Electrochemical oxidation of boron containing compounds on titanium carbide and its implications to direct fuel cells

Electrochemical oxidation of sodium borohydride (NaBH(4)) and ammonia borane (NH(3)BH(3)) (AB) have been studied on titanium carbide electrode. The oxidation is followed by using cyclic voltammetry, chronoamperometry and polarization measurements. A fuel cell with TiC as anode and 40 wt% Pt/C as cathode is constructed and the polarization behaviour is studied with NaBH(4) as anodic fuel and hydrogen peroxide as catholyte. A maximum power density of 65 mW cm(-2) at a load current density of 83 mA cm(-2) is obtained at 343 K in the case of borhydride-based fuel cell and a value of 85 mW cm(-2) at 105 mA cm(-2) is obtained in the case of AB-based fuel cell at 353 K. (C) 2011 Elsevier Ltd. All rights reserved.

Study of surface oxidation of rare-earth-metals by photoelectron-spectroscopy

Surface oxidation of La, Ce, Sm and Tb metals has been investigated by He(II) ultraviolet photoelectron spectroscopy (u.p.s.) and X-ray photoelectron spectroscopy (X.p.s.). Oxidation of La gives rise to La2O3 on the surface. While Ce2O3 appears to be the stable oxide on the surface, we find evidence for formation of CeO2 at high oxygen exposure. Valence band of Sm clearly shows the presence of both divalent and trivalent states due to interconfigurational fluctuation. Exposure of Sm to oxygen first depletes the divalent Sm at the surface. While Sm2O3 is the stable oxide on the surface of Sm, Tb2O3 is the stable oxide on the surface of Tb (and not any of the higher oxides).

Dioxomolybdenum reagents in organic synthesis: utility of redox capability to design reduction and oxidation

The usefulness of dioxomolybdenum reagents in oxo-transfer reactions have been reviewed. The redox ability of dioxomolybdenum reagent has been utilized in designing several synthetic methods, which are useful in organic synthesis. Several reactions such as oxidation of alcohols, sulfides, amines, azides olefins etc are accomplished by using dioxomolybdenum reagents. Similarly, it is also demonstrated that dioxomolybdenum complex is useful in performing reduction of aldehydes, ketones, esters, azides etc. A fine tuning of reaction conditions provides suitable conditions to perform either oxidation or reduction by using catalytic amount of reagents. The oxidation reactions are further simplified by employing the polymer supported molybdenum reagents.

Evidences for ambient oxidation of indium nitride quantum dots

Investigations were carried out on the ambient condition oxidation of self-assembled, fairly uniform indium nitride (InN) quantum dots (QDs) fabricated on p-Si substrates. Incorporation of oxygen in to the outer shell of the QDs was confirmed by the results of transmission electron microscopy (TEM), X-ray photoemission spectroscopy (XPS). As a consequence, a weak emission at high energy (similar to 1.03?eV) along with a free excitonic emission (0.8?eV) was observed in the photoluminescence spectrum. The present results confirm the incorporation of oxygen into the lattice of the outer shell of InN QDs, affecting their emission properties. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Kinetics of carbon monoxide oxidation with Sn(0.95)M(0.05)O(2-delta) (M = Cu, Fe, Mn, Co) catalysts

Base metal substituted Sn(0.95)M(0.05)O(2-delta) (M = Cu, Fe, Mn, Co) catalysts were synthesized by the solution combustion method and characterized by XRD, XPS, TEM and BET surface area analysis. The catalytic activities of these materials were investigated by performing CO oxidation. The rates and the apparent activation energies of the reaction for CO oxidation were determined for each catalyst. All the substituted catalysts showed high rates and lower activation energies for the oxidation of CO as compared to unsubstituted SnO(2). The rate was found to be much higher over copper substituted SnO(2) as compared to other studied catalysts. 100% CO conversion was obtained below 225 degrees C over this catalyst. A bifunctional reaction mechanism was developed that accounts for CO adsorption on base metal and support ions and O(2) dissociation on the oxide ion vacancy. The kinetic parameters were determined by fitting the model to the experimental data. The high rates of the CO oxidation reactions at low temperatures were rationalized by the high dissociative chemisorption of adsorbed O(2) over these catalysts.

