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While molecular farming is one application of genetic engineering, there are concerns that are unique to it. In the case of genetically modified (GM) foods, concerns focus on the safety of the food for human consumption. In response, it has been argued that the genes that enhance a crop in some way, such as drought resistance or pesticide resistance, are not believed to affect the food itself. Other GM foods in development, such as fruits designed to ripen faster or grow larger, are believed not to affect humans any differently from non-GM varieties.
In contrast, molecular farming is not intended for crops destined for the food chain. It produces plants that contain physiologically active compounds that accumulate in the plant’s tissues. Considerable attention is focused, therefore, on the restraint and caution necessary to protect both consumer health and environmental biodiversity.
The fact that the plants are used to produce drugs alarms activists. They worry that once production begins, the altered plants might find their way into the food supply or cross-pollinate with conventional, non-GM crops. These concerns have historical validation from the ProdiGene incident, and from the StarLink incident, in which GMO corn accidentally ended up in commercial food products. Activists also are concerned about the power of business. According to the Canadian Food Inspection Agency, in a recent report, says that U.S. demand alone for biotech pharmaceuticals is expanding at 13 percent annually and to reach a market value of $28.6 billion in 2004. Pharming is expected to be worth $100 billion globally by 2020. | 1 | Applied and Interdisciplinary Chemistry |
Asymmetric induction by the molecular framework of an acyclic substrate is the idea that asymmetric steric and electronic properties of a molecule may determine the chirality of subsequent chemical reactions on that molecule. This principal is used to design chemical syntheses where one stereocentre is in place and additional stereocentres are required.
When considering how two functional groups or species react, the precise 3D configurations of the chemical entities involved will determine how they may approach one another. Any restrictions as to how these species may approach each other will determine the configuration of the product of the reaction. In the case of asymmetric induction, we are considering the effects of one asymmetric centre on a molecule on the reactivity of other functional groups on that molecule. The closer together these two sites are, the larger an influence is expected to be observed. A more holistic approach to evaluating these factors is by computational modelling, however, simple qualitative factors may also be used to explain the predominant trends seen for some synthetic steps. The ease and accuracy of this qualitative approach means it is more commonly applied in synthesis and substrate design. Examples of appropriate molecular frameworks are alpha chiral aldehydes and the use of chiral auxiliaries. | 0 | Theoretical and Fundamental Chemistry |
Histatins are histidine-rich (cationic) antimicrobial proteins found in saliva. Histatin's involvement in antimicrobial activities makes histatin part of the innate immune system.
Histatin was first discovered (isolated) in 1988, with functions that's responsible in keeping homeostasis inside the oral cavity, helping in the formation of pellicles, and assist in bonding of metal ions.
__TOC__ | 1 | Applied and Interdisciplinary Chemistry |
Capnellene has been a popular target for synthesis due to its molecular architecture, its role in the defense mechanism of soft corals, and the challenge posed by the high degree of stereochemical sophistication and the complexity of the undecane skeleton. In 1981, the first stereocontrolled synthesis of (±)-Δ-capnellene was performed in nine steps, with an overall yield of 60%. Their starting reagent was a dimethylated cyclopentenyl carboxaldehyde and the overall synthesis took the form of a series of pentane ring annulations. The second pentane ring was formed by condensation of the aldehyde by vinylmagnesium bromide, followed by Nazarov cyclization of the dienone. A regiospecific [3+2] cyclopentannulation, using ozonolysis and an intramolecular aldol condensation, formed the third ring and a simple dehydration reaction yielded the target capnellene.
Since the first synthesis, many investigators have successfully assembled capnellene and its derivatives. Approaches to this synthesis are diverse, and include central steps such as annululation, olefin metathesis, radical cyclization, and trapping reactions. The most heavily cited synthesis in the literature involves two key intermediates formed by a Stille reaction, the palladium-catalyzed coupling of vinyl triflate with vinyl stannane. The readily prepared trimethylcyclopentanone can be converted into vinyl triflate, which is coupled with vinylstannane in the first palladium-catalyzed step to yield the desired divinyl ketone. The second 5-membered ring is formed via Nazarov cyclization, and the product is prepared for a second palladium-catalyzed coupling. This step yields another divinyl ketone, which can be cyclized to an enone, hydrated, and converted to an alkene via olefination to yield capnellene. | 0 | Theoretical and Fundamental Chemistry |
Amylose and cellulose cannot be used as such due to poor resolution and difficulty in handling. But the carbamate and benzoate derivatives of these polymers, especially amylose and cellulose, demonstrate excellent properties as chiral selectors for chromatographic separation. A large number of polysaccharide-based CSPs are commercially available for chiral separation. These CSPs showed tremendous chiral recognition capability to resolve a wide range of chiral analytes. Many of these CSPs have been marketed by Daicel Chemical Industries, Ltd., and some of the popular ones are listed in the table.
These CSPs are compatible with NP/RP and SFC and also used for analytical, semi-preparative and preparative separations. Many screening research studies conducted at different labs go to suggest that the four CSPs namely Chiralcel OD, Chiralcel OJ, Chiralpak AD, and Chiralpak As are capable of resolving more than 80% of the chiral separations due to their adaptability and high loading capacity. These four polysaccharide chiral stationary stationary phases are referred to as the "golden four".
Polysaccharide CSPs are prepared with high quality silica support on to which the polymeric chiral selector (amylose/cellulose dr.) is physically coated (coated CSP) or chemically immobilized (immobilized CSP). Separations can be done in normal phase, reversed-phase, and polar organic mode. While working with coated polysaccharide CSP solvent selection should be done with caution. One should not use drastic solvents such as dichloromethane, chloroform, toluene, ethyl acetate, THF; 1,4-dioxane; acetone; DMSO, etc. These so called "non-standard" solvents will dissolve the silica and irreversibly destroy the stationary phase. The limited resistance of these coated phases to many solvents lead to the development of immobilized polysaccharide CSP. The table below presents some of the immobilized CSP commercially available and with the alternates wherever accessible.
These immobilized CSP are much more rugged and the "non-standard" solvents can be employed. Thus expanding the choice of co-solvent. The major strength of immobilized CSPs are high solvent versatility in selection of mobile phase composition, enhanced sample solubility, high selectivity, robustness and extended durability, excellent column efficiency, and broad application domain in the resolution of enantiomers. Solvent is a key factor in HPLC MD. More solvents to play with means better sample solubility, Improves resolution, and enables effective chiral method development. | 0 | Theoretical and Fundamental Chemistry |
* Connected Waters Initiative, University of New South Wales – Investigating and raising awareness of groundwater and water resource issues in Australia
* Murray Darling Basin Initiative, Department of Environment and Heritage, Australia | 1 | Applied and Interdisciplinary Chemistry |
The key to engineering a glass-ceramic material is controlling the nucleation and growth of crystals in the base glass. The amount of crystallinity will vary depending on the amount of nuclei present and the time and temperature at which the material is heated. It is important to understand the types of nucleation occurring in the material, whether it is homogeneous or heterogeneous.
Homogeneous nucleation is a process resulting from the inherent thermodynamic instability of a glassy material. When enough thermal energy is applied to the system, the metastable glassy phase begins to return to the lower-energy, crystalline state. The term "homogeneous" is used here because the formation of nuclei comes from the base glass without any second phases or surfaces promoting their formation.
The rate of homogenous nucleation in a condensed system can be described with the following equation, proposed by Becker in 1938.
Where Q is the activation energy for diffusion across the phase boundary, A is a constant, and is the maximum activation energy for formation of a stable nucleus, as given by the equation below.
Where is the change of free energy per unit volume resulting from the transformation from one phase to the other, and can be equated with interfacial tension.
Heterogeneous nucleation is a term used when a nucleating agent is introduced into the system to aid and control the crystallization process. The presence of this nucleating agent, in the form of an additional phase or surface, can act as a catalyst for nucleation and is particularly effective if there is epitaxy between the nucleus and the substrate. There are a number of metals that can act as nucleating agents in glass because they can exist in the glass in the form of particle dispersion of colloidal dimensions. Examples include copper, metallic silver, and platinum. It was suggested by Stookey in 1959 that the effectiveness of metallic nucleation catalysts relates to the similarities between the crystal structures of the metals and the phase being nucleated.
The most important feature of heterogenous nucleation is that the interfacial tension between the heterogeneity and the nucleated phase is minimized. This means that the influence that the catalyzing surface has on the rate of nucleation is determined by the contact angle at the interface. Based on this, Turnbull and Vonnegut (1952) modified the equation for homogenous nucleation rate to give an expression for heterogenous nucleation rate.
If activation energy for diffusion is included, as suggested by Stokey (1959a), the equation then becomes:
From these equations, heterogeneous nucleation can be described in terms of the same parameters as homogeneous nucleation with a shape factor, which is a function of θ (contact angle). The term is given by:
if the nucleus has the form of a spherical cap.
In addition to nucleation, crystal growth is also required for the formation of glass ceramics. The crystal growth process is of considerable importance in determining the morphology of the produced glass ceramic composite material. Crystal growth is primarily dependent on two factors. First, it is dependent upon the rate at which the disordered structure can be re-arranged into a periodic lattice with longer-range order. Second, it is dependent upon the rate at which energy is released in the phase transformation (essentially the rate of cooling at the interface). | 0 | Theoretical and Fundamental Chemistry |
The glass–liquid transition, or glass transition, is the gradual and reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle "glassy" state into a viscous or rubbery state as the temperature is increased. An amorphous solid that exhibits a glass transition is called a glass. The reverse transition, achieved by supercooling a viscous liquid into the glass state, is called vitrification.
The glass-transition temperature T of a material characterizes the range of temperatures over which this glass transition occurs (as an experimental definition, typically marked as 100 s of relaxation time). It is always lower than the melting temperature, T, of the crystalline state of the material, if one exists.
Hard plastics like polystyrene and poly(methyl methacrylate) are used well below their glass transition temperatures, i.e., when they are in their glassy state. Their T values are both at around . Rubber elastomers like polyisoprene and polyisobutylene are used above their T, that is, in the rubbery state, where they are soft and flexible; crosslinking prevents free flow of their molecules, thus endowing rubber with a set shape at room temperature (as opposed to a viscous liquid).
Despite the change in the physical properties of a material through its glass transition, the transition is not considered a phase transition; rather it is a phenomenon extending over a range of temperature and defined by one of several conventions. Such conventions include a constant cooling rate () and a viscosity threshold of 10 Pa·s, among others. Upon cooling or heating through this glass-transition range, the material also exhibits a smooth step in the thermal-expansion coefficient and in the specific heat, with the location of these effects again being dependent on the history of the material. The question of whether some phase transition underlies the glass transition is a matter of ongoing research. | 0 | Theoretical and Fundamental Chemistry |
The anabolism of oligosaccharides - and, hence, the role of nucleotide sugars - was not clear until the 1950s when Leloir and his coworkers found that the key enzymes in this process are the glycosyltransferases. These enzymes transfer a glycosyl group from a sugar nucleotide to an acceptor. | 0 | Theoretical and Fundamental Chemistry |
CDs and DVDs have a protective film which must be stripped to reveal the gold reflective film or polycarbonate (PC) base. The surface of the disk can be activated to reveal the metal layer which allows compounds to bind to it. Compounds such as UV/ozone or an oxygen plasma treatment can be used to activate the disk to produce a hydrophilic surface with densely packed carboxylic acid groups.
