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Stays made from puddled iron bar were used as a cheaper alternative to copper for joining the inner and outer firebox plates of steam locomotives. The incorporated stringers gave flexibility akin to stranded wire rope and stays made of the material were therefore resistant to snapping in service. Wrought iron rivets made from iron bar typically contained stringer filaments running the length of the rivet, but filaments at right angles to the tension, particularly beneath the head, caused weakness. | 1 | Applied and Interdisciplinary Chemistry |
3D printing for the manufacturing of artificial organs has been a major topic of study in biological engineering. As the rapid manufacturing techniques entailed by 3D printing become increasingly efficient, their applicability in artificial organ synthesis has grown more evident. Some of the primary benefits of 3D printing lie in its capability of mass-producing scaffold structures, as well as the high degree of anatomical precision in scaffold products. This allows for the creation of constructs that more effectively resemble the microstructure of a natural organ or tissue structure. Organ printing using 3D printing can be conducted using a variety of techniques, each of which confers specific advantages that can be suited to particular types of organ production. | 1 | Applied and Interdisciplinary Chemistry |
A quantum dot is a semiconductor nano-particle that is often used in quantum optical systems. This includes their ability to be placed in optical microcavities where they can act as two-level systems. In this process, quantum dots are placed in cavities which allow for the discretization of the possible energy states of the quantum dot coupled with the vacuum field. The vacuum field is then replaced by an excitation field and resonance fluorescence is observed. Current technology only allows for population of the dot in an excited state (not necessarily always the same), and relaxation of the quantum dot back to its ground state. Direct excitation followed by ground state collection was not achieved until recently. This is mainly due to the fact that as a result of the size of quantum dots, defects and contaminants create fluorescence of their own apart from the quantum dot. This desired manipulation has been achieved by quantum dots by themselves through a number of techniques including four-wave mixing and differential reflectivity, however no techniques had shown it to occur in cavities until 2007. Resonance fluorescence has been seen in a single self-assembled quantum dot as presented by Muller among others in 2007.
In the experiment they used quantum dots that were grown between two mirrors in the cavity. Thus the quantum dot was not placed in the cavity, but instead created in it. They then coupled a strong in-plane polarized tunable continuous-wave laser to the quantum dot and were able to observe resonance fluorescence from the quantum dot. In addition to the excitation of the quantum dot that was achieved, they were also able to collect the photon that was emitted with a micro-PL setup. This allows for resonant coherent control of the ground state of the quantum dot while also collecting the photons emitted from the fluorescence. | 0 | Theoretical and Fundamental Chemistry |
Environmentally sensitive applications (e.g. farm tractors and marine dredging) may benefit from using biodegradable hydraulic fluids based upon rapeseed vegetable oil when there is the risk of an oil spill from a ruptured oil line. Typically these oils are available as ISO 32, ISO 46, and ISO 68 specification oils. ASTM standards ASTM-D-6006, Guide for Assessing Biodegradability of Hydraulic Fluids and ASTM-D-6046, Standard Classification of Hydraulic Fluids for Environmental Impact are relevant. | 1 | Applied and Interdisciplinary Chemistry |
Humans and chimpanzees share ten NANOG pseudogenes (NanogP2-P11) during evaluation, two of them are located on the X chromosome and they characterized by the 5’ promoter sequences and the absence of introns as a result of mRNA retrotransposition all in the same places: one duplication pseudogene and nine retropseudogenes. Of the nine shared NANOG retropseudogenes, two lack the poly-(A) tails characteristic of most retropseudogenes, indicating that copying errors occurred during their creation. Due to the high improbability that the same pseudogenes (copying errors included) would exist in the same places in two unrelated genomes, evolutionary biologists point to NANOG and its pseudogenes as providing evidence of common descent between humans and chimpanzees. | 1 | Applied and Interdisciplinary Chemistry |
Ty5 is a relative of the Retroviridae family of retroviruses, which includes the human pathogen HIV. Ty5 is a tractable system in which to study the biology of retrovirus integration. | 1 | Applied and Interdisciplinary Chemistry |
This compound is commercially available. It may be prepared by oxidation of to the sulfoxide, followed by reaction with palladium acetate. | 0 | Theoretical and Fundamental Chemistry |
A non-combustible material is a substance that does not ignite, burn, support combustion, or release flammable vapors when subject to fire or heat, in the form in which it is used and under conditions anticipated. Any solid substance complying with either of two sets of passing criteria listed in Section 8 of ASTM E 136 when the substance is tested in accordance with the procedure specified in ASTM E 136 is considered to be non-combustible. | 0 | Theoretical and Fundamental Chemistry |
By wind tunnel experiments, it has been found that the behavior of an airfoil under unsteady motion is quite different from that under quasi-steady motion. Flow separation is less likely to happen on the upper airfoil surface with a larger value of AoA than the latter, which can increase the maximum lift coefficient to a certain extent. Three primary unsteady phenomena have been identified to contribute to the delay in the onset of flow separation under unsteady condition:
* During the condition where the AoA is increasing with respect to time, the unsteadiness of the flow resulting from circulation that is shed into the wake at the trailing edge of the airfoil causes a reduction in the lift and adverse pressure gradients compared to the steady case at the same AoA;
* By virtue of a kinematic induced camber effect, a positive pitch rate further decreases the leading edge pressure and pressure gradients for a given value of lift;
* In response to the external pressure gradients, there are also additional unsteady effects that occur within the boundary layer, including the existence of flow reversals in the absence of any significant flow separation.
The development process of dynamic stall on 2D airfoil can be summarized in several stages:
* Stage 1: the AoA exceeds the static stall angle but the flow separation is delayed due to the reduction of adverse pressure gradients produced by the kinematics of pitch rate.
* Stage 2: flow separation and the formation of a vortex disturbance is cast-off from the leading edge region of the airfoil. This vortex, called leading edge vortex (LEV) or dynamic stall vortex (DSV), provides an additional lift for the airfoil so long as it stays over the upper surface, and also noteworthy increases in nose-down pitching moment (moment break, moment stall) while it moves downstream across the chord.
* Stage 3: a steep decrease of the lift coefficient (lift break, lift stall) occurs as the DSV passes into the wake.
* Stage 4: full separation of the flow on the upper surface of the airfoil can be observed, accompanied by the peak of nose-down pitch moment.
* Stage 5: the full flow reattachment is achieved as the AoA gradually decreases until it is fairly smaller than the static stall angle. The reasons for the lag are, firstly, the reorganization of the flow from fully separated to reattached, and secondly, the reverse kinematic "induced camber" effect on the leading edge pressure gradient by the negative pitch rate. | 1 | Applied and Interdisciplinary Chemistry |
Due to the central role of the glyoxylate cycle in the metabolism of pathogenic species including fungi and bacteria, enzymes of the glyoxylate cycle are current inhibition targets for the treatment of diseases. Most reported inhibitors of the glyoxylate cycle target the first enzyme of the cycle (ICL). Inhibitors were reported for Candida albicans for potential use as antifungal agents. The mycobacterial glyoxylate cycle is also being targeted for potential treatments of tuberculosis. | 1 | Applied and Interdisciplinary Chemistry |
With the number of asymmetric synthetic challenges increasing as new targets for pharmaceuticals and materials grow, methods development becomes critical. Dynamic kinetic resolution is one solution to this ever growing demand, as one can take inexpensive racemic starting materials and come out with products in high yield and stereoselectivity. As the scope and application of this powerful concept increases, its utilization in the industrial and academic settings is likely to expand in the years to come. | 0 | Theoretical and Fundamental Chemistry |
A zonal mean flow with small perturbations was assumed, , and a meridional flow with a zero mean, . Since it was assumed that the perturbations are small, a linearization can be performed on the barotropic vorticity equation above, ignoring all the non-linear terms (terms where two or more small variables, i.e. , are multiplied with one another). Also the derivative of in the zonal direction, the time derivative of the mean flow and the time derivative of are zero. This results in a simplified equation:
With as defined above () and and the small perturbations in the zonal and meridional components of the flow. | 1 | Applied and Interdisciplinary Chemistry |
Conduction through cylindrical shells (e.g. pipes) can be calculated from the internal radius, , the external radius, , the length, , and the temperature difference between the inner and outer wall, .
The surface area of the cylinder is
When Fourier's equation is applied:
and rearranged:
then the rate of heat transfer is:
the thermal resistance is:
and , where . It is important to note that this is the log-mean radius. | 1 | Applied and Interdisciplinary Chemistry |
Most sinusitis infections are caused by viruses, for which amoxicillin and amoxicillin-clavulanate are ineffective, and the small benefit gained by amoxicillin may be overridden by the adverse effects.
Amoxicillin is considered the first-line empirical treatment for most cases of uncomplicated bacterial sinusitis in children and adults when culture data is unavailable. Amoxicillin is recommended as the preferred first-line treatment for community-acquired pneumonia in adults by the National Institute for Health and Care Excellence, either alone (mild to moderate severity disease) or in combination with a macrolide. The World Health Organization (WHO) recommends amoxicillin as first-line treatment for pneumonia that is not "severe". Amoxicillin is used in post-exposure inhalation of anthrax to prevent disease progression and for prophylaxis. | 0 | Theoretical and Fundamental Chemistry |
CAPS is the common name for N-cyclohexyl-3-aminopropanesulfonic acid, a chemical used as buffering agent in biochemistry. The similar substance N-cyclohexyl-2-hydroxyl-3-aminopropanesulfonic acid (CAPSO) is also used as buffering agent in biochemistry. Its useful pH range is 9.7-11.1. | 1 | Applied and Interdisciplinary Chemistry |
UVGI is often used to disinfect equipment such as safety goggles, instruments, pipettors, and other devices. Lab personnel also disinfect glassware and plasticware this way. Microbiology laboratories use UVGI to disinfect surfaces inside biological safety cabinets ("hoods") between uses. | 0 | Theoretical and Fundamental Chemistry |
Manufacturers recommend that carbon tetraiodide be stored near . As a ready source of iodine, it is an irritant. Its LD on rats is 18 mg/kg. In general, organic compounds should be considered toxic, with the narrow exception of small perfluoroalkanes (essentially inert due to the strength of the C-F bond). | 0 | Theoretical and Fundamental Chemistry |
Sigma-2 receptors have been associated with pancreatic cancer, lung cancer, breast cancer, melanoma, prostate cancer, and ovarian cancer. Tumor cells are shown to over-express sigma-2 receptors, allowing for potential cancer therapies as many sigma-2 receptor mediated cell responses happen only in tumor cells. Tumor cell responses are modulated via ligand binding. Sigma receptor ligands can act as agonists or antagonists, generating different cellular responses. Agonists inhibit tumor cell proliferation and induce apoptosis, which is thought to be triggered by caspase-3 activity. Antagonists promote tumor cell proliferation, but this mechanism is less understood. Sigma receptor ligands have been conjugated to nanoparticles and peptides to deliver cancer treatment to tumor cells without targeting other tissues. The success with these methods have been limited to in vitro trials. Additionally, using sigma-2 receptors to target tumor cells allows for synergizing anti-cancer drug therapies. Some studies have shown that certain sigma receptor inhibitors increase cancer cells' susceptibility to chemotherapy. Other types of binding to sigma-2 receptors increases cytotoxicity of doxorubicin, antinomyocin, and other cancer cell killing drugs. | 1 | Applied and Interdisciplinary Chemistry |
* Orbifold signature:
* Coxeter notation: [(∞,2),∞] or [∞,(2,∞)]
* Lattice: rectangular
* Point group: D
* The group pmg has two rotation centres of order two (180°), and reflections in only one direction. It has glide reflections whose axes are perpendicular to the reflection axes. The centres of rotation all lie on glide reflection axes.
