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Her awards and honours include:
* 2003 National Science Foundation CAREER Award
* 2004 University of Delaware Francis Alison Young Scholar Award
* 2010 University of Minnesota Etter Memorial Lectureship in Chemistry
* 2012 University of Delaware Trabant Award for Women's Equity
* 2014 University of Southern Mississippi Bayer Distinguished Lectureship
* 2014 Elected a fellow of the American Chemical Society (ACS)
* 2014 Elected a fellow of the American Institute for Medical and Biological Engineering (AIMBE)
* 2015 University of Southern Mississippi Covestro Distinguished Lectureship
* 2019 Fulbright Program Scholar
* 2019 Elected a fellow of the National Academy of Inventors | 0 | Theoretical and Fundamental Chemistry |
It is important to note that even while kinetic analysis is a powerful tool for determining the stoichiometry of the turn-over limiting transition state relative to the ground state, it cannot answer all mechanistic questions. It is possible for two mechanisms to be kinetically indistinguishable, especially under catalytic conditions. For any thorough mechanistic evaluation it is necessary to conduct kinetic analysis of both the catalytic process and its individual steps (when possible) in concert with other forms of analysis such as evaluation of linear free energy relationships, isotope effect studies, computational analysis, or any number of alternative approaches. Finally, it is important to note that no mechanistic hypothesis can ever be proven; alternative mechanistic hypothesis can only be disproven. It is, therefore, essential to conduct any investigation in a hypothesis-driven manner. Only by experimentally disproving reasonable alternatives can the support for a given hypothesis be strengthened. | 0 | Theoretical and Fundamental Chemistry |
Solarization refers to a phenomenon in physics where a material undergoes a temporary change in color after being subjected to high-energy electromagnetic radiation, such as ultraviolet light or X-rays. Clear glass and many plastics will turn amber, green or other colors when subjected to X-radiation, and glass may turn blue after long-term solar exposure in the desert. It is believed that solarization is caused by the formation of internal defects, called color centers, which selectively absorb portions of the visible light spectrum. In glass, color center absorption can often be reversed by heating the glass to high temperatures (a process called thermal bleaching) to restore the glass to its initial transparent state. Solarization may also permanently degrade a material's physical or mechanical properties, and is one of the mechanisms involved in the breakdown of plastics within the environment. | 0 | Theoretical and Fundamental Chemistry |
Affinity-trap polyacrylamide gel electrophoresis (PAGE) has become one of the most popular methods of protein separation. This is not only due to its separation qualities, but also because it can be used in conjunction with a variety of other analytic methods, such as mass spectrometry, and western blotting. In addition to helping isolate and purify proteins from biological samples, AT-PAGE is anticipated to be helpful in analyses of variations in the expression of particular proteins as well as in investigations of posttranslational modifications of proteins. This method utilizes a two-step approach. First, a protein sample is run through a polyacrylamide gel using electrophoresis. Then, the sample is transferred to a different polyacrylamide gel (the affinity-trap gel) where affinity probes are immobilized. The proteins that do not have affinity for the affinity probes pass through the affinity-trap gel, and proteins with affinity for the probes will be "trapped" by the immobile affinity probes. These trapped proteins are then visualized and identified using mass spectrometry after in-gel digestion. | 1 | Applied and Interdisciplinary Chemistry |
Neil Bartlett was born on 15 September 1932 in Newcastle-upon-Tyne, England. Bartletts interest in chemistry dated back to an experiment at Heaton Grammar School when he was only eleven years old, in which he prepared "beautiful, well-formed" crystals by reaction of aqueous ammonia with copper sulfate. He explored chemistry by constructing a makeshift lab in his parents home using chemicals and glassware he purchased from a local supply store. He went on to attend King's College, University of Durham (which went on to become Newcastle University) in the United Kingdom where he obtained a Bachelor of Science (1954) and then a doctorate (1958) in the inorganic chemistry research group of Dr. P.L. Robinson.
In 1958, Bartlett's career began upon being appointed a lecturer in chemistry at the University of British Columbia in Vancouver, BC, Canada where he would ultimately reach the rank of full professor. During his time at the university he made his discovery that noble gases were indeed reactive enough to form bonds. He remained there until 1966, when he moved to Princeton University as a professor of chemistry and a member of the research staff at Bell Laboratories. He then went on to join the chemistry department at the University of California, Berkeley in 1969 as a professor of chemistry until his retirement in 1993. He was also a staff scientist at Lawrence Berkeley National Laboratory from 1969 to 1999. In 2000, he became a naturalized citizen of the United States. He died on 5 August 2008 of a ruptured aortic aneurysm. He lived with his wife Christina Bartlett until his death. They had four children. | 0 | Theoretical and Fundamental Chemistry |
For a finite volume gravity current, perhaps the simplest modelling approach is via a box model where a "box" (rectangle for 2D problems, cylinder for 3D) is used to represent the current. The box does not rotate or shear, but changes in aspect ratio (i.e. stretches out) as the flow progresses. Here, the dynamics of the problem are greatly simplified (i.e. the forces controlling the flow are not direct considered, only their effects) and typically reduce to a condition dictating the motion of the front via a Froude number and an equation stating the global conservation of mass, i.e. for a 2D problem
where is the Froude number, is the speed at the front, is the reduced gravity, is the height of the box, is the length of the box and is the volume per unit width. The model is not a good approximation in the early slumping stage of a gravity current, where along the current is not at all constant, or the final viscous stage of a gravity current, where friction becomes important and changes . The model is a good in the stage between these, where the Froude number at the front is constant and the shape of the current has a nearly constant height.
Additional equations can be specified for processes that would alter the density of the intruding fluid such as through sedimentation. The front condition (Froude number) generally cannot be determined analytically but can instead be found from experiment or observation of natural phenomena. The Froude number is not necessarily a constant, and may depend on the height of the flow in when this is comparable to the depth of overlying fluid.
The solution to this problem is found by noting that and integrating for an initial length, . In the case of a constant volume and Froude number , this leads to | 1 | Applied and Interdisciplinary Chemistry |
Prickle is also known as REST/NRSF-interacting LIM domain protein, which is a putative nuclear translocation receptor. Prickle is part of the non-canonical Wnt signaling pathway that establishes planar cell polarity. A gain or loss of function of Prickle1 causes defects in the convergent extension movements of gastrulation. In epithelial cells, Prickle2 establishes and maintains cell apical/basal polarity. Prickle1 plays an important role in the development of the nervous system by regulating the movement of nerve cells.
The first prickle protein was identified in Drosophila as a planar cell polarity protein. Vertebrate prickle-1 was first found as a rat protein that binds to a transcription factor, neuron-restrictive silencer factor (NRSF). It was then recognized that other vertebrates including mice and humans have two genes that are related to Drosophila prickle. Mouse prickle-2 was found to be expressed in mature neurons of the brain along with mouse homologs of Drosophila planar polarity genes flamingo and dischevelled. Prickle interacts with flamingo to regulate sensory axon advance at the transition between the peripheral nervous system and the central nervous system. Also, Prickle1 interacts with RE1-silencing transcription factor (REST) by transporting REST out of the nucleus. REST turns off several critical genes in neurons by binding to particular regions of DNA in the nucleus.
Prickle is recruited to the cell surface membrane by strabismus, another planar cell polarity protein. In the developing Drosophila wing, prickle becomes concentrated at the proximal side of cells. Prickle can compete with the ankyrin-repeat protein Diego for a binding site on Dishevelled.
In Drosophila, prickle is present inside cells in multiple forms due to alternative splicing of the prickle mRNA. The relative levels of the alternate forms may be regulated and involved in the normal control of planar cell polarity.
Mutations in Prickle genes can cause epilepsy in humans by perturbing Prickle function. One mutation in Prickle1 gene can result in Prickle1-Related Progressive Myoclonus Epilepsy-Ataxia Syndrome. This mutation disrupts the interaction between prickle-like 1 and REST, which results in the inability to suppress REST. Gene knockdown of Prickle1 by shRNA or dominant-negative constructs results in decreased axonal and dendritic extension in neurons in the hippocampus. Prickle1 gene knockdown in neonatal retina causes defects in axon terminals of photoreceptors and in inner and outer segments. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a metallaborane is a compound that contains one or more metal atoms and one or more boron hydride. These compounds are related conceptually and often synthetically to the boron-hydride clusters by replacement of BH units with metal-containing fragments. Often these metal fragments are derived from metal carbonyls or cyclopentadienyl complexes. Their structures can often be rationalized by polyhedral skeletal electron pair theory. The inventory of these compounds is large, and their structures can be quite complex. | 0 | Theoretical and Fundamental Chemistry |
The Uhp system uptakes phosphorylated hexose sugars into bacteria. The system is triggered by phosphorylated hexose sugars on the outside of the cell. UhpC binds to the phosphorylated hexose, which allows the phosphorylation of UhpB on one of its cytoplasmic histidines. This facilitates the phosphorylation of an aspartate on UhpA, and the phosphorylated UhpA activates the transcription of UhpT. UhpT then facilitates the transport of the phosphorylated hexose sugars into the cell. | 1 | Applied and Interdisciplinary Chemistry |
The Gunpowder Empires generally refer to the Islamic Ottoman, Safavid and Mughal empires. The phrase was first coined by Marshall Hodgson in the title of Book 5 ("The Second Flowering: The Empires of Gunpowder Times") of his highly influential three-volume work, The Venture of Islam (1974).
Hogdson applied the term "gunpowder empire" to three Islamic political entities he identified as separate from the unstable, geographically limited confederations of Turkic clans that prevailed in post-Mongol times. He called them "military patronage states of the Later Middle Period," which possessed three defining characteristics: first, a legitimization of independent dynastic law; second, the conception of the whole state as a single military force; third, the attempt to explain all economic and high cultural resources as appanages of the chief military families. Connecting these empires were their traditions which grew "out of Mongol notions of greatness," but "[s]uch notions could fully mature and create stable bureaucratic empires only after gunpowder weapons and their specialized technology attained a primary place in military life."
William H. McNeill further expanded on the concept of gunpowder empires by arguing that such states "were able to monopolize the new artillery, central authorities were able to unite larger territories into new, or newly consolidated, empires."
In 2011 Douglas E. Streusand criticized the Hodgson-McNeill Gunpowder-Empire hypothesis, calling it into disfavor as a neither "adequate [n]or accurate" explanation, although the term remains in use. The main problem he saw with the Hodgson-McNeill theory is that the acquisition of firearms does not seem to have preceded the initial acquisition of territory constituting the imperial critical mass of any of the three early modern Islamic empires, except in the case of the Mughals. Moreover, it seems that the commitment to military autocratic rule pre-dated the acquisition of gunpowder weapons in all three cases.
