Résumé: Nous avons cherché à vérifier si l’atténuation du stress oxydatif lié au diabète pourrait diminuer le processus de la mort des cellules cardiaques. Notre étude a montré que l’apoptose ...cardiaque est semblable à une des réponses cellulaires majeures au diabète: induite par un stress oxydatif. La Glisodin®, une association de SOD de melon et de protéine de blé, également un puissant antioxydant, a freiné le développement de la cardiomyopathie diabétique. Nos résultats montrent une réduction significative des TUNEL-positifs dans les cardiomyocytes, observée chez le groupe diabétique traité par la Glisodin®. On a observé une diminution significative de la teneur en glutathion réduit, de l’activité de la SOD et de la catalase dans le cœur de rats diabétiques accompagnée par une augmentation des concentrations plasmatiques des LPO en comparaison aux rats traités par Glisodin®. Le traitement des rats diabétiques par la Glisodin® a rétabli l’augmentation de l’activité de la LDH et de la CPK exprimée chez les rats non traités. En conclusion, nos résultats suggèrent que l’atténuation de l’apoptose des cellules cardiaques par la Glisodin® assoie son effet préventif contre le développement de la cardiomyopathie diabétique. Toutefois, cet effet est principalement médié par une action antioxydante suppressive du stress oxydatif plutôt que par une action hypoglycémiante.
Abstract: We aimed to test whether attenuation of cardiac cell death can prevent diabetic cardiomyopathy. Our study showed that cardiac apoptosis as a major cellular response to diabetes is induced by hyperglycemia-derived oxidative stress. Glisodin® as a potent antioxidant prevents the development of diabetic cardiomyopathy. Eight weeks after STZ treatment, cardiac apoptosis was examined by terminal deoxynucleotidyl transferase-mediated dUTP labeling (TUNEL) assay. Oxidative stress in the heart tissue was evaluated by measuring GSH content, LPO level, and catalase and SOD activities. Cardiomyopathy was evaluated by measuring LDH and CPK activities. Our results show a significant reduction in diabetesinduced increases in TUNEL-positive cells was observed in a Glisodin® treatment group. A significant decrease of reduced glutathione content, superoxide dismutase, and catalase activities in the heart of diabetic rats accompanied by increased LPO plasma levels, but not in Glisodin®-treated rats, was observed. LDH and CPK activities as biomarkers of cardiomyopathy were decreased in Glisodin®-treated diabetic rats compared to diabetic-controlled rats. In conclusion, our results suggest that attenuation of cardiac cell death by Glisodin® treatment results in a significant prevention of the development of diabetic cardiomyopathy. This process is mediated by the antioxidant effect of Glisodin® to suppress oxidative stress in the heart.
Heavy-ion microbeams are employed for probing the radiation-sensitive regions in commercial silicon carbide (SiC) vertical double-diffused power (VD)-MOSFETs with micrometer accuracy. By scanning the ...beam spot over the die, a spatial periodicity was observed in the leakage current degradation, reflecting the striped structure of the power MOSFET investigated. Two different mechanisms were observed for degradation. At low drain bias (gate and source grounded), only the gate-oxide (at the JFET or neck region) is contributing in the ion-induced leakage current. For exposures at drain-source bias voltages higher than a specific threshold, additional higher drain leakage current is observed in the p-n junction region. This provides useful insights into the understanding of basic phenomena of single-event effects in SiC power devices.
High sensitivity of silicon-carbide (SiC) power MOSFETs has been observed under heavy-ion irradiation, leading to permanent increase of drain and gate leakage currents. The electrical postirradiation ...analysis confirmed the degradation of the gate oxide and the blocking capability of the devices. At low drain bias, the leakage path is formed between drain and gate, while at higher bias the heavy-ion-induced leakage path is mostly from drain to source. An electrical model is proposed to explain the current transport mechanism for heavy-ion degraded SiC power MOSFETs.