;Examples of group pmg | 0 | Theoretical and Fundamental Chemistry |
Other methods of refrigeration include the air cycle machine used in aircraft; the vortex tube used for spot cooling, when compressed air is available; and thermoacoustic refrigeration using sound waves in a pressurized gas to drive heat transfer and heat exchange; steam jet cooling popular in the early 1930s for air conditioning large buildings; thermoelastic cooling using a smart metal alloy stretching and relaxing. Many Stirling cycle heat engines can be run backwards to act as a refrigerator, and therefore these engines have a niche use in cryogenics. In addition, there are other types of cryocoolers such as Gifford-McMahon coolers, Joule-Thomson coolers, pulse-tube refrigerators and, for temperatures between 2 mK and 500 mK, dilution refrigerators. | 0 | Theoretical and Fundamental Chemistry |
Alberts writings collected in 1899 went to thirty-eight volumes. These displayed his prolific habits and encyclopedic knowledge of topics such as logic, theology, botany, geography, astronomy, astrology, mineralogy, alchemy, zoology, physiology, phrenology, justice, law, friendship, and love. He digested, interpreted, and systematized the whole of Aristotles works, gleaned from the Latin translations and notes of the Arabian commentators, in accordance with Church doctrine. Most modern knowledge of Aristotle was preserved and presented by Albert.
His principal theological works are a commentary in three volumes on the Books of the Sentences of Peter Lombard (Magister Sententiarum), and the Summa Theologiae in two volumes. The latter is in substance a more didactic repetition of the former.
Alberts activity, however, was more philosophical than theological (see Scholasticism). The philosophical works, occupying the first six and the last of the 21 volumes, are generally divided according to the Aristotelian scheme of the sciences, and consist of interpretations and condensations of Aristotles relative works, with supplementary discussions upon contemporary topics, and occasional divergences from the opinions of the master. Albert believed that Aristotle's approach to natural philosophy did not pose any obstacle to the development of a Christian philosophical view of the natural order.
Alberts knowledge of natural science was considerable and for the age remarkably accurate. His industry in every department was great: not only did he produce commentaries and paraphrases of the entire Aristotelian corpus, including his scientific works, but Albert also added to and improved upon them. His books on topics like botany, zoology, and minerals included information from ancient sources, but also results of his own empirical investigations. These investigations pushed several of the special sciences forward, beyond the reliance on classical texts. In the case of embryology, for example, it has been claimed that little of value was written between Aristotle and Albert, who managed to identify organs within eggs. Furthermore, Albert also effectively invented entire special sciences, where Aristotle has not covered a topic. For example, prior to Albert, there was no systematic study of minerals. For the breadth of these achievements, he was bestowed the name Doctor Universalis.'
Much of Alberts empirical contributions to the natural sciences have been superseded, but his general approach to science may be surprisingly modern. For example, in De Mineralibus' (Book II, Tractate ii, Ch. 1) Albert claims, "For it is [the task] of natural science not simply to accept what we are told but to inquire into the causes of natural things." | 1 | Applied and Interdisciplinary Chemistry |
In addition to wild type forms of Rhodopseudomonas palustris, scientists have used genetically modified forms to produce hydrogen as well. Other explorations include expanding the bioreactor system to hold a combination of bacteria, algae or cyanobacteria. Ethanol production is performed by the algae Chlamydomonas reinhardtii, among other species, in cycling light and dark environments. The cycling of light and dark environments has also been explored with bacteria for hydrogen production, increasing hydrogen yield. | 1 | Applied and Interdisciplinary Chemistry |
Human chorionic gonadotropin injection is extensively used for final maturation induction in lieu of luteinizing hormone. In the presence of one or more mature ovarian follicles, ovulation can be triggered by the administration of HCG. As ovulation will happen between 38 and 40 hours after a single HCG injection, procedures can be scheduled to take advantage of this time sequence, such as intrauterine insemination or sexual intercourse. Also, patients that undergo IVF, in general, receive HCG to trigger the ovulation process, but have an oocyte retrieval performed at about 34 to 36 hours after injection, a few hours before the eggs actually would be released from the ovary.
As hCG supports the corpus luteum, administration of HCG is used in certain circumstances to enhance the production of progesterone.
In the male, hCG injections are used to stimulate the Leydig cells to synthesize testosterone. The intratesticular testosterone is necessary for spermatogenesis from the sertoli cells. Typical uses for hCG in men include hypogonadism and fertility treatment, including during testosterone replacement therapy to restore or maintain fertility and prevent testicular atrophy.
Several vaccines against human chorionic gonadotropin (hCG) for the prevention of pregnancy are currently in clinical trials. | 1 | Applied and Interdisciplinary Chemistry |
A hydrostatic test is a way in which pressure vessels such as pipelines, plumbing, gas cylinders, boilers and fuel tanks can be tested for strength and leaks. The test involves filling the vessel or pipe system with a liquid, usually water, which may be dyed to aid in visual leak detection, and pressurization of the vessel to the specified test pressure. Pressure tightness can be tested by shutting off the supply valve and observing whether there is a pressure loss. The location of a leak can be visually identified more easily if the water contains a colorant. Strength is usually tested by measuring permanent deformation of the container.
Hydrostatic testing is the most common method employed for testing pipes and pressure vessels. Using this test helps maintain safety standards and durability of a vessel over time. Newly manufactured pieces are initially qualified using the hydrostatic test. They are then revalidated at regular intervals according to the relevant standard. In some cases where a hydrostatic test is not practicable a pneumatic pressure test may be an acceptable alternative.
Testing of pressure vessels for transport and storage of gases is very important because such containers can explode if they fail under pressure. | 1 | Applied and Interdisciplinary Chemistry |
In biology literature, the term topology is also used to refer to mutual orientation of regular secondary structures, such as alpha-helices and beta strands in protein structure [http://www.diss.fu-berlin.de/diss/servlets/MCRFileNodeServlet/FUDISS_derivate_000000003407/08_kapitel3.pdf?hosts=]. For example, two adjacent interacting alpha-helices or beta-strands can go in the same or in opposite directions. Topology diagrams of different proteins with known three-dimensional structure are provided by PDBsum ([http://www.ebi.ac.uk/thornton-srv/databases/cgi-bin/pdbsum/GetPage.pl?pdbcode=1qjp&template=protein.html&r=wiring&l=1&chain=A an example]). | 0 | Theoretical and Fundamental Chemistry |
Ferhan Çeçen (born June 15, 1961) is a Turkish environmental engineer and chemist, researching wastewater treatment, environmental biotechnology, and adsorption processes. She is a professor at the Boğaziçi University Institute of Environmental Sciences. | 1 | Applied and Interdisciplinary Chemistry |
The general goal of the technique is similar to the DNA microarray. However, SAGE sampling is based on sequencing mRNA output, not on hybridization of mRNA output to probes, so transcription levels are measured more quantitatively than by microarray. In addition, the mRNA sequences do not need to be known a priori, so genes or gene variants which are not known can be discovered. Microarray experiments are much cheaper to perform, so large-scale studies do not typically use SAGE. Quantifying gene expressions is more exact in SAGE because it involves directly counting the number of transcripts whereas spot intensities in microarrays fall in non-discrete gradients and are prone to background noise. | 1 | Applied and Interdisciplinary Chemistry |
quinolinium - based Cl indicators are based on the capability of halides to quench the fluorescence of heterocyclic organic compounds with quaternary nitrogen. Fluorescence is quenched by a collision mechanism with a linear Stern–Volmer relationship:
where:<br>
is the fluorescence in the absence of halide<br>
is the fluorescence in the presence of halide<br>
is the Stern–Volmer quenching constant, which depends on the chloride concentration, . in a linear manner.
Thus, quinoline-based indicators are one-wavelength dyes - the signal results from monitoring the fluorescence at a single wavelength. Ratiometric measurement of halide concentration is not possible with quinolinium dyes. The kinetics of collision quenching are diffusion-limited only, and these indicators provide submillisecond time resolution. Quinolinium-based dyes are insensitive to physiological changes in pH, but they are prone to strong bleaching and demand ultraviolet excitation, which is harmful for living organisms. Because quinolinium is not occurring in the cells naturally, cell loading is necessary. However, quinolinium-based dyes arent retained perfectly in the cell and cant be targeted easily to subcellular organelles. Also, they cannot be designed specific to a certain type of cell.
The most used quinolinium-based Cl indicators are 6-methoxy-1-(3-sulfonatopropyl) quinolinium (SPQ), 6-methoxy-N-ethylquinolium Cl (MEQ), and N-(6-methoxyquinolyl)-acetoethyl ester (MQAE). | 0 | Theoretical and Fundamental Chemistry |
There are currently several labeling methods for tracking biomolecules. Some of the methods include the following. | 1 | Applied and Interdisciplinary Chemistry |
OFM can be fabricated into a range of different product presentations for tissue engineering applications, and can be functionalized with therapeutic agents including silver, doxycycline and hyaluronic acid. OFM has been commercialized as single and multi-layered sheets, reinforced biologics and powders.
