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Recent advances in film dosimetry for quality assurance in microbeam radiation therapy
No full textInternational audienceMicrobeam Radiation Therapy (MRT) is currently on the verge of entering the clinical phase, necessitating robust quality assurance (QA) with appropriate dosimeters to ensure patient safety. However, MRT dosimetry presents significant challenges due to its intrinsic characteristics, including steep dose gradients with alternating high and low dose regions—referred to as peaks and valleys (valley doses comprising only 5–7 of peak doses)—micrometric resolution requirements, the use of low-to-medium energy X-rays and extremely high dose rates of up to 16 kGy/s. Currently, Gafchromic films are considered the gold standard for patient QA. Previous studies have reported discrepancies of 10–30 between measured and calculated peak and valley doses. This study aimed to evaluate four types of films (EBT-3, EBT-XD, MD-V3, and HD-V2) to determine the most suitable option for MRT QA. To support dosimetric benchmarking, the microDiamond detector was used as the reference for MRT measurements, and the ionization chamber for broad beam reference dosimetry. Discrepancies were observed between calculated and film-measured peak and valley doses, and several hypotheses were proposed to explain these differences. Possible causes include simplifications in dose calculation engines, intrinsic limitations of the films, uncertainties in experimental setups, and variations in readout methods. The study suggests that MD-V3 may be the most suitable film for MRT dosimetry, offering a dynamic range that effectively covers both peak and valley doses
Multi-scale magnetic aging model: Precipitation kinetics and magnetic hysteresis coupling
No full textInternational audienc
A random polymer approach to the weak disorder phase of the vertex reinforced jump process
No full textIn this paper, we study the transient phase of the Vertex Reinforced Jump Process (VRJP) in dimension d ≥ 3. In [29], the authors introduce a positive martingale and show that the VRJP is recurrent if and only if that martingale converges to 0. On , d ≥ 3, with constant conductances W , it can be shown that there is a critical value 0 < Wc() < ∞, such that the martingale converges to 0 if W < Wc() or to a positive limit if W > Wc(). On the other hand, the VRJP martingale can be interpreted as the partition function of a non-directed polymer with a very specific 1-dependent random potential. In this paper, we focus on the question of the Lp integrability of the VRJP martingale, which is related to the (diffusive) behavior of the VRJP. First, taking inspiration from the work of Junk [15] for directed polymers in , we prove that on the half-space of , for all W > Wc() there is some δ > 0 such that the VRJP martingale is in L. Second, we prove that, in dimension d ≥ 4, the VRJP martingale is in L for all p > 1 above the slab critical point W) = limm→∞ Wc( x [-m, m] We also propose some related conjectures
All Together Now: A Synchronous Platform for Distributed Spatial Audio
No full textInternational audienceState-of-the-art systems for spatial and immersive audio lie beyond the reach of many potential users due to the financial and technical investments that they demand. The risks associated with buying into a closed, centralised system of inflexible hardware and specialist software mean that, although areas of considerable research interest in recent years, significant barriers-to-entry exist with regard to immersive audio and virtual acoustics via practical application of sound field synthesis techniques. It is possible, however, to parallelise sound field synthesis algorithms and distribute them, subject to guarantees regarding the timing of distributed signal processors. Exploiting one of a number of low-cost embedded hardware platforms to have emerged over the past decade, and open-source software implementing the network Precision Time Protocol, we show that low-cost, networked audio devices can be synchronised to a degree sufficient to support time-sensitive audio applications
Investiguer les effets à long terme de la construction d’un barrage et de la restauration sur la biodiversité dans des chenaux secondaires à partir des macro-restes issus de carottes de sédiments fluviatiles
No full textInternational audienceThis research aims at reconstructing long-term (post-1950) biodiversity changes on side channels by analysingmacrofossils (plant, animal or abiotic remains < 5 mm) accumulated in sediment deposits. This approach relieson river cores dated by radionuclide along the Rhone River. Macrofossils, especially forest and aquatic taxa,provide a history of habitats and biodiversity since 1950, revealing three main hydro-ecological phases linked toriver developments and management. The first phase, before dam construction, highlights a diversified riverineforest marked by black alder scales, strawberry seeds and wood fragments. The second phase, in the 1980s-1990s, indicates a transition to terrestrial ecosystems due to water diversion, and the expansion of nitrophilousplants. Then, after 2000, macrofossil data reveal new wetland and aquatic plants after channel restoration. Thestudy of these bioindicators provide a valuable complement to sedimentological data and to plant inventories