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Dextrorotation and laevorotation (also spelled levorotation) in chemistry and physics are the optical rotation of plane-polarized light. From the point of view of the observer, dextrorotation refers to clockwise or right-handed rotation, and laevorotation refers to counterclockwise or left-handed rotation.
A chemical compound that causes dextrorotation is dextrorotatory or dextrorotary, while a compound that causes laevorotation is laevorotatory or laevorotary. Compounds with these properties consist of chiral molecules and are said to have optical activity. If a chiral molecule is dextrorotary, its enantiomer (geometric mirror image) will be laevorotary, and vice versa. Enantiomers rotate plane-polarized light the same number of degrees, but in opposite directions. | 0 | Theoretical and Fundamental Chemistry |
The two first partial derivatives of the vdW equation are
The first equation is , while the second is , where , the isothermal compressibility, is a measure of the relative increase of volume from an increase of pressure, at constant temperature, while , the coefficient of thermal expansion, is a measure of the relative increase of volume from an increase of temperature, at constant pressure. Therefore
In the limit while . Since the vdW equation in this limit becomes , finally . Both of these are the ideal gas values, which is consistent because, as noted earlier, the vdW fluid behaves like an ideal gas in this limit.
The specific heat at constant pressure, is defined as the partial derivative . However, it is not independent of , they are related by the Mayer equation, . Then the two partials of the vdW equation can be used to express as
Here in the limit , , which is also the ideal gas result as expected; however the limit gives the same result, which does not agree with experiments on liquids.
In this liquid limit we also find , namely that the vdW liquid is incompressible. Moreover, since , it is also mechanically incompressible, that is faster than .
Finally , and are all infinite on the curve . This curve, called the spinodal curve, is defined by , and is discussed at length in the next section. | 0 | Theoretical and Fundamental Chemistry |
The Chesapeake Bay is home to numerous fauna that either migrate to the Bay at some point during the year or live there year-round. There are over 300 species of fish and numerous shellfish and crab species. Some of these include the Atlantic menhaden, striped bass, American eel, eastern oyster, Atlantic horseshoe crab, and the blue crab.
Birds include ospreys, great blue herons, bald eagles, and peregrine falcons, the last two of which were threatened by DDT; their numbers plummeted but have risen in recent years. The piping plover is a near threatened species that inhabits the wetlands.
Larger fish such as Atlantic sturgeon, varieties of sharks, and stingrays visit the Chesapeake Bay. The waters of the Chesapeake Bay have been regarded as one of the most important nursery areas for sharks along the east coast. Megafaunas such as bull sharks, tiger sharks, scalloped hammerhead sharks, and basking sharks and manta rays are also known to visit. Smaller species of sharks and stingrays that are known to be regular to occasional residents in the bay include the smooth dogfish, spiny dogfish, cownose ray, and bonnethead.
Bottlenose dolphins are known to live seasonally/yearly in the Bay. There have been unconfirmed sightings of humpback whales in recent years. Endangered North Atlantic right whale and fin, and minke and sei whales have also been sighted within and in the vicinity of the Bay.
A male manatee visited the Bay several times between 1994 and 2011, even though the area is north of the species normal range. The manatee, recognizable due to distinct markings on its body, was nicknamed "Chessie" after a legendary sea monster that was allegedly sighted in the Bay during the 20th century. The same manatee has been spotted as far north as Rhode Island, and was the first manatee known to travel so far north. Other manatees are occasionally seen in the Bay and its tributaries, which contain sea grasses that are part of the manatees diet.
Loggerhead turtles are known to visit the Bay.
The Chesapeake Bay is also home to a diverse flora, both land and aquatic. Common submerged aquatic vegetation includes eelgrass and widgeon grass. A report in 2011 suggested that information on underwater grasses would be released, because "submerged grasses provide food and habitat for a number of species, adding oxygen to the water and improving water clarity." Other vegetation that makes its home in other parts of the Bay are wild rice, various trees like the red maple, loblolly pine and bald cypress, and spartina grass and phragmites. Invasive plants have taken a significant foothold in the Bay. Plants such as Phragmites, Purple loosestrife and Japanese stiltgrass have established high levels of permanency in Chesapeake wetlands. Additionally, plants such as Brazilian waterweed, native to South America, have spread to most continents with the help of aquarium owners, who often dump the contents of their aquariums into nearby lakes and streams. It is highly invasive and has the potential to flourish in the low-salinity tidal waters of the Chesapeake Bay. Dense stands of Brazilian waterweed can restrict water movement, trap sediment and affect water quality. Various local K-12 schools in the Maryland and Virginia region often have programs that cultivate native bay grasses and plant them in the Bay. | 1 | Applied and Interdisciplinary Chemistry |
SNP detection through molecular beacons makes use of a specifically engineered single-stranded oligonucleotide probe. The oligonucleotide is designed such that there are complementary regions at each end and a probe sequence located in between. This design allows the probe to take on a hairpin, or stem-loop, structure in its natural, isolated state. Attached to one end of the probe is a fluorophore and to the other end a fluorescence quencher. Because of the stem-loop structure of the probe, the fluorophore is close to the quencher, thus preventing the molecule from emitting any fluorescence. The molecule is also engineered such that only the probe sequence is complementary to the genomic DNA that will be used in the assay (Abravaya et al. 2003).
If the probe sequence of the molecular beacon encounters its target genomic DNA during the assay, it will anneal and hybridize. Because of the length of the probe sequence, the hairpin segment of the probe will be denatured in favour of forming a longer, more stable probe-target hybrid. This conformational change permits the fluorophore and quencher to be free of their tight proximity due to the hairpin association, allowing the molecule to fluoresce.
If on the other hand, the probe sequence encounters a target sequence with as little as one non-complementary nucleotide, the molecular beacon will preferentially stay in its natural hairpin state and no fluorescence will be observed, as the fluorophore remains quenched.
The unique design of these molecular beacons allows for a simple diagnostic assay to identify SNPs at a given location. If a molecular beacon is designed to match a wild-type allele and another to match a mutant of the allele, the two can be used to identify the genotype of an individual. If only the first probes fluorophore wavelength is detected during the assay then the individual is homozygous to the wild type. If only the second probes wavelength is detected then the individual is homozygous to the mutant allele. Finally, if both wavelengths are detected, then both molecular beacons must be hybridizing to their complements and thus the individual must contain both alleles and be heterozygous. | 1 | Applied and Interdisciplinary Chemistry |
The planning of radiation therapy treatment has been revolutionized by the ability to delineate tumors and adjacent normal structures in three dimensions using specialized CT and/or MRI scanners and planning software.
Virtual simulation, the most basic form of planning, allows more accurate placement of radiation beams than is possible using conventional X-rays, where soft-tissue structures are often difficult to assess and normal tissues difficult to protect.
An enhancement of virtual simulation is 3-dimensional conformal radiation therapy (3DCRT), in which the profile of each radiation beam is shaped to fit the profile of the target from a beam's eye view (BEV) using a multileaf collimator (MLC) and a variable number of beams. When the treatment volume conforms to the shape of the tumor, the relative toxicity of radiation to the surrounding normal tissues is reduced, allowing a higher dose of radiation to be delivered to the tumor than conventional techniques would allow. | 0 | Theoretical and Fundamental Chemistry |
A capsule is a gelatinous envelope enclosing the active substance. Capsules can be designed to remain intact for some hours after ingestion in order to delay absorption. They may also contain a mixture of slow and fast
release particles to produce rapid and sustained absorption in the same dose. | 1 | Applied and Interdisciplinary Chemistry |
A pair of cyclopentadienyl ligands can be covalently linked giving rise to so-call ansa metallocenes. The angle between the two Cp rings is fixed. Rotation of the rings about the metal-centroid axis is stopped as well. A related class of derivatives give rise to the constrained geometry complexes. In these cases, a Cp ligand as linked to a non-Cp ligand. Such complexes have been commercialized for the production of polypropylene. | 0 | Theoretical and Fundamental Chemistry |
The helium trimer (or trihelium) is a weakly bound molecule consisting of three helium atoms. Van der Waals forces link the atoms together. The combination of three atoms is much more stable than the two-atom helium dimer. The three-atom combination of helium-4 atoms is an Efimov state. Helium-3 is predicted to form a trimer, although ground state dimers containing helium-3 are completely unstable.
Helium trimer molecules have been produced by expanding cold helium gas from a nozzle into a vacuum chamber. Such a set up also produces the helium dimer and other helium atom clusters. The existence of the molecule was proven by matter wave diffraction through a diffraction grating. Properties of the molecules can be discovered by Coulomb explosion imaging. In this process, a laser ionizes all three atoms simultaneously, which then fly away from each other due to electrostatic repulsion and are detected.
The helium trimer is large, being more than 100 Å, which is even larger than the helium dimer. The atoms are not arranged in an equilateral triangle, but instead form random shaped triangles.
Interatomic Coulombic decay can occur when one atom is ionised and excited. It can transfer energy to another atom in the trimer, even though they are separated. However this is much more likely to occur when the atoms are close together, and so the interatomic distances measured by this vary with half full height from 3.3 to 12 Å. The predicted mean distance for Interatomic Coulombic decay in He is 10.4 Å. For HeHe this distance is even larger at 20.5 Å. | 0 | Theoretical and Fundamental Chemistry |
In transhydrocyanation, an equivalent of HCN is transferred from a cyanohydrin, e.g. acetone cyanohydrin, to another HCN acceptor. The transfer is an equilibrium process, initiated by base. The reaction can be driven by trapping reactions or by the use of a superior HCN acceptor, such as an aldehyde. | 0 | Theoretical and Fundamental Chemistry |
For some uses in nuclear technology, the content of zinc-64 in zinc metal has to be lowered in order to prevent formation of radioisotopes by its neutron activation. Diethyl zinc is used as the gaseous feed medium for the centrifuge cascade. An example of a resulting material is depleted zinc oxide, used as a corrosion inhibitor. | 0 | Theoretical and Fundamental Chemistry |
Polypyrrole (PPy) is suited for PTT applications because of its strong NIR absorbance, large PCE, stability, and biocompatibility. In vivo experiments show that tumors treated with PPy NPs could be effectively eliminated under the irradiation of an 808 nm laser (1 W cm, 5 min). PPy nanosheets exhibit promising photothermal ablation ability toward cancer cells in the NIR II window for deep-tissue PTT.
