text
stringlengths 105
4.44k
| label
int64 0
9
| label_text
stringclasses 10
values |
|---|---|---|
Very small changes in temperature can produce a pyroelectric potential. Passive infrared sensors are often designed around pyroelectric materials, as the heat of a human or animal from several feet away is enough to generate a voltage. | 7 | Physical Chemistry |
The Electrochemical Society was founded in 1902 in Philadelphia, PA. At the beginning, ECS was called the American Electrochemical Society.
The 19th century saw many applications of electricity to chemical processes and chemical understanding. Bridging the gap between electrical engineering and chemistry led people in industrial and academic circles to search for a new forum to discuss developments in the burgeoning field of electrochemistry.
The original constitution of the Society called for holding meetings and publishing papers presented there and the ensuing discussions. In 1902 the Society ushered in a new publication, Transactions of the American Electrochemical Society. In 1907 the first “local” section was formed at the University of Wisconsin. That same year, the American Electrochemical Society Bulletin was launched; it became the Journal of The Electrochemical Society in 1948.
In the 1920s, topical interest area divisions began to be founded, including the High Temperature Materials Division and the Electrodeposition Division. In 1930, the international nature of the Society was officially recognized by dropping “American” from the name. A new category of membership was started in 1941 to permit industrial companies to support the Society’s mission. ECS began fulfilling the need for critical textbooks with the publication of its second monograph, the Corrosion Handbook, by H. H. Uhlig in 1948.
Throughout the latter half of the 20th century, the Society continued to grow in size and importance, expanding the number of its publications, and the significance of the technical research unveiled at its meetings.
Over time, the Society’s members and publications’ authors have included many distinguished scientists and engineers. The Society’s original charter members included:
* E. G. Acheson, who commercialized carborundum, an artificial graphite;
* H. H. Dow, the founder of Dow Chemical Company;
* C. M. Hall, the inventor of the Hall process for the manufacture of aluminum;
* Edward Weston, the founder of Weston Instruments.
Thomas A. Edison joined the Society in 1903 and enjoyed membership for 28 years. In 1965, Gordon Moores seminal prediction, Moores Law, developed its roots within the Society. ECS has included numerous Nobel laureates among its members, most recently the three co-winners of the 2019 Nobel Prize in Chemistry. John B. Goodenough, M. Stanley Whittingham, and Akira Yoshino shared the prize “for the development of lithium-ion batteries.” | 7 | Physical Chemistry |
First Example: Let gas 1 be H and gas 2 be O. (This example is solving for the ratio between the rates of the two gases)
Therefore, hydrogen molecules effuse four times faster than those of oxygen.
Graham's Law can also be used to find the approximate molecular weight of a gas if one gas is a known species, and if there is a specific ratio between the rates of two gases (such as in the previous example). The equation can be solved for the unknown molecular weight.
Graham's law was the basis for separating uranium-235 from uranium-238 found in natural uraninite (uranium ore) during the Manhattan Project to build the first atomic bomb. The United States government built a gaseous diffusion plant at the Clinton Engineer Works in Oak Ridge, Tennessee, at the cost of $479 million (equivalent to $ in ). In this plant, uranium from uranium ore was first converted to uranium hexafluoride and then forced repeatedly to diffuse through porous barriers, each time becoming a little more enriched in the slightly lighter uranium-235 isotope.
Second Example: An unknown gas diffuses 0.25 times as fast as He. What is the molar mass of the unknown gas?
Using the formula of gaseous diffusion, we can set up this equation.
Which is the same as the following because the problem states that the rate of diffusion of the unknown gas relative to the helium gas is 0.25.
Rearranging the equation results in | 7 | Physical Chemistry |
If the values of the predicted rate constants are compared with the values of known rate constants, it is noticed that collision theory fails to estimate the constants correctly, and the more complex the molecules are, the more it fails. The reason for this is that particles have been supposed to be spherical and able to react in all directions, which is not true, as the orientation of the collisions is not always proper for the reaction. For example, in the hydrogenation reaction of ethylene the H molecule must approach the bonding zone between the atoms, and only a few of all the possible collisions fulfill this requirement.
To alleviate this problem, a new concept must be introduced: the steric factor ρ. It is defined as the ratio between the experimental value and the predicted one (or the ratio between the frequency factor and the collision frequency):
and it is most often less than unity.
Usually, the more complex the reactant molecules, the lower the steric factor. Nevertheless, some reactions exhibit steric factors greater than unity: the harpoon reactions, which involve atoms that exchange electrons, producing ions. The deviation from unity can have different causes: the molecules are not spherical, so different geometries are possible; not all the kinetic energy is delivered into the right spot; the presence of a solvent (when applied to solutions), etc.
Collision theory can be applied to reactions in solution; in that case, the solvent cage has an effect on the reactant molecules, and several collisions can take place in a single encounter, which leads to predicted preexponential factors being too large. ρ values greater than unity can be attributed to favorable entropic contributions. | 7 | Physical Chemistry |
Aqueous carbon dioxide reacts with water to form carbonic acid which is very unstable and will dissociate rapidly into hydronium and bicarbonate. Therefore, in seawater, dissolved inorganic carbon is commonly referred to as the collection of bicarbonate, carbonate ions, and dissolved carbon dioxide (CO, HCO, , ).
:CO(aq) + HO HCO + H + 2 H
More than 99% of dissolved inorganic carbon is in the form of bicarbonate and carbonate ions meaning that most of the ocean’s carbon storing ability is due to this chemical reactivity. Sea-air flux of CO and the resulting dissolved inorganic carbon is affected by physical processes such as strong winds and vertical mixing, and the biological processes of photosynthesis, respiration, and decomposition. | 9 | Geochemistry |
In this approach, a narrow pulse of light (and respectively.
Multiple scattering events broaden the DTOF and the attenuation of a result of both absorption and scattering as they divert photons from the direction of the detector. Higher scattering leads to a more delayed and a broader DTOF and higher absorption reduces the amplitude and changes the slope of the tail of the DTOF. Since absorption and scattering have different effects on the DTOF, they can be extracted independently while using a single source-detector separation. Moreover, the penetration depth in TD depends solely on the photon arrival times and is independent of the source-detector separation unlike in CW approach.
The theory of light propagation in diffusive media is usually dealt with using the framework of radiative transfer theory under the multiple scattering regime. It has been demonstrated that radiative transfer equation under the diffusion approximation yields sufficiently accurate solutions for practical applications. For example, it can be applied for the semi-infinite geometry or the infinite slab geometry, using proper boundary conditions. The system is considered as a homogeneous background and an inclusion is considered as an absorption or scattering perturbation.
The time-resolved reflectance curve at a point from the source for a semi-infinite geometry is given by
where is the diffusion coefficient, is the reduced scattering coefficient and is asymmetry factor, is the photon velocity in the medium, takes into account the boundary conditions and is a constant.
The final DTOF is a convolution of the instrument response function (IRF) of the system with the theoretical reflectance curve.
When applied to biological tissues estimation of <math>\mu_a
allows us to then estimate the concentration of the various tissue constituents as well as provides information about blood oxygenation (oxy and deoxy-hemoglobin) as well as saturation and total blood volume. These can then be used as biomarkers for detecting various pathologies. | 7 | Physical Chemistry |
Alus are the most common SINE in primates. They are approximately 350 base pairs long, do not encode proteins and can be recognized by the restriction enzyme AluI (hence the name). Their distribution may be important in some genetic diseases and cancers. Copy and pasting Alu RNA requires the Alu's adenine-rich end and the rest of the sequence bound to a signal. The signal-bound Alu can then associate with ribosomes. LINE RNA associates on the same ribosomes as the Alu. Binding to the same ribosome allows Alus of SINEs to interact with LINE. This simultaneous translation of Alu element and LINE allows SINE copy and pasting. | 1 | Biochemistry |
Mathematical and computational models are essential for understanding the action potential, and offer predictions that may be tested against experimental data, providing a stringent test of a theory. The most important and accurate of the early neural models is the Hodgkin–Huxley model, which describes the action potential by a coupled set of four ordinary differential equations (ODEs). Although the Hodgkin–Huxley model may be a simplification with few limitations compared to the realistic nervous membrane as it exists in nature, its complexity has inspired several even-more-simplified models, such as the Morris–Lecar model and the FitzHugh–Nagumo model, both of which have only two coupled ODEs. The properties of the Hodgkin–Huxley and FitzHugh–Nagumo models and their relatives, such as the Bonhoeffer–Van der Pol model, have been well-studied within mathematics, computation and electronics. However the simple models of generator potential and action potential fail to accurately reproduce the near threshold neural spike rate and spike shape, specifically for the mechanoreceptors like the Pacinian corpuscle. More modern research has focused on larger and more integrated systems; by joining action-potential models with models of other parts of the nervous system (such as dendrites and synapses), researchers can study neural computation and simple reflexes, such as escape reflexes and others controlled by central pattern generators. | 7 | Physical Chemistry |
Pyridine can cause chemical burns on contact with the skin and its fumes may be irritating to the eyes or upon inhalation. Pyridine depresses the nervous system giving symptoms similar to intoxication with vapor concentrations of above 3600 ppm posing a greater health risk. The effects may have a delayed onset of several hours and include dizziness, headache, lack of coordination, nausea, salivation, and loss of appetite. They may progress into abdominal pain, pulmonary congestion and unconsciousness. The lowest known lethal dose (LD) for the ingestion of pyridine in humans is 500 mg·kg. | 0 | Organic Chemistry |
Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U).
Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), Valine (Val, V) | 1 | Biochemistry |
Neurotrophin-3, or NT-3, is a neurotrophic factor, in the NGF-family of neurotrophins. It is a protein growth factor that has activity on certain neurons of the peripheral and central nervous system; it helps to support the survival and differentiation of existing neurons, and encourages the growth and differentiation of new neurons and synapses. NT-3 is the third neurotrophic factor to be characterized, after NGF and BDNF.
