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Reduction of [PtCl6]2- by L-ascorbic acid (H2ASc) in 0.1M aqueous acid medium has been investigated spectrophotometrically under pseudo-first order condition at [PtCl6]2- = 0.005-0.007 mol dm-3, 0.05 ⩽ [H2ASc]/moldm-3 ⩽0.3, 298 K ⩽ T ⩽308 K, [H+] = 0.14 mol dm-3, I = 0.5moldm-3 . The redox reaction follows the rate law: d[Pt(IV)]/dt = k[H2ASc][Pt(IV)], where k is the second-order rate constant and [H2ASc] is the total concentration of ascorbic acid. Electron transfer from [H2ASc] to Pt(IV) center leading to the release of two halide ions and formation of the reaction products, square planner Pt(II) halide complex, and dehydrated ascorbic acid is suggested. This redox reaction follows an outersphere mechanism as Pt(IV) complex is substituted inert. Activation parameters were calculated corresponding to rate of electron transfer reaction k. Activation parameters favor the electron transfer reaction. [ABSTRACT FROM AUTHOR]

Necessary condition for β-decay suppression of a neutron in degenerate magnetized electron gas is formulated. Based on this, it is shown that, in superstrong magnetic field, equilibrium radius of a neutron star is approximately several times smaller than without the field influence. Therefore, we can make a prediction that in short-period pulsars, such fields can be observed. In fact, possible existence of new class of stellar objects is noted, the objects with superstrong magnetic field and supersmall radius about 1 km which we named minimagnetars. They can be detected by gravitational red shift of their radiation. [ABSTRACT FROM AUTHOR]

The minimum speed for just-suspension, Njs, of porous palm shell-activated carbon (PSAC) particles has been determined in a 15 cm diameter cylindrical tank using a 6-curved blade (6CB) impeller, compared to a 6-blade downpumping mixed-flow (6MFD) impeller and a Rushton turbine (6DT). The particles size ranged from 0.75-1.00 mm, 1.00-1.40 mm, and 1.40-2.36mm with concentrations between 0 and 5% by weight. The 6CB being a radial impeller performed similarly to 6DT in terms of speed and power requirement at just-suspension, and particles distribution on the base. The 6MFD, with power requirement 100% to 200% less than the radial impellers, was the most efficient for suspending the particles, as usually reported for the range of solid concentrations used here. Specific power per unit mass for all three impellers showed reduction towards minima as the concentration of particles increased. The geometric factor, S, values agreed reasonably with published data, when the particle density was adjusted taking into account water filling the pores of the submerged activated carbon. This result means that Zwietering's equation can be used to predict suspension for porous particles with adjustment to the particle density. S values for curved-blade impellers are presented for the first time. [ABSTRACT FROM AUTHOR]

Protein wastes (feathers, goat hair) and cellulosic wastes (corn cob, coconut husks) were collected and washed with detergent solution, thoroughly rinsed and sun dried for 2 days before drying in an oven, and then ground. One-half of ground material was carbonized at a maximum temperature of 500°C after mixing with H2SO4. The carbonized parts were pulverized; both carbonized and uncarbonized sorbents were sieved into two particle sizes of 325 and 625 μm using mechanical sieve. Sorbents of a given particle size were packed into glass column. Then, textile wastewater that had its physicochemical parameters previously determined was eluted into each glass column and a contact time of 60 and 120 mins was allowed before analysis. Results showed 48.15-99.98 percentage reduction of NO3 -, EC,Cl-, BOD, COD,DO, TSS, and TDS, 34.67-99.93 percentage reduction of NO3 -, EC,Cl-, BOD, COD, DO, TSS, and TDS, 52.83-97.95 percentage reduction of Pb2+, Ni2+, Cr3+ and Mn2+ and 34.59-94.87 percentage reduction of Pb2+, Ni2+, Cr3+ and Mn2+. Carbonization, small particle, size and longer contact time enhanced the sorption capabilities of the sorbents. These show that protein and cellulosic wastes can be used to detoxify wastewater. [ABSTRACT FROM AUTHOR]

A versatile and convenient synthesis of 2-substituted benzimidazoles, using o-nitroaniline as starting material with several aryl aldehydes, has been accomplished by using a small amount of a reluctant agent. The reaction was carried out under very mild conditions at room temperature. The yields obtained are very good in reasonably short reaction times. [ABSTRACT FROM AUTHOR]

