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Tholins were detected in situ by the Rosetta mission to comet 67P/Churyumov–Gerasimenko. Tholins are not typically characteristic of main-belt asteroids, but have been detected on the asteroid 24 Themis. | 0 | Theoretical and Fundamental Chemistry |
A potentiometric sensor is a type of chemical sensor that may be used to determine the analytical concentration of some components of the analyte gas or solution. These sensors measure the electrical potential of an electrode when no current is present. | 0 | Theoretical and Fundamental Chemistry |
Corrosion inhibitors are substances used in the oil industry to protect equipment and pipes against corrosion. Corrosion is a common problem in the oil industry due to the presence of water, gases, and other corrosive contaminants in the production environment.
Anodic inhibitors and cathodic inhibitors are the two main categories of corrosion inhibitors. While cathodic inhibitors act as catalysts to slow down corrosion, anodic inhibitors protect metal surfaces by acting as physical barriers. They can also be divided into organic and inorganic corrosion inhibitors based on their chemical composition.
Corrosion inhibitors are used in the petroleum industry in several steps, including drilling, production, transportation, and storage of oil and gas. They can mitigate different types of corrosion in the petroleum industry, such as generalized corrosion, pitting corrosion, erosion corrosion, stress corrosion, galvanic corrosion, cavitation corrosion, and hydrogen blister. | 0 | Theoretical and Fundamental Chemistry |
Initially, in a glutamatergic synapse, the neurotransmitter glutamate is released from the neurons and is taken up into the synaptic cleft. Glutamate residing in the synapse must be rapidly removed in one of three ways:
# Uptake into the postsynaptic compartment,
# Re-uptake into the presynaptic compartment, or
# Uptake into a third, nonneuronal compartment.
Postsynaptic neurons remove little glutamate from the synapse. There is active reuptake into presynaptic neurons, but this mechanism appears to be less important than astrocytic transport. Astrocytes could dispose of transported glutamate in two ways. They could export it to blood capillaries, which abut the astrocyte foot processes. However, this strategy would result in a net loss of carbon and nitrogen from the system. An alternate approach would be to convert glutamate into another compound, preferably a non-neuroactive species. The advantage of this approach is that neuronal glutamate could be restored without the risk of trafficking the transmitter through extracellular fluid, where glutamate would cause neuronal depolarization. Astrocytes readily convert glutamate to glutamine via the glutamine synthetase pathway and released into the extracellular space. The glutamine is taken into the presynaptic terminals and metabolized into glutamate by the phosphate-activated glutaminase (a mitochondrial enzyme). The glutamate that is synthesized in the presynaptic terminal is packaged into synaptic vesicles by the glutamate transporter, VGLUT. Once the vesicle is released, glutamate is removed from the synaptic cleft by excitatory amino-acid transporters (EAATs). This allows synaptic terminals and glial cells to work together to maintain a proper supply of glutamate, which can also be produced by transamination of 2-oxoglutarate, an intermediate in the citric acid cycle. Recent electrophysiological evidence suggests that active synapses require presynaptically localized glutamine glutamate cycle to maintain excitatory neurotransmission in specific circumstances. In other systems, it has been suggested that neurons have alternate mechanisms to cope with compromised glutamate–glutamine cycling. | 1 | Applied and Interdisciplinary Chemistry |
Gold(III) bromide can be used as a testing reagent for the presence of ketamine.
0.25% 0.1M NaOH is prepared to give a brownish-yellow solution. Two drops of this are added to a spotting plate and a small amount of ketamine is added. The mixture gives a deep purple color within approximately one minute, which turns to a dark, blackish-purple color within approximately two minutes.
Acetaminophen, ascorbic acid, heroin, lactose, mannitol, morphine, and sucrose all cause an instant colour change to purple, as do other compounds with phenol and hydroxyl groups.
Nothing commonly found in conjunction with ketamine gave the same colour change in the same time.
"The initial purple color may be due to the formation of a complex between the gold and the ketamine. The cause for the change of color from purple to dark blackish-purple is unknown; however, it may be due to a redox reaction that produces a small amount of colloidal gold." | 0 | Theoretical and Fundamental Chemistry |
Consider two stationary plane walls with a constant volume flow rate is injected/sucked at the point of intersection of plane walls and let the angle subtended by two walls be . Take the cylindrical coordinate system with representing point of intersection and the centerline and are the corresponding velocity components. The resulting flow is two-dimensional if the plates are infinitely long in the axial direction, or the plates are longer but finite, if one were neglect edge effects and for the same reason the flow can be assumed to be entirely radial i.e., .
Then the continuity equation and the incompressible Navier–Stokes equations reduce to
The boundary conditions are no-slip condition at both walls and the third condition is derived from the fact that the volume flux injected/sucked at the point of intersection is constant across a surface at any radius. | 1 | Applied and Interdisciplinary Chemistry |
NB: the above classification is very rough. Undular hydraulic jumps have been observed with inflow/prejump Froude numbers up to 3.5 to 4. | 1 | Applied and Interdisciplinary Chemistry |
The furanose ring is a cyclic hemiacetal of an aldopentose or a cyclic hemiketal of a ketohexose.
A furanose ring structure consists of four carbon and one oxygen atom with the anomeric carbon to the right of the oxygen. The highest numbered chiral carbon (typically to the left of the oxygen in a Haworth projection) determines whether or not the structure has a -configuration or -configuration. In an -configuration furanose, the substituent on the highest numbered chiral carbon is pointed downwards out of the plane, and in a -configuration furanose, the highest numbered chiral carbon is facing upwards.
The furanose ring will have either alpha or beta configuration, depending on which direction the anomeric hydroxy group is pointing. In a -configuration furanose, alpha configuration has the hydroxy pointing down, and beta has the hydroxy pointing up. It is the opposite in an -configuration furanose. Typically, the anomeric carbon undergoes mutarotation in solution, and the result is an equilibrium mixture of α and β configurations. | 0 | Theoretical and Fundamental Chemistry |
Most plant species studied to date are recognised to constitutively express paucimannosidic N-glycoproteins. The paucimannosidic N-glycoproteins are abundantly expressed in the vacuoles of plants such as the legume seeds of Lotus japonicus, the rice seeds and leaves of Oryza sativa. Literature has provided evidence for plant-specific paucimannosidic glycan structures modified with Xyl and Fuc. Such structures are found across the broad Streptophyta (land plants) and Chlorophyta (green algae) clade and in diatoms such as Phaeodactylum tricornutum. Less reported bixylosylated paucimannosidic glycans have also been documented. | 1 | Applied and Interdisciplinary Chemistry |
The term Reststrahlen was coined following the observation by Heinrich Rubens in 1898 that repeated reflection of an infrared beam at the surface of a given material suppresses radiation at all wavelengths except for certain spectral intervals, and Rubens detected wavelengths of sizes around 60 μm. The measured intensity for these special intervals (the Reststrahlen range) indicates a reflectance of up to 80% or even more, while the maximum reflectance due to infrared bands of dielectric materials are usually compared to the intensity of the incident radiation, while the light in the Reststrahlen range can maintain 40% of its original intensity by the time it reaches the detector. Obviously, this contrast increases with the number of reflections and explains the observation made by Rubens and the term Reststrahlen (residual rays) used to describe this spectral selection.
Reststrahlen bands manifest in diffuse reflectance infrared absorption spectra as complete band reversal, or in infrared emission spectra as a minimum in emissivity. | 0 | Theoretical and Fundamental Chemistry |
Lactones are cyclic carboxylic esters are intramolecular esters derived from hydroxy carboxylic acids. They can be saturated or unsaturated. Some contain heteroatoms replacing one or more carbon atoms of the ring.
Lactones are formed by intramolecular esterification of the corresponding hydroxycarboxylic acids, which takes place spontaneously when the ring that is formed is five- or six-membered. Lactones with three- or four-membered rings (α-lactones and β-lactones) are very reactive, making their isolation difficult. Special methods are normally required for the laboratory synthesis of small-ring lactones as well as those that contain rings larger than six-membered. | 0 | Theoretical and Fundamental Chemistry |
In eukaryotes, ribosomal rRNA and the tRNAs involved in translation are controlled by RNA polymerase I (Pol I) and RNA polymerase III (Pol III) . RNA Polymerase II (Pol II) is responsible for the production of messenger RNA (mRNA) within the cell. Particularly for Pol II, much of the regulatory checkpoints in the transcription process occur in the assembly and escape of the pre-initiation complex. A gene-specific combination of transcription factors will recruit TFIID and/or TFIIA to the core promoter, followed by the association of TFIIB, creating a stable complex onto which the rest of the General Transcription Factors (GTFs) can assemble. This complex is relatively stable, and can undergo multiple rounds of transcription initiation.
After the binding of TFIIB and TFIID, Pol II the rest of the GTFs can assemble. This assembly is marked by the post-translational modification (typically phosphorylation) of the C-terminal domain (CTD) of Pol II through a number of kinases. The CTD is a large, unstructured domain extending from the RbpI subunit of Pol II, and consists of many repeats of the heptad sequence YSPTSPS. TFIIH, the helicase that remains associated with Pol II throughout transcription, also contains a subunit with kinase activity which will phosphorylate the serines 5 in the heptad sequence. Similarly, both CDK8 (a subunit of the massive multiprotein Mediator complex) and CDK9 (a subunit of the p-TEFb elongation factor), have kinase activity towards other residues on the CTD. These phosphorylation events promote the transcription process and serve as sites of recruitment for mRNA processing machinery. All three of these kinases respond to upstream signals, and failure to phosphorylate the CTD can lead to a stalled polymerase at the promoter. | 1 | Applied and Interdisciplinary Chemistry |
Suppressor of cytokine signaling 1 is a protein that in humans is encoded by the SOCS1 gene. SOCS1 orthologs have been identified in several mammals for which complete genome data are available. | 1 | Applied and Interdisciplinary Chemistry |
The second most studied triad is the Cysteine-Histidine-Aspartate motif. Several families of cysteine proteases use this triad set, for example TEV protease and papain. The triad acts similarly to serine protease triads, with a few notable differences. Due to cysteines low pK, the importance of the Asp to catalysis varies and several cysteine proteases are effectively Cys-His dyads (e.g. hepatitis A virus protease), whilst in others the cysteine is already deprotonated before catalysis begins (e.g. papain). This triad is also used by some amidases, such as N'-glycanase to hydrolyse non-peptide C-N bonds. | 1 | Applied and Interdisciplinary Chemistry |
The John J. Abel Award is an annual award presented by the American Society for Pharmacology and Experimental Therapeutics (ASPET). The award is given for outstanding research in the field of pharmacology and/or experimental therapeutics; which comes with a $5000 prize, An engraved plaque, and all travel expenses paid to attend the ASPET Annual Meeting at Experimental Biology. The Award is named after American biochemist and pharmacologist, John Jacob Abel. | 1 | Applied and Interdisciplinary Chemistry |
Life in sea ice is energetically demanding, and sets limits at any hierarchical, organizational, and organismic level, ranging from molecules to everything that an organism does. Despite this fact, the brine-containing interstices and pockets found in sea ice host a variety of organisms, including bacteria, autotrophic and heterotrophic protists, microalgae, and metazoa. | 0 | Theoretical and Fundamental Chemistry |
Caused by different structural modifications in the genome, fusion genes have gained attention because of their relationship with cancer. The ability of RNA-Seq to analyze a sample's whole transcriptome in an unbiased fashion makes it an attractive tool to find these kinds of common events in cancer.
