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Along the coast of northwestern Alaska, architectural wood remains are well preserved in the Birnirk and Thule coastal sites of the early 2nd millennium CE. These structural wood elements are unique archives for documenting climatic variations and cultural transformations during this key development period of Inuit culture. Along this treeless Arctic coast, driftwood accumulates from the subarctic forests of interior Alaska. Except for northwestern Alaska, regional tree-ring chronologies are too short (at best 350–400 years) to successfully date archaeological wood remains from Birnirk and Thule coastal sites using conventional dendrochronology. This paper examines the potential of tree-ring derived δ18O signal to annually date eight architectural wood samples from the Rising Whale (KTZ-304) site at Cape Espenberg, northwestern Alaska. We developed a δ18O master chronology, covering the period 935–1157 CE, using five wood samples from the KTZ-304 site. Blind isotope cross-dating of individual series belonging to this δ18O master chronology (one against the other four) showed conclusive dating and a very strong coherence of the isotopic signal. We, then, used the δ18O master chronology to cross-date three other wood samples for which we knew, from previous 14C wiggle-matching procedure, the first measured ring to be in this time interval, within a ± 18 to 30-year precision. Oxygen isotope dendrochronology provided a plausible date for one of the samples (the first measured ring at 1073 CE). This preliminary study encourages us to acquire additional data to extend in time and strengthen the δ18O master chronology of northwestern Alaska (NWAK18O) and help refine our understanding of climate and culture change during the 2nd millennium CE. International audience

ABSTRACT Exogamous marriage alliances involving royal women played a prominent role in the conversion of the Anglo-Saxon kingdoms to Christianity in the seventh century AD. Yet the large number of well-furnished female burials from this period suggests a broader change in the role of women. The authors present the results of isotopic analysis of seventh-century burials, comparing male and female mobility and the mobility of females from well-furnished versus poorly/unfurnished burials. Results suggest increased mobility during the Conversion Period that is, paradoxically, most noticeable among women buried in poorly furnished graves; their well-furnished contemporaries were more likely to have grown up near to their place of burial.

Recent paleoclimatic research has revealed that volcanic events around 536-540 AD caused severe, short-term global cooling. For this same period, archeological research from various regions evidences significant cultural transformation. However, there is still a lack of understanding of how human societies responded and adapted to extreme climate variability and new circumstances. This study focuses on the effects of the 536/540 AD volcanic event in four Scandinavian regions by exploring the shift in demographic and land use intensity before, during, and after this abrupt climate cooling. To achieve this, we performed climate simulations with and without volcanic eruptions using a dynamically downscaled climate model (iLOVECLIM) at a high resolution (0.25° or ~25 km). We integrated the findings with a comprehensive collection of radiocarbon dates from excavated archeological sites across various Scandinavian regions. Our Earth System Model simulates pronounced cooling (maximum ensemble mean-1.1°C), an abrupt reduction in precipitation, and a particularly acute drop in growing degree days (GDD0) after the volcanic event, which can be used to infer likely impacts on agricultural productivity. When compared to the archeological record, we see considerable regional diversity in the societal response to this sudden environmental event. As a result, this study provides a more comprehensive insight into the demographic chronology of Scandinavia and a deeper understanding of the land-use practices its societies depended on during the 536/540 AD event. Our results suggest that this abrupt climate anomaly amplified a social change already in progress. International audience

The last deglaciation (21 to 8 ka) of the Eurasian ice sheet (EIS) is thought to have been responsible for a sea level rise of about 20 m. While many studies have examined the timing and rate of the EIS retreat during this period, many questions remain about the key processes that triggered the EIS deglaciation 21 kyr ago. Due to its large marine-based parts in the Barents-Kara (BKIS) and British Isles sectors, the BKIS is often considered to be a potential analogue of the current West Antarctic ice sheet (WAIS). Identifying the mechanisms that drove the EIS evolution might provide a better understanding of the processes at play in the West Antarctic destabilization. To investigate the relative impact of key drivers on the EIS destabilization, we used the threedimensional ice sheet model GRISLI (GRenoble Ice Shelf and Land Ice) (version 2.0) forced by climatic fields from five Paleoclimate Modelling Intercomparison Project phases 3 and 4 (PMIP3, PMIP4) Last Glacial Maximum (LGM) simulations. In this study, we performed sensitivity experiments to test the response of the simulated Eurasian ice sheets to surface climate, oceanic temperatures (and thus basal melting under floating ice tongues), and sea level perturbations. Our results highlight that the EIS retreat simulated with the GRISLI model is primarily triggered by atmospheric warming. Increased atmospheric temperatures further amplify the sensitivity of the ice sheets to sub-shelf melting. These results contradict those of previous modelling studies mentioning the central role of basal melting on the deglaciation of the marine-based Barents-Kara ice sheet. However, we argue that the differences with previous works are mainly related to differences in the methodology followed to generate the initial LGM ice sheet. Due to the strong sensitivity of EIS to the atmospheric forcing highlighted with the GRISLI model and the limited extent of the confined ice shelves during the LGM, we conclude by questioning the analogy between EIS and the current WAIS. However, because of the expected rise in atmospheric temperatures, the risk of hydrofracturing is increasing and could ultimately put the WAIS in a configuration similar to the past Eurasian ice sheet. International audience