Spatiotemporal chaos in a model for CO oxidation on Pt(110)

We present numerical studies of a model for CO oxidation on the surface of Pt(110) proposed in Ref. 1. The model shows several interesting regimes, some of which exhibit spatiotemporal chaos. The time series of the CO concentration at a given point consists of a sequence of pulses. We concentrate on interpulse intervals theta and show that their distribution P(theta) approaches a delta function continuously as the system goes from a state M, with meandering spirals, to a state S, with spatially frozen spiral cores. This should be verifiable experimentally.

Fourier transform infrared microspectroscopy identifies protein propionylation in histone deacetylase inhibitor treated glioma cells

Histone deacetylase inhibitors (HDIs) have attracted considerable attention as potential drug molecules in tumour biology. In order to optimise chemotherapy, it is important to understand the mechanisms of regulation of histone deacetylase (HDAC) enzymes and modifications brought by various HDIs. In the present study, we have employed Fourier transform infrared microspectroscopy (FT-IRMS) to evaluate modifications in cellular macromolecules subsequent to treatment with various HDIs. In addition to CH3 (methyl) stretching bands at 2872 and 2960 cm1, which arises due to acetylation, we also found major changes in bands at 2851 and 2922 cm1, which originates from stretching vibrations of CH2 (methylene) groups, in valproic acid treated cells. We further demonstrate that the changes in CH2 stretching are concentration-dependent and also induced by several other HDIs. Recently, HDIs have been shown to induce propionylation besides acetylation [1]. Since propionylation involves CH2 groups, we hypothesized that CH2 vibrational frequency changes seen in HDI treated cells could arise due to propionylation. As verification, pre-treatment of cells with propionyl CoA synthetase inhibitor resulted in loss of CH2 vibrational changes in histones, purified from valproic acid treated cells. This was further proved by western blot using propionyl-lysine specific antibody. Thus we demonstrate for the first time that propionylation could be monitored by studying CH2 stretching using IR spectroscopy and further provide a platform for monitoring HDI induced multiple changes in cells. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Performance evaluation of nonthermal plasma reactors for NO oxidation in diesel engine exhaust gas treatment

The discharge plasma-chemical hybrid process for NO/sub x/ removal from the due gas emissions is an extremely effective and economical approach in comparison with the conventional selective catalytic reduction system. In this paper we bring out a relative comparison of several discharge plasma reactors from the point of NO removal efficiency. The reactors were either energized by AC or by repetitive pulses. Ferroelectric pellets were used to study the effect of pellet assisted discharges on gas cleaning. Diesel engine exhaust, at different loads, is used to approximately simulate the due gas composition. Investigations were carried out at room temperature with respect to the variation of reaction products against the discharge power. Main emphasis is laid on the oxidation of NO to NO/sub 2/, without reducing NOx concentration (i.e., minimum reaction byproducts), with least power consumption. The produced NO/sub 2/ will be totally converted to N/sub 2/ and Na/sub 2/SO/sub 4/ using Na/sub 2/SO/sub 3/. The AC packed bed reactor and pelletless pulsed corona reactor showed better performance, with minimum reaction products for a given power, when the NO concentration was low (/spl sim/100 ppm). At high engine loads (NO>300 ppm) there was not much decrease in NO/sub x/ reduction and more or less all the reactors performed equally. The paper discusses these observations in detail.

Lewis Base Catalysis by Thiourea: N-Bromosuccinimide-Mediated Oxidation of Alcohols

In recent times, (thio)urea derivatives have become synonymous with hydrogen bonding owing to their extensive applicability as small molecule organocatalysts. In this paper, another activation mode by thiourea derivatives, namely via Lewis base catalysis, is disclosed for the NBS-mediated oxidation of alcohols. The mild reaction conditions employed here is suitable for chemoselective oxidation of secondary alcohol in the presence of primary alcohol.