When placed in the body OFM does not elicit a negative inflammatory response and is absorbed into the regenerating tissues via a process called tissue remodeling. | 1 | Applied and Interdisciplinary Chemistry |
Commercially available nitric acid is an azeotrope with water at a concentration of 68% . This solution has a boiling temperature of 120.5 °C (249 °F) at 1 atm. It is known as "concentrated nitric acid". The azeotrope of nitric acid and water is a colourless liquid at room temperature.
Two solid hydrates are known: the monohydrate or oxonium nitrate and the trihydrate .
An older density scale is occasionally seen, with concentrated nitric acid specified as 42 Baumé. | 0 | Theoretical and Fundamental Chemistry |
The ZND detonation model is a one-dimensional model for the process of detonation of an explosive. It was proposed during World War II independently by Y. B. Zel'dovich, John von Neumann, and Werner Döring, hence the name.
This model admits finite-rate chemical reactions and thus the process of detonation consists of the following stages. First, an infinitesimally thin shock wave compresses the explosive to a high pressure called the von Neumann spike. At the von Neumann spike point the explosive still remains unreacted. The spike marks the onset of the zone of exothermic chemical reaction, which finishes at the Chapman–Jouguet condition. After that, the detonation products expand backward.
In the reference frame in which the shock is stationary, the flow following the shock is subsonic. Because of this, energy release behind the shock is able to be transported acoustically to the shock for its support. For a self-propagating detonation, the shock relaxes to a speed given by the Chapman–Jouguet condition, which induces the material at the end of the reaction zone to have a locally sonic speed in the reference frame in which the shock is stationary. In effect, all of the chemical energy is harnessed to propagate the shock wave forward.
However, in the 1960s, experiments revealed that gas-phase detonations were most often characterized by unsteady, three-dimensional structures, which can only in an averaged sense be predicted by one-dimensional steady theories. Indeed, such waves are quenched as their structure is destroyed. The Wood–Kirkwood detonation theory can correct for some of these limitations. | 1 | Applied and Interdisciplinary Chemistry |
In March, researchers announced the successful use of gene therapy to treat two adult patients for X-linked chronic granulomatous disease, a disease which affects myeloid cells and damages the immune system. The study is the first to show that gene therapy can treat the myeloid system.
In May, a team reported a way to prevent the immune system from rejecting a newly delivered gene. Similar to organ transplantation, gene therapy has been plagued by this problem. The immune system normally recognizes the new gene as foreign and rejects the cells carrying it. The research utilized a newly uncovered network of genes regulated by molecules known as microRNAs. This natural function selectively obscured their therapeutic gene in immune system cells and protected it from discovery. Mice infected with the gene containing an immune-cell microRNA target sequence did not reject the gene.
In August, scientists successfully treated metastatic melanoma in two patients using killer T cells genetically retargeted to attack the cancer cells.
In November, researchers reported on the use of VRX496, a gene-based immunotherapy for the treatment of HIV that uses a lentiviral vector to deliver an antisense gene against the HIV envelope. In a phase I clinical trial, five subjects with chronic HIV infection who had failed to respond to at least two antiretroviral regimens were treated. A single intravenous infusion of autologous CD4 T cells genetically modified with VRX496 was well tolerated. All patients had stable or decreased viral load; four of the five patients had stable or increased CD4 T cell counts. All five patients had stable or increased immune response to HIV antigens and other pathogens. This was the first evaluation of a lentiviral vector administered in a US human clinical trial. | 1 | Applied and Interdisciplinary Chemistry |
The potential of using bioartificial pancreas, for treatment of diabetes mellitus, based on encapsulating islet cells within a semi permeable membrane is extensively being studied by scientists. These devices could eliminate the need for of immunosuppressive drugs in addition to finally solving the problem of shortage of organ donors. The use of microencapsulation would protect the islet cells from immune rejection as well as allow the use of animal cells or genetically modified insulin-producing cells. It is hoped that development of these islet encapsulated microcapsules could prevent the need for the insulin injections needed several times a day by type 1 diabetic patients. The Edmonton protocol involves implantation of human islets extracted from cadaveric donors and has shown improvements towards the treatment of type 1 diabetics who are prone to hypoglycemic unawareness. However, the two major hurdles faced in this technique are the limited availability of donor organs and with the need for immunosuppresents to prevent an immune response in the patient's body.
Several studies have been dedicated towards the development of bioartificial pancreas involving the immobilization of islets of Langerhans inside polymeric capsules. The first attempt towards this aim was demonstrated in 1980 by Lim et al. where xenograft islet cells were encapsulated inside alginate polylysine microcapsules and showed significant in vivo results for several weeks. It is envisaged that the implantation of these encapsulated cells would help to overcome the use of immunosuppressive drugs and also allow the use of xenograft cells thus obviating the problem of donor shortage.
The polymers used for islet microencapsulation are alginate, chitosan, polyethylene glycol (PEG), agarose, sodium cellulose sulfate and water-insoluble polyacrylates with alginate and PEG being commonly used polymers.
With successful in vitro studies being performed using this technique, significant work in clinical trials using microencapsulated human islets is being carried out. In 2003, the use of alginate/PLO microcapsules containing islet cells for pilot phase-1 clinical trials was permitted to be carried out at the University of Perugia by the Italian Ministry of Health. In another study, the potential of clinical application of PEGylation and low doses of the immunosuppressant cyclosporine A were evaluated. The trial which began in 2005 by Novocell, now forms the phase I/II of clinical trials involving implantation of islet allografts into the subcutaneous site. However, there have been controversial studies involving human clinical trials where Living Cell technologies Ltd demonstrated the survival of functional xenogeneic cells transplanted without immunosuppressive medication for 9.5 years. However, the trial received harsh criticism from the International Xenotransplantation Association as being risky and premature.
However, even though clinical trials are under way, several major issues such as biocompatibility and immunoprotection need to be overcome.
Potential alternatives to encapsulating isolated islets (of either allo- or xenogeneic origin) are also being explored. Using sodium cellulose sulphate technology from [https://austrianova.com/ Austrianova Singapore] an islet cell line was encapsulated and it was demonstrated that the cells remain viable and release insulin in response to glucose. In pre-clinical studies, implanted, encapsulated cells were able to restore blood glucose levels in diabetic rats over a period of 6 months. | 1 | Applied and Interdisciplinary Chemistry |
Translation is carried out by more than one ribosome simultaneously. Because of the relatively large size of ribosomes, they can only attach to sites on mRNA 35 nucleotides apart. The complex of one mRNA and a number of ribosomes is called a polysome or polyribosome. | 1 | Applied and Interdisciplinary Chemistry |
In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid) is a solid that lacks the long-range order that is characteristic of a crystal. The terms "glass" and "glassy solid" are sometimes used synonymously with amorphous solid; however, these terms refer specifically to amorphous materials that undergo a glass transition. Examples of amorphous solids include glasses, metallic glasses, and certain types of plastics and polymers. | 0 | Theoretical and Fundamental Chemistry |
Aerogels are highly porous ultralight materials in which the liquid component of a gel has been replaced with a gas, and are noteworthy for being solids that are extremely effective thermal insulators with very low density. Aerogels can be prepared in a variety of ways, and though most have been based on silica, materials based on zirconia, titania, cellulose, polyurethane, and resorcinol—formaldehyde systems, amongst others, have been reported and explored. The prime disadvantage of a silica-based aerogel is its fragility, though NASA has used them for insulation on Mars rovers, the Mars Pathfinder and they have been used commercially for insulating blankets and between glass panes for translucent day-lighting panels. Particulate gels prepared by the Stöber process can be dehydrated rapidly to produce highly effective silica aerogels, as well as xerogels. They key step is the use of supercritical fluid extraction to remove water from the gel while maintaining the gel structure, which is typically done with supercritical carbon dioxide, as NASA does. The resulting aerogels are very effective thermal insulators because of their high porosity with very small pores (in the nanometre range). Conduction of heat through the gas phase is poor, and as the structure greatly inhibits movement of air molecules through the structure, heat transfer through the material is poor, as can be seen in the image at right where heat from a Bunsen burner transfers so poorly that crayons resting on the aerogel do not melt. Due to their low density, aerogels have also been used to capture interstellar dust particles with minimal heat changes in slowing them down (to prevent heat-induced changes in the particles) as part of the Stardust mission.
One method to produce a silica aerogel uses a modified Stöber process and supercritical drying. The product appears translucent with a blue tinge as a consequence of Rayleigh scattering; when placed in front of a light source, it becomes yellowish due to Mie scattering. This aerogel has a surface area of 700 m g and a density of 0.040 g cm; by way of contrast, the density of air is 0.0012 g cm (at 15 °C and 1 atm).
Silica aerogels held 15 entries for materials properties in the Guinness World Records in 2011, including for best insulator and lowest-density solid, though aerographite took the latter title in 2012.
Aerographene, with a density of just 13% of that of room temperature air and less dense than helium gas, became the lowest-density solid yet developed in 2013. Stöber-like methods have been applied in the preparation of aerogels in non-silica systems. NASA has developed silica aerogels with a polymer coating to reinforce the structure, producing a material roughly two orders of magnitude stronger for the same density, and also polymer aerogels, which are flexible and can be formed into a bendable thin film. | 0 | Theoretical and Fundamental Chemistry |
Abelson received many distinguished awards, including the National Medal of Science in 1987, the National Science Foundations Distinguished Achievement Award, the American Medical Associations Scientific Achievement Award, the Navy Distinguished Civilian Service Medal and the Waldo E. Smith Medal in 1988. In 1992 he was awarded the Public Welfare Medal, the National Academy of Sciences's highest honor. He was elected a fellow of the American Physical Society in 1949 and the American Academy of Arts and Sciences in 1958. He was elected to the American Philosophical Society in 1961.
The mineral abelsonite is named after Abelson in recognition of his contribution to organic geochemistry.
The Philip and Neva Abelson Hall at Washington State University was named in his honor.
