Plane Symmetric Viscous Fluid Cosmological Models with Varying <Emphasis Type="Italic">Λ</Emphasis>-Term

Plane symmetric viscous fluid cosmological models of the universe with a variable cosmological term are investigated. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density whereas the coefficient of shear viscosity is to be proportional to rate of expansion in the model. We have also obtained a special model in which the shear viscosity is assumed to be zero. The cosmological constant Λ is found to be a decreasing function of time and a positive which is supported by results from recent supernovae Ia observations. Some physical and geometric properties of the models are also discussed.     

Dielectric, magnetic and magnetoelectric properties of La and Nb codoped bismuth ferrite

Single-phase Bi(0.80)La(0.20)FeO(3) (BLFO) and Bi(0.80)La(0.20)Fe(1-x)Nb(x)O(3) (BLFNO) samples were prepared in order to study the dielectric, magnetic and magnetoelectric properties of La and Nb codoped BiFeO3. Rietveld refinement of x-ray diffraction patterns of La and Nb codoped samples has been performed using the R3c space group. Magnetic hysteresis loops revealed that codoping can effectively increase the spontaneous magnetization due to change in the bond angle of Fe-O-Fe as a result of distortion created by the Nb5+ doping. Magnetic field-induced relative change of the dielectric constant for BLFO and BLFNO samples is a signature of magnetoelectric coupling.     

Short and Stereoselective Syntheses of Pheromone Components of Aproaerema Modicella

Efficient syntheses of pheromone components of Aproaerema modicella starting from a common intermediate 7-octyn-1-ol is described.     

Stereoselective and facile total synthesis of (+)-goniodiol,a styryllactone from carbohydrates

The stereoselective synthesis of (+)-goniodiol, a cytotoxic styryllactone, has been accomplished in 10 steps starting from inexpensive and readily available d-manitol and δ-gluconolactone involving the direct and straightforward reaction conditions of Grignard addition, chain elongation, and hydroboration, thus making the synthesis simple and convenient.     

Stabilization of ferromagnetism in Mn doped ZnO with C co-doping

We present a method for stabilizing ferromagnetism in Mn doped ZnO. We find that Mn doped ZnO show anti-ferromagnetic order in the absence of additional carriers. When Mn doped ZnO is co-doped with C atom at O sites ferromagnetic state gets stabilized. The C doping creates holes which leads to stabilization of ferromagnetic state via hole mediated double exchange mechanism.     

Characterization and Control of Residual Stress and Curvature in Anodically Bonded Devices and Substrates with Etched Features

While anodic bonding is commonly used in a variety of microelectromechanical systems (MEMS) applications, devices and substrates that incorporate this processing technique are often subjected to significant residual stress and curvature that create post-processing and reliability issues. Here, using an anisothermal anodic bonding procedure, residual stresses and the resulting wafer curvature in these structures are controlled by varying the initial bond temperatures of the silicon and Pyrex wafers independently. Residual stresses are quantified by measuring bulk wafer curvature and, locally, stress concentrations are measured using infrared photoelasticity accompanied by 3-D thermomechanical finite element analysis. Based on the good agreement between numerical predictions and experimental results, this process can be used to determine the bulk post-bond wafer curvature and to reduce the likelihood of structural failure at these sites, by changing the residual stresses from tensile in nature, which may drive initiation and growth of cracks, to compressive, which can suppress such failures.     

Synthesis of C–N nanotube blocks and Y-junctions in bamboo-like C–N nanotubes

We report the observations made on the synthesis and characterization of C–N nanotube blocks and Y-junctions in bamboo-like C–N nanotubes. The C–N nanotube Blocks have been synthesized by pyrolyzing the mixture of silver nitrate acetonitrile solution and ferrocene benzene solution. The structural/microstructural characterization of the as-synthesized material has been done using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray photoelectron spectroscopic (XPS) analysis has been carried out to confirm the presence of nitrogen in nanotubes. These investigations reveal the formation of blocks of bamboo-like nanotubes having the dimension 300 × 200 × 30 μm and the diameter is 20–50 nm. We also observe the formation of Y-junctions in bamboo-like nanotubes as we spray the acetonitrile ferrocene and AgNO₃ mixture. The length of the synthesized Y-junction nanotube bundles is ~2 μm. Some more complex Ψ-shaped junctions are also found to be present. The diameters of the Y-junction nanotubes is ~80 nm at the junction and 25–50 nm at the branches.     

Studies of the reactions of thiocyanate ion with pentammine dinitrogen ruthenium(II) dibromide at different temperatures

The salts of the linkage isomers of thiocyanatopentammineruthenium(III) [Ru(NH₃)₅(NCS)]²⁺, [Ru(NH₃)₅(SCN)]²⁺ and dithiocyanatotetrammineruthenium(III) [Ru(NH₃)₄(NCS)₂]⁺ along with those of tetrathiocyanatodiammineruthenate(III) [Ru(NH₃)₂(SCN)₄]^? have been synthesized. The insoluble polymeric complex [Ru(NH₃)₂(SCN)₂]_n has also been prepared. The compounds have been characterized by chemical analyses, spectral (IR, UV and visible), magnetic susceptibility, conductivity, cyclic voltammetry and chromatography studies.     

Raman and infrared spectra of tere-phthalaldehyde

The laser Raman spectrum of tere-phthalaldehyde powder has been recorded on a Jobin Yvonhg 2S spectrophotometer with a~100 mW Argon-Ion laser. The infrared spectrum of the solid substance has been recorded on a Perkin-Elmer 621 spectrophotometer in the region 300–4000 cm^-1 using KBr and nujol mull techniques. The observed frequencies have been assigned in terms of the fundamentals, overtones and combinations assumingD _2h point-group symmetry.