Geochemical characteristics and zones of surface snow on east Antarctic Ice Sheet

The surface-snow geochemical characteristics are discussed on the East Antarctic Ice Sheet, depending on the stable isotopes ratios of oxygen and hydrogen, concentration of impurities (soluble-ions and insoluble micro-particle) in surface snow collected on the ice sheet. The purpose is to study geochemical zones on the East Antarctic Ice Sheet and to research sources and transportation route of the water vapor and the impurities in surface snow. It has been found that the ratio coefficients, as S1, d1 in the equation δD =S1δ^18O d1, are changed near the elevation 2000 m on the ice sheet. The weight ratio of Cl^-/Na^ at the area below the elevation of 2000 m is close to the ratio in the sea salt; but it is about 2 times that of the sea salt, at the inland area up to the elevation of 2000 m. The concentrations of non-sea-salt Ca^2 ion (nssCa^2 ) and fine-particle increase at the interior up to the elevation 2000 m. At the region below the elevation of 2000 m, the impurity concentration is decreasing with the elevation increasing. Near coastal region, the surface snow has a high concentration of impurity, where the elevation is below 800 m. Combining the translating processes of water.vapor and impurities, it suggests that the region up to the elevation 2000 m is affected by large-scale circulation with longitude-direction, and that water-vapor and impurities in surface snow come from long sources. The region below the elevation 2000 m is affected by some strong cyclones acting at peripheral region of the ice sheet, and the sources of water and impurities could be at high latitude sea and coast. The area below elevation 800 m is affected by local coastal cyclones.     

Design and implementation of a proxy caching system for streaming media

With the widespread use of streaming media application on the Internet, a significant change in Internet workload will be provoked. Caching is one of the applied techniques for enhancing the scalability of streaming system and reducing the workload of server/network. Aiming at the characteristics of broadband network in community, we propose a popularity-based server-proxy caching strategy for streaming medias, and implement the prototype of streaming proxy caching based on this strategy, using RTSP as control protocol and RTP for content transport. This system can play a role in decreasing server load, reducing the traffic from streaming server to proxy, and improving the start-up latency of the client.     

Systematic generation of high-resolution deletion coverage of the Drosophila melanogaster genome

In fruit fly research, chromosomal deletions are indispensable tools for mapping mutations, characterizing alleles and identifying interacting loci. Most widely used deletions were generated by irradiation or chemical mutagenesis. These methods are labor-intensive, generate random breakpoints and result in unwanted secondary mutations that can confound phenotypic analyses. Most of the existing deletions are large, have molecularly undefined endpoints and are maintained in genetically complex stocks. Furthermore, the existence of haplolethal or haplosterile loci makes the recovery of deletions of certain regions exceedingly difficult by traditional methods, resulting in gaps in coverage. Here we describe two methods that address these problems by providing for the systematic isolation of targeted deletions in the D. melanogaster genome. The first strategy used a P element-based technique to generate deletions that closely flank haploinsufficient genes and minimize undeleted regions. This deletion set has increased overall genomic coverage by 5-7%. The second strategy used FLP recombinase and the large array of FRT-bearing insertions described in the accompanying paper to generate 519 isogenic deletions with molecularly defined endpoints. This second deletion collection provides 56% genome coverage so far. The latter methodology enables the generation of small custom deletions with predictable endpoints throughout the genome and should make their isolation a simple and routine task.     

Response of global lightning activity to air temperature variation

It is an issue of great attention but yet not very clear whether lightning activities increase or decrease on a warmer world. Reeve et al. presented that lightning activities in global land and the Northern Hemisphere land have positive response to the increase of wet bulb temperature at 1000hPa. Is this positive response restricted only to wet bulb temperature or in land？ What is the response of global lightning activities （in both land and ocean） to the global surface air temperature variation like？ This paper, based on the 5-year or 8-year OTD/LIS satellite-based lightning detecting data and the NCEP reanalysis data, makes a reanalysis of the response of the global and regional lightning activities to temperature variations. The results show that on the interannual time scale the global total flash rate has positive response to the variation in global surface air temperature, with the sensitivity of 17±7% K^-l. Also, the seasonal mean flash rate of continents all over the world and that of continents in the Northern Hemisphere have sensitive positive response to increase of global surface air temperature and wet bulb temperature, with the sensitivity of about 13±5% K^-1, a bit lower than estimation of 40% K^-1 in Reeve et al. However, the Southern Hemisphere and other areas like the tropics show no significant correlation.     

