Zinc-substituted alpha-nickel hydroxide as an electrode material for alkaline secondary cells

Double hydroxides of the formula, Ni1-xZn2x (OH)(2) (CO3)(x). nH(2)O (x = 0.1 to 0.25) having the same structure as that of alpha-nickel hydroxide have been synthesized by partial substitution of zinc for nickel. The hydroxide having the composition x = 0.25 exhibits prolonged stability in 6 M KOH. Pasted electrodes comprising this material are rechargeable with a stabilized reversible discharge capacity of 410 +/- 15 mAh g(-1) of nickel even under suboptimal conditions of electrode fabrication. This compares favorably with the capacity values achieved for beta-nickel hydroxide (221 mAh g(-1)', This work; 297 mAh g(-1), Delahaye-Vidal and Figlarz;(1) 456 mAh g(-1), theoretical). (C) 1999 The Electrochemical Society. S0013-4651(98)01-071-4. All rights reserved.

High-pressure kinetics of oxidative copolymerization of styrene with alpha-methyl styrene

This is the first report on the study carried out on high-pressure free-radical initiated oxidated copolymerization of styrene (STY) with alpha-methylstyrene (AMS) at various temperatures (45-65degreesC) at constant pressure (100 psi) and then at various pressures (50-300 psi) keeping the temperature (50degreesC) constant. The compositions of the copolyperoxides obtained from the H-1 NMT spectra were utilized to determine the reactivity ratios of the monomers. The reactivity ratios indicate that STY forms an ideal copolyperoxide with AMS and the copolyperoxide is richer in AMS. The effect of temperature and oxygen pressure in the reactivity ratios of the monomers was studied. The rates of copolymerization (R-p) were used to determine the overall activation energies (E-a) and activation volume (DeltaV(#)) of copolymerization. The unusually higher values of the DeltaV(#) may be due to the pressurizing fluid oxygen which itself is a reactant in the copolymerization, the side reactions, and the chain-transfer reactions occuring during copolymerizations.

On the importance of backbone loop and peptide flip in the Walker sequence in F-1-ATPase action

The Walker sequence, GXXXXGKT, present in all the six subunits of F-1-ATPase exists in a folded form, known as phosphate-binding loop (P-loop). Analysis of the Ramachandran angles showed only small RMS deviation between the nucleotide-bound and nucleotide-free forms. This indicated a good overlap of the backbone loops. The catalytic beta-subunits (chains D, E and F) showed significant changes in the Ramachandran angles and the side chain torsion angles, but not the structural alpha-subunits (chains A, B and C). Most striking among these are the changes associated with Val160 and Gly161 corresponding to a flip in the peptide unit between them when a nucleotide is bound (chains D or F compared to nucleotide-free chain E). The conformational analysis further revealed a hitherto unnoticed hydrogen bond between amide-N of the flipped Gly161 and terminal phosphate-O of the nucleotide. This assigns a role for this conserved amino acid, otherwise ignored, of making an unusual direct interaction between the peptide backbone of the enzyme protein and the incoming nucleotide substrate. Significance of this interaction is enhanced, as it is limited only to the catalytic subunits, and also likely to involve a mechanical rotation of bonds of the peptide unit. Hopefully this is part of the overall events that link the chemical hydrolysis of ATP with the mechanical rotation of this molecule, now famous as tiny molecular motor.

Pressure-induced phase transitions in alpha-ZrMo2O8

We report high-pressure Raman, infrared (IR), and optical-absorption spectra of alpha-ZrMo2O8 (trigonal) up to 38 GPa at room temperature. The spectroscopic studies are consistent with diffraction results that show that alpha-ZrMo2O8 transforms into delta-ZrMo2O8 (monoclinic) at about 1 GPa and the delta phase converts to the epsilon phase (trielinic) at about 2.0 GPa. Optical-absorption measurements give an estimate of the band gap of about 0.6 eV at the lowest pressure. Band-gap changes with pressure are confirmed with visual observations. ZrMo2O8 changes from transparent at 5 GPa to yellow at 10 GPa, red at 18 GPa, and at about 30 GPa it becomes opaque.

Structural model for the Cu-B site of dopamine beta-hydroxylase: Crystal structure of a copper(II) complex showing N3OS coordination with an axial sulfur ligation

A copper(II) complex containing a NSO-donor Schiff base and NN-donor 2,2'-bipyridine has been prepared and structurally characterized. The square pyramidal complex with an axial sulfur ligation is a structural model for the CUB site of dopamine-hydroxylase in its oxidized form. The copper(II) complex is catalytically active in the oxidation of ascorbic acid by dioxygen mediated by a copper(I) species which is proposed to have a four-coordinate structure with a N3S coordination geometry.