PPy nanoparticles and its derivative nanomaterials can also be combined with imaging contrast agents and diverse drugs to construct multifunctional theranostic applications in imaging-guided PTT and synergistic treatment, including fluorescent imaging, magnetic resonance imaging (MRI), photoacoustic imaging (PA), computed tomography (CT), photodynamic therapy (PDT), chemotherapy, etc. For example, PPy has been used to encapsulate ultrasmall iron oxide nanoparticles (IONPs) and finally develop IONP@PPy NPs for in vivo MR and PA imaging-guided PTT. Polypyrrole (I-PPy) nanocomposites have been investigated for CT imaging-guided tumor PTT. | 0 | Theoretical and Fundamental Chemistry |
Even though the sequencing accuracy for each individual nucleotide is very high, the very large number of nucleotides in the genome means that if an individual genome is only sequenced once, there will be a significant number of sequencing errors. Furthermore, many positions in a genome contain rare single-nucleotide polymorphisms (SNPs). Hence to distinguish between sequencing errors and true SNPs, it is necessary to increase the sequencing accuracy even further by sequencing individual genomes a large number of times. | 1 | Applied and Interdisciplinary Chemistry |
Gated drug delivery systems are a method of controlled drug release that center around the use of physical molecules that cover the pores of drug carriers until triggered for removal by an external stimulus. Gated drug delivery systems are a recent innovation in the field of drug delivery and pose as a promising candidate for future drug delivery systems that are effective at targeting certain sites without having leakages or off target effects in normal tissues. This new technology has the potential to be used in a variety of tissues over a wide range of disease states and has the added benefit of protecting healthy tissues and reducing systemic side effects. | 1 | Applied and Interdisciplinary Chemistry |
Carmalt studied chemistry at Newcastle University. She graduated with first class honours in 1992 before starting her doctoral research with Nick Norman. Her research considered the heavy elements of the Boron group and Pnictogen group. After earning her doctorate she spent two years as a postdoc at the University of Texas at Austin where she worked alongside Alan Cowley. She focussed on the design and synthesis of precursors to allow thin film growth. | 0 | Theoretical and Fundamental Chemistry |
After earning her PhD, Simon was offered a position at DuPont’s Pioneer Research Lab in Buffalo, New York. Here, she worked to develop new catalysts to change the properties of synthetic polymers. This work led to the development of two polymers which would later be named Dacron and Orlon.
After completing her work with DuPont, Simon transferred to Oak Ridge National Laboratory, in Oak Ridge, Tennessee. Here, she made discoveries in the field of radiochemistry in studying the triple-fission of uranium. While at ORNL, Simon also became the first to discover a new isotope of calcium. For a short period of time after leaving ORNL, she continued with similar research regarding uranium at Argonne National Laboratory in Chicago, Illinois.
In 1949, Simon began work at Lewis Research Center in Cleveland, Ohio, a division of the National Advisory Committee for Aeronautics (NACA), the predecessor of NASA. Once here, she was assigned to the fuels and combustion division, where she conducted research regarding flame velocities and types of fuel for aerospace applications. She also conducted studies to determine the minimum diameter of tubing necessary to maintain an engine flame. This led to Simon being credited in numerous technical publications and research papers for her work, and led to improvements in engine designs for aeronautic and spaceflight purposes.
As a result of her work at NACA, Simon was given the Rockefeller Federal Service Award, which entailed a $10,000 (~$110,000 in 2022) grant from the Rockefeller Foundation. She used this award to travel to Europe to further her education at the University of Cambridge in Cambridge, England. Simon also toured around Europe where she met with scientists from Germany, England, France, and Italy to examine their research regarding physical chemistry and radiochemistry. Upon returning from her tour, she was promoted to assistant chief of NACA’s combustion branch, where she became a pioneer in female corporate management. Throughout the 1950’s she served as an advocate for women in science and education, appearing in several radio shows and magazines.
Once leaving NACA, Simon briefly held a position at Magnolia Petroleum in Texas, where she did work regarding oil sands.
In 1956, Simon took a position at AVCO corporation, an aviation conglomerate in New England. There, she applied her previous experience with polymer construction and physical chemistry to develop the technology for early aerospace heat shields, which were critical to NASA’s crewed spacecraft endeavors. This technology would go on to be used most notably during NASA’s Apollo program, and later was applied to ballistic missiles at the height of the Cold War. Simon remained at AVCO for 30 years, during which she held the titles of vice president and director of research at the company, becoming the company’s first female corporate officer. | 0 | Theoretical and Fundamental Chemistry |
Cisplatin is the square planar coordination complex cis-[Pt(NH)Cl]. The prefix cis indicates the cis isomer in which two similar ligands are in adjacent positions. The systematic chemical name of this molecule is cis–diamminedichloroplatinum, where ammine with two m's indicates an ammonia (NH) ligand, as opposed to an organic amine with one m. | 1 | Applied and Interdisciplinary Chemistry |
Turbidity in open water may be caused by growth of phytoplankton. Human activities that disturb land, such as construction, mining and agriculture, can lead to high sediment levels entering water bodies during rain storms due to storm water runoff. Areas prone to high bank erosion rates as well as urbanized areas also contribute large amounts of turbidity to nearby waters, through stormwater pollution from paved surfaces such as roads, bridges, parking lots and airports. Some industries such as quarrying, mining and coal recovery can generate very high levels of turbidity from colloidal rock particles.
In drinking water, the higher the turbidity level, the higher the risk that people may develop gastrointestinal diseases. This is especially problematic for immunocompromised people, because contaminants like viruses or bacteria can become attached to the suspended solids. The suspended solids interfere with water disinfection with chlorine because the particles act as shields for viruses and bacteria. Similarly, suspended solids can protect bacteria from ultraviolet (UV) sterilization of water.
In water bodies such as lakes, rivers and reservoirs, high turbidity levels can reduce the amount of light reaching lower depths, which can inhibit growth of submerged aquatic plants and consequently affect species which are dependent on them, such as fish and shellfish. High turbidity levels can also affect the ability of fish gills to absorb dissolved oxygen. This phenomenon has been regularly observed throughout the Chesapeake Bay in the eastern United States.
For many mangrove areas, high turbidity is needed in order to support certain species, such as to protect juvenile fish from predators. For most mangroves along the eastern coast of Australia, in particular Moreton Bay, turbidity levels as high as 600 Nephelometric Turbidity Units (NTU) are needed for proper ecosystem health. | 0 | Theoretical and Fundamental Chemistry |
Heterogeneous catalysts are easily removed from a reaction mixture by filtration. Although some amount of metal catalyst typically remains in the product from leaching, these amounts tend to be lower than those remaining after workup of a homogenous metal-catalyzed cross-coupling. | 0 | Theoretical and Fundamental Chemistry |
The al-Hijarah missile warhead was probably filled with chemical weapons and biological weapons possessed by Iraq at that time like anthrax, botulinum toxin, aflatoxin, sarin, cyclosarin and VX nerve agent. The al-Hijarah missile being a version of the al Hussein also suffered from flight instability and improper guidance. Iraq itself at that time was almost fully indigenous when it came to ballistic missile components and only lacked the ability to locally manufacture Gyroscopes. | 1 | Applied and Interdisciplinary Chemistry |
Fluxing salt, like chlorides are also liquid inclusions. They come from flux treatments added to the melt for cleaning. | 1 | Applied and Interdisciplinary Chemistry |
For liquid moving quickly over a surface, the contact angle can be altered from its value at rest. The advancing contact angle will increase with speed, and the receding contact angle will decrease. The discrepancies between static and dynamic contact angles are closely proportional to the capillary number, noted . | 0 | Theoretical and Fundamental Chemistry |
Most mononuclear carbonyl complexes are colorless or pale yellow volatile liquids or solids that are flammable and toxic. Vanadium hexacarbonyl, a uniquely stable 17-electron metal carbonyl, is a blue-black solid. Dimetallic and polymetallic carbonyls tend to be more deeply colored. Triiron dodecacarbonyl (Fe(CO)) forms deep green crystals. The crystalline metal carbonyls often are sublimable in vacuum, although this process is often accompanied by degradation. Metal carbonyls are soluble in nonpolar and polar organic solvents such as benzene, diethyl ether, acetone, glacial acetic acid, and carbon tetrachloride. Some salts of cationic and anionic metal carbonyls are soluble in water or lower alcohols. | 0 | Theoretical and Fundamental Chemistry |
Similarly, if a fraction of moles of solute associate to form one mole of an n-mer (dimer, trimer, etc.), then
For the dimerisation of acetic acid in benzene:
: 2 CHCOOH (CHCOOH)
2 moles of acetic acid associate to form 1 mole of dimer, so that
For association in the absence of dissociation, the van 't Hoff factor is: | 0 | Theoretical and Fundamental Chemistry |
A cap-membrane-binding domain is found in prokaryotic lactate dehydrogenase. This consists of a large seven-stranded antiparallel beta-sheet flanked on both sides by alpha-helices. It allows for membrane association. | 1 | Applied and Interdisciplinary Chemistry |
Many classes of compounds with C–O–C linkages are not considered ethers: Esters (R–C(=O)–O–R′), hemiacetals (R–CH(–OH)–O–R′), carboxylic acid anhydrides (RC(=O)–O–C(=O)R′).
There are compounds which, instead of C in the linkage, contain heavier group 14 chemical elements (e.g., Si, Ge, Sn, Pb). Such compounds are considered ethers as well. Examples of such ethers are silyl enol ethers (containing the linkage), disiloxane (the other name of this compound is disilyl ether, containing the linkage) and stannoxanes (containing the linkage). | 0 | Theoretical and Fundamental Chemistry |
Composition of isometries mixes kinds in assorted ways. We can think of the identity as either two mirrors or none; either way, it has no effect in composition. And two reflections give either a translation or a rotation, or the identity (which is both, in a trivial way). Reflection composed with either of these could cancel down to a single reflection; otherwise it gives the only available three-mirror isometry, a glide reflection. A pair of translations always reduces to a single translation; so the challenging cases involve rotations. We know a rotation composed with either a rotation or a translation must produce an even isometry. Composition with translation produces another rotation (by the same amount, with shifted fixed point), but composition with rotation can yield either translation or rotation. It is often said that composition of two rotations produces a rotation, and Euler proved a theorem to that effect in 3D; however, this is only true for rotations sharing a fixed point. | 0 | Theoretical and Fundamental Chemistry |
MUSE system mainly serves as a low-cost alternative to traditional histological analysis for cancer diagnostics with simpler and less time-consuming techniques. By integrating microscopy and fresh tissue fluorescence staining into an automated optical system, the overall acquiring time needed for getting digital images with diagnostic values can be much shortened into the scale of minutes comparing with conventional pathology, where general procedure can take from hours to days. The color-mapping techniques that correlated fluorescence staining to traditional H&E staining provide the same visual representation to pathologists based on existing knowledge with no need for additional training on image recognition.
