Substrate selection and seasonal variation in abundance and size composition of isopod Lirceus fontinalis in Ontario streams, Canada

The abundance and size composition of stream isopods Lirceus fontinalis were investigated from April 2001 to August 2002 in 3 streams in southern Ontario, Canada. Effects of current speed was released from the analysis by choosing slow flowing water. The effects of substrate, season and water depth on the abundance, distribution and size composition of the isopods were analyzed. It was found that substrate and season influence isopods the most. The rocky substrate with attached filamentous macro-algae contains an isopod abundance 7.05 times that of bare rock substrate and 14.6 times that of fine-sand and mud substrate. There was a large variation with respect to seasonality in both abundance and size composition of the isopods, with the highest abundance occurring in summer and the lowest in winter and spring; individual isopods also tend to be larger in the winter and spring. In all substrates, shallow areas tend to support higher densities of isopods than deeper areas.     

Automatic Normalization and Equivalent-Width Measurement of High-Resolution Stellar Spectra

It is well known that normalization, radial velocity correction and equivalent-width measurement of high-resolution stellar spectra are time-consuming work. In order to improve the efficiency we present an automatic method for these routines. The continuum is determined by fitting the 'high points' in the spectrum. After continuum normalization, the program automatically searches for the position of the Ha line and obtains a rough radial velocity, then computes an accurate radial velocity by cross-correlation between the given spectrum and the solar spectrum. In this method, the equivalent-width is automatically measured using Gaussian fitting. A comparison between our results and those from traditional analysis shows that the typical error for equivalent width is around 3.8% in our method. Developing such automatic routines does not mean to replace the interactive reduction method: it is just for a quick extraction of information from the spectra, especially those obtained in large sky surveys.     

基于FastICA算法和MODIS数据的水稻面积提取

以苏、皖、赣三省为研究区域,采用FastICA算法从MODIS数据中提取2010年水稻种植面积,并验证该算法在混合像元分解中的有效性。在对2010年46景8 d合成地表反射率产品数据进行预处理的基础上,结合MODIS土地利用产品和平滑滤波算法,构建耕地类型像元的I_LSW和I_NDV时相变化曲线。依据I_LSW和I_NDV曲线在水稻移栽期前后的变化规律,并根据由各地区水稻I_NDV时相曲线计算得到水稻相似性指数,从MODIS影像中提取水稻像元。采用FastICA算法对潜在水稻像元水稻生长期内的I_NDV时相曲线进行分解,计算每个像元的水稻丰度,绘制水稻丰度图,获取研究区各省水稻分布和种植面积。利用统计年鉴数据和样方资料对FastICA算法提取的水稻面积进行了验证。结果显示:采用水稻相似性曲线有利于提高稻田识别效率,所获取的水稻分布与实际情况吻合;FastICA算法能够分解不同地区水稻I_NDV时相曲线;与统计资料比较,江苏、安徽、江西三省水稻面积的提取精度分别为86.4%、87.9%、51.5%。江西水稻面积提取误差主要出现在地形起伏较大的山区。     

A Differential Abundance Analysis of HD219175 A and B

The abundances of the wide binary pair HD 219175 A and B are determined and compared using a line-by-line differential analysis. No evidence for difference has been found in the abundances of Fe, O, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Ni, Cu and Ba. Our results support a physical relation between the two components of HD 219175.     

科技短消息

癌细胞进入大脑的单程票?有10%的癌症患者的癌细胞会扩散至脑部并发展成脑部肿瘤。一个一直困扰着学术界的问题是:癌细胞是如何通过血脑屏障的?血脑屏障是中枢神经系统中的一种细胞结构,它可以限制化学物质和     

改进技术方法,加强对矿石的表征能力

虽然全球对矿产的需求不断加大,而近年发现的高质量矿床却在不断减少。目前正在寻找的矿床大多属于复合式矿床,目标元素丰度低,通常与细粒多相矿物组合半生,或者产在亚微粒颗粒中,这样就大大降低了矿石处理效率和回收率。了解矿石的化学成分、矿物成分和结构特征,有助于调整甚至改变矿石处理工艺,     

无磷条件诱导铜绿微囊藻(Microcystis aeruginosa)释放挥发性有机化合物对莱茵衣藻(Chlamydomonas reinhardtii)的影响

为了揭示磷(P)营养缺乏对蓝藻释放挥发性有机化合物(VOCs)的影响及其对其他藻类的化感作用,以形成蓝藻水华的主要种类铜绿微囊藻(Microcystis aeruginosa)为材料,在无P培养条件下对其释放的VOCs进行分析,同时测定VOCs对莱茵衣藻(Chlamydomonas reinhardtii)生长、光合色素含量和光合性能的影响.结果表明,采用无P培养基培养铜绿微囊藻24 h后,其释放的VOCs种类和含量均明显增加,与标准培养基培养相比,VOCs总释放量增加了73.4%,并出现7种新化合物.将铜绿微囊藻释放的VOCs通入莱茵衣藻溶液中,在标准培养基中铜绿微囊藻释放的VOCs对莱茵衣藻生长无显著影响,而无P条件下释放的VOCs则明显抑制莱茵衣藻生长,其响应指数(RI)为-0.25.此外,莱茵衣藻光合色素含量、光系统II(PSII)最大光化学量子产量(Fv/Fm)、有效光化学量子产量[Y(II)]、光化学淬灭系数(q P)和光合电子传递速率(ETR)也明显降低,而非光化学淬灭系数(NPQ)则明显升高,其RI为0.26.由此可见,蓝藻在富营养化水体中大量繁殖以及P自身沉降特性导致的P缺乏会促进蓝藻释放VOCs,同时这些VOCs在保持蓝藻营养竞争优势和水体藻类多样性减少中具有化感抑制作用.     

Metabolites from mangrove endophytic fungus Dothiorella sp.

Mangroves are special woody plant communities in the intertidal zone of tropical and subtropical coasts. They prove to be a natural microorganisms and new metabolites storage. In the study of mangrove endophytic fungi metabolites, four new compounds, Compounds 1, 2, 3 and 4, as well as a known octaketide, cytosporone B (5), are isolated from an endophytic fungus, Dothiorella sp., HTF3. They all show cytotoxic activities. The elucidation of these structures is mainly based on 1D/2D NMR and ESI-MS spectral analyses.     

钡星重元素丰度的再研究

在包括双星及逃逸物质的系统总角动量守恒模型的基础上,采用了星风质量吸积机制、由伴星通过逐次脉冲从主星吸积物质并与其外包层进行混合的模型出发,自洽地计算了钡星的重元素超丰,并给出理论计算结果与观测值的比较,计算结果表明,当取Ｂｏｎｄｉ－Ｈｏｙｌｅ质量吸积率的五分之一作为实际吸积率时,对于轨道周期较长、相距较远的钡星系统。在误差范围内,理论计算曲线与在多数样品星的重元素观测值相符合;而对于ＨＤ２０４０     

NEW OBSERVATIONS ON THE MEIOTIC PROCESS IN THE MARINE DINOFLAGELLATE NOCTILUCA SCINTILIANS （NOCTILUCALES, DINOPHYCEAE）

The meiotic process in Noctiluca scintillans were observed under light microscope.Some abnormal cell divisions, incompletely separated “zoospores” and the changes of the zoospores are described in this paper. Together with the fmdings of field samplings and the previous results by other researchers, the process of meiosis in N. scintillans was supposed to be a pathway to reduce the extra high density of NH3-N within the cell in order to ensure normal population growth.