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  • 11
    Publication Date: 2016-11-29
    Description: Mesoscale model simulations were conducted for the Weddell Sea region for the autumn and winter periods of 2008 using a high-resolution, limited-area, non-hydrostatic atmospheric model. A sea ice–ocean model was run with enhanced horizontal resolution and high-resolution forcing data of the atmospheric model. Daily passive thermal and microwave satellite data was used to derive the polynya area in the Weddell Sea region. The focus of the study is on the formation of polynyas in the coastal region of Coats Land, which is strongly affected by katabatic flows. The polynya areas deduced from two independent remote sensing methods and data sources show good agreement, while the results of the sea ice simulation show some weaknesses. Linkages between the pressure gradient force composed of a katabatic and a synoptic component, offshore wind regimes and polynya area are identified. It is shown that the downslope surface offshore wind component of Coats Land is the main forcing factor for polynya dynamics, which is mainly steered by the offshore pressure gradient force, where the katabatic force is the dominant term. We find that the synoptic pressure gradient is opposed to the katabatic force during major katabatic wind events.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 12
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Cytochrome c 1 ; Promoter dissection ; HAP1, HAP2 transcription factors ; Centromere and promoter-binding factor (CPF1)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nuclear gene for cytochrome c 1 in Saccharomyces cerevisiae (CYT1) was localized on chromosome XV. Its upstream region was identified by functional complementation. Fusion to the lacZ reporter gene on a CEN plasmid allowed study of the effect of carbon sources and of specific deletion mutations on expression of the gene in yeast transformants. Detailed promoter analysis combined with expression studies in recipient strains defective in regulatory genes identified cis-acting sites and transcription factors involved in the regulated expression of the cytochrome c 1 gene. These analyses showed that, in the presence of glucose, transcription of CYT1 is positively controlled by oxygen, presumably through the haem signal, and mediated by the HAP1-encoded transactivator. It is additionally regulated by the HAP2/3/4 complex which mediates gene activation mainly under glucose-free conditions. Basal transcription is, in part, effected by CPF1, a centromere and promoter-binding factor.
    Type of Medium: Electronic Resource
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  • 13
    ISSN: 1617-4623
    Keywords: Chloramphenicol resistance ; frameshifting Mitochondria ; 21S rRNA ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A mutation shown to cause resistance to chloramphenicol inSaccharomyces cerevisiae was mapped to the central loop in domain V of the yeast mitochondrial 21S rRNA. The mutant 21S rRNA has a base pair exchange from U2677 (corresponding to U2504 inEscherichia coli) to C2677, which significantly reduces rightward frameshifting at a UU UUU UCC A site in a + 1 U mutant. There is evidence to suggest that this reduction also applies to leftward frameshifting at the same site in a − 1 U mutant. The mutation did not increase the rate of misreading of a number of mitochondrial missense, nonsense or frameshift (of both signs) mutations, and did not adversely affect the synthesis of wild-type mitochondrial gene products. It is suggested here that ribosomes bearing either the C2677 mutation or its wild-type allele may behave identically during normal decoding and only differ at sites where a ribosomal stall, by permitting non-standard decoding, differentially affects the normal interaction of tRNAs with the chloramphenicol resistant domain V. Chloramphenicol-resistant mutations mapping at two other sites in domain V are described. These mutations had no effect on frameshifting.
    Type of Medium: Electronic Resource
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  • 14
    ISSN: 1617-7134
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Conclusion Concerning the interpretation of the positive association between seller concentration and profitability we suggest that concentration should primarily be considered as an indicator of monopoly power. This proposition is based on the finding of an inverse relationship between concentration and wages which, theoretically, can be traced back to monopoly. By the same standard of evaluation, vertical integration of successive stages of production within a single firm appears to yield efficiency gains on balance whereas in the case of cartels of the kind permitted in West Germany monopolizing and efficiency raising effects appear to just cancel.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Biochemistry 18 (1979), S. 1212-1217 
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 16
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Non-heterocystous, mostly filamentous cyanobacteria were isolated from the crust of stones, from the periphyton of two macrophytes from the littoral zone and from the pelagic environment of Lake Constance. All isolates were cultivated as unialgal strains. DNA analysis by restriction fragment length polymorphism with the psbA gene probe revealed high genetic diversity among the strains from the littoral zone. For all genotypes, the occurrence of the nifH gene encoding a nitrogenase subunit and of genes encoding subunits of phycoerythrin and phycocyanin were tested by Southern blot hybridization. In addition, the isolates were investigated for their ability for complementary chromatic adaptation (CCA) and for anaerobic N2-fixation. With respect to these characteristics, all cyanobacteria included in this study were assigned to four different types: (1) strains without the capability to fix N2 or to perform CCA of the group III type (CCA III); (2) strains which show both features; (3) strains with the ability to fix nitrogen, but that do not show any CCA III; and (4) strains that produce phycoerythrin, but without the capacity for CCA III or N2-fixation. By examining the frequency distribution of isolates, these types were shown to prefer different habitats. While cyanobacterial strains capable of N2-fixation, but without CCA III, were mainly obtained from stone crusts in the supralittoral zone, those with the potential for N2-fixation as well as for CCA III were largely isolated from submersed macrophytes. Cyanobacteria that produce phycoerythrin, but do not perform CCA III or N2-fixation, were found in the pelagic zone only.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 213 (1967), S. 420-421 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] This requirement for light is mediated by phytochrome. Considerable evidence indicates that phytochrome must be converted to the P/r form (with an absorbance maximum at 735 m[jt,) for germination to occur3. We have administered CIPC to seeds imbibing in darkness, irradiated them with red light ...
