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131.
介绍了目前常规的排水体制,认为农村集镇应因地制宜地选择排水体制,重点区域在考虑到当地政府财政支付能力的前提下,应尽可能选择雨污分流兼初期雨水截流。 相似文献
132.
The ant genus Cardiocondyla is characterized by a bizarre male polymorphism with wingless fighter males and winged disperser males. Winged males have
been lost convergently in several clades, and in at least one of them, wingless males have evolved mutual tolerance. To better
understand the evolutionary pathways of reproductive tactics, we investigated Cardiocondyla venustula, a species, which in a phylogenetic analysis clusters with species with fighting and species with mutually tolerant, wingless
males. Wingless males of C. venustula use their strong mandibles to kill freshly eclosed rival males and also engage in short fights with other adult males, but
in addition show a novel behavior hitherto not reported from social insect males: they spread out in the natal nest and defend
“territories” against other males. Ant males therefore show a much larger variety of reproductive tactics than previously
assumed. 相似文献
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134.
Occupational exposure limits (OELs) developed by authorities play a key role in the implementation of programs to protect workers against hazardous chemicals. Unfortunately, many hazardous substances do not have OELs or the OEL could be outdated. To assure the health of the workers, it is therefore useful for companies to develop corporate OELs. An inhouse strategy will be presented hereafter. Expertise in toxicology, industrial hygiene, and occupational health should be available within the company and clear selection criteria for substances are needed. A corporate OEL is only developed for hazardous substances (e.g., carcinogenic or reprotoxic) with a high potential for worker exposure when an appropriate national OEL or threshold limit value is not available. The methodology to calculate corporate OELs is based on the existing methods for national or community OELs and also on the guidance from the European Union's (EU) regulation on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH). For carcinogenic substances with a nonthreshold mode of action, there is always a residual chance that a cancer develops even when the exposure of workers is low. To establish an OEL for these substances, the “German traffic light model” is recommended. It is pragmatic, defines an unacceptable, tolerable, and acceptable risk level when workers are exposed to these substances, and determines risk management for exposure reduction. Overall, the professional practice to develop OELs is a good example of corporate leadership to proactively protect the health of workers. 相似文献
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为了解决在不同区域和不同河流类型间等大尺度范围内F-IBI(鱼类生物完整性指数)评价方法体系的建立问题,以浑河-太子河(下称浑太河)流域为研究区域,构建符合区域性特征的生物完整性评价体系并进行应用研究. 于2014年5月对浑太河流域32个采样点的鱼类进行采样调查,根据鱼类群落特征的空间差异和浑太河流域水生态分区,将采样点分为中上游和下游区域两种类型. 通过综合栖息地和水质的标准化方法确定参照点和受损点,依据候选指标分布范围检验、敏感性分析和相关性检验,筛选出浑太河流域中上游F-IBI核心指标包括总物种数、Shannon-Wiener多样性指数、鲤形目鱼类物种数百分比、雅罗鱼亚科个体数百分比、鳅科鱼类物种数百分比、鲈形目鱼类物种数百分比、杂食性鱼类物种数百分比、肉食性鱼类物种数百分比、敏感性鱼类个体数百分比等9个指标;下游筛选出F-IBI核心指标包括总物种数、Shannon-Wiener多样性指数、鮈亚科鱼类物种数百分比、鲈形目鱼类物种数百分比、虾虎鱼科鱼类物种数百分比、中上层鱼类物种数百分比、东北特有鱼类物种数百分比、无脊椎动物食性鱼类物种数百分比、耐受性鱼类个体数百分比等9个指标. 分别提出了浑太河流域中上游和下游的参数标准化公式和健康评价标准,依此将浑太河流域健康状态划分为极好、好、一般、差和极差5个健康等级. 评价结果表明,浑太河流域健康状况整体偏差,在32个采样点中,健康状况处于差和极差的采样点占采样点总数的37.5%,一般的采样点占21.88%,仅有6.25%的采样点处于极好状态. Pearson相关性分析结果显示,F-IBI分值与电导率、ρ(BOD5)、ρ(CODCr)、ρ(NH3-N)和ρ(TN)均呈显著负相关,而与栖息地综合指数呈显著正相关,表明F-IBI可有效评估浑太河流域的健康状况. 相似文献
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139.
在研究和指出灰色建模常规方法理论缺陷的基础上,结合某化工厂废气排放预测实践,初步探讨和提出了将原始动态数据序列经过线性或指数变换,采用黄金分割法选取背景值的直接建模方法。初步研究表明,该方法较灰色建模常规方法在改善序列随机性、提高预测精度等方面,具有较明显的优越性和合理性,拓宽了GM(1,1)模型在环境科学领域中的应用范围。 相似文献
140.
Robert L. McLaughlin Moira M. Ferguson David L. G. Noakes 《Behavioral ecology and sociobiology》1999,45(5):386-395
Some recently emerged brook charr (Salvelinus fontinalis) inhabiting still-water pools along the sides of streams are sedentary and eat crustaceans from the lower portion of the
water column. Others are more active and eat insects from the upper portion of the water column. We provide evidence that
this divergent foraging behavior reflects short-term divergent selection brought about by intraspecific competition in the
presence of alternative food sources. Rates of encounters and interactions between individuals were density dependent, and
encounter and interaction events were closely timed with prey capture attempts. In addition, aggressive fish made more foraging
attempts per minute than nonaggressive fish. Aggressive fish were also either inactive or very active, while nonaggressive
fish exhibited intermediate levels of activity. Growth rate potential, an important component of fitness during the early
life stages of brook charr, was assessed using tissue concentrations of RNA and found to be highest for sedentary fish and
for active fish making frequent foraging attempts, and lower for fish exhibiting intermediate levels of activity. Our findings
support contentions that individual behavior plays an important role during initial steps in the evolution of resource polymorphisms.
Received: 27 July 1998 / Accepted after revision: 16 November 1998 相似文献