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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Hydrogeology journal 8 (2000), S. 279-294 
    ISSN: 1435-0157
    Keywords: Key words groundwater development ; crystalline rocks ; geomorphology ; tectonics ; Uganda
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Résumé Les roches cristallines profondément altérées constituent d'importants aquifères captés pour l'eau potable dans les régions de basse latitude d'Afrique australe, d'Amérique du Sud et d'Asie, mais ces aquifères possèdent une hétérogénéité considérable et le rendement des forages y est faible. Ces aquifères se développent dans le substratum et dans sa couverture d'altération; ils résultent des actions géomorphologiques de l'eau météorique, principalement l'altération profonde et le décapage. La relation fondamentale entre l'hydrogéologie et la géomorphologie de ces terrains reste cependant non résolue. Cette étude démontre les possibilités d'un modèle tectono-géomorphologique récemment développé de l'évolution des paysages en Ouganda pour expliquer les caractéristiques hydrogéologiques de deux bassins, définies en utilisant une combinaison de l'analyse texturale, de slug tests, d'essais entre packers et d'essais de pompage. Les marques de l'altération profonde à long terme et du décapage de la couverture sont révélées par l'hétérogénéité verticale des aquifères du substratum fracturé et de sa couverture d'altération; l'hétérogénéité horizontale est contrôlée par la lithologie. Les deux unités forment un système aquifère intégré dans lequel la couverture d'altérites poreuses plus transmissive (5 à 20 m2/j, soit 6 à 20×10–4 m2/s) constitue la zone de stockage des fractures du substratum sous-jacent (T=1 m2/j, soit 1×10–5 m2/s). L'épaisseur et l'extension de l'aquifère de la couverture d'altérites plus productive sont fonctions des processus géomorphologiques actuels. L'intérêt du modèle tectono-géomorphologique, applicable à des environnements profondément altérés, réside dans le fait qu'il décrit de manière cohérente à l'échelle du bassin les caractéristiques hydrogéologiques de ces terrains complexes.
    Abstract: Resumen Las formaciones de rocas cristalinas muy meteorizadas constituyen acuíferos notables para el abastecimiento público de agua en todas las regiones meridionales de África, Sudamérica y Asia. Sin embargo, se trata de acuíferos considerablemente heterogéneos, donde se construyen pozos de escaso caudal. Los acuíferos se localizan en la roca sana y en la capa superior meteorizada, y son consecuencia de la actividad modeladora del agua de lluvia, fundamentalmente por meteorización intensa y exfoliación. No obstante, la relación fundamental entre la hidrogeología y la geomorfología de estos terrenos no ha podido ser resuelta. El presente estudio demuestra la capacidad de un modelo tectono-geomorfológico, recientemente desarrollado, sobre la evolución del paisaje en Uganda para explicar las características hidrogeológicas de dos cuencas. El estudio ha combinado diversas técnicas, como el análisis textural, ensayos de cuchareo, ensayos con obturadores y ensayos de bombeo. La huella de la meteorización prolongada y de la descarga erosiva queda registrada en la heterogeneidad vertical de los acuíferos situados en la roca fracturada y en la capa meteorizada. La heterogeneidad horizontal, por su parte, está controlada por la litología. Las dos unidades forman un sistema acuífero en el que la zona más transmisiva (entre 5 y 20 m2 d−1) y porosa de la capa superior proporciona el almacenamiento a las fracturas de la matriz subyaciente, cuya transmisividad es del orden de 1 m2 d−1. El espesor y extensión del acuífero más productivo de la capa meteorizada dependen de procesos geomorfológicos contemporáneos. La utilidad del modelo tectono-geomorfológico, aplicable a medios altamente meteorizados, radica en que es capaz de describir de forma coherente las características hidrogeológicas de estas complicadas formaciones en el ámbito de la cuenca.
