多层螺旋CT胸部扫描参数的优化研究

目的:比较16层螺旋CT的4种不同胸部的扫描技术参数,探讨胸部检查最适合的扫描参数。资料与方法:回顾性分析2003年6月至2011年4月间CT检查采用此4种扫描参数的患者100例,肺部低剂量检查和常规剂量检查均分别采用1.5mm×16(24mm)及0.75mm×16(12mm)宽探测器进行扫描;有效mAs分别为20mAs及100mAs;管电压、扫描周期及重建层厚等均相同,为120kV、0.5s、5mm。再分别重叠50%重组2mm及1mm的最薄层图像用于三维后处理用,对照分析其影像及后处理重建图像的质量。结果:4种扫描检查方法所得的肺部影像正常结构及所显示的病灶均无明显差异,图像质量优良;采用较宽探测器和低剂量扫描方案的扫描时间及X线剂量均明显减少,所产生的X线辐射也大幅减少。结论:胸部CT扫描采用宽(1.5mm)探测器和低剂量扫描方案进行时,其辐射剂量(CTDIvol)只为窄(0.75mm)探测器和常规剂量扫描方案的20%,但能提供相近的诊断信息。     

测量标志保护存在的问题及对策

测量标志是标定地面测量控制点位置的标石、觇标以及其他用于测量的标记物的通称,其为社会经济发展、国防建设和科学研究做出了重要贡献。但近年来,测量标志损毁严重。文章分析了测量标志损毁破坏的原因,提出了解决问题的对策。     

天然河流水资源开发中的水环境保护问题

人类在发展社会经济的同时,出于商业目的和个人利益,争相控制水资源,随意向河流排污,导致天然河流、湖泊及附近地区水环境恶化.保护天然河流和水资源是人类共同的责任,不能以牺牲环境为代价,要有统一的认识、统一的措施来进行水资源的保护工作.     

把基本农田纳入地理国情监测内容的思考

基本农田是“吃饭田”、“保命田”,保护基本农田关乎国计民生、社会稳定,把基本农田纳入地理国情监测内容符合国情需要,也能起到加强基本农田保护的实效性与时效性的作用.本文阐述了把基本农田纳入地理国情监测内容的必要性、可行性,并对监测的内容与方法提出了想法.     

Applications of remote sensing and GIS to the assessment of riparian zones for environmental restoration in agricultural watersheds

Geographical design of riparian buffers with long-term vegetation cover for environmental restoration in agricultural watersheds needs to assess how much farmland is located in the buffers of a concerned watershed. Traditionally, this assessment was done by field surveying and manual mapping, which was a time-consuming and costly process for a large region. In this paper, remote sensing (RS) and geographical information system (GIS) as cost-effective techniques were used to develop a catchments-based approach for identifying critical sites of agricultural riparian buffer restoration. The method was explained through a case study of watershed with 11 catchments and results showed that only four of the catchments were eligible in terms of higher priority for riparian buffer restoration. This research has methodological contributions to the spatial assessment of farming intensities in catchments-based riparian buffers across a watershed and to the geographical designs of variable buffering scenarios within catchments. The former makes the catchments-based management strategy possible, and the latter provides alternative restoration scenarios to meet different management purposes, both of which have direct implementations to the environmental restoration of riparian buffers in the real world. This study, thus, highlights the great potential of RS and GIS applications to the planning and management of riparian buffer restoration in agricultural watersheds.     

Another Important Factor of Rising Sea Level: Soil Erosion

Global mean sea level is a sensitive factor of climate change. Global warming will contribute to worldwide sea‐level rise from thermal expansion of ocean water, melting of glaciers and polar ice. Consideration of global soil erosion, water vapor cycle, and hydraulic actions suggests that soil erosion is another important factor contributing to sea‐level rise in addition to global warming. Much terrestrial sediment flows into the rivers each year but cannot be replenished, resulting in land surface declines. Moreover, sediment flow into rivers and oceans contributes to rising sea level. Ecological protection measure was proposed to prevent rising sea levels caused by soil erosion. This commentary should be useful to attract attention on rising sea levels caused by soil erosion.     