NT-3 is unique among the neurotrophins in the number of neurons it has potential to stimulate, given its ability to activate two of the receptor tyrosine kinase neurotrophin receptors (TrkC and TrkB). Mice born without the ability to make NT-3 have loss of proprioceptive and subsets of mechanoreceptive sensory neurons. | 1 | Biochemistry |
The ionic strength plays a central role in the Debye–Hückel theory that describes the strong deviations from ideality typically encountered in ionic solutions. It is also important for the theory of double layer and related electrokinetic phenomena and electroacoustic phenomena in colloids and other heterogeneous systems. That is, the Debye length, which is the inverse of the Debye parameter (κ), is inversely proportional to the square root of the ionic strength. Both molar and molal ionic strength have been used, often without explicit definition. Debye length is characteristic of the double layer thickness. Increasing the concentration or valence of the counterions compresses the double layer and increases the electrical potential gradient.
Media of high ionic strength are used in stability constant determination in order to minimize changes, during a titration, in the activity quotient of solutes at lower concentrations. Natural waters such as mineral water and seawater have often a non-negligible ionic strength due to the presence of dissolved salts which significantly affects their properties. | 7 | Physical Chemistry |
Suggested by the idea that the structure of chromatin can be modified to allow or deny access of transcription activators, regulatory functions of histone acetylation and deacetylation can have implications with genes that cause other diseases. Studies on histone modifications may reveal many novel therapeutic targets.
Based on different cardiac hypertrophy models, it has been demonstrated that cardiac stress can result in gene expression changes and alter cardiac function. These changes are mediated through HATs/HDACs posttranslational modification signaling. HDAC inhibitor trichostatin A was reported to reduce stress induced cardiomyocyte autophagy. Studies on p300 and CREB-binding protein linked cardiac hypertrophy with cellular HAT activity suggesting an essential role of histone acetylation status with hypertrophy responsive genes such as GATA4, SRF, and MEF2.
Epigenetic modifications also play a role in neurological disorders. Deregulation of histones modification are found to be responsible for deregulated gene expression and hence associated with neurological and psychological disorders, such as Schizophrenia and Huntington disease. Current studies indicate that inhibitors of the HDAC family have therapeutic benefits in a wide range of neurological and psychiatric disorders. Many neurological disorders only affect specific brain regions; therefore, understanding of the specificity of HDACs is still required for further investigations for improved treatments. | 0 | Organic Chemistry |
Persistent organic pollutants such as dichlorodiphenyltrichloroethane (DDT), polychlorinated biphenols, dioxins, are all assessed in AOX analysis. Generally, the higher the amount of chlorine in an organic compound, the more toxic it is considered. While there are several biochemical or electrochemical methods to remove organic halides, AOX has been preferred due to its low cost of operation and simplicity of design.
In a lab, the determination of AOX parameter consists of adsorption of organic halides from the sample on to an activated carbon. The activated carbon can be powdered or granular and adsorbed using microcolumns or a batch process, if the samples are rich in humic acids. Vigorous shaking is often employed in the event of a batch process to favor the adsorption of organic halide on to the activated carbon due to its electronegativity and presence of lone pairs. The inorganic halides that are also adsorbed are washed away using a strong acid such as nitric acid. The carbon with adsorbed organic halide is obtained by filtration, after which the filter containing the carbon is burnt in the presence of oxygen. While combustion of hydrocarbon part of the compounds form CO and HO, halo acids are formed from the halogens. These haloacids are absorbed into acetic acid. Subsequent use of microcolumetric titration, an electrochemical quantification method, provides the AOX content in the sample. Using the dilution ratio, the total AOX content at the location can be estimated. Alternatively, the chlorinated compounds in the sample can be determined by using pentane extraction followed by capillary gas chromatography and electron capture (GC-ECD). The organic carbon that was remaining after the nitric acid purge can be analyzed using UV-persulfate wet oxidation followed by Infrared-detection (IR). Several other analytical techniques such as high performance liquid chromatography (HPLC) could also be implemented to quantify AOX levels. The general adsorption procedure is given below:
Where is the activated carbon and is any organic halide.
is the organic halide - activated carbon complex that can be filtered out. | 2 | Environmental Chemistry |
Garson was born in Rugby, England, the daughter of an engineer and botanist. She took her B.A with Honours from the University of Cambridge, Newnham College in 1974. Garson's focus was the natural sciences, specializing in chemistry. She obtained an MA in Natural Sciences and she took her PhD in organic chemistry from Cambridge in 1977. | 0 | Organic Chemistry |
Most methods for nucleic acid secondary structure prediction rely on a nearest neighbor thermodynamic model. A common method to determine the most probable structures given a sequence of nucleotides makes use of a dynamic programming algorithm that seeks to find structures with low free energy. Dynamic programming algorithms often forbid pseudoknots, or other cases in which base pairs are not fully nested, as considering these structures becomes computationally very expensive for even small nucleic acid molecules. Other methods, such as stochastic context-free grammars can also be used to predict nucleic acid secondary structure.
For many RNA molecules, the secondary structure is highly important to the correct function of the RNA — often more so than the actual sequence. This fact aids in the analysis of non-coding RNA sometimes termed "RNA genes". One application of bioinformatics uses predicted RNA secondary structures in searching a genome for noncoding but functional forms of RNA. For example, microRNAs have canonical long stem-loop structures interrupted by small internal loops.
RNA secondary structure applies in RNA splicing in certain species. In humans and other tetrapods, it has been shown that without the U2AF2 protein, the splicing process is inhibited. However, in zebrafish and other teleosts the RNA splicing process can still occur on certain genes in the absence of U2AF2. This may be because 10% of genes in zebrafish have alternating TG and AC base pairs at the 3 splice site (3ss) and 5 splice site (5ss) respectively on each intron, which alters the secondary structure of the RNA. This suggests that secondary structure of RNA can influence splicing, potentially without the use of proteins like U2AF2 that have been thought to be required for splicing to occur. | 4 | Stereochemistry |
# The citrate binds to citrate transporters.
# The shuttle delivers the citrate from the inner membrane to the intermembrane space.
# There is a net movement of the citrate from the intermembrane space to the cytosol across the outer membrane, following the concentration gradient. | 1 | Biochemistry |
Transition-metal allyl complexes are coordination complexes with allyl and its derivatives as ligands. Allyl is the radical with the connectivity CHCHCH, although as a ligand it is usually viewed as an allyl anion CH=CH−CH, which is usually described as two equivalent resonance structures. | 0 | Organic Chemistry |
The ore is comminuted using grinding machinery. Depending on the ore, it is sometimes further concentrated by froth flotation or by centrifugal (gravity) concentration. Water is added to produce a slurry or pulp. The basic ore slurry can be combined with a solution of sodium cyanide or potassium cyanide; many operations use calcium cyanide, which is more cost effective.
To prevent the creation of toxic hydrogen cyanide during processing, slaked lime (calcium hydroxide) or soda (sodium hydroxide) is added to the extracting solution to ensure that the acidity during cyanidation is maintained over pH 10.5 - strongly basic.
Lead nitrate can improve gold leaching speed and quantity recovered, particularly in processing partially oxidized ores. | 8 | Metallurgy |
The direhorse (Pali in Navi ) is a bioluminescent, hexapodal, superficially equine animal. It is scientifically known as Equidirus hoplites. The Navi use the direhorse to hunt. The direhorse was conceived and designed by Cameron and Stan Winston Studios. The direhorse is grey with blue stripes and stands tall, long. The Navi "break" a direhorse by connecting the fleshy tip of their hair to the animals antennae. Xenobiologists call this a neural whip. Once intertwined, the Navi rider can communicate motor commands instantly through the neural interface; however, this connection does not lead to a lifelong, exclusive bond, as it does with the mountain banshee. Cameron described the creature as a "six-legged alien Clydesdale with moth-like antennae". The direhorse uses its long tongue to eat the sap out of pitcher plants. | 1 | Biochemistry |
Hydrogen-terminated silicon surface is a chemically passivated silicon substrate where the surface Si atoms are bonded to hydrogen. The hydrogen-terminated surfaces are hydrophobic, luminescent, and amenable to chemical modification. Hydrogen-terminated silicon is an intermediate in the growth of bulk silicon from silane:
:SiH → Si + 2H | 6 | Supramolecular Chemistry |
Antigenic specificity is the ability of the host cells to recognize an antigen specifically as a unique molecular entity and distinguish it from another with exquisite precision. Antigen specificity is due primarily to the side-chain conformations of the antigen. It is measurable and need not be linear or of a rate-limited step or equation. Both T cells and B cells are cellular components of adaptive immunity. | 1 | Biochemistry |
Boom method (aka Boom nucleic acid extraction method) is a solid phase extraction method for isolating nucleic acid from a biological sample. This method is characterized by "absorbing the nucleic acids (NA) to the silica beads". | 1 | Biochemistry |
The bromine cycle is a biogeochemical cycle of bromine through the atmosphere, biosphere, and hydrosphere. | 9 | Geochemistry |
In 1958, Frederick C. Frank and John S. Kasper, in their original work investigating many complex alloy structures, showed that non-icosahedral environments form an open-end network which they called the major skeleton, and is now identified as the declination locus. They came up with the methodology to pack asymmetric icosahedra into crystals using other polyhedra with larger coordination numbers. These coordination polyhedra were constructed to maintain topological close packing (TCP). | 8 | Metallurgy |
In deriving the first equation, Darken referenced Simgelskas and Kirkendall's experiment, which tested the mechanisms and rates of diffusion and gave rise to the concept now known as the Kirkendall effect. For the experiment, inert molybdenum wires were placed at the interface between copper and brass components, and the motion of the markers was monitored. The experiment supported the concept that a concentration gradient in a binary alloy would result in the different components having different velocities in the solid solution. The experiment showed that in brass zinc had a faster relative velocity than copper, since the molybdenum wires moved farther into the brass. In establishing the coordinate axes to evaluate the derivation, Darken refers back to Smigelskas and Kirkendall’s experiment which the inert wires were designated as the origin.
In respect to the derivation of the second equation, Darken referenced W. A. Johnson’s experiment on a gold–silver system, which was performed to determine the chemical diffusivity. In this experiment radioactive gold and silver isotopes were used to measure the diffusivity of gold and silver, because it was assumed that the radioactive isotopes have relatively the same mobility as the non-radioactive elements. If the gold–silver solution is assumed to behave ideally, it would be expected the diffusivities would also be equivalent. Therefore, the overall diffusion coefficient of the system would be the average of each components diffusivity; however, this was found not to be true. This finding led Darken to analyze Johnson's experiment and derive the equation for chemical diffusivity of binary solutions. | 7 | Physical Chemistry |
A dystrophin-associated protein is a protein that helps to form the connection between intracellular dystrophin and the extracellular basal lamina.
