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排序方式: 共有409条查询结果,搜索用时 15 毫秒
261.
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Ying Li Godelieve C. M. L. Page-Christiaens Johan J. P. Gille Wolfgang Holzgreve Sinuhe Hahn 《黑龙江环境通报》2007,27(1):11-17
Achondroplasia is the most common form of short-limbed dwarfism in humans and is caused by mutations in the FGFR3 gene. Currently, prenatal diagnosis of this disorder relies on invasive procedures. Recent studies have shown that fetal single gene point mutations could be detected in cell-free DNA (cf-DNA) from maternal plasma by either the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) assay with single allele base extension reaction (SABER) approach or the size fractionation of cf-DNA in maternal plasma. Here, we combined the two approaches to non-invasively examine the fetal G1138A mutation in maternal plasma. cf-DNA was extracted from maternal plasma samples obtained from two pregnant women at risk for achondroplasia. The fetal G1138A mutation was determined by the analysis of size-fractionated cf-DNA in maternal plasma using MALDI-TOF MS with SABER approach and homogenous MassEXTEND (hME) assay, respectively. The fetal G1138A mutation was detectable in the two achondroplasia-affected pregnancies by the analysis of cf-DNA in maternal plasma using MALDI-TOF MS. However, the size-fractionation approach led to a more precise detection of the fetal mutation in both analyses. This analysis would be suitable for non-invasive prenatal diagnosis of diseases caused by fetal single gene point mutations. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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An isobole-based statistical model and test for synergism/antagonism in binary mixture toxicity experiments 总被引:4,自引:0,他引:4
Helle Sørensen Nina Cedergreen Ib M. Skovgaard Jens C. Streibig 《Environmental and Ecological Statistics》2007,14(4):383-397
Synergism and antagonism are often defined in relation to the model of Concentration Addition (CA). Hence, it is vital for
the conclusion of mixture toxicity studies to be able to test whether an observed deviation from CA reflects a true deviation
or whether it is simply due to random variation. In this paper we consider a non-linear regression model for the classical
ray designs for binary mixture experiments. The model combines dose–response curves for each mixture in the experiment with
an isobole model, describing possible deviations from CA. The method allows us to test whether the chosen isobole model is
reasonable for the data and to test the hypothesis of CA. Furthermore, it provides us with a measure of the degree of synergism/antagonism.
The method is flexible since both the dose–response relationships and the isobole model can be chosen arbitrarily. We demonstrate
the use of the method on datasets where combinations of pesticides are tested on a floating plant, Lemna minor, and an algae, Pseudokirchneriella subcapitata. Furthermore, we conduct a simulation study in order to explore the power with which a specific deviation from CA can be
distinguished in different test-systems. 相似文献
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Hanne Marie Kvamsdal Jens Hetland Geir Haugen Hallvard F. Svendsen Fredrik Major Vemund Kårstad Göran Tjellander 《International Journal of Greenhouse Gas Control》2010,4(4):613-622
A post-combustion CO2 capture process intended for offshore operations has been designed and optimised for integration with a natural gas-fired power plant on board a floating structure developed by the Norway-based company Sevan Marine ASA—designated Sevan GTW (gas-to-wire). The concept is constrained by the structure of the floater carrying a SIEMENS modular power system rated at 450 MWe, with a capture rate of 90% and CO2 compression (1.47 Mtpa) for pipeline pressure at 12 MPa. A net efficiency of 45% (based on a lower heating value) is estimated for the system with CO2 capture, thus suggesting that the post-combustion CO2 capture system is accountable for a fuel penalty of nine percentage points.The rationale behind the technology selection is the urgency of replacing the dispersed aero-derivative gas turbines which power the offshore oil and gas production units in Norwegian waters with near-zero emission power.As (inherently) fresh water usually constitutes a limiting factor in sea operations, efforts are made to obtain a neutral water balance to obtain an optimal design. This is primarily achieved by controlling the cleaned flue gas temperature at the top of the absorber column. 相似文献
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Tobias Hahn Frank Figge Andrea Liesen Ralf Barkemeyer 《Journal of environmental management》2010,91(10):1997-2007
In this paper, we propose the return-to-cost-ratio (RCR) as an alternative approach to the analysis of operational eco-efficiency of companies based on the notion of opportunity costs. RCR helps to overcome two fundamental deficits of existing approaches to eco-efficiency. (1) It translates eco-efficiency into managerial terms by applying the well-established notion of opportunity costs to eco-efficiency analysis. (2) RCR allows to identify and quantify the drivers behind changes in corporate eco-efficiency. RCR is applied to the analysis of the CO2-efficiency of German companies in order to illustrate its usefulness for a detailed analysis of changes in corporate eco-efficiency as well as for the development of effective environmental strategies. 相似文献
270.
Regime shift in a coastal marine ecosystem 总被引:1,自引:0,他引:1
Jens Kjerulf Petersen Jens Würgler Hansen Martha Brogaard Laursen Preben Clausen Jacob Carstensen Daniel J Conley 《Ecological applications》2008,18(2):497-510
We demonstrate changes in ecosystem stable states in a coastal lagoon that are consistent with what a regime shift would hypothesize. In the nutrient-stressed Ringk?bing Fjord, Denmark, a small change in one variable (salinity) facilitated by a change in sluice management, caused a sudden regime shift from a bottom-up controlled turbid state, into a top-down controlled clear-water state. The change in dominating pathway of organic matter production from pelagic turnover to benthic-pelagic coupling was facilitated by new recruitment and growth of existing suspension-feeding clams, Mya arenaria. With the invasion of clams, benthic grazing became the key feature of the biological structure. Phytoplankton composition and zooplankton abundance were also affected by the change in biological structure. The small, but sudden, increase in salinity caused by the change in sluice management led to a dramatic reduction in biomass and coverage of benthic vegetation and thus affected herbivorous waterbird populations. In recent years, plant coverage has been increasing, as can be expected with increased water transparency. The regime shift has some major implications for coastal water management and revealed some conflicts between different types of nature and environmental protection legislation. 相似文献