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Strontium oxalate is a compound with the chemical formula . Strontium oxalate can exist either in a hydrated form () or as the acidic salt of strontium oxalate (). | 0 | Theoretical and Fundamental Chemistry |
A wide range of possible FCS experiments involve chemical reactions that continually fluctuate from equilibrium because of thermal motions (and then "relax"). In contrast to diffusion, which is also a relaxation process, the fluctuations cause changes between states of different energies. One very simple system showing chemical relaxation would be a stationary binding site in the measurement volume, where particles only produce signal when bound (e.g. by FRET, or if the diffusion time is much faster than the sampling interval). In this case the autocorrelation is:
where
is the relaxation time and depends on the reaction kinetics (on and off rates), and:
is related to the equilibrium constant K.
Most systems with chemical relaxation also show measurable diffusion as well, and the autocorrelation function will depend on the details of the system. If the diffusion and chemical reaction are decoupled, the combined autocorrelation is the product of the chemical and diffusive autocorrelations. | 0 | Theoretical and Fundamental Chemistry |
The bond valence model can be reduced to the traditional ionic model if certain conditions are satisfied. These conditions require that atoms be divided into cations and anions in such a way that (a) the electronegativity of every anion is equal to, or greater than, the electronegativity of any of the cations, (b) that the structure is electroneutral when the ions carry charges equal to their valence, and (c) that all the bonds have a cation at one end and an anion at the other. If these conditions are satisfied, as they are in many ionic and covalent compounds, the electrons forming a bond can all be formally assigned to the anion. The anion thus acquires a formal negative charge and the cation a formal positive charge, which is the picture on which the ionic model is based. The electrostatic flux that links the cation core to its bonding electrons now links the cation core to the anion. In this picture, a cation and anion are bonded to each other if they are linked by electrostatic flux, with the flux being equal to the valence of the bond. In a representative set of compounds Preiser et al. have confirmed that the electrostatic flux is the same as the bond valence determined from the bond lengths using Eq. 2.
The association of the cation bonding electrons with the anion in the ionic model is purely formal. There is no change in physical locations of any electrons, and there is no change in the bond valence. The terms "anion" and "cation" in the bond valence model are defined in terms of the bond topology, not the chemical properties of the atoms. This extends the scope of the ionic model well beyond compounds in which the bonding would normally be considered as "ionic". For example, methane, CH, obeys the conditions for the ionic model with carbon as the cation and hydrogen as the anion (or vice versa, since carbon and hydrogen have the same electronegativity).
For compounds that contain cation-cation or anion-anion bonds it is usually possible to transform these homoionic bonds into cation-anion bonds either by treating the atoms linked by the homoionic bond as a single complex cation (e.g., Hg), or by treating the bonding electrons in the homoionic bond as a pseudo-anion to transform a cation-cation bond into two cation - pseudo-anion bonds, e.g., Hg-e-Hg. | 0 | Theoretical and Fundamental Chemistry |
octreotide - odorant receptor - olfaction - olfactory receptor neuron - oligopeptide - oncogene - oncogene protein - oncogene proteins V-abl - oncogenic retroviridae protein - open reading frame - opioid receptor - opsin - optical isomerism - organ (anatomy) - organelle - organic chemistry - organic compound - organic nomenclature - organic reaction - organism - osmosis - osteocalcin - outer hair cell - outline of biochemical techniques - ovalbumin - oxidation - oxidation number - oxidation state - oxidative decarboxylation - oxidative phosphorylation - oxygen - oxytocin - oxytocin receptor | 1 | Applied and Interdisciplinary Chemistry |
The US National Academy of Medicine updated Dietary Reference Intakes (DRIs) in 2001 for vitamin A, which included Recommended Dietary Allowances (RDAs). For infants up to 12 months there was not sufficient information to establish a RDA, so Adequate Intake (AI) is shown instead. As for safety, tolerable upper intake levels (ULs) were also established. For ULs, carotenoids are not added when calculating total vitamin A intake for safety assessments.
The European Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR. AI and UL defined the same as in United States. For women and men of ages 15 and older, the PRIs are set respectively at 650 and 750 μg RE/day. PRI for pregnancy is 700 μg RE/day, for lactation 1300/day. For children of ages 1–14 years, the PRIs increase with age from 250 to 600 μg RE/day. These PRIs are similar to the US RDAs. The EFSA reviewed the same safety question as the United States, and set ULs at 800 for ages 1–3, 1100 for ages 4–6, 1500 for ages 7–10, 2000 for ages 11–14, 2600 for ages 15–17 and 3000 μg/day for ages 18 and older for preformed vitamin A, i.e., not including dietary contributions from carotenoids. | 1 | Applied and Interdisciplinary Chemistry |
Cis–trans isomerism occurs in octahedral and square planar complexes (but not tetrahedral). When two ligands are adjacent they are said to be cis, when
opposite each other, trans. When three identical ligands occupy one face of an octahedron, the isomer is said to be facial, or fac. In a fac isomer, any two identical ligands are adjacent or cis to each other. If these three ligands and the metal ion are in one plane, the isomer is said to be meridional, or mer. A mer isomer can be considered as a combination of a trans and a cis, since it contains both trans and cis pairs of identical ligands. | 0 | Theoretical and Fundamental Chemistry |
About 1 in 4,000 children in the United States will develop mitochondrial disease by the age of 10 years. Up to 4,000 children per year in the US are born with a type of mitochondrial disease. Because mitochondrial disorders contain many variations and subsets, some particular mitochondrial disorders are very rare.
The average number of births per year among women at risk for transmitting mtDNA disease is estimated to approximately 150 in the United Kingdom and 800 in the United States. | 1 | Applied and Interdisciplinary Chemistry |
Type T (copper–constantan) thermocouples are suited for measurements in the −200 to 350 °C range. Often used as a differential measurement, since only copper wire touches the probes. Since both conductors are non-magnetic, there is no Curie point and thus no abrupt change in characteristics. Type-T thermocouples have a sensitivity of about 43 μV/°C. Note that copper has a much higher thermal conductivity than the alloys generally used in thermocouple constructions, and so it is necessary to exercise extra care with thermally anchoring type-T thermocouples. A similar composition is found in the obsolete Type U in the German specification DIN 43712:1985-01. | 1 | Applied and Interdisciplinary Chemistry |
Thiophenes are a special class of sulfide-containing heterocyclic compounds. Because of their aromatic character, they are non-nucleophilic. The nonbonding electrons on sulfur are delocalized into the π-system. As a consequence, thiophene exhibits few properties expected for a sulfide – thiophene is non-nucleophilic at sulfur and, in fact, is sweet-smelling. Upon hydrogenation, thiophene gives tetrahydrothiophene, CHS, which indeed does behave as a typical sulfide. | 0 | Theoretical and Fundamental Chemistry |
The contact graph of an arbitrary finite packing of unit balls is the graph whose vertices correspond to the packing elements and whose two vertices are connected by an edge if the corresponding two packing elements touch each other. The cardinality of the edge set of the contact graph gives the number of touching pairs, the number of 3-cycles in the contact graph gives the number of touching triplets, and the number of tetrahedrons in the contact graph gives the number of touching quadruples (in general for a contact graph associated with a sphere packing in n dimensions that the cardinality of the set of n-simplices in the contact graph gives the number of touching (n + 1)-tuples in the sphere packing). In the case of 3-dimensional Euclidean space, non-trivial upper bounds on the number of touching pairs, triplets, and quadruples were proved by Karoly Bezdek and Samuel Reid at the University of Calgary.
The problem of finding the arrangement of n identical spheres that maximizes the number of contact points between the spheres is known as the "sticky-sphere problem". The maximum is known for n ≤ 11, and only conjectural values are known for larger n. | 0 | Theoretical and Fundamental Chemistry |
Elimination, bimolecular reactions are one step, concerted reaction where both base and substrate participate in the rate limiting step. In an E2 mechanism, a base takes a proton near the leaving group, forcing the electrons down to make a double bond, and forcing off the leaving group-all in one concerted step. The rate law depends on the first order concentration of two reactants, making it a 2nd order (bimolecular) elimination reaction. Factors that affect the rate determining step are stereochemistry, leaving groups, and base strength.
A theory, for an E2 reaction, by Joseph Bunnett suggests the lowest pass through the energy barrier between reactants and products is gained by an adjustment between the degrees of C-H and C-X rupture at the transition state. The adjustment involves much breaking of the bond more easily broken, and a small amount of breaking of the bond which requires more energy. This conclusion by Bunnett is a contradiction from the Hammond postulate. The Hammond postulate is the opposite of what Bunnett theorized. In the transition state of a bond breaking step it involves little breaking when the bond is easily broken and much breaking when it is difficult to break. Despite these differences, the two postulates are not in conflict since they are concerned with different sorts of processes. Hammond focuses on reaction steps where one bond is made or broken, or the breaking of two or more bonds occur simultaneously. The E2 theory transition state concerns a process when bond formation or breaking are not simultaneous. | 0 | Theoretical and Fundamental Chemistry |
Lanthanide salts often or perhaps characteristically form aquo complexes. The homoleptic tricationic aquo complexes have nine water ligands. | 0 | Theoretical and Fundamental Chemistry |
Lichens are classified by the fungal component. Lichen species are given the same scientific name (binomial name) as the fungus species in the lichen. Lichens are being integrated into the classification schemes for fungi. The alga bears its own scientific name, which bears no relationship to that of the lichen or fungus. There are about 20,000 identified lichen species, and taxonomists have estimated that the total number of lichen species (including those yet undiscovered) might be as high as 28,000. Nearly 20% of known fungal species are associated with lichens.
"Lichenized fungus" may refer to the entire lichen, or to just the fungus. This may cause confusion without context. A particular fungus species may form lichens with different algae species, giving rise to what appear to be different lichen species, but which are still classified (as of 2014) as the same lichen species.
Formerly, some lichen taxonomists placed lichens in their own division, the Mycophycophyta, but this practice is no longer accepted because the components belong to separate lineages. Neither the ascolichens nor the basidiolichens form monophyletic lineages in their respective fungal phyla, but they do form several major solely or primarily lichen-forming groups within each phylum. Even more unusual than basidiolichens is the fungus Geosiphon pyriforme, a member of the Glomeromycota that is unique in that it encloses a cyanobacterial symbiont inside its cells. Geosiphon is not usually considered to be a lichen, and its peculiar symbiosis was not recognized for many years. The genus is more closely allied to endomycorrhizal genera. Fungi from Verrucariales also form marine lichens with the brown algae Petroderma maculiforme, and have a symbiotic relationship with seaweed (such as rockweed) and Blidingia minima, where the algae are the dominant components. The fungi is thought to help the rockweeds to resist desiccation when exposed to air. In addition, lichens can also use yellow-green algae (Heterococcus) as their symbiotic partner.
