Search results for "RADIATION"
showing 10 items of 5298 documents
Effects induced by 4.7 eV UV laser irradiation on pure silica core multimode optical fibers investigated by in situ optical absorption measurements
2011
We investigated by in situ optical absorption measurements the effects induced by 4.7 eV UV laser irradiation on pure silica core optical fibers. Laser irradiation with 100 MWcm−2 laser intensity generates in the fiber E′ centers which partially decay after irradiation due to their reaction with diffusing H2. An absorption band peaked at 5.3 eV is observed to grow in the post-irradiation stage with a kinetics anti-correlated to the decay of the 5.8 eV band of the E′ centers. The defect absorbing at 5.3 eV is proposed to be formed by trapping on pre-existing precursors of hydrogen atoms made available by breaking of H2 on E′.We also show by repeated irradiation experiments that the 5.3 eV-ab…
Investigation on the ganaration process of HO2• radicals by γ-ray irradiation in O2-loaded fumed silica
2013
Abstract We report an experimental investigation on the effects of γ-ray irradiation in three types of fumed silica previously loaded with O 2 molecules. Our data indicate that the main effect of irradiation in these systems is to generate a very large concentration of HO 2 interstitial radicals (about 10 18 molecules/cm 3 ). Furthermore, the number of generated HO 2 was found to be larger in the samples with higher O 2 contents before irradiation. This correlation suggests that HO 2 radicals are induced by reaction of interstitial O 2 molecules with radiolytic H atoms, as previously suggested for O 2 -loaded bulk amorphous silicon dioxide (a-SiO 2 or silica) samples. However, at variance …
Photochemical Size Reduction of CdSe and CdSe/ZnS Semiconductor Nanoparticles Assisted by nπ* Aromatic Ketones
2009
A novel effect of n pi* aromatic ketones on the quantum dots optical properties is reported. By controlling experimental conditions such as time of irradiation, presence of air in the media, hydrogen donor capacity of the solvent, and irradiation wavelength, core and core-shell CdSe QDs can be resized as convenient.
Estimation of winter leaf area index and sky view fraction for snow modelling in boreal coniferous forests: consequences on snow mass and energy bala…
2012
Abstract in Undetermined Leaf area index (LAI) and canopy coverage are important parameters when modelling snow process in coniferous forests, controlling interception and transmitting radiation. Estimates of LAI and sky view factor show large variability depending on the estimation method used, and it is not clear how this is reflected in the calculated snow processes beneath the canopy. In this study, the winter LAI and sky view fraction were estimated using different optical and biomass-based approximations in several boreal coniferous forest stands in Fennoscandia with different stand density, age and site latitude. The biomass-based estimate of LAI derived from forest inventory data wa…
Estimating Maize (Zea mays) cvapotranspiration from NOAA-AVHRR thermal data in the Albacete area, Spain
1994
Abstract We have estimated evapotranspiration from maize (Zca mays) using NOAA thermal images infrared and meteorological data, by means of the relation where Ed is the daily evapotranspiration, is the daily net radiation expressed in mm of water per day, (Ta−Ts)i is the temperature difference between air and corn surface obtained near midday, and Bi is a semi-empirical constant which has been calculated as 0·53±0·10mm day−1K−1. We have tested the method obtaining actual daily evapotranspiration of maize with an acceptable precision (±0·9 mm day−1 taken Penman's method as the standard). Finally, a practical example is included, in which the different steps followed for applying the develope…
Optical Gating of Photosensitive Synthetic Ion Channels
2011
4-oxo-4-(pyren-4-ylmethoxy) butanoic acid is used as a photolabile protecting group to show the optical gating of nanofluidic devices based on synthetic ion channels. The inner surface of the channels is decorated with monolayers of photolabile hydrophobic molecules that can be removed by irradiation, which leads to the generation of hydrophilic groups. This process can be exploited in the UV-light-triggered permselective transport of ionic species in aqueous solution through the channels. The optical gating of a single conical nanochannel and multichannel polymeric membranes is characterised experimentally and theoretically by means of current-voltage and selective permeation measurements,…
Neutron-Induced Effects on a Self-Refresh DRAM
2022
International audience; The field of radiation effects in electronics research includes unknowns for every new device, node size, and technical development. In this study, static and dynamic test methods were used to define the response of a self-refresh DRAM under neutron irradiation. The neutron-induced effects were investigated and characterised by event cross sections, soft-error rate, and bitmaps evaluations, leading to an identification of permanent and temporary stuck cells, single-bit upsets, and block errors. Block errors were identified in different patterns with dependency in the addressing order, leading to up to two thousand faulty words per event, representing a real threat fr…
Effectiveness of Respiratory Hyperoxia, of Normobaric and of Hyperbaric Oxygen Atmospheres in Improving Tumor Oxygenation
1984
A restriction and an inhomogeneous distribution of diffusive and convective oxygen supply is considered the main cause for pronounced radioresistance in solid tumors (Thomlinson and Gray, 1955; Tannock, 1972). One way to alleviate this crucial problem in tumor therapy is the direct enhancement of oxygen delivery to the cancer cells. This can be performed either by the tumor host breathing pure O2 (respiratory hyperoxia, RHO) or by whole body exposure to pure O2 atmospheres at normobaric or hyperbaric pressures (normobaric oxygenation NMO, and hyperbaric oxygenation, HPO, respectively). Numerous investigations have been undertaken both in animals and in man using RHO, NMO, or HPO as an adjuv…
Engineering the hypersonic phononic band gap of hybrid Bragg stacks.
2012
We report on the full control of phononic band diagrams for periodic stacks of alternating layers of poly(methyl methacrylate) and porous silica combining Brillouin light scattering spectroscopy and theoretical calculations. These structures exhibit large and robust on-axis band gaps determined by the longitudinal sound velocities, densities, and spacing ratio. A facile tuning of the gap width is realized at oblique incidence utilizing the vector nature of the elastic wave propagation. Off-axis propagation involves sagittal waves in the individual layers, allowing access to shear moduli at nanoscale. The full theoretical description discerns the most important features of the hypersonic one…
Physiological Effects of Hyperthermia
1987
Hyperthermia as a modality for the treatment of malignant tumors, either alone or in combination with radiation or anticancer drugs, is rapidly becoming a clinical reality. Three different mechanisms of action have provided the rationale for considering the use of hyperthermia as an antitumor agent. At moderate hyperthermia (T=40˚ -42.5˚ C), heat can increase cell killing in a synergistic way following exposure of a tumor to ionizing radiation. This radiosensitization is probably based on, among other things, the inhibited repair of radiation-induced DNA lesions. Elevated tissue temperatures at 40˚ -42.5˚ C also sensitize tumor cells to certain chemotherapeutic drugs, particularly to alkyla…