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排序方式: 共有252条查询结果,搜索用时 31 毫秒
41.
Dr Theresa M. Marteau Rachel Cook Jane Kidd Susan Michie Marie Johnston Joan Slack Robert W. Shaw 《黑龙江环境通报》1992,12(3):205-214
The purpose of the study was to describe the impact of false-positive results from initial maternal serum alpha-fetoprotein (MS-AFP) screening. The analyses compared two groups of women, those receiving a negative result (n = 346) and those receiving an initial positive result (n = 26), over four time points—prior to testing, immediately after testing, later in pregnancy, and in the post-partum period. Receiving an abnormal result was associated with high levels of anxiety which were reflected in increased worry about the baby's health and a more negative attitude towards the pregnancy and the baby. Women who had an initial abnormal result were offered a variety of further tests. Those women who went on to have amniocentesis were less worried about their baby's health in the third trimester and also less anxious post-partum than those who did not have amniocentesis. In view of the increasing number of screening tests available, it is necessary to establish whether and how these levels of distress can best be reduced. 相似文献
42.
Graeme J Inglis Helen Hurren John Oldman Rachel Haskew 《Ecological applications》2006,16(4):1377-1390
Eradication and control of invasive species are often possible only if populations are detected when they are small and localized. To be efficient, detection surveys should be targeted at locations where there is the greatest risk of incursions. We examine the utility of habitat suitability index (HSI) and particle dispersion models for targeting sampling for marine pests. Habitat suitability index models are a simple way to identify suitable habitat when species distribution data are lacking. We compared the performance of HSI models with statistical models derived from independent data from New Zealand on the distribution of two nonindigenous bivalves: Theora lubrica and Musculista senhousia. Logistic regression models developed using the HSI scores as predictors of the presence/absence of Theora and Musculista explained 26.7% and 6.2% of the deviance in the data, respectively. Odds ratios for the HSI scores were greater than unity, indicating that they were genuine predictors of the presence/ absence of each species. The fit and predictive accuracy of each logistic model were improved when simulated patterns of dispersion from the nearest port were added as a predictor variable. Nevertheless, the combined model explained, at best, 46.5% of the deviance in the distribution of Theora and correctly predicted 56% of true presences and 50% of all cases. Omission errors were between 6% and 16%. Although statistical distribution models built directly from environmental predictors always outperformed the equivalent HSI models, the gain in model fit and accuracy was modest. High residual deviance in both types of model suggests that the distributions realized by Theora and Musculista in the field data were influenced by factors not explicitly modeled as explanatory variables and by error in the environmental data used to project suitable habitat for the species. Our results highlight the difficulty of accurately predicting the distribution of invasive marine species that exhibit low habitat occupancy and patchy distributions in time and space. Although the HSI and statistical models had utility as predictors of the likely distribution of nonindigenous marine species, the level of spatial accuracy achieved with them may be well below expectations for sensitive surveillance programs. 相似文献
43.
Indirect Effects of Feral Horses on Estuarine Communities 总被引:1,自引:1,他引:1
Phillip S. Levin ‡ Julie Ellis Rachel Petrik Mark E. Hay† 《Conservation biology》2002,16(5):1364-1371
44.
Rachel?G.?Ravago-GotancoEmail author Marie?Antonette?Juinio-Me?ez 《Marine Biology》2004,145(4):789-801
The milkfish, Chanos chanos (Forsskål, 1775) is a pelagic, monotypic gonorhynchiform widely distributed in the tropical Indo-Pacific. This study evaluates temporal variability of milkfish samples from the Philippine archipelago, and spatial variability at two geographic scales based on restriction fragment length polymorphism (RFLP) analysis of a portion of the mitochondrial control region. High levels of genetic diversity characterize the milkfish control region (mean h=0.908, =1.59%), with 74 haplotypes detected among the 367 fish analyzed. For temporal analysis of Philippine samples, milkfish were collected over 2 years from three sites (inter-annual variation), and sampled twice within a year during different seasons at four sites (intra-annual variation). No significant temporal variability was detected between or within years. Significant spatial differentiation among the Philippine samples was observed (FST=0.006, P<0.05), with two northeastern samples, Claveria and Dingalan, found to be genetically distinct. However, an hierarchical analysis of molecular variance (AMOVA), where samples were grouped into four geographic regions, revealed very low levels of genetic partitioning, with less than 1% of the total variation attributed to between-region differences, and lack of genetic structure. Nonetheless, the existence of putative northeastern Philippine populations is not discounted. Strong genetic structure across broad geographical scales was revealed by AMOVA, with 11% of the molecular variance based on haplotype frequencies allocated between three distinct groups: Indian Ocean, west Pacific (Philippines) and north central Pacific (Hawaii) The broad-scale genetic structure points to limited gene flow among disjunct Indo-Pacific populations.Communicated by T. Ikeda, Hakodate 相似文献
45.
