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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal for general philosophy of science 27 (1996), S. 325-346 
    ISSN: 1572-8587
    Keywords: Imre Lakatos ; Scientific Research Programmes ; Rational Reconstruction ; Origin of Life Theories ; Oparin-S. Fox ; Haldane-Muller ; Orgel-Crick-Spiegelman ; Ribozymes ; Qßreplicase System
    Source: Springer Online Journal Archives 1860-2000
    Topics: Philosophy , Nature of Science, Research, Systems of Higher Education, Museum Science
    Notes: Summary During the course of its short history the discipline concerned with the origin of life has given birth to several scientific programmes in the Lakatosian sense, two of the most prominent and widespread being those initiated by Oparin (life began from protein entities) and Muller-Haldane (life began from genetic entities). The present paper sets down the abses for the rational reconstruction of both views by identifying theirhard core and some of their successivedevelopments. An assessment is made of the various stages in the evolution of these programmes with respect to the crucial Lakatosian notions ofprogressivity andregressivity and of how their arguments stand up against one another. This epistemological analysis also establishes the internal reasons why the RNA version of thegenotype programme (developed in particulr by L. Orgel and S. Spiegelman) has today taken on a progressive character and enjoys recognition by the international scientific cvommunity.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 46 (1980), S. 161-163 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This paper reports the results of experimental defoliation of two common matorral species: Lithraea caustica and Colliguaya odorifera. L. caustica and C. odorifera are the matorral species previously shown to exhibit the highest and lowest levels of natural defoliation by browsing. Experimental defoliation was performed at four levels: 0% (controls), 25%, 66%, and 100%. C. odorifera exhibited vegetative responses stronger than controls only in the two highest levels of defoliation (66% and 100%), whereas L. caustica responded vigorously at the 25% and 100% levels. The results are related to the observed position of both species in the matorral community and their relative defoliation risks by natural and introduced herbivores.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The visual computer 13 (1997), S. 64-77 
    ISSN: 1432-2315
    Keywords: Key words: Theoretical computer graphics ; Solid modelling ; B-rep
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-4919
    Keywords: Escherichia coli mutants ; glutathione reductase-deficiency ; glutathione biosynthesis ; glutathione status ; sensitivity to thiol-reacting compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The intracellular concentrations of total glutathione, GSSG and protein · S-SG, the total excreted glutathione concentration, and the susceptibility towards GSH-reacting compounds were assayed in strains of Escherichia coli deficient in biosynthesis and/or reduction of glutathione. A deficiency in glutathione reductase displaced the glutathione status towards the oxidized forms. This displacement was more clearly appreciated in strains additionally deficient in glutathione biosynthesis. A deficiency in catalase activity also produced an increase in the oxidation of glutathione. The most severe changes were observed in the concentrations of protein-glutathione mixed disulfides and in the amount of glutathione excreted to the medium. Increased sensitivities towards compounds known to interact with cellular GSH were observed in glutathione reductase deficient strains, although these effects were enhanced in strains additionally deficient in GSH biosynthesis
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular neurobiology 5 (1985), S. 303-309 
    ISSN: 1573-6830
    Keywords: asymmetric acetylcholinesterase (AChE) ; heparan sulfate ; AChE aggregates ; neuromuscular junction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. It has been reported previously that heparin, a sulfated glycosaminoglycan, releases the asymmetric 16 S form of acetylcholinesterase (AChE) from cholinergic synapses. Here it is shown that heparin releases the synaptic AChE not as individual 16 S species but as multimolecular aggregates (30 S) of such molecules. 2. Heparin is able to convert low-ionic strength AChE aggregates into a heparin type of AChE aggregates. 3. Our results suggest that the AChE aggregates detached by heparin are likely to be the physiologically important state of aggregation of the 16 S AChE form in the synaptic basal lamina.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Biodiversity and conservation 6 (1997), S. 1103-1121 
    ISSN: 1572-9710
    Keywords: Caribbean ; insects ; island ; equilibrium ; extinction ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ants were studied on Puerto Rico and 44 islands surrounding Puerto Rico. Habitat diversity was the best predictor of the number of species per island and the distributions of species followed a nested subset pattern. The number of extinctions per island was low, approximately 1–2 extinctions per island in a period of 18 years, and the rates of colonization seem to be greater than the extinction rates. Ant dynamics on these islands do not seem to support the basic MacArthur and Wilson model of island biogeography. The MacArthur and Wilson equilibrium is based on the notion that species are interchangeable, but some extinctions and colonizations can change the composition and number of species drastically.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 150 (1992), S. 456-462 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The binding to resting and activated T lymphocytes of two radiolabelled fatty acids (oleic and arachidonic) was studied in the presence or in the absence of alphafetoprotein (AFP) as carrier protein. Fatty acid binding by resting and activated T lymphocytes was determined at 4°C as a function of the concentration of fatty acid and AFP. Under the conditions employed, the following observations were made: (1) in the presence of AFP, fatty acids (oleic and arachidonic acid) are bound to cells by a two-component pathway; one is a saturable process, evidenced when the fatty acid to AFP (FA/AFP) molar ratio was fixed at 1 and the concentration of the fatty acid and the protein varied from 0.1 to 3.2 μM, and the second is a nonsaturable function of FA/AFP molar ratio and was linearly related to the unbound fatty acid concentration in the medium over the entire range studied; (2) in the absence of AFP, the nonsaturable process appears to