Thermal convection problem of micropolar fluid subjected to hall current

Thermal instability of a micropolar fluid layer heated from below in the presence of hall currents is investigated. Using the appropriate boundary conditions on the boundary surfaces of the fluid layer, the frequency equation is derived and then critical Rayleigh number is determined. It is found that hall current parameter has destabilizing effect on the system. For specific values of parameters, oscillatory convection in observed in the system. The behavior of Rayleigh number with wavenumber is also computed for different values of various parameters. The results of some earlier workers have been reduced as a special case from the present problem.     

In Vivo Evalution of Hypoglycemic Activity of <Emphasis Type="BoldItalic">Aloe</Emphasis> spp. and Identification of Its Mode of Action on GLUT-4 Gene Expression In Vitro

The present study evaluated the hypoglycemic activity of Aloe extract on streptozotocin-induced diabetic mice and focuses its effect on GLUT-4 gene expression under in vitro cell-culture system. Administration of extract at the dosage of 130 mg/kg body weight per day for 4 weeks resulted in significant decrease in blood glucose and total cholesterol in streptozotocin (60 mg/kg body weight) induced diabetic mice. The hypoglycemic effect was compared with metformin. The activities of carbohydrate metabolizing enzymes were brought back to near normal level after the treatment and glucose homeostasis was maintained. Lyophilized aqueous Aloe extract (1 mg/ml) upregulated the GLUT-4 mRNA synthesis in mouse embryonic NIH/3T3 cells.     

Gamma radiation induced changes in nuclear waste glass containing Eu

Gamma radiation induced changes were investigated in sodium-barium borosilicate glasses containing Eu. The glass composition was similar to that of nuclear waste glasses used for vitrifying Trombay research reactor nuclear waste at Bhabha Atomic Research Centre, India. Photoluminescence (PL) and electron paramagnetic resonance (EPR) techniques were used to study the speciation of the rare earth (RE) ion in the matrix before and after gamma irradiation. Judd-Ofelt (J-O) analyses of the emission spectra were done before and after irradiation. The spin counting technique was employed to quantify the number of defect centres formed in the glass at the highest gamma dose studied. PL data suggested the stabilisation of the trivalent RE ion in the borosilicate glass matrix both before and after irradiation. It was also observed that, the RE ion distributes itself in two different environments in the irradiated glass. From the EPR data it was observed that, boron oxygen hole centre based radicals are the predominant defect centres produced in the glass after irradiation along with small amount of E’ centres. From the spin counting studies the concentration of defect centres in the glass was calculated to be 350 ppm at 900 kGy. This indicated the fact that bulk of the glass remained unaffected after gamma irradiation up to 900 kGy.     

Axisymmetric vibrations of a circular plate of linearly varying thickness on an elastic foundation according to Mindlin theory

Free axisymmetric vibrations of an elastic circular plate of linearly varying thickness on an elastic foundation have been studied on the basis of shear theory [1,2]. The transverse displacement and local rotation are expressed as an infinite series. The frequencies corresponding to the first two modes of vibrations are obtained for a circular plate with clamped and simply supported edge conditions for various values of the taper constant and the foundation modulus. The results have been compared with those of reference [3].     

Analysis of the nonlinear vibration of a two-mass–spring system with linear and nonlinear stiffness

An analytical approach is developed for areas of nonlinear science such as the nonlinear free vibration of a conservative, two-degree-of-freedom mass–spring system having linear and nonlinear stiffnesses. The main contribution of this research is twofold. First, it introduces the transformation of two nonlinear differential equations for a two-mass system using suitable intermediate variables into a single nonlinear differential equation and, more significantly, the treatment of a nonlinear differential system by linearization coupled with Newton’s method. Secondly, the major section is the solving of the governing nonlinear differential equation where the displacement of the two-mass system can be obtained directly from the linear second-order differential equation using a first-order variational approach. The aforementioned approach proposed by J.H. He, who actually developed the method, is exactly He’s variational method. This approach is an explicit method with high validity for resolving strong nonlinear oscillation system problems. Two examples of nonlinear two-degree-of-freedom mass–spring systems are analyzed, and verified with published results and exact solutions. The method can be easily extended to other nonlinear oscillations and so could be widely applicable in engineering and science.     

Impedance spectroscopy and conductivity studies in SrBi2(Ta1−xWx)2O9 ferroelectric ceramics

Complex impedance spectroscopy (CIS) technique has been utilized to investigate the intra- and intergranular contributions to the impedance in pristine and wolframium (tungsten, W) -substituted strontium bismuth tantalate [SrBi₂(Ta_1−xW_x)₂O₉ (SBTW); x=0.0, 0.025, 0.05, 0.075, 0.1 and 0.2] ceramics as a function of temperature and frequency. CIS studies reveal that the electrical relaxation process was temperature dependent and non-Debye type. The temperature dependence of the relaxation time was found to obey the Arrhenius law. DC conductivity of the studied samples obtained from the CIS data decreased for W content upto x=0.05, followed by a subsequent increase with x>0.05. Electrical conductivity data including the typical values of the activation energies at high temperature indicated that the conductivity in the studied ceramics was essentially due to the contribution of doubly ionized oxygen vacancies to the conduction process.     