Orientation can be difficult for nocturnal bird migrants at high northern latitudes because of the large changes of magnetic
declinations, rapid longitudinal time-shifts experienced during a long-distance flight and the invisibility of stars during
the polar summer. Both sunset cues as well as geomagnetic cues have been shown to be of great importance in the orientation
system of Savannah sparrows, Passerculus sandwichensis. We used clock-shift experiments to investigate whether geomagnetic and sunset cues were used for migratory orientation by
wild-caught young Savannah sparrows at high geomagnetic latitudes in Northern Canada. We exposed birds to a 4-h slow clock-shift,
expecting a 60° clock-wise shift in orientation after the treatment. Under natural clear skies in the local geomagnetic field,
the birds responded by showing a significant axial mean orientation directed towards the position of the setting sun in the
NW and towards their preferred migratory direction in the SE. After exposure to the clock-shift for 6 days and nights the
birds showed a clear response to the treatment and shifted significantly towards NNE. Birds that first oriented towards NW
in the experiments before clock-shift tended to shift clock-wise, thus reacted to the clock-shift in the expected way. The
reaction of the individual birds that originally oriented towards SE seems to vary. In summary, our birds did not select a
constant angle (menotaxis) in relation to the sun's position during the experiments, but presumably were affected by the sun
showing phototaxis or followed their magnetic compass. Possible explanations of the unexpected experimental results are discussed.
Electronic Publication 相似文献
46.
Rachel Vallender Vicki L. Friesen Raleigh J. Robertson 《Behavioral ecology and sociobiology》2007,61(12):1797-1807
We examined two components of reproduction in a population of golden-winged warblers in the initial stages of hybridization
with blue-winged warblers. First, we used genetic analyses of mate choice to determine whether copulations outside the social
pairbond (extra-pair copulations; EPCs) occur in these species and their hybrids. Second, we compared several aspects of reproduction
(pairing success, clutch size, hatching success, fledging success, and loss of paternity) in nests raised by phenotypic golden-winged
warblers to those raised by hybrid individuals. Together, these data provide us with the first quantitative analysis of reproduction
within this hybrid system. Our data suggest several reasons why the level of hybridization between these species is likely
being underestimated. First, many birds in our population showed only subtle phenotypic signs of introgression indicating
that hybrid status can only be determined by close examination. Second, high rates of extra-pair paternity indicate that we
cannot base our estimates of hybridization on pairbond data alone. More than 30% of nestlings were the result of EPCs, occurring
in 55% of all nests. Third, there was no difference in the number of hybrid or “pure” golden-winged warbler males chosen as
social mates, relative to their abundance. Indeed, based on several components of nesting success, it appears as though hybrids
are having as great realized reproductive success as are phenotypic golden-winged warblers in our population. Accordingly,
we argue that hybrid reproductive success and extra-pair fertilizations are likely playing a major role in the ongoing hybridization
between blue-winged and golden-winged warblers. Studies such as this one are important to our understanding of the process
and implications of hybridization, and findings may be applicable to other hybrid zones. 相似文献
47.
Central nervous system anomalies in trisomy 18 are usually confined to structural abnormalities of brain development. Despite the recognized association of neural tube defects and trisomy 18, primary (true) anencephaly is uncommon in the classical trisomy 18 phenotype. A case of anencephaly with trisomy 18, diagnosed prenatally, is presented with a review of the literature of this association. 相似文献
48.
Rachel Kulick 《Local Environment》2019,24(1):37-51
There is increased attention to alternative food efforts as individuals and groups seek to build stronger local food infrastructures to increase accessibility, transparency, and fairness with how food is grown, produced, and distributed. In considering individuals and families contending with food injustices and insecurities; concerns and questions have surfaced about what it means to privilege the leadership and participation of these communities in alternative food efforts. While there are no linear answers to these questions, this paper explores how one statewide food network in the United States seeks to involve youth contending with the juvenile justice system in a job readiness programme, Youth Kitchen, that interfaces the youth with farmers, chef educators, community organisations, and farmers markets. This paper contends that integrating alternative food and juvenile justice work is a complex terrain that both advances social justice and reproduces existing power asymmetries within alternative food networks. The inclusion of accounts from multiple stakeholders in the local food and juvenile justice system generates a multilayered view that moves away from an either sustainability or social justice rubric to a more process-oriented lens that reveals the strategic dilemmas that alternative food networks encounter. On the one hand, the social landscape of this programme promotes an ethic of care and shared ownership between the staff and participating youth. At the same time, akin to many alternative food networks, neoliberal interests bump against this ethic of care and white privilege seeps into staffing patterns and everyday programmes in ways that reproduce the status quo. 相似文献
49.
Rachel Morrow Paula Brough 《International journal of occupational safety and ergonomics》2019,25(3):467-475
Purpose. Person–environment fit asserts that incompatibility between an employee and aspects of their work environment is more likely to lead to occupational stress. The aim of this study was to investigate the impact that varying levels of person–environment fit had on key criterion outcomes including work engagement, work-related wellbeing and turnover intentions in a unique sample of managerial and administrative mining personnel. Method. An online self-report survey was distributed to an Australian mining organization by the company’s Chief Executive Officer. Anonymous survey links were sent to staff, of which 118 participants responded. The survey consisted of previously validated measures. Results. Hierarchical multiple regression analyses revealed significant relationships between abilities–demand fit, needs–supply fit and work engagement. Additionally, work-related wellbeing was significantly associated with increased person–organization fit and needs–supply fit. However, only needs–supply fit had a significant negative relationship with turnover intentions. Needs–supply fit significantly predicted all criterion variables. Conclusions. This study found that personal need fulfilment through work-related activities had the most significant impact on work-related wellbeing and work engagement. Personal need fulfilment through work also produced the most significant negative relationship with turnover intentions. 相似文献
50.