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  • 1
    Electronic Resource
    Electronic Resource
    A New Method of Resolving a Racemic Compound (1938)
    [s.l.] : Nature Publishing Group
    Nature 142 (1938), S. 163-163 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] WE are greatly interested to read of the success obtained by Prof. Karagunis and G. Coumoulos in effecting a partial resolution of a complex chromium salt by the use of active quartz. Following up the work of Tsuchida, Kobayashi and Nakamura1 upon the detection of a raeemic ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/142163a0
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Strong responses of Southern Ocean phytoplankton communities to volcanic ash (2014)
    AGU (American Geophysical Union) | Wiley
    In:  Geophysical Research Letters, 41 (8). pp. 2851-2857.
    Details
    Publication Date: 2021-04-23
    Description: Volcanic eruptions have been hypothesized as an iron supply mechanism for phytoplankton blooms; however, little direct evidence of stimulatory responses has been obtained in the field. Here we present the results of twenty-one 1-2day bottle enrichment experiments from cruises in the South Atlantic and Southern Ocean which conclusively demonstrated a photophysiological and biomass stimulation of phytoplankton communities following supply of basaltic or rhyolitic volcanic ash. Furthermore, experiments in the Southern Ocean demonstrated significant phytoplankton community responses to volcanic ash supply in the absence of responses to addition of dissolved iron alone. At these sites, dissolved manganese concentrations were among the lowest ever measured in seawater, and we therefore suggest that the enhanced response to ash may have been a result of the relief of manganese (co)limitation. Our results imply that volcanic ash deposition events could trigger extensive phytoplankton blooms, potentially capable of significant impacts on regional carbon cycling.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2014GL059364
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Nutrient regimes control phytoplankton ecophysiology in the South Atlantic (2014)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 11 (2). pp. 463-479.
    Details
    Publication Date: 2014-12-16
    Description: Fast Repetition Rate fluorometry (FRRf) measurements of phytoplankton photophysiology from an acrossbasin South Atlantic cruise (as part of the GEOTRACES programme) characterised two dominant ecophysiological regimes which were interpreted on the basis of nutrient limitation. South of the South Subtropical Convergence (SSTC) in the northern sub-Antarctic sector of the Antarctic Circumpolar Current (ACC) in the Eastern Atlantic Basin, waters are characterised by elevated chlorophyll concentrations, a dominance by larger phytoplankton cells, and low apparent photochemical efficiency (Fv / Fm). Shipboard 24 h iron (Fe) addition incubation experiments confirmed that Fe stress was primarily responsible for the low Fv / Fm, with Fe addition to these waters, either within the artificial bottle additions or naturally occurring downstream enrichment from Gough Island, significantly increasing Fv / Fm values. To the north of the SSTC at the southern boundary of the South Atlantic Gyre, phytoplankton are characterised by high values of Fv / Fm which, coupled with the low macronutrient concentrations and increased presence of picocyanobacteria, are interpreted as conditions of Fe replete, balanced macronutrient-limited growth. Spatial correlation was found between Fv / Fm and Fe:nitrate ratios, supporting the suggestion that the relative supply ratios of these two nutrients can control patterns of limitation and consequently the ecophysiology of phytoplankton in subtropical gyre and ACC regimes.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.5194/bg-11-463-2014
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Relative paleo intensities and 〈sup〉10〈/sup〉Be production rates during the Iceland Basin excursion (2006)
    In:  [Other] In: AGU Fall Meeting, 11.12, San Francisco, California, USA .
    Details
    Publication Date: 2012-02-23
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Talk
  • 5
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    High-resolution records of 〈sup〉10〈/sup〉Be production rates during the Iceland Basin excursion (2006)
    In:  [Other] In: Goldschmidt Conference, 29.08, Melbourne, Australia .
    Details
    Publication Date: 2012-02-23
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Talk
  • 6
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    Coral Li/Ca in micro-structural domains as a temperature proxy (2008)
    In:  [Poster] In: Goldschmidt Conference, 13.07.-18.07, Vancouver, British Columbia, Canada .
    Details
    Publication Date: 2012-02-23
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Poster
  • 7
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    Cd as a micronutrient and macrotoxin in the oceans [Physical Sciences] (2013)
    National Academy of Sciences
    Details
    Publication Date: 2013-05-22
    Description: We thank François Morel for his interest in our study. Morel states that our conclusions are based on the approximate match between the Cd-isotope composition of cultured bacteria and the fractionation of Cd isotopes seen in seawater (1). This match is only a minor component of our argument, and we...
