disability is not understood, the cause of it can potentially be determined using FISH and cytogenetic techniques. Examples of diseases that are diagnosed using FISH include Prader-Willi syndrome, Angelman syndrome, 22q13 deletion syndrome, chronic myelogenous leukemia, acute lymphoblastic leukemia, Cri-du-chat, Velocardiofacial syndrome, and Down syndrome. FISH on sperm cells is indicated for men with an abnormal somatic or meiotic karyotype as well as those with oligozoospermia, since approximately 50% of oligozoospermic men have an increased rate of sperm chromosome abnormalities. The analysis of chromosomes 21, X, and Y is enough to identify oligozoospermic individuals at risk.
In medicine, FISH can be used to form a diagnosis, to evaluate prognosis, or to evaluate remission of a disease, such as cancer. Treatment can then be specifically tailored. A traditional exam involving metaphase chromosome analysis is often unable to identify features that distinguish one disease from another, due to subtle chromosomal features; FISH can elucidate these differences. FISH can also be used to detect diseased cells more easily than standard Cytogenetic methods, which require dividing cells and requires labor and time-intensive manual preparation and analysis of the slides by a technologist. FISH, on the other hand, does not require living cells and can be quantified automatically, a computer counts the fluorescent dots present. However, a trained technologist is required to distinguish subtle differences in banding patterns on bent and twisted metaphase chromosomes. FISH can be incorporated into Lab-on-a-chip microfluidic device. This technology is still in a developmental stage but, like other lab on a chip methods, it may lead to more portable diagnostic techniques. | 1 | Applied and Interdisciplinary Chemistry |
Bacterial food cultures can be divided into starter cultures and probiotics.
Starter cultures have mainly a technological function in the food manufacturing. They are used as food ingredients at one or more stages in the food manufacturing process and develop the desired metabolic activity during the fermentation or ripening process. They contribute to the one or multiple unique properties of a foodstuff especially in regard to taste, flavour, colour, texture, safety, preservation, nutritional value, wholesomeness and/or health benefits.
Probiotics have a functional role, which refers to the ability of certain microbes to confer health benefits to the consumer.
Generally, the bacteria used as starter culture are not the same used as probiotics. There are, however, cases when one bacterium can be used both as starter culture and as probiotic. The scientific community is presently trying to deepen understanding of the roles played by microbes in food processing and human health.
The most important bacteria in food manufacturing are Lactobacillus species, belonging to the group of lactic acid bacteria.
Bacterial food cultures are responsible for the aroma, taste and texture of cheeses and fermented milk products such as yogurts, ayran, doogh, skyr or ymer. They contribute to developing the flavour and colour of such fermented products as salami, pepperoni and dried ham. Lactic acid bacteria converts the unstable malic acid that is naturally present in wine into the stable lactic acid. This malolactic fermentation gives the stability that is characteristic of high-quality wines that improve on storage.
Lactic acid bacteria are also used in food supplements as probiotics which help to restore the balance in human intestinal biota. | 1 | Applied and Interdisciplinary Chemistry |
In the mathematical description it is assumed that no clustering occurs within the alloy. Then, for a binary alloy of the form , e.g. , the standard deviation of the composition is given by:
where is the number of atoms within the excitons' volume, i.e. with being the atoms per volume.
In general, the band gap energy of a semiconducting alloy depends on the composition, i.e. . The band gap energy can be considered to be the fluorescence energy. Therefore, the standard deviation in fluorescence is
As the alloy broadening belongs to the group of inhomogeneous broadenings the line shape of the fluorescence intensity is Gaussian: | 0 | Theoretical and Fundamental Chemistry |
Jiva means "soul" in Jainism, and is also called jivatman. It is a core concept and the fundamental focus of the Jain theology. The soul is believed to be eternal, and a substance that undergoes constant modifications, in every life, after every rebirth of a living being. Jiva consists of pure consciousness in the Jain thought, has innate "free will" that causes it to act but is believed to be intangible and formless. It is the soul that experiences existence and gains knowledge, not mind nor body both believed to a heap of matter. Jain philosophy further believes that the soul is the mechanism of rebirth and karma accumulation. It is the same size in all living beings, such as a human being, a tiny insect and a large elephant. Jiva is everywhere, filling and infused in every minuscule part of the entire loka (realm of existence), according to Jainism. The soul has the potential to reach omniscience and eternal bliss, and end the cycles of rebirth and associated suffering, which is the goal of Jain spirituality.
