53 research outputs found
Dark Matter directional detection: comparison of the track direction determination
Several directional techniques have been proposed for a directional detection
of Dark matter, among others anisotropic crystal detectors, nuclear emulsion
plates, and low-pressure gaseous TPCs. The key point is to get access to the
initial direction of the nucleus recoiling due to the elastic scattering by a
WIMP. In this article, we aim at estimating, for each method, how the
information of the recoil track initial direction is preserved in different
detector materials. We use the SRIM simulation code to emulate the motion of
the first recoiling nucleus in each material. We propose the use of a new
observable, D, to quantify the preservation of the initial direction of the
recoiling nucleus in the detector. We show that in an emulsion mix and an
anisotropic crystal, the initial direction is lost very early, while in a
typical TPC gas mix, the direction is well preserved.Comment: 9 pages, 5 figure
A distributional approach to obtain adjusted comparisons of proportions of a population at risk
Dark Matter Directionality Detection performance of the Micromegas-based TPC-MIMAC detector
Directional Dark Matter Detection (DDMD) can open a new signature for Weakly
Massive Interacting Particles (WIMPs) Dark Matter. The directional signature
provides in addition, an unique way to overcome the neutron and neutrino
backgrounds. In order to get the directional signature, the DDM detectors
should be sensitive to low nuclear energy recoils in the keV range and have an
angular resolution better than . We have performed experiments with
low energy () ion beam facilities to measure the angular
distribution of nuclear recoil tracks in a MIMAC detector prototype. In this
paper, we study angular spreads with respect to the electron drift direction
( incident angle) of Fluorine nuclear tracks in this low energy
range, and show nuclear recoil angle reconstruction produced by a monoenergetic
neutron field experiment. We find that a high-gain systematic effect leads to a
high angular resolution along the electron drift direction. The measured
angular distribution is impacted by diffusion, and space charge or ion feedback
effects, which can be corrected for by an asymmetry factor observed in the
flash-ADC profile. The estimated angular resolution of the incident
ion is better than at keV kinetic energy and agrees with the
simulations within %. The distributions from the nuclear recoils have been
compared with simulated results based on a modified Garfield++ code. Our study
shows that protons would be a more adapted target than heavier nuclei for DDMD
of light WIMPs. We demonstrate that directional signature from the Galactic
halo origin of a Dark Matter WIMP signal is experimentally achievable, with a
deep understanding of the operating conditions of a low pressure detector with
its diffusion mechanism.Comment: 19 pages, 12 figure
Evolution of AANAT: expansion of the gene family in the cephalochordate amphioxus
<p>Abstract</p> <p>Background</p> <p>The arylalkylamine <it>N</it>-acetyltransferase (AANAT) family is divided into structurally distinct vertebrate and non-vertebrate groups. Expression of vertebrate AANATs is limited primarily to the pineal gland and retina, where it plays a role in controlling the circadian rhythm in melatonin synthesis. Based on the role melatonin plays in biological timing, AANAT has been given the moniker "the Timezyme". Non-vertebrate AANATs, which occur in fungi and protists, are thought to play a role in detoxification and are not known to be associated with a specific tissue.</p> <p>Results</p> <p>We have found that the amphioxus genome contains seven <it>AANAT</it>s, all having non-vertebrate type features. This and the absence of <it>AANATs </it>from the genomes of Hemichordates and Urochordates support the view that a major transition in the evolution of the <it>AANATs </it>may have occurred at the onset of vertebrate evolution. Analysis of the expression pattern of the two most structurally divergent <it>AANAT</it>s in <it>Branchiostoma lanceolatum </it>(<it>bl</it>) revealed that they are expressed early in development and also in the adult at low levels throughout the body, possibly associated with the neural tube. Expression is clearly not exclusively associated with the proposed analogs of the pineal gland and retina. blAANAT activity is influenced by environmental lighting, but light/dark differences do not persist under constant light or constant dark conditions, indicating they are not circadian in nature. bfAANATα and bfAANATΎ' have unusually alkaline (> 9.0) optimal pH, more than two pH units higher than that of vertebrate AANATs.</p> <p>Conclusions</p> <p>The substrate selectivity profiles of bfAANATα and Ύ' are relatively broad, including alkylamines, arylalkylamines and diamines, in contrast to vertebrate forms, which selectively acetylate serotonin and other arylalkylamines. Based on these features, it appears that amphioxus AANATs could play several roles, including detoxification and biogenic amine inactivation. The presence of seven AANATs in amphioxus genome supports the view that arylalkylamine and polyamine acetylation is important to the biology of this organism and that these genes evolved in response to specific pressures related to requirements for amine acetylation.</p
Theoretical approach based on Monte-Carlo simulations to predict the cell survival following BNCT
International audienceWe present here a very preliminary work on BNCT Dosimetry. The approach is as follows:A full Monte Carlo calculation is used to separate all dose components and determine the corresponding physical dose fractions with a realistic clinical model.These dose fractions are then used as mixed fields to predict cell-survivals and RBE values for a specific cell-line, thanks to the radiobiological model NanOxTM
Bypass and hyperbole in soil science:A perspective from the next generation of soil scientists
International audienceWe, the coâauthors of this letter, are an international group of soil scientists at early career stages, from PhD students to postdoctoral researchers, lecturers, and research fellows with permanent positions. Here, we present our collective musings on soil research challenges and opportunities and, in particular, the points raised by Philippe Baveye (Baveye, 2020a, 2020b) and Johan Bouma (Bouma, 2020) on bypass and hyperbole in soil science. Raising awareness about these issues is a first and necessary step. To this end, we would like to thank Philippe Baveye and Johan Bouma for initiating this debate.......
