Gamma effect on track properties of PADC detector

Effect of high gamma irradiation on track properties of PADC (Homalite) has been studied in the dose range of 10¹–10⁶ Gy. The properties like bulk-etch rates and track-etch rates of the detector are found to increase due to gamma exposure. Etching efficiency of the detector increases due to exposure and it is significant at the dose higher than 10³ Gy. Another track property, the critical angle, is also influenced by gamma exposure and is found to decrease with increasing dose. In all cases it is observed that the post-gamma exposure has greater effect than the pre-gamma exposure. The experimental results are presented and discussed in details.     

Oscillation of fourth order nonlinear neutral difference equations-II

Oscillatory and asymptotic behaviour of solutions of a class of fourth order nonlinear neutral difference equations of the form

Statistically convergent difference double sequence spaces

In this article we define the notion of statistically convergent difference double sequence spaces. We examine the spaces 2l∞（△, q）, 2c（△, q）, 2cB（△, q）, 2cR（△, q）, 2cBR（△,q） etc. being symmetric, solid, monotone, etc. We prove some inclusion results too.     

Cobalt‐Catalyzed Intermolecular C(sp2)O Cross‐Coupling

Cobalt(II)‐catalyzed C(sp²)?O cross‐coupling between aryl/heteroaryl alcohols and vinyl/aryl halides in the presence of Cu^I has been achieved under ligand‐free conditions. In this reaction, copper plays a significant role in transmetalation rather than being directly involved in the C?O coupling. This unique Co/Cu‐dual catalyst system provides an easy access to a library of aryl–vinyl, heteroaryl–styryl, aryl–aryl, and heteroaryl–heteroaryl ethers in the absence of any ligand or additive.     

Spectroscopic and thermal studies of gamma irradiated polypropylene polymer

Thin films of polypropylene have been irradiated with different doses of gamma radiation from a ⁶⁰Co source. IR, UV-VIS spectra of this polymer before and after irradiation have been recorded and from the spectral data some modifications in the properties have been investigated. The spectra indicated that polypropylene film was oxidised at the dose of 10⁶ Gy. Due to the removal of additives, total destruction of the polymer takes place at this dose. Isotactic arrangement of the polymer is no longer present after irradiation. Growth of carbon cluster takes place above a gamma dose of 10² Gy. Thermal stability of the polymer changes due to irradiation and the polymer seems to decompose in four different steps at the highest dose of 10⁶ Gy.     

Response of Cellulose detectors to different doses of 62?MeV protons

Optical and thermal responses of two cellulose detectors, Cellulose triacetate (Triafol-TN) and Cellulose acetate butyrate (Triafol-BN), to four different doses of 62 MeV protons were studied using spectroscopic, thermal and track-etching techniques. The spectroscopic analysis revealed that though the optical band-gap in the polymers was affected by proton irradiation, the polymers showed high resistance against any major structural modification by radiation. The thermal stability of the polymers was found to be affected by proton irradiation. The activation energy of etching was found to be almost constant for both the polymers even after irradiation. It is hoped that the findings in this work would be of significant relevance to material science and applications of polymers.     

Metal‐nanoparticle‐coating‐induced enhancement and weakening of resonant Raman scattering in ZnO: effect of surface electric field

Effects of Ag and Ti nanoparticle coatings on resonant Raman scattering in various ZnO thin films are presented. The longitudinal optical (LO) phonons, irrespective of the ZnO quality, exhibit an enhancement and a weakening by the Ag and Ti nanoparticle coatings, respectively. The enhancement (weakening) is always accompanied by a reduced (an increased) intensity ratio of the second to first‐order LO phonons, which can be associated with changes in the electron‐phonon coupling strength in the probed area of ZnO. Angle‐resolved X‐ray photoelectron spectroscopy provides evidence for the bending of the surface energy bands and their changes induced by the metal coatings. The effect of metal nanoparticle coatings on the Raman scattering of ZnO is thus attributed to the changes in the surface electric field. Copyright © 2011 John Wiley & Sons, Ltd.     

Superconvergence of H 1-Galerkin mixed finite element methods for parabolic problems

In this article, we study the semidiscrete H ¹-Galerkin mixed finite element method for parabolic problems over rectangular partitions. The well-known optimal order error estimate in the L ²-norm for the flux is of order 𝒪(h ^k+1) (SIAM J. Numer. Anal. 35 (2), (1998), pp. 712–727), where k ≥ 1 is the order of the approximating polynomials employed in the Raviart–Thomas element. We derive a superconvergence estimate of order 𝒪(h ^k+3) between the H ¹-Galerkin mixed finite element approximation and an appropriately defined local projection of the flux variable when k ≥ 1. A the new approximate solution for the flux with superconvergence of order 𝒪(h ^k+3) is realized via a postprocessing technique using local projection methods.     

An alternate mode of binding of the polyphenol quercetin with serum albumins when complexed with Cu(II)

Polyphenols find wide use as antioxidants, cancer chemopreventive agents and metal chelators. The latter activity has proved interesting in many aspects. We have probed the binding characteristics of the polyphenol quercetin–Cu(II) complex with human serum albumin (HSA) and bovine serum albumin (BSA). Fluorescence studies reveal that the quercetin–Cu(II) complex can quench the fluorescence of the serum albumins. The binding constant (K_b) values are of the order of 10⁵ M^?1 which increased with rise in temperature in case of HSA and BSA interacting with the quercetin–Cu(II) complex. Displacement studies reveal that both the ligands bind to site 1 (subdomain IIA) of the serum albumins. However, thermodynamic parameters calculated from temperature dependent studies indicated that the mode of interaction of the complexes with the proteins differs. Both ΔH° and ΔS° were positive for the interaction of the quercetin–Cu(II) complex with both proteins but the value of ΔH° was negative in case of the interaction of quercetin with the proteins. This implies that after chelation with metal ions, the polyphenol alters its mode of interaction which could have varying implications on its other physicochemical activities.