A fussy revisitation of antiprotons as a tool for Dark Matter searches

Antiprotons are regarded as a powerful probe for Dark Matter (DM) indirect detection and indeed current data from PAMELA have been shown to lead to stringent constraints. However, in order to exploit their constraining/discovery power properly and especially in anticipation of the exquisite accuracy of upcoming data from AMS, great attention must be put into effects (linked to their propagation in the Galaxy) which may be perceived as subleasing but actually prove to be quite relevant. We revisit the computation of the astrophysical background and of the DM antiproton fluxes fully including the effects of: diffusive reacceleration, energy losses including tertiary component and solar modulation (in a force field approximation). We show that their inclusion can somewhat modify the current bounds, even at large DM masses, and that a wrong interpretation of the data may arise if they are not taken into account. The numerical results for the astrophysical background are provided in terms of fit functions; the results for Dark Matter are incorporated in the new release of the PPPC4DMID.Comment: v3: small comments and references added, matches journal versio

Multi–scale modelling of timber–frame structures under seismic loads

This paper introduces a versatile hysteretic constitutive law, developed for various joints with steel fasteners commonly used in timber structures (nails, screws, staples, 3D connectors of bracket type, punched plates). Compared to previous models available in literature, the proposed one improves numerical robustness and represents a step forward by taking into account the damaging process of joints with metal fasteners. Experimental tests carried out on joints are used for calibration purpose, and quasi–static and dynamic tests performed on shear walls allow validating the proposed Finite Element model. Finally, the development of a computationally efficient simplified FE model of timber–frame structures for shear walls is described, with emphasis on its validation and its use at the scale of a complete structure

Mettre en place des services en direction de la petite enfance en bibliothèque municipale

La fiche montre les enjeux des services en direction de la petite enfance en bibliothèque municipale : des espaces aux actions de sensibilisation "bébés lecteurs" en passant par les collections et les animations

IL-33 upregulates cysteinyl-leukotriene receptor type 1 expression in human peripheral blood lymphocytes

Au cours d’une réaction asthmatique, l’interleukine (IL)-33 est abondamment libérée par les cellules épithéliales et fibroblastiques endommagées des voies respiratoires. Suite à un clivage protéolytique, la cytokine est reconnue par son récepteur ST2L, exprimé à la surface des cellules immunes, conduisant à la production d’IL-5 et IL-13, à l’origine des caractéristiques immunes et symptomatiques de l’asthme. En plus des cytokines inflammatoires, les cystéinyl-leucotriènes (cysLTs) sont de puissants broncho-constricteurs et contribuent à l’inflammation de type Th2 dans le contexte de l’asthme. Les cysLTs sont des médiateurs lipidiques dérivés du métabolisme de l’acide arachidonique et incluent le leucotriène (LT)D4, le LTC4 et le LTE4. La plupart des propriétés inflammatoires des cysLTs sont transduites par le récepteur CysLT1 dont l’expression à la surface des leucocytes est régulée par les cytokines de l’environnement inflammatoire. L’objectif de cette étude est d’explorer la régulation de l’expression de CysLT1 par l’IL-33 dans les lymphocytes du sang périphérique humain de donneurs en santé. Les résultats obtenus montrent que l’axe IL-33/ST2L/TAK-1 augmente l’expression du récepteur CysLT1 après un traitement de 9h avec 5ng/ml d’IL-33. Dans ces conditions, l’augmentation de l’expression de CysLT1 est accompagnée d’une augmentation de la mobilisation calcique et de la migration des lymphocytes T CD4+ en réponse au LTD4. Pour la première fois, nous montrons que les lymphocytes T naïfs purifiés expriment ST2L et répondent à l’IL-33 en absence de stimulation du TCR. Contrairement aux cytokines connues pour pouvoir réguler l’expression de CysLT1 dans les leucocytes, l’IL-33 augmente l’expression de CysLT1 au niveau protéique mais pas au niveau de l’ARNm, suggérant une régulation post-transcriptionnelle. Après 7h30 de stimulation, l’IL-33 augmente le ratio d’expression du transcrit 1 par rapport au transcrit 4 de CysLT1. De plus, les inhibiteurs des voies de dégradation n’affectent pas l’augmentation d’expression du récepteur induite par la cytokine, appuyant l’hypothèse d’une régulation de l’épissage alternatif ou de la stabilité des transcrits de CysLT1 par l’IL-33. Cette étude contribue à élargir les connaissances sur les mécanismes immuns potentiellement impliqués dans la pathologie de l’asthme et propose des nouvelles perspectives dans l’étude de l’IL-33 et du récepteur CysLT1.Abstract: During an asthmatic reaction, interleukin (IL)-33 is released as an alarmin by damaged airway epithelial cells and fibroblasts. Following a proteolytic cleavage, the cytokine binds to its specific receptor ST2L at the surface of leukocytes, leading to IL-5 and IL-13 release and initiating asthma-associated inflammation and symptoms. In addition to inflammatory cytokines, cysteinyl-leukotrienes (cysLTs) are potent bronchoconstrictors and take part in the type 2 inflammation in asthma. CysLTs are lipid mediators derived from arachidonic acid metabolism and include leukotriene (LT)D4, LTC4 and LTE4. Most of the inflammatory properties of cysLTs are transduced by CysLT1 receptor that is expressed by leukocytes and regulated by cytokines in the inflammatory environment. This study aimed to explore the regulation of CysLT1 expression by IL-33 in human peripheral blood lymphocytes from healthy donors. Results show that the IL-33/ST2L/TAK-1 pathway increased CysLT1 expression after 9h of stimulation with 5ng/ml of IL-33. CysLT1 upregulation was correlated with an increase in LTD4-induced calcium mobilisation and migration in T CD4+ lymphocytes. Furthermore, we show, for the first time, that purified naïve T cells express ST2L and respond to IL-33 in the absence of TCR stimulation. Unlike other cytokines previously shown to regulate CysLT1 expression in leukocytes, IL-33 increased CysLT1 expression at the protein but not at the mRNA level, suggesting post-transcriptional regulation. Indeed, after a 7h30 stimulation, IL-33 increased the CysLT1 transcript 1/transcript 4 ratio. Moreover, proteasomal and lysosomal inhibitors did not block IL-33- induced CysLT1 expression, suggesting a regulation of mRNA alternative splicing or transcript stability. Thus, this work contributes to broaden the knowledge on the immune mechanisms potentially involved in asthma pathogenesis. In addition, new perspectives are provided for the study of IL-33 and CysLT1

