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  • 1
    Electronic Resource
    Electronic Resource
    Mikroskopische Untersuchungen von Kautschukdispersionen in Bitumen (1958)
    Springer
    Colloid & polymer science 156 (1958), S. 122-132 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Zusammenfassung Mikroskopische Untersuchungen zeigen, daß der Kautschuk in Bitumen-Kautschuk-Mischungen kolloid in Form von Molekülaggregaten dispergiert ist, die im mikroskopischen Bild Kugelgestalt haben, solange die Konzentration an Kautschuk einen bestimmten Betrag nicht überschreitet bzw. die Restbitumenphase zu hart wird. Für die Teilchengröße der Kautschukkugeln ist in erster Linie das verwendete Bitumen maßgebend; in einem aromatischen Bitumen (Wonokromo) sind die Teilchen etwa halb so groß wie in einem normalen Bitumen (Stanvac), obgleich die qualitativen Vergleichsmessungen zeigen, daß in ersteren die Quellung des Kautschuks bedeutend höher ist. Solange die Temperatur beim Einmischen des Kautschuks in Bitumen niedriger als 250° C ist, wird der Kautschuk nicht abgebaut und das mikroskopische Bild bleibt unverändert; dies wird auf eine starke antioxydierende Wirkung des Bitumens zurückgeführt. Oberhalb 250° C tritt eine thermische Zersetzung des Kautschuks ein und es sind keine Kautschukteilchen mehr sichtbar. Die Untersuchungen über die Löslichkeit des Kautschuks in Acetonextrakten vom Bitumen und das Verschwinden der Kautschukteilchen bei Zusatz von Kautschuklösungsmitteln zeigen, daß Kautschuk in ein Lösungsmittel-Fällungsmittel-Gemisch eingebettet ist, dessen Fällungsmittel-Konzentration so hoch ist, daß sich der Kautschuk bezüglich seines Dispersionszustandes weit im Koagulationsgebiet befindet. Als Kautschuk-Fällungsmittel sind dunkle Bitumenbestandteile (evtl. Harze) und Asphaltene anzusehen. Vergleich zwischen rheologischen Verstärkungswerten und Dispersionsgrad des Kautschuks im Bitumen ergibt keine erkennbare Beziehung; dies wird darauf zurückgeführt, daß die Messung des Penetrationsindex nur die Restbitumenphase erfaßt. Während einer längeren Lagerung bei Zimmertemperatur von Kautschuk-Bitumen-Mischungen können nur ölartige Bestandteile durch den Kautschuk aufgenommen werden, der Dispersionszustand des Kautschuks bleibt jedoch nahezu unverändert. Weiterhin zeigen unsere Untersuchungen, daß die in manchen Bitumen vorliegenden weißen Kristalle (vermutlich Paraffine) beim Einmischen von genügend Kautschuk verschwinden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01679776
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Diffusion, thermodiffusion, and thermal diffusion of polystyrene in solution (1962)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 57 (1962), S. 227-239 
    Details
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Diffusion coefficients D and Ludwig-Soret coefficients D′/D of polystyrene in toluene were determined in a convection-free thermodiffusion cell of 1 to 4 mm. height, 100 mm. length, and at a temperature differences of 0.1 to 0.3°C. The cell had two chambers, thus allowing observation of the concentration gradient alone by optical elimination of the temperature gradient. Philpot-Svensson and Gouy optical methods were used. Both equilibration from homogeneous concentration to Ludwig-Soret equilibrium and from this back to homogeneous concentration lead to D and D′/D. The last method, operating with ΔT = 0 gave more exact results. It was possible to measure very low diffusion coefficients (below 10-7 cm.2sec.-1). For sharp fractions the agreement with the free diffusion is good. For broader samples the thermodiffusional D is smaller than D of free diffusion. This difference is in accordance with the different averaging of the two methods. Up to ΔT = 0.3°C. no variation of D′/D with temperature was found. The Ludwig-Soret coefficients increase with increasing molecular weight M and decreasing concentration. The thermal diffusion coefficient D′ is nearly independent of M and shows only a very slight decline with concentration. The results of our experiments are discussed together with the work of other authors using different techniques.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1962.1205716518
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  • 3
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    Mikroskopische Untersuchungen von Kautschukdispersionen in Bitumen (1958)
    Springer
    Details
    Publication Date: 1958-02-01
    Print ISSN: 0372-820X
    Electronic ISSN: 1435-1536
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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  • 4
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    Maximum rates of N2 fixation and primary production are out of phase in a developing cyanobacterial bloom in the Baltic Sea (2002)
    Wiley
    Details
    Publication Date: 2002-09-01
    Print ISSN: 0024-3590
    Electronic ISSN: 1939-5590
    Topics: Biology , Geosciences , Physics
    Published by Wiley on behalf of Association for the Sciences of Limnology and Oceanography.