    Keywords: Letters
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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    PAPER CURRENT
  • 8
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    High-resolution record of the Laschamp geomagnetic excursion at the Blake-Bahama Outer Ridge (2013)
    Oxford University Press
    Details
    Publication Date: 2013-11-04
    Description: Geomagnetic excursions are brief deviations of the geomagnetic field from behaviour expected during ‘normal secular’ variation. The Laschamp excursion at ~41 ka was one such deviation. Previously published records suggest rapid changes in field direction and a concurrent substantial decrease in field intensity associated with this excursion. Accurate dating of excursions, and determination of their durations from multiple locations, is vital to our understanding of global field behaviour during these deviations. We present here high-resolution palaeomagnetic records of the Laschamp excursion obtained from two Ocean Drilling Program (ODP) Sites, 1061 and 1062 on the Blake-Bahama Outer Ridge (ODP Leg 172). High sedimentation rates (~30–40 cm kyr –1 ) at these locations allow determination of transitional field behaviour during the excursion. Palaeomagnetic measurements of discrete samples from four cores reveal a single excursional feature, across an interval of 30 cm, associated with a broader palaeointensity low. We determine the age and duration of the Laschamp excursion using a stratigraphy linked to the 18 O record from the Greenland ice cores. This chronology dates the Laschamp excursion at the Blake Ridge to 41.3 ka. The excursion is characterized by rapid transitions (less than 200 yr) between stable normal polarity and a partially reversed polarity state. The palaeointensity record is in good agreement between the two sites, revealing two prominent minima. The first minimum is associated with the Laschamp excursion at 41 ka and the second corresponds to the Mono Lake excursion at ~35.5 ka. We determine that the directional excursion during the Laschamp at this location was no longer than ~400 yr, occurring within a palaeointensity minimum that lasted 2000 yr. The Laschamp excursion at this location is much shorter in duration than the Blake and Iceland Basin excursions.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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    PAPER CURRENT
  • 9
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    231Pa/230Th fractionation by ocean transport, biogenic particle flux and particle type (2005)
    Elsevier
    In:  Earth and Planetary Science Letters, 237 . pp. 135-155.
    Details
    Publication Date: 2016-12-21
    Description: 231Pa and 230Th are removed from the water column by a process of reversible scavenging which quickly removes 230Th to the sediment. 231Pa is less efficiently scavenged onto particles than 230Th and is therefore more effectively transported via advection and diffusion before it reaches the ocean sediment. This study combines particle fields (dust, opal, CaCO3, POC) derived from observations with the Bern3D intermediate complexity ocean model and an equilibrium-scavenging model for isotopes. The equilibrium partition coefficient for particulate versus dissolved isotope activity is varied with particle type. The model can explain many of the features of the global 231Pa and 230Th distribution. The success of such a simple model at representing the global pattern of 231Pa / 230Th activity ratio supports the use of this proxy in paleoceanographic studies. We use the model to address the controversy concerning which particle types are dominant in fractionating 231Pa / 230Th in the ocean. The lithogenic (dust) flux is found to be unimportant for 231Pa / 230Th fractionation— the ocean fractionation of 231Pa / 230Th is dominated by the distribution of the CaCO3 and opal flux. We also confirm that opal is a weak scavenger of 230Th.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1016/j.epsl.2005.05.031
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    In-phase anomalies in Beryllium-10 production and palaeomagentic field behaviour during the Iceland Basin geomagnetic excursion (2008)
    Elsevier
    In:  Earth and Planetary Science Letters, 265 . pp. 588-599.
    Details
    Publication Date: 2019-09-23
    Description: Increases in the production rate of cosmogenic radionuclides associated with geomagnetic excursions have been used as global tie-points for correlation between records of past climate from marine and terrestrial archives. We have investigated the relative timing of variations in 10Be production rate and the corresponding palaeomagnetic signal during one of the largest Pleistocene excursions, the Iceland Basin (IB) event (ca. 190 kyr), as recorded in two marine sediment cores (ODP Sites 1063 and 983) with high sedimentation rates. Variations in 10Be production rate during the excursion were estimated by use of 230Thxs normalized 10Be deposition rates and authigenic 10Be/9Be. Resulting 10Be production rates are compared with high-resolution records of geomagnetic field behaviour acquired from the same discrete samples. We find no evidence for a significant lock-in depth of the palaeomagnetic signal in these high sedimentation-rate cores. Apparent lock-in depths in other cores may sometimes be the result of lower sample resolution. Our results also indicate that the period of increased 10Be production during the IB excursion lasted longer and, most likely, started earlier than the corresponding palaeomagnetic anomaly, in accordance with previous observations that polarity transitions occur after periods of reduced geomagnetic field intensity prior to the transition. The lack of evidence in this study for a significant palaeomagnetic lock-in depth suggests that there is no systematic offset between the 10Be signal and palaeomagnetic anomalies associated with excursions and reversals, with significance for the global correlation of climate records from different archives.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.epsl.2007.10.051
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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