A non-metal catalysed oxidation of primary azides to nitriles at ambient temperature

A novel non-metal catalyzed oxidation of organic azides to nitriles under solvent-free conditions is presented employing catalytic amounts of KI, and DABCO in aq. TBHP at room temperature. This nonmetal catalyzed oxidation of azides provides good selectivity as double and triple bonds were not oxidized under the present reaction conditions.

Higher topoisomerase 2 alpha gene transcript levels predict better prognosis in GBM patients receiving temozolomide chemotherapy: identification of temozolomide as a TOP2A inhibitor

The search for molecular markers which predict response to chemotherapy is an important aspect of current neuro-oncology research. MGMT promoter methylation is the only proved marker of glioblastoma. The purpose of this study was to assess the effect of topoisomerase expression on glioblastoma survival and study the mechanisms involved. The transcript levels of all isoforms of the topoisomerase family in all grades of diffuse astrocytoma were assessed. A prospective study of patients with glioblastoma treated by a uniform treatment procedure was performed with the objective of correlating outcome with gene expression. The ability of TOP2A enzyme to relax the super coiled plasmid DNA in the presence of temozolomide was evaluated to assess its effect on TOP2A. The temozolomide cyctotoxicity of TOP2A-silenced U251 cells was assessed. The transcript levels of TOP2A, TOP2B, and TOP3A are upregulated significantly in GBM in comparison with lower grades of astrocytoma and normal brain samples. mRNA levels of TOP2A correlated significantly with survival of the patients. Higher TOP2A transcript levels in GBM patients predicted better prognosis (P = 0.043; HR = 0.889). Interestingly, we noted that temozolomide inhibited TOP2A activity in in-vitro enzyme assays. We also noted that siRNA knock down of TOP2A rendered a glioma cell line resistant to temozolomide chemotherapy. We demonstrated for the first time that temozolomide is also a TOP2A inhibitor and established that TOP2A transcript levels determine the chemosensitivity of glioblastoma to temozolomide therapy. Very high levels of TOP2A are a good prognostic indicator in GBM patients receiving temozolomide chemotherapy.

Role of electrolyte additives on in-vitro electrochemical behavior of micro arc oxidized titania films on Cp Ti

The present work is aimed at studying the influence of electrolyte chemistry on the voltage-time (V-T) response characteristics, phase structure, surface morphology, film growth rate and corrosion properties of titania films fabricated by micro arc oxidation (MAO) on Cp Ti. The titania films were developed with a sodium phosphate based reference electrolyte comprising the additives such as sodium carbonate (Na2CO3), sodium nitrite (NaNO2) and urea (CO(NH2)(2)). The phase composition, surface morphology, elemental composition and thickness of the films were assessed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques. The corrosion characteristics of the fabricated films were studied under Kokubo simulated body fluid (SBF) condition by potentiodynamic polarization, long term potential and linear polarization resistance (LPR) measurements and electrochemical impedance spectroscopy (EIS) methods. In addition, the corrosion characteristics of the grown films were analyzed by EIS curve fitting and equivalent circuit modeling. Salt spray test (SST) as per ASTM B 117 standard was also conducted to verify the corrosion resistance of the grown films. The XRD results showed that the titania films were composed of both anatase and rutile phases at different proportions. Besides, the films grown in carbonate and nitrite containing electrolyte systems showed an enhanced growth of their rutile phase in the 1 0 1] direction which could be attributed to the modifications introduced in the growth process by the abundant oxygen available during the process. The SEM-EDX and elemental mapping results showed that the respective electrolyte borne elements were incorporated and distributed uniformly in all the films. Among all the grown films under study, the film developed in carbonate containing electrolyte system exhibited considerably improved corrosion resistance due to suitable modifications in its structural and morphological characteristics. The rate of anatase to rutile phase transformation and the rutile growth direction were strongly influenced by the abundant oxidizing species available during the film growth process. (C) 2012 Elsevier B. V. All rights reserved.