Whether or not gunpowder was inherently linked to the existence of any of these three empires, it cannot be questioned that each of the three acquired artillery and firearms early in their history and made such weapons an integral part of their military tactics. | 1 | Applied and Interdisciplinary Chemistry |
The best Lewis structure for an oxocarbenium ion contains an oxygen–carbon double bond, with the oxygen atom attached to an additional group and consequently taking on a formal positive charge. In the language of canonical structures (or "resonance"), the polarization of the π bond is described by a secondary carbocationic resonance form, with a formal positive charge on carbon (see above). In terms of frontier molecular orbital theory, the Lowest Unoccupied Molecular Orbital (LUMO) of the oxocarbenium ion is a π* orbital that has the large lobe on the carbon atom; the more electronegative oxygen contributes less to the LUMO. Consequently, in an event of a nucleophilic attack, the carbon is the electrophilic site. Compared to a ketone, the polarization of an oxocarbenium ion is accentuated: they more strongly resemble a "true" carbocation, and they are more reactive toward nucleophiles. In organic reactions, ketones are commonly activated by the coordination of a Lewis acid or Brønsted acid to the oxygen to generate an oxocarbenium ion as an intermediate.
Numerically, a typical partial charge (derived from Hartree-Fock computations) for the carbonyl carbon of a ketone RC=O (like acetone) is δ+ = 0.51. With the addition of an acidic hydrogen to the oxygen atom to produce [RC=OH], the partial charge increases to δ+ = 0.61. In comparison, the nitrogen analogues of ketones and oxocarbenium ions, imines (RC=NR) and iminium ions ([RC=NRH]), respectively, have partial charges of δ+ = 0.33 and δ+ = 0.54, respectively. The order of partial positive charge on the carbonyl carbon is therefore imine < ketone < iminium < oxocarbenium.
This is also the order of electrophilicity for species containing C=X (X = O, NR) bonds. This order is synthetically significant and explains, for example, why reductive aminations are often best carried out at pH = 5 to 6 using sodium cyanoborohydride (Na[HB(CN)]) or sodium triacetoxyborohydride (Na[HB(OAc)]) as a reagent. Bearing an electron-withdrawing group, sodium cyanoborohydride and sodium triacetoxyborohydride are poorer reducing agents than sodium borohydride, and their direct reaction with ketones is generally a slow and inefficient process. However, the iminium ion (but not the imine itself) formed in situ during a reductive amination reaction is a stronger electrophile than the ketone starting material and will react with the hydride source at a synthetically useful rate. Importantly, the reaction is conducted under mildly acidic conditions that protonate the imine intermediate to a significant extent, forming the iminium ion, while not being strongly acidic enough to protonate the ketone, which would form the even more electrophilic oxocarbenium ion. Thus, the reaction conditions and reagent ensure that amine is formed selectively from iminium reduction, instead of direct reduction of the carbonyl group (or its protonated form) to form an alcohol. | 0 | Theoretical and Fundamental Chemistry |
In the absence of an external field, the director of a liquid crystal is free to point in any direction. It is possible, however, to force the director to point in a specific direction by introducing an outside agent to the system. For example, when a thin polymer coating (usually a polyimide) is spread on a glass substrate and rubbed in a single direction with a cloth, it is observed that liquid crystal molecules in contact with that surface align with the rubbing direction. The currently accepted mechanism for this is believed to be an epitaxial growth of the liquid crystal layers on the partially aligned polymer chains in the near surface layers of the polyimide.
Several liquid crystal chemicals also align to a command surface which is in turn aligned by electric field of polarized light. This process is called photoalignment. | 0 | Theoretical and Fundamental Chemistry |
In the field of solid catalysis, the surface area of catalysts is an important factor in catalytic activity. Inorganic materials such as mesoporous silica and layered clay minerals have high surface areas of several hundred m/g calculated by the BET method, indicating the possibility of application for efficient catalytic materials. | 0 | Theoretical and Fundamental Chemistry |
Oxanorbornadiene (or another activated alkene) reacts with azides, giving triazoles as a product. However, these product triazoles are not aromatic as they are in the CuAAC or SPAAC reactions, and as a result are not as stable. The activated double bond in oxanobornadiene makes a triazoline intermediate that subsequently spontaneously undergoes a retro Diels-alder reaction to release furan and give 1,2,3- or 1,4,5-triazoles. Even though this reaction is slow, it is useful because oxabornodiene is relatively simple to synthesize. The reaction is not, however, entirely chemoselective. | 0 | Theoretical and Fundamental Chemistry |
A thermocouple, also known as a "thermoelectrical thermometer", is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of the Seebeck effect, and this voltage can be interpreted to measure temperature. Thermocouples are widely used as temperature sensors.
Commercial thermocouples are inexpensive, interchangeable, are supplied with standard connectors, and can measure a wide range of temperatures. In contrast to most other methods of temperature measurement, thermocouples are self-powered and require no external form of excitation. The main limitation with thermocouples is accuracy; system errors of less than one degree Celsius (°C) can be difficult to achieve.
Thermocouples are widely used in science and industry. Applications include temperature measurement for kilns, gas turbine exhaust, diesel engines, and other industrial processes. Thermocouples are also used in homes, offices and businesses as the temperature sensors in thermostats, and also as flame sensors in safety devices for gas-powered appliances. | 1 | Applied and Interdisciplinary Chemistry |
*Bioceramic-based bone-grafting materials and scaffolds for regenerative biomedicine.
* Production and study of bioceramic systems for controlled release of biotechnological and antitumoral species.
* Nanoparticles and biocompatible matrices for biotechnological applications.
* Silica-based ordered mesoporous materials as release systems of biologically active species, cell encapsulation in silica porous materials, mesoporous materials for gene therapy and transfection, organic-inorganic hybrid materials. | 0 | Theoretical and Fundamental Chemistry |
Almost half of the genes of the bacterium E. coli that are repressed during cold shock are similarly repressed when Gyrase is blocked by the antibiotic Novobiocin. Moreover, during cold shocks, the density of nucleoids increases, and the protein gyrase and the nucleoid become colocalized (which is consistent with a reduction in DNA relaxation). This is evidence that the reduction of negative supercoiling of the DNA is one of the main mechanisms responsible for the blocking of transcription of half of the genes that conduct the cold shock transcriptional response program of bacteria. Based on this, a stochastic model of this process has been proposed. This model is illustrated in the figure, where reactions 1 represent transcription and its locking due to supercoiling. Meanwhile, reactions 2 to 4 model, respectively, translation, and RNA and protein degradation. | 1 | Applied and Interdisciplinary Chemistry |
Pollutants can be deleted from groundwater by perstraction. Different techniques have been patented. The oldest one has published in 1990 and the youngest one in 1998. In the 2000s has been done few patent applications but no granted patents.
Organic compounds through a membrane has been concentrated from groundwater. The concentration factor is from 1 000 to 10 000 bringing 0.1 ppb concentrations to between 0.1 and 1.0 ppm. Besides the concentration of a contaminant has been analyzed in real-time. The membrane is polymer like polysulphane. The hole diameter is 300 µm and thickness is 30 µm. | 0 | Theoretical and Fundamental Chemistry |
A geminal diol has two hydroxyl groups bonded to the same atom. These species arise by hydration of the carbonyl compounds. The hydration is usually unfavorable, but a notable exception is formaldehyde which, in water, exists in equilibrium with methanediol HC(OH). Another example is (FC)C(OH), the hydrated form of hexafluoroacetone. Many gem-diols undergo further condensation to give dimeric and oligomeric derivatives. This reaction applies to glyoxal and related aldehydes. | 0 | Theoretical and Fundamental Chemistry |
Some of the most common DNA extraction methods include organic extraction, Chelex extraction, and solid phase extraction. These methods consistently yield isolated DNA, but they differ in both the quality and the quantity of DNA yielded. When selecting a DNA extraction method, there are multiple factors to consider, including cost, time, safety, and risk of contamination.
Organic extraction involves the addition of incubation in multiple different chemical solutions; including a lysis step, a phenol-chloroform extraction, an ethanol precipitation, and washing steps. Organic extraction is often used in laboratories because it is cheap, and it yields large quantities of pure DNA. Though it is easy, there are many steps involved, and it takes longer than other methods. It also involves the unfavorable use of the toxic chemicals phenol and chloroform, and there is an increased risk of contamination due to transferring the DNA between multiple tubes. Several protocols based on organic extraction of DNA were effectively developed decades ago, though improved and more practical versions of these protocols have also been developed and published in the last years.
The chelex extraction method involves adding the Chelex resin to the sample, boiling the solution, then vortexing and centrifuging it. The cellular materials bind to the Chelex beads, while the DNA is available in the supernatant. The Chelex method is much faster and simpler than organic extraction, and it only requires one tube, which decreases the risk of DNA contamination. Unfortunately, Chelex extraction does not yield as much quantity and the DNA yielded is single-stranded, which means it can only be used for PCR-based analyses and not for RFLP.
Solid phase extraction such as using a spin-column-based extraction method takes advantage of the fact that DNA binds to silica. The sample containing DNA is added to a column containing a silica gel or silica beads and chaotropic salts. The chaotropic salts disrupt the hydrogen bonding between strands and facilitate the binding of the DNA to silica by causing the nucleic acids to become hydrophobic. This exposes the phosphate residues so they are available for adsorption. The DNA binds to the silica, while the rest of the solution is washed out using ethanol to remove chaotropic salts and other unnecessary constituents. The DNA can then be rehydrated with aqueous low-salt solutions allowing for elution of the DNA from the beads.
This method yields high-quality, largely double-stranded DNA which can be used for both PCR and RFLP analysis. This procedure can be automated and has a high throughput, although lower than the phenol-chloroform method. This is a one-step method i.e. the entire procedure is completed in one tube. This lowers the risk of contamination making it very useful for the forensic extraction of DNA. Multiple solid-phase extraction commercial kits are manufactured and marketed by different companies; the only problem is that they are more expensive than organic extraction or Chelex extraction. | 1 | Applied and Interdisciplinary Chemistry |
Epi-lipoxins are trihydroxy (i.e. containing 3 hydroxyl residues) metabolites of arachidonic acid. They are 15R-epimers of their lipoxin counterparts; that is, the epi-lipoxins, 15-epi-lipoxin A4 (15-epi-LxA4) and 15-epi-lipoxin B4 (15-epi-LXB4), differ from their respective lipoxin A4 (LxA4) and lipoxin B4 (LxB4) epimers in that their 15-hydroxy residue has R rather than S chirality. Formulae for these lipoxins (Lx) are:
*LxA4: 5S,6R,15S-trihydroxy-7E,9E,11Z,13E-ETE
*LxB4: 5S,14R,15S-trihydroxy-6E,8Z,10E,12E-ETE
*15-epi-LxA4: 5S,6R,15R-trihydroxy-7E,9E,11Z,13E-eicosatetraenoic acid
*15-epi-LxB4: 5S,14R,15R-trihydroxy-6E,8Z,10E,12E-eicosatrienoic acid
The two-epi-Lxs as well as the two lxs are nonclassic eicosanoids that, like other members of the specialized pro-resolving mediators class of autocoids, form during and act to resolve inflammatory responses. Synthesis of the lipoxins typically involves a lipoxygenase enzyme which acts to add a 15S-hydroxyl residue to the lipoxin precursor, arachidonic acid, whereas synthesis of the epi-lipoxins involves aspirin-pretreated cyclooxygenase 2 or a cytochrome P450 enzyme which adds a 15R-hydroxyl residue to arachidonic acid. In acknowledgement of the role played by aspirin-treated cyclooxygenase 2 in forming these products, the epi-lipoxins are sometimes termed ATL which stands for Aspirin-Triggered Lipoxins.
