Tracking millisecond pulsars responsible for the Fermi GeV excess

More than 10 years ago, an excess of γ-ray photons coming from the Galactic center was discovered in the Fermi-LAT data. First attributed to dark matter, it has since been shown that it should have at least a partial stellar origin. One hypothesis is the presence of a population of millisecond pulsars (MSPs) confined in the Galactic bulge. We here present our recent progress in the selection of MSP candidates

Primordial Black Holes as dark matter candidates: Constraints from the diffuse MeV emission

For more than 20 years, the Compton telescope had provided the best measurements of the Galactic diffuse MeV spectrum. Recently, our analysis of 16 years of data from the SPectrometer on INTEGRAL (SPI) measured this emission with a higher signal-to-noise ratio. At MeV energies, the dominant contribution to the diffuse emission comes from inverse Compton scattering. Nonetheless, sub-dominant emission from Primordial Black Hole (PBH) Dark Matter (DM) can be searched for in these data. Hypothetically formed from the collapse of over-densities before Big Bang nucleosynthesis, PBHs are interesting candidates for DM in the ΛCDM model of cosmology. PBHs of masses between 1016 and 1018 g, in the so-called asteroid mass range, are currently unconstrained and can saturate the DM cosmological abundance. MeV emission from PBH in this mass range is expected to come from PBH evaporation. We searched for the PBH signal with 16 years of SPI data, and demonstrated that PBHs cannot account for all the DM if their mass is smaller than 4 × 1017 g

Rapid, energy-efficient synthesis of the layered carbide, Al₄C₃

The phase-pure binary aluminium carbide, Al4C3 can be synthesised in vacuo from the elements in 30 minutes via microwave heating in a multimode cavity reactor. The success of the reaction is dependent on the use of finely divided aluminium and graphite starting materials, both of which couple effectively to the microwave field. The yellow-brown powder product was characterised by powder X-ray diffraction, scanning electron microscopy/energy dispersive X-ray spectroscopy thermogravimetric-differential thermal analysis and Raman spectroscopy. Powders were composed of hexagonal single crystallites tens of microns in diameter (rhombohedral space group R[3 with combining macron]m; Z = 3; a = 3.33813(5) Å, c = 25.0021(4) Å) and were stable to 1000 °C in air, argon and nitrogen. Equivalent microwave reactions of the elements in air led to the formation of the oxycarbide phases Al2OC and Al4O4C

In Situ Monitoring of Microwave Processing of Materials at High Temperatures through Dielectric Properties Measurement

[EN] Microwave-assisted processes have recognized advantages over more conventional heating techniques. However, the effects on the materials¿ microstructure are still a matter of study, due to the complexity of the interaction between microwaves and matter, especially at high temperatures. Recently developed advanced microwave instrumentation allows the study of high temperature microwave heating processes in a way that was not possible before. In this paper, different materials and thermal processes induced by microwaves have been studied through the in situ characterization of their dielectric properties with temperature. This knowledge is crucial in several aspects: to analyze the effects of the microwave field on the reaction pathways; to design and optimize microwave-assisted processes, and to predict the behavior of materials leading to repeatable and reliable heating processes, etc.García Baños, B.; Catalá Civera, JM.; Peñaranda Foix, FL.; Plaza González, PJ.; Llorens Vallés, G. (2016). In Situ Monitoring of Microwave Processing of Materials at High Temperatures through Dielectric Properties Measurement. Materials. 9(5):1-10. doi:10.3390/ma9050349S1109

BMC Cancer

BACKGROUND: Although some countries have observed a stabilization in the incidence of CNS, an increasing incidence has been reported from multiple studies. Recent observations point out to the heterogeneity of incidence trends according to histological subtypes, gender and age-groups. Using a high-quality regional CNS tumor registry, this article describes the trends of CNS tumor incidence for main histological subtypes, including benign and malignant tumors, in the French department of Gironde from 2000 to 2012. METHODS: Crude and age-standardized incidence rates were calculated globally, by histological subtypes, malignant status, gender and age groups. For trends, annual percent changes (APC) were obtained from a piecewise log-linear model. RESULTS: A total of 3515 CNS tumors was registered during the period. The incidence of overall CNS tumors was 19/100000 person-years (8.3/100000 for neuroepithelial tumors and 7.3/100000 for meningeal tumors). An increased incidence of overall CNS tumors was observed from 2000 to 2012 (APC = + 2.7%; 95%-confidence interval (CI): 1.8-3.7). This trend was mainly explained by an increase in the incidence of meningiomas over the period (APC = + 5.4%, 95%-CI: 3.8-7.0). The increased incidence rate of CNS tumors was more pronounced in female and in older patients even though the incidence rate increased in all age groups. CONCLUSIONS: Part of the temporal variation may be attributed to improvement in registration, diagnosis and clinical practices but also to changes in potential risk factors. Thus, etiological studies on CNS tumors are needed to clarify this rising trend

Interaction des microondes avec les milieux vivants

L'absorption des microondes et des hautes fréquences par les milieux vivants présente un caractère spécifique lié notamment à la caractéristique diélectrique des divers tissus (quantité et état de l’eau), à la profondeur de pénétration de l’onde, à la forme et aux dimensions du milieu. On définit classiquement un taux d’absorption spécifique (SAR) variable en fréquence et on montre que les normes d’exposition sont étroitement dépendantes du SAR. Ces diverses données biophysiques illustrent la complexité d’interprétation des effets biologiques décrits dans la littérature

Encres conductrices thermodurcissables et leurs applications

Thick film polymer pastes with carbon or metallic charges can be used as passive components or electrical connecting elements in hybrid circuit technology. Thermosetting polymer pastes have been prepared to allow utilization temperatures until 125 °C. Carbon pastes have resistivity between 1 MΩ/□ to 10 Ω/□ whereas silver pastes have resistivity lower than 50 mΩ/□. Copper pastes have been recently made to attain a resistivity lower than 20 mΩ/□ with a good solderability. A new curing process using microwave technology allows very short curing time to be attained (some minutes) as for a low resistivity near 10 mΩ/□. Thermal stability and ageing factor are also in favour of microwave technology. Other applications of conducting polymer pastes are mentioned for absorbing materials.Les polymères en couches épaisses avec charges au carbone ou métalliques peuvent constituer des composants passifs (résistances variables) ou des connexions conductrices pouvant entrer dans la fabrication des composants électroniques. Nous avons étudié la mise en oeuvre de liants thermodurcissables pour étendre les gammes d'utilisation jusqu'à 125 °C. Les encres au carbone mises au point permettent la constitution d'une gamme de résistances allant de 1 MΩ/□ à 10 Ω/□ alors que les encres à l'argent ont des résistances inférieures à 50 mΩ/□. Plus récemment des encres thermodurcissables au cuivre ont été élaborées et fournissent des conductivités exceptionnelles de l'ordre de 20 à 30 mΩ/□ ainsi que la possibilité d'être soudées. Une nouvelle technique de réticulation des encres au cuivre par mise en oeuvre des micro-ondes a permis de réticuler les encres en une dizaine de minutes, avec une résistivité finale de l'ordre de 10 mΩ/□ ce qui constitue une valeur jamais atteinte. La stabilité thermique et le facteur de vieillissement sont très élevés. Les applications de ces encres sont en cours dans l'industrie des composants électroniques ou envisagés pour la constitution des absorbants