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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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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Coordinate late expression of trefoil peptide genes (pS2/TFF1 and ITF/TFF3) in human breast, colon, and gastric tumor cells exposed to X-rays

The trefoil factors (TFFs) are pleiotropic factors involved in organization and homeostasis of the gastrointestinal tract, estrogen responsiveness, inflammatory disorders, and carcinogenesis. In an earlier study using cDNA array technologies to identify new genes expressed in irradiated cell survivors, we isolated a cDNA clone corresponding to the reported human TFF1 gene (E. K. Balcer-Kubiczek et al., Int. J. Radiat. Biol., 75: 529-541, 1999). To determine whether expression of other TFFs is altered by ionizing radiation, we quantified changes in expression of TFF3 as well as TFF1 in RNA samples obtained from irradiated and control human tumor breast, colon, and gastric tumor cells and examined expression kinetics up to 2 weeks after irradiation. X-ray-induced TFF1 and TFF3 expression profiles were compared with those induced by hydrogen peroxide (H2O2) or 17beta-estradiol (ES). The results revealed that TFF1 and TFF3 mRNA are coinduced by X-irradiation in a subset of the lines, but substantial heterogeneity in their responses was observed in cells derived from a single cell type. TFF1 and TFF3 transcriptional response to X-irradiation differed from that to H2O2 or ES in the timing of their induction as well as tissue-type dependence, i.e., their induction pattern after X-irradiation was late and sustained, whereas their induction by H2O2 or ES was early and transient. TFF1 mRNA, protein production in the cytoplasm, and secretion in the culture supernatant were coordinately regulated after X-irradiation. There was no requirement for TP53 in this induction. These results demonstrate the existence of a novel class of radiation-responsive genes that might be involved in bystander effects.

Non-NASA Center↗
NASA NTRS2017

Radiation Chemistry of Solid Acetone in the Interstellar Medium - A New Dimension to an Old Problem

A laboratory investigation of acetone, an interstellar and cometary molecule, has produced new results concerning its decomposition in a radiation environment. Mid-infrared spectroscopy has been used to follow amorphous acetone's destruction by ionizing radiation (1 MeV protons) at 20 K. Radiation products identified are the CH4, CO, and CO2 usually made in such experiments, along with ketene, allene, and the acetonyl radical, all identified here for the first time in irradiated solid acetone. Evidence for the reduction product 2-propanol was suggestive, but a firm identification could not be made either for it or for the C2 hydrocarbons (i.e., C2H6, C2H4, C2H2). The acetyl radical was not observed as a radiation product. Isotopically labeled reagents were used to demonstrate ketene formation and to emphasize that multiple approaches are needed for robust assignments of infrared spectral features of irradiated icy solids. Results from a supporting radiation experiment with isotopically labeled acetic acid are described. Comparisons are made to a previous study of acetone's stability in extraterrestrial radiation environments, and caution is urged in measuring and interpreting CO abundances in irradiated icy solids.

cometary molecule↗
NASA NTRS2017

Radiation Chemistry of Solid Acetone in the Interstellar Medium - A New Dimension to an Old Problem

A laboratory investigation of acetone, an interstellar and cometary molecule, has produced new results concerning its decomposition in a radiation environment. Mid-infrared spectroscopy has been used to follow amorphous acetone’s destruction by ionizing radiation (1 MeV protons) at 20 K. Radiation products identified are the CH4, CO, and CO2 usually made in such experiments, along with ketene, allene, and the acetonyl radical, all identified here for the first time in irradiated solid acetone. Evidence for the reduction product 2-propanol was suggestive, but a firm identification could not be made either for it or for the C2 hydrocarbons (i.e., C2H6, C2H4, C2H2). The acetyl radical was not observed as a radiation product. Isotopically labeled reagents were used to demonstrate ketene formation and to emphasize that multiple approaches are needed for robust assignments of infrared spectral features of irradiated icy solids. Results from a supporting radiation experiment with isotopically labeled acetic acid are described. Comparisons are made to a previous study of acetone’s stability in extraterrestrial radiation environments, and caution is urged in measuring and interpreting CO abundances in irradiated icy solids.

