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891.
Mark R. L. Forbes Robert G. Clark Patrik J. Weatherhead Terry Armstrong 《Behavioral ecology and sociobiology》1994,34(2):79-85
We tested several predictions of nest defense theory by observing variation in flushing distance and probability of nest abandonment within and between six species of waterfowl. In these species, only the females incubate eggs and attend offspring. First, we examined whether flushing distance by females varied in relation to clutch size, stage of incubation, and time of season, after controlling for the number of visits made to nests by observers. Revisits by observers appeared to affect flushing distance by females for reasons unrelated to the relative value of the current clutch. We found that as incubation progressed, females allowed observers to approach more closely before flushing from the nest. In some species, females with larger clutches allowed closer approaches to nests before flushing which was also consistent with nest defense theory. In contrast, time of season (Julian date) did not relate to flushing distance for any species. When species were compared, we found that species with moderate to high yearly mortality and high reproductive output per breeding attempt (e.g., northern shoveler and blue-winged teal) were less likely to abandon nesting attempts and exhibited riskier behavior (remained at nests when approached closely by observers) than species that had lower yearly mortality (e.g., mallard). Our results show that flushing distance and patterns of nest abandonment by female ducks conform to several predictions of nest defense theory.Correspondence to: M.R.L. Forbes 相似文献
892.
多污染因子健康影响的区域性综合评价方法 总被引:1,自引:0,他引:1
本文介绍了一种多污染因子健康影响的区域性综合评价方法.运用该方法进行办北京市大气污染对居民健康影响的研究》不仅证明了大气污染对居民健康的影响,还将北京市城、近郊区划分为影响程度不等的四个区.四个区健康指标水平间的比较,证明划分结果是合理的.方法可用于区域性、多项观察指标的大气污染及其他经环境介质污染健康影响的评价. 相似文献
893.
Chains of accidents (the domino effect) have been occurring with ever increasing frequency in chemical process industries. This is reflected in several accidents ‘J Loss Prevent Process Ind 12 (1999a) 361’; the world's worst industrial accident of the 1990s — the Vishakhpatnam disaster — also involved the domino effect ‘J Loss Prevent Process Ind 12 (1999a) 361; and Process Safety Prog 18 (1999b) 135’. Such chains of accidents have a greater propensity to cause damage than stand-alone accidents ‘Process Safety Prog 17(2) (1998a) 107; and J Loss Prevent Process Ind 12 (1999a) 361’.In order to assess the likelihood of occurrence of the domino effect and its damage potential, use of deterministic models in conjunction with probabilistic analysis is required. Recently we have proposed a systematic methodology called ‘domino effect analysis’ (DEA). A computer-automated tool, DOMIFFECT, has also been developed by us based on DEA ‘Process Safety Prog 17(2) (1998a) 107; Environment Model Software 13 (1998b) 163; and Risk assessment in chemical process industries: advanced techniques. Discovery Publishing House (1998c)’.This paper illustrates the application of DEA and DOMIFFECT to an industrial complex comprising 16 different industries. Out of 12 credible accident scenarios envisaged in three different industries — namely Madras Refineries Limited (MRL), UB Petrochemicals (UBP) and Indian Organic Chemicals Limited (IOCL), eight scenarios are likely to cause the domino effect. A further detailed analysis reveals that accidents in the storage of liquified petroleum gas and propylene and in the reflux drum units of MRL may cause domino effects. Similarly, propylene storage of UBP and monoethylene glycol storage of IOCL are also likely to cause domino effects. The impact of various chains of accidents has been forecast which reveals that in several cases the accidents may be catastrophic, harming the entire industrial complex of 16 industries. The study leads to the identification of ‘hot spots’ — units that pose the greatest risk — in turn forewarning the industries concerned and enabling them to prioritize and augment accident-prevention steps. 相似文献
894.
Current algorithms to determine eligibility for prenatal cytogenetic diagnostic services depend critically on the accuracy and precision of the underlying rates of cytogenetic abnormality used in the calculations. We examine the maternal age-specific rates of Down syndrome livebirths in eight studies of European-origin populations, pooled rates from which are widely used for baseline calculations in biochemical screening. These studies vary significantly in such factors as methods of ascertainment of cases, likelihood of complete ascertainment, and methods of correction, if any, for underascertainment. Restriction of analysis to those two studies among the eight whose methods suggest the greatest likelihood of complete ascertainment for Down syndrome generates rates significantly higher than those in widespread use. Confidence intervals about previously reported and currently derived rates indicate that even with large-scale data, there is considerable residual uncertainty in derived rates. 相似文献
895.
IntroductionTheprintinganddyeingindustryhasahighpotentialenvironmentalimpact,principallyduetothereleaseoflargevolumesofwastewaterthatcontainhighorganicchargeandstrongcoloration .Therearemanyprocessestotreatwastewaterfromprintinganddyeingindustry ,butth… 相似文献
896.
897.
898.
粉煤灰的粉体特性及其对减水效应的影响 总被引:4,自引:0,他引:4
通过对粉煤灰颗粒形貌、平均粒径、粒度分布等粉体特性参量的测定和计算分析 ,发现粉煤灰的减水效应主要来自圆球形玻璃微珠的滚珠轴承润滑作用或对水泥絮凝结构的分散作用。过细的粉煤灰大掺量取代水泥后有可能会降低其减水效应 相似文献
899.
Bruno Brambati Giuseppe Simoni Maurizio Travi Cesare Danesino Lucla Tului Orsola Privitera Sabine Stioui Silvana Tedeschi Silvia Russo Paola Primignani 《黑龙江环境通报》1992,12(10):789-799
Transabdominal chorionic villus sampling (TA-CVS) was attempted in 328 high-risk pregnancies at 6–7 weeks of gestation. Sampling was feasible in 97.7 per cent of cases; chorionic tissue specimens of more than 10 mg were obtained in 94.4 per cent ofcases at the first needle insertion and in 100 per cent after a second attempt. Fetal karyotyping succeeded in 99.4 per cent of cases, while no diagnostic failures were reported in enzymatic and DNA analyses. Fetal loss rate in the first 4 weeks after CVS was significantly higher than in the later CVS series (7.2 vs. 2.5 per cent), but 50 per cent of losses were observed within 2 weeks in cases of inviable aneuploidies. A high incidence of severe limb abnormalities (1.6 per cent) was detected in pregnancies intended to continue, confirming the aetiological role of early CVS. Unclear visualization of the placental limits and poor control of the needle path are thought to be the main reasons for the vascular disruption of the chorionic plate, and thereby hypoxic embryo tissue damage. A better selection of cases, together with high-resolution vaginal ultrasound visualization, and analytical techniques requiring a minimal amount of tissue should avoid any teratogenic effect of early CVS. 相似文献
900.