PET Vascular prostheses are susceptible to physical modification and chemical degradation leading sometimes to global deterioration and rupture of the product. To understand the mechanisms of degradation, we studied 6 vascular prostheses that were explanted due to medical complications. We characterized their level of degradation by comparing them with a virgin prosthesis and carried out physicochemical and mechanical analyses. Results showed an important reduction of the fabric's mechanical properties in specific areas. Moreover, PET taken from these areas exhibited structural anomalies and was highly degraded even in virgin prostheses. These results suggest that vascular prostheses have weak areas prior to implantation and that these areas are much more prone to in vivo degradation by human metabolism. Manufacturing process could be responsible for these weaknesses as well as designing of the compound. Therefore, we suggest that a more controlled manufacturing process could lead to a vascular prosthesis with enhanced lifespan. [ABSTRACT FROM AUTHOR]

In our study, graphene oxide is synthesized by Hummers method. And then, carboxylic acid functionalized graphene (graphene- COOH), thiol-functionalized graphene (graphene-SH), and highly dispersive graphene are prepared by chemical modification of respective groups on the graphene surface. Furthermore, we explore a solution-based approach to prepare three differently functionalized graphene-gold composites by one-step chemical reduction of AuCl4- ions in respective functionalized graphene suspensions, where the gold nanoparticles are deposited on the functionalized graphene surface during their synthesis process. In addition, we compare the influence of surface functionalization on the growth of gold nanoparticles on graphene surface. Transmission electron morphology (TEM) and ultraviolet-visible (UV-Vis) spectroscopy are employed to study the effect of surface functionalities on AuNPs distribution onto the graphene surface and demonstrate the successful immobilization of AuNPs on graphene surface. [ABSTRACT FROM AUTHOR]

The aims of this study, firstly, to obtain high degree of clay exfoliation in the epoxy matrix by three dispersion methods such as normal mixing, shear mixing, and high-speed mixing and, secondly, to investigate corrosion behavior of epoxy/organoclay nanocomposite, immersion test, weight change, and penetration behavior were conducted. From the three mixing methods, the high-speed mixing method showed larger clay interlayer distance, smaller clay aggregate, and more homogeneity and expectedly resulted in high anticorrosive properties. Penetration depths of these nanocomposites showed a small difference; however, the most noticeable improvements in anticorrosion performance for epoxy/organoclay nanocomposites under high-speed mixing method were found to reduce penetration and weight uptake which are described via the model of nanoparticulate-filled structure and discussed in corrosion protection mechanism against environmental liquid penetration. [ABSTRACT FROM AUTHOR]

This paper describes the electrocatalytic activity for CO, MeOH, and EtOH oxidation on the surface of Pt-Ru nanoparticles supported by metal oxide (Nb-TiO2-H) prepared for use in a fuel cell. To prepare Nb-TiO2-supported Pt-Ru nanoparticles, first, the Nb-TiO2 supports were prepared by sol-gel reaction of titanium tetraisopropoxide with a small amount of the niobium ethoxide in polystyrene (PS) colloids. Second, Pt-Ru nanoparticles were then deposited by chemical reduction of the Pt4+ and Ru3+ ions onto Nb-TiO2 supports (Pt-Ru@Nb-TiO2-CS). Nb element was used to reduce electrical resistance to facilitate electron transport during the electrochemical reactions on a fuel cell electrode. Finally, the Pt-Ru@Nb-TiO2-H catalysts were formed by the removal of core-polystyrene ball from Pt-Ru@TiO2-CS at 500°C. The successfully prepared Pt-Ru electrocatalysts were confirmed via TEM, XPS, and ICP analysis. The electrocatalytic efficiency of Pt-Ru nanoparticles was evaluated via CO, MeOH, and EtOH oxidation for use in a directmethanol fuel cell (DMFC). As a result, the Pt-Ru@Nb-TiO2-H electrodes showed high electrocatalytic activity for the electrooxidation of CO, MeOH, and EtOH. [ABSTRACT FROM AUTHOR]

Bimetallic nanoparticles are important because they possess catalytic and electronic properties with potential applications in medicine, electronics, and chemical industries. A galvanic replacement reaction synthesis has been used in this research to form bimetallic nanoparticles. The complete description of the synthesis consists of using the chemical reduction of metallic silver nitrite (AgNO3) and gold-III chloride hydrate (HAuCl) salt precursors. The nanoparticles display round shapes, as revealed by high resolution transmission electron microscope (HRTEM). In order to better understand the colloidal structure, it was necessary to employ computational models which involved the simulations of HRTEM images. [ABSTRACT FROM AUTHOR]

Parathion has been determined with voltammetric technique based on a novel sensor fabricated by electropolymerization of safranine on a glassy carbon electrode (GCE). The electrochemical behavior of poly(safranine) film electrode and its electrocatalytic activity toward parathion were studied in detail by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). All experimental parameters were optimized, and LSV was proposed for its determination. In optimal working conditions, the reduction current of parathion at this poly(safranine)-modified electrode exhibited a good linear relationship with parathion concentration in the range of 3.43 × 10-8 to 3.43 × 10-5 mol L-1. The detection limit was 1.0 × 10-8 mol L-1. The high sensitivity and selectivity of the sensor were demonstrated by its practical application for the determination of trace amounts of parathion in fruit samples. [ABSTRACT FROM AUTHOR]

