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At least 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Biological countermeasures in space radiation health

Exposure to the types of ionizing radiation encountered during space travel may cause a number of health-related problems, but the primary concern is related to the increased risk of cancer induction in astronauts. The major types of radiation considered to be of importance during space travel are protons and particles of high atomic number and high energy (HZE particles). It is now clear that biological countermeasures can be used to prevent or reduce the levels of biological consequences resulting from exposure to protons or HZE particles, including the induction of cancer, immunosuppression and neurological defects caused by these types of ionizing radiation. Research related to the dietary additions of agents to minimize the risks of developing health-related problems which can result from exposure to space radiations is reviewed.

NASA Discipline Radiation Health↗
NASA NTRS1994

Radiation protection issues in galactic cosmic ray risk assessment

Radiation protection involves the limitation of exposure to below threshold doses for direct (or deterministic) effects and a knowledge of the risk of stochastic effects after low doses. The principal stochastic risk associated with low dose rate galactic cosmic rays is the increased risk of cancer. Estimates of this risk depend on two factors (a) estimates of cancer risk for low-LET radiation and (b) values of the appropriate radiation weighting factors, WR, for the high-LET radiations of galactic cosmic rays. Both factors are subject to considerable uncertainty. The low-LET cancer risk derived from the late effects of the atomic bombs is vulnerable to a number of uncertainties including especially that from projection in time, and from extrapolation from high to low dose rate. Nevertheless, recent low dose studies of workers and others tend to confirm these estimates. WR, relies on biological effects studied mainly in non-human systems. Additional laboratory studies could reduce the uncertainties in WR and thus produce a more confident estimate of the overall risk of galactic cosmic rays.

NASA Program Radiation Health↗
NASA NTRS1964

Applications of the method of Monte Carlo to problems in thermal radiation

A summary of the work involving the Monte Carlo method in the solution of problems in thermal radiation transfer is presented, which indicates general methods previously used for solving problems in which radiation is coupled with other modes of energy transfer. Previous work involving radiation in absorbing-emitting media is included. An example is outlined to indicate the use of the Monte Carlo method in the design of a space radiator. Suggestions are given for solution of a complex case incorporating the effects of coupled conduction, convection and radiation, wavelength dependent and selective surfaces, nonisothermal conditions, and strongly directional or nondiffuse emitting and reflecting surfaces. A discussion is given of the factors that may affect convergence, running time, and accuracy of the Monte Carlo solutions and of the advantages and disadvantages of this approach for practical problems. Also discussed are the case of programming for complex problems and the probable machine time requirements of the method.

THERMAL RADIATION↗
NASA NTRS2002

Clustered DNA damages induced in human hematopoietic cells by low doses of ionizing radiation

Ionizing radiation induces clusters of DNA damages--oxidized bases, abasic sites and strand breaks--on opposing strands within a few helical turns. Such damages have been postulated to be difficult to repair, as are double strand breaks (one type of cluster). We have shown that low doses of low and high linear energy transfer (LET) radiation induce such damage clusters in human cells. In human cells, DSB are about 30% of the total of complex damages, and the levels of DSBs and oxidized pyrimidine clusters are similar. The dose responses for cluster induction in cells can be described by a linear relationship, implying that even low doses of ionizing radiation can produce clustered damages. Studies are in progress to determine whether clusters can be produced by mechanisms other than ionizing radiation, as well as the levels of various cluster types formed by low and high LET radiation.

NASA Discipline Radiation Health↗
NASA NTRS2002

Brain signaling and behavioral responses induced by exposure to (56)Fe-particle radiation

Previous experiments have demonstrated that exposure to 56Fe-particle irradiation (1.5 Gy, 1 GeV) produced aging-like accelerations in neuronal and behavioral deficits. Astronauts on long-term space flights will be exposed to similar heavy-particle radiations that might have similar deleterious effects on neuronal signaling and cognitive behavior. Therefore, the present study evaluated whether radiation-induced spatial learning and memory behavioral deficits are associated with region-specific brain signaling deficits by measuring signaling molecules previously found to be essential for behavior [pre-synaptic vesicle proteins, synaptobrevin and synaptophysin, and protein kinases, calcium-dependent PRKCs (also known as PKCs) and PRKA (PRKA RIIbeta)]. The results demonstrated a significant radiation-induced increase in reference memory errors. The increases in reference memory errors were significantly negatively correlated with striatal synaptobrevin and frontal cortical synaptophysin expression. Both synaptophysin and synaptobrevin are synaptic vesicle proteins that are important in cognition. Striatal PRKA, a memory signaling molecule, was also significantly negatively correlated with reference memory errors. Overall, our findings suggest that radiation-induced pre-synaptic facilitation may contribute to some previously reported radiation-induced decrease in striatal dopamine release and for the disruption of the central dopaminergic system integrity and dopamine-mediated behavior.