Additionally, this system also has great potential to be used for intraoperative consultation, a method performed in pathologists lab that examine the microscopic features of tissue during oncological surgery usually for rapid cancer lesion and margin detection. It also can play an important role in biological and medical research, which might require examination on cellular features of tissue samples. In the future, the system can be further optimized to include more features including staining protocol, LEDs wavelength for more research usages and applications. | 0 | Theoretical and Fundamental Chemistry |
In the glassy state, the movements of the long chain segments are frozen, the movements of these segments depend on an activation temperature that brings the polymer to a smoothing and elastic state, the rotation on the carbon bonds and the movements of the chains no longer have strong impediments to accommodate and acquire the conformation that requires less energy, the chains then "unravel" forming random strings, without order and therefore with higher entropy.
If a polymer sample is stretched for a short time in the elastic range, when the load is removed, the sample will recover its original shape, but if the load remains for a sufficiently long period, the chains rearrange and the original shape is not recovered, the result is an irreversible deformation, also called relaxation process (in this case: creep).
In order for a polymer to exhibit the thermally induced shape-memory effect, it is necessary to fix the chains with anchor points to avoid these relaxation processes that inelastically modify the system. | 0 | Theoretical and Fundamental Chemistry |
The dextrorotary (+)- or d- enantiomer is (1S,2S)-pseudoephedrine, whereas the levorotating (−)- or l- form is (1R,2R)-pseudoephedrine.
In the outdated system (+)-pseudoephedrine is also referred to as pseudoephedrine and (−)-pseudoephedrine as pseudoephedrine (in the Fisher projection then the phenyl ring is drawn at bottom).
Often the system (with small caps) and the d/l system (with lower-case) are confused. The result is that the dextrorotary d-pseudoephedrine is wrongly named pseudoephedrine and the levorotary l-ephedrine (the diastereomer) wrongly ephedrine.
The IUPAC names of the two enantiomers are (1S,2S)- respectively (1R,2R)-2-methylamino-1-phenylpropan-1-ol. Synonyms for both are psi-ephedrine and threo-ephedrine.
Pseudoephedrine is the International Nonproprietary Name of the (+)-form, when used as pharmaceutical substance. | 0 | Theoretical and Fundamental Chemistry |
The following inclusion types can also be found in aluminium alloys: alumina needles (AlO), nitrides (AlN), iron oxides (FeO), manganese oxides (MnO), fluorides (NaAlF, NaF, CaF, …), aluminium borides (AlB, AlB), borocarbides (AlCB).
Bone ash (Ca(PO)) sometimes added to patch cracks in the trough can be found as inclusions in the melt. | 1 | Applied and Interdisciplinary Chemistry |
In 1954, research into the chemistry of ferrocene began at the Department of Organic Chemistry at Moscow State University and at INEOS under the direction of Nesmeyanov. It turned out that the functional derivatives of ferrocene react similarly to aromatic compounds. However, it has been shown that the electronic effects of the substituents are transmitted through the metallocene core by an inductive mechanism, and therefore have a lesser effect than on benzene derivatives. Research on ferrocene and its derivatives made it possible to create a number of photosensitive compositions that allow obtaining a stable image on paper, fabric, plastics and metals, and also led to the creation of a new drug, ferrocerone, which fights diseases associated with iron deficiency. On the basis of cymantrene, Nesmeyanov proposed a new antiknock agent for motor gasoline. | 0 | Theoretical and Fundamental Chemistry |
The mechanism by which conservative transposition occurs is called the "cut-and-paste" method, which involves five main steps:
# The transposase enzyme is bound to the inverted repeated sequences flanking the ends of the transposon Inverted repeats define the ends of transposons and provide recognition sites for transposase to bind.
# The formation of the transposition complex In this step the DNA bends and folds into a pre-excision synaptic complex so the two transposases enzymes can interact.
# The interaction of these transposases activates the complex; transposase makes double stranded breaks in the DNA and the transposon is fully excised.
# The transposase enzymes locate, recognize and bind to the target site within the target DNA.
# Transposase creates a double stranded break in the DNA and integrates the transposon into the target site.
Both the excision and insertion of the transposon leaves single or double stranded gaps in the DNA, which are repaired by host enzymes such as DNA polymerase. | 1 | Applied and Interdisciplinary Chemistry |
Oxygen and nitrogen occur in the form of different isotopes which vary in their proportions geospatially and climatically. Oxygen is absorbed into the body in the form of HO and is used in the growth of tissues. As with carbon, oxygen isotopic ratio variances can be attributed to specific locations and the proportion of O isotopes can therefore contribute to the reconstruction of past climates, understanding of diets and water consumption, seasonality, mobility patterns, life history and elements of culture. | 0 | Theoretical and Fundamental Chemistry |
The association of phosphorylation and the reduction of an electron acceptor such as ferricyanide increase similarly with the addition of phosphate, magnesium (Mg), and ADP. The existence of these three components is important for maximal reductive and phosphorylative activity. Similar increases in the rate of ferricyanide reduction can be stimulated by a dilution technique. Dilution does not cause a further increase in the rate in which ferricyanide is reduced with the accumulation of ADP, phosphate, and Mg to a treated chloroplast suspension. ATP inhibits the rate of ferricyanide reduction. Studies of light intensities revealed that the effect was largely on the light-independent steps of the Hill reaction. These observations are explained in terms of a proposed method in which phosphate esterifies during electron transport reactions, reducing ferricyanide, while the rate of electron transport is limited by the rate of phosphorylation. An increase in the rate of phosphorylation increases the rate by which electrons are transported in the electron transport system. | 0 | Theoretical and Fundamental Chemistry |
Some amphibians and reptiles have the ability to regenerate limbs, eyes, spinal cords, hearts, intestines, and upper and lower jaws. The Japanese fire belly newt can regenerate its eye lens 18 times over a period of 16 years and retain its structural and functional properties. The cells at the site of the injury have the ability to undifferentiate, reproduce rapidly, and differentiate again to create a new limb or organ.
Hox genes are a group of related genes that control the body plan of an embryo along the head-tail axis. They are responsible for body segment differentiation and express the arrangement of numerous body components during initial embryonic development. Primarily, these sets of genes are utilized during the development of body plans by coding for the transcription factors that trigger production of body segment specific structures. Additionally in most animals, these genes are laid out along the chromosome similar to the order in which they are expressed along the anterior–posterior axis.
Variants of the Hox genes are found almost in every phylum with the exception of the sponge which use a different type of developmental genes. The homology of these genes is of important interest to scientists as they may hold more answers to the evolution of many species. In fact, these genes demonstrate such a high degree of homology that a human Hox gene variant – HOXB4 – could mimic the function of its homolog in the fruit fly (Drosophila). Studies suggest that the regulation and other target genes in different species are actually what causes such a great difference in phenotypic difference between species.
Hox genes contain a DNA sequence known as the homeobox that are involved in the regulation of patterns of anatomical development. They contain a specific DNA sequence with the aim of providing instructions for making a string of 60 protein building blocks - amino acids- which are referred to as the homeodomain. Most homeodomain-containing proteins function as transcription factors and fundamentally bind and regulate the activity of different genes. The homeodomain is the segment of the protein that binds to precise regulatory regions of the target genes. Genes within the homeobox family are implicated in a wide variety of significant activities during growth. These activities include directing the development of limbs and organs along the anterior-posterior axis and regulating the process by which cells mature to carry out specific functions, a process known as cellular differentiation. Certain homeobox genes can act tumor suppressors, which means they help prevent cells from growing and dividing too rapidly or in an uncontrolled way.
Due to the fact that homeobox genes have so many important functions, mutations in these genes are accountable for a wide array of developmental disorders. Changes in certain homeobox genes often result in eye disorders, cause abnormal head, face, and tooth development. Additionally, increased or decreased activity of certain homeobox genes has been associated with several forms of cancer later in life. | 1 | Applied and Interdisciplinary Chemistry |
In the first human genome draft the fraction of LINE elements of the human genome was given as 21% and their copy number as 850,000. Of these, L1, L2 and L3 elements made up 516,000, 315,000 and 37,000 copies, respectively. The non-autonomous SINE elements which depend on L1 elements for their proliferation make up 13% of the human genome and have a copy number of around 1.5 million. They probably originated from the RTE family of LINEs. Recent estimates show the typical human genome contains on average 100 L1 elements with potential for mobilization, however there is a fair amount of variation and some individuals may contain a larger number of active L1 elements, making these individuals more prone to L1-induced mutagenesis.
Increased L1 copy numbers have also been found in the brains of people with schizophrenia, indicating that LINE elements may play a role in some neuronal diseases. | 1 | Applied and Interdisciplinary Chemistry |
As an ordinary acid chloride, isobutyryl chloride is the subject of many reported transformations. Dehydrohalogenation of isobutyryl chloride with triethylamine gives 2,2,4,4-tetramethylcyclobutanedione. Treatment of isobutyryl chloride with hydrogen fluoride gives the acid fluoride. | 0 | Theoretical and Fundamental Chemistry |
Carbon has two stable isotopes, C and C, and one radioactive isotope, C.
The stable carbon isotope ratio, δC, is measured against Vienna Pee Dee Belemnite (VPDB). The stable carbon isotopes are fractionated primarily by photosynthesis (Faure, 2004). The C/C ratio is also an indicator of paleoclimate: a change in the ratio in the remains of plants indicates a change in the amount of photosynthetic activity, and thus in how favorable the environment was for the plants. During photosynthesis, organisms using the C pathway show different enrichments compared to those using the C pathway, allowing scientists not only to distinguish organic matter from abiotic carbon, but also what type of photosynthetic pathway the organic matter was using. Occasional spikes in the global C/C ratio have also been useful as stratigraphic markers for chemostratigraphy, especially during the Paleozoic.
The C ratio has been used to track ocean circulation, among other things. | 0 | Theoretical and Fundamental Chemistry |
Some microorganisms utilize selenium in formate dehydrogenase. Formate is produced in large amounts in the hepatic (liver cells) mitochondria of embryonic cells and in cancer cells by the folate cycle.