Examples include sarcoglycan and dystroglycan. | 1 | Biochemistry |
Meromyosin is a part of myosin (mero meaning "part of"). With regards to human anatomy myosin and actin constitute the basic functional unit of a muscle fiber, called sarcomere, playing a role in muscle contraction.
Biochemically viewed meromyosin form subunits of the actin-associated motor protein, myosin, Following proteolysis, two types of meromyosin are formed: heavy meromyosin (HMM) and light meromyosin (LMM).
Light meromyosin has a long, straight portion in the “tail” region. Heavy meromyosin (HMM) is a protein chain terminating in a globular head portion/cross bridge. HMM consists of two subunits, Heavy Meromyosin Subunit 1 and 2 (HMMS-1 and HMMS-2). The majority of myosin activity is concentrated in HMMS-1. HMMS-1 has an actin binding site and ATP binding site (myosin ATPase) that determines the rate of muscle contraction when muscle is stretched.
Light and heavy meromyosin are subunits of myosin filaments (thick myofilaments). | 1 | Biochemistry |
Birch reduction of D-α-phenylglycine led to diene (2). This was N-protected using tert-butoxycarbonylazide and activated for amide formation via the mixed anhydride method using isobutylchloroformate to give 3. Mixed anhydride 3 reacted readily with 7-aminodesacetoxycephalosporanic acid to give, after deblocking, cephradine (5). | 4 | Stereochemistry |
Asymmetric catalysis relies on chiral ligands, which in turn are generally derived from the chiral pool. For example enantiopure 2,3-butanediol, derived from abundantly available tartaric acid, is used to synthesize chiraphos, a component of catalysts used for asymmetric hydrogenation: | 0 | Organic Chemistry |
This compound has the best antibacterial activity of Endiandrianic acid A-G compounds. Endiandric acid C was tested towards five strains of bacteria, which included Bacillus subtilis, Micococcus luteus, Streptococcus faecalis, Pseudomonas palida, and Escherichia coli through examining zone inhibition and minimum concentration, which was found to range between 0.24 µg/mL and 500 µg/mL. Endiandric acid C has also been used to cure uterine tumors, rubella, and female genital infections, and rheumatisms. | 0 | Organic Chemistry |
PA 11 is a biopolymer derived from natural oil. It is also known under the tradename Rilsan B, commercialized by Arkema. PA 11 belongs to the technical polymers family and is not biodegradable. Its properties are similar to those of PA 12, although emissions of greenhouse gases and consumption of nonrenewable resources are reduced during its production. Its thermal resistance is also superior to that of PA 12. It is used in high-performance applications like automotive fuel lines, pneumatic airbrake tubing, electrical cable antitermite sheathing, flexible oil and gas pipes, control fluid umbilicals, sports shoes, electronic device components, and catheters.
A similar plastic is Polyamide 410 (PA 410), derived 70% from castor oil, under the trade name EcoPaXX, commercialized by DSM.
PA 410 is a high-performance polyamide that combines the benefits of a high melting point (approx. 250 °C), low moisture absorption and excellent resistance to various chemical substances. | 7 | Physical Chemistry |
One of the shortcoming of electrochemical window (EW) in predicting the stability of the electrolyte towards anode or cathode materials ignores the voltage and the ionic conductivity, which are also important. | 7 | Physical Chemistry |
Adduct purification is a technique for preparing extremely pure simple organometallic compounds, which are generally unstable and hard to handle, by purifying a stable adduct with a Lewis acid and then obtaining the desired product from the pure adduct by thermal decomposition.
Epichem Limited is the licensee of the major patents in this field, and uses the trademark EpiPure to refer to adduct-purified materials; Professor Anthony Jones at Liverpool University is the initiator of the field and author of many of the important papers.
The choice of Lewis acid and of reaction medium is important; the desired organometallics are almost always air- and water-sensitive. Initial work was done in ether, but this led to oxygen impurities, and so more recent work involves tertiary amines or nitrogen-substituted crown ethers. | 3 | Analytical Chemistry |
Numerous fields would be able to benefit from the protection of tissue damage by freezing. Businesses are currently investigating the use of these proteins in:
* Increasing freeze tolerance of crop plants and extending the harvest season in cooler climates
* Improving farm fish production in cooler climates
* Lengthening shelf life of frozen foods
* Improving cryosurgery
* Enhancing preservation of tissues for transplant or transfusion in medicine
* Therapy for hypothermia
* Human Cryopreservation (Cryonics)
Unilever has obtained UK, US, EU, Mexico, China, Philippines, Australia and New Zealand approval to use a genetically modified yeast to produce antifreeze proteins from fish for use in ice cream production. They are labeled "ISP" or ice structuring protein on the label, instead of AFP or antifreeze protein. | 1 | Biochemistry |
The lower-limit size of a coffee ring depends on the time scale competition between the liquid evaporation and the movement of suspended particles. When the liquid evaporates much faster than the particle movement near a three-phase contact line, coffee ring cannot be formed successfully. Instead, these particles will disperse uniformly on a surface upon complete liquid evaporation. For suspended particles of size 100 nm, the minimum diameter of the coffee ring structure is found to be 10 μm, or about 10 times smaller than the width of human hair. The shape of particles in the liquid is responsible for coffee ring effect. On porous substrates, the competition among infiltration, particle motion and evaporation of the solvent governs the final deposition morphology.
The pH of the solution of the drop influences the final deposit pattern. The transition between these patterns is explained by considering how DLVO interactions such as the electrostatic and Van der Waals forces modify the particle deposition process. | 7 | Physical Chemistry |
The Petasis reagent, named after Nicos A. Petasis, is an organotitanium compound with the formula CpTi(CH). It is an orange-colored solid. | 0 | Organic Chemistry |
Sulfuric acid is non-flammable.
The main occupational risks posed by this acid are skin contact leading to burns (see above) and the inhalation of aerosols. Exposure to aerosols at high concentrations leads to immediate and severe irritation of the eyes, respiratory tract and mucous membranes: this ceases rapidly after exposure, although there is a risk of subsequent pulmonary edema if tissue damage has been more severe. At lower concentrations, the most commonly reported symptom of chronic exposure to sulfuric acid aerosols is erosion of the teeth, found in virtually all studies: indications of possible chronic damage to the respiratory tract are inconclusive as of 1997. Repeated occupational exposure to sulfuric acid mists may increase the chance of lung cancer by up to 64 percent. In the United States, the permissible exposure limit (PEL) for sulfuric acid is fixed at 1 mg/m: limits in other countries are similar. There have been reports of sulfuric acid ingestion leading to vitamin B12 deficiency with subacute combined degeneration. The spinal cord is most often affected in such cases, but the optic nerves may show demyelination, loss of axons and gliosis. | 7 | Physical Chemistry |
Cooperativity is not only a phenomenon of ligand binding, but also applies anytime energetic interactions make it easier or more difficult for something to happen involving multiple units as opposed to with single units. (That is, easier or more difficult compared with what is expected when only accounting for the addition of multiple units). For example, unwinding of DNA involves cooperativity: Portions of DNA must unwind in order for DNA to carry out replication, transcription and recombination. Positive cooperativity among adjacent DNA nucleotides makes it easier to unwind a whole group of adjacent nucleotides than it is to unwind the same number of nucleotides spread out along the DNA chain. The cooperative unit size is the number of adjacent bases that tend to unwind as a single unit due to the effects of positive cooperativity. This phenomenon applies to other types of chain molecules as well, such as the folding and unfolding of proteins and in the "melting" of phospholipid chains that make up the membranes of cells. Subunit cooperativity is measured on the relative scale known as Hill's Constant. | 1 | Biochemistry |
Whole genome sequencing (WGS), also known as full genome sequencing, complete genome sequencing, or entire genome sequencing, is the process of determining the entirety, or nearly the entirety, of the DNA sequence of an organisms genome at a single time. This entails sequencing all of an organisms chromosomal DNA as well as DNA contained in the mitochondria and, for plants, in the chloroplast.
Whole genome sequencing has largely been used as a research tool, but was being introduced to clinics in 2014. In the future of personalized medicine, whole genome sequence data may be an important tool to guide therapeutic intervention. The tool of gene sequencing at SNP level is also used to pinpoint functional variants from association studies and improve the knowledge available to researchers interested in evolutionary biology, and hence may lay the foundation for predicting disease susceptibility and drug response.
Whole genome sequencing should not be confused with DNA profiling, which only determines the likelihood that genetic material came from a particular individual or group, and does not contain additional information on genetic relationships, origin or susceptibility to specific diseases. In addition, whole genome sequencing should not be confused with methods that sequence specific subsets of the genome – such methods include whole exome sequencing (1–2% of the genome) or SNP genotyping (< 0.1% of the genome). | 1 | Biochemistry |
Prostanoids were discovered through biological research studies conducted in the 1930s. The first discovery was seen through semen by a Swedish Physiologist Ulf von Euler, who assumed they originated from the prostate. After intensive study throughout the 1960-1970s Sune K. Bergström and Bengt Ingemar Samuelsson and British biochemist Sir John Robert Vane were able to understand the function and chemical formation of Prostanoids: receiving a Nobel Prize for their analysis of prostanoids. | 1 | Biochemistry |
Many different color reagents have been developed for determining the concentrations of different substances. For example, Nessler's reagent can be used to determine the concentration of a solution of ammonia. | 7 | Physical Chemistry |
In a new bottle of soda, the concentration of carbon dioxide in the liquid phase has a particular value. If half of the liquid is poured out and the bottle is sealed, carbon dioxide will leave the liquid phase at an ever-decreasing rate, and the partial pressure of carbon dioxide in the gas phase will increase until equilibrium is reached. At that point, due to thermal motion, a molecule of CO may leave the liquid phase, but within a very short time another molecule of CO will pass from the gas to the liquid, and vice versa. At equilibrium, the rate of transfer of CO from the gas to the liquid phase is equal to the rate from liquid to gas. In this case, the equilibrium concentration of CO in the liquid is given by Henry's law, which states that the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas above the liquid. This relationship is written as
where K is a temperature-dependent constant, P is the partial pressure, and c is the concentration of the dissolved gas in the liquid. Thus the partial pressure of CO in the gas has increased until Henry's law is obeyed. The concentration of carbon dioxide in the liquid has decreased and the drink has lost some of its fizz.