The AAAS Philip Hauge Abelson Prize is named after Philip Abelson. | 1 | Applied and Interdisciplinary Chemistry |
Counterfeit THC oil has been detected to contain synthetic cannabinoids. Several school kids in Greater Manchester collapsed after vaping Spice mis-sold as natural cannabis. | 0 | Theoretical and Fundamental Chemistry |
Mechanical ventilation of buildings and structures can be achieved by the use of the following techniques:
*Whole-house ventilation
*Mixing ventilation
*Displacement ventilation
*Dedicated subaerial air supply | 1 | Applied and Interdisciplinary Chemistry |
The boiler feed water used in the steam boiler is a means of transferring heat energy from the burning fuel to the mechanical energy of the spinning steam turbine. The total feed water consists of recirculated condensate water and purified makeup water. Because the metallic materials it contacts are subject to corrosion at high temperatures and pressures, the makeup water is highly purified before use. A system of water softeners and ion exchange demineralizes produces water so pure that it coincidentally becomes an electrical insulator, with conductivity in the range of 0.3–1.0 microsiemens per centimeter. The makeup water in a 500 MWe plant amounts to perhaps 120 US gallons per minute (7.6 L/s) to replace water drawn off from the boiler drums for water purity management, and to also offset the small losses from steam leaks in the system.
The feed water cycle begins with condensate water being pumped out of the condenser after traveling through the steam turbines. The condensate flow rate at full load in a 500 MW plant is about 6,000 US gallons per minute (400 L/s).
The water is usually pressurized in two stages, and typically flows through a series of six or seven intermediate feed water heaters, heated up at each point with steam extracted from an appropriate extraction connection on the turbines and gaining temperature at each stage. Typically, in the middle of this series of feedwater heaters, and before the second stage of pressurization, the condensate plus the makeup water flows through a deaerator that removes dissolved air from the water, further purifying and reducing its corrosiveness. The water may be dosed following this point with hydrazine, a chemical that removes the remaining oxygen in the water to below 5 parts per billion (ppb). It is also dosed with pH control agents such as ammonia or morpholine to keep the residual acidity low and thus non-corrosive. | 1 | Applied and Interdisciplinary Chemistry |
Caesium carbonate can be prepared by thermal decomposition of caesium oxalate. Upon heating, caesium oxalate is converted to caesium carbonate with emission of carbon monoxide.
It can also be synthesized by reacting caesium hydroxide with carbon dioxide. | 0 | Theoretical and Fundamental Chemistry |
Landes was an undergraduate student in chemistry at George Mason University. She moved to Georgia Tech for her doctoral research, where she majored in physical chemistry under the supervision of Mostafa El-Sayed. After earning her doctorate, Landes joined the University of Oregon as a postdoctoral researcher with Geraldine L. Richmond, where she spent one year before joining the University of Texas at Austin with Paul Barbara. | 0 | Theoretical and Fundamental Chemistry |
* [https://www.rickallmendinger.net/stereonet Stereonet], a software tool for structural geology by Rick Allmendinger.
* [http://sourceforge.net/projects/tclab/ PTCLab], the phase transformation crystallography lab
* [http://sourceforge.net/projects/sphaerica Sphaerica], software tool for straightedge and compass construction on the sphere, including a stereographic projection display option
* [http://estereo.reyuntec.ar/ Estereografica Web], a web application for stereographic projection in structural geology and fault kinematics by Ernesto Cristallini. | 0 | Theoretical and Fundamental Chemistry |
The Greenhouse Gases Observing Satellite-2 (GOSAT-2), also known as , is an Earth observation satellite dedicated to greenhouse gas monitoring. It is a successor of Greenhouse Gases Observing Satellite (GOSAT). The GOSAT-2 was developed as a joint project of the Japan Aerospace Exploration Agency (JAXA), Ministry of the Environment, and the National Institute for Environmental Studies (NIES). It was launched on 29 October 2018 from the Tanegashima Space Center aboard the H-IIA rocket. | 1 | Applied and Interdisciplinary Chemistry |
In Classical antiquity, anaesthetics were described by:
* Pedanius Dioscorides (De Materia Medica), a Greek physician living in Rome during the first century A.D., who is recorded as the first person to make explicit reference to the administration of mandrake-induced anesthesia to facilitate a surgical intervention.
* Galen
* Hippocrates
* Theophrastus (Historia Plantarum) | 1 | Applied and Interdisciplinary Chemistry |
Some hydrophilic polymer can be made into hydrogel fiber via melt-spinning method, where the solidification is done by the phase transition from the molten state. Similar to the electro-spinning, the pregel solution was kept liquid in the container. After leaving the nuzzle at filament state, the fiber solidified after the encounter of cool ambient air and maintained their shape.
An example would be the meltspinning apparatus built by Long et al., where meltspinning of polylactic acid (PLA) and polycaprolactone (PCL) fiber are achieved. | 0 | Theoretical and Fundamental Chemistry |
The perturbation in atmospheric C from the bomb testing was an opportunity to validate atmospheric transport models, and to study the movement of carbon between the atmosphere and oceanic or terrestrial sinks. | 0 | Theoretical and Fundamental Chemistry |
Metal halides are often readily available precursors for other inorganic compounds. Mentioned above, the halide compounds can be made anhydrous by heat, vacuum, or treatment with thionyl chloride.
Halide ligands may be abstracted by silver(I), often as the tetrafluoroborate or the hexafluorophosphate. In many transition metal compounds, the empty coordination site is stabilized by a coordinating solvent like tetrahydrofuran. Halide ligands may also be displaced by the alkali salt of an X-type ligand, such as a salen-type ligand. This reaction is formally a transmetallation, and the abstraction of the halide is driven by the precipitation of the resultant alkali halide in an organic solvent. The alkali halides generally have very high lattice energies.
For example, sodium cyclopentadienide reacts with ferrous chloride to yield ferrocene:
:2 NaCH + FeCl → Fe(CH) + 2 NaCl
While inorganic compounds used for catalysis may be prepared and isolated, they may at times be generated in situ by addition of the metal halide and the desired ligand. For example, palladium chloride and triphenylphosphine may be often be used in lieu of bis(triphenylphosphine)palladium(II) chloride for palladium-catalyzed coupling reactions. | 0 | Theoretical and Fundamental Chemistry |
The regulation of medicinal products by officials in the United Kingdom dates back to the reign of King Henry VIII (1491–1547). The Royal College of Physicians of London had the power to inspect apothecaries’ products in the London area, and to destroy defective stock. The first list of approved drugs, with information on how they should be prepared, was the London Pharmacopoeia, published in 1618. The first edition of what is now known as the British Pharmacopoeia was published in 1864, and was one of the first attempts to harmonise pharmaceutical standards, through the merger of the London, Edinburgh and Dublin Pharmacopoeias. The Neo-Latin name that had some currency at the time was Pharmacopoeia Britannica (Ph. Br.).
In 1844, concern about the dangers of unregulated manufacture and use led William Flockhart – who had provided chloroform to Doctor (later Sir) James Young Simpson for his experiment on anaesthesia – to recommend the creation of a Universal Phamacopoeia for Great Britain in his inaugural speech as president of the Northern British branch of the Pharmaceutical Society.
A commission was first appointed by the General Medical Council (GMC), when the body was made statutorily responsible under the Medical Act 1858 for producing a British pharmacopoeia on a national basis. In 1907, the British Pharmacopoeia was supplemented by the British Pharmaceutical Codex, which gave information on drugs and other pharmaceutical substances not included in the BP, and provided standards for these.
The Medicines Act 1968 established the legal status of the British Pharmacopoeia Commission, and of the British Pharmacopoeia, as the UK standard for medicinal products under section 4 of the Act. The British Pharmacopoeia Commission continues the work of the earlier Commissions appointed by the GMC, and is responsible for preparing new editions of the British Pharmacopoeia and the British Pharmacopoeia (Veterinary), and for keeping them up to date. Under Section 100 of the Medicines Act, the Commission is also responsible for selecting and devising British Approved Names.
Since its first publication in 1864, the distribution of the British Pharmacopoeia has grown throughout the world and it is now used in over 100 countries. Australia and Canada are two of the countries that have adopted the BP as their national standard; in other countries, such as South Korea, the BP is recognised as an acceptable reference standard. | 1 | Applied and Interdisciplinary Chemistry |
An example that illustrates nuclear binding energy is the nucleus of C (carbon-12), which contains 6 protons and 6 neutrons. The protons are all positively charged and repel each other, but the nuclear force overcomes the repulsion and causes them to stick together. The nuclear force is a close-range force (it is strongly attractive at a distance of 1.0 fm and becomes extremely small beyond a distance of 2.5 fm), and virtually no effect of this force is observed outside the nucleus. The nuclear force also pulls neutrons together, or neutrons and protons.
The energy of the nucleus is negative with regard to the energy of the particles pulled apart to infinite distance (just like the gravitational energy of planets of the Solar System), because energy must be utilized to split a nucleus into its individual protons and neutrons. Mass spectrometers have measured the masses of nuclei, which are always less than the sum of the masses of protons and neutrons that form them, and the difference—by the formula —gives the binding energy of the nucleus. | 0 | Theoretical and Fundamental Chemistry |
The process occurs in two cellular locations: the cytosol and the mitochondria matrix. A cycle is formed by the system, ensuring that the conversion between acetylene, oxaloacetate, citrate, and malate can continue without the need for foreign molecule addition.
It involves six major steps: | 1 | Applied and Interdisciplinary Chemistry |
The use of Fmoc as a temporary protecting group for amine at the N-terminus in SPPS is very widespread for Fmoc/tBu approach, because its removal with piperidine solution does not disturb the acid-labile linker between the peptide and the resin. A typical SPPS Fmoc deprotection is performed with a solution of 20% piperidine in N,N-dimethylformamide (DMF).
Common deprotection cocktails for Fmoc during SPPS:
* 20% piperidine in DMF (Fmoc group has an approximate half life of 6 seconds in this solution)
* 5% piperazine, 1% DBU and 1% formic acid in DMF. This method avoids the use of strictly controlled piperidine. No side product was observed for a peptide with 9 residues synthesized with this method. | 1 | Applied and Interdisciplinary Chemistry |
Momordicilin or 24-[1′-hydroxy,1′-methyl-2′-pentenyloxyl]-ursan-3-one is a chemical compound, a triterpenoid with formula , found in the fresh fruit of the bitter melon (Momordica charantia).
The compound is soluble in ethyl acetate and chloroform but not in petrol. It crystallizes as needles that melt at 170−171 °C. It was isolated in 1997 by S. Begum and others. | 1 | Applied and Interdisciplinary Chemistry |
Isotope analysis has widespread applicability in the natural sciences. These include numerous applications in the biological, earth and environmental sciences. | 0 | Theoretical and Fundamental Chemistry |
Nanoparticles of sufficiently uniform size may spontaneously settle into regular arrangements, forming a colloidal crystal. These arrangements may exhibit original physical properties, such as observed in photonic crystals. | 0 | Theoretical and Fundamental Chemistry |
The equatorial plane of a cell-like structure can be imaged using phase contrast microscopy to obtain a video showing the fluctuations of the membrane.
