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Alexander Sekita,1 Harald Unterweger,1 Sonja Berg,1 Sabine Ohlmeyer,2 Tobias Bäuerle,3 Kang H Zheng,4 Bram F Coolen,5 Aart J Nederveen,6 Claudia Cabella,7 Silvia Rossi,7 Erik SG Stroes,4 Christoph Alexiou,1 Stefan Lyer,1,* Iwona Cicha1,* 1ENT-Department, Section of Experimental Oncology Und Nanomedicine (SEON), Else Kröner-Fresenius-Stiftung-Professorship, Universitätsklinikum Erlangen, Erlangen, Germany; 2Institute of Radiology, Universitätsklinikum Erlangen, Erlangen, Germany; 3Preclinical Imaging Platform Erlangen (PIPE), Universitätsklinikum Erlangen, Erlangen, Germany; 4Department of Vascular Medicine, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, the Netherlands; 5Department of Biomedical Engineering and Physics, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, the Netherlands; 6Department of Radiology and Nuclear Medicine, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, the Netherlands; 7Bracco Imaging SpA, Centro Ricerche Bracco, Colleretto Giacosa, Turin, Italy*These authors contributed equally to this workCorrespondence: Iwona Cicha, Universitätsklinikum Erlangen, Glückstr, 10a, Erlangen, 91054, Germany, Tel +49 9131 85 43953, Fax +49 9131 85 34828, Email Iwona.Cicha@uk-erlangen.dePurpose: In this study, a detailed characterization of a rabbit model of atherosclerosis was performed to assess the optimal time frame for evaluating plaque vulnerability using superparamagnetic iron oxide nanoparticle (SPION)-enhanced magnetic resonance imaging (MRI).Methods: The progression of atherosclerosis induced by ballooning and a high-cholesterol diet was monitored using angiography, and the resulting plaques were characterized using immunohistochemistry and histology. Morphometric analyses were performed to evaluate plaque size and vulnerability features. The accumulation of SPIONs (novel dextran-coated SPIONDex and ferumoxytol) in atherosclerotic plaques was inve

Antarctic sea ice is a critical component of the climate system affecting a range of physical and biogeochemical feedbacks and supporting unique ecosystems. During the last glacial stage, Antarctic sea ice was more extensive than today, but uncertainties in geological (marine sediments), glaciological (ice core), and climate model reconstructions of past sea-ice extent continue to limit our understanding of its role in the Earth system. Here, we present a novel archive of past sea-ice environments from regurgitated stomach oils of snow petrels (Pagodroma nivea) preserved at nesting sites in Dronning Maud Land, Antarctica. We show that by combining information from fatty acid distributions and their stable carbon isotope ratios with measurements of bulk carbon and nitrogen stable isotopes and trace metal data, it is possible to reconstruct changing snow petrel diet within Marine Isotope Stage 2 (ca. 24.3–30.3 cal kyr BP). We show that, as today, a mixed diet of krill and fish characterizes much of the record. However, between 27.4 and 28.7 cal kyr BP signals of krill almost disappear. By linking dietary signals in the stomach-oil deposits to modern feeding habits and foraging ranges, we infer the use by snow petrels of open-water habitats (“polynyas”) in the sea ice during our interval of study. The periods when consumption of krill was reduced are interpreted to correspond to the opening of polynyas over the continental shelf, which became the preferred foraging habitat. Our results show that extensive, thick, and multiyear sea ice was not always present close to the continent during the last glacial stage and highlight the potential of stomach-oil deposits as a palaeoenvironmental archive of Southern Ocean conditions.

Loess-paleosol sequences (LPSs) are important terrestrial archives of paleoenvironmental and paleoclimatic information. One of the main obstacles for the investigation and interpretation of these archives is the uncertainty of their age-depth relationship. In this study, four different dating techniques were applied to the Late Pleistocene to Holocene LPS Balta Alba Kurgan (Romania) in order to achieve a robust chronology. Luminescence dating includes analysis of different grain-size fractions of both quartz and potassium feldspar and the best results are obtained using fine-grained quartz blue-stimulated and polymineral post-infrared infrared-stimulated luminescence measurements. Radiocarbon (C-14) dating is based on the analysis of bulk organic carbon (OC) and compound-specific radiocarbon analysis (CSRA). Bulk OC and leaf wax-derived n-alkane C-14 ages provide reliable age constraints for the past c. 25-27 kyr. CSRA reveals post-depositional incorporation of roots and microbial OC into the LPS limiting the applicability of C-14 dating in older parts of the sequence. Magnetic stratigraphy data reveal good correlation of magnetic susceptibility and the relative paleointensity of the Earth's magnetic field with one another as well as reference records and regional data. In contrast, the application of paleomagnetic secular variation stratigraphy is limited by a lack of regional reference data. The identification of the Campanian Ignimbrite/Y-5 tephra layer in the outcrop provides an independent time marker against which results from the other dating methods have been tested. The most accurate age constraints from each method are used for two Bayesian age-depth modeling approaches. The systematic comparison of the individual results exemplifies the advantages and disadvantages of the respective methods. Taken as a whole, the two age-depth models agree very well, our study also demonstrates that the multi-method approach can improve the accuracy and precision of datin