Lichens independently emerged from fungi associating with algae and cyanobacteria multiple times throughout history. | 1 | Applied and Interdisciplinary Chemistry |
Primary treatment for wastewater or drinking water includes settling in a sedimentation chamber to remove as much of the solid matter as possible before applying additional treatments. The amount removed is controlled by the hydraulic residence time (HRT). When water flows through a volume at a slower rate, less energy is available to keep solid particles entrained in the stream and there is more time for them to settle to the bottom. Typical HRTs for sedimentation basins are around two hours, although some groups recommend longer times to remove micropollutants such as pharmaceuticals and hormones.
Disinfection is the last step in the tertiary treatment of wastewater or drinking water. The types of pathogens that occur in untreated water include those that are easily killed like bacteria and viruses, and those that are more robust such as protozoa and cysts. The disinfection chamber must have a long enough HRT to kill or deactivate all of them. | 0 | Theoretical and Fundamental Chemistry |
The modest acidity of carbons adjacent to the sulfonyl group has made sulfones useful for organic synthesis. Upon removal of the sulfonyl group with desulfonylation or reductive elimination, the net result is the formation of a carbon-carbon bond single or double bond between two unfunctionalized carbons, a ubiquitous motif in synthetic targets. In a synthesis of (–)-anthoplalone, Julia olefination was used to establish the (E)-alkene in the target.
Reductive desulfonylation is employed when the establishment of a carbon-carbon single bond is the goal. In a synthesis of (+)-chatancin, alkylation of an α-sulfonyl carbanion followed by desulfonylation established a key allylic carbon-carbon bond. | 0 | Theoretical and Fundamental Chemistry |
The Arrhenius equation gives the dependence of the rate constant of a chemical reaction on the absolute temperature as
where
* is the rate constant (frequency of collisions resulting in a reaction),
* is the absolute temperature,
* is the pre-exponential factor or Arrhenius factor or frequency factor. Arrhenius originally considered A to be a temperature-independent constant for each chemical reaction. However more recent treatments include some temperature dependence – see below.
* is the molar activation energy for the reaction,
* is the universal gas constant.
Alternatively, the equation may be expressed as
where
* is the activation energy for the reaction (in the same unit as kT),
* is the Boltzmann constant.
The only difference is the unit of : the former form uses energy per mole, which is common in chemistry, while the latter form uses energy per molecule directly, which is common in physics.
The different units are accounted for in using either the gas constant, , or the Boltzmann constant, , as the multiplier of temperature .
The unit of the pre-exponential factor are identical to those of the rate constant and will vary depending on the order of the reaction. If the reaction is first order it has the unit s, and for that reason it is often called the frequency factor or attempt frequency of the reaction. Most simply, is the number of collisions that result in a reaction per second, is the number of collisions (leading to a reaction or not) per second occurring with the proper orientation to react and is the probability that any given collision will result in a reaction. It can be seen that either increasing the temperature or decreasing the activation energy (for example through the use of catalysts) will result in an increase in rate of reaction.
Given the small temperature range of kinetic studies, it is reasonable to approximate the activation energy as being independent of the temperature. Similarly, under a wide range of practical conditions, the weak temperature dependence of the pre-exponential factor is negligible compared to the temperature dependence of the factor ; except in the case of "barrierless" diffusion-limited reactions, in which case the pre-exponential factor is dominant and is directly observable.
With this equation it can be roughly estimated that the rate of reaction increases by a factor of about 2 to 3 for every 10 °C rise in temperature, for common values of activation energy and temperature range.
The factor denotes the fraction of molecules with energy greater than or equal to . | 0 | Theoretical and Fundamental Chemistry |
Textbooks in physical chemistry generally give two derivations of the title equation. One is the conventional derivation that goes back to Van der Waals, a mechanical equation of state that cannot be used to specify all thermodynamic functions; the other is a statistical mechanics derivation that makes explicit the intermolecular potential neglected in the first derivation. A particular advantage of the statistical mechanical derivation is that it yields the partition function for the system, and allows all thermodynamic functions to be specified (including the mechanical equation of state). | 0 | Theoretical and Fundamental Chemistry |
This trend is also generally true of pentacoordinated main-group elements with one or more lone-pair-containing ligand, including the oxygen-pentacoordinated silicon examples shown below.
The Si-halogen bonds range from close to the expected van der Waals value in A (a weak bond) almost to the expected covalent single bond value in C (a strong bond). | 0 | Theoretical and Fundamental Chemistry |
The simple Streeter–Phelps model is based on the assumptions that a single BOD input is distributed evenly at the cross section of a stream or river and that it moves as plug flow with no mixing in the river. Furthermore, only one DO sink (carbonaceous BOD) and one DO source (reaeration) is considered in the classical Streeter–Phelps model. These simplifications will give rise to errors in the model. For example the model does not include BOD removal by sedimentation, that suspended BOD is converted to a dissolved state, that sediment has an oxygen demand and that photosynthesis and respiration will impact the oxygen balance. | 1 | Applied and Interdisciplinary Chemistry |
The theory of relativistic heat conduction is a model that is compatible with the theory of special relativity. For most of the last century, it was recognized that the Fourier equation is in contradiction with the theory of relativity because it admits an infinite speed of propagation of heat signals. For example, according to the Fourier equation, a pulse of heat at the origin would be felt at infinity instantaneously. The speed of information propagation is faster than the speed of light in vacuum, which is physically inadmissible within the framework of relativity. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, helicity is, under appropriate conditions, an invariant of the Euler equations of fluid flow, having a topological interpretation as a measure of linkage and/or knottedness of vortex lines in the flow. This was first proved by Jean-Jacques Moreau in 1961 and Moffatt derived it in 1969 without the knowledge of Moreaus paper. This helicity invariant is an extension of Woltjers theorem for magnetic helicity.
Let be the velocity field and the corresponding vorticity field. Under the following three conditions, the vortex lines are transported with (or frozen in) the flow: (i) the fluid is inviscid; (ii) either the flow is incompressible (), or it is compressible with a barotropic relation between pressure and density ; and (iii) any body forces acting on the fluid are conservative. Under these conditions, any closed surface whose normal vectors are orthogonal to the vorticity (that is, ) is, like vorticity, transported with the flow.
Let be the volume inside such a surface. Then the helicity in , denoted , is defined by the volume integral
For a localised vorticity distribution in an unbounded fluid, can be taken to be the whole space, and is then the total helicity of the flow. is invariant precisely because the vortex lines are frozen in the flow and their linkage and/or knottedness is therefore conserved, as recognized by Lord Kelvin (1868). Helicity is a pseudo-scalar quantity: it changes sign under change from a right-handed to a left-handed frame of reference; it can be considered as a measure of the handedness (or chirality) of the flow. Helicity is one of the four known integral invariants of the Euler equations; the other three are energy, momentum and angular momentum.
For two linked unknotted vortex tubes having circulations and , and no internal twist, the helicity is given by , where is the Gauss linking number of the two tubes, and the plus or minus is chosen according as the linkage is right- or left-handed.
For a single knotted vortex tube with circulation , then, as shown by Moffatt & Ricca (1992), the helicity is given by , where and are the writhe and twist of the tube; the sum is known to be invariant under continuous deformation of the tube.
The invariance of helicity provides an essential cornerstone of the subject topological fluid dynamics and magnetohydrodynamics, which is concerned with global properties of flows and their topological characteristics. | 1 | Applied and Interdisciplinary Chemistry |
A pH meter is a scientific instrument that measures the hydrogen-ion activity in water-based solutions, indicating its acidity or alkalinity expressed as pH. The pH meter measures the difference in electrical potential between a pH electrode and a reference electrode, and so the pH meter is sometimes referred to as a "potentiometric pH meter". The difference in electrical potential relates to the acidity or pH of the solution. Testing of pH via pH meters (pH-metry) is used in many applications ranging from laboratory experimentation to quality control. | 0 | Theoretical and Fundamental Chemistry |
The particular drawing on the pediment of the gate, with two overlapping triangles and Latin inscriptions, recapitulates the title page in the posthumous 1677 edition—which differed from the title page of the first edition—of the alchemical book Aureum Saeculum Redivivum (1621) by Adrian von Mynsicht (known also as Madathanus). In 1747 the emblem was used by Wienner von Sonnenfels in his Splendor lucis, oder Glanz des Lichts. Similarly, the lower part of the emblem by von Mynsicht depicting a "centrum in trigono centri", was reproduced in a manuscript called the Geheime Figuren der Rosencreutzer (1785–88). The same drawing appear in a bookmark possessed by Bérenger Saunière, a parish priest at Rennes-le-Château in 1885.
It is suggested as well that the geometrical construction of the gate is similar to that of the 21st emblem of Michael Maier’s Atalanta Fugiens (1617). | 1 | Applied and Interdisciplinary Chemistry |
Boiling point is the temperature at which the vapor pressure of a liquid is equal to the surrounding pressure, causing the liquid to rapidly evaporate, or boil. It is closely related to vapor pressure, but is dependent on pressure. The normal boiling point is the boiling point at atmospheric pressure, but it can also be reported at higher and lower pressures. | 0 | Theoretical and Fundamental Chemistry |
* Infant formula: Historically HMOs were not part of infant formula, and bottle-fed babies could not benefit from their positive health effects. However recently more and more HMOs, including 2'-Fucosyllactose and Lacto-N-neotetraose, are being added as supplements to modern infant formula. Recently an infant formula with a combination of 5 different HMOs (2′-fucosyllactose, 2′,3-di-fucosyllactose, lacto-N-tetraose, 3′-sialyllactose, and 6′-sialyllactose) was tested in a clinical trial with positive effects on gut microflora. However it is important to note that even this type of infant formula is far from the natural abundance of nearly 200 HMOs present in human milk.
* Irritable bowel syndrome: Human milk oligosaccharides are also used to treat the symptoms of irritable bowel syndrome (IBS), which is a gastrointestinal disorder affecting 10–15% of the developed world. A 12-week treatment with an orally taken HMO mixture showed significant improvement of the life quality of IBS patients. | 0 | Theoretical and Fundamental Chemistry |
To derive the Turbine specific speed equation we first start with the Power formula for water then using proportionalities with η,ρ, and g being constant they can be removed. The power of the turbine is therefore only dependent on the head H and flow Q.
