Theoretical investigation of novel silsesquioxane-supported Phillips-type catalyst by density functional theory (DFT) method

In spite of great commercial importance of the Phillips CrO_x/SiO₂ catalyst and long term research efforts, the precise physicochemical nature of active sites and polymerization mechanisms still remains unclear. The difficulties in a clear mechanistic understanding of this catalyst mainly come from the complexity of the surface chemistry of the amorphous silica gel support. In this work, novel silsesquioxane-supported Phillips Cr catalysts are utilized as realistic models of the industrial catalyst for theoretical investigation using the density functional theory (DFT) method in order to elucidate the effects of surface chemistry of silica gel in terms of supporting of chromium compounds and fluorination of the silica surface on the catalytic properties of the Phillips catalyst. Both qualitative and quantitative aspects with respect to various electronic properties and thermodynamic characteristics of the model catalysts were achieved. The future prospects of a state-of-the-art catalyst design and mechanistic approaches for the heterogeneous SiO₂-supported Phillips catalyst has been demonstrated. The text was submitted by the authors in English.     

Rheological Behavior for Mica-filled Polypropylene Composite Melts

The study on rheological properties of a series of mica-filled polypropylene (PP) composites was carried out. The influence of surface-treatment of mica particles on dynamic rheological behavior of the composites were dealt with. The viscosity (η) and dynamic modulus ( G‘ ) of the composite melts were higher than those of PP matrix, especially those for systems treated with silane, which was attributed to the interfacial adhesion enhancement. However, surface-treatment of mica by titanate resulted in lower η and G‘, as compared with the treatment by silane. The reason for this is believed to be the formation of the mono-molecular layer on the mica surface.     

Theoretical study of the surface energy and electronic structure of pyrite FeS2 (100) using a total-energy pseudopotential method, CASTEP

The geometric and electronic structures of FeS(2) (100) surface have been studied by a quantum-mechanical calculation using a total-energy pseudopotential code, CASTEP. The (100) surface is very stable and does not give any significant geometric relaxation. The electronic structure of FeS(2) (100) surface is characterized by the appearance of new native surface states in the bulk band gap, which correspond to antibonding mixed Fea-Ssp(3) states. These surface states play an important role as mediators of electron transfer on both anodic and cathodic sites in the incipient oxidation of pyrite. Moreover, the (100) surface has small band gaps and shows some metallic character. It is predicted that the rate of cathodic reductive reaction of O(2) in the incipient oxidation of pyrite is much faster than previously considered. The transport of electrons from the anodic sites to the cathodic sites on the (100) surface is faster and hole injection of anodic sites is not the rate-determining step. So we can deduce that the rate-determining step of incipient oxidation for pyrite consists of both electron transfer of pyrite/aqueous O(2) interface and the splitting of H(2)O.     

A dual-electrode approach for highly selective detection of glucose based on diffusion layer theory: experiments and simulation

A dual-electrode configuration for the highly selective detection of glucose in the diffusion layer of the substrate electrode is presented. In this approach, a glassy carbon electrode (GCE, substrate) modified with a conductive layer of glucose oxidase/Nafion/graphite (GNG) was used to create an interference-free region in its diffusion layer by electrochemical depletion of interfering electroactive species. A Pt microelectrode (tip, 5 microm in radius) was located in the diffusion layer of the GNG-modified GCE (GNG-G) with the help of scanning electrochemical microscopy. Consequently, the tip of the electrode could sense glucose selectively by detecting the amount of hydrogen peroxide (H2O2) formed from the oxidization of glucose on the glucose oxidase layer. The influences of parameters, including tip-substrate distance, substrate potential, and electrolyzing time, on the interference-removing efficiency of this dual-electrode approach have been investigated systematically. When the electrolyzing time was 30 s, the tip-substrate distance was 1.8 a (9.0 microm) (where a is the radius of the tip electrode), the potentials of the tip and substrate electrodes were 0.7 V and 0.4 V, respectively, and a mixture of ascorbic acid (0.3 mM), uric acid (0.3 mM), and 4-acetaminophen (0.3 mM) had no influence on the glucose detection. In addition, the current-time responses of the tip electrode at different tip-substrate distances in a solution containing interfering species were numerically simulated. The results from the simulation are in good agreement with the experimental data. This research provides a concept of detection in the diffusion layer of a substrate electrode, as an interference-free region, for developing novel microelectrochemical devices.     

