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Topic Review
Tetrasubstituted α-Aminophosphonic Acid Derivatives
Due to their structural similarity with natural α-amino acids, α-aminophosphonic acid derivatives are known biologically active molecules. In view of the relevance of tetrasubstituted carbons in nature and medicine and the strong dependence of the biological activity of chiral molecules into their absolute configuration, the synthesis of α-aminophosphonates bearing tetrasubstituted carbons in an asymmetric fashion has grown in interest in the last decades. In the following lines, the existing literature for the synthesis of optically active tetrasubstituted α-aminophosphonates are summarized, comprising diastereoselective and enantioselective approaches.
  • 918
  • 19 Jun 2021
Topic Review
Cracking
In petrochemistry, petroleum geology and organic chemistry, cracking is the process whereby complex organic molecules such as kerogens or long-chain hydrocarbons are broken down into simpler molecules such as light hydrocarbons, by the breaking of carbon-carbon bonds in the precursors. The rate of cracking and the end products are strongly dependent on the temperature and presence of catalysts. Cracking is the breakdown of a large alkane into smaller, more useful alkenes. Simply put, hydrocarbon cracking is the process of breaking a long chain of hydrocarbons into short ones. This process requires high temperatures. More loosely, outside the field of petroleum chemistry, the term "cracking" is used to describe any type of splitting of molecules under the influence of heat, catalysts and solvents, such as in processes of destructive distillation or pyrolysis. Fluid catalytic cracking produces a high yield of petrol and LPG, while hydrocracking is a major source of jet fuel, diesel fuel, naphtha, and again yields LPG.
  • 918
  • 27 Oct 2022
Topic Review
Polysaccharides in Agro-Industrial Biomass Residues
The use of waste biomass to produce biopolymers and nutricosmetic or pharmacological materials is increasing, although still scarcely compared to its great potential, employment, and valorization. Organic waste biomass is a great source of natural polysaccharides such as cellulose, chitin, hyaluronic acid, inulin, and pectin. Biomass from the agricultural sectors is a relevant part of waste generation and commonly comprises leaves, roots, stalks, bark, bagasse, seeds, straw, wood, animal parts, crustacean shells, and others. Polysaccharides are the most abundant biological materials on the planet. This natural abundance contributes to the discovery of their novel applications. Their industrial use is still very modest considering their versatility and great potential, although it has recently seen significant increases.
  • 917
  • 18 Mar 2022
Topic Review
Supercritical Fluid Extraction as a Green Extraction
Extraction is a technique of isolating components from natural materials using chemical or physical methods. The world has turned to using green extraction as part of its efforts to preserve the environment. Green extraction is based on procedures that require less energy, allow for the use of alternative solvents and sustainable natural resources, and offer a safe and high-quality extract. Supercritical fluid extraction (SFE) procedures are compatible with the principles of green extraction.
  • 917
  • 26 Oct 2022
Topic Review
Liquid Crystal Waveguide Structures
Liquid crystal materials can be used to make either a core, in which light beams can be confined, or a cladding of optical waveguides.
  • 917
  • 02 Nov 2021
Topic Review
MoS2 Energy Applications
MoS2 is one of the transition metal dichalcogenides (TMDs) that has gained a high reputation in recent years due to its distinct chemical, electronic, mechanical, magnetic, and optical properties. Its unique properties enabled its use in different applications such as sensing applications, high-efficiency field effect transistors, and energy and medical (curing) applications. MoS2 exists in different crystalline structures, such as hexagonal (H), tetrahedral (T), or rhombohedral (R). It naturally exists as 2H MoS2, and its most popular structures are the semiconducting 2H and 3R phases and the 1T metallic phase, where 2H is more stable but less conductive than 1T. Metallic MoS2 has a higher conductivity (105 times) than semiconducting 2H MoS2 and high catalytic activity.
  • 916
  • 16 Sep 2021
Topic Review
Ion-Imprinted Polymers
Growing concern over the hazardous effect of radionuclides on the environment is driving research on mitigation and deposition strategies for radioactive waste management. Currently, there are many techniques used for radionuclides separation from the environment such as ion exchange, solvent extraction, chemical precipitation and adsorption. Adsorbents are the leading area of research and many useful materials are being discovered in this category of radionuclide ion separation. The adsorption technologies lack the ability of selective removal of metal ions from solution. This drawback is eliminated by the use of ion-imprinted polymers, these materials having targeted binding sites for specific ions in the media.
  • 915
  • 28 Sep 2021
Topic Review
Commercial Antimicrobial Wound Dressings Based on Polyhexanide-Releasing Membranes
The prevalence of chronic, non-healing skin wounds in the general population, most notably diabetic foot ulcers, venous leg ulcers and pressure ulcers, is approximately 2% and is expected to increase, driven mostly by the aging population and the steady rise in obesity and diabetes. Non-healing wounds often become infected, increasing the risk of life-threatening complications, which poses a significant socioeconomic burden. Aiming at an improved management of infected wounds, a variety of wound dressings that release the antiseptic polyhexanide (poly(hexamethylene biguanide); PHMB), has been introduced in the wound-care market. An overview of the main characteristics and applications of PHMB and of the main fabrication methods and characteristics of commercial PHMB-releasing wound dressings is presented.
  • 915
  • 05 Jan 2023
Topic Review
Grapevine Cane Extracts
Grapevine canes are viticulture waste that is usually discarded without any further use. However, recent studies have shown that they contain significant concentrations of healthpromoting compounds, such as stilbenes, secondary metabolites of plants produced as a response to biotic and abiotic stress from fungal disease or dryness. Stilbenes have been associated with antioxidant, anti‐inflammatory, and anti‐microbial properties and they have been tested as potential treatments of cardiovascular and neurological diseases, and even cancer, with promising results. Stilbenes have been described in the different genus of the Vitaceae family, the Vitis genera being one of the most widely studied due to its important applications and economic impact around the world. This entry presents an in‐depth study of the composition and concentration of stilbenes in grapevine canes. The results show that the concentration of stilbenes in grapevine canes is highly influenced by the Vitis genus and cultivar aspects (growing conditions, ultraviolet radiation, fungal attack, etc.). Different methods for extracting stilbenes from grapevine canes have been reviewed, and the extraction conditions have also been studied, underlining the advantages and disadvantages of each technique. After the stilbenes were extracted, they were analyzed to determine the stilbene composition and concentration. Analytical techniques have been employed with this aim, in most cases using liquid chromatography, coupled with others such as mass spectrometry and/or nuclear magnetic resonance to achieve the individual quantification. Finally, stilbene extracts may be applied in multiple fields based on their properties. The five most relevant are preservative, antifungal, insecticide, and biostimulant applications. The current state‐of‐the‐art of the above applications and their prospects are discussed.
  • 915
  • 11 Sep 2020
Topic Review
Organic Coatings for Marine Applications
Organic coatings for marine applications must have great corrosion protection and antifouling performance. This review presents an overview of recent investigations into coating microstructure, corrosion protection performance, antifouling behavior, and evaluation methods, particularly the substrate effect and environmental influence on coating protectiveness, aiming to improve operational practice in the coating industry. 
  • 915
  • 21 Jan 2021
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