:so
let:
: = Diameter of the turbine runner
: = Width of the turbine runner
: = Speed of the turbine (rpm)
: = Tangential velocity of the turbine blade (m/s)
: = Specific Speed of the Turbine
: = Velocity of water at turbine (m/s)
Now utilising the constant speed ratio at the turbine tip, the following proportionality can be made that the tangential velocity of the turbine blade is proportional to the square root of the head.
:Speed ratio
:so
But from rotational speed in RPM to linear speed in m/s the following equation and proportionality can be made.
:so
The flow through a turbine is the product of flow velocity and area so the flow through a turbine can be quantified.
:with
and as shown previously:
So using the above 2 , the following is obtained
By combining the equation for diameter and tangential speed, with tangential speed and head a relationship between flow and head can be reached.
Substituting this back into the power equation gives:
To convert this proportionality into an equation a factor of proportionality, say K, must be introduced which gives:
Now assuming our original proposition of producing 1 kilowatt at 1m head our speed N becomes our specific speed . So substituting these values into our equation gives:
Now we know we have a complete formula for specific speed,:
So rearranging for Specific Speed give the final following result:
where:
* = Wheel speed (rpm)
* = Power (kW)
* = Water head (m) | 1 | Applied and Interdisciplinary Chemistry |
Gaps often remain after initial BAC contig construction. These gaps occur if the Bacterial Artificial Chromosome (BAC) library screened has low complexity, meaning it does not contain a high number of STS or restriction sites, or if certain regions were less stable in cloning hosts and thus underrepresented in the library. If gaps between contigs remain after STS landmark mapping and restriction fingerprinting have been performed, the sequencing of contig ends can be used to close these gaps. This end-sequencing strategy essentially creates a novel STS with which to screen the other contigs. Alternatively, the end sequence of a contig can be used as a primer to primer walk across the gap. | 1 | Applied and Interdisciplinary Chemistry |
In titrations, the concentration of analyte in solution can be determined by titrating the standard solution against the analyte solution to determine the threshold of neutralization. For example, to calculate the concentration of hydrogen chloride, a standard solution of known concentration, such as 0.5 M sodium hydroxide, is titrated against the hydrogen chloride solution. | 0 | Theoretical and Fundamental Chemistry |
Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell (cytotoxicity) or an organ such as the liver (hepatotoxicity). Sometimes the word is more or less synonymous with poisoning in everyday usage.
A central concept of toxicology is that the effects of a toxicant are dose-dependent; even water can lead to water intoxication when taken in too high a dose, whereas for even a very toxic substance such as snake venom there is a dose below which there is no detectable toxic effect. Toxicity is species-specific, making cross-species analysis problematic. Newer paradigms and metrics are evolving to bypass animal testing, while maintaining the concept of toxicity endpoints. | 1 | Applied and Interdisciplinary Chemistry |
There are no widely accepted functions for the resulting truncated RNA transcripts. However, a study in 1981 found evidence that there was a relationship between the number of abortive transcripts produced and the time until long RNA strands are successfully produced. When RNA polymerase undergoes abortive transcription in the presence of ATP, UTP, and GTP, a complex is formed that has a much lower capacity for abortive recycling and a much higher rate of synthesis of the full-length RNA transcript. A study in 2010 found evidence that these truncated transcripts inhibit termination of RNA synthesis by a RNA hairpin-dependent intrinsic terminator. | 1 | Applied and Interdisciplinary Chemistry |
Poliakoff is the most visible presenter on the videos; his hair, reminiscent of Albert Einstein or a mad scientist, is frequently commented upon. The combination of the professors hair and amusing experiments has made these videos quite popular. Although uncertain what to think about the attention given to his hair, Professor Poliakoff is excited with the success of the videos, stating "With a few hours of work, I have lectured to more students than I have reached in my entire career." The YouTube channel as of December 2021, has over 1.5 million subscribers and the videos have surpassed 260 million views. The YouTube channel is now one of the most popular chemistry related channels on all of YouTube. The producers of the videos have received praise from Nobel Laureates, chemistry professors, and the general public, says Professor Poliakoff. Chemistry Nobel Laureate Roald Hoffmann has even offered his praise of the videos, stating they "are like the best reality show Ive ever seen – the universe revealing itself, element by element." In 2019, Poliakoff was awarded the Royal Society of London Michael Faraday Prize for science communication for his work on the videos.
The videos feature various experiments and demonstrations of the elements, some too dangerous to be performed in a classroom. Though the presenters take appropriate precautions when doing such experiments and provide adequate warnings, some scientists have criticized the dangerous experiments fearing people might try them at home and get hurt. The intent of the videos is to bring chemistry to a new generation of students and to get them enthused about science and understand how chemists think and what chemists are trying to do. Many school teachers now incorporate these videos into their classes, and the professor has even recorded video responses to some of the students' questions. Some of the most popular videos are those of sodium, potassium, and uranium.
The Periodic Table of Videos team has also performed live. Their first performance was in May 2009 at the Broadway Media Centre in Nottingham; in July 2010 they performed at the EuroScience Open Forum (ESOF) in Turin, Italy. | 1 | Applied and Interdisciplinary Chemistry |
Amphoteric or zwitterionic detergents have zwitterions within a particular pH range, and possess a net zero charge arising from the presence of equal numbers of +1 and −1 charged chemical groups. Examples include CHAPS. | 0 | Theoretical and Fundamental Chemistry |
A couple of Escherichia coli mutant strains have been bioengineered to ferment glucose under aerobic conditions. One group developed the ECOM3 (E. coli cytochrome oxidase mutant) strain by removing three terminal cytochrome oxidases (cydAB, cyoABCD, and cbdAB) to reduce oxygen uptake. After 60 days of adaptive evolution on glucose media, the strain displayed a mixed phenotype. In aerobic conditions, some populations' fermentation solely produced lactate, while others performed mixed-acid fermentation. | 1 | Applied and Interdisciplinary Chemistry |
An inert gas (or noble gas), such as helium, is one that does not react with other elements or compounds. Adding an inert gas into a gas-phase equilibrium at constant volume does not result in a shift. This is because the addition of a non-reactive gas does not change the equilibrium equation, as the inert gas appears on both sides of the chemical reaction equation. For example, if A and B react to form C and D, but X does not participate in the reaction: . While it is true that the total pressure of the system increases, the total pressure does not have any effect on the equilibrium constant; rather, it is a change in partial pressures that will cause a shift in the equilibrium. If, however, the volume is allowed to increase in the process, the partial pressures of all gases would be decreased resulting in a shift towards the side with the greater number of moles of gas. The shift will never occur on the side with fewer moles of gas. It is also known as Le Chatelier's postulate. | 0 | Theoretical and Fundamental Chemistry |
Euromaster is a registered trademark and an initiative adopted by the EuCheMS General Assembly in 2005. It is associated with the Chemistry Quality Eurolabels. As of 8 April 2013, 36 Euromaster quality labels have been awarded. The label is intended for master's degrees.
Euromaster, introduced after Eurobachelor, is intended for second cycle qualifications (postgraduate degrees). | 1 | Applied and Interdisciplinary Chemistry |
Variations in iron isotopes are caused by a number of chemical processes which result in the preferential incorporation of certain isotopes of iron into certain phases. Many of the chemical processes which fractionate iron are not well understood and are still being studied. The most well-documented chemical processes which fractionate iron isotopes relate to its redox chemistry, the evaporation and condensation of iron, and the diffusion of dissolved iron through systems. These processes are described in more detail below. | 0 | Theoretical and Fundamental Chemistry |
An example of a Curtin–Hammett scenario in which the more stable conformational isomer reacts more quickly is observed during the oxidation of piperidines. In the case of N-methyl piperidine, inversion at nitrogen between diastereomeric conformers is much faster than the rate of amine oxidation. The conformation which places the methyl group in the equatorial position is 3.16 kcal/mol more stable than the axial conformation. The product ratio of 95:5 indicates that the more stable conformer leads to the major product. | 0 | Theoretical and Fundamental Chemistry |
There are several types of glycosylation, although the first two are the most common.
* In N-glycosylation, sugars are attached to nitrogen, typically on the amide side-chain of asparagine.
* In O-glycosylation, sugars are attached to oxygen, typically on serine or threonine, but also on tyrosine or non-canonical amino acids such as hydroxylysine and hydroxyproline.
* In P-glycosylation, sugars are attached to phosphorus on a phosphoserine.
* In C-glycosylation, sugars are attached directly to carbon, such as in the addition of mannose to tryptophan.
* In S-glycosylation, a beta-GlcNAc is attached to the sulfur atom of a cysteine residue.
* In glypiation, a GPI glycolipid is attached to the C-terminus of a polypeptide, serving as a membrane anchor.
* In glycation, also known as non-enzymatic glycosylation, sugars are covalently bonded to a protein or lipid molecule, without the controlling action of an enzyme, but through a Maillard reaction. | 0 | Theoretical and Fundamental Chemistry |
Clathrate hydrates were discovered in 1810 by Humphry Davy. Clathrates were studied by P. Pfeiffer in 1927 and in 1930, E. Hertel defined "molecular compounds" as substances decomposed into individual components following the mass action law in solution or gas state. Clathrate hydrates were discovered to form blockages in gas pipelines in 1934 by Hammerschmidt that led to increase in research to avoid hydrate formation. In 1945, H. M. Powell analyzed the crystal structure of these compounds and named them clathrates. Gas production through methane hydrates has since been realized and has been tested for energy production in Japan and China. | 0 | Theoretical and Fundamental Chemistry |
Consider two coupled ultrasensitive modules, disregarding effects of sequestration of molecular components between layers. In this case, the expression for the system's dose-response curve, , results from the mathematical composition of the functions, , which describe the input/output relationship of isolated modules :
Brown et al. (1997) have shown that the local ultrasensitivity of the different layers combines multiplicatively:
In connection with this result, Ferrell et al. (1997) showed, for Hill-type modules, that the overall cascade global ultrasensitivity had to be less than or equal to the product of the global ultrasensitivity estimations of each cascade's layer,
where and are the Hill coefficient of modules 1 and 2 respectively.
Altszyler et al. (2017) have shown that the cascade's global ultrasensitivity can be analytically calculated:
where and delimited the Hill inputs working range of the composite system, i.e. the input values for the i-layer so that the last layer (corresponding to in this case) reached the 10% and 90% of it maximal output level. It followed this equation that the systems Hill coefficient could be written as the product of two factors, and , which characterized local average sensitivities over the relevant input region for each layer: , with in this case.