The idea follows from the process of aligning the short transcriptomic reads to a reference genome. Most of the short reads will fall within one complete exon, and a smaller but still large set would be expected to map to known exon-exon junctions. The remaining unmapped short reads would then be further analyzed to determine whether they match an exon-exon junction where the exons come from different genes. This would be evidence of a possible fusion event, however, because of the length of the reads, this could prove to be very noisy. An alternative approach is to use paired-end reads, when a potentially large number of paired reads would map each end to a different exon, giving better coverage of these events (see figure). Nonetheless, the end result consists of multiple and potentially novel combinations of genes providing an ideal starting point for further validation. | 1 | Applied and Interdisciplinary Chemistry |
An alternative classification with broader scope is suggested by Yujiro Hayashi as he describes certain organocatalytic Aldol reactions as taking place in the presence of water. The observed effect in these reactions is not rate acceleration (that would be on water), but an increase in enantioselectivity.
In the context of organocatalysis, both concepts of on-water reactions and in-the-presence-of-water reactions were criticized in 2007 as not so environmentally friendly by Donna Blackmond. According to Blackmond, separation of reaction product from the water phase usually requires organic solvent anyway, and in reported aqueous systems the water phase can in reality be less than 10% of the total reaction mixture with another component forming the actual solvent. Blackmond also notes that in reported instances, the observed rate-acceleration in presence of water is due to water suppressing reaction deactivation. | 0 | Theoretical and Fundamental Chemistry |
Because they form a strong electrophile when treated with Lewis acids, acyl halides are commonly used as acylating agents. For example, Friedel–Crafts acylation uses acetyl chloride () as the agent and aluminum chloride () as a catalyst to add an acetyl group to benzene:
This reaction is an example of electrophilic aromatic substitution.
Acyl halides and acid anhydrides of carboxylic acids are also common acylating agents. In some cases, active esters exhibit comparable reactivity. All react with amines to form amides and with alcohols to form esters by nucleophilic acyl substitution.
Acylation can be used to prevent rearrangement reactions that would normally occur in alkylation. To do this an acylation reaction is performed, then the carbonyl is removed by Clemmensen reduction or a similar process. | 0 | Theoretical and Fundamental Chemistry |
* EAS Award for Outstanding Achievements in the Fields of Analytical Chemistry (2023)
* Martin Medal (2019)
* Ralph N. Adams Award in Bioanalyical Chemistry (2016)
* ACS Award in Chromatography (2017)
* CASSS Award for Outstanding Achievements in Separation Science (2017)
* Marcel Golay Award for Lifetime Achievement in Capillary Chromatography (2012)
* Eastern Analytical Symposium Award for Separation Science (2012)
* McKnight Award for Technical Innovations in Neuroscience (2010)
* Rackham Distinguished Faculty Achievement Award (2009)
* American Microchemical Society’s Benedetti-Pichler Memorial Award (2001) | 0 | Theoretical and Fundamental Chemistry |
Gamma rays are produced during gamma decay, which normally occurs after other forms of decay occur, such as alpha or beta decay. A radioactive nucleus can decay by the emission of an alpha particle| or beta particle| particle. The daughter nucleus that results is usually left in an excited state. It can then decay to a lower energy state by emitting a gamma ray photon, in a process called gamma decay.
The emission of a gamma ray from an excited nucleus typically requires only 10 seconds. Gamma decay may also follow nuclear reactions such as neutron capture, nuclear fission, or nuclear fusion. Gamma decay is also a mode of relaxation of many excited states of atomic nuclei following other types of radioactive decay, such as beta decay, so long as these states possess the necessary component of nuclear spin. When high-energy gamma rays, electrons, or protons bombard materials, the excited atoms emit characteristic "secondary" gamma rays, which are products of the creation of excited nuclear states in the bombarded atoms. Such transitions, a form of nuclear gamma fluorescence, form a topic in nuclear physics called gamma spectroscopy. Formation of fluorescent gamma rays are a rapid subtype of radioactive gamma decay.
In certain cases, the excited nuclear state that follows the emission of a beta particle or other type of excitation, may be more stable than average, and is termed a metastable excited state, if its decay takes (at least) 100 to 1000 times longer than the average 10 seconds. Such relatively long-lived excited nuclei are termed nuclear isomers, and their decays are termed isomeric transitions. Such nuclei have half-lifes that are more easily measurable, and rare nuclear isomers are able to stay in their excited state for minutes, hours, days, or occasionally far longer, before emitting a gamma ray. The process of isomeric transition is therefore similar to any gamma emission, but differs in that it involves the intermediate metastable excited state(s) of the nuclei. Metastable states are often characterized by high nuclear spin, requiring a change in spin of several units or more with gamma decay, instead of a single unit transition that occurs in only 10 seconds. The rate of gamma decay is also slowed when the energy of excitation of the nucleus is small.
An emitted gamma ray from any type of excited state may transfer its energy directly to any electrons, but most probably to one of the K shell electrons of the atom, causing it to be ejected from that atom, in a process generally termed the photoelectric effect (external gamma rays and ultraviolet rays may also cause this effect). The photoelectric effect should not be confused with the internal conversion process, in which a gamma ray photon is not produced as an intermediate particle (rather, a "virtual gamma ray" may be thought to mediate the process). | 0 | Theoretical and Fundamental Chemistry |
Making a distinction between homogeneous and heterogeneous mixtures is a matter of the scale of sampling. On a coarse enough scale, any mixture can be said to be homogeneous, if the entire article is allowed to count as a "sample" of it. On a fine enough scale, any mixture can be said to be heterogeneous, because a sample could be as small as a single molecule. In practical terms, if the property of interest of the mixture is the same regardless of which sample of it is taken for the examination used, the mixture is homogeneous.
Gy's sampling theory quantitatively defines the heterogeneity of a particle as:
where , , , , and are respectively: the heterogeneity of the th particle of the population, the mass concentration of the property of interest in the th particle of the population, the mass concentration of the property of interest in the population, the mass of the th particle in the population, and the average mass of a particle in the population.
During sampling of heterogeneous mixtures of particles, the variance of the sampling error is generally non-zero.
Pierre Gy derived, from the Poisson sampling model, the following formula for the variance of the sampling error in the mass concentration in a sample:
in which V is the variance of the sampling error, N is the number of particles in the population (before the sample was taken), q is the probability of including the ith particle of the population in the sample (i.e. the first-order inclusion probability of the ith particle), m is the mass of the ith particle of the population and a is the mass concentration of the property of interest in the ith particle of the population.
The above equation for the variance of the sampling error is an approximation based on a linearization of the mass concentration in a sample.
In the theory of Gy, correct sampling is defined as a sampling scenario in which all particles have the same probability of being included in the sample. This implies that q no longer depends on i, and can therefore be replaced by the symbol q. Gy's equation for the variance of the sampling error becomes:
where a is that concentration of the property of interest in the population from which the sample is to be drawn and M is the mass of the population from which the sample is to be drawn. | 0 | Theoretical and Fundamental Chemistry |
There are three processes for metallic pipe manufacture. Centrifugal casting of hot alloyed metal is one of the most prominent process. Ductile iron pipes are generally manufactured in such a fashion.
Seamless pipe (SMLS) is formed by drawing a solid billet over a piercing rod to create the hollow shell in a process called rotary piercing. As the manufacturing process does not include any welding, seamless pipes are perceived to be stronger and more reliable. Historically, seamless pipe was regarded as withstanding pressure better than other types, and was often more available than welded pipe.
Advances since the 1970s, in materials, process control, and non-destructive testing, allow correctly specified welded pipe to replace seamless in many applications. Welded pipe is formed by rolling plate and welding the seam (usually by Electric resistance welding ("ERW"), or Electric Fusion Welding ("EFW")). The weld flash can be removed from both inner and outer surfaces using a scarfing blade. The weld zone can also be heat-treated to make the seam less visible. Welded pipe often has tighter dimensional tolerances than the seamless type, and can be cheaper to manufacture.
There are a number of processes that may be used to produce ERW pipes. Each of these processes leads to coalescence or merging of steel components into pipes. Electric current is passed through the surfaces that have to be welded together; as the components being welded together resist the electric current, heat is generated which forms the weld. Pools of molten metal are formed where the two surfaces are connected as a strong electric current is passed through the metal; these pools of molten metal form the weld that binds the two abutted components.
ERW pipes are manufactured from the longitudinal welding of steel. The welding process for ERW pipes is continuous, as opposed to welding of distinct sections at intervals. ERW process uses steel coil as feedstock.
The High Frequency Induction Technology (HFI) welding process is used for manufacturing ERW pipes. In this process, the current to weld the pipe is applied by means of an induction coil around the tube. HFI is generally considered to be technically superior to "ordinary" ERW when manufacturing pipes for critical applications, such as for usage in the energy sector, in addition to other uses in line pipe applications, as well as for casing and tubing.
Large-diameter pipe ( or greater) may be ERW, EFW, or Submerged Arc Welded ("SAW") pipe. There are two technologies that can be used to manufacture steel pipes of sizes larger than the steel pipes that can be produced by seamless and ERW processes. The two types of pipes produced through these technologies are longitudinal-submerged arc-welded (LSAW) and spiral-submerged arc-welded (SSAW) pipes. LSAW are made by bending and welding wide steel plates and most commonly used in oil and gas industry applications. Due to their high cost, LSAW pipes are seldom used in lower value non-energy applications such as water pipelines. SSAW pipes are produced by spiral (helicoidal) welding of steel coil and have a cost advantage over LSAW pipes, as the process uses coils rather than steel plates. As such, in applications where spiral-weld is acceptable, SSAW pipes may be preferred over LSAW pipes. Both LSAW pipes and SSAW pipes compete against ERW pipes and seamless pipes in the diameter ranges of 16”-24”.
Tubing for flow, either metal or plastic, is generally extruded. | 1 | Applied and Interdisciplinary Chemistry |
Biological crosstalk refers to instances in which one or more components of one signal transduction pathway affects another. This can be achieved through a number of ways with the most common form being crosstalk between proteins of signaling cascades. In these signal transduction pathways, there are often shared components that can interact with either pathway. A more complex instance of crosstalk can be observed with transmembrane crosstalk between the extracellular matrix (ECM) and the cytoskeleton. | 1 | Applied and Interdisciplinary Chemistry |
Silicate, or silicic acid (HSiO), is an important nutrient in the ocean. Unlike the other major nutrients such as phosphate, nitrate, or ammonium, which are needed by almost all marine plankton, silicate is an essential chemical requirement for very specific biota, including diatoms, radiolaria, silicoflagellates, and siliceous sponges. These organisms extract dissolved silicate from open ocean surface waters for the buildup of their particulate silica (SiO), or opaline, skeletal structures (i.e. the biota's hard parts). Some of the most common siliceous structures observed at the cell surface of silica-secreting organisms include: spicules, scales, solid plates, granules, frustules, and other elaborate geometric forms, depending on the species considered. | 1 | Applied and Interdisciplinary Chemistry |
Because of the small size of the fluidic conduits, nanofluidic structures are naturally applied in situations demanding that samples be handled in exceedingly small quantities, including Coulter counting,
analytical separations and determinations of biomolecules, such as proteins and DNA,
and facile handling of mass-limited samples. One of the more promising areas of nanofluidics is its potential for integration into microfluidic systems, i.e. micrototal analytical systems or lab-on-a-chip structures. For instance, NCAMs, when incorporated into microfluidic devices, can reproducibly perform digital switching, allowing transfer of fluid from one microfluidic channel to another,
selectivity separate and transfer analytes by size and mass,
mix reactants efficiently,
and separate fluids with disparate characteristics.