Phyto-Sol : systÚmes de culture multi-performants sous contrainte de travail réduit du sol
Le projet Phyto-Sol a permis de mettre au point et dâĂ©valuer des systĂšmes de culture innovants visant Ă
concilier rĂ©duction de lâusage des intrants et maintien des rendements et des marges, le tout sous
contrainte de travail réduit du sol. Des expérimentations systÚme de culture ont été mises en place
dans trois contextes (limons sableux et argilo-calcaires superficiels du Centre-Val de Loire et limons
profonds des Hauts-de-France) pour comparer un systĂšme de culture innovant et un systĂšme de
rĂ©fĂ©rence, pendant la durĂ©e dâune rotation. Les stratĂ©gies innovantes de gestion de lâazote ont permis
des rĂ©ductions de lâusage de lâazote minĂ©ral et des gaz Ă effet de serre de 20 Ă 30 % dans les trois
systĂšmes innovants. La rĂ©duction de lâusage des produits phytosanitaires nâa pas dĂ©passĂ© 30 %, et nâa
donc pas atteint lâobjectif de -50 %. La rĂ©duction des rendements a Ă©tĂ© systĂ©matique. Selon les sites et
les indicateurs choisis, la rentabilitĂ© a Ă©tĂ© dĂ©gradĂ©e, maintenue ou amĂ©liorĂ©e. Davantage dâinnovations
sont donc nécessaires pour atteindre et concilier des objectifs ambitieux. Ces expérimentations ont en
outre permis de montrer lâintĂ©rĂȘt de stratĂ©gies/pratiques : insertion de lĂ©gumineuses dans les rotations,
colza associé, pois associé, couplage strip-till / binage / traitements localisés sur le rang, et de préciser
les conditions dâadaptation de la succession protĂ©agineux-colza.Cropping system experiments were set up in three contexts to compare an innovative cropping system
and a reference system, during one rotation. Innovative nitrogen management strategies have led to
reduce the use of mineral nitrogen fertilizers and greenhouse gas emissions by 20 to 30 % in the three
innovative systems. The reduction in the use of pesticides did not exceed 30 %, and therefore did not
reach the target of -50 %. Yields have decreased at the three sites. Depending on the sites and
indicators selected, profitability has been degraded, maintained or improved. More innovation is needed
to achieve and reconcile ambitious goals. These experiments also highlighted efficient strategies /
practices: the insertion of legume crops in the rotations, intercropping rapeseed, intercropping winter peas, coupling strip-till / hoeing / localized treatments on the row, and to specify the adaptation
conditions of the legume crop-rapeseed succession
Directional detection of keV proton and carbon recoils with MIMAC
International audienceDirectional detection is the dedicated strategy to demonstrate that DM-like signals measured by direct detectors are indeed produced by DM particles from the galactic halo. The experimental challenge of measuring the direction of DM-induced nuclear recoils with (sub-)millimeter tracks has limited, so far, the maximal directional reach to DM masses around . In this paper, we expose the MIMAC detector to three different neutron fields and we develop a method to reconstruct the direction of the neutron-induced nuclear recoils. We measure an angular resolution better than for proton recoils down to a kinetic energy of and for carbon recoils down to a kinetic energy of . For the first time, a detector achieves the directional measurement of proton and carbon recoils with kinetic energies in the keV range without any restriction on the direction of the incoming particle. This work demonstrates that directional detection is around the corner for probing DM with masses down to
Cathode signal in a TPC directional detector: implementation and validation measuring the drift velocity
International audienceLow-pressure gaseous TPCs are well suited detectors to correlate the directions of nuclear recoils to the galactic Dark Matter (DM) halo. Indeed, in addition to providing a measure of the energy deposition due to the elastic scattering of a DM particle on a nucleus in the target gas, they allow for the reconstruction of the track of the recoiling nucleus. In order to exclude the background events originating from radioactive decays on the surfaces of the detector materials within the drift volume, efforts are ongoing to precisely localize the track nuclear recoil in the drift volume along the axis perpendicular to the cathode plane. We report here the implementation of the measure of the signal induced on the cathode by the motion of the primary electrons toward the anode in a MIMAC chamber. As a validation, we performed an independent measurement of the drift velocity of the electrons in the considered gas mixture, correlating in time the cathode signal with the measure of the arrival times of the electrons on the anode
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