The counter-regulatory role of the epi-lipoxins in serving as stop signals for diverse inflammation responses is detailed at the lipoxin site. | 1 | Applied and Interdisciplinary Chemistry |
The dihydrolipoate, covalently bound to a lysine residue of the complex, is then transfered to the dihydrolipoyl dehydrogenase (E3) active site, where it undergoes a flavin-mediated oxidation, similar in chemistry to e.g. thioredoxin reductase. First, FAD oxidizes dihydrolipoate back to its lipoate (disulfide) resting state, producing FADH. Then, the substrate NAD oxidizes FADH back to its FAD resting state, producing NADH and H. | 1 | Applied and Interdisciplinary Chemistry |
The Magnus effect can also be found in advanced external ballistics. First, a spinning bullet in flight is often subject to a crosswind, which can be simplified as blowing from either the left or the right. In addition to this, even in completely calm air a bullet experiences a small sideways wind component due to its yawing motion. This yawing motion along the bullet's flight path means that the nose of the bullet points in a slightly different direction from the direction the bullet travels. In other words, the bullet "skids" sideways at any given moment, and thus experiences a small sideways wind component in addition to any crosswind component.
The combined sideways wind component of these two effects causes a Magnus force to act on the bullet, which is perpendicular both to the direction the bullet is pointing and the combined sideways wind. In a very simple case where we ignore various complicating factors, the Magnus force from the crosswind would cause an upward or downward force to act on the spinning bullet (depending on the left or right wind and rotation), causing deflection of the bullet's flight path up or down, thus influencing the point of impact.
Overall, the effect of the Magnus force on a bullets flight path itself is usually insignificant compared to other forces such as aerodynamic drag. However, it greatly affects the bullets stability, which in turn affects the amount of drag, how the bullet behaves upon impact, and many other factors. The stability of the bullet is affected, because the Magnus effect acts on the bullets centre of pressure instead of its centre of gravity. This means that it affects the yaw angle of the bullet; it tends to twist the bullet along its flight path, either towards the axis of flight (decreasing the yaw thus stabilising the bullet) or away from the axis of flight (increasing the yaw thus destabilising the bullet). The critical factor is the location of the centre of pressure, which depends on the flowfield structure, which in turn depends mainly on the bullets speed (supersonic or subsonic), but also the shape, air density and surface features. If the centre of pressure is ahead of the centre of gravity, the effect is destabilizing; if the centre of pressure is behind the centre of gravity, the effect is stabilising. | 1 | Applied and Interdisciplinary Chemistry |
The anti cryptophane isomer belongs to the D point group and the syn cryptophane isomer belongs to the C point group. Both molecules therefore do not exhibit a dipole moment. | 0 | Theoretical and Fundamental Chemistry |
Incorrect chemical shift referencing is a particularly acute problem in biomolecular NMR. It has been estimated that up to 20% of 13C and up to 35% of 15N shift assignments are improperly referenced.
Given that the structural and dynamic information contained within chemical shifts is often quite subtle, it is critical that protein chemical shifts be properly referenced so that these subtle differences can be detected. Fundamentally, the problem with chemical shift referencing comes from the fact that chemical shifts are relative frequency measurements rather than absolute frequency measurements. Because of the historic problems with chemical shift referencing, chemical shifts are perhaps the most precisely measurable but the least accurately measured parameters in all of NMR spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
*Ancient Microbial Communities is part of Sumner's research which includes understanding microbial evolution and ecology and Earth history through microbial signatures in the rock record. Her publications feature new developments in how to interpret ancient biological responses to environmental factors, tracing oxygenation and the impact on carbonate microbial biological signatures. Sumner has also studied carbon isotopes of specific carbonates in order to find evidence of life.
*Antarctic Lakes Sumner's research utilizes Antarctic lakes as a model system for understanding microbial processes, early oxygenic photosynthesis, and life on other planets. This work includes the discovery of pinnacles of microbial growth under ice-covered lakes and describes multiple microbial communities involved in the development of these features. Similar features in another Antarctic lake appear to record changes in the lake environment, including sea level, through time.
*Exploration of Mars and its Environments Professor Sumners research with the Mars Science Laboratory has generated over three dozen collaborative publications and helped uncover evidence of ancient lakes on Mars. Sumners research has established that parts of ancient Mars could have hosted life as we know it on Earth, and contributed to the discovery of organic molecules on Mars. As a geologist, Sumner applies many of the same principles that would be used on earth, such as stratigraphy and geochemistry, to the Martian environment. Sumner is a MSL “long term planner”, one of several lead geoscientists amongst more than five hundred scientists not directly employed by NASA on this project. Sumner was involved in the creation of a geological map of Gale crater, and selecting the landing site of Curiosity. Sumner was partially responsible for the assignment of daily operations to fit the long-term missions goals. and also involved in future planning for additional Mars exploration, including a mission in 2020.
*Neoarchean Geological Time Period is a part of Professor Sumners research that has been accumulated in South Africa. Sumner has studied the precipitation of multiple elements including carbonate and aragonite. This research has led Sumner to develop new understandings of the oceans pH in Neoarchean time period which can lead to discoveries in the changes of the oceans pH through time. Sumners conducted this research using methods of stratigraphy and petrography. | 0 | Theoretical and Fundamental Chemistry |
When pressure approaches zero, all real gas will behave like ideal gas, that is, of a mole of gas relying only on temperature. Therefore, we can design a scale with as its argument. Of course any bijective function will do, but for convenience's sake a linear function is the best. Therefore, we define it as
The ideal gas scale is in some sense a "mixed" scale. It relies on the universal properties of gas, a big advance from just a particular substance. But still it is empirical since it puts gas at a special position and thus has limited applicability—at some point no gas can exist. One distinguishing characteristic of ideal gas scale, however, is that it precisely equals thermodynamical scale when it is well defined (see ). | 0 | Theoretical and Fundamental Chemistry |
The translations form a normal abelian subgroup of rank 3, called the Bravais lattice (so named after French physicist Auguste Bravais). There are 14 possible types of Bravais lattice. The quotient of the space group by the Bravais lattice is a finite group which is one of the 32 possible point groups. | 0 | Theoretical and Fundamental Chemistry |
The surface temperature of a single layer
The frequency domain solution for a semi-infinite solid which is heated by a point source with angular frequency can be expressed by the following equation.
where (1)
(Λ: thermal conductivity of the solid, D: thermal diffusivity of the solid, r: radial coordinate)
In a typical time-domain thermoreflectance experiment, the co-aligned laser beams have cylindrical symmetry, therefore the
Hankel Transform can be used to simplify the computation of the convolution of equation (1) with the distributions of the laser intensities.
(The Hankel transform is an integral transform equivalent to a two-dimensional Fourier transform with a radially symmetric integral kernel)
Here g(r) is radially symmetric and by the definition of Hankel transform using Eq. (1),
Since the pump and probe beams used here have Gaussian distribution, the radius of the pump and probe beam are and respectively.
The surface is heated by the pump laser beam with the intensity , i.e.
where is the amplitude of the heat absorbed by the sample at frequency .
Then the Hankel transform of is
Then the distributions of temperature oscillations at the surface is the inverse Hankel transforms of the product and , i.e.
The surface temperatures are measured due to the change in the reflectivity with the temperature , i.e. ,
while this change is measured by the changes in the reflected intensity of a probe laser beam.
The probe laser beam measures a weighted average of the temperature , i.e.
(6a)
This last integral (6a) can be simplified to an integral over :
(6b)
The surface temperature of a layered structure
In the similar way, frequency domain solution for the surface temperature of a layered structure can be acquired. Instead of Eq. (2), Eq. (7) will be used for a layered structure.
(Λn: thermal conductivity of nth layer, Dn: thermal diffusivity of nth layer, Ln: thickness of nth layer)
Using Eqs. (6) and (7), we can calculate the changes of temperature of a layered structure.
Modeling of data acquired in time-domain thermoreflectance
The acquired data from time-domain thermoreflectance experiments are required to be compared with the model.
(Q: quality factor of the resonant circuit)
This calculated Vf/V0 would be compared with the measured one. | 0 | Theoretical and Fundamental Chemistry |
In the general context, strange matter might occur inside neutron stars, if the pressure at their core is high enough to provide a sufficient gravitational force (i.e. above the critical pressure). At the sort of densities and high pressures we expect in the center of a neutron star, the quark matter would probably be strange matter. It could conceivably be non-strange quark matter, if the effective mass of the strange quark were too high. Charm quarks and heavier quarks would only occur at much higher densities.
Strange matter comes about as a way to relieve degeneracy pressure. The Pauli exclusion principle forbids fermions such as quarks from occupying the same position and energy level. When the particle density is high enough that all energy levels below the available thermal energy are already occupied, increasing the density further requires raising some to higher, unoccupied energy levels. This need for energy to cause compression manifests as a pressure. Neutrons consist of twice as many down quarks (charge − e) as up quarks (charge + e), so the degeneracy pressure of down quarks usually dominates electrically neutral quark matter. However, when the required energy level is high enough, an alternative becomes available: half of the down quarks can be transmuted to strange quarks (charge − e). The higher rest mass of the strange quark costs some energy, but by opening up an additional set of energy levels, the average energy per particle can be lower, making strange matter more stable than non-strange quark matter.
A neutron star with a quark matter core is often called a hybrid star. However, it is difficult to know whether hybrid stars really exist in nature because physicists currently have little idea of the likely value of the critical pressure or density. It seems plausible that the transition to quark matter will already have occurred when the separation between the nucleons becomes much smaller than their size, so the critical density must be less than about 100 times nuclear saturation density. But a more precise estimate is not yet available, because the strong interaction that governs the behavior of quarks is mathematically intractable, and numerical calculations using lattice QCD are currently blocked by the fermion sign problem.
One major area of activity in neutron star physics is the attempt to find observable signatures by which we could tell whether neutron stars have quark matter (probably strange matter) in their core.
