Generation of low-molecular-weight organic compounds in water by titania photocatalyst under UV-Vis light radiation

We attempted to develop a new type titania photocatalyst that, when activated, responded in not only the ultraviolet rays region but also visible light radiation region by the new titania photocatalyst with the zirconia and nitrogen simultaneously introduced in the titania lattice. The decomposition performance of the standard organic compound in water by this new type titania photocatalyst nanoparticle was compared with the conventional type under both the ultraviolet ray and visible light radiation conditions. It was suggested that the low-molecular-weight organic compounds were also generated from the organic compound in water by the new type titania photocatalyst activities under the visible light radiation.     

A Comparison of Corona-Treated and Flame-Treated Polypropylene Films

The comparison of corona-treated and flame-treated polypropylene (PP) films provides insight into the mechanism of these surface-oxidation processes. Atomic force microscopy (AFM), contact-angle measurements, and X-ray photoelectron spectroscopy (XPS or ESCA) were used to characterize surface-treated biaxially oriented PP. While both processes oxidize the PP surface, corona treatment leads to the formation of water-soluble low-molecular-weight oxidized materials (LMWOM), while flame treatment does not. Computational modeling of the gas-phase chemistry in an air corona was performed using a zero-dimensional plasma-chemistry model. The modeling results indicate that the ratio of O to OH is much higher in a corona discharge than in a flame. Chain scission and the formation of LMWOM are associated with reactions involving O atoms. The higher ratios of O to OH in a corona are more conducive to LMWOM production. Surface-oxidized PP exhibits considerable thermodynamic contact-angle hysteresis that is primarily caused by microscopic chemical heterogeneity.     

Oxidation of Methanol and Other Low-Molecular-Weight Alcohols on the RuNi Catalysts in an Alkaline Environment

The results of investigations of the RuNi catalysts, which are designed for the electrooxidation of methanol and other low-molecular-weight alcohols in alkaline solutions, are presented. It is shown that the maximum catalytic activity in this reaction is exhibited by a catalyst, which was synthesized thermochemically on acetylene black AD100 containing 15 wt % RuNi at a 68 : 32 atomic ratio (in at. %) between the metals. The structure of the synthesized catalysts is studied by the methods of x-ray photoelectron spectroscopy and x-ray diffraction analysis (XRDA). The area of the metal surface is determined on the basis of the magnitude of the adsorption of CO from the voltammetric curves. An analysis of the data obtained in this work leads to the conclusion that ruthenium in the composition of the catalyst exists in metallic and partially oxidized states and nickel exists in the form of a nonstoichiometric oxide. In addition it is found that the insertion of nickel into the system leads, as follows from the XRDA data, to the dispersion of ruthenium and, as follows from the voltammetric curves, to a decrease in the specific surface area accessible to the adsorption of CO. This is probably connected with the decoration and blockade of a portion of the ruthenium surface by some nickel oxides. Data on the influence, which is exerted by the concentration of methanol, alkali, and temperature on the electrocatalytic activity of the AD100 + 15 wt % RuNi catalyst at a 68 : 32 atomic ratio (in at. %) between the components, are presented. Rates of the oxidation of methanol, ethanol, n-butanol, and ethylene glycol in identical conditions on the catalyst AD100 + 15 wt % RuNi (68 : 32 at. %) between the metals are compared with one another. The oxidation currents, which are observed at a potential of 0.3 V, are equal to 5.48, 2.67, 0.48, and 0.47 A per gram of the catalyst for ethanol, ethylene glycol, methanol, and n-butanol, respectively.__________Translated from Elektrokhimiya, Vol. 41, No. 7, 2005, pp. 829–839.Original Russian Text Copyright © 2005 by Tarasevich, Karichev, Bogdanovskaya, Kapustin, Lubnin, Osina.     

The variations of the configurational and solvency properties of low molecular weight sodium polyacrylate with ionic strength

The configurational and solvency properties of low molecular weight sodium polyacrylate have been determined for a wide range of ionic strength solutions, from intrinsic viscosity data in the polymer literature.The variations of the polymer properties with ionic strength (I) are described very well by simple mathematical expressions. Thus, a linear relationship was found between the solvency parameter and 1/I ^(1/2), while the variations of the expansion factor and the radius of gyration with 1/I ^(1/2) were described by second order polynomials.LowI solutions (i.e. < 0.01) have a high solvency for sodium polyacrylate. In such solutions the polymer is in a highly expanded configuration. Thus, the radius of gyration of a typical, low molecular weight (ca. 5000 g mol^–1) sodium polyacrylate approaches the limiting value of ca. 4.5 nm atI<0.01.Conversely, high ionic strength solutions (i.e. >0.10) have a low solvency for sodium polyacrylate. In such solutions the polymer is in a virtually unexpanded configuration. Thus, the radius of gyration of a typical, low molecular weight sodium polyacrylate approaches the limiting value of ca. 2.0 nm atI>0.10.     