R. L. Hudson↗
NASA NTRSDate not supplied

The Efficacy of Dried Plum to Counter Spaceflight Microgravity and Radiation

Human exploration of the space environment has been a topic of interest for decades; however, the threat to physiological health posed by ionizing radiation and microgravity effects remains a concern. Previous research utilizing combined hindlimb unloading and irradiation to simulate spaceflight effects found that a dried plum diet can mitigate adverse effects of simulated spaceflight on skeletal health. Though the mechanism is not fully understood we believe this protective effect is due to its high antioxidant capacity and polyphenolic content. This study seeks to extend these findings to investigate if dried plum is an effective countermeasure in other tissues relating to aging and neurotoxicity. Male C57BL/6 J mice were assigned to one of eight groups (n = 10/group) and were fed either a controlled diet or dried plum diet, underwent normal loading or hindlimb unloading as well as exposure 2 Gy gamma radiation or sham exposure. At the end of the experiment, mice were euthanized, and RNA was extracted from brain and bone marrow tissue and PCR was employed to analyze significant changes in gene expression profiles. Analysis of five house-keeping genes revealed genes B2M (neurotoxicity) and GUSB (aging) to be the most stable genes across all treatments and were used to find the fold change within our genes of interest. Through this, and analysis via ANOVA, we were able to identify genes with significant altered expression levels within brain and bone marrow tissues related to neurotoxicity and aging. Considering previous research, we hypothesize that the dried plum diet’s antioxidative properties ameliorated the oxidative stress from irradiation and microgravity via altered levels of gene expression. Identified expression changes will provide insights into molecular mechanisms behind the observed protective effects. These findings present potential avenues for future interventions to alleviate negative impacts of spaceflight on astronaut health.

Faisal Ahmad↗
DOE OSTI2024

Tunnel oxide passivating contact enabled by polysilicon on ultra-thin SiO 2 for advanced silicon radiation detectors

Conventional silicon junction detectors encounter significant carrier recombination within the heavily doped p⁺ and n⁺ layers, as well as beneath the metal contact regions, creating the so-called “dead layers”, especially on the detector side. In this study, we present the tunnel oxide passivating contact with doped polysilicon on oxide, which demonstrates exceptional surface passivation and carrier selectivity. The key innovation lies in an ultra-thin (~ 1.5 nm) interfacial oxide layer that facilitates efficient majority carrier transportation via tunneling while effectively block minority carriers. Remarkably low saturation current densities, ranging from 5 to 10 fA/cm² even with the metal contact, underscore the superiority of both n-type and p-type tunnel oxide passivating contacts. In contrast, conventional p–n junction or high-low junction exhibit saturation current densities ranging from 10 to 90 fA/cm² in the studied p⁺ and n⁺ layers with surface passivation schemes due to Auger recombination and surface recombination, and 1000–6000 fA/cm² with metal contacts due to intense metal-induced recombination at the interface. These findings indicate the potential and superiority of implementing n-type tunnel oxide passivating contact on the detector side and p-type contact on the back side for advanced silicon radiation detectors. This approach would enable thorough collection of generated charge carriers along the track of incident ionizing radiation particles, leading to improved energy resolution and reduced noise levels.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1993

Degradation of optical components in space

This report concerns two types of optical components: multilayer filters and mirrors, and self-scanned imaging arrays using charge coupled device (CCD) readouts. For the filters and mirrors, contamination produces a strong reduction in transmittance in the ultraviolet spectral region, but has little or no effect in the visible and infrared spectral regions. Soft substrates containing halides are unsatisfactory as windows or substrates. Materials choice for dielectric layers should also reflect such considerations. Best performance is also found for the harder materials. Compaction of the layers and interlayer diffusion causes a blue shift in center wavelength and loss of throughput. For sensors using CCD's, shifts in gate voltage and reductions in transfer efficiency occur. Such effects in CCD's are in accord with expectations of the effects of the radiation dose on the device. Except for optical fiber, degradation of CCD's represents the only ionizing-radiation induced effect on the Long Duration Exposure Facility (LDEF) optical systems components that has been observed.

Blue, M. D.↗
NASA NTRS1994

UV extinction and IR emission in diffuse H2 regions

HII regions occupy a unique position in our understanding of the physical relationships between stars, the interstellar medium, and galactic structure. Observations show a complex interaction between a newly formed hot star and its surroundings. In particular, the ultraviolet radiation from the stars modifies the pre-existing dust, which again affects both the amount of ionizing radiation absorbed by the gas, and the infrared spectrum emitted by the heated dust. The aim of this project was to use UV and far-UV observations to gain information on the nebular dust, and to use this dust to model the far-IR emission, for a consistent picture of a few selected diffuse HII regions. Using archival data from the IUE and Voyager data banks and computed model atmospheres, we have deduced extinction curves for early-types stars. The requisite spectral resolution turned out to be a major task. We have successfully modelled these curves in terms of a multi-component, multi-size distribution of dust grains, and interpret the differences in the curves as primarily due to the presence or non-presence of intermediate size grains (0.01 to 0.04 micron). Much smaller (0.005 micron) grains must also be present. Finally, we have made calculations of the temperature fluctuations and the corresponding infra-red emission in such small grains.

