Photobiological information obtained from XPA gene-deficient mice

The XPA gene-deficient mouse, an animal model of xeroderma pigmentosum (XP), develops enhanced photobiologic reactions including acute inflammation, immunosuppression and skin carcinogenesis, because of the defect in the excision repair of ultraviolet-induced DNA lesions. The results strongly suggest that nuclear DNA is an important chromophore to initiate acute and chronic skin damages. The model mouse is a useful experimental animal not only to investigate the mechanisms of photosensitivity in XP, but also to study physiological photobiology in humans, because photobiologic reactions are greatly intensified in this mouse.     

Thiophene- and selenophene-based heteroacenes: combined quantum chemical DFT and spectroscopic Raman and UV-Vis-NIR study

In this article, we report the characterization of a series of thiophene- and selenophene-based heteroacenes, materials with potential applications in organic electronics. In contrast to the usual alpha-oligothiophenes, these annelated oligomers have a larger band gap than most semiconductors currently used in the fabrication of organic field-effect transistors (OFETs) and therefore they are expected to be more stable in air. The synthesis of these fused-ring molecular materials was motivated by the notion that a more rigid and planar structure should reduce defects (such as torsion about single bonds between alpha-linked units or S-syn defects) and thus improve pi-conjugation for better charge-carrier mobility. The conjugational properties of these heteroacenes have been investigated by means of FT-Raman spectroscopy, revealing that pi-conjugation increases with the increasing number of annelated rings. DFT and TDDFT quantum chemical calculations have been performed, at the B3LYP/6-31G** level, to assess information regarding the minimum-energy molecular structure, topologies, and absolute energies of the frontier molecular orbitals around the gap, vibrational normal modes related to the main Raman features, and vertical one-electron excitations giving rise to the main optical absorptions.     

Synthesis,X-ray crystal structure and magnetic study of the 1D {[Cu(N,N-diethyl-1,2-ethanediamine)(μ1,5-dca)(dca)]}n complex

A new complex, {[CuL(μ_1,5-dca)(dca)]}_n (1), has been synthesized from the reaction of Cu(NO₃)₂ · 3H₂O, N,N-diethyl-1,2-ethanediamine (L) and sodium dicyanamide (Nadca) in aqueous medium. Single crystal X-ray analysis reveals that the complex has a 1D infinite zigzag chain structure in which copper(II) ions are bridged by single dicyanamide ligands in an end-to-end fashion. The chains propagate parallel to the crystallographic b-axis and they are stacked one upon another along the c-axis. The coordination environment of the copper(II) centers are distorted square-pyramidal. Of the four coordination sites of the basal plane of the square-pyramid, two are occupied by the nitrogen atoms of the diamine and the remaining two sites are occupied by the terminal nitrogen atoms of the bridging dca groups. One terminal nitrogen atom of a monodentate dca group occupies the apical position of the coordinated polyhedra. [CuL(dca)] units are then connected to each other through a μ_1,5-dca bridge to form 1D chains. The variable temperature magnetic susceptibility measurements evidenced weakly antiferromagnetic interactions (J = −0.35 cm⁻¹) in {[CuL(μ_1,5-dca)(dca)]}_n (1).     

Recent progress of integrated optics planar lightwave circuits

Planar lightwave circuits (PLCs) are waveguide devices that integrate fiber-matched optical waveguides on silicon or glass substrate to provide an efficient means of interaction for the guided-wave optical signals. PLCs provide various important and functional devices for optical wavelength division multiplexing (WDM), time division multiplexing (TDM) systems and subscriber networks. This paper reviews the recent progress and future prospects of PLC technologies including arrayed-waveguide grating multiplexers, optical add/drop multiplexers, programmable dispersion equalizers and hybrid optoelectronics integration technologies.     

Effect of absorption on surface speckles in random media

We investigate the intensity fluctuations of light backscattered from absorbing random media. A numerical simulation which takes into account the interference among different scattering paths reveals that the contrast of speckle patterns appearing at the surface of the medium decreases with an increase of absorption in weak absorption regime, but increases for strong absorption. It is shown from a simple theoretical model that such a contrast variation is caused by changes in the power of diffusive-scattering waves and in the amplitude distribution of single and low-order scattering waves.     

The possibility of graded-index plastic optical fibers containing lanthanide chelates for amplifiers and lasers

Absorption spectra of lanthanide ions in perfluorinated (PF) plastic solution were measured, and Judd-Ofelt parameters (Ω₂, Ω₄, Ω₆) were determined by the absorption measurements. Fluorescence spectrum of Nd³⁺ in PF plastic solution from 900 nm to 1350 nm, pumped at 580 nm, were measured for the first time.