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PD Dr Ingo Kennerknecht Gotthold Barbi Michael Wolf Mahmoud Djalali Dieter Grab Rainer Terinde Walther Vogel 《黑龙江环境通报》1993,13(10):929-944
An increasing number of cytogenetic prenatal diagnoses are performed on chorionic villus samplings. The accuracy of this method is influenced by chromosomal mosaicism, mostly confined to direct preparation methods. Especially those investigators who have experienced false-negative and false-positive findings propagate the combined use of direct and culture methods. Yet large collaborative studies have shown that in approximately two-thirds of diagnostic cases only one procedure is applied. Moreover, the accuracy of a cytogenetic investigation depends not only on the ontogenetic origin of the tissues investigated, but also on interacting factors such as the ‘a priori risk’ and the ‘predictive value of a cytogenetic finding’. On this basis a differentiated prenatal diagnostic procedure is discussed, including either sole short-term culture (STC), combined STC and long-term culture (LTC), primary amniocentesis (AC), or primary percutaneous umbilical blood sampling (PUBS). The predictive value of the cytogenetic diagnosis from CVS varies significantly dependent on the a priori risk of a chromosome aberration and, in the case of an abnormal karyotype, on the specific chromosome involved. A non-mosaic and ‘non-lethal’ trisomy detected in STC is highly representative of the embryo/fetus, but there are exceptions of limited predictive value, e.g., trisomy 18. Guided by the strategy of an optional follow-up by LTC, AC, or PUBS in 1317 successive CV samplings, we are not aware of a false-negative diagnosis, but probably had one false-positive diagnosis: 47,XXY after STC; 46,XY after LTC. When referring to the rate of fetuses with an unbalanced karyotype expected in the different indication groups, a relative increase of false-positive findings in the very-low-risk group (maternal age ⩽35 years of age) and of false-negative findings in the very-high-risk group (abnormal ultrasonographic findings) of pregnant women when only performing CVS becomes obvious. Because of this dilemma, AC or—especially in the latter group—PUBS might be primarily offered to these indication groups instead of CVS. 相似文献
217.
Dieter Lietze 《Journal of Loss Prevention in the Process Industries》1995,8(6):319-324
This paper describes the results of extensive research to determine the limit of safety against flame transmission for sintered metal flame arrester elements when stressed by a flashback in a fuel-gas/oxygen mixture and when stressed through a stabilized burning of a flowing mixture of fuel-gas and air and of fuel-gas and oxygen at the sintered metal element. On the basis of the results of these investigations, the limit of safety against flame transmission for sintered metal flame arrester elements can be estimated and the conditions for testing can be specified. An analysis of the protection of gas outlets on gas distribution lines for welding, cutting and allied processes has been carried out, resulting in recommendations for necessary changes to the regulations for testing of safety devices with sintered metal flame arrester elements, which should be made in the next revision of the corresponding technical regulations for acetylene installations and calcium carbide stores (TRAC), and the standards DIN 8521, EN 730 and ISO 5175. 相似文献
218.
The term ‘sustainable development’ is defined and discussed with regard to its significance and its application in the field of chemistry. This is presented using the synthetic organic chemistry as an example. A review of the history of chemistry indicates clearly the necessity for further developments in the course of concepts involving sustainability. Following the eras of bituminous coal tar and mineral oil in both of the two past centuries, a search for new raw materials and a reduction in the global ecotoxicological potential for danger is being strived for. Critical contemplations are mandatory in order to avoid making this term ‘persistence’ into a keyword. Consequently, one must take into consideration the field of research and development as well as reflecting about the classification of chemical and scientific research projects, and their political as well as social relationships. Aside from the new methods of synthesis, this will also require the formulation of other decision-relevant criteria. 相似文献
219.
Spranger Till Kunze Frank Gauger Thomas Nagel Dieter Bleeker Albert Draaijers Geert 《Water, Air, & Soil Pollution: Focus》2001,1(1-2):335-351
Critical load exceedances have been used as an effects-related parameter for guiding international air emission control negotiations. High-resolution critical load data are combined with low-resolution deposition data.This article shows that doing so systematicallyunderestimates `true' critical load exceedances as obtainedfrom combining critical load and deposition data of identicalhigh spatial resolution. 95th percentile critical loadexceedances in EMEP grids based on high resolution depositiondata are 60 and 150% higher (mean values for nutrientnitrogen and acidity, respectively) than critical loadexceedances based on the low resolution EMEP depositionmodel. The latter are used in international negotiations. Differences in individual EMEP grid squares vary betweeninsignificantly different from zero and 340%, depending onregional deposition and critical load characteristics andcritical load types (nutrient nitrogen versus acidity).Exceedances based on high-resolution deposition values arealso compared to EMEP grid averages of these values forforests only. This comparison excludes the effect ofsystematically higher depositions to forests. Still, thescale difference of (averaged, low-resolution) deposition and(high-resolution) critical loads data yields underestimatesof the 95th percentiles by on average ca. 20%.These systematic errors due to the scale dependence should beborne in mind when interpreting effects of internationalemission control measures. 相似文献
220.
Dieter Heylen Wendt Müller Ton G. G. Groothuis Erik Matthysen 《Behavioral ecology and sociobiology》2012,66(2):287-293
In birds as in many other taxa, parasites can have deleterious effects on offspring development. Therefore, avian mothers
have evolved responses to counteract parasite virulence in offspring via transgenerational defense mechanisms that is the
transfer of immune-enhancing substances such as antibodies to their eggs. Another maternal pathway is suggested by the finding
that infested great tit mothers produced eggs with lower androgens, since these yolk androgens are immunosuppressive and potentially
affect parasite susceptibility of the nestlings. However, whether this pathway is a specific adaptation to infestation with
parasites that affect the offspring or an epiphenomenon of lower androgen production in the female due to the parasite effects
on the mother itself is as yet unclear. In this study we infested female great tits (Parus major) with sheep ticks (Ixodes ricinus), which are nonnidicolous ectoparasites with low vertical transmission capability, and evaluated the effects on yolk androgen
deposition. Tick-infested females did not significantly reduce their deposition of androgens (androstenedione (A4) and testosterone) compared to tick-reduced females, which is in contrast to a previous study showing a lowered deposition
of A4 and testosterone when females were exposed to the nidicolous hen flea. Thus, females alter their hormone deposition, and
thus likely offspring phenotype, when exposed to parasites that also form the parasitic environment of their offspring, but
not when temporarily infested with the field-dwelling sheep ticks with low transmission capability. This suggests that selection
favored the evolution of an adaptive transgenerational effect by acting mainly on the parasite-induced maternal effect. 相似文献