Mechanism of plasma polymerization ofN-silyl-substituted cyclodisilazane: Structure and properties of polymer film

NN-Bis(dimethylsilyl)tetramethylcyclodisilazane (NSCDSN) was selected for plasma polymerization as a model monomer representing N-silyl-substituted cyclodisilazanes. Owing to the aromatic character resulting from the strong (d-p) coupling between silicon and nitrogen atoms, these compounds manifest the highest thermal stability among the organosilicones. GC/MS examination of a low-molecular-weight fraction evaporated from the plasma polymer revealed the presence of various monomer derivatives having mostly the general structure of N-silyl-substituted cyclodisilazane (Si₄N₂) units. GC/MS and ATR/IR studies have shown that the Si₄N₂ skeleton displays a high resistance to plasma fragmentation and that it was incorporated as such into the polymer film. A radical mechanism for plasma polymerization was postulated assuming the formation of and propagation precursors. The low value found for the polar component of the surface free energy confirmed the contribution of Si₄N₂ units to the polymer film. TGA investigation showed the rate and degree of thermal decomposition of plasma-polymerized (PP) NSCDSN to be lower than those of plasma polymers from N-hydrogen-substituted silazanes. Vacuum pyrolysis, at 800°C, converted the polymer film into a glassy, dense, and almost inorganic material with a strong adhesion to the metal substrates.     

用毛细管电泳方法分离有机酸的研究

利用3-氨丙基三甲氧基硅烷（3-APS）作为偶联剂将2，4-二硝基氯苯键合到电泳毛细管内壁上，形成具有一定疏水性的键合相，考察了改性柱对小分子有机酸的分离情况，在40mmol/L的KH2PO4（pH=5.5）缓冲溶液中可得最佳分离，结合量子化学计算数据进行保留机理的探索，可以确定存在着不同电性的集团间的相互作用。     

Methodological Fallacies in the Determination of Serum/Plasma Glutathione Limit Its Translational Potential in Chronic Obstructive Pulmonary Disease

This study aimed to review and critically appraise the current methodological issues undermining the suitability of the measurement of serum/plasma glutathione, both in the total and reduced form, as a measure of systemic oxidative stress in chronic obstructive pulmonary disease (COPD). Fourteen relevant articles published between 2001 and 2020, in 2003 subjects, 1111 COPD patients, and 892 controls, were reviewed. Nine studies, in 902 COPD patients and 660 controls, measured glutathione (GSH) in the reduced form (rGSH), while the remaining five, in 209 COPD patients and 232 controls, measured total GSH (tGSH). In the control group, tGSH ranged between 5.7 and 7.5 µmol/L, whilst in COPD patients, it ranged between 4.5 and 7.4 µmol/L. The mean tGSH was 6.6 ± 0.9 µmol/L in controls and 5.9 ± 1.4 µmol/L in patients. The concentrations of rGSH in the control group showed a wide range, between 0.47 and 415 µmol/L, and a mean value of 71.9 ± 143.1 µmol/L. Similarly, the concentrations of rGSH in COPD patients ranged between 0.49 and 279 µmol/L, with a mean value of 49.9 ± 95.9 µmol/L. Pooled tGSH concentrations were not significantly different between patients and controls (standard mean difference (SMD) = −1.92, 95% CI −1582 to 0.0219; p = 0.057). Depending on whether the mean concentrations of rGSH in controls were within the accepted normal range of 0.5–5.0 µmol/L, pooled rGSH concentrations showed either a significant (SMD = −3.8, 95% CI −2.266 to −0.709; p < 0.0001) or nonsignificant (SMD = −0.712, 95% CI −0.627 to 0.293; p = 0.48) difference. These results illustrate the existing and largely unaddressed methodological issues in the interpretation of the serum/plasma concentrations of tGSH and rGSH in COPD.     

Simultaneous Determination of Human Serum Albumin and Low-Molecular-Weight Thiols after Derivatization with Monobromobimane

Biothiols are extremely powerful antioxidants that protect cells against the effects of oxidative stress. They are also considered relevant disease biomarkers, specifically risk factors for cardiovascular disease. In this paper, a new procedure for the simultaneous determination of human serum albumin and low-molecular-weight thiols in plasma is described. The method is based on the pre-column derivatization of analytes with a thiol-specific fluorescence labeling reagent, monobromobimane, followed by separation and quantification through reversed-phase high-performance liquid chromatography with fluorescence detection (excitation, 378 nm; emission, 492 nm). Prior to the derivatization step, the oxidized thiols are converted to their reduced forms by reductive cleavage with sodium borohydride. Linearity in the detector response for total thiols was observed in the following ranges: 1.76–30.0 mg mL⁻¹ for human serum albumin, 0.29–5.0 nmol mL⁻¹ for α-lipoic acid, 1.16–35 nmol mL⁻¹ for glutathione, 9.83–450.0 nmol mL⁻¹ for cysteine, 0.55–40.0 nmol mL⁻¹ for homocysteine, 0.34–50.0 nmol mL⁻¹ for N-acetyl-L-cysteine, and 1.45–45.0 nmol mL⁻¹ for cysteinylglycine. Recovery values of 85.16–119.48% were recorded for all the analytes. The developed method is sensitive, repeatable, and linear within the expected ranges of total thiols. The devised procedure can be applied to plasma samples to monitor biochemical processes in various pathophysiological states.     

Catalytic and physicochemical properties of crystalline pentasils in transformations of low-molecular-weight olefins and paraffins

The features of the catalytic action of pentasil type zeolites in transformations of low-molecular-weight olefins and paraffins are reviewed. Principal results describing the physicochemical properties of pentasils elucidated by IR spectroscopy, electron microscopy, XPS, and ESR are discussed. The mechanism of the formation of catalytically active sites on the surface of pentasils and the location of modifying elements in the zeolite frameworks are examined. The role of Lewis and Bronsted acid sites in promoting single pathways in the transformations of lower hydrocarbons is specified.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1018–1028, June, 1993.