巢湖富营养化对河蚬和环棱螺分布及种群密度影响

2001年9月和2002年9月两次对巢湖河蚬和环棱螺的调查表明,在富营养化程度较重的西湖区,河蚬生物量分别为17.87和47.29g.m-2;环棱螺生物量分别为45.45和12.56g.m-2.而在富营养化程度较轻的东湖区,河蚬的生物量分别为67.86和96.18g.m-2;环棱螺的生物量分别为32.00和31.21g.m-2.河蚬和环棱螺的种群密度和生物量均随水体富营养化的加剧而下降.近岸带河蚬和环棱螺的密度和生物量明显高于敞水区.河蚬的分布型为核心型,而环棱螺更接近随机性分布.河蚬和环棱螺的种群密度和

Growth and food availability of silver and bighead carps: evidence from stable isotope and gut content analysis

A 2-year investigation of growth and food availability of silver carp and bighead was carried out using stable isotope and gut content analysis in a large pen in Meiliang Bay of Lake Taihu, China. Both silver carp and bighead exhibited significantly higher delta 13C in 2005 than in 2004, which can probably be attributed to two factors: (i) the difference between isotopic compositions at the base of the pelagic food web and (ii) the difference between the compositions of prey items and stable isotopes. The significantly positive correlations between body length, body weight and stable isotope ratios indicated that isotopic changes in silver carp and bighead resulted from the accumulation of biomass concomitant with rapid growth. Because of the drastic decrease in zooplankton in the diet in 2005, silver carp and bighead grew faster in 2004 than in 2005. Bighead carp showed a lower trophic level than silver carp in 2005 as indicated by stable nitrogen isotope ratios, which was possibly explained by the interspecific difference between the prey species and the food quality of silver carp and bighead.

Photosynthetic physiology and growth as a function of colony size in the cyanobacterium Nostoc sphaeroides

Algal size can affect the rate of metabolism and of growth. Different sized colonies of Nostoc sphaeroides were used with the aim of determining the effects of colony size on photosynthetic physiology and growth. Small colonies showed higher maximum photosynthetic rates per unit chlorophyll, higher light saturation point, and higher photosynthetic efficiency (a) than large colonies. Furthermore, small colonies had a higher affinity for DIC and higher DIC-saturated photosynthetic rates. In addition, small colonies showed higher photosynthetic rates from 5-45degreesC than large colonies. There was a greater decrease in Fv/Fm after exposure to high irradiance and less recovery in darkness for large colonies than for small colonies. Relative growth rate decreased with increasing colony size. Small colonies had less chl a and mass per unit surface area. The results indicate that small colonies can harvest light and acquire DIC more efficiently and have higher maximum photosynthetic rates and growth rates than large colonies.

Antibunching and blinking from a single colloidal CdSe quantum dot

We have investigated the optical properties of single CdSe/ZnS nanocrystals by conducting combinations of experiments on antibunching and photoluminescence intermittence under different experimental conditions. Based on photoluminescence in an antibunching experiment, we analyzed the emission lifetime of QDs by using stretched exponentials. The difference between the parameters obtained from average lifetimes and stretched exponents were analyzed by considering the effect of nonradiative emission. An Auger-assisted tunneling model was used to explain the power law exponents of off time distribution. The power law exponent under high excitation power was correlated with a higher Auger ionization rate. Using the parameters obtained from stretched exponential function and power law, the antibunching phenomena at different time and under different excitation intensity were analyzed.

Directional emission InP/GaInAsP square-resonator microlasers

InP/GaInAsP square-resonator microlasers with an output waveguide connected to the midpoint of one side of the square are fabricated by standard photolithography and inductively-coupled-plasma etching technique. For a 20-mu m-side square microlaser with a 2-mu m-wide output waveguide, cw threshold current is 11 mA at room temperature, and the highest mode Q factor is 1.0 X 10(4) measured from the mode linewidth at the injection current of 10 mA. Multimode oscillation is observed with the lasing mode wavelength 1546 nm and the side-mode suppression ratio of 20 dB at the injection current of 15 mA. (C) 2008 Optical Society of America

Growth and characterization of GaInNAs by molecular beam epitaxy using a nitrogen irradiation method

We propose an innovative technique, making use of the In segregation effect, referred as the N irradiation method, to enhance In-N bonding and extend the emission wavelength of GaInNAs quantum wells (QWs). After the formation of a complete In floating layer, the growth is interrupted and N irradiation is initiated. The majority of N atoms are forced to bond with In atoms and their incorporation is regulated independently by the N exposure time and the As pressure. The effect of the N exposure time and As pressure on the N incorporation and the optical quality of GaInNAs QWs were investigated. Anomalous photoluminescence (PL) wavelength red shifts after rapid thermal annealing (RTA) were observed in the N-irradiated samples, whereas a normal GaInNAs sample revealed a blue shift. This method provides an alternative way to extend the emission wavelength of GaInNAs QWs with decent optical quality. We demonstrate light emission at 1546 nm from an 11-nm-thick QW, using this method and the PL intensity is similar to that of a 7-nm-thick GaInNAs QW grown at a reduced rate. (C) 2008 Elsevier B.V. All rights reserved.