On the video, the contours can be found using image analysis algorithms, which can then be used to determine the power spectrum of the fluctuation modes in real space amplitude. This can be used, following the steps above, to obtain relevant parameters such as the bending modulus, which is useful for a number of applications in membrane structure research. | 0 | Theoretical and Fundamental Chemistry |
The term can also refer to octahedral influenced by the Jahn–Teller effect, which is a common phenomenon encountered in coordination chemistry. This reduces the symmetry of the molecule from O to D and is known as a tetragonal distortion. | 0 | Theoretical and Fundamental Chemistry |
Pancuronium remains one of the few muscle relaxants logically and rationally designed from structure-action / effects relationship data. A steroid skeleton was chosen because of its appropriate size and rigidness. Acetylcholine moieties were inserted to increase receptor affinity. Although having many unwanted side-effects, a slow onset of action and recovery rate it was a big success and at the time the most potent neuromuscular drug available. Pancuronium and some other neuromuscular blocking agents block M2-receptors and therefore affect the vagus nerve, leading to hypotension and tachycardia. This muscarinic blocking effect is related to the acetylcholine moiety on the A ring on pancuronium. Making the N atom on the A ring tertiary, the ring loses its acetylcholine moiety, and the resulting compound, vecuronium, has nearly 100 times less affinity to muscarin receptors while maintaining its nicotinic affinity and a similar duration of action. Vecuronium is, therefore, free from cardiovascular effects. The D ring shows excellent properties validating Beers and Reich's rule with great precision. As a result, vecuronium has the greatest potency and specificity of all mono-quaternary compounds. | 1 | Applied and Interdisciplinary Chemistry |
As disulfide bonds can be reversibly reduced and re-oxidized, the redox state of these bonds has evolved into a signaling element. In chloroplasts, for example, the enzymatic reduction of disulfide bonds has been linked to the control of numerous metabolic pathways as well as gene expression. The reductive signaling activity has been shown, thus far, to be carried by the ferredoxin-thioredoxin system, channeling electrons from the light reactions of photosystem I to catalytically reduce disulfides in regulated proteins in a light dependent manner. In this way chloroplasts adjust the activity of key processes such as the Calvin–Benson cycle, starch degradation, ATP production and gene expression according to light intensity. Additionally, It has been reported that disulfides plays a significant role on redox state regulation of Two-component systems (TCSs), which could be found in certain bacteria including photogenic strain. A unique intramolecular cysteine disulfide bonds in the ATP-binding domain of SrrAB TCs found in Staphylococcus aureus is a good example of disulfides in regulatory proteins, which the redox state of SrrB molecule is controlled by cysteine disulfide bonds, leading to the modification of SrrA activity including gene regulation. | 0 | Theoretical and Fundamental Chemistry |
More complex anions can be formed by condensing borate triangles or tetrahedra with other oxyanions to yield materials such as borosulfates, boroselenates, borotellurates, boroantimonates, borophosphates, or boroselenites.
Borosilicate glass, also known as pyrex, can be viewed as a silicate in which some [SiO] units are replaced by [BO] centers, together with additional cations to compensate for the difference in valence states of Si(IV) and B(III). Because this substitution leads to imperfections, the material is slow to crystallise and forms a glass with low coefficient of thermal expansion, thus resistant to cracking when heated, unlike soda glass. | 0 | Theoretical and Fundamental Chemistry |
Although the presence of carbon in the Earths core is well-constrained, recent studies suggest large inventories of carbon could be stored in this region. Shear (S) waves moving through the inner core travel at about fifty percent of the velocity expected for most iron-rich alloys. Because the cores composition is believed to be an alloy of crystalline iron and a small amount of nickel, this seismic anomaly indicates the presence of light elements, including carbon, in the core. In fact, studies using diamond anvil cells to replicate the conditions in the Earths core indicate that iron carbide (FeC) matches the inner cores wave speed and density. Therefore, the iron carbide model could serve as an evidence that the core holds as much as 67% of the Earths carbon. Furthermore, another study found that in the pressure and temperature condition of the Earths inner core, carbon dissolved in iron and formed a stable phase with the same FeC composition—albeit with a different structure from the one previously mentioned. In summary, although the amount of carbon potentially stored in the Earth's core is not known, recent studies indicate that the presence of iron carbides can explain some of the geophysical observations. | 0 | Theoretical and Fundamental Chemistry |
The substrate(s) and physiological function of Peg1/MEST are not known; however, the protein may play a role in mammalian development and abnormalities in its expression by its gene (PEG1/MEST)by, for example, loss of Genomic imprinting, overexpression, or promoter switching, has been linked to certain types of cancer and tumors in humans such as invasive cervical cancer, uterine leiomyomas, and cancers of the breast, lung, and colon (see MEST (gene)). | 1 | Applied and Interdisciplinary Chemistry |
When atoms or molecules are adsorbed on a surface, two phenomena can lead to a change in the surface stress. One is a change in the electron density of the atoms in the surface, which changes the in-plane bonding and thus the surface stress. A second is due to interactions between the adsorbed atoms or molecules themselves, which may want to be further apart (or closer) than is possible with the atomic spacings in the surface. Note that since adsorption often depends strongly upon the environment, for instance gas pressure and temperature, the surface stress tensor will show a similar dependence. | 0 | Theoretical and Fundamental Chemistry |
There is one assay office at Espoo.
The assay office is privatized and the concession was awarded to Inspecta Corporation is an independent, international qualification requirements fulfilling inspection, testing, measurement and certification services provider. | 0 | Theoretical and Fundamental Chemistry |
In 1962, the US had resumed atmospheric tests of nuclear weapons at the Nevada test site in 1962. The State of Utah had set up its own network of monitoring facilities to test milk for radioiodine, since "data pertaining to the safety of the citizens of Utah was not forthcoming from the AEC", and the levels of radioactivity were found to be close to the limits prescribed by the Federal Radiation Council. The Commissioners of the AEC were "on the hot seat" and announced "a comprehensive, long-range program" to explore the effects of man-made radioactivity "upon plants, animals and human beings". At the request of the US Atomic Energy Commission and of LLNL's director John Foster, Gofman reluctantly accepted to establish the Biomedical Research Division for the LLNL in 1963. He served as the first director of the LLNL biomedical research division from 1963 to 1965 and as one of the nine associate directors of the entire lab until 1969. | 0 | Theoretical and Fundamental Chemistry |
Using the model organism Drosophila melanogaster, data has been compiled regarding the genomic information and sequencing of this organism. A prediction model exists in which a researcher can upload his or her genomic information and use a splice site prediction database to gather information about where the splice sites could be located. [http://www.fruitfly.org/about/index.html The Berkeley Drosophila Project] can be used to incorporate this research, as well as annotate high quality euchromatic data. The splice site predictor can be a great tool for researchers studying human disease in this model organism.
Splice site mutations can be analyzed using information theory. | 1 | Applied and Interdisciplinary Chemistry |
The ocular space is a difficult area to deliver drugs into and therefore special drug delivery considerations need to be taken into account. Intravitreal injections are a common method of delivery drugs to the eye. Pullulan systems can be utilized in intravitreal injections in order to develop drugs that are long lasting and therefore require less frequent injections. One study looked at different chemical linkers to pullulan to test efficacy of said linkers in extending the release of rhodamine B (RhB). This study used ether (Pull-Et-RhB), hydrazone (Pull-Hy-RhB), and ester (Pull-Es-RhB) linkers to generate pullulan bioconjugates. Ex vivo modeling of the drug release indicated that the drug diffuses slower in the vitreous humor than in water. The ether bond was stable at differing pH, while the hydrazone and ester bond released the drug faster in more acidic pH, that reflected the pH of endosomes. The Pull-Hy-RhB demonstrated that this drug delivery system was capable of delivering the drug to the retina through testing of the blood in the vessels of the retina.
Further studies have investigated the creation and efficacy of pullulan-dexamethasone bioconjugates for intravitreal injections. The study synthesized self-assembling pullulan nanoparticles with dexamethasone attached through hydrazone bonds. This study reiterated that the drug release was fast in acidic pH that mimicked the pH of lysosomes. The variation in drug release was that at the pH of the vitreous humor the drug took two weeks to release half of the drug, while took only two days, when in a lysosomal pH. Pharmacokinetic analysis was performed on this bioconjugate system and revealed that dexamethasone was released in the vitreous humor and that it remained for sixteen days and that a substantial amount of the bioconjugate left the vitreous humor intact. Overall the studies regarding pullulan bioconjugates for the application in intravitreal injections demonstrate that pullulan can provide sustained release as well as allow the drug to reach the retina. | 1 | Applied and Interdisciplinary Chemistry |
In physiology, base excess and base deficit refer to an excess or deficit, respectively, in the amount of base present in the blood. The value is usually reported as a concentration in units of mEq/L (mmol/L), with positive numbers indicating an excess of base and negative a deficit. A typical reference range for base excess is −2 to +2 mEq/L.
Comparison of the base excess with the reference range assists in determining whether an acid/base disturbance is caused by a respiratory, metabolic, or mixed metabolic/respiratory problem. While carbon dioxide defines the respiratory component of acid–base balance, base excess defines the metabolic component. Accordingly, measurement of base excess is defined, under a standardized pressure of carbon dioxide, by titrating back to a standardized blood pH of 7.40.