As one-off microassay can be printed onto the activated disks using a noncontact printer to dispel nanoliter quantities of coating conjugates onto the disk. Proteins or antibodies acting as probe molecules can then covalently bind to the disk surface and can be incubated. A polydimethylsiloxane (PDMS) channel plate can also be used to immobilize the probes in a line array. The plate is removed, and the process is repeated with another plate to deliver analyte samples in a line array perpendicular to the probe array. The probe and analyte samples can bind or hybridize at the intersections of the arrays to create rectangular hybridization sites. The disk is washed, rinsed, and dried prior to reading. This process can be done manually or automated; in theory discs with pre-made assays could be manufactured and sold en masse. | 1 | Applied and Interdisciplinary Chemistry |
Emission factors assume a linear relation between the intensity of the activity and the emission resulting from this activity:
Emission = Activity * Emission Factor
Intensities are also used in projecting possible future scenarios such as those used in the IPCC assessments, along with projected future changes in population, economic activity and energy technologies. The interrelations of these variables is treated under the so-called Kaya identity.
The level of uncertainty of the resulting estimates depends significantly on the source category and the pollutant. Some examples:
*Carbon dioxide (CO) emissions from the combustion of fuel can be estimated with a high degree of certainty regardless of how the fuel is used as these emissions depend almost exclusively on the carbon content of the fuel, which is generally known with a high degree of precision. The same is true for sulphur dioxide (SO), since sulphur contents of fuels are also generally well known. Both carbon and sulphur are almost completely oxidized during combustion and all carbon and sulphur atoms in the fuel will be present in the flue gases as CO and SO respectively.
*In contrast, the levels of other air pollutants and non-CO greenhouse gas emissions from combustion depend on the precise technology applied when fuel is combusted. These emissions are basically caused by either incomplete combustion of a small fraction of the fuel (carbon monoxide, methane, non-methane volatile organic compounds) or by complicated chemical and physical processes during the combustion and in the smoke stack or tailpipe. Examples of these are particulates, NO, a mixture of nitric oxide, NO, and nitrogen dioxide, NO).
*Nitrous oxide (NO) emissions from agricultural soils are highly uncertain because they depend very much on both the exact conditions of the soil, the application of fertilizers and meteorological conditions. | 1 | Applied and Interdisciplinary Chemistry |
The matrix is the space enclosed by the inner membrane. It contains about 2/3 of the total proteins in a mitochondrion. The matrix is important in the production of ATP with the aid of the ATP synthase contained in the inner membrane. The matrix contains a highly concentrated mixture of hundreds of enzymes, special mitochondrial ribosomes, tRNA, and several copies of the mitochondrial DNA genome. Of the enzymes, the major functions include oxidation of pyruvate and fatty acids, and the citric acid cycle. The DNA molecules are packaged into nucleoids by proteins, one of which is TFAM. | 1 | Applied and Interdisciplinary Chemistry |
Several studies have demonstrated the possibility to develop chemical cells inspired by biological models to produce molecular hydrogen, for example: Selvaggi et al. explored the possibility to use energy captured by the PSII, developing for that goal, an organic-inorganic hybrid system replacing the PSII protein complex by microspheres of TiO a photo-inducible compound. In order to get the hydrogen production, the TiO microspheres were covered with hydrogenases extracted from the marine thermophile Pyrococcus furiosus, in that way the energy of the light was captured by the TiO microspheres and used to generate protons and electrons from water with the subsequent production of 29 µmol de H hour.
The obtained results from immobilization of hydrogenases on the surface of electrodes have demonstrated the viability of incorporating these enzymes in electrochemical cells, due to their ability to produce gaseous hydrogen through a redox reaction. (Hallenbeck and Benemann). This opens the possibility of using biomimetic compounds in electrodes to generate hydrogen.
Until the present day several bio-mimetic compounds have been developed: Collman et al. produced ruthenium porphyrins, furthermore of the bio-mimetic compounds published by the research teams of Rauchfuss, Darensbourg and Pickett (in Artero and Fontecave) who developed bio-mimetic compounds of the [Fe] hydrogenase. More recently Manor and Rauchfuss presented a very interesting mimic compound based in the [NiFe] hydrogenase with bidirectional properties, this compound has the characteristic that it carries two borane protected cyanide ligands at the iron atom. Some works about bio-mimetic compounds of hydrogenases are summarized in table 1.
Table 1. Bio-mimetic compounds of hydrogenases
However, obtaining bio-mimetic compounds able to hydrogen production on an industrial scale still is elusive. For that reason, the research of this topic is a hot spot in science which has taken the efforts of researchers around the world. Recently a review of the works done in bio-mimetic compounds was published by Schilter et al.. Showing that some studies have got promising results in bio-mimetic compounds synthesized in laboratory. | 1 | Applied and Interdisciplinary Chemistry |
Fluid–structure interaction (FSI) is the interaction of some movable or deformable structure with an internal or surrounding fluid flow. Fluid–structure interactions can be stable or oscillatory. In oscillatory interactions, the strain induced in the solid structure causes it to move such that the source of strain is reduced, and the structure returns to its former state only for the process to repeat. | 1 | Applied and Interdisciplinary Chemistry |
The Karplus equation, named after Martin Karplus, describes the correlation between J-coupling constants and dihedral torsion angles in nuclear magnetic resonance spectroscopy:
where J is the J coupling constant, is the dihedral angle, and A, B, and C are empirically derived parameters whose values depend on the atoms and substituents involved. The relationship may be expressed in a variety of equivalent ways e.g. involving cos 2φ rather than cos φ —these lead to different numerical values of A, B, and C but do not change the nature of the relationship.
The relationship is used for J coupling constants. The superscript "3" indicates that a H atom is coupled to another H atom three bonds away, via H-C-C-H bonds. (Such hydrogens bonded to neighbouring carbon atoms are termed vicinal). The magnitude of these couplings are generally smallest when the torsion angle is close to 90° and largest at angles of 0 and 180°.
This relationship between local geometry and coupling constant is of great value throughout nuclear magnetic resonance spectroscopy and is particularly valuable for determining backbone torsion angles in protein NMR studies. | 0 | Theoretical and Fundamental Chemistry |
The concept of "molecular glue" originated in the late 20th century, with immunosuppressants like cyclosporine A (CsA) and FK506 identified as pioneering examples. CsA, discovered in 1971 during routine screening for antifungal antibiotics, exhibited immunosuppressive properties by inhibiting the peptidyl–prolyl isomerase activity of cyclophilin, ultimately preventing organ transplant rejections. By 1979, CsA was used clinically, and FK506 (tacrolimus), discovered in 1987 by Fujisawa, emerged as a more potent immunosuppressant. The ensuing 4-year race to understand CsA and FK506's mechanisms led to the identification of FKBP12 as a common binding partner, marking the birth of the "molecular glue" concept. The term molecular glue found its way into publications in 1992, highlighting the selective gluing of specific proteins by antigenic peptides, akin to immunosuppressants acting as docking assemblies.
In the early 1990s, researchers delved into understanding the role of proximity in biological processes. The creation of synthetic "chemical inducers of proximity" (CIPs), such as FK1012, opened the door to more complex molecular glues. Rimiducid, a purposefully synthesized molecular glue, demonstrated its effectiveness in eliminating graft-versus-host disease by inducing dimerization of death-receptor fusion targets.
The exploration of molecular glues took a significant turn in 1996 with the discovery that discodermolide stabilized the association of alpha and beta tubulin monomers, functioning as a "molecular clamp" rather than inducing neo-associations. In 2000, the revelation that a synthetic compound, synstab-A, could induce associations of native proteins marked a shift towards the discovery of non-natural molecular glues.
In 2013, the mechanism of thalidomide analogs as molecular glue degraders had been explained. Notably, thalidomide, discovered as a CRBN ligand in 2010, and lenalidomide formed a complex with CK1α, solidifying their role as molecular glues. Subsequently, indisulam was identified as a molecular glue capable of degrading RBM39 in 2017.
The year 2020 saw the discovery of autophagic molecular degraders and the identification of BI-3802 as a molecular glue inducing the polymerization and degradation of BCL6. Additionally, chemogenomic screening revealed structurally diverse molecular glue degraders targeting cyclin K. The discovery that manumycin polyketides acted as molecular glues, fostering interactions between UBR7 and P53, further expanded the understanding of molecular glue functions.
In recent years, the field of molecular glues has witnessed an explosion of discoveries targeting native proteins. Examples include synthetic FKBP12-binding glues like FKBP12-rapadocin, which targets the adenosine transporter SLC29A1. Thalidomide and lenalidomide, classified as immunomodulatory drugs (IMiDs), were identified as small-molecule glues inducing ubiquitination of transcription factors via E3 ligase complexes. Computational searches for molecular-glue degraders in 2020 added novel probes to the ever-expanding landscape of molecular glues.
The transformative power of molecular glues in medicine became evident as drugs like sandimmune, tacrolimus, sirolimus, thalidomide, lenalidomide, and taxotere proved effective. The concept of inducing protein associations has shown promise in gene therapy and has become a potent tool in understanding cell circuitry. As the field continues to advance, the discovery of new molecular glues offers the potential to reshape drug discovery and overcome previously labeled "undruggable" targets. The future of molecular glues holds promise for rewiring cellular circuitry and providing innovative solutions in precision medicine. | 1 | Applied and Interdisciplinary Chemistry |
In order to provide optimal performance, pigment particles must act independently of each other in the coating film and thus must remain well dispersed throughout manufacture, storage, application, and film formation. Unfortunately, colloidal dispersions such as the pigment dispersions in liquid coatings are inherently unstable, and they must be stabilized against the flocculation that might occur. | 0 | Theoretical and Fundamental Chemistry |
Albert married Catherine Robson in Cambridge in 1940. They had two children: Naomi, born in 1944 and a son, William Neil, known as Neil. Naomi was killed in a car crash in the USA in 1966.
Catherine died of cancer 14 November 1963. Two years later, on 10 December 1965 Alexander married Gisela Gudrum Baker (née Zutavern, of Heidelberg), the widow of Kingsley Ferguson Baker, a Sydney industrial chemist, at the Presbyterian Church in Pymble. Stricken by a brain tumour in 1969 when serving as dean of science, he died at his Mosman home on 23 May 1970 and was cremated. His wife, and the son of his first marriage, survived him. The Pymble Church “was packed by friends, colleagues, and students on 26 May for a funeral service during which a moving panegyric was spoken by Professor I.G. Ross”.
One obituary summed up Alexander the man thus: | 0 | Theoretical and Fundamental Chemistry |
As with conventional manufactured drugs, the main challenge in developing successful offshoots of the RNAi-based drugs is the precise delivery of the RNAi triggers to where they are needed in the body. The reason that the ocular macular degeneration antidote was successful sooner than the antidote with other diseases is that the eyeball is almost a closed system, and the serum can be injected with a needle exactly where it needs to be. The future successful drugs will be the ones who are able to land where needed, probably with the help of nanobots. Below is a rendition of a table that shows the existing means of delivery of the RNAi triggers. | 1 | Applied and Interdisciplinary Chemistry |
In his epic poem On the Nature of Things, Lucretius depicts Epicurus as the hero who crushed the monster Religion through educating the people in what was possible in atoms and what was not possible in atoms. However, Epicurus expressed a non-aggressive attitude characterized by his statement:
However, according to science historian Charles Coulston Gillispie:
The possibility of a vacuum was accepted—or rejected—together with atoms and atomism, for the vacuum was part of that same theory. | 1 | Applied and Interdisciplinary Chemistry |
C-reactive protein (CRP) is an annular (ring-shaped) pentameric protein found in blood plasma, whose circulating concentrations rise in response to inflammation. It is an acute-phase protein of hepatic origin that increases following interleukin-6 secretion by macrophages and T cells. Its physiological role is to bind to lysophosphatidylcholine expressed on the surface of dead or dying cells (and some types of bacteria) in order to activate the complement system via C1q.
CRP is synthesized by the liver in response to factors released by macrophages, T cells and fat cells (adipocytes). It is a member of the pentraxin family of proteins. It is not related to C-peptide (insulin) or protein C (blood coagulation). C-reactive protein was the first pattern recognition receptor (PRR) to be identified. | 1 | Applied and Interdisciplinary Chemistry |
Introduced in 2007, ChIP sequencing (ChIP-seq) is a technology that uses chromatin immunoprecipitation to crosslink the proteins of interest to the DNA but then instead of using a micro-array, it uses the more accurate, higher throughput method of sequencing to localize interaction points.
