Calorimetric characterization of membrane materials based on polyvinyl alcohol

There is ample scope for modification of polyvinyl alcohol (PVA) to derive diverse range of properties because of the presence of hydroxyl group in its chain. In the present work, PVA has been modified to carboxymethylated polyvinyl alcohol (CPVA) — a carboxy-functionalized membrane material. Generally the cohesive energy density has incremental influence on the melting point and mechanical strength of a material but in this case of CPVA even though theoretical cohesive energy density of CPVA is lower than that of PVA but paradoxically its mechanical strength was found to be higher than that of PVA (∼202 vis-à-vis 207°C and ∼174 vis-à-vis ∼58 MPa, respectively). Calorimetric evaluation along with the energy balance concept have provided meaningful information to justify such paradoxical feature as a result of the dominating role of intermolecular hydrogen bonding in CPVA to compensate for its relatively lower cohesive energy density typically 0.05 J m^−3/2. Thermal analysis has been made to examine the role of PVA and its carboxymethylated derivative (CPVA) towards moisture. It was observed that PVA membrane surface became sticky on exposure to water at 30°C for a period of 30 min, whereas under the same condition CPVA counterpart remained practically unaffected.     

Period adding bifurcation in a logistic map with memory

We introduce a single step memory dependence in the fully chaotic logistic map. This makes it a two dimensional system in general. However, we show that by using composite functions to define two one dimensional maps, it is possible to obtain some analytic results for the bifurcation structure. Numerical results support the calculated bifurcation scheme and, in addition, yield a further insight which allows the calculation of the convergence ratio for a new period adding scenario.     

Markov property of continuous dislocation band propagation

Tensile tests were carried out by deforming polycrystalline samples of substitutional Al–2.5%Mg alloy at room temperature for a range of strain rates. The Portevin–Le Chatelier (PLC) effect was observed throughout the strain rate regime. The deformation bands in this region are found to be of type A in nature. From the analysis of the experimental stress time series data we could infer that the dynamics of type A dislocation band propagation is a Markov process.     

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Two highly unsymmetrical tetradentate (N3O) Schiff base copper(II) complexes: Template synthesis,structural characterization,magnetic and computational studies

Two new copper(II) complexes, [Cu₂(L¹)₂](ClO₄)₂ (1) and [Cu(L²)(ClO₄)] (2), of the highly unsymmetrical tetradentate (N₃O) Schiff base ligands HL¹ and HL² (where HL¹ = N-(2-hydroxyacetophenone)-bis-3-aminopropylamine and HL² = N-(salicyldehydine)-bis-3-aminopropylamine) have been synthesised using a template method. Their single crystal X-ray structures show that in complex 1 two independent copper(II) centers are doubly bridged through phenoxo-O atoms (O1A and O1B) of the two ligands and each copper atom is five-coordinated with a distorted square pyramidal geometry. The asymmetric unit of complex 2 consists of two crystallographically independent N-(salicylidene)-bis(aminopropyl)amine-copper(II) molecules, A and B, with similar square pyramidal geometries. Cryomagnetic susceptibility measurements (5–300 K) on complex 1 reveal a distinct antiferromagnetic interaction with J = ?23.6 cm^?1, which is substantiated by a DFT calculation (J = ?27.6 cm^?1) using the B3LYP functional. Complex 1, immobilized over highly ordered hexagonal mesoporous silica, shows moderate catalytic activity for the epoxidation of cyclohexene and styrene in the presence of TBHP as an oxidant.     

Synthesis,X‐ray powder structure analysis and biological properties of a mononuclear Cu(II) complex of N‐2‐hydroxyhippuric acid

A mononuclear copper (II) complex of N‐2‐hydroxyhippuric acid (2HHA), [Cu(HA)(H₂O)₂], has been synthesized and characterized by spectroscopic and X‐ray powder diffraction studies. Crystal structure of [Cu(HA)(H₂O)₂] reveals a distorted square‐pyramidal geometry around the metal center. The crystal packing in the complex exhibits a three‐dimensional framework formed by intermolecular O? ; H···O and C? H···O hydrogen bonds. Toxicity and antitumor properties of the complex have been studied in vivo. The complex, capable of depleting glutathione (GSH) at nontoxic doses, may be utilized to sensitize drug‐resistant cells where resistance is due to an elevated level of GSH. Copyright © 2009 John Wiley & Sons, Ltd.     

Electron and Photon Performance in CMS in Run-2 and Prospects for Run-3

Physics of Atomic Nuclei - The rich physics program of CMS experiment depends on the ability to trigger, reconstruct and identify events with electrons and photons with the CMS detector with...     

A facile and versatile protocol for the one-pot PhI(OAc)2 mediated divergent synthesis of quinazolines from 2-aminobenzylamine

In this present work iodobenzenediacetate (PIDA) has been found to be the key reagent in absence or presence of catalytic amount of molecular iodine (I₂)/zinc chloride (ZnCl₂) to construct quinazoline scaffold from 2-aminobenzylamine and a variety of easily available aldehydes, aryl and aliphatic amines, aliphatic and aryl alcohols and nitriles. This protocol provides mild and robust conditions along with great versatility to synthesize 2-substituted quinazolines from diverse starting materials in good to excellent yields. The developed protocol is also well applicable to reactants containing ease to oxidation prone functional groups.     

Oleic acid-assisted phase transfer of nanosized silver colloids

In this study, it is demonstrated that silver nanoparticles can be transferred from formamide to chloroform using oleic acid as a phase transfer agent with a transfer efficiency of 90–95%. The silver nanoparticles are initially formed as an organosol by the reduction of silver ions with formamide. On aging the complex, the particles self-assemble to form an ordered close-packed two-dimensional array of silver nanocrystals when dissolved in CHCl₃. The size distribution of the colloidal silver particles after transfer in different solvents remains almost the same. On the basis of IR spectroscopy, we discuss the adsorption of oleic acid over the silver particles.