text
stringlengths 105
4.57k
| label
int64 0
1
| label_text
stringclasses 2
values |
|---|---|---|
A typical bioreactor consists of following parts:
Agitator – Used for the mixing of the contents of the reactor which keeps the cells in the perfect homogenous condition for better transport of nutrients and oxygen to the desired product(s).
Baffle – Used to break the vortex formation in the vessel, which is usually highly undesirable as it changes the center of gravity of the system and consumes additional power.
Sparger – In aerobic cultivation process, the purpose of the sparger is to supply adequate oxygen to the growing cells.
Jacket – The jacket provides the annular area for circulation of constant temperature of water which keeps the temperature of the bioreactor at a constant value. | 1 | Applied and Interdisciplinary Chemistry |
Currently, there are 14 scientific divisions in the chemistry department:
* Analytical chemistry
* Chemistry of macromolecular compounds
* Chemistry of natural compounds
* Colloid chemistry
* Electrochemistry
* General and Inorganic chemistry
* Laser Chemistry and Laser Material Science
* Organic chemistry
* Physical chemistry
* Physical organic chemistry
* Radiochemistry
* Quantum chemistry
* Solid state chemistry
* Chemical Thermodynamics and Kinetics
* Laboratory of Biomedical Chemistry
* Laboratory of Chemical Pharmacology | 1 | Applied and Interdisciplinary Chemistry |
In colloidal chemistry, flocculation is a process by which colloidal particles come out of suspension to sediment in the form of floc or flake, either spontaneously or due to the addition of a clarifying agent. The action differs from precipitation in that, prior to flocculation, colloids are merely suspended, under the form of a stable dispersion (where the internal phase (solid) is dispersed throughout the external phase (fluid) through mechanical agitation) and are not truly dissolved in solution.
Coagulation and flocculation are important processes in water treatment with coagulation aimed to destabilize and aggregate particles through chemical interactions between the coagulant and colloids, and flocculation to sediment the destabilized particles by causing their aggregation into floc. | 1 | Applied and Interdisciplinary Chemistry |
The plant immune system carries two interconnected tiers of receptors, one most frequently sensing molecules outside the cell and the other most frequently sensing molecules inside the cell. Both systems sense the intruder and respond by activating antimicrobial defenses in the infected cell and neighboring cells. In some cases, defense-activating signals spread to the rest of the plant or even to neighboring plants. The two systems detect different types of pathogen molecules and classes of plant receptor proteins.
The first tier is primarily governed by pattern recognition receptors that are activated by recognition of evolutionarily conserved pathogen or microbial–associated molecular patterns (PAMPs or MAMPs). Activation of PRRs leads to intracellular signaling, transcriptional reprogramming, and biosynthesis of a complex output response that limits colonization. The system is known as PAMP-triggered immunity or as pattern-triggered immunity (PTI).
The second tier, primarily governed by R gene products, is often termed effector-triggered immunity (ETI). ETI is typically activated by the presence of specific pathogen "effectors" and then triggers strong antimicrobial responses (see R gene section below).
In addition to PTI and ETI, plant defenses can be activated by the sensing of damage-associated compounds (DAMP), such as portions of the plant cell wall released during pathogenic infection.
Responses activated by PTI and ETI receptors include ion channel gating, oxidative burst, cellular redox changes, or protein kinase cascades that directly activate cellular changes (such as cell wall reinforcement or antimicrobial production), or activate changes in gene expression that then elevate other defensive responses.
Plant immune systems show some mechanistic similarities with the immune systems of insects and mammals, but also exhibit many plant-specific characteristics. The two above-described tiers are central to plant immunity but do not fully describe plant immune systems. In addition, many specific examples of apparent PTI or ETI violate common PTI/ETI definitions, suggesting a need for broadened definitions and/or paradigms.
The term quantitative resistance (discussed below) refers to plant disease resistance that is controlled by multiple genes and multiple molecular mechanisms that each have small effects on the overall resistance trait. Quantitative resistance is often contrasted to ETI resistance mediated by single major-effect R genes. | 1 | Applied and Interdisciplinary Chemistry |
The bacteria R-M system has been proposed as a model for devising human anti-viral gene or genomic vaccines and therapies since the RM system serves an innate defense-role in bacteria by restricting tropism of bacteriophages. Research is on REases and ZFN that can cleave the DNA of various human viruses, including HSV-2, high-risk HPVs and HIV-1, with the ultimate goal of inducing target mutagenesis and aberrations of human-infecting viruses. The human genome already contains remnants of retroviral genomes that have been inactivated and harnessed for self-gain. Indeed, the mechanisms for silencing active L1 genomic retroelements by the three prime repair exonuclease 1 (TREX1) and excision repair cross complementing 1 (ERCC) appear to mimic the action of RM-systems in bacteria, and the non-homologous end-joining (NHEJ) that follows the use of ZFN without a repair template.
A major advance is the creation of artificial restriction enzymes created by linking the FokI DNA cleavage domain with an array of DNA binding proteins or zinc finger arrays, denoted now as zinc finger nucleases (ZFN). ZFNs are a powerful tool for host genome editing due to their enhanced sequence specificity. ZFN work in pairs, their dimerization being mediated in-situ through the FoKI domain. Each zinc finger array (ZFA) is capable of recognizing 9–12 base-pairs, making for 18–24 for the pair. A 5–7 bp spacer between the cleavage sites further enhances the specificity of ZFN, making them a safe and more precise tool that can be applied in humans. A recent Phase I clinical trial of ZFN for the targeted abolition of the CCR5 co-receptor for HIV-1 has been undertaken. | 1 | Applied and Interdisciplinary Chemistry |
Lowthian Bell (1816–1904) was, like Abraham Darby, the forceful patriarch of an ironmaking dynasty. Both his son Hugh Bell and his grandson Maurice Bell were directors of the Bell iron and steel company. His father, Thomas Bell, was a founder of Losh, Wilson and Bell, an iron and alkali company. The firm had works at Walker, near Newcastle upon Tyne, and at Port Clarence, Middlesbrough, contributing largely to the growth of those towns and of the economy of the northeast of England. Bell accumulated a large fortune, with mansions including Washington New Hall, Rounton Grange near Northallerton, and the mediaeval Mount Grace Priory near Osmotherley. | 1 | Applied and Interdisciplinary Chemistry |
With her expertise on peptide synthesis, Photaki examined the biocatalytic properties and kinetics of enzyme active site analogues she prepared.
Another research topic she developed in the early part of her career was the chemical transformation of carbohydrates and glycosylated species, such as the stereoselective conversion of -glucosamine to -serinaldehyde which formed the basis of her doctoral thesis.
Finally, she examined some of the coordination complexes formed by histidine-containing peptides with , , and , and after the antitumour properties of platinum complexes were realised, she also worked on the peptide enzymatic reactions in the presence of amine complexes. | 0 | Theoretical and Fundamental Chemistry |
Glycosylation reactions are very important reactions in carbohydrate chemistry, leading to the synthesis of oligosaccharides, preferably in a stereoselective manner. The stereoselectivity of these reactions has been shown to be affected by both the nature and the configuration of the protecting group at C-2 on the glycosyl donor ring. While 1,2-trans-glycosides (e.g. α-mannosides and β-glucosides) can be synthesised easily in the presence of a participating group (such as OAc, or NHAc) at the C-2 position in the glycosyl donor ring, 1,2-cis-glycosides are more difficult to prepare. 1,2-cis-glycosides with the α configuration (e.g. glucosides or galactosides) can often be prepared using a non-participating protecting group (such as Bn, or All) on the C-2 hydroxy group. However, 1,2-cis-glycosides with the β configuration are the most difficult to achieve, and present the greatest challenge in glycosylation reactions.
One of the most recent approaches to prepare 1,2-cis-β-glycosides in a stereospecific manner is termed ‘Intramolecular Aglycon Delivery’, and various methods have been developed based on this approach.
In this approach, the glycosyl acceptor is tethered onto the C-2-O-protecting group (X) in the first step. Upon activation of the glycosyl donor group (Y) (usually SR, OAc, or Br group) in the next step, the tethered aglycon traps the developing oxocarbenium ion at C-1, and is transferred from the same face as OH-2, forming the glycosidic bond stereospecifically. The yield of this reaction drops as the bulkiness of the alcohol increases. | 0 | Theoretical and Fundamental Chemistry |
CRTC2, initially called TORC2, is a transcriptional coactivator for the transcription factor CREB and a central regulator of
gluconeogenic gene expression in response to cAMP. CRTC2 is thought to drive tumorigenesis in STK11(LKB1)-null non-small cell lung cancers (NSCLC). | 1 | Applied and Interdisciplinary Chemistry |
Cytoplasmic abundant heat soluble (CAHS) proteins are highly expressed in response to desiccation. There are two hypotheses for their function in tardigrades. The vitrification hypothesis is the idea that, when a tardigrade becomes desiccated, the viscosity within its cells increases to the point that denaturation and membrane fusion in proteins would stop. A second hypothesis, the water replacement hypothesis, posits that CAHS proteins replace water in other desiccation-sensitive proteins, protecting the hydrogen bonds normally reliant on water. CAHS proteins are dispersed throughout the cell in normal conditions, but form a network of filaments during environmentally stressful conditions. This network transforms the cytoplasm into a gel-like matrix and prevents the cell from collapsing as water leaches out. This state is reversible and the proteins disaggregate when exposed to less stressful conditions.
When forming the filament network, CAHS proteins have long helical domains that interact in a coiled manner with each other. These interactions are possible due to the proteins' partial disorder, with two flexible tails surrounding the helical domains.
CAHS proteins have been studied to observe their interactions with trehalose, a sugar used by other species to prevent desiccation. Trehalose was found to interact at higher levels with CAHS proteins than other sugars such as sucrose. However, the exact functions of trehalose inside tardigrade cells are still unknown. | 1 | Applied and Interdisciplinary Chemistry |
Photochlorination is a chlorination reaction that is initiated by light. Usually a C-H bond is converted to a C-Cl bond. Photochlorination is carried out on an industrial scale. The process is exothermic and proceeds as a chain reaction initiated by the homolytic cleavage of molecular chlorine into chlorine radicals by ultraviolet radiation. Many chlorinated solvents are produced in this way. | 0 | Theoretical and Fundamental Chemistry |
A key tool used to determine the stability of a flow is the Reynolds number (Re), first put forward by George Gabriel Stokes at the start of the 1850s. Associated with Osborne Reynolds who further developed the idea in the early 1880s, this dimensionless number gives the ratio of inertial terms and viscous terms. In a physical sense, this number is a ratio of the forces which are due to the momentum of the fluid (inertial terms), and the forces which arise from the relative motion of the different layers of a flowing fluid (viscous terms). The equation for this is
where
The Reynolds number is useful because it can provide cut off points for when flow is stable or unstable, namely the Critical Reynolds number . As it increases, the amplitude of a disturbance which could then lead to instability gets smaller. At high Reynolds numbers it is agreed that fluid flows will be unstable. High Reynolds number can be achieved in several ways, e.g. if is a small value or if and are high values. This means that instabilities will arise almost immediately and the flow will become unstable or turbulent. | 1 | Applied and Interdisciplinary Chemistry |
Since the diameter of the probing convergent beam is smaller than in the case of a parallel beam, most of the information in the CBED pattern is obtained from very small regions, which other methods cannot reach. For example, in Selected Area Electron Diffraction (SAED), where a parallel beam illumination is used, the smallest area that can be selected is 0.5 µm at 100 kV, whereas in CBED, it is possible to go to areas smaller than 100 nm. Also, the amount of information that is obtained from a CBED pattern is larger than that from a SAED pattern.