The predominant base contributing to base excess is bicarbonate. Thus, a deviation of serum bicarbonate from the reference range is ordinarily mirrored by a deviation in base excess. However, base excess is a more comprehensive measurement, encompassing all metabolic contributions. | 1 | Applied and Interdisciplinary Chemistry |
Although the nucleosome is a very stable protein-DNA complex, it is not static and has been shown to undergo a number of different structural re-arrangements including nucleosome sliding and DNA site exposure. Depending on the context, nucleosomes can inhibit or facilitate transcription factor binding. Nucleosome positions are controlled by three major contributions: First, the intrinsic binding affinity of the histone octamer depends on the DNA sequence. Second, the nucleosome can be displaced or recruited by the competitive or cooperative binding of other protein factors. Third, the nucleosome may be actively translocated by ATP-dependent remodeling complexes. | 1 | Applied and Interdisciplinary Chemistry |
Binding curves describe the binding behavior of ligand to a protein. Curves can be characterized by their shape, sigmoidal or hyperbolic, which reflect whether or not the protein exhibits cooperative or noncooperative binding behavior respectively. Typically, the x-axis describes the concentration of ligand and the y-axis describes the fractional saturation of ligands bound to all available binding sites. The Michaelis Menten equation is usually used when determining the shape of the curve. The Michaelis Menten equation is derived based on steady-state conditions and accounts for the enzyme reactions taking place in a solution. However, when the reaction takes place while the enzyme is bound to a substrate, the kinetics play out differently.
Modeling with binding curves are useful when evaluating the binding affinities of oxygen to hemoglobin and myoglobin in the blood. Hemoglobin, which has four heme groups, exhibits cooperative binding. This means that the binding of oxygen to a heme group on hemoglobin induces a favorable conformation change that allows for increased binding favorability of oxygen for the next heme groups. In these circumstances, the binding curve of hemoglobin will be sigmoidal due to its increased binding favorability for oxygen. Since myoglobin has only one heme group, it exhibits noncooperative binding which is hyperbolic on a binding curve. | 1 | Applied and Interdisciplinary Chemistry |
The proof that a spatial displacement can be decomposed into a rotation around, and translation along, a line in space is attributed to Michel Chasles in 1830. Recently the work of Giulio Mozzi has been identified as presenting a similar result in 1763. | 0 | Theoretical and Fundamental Chemistry |
Chlorine-36 (Cl) is an isotope of chlorine. Chlorine has two stable isotopes and one naturally occurring radioactive isotope, the cosmogenic isotope Cl. Its half-life is 301,300 ± 1,500 years. Cl decays primarily (98%) by beta-minus decay to Ar, and the balance to S.
Trace amounts of radioactive Cl exist in the environment, in a ratio of about (7–10) × 10 to 1 with stable chlorine isotopes. This corresponds to a concentration of approximately 1 Bq/(kg Cl).
Cl is produced in the atmosphere by spallation of Ar by interactions with cosmic ray protons. In the top meter of the lithosphere, Cl is generated primarily by thermal neutron activation of Cl and spallation of K and Ca. In the subsurface environment, muon capture by Ca becomes more important. The production rates are about 4200 atoms Cl/yr/mole K and 3000 atoms Cl/yr/mole Ca, due to spallation in rocks at sea level.
The half-life of this isotope makes it suitable for geologic dating in the range of 60,000 to 1 million years. Its properties make it useful as a proxy data source to characterize cosmic particle bombardment and solar activity of the past.
Additionally, large amounts of Cl were produced by irradiation of seawater during atmospheric and underwater test detonations of nuclear weapons between 1952 and 1958. The residence time of Cl in the atmosphere is about 2 years. Thus, as an event marker of 1950s water in soil and ground water, Cl is also useful for dating waters less than 50 years before the present. Cl has seen use in other areas of the geological sciences, including dating ice and sediments. | 0 | Theoretical and Fundamental Chemistry |
Krefts dichromaticity index (DI) is a measure for quantification of dichromatism. It is defined as the difference in hue angle (Δh) between the color of the sample at the dilution, where the chroma (color saturation) is maximal, and the color of four times more diluted (or thinner) and four times more concentrated (or thicker) sample. The two hue angle differences are called the dichromaticity index towards lighter (Krefts DI) and
dichromaticity index towards darker (Krefts DI) respectively. Krefts dichromaticity indexes DI and DI for pumpkin seed oil, which is one of the most dichromatic substances, are −9 and −44, respectively. This means, that pumpkin seed oil changes its color from green-yellow to orange-red (for 44 degrees in Lab color space) when the thickness of the observed layer is increased from cca 0.5 mm to 2 mm; and it changes slightly towards green (for 9 degrees) if its thickness is reduced for four-fold.
The color of pumpkin oil at increasing thickness or concentration presented in CIELAB colorspace diagram. Straight lines are vectors showing hue (angle) and chroma (length) of the color at maximal chroma (toward the square mark), and the colors of four-fold less or more diluted or thick pumpkin oil (DI and DI). Note that DI is −44.1 degrees and DI corresponds to −8.97 degrees.
Dichromaticity (DI and DI) of selected substances, calculated from their VIS absorption spectra by the computer algorithm “Dichromaticity index calculator”:
Maximal chroma: chroma at concentration (thickness) where the color of the substance has maximal chroma (saturation). Angle at maximal chroma: the hue, which is represented by the angle of the vector to the color with maximal chroma in the CIELAB colorspace diagram. | 0 | Theoretical and Fundamental Chemistry |
Polyaddition (or addition polymerisation ) is a polymerization reaction that forms polymers via individual independent addition reactions. Polyaddition occurs as a reaction between functional groups on molecules with low degrees of polymerization, such as dimers, trimers and oligomers, to form species of higher molar mass. Only at nearly complete conversions does the polymer form, as in polycondensation and in contrast to chain polymerization.
A typical polyaddition is the formation of a polyurethane. | 0 | Theoretical and Fundamental Chemistry |
The radical pair mechanism is currently accepted as the most common cause of CIDNP. This theory was proposed by Closs, and, independently, by Kaptein and Oosterhoff. There are, however, exceptions, and the DNP mechanism was found to be operational, for example, in many fluorine-containing radicals.
The chemical bond is a pair of electrons with opposite spins. Photochemical reactions or heat can cause an electron in the bond to change its spin. The electrons are now unpaired, in what is known as a triplet state, and the bond is broken. The orientation of some of the nuclear spins will favour some unpaired electrons changing their spins and so revert to the normal pairs as chemical bonds. This quantum interaction is known as spin–orbit coupling. Other nuclear spins will exert a different influence on the triplet pairs, giving the radical pairs more time to separate and react with other molecules. Consequently, the products of recombination will have different distributions of nuclear spins from the products produced by separated radicals. | 0 | Theoretical and Fundamental Chemistry |
The Hammett equation (Equation 1) provides the relationship between the substituent on the benzene ring and the ionizing rate constant of the reaction. Hammett used the ionization of benzoic acid as the standard reaction to define a set of substituent parameters σ, and then to generate the ρ values, which represent ionizing abilities of different substrates. This relationship can be visualized through a Hammett plot.
However, if the solvent of the reaction is changed, but not the structure of the substrate, the rate constant may change too. Following this idea, Grunwald and Winstein plotted the relative rate constant vs. the change of solvent system, and formulated this behavior in the Grunwald–Winstein equation. Since the equation has the same pattern as the Hammett equation but captures the change of the solvent system, it is considered as an extension of the Hammett equation. | 0 | Theoretical and Fundamental Chemistry |
There are a number of variations of the experiments, for example, a symmetric refocusing step or an extra 90° H pulse may be added, and there are also reverse INEPT pulse sequences. | 0 | Theoretical and Fundamental Chemistry |
The lipid world theory postulates that the first self-replicating object was lipid-like. Phospholipids form lipid bilayers in water while under agitation—the same structure as in cell membranes. These molecules were not present on early Earth, but other amphiphilic long-chain molecules also form membranes. These bodies may expand by insertion of additional lipids, and may spontaneously split into two offspring of similar size and composition. The main idea is that the molecular composition of the lipid bodies is a preliminary to information storage, and that evolution led to the appearance of polymers like RNA that store information. Studies on vesicles from amphiphiles that might have existed in the prebiotic world have so far been limited to systems of one or two types of amphiphiles.
A lipid bilayer membrane could be composed of a huge number of combinations of arrangements of amphiphiles. The best of these would have favored the constitution of a hypercycle, actually a positive feedback composed of two mutual catalysts represented by a membrane site and a specific compound trapped in the vesicle. Such site/compound pairs are transmissible to the daughter vesicles leading to the emergence of distinct lineages of vesicles, which would have allowed natural selection.
A protocell is a self-organized, self-ordered, spherical collection of lipids proposed as a stepping-stone to the origin of life. The theory of classical irreversible thermodynamics treats self-assembly under a generalized chemical potential within the framework of dissipative systems.
A central question in evolution is how simple protocells first arose and differed in reproductive contribution to the following generation, thus driving the evolution of life. A functional protocell has (as of 2014) not yet been achieved in a laboratory setting. Self-assembled vesicles are essential components of primitive cells. The second law of thermodynamics requires that the universe move in a direction in which entropy increases, yet life is distinguished by its great degree of organization. Therefore, a boundary is needed to separate life processes from non-living matter. Irene Chen and Jack W. Szostak suggest that elementary protocells can give rise to cellular behaviors including primitive forms of differential reproduction, competition, and energy storage. Competition for membrane molecules would favor stabilized membranes, suggesting a selective advantage for the evolution of cross-linked fatty acids and even the phospholipids of today. Such micro-encapsulation would allow for metabolism within the membrane and the exchange of small molecules, while retaining large biomolecules inside. Such a membrane is needed for a cell to create its own electrochemical gradient to store energy by pumping ions across the membrane. Fatty acid vesicles in conditions relevant to alkaline hydrothermal vents can be stabilized by isoprenoids which are synthesized by the formose reaction, the advantages and disadvantages of isoprenoids incorporated within the lipid bilayer in different microenvironments might have led to the divergence of the membranes of archaea and bacteria. | 0 | Theoretical and Fundamental Chemistry |
In Type II photosensitized reactions, the photosensitizer is excited by a light source into a triplet state. The excited photosensitizer then reacts with a ground state, triplet oxygen molecule. This excites the oxygen molecule into the singlet state, making it a reactive oxygen species. Upon excitation, the singlet oxygen molecule reacts with a substrate to form a product. Type II photosensitized reaction result in the photosensitizer being quenched by a ground state oxygen molecule which then goes on to react with a substrate to form a product. | 0 | Theoretical and Fundamental Chemistry |
Ionophores are chemical compounds that reversibly bind and transport ions through biological membranes in the absence of a protein pore. This can disrupt the membrane potential, and thus these substances could exhibit cytotoxic properties. Ionophores modify the permeability of biological membranes toward certain ions to which they show affinity and selectivity. Many ionophores are lipid-soluble and transport ions across hydrophobic membranes, such as lipid bilayers found in the living cells or synthetic vesicles (liposomes), or liquid polymeric membranes (carrier-based ion selective electrodes). Structurally, an ionophore contains a hydrophilic center and a hydrophobic portion that interacts with the membrane. Ions are bound to the hydrophilic center and form an ionophore-ion complex. The structure of the ionophore-ion complex has been verified by X-ray crystallography. | 0 | Theoretical and Fundamental Chemistry |
Cycle of quantification/qualification (C) is a parameter used in real-time polymerase chain reaction techniques, indicating the cycle number where a PCR amplification curve meets a predefined mathematical criterion. A C may be used for quantification of the target sequence or to determine whether the target sequence is present or not.
