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Stringers are filaments of slag left in wrought iron after the production process. In their correct proportions their presence is beneficial, as they help to control the ductility of the finished product, but when the proportion of slag is too high, or when the filaments run at right angles to the direction of tension, they can cause weakness. | 8 | Metallurgy |
Parkinsons disease is characterized by the death of cells that produce dopamine, a neurotransmitter. An enzyme called monoamine oxidase (MAO) breaks down neurotransmitters. MAO has two forms, MAO-A and MAO-B. MAO-B is generally believed to break down dopamine; however, recent evidence suggests that MAO-A may mostly or entirely be responsible for dopamine metabolism. Rasagiline prevents the breakdown of dopamine by irreversibly binding to MAO-B. Dopamine is therefore more available, somewhat compensating for the diminished quantities made in the brains of people with Parkinsons.
Selegiline was the first selective MAO-B inhibitor. It is partly metabolized to levomethamphetamine (l-methamphetamine), one of the two enantiomers of methamphetamine, in vivo. While these metabolites may contribute to selegilines ability to inhibit reuptake of the neurotransmitters dopamine and norepinephrine, they have also been associated with orthostatic hypotension and hallucinations in some people. Rasagiline metabolizes into 1(R')-aminoindan which has no amphetamine-like characteristics and has neuroprotective properties in cells and in animal models.
It is selective for MAO type B over type A by a factor of fourteen. | 4 | Stereochemistry |
Both the fluorescence excitation and emission spectrums of wild-type EosFP are shifted ~65 nm to the right upon excitation toward the red end of the spectrum. This spectral change is caused by an extension of the chromophore accompanied by a break in the peptide backbone between Phe-61 and His-62 in an irreversible mechanism. The presence of a crisp isosbestic point at 432 nm also suggests an interconversion between two species. An absorption peak at 280 nm is visible due to aromatic amino acids which transfer their excitation energy to the green chromophore. The quantum yield of the green-emitting form of Eos is 0.7. In the red shifted species, there are pronounced vibronic sidebands separate from the main peak at 533 nm and 629 nm in the excitation spectrum and emission spectrum respectively. There is another peak in the red excitation spectrum at 502 nm likely due to FRET excitation of the red fluorophore. The quantum yield of the red-emitting form is 0.55.
EosFPs variants show almost no difference in spectroscopic properties, therefore, it is likely that the structural modifications which arise from separation of interfaces have little to no effect on the structure of the fluorophore-binding site. | 1 | Biochemistry |
The Thyroid Feedback Quantile-based Index (TFQI) is a calculated parameter for thyrotropic pituitary function. It was defined to be more robust to distorted data than established markers including Jostel's TSH index (JTI) and the thyrotroph thyroid hormone sensitivity index (TTSI). | 1 | Biochemistry |
In addition to a material being certified as biocompatible, biomaterials must be engineered specifically to their target application within a medical device. This is especially important in terms of mechanical properties which govern the way that a given biomaterial behaves. One of the most relevant material parameters is the Youngs Modulus, E, which describes a materials elastic response to stresses. The Youngs Moduli of the tissue and the device that is being coupled to it must closely match for optimal compatibility between device and body, whether the device is implanted or mounted externally. Matching the elastic modulus makes it possible to limit movement and delamination at the biointerface between implant and tissue as well as avoiding stress concentration that can lead to mechanical failure. Other important properties are the tensile and compressive strengths which quantify the maximum stresses a material can withstand before breaking and may be used to set stress limits that a device may be subject to within or external to the body. Depending on the application, it may be desirable for a biomaterial to have high strength so that it is resistant to failure when subjected to a load, however in other applications it may be beneficial for the material to be low strength. There is a careful balance between strength and stiffness that determines how robust to failure the biomaterial device is. Typically, as the elasticity of the biomaterial increases, the ultimate tensile strength will decrease and vice versa. One application where a high-strength material is undesired is in neural probes; if a high-strength material is used in these applications the tissue will always fail before the device does (under applied load) because the Youngs Modulus of the dura mater and cerebral tissue is on the order of 500 Pa. When this happens, irreversible damage to the brain can occur, thus the biomaterial must have an elastic modulus less than or equal to brain tissue and a low tensile strength if an applied load is expected.
For implanted biomaterials that may experience temperature fluctuations, e.g., dental implants, ductility is important. The material must be ductile for a similar reason that the tensile strength cannot be too high, ductility allows the material to bend without fracture and also prevents the concentration of stresses in the tissue when the temperature changes. The material property of toughness is also important for dental implants as well as any other rigid, load-bearing implant such as a replacement hip joint. Toughness describes the material's ability to deform under applied stress without fracturing and having a high toughness allows biomaterial implants to last longer within the body, especially when subjected to large stress or cyclically loaded stresses, like the stresses applied to a hip joint during running.
For medical devices that are implanted or attached to the skin, another important property requiring consideration is the flexural rigidity, D. Flexural rigidity will determine how well the device surface can maintain conformal contact with the tissue surface, which is especially important for devices that are measuring tissue motion (strain), electrical signals (impedance), or are designed to stick to the skin without delaminating, as in epidermal electronics. Since flexural rigidity depends on the thickness of the material, h, to the third power (h), it is very important that a biomaterial can be formed into thin layers in the previously mentioned applications where conformality is paramount. | 1 | Biochemistry |
The commercial semisynthesis (by Bristol-Myers Squibb) of paclitaxel starting from 10-deacetylbaccatin III (isolated from the European yew) is based on tail addition of the so-called Ojima lactam to its free hydroxyl group:
Another commercial semisynthesis (by the company Natural Pharmaceuticals) relies on the isolation of a group of paclitaxel derivatives isolated from primary ornamental taxanes. These derivatives have the same skeleton as paclitaxel except for the organic residue R of the terminal tail amide group which can be phenyl, or propyl or pentyl (among others) whereas in paclitaxel it is an explicit phenyl group. The semisynthesis consists of conversion of the amide group to an amine with Schwartz's reagent through an imine followed by acidic workup and a benzoylation.
In the production process Michigan grown yews which mature in 8 years are periodically topped and dried. This material is shipped to Mexico for a first extraction step (10% paclitaxel content) and then to Canada for further purification to 95% purity. The semisynthesis to final product takes place in China. | 0 | Organic Chemistry |
Water treatment systems often require the degradation of hazardous compounds. These treatment processes are dubbed Advanced oxidation processes, and are key in destroying byproducts from disinfection, pesticides, and other hazardous compound. There is an emerging effort to enable these processes to destroy more tenacious compounds, especially PFAS | 7 | Physical Chemistry |
Inhalation of the Denigés' reagent can result in acute poisoning: causing tightness in the chest, difficulties breathing, coughing and pain. Exposure of mercury sulfate to the eyes can cause ulceration of conjunctiva and cornea. If mercury sulfate is exposed to the skin it may cause sensitization dermatitis. Lastly, ingestion of mercury sulfate will cause necrosis, pain, vomiting, and severe purging. Ingestion can result in death within a few hours due to peripheral vascular collapse. | 3 | Analytical Chemistry |
Chromosome jumping libraries help address the complication of standard cloning techniques with large molecular distances. This process allowed the possibility to use the chromosome jumping library for other genetic disorders that requires 100 kilobases jumps. Particularly for genetic disorders such as cystic fibrosis, its gene is located in human chromosome 7, was able to utilize the chromosome jumping library to search for a jumping clone, met oncogene. Identification of the cystic fibrosis was complicated due to it existing in eukaryotic genes that is composed with coding (exons) and non-coding (introns) segments, where introns are small in size making them difficult for detection. Another struggle in recognizing cystic fibrosis gene is because mammalian cells contains variety of repetitive DNA that can lead to incorrect cloning and blockage of DNA Replication and can cause instability. Both these complications, traditional cloning techniques are unable to process because large yield of exons would have to be visible to produce a signal for the cystic fibrosis gene to be identified and DNA would have to be free of any repetitive elements. | 1 | Biochemistry |
The transport of electrons from redox pair NAD/ NADH to the final redox pair 1/2 O/ HO can be summarized as
1/2 O + NADH + H → HO + NAD
The potential difference between these two redox pairs is 1.14 volt, which is equivalent to -52 kcal/mol or -2600 kJ per 6 mol of O.
When one NADH is oxidized through the electron transfer chain, three ATPs are produced, which is equivalent to 7.3 kcal/mol x 3 = 21.9 kcal/mol.
The conservation of the energy can be calculated by the following formula
Efficiency = (21.9 x 100%) / 52 = 42%
So we can conclude that when NADH is oxidized, about 42% of energy is conserved in the form of three ATPs and the remaining (58%) energy is lost as heat (unless the chemical energy of ATP under physiological conditions was underestimated). | 1 | Biochemistry |
An alternative classification with broader scope is suggested by Yujiro Hayashi as he describes certain organocatalytic Aldol reactions as taking place in the presence of water. The observed effect in these reactions is not rate acceleration (that would be on water), but an increase in enantioselectivity.
In the context of organocatalysis, both concepts of on-water reactions and in-the-presence-of-water reactions were criticized in 2007 as not so environmentally friendly by Donna Blackmond. According to Blackmond, separation of reaction product from the water phase usually requires organic solvent anyway, and in reported aqueous systems the water phase can in reality be less than 10% of the total reaction mixture with another component forming the actual solvent. Blackmond also notes that in reported instances, the observed rate-acceleration in presence of water is due to water suppressing reaction deactivation. | 0 | Organic Chemistry |
The spectrum of action includes many Gram-positive and Gram-negative bacteria (including Pseudomonas) and anaerobic bacteria. The overall spectrum is similar to that of imipenem, although meropenem is more active against Enterobacteriaceae and less active against Gram-positive bacteria. It works against extended-spectrum β-lactamases, but may be more susceptible to metallo-β-lactamases. Meropenem is frequently given in the treatment of febrile neutropenia. This condition frequently occurs in patients with hematological malignancies and cancer patients receiving anticancer drugs that suppress bone marrow formation. It is approved for complicated skin and skin structure infections, complicated intra-abdominal infections and bacterial meningitis.
In 2017, the U.S. Food and Drug Administration (FDA) granted approval for the combination of meropenem and vaborbactam to treat adults with complicated urinary tract infections. | 4 | Stereochemistry |
As described in the article Nociception, nociception is the sensory nervous system's response to harmful stimuli, such as a toxic chemical applied to a tissue. In nociception, chemical stimulation of sensory nerve cells called nociceptors produces a signal that travels along a chain of nerve fibers via the spinal cord to the brain. Nociception triggers a variety of physiological and behavioral responses and usually results in a subjective experience, or perception, of pain.