Formate is reversibly oxidized by the enzyme formate dehydrogenase:
:HCO → CO + H + 2 e | 1 | Applied and Interdisciplinary Chemistry |
Pipe bursting may also be used to expand pipeline carrying capacity by replacing smaller pipes with larger ones, or "upsizing." Extensive proving work by the gas and water industries has demonstrated the feasibility of upsizing gas mains, water mains and sewers. Upsizing from 100mm to 225mm diameter is now well established, and pipes of up to 36 inch diameter and greater have been replaced. | 1 | Applied and Interdisciplinary Chemistry |
Transcription factor II D (TFD) is one of several general transcription factors that make up the RNA polymerase II preinitiation complex. RNA polymerase II holoenzyme is a form of eukaryotic RNA polymerase II that is recruited to the promoters of protein-coding genes in living cells. It consists of RNA polymerase II, a subset of general transcription factors, and regulatory proteins known as SRB proteins. Before the start of transcription, the transcription Factor II D (TFD) complex binds to the core promoter DNA of the gene through specific recognition of promoter sequence motifs, including the TATA box, Initiator, Downstream Promoter, Motif Ten, or Downstream Regulatory elements. | 1 | Applied and Interdisciplinary Chemistry |
Ekimov was awarded the 1975 USSR State Prize in Science and Engineering for work on electron spin orientation in semiconductors. He is co-recipient of the 2006 R. W. Wood Prize of the Optical Society of America for "discovery of nanocrystal quantum dots and pioneering studies of their electronic and optical properties" shared with Alexander Efros and Louis E. Brus.
Ekimov, Brus and Moungi Bawendi were the recipients of the 2023 Nobel Prize in Chemistry "for the discovery and synthesis of quantum dots". | 0 | Theoretical and Fundamental Chemistry |
Iphigenia Photaki (, ; also known after marriage as Iphigenia Vourvidou-Photaki, ; 1921–1983) was a Greek organic chemist remembered for her contributions in peptide chemical synthesis, especially in the synthesis of biologically/enzymatically active peptides.
Photaki was in 1965 the fourth woman overall to be habilitated in a scientific discipline in Greece, and the second to do so in the field of Chemistry. She specialised in peptide synthesis, influenced by her mentor and doctoral advisor Leonidas Zervas, a global authority on the subject. After distinguished research in Basel, Athens, and later Cornell, Photaki eventually rose to Professor of Organic Chemistry and Head of the Laboratory of Organic Chemistry of the University of Athens. | 0 | Theoretical and Fundamental Chemistry |
Ionium-thorium dating is a technique for determining the age of marine sediments based upon the quantities present of nearly stable thorium-232 and more radioactive thorium-230. (Th was once known as ionium, before it was realised it was the same element as Th.)
Uranium (in nature, predominantly uranium-238) is soluble in water. However, when it decays into thorium, the latter element is insoluble and so precipitates out to become part of the sediment. Thorium-232 has a half-life of 14.5 billion years, but thorium-230 has a half-life of only 75,200 years, so the ratio is useful for dating sediments up to 400,000 years old. Conversely, this technique can be used to determine the rate of ocean sedimentation over time.
The ionium/thorium method of dating assumes that the proportion of thorium-230 to thorium-232 is a constant during the time period that the sediment layer was formed. Likewise, both thorium-230 and thorium-232 are assumed to precipitate out in a constant ratio; no chemical process favors one form over the other. It must also be assumed that the sediment does not contain any pre-existing particles of eroded rock, known as detritus, that already contain thorium isotopes. Finally, there must not be a process that causes the thorium to shift its position within the sediment. If these assumptions are correct, this dating technique can produce accurate results. | 0 | Theoretical and Fundamental Chemistry |
* National Representative for Greece in Horizon 2020 Committee in the European Union for the European Research Council (ERC),
the Mari Sklodowska-Curie actions, and the Future and Emerging Technologies (FET) Brussels, Belgium (2014–present)
* National Deputy Representative for Greece and Specialist for Nanotechnology in the European Union, Brussels (2007-2010)
* President, Society for Applied Spectroscopy (SAS), 2001.
* Board of Governors, Eastern Analytical Symposium (EAS), 1998 - .
* President, New England Section, Society for Applied Spectroscopy (1997 –1998).
* National Research Service Award recipient, NIH postdoctoral fellowship, Princeton University, 1994.
* Tomas Hirschfeld Award, Federation of Analytical Chemistry and Spectroscopy Societies (FACSS), 1992.
* Coblentz Society Student Award, 1992. | 0 | Theoretical and Fundamental Chemistry |
Silencing of transposon transcripts can vary in completeness of silencing as well as in duration of alteration. Plants employ a number of methods, which range from elimination of transcripts to complete epigenetic silencing. In general, these can be sorted into two strategies:
* Gene silencing#Post-transcriptional gene silencing PTGS], post-transcriptional gene silencing, in which siRNA or miRNA derived from transposon activity are loaded onto an RNA-induced silencing complex (RISC), which cleaves targeted mRNA transcripts
* Gene silencing#Transcriptional gene silencing TGS], transcriptional gene silencing, in which siRNA transposon transcript is loaded onto an RNA-Directed DNA Methylation complex, which methylates the region of DNA which is reactive to the siRNA used in the complex. This can lead to histone modification and, if further epigenetic modification occurs, heterochromatin formation. This process is not well understood, as almost all information regarding it comes to us from the study of the FWA gene in Arabidopsis thaliana, a relatively TE-poor example in the plant kingdom. This paucity of information is further complicated by the relatively small genome and the low variability of the Arabidopsis epigenetic code.
In general, initiation of transposon silencing has yet to be fully explained. For example, there have been recorded incidences of spontaneous silencing in maize, which carries a high number of transposons (~85% of the genome), though the mechanism by which this occurs is unknown. While it is known that heritable methylation occurs, and must occur with frequency, and must be initiated, triggered by some distinct factor, the only known example of this is in the case of Mu killer (Muk), a gene in maize that silences MuDR, a class II autonomous transposable element. Muk encodes a natural inverted derivative of the transposase coding sequence in MuDR, which, when transcribed, forms a dsRNA that is subsequently cut into siRNA, which renders MUDR incapable of cutting and pasting itself by way of RNAi interference of the transposase. Muk also engages RNAi-Directed Methylation to create a stable and heritable suppression. | 1 | Applied and Interdisciplinary Chemistry |
Particle-induced X-ray emission or proton-induced X-ray emission (PIXE) is a technique used for determining the elemental composition of a material or a sample. When a material is exposed to an ion beam, atomic interactions occur that give off EM radiation of wavelengths in the x-ray part of the electromagnetic spectrum specific to an element. PIXE is a powerful yet non-destructive elemental analysis technique now used routinely by geologists, archaeologists, art conservators and others to help answer questions of provenance, dating and authenticity.
The technique was first proposed in 1970 by Sven Johansson of Lund University, Sweden, and developed over the next few years with his colleagues Roland Akselsson and Thomas B Johansson.
Recent extensions of PIXE using tightly focused beams (down to 1 μm) gives the additional capability of microscopic analysis. This technique, called microPIXE, can be used to determine the distribution of trace elements in a wide range of samples. A related technique, particle-induced gamma-ray emission (PIGE) can be used to detect some light elements. | 0 | Theoretical and Fundamental Chemistry |
Schulze in 1967 defined intermetallic compounds as solid phases containing two or more metallic elements, with optionally one or more non-metallic elements, whose crystal structure differs from that of the other constituents. Under this definition, the following are included:
# Electron (or Hume-Rothery) compounds
# Size packing phases. e.g. Laves phases, Frank–Kasper phases and Nowotny phases
# Zintl phases
The definition of a metal is taken to include:
# post-transition metals, i.e. aluminium, gallium, indium, thallium, tin, lead, and bismuth.
# metalloids, e.g. silicon, germanium, arsenic, antimony and tellurium.
Homogeneous and heterogeneous solid solutions of metals, and interstitial compounds such as the carbides and nitrides are excluded under this definition. However, interstitial intermetallic compounds are included, as are alloys of intermetallic compounds with a metal. | 1 | Applied and Interdisciplinary Chemistry |
Burying biomass (such as trees) directly mimics the natural processes that created fossil fuels. The global potential for carbon sequestration using wood burial is estimated to be 10 ± 5 GtC/yr and largest rates in tropical forests (4.2 GtC/yr), followed by temperate (3.7 GtC/yr) and boreal forests (2.1 GtC/yr). In 2008, Ning Zeng of the University of Maryland estimated 65 GtC lying on the floor of the world's forests as coarse woody material which could be buried and costs for wood burial carbon sequestration run at 50 USD/tC which is much lower than carbon capture from e.g. power plant emissions. CO fixation into woody biomass is a natural process carried out through photosynthesis. This is a nature-based solution and suggested methods include the use of "wood vaults" to store the wood-containing carbon under oxygen-free conditions.
In 2022 a certification organization published methodologies for biomass burial. Other biomass storage proposals have included the burial of biomass deep underwater, including at the bottom of the Black Sea. | 0 | Theoretical and Fundamental Chemistry |
Available dosage forms include liquids, syrups, drops, elixirs, effervescent tablets and powders for mixing with water, capsules, tablets including extended-release formulations, suppositories, compounding powder, and injections. | 0 | Theoretical and Fundamental Chemistry |
A chaotropic agent is a molecule in water solution that can disrupt the hydrogen bonding network between water molecules (i.e. exerts chaotropic activity). This has an effect on the stability of the native state of other molecules in the solution, mainly macromolecules (proteins, nucleic acids) by weakening the hydrophobic effect. For example, a chaotropic agent reduces the amount of order in the structure of a protein formed by water molecules, both in the bulk and the hydration shells around hydrophobic amino acids, and may cause its denaturation.
Conversely, an antichaotropic agent (kosmotropic) is a molecule in an aqueous solution that will increase the hydrophobic effects within the solution. Antichaotropic salts such as ammonium sulphate can be used to precipitate substances from the impure mixture. This is used in protein purification processes, to remove undesired proteins from solution. | 1 | Applied and Interdisciplinary Chemistry |
The first high-volume product (> 5Mio actuators / year) is an automotive valve used to control low pressure pneumatic bladders in a car seat that adjust the contour of the lumbar support / bolsters. The overall benefits of SMA over traditionally-used solenoids in this application (lower noise/EMC/weight/form factor/power consumption) were the crucial factor in the decision to replace the old standard technology with SMA.
