On the homogenization of metal matrix composites using strain gradient plasticity

The homogenized response of metal matrix composites（MMC） is studied using strain gradient plasticity.The material model employed is a rate independent formulation of energetic strain gradient plasticity at the micro scale and conventional rate independent plasticity at the macro scale. Free energy inside the micro structure is included due to the elastic strains and plastic strain gradients. A unit cell containing a circular elastic fiber is analyzed under macroscopic simple shear in addition to transverse and longitudinal loading. The analyses are carried out under generalized plane strain condition. Micro-macro homogenization is performed observing the Hill-Mandel energy condition,and overall loading is considered such that the homogenized higher order terms vanish. The results highlight the intrinsic size-effects as well as the effect of fiber volume fraction on the overall response curves, plastic strain distributions and homogenized yield surfaces under different loading conditions. It is concluded that composites with smaller reinforcement size have larger initial yield surfaces and furthermore,they exhibit more kinematic hardening.     

The Sinc–Legendre collocation method for a class of fractional convection–diffusion equations with variable coefficients

This paper deals with the numerical solution of classes of fractional convection–diffusion equations with variable coefficients. The fractional derivatives are described based on the Caputo sense. Our approach is based on the collocation techniques. The method consists of reducing the problem to the solution of linear algebraic equations by expanding the required approximate solution as the elements of shifted Legendre polynomials in time and the Sinc functions in space with unknown coefficients. The properties of Sinc functions and shifted Legendre polynomials are then utilized to evaluate the unknown coefficients. Several examples are given and the numerical results are shown to demonstrate the efficiency of the newly proposed method.     

Gravitational induced uncertainty and dynamics of harmonic oscillator

As a consequence of gravitational induced uncertainty, equation of motion for harmonic oscillator differs considerably from usual quantum mechanical situation. This paper considers the dynamics of a simple harmonic oscillator in the context of Generalized (Gravitational) Uncertainty Principle (GUP). Using Heisenberg Picture of quantum mechanics, we find time evolution of position and momentum operators and we will show that expectation values have an unusual complicated mass dependence. Also we will show that since the notion of locality breaks down, Ehrenfest theorem is not satisfied for harmonic oscillator in GUP.     

Interaction of zanamivir with DNA and RNA: Models for drug–DNA and drug–RNA bindings

Zanamivir (ZAN) is the first of a new generation of influenza virus-specific drugs known as neuraminidase inhibitors, which acts by interfering with life cycles of influenza viruses A and B. It prevents the virus spreading infection to other cells by blocking the neuraminidase enzyme present on the surface of the virus. The aim of this study was to examine the stability and structural features of calf thymus DNA and yeast RNA complexes with zanamivir in aqueous solution, using constant DNA or RNA concentration (12.5 mM) and various zanamivir/polynucleotide (P) ratios of 1/20, 1/10, 1/4, and 1/2. FTIR and UV–visible spectroscopy are used to determine the drug external binding modes, the binding constant and the stability of zanamivir–DNA and RNA complexes in aqueous solution. Structural analysis showed major interaction of zanamivir with G-C (major groove) and A-T (minor groove) base pairs and minor perturbations of the backbone PO₂ group with overall binding constants of K_{zanamivir–DNA} = 1.30 × 10⁴ M⁻¹ and K_{zanamivir–RNA} = 1.38 × 10⁴ M⁻¹. The drug interaction induces a partial B to A-DNA transition, while RNA remains in A-conformation.     

Efficient and practical protocol for silylation of hydroxyl groups using reusable lithium perchlorate dispread in silica gel under neutral condition

A very efficient and mild procedure for the trimethylsilylation of a wide variety of alcohols, including primary, allylic, benzylic, secondary, hindered secondary, tertiary, and phenols with hexamethyldisilazane on the surface of silica gel dispersed with LiClO₄ in room temperature at few minutes in excellent yields under neutral conditions is reported. This procedure also allows the excellent selectivity under LP-SiO₂ system for silylation of alcohols in the presence of amine and phenolic hydroxy groups.     

Highly efficient ring opening reactions of epoxides with deactivated aromatic amines catalyzed by heteropoly acids in water

Heteropoly acid was found to be an effective and efficient catalyst for the ring opening reaction of epoxides with various aromatic amines to produce the corresponding β-amino alcohols in moderate to excellent yields in water. This method provides a new and efficient protocol in terms of mild reaction conditions, clean reaction profiles, small quantity of catalyst, and simple work-up procedure.     

Palladium–quaternary phosphonium phase transfer catalyst brush assembly as reusable and environmentally benign catalyst for coupling of aryl halides and sodium tetraphenylborate in neat water

A first example of simultaneous covalent anchoring of a palladate anion–phosphonium cation matrix on the surface of silica nanoparticles and application in the Suzuki coupling reaction of a variety of different haloarenes and sodium tetraphenylborate in neat aqueous media without the addition of any organic co‐solvent are described. Copyright © 2015 John Wiley & Sons, Ltd.     

Lithium Perchlorate Diethyl Ether Solution: A Highly Efficient Media for the Abramov Reaction

The f -hydroxy phosphonates are readily prepared by treating aromatic or aliphatic aldehydes and ketones with trialkylphosphite in the presence of trimethylsilylchloride in a very short time and in almost quantitative yields.     

Novel nano-zeolite modified carbon paste electrode for electrocatalytic oxidation of methanol

Abstract  

Methanol is used as a fuel in the direct methanol fuel cell. Direct oxidation of methanol encounters large overvoltages at most unmodified electrode surfaces. The development of new procedures for electrocatalytic oxidation of methanol to decrease this overvoltage is therefore very desirable. In this paper, we report a new zeolite-modified carbon paste electrode based on Ni-ZSM-5 for methanol electrooxidation. Nanocrystallites of ZSM-5 (Si/Al of 50) with average particle size of 58 nm were synthesized using clear solutions at low temperature (90 °C) under atmospheric pressure. Ni(II) ions were incorporated into the zeolite by immersion of the modified carbon paste electrode with synthesized zeolite in a 1.0 M nickel chloride solution. Cyclic voltammetry showed that by using nano-sized zeolite, the oxidation current increased compared with that of micron-sized zeolite crystallites.