In addition, there is a natural analogy between the fluid handling capabilities of nanofluidic structures and the ability of electronic components to control the flow of electrons and holes. This analogy has been used to realize active electronic functions such as rectification
and field-effect
and bipolar transistor
action with ionic currents. Application of nanofluidics is also to nano-optics for producing tuneable microlens array
Nanofluidics have had a significant impact in biotechnology, medicine and clinical diagnostics with the development of lab-on-a-chip devices for PCR and related techniques. Attempts have been made to understand the behaviour of flowfields around nanoparticles in terms of fluid forces as a function of Reynolds and Knudsen number using computational fluid dynamics. The relationship between lift, drag and Reynolds number has been shown to differ dramatically at the nanoscale compared with macroscale fluid dynamics. | 0 | Theoretical and Fundamental Chemistry |
An experiment observing chilling stress on the tropical plant species, Spathiphyllum wallisii by scientists Maria Segura and Maria Quiles, showcased varying responses by chlororespiratory pathways when different parts of the plant were chilled at 10 degrees Celsius.
Segura and Quiles noticed that when the roots of the plant were subjected to low temperatures (10 degrees Celsius), the level of chlororespiratory molecules (NADPH and PTOX) slightly varied when compared to the level of NADPH and PTOX within the controlled plant. However, when the stem alone was cooled at 10 degrees Celsius, then the molecules NADPH, NDH and PTOX increased in amount as a result of reduced PS I activity. Segura and Quiles then compared this result, by subjecting only the leaves of the plant to 10 degrees Celsius. They noticed that this had caused the PS II activity to stop, and thus inhibit the process of photosynthesis. The lack in photosynthetic activity, in combination with the incline in NADPH and PTOX molecules, then triggered chlororespiratory pathways to begin chemical energy synthesis.
Furthermore, Segura and Quiles also noted that the simultaneous chilling of the leaves and heating of the roots (whilst the plant is under illumination), can cause the slowing and eventual inhibition of the ETC in PS II. This then led to an over-reduction in the PQ pool., which ultimately stimulated chlororespiration.
Segura and Quiles utilised the Fluorescence imaging technique to determine the level of photosynthetic activity in the leaves of the plants. By discerning the percentage of photosynthesis efficiency, Segura and Quiles were able to determine the likelihood of triggering chlororespiratory pathways. They noticed that the percentage of photosynthesis efficiency remained high in test subjects where:
* only the leaves were chilled
* only the stem was chilled
* only the roots were chilled
This high percentage of photosynthesis efficiency meant that the chances of chlororespiration taking place are slim. However, this was not true for the plant that underwent both stem chilling at 10 degrees Celsius and root heating at 24 degrees Celsius. The photosynthesis efficiency of this test subject was significantly lower when compared to the experimental control. This also indicated the inhibition of PS II activity which then caused chlororespiration to begin.
Segura and Quiles also used an immunoblot analysis to deduce the effect of varying temperatures on different parts of the plant. Specifically, the immunoblot measures the amount of PTOX and NDH complex accumulated within the thylakoid membrane of the chloroplast organelle. An increase in NDH complex was evident in the plant where the stem was chilled at 10 degrees Celsius and the root heated at 24 degrees Celsius. Chlororespiration was stimulated in this plant. Dissimilarly, the immunoblot analysis detected no variation in the levels NDH complex and PTOX molecules in test subjects where:
* only the leaves were chilled
* only the stem was chilled
* only the roots were chilled
These test subjects had similar concentrations of NDH and PTOX when compared to the concentration of NDH complex and PTOX molecules within the experimental control. | 1 | Applied and Interdisciplinary Chemistry |
Rudd serves as an associate of the Anglican Church at the Community of St Mary the Virgin in Wantage, Oxfordshire. She took a fifteen-year career break to raise her four children. | 1 | Applied and Interdisciplinary Chemistry |
The third line shape that has a theoretical basis is the Voigt function, a convolution of a Gaussian and a Lorentzian,
where σ and γ are half-widths. The computation of a Voigt function and its derivatives are more complicated than a Gaussian or Lorentzian. | 0 | Theoretical and Fundamental Chemistry |
In epigenetics, a paramutation is an interaction between two alleles at a single locus, whereby one allele induces a heritable change in the other allele. The change may be in the pattern of DNA methylation or histone modifications. The allele inducing the change is said to be paramutagenic, while the allele that has been epigenetically altered is termed paramutable. A paramutable allele may have altered levels of gene expression, which may continue in offspring which inherit that allele, even though the paramutagenic allele may no longer be present. Through proper breeding, paramutation can result in siblings that have the same genetic sequence, but with drastically different phenotypes.
Though studied primarily in maize, paramutation has been described in a number of other systems, including animal systems like Drosophila melanogaster and mice. Despite its broad distribution, examples of this phenomenon are scarce and its mechanism is not fully understood. | 1 | Applied and Interdisciplinary Chemistry |
Titration (also known as titrimetry and volumetric analysis) is a common laboratory method of quantitative chemical analysis to determine the concentration of an identified analyte (a substance to be analyzed). A reagent, termed the titrant or titrator, is prepared as a standard solution of known concentration and volume. The titrant reacts with a solution of analyte (which may also be termed the titrand) to determine the analytes concentration. The volume of titrant that reacted with the analyte is termed the titration volume'. | 0 | Theoretical and Fundamental Chemistry |
Jones was honoured with a stone grotesque in the Great Court of the University of Queensland placed on the Forgan Smith building. An annual lecture is presented in his name at the University of Queensland in the School of Chemistry of Molecular Biosciences. | 0 | Theoretical and Fundamental Chemistry |
Permeable pavements enable greater retention of water in city environments, which are at greater risk for high temperatures due to the heat island effect. Similar to green roofs, permeable paving keeps water within the local microecosystem, which in turn keeps temperatures cooler when compared to a non-permeable paving system. | 1 | Applied and Interdisciplinary Chemistry |
As far as we can tell, oxygenic photosynthesis only evolved once (in prokaryotic cyanobacteria), and all photosynthetic eukaryotes (including all plants and algae) have acquired this ability from them. In other words, all the oxygen that makes the atmosphere breathable for aerobic organisms originally comes from cyanobacteria or their later descendants.
Cyanobacteria remained the principal primary producers throughout the Proterozoic Eon (2500–543 Ma), in part because the redox structure of the oceans favored photoautotrophs capable of nitrogen fixation. However, their population is argued to have varied considerably across this eon. Green algae joined blue-greens as major primary producers on continental shelves near the end of the Proterozoic, but only with the Mesozoic (251–65 Ma) radiations of dinoflagellates, coccolithophorids, and diatoms did primary production in marine shelf waters take modern form. Cyanobacteria remain critical to marine ecosystems as primary producers in oceanic gyres, as agents of biological nitrogen fixation, and, in modified form, as the plastids of marine eukaryotic algae. | 0 | Theoretical and Fundamental Chemistry |
The properties of many polymers are affected by hydrogen bonds within and/or between the chains. Prominent examples include cellulose and its derived fibers, such as cotton and flax. In nylon, hydrogen bonds between carbonyl and the amide NH effectively link adjacent chains, which gives the material mechanical strength. Hydrogen bonds also affect the aramid fibre, where hydrogen bonds stabilize the linear chains laterally. The chain axes are aligned along the fibre axis, making the fibres extremely stiff and strong. Hydrogen-bond networks make both polymers sensitive to humidity levels in the atmosphere because water molecules can diffuse into the surface and disrupt the network. Some polymers are more sensitive than others. Thus nylons are more sensitive than aramids, and nylon 6 more sensitive than nylon-11. | 0 | Theoretical and Fundamental Chemistry |
Christopher Bruce Murray is the Richard Perry University Professor of Chemistry and Materials Science and Engineering at the University of Pennsylvania. He is a member of the National Academy of Engineering and a Fellow of the Materials Research Society. He was a Clarivate Citation Laureate in 2020. He is known for his contributions to quantum dots and other nanoscale materials. | 0 | Theoretical and Fundamental Chemistry |
Making the connections stiffer and stronger than the strut members means that stress response is governed by the struts. Extending dimensional scaling methods to include the connections shows that the mass density cost of robust connections – which scale with the strut's cross-sectional area – is low for ultralight materials, where strut diameter dominates mass density scaling. The relative density (ρ/ρs) of these materials is the sum of the relative density contribution of the strut members (ρm/ρs) and the relative density contribution of the connections (ρc/ρs). The strut members have a thickness t and length L. The connections transfer forces through load-bearing surface contacts, requiring that the characteristic dimensions of the connections scale with the cross section of the attached strut members, t2, because this dimension determines the maximum stress transferable through the joint.
These definitions give a cubic scaling relation between the relative mass contribution of the joints and the struts thickness-to-length ratio (ρc/ρs ∝ Cc(t/L)3, where Cc is the connection contribution constant determined by the lattice geometry). The struts relative density contribution scales quadratically with the thickness-to-length ratio of the struts (ρm/ρs ∝ Cm (t/L)2), which agrees with the literature on classical cellular materials. Mechanical properties (such as modulus and strength) scale with overall relative density, which in turn scales primarily with the strut and not the connection, considering only open cell lattices with slender struts [t/L < 0.1 (7)], given that the geometric constants Cc and Cm are of the same order of magnitude [ρ/ρs ∝ Cc (t/L)3 + Cm (t/L)2]. The density cost of the mechanical joints decreases with increasing strut member slenderness (decreasing t/L) and decreasing relative density.
Tiling the cross-shaped parts forms the lattice structure. Each part contributes four conjoined strut members to one locally central node and one strut to four peripheral nodes. A shear clip inserted through the four coincident connection holes links the cells.
Each cell includes aligned fiber composite beams and looped fiber load-bearing holes that reversibly chain together to form volume-filling lattices. Mass-produced cells can be assembled to fill arbitrary structural shapes, with a resolution prescribed by the part scale that matches the variability of an application's boundary stress. The periodic nature of assemblies simplifies behavior analysis and prediction. | 0 | Theoretical and Fundamental Chemistry |
The Société Coloniale des Chaux et Ciments de Portland de Marseille (Colonial Company for Lime and Portland Cements in Marseille) owned and operated cement works in L'Estaque near Marseille in the department of Bouches-du-Rhône. | 1 | Applied and Interdisciplinary Chemistry |
The lactate shuttle hypothesis describes the movement of lactate intracellularly (within a cell) and intercellularly (between cells). The hypothesis is based on the observation that lactate is formed and utilized continuously in diverse cells under both anaerobic and aerobic conditions. Further, lactate produced at sites with high rates of glycolysis and glycogenolysis can be shuttled to adjacent or remote sites including heart or skeletal muscles where the lactate can be used as a gluconeogenic precursor or substrate for oxidation. The hypothesis was proposed by professor George Brooks of the University of California at Berkeley.