The 2014 Chevrolet Corvette became the first vehicle to incorporate SMA actuators, which replaced heavier motorized actuators to open and close the hatch vent that releases air from the trunk, making it easier to close. A variety of other applications are also being targeted, including electric generators to generate electricity from exhaust heat and on-demand air dams to optimize aerodynamics at various speeds. | 1 | Applied and Interdisciplinary Chemistry |
Supercritical drying is a method of removing solvent without surface tension effects. As a liquid dries, the surface tension drags on small structures within a solid, causing distortion and shrinkage. Under supercritical conditions there is no surface tension, and the supercritical fluid can be removed without distortion. Supercritical drying is used in the manufacturing process of aerogels and drying of delicate materials such as archaeological samples and biological samples for electron microscopy. | 0 | Theoretical and Fundamental Chemistry |
Sometimes referred to as a PIG (pipeline inspection gauge), the camera and lights are mounted in a swivelling head attached to a cylindrical body. The camera head can pan and tilt remotely. Integrated into the camera head are lighting devices, typically LEDs, for illuminating the pipeline. The camera is connected to display equipment via a long cable wound upon a winch. Some companies, such as Rausch Electronics USA, incorporate a series of lasers in the camera to accurately measure the pipe diameter and other data. | 1 | Applied and Interdisciplinary Chemistry |
To determine whether the flow is stable or unstable, one often employs the method of linear stability analysis. In this type of analysis, the governing equations and boundary conditions are linearized. This is based on the fact that the concept of stable or unstable is based on an infinitely small disturbance. For such disturbances, it is reasonable to assume that disturbances of different wavelengths evolve independently. (A nonlinear governing equation will allow disturbances of different wavelengths to interact with each other.) | 1 | Applied and Interdisciplinary Chemistry |
Antisense transcripts are stretches of non coding mRNA that are complementary to the coding sequence. Genome wide studies have shown that RNA antisense transcripts occur commonly within nature. They are generally believed to increase the coding potential of the genetic code and add an overall layer of complexity to gene regulation. So far, it is known that 40% of the human genome is transcribed in both directions, underlining the potential significance of reverse transcription.
It has been suggested that complementary regions between sense and antisense transcripts would allow generation of double stranded RNA hybrids, which may play an important role in gene regulation. For example, hypoxia-induced factor 1α mRNA and β-secretase mRNA are transcribed bidirectionally, and it has been shown that the antisense transcript acts as a stabilizer to the sense script. | 1 | Applied and Interdisciplinary Chemistry |
We would normally use pressure head calculations in areas in which is constant. However, if the gravitational field fluctuates, we can prove that pressure head fluctuates with it.
* If we consider what would happen if gravity decreases, we would expect the fluid in the venturi meter shown above to withdraw from the pipe up into the vertical columns. Pressure head is increased.
* In the case of weightlessness, the pressure head approaches infinity. Fluid in the pipe may "leak out" of the top of the vertical columns (assuming ).
* To simulate negative gravity, we could turn the venturi meter shown above upside down. In this case gravity is negative, and we would expect the fluid in the pipe to "pour out" the vertical columns. Pressure head is negative (assuming ).
* If and , we observe that the pressure head is also negative, and the ambient air is sucked into the columns shown in the venturi meter above. This is called a siphon, and is caused by a partial vacuum inside the vertical columns. In many venturis, the column on the left has fluid in it (), while only the column on the right is a siphon ().
* If and , we observe that the pressure head is again positive, predicting that the venturi meter shown above would look the same, only upside down. In this situation, gravity causes the working fluid to plug the siphon holes, but the fluid does not leak out because the ambient pressure is greater than the pressure in the pipe.
* The above situations imply that the Bernoulli equation, from which we obtain static pressure head, is extremely versatile. | 1 | Applied and Interdisciplinary Chemistry |
Organic peroxides are widely used to initiate polymerization of olefins, e.g. the formation of polyethylene. A key step is homolysis:
The tendency to homolyze is also exploited to modify polymers by grafting or visbreaking, or cross-link polymers to create a thermoset. When used for these purposes, the peroxide is highly diluted, so the heat generated by the exothermic decomposition is safely absorbed by the surrounding medium (e.g. polymer compound or emulsion). | 0 | Theoretical and Fundamental Chemistry |
In addition to being parasites themselves, copepods are subject to parasitic infection. The most common parasites are marine dinoflagellates of the genus Blastodinium, which are gut parasites of many copepod species. Twelve species of Blastodinium are described, the majority of which were discovered in the Mediterranean Sea. Most Blastodinium species infect several different hosts, but species-specific infection of copepods does occur. Generally, adult copepod females and juveniles are infected.
During the naupliar stage, the copepod host ingests the unicellular dinospore of the parasite. The dinospore is not digested and continues to grow inside the intestinal lumen of the copepod. Eventually, the parasite divides into a multicellular arrangement called a trophont. This trophont is considered parasitic, contains thousands of cells, and can be several hundred micrometers in length. The trophont is greenish to brownish in color as a result of well-defined chloroplasts. At maturity, the trophont ruptures and Blastodinium spp. are released from the copepod anus as free dinospore cells. Not much is known about the dinospore stage of Blastodinium and its ability to persist outside of the copepod host in relatively high abundances.
The copepod Calanus finmarchicus, which dominates the northeastern Atlantic coast, has been shown to be greatly infected by this parasite. A 2014 study in this region found up to 58% of collected C. finmarchicus females to be infected. In this study, Blastodinium-infected females had no measurable feeding rate over a 24-hour period. This is compared to uninfected females which, on average, ate 2.93 × 10 cells per day. Blastodinium-infected females of C. finmarchicus exhibited characteristic signs of starvation, including decreased respiration, fecundity, and fecal pellet production. Though photosynthetic, Blastodinium spp. procure most of their energy from organic material in the copepod gut, thus contributing to host starvation. Underdeveloped or disintegrated ovaries and decreased fecal pellet size are a direct result of starvation in female copepods. Parasitic infection by Blastodinium spp. could have serious ramifications on the success of copepod species and the function of entire marine ecosystems. Blastodinium parasitism is not lethal, but has negative impacts on copepod physiology, which in turn may alter marine biogeochemical cycles.
Freshwater copepods of the Cyclops genus are the intermediate host of the Guinea worm (Dracunculus medinensis), the nematode that causes dracunculiasis disease in humans. This disease may be close to being eradicated through efforts by the U.S. Centers for Disease Control and Prevention and the World Health Organization. | 1 | Applied and Interdisciplinary Chemistry |
Excimer lamps emit narrow-band UVC and vacuum-ultraviolet radiation at a variety of wavelengths depending on the medium. They are mercury-free and reach full output quicker than a mercury lamp, and generate less heat. Excimer emission at 207 and 222 nm appears to be safer than traditional 254 nm germicidal radiation, due to greatly reduced penetration of these wavelengths in human skin. | 0 | Theoretical and Fundamental Chemistry |
Since the metabolic pathway is conserved across species, the genes are similar too. Extensive studies on the regulation in Saccharomyces cerevisiae have been done. The IMD family of genes and gua1 in yeast correspond to guaB and guaA. Here only IMD genes are guanine sensitive and not gua1 unlike in prokaryotes where the entire operon is sensitive. Mycophenolic acid, a drug which is an inhibitor of IMP dehydrogenase, is an inducer of IMD 2 gene (and hence IMD 2 probably has intrinsic drug activity. Another aspect in which the eukaryotic regulation is very different is that eukaryotes have differential regulation of the branches leading to AMP and GMP. For example, in yeasts AMP synthesis genes are poorly repressed by guanine whereas GMP synthesis genes are not affected by adenine and in humans IMP dehydrogenase synthesis is repressed in the presence of guanosine but not adenosine. | 1 | Applied and Interdisciplinary Chemistry |
Aerobic digestion is a process in sewage treatment designed to reduce the volume of sewage sludge and make it suitable for subsequent use. More recently, technology has been developed that allows the treatment and reduction of other organic waste, such as food, cardboard and horticultural waste.
It is a bacterial process occurring in the presence of oxygen. Bacteria rapidly consume organic matter and convert it into carbon dioxide, water and a range of lower molecular weight organic compounds. As there is no new supply of organic material from sewage, the activated sludge biota begin to die and are used as food by saprotrophic bacteria. This stage of the process is known as endogenous respiration and it is process that reduces the solid concentration in the sludge. | 1 | Applied and Interdisciplinary Chemistry |
Molten chloride salt mixtures are commonly used as quenching baths for various alloy heat treatments, such as annealing and martempering of steel. Cyanide and chloride salt mixtures are used for surface modification of alloys such as carburizing and nitrocarburizing of steel.
Cryolite (a fluoride salt) is used as a solvent for aluminium oxide in the production of aluminium in the Hall-Héroult process.
Fluoride, chloride, and hydroxide salts can be used as solvents in pyroprocessing of nuclear fuel. | 1 | Applied and Interdisciplinary Chemistry |
The spatial arrangement of the selected plant species influences the vegetation system and the greater habitat system. Spatial planning determines interactions between plant species. These interactions can be facilitative or competitive. Planting certain species together can protect one or both from extreme temperature fluctuations, drying out in the sun, harsh winds, and predators, in addition to improving soil composition. Competition can occur within or between species, and generally weaker individuals and weaker species die out, resulting in increased plant spacing. Spatial arrangement of revegetation species also influences pollination and seed dispersal. For species whose seeds are wind-dispersed and animal-dispersed, plant diversity in seed dispersal range is important for genetic fitness. However, too much competition within the seed dispersal range can cause reproduction to be suppressed, so it is important to balance.
