Crystal structures and mesomorphic properties of Schiff base homologs and derivatives,and magnetic properties of their dimeric and dinuclear copper(II) complexes

Three N₂O₄ Schiff. base homologs, H₂L1 (n = 8), H₂L3 ((n = 9), and H₂L4 (n = 10) were obtained from the reactions of 2-HOC₆H₄CHO with H₂N(CH₂)_8-10NH₂, while a derivative of H₂L1, namely, H₂L2, was obtained from the reaction of 3,5-X₂-2-HOC₆H₂CHO (X = tert-butyl) with H₂N(CH₂)₈NH₂. The Schiff bases H₂L2 (triclinic; P-1), H₂L3 (monoclinic; C2/c), and H₂L4 (monoclinic; P21/c) were single crystals with low melting temperatures (less than 100°C). The homologs exhibited mesomorphisms, while the derivative was not mesomorphic and did not reform crystals from its melt. Copper(II) complexes of H₂L1, H₂L2 and H₂L4 were dimeric, while that of H₂L3 was dinuclear with chelating CH₃COO ligand. These complexes were paramagnetic with insignificant interactions between the copper(II) atoms and have high decomposition temperatures (T_dec = 268–304°C). Their melting temperatures (T_melt = 138.9–190.2°C) were higher than the corresponding Schiff bases, but they were not mesomorphic.     

Translucent Optical Networks Design for Static Traffic

A routing and wavelength assignment algorithm is proposed to minimize the number of wavelengths and transceivers required simultaneously under static traffic in translucent optical networks design.     

Degenerate four-wave mixing based all-optical wavelength conversion in a semiconductor optical amplifier and highly-nonlinear photonic crystal fiber parametric loop mirror

The idler is separated from the co-propagating pump in a degenerate four-wave mixing (DFWM) with a symmetrical parametric loop mirror (PALM), which is composed of two identical SOAs and a 70 m highly-nonlinear photonic crystal fiber (HN-PCF). The signal and pump are coupled into the symmetrical PALM from different ports, respectively. After the DFWM based wavelength conversion (WC) in the clockwise and anticlockwise, the idler exits from the signal port, while the pump outputs from its input port. Therefore, the pump is effectively suppressed in the idler channel without a high-speed tunable filter. Contrast to a traditional PALM, the DFWM based conversion efficiency is increased greatly, and the functions of the amplification and the WC are integrated in the smart SOA and HN-PCF PALM.     

10 Gb/s WDM-PON based on FP-LDs injection locked by downlink optical carrier

We propose and demonstrate a 10 Gb/s wavelength division multiplexed passive optical network (WDM-PON) where subcarriers are employed to transmit the downstream data and optical carriers of the downlink subcarrier modulated (SCM) lights are reused to injection lock Fabry-Perot laser diodes (FP-LDs) for uplink transmission. Experiment results show that a very good BER performance can be achieved for both uplink and downlink at 10 Gb/s. The impact of optical carrier to subcarrier ratio and wavelength mismatching is also investigated.     

Plasmon‐enhanced polarized Raman spectroscopy for sensitive surface characterization

Local‐mode and localized surface plasmons generated on the silver thin film can selectively enhance the Raman signal from the surface. Further improvement of surface signal can be obtained by using the polarized Raman technique that results in a dramatic enhancement of the surface sensitivity by up to 25.4 times as compared to that without a silver coating. This technique will be very useful for Raman study on samples that suffer overlapping background signal. In this article, we show that it can be used to significantly improve the signal of thin strained‐Si layer on top of SiGe buffer layer. Copyright © 2008 John Wiley & Sons, Ltd.     

A Three-Phase Simulation System Written in Pascal

A three-phase simulation system written in Pascal for use on microcomputers, minis and mainframes is presented. The advantages of the three-phase method are discussed, and the basis of the system explained. Although a traditional, textbook example is used to aid explanation and discussion, the system described in this paper has been used in real applications and in the teaching of simulation at Lancaster University and the London School of Economics. It also provides a basis for further research in simulation within both institutions.