Spawning areas and early development of long spiky-head carp (Luciobrama macrocephalus) in the Yangtze River and Pearl River, China

The spawning areas and early development of long spiky-head carp, Luciobrama macrocephalus (Lacepede), an endemic fish species in China, were investigated in the Yangtze River and Pearl River of central and southeastern China between 1961 and 1993. The potamodromous fish migrated upstream to spawn between May and July as the floodwater began to rise. The water-hardened eggs drifted down the river, and the embryos and larvae developed in the course of drifting. The spawning areas of the fish were widely found in the upper and middle main channels and large tributaries. Two large dams (Gezhouba dam and Danjiangkou dam) did not significantly impact on the reproduction of the fish. Fifty stages of the early development from one cell to the juvenile with fully formed fins were observed and characterized pictorially. The larvae of long spiky-head carp could be distinguished from the larvae of other co-occurring species by counting the number of somites and comparing the proportion of sizes of eye to otic capsule.

MOCVD growth of InN using a GaN buffer

We have investigated MOCVD growth of InN oil sapphire with and without a GaN buffer between 490 and 520 degrees C. The buffer significantly improves the surface morphological uniformity and electrical properties of InN epilayers. Characterization of the as-grown epilayers with the buffer reveals that kinetics-limited islands are formed at lower temperatures, whereas islands with equilibrium shape are obtained at higher temperatures. Below 520 degrees C, increasing temperature improves structural quality but degrades electrical properties. Hall data from this study Suggest that V-N-related defects/impurities are the possible donor species and compensation varies with charged dislocation acceptors. We believe that reducing carrier concentration and dislocation density is effective to increase the Hall mobility of InN. (C) 2007 Elsevier Ltd. All rights reserved.

1.58 mu m InGaAs quantum well laser on GaAs

We demonstrate the 1.58 mu m emission at room temperature from a metamorphic In0.6Ga0.4As quantum well laser grown on GaAs by molecular beam epitaxy. The large lattice mismatch was accommodated through growth of a linearly graded buffer layer to create a high quality virtual In0.32Ga0.68As substrate. Careful growth optimization ensured good optical and structural qualities. For a 1250x50 mu m(2) broad area laser, a minimum threshold current density of 490 A/cm(2) was achieved under pulsed operation. This result indicates that metamorphic InGaAs quantum wells can be an alternative approach for 1.55 mu m GaAs-based lasers. (C) 2007 American Institute of Physics.

A Fully Integrated 900-MHz Passive RFID Transponder Front End With Novel Zero-Threshold RF-DC Rectifier

This paper presents a fully integrated CMOS analog front end for a passive 900-MHz radio-frequency identification (RFID) transponder. The power supply in this front end is generated from the received RF electromagnetic energy by using an RF-dc voltage rectifier. In order to improve the compatibility with standard CMOS technology, Schottky diodes in conventional RF-dc rectifiers are replaced by diode-connected MOS transistors with zero threshold. Meanwhile, theoretical analyses for the proposed rectifier are provided and verified by both simulation and measurement results. The design considerations of the pulsewidth-modulation (PWM) demodulator and the backscatter modulator in the front end are also discussed for low-power applications. The proposed front end is implemented in a 0.35-mu m 2P4M CMOS technology. The whole chip occupies a die area of 490 x 780 mu m(2) and consumes only 2.1 mu W in reading mode under a self-generated 1.5-V supply voltage. The measurement results show that the proposed rectifier can properly operate with a - 14.7-dBm input RF power at a power conversion efficiency of 13.0%. In the proposed RFID applications, this sensitivity corresponds to 10.88-m communication distance at 4-W equivalent isotropically radiated power from a reader base station.

Growth of heavily Zn-doped InGaAs at low temperature by LP-MOCVD

Epitaxial growth of Zn-doped InGaAs on InP substrates has been carried out at 550degreesC by LP-MOCVD. Hole concentration as high as 6 x 10(19)cm(-3) has been achieved at the H-2 flow rate of 20 sccm through DEZn bubbler. The lattice constant of Zn-doped InGaAs was found to be dependent on the flow rate of DEZn, and the tensile strain mismatch increases with increasing H-2 flow rate of DEZn. The negative lattice mismatch of heavily Zn-dopped InGaAs may be due to, the small covalent bonding radius of zinc and the combination of butane from ethyl of DEZn,and TEGa. And the latter accelerates the pyrolysis of TEGa, which is the dominant mechanism in determining the negative mismatch of Zn-doped InGaAs. (C) 2003 Elsevier B.V. All rights reserved.