According to Jain philosophy, this universe consists of infinite jivas or souls that are uncreated and always existing. There are two main categories of souls: un-liberated mundane embodied souls that are still subject to transmigration and rebirths in this samsara due to karmic bondage and the liberated souls that are free from birth and death. All souls are intrinsically pure but are found in bondage with karma since beginning-less time. A soul has to make efforts to eradicate the karmas attain its true and pure form.
10th-century Jain monk Nemichandra describes the soul in Dravyasamgraha:
The qualities of the soul are chetana (consciousness) and upyoga (knowledge and perception). Though the soul experiences both birth and death, it is neither really destroyed nor created. Decay and origin refer respectively to the disappearing of one state and appearing of another state and these are merely the modes of the soul. Thus Jiva with its attributes and modes, roaming in samsara (universe), may lose its particular form and assume a new one. Again this form may be lost and the original acquired.
Jivas are believed to be of two types: stationary and mobile. Illustration of the former are plants, while moving jivas include examples such as human beings, animals, gods, hell beings and insects. Jivas are further classified in Jain philosophy by an assigned number of senses which range from one to five sensory organs. Inert world such as air, fire or clod of dirt, considered non-sensate in contemporary science, are asserted in historic texts of Jainism to be living and with sensory powers. | 1 | Applied and Interdisciplinary Chemistry |
is variable fluorescence. Calculated as = - .
is the ratio of variable fluorescence to maximal fluorescence. Calculated as . This is a measure of the maximum efficiency of PSII (the efficiency if all PSII centres were open). can be used to estimate the potential efficiency of PSII by taking dark-adapted measurements.
measures the efficiency of Photosystem II. Calculated as = . This parameter measures the proportion of light absorbed by PSII that is used in photochemistry. As such, it can give a measure of the rate of linear electron transport and so indicates overall photosynthesis.
(photochemical quenching). Calculated as . This parameter approximates the proportion of PSII reaction centres that are open.
Whilst gives an estimation of the efficiency, and tell us which processes which have altered the efficiency. Closure of reaction centers as a result of a high intensity light will alter the value of . Changes in the efficiency of non-photochemical quenching will alter the ratio . | 0 | Theoretical and Fundamental Chemistry |
A carrier-powered radio is a batteryless radio which "leeches" its power from the incoming electromagnetic wave. A simple circuit (very similar to a crystal set) rectifies the incoming signal and this DC current is then used to power a small transistor amplifier. Typically a strong local station is tuned in to provide power, leaving the listener free to listen to weaker and more distant stations. | 0 | Theoretical and Fundamental Chemistry |
* University of Chicago Board of Governors' Distinguished Performance Award, 2009.
* Fellow of the American Association for the Advancement of Science, 2013.
*Argonne Distinguished Fellow, 2016
* DOE materials sciences research competition for Outstanding Scientific Accomplishments in Solid State Physics, 1987. | 0 | Theoretical and Fundamental Chemistry |
2,2′-Dipyridyldisulfide, sometimes known as DPS, is used for preparing thiols and activating carboxylic acid for coupling reactions, as in the following reaction: | 0 | Theoretical and Fundamental Chemistry |
The only oceanic anoxic event documented from the Jurassic took place during the early Toarcian (~183 Ma). Since no DSDP (Deep Sea Drilling Project) or ODP (Ocean Drilling Program) cores have recovered black shales of this age—there being little or no Toarcian ocean crust remaining—the samples of black shale primarily come from outcrops on land. These outcrops, together with material from some commercial oil wells, are found on all major continents and this event seems similar in kind to the two major Cretaceous examples. | 0 | Theoretical and Fundamental Chemistry |
For superconductors the bosons involved are the so-called Cooper pairs which are quasiparticles formed by two electrons. Hence m = 2m and q = −2e where m and e are the mass of an electron and the elementary charge. It follows from Eq. () that
Integrating Eq. () over a closed loop gives
As in the case of helium we define the vortex strength
and use the general relation
where Φ is the magnetic flux enclosed by the loop. The so-called fluxoid is defined by
In general the values of κ and Φ depend on the choice of the loop. Due to the single-valued nature of the wave function and Eq. () the fluxoid is quantized
The unit of quantization is called the flux quantum
The flux quantum plays a very important role in superconductivity. The earth magnetic field is very small (about 50 μT), but it generates one flux quantum in an area of 6 μm by 6 μm. So, the flux quantum is very small. Yet it was measured to an accuracy of 9 digits as shown in Eq. (). Nowadays the value given by Eq. () is exact by definition.
