共查询到20条相似文献,搜索用时 15 毫秒
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《人与生物圈》1996,(2)
1. The background is a maple leaf, whose vein is the transformation of the first letter of "Jiu", that is J. In the front, there is a waterfall, which is the transformati on of Z, the first letter of Zhai. This makes "Jiuzhai" obvious. The first letter of China, "C", is transformed into a globe, symbol- 相似文献
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Petsko GA 《Genome biology》2004,5(5):106-3
Anyone who cares about the moral and social implications of genomics, genetic engineering and biotechnology should read Michael J. Sandel's article, 'The Case Against Perfection', in the April 2004 issue of The Atlantic Monthly. 相似文献
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This paper explains the objectives of organising the symposium ‘The Other North Sea’. A major goal is the submission of the
conclusions and content of this symposium to the North Sea Task Force, an initiative of the Second Conference on the Protection
of the North Sea (London, 1987) which is responsible for preparing a Quality Status Report on the North Sea by mid-1993. The
conclusions and recommendations of the symposium are summarised and presented to the North Sea Task Force in connection with
the preparations for the 1993 Quality Status Report. The paper stresses the need to subdivide the North Sea into areas of
ecological entity and underlines the advantages of using diatom and meiofauna assemblages as indicators for present and past
environmental actors in sediment conditions. A plea is also made for the promotion of research to improve understanding of
disturbance of sensory perception and behaviour as an ecologically relevant early warning signal. The major role of fisheries
in inducing changes of seabird and harbour porpoise populations is highlighted. 相似文献
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《中国实验动物学报》2005,(Z1)
The first case of severe acute respiratory syndrome(SARS)in Guangdong province was reported on2Jan2003,whileretrospective survey has datedthe first index case on16Nov2002.In months that followed,pandemic of SARS widelyspread over the world until July2003,infecting8454people and claiming908deathsin39countries andregions global-ly.On16Dec2003,a32years old photographerlivinginsuburban Guangzhou presented withsymptoms of SARSinfec-tion.There were3other ensuing cases betweenthe end of2003and… 相似文献
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1. The rates of deacylation of acyl-alpha-chymotrypsins in which the hydrogen-bonding capacity of the acylamino group of the substrate has been systematically removed were measured. 2. The ratio of deacylation rates of l- and d-acyl-enzymes is found to depend largely on the existence in the substrate of an amido -NH- group. 3. The data presented agree with the postulate that the stereospecificity of alpha-chymotrypsin is exercised in catalytic rather than binding steps, and that the active site of the enzyme presents three loci to the substrate: the site containing the catalytic functionalities (including serine-195), the hydrophobic area for amino acid side-chain binding, and a hydrogen-bond acceptor site for acylamino group binding. 4. It is noted that, though the hydrogen-bonding site is crucial for the stereospecificity, the free energy of binding of substrates and inhibitors is dominated by the hydrophobic interaction. 5. It is tentatively proposed that alpha-chymotrypsin selects a high-energy conformation of the substrate when the latter binds at the enzyme's active site. 相似文献
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Jay Odenbaugh 《Biology & philosophy》2006,21(5):607-621
In this essay, I argue for four related claims. First, Richard Levins’ classic “The Strategy of Model Building in Population
Biology” was a statement and defense of theoretical population biology growing out of collaborations between Robert MacArthur,
Richard Lewontin, E. O. Wilson, and others. Second, I argue that the essay served as a response to the rise of systems ecology
especially as pioneered by Kenneth Watt. Third, the arguments offered by Levins against systems ecology and in favor of his
own methodological program are best construed as “pragmatic”. Fourth, I consider limitations of Levins’ arguments given contemporary
population biology.