In addition to its role as a fuel source predominantly in the muscles, heart, brain, and liver, the lactate shuttle hypothesis also relates the role of lactate in redox signalling, gene expression, and lipolytic control. These additional roles of lactate have given rise to the term ‘lactormone’, pertaining to the role of lactate as a signalling hormone. | 1 | Applied and Interdisciplinary Chemistry |
Here, the OAA produced by PEPC is transaminated by aspartate aminotransferase to aspartate (ASP) which is the metabolite diffusing to the bundle sheath. In the bundle sheath ASP is transaminated again to OAA and then undergoes a futile reduction and oxidative decarboxylation to release . The resulting Pyruvate is transaminated to alanine, diffusing to the mesophyll. Alanine is finally transaminated to pyruvate (PYR) which can be regenerated to PEP by PPDK in the mesophyll chloroplasts. This cycle bypasses the reaction of malate dehydrogenase in the mesophyll and therefore does not transfer reducing equivalents to the bundle sheath. | 0 | Theoretical and Fundamental Chemistry |
Some debate exists surrounding the exact cause of whiting events. And although much research exists on the subject, there is still no definitive consensus on the chemical mechanisms behind it. The three most common suggested causes for the phenomenon are: microbiological processes, re-suspension of marine or bottom sediments, and spontaneous direct precipitation from water. Of these three, the last has been ruled unlikely due to the unfavorable reaction kinetics of spontaneous calcium carbonate precipitation. It is also worth noting that it may be possible for more than one of the aforementioned factors to contribute to whiting events in the same region. | 0 | Theoretical and Fundamental Chemistry |
Raphaël Horace Dubois (20 June 1849, Le Mans – 21 January 1929) was a French pharmacologist known for his work on bioluminescence and anesthesia. He coined the terms proteon and bioproteon, from the Greek "proteon" for matter and "bios" for life. Bioproteon means "living matter". He concluded that there was no difference between matter and living matter.
Dubois bioluminescence work began when he became a research assistant to Paul Bert in 1882. While initially planning to study the effects of anesthesia on mollusks, witnessing the bioluminescence of Pyrophorus noctilucus inspired him to study the beetle more in depth. Dubois discovered that not only do the adults glow, but so do the unfertilized eggs, embryo, and larvae. Dubois later conducted studies on Scolioplanes crassipes, wherein Dubois discovered the source of its luminescence is in cells of the wall of the gut. Dubois published a paper studying the light production of Pholas dactylus' in 1887, in which he coined the terms luciferin and luciferase. | 1 | Applied and Interdisciplinary Chemistry |
Kerker was born on September 25, 1920, in Utica, New York. He received his A.B. in chemistry from Columbia University in 1941. From 1942 to 1945, he was a member of United States Army and received Bronze Star Medal for his service. He married his wife, Reva Stemerman, in 1946. Graduating from Columbia University with a PhD in chemistry in 1949, he joined Clarkson University as a professor in the same year. He acted as the chair of the department of chemistry from 1960 to 1964, as well as the dean of science from 1964 to 1966 and from 1981 to 1985. He retired from Clarkson University in 1991. Serving as the editor of Journal of Colloid and Interface Science from 1965 to 1992, he was also granted fellowships by Optical Society, American Chemical Society and Ford Foundation. Kerker died on May 2, 2016, in Thousand Oaks, California, U.S., and was survived by his wife and four children. He was a contributor to Midstream magazine and Jewish Theological Seminary of America, as well as Isis journal.
Kerkers work encompassed aerosol and colloid science, as well as their relation to light scattering by small particles. He is known for authoring the 1969 textbook on the subject, The Scattering of Light and Other Electromagnetic Radiation'. Regarded as a pioneer of surface-enhanced Raman spectroscopy (SERS), he has worked on the mathematical models in the field. In 1986, Kerker also coauthored the article on light scattering by hypothetical magnetic spheres, which hypothesized a distinct absence of backscattering for small particles with equal relative permittivities and permeabilities. While being largely unnoticed at the time of its publication, the work has since attracted attention with the advent of metamaterials and nanophotonics; the associated phenomenon, named as Kerker effect, was later verified experimentally. | 0 | Theoretical and Fundamental Chemistry |
Benzyl carbamate is the organic compound with the formula CHCHOC(O)NH. The compound can be viewed as the ester of carbamic acid (O=C(OH)(NH)) and benzyl alcohol, although it is produced from benzyl chloroformate with ammonia. It is a white solid that is soluble in organic solvents and moderately soluble in water. Benzyl carbamate is used as a protected form of ammonia in the synthesis of primary amines. After N-alkylation, CHCHOC(O) group is removable with Lewis acids. | 0 | Theoretical and Fundamental Chemistry |
Another major use of -ascorbic acid is as a dietary supplement. It is on the World Health Organization's List of Essential Medicines. | 1 | Applied and Interdisciplinary Chemistry |
In recent years, pheromone traps also partook in the digital transformation in agriculture, and agritech companies introduced digital pheromone traps. Also known as Pest Traps, digital pheromone traps are IoT devices that include systems to detect and identify pests in the field. Their main goal is to notice pests and manage pesticide spraying. They involve sticky papers, in-built cameras, and various software systems that enable pest detection and identification. Some pheromone traps such as [https://doktar.com Doktar]'s [https://www.doktar.com/en/pheromone-trap PestTrapp], utilize machine learning technologies to automatize the detection process for farmers and agricultural busines<nowiki/>ses. Smart farming practices have adapted using Digital Pest Traps as financially beneficial and environmentally friendly tools. | 1 | Applied and Interdisciplinary Chemistry |
Many of the noble metals can act as catalysts. For example, platinum is used in catalytic converters, devices which convert toxic gases produced in car engines, such as the oxides of nitrogen, into non-polluting substances.
Gold has many industrial applications; it is used as a catalyst in hydrogenation and the water gas shift reaction. | 1 | Applied and Interdisciplinary Chemistry |
Soddy and Kasimir Fajans independently observed in 1913 that alpha decay caused atoms to shift down two places in the periodic table, while the loss of two beta particles restored it to its original position. In the resulting reorganisation of the periodic table, radium was placed in group II, actinium in group III, thorium in group IV and uranium in group VI. This left a gap between thorium and uranium. Soddy predicted that this unknown element, which he referred to (after Dmitri Mendeleev) as "ekatantalium", would be an alpha emitter with chemical properties similar to tantalium (now known as tantalum). It was not long before Fajans and Oswald Helmuth Göhring discovered it as a decay product of a beta-emitting product of thorium. Based on the radioactive displacement law of Fajans and Soddy, this was an isotope of the missing element, which they named "brevium" after its short half-life. However, it was a beta emitter, and therefore could not be the mother isotope of actinium. This had to be another isotope.
Two scientists at the Kaiser Wilhelm Institute (KWI) in Berlin-Dahlem took up the challenge of finding the missing isotope. Otto Hahn had graduated from the University of Marburg as an organic chemist, but had been a post-doctoral researcher at University College London under Sir William Ramsay, and under Rutherford at McGill University, where he had studied radioactive isotopes. In 1906, he returned to Germany, where he became an assistant to Emil Fischer at the University of Berlin. At McGill he had become accustomed to working closely with a physicist, so he teamed up with Lise Meitner, who had received her doctorate from the University of Vienna in 1906, and had then moved to Berlin to study physics under Max Planck at the Friedrich-Wilhelms-Universität. Meitner found Hahn, who was her own age, less intimidating than older, more distinguished colleagues. Hahn and Meitner moved to the recently established Kaiser Wilhelm Institute for Chemistry in 1913, and by 1920 had become the heads of their own laboratories there, with their own students, research programs and equipment. The new laboratories offered new opportunities, as the old ones had become too contaminated with radioactive substances to investigate feebly radioactive substances. They developed a new technique for separating the tantalum group from pitchblende, which they hoped would speed the isolation of the new isotope.
The work was interrupted by the outbreak of the First World War in 1914. Hahn was called up into the German Army, and Meitner became a volunteer radiographer in Austrian Army hospitals. She returned to the Kaiser Wilhelm Institute in October 1916. Hahn joined the new gas command unit at Imperial Headquarters in Berlin in December 1916 after travelling between the western and eastern fronts, Berlin and Leverkusen between the summer of 1914 and late 1916.
Most of the students, laboratory assistants and technicians had been called up, so Hahn, who was stationed in Berlin between January and September 1917, and Meitner had to do everything themselves. By December 1917 she was able to isolate the substance, and after further work were able to prove that it was indeed the missing isotope. Meitner submitted her and Hahns findings for publication in March 1918 to the scientific paper Physikalischen Zeitschrift' under the title .
Although Fajans and Göhring had been the first to discover the element, custom required that an element was represented by its longest-lived and most abundant isotope, and brevium did not seem appropriate. Fajans agreed to Meitner and Hahn naming the element protactinium, and assigning it the chemical symbol Pa. In June 1918, Soddy and John Cranston announced that they had extracted a sample of the isotope, but unlike Hahn and Meitner were unable to describe its characteristics. They acknowledged Hahns and Meitners priority, and agreed to the name. The connection to uranium remained a mystery, as neither of the known isotopes of uranium decayed into protactinium. It remained unsolved until uranium-235 was discovered in 1929.
For their discovery Hahn and Meitner were repeatedly nominated for the Nobel Prize in Chemistry in the 1920s by several scientists, among them Max Planck, Heinrich Goldschmidt, and Fajans himself. In 1949, the International Union of Pure and Applied Chemistry (IUPAC) named the new element definitively protactinium, and confirmed Hahn and Meitner as discoverers. | 0 | Theoretical and Fundamental Chemistry |
A neutral atom has the same number of electrons as protons. Thus different isotopes of a given element all have the same number of electrons and share a similar electronic structure. Because the chemical behavior of an atom is largely determined by its electronic structure, different isotopes exhibit nearly identical chemical behavior.
The main exception to this is the kinetic isotope effect: due to their larger masses, heavier isotopes tend to react somewhat more slowly than lighter isotopes of the same element. This is most pronounced by far for protium (), deuterium (), and tritium (), because deuterium has twice the mass of protium and tritium has three times the mass of protium. These mass differences also affect the behavior of their respective chemical bonds, by changing the center of gravity (reduced mass) of the atomic systems. However, for heavier elements, the relative mass difference between isotopes is much less so that the mass-difference effects on chemistry are usually negligible. (Heavy elements also have relatively more neutrons than lighter elements, so the ratio of the nuclear mass to the collective electronic mass is slightly greater.) There is also an equilibrium isotope effect.
Similarly, two molecules that differ only in the isotopes of their atoms (isotopologues) have identical electronic structures, and therefore almost indistinguishable physical and chemical properties (again with deuterium and tritium being the primary exceptions). The vibrational modes of a molecule are determined by its shape and by the masses of its constituent atoms; so different isotopologues have different sets of vibrational modes. Because vibrational modes allow a molecule to absorb photons of corresponding energies, isotopologues have different optical properties in the infrared range. | 0 | Theoretical and Fundamental Chemistry |
In the Arrhenius equation, the term activation energy (E) is used to describe the energy required to reach the transition state, and the exponential relationship holds. In transition state theory, a more sophisticated model of the relationship between reaction rates and the transition state, a superficially similar mathematical relationship, the Eyring equation, is used to describe the rate constant of a reaction: . However, instead of modeling the temperature dependence of reaction rate phenomenologically, the Eyring equation models individual elementary steps of a reaction. Thus, for a multistep process, there is no straightforward relationship between the two models. Nevertheless, the functional forms of the Arrhenius and Eyring equations are similar, and for a one-step process, simple and chemically meaningful correspondences can be drawn between Arrhenius and Eyring parameters.
