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Topic Review
The NifA–NifL System for Nitrogen Fixation
Nitrogen–fixing bacteria execute biological nitrogen fixation through nitrogenase, converting inert dinitrogen (N2) in the atmosphere into bioavailable nitrogen. Elaborating the molecular mechanisms of orderly and efficient biological nitrogen fixation and applying them to agricultural production can alleviate the “nitrogen problem”. Azotobacter vinelandii is a well–established model bacterium for studying nitrogen fixation, utilizing nitrogenase encoded by the nif gene cluster to fix nitrogen. In Azotobacter vinelandii, the NifA–NifL system fine–tunes the nif gene cluster transcription by sensing the redox signals and energy status, then modulating nitrogen fixation. 
  • 3.1K
  • 06 Feb 2023
Topic Review
Red Seaweed Pigments
Algae taxa are notably diverse regarding pigment diversity and composition, red seaweeds (Rhodophyta) being a valuable source of phycobiliproteins (phycoerythrins, phycocyanin, and allophycocyanin), carotenes (carotenoids and xanthophylls), and chlorophyll a. These pigments have a considerable biotechnological potential, which has been translated into several registered patents and commercial applications. 
  • 3.1K
  • 20 Jan 2022
Topic Review
Global Navigation Satellite System, Datums and Mapping Accuracy
Current Global Navigation Satellite System (GNSS)-based geodetic techniques allow up to millimeter accuracy in positioning to be achieved globally, and high-precision mass-market positioning is becoming available to an accuracy of 5–10 cm.
  • 3.1K
  • 12 Oct 2023
Topic Review
Eurypterus
Eurypterus (/jʊəˈrɪptərəs/ yoo-RIP-tər-əs) is an extinct genus of eurypterid, a group of organisms commonly called "sea scorpions". The genus lived during the Silurian period, from around 432 to 418 million years ago. Eurypterus is by far the most well-studied and well-known eurypterid. Eurypterus fossil specimens probably represent more than 95% of all known eurypterid specimens. There are fifteen species belonging to the genus Eurypterus, the most common of which is E. remipes, the first eurypterid fossil discovered and the state fossil of New York. Members of Eurypterus averaged at about 13 to 23 cm (5 to 9 in) in length, but the largest individual discovered was estimated to be 60 cm (24 in) long. They all possessed spine-bearing appendages and a large paddle they used for swimming. They were generalist species, equally likely to engage in predation or scavenging.
  • 3.1K
  • 09 Nov 2022
Topic Review
Glucosinolates
Glucosinolates (GSLs) are secondary plant metabolites abundantly found in plant order Brassicales. GSLs are constituted by an S-β-d-glucopyrano unit anomerically connected to O-sulfated (Z)-thiohydroximate moiety. The side-chain of the O-sulfate thiohydroximate moiety, which is derived from a different amino acid, contributes to the diversity of natural GSL, with more than 130 structures identified and validated to this day. Both the structural diversity of GSL and their biological implication in plants have been biochemically studied. While intact GSLs are biologically inactive, various products, including isothiocyanates, nitriles, epithionitriles, and cyanides obtained through enzyme-catalyzed hydrolysis of GSLs, exhibit many different biological activities, among which several therapeutic benefits have been suggested. 
  • 3.1K
  • 12 Oct 2020
Topic Review
Cyanobacteria: Model Microorganisms and Beyond
Cyanobacteria, also formerly called “blue-green algae”, are photosynthetic prokaryotes with ~3500 million years of existence on the planet earth. They live in a diverse range of environments, from freshwater and marine to terrestrial ecosystems. Cyanobacteria can tolerate and live in the most extreme habitats including geothermal habitats, frozen systems, and hypersaline environments.
  • 3.1K
  • 14 Apr 2022
Topic Review
Regulationary Factors of the Peroxisomal β-Oxidation
Beta-oxidation(β-oxidation) is an important metabolic process involving multiple steps by which fatty acid molecules are broken down to produce energy. The very long-chain fatty acids (VLCFAs), a type of fatty acid (FA), are usually highly toxic when free in vivo, and their oxidative metabolism depends on the peroxisomal β-oxidation. Although peroxisomal β-Oxidation attracts less research than mitochondria, the importance of the peroxisomal β-oxidation molecular mechanism can still be spotted from some mechanisms involved in upstream regulation.
