香溪河小水电的梯级开发对浮游藻类的影响

以香溪河干流上5个连续的小水电站为对象,于2005年10月20—22日分别对其浮游藻类和主要理化指标进行研究.结果表明:硅藻占绝对优势(95.54%),其中,线性曲壳藻(Achnanthes linearis)、披针曲壳藻椭圆变种(A.lanceolatavar.elliptica)、扁圆卵形藻(Cocconeisplacentula)为绝对优势种,其平均相对丰富度分别为23.96%、18.62%和12.48%;所有样点的平均藻类密度为6.29×105ind.L-1,最高为1.81×106ind.L-1,

Simultaneous determination of microcystin-LR and its glutathione conjugate in fish tissues by liquid chromatography-tandem mass spectrometry

A sensitive and selective liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous quantitative determination of microcystin-LR (MC-LR) and its glutathione conjugate (MC-LR-GSH) in fish tissues. The analytes were extracted from fish liver and kidney using 0.01 M EDTA-Na-2-5% acetic acid, followed by a solid-phase extraction (SPE) on Oasis HLB and silica cartridges. High-performance liquid chromatography (HPLC) with electrospray ionization mass spectrometry, operating in selected reaction monitoring (SRM) mode, was used to quantify MC-LR and its glutathione conjugate in fish liver and kidney. Recoveries of analytes were assessed at three concentrations (0.2, 1.0, and 5 mu g g(-1) dry weight [DW]) and ranged from 91 to 103% for MC-LR, and from 65.0 to 75.7% for MC-LR-GSH. The assay was linear within the range from 0.02 to 5.0 mu g g(-1) DW, with a limit of quantification (LOQ) of 0.02 mu g g(-1) DW. The limit of detection (LOD) of the method was 0.007 mu g g(-1) DW in both fish liver and kidney. The overall precision was determined on three different days. The values for within- and between-day precision in liver and kidney were within 15%. This method was applied to the identification and quantification of MC-LR and its glutathione conjugate in liver and kidney of fish with acute exposure of MC-LR. (c) 2007 Elsevier B.V. All rights reserved.

1.3 mu m gain coupled DFB laser with InGaAlAs MQW grown on absorptive InGaAsP corrugation

An InGaA1As multiquantum well (MQW) has been successfully overgrown on the absorptive InGaAsP corrugation for fabricating the 1.3 mu m gain coupled distributed feedback (DFB) lasers. The absorptive InGaAsP corrugation was efficaciously preserved during the overgrowth of the InGaA1As MQW active region. The absorptive InGaAsP corrugation has a relatively high intensity around the PL peak wavelength in comparison with that of the InGaA1As MQW. The fabricated DFB laser exhibited a side mode suppression ratio of 40 dB together with a high single-mode yield of 90%.

黄土丘陵区土壤基础呼吸对草地植被恢复的响应及其影响因素

为探讨黄土丘陵区草地植被自然恢复过程中土壤微生物活性的变化特征及其影响因素,采用"时空互代"法采集宁夏云雾山自然保护区8个不同植被恢复年限的春、夏两季0～20cm和20～40cm的土样,用室内密闭静态培养—碱液吸收法测定了新鲜和风干土样的基础呼吸。结果表明:土壤基础呼吸随植被恢复年限增加呈增加趋势,土壤呼吸强度和累积呼吸量都表现为植被恢复73年和78年较高,而耕地和植被恢复3年最低。采样季节对呼吸强度测定有较大影响,春季土样能更好地反映土壤微生物活性的变化。风干土样可以通过预培养后测定土壤的呼吸作用,且能更加稳定地反映不同土壤之间的差异。在测定土壤基础呼吸时,利用1d或3d的培养平均值能更稳定地表现不同土壤的特性。累积呼吸量可较呼吸强度更直观地反映不同土壤的微生物活性。土壤有机质和全氮含量与土壤呼吸强度密切相关。

原状土通气培养法测定黄土高原土壤供氮能力的研究

评价原状土通气培养法在反映黄土高原土壤供氮能力方面的效果。【方法】以采自于黄土高原差异较大的11个农田耕层土壤为供试土样,以包括和不包括土壤起始NO3--N原状土盆栽黑麦草累积吸氮量为参比,进行室内原状土通气培养法测定土壤供氮能力的研究。【结果】以包括土壤起始NO3--N盆栽试验植物吸氮量为参比,通气培养前CaCl2所淋洗起始NO3--N和起始矿质氮与5期黑麦草地上部氮素累积量密切相关,相关系数分别为0.856和0.862,达1%显著水平;与此相反,通气培养30周所矿化氮素、土壤起始矿质氮+通气培养30周矿化氮素、氮素矿化势(N0)及N0+起始矿质氮与5期黑麦草地上部氮素累积量间无显著相关关系,相关系数分别仅为0.410、0.553、0.492和0.419。以不包括土壤起始NO3--N盆栽试验植物吸氮量为参比,通气培养前CaCl2淋洗起始NO3--N和起始矿质氮与五期黑麦草地上部氮素累积量间的相关性尽管有所降低,但相关性仍达5%显著水平,相关系数分别为0.613和0.607;而通气培养30周矿化氮素、土壤起始矿质氮+通气培养30周矿化氮素、N0及N0+起始矿质氮与五期黑麦草地上部吸氮量的相关系数却明显...