Instead of also using E, the Eyring equation uses the concept of Gibbs energy and the symbol ΔG to denote the Gibbs energy of activation to achieve the transition state. In the equation, k and h are the Boltzmann and Planck constants, respectively. Although the equations look similar, it is important to note that the Gibbs energy contains an entropic term in addition to the enthalpic one. In the Arrhenius equation, this entropic term is accounted for by the pre-exponential factor A. More specifically, we can write the Gibbs free energy of activation in terms of enthalpy and entropy of activation: . Then, for a unimolecular, one-step reaction, the approximate relationships and hold. Note, however, that in Arrhenius theory proper, A is temperature independent, while here, there is a linear dependence on T. For a one-step unimolecular process whose half-life at room temperature is about 2 hours, ΔG is approximately 23 kcal/mol. This is also the roughly the magnitude of E for a reaction that proceeds over several hours at room temperature. Due to the relatively small magnitude of TΔS and RT at ordinary temperatures for most reactions, in sloppy discourse, E, ΔG, and ΔH are often conflated and all referred to as the "activation energy".
The enthalpy, entropy and Gibbs energy of activation are more correctly written as ΔH, ΔS and ΔG respectively, where the o indicates a quantity evaluated between standard states. However, some authors omit the o in order to simplify the notation.
The total free energy change of a reaction is independent of the activation energy however. Physical and chemical reactions can be either exergonic or endergonic, but the activation energy is not related to the spontaneity of a reaction. The overall reaction energy change is not altered by the activation energy. | 0 | Theoretical and Fundamental Chemistry |
* when a non-innocent ligand is present, of hidden or unexpected redox properties that could otherwise be assigned to the central atom. An example is the nickel dithiolate complex, .
* when the redox ambiguity of a central atom and ligand yields dichotomous oxidation states of close stability, thermally induced tautomerism may result, as exemplified by manganese catecholate, . Assignment of such oxidation states requires spectroscopic, magnetic or structural data.
* when the bond order has to be ascertained along with an isolated tandem of a heteronuclear and a homonuclear bond. An example is thiosulfate having two possible oxidation states (bond orders are in blue and formal charges in green):
:The S–S distance measurement in thiosulfate is needed to reveal that this bond order is very close to 1, as in the formula on the left. | 0 | Theoretical and Fundamental Chemistry |
Paramanu is a technical term in Hinduism. It is defined as the smallest and indivisible particle of matter. In Hindi and Bengali language paramanu refers to the atom.
In Jainism it is one of the two types of Pudgala (matter), the other being Skandha. It also helps to define smallest measure of space. All the Parmanus occupy exactly same amount of space. The measure of the space occupied by one Parmanu is called Pradesha. | 1 | Applied and Interdisciplinary Chemistry |
Lightweight textiles with porous surfaces are the most flammable fabrics. Wool is less flammable than cotton, linen, silk, or viscose (rayon). Polyester and nylon resist ignition, and melt rather than catch fire. Acrylic is the most flammable synthetic fiber. | 0 | Theoretical and Fundamental Chemistry |
The largest number of lichenized fungi occur in the Ascomycota, with about 40% of species forming such an association. Some of these lichenized fungi occur in orders with nonlichenized fungi that live as saprotrophs or plant parasites (for example, the Leotiales, Dothideales, and Pezizales). Other lichen fungi occur in only five orders in which all members are engaged in this habit (Orders Graphidales, Gyalectales, Peltigerales, Pertusariales, and Teloschistales). Overall, about 98% of lichens have an ascomycetous mycobiont. Next to the Ascomycota, the largest number of lichenized fungi occur in the unassigned fungi imperfecti, a catch-all category for fungi whose sexual form of reproduction has never been observed. Comparatively few basidiomycetes are lichenized, but these include agarics, such as species of Lichenomphalia, clavarioid fungi, such as species of Multiclavula, and corticioid fungi, such as species of Dictyonema. | 1 | Applied and Interdisciplinary Chemistry |
This phenomenon was first discovered by Dorn in 1879. He observed that a vertical electric field had developed in a suspension of glass beads in water, as the beads were settling. This was the origin of sedimentation potential, which is often referred to as the Dorn effect.
Smoluchowski built the first models to calculate the potential in the early 1900s. Booth created a general theory on sedimentation potential in 1954 based on Overbeeks 1943 theory on electrophoresis. In 1980, Stigter extended Booths model to allow for higher surface potentials. Ohshima created a model based on OBrien and White s 1978 model used to analyze the sedimentation velocity of a single charged sphere and the sedimentation potential of a dilute suspension. | 0 | Theoretical and Fundamental Chemistry |
Chayen is best known for her invention of novel protein crystallization methods. In 1990, she first published a method of suspending droplets of protein solution and precipitant solutions in low-density paraffin oil to prevent evaporation during the microbatch crystallization process. The microbatch process can be suitable for membrane proteins, which are ordinarily difficult to crystallize. Chayen's method has since been applied towards the analysis of many biomolecules that are relevant to human diseases such as cancer, HIV, diabetes, and heart disease.
In addition to her work on microbatch methods, Chayen invented a novel gel-glass nucleant now known as "Naomis Nucleant." Naomis Nucleant has been used to crystallize more than 20 proteins, the most of any single nucleant. In 2015, she collaborated with Subrayal Reddy at University of Central Lancashire to develop the first non-protein nucleant, a semi-liquid molecularly imprinted polymer designed for high-throughput screening. The nucleant was commercialized as "Chayen Reddy MIP."
Chayen's current research interests include protein crystallization, structural biology, and structural genomics and proteomics. | 1 | Applied and Interdisciplinary Chemistry |
The function of the central carbon metabolism (metabolism of glucose) has been fine-tuned to exactly meet the needs of the building blocks and Gibbs free energy in conjunction with cell growth. There is therefore tight regulation of the fluxes through the central carbon metabolism.
The flux in a reaction can be defined based on one of three things
*The activity of the enzyme catalysing the reaction
*The properties of the enzyme
*The metabolite concentration affecting enzyme activity.
Considering the above, the metabolic fluxes can be described as the ultimate representation of the cellular phenotype when expressed under certain conditions. | 1 | Applied and Interdisciplinary Chemistry |
Next to the potential antimicrobial functionality, quorum-sensing derived molecules, especially the peptides, are being investigated for their use in other therapeutic domains as well, including immunology, central nervous system disorders and oncology. Quorum-sensing peptides have been demonstrated to interact with cancer cells, as well as to permeate the blood–brain barrier reaching the brain parenchyma. | 1 | Applied and Interdisciplinary Chemistry |
The chemiluminescence of the system luminol/cobalt(II) chloride is dramatically enhanced by the addition of hydroxylamine-O-sulfonic acid. | 0 | Theoretical and Fundamental Chemistry |
The White catalyst has been found to be an effective catalyst for an oxidative version of the classic Heck reaction. Rather than performing allylic C-H cleavage—a relatively slow process—the catalyst quickly transmetallates with a boronic acid. This aryl palladium intermediate undergoes a 1,2-addition across the alkene double bond. β-Hydride elimination releases the product. The oxidative Heck was originally reported as a sequential process following allylic C-H esterification. It was subsequently demonstrated as a stand-alone method for a broad range of α-olefin substrates. The regioselectivity of the reaction is controlled by directing groups such as carbonyls, alcohols and amines. | 0 | Theoretical and Fundamental Chemistry |
Reactivity ratios indicate preference for propagation. Large indicates a tendency for to add , while small corresponds to a tendency for to add . Values of describe the tendency of to add or . From the definition of reactivity ratios, several special cases can be derived:
* If both reactivity ratios are very high, the two monomers only react with themselves and not with each other. This leads to a mixture of two homopolymers.
* . If both ratios are larger than 1, homopolymerization of each monomer is favored. However, in the event of crosspolymerization adding the other monomer, the chain-end will continue to add the new monomer and form a block copolymer.
* . If both ratios are near 1, a given monomer will add the two monomers with comparable speeds and a statistical or random copolymer is formed.
* If both values are near 0, the monomers are unable to homopolymerize. Each can add only the other resulting in an alternating polymer. For example, the copolymerization of maleic anhydride and styrene has reactivity ratios = 0.01 for maleic anhydride and = 0.02 for styrene. Maleic acid in fact does not homopolymerize in free radical polymerization, but will form an almost exclusively alternating copolymer with styrene.
* In the initial stage of the copolymerization, monomer 1 is incorporated faster and the copolymer is rich in monomer 1. When this monomer gets depleted, more monomer 2 segments are added. This is called composition drift.
* When both , the system has an azeotrope, where feed and copolymer composition are the same. | 0 | Theoretical and Fundamental Chemistry |
There are two limiting cases of the Butler–Volmer equation:
* the low overpotential region (called "polarization resistance", i.e., when E ≈ E), where the Butler–Volmer equation simplifies to:
* the high overpotential region, where the Butler–Volmer equation simplifies to the Tafel equation. When , the first term dominates, and when , the second term dominates.
: for a cathodic reaction, when E , or
: for an anodic reaction, when E >> E
where and are constants (for a given reaction and temperature) and are called the Tafel equation constants. The theoretical values of the Tafel equation constants are different for the cathodic and anodic processes. However, the Tafel slope can be defined as:
where is the faradaic current, expressed as , being and the cathodic and anodic partial currents, respectively. | 0 | Theoretical and Fundamental Chemistry |
A further subclass of catalytic triad variants are pseudoenzymes, which have triad mutations that make them catalytically inactive, but able to function as binding or structural proteins. For example, the heparin-binding protein Azurocidin is a member of the PA clan, but with a glycine in place of the nucleophile and a serine in place of the histidine. Similarly, RHBDF1 is a homolog of the S54 family rhomboid proteases with an alanine in the place of the nucleophilic serine. In some cases, pseudoenzymes may still have an intact catalytic triad but mutations in the rest of the protein remove catalytic activity. The CA clan contains catalytically inactive members with mutated triads (calpamodulin has lysine in place of its cysteine nucleophile) and with intact triads but inactivating mutations elsewhere (rat testin retains a Cys-His-Asn triad). | 1 | Applied and Interdisciplinary Chemistry |
The following derivation is adapted from Foundations of Chemical Kinetics.
This derivation assumes the reaction . Consider a sphere of radius , centered at a spherical molecule A, with reactant B flowing in and out of it. A reaction is considered to occur if molecules A and B touch, that is, when the distance between the two molecules is apart.
If we assume a local steady state, then the rate at which B reaches is the limiting factor and balances the reaction.
Therefore, the steady state condition becomes
where
is the flux of B, as given by Fick's law of diffusion,
where is the diffusion coefficient and can be obtained by the Stokes-Einstein equation, and the second term is the gradient of the chemical potential with respect to position. Note that [B] refers to the average concentration of B in the solution, while [B](r) is the "local concentration" of B at position r.