  • 3.1K
  • 07 Jul 2022
Biography
Michel de Montaigne
Michel Eyquem de Montaigne (/mɒnˈteɪn/ mon-TAYN;[1] French: [miʃɛl ekɛm də mɔ̃tɛɲ]; 28 February 1533 – 13 September 1592[2]), also known as Lord of Montaigne, was one of the most significant philosophers of the French Renaissance. He is known for popularizing the essay as a literary genre. His work is noted for its merging of casual anecdotes[3] and autobiography with intellectual
  • 3.1K
  • 05 Dec 2022
Topic Review
Proposed Melbourne Rail Extensions
Several proposals have been put forward by various groups to expand the Melbourne rail network—proposals for additional rail lines, extensions to existing lines, as well as electrification to existing lines and new stations on existing lines. Some of these plans were so seriously considered at various times that they appeared in the Melway street directory, and on suburban train destination rolls.
  • 3.1K
  • 31 Oct 2022
Topic Review
Titanium Aluminides
Titanium aluminides (TiAl) have the potential of substituting nickel-based superalloys (NBSAs) in the aerospace industries owing to their lightweight, good mechanical and oxidation properties. Functional simplicity, control of sintering parameters, exceptional sintering speeds, high reproducibility, consistency and safety are the main benefits of spark plasma sintering (SPS) over conventional methods. Though TiAl exhibit excellent high temperature properties, SPS has been employed to improve on the poor ductility at room temperature. Powder metallurgical processing techniques used to promote the formation of refined, homogeneous and contaminant-free structures, favouring improvements in ductility and other properties are discussed. This article further reviews published work on phase constituents, microstructures, alloy developments and mechanical properties of TiAl alloys produced by SPS. Finally, an overview of challenges in as far as the implementation of TiAl in industries of interest are highlighted.
  • 3.1K
  • 07 Jan 2021
Topic Review
Buddhist Tantras
The Buddhist Tantras are a varied group of Indian and Tibetan texts which outline unique views and practices of the Buddhist tantra religious systems.
  • 3.1K
  • 14 Oct 2022
Topic Review
Cardiac Glycosides
Cardiac glycosides (CG’s) are naturally occurring biologically active small molecules, used to diagnose a diversity of heart diseases such as congestive heart failure and cardiac arrhythmia. The story of CG’s started over 100 years ago when Sir William Withering reported the use of foxglove plant for treating “dropsy” associated with congestive heart failure and the foxglove plant (Digitalis purpurea) was still in the use for the extraction of Digoxin, a cardiac glycoside used to treat congestive heart failures (Johnson., 2012). The core structure of CGs comprises a steroid nucleus attached to a five-membered lactone ring (cardenolide) or six-membered lactone rings (bufadienolides) along with sugar moieties. Major plant-derived CGs were obtained from plant families of Apocynaceae, Scrophulariaceae, and Asparagaceae (Thevitia neriifolia, Neerium oleander, Digitalis purpurea, Digitalis lanata, Urginea maritime, and Strophanthus kombe). Structurally, all these contain a core steroid nucleus connected with sugar moiety at C3 position and lactone moiety at C17 position (Figure 1.3). The pharmacological significance of all the CG’s lies in the core steroid confirmation that contains A/B and C/D cis- portions and the properties such as pharmacokinetics and pharmacodynamics lie between the confined sugars molecules (Pongrakhananon., 2013). Apart from the plant sources, CG’s were also isolated from several animal species such as bufadienolide was isolated from frogs, and also mammalian tissues contain a cardiac glycoside which is similar to endogenous digitalis (Melero et al., 2000). Quite a few studies have conveyed that the human body does contain a lot more CG’s in different parts. For example, the plasma membrane contains Ouabain and Proscillaridin A and human urine contains digoxin and marinobufagenin whereas human lenses consist of 19-norbufalin (Schoner and Scheiner-Bobis., 2007). In the year 1785, William Withering was the first person to use a digitalis compound from Digitalis purpurea to treat congestive heart failures. Currently, Digoxin is used for treating congestive heart failures. The mechanism of action of Digoxin is that it can inhibit the sodium-potassium pump (Na+/K+-ATPase). Living organisms maintain more percentage of K+ within the cell and less percentage of Na+. However, the scenario at the outside of the cell is quite opposite to the intracellular conditions where a high percentage of Na+ and less percentage of K+ will be maintained. Hence, there is a concentration incline that exists between the outside and inside cellular environments, which will be maintained by sodium-potassium pump. The Na+/K+-ATPase is recognized as a transmembrane protein whose functions are to maintain ionic balance in the heart tissue. Na+/K+-ATPase utilizes ATP as the whole energy source, to exchange two K+ ions inside the cell and pushes three Na+ ions outside to maintain intra cellular homeostasis. Also, Na+/K+-ATPase transports glucose and amino acids by keeping less concentration of Na+ within the cell and helps in the maintenance of electrochemical incline. The increment of the Na+ level inside the cell retort to CGs fortifies the ion exchange mechanism. This leads to the expansion of intracellular Ca2+ percentage which therefore promotes organelle instances such as myocardial contractibility, and generates optimistic inotropic effects in the heart cell with CGs (Kaplan., 2002).  
