Fabrication of monolithic twin-GaInAs pin photodiode for balanceddual-detector optical coherent receivers

A monolithic twin-GaInAs/InP pin photodiode with planar, embedded structure has been fabricated for optical coherent receiver applications. High-uniformity (±1·5%) quantum efficiency and low capacitance (0·3 pF) have been achieved, and its advantage has been demonstrated by the intensity noise suppressions of a dual-detector balanced heterodyne receiver (better than -15 dB up to 4·2 GHz)     

High-speed monolithic GaInAs pinFET

A monolithic planar structure pin photodiode/field-effect transistor (pinFET) consisting of a low capacitance InP/GaInAs embedded pin photodiode and an AlInAs/GaInAs FET has been developed for long wavelength optical communications. Very high bitrate response capability of over 8 Gbit/s and good receiver performance at 2 Gbit/s have both been demonstrated     

Syntheses and comparison of 2,6-di-O-methyl celluloses from natural and synthetic celluloses

2,6-Di-O-methylcellulose was prepared from natural and synthetic celluloses. Natural cellulose was converted to 2,6-di-O-thexyldimethylsilylcellulose, then to 3-mono-O-allyl-2,6-di-O-methylcellulose, and finally into 2,6-di-O-methylcellulose. Alternatively, 2,6 di-O-methylcellulose was synthesized from the synthetic cellulose derivative 3-mono-O-benzyl-2,6-di-O-pivaloylcellulose by depivaloylation and methylation to give 3-mono-O-benzyl-2,6-di-O-methylcellulose, which was debenzylated to yield the dimethyl ether. Both types of 2,6-di-O-methylcellulose are insoluble in water and common organic solvents. The structures of all cellulose derivatives were determined by NMR.     

Polysiloxane-poly(propylene oxide) hybrid discs as solid phase in anti-HCV detection using a recombinant core protein

In this work, siloxane-poly(propylene oxide) discs (PPO disc) prepared using the sol-gel process were used as solid phase in enzyme-linked immunosorbent assays (ELISA) for the detection of anti-hepatitis C virus (HCV) antibodies. The HCV RNA from serum (genotype 1b) was submitted to the RT-PCR technique and subsequent amplification of the HCV core 408 pb. This fragment was cloned into expression vector pET42a and expressed in Escherichia coli as recombinant protein with glutathione S-transferase (GST). Cell cultures were grown and induced having a final concentration of 0.4 x 10(-3) mol L(-1) of IPTG. After induction, the cells were harvested and the soluble fraction was analyzed using polyacrilamide gel 15% showing a band with an approximate molecular weight of 44 kDa, the expected size for this GST-fused recombinant protein. The recombinant protein was purified and confirmed by immunological detection using HCV-positive serum and showed no cross-reactivity with positive samples for other infectious diseases. An ELISA was established using 1.25 ng of recombinant protein per PPO disc, a dilution of 1:10,000 and 1:40 for a peroxidase conjugate and serum, respectively, and solutions of hydrogen peroxide and 3,3',5,5'-tetra-methylbenzidine in a ratio of 1:1. The proposed methodology was compared with the ELISA conventional polystyrene-plate procedure and the performance of the PPO discs as a matrix for immunodetection gave an easy synthesis, good performance and reproducibility for commercial application.     

Thermally and Photochemically Induced Charge-Transfer Polymerizations

Polymerizations involving electron donor-acceptor interactions or charge-transfer interactions have been a topic of interest in recent years. Two classes of polymerization are the subjects of major concern in this area. One is a polymerization initiated via charge-transfer interactions involving monomers as one component, which is termed charge-transfer polymerization. The charge-transfer polymerization encompasses both thermal and photochemical processes. The other is an alternating radical copolymerization in which it is thought to be likely that a charge-transfer complex formed between monomer pairs participates as a monomer species in the propagation process of polymerization, the mechanism of which has long been a subject of controversy. Some of the alternating radical copolymerizations are initiated spontaneously via charge-transfer interactions between monomer pairs.     

Synthese und dielektrische Eigenschaften des 9-Acridinaldehyd-Acetals und des 3-Pyrenaldehyd-Acetals von Polyvinylalkohol

Ohne Zusammenfassung     

Incident wavelength dependence of pulse responses in InP/InGaAsP/InGaAs avalanche photodiodes

Pulse responses of InP/InGaAsP/InGaAs APDs have been studied at 1.3 and 1.55 ?m. A faster response rise-up characteristic was observed at 1.55 ?m than at 1.3 ?m. This result indicates that response speed depends on the hole generating region and hole pile-up at the heterojunction is decreased by introducing a hole-acceleration layer such as InGaAsP.     

Singlet Excitation Energy Migration in the Glassy and Single Crystalline States of 1,3-Diphenyl-5-(p-chlorophenyl)-2-pyrazoline

The crystal and molecular structure of the title compound were determined: a = 14.375(3), b = 11.534(3), c = 7.972(2) Å, α = 71.694(5), β = 79.125(5), γ - 74.861(5)°; space group PI. Refinement including all of the observed reflections (3145) leads to R = 0.086 (R_w= 0.074).

The molecular form in the crystalline state is fully extended in agreement with the suggestion by Birner et al. (Mol. Cryst. Liq. Cryst., 80, 11 (1982)), based on a NDDO-semiempirical calculation.

Whereas for the molecular form in the nematic liquid crystalline state a slightly parallel arrangement (～ 60°) of the dipole moment components perpendicular to the long axis is proposed, in the crystalline state these components are at an angle ～ 120° to each other, and somewhat antiparallel.

Preceding the melting point by approximately 10 degrees, DSC and thermal microscopy signals were observed; these depend eventually on solid-state polymorphism.     

Structure and gas permeability of asymmetric polyimide membranes made by dry–wet phase inversion: Influence of alcohol as casting solution

In this article, we have reported the influence of alcohol as a casting solution on the structure and the gas permeability of asymmetric polyimide membranes made by dry–wet phase inversion. The apparent skin layer thickness of the asymmetric membrane decreased with an increase in molecular weight of the alcohol, and the thicknesses of the membranes made from methanol, ethanol, propanol, and butanol were 250, 120, 61, and 31 nm, respectively. We found that χ₁₂ as an interaction parameter of solvent–nonsolvent had a significant influence on the phase inversion occurring in the coagulant medium. On the other hand, the gas permeance and the gas selectivity in the asymmetric membranes increased with the increasing molecular weight of the alcohol. We believe that a more packed structure formed in the asymmetric polyimide membrane with a thinner surface skin layer is also responsible for the thickness‐dependence of the gas selectivity obtained in this study. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2739–2746, 2007