Inserting 2 into 1 results in
It is convenient at this point to use the identity
allowing us to rewrite 3 as
Rearranging 4 allows us to write
Using the boundary conditions that , ie the local concentration of B approaches that of the solution at large distances, and consequently , as , we can solve 5 by separation of variables, we get
or
7. <math> \frac{k[B]}{4\pi D_{AB}\beta }=
[B]-[B](R_{AB})\exp(U(R_{AB})/k_{B}T ) )
For the reaction between A and B, there is an inherent reaction constant , so . Substituting this into 7 and rearranging yields | 0 | Theoretical and Fundamental Chemistry |
However, most plants do not have CAM and must therefore open and close their stomata during the daytime, in response to changing conditions, such as light intensity, humidity, and carbon dioxide concentration. When conditions are conducive to stomatal opening (e.g., high light intensity and high humidity), a proton pump drives protons (H) from the guard cells. This means that the cells electrical potential becomes increasingly negative. The negative potential opens potassium voltage-gated channels and so an uptake of potassium ions (K) occurs. To maintain this internal negative voltage so that entry of potassium ions does not stop, negative ions balance the influx of potassium. In some cases, chloride ions enter, while in other plants the organic ion malate is produced in guard cells. This increase in solute concentration lowers the water potential inside the cell, which results in the diffusion of water into the cell through osmosis. This increases the cells volume and turgor pressure. Then, because of rings of cellulose microfibrils that prevent the width of the guard cells from swelling, and thus only allow the extra turgor pressure to elongate the guard cells, whose ends are held firmly in place by surrounding epidermal cells, the two guard cells lengthen by bowing apart from one another, creating an open pore through which gas can diffuse.
When the roots begin to sense a water shortage in the soil, abscisic acid (ABA) is released. ABA binds to receptor proteins in the guard cells' plasma membrane and cytosol, which first raises the pH of the cytosol of the cells and cause the concentration of free Ca to increase in the cytosol due to influx from outside the cell and release of Ca from internal stores such as the endoplasmic reticulum and vacuoles. This causes the chloride (Cl) and organic ions to exit the cells. Second, this stops the uptake of any further K into the cells and, subsequently, the loss of K. The loss of these solutes causes an increase in water potential, which results in the diffusion of water back out of the cell by osmosis. This makes the cell plasmolysed, which results in the closing of the stomatal pores.
Guard cells have more chloroplasts than the other epidermal cells from which guard cells are derived. Their function is controversial. | 0 | Theoretical and Fundamental Chemistry |
Ammonia oxidation in autotrophic nitrification is a complex process that requires several enzymes as well as oxygen as a reactant. The key enzymes necessary for releasing energy during oxidation of ammonia to nitrite are ammonia monooxygenase (AMO) and hydroxylamine oxidoreductase (HAO). The first is a transmembrane copper protein which catalyzes the oxidation of ammonia to hydroxylamine () taking two electrons directly from the quinone pool. This reaction requires O.
The second step of this process has recently fallen into question. For the past few decades, the common view was that a trimeric multiheme c-type HAO converts hydroxylamine into nitrite in the periplasm with production of four electrons (). The stream of four electrons is channeled through cytochrome c to a membrane-bound cytochrome c. Two of the electrons are routed back to AMO, where they are used for the oxidation of ammonia (quinol pool). The remaining two electrons are used to generate a proton motive force and reduce NAD(P) through reverse electron transport.
Recent results, however, show that HAO does not produce nitrite as a direct product of catalysis. This enzyme instead produces nitric oxide and three electrons. Nitric oxide can then be oxidized by other enzymes (or oxygen) to nitrite. In this paradigm, the electron balance for overall metabolism needs to be reconsidered. | 1 | Applied and Interdisciplinary Chemistry |
Thionyl chloride converts phosphonic acids and phosphonates into phosphoryl chlorides. It is for this type of reaction that thionyl chloride is listed as a Schedule 3 compound, as it can be used in the "di-di" method of producing G-series nerve agents. For example, thionyl chloride converts dimethyl methylphosphonate into methylphosphonic acid dichloride, which can be used in the production of sarin and soman. | 0 | Theoretical and Fundamental Chemistry |
NURF interacts with chromatin by binding to modified histones or interacting with various transcription factors. NURF catalyzes nucleosome sliding in either direction on DNA without any apparent modifications to the histone octamer itself. NURF is essential for the expression of homeotic genes. The ISWI ATPase specifically recognizes intact N-terminal histone tails. In Drosophila, NURF interacts with the transcription factor GAGA to remodel chromatin at the hsp70 promoter, and null mutations in the Nurf301 subunit prevent larval metamorphosis. Other NURF mutants cause the development of melanotic tumors from larval blood cells. In humans, hNURF is involved in neuronal development and has been shown to enhance neurite outgrowth in vitro. | 1 | Applied and Interdisciplinary Chemistry |
Solutions of urea and ammonium nitrate in water (UAN) are commonly used as a liquid fertilizer. In admixture, the combined solubility of ammonium nitrate and urea is so much higher than that of either component alone that it gives a stable solution with a total nitrogen content (32%) approaching that of solid ammonium nitrate (33.5%), though not, of course, that of urea itself (46%). UAN allows use of ammonium nitrate without the explosion hazard. In UAN accounts for 80% of the liquid fertilizers in the US. | 0 | Theoretical and Fundamental Chemistry |
Of all light emitters in the ocean, bio-luminescent bacteria is the most abundant and diverse. However, the distribution of bio-luminescent bacteria is uneven, which suggests evolutionary adaptations. The bacterial species in terrestrial genera such as Photorhabdus are bio-luminescent. On the other hand, marine genera with bio-luminescent species such as Vibrio and Shewanella oneidensis have different closely related species that are not light emitters. Nevertheless, all bio-luminescent bacteria share a common gene sequence: the enzymatic oxidation of Aldehyde and reduced Flavin mononucleotide by luciferase which are contained in the lux operon. Bacteria from distinct ecological niches contain this gene sequence; therefore, the identical gene sequence evidently suggests that bio-luminescence bacteria result from evolutionary adaptations. | 1 | Applied and Interdisciplinary Chemistry |
Dibasic esters are used in paints, coil coatings, paint strippers, coatings, plasticisers, resins, binders, solvents, polyols, soil stabilization, chemical grouting, oilfield drilling fluids, crop protection products, cedar spray, and adhesives. | 0 | Theoretical and Fundamental Chemistry |
Tritium is a low-energy beta emitter commonly used as a radiotracer in research and in traser self-powered lightings. The half-life of tritium is 12.3 years. The electrons from beta emission from tritium are so low in energy (average decay energy 5.7 keV) that a Geiger counter cannot be used to detect them. An advantage of the low energy of the decay is that it is easy to shield, since the low energy electrons penetrate only to shallow depths, reducing the safety issues in deal with the isotope.
Tritium can also be found in metal work in the form of a tritiated rust, this can be treated by heating the steel in a furnace to drive off the tritium-containing water.
Tritium can be made by the neutron irradiation of lithium. | 0 | Theoretical and Fundamental Chemistry |
Coomber's relationship can be used to describe how the internal pressure and dielectric constant of a non-polar liquid are related.
As , which defines the internal pressure of a liquid, it can be found that:
where
* is equal to the number of molecules
* is the ionization potential of the liquid
* is a temperature dependent relation based on numerical constants of the pair summation from inter-particle geometry
* is the polarizability
* is the volume of the liquid
where for most non-polar liquids | 0 | Theoretical and Fundamental Chemistry |
A paracrystalline lattice, or paracrystal, is a molecular or atomic lattice with significant amounts (e.g., larger than a few percent) of partial disordering of molecular arrangements. Limiting cases of the paracrystal model are nanostructures, such as glasses, liquids, etc., that may possess only local ordering and no global order. A simple example of a paracrystalline lattice is shown in the following figure for a silica glass:
Liquid crystals also have paracrystalline rather than crystalline structures.
Highly hydrated B-DNA occurs naturally in living cells in such a paracrystalline state, which is a dynamic one despite the relatively rigid DNA double helix stabilized by parallel hydrogen bonds between the nucleotide base-pairs in the two complementary, helical DNA chains (see figures). For simplicity most DNA molecular models omit both water and ions dynamically bound to B-DNA, and are thus less useful for understanding the dynamic behaviors of B-DNA in vivo. The physical and mathematical analysis of X-ray and spectroscopic data for paracrystalline B-DNA is thus far more complex than that of crystalline, A-DNA X-ray diffraction patterns. The paracrystal model is also important for DNA technological applications such as DNA nanotechnology. Novel methods that combine X-ray diffraction of DNA with X-ray microscopy in hydrated living cells are now also being developed. | 0 | Theoretical and Fundamental Chemistry |
The replication of technique in copper production includes a vast number of possibilities in trying to recreate what has been found through archaeological excavation. Tylecote and Boydell have experimented on possible explanations for the levels of iron found in certain copper objects and the possibility of removing excess iron through the re-melting of the copper. Crew has also done experimental work on iron to show possible loss in iron mass due to the processes involved with working the metal from bloom to billet which concluded with a loss of 75% in slag, impurities, and iron metal. | 1 | Applied and Interdisciplinary Chemistry |
Meyer sets include
*The points of any lattice
*The vertices of any rhombic Penrose tiling
*The Minkowski sum of another Meyer set with any nonempty finite set
*Any relatively dense subset of another Meyer set | 0 | Theoretical and Fundamental Chemistry |
The construction of more complex molecular machines is an active area of theoretical and experimental research. Though a diverse variety of AMMs are known today, experimental studies of these molecules are inhibited by the lack of methods to construct these molecules. In this context, theoretical modeling has emerged as a pivotal tool to understand the self-assembly or -disassembly processes in these systems.
A wide range of applications have been demonstrated for AMMs, including those integrated into polymeric, liquid crystal, and crystalline systems for varied functions. Homogenous catalysis is a prominent example, especially in areas like asymmetric synthesis, utilizing noncovalent interactions and biomimetic allosteric catalysis. AMMs have been pivotal in the design of several stimuli-responsive smart materials, such as 2D and 3D self-assembled materials and nanoparticle-based systems, for versatile applications ranging from 3D printing to drug delivery.
AMMs are gradually moving from the conventional solution-phase chemistry to surfaces and interfaces. For instance, AMM-immobilized surfaces (AMMISs) are a novel class of functional materials consisting of AMMs attached to inorganic surfaces forming features like self-assembled monolayers; this gives rise to tunable properties such as fluorescence, aggregation and drug-release activity.
Most of these applications remain at the proof-of-concept level, and need major modifications to be adapted to the industrial scale. Challenges in streamlining macroscale applications include autonomous operation, the complexity of the machines, stability in the synthesis of the machines and the working conditions. | 0 | Theoretical and Fundamental Chemistry |
The most reliable methods are direct plate count method and membrane filtration method. mEndo Agar is used in the membrane filtration while VRBA Agar is used in the direct plate count method. VRBA stands for violet red bile agar. A media that contains bile salts which promotes the growth of gram negative and has inhibitory characteristic to gram positive although not complete inhibitory.