Henrys law may be derived by setting the chemical potentials of carbon dioxide in the two phases to be equal to each other. Equality of chemical potential defines chemical equilibrium. Other constants for dynamic equilibrium involving phase changes, include partition coefficient and solubility product. Raoults law defines the equilibrium vapor pressure of an ideal solution
Dynamic equilibrium can also exist in a single-phase system. A simple example occurs with acid-base equilibrium such as the dissociation of acetic acid, in an aqueous solution.
At equilibrium the concentration quotient, K, the acid dissociation constant, is constant (subject to some conditions)
In this case, the forward reaction involves the liberation of some protons from acetic acid molecules and the backward reaction involves the formation of acetic acid molecules when an acetate ion accepts a proton. Equilibrium is attained when the sum of chemical potentials of the species on the left-hand side of the equilibrium expression is equal to the sum of chemical potentials of the species on the right-hand side. At the same time, the rates of forward and backward reactions are equal to each other. Equilibria involving the formation of chemical complexes are also dynamic equilibria and concentrations are governed by the stability constants of complexes.
Dynamic equilibria can also occur in the gas phase as, for example when nitrogen dioxide dimerizes.
In the gas phase, square brackets indicate partial pressure. Alternatively, the partial pressure of a substance may be written as P(substance). | 7 | Physical Chemistry |
A matrix metalloproteinase inhibitor (MMPI, INN stem ) inhibits matrix metalloproteinases. Because they inhibit cell migration, they have antiangiogenic effects. They may be both endogenous and exogenous.
The most notorious endogenous metalloproteinases are tissue inhibitors of metalloproteinases (TIMPs). There are also cartilage-derived angiogenesis inhibitors.
Exogenous matrix metalloproteinase inhibitors were developed as anticancer drugs. Examples include:
* Batimastat
* Cipemastat
* Ilomastat
* Marimastat
* MMI270
* Prinomastat
* Rebimastat
* Ro 28-2653
* Tanomastat
Metalloproteinase inhibitors are found in numerous marine organisms, including fish, cephalopods, mollusks, algae, and bacteria. | 1 | Biochemistry |
Ca plays an important role in nodule formation in legumes. Nitrogen is an essential element required in plants and many legumes, unable to fix nitrogen independently, pair symbiotically with nitrogen-fixing bacteria that reduce nitrogen to ammonia. This legume-Rhizobium interaction establishment requires the Nod factor that is produced by the Rhizobium bacteria. The Nod factor is recognized by the root hair cells that are involved in the nodule formation in legumes. Ca responses of varied nature are characterized to be involved in the Nod factor recognition. There is a Ca flux at the tip of the root hair initially followed by repetitive oscillation of Ca in the cytosol and also Ca spike occurs around the nucleus. DMI3, an essential gene for Nod factor signaling functions downstream of the Ca spiking signature, might be recognizing the Ca signature. Further, several CaM and CML genes in Medicago and Lotus are expressed in nodules. | 1 | Biochemistry |
Across mammalian species, VMATs have been found to be structurally well conserved; VMAT1s have an overall sequence identity exceeding 80%. However, there exists only a 60% sequence identity between the human VMAT1 and VMAT2.
VMAT1 is an acidic glycoprotein with an apparent weight of 40 kDa. Although the crystallographic structure has not yet been fully resolved, VMAT1 is known to have either twelve transmembrane domains (TMDs), based on Kyte-Doolittle hydrophobicity scale analysis or ten TMDs, based on MAXHOM alignment. MAXHOM alignment was determined using the "profile-fed neural network systems from Heidelberg" (PHD) program. The main difference between these two models arises from the placement of TMDs II and IV in the vesicle lumen or the cytoplasm. | 1 | Biochemistry |
The thylakoid membrane is the site of the light-dependent reactions of photosynthesis with the photosynthetic pigments embedded directly in the membrane. It is an alternating pattern of dark and light bands measuring each 1 nanometre. The thylakoid lipid bilayer shares characteristic features with prokaryotic membranes and the inner chloroplast membrane. For example, acidic lipids can be found in thylakoid membranes, cyanobacteria and other photosynthetic bacteria and are involved in the functional integrity of the photosystems. The thylakoid membranes of higher plants are composed primarily of phospholipids and galactolipids that are asymmetrically arranged along and across the membranes. Thylakoid membranes are richer in galactolipids rather than phospholipids; also they predominantly consist of hexagonal phase II forming monogalacotosyl diglyceride lipid. Despite this unique composition, plant thylakoid membranes have been shown to assume largely lipid-bilayer dynamic organization. Lipids forming the thylakoid membranes, richest in high-fluidity linolenic acid are synthesized in a complex pathway involving exchange of lipid precursors between the endoplasmic reticulum and inner membrane of the plastid envelope and transported from the inner membrane to the thylakoids via vesicles. | 5 | Photochemistry |
The sodium adsorption ratio (SAR) is an irrigation water quality parameter used in the management of sodium-affected soils. It is an indicator of the suitability of water for use in agricultural irrigation, as determined from the concentrations of the main alkaline and earth alkaline cations present in the water. It is also a standard diagnostic parameter for the sodicity hazard of a soil, as determined from analysis of pore water extracted from the soil.
The formula for calculating the sodium adsorption ratio (SAR) is:
where sodium, calcium, and magnesium concentrations are expressed in milliequivalents/liter.
SAR allows assessment of the state of flocculation or of dispersion of clay aggregates in a soil. Sodium and potassium ions facilitate the dispersion of clay particles while calcium and magnesium promote their flocculation. The behaviour of clay aggregates influences the soil structure and affects the permeability of the soil on which directly depends the water infiltration rate. It is important to accurately know the nature and the concentrations of cations at which the flocculation occurs: critical flocculation concentration (CFC). The SAR parameter is also used to determine the stability of colloids in suspension in water.
Although SAR is only one factor in determining the suitability of water for irrigation, in general, the higher the sodium adsorption ratio, the less suitable the water is for irrigation. Irrigation using water with high sodium adsorption ratio may require soil amendments to prevent long-term damage to the soil.
If irrigation water with a high SAR is applied to a soil for years, the sodium in the water can displace the calcium and magnesium in the soil. This will cause a decrease in the ability of the soil to form stable aggregates and a loss of soil structure and tilth. This will also lead to a decrease in infiltration and permeability of the soil to water, leading to problems with crop production. Sandy soils will have less problems, but fine-textured soils will have severe problems if SAR is greater than 9. When SAR is less than 3, there will not be a problem.
The concept of SAR addresses only the effects of sodium on the stability of soil aggregates. However, high K and Mg concentrations have also negative effects on soil permeability. The effect of potassium can be similarly treated by means of the potassium adsorption ratio (PAR). To take into account simultaneously all major cations present in water, a new irrigation water quality parameter was defined: the cation ratio of structural stability (CROSS), a generalization of SAR. | 9 | Geochemistry |
In September researchers were able to give trichromatic vision to squirrel monkeys. In November 2009, researchers halted a fatal genetic disorder called adrenoleukodystrophy in two children using a lentivirus vector to deliver a functioning version of ABCD1, the gene that is mutated in the disorder. | 1 | Biochemistry |
Two-stroke, Four-stroke, and continuous machine are very different from each other. However it was shown that there is a quantum regime where all these machines become thermodynamically equivalent to each other. While the intra cycle dynamics in the equivalence regime is very different in different engine types, when the cycle is completed they all turn out to provide the same amount of work and consume the same amount of heat (hence they share the same efficiency as well). This equivalence is associated with a coherent work extraction mechanism and has no classical analogue. These quantum features have been demonstrated experimentally. | 7 | Physical Chemistry |
When an electronic conductor is brought in contact with a solid or liquid ionic conductor (electrolyte), a common boundary (interface) among the two phases appears. Hermann von Helmholtz was the first to realize that charged electrodes immersed in electrolyte solutions repel the co-ions of the charge while attracting counterions to their surfaces. Two layers of opposite polarity form at the interface between electrode and electrolyte. In 1853 he showed that an electrical double layer (DL) is essentially a molecular dielectric and stores charge electrostatically. Below the electrolyte's decomposition voltage, the stored charge is linearly dependent on the voltage applied.
This early model predicted a constant differential capacitance independent from the charge density depending on the dielectric constant of the electrolyte solvent and the thickness of the double-layer.
This model, with a good foundation for the description of the interface, does not consider important factors including diffusion/mixing of ions in solution, the possibility of adsorption onto the surface, and the interaction between solvent dipole moments and the electrode. | 7 | Physical Chemistry |
The species was formerly grouped with the western meadow vole (M. drummondii) and the Florida salt marsh vole (M. dukecampbelli) as a single species with a very large range, but genetic evidence indicates that these are all distinct species. | 2 | Environmental Chemistry |
The rate of a chemical reaction is influenced by many different factors, such as temperature, pH, reactant, and product concentrations and other effectors. The degree to which these factors change the reaction rate is described by the elasticity coefficient. This coefficient is defined as follows:
where denotes the reaction rate and denotes the substrate concentration. Be aware that the notation will use lowercase roman letters, such as to indicate concentrations.
The partial derivative in the definition indicates that the elasticity is measured with respect to changes in a factor S while keeping all other factors constant. The most common factors include substrates, products, enzyme, and effectors. The scaling of the coefficient ensures that it is dimensionless and independent of the units used to measure the reaction rate and magnitude of the factor. The elasticity coefficient is an integral part of metabolic control analysis and was introduced in the early 1970s and possibly earlier by Henrik Kacser and Burns in Edinburgh and Heinrich and Rapoport in Berlin.