The electrochemical properties of silver nanoparticle (d ∼ 5 nm) synthesized within aminosilica film from spontaneous reduction reaction were examined using cyclic voltammetry and the results show that the nanocomposite film exhibits similar redox property as solution-synthesized silver nanoparticles whenmeasuring in phosphate buffer solution and its redox potentials were found to be sensitive to the presence of chloride ions. It also shows that silver nanoparticles and hydrolyzed aminosilica increase the electron diffusivity of the aminosilica film. Both results confirm that an accurate reference electrode suitable for microfluidic devices can be created simply by treating an aminosilica-coated electrode with a silver nitrate solution. Furthermore, a humidity sensor based on silver-silica nanocomposite film has also been demonstrated. [ABSTRACT FROM AUTHOR]

It was previously reported that CO2 could be reduced into CO, CH4, and so forth, which can be used as fuels, by TiO2 as the photocatalyst under UV radiation. To increase the concentration of fuel and improve CO2 reduction performance on TiO2 photocatalyst, a membrane reactor composed of TiO2 and gas separation membrane prepared by sol-gel and dip-coating method has been built. Factors such as rising speed (RS) in the dip-coating process and the timing and amount of water injected in the membrane reactor in CO2 reduction experiment have been investigated. As a result, the largest amount of TiO2 film is obtained for RS = 0.66 mm/s among various RS conditions investigated in this study. According to CO2 reduction experiment by gas circulation type reactor, too much water which cannot be consumed in CO2 reduction process would not help improving the CO2 reduction performance. [ABSTRACT FROM AUTHOR]

The kinetics of the reduction of colloidal MnO2 by glyphosate has been investigated spectrophotometrically in an aqueous and micellar (cetyltrimethylammonium bromide, sodium lauryl sulfate) media. The reaction follows first-order kinetics with respect to colloidal MnO2 in both the aqueous and micellar media. The rate of oxidation increases with increase in [glyphosate] in the lower concentration range but becomes independent at its higher concentrations. The addition of both the anionic (NaLS) and cationic (CTAB) micelles increased the rate of reduction of colloidal MnO2 by glyphosate while the nonionic TX-100 micelles did not influence the rate of reaction. In both aqueous and micellar media, the oxidation of glyphosate occurs through its adsorption over colloidal MnO2 surface. The reaction in micellar media was treated by considering the pseudophase model. The values of reaction rates and binding constants in the presence of micelles were determined [ABSTRACT FROM AUTHOR]

Two novel transition metal complexes with malonate and reduced imino nitroxide radicals, [Co(mal)(Him2-py)2] (ClO4)1 and [Mn(mal)(Him2-py) 2] (H2O)2 (Him2-py = 1-hydroxy-2-(2'-pyridyl)-4,4,5,5-tetramethylimidazoline) have been synthesized and their crystal structures were determined by X-ray diffraction method. During the reaction, one-electron reduction of the N-O radical moiety in IM2py has been reviewed. The structural analyses reveal that two title complexes are isostructural and crystallize in monoclinic space group C2. For the complex 1, a = 17.004(9), b = 10.753(5), c = 9.207(5) Åwith β = 113.856(8)°. For the complex 2, a = 16.721(5), b = 10.897(5), c = 9.253(3) Åwith β = 120.807(6)°. In two complexes, the coordination number around the metal ion is six, and the coordination sphere is a distorted octahedron. Two nitrogen atoms from Him2-py and two oxygen atoms from malonate are in the basal plane, and two nitrogen atoms from pyridyl rings of Him2-py at the axial position [ABSTRACT FROM AUTHOR]

The electrochemical reduction behavior of fluchloralin has been studied by D.C.polarography, differential pulse polarography, millicoulometry and controlled potential electrolysis in the universal buffers ranging from 2.0 to 12.0. Kinetic parameters were evaluated and a reduction mechanism was proposed. A simple and rapid differential pulse polarographic method has been developed for the determination of fluchloralin in formulations, grains, soils and spiked water samples. The lower detection limit was found to be 1.5×10-8 M. Both the standard addition and calibration methods were used for the analytical measurements. [ABSTRACT FROM AUTHOR]

Arc-fabricated copper nanoparticles (Cu Nps) size, morphology and the crystalline structure, as well as the yields of Nps appear sensitive to the applied currents (50-160 A) in distilled water. The results indicate that the sizes of Cu Nps are directly proportional to the currents employed. At 50 A, TEM, XRD, and SEM analyses show fabrication of relatively purest, the most dispersed, facecentered cubic (fcc) brown Cu Nps with rather smallest average size of 20 nm. At the same current, the TGA-DTA analysis reveals neither weight loss nor gain, indicating thermal stability of the fabricated Cu Nps. [ABSTRACT FROM AUTHOR]

