text stringlengths 105 4.57k | label int64 0 1 | label_text stringclasses 2
values |
|---|---|---|
Vertical stratification including an aerobic surface layer, an anaerobic bottom layer, and a facultative intermediate layer is essential to proper functioning of a facultative lagoon ecosystem. Stratification is maintained by a thermal gradient of cool, dense water at the bottom of the lagoon overlain by warmer, less dense water on the surface. This thermal gradient becomes unstable when water reaches its maximum density at 4 degrees Celsius (39 degrees Fahrenheit). Facultative lagoons are impractical in cold climates, because the lagoons become non-functional when cooler air temperatures depress water temperatures below this critical value. | 1 | Applied and Interdisciplinary Chemistry |
Harry Julian Allen and Alfred J. Eggers of NACA used an insight about ram pressure to propose the blunt-body concept: a large, blunt body entering the atmosphere creates a boundary layer of compressed air which serves as a buffer between the body surface and the compression-heated air. In other words, kinetic energy is converted into heated air via ram pressure, and that heated air is quickly moved away from object surface with minimal physical interaction, and hence minimal heating of the body. This was counter-intuitive at the time, when sharp, streamlined profiles were assumed to be better. This blunt-body concept was used in Apollo-era capsules. | 1 | Applied and Interdisciplinary Chemistry |
Green sulfur bacteria contain a photosystem that is analogous to PSI in chloroplasts:
P840 → P840 → ferredoxin → NADH
cyt c ← bc ← menaquinol
There are two pathways of electron transfer. In cyclic electron transfer, electrons are removed from an excited chlorophyll molecule, passed through an electron transport chain to a proton pump, and then returned to the chlorophyll. The mobile electron carriers are, as usual, a lipid-soluble quinone and a water-soluble cytochrome. The resulting proton gradient is used to make ATP.
In noncyclic electron transfer, electrons are removed from an excited chlorophyll molecule and used to reduce NAD to NADH. The electrons removed from P840 must be replaced. This is accomplished by removing electrons from , which is oxidized to sulfur (hence the name "green sulfur bacteria").
Purple bacteria and green sulfur bacteria occupy relatively minor ecological niches in the present day biosphere. They are of interest because of their importance in precambrian ecologies, and because their methods of photosynthesis were the likely evolutionary precursors of those in modern plants. | 0 | Theoretical and Fundamental Chemistry |
In bacteria, the level of cAMP varies depending on the medium used for growth. In particular, cAMP is low when glucose is the carbon source. This occurs through inhibition of the cAMP-producing enzyme, adenylate cyclase, as a side-effect of glucose transport into the cell. The transcription factor cAMP receptor protein (CRP) also called CAP (catabolite gene activator protein) forms a complex with cAMP and thereby is activated to bind to DNA. CRP-cAMP increases expression of a large number of genes, including some encoding enzymes that can supply energy independent of glucose.
cAMP, for example, is involved in the positive regulation of the lac operon. In an environment with a low glucose concentration, cAMP accumulates and binds to the allosteric site on CRP (cAMP receptor protein), a transcription activator protein. The protein assumes its active shape and binds to a specific site upstream of the lac promoter, making it easier for RNA polymerase to bind to the adjacent promoter to start transcription of the lac operon, increasing the rate of lac operon transcription. With a high glucose concentration, the cAMP concentration decreases, and the CRP disengages from the lac operon. | 1 | Applied and Interdisciplinary Chemistry |
The Newton–Raphson method or a different fixed-point iteration can be used to solve FSI problems. Methods based on Newton–Raphson iteration are used in both the monolithic
and the partitioned approach. These methods solve the nonlinear flow equations and the structural equations in the entire fluid and solid domain with the Newton–Raphson method. The system of linear equations within the Newton–Raphson iteration can be solved without knowledge of the Jacobian with a matrix-free iterative method, using a finite difference approximation of the Jacobian-vector product.
Whereas Newton–Raphson methods solve the flow and structural problem for the state in the entire fluid and solid domain, it is also possible to reformulate an FSI problem as a system with only the degrees of freedom in the interface’s position as unknowns. This domain decomposition condenses the error of the FSI problem into a subspace related to the interface. The FSI problem can hence be written as either a root finding problem or a fixed point problem, with the interface’s position as unknowns.
Interface Newton–Raphson methods solve this root-finding problem with Newton–Raphson iterations, e.g. with an approximation of the Jacobian from a linear reduced-physics model. The interface quasi-Newton method with approximation for the inverse of the Jacobian from a least-squares model couples a black-box flow solver and structural solver by means of the information that has been gathered during the coupling iterations. This technique is based on the interface block quasi-Newton technique with an approximation for the Jacobians from least-squares models which reformulates the FSI problem as a system of equations with both the interface’s position and the stress distribution on the interface as unknowns. This system is solved with block quasi-Newton iterations of the Gauss–Seidel type and the Jacobians of the flow solver and structural solver are approximated by means of least-squares models.
The fixed-point problem can be solved with fixed-point iterations, also called (block) Gauss–Seidel iterations, which means that the flow problem and structural problem are solved successively until the change is smaller than the convergence criterion. However, the iterations converge slowly if at all, especially when the interaction between the fluid and the structure is strong due to a high fluid/structure density ratio or the incompressibility of the fluid. The convergence of the fixed point iterations can be stabilized and accelerated by Aitken relaxation and steepest descent relaxation, which adapt the relaxation factor in each iteration based on the previous iterations.
If the interaction between the fluid and the structure is weak, only one fixed-point iteration is required within each time step. These so-called staggered or loosely coupled methods do not enforce the equilibrium on the fluid–structure interface within a time step but they are suitable for the simulation of aeroelasticity with a heavy and rather stiff structure.
Several studies have analyzed the stability of partitioned algorithms for the simulation of fluid-structure interaction | 1 | Applied and Interdisciplinary Chemistry |
Medicinal Research Reviews is a bimonthly peer-reviewed scientific journal that publishes reviews on topics related to medicinal research. It is published by Wiley and was established in 1980. The editor-in-chief is Amanda E. Hargrove (Duke University).
The journal publishes critical reviews of topics include pathophysiology, genomics and proteomics, and clinical characteristics of important drugs. | 1 | Applied and Interdisciplinary Chemistry |
Related to the Fermi energy, a few useful quantities also occur often in modern literature.
The Fermi temperature is defined as , where is the Boltzmann constant. The Fermi temperature can be thought of as the temperature at which thermal effects are comparable to quantum effects associated with Fermi statistics. The Fermi temperature for a metal is a couple of orders of magnitude above room temperature. Other quantities defined in this context are Fermi momentum , and Fermi velocity , which are the momentum and group velocity, respectively, of a fermion at the Fermi surface. The Fermi momentum can also be described as , where is the radius of the Fermi sphere and is called the Fermi wave vector.
Note that these quantities are not well-defined in cases where the Fermi surface is non-spherical. | 0 | Theoretical and Fundamental Chemistry |
It was first consciously applied to modern physics by Frederick Soddy when he, along with Ernest Rutherford in 1901, discovered that radioactive thorium was converting itself into radium. At the moment of realization, Soddy later recalled, he shouted out: "Rutherford, this is transmutation!" Rutherford snapped back, "For Christs sake, Soddy, dont call it transmutation. They'll have our heads off as alchemists."
Rutherford and Soddy were observing natural transmutation as a part of radioactive decay of the alpha decay type. The first artificial transmutation was accomplished in 1925 by Patrick Blackett, a research fellow working under Rutherford, with the transmutation of nitrogen into oxygen, using alpha particles directed at nitrogen N + α → O + p. Rutherford had shown in 1919 that a proton (he called it a hydrogen atom) was emitted from alpha bombardment experiments but he had no information about the residual nucleus. Blacketts 1921–1924 experiments provided the first experimental evidence of an artificial nuclear transmutation reaction. Blackett correctly identified the underlying integration process and the identity of the residual nucleus. In 1932, a fully artificial nuclear reaction and nuclear transmutation was achieved by Rutherfords colleagues John Cockcroft and Ernest Walton, who used artificially accelerated protons against lithium-7 to split the nucleus into two alpha particles. The feat was popularly known as "splitting the atom," although it was not the modern nuclear fission reaction discovered in 1938 by Otto Hahn, Lise Meitner and their assistant Fritz Strassmann in heavy elements. In 1941, Rubby Sherr, Kenneth Bainbridge and Herbert Lawrence Anderson reported the nuclear transmutation of mercury into gold.
Later in the twentieth century the transmutation of elements within stars was elaborated, accounting for the relative abundance of heavier elements in the universe. Save for the first five elements, which were produced in the Big Bang and other cosmic ray processes, stellar nucleosynthesis accounted for the abundance of all elements heavier than boron. In their 1957 paper Synthesis of the Elements in Stars, William Alfred Fowler, Margaret Burbidge, Geoffrey Burbidge, and Fred Hoyle explained how the abundances of essentially all but the lightest chemical elements could be explained by the process of nucleosynthesis in stars. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are Lewis bases.
Nucleophilic describes the affinity of a nucleophile to bond with positively charged atomic nuclei. Nucleophilicity, sometimes referred to as nucleophile strength, refers to a substance's nucleophilic character and is often used to compare the affinity of atoms. Neutral nucleophilic reactions with solvents such as alcohols and water are named solvolysis. Nucleophiles may take part in nucleophilic substitution, whereby a nucleophile becomes attracted to a full or partial positive charge, and nucleophilic addition. Nucleophilicity is closely related to basicity. The difference between the two is, that basicity is a thermodynamic property (i.e. relates to an equilibrium state), but nucleophilicity is a kinetic property, which relates to rates of certain chemical reactions. | 0 | Theoretical and Fundamental Chemistry |
All shock waves, that each by itself would have had an angle between 33° and 72°, are compressed into a narrow band of wake with angles between 15° and 19°, with the strongest constructive interference at the outer edge (angle arcsin(1/3) = 19.47°), placing the two arms of the V in the celebrated Kelvin wake pattern.
A concise geometric construction demonstrates that, strikingly, this group shock angle w.r.t. the path of the boat, 19.47°, for any and all of the above , is actually independent of
, , and ; it merely relies on the fact that the group velocity is half of the phase velocity . On any planet, slow-swimming objects have "effective Mach number" 3.
For slow swimmers, low Froude number, the Lighthill−Whitham geometric argument that the opening of the Kelvin chevron (wedge, V pattern) is universal goes as follows. Consider a boat moving from right to left with constant speed v, emitting waves of varying wavelength, and thus wavenumber and phase velocity , of interest when < v for a shock wave (cf., e.g., Sonic boom or Cherenkov radiation). Equivalently, and more intuitively, fix the position of the boat and have the water flow in the opposite direction, like a piling in a river.
Focus first on a given , emitting (phase) wavefronts whose stationary position w.r.t. the boat assemble to the standard shock wedge tangent to all of them, cf. Fig.12.3.
As indicated above, the openings of these chevrons vary with wavenumber, the angle between the phase shock wavefront and the path of the boat (the water) being = arcsin(/v) ≡ . Evidently, increases with . However, these phase chevrons are not visible: it is their corresponding group wave manifestations which are observed.
Consider one of the phase circles of Fig.12.3 for a particular , corresponding to the time in the past, Fig.12.2. Its radius is QS, and the phase chevron side is the tangent PS to it. Evidently, PQ= and SQ = = , as the right angle PSQ places S on the semicircle of diameter PQ.
Since the group velocity is half the phase velocity for any and all , however, the visible (group) disturbance point corresponding to S will be T, the midpoint of SQ. Similarly, it lies on a semicircle now centered on R, where, manifestly, RQ=PQ/4, an effective group wavefront emitted from R, with radius v/4 now.