DamID is an alternative method that does not require antibodies.
ChIP-exo uses exonuclease treatment to achieve up to single base pair resolution.
CUT&RUN sequencing uses antibody recognition with targeted enzymatic cleavage to address some technical limitations of ChIP. | 1 | Applied and Interdisciplinary Chemistry |
Carbohydrate–protein interactions are the intermolecular and intramolecular interactions between protein and carbohydrate moieties. These interactions form the basis of specific recognition of carbohydrates by lectins. Carbohydrates are important biopolymers and have a variety of functions. Often carbohydrates serve a function as a recognition element. That is, they are specifically recognized by other biomolecules. Proteins which bind carbohydrate structures are known as lectins. Compared to the study of protein–protein and protein–DNA interaction, it is relatively recent that scientists get to know the protein–carbohydrate binding.
Many of these interactions involved carbohydrates found at the cell surface, as part of a membrane glycoprotein or glycolipid. These interactions can play a role in cellular adhesion and other cellular recognition events. Intramolecular carbohydrate–protein interactions refer to interactions between glycan and polypeptide moieties in glycoproteins or the glycosylated proteins. | 0 | Theoretical and Fundamental Chemistry |
The beginnings of the modern era of cancer chemotherapy can be traced directly to the German introduction of chemical warfare during World War I. Among the chemical agents used, mustard gas was particularly devastating. Although banned by the Geneva Protocol in 1925, the advent of World War II caused concerns over the possible re-introduction of chemical warfare. Such concerns led to the discovery of nitrogen mustard, a chemical warfare agent, as an effective treatment for some types of cancer. Two pharmacologists from the Yale School of Medicine, Louis S. Goodman and Alfred Gilman, were recruited by the US Department of Defense to investigate potential therapeutic applications of chemical warfare agents. Goodman and Gilman observed that mustard gas was too volatile an agent to be suitable for laboratory experiments. They exchanged a nitrogen molecule for sulfur and had a more stable compound in nitrogen mustard. A year into the start of their research, a German air raid in Bari, Italy led to the exposure of more than 1000 people to the SS John Harvey's secret cargo composed of mustard gas bombs. Dr. Stewart Francis Alexander, a lieutenant colonel who was an expert in chemical warfare, was subsequently deployed to investigate the aftermath. Autopsies of the victims suggested that profound lymphoid and myeloid suppression had occurred after exposure. In his report, Dr. Alexander theorized that since mustard gas all but ceased the division of certain types of somatic cells whose nature was to divide fast, it could also potentially be put to use in helping to suppress the division of certain types of cancerous cells.
Using that information, Goodman and Gilman reasoned that this agent could be used to treat lymphoma, a tumor of lymphoid cells. They first set up an animal model by establishing lymphomas in mice and demonstrated they could treat them with mustard agents. Next, in collaboration with a thoracic surgeon, Gustaf Lindskog, they injected a related agent, mustine (the prototype nitrogen mustard anticancer chemotherapeutic), into a patient with non-Hodgkins lymphoma. The patient, a Polish immigrant to Connecticut known in literature only as JD, received his first injections on August 27, 1942 at 10 a.m. The doctors observed a dramatic reduction in the patients tumor masses. Although the effect lasted only a few weeks, and the patient had to return for another set of treatment, that was the first step to the realization that cancer could be treated by pharmacological agents. The patient ultimately died of cancer on December 1, 1942, 96 days after his first dose. Publication of the first clinical trials was reported in 1946 in The New York Times. | 1 | Applied and Interdisciplinary Chemistry |
* The compressive residual stresses imparted by laser peening are precisely controlled both in location and intensity and can be applied to mitigate sharp transitions into tensile regions. Laser peening imparts deep compressive residual stresses on the order of 10 to 20 times deeper than conventional shot peening, making them significantly more beneficial at preventing SCC. Laser peening is widely used in the aerospace and power generation industries in gas fired turbine engines.
* Material Selection: Choosing the right material for a specific environment can help prevent SCC. Materials with higher resistance to corrosion and stress corrosion cracking should be used in corrosive environments. For example, using stainless steel instead of carbon steel in a marine environment can reduce the likelihood of SCC.
* Protective Coatings: Applying a protective coating or barrier can help prevent corrosive substances from coming into contact with the metal surface, thus reducing the likelihood of SCC. For example, using an epoxy coating on the interior surface of a pipeline can reduce the likelihood of SCC.
* Cathodic Protection: Cathodic protection is a technique used to protect metals from corrosion by applying a small electrical current to the metal surface. This technique can also help prevent SCC by reducing the corrosion potential of the metal.
* Environmental Controls: Controlling the environment around the metal can help prevent SCC. For example, reducing the temperature or acidity of the environment can help prevent SCC.
* Inspection and Maintenance: Regular inspections and maintenance can help detect SCC before it causes a failure. This includes visual inspections, non-destructive testing, and monitoring of environmental factors. | 1 | Applied and Interdisciplinary Chemistry |
Industrial wastewater BMPs are considered an adjunct to engineered treatment systems. Typical BMPs include operator training, maintenance practices, and spill control procedures for treatment chemicals. There are also many BMPs available which are specific to particular industrial processes, for example:
* source reduction practices in metal finishing industries (e.g. substituting less toxic solvents or using water-based cleaners);
* in the chemical industry, capturing equipment washdown waters for recycle/reuse at various process stages;
* in the paper industry, using process control monitoring to optimize bleaching processes, and reduce the overall amount of bleach used. | 1 | Applied and Interdisciplinary Chemistry |
A common 1,4-dithiol is dithiothreitol (DTT), HSCHCH(OH)CH(OH)CHSH, sometimes called Cleland's reagent, for to reduce protein disulfide bonds. Oxidation of DTT results a stable six-membered heterocyclic ring with an internal disulfide bond. | 0 | Theoretical and Fundamental Chemistry |
The mechanical properties of the fibers are tested, but the process can be tricky due to practical reasons. The mechanical properties are tested with Universal Test Machine by fixing the hydrogel fibers between two holders. However, due to the compress of the holder, hydrogel fiber might have a trend to break at the holding point. Also, the loss of water during the test will impact the resulting data, and precaution needs to be taken to meditate the loss. And the tensile strength of the hydrogel fiber is usually smaller than 1 MPa. | 0 | Theoretical and Fundamental Chemistry |
The natural resistance to oxidation exhibited by silicon carbide, as well as the discovery of new ways to synthesize the cubic β-SiC form, with its larger surface area, has led to significant interest in its use as a heterogeneous catalyst support. This form has already been employed as a catalyst support for the oxidation of hydrocarbons, such as n-butane, to maleic anhydride. | 1 | Applied and Interdisciplinary Chemistry |
Charlestown is the home of Broomhall Cricket Club, named after Broomhall, the nearby home of Lord Elgin. They have a 1st XI and a 2nd XI that play in the Scottish East League run by the East of Scotland Cricket Association and have junior, midweek and Sunday teams as well. They play at The Cairns, Charlestown. | 1 | Applied and Interdisciplinary Chemistry |
In the 19th century new developments such as the discovery of photography, Rowlands invention of the concave diffraction grating, and Schumanns works on discovery of vacuum ultraviolet (fluorite for prisms and lenses, low-gelatin photographic plates and absorption of UV in air below 185 nm) made advance to shorter wavelengths very fast. At the same time Dewar observed series in alkali spectra, Hartley found constant wave-number differences, Balmer discovered a relation connecting wavelengths in the visible hydrogen spectrum, and finally Rydberg derived a formula for wave-numbers of spectral series. Meanwhile, the substantial summary of past experiments performed by Maxwell (1873), resulted in his equations of electromagnetic waves.
In 1895, the German physicist Wilhelm Conrad Röntgen discovered and extensively studied X-rays, which were later used in X-ray spectroscopy. One year later, in 1896, French physicist Antoine Henri Becquerel discovered radioactivity, and Dutch physicist Pieter Zeeman observed spectral lines being split by a magnetic field.
In 1897, theoretical physicist, Joseph Larmor explained the splitting of the spectral lines in a magnetic field by the oscillation of electrons.
Physicist, Joseph Larmor, created the first solar system model of the atom in 1897. He also postulated the proton, calling it a “positive electron.” He said the destruction of this type of atom making up matter “is an occurrence of infinitely small probability.” | 0 | Theoretical and Fundamental Chemistry |
Under very oxidising or very reducing conditions, the steady-state catalytic current sometimes tends to a limiting value (a plateau) which (still provided there is no mass transport limitation) relates to the activity of the fully oxidised or fully reduced enzyme, respectively. If interfacial electron transfer is slow and if there is a distribution of electron transfer rates (resulting from a distribution of orientations of the enzymes molecules on the electrode), the current keeps increasing linearly with potential instead of reaching a plateau; in that case the limiting slope is proportional to the turnover rate of the fully oxidised or fully reduced enzyme.
The change in steady-state current against potential is often complex (e.g. not merely sigmoidal). | 0 | Theoretical and Fundamental Chemistry |
Nitroso compounds can be prepared by the reduction of nitro compounds or by the oxidation of hydroxylamines.
Ortho-nitrosophenols may be produced by the Baudisch reaction. In the Fischer–Hepp rearrangement aromatic 4-nitrosoanilines are prepared from the corresponding nitrosamines. | 0 | Theoretical and Fundamental Chemistry |
Measurement of the ratios of naturally occurring stable isotopes (isotope analysis) plays an important role in isotope geochemistry, but stable isotopes (mostly hydrogen, carbon, nitrogen, oxygen and sulfur) are also finding uses in ecological and biological studies. Other workers have used oxygen isotope ratios to reconstruct historical atmospheric temperatures, making them important tools for paleoclimatology.
These isotope systems for lighter elements that exhibit more than one primordial isotope for each element have been under investigation for many years in order to study processes of isotope fractionation in natural systems. The long history of study of these elements is in part because the proportions of stable isotopes in these light and volatile elements is relatively easy to measure. However, recent advances in isotope ratio mass spectrometry (i.e. multiple-collector inductively coupled plasma mass spectrometry) now enable the measurement of isotope ratios in heavier stable elements, such as iron, copper, zinc, molybdenum, etc. | 0 | Theoretical and Fundamental Chemistry |
Biosynthesis by the transsulfuration pathway starts with aspartic acid. Relevant enzymes include aspartokinase, aspartate-semialdehyde dehydrogenase, homoserine dehydrogenase, homoserine O-transsuccinylase, cystathionine-γ-synthase, Cystathionine-β-lyase (in mammals, this step is performed by homocysteine methyltransferase or betaine—homocysteine S-methyltransferase.)
Methionine biosynthesis is subject to tight regulation. The repressor protein MetJ, in cooperation with the corepressor protein S-adenosyl-methionine, mediates the repression of methionine's biosynthesis. The regulator MetR is required for MetE and MetH gene expression and functions as a transactivator of transcription for these genes. MetR transcriptional activity is regulated by homocystein, which is the metabolic precursor of methionine. It is also known that vitamin B12 can repress MetE gene expression, which is mediated by the MetH holoenzyme. | 1 | Applied and Interdisciplinary Chemistry |
One of the most studied methods is to use the patients own cells to generate a new organ, ex-vivo Specifically, researchers have chosen to focus on adult stem cells, or somatic stem cells, for the generation of new organ cells to create organs. There has been success in the production and use of some organs. The first stem-cell based organ, a tracheal graft, was transplanted successfully in 2008. The method involves obtaining a donor organ, removing the cells and MHC antigens from the donor organ, and colonizing it with stem cells obtained from the patient. This method does not create an entire organ from stem cells, and it still requires a donor to provide the decellularized graft. However, the first surgery done with this method was successful and the patient has shown no signs of rejection since. The current debate with this method is whether the decellularized graft was only used to provide the shape of the organ, or whether it provided benefits from it being a donor graft. Current research is being done to find ways to use adult stem cells for neo-organs without using decellularized donor organs for structural support. | 1 | Applied and Interdisciplinary Chemistry |
In plants and animals, mineral absorption, also called mineral uptake is the way in which minerals enter the cellular material, typically following the same pathway as water. In plants, the entrance portal for mineral uptake is usually through the roots. Some mineral ions diffuse in-between the cells. In contrast to water, some minerals are actively taken up by plant cells. Mineral nutrient concentration in roots may be 10,000 times more than in surrounding soil. During transport throughout a plant, minerals can exit xylem and enter cells that require them. Mineral ions cross plasma membranes by a chemiosmotic mechanism. Plants absorb minerals in ionic form: nitrate (NO), phosphate (HPO) and potassium ions (K); all have difficulty crossing a charged plasma membrane.
