Components irradiation test no. 15 - 2N708, 2N918, S2N1486 and S2N2412 transistors and 2N2498 field effect transistor
Neutron and gamma radiation effects on field effect transistor and injection transistors
RADIATION EFFECT↗
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Niobium hyperfine structure in crystal calcium tungstate
A study of the niobium hyperfine structure in single crystal calcium tungstate was made by the combination of the technique of electron paramagnetic resonance and electron nuclear double resonance (EPR/ENDOR). The microwave frequency was about 9.4 GHz and the radio frequency from 20MHz to 70 MHz. The rare earth ions Nd(3+), U(3+), or Tm(3+) were added as the charge compensator for Nb(5+). To create niobium paramagnetic centers, the sample was irradiated at 77 deg K with a 10 thousand curie Co-60 gamma source for 1 to 2 hours at a dose rate of 200 K rads per hour and then transferred quickly into the cavity. In a general direction of magnetic field, the spectra showed 4 sets of 10 main lines corresponding to 4 nonequivalent sites of niobium with I = 9/2. These 4 sets of lines coalesced into 2 sets of 10 in the ab-plane and into a single set of 10 along the c-axis. This symmetry suggested that the tungsten ions are substituted by the niobium ions in the crystal.
Tseng, D. L.↗
Radiation effects on power transistor performance
The D60T, D62T, and D75T transistors in the nuclear reactor were irradiated with bias voltage and high current I sub c vs. V sub ec curves were obtained to evaluate gain degradation at high power levels. Pre- and post-irradiation high current switching tests were performed to evaluate the response. The gamma ray damage work done at Sandia was correlated with the neutron work done at the O.S.U. reactor with the above specified transistors. Theoretical analyses of damage and electrical performance were conducted in terms of semiconductor physics. The experimental high current pulser was improved in order to measure switching time changes which are less than one microsecond at currents of 100 to 200 amperes for in-situ testing.
Frasca, Albert J.↗
Cataractogenesis from high-LET radiation and the Casarett model
The long-term effects on specific animal tissues of exposure to heavy ion irradiation are studied in experiments on cataractogenesis in mice and rabbits. Five groups of rabbits at ages from 8 weeks to 5.3 years were irradiated to a dose of 9.0 Gy of Bragg plateau Ne-20 ions, while mice were exposed to single and total fractionated doses of 4.17 Gy gamma rays or 0.40 to 1.20 Gy of C-12, Ne-20 or Ar-40 particles. Measurements of lens opacities over time show that in the year since irradiation, cataractogenesis is delayed and less severe in rabbits irradiated at age 6 months compared to younger animals, although it is possible that the late effects in adults will surpass those found in the young. The fractionation of the total dose of gamma rays in mice is observed to lead to a marked reduction in the extent of lens opacity after one year, while fractionated heavy ion doses caused a greater degree of posterior lens opacification. Evaluations of the effects of the LET of different ions on cataractogenesis are consistent with RBEs of about 5, 3 and 1-2 for Ar-40, Ne-20 and C-12 ions, respectively. Results thus support the Casarett model of radiation damaging stem cell populations that are not necessarily part of the vasculature.
Cox, A. B.↗
Comparison of F ratios generated from interphase and metaphase chromosome damage induced by high doses of low- and high-LET radiation
Although biophysical models predict a difference in the ratio of interchromosomal to intrachromosomal interarm exchanges (F ratio) for low- and high-LET radiations, few experimental data support this prediction. However, the F ratios in experiments to date have been generated using data on chromosome aberrations in samples collected at the first postirradiation mitosis, which may not be indicative of the aberrations formed in interphase after exposure to high-LET radiations. In the present study, we exposed human lymphocytes in vitro to 2 and 5 Gy of gamma rays and 3 Gy of 1 GeV/nucleon iron ions (LET = 140 keV/micrometer), stimulated the cells to grow with phytohemagglutinin (PHA), and collected the condensed chromosomes after 48 h of incubation using both chemically induced premature chromosome condensation (PCC) and the conventional metaphase techniques. The PCC technique used here condenses chromosomes mostly in the G(2) phase of the cell cycle. The F ratio was calculated using data on asymmetrical chromosome aberrations in both the PCC and metaphase samples. It was found that the F ratios were similar for the samples irradiated with low- and high-LET radiation and collected at metaphase. However, for irradiated samples assayed by PCC, the F ratio was found to be 8.2 +/- 2.0 for 5 Gy gamma rays and 5.2 +/- 0.9 for 3 Gy iron ions. The distribution of the aberrations indicated that, in the PCC samples irradiated with iron ions, most of the centric rings occurred in spreads containing five or more asymmetrical aberrations. These heavily damaged cells, which were either less likely to reach mitosis or may reach mitosis at a later time, were responsible for the difference in the F ratios generated from interphase and metaphase analysis after exposure to iron ions.