These media contain lactose which is usually fermented by lactose fermenting bacteria producing colonies that can be identified and characterised. Lactose fermenting produce colored colonies while non lactose fermenting produce colorless ones. Because the analysis is always based on a very small sample taken from a very large volume of water, all methods rely on statistical principles. | 0 | Theoretical and Fundamental Chemistry |
In 1878, along with Jacques-Louis Soret, Delafontaine first observed holmium spectroscopically. In 1879, Per Teodor Cleve chemically separated it from thulium and erbium. All three men are given credit for the element's discovery. | 1 | Applied and Interdisciplinary Chemistry |
Cieplak's proposal is supported by investigating the effects of various electronic substituents on product distribution. By installing an electron-withdrawing substituent such as a methoxy group at the C2 position, the reduction of substituted cyclohexanones begins to favor equatorial attack. This is because the axial C-O bond is a worse electron donor than a C–C bond, so axial attack is less favored.
Cieplak also demonstrated this effect by introducing electron withdrawing substituents on C3, which decrease the electron-donating capability of the ring C–C bond and therefore disfavor equatorial attack, which is antiperiplanar to this bond. Electron-donating substituents at C3 subsequently favor equatorial approach, since increasing C–C electron density favors σ donation into σ* and thereby encourages equatorial approach.
This effect can also be investigated by changing the electronic nature of the nucleophile. In the case of an electron-deficient nucleophile, the σ* of the forming C-Nuc bond is lower in energy and better stabilized by attack antiperiplanar to electron-rich axial C-H bonds. Attack therefore occurs axially. If the nucleophile is electron-rich, however, the donation of more electron density is less favored and equatorial attack may prevail. These trends have been observed even when normalizing for steric bulk of the nucleophile.
In substituted norbornones, nucleophilic attack will come antiperiplanar to the bonds which can best donate into σ*. The bonds positioned for this interaction are the bridgehead C–C bonds on the six-membered ring. Substituents which donate electron density to these bonds, such as ethyl groups, increase the rate of addition anti to the alkyl groups, which is the antiperiplanar trajectory. If electron-withdrawing substituents such as esters are appended to the C–C bonds, however, the selectivity favors syn addition, so that the bonds donating into σ* are the more electron-rich C–C bonds which are hydrogen-substituted.
A similar example is seen in substituted 2-adamantones, where varying the electronic properties at the remote 5 position has profound effects on product distribution. A hydroxyl group is able to donate electron density inductively to the forming σ* bond antiperiplanar, so attack from that side is favored. The electron-withdrawing ester substituent, however, lacks this stabilization ability. Instead, the C–H bonds are better electron donors than the C–COMe bonds, so attack comes anti to the hydrogen substituents and subsequently syn to the ester group. This explains the effect of remote electron-donor groups on stereochemical outcomes, which has been difficult to explain with other stereochemical models. The rigidity of the adamantone skeleton allows for tight control of conformation and minimization of competing effects. | 0 | Theoretical and Fundamental Chemistry |
If V is the molar volume and T the critical temperature of a liquid the surface tension γ is given by
where k is a constant valid for all liquids, with a value of 2.1×10 J/(K·mol).
More precise values can be gained when considering that the line normally passes the temperature axis 6 K before the critical point:
The molar volume V is given by the molar mass M and the density ρ
The term is also referred to as the "molar surface tension" γ :
A useful representation that prevents the use of the unit mol is given by the Avogadro constant N :
As John Lennard-Jones and Corner showed in 1940 by means of the statistical mechanics the constant k′ is nearly equal to the Boltzmann constant. | 0 | Theoretical and Fundamental Chemistry |
A myokine is one of several hundred cytokines or other small proteins (~5–20 kDa) and proteoglycan peptides that are produced and released by skeletal muscle cells (muscle fibers) in response to muscular contractions. They have autocrine, paracrine and/or endocrine effects; their systemic effects occur at picomolar concentrations.
Receptors for myokines are found on muscle, fat, liver, pancreas, bone, heart, immune, and brain cells. The location of these receptors reflects the fact that myokines have multiple functions. Foremost, they are involved in exercise-associated metabolic changes, as well as in the metabolic changes following training adaptation. They also participate in tissue regeneration and repair, maintenance of healthy bodily functioning, immunomodulation; and cell signaling, expression and differentiation. | 1 | Applied and Interdisciplinary Chemistry |
mRNA display is a display technique used for in vitro protein, and/or peptide evolution to create molecules that can bind to a desired target. The process results in translated peptides or proteins that are associated with their mRNA progenitor via a puromycin linkage. The complex then binds to an immobilized target in a selection step (affinity chromatography). The mRNA-protein fusions that bind well are then reverse transcribed to cDNA and their sequence amplified via a polymerase chain reaction. The result is a nucleotide sequence that encodes a peptide with high affinity for the molecule of interest.
Puromycin is an analogue of the 3’ end of a tyrosyl-tRNA with a part of its structure mimics a molecule of adenosine, and the other part mimics a molecule of tyrosine. Compared to the cleavable ester bond in a tyrosyl-tRNA, puromycin has a non-hydrolysable amide bond. As a result, puromycin interferes with translation, and causes premature release of translation products.
All mRNA templates used for mRNA display technology have puromycin at their 3’ end. As translation proceeds, ribosome moves along the mRNA template, and once it reaches the 3’ end of the template, the fused puromycin will enter ribosome’s A site and be incorporated into the nascent peptide. The mRNA-polypeptide fusion is then released from the ribosome (Figure 1).
To synthesize an mRNA-polypeptide fusion, the fused puromycin is not the only modification to the mRNA template. Oligonucleotides and other spacers need to be recruited along with the puromycin to provide flexibility and proper length for the puromycin to enter the A site. Ideally, the linker between the 3’ end of an mRNA and the puromycin has to be flexible and long enough to allow the puromycin to enter the A site upon translation of the last codon. This enables the efficient production of high-quality, full-length mRNA-polypeptide fusion. Rihe Liu et al. optimized the 3’-puromycin oligonucleotide spacer. They reported that dA25 in combination with a Spacer 9 (Glen Research), and dAdCdCP at the 5’ terminus worked the best for the fusion reaction. They found that linkers longer than 40 nucleotides and shorter than 16 nucleotides showed greatly reduced efficiency of fusion formation. Also, when the sequence rUrUP presented adjacent to the puromycin, fusion did not form efficiently.
In addition to providing flexibility and length, the poly dA portion of the linker also allows further purification of the mRNA-polypeptide fusion due to its high affinity for dT cellulose resin. The mRNA-polypeptide fusions can be selected over immobilized selection targets for several rounds with increasing stringency. After each round of selection, those library members that stay bound to the immobilized target are PCR amplified, and non-binders are washed off. | 1 | Applied and Interdisciplinary Chemistry |
Polymers are high molecular mass compounds formed by polymerization of monomers. They are synthesized by the polymerization process and can be modified by the additive of monomers. The additives of monomers change polymers mechanical property, processability, durability and so on. The simple reactive molecule from which the repeating structural units of a polymer are derived is called a monomer. A polymer can be described in many ways: its degree of polymerisation, molar mass distribution, tacticity, copolymer distribution, the degree of branching, by its end-groups, crosslinks, crystallinity and thermal properties such as its glass transition temperature and melting temperature. Polymers in solution have special characteristics with respect to solubility, viscosity, and gelation. Illustrative of the quantitative aspects of polymer chemistry, particular attention is paid to the number-average and weight-average molecular weights and , respectively.
<br>
The formation and properties of polymers have been rationalized by many theories including Scheutjens–Fleer theory, Flory–Huggins solution theory, Cossee–Arlman mechanism, Polymer field theory, Hoffman Nucleation Theory, Flory–Stockmayer theory, and many others.
The study of polymer thermodynamics helps improve the material properties of various polymer-based materials such as polystyrene (styrofoam) and polycarbonate. Common improvements include toughening, improving impact resistance, improving biodegradability, and altering a material's solubility. | 0 | Theoretical and Fundamental Chemistry |
Anaerobic membrane bioreactor or AnMBR is the name of a technology utilized in wastewater treatment. It is a technology in membrane filtration for biomass retention. AnMBR works by using a membrane bioreactor (MBR) in a anaerobic environment. Anaerobic bacteria ( Mesophile or Thermophile) and archaea convert organic materials into carbon dioxide (CO2) and methane (CH4). The sewage is filtered and separated by membranes leaving the effluent and sludge apart. The produced biogas can later be combusted to generate heat or electricity. It can also be upgraded (purified) into Renewable natural gas of household quality. AnMBR is considered to be a sustainable alternative for sewage treatment because the energy that can be generated by methane combustion can exceed the energy required for maintaining the process. | 1 | Applied and Interdisciplinary Chemistry |
The Zisman plot the graphical method of the Zisman theory or the Zisman method for characterizing the wettability of a solid surface [https://www.kruss-scientific.com/services/education-theory/glossary/method-according-to-zisman/], named for the American chemist and geophysicist, William Albert Zisman (1905–1986). It is a prominent Sessile drop technique used for characterizing liquid-surface interactions based on the contact angle of a single drop of liquid sitting on the solid surface. | 0 | Theoretical and Fundamental Chemistry |
BioLiP is a comprehensive ligand–protein interaction database, with the 3D structure of the ligand–protein interactions taken from the Protein Data Bank. [http://manoraa.org/ MANORAA] is a webserver for analyzing conserved and differential molecular interaction of the ligand in complex with protein structure homologs from the Protein Data Bank. It provides the linkage to protein targets such as its location in the biochemical pathways, SNPs and protein/RNA baseline expression in target organ. | 0 | Theoretical and Fundamental Chemistry |
In humans endoglin may be involved in the autosomal dominant disorder known as hereditary hemorrhagic telangiectasia (HHT) type 1. HHT is actually the first human disease linked to the TGF beta receptor complex. This condition leads to frequent nose bleeds, telangiectases on skin and mucosa and may cause arteriovenous malformations in different organs including brain, lung, and liver. | 1 | Applied and Interdisciplinary Chemistry |
Complex metallic alloys (CMAs) or complex intermetallics (CIMs) are intermetallic compounds characterized by the following structural features:
#large unit cells, comprising some tens up to thousands of atoms,
#the presence of well-defined atom clusters, frequently of icosahedral point group symmetry,
#the occurrence of inherent disorder in the ideal structure. | 1 | Applied and Interdisciplinary Chemistry |
Dettre and Johnson discovered in 1964 that the superhydrophobic lotus effect phenomenon was related to rough hydrophobic surfaces, and they developed a theoretical model based on experiments with glass beads coated with paraffin or TFE telomer. The self-cleaning property of superhydrophobic micro-nanostructured surfaces was reported in 1977. Perfluoroalkyl, perfluoropolyether, and RF plasma -formed superhydrophobic materials were developed, used for electrowetting and commercialized for bio-medical applications between 1986 and 1995. Other technology and applications have emerged since the mid-1990s. A durable superhydrophobic hierarchical composition, applied in one or two steps, was disclosed in 2002 comprising nano-sized particles ≤ 100 nanometers overlaying a surface having micrometer-sized features or particles ≤ 100 micrometers. The larger particles were observed to protect the smaller particles from mechanical abrasion.