  • 3.1K
  • 12 Aug 2020
Topic Review
Grape Phenolics
Grapes are rich in primary and secondary metabolites. Among the secondary metabolites, polyphenolic compounds are the most abundant in grape berries. Besides their important impacts on grape and wine quality, this class of compounds has beneficial effects on human health. Due to their antioxidant activity, polyphenols and phenolic acids can act as anti-inflammatory and anticancerogenic agents, and can modulate the immune system. In grape berries, polyphenols and phenolic acids can be located in the pericarp and seeds, but distribution differs considerably among these tissues. Although some classes of polyphenols and phenolic acids are under strict genetic control, the final content is highly influenced by environmental factors, such as climate, soil, vineyard, and management. 
  • 3.1K
  • 13 Jan 2021
Topic Review
Mechanisms of Exosome Biogenesis
Exosomes are nanometer-sized vesicles released by different cells that are important in the normal functioning of the body. In cancer, exosomes have been found to promote tumor growth and metastasis by carrying functional biomolecules and acting on different target sites in the body. Understanding the mechanism by which cancers modulate exosome secretion is crucial to studying cancer biology and developing new therapeutic approaches.
  • 3.1K
  • 18 Apr 2023
Topic Review
Strain Rate Sensitivity
Strain rate is a parameter related with dynamic loading phenomena, which are common in industrial applications.
  • 3.1K
  • 06 Sep 2021
Topic Review
Removal of Inorganic Nitrogen from Wastewater
Water contamination due to various nitrogenous pollutants generated from wastewater treatment plants is a crucial and ubiquitous environmental problem nowadays. Nitrogen contaminated water has manifold detrimental effects on human health as well as aquatic life. Consequently, various biological and bioelectrochemical treatment processes are employed to transform the undesirable forms of nitrogen in wastewater to safer ones for subsequent discharge.
  • 3.1K
  • 27 May 2022
Topic Review
Envy
Envy (from Latin invidia) is an emotion which occurs when a person lacks another's superior quality, achievement, or possession and either desires it or wishes that the other lacked it. Aristotle defined envy as pain at the sight of another's good fortune, stirred by "those who have what we ought to have". Bertrand Russell said that envy was one of the most potent causes of unhappiness. Not only is the envious person rendered unhappy by their envy, Russell argued, but that person may also wish to inflict misfortune on others to reduce their status.
  • 3.1K
  • 14 Nov 2022
Topic Review
Faults in a Photovoltaic System
Photovoltaic systems are prone to breaking down due to harsh conditions. In photovoltaic systems, various types of faults can cause power loss in some way. To improve the reliability of these systems, diagnostic methods using Machine Learning (ML) have been developed. 
  • 3.1K
  • 15 Mar 2024
Topic Review
Coumarin-Based Profluorescent and Fluorescent Substrates
Activities of xenobiotic-metabolizing enzymes have been measured with various in vitro and in vivo methods, such as spectrophotometric, fluorometric, mass spectrometric and radioactivity-based techniques. In fluorescence-based assays, the reaction produces a fluorescent product from a nonfluorescent substrate or vice versa. We describe here historical highlights and current use of (pro)fluorescent coumarin derivatives in evaluating activities of the major types of xenobiotic-metabolizing enzyme systems. Traditionally coumarin substrates have been used to measure oxidative activities of cytochrome P450 (CYP) enzymes. For this purpose, profluorescent coumarins are very sensitive, but generally lack selectivity for individual CYP forms. The entry describes several new coumarin-based substrates for measuring activities of CYP and conjugating enzymes with improved selectivity.
  • 3.1K
  • 14 Jul 2020
Topic Review
Localization of a Ring
In commutative algebra, localization is a systematic method of adding multiplicative inverses to a ring. Given a ring R and a subset S, one wants to construct some ring R* and ring homomorphism from R to R*, such that the image of S consists of units (invertible elements) in R*. Further one wants R* to be the 'best possible' or 'most general' way to do this—in the usual fashion this should be expressed by a universal property. The localization of R by S is usually denoted by S −1R; however other notations are used in some important special cases. If S is the set of the non zero elements of an integral domain, then the localization is the field of fractions and thus usually denoted Frac(R). If S is the complement of a prime ideal I the localization is denoted by RI, and Rf is used to denote the localization by the powers of an element f. The two latter cases are fundamental in algebraic geometry and scheme theory. In particular the definition of an affine scheme is based on the properties of these two kinds of localizations.
  • 3.1K
  • 26 Oct 2022
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