Fjords are recognized as hotspots of organic carbon (OC) burial in the coastal ocean. In fjords with glaciated catchments, glacier discharge carries large amounts of suspended matter. This sedimentary load includes OC from bedrock and terrigenous sources (modern vegetation, peat, soil deposits), which is either buried in the fjord or remineralized during export, acting as a potential source of CO2 to the atmosphere. In sub-Antarctic South Georgia, fjord-terminating glaciers have been retreating during the past decades, likely as a response to changing climate conditions. We determine sources of OC in surface sediments of Cumberland Bay, South Georgia, using lipid biomarkers and the bulk C-14 isotopic composition, and quantify OC burial at present and for the time period of documented glacier retreat (between 1958 and 2017). Petrogenic OC is the dominant type of OC in proximity to the present-day calving fronts (60.4 +/- 1.4% to 73.8 +/- 2.6%) and decreases to 14.0 +/- 2.7% outside the fjord, indicating that petrogenic OC is effectively buried in the fjord. Beside of marine OC, terrigenous OC comprises 2.7 +/- 0.5% to 7.9 +/- 5.9% and is mostly derived from modern plants and Holocene peat and soil deposits that are eroded along the flanks of the fjord, rather than released by the retreating fjord glaciers. We estimate that the retreat of tidewater glaciers between 1958 and 2017 led to an increase in petrogenic carbon accumulation of 22% in Cumberland West Bay and 6.5% in Cumberland East Bay, suggesting that successive glacier retreat does not only release petrogenic OC into the fjord, but also increases the capacity of OC burial.

Unglaciated coastal areas in East Antarctica provide records of past ice sheet and glacier fluctuations and subsequent environmental conditions. In this paper we review lithological, geochemical, diatom and radiocarbon data from sediment records from inland and epishelf lakes in Bunger Hills, East Antarctica. While some hilltops were unglaciated during the Last Glacial Maximum, till deposits in lake basins indicate infilling by glacier ice prior to the Holocene. Proglacial sedimentation occurred in lakes during the early Holocene. Around 9.6 ka bp, deposition of marine sapropel started under relatively warm climate conditions. Inland lakes were affected by high clastic input from meltwater runoff until c. 7.9 ka bp, when deposition became highly organic and biogenic proxies indicate a period of cooler conditions. Epishelf lakes experienced a decrease in water exchange with the ocean and increased freshwater input around 7.7 +/- 0.2 ka bp and after 2.2 ka bp. This probably resulted from grounding line advances of the bounding glaciers, which could be either controlled by relative sea level (RSL) lowering and/or climate-driven glacier dynamics. The absence of marine sediments in the postglacial record of Algae Lake indicates that Holocene RSL probably reached a maximum at or below 10 m above present sea level.

The subantarctic island of South Georgia provides terrestrial and coastal marine records of climate variability, which are crucial for the understanding of the drivers of Holocene climate changes in the subantarctic region. Here we investigate a sediment core (Co1305) from a coastal inlet on South Georgia using elemental, lipid biomarker, diatom, and stable isotope data to infer changes in environmental conditions and to constrain the timing of late-glacial and Holocene glacier fluctuations. Because of the scarcity of terrestrial macrofossils and the presence of redeposited and relict organic matter in the sediments, age control for the record was obtained by compound-specific radiocarbon dating of mostly marine-derived n-C-16 fatty acids. A basal till layer recovered in Little Jason Lagoon was likely deposited during an advance of local glaciers during the Antarctic cold reversal. After glacier retreat, an oligotrophic lake occupied the site, which transitioned to a marine inlet around 8.0 +/- 0.9 ka because of relative sea-level rise. From 7.0 +/- 0.6 to 4.0 +/- 0.4 ka, reduced vegetation coverage in the catchment, as well as high siliciclastic input and deposition of ice-rafted debris, indicates glacier advances in the terrestrial catchment and likely in the adjacent fjord. A second, less extensive period of glacier advances occurred in the late Holocene, after 1.8 +/- 0.3 ka.

The sub-Antarctic island of South Georgia provides terrestrial and coastal marine records of climate variability, which are crucial for the understanding of the drivers of Holocene climate changes in the sub-Antarctic region. Here we investigate a sediment core (Co1305) from a coastal inlet on South Georgia using elemental, lipid biomarker, diatom and stable isotope data to infer changes in environmental conditions and to constrain the timing of Late glacial and Holocene glacier fluctuations. Due to the scarcity of terrestrial macro-fossils and relict organic matter in the sediments, age control was obtained by compound-specific radiocarbon dating of mostly marine derived n-C16 fatty acids. A basal till layer recovered in Co1305 was likely deposited during an advance of local glaciers during the Antarctic cold eversal. After glacier retreat an oligotrophic lake occupied the site, which transitioned to a marine inlet around 8.0±0.9 ka due to relative sea level rise. From 7.0±0.6 to 4.0±0.4 ka reduced vegetation coverage in the catchment as well as high siliciclastic input and deposition of ice rafted debris indicate glacier advances in the terrestrial catchment and likely in the adjacent fjord. A second, less extensive period of glacier advances occurred in the late Holocene, after 1.8±0.3 ka.

Marine based ice sheets are subject to rapid destabilisation during periods of increasing sea level and ocean temperature, especially in areas with an inland-sloping bed. Considerable portions of the East Antarctic Ice Sheet are grounded below sea level, and are thus theoretically prone to marine ice sheet instabilities. However, the response of this potentially susceptible East Antarctic ice is presently unclear, as there is limited evidence of the rate and timing of past deglacial events in such areas. We use a combination of new onshore cosmogenic dating and offshore multibeam bathymetry, alongside existing radiocarbon dating, to show that the East Antarctic Ice sheet displayed a marine ice sheet instability response following the Last Glacial Maximum, c. 20,000 years before present. We find that the ice sheet in east Prydz Bay retreated rapidly across 200 km of inland sloping bed during a period of sustained ocean warming. We also employ a numerical model that replicates the pattern and timing of retreat in Prydz Bay to demonstrate that instabilities also occurred elsewhere with similar basal topographies.