GaAs/GaAlAs RIB waveguide grating filters for ? = 1.5?m

First-order Bragg grating filters have been realised in GaAs/GaAlAs rib waveguides for operation at ? ? 1.5?m. Singlemode devices with rib widths of 2 to 5 ?m and incorporating a 2.5 mm length of 225 nm period grating have been evaluated using a tunable T1:KCl colour-centre laser. Rejection ratios of 95% to 39% and 3dB bandwidths of 3.5 ? to 7.9 ? have been measured.     

1H magnetic resonance spectroscopy of chronic cerebral white matter lesions and normal appearing white matter in multiple sclerosis

OBJECTIVES: To test the hypothesis that irrecoverable neurological deficit in multiple sclerosis is associated with axonal loss. METHODS: 1H magnetic resonance spectroscopy (MRS) was carried out in a group of patients with clinically definite multiple sclerosis (n=31). Using this technique, the apparent concentration of NA ([NA] the sum of N-acetyl aspartate (NAA), a neuronal marker, and N-acetylaspartylglutamate has been compared in four groups of patients with multiple sclerosis classified as relapsing-remitting, secondary progressive, primary progressive, benign, and a control group. RESULTS: In the patients with relapsing-remitting disease (n=9) there was a highly significant reduction of apparent NA (median 8.73 mM, range 6.86 mM-10.74 mM, P=0.0008) from an area of high signal compared with the control group (median 11.97 mM, range 10.55 mM-14.5 mM). In the patients with secondary progressive disease (n=10), there was again a highly significant reduction of apparent NA (median 7.82 mM, range 3.5 mM-10.3 mM, P=0.0003) from an area of high signal compared with the control group. In the patients with primary progressive disease (n=6) there was once again a highly significant reduction of apparent NA (median 8.83 mM, range 6.95 mM-9.89 mM, P<0.002) from an area of high signal compared with the control group. In the patients with benign disease, however, there was no significant difference in the apparent NA (median 10.5 mM, range 8.53 mM-12.8 mM, P>0.05) from an area of high signal compared with the control group. In the patients with benign disease (n=5) there was also no significant difference in the apparent NA (median 10.74 mM, range 8.58 mM-13.4 mM, P>0.3) from an area of normal appearing white matter compared with the control group. In the patients with primary progressive disease, however, there was a significant reduction of apparent NA from an area of normal appearing white matter (median 8.78 mM, range 8.7 mM-12.38 mM, P< 0.025) compared with the control group. There was a significant inverse correlation between [NA] from lesions in the patients with multiple sclerosis and disability as measured on the Kurtzke expanded disability scale score (r= -0.364, 0.05>P>0.02). CONCLUSION: These findings support the hypothesis that axonal loss is important in the development of disability in multiple sclerosis. They also provide evidence for axonal loss in normal appearing white matter in patients with primary progressive disease.     

An analysis of the outcomes of treatment of small cell lung cancer in the elderly

BACKGROUND: Many cases of small cell lung cancer will occur in the elderly population but optimal management of the disease in this age group remains uncertain. AIMS: To evaluate treatment of small cell lung cancer in the elderly in Australia and to compare treatment received and outcomes with those of younger patients. To draw insights from these observations into the optimal management of small cell lung cancer in the elderly. METHODS: A retrospective review of treatment charts and case notes for 51 elderly patients and 102 younger patients was undertaken. RESULTS: Elderly patients had similar baseline parameters with respect to disease stage and performance status. Elderly patients were mostly treated uniformly with combination chemotherapy, but suffered more dose reductions than younger patients. Benefits of chemotherapy were seen even in patients with poor performance status. Despite the dose reductions, response rates and survival times for elderly patients were usually similar to younger patients. CONCLUSIONS: Combination chemotherapy is beneficial to elderly patients with small cell lung cancer. Optimal therapy for the elderly may be different from that for younger patients and should be defined through prospective randomised clinical trials.     

Brain protection for cerebral aneurysm surgery

The modern management of patients undergoing surgery for intracranial aneurysm often includes temporary periods of cerebral ischemia to minimize the risks final dissection and clipping or to allow vascular reconstruction. This article reviews the concepts of ischemic thresholds and examines the effects of the physiologic variables that may affect outcome from an ischemic episode. The protective agents presently available and the agents in development that may limit the extent of ischemic injury are reviewed extensively as well.     

An aggregation composition compensation method based on paired net

With regard to the failure and cancellation of business logic of web services composition(WSC),this paper propose a novel web services transaction compensation mechanism based on paired net which can dynamically establish agile compensation-triggered process(CSCP-Nets),and satisfy prospective compensation requirements.The related execution semantics of five usual composition compensation patterns based on paired net are analyzed in the situations of successful execution,failure compensation and failure recovery.Paired net based application of trip reservation process(TRP) shows that it is feasible.     

考虑机器故障的短生命周期产品库存模型

在考虑机器故障、返修费用和担保费用以及短生命周期产品库存成本随着时间呈非线关系的情况下建立短生命周期产品经济制造批量模型,并提供了寻求上述模型唯一最优解的简便方法.举数字实例进行了说明,计算实例验证了该方法的有效性.研究分析了机器故障率、返修费用和担保费用对最优生产批量和单位时间总成本的影响,同时比较了一般产品与短生命周期产品在生产策略上的一些区别,得到了一些有价值的结论.     

光纤布拉格光栅传感特性及实验研究

本文分析了光纤布拉格光栅传感温度和应变的基本原理及其灵敏度,构建了光纤布拉格光栅传感特性实验系统,介绍了光路系统的组成结构、原理及其相关器件特性,完成了温度和应变量的测量实验。实验结果表明,采用光纤布拉格光栅能够实现应变和温度的测量,从而证明了光纤布拉格光栅传感技术理论分析的正确性和实验系统设计的合理性。     

Optical coupling of GaAs photodetectors integrated with lithiumniobate waveguides

The optical coupling of GaAs photodetectors integrated with LiNbO ₃ waveguides using epitaxial liftoff is measured and compared to calculations based on a complex index model. The measured coupling is found to be comparable to that obtained in epitaxial semiconductor waveguide detectors, but it is lower than expected. Low coupling efficiency is attributed to the presence of a low index barrier layer, not present in semiconductor-based structures, at the GaAs-LiNbO₃ interface. A simple method of restoring the coupling to its original value without the need to eliminate the barrier layer is proposed     

Phase modulation characteristics of 1.5 mu m strained-layer multiple quantum well laser amplifiers

Phase modulation characteristics of strained-layer multiple quantum well laser amplifiers were measured to 4 GHz. A phase modulation efficiency of 2.6 degrees /mA was observed at 1 GHz, with a fibre-to-fibre gain of 7 dB and a residual AM modulation of 5%. The characteristics are independent of the input power up to -12 dBm.<>