Work by Pan et al. first showed that TET1 and TET3 proteins are normally present in the spinal cords of mice. They used a pain inducing model of intra plantar injection of 5% formalin into the dorsal surface of the mouse hindpaw and measured time of licking of the hindpaw as a measure of induced pain. Protein expression of TET1 and TET3 increased by 152% and 160%, respectively, by 2 hours after formalin injection. Forced reduction of expression of TET1 or TET3 by spinal injection of Tet1-siRNA or Tet3-siRNA for three consecutive days before formalin injection alleviated the mouse perception of pain. On the other hand, forced overexpression of TET1 or TET3 for 2 consecutive days significantly produced pain-like behavior as evidenced by a decrease in the mouse of the thermal pain threshold.
They further showed that the nociceptive pain effects occurred through TET mediated conversion of 5-methylcytosine to 5-hydroxymethylcytosine in the promoter of a microRNA designated miR-365-3p, thus increasing its expression. This microRNA, in turn, ordinarily targets (decreases expression of) the messenger RNA of Kcnh2, that codes for a protein known as K11.1 or KCNH2. KCNH2 is the alpha subunit of a potassium ion channel in the central nervous system. Forced decrease in expression of TET1 or TET3 through pre-injection of siRNA reversed the decrease of KCNH2 protein in formalin-treated mice. | 1 | Biochemistry |
Carbon dioxide (CO) can be reduced to carbon monoxide (CO) and other more reduced compounds, such as methane, using the appropriate photocatalysts. One early example was the use of Tris(bipyridine)ruthenium(II) chloride (Ru(bipy)Cl) and cobalt chloride (CoCl) for CO reduction to CO. In recent years many new catalysts have been found to reduce CO into CO, after which the CO could be used to make hydrocarbons using for example the Fischer-Tropsch process. The most promising system for the solar-powered reduction of CO is the combination of a photovoltaic cell with an electrochemical cell (PV+EC). Using solar-driven processes, CO can also be converted to other products such as formate and alcohols.
For the photovoltaic cell the highly efficient GaInP/GaAs/Ge solar cell has been used, but many other series-connected and/or tandem (multi-junction) PV architectures can be employed to deliver the required voltage and current density to drive the CO reduction reactions and provide reasonable product outflow. The solar cells/panels can be placed in direct contact with the electrolyzer(s), which can bring advantages in terms of system compactness and thermal management of both technologies, or separately for instance by placing the PV outdoors exposed to sunlight and the EC systems protected indoors.
The currently best performing electrochemical cell is the gas diffusion electrode (GED) flow cell. In which the CO reacts on Ag nanoparticles to produce CO. Solar to CO efficiencies of up to 19% have been reached, with minimal loss in activity after 20h.
CO can also be produced without a catalyst using microwave plasma driven dissociation of CO. This process is relatively efficient, with an electricity to CO efficiency of up to 50%, but with low conversion around 10%. These low conversions are not ideal, because CO and CO are hard to separate at large scale in a efficient manner. The big upside of this process is that it can be turned off and on quite rapidly and does not use scarce materials. The (weakly ionised) plasma is produced using microwaves, these microwaves can accelerate the free electrons in the plasma. These electrons interact with the CO which vibrationally excite the CO, this leads to dissociation of the CO to CO. The excitation and dissociation happens fast enough that only a little bit of the energy is converted to heat, which keeps the efficiency high. The dissociation also produces an oxygen radical, which reacts with CO to CO and O.
Also in this case, the use of microorganisms has been explored. Using genetic engineering and synthetic biology techniques, parts of or whole biofuel-producing metabolic pathways can be introduced in photosynthetic organisms. One example is the production of 1-butanol in Synechococcus elongatus using enzymes from Clostridium acetobutylicum, Escherichia coli and Treponema denticola. One example of a large-scale research facility exploring this type of biofuel production is the AlgaePARC in the Wageningen University and Research Centre, Netherlands. | 5 | Photochemistry |
Thermodynamically, proton coupled multiple-electron reduction of CO is easier than single electron reduction. But to manage multiple proton coupled multiple-electron processes is a huge challenge kinetically. This leads to a high overpotential for electrochemical heterogeneous reduction of CO to hydrocarbons and alcohols. Even further heterogeneous reduction of singly reduced CO radical anion is difficult because of repulsive interaction between negatively biased electrode and negatively charged anion.
Figure 2 shows that in case of a p-type semiconductor/liquid junction photo generated electrons are available at the semiconductor/liquid interface under illumination. The reduction of redox species happens at less negative potential on illuminated p-type semiconductor compared to metal electrode due to the band bending at semiconductor/liquid interface. Figure 3 shows that thermodynamically, some of the proton-coupled multi-electron CO reductions are within semiconductors band gap. This makes it feasible to photo-reduce CO on p-type semiconductors. Various p-type semiconductors have been successfully employed for CO photo reduction including p-GaP, p-CdTe, p-Si, p-GaAs, p-InP, and p-SiC. Kinetically, however, these reactions are extremely slow on given semiconductor surfaces; this leads to significant overpotential for CO reduction on these semiconductor surfaces. Apart from high overpotential; these systems have a few advantages including sustainability (nothing is consumed in this system apart from light energy), direct conversion of solar energy to chemical energy, utilization of renewable energy resource for energy intensive process, stability of the process (semiconductors are really stable under illumination) etc. A different approach for photo-reduction of CO involves molecular catalysts, photosensitizers and sacrificial electron donors. In this process sacrificial electron donors are consumed during the process and photosensitizers degrade under long exposure to illumination. | 5 | Photochemistry |
NanoDSF is a modified differential scanning fluorimetry method to determine protein stability employing intrinsic tryptophan or tyrosine fluorescence.
Protein stability is typically addressed by thermal or chemical unfolding experiments. In thermal unfolding experiments, a linear temperature ramp is applied to unfold proteins, whereas chemical unfolding experiments use chemical denaturants in increasing concentrations.
The thermal stability of a protein is typically described by the melting temperature or Tm, at which 50% of the protein population is unfolded, corresponding to the midpoint of the transition from folded to unfolded.
In contrast to conventional DSF methods, nanoDSF uses tryptophan or tyrosine fluorescence to monitor protein unfolding. Both the fluorescence intensity and the fluorescence maximum strongly depends on the close surroundings of the tryptophan. Therefore, the ratio of the fluorescence intensities at 350 nm and 330 nm is suitable to detect any changes in protein structure, for example due to protein unfolding.
Its applications include antibody engineering, membrane protein research, quality control and formulation development. NanoDSF has also been utilized to rapidly evaluate the melting points of enzyme libraries for biotechnological applications. | 1 | Biochemistry |
Transition metal carbon dioxide complexes undergo a variety of reactions. Metallacarboxylic acids protonate at oxygen and eventually convert to metal carbonyl complexes:
:[LMCO] + 2 H → [LMCO] + HO
This reaction is relevant to the potential catalytic conversion of CO to fuels. | 0 | Organic Chemistry |
In compound B in Figure 10 B, the bottom section contains a tertiary amino group, also capable of binding to protons. In this system, fluorescence only takes place when both cations available. The presence of both cations hinders photoinduced electron transfer (PET) allowing compound B to fluoresce. In the absence of both or either ion, fluorescence is quenched by PET, which involves an electron transfer from either the nitrogen atom or the oxygen atoms, or both to the anthracenyl group. When both receptors are bound to calcium ions and protons respectively, both PET channels are shut off. The overall result of Compound B is AND logic, since an output of "1" (fluorescence) occurs only when both Ca and H are present in solution, that is, have values as "1". With both systems run in parallel and with monitoring of transmittance for system A and fluorescence for system B the result is a half-adder capable of reproducing the equation 1 + 1 = 2.
In a modification of system B, not two, but three chemical inputs are simultaneously processed in an AND logic gate. An enhanced fluorescence signal is observed only in the presence of excess protons, zinc and sodium ions through interactions with their respective amine, phenyldiaminocarboxylate, and crown ether receptors. The processing mode operates similarly as discussed above – fluorescence is observed due to the prevention of competing photoinduced electron transfer reactions from the receptors to the excited anthracene fluorophore. The absence of one, two, or all three ion inputs results in a low fluorescence output. Each receptor is selective for its specific ion as an increase in the concentration of the other ions does not yield a high fluorescence. The specific concentration threshold of each input must be reached to achieve a fluorescent output in accordance with combinatorial AND logic. | 6 | Supramolecular Chemistry |
An initial metabolic reconstruction of a genome is typically far from perfect due to the high variability and diversity of microorganisms. Often, metabolic pathway databases such as KEGG and MetaCyc will have "holes", meaning that there is a conversion from a substrate to a product (i.e., an enzymatic activity) for which there is no known protein in the genome that encodes the enzyme that facilitates the catalysis. What can also happen in semi-automatically drafted reconstructions is that some pathways are falsely predicted and don't actually occur in the predicted manner. Because of this, a systematic verification is made in order to make sure no inconsistencies are present and that all the entries listed are correct and accurate. Furthermore, previous literature can be researched in order to support any information obtained from one of the many metabolic reaction and genome databases. This provides an added level of assurance for the reconstruction that the enzyme and the reaction it catalyzes do actually occur in the organism.
Enzyme promiscuity and spontaneous chemical reactions can damage metabolites. This metabolite damage, and its repair or pre-emption, create energy costs that need to be incorporated into models. It is likely that many genes of unknown function encode proteins that repair or pre-empt metabolite damage, but most genome-scale metabolic reconstructions only include a fraction of all genes.
Any new reaction not present in the databases needs to be added to the reconstruction. This is an iterative process that cycles between the experimental phase and the coding phase. As new information is found about the target organism, the model will be adjusted to predict the metabolic and phenotypical output of the cell. The presence or absence of certain reactions of the metabolism will affect the amount of reactants/products that are present for other reactions within the particular pathway. This is because products in one reaction go on to become the reactants for another reaction, i.e. products of one reaction can combine with other proteins or compounds to form new proteins/compounds in the presence of different enzymes or catalysts.
Francke et al. provide an excellent example as to why the verification step of the project needs to be performed in significant detail. During a metabolic network reconstruction of Lactobacillus plantarum, the model showed that succinyl-CoA was one of the reactants for a reaction that was a part of the biosynthesis of methionine. However, an understanding of the physiology of the organism would have revealed that due to an incomplete tricarboxylic acid pathway, Lactobacillus plantarum does not actually produce succinyl-CoA, and the correct reactant for that part of the reaction was acetyl-CoA.