During the merger of two neutron stars, strange matter may be ejected out into the space around the stars, which may allow for the studying of strange matter. However, the rate at which strange matter decays is unknown, and there are very few binary pairs of neutron stars nearby to the Solar System, which could make the official discovery of strange matter very difficult. | 0 | Theoretical and Fundamental Chemistry |
Emerin is a protein that in humans is encoded by the EMD gene, also known as the STA gene. Emerin, together with LEMD3, is a LEM domain-containing integral protein of the inner nuclear membrane in vertebrates. Emerin is highly expressed in cardiac and skeletal muscle. In cardiac muscle, emerin localizes to adherens junctions within intercalated discs where it appears to function in mechanotransduction of cellular strain and in beta-catenin signaling. Mutations in emerin cause X-linked recessive Emery–Dreifuss muscular dystrophy, cardiac conduction abnormalities and dilated cardiomyopathy.
It is named after Alan Emery. | 1 | Applied and Interdisciplinary Chemistry |
An important application of mass spectrometric immunoassy is that it can be used as a rapid, sensitive and accurate screening of apolipoproteins and mutations of them. Apolipoproteins represent a groups of proteins with many functions such as transport and clearance as well as enzyme activation. Recent studies have claimed that mutations in apopliproteins result in, or assist in the progression of various associated diseases including amyloidosis, amyloid cardiomyopathy, Alzheimer's disease, hypertriglyceridemic, lowered cholesterol, hyperlipidemia and atherosclerosis to name a few. Nelson and colleagues did a study using MSIA to characterize and isolate apolipoproteins species. | 1 | Applied and Interdisciplinary Chemistry |
In 1886, Winkler was provided with a new mineral from the Himmelsfürst mine near Freiberg. The mineral, called argyrodite, was found by chemists to contain silver and sulfur. When Winkler subsequently analyzed the mineral, he found that the individual components only added up to about 93–94% of its total mass, leading him to suspect that a new and previously unknown element must be present. After additional chemical purification steps over several months, Winkler isolated the pure element, germanium, on February 6, 1886 and published his results. The mineral argyrodite that was Winkler's start toward finding germanium is now known to be a double sulfide with formula GeS · 4AgS.
To place germanium into the periodic table, Mendeleev suggested that it might be ekacadmium, an element he had predicted earlier. In contrast, Lothar Meyer favored an identification of germanium with ekasilicon, a different predicted element. Winkler isolated more of the pure material, and eventually obtained enough to measure some of its physical and chemical properties. His results showed unequivocally that Meyers interpretation was the correct one and that nearly all of the new elements properties matched Mendeleev predictions. The close match between what had been predicted for ekasilicon and what was found for germanium was clear evidence for the utility and power of the periodic table and the concept of periodicity. | 1 | Applied and Interdisciplinary Chemistry |
The primary form of inorganic carbon that is fixed is carbon dioxide (CO). It is estimated that approximately 250 billion tons of carbon dioxide are converted by photosynthesis annually. The majority of the fixation occurs in terrestrial environments, especially the tropics. The gross amount of carbon dioxide fixed is much larger since approximately 40% is consumed by respiration following photosynthesis. Historically it is estimated that approximately 2×10 billion tons of carbon has been fixed since the origin of life. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, disproportionation, sometimes called dismutation, is a redox reaction in which one compound of intermediate oxidation state converts to two compounds, one of higher and one of lower oxidation states. The reverse of disproportionation, such as when a compound in an intermediate oxidation state is formed from precursors of lower and higher oxidation states, is called comproportionation, also known as synproportionation.
More generally, the term can be applied to any desymmetrizing reaction where two molecules of one type react to give one each of two different types:
This expanded definition is not limited to redox reactions, but also includes some molecular autoionization reactions, such as the self-ionization of water. In contrast, some authors use the term redistribution to refer to reactions of this type (in either direction) when only ligand exchange but no redox is involved and distinguish such processes from disproportionation and comproportionation.<br />For example, the Schlenk equilibrium
is an example of a redistribution reaction. | 0 | Theoretical and Fundamental Chemistry |
The simplest concept is the measurement made using two microphones and a fast recording device such as a digital storage scope. This method uses the following idea.
If a sound source and two microphones are arranged in a straight line, with the sound source at one end, then the following can be measured:
# The distance between the microphones (), called microphone basis.
# The time of arrival between the signals (delay) reaching the different microphones ().
Then . | 1 | Applied and Interdisciplinary Chemistry |
The SKP technique is based on parallel plate capacitor experiments performed by Lord Kelvin in 1898. In the 1930s William Zisman built upon Lord Kelvin's experiments to develop a technique to measure contact potential differences of dissimilar metals. | 0 | Theoretical and Fundamental Chemistry |
Transduction is the process by which foreign DNA is introduced into a cell by a virus or viral vector. An example is the viral transfer of DNA from one bacterium to another and hence an example of horizontal gene transfer. Transduction does not require physical contact between the cell donating the DNA and the cell receiving the DNA (which occurs in conjugation), and it is DNase resistant (transformation is susceptible to DNase). Transduction is a common tool used by molecular biologists to stably introduce a foreign gene into a host cell's genome (both bacterial and mammalian cells). | 1 | Applied and Interdisciplinary Chemistry |
The Phillips catalyst, or the Phillips supported chromium catalyst, is the catalyst used to produce approximately half of the world's polyethylene. A heterogeneous catalyst, it consists of a chromium oxide supported on silica gel. Polyethylene, the most-produced synthetic polymer, is produced industrially by the polymerization of ethylene:
:n CH → (CH)
Although exergonic (i.e., thermodynamically favorable), the reaction requires catalysts. Three main catalysts are employed commercially: the Phillips catalyst, Ziegler–Natta catalysts (based on titanium trichloride), and, for specialty polymers, metallocene-based catalysts. | 0 | Theoretical and Fundamental Chemistry |
DNA editing proteins edit and permanently change gene sequence, and subsequently the gene expression of the cell. All progenies of the cell will inherit the edited gene sequence. DNA editing proteins often take part in the immune response system of both prokaryotes and eukaryotes, providing high variance in gene expression in adaptation to various pathogens.
Specific examples include:
* RAG1/RAG2
* TdT
* Cas1/Cas2 | 1 | Applied and Interdisciplinary Chemistry |
Copper does not require cleaning or maintenance. It is particularly suited for areas that are difficult or dangerous to access after installation. | 1 | Applied and Interdisciplinary Chemistry |
A new pathway was suspected when RuBisCO was not found in the methanotroph Methylmonas methanica. Through radio-labelling experiments, it was shown that M. methanica used the Ribulose monophate (RuMP) pathway. This has led researchers to propose that the RuMP cycle may have preceded the RuBP cycle.
Like the RuBP cycle, this cycle begins with 3 molecules of ribulose-5-phosphate. However, instead of phosphorylating ribulose-5-phosphate, 3 molecules of formaldehyde form a C-C bond through an aldol condensation, producing 3 molecules of 3-hexulose 6-phosphate (hexulose phosphate). One of these molecules of hexulose phosphate is converted into GAP and either pyruvate or dihydroxyacetone phosphate (DHAP). The pyruvate or DHAP is used towards biomass while the other 2 hexulose phosphate molecules and the molecule of GAP are used to regenerate the 3 molecules of ribulose-5-phosphate. | 0 | Theoretical and Fundamental Chemistry |
The psychrometric constant relates the partial pressure of water in air to the air temperature. This lets one interpolate actual vapor pressure from paired dry and wet thermometer bulb temperature readings.
: psychrometric constant [kPa °C],
: P = atmospheric pressure [kPa],
: latent heat of water vaporization, 2.45 [MJ kg],
: specific heat of air at constant pressure, [MJ kg °C],
: ratio molecular weight of water vapor/dry air = 0.622.
Both and are constants.<br>
Since atmospheric pressure, P, depends upon altitude, so does .<br>
At higher altitude water evaporates and boils at lower temperature.
Although is constant, varied air composition results in varied .
Thus on average, at a given location or altitude, the psychrometric constant is approximately constant. Still, it is worth remembering that weather impacts both atmospheric pressure and composition. | 0 | Theoretical and Fundamental Chemistry |
Grasselli Brown has been married twice, to coworker Robert Grasselli (1957–1985) and to coworker Glenn Brown (1987–). Brown had two children from his previous marriage, Robyn and Eric; they now have three grandchildren. Jeanette continues to use the name Grasselli since it is the name she is known by professionally. | 0 | Theoretical and Fundamental Chemistry |
Most molecular carbido complexes are clusters, usually featuring carbide as a six-fold bridging ligand. Examples include [C(CO)], and [C(CO)]. Though exceptions exist, such as the nonanuclear Ruthenium cluster (μ-C)Ru(CO) (μ-η: η:η-CH) containing a tripped trigonal prism geometry around the carbide.
The iron carbonyl carbides exist not only in the encapsulated carbon ([C(CO)]) but also with exposed carbon centres as in FeC(CO) and FeC(CO)
Bimetallic and exotic clusters such as metal carbide clusterfullerenes (MCCF's) have also been able to be prepared. | 0 | Theoretical and Fundamental Chemistry |
Bis(trifluoromethanesulfonyl)aniline is the organic compound with the formula CHN(SOCF). It is a white solid. The compound is used to install the triflyl group (SOCF). Its behavior is akin to that of triflic anhydride, but milder. | 0 | Theoretical and Fundamental Chemistry |
In 1955, Siekevitz and Potter demonstrated that adenine nucleotides were distributed in cells in two pools located in the mitochondrial and cytosolic compartments. Shortly thereafter, Pressman hypothesized that the two pools could exchange nucleotides. However, the existence of an ADP/ATP transporter was not postulated until 1964 when Bruni et al. uncovered an inhibitory effect of atractyloside on the energy-transfer system (oxidative phosphorylation) and ADP binding sites of rat liver mitochondria.