Two criteria to determine the C are used by different thermocyclers:
threshold cycle (C) is the number of cycles required for the fluorescent signal to cross a given value threshold. Usually, the threshold is set above the baseline, about 10 times the standard deviation of the noise of the baseline, to avoid random effects on the C. However, the threshold shouldn't be set much higher than that to avoid reduced reproducibility due to uncontrolled factors.
Crossing point (Cp) and Take off point (TOP) are the cycle value of the maximum second derivative of the amplification curve. | 1 | Applied and Interdisciplinary Chemistry |
One of the theories on the specific formation mechanism for bainite is that it occurs by a shear transformation, as in martensite. The crystal structure change is achieved by a deformation rather than by diffusion. The shape change associated with bainite is an invariant—plane strain with a large shear component. This kind of deformation implies a disciplined motion of atoms (rather than a chaotic transfer associated with diffusion), and is typical of all displacive transformations in steels, for example, martensite, bainite and Widmanstaetten ferrite. There is a strain energy associated with such relief, that leads to the plate shape of the transformation product Any diffusion is subsequent to the diffusionless transformation of austenite, for example the partitioning of carbon from supersaturated bainitic ferrite, or the precipitation of carbides; this is analogous to the tempering of martensite.
There are many features of bainite that are correctly predicted by this theory, including:
* the plate shape, which is a consequence of the minimisation of strain energy due to the shape deformation accompanying transformation.
* The fact that excess carbon is retained inside the even defect-free regions of bainitic ferrite.
* The fact that the unit cell of bainitic ferrite can be tetragonal rather than cubic.
* The fact that the bainite transformation can be dramatically retarded when the austenite is first plastically deformed, a phenomenon known as mechanical stabilisation, which is unique to displacive transformations.
* The obvious fact that displacements occur when bainite grows. The transformation is a combination of deformation and crystal structure change, just like martensite. | 1 | Applied and Interdisciplinary Chemistry |
The Pleistocene is a geological epoch that began about 2.6 million years ago. The Holocene, the current geological epoch, begins about 11,700 years ago when the Pleistocene ends. Establishing the date of this boundary − which is defined by sharp climatic warming − as accurately as possible has been a goal of geologists for much of the 20th century. At Two Creeks, in Wisconsin, a fossil forest was discovered (Two Creeks Buried Forest State Natural Area), and subsequent research determined that the destruction of the forest was caused by the Valders ice readvance, the last southward movement of ice before the end of the Pleistocene in that area. Before the advent of radiocarbon dating, the fossilized trees had been dated by correlating sequences of annually deposited layers of sediment at Two Creeks with sequences in Scandinavia. This led to estimates that the trees were between 24,000 and 19,000 years old, and hence this was taken to be the date of the last advance of the Wisconsin glaciation before its final retreat marked the end of the Pleistocene in North America. In 1952 Libby published radiocarbon dates for several samples from the Two Creeks site and two similar sites nearby; the dates were averaged to 11,404 BP with a standard error of 350 years. This result was uncalibrated, as the need for calibration of radiocarbon ages was not yet understood. Further results over the next decade supported an average date of 11,350 BP, with the results thought to be the most accurate averaging 11,600 BP. There was initial resistance to these results on the part of Ernst Antevs, the palaeobotanist who had worked on the Scandinavian varve series, but his objections were eventually discounted by other geologists. In the 1990s samples were tested with AMS, yielding (uncalibrated) dates ranging from 11,640 BP to 11,800 BP, both with a standard error of 160 years. Subsequently, a sample from the fossil forest was used in an interlaboratory test, with results provided by over 70 laboratories. These tests produced a median age of 11,788 ± 8 BP (2σ confidence) which when calibrated gives a date range of 13,730 to 13,550 cal BP. The Two Creeks radiocarbon dates are now regarded as a key result in developing the modern understanding of North American glaciation at the end of the Pleistocene. | 0 | Theoretical and Fundamental Chemistry |
Up to now, seven meetings have been held:
* ACEPS-1, November 15–17, 2006, Kyoto, Japan
* ACEPS-2, October 21–23, 2007, Fudan University, Shanghai, China
* ACEPS-3, November, 2008, Korea University, Seoul, South Korea
* ACEPS-4, November 8–12, 2009, National Taiwan University of Science and Technology, Taipei, Taiwan
* ACEPS-5, September 17–20, 2010, Singapore
* ACEPS-6, January 5–8, 2012, Indian Institute of Science and Central Electro Chemical Research Institute, India
* ACEPS-7, November 24–27, 2013, Co-Sponsored by Electrochemical Society of Japan and Chemical Society of Japan,
* ACEPS-8, August 21–25, 2015, Kai Wah Plaza Hotel, Kunming, Co-Sponsored by Fudan University, Shanghai, China,
* ACEPS-9, August 20–23, 2017, Gyeongju, South Korea,
* ACEPS-10, November 24–27, 2019, Kaohsiung, Taiwan,
* ACEPS-11, December 11–14, 2022, National University of Singapore, Singapore
* ACEPS-12, scheduled in 2024, Nara or Kyoto, Japan | 0 | Theoretical and Fundamental Chemistry |
Several important anticancer agents both bind to DNA and generate reactive oxygen species. These include adriamycin and other anthracyclines, bleomycin, and cisplatin. These agents may show specific toxicity towards cancer cells because of the low level of antioxidant defenses found in tumors. Recent research demonstrates that redox dysregulation originating from metabolic alterations and dependence on mitogenic and survival signaling through reactive oxygen species represents a specific vulnerability of malignant cells that can be selectively targeted by pro-oxidant non-genotoxic redox chemotherapeutics.
Photodynamic therapy is used to treat some cancers as well as other conditions. It involves the administration of a photosensitizer followed by exposing the target to appropriate wavelengths of light. The light excites the photosensitizer, causing it to generate reactive oxygen species, which can damage or destroy diseased or unwanted tissue. | 1 | Applied and Interdisciplinary Chemistry |
Consider the problem where the fluid in the far stream exhibit uniform axial velocity and rotates with angular velocity . This upstream motion corresponds to
From these, we obtain
indicating that in this case, and are simple linear functions of . The Hicks equation itself becomes
which upon introducing becomes
where . | 1 | Applied and Interdisciplinary Chemistry |
Optical properties are tested for optical sensing-related applications. This can include light attenuation, refractive index, transmission, etc. These optical properties are significantly influenced by the composition of the hydrogel. | 0 | Theoretical and Fundamental Chemistry |
Iodine-transfer polymerization (ITP, also called ITRP), developed by Tatemoto and coworkers in the 1970s gives relatively low polydispersities for fluoroolefin polymers. While it has received relatively little academic attention, this chemistry has served as the basis for several industrial patents and products and may be the most commercially successful form of living free radical polymerization. It has primarily been used to incorporate iodine cure sites into fluoroelastomers.
The mechanism of ITP involves thermal decomposition of the radical initiator (typically persulfate), generating the initiating radical In•. This radical adds to the monomer M to form the species P•, which can propagate to P•. By exchange of iodine from the transfer agent R-I to the propagating radical P• a new radical R• is formed and P• becomes dormant. This species can propagate with monomer M to P•. During the polymerization exchange between the different polymer chains and the transfer agent occurs, which is typical for a degenerative transfer process.
Typically, iodine transfer polymerization uses a mono- or diiodo-perfluoroalkane as the initial chain transfer agent. This fluoroalkane may be partially substituted with hydrogen or chlorine. The energy of the iodine-perfluoroalkane bond is low and, in contrast to iodo-hydrocarbon bonds, its polarization small. Therefore, the iodine is easily abstracted in the presence of free radicals. Upon encountering an iodoperfluoroalkane, a growing poly(fluoroolefin) chain will abstract the iodine and terminate, leaving the now-created perfluoroalkyl radical to add further monomer. But the iodine-terminated poly(fluoroolefin) itself acts as a chain transfer agent. As in RAFT processes, as long as the rate of initiation is kept low, the net result is the formation of a monodisperse molecular weight distribution.
Use of conventional hydrocarbon monomers with iodoperfluoroalkane chain transfer agents has been described. The resulting molecular weight distributions have not been narrow since the energetics of an iodine-hydrocarbon bond are considerably different from that of an iodine-fluorocarbon bond and abstraction of the iodine from the terminated polymer difficult. The use of hydrocarbon iodides has also been described, but again the resulting molecular weight distributions were not narrow.
Preparation of block copolymers by iodine-transfer polymerization was also described by Tatemoto and coworkers in the 1970s.
Although use of living free radical processes in emulsion polymerization has been characterized as difficult, all examples of iodine-transfer polymerization have involved emulsion polymerization. Extremely high molecular weights have been claimed.
Listed below are some other less described but to some extent increasingly important living radical polymerization techniques. | 0 | Theoretical and Fundamental Chemistry |
From calculus it is known that the gradient vector is normal to the curve (see e.g. Level set#Level sets versus the gradient). If it is shown that everywhere using the formula for in terms of then this proves that level curves of are streamlines.
;Cylindrical coordinates:
In cylindrical coordinates,
and
So that
;Spherical coordinates:
And in spherical coordinates
and
So that | 1 | Applied and Interdisciplinary Chemistry |
Pteropods and brittle stars both form the base of the Arctic food webs and are both seriously damaged from acidification. Pteropods shells dissolve with increasing acidification and the brittle stars lose muscle mass when re-growing appendages. For pteropods to create shells they require aragonite which is produced through carbonate ions and dissolved calcium and strontium. Pteropods are severely affected because increasing acidification levels have steadily decreased the amount of water supersaturated with carbonate. The degradation of organic matter in Arctic waters has amplified ocean acidification; some Arctic waters are already undersaturated with respect to aragonite.