The elasticity concept has also been described by other authors, most notably Savageau in Michigan and Clarke at Edmonton. In the late 1960s Michael Savageau developed an innovative approach called biochemical systems theory that uses power-law expansions to approximate the nonlinearities in biochemical kinetics. The theory is very similar to metabolic control analysis and has been very successfully and extensively used to study the properties of different feedback and other regulatory structures in cellular networks. The power-law expansions used in the analysis invoke coefficients called kinetic orders, which are equivalent to the elasticity coefficients.
Bruce Clarke in the early 1970s, developed a sophisticated theory on analyzing the dynamic stability in chemical networks. As part of his analysis, Clarke also introduced the notion of kinetic orders and a power-law approximation that was somewhat similar to Savageaus power-law expansions. Clarkes approach relied heavily on certain structural characteristics of networks, called extreme currents (also called elementary modes in biochemical systems). Clarke's kinetic orders are also equivalent to elasticities.
Elasticities can also be usefully interpreted as the means by which signals propagate up or down a given pathway.
The fact that different groups independently introduced the same concept implies that elasticities, or their equivalent, kinetic orders, are most likely a fundamental concept in the analysis of complex biochemical or chemical systems. | 7 | Physical Chemistry |
The adsorbent, loaded with adsorbed pollutant on its surface sediments and forms a bed in the regeneration zone in the cell. The mass of the Nyex causes the bed to travel down the regeneration column slowly and eventually pass back into the cell. During the journey down the regeneration column, a DC current is passed across the electrochemical cell of which the adsorbent forms the anode. The applied current causes the pollutants adsorbed on the surface of the Nyex to be electrochemically oxidised regenerating the adsorbent surface restoring its full adsorptive capacity completing the adsorption-regeneration cycle. | 7 | Physical Chemistry |
Thiols, especially in the presence of base, are readily oxidized by reagents such as bromine and iodine to give an organic disulfide (R−S−S−R).
: 2 R−SH + Br → R−S−S−R + 2 HBr
Oxidation by more powerful reagents such as sodium hypochlorite or hydrogen peroxide can also yield sulfonic acids (RSOH).
: R−SH + 3 HO → RSOH + 3 HO
Oxidation can also be effected by oxygen in the presence of catalysts:
: 2 R–SH + O → RS−SR + HO
Thiols participate in thiol-disulfide exchange:
:RS−SR + 2 R′SH → 2 RSH + R′S−SR′
This reaction is important in nature. | 0 | Organic 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 | Organic Chemistry |
The formation of small particles of a substance with a narrow size distribution is an important process in the pharmaceutical and other industries. Supercritical fluids provide a number of ways of achieving this by rapidly exceeding the saturation point of a solute by dilution, depressurization or a combination of these. These processes occur faster in supercritical fluids than in liquids, promoting nucleation or spinodal decomposition over crystal growth and yielding very small and regularly sized particles. Recent supercritical fluids have shown the capability to reduce particles up to a range of 5-2000 nm. | 7 | Physical Chemistry |
A Woods lamp may be used to rapidly assess whether an individual is suffering from ethylene glycol poisoning as a consequence of antifreeze ingestion. Manufacturers of ethylene glycol-containing antifreezes commonly add fluorescein, which causes the patients urine to fluoresce under Wood's lamp. | 5 | Photochemistry |
Photochromism is the reversible change of color upon exposure to light. It is a transformation of a chemical species (photoswitch) between two forms by the absorption of electromagnetic radiation (photoisomerization), where the two forms have different absorption spectra. | 5 | Photochemistry |
Regardless of the presence or absence of an oxidant, the first step of the reaction is photochemical excitation of a stilbene or similar structure, leading to formation of a dihydrophenanthrene or similar intermediate. For stilbene and other chemicals containing a double-bond linker between the two aromatic rings, the excited structure can undergo reversible cis-trans isomerization. Although only cis structures can undergo the cyclization step themselves, trans structures can isomerize in situ and then cyclize. In keeping with the Woodward–Hoffmann rules, molecular orbital symmetry analysis of the photochemical reaction of the six-electron system explains the trans relative configuration at the newly bound centers by a conrotatory process.
This cyclization is reversible, but several other subsequent reactions can occur instead, depending on structural details and whether certain other reagents are present. | 5 | Photochemistry |
The Electrochemical Society Interface is a publication for those in the field of solid-state and electrochemical science and technology. Published quarterly, this four-color magazine contains technical articles about the latest developments in the field and presents news and information about and for Society members. | 7 | Physical Chemistry |
Often, the largest source of error in a study that depends on the natural abundance of carbon is the slight variation in natural C abundance itself. Such variations arise because the starting materials used in the reaction are themselves products of some other reactions that have kinetic isotope effects and corresponding isotopic enrichments in the products. To compensate for this error when NMR spectroscopy is used to determine the kinetic isotope effect, the following guidelines have been proposed:
* Choose a carbon that is remote from the reaction center that will serve as a reference and assume it does not have a kinetic isotope effect in the reaction.
* In the starting material that has not undergone any reaction, determine the ratios of the other carbon NMR peak integrals to that of the reference carbon.
* Obtain the same ratios for the carbons in a sample of the starting material after it has undergone some reaction.
* The ratios of the latter ratios to the former ratios yields R/R.
If these as well as some other precautions listed by Jankowski are followed, kinetic isotope effects with precisions of three decimal places can be achieved. | 7 | Physical Chemistry |
There are several mechanisms by which passing a current through the electrochemical cell can encourage pollutant desorption. Ions generated at the electrodes can change local pH conditions in the divided cell which affect the adsorption equilibrium and have been shown to promote desorption of organic pollutants such as phenols from the carbon surface. Other mechanisms include reactions between the ions generated and the adsorbed pollutants resulting in the formation of a species with a lower adsorptive affinity for activated carbon that subsequently desorb, or the oxidative destruction of the organics on the carbon surface. It is agreed that the main mechanisms are based on desorption induced regeneration as electrochemical effects are confined to the surface of the porous carbons so cannot be responsible for bulk regeneration.
The performance of different regeneration methods can be directly compared using the regeneration efficiency. This is defined as: | 7 | Physical Chemistry |
The third commercial copper ISASMELT plant was installed in MIM's Mount Isa copper smelter at a cost of approximately A$100 million. It was designed to treat 104 t/h of copper concentrate, containing 180,000 t/y of copper, and it began operation in August 1992.
A significant difference between the Mount Isa copper ISASMELT plant and all the others is that it uses an Ahlstrom Fluxflow waste heat boiler to recover heat from the furnace waste gas. This boiler uses a recirculating fluid bed of particles to rapidly quench the gas as it leaves the furnace, and then uses the enhanced heat transfer properties of solid–solid contact to cool the particles as they are carried past boiler tubes that are suspended in a shaft above the bed. The high heat transfer rate means that the Fluxflow boiler is relatively compact compared with conventional waste heat boilers and the rapid cooling of the waste gas limits the formation of sulfur trioxide ("SO"), which in the presence of water forms sulfuric acid that can cause corrosion of cool surfaces.
In its early years, the Fluxflow boiler was the cause of significant down time, because the rate of wear of the boiler tubes was much higher than expected. The problems were solved by understanding the gas flows within the boiler and redesigning the boiler tubes to minimise the effects of erosion.
The life of the refractory bricks in the ISASMELT furnace was initially shorter than expected and a water cooling system was briefly considered to extend them; however, this was not installed and operational improvements resulted in a significant extension of the lining life without this capital and operating expense. Since 1998, the refractory lining lives have exceeded their two-year design, with lives of the 8th and 9th linings nearly reaching three years. The most recent lining lasted for 50 months, with the one before that lasting for 44 months.
In the first years of operation at Mount Isa, the throughput of the ISASMELT furnace was constrained by problems with some of the ancillary equipment in the plant, including the boiler, slag granulation system and concentrate filters. The ultimate constraint was the decision during its construction to keep one of the two reverberatory furnaces on line to increase the copper smelter production to 265,000 t/y of anode copper. The smelter's Peirce-Smith converters became a bottleneck and the feed rate of the ISASMELT furnace had to be restrained to allow sufficient matte to be drawn from the reverberatory furnace to prevent it freezing solid. The ISASMELT 12-month rolling average of the feed rate fell just short of 100 t/h for much of this period, not quite reaching the design annual average of 104 t/h. MIM decided to shut down the reverberatory furnace in 1997, and the ISASMELT plant 12-month rolling mean feed rate quickly exceeded the 104 t/h design when this constraint was lifted.
The performance of the ISASMELT plant was sufficiently encouraging that MIM decided to expand the ISASMELT treatment rate to 166 t/h by adding a second oxygen plant to allow higher enrichment of the lance air. As a result, by late 2001 it had achieved a peak rate of 190 t/h of concentrate, and the smelter produced a peak annual total of 240,000 t of anode copper. At that time, the Mount Isa copper smelter, together with its copper refinery in Townsville, was among the lowest cost copper smelters in the world.
Lance life is typically two weeks, with lance changes taking 30 to 40 minutes, and repairs usually being limited to replacement of the lance tips.
