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排序方式: 共有4216条查询结果,搜索用时 609 毫秒
481.
Yifat Ochshorn Michael J. Kupferminc Amiram Eldor Igal Wolman Joseph B. Lessing Yuval Yaron 《黑龙江环境通报》2001,21(8):658-661
Obstetric complications, such as severe pre-eclampsia, fetal growth restriction, abruptio placentae, or stillbirth are associated with abnormally elevated second-trimester maternal serum alpha-fetoprotein (MSAFP) and β subunit of human chorionic gonadotrophin (βhCG). This has been attributed to placental abnormalities. Women with thrombophilias have been shown to have abnormalities of the placenta resulting in adverse pregnancy outcome in these patients. The purpose of the present study was to evaluate whether women with pregnancy complications and inherited thrombophilias have abnormally elevated second-trimester MSAFP or βhCG. Sixty-two women with pregnancy complications were tested for inherited thrombophilias several months after delivery. The thrombophilia group included 29 women with pregnancy complications and an inherited thrombophilia and the control group included 33 other patients without thrombophilia. Patients in the thrombophilia group had a higher median MoM MSAFP compared to the controls (1.337 vs 1.086, p=0.0516). The incidence of abnormally elevated MSAFP (>2.5 MoM) was also significantly higher in the thrombophilia group compared to controls (21% vs 3%, p=0.04). Neither the median MoM βhCG nor the incidence of abnormally elevated βhCG were significantly different between the groups. We conclude that second trimester MSAFP, but not βhCG, is abnormally elevated in patients with thrombophilia and obstetric complications. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Martin Drechsler Karin Johst Frank W?tzold Michael I Westphal 《Ecological applications》2006,16(5):1959-1966
Flexible conservation management, where measures (e.g., mowing of meadows, removing invasive species) are selected in each decision period depending on the current state of the ecological system, is generally perceived as superior to fixed management, where the same measure is applied in each decision period independent of the current state of the system. In past comparisons of fixed and flexible conservation strategies the additional costs that arise only in flexible strategies have usually been ignored. In this paper, we present a framework to integrate costs of flexible management into the evaluation of flexible conservation strategies. Using the example of an endangered butterfly species we demonstrate that the costs of flexible management may reverse the rank order of flexible and fixed conservation strategies, such that fixed strategies may lead to better ecological results than flexible ones for the same financial budget. 相似文献
485.
The persistence of pharmaceuticals, hormones, and household and industrial chemicals through a pure-oxygen activated sludge, nitrification, denitrification wastewater treatment facility was evaluated. Of the 125 micropollutants that were tested in this study, 55 compounds were detected in the untreated wastewater, and 27 compounds were detected in the disinfected effluent. The persistent compounds included surfactants, fire-retardant chemicals, pesticides, fragrance compounds, hormones, and one pharmaceutical. Physical-chemical properties of micropollutants that affected partitioning onto wastewater solids included vapor pressure and octanol-water partition coefficients. 相似文献
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Michael C. Osborne 《Environment international》1989,15(1-6)
Significantly elevated radon concentrations were found in several adjacent houses in Clinton, New Jersey. The United States Environmental Protection Agency screened 56 of the houses and selected 10 for demonstration of radon-reduction techniques. Each of the 10 houses received an intensive radon diagnostic evaluation before a house-specific radon reduction plan was developed. Depressurization effects caused by temperature differentials and the operation of mechanical equipment were quantified. Before and after radon reduction plans were implemented, radon concentrations were determined by charcoal canisters and continuous radon monitors. A variety of sealing and subslab depressurization techniques were applied to the 10 houses. Radon concentrations were reduced by over 95% in all 10 houses. The cost of applying radon reduction techniques ranged from $1500 to $8500 per house. House construction characteristics were described which contributed to the high cost of radon reduction. In summary, the 10-house radon reduction demonstration in Clinton, New Jersey was successful in showing homeowners with similar house types some effective ways of reducing radon concentrations. 相似文献
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Several factors thought to be important for the evolution of cooperative breeding in vertebrates have received little attention
in facultatively social insects. One of these, the “habitat saturation hypothesis” of Selander (1964), predicts that colony
sizes will be greater in breeding units where dispersal opportunities are limited, suggesting that group living is a secondary
option to independent reproduction. The Australian allodapine bee Exoneura bicolor exhibits a number of traits that occur in cooperatively breeding bird species, including long life-span, repeated opportunities
for reproduction, and vulnerability to brood predation and parasitism. We experimentally examined the effect of a potentially
limiting environmental factor, nesting substrate availability, as an agent influencing sociality in E. bicolor. We manipulated nesting substrate availability in two separate locations during a time when foundress dispersal is common.
No significant difference was found between colony sizes in cases where dispersal options were abundant and cases where dispersal
options were limited. An increase in opportunities for dispersal did not lead to higher rates of independent nesting, suggesting
that cooperative nesting is a preferred strategy regardless of distance-related costs of dispersal. Reproductivity per female
and brood survival were examined as factors selecting for group living. Low survival of brood in single-female nests has the
potential to select for cooperative nesting in this bee.
Received: 29 September 1995/Accepted after revision: 24 June 1996 相似文献