Therefore, systematic verification of the initial reconstruction will bring to light several inconsistencies that can adversely affect the final interpretation of the reconstruction, which is to accurately comprehend the molecular mechanisms of the organism. Furthermore, the simulation step also ensures that all the reactions present in the reconstruction are properly balanced. To sum up, a reconstruction that is fully accurate can lead to greater insight about understanding the functioning of the organism of interest. | 1 | Biochemistry |
For compounds with the formula MX, the chief alternative to octahedral geometry is a trigonal prismatic geometry, which has symmetry D. In this geometry, the six ligands are also equivalent. There are also distorted trigonal prisms, with C symmetry; a prominent example is . The interconversion of Δ- and Λ-complexes, which is usually slow, is proposed to proceed via a trigonal prismatic intermediate, a process called the "Bailar twist". An alternative pathway for the racemization of these same complexes is the Ray–Dutt twist. | 4 | Stereochemistry |
Photochlorinations are usually effected in the liquid phase, usually employing chemically inert solvents. | 5 | Photochemistry |
Briefly, when sheared genomic DNA in solution is heated to near boiling temperature, the molecular forces holding complementary base pairs together are disrupted, and the two strands of each double-helix dissociate or ‘denature.’ If the denatured DNA is then slowly returned to a cooler temperature, sequences will begin to ‘reassociate’ (renature) with complementary strands.
The temperature at which renaturation occurs can be regulated so that little or no sequence mismatch is tolerated. The rate at which a sequence finds a complementary strand with which to hybridize is directly related to how common that sequence is in the genome. In other words, those sequences that are extremely abundant (on average) find complementary strands with which to pair relatively quickly while single-copy sequences take much longer to find complements.
In CF, genomic DNA is heat-denatured and allowed to renature to a Cot value (Cot = DNA concentration x time x a factor based on the cation concentration of the buffer) at which the majority of repetitive elements have reassociated but single and low-copy elements remain single stranded. Double-stranded, repetitive DNA is separated from single-stranded, low-copy DNA by hydroxyapatite chromatography or other means. | 1 | Biochemistry |
The Arthashastra lays down the role of the Director of Metals, the Director of Forest Produce and the Director of Mining. It is the duty of the Director of Metals to establish factories for different metals. The Director of Mines is responsible for the inspection of mines. The Arthashastra also refers to counterfeit coins. | 8 | Metallurgy |
There are several biologically important kinds of heme:
The most common type is heme B; other important types include heme A and heme C. Isolated hemes are commonly designated by capital letters while hemes bound to proteins are designated by lower case letters. Cytochrome a refers to the heme A in specific combination with membrane protein forming a portion of cytochrome c oxidase. | 1 | Biochemistry |
In organometallic chemistry, alpha elimination refers to reactions of this type (other spectator ligands omitted):
:X-M-CHR → M=CHR + HX
Well studied case are found in organotantalum chemistry leading to an alkylidene derivatives. Specifically, tetraalkyl-monochloro-tantalum complex undergoes α-hydrogen elimination, followed by alkylation of the remaining chloride to give a derivative with a Ta=C bond.
Alpha elimination contrasts with β-hydride elimination, whereby an alkyl group bonded to a metal centre is converted into the corresponding metal-bonded hydride and an alkene.
Both α- and β-eliminations proceed via agostic intermediates. | 0 | Organic Chemistry |
Levonorgestrel is marketed alone or in combination with an estrogen (specifically ethinylestradiol, estradiol, or estradiol valerate) under a multitude of brand names throughout the world, including Alesse, Altavera, Alysena, Amethia, Amethyst, Ashlyna, Aviane, Camrese, Chateal, Climara Pro, Cycle 21, Daysee, Emerres, Enpresse, Erlibelle, Escapelle, Falmina, Introvale, Isteranda, Jadelle, Jaydess, Jolessa, Klimonorm, Kurvelo, Kyleena, Lessina, Levlen, Levodonna, Levonelle, Levonest, Levosert, Levora, Liletta, Loette, Logynon, LoSeasonique, Lutera, Lybrel, Marlissa, Microgynon, Microlut, Microvlar, Min-Ovral, Miranova, Mirena, My Way, Myzilra, Next Choice, Nordette, Norgeston, NorLevo, Norplant, One Pill, Option 2, Orsythia, Ovima, Ovranette, Plan B, Plan B One-Step, Portia, Postinor, Postinor-2, Preventeza, Ramonna, Rigevidon, Quartette, Quasense, Seasonale, Seasonique, Skyla, Sronyx, Tri-Levlen, Trinordiol, Triphasil, Triquilar, Tri-Regol, Trivora, and Upostelle, among many others. These formulations are used as emergency contraceptives, normal contraceptives, or in menopausal hormone therapy for the treatment of menopausal symptoms.
As an emergency contraceptive, levonorgestrel is often referred to colloquially as the "morning-after pill". | 4 | Stereochemistry |
Protein–protein interaction screening refers to the identification of Protein–protein interaction with high-throughput screening methods such as computer- and/or robot-assisted plate reading, flow cytometry analyzing.
The interactions between proteins are central to virtually every process in a living cell. Information about these interactions improves understanding of diseases and can provide the basis for new therapeutic approaches. | 1 | Biochemistry |
* Gyftopoulos, E.P., & Beretta, G.P. (1991). Thermodynamics: foundations and applications. (Dover Publications)
* Hatsopoulos, G.N., & Keenan, J.H. (1981). Principles of general thermodynamics. RE Krieger Publishing Company. | 7 | Physical Chemistry |
Porphyrins ( ) are a group of heterocyclic macrocycle organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges (=CH−). In vertebrates, an essential member of the porphyrin group is heme, which is a component of hemoproteins, whose functions include carrying oxygen in the bloodstream. In plants, an essential porphyrin derivative is chlorophyll, which is involved in light harvesting and electron transfer in photosynthesis.
The parent of porphyrins is porphine, a rare chemical compound of exclusively theoretical interest. Substituted porphines are called porphyrins. With a total of 26 π-electrons, of which 18 π-electrons form a planar, continuous cycle, the porphyrin ring structure is often described as aromatic. One result of the large conjugated system is that porphyrins typically absorb strongly in the visible region of the electromagnetic spectrum, i.e. they are deeply colored. The name "porphyrin" derives from the Greek word πορφύρα (porphyra), meaning purple. | 1 | Biochemistry |
Bis(trimethylsilyl)amine is synthesized by treatment of trimethylsilyl chloride with ammonia:
:2 (CH)SiCl + 3 NH → [(CH)Si]NH + 2 NHCl
Ammonium nitrate together with triethylamine can be used instead. This method is also useful for N isotopic enrichment of HMDS.
Alkali metal bis(trimethylsilyl)amides result from the deprotonation of bis(trimethylsilyl)amine. For example, lithium bis(trimethylsilyl)amide (LiHMDS) is prepared using n-butyllithium:
:[(CH)Si]NH + BuLi → [(CH)Si]NLi + BuH
LiHMDS and other similar derivatives: sodium bis(trimethylsilyl)amide (NaHMDS) and potassium bis(trimethylsilyl)amide (KHMDS) are used as a non-nucleophilic bases in synthetic organic chemistry. | 0 | Organic Chemistry |
A molecular logic gate can processes modulators much like the setup seen in de Silva’s proof-of-principle, but incorporating different logic gates on the same molecule is challenging. Such a function is called integrated logic and is exemplified by the BODIPY-based, half-subtractor logic gate illustrated by Coskun, Akkaya, and their colleagues. When monitored at two different wavelengths, 565 and 660 nm, XOR and INHIBIT logic gates operations are realized at the respective wavelengths. Optical studies of this compound in THF reveal an absorbance peak at 565 nm and an emission peak at 660 nm. Addition of an acid results in a hypsochromic shift of both peaks as protonation of the tertiary amine results in an internal charge transfer. The colour of the emission observed is yellow. Upon the addition of a strong base, the phenolic hydroxyl group is rendered deprotonated, resulting in a photoinduced electron transfer, which in turn renders the molecule non-emissive. Upon addition of both an acid and a base, the emission of the molecule is observed as red, as the tertiary amine would not be protonated while the hydroxyl group would remain protonated, resulting in the absence of both PET and intramolecular charge transfer (ICT). Due to the great difference in emission intensity, this single molecule is capable of carrying out an arithmetic operation - subtraction - at a nanoscale level.
A full adder system based on fluorescein has also been constructed by Shanzer et al. The system is able to compute 1+1+1=3. | 6 | Supramolecular Chemistry |
CMTM6 localizes with and binds to cell PD-L1 protein located on cell surface membranes thereby maintaining PD-L1'S expression at this site; it also localizes with PD-L1 protein located in recycling endosomes and thereby prevents PD-L1 from being degraded by lysosomal enzymes. These actions increase and maintain high levels of PD-L1 on cell surface membranes. PD-L1 protein on the surface of normal cells binds to PD-1 receptors on a type of cytotoxic T cells (i.e. CD8+ T cells) and thereby blocks these T-cells from organizing an immune response that would kill them. This PD-L1/CD8+ T cell circuit is one of several immune checkpoint mechanisms for maintaining self-tolerance, i.e. for preventing CD8+ T cells from attacking normal cells. Tumor cells may employ this immune-evading tactic: they may express PD-L1 and thereby block CD8+ T cell-mediated immune responses to themselves. In effect, the robust expression of PD-L1 helps not only normal cells but also cancer cells to evade immune destruction. | 1 | Biochemistry |
Non-viral vectors for gene therapy present certain advantages over viral methods, such as large scale production and low host immunogenicity. However, non-viral methods initially produced lower levels of transfection and gene expression, and thus lower therapeutic efficacy. Newer technologies offer promise of solving these problems, with the advent of increased cell-specific targeting and subcellular trafficking control.
Methods for non-viral gene therapy include the injection of naked DNA, electroporation, the gene gun, sonoporation, magnetofection, the use of oligonucleotides, lipoplexes, dendrimers, and inorganic nanoparticles. These therapeutics can be administered directly or through scaffold enrichment.
More recent approaches, such as those performed by companies such as Ligandal, offer the possibility of creating cell-specific targeting technologies for a variety of gene therapy modalities, including RNA, DNA and gene editing tools such as CRISPR. Other companies, such as Arbutus Biopharma and Arcturus Therapeutics, offer non-viral, non-cell-targeted approaches that mainly exhibit liver trophism. In more recent years, startups such as Sixfold Bio, GenEdit, and Spotlight Therapeutics have begun to solve the non-viral gene delivery problem. Non-viral techniques offer the possibility of repeat dosing and greater tailorability of genetic payloads, which in the future will be more likely to take over viral-based delivery systems.
Companies such as Editas Medicine, Intellia Therapeutics, CRISPR Therapeutics, Casebia, Cellectis, Precision Biosciences, bluebird bio, Excision BioTherapeutics, and Sangamo have developed non-viral gene editing techniques, however frequently still use viruses for delivering gene insertion material following genomic cleavage by guided nucleases. These companies focus on gene editing, and still face major delivery hurdles.