Environmental factors that affect sheep production in Brazil

Sheep were originally brought to Brazil approximately 500 years ago from Europe and Northern Africa; they adapted quickly to their new environments and developed unique traits. The objective of this study was to correlate environmental variables with sheep production in Brazil to promote the development of this activity. Brazil has several distinct environments as shown in this paper. These variables included vegetation cover (NDVI), precipitation, temperature, altitude, relative humidity (RH), solar radiation and the temperature humidity index (THI). Correlation analyses were performed with environmental variables and production levels at national and regional level. A factor analysis was performed to characterize the covariance between variables. We formed groups (clusters) due to productivity levels and performed canonical discriminant analyses to determine which variables were associated with different levels of production. The municipalities with the highest levels of sheep production were selected to define the intervals of each environmental variable. A map was drafted in ArcGis 9.3 to illustrate the landscape features where the highest levels of production are located. The results showed that, nationally, production is influenced by a great diversity of environments, thus masking possible correlations. When the correlation analysis was carried out by region, significant correlations were observed. Cluster analysis identified two dominant, clearly separated producing regions (northeast and south). The canonical analysis indicated that the most important variables delineating the clusters were precipitation, THI, temperature and RH. The map showing the landscape features where the highest production levels are located indicated that the breeds in the northeast are reared on an area of approximately 900,000 km², while those from the south are reared on an area of approximately 1,100 million km². This study showed that it is important to consider the environmental characteristics of different regions of Brazil when proposing public policies related to sheep production.     

Assembling insurgent citizenship: immigrant advocacy struggles in the Washington DC metropolitan area

This article examines the political and spatial registers of struggles against exclusionary local immigration policies and for more welcoming policies in the Washington DC metropolitan area, one of the hotspots for both local anti-immigration policies and immigrant advocacy in the United States. We conceptualize immigrant advocacy not simply as an alliance, but instead as an assemblage that brings together a diverse set of differently positioned actors and nonhuman actants. The assemblage enacts a diverse politics that deploys different forms of activism, while engaging different publics (e.g., religious communities, unions, the larger public sphere in public spaces, etc.) and the state in complex ways. From acting outside the state to engaging in claims-making towards the state, immigrant advocates are making claims and actions that challenge and go beyond dominant conceptions of citizenship rights and liberal democratic politics. The spatial register is similarly diverse. The immigrant advocacy assemblage is confronted with and enacts a different politics of place in central cities and inner- and outer-ring suburbs. Contestations of exclusionary local policies, however, are not simply about a local politics of place. To the contrary, some actors and actants in the assemblage are actively involved in extra-local networking, collaborating across jurisdictional boundaries—between central cities and inner-and outer-ring suburbs within the Washington DC metropolitan area and across the United States. The complexities of these contestations call into question post-political narratives of “proper” politics, underscoring the need for an empirically grounded critical theory of democracy. This article contributes to this task by providing a geographically and historically sensitive analysis of the immigrant advocacy assemblage.     

Playing Both "Inside" and "Outside Games"? Evidence From Expert Interviews in Mature Suburbs in Ohio

In recent years, concern has arisen about decline in mature suburbs, and has been addressed primarily by research that has concentrated on quantitative analyses. Only a few works have used qualitative data to explore policies and tools in mature suburbs. We use expert interviews and Rusk's (1999) "inside game/outside game" framework to explore decline and the status of advocacy among select mature suburbs in three study communities in Ohio. We find a lack of awareness of the "inside game." We attribute this to funding streams that continue to favor suburbs and do not require explicit, repeated appropriations from Washington. On the other hand, we find attention being paid to the "outside game." We conclude that mature suburbs seem to be playing both "inside" and "outside" games, depending on the policy domain and the particular funding stream they require.     

建水县林地保护利用研究

利用实地调查法、GIS和相关分析法研究分析建水县林地保护利用现状及存在的问题,研究发现：建水县建设占用与林地保护矛盾突出;林地生产力较低;林地树种结构较单一,生态功能比较脆弱;大多数林地分布在地质灾害中高易发区,地质灾害对林地破坏较大;林地保护管理队伍难以满足现实需求.研究结论：根据林地保护级别对林地实施分级管护,要依法正确处理林地保护和建设占用的关系,完善林地保护管理队伍,建立健全管理机构,加强林地的防灾、抗灾、减灾能力建设,大力促进天然林、人工林和经济林的合理有效培养和发展.