The brittle star's eggs die within a few days when exposed to expected conditions resulting from Arctic acidification. Similarly, when exposed in experiments to pH reduced by 0.2 to 0.4, larvae of a temperate brittle star, a relative of the common sea star, fewer than 0.1 percent survived more than eight days. | 0 | Theoretical and Fundamental Chemistry |
Some polysilicates are ladder polymers. One example is provided by the mineral tremolite.
In the area of coordination chemistry, the ladder structure is seen in some coordination polymers. Illustrative is the polymer [CuI(2-picoline]. When the 2-picoline is replaced by a tertiary phosphine, it forms a tetrameric cubane-type cluster, [CuI(PR. In both cases, the Cu(I) centers adopt tetrahedral molecular geometry. | 0 | Theoretical and Fundamental Chemistry |
The majority of observed photogeochemical reactions involve a mineral catalyst. Many naturally occurring minerals are semiconductors that absorb some portion of solar radiation. These semiconducting minerals are frequently transition metal oxides and sulfides and include abundant, well-known minerals such as hematite (FeO), magnetite (FeO), goethite and lepidocrocite (FeOOH), and pyrolusite (MnO). Radiation of energy equal to or greater than the band gap of a semiconductor is sufficient to excite an electron from the valence band to a higher energy level in the conduction band, leaving behind an electron hole (h); the resulting electron-hole pair is called an exciton. The excited electron and hole can reduce and oxidize, respectively, species having suitable redox potentials relative to the potentials of the valence and conduction bands. Semiconducting minerals with appropriate band gaps and appropriate band energy levels can catalyze a vast array of reactions, most commonly at mineral-water or mineral-gas interfaces. | 0 | Theoretical and Fundamental Chemistry |
The word "chemurgy" decreased in use by 1950. By this point, the methods had yielded modest inroads to industry and research, including four national research laboratories, the development of the Southern pine industry, and the initial emergence of the American flax paper industry. After this time, awareness of the term as connoting a distinct set of industrial techniques faded, and the methods themselves did not spread further.
Explanations for the decline vary. From a market perspective, the simplest explanation is substitution by fossil fuels, which proved cheaper for industrial production of many materials. Beyond this, misaligned incentives and cultural aspects of the industry may have restrained investor enthusiasm and adoption by farmers. From an investment perspective, chemurgical projects often failed to move from pilot products to full-scale production. This leads some analysts to suggest that chemurgy disappointed too many investors in particular projects over time. Indeed, a related problem was in the industry's leadership and funding: a small number of private investors supplied the majority of the industry, and many decisions in it were guided by leadership personality conflicts in the small cadre of corporate-technocratic scientists in industry. This emphasis in the industry on the technological side may have dampened enthusiasm among farmers. The leaders of the industry promoted rapid technological shifts in agricultural production, which was opposed by the more conservative uptake of new technologies in agriculture. Finally, public programs aligned incentives against the industry. The New Deal provided immediate subsidies to farmers, whereas chemurgy as an industry required a longer-term program.
Prospects for chemurgy appeared promising into the 1950s. An article in the December 3, 1951 issue of Newsweek, said "the flood of chemurgy seems to be swelling." But as uses of agricultural raw materials advanced, so did uses for petrochemicals, and non-renewable materials eventually won out in a number of markets. Petrochemical detergents were widely used in place of agriculturally derived soaps, and petrochemical plastic wrapping material largely replaced cellophane. The Chemurgic Council went through a period of decline and finally closed its doors in 1977.
In recent years, there has been a resurgence of interest in chemurgy, although the word itself has largely fallen out of usage. In 1990, Wheeler McMillen then 97 years old, addressed a national conference of latter-day chemurgic enthusiasts in Washington, DC. The conference served to launch the New Uses Council, which seeks to further the cause formerly promoted by the Chemurgic Council.
George Washington Carver was one of the most famous scientists of this field. In the Environmental Biography of George Washington Carver titled "My Work is that of Conservation" author Mark D. Hersey writes, "Thus, although he accepted the honorary mantle of "the first and greatest chemurgist," he was hardly in its mainstream. On the contrary, Carver often misconstrued the movement's aims, imagining they fell more in line with his own than in fact they did. Because Carver had devoted his energies to improving the lives of impoverished black farmers, he saw chemurgy as a field in which science addressed "a great human problem." His 1936 injunction to "chemicalize the farm" sprang from his abhorrence of waste rather than a desire for profit, let alone an affinity for chemical pesticides and fertilizers. He wanted "waste products of the farm" to be used for making "insulating boards, paints, dyes, industrial alcohol, plastics of various kinds, rugs, mats and cloth from fiber plants, oils, gums and waxes, etc." | 1 | Applied and Interdisciplinary Chemistry |
GenePattern is a freely available computational biology open-source software package originally created and developed at the Broad Institute for the analysis of genomic data. Designed to enable researchers to develop, capture, and reproduce genomic analysis methodologies, GenePattern was first released in 2004. GenePattern is currently developed at the University of California, San Diego. | 1 | Applied and Interdisciplinary Chemistry |
Coordination complexes with octahedral or square planar geometries can also exhibit cis-trans isomerism.
For example, there are two isomers of square planar Pt(NH)Cl, as explained by Alfred Werner in 1893. The cis isomer, whose full name is cis-diamminedichloroplatinum(II), was shown in 1969 by Barnett Rosenberg to have antitumor activity, and is now a chemotherapy drug known by the short name cisplatin. In contrast, the trans isomer (transplatin) has no useful anticancer activity. Each isomer can be synthesized using the trans effect to control which isomer is produced.
For octahedral complexes of formula MXY, two isomers also exist. (Here M is a metal atom, and X and Y are two different types of ligands.) In the cis isomer, the two Y ligands are adjacent to each other at 90°, as is true for the two chlorine atoms shown in green in cis-[Co(NH)Cl], at left. In the trans isomer shown at right, the two Cl atoms are on opposite sides of the central Co atom.
A related type of isomerism in octahedral MXY complexes is
facial–meridional (or fac–mer) isomerism, in which different numbers of ligands are cis or trans to each other. Metal carbonyl compounds can be characterized as fac or mer using infrared spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
The effectiveness of methods such as chemotherapy to treat cancer tends to plateau after some initial time as the cells undergo molecular changes that render them insensitive to the effect of anticancer drugs. Hence, it is imperative to detect the presence of cancerous cells early. An important biomarker, microRNA (miRNA), is crucial in this detection via its expression patterns. Zhang et al. have demonstrated an INHIBIT-OR gate cascade for the purpose, Yue and co. used an AND gate to construct a system with two miRNA inputs and a quantum dot photoluminescence output, and Peng et al. also constructed an AND gate-based dual-input system for the simultaneous detection of miRNAs from tumor cells.
Akkaya et al. illustrated the application of a logic gate for photodynamic therapy in their work. A bodipy dye attached to a crown-ether and two pyridyl groups separated by spacers works according to an AND logic gate. The molecule works as a photodynamic agent upon irradiation at 660 nm under conditions of relatively high sodium and proton ion concentrations by converting triplet oxygen to cytotoxic singlet oxygen. This prototypical example would take advantage of the higher sodium levels and lower pH in tumor tissue compared to the levels in normal cells. When these two cancer-related cellular parameters are satisfied, a change is observed in the absorbance spectrum. This technique could be useful for the treatment of malignant tumors as it is non-invasive and specific. | 0 | Theoretical and Fundamental Chemistry |
Fura-2-acetoxymethyl ester, often abbreviated Fura-2AM, is a membrane-permeant derivative of the ratiometric calcium indicator Fura-2 used in biochemistry to measure cellular calcium concentrations by fluorescence. When added to cells, Fura-2AM crosses cell membranes and once inside the cell, the acetoxymethyl groups are removed by cellular esterases. Removal of the acetoxymethyl esters regenerates "Fura-2", the pentacarboxylate calcium indicator. Measurement of Ca-induced fluorescence at both 340 nm and 380 nm allows for calculation of calcium concentrations based 340/380 ratios. The use of the ratio automatically cancels out certain variables such as local differences in fura-2 concentration or cell thickness that would otherwise lead to artifacts when attempting to image calcium concentrations in cells. | 1 | Applied and Interdisciplinary Chemistry |
Iron is an important nutrient for the bacterium Pseudomonas aeruginosa, however, iron is not easily accessible in the environment. To overcome this problem, P. aeruginosa produces siderophores to bind and transport iron. But the bacterium that produced the siderophores does not necessarily receive the direct benefit of iron intake. Rather all members of the cellular population are equally likely to access the iron-siderophore complexes. The production of siderophores also requires the bacterium to expend energy. Thus, siderophore production can be looked at as an altruistic trait because it is beneficial for the local group but costly for the individual. This altruistic dynamic requires every member of the cellular population to equally contribute to siderophore production. But at times mutations can occur that result in some bacteria producing lower amounts of siderophore. These mutations give an evolutionary advantage because the bacterium can benefit from siderophore production without suffering the energy cost. Thus, more energy can be allocated to growth. Members of the cellular population that can efficiently produce these siderophores are commonly referred to as cooperators; members that produce little to no siderophores are often referred to as cheaters. Research has shown when cooperators and cheaters are grown together, cooperators have a decrease in fitness while cheaters have an increase in fitness. It is observed that the magnitude of change in fitness increases with increasing iron-limitation. With an increase in fitness, the cheaters can outcompete the cooperators; this leads to an overall decrease in fitness of the group, due to lack of sufficient siderophore production. | 1 | Applied and Interdisciplinary Chemistry |
As a material cools, the relative motion of its component molecules/atoms decreases - its temperature decreases. Cooling can continue until all motion ceases, and its kinetic energy, or energy of motion, disappears. This condition is known as absolute zero and it forms the basis for the Kelvin temperature scale, which measures the temperature above absolute zero. Zero degrees Celsius (°C) coincides with 273 Kelvin.
At absolute zero most elements become a solid, but not all behave as predictably as this; for instance, helium becomes a highly unusual liquid. The chemistry between substances, however, does not disappear, even near absolute zero temperatures, since separated molecules/atom can always combine to lower their total energy. Almost every molecule or element will show different properties at different temperatures; if cold enough, some functions are lost entirely. Cryogenic chemistry can lead to very different results compared with standard chemistry, and new chemical routes to substances may be available at cryogenic temperatures, such as the formation of argon fluorohydride, which is only a stable compound at or below . | 0 | Theoretical and Fundamental Chemistry |
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