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  • 5
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    Nitrogen and phosphorus co-limitation of bacterial productivity and growth in the oligotrophic subtropical North Atlantic (2008)
    Wiley
    Details
    Publication Date: 2008-03-01
    Print ISSN: 0024-3590
    Electronic ISSN: 1939-5590
    Topics: Biology , Geosciences , Physics
    Published by Wiley on behalf of Association for the Sciences of Limnology and Oceanography.
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  • 6
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    Element budgets in an Arctic mesocosm CO2 perturbation study (2012)
    Copernicus
    Details
    Publication Date: 2012-08-31
    Description: Recent studies on the impacts of ocean acidification on pelagic communities have identified changes in carbon to nutrient dynamics with related shifts in elemental stoichiometry. In principle, mesocosm experiments provide the opportunity of determining the temporal dynamics of all relevant carbon and nutrient pools and, thus, calculating elemental budgets. In practice, attempts to budget mesocosm enclosures are often hampered by uncertainties in some of the measured pools and fluxes, in particular due to uncertainties in constraining air/sea gas exchange, particle sinking, and wall growth. In an Arctic mesocosm study on ocean acidification using KOSMOS (Kiel Off-Shore Mesocosms for future Ocean Simulation) all relevant element pools and fluxes of carbon, nitrogen and phosphorus were measured, using an improved experimental design intended to narrow down some of the mentioned uncertainties. Water column concentrations of particulate and dissolved organic and inorganic constituents were determined daily. New approaches for quantitative estimates of material sinking to the bottom of the mesocosms and gas exchange in 48 h temporal resolution, as well as estimates of wall growth were developed to close the gaps in element budgets. Future elevated pCO2 was found to enhance net autotrophic community carbon uptake in 2 of the 3 experimental phases but did not significantly affect particle elemental composition. Enhanced carbon consumption appears to result in accumulation of dissolved organic compounds under nutrient recycling summer conditions. This carbon over-consumption effect becomes evident from budget calculations, but was too small to be resolved by direct measurements of dissolved organics. The out-competing of large diatoms by comparatively small algae in nutrient uptake caused reduced production rates under future ocean CO2 conditions in the end of the experiment. This CO2 induced shift away from diatoms towards smaller phytoplankton and enhanced cycling of dissolved organics was pushing the system towards a retention type food chain with overall negative effects on export potential.
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 7
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    Time depending shortest-path problems with applications to railway networks (1995)
    Elsevier
    Details
    Publication Date: 1995-05-01
    Print ISSN: 0377-2217
    Electronic ISSN: 1872-6860
    Topics: Mathematics , Economics
    Published by Elsevier
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  • 8
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    The significance of nitrogen fixation to new production during early summer in the Baltic Sea (2007)
    Copernicus
    Details
    Publication Date: 2007-01-18
    Description: Rates of dinitrogen (N2) fixation and primary production were measured during two 9 day transect cruises in the Baltic proper in June–July of 1998 and 1999. Assuming that the early phase of the bloom of cyanobacteria lasted a month, total rates of N2 fixation contributed 15 mmol N m−2 (1998) and 33 mmol N m−2 (1999) to new production (sensu Dugdale and Goering, 1967). This constitutes 12–26% more new N than other annual estimates (mid July–mid October) from the same region. The between-station variability observed in both total N2 fixation and primary productivity greatly emphasizes the need for multiple stations and seasonal sampling strategies in biogeochemical studies of the Baltic Sea. The majority of new N from N2 fixation was contributed by filamentous cyanobacteria. On average, cyanobacterial cells 〉20 µm were able to supply a major part of their N requirements for growth by N2 fixation in both 1998 (73%) and 1999 (81%). The between-station variability was high however, and ranged from 28–150% of N needed to meet the rate of C incorporation by primary production. The molar C:N rate incorporation ratio (C:NRATE) in filamentous cyanobacterial cells was variable (range 7–28) and the average almost twice as high as the Redfield ratio (6.6) in both years. Since the molar C:N mass ratio (C:NMASS) in filamentous cyanobacterial cells was generally lower than C:NRATE at a number of stations, we suggest that the diazotrophs incorporated excess C on a short term basis (carbohydrate ballasting and buoyancy regulation), released nitrogen or utilized other regenerated sources of N nutrients. Measured rates of total N2 fixation contributed only a minor fraction of 13% (range 4–24) in 1998 and 18% (range 2–45) in 1999 to the amount of N needed for the community primary production. An average of 9 and 15% of total N2 fixation was found in cells