In 2006, MIM commissioned a second rotary holding furnace that operates in parallel with the existing holding furnace. | 8 | Metallurgy |
Glyceraldehyde 3-phosphate and pyruvate, intermediates of photosynthesis, are converted to deoxy-D-xylulose 5-phosphate (DXP) catalyzed by DXP synthase (DXS). DXP reductoisomerase catalyzes the reduction by NADPH and subsequent rearrangement. The resulting MEP is converted to 4-(cytidine 5’-diphospho)-2-C-methyl-D-erythritol (CDP-ME) in the presence of CTP using the enzyme MEP cytidylyltransferase. CDP-ME is then converted, in the presence of ATP, to 2-phospho-4-(cytidine 5’-diphospho)-2-C-methyl-D-erythritol (CDP-ME2P). The conversion to CDP-ME2P is catalyzed by CDP-ME kinase. Next, CDP-ME2P is converted to 2-C-methyl-D-erythritol 2,4-cyclodiphosphate (MECDP). This reaction occurs when MECDP synthase catalyzes the reaction and CMP is eliminated from the CDP-ME2P molecule. MECDP is then converted to (e)-4-hydroxy-3-methylbut-2-en-1-yl diphosphate (HMBDP) via HMBDP synthase in the presence of flavodoxin and NADPH. HMBDP is reduced to IPP in the presence of ferredoxin and NADPH by the enzyme HMBDP reductase. The last two steps involving HMBPD synthase and reductase can only occur in completely anaerobic environments. IPP is then able to isomerize to DMAPP via IPP isomerase. | 5 | Photochemistry |
Stains-all stains nucleic acids, anionic proteins, anionic polysaccharides such as alginate and pectinate, hyaluronic acid and dermatan sulfate, heparin, heparan sulfate and chondroitin sulfate. It is used in SDS-PAGE, agarose gel electrophoresis and histologic staining, e.g. staining of growth lines in bones. | 1 | Biochemistry |
AMGs have a large impact on biogeochemical cycles in multiple environments through nutrient degradation, mineralization, transportation, assimilation, and transformation. By enhancing the metabolic capabilities of their hosts, bacteriophages contribute to the recycling of organic matter, influencing the availability of nutrients for other organisms in the ecosystem. Lytic viruses in particular have been shown to increase ammonium oxidation, nitric oxide reduction, nitrification, and denitrification to balance nutrient levels in nitrogen polluted environments. Nutrient-enriched wetlands contain AMGs related to sulfur transport and metabolism. AMG modification of host processes is another means other than the viral shunt by which viruses can directly impact biogeochemical cycles. | 1 | Biochemistry |
Karl Schlögl (October 5, 1924 – May 4, 2007) was professor of organic chemistry at the University of Vienna and secretary as well as vice-president of the Austrian Academy of Sciences. | 0 | Organic Chemistry |
In 2005, Meyers et al. Proposed the following mechanism for the decarboxylative cross-coupling reaction. The initial and rate determining step is the decarboxylation. The ipso carbon of the arene ring is thought to coordinate to the palladium centre initially and is followed by the expulsion of carbon dioxide, forming an aryl–palladium intermediate. The olefin then inserts between the arene and palladium center, which then undergoes beta elimination to form the desired vinyl halide, as well as a palladium hydride. This proton is abstracted by silver carbonate, which acts as both a base and an oxidant to regenerate the starting palladium complex completing the catalytic cycle. | 0 | Organic Chemistry |
Chirilă was born and educated in Romania, where he obtained a BEng in polymer technology (1972) and a PhD in organic chemistry (1981) from the Polytechnic University of Timișoara.
After ten years of research in polymers and organic chemistry, he relocated to Australia. During 1984 he was a research fellow at the Curtin School of Applied Chemistry. In 1986 he joined Lions Eye Institute in Perth as a senior scientist with the task of establishing a department for research and development of polymeric biomaterials for ophthalmology. In 2005, he joined the newly founded Queensland Eye Institute in Brisbane, where he was offered a position of senior scientist to continue his research and to establish a department of ophthalmic bioengineering. He was made a fellow of Royal Australian Chemical Institute (RACI) in 1992. Currently, he holds three adjunct professorships at the School of Physical and Chemical Sciences of Queensland University of Technology, Australian Institute for Bioengineering and Nanotechnology of University of Queensland, and Faculty of Health Sciences of University of Queensland. | 0 | Organic Chemistry |
Ionic bonding can result from a redox reaction when atoms of an element (usually metal), whose ionization energy is low, give some of their electrons to achieve a stable electron configuration. In doing so, cations are formed. An atom of another element (usually nonmetal) with greater electron affinity accepts one or more electrons to attain a stable electron configuration, and after accepting electrons an atom becomes an anion. Typically, the stable electron configuration is one of the noble gases for elements in the s-block and the p-block, and particular stable electron configurations for d-block and f-block elements. The electrostatic attraction between the anions and cations leads to the formation of a solid with a crystallographic lattice in which the ions are stacked in an alternating fashion. In such a lattice, it is usually not possible to distinguish discrete molecular units, so that the compounds formed are not molecular. However, the ions themselves can be complex and form molecular ions like the acetate anion or the ammonium cation.
For example, common table salt is sodium chloride. When sodium (Na) and chlorine (Cl) are combined, the sodium atoms each lose an electron, forming cations (Na), and the chlorine atoms each gain an electron to form anions (Cl). These ions are then attracted to each other in a 1:1 ratio to form sodium chloride (NaCl).
: Na + Cl → Na + Cl → NaCl
However, to maintain charge neutrality, strict ratios between anions and cations are observed so that ionic compounds, in general, obey the rules of stoichiometry despite not being molecular compounds. For compounds that are transitional to the alloys and possess mixed ionic and metallic bonding, this may not be the case anymore. Many sulfides, e.g., do form non-stoichiometric compounds.
Many ionic compounds are referred to as salts as they can also be formed by the neutralization reaction of an Arrhenius base like NaOH with an Arrhenius acid like HCl
: NaOH + HCl → NaCl + HO
The salt NaCl is then said to consist of the acid rest Cl and the base rest Na.
The removal of electrons to form the cation is endothermic, raising the systems overall energy. There may also be energy changes associated with breaking of existing bonds or the addition of more than one electron to form anions. However, the action of the anions accepting the cation's valence electrons and the subsequent attraction of the ions to each other releases (lattice) energy and, thus, lowers the overall energy of the system.
Ionic bonding will occur only if the overall energy change for the reaction is favorable. In general, the reaction is exothermic, but, e.g., the formation of mercuric oxide (HgO) is endothermic. The charge of the resulting ions is a major factor in the strength of ionic bonding, e.g. a salt CA is held together by electrostatic forces roughly four times weaker than CA according to Coulomb's law, where C and A represent a generic cation and anion respectively. The sizes of the ions and the particular packing of the lattice are ignored in this rather simplistic argument. | 6 | Supramolecular Chemistry |
TFIIB is phosphorylated at serine 65 which is found in the B reader domain. Without this phosphorylation, transcription initiation does not occur. It has been suggested that the general transcription factor TFIIH could act as the kinase for this phosphorylation although more evidence is needed to support this. Although TFIIB does not travel with the RNA polymerase II complex along the DNA during elongation, it has been recently suggested that it has a role in gene looping which links the promoter to the terminator of the gene. however, recent research has shown that a depletion in TFIIB is not lethal to cells and transcription levels are not significantly affected. This is because over 90% of mammalian promoters do not contain a BRE (B recognition element) or TATA box sequence which are required for TFIIB to bind. In addition to this, TFIIB levels have been shown to fluctuate in different types of cell, and at different points in the cell cycle, supporting the evidence that it is not required for all RNA polymerase II transcription. Gene looping is reliant on the interaction between phosphorylated serine residues found on the C terminal domain of RNA polymerase II and polyadenylation factors. TFIIB is needed for the interaction of promoters with these polyadenylation factors, such as SSu72 and CstF-64. It has also been suggested that both gene loop formation and the collapse of the DNA bubble are a result of TFIIB phosphorylation; however, it is unclear whether this gene loop formation is a cause or consequence of transcription initiation. | 1 | Biochemistry |
In 2021, evidence for OH in the dayside atmosphere of the exoplanet WASP-33b was found in its emission spectrum at wavelengths between 1 and 2 micrometers. Evidence for OH in the atmosphere of exoplanet WASP-76b was subsequently found. Both WASP-33b and WASP-76b are ultra-hot Jupiters and it is likely that any water in their atmospheres is present as dissociated ions. | 0 | Organic Chemistry |
Engineers can use the Brinell hardness of materials in their calculations to avoid this mode of failure. A rolling element bearing's static load rating is defined to avoid this failure type. Increasing the number of elements can provide better distribution of the load, so bearings intended for a large load may have many balls, or use needles instead. This decreases the chances of brinelling, but increases friction and other factors. However, although roller and ball bearings work well for radial and thrust loading, they are often prone to brinelling when very high impact loading, lateral loading, or vibration are experienced. Babbitt bearings or bronze bushings are often used instead of roller bearings in applications where such loads exist, such as in automotive crankshafts or pulley sheaves, to decrease the possibility of brinelling by distributing the force over a very large surface area.
A common cause of brinelling is the use of improper installation procedures. Brinelling often occurs when pressing bearings into holes or onto shafts. Care must usually be taken to ensure that pressure is applied to the proper bearing race to avoid transferring the pressure from one race to the other through the balls or rollers. If pressing force is applied to the wrong race, brinelling can occur to either or both of the races. The act of pressing or clamping can also leave brinell marks, especially if the vise or press has serrated jaws or roughened surfaces. Flat pressing plates are often used in the pressing of bearings, while soft copper, brass, or aluminum jaw covers are often used in vises to help avoid brinell marks from being forced into the workpiece. | 8 | Metallurgy |
Members of the society are required to have worked in geochemistry for at least two years at the time of application; student members are admitted if they are enrolled in courses recognised by the Association. To become a voting member, or fellow, members must satisfy the society that they have adequate training and experience in the field. Membership in the society has been used to measure total numbers of working geochemists. | 9 | Geochemistry |
The concept of hydrogen bonding once was challenging. Linus Pauling credits T. S. Moore and T. F. Winmill with the first mention of the hydrogen bond, in 1912. Moore and Winmill used the hydrogen bond to account for the fact that trimethylammonium hydroxide is a weaker base than tetramethylammonium hydroxide. The description of hydrogen bonding in its better-known setting, water, came some years later, in 1920, from Latimer and Rodebush. In that paper, Latimer and Rodebush cited the work of a fellow scientist at their laboratory, Maurice Loyal Huggins, saying, "Mr. Huggins of this laboratory in some work as yet unpublished, has used the idea of a hydrogen kernel held between two atoms as a theory in regard to certain organic compounds." | 6 | Supramolecular Chemistry |
In a low concentration (approximately 10%), nitric acid is often used to artificially age pine and maple. The color produced is a grey-gold very much like very old wax- or oil-finished wood (wood finishing). | 3 | Analytical Chemistry |
Enantioselective benzylic functionalization reactions depend on the use of enantiomerically pure, planar chiral chromium arene complexes. This section describes methods for the enantioselective synthesis of planar chiral chromium arene complexes, then outlines methods for functionalization of both sp- and sp-hybridized benzylic positions. | 0 | Organic Chemistry |
The GHK voltage equation for monovalent positive ionic species and negative:
This results in the following if we consider a membrane separating two -solutions:
It is "Nernst-like" but has a term for each permeant ion:
* = the membrane potential (in volts, equivalent to joules per coulomb)
* = the selectivity for that ion (in meters per second)
* = the extracellular concentration of that ion (in moles per cubic meter, to match the other SI units)
* = the intracellular concentration of that ion (in moles per cubic meter)
* = the ideal gas constant (joules per kelvin per mole)
* = the temperature in kelvins
* = Faraday's constant (coulombs per mole)
is approximately 26.7 mV at human body temperature (37 °C); when factoring in the change-of-base formula between the natural logarithm, ln, and logarithm with base 10 , it becomes , a value often used in neuroscience.