It has long been known plants expend energy to actively take up and concentrate mineral ions. Proton pump hydrolyzes adenosine triphosphate (ATP) to transport H ions out of cell; this sets up an electrochemical gradient that causes positive ions to flow into cells. Negative ions are carried across the plasma membrane in conjunction with H ions as H ions diffuse down their concentration gradient.
In animals, minerals found in low small amounts are microminerals while the seven elements that are required in large quantity are known as macrominerals; these are Ca, P, Mg, Na, K, Cl, and S. In most cases, minerals that enter the blood pass through the epithelial cells which line the gastrointestinal mucosa of the small intestine. Minerals can diffuse through the pores of the tight junction in paracellular absorption if there is an electrochemical gradient. Through the process of solvent drag, minerals can also enter with water when solubilized by dipole-ion interactions. Furthermore, the absorption of trace elements can be enhanced by the presence of amino acids that are covalently bonded to the mineral. | 1 | Applied and Interdisciplinary Chemistry |
The most common adverse effects of esketamine for depression (≥5% incidence) include dissociation, dizziness, sedation, nausea, vomiting, vertigo, numbness, anxiety, lethargy, increased blood pressure, and feelings of drunkenness. Long-term use of esketamine has been associated with bladder disease. | 0 | Theoretical and Fundamental Chemistry |
Martin's sulfurane is the organosulfur compound with the formula PhS[OC(CF)Ph] (Ph = CH). It is a white solid that easily undergoes sublimation. The compound is an example of a hypervalent sulfur compound called a sulfurane. As such, the sulfur adopts a see-saw structure, with a lone pair of electrons as the equatorial fifth coordinate of a trigonal bipyramid, like that of sulfur tetrafluoride (SF). The compound is a reagent in organic synthesis. One application is for the dehydration of a secondary alcohol to give an alkene:
:RCH(OH)CHR + PhS[OC(CF)Ph] → RCH=CHR + PhSO + 2 HOC(CF)Ph | 0 | Theoretical and Fundamental Chemistry |
For metal oxides acidity and basicity are dependent on the charge and the radius of the metal ions as well as the character of the metal oxygen bond. The bond between oxygen and the metal is influenced by the coordination of the metal cations and the oxygen anions as well as the filling of the metal d-orbitals. The surface coordination is controlled by the face that is exposed and by the surface relaxation. Structural defects can greatly contribute to the acidity or basicity as sites of high unsaturation can occur from oxygen or metal ion vacancies. | 0 | Theoretical and Fundamental Chemistry |
A rooster tail is a term used in fluid dynamics, automotive gear shifting, and meteorology. It is a region of commotion or turbulence within a fluid, caused by movement. In fluid dynamics, it lies directly in the wake of an object traveling within a fluid, and is accompanied by a vertical protrusion. If it occurs in a river, wise boaters upstream steer clear of its appearance. The degree of their formation can indicate the efficiency of a boats hull design. The magnitude of these features in a boat increases with speed, while the relationship is inversely proportional for airplanes. Energetic volcanic eruptions can create rooster tail formations from their ejecta. They can form in relation to coronal loops near the Suns surface.
In gear shifting in motor vehicles, it is the relation between the coefficient of friction and the sliding speed of the clutch. Cars can throw rooster tails in their wake and loose materials under its wheels. In meteorology, a rooster tail satellite pattern can be applied to either low or high level cloudiness, with the low cloud line seen in the wake of tropical cyclones and the high cloud pattern seen either within mare's tails or within the outflow jet of tropical cyclones. | 1 | Applied and Interdisciplinary Chemistry |
Hexamethyldisilazane is employed as a reagent in many organic reactions:
1) HMDS is used as a reagent in condensation reactions of heterocyclic compounds such as in the microwave synthesis of a derivative of xanthine:
2) The HMDS mediated trimethylsilylation of alcohols, thiols, amines and amino acids as protective groups or for intermediary organosilicon compounds is found to be very efficient and replaced TMSCl reagent.
Silylation of glutamic acid with excess hexamethyldisilazane and catalytic TMSCl in either refluxing xylene or acetonitrile followed by dilution with alcohol (methanol or ethanol) yields the derived lactam pyroglutamic acid in good yield.
HMDS in the presence of catalytic iodine facilitates the silylation of alcohols in excellent yields.
3) HMDS can be used to silylate laboratory glassware and make it hydrophobic, or automobile glass, just as Rain-X does.
4) In gas chromatography, HMDS can be used to silylate OH groups of organic compounds to increase volatility, this way enabling GC-analysis of chemicals that are otherwise non-volatile. | 0 | Theoretical and Fundamental Chemistry |
In the seminar paper on the total synthesis of (+)-monensin, Kishi and co-workers utilized the allylic strain to induce asymmetric induction in the hydroboration oxidation reaction. The reaction is regioselective and stereoselective. The regioselectivity of the reaction is due to the significant positive character developed at the tertiary carbon. The stereoselectivity of the reaction is due to the attack by the borane from the least hindered side to which is where the methyl group lies at. | 0 | Theoretical and Fundamental Chemistry |
p-Dimethylaminocinnamaldehyde (DMACA) is an aromatic hydrocarbon. It is used in an acidic solution to detect indoles. | 0 | Theoretical and Fundamental Chemistry |
The reagent is prepared from chlorosulfonylisocyanate by reaction with methanol and triethylamine in benzene: | 0 | Theoretical and Fundamental Chemistry |
Reductive desulfonylation reactions lead to the replacement of a carbon-sulfur bond in the sulfonyl group with a carbon-hydrogen bond. Because the sulfonyl group is by definition attached to two carbons, however, reduction to two sets of products is possible. Mechanistic studies of reductions employing metal amalgams as the reducing agent suggest that upon electron transfer to the sulfone, fragmentation to a sulfinate anion and the more stable organic radical occurs. Immediate reduction of the radical and protonation then occur to afford the sulfur-free product derived from the more stable radical. Thus, S-alkyl bonds are cleaved in preference to S-aryl or S-alkenyl bonds.
Samarium(II) iodide may be used to reductively cleave α-keto sulfones; in the presence of hexamethylphosphoramide (HMPA), SmI is able to effect reductive elimination of α-functionalized sulfones (see equation () below).
Tin hydrides reduce α-keto and allylic sulfones. The mechanisms of these processes involve the addition of a tin-centered radical to the substrate followed by elimination of a sulfinyl radical, which abstracts a hydrogen from a molecule of tin hydride to propagate the radical chain. Protonation of the organotin intermediates thus formed (by sulfinic acid generated in situ) leads to reduced products. Addition of a stoichiometric amount of proton source allows the use of tin hydride in catalytic amounts. Although desulfonylations of allylic sulfones are site selective (providing only products of allylic transposition), they are not stereoselective and afford mixtures of double bond isomers. The mechanism of desulfonylation of α-keto sulfones is similar.
Transition-metal-mediated reductive desulfonylations rely on the generation of an intermediate π-allyl complex, which undergoes nucleophilic attack by hydride or another nucleophile to afford reduced products. Nucleophilic attack generally occurs at the less substituted position of the π-allyl moiety, although site selectivity depends strongly on the substrate and reaction conditions. Palladium(0) complexes are the most commonly used precatalysts. | 0 | Theoretical and Fundamental Chemistry |
By integrating the above four data sets, CTD automatically constructs putative chemical-gene-phenotype-disease networks to illuminate molecular mechanisms underlying environmentally-influenced diseases.
These inferred relationships are statistically scored and ranked and can be used by scientists and computational biologists to generate and verify testable hypotheses about toxicogenomic mechanisms and how they relate to human health.
Users can search CTD to explore scientific data for chemicals, genes, diseases, or interactions between any of these three concepts. Currently, CTD integrates toxicogenomic data for vertebrates and invertebrates.
CTD integrates data from or hyperlinks to these databases:
*ChemIDplus, a dictionary of more than 400,000 chemicals housed in the US National Library of Medicine
*DrugBank
*Data Infrastructure for Chemical Safety project (diXa) Data Warehouse by the European Bioinformatics Institute which as of November 2015 contained 469 compounds, 188 disease datasets in three sub-categories liver, kidney and cardiovascular disease.
*Gene Ontology Consortium
*KEGG
*NCBI Entrez-Gene
*NCBI PubMed
*NCBI Taxonomy
*NLM Medical Subject Headings
*OMIM
*Reactome | 1 | Applied and Interdisciplinary Chemistry |
The Gibbs adsorption isotherm for multicomponent systems is an equation used to relate the changes in concentration of a component in contact with a surface with changes in the surface tension, which results in a corresponding change in surface energy. For a binary system, the Gibbs adsorption equation in terms of surface excess is:
where
: is the surface tension,
: is the surface excess concentration of component i,
: is the chemical potential of component i. | 0 | Theoretical and Fundamental Chemistry |
Levomethamphetamine crosses the blood-brain-barrier and acts as a norepinephrine transporter inhibitor and TAAR1 agonist, functioning as a selective norepinephrine releasing agent (with limited effects on the release of dopamine), thus levomethamphetamine affects the central nervous system, although its effects are qualitatively distinct relative to those of dextromethamphetamine. It does not possess the same potential for euphoria or addiction that dextromethamphetamine possesses. Among its physiological effects are the vasoconstriction that makes it useful for nasal decongestion. | 0 | Theoretical and Fundamental Chemistry |
CaO is also prone to sintering, or change in pore shape, shrinkage and grain growth during heating. Ionic compounds such as CaO mostly sinter because of volume diffusion or lattice diffusion mechanics. As described by sintering theory, vacancies generated by temperature sensitive defects direct void sites from smaller to larger ones, explaining the observed growth of large pores and the shrinkage of small pores in cycled limestone. It was found that sintering of CaO increases at higher temperatures and longer calcination durations, whereas carbonation time has minimal effect on particle sintering. A sharp increase in sintering of particles is observed at temperatures above 1173 K, causing a reduction in reactive surface area and a corresponding decrease in reactivity.
Solutions: Several options to reduce sorbent deactivation are currently being researched. An ideal sorbent would be mechanically strong, maintain its reactive surface through repeated cycles, and be reasonably inexpensive. Using thermally pre-activated particles or reactivating spent sorbents through hydration are two promising options. Thermally pre-activated particles have been found to retain activity for up to a thousand cycles. Similarly, particles reactivated by hydration show improved long term (after~20 cycles) conversions. | 1 | Applied and Interdisciplinary Chemistry |
The term (kryptoracemate) was coined by Ivan Bernal who employed this term during a meeting of the American Crystallographic Association in 1995.