Significantly, the resulting wavefront angle with the boats path, the angle of the tangent from P to this smaller circle, obviously has a sine of TR/PR=1/3, for any and all , , , , etc.: Strikingly, virtually all parameters of the problem have dropped out, except for the deep-water group-to-phase-velocity relation! Note the (highly notional) effective group disturbance emitter moves slower, at 3v'/4.
Thus, summing over all relevant and s to flesh out an effective Fig.12.3 shock pattern, the universal Kelvin wake pattern arises: the full visible chevron angle is twice that, 2arcsin(1/3) ≈ 39°.
The wavefronts of the wavelets in the wake are at 53°, which is roughly the average of 33° and 72°.
The wave components with would-be shock wave angles between 73° and 90° dominate the interior of the V. They end up half-way between the point of generation and the current location of the wake source. This explains the curvature of the arcs.
Those very short waves with would-be shock wave angles below 33° lack a mechanism to reinforce their amplitudes through constructive interference and are usually seen as small ripples on top of the interior transverse waves.
The nature of two types of crests, longitudinal and transverse, is graphically illustrated by the pattern of wavefronts of a moving point source in proper frame. The radii of wavefronts are proportional, due to dispersion, to the square of time (measured from the moment of emission), and the envelope of the wavefronts represents the Kelvin wake pattern. | 1 | Applied and Interdisciplinary Chemistry |
Isothermal transformation diagrams (also known as time-temperature-transformation (TTT) diagrams) are plots of temperature versus time (usually on a logarithmic scale). They are generated from percentage transformation-vs time measurements, and are useful for understanding the transformations of an alloy steel at elevated temperatures.
An isothermal transformation diagram is only valid for one specific composition of material, and only if the temperature is held constant during the transformation, and strictly with rapid cooling to that temperature. Though usually used to represent transformation kinetics for steels, they also can be used to describe the kinetics of crystallization in ceramic or other materials. Time-temperature-precipitation diagrams and time-temperature-embrittlement diagrams have also been used to represent kinetic changes in steels.
Isothermal transformation (IT) diagram or the C-curve is associated with mechanical properties, microconstituents/microstructures, and heat treatments in carbon steels. Diffusional transformations like austenite transforming to a cementite and ferrite mixture can be explained using the sigmoidal curve; for example the beginning of pearlitic transformation is represented by the pearlite start (P) curve. This transformation is complete at P curve. Nucleation requires an incubation time. The rate of nucleation increases and the rate of microconstituent growth decreases as the temperature decreases from the liquidus temperature reaching a maximum at the bay or nose of the curve. Thereafter, the decrease in diffusion rate due to low temperature offsets the effect of increased driving force due to greater difference in free energy. As a result of the transformation, the microconstituents, pearlite and bainite, form; pearlite forms at higher temperatures and bainite at lower.
Austenite is slightly undercooled when quenched below Eutectoid temperature. When given more time, stable microconstituents can form: ferrite and cementite. Coarse pearlite is produced when atoms diffuse rapidly after phases that form pearlite nucleate. This transformation is complete at the pearlite finish time (P).
However, greater undercooling by rapid quenching results in formation of martensite or bainite instead of pearlite. This is possible provided the cooling rate is such that the cooling curve intersects the martensite start temperature or the bainite start curve before intersecting the Pcurve. The martensite transformation being a diffusionless shear transformation is represented by a straight line to signify the martensite start temperature. | 1 | Applied and Interdisciplinary Chemistry |
Zara joined the Business Evaluation Department in the Corporate Planning Unit of Petronas in December 1995 and was part of the team responsible for the successful establishment of the Kertih and Kuantan integrated petrochemical complexes, whose foreign partners included BP, BASF, Dow Chemicals and Mitsubishi.
She then became a project analyst in the Petronas Petrochemical Business Unit and was part of the core team developing the Petronas brand essence, which now forms part of the Petronas global branding strategy.
Between February 1999 and October 2000, she was a product manager at Petlin (Malaysia) Sdn Bhd, a Petronas joint venture with DSM of the Netherlands and Sasol of South Africa. She was also part of the Petronas project team to operationalise the largest single-train low-density polyethylene (LDPE) plant in the world at Kertih.
Zara left Petronas in November 2001 to become an account manager at Formis Network Services Sdn Bhd and then assumed the post of vice-president of partnerships and alliances at Formis (Malaysia) Berhad, a technology-based company listed on Bursa Malaysia, between 2003 and 2005.
Between 2005 and 2007, Zara, who is a certified life-saver and adventure sports enthusiast, became the managing director of Forthwave Consulting Sdn Bhd, a hydrocarbon technical engineering and software development company in Kuala Lumpur. | 1 | Applied and Interdisciplinary Chemistry |
Alternative splicing, or alternative RNA splicing, or differential splicing, is an alternative splicing process during gene expression that allows a single gene to code for multiple proteins. In this process, particular exons of a gene may be included within or excluded from the final, processed messenger RNA (mRNA) produced from that gene. This means the exons are joined in different combinations, leading to different (alternative) mRNA strands. Consequently, the proteins translated from alternatively spliced mRNAs usually contain differences in their amino acid sequence and, often, in their biological functions (see Figure).
Biologically relevant alternative splicing occurs as a normal phenomenon in eukaryotes, where it increases the number of proteins that can be encoded by the genome. In humans, it is widely believed that ~95% of multi-exonic genes are alternatively spliced to produce functional alternative products from the same gene but many scientists believe that most of the observed splice variants are due to splicing errors and the actual number of biologically relevant alternatively spliced genes is much lower.
Alternative splicing enables the regulated generation of multiple mRNA and protein products from a single gene.
There are numerous modes of alternative splicing observed, of which the most common is exon skipping. In this mode, a particular exon may be included in mRNAs under some conditions or in particular tissues, and omitted from the mRNA in others.
The production of alternatively spliced mRNAs is regulated by a system of trans-acting proteins that bind to cis-acting sites on the primary transcript itself. Such proteins include splicing activators that promote the usage of a particular splice site, and splicing repressors that reduce the usage of a particular site. Mechanisms of alternative splicing are highly variable, and new examples are constantly being found, particularly through the use of high-throughput techniques. Researchers hope to fully elucidate the regulatory systems involved in splicing, so that alternative splicing products from a given gene under particular conditions ("splicing variants") could be predicted by a "splicing code".
Abnormal variations in splicing are also implicated in disease; a large proportion of human genetic disorders result from splicing variants. Abnormal splicing variants are also thought to contribute to the development of cancer, and splicing factor genes are frequently mutated in different types of cancer. | 1 | Applied and Interdisciplinary Chemistry |
* Iodine heptafluoride (IF) with 7 bonding groups
* Rhenium heptafluoride (ReF)
* Peroxo chromium(IV) complexes, e.g. [Cr(O)(NH)] where the peroxo groups occupy four of the planar positions.
* and | 0 | Theoretical and Fundamental Chemistry |
The wire-cut type of machine arose in the 1960s for making tools (dies) from hardened steel. The tool electrode in wire EDM is simply a wire. To avoid the erosion of the wire causing it to break, the wire is wound between two spools so that the active part of the wire is constantly changing. The earliest numerical controlled (NC) machines were conversions of punched-tape vertical milling machines. The first commercially available NC machine built as a wire-cut EDM machine was manufactured in the USSR in 1967. Machines that could optically follow lines on a master drawing were developed by David H. Dulebohn's group in the 1960s at Andrew Engineering Company for milling and grinding machines. Master drawings were later produced by computer numerical controlled (CNC) plotters for greater accuracy. A wire-cut EDM machine using the CNC drawing plotter and optical line follower techniques was produced in 1974. Dulebohn later used the same plotter CNC program to directly control the EDM machine, and the first CNC EDM machine was produced in 1976.
Commercial wire EDM capability and use has advanced substantially during recent decades. Feed rates have increased and surface finish can be finely controlled. | 1 | Applied and Interdisciplinary Chemistry |
The following is an overview of each cycle in the optical sequencing process.
Step 1: DNA barcoding<br />
Cells are lysed to release genomic DNA. These DNA molecules are untangled, placed onto optical mapping surface containing microfluidic channels and the DNA is allowed to flow through the channels. These molecules are then barcoded by restriction enzymes to allow for genomic localization through the technique of optical mapping. See the above section on "Technology" for those steps.
Step 2: Template nicking<br />
DNase I is added to randomly nick the mounted DNA molecules. A wash is then performed to remove the DNase I. The mean number of nicks that occur per template is dependent on the concentration of DNase I as well as the incubation time.
Step 3: Gap formation<br />
T7 exonuclease is added which uses the nicks in the DNA molecules to expand the gaps in a 5–3 direction. Amount of T7 exonuclease must be carefully controlled to avoid overly high levels of double-stranded breaks.
Step 4: Fluorochrome incorporation<br />
DNA polymerase is used to incorporate fluorochrome-labelled nucleotides (FdNTPs) into the multiple gapped sites along each DNA molecule. During each cycle, the reaction mixture contains a single type of FdNTP and allows for multiple additions of that nucleotide type. Various washes are then performed to remove unincorporated fdNTPs in preparation for imaging and the next cycle of FdNTP addition.
Step 5: Imaging<br />
This step counts the number of incorporated fluorochrome-labeled nucleotides at the gap regions using fluorescence microscopy.
Step 6: Photobleaching<br />
The laser illumination that is used to excite the fluorochrome is also used here to destroy the fluorochrome signal. This essentially resets the fluorochrome counter, and prepares the counter for the next cycle. This step is a unique aspect of optical sequencing as it does not actually remove the fluorochrome label of the nucleotide after its incorporation. not removing the fluorochrome label makes sequencing more economical, but it results in the need to incorporate fluorochrome labels consecutively which can result in problems due to the bulkiness of the labels.
Step 7: Repeat steps 4–6<br />
Steps 4-6 are repeated with step 4 using a reaction mixture that contains a different fluorochrome-labeled nucleotide (FdNTP) each time. This is repeated until the desired region is sequenced. | 1 | Applied and Interdisciplinary Chemistry |
Liquid–liquid transitions were originally considered by Rapoport in 1967 in order to explain high pressure melting curve maxima of some liquid metals. Rapoport's theory requires the existence of a melting curve maximum in polyamorphic systems. | 0 | Theoretical and Fundamental Chemistry |
MGI evolved from a project funded by the National Center for Human Genome Research in 1989 to combine the databases of several Jackson Laboratory scientists and create a tool for visualizing data on the mouse genome. The result of that project, led by Joseph H. Nadeau, Larry E. Mobraaten, and Janan T. Eppig, was called the "Encyclopedia of the Mouse Genome" and distributed via floppy disk semi-annually to around 300 scientists around the world. In 1992, that group joined with the team responsible for developing the "Genomic Database for Mouse", led by Muriel T. Davisson and Thomas H. Roderick, to start the "Mouse Genome Informatics" project. That project resulted in the first online release of the "Mouse Genome Database" in 1994. | 1 | Applied and Interdisciplinary Chemistry |
Binary (involving one other metal) and ternary (involving two other metals) intermetallic stannides have been investigated. Niobium stannide, NbSn is perhaps the best known superconducting tin intermetallics. This is more commonly called "niobium-tin". | 0 | Theoretical and Fundamental Chemistry |
In the 1960s, South Korea faced a significant shortage of agricultural land, prompting plans for large reclamation projects, including the construction of closure dams. These projects were carried out between 1975 and 1995, incorporating the expertise and experience from the Netherlands. Over time, attitudes towards closure works in South Korea evolved, leading to considerable delays and modifications in the plans for the Hwaong and Saemangeum projects. | 1 | Applied and Interdisciplinary Chemistry |
*Biological transmutation
*Chemistry
*Historicism
*Nuclear transmutation
*Obsolete scientific theories
*Physics
*Scientific method
*Synthesis of noble metals | 1 | Applied and Interdisciplinary Chemistry |
Fas ligand or FasL is a type II transmembrane protein belonging to the tumor necrosis factor superfamily (TNFSF). It is homotrimeric, which means it consists of three identical polypeptides. It has a long cytoplasmic domain, a stalk region, a transmembrane domain (TM), a TNF homology domain (THD) responsible for the homotrimerization. Including a C-terminal region involved in binding to CD95, also known as the fas receptor.
