219 resultados para Michels
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Pamphlet containing notes on various cases, including a case "for not delivering goods put on board the defendant's vessel" and another "for concealing a pregnancy."
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The mesozooplankton community, with special emphasis on calanoid copepods, was studied with respect to its species composition, abundance, vertical distribution and developmental structure during the ISPOL expedition to the ice covered western Weddell Sea. Stratified zooplankton tows were carried out nine times between December 1, 2004 and January 2, 2005 with a multiple opening-closing net between 0 and 1000 m depth. Copepods were by far the most abundant taxon contributing more than 94% of the total mesozooplankton. Numerical dominants were cyclopoid copepods, mostly Oncaea spp. A total of 66 calanoid copepod species were identified, but the calanoid copepod community was characterised by the dominance of only a few species. The most numerous species was Microcalanus pygmaeus, which comprised on average 70% of all calanoids. Calanoides acutus and Metridia gerlachei represented other abundant calanoid species contributing an average of 8 and 7%, respectively. All other species comprised less than 3%. The temporal changes in the abundance and population structure of M. pygmaeus and M. gerlachei were small while a shift in the stage frequency distribution of C. acutus was observed during the study: CIV dominated the C. acutus population with 48 to 50% during the first week of December, while CV comprised 48% in late December. CI and CII of C. acutus were absent in the samples and males occurred only in very low numbers in greater depths. In M. gerlachei, CI was not found, whereas all developmental stages of M. pygmaeus occurred throughout the study. All three species showed migratory behaviour, and they occurred in upper water layers towards the end of the investigation. This vertical ascent was most pronounced in C. acutus and relatively weak in the other two species. In M. pygmaeus and M. gerlachei, copepodite stages were responsible for the upward migration in late December, while the vertical distribution of adults did not change. In C. acutus all abundant developmental stages (CIV, CV and females) ascended to upper water layers. Almost exclusively (93%) medium- and semi-ripe females of C. acutus and M. gerlachei were found, and only 3 - 4% of the ovaries were ripe. The absence of CI and the low number of ripe females indicate that the main reproductive period had not started in C. acutus and M. gerlachei until the end of our study in early January. In contrast, the high portion of CI and CII of M. pygmaeus suggests that reproduction of this species had started in October-November and hence, before the onset of the phytoplankton bloom in the water. The community structure did not differ between stations with one exception on December 26, when the station was strongly influenced by the continental shelf.
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Die Rekonstruktion des Einflusses von Strömungen und glazialmarinen Prozessen auf das Sedimentationsgeschehen am Kontinentalhang der Antarktischen Halbinsel im westlichen Weddellmeer basiert auf sedimentologischen und geophysikalischen Daten eines Kolbenlotkerns. Der Sedimentkern wurde während des Fahrtabschnitts ANT-XIV/3 mit dem FS "Polarstern" aus einer mächtigen Levee-Struktur eines Rinnen-Rückensystems gewonnen. Es wurden sedimentologische sowie sedimentphysikalische Untersuchungen an dem Kernmaterial durchgeführt. Die texturellen Änderungen im Kern und die Variationen der gemessenen Parameter ermöglichen eine lithofazielle Gliederung und stratigraphische Einstufung der Sedimentabfolge. Die untersuchten Sedimente umfassen den Zeitraum der vier letzten Klimazyklen bis heute und repräsentieren die Ablagerungsbedingungen von mehr als 340 000 Jahren. Vier Faziestypen wurden unterschieden, die sowohl glaziale als auch interglaziale Ablagerungsräume charakterisieren. (1) Die überwiegend groblaminierten Sedimentabfolgen wurden der Laminitfazies zugeordnet. Unter glazialen Umweltbedingungen kam es infolge schwacher Bodenströmungen zur Ablagerung feinkörniger, laminierter, strömungsbetonter Sedimente. (2) Strukturlose, sehr homogene Sedimentabfolgen des Kems beschreiben einen weiteren, den Kaltzeiten zugeordneten, Faziestyp, der durch geringe Variationen in den Sedimenteigenschaften charakterisiert ist. (3) Kernabschnitte, die weitgehend strukturlos sind bzw. leichte Bioturbationen und relativ viel eistransportiertes Material aufweisen, wurden als IRD-Fazies bezeichnet. Sie repräsentiert den Übergang vom Glazial zum Interglazial, in dem sich das Schelfeis und die Meereisbeckung zurückzogen. In den Sedimenten kam es infolge der gesteigerten Kalbungsrate zur Anreicherung der Eisfracht. (4) Die relativ biogenreichen, hellen Ablagerungen wurden der interglazialzeitlichen Karbonatfazies zugeteilt. Der signifikant erhöhte Anteil planktischer Foraminiferen weist auf eine gesteigerte Bioproduktivität im Oberflächenwasser hin, die aus verstärkten jahreszeitlichen Schwankungen der Meereisbedeckung resultiert. Die betrachteten Sedimentationsprozesse, wie biologische Produktivität, Umlagerungsprozesse durch Meeresströmungen, gravitativer Sedimenttransport und Eistransport, sind das Abbild komplexer Wechselwirkungen aus Meeresspiegelschwankungen, Änderungen ozeanographischer Bedingungen und der Vereisungsdynamik. Das Sedimentationsgeschehen im Untersuchungsgebiet wurde folglich durch die Variationen der vorherrschenden Umweltbedingungen bestimmt. Im Glazial kam es unter einer geschlossenen Meereisbedeckung zur Ablagerung feinkörniger, geschichteter Sedimente. Vorwiegend Turbiditströmungen