Soon after, an overwhelming amount of research was done in proving the existence and elucidating the link between ADP/ATP translocase and energy transport. cDNA of ADP/ATP translocase was sequenced for bovine in 1982 and a yeast species Saccharomyces cerevisiae in 1986 before finally Battini et al. sequenced a cDNA clone of the human transporter in 1989. The homology in the coding sequences between human and yeast ADP/ATP translocase was 47% while bovine and human sequences extended remarkable to 266 out of 297 residues, or 89.6%. In both cases, the most conserved residues lie in the ADP/ATP substrate binding pocket. | 1 | Applied and Interdisciplinary Chemistry |
Carboxylic acids are esterified by treatment with epoxides, giving β-hydroxyesters:
This reaction is employed in the production of vinyl ester resin from acrylic acid. | 0 | Theoretical and Fundamental Chemistry |
In the late 19th Century and into the very early 20th Century, except for staple foods (sugar, rice, and beans) that needed no refrigeration, the available foods were affected heavily by the seasons and what could be grown locally. Refrigeration has removed these limitations. Refrigeration played a large part in the feasibility and then popularity of the modern supermarket. Fruits and vegetables out of season, or grown in distant locations, are now available at relatively low prices. Refrigerators have led to a huge increase in meat and dairy products as a portion of overall supermarket sales. As well as changing the goods purchased at the market, the ability to store these foods for extended periods of time has led to an increase in leisure time. Prior to the advent of the household refrigerator, people would have to shop on a daily basis for the supplies needed for their meals. | 0 | Theoretical and Fundamental Chemistry |
The radial spoke is a multi-unit protein structure found in the axonemes of eukaryotic cilia and flagella. Although experiments have determined the importance of the radial spoke in the proper function of these organelles, its structure and mode of action remain poorly understood. | 1 | Applied and Interdisciplinary Chemistry |
For his work, Woodward received many awards, honors and honorary doctorates, including election to the American Academy of Arts and Sciences in 1948, the National Academy of Sciences in 1953, the American Philosophical Society in 1962, and membership in academies around the world. He was also a consultant to many companies such as Polaroid, Pfizer, and Merck. Other awards include:
* John Scott Medal, from the Franklin Institute and City of Philadelphia, 1945
* Leo Hendrik Baekeland Award, from the North Jersey Section of the American Chemical Society, 1955
* Elected a Foreign Member of the Royal Society (ForMemRS) in 1956
* Davy Medal, from the Royal Society in 1959
* Roger Adams Medal, from the American Chemical Society in 1961
* Pius XI Gold Medal, from the Pontifical Academy of Sciences in 1969
* National Medal of Science from the United States in 1964 ("For an imaginative new approach to the synthesis of complex organic molecules and, especially, for his brilliant syntheses of strychnine, reserphine, lysergic acid, and chlorophyll.")
* Nobel Prize in Chemistry in 1965
* Willard Gibbs Award from the Chicago Section of the American Chemical Society in 1967
* Lavoisier Medal from the Société chimique de France in 1968
* The Order of the Rising Sun, Second Class from the Emperor of Japan in 1970
* Hanbury Memorial Medal from The Pharmaceutical Society of Great Britain in 1970
* Pierre Bruylants Medal from the University of Louvain in 1970
* AMA Scientific Achievement Award in 1971
* Cope Award from the American Chemical Society, shared with Roald Hoffmann in 1973
* Copley Medal from the Royal Society, London in 1978 | 0 | Theoretical and Fundamental Chemistry |
An electrochemical cell is a device that produces an electric current from energy released by a spontaneous redox reaction. This kind of cell includes the Galvanic cell or Voltaic cell, named after Luigi Galvani and Alessandro Volta, both scientists who conducted experiments on chemical reactions and electric current during the late 18th century.
Electrochemical cells have two conductive electrodes (the anode and the cathode). The anode is defined as the electrode where oxidation occurs and the cathode is the electrode where the reduction takes place. Electrodes can be made from any sufficiently conductive materials, such as metals, semiconductors, graphite, and even conductive polymers. In between these electrodes is the electrolyte, which contains ions that can freely move.
The galvanic cell uses two different metal electrodes, each in an electrolyte where the positively charged ions are the oxidized form of the electrode metal. One electrode will undergo oxidation (the anode) and the other will undergo reduction (the cathode). The metal of the anode will oxidize, going from an oxidation state of 0 (in the solid form) to a positive oxidation state and become an ion. At the cathode, the metal ion in solution will accept one or more electrons from the cathode and the ion's oxidation state is reduced to 0. This forms a solid metal that electrodeposits on the cathode. The two electrodes must be electrically connected to each other, allowing for a flow of electrons that leave the metal of the anode and flow through this connection to the ions at the surface of the cathode. This flow of electrons is an electric current that can be used to do work, such as turn a motor or power a light.
A galvanic cell whose electrodes are zinc and copper submerged in zinc sulfate and copper sulfate, respectively, is known as a Daniell cell.
The half reactions in a Daniell cell are as follows:
:Zinc electrode (anode): Zn → Zn + 2 e
:Copper electrode (cathode): Cu + 2 e → Cu
In this example, the anode is the zinc metal which is oxidized (loses electrons) to form zinc ions in solution, and copper ions accept electrons from the copper metal electrode and the ions deposit at the copper cathode as an electrodeposit. This cell forms a simple battery as it will spontaneously generate a flow of electric current from the anode to the cathode through the external connection. This reaction can be driven in reverse by applying a voltage, resulting in the deposition of zinc metal at the anode and formation of copper ions at the cathode.
To provide a complete electric circuit, there must also be an ionic conduction path between the anode and cathode electrolytes in addition to the electron conduction path. The simplest ionic conduction path is to provide a liquid junction. To avoid mixing between the two electrolytes, the liquid junction can be provided through a porous plug that allows ion flow while minimizing electrolyte mixing. To further minimize mixing of the electrolytes, a salt bridge can be used which consists of an electrolyte saturated gel in an inverted U-tube. As the negatively charged electrons flow in one direction around this circuit, the positively charged metal ions flow in the opposite direction in the electrolyte.
A voltmeter is capable of measuring the change of electrical potential between the anode and the cathode.
The electrochemical cell voltage is also referred to as electromotive force or emf.
A cell diagram can be used to trace the path of the electrons in the electrochemical cell. For example, here is a cell diagram of a Daniell cell:
:Zn | Zn (1 M) || Cu (1 M) | Cu
First, the reduced form of the metal to be oxidized at the anode (Zn) is written. This is separated from its oxidized form by a vertical line, which represents the limit between the phases (oxidation changes). The double vertical lines represent the saline bridge on the cell. Finally, the oxidized form of the metal to be reduced at the cathode, is written, separated from its reduced form by the vertical line. The electrolyte concentration is given as it is an important variable in determining the exact cell potential. | 0 | Theoretical and Fundamental Chemistry |
In 1815 Davy also suggested that acids were substances that contained replaceable hydrogen ions;– hydrogen that could be partly or totally replaced by reactive metals which are placed above hydrogen in the reactivity series. When acids reacted with metals they formed salts and hydrogen gas. Bases were substances that reacted with acids to form salts and water. These definitions worked well for most of the nineteenth century. | 1 | Applied and Interdisciplinary Chemistry |
When writing sequences for systematic biology it may be necessary to have IUPAC codes that mean "any of the two" or "any of the three". The IUPAC code R (any purine) is complementary to Y (any pyrimidine) and M (amino) to K (keto). W (weak) and S (strong) are usually not swapped but have been swapped in the past by some tools. W and S denote "weak" and "strong", respectively, and indicate a number of the hydrogen bonds that a nucleotide uses to pair with its complementing partner. A partner uses the same number of the bonds to make a complementing pair.
An IUPAC code that specifically excludes one of the three nucleotides can be complementary to an IUPAC code that excludes the complementary nucleotide. For instance, V (A, C or G - "not T") can be complementary to B (C, G or T - "not A"). | 1 | Applied and Interdisciplinary Chemistry |
A nanoparticle is defined as having one dimension 100 nm or less in size. Environmentally toxic or biologically hazardous reducing agents are typically involved in the chemical synthesis of nanoparticles so there has been a search for greener production alternatives. Current research has shown that microorganisms, plant extracts, and fungi can produce nanoparticles through biological pathways. The most common nanoparticles synthesized by fungi are silver and gold, however fungi have been utilized in the synthesis other types of nanoparticles including zinc oxide, platinum, magnetite, zirconia, silica, titanium, and cadmium sulfide and cadmium selenide quantum dots. | 0 | Theoretical and Fundamental Chemistry |
Triglycerides are built from three fatty acids, esterified onto each of three hydroxy groups of glycerol, which is derived from glycerol 3-phosphate. In mammals, glycerol 3-phosphate is usually synthesized through glycolysis, a metabolic pathway that degrades glucose into fructose 1,6-bisphosphate and then into two molecules of dihydroxyacetone phosphate, which beget glycerol 3-phosphate and glyceraldehyde 3-phosphate. When an organism is deficient in glucose, from (for example) fasting or a low carbohydrate intake, glycerol 3-phosphate is generated by glyceroneogenesis instead. As well as synthesizing lipids for use in other metabolic processes, glyceroneogenesis regulates lipid levels in the cytosol. | 1 | Applied and Interdisciplinary Chemistry |
A wide variety of sphagnum, sedges, rushes and other characteristic bog species inhabit Portlethen Moss. Sometimes insectivorous plants reside in mosses, since the soils are generally nutrient poor. The heath also serves as a food source for area roe deer, while Corydalis claviculata is an attractive host for numerous butterfly larvae. Representative plant species found in this nature reserve include: | 1 | Applied and Interdisciplinary Chemistry |
Eszopiclone acts on benzodiazepine binding site situated on GABA neurons as a positive allosteric modulator.
Eszopiclone is rapidly absorbed after oral administration, with serum levels peaking between .45 and 1.3 hours. The elimination half-life of eszopiclone is approximately 6 hours and it is extensively metabolized by oxidation and demethylation. Approximately 52% to 59% of a dose is weakly bound to plasma protein. Cytochrome P450 (CYP) isozymes CYP3A4 and CYP2E1 are involved in the biotransformation of eszopiclone; thus, drugs that induce or inhibit these CYP isozymes may affect the metabolism of eszopiclone. Less than 10% of the orally administered dose is excreted in the urine as racemic zopiclone. In terms of benzodiazepine receptor binding and relevant potency, 3 mg of eszopiclone is equivalent to 10 mg of diazepam. | 0 | Theoretical and Fundamental Chemistry |
TosMIC (toluenesulfonylmethyl isocyanide) is an organic compound with the formula CHCHSOCHNC. The molecule contains both sulfonyl and isocyanide groups. It is a colourless solid that, unlike many isocyanides, is odorless. It is prepared by dehydration of the related formamide derivative. It is used in the Van Leusen reaction which is used to convert ketones to nitriles or in the preparation of oxazoles and imidazoles. The versatility of TosMIC in organic synthesis has been documented. It is a fairly strong carbon acid, with an estimated pK of 14 (compared to 29 for methyl tolyl sulfone), the isocyano group acting as an electron acceptor of strength comparable to an ester group. | 0 | Theoretical and Fundamental Chemistry |
Professor Paul Karrer FRS FRSE FCS (21 April 1889 – 18 June 1971) was a Swiss organic chemist best known for his research on vitamins. He and Norman Haworth won the Nobel Prize for Chemistry in 1937. | 0 | Theoretical and Fundamental Chemistry |
Consider a steady supersonic flow past a solid cone that has a semi-vertical angle . A conical shock wave can form in this situation, with the vertex of the shock wave lying at the vertex of the solid cone. If it were a two-dimensional problem, i.e., for a supersonic flow past a wedge, then the incoming stream would have deflected through an angle upon crossing the shock wave so that streamlines behind the shock wave would be parallel to the wedge sides. Such a simple turnover of streamlines is not possible for three-dimensional case. After passing through the shock wave, the streamlines are curved and only asymptotically they approach the generators of the cone. The curving of streamlines is accompanied by a gradual increase in density and decrease in velocity, in addition to those increments/decrements effected at the shock wave.
