Synthesis,characterization and kinetic study of the Sr2FeMoO6-δ double perovskite: New findings on the calcination of one of its precursors

Sr₂FeMoO_6-δ double perovskites are widely-recognized due to several important factors: high electronic conductivity and electrocatalytic activity, structural stability under reducing atmospheres, high transition temperature, enormous magnetoresistance, reasonable tolerance to carbon formation, and their desirable capacity to avoid sulfur poisoning. One of the methods most commonly-used to synthetize these perovskites is solid-state reaction. The precursor phases usually associated with this method are the oxides SrMoO₄ and SrFeO_3-δ when Fe2O₃, SrCO₃, and MoO₃ are the initial reagents used. Morphological, XRD (Rietveld), and thermogravimetry (calcination and reduction) analyses are steps or routes towards achieving the final result. While recent studies suggest that the temperature of calcination is always 900 °C and that reduction occurs at 1200 °C, they fail to explain why this occurs. This article demonstrates, according to the results of thermogravimetric analysis (TGA), that as calcination advances weight loss increases until a temperature of 850 °C is reached. In addition, it stresses the importance of the ball milling technique at ambient temperature to prevent sublimation of the MoO₃ compound at 700 °C in the later steps of synthesis, such as calcination and reduction. According to the kinetic study, the values of activation energy (Ea) and reaction order (n) were 130.47 kJ/mol and 1 respectively.     

Coal liquefaction by the hydrogen produced from methanol

Methanol was used as an in-situ hydrogen source, following its decomposition over ZnO-Cr₂O₃, for the hydrogenation of coal. The reaction was carried out in a high pressure autoclave at ≈400–440 °C, in the presence of different hydrogenation catalysts. Stabilized nickel, stabilized Co and Ni-Cr-Cu catalysts gave excellent results. The maximum conversion was 100% for pyridine, 94.4% for benzene and 66.2% for straight-chain hexane.     

Thermodynamic evaluation of steam gasification mechanisms of carbonaceous materials

Reactions of water with clean, oxidized, and hydrogenated carbon surfaces were investigated using density functional theory. It was confirmed that H₂O can dissociatively chemisorb through highly exothermic reactions on the active sites of clean zigzag and armchair carbonaceous models to yield stable intermediates such as hydroxyl, semiquinone, and cyclic ether functional groups. Since the main products of the carbon-steam gasification process are molecular hydrogen and carbon monoxide, several pathways for their evolution are proposed, all of which are endothermic reactions. The interaction of H₂O with an oxidized surface in some cases is even more exothermic than the interaction with the active sites of a clean surface. However, it becomes endothermic when H₂O interacts with a hydrogen saturated surface. Thus, the presence of hydrogen hinders the gasification reactions by blocking of the active sites rather than by removing surface oxygen.     

Effect of Thermoplastic Starch and Photocrosslinking on the Properties and Morphology of Electrospun Poly(ethylene-co-vinyl alcohol) Mats

Nonwoven fibrous mats of poly(ethylene-co-vinyl alcohol) (EVOH) and thermoplastic starch (TPS) blends were successfully prepared through the electrospinning technique using a mixed solvent system of isopropyl alcohol and water. The influence of TPS on the morphology and structure of the fibrous mats was investigated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. The addition of TPS to EVOH resulted in beaded electrospun fibers. The SEM images revealed decreasing average width of the blend fibers and increasing quantity of beads with an increased TPS content. EVOH/TPS fibers mats irradiated under ultraviolet light using sodium benzoate as a photosensitizer were also prepared. The size and number of beads were diminished in the photocrosslinked EVOH/TPS fiber mats. The as-spun and crosslinked EVOH/TPS fiber mats exhibit a superior fluid uptake ability (with 20 wt% of TPS) and superior barrier properties (with 20 and 40 wt% of TPS) in comparison to those observed in neat electrospun EVOH mats. These properties are of particular interest for use in dressing materials for the medical industry and for use in multilayer plastic fuel tanks for the automotive industry, respectively. POLYM. ENG. SCI., 60:474–480, 2020. © 2019 Society of Plastics Engineers     

Desorption activation energy distribution function of nitric oxide chemisorbed on carbonaceous materials at 373 K

The distribution function for the activation energy of NO desorption from carbonaceous materials treated with mixtures of NO, NO/O₂ and NO/H₂O/O₂ at 373 K, was determined. The algorithm employed in the calculation was a variation of the stochastic method commonly used for the evaluation of the activation energies from TPD data. The calculated distribution function is a combination of two normal distribution functions, centered at energies around 150 and 190 kJ/mol which corresponds to the desorption of NO from organic structures as was previously determined by XPS analysis. The higher activation energy complex is promoted by the catalytic activity of the mineral matter in the char. Molecular oxygen enhances the NO reversible chemisorption while water partly inhibits this effect.     