Structural and optical properties of self-assembled InAs quantum dots grown on GaAs (311) A substrate

We report the structural and optical characteristics of InAs quantum dots (QDs) grown on GaAs (311)A substrates. Atomic force microscopic result shows that QDs on (311)A surface exhibit a nonconventional, faceted, arrowhead-like shapes aligned in the [233] direction. The photoluminescence (PL) intensity, peak position and the full width at half maxinum (FWHM) are all closely related to the measurement temperature. The fast redshift of PL energy and monotonous decrease of linewidth with increasing temperature were observed and explained by carriers being thermally activated to the barrier produced by the wetting layer and then being retrapped and recombined in energetically lower-lying QDs states. This model explains our results well.

基于组件属性的远程证明

提出了一个组件级的细粒度属性证明方案,用于向远程依赖方证明用户平台满足某种安全属性.与现有的远程证明方案相比,组件属性远程证明具有一定的语义和属性表述性等优势.该方案不但证明粒度细和扩展性强,而且属性证书的颁发、验证和撤销实现简单;本方案以组件承诺的方法保证属性证明的真实性,采用零知识证明实现平台组件的隐私性.基于强RSA假设,在Random Oracle模型下可被证明是安全的.实现的原型系统实验结果表明,组件属性证明是一种灵活、实用、高效的证明,对系统性能没有影响.

基于MDA的TRISO-Model模型管理方法及应用

TRISO-Model(tridimensional integrated software development model)是为处理软件开发的复杂性和动态性而提出的三维集成软件开发方法学,其中,多维模型之间的语义一致性维护以及对模型应用中公共操作部分的重用,提出了基于一致语义进行模型管理的需求.给出了基于MDA(model driven architecture)进行模型管理的方法MDA-MMMethod(MDA based model management method),应用MDA的4层模型管理结构,基于MDA核心标准MOF(meta object facility)所提供的公共语义基础管理模型和元模型,MDA-MMMethod支持各种MDA模型操作标准实现在TRSIO-model应用中的重用.开发了相应的支持系统MDA-MMSystem(MDA based model management system),应用于SoftPM的项目实践中.与传统方法相比,模型应用的开发效率得到了显著提高,同时降低了开发成本.最后,给出了模型融合的应用实例介绍.

基于本体的发布/订阅系统的数据模型和匹配算法

现有的发布／订阅系统不能根据事件的语义来进行事件与订阅的匹配，且不能支持具有复杂结构（如图状结构）的事件．将语义Web技术引入发布／订阅系统中，提出一种基于本体的发布／订阅系统．该系统采用本体来表示事件的概念模型，采用RDF图来表示事件，采用图模式来表示订阅条件．它能较好地解决现有的发布／订阅系统的上述问题．实验结果表明，该系统具有较高的订阅匹配效率．

超声波对HCFC-141b水合物形成过程的影响研究

针对水合物形成过程中存在成核诱导期长、过冷度大，形成速度慢的问题，本文以HCFC-141b（1，1-dichloro-1-flooroethane）作为研究工质，将超声波引入水合物形成过程中，研究超声波对水合物形成的影响。建立了包括超声波水合反应系统、数据采集和图像采集系统的可视化低温实验系统。利用这套实验系统，分别实验研究了频率为20kHz和15kHz，功率为0-1000w的超声波对HCFC-141b水合物的形成影响。实验结果表明，超声波对水合物的形成有明显的影响。水合物形成过程主要分为三阶段：冷却期、

玉米根系吸水能力细胞水平的杂种优势

在人工气候室水培条件下,以玉米(ZeamaysL.)杂交种F1代户单4号及其母本天四和父本478为材料,用细胞压力探针技术研究了正常供水和PEG-6000模拟–0.2MPa水分胁迫条件下,玉米根皮层细胞水分关系参数的基因型差异。结果表明,根皮层细胞的直径、长度和体积均为F1代>母本>父本;正常供水条件下3个玉米品种的根皮层细胞膨压均在0.6MPa左右且品种间差异不显著,水分胁迫抑制了细胞的延伸生长且F1代和母本的细胞膨压显著高于父本;根皮层细胞壁体积弹性模量均为父本>母本>F1代,水分胁迫条件下的品种间差异显著;与正常供水条件相比,水分胁迫条件下细胞膨压显著降低,而弹性模量则大幅度提高;在两种水分条件下,水分跨细胞膜运转的半时间均为父本>母本>F1代,且半时间在水分胁迫条件下均显著高于正常供水条件下;HgCl2处理引起了半时间的延长,2-巯基乙醇则部分逆转了HgCl2的效应;在两种水分条件下,根皮层细胞水导均为F1代>母本>父本且品种间差异显著,水分胁迫则显著降低了细胞水导。试验证明杂交种F1代的细胞水平根系吸水能力优于亲本,体现了杂种优势。