For the more general case of a cascade of modules, the Hill Coefficient can be expressed as: | 1 | Applied and Interdisciplinary Chemistry |
For a single Ca-looping cycle installed on a 500MW power plant:
# Amount of CaO from purge annually = 12.6 kg CaO/s × 365 days/year × 24 hr/day × 3600s / hour = 3.97 × 10 kg CaO/ year
# Cement that can be obtained from purge annually= 3.97 × 10 kg CaO/ year × 1 kg cement/ 0.65 kg CaO = 6.11 × 10 kg cement/year
# Net electricity generation in US: (415 + 318 + 51) GW = 784 GW = 7.84 × 10 W
# Number of 500 MW power plants: 7.84 × 10 W / 5.00 × 10 W = 1568 power plants
# Amount of cement that can be produced from Ca-looping waste: 1568 × 6.11 × 10 kg cement/ year = 9.58 × 10 kg cement/year
# Production from Ca-looping waste as percent of total annual cement consumption = [(9.58 × 10 kg)/ (1.10470 × 10 kg)] × 100 = 870%
Therefore, amount of cement production from Ca-looping waste of all fossil fuel based electric power plants in US will be far greater than net consumption. To make Ca-looping more viable, waste must be minimized (i.e. sorbent degradation reduced) to ideally about 1/10th of current levels. | 1 | Applied and Interdisciplinary Chemistry |
PaNie is a 25 kDa protein produced by the root rot disease-causing pathogen Pythium aphanidermatum. It stands for Pythium aphanidermatum Necrosis inducing elicitor. PaNie (aka NLP) belongs to a family of elicitors named the Nep1-like proteins (NLPs), which cause necrosis when injected into the leaves of dicotyledonous plants. | 1 | Applied and Interdisciplinary Chemistry |
*Benzylidene acetal and acetonide, protecting groups
*Dimethoxymethane, a solvent, a.k.a. methylal, a.k.a. formal [ambiguous]
*Dioxolane
*Metaldehyde
*Paraldehyde
*1,3,5-Trioxane
*Phenylsulfonylethylidene (PSE) acetal is an example of arylsulfonyl acetal possessing atypical properties, like resistance to acid hydrolysis which leads to selective introduction and removal of the protective group.
*Most glycosidic bonds in carbohydrates and other polysaccharides are acetal linkages.
**Cellulose is a ubiquitous example of a polyacetal.
Although many compounds contain an acetal functional group, at least two acetal compounds are called "acetal" for short:
*Polyoxymethylene (POM) plastic, also known as "acetal" or "polyacetal", is a polyacetal (and a polyether), and a polymer of formaldehyde.
*1,1-Diethoxyethane (acetaldehyde diethyl acetal), sometimes called simply "acetal", is an important flavouring compound in distilled beverages. | 0 | Theoretical and Fundamental Chemistry |
Similar to xylitol, hydrogenated starch hydrolysates are not readily fermented by oral bacteria and are used to formulate sugarless products that do not promote dental caries.
HSHs are also more slowly absorbed in the digestive tract, thus, have a reduced glycemic potential relative to glucose. However, they do have a laxative effect when consumed in large amounts. | 0 | Theoretical and Fundamental Chemistry |
Chlorophyll fluorescence appears to be a measure of photosynthesis, but this is an over-simplification. Fluorescence can measure the efficiency of PSII photochemistry, which can be used to estimate the rate of linear electron transport by multiplying by the light intensity. However, researchers generally mean carbon fixation when they refer to photosynthesis. Electron transport and CO fixation can correlate well, but may not correlate in the field due to processes such as photorespiration, nitrogen metabolism and the Mehler reaction. | 0 | Theoretical and Fundamental Chemistry |
Common methods include those of the DISCO family, including 3DISCO, and CLARITY and related protocols. Others include BABB, PEGASOS, SHANEL, SeeDB, CUBIC, ExM, and SHIELD. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, an oxime is an organic compound belonging to the imines, with the general formula , where R is an organic side-chain and R' may be hydrogen, forming an aldoxime, or another organic group, forming a ketoxime. O-substituted oximes form a closely related family of compounds. Amidoximes are oximes of amides () with general structure .
Oximes are usually generated by the reaction of hydroxylamine with aldehydes () or ketones (). The term oxime dates back to the 19th century, a combination of the words oxygen and imine. | 0 | Theoretical and Fundamental Chemistry |
Vitamin A deficiency is common in developing countries, especially in Sub-Saharan Africa and Southeast Asia. Deficiency can occur at any age, but is most common in pre-school-age children and pregnant women, the latter due to a need to transfer retinol to the fetus. The causes are low intake of retinol-containing, animal-sourced foods and low intake of carotene-containing, plant-sourced foods. Vitamin A deficiency is estimated to affect approximately one third of children under the age of five around the world, possibly leading to the deaths of 670,000 children under five annually.
Between 250,000 and 500,000 children in developing countries become blind each year owing to vitamin A deficiency. Vitamin A deficiency is "the leading cause of preventable childhood blindness", according to UNICEF. It also increases the risk of death from common childhood conditions, such as diarrhea. UNICEF regards addressing vitamin A deficiency as critical to reducing child mortality, the fourth of the United Nations' Millennium Development Goals.
During diagnosis, night blindness and dry eyes are signs of vitamin A deficiency that can be recognized without requiring biochemical tests. Plasma retinol is used to confirm vitamin A status. A plasma concentration of about 2.0 μmol/L is normal; less than 0.70 μmol/L (equivalent to 20 μg/dL) indicates moderate vitamin A deficiency, and less than 0.35 μmol/L (10 μg/dL) indicates severe vitamin A deficiency. Breast milk retinol of less than 8 μg/gram milk fat is considered insufficient. One weakness of these measures is that they are not good indicators of liver vitamin A stores as retinyl esters in hepatic stellate cells. The amount of vitamin A leaving the liver, bound to retinol binding protein (RBP), is under tight control as long as there are sufficient liver reserves. Only when liver content of vitamin A drops below approximately 20 μg/gram will concentration in the blood decline. | 1 | Applied and Interdisciplinary Chemistry |
*1913 - Radioactive Transformations and the Periodic System of the Elements
*1941 - Artificial radioactive isotopes of Thallium, Lead and Bismuth
*1947 - Application of the resonance theory to the structure of the water molecule
*1948 - Electronic structure of molecules | 1 | Applied and Interdisciplinary Chemistry |
All peroxisomal proteins are synthesized in the cytoplasm and must be directed to the peroxisome. The first step in this process is the binding of the protein to a receptor. The receptor then directs the complex to the peroxisome. Receptors recognize and bind to a region of the peroxisomal protein called a peroxisomal targeting signal, or PTS.
Peroxisomes consist of a matrix surrounded by a specific membrane. Most peroxisomal matrix proteins contain a short sequence, usually three amino acids at the extreme carboxy tail of the protein, that serves as the PTS. The prototypic sequence (many variations exist) is serine-lysine-leucine (-SKL in the one-letter amino acid code). This motif, and its variations, is known as the PTS1, and the receptor is termed the PTS1 receptor.
It was found that the PTS1 receptor is encoded by the PEX5 gene. PEX5 imports folded proteins into the peroxisome, shuttling between the peroxisome and cytosol. PEX5 interacts with a large number of other proteins, including Pex8p, 10p, 12p, 13p, 14p.
A few peroxisomal matrix proteins have a different, and less conserved sequence, at their amino termini. This PTS2 signal is recognized by the PTS2 receptor, encoded by the PEX7 gene.
"PEX" refers to a group of genes that were identified as being important for peroxisomal synthesis. The numerical attributions, such as PEX5, generally refer to the order in which they were first discovered.
A distinct motif is used for proteins destined for the peroxisomal membrane called the "mPTS" motif, which is more poorly defined and may consist of discontinuous subdomains. One of these usually is a cluster of basic amino acids (arginines and lysines) within a loop of protein (i.e., between membrane spans) that will face the matrix. The mPTS receptor is the product of PEX19. | 1 | Applied and Interdisciplinary Chemistry |
The Marchywka effect refers to electrochemical cleaning of diamond using an electric field induced with remote electrodes. | 0 | Theoretical and Fundamental Chemistry |
The six bonding molecular orbitals that are formed are "filled" with the electrons from the ligands, and electrons from the d-orbitals of the metal ion occupy the non-bonding and, in some cases, anti-bonding MOs. The energy difference between the latter two types of MOs is called Δ (O stands for octahedral) and is determined by the nature of the π-interaction between the ligand orbitals with the d-orbitals on the central atom. As described above, π-donor ligands lead to a small Δ and are called weak- or low-field ligands, whereas π-acceptor ligands lead to a large value of Δ and are called strong- or high-field ligands. Ligands that are neither π-donor nor π-acceptor give a value of Δ somewhere in-between.
The size of Δ determines the electronic structure of the d - d ions. In complexes of metals with these d-electron configurations, the non-bonding and anti-bonding molecular orbitals can be filled in two ways: one in which as many electrons as possible are put in the non-bonding orbitals before filling the anti-bonding orbitals, and one in which as many unpaired electrons as possible are put in. The former case is called low-spin, while the latter is called high-spin. A small Δ can be overcome by the energetic gain from not pairing the electrons, leading to high-spin. When Δ is large, however, the spin-pairing energy becomes negligible by comparison and a low-spin state arises.
The spectrochemical series is an empirically-derived list of ligands ordered by the size of the splitting Δ that they produce. It can be seen that the low-field ligands are all π-donors (such as I), the high field ligands are π-acceptors (such as CN and CO), and ligands such as HO and NH, which are neither, are in the middle.
IOO < NCSCN < py (pyridine) < NH < en (ethylenediamine) < bipy (2,2'-bipyridine) < phen (1,10-phenanthroline) < NO < CN</sup> < CO | 0 | Theoretical and Fundamental Chemistry |
*AMCA Publication 99 - Standards Handbook is a compilation of important AMCA standards that include the Fan Laws, common industry terminology and symbols, classifications for spark resistant construction, and various other useful data.
*AMCA Publication 200 - Air Systems. Part 1 of the Fan Application Manual, this publication provides basic information necessary for the design of energy efficient air systems. This edition includes examples in both the Inch-Pound and SI systems as the reader is provided with basic information on air systems.
*AMCA Publication 201 - Fans and Systems. Part 2 of the Fan Application Manual, discusses the effect of inlet and outlet connections on fan performance. It includes separate axial fan factors and is aimed primarily at the designer of the air moving system.
*AMCA Publication 202 - Troubleshooting. Part 3 of the Fan Application Manual, helps to identify and correct problems with the performance and operation of the air moving system after fan installation.