Nonetheless, CBED also has its disadvantages. The focused probe may generate contamination, which can cause localized stresses. But this was more of a problem in the past, and now, with the high vacuum conditions, one should be able to probe a clean region of the specimen in minutes to hours. Another disadvantage is that the convergent beam may heat or damage the chosen region of the specimen.
Since 1939, CBED has been mainly used to study thicker materials. | 0 | Theoretical and Fundamental Chemistry |
In solid samarium(II) iodide, the metal centers are seven-coordinate with a face-capped octahedral geometry.
In its ether adducts, samarium remains heptacoordinate with five ether and two terminal iodide ligands. | 0 | Theoretical and Fundamental Chemistry |
Human skin is the first line of defense against many pathogens and can itself be subject to a variety of diseases and issues, such as cancers and inflammation. As such, skin-on-a-chip (SoC) applications include testing of topical pharmaceuticals and cosmetics, studying the pathology of skin diseases and inflammation, and "creating noninvasive automated cellular assays" to test for the presence of antigens or antibodies that could denote the presence of a pathogen. Despite the wide variety of potential applications, relatively little research has gone into developing a skin-on-a-chip compared to many other organ-on-a-chips, such as lungs and kidneys. Issues such as detachment of the collagen scaffolding from microchannels, incomplete cellular differentiation, and predominant use of poly(dimethysiloxane) (PDMS) for device fabrication, which has been shown to leach chemicals into biological samples and cannot be mass-produced stymie standardization of a platform. One additional difficulty is the variability of cell-culture scaffolding, or the base substance in which to culture cells, that is used in skin-on-chip devices. In the human body, this substance is known as the extracellular matrix.
The extracellular matrix (ECM) is composed primarily of collagen, and various collagen-based scaffolding has been tested in SoC models. Collagen tends to detach from the microfluidic backbone during culturing due to the contraction of fibroblasts. One study attempted to address this problem by comparing the qualities of collagen scaffolding from three different animal sources: pig skin, rat tail, and duck feet. Other studies also faced detachment issues due to contraction, which can problematic considering that the process of full skin differentiation can take up to several weeks. Contraction issues have been avoided by replacing collagen scaffolding with a fibrin-based dermal matrix, which did not contract. Greater differentiation and formation of cell layers was also reported in microfluidic culture when compared to traditional static culture, agreeing with earlier findings of improved cell-cell and cell-matrix interactions due to dynamic perfusion, or increased permeation through interstitial spaces due to the pressure from continuous media flow. This improved differentiation and growth is thought to be in part a product of shear stress created by the pressure gradient along a microchannel due to fluid flow, which may also improve nutrient supply to cells not directly adjacent to the medium. In static cultures, used in traditional skin equivalents, cells receive nutrients in the medium only through diffusion, whereas dynamic perfusion can improve nutrient flow through interstitial spaces, or gaps between cells. This perfusion has also been demonstrated to improve tight junction formation of the stratum corneum, the tough outer layer of the epidermis, which is the main barrier to penetration of the surface layer of the skin.
Dynamic perfusion may also improve cell viability, demonstrated by placing a commercial skin equivalent in a microfluidic platform that extended the expected lifespan by several weeks. This early study also demonstrated the importance of hair follicles in skin equivalent models. Hair follicles are the primary route into the subcutaneous layer for topical creams and other substances applied to the surface of the skin, a feature that more recent studies have often not accounted for.
One study developed a SoC consisting of three layers, the epidermis, dermis, and endothelial layer, separated by porous membranes, to study edema, swelling due to extracellular fluid accumulation, a common response to infection or injury and an essential step for cellular repair. It was demonstrated that pre-application of Dex, a steroidal cream with anti-inflammatory properties, reduced this swelling in the SoC. | 1 | Applied and Interdisciplinary Chemistry |
A biological pathway is a series of interactions among molecules in a cell that leads to a certain product or a change in a cell. Such a pathway can trigger the assembly of new molecules, such as a fat or protein. Pathways can also turn genes on and off, or spur a cell to move. Some of the most common biological pathways are involved in metabolism, the regulation of gene expression and the transmission of signals. Pathways play a key role in advanced studies of genomics.
Most common types of biological pathways:
*Metabolic pathway
*Genetic pathway
*Signal transduction pathway | 1 | Applied and Interdisciplinary Chemistry |
Ascorbic acid is an organic compound with formula , originally called hexuronic acid. It is a white solid, but impure samples can appear yellowish. It dissolves freely in water to give mildly acidic solutions. It is a mild reducing agent.
Ascorbic acid exists as two enantiomers (mirror-image isomers), commonly denoted "" (for "levo") and "" (for "dextro"). The isomer is the one most often encountered: it occurs naturally in many foods, and is one form ("vitamer") of vitamin C, an essential nutrient for humans and many animals. Deficiency of vitamin C causes scurvy, formerly a major disease of sailors in long sea voyages. It is used as a food additive and a dietary supplement for its antioxidant properties. The "" form can be made via chemical synthesis, but has no significant biological role. | 1 | Applied and Interdisciplinary Chemistry |
Blood pressure and fluid and electrolyte homeostasis is regulated by the renin–angiotensin–aldosterone system.
Renin, an enzyme released from the kidneys, converts the inactive plasma protein angiotensinogen into angiotensin I (Ang I). Then Ang I is converted to Ang II with angiotensin converting enzyme (ACE), see figure 2. Ang II in plasma then binds to AT-receptors.
ARBs are blocking the last part of the renin–angiotensin pathway and block the pathway more specifically than ACE inhibitors.
The AT receptor mediates Ang II to cause increased cardiac contractility, sodium reabsorption and vasoconstriction which all lead to increased blood pressure. By blocking AT receptors, ARBs lead to lower blood pressure.
An insurmountable inhibition of the AT receptor is achieved when the maximum response of Ang II cannot be restored in the presence of the ARB, no matter how high the concentration of Ang II is.
The angiotensin receptor blockers can inhibit the receptor in a competitive surmountable, competitive insurmountable or noncompetitive fashion, depending upon the rate at which they dissociate from the receptor. | 1 | Applied and Interdisciplinary Chemistry |
Chlorophenol red is an indicator dye that changes color from yellow to violet in the pH range 5.4 to 6.8. The pH of a substance is determined by taking the negative logarithm of the Hydronium ion concentration and the indictor changes color due to the dissociation of H ions. The lambda max is at 572 nm. | 0 | Theoretical and Fundamental Chemistry |
Mixtures relying on the use of acid base slushes are of limited practical value beyond producing melting point references as the enthalpy of dissolution for the melting point depressant is often significantly greater (e.g. ΔH -57.61 kJ/mol for KOH) than the enthalpy of fusion for water itself (ΔH 6.02 kJ/mol); for reference, ΔH for the dissolution of NaCl is 3.88 kJ/mol. This results in little to no net cooling capacity at the desired temperatures and an end mixture temperature that is higher than it was to begin with. The values claimed in the table are produced by first precooling and then combining each subsequent mixture with it surrounded by a mixture of the previous temperature increment; the mixtures must be stacked within one another.
Such acid base slushes are corrosive and therefore present handling problems. Additionally, they can not be replenished easily, as the volume of the mixture increases with each addition of refrigerant; the container (be it a bath or cold finger) will eventually need emptying and refilling to prevent it from overflowing. This makes these mixtures largely unsuitable for use in synthetic applications, as there will be no cooling surface present during the emptying of the container. | 0 | Theoretical and Fundamental Chemistry |
Kennedy became a professor of chemistry at the University of Florida in 1991. After 11 years, he moved to the University of Michigan. He has graduated approximately 80 graduate students. Kennedy’s research focuses on developing analytical instrumentation and methods that can help solve biological problems. He is considered a leader in the field of analytical chemistry, and an expert in endocrinology, neurochemistry, and high-throughput analysis. Major contributions to analytical chemistry include affinity probe capillary electrophoresis, in vivo neurochemical measurements, and ultra-high pressure liquid chromatography. He has been a Lilly Analytical Research Fellow, Alfred P. Sloan Fellow, NSF Presidential Faculty Fellow, and AAAS Fellow. | 0 | Theoretical and Fundamental Chemistry |
In-phase (IP) and out-of-phase (OOP) sequences correspond to paired gradient echo sequences using the same repetition time (TR) but with two different echo times (TE). This can detect even microscopic amounts of fat, which has a drop in signal on OOP compared to IP. Among renal tumors that do not show macroscopic fat, such a signal drop is seen in 80% of the clear cell type of renal cell carcinoma as well as in minimal fat angiomyolipoma. | 0 | Theoretical and Fundamental Chemistry |
Pure zirconium dioxide undergoes a phase transformation from monoclinic (stable at room temperature) to tetragonal (at about 1173 °C) and then to cubic (at about 2370 °C), according to the scheme
: monoclinic (1173 °C) ↔ tetragonal (2370 °C) ↔ cubic (2690 °C) ↔ melt.
Obtaining stable sintered zirconia ceramic products is difficult because of the large volume change, about 5%, accompanying the transition from tetragonal to monoclinic. Stabilization of the cubic polymorph of zirconia over wider range of temperatures is accomplished by substitution of some of the Zr ions (ionic radius of 0.82 Å, too small for ideal lattice of fluorite characteristic for the cubic zirconia) in the crystal lattice with slightly larger ions, e.g., those of Y (ionic radius of 0.96 Å). The resulting doped zirconia materials are termed stabilized zirconias.
Materials related to YSZ include calcia-, magnesia-, ceria- or alumina-stabilized zirconias, or partially stabilized zirconias (PSZ). Hafnia-stabilized zirconia has about 25% lower thermal conductivity, making it more suitable for thermal barrier applications.
Although 8–9 mol% YSZ is known to not be completely stabilized in the pure cubic YSZ phase up to temperatures above 1000 °C.