Self-organized superlattices along the [001] growth direction in In0.52Al0.48As layers grown on nominally (001) InP substrates by molecular beam epitaxy

Horizontal self-organized superlattice structures consisting of alternating In-rich and Al-rich layers formed naturally during solid-source molecular beam epitaxy (MBE) growth of In0.52Al0.48As on exactly (001) InP substrates, with In and At fluxes unchanged. The growth temperatures were changed from 490 to 510 degrees C, the most commonly used growth temperature for In0.52Al0.48As alloy. No self-organized superlattices (SLs) were observed at the growth temperature 490 degrees C, and self-organized SLs were observed in InAlAs layers at growth temperatures ranging from 498 to 510 degrees C. The results show that the period of the SLs is very highly regular, with the value of similar to 6 nm, and the composition of In or Al varies approximately sinusoidally along the [001] growth direction. The theoretical simulation results confirm that the In composition modulation amplitude is less than 0.02 relative the In composition of the In0.52Al0.48As lattice matched with the InP substrate. The influence of InAs self-organized quantum wires on the spontaneously formed InxAl1-xAs/InyAl1-yAs SLs was also studied and the formation of self-organized InxAl1-xAs/InyAl1-yAs SLs was attributed to the strain-mediated surface segregation process during MBE growth of In0.52Al0.48As alloy. (C) 2005 Published by Elsevier Ltd.

The growth and characterization of GaN grown on an Al2O3 coated (001)Si substrate by metalorganic vapor phase epitaxy

Single crystal GaN films have been grown on to an Al2O3 coated (001)Si substrate in a horizontal-type low-pressure MOVPE system. A thin Al2O3 layer is an intermediate layer for the growth of single crystal GaN on to Si although it is only an oriented polycrystal him as shown by reflection high electron diffraction. Moreover, the oxide was not yet converted to a fully single crystal film, even at the stage of high temperature for the GaN overlayer as studied by transmission electron microscopy. Double crystal X-ray diffraction showed that the linewidth of (0002) peak of the X-ray rocking curve of the 1.3 mu m sample was 54 arcmin and the films had heavy mosaic structures. A near band edge peaking at 3.4 eV at room temperature was observed by photoluminescence spectroscopy. (C) 1998 Elsevier Science B.V. All rights reserved.

An Improved Selective Area Growth Method in Fabrication of Electroabsorption Modulated Laser

An improved selective area growth (SAG) method is proposed to better the fabrication and performance of the Electroabsorption modulated laser The typical threshold current of the EML is 18mA, and the output power is 5.6mW at EAM facet.

The difference of Si doping efficiency in GaN and AlGaN in GaN-based HBT structure

An AlGaN/GaN HBT structure was grown by low-pressure metalorganic chemical vapor deposition (MOCVD) on sapphire substrate. From the high-resolution x-ray diffraction and transmission electron microscopy (TEM) measurements, it was indicated that the structure is of good quality and the AlGaN/GaN interfaces are abrupt and smooth. In order to obtain the values of Si doping and electronic concentrations in the AlGaN emitter and GaN emitter cap layers, Secondary Ion Mass Spectroscopy (SIMS) and electrochemical CV measurements were carried out. The results showed that though the flow rate of silane (SiH4) in growing the AlGaN emitter was about a quarter of that in growing GaN emitter cap and subcollector layer, the Si sputtering yield in GaN cap layer was much smaller than that in the AlGaN emitter layer. The electronic concentration in GaN was about half of that in the AlGaN emitter layer. It is proposed that the Si, Al co-doping in growing the AlGaN emitter layer greatly enhances the Si dopant efficiency in the AlGaN alloy. (c) 2006 WILEY-VCH Verlag GmbH & Co KGaA, Weinheim.