The ionic charge determines the sign of the membrane potential contribution. During an action potential, although the membrane potential changes about 100mV, the concentrations of ions inside and outside the cell do not change significantly. They are always very close to their respective concentrations when the membrane is at their resting potential. | 7 | Physical Chemistry |
* "Surface Tension", (1891) Nature, 46, 437.
* "[https://archive.org/details/paper-doi-10_1038_046418e0/mode/2up On the relative contamination of the water-surface by equal quantities of different substances]", (1892) Nature 47, 418.
* "Relations between the surface tension and relative contamination of water surfaces", (1893) Nature, 48, 152.
* "On the spreading of oil upon water", (1894) Nature 50, 223.
* "Beobachtungen über die Adhäsion verschiedener Flüssigkeiten an Glas", (Observations about the Adhesion of Different Liquids on Glass), (1898) Naturwissenschaftliche Rundschau, 14, 190.
* "Randwinkel gesättigter Lösungen an Kristallen" (Contact Angles of Saturated Solutions on Crystals), (1899), Naturwissenschaftliche Rundschau, 14, 383.
* "Untersuchungen von Grenzflächenspannungen mit der Cohäsionswaage", (Investigations of the Surface Tension with the Cohesion Balance), (1899) Annalen der Physik, 67, 668.
* "Über das spontane Sinken der Oberflächenspannung von Wasser, wässerigen Lösungen und Emulsionen", (On the Spontaneous Decrease of the Surface Tension of Water, Aqueous Solutions and Emulsions), (1902) Annalen der Physik', 8, 854.
* "Über Randwinkel und Ausbreitung von Flüssigkeiten auf festen Körpern" (On Contact Angles and the Flow of Fluids on Solid Bodies), (1914) Physikalische Zeitschrift, 15, 39.
* "Zur Frage der zeitlichen Veränderung der Oberflächenspannun" (On the Changes of the Surface Tension with Time), (1916) Physikalische Zeitschrift', 17, 141
* "Über die Ausbreitung reiner und gemischter Flüssigkeiten auf Wasser" (On the Spreading of Pure and Mixed Liquids on Water) (1916) Physikalische Zeitschrift, 17, 142.
* "Die Anomalie der Wasseroberfläche" (The Anomalous State of the Water Surface) (1917) Die Naturwissenschaften, 5, 137 u. 149.
* "Zur Frage der Ölflecke auf Seen" (On Oil Stains on Lakes) (1918) Die Naturwissenschaften, 6, 118.
* "The measurement of surface tension with the balance" (1926) Science 64, 304. | 7 | Physical Chemistry |
A carbometallation is any reaction where a carbon-metal bond reacts with a carbon-carbon π-bond to produce a new carbon-carbon σ-bond and a carbon-metal σ-bond. The resulting carbon-metal bond can undergo further carbometallation reactions (oligomerization or polymerization see Ziegler-Natta polymerization) or it can be reacted with a variety of electrophiles including halogenating reagents, carbonyls, oxygen, and inorganic salts to produce different organometallic reagents. Carbometallations can be performed on alkynes and alkenes to form products with high geometric purity or enantioselectivity, respectively. Some metals prefer to give the anti-addition product with high selectivity and some yield the syn-addition product. The outcome of syn and anti- addition products is determined by the mechanism of the carbometallation. | 0 | Organic Chemistry |
Stars that burn hydrogen are called main sequence (MS) stars - these are by far the most common objects in the night sky. When the hydrogen fuel is exhausted and temperatures begin to fall, the object undergoes various transformations
and a white dwarf star is eventually born, the ember of the expired MS star. Temperatures of a new-born white dwarf may be in the hundreds of thousand kelvin, but if the mass of the white dwarf is less than just a few solar masses, burning of He to C and O is not possible and the star will slowly cool down forever. The coolest white dwarfs observed have temperatures of roughly 4000 K, which must mean that the universe is not old enough so that lower temperature stars cannot be found. The emission spectra of "cool" white dwarfs does not at all look like a Planck blackbody spectrum. Instead, nearly the whole infrared is attenuated or missing altogether from the star's emission, owing to CIA in the hydrogen-helium atmospheres surrounding their cores. The impact of CIA on the observed spectral energy distribution is well understood and accurately modeled for most cool white dwarfs. For white dwarfs with a mix H/He atmosphere, the intensity of the H-He CIA can be used to infer the hydrogen abundance at the white dwarf photosphere. However, predicting CIA in the atmospheres of the coolest white dwarfs is more challenging, in part because of the formation of many-body collisional complexes. | 7 | Physical Chemistry |
ACE-inhibitors like lisinopril are considered to be generally safe for people undergoing routine dental care, though the use of lisinopril prior to dental surgery is more controversial, with some dentists recommending discontinuation the morning of the procedure. People may present to dental care suspicious of an infected tooth, but the swelling around the mouth may be due to lisinopril-induced angioedema, prompting emergency and medical referral. | 4 | Stereochemistry |
It has been proposed that ThTP has a specific role in nerve excitability, but this has never been confirmed and recent results suggest that ThTP probably plays a role in cell energy metabolism. Low or absent levels of thiamine triphosphate have been found in Leighs disease.
In E. coli, ThTP is accumulated in the presence of glucose during amino acid starvation. On the other hand, suppression of the carbon source leads to the accumulation, of adenosine thiamine triphosphate (AThTP). | 1 | Biochemistry |
Common side effects associated with the use of flucloxacillin include: diarrhoea, nausea, rash, urticaria, pain and inflammation at injection site, superinfection (including candidiasis), allergy, and transient increases in liver enzymes and bilirubin.
Rarely, in fewer than 1 in 1,000 people, cholestatic jaundice (also referred to as cholestatic hepatitis) has been associated with flucloxacillin therapy. It may appear as pale stool with dark urine, and yellowish eyes and skin. The reaction may occur up to several weeks after treatment has stopped, and takes weeks to resolve. The estimated incidence is one in 15,000 exposures, and is more frequent in people over the age of 55, females, and those with a treatment duration of longer than two weeks.
Flucloxacillin is contraindicated in those with a previous history of allergy to penicillins, cephalosporins, or carbapenems. It should also not be used in the eye, or administered to those with a history of cholestatic hepatitis associated with the use of dicloxacillin or flucloxacillin.
It should be used with caution in the elderly, patients with renal impairment where a reduced dose is required, and those with hepatic impairment, due to the risk of cholestatic hepatitis.
It should be taken on an empty stomach, one half to one hour before food, as absorption is reduced when taken with food, though some studies suggest that this does not compromise flucloxacillin plasma concentrations in most circumstances.
The UK's National Health Service recommends taking at least 30 minutes before food and at least 2 hours after. | 4 | Stereochemistry |
A Langmuir monolayer or insoluble monolayer is a one-molecule thick layer of an insoluble organic material spread onto an aqueous subphase in a Langmuir-Blodgett trough. Traditional compounds used to prepare Langmuir monolayers are amphiphilic materials that possess a hydrophilic headgroup and a hydrophobic tail. Since the 1980s a large number of other materials have been employed to produce Langmuir monolayers, some of which are semi-amphiphilic, including polymeric, ceramic or metallic nanoparticles and macromolecules such as polymers. Langmuir monolayers are extensively studied for the fabrication of Langmuir-Blodgett film (LB films), which are formed by transferred monolayers on a solid substrate.
A Gibbs monolayer or soluble monolayer is a monolayer formed by a compound that is soluble in one of the phases separated by the interface on which the monolayer is formed. | 7 | Physical Chemistry |
Trapped bubbles of air and water within fossil amber can be analyzed to provide direct evidence of the climate conditions existing when the resin or tree sap formed. The analysis of these trapped air bubbles provides a record of atmosphere composition going back 140 million years. The data indicate that the oxygen content of the atmosphere reached a high of nearly 35% during the Cretaceous Period and then plummeted to near present levels during the early Tertiary. The abrupt decline corresponds to or closely follows the Cretaceous–Paleogene extinction event and may be the result of a major meteorite impact that created the Chicxulub Crater.
In paleoceanography studies, fluid inclusions can inform about the chemical composition of seawater. The trapped seawater in sediments evaporates and leaves behind the salt content. The depth at which these evaporites are found relative to the composition of the trapped salt allows oceanographers to reconstruct seawater evolution. Air bubbles trapped within the deep ice caps can also be analyzed for clues to ancient climate conditions. | 9 | Geochemistry |
Pseudotropine (3β-tropanol, ψ-tropine, 3-pseudotropanol, or PTO) is a derivative of tropane and an isomer of tropine. Pseudotropine can be found in the Coca plant along with several other alkaloids | 1 | Biochemistry |
Ted Ellis and his wife are both natives of New Orleans, and much of his art along with his passion for art are inspired by the vibrant city. As a young man, he would search the colorful French Quarter for subjects to paint. In the aftermath of Hurricane Katrina and the devastation of parts of the city, the city's role in his art drastically changed so as to reflect the story of hope and rebirth that he saw in the disaster.
On the night before the storm hit Louisiana, the Ellis home in Texas was a refuge for 10 New Orleans families, 50 people in all. After the storm, Ellis helped fly home friends stranded outside New Orleans, and he organized colleagues in the art community behind the relief effort.
Ellis was allowed to enter the city two weeks after the flood waters subsided in order to survey the damage to his mothers home in the Lower Ninth Ward and salvage her possessions. While travelling among the destroyed houses and deserted city, Ellis witnessed a lone man repairing his homes roof. The contrast resonated with Ellis, and he memorialized the hope he saw in the mans actions through his piece Surviving Katrina. The scene is of rising floodwater that traps a family on their houses roof while the father holds up the Flag of the United States, a flag that to Ellis symbolizes the need for the nation to come together to aid those affected by the storm.