Accelerated terrestrial neutron irradiations were performed on different commercial SiC power MOSFETs with planar, trench, and double-trench architectures. The results were used to calculate the ...failure cross sections and the failure-in-time (FIT) rates at sea level. Enhanced gate and drain leakage were observed in some devices which did not exhibit a destructive failure during the exposure. In particular, a different mechanism was observed for planar and trench gate MOSFETs, the first showing a partial gate rupture with a leakage path mostly between the drain and the gate, similar to what was previously observed with heavy ions, while the second exhibiting a complete gate rupture. The observed failure mechanisms and the postirradiation gate stress (PIGS) tests are discussed for different technologies.
The advantages of silicon carbide (SiC) power MOSFETs make this technology attractive for space, avionics and high-energy accelerator applications. However, the current commercial technologies are ...still susceptible to Single Event Effects (SEEs) and latent damages induced by the radiation environment. Two types of latent damage were experimentally observed in commercial SiC power MOSFETs exposed to heavy-ions. One is observed at bias voltages just below the degradation onset and it involves the gate oxide. The other damage type is observed at bias voltages below the Single Event Burnout (SEB) limit, and it is attributed to alterations of the SiC crystal-lattice. Focused ion beam (FIB) and scanning electron microscopy (SEM) were used to investigate the damage site. Finally, a summary of the different types of damage induced by the heavy ion in SiC MOSFETs is given as a function of the ion LET and operational bias.
•SiC MOSFETs•Heavy-ion•Latent damage•SEEs•Radiation effects
In this paper, we report on the development and first deployment of a distributed optical fiber radiation sensor (DOFRS) for the online monitoring of radiation levels in the high-energy accelerator ...facilities of CERN. The DOFRS is composed of two basic parts: a set of suitably chosen radiation sensitive optical fibers (OFs), to be installed in the machine tunnel, and an optical time domain reflectometer (OTDR), to be installed in a radiation-free area. We carried out a calibration of the radiation response of a P-doped multimode OF under 60 Co <inline-formula> <tex-math notation="LaTeX">\gamma </tex-math></inline-formula>-rays and in the mixed-field radiation environment of the CHARM facility at CERN. By performing OTDR measurements, we are able to probe the radiation-induced attenuation in the OF along its length and calculate the deposited radiation dose with a spatial resolution of 1 m. In this paper, we describe the main features associated with DOFRS implementation in the proton synchrotron booster (PSB) at CERN. We also report the first results obtained from the monitoring of PSB radiation levels since its recommissioning in April 2017. The performances and advantages of the DOFRS system are discussed.
•We propose a tuning of room temperature ferromagnetism by co-doping the In2O3-system through nonmagnetic atoms (Mg).•A new doping process was developed to avoid the formation of magnetic ...nanoparticles.•The analysis revealed that Fe and Mg ions were incorporated into the In3+ sites in the In2O3 lattice without altering the cubic bixbyite structure.•RTFM ordering with remarkable enhancement of the saturation magnetization with decreasing Fe ions and increasing nonmagnetic Mg concentrations was observed.•The enhancement in the magnetic moment with increasing Mg doping is attributed to oxygen vacancies induced by the substitution of Fe and Mg ions into the In3+.
Iron-doped indium oxide is a promising material for spin electronics (spintronics) applications. Herein, an experimental investigation of the effect of adding a nonmagnetic element (magnesium) on the enhancement of the room-temperature ferromagnetism in substitutional iron-doped In2O3 powder was conducted. A new doping process, which avoids the formation of Fe nanoclusters in (In0.85Fe0.15−xMgx)2O3 (x = 0.00, 0.01, 0.03, 0.05) powders, was developed. The resulting powders were characterised by X-ray diffraction (XRD), superconducting quantum interference device, Mössbauer spectroscopy, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy. The XRD analysis revealed that Fe and Mg ions were incorporated into the In3+ sites in the In2O3 lattice without altering the cubic bixbyite structure. Magnetic measurements indicated the coexistence of ferromagnetic and paramagnetic phases. Room-temperature ferromagnetic behaviour with remarkable enhancement of the saturation magnetisation was observed for decreasing Fe ions and increasing nonmagnetic Mg concentrations. Mössbauer spectra confirmed the coexistence of ferromagnetic (sextet) and paramagnetic (doublet) phases, with a clear effect of Mg concentration. The enhancement in the magnetic moment with increasing Mg doping is attributed to the large defects and oxygen vacancies induced in In2O3 by Fe and Mg co-doping. These results will be useful for the development of Fe-doped In2O3 semiconductor materials for advanced applications.
