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191.
The Science of Nature - The proposed model for a ‘realistic hypercycle’ is closely associated with the molecular organization of a primitive replication and translation apparatus.... 相似文献
192.
This article considers the growth in stockpiles of natural and enriched uranium, which have now reached such significant proportions and analyses the effect that the stockpiles might have on the market for natural uranium in the coming years. While stockpiles have not yet reached their peak in absolute terms, they have already passed it in relative terms, ie in multiples of annual demand. 相似文献
193.
Manfred Stock 《Environmental Sciences Europe》2004,16(2):115-124
Some case studies are described to show progress, potentials and limits of present day climate impact research. The examples given cover impacts on Lakes worldwide, Europe's cost lines, landscapes in the USA, South America and in Germany and on the people living there. Forecasts using not only future scenarios of climatic but of socieal change as well are rare. It is rather state of the art to use future climate scenarios to analyse the vulnerability of today's regional structures. The objective is to identify weak points and measures to eliminate them. Mostly the analysis is based on the consideration of global climate scenarios on one hand and regionally specific economic patterns on the other. But now regionalized climate models and scenarios are used more and more to describe climate change. In most impact studies more accurate and concrete results are obtained and this is demonstrated in the Brandenburg study. 相似文献
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James P. Bennett Robert L. Anderson Manfred L. Mielke James J. Ebersole 《Environmental monitoring and assessment》1994,30(3):247-274
A thorough review and critical evaluation of field surveys from 1900 to the present of foliar injury to Pinus strobus L. supposedly caused by air pollution was undertaken. Ninety percent of the surveys failed to meet current scientific standards of acceptability. The conduct and peer review of surveys has been poor and the correct injury symptoms have not always been used. Data were obtained for nine that met screening criteria and injury incidence and severity were mapped. Three fourths of the counties in the natural and planted range of eastern white pine have not been scientifically surveyed, so generalizations regarding large-scale spatial patterns of eastern white pine foliar pathological conditions were not possible. However, recent growth and inventory data indicate that growth throughout the natural range regardless of air pollution or other stresses (e.g. blister rust) is excellent, suggesting that regional performance and foliar conditions are unrelated. Sufficient compelling corroborative evidence was found to conclude that a general decline of eastern white pine throughout its range is not a tenable finding.The putative air pollution sensitivity of eastern white pine appears to be based on studies published between 1963 and 1973 on hypersensitive individuals that are no longer being observed in the field. More recent research on eastern white pine has noted a lack of sensitivity and/or high variability of response. The idea that eastern white pine as a species is highly sensitive to air pollution is no longer supported by the available evidence. However, hypersensitive juvenile individuals comprising no more than 8–9% of the total population may still germinate and grow for a brief period of time (because old enough parent trees are still alive) but soon succumb to current levels of ozone and sulfur dioxide in the environment or are suppressed by tolerant neighbors. This phenomenon has been documented anecdotally and is more aptly called tree decline instead of forest decline. An emerging working hypothesis to explain recent reports of unusual eastern white pine tolerance is that sufficient time has elapsed for tree decline to have occurred leading to a gradual elimination of sensitive genotypes from populations. 相似文献
196.
Manfred Niecke Andreas Krüger Peter Hauff Hermann Ellenberg Ralph Labes und Susanne Niecke 《Umweltwissenschaften und Schadstoff-Forschung》1998,10(1):3-14
Zusammenfassung Mit der Hamburger Protonenmikrosonde untersuchen wir den Quecksilbergehalt in Seeadlerfedern, die in Mecklenburg-Vorpommern
über Jahrzehnte gesammelt wurden. Anhand der Fundorte und Funddaten ist es m?glich, ein zeitliches und regional differenziertes
Bild der Quecksilberbelastung, die vorwiegend durch Hg-halrige Saargutbeizen in der Landwirtschaft verursacht wurden, zu erstellen.
Wir vergleichen die gefundenen Konzentrationen mit der ‘geogenen’ Grundbelastung, die an Federproben des vorigen Jahrhunderts
von Museumstieren ermittelt wurde.
相似文献
197.
Gerd Bauer Manfred Deistler Andreas Gleiß Emmanuel Glenck Thomas Matyus 《Environmental science and pollution research international》1997,4(2):105-112
Material Flow Analysis (MFA) has become an important instrument in environmental science and pollution research. In this paper, we look at the MFA problem as a particularly structured system identification problem. Special emphasis is given to the linear, static case, where we describe a procedure for reconciliating the flow measurements and for estimating the unmeasured flows and the transfer coefficients by taking into account a priori restrictions such as balance equations. 相似文献
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