聚光光伏系统

随着传统化石类能源的枯竭和环境污染的日益严重,太阳能光伏发电技术倍受瞩目,但较高的发电成本及原材料的缺乏制约了其大规模发展.以高转换效率、低芯片消耗为核心的聚光光伏技术,在降低光伏发电成本方面被人们寄予厚望.文章主要介绍了聚光光伏系统发展的历史和现状,工作原理及存在的关键问题,并对其发展前景进行了展望.

Sensitivity of Total-Dose Radiation Hardness of SIMOX Buried Oxides to Doses of Nitrogen Implantation into Buried Oxides

In order to improve the total-dose radiation hardness of the buried oxides(BOX) in the structure of separa tion-by-implanted-oxygen(SIMOX) silicon-on-insulator(SOI), nitrogen ions are implanted into the buried oxides with two different doses,2 × 1015 and 3 × 1015 cm-2 , respectively. The experimental results show that the radiation hardness of the buried oxides is very sensitive to the doses of nitrogen implantation for a lower dose of irradiation with a Co-60 source. Despite the small difference between the doses of nitrogen implantation, the nitrogen-implanted 2 × 1015 cm-2 BOX has a much higher hardness than the control sample (i. e. the buried oxide without receiving nitrogen implantation) for a total-dose irradiation of 5 × 104rad(Si), whereas the nitrogen-implanted 3 × 1015 cm-2 BOX has a lower hardness than the control sample. However,this sensitivity of radiation hardness to the doses of nitrogen implantation reduces with the increasing total-dose of irradiation (from 5 × 104 to 5 × 105 rad (Si)). The radiation hardness of BOX is characterized by MOS high-frequency (HF) capacitance-voltage (C-V) technique after the top silicon layers are removed. In addition, the abnormal HF C-V curve of the metal-silicon-BOX-silicon(MSOS) structure is observed and explained.

SiON对Si基SiO_2 AWG偏振补偿的数值分析

采用全矢量交替方向隐含迭代方法系统分析了高折射率SiON薄膜对Si基SiO2阵列波导光栅中波导应力双折射的影响.分析结果表明在芯区上或下表面沉积SiON薄膜可以明显减小Si基SiO2阵列波导光栅(AWG)中波导的应力双折射,但这两种补偿方法容易使模场偏移中心位置,不利于波导与光纤的耦合.理想的补偿方法是在芯区上下同时补偿,可减小模场偏移,并用该方法设计了偏振无关的16通道AWG.

斩波式自适应移相干涉技术

研究对环境振动和空气扰动所造成的两相干光束间常数项光程变化不敏感的自适应移相干涉系统。利用偏振分光技术，采用闭环控制，并将高频振幅调制与锁相技术相结合，建立一斩波式自适应移相干涉系统，可对环境振动引起的干涉条纹的抖动进行实时探测并予以光程补偿，将干涉条纹依次锁定在与任意相位差相对应的位置。该方法不受两相干光束间光程差大小的限制且具有高信噪比。阐述了该方法的原理，描述了所建立的系统，并给出了实验结果。

用固相外延方法制备Si_(1-x-y)Ge_xC_y三元材料

分析了Si_(1-x-y)Ge_xC_y三元系材料外延生长的特点，指出原子性质上的巨大差异使Si_(1-x-y)G_xC_y材料的制备比较困难。固相外延生长是制备Si_(1-x-y)Ge_xC_y的有效方法，但必须对制备过程各环节的条件进行优化选择。通过实验系统地研究了离子注入过程中温度条件的控制对外延层质量的影响以及外延退火条件的造反与外延层结晶质量的关系。指出在液氮温度下进行离子注入能够提高晶体质量，而注入过程中靶温过高会导致动态退火效应，影响以后的再结晶过程。采用两步退火方法有利于消除注入引入的点缺陷，而二次外延退火存在着一个最佳退火温区，在此基础上优化得出了固相外延方法制备Si_(1-x-y)Ge_xC_y/Si材料的最佳条件。