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排序方式: 共有149条查询结果,搜索用时 31 毫秒
61.
62.
David R. Johnson MD Rachel A. Fisher Jenny J. Helwick Dennis L. Murray Maria J. Patterson Frances P. Downes 《黑龙江环境通报》1994,14(6):455-458
The association between gestational infection with human parvovirus (B19) and fetal loss has increased interest in this virus and demand for diagnostic testing. However, serological assays for B19 are not yet widely available. Maternal serum alpha-fetoprotein (MSAFP) testing is commonly used during the second trimester to screen for various fetal defects. We attempted to determine whether an elevated level of MSAFP would be an appropriate indication for B19-specific tests. Over a 26-month period, MSAFP tests were performed at Michigan State University for 21 392 women. Sera remaining after that testing were stored frozen. Of these, 22 case samples—from women with MSAFP levels greater than 3·0 multiples of the median (MOM) and pregnancies that ended in fetal loss—and 44 matched control samples—from women with MSAFP levels greater than 0·4 and less than 2·2 MOM and live births at term—were tested for B19 antibodies. None of the 66 samples was IgM positive, while 33 (50 per cent) were IgG positive. The presence of IgG was not significantly associated with case or control status (matched odds ratio=0·77, 95 per cent confidence interval 0·28–2·11). These findings are consistent with other studies indicating prior infection in approximately half of adults and suggest that elevated screening MSAFP levels, in the absence of other evidence of B19 infection, should not prompt B19-specific testing. 相似文献
63.
Koziel JA Spinhirne JP Lloyd JD Parker DB Wright DW Kuhrt FW 《Journal of the Air & Waste Management Association (1995)》2005,55(8):1147-1157
Odorous gases associated with livestock operations are complex mixtures of hundreds if not thousands of compounds. Research is needed to know how best to sample and analyze these compounds. The main objective of this research was to compare recoveries of a standard gas mixture of 11 odorous compounds from the Carboxen/PDMS 75-microm solid-phase microextraction fibers, polyvinyl fluoride (PVF; Tedlar), fluorinated ethylene propylene copolymer (FEP; Teflon), foil, and polyethylene terephthalate (PET; Melinex) air sampling bags, sorbent 2,b-diphenylene-oxide polymer resin (Tenax TA) tubes, and standard 6-L Stabilizer sampling canisters after sample storage for 0.5, 24, and 120 (for sorbent tubes only) hrs at room temperature. The standard gas mixture consisted of 7 volatile fatty acids (VFAs) from acetic to hexanoic, and 4 semivolatile organic compounds including p-cresol, indole, 4-ethylphenol, and 2'-aminoacetophenone with concentrations ranging from 5.1 ppb for indole to 1270 ppb for acetic acid. On average, SPME had the highest mean recovery for all 11 gases of 106.2%, and 98.3% for 0.5- and 24-hr sample storage time, respectively. This was followed by the Tenax TA sorbent tubes (94.8% and 88.3%) for 24 and 120 hr, respectively; PET bags (71.7% and 47.2%), FEP bags (75.4% and 39.4%), commercial Tedlar bags (67.6% and 22.7%), in-house-made Tedlar bags (47.3% and 37.4%), foil bags (16.4% and 4.3%), and canisters (4.2% and 0.5%), for 0.5 and 24 hr, respectively. VFAs had higher recoveries than semivolatile organic compounds for all of the bags and canisters. New FEP bags and new foil bags had the lowest and the highest amounts of chemical impurities, respectively. New commercial Tedlar bags had measurable concentrations of N,N-dimethyl acetamide and phenol. Foil bags had measurable concentrations of acetic, propionic, butyric, valeric, and hexanoic acids. 相似文献
64.
Two vegetation-monitoring methods were compared: subplot frequency analysis (SF) and visual estimation of percentage cover (VE). Two independent observers collected data from two semi-natural, species-rich grasslands on three different occasions during the growth-season. During the last data collection period, survey times were also recorded. The two different data sets from the two methods were compared using partial Redundancy Analyses. The purpose of the comparison was to identify the method that explains most of the relevant variation in biodiversity-monitoring (inter-and intra-site variation), and the variation irrelevant when evaluating data (systematic inter-observer variation and variation due to phenological changes). Compared with VE data, more variation in SF data could be explained by spatial variables, while less variation depended on the observer and time of year surveyed. SF also found more species per plot but took on average five times longer to complete than VE. In conclusion, the different methods are suitable for different purposes: SF is more suitable for purposes demanding high accuracy and high precision, such as long-term biodiversity-monitoring when the identification of small changes has high priority, while VE might be more suitable for a one-time mapping of a large area. 相似文献
65.
Jacquelyn L. Gill Jessica L. Blois Blas Benito Solomon Dobrowski Malcolm L. Hunter Jr. Jenny L. McGuire 《Conservation biology》2015,29(3):640-648
Climate change will require novel conservation strategies. One such tactic is a coarse‐filter approach that focuses on conserving nature's stage (CNS) rather than the actors (individual species). However, there is a temporal mismatch between the long‐term goals of conservation and the short‐term nature of most ecological studies, which leaves many assumptions untested. Paleoecology provides a valuable perspective on coarse‐filter strategies by marshaling the natural experiments of the past to contextualize extinction risk due to the emerging impacts of climate change and anthropogenic threats. We reviewed examples from the paleoecological record that highlight the strengths, opportunities, and caveats of a CNS approach. We focused on the near‐time geological past of the Quaternary, during which species were subjected to widespread changes in climate and concomitant changes in the physical environment in general. Species experienced a range of individualistic responses to these changes, including community turnover and novel associations, extinction and speciation, range shifts, changes in local richness and evenness, and both equilibrium and disequilibrium responses. Due to the dynamic nature of species responses to Quaternary climate change, a coarse‐filter strategy may be appropriate for many taxa because it can accommodate dynamic processes. However, conservationists should also consider that the persistence of landforms varies across space and time, which could have potential long‐term consequences for geodiversity and thus biodiversity. 相似文献
66.