In Fig. 3 two situations are depicted of superconducting rings in an external magnetic field. One case is a thick-walled ring and in the other case the ring is also thick-walled, but is interrupted by a weak link. In the latter case we will meet the famous Josephson relations. In both cases we consider a loop inside the material. In general a superconducting circulation current will flow in the material. The total magnetic flux in the loop is the sum of the applied flux Φ and the self-induced flux Φ induced by the circulation current | 0 | Theoretical and Fundamental Chemistry |
Gas generation by radiolytic decomposition of hydrogen-containing materials has been an area of concern for the transport and storage of radioactive materials and waste for a number of years. Potentially combustible and corrosive gases can be generated while at the same time, chemical reactions can remove hydrogen, and these reactions can be enhanced by the presence of radiation. The balance between these competing reactions is not well known at this time. | 0 | Theoretical and Fundamental Chemistry |
The saprobic system has a long history in German-language countries. The idea of saprobes to estimate water quality has been foreshadowed by the works of Arthur Hill Hassall (1850) and Ferdinand Julius Cohn (1853). In a series of publications, the Germans botanists Richard Kolkwitz and Maximilian Marsson (1902, 1908, 1909) have developed the saprobic system to judge water quality. They compiled a list of about 300 plant and 500 animal species (excluding fish), and estimated saprobic values for them.
In 1955, H. Knöpp introduced abundance classes, and the calculation of a water quality index was established during the 1950s and 1960s (Pantle & Buck, 1955; Zelinka & Marvan, 1961; Marvan, 1969).
In 2000, the Pantle & Buck technique has been criticized because it requires the surveyed organisms to be identified by genus, something that freshwater ecologists are rarely trained for. Furthermore, it focuses on aquatic organisms that are prevalent in Western Europe, something that hampers water quality assays in Eastern Europe and Asia.
The procedure used in Germany to estimate the saprobic index has been standardized in DIN 38410. | 1 | Applied and Interdisciplinary Chemistry |
These forming processes modify metal or workpiece by deforming the object, that is, without removing any material. Forming is done with a system of mechanical forces and, especially for bulk metal forming, with heat. | 1 | Applied and Interdisciplinary Chemistry |
A reduction–oxidation (redox) equilibrium can be handled in exactly the same way as any other chemical equilibrium. For example,
:Fe + Ce Fe + Ce;
However, in the case of redox reactions it is convenient to split the overall reaction into two half-reactions. In this example
:Fe + e Fe
:Ce + e Ce
The standard free energy change, which is related to the equilibrium constant by
can be split into two components,
The concentration of free electrons is effectively zero as the electrons are transferred directly from the reductant to the oxidant. The standard electrode potential, E for the each half-reaction is related to the standard free energy change by
where n is the number of electrons transferred and F is the Faraday constant. Now, the free energy for an actual reaction is given by
where R is the gas constant and Q a reaction quotient. Strictly speaking Q is a quotient of activities, but it is common practice to use concentrations instead of activities. Therefore:
For any half-reaction, the redox potential of an actual mixture is given by the generalized expression
This is an example of the Nernst equation. The potential is known as a reduction potential. Standard electrode potentials are available in a table of values. Using these values, the actual electrode potential for a redox couple can be calculated as a function of the ratio of concentrations.
The equilibrium potential for a general redox half-reaction (See #Equilibrium constant above for an explanation of the symbols)
:α A + β B... + n e σ S + τ T...
is given by
Use of this expression allows the effect of a species not involved in the redox reaction, such as the hydrogen ion in a half-reaction such as
: + 8 H + 5 e Mn + 4 HO
to be taken into account.
The equilibrium constant for a full redox reaction can be obtained from the standard redox potentials of the constituent half-reactions. At equilibrium the potential for the two half-reactions must be equal to each other and, of course, the number of electrons exchanged must be the same in the two half reactions.
