Detecting lineage-specific adaptive evolution of brain-expressed genes in human using rhesus macaque as outgroup

Comparative genetic analysis between human and chimpanzee may detect genetic divergences responsible for human-specific characteristics. Previous studies have identified a series of genes that potentially underwent Darwinian positive selection during huma

Principles of sensorimotor learning.

The exploits of Martina Navratilova and Roger Federer represent the pinnacle of motor learning. However, when considering the range and complexity of the processes that are involved in motor learning, even the mere mortals among us exhibit abilities that are impressive. We exercise these abilities when taking up new activities - whether it is snowboarding or ballroom dancing - but also engage in substantial motor learning on a daily basis as we adapt to changes in our environment, manipulate new objects and refine existing skills. Here we review recent research in human motor learning with an emphasis on the computational mechanisms that are involved.

微囊藻毒素LR诱导无DNA片断化的细胞凋亡

目的研究微囊藻毒素(microcystin,MC)损伤肝细胞的毒性机制。方法以不同浓度的微囊藻毒素LR(MCLR)处理L-02肝细胞,通过光镜和电镜下的形态观察、DNA片断化分析、线粒体膜电位变化等了解MCLR对肝细胞的毒性效应。结果光镜下观察表明,50!g/mlMCLR处理可使细胞变圆、萎缩、不贴壁生长,电镜下L-02细胞呈现皱缩、膜发泡及染色质凝聚并边缘化等变化,这是典型的细胞凋亡形态特征,但电镜下没有观察到凋亡小体的形成;DNA电泳表明凋亡细胞没有出现明显的DNAladder,与电镜观察的结果一致。

Monitoring organochlorine pesticides and polychlorinated biphenyls in Baiyangdian Lake using microbial communities

We used polyurethane foam units (PFUs) to collect persistent organic pollutants (POPs) from four sites in Baiyangdian Lake in July 2003. Following extraction from the PFUs, relative concentrations of seven organochlorine pesticides (OCPs) and ten polychlorinated biphenyls (PCBs) were determined by gas chromatography. OCPs and PCBs were detected in the microbial communities from all the four sampling stations. In terms of the total concentration of POPs (OCPs+ PCBs), two river estuary stations had more POP (18.45 mu g/L and 9.77 mu g/L) than the two mid-lake stations (4.75 mu g/L and 5.21 mu g/L), indicating that Baiyangdian Lake was significantly impacted by inflow from the Fu River and Baigou River.

Fabrication of ultra-low density and long-wavelength emission InAs quantum dots

By optimizing the molecular beam epitaxy growth conditions of self-organized InAs/GaAs quantum dots (QDs), we obtained an ultra-low density system of InAs QDs (4 x 10(6)cm(-2)). Photoluminescence (PL) spectroscopy reveals the emission wavelength at room temperature to be longer than 1300 nm with a GaAs capping layer. (c) 2007 Elsevier B.V. All rights reserved.

The keys to get high transconductance of AlGaAs/InGaAs/GaAs pseudomorphic HEMTs devices

There are two key points to get high transconductance of pseudomorphic HEMTS (pHEMTs) devices. From the point view of materials, the transfer efficiency of the electrons from the delta -doped AlGaAs layer to the InGaAs channel must be high. From the point view of device processing, the gate recess depth must be carefully controlled. In the present work, AlGaAs/InGaAs/GaAs pHEMTs structures were grown by molecular beam epitaxy. Layer structures of the pHEMTs were optimized to get high transfer efficiency of the electrons. Gate recess depth was also optimized. A 0.2 mum pHEMT was fabricated on the materials with optimized layer structure using the optimized gate recess depth. The maximum transconductance of 650 mS/mm and the cut-off frequency of 81 GHz were achieved. (C) 2001 published by Elsevier Science Ltd.

InP-based optoelectronic devices for optical fiber communications

In this contribution we report the research and development of 1.55 mu m InGaAsP/InP gain-coupled DFB laser with an improved injection-carrier induced grating and of high performance 1.3 mu m and 1.55 mu m InGaAsP/InP FP and DFB lasers for communications. Long wavelength strained MQW laser diodes with a very low threshold current (7-10 mA) have been fabricated. Low pressure MOVPE technology has been employed for the preparation of the layered structure. A novel gain-coupled DFB laser structure with an improved injection-carrier modulated grating has been proposed and fabricated. The laser structures have been prepared by hybrid growth of MOVPE and LPE techniques and reasonably good characteristics have been achieved for resultant lasers. High performance 1.3 mu m and 1.55 mu m InGaAsP/InP DFB lasers have successfully been developed for CATV and trunk line optical fiber communication.

垂直腔面发射激光器的TO封装的耦合效率模拟分析

采用FRESNEL光学软件和MATLAB软件，详细分析了垂直腔面发射激光器的TO封装组件对耦合效率的影响．发现增加耦合透镜的折射率、减少管帽的高度和耦合透镜的尺寸可以提高耦合效率。