Commonly used abbreviations in conjunction with yttria-stabilized zirconia are:
* Partly stabilized zirconia ZrO:
** PSZ – partially stabilized zirconia
** TZP – tetragonal zirconia polycrystal
** 4YSZ: with 4 mol% YO partially stabilized ZrO, yttria-stabilized zirconia
* Fully stabilized zirconias ZrO:
** FSZ – fully stabilized zirconia
** CSZ – cubic stabilized zirconia
** 8YSZ – with 8 mol% YO fully stabilized ZrO
** 8YDZ – 8–9 mol% YO-doped ZrO: the material is not completely stabilized and decomposes at high application temperatures, see next paragraphs) | 0 | Theoretical and Fundamental Chemistry |
Chromosome walking can be used for the purpose of cloning a gene. It does this by using the known gene’s markers that are closest and can therefore be used in techniques like isolating DNA sequences and aiding in the sequencing and cloning of the DNA of organisms. Chromosome walking is also useful when it comes to filling in the gaps that may be present in genomes by locating clones that overlap with a library clone end. This means that for chromosome walking to be carried out, it requires a clone library of a genomic format. This is why Vectorette PCR is one of the methods that can be used to create this library for chromosome walking to occur. Vectorette PCR comes in handy when it is necessary to obtain the regions that are both upstream and downstream and flank a sequence that is already known. By obtaining these regions, it provides the library of a genomic format that chromosome walking requires. | 1 | Applied and Interdisciplinary Chemistry |
Although they are small, melt inclusions can provide an abundance of useful information. Using microscopic observations and a range of chemical microanalysis techniques geochemists and igneous petrologists can obtain a range of unique information from melt inclusions. There are various techniques used in analyzing melt inclusion HO and CO contents, major, minor and trace elements including double-sided FTIR micro transmittance, single-sided FTIR micro reflectance, Raman spectroscopy, microthermometry, Secondary Ion Mass Spectroscopy (SIMS), Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS), Scanning Electron Microscopy (SEM) and electron microprobe analysis (EMPA). If there is a vapor bubble present within the melt inclusion, analysis of the vapor bubble must be taken into consideration when reconstructing the total volatile budget of the melt inclusion. | 0 | Theoretical and Fundamental Chemistry |
In some applications, such as the evaporation of spherical liquid droplets in air, the following correlation is used: | 1 | Applied and Interdisciplinary Chemistry |
Nathalie Helene Katsonis (born 22 February 1978 in Vienna, Austria) is a Professor of Active Molecular Systems at the Stratingh Institute for Chemistry, University of Groningen. In 2016 she was awarded the Royal Netherlands Chemical Society Gold Medal. | 0 | Theoretical and Fundamental Chemistry |
Sonoporation, or cellular sonication, is the use of sound in the ultrasonic range for increasing the permeability of the cell plasma membrane. This technique is usually used in molecular biology and non-viral gene therapy in order to allow uptake of large molecules such as DNA into the cell, in a cell disruption process called transfection or transformation. Sonoporation employs the acoustic cavitation of microbubbles to enhance delivery of these large molecules. The exact mechanism of sonoporation-mediated membrane translocation remains unclear, with a few different hypotheses currently being explored.
Sonoporation is under active study for the introduction of foreign genes in tissue culture cells, especially mammalian cells. Sonoporation is also being studied for use in targeted Gene therapy in vivo, in a medical treatment scenario whereby a patient is given modified DNA, and an ultrasonic transducer might target this modified DNA into specific regions of the patient's body. The bioactivity of this technique is similar to, and in some cases found superior to, electroporation. Extended exposure to low-frequency (<MHz) ultrasound has been demonstrated to result in complete cellular death (rupturing), thus cellular viability must also be accounted for when employing this technique. | 1 | Applied and Interdisciplinary Chemistry |
In 1893, Werner was the first to propose correct structures for coordination compounds containing complex ions, in which a central transition metal atom is surrounded by neutral or anionic ligands.
For example, it was known that cobalt forms a "complex" hexamine cobalt (III) chloride, with formula CoCl•6NH, but the nature of the association indicated by the dot was mysterious. Werner proposed the structure [[Cobalt(III) hexammine chloride|Co(NH)Cl]], with the Co ion surrounded by six NH at the vertices of an octahedron. The three Cl are dissociated as free ions, which Werner confirmed by measuring the conductivity of the compound in an aqueous solution, and also by chloride anion analysis using precipitation with silver nitrate. Later, magnetic susceptibility analysis was also used to confirm Werner's proposal for the chemical nature of CoCl•6NH.
For complexes with more than one type of ligand, Werner succeeded in explaining the number of isomers observed. For example, he explained the existence of two tetramine isomers, "Co(NH)Cl", one green and one purple. Werner proposed that these are two geometric isomers of formula [Co(NH)Cl]Cl, with one Cl ion dissociated as confirmed by conductivity measurements. The Co atom is surrounded by four NH and two Cl ligands at the vertices of an octahedron. The green isomer is "trans" with the two Cl ligands at opposite vertices, and the purple is "cis" with the two Cl at adjacent vertices.
Werner also prepared complexes with optical isomers, and in 1914 he reported the first synthetic chiral compound lacking carbon, known as hexol with formula [Co(Co(NH)(OH))]Br. | 0 | Theoretical and Fundamental Chemistry |
Polymersomes are synthetic versions of liposomes (vesicles with a lipid bilayer), made of amphiphilic block copolymers. They can encapsulate either hydrophilic or hydrophobic contents and can be used to deliver cargo such as DNA, proteins, or drugs to cells. Advantages of polymersomes over liposomes include greater stability, mechanical strength, blood circulation time, and storage capacity. | 1 | Applied and Interdisciplinary Chemistry |
A number of public and private companies are competing to develop a full genome sequencing platform that is commercially robust for both research and clinical use, including Illumina, Knome, Sequenom,
454 Life Sciences, Pacific Biosciences, Complete Genomics,
Helicos Biosciences, GE Global Research (General Electric), Affymetrix, IBM, Intelligent Bio-Systems, Life Technologies, Oxford Nanopore Technologies, and the Beijing Genomics Institute. These companies are heavily financed and backed by venture capitalists, hedge funds, and investment banks.
A commonly-referenced commercial target for sequencing cost until the late 2010s was $1,000USD, however, the private companies are working to reach a new target of only $100. | 1 | Applied and Interdisciplinary Chemistry |
A rupture disc, also known as a pressure safety disc, burst disc, bursting disc, or burst diaphragm, is a non-reclosing pressure relief safety device that, in most uses, protects a pressure vessel, equipment or system from overpressurization or potentially damaging vacuum conditions.
A rupture disc is a type of sacrificial part because it has a one-time-use membrane that fails at a predetermined differential pressure, either positive or vacuum and at a coincident temperature. The membrane is usually made out of metal, but nearly any material (or different materials in layers) can be used to suit a particular application. Rupture discs provide instant response (within milliseconds or microseconds in very small sizes) to an increase or decrease in system pressure, but once the disc has ruptured it will not reseal. Major advantages of the application of rupture discs compared to using pressure relief valves include leak-tightness, cost, response time, size constraints, flow area, and ease of maintenance.
Rupture discs are commonly used in petrochemical, aerospace, aviation, defense, medical, railroad, nuclear, chemical, pharmaceutical, food processing and oil field applications. They can be used as single protection devices or as a secondary relief device for a conventional safety valve; if the pressure increases and the safety valve fails to operate or can not relieve enough pressure fast enough, the rupture disc will burst. Rupture discs are very often used in combination with safety relief valves, isolating the valves from the process, thereby saving on valve maintenance and creating a leak-tight pressure relief solution. It is sometimes possible and preferable for highest reliability, though at higher initial cost, to avoid the use of emergency pressure relief devices by developing an intrinsically safe mechanical design that provides containment in all cases.
Although commonly manufactured in disc form, the devices also are manufactured as rectangular panels (rupture panels, vent panels or explosion vents) and used to protect buildings, enclosed conveyor systems or any very large space from overpressurization typically due to an explosion. Rupture disc sizes range from to over , depending upon the industry application. Rupture discs and vent panels are constructed from carbon steel, stainless steel, hastelloy, graphite, and other materials, as required by the specific use environment.
Rupture discs are widely accepted throughout industry and specified in most global pressure equipment design codes (American Society of Mechanical Engineers (ASME), Pressure Equipment Directive (PED), etc.). Rupture discs can be used to specifically protect installations against unacceptably high pressures or can be designed to act as one-time valves or triggering devices to initiate with high reliability and speed a sequence of actions required. | 1 | Applied and Interdisciplinary Chemistry |
Distal promoter elements are regulatory DNA sequences that can be many kilobases distant from the gene that they regulate.
They can either be enhancers (increasing expression) or silencers (decreasing expression). They act by binding activator or repressor proteins (transcription factors) and the intervening DNA bends such that the bound proteins contact the core promoter and RNA polymerase. | 1 | Applied and Interdisciplinary Chemistry |
Jelly-falls are marine carbon cycling events whereby gelatinous zooplankton, primarily cnidarians, sink to the seafloor and enhance carbon and nitrogen fluxes via rapidly sinking particulate organic matter. These events provide nutrition to benthic megafauna and bacteria. Jelly-falls have been implicated as a major “gelatinous pathway” for the sequestration of labile biogenic carbon through the biological pump. These events are common in protected areas with high levels of primary production and water quality suitable to support cnidarian species. These areas include estuaries and several studies have been conducted in fjords of Norway. | 0 | Theoretical and Fundamental Chemistry |
Liquids are useful as lubricants due to their ability to form a thin, freely flowing layer between solid materials. Lubricants such as oil are chosen for viscosity and flow characteristics that are suitable throughout the operating temperature range of the component. Oils are often used in engines, gear boxes, metalworking, and hydraulic systems for their good lubrication properties. | 0 | Theoretical and Fundamental Chemistry |
Bipolar electrochemistry is a phenomenon in electrochemistry based on the polarization of conducting objects in electric fields. Indeed, this polarization generates a potential difference between the two extremities of the substrate that is equal to the electric field value multiplied by the size of the object. If this potential difference is important enough, then redox reactions can be generated at the extremities of the object, oxidations will occur at one extremity coupled simultaneously to reductions at the other extremity. In a simple experimental setup consisting of a platinum wire in a weighing boat containing a pH indicator solution, a 30 V voltage across two electrodes will cause water reduction at one end of the wire (the cathode) and a pH increase (OH formation) and water oxidation at the anodic end and a pH decrease. The poles of the bipolar electrode also align themselves with the applied electric field. | 0 | Theoretical and Fundamental Chemistry |
James Cullen Kirkcaldie (18 April 1875 – 16 August 1931) was a New Zealand cricketer. He played in one first-class match for Wellington in 1903/04.
