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  • 1985-1989  (21)
  • 1980-1984  (27)
  • 1955-1959  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 108 (1986), S. 8171-8175 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Environmental geology 5 (1983), S. 151-157 
    ISSN: 1432-0495
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Sedimentation rates were determined by210Pb in three sediment cores from the main basin of Lake Constance. Rates vary from 0.094 to 0.133 g cm−2y−1, in agreement with previous determinations. A constant radionuclide flux (CR) model reveals long-term, quasi-synchronous fluctuations of sedimentation rate on the basin-wide scale. On average, the rate of sedimentation remains much the same from the beginning of this century indicating little effect of human activity in the watershed on fine-silt sediment supply. The anthropogenic fluxes of Zn, Pb, and Cd in the three cores are compared and the application of210Pb as a heavy metal tracer in Lake Constance is examined. It seems to be a very good tracer for Pb, moderately good for Zn and Cu, and not useful for Cd.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 58 (1987), S. 78-82 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This paper describes a real-time speckle interferometer specially designed to measure the thermal expansion of a large class of intermetallic compounds for which surface optical treatments are difficult or even impossible. The instruments' 5% accuracy, experimentally checked over the range 300–900 K, makes it a more accurate and cheaper alternative to the x-ray devices commonly used for the above-mentioned compounds. Moreover, the extreme simplicity of the optical setup allows an almost immediate alignment procedure and therefore makes the instrument suitable for routine measurements. The advantages of simultaneous measurements in different spots of the sample surface are also outlined. A comparison with standards, together with the measured expansion anomaly of an intermetallic compound (Ce24Co11) are presented.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 28 (1981), S. 0 
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Sedimentation rates were determined with the 210Pb method in eight sediment cores from Lake Constance. The rate of deposition in the main basin (Obersee) varies from about 0.06 g cm−2 y−1 in the central part to 0.13 g cm−2 y−1 in the eastern part of the lake and then increases rapidly towards the Rhine delta.In the central lake area the rate of deposition has been approximately constant since 1900, and dating with the 210Pb method is in good agreement with sedimentological observations. In the Konstanzer Trichter area, the deposition rate has been increasing since about 1955 as a result of eutrophication and subsequent high carbonate production.Dating with 137Cs is fairly accurate for sediments deposited at a high rate, but is questionable for slowly accumulating ones.A positive correlation of 210Pb fluxes and sedimentation rates indicates that 210Pb flux into sediments follows the distribution pattern of solids. 210Pb profiles in four sediment cores interpreted in terms of a constant flux model display synchronous fluctuations of the sedimentation rate; however, their relation to long-range particulate input variations remains to be proved.Sedimentation rates determined with the 210Pb method were used to calculate recent nutrient and heavy metal fluxes. Anthropogenic fluxes of Zn and Pb are in the same range of magnitude as in other polluted areas in Europe and America.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 304 (1983), S. 716-719 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In early diagenetic and mixed type nodules Co displays a positive correlation with Fe (r = 0.77)3 and no correlation to Mn, whereas in hydrogenetic nodules Co correlates to Mn (r = 0.79)3. Hydrogenetic nodules and crusts show generally higher Co contents than diagenetically formed nodules. This ...
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    International journal of earth sciences 73 (1984), S. 1055-1080 
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract The mineralogy and composition of sediments and manganese micronodules from the northern and central sectors of the Peru Basin are discussed. Because of the proximity of the basin to the Carbonate Compensation Depth (C.C.D.), surface sediments vary between calcareous oozes and siliceous muds. Besides biogenic components clay minerals are important. By far the most abundant clay mineral is smectite which is thought to be of diagenetic origin. On a carbonate-free basis, the surface sediments are rather uniform in composition throughout the basin and are similar in composition to those of the equatorial Pacific. Sedimentation rates for the uppermost core sections are in the range of 3 to 5 mm/ 1000 yr. Micronodule compositions show significant variations related to the size class of the micronodules and the depth of occurrence within the sediment column. In general, the chemistry of the micronodules can be explained by the reductive mobilization of Mn within the sediment column and by oxic diagenetic reactions between ferromanganese hydroxides and biogenic opal. The dominant mineral phase is todorokite.