Redox equilibrium play an important role in the electron transport chain. The various cytochromes in the chain have different standard redox potentials, each one adapted for a specific redox reaction. This allows, for example, atmospheric oxygen to be reduced in photosynthesis. A distinct family of cytochromes, the cytochrome P450 oxidases, are involved in steroidogenesis and detoxification. | 0 | Theoretical and Fundamental Chemistry |
There have been a few technical issues that have limited adoption of SFC technology in the past. First of all, is the need to keep a high gas pressure in the operating conditions. High-pressure vessels are expensive and bulky, and special materials are often needed to avoid dissolving gaskets and O-rings in the supercritical fluid. A second drawback is difficulty in maintaining pressure constant (by back-pressure regulation). Whereas liquids are nearly incompressible, so their densities are constant regardless of pressure, supercritical fluids are highly compressible and their physical properties change with pressure – such as the pressure drop across a packed-bed column. Currently, automated backpressure regulators can maintain a constant pressure in the column even if flow rate varies, mitigating this problem. A third drawback is difficulty in gas/liquid separation during collection of product. Upon depressurization, the CO rapidly turns into gas and aerosolizes any dissolved analyte in the process. Cyclone separators have lessened difficulties in gas/liquid separations. | 0 | Theoretical and Fundamental Chemistry |
Consider two coupled ultrasensitive modules, disregarding effects of sequestration of molecular components between layers. In this case, the expression for the system's dose-response curve, , results from the mathematical composition of the functions, , which describe the input/output relationship of isolated modules :
Brown et al. (1997) have shown that the local ultrasensitivity of the different layers combines multiplicatively:
In connection with this result, Ferrell et al. (1997) showed, for Hill-type modules, that the overall cascade global ultrasensitivity had to be less than or equal to the product of the global ultrasensitivity estimations of each cascade's layer,
where and are the Hill coefficient of modules 1 and 2 respectively.
Altszyler et al. (2017) have shown that the cascade's global ultrasensitivity can be analytically calculated:
where and delimited the Hill inputs working range of the composite system, i.e. the input values for the i-layer so that the last layer (corresponding to in this case) reached the 10% and 90% of it maximal output level. It followed this equation that the systems Hill coefficient could be written as the product of two factors, and , which characterized local average sensitivities over the relevant input region for each layer: , with in this case.
For the more general case of a cascade of modules, the Hill coefficient can be expressed as: | 1 | Applied and Interdisciplinary Chemistry |
The anhydrous material crystallizes in the CdCl motif, featuring octahedral coordination geometry at each Ni(II) center. NiI is prepared by dehydration of the pentahydrate.
NiI readily hydrates, and the hydrated form can be prepared by dissolution of nickel oxide, hydroxide, or carbonate in hydroiodic acid. The anhydrous form can be produced by treating powdered nickel with iodine. | 0 | Theoretical and Fundamental Chemistry |
An old style mercury barometer consists of a vertical glass tube about 1 cm in diameter partially filled with mercury, and with a vacuum (called Torricelli's vacuum) in the unfilled volume (see diagram to the right). Notice that the mercury level at the center of the tube is higher than at the edges, making the upper surface of the mercury dome-shaped. The center of mass of the entire column of mercury would be slightly lower if the top surface of the mercury were flat over the entire cross-section of the tube. But the dome-shaped top gives slightly less surface area to the entire mass of mercury. Again the two effects combine to minimize the total potential energy. Such a surface shape is known as a convex meniscus.
We consider the surface area of the entire mass of mercury, including the part of the surface that is in contact with the glass, because mercury does not adhere to glass at all. So the surface tension of the mercury acts over its entire surface area, including where it is in contact with the glass. If instead of glass, the tube was made out of copper, the situation would be very different. Mercury aggressively adheres to copper. So in a copper tube, the level of mercury at the center of the tube will be lower than at the edges (that is, it would be a concave meniscus). In a situation where the liquid adheres to the walls of its container, we consider the part of the fluids surface area that is in contact with the container to have negative' surface tension. The fluid then works to maximize the contact surface area. So in this case increasing the area in contact with the container decreases rather than increases the potential energy. That decrease is enough to compensate for the increased potential energy associated with lifting the fluid near the walls of the container.
