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  • 1
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. Macro-invertebrate species lists were obtained for 268 sites on forty-one river systems throughout Great Britain by qualitative sampling in spring, summer and autumn. Information on twenty-eight environmental variables was also collated for each site. The sites were ordinated on the basis of their species content using detrended correspondence analysis (DCA) and classified by two-way indicator species analysis (TWINSPAN). Correlation coefficients between ordination scores and single environmental variables indicated that Axis 1 distinguished between types of rivers and Axis 2 reflected variation along the length of rivers. A preliminary classification of sites into sixteen groups has been proposed, together with a key which allows new sites to be classified. Information on the species and environmental features which characterize each group is also presented.2. Multiple discriminant analysis (MDA) was employed to predict the group membership of the 268 sites using the twenty-eight environmental variables. 76.1% of sites were classified correctly. An independent assessment of predictive ability using forty test sites yielded a 50% success rate. Predictive ability was higher for the classification presented in this paper than in fifteen additional classifications produced using data from single seasons and/or different taxonomic treatments.3. TWINSPAN and MDA were found to be useful approaches to the classification of running-water sites by their macro-invertebrate fauna and the prediction of community type (as indicated by the occurrence of species in the sites comprising the group) using environmental variables. Extension of the scope of the classification, coupled with the use of additional environmental variables to increase predictive ability, is now in progress.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. Macro-invertebrate samples were collected from 268 running-water sites in Great Britain in each of three seasons (spring, summer and autumn). A combined seasons’treatment was generated by amalgamating the individual seasons’data. These four seasonal options were each subjected to four distinct taxonomic analyses differing in level of identification and whether the data were quantitative or qualitative. Thus sixteen data-sets were available for analysis. Environmental data on physical and chemical variables, macrophyte cover and date of sampling were also recorded for each site.2. All sixteen data-sets were ordinated by detrended correspondence analysis and classified by two-way indicator species analysis. There were strong correlations between the sixteen ordinations and significant concordance between classifications.3. The relationships between ordination scores and single environmental variables were investigated. Muhiple discriminant analysis was used to fit environmental data to eight selected classifications covering the full range of seasonal and taxonomic treatments. The environmental variables most useful in distinguishing between rivers were substratum characteristics, alkalinity and total oxidized nitrogen. Within-river differences were often highly correlated with discharge, distance from source, width and depth. Slope and altitude contributed strongly to both between-river and within-river distinctions.4. Between-site variation (beta diversity), eigenvalues of ordination, the reliability of classifications, the proportion of sites correctly assigned to their biological group using environmental data and the standardized similarity between observed and predicted fauna were all higher when identifications were taken to species level, rather than one of three family treatments. Qualitative data on a reduced list of families gave comparable or better results than more detailed family treatments.5. Combined seasons’data enabled better categorization and prediction than single season's.6. The values of the Czekanowski Index of Similarity between the observed and predicted fauna of test sites were close to realistic maximum values.7. Recommendations are made concerning potential usages of the various classifications. The species level classification has uses in the field of conservation and in the prediction of biological response to environmental change. The family level classifications have value in developing local site inventories and in the interpretation of pollution surveillance programmes.
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  • 3
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] EB virus-specific memory T cells are present exclusively in seropositive individuals and can be reactivated in vitro by co-cultivation either with freshly-infected autologous B cells6 or with low numbers of cells from the autologous EB virus-transformed B cell line11. Such reactivated T-cell ...
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 37 (1981), S. 446-446 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 39 (1983), S. 196-199 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A method of combining interactive molecular graphics with restrained least-squares refinement is described. This enables a researcher using the interactive computer graphics terminal to weight the shifts applied to the individual atoms in following cycles of refinement according to the confidence in their positions. The weights are incorporated into the least-squares procedure using the Marquardt factor which was originally introduced to handle the ill-conditioned case [Moss & Morffew (1982). Comput. Chem. 6, 1-3; Marquardt (1963). SIAM J. Appl. Math. 11, 431-441]. The described refinement strategy has been implemented at Birkbeck College, London, and, using avian pancreatic polypeptide (APP) as test data, some refinements have been carried out. In order to compare the results of these refinements, histograms have been drawn that show the distribution of distances between the corresponding atoms in the different models. These histograms show that the model is improved by including the 'confidence' weighting. An improvement of 7.5% was achieved in the mean distance between the corresponding atoms in the fully refined model and a model resulting from four cycles of restrained least squares. When the 'confidence' weighting was included this improvement rose to 14-0%.
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  • 6
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 38 (1982), S. 2210-2217 
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 40 (1984), S. 1960-1963 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 8
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    Saskatoon : Periodicals Archive Online (PAO)
    Canadian journal of history/Annales canadiennes d'histoire. 16:2 (1981:Aug.) 327 
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 172 (1953), S. 585-586 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A sample of the latter compound was prepared by fractional distillation from oil of Californian laurel, and was subjected to chromatography on an alumina column, using petroleum ether as developing solvent. Although the starting material was colourless, a faint yellow coloration (easily visible ...
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 1 (1983), S. 70-74 
    ISSN: 0263-6484
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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