BioNTech, Moderna Therapeutics and CureVac focus on delivery of mRNA payloads, which are necessarily non-viral delivery problems.
Alnylam, Dicerna Pharmaceuticals, and Ionis Pharmaceuticals focus on delivery of siRNA (antisense oligonucleotides) for gene suppression, which also necessitate non-viral delivery systems.
In academic contexts, a number of laboratories are working on delivery of PEGylated particles, which form serum protein coronas and chiefly exhibit LDL receptor mediated uptake in cells in vivo. | 1 | Biochemistry |
One-compartment kinetics for a chemical compound specifies that the uptake in the compartment is proportional to the concentration outside the compartment, and the elimination is proportional to the concentration inside the compartment. Both the compartment and the environment outside the compartment are considered to be homogeneous (well mixed).The compartment typically represents some organism (e.g. a fish or a daphnid).
This model is used in the simplest versions of the DEBtox method for the quantification of effects of toxicants. | 1 | Biochemistry |
Multicomponent solvents appeared after World War II in the USSR, and continue to be used and produced in the post-Soviet states. These solvents may have one or more applications, but they are not universal preparations. | 2 | Environmental Chemistry |
Suzuki has not obtained a patent on Suzuki reaction technology because he thinks that the research was supported by government funds, therefore coupling technology has become widespread, and many products using this technology have been put into practical use. To date, there are more than 6,000 papers and patents related to Suzuki reaction. | 0 | Organic Chemistry |
The symmetry factor (or barrier symmetry factor) is a coefficient similar to the transfer coefficient, but applicable only to single-step reactions.
The sum of anodic symmetry factor and cathodic symmetry factor is equal to one: | 7 | Physical Chemistry |
* 1.H.1 The Claudin Tight Junction (Claudin1) Family
* 1.H.2 The Invertebrate PMP22-Claudin (Claudin2) Family | 1 | Biochemistry |
The ratio of N to N is of relevance because in most biological contexts, N is preferentially uptaken as the lighter isotope. As a result, samples enriched in N can often be introduced through a non-biological context.
One use of N is as a tracer to determine the path taken by fertilizers applied to anything from pots to landscapes. Fertilizer enriched in N to an extent significantly different from that prevailing in the soil (which may be different from the atmospheric standard a) is applied at a point and other points are then monitored for variations in .
Another application is the assessment of human waste water discharge into bodies of water. The abundance of N is greater in human waste water than in natural water sources. Hence in benthic sediment gives an indication of the contribution of human waste to the total nitrogen in the sediment. Sediment cores analyzed for yield an historical record of such waste, with older samples at greater depths.
is also used to measure food chain length and the trophic level of a given organism; high values are positively correlated with higher trophic levels; likewise, organisms low on the food chain generally exhibit lower values. Higher values in apex predators generally indicate longer food chains. | 9 | Geochemistry |
The term is used to describe a transient chemical species. As a general example, if a molecule exists in a particular conformation for a short lifetime, before adopting a lower energy conformation (structural arrangement), the former molecular structure is said to have high lability (such as C, a 25-carbon fullerene spheroid). The term is sometimes also used in reference to reactivity – for example, a complex that quickly reaches equilibrium in solution is said to be labile (with respect to that solution). Another common example is the cis effect in organometallic chemistry, which is the labilization of CO ligands in the cis position of octahedral transition metal complexes. | 1 | Biochemistry |
A stock BCA solution contains the following ingredients in a highly alkaline solution with a pH 11.25: bicinchoninic acid, sodium carbonate, sodium bicarbonate, sodium tartrate, and copper(II) sulfate pentahydrate.
The BCA assay primarily relies on two reactions. First, the peptide bonds in protein reduce Cu ions from the copper(II) sulfate to Cu (a temperature dependent reaction). The amount of Cu reduced is proportional to the amount of protein present in the solution. Next, two molecules of bicinchoninic acid chelate with each Cu ion, forming a purple-colored complex that strongly absorbs light at a wavelength of 562 nm.
The bicinchoninic acid Cu complex is influenced in protein samples by the presence of cysteine/cystine, tyrosine, and tryptophan side chains. At higher temperatures (37 to 60 °C), peptide bonds assist in the formation of the reaction complex. Incubating the BCA assay at higher temperatures is recommended as a way to increase assay sensitivity while minimizing the variances caused by unequal amino acid composition.
The amount of protein present in a solution can be quantified by measuring the absorption spectra and comparing with protein solutions of known concentration. | 1 | Biochemistry |
A Canadian study of pregnant women suggests that those taking any type or amount of NSAIDs (including ibuprofen, diclofenac, and naproxen) were 2.4 times more likely to miscarry than those not taking the medications. However, an Israeli study found no increased risk of miscarriage in the group of mothers using NSAIDs. | 4 | Stereochemistry |
Structural differences between capsaicin and members of the capsinoid family of compounds are illustrated below. Capsinoids have an ester bond in their structures, as compared with the amide bond characteristic of capsaicin. | 1 | Biochemistry |
The mitochondrial unfolded protein response (UPR) is a cellular stress response related to the mitochondria. The UPR results from unfolded or misfolded proteins in mitochondria beyond the capacity of chaperone proteins to handle them. The UPR can occur either in the mitochondrial matrix or in the mitochondrial inner membrane. In the UPR, the mitochondrion will either upregulate chaperone proteins or invoke proteases to degrade proteins that fail to fold properly. UPR causes the sirtuin SIRT3 to activate antioxidant enzymes and mitophagy.
Mitochondrial electron transport chain mutations that extend the life span of Caenorhabditis elegans (nematode worms) also activate the UPR. Activation of the UPR in nematode worms by increasing NAD+ by supplementation with nicotinamide or nicotinamide riboside has been shown to extend lifespan. Glial and germline mitochondria has been found to play a significant role in the signalling and regulation of UPR have been shown to play a central role Nicotinamide riboside supplementation in mice has also been shown to activate the UPR. | 1 | Biochemistry |
Topochemical polymerization can also be triggered by pressure. It has been reported that the cocrystal of diododiacetylene (guest) and bispyridyl oxalamide (host) could be polymerized under pressure. Interestingly, no polymerization was observed under light or heat due to the unfavorable distance between diacetylene units. The researcher postulated that the high pressure might "squeeze" the reactive site together and initiate the polymerization. | 7 | Physical Chemistry |
The Langmuir adsorption model deviates significantly in many cases, primarily because it fails to account for the surface roughness of the adsorbent. Rough inhomogeneous surfaces have multiple site types available for adsorption, with some parameters varying from site to site, such as the heat of adsorption. Moreover, specific surface area is a scale-dependent quantity, and no single true value exists for this parameter. Thus, the use of alternative probe molecules can often result in different obtained numerical values for surface area, rendering comparison problematic.
The model also ignores adsorbate–adsorbate interactions. Experimentally, there is clear evidence for adsorbate–adsorbate interactions in heat of adsorption data. There are two kinds of adsorbate–adsorbate interactions: direct interaction and indirect interaction. Direct interactions are between adjacent adsorbed molecules, which could make adsorbing near another adsorbate molecule more or less favorable and greatly affects high-coverage behavior. In indirect interactions, the adsorbate changes the surface around the adsorbed site, which in turn affects the adsorption of other adsorbate molecules nearby. | 7 | Physical Chemistry |
The following table lists the sensitivity of different types of ANAs for different diseases.
Some ANAs appear in several types of disease, resulting in lower specificity of the test. For example, IgM-rheumatoid factor (IgM-RF) have been shown to cross-react with ANA giving falsely positive immunofluorescence. Positive ANA as well as anti-DNA antibodies have been reported in patients with autoimmune thyroid disease. ANA can have a positive test result in up to 45% of people with autoimmune thyroid conditions or rheumatoid arthritis and up to 15% of people with HIV or hepatitis C. As per Lupus Foundation of America, "about 5% of the general population will have a positive ANA. However, at least 95% of the people who have a positive ANA do not have lupus. A positive ANA test can sometimes run in families, even if family members have no evidence of lupus." On the other hand, they say, although 95% of the patients who actually have lupus test positive for ANA, "Only a small percentage have a negative ANA, and many of those have other antibodies (such as anti-phospholipid antibodies, anti-Ro, anti-SSA) or their ANA converted from positive to negative from steroids, cytotoxic medications, or uremia (kidney failure)." | 1 | Biochemistry |
LNGFR also activates a caspase-dependent signaling pathway that promotes developmental axon pruning, and axon degeneration in neurodegenerative disease.
In the apoptosis pathway, members of the TNF receptor superfamily assemble a death-inducing signaling complex (DISC) in which TRADD or FADD bind directly to the receptor's death domain, thereby allowing aggregation and activation of Caspase 8 and subsequent activation of the Caspase cascade. However, Caspase 8 induction does not appear to be involved in p75NTR-mediated apoptosis, but Caspase 9 is activated during p75NTR-mediated killing. | 1 | Biochemistry |
The pH-metric set of techniques determine lipophilicity pH profiles directly from a single acid-base titration in a two-phase water–organic-solvent system. Hence, a single experiment can be used to measure the logarithms of the partition coefficient (log P) giving the distribution of molecules that are primarily neutral in charge, as well as the distribution coefficient (log D) of all forms of the molecule over a pH range, e.g., between 2 and 12. The method does, however, require the separate determination of the pK value(s) of the substance. | 7 | Physical Chemistry |
The Lewis basic lone pairs on sulfur dominate the sulfides' reactivity. Sulfides readily alkylate to stable sulfonium salts, such as trimethylsulfonium iodide:
Sulfides also oxidize easily to sulfoxides (), which can themselves be further oxidized to sulfones (). Hydrogen peroxide is a typical oxidant—for example, with dimethyl sulfide ():
In analogy to their easy alkylation, sulfides bind to metals to form thioether complexes. Consequently Lewis acids do not decompose thioethers as they do ethers. Sulfides are soft ligands, but their affinity for metals is lower than typical phosphines. Chelating thioethers are known, such as 1,4,7-trithiacyclononane.
Sulfides undergo hydrogenolysis in the presence of certain metals:
Raney nickel is useful for stoichiometric reactions in organic synthesis whereas molybdenum-based catalysts are used to "sweeten" petroleum fractions, in the process called hydrodesulfurization.
Unlike ethers, thioethers are stable in the presence of Grignard reagents. The protons adjacent to the sulfur atom are labile, and can be deprotonated with strong bases. | 0 | Organic Chemistry |
The magnitude of the Coulomb interaction F between two ions of charge q and Q a distance R apart is given by
directed along the axis between the two ions, where a positive value represents a repulsive force and vice versa.
