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121.
Section 7(a)(2) of the Endangered Species Act directs federal agencies to ensure that their actions do not jeopardize the
continued existence of endangered and threatened species. The US Fish and Wildlife Service (USFWS) issues jeopardy or nonjeopardy
biological opinions on proposed federal actions that affect endangered and threatened species. We summarize several biological
opinions issued by the USFWS to protect the threatened piping plover (Charadrius melodus). These opinions address federal actions involving hundreds of piping plovers on the Missouri River system and a few piping
plover pairs on short stretches of Atlantic coast beach. Some of these opinions are decisive, but most allow the proposed
action to proceed conditional upon a lengthy set of reasonable and prudent alternatives to protect the piping plover. These
conditions may prove difficult to track and will add to the workload of the USFWS. 相似文献
122.
Kristiina A. Vogt Karen H. Beard Shira Hammann Jennifer O''''Hara Palmiotto Daniel J. Vogt Frederick N Scatena Brooke P. Hecht 《Ambio-人类环境杂志》2002,31(6):485-490
本研究运用满月时收获非木材林产品的当地实践如识,来证明控制叶片分解速率的化学物质随月亮周期而波动,并且这种现象可能已发展为一种植物一食草动物之间的相互关系.当地知识认为,满月期收获的叶片更为耐用.满月期收获的棕榈叶片具有较高的总碳量、半纤维素和碳化合物、而钙的浓度则较低.这些化学上的变化使棕榈叶在满月收获时对食草动物不太敏感且更为耐用.本研究提出了热带植物减少食叶功物食用及影响衰老叶片的分解速度和耐用性(尤其在满月期)的作用机制.本研究认为森林经营中有必要利用天然的生命周期,并为当地人的收获实践提供了科学依据. 相似文献
123.
Karen Filkins M.D. F.A.C.O.G. Joseph Russo Thomas Brown Susan Schmerler Bernard Searle 《黑龙江环境通报》1984,4(3):223-226
Thirty-one genetic amniocenteses involving multiple gestations were performed in the genetics unit between 1976 and 1982. Three sets of triplets were included. Precise locations of the sacs were determined using real-time ultrasonography and successful sampling of all sacs was accomplished. Spontaneous abortions occurred in two normal twins and one normal triplet gestation. Two therapeutic abortions were performed for fetal abnormalities. Two cases of discordance for trisomy 21 (one twin and one triplet) were allowed to continue; the twin case terminated at 25 weeks' gestation with neonatal deaths and the triplets are alive and well. 相似文献
124.
Leichenko Robin M. O'Brien Karen L. 《Mitigation and Adaptation Strategies for Global Change》2002,7(1):1-18
Research on the agricultural impacts of global change frequently emphasizesthe physical and socioeconomic impacts of climate change, yet globalchanges associated with the internationalization of economic activity mayalso have significant impacts on food systems. Together, climate change andglobalization are exposing farmers to new and unfamiliar conditions.Although some farmers may be in a position to take advantage of thesechanges, many more are facing increased vulnerability, particularly in thedeveloping world. This paper considers the dynamics of agriculturalvulnerability to global change through the example of southern Africa. Wedemonstrate that the combination of global and national economic changesis altering the context under which southern African farmers cope withclimate variability and adapt to long-term change. We find that farmers whoformerly had difficulty adapting to climatic variability may become lessvulnerable to drought-related food shortages as the result of tradeliberalization. At the same time, however, removal of national credit andsubsidies may constrain or limit adaptation strategies of other farmers,leaving them more vulnerable to climate variability and change. 相似文献
125.