We evaluated the chemopreventive effect of nonsteroidal anti-inflammatory drug (NSAID) use in head and neck squamous cell carcinomas (HNSCC) by conducting a case-control study based on the administration of a standardized questionnaire to 71 incident HNSCC cases and same number of healthy controls. NSAID use was associated with a 75% reduction in risk of developing HNSCC. A significant risk reduction was noted in association with frequency of NSAID use. Restricting the analysis to aspirin users revealed a significant 90% reduction in risk of developing HNSCC. This study provides evidence for a significant reduction in the risk of developing HNSCC in users of NSAIDs, and specifically aspirin users. [ABSTRACT FROM AUTHOR]

A reverse phase HPLC method is described for the determination of cinitapride hydrogen tartrate in the presence of its degradation products in bulk drug. A drug was subjected to all stress conditions such as reduction, oxidation acidic and alkaline medium. Chromatography was recorded on an Intersil ODS-3 column using mixture of acetonitrile and phosphate buffer, pH adjusted to 6.7 in the ratio (70:30 v/v) as the mobile phase at the rate of 1.0 mL/min with detection at 260 nm. Glimepride was used as internal standard. The retention time of drug cinitapride was 3.8 min and glimepride an internal standard was 2.5 minute. The drug was found to degrade extensively in reduction conditions and mild degradation in the presence of in alkaline, acidic and oxidative but the drug was stable in thermal stress. The method was validated by determining its specificity, linearity, precision and accuracy. The developed method with good separation of all degradation products from drug could be successfully applied for the determination of cinitapride in the presence of its degradation products in the bulk drug. The proposed method is simple, fast, accurate and precise and hence applied for routine quality control of cinitapride in bulk drug. It can be used for analysis of samples during stability testing. [ABSTRACT FROM AUTHOR]

Reduction mechanisms of oxygen molecule to water molecules in the fully reduced (FR) and mixed-valence (MV) bovine cytochrome c oxidases (CcO) have been systematically examined based on the B3LYP calculations. The catalytic cycle using four electrons and four protons has been also shown consistently. The MV CcO catalyses reduction to produce one water molecule, while the FR CcO catalyses to produce two water molecules. One water molecule is added into vacant space between His240 and His290 in the catalytic site. This water molecule constructs the network of hydrogen bonds of Tyr244, farnesyl ethyl, and Thr316 that is a terminal residue of the K-pathway. It plays crucial roles for the proton transfer to the dioxygen to produce the water molecules in both MV and FR CcOs. Tyr244 functions as a relay of the proton transfer from the K-pathway to the added water molecule, not as donors of a proton and an electron to the dioxygen. The reduction mechanisms of MV and FR CcOs are strictly distinguished. In the FR CcO, the Cu atom at the CuB site maintains the reduced state Cu(I) during the process of formation of first water molecule and plays an electron storage. At the final stage of formation of first water molecule, the Cu(I) atom releases an electron to Fe-O. During the process of formation of second water molecule, the Cu atom maintains the oxidized state Cu(II). In contrast with experimental proposals, the K-pathway functions for formation of first water molecule, while the D-pathway functions for second water molecule. The intermediates, PM, PR, F, and O, obtained in this work are compared with those proposed experimentally. [ABSTRACT FROM AUTHOR]

The synthesis of new trans A2B2-substituted porphyrins bearing oxygenic substituent (methoxy, acetoxy, hydroxy) at the periphery of the ring are described. All of the synthesized products were characterized by ¹H-N.M.R., 13C-N.M.R., and H.R.M.S. Electrochemical studies revealed two one-electron oxidations and two reductions. In addition, the X-ray structure of onemethoxy- derivative was determined. [ABSTRACT FROM AUTHOR]

A simazine sensing system, composed of column packed with a molecularly imprinted polymer (Sim-MIP) and an electrochemical analyzer, was scaled down in order to easily determine the concentration of simazine, an environmentally restricted chemical, in tap water. In order to enhance the detection limit, the ratio of the eluent (dilution rate) in the electrolyte was optimized to 10%. A new in-house built column size with ∅=1.5mm was prepared, and 3mg of Sim-MIP particles was packed in the column. During the sensing process, 90% of the simazine loaded to the column was collected by elution. The reductive current of simazine was determined up to 1-10μM. Solid phase extraction through the Sim-MIP column enabled simazine to be selectively detected from a mixed aqueous solution containing structural analogues in the range of 10-40 nM. Whether the concentration of simazine in tap water had reached environmentally restricted levels (10-40 nM) was determined within 1 hour using this system. [ABSTRACT FROM AUTHOR]