Sorption of Eu(III) by amorphous titania, anatase and rutile

Sorption of Eu(III), an analogue of trivalent actinides (Am, Cm), by amorphous titania as well as different crystalline phases of titania, namely anatase and rutile, have been studied as a function of pH, using ¹⁵⁴Eu (half life?=?8.8 yrs, E_???=?123,247?keV) as a radiotracer. The objective of this study was to investigate the effect of the crystalline phase of the titania on their sorption behaviour towards the metal ion. Amorphous titania was prepared by organic route and was converted into anatase and rutile by heating at elevated temperatures based on the differential thermal analysis studies. Eu(III) sorption by all forms of titania rises sharply with the pH of the suspension, with the sorption edge shifting to higher value in the order; amorphous?<?anatase?<?rutile. However, the normalization of the sorption data to the surface area of the sorbents resulted in the overlapping of the sorption curves for amorphous and anatase phases, with the data being higher for rutle in the lower pH region, indicating the effect of the crystal phase on sorption behaviour of Eu(III).     

Separation of no-carrier-added <Superscript>149</Superscript>Gd from <Superscript>12</Superscript>C activated natural praseodymium matrix

¹⁴⁹Gd was produced from the ¹²C induced reaction on natural praseodymium target. No-carrier-added (nca) ¹⁴⁹Gd was separated from the bulk target matrix by liquid–liquid extraction (LLX) using cation exchanger di-(2-ethylhexyl)phosphoric acid (HDEHP) dissolved in cyclohexane. High separation factor of 2,450 was achieved at the optimal experimental condition when 1% HDEHP and 0.1 M HCl were used as organic and aqueous phases respectively. The result was also compared with the previous reports.     

Selective transport of zinc and copper ions by synthetic ionophores using liquid membrane technology

This work highlights the role of synthetic carrier (ionophore) in the separation of heavy metal ions. A new series of ionophores; 4,4′-nitrophenyl-azo-O,O′-phenyl-3,6,9-trioxaundecane-1,10-dioate (R₁), bis[4,4′nitro-phenylazo-naphthyl-(2,2-dioxydiethylether)] (R₂) 1,8-bis-(2-naphthyloxy)-3,6-dioxaoctane (R₃), 1,11-bis-(2-naphthyloxy)-3,6,9-trioxaunde-cane (R₄), 1,5-bis-(2-naphthyloxy)-3-oxa-pentane (R₅) have been synthesized and used as extractant as well as carrier for the transport of various metal ions (Na⁺, K⁺, Mg²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) through liquid membranes. Effect of various parameters such as metal ion concentration, ionophore concentration, liquid–liquid extraction, back extraction, comparison of transport efficiency of BLM and SLM and different membrane support (hen’s egg shell and PTFE) have been studied. In BLM ionophores (R₂–R₅) transport Zn⁺ at greater extent and the observed trend for the transport of Zn²⁺ is R₂?>?R₄?>?R₃?>?R₅ respectively. Further transport efficiency is increased in SLM. In egg shell membrane ionophores (R₂–R₅) transport Zn⁺ due to their non-cyclic structure and pseudo cavity formation while ionophore R₁ transports Cu²⁺ ions at greater extent due to its cyclic structure and cavity size. Among the membrane support used egg shell membrane is found best for the transport of zinc ions because of its hydrophobic nature and exhibits electrostatic interactions between positively charged zinc ions and –COOH group of egg shell membrane. Thus structure of ionophores, hydrophobicity and porosity of the membrane support plays important role in separation of metal ions.     

Sample complexity reduction aids efficient detection of low‐abundant proteins from human amniotic fluid

Working with biological fluids poses a challenge of visualizing proteins present in lower concentrations. This study describes a batch‐mode chromatographic method for the fractionation of human amniotic fluid (AF). This method is easy to use with minimal sample quantity, resin volume and sample processing time. For albumin depletion, two methods were evaluated. The results demonstrated that specific depletion of albumin, using affinity‐ligand‐based resin, is more efficient than the conventional dye‐based method. The albumin‐depleted human AF was fractionated by strong anion‐exchange resin in spin devices, for sample, complexity reduction and enrichment of low‐abundant proteins. Analysis of four eluate fractions generated after this step shows enrichment of few low‐abundant proteins. Two novel low‐abundant proteins, Rab GDP dissociation inhibitor β and peptide methionine sulfoxide reductase, were identified from human AF. α‐1‐B Glycoprotein was successfully identified by this strategy, whereas the published literature reports that it was not identified by strong anion‐exchange FPLC followed by SDS‐PAGE. Therefore, the current method has distinct advantages over the conventional column‐based chromatography. This study also reports altered expression of some proteins in Rh‐isoimmunized AF samples in comparison with normal AF.