AMS-02 antiprotons, at last! Secondary astrophysical component and immediate implications for Dark Matter

Using the updated proton and helium fluxes just released by the AMS-02 experiment we reevaluate the secondary astrophysical antiproton to proton ratio and its uncertainties, and compare it with the ratio preliminarly reported by AMS-02. We find no unambiguous evidence for a significant excess with respect to expectations. Yet, some preference for a flatter energy dependence of the diffusion coefficient starts to emerge. Also, we provide a first assessment of the room left for exotic components such as Galactic Dark Matter annihilation or decay, deriving new stringent constraints.Comment: 12 pages, 5 figures; Comments and clarifications added (including an appendix), matches version published on JCA

A new look at the cosmic ray positron fraction

The positron fraction in cosmic rays was found to be a steadily increasing in function of energy, above $\sim$ 10 GeV. This behaviour contradicts standard astrophysical mechanisms, in which positrons are secondary particles, produced in the interactions of primary cosmic rays during the propagation in the interstellar medium. The observed anomaly in the positron fraction triggered a lot of excitement, as it could be interpreted as an indirect signature of the presence of dark matter species in the Galaxy. Alternatively, it could be produced by nearby astrophysical sources, such as pulsars. Both hypotheses are probed in this work in light of the latest AMS-02 positron fraction measurements. The transport of the primary and secondary positrons in the Galaxy is described using a semi-analytic two-zone model. MicrOMEGAs is used to model the positron flux generated by dark matter species. The description of the positron fraction from astrophysical sources is based on the pulsar observations included in the ATNF catalogue. We find that the mass of the favoured dark matter candidates is always larger than 500 GeV. The only dark matter species that fulfils the numerous gamma ray and cosmic microwave background bounds is a particle annihilating into four leptons through a light scalar or vector mediator, with a mixture of tau (75%) and electron (25%) channels, and a mass between 0.5 and 1 TeV. The positron anomaly can also be explained by a single astrophysical source and a list of five pulsars from the ATNF catalogue is given. Those results are obtained with the cosmic ray transport parameters that best fit the B/C ratio. Uncertainties in the propagation parameters turn out to be very significant. In the WIMP annihilation cross section to mass plane for instance, they overshadow the error contours derived from the positron data.Comment: 20 pages, 16 figures, accepted for publication in A&A, corresponds to published versio

Maternal diet and gut microbiome composition modulate early-life immune development.

In early life, the intestinal mucosa and immune system undergo a critical developmental process to contain the expanding gut microbiome while promoting tolerance toward commensals, yet the influence of maternal diet and microbial composition on offspring immune maturation remains poorly understood. We colonized germ-free mice with a consortium of 14 strains, fed them a standard fiber-rich chow or a fiber-free diet, and then longitudinally assessed offspring development during the weaning period. Unlike pups born to dams fed the fiber-rich diet, pups of fiber-deprived dams demonstrated delayed colonization with Akkermansia muciniphila, a mucin-foraging bacterium that can also use milk oligosaccharides. The pups of fiber-deprived dams exhibited an enrichment of colonic transcripts corresponding to defense response pathways and a peak in Il22 expression at weaning. Removal of A. muciniphila from the community, but maintenance on the fiber-rich diet, was associated with reduced proportions of RORγt-positive innate and adaptive immune cell subsets. Our results highlight the potent influence of maternal dietary fiber intake and discrete changes in microbial composition on the postnatal microbiome assemblage and early immune development

Piezoelectric Ceramic Transducers as Time-Varying Displacement Sensors in Nanopositioners

We present a direct measurement of stage displacement in piezo- driven nanopositioners via piezoelectric (PZT) ceramics. In addition to compactness and affordability, our study shows that within the sensing bandwidth, the sensor is able to track time-varying large signal profiles of stage displacement accurately without utilizing signal conditioning devices. Also, the sensor can be used to capture cross coupling effect in orthogonal axes of motion. For the full-scale range, accuracy of the suggested sensor is less than 27 nm in the sensing bandwidths when the sensor is calibrated with a constant scaling factor. The 3s-resolution of the sensor is 1.9 nm