On the ecosystem level, the spatial planning of revegetation species influences animal species. A more varied plant species composition is more likely to be used by a wider variety of animal species. High-density edible plants mean animals do not have to forage as far to eat, and a plant species even being in the presence of palatable species could lead to it having more interaction with animals. Abiotic aspects of the ecosystem are also altered. Higher density revegetation can reduce erosion, protect against extreme temperatures, decrease evaporative losses of water, and increase water filtration and reinfiltration. However, higher density revegetation requires the use of more soil nutrients and water, which can potentially dry out and deplete the soil. For riparian revegetation, plant roots help to increase the shear strength of bank soil, and if tree roots begin to lose their strength, the bank is susceptible to land slips. Fibrous or matted roots in particular help to prevent against soil erosion, and are typically found in reed and sedge species. | 1 | Applied and Interdisciplinary Chemistry |
Expression of phosphocholine-modified and unsubstituted C. elegans paucimannosidic glycans is reportedly development stage-specific, implying important roles in nematodal development. In support, C. elegans hex-2 gene knock-out mutants displayed reduced paucimannosidic protein levels and altered sensitivity towards nematotoxic lectins relative to wild-type worms, a correlation suggesting involvement of paucimannosidic proteins in key C. elegans survival processes. Functionally, phosphocholine-containing paucimannosidic glycans were demonstrated to display immune-modulating roles in parasitic nematodes. Paucimannosidic glycans were suggested to play roles in the nematodal innate immune system by impacting the nematode's ability to fight and survive pathogenic bacteria | 1 | Applied and Interdisciplinary Chemistry |
Detonation spray coatings are applied using a detonation gun (D-gun) which is composed of a long-water-cooled metal barrel containing inlet valves for introducing gases and powders into the chamber. A preselected amount of the desired protective coating material known as feedstock (in powder form of particle size 5–60μm) is introduced into the chamber (at common powder flow rates of 16–40 g/min). Here oxygen and fuel (generally acetylene) are ignited by a spark plug to create a supersonic shock wave that propels the mixture of melted and/or partially-melted and/or solid feedstock (depending on the type of material used) out of the barrel and onto the subject being sprayed. The barrel is then cleared using a short burst of nitrogen before the D-gun is ready to be fired again. This is an important step because the heat from the residual gases can cause the new fuel mixture to combust which would in turn cause an uncontrollable reaction. Also a small amount of inert nitrogen gas inserted between the two mixtures of fuel and feedstock prior to firing, helps to prevent backfiring. D-guns typically operate at firing rates of between 1–10 Hz. Many different mixtures of coating powders and D-gun settings can be used during detonation gun spraying of a material, all of which influence the final surface characteristics of the sprayed coating. Common powder materials used include but are not limited to: alumina-titania, alumina, tungsten carbide-tungsten-chromium carbide mixture with nickel-chromium alloy binder, chromium carbide, tungsten carbide with cobalt binder.
Metallurgists consider the measurements of surface oxygen content, macro and micro-hardness, porosity, bond strength and surface roughness when determining the quality of a thermally sprayed coating. | 1 | Applied and Interdisciplinary Chemistry |
Heat of formation group additivity methods in thermochemistry enable the calculation and prediction of heat of formation of organic compounds based on additivity. This method was pioneered by S. W. Benson. | 0 | Theoretical and Fundamental Chemistry |
NS5A is a large hydrophilic phosphoprotein that is essential for the HCV life cycle and is found in association with virus-induced membrane vesicles, termed the membranous web. NS5A is a proline-rich protein composed of approximately 447 amino acids, which is divided into three domains. These domains are linked by two low-complexity sequences that are either serine- or proline-rich. Domain I is a zinc binding domain and X-ray crystallography studies indicated alternative dimer conformations of domain I of NS5A. Domain II and III are unstructured, shown by NMR studies. Domain I is preceded by an N-terminal amphipathic helix which allows the protein to associate with endoplasmic reticulum-derived membranes. Although X-ray crystallographic studies revealed dimer conformations of NS5A domain1, recent in solution structural characterization studies showed that NS5A proteins form higher-order structures by dimeric subunits of NS5A domain 1. Moreover, the overall structural model of NS5A highlights the variability of intrinsic conformations of the D2 and D3 domains between HCV genotypes. Therefore, it is still under debate which conformation\s of NS5A is functional and also targeted by NS5A inhibitors.
NS5A mainly exists in two distinct phosphorylated forms, a hypophosphorylated and a hyperphosphorylated form, but the exact function of the phosphorylation has not been determined. | 1 | Applied and Interdisciplinary Chemistry |
The fundamental unit within a geopolymer structure is a tetrahedral complex consisting of Si or Al coordinated through covalent bonds to four oxygens. The geopolymer framework results from the cross-linking between these tetrahedra, which leads to a 3-dimensional aluminosilicate network, where the negative charge associated with tetrahedral aluminium is balanced by a small cationic species, most commonly an alkali metal cation. These alkali metal cations are often ion-exchangeable, as they are associated with, but only loosely bonded to, the main covalent network, similarly to the non-framework cations present in zeolites. | 0 | Theoretical and Fundamental Chemistry |
In the 1920s, Otto Heinrich Warburg discovered an intriguing bioenergetic phenotype shared by most tumor cells: a higher-than-normal reliance on lactic acid fermentation for energy generation. He is known as the "Father of Oncometabolism". Although the roots of this research field trace back to the 1920s, it was only recently recognized Over the last decade, research on cancer progression has focused on the role of shifting metabolic pathways for both the cancer and immune cells, leading to an increase interest in characterizing the metabolic alterations that cells undergo in the TME. | 1 | Applied and Interdisciplinary Chemistry |
A method for nitrogen fixation was first described by Henry Cavendish in 1784 using electric arcs reacting nitrogen and oxygen in air. This method was implemented in the Birkeland–Eyde process of 1903. The fixation of nitrogen by lightning is a very similar natural occurring process.
The possibility that atmospheric nitrogen reacts with certain chemicals was first observed by Desfosses in 1828. He observed that mixtures of alkali metal oxides and carbon react with nitrogen at high temperatures. With the use of barium carbonate as starting material, the first commercial process became available in the 1860s, developed by Margueritte and Sourdeval. The resulting barium cyanide reacts with steam, yielding ammonia. In 1898 Frank and Caro developed what is known as the Frank–Caro process to fix nitrogen in the form of calcium cyanamide. The process was eclipsed by the Haber process, which was discovered in 1909. | 1 | Applied and Interdisciplinary Chemistry |
The nitrogen centres of hexachlorophosphazene are weakly basic, and this Lewis base behaviour has been suggested to play a role in the polymerisation mechanism. Specifically, hexachlorophosphazene has been reported to form adducts of various stoichiometries with Lewis acids Aluminium chloride|, Aluminium bromide|, Gallium trichloride|, Sulfur trioxide|, Tantalum(V) chloride|, Vanadium oxytrichloride|, but no isolable product with Boron trichloride|.
Among these, the best structurally characterised are the 1:1 adducts with aluminium trichloride or with gallium trichloride; they are found with the Al/Ga atom bound to a N and assume a more prominently distorted chair conformation compared to the free hexachlorophosphazene. The adducts also exhibit fluxional behaviour in solution for temperatures down to −60 °C, which can be monitored with N and P-NMR. | 0 | Theoretical and Fundamental Chemistry |
Repurposing generics can have groundbreaking effects for patients: 35% of transformative drugs approved by the US FDA are repurposed products. Repurposing is especially relevant for rare or neglected diseases.
A number of successes have been achieved, the foremost including sildenafil (Viagra) for erectile dysfunction and pulmonary hypertension and thalidomide for leprosy and multiple myeloma. Clinical trials have been performed on posaconazole and ravuconazole for Chagas disease.
Other antifungal agents clotrimazole and ketoconazole have been investigated for anti-trypanosome therapy. Successful repositioning of antimicrobials has led to the discovery of broad-spectrum therapeutics, which are effective against multiple infection types. | 1 | Applied and Interdisciplinary Chemistry |
Acids with a pH of less than 2 or alkalis with a pH above 12 are capable of causing the most extensive injuries in ingestions. Alkalis damage tissue by saponifying fats, leading to liquefaction necrosis which allows the alkalis to reach deeper tissues. Acids denature proteins via coagulation necrosis, this type of necrosis is thought to prevent the acid from reaching deeper tissues. Clinically, the pH, concentration, volume of ingested substance in addition to the duration of time in contact with tissue as well as percentage of body surface area involved determine the severity of the injury. | 1 | Applied and Interdisciplinary Chemistry |
Colorimetric analysis is a method of determining the concentration of a chemical element or chemical compound in a solution with the aid of a color reagent. It is applicable to both organic compounds and inorganic compounds and may be used with or without an enzymatic stage. The method is widely used in medical laboratories and for industrial purposes, e.g. the analysis of water samples in connection with industrial water treatment. | 0 | Theoretical and Fundamental Chemistry |
The RNA world hypothesis assumes that very early in evolution, prior to the emergence of DNA as a genetic material and prior to the emergence of protein enzymes, RNA was the key player in the emergence of life. A central idea in this hypothesis is an RNA replicase (ribozyme) that is capable of copying its own genome. A holopolymerase ribozyme has been engineered that uses a sigma factor-like specificity primer to recognize an RNA promoter sequence. This ribozyme can then, in a second step rearrange to a processive form that can polymerize from certain RNA promoters and not others. | 1 | Applied and Interdisciplinary Chemistry |
Spectral and spatial is collected by the detection system. The spatial component catches the position of the particles distribution across the width of the sorting machine, which is then used in case the ejection mechanism is activated for a single particle. Spectral data comprises the features that are used for material discrimination. In a superseding processing step, spectral and spatial can be combined to include patterns into the separation criterion. Huge amount of data is collected in real time multiple processing and filtering steps are bringing the data down to the Yes/no decision – either for ejecting a particle or for keeping the ejection mechanism still for that one. | 0 | Theoretical and Fundamental Chemistry |
The main disadvantage of green roofs is that the initial cost of installing a green roof can be double that of a normal roof. Depending on what kind of green roof it is, the maintenance costs could be higher, but some types of green roof have little or no ongoing cost. Some kinds of green roofs also place higher demands on the waterproofing system of the structure, both because water is retained on the roof and due to the possibility of roots penetrating the waterproof membrane. Another disadvantage is that the wildlife they attract may include pest insects which could easily infiltrate a residential building through open windows.
The additional mass of the soil substrate and retained water places a large strain on the structural support of a building. This makes it unlikely for intensive green roofs to become widely implemented due to a lack of buildings that are able to support such a large amount of added weight as well as the added cost of reinforcing buildings to be able to support such weight. Some types of green roofs do have more demanding structural standards especially in seismic regions of the world. Some existing buildings cannot be retrofitted with certain kinds of green roofs because of the weight load of the substrate and vegetation exceeds permitted static loading. The weight of a green roof caused the collapse of a large sports hall roof in Hong Kong in 2016. In the wake of the disaster numerous other green roofs around the territory were removed.