Kirkcaldie was an analytical chemist. | 0 | Theoretical and Fundamental Chemistry |
This page describes how uranium dioxide nuclear fuel behaves during both normal nuclear reactor operation and under reactor accident conditions, such as overheating. Work in this area is often very expensive to conduct, and so has often been performed on a collaborative basis between groups of countries, usually under the aegis of the Organisation for Economic Co-operation and Development's Committee on the Safety of Nuclear Installations (CSNI). | 0 | Theoretical and Fundamental Chemistry |
Ang II binds to AT receptors via various binding sites. The primary binding site is at the extracellular region of the AT receptor where Ang II interacts with residues in the N-terminus of the AT receptor and its first and third extracellular loops. The transmembrane helices also contribute to the binding via the C-terminal carboxyl group that interacts with Lys in the upper part of helix 5 of the receptor; see figure 1 for details.<br />
The ionic bridge formed between Lys and the carboxyl terminal group of the Phe residue of Ang II is most likely stabilized by the Trp residue. In addition, Phe and Asp in transmembrane helix 6 and Lys and Ser in the outer region of transmembrane helix 3 have also been implicated in Ang II binding. This region may possibly participate in the stabilization of the receptor's ratification and in the formation of the intramembrane binding pocket. | 1 | Applied and Interdisciplinary Chemistry |
The simplest forge, known as the Corsican, was used prior to the advent of Christianity. Examples of improved bloomeries are the Stuckofen, sometimes called wolf-furnace,) which remained until the beginning of the 19th century. Instead of using natural draught, air was pumped in by a trompe, resulting in better quality iron and an increased capacity. This pumping of air in with bellows is known as cold blast, and it increases the fuel efficiency of the bloomery and improves yield. They can also be built bigger than natural draught bloomeries. | 1 | Applied and Interdisciplinary Chemistry |
The pipe is filled with a water solution, frozen, and bent while cold. The solute (soap can be used) makes the ice flexible. This technique is used to make trombones. | 1 | Applied and Interdisciplinary Chemistry |
Gilbert studied for a Bachelor of Science at the University of Florida, from 1940 to 1942. He then moved to the University of Wisconsin–Madison for this PhD, which he obtained in 1945 under the supervision of Samuel M. McElvain. While at Wisconsin he met Carl Djerassi, with whom he would go on to form a lasting friendship. | 0 | Theoretical and Fundamental Chemistry |
*1979 Can Test Award by the Chemical Institute of Canada
*1983 Science & Engineering Research Council Senior Fellowship
*1983 Co-recipient of an IR-100 Award
*1984 Meggers Award by the Society for Applied Spectroscopy
*1984 Lester W. Strock Award by the Society for Applied Spectroscopy
*1984 Anachem Award
*1985 Chemical Instrumentation Award by the American Chemical Society
*1986 Pittsburgh Analytical Chemistry Award from the Royal Society of Chemistry
*1986 Theophilus Redwood Award from the Royal Society of Chemistry
*1987 American Chemical Society Award in Analytical Chemistry
*1987 Tracy M. Sonneborn Teacher-Scholar Award from Indiana University
*1987 Elected to Fellowship in the American Association for the Advancement of Science
*1988 R&D 100 Award by Research & Development Magazine
*1989 ACS Award in Spectrochemical Analysis from the Analytical Chemistry Division of the American Chemical Society
*1989 Indiana Academy of Science, Fellow
*1991 Received the Gold Medal of the Quality Control Academy of the Upjohn Company
*1991 Pergamon/Spectrochimica Acta Atomic Spectroscopy Award
*1992 Eastern Analytical Symposium Award for Outstanding Achievements in the Fields of Analytical Chemistry
*1992 Awarded a second Lester W. Strock Award
*1993 Distinguished Faculty Award from the College of Arts and Sciences alumni of Indiana University
*1993 Golden Key National Honor Society, Honorary Member
*1995 Honorary Professor of Jilin University, Jilin, China
*1996 Humboldt Research Award for Senior U.S. Scientists
*1996 Meggers Award from the Society for Applied Spectroscopy
*1998 ACS-Analytical Division Award for Excellence in Teaching
*1999 Awarded Honorary Membership in the Society for Applied Spectroscopy
*1999-00 Director of the Linda and Jack Gill Center for Instrumentation and Measurement Science at Indiana University
*2000 Appointed to the Robert and Marjorie Mann Chair of Chemistry
*2000-01 Indiana Academy of Science Speaker of the Year
*2001 Pittsburgh Spectroscopy Award
*2002 Trustees Teaching Award at Indiana University
*2004 New York Section of the Society for Applied Spectroscopy Gold Medal Award
*2004 Monie A. Ferst Award (Sigma Xi)
*2004 Society for Applied Spectroscopy, Fellow
*2005 Royal Society of Chemistry, Fellow
*2007 CSI XXXV Award, sponsored by Wiley
*2009 Maurice Hasler Award
*2010 USP Award for an Outstanding Contribution to the Standard-Setting Process
*2010 Robert Boyle Prize for Analytical Science
*2011 American Chemical Society (ACS) Fellow
*2011 R&D 100 Award by Research and Development Magazine
*2012 Distinguished Service Award by the American Chemical Society-Analytical Division
*2012 Ralph and Helen Oesper Award by the University of Cincinnati
*2020 Bicentennial Medal | 0 | Theoretical and Fundamental Chemistry |
Since alkenes are mainly produced as mixtures with alkanes, the separation of alkanes and alkenes is of commercial interest. Separation technologies often rely on facilitated transport membranes containing Ag or Cu salts that reversibly bind alkenes.
In argentation chromatography, stationary phases that contain silver salts are used to analyze organic compounds on the basis of the number and type of alkene (olefin) groups. This methodology is commonly employed for the analysis of the unsaturated content in fats and fatty acids. | 0 | Theoretical and Fundamental Chemistry |
Nitro compounds participate in several organic reactions, the most important being their reduction to the corresponding amines:
:RNO + 3 H → RNH + 2 HO
Virtually all aromatic amines (e.g. aniline) are derived from nitroaromatics through such catalytic hydrogenation. A variation is formation of a dimethylaminoarene with palladium on carbon and formaldehyde:
The α-carbon of nitroalkanes is somewhat acidic. The pK values of nitromethane and 2-nitropropane are respectively 17.2 and 16.9 in dimethyl sulfoxide (DMSO) solution, suggesting an aqueous pK of around 11. In other words, these carbon acids can be deprotonated in aqueous solution. The conjugate base is called a nitronate, and behaves similar to an enolate. In the nitroaldol reaction, it adds directly to aldehydes, and, with enones, can serve as a Michael donor. Conversely, a nitroalkene reacts with enols as a Michael acceptor.
Nitronates are also key intermediates in the Nef reaction: when exposed to acids or oxidants, a nitronate hydrolyzes to a carbonyl and azanone.
Grignard reagents combine with nitro compounds to give a nitrone; but a Grignard reagent with an α hydrogen will then add again to the nitrone to give a hydroxylamine salt. | 0 | Theoretical and Fundamental Chemistry |
All of these forms of crack development are the result of the cylinder being subject to high pressure for prolonged periods. The cracks are intergranular and occur at grain boundaries. There is no evidence of stress corrosion or fatigue.
The presence of a relatively high lead content has been identified as a contributory factor. Cracking at the grain boundaries is accelerated in the presence of lead. The presence of bismuth is also suspected to be contributory.
Alloy composition has also been found to be a factor. Alloy 6061 has shown good resistance to SLC, as have alloys 5283 and 7060.
Manufacturing defects such as folds on the inside surface have been shown to be harmful, particularly for parallel-threaded cylinders.
Grain size has been shown to be of relatively minor importance. | 1 | Applied and Interdisciplinary Chemistry |
Cyanobacteria, the precursor to chloroplasts found in green plants, have both photosystems with both types of reaction centers. Combining the two systems allows for producing oxygen. | 0 | Theoretical and Fundamental Chemistry |
Reducing agents can also be considered in demand as the rapid rise of low oxidation state chemistry has been reliant on them. Common compounds include but are not limited to potassium graphite (KC), sodium naphthalenide and its alkali derivatives, or s-block metals in their elemental form, such as lithium. However, these reducing agents can have drawbacks, especially concerning accessing low oxidation states. For instance, these complexes may not be soluble in certain solutions, may lack certain selectivity, or can have an over-reduction effect of the initial precursor. Additionally, other side reactions can occur. More importantly, corrosion can be considered. Pure magnesium can be employed as an example. As the humidity increases, the corrosion rate of pure magnesium increases. At 10% humidity, there is no corrosion; at 30% there is a small layer of surface oxide, with slight corrosion evident; at 80% an amorphous phase coats about 30% of the surface and shows significant corrosion. Instances like these concerning the disadvantages of reducing agents, can make the dimers more appealing to certain chemical synthesizes. | 0 | Theoretical and Fundamental Chemistry |
An overdose of ouabain can be detected by the presence of the following symptoms: rapid twitching of the neck and chest musculature, respiratory distress, increased and irregular heartbeat, rise in blood pressure, convulsions, wheezing, clicking, and gasping rattling. Death is caused by cardiac arrest. | 0 | Theoretical and Fundamental Chemistry |
The fourteen massive lime kilns built of dressed-sandstone are a remarkable feature of Charlestown. They are regarded as one of the most important Industrial Revolution remains in Scotland and indeed the United Kingdom, being Scottish Category A Listed buildings. Built into the hillside below the village, they form a stone facade 110 metres long by 10 metres high. They are in a generally stable state of preservation with many features relating to the operation of the kilns still in situ. Most of the kilns were re-faced, probably in the 19th century.
The kilns were built by Charles Bruce, 5th Earl of Elgin, in the late 18th century, building dates quoted vary, but Pevsner states that the first nine were built 1777 to 1778 and the last five in 1792. They were the largest group of lime kilns in Scotland, producing a third of all lime production, and were particularly important to agriculture for soil improvement but also for building work to produce mortar, plaster and other lime based products.
Through the late eighteenth and nineteenth centuries, the kilns were part of a major industrial complex of the time, including coal mining, ironworking and salt extraction. Coal and limestone were brought in from the local quarries, also on the Earl's estate. The adjacent harbour was as well built by the Earl and used for transporting the lime products, limestone and importantly coal. There were local railway lines, also a railway link to Dunfermline. Around the lime kilns there were many ancillary buildings, these have almost entirely gone. The operation ran down from the 1930s and finally closed in 1956. The site is owned by the Broomhall Estate. | 1 | Applied and Interdisciplinary Chemistry |
The main use for phosphorus tribromide is for conversion of primary or secondary alcohols to alkyl bromides, as described above. PBr usually gives higher yields than hydrobromic acid, and it avoids problems of carbocation rearrangement- for example even neopentyl bromide can be made from the alcohol in 60% yield.
Another use for PBr is as a catalyst for the α-bromination of carboxylic acids. Although acyl bromides are rarely made in comparison with acyl chlorides, they are used as intermediates in Hell-Volhard-Zelinsky halogenation.
Initially PBr reacts with the carboxylic acid to form the acyl bromide, which is more reactive towards bromination. The overall process can be represented as
On a commercial scale, phosphorus tribromide is used in the manufacture of pharmaceuticals such as alprazolam, methohexital and fenoprofen. It is also a potent fire suppression agent marketed under the name PhostrEx.
Phosphorus tribromide is used for doping in microelectronics. | 0 | Theoretical and Fundamental Chemistry |
Olbers paradox is another paradox which aims to disprove an infinitely old static universe, but it only fits with a static universe scenario. Also, unlike Kelvins paradox, it relies on cosmology rather than thermodynamics. The Boltzmann Brain can also be related to Kelvin's, as it focuses on the spontaneous generation of a brain (filled with false memories) from entropy fluctuations, in a universe which has been lying in a heat death state for an indefinite amount of time. | 0 | Theoretical and Fundamental Chemistry |
Single-nucleotide polymorphisms may fall within coding sequences of genes, non-coding regions of genes, or in the intergenic regions (regions between genes). SNPs within a coding sequence do not necessarily change the amino acid sequence of the protein that is produced, due to degeneracy of the genetic code.
SNPs in the coding region are of two types: synonymous SNPs and nonsynonymous SNPs. Synonymous SNPs do not affect the protein sequence, while nonsynonymous SNPs change the amino acid sequence of protein.
* SNPs in non-coding regions can manifest in a higher risk of cancer, and may affect mRNA structure and disease susceptibility. Non-coding SNPs can also alter the level of expression of a gene, as an eQTL (expression quantitative trait locus).
* SNPs in coding regions:
** synonymous substitutions by definition do not result in a change of amino acid in the protein, but still can affect its function in other ways. An example would be a seemingly silent mutation in the multidrug resistance gene 1 (MDR1), which codes for a cellular membrane pump that expels drugs from the cell, can slow down translation and allow the peptide chain to fold into an unusual conformation, causing the mutant pump to be less functional (in MDR1 protein e.g. C1236T polymorphism changes a GGC codon to GGT at amino acid position 412 of the polypeptide (both encode glycine) and the C3435T polymorphism changes ATC to ATT at position 1145 (both encode isoleucine)).