The name is made of (from Ancient Greek: κρυπτός, "the hidden one") and racemic. It comes from the fact that the racemic composition is "hidden" in a Sohncke space group (usually enantiomerically pure). | 0 | Theoretical and Fundamental Chemistry |
Possible complications may include: infection, bleeding, dysrhythmias and high blood sugar. One review found an increased risk of pneumonia and sepsis but not the overall risk of infection. Another review found a trend towards increased bleeding but no increase in severe bleeding. Hypothermia induces a "cold diuresis" which can lead to electrolyte abnormalities – specifically hypokalemia, hypomagnesaemia, and hypophosphatemia, as well as hypovolemia. | 1 | Applied and Interdisciplinary Chemistry |
Thermal mass flowmeters generally use combinations of heated elements and temperature sensors to measure the difference between static and flowing heat transfer to a fluid and infer its flow with a knowledge of the fluid's specific heat and density. The fluid temperature is also measured and compensated for. If the density and specific heat characteristics of the fluid are constant, the meter can provide a direct mass flow readout, and does not need any additional pressure temperature compensation over their specified range.
Technological progress has allowed the manufacture of thermal mass flowmeters on a microscopic scale as MEMS sensors; these flow devices can be used to measure flow rates in the range of nanoliters or microliters per minute.
Thermal mass flowmeter (also called thermal dispersion or thermal displacement flowmeter) technology is used for compressed air, nitrogen, helium, argon, oxygen, and natural gas. In fact, most gases can be measured as long as they are fairly clean and non-corrosive. For more aggressive gases, the meter may be made out of special alloys (e.g. Hastelloy), and pre-drying the gas also helps to minimize corrosion.
Today, thermal mass flowmeters are used to measure the flow of gases in a growing range of applications, such as chemical reactions or thermal transfer applications that are difficult for other flowmetering technologies. Some other typical applications of flow sensors can be found in the medical field like, for example, CPAP devices, anesthesia equipment or respiratory devices. This is because thermal mass flowmeters monitor variations in one or more of the thermal characteristics (temperature, thermal conductivity, and/or specific heat) of gaseous media to define the mass flow rate. | 1 | Applied and Interdisciplinary Chemistry |
Octanoyl-coenzyme A is the endpoint of beta oxidation in peroxisomes. It is produced alongside acetyl-CoA and transferred to the mitochondria to be further oxidized into acetyl-CoA. | 1 | Applied and Interdisciplinary Chemistry |
The principal mission of iron foundry is the conversion of iron oxides (purified iron ores) to iron metal. This reduction is usually effected using a reducing atmosphere consisting of some mixture of natural gas, hydrogen (H), and carbon monoxide. The byproduct is carbon dioxide. | 1 | Applied and Interdisciplinary Chemistry |
Born in Nantes in Brittany, France, Dauphas received a B.Sc. degree from in 1998. The same year, he obtained an M.Sc. from , at the National Polytechnic Institute of Lorraine (; INPL). In 2002, also from INPL, he was awarded a Ph.D. in geochemistry and cosmochemistry, working with Bernard Marty and Laurie Reisberg. He then completed his postdoctoral research at the Enrico Fermi Institute of the University of Chicago and the Field Museum of Natural History from 2002 to 2004, before joining the faculty at the University of Chicago in 2004. | 0 | Theoretical and Fundamental Chemistry |
The Sawmill is run by a D-3000 Cat diesel engine, Hawthorne Machinery in San Diego provided the cylinder liners. The Sawmill was re-assembled and improved following a donation from the Pederson Brothers who had operated it in the Big Bear area years ago. This is likely the only Sawmill that can be seen operating in San Diego County. | 1 | Applied and Interdisciplinary Chemistry |
Despite being one of the most abundant elements in the Earth's crust, iron is not readily bioavailable. In most aerobic environments, such as the soil or sea, iron exists in the ferric (Fe) state, which tends to form insoluble rust-like solids. To be effective, nutrients must not only be available, they must be soluble. Microbes release siderophores to scavenge iron from these mineral phases by formation of soluble Fe complexes that can be taken up by active transport mechanisms. Many siderophores are nonribosomal peptides, although several are biosynthesised independently.
Siderophores are also important for some pathogenic bacteria for their acquisition of iron. In mammalian hosts, iron is tightly bound to proteins such as hemoglobin, transferrin, lactoferrin and ferritin. The strict homeostasis of iron leads to a free concentration of about 10 mol L, hence there are great evolutionary pressures put on pathogenic bacteria to obtain this metal. For example, the anthrax pathogen Bacillus anthracis releases two siderophores, bacillibactin and petrobactin, to scavenge ferric ion from iron containing proteins. While bacillibactin has been shown to bind to the immune system protein siderocalin, petrobactin is assumed to evade the immune system and has been shown to be important for virulence in mice.
Siderophores are amongst the strongest binders to Fe known, with enterobactin being one of the strongest of these. Because of this property, they have attracted interest from medical science in metal chelation therapy, with the siderophore desferrioxamine B gaining widespread use in treatments for iron poisoning and thalassemia.
Besides siderophores, some pathogenic bacteria produce hemophores (heme binding scavenging proteins) or have receptors that bind directly to iron/heme proteins. In eukaryotes, other strategies to enhance iron solubility and uptake are the acidification of the surroundings (e.g. used by plant roots) or the extracellular reduction of Fe into the more soluble Fe ions. | 1 | Applied and Interdisciplinary Chemistry |
In some cases, such as the decay of , the bremsstrahlung produced by shielding the beta radiation with the normally used dense materials (e.g. lead) is itself dangerous; in such cases, shielding must be accomplished with low density materials, such as Plexiglas (Lucite), plastic, wood, or water; as the atomic number is lower for these materials, the intensity of bremsstrahlung is significantly reduced, but a larger thickness of shielding is required to stop the electrons (beta radiation). | 0 | Theoretical and Fundamental Chemistry |
Support for this theory has been bolstered by studies linking a lower basal metabolic rate (evident with a lowered heartbeat) to increased life expectancy. This has been proposed by some to be the key to why animals like the giant tortoise can live over 150 years.
However, the ratio of resting metabolic rate to total daily energy expenditure can vary between 1.6 and 8.0 between species of mammals. Animals also vary in the degree of coupling between oxidative phosphorylation and ATP production, the amount of saturated fat in mitochondrial membranes, the amount of DNA repair, and many other factors that affect maximum life span. Furthermore, a number of species with high metabolic rate, like bats and birds, are long-lived. In a 2007 analysis it was shown that, when modern statistical methods for correcting for the effects of body size and phylogeny are employed, metabolic rate does not correlate with longevity in mammals or birds. | 1 | Applied and Interdisciplinary Chemistry |
A 2015 study, reported in the journal Ergonomics, showed that, for twenty healthy subjects, exposure to blue-enriched light during the post-lunch dip period significantly reduced the EEG alpha activity, and increased task performance. | 1 | Applied and Interdisciplinary Chemistry |
In the context of climate change and in particular mitigation, a sink is defined as "Any process, activity or mechanism which removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas from the atmosphere".
In the case of non- greenhouse gases, sinks need not store the gas. Instead they can break it down into substances that have a reduced effect on global warming. For example, nitrous oxide can be reduced to harmless N.
Related terms are "carbon pool, reservoir, sequestration, source and uptake". The same publication defines carbon pool as "a reservoir in the Earth system where elements, such as carbon [...], reside in various chemical forms for a period of time."
Both carbon pools and carbon sinks are important concepts in understanding the carbon cycle, but they refer to slightly different things. A carbon pool can be thought of as the overarching term, and carbon sink is then a particular type of carbon pool: A carbon pool is all the places where carbon can be (for example the atmosphere, oceans, soil, plants, and fossil fuels). A carbon sink, on the other hand, is a type of carbon pool that has the capability to take up more carbon from the atmosphere than it releases. | 0 | Theoretical and Fundamental Chemistry |
Phosphonium betaines are intermediates in the Wittig reaction. The addition of betaine to polymerase chain reactions improves the amplification of DNA by reducing the formation of secondary structure in GC-rich regions. The addition of betaine may enhance the specificity of the polymerase chain reaction by eliminating the base pair composition dependence of DNA melting. | 0 | Theoretical and Fundamental Chemistry |
Epoxides are typically prepared by oxidation of alkenes. The most important epoxide in terms of industrial scale is ethylene oxide, which is produced by oxidation of ethylene with oxygen. Other epoxides are produced by one of two routes:
* By the oxidation of alkenes with a peroxyacid such as m-CPBA.
* By the base intramolecular nucleophilic substitution of a halohydrin.
Many ethers, ethoxylates and crown ethers, are produced from epoxides. | 0 | Theoretical and Fundamental Chemistry |
DNA–DNA hybridization (DDH) is used as a primary method to distinguish bacterial species as it is difficult to visually classify them accurately. This technique is not widely used on larger organisms where differences in species are easier to identify. In the late 1900s, strains were considered to belong to the same species if they had a DNA–DNA similarity value greater than 70% and their melting temperatures were within 5 °C of each other. In 2014, a threshold of 79% similarity has been suggested to separate bacterial subspecies.
DDH is a common technique for bacteria, but it is labor intensive, error-prone, and technically challenging. In 2004, a new DDH technique was described. This technique utilized microplates and colorimetrically labelled DNA to decrease the time needed and increase the amount of samples that can be processed. This new DDH technique became the standard for bacterial taxonomy. | 1 | Applied and Interdisciplinary Chemistry |
Hydrolysis (breaking) of phosphodiester bonds can be promoted in several ways. Phosphodiesterases are enzymes that catalyze the hydrolysis of the phosphodiester bond. These enzymes are involved in repairing DNA and RNA sequences, nucleotide salvage, and in the conversion of cGMP and cAMP to GMP and AMP, respectively. Hydrolysis of the phosphodiester bond also occurs chemically and spontaneously, without the aid of enzymes. For example, simple ribose (in RNA) has one more hydroxyl group than deoxyribose (in DNA), making the former less stable and more susceptible to alkaline hydrolysis, wherein relatively high pH conditions induce the breaking of the phosphodiester linkage between two ribonucleotides. The relative instability of RNA under hydroxyl attack of its phosphodiester bonds makes it inadequate for the storage of genomic information, but contributes to its usefulness in transcription and translation. | 1 | Applied and Interdisciplinary Chemistry |
The voltage (electromotive force E) produced by a galvanic cell can be estimated from the standard Gibbs free energy change in the electrochemical reaction according to:
where ν is the number of electrons transferred in the balanced half reactions, and F is Faradays constant. However, it can be determined more conveniently by the use of a standard potential table for the two half cells involved. The first step is to identify the two metals and their ions reacting in the cell. Then one looks up the standard electrode potential, E, in volts, for each of the two half reactions. The standard potential of the cell is equal to the more positive E value minus the more negative E' value.
For example, in the figure above the solutions are CuSO and ZnSO. Each solution has a corresponding metal strip in it, and a salt bridge or porous disk connecting the two solutions and allowing ions to flow freely between the copper and zinc solutions. To calculate the standard potential one looks up copper and zinc's half reactions and finds:
:Cu + 2 Cu E = +0.34 V
:Zn + 2 Zn E = −0.76 V
Thus the overall reaction is:
:Cu + Zn Cu + Zn
The standard potential for the reaction is then +0.34 V − (−0.76 V) = 1.10 V. The polarity of the cell is determined as follows. Zinc metal is more strongly reducing than copper metal because the standard (reduction) potential for zinc is more negative than that of copper. Thus, zinc metal will lose electrons to copper ions and develop a positive electrical charge. The equilibrium constant, K, for the cell is given by:
where F is the Faraday constant, R is the gas constant and T is the temperature in kelvins. For the Daniell cell K is approximately equal to . Thus, at equilibrium, a few electrons are transferred, enough to cause the electrodes to be charged.
Actual half-cell potentials must be calculated by using the Nernst equation as the solutes are unlikely to be in their standard states:
where Q is the reaction quotient. When the charges of the ions in the reaction are equal, this simplifies to:
where {M} is the activity of the metal ion in solution. In practice concentration in mol/L is used in place of activity. The metal electrode is in its standard state so by definition has unit activity. The potential of the whole cell is obtained as the difference between the potentials for the two half-cells, so it depends on the concentrations of both dissolved metal ions. If the concentrations are the same, and the Nernst equation is not needed under the conditions assumed here.