NASA Discipline Radiation Health↗
Pathology effects at radiation doses below those causing increased mortality
Mortality data from experiments conducted at the Argonne National Laboratory (ANL) on the long-term effects of external whole-body irradiation on B6CF(1) mice were used to investigate radiation-induced effects at intermediate doses of (60)Co gamma rays or fission-spectrum neutrons either delivered as a single exposure or protracted over 60 once-weekly exposures. Kaplan-Meier analyses were used to identify the lowest dose in the ANL data (within radiation quality, pattern of exposure, and sex) at which radiation-induced mortality caused by primary tumors could be detected (approximately 1-2 Gy for gamma rays and 10-15 cGy for neutrons). Doses at and below these levels were then examined for radiation-induced shifts in the spectrum of pathology detected at death. To do this, specific pathology events were pooled into larger assemblages based on whether they were cancer, cardiovascular disease or non-neoplastic diseases detected within the lungs and pleura, liver and biliary tract, reproductive organs, or urinary tract. Cancer and cardiovascular disease were further subdivided into categories based on whether they caused death, contributed to death, or were simply observed at death. Counts of how often events falling within each of these combined pathology categories occurred within a mouse were then used as predictor variables in logistic regression to determine whether irradiated mice could be distinguished from control mice. Increased pathology burdens were detected in irradiated mice at doses lower than those causing detectable shifts in mortality-22 cGy for gamma rays and 2 cGy for neutrons. These findings suggest that (1) models based on mortality data alone may underestimate radiation effects, (2) radiation may have adverse health consequences (i.e. elevated health risks) even when mortality risks are not detected, and (3) radiation-induced pathologies other than cancer do occur, and they involve multiple organ systems.
Non-NASA Center↗
Simple model for the reconstruction of radionuclide concentrations and radiation exposures along the Techa River
The Techa River (Southern Urals, Russia) was contaminated in 1949-1956 by liquid radioactive wastes from the Mayak complex, the first Russian facility for the production of plutonium. The measurements of environmental contamination were started in 1951. A simple model describing radionuclide transport along the free-flowing river and the accumulation of radionuclides by bottom sediments is presented. This model successfully correlates the rates of radionuclide releases as reconstructed by the Mayak experts, hydrological data, and available environmental monitoring data for the early period of contamination (1949-1951). The model was developed to reconstruct doses for people who lived in the riverside communities during the period of the releases and who were chronically exposed to external and internal irradiation. The model fills the data gaps and permits reconstruction of external gamma-exposure rates in air on the river bank and radionuclide concentrations in river water used for drinking and other household needs in 1949-1951.
Non-NASA Center↗
Radio-Adaptive Responses of Mouse Myocardiocytes
One of the most significant occupational hazards to an astronaut is the frequent exposure to radiation. Commonly associated with increased risk for cancer related morbidity and mortality, radiation is also known to increase the risk for cardiovascular related disorders including: pericarditis, hypertension, and heart failure. It is believed that these radiation-induced disorders are a result of abnormal tissue remodeling. It is unknown whether radiation exposure promotes remodeling through fibrotic changes alone or in combination with programmed cell death. Furthermore, it is not known whether it is possible to mitigate the hazardous effects of radiation exposure. As such, we assessed the expression and mechanisms of radiation-induced tissue remodeling and potential radio-adaptive responses of p53-mediated apoptosis and fibrosis pathways along with markers for oxidative stress and inflammation in mice myocardium. 7 week old, male, C57Bl/6 mice were exposed to 6Gy (H) or 5cGy followed 24hr later with 6Gy (LH) Cs-137 gamma radiation. Mice were sacrificed and their hearts extirpated 4, 24, or 72hr after final irradiation. Real Time - Polymerase Chain Reaction was used to evaluate target genes. Pro-apoptotic genes Bad and Bax, pro-cell survival genes Bcl2 and Bcl2l2, fibrosis gene Vegfa, and oxidative stress genes Sod2 and GPx4 showed a reduced fold regulation change (Bad,-6.18; Bax,-6.94; Bcl2,-5.09; Bcl2l2,-4.03; Vegfa, -11.84; Sod2,-5.97; GPx4*,-28.72; * = Bonferroni adjusted p-value . 0.003) 4hr after H, but not after 4hr LH when compared to control. Other p53-mediated apoptosis genes Casp3, Casp9, Trp53, and Myc exhibited down-regulation but did not achieve a notable level of significance 4hr after H. 24hr after H, genetic down-regulation was no longer present compared to 24hr control. These data suggest a general reduction in genetic expression 4hrs after a high dose of gamma radiation. However, pre-exposure to 5cGy gamma radiation appears to facilitate a radio-adaptive response that mitigates the reduction in genetic expression associated with single high-dose gamma radiation exposure. This radio-adaptive response may serve as a potential countermeasure to radiation-induced myocardial remodeling and preserve the cardiovascular health of astronauts; thus, reducing the risks of human space exploration.