FasL binds to fas, leading to the formation of fas:FasL assemble. This interaction initiates the formation of the death-inducing signaling complex, resulting in apoptosis.
FasL is expressed on various cell types, including T cells, natural killer cells, monocytes, neutrophils, and vascular endothelial cells. FasL exists in both membrane-anchored and soluble forms. | 1 | Applied and Interdisciplinary Chemistry |
Neck cracks are readily observed during inspection, but body and shoulder cracks are more difficult to detect. Neck thread cracks can be non-destructively tested using eddy-current crack-detection equipment. This is reported to be reliable for alloy 6351, but false positives have been reported for tests on alloy 6061. | 1 | Applied and Interdisciplinary Chemistry |
Mikael Bols (born July 28, 1961) is a synthetic organic chemist who is mainly known for his work on carbohydrates and artificial enzymes. | 0 | Theoretical and Fundamental Chemistry |
Xenon trioxide is an unstable compound of xenon in its +6 oxidation state. It is a very powerful oxidizing agent, and liberates oxygen from water slowly, accelerated by exposure to sunlight. It is dangerously explosive upon contact with organic materials. When it detonates, it releases xenon and oxygen gas. | 0 | Theoretical and Fundamental Chemistry |
Reanalysis of a large number of various most typical ambident organic system reveals that thermodynamic/kinetic control describes reactivity of organic compounds perfectly, whereas the HSAB principle fails and should be abandoned in the rationalization of ambident reactivity of organic compounds. | 0 | Theoretical and Fundamental Chemistry |
Grotthuss was born in 1785 in Leipzig, Electorate of Saxony, Holy Roman Empire, during an extended stay of his parents away from their home in northern Grand Duchy of Lithuania. He showed interest in natural sciences and went to study first in Leipzig and later in Paris at the École Polytechnique. Several renowned scientists taught at the École Polytechnique at that time, including Antoine François, comte de Fourcroy, Claude Louis Berthollet and Louis Nicolas Vauquelin.
Because of some tensions in the relations between Russia and France, Grotthuss had to leave for Italy where he stayed at Naples for one year. The discovery of the first electric cell in 1800 by Alessandro Volta provided the scientists a source of electricity which was used in various laboratory experiments around Europe. The electrolysis of water, acids and salt solutions was reported, but a good explanation was missing. Grotthuss actively contributed to this area both in terms of electrolysis experiments and their interpretation. During his stay in Italy, he published his work on electrolysis in 1806. His idea that the charge is not transported by the movement of particles but by breaking and reformation of bonds was the first basically correct concept for the charge transport in electrolytes; it is still valid for the charge transport in water, and the current proton hopping mechanism is a modified version of the original Grotthuss mechanism.
The following two years Grotthuss spent in Rome, some other Italian cities, and Paris, and then went back to Russia via Munich and Vienna. From 1808 on he lived at the estate of his mother in northern Lithuania. There he conducted research on electricity and light with the limited research equipment he could assemble. Grotthuss committed suicide in the spring of 1822 during a depression caused by health problems. | 0 | Theoretical and Fundamental Chemistry |
At Eli Lilly in the 1960s, Schmiegel and Bryan Molloy, with the help of David Wong, searched for a compound to combat depression. Because depression and similar psychiatric disorders are associated with reduced serotonin levels, they focused their approach on prohibiting serotonin reuptake. During a regular nerve signal transmission, a neurotransmitter such as serotonin travels from a presynaptic neuron to a postsynaptic neuron; the neurotransmitter returns to the presynaptic neuron after fulfilling its function, the reuptake process. Therefore, slowing and diminishing serotonin reuptake boosts serotonin levels in the brain.
The scientists based their search on the template of the antihistamine drug diphenhydramine hydrochloride, commonly known as Benadryl. After many failures, the research team synthesized a group of compounds called aryloxyphenylpropylamines. Upon testing, a member of the group, fluoxetine hydrochloride, proved to affect only the neurotransmitter serotonin. This compound became the first selective serotonin reuptake inhibitor (SSRI) and the active ingredient in the vastly popular and effective drug Prozac. | 0 | Theoretical and Fundamental Chemistry |
Protein adsorption can also occur as a direct result of heating a mixture. Protein adsorption in milk processing is often used as a model for this type of adsorption in other situations. Milk is composed mainly of water, with less than 20% of suspended solids or dissolved proteins. Proteins make up only 3.6% of milk in total, and only 26% of the components that are not water. These proteins are all responsible for fouling that occurs during pasteurization.
As milk is heated during pasteurization many of the proteins in the milk are denatured. Pasteurization temperatures can reach 161 °F (71.7 °C). This temperature is high enough to denature the proteins below, lowering the nutritional value of the milk and causing fouling. Milk is heated to these high temperatures for a short time (15–20 seconds) to reduce the amount of denaturization. However fouling from denatured proteins is still a significant problem.
Denaturation exposes hydrophobic amino acid residues in the protein, which had been previously protected by the protein. The exposed hydrophobic amino acids decrease the entropy of the water surrounding them, making it favorable for surface adsorption. Some of the β-lactoglobulin (β-lg) will adsorb directly onto the surface of a heat exchanger or container. Other denatured β-lg molecules adsorb to casein micelles, which are also present in the milk. As more and more β-lg proteins bind to the casein micelle it forms an aggregate, which will then diffuse to the heat exchanger and/or surface of the container. | 1 | Applied and Interdisciplinary Chemistry |
Survivin is known to be highly expressed in most tumour cell types and absent in normal cells, making it a good target for cancer therapy. The exploitation of survivin's over-active promoter in most cancer cell types allows for the delivery of therapeutics only in cancer cells and removed from normal cells.
Small interfering RNA (siRNA) are synthetic antisense oligonucleotides to the mRNA of the gene of interest that works to silence the expression of a particular gene by its complementary binding. siRNAs, such as LY2181308, bound to the respective mRNA results in disruption of translation of that particular gene and thus the absence of that protein in the cell. Thus, the use of siRNAs has great potential to be a human therapeutic, as it can target and silence the expression of potentially any protein you want. A problem arises when siRNA expression in a cell cannot be controlled, allowing its constitutive expression to cause toxic side-effects. With regard to practical treatment of cancer, it is required to either deliver the siRNAs specifically into cancer cells or control the siRNA expression. Previous methods of siRNA therapy employ the use of siRNA sequences cloned into vectors under the control of constitutively active promoters. This causes a problem, as this model is non-specific to cancer cells and damages normal cells too. Knowing that survivin is over-expressed specifically in cancer cells and absent in normal cells, one can imply that the survivin promoter is active only in cancer cells. Thus, the exploitation of this difference between cancer cells and normal cells will allow appropriate therapy directed only at the cells in a patient that are harmful. In an experiment to demonstrate this idea, Trang et al. have created a cancer-specific vector expressing siRNA for green fluorescent protein (GFP) under the human survivin promoter. MCF7 breast cancer cells were cotransfected with this vector and a GFP-expressing vector as well. Their major finding was that MCF7 cells transfected with the siRNA vector for GFP under the survivin promoter had a significant reduction in GFP expression then the cells transfected with the siRNA vector under a cancer non-specific promoter. Moreover, normal non-cancerous cells transfected in the same way mentioned above showed no significant reduction in GFP expression. This is implying that, in normal cells, survivin promoter is not active, and, thus, the siRNA will not be expressed under an inactive survivin promoter. | 1 | Applied and Interdisciplinary Chemistry |
The IIR is a bilingual organization that works in both English and French and operates thanks to:
* the activities of its international network comprising over 300 Commission members
* its benefactor, corporate and private members
* the annual contributions from its 59 member countries. | 0 | Theoretical and Fundamental Chemistry |
Jenny Zhenqi Zhang is a Chinese-Australian chemist and BBSRC David Phillips Research Fellow of the Department of Chemistry, University of Cambridge, where she is also a Fellow of Corpus Christi College (2019-present). She was awarded the 2020 RSC Felix Franks Biotechnology Medal for her research into re-wiring photosynthesis to provide sustainable fuel sources. | 0 | Theoretical and Fundamental Chemistry |
A simple cubic unit cell, with stacks of atoms arranged as if at the eight corners of a cube would form a single cubic hole or void in the center. If these voids are occupied by ions of opposite charge from the parent lattice, the cesium chloride structure is formed. | 0 | Theoretical and Fundamental Chemistry |
Biosynthesis of coelenterazine in Metridia starts from two molecules of tyrosine and one molecule of phenylalanine, and some researchers believe this comes in the form of a cyclized "Phe-Tyr-Tyr" (FYY) peptide.
Many members of the genus Metridia also produce luciferases that use this compound, some of which are secreted into extracellular space, an unusual property for luciferases. | 1 | Applied and Interdisciplinary Chemistry |
Basaltic magma is the most abundant in iron, magnesium, and calcium but the lowest in silica, potassium, and sodium. The composition of silica within basaltic magma ranges from 45-55 weight percent (wt.%), or mass fraction of a species. It forms in temperatures ranging from approximately 1830 °F to 2200 °F. Basaltic magma has the lowest viscosity and volatiles content, yet still may be up to 100,000 times more viscous than water. Because of its low viscosity, this is the least explosive form of magma. Basaltic magma may found in regions such as Hawaii, known for its shield volcanoes.
Basaltic magma forms minerals such as calcium-rich plagioclase feldspar and pyroxene. The water composition of basaltic magma varies dependent on the evolution of the magma chamber. Arc magmas, such as Izarú in Costa Rica, range from 3.2-3.5 wt.%. | 0 | Theoretical and Fundamental Chemistry |
The reaction of calcium carbide with water, producing acetylene and calcium hydroxide, was discovered by Friedrich Wöhler in 1862.
:CaC(s) + 2HO(l) → CH(g) + Ca(OH)(aq)
This reaction was the basis of the industrial manufacture of acetylene, and is the major industrial use of calcium carbide.
Today acetylene is mainly manufactured by the partial combustion of methane or appears as a side product in the ethylene stream from cracking of hydrocarbons. Approximately 400,000 tonnes are produced this way annually (see acetylene preparation).
In China, acetylene derived from calcium carbide remains a raw material for the chemical industry, in particular for the production of polyvinyl chloride. Locally produced acetylene is more economical than using imported oil. Production of calcium carbide in China has been increasing. In 2005 output was 8.94 million tons, with the capacity to produce 17 million tons.
In the United States, Europe, and Japan, consumption of calcium carbide is generally declining. Production levels in the US during the 1990s were 236,000 tons per year. | 1 | Applied and Interdisciplinary Chemistry |
The Q cycle (named for quinol) describes a series of reactions that describe how the sequential oxidation and reduction of the lipophilic electron carrier Coenzyme Q (CoQ) between the ubiquinol and ubiquinone forms, can result in the net movement of protons across a lipid bilayer (in the case of the mitochondria, the inner mitochondrial membrane).
