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排序方式: 共有381条查询结果,搜索用时 15 毫秒
371.
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373.
Wilhelm Von Sander 《Die Naturwissenschaften》1957,44(19):504-506
374.
H. Borchert H. Seilkopf H. Musso G. Schramm Hans Ulrich 《Die Naturwissenschaften》1955,42(11):351-352
375.
Photosynthetic rates of benthic marine algae in relation to light intensity and seasonal variations 总被引:4,自引:0,他引:4
The effect of light intensity on rate of photosynthesis was measured at irregular intervals over a 12-month period for 22 benthic marine algae in the western Baltic Sea. In most species photosynthesis (mg O2·g dry weight-1·h-1) was highest in spring and summer, corresponding to the seasonal growth pattern of the algae. In winter all the species showed adaptation of the light compensation point. Highest productivity was shown by algae which are: short-lived annual species rather than perennials, eulittoral rather than sublittoral, and which possess sheet-like or filamentous thalli rather than coarsely branched forms. These factors are clearly inter-related.This research was carried out while one of us (R.J.K.) was an Alexander von Humboldt fellow at the University of Kiel, and is part of the programme Sonderforschungsbereich 95, Wechselwirkung Meer-Meeresboden, Universität Kiel. 相似文献
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377.
Ivonne Bedei Tascha Gehrke Karl-Philipp Gloning Matthias Meyer-Wittkopf Daria Willner Martin Krapp Alexander Scharf Jan Degenhardt Kai-Sven Heling Peter Kozlowski Kathrin Trautmann Kai M. Jahns Annegret Geipel Jan-Erik Baumüller Lucas Wilhelm Ingo Gottschalk Andreas Schröer Alexander Graf Aline Wolter Johanna Schenk Axel Weber Ignatia B. Van den Veyver Roland Axt-Fliedner 《黑龙江环境通报》2023,43(2):192-206
Objective
We aimed to investigate how the presence of fetal anomalies and different X chromosome variants influences Cell-free DNA (cfDNA) screening results for monosomy X.Methods
From a multicenter retrospective survey on 673 pregnancies with prenatally suspected or confirmed Turner syndrome, we analyzed the subgroup for which prenatal cfDNA screening and karyotype results were available. A cfDNA screening result was defined as true positive (TP) when confirmatory testing showed 45,X or an X-chromosome variant.Results
We had cfDNA results, karyotype, and phenotype data for 55 pregnancies. cfDNA results were high risk for monosomy X in 48/55, of which 23 were TP and 25 were false positive (FP). 32/48 high-risk cfDNA cases did not show fetal anomalies. Of these, 7 were TP. All were X-chromosome variants. All 16 fetuses with high-risk cfDNA result and ultrasound anomalies were TP. Of fetuses with abnormalities, those with 45,X more often had fetal hydrops/cystic hygroma, whereas those with “variant” karyotypes had different anomalies.Conclusion
Both, 45,X or X-chromosome variants can be detected after a high-risk cfDNA result for monosomy X. When there are fetal anomalies, the result is more likely a TP. In the absence of fetal anomalies, it is most often an FP or X-chromosome variant. 相似文献378.
379.
Geyer HJ Schramm KW Feicht EA Behechti A Steinberg C Brüggemann R Poiger H Henkelmann B Kettrup A 《Chemosphere》2002,48(6):631-644
The elimination half-lives (t1/2) in Sprague-Dawley rats for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 1,2, 3,7,8-pentachlorodibenzo-p-dioxin (PeCDD), 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin (HxCDD), 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD) and 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin (OCDD) were estimated in long-term studies by Schlatter, Poiger and others. Furthermore, there are some published half-lives of TCDD in adult humans. The average half-life of TCDD in adult humans is approximately 2840 days, while in Sprague-Dawley rats the average t1/2 of TCDD is 19 days. The t1/2 of TCDD in humans is about 150 times that of rats. This factor was used to calculate the t1/2 values of the other polychlorinated dibenzo-p-dioxins (PCDDs) in humans from the rat data. Furthermore, the terminal t1/2 values of PCDDs in adult humans were calculated from the regression equation: logt1/2H = 1.34 logt1/2R + 1.25 which was recently established for 50 xenobiotics (t1/2H = terminal half-lives in days for humans, t1/2R = terminal half-lives in days for rats). The following terminal half-lives in adult humans were obtained: 12.6 years for 1,2,3,7,8-PeCDD, 26-45 years for 1,2,3,4,7,8-HxCDD, 80-102 years for 1,2,3,4,6,7,8-HpCDD and ca. 112-132 years for OCDD. These half-lives of PCDDs are critically compared with measured t1/2 values of PCDDs and other persistent organic pollutants in rats, monkeys and humans. 相似文献
380.
In the present study 83 finished drinking water samples from 50 cities in Germany were analyzed for methyl tert-butyl ether (MTBE) content with a detection limit of 10 ng/L. The detection frequency was 46% and the concentrations ranged between 17 and 712 ng/L. Highest concentrations were found in the community water systems (CWSs) of Leuna and Spergau in Saxony-Anhalt. These CWSs are supplied with water possibly affected by MTBE contaminated groundwater. MTBE was detected at concentrations lower than 100 ng/L in drinking water supplied by CWSs using bank filtered water from Rhine and Main Rivers. The results from Leuna and Spergau show that large groundwater contaminations in the vicinity of CWSs pose the highest risk for MTBE contamination in drinking water. CWSs using bank filtered water from Rhine and Main Rivers are susceptible to low MTBE contaminations in finished drinking water. All measured MTBE concentrations were below proposed limit values for drinking water. 相似文献