The value of 2.303 is , so at 25 °C (298.15 K) the half-cell potential will change by only 0.05918 V/ν if the concentration of a metal ion is increased or decreased by a factor of 10.
These calculations are based on the assumption that all chemical reactions are in equilibrium. When a current flows in the circuit, equilibrium conditions are not achieved and the cell voltage will usually be reduced by various mechanisms, such as the development of overpotentials. Also, since chemical reactions occur when the cell is producing power, the electrolyte concentrations change and the cell voltage is reduced. A consequence of the temperature dependency of standard potentials is that the voltage produced by a galvanic cell is also temperature dependent. | 1 | Applied and Interdisciplinary Chemistry |
Contact angles are extremely sensitive to contamination; values reproducible to better than a few degrees are generally only obtained under laboratory conditions with purified liquids and very clean solid surfaces. If the liquid molecules are strongly attracted to the solid molecules then the liquid drop will completely spread out on the solid surface, corresponding to a contact angle of 0°. This is often the case for water on bare metallic or ceramic surfaces, although the presence of an oxide layer or contaminants on the solid surface can significantly increase the contact angle. Generally, if the water contact angle is smaller than 90°, the solid surface is considered hydrophilic and if the water contact angle is larger than 90°, the solid surface is considered hydrophobic. Many polymers exhibit hydrophobic surfaces. Highly hydrophobic surfaces made of low surface energy (e.g. fluorinated) materials may have water contact angles as high as ≈ 120°. Some materials with highly rough surfaces may have a water contact angle even greater than 150°, due to the presence of air pockets under the liquid drop. These are called superhydrophobic surfaces.
If the contact angle is measured through the gas instead of through the liquid, then it should be replaced by 180° minus their given value. Contact angles are equally applicable to the interface of two liquids, though they are more commonly measured in solid products such as non-stick pans and waterproof fabrics. | 0 | Theoretical and Fundamental Chemistry |
Lipomannan is a mycobacterium immune agonist. In addition, it is a major constituent of the mycobacterium cell wall. This glycoconjugate is a virulence factor that plays a key role in the human immune system via interaction with various immune cells. It is also considered to be a precursor of lipoarabinomannans.
It is a trigger for TLR 2.
It consists of an α-linked mannan, which consists of 50–70 residues, with some branches points linked glycosidically to a diglyceride of which the fatty acids are similar to those of the whole cell lipid. In addition, succinic acid residues are present as O-acyl substituents on about one in four of the mannose residues, the terminal carboxyl group of the succinic acid providing the whole polymer with a considerable number of acidic functions.
Lipomannan has functional components that resemble lipoteichoic acids; a lipophilic region and a hydrophilic portion with frequent acid groups.
Lipomannan is a phosphorylated polysaccharide associated with the cell envelope and is considered to be the multimannosylated form of PIM which is primarily located in the plasma membrane. Structurally, LM is composed of two segments: a PI anchor to which is attached an α-D-mannan domain; both play key roles in inducing cytokine production by phagocytic cells. Mannose core consists of a linear α(1-6)-linked mannan backbone extending from the c-6 of the myo-inositol; the mannan chains is further substituted by α-(1-2) man-p side branches. | 1 | Applied and Interdisciplinary Chemistry |
The Wnt signaling pathways are initiated by the binding of the Wnt ligand to the Fz receptor. There are three different molecular pathways downstream of the Wnt/Fz interaction. The majority of research has focused on the Wnt/β-catenin pathway (also known as the "canonical" Wnt pathway), which manages cell fate determination by regulating gene expression. The Wnt/Ca and Wnt/polarity pathways are known as the "non-canonical pathways". The decision of which pathway is activated most likely depends on which Wnt ligand and Fz receptor are present, as well as the cellular context. Nineteen Wnt ligands and ten different members of the Fz seven-transmembrane receptor family have been described in the human genome. As a result, a large variety of responses could be initiated from the Wnt/Fz interactions.
The Wnt/β-catenin pathway starts with the binding of Wnt to a receptor complex encompassing a Fz receptor and LRP co-receptor. After Wnt binds, an intracellular protein named Dishevelled (Dvl) is activated via phosphorylation. β-catenin degradation complexes in the cytoplasm are composed of adenomatous polyposis coli (APC), glycogen synthase kinase 3β (GSK3β) and Axin. APC promotes the degradation of β-catenin by increasing the affinity of the degradation complex to β-catenin. Axin is a scaffolding protein which holds the degradation complex together. The activated Dvl associates with Axin and prevents GSK3β and casein kinase 1α (CK1α) from phosphorylating critical substrates, such as β-catenin. Phosphorylation of β-catenin marks the protein for ubiquitylation and rapid degradation by proteasomes. Thus, the binding of Wnt to the receptor results in a non-phosphorylated form of β-catenin which localizes to the nucleus and, after displacing the Groucho corepressor protein, forms a complex with Tcf/Lef transcription factors and co-activators (such as CREB binding protein) and induces the expression of downstream target genes.
β-catenin is actively stabilized in over 50% of breast cancers and its nuclear localization correlates with poor patient prognosis. Several target genes of the Wnt signaling pathway, such as cyclin D1, are activated in a significant proportion of breast tumours. It has been shown that SFRP1 transcription can be driven by B-catenin in normal intestinal epithelial cells. Neoplastic epithelial cells were treated with lithium chloride, which inhibits GSK3B and thus stabilizes B-catenin. Lithium chloride is widely used to mimic Wnt signaling. Rather than suppressing SFRP1 expression, B-catenin/TCF activity was associated with the induction of SFRP1. This is consistent with a negative feedback response restricting the exposure of a normal cell to a prolonged Wnt growth factor signal.
Hedgehog signaling in the intestinal epithelium represses the canonical Wnt signaling to restrict expression of Wnt target genes to stem or progenitor cells. It was thought that the Hedgehog signaling pathway does this via the induction of the secreted-type Wnt inhibitor. Katoh et al. searched for the GLI-binding site within the promoter region of Wnt inhibitor genes. GLI are transcription factors that activate the transcription of Hedgehog target genes. The GLI-binding site was identified within the 5’-flanking promoter region of the human SFRP1 gene. The GLI-binding site was conserved among promoter regions of mammalian SFRP1 orthologs. These facts indicate that the SFRP1 gene was identified as the evolutionarily conserved target of the Hedgehog-GLI signaling pathway. SFRP1 was found to be expressed in mesenchymal cells. Hedgehog is secreted from differentiated epithelial cells to induce SFRP1 expression in mesenchymal cells, which keeps differentiated epithelial cells away from the effect of canonical Wnt signaling. Thus, SFRP1 is most likely the Hedgehog target to confine canonical Wnt signaling within stem or progenitor cells. Epigenetic CpG hypermethylation of the SFRP1 promoter during chronic persistent inflammation and aging leads to the occurrence of gastrointestinal cancers, such as colorectal cancer and gastric cancer, through the breakdown of Hedgehog-dependent Wnt signal inhibition. | 1 | Applied and Interdisciplinary Chemistry |
The mass of an atomic nucleus is given by
where and are the rest mass of a proton and a neutron, respectively, and is the total binding energy of the nucleus. The mass–energy equivalence is used here. The binding energy is subtracted from the sum of the proton and neutron masses because the mass of the nucleus is less than that sum. This property, called the mass defect, is necessary for a stable nucleus; within a nucleus, the nuclides are trapped by a potential well. A semi-empirical mass formula states that the binding energy will take the form
The difference between the mass of a nucleus and the sum of the masses of the neutrons and protons that comprise it is known as the mass defect. E is often divided by the mass number to obtain binding energy per nucleon for comparisons of binding energies between nuclides. Each of the terms in this formula has a theoretical basis. The coefficients , , , and a coefficient that appears in the formula for are determined empirically.
The binding energy expression gives a quantitative estimate for the neutron-proton ratio. The energy is a quadratic expression in that is minimized when the neutron-proton ratio is . This equation for the neutron-proton ratio shows that in stable nuclides the number of neutrons is greater than the number of protons by a factor that scales as .
The figure at right shows the average binding energy per nucleon as a function of atomic mass number along the line of beta stability, that is, along the bottom of the valley of stability. For very small atomic mass number (H, He, Li), binding energy per nucleon is small, and this energy increases rapidly with atomic mass number. Nickel-62 (28 protons, 34 neutrons) has the highest mean binding energy of all nuclides, while iron-58 (26 protons, 32 neutrons) and iron-56 (26 protons, 30 neutrons) are a close second and third. These nuclides lie at the very bottom of the valley of stability. From this bottom, the average binding energy per nucleon slowly decreases with increasing atomic mass number. The heavy nuclide U is not stable, but is slow to decay with a half-life of 4.5 billion years. It has relatively small binding energy per nucleon.
For β decay, nuclear reactions have the generic form
where and are the mass number and atomic number of the decaying nucleus, and X and X′ are the initial and final nuclides, respectively. For β decay, the generic form is
These reactions correspond to the decay of a neutron to a proton, or the decay of a proton to a neutron, within the nucleus, respectively. These reactions begin on one side or the other of the valley of stability, and the directions of the reactions are to move the initial nuclides down the valley walls towards a region of greater stability, that is, toward greater binding energy.
The figure at right shows the average binding energy per nucleon across the valley of stability for nuclides with mass number A = 125. At the bottom of this curve is tellurium (Te), which is stable. Nuclides to the left of Te are unstable with an excess of neutrons, while those on the right are unstable with an excess of protons. A nuclide on the left therefore undergoes β decay, which converts a neutron to a proton, hence shifts the nuclide to the right and toward greater stability. A nuclide on the right similarly undergoes β decay, which shifts the nuclide to the left and toward greater stability.
Heavy nuclides are susceptible to α decay, and these nuclear reactions have the generic form,
As in β decay, the decay product X′ has greater binding energy and it is closer to the middle of the valley of stability. The α particle carries away two neutrons and two protons, leaving a lighter nuclide. Since heavy nuclides have many more neutrons than protons, α decay increases a nuclide's neutron-proton ratio. | 0 | Theoretical and Fundamental Chemistry |
Immunological methods using monoclonal antibodies can be used to detect indicator bacteria in water samples. Precultivation in select medium must preface detection to avoid detection of dead cells. ELISA antibody technology has been developed to allow for readable detection by the naked eye for rapid identification of coliform microcolonies. Other uses of antibodies in detection use magnetic beads coated with antibodies for the concentration and separation of the oocysts and cysts as described below for immunomagnetic separation (IMS) methods. | 0 | Theoretical and Fundamental Chemistry |
Laser diffraction analysis, also known as laser diffraction spectroscopy, is a technology that utilizes diffraction patterns of a laser beam passed through any object ranging from nanometers to millimeters in size to quickly measure geometrical dimensions of a particle. This particle size analysis process does not depend on volumetric flow rate, the amount of particles that passes through a surface over time. | 0 | Theoretical and Fundamental Chemistry |
The optimal configurations of scanning helium microscopes are geometrical configurations that maximise the intensity of the imaging beam within a given lateral resolution and under certain technological constraints.
When designing a scanning helium microscope, scientists strive to maximise the intensity of the imaging beam while minimising its width. The reason behind this is that the beam's width gives the resolution of the microscope while its intensity is proportional to its signal to noise ratio. Due to their neutrality and high ionisation energy, neutral helium atoms are hard to detect. This makes high-intensity beams a crucial requirement for a viable scanning helium microscope.
In order to generate a high-intensity beam, scanning helium microscopes are designed to generate a supersonic expansion of the gas into vacuum, that accelerates neutral helium atoms to high velocities. Scanning helium microscopes exist in two different configurations: the pinhole configuration and the zone plate configuration. In the pinhole configuration, a small opening (the pinhole) selects a section of the supersonic expansion far away from its origin, which has previously been collimated by a skimmer (essentially, another small pinhole). This section then becomes the imaging beam. In the zone plate configuration a Fresnel zone plate focuses the atoms coming from a skimmer into a small focal spot.