kontrollierten das Sedimentationsgeschehen innerhalb des betrachteten Rinnen-Rückensystems. Unter dem Einfluß der Coriolis-Kraft und wahrscheinlich einer Konturströmung wurden die suspendierten, feinkörnigen Partikel aus dem zentralen Bereich der Rinne verdriftet und über dem nördlichen Uferwall abgelagert. Höherenergetische gravitative Prozesse beeinflußten das Sedimentationsgeschehen episodisch und sind durch gut sortierte Ablagerungen mit erhöhten Gehalten im Mittel- bis Grobsiltbereich dokumentiert. Höhere Sedimentationsraten in den Glazialen trugen verstärkt zur Bildung des Uferwalls bei. Die Ablagerungen der ebenfalls glazialzeitlichen homogenen Fazies belegen unterschiedliche Ablagerungsbedingungen und eine Verschiebung der dominierenden Prozesse. Während des Übergangs vom Glazial zum Interglazial nahm die Bodenwasserbildungsrate durch das Aufschwimmen des Schelfeises zu, wodurch die Strömungsintensität gesteigert wurde. Eine verstärkte Eisbergaktivität wird durch die Anreichung des IRD-Materials dokumentiert. Während interglazialer Zeiten ermöglichten offen-marine Bedingungen im Südsommer eine leicht erhöhte biologische Produktivität, so daß der Ablagerungsraum durch die Sedimentation biogener Komponenten verstärkt beeinflußt wurde.
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Sedimentary processes in the southeastern Weddell Sea are influenced by glacial-interglacial ice-shelf dynamics and the cyclonic circulation of the Weddell Gyre, which affects all water masses down to the sea floor. Significantly increased sedimentation rates occur during glacial stages, when ice sheets advance to the shelf edge and trigger gravitational sediment transport to the deep sea. Downslope transport on the Crary Fan and off Dronning Maud and Coats Land is channelized into three huge channel systems, which originate on the eastern-, the central and the western Crary Fan. They gradually turn from a northerly direction eastward until they follow a course parallel to the continental slope. All channels show strongly asymmetric cross sections with well-developed levees on their northwestern sides, forming wedge-shaped sediment bodies. They level off very gently. Levees on the southeastern sides are small, if present at all. This characteristic morphology likely results from the process of combined turbidite-contourite deposition. Strong thermohaline currents of the Weddell Gyre entrain particles from turbidity-current suspensions, which flow down the channels, and carry them westward out of the channel where they settle on a surface gently dipping away from the channel. These sediments are intercalated with overbank deposits of high-energy and high-volume turbidity currents, which preferentially flood the left of the channels (looking downchannel) as a result of Coriolis force. In the distal setting of the easternmost channel-levee complex, where thermohaline currents are directed northeastward as a result of a recirculation of water masses from the Enderby Basin, the setting and the internal structures of a wedge-shaped sediment body indicate a contourite drift rather than a channel levee. Dating of the sediments reveals that the levees in their present form started to develop with a late Miocene cooling event, which caused an expansion of the East Antarctic Ice Sheet and an invigoration of thermohaline current activity.
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The main emphasis of this study was to analyse the short-term development of abundance, population structure and vertical distribution of the dominant calanoid copepods during a phytoplankton bloom in the coastal area of the eastern Weddell Sea in December 2003. Microcalanus pygmaeus was by far the most abundant calanoid species. Metridia gerlachei, Ctenocalanus citer, Calanoides acutus, Calanus propinquus and the ice-associated Stephos longipes were also present in considerable proportions. The observed changes in the population characteristics and parameters of these species are described in detail and discussed in the context of the spring phytoplankton bloom. A conspicuous event occurring during the final stage of the study was the development of a strong storm. While the results suggest that this storm did not have any considerable influence on the populations of all other investigated copepod species, it very likely caused pronounced changes in the S. longipes population present in the water column. Before the storm, S. longipes was found primarily in the upper 100 m of the water column, and its population was dominated by adults (mean proportion = 41%) and the copepodite stage I (mean proportion = 30%). After the storm, the abundance increased considerably, and the copepodite stage I contributed by far the largest proportion (53%) of the total population indicating that the early copepodite stages probably had been released from the sea ice into the under ice water layer due to ice break-up and ice melt processes caused by the storm.
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Texto con apostillas marginales.
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Bibliographical footnotes.
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Mode of access: Internet.
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Editors: 1904- , H. Braun, W. Sombart, M. Weber, E. Jaffé, and R. Michels--1922- , E. Lederer.
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Mode of access: Internet.
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Mode of access: Internet.
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"References" at end of each chapter except chapter 11.
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Based on his Advanced electrical measurements.
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Mode of access: Internet.