NASA Discipline Radiation Health↗
NASA NTRS1992

Chromosomal changes in cultured human epithelial cells transformed by low- and high-LET radiation

For a better assessment of radiation risk in space, an understanding of the responses of human cells, especially the epithelial cells, to low- and high-LET radiation is essential. In our laboratory, we have successfully developed techniques to study the neoplastic transformation of two human epithelial cell systems by ionizing radiation. These cell systems are human mammary epithelial cells (H184B5) and human epidermal keratinocytes (HEK). Both cell lines are immortal, anchorage dependent for growth, and nontumorigenic in athymic nude mice. Neoplastic transformation was achieved by irradiating cells successively. Our results showed that radiogenic cell transformation is a multistep process and that a single exposure of ionizing radiation can cause only one step of transformation. It requires, therefore, multihits to make human epithelial cells fully tumorigenic. Using a simple karyotyping method, we did chromosome analysis with cells cloned at various stages of transformation. We found no consistent large terminal deletion of chromosomes in radiation-induced transformants. Some changes of total number of chromosomes, however, were observed in the transformed cells. These transformants provide an unique opportunity for further genetic studies at a molecular level.

NASA Discipline Number 04-10↗
NASA NTRS1999

Theoretical and experimental tests of a chromosomal fingerprint for densely ionizing radiation based on F ratios calculated from stable and unstable chromosome aberrations

In the present study, F ratios for both stable chromosome aberrations, i.e. ratios of translocations to pericentric inversions, and unstable aberrations, i.e. dicentrics and centric rings, were measured using fluorescence in situ hybridization. F ratios for stable aberrations measured after exposure to low (2.89 Gy 60Co gamma rays) and high-LET (0.25 Gy 56Fe ions; 1.25 Gy 56Fe ions; 3.0 Gy 12C ions) radiation were 6.5 +/- 1.5, 4.7 +/- 1.6, 9.3 +/- 2.5 and 10.4 +/- 3.0, respectively. F ratios for unstable aberrations measured after low (2.89 Gy 60Co gamma rays) and high-LET (0.25 Gy 56Fe ions; 3.0 Gy 12C ions) radiations were 6.5 +/- 1.6, 6.3 +/- 2.3 and 11.1 +/- 3.7, respectively. No significant difference between the F ratios for low- and high-LET radiation was found. Further tests on the models for calculation of the F ratio proposed by Brenner and Sachs (Radiat. Res. 140, 134-142, 1994) showed that the F ratio may not be straightforward as a practical fingerprint for densely ionizing radiation.

NASA Center JSC↗
NASA NTRS2020

The HadGEM3-GA7.1 radiative kernel: the importance of a well-resolved stratosphere

We present top-of-atmosphere and surface radiative kernels based on the atmospheric component (GA7.1) of the HadGEM3 general circulation model developed by the UK Met Office. We show that the utility of radiative kernels for forcing adjustments in idealised CO2 perturbation experiments is greatest where there is sufficiently high resolution in the stratosphere in both the target climate model and the radiative kernel. This is because stratospheric cooling to a CO2 perturbation continues to increase with height, and low-resolution or low-top kernels or climate model output are unable to fully resolve the full stratospheric temperature adjustment. In the sixth phase of the Coupled Model Intercomparison Project (CMIP6), standard atmospheric model data are available up to 1 hPa on 19 pressure levels, which is a substantial advantage compared to CMIP5. We show in the IPSL-CM6A-LR model where a full set of climate diagnostics are available that the HadGEM3-GA7.1 kernel exhibits linear behaviour and the residual error term is small, as well as from a survey of kernels available in the literature that in general low-top radiative kernels underestimate the stratospheric temperature response. The HadGEM3-GA7.1 radiative kernels are available at https://doi.org/10.5281/zenodo.3594673 (Smith, 2019).

radiative kernels↗
NASA NTRSDate not supplied

A Somewhat Detailed Overview of Cloud Impact on the Earth's Radiation Budget

Using a recent edition of CERES EBAF data I will provide an overview of how present-day clouds affect the shortwave and longwave radiation budget of the planet as a whole, and separately its surface and atmosphere. The overview will make the point that different classes of clouds have distinct radiative effects which are also seasonally varying to a substantial degree. I will then show results from my recent work where cloud classes have been defined from active observations according to their vertical stratification. The observed contribution of the various classes to cloud radiative effect components will be detailed, followed by a comparison with a global model where a similar cloud decomposition yields mixed results about the verisimilitude of its cloud-radiation coupling. Time permitting, I will show how cloud classes allow us to build a framework to study the various factors that contribute to cloud radiative effect anomalies.

