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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Ag species paramagnetic relaxation in gamma- irradiated frozen aqueous solutions and in frozen methanol, relating spin-lattice relaxation to isotropic coupling
Free radical formation in irradiated pyrimidines from ESR spectrum analysis of gamma irradiated single crystals of alloxantin, confirming radical stability
Density measurement of defects from Compton electrons formed by incident gamma irradiation
Electron spin resonance of gamma irradiated single crystal of barbituric acid dihydrate, noting formation and Hamiltonian parameters of free radicals
Silica optical fiber sensors offer a fast, distributed measurement solution in various cryogenic and radiation environments, such as magnets for fusion power. Under these conditions, light-absorbing point defects limit lifetime via radiation-induced attenuation (RIA). To support RIA kinetics prediction, we present an in situ, broadband absorption spectroscopy setup combining gamma irradiation with liquid nitrogen cooling. The apparatus enables continuous monitoring of narrowband RIA levels and the use of secondary optical annealing light sources, alongside broadband spectrum measurements to characterize RIA defects through spectrum decomposition. Initial results confirm the inevitable photobleaching effect of the probe light source, which must be accounted for. In addition, we report RIA kinetics during cycles of gamma irradiation at 77 K and isochronal thermal annealing steps from liquid nitrogen to room temperature, showcasing the setup’s ability to replicate real fiber operation scenarios. These instruments form an ideal platform to further study the kinetics of RIA coupled with thermal and optical annealing.
The objective of this study was to determine whether connexin 32-type gap junctions contribute to the "contact effect" in follicular thyrocytes and whether the response is influenced by radiation quality. Our previous studies demonstrated that early-passage follicular cultures of Fischer rat thyroid cells express functional connexin 32 gap junctions, with later-passage cultures expressing a truncated nonfunctional form of the protein. This model allowed us to assess the role of connexin 32 in radiation responsiveness without relying solely on chemical manipulation of gap junctions. The survival curves generated after gamma irradiation revealed that early-passage follicular cultures had significantly lower values of alpha (0.04 Gy(-1)) than later-passage cultures (0.11 Gy(-1)) (P < 0.0001, n = 12). As an additional way to determine whether connexin 32 was contributing to the difference in survival, cultures were treated with heptanol, resulting in higher alpha values, with early-passage cultures (0.10 Gy(-1)) nearly equivalent to untreated late-passage cultures (0.11 Gy(-1)) (P > 0.1, n = 9). This strongly suggests that the presence of functional connexin 32-type gap junctions was contributing to radiation resistance in gamma-irradiated thyroid follicles. Survival curves from proton-irradiated cultures had alpha values that were not significantly different whether cells expressed functional connexin 32 (0.10 Gy(-1)), did not express connexin 32 (0.09 Gy(-1)), or were down-regulated (early-passage plus heptanol, 0.09 Gy(-1); late-passage plus heptanol, 0.12 Gy(-1)) (P > 0.1, n = 19). Thus, for proton irradiation, the presence of connexin 32-type gap junctional channels did not influence their radiosensitivity. Collectively, the data support the following conclusions. (1) The lower alpha values from the gamma-ray survival curves of the early-passage cultures suggest greater repair efficiency and/or enhanced resistance to radiation-induced damage, coincident with the expression of connexin 32-type gap junctions. (2) The increased sensitivity of FRTL-5 cells to proton irradiation was independent of their ability to communicate through connexin 32 gap junctions. (3) The fact that the beta components of the survival curves from both gamma rays and proton beams were similar (average 0.022 +/- 0.008 Gy(-2), P > 0.1, n = 39) suggests that at higher doses the loss of viability occurs at a relatively constant rate and is independent of radiation quality and the presence of functional gap junctions.
Free radicals in gamma irradiated 5-nitro-6- methyluracil identified with electron spin resonance spectra
Electron spin resonance of gamma irradiated 3 prime-cytidylic acid single crystal, identifying primary radical formed
Electron spin resonance spectra of gamma irradiated single crystals of 9-methyladenine, analyzing H abstraction radical and temperature effects
Gamma irradiation effects on thermal stability and decomposition of ammonium perchlorate
Computer study of electron flux in thin silicon samples during gamma irradiation
Cobalt 60 gamma irradiation effects on P doped p- and n-type Si surface and bulk recombination rates
Free radicals formation in gamma irradiated pyrimidine-purine co-crystal complex, using electron spin resonance spectroscopy
Effect of penetrating radiation on vestibular functions of equilibrium organ after acute whole-body gamma irradiation
Shielding effects on rat survival rates after gamma irradiation
Influence of cobalt 60 gamma irradiation on bulk and surface recombination rates in n-type and p-type semiconductors
Trapped Ag atoms production in silver nitrate ice by gamma irradiation, discussing reaction enhancement by flouride ion
The two types of radicals trapped in gamma-irradiated PEN 2,6 are identified by ESR as - O - CH - CH2 - O - (radical I) and a radical located on the naphthalene ring (radical II). The concentrations of the radicals in the gross polyer are 10 to 20% of I and 80 to 90% of II. Similar trapped radicals are established in beta-irradiated PET, a structurally related polymer.