*AMCA Publication 203 - Field Performance Measurement of Fan Systems. Part 4 of the Fan Application Manual, reviews the methods of making field measurements for calculating the actual performance of the fan and system.
*AMCA Publication 801 - Industrial Process/Power Generation Fans: Specification Guidelines provides information on testing and rating power plant fans and covers construction features and related accessories. Sample equipment specifications are included which outline the information a fan manufacturer requires to select the best fan for an application. Common fan industry practices are also defined and explained.
*AMCA Publication 802 - Establishing Performance Using Laboratory Models outlines methods used to determine the performance of full size power plant fans from tests of models. Provides information on variables that affect fan ratings and establishes rules and limitations in converting the performance of geometrically similar fans.
*AMCA Publication 850 - Heavy Duty Dampers for Isolation and Control provides basic pertinent information in order to simplify communications between damper manufacturers and designers, specifiers, and users of such equipment.
*External Shading Devices in Commercial Buildings - The Impact on Energy Use, Peak Demand, and Glare Control by John Carmody details the several advantages that contribute to a more sustainable building such as reducing solar gain, peak electricity demand and glare conditions. It is intended to help the designer quickly narrow the range of possibilities and understand the impact of shading devices in commercial office buildings during the early stages of design.
*Fan Acoustics - Noise Generation and Control Methods by Alain Guédel discusses the sources of noise generation in fan construction and system installation. | 1 | Applied and Interdisciplinary Chemistry |
Where a given letter is used in both capital and lower case form (, and , ) the capital letter refers to the macroscopic observable and the lower case letter to the corresponding variable for an individual particle or layer of the material. Greek symbols are used for properties of a single particle.
* – absorption fraction of a single layer
* – remission fraction of a single layer
* – transmission fraction of a single layer
* A, R, T – The absorption, remission, and transmission fractions for a sample composed of n layers
* α – absorption fraction of a particle
* β – back-scattering from a particle
* σ – isotropic scattering from a particle
*– absorption coefficient defined as the fraction of incident light absorbed by a very thin layer divided by the thickness of that layer
* – scattering coefficient defined as the fraction of incident light scattered by a very thin layer divided by the thickness of that layer | 0 | Theoretical and Fundamental Chemistry |
Individual species’ reactions to eutrophication can vary widely. For example, some organisms, such as primary producers, can adapt very quickly and even thrive under anoxic conditions. However, most organisms are extremely susceptible to slight changes in aquatic oxygen levels. Simply put - if a respirating organism is presented with little to no oxygen, its chances of survival will decrease. Therefore, eutrophication and anoxic conditions in water leads to a decrease in biodiversity.
For example, the soft coral Xenia umbellata can resist some anoxic conditions for short periods of time, but after about 3 weeks, mean survival decreases to about 81% and about 40% of surviving species experience size reductions, lessening in coloration, and compromised pinnate structures (Simancas-Giraldo et al., 2021). Another example of a susceptible organism is observed with The Sydney Cockle, Anadara trapezia. Enriched sediments have lethal and sublethal effects on this Cockle and, as stated in [Vadillo Gonzalez et al., 2021], “movement of cockles was reduced in enriched sediments compared to natural treatments.” These are just a few examples of the hundreds of thousands of aquatic species that exist, but these and other examples show important results.
A study collecting over 850 published experiments "reporting oxygen thresholds and/or lethal times for a total of 206 species spanning the full taxonomic range of benthic metazoans."
Individual species will have different adaptive responses to anoxic conditions based on their biological makeup and the condition of their habitat. While some are able to pump oxygen from higher water levels down into the sediment, other adaptations include specific hemoglobins for low oxygen environments, slow movement to reduce rate of metabolism, and symbiotic relationships with anaerobic bacteria. In all cases, the prevalence of excess nutrients results in low levels of biologic activity and a lower level of species diversity if the area is not normally anoxic. | 0 | Theoretical and Fundamental Chemistry |
Two main trends impinge on the industry. On the supply side, biotechnology is rapidly gaining importance. In the synthesis of small molecule fine chemicals, the use of biocatalysts and microbial fermentation enable both a more sustainable and economic production than conventional organic chemistry. In the synthesis of big molecules, such as biopharmaceuticals, it is the method of choice. Biopharmaceuticals are expected to grow 15% per year, three times as fast as small molecule drugs. Five of the top ten drugs were biopharmaceuticals in 2010 (see table 6), and this is expected to grow to eight by 2016 (see table 2).
On the demand side, the main customer base for fine chemicals, the pharmaceutical industry, is faced with slower growth of demand, patent expirations of many lucrative blockbuster drugs and stalling new product launches. In order to restrain these challenges, the leading companies are implementing restructuring programs. They comprise a reduction of in-house chemical manufacturing and plant eliminations. Outsourcing is moving up from a purely opportunistic to a strategic approach. It is difficult to make a judgment, whether the positive or negative effects of these initiatives will prevail. In a worst-case scenario, a condition could develop, whereby even top-tier mid-sized, family-owned fine-chemical companies with state-of-the-art plants and processes could be relegated to producing small quantities of fine chemicals for new life-science products in late stage of development. In agro fine chemicals, the active ingredients become more sophisticated and performing. Therefore, they require multipurpose instead of dedicated plants prevailing in the industry so far. At the same token, outsourcing is gaining ground.
Globalization results in a shift of fine chemical production from the industrialized to developing countries. The latter benefit not only from a "low cost / high skill" advantage, but also from a rapidly rising domestic demand for Western medicine. Despite the mantras of Western industry leaders, the cost advantage of the Asian producers is going to persist. As the pharmemerging countries mainly use generics, their market share continues to grow to the detriment of originator pharmaceuticals and agrochemicals. This is also the case for biosimilars, the generic versions of biopharmaceuticals.
As a consequence of the harsh business climate, many Western fine chemical companies or divisions created during the "irrational exuberance" at the end of the 20th century already have exited from the sector. Others will follow suit or will be acquired by private equity firms. Survival strategies include implementation of lean production principles originally developed by the automotive industry and extending the business model to include also contract research at the beginning and active drug formulation towards the end of the added value chain. This latter strategy, however, is not finding unanimous approval by industry experts.
Although the demand for fine chemicals on the merchant market has not grown to the extent originally anticipated, fine chemicals still provide attractive opportunities for well-run companies, which are fostering the critical success factors, namely running fine chemicals as a core business, pursuing niche technologies—primarily biotechnology—and taking advantage of the opportunities offered by the Asian market. | 0 | Theoretical and Fundamental Chemistry |
* [https://archive.org/details/radioactivity00ruthgoog Radio-activity] (1904), 2nd ed. (1905),
* [https://archive.org/details/radioactivetran02ruthgoog Radioactive Transformations (1906)],
* [https://archive.org/details/radioactivesubst00ruthuoft Radioactive Substances and their Radiations (1913)]
* The Electrical Structure of Matter (1926)
* The Artificial Transmutation of the Elements (1933)
* The Newer Alchemy (1937) | 1 | Applied and Interdisciplinary Chemistry |
The WPB placed penicillin under a wartime allocation system on 16 July 1943. All supplies were designated for use by the armed forces and the Public Health Service. Penicillin production in the United States ramped up from 800 million Oxford units in the first half of 1943 to 20 billion units in the second half. The US government built six production plants at a cost of $7.6 million (equivalent to $ million in ). These were sold after the war to the companies that operated them for $3.4 million (equivalent to $ million in ). Another sixteen plants were built by the private sector for $22.6 million (equivalent to $ million in ), although $14.5 million (equivalent to $ million in ) was approved for accelerated depreciation under which the cost could be written off in five years instead of the usual twelve to fifteen.
US penicillin production rose from 21.192 billion units in 1943, to 1,663 billion units in 1944, and an estimated 6,852 billion units in 1945. By June 1944, Pfizer alone was producing 70 billion units per month. Monthly production dropped off after July 1945 due to a shortage of corn-steep liquor. The price offered by the CMR for a million units fell from $200 in 1943 (), which was below its manufacturing cost, to $6 in 1945 ().
The chairman of the NRC committee on chemotherapy, Chester Keefer was responsible for administering the equitable distribution of penicillin for civilian use on behalf of the CMR. As the news of the effectiveness of penicillin spread, he had to deal with a large volume of requests for the drug. Supplies for civilian use were initially small, and penicillin was initially provided only for cases with a high mortality rate that did not respond to other forms of treatment. In January 1943, he reported to OSRD on the results of the treatment of the first 100 patients; by August, 500 patients had been treated. Military requirements consumed 85 per cent of production in 1944. This dropped to 30 per cent in 1945, but civilian demands for penicillin exceeded allocations.
By April 1944 supply and demand had exceeded the ability of one man to administer, and the task was handed over to a Penicillin Producers Industry Advisory Committee that distributed supplies through a network of depot hospitals. By 1945, there were 2,700 depot hospitals holding supplies of penicillin, and another 5,000 hospitals receiving supplies through them. Penicillin became commercially available by the end of the year, by which time the United States was exporting 200 billion units a month. By 1956, only twelve of the twenty-one firms that produced penicillin during the war were still involved in its manufacture. | 1 | Applied and Interdisciplinary Chemistry |
Prime editor 4 utilizes the same machinery as PE2, but also includes a plasmid that encodes for dominant negative MMR protein MLH1. Dominant negative MLH1 is able to essentially knock out endogenous MLH1 by inhibition, thereby reducing cellular MMR response and increasing prime editing efficiency. | 1 | Applied and Interdisciplinary Chemistry |
The solid medium is used to grow lactose-fermenting coliforms and utilizes a neutral red pH indicator. Pink colonies appear when lactose is fermented and are surrounded by bile that has precipitated out. To confirm if these colonies are coliforms, they are transferred to brilliant green lactose bile (BGLB) and incubated. If gas is visible after incubation, it can be confirmed that the sample had coliforms present. | 0 | Theoretical and Fundamental Chemistry |
At non-relativistic energies, single particles generally produce effects too small to enable their direct detection. The microchannel plate functions as a particle amplifier, turning a single impinging particle into a cloud of electrons. By applying a strong electric field across the MCP, each individual microchannel becomes a continuous-dynode electron multiplier.
A particle or photon that enters one of the channels through a small orifice is guaranteed to hit the wall of the channel, due to the channel being at an angle to the plate. The impact starts a cascade of electrons that propagates through the channel, amplifying the original signal by several orders of magnitude, depending on the electric field strength and the geometry of the microchannel plate. After the cascade, the microchannel takes time to recover (or recharge) before it can detect another signal.