Green roofs require significantly more maintenance and maintenance energy compared to a standard roof. Standard maintenance include removing debris, controlling weeds, deadhead trimming, checking moisture levels, and fertilizing. The maintenance energy use for green roofs has many variables including: climate, intensity of rainfall, type of building, type of vegetation, and external coatings. The most significant effect comes from scarce rainfall which will increase the maintenance energy due to the watering required. During a 10-year roof maintenance cycle a house with a green roof requires more retrofit embodied energy than a house with a white roof. The individual components of a green roof have implications during the manufacturing process have additional implications compared to a conventional roof. The embodied energy for green roof components are of green roof. This value is equivalent to 6448 g C m which is significantly greater than 378 g C m Criteria for waste management practices when green roofs reach their end-of-life remain uncodified.
Both sod roofs and LWA-based (Lightweight Aggregates) roofs have been found to have a negative impact on the quality of their resulting runoff. | 1 | Applied and Interdisciplinary Chemistry |
In this context exposure is defined as the contact between an agent and a target. Contact takes place at an exposure surface over an exposure period.
Mathematically, exposure is defined as <br>
where is exposure, is a concentration that varies with time between the beginning and end of exposure. It has dimensions of mass times time divided by volume. This quantity is related to the potential dose of contaminant by multiplying it by the relevant contact rate, such as breathing rate, food intake rate etc. The contact rate itself may be a function of time. | 1 | Applied and Interdisciplinary Chemistry |
The physical process of non-linear inverse Compton scattering has been first introduced theoretically in different scientific articles starting from 1964. Before this date, some seminal works had emerged dealing with the description of the classical limit of NICS, called non-linear Thomson scattering or multiphoton Thomson scattering. In 1964, different papers were published on the topic of electron scattering in intense electromagnetic fields by L. S. Brown and T. W. B. Kibble, and by A. I. Nikishov and V. I. Ritus, among the others. The development of the high-intensity laser systems required to study the phenomenon has motivated the continuous advancements in the theoretical and experimental studies of NICS. At the time of the first theoretical studies, the terms non-linear (inverse) Compton scattering and multiphoton Compton scattering were not in use yet and they progressively emerged in later works. The case of an electron scattering off high-energy photons in the field of a monochromatic background plane wave with either circular or linear polarization was one of the most studied topics at the beginning. Then, some groups have studied more complicated non-linear inverse Compton scattering scenario, considering complex electromagnetic fields of finite spatial and temporal extension, typical of laser pulses.
The advent of laser amplification techniques and in particular of chirped pulse amplification (CPA) has allowed to reach sufficiently high-laser intensities to study new regimes of light-matter interaction and to significantly observe non-linear inverse Compton scattering and its peculiar effects. Non-linear Thomson scattering was first observed in 1983 with keV electron beam colliding with a Q-switched Nd:YAG laser delivering an intensity of W/cm (), photons of frequency two times the one of the laser were produced, then in 1995 with a CPA laser of peak intensity around W/cm interacting with neon gas, and in 1998 in the interaction of a mode-locked Nd:YAG laser ( W/cm, ) with plasma electrons from a helium gas jet, producing multiple harmonics of the laser frequency. NICS was detected for the first time in a pioneering experiment at the SLAC National Accelerator Laboratory at Stanford University, USA. In this experiment, the collision of an ultra-relativistic electron beam, with energy of about GeV, with a terawatt Nd:glass laser, with an intensity of W/cm (, ), produced NICS photons which were observed indirectly via a nonlinear energy shift in the spectrum of electrons in output; consequent positron generation was also observed in this experiment.
Multiple experiments have been then performed by crossing a high-energy laser pulse with a relativistic electron beam from a conventional linear electron accelerator, but a further achievement in the study of non-linear inverse Compton scattering has been achieved with the realization of all-optical setups. In these cases, a laser pulse is both responsible for the electron acceleration, through the mechanisms of plasma acceleration, and for the non-linear inverse Compton scattering occurring in the interaction of accelerated electrons with a laser pulse (possibly counter-propagating with respect to electrons). One of the first experiment of this type was made in 2006 producing photons of energy from to keV with a Ti:Sa laser beam (W/cm). Research is still ongoing and active in this field as attested by the numerous theoretical and experimental publications. | 0 | Theoretical and Fundamental Chemistry |
* Promoter - commonly used inducible promoters are promoters derived from lac operon and the T7 promoter. Other strong promoters used include Trp promoter and Tac-Promoter, which are a hybrid of both the Trp and Lac Operon promoters.
* Ribosome binding site (RBS) - follows the promoter, and promotes efficient translation of the protein of interest.
* Translation initiation site - Shine-Dalgarno sequence enclosed in the RBS, 8 base-pairs upstream of the AUG start codon. | 1 | Applied and Interdisciplinary Chemistry |
Naturally occurring moissanite is found in only minute quantities in certain types of meteorite, corundum deposits, and kimberlite. Virtually all the silicon carbide sold in the world, including moissanite jewels, is synthetic.
Natural moissanite was first found in 1893 as a small component of the Canyon Diablo meteorite in Arizona by Ferdinand Henri Moissan, after whom the material was named in 1905. Moissan's discovery of naturally occurring SiC was initially disputed because his sample may have been contaminated by silicon carbide saw blades that were already on the market at that time.
While rare on Earth, silicon carbide is remarkably common in space. It is a common form of stardust found around carbon-rich stars, and examples of this stardust have been found in pristine condition in primitive (unaltered) meteorites. The silicon carbide found in space and in meteorites is almost exclusively the beta-polymorph. Analysis of SiC grains found in the Murchison meteorite, a carbonaceous chondrite meteorite, has revealed anomalous isotopic ratios of carbon and silicon, indicating that these grains originated outside the solar system. | 1 | Applied and Interdisciplinary Chemistry |
Hybrid dysgenesis refers to the high rate of mutation in germ line cells of Drosophila strains resulting from a cross of males with autonomous P elements (P Strain/P cytotype) and females that lack P elements (M Strain/M cytotype). The hybrid dysgenesis syndrome is marked by temperature-dependent sterility, elevated mutation rates, and increased chromosomal rearrangement and recombination.
The hybrid dysgenesis phenotype is affected by the transposition of P elements within the germ-line cells of offspring of P strain males with M strain females. Transposition only occurs in germ-line cells, because a splicing event needed to make transposase mRNA does not occur in somatic cells.
Hybrid dysgenesis manifests when crossing P strain males with M strain females and not when crossing P strain females (females with autonomous P elements) with M strain males. The eggs of P strain females contain high amounts of a repressor protein that prevents transcription of the transposase gene. The eggs of M strain mothers, which do not contain the repressor protein, allow for transposition of P elements from the sperm of fathers. In P strain females, the repressors are found in the cytoplasm. Hence, when P strain males fertilize M strain females (whose cytoplasm contain no repressor), the male contributes its genome with the P element but not the male cytoplasm leading to P strain progeny.
This effect contributes to piRNAs being inherited only in the maternal line, which provides a defense mechanism against P elements. | 1 | Applied and Interdisciplinary Chemistry |
To diketone 23, sodium acetylide(Alkynylation) was added (bringing in carbon atoms 22 and 23) to give alkyne 24. This compound was reduced to the allyl alcohol 25 using the Lindlar catalyst and lithium aluminium hydride removed the remaining amide group in 26. An allylic rearrangement to alcohol 27 (isostrychnine) was brought about by hydrogen bromide in acetic acid followed by hydrolysis with sulfuric acid. In the final step to (−)-strychnine 28 treatment of 27 with ethanolic potassium hydroxide caused rearrangement of the C12-13 double bond and ring closure in a conjugate addition by the hydroxyl anion. | 0 | Theoretical and Fundamental Chemistry |
As a separation technique, GPC has many advantages. First of all, it has a well-defined separation time due to the fact that there is a final elution volume for all unretained analytes. Additionally, GPC can provide narrow bands, although this aspect of GPC is more difficult for polymer samples that have broad ranges of molecular weights present. Finally, since the analytes do not interact chemically or physically with the column, there is a lower chance for analyte loss to occur. For investigating the properties of polymer samples in particular, GPC can be very advantageous. GPC provides a more convenient method of determining the molecular weights of polymers. In fact most samples can be thoroughly analyzed in an hour or less. Other methods used in the past were fractional extraction and fractional precipitation. As these processes were quite labor-intensive molecular weights and mass distributions typically were not analyzed. Therefore, GPC has allowed for the quick and relatively easy estimation of molecular weights and distribution for polymer samples | 0 | Theoretical and Fundamental Chemistry |
In chemistry and biochemistry, the Henderson–Hasselbalch equation
relates the pH of a chemical solution of a weak acid to the numerical value of the acid dissociation constant, K, of acid and the ratio of the concentrations, of the acid and its conjugate base in an equilibrium.
For example, the acid may be acetic acid
The Henderson–Hasselbalch equation can be used to estimate the pH of a buffer solution by approximating the actual concentration ratio as the ratio of the analytical concentrations of the acid and of a salt, MA.
The equation can also be applied to bases by specifying the protonated form of the base as the acid. For example, with an amine, | 0 | Theoretical and Fundamental Chemistry |
Genomic biomarkers analyze DNA by identifying irregular sequences in the genome, typically a single nucleotide polymorphism. Genetic biomarkers are particularly significant in cancer because most cancer cell lines carry somatic mutations. Somatic mutations are distinguishable from hereditary mutations because the mutation is not in every cell; just the tumor cells, making them easy targets. | 1 | Applied and Interdisciplinary Chemistry |
As the surface object moves, it continuously generates small disturbances which are the sum of sinusoidal waves with a wide spectrum of wavelengths. Those waves with the longest wavelengths have phase speeds above and dissipate into the surrounding water and are not easily observed. Other waves with phase speeds at or below , however, are amplified through constructive interference and form visible shock waves, stationary in position w.r.t. the boat.
The angle between the phase shock wave front and the path of the object is = . If c/v > 1 or < −1, no later waves can catch up with earlier waves and no shockwave forms.
