Chemistry

Abstract: This book discusses the engineering problem of determining surface heat flux and temperature history based on interior temperature measurements. It also provides the analytical techniques needed to arrive at otherwise difficult solutions, summarizing the findings of the last ten years. Topics include the steady state solution, Duhammel's Theorem, ill-posed problems, single future time step, and more.

Abstract: The newly reported Omicron variant is poised to replace Delta as the most prevalent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant across the world. Cryo–electron microscopy (cryo-EM) structural analysis of the Omicron variant spike protein in complex with human angiotensin-converting enzyme 2 (ACE2) reveals new salt bridges and hydrogen bonds formed by mutated residues arginine-493, serine-496, and arginine-498 in the receptor binding domain with ACE2. These interactions appear to compensate for other Omicron mutations such as the substitution of asparagine for lysine at position 417 (K417N) that are known to reduce ACE2 binding affinity, resulting in similar biochemical ACE2 binding affinities for the Delta and Omicron variants. Neutralization assays show that pseudoviruses that display the Omicron spike protein exhibit increased antibody evasion. The increase in antibody evasion and the retention of strong interactions at the ACE2 interface thus represent important molecular features that likely contribute to the rapid spread of the Omicron variant. Description Antibody-evading Omicron keeps function The Omicron variant of severe acute respiratory syndrome coronavirus 2 was reported in November 2021 and was quickly identified as a variant of concern because of its rapid spread. Relative to the original Wuhan-Hu-1 strain, this variant has 37 mutations in the spike protein that is responsible for binding and entry into host cells. Fifteen mutations are in the receptor-binding domain, which binds the host angiotensin-converting enzyme 2 (ACE2) receptor and is also the target of many neutralizing antibodies. Mannar et al. report a structure of the Omicron variant spike protein bound to human ACE2. The structure rationalizes the evasion of antibodies elicited by previous vaccination or infection and shows how mutations that weaken ACE2 binding are compensated for by mutations that make new interactions. —VV Cryo-EM analysis of the Omicron spike protein reveals how ACE2 binding occurs despite high mutational escape from antibodies.

Abstract: Genesis of the concept: intermolecular ferromagnetic spin exchange structural determinants of the chemical and magnetic properties of non-kekule molecules antiaromatic triplet ground state molecules - building blocks for organic magnets. Theory of exchange in organic systems: resonating valence bond theory and magnetic properties qualitative and quantitative predictions and measurements of singlet-triplet splittings in non-Kekule hydrocarbon diradicals and heteroatom derivatives. Exchange in small organic open-shell systems: conformational exchange modulation in trimethylenemethane-type biradicals use of dinitrenes as models for intramolecular exchange radical ion building blocks for organic magnetic materials - computational and experimental approaches. Exchange in polymeric organic systems: design and experimental investigation of high-spin organic systems synthesis and properties of organic conjugated polyradicals pendant and conjugated organic polyradicals. Theory of organic magnetism in condensed phases: band theory of exchange effects in organic open shell systems orbital interactions determining the exchange effects in organic molecular crystals molecular orbital theoretical elucidation of spin alignments in organic magnetic crystals. Magnetism in organic condensed phases: exchange effects in three dimensions - real materials bulk magnetic properties of organic verdazyl radical crystals neutron diffraction studies of spin densities in magnetic molecular materials heat capacity studies of organic radical crystals. Summation: an integrated approach to organic-based molecular magnetic materials.

Abstract: Marbofloxacin (MAR) is an antimicrobial for veterinary use, and it does not have a monograph in an official compendium for the pharmaceutical form in tablets.In this context, the objective of this work was to develop and validate an effective, eco-friendly, and indicative of stability method by spectrophotometry in the ultraviolet region (UV) for quantitative evaluation of MAR in tablets.Purified water-ethanol (80:20, v/v) as a diluent, quartz cubette and 296 nm were used.The method was linear in the range of 3-9 µg/mL (0.9994) with detection and quantification limits of 0.39 and 1.18 µg/mL, respectively, selective in the comparison of standard and sample, precise in intraday (RSD 1.20%), interday (RSD 1.68%), and between analysts (RSD 3.26%) levels, exact with average recovery of 100.39% and robust against small changes in wavelength, diluent concentration, and the use of the ultrasound device. The forced degradation test (sample solutions prepared in 0.1 M HCl, 0.1 M NaOH, and neutral conditions and kept at 60°C during 2 h, and exposure to UV 254 nm lamp at ambient temperature during 2 h) showed that the proposed method is able to assess the susceptibility of MAR.The method can be reliably applied in routine analysis of MAR in tablets as well as being stable, eco-friendly, effective, accessible, and following the principles of green analytical chemistry.MAR, an antimicrobial for veterinary use, does not have a monograph in an official compendium for final product evaluation. The use of MAR-based products with inadequate quality can leave residues in foods of animal origin and can also contribute to microbial resistance. So, an ecologically correct and reliable method was developed to evaluate MAR in a final product.