Attitudes towards sex selection for non-medical reasons: a review

Early non-invasive fetal sexing is widely available over the Internet, leading to concerns about its possible use for sex selection. The aim of this review is to summarise the results of surveys describing lay attitudes towards sex selection for non-medical reasons to help address or inform such concerns. A search of electronic databases and key journals was supplemented by an Internet search and citation-tracking. Twenty-one quantitative studies were identified. Most were conducted in the US, with five recent studies in the UK and Germany. Most studies found that, overall, people were not in favour of sex selection. However, this varied from 94 to 18%. People may hold more negative attitudes when the method of sex selection is specified, particularly if this involves termination of pregnancy (TOP). Attitudes towards the general availability of sex selection are less negative than those towards personal use. Attitudes were consistently negative in German surveys. Little is known of such attitudes outside the US, the UK and Germany, and how such attitudes may change as new sex selection technologies become available. Studies of use of early non-invasive fetal sexing for sex selection for non-medical reasons are needed to assess the extent to which concerns about usage are justified and to assist in debates on how these might be most appropriately addressed. Copyright © 2006 John Wiley & Sons, Ltd.     

输气场站工艺安全风险分析

针对输气场站HAZOP风险评估出的天然气泄漏风险进行工艺安全量化分析,通过天然气泄漏喷射火模拟,对天然气泄漏风险进行量化,为输气场站的安全管理提供有效的技术支持。通过量化,分析出对天然气泄漏喷射火造成后果大小的影响因素,提高了HAZOP风险分析的准确性和科学性,对输气场站的风险管理具有参考意义。     

基于神经网络的压铸合金选择

在归纳总结压铸合金选择经验和知识的基础上 ,对压铸合金性能进行评价。采用BP神经网络方法建立了快捷的压铸合金材料选择系统 ,提出了一种将模糊化性能要求量化 ,增加训练样本集的方法。     

江苏省丹阳市水稻土自然生产潜力的初步研究

本文借助作物生长模型与模糊数学的方法对江苏省丹阳市的两种种植制度的土壤自然生产潜力进行了初步的分析研究。结果表明,模拟的小麦/玉米-晚稻种植制度的气候生产潜力比小麦-单季稻高3000kg/ha 左右。指出丹阳的小麦生产应以挖掘、提高土壤自然生产潜力为主,而单季稻的生产则应以提高品种的气候生产潜力为方向。     

西藏食物保障的自然资源相对优势分析

对西藏食物保障的自然资源相对优势研究表明 ,光能、生物、旅游资源是西藏食物保障的突出相对优势。这些资源具有独特、再生和易于持续开发利用等突出特点 ;水利资源和矿产资源具有明显的开发利用优势 ,但是 ,与经济落后形成了极大的反差 ,目前开发乏力 ,开发利用将带来后续管理与环境保护的沉重负担 ;耕地、草地与森林资源既具有明显的优势 ,又有突出的劣势 ,主要表现为数量的优势与质量的劣势。西藏未来食物保障 ,取决于如何将这些资源的相对优势有效组合、综合管理和合理开发利用。     

我国环境资源立法的缺陷与完善初探

我国环境资源立法虽然已有一定基础，但仍然存在诸如体系结构 不完善、内容滞后、操作性不强等问题，急需根据市场经济与可持续发展的要求进一步完善其体系、健全其内容。     

Life cycle analysis and choice of natural gas-based automotive alternative fuels in Chongqing Municipality,China

Road transport produces significant amounts of emissions by using crude oil as the primary energy source. A reduction of emissions can be achieved by implementing alternative fuel chains. The objective of this study is to carry out an economic, environmental and energy (EEE) life cycle study on natural gas-based automotive fuels with conventional gasoline in an abundant region of China. A set of indices of four fuels/vehicle systems on the basis of life cycle are assessed in terms of impact of EEE, in which natural gas produces compressed natural gas (CNG), methanol, dimethylether (DME) and Fischer Tropsch diesel (FTD). The study included fuel production, vehicle production, vehicle operation, infrastructure and vehicle end of life as a system for each fuel/vehicle system. A generic gasoline fueled car is used as a baseline. Data have been reviewed and modified based on the best knowledge available to Chongqing local sources. Results indicated that when we could not change electric and hydrogen fuel cell vehicles into commercial vehicles on a large scale, direct use of CNG in a dedicated or bi-fuel vehicle is an economical choice for the region which is most energy efficient and more environmental friendly. The study can be used to support decisions on how natural gas resources can best be utilized as a fuel/energy resource for automobiles, and what issues need to be resolved in Chongqing. The models and approaches for this study can be applied to other regions of China as long as all the assumptions are well defined and modified to find a substitute automotive energy source and establish an energy policy in a specific region.     

自然条件下石羊河终闾湖泊模拟研究

石羊河流域史前曾存在大面积的终闾湖泊---猪野泽。自西汉开拓河西以后的两千多年以来,受人类活动影响,石羊河流域土地覆盖发生了显著的变化。灌溉农田取代了天然绿洲,而且面积逐步扩大,农业用水急剧增加,猪野泽逐渐退缩成许多小湖,并于近代干涸。在假设人类活动（主要是灌溉）对水资源未加利用的条件下（理想状态）,通过确定流域的水量收支和改进水量平衡模型,对石羊河流域现代自然条件下“终闾湖”的面积进行了模拟重建,得出现代终闾湖的面积至少应为５８０ｋｍ^２。     

The superseded female's dilemma: ultimate and proximate factors that influence guarding behaviour of the carpenter bee Xylocopa pubescens

Both solitary and primitively social nests of the facultatively social carpenter bee Xylocopa pubescens can be found throughout most of the breeding season. In social nests there is reproductive division of labour between a dominant forager and a guarding female. Two types of guarding females can be discerned: the young pre-reproductive guards, and older, formerly reproductive guards. The latter type of guard is found when, after a take-over of reproductive dominance either by a nestmate (mostly a daughter) or an intruder, the defeated female stays in the nest instead of leaving to try and found or usurp another nest. She is then manipulated into the role of a guard. The dominant female profits from the presence of the guard since she protects the nest against pollen robbery by conspecifics (Hogendoorn and Velthuis 1993). We have studied why superseded females might prefer to remain as a guard, rather than try their luck somewhere else. The hypotheses investigated pertain to (1) the difficulty for the defeated female of finding a new nest and of restarting reproductive activities due to (a) ecological constraints (nest and pollen shortage) and (b) the effect of age and wear on the defeated female; (2) the effects of guarding in terms of inclusive fitness. We found that superseded females remained as guards significantly more often when a nestmate (not necessarily close kin) took over reproductive dominance than when an intruder did so. Other factors associated with the decision of the defeated female to stay or leave were her age and the number of her own young still present after the supersedure. The probability of finding or constructing a new nest was lower for old than for young females. After finding a nest, old females produced less brood than young foundresses. As a result of these two factors old superseded females gained, in terms of inclusive fitness, by staying as guards, whereas young females profited from leaving the nest. We interpret these results as an indication that guarding behaviour has evolved due to kin selection. However, kin discrimination apparently did not occur. Therefore we conclude that in this species kin selection is not, in the proximate frame of reference, based on kin recognition and preference for helping kin. Correspondence to: K. Hogendoorn     

炼铁厂高炉原料仓料位计的选择与应用

高炉料仓环境条件恶劣，而高炉生产又要掌握料位情况。比较了2种料位计，最终选择了SA—2型料位计。