The morphology of Zn3P2 single crystals grown from the vapour phase

The morphology of Zn₃P₂ single crystals, grown from the vapour phase by sublimation of bulk Zn₃P₂ in a sealed quartz tube pulled through a high temperature gradient, has been investigated. X-ray diffraction examination showed that the main direction of crystal growth with a tetragonal unit cell is the [021] direction which corresponds to the [111] direction in the pseudocubic system. Transverse and longitudinal cross sections of the single crystals were mechanically polished and chemically etched. Optical examination of the cross sections indicated that the growth of Zn₃P₂ begins most frequently in the (011) plane. Striae which appeared in a cross section after chemical etching are attributed to the existence of strain fields generated in the sample as a result of temperature fluctuations or as a result of crystal structure defects in the core region.     

Kinetics and mechanism of oxidation of arsenious acid by tetrachloroaurate(III) in hydrochloric acid medium

Kinetics of the oxidation of arsenious acid by tetrahcloroaurate(III) have been studied spectrophotometrically in hydrochloric acid medium. Initial complex formation between As(III) and Au(III) followed by the decomposition of the intermediate complex to give products of the reaction is suggested. The empirical rate law is

k and K are found to be 13.9 × 10^?4 s^?1 and 24.2 M^?1 respectively at 30°C and μ = 1.0 M. ΔH³ and ΔS³ for k are found to be 49.2 kJ mol^?1 and - 137.2 JK^?1 mol^?1 whereas ΔH and ΔS associated with K are - 6.75 kJ mol^?1 and 4.14 JK^?1 respectively.     

Effect of PHB on the properties of biodegradable PLA blends

Blends of biodegradable polymers polylactic acid/thermoplastic starch/polyhydroxybutyrate (PLA/TPS/PHB) were prepared using a twin-screw extruder. The TPS content was constant (50 %) and the PHB content in the blends was gradually changed from 0 mass % to 20 mass %. TPS was prepared by melting, where a mixture of native starch, water and glycerol was fed into the twinscrew extruder. Average temperature of extrusion was 180°C and the concentration of glycerol was 40 mass %. Influence of the PHB concentration in the blend and that of the processing technology on the mechanical and rheological properties of the PLA/PHB composition containing TPS were studied. Mechanical properties were measured 24 h after the film and monofilament preparation and also after the specific storage time to study the effect of storage on the properties. The results indicate that differences in morphology strongly influence the mechanical properties of the studied materials with identical material composition.     

Representations of étale Lie groupoids and modules over Hopf algebroids

The classical Serre-Swan’s theorem defines an equivalence between the category of vector bundles and the category of finitely generated projective modules over the algebra of continuous functions on some compact Hausdorff topological space. We extend these results to obtain a correspondence between the category of representations of an étale Lie groupoid and the category of modules over its Hopf algebroid that are of finite type and of constant rank. Both of these constructions are functorially defined on the Morita category of étale Lie groupoids and we show that the given correspondence represents a natural equivalence between them.     

Deoxycholate induced tetramer of αA-crystallin and sites of phosphorylation: fluorescence correlation spectroscopy and femtosecond solvation dynamics

Structure and dynamics of acrylodan labeled αA-crystallin tetramer formed in the presence of a bile salt (sodium deoxycholate, NaDC) has been studied using fluorescence correlation spectroscopy (FCS) and femtosecond up-conversion techniques. Using FCS it is shown that, the diffusion constant (D(t)) of the αA-crystallin oligomer (mass ~800 kDa) increases from ~35 μm(2) s(-1) to ~68 μm(2) s(-1). This corresponds to a decrease in hydrodynamic radius (r(h)) from ~6.9 nm to ~3.3 nm. This corresponds to about 10-fold decrease in molecular mass to ~80 kDa and suggests formation of a tetramer (since mass of αA-crystallin monomer is ~20 kDa). The steady state emission maximum and average solvation time (<τ(s)>) of acrylodan labeled at cysteine 131 position of αA-crystallin is markedly affected on addition of NaDC, while the tryptophan (trp-9) becomes more exposed. This suggests that NaDC binds near the cys-131 and makes the terminal region of αA-crystallin exposed. This may explain the enhanced auto-phosphorylation activity of αA-crystallin near the terminus of the 173 amino acid protein (e.g., at the threonine 13, serine 45, or serine 169 and 172) and suggests that phosphorylation at ser-122 (close to cys-131) is relatively less important.     

