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91.
Juan Moreno Santiago Merino Jaime Potti Ana de León Rosa Rodríguez 《Behavioral ecology and sociobiology》1999,46(4):244-251
We manipulated parental work load without changing brood size in a population of pied flycatchers Ficedula hypoleuca by removing two primaries (7 and 9) from each wing of females, thus reducing wing area and increasing flight costs. At other
nests, we offered supplementary food in the form of live mealworms (10–20 g daily from hatching) to reduce brood demand and
thus parental foraging costs. Other nests were left as controls. The daily energy expenditure of females feeding 12-day-old
nestlings was measured with doubly labelled water D2
18O. Females in both treatments expended the same amount of energy, fed at the same rate and had similar body masses to birds
in the control group. No effect of treatment on male mass and feeding effort was detected. More nestlings, however, died in
nests of handicapped females. Nestlings of handicapped females had significantly lower body mass and haematocrit values than
nestlings in food-supplemented nests, with nestlings in control nests occupying an intermediate position. The effects of both
treatments on nestling mass, haematocrit values and mortality rates were only noticeable in nests infested with mites. Maternal
energy expenditure is apparently constrained and offspring pay the costs imposed by reduced provisioning rate or increased
demand caused by ectoparasites, while receiving benefits when food supply improves. The presumption that avian reproductive
costs derive from changes in a flexible energy output may not be met in many cases.
Received: 24 October 1998 / Received in revised form: 15 March 1999 / Accepted: 26 April 1999 相似文献
92.
Vijayaraghavan M Lievano F Cairns L Wolfson L Nandy R Ansari A Golaz A Mashal T Salama P 《Disasters》2006,30(2):256-269
This paper assesses the cost-effectiveness of, and the return on the investment in, the 2002 catch-up and the 2003 follow-up measles campaigns in Afghanistan from the perspective of the donor. The catch-up campaign targeted nearly 12 million children aged between six months and 12 years, while the follow-up campaign targeted over five million children aged between 9 and 59 months. Both campaigns successfully vaccinated approximately 96 per cent of the respective target populations, and are expected to avert an estimated 301,000 measles deaths over the next 10 years. The average cost per dose of measles vaccine delivered was USD 0.40. The cost per death prevented is USD 23.6, assuming a case fatality rate of 10 per cent and a discount rate of three per cent. With more than 42,000 measles deaths avoided for every one million US dollars spent, the campaigns are an excellent public health investment for precluding childhood mortality in a country affected by a complex emergency. 相似文献
93.
A good estimate of the design effect is critical for calculating the most efficient sample size for cluster surveys. We reviewed the design effects for seven nutrition and health outcomes from nine population-based cluster surveys conducted in emergency settings. Most of the design effects for outcomes in children, and one-half of the design effects for crude mortality, were below two. A reassessment of mortality data from Kosovo and Badghis, Afghanistan revealed that, given the same number of clusters, changing sample size had a relatively small impact on the precision of the estimate of mortality. We concluded that, in most surveys, assuming a design effect of 1.5 for acute malnutrition in children and two or less for crude mortality would produce a more efficient sample size. In addition, enhancing the sample size in cluster surveys without increasing the number of clusters may not result in substantial improvements in precision. 相似文献
94.
Hemlock Woolly Adelgid (Adelges tsugae) is spreading across forests in eastern North America, causing mortality of eastern hemlock (Tsuga canadensis [L.] Carr.) and Carolina hemlock (Tsuga caroliniana Engelm.). The loss of hemlock from riparian forests in Great Smoky Mountains National Park (GSMNP) may result in significant
physical, chemical, and biological alterations to stream environments. To assess the influence of riparian hemlock stands
on stream conditions and estimate possible impacts from hemlock loss in GSMNP, we paired hardwood- and hemlock-dominated streams
to examine differences in water temperature, nitrate concentrations, pH, discharge, and available photosynthetic light. We
used a Geographic Information System (GIS) to identify stream pairs that were similar in topography, geology, land use, and
disturbance history in order to isolate forest type as a variable. Differences between hemlock- and hardwood-dominated streams
could not be explained by dominant forest type alone as forest type yields no consistent signal on measured conditions of
headwater streams in GSMNP. The variability in the results indicate that other landscape variables, such as the influence
of understory Rhododendron species, may exert more control on stream conditions than canopy composition. The results of this study suggest that the
replacement of hemlock overstory with hardwood species will have minimal impact on long-term stream conditions, however disturbance
during the transition is likely to have significant impacts. Management of riparian forests undergoing hemlock decline should,
therefore, focus on facilitating a faster transition to hardwood-dominated stands to minimize long-term effects on water quality. 相似文献
95.
The effects of increasing Cu, Ni and Cr concentrations (0.5, 5, 10, 20 and 40 mg L−1) on microtubule organization and the viability of leaf cells of the seagrass Cymodocea nodosa for 13 consecutive days were investigated under laboratory conditions. Increased oblique microtubule orientation, microtubule depolymerization at the 5–40 mg L−1 Ni treatments after 3 d of exposure, and a complete microtubule depolymerization at all Ni treatments after 5 d were observed. Cu depolymerised microtubules after three to 7 d of exposure, while Cr caused an extensive microtubule bundling after 9 or 11 d of exposure, depending on metal dosage. Fluorescence intensity measurements further consolidated the above phenomena. Cell death, occurring at later time than microtubule disturbance, was also observed at all Cu and Ni treatments and at the 10–40 mg L−1 Cr treatments and adding to the above quantification of the number of dead cells clearly showed that only a portion of the cell population studied died. The data presented, being the first assessment of microtubule disturbance in seagrasses, indicate that microtubules in seagrass leaf cells could be used as a valuable and early marker of metal-induced stress in biomonitoring programmes. 相似文献
96.