** nonsynonymous substitutions:
*** missense – single change in the base results in change in amino acid of protein and its malfunction which leads to disease (e.g. c.1580G>T SNP in LMNA gene – position 1580 (nt) in the DNA sequence (CGT codon) causing the guanine to be replaced with the thymine, yielding CTT codon in the DNA sequence, results at the protein level in the replacement of the arginine by the leucine in the position 527, at the phenotype level this manifests in overlapping mandibuloacral dysplasia and progeria syndrome)
*** nonsense – point mutation in a sequence of DNA that results in a premature stop codon, or a nonsense codon in the transcribed mRNA, and in a truncated, incomplete, and usually nonfunctional protein product (e.g. Cystic fibrosis caused by the G542X mutation in the cystic fibrosis transmembrane conductance regulator gene).
SNPs that are not in protein-coding regions may still affect gene splicing, transcription factor binding, messenger RNA degradation, or the sequence of noncoding RNA. Gene expression affected by this type of SNP is referred to as an eSNP (expression SNP) and may be upstream or downstream from the gene. | 1 | Applied and Interdisciplinary Chemistry |
The folded protein complexes of interest separate cleanly and predictably without the risk of denaturation due to the specific properties of the polyacrylamide gel, electrophoresis buffer solution, electrophoretic equipment and standardized parameters used. The separated proteins are continuously eluted into a physiological eluent and transported to a fraction collector. In four to five PAGE fractions each the different metal cofactors can be identified and absolutely quantified by high-resolution ICP-MS. The associated structures of the isolated metalloproteins in these fractions can be specifically determined by solution NMR spectroscopy. | 1 | Applied and Interdisciplinary Chemistry |
Electrokinesis is the particle or fluid transport produced by an electric field acting on a fluid having a net mobile charge. (See -kinesis for explanation and further uses of the -kinesis suffix.) Electrokinesis was first observed by Ferdinand Frederic Reuss during 1808, in the electrophoresis of clay particles The effect was also noticed and publicized in the 1920s by Thomas Townsend Brown which he called the Biefeld–Brown effect, although he seems to have misidentified it as an electric field acting on gravity. The flow rate in such a mechanism is linear in the electric field. Electrokinesis is of considerable practical importance in microfluidics, because it offers a way to manipulate and convey fluids in microsystems using only electric fields, with no moving parts.
The force acting on the fluid, is given by the equation
where, is the resulting force, measured in newtons, is the current, measured in amperes, is the distance between electrodes, measured in metres, and is the ion mobility coefficient of the dielectric fluid, measured in m/(V·s).
If the electrodes are free to move within the fluid, while keeping their distance fixed from each other, then such a force will actually propel the electrodes with respect to the fluid.
Electrokinesis has also been observed in biology, where it was found to cause physical damage to neurons by inciting movement in their membranes. It is discussed in R. J. Elul's "Fixed charge in the cell membrane" (1967). | 1 | Applied and Interdisciplinary Chemistry |
EPA issued a drinking water health advisory for MTBE, a guidance document for water utilities and the public, in 1997. The Agency first listed MTBE in 1998 as a candidate for development of a national Maximum Contaminant Level (MCL) standard in drinking water. As of 2020 EPA has not announced whether it will develop an MCL. EPA uses toxicity data in developing MCLs for public water systems.
California established a state-level MCL for MTBE in 2000. | 1 | Applied and Interdisciplinary Chemistry |
DNA digital data storage is the process of encoding and decoding binary data to and from synthesized strands of DNA.
While DNA as a storage medium has enormous potential because of its high storage density, its practical use is currently severely limited because of its high cost and very slow read and write times.
In June 2019, scientists reported that all 16 GB of text from the English Wikipedia had been encoded into synthetic DNA. In 2021, scientists reported that a custom DNA data writer had been developed that was capable of writing data into DNA at 18 Mbps. | 1 | Applied and Interdisciplinary Chemistry |
*Represents the majority 85-90% of typical tall oil.
*abietic acid
**abieta-7,13-dien-18-oic acid
**13-isopropylpodocarpa -7,13-dien-15-oic acid
*Neoabietic acid
*Dehydroabietic acid
*Palustric acid
*Levopimaric acid
*Simplified formula CHO, or CHCOOH
*molecular weight 302 | 1 | Applied and Interdisciplinary Chemistry |
Ultrasonic cure monitoring methods are based on the relationships between changes in the characteristics of propagating ultrasound and the real-time mechanical properties of a component, by measuring:
*ultrasonic time of flight, both in through-transmission and pulse-echo modes;
*natural frequency using impact excitation and laser-induced surface acoustic wave velocity measurement. | 0 | Theoretical and Fundamental Chemistry |
IUPAC nomenclature has extensive rules to cover the naming of cyclic structures, both as core structures, and as substituents appended to alicyclic structures. The term macrocycle is used when a ring-containing compound has a ring of 12 or more atoms. The term polycyclic is used when more than one ring appears in a single molecule. Naphthalene is formally a polycyclic compound, but is more specifically named as a bicyclic compound. Several examples of macrocyclic and polycyclic structures are given in the final gallery below.
The atoms that are part of the ring structure are called annular atoms. | 0 | Theoretical and Fundamental Chemistry |
Photogeochemistry merges photochemistry and geochemistry into the study of light-induced chemical reactions that occur or may occur among natural components of Earth's surface. The first comprehensive review on the subject was published in 2017 by the chemist and soil scientist Timothy A Doane, but the term photogeochemistry appeared a few years earlier as a keyword in studies that described the role of light-induced mineral transformations in shaping the biogeochemistry of Earth; this indeed describes the core of photogeochemical study, although other facets may be admitted into the definition. | 0 | Theoretical and Fundamental Chemistry |
Studies on how people transform the substances that they ingest began in the mid-nineteenth century, with chemists discovering that organic chemicals such as benzaldehyde could be oxidized and conjugated to amino acids in the human body. During the remainder of the nineteenth century, several other basic detoxification reactions were discovered, such as methylation, acetylation, and sulfonation.
In the early twentieth century, work moved on to the investigation of the enzymes and pathways that were responsible for the production of these metabolites. This field became defined as a separate area of study with the publication by Richard Williams of the book Detoxication mechanisms in 1947. This modern biochemical research resulted in the identification of glutathione S-transferases in 1961, followed by the discovery of cytochrome P450s in 1962, and the realization of their central role in xenobiotic metabolism in 1963. | 1 | Applied and Interdisciplinary Chemistry |
The functional group will readily hydrolyse to give a phosphine oxide and an amine
:RP=NR + HO → RP=O + RNH
Phosphinimide ligands of the general formula NPR form transition metal phosphinimide complexeses. Some of these complexes are potential catalysts for the synthesis of polyethylene. | 0 | Theoretical and Fundamental Chemistry |
Färber (spelling changed in 1938) grew up in Leipzig as the son of a businessman and studied natural sciences (chemistry, physics, and mineralogy) in Leipzig with doctorate in 1916. He then became an assistant to Carl Neuberg at the Kaiser-Wilhelm-Institut für Experimentelle Therapie in Berlin. Due to an eye ailment he was not drafted in World War I, but worked at a laboratory in 1917/18 in Budapest in the conversion of a fermentation factory into a factory for glycerol production used in the ammunition industry. After the war he became chief chemist and chemical research director of Deutsche Bergin A.G. and
Holzhydrolyse A.G. at Mannheim-Rheinau and Heidelberg. In National Socialist Germany, he anticipated an unfavorable future and in 1938 immigrated with his family to the United States, where he again worked in the chemical industry and as a consultant. In 1943 he became head of chemical research at Timber Engineering Corp. in Washington, D.C. In 1957 he retired, but remained active as a consultant.
He held 85 US patents and published about 50 papers as an industrial chemist. But he is known for his work on the history of chemistry. Already in Berlin he was interested in the history of chemistry. He was inspired by the book Die Geschichte der Chemie von den ältesten Zeiten bis our Gegenwart (1899) by Ernst von Meyer. In that book and in other books on the history of chemistry, Farber thought that there was insufficient social and economic context for the chemical developments. Thus he wrote his own book (funded by Neuberg) on the history of chemistry, which was published in 1921 by Springer. In 1929/30 he contributed five biographical sketches to the anthology of Günther Bugge Das Buch der Großen Chemiker (The book of the great chemists). In 1955/56 Farber was the director of the Historical Section of the American Chemical Society.
In 1962 he became an adjunct professor at the American University in Washington, D.C. He was an advisor to the Smithsonian Institution.
In 1964 he received the Dexter Award for Outstanding Achievement in the History of Chemistry from the American Chemical Society. | 1 | Applied and Interdisciplinary Chemistry |
Middle-of-house testing is a new development, started by The Loop in the UK. Testing happens on-site, but without face-to-face interaction with the public. Samples from medical incidents are tested and alerts can be issued after multiple incidents with a trend are identified. | 0 | Theoretical and Fundamental Chemistry |
Recovery of metals from oxide matrixes is generally carried out using mineral acids. However, electrochemical dissolution of metal oxides in DES can allow to enhance the dissolution up to more than 10 000 times in pH neutral solutions.
Studies have shown that ionic oxides such as ZnO tend to have high solubility in ChCl:malonic acid, ChCl:urea and Ethaline, which can resemble the solubilities in aqueous acidic solutions, e.g., HCl. Covalent oxides such as TiO, however, exhibits almost no solubility. The electrochemical dissolution of metal oxides is strongly dependent on the proton activity from the HBD, i.e. capability of the protons to act as oxygen acceptors, and on the temperature. It has been reported that eutectic ionic fluids of lower pH-values, such as ChCl:oxalic acid and ChCl:lactic acid, allow a better solubility than that of higher pH (e.g., ChCl:acetic acid). Hence, different solubilities can be obtained by using, for instance, different carboxylic acids as HBD. | 1 | Applied and Interdisciplinary Chemistry |
* rs6311 and rs6313 are SNPs in the Serotonin 5-HT2A receptor gene on human chromosome 13.
* The SNP − 3279C/A (rs3761548) is amongst the SNPs locating in the promoter region of the Foxp3 gene, might be involved in cancer progression.
* A SNP in the F5 gene causes Factor V Leiden thrombophilia.
* rs3091244 is an example of a triallelic SNP in the CRP gene on human chromosome 1.
* TAS2R38 codes for PTC tasting ability, and contains 6 annotated SNPs.
* rs148649884 and rs138055828 in the FCN1 gene encoding M-ficolin crippled the ligand-binding capability of the recombinant M-ficolin.
* An intronic SNP in DNA mismatch repair gene PMS2 (rs1059060, Ser775Asn) is associated with increased sperm DNA damage and risk of male infertility. | 1 | Applied and Interdisciplinary Chemistry |
* McGrew, Roderick. Encyclopedia of Medical History (1985), brief history pp 25–30
* [http://dels.nas.edu/metagenomics Our Microbial Planet] A free poster from the National Academy of Sciences about the positive roles of micro-organisms.