Horseradish Peroxidase as a Catalyst for Atom Transfer Radical Polymerization

The hemoprotein horseradish peroxidase (HRP) catalyzes the polymerization of N‐isopropylacrylamide with an alkyl bromide initiator under conditions of activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) in the absence of any peroxide. This is a novel activity of HRP, which we propose to name ATRPase activity. Bromine‐terminated polymers with polydispersity indices (PDIs) as low as 1.44 are obtained. The polymerization follows first order kinetics, but the evolution of molecular weight and the PDI upon increasing conversion deviate from the results expected for an ATRP mechanism. Conversion, and PDI depend on the pH and on the concentration of the reducing agent, sodium ascorbate. HRP is stable during the polymerization and does not unfold or form conjugates.

     

Two new graph-theoretical methods for generation of eigenvectors of chemical graphs

Two new graph-theoretical methods, (A) and (B), have been devised for generation of eigenvectors of weighted and unweighted chemical graphs. Both the methods show that not only eigenvalues but also eigenvectors have full combinatorial (graph-theoretical) content. Method (A) expresses eigenvector components in terms of Ulam’s subgraphs of the graph. For degenerate eigenvalues this method fails, but still the expressions developed yield a method for predicting the multiplicities of degenerate eigenvalues in the graph-spectrum. Some well-known results about complete graphs (K _n) and annulenes (C _n ), viz. (i)K _n has an eigenvalue −1 with (n−1)-fold degeneracy and (ii) C _n cannot show more than two-fold degeneracy, can be proved very easily by employing the eigenvector expression developed in method (A). Method (B) expresses the eigenvectors as analytic functions of the eigenvalues using the cofactor approach. This method also fails in the case of degenerate eigenvalues but can be utilised successfully in case of accidental degeneracies by using symmetry-adapted linear combinations. Method (B) has been applied to analyse the trend in charge-transfer absorption maxima of the some molecular complexes and the hyperconjugative HMO parameters of the methyl group have been obtained from this trend.     

Facile synthesis,characterization and application of magnetic Fe3O4-coir pith composites for the removal of methyl violet from aqueous solution: Kinetics,isotherm, thermodynamics and parametric optimization

Dyes are commonly used in coloring clothes; in fertilizers, as anti-freezers, as detergents and so on. The use of such dyes has carcinogenic and genotoxic effects. These dyes require proper removal from the environment. Subsequently, a green and low-cost approach promises to adhere to sustainability of the environment while maximum removal of these toxic dyes. The present study describes removal of methyl violet (MV) dye by adsorption process magnetically separable Fe₃O₄-coir pith composites. The study was evaluated in batch system taking the optimum conditions as: pH: 7, contact time: 12 h, stirring speed: 200 rpm, concentration of dye: 100 mg/L, adsorbent weight: 3 g/L, temp.: 308 K. The central composite design approach of response surface methodology in design-expert software showed maximum removal efficiency (>98%) for optimal parameters. The experimental equilibrium data fitted reasonably well to Langmuir isotherm model. ANOVA analysis along with Fisher's statistical test was also performed to validate the model. The predicted model was at par with the experimental values with adjusted R² of 0.9914. A thorough investigation of kinetic ($R_{\text{Pseudo second order}}^2$ = 0.99; $R_{\text{Pseudo second order}}^2=0.97;R_{\text{intra}?\text{particle diffusion}}^2=0.98)$, thermodynamic, adsorption isotherm $(R_{\text{Langmuir isotherm}}^2=0.997$ $R_{\text{Freundlich isotherm}}^2=0.99$ and eco-toxicological characteristics were performed for proper evaluations of the properties as well as sustainability of the adsorbent material. The whole research indicated encouraging potential of the developed material for adsorption, reusability and sustainability in applications for industrial scale wastewater treatment.