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  • 18
    Publication Date: 2014-12-11
    Description: The thermohaline circulation of the world ocean is partly driven by deep water formation at high-latitudes. In the Southern Ocean, deep and bottom water formation in the marginal seas is induced by high freezing rates as generally found at coastal polynyas. Atmospheric cooling and brine-release enable the production of very cold and saline water masses. In the southwestern Weddell Sea, wide shelves allow for a strong salinification of the whole water column and the formation of High Salinity Shelf Water (HSSW). The impact of coastal polynyas on ice production and water mass formation in the southwestern Weddell Sea was studied employing the Finite Element Sea ice-Ocean Model (FESOM) of the Alfred Wegener Institute, Bremerhaven. FESOM is a coupled system of a primitive-equation, hydrostatic ocean model and a dynamic-thermodynamic sea ice model. Simulations were conducted on a global unstructured mesh with a strong focus on the southwestern Weddell Sea coastline (up to 3 km resolution). In vertical direction, the grid features 37 z-coordinate depth levels of which 6 are within the uppermost 100 m. The model runs were initialised in 1980 and forced with NCEP reanalysis data (daily resolution). The year 2008 was also simulated with higher-resolution GME and regional COSMO forcing data. For data evaluation and analysis the period 1990-2009 is used. A comparison of AMSR sea ice concentration and model results shows good accordance in spatial and temporal polynya extent. Also, calculated vertical temperature and salinity profiles agree well with CTD measurements. Our simulations feature a 20-year winter mean area of coastal polynyas of 6.7 x 10-3 km-2 (0.4% of the continental shelf area) in the southwestern Weddell Sea which is in good agreement with observations. Winter sea ice production within the coastal polynyas exceeds the ice production of the surrounding ice-covered area by a factor of 7 in the 20-year mean, so that the polynya contribution to total sea ice formation averages at about 3%. This small percentage is due to their even smaller areal percentage and the existence of leads and small polynyas in the so-called ice-covered ocean. The latter give a major contribution to sea ice production, but do not contribute to bottom water formation since they are transient elements that open, move and close dependent on the ice drift, whereas coastal polynyas are spatially fixed and open often for days, which is essential to achieve the salinification necessary for the formation of HSSW. From our simulations we derive a 20-year mean HSSW-formation of 4.2 x 10-5 km-3/season, but only 0.5 Sv thereof are exported over the shelf break, the rest stays on the shelf and is warmed and diluted during summer. The WSBW formation rate for the southwestern Weddell Sea continental shelf in our simulation is about 6.3 x 10-4 km-3/yr (2 Sv), which is on the low side but still reasonable compared to independent estimates. We conclude that in the Weddell Sea the role of coastal polynyas for sea ice production is not as big as is widely assumed, but they are indispensable for the formation of HSSW and thus for bottom water formation.
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 19
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    In:  [Other] In: 24. Internationale Polartagung, 06.09.-10.09.2010, Obergurgl, Austria .
    Publication Date: 2014-12-18
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 20
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    In:  [Poster] In: SCAR and Open Science Conference "Antarctic Perspectives - Connecting the Arts to Science", 16.07.-19.07.2012, Portland, Oregeon, USA .
    Publication Date: 2014-12-12
    Description: For any climate signal to leave an imprint on the Antarctic Bottom Water (AABW) that fills the World Ocean abyss, it has to pass through the process of bottom water formation in the marginal seas of the Southern Ocean. An indispensable component of AABW is the dense shelf waters created on the continental shelves around Antarctica, particularly in the Ross and Weddell Seas. At coastal polynyas we find strong atmospheric cooling and high freezing rates that lead to a strong salinification of the water column. Here the bulk of High Salinity Shelf Water (HSSW) is formed. The impact of coastal polynyas on ice production and water mass formation in the southwestern Weddell Sea was studied employing the Finite Element Sea ice-Ocean Model (FESOM) of Alfred Wegener Institute, Bremerhaven. FESOM is a coupled system of a primitive-equation, hydrostatic ocean model and a dynamic-thermodynamic sea ice model. Simulations were conducted on a global unstructured mesh with a strong focus on the southwestern Weddell Sea coastline (up to 3 km resolution). The model runs were initialised in 1980 and forced with NCEP reanalysis data (daily resolution). For 2008 also higher-resolution GME data and results from the regional COSMO atmosphere model of University Trier were applied as atmospheric forcing data. The period 1990-2009 is used for data analysis. Our simulations indicate that mean winter sea ice production within the coastal polynyas exceeds the surrounding area’s ice production by a factor of 7, giving a polynya contribution to total sea ice formation of 3 %. This small percentage is due to their even smaller areal percentage (0.4 %), and also the existence of leads and small polynyas in the ‘ice-covered’ ocean. The latter contribute substantially to sea ice production, but not to bottom water formation since they are transient elements that open, move and close dependent on the ice drift, whereas coastal polynyas are fixed in space and often open for days, enabling the salinification necessary for HSSW formation. From our simulations we derive a mean HSSW-formation of 4.2∙10^5 km^3/winter, but only 0.5 Sv thereof are exported over the shelf break, the rest stays on the shelf and is warmed and diluted during the following summer. The WSBW formation rate for the southwestern Weddell Sea continental shelf in our simulation is about 6.3∙10^4 km^3/yr (2 Sv), which is on the low side but still reasonable compared to independent estimates.
    Type: Conference or Workshop Item , NonPeerReviewed
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