Trapping techniques include variations on the Paul trap and Penning trap, where the former uses only electric fields while the latter also uses magnetic fields to confine the ions. Considering the simple case of two ions confined in a linear Paul trap, we have a radiofrequency oscillating field, which itself can confine a single ion in the (axial?) direction. | 7 | Physical Chemistry |
Materials may be used to control and manipulate light via a variety of mechanisms to produce useful effects involving color. For instance, a change of orientation of molecules to produce a visual effect as in liquid crystal displays. Other materials operate by producing a physical effect, by interference and diffraction as in lustre pigments and optically variable pigments, colloidal photonic crystals and in holography. Increasingly inspiration is coming from Nature, in the form of bioinspired structural colors. Molecular materials are also used to increase the intensity of light by modifying its movement through the materials by electrical means, so increasing its intensity as in organic lasers, or in modifying the transmission of light through materials, as in opto-electronics, or by purely by all optical means as in optical limiters. | 5 | Photochemistry |
Partial agonists are defined as drugs that, at a given receptor, might differ in the amplitude of the functional response that they elicit after maximal receptor occupancy. Although they are agonists, partial agonists can act as a competitive antagonist in the presence of a full agonist, as it competes with the full agonist for receptor occupancy, thereby producing a net decrease in the receptor activation as compared to that observed with the full agonist alone. Clinically, their usefulness is derived from their ability to enhance deficient systems while simultaneously blocking excessive activity. Exposing a receptor to a high level of a partial agonist will ensure that it has a constant, weak level of activity, whether its normal agonist is present at high or low levels. In addition, it has been suggested that partial agonism prevents the adaptive regulatory mechanisms that frequently develop after repeated exposure to potent full agonists or antagonists. E.g. Buprenorphine, a partial agonist of the μ-opioid receptor, binds with weak morphine-like activity and is used clinically as an analgesic in pain management and as an alternative to methadone in the treatment of opioid dependence. | 1 | Biochemistry |
Brown dwarfs have greater internal heating than gas giants but not as great as stars. The internal heating within brown dwarfs (initially generated by gravitational contraction) is great enough to ignite and sustain fusion of deuterium with hydrogen to helium; for the largest brown dwarfs, it is also enough to ignite and sustain fusion of lithium with hydrogen, but not fusion of hydrogen with itself. Like gas giants, brown dwarfs can have weather and wind powered by internal heating. Brown dwarfs are substellar objects not massive enough to sustain hydrogen-1 fusion reactions in their cores, unlike main-sequence stars. Brown dwarfs occupy the mass range between the heaviest gas giants and the lightest stars, with an upper limit around 75 to 80 Jupiter masses (MJ). Brown dwarfs heavier than about 13 MJ are thought to fuse deuterium and those above ~65 MJ, fuse lithium as well. | 7 | Physical Chemistry |
Bacteriophage P1 vectors can hold inserts 70 – 100kb in size. They begin as linear DNA molecules packaged into bacteriophage P1 particles. These particles are injected into an E. coli strain expressing Cre recombinase. The linear P1 vector becomes circularized by recombination between two loxP sites in the vector. P1 vectors generally contain a gene for antibiotic resistance and a positive selection marker to distinguish clones containing an insert from those that do not. P1 vectors also contain a P1 plasmid replicon, which ensures only one copy of the vector is present in a cell. However, there is a second P1 replicon- called the P1 lytic replicon- that is controlled by an inducible promoter. This promoter allows the amplification of more than one copy of the vector per cell prior to DNA extraction. | 1 | Biochemistry |
Brown adipose tissue stores free fatty acids rather than triglycerides, and is especially abundant in newborn and hibernating mammals. Brown adipose tissue is involved in thermogenesis, and has a considerably higher glyceroneogenesis activity. Brown adipose tissue contains more glyceroneogenesis-related enzymes, in particular PEPC-K and glycerol kinase. PEPC-K is around 10 times more active than in white adipose tissue, and is the key regulatory enzyme that controls the activity of the pathway. Glycerol kinase phosphorylates glycerol to generate glycerol 3-phosphate, which is used to build triglycerides. An increase in the activity of glycerol kinase will increase the production of glycerol 3-phosphate.
Glyceroneogenesis in brown adipose tissue contributes to thermogenesis, a process that generates heat in warm-blooded animals by delivering free fatty acids to the mitochondria. In normal conditions, thermogenesis is down-regulated by the low concentration of free fatty acids in the cytosol, because glyceroneogenesis re-esterifies fatty acids to triglycerides. When exposed to cold, a neurotransmitter hormone called norepinephrine suppresses the activity of PEPC-K and thus the glyceroneogenesis re-esterification, increasing the availability of free fatty acids within the cell. Excess free fatty acids in the cytosol will consequently be delivered to the mitochondria for thermogenesis. | 1 | Biochemistry |
Hydrogen-bonded organic frameworks are crystalline porous polymers assembled from organic monomers linked through hydrogen bonds. | 6 | Supramolecular Chemistry |
The nines are a count of the leftmost digits 9 that appear in a proportion. For example, 90% would be described as "one nine"; 99% as "two nines"; 99.9% as "three nines"; and so forth.
However, there are different conventions for representing inexact multiples of 9. For example, a percentage of 99.5% could be expressed as "two nines five" (2N5, or N2.5) or as 2.3 nines, following from the logarithm definition.
A percentage of 100% would, in theory, have an infinite number of nines – though, in the context of purity of materials, 100% is virtually unachievable.
The number of nines of a proportion is: | 8 | Metallurgy |
In 2003, a research team inserted genes into the brain for the first time. They used liposomes coated in a polymer called polyethylene glycol, which unlike viral vectors, are small enough to cross the blood–brain barrier.
Short pieces of double-stranded RNA (short, interfering RNAs or siRNAs) are used by cells to degrade RNA of a particular sequence. If a siRNA is designed to match the RNA copied from a faulty gene, then the abnormal protein product of that gene will not be produced.
Gendicine is a cancer gene therapy that delivers the tumor suppressor gene p53 using an engineered adenovirus. In 2003, it was approved in China for the treatment of head and neck squamous cell carcinoma. | 1 | Biochemistry |
The photophysical properties of the FbFPs are determined by the chromophore itself and its chemical surrounding in the protein. The extinction coefficient (ε) is around 14.200 Mcm at 450 nm for all described FbFPs, which is slightly higher than that of free FMN (ε = 12.200 Mcm ). The Fluorescence-Quantum yield (Φ) varies significantly between different FbFPs and ranges from 0.2 (phiLOV2.1) to 0.44 (EcFbFP and iLOV). This represents an almost twofold increase compared to free FMN (Φ = 0.25).<br />
The difference to free FMN is even more significant in the case of the photostabaility, the proteins resistance to bleach out during prolonged and intense irradiation with blue light. Based on the bleaching-halftime (the times it takes to reduce the initial fluorescence intensity to 50% upon illumination) the genetically engineered variant phiLOV2.1 is approximately 40x as stable as free FMN. This stabilizing effect can be observed for almost all FbFPs, although it is usually in the range of 5x - 10x.<br />
The average fluorescence lifetime of FbFPs is in the range of 3.17 (Pp2FbFP) and 5.7 ns (e.g. EcFbFP). They are thereby much longer than the ones of GFP derivatives, which are usually between 1,5 and 3 ns.
FbFPs are therefore well suited as donor domains in Förster resonance energy transfer (FRET) systems in conjunction with GFP derivatives like YFP as acceptor domains. | 1 | Biochemistry |
Phosphorus trichloride () is popular, although excess reagent is required. Phosphorus pentachloride () is also effective, but only one chloride is transferred: | 0 | Organic Chemistry |
Electrofiltration is a method that combines membrane filtration and electrophoresis in a dead-end process.
Electrofiltration is regarded as an appropriate technique for concentration and fractionation of biopolymers. The film formation on the filter membrane which hinders filtration can be minimized or completely avoided by the application of electric field, improving filtration’s performance and increasing selectivity in case of fractionation. This approach reduces significantly the expenses for downstream processing in bioprocesses. | 3 | Analytical Chemistry |
Ketosis is a metabolic state characterized by elevated levels of ketone bodies in the blood or urine. Physiological ketosis is a normal response to low glucose availability, such as low-carbohydrate diets or fasting, that provides an additional energy source for the brain in the form of ketones. In physiological ketosis, ketones in the blood are elevated above baseline levels, but the body's acid–base homeostasis is maintained. This contrasts with ketoacidosis, an uncontrolled production of ketones that occurs in pathologic states and causes a metabolic acidosis, which is a medical emergency. Ketoacidosis is most commonly the result of complete insulin deficiency in type 1 diabetes or late-stage type 2 diabetes. Ketone levels can be measured in blood, urine or breath and are generally between 0.5 and 3.0 millimolar (mM) in physiological ketosis, while ketoacidosis may cause blood concentrations greater than 10 mM.
Trace levels of ketones are always present in the blood and increase when blood glucose reserves are low and the liver shifts from primarily metabolizing carbohydrates to metabolizing fatty acids. This occurs during states of increased fatty acid oxidation such as fasting, starvation, carbohydrate restriction, or prolonged exercise. When the liver rapidly metabolizes fatty acids into acetyl-CoA, some acetyl-CoA molecules can then be converted into ketone bodies: pyruvate, acetoacetate, beta-hydroxybutyrate, and acetone. These ketone bodies can function as an energy source as well as signalling molecules. The liver itself cannot utilize these molecules for energy, so the ketone bodies are released into the blood for use by peripheral tissues including the brain.
When ketosis is induced by carbohydrate restriction, it is sometimes referred to as nutritional ketosis. A low-carbohydrate, moderate protein diet that can lead to ketosis is called a ketogenic diet. Ketosis is well-established as a treatment for epilepsy and is also effective in treating type 2 diabetes. | 1 | Biochemistry |
As a postdoctoral researcher, Holmes worked on the total synthesis of Vitamin B with Albert Eschenmoser.
In 1972 he was appointed as a demonstrator to the University of Cambridge where he stayed for 32 years, ultimately as Professor of Organic and Polymer Chemistry, and Director of the Melville Laboratory for Polymer Synthesis where he oversaw the founding and initial decade of the Melville Laboratory.
Holmes early work at Cambridge expanded his interest in new techniques for synthesising small molecules that are biologically-active and practically-useful, including natural products (such as alkaloids) and peptidomimetics. In 1989, during systematic characterisation of a newly synthesised conductive polymer, Chloe Jennings working in Holmes research group observed that the polymer emitted light when a current was passed through it. An intensive period of research in Holmes group, and other polymer chemistry groups, led to the discovery of differently-coloured light-emitting polymers that spanned the visible colour spectrum. A subsequent collaboration with physicist Richard Friend and co-workers at Cambridges Cavendish Laboratory revealed the potential of these conjugated polymers for applications such as organic LEDs and rollable displays.