cloud radiative effect↗
NASA NTRS2021

Genomic Changes Driven by Radiation-Induced DNA Damage and Microgravity in Human Cells

The space environment consists of a complex mixture of different types of ionizing radiation and altered gravity that represents a threat to humans during space missions. In particular, individual radiation sensitivity is strictly related to the risk of space radiation carcinogenesis. Therefore, in view of future missions to the Moon and Mars, there is an urgent need to estimate as accurately as possible the individual risk from space exposure to improve the safety of space exploration. In this review, we survey the combined effects from the two main physical components of the space environment, ionizing radiation and microgravity, to alter the genetics and epigenetics of human cells, considering both real and simulated space conditions. Data collected from studies on human cells are discussed for their potential use to estimate individual radiation carcinogenesis risk from space exposure.

space radiation↗
NASA NTRSDate not supplied

Radiation Data Collection and Risk Assessment

In order to advance the approach for parts assurance in the space community to the current decade and to remain nimble for the future, NASA GSFC, in collaboration with the Aerospace Corporation’s Mission Success Improvement Workshop and broad space community participation, has been reviewing and categorizing 40 years’ worth of on-orbit anomaly data to support broad assessments of radiation-related risk and the development of tools to rigorously assess risk in general project situations. Part of the changing approach in parts assurance involves phasing in the use of COTS parts (or as preferred, alternate grade parts). This talk will convey some of the early findings of the effort, including the fact that expanded use of COTS parts does not increase radiation-related risk, while also pointing out that a very small percentage of parts in a typical parts list are actives and thus require radiation assessment. These are important because they remove radiation as a factor in broad consideration in the use of COTS, without diminishing the importance of addressing the effects of radiation in space.

risk↗
NASA NTRS2001

Response of Silicon-Based Linear Energy Transfer Spectrometers: Implication for Radiation Risk Assessment in Space Flights

There is considerable interest in developing silicon-based telescopes because of their compactness and low power requirements. Three such telescopes have been flown on board the Space Shuttle to measure the linear energy transfer spectra of trapped, galactic cosmic ray, and solar energetic particles. Dosimeters based on single silicon detectors have also been flown on the Mir orbital station. A comparison of the absorbed dose and radiation quality factors calculated from these telescopes with that estimated from measurements made with a tissue equivalent proportional counter show differences which need to be fully understood if these telescopes are to be used for astronaut radiation risk assessments. Instrument performance is complicated by a variety of factors. A Monte Carlo-based technique was developed to model the behavior of both single element detectors in a proton beam, and the performance of a two-element, wide-angle telescope, in the trapped belt proton field inside the Space Shuttle. The technique is based on: (1) radiation transport intranuclear-evaporation model that takes into account the charge and angular distribution of target fragments, (2) Landau-Vavilov distribution of energy deposition allowing for electron escape, (3) true detector geometry of the telescope, (4) coincidence and discriminator settings, (5) spacecraft shielding geometry, and (6) the external space radiation environment, including albedo protons. The value of such detailed modeling and its implications in astronaut risk assessment is addressed. c2001 Elsevier Science B.V. All rights reserved.

manned↗
NASA NTRS1996

Measurements of the linear energy transfer spectra on the Mir orbital station and comparison with radiation transport models

A tissue equivalent proportional counter designed to measure the linear energy transfer spectra (LET) in the range 0.2-1250 keV/micrometer was flown in the Kvant module on the Mir orbital station during September 1994. The spacecraft was in a 51.65 degrees inclination, elliptical (390 x 402 km) orbit. This is nearly the lower limit of its flight altitude. The total absorbed dose rate measured was 411.3 +/- 4.41 microGy/day with an average quality factor of 2.44. The galactic cosmic radiation (GCR) dose rate was 133.6 microGy/day with a quality factor of 3.35. The trapped radiation belt dose rate was 277.7 microGy/day with an average quality factor of 1.94. The peak rate through the South Atlantic Anomaly was approximately 12 microGy/min and nearly constant from one pass to another. A detailed comparison of the measured LET spectra has been made with radiation transport models. The GCR results are in good agreement with model calculations; however, this is not the case for radiation belt particles and again points to the need for improving the AP8 omni-directional trapped proton models.

Mir Project↗
NASA NTRS2003

Radiation risk and human space exploration

Radiation protection is essential to enable humans to live and work safely in space. Predictions about the nature and magnitude of the risks posed by space radiation are subject to very large uncertainties. Prudent use of worst-case scenarios may impose unacceptable constraints on shielding mass for spacecraft or habitats, tours of duty of crews on Space Station, and on the radius and duration of sorties on planetary surfaces. The NASA Space Radiation Health Program has been devised to develop the knowledge required to accurately predict and to efficiently manage radiation risk. The knowledge will be acquired by means of a peer-reviewed, largely ground-based and investigator-initiated, basic science research program. The NASA Strategic Plan to accomplish these objectives in a manner consistent with the high priority assigned to the protection and health maintenance of crews will be presented. Published by Elsevier Science Ltd on behalf of COSPAR.