*[https://web.archive.org/web/20080527234727/http://www.asm.org/ASM/files/ccLibraryFiles/Filename/000000003691/Uncharted_Microbial_World.pdf "Uncharted Microbial World: Microbes and Their Activities in the Environment"] Report from the American Academy of Microbiology
* [http://dels.nas.edu/dels/rpt_briefs/metagenomics_final.pdf Understanding Our Microbial Planet: The New Science of Metagenomics] A 20-page educational booklet providing a basic overview of metagenomics and our microbial planet.
* [http://tolweb.org/Eukaryotes/3 Tree of Life Eukaryotes]
* [http://www.genomenewsnetwork.org/categories/index/microbes.php Microbe News from Genome News Network]
* [https://web.archive.org/web/20090920024442/http://gsbs.utmb.edu/microbook/toc.htm Medical Microbiology] On-line textbook
* [http://www.microbiologytext.com/index.php?module=Book&func=toc&book_id=4 Through the microscope: A look at all things small] On-line microbiology textbook by Timothy Paustian and Gary Roberts, University of Wisconsin-Madison | 1 | Applied and Interdisciplinary Chemistry |
Classically, the kinetic energy of rotation is
:where
:: is the angular momentum
:: is the moment of inertia of the molecule
For microscopic, atomic-level systems like a molecule, angular momentum can only have specific discrete values given by
:where is a non-negative integer and is the reduced Planck constant.
Also, for a diatomic molecule the moment of inertia is
:where
:: is the reduced mass of the molecule and
:: is the average distance between the centers of the two atoms in the molecule.
So, substituting the angular momentum and moment of inertia into E, the rotational energy levels of a diatomic molecule are given by: | 0 | Theoretical and Fundamental Chemistry |
Alizarine Yellow R is produced by azo coupling of salicylic acid and diazonium derivative of 4-Nitroaniline | 0 | Theoretical and Fundamental Chemistry |
The derivation starts with Ficks first law using a uniform distance axis y as the coordinate system and having the origin fixed to the location of the markers. It is assumed that the markers move relative to the diffusion of one component and into one of the two initial rods, as was chosen in Kirkendalls experiment. In the following equation, which represents Ficks first law for one of the two components, D is the diffusion coefficient of component one, and C' is the concentration of component one:
This coordinate system only works for short range from the origin because of the assumption that marker movement is indicative of diffusion alone, which is not true for long distances from the origin as stated before. The coordinate system is transformed using a Galilean transformation, y = x − νt, where x is the new coordinate system that is fixed to the ends of the two rods, ν is the marker velocity measured with respect to the x axis. The variable t, time, is assumed to be constant, so that the partial derivative of C with respect to y is equal to the partial of C with respect to x. This transformation then yields
The above equation, in terms of the variable x, only takes into account diffusion, so the term for the motion of the markers must also be included, since the frame of reference is no longer moving with the marker particles. In the equation below, is the velocity of the markers.
Taking the above equation and then equating it to the accumulation rate in a volume results in the following equation. This result is similar to Fick's second law, but with an additional advection term:
The same equation can be written for the other component, designated as component two:
Using the assumption that C, the total concentration, is constant, C and C can be related in the following expression:
The above equation can then be used to combine the expressions for and to yield
Since C is constant, the above equation can be written as
The above equation states that is constant because the derivative of a constant is equal to zero. Therefore, by integrating the above equation it is transforms to , where is an integration constant.
At relative infinite distances from the initial interface, the concentration gradients of each of the components and the marker velocity can be assumed to be equal to zero. Based on this condition and the choice for the coordinate axis, where the x axis fixed at the far ends of the rods, I is equal zero. These conditions then allow the equation to be rearranged to give
Since C is assumed to be constant, . Rewriting this equation in terms of atom fraction and yields | 0 | Theoretical and Fundamental Chemistry |
Topology of a transmembrane protein refers to locations of N- and C-termini of membrane-spanning polypeptide chain with respect to the inner or outer sides of the biological membrane occupied by the protein.
Several databases provide experimentally determined topologies of membrane proteins. They include Uniprot, TOPDB, OPM, and ExTopoDB. There is also a database of domains located conservatively on a certain side of membranes, TOPDOM.
Several computational methods were developed, with a limited success, for predicting transmembrane alpha-helices and their topology. Pioneer methods utilized the fact that membrane-spanning regions contain more hydrophobic residues than other parts of the protein, however applying different hydrophobic scales altered the prediction results. Later, several statistical methods were developed to improve the topography prediction and a special alignment method was introduced. According to the positive-inside rule, cytosolic loops near the lipid bilayer contain more positively-charged amino acids. Applying this rule resulted in the first topology prediction methods. There is also a negative-outside rule in transmembrane alpha-helices from single-pass proteins, although negatively charged residues are rarer than positively charged residues in transmembrane segments of proteins. As more structures were determined, machine learning algorithms appeared. Supervised learning methods are trained on a set of experimentally determined structures, however, these methods highly depend on the training set. Unsupervised learning methods are based on the principle that topology depends on the maximum divergence of the amino acid distributions in different structural parts. It was also shown that locking a segment location based on prior knowledge about the structure improves the prediction accuracy. This feature has been added to some of the existing prediction methods. The most recent methods use consensus prediction (i.e. they use several algorithm to determine the final topology) and automatically incorporate previously determined experimental informations. HTP database provides a collection of topologies that are computationally predicted for human transmembrane proteins.
Discrimination of signal peptides and transmembrane segments is an additional problem in topology prediction treated with a limited success by different methods. Both signal peptides and transmembrane segments contain hydrophobic regions which form α-helices. This causes the cross-prediction between them, which is a weakness of many transmembrane topology predictors. By predicting signal peptides and transmembrane helices simultaneously (Phobius), the errors caused by cross-prediction are reduced and the performance is substantially increased. Another feature used to increase the accuracy of the prediction is the homology (PolyPhobius).”
It is also possible to predict beta-barrel membrane proteins' topology. | 0 | Theoretical and Fundamental Chemistry |
Levomethamphetamine is an active metabolite of the antiparkinson's drug selegiline. Selegiline, a selective monoamine oxidase B (MAO) inhibitor at low doses, is also metabolized into levomethamphetamine and levoamphetamine. This has caused users to test positive for amphetamines.
Selegiline itself has neuroprotective and neuro-rescuing effects, but concern over the resulting levomethamphetamine's neurotoxicity led to development of alternative MAO inhibitors, such as rasagiline, that do not produce toxic metabolites. | 0 | Theoretical and Fundamental Chemistry |
Molecular-weight size markers can be broken up into two categories: molecular weight markers vs. molecular ladder markers. Markers are either stained or unstained, and depending on the circumstance, one may be more appropriate than another. Molecular-weight size markers can also be biochemically altered. The conjugation with biotin is the most common. Molecular-weight size markers are most commonly used in SDS-polyacrylamide gel electrophoresis and western blotting.
With all the different types and uses of molecular-weight size markers, it is important to choose the appropriate protein standard. Besides the most common use, as a way to calculate the molecular weight of the samples, other uses include allowing visual evidence of protein migration and transfer efficiency and are sometimes even used for positive control. | 1 | Applied and Interdisciplinary Chemistry |
Glycoside hydrolases are predicted to gain increasing roles as catalysts in biorefining
applications in the future bioeconomy. These enzymes have a variety of uses including degradation of plant materials (e.g., cellulases for degrading cellulose to glucose, which can be used for ethanol production), in the food industry (invertase for manufacture of invert sugar, amylase for production of maltodextrins), and in the paper and pulp industry (xylanases for removing hemicelluloses from paper pulp). Cellulases are added to detergents for the washing of cotton fabrics and assist in the maintenance of colours through removing microfibres that are raised from the surface of threads during wear.
In organic chemistry, glycoside hydrolases can be used as synthetic catalysts to form glycosidic bonds through either reverse hydrolysis (kinetic approach) where the equilibrium position is reversed; or by transglycosylation (kinetic approach) whereby retaining glycoside hydrolases can catalyze the transfer of a glycosyl moiety from an activated glycoside to an acceptor alcohol to afford a new glycoside.
Mutant glycoside hydrolases termed glycosynthases have been developed that can achieve the synthesis of glycosides in high yield from activated glycosyl donors such as glycosyl fluorides. Glycosynthases are typically formed from retaining glycoside hydrolases by site-directed mutagenesis of the enzymic nucleophile to some other less nucleophilic group, such as alanine or glycine. Another group of mutant glycoside hydrolases termed thioglycoligases can be formed by site-directed mutagenesis of the acid-base residue of a retaining glycoside hydrolase. Thioglycoligases catalyze the condensation of activated glycosides and various thiol-containing acceptors.
Various glycoside hydrolases have shown efficacy in degrading matrix polysaccharides within the extracellular polymeric substance (EPS) of microbial biofilms. Medically, biofilms afford infectious microorganisms a variety of advantages over their planktonic, fre-floating counterparts, including greatly increased tolerances to antimicrobial agents and the host immune system. Thus, degrading the biofilm may increase antibiotic efficacy, and potentiate host immune function and healing ability. For example, a combination of alpha-amylase and cellulase was shown to degrade polymicrobial bacterial biofilms from both in vitro and in vivo sources, and increase antibiotic effectiveness against them. | 0 | Theoretical and Fundamental Chemistry |
The main shortcoming related to the free volume concept is that it is not so well defined at the molecular level. A more precise, molecular-level derivation of the Flory–Fox equation has been developed by Alessio Zaccone and Eugene Terentjev. The derivation is based on a molecular-level model of the temperature-dependent shear modulus G of glassy polymers. The shear modulus of glasses has two main contributions, one which is related to affine displacements of the monomers in response to the macroscopic strain, which is proportional to the local bonding environment and also to the non-covalent van der Waals-type interactions, and a negative contribution that corresponds to random (nonaffine) monomer-level displacements due to the local disorder. Due to thermal expansion, the first (affine) term decreases abruptly near the glass transition temperature T because of the weakening of the non-covalent interactions, while the negative nonaffine term is less affected by temperature. Experimentally, it is observed indeed that G drops sharply by many orders of magnitude at or near T (it does not really drop to zero but to the much lower value of the rubber elasticity plateau). By setting at the point where the G drops abruptly and solving for T, one obtains the following relation:
In this equation, is the maximum volume fraction, or packing fraction, occupied by the monomers at the glass transition if there were no covalent bonds, i.e. in the limit of average number of covalent bonds per monomer .
If the monomers can be approximated as soft spheres, then as in the jamming of soft frictionless spheres.
In the presence of covalent bonds between monomers, as is the case in the polymer, the packing fraction is lowered, hence , where is a parameter that expresses the effect of topological constraints due to covalent bonds on the total packing fraction occupied by the monomers in a given polymer.
Finally, the packing fraction occupied by the monomers in the absence of covalent bonds is related to via thermal expansion, according to , which comes from integrating the thermodynamic relation between thermal expansion coefficient and volume V, , where is the coefficient of thermal expansion of the polymer in the glassy state. Note the relation between packing fraction and total volume given by , where is the total number of monomers, with molecular volume , contained in the total volume of the material, which has been used above. Hence is the integration constant in , and it was found that for the case of polystyrene. Also, is the molecular weight of one monomer in the polymer chain.