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Jay OdenbaughEmail: |
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S. Morimoto K. Kawashiro H. Yoshida 《Origins of life and evolution of the biosphere》1977,8(4):341-346
The mixture of -aminopropionitrile and ,-iminodipropionitrile polymerized to solidify almost at the temperature near 0°C during 8 years. The conversions based on decreasing of those reactants were 61 and 98% at 4 and 8 years, respectively. The fractionation of 4 and 8 years product using Sephadex G 10 yielded their predominant amounts in the oligomer and polymer section, respectively. The oligomer section product of 8 years product was analyzed by means of ion exchange chromatography and its trimethylsilyl derivative was also analyzed by means of gas chromatography combined with mass spectrometry. These results identified dialanine and trialanine and their amides and nitriles. 相似文献
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Scoble MJ 《Trends in ecology & evolution》1997,12(12):465-466
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The characterization of the whey proteins of guinea-pig milk: The isolation and properties of α-lactalbumin 总被引:2,自引:0,他引:2 下载免费PDF全文
1. The whey proteins of guinea-pig milk were examined by electrophoresis on paper, cellulose acetate, starch gel and polyacrylamide gel. 2. Two major proteins were detected, one of which was identified as blood serum albumin. 3. The major whey protein was isolated by CM-cellulose chromatography and on columns of Sephadex G-100. 4. The amino acid composition of the protein, taken in conjunction with its other properties, indicated that the major whey protein in guinea-pig milk is homologous with cow α-lactalbumin and that β-lactoglobulin is absent from guinea-pig milk. 5. Guinea-pig α-lactalbumin, which was obtained crystalline, had mol.wt. 15800, N-terminal lysine and C-terminal glutamine. 相似文献
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《Studies in History and Philosophy of Science Part C: Studies in History and Philosophy of Biological and Biomedical Sciences》2001,32(3):413-433
Modern science has undoubtedly become one the principal engines of economic growth, even though the epistemological status of scientific knowledge has been continuously contested. Leaving the philosophical problem of knowledge aside, this paper examines how scientific discovery contributes to the production of wealth. The analysis focuses on a recent achievement at the crossroads of chemistry, immunology and biotechnology: antibody catalysis. For this purpose, we develop a model of entrepreneurial work to explain how the discovery of natural products and processes generates new economic opportunities. The proposed model is based on the assumption that scientists believe that the natural environment is a repository of ‘natural capital’. Natural capital includes goods that are not made by humans but can be used to produce other goods and services. The belief in natural capital induces scientists to search for and identify a natural property that, in the specific cultural context of their work, is recognized as a valuable resource. The selection of such a property forms the initial phase of the discovery process. Certain research methods are then deployed to create novel empirical conditions within which the selected property is transformed into a specific good. The discovery of natural capital thus comprises a historically accountable entrepreneurial endeavour. 相似文献
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KAMALSHARMA YUFANGSHI 《Cell research》1999,9(1):1-10
Since their discovery over 100 years ago,sphingolipids have caught the eyes and the imagination of scientists.Modern science has made many new insights on the cell biology and day-to-day functions of many integral sphingolipids,especially those of ceramids.Ceramide is recognized as a vital second messenger in the signal transduction process mediated by receptors of many cytokines and growth factors.A great part of our current understanding of ceramide has been achieved from apoptosis-related studies,however recent data in the fields of immunology,endocrinology and neurobiology,also suggest a fundamental involvement of ceramide in the onset of diseases.Therefore,understanding the diology of ceramide could be a key to unraveling many biological mechanisms and provide information for the treatment of some common diseases. 相似文献
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In the 80 years since their discovery the β-lactam antibiotics have progressed through structural generations, each in response to the progressive evolution of bacterial resistance mechanisms. The generational progression was driven by the ingenious, but largely empirical, manipulation of structure by medicinal chemists. Nonetheless, the true creative force in these efforts was Nature, and as the discovery of new β-lactams from Nature has atrophied while at the same time multi-resistant and opportunistic bacterial pathogens have burgeoned, the time for empirical drug discovery has passed. We concisely summarize recent developments with respect to bacterial resistance, the identity of the new β-lactams, and the emerging non-empirical strategies that will ensure that this incredible class of antibiotics has a future. 相似文献
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Lawrence C. Davies 《Nucleosides, nucleotides & nucleic acids》2013,32(5-6):1053-1054
Abstract It has been shown by many workers that nucleotides containing an ap methylene link have interesting biochemical properties compared to those containing an αβ 0x0 linkage.1 In our laboratory af3 methylene thymidine triphosphate has been shown to be a more powerful inhibitorof thymidine kinase than thymidine triphosphate but a weaker inhibitor of ribonucleotide reductase and cytidine deaminase. We have been interested in examining the properties of the af3 imido analogue. Several routes to prepare the unknown ap imidothymidine triphosphate were unsuccessfully tried:
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Reaction of 3′-O-Acetylthymidine with the tributylammonium salt of dicyclohexylcarbodiimide.
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Reaction of 5′-O-tosylthymidine with the tributylammonium salt 3 of imidodiphosphoric acid in hot dimethylacetamide.