Synthesis and study of electrical and magnetic properties of vanadium oxide micro and nanosized rods grown using pulsed laser deposition technique

Vanadium oxide micro and nanosized rods were grown using pulsed laser deposition technique under different oxygen pressures. X-ray diffractogram shows a predominant mixture of vanadium dioxide, VO₂ and Magneli phase, V₃O₇. The diameters of the rods were found to increase from 300 nm to 2.3 μm with increase in oxygen pressure from 0.1 mbar to 0.5 mbar as seen from high resolution scanning electron microscope images. Raman spectra of the rods show peaks at all the characteristic vibrations corresponding to that of V O_x phase. The 0.5 mbar oxygen deposited sample shows a semiconducting behavior from 300 to 77 K and is paramagnetic down to 5 K. Using versatile pulsed laser deposition we have established the tunability of the dimensions of V O_x nanorods which can find numerous potential applications in electrochemistry, catalysis, etc.     

Michael reaction of ketones and β-nitrostyrenes catalyzed by camphor-10-sulfonamide-based prolinamide

Novel camphor sulfonamide based organocatalysts were evaluated for their catalytic activity in the Michael reaction of ketones with nitroolefins. Reaction of ketones with β-nitrostyrenes in the presence of 20 mol % organocatalyst 1a and benzoic acid under solvent-free conditions at 0 °C provided the desired Michael adducts with high chemical yields (up to 97%) and excellent stereoselectivities (>99:1).     

Universal behavior of entrainment due to coherent structures in turbulent shear flow

A solution is suggested for a persistent mystery in the physics of turbulent flows: cumulus clouds rise to towering heights, practically without entraining the ambient medium, while apparently similar turbulent jets quickly lose their identity through entrainment and mixing. Dynamical system computations on a model vortical flow show that entrainment due to coherent structures depends sensitively on relative speeds of fluid parcels. Local heating, for example, can alter drastically the sizes of Kolmogorov-Arnol'd-Moser tori and chaotic mixing regions. The entrainment rate and, hence, the lifetime of a turbulent shear flow show a universal, nonmonotone dependence on the heating.     

Multiple scattering of gamma rays in water,concrete and sand

The transmitted photon spectra of¹³³Ba,²²Na,¹³⁷Cs,⁵⁴Mn and⁶⁰Co point sources are measured through different thicknesses of water, concrete and sand. The multiple-scatter peaks observed in these materials at 60, 90 and 100 keV energies respectively are found to be independent of incident photon energy and thickness of the medium.     

Slow magnetohydrodynamic flow past a circular cylinder

Oseen’ approximations are used to study the slow motion of a viscous, incompressible, electrically conducting fluid past a circular cylinder in the presence of a uniform aligned magnetic field. Using series truncation method, the analytical solutions for the first three terms in the Fourier sine series expansion of the stream function are obtained. Numerical values of the tangential drag for different values of magnetic interaction parameter and viscous Reynolds number are calculated.     

Highly efficient deprotection of aromatic acetals under neutral conditions using beta-cyclodextrin in water

Aromatic acetals have been deprotected to the corresponding aldehydes under biomimetic conditions for the first time using beta-cyclodextrin in water under neutral conditions, thereby overcoming many of the drawbacks associated with earlier methodologies. This method, apart from being simple with regard to recycling of the catalyst, also has the potential for industrial applications.     

Custom‐Fit Ruthenium(II) Metallopeptides: A New Twist to DNA Binding With Coordination Compounds

A new bipyridine building block has been used for the solid‐phase synthesis of dinuclear DNA‐binding ruthenium(II) metallopeptides. Detailed spectroscopic studies suggest that these compounds bind to the DNA by insertion into the DNA minor groove. Moreover, the potential of the solid‐phase peptide synthesis approach is demonstrated by the straightforward synthesis of an octaarginine derivative that shows effective cellular internalization and cytotoxicity linked with strong DNA interaction, as evidenced by steady‐state fluorescence spectroscopy and AFM studies.     

Probabilistic finite element analysis of a non-gasketed flange

Stress analysis of a non-gasketed flange was computationally simulated by a finite-element method and probabilistically evaluated in view of several uncertainties in the performance parameters. Cumulative distribution functions and sensitivity factors were computed for overall heat transfer rate due to the structural and thermodynamic random variables. These results can be used to quickly identify the most critical design variables in order to optimize the design and make it cost effective. The analysis leads to the selection of the appropriate measurements to be used in structural and heat transfer analysis and to the identification of both the most critical measurements and parameters Published in Prikladnaya Mekhanika, Vol. 44, No. 5, pp. 133–143, May 2008.     

Asymptotic properties of Rao's test for testing hypotheses in discrete parameter stochastic processes

Summary In this note some asymptotically optimum tests for testing hypotheses concerning parameters when the observations are dependent are obtained. Test statistics based on the score functions, similar to the one proposed by Rao in the case when the observations are i.i.d. are proposed. Asymptotically UMP tests for one sided hypotheses against one sided alternatives and asymptotically UMP unbiased test for a simple hypothesis against two sided alternatives are derived. In the multiparameter case tests for simple hypotheses that have asymptotically best constant power on some family of surfaces in the parameter space are derived.