The Q cycle was first proposed by Peter D. Mitchell, though a modified version of Mitchell's original scheme is now accepted as the mechanism by which Complex III moves protons (i.e. how complex III contributes to the biochemical generation of the proton or pH, gradient, which is used for the biochemical generation of ATP).
The first reaction of Q cycle is the 2-electron oxidation of ubiquinol by two oxidants, c (Fe) and ubiquinone:
: CoQH + cytochrome c (Fe) + CoQ → CoQ + CoQ + cytochrome c (Fe) + 2 H (intermembrane)
The second reaction of the cycle involves the 2-electron oxidation of a second ubiquinol by two oxidants, a fresh c (Fe) and the CoQ' produced in the first step:
: CoQH + cytochrome c (Fe) + CoQ + 2 H (matrix)→ CoQ + CoQH + cytochrome c (Fe) + 2 H (intermembrane)
These net reactions are mediated by electron-transfer mediators including a Rieske 2Fe-2S cluster (shunt to c) and c (shunt to CoQ and later to CoQ)
In chloroplasts, a similar reaction is done with plastoquinone by cytochrome b6f complex. | 1 | Applied and Interdisciplinary Chemistry |
* 2005 Beckman Young Investigators Award
*2006 O’Donnell Award from the Academy of Medicine, Engineering and Science of Texas
*2008 Alfred P. Sloan Foundation Fellowship
*2010 John H. Dillon Medal from the American Physical Society
*2011 Appointed to the Global Young Academy
*2012 Owens Corning Early Career Award
*2013 Elected Fellow of the American Physical Society
*2015 Finalist for the Blavatnik Awards for Young Scientists National Awards in the Physical Sciences & Engineering category
* 2020 Elected Fellow of the Materials Research Society | 1 | Applied and Interdisciplinary Chemistry |
Neuraminidase inhibitors (NAIs) are a class of drugs which block the neuraminidase enzyme. They are a commonly used antiviral drug type against influenza. Viral neuraminidases are essential for influenza reproduction, facilitating viral budding from the host cell. Oseltamivir (Tamiflu), zanamivir (Relenza), laninamivir (Inavir), and peramivir belong to this class. Unlike the M2 inhibitors, which work only against the influenza A virus, NAIs act against both influenza A and influenza B.
The NAIs oseltamivir and zanamivir were approved in the US and Europe for treatment and prevention of influenza A and B. Peramivir acts by strongly binding to the neuraminidase of the influenza viruses and inhibits activation of neuraminidase much longer than oseltamivir or zanamivir. However, laninamivir in the cells is slowly released into the respiratory tract, resulting in long-lasting anti-influenza virus activity. Thus the mechanism of the long-lasting activity of laninamivir is basically different from that of peramivir.
The efficacy was highly debated in recent years. However, after the pandemic caused by H1N1 in 2009, the effectiveness of early treatment with neuraminidase inhibitors in reducing serious cases and deaths was reported in various countries.
In countries where influenza-like illness is treated using NAIs on a national level, statistical reports show a low fatality record for symptomatic illness because of the universal implementation of early treatment using this class of drugs. Although oseltamivir is widely used in these countries, there have been no outbreaks caused by oseltamivir-resistant viruses and also no serious illness caused by oseltamivir-resistant viruses has ever been reported. The United States Centers for Disease Control and Prevention continues to recommend the use of oseltamavir treatment for people at high risk for complications and the elderly and those at lower risk who present within 48 hours of first symptoms of infection.
Common side effects include nausea and vomiting. The abnormal behaviors of children after taking oseltamivir that have been reported may be an extension of delirium or hallucinations caused by influenza. It occurs in the early stages of the illness, such as within 48 hours after onset of the illness. Therefore, children with influenza are advised to be observed by their parents until 48 hours after the onset of the influenza illness, regardless of whether the child is treated with NAIs. | 0 | Theoretical and Fundamental Chemistry |
Derepression of translation increases protein production without altering the levels of mRNA in the cell. miRNAs are a common mechanism of translation repression, binding to the mRNA through complementary base pairing to silence them. Certain RNA binding proteins have been shown to target untranslated regions of the mRNAs and upregulate the translation initiation rates by alleviating the repressive miRNA effects. | 1 | Applied and Interdisciplinary Chemistry |
Chromatin remodeling provides fine-tuning at crucial cell growth and division steps, like cell-cycle progression, DNA repair and chromosome segregation, and therefore exerts tumor-suppressor function. Mutations in such chromatin remodelers and deregulated covalent histone modifications potentially favor self-sufficiency in cell growth and escape from growth-regulatory cell signals - two important hallmarks of cancer.
* Inactivating mutations in SMARCB1, formerly known as hSNF5/INI1 and a component of the human SWI/SNF remodeling complex have been found in large number of rhabdoid tumors, commonly affecting pediatric population. Similar mutations are also present in other childhood cancers, such as choroid plexus carcinoma, medulloblastoma and in some acute leukemias. Further, mouse knock-out studies strongly support SMARCB1 as a tumor suppressor protein. Since the original observation of SMARCB1 mutations in rhabdoid tumors, several more subunits of the human SWI/SNF chromatin remodeling complex have been found mutated in a wide range of neoplasms.
* The SWI/SNF ATPase BRG1 (or SMARCA4) is the most frequently mutated chromatin remodeling ATPase in cancer. Mutations in this gene were first recognized in human cancer cell lines derived from lung. In cancer, mutations in BRG1 show an unusually high preference for missense mutations that target the ATPase domain. Mutations are enriched at highly conserved ATPase sequences, which lie on important functional surfaces such as the ATP pocket or DNA-binding surface. These mutations act in a genetically dominant manner to alter chromatin regulatory function at enhancers and promoters.
* Inactivating mutations in BCL7A in Diffuse large B-cell lymphoma (DLBCL) and in other haematological malignancies
* PML-RARA fusion protein in acute myeloid leukemia recruits histone deacetylases. This leads to repression of genes responsible for myelocytes to differentiate, leading to leukemia.
* Tumor suppressor Rb protein functions by the recruitment of the human homologs of the SWI/SNF enzymes BRG1, histone deacetylase and DNA methyltransferase. Mutations in BRG1 are reported in several cancers causing loss of tumor suppressor action of Rb.
* Recent reports indicate DNA hypermethylation in the promoter region of major tumor suppressor genes in several cancers. Although few mutations are reported in histone methyltransferases yet, correlation of DNA hypermethylation and histone H3 lysine-9 methylation has been reported in several cancers, mainly in colorectal and breast cancers.
* Mutations in Histone Acetyl Transferases (HAT) p300 (missense and truncating type) are most commonly reported in colorectal, pancreatic, breast and gastric carcinomas. Loss of heterozygosity in coding region of p300 (chromosome 22q13) is present in large number of glioblastomas.
* Further, HATs have diverse role as transcription factors beside having histone acetylase activity, e.g., HAT subunit, hADA3 may act as an adaptor protein linking transcription factors with other HAT complexes. In the absence of hADA3, TP53 transcriptional activity is significantly reduced, suggesting role of hADA3 in activating TP53 function in response to DNA damage.
* Similarly, TRRAP, the human homolog to yeast Tra1, has been shown to directly interact with c-Myc and E2F1, known oncoproteins. | 1 | Applied and Interdisciplinary Chemistry |
The triple-alpha process is a set of nuclear fusion reactions by which three helium-4 nuclei (alpha particles) are transformed into carbon. | 0 | Theoretical and Fundamental Chemistry |
After Moseleys death in 1915, the atomic numbers of all known elements from hydrogen to uranium (Z = 92) were examined by his method. There were seven elements (with Z < 92) which were not found and therefore identified as still undiscovered, corresponding to atomic numbers 43, 61, 72, 75, 85, 87 and 91. From 1918 to 1947, all seven of these missing elements were discovered. By this time, the first four transuranium elements had also been discovered, so that the periodic table was complete with no gaps as far as curium (Z' = 96). | 0 | Theoretical and Fundamental Chemistry |
In macromolecular chemistry, a catenane () is a mechanically interlocked molecular architecture consisting of two or more interlocked macrocycles, i.e. a molecule containing two or more intertwined rings. The interlocked rings cannot be separated without breaking the covalent bonds of the macrocycles. They are conceptually related to other mechanically interlocked molecular architectures, such as rotaxanes, molecular knots or molecular Borromean rings. Recently the terminology "mechanical bond" has been coined that describes the connection between the macrocycles of a catenane. Catenanes have been synthesised in two different ways: statistical synthesis and template-directed synthesis. | 0 | Theoretical and Fundamental Chemistry |
Several databases exist for restriction sites and enzymes, of which the largest noncommercial database is REBASE. Recently, it has been shown that statistically significant nullomers (i.e. short absent motifs which are highly expected to exist) in virus genomes are restriction sites indicating that viruses have probably got rid of these motifs to facilitate invasion of bacterial hosts. [https://www.nullomers.org/ Nullomers Database] contains a comprehensive catalogue of minimal absent motifs many of which might potentially be not-yet-known restriction motifs. | 1 | Applied and Interdisciplinary Chemistry |
The function of neurons depends upon cell polarity. The distinctive structure of nerve cells allows action potentials to travel directionally (from dendrites to cell body down the axon), and for these signals to then be received and carried on by post-synaptic neurons or received by effector cells. Nerve cells have long been used as models for cellular polarization, and of particular interest are the mechanisms underlying the polarized localization of synaptic molecules. PIP2 signaling regulated by IMPase plays an integral role in synaptic polarity.
Phosphoinositides (PIP, PIP2, and PIP3) are molecules that have been shown to affect neuronal polarity. A gene (ttx-7) was identified in Caenorhabditis elegans that encodes myo-inositol monophosphatase (IMPase), an enzyme that produces inositol by dephosphorylating inositol phosphate. Organisms with mutant ttx-7 genes demonstrated behavioral and localization defects, which were rescued by expression of IMPase. This led to the conclusion that IMPase is required for the correct localization of synaptic protein components. The egl-8 gene encodes a homolog of phospholipase Cβ (PLCβ), an enzyme that cleaves PIP2. When ttx-7 mutants also had a mutant egl-8 gene, the defects caused by the faulty ttx-7 gene were largely reversed. These results suggest that PIP2 signaling establishes polarized localization of synaptic components in living neurons. | 1 | Applied and Interdisciplinary Chemistry |
Using plants and plant substances to treat all kinds of diseases and medical conditions is believed to date back to prehistoric medicine.
The Kahun Gynaecological Papyrus, the oldest known medical text of any kind, dates to about 1800 BC and represents the first documented use of any kind of drug. It and other medical papyri describe Ancient Egyptian medical practices, such as using honey to treat infections and the legs of bee-eaters to treat neck pains.
Ancient Babylonian medicine demonstrated the use of medication in the first half of the 2nd millennium BC. Medicinal creams and pills were employed as treatments.
On the Indian subcontinent, the Atharvaveda, a sacred text of Hinduism whose core dates from the second millennium BC, although the hymns recorded in it are believed to be older, is the first Indic text dealing with medicine. It describes plant-based drugs to counter diseases. The earliest foundations of ayurveda were built on a synthesis of selected ancient herbal practices, together with a massive addition of theoretical conceptualizations, new nosologies and new therapies dating from about 400 BC onwards. The student of Āyurveda was expected to know ten arts that were indispensable in the preparation and application of his medicines: distillation, operative skills, cooking, horticulture, metallurgy, sugar manufacture, pharmacy, analysis and separation of minerals, compounding of metals, and preparation of alkalis.