Fisher WS Davis WP Quarles RL Patrick J Campbell JG Harris PS Hemmer BL Parsons M 《Environmental monitoring and assessment》2007,125(1-3):347-360
Coral reefs provide shoreline protection, biological diversity, fishery harvests, and tourism, all values that stem from the
physically-complex coral infrastructure. Stony corals (scleractinians) construct and maintain the reef through deposition
of calcium carbonate. Therefore, assessment of coral reefs requires at least some measurement endpoints that reflect the biological
and physical condition of stony corals. Most monitoring programs portray coral quantity as live coral cover, which is the
two-dimensional proportion of coral surface to sea floor viewed from above (planar view). The absence of the third dimension,
however, limits our ability to characterize coral reef value, physiology, health and sustainability. A three-dimensional (3D)
approach more realistically characterizes coral structure available as community habitat and, when combined with estimates
of live coral tissue, quantifies the amount of living coral available for photosynthesis, growth and reproduction. A rapid
coral survey procedure that coupled 3D coral quantification with more traditional survey measurements was developed and tested
in the field. The survey procedure relied on only three underwater observations – species identification, colony size, and
proportion of live tissue – made on each colony in the transect. These observations generated a variety of metrics, including
several based on 3D colony surface area, that are relevant to reef management. 相似文献
97.
Persistent organic pollutants (POPs) in Caspian seals of unusual mortality event during 2000 and 2001 总被引:1,自引:0,他引:1
Kajiwara N Watanabe M Wilson S Eybatov T Mitrofanov IV Aubrey DG Khuraskin LS Miyazaki N Tanabe S 《Environmental pollution (Barking, Essex : 1987)》2008,152(2):431-442
Persistent organic pollutants including organochlorine pesticides, PCBs, and PCDDs/DFs were determined in the blubber of Caspian seals, which died during an outbreak of canine distemper virus in 2000 and 2001. DDTs were the predominant contaminants that ranged from 3.1 to 560 microg/g lipid. A negative correlation was observed between concentration of contaminants and blubber thickness. During spring, as the blubber layer becomes thin after breeding and moulting, seals may face higher risk due to the increased concentration of organochlorines in their bodies. TEQs in the blubber of Caspian seals (10-340 pg TEQ/g) were lower than those in seals from other locations, suggesting that toxic effects of these contaminants are a deal less in the present population and they are unlikely to be linked to mass mortality. The levels of PCBs and pesticides in Caspian seals, however, comparable to those in other aquatic mammals that have suffered from epizootics, might pose a risk of immunosuppression. 相似文献
98.
Analysis of the National Center for Health Statistics' Compressed Mortality File showed that between 1979 and 2004, natural events caused 21,491 deaths in the United States. During this 26-year period, there were 10,827 cold-related deaths and 5,279 heat-related deaths. Extreme cold or heat accounted for 75 per cent of the total number of deaths attributed to natural events— more than all of deaths resulting from lightning, storms and foods, and earth movements, such as earthquakes and landslides. Cold-related death rates were highest in the states of Alaska, Montana, New Mexico, and South Dakota, while heat-related deaths were highest in the states of Arizona, Missouri, and Arkansas. These deaths occurred more often among the elderly and black men. Other deaths were attributed to lightning (1,906), storms and foods (2,741), and earth movements (738). Most deaths associated with natural events are preventable and society can take action to decrease the morbidity and mortality connected with them. 相似文献
99.
Heavy metal concentrations in plants and different harvestable parts: A soil-plant equilibrium model
Sebastián D. Guala Emma F. Covelo 《Environmental pollution (Barking, Essex : 1987)》2010,158(8):2659-2663
A mathematical interaction model, validated by experimental results, was developed to modeling the metal uptake by plants and induced growth decrease, by knowing metal in soils. The model relates the dynamics of the uptake of metals from soil to plants. Also, two types of relationships are tested: total and available metal content. The model successfully fitted the experimental data and made it possible to predict the threshold values of total mortality with a satisfactory approach. Data are taken from soils treated with Cd and Ni for ryegrass (Lolium perenne, L.) and oats (Avena sativa L.), respectively. Concentrations are measured in the aboveground biomass of plants. In the latter case, the concentration of metals in different parts of the plants (tillering, shooting and earing) is also modeled. At low concentrations, the effects of metals are moderate, and the dynamics appear to be linear. However, increasing concentrations show nonlinear behaviors. 相似文献
100.
长江靖江段沿岸似鳊生长及种群参数估算 总被引:2,自引:0,他引:2
2012年1月~2013年12月连续24个月在长江靖江段沿岸收集似鳊标本2 334尾,采用基于体长频率数据的ELEFAN I技术估算长江近口段沿岸似鳊的生长参数与种群参数。结果表明:似鳊体长(L,cm)与体质量(W,g)幂函数关系为:W=0.0182×L~(2.948)(r=0.9823,n=2334)。Von Bertalanffy生长方程描述的似鳊生长参数为:极限体长(L_∞)=19.25 cm,生长系数(K)=0.2/a,理论生长起点年龄(t_0)为-1.59 a,体质量的生长拐点年龄为3.55 a。采用Pauly的经验公式估算似鳊自然死亡系数(M)为0.556/a。由长度变换渔获曲线法估算出的似鳊总死亡系数(Z)为1.638/a,捕捞死亡系数(F)和开发率(E)分别为1.082/a和0.66/a。2012~2013年长江靖江段沿岸似鳊年均资源重量和资源数量分别为120.59 t和947.4万尾。经相关估算参数和相对单位补充渔获量分析得出,当前长江靖江段沿岸似鳊已处于过度捕捞状态。建议将沿岸水域禁渔期延长至9月(即4~9月),以实现似鳊资源的恢复和可持续发展。 相似文献