Hence the above equation clearly recovers the Flory–Fox equation with its dependence on the number average molecular weight , and provides a molecular-level meaning to the empirical parameters present in the Fox-Flory equation. Furthermore, it predicts that , i.e. that the glass transition temperature is inversely proportional to the thermal expansion coefficient in the glass state. | 0 | Theoretical and Fundamental Chemistry |
Metal carbonyls are coordination complexes of transition metals with carbon monoxide ligands. Metal carbonyls are useful in organic synthesis and as catalysts or catalyst precursors in homogeneous catalysis, such as hydroformylation and Reppe chemistry. In the Mond process, nickel tetracarbonyl is used to produce pure nickel. In organometallic chemistry, metal carbonyls serve as precursors for the preparation of other organometallic complexes.
Metal carbonyls are toxic by skin contact, inhalation or ingestion, in part because of their ability to carbonylate hemoglobin to give carboxyhemoglobin, which prevents the binding of oxygen. | 0 | Theoretical and Fundamental Chemistry |
In a sense, any spectrum analyzer that has vector signal analyzer capability is a realtime analyzer. It samples data fast enough to satisfy Nyquist Sampling theorem and stores the data in memory for later processing. This kind of analyser is only realtime for the amount of data / capture time it can store in memory and still produces gaps in the spectrum and results during processing time. | 0 | Theoretical and Fundamental Chemistry |
The speed of sound in mathematical notation is conventionally represented by c, from the Latin celeritas meaning "swiftness".
For fluids in general, the speed of sound c is given by the Newton–Laplace equation:
where
* is a coefficient of stiffness, the isentropic bulk modulus (or the modulus of bulk elasticity for gases);
* is the density.
Note that , where is the pressure and the derivative is taken isentropically, that is, at constant entropy s. This is because a sound wave travels so fast that its propagation can be approximated as an adiabatic process, meaning that there isn't enough time, during a pressure cycle of the sound, for significant heat conduction and radiation to occur.
Thus, the speed of sound increases with the stiffness (the resistance of an elastic body to deformation by an applied force) of the material and decreases with an increase in density. For ideal gases, the bulk modulus K is simply the gas pressure multiplied by the dimensionless adiabatic index, which is about 1.4 for air under normal conditions of pressure and temperature.
For general equations of state, if classical mechanics is used, the speed of sound c can be derived as follows:
Consider the sound wave propagating at speed through a pipe aligned with the axis and with a cross-sectional area of . In time interval it moves length . In steady state, the mass flow rate must be the same at the two ends of the tube, therefore the mass flux is constant and . Per Newton's second law, the pressure-gradient force provides the acceleration:
And therefore:
If relativistic effects are important, the speed of sound is calculated from the relativistic Euler equations.
In a non-dispersive medium, the speed of sound is independent of sound frequency, so the speeds of energy transport and sound propagation are the same for all frequencies. Air, a mixture of oxygen and nitrogen, constitutes a non-dispersive medium. However, air does contain a small amount of CO which is a dispersive medium, and causes dispersion to air at ultrasonic frequencies ().
In a dispersive medium, the speed of sound is a function of sound frequency, through the dispersion relation. Each frequency component propagates at its own speed, called the phase velocity, while the energy of the disturbance propagates at the group velocity. The same phenomenon occurs with light waves; see optical dispersion for a description. | 1 | Applied and Interdisciplinary Chemistry |
The Trust for Public Land has completed 183 green school yards across the 5 boroughs in New York. Existing asphalt school yards are converted to a more vibrant and exciting place while also incorporating infrastructure to capture and store rainwater: rain garden, rain barrel, tree groves with pervious pavers, and an artificial field with a turf base. The children are engaged in the design process, lending to a sense of ownership and encourages children to take better care of their school yard. Success in New York has allowed other cities like Philadelphia and Oakland to also convert to green school yards. | 1 | Applied and Interdisciplinary Chemistry |
Typical for platinum(IV) complexes, [Pt(NH)] is diamagnetic and kinetically inert, e.g. unaffected by strong acids. The cation obeys the 18-electron rule. It is prepared by treatment of methylamine complex [Pt(NHCH)Cl]Cl with ammonia.
The complex [Pt(NH)] is a rare example of a tetracationic ammine complex. Its conjugate bases [Pt(NH)NH] and [Pt(NH)(NH)] have been characterized. | 0 | Theoretical and Fundamental Chemistry |
The formation of dropwise condensation on PDRC surfaces can alter the infrared emittance of the surface of selective PDRC emitters, which can weaken their performance. Even in semi-arid environments, dew formation on PDRC surfaces can occur. Thus, the cooling power of selective emitters "may broaden the narrowband emittances of the selective emitter and reduce their sub-ambient cooling power and their supposed cooling benefits over broadband emitters," as per Simsek et al., who discuss the implications on the performance of selective emitters: | 0 | Theoretical and Fundamental Chemistry |
Sources of manganese ore generally also contain iron oxides. As manganese is harder to reduce than iron, during the reduction of manganese ore, iron is also reduced and mixed with the manganese in the melt, unlike other oxides such as SiO, AlO and CaO.
Reduction is achieved using a submerged arc furnance. There are two main industrial procedures to perform the reduction, the discard slag method (or flux method) and the duplex method (or fluxless method). Despite the name, the differences in the method are not in the addition of flux, but rather in the number of stages required. In the flux method, basic fluxes such as CaO are added in order to electrolytically reduce the manganese ore:
The remaining slag after the reduction process has approximately 15-20% manganese content, which is usually discarded.
In the fluxless method, carbon reduction is also used in the first stage, but the fluxes added do not necessarily increase the activity of the manganese. As a result, the remaining slag has a concentration of 30% to 50% of the manganese. This is then reprocessed with quartzite to make silicomanganese alloys. The resultant discarded slag has a manganese content of less than 5%, increasing the yield. As a result, this method is used more often in industry.
In both methods, due to the addition of carbon as an reducing agent, the alloy produced is referred to as high-carbon ferromanganese (HCFM), with a carbon content of up to 6%.
A correct mix of coke, flux and ore composition is required to give high yield and reliable furnance operation, by achieving the desired chemical properties, viscosity and smelting temperature in the resulting melt. Since the iron to manganese ratio of natural manganese sources vary greatly, mixing ores from several sources is sometimes done to give a certain desired ratio.
In the manufacture of steel, low-carbon ferromanganese (LCFM) is preferred due to the ability to accurately control the amount of carbon in the resultant steel. To arrive at LCFM from HCFM, there are also two main methods: silicothermal reduction and oxygen refinement.
In silicothermal reduction, silicomanganese from the second step of the duplex process is used as a reductant. After a variety of mixing and meting steps to reduce the silicon content, a low-carbon allow with less than 0.8% carbon and 1% silicon by weight can be obtained.
In the oxygen refinement method, HCFM is melted and heated to a high temperature of . Oxygen is then blown in to oxidise the carbon into CO and CO. The disadvantage of this process is that the metal is also oxidised at these high temperatures. Manganese oxide collects mainly in the form of MnO in the dust blown out from the crucible. | 1 | Applied and Interdisciplinary Chemistry |
An organic acid anhydride is an acid anhydride that is also an organic compound. An acid anhydride is a compound that has two acyl groups bonded to the same oxygen atom. A common type of organic acid anhydride is a carboxylic anhydride, where the parent acid is a carboxylic acid, the formula of the anhydride being (RC(O))O. Symmetrical acid anhydrides of this type are named by replacing the word acid in the name of the parent carboxylic acid by the word anhydride. Thus, (CHCO)O is called acetic anhydride. Mixed (or unsymmetrical) acid anhydrides, such as acetic formic anhydride (see below), are known, whereby reaction occurs between two different carboxylic acids. Nomenclature of unsymmetrical acid anhydrides list the names of both of the reacted carboxylic acids before the word "anhydride" (for example, the dehydration reaction between benzoic acid and propanoic acid would yield "benzoic propanoic anhydride").
One or both acyl groups of an acid anhydride may also be derived from another type of organic acid, such as sulfonic acid or a phosphonic acid. One of the acyl groups of an acid anhydride can be derived from an inorganic acid such as phosphoric acid. The mixed anhydride 1,3-bisphosphoglyceric acid, an intermediate in the formation of ATP via glycolysis, is the mixed anhydride of 3-phosphoglyceric acid and phosphoric acid. Acidic oxides are also classified as acid anhydrides. | 0 | Theoretical and Fundamental Chemistry |
Thermal expansion coefficients of solids usually show little dependence on temperature (except at very low temperatures) whereas liquids can expand at different rates at different temperatures. There are some exceptions: for example, cubic boron nitride exhibits significant variation of its thermal expansion coefficient over a broad range of temperatures. Another example is paraffin which in its solid form has a thermal expansion coefficient that is dependent on temperature. | 0 | Theoretical and Fundamental Chemistry |
Most supramolecular catalysts are developed from rigid building blocks because rigid blocks are less complicated than flexible parts in constructing a desired shape and placing functional groups where the designer wants. Due to the rigidity, however, a slight mismatch from the transition state inevitably leads to poor stabilization and thus poor catalysis. In nature, enzymes are flexible and could change their structures to bind a transition state better than their native form. | 0 | Theoretical and Fundamental Chemistry |
The other pathway, non-cyclic photophosphorylation, is a two-stage process involving two different chlorophyll photosystems in the thylakoid membrane. First, a photon is absorbed by chlorophyll pigments surrounding the reaction core center of photosystem II. The light excites an electron in the pigment P680 at the core of photosystem II, which is transferred to the primary electron acceptor, pheophytin, leaving behind P680. The energy of P680 is used in two steps to split a water molecule into 2H + 1/2 O + 2e (photolysis or light-splitting). An electron from the water molecule reduces P680 back to P680, while the H and oxygen are released. The electron transfers from pheophytin to plastoquinone (PQ), which takes 2e (in two steps) from pheophytin, and two H Ions from the stroma to form PQH. This plastoquinol is later oxidized back to PQ, releasing the 2e to the cytochrome bf complex and the two H ions into the thylakoid lumen. The electrons then pass through Cyt b and Cyt f to plastocyanin, using energy from photosystem I to pump hydrogen ions (H) into the thylakoid space. This creates a H gradient, making H ions flow back into the stroma of the chloroplast, providing the energy for the (re)generation of ATP.
The photosystem II complex replaced its lost electrons from HO, so electrons are not returned to photosystem II as they would in the analogous cyclic pathway. Instead, they are transferred to the photosystem I complex, which boosts their energy to a higher level using a second solar photon. The excited electrons are transferred to a series of acceptor molecules, but this time are passed on to an enzyme called ferredoxin-NADP reductase, which uses them to catalyze the reaction
:NADP + 2H + 2e → NADPH + H
This consumes the H ions produced by the splitting of water, leading to a net production of 1/2O, ATP, and NADPH + H with the consumption of solar photons and water.
The concentration of NADPH in the chloroplast may help regulate which pathway electrons take through the light reactions. When the chloroplast runs low on ATP for the Calvin cycle, NADPH will accumulate and the plant may shift from noncyclic to cyclic electron flow. | 0 | Theoretical and Fundamental Chemistry |
;Temperature
:When the foraging organism's optimal foraging temperature is present, the organism will be more likely to search for food. Often, the further temperature falls out of this range, the less likely foraging will occur, thus, the less likely trail pheromones will be deposited.
;Season
:Alongside with temperature, foraging occurs more during some seasons than others. With a change in season comes additional factors: a change in predators organism to avoid, change in food supply, and change in light availability. Often foraging organisms choose preference over such factors.
