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391.
海岸带可持续性管理(SUCOZOMA)研究计划的首要目的是实现从科学界到研究用户的知识转让.该文描述了计划中知识转让的目标,不仅反映了其财政资助者--瑞典环境战略研究基金会的目的,同时也是研究政策的一般趋势.该文主要研究SUCOZOMA积极从事的知识向管理层和各实践者的转让的领域,介绍了许多该计划中研究用户交流和参与的实例.同时,该文也对交流中存在的瓶颈和局限进行分析.  相似文献   
392.
在环境监测中,监测系统在非预期事件出现时能够发出早期预警是很重要的.这些事件具有突发,或者难以观测到的性质.在设计这类监测系统时,必须在成本和风险之间达到一个适当的平衡.传统意义上有两类和早期预警系统相关联的风险,即没有检测到重要变化的风险和错误预警的风险.本文的目的是阐述一种在考虑了传统类型的风险和成本的情况下来比较不同监测系统性能的方法.这个方法被试用于地衣植被的监测中,并采用预期效应作为性能的度量标准.在估计事件的概率时,应用了空间微观模拟技术(spatial microsimulation)和蒙特卡罗模拟技术.所评估的监测计划基于卫星图像、航空照片、野外采样和土地覆被图.研究的主要结论是,标准化质量度量在环境监测方法可用性的评估中是极为有用的.另外,空间微观模拟技术在效益和成本估计中是可用的.不过要改进算法,还需要应用宏观约束(macroconstraints)来修正模拟模型.  相似文献   
393.
 Carotenoid-based integument colour in animals has been hypothesised to signal individual phenotypic quality because it reliably reflects either foraging efficiency or health status. We investigated whether carotenoid-derived yellow plumage coloration of fledgling great tits (Parus major) reflects their nestling history. Great tit fledglings reared in a poor year (1998) or in the urban habitat were less yellow than these reared in a good year (1999) or in the forest. The origin of nestlings also affected their coloration since nestlings from a city population did not improve their coloration when transferred to the forest. Brood size manipulation affected fledgling colour, but only in the rural population, where nestlings from reduced broods developed more yellow coloration than nestlings from increased and control broods. Effect of brood size manipulation on fledgling plumage colour was independent of the body mass, indicating that growth environment affects fledgling body mass and plumage colour by different pathways. Received: 20 March 2000 / Accepted in revised form: 4 September 2000  相似文献   
394.
本文利用非侵入计算层析X射线摄影法(pQCT)研究了雄性波罗的海灰海豹(4~23岁龄)骨组织的矿物密度(mg/cm3).资料按照收集的年份分组.A组1850~1955年,有机氯(OCs)大量引入之前的时期;B组1965~1985年,OC污染十分严重的时期;C组1986~1997年,OCs浓度逐渐减小的时期.测量结果的复现性良好,变异系数(CV)为0.1%~2.1%.1986~1997年收集的标本中桡骨小梁的矿物密度比1965~1985年收集的标本的明显要高(p<0.05).1986~1997年收集的标本中,下颌骨的皮层骨矿物密度明显地低于1850~1955年收集的标本(p<0.05).这些结果表明小梁和皮层骨在一段时间内的不同响应.在OC污染非常严重的时期(1965~1985年),小梁骨矿物密度最低,而在1985~1997年收集的标本中,皮层骨密度最低,该时段是一个OC污染程度相当低的时期.有关这些效应背后的机制目前尚不知道.但是,可以假定这里涉及到OCs.由于目前缺乏有关研究个体中OCs残留水平的资料,因此不可能评估OCs在这方面的影响.  相似文献   
395.
