Hydrogen bonded nonlinear optical γ-glycine: Crystal growth and characterization

Single crystals of γ-glycine(GG) were grown by solvent evaporation technique from a mixture of aqueous solutions of glycine and ammonium nitrate at ambient temperature. X-ray diffraction, thermogravimetric/differential thermal analysis, Fourier transform infrared spectral techniques were employed to characterize the crystal. The lattice parameters were calculated and they agree well with the reported values. GG exists as dipolar ions in which the carboxyl group is present as a carboxylate ion and the amino group as an ammonium ion. Due to this dipolar nature, glycine has a high decomposition temperature. The UV cutoff of GG is below 300 nm and has a wide transparency window, which is suitable for second harmonic generation of laser in the blue region. Nonlinear optical characteristics of GG were studied using Q switched Nd:YAG laser (). The second harmonic generation conversion efficiency of GG is 1.5 times that of potassium dihydrogen phosphate . The X-ray diffraction and Fourier transform infrared spectral studies show the presence of strong hydrogen bonds which create and stabilize the crystal structure in GG. The main contributions to the nonlinear optical properties in GG results from the presence of the hydrogen bond and from the vibrational part due to very intense infrared bands of the hydrogen bond vibrations. GG is thermally stable up to 441 K.     

Some remarks on quasi-Chebyshev subspaces

We give simple proofs of some results of Mohebi [H. Mohebi, On quasi-Chebyshev subspaces of Banach spaces, J. Approx. Theory 107 (2000) 87-95] on quasi-Chebyshev subspaces.     

Thin films of metal-organic compounds and metal nanoparticle-embedded polymers for nonlinear optical applications

Thin films based on two very different metal-organic systems are developed and some nonlinear optical applications are explored. A family of zinc complexes which form perfectly polar assemblies in their crystalline state are found to organize as uniaxially oriented crystallites in vapor deposited thin films on glass substrate. Optical second harmonic generation from these films is investigated. A simple protocol is developed for thein-situ fabrication of highly monodisperse silver nanoparticles in a polymer film matrix. The methodology can be used to produce free-standing films. Optical limiting capability of the nanoparticle-embedded polymer film is demonstrated     

Gallium iodide/iodine as a versatile reagent for the aza-Prins cyclization: an expeditious synthesis of 4-iodopiperidines

4-Iodopiperidines are prepared in good yields and with high selectivity by means of aza-Prins-cyclization using a catalytic amount of gallium(III) iodide and a stoichiometric amount of iodine under mild reaction conditions. This is the first report on the preparation of 4-iodopiperidines via aza-Prins-cyclization.     

Flag transitive planes of dimension four over GF(3)

Two non desarguesian flag transitive planes of order 3⁴ whose Kernel is GF(3) are constructed. These planes are distinct from the planes of the same order contained in the class constructed by Narayana Rao M. L. (Proceedings of American Mathematical Society 39 (1973) 51–56) and Ebert, G.L. and Baker, R. (Enumeration of two dimensional Flag-Transitive planes, Algebras, Groups and Geometries 3 (1985) 248–257). The Flag Transitive group modulo the scalar collineations of these planes is generated by two elements and is of order 328.     

Synthesis and reactivity of sulfur and silyl substituted α-alkylidene-β-lactams

Synthetically valuable α-alkylidene-β-lactams are produced from the addition of chlorosulfonyl isocyanate to allenyl sulfides.     

Laminar flow and heat transfer over a two-dimensional triangular step

The velocity correction algorithm is used in the finite element method to solve forced convection problems between parallel plates with a triangular step, for Reynolds numbers up to 1000. Equal-order interpolation functions for velocity, pressure and temperature are used. The solutions show a smooth variation of pressure. The streamfunction, isotherms, isobars and velocity profiles are presented for a typical Reynolds number of 500. The skin friction and heat transfer results are presented for Reynolds numbers up to 1000.     

Determination of thermal properties of food materials theory and experiments

Mathematical models are presented for predicting the time-temperature characteristics during air cooling of moist food products in the shape of infinite slab, infinite cylinder and sphere, taking into account the mass transfer effects at the surface. An experiment to determine the time-temperature characteristics of food products from which the thermal properties can be determined using the proposed mathematical model is described. The present analysis predicts faster cooling rates compared to an analysis which considers only pure convection heat transfer at the boundary. Time-temperature histories of some food models, fruits and vegetables are obtained experimentally. A nonlinear estimation procedure is used to match the experimentally obtained time-temperature histories with theoretical results to evaluate the unknown thermal properties of the products studied.     

Trace analysis of mercury by a radiochemical displacement method using cobalt(III) diethyldithiocarbamate

A radiochemical displacement method was utilized for the determination of traces of mercury in water taking advantage of its ability to displace cobalt from cobalt(III) diethyldithiocarbamate tagged with⁶⁰Co. The method is found to be applicable in the concentration range of 50–200 g/ml mercury. The interfernces from various cations like Fe(III), Co(II), Cu(II), Pb(II) and Ag(I) ions were studied.