;Humidity
:If it is too humid or not humid enough, organisms may choose not to forage.
;Other chemicals
:Other surrounding chemicals may interfere with strength of pheromones. | 1 | Applied and Interdisciplinary Chemistry |
The Bradford protein assay (also known as the Coomassie protein assay) was developed by Marion M. Bradford in 1976. It is a quick and accurate spectroscopic analytical procedure used to measure the concentration of protein in a solution. The reaction is dependent on the amino acid composition of the measured proteins. | 0 | Theoretical and Fundamental Chemistry |
The home/bomb shelter was designed by architect Jay Swayze. Swayze, a proponent of underground living, constructed and lived in his own underground bunker-house in Plainview, Texas, which he named Atomitat.
Built during the Cold War only two years after the Cuban Missile Crisis, it was the promotion of the company "Underground World Homes", which was owned by Avon investor and millionaire Girard B. Henderson, who remained convinced that tensions between the U.S. and the U.S.S.R. would escalate eventually escalate to WWIII. (In addition to the prototypical underground home/bomb shelter, there was companion chthonic exhibit sponsored by Henderson: "Why Live Underground?") The brochure for the Underground World Home touted its comfort, luxury, interior design and safety. However, the $1.00 for adults and 50¢ on top of the expos fee entry, plus the expos numerous, much more glamorous exhibits, deterred many potential tourists. A May 1964 LIFE magazine cover story on the exposition did not so much as mention the Underground World Home.
Exhibits were contractually required to be dismantled and removed after the fair. Swayze eventually wrote a book, Underground Gardens & Homes: The Best of Two Worlds, Above and Below, but the building's fate was not mentioned. The New York Public Library held archives on the expo, however, and in 2017 it was found that the demolition of the home had been completed on 15 March 1966. Only its foundations, if anything, remain. | 0 | Theoretical and Fundamental Chemistry |
When collecting data in the full scan mode, a target range of mass fragments is determined and put into the instruments method. An example of a typical broad range of mass fragments to monitor would be m/z 50 to m/z 400. The determination of what range to use is largely dictated by what one anticipates being in the sample while being cognizant of the solvent and other possible interferences. A MS should not be set to look for mass fragments too low or else one may detect air (found as m/z 28 due to nitrogen), carbon dioxide (m/z' 44) or other possible interference. Additionally if one is to use a large scan range then sensitivity of the instrument is decreased due to performing fewer scans per second since each scan will have to detect a wide range of mass fragments.
Full scan is useful in determining unknown compounds in a sample. It provides more information than SIM when it comes to confirming or resolving compounds in a sample. During instrument method development it may be common to first analyze test solutions in full scan mode to determine the retention time and the mass fragment fingerprint before moving to a SIM instrument method. | 0 | Theoretical and Fundamental Chemistry |
A cell saline buffer containing the TIVA tag is added to the coverslip and incubated. During the incubation period, the TIVA tag penetrates the cell membrane via the CPP that is bound to it. Subsequently, the cytosolic environment cleaves the CPP and the TIVA tag is trapped inside the cell. After incubation, the coverslip is rinsed twice with cell saline buffer and then transferred to an imaging chamber. Using a confocal microscope, loading of the tag is confirmed by detecting the Cy5 signal at a wavelength of 561 nm. | 1 | Applied and Interdisciplinary Chemistry |
Robert Travis Kennedy is an American chemist specializing in bioanalytical chemistry including liquid chromatography, capillary electrophoresis, and microfluidics. He is currently the Hobart H. Willard Distinguished University Professor of Chemistry and the chair of the department of chemistry at the University of Michigan. He holds joint appointments with the Department of Pharmacology and Department Macromolecular Science and Engineering. Kennedy is an Associate Editor of Analytical Chemistry and ACS Measurement Science AU. | 0 | Theoretical and Fundamental Chemistry |
In the gas experiments Davy ran considerable risks. His respiration of nitric oxide which may have combined with air in the mouth to form nitric acid (HNO), severely injured the mucous membrane, and in Davy's attempt to inhale four quarts of "pure hydrocarbonate" gas in an experiment with carbon monoxide he "seemed sinking into annihilation." On being removed into the open air, Davy faintly articulated, "I do not think I shall die," but some hours elapsed before the painful symptoms ceased. Davy was able to take his own pulse as he staggered out of the laboratory and into the garden, and he described it in his notes as "threadlike and beating with excessive quickness". | 1 | Applied and Interdisciplinary Chemistry |
The Heart, arteries, and veins (a network of tubes to carry blood) constitute the cardiovascular system or circulatory system of our body which transports the blood throughout the body. The heart can be thought of as a muscular pump, consisting of four chambers, and pulsatile muscles which pump and circulates the blood through the vasculature. Arteries, arterioles, capillaries, venules, and veins make up the vasculature. The cardiovascular system circulates about 5 liters of blood at a rate of approximately 6 L/m. The pulmonary and the systemic circulations are the two parts of the vasculature. The pulmonary circulation system consists of the network of blood vessels from the right heart to the lungs and back to the left heart. The rest of the blood flow loop is called systemic circulation system. The pulmonary and systemic circulations take the blood through large arteries first and then branches into smaller arteries before reaching arterioles and capillaries. After capillaries, the blood enters the venules before joining smaller veins first and then larger veins before reaching the right heart. Thus completing the cycle of blood going to heart and then coming from it and going to all parts of the body.
The tricuspid valve, right heart (right ventricle), pulmonary valve, pulmonary artery, lungs, pulmonary veins and right heart are the elements of the Pulmonary Circulation System. The process of gas exchange, that is, exchange of carbon dioxide with oxygen in the lungs is the main function of the pulmonary system. The de-oxygenated blood from the right ventricle is pumped to the lungs where the capillaries surrounding the alveoli sacks exchange carbon dioxide for oxygen. The red blood cells and the hemoglobin present in the blood, which is the main carrier of oxygen in the blood are responsible for this exchange of gases before they are carried to the left ventricle of the heart. The systemic circulation is responsible for taking the oxygenated blood to various organs and tissues via the arterial tree before taking the deoxygenated blood to the right ventricle using the venous system (a network of veins). Arteries carry the oxygenated blood while the veins carry the deoxygenated blood. | 1 | Applied and Interdisciplinary Chemistry |
*Orexins (-A and -B) are involved in a number of cognitive processes, including appetite, arousal, and reward, among many others.
*Neurohypophysial hormones:
**Arginine-vasopressin
**Oxytocin regulates social cognition (e.g., trust and pair-bonding) and modulates maternal behavior.
*Endogenous opioids:
**Dynorphins
**Endorphins
**Endomorphins
**Enkephalins
* Neurotrophic factors are biomolecules – nearly all of which are peptides or small proteins – that support the growth, survival, and differentiation of both developing and mature neurons. Examples of notable neurotrophic factors include:
** Insulin-like growth factor-1 (IGF-1)
** Glial cell line-derived neurotrophic factor (GDNF)
** Vascular endothelial growth factor (VEGF)
** Brain-derived neurotrophic factor (BDNF)
** Nerve growth factor
** Neurotrophin-3
** Neurotrophin-4
** Ephrins
** Neuregulins | 1 | Applied and Interdisciplinary Chemistry |
Jay Hyung Lee is a professor at Department of Chemical and Biomolecular Engineering in KAIST (Korea Advanced Institute of Science and Technology). His h-index is 55 according to Google Scholar. Lee was a professor at Georgia Institute of Technology in the United States from 2000 to 2010. Lee is a fellow of Institute of Electrical and Electronics Engineers (IEEE). He is an editor of Computers & Chemical Engineering journal. | 1 | Applied and Interdisciplinary Chemistry |
The beginning of the 1970s saw the first investigations of the effects of pulsed laser irradiation within the target material. L. I. Mirkin observed twinning in ferrite grains in steel under the crater created by laser irradiation in vacuum. S. A. Metz and F. A. Smidt, Jr. irradiated nickel and vanadium foils in air with a pulsed laser at a low power density and observed voids and vacancy loops after annealing the foils, suggesting that a high concentration of vacancies was created by the stress wave. These vacancies subsequently aggregated during post-iradiation annealing into the observed voids in nickel and dislocation loops in vanadium.
In 1971, researchers at Battelle Memorial Institute in Columbus, Ohio began investigating whether the laser shocking process could improve metal mechanical properties using a high-energy pulsed laser. In 1972, the first documentation of the beneficial effects of laser shocking metals was published, reporting the strengthening of aluminum tensile specimens using a quartz overlay to confine the plasma. Subsequently, the first patent on laser shock peening was granted to Phillip Mallozzi and Barry Fairand in 1974. Research into the effects and possible applications of laser peening continued throughout the 1970s and early 1980s by Allan Clauer, Barry Fairand, and coworkers, supported by funding from the National Science Foundation, NASA, Army Research Office, U.S. Air Force, and internally by Battelle. This research explored the in-material effects in more depth and demonstrated the creation of deep compressive stresses and the accompanying increase in fatigue and fretting fatigue life achieved by laser peening. | 1 | Applied and Interdisciplinary Chemistry |
Using planar laser-induced fluorescence (PLIF) and particle image velocimetry (PIV) processes, there has been on-going research on the effects of turbulent diffusion in flames. Main areas of study include combustion systems in gas burners used for power generation and chemical reactions in jet diffusion flames involving methane (CH), hydrogen (H) and nitrogen (N). Additionally, double-pulse Rayleigh temperature imaging has been used to correlate extinction and ignition sites with changes in temperature and the mixing of chemicals in flames. | 1 | Applied and Interdisciplinary Chemistry |
Degrading concrete has been the focus of many studies and the most obvious sign is calcium-rich leachate seeping from a concrete structure.
Calthemite stalactites can form on concrete structures and "artificial caves" lined with concrete (e.g. mines and tunnels) significantly faster than those in limestone, marble or dolomite caves. This is because the majority of calthemites are created by chemical reactions which are different from normal "speleothem" chemistry.
Calthemites are usually the result of hyperalkaline solution (pH 9–14) seeping through a calcareous man-made structure until it comes into contact with the atmosphere on the underside of the structure, where carbon dioxide (CO) from the surrounding air facilitates the reactions to deposit calcium carbonate as a secondary deposit. CO is the reactant (diffuses into solution) as opposed to speleothem chemistry where CO is the product (degassed from solution).
It is most likely that the majority of calcium carbonate (CaCO) creating calthemites in shapes which, mimicking speleothems, is precipitated from solution as calcite as opposed to the other, less stable, polymorphs of aragonite and vaterite.
Calthemites are generally composed of calcium carbonate (CaCO) which is predominantly coloured white, but may be coloured red, orange or yellow due to iron oxide (from rusting reinforcing) being transported by the leachate and deposited along with the CaCO. Copper oxide from copper pipes may cause calthemites to be coloured green or blue. Calthemites may also contain minerals such as gypsum.
The definition of calthemites also includes secondary deposits which may occur in manmade mines and tunnels with no concrete lining, where the secondary deposit is derived from limestone, dolomite or other calcareous natural rock into which the cavity has been hollowed out. In this instance the chemistry is the same as that which creates speleothems in natural limestone caves (equations 5 to 8) below. It has been suggested the deposition of calthemite formations are one example of a natural process which has not previously occurred prior to the human modification of the Earth's surface, and therefore represents a unique process of the Anthropocene. | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.