After the discovery of the Higgs boson at the LHC, particle physics community is exploring and proposing next accelerators, to address the remaining open questions on the underlying mechanisms and constituents of the present universe. One of the studied possibilities is FCC (Future Circular Collider), a 100 km long collider at CERN. The feasibility study of this future proposed accelerator implies the definition of tolerances on magnets imperfections and of the strategies of correction in order to guarantee the target performances of the High Energy Booster ring. The efficiency of the correction scheme, used to control the orbit, directly bounds the corrector needs and magnet tolerances. Analytic formulae give a first estimation of the average rms value of the required linear correctors' strengths and of the allowed magnets misalignments and field quality along the entire ring. The distribution of the correctors along the ring is simulated in order to verify the quality of the residual orbit after the proposed correction strategy and compared with the analytical predictions. First specifications of the orbit correctors strength and tolerances for the alignment of the main elements of the ring are presented. The limits of the studied correction scheme and method are also discussed. International audience

Metal corrosion and its mitigation using alkoxysilane based sol-gel coatings presenting specific properties are a matter of interest in many areas of applications, from industrial to cultural heritage materials. Thanks to their adhesive and coupling nature with different molecules and substrates, they show excellent results against aggressive environments. This study focuses on the protection of historical copper-based alloys. A tetramethyl orthosilicate-based (TMOSbased) sol-gel coating was doped with carboxylic acid compounds (heptanoic, octanoic and decanoic acids) recognized for their non-toxicity and their interesting corrosion inhibition properties on ancient corroded copper. The development of the coating and the basic understanding of the fundamental chemistry as well as the protection mechanism on the historical samples were studied. Contact angle measurements allowed to show that the resulting coating displayed a hydrophobic protection at the surface of the samples while its chemical composition was evaluated using thermogravimetric analysis, SEM-EDS and Raman spectroscopy. The porosity of the sol-gel matrix and the distribution of the acids in the porous silica network were then investigated by establishing nitrogen adsorption/desorption isotherms at liquid N2 temperature. Examination of the sample's cross-section by SEM-EDS showed that the TMOS-based coatings doped with carboxylic acids penetrated up to 60% in depth in the corrosion layer of the ancient copper, while the Raman analyses showed that the acids formed organometallic complexes both at the surface and in the corrosion layer, leading to the protection of the metallic substrate against further corrosion. Highlights-Sol-gel synthesis with carboxylic acid was successfully used to coat ancient copper.-Carboxylic acid complexes at the surface and in the corrosion layer, protecting it.-Doped coating provides hydrophobic property to the surface of the copper.-Carboxylic acid penetrates up to 60% of the corrosion layer thanks to silica matrix.-Silica matrix displays a carboxylic acid reservoir for long term corrosion inhibition. International audience

An Inverse Compton Scattering (ICS) X-ray source is under development at the ELSA electron RF linac of CEA DIF. The X-rays are emitted by the interaction of a 30-MeV electron bunch with a visible (532nm) or infrared (1064nm) Nd:YAG laser pulse. The radiation spectrum lies in a 10-100 keV range. The electron bunches duration is 30 ps after compression in double-alpha magnets. In such a system, electron trajectories are curved with a short radius, resulting in a noticeable degradation of the beam emittance, that might be a limitation cap to our source yield optimization in our effort to raise the bunch charge from 0.1 to 3 nC. In the specific case of strongly curved trajectories, the symmetry hypotheses used for space charge calculation in several simulation codes are questionable, especially when calculations are made in the reference particle frame, leading to inaccurate compensation of electric and magnetic components of Lorentz force. We ran simulations of electron beam dynamics within the double-alpha magnets, using codes with different architectures (PIC, PIC Slice, envelope) and space-charge routines such as CST MWS and TraceWin/Partran, that rely on different models and frame references. We compared these results with experiments in order to evaluate the order of magnitude of these errors and to validate the use of a simulation tool to optimize our ICS source. International audience

PERLE (Powerful Energy Recovery LINAC for Experiment) is a three turns high-power Energy Recovery LINAC (ERL) facility with 20 mA beam current and beam energy from 250 MeV to 500 MeV. It is a testbed to validate multi-turn high current ERL operation for the future LHeC and will be the first ERL for nuclear applications. In this work, the design and optimization of the commutational magnet (B-com) used to spread/combine the three beams and one series of quadrupole magnets is discussed. The B-com magnet is optimized for a 30° bending angle with harmonic content of 0.036%. The quadrupole magnets generate a field gradient of 34.15 T/m. Further studies to suppress saturation at a maximum gradient of 44.1 T/m are undergoing. International audience