Lillian Y. F. Hsu MD Sara Kaffe Edmund C. Jenkins Lita Alonso Peter A. Benn Karen David Kurt Hirschhorn Ernest Lieber Alan Shanske Lawrence R. Shapiro Edward Schutta Dorothy Warburton 《黑龙江环境通报》1992,12(7):555-573
Currently, accepted protocol which has been developed at the Prenatal Diagnosis Laboratory of New York City (PDL) requires that when a chromosome abnormality is found in one or more cells in one flask, another 20–40 cells must be examined from one or two additional flasks. Chromosome mosaicism is diagnosed only when an identical abnormality is detected in cells from two or more flasks. In a recent PDL series of 12 000 cases studied according to this protocol, we diagnosed 801 cases (6.68 per cent) of single-cell pseudomosaicism (SCPM), 126 cases (1.05 per cent) of multiple-cell pseudomosaicism (MCPM), and 24 cases (0.2 per cent) of true mosaicism. Pseudomosaicism (PM) involving a structural abnormality was a frequent finding (2/3 of SCPM and 3/5 of MCPM), with an unbalanced structural abnormality in 55 per cent of SCPM and 24 per cent of MCPM. We also reviewed all true mosaic cases (a total of 50) diagnosed in the first 22000 PDL cases. Of these 50 cases, 23 were sex chromosome mosaics and 27 had autosomal mosaicism; 48 cases had numerical abnormalities and two had structural abnormalities. Twenty-five cases of mosaicism were diagnosed in the first 20 cells from two flasks, i.e., without additional work-up, whereas the other 25 cases required extensive work-up to establish a diagnosis (12 needed additional cell counts from the initial two culture flasks; 13 required harvesting a third flask for cell analysis). Our data plus review of other available data led us to conclude that rigorous efforts to diagnose true mosaicism have little impact in many instances, and therefore are not cost-effective. On the basis of all available data, a work-up for potential mosaicism involving a sex chromosome aneuploidy or structural abnormality should have less priority than a work-up for a common viable autosomal trisomy. We recommend revised guidelines for dealing with (1) a numerical versus a structural abnormality and (2) an autosomal versus a sex chromosome numerical aneuploidy. Emphasis should be placed on autosomes known to be associated with phenotypic abnormalities. These new guidelines, which cover both flask and in situ methods, should result in more effective prenatal cytogenetic diagnosis and reduced patient anxiety. 相似文献
126.
Karen J. Nutt 《Behavioral ecology and sociobiology》2007,61(11):1651-1663
Current mating system theory predicts that the number of females breeding in a group will depend on the number of females
in the group and the accessibility of unrelated males, whereas the number of males breeding in a group will depend on the
ability of males to control access to reproductive females. By combining information on group composition with genetic data,
I determined whether breeding patterns in a rock-dwelling rodent, Ctenodactylus gundi, were concordant with these expectations. C. gundi breeding patterns varied from facultative monogamy to uni-male polygyny to multi-male polygyny. The number of reproductive
individuals of each sex in a group increased with group size. Whereas communal breeding among related females tended to increase
female reproductive success, males breeding in the same group were unrelated to other group members and seemed to compete
over access to matings. While some males were assigned offspring from neighboring social groups, most group-living males successfully
monopolized the reproduction of females within their group. There was no evidence that females had multiply sired litters,
although some bred with alternative males in separate breeding attempts. Although numerous individuals were not assigned as
parents or offspring, genetic information enabled me to determine that most unassigned individuals were philopatric group
members, whereas only a few were unrelated immigrants into their current social group. Together, these results provide evidence
that C. gundi social groups represent fairly distinct reproductive units whose breeding patterns are dependent on group size and composition
in accordance with theoretical predictions.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
127.