In deep water, shock waves form even from slow-moving sources, because waves with short enough wavelengths move slower. These shock waves are at sharper angles than one would naively expect, because it is group velocity that dictates the area of constructive interference and, in deep water, the group velocity is half of the phase velocity. | 1 | Applied and Interdisciplinary Chemistry |
Any signal that can be represented as a variable that varies in time has a corresponding frequency spectrum. This includes familiar entities such as visible light (perceived as color), musical notes (perceived as pitch), radio/TV (specified by their frequency, or sometimes wavelength) and even the regular rotation of the earth. When these signals are viewed in the form of a frequency spectrum, certain aspects of the received signals or the underlying processes producing them are revealed. In some cases the frequency spectrum may include a distinct peak corresponding to a sine wave component. And additionally there may be peaks corresponding to harmonics of a fundamental peak, indicating a periodic signal which is not simply sinusoidal. Or a continuous spectrum may show narrow frequency intervals which are strongly enhanced corresponding to resonances, or frequency intervals containing almost zero power as would be produced by a notch filter. | 0 | Theoretical and Fundamental Chemistry |
Isometries of the Euclidean plane fall into four categories (see the article Euclidean plane isometry for more information).
*Translations, denoted by T, where v is a vector in R. This has the effect of shifting the plane applying displacement vector v.
*Rotations, denoted by R, where c is a point in the plane (the centre of rotation), and θ is the angle of rotation.
*Reflections, or mirror isometries, denoted by F, where L is a line in R. (F is for "flip"). This has the effect of reflecting the plane in the line L, called the reflection axis or the associated mirror.
*Glide reflections, denoted by G, where L is a line in R and d is a distance. This is a combination of a reflection in the line L and a translation along L by a distance d. | 0 | Theoretical and Fundamental Chemistry |
Peter Jonathan Rutledge is a New Zealand chemist and professor at the School of Chemistry, University of Sydney. His research has focused on drug development for tuberculosis, antibiotics, and metal sensing. He has engaged in some research activity on catalysis. | 0 | Theoretical and Fundamental Chemistry |
Tar was used as seal for roofing shingles and tar paper and to seal the hulls of ships and boats. For millennia, wood tar was used to waterproof sails and boats, but today, sails made from inherently waterproof synthetic substances have reduced the demand for tar. Wood tar is still used to seal traditional wooden boats and the roofs of historic, shingle-roofed churches, as well as painting exterior walls of log buildings. Tar is also a general disinfectant. Pine tar oil, or wood tar oil, is used for the surface treatment of wooden shingle roofs, boats, buckets, and tubs and in the medicine, soap, and rubber industries. Pine tar has good penetration on the rough wood. An old wood tar oil recipe for the treatment of wood is one-third each genuine wood tar, balsam turpentine, and boiled or raw linseed oil or Chinese tung oil.
In Finland, wood tar was once considered a panacea reputed to heal "even those cut in twain through their midriff". A Finnish proverb states that "if sauna, vodka and tar won't help, the disease is fatal." Wood tar is used in traditional Finnish medicine because of its microbicidal properties.
Wood tar is also available diluted as tar water, which has numerous uses:
*As a flavoring for candies (e.g., Terva Leijona) and alcohol (Terva Viina).
*As a spice for food, like meat.
*As a scent for saunas. Tar water is mixed into water, which is turned into steam in the sauna.
*As an anti-dandruff agent in shampoo.
*As a component of cosmetics.
Mixing tar with linseed oil varnish produces tar paint. Tar paint has a translucent brownish hue and can be used to saturate and tone wood and protect it from weather. Tar paint can also be toned with various pigments, producing translucent colors and preserving the wood texture.
Tar was once used for public humiliation, known as tarring and feathering. By pouring hot wood tar onto somebody's bare skin and waiting for it to cool, they would remain stuck in one position. From there, people would attach feathers to the tar, which would remain stuck on the tarred person for the duration of the punishment. That person would then become a public example for the rest of the day.
Pitch was familiar in 9th-century Iraq, derived from petroleum that became accessible from natural fields in the region. It was sometimes used in the construction of baths or in shipbuilding. | 0 | Theoretical and Fundamental Chemistry |
The transformation that converts 7-dehydrocholesterol to vitamin D occurs in two steps. First, 7-dehydrocholesterol is photolyzed by ultraviolet light in a 6-electron conrotatory ring-opening electrocyclic reaction; the product is previtaminD. Second, previtaminD spontaneously isomerizes to vitaminD (cholecalciferol) in an antarafacial [[Sigmatropic shift#.5B1,7.5D Shifts|sigmatropic [1,7] hydride shift]]. At room temperature, the transformation of previtaminD to vitamin D in an organic solvent takes about 12 days to complete. The conversion of previtaminD to vitamin D in the skin is about 10 times faster than in an organic solvent.
The conversion from ergosterol to vitamin D follows a similar procedure, forming previtaminD by photolysis, which isomerizes to vitamin D (ergocalciferol). The transformation of previtaminD to vitamin D in methanol has a rate comparable to that of previtaminD. The process is faster in white button mushrooms. | 1 | Applied and Interdisciplinary Chemistry |
Broad-base adoption of mass timber and their role in substituting steel and concrete in new mid-rise construction projects over the next few decades has the potential to turn timber buildings into carbon sinks, as they store the carbon dioxide taken up from the air by trees that are harvested and used as mass timber. This could result in storing between 10 million tons of carbon per year in the lowest scenario and close to 700 million tons in the highest scenario. For this to happen, the harvested forests would need to be sustainably managed and wood from demolished timber buildings would need to be reused or preserved on land in various forms. | 0 | Theoretical and Fundamental Chemistry |
The first iron-cased and metal-cylinder rockets (Mysorean rockets) were developed by the Mysorean army of the South Indian Kingdom of Mysore in the 1780s. The Mysoreans successfully used these iron-cased rockets against the Presidency armies of the East India Company during the Anglo-Mysore Wars. | 1 | Applied and Interdisciplinary Chemistry |
Let q = (q, q, q) and p = (p, p, p) denote the position vector and momentum vector of a particle of an ideal gas, respectively. Let F denote the net force on that particle. Then (two times) the time-averaged kinetic energy of the particle is:
where the first equality is Newtons second law, and the second line uses Hamiltons equations and the equipartition theorem. Summing over a system of N particles yields
By Newtons third law and the ideal gas assumption, the net force of the system is the force applied by the walls of the container, and this force is given by the pressure P' of the gas. Hence
where dS is the infinitesimal area element along the walls of the container. Since the divergence of the position vector q is
the divergence theorem implies that
where dV is an infinitesimal volume within the container and V is the total volume of the container.
Putting these equalities together yields
which immediately implies the ideal gas law for N particles:
where n = N/N is the number of moles of gas and R = Nk is the gas constant. | 0 | Theoretical and Fundamental Chemistry |
In biochemistry, mixed acid fermentation is the metabolic process by which a six-carbon sugar (e.g. glucose, ) is converted into a complex and variable mixture of acids. It is an anaerobic (non-oxygen-requiring) fermentation reaction that is common in bacteria. It is characteristic for members of the Enterobacteriaceae, a large family of Gram-negative bacteria that includes E. coli.
The mixture of end products produced by mixed acid fermentation includes lactate, acetate, succinate, formate, ethanol and the gases and . The formation of these end products depends on the presence of certain key enzymes in the bacterium. The proportion in which they are formed varies between different bacterial species. The mixed acid fermentation pathway differs from other fermentation pathways, which produce fewer end products in fixed amounts. The end products of mixed acid fermentation can have many useful applications in biotechnology and industry. For instance, ethanol is widely used as a biofuel. Therefore, multiple bacterial strains have been metabolically engineered in the laboratory to increase the individual yields of certain end products. This research has been carried out primarily in E. coli and is ongoing. Variations of mixed acid fermentation occur in a number of bacterial species, including bacterial pathogens such as Haemophilus influenzae where mostly acetate and succinate are produced and lactate can serve as a growth substrate. | 1 | Applied and Interdisciplinary Chemistry |
Carbon tetraiodide is a tetrahalomethane with the molecular formula CI. Being bright red, it is a relatively rare example of a highly colored methane derivative. It is only 2.3% by weight carbon, although other methane derivatives are known with still less carbon. | 0 | Theoretical and Fundamental Chemistry |
The Dutch (the Netherlands), who are members of the International Hallmarking Convention, have been striking hallmarks since at least 1814, and boast a 600-year history of hallmarking in Dutch territories. Like many other nations, the Dutch require the registration and use of Responsibility Marks since 1797. The Dutch also use a date letter code.
After the French defeat at Leipzig 1813 the Kingdom of the Netherlands was established. William VI, prince of Orange (known in Dutch as Willem Frederik), was proclaimed the sovereign. On March 15, 1815, with the support of the powers gathered at the Congress of Vienna, William proclaimed himself King William I of the Netherlands. He was also made grand duke of Luxembourg. The two countries remained separate despite sharing a common monarch. For our purposes, he retained much of the French legislation, including the precious metal guarantee law of November 9, 1787. On December 26, 1813, the precious metal laws were however, modified and the French hallmarks, the Gaul cockerels were replaced with Dutch lions. The existing guarantee offices were reopened after re-staffing and the production of the new hallmark dies. Willem abdicated in 1840. As of January 1, 1853, the out-of-date French guarantee law was replaced by a new Dutch law. This law of September 18, 1852, in a modified form (last modified in 1986 as the "Dutch Assay Law of 1986") is in still effective. As a result of the Benelux treaty the guarantee tax was abolished in 1953. At the same time gold and silver fineness standards were adapted to conform to international standards. Also the assaying of platinum was introduced in 1953.
In 1987, the assay system was privatized and since 1988 has been located in only an office at Gouda. The system is overseen by the Dutch Ministry of Economic Affairs which appointed Edelmetaal Waarborg Nederland B.V. as of March 11, 2002. In 1999, the Netherlands ratified the Vienna Convention on the Control of the Fineness and the Hallmarking of Precious Metal Objects.
Dutch hallmarks are recognized in Austria, France, Ireland, Portugal, Spain and the United Kingdom without further testing and have also been recognized in Belgium, Denmark, Finland and Sweden, which have voluntary hallmarking systems. All jewelry produced in the Netherlands or imported for the Dutch market must carry hallmarks. | 0 | Theoretical and Fundamental Chemistry |
Diffusion hardening is performed by completely surrounding a metal part with the element to be diffused into it in either the solid, liquid, or gas phase depending on the type of diffusion process being performed. The concentration of the diffusing element surrounding the part must be higher than the concentration of the element inside the part, or diffusion will not occur. The metal and the surrounding element must then be heated to a temperature sufficiently high for diffusion to occur. In the case of pack carburizing, the temperature must be 900 °C and the part must be allowed to sit for 12 to 72 hours for the correct amount of diffusion to occur. | 1 | Applied and Interdisciplinary Chemistry |
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