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Population of giant planets around B stars from the first part of the BEAST survey

Exoplanets form from circumstellar protoplanetary disks whose fundamental properties (notably their extent, composition, mass, temperature, and lifetime) depend on the host star properties, such as their mass and luminosity. B stars are among the most massive stars and their protoplanetary disks test extreme conditions for exoplanet formation. This paper investigates the frequency of giant planet companions around young B stars (median age of 16 Myr) in the Scorpius-Centaurus (Sco-Cen) association, the closest association containing a large population of B stars. We systematically searched for massive exoplanets with the high-contrast direct imaging instrument SPHERE using the data from the BEAST survey, which targets a homogeneous sample of young B stars from the wide Sco-Cen association. We derived accurate detection limits in the case of non-detections. We found evidence in previous papers for two substellar companions around 42 stars. The masses of these companions are straddling the sim 13 Jupiter mass deuterium burning limit, but their mass ratio with respect to their host star is close to that of Jupiter. We derived a frequency of such massive planetary-mass companions around B stars of $11_ $<!PCT!>, accounting for the survey sensitivity. The discoveries of substellar companions b and B happened after only a few stars in the survey had been observed, raising the possibility that massive Jovian planets might be common around B stars. However, our statistical analysis shows that the occurrence rate of such planets is similar around B stars and around solar-type stars of a similar age, while B-star companions exhibit low mass ratios and a larger semi-major axis.

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EXTH-25. OPTIMIZATION OF NEW CHEMOTHERAPEUTIC AGENTS BY INTRA-ARTERIAL INFUSION IN GLIOBLASTOMAS

Abstract Being the most aggressive malignant primary brain tumor, glioblastoma (GBM) is a difficult disease to treat. The first line treatment is well established, but most patients will relapse before or during the treatments. The overall survival is only 14,6 months while the progression-free survival is 6,9 months. In Sherbrooke, Dr Fortin prioritize the intra-arterial (IA) administration of chemotherapeutic agents (CTA) as a second line treatment. Unfortunately, certain patients will not respond or will even develop chemoresistance to the agents. Therefore, there is a strong need for bringing more CTAs onto clinical care. The maximal tolerable dosage (MTD) of every agent was first determined. Every CTAs were then administered IA by retrograde infusion in the external carotid but also intravenously (IV) by the caudal vein. We used the Fischer-F98 glioma rat model in our studies. For the efficacy study, we implanted 10 000 F98 cells into their brain. After 10 days, they received the treatment associated to their group. The animals were followed every day and were euthanized when their condition was too deteriorated. The dosages found in the MTD study for topotecan and cytarabine was 4 mg/kg and 8,75 mg/kg respectively while paclitaxel was too toxic. As for the efficacy study, the IA group of topotecan showed a promising outcome with a higher survival rate (29 days) compared to the IV one (23,5 days). As for the cytarabine, the opposite was observed (IA: 22 days, IV: 26,5 days). While topotecan and cytarabine could be given intra-arterially, only topotecan showed conclusive results. More animals will be added to this group to confirm this outcome. Cytarabine is not a good option since the IV group survived a longer time than the IA group. As for the paclitaxel, the intra-tumoral infusion will be tested to see if we can get positive results.

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