石羊河流域水资源开发对生态环境的影响

石羊河流域位于甘肃省河西走廊东端,是我国西北干旱地区水资源开发利用强度很高的地区。随着灌溉农业的发展,自70年代以来,用水量大幅度地增加,地下水的开发利用也超过了极限。由于水资源缺乏合理的开发利用,对生态环,境影响很大。上游山区毁林开荒,植被破坏,水土流失严重。平原区地下水超量开采,地下水位大幅度下降,农业生产受到影响,大部分沙生植物枯萎、退化成死亡,沙漠化严重,尤其民勤北部湖区地下水水质恶化,人畜饮水困难,生态环境恶化已成为制约本地区国民经济发展的一个重要因素,本文就石羊河流域水资源不合理开发对生态环境的影响及其解决途径,提出初步意见,仅供有关部门参考。     

节水灌溉工程的建设与管理探讨

灌溉是水利工程的一项重要功能,而在我国水资源日益紧缺的形势下,节水灌溉成为水利工程发展的主要趋势。节水灌溉工程能够有效的节约水资源,提高水资源的利用效率,既能够保证水利工程的经济效益,又能够获取生态效益,所以应该加强节水灌溉工程的建设与管理。节水灌溉是一项比较系统的工程,需要根据当地的实际发展状况进行合理的规划,然后采取适宜的灌溉措施,以达到节约水资源,提高农业发展水平的目的。对于节水灌溉工程的建设与管理的现状进行了分析,然后提出了有效的改善措施,对于促进节水灌溉工程的发展具有重要的意义。     

节水灌溉技术方案的选择

节水灌溉是根据作物需水规律及当地供水条件,为了有效地利用水资源,获取农业最佳经济效益、社会效益、生态环境效益而采取的多种措施的总称。一般采用输水技术、灌水技术、农业节水技术和节水管理技术等四项基本技术措施     

水资源稀缺性感知影响农户地下水利用效率的路径分析——基于华北井灌区1168份调查数据的实证

本文将水资源稀缺性感知划分为水量短缺认知、水位下降认知、风险认知、机井使用感受和灌溉感受五个维度,利用华北井灌区1168户农户户主的调查数据,运用边际结构模型(MSM)逆向概率加权(IPW)估计方法剔除气候、资源禀赋等伪关联因素的影响,实证分析了水资源稀缺性感知对农户地下水资源利用效率的影响机制。结果发现:稀缺性感知影响地下水利用效率既有直接影响也有间接影响,其中间接影响发挥作用更大。直接影响是通过水量短缺认知和水位下降认知来实现的,即认知水平越高,地下水利用效率越高。稀缺性感知通过影响超采行为、节水技术采用行为和水利设施维护等投入行为决策间接作用于地下水利用效率,且风险认知、灌溉感受和行为决策间存在交互效应。风险认知水平高导致超采行为频发,降低地下水利用效率;灌溉感受越差的农户水利设施维护动力越强烈,从而提高地下水利用效率;节水技术采用行为有利于实现地下水的高效利用。     

努力构建节水型社会

我国北方干旱地区水资源短缺严重制约了经济社会的发展.本文针对这一地区存在的较为普遍的用水浪费现象以及水资源利用效率及效益低下的问题,论述了大力推行节约用水、建设节水型社会对保障北方干旱地区可持续发展的重要性.     

农艺节水是干旱区水资源高效利用的有效方法

近年来,随着我国经济的飞速发展,推动了农业发展。农艺节水作为节水农业中重要的组成部分之一,其重要性日益凸显。尤其是在我国一些干旱地区,农艺节水的作用更加明显。利用农艺节水能够有效地提高干旱区的水资源利用效率,进而使田间作物增产。基于此点,首先对农艺节水技术进行概述,并在此基础上提出提高干旱区水资源高效利用的有效方法。     

“十一五”期间中国主要工业部门节能的节水效果分析

能源和水资源已经成为制约我国经济社会可持续发展的主要瓶颈,因此节能减排和水资源优化管理对我国经济可持续发展具有重要的意义。在国家制订的宏观能源政策中,没有考虑对于水资源的影响,而有关水资源的政策中也没有考虑到对能源消耗以及GHG排放的影响,缺乏二者之间相互影响的定量分析。本文从中国能源-水的关系入手,基于投入产出表构建评价模型,建立能源部门和水供应部门的关联系数,分析工业节能政策对于节水的效果,对选定的重点部门如黑色金属行业、石化行业、建材行业、有色金属行业和轻工重点行业,测算"十一五"期间以上部门实现节能而带来的节水效益,揭示节能与节水之间的内在联系。     

