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51.
The lessons of history indicate that mismanagement of natural resources and the environment often leads to potentially adverse consequences.The increasing interest in economic development,particularly in the developing countries of the world coupled with increasing population pressures and the globalization of economic activity is placing noticeable stresses on the ultimate sustainability of both human and environmental systems.Sustainable development is not a new concept.It has been an area of concern for different elements of society for some time.Yet efforts to understand the implications of sustainable development have not,until recently,been formalized.We have focused singularly on economic development and environmental quality as if they were mutually exclusive.This paper focuses on the concept of concurrency as both a conceptual framework and practicable method of understanding and implementing the ecology and economy of sustainability. 相似文献
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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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R. Geiger 《Die Naturwissenschaften》1984,71(5):252-258
Peptide chemistry has reached a plateau on which more work is devoted to the improvement of known basic principles than to the development of really new methods. As a consequence, routine syntheses of peptides concentrate on few protecting groups and coupling procedures only. The recent progress in purification of peptides by liquid chromatography helped to promote this trend. Meanwhile, recombinant technology permits the synthesis of proteins and possibly of some lower peptides, too. It cannot compete, however, with chemical solid-phase synthesis of a newly discovered peptide with up to about 40 amino acids in speed but may take over the synthesis for large-scale production. Peptides containing modified or non-natural structures, which are often superior to the natural compounds as drugs, will remain subject of chemical synthesis, too. Present research focuses on the role of peptide and protein factors in the immune response and on structure and biological activities of neuropeptides. 相似文献
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