832 research outputs found
Displacement Damage dose and DLTS Analyses on Triple and Single Junction solar cells irradiated with electrons and protons
Space solar cells radiation hardness is of fundamental importance in view of
the future missions towards harsh radiation environment (like e.g. missions to
Jupiter) and for the new spacecraft using electrical propulsion. In this paper
we report the radiation data for triple junction (TJ) solar cells and related
component cells. Triple junction solar cells, InGaP top cells and GaAs middle
cells degrade after electron radiation as expected. With proton irradiation, a
high spread in the remaining factors was observed, especially for the TJ and
bottom cells. Very surprising was the germanium bottom junction that showed
very high degradation after protons whereas it is quite stable against
electrons. Radiation results have been analyzed by means of the Displacement
Damage Dose method and DLTS spectroscopy.Comment: Abstract accepted for poster session at 2017 IEEE Nuclear and Space
Radiation Effects Conference, July 17-21, New Orlean
Nonlinear Bethe-Heitler pair creation with attosecond laser pulses at the LHC
The creation of lepton pairs ( and ) via multiphoton
absorption in collisions of ultrarelativistic ion beams with ultrashort
high-frequency laser pulses is considered. Both the free and the bound-free
production channels are addressed, where in the latter case the negatively
charged lepton is created in a bound atomic state. It is shown that these
nonlinear QED processes are observable when a table-top source of intense xuv
or x-ray laser radiation is operated in conjunction with the LHC. We discuss
the relative effectiveness of protons versus Pb ions and specify for each pair
production channel the most suitable collision system.Comment: 6 pages, 1 tabl
Iron mineral dissolution releases iron and associated organic carbon during permafrost thaw
It has been shown that reactive soil minerals, specifically iron(III) (oxyhydr)oxides, can trap organic carbon in soils overlying intact permafrost, and may limit carbon mobilization and degradation as it is observed in other environments. However, the use of iron(III)-bearing minerals as terminal electron acceptors in permafrost environments and thus their stability and capacity to prevent carbon mobilization during permafrost thaw is poorly understood. We have followed the dynamic interactions between iron and carbon, using a space for time-approach, across a thaw gradient in Abisko (Sweden), where wetlands are expanding rapidly due to permafrost thaw. We show through bulk (selective extractions, EXAFS) and nanoscale analysis (correlative SEM and nanoSIMS) that organic carbon is bound to reactive Fe primarily in the transition between organic and mineral horizons in palsa underlain by intact permafrost (41.8 ± 10.8 mg carbon per g soil, 9.9 to 14.8% of total soil organic carbon). During permafrost thaw, water-logging and O2 limitation lead to reducing conditions and an increase in abundance of Fe(III)-reducing bacteria which favor mineral dissolution and drive mobilization of both iron and carbon along the thaw gradient. By providing a terminal electron acceptor, this rusty carbon sink is effectively destroyed along the thaw gradient and cannot prevent carbon release with thaw
Phenomenological model of multiphoto-production of charged pion pairs on the proton
The production of charged pion pairs via multiphoton absorption from an
intense X-ray laser wave colliding with an ultrarelativistic proton beam is
studied. Our calculations include the contributions from both the
electromagnetic and hadronic interactions where the latter are described
approximately by a phenomenological Yukawa potential. Order-of-magnitude
estimates for production on the proton by two- and three-photon
absorption from the high-frequency laser field are obtained and compared with
the corresponding rates for pair creation.Comment: 6 pages, 3 figure
MRI-TRUS fusion for electrode positioning during irreversible electroporation for treatment of prostate cancer
We aimed to introduce an approach for image-guided positioning of electrodes for irreversible electroporation (IRE) in patients with prostate cancer using a magnetic resonance imaging-transrectal ultrasonography (MRI-TRUS) fusion technique. In 10 consecutive patients with biopsy-proven Gleason score ≤3+4 prostate cancer, 19 G electrodes were inserted into the prostate using a transperineal access. Magnetic resonance images of the prostate acquired before IRE were fused with transrectal ultrasound images acquired during IRE. The position of the ultrasound probe was tracked via a sensor and corresponding magnetic resonance images were calculated in real-time. While MRI allowed delineation of the target volume, the position of the electrodes could be visualized on ultrasound images; the distance between individual electrode pairs was measured. Based on these measurements the software installed on the IRE unit was able to calculate the voltage necessary to generate the electric field for ablation. Using contrast-enhanced ultrasound, changes in perfusion within the ablation zone after IRE were documented. This technique allowed positioning of the electrodes around the target volume under image guidance in all patients treated with IRE. The target lesion and a safety margin were covered within the estimated ablation zone. MRI-TRUS guidance for IRE combines the advantages of good visualization of the target lesion on MRI with the ability of ultrasound to acquire imaging in real-time with a mobile device
Micro-CT evaluation of the radioprotective effect of resveratrol on the mandibular incisors of irradiated rats
Abstract The purpose of this study was to perform a microcomputed tomographic evaluation of the radioprotective effect of resveratrol on the volume of mandibular incisors of irradiated rats. A second aim was to make a quantitative assessment of the effect of x-ray exposure on these dental tissues. Twenty adult male rats were divided into four groups: control, irradiated control, resveratrol, and irradiated resveratrol. The resveratrol groups received 100 mg/kg of resveratrol, whereas the irradiated groups were exposed to 15 Gy of irradiation. The animals were sacrificed 30 days after the irradiation procedure, and their mandibles were removed and scanned in a microcomputed tomography unit. The images were loaded into Mimics software to allow segmentation of the mandibular incisor and assessment of its volume. The results were compared by One-way ANOVA and Tukey’s post hoc test, considering a 5% significance level. The irradiated groups showed significantly diminished volumes of the evaluated teeth, as compared with the control group (p < 0.05). The resveratrol group presented higher values than those of the irradiated groups, and volumes similar to those of the control group. High radiation doses significantly affected tooth formation, resulting in alterations in the dental structure, and thus lower volumes. Moreover, resveratrol showed no effective radioprotective impact on dental tissues. Future studies are needed to evaluate different concentrations of this substance, in an endeavor to verify its potential as a radioprotector for these dental tissues
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