Subject:
All Disciplines Arts & Humanities Biology & Life Sciences Business & Economics Chemistry & Materials Science Computer Science & Mathematics Engineering Environmental & Earth Sciences Medicine & Pharmacology Physical Sciences Public Health & Healthcare Social Sciences
Sort:
Hottest Latest Alphabetical (A-Z) Alphabetical (Z-A)
Type:
All Topic Review Biography
Topic Review
Waste Plastics’ Liquefaction into Fuel Fraction
Polymers and plastics are crucial materials in many sectors of our economy, due to their numerous advantages. They also have some disadvantages, among the most important are problems with the recycling and disposal of used plastics. The recovery of waste plastics is increasing every year, but over 27% of plastics are landfilled. The rest is recycled, where, unfortunately, incineration is still the most common management method. From an economic perspective, waste management methods that lead to added-value products are most preferred—as in the case of material and chemical recycling. Since chemical recycling can be used for difficult wastes (poorly selected, contaminated), it seems to be the most effective way of managing these materials. Moreover, as a result this of kind of recycling, it is possible to obtain commercially valuable products, such as fractions for fuel composition and monomers for the reproduction of polymers. 
  • 708
  • 06 Dec 2022
Topic Review
Carbon Fixation
Carbon fixation or сarbon assimilation is the process by which inorganic carbon (particularly in the form of carbon dioxide) is converted to organic compounds by living organisms. The compounds are then used to store energy and as structure for other biomolecules. Carbon is primarily fixed through photosynthesis, but some organisms use a process called chemosynthesis in the absence of sunlight. Organisms that grow by fixing carbon are called autotrophs, which include photoautotrophs (which use sunlight), and lithoautotrophs (which use inorganic oxidation). Heterotrophs are not themselves capable of carbon fixation but are able to grow by consuming the carbon fixed by autotrophs or other heterotrophs. "Fixed carbon", "reduced carbon", and "organic carbon" may all be used interchangeably to refer to various organic compounds.
  • 1.4K
  • 06 Dec 2022
Topic Review
Energy Calibration for a Sectional Scan
For a sectional scan, the spectral energies within each scan need to be re-distributed point by point with a linear function of the accumulated time scanned rather than be scaled with a universal constant as in a traditional energy calibration.
  • 509
  • 06 Dec 2022
Topic Review
Nanoparticles in Chemical Enhanced Oil Recovery
Nanotechnology in Chemical Enhanced Oil Recovery deals with the application of materials based on nanometer scale to the recovery of difficult-to-access oil from reservoirs. Additional recoveries (after brine flooding) up to 15% of the original oil in place, or higher when combined with smart water or magnetic fields, have been found with formulations consisting of simple nanoparticles in water or brine. The functionalization of nanoparticles and their combination with surfactants and/or polymers take advantage of the synergy of different EOR methods and can lead to higher additional recoveries. The cost, difficulty of preparation, and stability of the formulations are problems that face practical applications.
  • 447
  • 06 Dec 2022
Topic Review
Synthetic Hemorphin Analogs Containing Non-Natural Amino Acids
The endogenous hemorphins are bioactive peptides with activity on opioid receptors. Several research teams have synthesized, characterized, and pharmacologically evaluated synthetic hemorphin analogs containing unusual amino acids, D-amino acids, α-aminophosphonic acids, and their derivatives. Research focuses on the structure-activity relationship analysis, details on specific methods for their characterization, and the advantage of synthetic hemorphin analogs compared to endogenous peptides as potent biologically active compounds with a complex mechanism of action.
  • 721
  • 05 Dec 2022
Topic Review
The Peculiar Properties of Human mitoNEET
The outer mitochondrial membrane (OMM) protein mitoNEET, also known as CDGSH Fe-S domain-containing protein-1 (CISD1), is composed of 108 amino acids, encompassing a N-terminal transmembrane helix (residues 14–32) that anchors the protein to the OMM, and a cytosolic portion (residues 33–108) that has been widely investigated through X-ray crystallography, showing a unique, highly conserved folding.
  • 434
  • 05 Dec 2022
Topic Review
Meso-Zeaxanthin
Meso-zeaxanthin (3R,3´S-zeaxanthin) is a xanthophyll carotenoid, as it contains oxygen and hydrocarbons, and is one of the three stereoisomers of zeaxanthin. Of the three stereoisomers, meso-zeaxanthin is the second most abundant in nature after 3R,3´R-zeaxanthin, which is produced by plants and algae. To date, meso-zeaxanthin has been identified in specific tissues of marine organisms and in the macula lutea, also known as the "yellow spot", of the human retina.
  • 885
  • 02 Dec 2022
Topic Review
Atomic Radii of the Elements (Data Page)
The atomic radius of a chemical element is the distance from the center of the nucleus to the outermost shell of an electron. Since the boundary is not a well-defined physical entity, there are various non-equivalent definitions of atomic radius. Depending on the definition, the term may apply only to isolated atoms, or also to atoms in condensed matter, covalently bound in molecules, or in ionized and excited states; and its value may be obtained through experimental measurements, or computed from theoretical models. Under some definitions, the value of the radius may depend on the atom's state and context. Atomic radii vary in a predictable and explicable manner across the periodic table. For instance, the radii generally decrease rightward along each period (row) of the table, from the alkali metals to the noble gases; and increase down each group (column). The radius increases sharply between the noble gas at the end of each period and the alkali metal at the beginning of the next period. These trends of the atomic radii (and of various other chemical and physical properties of the elements) can be explained by the electron shell theory of the atom; they provided important evidence for the development and confirmation of quantum theory.
  • 841
  • 02 Dec 2022
Topic Review
Gold Nanoclusters in Tumor Theranostic and Combination Therapy
The rising incidence and severity of malignant tumors threaten human life and health, and the current lagged diagnosis and single treatment in clinical practice are inadequate for tumor management. Gold nanoclusters (AuNCs) are nanomaterials with small dimensions (≤3 nm) and few atoms exhibiting unique optoelectronic and physicochemical characteristics, such as fluorescence, photothermal effects, radiosensitization, and biocompatibility.
  • 378
  • 02 Dec 2022
Topic Review
Indium-Mediated Allylation
Indium-Mediated Allylations (IMAs) are important chemical reactions for the formation of carbon–carbon bonds. This reaction has two steps: first, indium inserts itself between the carbon–halogen bond of an allyl halide, becoming the organoindium intermediate; second, this allyl indide intermediate reacts with an electrophile to synthesize one of a wide range of compounds, such as carbohydrates and antihelminthic drugs. This reaction is depicted in the scheme below: Although this reaction occurs in two steps, it is commonly done as a Barbier reaction where the indium, allyl halide, and electrophile are all mixed together in a one-pot process. Indium reacts more readily than other metals, such as Mg, Pb, Bi, or Zn and does not require a promoter or flammable organic solvent to drive the reaction. IMAs have advantages over other carbon bond forming reactions because of their ability to be carried out in water, which is cheap and environmentally friendly. Therefore, these reactions represent Green chemistry, providing a safer alternative to the very common Grignard reaction, performed with Mg. Reactions yield high stereo- and regio-selectivity with few by-products making it easy to purify the desired product.
  • 860
  • 02 Dec 2022
  • Page
  • of
  • 467
Featured Entry Collections
>>

Featured Books

>>
Encyclopedia of Social Sciences
Encyclopedia of COVID-19
Encyclopedia of Fungi
Encyclopedia of Digital Society, Industry 5.0 and Smart City
ScholarVision Creations
Feedback