NASA Discipline Radiation Health↗
NASA NTRS2001

New measurements for hadrontherapy and space radiation: biology

The dual goals of optimizing clinical efficacy of hadrontherapy and determining radiation risk estimates for space research have intersected to a common focus for investigation of the biological effects of charged particles. This paper briefly highlights recent international progress at accelerator facilities engaged in both biological and clinical studies of the effects of particle beams, primarily protons, carbon and iron ions. Basic mechanisms of molecular, cellular and tissue responses continue under investigation for radiations with a range of ionization densities. Late normal tissue effects, including the risk of cancer in particular, are of importance for both research fields. International cooperation has enhanced the rate of progress as evidenced by recent publications. Specific areas of biomedical research related to the biological radiotoxicity of critical organs (especially the central nervous system), individual radiosensitivities to radiation carcinogenesis, and the analysis of effects in mixed radiation fields still require more research. Recommendations for addressing these issues are made.

Review↗
NASA NTRS1996

Model calculations of the radiation dose and LET spectra on LDEF and comparisons with flight data

Ionizing radiation environment models, a 3-D spacecraft mass model, and radiation transport codes have been used to predict the radiation dose and linear energy transfer (LET) spectra measured at various locations on the LDEF satellite. The predictions are compared with thermoluminescent dosimeter measurements of the trapped proton and electron doses and with LET spectra measured by plastic nuclear track detectors. The predicted vs observed comparisons indicate some of the uncertainties of present ionizing radiation environment models for low Earth-orbit missions.

LDEF Project↗
NASA NTRS1996

In-flight radiation measurements on STS-60

A joint investigation between the United States and Russia to study the radiation environment inside the Space Shuttle flight STS-60 was carried out as part of the Shuttle-Mir Science Program (Phase 1). This is the first direct comparison of a number of different dosimetric measurement techniques between the two countries. STS-60 was launched on 3 February 1994 in a nearly circular 57 degrees x 353 km orbit with five U.S. astronauts and one Russian cosmonaut for 8.3 days. A variety of instruments provided crew radiation exposure, absorbed doses at fixed locations, neutron fluence and dose equivalent, linear energy transfer (LET) spectra of trapped and galactic cosmic radiation, and energy spectra and angular distribution of trapped protons. In general, there is good agreement between the U.S. and Russian measurements. The AP8 Min trapped proton model predicts an average of 1.8 times the measured absorbed dose. The average quality factor determined from measured lineal energy, y, spectra using a tissue equivalent proportional counter (TEPC), is in good agreement with that derived from the high temperature peak in the 6LiF thermoluminescent detectors (TLDs). The radiation exposure in the mid-deck locker from neutrons below 1 MeV was 2.53 +/- 1.33 microSv/day. The absorbed dose rates measured using a tissue equivalent proportional counter, were 171.1 +/- 0.4 and 127.4 +/- 0.4 microGy/day for trapped particles and galactic cosmic rays, respectively. The combined dose rate of 298.5 +/- 0.82 microGy/day is about a factor of 1.4 higher than that measured using TLDs. The westward longitude drift of the South Atlantic Anomaly (SAA) is estimated to be 0.22 +/- 0.02 degrees/y. We evaluated the effects of spacecraft attitudes on TEPC dose rates due to the highly anisotropic low-earth orbit proton environment. Changes in spacecraft attitude resulted in dose-rate variations by factors of up to 2 at the location of the TEPC.

NASA Discipline Radiation Health↗
NASA NTRS1995

Use of non-subjective analysis of lens transparency in experimental radiation cataract research

Historically the major impediment to radiation cataract follow-up has been the necessarily subjective nature of assessing the degree of lens transparency. This has spurred the development of instruments which produce video images amenable to digital analysis. One such system, the Zeiss Scheimpflug slit lamp measuring system (SLC), was incorporated into our ongoing studies of radiation cataractogenesis. It was found that the Zeiss SLC measuring system has high resolution and permits the acquisition of reproducible images of the anterior segment of the eye. Our results, based on about 650 images of lenses followed over a period of 91 weeks of radiation cataract development, showed that the changes in the light scatter of the lens correlated well with conventional assessment of radiation cataracts with the added advantages of objectivity, permanent and transportable records and linearity as cataracts become more severe. This continuous data acquisition, commencing with cataract onset, can proceed through more advanced stages. The SLC exhibits much greater sensitivity reflected in a continuously progressive severity thereby avoiding the artifactual plateaus in staging which occur using conventional scoring methods.

NASA Discipline Number 04-10↗