    Abstract: Résumé Cette note décrit la minéralogie et la composition des sédiments et des nodules polymétalliques de la partie septentrionale et centrale du bassin de Perou. Les sédiments de surface consistent en dépôts calcaires ou siliceux selon leur situation par rapport à la profondeur de compensation des carbonates (C. C. D.). A côté des composants biogènes, des minéraux argileux (smectites, illites) sont présents en quantité importante. Le minéral argileux le plus fréquent est une smectite diagenétique. La composition chimique de la fraction non carbonatée des sédiments est uniforme, comparable au chimisme de ceux du Pacifique central. Dans les couches les plus élevées, la vitesse de sédimentation, basée sur des datations par230Th, est de 3 à 5 mm/1000 ans. Le chimisme des micronodules polymétalliques est très variable et dépend de leur profondeur dans le sédiment et de leur dimension. Le chimisme est déterminé par des processus de remobilisation en conditions réductrices dans la colonne sêdimentaire, ainsi que par des réactions diagénétiques entre les hydroxydes de Fe-Mn et l'opale biogène. Le minéral dominant est la todorokite.
    Notes: Zusammenfassung Mineralogie und chemische Zusammensetzung von Sedimenten und Manganmikroknollen aus dem nördlichen und zentralen Teil des Peru-Beckens werden beschrieben. Die Oberflächensedimente bestehen je nach der Lage zur Karbonatkompensationstiefe (C.C.D.) aus karbonatischen bzw. kieseligen Ablagerungen. Neben den biogenen Komponenten sind Tonmineralien (Smektit, Illit) von Bedeutung. Das häufigste Tonmineral ist diagenetisch gebildeter Smektit. Auf karbonatfreier Basis ist die chemische Zusammensetzung der Sedimente sehr einheitlich, vergleichbar mit dem Chemismus zentralpazifischer Sedimente.230Th-Datierungen ergeben eine Sedimentationsrate von 3–5 mm/1000 a für die obersten Sedimentschichten. In Abhängigkeit von der Korngrößenklasse und der Tiefe in der Sedimentsäule zeigen die Manganmikroknollen große Schwankungen im Chemismus. Remobilisationsprozesse unter reduzierenden Bedingungen in der Sedimentsäule sowie die diagenetischen Reaktionen zwischen Fe-Mn-Hydroxiden und biogenem Opal bestimmen die chemische Zusammensetzung der Manganmikroknollen. Die vorherrschende Mineralphase ist Todorokit.
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  • 7
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract Manganese nodules from the Kane Gap (a deep sea channel connecting the Sierra Leone and Gambia Basins off West Africa) were investigated chemically and dated by10Be along cross-sections. Comparing the nodule structure with the stratigraphy of the related sediments, the following conclusions are drawn concerning the sedimentation processes during the last 4 to 6×106 years: The growth of the nodules started about 4 to 4.5 Ma before present during or near to the end of a period of erosion on a fossil-free, probably Miocene sediment. During the first phase of only a few hundred thousandyears, the nodules grew very quickly (7 to 〉18 mm/Ma). Fe-rich hydrogenetic material formed the internal sections of the nodules during this time. Slowing down of the bottom currents, resulting in deposition of thin sediment covers for short intervals, caused the character of the nodules to change to a more diagenetic composition. The growth rates were reduced to about 1 to 2 mm/Ma. The time of slowing is roughly 3 to 4 Ma BP. Probable uncertainties of the dating and growth rates resulting from supposed changes of the10Be supply to the nodules due to variations of the near bottom environment are discussed.