Complexation of plutonium(IV) with sulfate at variable temperatures

The complexation of plutonium(IV) with sulfate at variable temperatures has been investigated by solvent extraction method. A NaBrO₃ solution was used as holding oxidant to maintain the plutonium(IV) oxidation state throughout the experiments. The distribution ratio of Pu(IV) between the organic and aqueous phases was found to decrease as the concentrations of sulfate were increased. Stability constants of the 1:1 and 1:2 Pu(IV)-HSO₄ ⁻ complexes, dominant in the aqueous phase, were calculated from the effect of [HSO₄ ⁻] on the distribution ratio. The enthalpy and entropy of complexation were calculated from the stability constants at different temperatures using the Van’t Hoff equation.     

Interfacial Adhesion between Fatty Acid Collectors and Hydrophilic Surfaces: Implications for Low-Rank Coal Flotation

Fatty acids, which are enriched in vegetable oil, have attracted much attention in low-rank coal flotation because of their unique chemical structure. In this study, density functional theory calculations, molecular dynamics simulations, and atomic force microscopy were employed to investigate the adsorption structure and forces between collectors and hydrophilic surfaces. The results show that fatty acids can be easily adsorbed onto surfaces through hydrogen bonds, and can cover the oxygen sites. The existence of hydration film on hydrophilic surfaces prevented nonpolar molecules from being able to adsorb, while polar fatty acids could adsorb and expel water molecules. The adhesion force between the RCOOH-terminated probe and the surface appeared in the retraction process, which differed significantly from that of the RCH₃-terminated probe, indicating that polar fatty acids are more suitable as flotation collectors for low-rank coal than nonpolar hydrocarbon oil. The simulation and AFM test revealed the mechanisms of polar fatty acids, and can provide guidance for low-rank coal flotation applications.     

Symplectic perturbation series methodology for non-conservative linear Hamiltonian system with damping

In this paper,the symplectic perturbation series methodology of the non-conservative linear Hamiltonian system is presented for the structural dynamic response ...     

Synthesis of Halopyrazole Matrine Derivatives and Their Insecticidal and Fungicidal Activities

Matrine is a traditional botanical pesticide with a broad-spectrum biological activity that is widely applied in agriculture. Halopyrazole groups are successfully introduced to the C13 of matrine to synthesize eight new derivatives with a yield of 78–87%. The insecticidal activity results show that the introduction of halopyrazole groups can significantly improve the insecticidal activity of matrine on Plutella xylostella, Mythimna separata and Spodoptera frugiperda with a corrected mortality rate of 100%, which is 25–65% higher than matrine. The fungicidal activity results indicate that derivatives have a high inhibitory effect on Ceratobasidium cornigerum, Cibberella sanbinetti, Gibberrlla zeae and Collectot tichum gloeosporioides. Thereinto, 4-Cl-Pyr-Mat has the best result, with an inhibition rate of 23–33% higher than that of matrine. Therefore, the introduction of halogenated pyrazole groups can improve the agricultural activity of matrine.     

Effect of Thermal Processing on the Metabolic Components of Black Beans on Ultra-High-Performance Liquid Chromatography Coupled with High-Field Quadrupole-Orbitrap High-Resolution Mass Spectrometry

An ultra-high-performance liquid chromatography coupled with high-field quadrupole-orbitrap mass spectrometry (UHPLC-QE-MS) histological platform was used to analyze the effects of two thermal processing methods (cooking and steaming) on the nutritional metabolic components of black beans. Black beans had the most amino acids, followed by lipids and polyphenols, and more sugars. Multivariate statistical analysis indicated that heat processing significantly affected the metabolic component content in black beans, with effects varying among different components. Polyphenols, especially flavonoids and isoflavones, were highly susceptible. A total of 197 and 210 differential metabolites were identified in both raw black beans and cooked and steamed black beans, respectively. Cooking reduced the cumulative content of amino acids, lipids, polyphenols, sugars, and nucleosides, whereas steaming reduced amino acid and lipid content, slightly increased polyphenol content, and significantly increased sugar and nucleoside content. Our results indicated that metabolic components were better retained during steaming than cooking. Heat treatment had the greatest impact on amino acids, followed by polyphenols, fatty acids, sugars, and vitamins, indicating that cooking promotes the transformation of most substances and the synthesis of a few. The results of this study provide a basis for further research and development of nutritional products using black beans.