If a tube is sufficiently narrow and the liquid adhesion to its walls is sufficiently strong, surface tension can draw liquid up the tube in a phenomenon known as capillary action. The height to which the column is lifted is given by Jurin's law:
where
* is the height the liquid is lifted,
* is the liquid–air surface tension,
* is the density of the liquid,
* is the radius of the capillary,
* is the acceleration due to gravity,
* is the angle of contact described above. If is greater than 90°, as with mercury in a glass container, the liquid will be depressed rather than lifted. | 0 | Theoretical and Fundamental Chemistry |
Axially chiral biaryl compounds are prepared by coupling reactions, e.g., Ullmann coupling, Suzuki–Miyaura reaction, or palladium-catalyzed arylation of arenes. Subsequent to the synthesis, the racemic biaryl is resolved by classical methods. Diastereoselective coupling can be achieved through the use of a chiral bridge that links the two aryl groups or through the use of a chiral auxiliary at one of the positions proximal to axial bridge. Enantioselective coupling can be achieved through the use of a chiral leaving group on one of the biaryls or under oxidative conditions that utilize chiral amines to set the axial configuration.
Individual atropisomers can be isolated by seed-directed crystallization of racemates. Thus, 1,1'-Binaphthyl crystallizes from the melt as individual enantiomers. | 0 | Theoretical and Fundamental Chemistry |
In chemistry and thermodynamics, the standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements in their reference state, with all substances in their standard states. The standard pressure value is recommended by IUPAC, although prior to 1982 the value 1.00 atm (101.325 kPa) was used. There is no standard temperature. Its symbol is ΔH. The superscript Plimsoll on this symbol indicates that the process has occurred under standard conditions at the specified temperature (usually 25 °C or 298.15 K).
Standard states are defined for various types of substances. For a gas, it is the hypothetical state the gas would assume if it obeyed the ideal gas equation at a pressure of 1 bar. For a gaseous or solid solute present in a diluted ideal solution, the standard state is the hypothetical state of concentration of the solute of exactly one mole per liter (1 M) at a pressure of 1 bar extrapolated from infinite dilution. For a pure substance or a solvent in a condensed state (a liquid or a solid) the standard state is the pure liquid or solid under a pressure of 1 bar.
For elements that have multiple allotropes, the reference state usually is chosen to be the form in which the element is most stable under 1 bar of pressure. One exception is phosphorus, for which the most stable form at 1 bar is black phosphorus, but white phosphorus is chosen as the standard reference state for zero enthalpy of formation.
For example, the standard enthalpy of formation of carbon dioxide is the enthalpy of the following reaction under the above conditions:
All elements are written in their standard states, and one mole of product is formed. This is true for all enthalpies of formation.
The standard enthalpy of formation is measured in units of energy per amount of substance, usually stated in kilojoule per mole (kJ mol), but also in kilocalorie per mole, joule per mole or kilocalorie per gram (any combination of these units conforming to the energy per mass or amount guideline).
All elements in their reference states (oxygen gas, solid carbon in the form of graphite, etc.) have a standard enthalpy of formation of zero, as there is no change involved in their formation.
The formation reaction is a constant pressure and constant temperature process. Since the pressure of the standard formation reaction is fixed at 1 bar, the standard formation enthalpy or reaction heat is a function of temperature. For tabulation purposes, standard formation enthalpies are all given at a single temperature: 298 K, represented by the symbol . | 0 | Theoretical and Fundamental Chemistry |
The Secret of the Golden Flower () is a Chinese Taoist book on neidan (inner alchemy) meditation, which also mixes Buddhist teachings with some Confucian thoughts. It was written by means of the spirit-writing (fuji) technique, through two groups, in 1688 and 1692. After publication of the translation by Richard Wilhelm, with commentary by Carl Gustav Jung, it became modernly popularized among Westerners as a Chinese "religious classic", and is read in psychological circles for analytical and transpersonal psychology considerations of Taoist meditations, although it received little attention in the East. | 1 | Applied and Interdisciplinary Chemistry |
Kerrigan's 2016 Agaricus of North America P45:
(Referring to Schaffers reaction) "In fact I recommend switching to the following modified test. Frank (1988) developed an alternative formulation in which aniline oil is combined with glacial acetic acid (GAA, essentially distilled vinegar) in a 50:50 solution. GAA is a much safer, less reactive acid. This single combined reagent is relatively stable over time. A single spot or line applied to the pileus (or other surface). In my experience the newer formulation works as well as Schaffers while being safer and more convenient." | 0 | Theoretical and Fundamental Chemistry |