Each of these configurations have different optimal designs, as they are defined by different optics equations. | 0 | Theoretical and Fundamental Chemistry |
The resistivity of solvent extract (ROSE) test is a test for the presence and average concentration of soluble ionic contaminants, for example on a printed circuit board (PCB). It was developed in the early 1970s. Some manufacturers use it as part of Six Sigma processes.
Some modern fluxes have low solubility in traditional ROSE solvents such as water and isopropyl alcohol, and therefore require the use of different solvents. | 0 | Theoretical and Fundamental Chemistry |
Warfarin treatment requires blood monitoring and dose adjustments regularly due to its narrow therapeutic window. If supervision isnt adequate warfarin poses a threat in causing, all too frequent, haemorrhagic events and multiple interactions with food and other drugs. Currently, the main problem with low molecular weight heparin (LMWH) is the administration route, as it has to be given subcutaneously. Because of these disadvantages there has been an urgent need for better anticoagulant drugs. For a modern society, convenient and fast drug administration is the key to a good drug compliance. In 2008 the first direct Xa inhibitor was approved for clinical use. Direct Xa inhibitors are just as efficacious as LMWH and warfarin but they are given orally and dont need as strict monitoring. Other Xa inhibitors advantages are rapid onset/offset, few drug interactions and predictable pharmacokinetics. The rapid onset/offset effect greatly reduces the need for “bridging” with parenteral anticoagulants after surgeries. Today there are four factor Xa inhibitors marketed: rivaroxaban, apixaban, edoxaban and betrixaban. | 1 | Applied and Interdisciplinary Chemistry |
Hurst returned to Cambridge after the war to complete his PhD in physical chemistry. In 1948 he joined the Atomic Energy Research Establishment at Harwell, working first on the chemistry of plutonium, before heading a team that investigated the potential of different types of nuclear reactors. In 1957, he was appointed chief chemist at the Atomic Energy Authority Industrial Research and Development branch at Risley, Cheshire, and in 1958 he was named as the first director of the Dounreay experimental fast-breeder reactor complex.
In 1963, Hurst left Dounreay to take up the directorship of the British Ship Research Association.
In the 1973 Queen's Birthday Honours, Hurst was appointed a Commander of the Order of the British Empire. | 0 | Theoretical and Fundamental Chemistry |
There are three main factors that affect the dispersion of volatiles in magma: confining pressure, composition of magma, temperature of magma. Pressure and composition are the most important parameters. To understand how the magma behaves rising to the surface, the role of solubility within the magma must be known. An empirical law has been used for different magma-volatiles combination. For instance, for water in magma the equation is n=0.1078 P where n is the amount of dissolved gas as weight percentage (wt%), P is the pressure in megapascal (MPa) that acts on the magma. The value changes, for example for water in rhyolite n = 0.4111 P and for the carbon dioxide n = 0.0023 P. These simple equations work if there is only one volatile in a magma. However, in reality, the situation is not so simple because there are often multiple volatiles in a magma. It is a complex chemical interaction between different volatiles.
Simplifying, the solubility of water in rhyolite and basalt is function of pressure and depth below the surface in absence of other volatiles. Both basalt and rhyolite lose water with decreasing pressure as the magma rises to the surface. The solubility of water is higher in rhyolite than in basaltic magma. Knowledge of the solubility allows the determination of the maximum amount of water that might be dissolved in relation with pressure. If the magma contains less water than the maximum possible amount, it is undersaturated in water. Usually insufficient water and carbon dioxide exist in the deep crust and mantle, so magma is often undersaturated in these conditions. Magma becomes saturated when it reaches the maximum amount of water that can be dissolved in it. If the magma continues to rise up to the surface and more water is dissolved, it becomes supersaturated. If more water is dissolved in magma, it can be ejected as bubbles or water vapor. This happens because pressure decreases in the process and velocity increases and the process has to balance also between decrease of solubility and pressure. Making a comparison with the solubility of carbon dioxide in magma, this is considerably less than water and it tends to exsolve at greater depth. In this case water and carbon dioxide are considered independent. What affects the behavior of the magmatic system is the depth at which carbon dioxide and water are released. Low solubility of carbon dioxide means that it starts to release bubbles before reaching the magma chamber. The magma is at this point already supersaturated. The magma enriched in carbon dioxide bubbles, rises up to the roof of the chamber and carbon dioxide tends to leak through cracks into the overlying caldera. Basically, during an eruption the magma loses more carbon dioxide than water, that in the chamber is already supersaturated. Overall, water is the main volatile during an eruption. | 0 | Theoretical and Fundamental Chemistry |
British physician and physiologist Henry Hyde Salter (1823–1871) included a chapter on treatment by "stimulants", in a book on asthma which was first published in 1860. He noted the benefits of strong coffee, presumably because it dispelled sleep, which favored asthma. Even more impressive to him, however, was the response to "strong mental emotion": "The cure of asthma by violent emotion is more sudden and complete than by any other remedy whatever; indeed, I know few things more striking and curious in the whole history of therapeutics. The cure takes no time; it is instantaneous, the intersect paroxysm ceases on the instant." The retrospective interpretation is that the "cure″ was due to the release of adrenaline from the adrenal glands.
At the same time, the French physician Alfred Vulpian also made discoveries about the adrenal medulla. Material scraped from the adrenal medulla turned green when ferric chloride was added. This did not occur with the adrenal cortex nor with any other tissue. Vulpian even came to the insight that the substance entered "le torrent circulator" ("the circulatory torrent"), as blood from the adrenal veins did give the ferric chloride reaction.
In the early 1890s, in the laboratory of Oswald Schmiedeberg in Strasbourg, the German pharmacologist Carl Jacob (1857–1944) studied the relationship between the adrenal glands and the intestine. Electrical stimulation of the vagus nerve or injection of muscarine elicited peristalsis. This peristalsis was promptly abolished by electrical stimulation of the adrenal glands. The experiment has been called "the first indirect demonstration of the role of the adrenal medulla as an endocrine organ and actually a more sophisticated demonstration of the adrenal medullary function than the classic study of Oliver and Schafer". While this may be true, Jacob did not envisage a chemical signal secreted into the blood to influence distant organs, the actual function of a hormone, but nerves running from the adrenals to the gut, "Hemmungsbahnen für die Darmbewegung". | 1 | Applied and Interdisciplinary Chemistry |
This fjord is marked by a highly mobile chemocline with a depth that is thought to be related to temperature effects. Local reports of strong rotten egg smell- the smell of sulfur- during numerous summers around the fjord provide evidence that, like the Framvaren fjord, the chemocline has breached the surface of the fjord at least five times in the last century. Sediments export during these events increased the concentrations of dissolved phosphates, inorganic bioavailable nitrogen, and other nutrients, resulting in a harmful algal bloom. | 0 | Theoretical and Fundamental Chemistry |
Tetanolysin is a toxin produced by Clostridium tetani bacteria. Its function is unknown, but it is believed to contribute to the pathogenesis of tetanus. The other C. tetani toxin, tetanospasmin, is more definitively linked to tetanus. It is sensitive to oxygen.
Tetanolysin belongs to a family of protein toxins known as thiol-activated cytolysins, which bind to cholesterol. It is related to streptolysin O and the θ-toxin of Clostridium perfringens. Cytolysins form pores in the cytoplasmic membrane that allows for the passage of ions and other molecules into the cell. The molecular weight of tetanolysin is around 55,000 daltons. | 1 | Applied and Interdisciplinary Chemistry |
"Actinic" lights are a high-color-temperature blue light. They are also used in electric fly killers to attract flies. | 0 | Theoretical and Fundamental Chemistry |
Consider a bathtub in which there is some bathing salt dissolved. We now fill in more water, keeping the bottom plug in. What happens?
Since there is no reaction, and since there is no outflow . The mass balance becomes
or
Using a mass balance for total volume, however, it is evident that and that Thus we get
Note that there is no reaction and hence no reaction rate or rate law involved, and yet . We can thus draw the conclusion that reaction rate can not be defined in a general manner using . One must first write down a mass balance before a link between and the reaction rate can be found. Many textbooks, however, define reaction rate as
without mentioning that this definition implicitly assumes that the system is closed, has a constant volume and that there is only one reaction. | 1 | Applied and Interdisciplinary Chemistry |
Carboxylation is a chemical reaction in which a carboxylic acid is produced by treating a substrate with carbon dioxide. The opposite reaction is decarboxylation. In chemistry, the term carbonation is sometimes used synonymously with carboxylation, especially when applied to the reaction of carbanionic reagents with CO. More generally, carbonation usually describes the production of carbonates. | 0 | Theoretical and Fundamental Chemistry |
Both the CB1 and CB2 receptors (the bonding site of anandamide) seem to play a role in the identification of positive and negative interpretation of environment and setting. In animal models, anandamide mediates the interpretation of stimulus; specifically, optimism and pessimism in the presence of an ambiguous cue. Anandamide has been shown to impair working memory in rats, while THC (the compound in cannabis that binds to the CB1 and CB2 receptors) also shows a deficit in working memory.
This binding relationship of anandamide and the CB1/CB2 may affect neurotransmission of dopamine, serotonin, GABA, and glutamate. There is currently encouraging, albeit embryonic, evidence for medicinal cannabis in the treatment of a range of psychiatric disorders. Supportive findings are emerging for some key isolates, however, clinicians need to be mindful of a range of prescriptive and occupational safety considerations, especially if initiating higher dose THC formulas.
Anandamide injected directly into the forebrain reward-related brain structure nucleus accumbens enhances the pleasurable responses of rats to a rewarding sucrose taste, and enhances food intake as well. Increasing anandamide seems to increase the intrinsic value of food, not necessarily by stimulation of appetite or hunger.
Anandamide may affect hunger, sleep, pain modulation, working memory, identification of novelty, and interpretation of environment. | 1 | Applied and Interdisciplinary Chemistry |
Modelling of two phase flow is still under development. Known methods are
*Volume of fluid method
*Level-set method
*Front tracking by Gretar Tryggvason
*Lattice Boltzmann methods
*Smoothed-particle hydrodynamics (SPH) | 1 | Applied and Interdisciplinary Chemistry |
Liquid crystals can change from liquid to solid in response to a change in temperature. At lower temperatures, the crystals are mostly solid and hardly reflect any light, causing it to appear black. As it gradually increases in temperature, the crystals become more spaced out, causing light to reflect differently and changing the color of the crystals. The temperatures at which these crystals change their properties can range from -30 °C to 90 °C. | 0 | Theoretical and Fundamental Chemistry |
Gordon Stone was born in Exeter, Devon in 1925, the only child of Sidney Charles Stone, a civil servant, and Florence Beatrice Stone (née Coles). He received his B.A. in 1948 and Ph.D. in 1951, both from Christ's College, Cambridge (Cambridge University), England, where he studied under Harry Julius Emeléus. | 0 | Theoretical and Fundamental Chemistry |
The Pelton wheel turbine (better described as a radial turbine) translates the mechanical action of the Pelton wheel rotating in the liquid flow around an axis into a user-readable rate of flow (gpm, lpm, etc.). The Pelton wheel tends to have all the flow traveling around it with the inlet flow focused on the blades by a jet. The original Pelton wheels were used for the generation of power and consisted of a radial flow turbine with "reaction cups" which not only move with the force of the water on the face but return the flow in opposite direction using this change of fluid direction to further increase the efficiency of the turbine. | 1 | Applied and Interdisciplinary Chemistry |
After insulin enters the bloodstream, it binds to a membrane-spanning receptor tyrosine kinase (RTK). This glycoprotein is embedded in the cellular membrane and has an extracellular receptor domain, made up of two α-subunits, and an intracellular catalytic domain made up of two β-subunits. The α-subunits act as insulin receptors and the insulin molecule acts as a ligand. Together, they form a receptor-ligand complex.