The direction and magnitude of the velocity immediately behind the oblique shock wave is given by weak branch of the shock polar. This particularly suggests that for each value of incoming Mach number , there exists a maximum value of beyond which shock polar do not provide solution under in which case the conical shock wave will have detached from the solid surface (see Mach reflection). These detached cases are not considered here. The flow immediately behind the oblique conical shock wave is typically supersonic, although however when is close to , it can be subsonic. The supersonic flow behind the shock wave will become subsonic as it evolves downstream.
Since all incident streamlines intersect the conical shock wave at the same angle, the intensity of the shock wave is constant. This particularly means that entropy jump across the shock wave is also constant throughout. In this case, the flow behind the shock wave is a potential flow. Hence we can introduce the velocity potential such that . Since the problem do not have any length scale and is clearly axisymmetric, the velocity field and the pressure field will be turn out to functions of the polar angle only (the origin of the spherical coordinates is taken to be located at the vertex). This means that we have
The steady potential flow is governed by the equation
where the sound speed is expressed as a function of the velocity magnitude only. Substituting the above assumed form for the velocity field, into the governing equation, we obtain the general Taylor–Maccoll equation
The equation is simplified greatly for a polytropic gas for which , i.e.,
where is the specific heat ratio and is the stagnation enthalpy. Introducing this formula into the general Taylor–Maccoll equation and introducing a non-dimensional function , where (the speed of the potential flow when it flows out into a vacuum), we obtain, for the polytropic gas, the Taylor–Maccoll equation,
The equation must satisfy the condition that (no penetration on the solid surface) and also must correspond to conditions behind the shock wave at , where is the half-angle of shock cone, which must be determined as part of the solution for a given incoming flow Mach number and . The Taylor–Maccoll equation has no known explicit solution and it is integrated numerically. | 1 | Applied and Interdisciplinary Chemistry |
The strength of adhesion by the dispersive mechanism depends on a variety of factors, including the chemical structure of the molecules involved in the adhesive system, the degree to which coatings wet each other, and the surface roughness at the interface. | 0 | Theoretical and Fundamental Chemistry |
The surface tension at the border between the fluid lining and the inhaled gas (gas/fluid interface) in alveoli determines the motion of the alveoli as a whole. According to Lapace's Law, high surface tension in the gas/fluid interface of alveoli prevents the alveoli from inflating, which causes lung collapse. lipid arrangement in the fluid lining of alveoli is the primary determining factor of this surface tension since the lipids form a thin film (monolayer) on the surface of the fluid lining at the gas/fluid interface. Different lipids allow for different ranges of motion and can be compacted different.
SP-B plays a role in this by selected certain lipids and inserting them into the gas/fluid interface. The lipid shown to be most needed on this surface (Dipalmitoylphosphatidylcholine) does not easily move to the gas/fluid interface, but SP-B helps ease and speed up this process.
SP-B also indirectly reduces surface tension by organizing the lipids underneath the surface of the gas/fluid interface in structures called tubular myelin. Effectively, SP-B cuts and pastes pieces of the lipid bilayers to form the three dimensional structure of the tubular myelin. This structure is the support and lipid source for the gas/fluid interface, where surface tension is a critical factor in lung function. | 0 | Theoretical and Fundamental Chemistry |
Enzyme assays are laboratory methods for measuring enzymatic activity. They are vital for the study of enzyme kinetics and enzyme inhibition. | 1 | Applied and Interdisciplinary Chemistry |
The configuration index is a single digit which is the priority number of the ligand trans to the ligand of lowest priority in the plane perpendicular to the 4 fold axis. (If there is more than one choice then the highest numerical value second digit is taken.) NB this procedure gives the same result as SP-4, however in this case the polyhedral symbol specifies that the complex is non-planar. | 0 | Theoretical and Fundamental Chemistry |
CSMBLM publishes the scientific journal Biochemia Medica in the English language three times a year. It is included in databases such as Current Contents (Clinical Medicine), Medline, PubMed Central (PMC), Science Citation Index Expanded™ (SCIE, Thomson Reuters), Journal Citation Reports/Science Edition (JCR, Thomson Reuters), EMBASE/Excerpta Medica, Scopus, CAS (Chemical Abstracts Service), EBSCO/Academic Search Complete and DOAJ (Directory of Open Access Journals). | 1 | Applied and Interdisciplinary Chemistry |
Cultural or anthropogenic eutrophication is the process that causes eutrophication because of human activity. The problem became more apparent following the introduction of chemical fertilizers in agriculture (green revolution of the mid-1900s). Phosphorus and nitrogen are the two main nutrients that cause cultural eutrophication as they enrich the water, allowing for some aquatic plants, especially algae to grow rapidly and bloom in high densities. Algal blooms can shade out benthic plants thereby altering the overall plant community. When algae die off, their degradation by bacteria removes oxygen, potentially, generating anoxic conditions. This anoxic environment kills off aerobic organisms (e.g. fish and invertebrates) in the water body. This also affects terrestrial animals, restricting their access to affected water (e.g. as drinking sources). Selection for algal and aquatic plant species that can thrive in nutrient-rich conditions can cause structural and functional disruption to entire aquatic ecosystems and their food webs, resulting in loss of habitat and species biodiversity.
There are several sources of excessive nutrients from human activity including run-off from fertilized fields, lawns, and golf courses, untreated sewage and wastewater and internal combustion of fuels creating nitrogen pollution. Cultural eutrophication can occur in fresh water and salt water bodies, shallow waters being the most susceptible. In shore lines and shallow lakes, sediments are frequently resuspended by wind and waves which can result in nutrient release from sediments into the overlying water, enhancing eutrophication. The deterioration of water quality caused by cultural eutrophication can therefore negatively impact human uses including potable supply for consumption, industrial uses and recreation. | 1 | Applied and Interdisciplinary Chemistry |
The inviscid Burgers' equation is a conservation equation, more generally a first order quasilinear hyperbolic equation. The solution to the equation and along with the initial condition
can be constructed by the method of characteristics. The characteristic equations are
Integration of the second equation tells us that is constant along the characteristic and integration of the first equation shows that the characteristics are straight lines, i.e.,
where is the point (or parameter) on the x-axis (t = 0) of the x-t plane from which the characteristic curve is drawn. Since at -axis is known from the initial condition and the fact that is unchanged as we move along the characteristic emanating from each point , we write on each characteristic. Therefore, the family of trajectories of characteristics parametrized by is
Thus, the solution is given by
This is an implicit relation that determines the solution of the inviscid Burgers equation provided characteristics dont intersect. If the characteristics do intersect, then a classical solution to the PDE does not exist and leads to the formation of a shock wave. Whether characteristics can intersect or not depends on the initial condition. In fact, the breaking time before a shock wave can be formed is given by | 1 | Applied and Interdisciplinary Chemistry |
Many mesoionic carbenes may not be able to be isolated as a free carbene; however, these MICs can be generated as a ligand for transition metal complexes. Numerous mesoionic carbene transition metal complexes are known with metals including Fe, Os, Rh, Ir, Ni, Pd, Pt, Cu, and Ag. Metal complexes with Sm and Y are also known. MIC complexes are formed by a variety of mechanisms.
Mesoionic carbenes may be generated in situ with addition of a strong base to their salt forms. The carbenes immediately form complexes with metals present in the reaction mixture through ligand exchange.
Direct metalation through C-H bond activation or C-H oxidative addition is one method often utilized. Activation of a C‒H bond leads to oxidative addition of the carbene ligand to the metal center. Typically, direct metalation requires the blockage of sites that would lead to normal NHC complexes — phenyl and isopropyl groups are good blocking substituents, as discussed earlier. Smaller substituents may be cleaved. Direct metalation by silver(I) with imidazolium salts can cause cleavage at the C2 position if methyl is used as the blocking group. The result is formation of normal NHC carbenes. n-alkyl and benzyl groups may undergo the same fate as the methyl group. Steric bulk may also influence the formation of MIC complexes over NHC complexes. For imidazolium salts, the C2 position may not need to be blocked if the nitrogen substituents (N1 or N3) are sterically-demanding. Interactions between the nitrogen substituents and the metal center prevent normal NHC complexes from forming. If the carbene is part of a bidentate ligand with a forced geometry, the MIC complex may form preferentially as well. The counteranion of imidazolium salts participates in NHC vs. MIC formation. NHC formation typically occurs by heterolytic bond cleavage, so small, coordinating anions favor this pathway. MIC formation typically occurs by an oxidative addition pathway, so non-coordinating and apolar anions are preferred, such as BF or SbF. Other techniques focus on the activation of the desired carbon rather than blocking undesired carbons. A carbon may be activated by a halogen. A C-X bond (X = halide) is more favorable for activation than a C-H bond. This pathway results in the oxidative addition of the MIC carbene halide to a low valent metal center.
Transmetalation is another method commonly utilized. Typically, a silver carbene complex is produced by direct metalation. This silver complex is reacted via transmetalation with a salt of the desired metal. The metal MIC complex is produced and silver salts generally precipitate. | 0 | Theoretical and Fundamental Chemistry |
Cyanate esters are chemical compounds in which the hydrogen atom of the cyanic acid is replaced by an organyl group (for example aryl group). The resulting compound is termed a cyanate ester, with the formula , where R is an organyl group. Cyanate esters contain a monovalent cyanate group . | 0 | Theoretical and Fundamental Chemistry |
The mitochondria-associated ER membrane (MAM) is another structural element that is increasingly recognized for its critical role in cellular physiology and homeostasis. Once considered a technical snag in cell fractionation techniques, the alleged ER vesicle contaminants that invariably appeared in the mitochondrial fraction have been re-identified as membranous structures derived from the MAM—the interface between mitochondria and the ER. Physical coupling between these two organelles had previously been observed in electron micrographs and has more recently been probed with fluorescence microscopy. Such studies estimate that at the MAM, which may comprise up to 20% of the mitochondrial outer membrane, the ER and mitochondria are separated by a mere 10–25 nm and held together by protein tethering complexes.
Purified MAM from subcellular fractionation is enriched in enzymes involved in phospholipid exchange, in addition to channels associated with Ca signaling. These hints of a prominent role for the MAM in the regulation of cellular lipid stores and signal transduction have been borne out, with significant implications for mitochondrial-associated cellular phenomena, as discussed below. Not only has the MAM provided insight into the mechanistic basis underlying such physiological processes as intrinsic apoptosis and the propagation of calcium signaling, but it also favors a more refined view of the mitochondria. Though often seen as static, isolated powerhouses hijacked for cellular metabolism through an ancient endosymbiotic event, the evolution of the MAM underscores the extent to which mitochondria have been integrated into overall cellular physiology, with intimate physical and functional coupling to the endomembrane system. | 1 | Applied and Interdisciplinary Chemistry |
9-BBN is prepared by the reaction of 1,5-cyclooctadiene and borane usually in ethereal solvents, for example:
The compound is commercially available as a solution in tetrahydrofuran and as a solid. 9-BBN is especially useful in Suzuki reactions.