黑龙江省水资源可持续发展水平变化研究

水是人类最重要的资源之一。本文从占有水平、消耗水平、利用效率、污染治理四个方面构建了指标体系黑龙江省水资源可持续发展的评价指标体系,采用AHP法确定了各指标的权重,采用2003-2008年间的统计资料,对黑龙江省的水资源可持续发展水平进行了定量研究。结果表明,总体水平得分明显下降,同时具有波动性;水资源占有水平的下降尤为明显,利用效率和污染治理大幅度提升;各要素层对总得分的贡献度变化悬殊。     

农业节水研究进展及未来发展战略

世界大多数地区水资源短缺都与农业生产有关,作为用水大户,农业水资源高效利用对于解决区域水资源短缺和保障粮食生产可持续发展具有极其重要的作用。我国农业节水研究经过20多年来的发展,逐步实现了从最初以农田节水特别是强调农田工程节水为主向更注重改良作物遗传品质节水、农田节水与区域水资源管理节水并重,以及多水源综合利用节水的多学科节水研究体系,大大提高了我国农田节水的潜力。然而生产实践中,受我国社会经济发展水平特别是小农经济制约,我国的农田节水水平和农田水分利用效率还不高,急需通过政府、民间的多渠道投入,通过机制和管理创新,建立起适合各地区经济发展水平的从供水环节、田间节水到区域水资源管理的现代综合农田灌溉节水体系,保障我国未来粮食安全。     

节水灌溉农业的空间认知与建议

水资源危机已经严重阻碍了社会经济的发展。作为耗水大户的农业,现在以及未来很长时间都将面临"以较少的水资源消耗生产更多粮食"的艰巨任务。自1980年以来,我国节水灌溉农业发展迅速,农业节水灌溉措施的实施极大地减少了农业灌溉取用水量,显著提高了灌溉效率,然而水资源危机并没有得到缓解,流域地下水水位持续下降的趋势并未得到遏制,这一现状使人们不得不重新审视节水农业存在的问题。文章从水资源消耗的视角,充分利用遥感技术在作物分布、蒸散发、产量空间格局和时间动态变化监测的优势,在区域尺度上认识节水灌溉农业发展中存在的问题和面临的挑战,提出利益相关者参与式的"耗水管理"是节水高效农业发展以及成功实施的必然途径。     

Low doses of a red wine ingredient figh diabetes in mice

Aresearch group led by Prof. ZHAI Qiwei from the Institute for Nutritional Sciences under the CAS Shanghai Institutes for Biological Sciences has discovered that even relatively low doses of resveratrol--a chemical found in the skins of red grapes and in red wine--can improve the sensitivity of mice to the hormone insulin, according to a report in the October,2007 issue of Cell Metabolism. As insulin resistance is often characterized as the most critical factor contributing to the development of Type 2 diabetes, the findings“provide a potential new therapeutic approach for preventing or treating” both conditions, the researchers said.     

Students' Reactions to the Introduction of Videoconferencing for Classroom Instruction

This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors.     

Molecular motor assembly of a biomimetic system

Active biological molecules and functional structures can be fabricated into a bio-mimetic system by using molecular assembly method. Such materials can be used for the drug delivery, disease diagnosis and therapy, and new nanodevice construction.     

Cooler temperatures inductive to locust outbreaks

Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007.     

To serve and promote science development via innovation

CAS should stick to the principle of rendering service to, and giving impetus for, the development of China＇s science enterprise by making S＆T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party＇s Leading-member Group at CAS, which was held from 7 to 11 January in Beijing.     

Exploring Multiplexity: Social Network Structures in a Computer-Supported Distance Learning Class

A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction.     

Tracing the origin and early radiation of birds——Paleornithologist ZHOU Zhonghe

With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants."     

The Role of Intermediating Institutions in the Diffusion of Electronic Data Interchange (EDI): How Industry Associations Intervened in Denmark, Finland, and Hong Kong

Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies.     

The Information Environment and Universal Service

This essay focuses on universal service and the Internet as means to support social and political participation. The emphasis on access to telecommunications systems in conventional approaches to universal service is contrasted with access to content. A model of the information environment is described that accounts for the roles of content and conduit, both of which are necessary conditions to achieve true access. A method is outlined for employing information indicators to observe or measure the information environment.     

How Electronic Publishers are Protecting Against Piracy: Doubts About Technical Systems of Protection

The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means.