The problem of integrating heat between hot and cold streams, and finding the optimal network, in particular in terms of costs, may today be solved with numerical algorithms. The network can be formulated as a so-called mixed integer non-linear programming (MINLP) problem and solved with an appropriate numerical solver. Nevertheless, large-scale MINLP problems can still be hard to solve for today's numerical algorithms. Alternatively, some attempts were made to formulate the MINLP problems to mixed integer linear problems, where then possible networks are screened and optimized. For simple networks of a few streams and heat exchangers, hand design methods with simple targeting software are often adequate, and aid the engineer in understanding the process. | 1 | Applied and Interdisciplinary Chemistry |
Exemestane is quickly absorbed from the gut, but undergoes a strong first-pass effect in the liver. Highest blood plasma concentrations are reached after 1.2 hours in breast cancer patients and after 2.9 hours in healthy subjects. Maximal aromatase inhibition occurs after two to three days. 90% of the absorbed substance are bound to plasma proteins. The liver enzyme CYP3A4 oxidizes the methylidene group in position 6, and the 17-keto group (on the five-membered ring) is reduced by aldo-keto reductases to an alcohol. Of the resulting metabolites, 40% are excreted via the urine and 40% via the feces within a week. The original substance accounts for only 1% of excretion in the urine. The terminal half-life is 24 hours. | 0 | Theoretical and Fundamental Chemistry |
Bacterial conjugation is the transfer of genetic material between bacterial cells by direct cell-to-cell contact or by a bridge-like connection between two cells. This takes place through a pilus. It is a parasexual mode of reproduction in bacteria.
It is a mechanism of horizontal gene transfer as are transformation and transduction although these two other mechanisms do not involve cell-to-cell contact.
Classical E. coli bacterial conjugation is often regarded as the bacterial equivalent of sexual reproduction or mating since it involves the exchange of genetic material. However, it is not sexual reproduction, since no exchange of gamete occurs, and indeed no generation of a new organism: instead an existing organism is transformed. During classical E. coli conjugation the donor cell provides a conjugative or mobilizable genetic element that is most often a plasmid or transposon. Most conjugative plasmids have systems ensuring that the recipient cell does not already contain a similar element.
The genetic information transferred is often beneficial to the recipient. Benefits may include antibiotic resistance, xenobiotic tolerance or the ability to use new metabolites. Other elements can be detrimental and may be viewed as bacterial parasites.
Conjugation in Escherichia coli by spontaneous zygogenesis and in Mycobacterium smegmatis by distributive conjugal transfer differ from the better studied classical E. coli conjugation in that these cases involve substantial blending of the parental genomes. | 1 | Applied and Interdisciplinary Chemistry |
The grid complexes exhibit pH-dependent changes in the optical absorption, electronic spin states and reversible redox states. The latticial metal complexes may thus be used theoretically for information storage and processing in the future. | 0 | Theoretical and Fundamental Chemistry |
Mg is the fourth-most-abundant metal ion in cells (per moles) and the most abundant free divalent cation — as a result, it is deeply and intrinsically woven into cellular metabolism. Indeed, Mg-dependent enzymes appear in virtually every metabolic pathway: Specific binding of Mg to biological membranes is frequently observed, Mg is also used as a signalling molecule, and much of nucleic acid biochemistry requires Mg, including all reactions that require release of energy from ATP. In nucleotides, the triple-phosphate moiety of the compound is invariably stabilized by association with Mg in all enzymatic processes. | 1 | Applied and Interdisciplinary Chemistry |
Progesterone and its neurosteroid active metabolite allopregnanolone appear to be importantly involved in libido in females. | 0 | Theoretical and Fundamental Chemistry |
Both TERS and SERS rely on a localized surface plasmon for increasing the ought-to-be weak Raman signal. The only difference between them is that the sample in SERS has a rough surface that hinders application of a sharp AFM-like tip. TERS, on the other hand, uses a metal-coated tip having some roughness at nanoscale. The “hot spot” theory is very popular in explaining the large enhancement in the signal. That is, the signal from “hot spots” on the surface of the sample dominates the total signal from the sample. This is also reinforced by the fact that the distance between nanoparticles and sample is an important factor in obtaining high Raman signal. | 0 | Theoretical and Fundamental Chemistry |
Janet Gretchen Osteryoung (March 1, 1939 – September 21, 2021) was an American chemist who was the director of the Chemistry Division of the National Science Foundation from 1994 to 2001. Her research furthered the development of electroanalysis and especially that of square wave voltammetry. She was elected a Fellow of the American Association for the Advancement of Science in 1984 and awarded the Garvan–Olin Medal in 1987. | 0 | Theoretical and Fundamental Chemistry |
Corrosion engineering is an engineering specialty that applies scientific, technical, engineering skills, and knowledge of natural laws and physical resources to design and implement materials, structures, devices, systems, and procedures to manage corrosion.