Its highly regioselective addition on alkenes allows the preparation of terminal alcohols by subsequent oxidative cleavage with HO in aqueous KOH. The steric demand of 9-BBN greatly suppresses the formation of the 2-substituted isomer compared to the use of borane. | 0 | Theoretical and Fundamental Chemistry |
Iron is used a great deal in biological systems, a fact that is well known due to its role in Hemoglobin. For it, there are many small molecule sensors including:
*Pryrene-TEMPO, in which the binding of iron to TEMPO quenches the fluorescence of pyrene when no Fe(II) is bound. Upon binding however, TEMPO is reduced and pyrene regains fluorescence. This probe is limited in that an analogous response can be generated by unwanted free radicals, and that it can only by used in acidic solution.
*DansSQ, in which Fe(II) binding increases fluorescence at 460 nm. It consists of a Dansyl group bound to styrylquinoline and operates by the disruption of intra-molecular charge transfer upon the binding of Fe(II). It is limited in that it is only soluble in acetonitrile in 10% HO. | 0 | Theoretical and Fundamental Chemistry |
In order to promote the transfer of research results into practice, the institute engages in technology transfer, promotes spin-offs and cooperates with industrial companies. | 1 | Applied and Interdisciplinary Chemistry |
Flared connectors should not be confused with compression connectors, which are generally not interchangeable. Lacking a compression ring, they use a tapered conical shaped connection instead. A specialized flaring tool is used to enlarge tubing into a 45º tapered bell shape matching the projecting shape of the flare fitting. The flare nut, which had previously been installed over the tubing, is then tightened over the fitting to force the tapered surfaces tightly together. Flare connectors are typically brass or plastic, but stainless steel or other materials may be used.
Although flare connections are labor-intensive, they are durable and reliable. Considered more secure against leaks and sudden failure, they are used in hydraulic brake systems and in other high-pressure, high-reliability applications. | 1 | Applied and Interdisciplinary Chemistry |
High-energy beta emitters, such as phosphorus-32 and yttrium-90 can also be counted in a scintillation counter without the cocktail, instead using an aqueous solution containing no scintillators. This technique, known as Cherenkov counting, relies on Cherenkov radiation being detected directly by the photomultiplier tubes. Cherenkov counting benefits from the use of plastic vials which scatter the emitted light, increasing the potential for light to reach the photomultiplier tube. | 0 | Theoretical and Fundamental Chemistry |
NMR tubes are typically made of borosilicate glass. They are available in seven and eight inch lengths; a 5 mm tube outer diameter is most common, but 3 mm and 10 mm outer diameters are available as well. Where boron NMR is desired, quartz NMR tubes containing low concentrations of boron (as opposed to borosilicate glass) are available. Specialized closures such as J. Young valves and screwcap closures are available aside from more common polyethylene caps.
Two common specifications for NMR tubes are concentricity and camber. Concentricity refers to the variation in the radial centers, measured at the inner and outer walls. Camber refers to the "straightness" of the tube. Poor values for either may cause poorer quality spectra by reducing the homogeneity of the sample. In particular, an NMR tube which has poor camber may wobble when rotated, giving rise to spinning side bands. With modern manufacturing techniques even cheap tubes give good spectra for routine applications. | 0 | Theoretical and Fundamental Chemistry |
Phenols form a complex with ferric ions. This complex has an intense colour, which may vary from blue, green or even red depending upon the nature of the phenol. As an example using the chemical phenol itself:
: 6 PhOH + Fe → [Fe(OPh)] | 0 | Theoretical and Fundamental Chemistry |
* Nesmeyanov A.N. D.I. Mendeleev's Periodic Table of Elements and Organic Chemistry. Series: Reports at the plenary session/ VIII Mendeleev Congress on General and Applied Chemistry. Moscow: Publishing House Acad. Sciences of the USSR, 1959.
* Nesmeyanov A.N. Ed. acad. A. V. Topchiev Selected Works. Moscow: Publishing House Acad. Sciences of the USSR, 1959.
* Ioffe S.T. and Nesmeyanov A.N. Ed. A. N. Nesmeyanova and К. A. Kocheshkova Magnesium, beryllium, calcium, strontium, barium. Series: Methods of elemental organic chemistry. Moscow: Publishing House Acad. Sciences of the USSR, 1963.
* Nesmeyanov A.N. and Sokolik R.A. Ed. A. N. Nesmeyanova and К. A. Kocheshkova Bor. Aluminum. Gallium. Indium. Thallium. Series: Methods of elemental organic chemistry. Moscow: Publishing House Acad. Sciences of the USSR, 1964.
* Makarova L.G. and Nesmeyanov A.N. Ed. A. N. Nesmeyanova and К. A. Kocheshkova Mercury. Series: Methods of elemental organic chemistry. Moscow: Publishing House Acad. Sciences of the USSR, 1965.
* Nesmeyanov A.N., Belikov V.M.Problem of food synthesis. Series: Report at the plenary session / XI Mendeleev Congress on General and Applied Chemistry. Moscow: Nauka, 1965.
* Nesmeyanov A.N.Research in Organic Chemistry. Selected works 1959-1969. Moscow: Nauka, 1971.
* Nesmeyanov A.N. and Nesmeyanov N.A. The Beginnings of Organic Chemistry. In two books. Moscow: Chemistry, 1969.
* Nesmeyanov A.N. and Nesmeyanov N.A. The Beginnings of Organic Chemistry. In two books. Moscow: Chemistry, 1970. | 0 | Theoretical and Fundamental Chemistry |
Cryolite (NaAlF) is the least abundant of the three major fluorine-containing minerals, but is a concentrated source of fluorine. It was formerly used directly in aluminium production. However, the main commercial mine, on the west coast of Greenland, closed in 1987. | 0 | Theoretical and Fundamental Chemistry |
Rapid advance in cancer genomics and high-throughput ChIP-chip, ChIP-Seq and Bisulfite sequencing methods are providing more insight into role of chromatin remodeling in transcriptional regulation and role in cancer. | 1 | Applied and Interdisciplinary Chemistry |
Phenyl isothiocyanate is reacted with an uncharged N-terminal amino group, under mildly alkaline conditions, to form a cyclical phenylthiocarbamoyl derivative. Then, under acidic conditions, this derivative of the terminal amino acid is cleaved as a thiazolinone derivative. The thiazolinone amino acid is then selectively extracted into an organic solvent and treated with acid to form the more stable phenylthiohydantoin (PTH)- amino acid derivative that can be identified by using chromatography or electrophoresis. This procedure can then be repeated again to identify the next amino acid. A major drawback to this technique is that the peptides being sequenced in this manner cannot have more than 50 to 60 residues (and in practice, under 30). The peptide length is limited due to the cyclical derivatization not always going to completion. The derivatization problem can be resolved by cleaving large peptides into smaller peptides before proceeding with the reaction. It is able to accurately sequence up to 30 amino acids with modern machines capable of over 99% efficiency per amino acid. An advantage of the Edman degradation is that it only uses 10 - 100 pico-moles of peptide for the sequencing process. The Edman degradation reaction was automated in 1967 by Edman and Beggs to speed up the process and 100 automated devices were in use worldwide by 1973. | 0 | Theoretical and Fundamental Chemistry |
The hydroxymethyl group is the name for a substituent with the structural formula . It consists of a methylene bridge ( unit) bonded to a hydroxyl group (). This makes the hydroxymethyl group an alcohol. It has the identical chemical formula with the methoxy group () that differs only in the attachment site and orientation to the rest of the molecule. However, their chemical properties are different.
Hydroxymethyl is the side chain of encoded amino acid serine. | 0 | Theoretical and Fundamental Chemistry |
Schwab received honours throughout his lifetime in recognition of his scientific work. In 1952 he became one of the only 45 ordinary members of the Bavarian Academy of Sciences, and in 1956 he was also inducted as a member of the Heidelberg Academy of Sciences and the German National Academy of Sciences Leopoldina.
In 1960 he was awarded the Liebig Medal of the German Chemical Society; he had also been awarded the Order of the Crown of Belgium (Officer class) as well as the Golden Cross of the Greek Order of George I.
Additionally, he was conferred honorary doctorates from the Sorbonne, the Free University of Berlin and the University of Liège, as well as an honorary professorship at the Central University of Venezuela. | 0 | Theoretical and Fundamental Chemistry |
Paper chromatography is an analytical method used to separate coloured chemicals or substances. It is now primarily used as a teaching tool, having been replaced in the laboratory by other chromatography methods such as thin-layer chromatography (TLC).
The setup has three components. The mobile phase is a solution that travels up the stationary phase by capillary action. The mobile phase is generally a mixture of non-polar organic solvent, while the stationary phase is polar inorganic solvent water. Here paper is used to support the stationary phase, water. Polar water molecules are held inside the void space of the cellulose network of the host paper. The difference between TLC and paper chromatography is that the stationary phase in TLC is a layer of adsorbent (usually silica gel, or aluminium oxide), and the stationary phase in paper chromatography is less absorbent paper.
A paper chromatography variant, two-dimensional chromatography, involves using two solvents and rotating the paper 90° in between. This is useful for separating complex mixtures of compounds having similar polarity, for example, amino acids. | 0 | Theoretical and Fundamental Chemistry |
H and C are not the only nuclei susceptible to NMR experiments. A number of different nuclei can also be detected, although the use of such techniques is generally rare due to small relative sensitivities in NMR experiments (compared to H) of the nuclei in question, the other factor for rare use being their slender representation in nature and organic compounds.
H, C, N, F and P are the five nuclei that have the greatest importance in NMR experiments:
* H because of high sensitivity and vast occurrence in organic compounds
* C because of being the key component of all organic compounds despite occurring at a low abundance (1.1%) compared to the major isotope of carbon C, which has a spin of 0 and therefore is NMR-inactive.
* N because of being a key component of important biomolecules such as proteins and DNA
* F because of high relative sensitivity
* P because of frequent occurrence in organic compounds and moderate relative sensitivity | 0 | Theoretical and Fundamental Chemistry |
Single doses of up to at least 32-fold (800 mg), as well as continuous therapy with 24-fold (600 mg) the usual daily dose are well tolerated. No life-threatening overdosing is known in humans, but only in animal studies with 2000- to 4000-fold doses (adjusted to body surface area). | 0 | Theoretical and Fundamental Chemistry |
Ramesh Jasti is a professor of organic chemistry at the University of Oregon. He was the first person to synthesize the elusive cycloparaphenylene in 2008 during post doctoral work in the laboratory of Professor Carolyn Bertozzi. He started his laboratory at Boston University where he was the recipient of the NSF CAREER award. His early lab repeatedly broke the record for the synthesis of the smallest cycloparaphenylene known. In 2014, he moved his laboratory to the University of Oregon where he expanded his focus to apply the molecules he discovered in the areas of organic materials, mechanically interlocked molecules, and biology. He is the Associate Director of the Materials Science Institute at the University of Oregon. | 0 | Theoretical and Fundamental Chemistry |
The first two STAT proteins were identified in the interferon system. There are seven mammalian STAT family members that have been identified: STAT1, STAT2, STAT3, STAT4, STAT5 (STAT5A and STAT5B), and STAT6.
