HAL-Université de Bretagne Occidentale
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GATE 10 Monte Carlo particle transport simulation: I. Development and new features
No full textInternational audienceWe present GATE version 10, a major evolution of the open-source Monte Carlo simulation application for medical physics, built on Geant4. This release marks a transformative evolution, featuring a modern Python-based user interface, enhanced multithreading and multiprocessing capabilities, the ability to be embedded as a library within other software, and a streamlined framework for collaborative development. In this Part 1 paper, we outline GATE’s position among other Monte Carlo codes, the core principles driving this evolution, and the robust development cycle employed. We also detail the new features and improvements. Part 2 will focus on the architectural innovations and technical challenges. By combining an open, collaborative framework with cutting-edge features, such a Monte Carlo platform supports a wide range of academic and industrial research, solidifying its role as a critical tool for innovation in medical physics
Iterative confidence-based pseudo-labeling for semi-supervised lung cancer segmentation under annotation scarcity
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Processing of Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) Using Acetic Acid: An Eco-friendly Alternative to Chloroform
No full textInternational audienceAbstract The pervasive accumulation of plastic waste in terrestrial and aquatic environments has become a critical environmental issue, largely due to the resistance of petroleum-derived polymers to microbial degradation. This persistence leads to the long-term generation of microplastics and widespread ecosystem contamination. As a response, biodegradable and bio-based materials such as polyhydroxyalkanoates (PHA) have emerged as promising sustainable alternatives. Among them, poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) is a microbial polyester that exhibits excellent biodegradability, biocompatibility, and tunable mechanical properties. Owing to these characteristics, P(3HB-co-4HB) can be employed in a wide range of applications, from environmentally friendly packaging to biomedical devices. However, its processing has traditionally relied on toxic solvents such as chloroform. In this study, acetic acid is evaluated as a green alternative solvent for producing P(3HB-co-4HB) films and porous gels. Compared with chloroform, acetic acid caused moderate reductions in molecular weight (–12% for 10 mol% 4HB and − 5% for 34 mol% 4HB) and slight decreases in thermal stability, while degradation kinetics remained unaffected. DSC analyses revealed enhanced melting enthalpy for P(3HB-co-10 mol%4HB) films and the emergence of additional crystalline populations for P(3HB-co-34 mol%4HB). Mechanical tests showed moderate reductions in ductility and modulus at low 4HB content, whereas high 4HB content was unaffected. FTIR spectra confirmed the absence of solvent-induced chemical modifications. In addition, a simple thermally induced phase separation method produced highly porous (≈ 90%) gels. Overall, this study demonstrates that acetic acid offers a sustainable processing route for P(3HB-co-4HB), while preserving key material properties comparable to those obtained with chloroform
Usefulness of 18F-FDG PET-CT in detecting subclinical arteritis and cancer associated with polymyalgia rheumatica
No full textInternational audienceTo assess the prevalence of giant cell arteritis (GCA) or cancer detected via 18F-fluorodeoxyglucose positron emission tomography-computed tomography (PET-CT) in patients with polymyalgia rheumatica (PMR) without clinical signs suggestive of GCA
Nonphotochemical quenching and beyond: multi-layered photoprotection shapes light-stress tolerance across seasonal niches in Arctic diatoms
No full textInternational audienceThroughout their species seasonal succession, diatoms of the Arctic Ocean experience a radical habitat transformation, from surviving the dimly lit winter within sea-ice or in the water column, to rapid growth under increasing irradiances, forming massive spring blooms beneath melting ice and later in open waters. Therefore, their evolutionary path has been moulded by the opposing challenges of maximizing light capture part of the year while maintaining highly efficient photoprotection capacities to limit photodamage upon bursts of supra-optimal illumination. Two main photoprotection mechanisms exist in diatoms i) nonphotochemical quenching (NPQ) supported primarily by the xanthophyll cycle (XC) and stress-related Lhcx antenna proteins and, ii) a rapid repair cycle of photosystem (PS) II core protein, PsbA, upon photodamage. Previous studies suggest that freezing temperatures slow protein turnover and favour photoprotection strategies that rely primarily upon XC-NPQ in polar taxa. We aim to revisit this hypothesis by dissecting the high-light response of five Arctic diatom species that dominate contrasting ecological niches: sea-ice, marginal ice-zone and open waters. We exposed each species to a high-light stress and subsequent recovery period under low light, with and without, inhibitors of XC-NPQ (dithiothreitol) or of plastid protein translation (lincomycin), blocking de novo replacement of PsbA. We confirmed the crucial role of XC-NPQ in protecting PSII but also report unexpected observations that challenge our current understanding of psychrophile species response to light stress. First, the impact of lincomycin on PSII photoinhibition was stronger than that of DTT, despite PsbA turnover being undetectable by immunoblots in most cases. Second, while our data support planktonic species showing better tolerance to high light than sympagic species, we found unsuspected diversity in photoprotection strategies. We hypothesize that these differences support a gradient from conservative strategies, possibly optimized for survival in the extreme sea-ice habitat of sympagic species, to productivity-oriented strategies in open water planktonic species dominating during the bloom period. In the transforming, brighter, Arctic Ocean, the adaptedness of this community-wide strategy scheme could be undermined, shaking up the historical dominance of certain diatom taxa