Fate of disinfection by-products in groundwater during aquifer storage and recovery with reclaimed water 总被引:3,自引:0,他引:3
Knowledge on the behaviour of disinfection by-products (DBPs) during aquifer storage and recovery (ASR) is limited even though this can be an important consideration where recovered waters are used for potable purposes. A reclaimed water ASR trial in an anoxic aquifer in South Australia has provided some of the first quantitative information at field-scale on the fate and transport of trihalomethanes (THMs) and haloacetic acids (HAAs). The results revealed that THM half-lives varied from <1 to 65 days, with persistence of chloroform being highest and bromoform lowest. HAA attenuation was rapid (<1 day). Rates of THM attenuation were shown to be highly dependent on the geochemical environment as evidenced by the 2-5 fold reduction in half-lives at the ASR well which became methanogenic during the storage phase of the trial, as compared to an observation well situated 4 m away, which remained nitrate-reducing. These findings agree with previous laboratory-based studies which also show persistence declining with increased bromination of THMs and reducing redox conditions. Modelling suggests that the chlorinated injectant has sufficient residual chlorine and natural organic matter for substantial increases in THMs to occur within the aquifer, however this is masked in some of the field observations due to concurrent attenuation, particularly for the more rapidly attenuated brominated compounds. The model is based on data taken from water distribution systems and may not be representative for ASR since bromide and ammonia concentrations in the injected water and the possible role of organic carbon in the aquifer were not taken into consideration. During the storage phase DBP formation potentials were reduced as a result of the removal of precursor material despite an increase in the THM formation potential per unit weight of total organic carbon. This suggests that water quality improvements with respect to THMs and HAAs can be achieved through ASR in anoxic aquifers. 相似文献
128.
Organochlorine pesticides were widely used in the past in Sumas Prairie, British Columbia, Canada. In the 1990s, the hatching success of amphibians from agricultural sites was significantly depressed in the Sumas Prairie compared to reference sites. Therefore, in this study, organochlorine pesticides and polychlorinated biphenyls (PCBs) were measured in eggs of red-legged frogs (Rana aurora) and northwestern salamanders (Ambystoma gracile) from the Sumas Prairie. Egg masses were sampled from three agricultural sites that were exposed to agricultural runoff, and three reference sites that had lower agricultural runoff exposures. Not only was there little difference in contamination between agricultural and reference sites, but the levels of pesticides and PCBs found were lower than the concentrations reported to cause developmental or behavioural problems in amphibians. 相似文献
129.
Chow JC Watson JG Lowenthal DH Magliano KL 《Journal of the Air & Waste Management Association (1995)》2005,55(8):1158-1168
Evaporative loss of particulate matter (with aerodynamic diameter < 2.5 microm, [PM2.5]) ammonium nitrate from quartz-fiber filters during aerosol sampling was evaluated from December 3, 1999, through February 3, 2001, at two urban (Fresno and Bakersfield) and three nonurban (Bethel Island, Sierra Nevada Foothills, and Angiola) sites in central California. Compared with total particulate nitrate, evaporative nitrate losses ranged from < 10% during cold months to > 80% during warm months. In agreement with theory, evaporative loss from quartz-fiber filters in nitric acid denuded samplers is controlled by the ambient nitric acid-to-particulate nitrate ratio, which is determined mainly by ambient temperature. Accurate estimation of nitrate volatilization requires a detailed thermodynamic model and comprehensive chemical measurements. For the 14-month average of PM2.5 acquired on Teflon-membrane filters, measured PM2.5 mass was 8-16% lower than actual PM2.5 mass owing to nitrate volatilization. For 24-hr samples, measured PM2.5 was as much as 32-44% lower than actual PM2.5 at three California Central Valley locations. 相似文献
130.
A review of perceived diversity in teams: Does how members perceive their team's composition affect team processes and outcomes? 下载免费PDF全文
In this paper, we review the growing literature on perceived diversity in teams. We aim to clarify the construct of perceived diversity and organize the findings in this emergent line of research. To do so, we develop a framework integrating research emerging on perceived diversity from across several different research fields. We propose that the nature of perceived diversity and its effects can be best understood by identifying the focal point of the diversity perceptions being studied: perceptions of self‐to‐team dissimilarity, of subgroup splits, and of group heterogeneity. Our review concludes that perceived self‐to‐team dissimilarity and perceived subgroup splits mostly have been linked to negative effects for individuals and groups, whereas perceived group heterogeneity has been shown to exert both positive and negative effects on group outcomes. Our review also draws attention to the problem that research on perceived diversity varies not only in definitions and conceptualizations, but also in the methodological approaches towards operationalizing perceived diversity. We conclude by discussing potential areas for future research. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献