Summary In the pipefish Syngnathus typhle, a species with exclusive male parental care, males limit female reproductive success because of their limited brood pouch space and long pregnancy. Sexual size dimorphism is absent in these 1-year-old animals but increases with age so that older females are larger than similarly aged males. Because fecundity is related to size in both sexes and increases more rapidly with body size in females than in males, the difference in growth increases female fecundity more, relative to male fecundity, as the fish get older. We therefore predicted that male limitation of female reproductive success is even more severe when all age classes are considered. To measure a female's maximum reproductive rate, she was provided with three males. Small 1-year-old females produced as many eggs, or produced eggs at the same rate, as a male of similar size could care for. Small females filled on average 1.06 males within the time span of one male pregnancy and actually produced on average 10 eggs fewer than needed to fill a similarly sized male. Large 2-year-old females, in contrast, produced on average a surplus of 149 eggs and filled 2.7 similarly sized males within the course of one pregnancy. The difference between females of the two size classes was highly significant. Males prefer to mate with larger females if given a choice. In nature sex ratios are equal, and males limit female reproductive success in the whole population. Therefore, small females are more severely constrained by mate availability than are larger females because males choose to mate with larger females. Offprint requests to: A Berglund  相似文献   
396.
The cytogenetic results of 1500 chorionic villus samples (CVS) are presented. In these 1500 samples, 23 samples (1·5 per cent) could not be provided with a diagnosis because of laboratory failure. This failure rate dropped from 3 per cent in the first 500 samples to 0·2 per cent in the last 500. In the remaining 1477 samples, 58 (3·9 per cent) chromosomal aberrations were found. Of these, 21 (36 per cent) proved not to represent the karyotype of the fetus proper. Predictive values of (different groups of) chromosomal aberrations in CVS are calculated. The impact of (differences between) the predictive value for some major chromosomal aberrations is discussed. A tissue- and chromosome-specific selection mechanism is postulated.  相似文献   
397.
Summary Badge size, which functions as a signal of dominance status in male house sparrows Passer domesticus, was significantly related to their sexual behavior. Males with large badges participated in communal displays (multi-male chases directed towards single females) more often than males with small badges, irrespective of whether the female involved was the male's mate or not. Experimentally released females were more often chased if they were fertile than if they were nonfertile. Estradiol-implanted females were chased more often than control females without a hormone implant, and males with large badges chased estradiol-implanted females more often than did males with small badges. Both forced extra-pair copulations during communal displays and unforced extra-pair copulations were more often achieved by males with large than small badges. Male house sparrows with large badges also copulated with their mates at a higher rate than did males with small badges. A higher certainty of paternity therefore is hypothetized to accrue to male house sparrows with large badges.  相似文献   
398.
In 2103 consecutive diagnostic chorionic villus samples, examined in a 4-year period in our clinical genetics unit, 26 samples (1.2 per cent) presented chromosomal mosaicism in the direct and/or long-term culture preparations. Only once (46,XX/47,XX,+9) was the mosaicism confirmed in the fetus. In the cytogenetic follow-up studies of the remaining 25 pregnancies, in no cases could the aberration be confirmed in amniotic fluid or fetal tissue. One patient requested a termination after the CVS result. Of the remaining 24 pregnancies, four (16.7 per cent) ended in a spontaneous abortion. These findings suggest an association between placental mosaicism and fetal loss.  相似文献   
399.
400.
This paper describes a method developed for quantification of gas emissions from the leachate collection system at landfills and present emission data measured at two Danish landfills with no landfill gas collection systems in place: Fakse landfill and AV Miljø. Landfill top covers are often designed to prevent infiltration of water and thus are made from low permeable materials. At such sites a large part of the gas will often emit through other pathways such as the leachate collection system. These point releases of gaseous constituents from these locations cannot be measured using traditional flux chambers, which are often used to measure gas emissions from landfills. Comparing tracer measurements of methane (CH4) emissions from leachate systems at Fakse landfill and AV Miljø to measurements of total CH4 emissions, it was found that approximately 47% (351 kg CH4 d?1) and 27% (211 kg CH4 d?1), respectively, of the CH4 emitting from the sites occurred from the leachate collection systems. Emission rates observed from individual leachate collection wells at the two landfills ranged from 0.1 to 76 kg CH4 d?1. A strong influence on emission rates caused by rise and fall in atmospheric pressure was observed when continuously measuring emission from a leachate well over a week. Emission of CH4 was one to two orders of magnitude higher during periods of decreasing pressure compared to periods of increasing pressure.  相似文献   
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