Seawright, John W.↗
Rapid Radiolytic Degradation of Amino Acids in the Martian Shallow Subsurface: Implications for the Search for Extinct Life
Amino acids are fundamental to life as we know them as the monomers of proteins and enzymes. They are also readily synthesized under a variety of plausible prebiotic conditions and are common in carbon-rich meteorites. Thus, they represent a reasonable class of organics to target in the search for prebiotic chemistry or chemical evidence of life on Mars. However, regardless of their origin, amino acids and other organic molecules present in near-surface regolith and rocks on Mars can be degraded by exposure to cosmic rays that can penetrate to a depth of a few meters. We exposed several pure amino acids in dry and hydrated silicate mixtures and in mixtures of silicates with perchlorate salts to gamma radiation at various temperatures and radiation doses representative of the martian near-subsurface. We found that irradiation of amino acids mixed with dry silica powder increased the rate of amino acid radiolysis, with the radiolysis constants of amino acids in silicate mixtures at least a factor of 10 larger compared with the radiolysis constants of amino acids alone. The addition of perchlorate salts to the silicate samples or hydration of silicate samples further accelerated the rate of amino acid destruction during irradiation and increased the radiolysis constants by a factor of *1.5. Our results suggest that even low-molecular-weight amino acids could degrade in just *20 million years in the top 10 cm of the martian surface regolith and rock, and even faster if the material contains elevated abundances of hydrated silicate minerals or perchlorates. We did not detect evidence of amino acid racemization after gamma radiation exposure of the samples, which indicates that the chirality of some surviving amino acids may still be preserved. Our experimental results suggest serious challenges for the search of ancient amino acids and other potential organic biosignatures in the top 2 m of the martian surface.
Alexander A. Pavlov↗
Induction of genomic instability in TK6 human lymphoblasts exposed to 137Cs gamma radiation: comparison to the induction by exposure to accelerated 56Fe particles
The induction of genomic instability in TK6 human lymphoblasts by exposure to (137)Cs gamma radiation was investigated by measuring the frequency and characteristics of unstable clones isolated approximately 36 generations after exposure. Clones surviving irradiation and control clones were analyzed for 17 characteristics including chromosomal aberrations, growth defects, alterations in response to a second irradiation, and mutant frequencies at the thymidine kinase and Na(+)/K(+) ATPase loci. Putative unstable clones were defined as those that exhibited a significant alteration in one or more characteristics compared to the controls. The frequency and characteristics of the unstable clones were compared in clones exposed to (137)Cs gamma rays or (56)Fe particles. The majority of the unstable clones isolated after exposure to either gamma rays or (56)Fe particles exhibited chromosomal instability. Alterations in growth characteristics, radiation response and mutant frequencies occurred much less often than cytogenetic alterations in these unstable clones. The frequency and complexity of the unstable clones were greater after exposure to (56)Fe particles than to gamma rays. Unstable clones that survived 36 generations after exposure to gamma rays exhibited increases in the incidence of dicentric chromosomes but not of chromatid breaks, whereas unstable clones that survived 36 generations after exposure to (56)Fe particles exhibited increases in both chromatid and chromosome aberrations.
