Comparative studies of the magnetic dipole and electric quadrupole hyperfine constants for the ground and low lying excited states of 25Mg+

We have employed the relativistic coupled cluster theory to calculate the magnetic dipole and electric quadrupole hyperfine constants for the ground and low lying excited states of singly ionized magnesium. Comparison with experimental and the other theoretical results are done and predictions are also made for a few low lying excited states which could be of interest. We have made comparative studies of the important many body effects contributing to the hyperfine constants for the different states of the ion.     

Synthesis of poly(butyl acrylate)/sodium silicate nanocomposite fire retardant

Poly(butyl acrylate) (PBA)/sodium silicate (SS) nanocomposites were prepared via emulsifier-free emulsion technique in presence of Cu(II)/glycine chelate complex and ammonium persulfate (APS) initiator. The strongly hydrophobic PBA was intercalated into the hydrophilic SS layer. Since the interlayers of silicate were filled with sodium cations, the hydrophilic properties were enhanced and lead to high degree of swelling. The formation of the PBA/SS nanocomposite was confirmed by infrared spectra (IR). Furthermore, as evidenced by transmission electron microscopy (TEM), the composite so obtained was found to have nanoscale structure. X-ray diffraction (XRD) was used to characterize the nanoscale dispersion of the layer silicate and useful for measurement of d-spacing in interlayer system. It was found from thermogravimetric analysis that PBA/SS nanocomposites had more thermal stability as compared to raw PBA due to intercalation. Burning test of the nanocomposites performance exhibited a flame retardant property, which was also verified from cone calorimeter analysis. For its commercialization, the ecological friendly nature was studied via biodegradation and was found to have better biodegradability than the raw PBA.     

Assessment of natural uranium and 226Ra concentration in ground water around the uranium mine at Narwapahar, Jharkhand, India and its radiological significance

A brief study on dissolved radionuclides in aquatic environment, especially in ground water, constitutes the key aspect for assessment and control of natural exposure. In the present study the distribution of natural uranium and ²²⁶Ra concentration were measured in ground water samples collected within a 10 km radius around the Narwapahar uranium mine in the Singhbhum thrust belt of Jharkhand, India in 2007–2008. The natural uranium content in the ground water samples in this region was found to vary from 0.1 to 3.75 μg L^?1 with an average of 0.87 ± 0.73 μg L^?1 and ²²⁶Ra concentration was found to vary from 5.2 to 38.1 mBq L^?1 with an average of 13.73 ± 7.34 mBq L^?1. The mean annual ingestion dose due to intake of natural uranium and ²²⁶Ra through drinking water pathway to male and female adults population was estimated to be 6.55 and 4.78 μSv y^?1, respectively, which constitutes merely a small fraction of the reference dose level of 100 μSv y^?1 as recommended by WHO.     

Bianchi Types V and VI<Subscript>0</Subscript> Cosmic Strings Coupled with Maxwell Fields in Bimetric Theory

Spatially homogeneous Bianchi types V and VI₀ cosmological models are studied with source cosmic cloud strings coupled with electromagnetic field in Rosen’s (Gen. Relativ. Gravit. 4:435, 1973) bimetric theory of relativity. It is observed that Bianchi type V space time is feasible whereas Bianchi type VI₀ is not feasible. In the feasible case different equations of state for cosmic strings with Maxwell fields do not survive in this theory and the space-time turns out to be flat.     

Synthesis and photo physical properties of Au @ Ag (core @ shell) nanoparticles disperse in poly vinyl alcohol matrix

Synthesis of core @ shell (Au @ Ag) nanoparticle with varying silver composition has been carried out in aqueous poly vinyl alcohol (PVA) matrix. Core gold nanoparticle (~15 nm) has been synthesized through seed-mediated growth process. Synthesis of silver shell with increasing thickness (~1–5 nm) has been done by reducing Ag⁺ over the gold sol in the presence of mild reducing ascorbic acid. Characterization of Au @ Ag nanoparticles has been done by UV–Vis, High resolution transmission electron microscope (HRTEM) and energy dispersive X-ray (EDX) spectroscopic study. The blue shift of surface plasmon resonance (SPR) band with increasing mole fraction of silver has been interpreted due to dampening of core, i.e. Au SPR by Ag. The dependence of nonlinear optical response of spherical core @ shell nanoparticles has been investigated as a function of relative composition of each metal. Simulation of SPR extinction spectra based on quasi-static theory is done. A comparison of our experimental and the simulated extinction spectra using quasi-static theory of nanoshell suggests that our synthesized bimetallic particles have core @ shell structure rather than bimetallic alloy particles.     

Gold nanoparticle induced conformational changes in heme protein

Change of α-helical structure of heme protein (Hb) to a β-sheet and random coil conformation because of the interaction of glycine capped gold nanoparticles (20–60 nm) as observed from attenuation total reflectance, absorption, Fourier transform infra red, and Circular Dichroism spectroscopy has been reported in this article. Upon interaction, protein takes a cylindrical shape of length 12 μm and diameter 0.35 μm as revealed from scanning electron microscopy and transmission electron microscopy. The Selected-Area Electron beam Diffraction pattern shows change of crystalline structure in GNP to amorphous nature with the interaction of Hb.     

Molecular conformation and liquid structure of 2-propanol through neutron diffraction

The neutron diffraction data analysis of deuterated liquid 2-propanol at room temperature to define its molecular conformation is presented. 2-Propanol being a large molecule with twelve atomic sites, the conformation analysis is tricky and an improved method of data analysis is given. The intermolecular structural correlations, i.e., hydrogen-bonded liquid structure, can be modelled accurately to extract the nature of the average hydrogen-bonded molecular association in liquid state at room temperature. Like other alcohols these are mostly hexamer ring chain (HRC) clusters. The cluster analysis of recent X-ray data available in the literature also support the same liquid structure.     

Second law analysis of a cyclic regenerator in presence of longitudinal heat conduction in matrix

The present analysis gives an account of exergy destruction in regenerative heat exchangers used in cryogenic applications from the view point of Second Law of Thermodynamics. Unlike the previous studies, the present work considers the solid storage matrix with temperature variation along both spatial and temporal co-ordinates. The present analysis also considers the effect of matrix longitudinal heat conduction on the Second Law behaviour. Finite longitudinal conductivity, which results from the distribution of temperature in the matrix, acts as a major non-ideality associated with the analyses done so far. The present analysis shows that the introduction of longitudinal conduction ensures the optimization of charging period for the regenerator. This makes it possible to optimize the regenerator performance globally to produce optimum combination of N _tu and charging time. It is also observed that a decrease in longitudinal conductivity reduces the optimum charging time. Thus the non-existence of thermodynamic optima at the absence of longitudinal conduction is explained adequately. Received on 12 May 1998     

均匀自由流动的非牛顿流体中连续表面上的磁流体动力学流动和热传递

分析在平行自由流动的非牛顿黏弹性导电流体中,连续平展表面移动时的稳态流和热传递特性,该流动处于横向均匀磁场作用下.以二阶流体构建它的本构方程,得到了速度分布和温度断面图的数值结果.讨论了诸如黏弹性参数、磁场参数和Prandtl数等不同物理参数对诸种动量和热传递特性的影响,并给出相关图示.