In recent research, superhydrophobicity has been reported by allowing alkylketene dimer (AKD) to solidify into a nanostructured fractal surface. Many papers have since presented fabrication methods for producing superhydrophobic surfaces including particle deposition, sol-gel techniques, plasma treatments, vapor deposition, and casting techniques. Current opportunity for research impact lies mainly in fundamental research and practical manufacturing. Debates have recently emerged concerning the applicability of the Wenzel and Cassie–Baxter models. In an experiment designed to challenge the surface energy perspective of the Wenzel and Cassie–Baxter model and promote a contact line perspective, water drops were placed on a smooth hydrophobic spot in a rough hydrophobic field, a rough hydrophobic spot in a smooth hydrophobic field, and a hydrophilic spot in a hydrophobic field. Experiments showed that the surface chemistry and geometry at the contact line affected the contact angle and contact angle hysteresis, but the surface area inside the contact line had no effect. An argument that increased jaggedness in the contact line enhances droplet mobility has also been proposed.
Many hydrophobic materials found in nature rely on Cassie's law and are biphasic on the submicrometer level with one component air. The lotus effect is based on this principle. Inspired by it, many functional superhydrophobic surfaces have been prepared.
An example of a bionic or biomimetic superhydrophobic material in nanotechnology is nanopin film.
One study presents a vanadium pentoxide surface that switches reversibly between superhydrophobicity and superhydrophilicity under the influence of UV radiation. According to the study, any surface can be modified to this effect by application of a suspension of rose-like VO particles, for instance with an inkjet printer. Once again hydrophobicity is induced by interlaminar air pockets (separated by 2.1 nm distances). The UV effect is also explained. UV light creates electron-hole pairs, with the holes reacting with lattice oxygen, creating surface oxygen vacancies, while the electrons reduce V to V. The oxygen vacancies are met by water, and it is this water absorbency by the vanadium surface that makes it hydrophilic. By extended storage in the dark, water is replaced by oxygen and hydrophilicity is once again lost.
A significant majority of hydrophobic surfaces have their hydrophobic properties imparted by structural or chemical modification of a surface of a bulk material, through either coatings or surface treatments. That is to say, the presence of molecular species (usually organic) or structural features results in high contact angles of water. In recent years, rare earth oxides have been shown to possess intrinsic hydrophobicity. The intrinsic hydrophobicity of rare earth oxides depends on surface orientation and oxygen vacancy levels, and is naturally more robust than coatings or surface treatments, having potential applications in condensers and catalysts that can operate at high temperatures or corrosive environments. | 0 | Theoretical and Fundamental Chemistry |
Many systems of interest have a total density of states with the power-law form:
for some values of , , . The results of preceding sections generalize to dimensions, giving a power law with:
* for non-relativistic particles in a -dimensional box,
* for non-relativistic particles in a -dimensional harmonic potential well,
* for hyper-relativistic particles in a -dimensional box.
For such a power-law density of states, the grand potential integral evaluates exactly to:
where is the complete Fermi–Dirac integral (related to the polylogarithm). From this grand potential and its derivatives, all thermodynamic quantities of interest can be recovered. | 0 | Theoretical and Fundamental Chemistry |
Agonists and antagonists form certain chemical bonds with amino acids that construct the MOR. The majority of antagonists, as well as agonists, are predicted to form charged interaction with Asp147 and a hydrogen bond with Tyr148. However, majority of antagonists also form additional polar interactions with other amino acid residues such as Lys233, Gln124, Gln229, Asn150, Trp318 and Tyr128. Only a small minority of agonists form the same additional polar interactions. Both agonists and antagonists are known to form hydrogen bonds with His297.
It can be concluded that interactions with the amino acid residues, Asp147 and Tyr148 are essential for the ligand to bind to the receptor and the molecules that form additional polar interactions with other residues are more often antagonists than agonists.
The N-substituent group can form hydrophobic bonds with Tyr326 and Trp293 and the aromatic and cyclohexane rings can form similar bonds to Met151. The backside of the ligand can also form a hydrophobic bond, but with Val300 and Ile296. | 1 | Applied and Interdisciplinary Chemistry |
The Chinese tradition of using toxic heavy metals in elixirs of immortality has historical parallels in Ayurvedic medicine. Rasa shastra is the practice of adding metals and minerals to herbal medicines, rasayana is an alchemical tradition that used mercury and cinnabar for lengthening lifespan, raseśvara is a tradition that advocated the use of mercury to make the body immortal, and samskara is a process said to detoxify heavy metals and toxic herbs.
The historians of Chinese science Joseph Needham and Ho Peng-Yoke wrote a seminal article about poisonous alchemical elixirs. Based upon early Chinese descriptions of elixir poisoning, they decisively demonstrated a close correspondence with the known medical symptoms of mercury poisoning, lead poisoning, and arsenic poisoning. Compare the historical descriptions of Jin Emperor Ai (d. 365) who "no longer knew what was going on around him" and Tang Emperor Wuzong (d. 846) who was "very irritable, losing all normal self-control in joy or anger ... he could not speak for ten days at a time" with the distinctive psychological effects of mercury poisoning: progressing from "abnormal irritability to idiotic, melancholic, or manic conditions". Needham and his collaborators further discussed elixir poisoning in the Science and Civilisation in China series.
Although Chinese elixir poisoning may lead some to dismiss Chinese alchemy as another example of human follies in history, Ho Peng-Yoke and F. Peter Lisowski note its positive aspect upon Chinese medicine. The caution given to elixir poisoning later led Chinese alchemy to "shade imperceptibly" into iatrochemistry, the preparation of medicine by chemical methods, "in other words chemotherapy".
A recent study found that Chinese emperors lived comparatively short lives, with a mean age at death of emperors at 41.3, which was significantly lower than that of Buddhist monks at 66.9 and traditional Chinese doctors at 75.1. Causes of imperial death were natural disease (66.4%), homicide (28.2%), drug toxicity (3.3%), and suicide (2.1%). Homicide resulted in a significantly lower age of death (mean age 31.1) than disease (45.6), suicide (38.8), or drug toxicity (43.1, mentioning Qin Shi Huang taking mercury pills of immortality). Lifestyles seem to have been a determining factor, and 93.2% of the emperors studied were overindulgent in drinking alcohol, sexual activity, or both. The study does not refer to the Chinese belief that the arsenic sulphides realgar and orpiment, frequently used in immortality elixirs, had aphrodisiac properties. | 1 | Applied and Interdisciplinary Chemistry |
The other use of additive effect is to detect antagonism. Similarly, additive effect can be considered as the baseline effect in methods of determining the presence of antagonistic effect between drugs. Pharmacists can confirm the presence of antagonism when the combination effect of drugs is less than additive effect. The combination of acetylsalicylic acid and ibuprofen demonstrates an antagonistic effect in relieving pain and inflammation. | 1 | Applied and Interdisciplinary Chemistry |
Chymia was an annual peer-reviewed academic journal published in 12 volumes from 1948 to 1967. In 1947 a committee chaired by Charles Albert Browne Jr. and consisting of four other members, Claude K. Deischer, Rudolf Hirsch, Herbert S. Klickstein, and Henry M. Leicester, established the journal. The first issue was published in 1948 with Tenney L. Davis (1890–1949) as editor-in-chief. Almost all of the articles were in English, but with a few in French or German.
In 1969 Chymia was incorporated into the new journal Historical Studies in the Physical Sciences established by Russell McCormmach. | 1 | Applied and Interdisciplinary Chemistry |
Oxacillin (trade name Bactocill) is a narrow-spectrum beta-lactam antibiotic of the penicillin class developed by Beecham.
It was patented in 1960 and approved for medical use in 1962. | 0 | Theoretical and Fundamental Chemistry |
The colloidal gold protein assay is a highly sensitive biochemical assay for determining the total concentration of protein in a solution (~0.1 ng/µL to 200 ng/µL). It was first described in 1987 by two groups who used commercially available "Aurodye" colloidal gold solutions. Notably, the formulation of Aurodye changed between 1987 and 1990 such that it became incompatible with protein assays, however vendors such as Bio-Rad & Diversified Biotech starting offering colloidal gold formulations that were suitable for protein assays. These products have since been discontinued and there are no vendors that currently explicitly sell colloidal gold for the assay, however detailed synthetic procedures were published to produce the ~17-40 nm gold nanoparticles that are suitable for the assay, along with modifications to increase the shelf stability of the colloidal gold & adapt the assay to microplate format & increase its sensitivity. Gold nanoparticles in the ~17-40 nm size range that are presumably compatible with the assay are currently commercially available. | 1 | Applied and Interdisciplinary Chemistry |
RNA editing through the addition and deletion of uracil has been found in kinetoplasts from the mitochondria of Trypanosoma brucei.
Because this may involve a large fraction of the sites in a gene, it is sometimes called "pan-editing" to distinguish it from topical editing of one or a few sites.
Pan-editing starts with the base-pairing of the unedited primary transcript with a guide RNA (gRNA), which contains complementary sequences to the regions around the insertion/deletion points. The newly formed double-stranded region is then enveloped by an editosome, a large multi-protein complex that catalyzes the editing. The editosome opens the transcript at the first mismatched nucleotide and starts inserting uridines. The inserted uridines will base-pair with the guide RNA, and insertion will continue as long as A or G is present in the guide RNA and will stop when a C or U is encountered. The inserted nucleotides cause a frameshift, and result in a translated protein that differs from its gene.
The mechanism of the editosome involves an endonucleolytic cut at the mismatch point between the guide RNA and the unedited transcript. The next step is catalyzed by one of the enzymes in the complex, a terminal U-transferase, which adds Us from UTP at the 3 end of the mRNA. The opened ends are held in place by other proteins in the complex. Another enzyme, a U-specific exoribonuclease, removes the unpaired Us. After editing has made mRNA complementary to gRNA, an RNA ligase rejoins the ends of the edited mRNA transcript. As a consequence, the editosome can edit only in a 3 to 5' direction along the primary RNA transcript. The complex can act on only a single guide RNA at a time. Therefore, a RNA transcript requiring extensive editing will need more than one guide RNA and editosome complex. | 1 | Applied and Interdisciplinary Chemistry |
Pyruvate cycling commonly refers to an intracellular loop of spatial movements and chemical transformations involving pyruvate. Spatial movements occur between mitochondria and cytosol and chemical transformations create various Krebs cycle intermediates. In all variants, pyruvate is imported into the mitochondrion for processing through part of the Krebs cycle. In addition to pyruvate, alpha-ketoglutarate may also be imported. At various points, the intermediate product is exported to the cytosol for additional transformations and then re-imported. Three specific pyruvate cycles are generally considered, each named for the principal molecule exported from the mitochondrion: malate, citrate, and isocitrate. Other variants may exist, such as dissipative or "futile" pyruvate cycles.
This cycle is usually studied in relation to Glucose Stimulated Insulin Secretion ( or GSIS ) and there is thought to be a relationship between the insulin response and NADPH produced from this cycle but the specifics are not clear and particular confusion exists about the role of malic enzymes. It has been observed in various cell types including islet cells.
The pyruvate-malate cycle was described in liver and kidney preparations as early as 1971. | 1 | Applied and Interdisciplinary Chemistry |
A reasonably accurate value of the atomic mass unit was first obtained indirectly by Josef Loschmidt in 1865, by estimating the number of particles in a given volume of gas. | 0 | Theoretical and Fundamental Chemistry |
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