基于ActiveX Scripting技术的测试软件开发

测试软件(Tester)的开发不同于一般的软件开发,在测试软件开发的过程中,涉及到测试软件本身和测试用例(Testcase)两者之间的划分和协作.目前的测试用例脚本大都是一些自定义的格式文本,通过测试软件的分析来执行测试逻辑,不仅需要编写大量复杂的脚本解析程序,而且难以阅读和维护.为了解决这个问题,提出了一种基于ActiveX Scripting技术的测试软件开发方法,该方法可以将测试逻辑按照需求分配到测试软件和测试用例,提供了一种统一的编程接口,易于学习和使用.

宁夏南部山区秸秆覆盖对春玉米水分利用及产量的影响

为研究秸秆覆盖在宁南山区对春玉米生长及其土壤水分的影响,在宁夏彭阳县对三种不同秸秆覆盖处理方式进行了试验研究。对比分析了不同覆盖措施下春玉米的生长状况、产量及水分利用效率变化的关系。结果表明:采用秸秆覆盖方式可使春玉米的株高、穗位高、穗长、生物产量及经济产量等指标得到显著提高,土壤的蓄水保墒性能增强,水分利用效率提高,增产增效明显;与传统方式相比,整秸秆覆盖可使春玉米的产量及水分利用效率分别提高3.5%及16.5%。

东亚人群 LMBR1 基因 Intron 5的遗传多样性研究

人LMBR1(Limb region 1 homolog (mouse)) 基因位于染色体7q36区域，全长约210.2 kb，含17个外显子，编码一个由490个氨基酸构成的跨膜蛋白。研究表明，LMBR1 基因的表达活性与脊椎动物四肢的手指或脚趾数目变化有关；另外，发生在其重要元件——intron 5 内的许多变异与多种表型的轴前多指症((PPD, Preaxial polydactyly)存在相关性，这主要是因为LMBR1 intron 5 内含有一个与骨骼系统发育有关的基因（SHH(Sonic hedgehog)基因）的远程顺式调控元件。本研究旨在探究LMBR1基因 intron 5 内的遗传多样性，进而评估HapMap计划的样本选择策略，并检测该区域是否受自然选择的作用。 国际人类基因组单体型图计划(HapMap Project，The International Haplotype Map Project) 于2002年10月正式启动，该计划旨在构建人类基因组中常见变异的遗传图式。自其数据发布以来，广泛应用于生物医学、群体遗传学等领域，在复杂疾病的遗传机理研究、自然选择的检测等方面做出了前所未有的贡献；但是HapMap计划中样本的代表性有待评估。 本研究中，我们综合考虑地理来源信息及线粒体单倍型类群 (Haplogroup)信息选择了41个东亚人作为样本（以保证样本的代表性），测定位于LMBR1 基因intron 5 内的目的片段中存在的单核苷酸多态性(SNP, Singe nucleotide polymorphism)位点，通过所得数据与HapMap数据的比较，发现二者之间差异显著且HapMap数据不能覆盖所有我们得到的常见变异，因而我们认为：HapMap计划中国部分的样本选择策略有待进一步完善。 关于自然选择的研究不仅可以使我们了解生物的进化机制，同时还对复杂疾病的遗传机理研究具有重要的提示作用，因而，对于自然选择的检测，一直以来都是生物学研究的重点。平衡选择是一种维持遗传多态性的自然选择方式，现已发现很多与特定疾病或性状相关的基因或调控序列受平衡选择的作用，如 G6PD 基因、PTC 基因、FMO3 基因、FSHB 基因及 CCR5 基因5’端顺式调控区等我们对41个东亚样本中LMBR1 intron 5 内一段长为9256 bp (Chr7: 156280954-156271699 (Build36))的序列进行以 Tajima’s D 检验为主的群体遗传学分析，发现该区域在进化历程中受到平衡选择的作用。LMBR1 intron 5 内的多态位点与多种表型的多指症存在相关性，受其调控的 SHH 基因在骨骼系统发育中具有重要作用，人类骨骼系统的适应性进化等三方面的因素为该区域受平衡选择的作用提供了进一步的佐证。 总之，本研究对HapMap计划的样本选择策略和数据应用提供了一定的参考；同时还发现一个与骨骼系统发育有关的基因调控元件受平衡选择的作用。