be the only component of fatty acid binding; (3) at all tested concentrations of free (unbound) fatty acid in the medium, net fatty acid binding by either resting or activated T cells was considerably greater in the presence than in the absence of AFP; (4) in the presence of AFP, fatty acid binding was much higher in activated T cells than in resting T cells, whereas in the absence of AFP, nonsignificant differences were observed between activated and resting T cells; and (5) the time course of fatty acid and AFP binding at 4°C revealed that, at equilibrium, the number of fatty acid molecules bound to the cell was much greater than that of AFP suggesting an accelerated dissociation of the fatty acid upon interaction of the AFP-fatty acid complex with putative cell receptors.It is concluded to the existence of an AFP/AFP-receptor pathway that facilitates the binding of fatty acids to T lymphocytes, particularly upon their blast transformation. This pathway may fulfill the increased requirement for fatty acids characteristic of proliferating cells and may serve to regulate the endocytosis of fatty acids with modulatory effects on lymphocyte function and to protect cells from their cytotoxic potential when internalized in excess.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Publication Date: 2021-05-19
    Description: Se presenta la información requerida para la calibración de un modelo matemático del ecosistema de la Ciénaga de Tesca de Cartagena, obtenida mediante la realización de experimentos químicos. Los parámetros cinéticos de la oxidación bioquímica se obtuvieron por el "método de la DBO", mientras que las tasas de flujo de amonio y fosfato a través de la interfase agua - sedimento fueron evaluadas por medio de la Ley de Fick y el "modelo de descomposición de la materia orgánica en sedimentos". La constante cinética del proceso de degradación de la materia orgánica resultó ser de 0.23 dial, así mismo se encontró que las constantes del primer y segundo estadío de la nitrificación son 0,09 y 0,44 día-1 respectivamente. Se observaron tasas de flujo de nutrientes que oscilaron entre 30 y 4300 mg.m-2 día -1 para el amonio y de 0.4 a 3.5 mg.m-2 día -1 día para el fosfato. Las tasas de flujo bental de nutrientes fueron varios órdenes de magnitud más altas que las reportadas para otros ecosistemas, indicando que cuantitativamente este proceso biogeoquímico aporta grandes cantidades de amonio y fosfatos al agua de la Ciénaga, afectando negativamente la calidad de agua de este ecosistema.
    Description: The information required for the calibration of a mathematical model of the ecosystem of Cienaga de Tesca (the Tesca Swamp) is presented, it was obtained by carrying out analytical techniques. The kinetic parameters of biochemical oxidation were obtained by the "DBO method", while the measurement of (luxes rates of nutrients across the interfase between the sediment and the water column were evaluated using Fick's Law and the umodel of organic matter decomposition." The kinetic constant of the ammonization process resulted in 0.23 dia l, and it was also found that the first and second state of nitrification were 0,09 y 0,44 día- ', respectively. High flow rates oí fluids were observed and oscillated between 30 to 4300 mg.m-2 día-1 for ammonia and 0.4 a 3.5 mg.m-2 día -1 for phosphate. Bental flow rates for nutrients were several orders of magnitude greater than the reported one in the fountains revised, indicating that quantitatively this biogeochemist process provides great amounts of ammonia and phosphate to the Marsh waters, negatively affecting negatively the water quality of this echosystem.
    Description: Published
    Keywords: Laguna ; Litoral. ; Temperatura. ; Modelo matemático ; ASFA_2015::C::Chemical oceanography ; ASFA_2015::M::Mathematical models
    Repository Name: AquaDocs
    Type: Journal Contribution , Not Known
    Format: pp.68-78
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  • 9
    Publication Date: 2021-05-19
    Description: Este informe fue desarrollado en respuesta al censo de Lobos Marinos desarrollado en la XV Región de Arica y Parinacota, I Región de Tarapacá y II Región de Antofagasta.Con el fin de actualizar la información que existe de las poblaciones de Otaria flavescens en la zona Norte de Chile (se efectuaron dos censos, el primero durante la temporada post-reproductiva del año 2012 y el segundo durante la temporada reproductiva del año 2013. Los censos fueron ejecutados mediante dos metodologías de observación; censo vía marítima-terrestre en las loberas más importantes y censo aéreo con fotografías verticales en la totalidad del sitio de estudio.
    Description: LICITACIÓN N° 4728-14-LP12 / Código 2012-6-FAP-1
    Description: Published
    Keywords: Censos ; Lobos ; Cuantificación ; Otaria flavescens
    Repository Name: AquaDocs
    Type: Report , Not Known
    Format: 94pp.
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  • 10
    Publication Date: 2022-05-25
    Description: Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B. V. for personal use, not for redistribution. The definitive version was published in Continental Shelf Research 26 (2006): 194-205, doi:10.1016/j.csr.2005.10.004.
    Description: The benthic communities of the deep insular shelf at the Hind Bank Marine Conservation District (MCD), an important spawning grouper aggregation site, were studied with the Seabed autonomous underwater vehicle (AUV) at depths between 32 to 54 m. Four digital phototransects provided data on benthic species composition and abundance of the insular shelf off St. Thomas, U.S. Virgin Islands. Within the western side of the MCD, well developed coral reefs with 43% mean living coral cover were found. The Montastrea annularis complex was dominant at all four sites between 33 to 47 m, the depth range where reefs were present. Maximum coral cover found was 70% at depths of 38 to 40 m. Quantitative determinations of sessile-benthic populations, as well as the presence of motile-megabenthic invertebrates and algae were obtained. The Seabed AUV provided new quantitative and descriptive information of a unique coral reef habitat found within this deeper insular shelf area.
    Description: Funding was provided in part by the CenSSIS ERC of the National Science Foundation under grant EEC-9986821 and by the Caribbean Fishery Management Council. University of the Virgin Islands staff time was supported by a grant from Sea Grant (R-101-1-02) to R. Nemeth.
    Keywords: Atlantic ; U.S. Virgin Islands ; Coral reef ; Deep hermatypic corals ; AUV
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: 907575 bytes
    Format: application/pdf
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