In Life Begins Anew, a father holds a baby above floodwaters while another man reaches out to take the child. Ellis describes the scene as symbolizing the promise of a new beginning for those who survived Katrina and its aftermath.
As its title indicates, the Katrina: The Hope, Healing and Rebirth of New Orleans collection was for Ellis about showing the power of art to assist the healing process: "The largest piece I did is about how life begins anew and how a person can find hope even after such devastation. I want this work to be uplifting, to be a fresh breath of life for the community." | 3 | Analytical Chemistry |
Potassium azodicarboxylate is a chemical compound with the formula CKNO. This chemical is used as a precursor to diimide. It can be synthesized by the reaction of potassium hydroxide with azodicarbonamide and it reacts with carboxylic acids to form diimide. | 0 | Organic Chemistry |
Vladimir Markovnikov was born on December 22, 1837, in Chernorechye near Nizhny Novgorod, Russian Empire (now Dzerzhinsk, Nizhny Novgorod Oblast, Russian Federation). Soon after his birth, his father retired and settled in a family estate received as a dowry from his wife's family at marriage, in the village of Ivanovo, Knyagininsky district of the Nizhny Novgorod province, where Markovnikov spent his early childhood.
He joined the cameral department of the law faculty of Kazan Imperial University in 1856. He moved to the natural department of the university, where he attended the lectures of A. M. Butlerov. In 1860, after completing a university course, he was left to prepare for a professorship and was appointed laboratory assistant at a chemical laboratory. In 1864 he defended his master's thesis. In the spring of 1869, he defended his doctoral dissertation. | 0 | Organic Chemistry |
Cyclamin is used as an ingredient for a nasal spray to reduce the tension of the wall and induce secretion of mucous. Furthermore, due to its toxic effects on different (cancer) cell types, cyclamin might be considered for use as chemotherapeutic drug. However, more research first has to be done to reduce its toxicity on normal human cells. | 0 | Organic Chemistry |
The dynamic energy budget (DEB) theory is a formal metabolic theory which provides a single quantitative framework to dynamically describe the aspects of metabolism (energy and mass budgets) of all living organisms at the individual level, based on assumptions about energy uptake, storage, and utilization of various substances. The DEB theory adheres to stringent thermodynamic principles, is motivated by universally observed patterns, is non-species specific, and links different levels of biological organization (cells, organisms, and populations) as prescribed by the implications of energetics. Models based on the DEB theory have been successfully applied to over a 1000 species with real-life applications ranging from conservation, aquaculture, general ecology, and ecotoxicology (see also the [https://www.bio.vu.nl/thb/deb/deblab/add_my_pet/species_list.html Add-my-pet collection]). The theory is contributing to the theoretical underpinning of the emerging field of metabolic ecology.
The explicitness of the assumptions and the resulting predictions enable testing against a wide variety of experimental results at the various levels of biological organization. The theory explains many general observations, such as the body size scaling relationships of certain physiological traits, and provides a theoretical underpinning to the widely used method of indirect calorimetry. Several popular empirical models are special cases of the DEB model, or very close numerical approximations. | 1 | Biochemistry |
Computational approaches have been regarded as a useful tool to elucidate the mechanism of action of enzymes. Molecular mechanics itself can not predict the electron transfer which is the fundamental of organic reaction but the molecular dynamics simulation provide sufficient information considering the flexibility of protein during catalytic reaction. The complementary method would be combined molecular mechanics/ quantum mechanics simulation (QM/MM)methods. With this approach, only the atoms responsible for enzymatic reaction in the catalytic region will be reared with quantum mechanics and the rest of the atoms were treated with molecular mechanics. | 1 | Biochemistry |
The International Association for Sports Surface Sciences (ISSS) is the union of labs and experts in the field of sports surfaces. It was founded in 1985 in Switzerland. Its aims are the exchange of information and ideas regarding testing sports surfaces such as sports hall floors, synthetic surfaces of athletic tracks and artificial turf surfaces. Members are located all over the world.
The ISSS is officially related to the IAAF. The ISSS has a board of directors consisting of Hans J. Kolitzus (CH/D), Vic Watson (GB), Ties Joosten (NL) and Alastair Cox (GB)). The head office is located in Switzerland. The ISSS organizes regular Technical Meetings with experts from the industry to discuss issues of common interest. | 7 | Physical Chemistry |
Enantiomeric excess is defined as the absolute difference between the mole fraction of each enantiomer:
where
In practice, it is most often expressed as a percent enantiomeric excess.
The enantiomeric excess can be determined in another way if we know the amount of each enantiomer produced. If one knows the moles of each enantiomer produced then:
Enantiomeric excess is used as one of the indicators of the success of an asymmetric synthesis. For mixtures of diastereomers, there are analogous definitions and uses for diastereomeric excess and percent diastereomeric excess.
As an example, a sample with 70 % of isomer and 30 % of will have a percent enantiomeric excess of 40. This can also be thought of as a mixture of 40 % pure with 60 % of a racemic mixture (which contributes half 30 % and the other half 30 % to the overall composition).
If given the enantiomeric excess of a mixture, the fraction of the main isomer, say , can be determined using and the lesser isomer .
A non-racemic mixture of two enantiomers will have a net optical rotation. It is possible to determine the specific rotation of the mixture and, with knowledge of the specific rotation of the pure enantiomer, the optical purity can be determined.
: optical purity (%) = · 100
Ideally, the contribution of each component of the mixture to the total optical rotation is directly proportional to its mole fraction, and as a result the numerical value of the optical purity is identical to the enantiomeric excess. This has led to informal use the two terms as interchangeable, especially because optical purity was the traditional way of measuring enantiomeric excess. However, other methods such as chiral column chromatography and NMR spectroscopy can now be used for measuring the amount of each enantiomer individually.
The ideal equivalence between enantiomeric excess and optical purity does not always hold. For example,
* the specific rotation of (S)-2-ethyl-2-methyl succinic acid is found to be dependent on concentration
* in what is known as the Horeau effect the relationship between mole based ee and optical rotation based ee can be non-linear i.d. in the succinic acid example the optical activity at 50% ee is lower than expected.
* the specific rotation of enantiopure 1-phenylethanol can be enhanced by the addition of achiral acetophenone as an impurity.
The term enantiomeric excess was introduced in 1971 by Morrison and Mosher in their publication Asymmetric Organic Reactions. The use of enantiomeric excess has established itself because of its historic ties with optical rotation. It has been suggested that the concept of ee should be replaced by that of er which stands for enantiomeric ratio or er (S:R) or q (S/R) because determination of optical purity has been replaced by other techniques which directly measure R and S and because it simplifies mathematical treatments such as the calculation of equilibrium constants and relative reaction rates. The same arguments are valid for changing diastereomeric excess (de) to diastereomeric ratio (dr). | 4 | Stereochemistry |
In Scanning fluorescence correlation spectroscopy (sFCS) the measurement volume is moved across the sample in a defined way. The introduction of scanning is motivated by its ability to alleviate or remove several distinct problems often encountered in standard FCS, and thus, to extend the range of applicability of fluorescence correlation methods in biological systems.
Some variations of FCS are only applicable to serial scanning laser microscopes. Image Correlation Spectroscopy and its variations all were implemented on a scanning confocal or scanning two photon microscope, but transfer to other microscopes, like a spinning disk confocal microscope. Raster ICS (RICS), and position sensitive FCS (PSFCS) incorporate the time delay between parts of the image scan into the analysis. Also, low-dimensional scans (e.g. a circular ring)—only possible on a scanning system—can access time scales between single point and full image measurements. Scanning path has also been made to adaptively follow particles. | 7 | Physical Chemistry |
The concentrations of species in equilibrium are usually calculated under the assumption that activity coefficients are either known or can be ignored. In this case, each equilibrium constant for the formation of a complex in a set of multiple equilibria can be defined as follows
:α A + β B ... AB...;
The concentrations of species containing reagent A are constrained by a condition of mass-balance, that is, the total (or analytical) concentration, which is the sum of all species' concentrations, must be constant. There is one mass-balance equation for each reagent of the type
There are as many mass-balance equations as there are reagents, A, B..., so if the equilibrium constant values are known, there are n mass-balance equations in n unknowns, [A], [B]..., the so-called free reagent concentrations. Solution of these equations gives all the information needed to calculate the concentrations of all the species.
Thus, the importance of equilibrium constants lies in the fact that, once their values have been determined by experiment, they can be used to calculate the concentrations, known as the speciation, of mixtures that contain the relevant species. | 7 | Physical Chemistry |
Here are some GeneRIFs taken from Entrez Gene for GeneID 7157, the human gene TP53.
The PubMed document identifiers have been omitted from the examples. Note the wide variability with respect to the presence or absence of punctuation and of sentence-initial capital letters.
* p53 and c-erbB-2 may have independent role in carcinogenesis of gall bladder cancer
* Degradation of endogenous HIPK2 depends on the presence of a functional p53 protein.
* p53 codon 72 alleles influence the response to anticancer drugs in cells from aged people by regulating the cell cycle inhibitor p21WAF1
* Logistic regression analysis showed p53 and COX-2 as dependent predictors in pancreatic carcinogenesis, and a reciprocal relationship to neoplastic progression between p53 and COX-2.
GeneRIFs are an unusual type of textual genre, and they have recently been the subject of a number of articles from the natural language processing community. | 1 | Biochemistry |
* All alcoholic drinks including beer, cider, kombucha, kvass, mead, perry, tibicos, wine, pulque, hard liquors (brandy, rum, vodka, sake, schnapps), and soured by-products including vinegar and alegar
* Yeast leavened breads including sourdough, salt-rising bread, and others
* Cheese and some dairy products including kefir and yogurt
* Chocolate
* Coffee
* Dishes including fermented fish, such as garum, surströmming, and Worcestershire sauce
* Some vegetables such as kimchi, some types of pickles (most are not fermented though), and sauerkraut
* A wide variety of fermented foods made from soybeans, including fermented bean paste, nattō, tempeh, and soya sauce | 1 | Biochemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.