The genetic history of Scandinavia from the Roman Iron Age to the present

The authors acknowledge support from the National Genomics Infrastructure in Stockholm funded by Science for Life Laboratory, the Knut and Alice Wallenberg Foundation and the Swedish Research Council, and SNIC/Uppsala Multidisciplinary Center for Advanced Computational Science for assistance with massively parallel sequencing and access to the UPPMAX computational infrastructure. We used resources from projects SNIC 2022/23-132, SNIC 2022/22-117, SNIC 2022/23-163, SNIC 2022/22-299, and SNIC 2021-2-17. This research was supported by the Swedish Research Council project ID 2019-00849_VR and ATLAS (Riksbankens Jubileumsfond). Part of the modern dataset was supported by a research grant from Science Foundation Ireland (SFI), grant number 16/RC/3948, and co-funded under the European Regional Development Fund and by FutureNeuro industry partners.Peer reviewedPublisher PD

M31N 2008-12a - the remarkable recurrent nova in M31: Pan-chromatic observations of the 2015 eruption

The Andromeda Galaxy recurrent nova M31N 2008-12a had been observed in eruption ten times, including yearly eruptions from 2008-2014. With a measured recurrence period of $P_\mathrm{rec}=351\pm13$ days (we believe the true value to be half of this) and a white dwarf very close to the Chandrasekhar limit, M31N 2008-12a has become the leading pre-explosion supernova type Ia progenitor candidate. Following multi-wavelength follow-up observations of the 2013 and 2014 eruptions, we initiated a campaign to ensure early detection of the predicted 2015 eruption, which triggered ambitious ground and space-based follow-up programs. In this paper we present the 2015 detection; visible to near-infrared photometry and visible spectroscopy; and ultraviolet and X-ray observations from the Swift observatory. The LCOGT 2m (Hawaii) discovered the 2015 eruption, estimated to have commenced at Aug. $28.28\pm0.12$ UT. The 2013-2015 eruptions are remarkably similar at all wavelengths. New early spectroscopic observations reveal short-lived emission from material with velocities $\sim13000$ km s$^{-1}$, possibly collimated outflows. Photometric and spectroscopic observations of the eruption provide strong evidence supporting a red giant donor. An apparently stochastic variability during the early super-soft X-ray phase was comparable in amplitude and duration to past eruptions, but the 2013 and 2015 eruptions show evidence of a brief flux dip during this phase. The multi-eruption Swift/XRT spectra show tentative evidence of high-ionization emission lines above a high-temperature continuum. Following Henze et al. (2015a), the updated recurrence period based on all known eruptions is $P_\mathrm{rec}=174\pm10$ d, and we expect the next eruption of M31N 2008-12a to occur around mid-Sep. 2016

Sex Determination:Why So Many Ways of Doing It?

Sexual reproduction is an ancient feature of life on earth, and the familiar X and Y chromosomes in humans and other model species have led to the impression that sex determination mechanisms are old and conserved. In fact, males and females are determined by diverse mechanisms that evolve rapidly in many taxa. Yet this diversity in primary sex-determining signals is coupled with conserved molecular pathways that trigger male or female development. Conflicting selection on different parts of the genome and on the two sexes may drive many of these transitions, but few systems with rapid turnover of sex determination mechanisms have been rigorously studied. Here we survey our current understanding of how and why sex determination evolves in animals and plants and identify important gaps in our knowledge that present exciting research opportunities to characterize the evolutionary forces and molecular pathways underlying the evolution of sex determination

a new approach for analysing the impact of nuclear data uncertainties on the astrid sodium void reactivity effect