Friend and Holmes co-founded the company Cambridge Display Technology for commercial exploitation of these materials – an early success story of Silicon Fen.
In 2004 Holmes returned to his native Australia on a Federation Fellowship, to lead a group at the newly established Bio21 Institute. He has pursued the application of photovoltaic polymers to solar energy, and was instrumental in forming the Victorian Organic Solar Cell Consortium. He has also continued to develop new syntheses of novel, biologically-useful materials. An example is his groups' synthesis of phosphoinositides, amphiphilic phospholipids situated in the cell membrane, which collaborators at the Ludwig Institute for Cancer Research have used to probe the dynamics of signal transduction (intercellular signalling being an important component of many aspects of cell biology, including that of tumors).
Holmes has served on the editorial or advisory boards of numerous learned scientific journals, including Organic Letters, Chemical Communications and Angewandte Chemie. In 2006, his 1998 paper on electroluminescent polymers was the most highly cited paper in Angewandte Chemie's 120-year history. By August 2012 he had authored over 490 scientific papers and 52 patent applications.
In 2014 he was appointed as President of the Australian Academy of Science. | 0 | Organic Chemistry |
Eoxin E4, also known as 14,15-leukotriene E4, is an eoxin. Cells make eoxins by metabolizing arachidonic acid with a 15-lipoxygenase enzyme to form 15(S)-hydroperoxyeicosapentaenoic acid (i.e. 15(S)-HpETE). This product is then converted serially to eoxin A4 (i.e. EXA4), EXC4, EXD4, and EXE4 by LTC4 synthase, an unidentified gamma-glutamyltransferase, and an unidentified dipeptidase, respectively, in a pathway which appears similar if not identical to the pathway which forms leukotreines, i.e. LTA4, LTC4, LTD4, and LTE4. This pathway is schematically shown as follows:
EXA is viewed as an intracellular-bound, short-lived intermediate which is rapidly metabolized to the down-stream eoxins. The eoxins down stream of EXA4 are secreted from their parent cells and, it is proposed but not yet proven, serve to regulate allergic responses and the development of certain cancers (see Eoxins). | 1 | Biochemistry |
Drospirenone is an antagonist of the MR, the biological target of mineralocorticoids like aldosterone, and hence is an antimineralocorticoid. It has about 100 to 500% of the affinity of aldosterone for the MR and about 50 to 230% of the affinity of progesterone for the MR. Drospirenone is about 5.5 to 11 times more potent as an antimineralocorticoid than spironolactone in animals. Accordingly, 3 to 4 mg drospirenone is said to be equivalent to about 20 to 25 mg spironolactone in terms of antimineralocorticoid activity. It has been said that the pharmacological profile of drospirenone more closely resembles that of progesterone than other progestins due to its antimineralocorticoid activity. Drospirenone is the only clinically used progestogen with prominent antimineralocorticoid activity besides progesterone. For comparison to progesterone, a 200 mg dose of oral progesterone is considered to be approximately equivalent in antimineralocorticoid effect to a 25 to 50 mg dose of spironolactone. Both drospirenone and progesterone are actually weak partial agonists of the MR in the absence of mineralocorticoids.
Due to its antimineralocorticoid activity, drospirenone increases natriuresis, decreases water retention and blood pressure, and produces compensatory increases in plasma renin activity as well as circulating levels and urinary excretion of aldosterone. This has been shown to occur at doses of 2 to 4 mg/day. Similar effects occur during the luteal phase of the menstrual cycle due to increased progesterone levels and the resulting antagonism of the MR. Estrogens, particularly ethinylestradiol, activate liver production of angiotensinogen and increase levels of angiotensinogen and angiotensin II, thereby activating the renin–angiotensin–aldosterone system. As a result, they can produce undesirable side effects including increased sodium excretion, water retention, weight gain, and increased blood pressure. Progesterone and drospirenone counteract these undesirable effects via their antimineralocorticoid activity. Accumulating research indicates that antimineralocorticoids like drospirenone and spironolactone may also have positive effects on adipose tissue and metabolic health. | 4 | Stereochemistry |
The plot is occasionally attributed to Augustinsson and referred to the Woolf–Augustinsson–Hofstee plot or simply the Augustinsson plot. However, although Haldane, Woolf or Eadie were not explicitly cited when Augustinsson introduced the versus equation, both the work of Haldane and of Eadie are cited at other places of his work and are listed in his bibliography. | 1 | Biochemistry |
This precatalyst was uncovered in attempts to use tris(triphenylphosphine)rhodium chloride as a hydroformylation catalyst. It was found that the complex would quickly carbonylate and that the catalytic activity of the resulting material was enhanced by a variety of additives but inhibited by halides. This inhibition did not occur in the presence of base, suggesting that the hydrido-complex represented the catalytic form of the complex. | 0 | Organic Chemistry |
or
This exact result can be obtained from the general BAR method, using (for example) the Metropolis function, in the limit . Indeed, in that case, the denominator of the general case expression above tends to 1, while the numerator tends to .
A direct derivation from the definitions is more straightforward, though. | 7 | Physical Chemistry |
Thin films are thin material layers ranging from fractions of a nanometer to several micrometers in thickness. Thin-film thermoelectric materials are grown by conventional semiconductor deposition methods and fabricated using conventional semiconductor micro-fabrication techniques.
Thin-film thermoelectrics have been demonstrated to provide high heat pumping capacity that far exceeds the capacities provided by traditional bulk pellet TE products. The benefit of thin-films versus bulk materials for thermoelectric manufacturing is expressed in Equation 1. Here the Qmax (maximum heat pumped by a module) is shown to be inversely proportional to the thickness of the film, L.
Eq. 1
As such, TE coolers manufactured with thin-films can easily have 10x – 20x higher Qmax values for a given active area A. This makes thin-film TECs ideally suited for applications involving high heat-flux flows. In addition to the increased heat pumping capability, the use of thin films allows for truly novel implementation of TE devices. Instead of a bulk module that is 1–3 mm in thickness, a thin-film TEC can be fabricated less than 100 um in thickness.
In its simplest form, the P or N leg of a TE couple (the basic building block of all thin-film TE devices) is a layer of thin-film TE material with a solder layer above and below, providing electrical and thermal functionality. | 7 | Physical Chemistry |
A spectral line corresponds to an electron transition in an atom, molecule or ion, which is associated with a specific amount of energy, E. When this energy is measured by means of some spectroscopic technique, the line is not infinitely sharp, but has a particular shape. Numerous factors can contribute to the broadening of spectral lines. Broadening can only be mitigated by the use of specialized techniques, such as Lamb dip spectroscopy. The principal sources of broadening are:
* Lifetime broadening. According to the uncertainty principle the uncertainty in energy, ΔE and the lifetime, Δt, of the excited state are related by
:This determines the minimum possible line width. As the excited state decays exponentially in time this effect produces a line with Lorentzian shape in terms of frequency (or wavenumber).
* Doppler broadening. This is caused by the fact that the velocity of atoms or molecules relative to the observer follows a Maxwell distribution, so the effect is dependent on temperature. If this were the only effect the line shape would be Gaussian.
* Pressure broadening (Collision broadening). Collisions between atoms or molecules reduce the lifetime of the upper state, Δt, increasing the uncertainty ΔE. This effect depends on both the density (that is, pressure for a gas) and the temperature, which affects the rate of collisions. The broadening effect is described by a Lorentzian profile in most cases.
* Proximity broadening. The presence of other molecules close to the molecule involved affects both line width and line position. It is the dominant process for liquids and solids. An extreme example of this effect is the influence of hydrogen bonding on the spectra of protic liquids.
Observed spectral line shape and line width are also affected by instrumental factors. The observed line shape is a convolution of the intrinsic line shape with the instrument transfer function.
Each of these mechanisms, and others, can act in isolation or in combination. If each effect is independent of the other, the observed line profile is a convolution of the line profiles of each mechanism. Thus, a combination of Doppler and pressure broadening effects yields a Voigt profile. | 7 | Physical Chemistry |
Two types of quantum efficiency of a solar cell are often considered:
*External quantum efficiency (EQE) is the ratio of the number of charge carriers collected by the solar cell to the number of photons of a given energy shining on the solar cell from outside (incident photons).
*Internal quantum efficiency (IQE) is the ratio of the number of charge carriers collected by the solar cell to the number of photons of a given energy that shine on the solar cell from outside and are absorbed by the cell.
The IQE is always larger than the EQE in the visible spectrum. A low IQE indicates that the active layer of the solar cell is unable to make good use of the photons, most likely due to poor carrier collection efficiency. To measure the IQE, one first measures the EQE of the solar device, then measures its transmission and reflection, and combines these data to infer the IQE.
The external quantum efficiency therefore depends on both the absorption of light and the collection of charges. Once a photon has been absorbed and has generated an electron-hole pair, these charges must be separated and collected at the junction. A "good" material avoids charge recombination. Charge recombination causes a drop in the external quantum efficiency.
The ideal quantum efficiency graph has a square shape, where the QE value is fairly constant across the entire spectrum of wavelengths measured. However, the QE for most solar cells is reduced because of the effects of recombination, where charge carriers are not able to move into an external circuit. The same mechanisms that affect the collection probability also affect the QE. For example, modifying the front surface can affect carriers generated near the surface. Highly doped front surface layers can also cause free carrier absorption which reduces QE in the longer wavelengths. And because high-energy (blue) light is absorbed very close to the surface, considerable recombination at the front surface will affect the "blue" portion of the QE. Similarly, lower energy (green) light is absorbed in the bulk of a solar cell, and a low diffusion length will affect the collection probability from the solar cell bulk, reducing the QE in the green portion of the spectrum. Generally, solar cells on the market today do not produce much electricity from ultraviolet and infrared light (<400 nm and >1100 nm wavelengths, respectively); these wavelengths of light are either filtered out or are absorbed by the cell, thus heating the cell. That heat is wasted energy, and could damage the cell. | 7 | Physical Chemistry |
Most nitrolic acids are laboratory curiosities. One exception is the compound HOC(CH)C(NO)=NOH, which is produced by the oxidation of cyclohexanone with nitric acid. This species decomposes to adipic acid and nitrous oxide:
:HOC(CH)C(NO)=NOH → HOC(CH)COH + NO
This conversion is thought to be the largest anthropogenic route to NO, which, on a molecule-to-molecule basis, has 298 times the atmospheric heat-trapping ability of carbon dioxide. Adipic acid is a precursor to many nylon polymers. In the end, nitrous oxide is produced in about one to one mole ratio to the adipic acid. | 0 | Organic Chemistry |
Cascade impactors – particulate matter is withdrawn isokinetically from a source and segregated by size in a cascade impactor at the sampling point exhaust conditions of temperature, pressure, etc. Cascade impactors use the principle of inertial separation to size segregate particle samples from a particle laden gas stream. The mass of each size fraction is determined gravimetrically. The California Air Resources Board Method 501 is currently the most widely accepted test method for particle size distribution emissions measurements. | 7 | Physical Chemistry |
Conventional mirrors reverse the handedness of circularly polarized waves upon reflection. In contrast, a chiral mirror reflects circularly polarized waves of one handedness without handedness change, while absorbing circularly polarized waves of the opposite handedness. A perfect chiral mirror exhibits circular conversion dichroism with ideal efficiency. Chiral mirrors can be realized by placing a planar chiral metamaterial in front of a conventional mirror. The concept has been exploited in holography to realize independent holograms for left-handed and right-handed circularly polarized electromagnetic waves. Active chiral mirrors that can be switched between left and right, or chiral mirror and conventional mirror, have been reported. | 4 | Stereochemistry |
The cantilever sensor is made out of single crystal SOI-silicon with a specially developed dry-etching process that leads to a highly stable and robust component; this is why the sensor is practically totally immune to temperature and humidity variations. In addition, the sensor does not suffer from wearing. The sensor and readout can be isolated in terms of temperature allowing heated gas cell which enables applications that require gas analysis at elevated temperatures such as chemical emissions monitoring and process control. | 7 | Physical Chemistry |
Superconducting fullerenes based on C are fairly different from other organic superconductors. The building molecules are no longer manipulated hydrocarbons but pure carbon molecules. In addition these molecules are no longer flat but bulky which gives rise to a three-dimensional, isotropic superconductor. The pure C grows in an fcc-lattice and is an insulator. By placing alkali atoms in the interstitials the crystal becomes metallic and eventually superconducting at low temperatures.
