清水江的鱼类区系及生态类型

为了系统研究清水江的鱼类区系和生态类型,在2002—2004年对清水江进行了鱼类标本的采集和生态学调查。共采集鱼类标本2500余号,经鉴定为71种(亚种)。其中中华花鳅、拟尖头鲌、长身鳜和长吻鮠等52种(亚种)鱼类为清水江鱼类新记录,而红尾副鳅、长薄鳅、海南拟、福建纹胸鮡和长须黄颡鱼则首次被发现分布于沅江水系。结合文献记录与调查表明:清水江共有鱼类4目13科57属86种(亚种),其中仅胡子鲇为外来种;清水江鱼类区系具有土著鱼类占优势、特有种类和易(濒)危种类较多、区系组成较复杂和与珠江水系之间存在着鱼类

Detection of the hepatotoxic microcystins in 36 kinds of cyanobacteria Spirulina food products in China

Gel filtration chromatography, ultra-filtration, and solid-phase extraction silica gel clean-up were evaluated for their ability to remove microcystins selectively from extracts of cyanobacteria Spirulina samples after using the reversed-phase octadecylsilyl ODS cartridge for subsequent analysis by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The reversed-phase ODS cartridge/silica gel combination were effective and the optimal wash and elution conditions were: H2O (wash), 20% methanol in water (wash), and 90% methanol in water (elution) for the reversed-phase ODS cartridge, followed by 80% methanol in water elution in the silica gel cartridge. The presence of microcystins in 36 kinds of cyanobacteria Spirulina health food samples obtained from various retail outlets in China were detected by LC-MS/MS, and 34 samples (94%) contained microcystins ranging from 2 to 163 ng g(-1) (mean=1427 ng g(-1)), which were significantly lower than microcystins present in blue green alga products previously reported. MC-RR-which contains two molecules of arginine (R)-(in 94.4% samples) was the predominant microcystin, followed by MC-LR-where L is leucine-(30.6%) and MC-YR-where Y is tyrose-(27.8%). The possible potential health risks from chronic exposure to microcystins from contaminated cyanobacteria Spirulina health food should not be ignored, even if the toxin concentrations were low. The method presented herein is proposed to detect microcystins present in commercial cyanobacteria Spirulina samples.

Nitrite utilization by Chaetoceros muelleri under elevated CO2 concentration

Chaetoceros muelleri (Lemn.) was cultured with nitrite (NO2-) or nitrate (NO3-) as the sole nitrogen source and aerated with air or with CO2-enriched air. Cells of C. muelleri excreted into the medium nitrite produced by reduction of nitrate when grown with 100 mu M NaNO3 as nitrogen source. Accordingly, NO2- concentration reached 10.4 mu M after 95 h at the low CO2 condition (aerated with air); while the maximum NO2- concentration was only around 2.0 mu M at the high CO2 condition (aerated with 5% CO2 in air), furthermore, after 30 h it decreased to no more than 1.0 mu M. NO2- was almost assimilated in 80 h when C. muelleri was cultured at the high CO2 condition with 100 mu M NaNO2 as sole nitrogen source. At the high CO2 condition, after 3 h the activity of nitrite reductase was as much as 50% higher than that at the low CO2 condition. It was indicated that enriched CO2 concentration could inhibit nitrite excretion and enhance nitrite assimilation by cells. Therefore, aeration with enriched CO2 might be an effective way to control nitrite content in aquaculture systems.

Cancer subtypes recognition and its gene expression profiles analysis based on geometrical learning

The accurate recognition of cancer subtypes is very significant in clinic. Especially, the DNA microarray gene expression technology is applied to diagnosing and recognizing cancer types. This paper proposed a method of that recognized cancer subtypes based on geometrical learning. Firstly, the cancer genes expression profiles data was pretreated and selected feature genes by conventional method; then the expression data of feature genes in the training samples was construed each convex hull in the high-dimensional space using training algorithm of geometrical learning, while the independent test set was tested by the recognition algorithm of geometrical learning. The method was applied to the human acute leukemia gene expression data. The accuracy rate reached to 100%. The experiments have proved its efficiency and feasibility.

基于约束的主动规则终止性分析

终止性是主动规则所需的最重要的一个性质,但规则的终止性检查通常是不可判定的.已有的静态分析方法非常保守,SQL3标准也没有提供保证终止的机制,所以商业数据库限制规则级联触发的最大次数确保终止.由于规则可看成数据库状态转换器,而约束能够表示所有可能的数据库状态,基于约束表示的数据库状态及约束求解,模拟规则处理,可得到更精确的终止性结论.

模拟降雨下初始含水量对砂黄土硝态氮迁移特征的影响

利用室内人工模拟降雨,研究了不同初始含水量砂黄土在降雨条件下入渗-径流、土壤侵蚀,以及NO3--N随径流流失和土壤深层淋溶特征。结果表明,初始含水量对产流时刻的影响在相对含水量为49.4%和76.9%之间存在一个转折点,高初始含水量较低含水量产流提前大约15 min;土壤侵蚀量随着土壤初始含水量的增加而增加,相对含水量为97.1%时,侵蚀泥沙量分别是相对含水量22.9%时的2.8倍,49.4%时的2.3倍,76.9%时的1.5倍。初始含水量高的处理径流初始NO3--N浓度高,随后各处理均衰减很快,10 min左右NO3--N含量趋于雨水本底值;土壤初始含水量越低,NO3--N被淋洗的程度越严重,土壤剖面中NO3--N的浓度峰越深。对于黄土高原坡地砂黄土NO3--N迁移特征来看,按照NO3--N迁移数量,随径流和泥沙流失量比向土壤深层迁移的数量小。说明在降雨条件下,NO3--N主要通过土壤深层淋溶损失,且土壤初始含水量越低其损失越严重。针对黄土高原降水量小、分布集中的特点,采取措施增加入渗,蓄积水分,在一定含水量下施肥,以提高氮肥利用率,降低NO3--N的淋溶。

An Integratable Distributed Bragg Reflector Laser by Low-Energy Ion Implantation Induced Quantum Well Intermixing

An integratable distributed Bragg reflector laser is fabricated by low-energy ion implantation induced quantum well intermixing. A 4.6nm quasi-continuous wavelength tuning range is achieved by controlling phase current and grating current simultaneously,and side mode suppression ratio maintains over 30dB throughout the tuning range except a few mode jump points.

在旋转磁场中海森伯自旋链的几何相位

用代数动力学方法,研究旋转磁场中海森伯自旋链的几何相位.选用一个有部分各向异性海森伯耦合的3自旋12粒子环链系统.发现系统的哈密顿量具有su(2)代数结构.通过选择一个最佳规范变换,运用代数动力学方法得到系统的精确解.计算了系统的非绝热和绝热几何相位.把部分各向异性海森伯耦合推广到一般情况下的海森伯耦合,发现:在绝热近似下,海森伯耦合强度不影响系统的几何相位.

霾和正常天气下西安大气颗粒物中水溶性离子特征

IEECAS SKLLQG