The electrons exit the channels on the opposite side of the plate, where they are collected on an anode. Some anodes are designed to allow spatially resolved ion collection, producing an image of the particles or photons incident on the plate.
Although in many cases the collecting anode functions as the detecting element, the MCP itself can also be used as a detector. The discharging and recharging of the plate produced by the electron cascade, can be decoupled from the high voltage applied to the plate and measured, to directly produce a signal corresponding to a single particle or photon.
The gain of an MCP is very noisy, meaning that two identical particles detected in succession will often produce wildly different signal magnitudes. The temporal jitter resulting from the peak height variation can be removed by using a constant fraction discriminator. Thusly employed, MCPs are capable of measuring particle arrival times with high resolution, making them ideal detectors for mass spectrometers. | 0 | Theoretical and Fundamental Chemistry |
NUT carcinoma is a rare, highly aggressive malignancy. Initially, it was regarded as occurring in the midline areas of the upper respiratory tract, upper digestive tract, and mediastinum (i.e. central compartment of the thoracic cavity) of young adults and to lesser extents children and infants. It was therefore termed NUT midline granuloma. However, subsequent studies defined these carcinomas based on the presence of a NUT fusion gene in their malignant cells. As so defined, this malignancy occurs in individuals of all ages and, while most commonly developing in the cited respiratory, gastrointestinal, and mediastinal areas, occasionally develops in the salivary glands, pancreas, urinary bladder, retroperitoneum (i.e. space behind the peritoneum of the abdominal cavity), endometrium, kidneys, ovaries, and other organs. Consequently, the name of this disorder was changed form NUT midline carcinoma to NUT carcinoma by the World Health Organization, 2015. NUT carcinomas are characterized histologically as tumors containing
primitive epithelioid cells (i.e. derived from activated macrophages and resembling epithelial cells) admixed with foci of keratinization (i.e. tissue areas that are rich in keratin fibers); NUT carcinomas are considered variants of squamous cell carcinomas. Studies have found that ~66 tp 80% of NUT carcinomas harbor a BRD4-NUTM1 fusion gene while the remaining NUT carcinomas, sometimes termed NUT variant carcinomas, involve the BRD3-NUTM1 (~10 to 25% of cases) or, rarely, the NSD3-NUTM1, ZNF532-NUTM1,, or ZNF592-NUTM1 fusion gene. It is thought that the latter fusions genes promote NUT carcinomas in manners at least somewhat similar to the BRD4-NUTM1 fusion gene. | 1 | Applied and Interdisciplinary Chemistry |
Typically, the mixture of "compound A" and "impurity B" is dissolved in the smallest amount of hot solvent to fully dissolve the mixture, thus making a saturated solution. The solution is then allowed to cool. As the solution cools the solubility of compounds in the solution drops. This results in the desired compound dropping (recrystallizing) from the solution. The slower the rate of cooling, the bigger the crystals form.
In an ideal situation the solubility product of the impurity, B, is not exceeded at any temperature. In that case, the solid crystals will consist of pure A and all the impurities will remain in the solution. The solid crystals are collected by filtration and the filtrate is discarded. If the solubility product of the impurity is exceeded, some of the impurities will co-precipitate. However, because of the relatively low concentration of the impurity, its concentration in the precipitated crystals will be less than its concentration in the original solid. Repeated recrystallization will result in an even purer crystalline precipitate. The purity is checked after each recrystallization by measuring the melting point, since impurities lower the melting point. NMR spectroscopy can also be used to check the level of impurity. Repeated recrystallization results in some loss of material because of the non-zero solubility of compound A.
The crystallization process requires an initiation step, such as the addition of a "seed" crystal. In the laboratory, a minuscule fragment of glass, produced by scratching the side of the glass recrystallization vessel, may provide the nucleus on which crystals may grow.
Successful recrystallization depends on finding the right solvent. This is usually a combination of prediction/experience and trial/error. The compounds must be more soluble at higher temperatures than at lower temperatures. Any insoluble impurity is removed by the technique of hot filtration. | 0 | Theoretical and Fundamental Chemistry |
Disrupting pRb expression in vitro, either by gene deletion or knockdown of pRb short interfering RNA, causes dendrites to branch out farther. In addition, Schwann cells, which provide essential support for the survival of neurons, travel with the neurites, extending farther than normal. The inhibition of pRb supports the continued growth of nerve cells. | 1 | Applied and Interdisciplinary Chemistry |
Magma exists in three main forms that vary in composition. When magma crystallizes within the crust, it forms an extrusive igneous rock. Dependent on the composition of the magma, it may form either rhyolite, andesite, or basalt. Volatiles, particularly water and carbon dioxide, significantly impact the behavior of each form of magma differently. Magma with a high concentration of volatiles has a significant reduction in temperature of up to hundreds of degrees, which reduces its inherent viscosity. The behavior of magma is also altered by varying mineralogic compositions, which is noted in Figure 1. For instance, magmatic water leads to the crystallization of several minerals abundant in hydroxyl- or halogenated-groups, including garnets. Analyses of these minerals can be used to analyze the conditions of formation in the interior of rocky planets. | 0 | Theoretical and Fundamental Chemistry |
An enthalpy–entropy chart, also known as the H–S chart or Mollier diagram, plots the total heat against entropy, describing the enthalpy of a thermodynamic system. A typical chart covers a pressure range of 0.01–1000 bar, and temperatures up to 800 degrees Celsius. It shows enthalpy in terms of internal energy , pressure and volume using the relationship (or, in terms of specific enthalpy, specific entropy and specific volume, ). | 0 | Theoretical and Fundamental Chemistry |
Black light incandescent lamps are also made from an incandescent light bulb with a filter coating which absorbs most visible light. Halogen lamps with fused quartz envelopes are used as inexpensive UV light sources in the near UV range, from 400 to 300 nm, in some scientific instruments. Due to its black-body spectrum a filament light bulb is a very inefficient ultraviolet source, emitting only a fraction of a percent of its energy as UV. | 0 | Theoretical and Fundamental Chemistry |
Eukaryotic initiation factors (eIFs) are proteins or protein complexes involved in the initiation phase of eukaryotic translation. These proteins help stabilize the formation of ribosomal preinitiation complexes around the start codon and are an important input for post-transcription gene regulation. Several initiation factors form a complex with the small 40S ribosomal subunit and Met-tRNA called the 43S preinitiation complex (43S PIC). Additional factors of the eIF4F complex (eIF4A, E, and G) recruit the 43S PIC to the five-prime cap structure of the mRNA, from which the 43S particle scans 5-->3 along the mRNA to reach an AUG start codon. Recognition of the start codon by the Met-tRNA promotes gated phosphate and eIF1 release to form the 48S preinitiation complex (48S PIC), followed by large 60S ribosomal subunit recruitment to form the 80S ribosome. There exist many more eukaryotic initiation factors than prokaryotic initiation factors, reflecting the greater biological complexity of eukaryotic translation. There are at least twelve eukaryotic initiation factors, composed of many more polypeptides, and these are described below. | 1 | Applied and Interdisciplinary Chemistry |
Nuclear fission produces radioactive fission products which can have half-lives from days to greater than 200,000 years. According to some toxicity studies, the thorium cycle can fully recycle actinide wastes and only emit fission product wastes, and after a few hundred years, the waste from a thorium reactor can be less toxic than the uranium ore that would have been used to produce low enriched uranium fuel for a light water reactor of the same power.
Other studies assume some actinide losses and find that actinide wastes dominate thorium cycle waste radioactivity at some future periods. Some fission products have been proposed for nuclear transmutation, which would further reduce the amount of nuclear waste and the duration during which it would have to be stored (whether in a deep geological repository or elsewhere). However, while the principal feasibility of some of those reactions has been demonstrated at laboratory scale, there is, as of 2022, no large scale deliberate transmutation of fission products anywhere in the world, and the upcoming MYRRHA research project into transmutation is mostly focused on transuranic waste. Furthermore, the cross section of some fission products is relatively low and others - such as caesium - are present as a mixture of stable, short lived and long lived isotopes in nuclear waste, making transmutation dependent on extremely expensive isotope separation. | 0 | Theoretical and Fundamental Chemistry |
Liquid marbles are non-stick droplets (normally aqueous) wrapped by micro- or nano-metrically scaled hydrophobic, colloidal particles (Teflon, polyethylene, lycopodium powder, carbon black, etc.); representing a platform for a diversity of chemical and biological applications. Liquid marbles are also found naturally; aphids convert honeydew droplets into marbles. A variety of non-organic and organic liquids may be converted into liquid marbles. Liquid marbles demonstrate elastic properties and do not coalesce when bounced or pressed lightly. Liquid marbles demonstrate a potential as micro-reactors, micro-containers for growing micro-organisms and cells, micro-fluidics devices, and have even been used in unconventional computing. Liquid marbles remain stable on solid and liquid surfaces. Statics and dynamics of rolling and bouncing of liquid marbles were reported. Liquid marbles coated with poly-disperse and mono-disperse particles have been reported. Liquid marbles are not hermetically coated by solid particles but connected to the gaseous phase. Kinetics of the evaporation of liquid marbles has been investigated. | 0 | Theoretical and Fundamental Chemistry |
The Biogeochemistry Department, headed by Ralf Conrad, is focused on the microbial metabolism and biogeochemical matter cycling in soil. Soil microbial metabolism plays an important role in the global cycling of matter and — through the formation of atmospheric trace gases such as methane and nitrous oxide — also influences the climate on Earth. The department examines the role of soil microorganisms in carbon and nitrogen cycling, particularly in chemically well-defined processes such as the production and consumption of methane, the oxidation of ammonia, or denitrification. There are four research leaders in charge of six research groups and two project groups:
Research Groups<br />
Ralf Conrad
* Methanogenic degradation
* Microbial metabolism of trace gases
Andreas Brune
* Microbial ecology of the termite gut
* Microbial symbioses
Werner Liesack
* Molecular biology and ecology of methanotrophs
* Environmental genomics and transcriptomics
Project Group<br />
Peter Frenzel
* Methane oxidation
* Biogeochemistry and microbial ecology of wetlands | 0 | Theoretical and Fundamental Chemistry |
The tendency in Europe is the increasing use of glass packaging to substitute plastic packaging. As a response to the increase of glass waste, the recycling and recovery rates has grown in the last 10 years.
To assure the circularity and recycling of glass packaging it's possible to follow these principles applied to glass bottles:
*Leave no bottle behind: Ensure consumers have a way to recycle every glass bottle at a cost lower than waste disposal.