Non-NASA Center↗
Preliminary Evaluation of Commercial Off the Shelf (COTS) Packing Materials for Flight Medication Dispenser (FMD) Technology Development
With the advent of longer duration space missions, pharmaceutical use in space has increased. During the first 33 space shuttle missions, crew members took more than 500 individual doses of 31 different medications . Anecdotal reports from crew members described medications as generally "well tolerated" and "effective". However, reported use of increased medication doses and discrepancies in ground vs. flight efficacy may result from reduced potency or altered bioavailability due to changes in chemical and/or physical parameters of pharmaceutical stability. Based on preliminary results from a ground-based irradiation and an inflight study on pharmaceutical stability, three susceptible medications, Amoxicillin/Clavulanate and Sulfamethoxazole/trimethoprim antibiotics tablets and promethazine (PMZ), an antihistamine were selected for testing using two types of Oliver-Tolas bags, TPC-1475(Clear) and TPF-0599B (Foil) for radiation Shielding effectiveness. The material composition of the bags included aluminum coated Mylar sheathing coated with multifunctional nanocomposities based on polyethylene with dispersed boron-rich nanophases. Two bags of each medication were irradiated for different time intervals with 14.6 rad/min to achieve 0.1 Gy, 1 Gy and 10 Gy of cumulative radiation dose. Active pharmaceutical content (API) in each medication was determined and results analyzed. No significant difference in API content was observed between control and irradiated samples for both antibiotic tablets suggesting both types of bags may offer protection against gamma radiation; results with PMZ were inconclusive. These preliminary results suggest that Oliver-Tolas TPL-1475 and TPF-0599B materials may possess characteristics suitable for protection against ionizing radiation and can be considered for designing and further testing of FMD technology.
Du, Brian↗
Early and Late Damages in Chromosome 3 of Human Lymphocytes After Radiation Exposure
Tumor formation in humans or animals is a multi-step process. An early stage of cancer development is believed to be genomic instability (GI) which accelerates the mutation rate in the descendants of the cells surviving radiation exposure. GI is defined as elevated or persistent genetic damages occurring many generations after the cells are exposed. While early studies have demonstrated radiation-induced GI in several cell types as detected in endpoints such as mutation, apoptosis and damages in chromosomes, the dependence of GI on the quality of radiation remains uncertain. To investigate GI in human lymphocytes induced by both low- and high-LET radiation, we initially exposed white blood cells collected from healthy subjects to gamma rays in vitro, and cultured the cells for multiple generations. Chromosome aberrations were analyzed in cells collected at first mitosis post irradiation and at several intervals during the culture period. Among a number of biological endpoints planned for the project, the multi-color banding fluorescent in situ hybridization (mBAND) allows identification of inversions that were expected to be stable. We present here early and late chromosome aberrations detected with mBAND in chromosome 3 after gamma exposure. Comparison of chromosome damages in between human lymphocytes and human epithelial cells is also discussed
Sunagawa, Mayumi↗
Effect of Additives: Gamma-Ray Sensors Based on Ionizing Organic Nanocomposites
We have developed ionizing organic-based composites which have demonstrated great promise for radiation sensing. Nickel oxide has been proven as an active material for detecting high energy radiation. The oxidation state of unusual oxides such as nickel oxide in nanocomposites of ionizing organics changes much faster than thin film or bulk, and hence increases the sensitivity for radiation sensing. The resistivity of the oxide composite increases following sequential irradiation processes because of the decrease in holes' concentration. In this paper, we will present the effect of additional oxidizing agent on the morphology, processing and sensing of gamma-rays by oxides - urea based nanocomposites. It was observed that addition of MnO2 decreases the sensitivity. However, it recovers to original properties after irradiation much faster than undoped composites.
Vishall Dayal↗
The nucleosynthesis of deterium and helium-3
A new model of the creation of D and 3He in supernova of the first generation was considered. It is based on the idea that a supernova event leads simultaneously to acceleration of particles in the shock wave front and to their interactions with supernova atmosphere matter. The D, 3He, Li, Be, B and bypassed isotopes are created in these interactions. The cosmic abundances of the bypassed isotopes with A or = 113 allowed to determine the integral proton flux I sub p (E sub p 25 MeV) = 5 x 10 to the 21/sq cm the spectral index - gamma = 3. The calculations of the D and 3He yields in various nuclear reactions at these irradiation conditions show that only the 4He(p,d)3He reaction leads to cosmic abundances of these isotopes on the assumption that all matter has been exposed.