    Abstract: Résumé Le «Kana Gap» est un chenal sous-marin qui relie les bassins de Sierra Leone et de Gambie, au large de l'Afrique occidentale. Des nodules de manganèse, recueillis le long de profils transversaux dans ce chenal, ont fait l'objet d'une étude chimique et d'une détermination d'âge10Be. La comparaison entre la structure des nodules et la stratigraphie des sédiments sous-jacents permet de tirer les conclusions suivantes relatives au processus sédimentaire au cours des 4 à 6 derniers Ma. La croissance des nodules a commencé il y a environ 4 à 4,5 Ma pendant ou juste après un épisode d'érosion sous-marine sur des sédiments non fossilifères, probablement miocènes. Au cours d'une première phase d'une durée de quelques centaines de milliers d'années, la croissance a été très rapide (7 à 〉 18 mm par Ma) avec formation de la partie centrale du nodule, constituée de matière hydrogénée riche en Fe. Ensuite, après ralentissement des courants de fond et dépôt probable d'une mince couche de sédiment, le caractère des nodules a évolué vers une composition plus diagénétique, avec réduction du taux de croissance à 1 à 2 mm par Ma. Le moment de ce changement de régime doit se situer entre 3 et 4 Ma. Des changements dans les conditions de milieu sur le fond de la mer pourraient avoir provoqué une variation de la quantité de10Be apportée aux nodules, d'où résulterait une incertitude sur l'estimation des âges et du taux de croissance; cette question est discutée par les auteurs.
    Notes: Zusammenfassung An Manganknollen aus der Kane-Lücke, dem Verbindungskanal zwischen Sierra Leone Becken und Gambia Becken (vor W-Afrika) wurden entlang Querprofilen durch mehrere Knollen chemische Untersuchungen und10Be Altersbestimmungen durchgeführt. Durch Vergleich des Aufbaus der Knollen mit der Stratigraphie des unterlagernden Sediments werden Rückschlüsse auf Veränderungen des Sedimentationsgeschehens während der letzten 4–6×106 Jahre gezogen. Hiernach begann das Wachstum der Knollen vor maximal 4.5×106 Jahren während oder gegen Ende einer Erosionsphase auf fossilfreiem, vermutlich miozänem Sediment. Während der ersten Phase wuchsen die Knollen über wenige 100000 Jahre sehr schnell (7 bis〉18 mm/106 Jahre). Hierbei schied sich Fe-reiche Knollensubstanz hydrogener Zusammensetzung ab. Nach Verringerung der Strömung und vermutlich zeitweiser Bildung von dünnen Sedimentschleiern änderte sich der Charakter der Knollen zu mehr diagnetischer Zusammensetzung bei wesentlich reduziertem Wachstum (ca. 1 bis 2 mm/106 Jahre). Der Zeitpunkt der Umstellung ist nur sehr grob zu ermitteln, er dürfte etwa zwischen 3 und 4×106 Jahren vor heute liegen. Eventuelle Unsicherheiten bei der Datierung und den Wachstumsraten, die möglicherweise aus milieubedingten Änderungen in der10Be Versorgung der Knollen resultieren, werden diskutiert.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 12 (1956), S. 49-50 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Riassunto Vengono studiati gli spettri di assorbimento u.v. del nitro-difenil-, nitro-fenil-benzil-solfuro e loro derivati X-sostituiti: dove X è eguale ad NH2, N(CH3)2, OH, OCH3 in posizione para- o meta- nel fenile non nitro-sostituito rispetto allo zolfo. Viene dimostrato che una coniugazione che si estenda da un fenile all'altro, attraverso il ponte di zolfo nella serie dei difenil-solfuri non è suffragata dai fatti spettroscopici.
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  • 9
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] During RV Valdivia cruise VA 13-2, 1976, a very thick ferromanganese crust (20-40 cm) was dredged near the summit of a submarine peak at a depth of 4,830m in the Central Pacific7'8. In this crust, which directly overlies altered basaltic rock, three macroscopically distinguishable main zones (top ...
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  • 10
    Publication Date: 1959-01-01
    Print ISSN: 0371-1951
    Electronic ISSN: 1873-3816
    Topics: Chemistry and Pharmacology , Physics
    Published by Elsevier
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