FT-Raman, FT-IR and surface enhanced Raman scattering spectra of sodium salicylate

FT-IR and FT-Raman spectra of sodium salicylate were recorded and analysed. Surface enhanced Raman scattering (SERS) spectrum was recorded is silver colloid. Comparisons of the SERS spectrum with the spectra in solution and of the solid sample are made. Sodium salicylate (an O donor ligand) is thought to adsorb in a somewhat 'tilted side on orientation' with respect to the silver surface.     

Fabrication and Characterization of Monolithically Fused Wavelength-Independent 1 × 4 Couplers

Abstract

A new method for the fabrication of a monolithic 1 × 4 single-mode fused coupler is described together with details of its performance in terms of coupling ratio, spectral response and polarization sensitivity. The fabricated device exhibits ultra-broadband performance with low polarization dependent loss. The coupling pattern exhibits identical coupling to all interacting fibers, enabling an easy control on fabrication parameters of the device.     

Bis[2,4‐diamino‐5‐(3,4,5‐trimethoxybenzyl)pyrimidin‐1‐ium] dl‐malate

<!?tpct=1pt>Racemic malic acid and trimethoprim [5‐(3,4,5‐trimethoxybenzyl)pyrimidine‐2,4‐diamine] form a 1:2 salt (monoclinic, P2₁/c), 2C₁₄H₁₉N₄O₃⁺·C₄H₄O₅²⁻, in which the malate component is disordered across a centre of inversion. The crystal structure of the salt consists of protonated trimethoprim residues and a malate dianion. The carboxylate group of the malate ion interacts with the trimethoprim cation in a linear fashion through pairs of N—H...O hydrogen bonds to form a cyclic hydrogen‐bonded motif. This is similar to the carboxylate–trimethoprim cation interaction observed earlier in the complex of dihydrofolate reductase with trimethoprim. The structure of the salt of trimethoprim with racemic dl ‐malic acid reported here is the first of its kind. The present study investigates the conformations and the hydrogen‐bonding interactions, which are very important for biological functions. The pyrimidine plane makes a dihedral angle of 78.08 (7)° with the benzene ring of the trimethoprim cation. The cyclic hydrogen‐bonded motif observed in this structure is self‐organized, leading to novel types of hydrogen‐bonding motifs in supramolecular patterns.     

Two novel bis‐azomethines derived from quinoxaline‐2‐carbaldehyde

The Schiff base compounds N,N′‐bis[(E)‐quinoxalin‐2‐ylmethylidene]propane‐1,3‐diamine, C₂₁H₁₈N₆, (I), and N,N′‐bis[(E)‐quinoxalin‐2‐ylmethylidene]butane‐1,4‐diamine, C₂₂H₂₀N₆, (II), crystallize in the monoclinic crystal system. These molecules have crystallographically imposed symmetry. Compound (I) is located on a crystallographic twofold axis and (II) is located on an inversion centre. The molecular conformations of these crystal structures are stabilized by aromatic π–π stacking interactions.     

Suppression of beating noise of narrow-linewidth erbium-doped fiber ring lasers by use of a semiconductor optical amplifier

Beating noise in narrow-linewidth erbium-doped fiber ring lasers puts severe limitations on applications of the lasers. We demonstrate the suppression of beating noise in fiber ring lasers by using a semiconductor optical amplifier in the laser cavity, which acts as a high-pass filter. Two different ring structures are presented as examples to demonstrate this beating noise suppression.     

Analysis of elastic scattering of 0.8 GeV polarized protons from 116Sn and 124Sn

Differential cross section and analyzing power data for elastic scattering of 0.8 GeV polarized protons from ¹¹⁶Sn and ¹²⁴Sn are analyzed in terms of a spin-dependent Kerman-McManus-Thaler formalism. Neutron matter densities and rms radii are deduced with careful attention to sources of error, and found to be in good agreement with Hartree-Fock predictions.     

Preparation and characterization of tris(iso‐propyl)stibine complexes of palladium and platinum

Tris(iso‐propyl)stibine complexes of palladium and platinum of the type [MX₂(SbⁱPr₃)₂] [M, X = Pd, Cl (1a), Pd, Br (1b), Pd, I (1c), Pt, Cl (2)] have been prepared and characterized by elemental analysis, IR and ¹H NMR spectral data. The structure of 1a, established by X‐ray structural analysis, revealed that the palladium atom is in a square planar environment with mutually trans SbⁱPr₃ ligands. Copyright © 2001 John Wiley & Sons, Ltd.     

Modeling of the electrostatic corona discharge reactor

A model is presented for the electrostatic corona discharge reactor (ECDR) in a pin-plate configuration. The main objective is to describe the fundamental chemistry and physics governing the discharge behavior and to predict the ECDR performance under various operating conditions. The electric field strength is estimated assuming a space-charge-free field. A two-term spherical harmonic expansion is used to solve the Boltzmann equation for the electron energy distribution function (EEDF) and calculate the electron-molecule reaction rates using collision cross-section data. Species continuity equations are solved for the dry and wet air systems to predict ozone and NO_x at various feed flow rates (1630, 4890, 14, 670 cm/s) and an applied voltage of 10 kV. Among the various results reported, it is noted that the calculations indicate the Maxwell EEDF cannot be used because it overpredicts the electron-molecule rate coefficients by several orders of magnitude     

Intermediate colloidal formation and the varying width of periodic precipitation bands in reaction-diffusion systems

The mechanism of rhythmic pattern formation in reaction-diffusion systems is investigated theoretically by introducing a new concept. The boundary that separates the two reacting species virtually migrates as the diffusion proceeds into the gelatinous medium. Based on this boundary migration scenario, all the well-established relations on Liesegang patterns could be proved, in a rather modified way. The idea of formation of intermediate colloidal haze prior to patterning along with the moving boundary model proved to be efficient in predicting the concentration dependence of the width of the spatiotemporal patterns. The experimental observations support the width law relation developed.