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  • 1
    Electronic Resource
    Electronic Resource
    Nitrate storage by phytoplankton in a coastal upwelling environment (1997)
    Springer
    Marine biology 129 (1997), S. 399-406 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The storage of nitrate by phytoplankton cells during the early phases of upwelling was studied in coastal stations off northern Spain (southern Bay of Biscay) between 1990 and 1994. In this region, a persistent upwelling during summer is characterised by intermittent pulses of variable intensity, and increased nutrient concentrations in the surface layer. The main effect of an upwelling pulse on phytoplankton distribution is the shifting of the chlorophyll a and primary production maxima to near the surface. When the upwelling relaxes, thermal stratification of the water column occurs, and a distinct subsurface chlorophyll maximum develops below the production maximum. An accumulation of intracellular nitrate characterized the early phases of upwelling (mean = 2.73 μmol N m−3), maximum concentrations being attained at depths where biomass and production values were moderate. In contrast, phytoplankton cells from non-upwelling situations contained significantly lower concentrations of intracellular nitrate (mean = 0.17 μmol N m−3). The variations in the intracellular pool of nitrate may result from the differential allocation of resources within the cell as a result of variations in the energy available, since the uptake and assimilation of nitrate is a relatively expensive process involving several enzymatic systems. We hypothesize that nitrate storage by phytoplankton cells is characteristic of early phases of upwelling and is linked to patterns of carbon fixation. Average nitrogen budgets for upwelling and non-upwelling situations indicate that intracellular nitrate reserves are not responsible for maintaining high phytoplankton growth rates, since they only account for 〈2% of daily primary production during upwelling events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050180
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  • 2
    Electronic Resource
    Electronic Resource
    Variability of biochemical composition and size distributions of seston in the euphotic zone of the Bay of Biscay: implications for microplankton trophic structure (1992)
    Springer
    Marine biology 114 (1992), S. 147-155 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Particle-size distributions and several biochemical components of seston were studied from October 1986 to December 1987 in surface waters of the Bay of Biscay. Variance partitioning of hydrographic and seston parameters indicates that, although seasonal variability related to the thermal cycle was important, most of the differences in seston concentration were caused by spatial components of variance. Changes in the vertical structure of the water column appeared to be the principal source of variability. Phytoplankton blooms in spring and fall and the effects of the coastal upwelling and the thermocline during summer were traced using seston concentration and biochemical composition. The different seston measurements were scaled according to their correlations with total concentration and particle size. Photosynthetic pigment biomass was related to both large and small partieles. However, concentrations of particulate proteins, lipids and carbohydrates were more related to small particles. Although not specifically analysed, low concentrations of inorganic particles and detritus can be expected in the study area, thus most of the particulate organic matter was associated with small, non-pigmented organisms, particularly in surface waters during the period of thermal stratification. The variability in concentrations of total seston and particulate organic matter was mainly due to variations in particulate proteins, lipids and carbohydrates; pigment concentrations were of secondary importance. Expressed as the ratio chlorophyll a: particulate protein-nitrogen, phytoplankton constituted an important fraction of the microplankton biomass only during spring blooms, when it averaged 75% of the particulate protein-nitrogen. In constrast, 〈30% of protein-nitrogen was related to chlorophyll a during the summer. These results suggest that an oligotrophic structure based on the “microbial-loop” prevails in microplankton assemblages of surface waters for most of the year.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350864
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  • 3
    Electronic Resource
    Electronic Resource
    A tightly coupled and hierarchical multiprocessor architecture
    Amsterdam : Elsevier
    Computer Physics Communications 37 (1985), S. 87-93 
    Details
    ISSN: 0010-4655
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Computer Science , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0010-4655(85)90139-0
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  • 4
    Electronic Resource
    Electronic Resource
    Monopole clusters and critical dynamics in four-dimensional U(1)
    Amsterdam : Elsevier
    Nuclear Physics B (Proceedings Supplements) 34 (1994), S. 549-551 
    Details
    ISSN: 0920-5632
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0920-5632(94)90443-X
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  • 5
    Electronic Resource
    Electronic Resource
    Grim4-C1, -C2p: combination solutions of the global earth gravity field (1993)
    Springer
    Surveys in geophysics 14 (1993), S. 381-393 
    Details
    ISSN: 1573-0956
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract On the basis of the GRIM4-S1 satellite-only Earth gravity model, being accomplished in a common effort by DGFI and GRGS, a combination solution, called GRIM4-C1, has been derivcd using 1° × 1° mean gravity anomalies and 1° × 1° Seasat altimeter derived mean geoid undulations. In the meantime improvements could be achieved by incorporating more tracking data (GEOSAT, SPOT2-DORIS) into the solution, resulting in the two new parallel versions, the satellite-only gravity model GRIM4-S2 and the combined solution GRIM4-C2p (preliminary). All GRIM4 Earth gravity models cover the spectral gravitational constituents complete up to degree and order 50. In this report the emphasis is on the discussion of the combined gravity models: combination and estimation techniques, capabilities for application in precise satellite orbit computation and accuracies in long wavelength geoid representation. It is shown that with the new generation of global gravity models general purpose satellite-only models are no longer inferior to combination solutions if applied to satellite orbit restitution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00690566
