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  • Springer  (33)
  • BioMed Central  (2)
  • 1990-1994  (32)
  • 1880-1889  (3)
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  • 1
    Digitale Medien
    Digitale Medien
    A comparison of carbon-specific respiration rates in gelatinous and non-gelatinous zooplankton: A search for general rules in zooplankton metabolism (1992)
    Springer
    Helgoland marine research 46 (1992), S. 377-388 
    Details
    ISSN: 1438-3888
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Using 470 data from the literature the dry weight-specific respiration rates of gelatinous zooplankton (cnidarians, ctenophores and salps) and non-gelatinous zooplankton (mainly crustacea) were converted to carbon-specific values. The resulting carbon-specific respiration rates showed no significant differences between the two groups of zooplankton, indicating similar oxygen requirements per gram of carbon biomass. From this finding, it can be suggested that the differences in the rates of oxygen consumption measured in the two types of zooplankton in the sea can be explained by the carbon biomass ratio between gelatinous and non-gelatinous zooplankton. Furthermore, the low rate of metabolism of gelatinous species compared with that of non-gelatinous animals of the same volume can be attributed predominantly to the relatively low organic matter content in the former. It is recommended that all weight-specific metabolism rates be expressed using carbon as body mass unit (e.g. mg O2 gC−1 d−1) which enables more accurate comparisons between individuals exhibiting different dry weight/carbon ratios.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02367205
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  • 2
    Digitale Medien
    Digitale Medien
    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
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02367034
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  • 3
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Phthalocyanine-cobalt complexes ; catalyst ; thiol oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00701033
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  • 4
    Digitale Medien
    Digitale Medien
    Advances in control-volume-based finite-element methods for compressible flows (1994)
    Springer
    Computational mechanics 14 (1994), S. 431-446 
    Details
    ISSN: 1432-0924
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00377597
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  • 5
    Digitale Medien
    Digitale Medien
    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
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01314803
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  • 6
    Digitale Medien
    Digitale Medien
    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
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00349556
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  • 7
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): modulation equations ; Ginzburg-Landau approximation ; nonlinear partial differential equations on unbounded domains
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Physik
    Notizen: 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)].
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02430625
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  • 8
    Digitale Medien
    Digitale Medien
    The effect of the environment on the permeability and composition of Citrus leaf cuticles (1990)
    Springer
    Planta 180 (1990), S. 154-165 
    Details
    ISSN: 1432-2048
    Schlagwort(e): Citrus ; Cuticle (composition, permeability) ; Lipid (soluble) ; Permeability (cuticle) ; Temperature and cuticle composition ; Wax (cuticle)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The constituents of the soluble cuticular lipids (SCL) of the leaf blades of Citrus aurantium L. were identified by gas chromatography-mass spectrometry and quantified. Major components were 1-alkanols (C24 to C40), n-alkyl esters (C36 to C56), n-alkanoic acids (C28 to C34), n-alkanes (C22 to C40) and triterpenones, while n-alkanals (C29 to C38), sterols, and alkyl benzenes (molecular weights 260, 274 and 288) made minor contributions. Leaf age and side significantly affected the quantitative composition of SCL. Increased day temperature during the development of leaves led to decreased amounts per unit area of n-alkanes, 1-alkanols, n-alkanoic acids and n-alkyl esters while increased night temperatures resulted in increased amounts of n-alkanes n-alkanoic acids and 1-alkanols. Relative humidity had no effect on the amounts or composition of SCL. The permeability of cuticular membranes to water (described in part I of this paper) and the composition of SCL were not related. A model for the molecular structure of the transport-limiting barrier of plant cuticles and for the transport of water across it is proposed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00193990
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  • 9
    Digitale Medien
    Digitale Medien
    Multi-element characterization of tobacco smoke condensate (1994)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 348 (1994), S. 218-225 
    Details
    ISSN: 1618-2650
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract In an interlaboratory study, 57 elements were assayed and 35 of them determined in cigarette smoke condensate of two different cigarette brands. The methods applied included inductively coupled plasma mass spectrometry, total reflection X-ray fluorescence analysis, instrumental neutron activation analysis and atomic absorption spectrometry. The main components carbon, hydrogen and nitrogen were determined by a CHN-combustion method. Sulphur was determined by a method based on the formation of hydrogen sulphide and precipitation micro-titrimetry. Considering the occurring concentrations and the toxicity, the most relevant elements in cigarette smoke condensate are arsenic, cadmium and lead which have relatively high transfer rates from tobacco into smoke.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00325364
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  • 10
    Digitale Medien
    Digitale Medien
    Ueber das optische Drehungsvermögen organischer Substanzen (1883)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 22 (1883), S. 112-114 
    Details
    ISSN: 1618-2650
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01338024
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