inorder to analyse the evolution of riparian habitats following developments or restoration actions. This approachcan help to define reference conditions and can be a tool improving the monitoring of alluvial wetlands, with aretrospective viewCette recherche vise à reconstruire les changements de biodiversité à long terme (post-1950) dans des chenaux secondaires en analysant les macro-restes (végétaux, animaux ou abiotiques < 5 mm) accumulés dans les sédiments fluviatiles. Cette approche s'appuie sur des carottes fluviales datées à l'aide de radionucléides le long du Rhône. Les macro-restes, notamment les taxons forestiers et aquatiques, permettent de reconstruire l'histoire des habitats et de la biodiversité depuis 1950, avec trois phases hydro-écologiques majeures, en lien avec l'aménagement et la gestion du fleuve. Une première phase, avant la construction du barrage, montre une ripisylve diversifiée, indiquée par la présence d'écailles d'aulne noir, de graines d'arbousier et de fragments de bois. La seconde phase, dans les années 1980-1990, voit une transition vers des écosystèmes terrestres suite à la mise en dérivation du tronçon étudié, et l'expansion de plantes nitrophiles. Puis, après 2000, les macro-restes révèlent l'établissement de nouvelles plantes aquatiques et de zones humides, faisant suite aux actions de restauration. L'étude de ces bioindicateurs offre un complément important par rapport aux données sédimentologiques et aux inventaires floristiques ponctuels pour analyser l'évolution des habitats ripariens suite aux aménagements du fleuve et aux actions de restauration. Cette approche peut aider à définir des conditions de référence et peut être un outil améliorant le suivi des zones humides alluviales, avec une vision rétrospective
A linear model of dynamical sea wavenumber spectra
No full textWe propose linear dynamics that can generate a given sea wavenumber spectrum via a linear partial differential equation stirred by an additive random forcing term that is δ-correlated in time. In particular, the correlation structure of the solution to this linear dynamics converges towards the target spectrum as time passes. The main linear mechanism is a transport in Fourier space, which models the transfer of energy from large scales towards small scales. The proposed linear dynamics generalize previous works for power-law spectra in the context of hydrodynamic turbulence to more general spectra, possibly non-radial, including sea wavenumber spectra such as the JONSWAP spectrum. Finally, we present simulations of the correlation structure of the solution to these dynamics in 2D, whose spectrum converges towards the JONSWAP spectrum. These simulations are based on a finite volume method in the Fourier domain and a splitting method in time, following a recently proposed numerical method by the same authors which improves on pseudospectral simulations
Porter attention aux pollutions qui hantent les sinistrés pour intégrer les enjeux de justice environnementale dans la compréhension des inondations en France et au Québec
No full textInternational audienceFlooding disrupts urban metabolism and generates pollution, seen here as materials that are out of place (Douglas, 1966). We were interested in how flood victims, in an urban context, “cope with” these pollutions (Benitez, 2018) during and after floods. A campaign of door-to-door semi-directive interviews was carried out in four neighborhoods that had experienced floods, in France and Quebec. The interviews were analyzed using a mixed method, between qualitative and quantitative approaches. Firstly, our research details the mechanisms that explain the lack of consideration, by flood victims, of pollution caused by flooding as a social problem. Secondly, we show that flood pollution haunts the bodies and emotions of flood victims. Finally, despite the existence of knowledge of these issues among flood victims, we show that the lack of social concern leads to these toxic realities becoming confined ordeals, in a context where an increasingly individualistic and apolitical resilience is encouraged, producing numerous injustices.Les inondations perturbent le métabolisme urbain et génèrent des pollutions, envisagées ici comme des matières qui ne sont pas à leur place (Douglas, 1966). Nous nous sommes intéressés à la façon dont les sinistrés, en contexte urbain, « vivent avec » ces pollutions (Benitez, 2018) pendant et après les inondations. Une campagne d’entretiens semi-directifs en porte à porte a été réalisée dans quatre quartiers ayant expérimenté des inondations par débordement, en France et au Québec. Les entretiens ont été analysés selon une méthode mixte, entre approches qualitative et quantitative. Dans un premier temps, notre recherche détaille les mécanismes qui expliquent pourquoi les sinistrés ne considèrent pas vraiment les pollutions causées par les inondations comme un problème social. Dans un deuxième temps, nous montrons que ces pollutions hantent pourtant les corps et les émotions des sinistrés. Enfin, malgré l’existence de connaissances engrangées par les sinistrés à l’égard de ces matières, nous démontrons que le défaut de préoccupation sociale conduit à faire de ces réalités toxiques des épreuves confinées, dans un contexte où une résilience de plus en plus individualisante et apolitique est encouragée, ce qui produit de nombreuses injustices
