•Single-session radiation treatments improve patient comfort by reducing the number of hospital visits.•They can also limit the risk of contamination in a pandemic context.•Single-sessions SBRT are a ...standard of care for small intracranial tumors, but their use for extracranial targets is debated.•They can be offered in selected patients and in trained teams.
Stereotactic Body Radiation Therapy (SBRT) is a standard of care for many localizations but the question of the optimal fractionation remains a matter of concern. If single fraction sessions are routinely used for intracranial targets, their utilization for mobile extracranial lesions is a source of debate and apprehension. Single session treatments improve patient comfort, provide a medico-economic benefit, and have proven useful in the context of the SARS-CoV2 pandemic. However, both technical and radiobiological uncertainties remain. Experience from intracranial radiosurgery has shown that the size of the target, its proximity to organs at risk, tumor histology, and the volume of normal tissue irradiated are all determining factors in the choice of fractionation. The literature on the use of single fraction for extracranial sites is still scarce. Only primary and secondary pulmonary tumors have been evaluated in prospective randomized trials, allowing the integration of these fractionation schemes in daily practice, for highly selected cases and in trained teams. The level of evidence for the other organs is mainly based on dose escalation or retrospective trials and calls for caution, with further studies being needed before routine use in clinical practice.
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The phase transformations induced by electronic excitation (Se) and ballistic processes (Sn) in Nd2Zr2O7 pyrochlores irradiated with heavy ions in three domains of energy (∼1GeV, ∼100MeV and a few ...MeV) were investigated by X-ray diffraction, Raman spectroscopy and transmission electron microscopy. In the Se regime at high energy, results show that: (i) ion tracks are formed above a Se threshold of 12.5keVnm−1; (ii) both pyrochlore→anion-deficient fluorite phase transition and amorphization occur; (iii) total amorphization is always observed at the highest fluences; (iv) the internal structure (amount of amorphous phase vs. its anion-deficient fluorite counterpart) and the diameter of tracks depend on many parameters such as Se, the deposited energy density and the recrystallization rate. For irradiations performed with low-energy ions in the Sn regime, only the anion-deficient fluorite phase is formed up to a dose of 40dpa. Thus Nd2Zr2O7 exhibits an unusual behaviour since this compound is amorphizable by Se and non-amorphizable by Sn. Annealing of totally amorphized Nd2Zr2O7 samples reveals strong differences in the recovery processes with other pyrochlore materials that are related to their different chemical compositions.
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Understanding complex non-equilibrium defect processes, where multiple irradiation mechanisms may take place simultaneously, is a long standing subject in material science. The separate and combined ...effects of elastic and inelastic energy loss are a very complicated and challenging topic. In this work, LiNbO3 has been irradiated with 0.9 MeV Si+ and 8 MeV O3+, which are representative of regimes where nuclear (Sn) and electronic (Se) energy loss are dominant, respectively. The evolution of damage has been investigated by Rutherford backscattering spectrometry (RBS) in channeling configuration. Pristine samples were irradiated with 0.9 MeV Si+ ions to create different pre-existing damage states. Below the threshold (Se,th = 5-6 keV nm−1) for amorphous track formation in this material, irradiation of the pristine samples with a highly ionizing beam of 8 MeV O3+ ions, with nearly constant Se of about 3 keV nm−1, induces a crystalline to amorphous phase transition at high ion fluences. In the pre-damaged samples, the electronic energy loss from the 8 MeV O3+ ions interacts synergistically with the pre-existing damage, resulting in a rapid, non-linear increase in damage production. There is a significant reduction in the incubation fluence for rapid amorphization with the increasing amount of pre-existing damage. These results highlight the important role of atomic-level defects on increasing the sensitivity of some oxides to amorphization induced by electronic energy loss. Controlling the nature and amount of pre-damage may provide a new approach to tuning optical properties for photonic device applications.
Why do we flush gas in gaseous detectors? Procureur, S.; Attié, D.; Bouteille, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2020, Volume:
955
Journal Article
Peer reviewed
Open access
The effects and the origin of the gas degradation in a gaseous detector-based tracker are investigated. The study focused on the so-called T2K gas, which turned out to be highly sensitive to ...pollutants. In particular the H2O and O2 concentrations were monitored online in different conditions to establish their influence on the gain of the detectors. This pollution was first mitigated by a recirculating and accelerating gas system with the use of a turbine and different absorbers. Further measurements revealed that this pollution originates from a continuous permeation process through the different materials of the gas circuit. In particular, polyurethane-based gas pipes or polyester materials largely increase the level of humidity. As a direct consequence of this work, the gas autonomy of the muon telescopes currently deployed inside the Khufu’s pyramid have been dramatically improved.
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Évaluer la relation entre les niveaux plasmatiques de sCD40L et la rétinopathie diabétique chez les patients atteints de diabète de type 2.
Dans le cadre d’une analyse transversale, 792 personnes ont ...été recrutées, réparties de la façon suivante : (1) patients atteints de DT2 sans rétinopathie, (2) patients atteints de DT2 avec rétinopathie(non proliférative et proliférative). Les différents paramètres cliniques et biochimiques ont été évalués et colligés pour analyser.
Les concentrations plasmatiques de sCD40L étaient significativement plus élevées chez les patients atteints de rétinopathie diabétique que chez ceux qui n’en avaient pas. Les taux plasmatiques moyens de sCD40L diffèrent significativement en fonction de la gravité de la rétinopathie diabétique (pas de rétinopathie diabétique, 85,62ng/mL, NPDR, 400,41ng/mL, PDR, 327,12ng/mL, p pour la tendance=0,000).
Les taux plasmatiques de sCD40L étaient positivement associés à la rétinopathie diabétique chez les patients atteints de diabète de type 2.
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•A six-parameter electrical model for a PV cell/module with CPC is presented.•Importance of each parameter is analysed through a robust sensitivity algorithm.•Scaling law is proposed for a PV cell ...with CPC operating under outdoor climate conditions.•Transient performance is examined by coupling optical, thermal and electrical effects.
It is known that compound parabolic concentrators (CPCs) can improve electrical performance of a photovoltaic (PV) flat-plate system. However, a lumped electrical model of a PV cell/module with CPC for assessing performance under different operating conditions is unavailable. In this paper, a six-parameter based model is developed and applied to a PV cell, two PV models with CPC, and a PV module with 2D asymmetric CPC (trough). For validation, CPC with a single PV cell and two CPC modules with 2×2 and 9×9 PV cells are fabricated and measured in an indoor laboratory under standard test conditions. Results show that the optimised algorithm precisely predicts the six model parameters. A sensitivity analysis is performed to identify the importance of each parameter in the model. Ideality factor, circuit current and reverse saturation current are found to be the most dominant factor, while shunt resistance is the least important with CPC gain coefficient and series resistance are in between. Transient performance of a PV cell with CPC under variable outdoor climate conditions is also examined by coupling optical, thermal and electrical effects.
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