Aannestad, Per A.↗
NASA NTRS2004

Ionization Cross Sections and Dissociation Channels of the DNA Sugar-Phosphate Backbone by Electron Collisions

It has been suggested that the genotoxic effects of ionizing radiation in living cells are not caused by the highly energetic incident radiation, but rather are induced by less energetic secondary species generated, the most abundant of which are free electrons.' The secondary electrons will further react to cause DNA damage via indirect and direct mechanisms. Detailed knowledge of these mechanisms is ultimately important for the development of global models of cellular radiation damage. We are studying one possible mechanism for the formation cf DNA strand breaks involving dissociative ionization of the DNA sugar-phosphate backbone induced by secondary electron co!lisions. We will present ionization cross sections at electron collision energies between threshold and 10 KeV using the improved binary encounter dipole (iBED) formulation' Preliminary results of the possible dissociative ionization pathways will be presented. It is speculated that radical fragments produced from the dissociative ionization can further react, providing a possible mechanism for double strand breaks and base damage.

Dateo, Christopher↗
NASA NTRS2018

Prevention of Spaceflight-Induced Bone Loss: A Promising Dietary Countermeasure

Space radiation is one of the challenges for long-term spaceflight, especially for missions beyond low Earth Orbit. We have shown that a diet composed of 25% dried plum (DP) prevents radiation-induced bone loss. The DP diet fully protected the cancellous bone microarchitecture of mice exposed to ionizing radiation (gamma, proton, and HZE). In particular relevant to space radiation, we showed that the DP diet prevents bone loss due to 1Gy of sequential exposure of proton (1H, low linear energy transfer -LET-), and 1Gy of iron (56Fe, high-LET). In addition, total body exposure to 1Gy of HZE radiation (56Fe) impaired the osteoprogenitors in mice fed the control diet, as indicated by decreased osteoblast mineralization. In contrast, marrow stem cells from mice fed the DP did not exhibit these deficits. Based on these promising results supporting DP as a countermeasure to prevent space radiation induced-tissue damage, we conducted additional studies to combine radiation and simulated microgravity. We exposed skeletally mature male mice to simulated microgravity (using hindlimb unloading, HU) or total body irradiation (TBI, 2Gy 137Cs) or in combination (HU+TBI). We observed bone loss in the mice fed the control diet (CD) exposed to simulated spaceflight, as measured by cancellous bone microarchitecture parameters such as percent bone volume (BV/TV). In contrast, mice fed the DP diet did not exhibit similar bone loss with either treatments (HU or TBI) or combined (HU+TBI) as seen in most parameters. This was observed in both long bones (tibia) and axial bones (vertebrae). Furthermore, preliminary data shows that pre-feeding with the DP diet attenuates the HU-induced decrement in bone-forming osteoblasts colony counts and mineralization capacity of the osteoprogenitor cells. We also performed DP feeding at lower doses (5%, 10%) and found that these doses are less effective in preventing the radiation-induced bone loss. All our studies with the DP diet as a countermeasure were done with a period of pre-feeding ranging from 14 to 21 days before irradiation, and in order to test the capacity of the DP diet as a countermeasure provided after exposure to radiation, we exposed mice to 2Gy gamma radiation and then provided the DP diet 24 hours post-IR. Preliminary data indicates that DP mitigated the radiation-induced deficits in certain cancellous bone structural parameters. Finally, we showed that mice fed with the control diet (CD) increased oxidative damage in the serum after radiation exposure, whereas mice fed the DP diet do did not show such an increase. In summary, the DP diet is a promising countermeasure for spaceflight-induced tissue damage.