Unfortunately C crystals are not stable at ambient atmosphere. They are grown and investigated in closed capsules, limiting the measurement techniques possible. The highest transition temperature measured so far was T = 33 K for CsRbC.The highest measured transition temperature of an organic superconductor was found in 1995 in CsC pressurized with 15 kbar to be T = 40 K. Under pressure this compound shows a unique behavior. Usually the highest T is achieved with the lowest pressure necessary to drive the transition. Further increase of the pressure usually reduces the transition temperature. However, in CsC superconductivity sets in at very low pressures of several 100 bar, and the transition temperature keeps increasing with increasing pressure. This indicates a completely different mechanism then just broadening of the bandwidth. | 0 | Organic Chemistry |
One source of reactive oxygen under normal conditions in humans is the leakage of activated oxygen from mitochondria during oxidative phosphorylation. E. coli mutants that lack an active electron transport chain produce as much hydrogen peroxide as wild-type cells, indicating that other enzymes contribute the bulk of oxidants in these organisms. One possibility is that multiple redox-active flavoproteins all contribute a small portion to the overall production of oxidants under normal conditions.
Other enzymes capable of producing superoxide are xanthine oxidase, NADPH oxidases and cytochromes P450. Hydrogen peroxide is produced by a wide variety of enzymes including several oxidases. Reactive oxygen species play important roles in cell signalling, a process termed redox signaling. Thus, to maintain proper cellular homeostasis, a balance must be struck between reactive oxygen production and consumption.
The best studied cellular antioxidants are the enzymes superoxide dismutase (SOD), catalase, and glutathione peroxidase. Less well studied (but probably just as important) enzymatic antioxidants are the peroxiredoxins and the recently discovered sulfiredoxin. Other enzymes that have antioxidant properties (though this is not their primary role) include paraoxonase, glutathione-S transferases, and aldehyde dehydrogenases.
The amino acid methionine is prone to oxidation, but oxidized methionine can be reversible. Oxidation of methionine is shown to inhibit the phosphorylation of adjacent Ser/Thr/Tyr sites in proteins. This gives a plausible mechanism for cells to couple oxidative stress signals with cellular mainstream signaling such as phosphorylation. | 1 | Biochemistry |
RNA interference (also called "RNA-mediated interference", abbreviated RNAi) is a mechanism for RNA-guided regulation of gene expression in which double-stranded ribonucleic acid inhibits the expression of genes with complementary nucleotide sequences. | 1 | Biochemistry |
Melanopsin is a visual opsin present in Intrinsically photosensitive retinal ganglion cell (ipRGC) also with a retinal chromaphore. However, unlike the rod and cone pigments, melanopsin has the ability to act as both the excitable photopigment and as a photoisomerase. Melanopsin is therefore able to isomerize all-trans-retinal into 11-cis-retinal itself when stimulated with another photon. An ipRGC therefore does not rely on Müller cells and/or retinal pigment epithelium cells for this conversion. | 1 | Biochemistry |
A splice site mutation is a genetic mutation that inserts, deletes or changes a number of nucleotides in the specific site at which splicing takes place during the processing of precursor messenger RNA into mature messenger RNA. Splice site consensus sequences that drive exon recognition are located at the very termini of introns. The deletion of the splicing site results in one or more introns remaining in mature mRNA and may lead to the production of abnormal proteins. When a splice site mutation occurs, the mRNA transcript possesses information from these introns that normally should not be included. Introns are supposed to be removed, while the exons are expressed.
The mutation must occur at the specific site at which intron splicing occurs: within non-coding sites in a gene, directly next to the location of the exon. The mutation can be an insertion, deletion, frameshift, etc. The splicing process itself is controlled by the given sequences, known as splice-donor and splice-acceptor sequences, which surround each exon. Mutations in these sequences may lead to retention of large segments of intronic DNA by the mRNA, or to entire exons being spliced out of the mRNA. These changes could result in production of a nonfunctional protein. An intron is separated from its exon by means of the splice site. Acceptor-site and donor-site relating to the splice sites signal to the spliceosome where the actual cut should be made. These donor sites, or recognition sites, are essential in the processing of mRNA. The average vertebrate gene consists of multiple small exons (average size, 137 nucleotides) separated by introns that are considerably larger. | 1 | Biochemistry |
Concentration-, concentratio, action or an act of coming together at a single place, bringing to a common center, was used in post-classical Latin in 1550 or earlier, similar terms attested in Italian (1589), Spanish (1589), English (1606), French (1632). | 3 | Analytical Chemistry |
There are several options to address biogenic sulfide corrosion problems: impairing HS formation, venting out the HS or using materials resistant to biogenic corrosion. For example, sewage flows more rapidly through steeper gradient sewers reducing time available for hydrogen sulfide generation. Likewise, removing sludge and sediments from the bottom of the pipes reduces the amount of anoxic areas responsible for sulfate reducing bacteria growth. Providing good ventilation of sewers can reduce atmospheric concentrations of hydrogen sulfide gas and may dry exposed sewer crowns, but this may create odor issues with neighbors around the venting shafts. Three other efficient methods can be used involving continuous operation of mechanical equipment: chemical reactant like calcium nitrate can be continuously added in the sewerage water to impair the HS formation, an active ventilation through odor treatment units to remove HS, or an injection of compressed air in pressurized mains to avoid the anaerobic condition to develop. In sewerage areas where biogenic sulfide corrosion is expected, acid resistant materials like calcium aluminate cements, PVC or vitrified clay pipe may be substituted to ordinary concrete or steel sewers.
Existing structures that have extensive exposure to biogenic corrosion such as sewer manholes and pump station wet wells can be rehabilitated. Rehabilitation can be done with materials such as a structural epoxy coating, this epoxy is designed to be both acid resistant and strengthen the compromised concrete structure. | 8 | Metallurgy |
The exact mechanism by which levetiracetam acts to treat epilepsy is unknown. Levetiracetam does not exhibit pharmacologic actions similar to that of classical anticonvulsants. It does not inhibit voltage-dependent Na+ channels, does not affect GABAergic transmission, and does not bind to GABAergic or glutamatergic receptors. However, the drug binds to SV2A, a synaptic vesicle glycoprotein, and inhibits presynaptic calcium channels, reducing neurotransmitter release and acting as a neuromodulator. This is believed to impede impulse conduction across synapses. | 4 | Stereochemistry |
In materials science, lamellar structures or microstructures are composed of fine, alternating layers of different materials in the form of lamellae. They are often observed in cases where a phase transition front moves quickly, leaving behind two solid products, as in rapid cooling of eutectic (such as solder) or eutectoid (such as pearlite) systems.
Such conditions force phases of different composition to form but allow little time for diffusion to produce those phases' equilibrium compositions. Fine lamellae solve this problem by shortening the diffusion distance between phases, but their high surface energy makes them unstable and prone to break up when annealing allows diffusion to progress. A deeper eutectic or more rapid cooling will result in finer lamellae; as the size of an individual lamellum approaches zero, the system will instead retain its high-temperature structure. Two common cases of this include cooling a liquid to form an amorphous solid, and cooling eutectoid austenite to form martensite.
In biology, normal adult bones possess a lamellar structure which may be disrupted by some diseases. | 7 | Physical Chemistry |
Carbon steels which can successfully undergo heat-treatment have a carbon content in the range of 0.30–1.70% by weight. Trace impurities of various other elements can significantly affect the quality of the resulting steel. Trace amounts of sulfur in particular make the steel red-short, that is, brittle and crumbly at high working temperatures. Low-alloy carbon steel, such as A36 grade, contains about 0.05% sulfur and melt around . Manganese is often added to improve the hardenability of low-carbon steels. These additions turn the material into a low-alloy steel by some definitions, but AISI's definition of carbon steel allows up to 1.65% manganese by weight.
There are two types of higher carbon steels which are high carbon steel and the ultra high carbon steel. The reason for the limited use of high carbon steel is that it has extremely poor ductility and weldability and has a higher cost of production. The applications best suited for the high carbon steels is its use in the spring industry, farm industry, and in the production of wide range of high-strength wires. | 8 | Metallurgy |
WDTC1 ("Adipose") is a gene associated with obesity.
WDTC1 is a gene that codes for a protein acting as a suppressor in lipid accumulation. WDTC1 protein consists of seven WD40 domains, three transient receptor potential channel protein-protein interaction domains, DDB1 binding elements, and a prenylated C-terminus. Reduced expression or disruption of WDTC1 gene is associated with obesity, increased triglyceride accumulation, and adipogenesis. WDTC1 is a factor in a complex composed of DDB1, CUL4, and ROC1 that restricts transcription in adipogenesis. | 1 | Biochemistry |
Schiff bases have been investigated in relation to a wide range of contexts, including antimicrobial, antiviral and anticancer activity. They have also been considered for the inhibition of amyloid-β aggregation.