    Notes: Abstract Deeply weathered crystalline rock forms important aquifers for public water supply throughout low-latitude regions of Africa, South America, and Asia, but these aquifers have considerable heterogeneity and produce low well yields. Aquifers occur in the bedrock and overlying weathered mantle and are the products of geomorphic activity of meteoric water, principally deep weathering and stripping. The fundamental relationship between the hydrogeology and geomorphology of these terrains has, however, remained unresolved. This study demonstrates the ability of a recently developed tectono-geomorphic model of landscape evolution in Uganda to explain the hydrogeological characteristics of two basins, as determined using a combination of textural analysis, slug tests, packer tests, and pumping tests. The geopetal imprint of long-term deep weathering and erosional unloading is identified in the vertical heterogeneity of the fractured-bedrock and weathered-mantle aquifers; horizontal heterogeneity is lithologically controlled. The two units form an integrated aquifer system in which the more transmissive (5–20 m2/d) and porous weathered mantle provides storage to underlying bedrock fractures (transmissivity, T, ≈1 m2/d). The thickness and extent of the more productive weathered-mantle aquifer are functions of contemporary geomorphic processes. The utility of the tectono-geomorphic model, applicable to deeply weathered environments, is that it coherently describes the basin-scale hydrogeological characteristics of these complex terrains.
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature biotechnology 22 (2004), S. 491-492 
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Coming off a year that brought biotech investment back up near 2000 boom levels, the first quarter of 2004 (1Q04) registered continued high investor confidence. But industry observers see a potential dark cloud looming in the shape of hype and a leaderless US Food and Drug Administration (FDA; ...
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature biotechnology 21 (2003), S. 1441-1446 
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] If a biological process could be said to be a media darling, RNA interference (RNAi) would be it. The naturally occurring process of RNA suppression of gene activity within a cell (also referred to as small interfering RNA or siRNA) is now being harnessed for target identification and validation ...
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature biotechnology 21 (2003), S. 1117-1118 
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] The first gene therapy trial for Parkinson disease performed this August at New York Weill Cornell Medical Center (New York, NY, USA) joins a short list of other phase 1 clinical gene therapy trials aimed at brain disorders currently underway in the United States. Although the trial is ...
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature biotechnology 21 (2003), S. 955-956 
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] In July, biotech companies Biogen (Cambridge, MA, USA), Genzyme (Cambridge, MA, USA) and Abbott Bioresearch Center (Abbott Park, IL, USA) filed a joint lawsuit against Columbia University (New York, NY, USA) in an attempt to invalidate a gene-splicing technology patent held by Columbia. The ...
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 338 (1989), S. 618-619 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] WHY does the fate of a cell depend on its position in the embryo? One simple mechanism involves diffusion of a morphogenetic molecule from a localized source to form a concentration gradient. The morphogen concentration, which depends on distance from the source, controls gene activity and so ...
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 317 (1985), S. 634-636 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In the ectoderm each segment consists of one anterior plus one posterior compartment3'6 and only the cells of posterior compartments require the engrailed gene for normal pattern formation?'11; transcription of the engrailed gene is therefore a marker for cells belonging to posterior compartments. ...
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 426 (2003), S. 696-697 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] ...How does the health of the general economy determine the fortunes of the high-tech and biotech sector? What country is the biggest challenge to the United States' dominance in these fields? Where does San Diego fit into the global high-tech enterprise? Nature asks some of San Diego's leading ...
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 396 (1998), S. 406-407 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] On page 466 of this issue, Van Doren et al. report the identification and analysis of a gene in Drosophila embryos that attracts the precursors for sperm and eggs — the germ cells — as they migrate to the gonad in order to mature. Christened columbus, this is the first gene to be ...
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 385 (1997), S. 64-67 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We have previously mapped the gene wunen (wun) to 45D on the second chromosome3, and subsequently identified a wun allele, wunKlom, induced by a marked P element from a large-scale screen5. Excision of this P element reverts wunKlom, indicating it is the wun mutagen in this allele. We cloned the ...
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