Lavrukhina, A. K.↗
Computation of Domain-Averaged Shortwave Irradiance by a One-Dimensional Algorithm Incorporating Correlations between Optical Thickness and Direct Incident Radiation
A one-dimensional radiative transfer algorithm that accounts for correlations between the optical thickness and the incident direct solar radiation is developed to compute the domain-averaged shortwave irradiance profile. It divides the direct irradiance into four components and treats the direct irradiance in two separate, clear and cloudy columns to account for the fact that clouds attenuate the direct irradiance more than clear-sky. The horizontal inhomogeneity of clouds in the cloudy column is treated by the gamma weighted two-stream approximation, which assumes that the optical thickness of clouds follows a gamma distribution. The algorithm inputs the cloud fraction, cumulative cloud fraction as a function of height, and a parameter expressing the shape of the probability density function of the cloud optical thickness distribution in addition to inputs required for a two-stream radiative transfer model. These cloud property inputs can be obtained using ground- and satellite-based instruments. Therefore, the algorithm can treat realistic cloud overlap features and horizontal inhomogeneity of clouds in a framework of one- dimensional radiative transfer. Heating rates computed by the algorithm using cloud fields generated by cloud resolving models agree with those computed with a Monte Carlo model. If optical properties in computational layers that divide a vertically extensive cloud are correlated, the irradiance profile computed by the algorithm further improves.
Kato, S.↗
Techniques of biological contamination avoidance by atmospheric probes
The likelihood of biologically contaminating a planet by an atmospheric probe has a low probability of occurring if the probe is kept biologically clean during terrestrial operations and if the structure remains in tact until the planets life zone is completely penetrated. High standards of cleanliness, monitoring and estimating for remedial actions must be maintained in a probe program. It is not a foregone conclusion, however, that heat sterilization needs to be employed. The use of several techniques having a good potential for lower probe costs are available and appear adequate to render a probe sterile within acceptable bounds. The techniques considered to be satisfactory for minimizing microbial load include: (1) combined heat (at 95-105 C) and gamma radiation; (2) short term heating at 105 + or - 5 C to inactivate all vegetative microbes; (3) irradiation routinely by ultraviolet light; (4) wiping by a bactericidal agent with or without a penetrant; and (5) cleanliness alone.
Defrees, R. E.↗
Developing High-Throughput Organ-On-A-Chip Models to Investigate the Effects of Ionizing Radiation on the Central Nervous System
One of the main health risks in human space exploration is central nervous system (CNS) damage by ionizing radiation. Irradiation with simulated GCRs or their components, or high doses of low-LET radiation such as gamma rays, in animal models has been shown to cause neuronal damage together with glial cell activation and neuroinflammation and has been associated with prolonged cognitive and behavioral dysfunction. The extent of CNS damage in response to any insult, including ionizing radiation, is partially regulated by the blood-brain barrier (BBB), which enables immune cells to enter the CNS. The main cellular regulators of BBB permeability are astrocytes, which also modulate neuronal death, immune responses and oxidative stress, and thus could serve as a robust CNS-specific target for countermeasure development. However, studies on BBB permeability and astrocyte functions in regulating CNS responses to ionizing radiation have been limited, especially in human tissue/organ analogs. Therefore, we have established a high throughput 3D organ-on-a-chip system to study human CNS functions in response to ionizing radiation, with the eventual goal of adapting it to spaceflight missions. We utilized commercially available OrganoPlate system (Mimetas, Inc.) seeded with primary or induced pluripotent stem cell-derived human cells for developing 3D neuronal-astrocytic and BBB models. We investigated both immediate and delayed CNS dose responses to 0.5-1 Gy X-rays by measuring BBB permeability and morphology, and astrocyte activation. We have also quantified secreted markers of oxidative stress and cell viability. In the future, we are planning to monitor dendritic, axonal and synaptic changes in neurons, evaluate the combined exposures to simulated microgravity and ionizing radiation, and compare the responses to low and high-LET ionizing radiation. We anticipate these studies could indicate novel cellular and mechanistic targets for countermeasure developments to improve CNS functions in astronauts.
Malkani, Sherina↗
Morphometric studies of heavy ion damage in the brains of rodents
The relative biological effectiveness (RBE) of different heavy ions for the mammalian brain was determined in mice irradiated at 100 days of age with He-4, C-12, Ne-20, Fe-56, Ar-40, or Co-60 gamma photons (with the primary particle LET values ranging from 2 to 650). Brain preparations were examined 16 months later for volume changes in the external plexiform layer (P-zone) of the olfactory bulb and an internal region (G-zone), which consists of the granule cells, the internal plexiform layer, and the mitral cell layer. The result indicate that the volume changes did occur in the olfactory bulb, not only in absolute terms but also when expressed as the ratio of the structures to each other and to the bulb as a whole. While the observed increased neuronal loss in mice receiving 700 cGy of Co-60 support the earlier data from irradiated rabbits, the increases observed in bulbar volumes and in the volume ratios of the P and the G zones measured in the mice given lower doses (320 or 160 cGy of He or C), were not expected.
Kraft, L. M.↗