27 research outputs found

    A comparison of volume-, temperature- and freshwater transports through arctic gateways

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    Der Arktische Ozean ist in vielerlei Hinsicht einzigartig. Das trifft nicht nur auf seine geografische Lage, sondern auch auf die Landmassen die ihn umgeben zu. Ziel dieser Masterarbeit ist die Flüsse von Volumen, Wärme und Süßwasser durch die arktischen Wasserstraßen (Davis Straße, Fram Straße, Barents Sea Opening und Bering Straße) mit Hilfe von Ozean Reanalysen zu bestimmen und mit be-obachtungsbasierten Daten zu vergleichen. Durch diesen Vergleich ist es möglich, die Güte der Ozean Reanalysen im Bereich der Arktis zu erfassen. Das Wissen über diese Güte ist vor allem im Zusammenhang mit der Bestimmung gekoppelter Energie-, Massen-, und Süßwasserhaushalte für die Arktis interessant, unter ande-rem aus Reanalysedaten. Verlässliche Ozean Reanalysen sind daher für eine gute Datengrundlage unerlässlich. Die Auswertung der Ergebnisse dieser Arbeit lässt allerdings keine klare Aussage über die Performance der Ozean Reanalysen zu. Im Großen und Ganzen können sowohl C-GLORSv5, als auch ORAS5 die Flüsse durch die Wasserstraßen adäquat wiedergeben. Betrachtet man die Wasserstraßen allerdings separat, so fallen doch größere Unterschiede auf. Die Ursachen für diese Unterschiede konnten im Zuge diese Arbeit lokalisiert und zum Teil auch begründet werden.The Arctic Ocean is unique in many ways, not only due to its geographic location, but also due to the land masses surrounding it. The aim of this master´s thesis is to determine the transport of volume, heat and freshwater through the Arctic Gateways (Davis Strait, Fram Strait, Barents Sea Opening and Bering Strait) out of different ocean reanalyses (Centro Euro-Mediterraneo sui Cambiamenti Climatici Global Ocean Reanalysis System (C-GLORSv5) & European Centre for Medium Range Weather Forecasts Ocean Reanalysis System (ORAS5)) and subsequently compare them to observation-based data from the Arctic Ocean Gateway array (ARCGATE). This comparison makes it possible to assess the quality of the ocean reanalyses in the Arctic domain. The knowledge about this quality is particularly interesting in connection with the determination of coupled energy, mass and freshwater budgets for the Arctic, among others from reanalysis data. Reliable ocean reanalyses are therefore essential for a good database. The evaluation of the results of this work does not allow a clear statement about the performance of ocean reanalysis. Generally, the reanalyses reflect adequately the regimes in the gateways and agree well with observations. However, if the gateways are treated separately, there are still major differences. The reasons for these differences could be localized in the course of this work and partly explained

    Volume transports and temperature distributions in the main Arctic Gateways: A comparative study between an ocean reanalysis and mooring-derived data

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    Oceanic transports through the Arctic gateways represent an integral part of the polar climate system, but comprehensive in-situ-based estimates of this quantity have been lacking in the past. New observation-based estimates of oceanic volume, temperature and freshwater transports have recently become available. Those estimates have been derived from moored observations in the four major gateways by applying mass and salinity constraints. We seize this opportunity to compare a recent ocean reanalysis with those observation-based estimates. First, time series of integrated volume transports through each strait are considered, along with the net heat transport into the Arctic Ocean. Good agreement is found for Davis Strait volume transports, but considerable disagreement of up to 1.1 Sv in Fram Strait and the Barents Sea Opening. The annual mean net volume export through the gateways is - 0.03 ± 0.23 Sv in the reanalysis, weaker than the - 0.15 ± 0.06 Sv derived from the observation-based estimate (uncertainties represent the monthly standard deviation). The net ocean heat transport to the Arctic Ocean is similar in the two datasets (observation-based: 153 ± 44 TW, reanalysis: 145 ± 35 TW). Discrepancies in the integrated transports are further investigated by studying cross-sections of velocity and potential temperature. These reveal good qualitative agreement in all straits, but considerable differences in the strength of major features like the East Greenland Current and the West Spitzbergen Current. Examination of the instrumental coverage reveals that areas of discrepancy are often co-located with poorly observed regions. In conclusion, both types of data sets have their merits and are recommended to be used complementarily for climate studies in this data-sparse region. The results presented in this study can contribute to the planning of future observational efforts and to the development of ocean reanalysis products

    Synthesis, in vitro and in silico assessment of organometallic Rhenium(I) and Technetium(I) thymidine complexes

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    Thymidine kinases have been identified as suitable targets for non-invasive imaging of gene therapy and cancer. Thus, there is a high interest in new, reliable and inexpensive radiolabeled thymidine analogues for these applications. In this study we present the synthesis and in vitro evaluation of M(CO)3-complexes of thymidine (M = 99mTc, Re) for potential use in SPECT tumor imaging. 5'-amino-5'-deoxythymidine was derivatized at position C5' with spacers of various lengths (not, vert, similar0–30 Å) carrying tridentate metal chelating entities such as iminodiacetic acid and picolylamine-N-monoacetic acid. The nucleoside derivatives were reacted with the precursors [ReBr3(CO)3]2− and [99mTc(OH2)3(CO)3]+, respectively. The organometallic thymidine complexes have been fully characterized by means of IR, NMR and mass spectrometry. Enzyme kinetic studies revealed mixed inhibition of the human cytosolic thymidine kinase with Ki values ranging from 4.4 to 334 μM for all thymidine complexes. Competitive inhibition of herpes simplex virus type 1 thymidine kinase was only achieved when thymidine and the metal core were separated by a spacer of approximately 30 Å length. These findings were supported by in silico molecular docking and molecular dynamic experiments
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