International audienceFor ensuring sustainable nuclear energy, France has chosen to develop sodium cooled fast reactors. The ASTRID project is a demonstrator of such technology exhibiting innovative features such as the CFV core which has a negative sodium void reactivity effect. In order to study in details the uncertainty associated to this parameter, we split it into two components : the central component (CC) which is a positive reactivity effect due to spectrum changes and the leakage component (LC) which is a negative reactivity effect due to the increase of the neutron mean free path. This paper presents the development of an innovative GPT procedure for computing sensitivities of the CC and the LC. With such sensitivities and the use of the COMAC-V2 covariance matrix, we are able to calculate the uncertainties due to nuclear data on each component using JEFF-3.2 nuclear data. The application of the method to the ASTRID CFV core shows a 2.44% uncertainty on the CC, a 2.98percent uncertainty on the LC and a 14.8percent on the total sodium void reactivity effect. There is a correlation factor of -0.5776 between the LC and CC uncertainties. This approach gives perspectives in studying experimental programmes performed in zero power facilities such as MASURCA

Analysis of material buckling experiments performed in the masurca facility in support of the astrid sfr prototype core balance

International audienceSodium Fast Reactors (SFR) are the solution for long term development of nuclear energy production as it allows the use of the entire Uranium ore and enables to burn long live radioactive waste. Since the neutron balance of the core is badly known due to the lack of accuracy in evaluated nuclear data, the material buckling offers a way to improve that situation. Indeed the material buckling is experimentally accessible from the curvatures of the different fission rate traverses in cores built in the MASURCA critical facility. This analysis takes advantage of the use of recent deterministic codes with a detailed assessment of the experimental uncertainty. This uncertainty is significantly smaller than the one associated to nuclear data. Hence, this offers the opportunity of reducing nuclear data uncertainties when the experimental material buckling from different MASURCA cores such as 1A', 1B, R2 and Z2 will be analyzed. The prediction of the material balance of the ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration) SFR core will then be significantly improved

Essai sur la théorie et la pratique des accouchemens... , par P. Dufay,...

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looking forward for a masurca experimental programme genesis in support to the astrid sfr core

International audienceThe characteristics of the ASTRID core (Advanced Sodium Technological Reactor for Industrial Demonstration) must be determined according to well-defined calculation conditions and accuracies. In order to achieve that goal, several steps are required such as mastering the computation procedures, checking the nuclear data in use and bringing evidence with experiments of the validity of the produced values and their uncertainties.Past experiments will allow a quantification of the uncertainties for core characteristics such as βeff or Doppler, a reduction of the uncertainties due to nuclear data (through assimilation) which might remain insufficient. Therefore, past experiments will not cover all requirements either because of the level of uncertainties or because it will not cover ASTRID core specificities such as sodium void reactivity, control rod worth and power map istribution over the cycle. The MASURCA facility is currently under refurbishment until 2023 and will exhibit improved performances. The future GENESIS experimental programme of the MASURCA facility will take advantage of advanced measurement techniques, on one hand, and the possibility of using fuel with degraded Pu vector to develop a solid knowledge of ASTRID core characteristics

Assessing the Uncertainty of Reactivity Worth Scale Measurements

International audienceThe characteristics of any nuclear power plant should be determined according to well-defined calculation conditions and accuracies. The neutronic tools should go under a series of verification, validation and uncertainty quantification processes. The proof of the best estimate values plus uncertainties of the neutronic tools should be achieved using measurements in critical facilities. Concerning the sodium void reactivity worths in sodium fast reactor cores (SFR), measurements can take the usual form of successive substitutions of different materials (voided rodlets replacing Na rodlets for instance) and different sizes in order to vary the relative importance of central and leakage components.The reactivity variations induced by these changes are compensated by a change in the position of the shim rod if the reactivity variation is smaller than half a $\beta_{eff}$ and if larger by the addition or the removal of peripheral sub-assemblies. The calibration of the shim rod is performed by measuring a fission chamber response when dropping a control rod and solving the Nordheim equation. This gives a S curve where the position of a control rod is associated to a reactivity expressed in S. In this study, the uncertainties associated to this calibration are revisited, not only due to and $\beta _{eff}$ value ($\sim$2%) but also to decay time constants associated to each family ($\sim$6%), these being quite different from one nuclear data evaluation to another