    Print ISSN: 1726-4170
    Electronic ISSN: 1726-4189
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 9
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    The significance of nitrogen fixation to new production during early summer in the Baltic Sea (2006)
    Copernicus
    Details
    Publication Date: 2006-08-09
    Description: Rates of dinitrogen (N2) fixation and primary production were measured during two 9 day transect cruises in the Baltic proper in June–July of 1998 and 1999. Assuming that the early phase of the bloom of cyanobacteria lasted a month, total rates of N2 fixation contributed 15 mmol N m-2 (1998) and 33 mmol N m-2 (1999) to new production (sensu Dugdale and Goering, 1967). This constitutes 12–26% more new N than other annual estimates (mid July–mid October) from the same region. The between-station variability observed in both total N2 fixation and primary productivity greatly emphasize the need for multiple stations and seasonal sampling strategies in biochemical studies of the Baltic Sea. The majority of new N from N2 fixation was contributed by filamentous cyanobacteria. On average, cyanobacterial cells 〉20 µm were able to supply a major part of their N requirements for growth by N2 fixation in both 1998 (73%) and 1999 (81%). The between-station variability was high however, and ranged from 28–150% of N needed to meet the rate of C incorporation by primary production. Since the molar C:N rate incorporation ratio (C:NRATE) in filamentous cyanobacterial cells was almost twice as high as the molar C:N mass ratio (C:NMASS) in both years, we suggest that the diazotrophs incorporated excess C on a short term basis (for carbohydrate ballasting and buoyancy regulation), released nitrogen or utilized other regenerated sources of N nutrients. Measured rates of total N2 fixation contributed only a minor fraction of 13% (range 4–24) in 1998 and 18% (range 2–45) in 1999 to the amount of N needed for the community primary production. An average of 9 and 15% of total N2 fixation was found in cells
    Print ISSN: 1810-6277
    Electronic ISSN: 1810-6285
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 10
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    Implications of elevated CO2 on pelagic carbon fluxes in an Arctic mesocosm study – an elemental mass balance approach (2013)
    Copernicus
    Details
    Publication Date: 2013-05-08
    Description: Recent studies on the impacts of ocean acidification on pelagic communities have identified changes in carbon to nutrient dynamics with related shifts in elemental stoichiometry. In principle, mesocosm experiments provide the opportunity of determining temporal dynamics of all relevant carbon and nutrient pools and, thus, calculating elemental budgets. In practice, attempts to budget mesocosm enclosures are often hampered by uncertainties in some of the measured pools and fluxes, in particular due to uncertainties in constraining air–sea gas exchange, particle sinking, and wall growth. In an Arctic mesocosm study on ocean acidification applying KOSMOS (Kiel Off-Shore Mesocosms for future Ocean Simulation), all relevant element pools and fluxes of carbon, nitrogen and phosphorus were measured, using an improved experimental design intended to narrow down the mentioned uncertainties. Water-column concentrations of particulate and dissolved organic and inorganic matter were determined daily. New approaches for quantitative estimates of material sinking to the bottom of the mesocosms and gas exchange in 48 h temporal resolution as well as estimates of wall growth were developed to close the gaps in element budgets. However, losses elements from the budgets into a sum of insufficiently determined pools were detected, and are principally unavoidable in mesocosm investigation. The comparison of variability patterns of all single measured datasets revealed analytic precision to be the main issue in determination of budgets. Uncertainties in dissolved organic carbon (DOC), nitrogen (DON) and particulate organic phosphorus (POP) were much higher than the summed error in determination of the same elements in all other pools. With estimates provided for all other major elemental pools, mass balance calculations could be used to infer the temporal development of DOC, DON and POP pools. Future elevated pCO2 was found to enhance net autotrophic community carbon uptake in two of the three experimental phases but did not significantly affect particle elemental composition. Enhanced carbon consumption appears to result in accumulation of dissolved organic carbon under nutrient-recycling summer conditions. This carbon over-consumption effect becomes evident from mass balance calculations, but was too small to be resolved by direct measurements of dissolved organic matter. Faster nutrient uptake by comparatively small algae at high CO2 after nutrient addition resulted in reduced production rates under future ocean CO2 conditions at the end of the experiment. This CO2 mediated shift towards smaller phytoplankton and enhanced cycling of dissolved matter restricted the development of larger phytoplankton, thus pushing the system towards a retention type food chain with overall negative effects on export potential.
    Print ISSN: 1726-4170
    Electronic ISSN: 1726-4189
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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