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191.
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W. Götz 《Die Naturwissenschaften》1963,50(17):567-567
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A very dry climate which prevailed during the last glacial maximum of the Pleistocene from India to the Sahara, was replaced by variable weather conditions with alternating more or less humid phases, starting from the Pleistocene-Holocene transition period and lasting up to about 3000 years ago, when present arid conditions set in. A particularly wet phase is recognized throughout the region some 5000 years ago. Phase shifts within the region and in particular changes in rain distribution patterns, are interpreted as due to shifting spheres of influence of the monsoonal circulation, of Atlantic depressions and moisture originating from the Mediterranean Sea. The condition of the Mediterranean Sea itself, which is influenced by runoff and melt waters from the European Continent and by the Nile floods, as well as by the eustatic sea-level changes, is not a good indicator of local climate conditions. 相似文献
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Neither the “Green Revolution” in the developing countries nor “yield explosion” in the agricultural production of the industrialized nations have reached the genetic and physiologic limits of crop growth. Breeding of better varieties is still the most promising defense against hunger. The ambiguity of modern agroindustry throughout the world resides in its high dependence on the existence of functional technological, economical, and political systems.
相似文献198.
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Amniocentesis and subsequent tests are reported on a fetus conceived of a rare mating type: its mother has an intermediate level of β hexosaminidase A (HEX A), characteristic of carriers of Tay-Sachs disease (TSD), while the father suffers from an adult-onset GM2 ganglio-sidosis (AOG) with severe HEX A deficiency. Activity of HEX A in the cultured fetal cells was very low when measured by the heat-inactivation method, thus showing the typical biochemical phenotype of TSD fetuses. However, upon separation of HEX isozymes by ion exchange chromatography, residual HEX A (17 per cent of total HEX) was demonstrated. Also in contrast to TSD fetuses, this fetus' fibroblasts were able to synthesize the precursor of a chains of HEX, and ultrastructural examination of its brain revealed few atypical lamellar bodies, unlike those found in TSD fetuses of the same gestational age. It is therefore concluded that the fetus was not affected with TSD, but rather with AOG. 相似文献
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