*Transform the recycling system: Develop infrastructure that is capable of economically sorting, processing, and transporting glass to manufacturing sites.
* Drive collective action: Identify collaboration opportunities between the private and public sectors to forge a nationwide commitment to solve the recycling challenge. | 0 | Theoretical and Fundamental Chemistry |
A chirality center (chiral center) is a type of stereocenter. A chirality center is defined as an atom holding a set of four different ligands (atoms or groups of atoms) in a spatial arrangement which is non-superposable on its mirror image. Chirality centers must be sp hybridized, meaning that a chirality center can only have single bonds. In organic chemistry, a chirality center usually refers to a carbon, phosphorus, or sulfur atom, though it is also possible for other atoms to be chirality centers, especially in areas of organometallic and inorganic chemistry.
The concept of a chirality center generalizes the concept of an asymmetric carbon atom (a carbon atom bonded to four different entities) to a broader definition of any atom with four different attachment groups in which an interchanging of any two attachment groups gives rise to an enantiomer. | 0 | Theoretical and Fundamental Chemistry |
Of commercial interest, acyl chlorides react with HF to give acyl fluorides. Aromatic (as well as aliphatic) acyl fluorides are conveniently prepared directly from carboxylic acids, using stable, inexpensive commodity chemicals: , NBS and in a bench-top protocol. Cyanuric fluoride converts carboxylic acids to acyl fluorides.
Carboxylic acids react with sulfur tetrafluoride to give the acyl fluoride: | 0 | Theoretical and Fundamental Chemistry |
According to Schlüter et al. (2004) chloride pore water profiles can be used to investigate submarine groundwater discharge. Chloride can be used as a conservative tracer, as it is enriched in seawater and depleted in groundwater. Three different shapes of chloride pore water profiles reflect three different transport modes within marine sediments. A chloride profile showing constant concentrations with depth indicates that no submarine groundwater is present. A chloride profile with a linear decline indicates a diffusive mixing between groundwater and seawater and a concave shaped chloride profile represents an advective admixture of submarine groundwater from below. Stable isotope ratios in the water molecule may also be used to trace and quantify the sources of a submarine groundwater discharge. | 0 | Theoretical and Fundamental Chemistry |
Thiourea reduces peroxides to the corresponding diols. The intermediate of the reaction is an unstable endoperoxide.
Thiourea is also used in the reductive workup of ozonolysis to give carbonyl compounds. Dimethyl sulfide is also an effective reagent for this reaction, but it is highly volatile (boiling point ) and has an obnoxious odor whereas thiourea is odorless and conveniently non-volatile (reflecting its polarity). | 0 | Theoretical and Fundamental Chemistry |
qPCR using reverse transcription (RT-qPCR) can be used to detect GMOs given its sensitivity and dynamic range in detecting DNA. Alternatives such as DNA or protein analysis are usually less sensitive. Specific primers are used that amplify not the transgene but the promoter, terminator or even intermediate sequences used during the process of engineering the vector. As the process of creating a transgenic plant normally leads to the insertion of more than one copy of the transgene its quantity is also commonly assessed. This is often carried out by relative quantification using a control gene from the treated species that is only present as a single copy. | 1 | Applied and Interdisciplinary Chemistry |
Single-cell AMTECs with open voltages as high as 1.55 V and maximum power density as high as 0.50 W/cm of solid electrolyte area at a temperature of 1173 K (900 °C) have been obtained with long-term stable refractory metal electrodes.
Efficiency of AMTEC cells has reached 16% in the laboratory. High-voltage multi-tube modules are predicted to have 20–25% efficiency, and power densities up to 0.2 kW/L appear to be achievable in the near future. Calculations show that replacing sodium with a potassium working fluid increases the peak efficiency from 28% to 31% at 1100 K with a 1 mm thick BASE tube.
Most work on AMTECs has concerned sodium working fluid devices. Potassium AMTECs have been run with potassium beta″-alumina solid electrolyte ceramics and show improved power at lower operating temperatures compared to sodium AMTECs.
A detailed quantitative model of the mass transport and interfacial kinetics behavior of AMTEC electrodes has been developed and used to fit and analyze the performance of a wide variety of electrodes, and to make predictions of the performance of optimized electrodes. The interfacial electrochemical kinetics can be further described quantitatively with a tunneling, diffusion, and desorption model. A reversible thermodynamic cycle for AMTEC shows that it is, at best, slightly less efficient than a Carnot cycle.
A related technology, the Johnson thermoelectric energy converter, uses a similar concept of pumping positive ions through an ion-selective membrane, using hydrogen rather than an alkali metal as the working fluid. | 0 | Theoretical and Fundamental Chemistry |
By the 14th century, the majority of the more easily accessible ore deposits were exhausted. Thus, more advanced technological achievements were introduced in order to keep up with the demand in metal. The alchemical laboratory, separating precious metals from the baser ones they are typically found with, was an essential feature of the metallurgical enterprise.
A significant hiatus in underground mining was noted during the 14th and the early 15th century due to a series of historical events with severe social and economic impacts. The Great Famine (1315–1317), the Black Death (1347–1353), which diminished the European population by one third to one half, and the Hundred Years War (1337–1453) between England and France, that, amongst others, caused severe deforestation, and had dramatic influences in metallurgical industry and trade.
Lead mining, for example, ground to a halt due to the Black Death pandemic, when atmospheric lead pollution from smelting dropped to natural levels (zero) for the first and only time in the last 2000 years. The great demand of metals, e.g. for armor, could not be met due to the lack of manpower and capital investment.
It was only by the end of the 13th century that great capital expenditures were invested and more sophisticated machinery was installed in underground mining, which resulted in reaching greater depths. The wider application of water and horse power was necessary for draining water out of these deep shafts. Also, acid parting in separating gold from silver was introduced in the 14th century (Bayley 2008). Signs of recovery were present only after the mid 15th century, when the improved methods were widely adopted (Nef 1987, 723).
The discovery of the New World had an impact on European metal production and trade, which has affected the world economy ever since. New, rich ore deposits found in Central Europe during the 15th century were dwarfed by the large amounts of precious metal imports from the Americas. | 1 | Applied and Interdisciplinary Chemistry |
The active transport of monoamines from the cytosol into storage vesicles operates against a large (>10) concentration gradient. Secondary active transport is the type of active transport used, meaning that VMAT1 is an antiporter. This transport is facilitated via proton gradient generated by the protein proton ATPase. The inward transport of the monoamine is coupled with the efflux of two protons per monoamine. The first proton is thought to cause a change in VMAT1's conformation, which pushes a high affinity amine binding site, to which the monoamine attaches. The second proton then causes a second change in the conformation which pulls the monoamine into the vesicle and greatly reduces the affinity of the binding site for amines. A series of tests suggest that His419, located between TMDs X and XI, plays the key role in the first of these conformational changes, and that Asp431, located on TMD XI, does likewise during the second change. | 1 | Applied and Interdisciplinary Chemistry |
* Alkalinity
* Biochemical oxygen demand (BOD)
* Chemical oxygen demand (COD)
* Dissolved oxygen (DO)
* Total hardness (TH)
* Heavy metals
* Nitrate
* Orthophosphates
* pH
* Pesticides
* Residual sodium carbonate index (RSC)
* Sodium adsorption ratio (SAR)
* Surfactants | 0 | Theoretical and Fundamental Chemistry |
An assay is a type of biological titration used to determine the concentration of a virus or bacterium. Serial dilutions are performed on a sample in a fixed ratio (such as 1:1, 1:2, 1:4, 1:8, etc.) until the last dilution does not give a positive test for the presence of the virus. The positive or negative value may be determined by inspecting the infected cells visually under a microscope or by an immunoenzymetric method such as enzyme-linked immunosorbent assay (ELISA). This value is known as the titer. | 0 | Theoretical and Fundamental Chemistry |
Yeast artificial chromosomes (YACs) are linear DNA molecules containing the necessary features of an authentic yeast chromosome, including telomeres, a centromere, and an origin of replication. Large inserts of DNA can be ligated into the middle of the YAC so that there is an “arm” of the YAC on either side of the insert. The recombinant YAC is introduced into yeast by transformation; selectable markers present in the YAC allow for the identification of successful transformants. YACs can hold inserts up to 2000kb, but most YAC libraries contain inserts 250-400kb in size. Theoretically there is no upper limit on the size of insert a YAC can hold. It is the quality in the preparation of DNA used for inserts that determines the size limit. The most challenging aspect of using YAC is the fact they are prone to rearrangement. | 1 | Applied and Interdisciplinary Chemistry |
When Hitchins first worked with Soddy, researchers were still searching for new chemical elements, and isotopes were not yet understood. As early as 1904, researchers had hypothesized that the decay of uranium resulted in the creation of radium, but how this occurred was not clear. In 1907, the American radiochemist Bertram Boltwood had isolated what he believed to be a new intermediate element in the decay chain between uranium and radium, "ionium". Researchers eventually determined that ionium was actually an isotope of thorium, Th.
Soddy asked Hitchins to investigate ionium. She selectively extracted uranium from ore samples to create purified uranium preparations and established a half-life for ionium. Her research also showed that there was a steady rate of increase in the amount of radium in her uranium solutions, the first direct experimental evidence that radium was formed by the decay of uranium. Her results were published in 1915. | 0 | Theoretical and Fundamental Chemistry |
Titanium foams are characterized structurally by their pore topology (relative percentage of open vs. closed pores), porosity (the multiplicative inverse of relative density), pore size and shape, and anisotropy. Microstructures are most often examined by optical microscopy, scanning electron microscopy and X-ray tomography.
Categorizing titanium foams in terms of pore structure (as either open- or close-celled) is the most basic form of differentiation. In close-celled foams, pores are composed of bubbles entrapped in the metallic solid. These foams consist of a continuous network of sealed pores wherein interconnections between the pores are virtually non-existent. Alternatively, in open-celled foams, the pores are interconnected and solid struts allow fluid to pass through.
Most manufactured foams contain both types of pores, although in many cases the subtype is minimal.
According to the IUPAC, pore sizes are classified into three categories: micro (less than 2 nm), meso (between 2 and 50 nm) and macro (larger than 50 nm) pores. | 0 | Theoretical and Fundamental Chemistry |
There remain a few ambiguities about the effect. The current theory of triboluminescence—based upon crystallographic, spectroscopic, and other experimental evidence—is that upon fracture of asymmetrical materials, charge is separated. When the charges recombine, the electrical discharge ionizes the surrounding air, causing a flash of light. Research further suggests that crystals that display triboluminescence often lack symmetry and are poor conductors. However, there are substances which break this rule, and which do not possess asymmetry, yet display triboluminescence, such as hexakis(antipyrine)terbium iodide. It is thought that these materials contain impurities, which make the substance locally asymmetric. Further information on some of the possible processes involved can be found in the page on the triboelectric effect.