STAT1 homodimers are involved in type II interferon signalling, and bind to the GAS (Interferon-Gamma Activated Sequence) promoter to induce expression of interferon stimulated genes (ISG). In type I interferon signaling, STAT1-STAT2 heterodimer combines with IRF9 (Interferon Response Factor) to form ISGF3 (Interferon Stimulated Gene Factor), which binds to the ISRE (Interferon-Stimulated Response Element) promoter to induce ISG expression. | 1 | Applied and Interdisciplinary Chemistry |
When the cell is operated at open circuit, I = 0 and the voltage across the output terminals is defined as the open-circuit voltage. Assuming the shunt resistance is high enough to neglect the final term of the characteristic equation, the open-circuit voltage V is:
Similarly, when the cell is operated at short circuit, V = 0 and the current I through the terminals is defined as the short-circuit current. It can be shown that for a high-quality solar cell (low R and I, and high R) the short-circuit current I is:
It is not possible to extract any power from the device when operating at either open circuit or short circuit conditions. | 0 | Theoretical and Fundamental Chemistry |
Octasulfur is not typically produced as per se. It is the main (99%) component of elemental sulfur, which is recovered from volcanic sources and is a major product of the Claus process, associated with petroleum refineries. | 1 | Applied and Interdisciplinary Chemistry |
The efficiency η of a thermogravitational cycle depends on the thermodynamic processes the working fluid goes through during each step of the cycle. Below some examples:
* If the heat exchanges at the bottom and top of the column with a hot source and cold source respectively, occur at constant pressure and temperature, the efficiency would be equal to the efficiency of a Carnot cycle:
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* If the working fluid stays at the liquid stage during the compression stage 1→2, the efficiency would be equal to the Rankine cycle efficiency. By noting h, h, h and h the specific enthalpies of the working fluid at stages 1,2,3 and 4 respectively:
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* If the working fluid remains a gas during all the steps of a thermogravitational cycle, the efficiency would be equal to the Brayton cycle efficiency. By noting γ the heat capacity ratio:
</div> | 0 | Theoretical and Fundamental Chemistry |
Cyclodextrins (CDs) are cyclic oligosaccharides of six, seven, or eight glucose units designated as α, β, and γ cyclodextrins respectively. Depicted in the diagram below. Daniel Armstrong is considered the pioneer of micelle and cyclodextrin-based separations. Cyclodextrins are covalently attached to silica by Armstrong process and provide stable CSPs. The primary hydroxyl groups are used to anchor the CD molecules to the modified silica surface. CDs are chiral because of innate chirality of the building blocks, glucose units. In cyclodextrin the glucose units are α-(1,4)- connected. The shape of CD looks like a shortened cone (see the sketch). The inner surface of the cone forms moderately hydrophobic pocket. The width of the CD-cavity is identified with the quantity of glucose units present. In cyclodextrins, secondary hydroxyl groups (OH-2 and - 3) line the upper rim of the cavity, and an essential 6-hydroxyl group is positioned at the lower rim. The hydroxyl group offer chiral binding points, which appear to be fundamental for enantioselectivity. Apolar glyosidic oxygen makes the pit hydrophobic and guarantees inclusion complexing of the hydrophobic moiety of analytes. Interactions between the polar area of an analyte and secondary hydroxyl groups at the mouth of the pit, joined with the hydrophobic connections inside the pit, give a unique two-point fit and lead to enantioselectivity.
Selectivity of a cyclodextrin phase is dependent on two key factors namely the size and structure of the analyte since it is based on a simple fit-unfit geometric criteria. An aromatic ring or cycloalkyl ring should be attached near the stereogenic center of the analyte. Substituents at or near the analyte chiral center must be able to interact with the hydroxyl groups at the entrance of the CD cavity through H-bonding. α-Cyclodextrin holds small aromatic molecules, whereas β-cyclodextrin incorporates both naphthyl groups and substituted phenyl groups. The aqueous compatibility of CD and its unique molecular structure make the CD- bonded phase highly suitable for use in chiral HPLC analysis of drugs. One further benefit of CD is that they are generally less expensive than the other CSPs. Some of the major shortcomings of CD CSPs is that it is limited to compounds that can enter into CD cavity, minor structural changes in analyte leads to unpredictable effect on resolution, often poor efficiency and cannot invert elution order.
Enantiomers of propranolol, metoprolol, chlorpheniramine, verapamil, hexobarbitaI, methadone and much more drugs have been separated using immobilized β-cyclodextrin.
Initially natural CDs have been used as the chiral selector. Later, modified cyclodextrin structures have been prepared by derivatizing the secondary hydroxyl groups present on the CD molecule. Incorporation of these additional functional groups may improve the chiral recognition capability by possibly modifying the chiral pocket and creating extra auxiliary interaction site. This approach enabled to expand the range of target chiral analytes that could be separated. A number of chiral pharmaceuticals has been resolved using derivatized CDs including ibuprofen, suprofen, flurbiprofen from NSAID category and b-blockers like metoprolol and atenolol. A brief list of cyclodextrin-based chiral stationary stationary phases available in the market is furnished in the table below. | 0 | Theoretical and Fundamental Chemistry |
Concerted metalation-deprotonation (CMD) is a mechanistic pathway through which transition-metal catalyzed C–H activation reactions can take place. In a CMD pathway, the C–H bond of the substrate is cleaved and the new C–Metal bond forms through a single transition state. This process does not go through a metal species that is bound to the cleaved hydrogen atom. Instead, a carboxylate or carbonate base deprotonates the substrate. The first proposal of a concerted metalation deprotonation pathway was by S. Winstein and T. G. Traylor in 1955 for the acetolysis of diphenylmercury. It was found to be the lowest energy transition state in a number of computational studies, was experimentally confirmed through NMR experiments, and has been hypothesized to occur in mechanistic studies.
While there are a number of different possible mechanisms for C–H activation, a CMD pathway is common for high valent, late transition metals like Pd, Rh, Ir, and Ru. The C–H bonds that have been found to undergo C–H activation through CMD include those that are aryl, alkyl, and alkenyl. Investigations into CMD paved the way for the development of many new C–H functionalization reactions, especially in the areas of direct arylation and alkylation by palladium and ruthenium. | 0 | Theoretical and Fundamental Chemistry |
Surfactants which are less effective at foam production, may have additional co-surfactants added to increase foaming. In which case, the co-surfactant is referred to as the foaming agent. These are surfactants used in lower concentration in a detergent system than the primary surfactant, often the cocamide family of surfactants. Cocamide foaming agents include the nonionic cocamide DEA and cocamidopropylamine oxide, and the zwitterionic cocamidopropyl betaine and cocamidopropyl hydroxysultaine. | 0 | Theoretical and Fundamental Chemistry |
Sometimes grouped into the chemical mechanism of adhesion, hydrogen bonding can increase adhesive strength by the dispersive mechanism. Hydrogen bonding occurs between molecules with a hydrogen atom attached to a small, electronegative atom such as fluorine, oxygen or nitrogen. This bond is naturally polar, with the hydrogen atom gaining a slight positive charge and the other atom becoming slightly negative. Two molecules, or even two functional groups on one large molecule, may then be attracted to each other via Keesom forces. | 0 | Theoretical and Fundamental Chemistry |
Alkyl cycloalkanes are chemical compounds with an alkyl group with a single ring of carbons to which hydrogens are attached according to the formula
:CH.
They are named analogously to their normal alkane counterpart of the same carbon count: methylcyclopropane, methylcyclobutane, methylcyclopentane, methylcyclohexane, etc.
Methylcycloalkanes are classed into compounds with small, normal and bigger cycloalkanes, where cyclopropane and cyclobutane are the small ones, cyclopentane, cyclohexane, cycloheptane are the normal ones and the rest are the bigger ones.
__TOC__ | 0 | Theoretical and Fundamental Chemistry |
Grinding is abrasion of the surface of interest by abrasive particles, usually diamond, that are bonded to paper or a metal disc. Grinding erases saw marks, coarsely smooths the surface, and removes stock to a desired depth. A typical grinding sequence for ceramics is one minute on a 240-grit metal-bonded diamond wheel rotating at 240 rpm and lubricated by flowing water, followed by a similar treatment on a 400-grit wheel. The specimen is washed in an ultrasonic bath after each step. | 1 | Applied and Interdisciplinary Chemistry |
In 1998 the consumption of phosphonates was 56,000 tons worldwide – 40,000 tons in the US, 15,000 tons in Europe and less than 800 tons in Japan. The demand of phosphonates grows steadily at 3% annually. | 0 | Theoretical and Fundamental Chemistry |
Retinal gene therapy holds a promise in treating different forms of non-inherited and inherited blindness.
In 2008, three independent research groups reported that patients with the rare genetic retinal disease Leber's congenital amaurosis had been successfully treated using gene therapy with adeno-associated virus (AAV). In all three studies, an AAV vector was used to deliver a functional copy of the RPE65 gene, which restored vision in children suffering from LCA. These results were widely seen as a success in the gene therapy field, and have generated excitement and momentum for AAV-mediated applications in retinal disease.
In retinal gene therapy, the most widely used vectors for ocular gene delivery are based on adeno-associated virus. The great advantage in using adeno-associated virus for the gene therapy is that it poses minimal immune responses and mediates long-term transgene expression in a variety of retinal cell types. For example, tight junctions that form the blood-retina barrier, separate subretinal space from the blood supply, providing protection from microbes and decreasing most immune-mediated damages.
There is still a lot of knowledge missing in regards of retina dystrophies. Detail characterization is needed in order to improve knowledge. To address this issue, creation of Registries is an attempt to grouped and characterize rare diseases. Registries help to localize, and measure all the phenotype of these conditions and therefore to provide easy follow-ups and provide a source of information to scientist community. Registry designs varies from region to region, however localization and characterization of the phenotype are the standard gold.
Examples of Registries are:
RetMxMap<ARVO 2009>. A Mexican and Latin-American registry created since 2009. This registry was created by Dr Adda Lízbeth Villanueva Avilés. She is a clinical-scientist gene mapping inherited retina dystrophies in Mexico and other Latin countries. | 1 | Applied and Interdisciplinary Chemistry |
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