From a holistic perspective, corrosion is the phenomenon of metals returning to the state they are found in nature. The driving force that causes metals to corrode is a consequence of their temporary existence in metallic form. To produce metals starting from naturally occurring minerals and ores, it is necessary to provide a certain amount of energy, e.g. Iron ore in a blast furnace. It is therefore thermodynamically inevitable that these metals when exposed to various environments would revert to their state found in nature. Corrosion and corrosion engineering thus involves a study of chemical kinetics, thermodynamics, electrochemistry and materials science. | 1 | Applied and Interdisciplinary Chemistry |
Thermal rearrangements of aromatic hydrocarbons are generally carried out through flash vacuum pyrolysis (FVP). In a typical FVP apparatus, a sample is sublimed under high vacuum (0.1-1.0 mmHg), heated in the range of 500-1100 °C by an electric furnace as it passes through a horizontal quartz tube, and collected in a cold trap. Sample is carried through the apparatus by nitrogen carrier gas.
FVP has numerous limitations:
*First, it requires a slow rate of sublimation to minimize bimolecular reactions in the gas phase, limiting the amount of material that can be reacted in a given amount of time.
*Second, the high temperatures used in FVP often lead to reactant or product degradation. Combined, these first two limitations restrict FVP yields to the range of 25-30%.
*Third, the high temperatures used in FVP do not allow for the presence of functional groups, thereby limiting possible products.
*Fourth, as FVP is a gas-phase process, difficulties are frequently encountered when scaling above the milligram level.
*Fifth, the FVP synthesis of strained systems mandates temperatures exceeding 1100 °C, which can lead to the degradation and softening of the expensive quartz apparati. | 0 | Theoretical and Fundamental Chemistry |
The crystallographic point group or crystal class is the mathematical group comprising the symmetry operations that leave at least one point unmoved and that leave the appearance of the crystal structure unchanged. These symmetry operations include
*Reflection, which reflects the structure across a reflection plane
*Rotation, which rotates the structure a specified portion of a circle about a rotation axis
*Inversion, which changes the sign of the coordinate of each point with respect to a center of symmetry or inversion point
*Improper rotation, which consists of a rotation about an axis followed by an inversion.
Rotation axes (proper and improper), reflection planes, and centers of symmetry are collectively called symmetry elements. There are 32 possible crystal classes. Each one can be classified into one of the seven crystal systems. | 0 | Theoretical and Fundamental Chemistry |
Brown and Goldstein discovered the LDL receptor and showed cholesterol is loaded into cells through receptor mediated endocytosis. Until recently cholesterol was thought of primarily as a structural component of the membrane. However, more recently, cholesterol uptake was shown to signal an immune response in macrophages. More importantly, the ability to efflux cholesterol through ABC transporters was shown to attenuate (i.e., shut down) the inflammatory response. | 1 | Applied and Interdisciplinary Chemistry |
As 1,3dipoles, nitrones perform [[1,3-dipolar cycloaddition|[3+2] cycloaddition]]s. For example, a dipolarophilic alkene combines to form isoxazolidine:
Other ring-closing reactions are known, including formal [3+3] and [5+2] cycloadditions. | 0 | Theoretical and Fundamental Chemistry |
Double diffusion convection plays a significant role in upwelling of nutrients and vertical transport of heat and salt in oceans. Salt fingering contributes to vertical mixing in the oceans. Such mixing helps regulate the gradual overturning circulation of the ocean, which control the climate of the earth. Apart from playing an important role in controlling the climate, fingers are responsible for upwelling of nutrients which supports flora and fauna. The most significant aspect of finger convection is that they transport the fluxes of heat and salt vertically, which has been studied extensively during the last five decades. | 1 | Applied and Interdisciplinary Chemistry |
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