The biological phenomenon of triboluminescence is thought to be controlled by recombination of free radicals during mechanical activation. | 0 | Theoretical and Fundamental Chemistry |
Gravimetric analysis describes a set of methods used in analytical chemistry for the quantitative determination of an analyte (the ion being analyzed) based on its mass. The principle of this type of analysis is that once an ions mass has been determined as a unique compound, that known measurement can then be used to determine the same analytes mass in a mixture, as long as the relative quantities of the other constituents are known.
The four main types of this method of analysis are precipitation, volatilization, electro-analytical and miscellaneous physical method. The methods involve changing the phase of the analyte to separate it in its pure form from the original mixture and are quantitative measurements. | 0 | Theoretical and Fundamental Chemistry |
* Grüner, George. Density Waves in Solids. Addison-Wesley, 1994.
* Review of experiments as of 2013 by Pierre Monceau. [https://arxiv.org/abs/1307.0929 Electronic crystals: an experimental overview]. | 0 | Theoretical and Fundamental Chemistry |
The concentration-intensity proportionality is valid at least in two very important cases that distinguish two corresponding classes of DDM methods:
# scattering-based DDM: where the image is the result of the superposition of the strong transmitted beam with the weakly scattered light from the particles. Typical cases where this condition can be obtained are bright field, phase contrast, polarized microscopes.
# fluorescence-based DDM: where the image is the result of the incoherent addition of the intensity emitted by the particles (fluorescence, confocal) microscopes
In both cases the convolution with the PSF in the real space corresponds to a simple product in the Fourier space, which guarantees that studying a given Fourier mode of the image intensity provides information about the corresponding Fourier mode of the concentration field. In contrast with particle tracking, there is no need of resolving the individual particles, which allows DDM to characterize the dynamics of particles or other moving entities whose size is much smaller than the wavelength of light. Still, the images are acquired in the real space, which provides several advantages with respect to traditional (far field) scattering methods. | 0 | Theoretical and Fundamental Chemistry |
Hydrogen and deuterium nuclei are grossly different in their magnetic properties. Thus it is possible to distinguish between them by NMR spectroscopy. Deuterons will not be observed in a H NMR spectrum and conversely, protons will not be observed in a H NMR spectrum. Where small signals are observed in a H NMR spectrum of a highly deuterated sample, these are referred to as residual signals. They can be used to calculate the level of deuteration in a molecule. Analogous signals are not observed in H NMR spectra because of the low sensitivity of this technique compared to the H analysis. Deuterons typically exhibit very similar chemical shifts to their analogous protons. Analysis via C NMR spectroscopy is also possible: the different spin values of hydrogen (/) and deuterium (1) gives rise to different splitting multiplicities. NMR spectroscopy can be used to determine site-specific deuteration of molecules.
Another method uses HSQC spectra. Typically HSQC spectra are recorded at a series of timepoints while the hydrogen is exchanging with the deuterium. Since the HSQC experiment is specific for hydrogen, the signal will decay exponentially as the hydrogen exchanges. It is then possible to fit an exponential function to the data, and obtain the exchange constant. This method gives residue-specific information for all the residues in the protein simultaneously The major drawback is that it requires a prior assignment of the spectrum for the protein in question. This can be very labor-intensive, and usually limits the method to proteins smaller than 25 kDa. Because it takes minutes to hours to record a HSQC spectrum, amides that exchange quickly must be measured using other pulse sequences. | 0 | Theoretical and Fundamental Chemistry |
Mobility and access to medical care are one of the major challenges for many disabled Iranian veterans. In Tehran alone there are very few wheelchair-accessible ramps, elevators and parking spots and the problem is more serious in smaller cities. This is while by 2018 over 5,000 disabled Iranian veterans, mostly living in the capital, are reliant on wheelchairs for mobility. According to the Tehran Metro Group many more elevators are needed in Tehran's subway system. To provide better services for disabled veterans, the Iranian government has announced that around $5 million has been dedicated to constructing ramps and wheelchair-accessible paths throughout Tehran. No similar official plans are dedicated for other cities in Iran.
In Tehran, chemical weapons victims are often referred to the Sasan Hospital.
The Tehran Peace Museum plans to focus on the enduring human consequences of Iran–Iraq War and serves as a centre for surviving victims of the war, especially chemical warfare veterans attacked by Saddam Hussein's forces.
In addition to numerous laws and regulations the Iranian government has passed to address disability related issues, the Disability Protect Act, including 16 articles
providing legal protections for disabled persons in areas such as public building access, education, housing and finance, has been Iran's
most progressive and comprehensive legislation concerning disabled persons which was passed in 2003.
The Janbazan Foundation is created by Iran government for the assistance of Iranian disabled veterans and for giving them special treatment. They also receive services such as financial loan from Foundation of Martyrs and Veterans Affairs. | 1 | Applied and Interdisciplinary Chemistry |
Two different variations of electron transport are used during photosynthesis:
*Noncyclic electron transport or non-cyclic photophosphorylation produces NADPH + H and ATP.
*Cyclic electron transport or cyclic photophosphorylation produces only ATP.
The noncyclic variety involves the participation of both photosystems, while the cyclic electron flow is dependent on only photosystem I.
*Photosystem I uses light energy to reduce NADP to NADPH + H, and is active in both noncyclic and cyclic electron transport. In cyclic mode, the energized electron is passed down a chain that ultimately returns it (in its base state) to the chlorophyll that energized it.
*Photosystem II uses light energy to oxidize water molecules, producing electrons (e), protons (H), and molecular oxygen (O), and is only active in noncyclic transport. Electrons in this system are not conserved, but are rather continually entering from oxidized 2HO (O + 4 H + 4 e) and exiting with NADP when it is finally reduced to NADPH. | 0 | Theoretical and Fundamental Chemistry |
Rapid fentanyl test strips are decriminalized in Tennessee. Representative William Lamberth, R-Portland, introduced HB2177 in the Tennessee General Assembly on January 31, 2022, followed by the introduction of SB2427 by Senator Jack Johnson, R-Franklin, the following day. The bill was eventually passed by Governor Bill Lee on March 31. Fentanyl test strips were previously considered drug paraphernalia by Tennessee Code Annotated §39-17-402, which defines terms such as controlled substance and drug paraphernalia in Tennessee state law. Per TCA §39-17-425, possession of fentanyl test strips was previously a Class A misdemeanor, punishable by up to 11 months, 29 days in jail and fines of up to $2,500; distributing them was previously a Class E felony, punishable by prison sentences of one to six years and fines of up to $3,000. | 0 | Theoretical and Fundamental Chemistry |
Stomatal crypts are sunken areas of the leaf epidermis which form a chamber-like structure that contains one or more stomata and sometimes trichomes or accumulations of wax. Stomatal crypts can be an adaption to drought and dry climate conditions when the stomatal crypts are very pronounced. However, dry climates are not the only places where they can be found. The following plants are examples of species with stomatal crypts or antechambers: Nerium oleander, conifers, Hakea and Drimys winteri which is a species of plant found in the cloud forest. | 0 | Theoretical and Fundamental Chemistry |
Several azo dyes like Metanil Yellow, Disperse Orange 1, and Acid orange 5 are derivatives of diphenylamine. | 0 | Theoretical and Fundamental Chemistry |
Irreversible inhibitors covalently bind to an enzyme, and this type of inhibition can therefore not be readily reversed. Irreversible inhibitors often contain reactive functional groups such as nitrogen mustards, aldehydes, haloalkanes, alkenes, Michael acceptors, phenyl sulfonates, or fluorophosphonates. These electrophilic groups react with amino acid side chains to form covalent adducts. The residues modified are those with side chains containing nucleophiles such as hydroxyl or sulfhydryl groups; these include the amino acids serine (that reacts with DFP, see the "DFP reaction" diagram), and also cysteine, threonine, or tyrosine.
Irreversible inhibition is different from irreversible enzyme inactivation. Irreversible inhibitors are generally specific for one class of enzyme and do not inactivate all proteins; they do not function by destroying protein structure but by specifically altering the active site of their target. For example, extremes of pH or temperature usually cause denaturation of all protein structure, but this is a non-specific effect. Similarly, some non-specific chemical treatments destroy protein structure: for example, heating in concentrated hydrochloric acid will hydrolyse the peptide bonds holding proteins together, releasing free amino acids.
Irreversible inhibitors display time-dependent inhibition and their potency therefore cannot be characterised by an IC value. This is because the amount of active enzyme at a given concentration of irreversible inhibitor will be different depending on how long the inhibitor is pre-incubated with the enzyme. Instead, k/[I] values are used, where k is the observed pseudo-first order rate of inactivation (obtained by plotting the log of % activity versus time) and [I] is the concentration of inhibitor. The k/[I] parameter is valid as long as the inhibitor does not saturate binding with the enzyme (in which case k = k) where k is the rate of inactivation. | 1 | Applied and Interdisciplinary Chemistry |
Dicumyl peroxide is an organic compound with the formula (Me = CH). Classified as a dialky peroxide, it is produced on a large scale industrially for use in polymer chemistry. It serves as an initiator and crosslinking agent in the production of low density polyethylene. | 0 | Theoretical and Fundamental Chemistry |
Solventogenic Clostridium species have a biphasic metabolism composed of an acidogenic phase and a solventogenic phase. During acidogenesis, these bacteria are able to convert several carbon sources into organic acids, commonly butyrate and acetate. As acid accumulates, cells begin to assimilate the organic acids to solvents. In Clostridium acetobutylicum, a model solventogenic Clostridium species, a combination of low pH and high undisociated butyrate, referred to as the "pH-acid effect", triggers the metabolic shift from acidogenesis to solventogenesis. | 1 | Applied and Interdisciplinary Chemistry |
An alternative hypothesis is that the pharmaceutical industry has become cartelized and formed a bureaucratic oligopoly, resulting in reduced innovation and efficiency. As of 2022, approximately 20 Big Pharma companies control the majority of global branded drug sales (on the scale of ±$1 trillion annually). Critics point out that Big Pharma has reduced investment in R&D, spending double on marketing, and have focused on elevating drug prices instead of risk-taking. | 1 | Applied and Interdisciplinary Chemistry |
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." | 0 | Theoretical and Fundamental Chemistry |
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