Schiff bases are common enzymatic intermediates where an amine, such as the terminal group of a lysine residue, reversibly reacts with an aldehyde or ketone of a cofactor or substrate. The common enzyme cofactor pyridoxal phosphate (PLP) forms a Schiff base with a lysine residue and is transaldiminated to the substrate(s). Similarly, the cofactor retinal forms a Schiff base in rhodopsins, including human rhodopsin (via Lysine 296), which is key in the photoreception mechanism. | 0 | Organic Chemistry |
* [https://www.bio.vu.nl/thb/deb/deblab/add_my_pet/index.html Add my pet (AmP)] project is a collection of DEB models for over 1000 species, and explores patterns in parameter values across taxa. Routines for parameter exploration are available in [https://www.bio.vu.nl/thb/deb/deblab/add_my_pet/AmPtool.html AmPtool] .
* Models based on DEB theory can be linked to more traditional bioenergetic models without deviating from the underlying assumptions. This allows comparison and testing of model performance .
* A DEB-module (physiological model based on DEB theory) was successfully applied to reconstruct and predict physiological responses of individuals under environmental constraints
* A DEB-module is also featured in the eco-toxicological mechanistic models ([http://www.debtox.info/software.html DEBtox implementation]) for modeling the sublethal effects of toxicants (e.g., change in reproduction or growth rate)
* Generality of the approach and applicability of the same mathematical framework to organisms of different species and life stages enables inter- and intra-species comparisons on the basis of parameter values, and theoretical/empirical exploration of patterns in parameter values in the evolutionary context, focusing for example on development, energy utilization in a specific environment, reproduction, comparative energetics, and toxicological sensitivity linked to metabolic rates.
* Studying patterns in body size scaling relationships: The assumptions of the model quantify all energy and mass fluxes in an organism (including heat, dioxygen, carbon dioxide, ammonia) while avoiding using the allometric relationships. In addition, same parameters describe same processes across species: for example, heating costs of endotherms (proportional to surface area) are regarded separate to volume-linked metabolic costs of both ectotherms and endotherms, and cost of growth, even though they all contribute to metabolism of the organism. Rules for the co-variation of parameter values across species are implied by model assumptions, and the parameter values can be directly compared without dimensional inconsistencies which might be linked to allometric parameters. Any eco-physiological quantity that can be written as function of DEB parameters which co-vary with size can, for this reason, also be written as function of the maximum body size.
* DEB theory provides constraints on the metabolic organisation of sub-cellular processes. Together with rules for interaction between individuals (competition, syntrophy, prey-predator relationships), it also provides a basis to understand population and ecosystem dynamics.
Many more examples of applications have been published in scientific literature. | 1 | Biochemistry |
AOAC has published the peer-reviewed Journal of AOAC International bimonthly since 1915. They also publish the Official Methods of Analysis (OMA) in hard copy and through the on-line database. The magazine Inside Laboratory Management is published bimonthly for members. | 3 | Analytical Chemistry |
A solution describes a homogeneous mixture where the dispersed particles will not settle if the solution is left undisturbed for a prolonged period of time.
A colloid is a heterogeneous mixture where the dispersed particles have at least in one direction a dimension roughly between 1 nm and 1 µm or that in a system discontinuities are found at distances of that order.
A suspension is a heterogeneous dispersion of larger particles in a medium. Unlike solutions and colloids, if left undisturbed for a prolonged period of time, the suspended particles will settle out of the mixture.
Although suspensions are relatively simple to distinguish from solutions and colloids, it may be difficult to distinguish solutions from colloids since the particles dispersed in the medium may be too small to distinguish by the human eye. Instead, the Tyndall effect is used to distinguish solutions and colloids. Due to the various reported definitions of solutions, colloids, and suspensions provided in the literature, it is difficult to label each classification with a specific particle size range. The International Union of Pure and Applied Chemistry attempts to provide a standard nomenclature for colloids as particles in a size range having a dimension roughly between 1 nm and 1 µm.
In addition to the classification by particle size, dispersions can also be labeled by the combination of the dispersed phase and the medium phase that the particles are suspended in. Aerosols are liquids dispersed in a gas, sols are solids in liquids, emulsions are liquids dispersed in liquids (more specifically a dispersion of two immiscible liquids), and gels are liquids dispersed in solids. | 7 | Physical Chemistry |
Rieche formylation is a type of formylation reaction. The substrates are electron rich aromatic compounds, such as mesitylene or phenols, with dichloromethyl methyl ether acting as the formyl source. The catalyst is titanium tetrachloride and the workup is acidic. The reaction is named after Alfred Rieche who discovered it in 1960. | 0 | Organic Chemistry |
Starpharma, an Australian pharmaceutical company, has multiple products that have either already been approved for use or are in the clinical trial phase. SPL7013, also known as astodrimer sodium, is a hyperbranched polymer used in Starpharma’s VivaGel line of pharmaceuticals that is currently approved to treat bacterial vaginosis and prevent the spread of HIV, HPV, and HSV in Europe, Southeast Asia, Japan, Canada, and Australia. Due to SPL7013’s broad antiviral action, it has recently been tested by the company as a potential drug to treat SARS-CoV-2. The company states preliminary in-vitro studies show high efficacy in preventing SARS-CoV-2 infection in cells. | 6 | Supramolecular Chemistry |
Tropical forests receive more insolation and rainfall over longer growing seasons than any other environment on earth. With these elevated temperatures, insolation and rainfall, biomass is extremely productive leading to the production of as much as 800 grams of carbon per square meter per year (8 tons of C/hectare/year). Higher temperatures and larger amounts of water contribute to higher rates of chemical weathering. Increased rates of decomposition cause smaller amounts of fulvic acid to percolate and leach metals from the zone of active weathering. Thus, in stark contrast to soil in temperate forests, tropical forests have little to no podzolization and therefore do not have marked visual and chemical contrasts with the soil layers. Instead, the mobile metals Mg, Fe and Al are precipitated as oxide minerals giving the soil a rusty red color. | 9 | Geochemistry |
Berylliosis, or chronic beryllium disease (CBD), is a chronic allergic-type lung response and chronic lung disease caused by exposure to beryllium and its compounds, a form of beryllium poisoning. It is distinct from acute beryllium poisoning, which became rare following occupational exposure limits established around 1950. Berylliosis is an occupational lung disease.
While there is no cure, symptoms can be treated. | 1 | Biochemistry |
Many important chemical compounds are derived from benzene by replacing one or more of its hydrogen atoms with another functional group. Examples of simple benzene derivatives are phenol, toluene, and aniline, abbreviated PhOH, PhMe, and PhNH, respectively. Linking benzene rings gives biphenyl, CH–CH. Further loss of hydrogen gives "fused" aromatic hydrocarbons, such as naphthalene, anthracene, phenanthrene, and pyrene. The limit of the fusion process is the hydrogen-free allotrope of carbon, graphite.
In heterocycles, carbon atoms in the benzene ring are replaced with other elements. The most important variations contain nitrogen. Replacing one CH with N gives the compound pyridine, CHN. Although benzene and pyridine are structurally related, benzene cannot be converted into pyridine. Replacement of a second CH bond with N gives, depending on the location of the second N, pyridazine, pyrimidine, or pyrazine. | 2 | Environmental Chemistry |
With the codename FL 1060, mecillinam was developed by the Danish pharmaceutical company Leo Pharmaceutical Products (now LEO Pharma). It was first described in the scientific literature in a 1972 paper. | 4 | Stereochemistry |
* 1983 — Member of the National Academy of Sciences
* 1985–1987 — President of the Geochemical Society
* 1992 — V. M. Goldschmidt Award, Geochemical Society
* 1997 — Harry Hess Medal, American Geophysical Union
* 2005 — Fellow of the American Academy of Arts and Sciences
* 2008 — Arthur L. Day Prize and Lectureship
* 2016 — William Bowie Medal | 9 | Geochemistry |
It is debated whether there is a significant reduction in NEAT after beginning a structured exercise program. | 1 | Biochemistry |
In the original product imaging paper, the positions of the ions are imaged onto a two-dimensional detector. A photolysis laser dissociates methyl iodide (CHI), while an ionization laser is used REMPI to ionize a particular vibrational level of the CH product. Both lasers are pulsed, and the ionization laser is fired at a delay short enough that the products have not moved appreciably. Because ejection of an electron by the ionization laser does not change the recoil velocity of the CH fragment, its position at any time following the photolysis is nearly the same as it would have been as a neutral. The advantage of converting it to an ion is that, by repelling it with a set of grids (represented by the vertical solid lines in the figure), one can project it onto a two-dimensional detector. The detector is a double microchannel plate consisting of two glass discs with closely packed open channels (several micrometres in diameter). A high voltage is placed across the plates. As an ion hits inside a channel, it ejects secondary electrons that are then accelerated into the walls of the channel. Since multiple electrons are ejected for each one that hits the wall, the channels act as individual particle multipliers. At the far end of the plates approximately 10 electrons leave the channel for each ion that entered. Importantly, they exit from a spot right behind where the ion entered. The electrons are then accelerated to a phosphor screen, and the spots of light are recorded with a gated charge-coupled device (CCD) camera. The image collected from each pulse of the lasers is then sent to a computer, and the results of many thousands of laser pulses are accumulated to provide an image such as the one for ozone shown previously.
In this position-sensing version of product imaging, the position of the ions as they hit the detector is recorded. One can imagine the ions produced by the dissociation and ionization lasers as expanding outward from the center-of-mass with a particular distribution of velocities. It is this three-dimensional object that we wish to detect. Since the ions created should be of the same mass, they will all be accelerated uniformly toward the detector. It takes very little time for the whole three-dimensional object to be crushed into the detector, so the position of an ion on the detector relative to the center position is given simply by v Δt, where v is its velocity and Δt is the time between when the ions were made and when they hit the detector. The image is thus a two-dimensional projection of the desired three-dimensional velocity distribution. Fortunately, for systems with an axis of cylindrical symmetry parallel to the surface of the detector, the three-dimensional distribution may be recovered from the two-dimensional projection by the use of the inverse Abel transform. The cylindrical axis is the axis containing the polarization direction of the dissociating light. It is important to note that the image is taken in the center-of-mass frame; no transformation, other than from time to speed, is needed.
A final advantage of the technique should also be mentioned: ions of different masses arrive at the detector at different times. This differential arises because each ion is accelerated to the same total energy, E, as it traverses the electric field, but the acceleration speed, v, varies as E = ½ mv. Thus, v varies as the reciprocal of the square root of the ion mass, or the arrival time is proportional to the square root of the ion mass. In a perfect experiment, the ionization laser would ionize only the products of the dissociation, and those only in a particular internal energy state. But the ionization laser, and perhaps the photolysis laser, can create ions from other material, such as pump oil or other impurities. The ability to selectively detect a single mass by gating the detector electronically is thus an important advantage in reducing noise. | 7 | Physical Chemistry |
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