The Hippocratic Oath for physicians, attributed to fifth century BC Greece, refers to the existence of "deadly drugs", and ancient Greek physicians imported drugs from Egypt and elsewhere. The pharmacopoeia , written between 50 and 70 CE by the Greek physician Pedanius Dioscorides, was widely read for more than 1,500 years. | 1 | Applied and Interdisciplinary Chemistry |
Organic matter is common throughout the ecosystem and is cycled through decomposition processes by soil microbial communities that are crucial for nutrient availability. After degrading and reacting, it can move into soil and mainstream water via waterflow. Organic matter provides nutrition to living organisms. Organic matter acts as a buffer in aqueous solution to maintain a neutral pH in the environment. The buffer acting component has been proposed to be relevant for neutralizing acid rain. | 0 | Theoretical and Fundamental Chemistry |
Specific surface area (SSA) is a property of solids defined as the total surface area (SA) of a material per unit mass, (with units of m/kg or m/g). Alternatively, it may be defined as SA per solid or bulk volume (units of m/m or m).
It is a physical value that can be used to determine the type and properties of a material (e.g. soil or snow). It has a particular importance for adsorption, heterogeneous catalysis, and reactions on surfaces. | 0 | Theoretical and Fundamental Chemistry |
Permeable interlocking concrete pavements are concrete units with open, permeable spaces between the units. They give an architectural appearance, and can bear both light and heavy traffic, particularly interlocking concrete pavers, excepting high-volume or high-speed roads. Some products are polymer-coated and have an entirely porous face. | 1 | Applied and Interdisciplinary Chemistry |
Boric acid was first registered in the US as an insecticide in 1948 for control of cockroaches, termites, fire ants, fleas, silverfish, and many other insects. The product is generally considered to be safe to use in household kitchens to control cockroaches and ants. It acts as a stomach poison affecting the insects metabolism, and the dry powder is abrasive to the insects exoskeletons. Boric acid also has the reputation as "the gift that keeps on killing" in that cockroaches that cross over lightly dusted areas do not die immediately, but that the effect is like shards of glass cutting them apart. This often allows a roach to go back to the nest where it soon dies. Cockroaches, being cannibalistic, eat others killed by contact or consumption of boric acid, consuming the powder trapped in the dead roach and killing them, too. | 0 | Theoretical and Fundamental Chemistry |
The cosmetic industry claims that the UV filter acts as an "artificial melanin". But those artificial substances used in sunscreens do not efficiently dissipate the energy of the UV photon as heat. Instead these substances have a very long excited state lifetime. In fact, the substances used in sunscreens are often used as photosensitizers in chemical reactions. (see Benzophenone).
Oxybenzone, titanium oxide and octyl methoxycinnamate are photoprotective agents used in many sunscreens, providing broad-spectrum UV coverage, including UVB and short-wave UVA rays. | 0 | Theoretical and Fundamental Chemistry |
For an isolated spherical solid particle of diameter in its own liquid, the Gibbs–Thomson equation for the structural melting point depression can be written:
where:
* T = bulk melting temperature
* σ = solid–liquid interface energy (per unit area)
* H = bulk enthalpy of fusion (per gram of material)
* ρ = density of solid
* r = radius of the nanoparticle | 0 | Theoretical and Fundamental Chemistry |
While the methods above are designed to reduce PD formation, another approach aims to minimize signal generated from PDs in quantitative PCR. This approach is useful as long as there are few PDs formed and their inhibitory effect on product accumulation is minor.
Four steps PCR: used when working with nonspecific dyes, such as SYBR Green I. It is based on the different length, and hence, different melting temperature of the PDs and the target sequence. In this method the signal is acquired below the melting temperature of the target sequence, but above the melting temperature of the PDs.
Sequence-specific probes: TaqMan and molecular beacon probes generate signal only in the presence of their target (complementary) sequence, and this enhanced specificity precludes signal acquisition (but not possible inhibitory effects on product accumulation) from PDs. | 1 | Applied and Interdisciplinary Chemistry |
Fractional anisotropy (FA) is a scalar value between zero and one that describes the degree of anisotropy of a diffusion process. A value of zero means that diffusion is isotropic, i.e. it is unrestricted (or equally restricted) in all directions. A value of one means that diffusion occurs only along one axis and is fully restricted along all other directions. FA is a measure often used in diffusion imaging where it is thought to reflect fiber density, axonal diameter, and myelination in white matter. The FA is an extension of the concept of eccentricity of conic sections in 3 dimensions, normalized to the unit range. | 1 | Applied and Interdisciplinary Chemistry |
The exposition begins with a virial expansion of the excess Gibbs free energy
W is the mass of the water in kilograms, b, b ... are the molalities of the ions and I is the ionic strength. The first term, f(I) represents the Debye–Hückel limiting law. The quantities λ(I) represent the short-range interactions in the presence of solvent between solute particles i and j. This binary interaction parameter or second virial coefficient depends on ionic strength, on the particular species i and j and the temperature and pressure. The quantities μ represent the interactions between three particles. Higher terms may also be included in the virial expansion.
Next, the free energy is expressed as the sum of chemical potentials, or partial molal free energy,
and an expression for the activity coefficient is obtained by differentiating the virial expansion with respect to a molality b.
For a simple electrolyte MX, at a concentration m, made up of ions M, and
are defined as
The term f is essentially the Debye–Hückel term. Terms involving and are not included as interactions between three ions of the same charge are unlikely to occur except in very concentrated solutions.
The B parameter was found empirically to show an ionic strength dependence (in the absence of ion-pairing) which could be expressed as
With these definitions, the expression for the osmotic coefficient becomes
A similar expression is obtained for the mean activity coefficient.
These equations were applied to an extensive range of experimental data at 25 °C with excellent agreement to about 6 mol kg for various types of electrolyte. The treatment can be extended to mixed electrolytes
and to include association equilibria. Values for the parameters β, β and C for inorganic and organic acids, bases and salts have been tabulated. Temperature and pressure variation is also discussed.
One area of application of Pitzer parameters is to describe the ionic strength variation of equilibrium constants measured as concentration quotients. Both SIT and Pitzer parameters have been used in this context, For example, both sets of parameters were calculated for some uranium complexes and were found to account equally well for the ionic strength dependence of the stability constants.
Pitzer parameters and SIT theory have been extensively compared. There are more parameters in the Pitzer equations than in the SIT equations. Because of this the Pitzer equations provide for more precise modelling of mean activity coefficient data and equilibrium constants. However, the determination of the greater number of Pitzer parameters means that they are more difficult to determine. | 0 | Theoretical and Fundamental Chemistry |
*RPL5
*RPL8
*RPL9
*RPL10A
*RPL11
*RPL14
*RPL25
*RPL26L1
*RPL27
*RPL30
*RPL32
*RPL34
*RPL35
*RPL35A
*RPL36AL
*RPS5
*RPS6
*RPS6KA3
*RPS6KB1
*RPS6KB2
*RPS13
RPS19BP1
*RPS20
*RPS23
*RPS24
*RPS27 transcribed with ubiquitin (see FAU (gene))
*RPN1 Ribophorin anchors the ribosome to rough endoplasmic reticulum | 1 | Applied and Interdisciplinary Chemistry |
In systems theory, a system is said to be transient or in a transient state when a process variable or variables have been changed and the system has not yet reached a steady state. In electrical engineering, the time taken for an electronic circuit to change from one steady state to another steady state is called the transient time. | 1 | Applied and Interdisciplinary Chemistry |
The oxidative aminations of olefins are generally conducted with amides or imides; amines are thought to be protonated by the acidic medium or to bind the metal center too tightly to allow for the catalytic chemistry to occur. These nitrogen nucleophiles are found to be competent in both intermolecular and intramolecular reactions, some examples are depicted (Figure 5, A, B) | 0 | Theoretical and Fundamental Chemistry |
Cryptic binding sites are the binding sites that are transiently formed in an apo form or that are induced by ligand binding. Considering the cryptic binding sites increases the size of the potentially “druggable” human proteome from ~40% to ~78% of disease-associated proteins. The binding sites have been investigated by: support vector machine applied to "CryptoSite" data set, Extension of "CryptoSite" data set, long timescale molecular dynamics simulation with Markov state model and with biophysical experiments, and cryptic-site index that is based on relative accessible surface area. | 1 | Applied and Interdisciplinary Chemistry |
In regards to rhythmicity of the clock in a free running setting PRR9 and PRR5 are associated with longer and shorter periods respectively. For each gene, the double mutant with PRR7 exacerbates observed trends in rhythmicity. The triple mutant renders the plant arrhythmic. | 1 | Applied and Interdisciplinary Chemistry |
Siddiqui migrated to Pakistan in 1951, four years after the emergence of Pakistan in 1947, after being offered and appointed as "science advisor" to the government by Prime minister Liaquat Ali Khan. He was appointed as Director of the Pakistan Department of Research that was reformulated in 1953 as Pakistan Council of Scientific and Industrial Research (PCSIR). The aim of PCSIR was to support the industrial infrastructure through research and development. The regional laboratories of the institution were located in Dhaka, Rajshahi and Chittagong (East Pakistan), and in Lahore and Peshawar (West Pakistan). In 1953, he founded the Pakistan Academy of Sciences as a non-political think tank of distinguished scientists in the country. In 1956, when Government of Pakistan established Pakistan Atomic Energy Commission (PAEC) as an atomic research agency, Siddiqui was designated as its technical member.
In recognition of his scientific leadership, Frankfurt University granted him the degree of D.Med. Honoris causa in 1958. Also in 1958, the Government of Pakistan awarded him with Tamgha-e-Pakistan. In 1960, he became the President of Pan-Indian Ocean Science Association. The same year, he was elected Fellow of the Royal Society. In 1962, he was awarded the Sitara-e-Imtiaz for distinguished merit in the fields of science and medicine. Siddiqui remained the director and chairman of PCSIR until the time of his retirement in 1966. In that year, the President of Pakistan awarded him the Pride of Performance Medal for the respectable completion of his service.
In 1967, Siddiqui was invited by University of Karachi to set up a Postgraduate Institute of Chemistry in affiliation with the Department of Chemistry. He was designated as the institute's Founder Director, whereas the additional research staff was provided by PCSIR.
In 1976, the institute was offered a generous donation from Hussain Jamal Foundation. In appreciation of this donation, the institute was renamed as Hussain Ebrahim Jamal Research Institute of Chemistry. In due time, Siddiqui transformed the institute into a distinguished centre of international excellence in the field of chemistry and natural products. In March 1975, he headed the National Commission for Indigenous Medicines His tireless efforts for the promotion of science and technology earned him Hilal-e-Imtiaz by the Government of Pakistan in 1980. In 1983, he played a major role in the establishment of the Third World Academy of Sciences and became its Founding Fellow. He remained the director of the Hussain Ebrahim Jamal Research Institute of Chemistry until 1990. Later on, he continued research in his personal laboratory. He published over 400 research papers and was granted 50 patents. | 0 | Theoretical and Fundamental Chemistry |
Synthetic approaches to CYN started with the piperidine ring (A), and progressed to annulation of rings B and C. The first total synthesis of CYN was reported in 2000 through a 20-step process.
