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  • 1990-1994  (76)
  • 1985-1989  (34)
  • 1925-1929  (1)
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  • 11
    Electronic Resource
    Electronic Resource
    A comparison of summer nutrient data obtained in Königshafen Bay (North Sea, German Bight) during two investigation periods: 1979–1983 and 1990–1992 (1994)
    Springer
    Helgoland marine research 48 (1994), S. 173-182 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A comparison of summer nutrients obtained during the investigation periods 1979–1983 and 1990–1992 was made, to elucidate whether or not changes have occurred in Königshafen Bay during the last decade. In both the flood current as well as in the ebb current, concentrations of silicate, phosphate, nitrite and nitrate have decreased. Ammonia, however, has increased by a factor of two in the flood current waters, but was similar in both investigation periods in the ebb current waters. In addition, a significant increase of salinity has been observed. The differences between flood and ebb current median nutrient concentrations suggest that the bay was a source of nutrients during the 1979–1983 period, exporting large amounts of silicate, nitrite and ammonia with the ebb current. Today, the bay appears to be more a sink than a source of nutrients. Export rates of silicate and nitrite are greatly reduced and phosphate and ammonia are imported nowadays. Nitrate fluxes were in balance during both periods. Reasons for the observed changes are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02367034
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  • 12
    Electronic Resource
    Electronic Resource
    Low molecular weight, polymeric, and covalently bound cobalt(II)-phthalocyanines for the oxidation of mercaptans (1991)
    Springer
    Journal of inorganic and organometallic polymers and materials 1 (1991), S. 115-130 
    Details
    ISSN: 1572-8870
    Keywords: Phthalocyanine-cobalt complexes ; catalyst ; thiol oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cobalt(II)-phthalocyanines in different environments are investigated as catalysts for the oxidation of thiols. Water-soluble low molecular weight 2,9,10,23-tetracarboxyphthalocyanine (1b) and polymeric phthalocyanine (2b) with carboxylic end groups are prepared. Compound1b is covalently bound at linear and cross-linked poly(chloromethylstyrene) in the presence of pyridine to obtain the water-soluble polymers (3a, b) and gel-type polymers (4a, b). Covalent binding of1b to surface modified silica was also realized. Low molecular weight and polymeric phthalocyanines (1a, 2a) are synthesized on silica, alumina, and charcoal. In addition,1a is encapsulated in the interior of NaX zeolite. All materials are efficient catalysts for the oxidation of 2-mercaptoethanol. The mechanism employing water-soluble catalysts is discussed in the direction of a mononuclear complex coordinating dioxygen and thiol. Heterogeneous catalysts containing1a and2a on the carriers show enhanced activity with increasing dispersion. The proposed mechanism considers different reaction sites for the coordination of O2 and thiol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00701033
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  • 13
    Electronic Resource
    Electronic Resource
    Structure Dependent Creep and Crack Propagation in Silicon Nitrides (1993)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 89-91 (Aug. 1993), p. 599-604 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/59/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.89-91.599.pdf
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  • 14
    Electronic Resource
    Electronic Resource
    Cadmium and copper levels in seals, penguins and skuas from the Weddell Sea in 1982/1983 (1986)
    Springer
    Polar biology 5 (1986), S. 139-143 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Samples of muscle, liver and kidney of Weddell and crabeater seals, Adélie and emperor penguins, and McCormick's skuas collected in the Weddell Sea in the summer 1982/83 were analysed for cadmium and copper. In general, the study aimed at contributing to the establishment of base-line data on potential pollutants in Antarctic ecosystems. In particular, it aimed at increasing the amount of data on Cd and Cu levels in the same species that that had been collected and analysed two years eralier, thus improving the possibility of statistical analyses into relationships between metal contents and biological parameters or sampling-sites of the animals, but the data basis is still too small for the letter purpose. In all species together, concentration ranges (on dry weight basis) were 0.16–0.77, 3.7–96.8 and 15.6–491 mg cadmium and 1.6–21.4, 14.9–149 and 12.6–47.7 mg copper per kg in muscles, livers and kidneys, respectively. The relatively high levels of both metals in all species analysed, in connexion with the available literature, suggest that levels in marine mammals and birds can only, if at all, to a minor extent reflect differences in environmental concentrations of these metals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00441693
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  • 15
    Electronic Resource
    Electronic Resource
    Thermodesorption of ultrathin organic films studied by reflection (1986)
    Springer
    Applied physics 39 (1986), S. 173-181 
    Details
    ISSN: 1432-0630
    Keywords: 44.50 ; 78.65 ; 81.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Optical reflection measurements are described as a new and simple technique to measure thicknesses and thickness changes of ultrathin organic overlayers on inorganic support. The prime advantages are high sensitivity in thickness measurements (0.1–1 Å), applicability under varying environmental conditions, nondestructiveness, applicability on different supports and high time resolution. These features are assessed theoretically and experimentally studying Langmuir-Blodgett films on SiO2 and Au supports. These films, in this work prepared with the model compound arachidic acid, provide the salient feature of well-defined thicknesses in integer multiples of 26.7 Å. Application of the technique in thermodesorption experiments reveals distinguished binding states with binding energies (73–110 kJ/mol) depending on the counterion (Mg2+ or Cd2+) used in preparing the films and ratios of different states depending on thickness. The binding energy for the main component of multilayers (73 and 81 kJ/mol) with thickness larger than 100 Å is comparable to the heat of evaporation of bulk fatty acids. In addition an analytic expression between layer thicknesses and reflection is derived from the Fresnel equation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00620732
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  • 16
    Electronic Resource
    Electronic Resource
    Advances in control-volume-based finite-element methods for compressible flows (1994)
    Springer
    Computational mechanics 14 (1994), S. 431-446 
    Details