•Possible use of optical fibers as radiation sensors at CERN.•Comparison of P-doped, P-Ce-doped and Al-doped SM fibers.•Temperature dependence of the RIA spectral features in the NIR ...domain.•Comparable RIA levels and kinetics under X- and γ-rays irradiation.•Influence of modal propagation on the RIA spectra in SM fiber.
We investigate the X-ray (40 keV) and γ-ray (1.2 MeV) radiation responses of three different radiation sensitive Optical Fibers (OFs) up to 100 Gy(SiO2). In particular, we study the Radiation Induced Attenuation (RIA) in the Near Infrared domain (NIR) for single mode OFs doped with Phosphorus (P), Aluminum (Al) and Phosphorus/Cerium (PCe) in their cores at three temperatures up to 50 °C. RIA levels and kinetics strongly depend on the operating wavelength and fiber composition. For both P and PCe-doped fibers, the P1 defects are the main contributors to the RIA, with Ce-codoping inducing a decrease of radiation sensitivity. For the Al-doped fiber, no specific absorption bands can be discriminated in the NIR. Both X- and γ-rays lead to the same RIA levels and kinetics. The RIA spectral dependences on dose and temperature highlight the potential of the three investigated fibers for radiation detection and dosimetry. To better discuss the properties of point defects responsible for the NIR RIA, we analyze how the fundamental mode propagation influences the RIA spectra of each fiber type. By reasonably assuming that the core RIA exceeds largely the cladding RIA and by calculating the mode Confinement Factor (CF), the RIA spectra of the core material are reconstructed and the spectral characteristics of defects are discussed for each type of fibers.
Beam cooling with ionization losses Rubbia, C.; Ferrari, A.; Kadi, Y. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2006, Letnik:
568, Številka:
2
Journal Article
Recenzirano
Odprti dostop
This novel type of
Ionization Cooling is an effective method in order to enhance the (strong) interaction probability of slow (few MeV/A) ions stored in a small ring. The many traversals through a ...thin target strongly improve the nuclear reaction rate with respect to a single-pass collision, in a steady configuration in which ionization losses of a target “foil” (typically few hundred μg/cm
2 thick) are continuously recovered by an RF-cavity. With a flat foil, betatron oscillations are “cooled”, but the momentum spread diverges exponentially, since faster (slower) particles ionize less (more) than the average. In order to “cool” the beam also longitudinally, a chromaticity has to be introduced with a wedge-shaped “foil”. Therefore, in equilibrium conditions, multiple scattering and straggling are both balanced by phase-space compression.
Classic Ionization Cooling A.A. Kolomensky, Atomnaya Energiya 19 (1965) 534; Yu.M. Ado, V.I. Balbekov, Atomnaya Energiya 31(1) (1971) 40–44; A.N. Skrinsky, V.V. Parkhomchuk, Sov. J. Nucl. Phys. 12 (1981) 3; E.A. Perevendentsev, A.N. Skrinsky, in: Proceedings of the 12th International Conference on High Energy Acceleration, 1983, p. 485 is designed to cool the direct beam until it has been compressed and extracted for further use. In practice, this limits its applicability to non-interacting muon beams. Instead, in this new method, applicable to strongly interacting collisions, the circulating beam is not extracted. Ionization cooling provides “in situ” storage of the beam until it is converted by a nuclear interaction with the target.
Simple reactions—for instance
7
Li
+
D
→
8
Li
+
p
—are more favourably produced in the “mirror” kinematical frame, namely with a heavier ion colliding against a gas-jet D
2 target. Kinematics is generally very favourable, with angles in a narrow angular cone (around ∼10° for the mentioned reaction) and with a relatively concentrated outgoing energy spectrum which allows an efficient collection of
8Li as a neutral gas in a tiny volume, a technology perfected by ISOLDE at high temperatures.
The method should be capable of producing a “table top” storage ring with an accumulation rate in excess of 10
14
8Li radioactive ion/s. It has however a much more general applicability to many other nuclear reactions.
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