Characterization of the Dickeya-specific PhiEC2 bacteriophage
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/613442/)International audienceMost bacteria belonging to the genus Dickeya exhibit a strong pectinolytic activity resulting in dramatic damages in hundreds of crops and ornamental plants. Dickeya, which is widely used as a model genus in phytopathology studies, is rated as one of the top ten most damaging plant pathogens based on negative economic impact [1]. Indeed, emerging species such as Dickeya solani are now classified as quarantine organisms in some countries of the European Union. Dickeya bacteria are somehow reluctant to transformation by conventional techniques such as conjugation or electroporation. However, generalized phage-mediated transduction appears as a successful technique to transform Dickeya bacteria. Bacteriophages (commonly referred to as phages) are bacteria-targeting viruses. They are considered as the most abundant biological entity on Earth (approx. 1031) and they are found in all ecological niches harboring bacteria. Forty years ago, the temperate bacteriophage PhiEC2 has been discovered and shown to be able to infect Dickeya bacteria [2]. We recently used this phage to successfully achieve the transfer of large DNA fragments from one Dickeya strain to another, and therefore decided to fully characterize it beyond the scarce initial description from 1984. We sequenced the genome of the phage PhiEC2 as well as of the D. dadantii 3937 lysogenic strain harboring the corresponding prophage. We combined genome sequence analyses and electron microscopy imaging to unravel many features of the Dickeya-specific PhiEC2 bacteriophage, including morphological data and information about the insertion of the prophage within the genome of the lysogen
Représentations dynamiques, virtuelles et tangibles de la ville
No full textThe objective of this thesis is to develop new forms of territorial representations based on 3D urban data. Behind these representations, we focus on three forms of representations: multimedia, spatio-temporal, and tangible. The integration of multimedia such as archival images, videos, and documents into a virtual 3D scene allows for the enhancement of a historical district or provides additional information on urban objects. Alongside this contextualization of urban data, we seek to introduce a temporal dimension into the digital city. This involves diachronic management of information integrated into a 3D environment, enabling the representation of the city's evolution, comparison of different versions, and visualization of morphological changes in buildings within the same context. Finally, beyond digital representations, physical models of a neighborhood or area can improve understanding by providing another form of mediation. Augmented models facilitate the organization of mediation workshops on urban themes. To enhance the comprehension process, we propose interactions with these devices to further engage the user.L'objectif de cette thèse est de développer de nouvelles formes de représentations territoriales basées sur des données urbaines 3D. Derrière ces représentations, nous nous intéressons à trois formes de représentations : multimédia, spatio-temporelles et tangibles. L'intégration de multimédias tels que des images d'archives, des vidéos et des documents dans une scène 3D virtuelle permet de mettre en valeur un quartier historique ou d'apporter des informations complémentaires sur des objets urbains. Parallèlement à cette contextualisation des données urbaines, nous cherchons à introduire une dimension temporelle dans la ville numérique. Cela passe par une gestion diachronique des informations intégrées dans un environnement 3D, permettant de représenter l'évolution de la ville, de comparer différentes versions et de visualiser les changements morphologiques des bâtiments dans un même contexte. Enfin, au-delà des représentations numériques, les modèles physiques d'un quartier ou d'une zone peuvent améliorer la compréhension en apportant une autre forme de médiation. Les maquettes augmentées facilitent l'organisation d'ateliers de médiation sur des thèmes urbains. Pour améliorer le processus de compréhension, nous proposons des interactions avec ces dispositifs afin d'impliquer davantage l'utilisateur
Assessing Test Scenarios for Autonomous Driving Using Probabilistic Model Checking
No full textInternational audienceTesting autonomous vehicles is a challenging task, usually carried out using test scenarios, which are often derived manually from accident statistics and real traffic datasets, relying on expert knowledge and intuition to select the most relevant ones, a cumbersome task given the large size of these datasets. In this paper, we suggest a model-based approach to compare scenarios using quantitative measures computed by probabilistic model checking of user-defined temporal logic properties characterizing interesting event sequences. This approach facilitates the selection of the scenarios having the best tradeoff between coverage and overall testing cost (both for simulation and field testing). We illustrate the approach by comparing variations of scenarios, derived from frequent situations in accident statistics, using measures such as collision probability, arrival probability, and duration