67.
Meine van Noordwijk Robin Matthews Fahmuddin Agus Jenny Farmer Louis Verchot Kristell Hergoualc’h Sebastian Persch Hesti Lestari Tata Betha Lusiana Atiek Widayati Sonya Dewi 《Mitigation and Adaptation Strategies for Global Change》2014,19(6):887-905
Tropical peatlands are known not only for their high, area-based, carbon emissions in response to land-use change but also as hot spots of debate about associated data uncertainties. Perspectives are still evolving on factors underlying the variability and uncertainty. Debate includes the ways of reducing emissions through rewetting, reforestation and agroforestry. A knowledge value-chain that is long and complex links (a) fundamental understanding of peat and peatland processes leading to sciencebased quantification and default values, (b) willingness and (c) ability to act towards emission reduction, and ultimately (d) to local, national and global actions that effectively provide rules, incentives and motivation to conserve peat and reduce emissions. We discuss this value chain, its stakeholders and issues that still remain partially unresolved. We conclude that, to shorten the denial and conspiracy-theory stages of debate that otherwise slow down steps B and C, networks of international and national scientists have to be involved at the early stage of identifying policysensitive environmental issues. Models span part of the knowledge value-chain but transition of analysis units requires specific attention, from soil volumes through area and commodity flows to opportunities for reductions. While drainage of peatlands triggers landscape-scale increases in emissions, factors beyond drainage depth, including nutrient supply, may have a major influence on decomposition rates. Attempts to disentangle the contributions of plant and peat-based respiration in surface flux measurements involve assumptions that cannot be easily verified in comparisons between land uses. With progress on A leading to new internationally accepted defaults and with resistance on step B reduced, the reality of C and lack of working solutions for D is currently constraining further progress. 相似文献
68.
Sara H. Williams Sarah A. Scriven David F. R. P. Burslem Jane K. Hill Glen Reynolds Agnes L. Agama Frederick Kugan Colin R. Maycock Eyen Khoo Alexander Y. L. Hastie John B. Sugau Reuben Nilus Joan T. Pereira Sandy L. T. Tsen Leung Y. Lee Suzika Juiling Jenny A. Hodgson Lydia E. S. Cole Gregory P. Asner Luke J. Evans Jedediah F. Brodie 《Conservation biology》2020,34(4):934-942
Conservation planning tends to focus on protecting species’ ranges or landscape connectivity but seldom both—particularly in the case of diverse taxonomic assemblages and multiple planning goals. Therefore, information on potential trade-offs between maintaining landscape connectivity and achieving other conservation objectives is lacking. We developed an optimization approach to prioritize the maximal protection of species’ ranges, ecosystem types, and forest carbon stocks, while also including habitat connectivity for range-shifting species and dispersal corridors to link protected area. We applied our approach to Sabah, Malaysia, where the state government mandated an increase in protected-area coverage of approximately 305,000 ha but did not specify where new protected areas should be. Compared with a conservation planning approach that did not incorporate the 2 connectivity features, our approach increased the protection of dispersal corridors and elevational connectivity by 13% and 21%, respectively. Coverage of vertebrate and plant species’ ranges and forest types were the same whether connectivity was included or excluded. Our approach protected 2% less forest carbon and 3% less butterfly range than when connectivity features were not included. Hence, the inclusion of connectivity into conservation planning can generate large increases in the protection of landscape connectivity with minimal loss of representation of other conservation targets. 相似文献
69.
Jenny Ivner Anna Elisabeth Björklund Karl-Henrik Dreborg Jessica Johansson Per Viklund Hans Wiklund 《Local Environment》2013,18(2):105-120
This article presents a model for local energy planning and its application in a full-scale experiment in a Swedish municipality. The model is based on legal requirement, research findings and standards of good practice and includes a combination of analytical and procedural tools intended to support rational decision-making: external scenarios, a citizens’ panel, life cycle analysis and qualitative environmental assessment (EA). The application of the model indicates that the decision-support tools selected can give several new and valuable inputs to local energy planning, such as local knowledge and values through citizen dialogue and comprehensive EAs. However, the experiment also shows that there are several challenges involved in applying the tools, for example, it is difficult to get citizens and the industry to participate and that it is complicated to combine several different tools for decision-making into a single planning process. Moreover, the experiences from the application suggest that the model for local energy planning show great potential but needs to be improved before it can be used as a standard of good practice. 相似文献
70.
Jenny Palm 《Local Environment》2013,18(4):445-457
Abstract Case studies of two Swedish municipalities indicate that the general energy area was divided into three independent policy areas: one dealing with supply, one with conservation and one with environmental questions related to the Agenda 21 vision of an ecologically sustainable energy system. However, the dominant energy policy area in the municipalities was supply policy. This article discusses why supply policy is dominant and the consequences of this for energy system development. Analysis of this pattern reveals that powerful actors, such as local energy companies, were able to mobilize support for supply policies, not least because they owned the energy plants and distribution networks. These actors were also represented in many different decision arenas; in contrast, actors representing the other energy policy areas often lacked power and resources, and were represented in only a few decision arenas. 相似文献