Improvements to synthetic methods led to a revision of the stereochemistry of CYN in 2001. A synthetic process controlling each of the six stereogenic centres of epiCYN established that the original assignments of both CYN and epiCYN were in fact a reversal of the correct structures. An alternative approach by White and Hansen supported these absolute configurations (Figure 5). At the time of this correct assignment, it was suggested that the enol form was not dominant. | 0 | Theoretical and Fundamental Chemistry |
The next generation of SNP annotation webservers can take advantage of the growing amount of data in core bioinformatics resources and use intelligent agents to fetch data from different sources as needed. From a user’s point of view, it is more efficient to submit a set of SNPs and receive results in a single step, which makes meta-servers the most attractive choice. However, if SNP annotation tools deliver heterogeneous data covering sequence, structure, regulation, pathways, etc., they must also provide frameworks for integrating data into a decision algorithms, and quantitative confidence measures so users can assess which data are relevant and which are not. | 1 | Applied and Interdisciplinary Chemistry |
The total synthesis of taxol is called one of the most hotly contested of the 1990s with around 30 competing research groups by 1992. The number of research groups actually having reported a total synthesis currently stands at 11 with the Holton group (article first accepted for publication) and the Nicolaou group (article first published) first and second in what is called a photo finish.
Some of the efforts are truly synthetic but in others a precursor molecule found in nature is included. The key data are collected below. What all strategies have in common is synthesis of the baccatin molecule followed by last stage addition of the tail, a process (except for one) based on the Ojima lactam.
# Holton Taxol total synthesis - year: 1994 - precursor: Patchoulol strategy: linear synthesis AB then C then D - references: see related article
# Nicolaou Taxol total synthesis - year: 1994 - precursor: Mucic acid strategy: convergent synthesis A and C merge to ABC then D - references: see related article
# Danishefsky Taxol total synthesis - year: 1996 - precursor: Wieland-Miescher ketone strategy: convergent synthesis C merges with D then with A merges to ABCD - references: See related article
# Wender Taxol total synthesis - year: 1997 - precursor: Pinene strategy: linear synthesis AB then C then D - references:
# Kuwajima Taxol total synthesis I. Kuwajima, - year: 1998 - precursor: synthetic building blocks strategy: linear synthesis A then B then C then D
# Mukaiyama Taxol total synthesis - year: 1998 - Precursor: L-serine strategy: linear synthesis B, then C, then A then D. References: see related article.
# Takahashi Taxol total synthesis - year: 2006 - Precursor: geraniol strategy: convergent synthesis A and C merge to ABC then D
# Sato-Chida Taxol total synthesis - year: 2015, formal synthesis to a Takahashi intermediate
# Nakada Taxol total synthesis - year: 2015, formal synthesis to a Takahashi intermediate
# Baran Taxol total synthesis - year: 2020, total synthesis via a two-phase divergent synthetic approach.
# Li Taxol total synthesis - year: 2021, total synthesis via B ring closure by forming C1–C2 bond.
Ongoing research efforts are directed at the synthesis of taxadiene and taxadienone intermediates. The synthesis of related taxanes decinnamoyltaxinine E and taxabaccatin III has been reported | 0 | Theoretical and Fundamental Chemistry |
Brinelling is the permanent indentation of a hard surface. It is named after the Brinell scale of hardness, in which a small ball is pushed against a hard surface at a preset level of force, and the depth and diameter of the mark indicates the Brinell hardness of the surface. Brinelling is permanent plastic deformation of a surface, and usually occurs while two surfaces in contact are stationary (such as rolling elements and the raceway of a bearings) and the material yield strength has been exceeded.
Brinelling is undesirable, as the parts often mate with other parts in very close proximity. The very small indentations can quickly lead to improper operation, such as chattering or excess vibration, which in turn can accelerate other forms of wear, such as spalling and ultimately, failure of the bearing. | 1 | Applied and Interdisciplinary Chemistry |
The glassworts are various succulent, annual halophytic plants, that is, plants that thrive in saline environments, such as seacoasts and salt marshes. The original English glasswort plants belong to the genus Salicornia, but today the glassworts include halophyte plants from several genera, some of which are native to continents unknown to the medieval English, and growing in ecosystems, such as mangrove swamps, never envisioned when the term glasswort was coined.
The common name "glasswort" came into use in the 16th century to describe plants growing in England whose ashes could be used for making soda-based (as opposed to potash-based) glass. | 0 | Theoretical and Fundamental Chemistry |
Papaver somniferum × Papaver bracteatum, also known as Sagan's poppy is a hybrid between the opium poppy and the Iranian poppy.
This hybrid, true poppy is diploid with 18 chromosomes and exhibits strongly reduced fitness relative to parents, possibly due to unpaired chromosomes since the Iranian and opium poppies do not have the same number. The clearest example of its reduced fitness is seen through semilethal dwarfism, with about 53.4% of specimens grown exhibiting dwarfism. While this hybrid does not possess the cold hardiness of the Iranian poppy (Papaver bracteatum), it does possess notably more cold tolerance than Papaver somniferum and in a greenhouse or protected setting could be grown as a perennial. Another notable feature of this hybrid is that it contains a higher concentration of morphinian alkaloids (including morphine) than any known cultivar of Papaver somniferum and Papaver bracteatum. This is despite one of its parents (Papaver bracteatum) producing negligible concentrations of morphine and is believed to be due to a greater expression of one of the rate-limiting enzymes of morphine synthesis. | 1 | Applied and Interdisciplinary Chemistry |
A cryophorus is a glass container containing liquid water and water vapor. It is used in physics courses to demonstrate rapid freezing by evaporation. A typical cryophorus has a bulb at one end connected to a tube of the same material. When the liquid water is manipulated into the bulbed end and the other end is submerged into a freezing mixture (such as liquid nitrogen), the gas pressure drops as it is cooled. The liquid water begins to evaporate, producing more water vapor. Evaporation causes the water to cool rapidly to its freezing point and it solidifies suddenly.
Wollaston's cryophorus was a precursor to the modern heat pipe. | 0 | Theoretical and Fundamental Chemistry |
Diphosphenes can bind to transition metal either in a η mode by donating a lone pair on phosphorus, or in a η behavior via a interaction. If the bulky groups are aryl- groups, arene-coordinated products of η-type coordination are also possible. | 0 | Theoretical and Fundamental Chemistry |
Diaconescu received a Sloan Fellowship in 2009, and received the Humboldt Foundation's Friedrich Wilhelm Bessel Research Award in 2014. In 2015, she was named a Guggenheim Fellow, and Diaconescu was named a fellow of the American Association for the Advancement of Science in 2019. | 0 | Theoretical and Fundamental Chemistry |
Extensive studies involving the phosphaethynolate anion have shown that it can react in a variety of ways. It has documented use in cycloadditions, as a phosphorus transfer agent, a synthetic building block and as pseudo halide ligands (as described above). | 0 | Theoretical and Fundamental Chemistry |
Pyrosequencing is a method of DNA sequencing (determining the order of nucleotides in DNA) based on the "sequencing by synthesis" principle, in which the sequencing is performed by detecting the nucleotide incorporated by a DNA polymerase. Pyrosequencing relies on light detection based on a chain reaction when pyrophosphate is released. Hence, the name pyrosequencing.
The principle of pyrosequencing was first described in 1993 by, Bertil Pettersson, Mathias Uhlen and Pål Nyren by combining the solid phase sequencing method using streptavidin coated magnetic beads with recombinant DNA polymerase lacking 3´to 5´exonuclease activity (proof-reading) and luminescence detection using the firefly luciferase enzyme. A mixture of three enzymes (DNA polymerase, ATP sulfurylase and firefly luciferase) and a nucleotide (dNTP) are added to single stranded DNA to be sequenced and the incorporation of nucleotide is followed by measuring the light emitted. The intensity of the light determines if 0, 1 or more nucleotides have been incorporated, thus showing how many complementary nucleotides are present on the template strand. The nucleotide mixture is removed before the next nucleotide mixture is added. This process is repeated with each of the four nucleotides until the DNA sequence of the single stranded template is determined.
A second solution-based method for pyrosequencing was described in 1998 by Mostafa Ronaghi, [https://www.kth.se/en/bio/research/proteomics/proteomics-researchers/mathias-uhlen-1.67763 Mathias Uhlen] and Pål Nyren. In this alternative method, an additional enzyme apyrase is introduced to remove nucleotides that are not incorporated by the DNA polymerase. This enabled the enzyme mixture including the DNA polymerase, the luciferase and the apyrase to be added at the start and kept throughout the procedure, thus providing a simple set-up suitable for automation. An automated instrument based on this principle was introduced to the market the following year by the company Pyrosequencing.
A third microfluidic variant of the pyrosequencing method was described in 2005 by Jonathan Rothberg and co-workers at the company 454 Life Sciences. This alternative approach for pyrosequencing was based on the original principle of attaching the DNA to be sequenced to a solid support and they showed that sequencing could be performed in a highly parallel manner using a microfabricated microarray. This allowed for high-throughput DNA sequencing and an automated instrument was introduced to the market. This became the first next generation sequencing instrument starting a new era in genomics research, with rapidly falling prices for DNA sequencing allowing whole genome sequencing at affordable prices. | 1 | Applied and Interdisciplinary Chemistry |
Norvaline is a non-proteinogenic unbranched-chain amino acid. It has previously been reported to be a natural component of an antifungal peptide of Bacillus subtilis. Norvaline and other modified unbranched chain amino acids have received attention because they appear to be incorporated in some recombinant proteins found in E. coli. Its biosynthesis has been examined. The incorporation of Nva into peptides reflects the imperfect selectivity of the associated aminoacyl-tRNA synthetase. In Miller–Urey experiments probing prebiotic synthesis of amino acids, norvaline, but also norleucine, are produced. | 1 | Applied and Interdisciplinary Chemistry |
Dissimilatory sulfate reduction is a relatively energetically poor process used by many Gram-negative bacteria found within the Thermodesulfobacteriota, Gram-positive organisms relating to Desulfotomaculum or the archaeon Archaeoglobus. Hydrogen sulfide () is produced as a metabolic end product. For sulfate reduction electron donors and energy are needed. | 1 | Applied and Interdisciplinary Chemistry |
The mechanism of action of the bisphosphonates (BPs) has evolved as new generations of drugs have been developed. The function of the first generation bisphosphonates differs from the more recent nitrogen containing BPs but both are apparently internalised by endocytosis of a membrane-bound vesicle where the drug is most likely in a complex with Ca ions. This does not concern other cells in the bone as this takes place by a selective uptake of osteoclasts.
The common function which applies to all bisphosphonate drugs is a physicochemical interaction with the bone mineral to prevent the physical resorption of the bone by the osteoclasts. This is especially relevant at sites where bone remodelling is most active. The bisphosphonates have an intrinsic affinity for the calcium ions (hydroxyapatite) of the bone mineral just as the endogenous pyrophosphates. The difference lies in the non-hydrolysable carbon-phosphorus bond of the bisphosphonates which prevents their metabolism and at the same time ensure an effective absorption from the gastrointestinal tract.
The primary inhibiting action of the first generation of bisphosphonates on osteoclasts is by inducing apoptosis. The mechanism of action is apparently by the formation of an ATP analogue or metabolite of the bisphosphonates like etidronic acid and clodronic acid. The ATP analogue accumulates in the cytosol of the osteoclast with a cytotoxic effect.