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  • 6
    Electronic Resource
    Electronic Resource
    Long-wavelength global gravity field models: GRIM4-S4, GRIM4-C4 (1997)
    Springer
    Journal of geodesy 71 (1997), S. 189-208 
    Details
    ISSN: 1432-1394
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Summary.  GFZ Potsdam and GRGS Toulouse/Grasse jointly developed a new pair of global models of the Earth's gravity field to satisfy the requirements of the recent and future geodetic and altimeter satellite missions. A precise gravity model is a prerequisite for precise satellite orbit restitution, tracking station positioning and altimeter data reduction. According to different applications envisaged, the new model exists in two parallel versions: the first one being derived exclusively from satellite tracking data acquired on 34 satellites, the second one further incorporating satellite altimeter data over the oceans and terrestrial gravity data. The most recent “satellite-only” gravity model is labelled GRIM4-S4 and the “combined” gravity model GRIM4-C4. The models are solutions in spherical harmonics and have a resolution up to degree and order 60 plus a few resonance terms in the case of GRIM4-S4, and up to degree/order 72 in the case of GRIM4-C4, corresponding to a spatial resolution of 555 km at the Earth's surface. The gravitational coefficients were estimated in a rigorous least squares adjustment simultaneously with ocean tidal terms and tracking station position parameters, so that each gravity model is associated with a consistent ocean tide model and a terrestrial reference frame built up by over 300 optical, laser and Doppler tracking stations. Comprehensive quality tests with external data and models, and test arc computations over a wide range of satellites have demonstrated the state-of-the-art capabilities of both solutions in long-wavelength geoid representation and in precise orbit computation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001900050087
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  • 7
    Electronic Resource
    Electronic Resource
    Energie- und CO2-Bilanzen von Solarkollektoranlagen (1999)
    Springer
    Forschung im Ingenieurwesen 64 (1999), S. 317-324 
    Details
    ISSN: 1434-0860
    Source: Springer Online Journal Archives 1860-2000
    Topics: Technology
    Description / Table of Contents: Abstract Energy systems based on solar collectors or other renewable energy sources are normally regarded as CO2 zero-emission systems because nearly no fossil fuels are used to operate the systems. But the complete evaluation of an energy system concerning its CO2 reduction potential must not be restricted to the emissions during the operation of the system. The cumulative energy demand and the cumulative CO2 emissions during the life cycle have to be considered. In case of a solar collector system, in particular the production-determined emissions and emissions due to the requirement of auxiliary electric power for the collector pump are important. An energy analysis of this kind was performed for solar domestic hot water systems. It is shown that the consideration of the life cycle emissions reduces significantly the CO2 reduction potential of solar collector systems whereby the design of the system has a major influence.
    Notes: Zusammenfassung Solarkollektoranlagen werden ebenso wie andere regenerative Energieanlagen meist als CO2-frei angesehen, da für ihren Betrieb keine fossilen Brennstoffe eingesetzt werden. Die umfassende Beurteilung eines Energiesystems hinsichtlich seines potentiellen Beitrags zur CO2-Minderung darf sich jedoch nicht auf die betriebsbedingten Emissionen beschränken, sondern muß den kumulierten Energieeinsatz und die hiermit verbundenen CO2-Emissionen im gesamten Lebensweg des Systems erfassen. Im Fall einer Solarkollektoranlage zählen hierzu insbesondere die herstellungsbedingten Emissionen und die Emissionen aufgrund des Strombedarfs der Kollektorkreispumpe. Eine solche Analyse wurde für Solarkollektoranlagen zur Brauchwasserbereitung durchgeführt. Es zeigt sich, daß das CO2-Minderungspotential von Solarkollektoranlagen bei Berücksichtigung dieser Emissionen signifikant vermindert wird, wobei die Auslegung der Anlage einen entscheidenden Einfluß besitzt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00010843
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  • 8
    Electronic Resource
    Electronic Resource
    Preliminary studies on the reproduction and population dynamics of Monodonta lineata and Gibbula umbilicalis (Mollusca, Gastropoda) on the central coast of Asturias (N. Spain) (1986)
    Springer
    Hydrobiologia 142 (1986), S. 31-39 
    Details
    ISSN: 1573-5117
    Keywords: reproduction ; dynamics ; Gastropoda ; Trochidae ; NE Atlantic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Populations of Monodonta lineata and Gibbula umbilicalis were studied at Aramar beach (Luanco, Asturias) from October 1982 to November 1983. Both species show a sexual ratio of 1: 1 but differ in their gonadal cycle patterns. M. lineata gonadal development stages are found from November to May–June in a significant part of the population. Breeding stages occur from June–July to September, and in some individuals to November, with complete discharge of all spawn at the end of the reproductive season. Some degree of inter-annual variation is detected. Spawning stages of mature G. umbilicalis are found through the year but the higher frequencies occur in summer and autumn samples, with development phases predominating in January to May. Animals over 10 mm in shell diameter maintain their gonads close to spawning stages, completely spawned individuals being less than 10 percent. In both species variability in gonad stages for a given month reduces as size increases, indicating a certain synchrony. The new recruits of M. lineata are detected on the bare rock by September to November and are recognizable through their first year. Due to the amplitude of the breeding period and differing growth rates size distribution within an age class is wide. Size class frequencies rapidly decrease after the second year of life. The data for G. umbilicalis are difficult to interpret given the scarce number of juveniles and size overlapping.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026745
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  • 9
    Electronic Resource
    Electronic Resource
    Naturmlaufverdampfer - Alles bekannt beim alten Bekannten? (1997)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 69 (1997), S. 1288-1288 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.3306909112
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