Journal of Next-Generation Research 5.0
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Combination of direct methods and homotopy in numerical optimal control: application to the optimization of chemotherapy in cancer
No full textInternational audienceWe consider a state-constrained optimal control problem of a system of two non-local partial-differential equations, which is an extension of the one introduced in a previous work in mathematical oncology. The aim is to minimize the tumor size through chemotherapy while avoiding the emergence of resistance to the drugs. The numerical approach to solve the problem was the combination of direct methods and continuation on discretization parameters, which happen to be insufficient for the more complicated model, where diffusion is added to account for mutations. In the present paper, we propose an approach relying on changing the problem so that it can theoretically be solved thanks to a Pontryagin Maximum Principle in infinite dimension. This provides an excellent starting point for a much more reliable and efficient algorithm combining direct methods and continuations. The global idea is new and can be thought of as an alternative to other numerical optimal control techniques
Intervention éducative : enjeux, problématiques et perspectives
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New insights into the plumbing system of Santorini using helium and carbon isotopes
No full textInternational audienceWe have analysed He, Ne and CO 2 concentrations and isotopic ratios in seawater samples collected using a ROV above hydrothermal fields and in CO 2-accumulating pools within Santorini caldera (Greece). Our results provide new insights on the plumbing and magmatic sources of this volcano, which is critical to understand and better predict its volcanic eruptions, and its relationships to nearby volcanic systems. The 3 He/ 4 He ratio is as high as 6.54 times the atmospheric ratio, and significantly higher than any other samples from Santorini, including the active eruptive centre of Nea Kameni (~3.6 Ra). The 3 He/ 4 He ratio, corrected for atmospheric helium dissolved in seawater is ~7 Ra, a value similar to that measured at the nearby Kolumbo submarine volcano crater. The fluids display typical mantle signatures never recorded before in the active centres of the island of Santorini, in which fluids and gases are contaminated at shallow depths. The helium isotopic signature suggests that the source of volatiles for these two volcanoes is similar to the MORB source instead of being the subcontinental lithospheric mantle as suggested previously
L'ambivalence des médicaments : Un « traitement qui tue » dans les Centres de Traitement Ebola (Guinée, 2014-2016)
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Spring and summer time ozone and solar ultraviolet radiation variations over Cape Point, South Africa
No full textInternational audienceThe correlation between solar ultraviolet radiation (UV) and atmospheric ozone is well understood. Decreased stratospheric ozone levels which led to increased solar UV radiation levels at the surface have been recorded. These increased levels of solar UV radiation have potential negative impacts on public health. This study was done to determine whether the break-up of the Antarctic ozone hole has an impact on stratospheric columnar ozone (SCO) and resulting ambient solar UV-B radiation levels at Cape Point, South Africa, over 2007–2016. We investigated the correlations between UV index, calculated from ground-based solar UV-B radiation measurements and satellite-retrieved column ozone data. The strongest anti-correlation on clear-sky days was found at solar zenith angle 25∘ with exponential fit R2 values of 0.45 and 0.53 for total ozone column and SCO, respectively. An average radiation amplification factor of 0.59 across all SZAs was calculated for clear-sky days. The MIMOSA-CHIM model showed that the polar vortex had a limited effect on ozone levels. Tropical air masses more frequently affect the study site, and this requires further investigation
« Révision du loyer : quelle portée probatoire pour l’expertise non contradictoire ? », note sous Cass. 3e civ. 15 novembre 2018, n° 16-26172
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