Silver nanoparticle deposition on hydrophilic multilayer film surface and its effect on antimicrobial activity

Silver nanoparticles were deposited on the surface of the external polyamide 6 (PA6) layer of a multilayer film, by spraying and ultrasound‐assisted methods. The effect of silver nanoparticles content and deposition method on the mechanical and optical properties of the multilayered films as well as the efficiency of silver ion release and their fungicidal characteristics were evaluated. Itaconic (IA) and Maleic anhydride (MA) were used as adhesion promoter agents for preventing the agglomeration of the silver nanoparticles and for improving the adhesion to the PA6 polymer surface. With IA, a homogeneous distribution of silver nanoparticles on the PA6 surface was achieved. The silver ion release and biocide effect of the multilayered films was found to be dependent on the anhydride type and on the deposition method used. The multilayer films with a layer of PA6‐silver nanocomposite demonstrated good fungicidal activity, specifically against fungus Aspergillius niger. The observed results could be applied in the design of industrial films for packaging. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The commercialization of nanomaterials: Today and tomorrow

Nanomaterials are receiving increasing attention in the technical community and the public at large. There are numerous activities throughout the world focusing on a wide range of developments, including privately and publicly funded work. From an industrial perspective, the measure of success of these programs will be the number of new products that are introduced to the market. The purpose of this article is to discuss issues related to the commercialization of nano-enhanced materials as well as to propose areas for future commercial developments. Author's Note: The material in this paper is intended for general information only. Any use of this material in relation to any specific application should be based on independent examination and verification of its unrestricted availability for such use, and a determination of suitability for the application by professionally qualified personnel. No license under any patents or other proprietary interest of any party is implied by the publication of this paper. Those making use of or relying upon any information furnished in this paper assume all risks and liability arising from such use or reliance, and no warranty of any kind is given with respect thereto, including, without limitation, any express or implied warranties of merchantability or fitness for an intended purpose. Editor's Note: A hypertext-enhanced version of this article is available on-line at www.tms.org/pubs/journals/JOM/0604/Osman-0604html.     

ATP‐Noncompetitive Inhibitors of CDK–Cyclin Complexes

Progression through the cell division cycle is controlled by a family of cyclin‐dependent kinases (CDKs), the activity of which depends on their binding to regulatory partners (cyclins A–H). Deregulation of the activity of CDKs has been associated with the development of infectious, neurodegenerative, and proliferative diseases such as Alzheimer's, Parkinson's, or cancer. Most cancer cells contain mutations in the pathways that control the activity of CDKs. This observation led this kinase family to become a central target for the development of new drugs for cancer therapy. A range of structurally diverse molecules has been shown to inhibit the activity of CDKs through their activity as ATP antagonists. Nevertheless, the ATP binding sites on CDKs are highly conserved, limiting the kinase specificity of these inhibitors. Various genetic and crystallographic approaches have provided essential information about the mechanism of formation and activation of CDK–cyclin complexes, providing new ways to implement novel research strategies toward the discovery of new, more effective and selective drugs. Herein we review the progress made in the development of ATP‐noncompetitive CDK–cyclin inhibitors.     

Peptides and Peptide Mimics as Modulators of Apoptotic Pathways

Cells in the balance : Programmed cell death is an important and stringently controlled process. Aberrancies in its control mechanisms can lead to disease; overactive apoptosis can cause neurodegenerative disorders, whereas deficient apoptotic activity can lead to cancer. Therefore, controlling apoptotic pathways with peptides is showing increasing promise as a strategy in drug development.

     

Conformationally restricted hydantoin-based peptidomimetics as inhibitors of caspase-3 with basic groups allowed at the S3 enzyme subsite

By using a combination of molecular modeling, combinatorial chemistry, and biological essays, novel scaffold molecules for the inhibition of caspase-3 have been developed. These compounds have an overall attenuated negative charge and show similar IC(50) values for both recombinant and human endogenous caspase-3. This might provide the basis for a novel strategy for the discovery of potent and more druglike inhibitors of caspase-3.