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Recent developments in the application of a control-volume-based finite-element method, that has proven successful in solving incompressible flow problems, to the solution of compressible flow problems are presented. The finite Element Differential Scheme (FIELDS) is demonstrated to retain the pressure checker boarding problem for the case of Euler flow under certain conditions of flow. The source of this is investigated and remedies are provided that surmount this problem for all flows including Euler flows. Success is demonstrated for incompressible flow and a formulation is provided for extension to compressible flows. One dimensional testing on a supersonic converging-diverging nozzle exhibits extremely high accuracy of flow prediction including both shock strength and sharpness of resolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377597
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  • 17
    Electronic Resource
    Electronic Resource
    A comparison of carbon based ammonia excretion rates between gelatinous and non-gelatinous zooplankton: Implications and consequences (1990)
    Springer
    Marine biology 106 (1990), S. 219-225 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract About 560 literature data on weight-specific ammonia excretion rates of gelatinous zooplankton (cnidarians, ctenophores and salps) and non-gelatinous zooplankton (mainly crustacea) were converted to carbon based units to enabel a better comparison between both groups. If carbon is used as body-mass unit ammonia excretion rates of gelatinous zooplankton are in the same range as values obtained for other zooplankton taxa, indicating a similar nitrogen output per unit of organic matter in both groups. These results suggest nutrient regeneration potential to be the same in gelatinous and non-gelatinous zooplankton, and that nutrient regeneration within the pelagic system depends more upon the carbon biomass ratio between gelatinous and other zooplankton than on physiological differences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01314803
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  • 18
    Electronic Resource
    Electronic Resource
    The common jellyfish Aurelia aurita: standing stock, excretion and nutrient regeneration in the Kiel Bight, Western Baltic (1989)
    Springer
    Marine biology 100 (1989), S. 507-514 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The population dynamics, ammonia and inorganic phosphate excretion, and nutrient regeneration of the common jellyfish Aurelia aurita was investigated from 1982 to 1984 in the Kiel Bight, western Baltic Sea. During summer 1982, medusae abundance ranged between 14 and 23 individuals 100 m-3, biomass was estimated at about 5 g C 100 m-3 and the mean final diameter of individuals was 22 cm. Abundance, based on numbers, in 1983 and 1984 was an order of magnitude lower; biomass was less than 2 g C 100 m-3 and jellyfish grew to 30 cm. During the summers of 1983 and 1984, A. aurita biomass constituted roughly 40% of that of the total zooplankton〉200 μm. In 1982, for which zooplankton data were lacking, it was assumed that medusae biomass was greater than that of all other zooplankton groups. Total ammonia excretion ranged between 6.5 and 36 μmol h-1 individual-1, whereas inorganic phosphate release was 1.4 to 5.7 μmol h-1 individual-1. Allometric equations were calculated and exponents of 0.93 for NH4−N release and 0.87 for PO4−P excretion were determined. Nitrogen and phosphorus turnover rates were 5.4 and 14.6% d-1, respectively. In 1982, the medusae population released 1 100 μmol NH4−N m-2 d-1, about 11% of the nitrogen requirements of the phytoplankton. The inorganic phosphate excretion (150 μmol m-2 d-1) sustained 23% of the nutrient demands of the primary producers. In the other two years the nutrient cycling of the medusae was much less important, and satisfied only 3 to 6% of the nutrient demands. It is suggested that in some years A. aurita is the second most important source of regenerated nutrients in Kiel Bight, next to sediment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394827
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  • 19
    Electronic Resource
    Electronic Resource
    Zooplankton standing stock and community size structure within the epipelagic zone: a comparison between the central Red Sea and the Gulf of Aden (1994)
    Springer
    Marine biology 119 (1994), S. 191-198 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Standing stock and size composition of the zooplankton comunity (〉100 μm) were studied in four depth strata of the upper 200 m of the water column during a “Meteor” cruise to the central Red Sea and Gulf of Aden in spring 1987. The central Red Sea was divided into a northern area of higher salinity and a less saline southern part. Both areas exhibited significant differences in zooplankton abundance and standing stock. The latter increased by the ratio 1:2:3 from the northern central Red Sea to its southern part and further south to the Gulf of Aden. For size structure analysis samples were fractionated into three size classes (100 to 300, 300 to 500, 500 to 5000 μm). In the central Red Sea the smallest size was dominant whereas in the Gulf of Aden the largest size fraction played a greater relative role than in the central Red Sea. This shift in size structure of the zooplankton community from the Red Sea to the Gulf of Aden is apparently primarily related to ecosystem difference between both areas, leading to a change in species composition. In addition, size reduction of individual species common to both seas may be of some significance in the extreme environment of the Red Sea.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349556
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  • 20
    Electronic Resource
    Electronic Resource
    A new estimate for the Ginzburg-Landau approximation on the real axis (1994)
    Springer
    Journal of nonlinear science 4 (1994), S. 23-34 
    Details
    ISSN: 1432-1467
    Keywords: modulation equations ; Ginzburg-Landau approximation ; nonlinear partial differential equations on unbounded domains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Summary Modulation equations play an essential role in the understanding of complicated systems near the threshold of instability. For scalar parabolic equations for which instability occurs at nonzero wavelength, we show that the associated Ginzburg-Landau equation dominates the dynamics of the nonlinear problem locally, at least over a long timescale. We develop a method which is simpler than previous ones and allows initial conditions of lower regularity. It involves a careful handling of the critical modes in the Fourier-transformed problem and an estimate of Gronwall's type. As an example, we treat the Kuramoto-Shivashinsky equation. Moreover, the method enables us to handle vector-valued problems [see G. Schneider (1992)].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02430625
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