The primary mechanism of action of the more developed nitrogen containing bisphosphonates is however by cellular effects on osteoclasts through inhibition of the mevalonate pathway and in particular the subsequent formation of isoprenoid lipids. The inhibition takes place at a key branch point in the pathway catalyzed by farnesyl pyrophosphate synthase (FPPS). Isoprenoid lipids are necessary for post-translational modifications of small GTP-binding regulatory proteins like Rac, Rho and Ras of the Ras superfamily. The function of osteoclasts depends on them for a variety of cellular processes like apoptosis. | 1 | Applied and Interdisciplinary Chemistry |
Previously, many science works used Mass Spectrometry (MS) in different fragmentation modes to detect AMPylated peptides. In responses to the distinctive fragmentation techniques, AMPylated protein sequences disintegrated at different parts of AMP. While electron transfer dissociation (ETD) creates minimum fragments and less complicated spectra, collision-induced dissociation (CID) and high-energy collision (HCD) fragmentation generate characteristic ions suitable for AMPylated proteins identification by generating multiple AMP fragments. Due to AMP's stability, peptide fragmentation spectra is easy to read manually or with search engines. | 1 | Applied and Interdisciplinary Chemistry |
Methods for taking physical measurements of capillary pressure in a microchannel have not been thoroughly studied, despite the need for accurate pressure measurements in microfluidics. The primary issue with measuring the pressure in microfluidic devices is that the volume of fluid is too small to be used in standard pressure measurement tools. Some studies have presented the use of microballoons, which are size-changing pressure sensors. Servo-nulling, which is historically used for measuring blood pressure, has also been demonstrated to provide pressure information in microfluidic channels with the assistance of a LabVIEW control system. Essentially, a micropipette is immersed in the microchannel fluid and is programmed to respond to changes in the fluid meniscus. A displacement in the meniscus of the fluid in the micropipette induces a voltage drop, which triggers a pump to restore the original position of the meniscus. The pressure exerted by the pump is interpreted as the pressure within the microchannel. | 1 | Applied and Interdisciplinary Chemistry |
Solid-state ionics is the study of ionic-electronic mixed conductor and fully ionic conductors (solid electrolytes) and their uses. Some materials that fall into this category include inorganic crystalline and polycrystalline solids, ceramics, glasses, polymers, and composites. Solid-state ionic devices, such as solid oxide fuel cells, can be much more reliable and long-lasting, especially under harsh conditions, than comparable devices with fluid electrolytes.
The field of solid-state ionics was first developed in Europe, starting with the work of Michael Faraday on solid electrolytes AgS and PbF in 1834. Fundamental contributions were later made by Walther Nernst, who derived the Nernst equation and detected ionic conduction in heterovalently doped zirconia, which he applied in his Nernst lamp. Another major step forward was the characterization of silver iodide in 1914. Around 1930, the concept of point defects was established by Yakov Frenkel, Walter Schottky and Carl Wagner, including the development of point-defect thermodynamics by Schottky and Wagner; this helped explain ionic and electronic transport in ionic crystals, ion-conducting glasses, polymer electrolytes and nanocomposites. In the late 20th and early 21st centuries, solid-state ionics focused on the synthesis and characterization of novel solid electrolytes and their applications in solid state battery systems, fuel cells and sensors.
The term solid state ionics was coined in 1967 by Takehiko Takahashi, but did not become widely used until the 1980s, with the emergence of the journal Solid State Ionics. The first international conference on this topic was held in 1972 in Belgirate, Italy, under the name "Fast Ion Transport in Solids, Solid State Batteries and Devices". | 0 | Theoretical and Fundamental Chemistry |
With the coming of the deadly Spanish flu pandemic in 1918, aspirin—by whatever name—secured a reputation as one of the most powerful and effective drugs in the pharmacopeia of the time. Its fever-reducing properties gave many sick patients enough strength to fight through the infection, and aspirin companies large and small earned the loyalty of doctors and the public—when they could manufacture or purchase enough aspirin to meet demand. Despite this, some people believed that Germans put the Spanish flu bug in Bayer aspirin, causing the pandemic as a war tactic.
The U.S. ASA patent expired in 1917, but Sterling owned the aspirin trademark, which was the only commonly used term for the drug. In 1920, United Drug Company challenged the Aspirin trademark, which became officially generic for public sale in the U.S. (although it remained trademarked when sold to wholesalers and pharmacists). With demand growing rapidly in the wake of the Spanish flu, there were soon hundreds of "aspirin" brands on sale in the United States.
Sterling Products, equipped with all of Bayer's U.S. intellectual property, tried to take advantage of its new brand as quickly as possible, before generic ASAs took over. However, without German expertise to run the Rensselaer plant to make aspirin and the other Bayer pharmaceuticals, they had only a finite aspirin supply and were facing competition from other companies. Sterling president William E. Weiss had ambitions to sell Bayer aspirin not only in the U.S., but to compete with the German Bayer abroad as well. Taking advantage of the losses Farbenfabriken Bayer (the German Bayer company) suffered through the reparation provisions of the Treaty of Versailles, Weiss worked out a deal with Carl Duisberg to share profits in the Americas, Australia, South Africa and Great Britain for most Bayer drugs, in return for technical assistance in manufacturing the drugs.
Sterling also took over Bayer's Canadian assets as well as ownership of the Aspirin trademark which is still valid in Canada and most of the world. Bayer bought Sterling Winthrop in 1994 restoring ownership of the Bayer name and Bayer cross trademark in the US and Canada as well as ownership of the Aspirin trademark in Canada. | 1 | Applied and Interdisciplinary Chemistry |
The primary amine on the aminoallyl nucleotide reacts with amino-reactive dyes such as a cyanine and patented dyes which contain a reactive leaving group, such as a succinimidyl ester (NHS).The amine groups directly attached to the ring of the base are not affected. These nucleotides are used for labeling DNA. | 1 | Applied and Interdisciplinary Chemistry |
This modification involves the addition of a methyl group to the 2 hydroxyl (-OH) group of the ribose sugar of RNA molecules. In contrast with the mA modification, it is the ribose sugar, a part of the backbone rather than the base that is altered. It is present in various kinds of cellular RNA, providing coding and structural support. 2-O-methylation of viral RNA is often accompanied by the addition of an inverted N-7methylguanosine to the 5 end on the phosphate group. These modifications regulate important functions of viral RNA such as metabolism and immune system interactions.
Different viruses have their mechanisms for acquiring this modification. Cytoplasmic RNA viruses like flaviridae and coronaviruses encode the required to catalyze cap formation reactions, with some needing one enzyme for the 5' cap and 2-O-methylation while others require two enzymes like poxviruses. Others, like influenza virus can hijack the methylguanosine caps from host cell mRNA and be preferentially translated. | 1 | Applied and Interdisciplinary Chemistry |
The technological features of FSL Kode constructs and the koding process can be summarized as follows:
* Rapid and simple – simple contact for 10–120 minutes and constructs spontaneously and stably incorporate – no washing required.
* Replicable – same variables (time, temperature, concentration) equals the same result.
* Toxicity – FSL constructs are biocompatible, disperse into biological solutions without solvents, detergents. They label non-covalently and are non-genetic. Normal vitality and functionality is maintained in modified cells/virions/organisms. Toxicity/vitality experiments in small laboratory animals, zebrafish, cell cultures, spermatozoa and embryos find no toxic effects within physiological ranges.
* Amphiphilic – the amphiphilic nature of the FSL Kode construct makes them water dispersible (clear solution of micelles), yet once interacted with a membrane they insert/coat and become water resistant
* Variable design – a single F can be presented in more than 100 ways by varying the spacer and lipid.
* High biovisibility – as the spacer holds the F moiety away for the membrane it is able to achieve increased sensitivity, specificity and reactivity can be optimized by use of multiple and variable biomarker presentations on the same surface.
* Additive – FSL modification is compatible with other technologies allowing users to add additional features to cells/viruses/organisms/surfaces already modified by more traditional methods. Multiple FSL constructs may be added to a surface simultaneously by simply creating a mix of FSL Kode constructs. Constructs insert into living or fixed cell (glutaraldehyde) membranes.
* Simple FSL peptide synthesis – there is a reactive-functional-group FSL Kode construct with maleimide as its functional group which can be used for preparation of FSLs from cysteine-containing peptides, proteins or any other thiols of biological interest. The effective synthetic approach is based on the well-known Michael nucleophilic addition to maleimides (Fig. 7).
* Synthetic "Gylcolipids" – one family of the FSL constructs are synthetic glycolipids with well-defined hydrophobic tails and carbohydrate head groups | 1 | Applied and Interdisciplinary Chemistry |
The "digital revolution" of the 21st century has brought newer technology to the art and science of tracheal intubation. Several manufacturers have developed video laryngoscopes which employ digital technology such as the CMOS active pixel sensor (APS) to generate a view of the glottis so that the trachea may be intubated. The Glidescope video laryngoscope is one example of such a device.
Xenon, which does not act as a greenhouse gas, has recently been approved in some jurisdictions as an anaesthetic agent. | 1 | Applied and Interdisciplinary Chemistry |
Aquasomes with calcium phosphate ceramic cores may be useful for the pharmaceutical administration of substrates such as insulin where drug action is conformationally specific. In a 2000 study by Cherian et al., disaccharides such as trehalose were used to coat the core before insulin was loaded onto the coated cores via adsorption. Albino rats were used as test subjects to test these aquasome insulin formulations, and the efficiency of different carbohydrate coat molecules on the aquasome was explored. Pyridoxal-5-phosphate-coated particles were shown to lower blood glucose levels more efficiently when compared to trehalose- or cellobiose-coated particles, which may be due to their differences in structural stability. The use of these nanoparticles for the delivery of insulin in vivo in rabbits demonstrated that insulin-bearing aquasomes showed slower release and prolonged activity compared to standard insulin solution. Similar to their role in carrying hemoglobin, the carbohydrate layer of aquasomes may be responsible for the ability to protect insulin from degradation when injected subcutaneously as in the albino rats tested. Aquasomes were also shown to release insulin in controlled manners, mimicking the typical release of insulin from the pancreas. This application shows the promise of aquasomes in aiding and improving the efficacy of insulin therapy, which may be used for diabetes treatment upon further investigation of aquasomes’ in vivo behavior. | 0 | Theoretical and Fundamental Chemistry |
Tetramethylguanidine is an organic compound with the formula HNC(N(CH)). This colourless liquid is a strong base, as judged by the high pK of it conjugate acid.
It was originally prepared from tetramethylthiourea via S-methylation and amination, but alternative methods start from cyanogen iodide. | 0 | Theoretical and Fundamental Chemistry |
Transport properties such as diffusivity describe how rapidly molecules move through the polymer matrix. These are very important in many applications of polymers for films and membranes.
The movement of individual macromolecules occurs by a process called reptation in which each chain molecule is constrained by entanglements with neighboring chains to move within a virtual tube. The theory of reptation can explain polymer molecule dynamics and viscoelasticity. | 0 | Theoretical and Fundamental Chemistry |
Plant defense against herbivory or host-plant resistance (HPR) is a range of adaptations evolved by plants which improve their survival and reproduction by reducing the impact of herbivores. Plants can sense being touched, and they can use several strategies to defend against damage caused by herbivores. Many plants produce secondary metabolites, known as allelochemicals, that influence the behavior, growth, or survival of herbivores. These chemical defenses can act as repellents or toxins to herbivores or reduce plant digestibility. Another defensive strategy of plants is changing their attractiveness. To prevent overconsumption by large herbivores, plants alter their appearance by changing their size or quality, reducing the rate at which they are consumed.
Other defensive strategies used by plants include escaping or avoiding herbivores at any time in any placefor example, by growing in a location where plants are not easily found or accessed by herbivores or by changing seasonal growth patterns. Another approach diverts herbivores toward eating non-essential parts or enhances the ability of a plant to recover from the damage caused by herbivory. Some plants encourage the presence of natural enemies of herbivores, which in turn protect the plant. Each type of defense can be either constitutive (always present in the plant) or induced (produced in reaction to damage or stress caused by herbivores).