The design and synthesis of redox core-alpha amino acid composites based on thiol-disulfide exchange mechanism and a comparative study of their zinc abstraction potential from [CCXX] boxes in proteins

The design and synthesis of agents that can abstract zinc from their [CCXX] (C=cysteine; X=cysteine/histidine) boxes by thioldisulfide exchange-having as control, the redox parities of the core sulfur ligands of the reagent and the enzyme, has been illustrated, and their efficiency demonstrated by monitoring the inhibition of the transcription of calf thymus DNA by E. coli RNA polymerase, which harbors two zinc atoms in their [CCXX] boxes of which one is exchangeable. Maximum inhibition possible with removal of the exchangeable zinc was seen with redox-sulfanilamide-glutamate composite. In sharp contrast, normal chelating agents (EDTA, phenanthroline) even in a thousand fold excess showed only marginal inhibition, thus supporting an exchange mechanism for the metal removal. (C) 2002 Elsevier Science Ltd. All rights reserved.

Optical and dielectric studies of gel grown alpha-hopeite single crystal

Single crystals of a-hopeite exhibiting high transparency were grown by single diffusion gel growth technique. Single crystal X-ray diffraction analysis reveals that the crystal belongs to orthorhombic system. The values of several structural and physical parameters have been determined for the grown crystal. The optical absorption study reveals the transparency of the crystal and is noticed in the entire visible region and the cut-off wavelength was found to be 230 nm. The optical band gap found to be at 3.25 eV. The dependence of extinction co-efficient (k) and the refractive index (n) on the wavelength was also shown. The dielectric constant and dielectric loss of the crystal was studied as a function of frequency and temperature. Transport properties of the grown crystal have been studied from the Cole-Cole plot. (C) 2010 Elsevier GmbH. All rights reserved.

Grafting of m-isopropenyl-alpha, alpha-dimethylbenzyl-isocyanate (m-TMI) onto isotactic polypropylene: Synthesis and characterization

A novel vinyl monomer with an isocyanate functional group, m-isopropenyl-alpha,alpha-dimethylbenzyl-isocyanate (m-TMI), was grafted onto isotactic polypropylene (i-PP) using dicumyl peroxide (DCP) as the initiator. This would open up the possibility of using the grafted polymer with the reactive isocyanate group as compatibilizer for blending carbohydrates such as cellulose with. polypropylene. The grafting was carried out in a Brabender Plasticoder at 180degreesC. The effects of monomer and initiator concentrations on the yield of grafting were investigated by performing statistical analysis. While the grafting yield increased with the concentration of DCP at any given concentration of m-TMI, the variation of the grafting yield with m-TMI concentration, for a given concentration of DCP, went through a maximum, the optimum yield of 7.8% (w/w) being obtained at 10 wt.% concentration of both DCP and m-TMI. The grafting reaction is. accompanied by considerable chain scission of I-PP, resulting in a decrease in the molecular weight of the grafted polymer. While the molecular weight drops sharply even at a low concentration of DCP, there occurs no further significant change in the molecular weight even at much higher concentrations of the initiator.

Synthesis of nanocrystalline alpha-Al2O3 by ultrasonic flame pyrolysis

Nanocrystalline alpha-alumina was synthesized in an indigenously built ultrasonic flame pyrolysis (UFP) setup. This paper describes the technical aspects of the apparatus and particle formation in the flame. Ultrasonically atomized aluminium nitrate dissolved in methanol-water mixture was pyrolyzed in an oxy-propane flame for yielding nanocrystalline alpha-alumina. The formation of nanophase alumina was confirmed by powder XRD analysis. Scanning electron microscopy (SEM) analysis was carried out to study particulate morphology. (C) 2003 Elsevier Science Ltd. All rights reserved.

Thermally induced phase separation in P alpha MSAN/PMMA blends in presence of functionalized multiwall carbon nanotubes: Rheology, morphology and electrical conductivity