Down-regulation of αGal epitopes by co-transfection of α1,3-galactosidase gene and α1,2–fucosyltransferase gene

The polycarbohydrate structure of Galα1- 3Ga1β1-4GluNAc-R （known as αGal epitopes of xenoantigen）, produced by α1-3-galactosyltransferase （α1,3-GT） in the course of animal development, is the major xenoantigen on the cell surface of porcine which causes hyperacute rejection in pig-to-human xenotransplantation. Alpha-1,3-galactosidase （AGL）, a hydrolytic enzyme, can remove the terminal α1,3-galactosyi from the Galα1-3Galβ1-4GluNAc-R structure resulting in cleaning αGai epitopes from the porcine cells. Aipha-1,2-fucosyitransferase （HT） can modify the surface carbohydrate phenotype of porcine cells, bringing about reduction of αGai epitopes expression. In this study, human AGL and HT gene were co-transfected to porcine fetal fibroblast （PFFb） in equimolar concentration to reduce the xenoantigen. Gene and protein of hAGL and HT were both detected to express at high level by RT-PCR and Western blot, respectively. There was an 84% reduction in αGai xenoantigen and an 82% increase in H antigen as assayed by flow cytometry in the AGL and HT gene co-transfected PFFb. The number and morphology of transgenic PFFb chromosome were normal. Findings indicate that Galα1-3Gal epitopes of PFFb could be down regulated by AGL and HT co-transfection without deleterious effects on the chromosomal profile of the transgenic ceil.     

中西文化差异与英语学习障碍

语言与文化关系密切,语言中的词汇更是与文化息息相关。因此,要学好一门语言就必须深入学习这门语言的文化,了解其民族文化特征。本文从中西文化差异着手,阐明英语学习中的一些障碍。其目的在于首先提高人们对英语语言的认识,以便提高我国英语教学质量。     

面向快速原型的数据处理与三维造型一体化软件系统

基于MDT软件环境，开发了面向快速原型（RP）的数据处理与三维造型一体化软件系统．首先对系统的集成框架进行描述，然后在深入研究MDT软件平台下CAD模型数据的内部表达方法以及拓扑信息和几何信息提取方法的基础上，运用基于网格划分的曲面与平面求交原理，构造并实现了一种法矢和面积双重判据的自适应直接分层算法．按照所提出的新型二维层片数据文件格式，运用VC＋＋6．0和MDT软件应用程序开发接口，对MDT软件进行二次开发，从而实现了CAD造型与RP数据处理的无缝集成．研究结果表明，该系统具有良好的柔性和实用性，可有效提高快速原型制件质量和简化数据前处理的过程。     

学校学生信息管理系统的设计与实现

本论文介绍了学校学生信息管理系统的实现过程:包括系统分析、系统调查、系统功能设计、系统实现、数据库设计等。本系统主要功能有对学生信息、学生选课信息、学生成绩、教师信息的录入、修改、删除、查询等。     

基于EHMM的人脸识别

人脸识别系统从广义上说大致可以分为人脸检测、定位与跟踪,人脸表征,人脸识别,表情/姿势分析,生理分类等五个方面.人脸的特征提取和人脸图像匹配这两部分是最重要的,也是决定人脸识别系统的准确性和效率所在.采用2D-DCT变换进行人脸特征提取和EHMM模型进行人脸图像匹配(人脸识别),并用多样本加权合成的EHMM训练的方法,取得了较高的速度和识别率.