Schreurs, Ann-Sofie↗
NASA NTRS2004

Molecular Data for a Biochemical Model of DNA Radiation Damage: Electron Impact Ionization and Dissociative Ionization of DNA Bases and Sugar-Phosphate Backbone

As part of the database for building up a biochemical model of DNA radiation damage, electron impact ionization cross sections of sugar-phosphate backbone and DNA bases have been calculated using the improved binary-encounter dipole (iBED) model. It is found that the total ionization cross sections of C3'- and C5'-deoxyribose-phospate, two conformers of the sugar-phosphate backbone, are close to each other. Furthermore, the sum of the ionization cross sections of the separate deoxyribose and phosphate fragments is in close agreement with the C3'- and C5'-deoxyribose-phospate cross sections, differing by less than 10%. Of the four DNA bases, the ionization cross section of guanine is the largest, then in decreasing order, adenine, thymine, and cytosine. The order is in accordance with the known propensity of oxidation of the bases by ionizing radiation. Dissociative ionization (DI), a process that both ionizes and dissociates a molecule, is investigated for cytosine. The DI cross section for the formation of H and (cytosine-Hl)(+), with the cytosine ion losing H at the 1 position, is also reported. The threshold of this process is calculated to be 17.1 eV. Detailed analysis of ionization products such as in DI is important to trace the sequential steps in the biochemical process of DNA damage.

Dateo, Christopher E.↗
DOE OSTI2025

Radiation Effects on Uranyl Tetrachloro Coordination Compounds: Impact of Lattice Water

Nuclear materials, such as uranium-bearing solids, are exposed to high levels of ionizing radiation throughout the nuclear fuel cycle; thus, it is important to develop a molecular-level understanding of how these materials behave and degrade in the presence of gamma (γ) irradiation. In the current study, three U(VI) tetrachloride complexes, M 2 [UO 2 Cl 4 ]·xH 2 O (where M = K + , Rb + , or Cs + and x = 0 or 2), and their respective chloride salts were exposed to 1–50 kGy of γ radiation using a 60 Co source. Irradiated materials were evaluated by using electron paramagnetic resonance (EPR) and Raman spectroscopy and were further explored by using density functional theory (DFT) methods. EPR spectra of the irradiated materials suggest the formation of a Cl-based radical for both the alkali salts and the uranyl tetrachloride compounds, and DFT calculations provide evidence that the Cl 2 –• radical is formed within these materials. The presence of water in the K + and Rb + compounds leads to additional spectroscopic signatures that could be traced back to water radiolysis and the formation of peroxide and superoxide species. DFT results support the formation of HO 2 • in the lattice and potentially the formation of a [UO 2 Cl 3 (O 2 )] 3– species, highlighting the impact of water within the hydrated material to alter U(VI) speciation by radiolysis.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Effects of He-Ion Radiation on Solid-State Uranyl Nitrate Compounds under Dry and Hydrated Atmospheric Conditions

Radioactive decay of uranium (U) and its related daughter/fission products emit ionizing radiation, including γ (γ) rays and α (α) particles, that result in the formation of radical species and induce chemical reactivity in materials. While radioactivity is inherent to the chemistry of U there are limited studies that detail changes at an atomistic level. Here, this work describes the He-ion radiolysis of four solid-state U(VI) species: [UO 2 (NO 3 ) 2 ]·3(H 2 O) and M[UO 2 (NO 3 ) 3 ] (M = K + , Rb + , Cs + ). These materials were irradiated under different conditions (i.e. closed, open – Ar gas, or open – H 2 O-saturated Ar gas) to further evaluate the impact of water radiolysis on the chemical modification of these materials. Pre- and post-irradiation analyses were conducted using EPR, Raman, and ATR-IR spectroscopy on materials irradiated to 0, 5, 10, and 25 MGy. The results indicated the presence of nitrate radical (NO 3 • ) formation in all solid-state materials with similarities to those observed in γ-radiation studies. Irradiation of [UO 2 (NO 3 ) 2 ]·3(H 2 O) did not show evidence of reactive oxygen species bound to the U(VI) cation under inert conditions; however, surface reactivity was observed for samples irradiated in the H 2 O-saturated environment. Similar chemical changes were observed in the uranyl trinitrato compounds irradiated in the presence of H 2 O vapor and there were observed differences in the reactivity depending on the identity of the alkali cation.

38 - RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCL↗
DOE OSTI2023

Risk of hematological malignancies from CT radiation exposure in children, adolescents and young adults

Over one million European children undergo computed tomography (CT) scans annually. Although moderate- to high-dose ionizing radiation exposure is an established risk factor for hematological malignancies, risks at CT examination dose levels remain uncertain. Here we followed up a multinational cohort (EPI-CT) of 948,174 individuals who underwent CT examinations before age 22 years in nine European countries. Radiation doses to the active bone marrow were estimated on the basis of body part scanned, patient characteristics, time period and inferred CT technical parameters. We found an association between cumulative dose and risk of all hematological malignancies, with an excess relative risk of 1.96 (95% confidence interval 1.10 to 3.12) per 100 mGy (790 cases). Similar estimates were obtained for lymphoid and myeloid malignancies. Results suggest that for every 10,000 children examined today (mean dose 8 mGy), 1–2 persons are expected to develop a hematological malignancy attributable to radiation exposure in the subsequent 12 years. Our results strengthen the body of evidence of increased cancer risk at low radiation doses and highlight the need for continued justification of pediatric CT examinations and optimization of doses.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1989

