Significance of different modes in dynamics of chains in a dense medium

Singular Value Decomposition technique is used to decompose the trajectory of the fluctuations of atom positions into their modes for a chain of fifty bonds embedded in a fluctuating environment. The temperature of the environment is changed according to a Monte Carlo Metropolis scheme. Results show that at low temperatures only a few modes are significant, these being the slowest ones. For high temperatures, on the other hand, higher modes corresponding to fast fluctuations of atom positions are significant as well.     

Effect of flow on solutions of rodlike molecules

A flow field imposed on a solution of rodlike particles tends to align the rods owing to friction between the fluid and the rods. The potential energy of rods in a steady-state, homogeneous, and irrotational flow is superposed on the equilibrium Gibbs free energy of the quiescent solution to obtain the total free energy. The exact lattice treatment of Flory and Ronca is used in formulating the problem. Effects of flow on the orientational distribution function of rods and phase separation are analyzed with particular reference to elongational and pure shear flows. Calculations carried out for various compositions and flow characteristics reveal the presence of a region where the order parameter is sensitive to changes in prevailing flow conditions. Experimental determination of orientation by measuring flow birefringence is discussed.     

Continuous-wave quasi-phase-matched generation of 60 mW at 465 nm by single-pass frequency doubling of a laser diode in backswitch-poled lithium niobate

We report continuous-wave single-pass second-harmonic generation (SHG) in 4-mum -period 0.5-mm-thick backswitch-poled lithium niobate. Pump sources at 920-930 nm include both Ti:sapphire and diode-oscillator-amplifier lasers. SHG of a Ti:sapphire laser at 6.1%/W efficiency, producing 61 mW of power at 460 nm, is demonstrated in 50-mm-long periodically poled lithium niobate samples with a nonlinear coefficient d(eff) approximately 9pm/V, and 60 mW at 465 nm and 2.8%/W efficiency is obtained by SHG of a laser-diode source.     

Synchrotron radiation induced photoionization and photodissociation of carbon monoxide in the 14–35 eV region

Carbon monoxide has been excited with monochromatic synchrotron radiation in the 14–35 eV range using the Swedish synchrotron facility MAX in Lund. The decay products were studied in various detection channels such as formed CO⁺ and C⁺ ions using mass spectroscopy and visible or VUV fluorescence using photon detection. A rich line structure is observed which is attributed to CO Rydberg series converging to theX,A,B,D,C andE states in CO⁺. While a great number of these lines are already known, some of them are classified here for the first time. The combination of information from the fluorescence spectra and the mass spectra contribute important information concerning the autoionization and predissociation of these various Rydberg series.     

Correlation of gas–liquid partition coefficients using a generalized linear solvation energy relationship

In a number of previous communications, we reported on the utility of the solvatochromic linear solvation energy relationship (LSER) method for the correlation of a number of solute and solvent-dependent properties. In those studies, it was our practice to examine the effect of a variety of solvents on a given solute or a number of solutes in a given solvent. Here we report on a novel generalized LSER in which the solute and solvent were both simultaneously varied so as to assess the validity of the entire LSER concept and define its limits. The Hildebrand solubility parameter, δ_H, the Kamlet–Taft solvatochromic parameters, π*, α, β and the solute molar volume, V₂, were used as the explanatory variables. The gas–liquid partition coefficient (K) was the property of interest. We have found that the correlation using the generalized linear solvation energy relationship is statistically as good as the previous LSER correlations despite the use of a far smaller number of freely adjustable parameters. Furthermore, the new approach is able to give reasonable predictions of K values of systems not included in the data set upon which the regression is based.     

Ethylenediamine diacetate (EDDA)-catalyzed one-pot synthesis of tetrahydroquinolines by domino Knoevenagel/hetero Diels–Alder reactions from 1,3-dicarbonyls

This paper describes new and efficient synthetic approaches for biologically interesting tetrahydroquinoline analogues. The key strategies involve the ethylenediamine diacetate-catalyzed cyclization of 1,3-dicarbonyls to aminobenzaldehydes through domino Knoevenagel/hetero Diels–Alder reactions. These reactions provide a rapid route for the synthesis of novel polycycles with the tetrahydroquinoline moiety.     

Molecular structure,spectroscopic, and density functional theory studies of o-Dianisidine

o-Dianisidine has been characterized by the FT-IR, UV-Vis, and X-ray single-crystal determination. The compound crystallizes in the orthorhombic space group Pbca with a = 7.2593 (4) Å, b = 21.3485 (10) Å, c = 16.5835 (11) Å and Z = 8. Density functional theory has been used in the computation of the molecular geometry and harmonic vibrational wavenumbers. The calculated molecular geometry parameters have been compared with X-ray data. UV-Vis spectra of the compound have been predicted using the time-dependent density functional theory and good agreement between the calculated and experiment is determined. Besides, molecular electrostatic potential, frontier orbital analysis, and nonlinear optical properties were performed by using density functional theory calculations.