Historically, insects have been the most significant herbivores, and the evolution of land plants is closely associated with the evolution of insects. While most plant defenses are directed against insects, other defenses have evolved that are aimed at vertebrate herbivores, such as birds and mammals. The study of plant defenses against herbivory is important, not only from an evolutionary viewpoint, but also for the direct impact that these defenses have on agriculture, including human and livestock food sources; as beneficial biological control agents in biological pest control programs; and in the search for plants of medical importance. | 1 | Applied and Interdisciplinary Chemistry |
Silicon carbide is used in the manufacturing of fishing guides because of its durability and wear resistance. Silicon Carbide rings are fit into a guide frame, typically made from stainless steel or titanium which keep the line from touching the rod blank. The rings provide a low friction surface which improves casting distance while providing adequate hardness that prevents abrasion from braided fishing line. | 1 | Applied and Interdisciplinary Chemistry |
Bamboos and the related rice have an improved C3 efficiency. This improvement might be due to its ability to recapture CO produced during photorespiration, a behavior termed "carbon refixation". These plants achieve refixation by growing chloroplast extensions called "stromules" around the stroma in mesophyll cells, so that any photorespired CO from the mitochondria has to pass through the RuBisCO-filled chloroplast.
Refixation is also performed by a wide variety of plants. The common approach involving growing a bigger bundle sheath leads down to C2 photosynthesis. | 0 | Theoretical and Fundamental Chemistry |
SCCmec, or staphylococcal cassette chromosome mec, is a mobile genetic element of Staphylococcus bacterial species. This genetic sequence includes the mecA gene coding for resistance to the antibiotic methicillin and is the only known way for Staphylococcus strains to spread the gene in the wild by horizontal gene transfer. SCCmec is a 21 to 60 kb long genetic element that confers broad-spectrum β-lactam resistance to MRSA. Moreover, additional genetic elements like Tn554, pT181, and pUB110 can be found in SCCmec, which have the capability to render resistance to various non-β-lactam drugs. | 1 | Applied and Interdisciplinary Chemistry |
The chirality of a molecule that has a helical, propeller, or screw-shaped geometry is called helicity or helical chirality. The screw axis or the D, or C principle symmetry axis is considered to be the axis of chirality. Some sources consider helical chirality to be a type of axial chirality, and some do not. IUPAC does not refer to helicity as a type of axial chirality.
Enantiomers having helicity may labeled by using the prefix notation (P) ("plus") or Δ (from Latin dexter, "right") for a right-handed helix, and (M) ("minus") or Λ (Latin levo, "left") for a left-handed helix. The P/M or Δ/Λ terminology is used particularly for molecules that actually resemble a helix, such as the helicenes. This notation can also be applied to non-helical structures having axial chirality by considering the helical orientation of the Cahn–Ingold–Prelog group rankings of the "front" groups compared to the "back", when viewed from either direction along the axis. | 0 | Theoretical and Fundamental Chemistry |
While the terms subsonic and supersonic, in the purest sense, refer to speeds below and above the local speed of sound respectively, aerodynamicists often use the same terms to talk about particular ranges of Mach values. This occurs because of the presence of a transonic regime around flight (free stream) M = 1 where approximations of the Navier-Stokes equations used for subsonic design no longer apply; the simplest explanation is that the flow around an airframe locally begins to exceed M = 1 even though the free stream Mach number is below this value.
Meanwhile, the supersonic regime is usually used to talk about the set of Mach numbers for which linearised theory may be used, where for example the (air) flow is not chemically reacting, and where heat-transfer between air and vehicle may be reasonably neglected in calculations.
In the following table, the regimes or ranges of Mach values are referred to, and not the pure meanings of the words subsonic and supersonic.
Generally, NASA defines high hypersonic as any Mach number from 10 to 25, and re-entry speeds as anything greater than Mach 25. Aircraft operating in this regime include the Space Shuttle and various space planes in development. | 1 | Applied and Interdisciplinary Chemistry |
Bauxite ore is a mixture of hydrated aluminium oxides and compounds of other elements such as iron. The aluminium compounds in the bauxite may be present as gibbsite (Al(OH)), böhmite (γ-AlO(OH)) or diaspore (α-AlO(OH)); the different forms of the aluminium component and the impurities dictate the extraction conditions. Aluminium oxides and hydroxides are amphoteric, meaning that they are both acidic and basic. The solubility of Al(III) in water is very low but increases substantially at either high or low pH. In the Bayer process, bauxite ore is heated in a pressure vessel along with a sodium hydroxide solution (caustic soda) at a temperature of 150 to 200 °C. At these temperatures, the aluminium is dissolved as sodium aluminate (primarily [Al(OH)]) in an extraction process. After separation of the residue by filtering, gibbsite is precipitated when the liquid is cooled and then seeded with fine-grained aluminium hydroxide crystals from previous extractions. The precipitation may take several days without addition of seed crystals.
The extraction process (digestion) converts the aluminium oxide in the ore to soluble sodium aluminate, NaAlO, according to the chemical equation:
:AlO + 2 NaOH → 2 NaAlO + HO
This treatment also dissolves silica, forming sodium silicate :
:2 NaOH + SiO → NaSiO + HO
The other components of Bauxite, however, do not dissolve. Sometimes lime is added at this stage to precipitate the silica as calcium silicate. The solution is clarified by filtering off the solid impurities, commonly with a rotary sand trap and with the aid of a flocculant such as starch, to remove the fine particles. The undissolved waste after the aluminium compounds are extracted, bauxite tailings, contains iron oxides, silica, calcia, titania and some unreacted alumina. The original process was that the alkaline solution was cooled and treated by bubbling carbon dioxide through it, a method by which aluminium hydroxide precipitates:
:2 NaAlO + 3 HO + CO → 2 Al(OH) + NaCO
But later, this gave way to seeding the supersaturated solution with high-purity aluminium hydroxide (Al(OH)) crystal, which eliminated the need for cooling the liquid and was more economically feasible:
:2 HO + NaAlO → Al(OH) + NaOH
Some of the aluminium hydroxide produced is used in the manufacture of water treatment chemicals such as aluminium sulfate, PAC (Polyaluminium chloride) or sodium aluminate; a significant amount is also used as a filler in rubber and plastics as a fire retardant. Some 90% of the gibbsite produced is converted into aluminium oxide, AlO, by heating in rotary kilns or fluid flash calciners to a temperature of about 1470 K.
:2 Al(OH) → AlO + 3 HO
The left-over, spent sodium aluminate solution is then recycled. Apart from improving the economy of the process, recycling accumulates gallium and vanadium impurities in the liquors, so that they can be extracted profitably.
Organic impurities that accumulate during the precipitation of gibbsite may cause various problems, for example high levels of undesirable materials in the gibbsite, discoloration of the liquor and of the gibbsite, losses of the caustic material, and increased viscosity and density of the working fluid.
For bauxites having more than 10% silica, the Bayer process becomes uneconomic because of the formation of insoluble sodium aluminium silicate, which reduces yield, so another process must be chosen.
1.9-3.6 tons of bauxite (corresponding to about 90% of the alumina content of the bauxite) is required to produce 1 ton of aluminium oxide. This is due to a majority of the aluminium in the ore being dissolved in the process. Energy consumption is between 7 GJ/tonne to 21 GJ/tonne (depending on process), of which most is thermal energy. Over 90% (95-96%) of the aluminium oxide produced is used in the Hall–Héroult process to produce aluminium. | 1 | Applied and Interdisciplinary Chemistry |
Initially devised by Mikhail Shneider and Richard Miles at Princeton University, coherent microwave scattering has become a valuable technique in applications ranging from photoionization and electron-loss rate measurements to trace species detection, gaseous mixture and reaction characterization, molecular spectroscopy, electron propulsion device characterization, standoff measurement of electron collision frequencies for momentum transfer through the scattered phase, and standoff measurement of local vector magnetic fields through magnetically-induced depolarization. | 0 | Theoretical and Fundamental Chemistry |
Multilocus sequence typing (MLST) is a technique in molecular biology for the typing of multiple loci, using DNA sequences of internal fragments of multiple housekeeping genes to characterize isolates of microbial species.
The first MLST scheme to be developed was for Neisseria meningitidis, the causative agent of meningococcal meningitis and septicaemia. Since its introduction for the research of evolutionary history, MLST has been used not only for human pathogens but also for plant pathogens. | 1 | Applied and Interdisciplinary Chemistry |
Metals typically are strong, dense, and good conductors of both electricity and heat.
The bulk of the elements in the periodic table, those to the left of a diagonal line drawn from boron to polonium, are metals.
Mixtures of two or more elements in which the major component is a metal are known as alloys.
People have been using metals for a variety of purposes since prehistoric times.
The strength and reliability of metals has led to their widespread use in construction of buildings and other structures, as well as in most vehicles, many appliances and tools, pipes, road signs and railroad tracks. Iron and aluminium are the two most commonly used structural metals. They are also the most abundant metals in the Earth's crust. Iron is most commonly used in the form of an alloy, steel, which contains up to 2.1% carbon, making it much harder than pure iron.
Because metals are good conductors of electricity, they are valuable in electrical appliances and for carrying an electric current over long distances with little energy loss or dissipation. Thus, electrical power grids rely on metal cables to distribute electricity. Home electrical systems, for example, are wired with copper for its good conducting properties and easy machinability. The high thermal conductivity of most metals also makes them useful for stovetop cooking utensils.
The study of metallic elements and their alloys makes up a significant portion of the fields of solid-state chemistry, physics, materials science and engineering.
Metallic solids are held together by a high density of shared, delocalized electrons, known as "metallic bonding". In a metal, atoms readily lose their outermost ("valence") electrons, forming positive ions. The free electrons are spread over the entire solid, which is held together firmly by electrostatic interactions between the ions and the electron cloud. The large number of free electrons gives metals their high values of electrical and thermal conductivity. The free electrons also prevent transmission of visible light, making metals opaque, shiny and lustrous.
More advanced models of metal properties consider the effect of the positive ions cores on the delocalised electrons. As most metals have crystalline structure, those ions are usually arranged into a periodic lattice. Mathematically, the potential of the ion cores can be treated by various models, the simplest being the nearly free electron model. | 0 | Theoretical and Fundamental Chemistry |
An adparticle is an atom, molecule, or cluster of atoms or molecules that lies on a crystal surface. The term is used in surface chemistry. The word is a contraction of "adsorbed particle". An adparticle that is a single atom may be referred to as an "adatom". | 0 | Theoretical and Fundamental Chemistry |
V. G. Khlopin’s work in this area concerns gas, volumetric, gravimetric and colorimetric analysis.
Gas analysis. V. G. Khlopin developed instruments for rapid assessment of the amount of helium and neon in gas mixtures (V. G. Khlopin, E. K. Gerling, 1932). These devices have simplified the analysis of noble gases so much that they have made it possible to include it in the general method of gas analysis.
Volumetric analysis. For the first time in the USSR, V. G. Khlopin introduced the method of differential reduction and differential oxidation with the simultaneous determination of several cations in a mixture (1922) and experimentally mastered the simultaneous determination of vanadium, iron and uranium - volumetric methods for the determination of vanadium and uranium were proposed.
Gravimetric analysis. V. G. Khlopin developed a quantitative method for separating tetravalent uranium in the form UFNHF/HO from hexavalent uranium and trivalent and divalent iron.
Colorimetric analysis. Scientists have proposed a method for determining small amounts of iridium in the presence of platinum.
Under the leadership of V.G. Khlopin, several methods of analysis were also developed: a volumetric method for determining small amounts of boron, a volumetric method for determining and , gravimetric methods for determining uranium, a colorimetric method for determining fluorine, and others. | 0 | Theoretical and Fundamental Chemistry |
There are many types of defects which result from many different causes. Some of the solutions to certain defects can be the cause for another type of defect.
The following defects can occur in sand castings. Most of these also occur in other casting processes. | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.