Binding of insulin to the α-subunit results in a conformational change of the protein, which activates tyrosine kinase domains on each β-subunit. The tyrosine kinase activity causes an autophosphorylation of several tyrosine residues in the β-subunit. The phosphorylation of 3 residues of tyrosine is necessary for the amplification of the kinase activity.
This autophosphorylation triggers the activation of the docking proteins, in this case IRS (1-4) on which Phosphatidylinositol-3-Kinase (PI-3K) can be attached or GRB2 where the ras Guanine nucleotide exchange factor (GEF) (also known as SOS) can be attached.
PI-3K causes the phosphorylation of PIP2 to PIP3. This protein acts as a docking site for PDPK1 and Protein kinase B (also known as AKT), which is then phosphorylated by the latter and PK2 to be activated. This leads to crucial metabolic functions such as synthesis of lipids, proteins and glycogen. It also leads to cell survival and cell proliferation. Most importantly, the PI-3K pathway is responsible for the distribution of glucose for important cell functions. For example, the suppression of hepatic glucose synthesis and the activation of glycogen synthesis. Hence, AKT possesses a crucial role in the linkage of the glucose transporter (GLUT4) to the insulin signaling pathway. The activated GLUT4 will translocate to the cell membrane and promotes the transportation of glucose into the intracellular medium.
The Ras-GEF stimulates the exchange of GDP to GTP in the RAS protein, causing it to activate. Ras then activates the Mitogen-activated protein kinase (MAP-Kinase) route, which ultimately results in changes in protein activity and gene expression.
Thus, insulin's role is more of a promoter for the usage of glucose in the cells rather than neutralizing or counteracting it. | 1 | Applied and Interdisciplinary Chemistry |
* 1994 – Progress Award in Synthetic Organic Chemistry, Japan
* 2000 – Division Award of Chemical Society of Japan (Organic Chemistry)
* 2001 – Japan IBM Science Prize
* 2009 – The Commendation for Science and Technology by the MEXT Prizes for Science and Technology
* 2010 – The 7th Leo Esaki Prize
* 2010 – Thomson Reuters Research Front Award
* 2011 – 3M Lectureship Award (The University of British Columbia)
* 2012 – Kharasch Lecturers (The University of Chicago)
* 2013 – Arthur C. Cope Scholar Award
* 2013 – The Chemical Society of Japan (CSJ) Award
* 2013 – Merck-Karl Pfister Visiting Professorship (MIT Lectureship award)
* 2014 – Medal with Purple Ribbon
* 2014 – Fred Basolo Medal (Northwestern University)
* 2018 – Wolf Prize in Chemistry
* 2019 – Paul Karrer Gold Medal
* 2020 – Clarivate Citation Laureate
* 2020 – Chu-Nichi Culture Award
* 2023 – Asahi Prize | 0 | Theoretical and Fundamental Chemistry |
Vaccine antigens are often encapsulated within microspheres or liposomes. Common microspheres made using Poly-lactic acid (PLA) and poly-lactic-co-glycolic acid (PLGA) allow for controlled antigen release by degrading in vivo while liposomes including multilamellar or unilamellar vesicles allow for prolonged release.
Polymer-based delivery systems confer advantages such as increased resistance to degradation in GI tract, controlled antigen release, raised particle uptake by immune cells and enhanced ability to induce cytotoxic T cell responses. An example of licensed recombinant vaccine utilising liposomal delivery is Shringrix. | 1 | Applied and Interdisciplinary Chemistry |
As a derivative of EDTA, dexrazoxane chelates iron and thus reduces the number of metal ions complexed with anthracycline and, consequently, decrease the formation of superoxide radicals. The exact chelation mechanism is unknown, but it has been postulated that dexrazoxane can be converted into ring-opened form intracellularly and interfere with iron-mediated free radical generation that is in part thought to be responsible for anthryacycline induced cardiomyopathy. It was speculated that dexrazoxane could be used for further investigation to synthesize new antimalarial drugs. | 0 | Theoretical and Fundamental Chemistry |
Gestonorone caproate, also known as gestronol hexanoate or norhydroxyprogesterone caproate and sold under the brand names Depostat and Primostat, is a progestin medication which is used in the treatment of enlarged prostate and cancer of the endometrium. It is given by injection into muscle typically once a week.
Side effects of gestonorone caproate include worsened glucose tolerance, decreased libido in men, and injection site reactions. Gestonorone caproate is a progestin, or a synthetic progestogen, and hence is an agonist of the progesterone receptor, the biological target of progestogens like progesterone. It has no other important hormonal activity.
Gestonorone caproate was discovered in 1960 and was introduced for medical use by 1973. It has been used widely throughout Europe, including in the United Kingdom, and has also been marketed in certain other countries such as Japan, China, and Mexico. However, it has since mostly been discontinued, and it remains available today only in a handful of countries, including the Czech Republic, Japan, Mexico, and Russia. | 0 | Theoretical and Fundamental Chemistry |
An aglycone (aglycon or genin) is the chemical compound remaining after the glycosyl group on a glycoside is replaced by a hydrogen atom. For example, the aglycone of a cardiac glycoside would be a steroid molecule. | 0 | Theoretical and Fundamental Chemistry |
In this simple model, can also be derived directly from the expression for fluid flow in the Stokes limit for an incompressible fluid, which is
for the fluid flow velocity and the pressure. We consider an infinite surface in the plane at , and enforce stick boundary conditions there, i.e., . We take the concentration gradient to be along the axis, i.e., . Then the only non-zero component of the flow velocity is along x, , and it depends only on height . So the only non-zero component of the Stokes' equation is
In diffusioosmosis, in the bulk of the fluid (i.e., outside the interface) the hydrostatic pressure is assumed to be uniform (as we expect any gradients to relax away by fluid flow) and so in bulk
for the solvent's contribution to the hydrostatic pressure, and the contribution of the solute, called the osmotic pressure. Thus in the bulk the gradients obey
As we have assumed the solute is ideal, , and so
Our solute is excluded from a region of width (the interfacial region) from the surface, and so in interface , and so there . Assuming continuity of the solvent contribution into the interface we have a gradient of the hydrostatic pressure in the interface
i.e., in the interface there is a gradient of the hydrostatic pressure equal to the negative of the bulk gradient in the osmotic pressure. It is this gradient in the interface in the hydrostatic pressure that creates the diffusioosmotic flow. Now that we have , we can substitute into the Stokes equation, and integrate twice, then
where , , and are integration constants. Far from the surface the flow velocity must be a constant, so . We have imposed zero flow velocity at , so . Then imposing continuity where the interface meets the bulk, i.e., forcing and to be continuous at we determine and , and so get
Which gives, as it should, the same expression for the slip velocity, as above. This result is for a specific and very simple model, but it does illustrate general features of diffusioosmoisis: 1) the hydrostatic pressure is, by definition (flow induced by pressure gradients in the bulk is a common but separate physical phenomenon) uniform in the bulk, but there is a gradient in the pressure in the interface, 2) this pressure gradient in the interface causes the velocity to vary in the direction perpendicular to the surface, and this results in a slip velocity, i.e., for the bulk of the fluid to move relative to the surface, 3) away from the interface the velocity is constant, this type of flow is sometimes called plug flow. | 0 | Theoretical and Fundamental Chemistry |
The "conventional recycle process" for recovering and reusing the reactants has largely been supplanted by a stripping process, developed in the early 1960s by Stamicarbon in The Netherlands, that operates at or near the full pressure of the reaction vessel. It reduces the complexity of the multi-stage recycle scheme, and it reduces the amount of water recycled in the carbamate solution, which has an adverse effect on the equilibrium in the urea conversion reaction and thus on overall plant efficiency. Effectively all new urea plants use the stripper, and many total recycle urea plants have converted to a stripping process.
In the conventional recycle processes, carbamate decomposition is promoted by reducing the overall pressure, which reduces the partial pressure of both ammonia and carbon dioxide, allowing these gasses to be separated from the urea product solution. The stripping process achieves a similar effect without lowering the overall pressure, by suppressing the partial pressure of just one of the reactants in order to promote carbamate decomposition. Instead of feeding carbon dioxide gas directly to the urea synthesis reactor with the ammonia, as in the conventional process, the stripping process first routes the carbon dioxide through the stripper. The stripper is a carbamate decomposer that provides a large amount of gas-liquid contact. This flushes out free ammonia, reducing its partial pressure over the liquid surface and carrying it directly to a carbamate condenser (also under full system pressure). From there, reconstituted ammonium carbamate liquor is passed to the urea production reactor. That eliminates the medium-pressure stage of the conventional recycle process. | 0 | Theoretical and Fundamental Chemistry |
In medicinal chemistry and pharmacology, a binding coefficient is a quantity representing the extent to which a chemical compound will bind to a macromolecule. The preferential binding coefficient can be derived from the Kirkwood-Buff solution theory of solutions. Preferential binding is defined as a thermodynamic expression that describes the binding of the cosolvent over the solvent. This is in a system that is open to both the solvent and cosolvent. Consequently, preferential interaction coefficients are measures of interactions that involve “solutes that participate in a reaction in solution.” | 1 | Applied and Interdisciplinary Chemistry |
He was awarded by the President of Chile, Eduardo Frei Ruiz-Tagle the Presidential Chair in Science in 1996 by a Committee chaired by a Nobel Prize in Chemistry Rudolph Marcus and including Physics Nobel Laureate David Gross. He received the Silver Medal “University Merit” in 1998 and the Gold Medal in 2002 and the Manuel Bulnes Medal in 2013. He was distinguished by Conicyt with “Fondecyt Diploma” for being awarded more than 10 consecutive research grants without rejects in 2012. He still remains unbeaten in Fondecyt. He has been awarded two Milenium Projects as Alternative Responsible Scientist and has participated in many other associative research projects in Chile and abroad. He was appointed by the President of Chile Sebastian Piñera Echeñique and the Minister of Education, Member of the Superior Council of Research of Conicyt for the period 2010–2013. In 2014 he received the Dr. Alberto Zanlungo Prize. He has received several distinctions from international scientific societies. He was appointed Fellow by the Royal Society of Chemistry (RSC) of the UK in 2018. He became a Member of the RSC in 2017. He received the Fellow Medal from the International Society of Electrochemistry based in Europe and the Fellow Medal from the US-based Electrochemical Society (ECS) both in 2014. This year he was incorporated as an Active Member to the Academy of Sciences of Latin America (ACAL) and became an Emeritus Member of The Electrochemical Society of the United States of America. He created the Chilean Secretary of ISE in 2003 and was his first chilean representative. He also created the Chile Section of ECS in 2011 and is presently its Chairman. He was a co-founder of the Chilean Society of Carbonaceous Materials and is presently its President. He is also the President of the Iberoamerican Chemical Society. | 0 | Theoretical and Fundamental Chemistry |
Although strong, the (aryl)C−SO bond can be broken by nucleophilic reagents. Of historic and continuing significance is the α-sulfonation of anthroquinone followed by displacement of the sulfonate group by other nucleophiles, which cannot be installed directly. An early method for producing phenol involved the base hydrolysis of sodium benzenesulfonate, which can be generated readily from benzene.
:CHSONa + NaOH → CHOH + NaSO
The conditions for this reaction are harsh, however, requiring fused alkali or molten sodium hydroxide at 350 °C for benzenesulfonic acid itself. Unlike the mechanism for the fused alkali hydrolysis of chlorobenzene, which proceeds through elimination-addition (benzyne mechanism), benzenesulfonic acid undergoes the analogous conversion by an SAr mechanism, as revealed by a C labeling, despite the lack of stabilizing substituents. Sulfonic acids with electron-withdrawing groups (e.g., with NO or CN substituents) undergo this transformation much more readily. | 0 | Theoretical and Fundamental Chemistry |
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