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  • 1
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    Transport bias by ocean currents in sedimentary microplankton assemblages: Implications for paleoceanographic reconstructions (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract Microfossils from plankton are used for paleoceanographic reconstructions. An often‐made assumption in quantitative microplankton‐based paleoceanographic reconstructions is that sedimentary assemblages represent conditions of the directly overlying surface water. However, any immobile particle sinking down the water column is subjected to transport by three‐dimensional currents, which results in a lateral relocation along transport. We model dinoflagellate cyst (dinocyst) transport in a high‐resolution (0.1° horizontally) global model of the present‐day ocean, and compare ocean conditions in the simulated origin of sedimentary particles to that in the directly overlying water. We find that the assumption that sedimentary particles represent the overlying surface waters is in most regions not valid. The bias induced by dinocyst transport depends on ocean current strength and direction, aggregation of particles which could increase the sinking speed, and the sediment sample depth. By using realistic sinking speeds of dinocysts and aggregates, extreme biases up to approximately ± 16°C warmer or ±4PSU saltier are found, while other regions show lower bias from particle transport. Our model results provide a way to mechanistically and statistically explain the unexpected occurrences of some dinocyst species outside of their `normal' occurrence region, such as the northerly occurrence of the allegedly sea‐ice‐affiliated dinocyst Selenopemphix antarctica. Exclusion of such outlier occurrences will yield better constrained ecological affinites for dinocyst species, which has implications for microfossil‐based quantitative and qualitative proxies for paleoceanographic conditions. We recommend paleoceanographers to a priori evaluate the (paleo‐)water depth, oceanographic setting, current strength and particle aggregation probability for their sedimentary microplankton assemblages.
    Print ISSN: 0883-8305
    Electronic ISSN: 2572-4525
    Topics: Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    On the state dependency of fast feedback processes in (palaeo) climate sensitivity (2014)
    Wiley
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    Publication Date: 2014-08-23
    Description: Palaeo data have been frequently used to determine the equilibrium (Charney) climate sensitivity S a , and — if slow feedback processes (e.g. land ice-albedo) are adequately taken into account — they indicate a similar range as estimates based on instrumental data and climate model results. Many studies assume the (fast) feedback processes to be independent of the background climate state, e.g., equally strong during warm and cold periods. Here we assess the dependency of the fast feedback processes on the background climate state using data of the last 800 kyr and a box-model of the climate system for interpretation. Applying a new method to account for background state dependency, we find S a  = 0.61 ± 0.07 K (W m − 2 ) − 1 (± 1 σ ) using the latest LGMtemperature reconstruction and significantly lower climate sensitivity during glacial climates. Due to uncertainties in reconstructing the LGM temperature anomaly, S a is estimated in the range S a = 0.54 – 0.95 K (W m − 2 ) − 1 .
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    MicroRNA-34a regulates cardiac ageing and function (2013)
    Nature Publishing Group (NPG)
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    Publication Date: 2013-02-22
    Description: Ageing is the predominant risk factor for cardiovascular diseases and contributes to a significantly worse outcome in patients with acute myocardial infarction. MicroRNAs (miRNAs) have emerged as crucial regulators of cardiovascular function and some miRNAs have key roles in ageing. We propose that altered expression of miRNAs in the heart during ageing contributes to the age-dependent decline in cardiac function. Here we show that miR-34a is induced in the ageing heart and that in vivo silencing or genetic deletion of miR-34a reduces age-associated cardiomyocyte cell death. Moreover, miR-34a inhibition reduces cell death and fibrosis following acute myocardial infarction and improves recovery of myocardial function. Mechanistically, we identified PNUTS (also known as PPP1R10) as a novel direct miR-34a target, which reduces telomere shortening, DNA damage responses and cardiomyocyte apoptosis, and improves functional recovery after acute myocardial infarction. Together, these results identify age-induced expression of miR-34a and inhibition of its target PNUTS as a key mechanism that regulates cardiac contractile function during ageing and after acute myocardial infarction, by inducing DNA damage responses and telomere attrition.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Boon, Reinier A -- Iekushi, Kazuma -- Lechner, Stefanie -- Seeger, Timon -- Fischer, Ariane -- Heydt, Susanne -- Kaluza, David -- Treguer, Karine -- Carmona, Guillaume -- Bonauer, Angelika -- Horrevoets, Anton J G -- Didier, Nathalie -- Girmatsion, Zenawit -- Biliczki, Peter -- Ehrlich, Joachim R -- Katus, Hugo A -- Muller, Oliver J -- Potente, Michael -- Zeiher, Andreas M -- Hermeking, Heiko -- Dimmeler, Stefanie -- England -- Nature. 2013 Mar 7;495(7439):107-10. doi: 10.1038/nature11919. Epub 2013 Feb 20.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Cardiovascular Regeneration, Centre of Molecular Medicine, Goethe University Frankfurt, 60590 Frankfurt, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23426265" target="_blank"〉PubMed〈/a〉
    Keywords: Aging/genetics/pathology/*physiology ; Animals ; Apoptosis ; DNA Damage ; Fibrosis/genetics/pathology ; Gene Deletion ; *Gene Expression Regulation ; Gene Knockout Techniques ; Genetic Therapy ; Heart/*physiology ; Mice ; Mice, Inbred C57BL ; MicroRNAs/*genetics/metabolism ; Myocardial Infarction/genetics/pathology/therapy ; Myocardium/cytology/*metabolism/pathology ; Myocytes, Cardiac/cytology/metabolism/pathology ; Substrate Specificity ; Telomere/genetics/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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