The focus of this work is the evaluation and analysis of the state of dispersion of functionalized multiwall carbon nanotubes (CNTs), within different morphologies formed, in a model LCST blend (poly[(alpha-methylstyrene)-co-(acrylonitrile)]/poly(methyl-methacryla te), P alpha MSAN/PMMA). Blend compositions that are expected to yield droplet-matrix (85/15 P alpha MSAN/PMMA and 15/85 P alpha MSAN/PMMA, wt/wt) and co-continuous morphologies (60/40 P alpha MSAN/PMMA, wt/wt) upon phase separation have been combined with two types of CNTs; carboxylic acid functionalized (CNTCOOH) and polyethylene modified (CNTPE) up to 2 wt%. Thermally induced phase separation in the blends has been studied in-situ by rheology and dielectric (conductivity) spectroscopy in terms of morphological evolution and CNT percolation. The state of dispersion of CNTs has been evaluated by transmission electron microscopy. The experimental results indicate that the final blend morphology and the surface functionalization of CNT are the main factors that govern percolation. In presence of either of the CNTs, 60/40 P alpha MSAN/PMMA blends yield a droplet-matrix morphology rather than co-continuous and do not show any percolation. On the other hand, both 85/15 P alpha MSAN/PMMA and 15/85 P alpha MSAN/PMMA blends containing CNTPEs show percolation in the rheological and electrical properties. Interestingly, the conductivity spectroscopy measurements demonstrate that the 15/85 P alpha MSAN/PMMA blends with CNTPEs that show insulating properties at room temperature for the miscible blends reveal highly conducting properties in the phase separated blends (melt state) as a result of phase separation. By quenching this morphology, the conductivity can be retained in the blends even in the solid state. (C) 2011 Elsevier Ltd. All rights reserved.

Physically consistent simulation of mesoscale chemical kinetics: The non-negative FIS-alpha method

Biochemical pathways involving chemical kinetics in medium concentrations (i.e., at mesoscale) of the reacting molecules can be approximated as chemical Langevin equations (CLE) systems. We address the physically consistent non-negative simulation of the CLE sample paths as well as the issue of non-Lipschitz diffusion coefficients when a species approaches depletion and any stiffness due to faster reactions. The non-negative Fully Implicit Stochastic alpha (FIS alpha) method in which stopped reaction channels due to depleted reactants are deleted until a reactant concentration rises again, for non-negativity preservation and in which a positive definite Jacobian is maintained to deal with possible stiffness, is proposed and analysed. The method is illustrated with the computation of active Protein Kinase C response in the Protein Kinase C pathway. (C) 2011 Elsevier Inc. All rights reserved.

Assessment of estrus cyclicity in the Asian elephant (Elephas maximus) by measurement of fecal progesterone metabolite 5 alpha-P-3OH, using a non-invasive assay

Reproductive management of the Asian elephant (Elephas maximus) is important for its conservation. To monitor its estrous cyclicity, we earlier used an indirect ELISA to show that levels of fecal progesterone (P(4))-metabolite (allopregnanolone: 5 alpha-P-3OH) in semi-captive females sampled randomly positively correlated with serum P(4) levels [12]. In this longitudinal study (51 weeks), we measured levels of fecal 5 alpha-P-3OH and serum P(4) in seven semi-captive female elephants. Females exhibited three types of hormonal profiles. Four females showed cyclical patterns of fecal 5 alpha-P-3OH and serum P(4) typical of normal estrous cycles, two showed acyclic pattern while one showed high values indicative of a pregnant animal. Values for anestrous or follicular phases were <= 0.3 mu g g(-1), (5 alpha-P-3OH) and <= 0.3 ng mL(-1) (P(4)); for luteal phase 0.32-11.09 mu g g(-1) (5 alpha-P-3OH) and 0.32-1.48 ng mL(-1) (P(4)); for pregnancy 1.41-7.38 mu g g(-1) (5 alpha-P-3OH) and 0.39-1.6 ng mL(-1) (R(4)). A positive correlation (t = 8.8, p < 0.01, n = 321) between levels of fecal 5 alpha-P-3OH and serum P4 was observed. A random sample of 30 free-ranging female elephants showed fecal 5 alpha-P-3OH values of 0.06-23.4 mu g g(-1), indicating them to be in different stages of estrous cyclicity. This study is the first to assess the reproductive phases of female Asian elephants based on the correlative-patterns of both the fecal 5 alpha-P-3OH and serum P(4) values over multiple estrous cycles. This has a potential application in the reproductive management and conservation of Asian elephants. (C) 2011 Elsevier Inc. All rights reserved.

C-H functionalization of tertiary amines by cross dehydrogenative coupling reactions: solvent-free synthesis of alpha-aminonitriles and beta-nitroamines under aerobic condition

A solvent-free synthesis of alpha-aminonitriles and beta-nitroamines by oxidative cross-dehydrogenative coupling under aerobic condition is reported. A catalytic amount of molybdenum(VI) acetylacetonoate was found to catalyze cyanation of tertiary amines to form alpha-aminonitriles, whereas vanadium pentoxide was found to promote aza-Henry reaction to furnish beta-nitroamines. Both of these environmentally benign reactions are performed in the absence of solvents using molecular oxygen as an oxidant.