Stabilizing Semiconductor Devices With Hydrogen

Damage by radiation healed rapidly. Feature provides continuous, rapid recovery of devices from degradation caused by hot electrons, photons, and ionizing radiation. Several candidate sites for palladium film catalysts, inserted during manufacture as integral parts of devices. Paladium films made by evaporation, sputtering, or chemical-vapor deposition. If additional storage required, thick layer of palladium plated on inside of package surrounding device. Hydrogen stored by exposing palladium to hydrogen gas just before package sealed hermetically.

Overhauser, Albert W.↗
NASA NTRSDate not supplied

BioSentinel ISS mission: Analysis of ISS Flight Data and Lessons Learned

As we prepare for a future with a human presence on the Moon, Mars, and beyond, the need for countermeasures to protect astronauts against deep space radiation is ever pressing. However, our understanding of how life operates in the space environment, especially past the protection of the Van Allen radiation belts, is critically limited. BioSentinel, a biological CubeSat, aims to further investigate the effects of deep space ionizing radiation, utilizing the budding yeast Saccharomyces cerevisiae to examine the cell’s DNA damage response. The yeast wild type and a rad51Δ mutant strain defective for DNA damage repair will be monitored via the redox dye alamarBlue and a 3-color LED detection system. Selected as a secondary payload on Artemis I, BioSentinel will be the first deep space biological experiment in a half-century and the first biological CubeSat or free-flyer to ever reach a heliocentric orbit. Notably, BioSentinel is the only biological CubeSat to include an ISS control study in addition to a ground control. Comparisons between the ground, ISS, and free-flyer experiments will allow us to isolate the effects of deep space radiation from those of microgravity. The ISS study also provides a unique platform to conduct important technological and biological testing of BioSentinel’s instrumentation in preparation for the deep space mission. In this work, we use a series of data processing tools and scripts to analyze ISS flight data as well as samples exposed to simulated space radiation at Brookhaven National Laboratory, specifically looking at cell growth, metabolic activity, and duplication rates based on optical absorbance and alamarBlue kinetics. These analyses provide a crucial set of controls and a framework for analyzing and interpreting future data sets from the free-flyer, helping us gain further insight into the health risks astronauts will face when exposed to deep space radiation.

Kylie Lauren Lo-Wen Akiyama↗
DOE OSTI2024

The Radiation-Induced Fate of Fission Product Iodine in Molten Salts

Understand and Predict Radiation-Induced Iodine Speciation, Chemistry, and Transport in High-Temperature Molten Salts Award Number: DE-AC07-05ID1451 Gregory P. Holmbeck (Gregory.Holmbeck@inl.gov), Center for Radiation Chemistry Research, Idaho National Laboratory, 1955 N. Fremont Avenue Idaho Falls, ID, 83415, USA. Project Scope The goal of this Chemical and Materials Sciences to Advance Clean Energy Technologies and Low-Carbon Manufacturing project is to understand and predict the radiation-induced speciation, chemistry, and transport of fission product iodine in the triumvirate extremes of high-temperature, ionizing radiation, and corrosive molten salts. This missing fundamental information is critical for the accelerated development and deployment of safe, clean nuclear energy based on molten salt reactor (MSR) and pyrochemical reprocessing technologies. The central hypothesis driving this research is, the radiation-induced conversion of iodide will yield an extensive suite of transient and steady-state iodine radiolysis products that will alter the bulk chemical and physical properties of the irradiated molten salt system—the speciation, distribution, and chemical transport of which will be dictated by the composition and the availability of multivalent metal cations and metal alloy interfaces. To test this hypothesis, this project initiated three synergistic Research Objectives: (1) determine how the inclusion of iodine/iodide influences the chemical and physical properties of complex molten salt mixtures; (2) elucidate the speciation and fundamental chemical behavior of transient and steady-state iodine/iodide species formed by the irradiation of molten and solid salt mixtures; and (3) understand the influence of interfacial processes on determining the final disposition of iodine in high temperature molten salts, notably the structure and chemical speciation of iodine at metal-salt interfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