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PubMed2005

Modelling radiation loads to detectors in a SNAP mission.

In order to investigate the degradation of optical detectors of the Supernova Acceleration Project (SNAP) space mission because of irradiation, a three-dimensional model of the satellite has been developed. A realistic radiation environment at the satellite orbit, including both galactic cosmic rays and cosmic ray trapped in radiation belts, has been taken into account. The modelling has been performed with the MARS14 Monte Carlo code. In a current design, the main contribution to dose accumulated in the photo-detectors is shown to be due to trapped protons. The contribution of primary alpha particles is estimated. Predicted performance degradation for the photodetector for a four-year space mission is 40% and this can be reduced further by means of shielding optimisation.

Alpha Particles↗
PubMed1975

Effects of space balloon flights on reproductive activity in Paramecium aurelia.

Post autogamous Paramecium aurelia cultures were placed in hermetic containers, including a heating device with accuracy kept around +/- 0.1 degrees C. Kinetics of cellular growth was determined by cell count, after recovery, on in-flight cultures and ground control cultures. Dosimetry was performed by thermoluminescent detectors (CaSO4 activated with dysprosium). Flight durations of maximum altitude (ceiling) ranged between 48 min and 15 hours (repeated flights). Conclusions are as follows: short flights result in a secondary stimulating effect, shown by post-flight increase of the growth rate (total dose above 2 mrads); long flights or repeated flights are accompanied by a decrease in growth rate (total dose ranging from 2 to 6 mrads); in the stimulation experiments, cell counts performed immediately after flight permit identification of a temporary decrease of growth rate. The biphasic character of the biological response after flights may be due to an ionization phenomena induced by cosmic rays. Indeed, the temporary drop of growth rate is not observed after recovery if the cells are subcultured in fresh medium and left on the earth's surface. We observe, on the contrary, an increase in growth rate. These findings confirm the great sensitivity of Paramecium aurelia to very low doses of ionizing radiations and demonstrate the biological effect of cosmic radiation.

Altitude↗
PubMed1996

Possible effects of protracted exposure on the additivity of risks from space radiations.

Conventional radiation risk assessments are presently based on the additivity assumption. This assumption states that risks from individual components of a complex radiation field involving many different types of radiation can be added to yield the total risk of the complex radiation field. If the assumption is not correct, the summations and integrations performed to obtain the presently quoted risk estimates are not appropriate. This problem is particularly important in the area of space radiation risk evaluation because of the many different types of high- and low-LET radiation present in the galactic cosmic ray environment. For both low- and high-LET radiations at low enough dose rates, the present convention is that the addivity assumption holds. Mathematically, the total risk, Rtot is assumed to be Rtot = summation (i) Ri where the summation runs over the different types of radiation present. If the total dose (or fluence) from each component is such that the interaction between biological lesions caused by separate single track traversals is negligible within a given cell, it is presently considered to be reasonable to accept the additivity assumption. However, when the exposure is protracted over many cell doubling times (as will be the case for extended missions to the moon or Mars), the possibility exists that radiation effects that depend on multiple cellular events over a long time period, such as is probably the case in radiation-induced carcinogenesis, may not be additive in the above sense and the exposure interval may have to be included in the evaluation procedure. It is shown, however, that "inverse" dose-rate effects are not expected from intermediate LET radiations arising from the galactic cosmic ray environment due to the "sensitive-window-in-the-cell-cycle" hypothesis.

Animals↗
PubMed2004

The energy spectrum of cosmic-ray induced neutrons measured on an airplane over a wide range of altitude and latitude.

Crews of high-altitude aircraft are exposed to radiation from galactic cosmic rays (GCRs). To help determine such exposures, the Atmospheric Ionizing Radiation Project, an international collaboration of 15 laboratories, made simultaneous radiation measurements with 14 instruments on a NASA ER-2 high-altitude airplane. The primary instrument was a sensitive extended-energy multisphere neutron spectrometer. Its detector responses were calculated for energies up to 100 GeV using the radiation transport code MCNPX 2.5.d with improved nuclear models and including the effects of the airplane structure. New calculations of GCR-induced particle spectra in the atmosphere were used to correct for spectrometer counts produced by protons, pions and light nuclear ions. Neutron spectra were unfolded from the corrected measured count rates using the deconvolution code MAXED 3.1. The results for the measured cosmic-ray neutron spectrum (thermal to >10 GeV), total neutron fluence rate, and neutron dose equivalent and effective dose rates, and their dependence on altitude and geomagnetic cut-off agree well with results from recent calculations of GCR-induced neutron spectra.

Aircraft↗
PubMedDate not supplied

Seasonal 7Be concentrations in near-surface air of Granada (Spain) in the period 1993-2001.

Near-surface air samples for assessment of seasonal 7Be levels were taken weekly at Granada, Spain, (37 degrees 10'50"N-3 degrees 35'44"W, altitude 670 m) in the period 1993-2001. The 7Be levels measured reflect strong seasonal trends. Concentrations during autumn and/or winter showed a minimum (ca. 1.5 mBq/m3), and in each year a fallout maximum was found in summer (ca. 7.6 mBq/m3). Multiple regression of 7Be concentrations with temperature and rainfall, and with sunspot number explained about 71% of the variance in the 7Be data. The data reveal strong variations in the mean annual 7Be concentrations due to variations in the flux of cosmic galactic primary radiation caused by the 11-year sunspot cycle. A difference of a factor of 2.6 was found between the highest level (5.8 mBq/m3) obtained in 1996 (beginning of the solar cycle 23) and the lowest (2.6 mBq/m3) obtained in 2000 (maximum of the solar cycle 23).

Air Pollution, Radioactive↗
PubMed2026

Leveraging bioinformatics approaches for drug repositioning in space radiation protection.

The health effects of space radiation, primarily Galactic Cosmic Rays (GCRs), on humans remain largely unknown, with potential cardiovascular consequences posing a significant threat to astronauts on long-duration spaceflight missions. Currently, there are no established pharmacological countermeasures for GCR exposure. Drug repositioning offers a promising strategy to accelerate pharmaceutical research in space medicine. This study leverages existing bioinformatics techniques to identify and prioritize potential drug candidates associated with proteomic perturbations following simulated GCR exposure using previously published murine cardiac proteomic data. A protein-protein interaction (PPI) network was constructed using the top differentially expressed proteins (DEPs) from murine heart tissue following exposure to 5-ion GCRs as seed nodes, focusing on experimentally supported interactions. Network topology, Markov clustering, and functional enrichment analyses were used to characterize biologically relevant proteins and pathways. Drug-protein interactions were predicted using Drugst.One and mapped to PPI clusters of interest to identify candidate drugs. Selected drug-macromolecule interactions were further explored using CB-Dock2 molecular docking and short-duration molecular dynamics simulations as hypothesis-generating structural assessments. Analysis of a key PPI network cluster consisting of several ATP synthase proteins identified 23 unique drug candidates. These analyses demonstrate a systematic approach for leveraging bioinformatics techniques to identify candidate molecular targets and generate pharmacological hypotheses in the context of space radiation countermeasures. Ultimately, this strategy introduces a hypothesis-generating framework for the prioritization of potential drug candidates for future computational characterization and experimental investigation against spaceflight stressors.

Animals↗
PubMed2001

Relative effectiveness of HZE iron-56 particles for the induction of cytogenetic damage in vivo.

One of the risks of prolonged manned space flight is the exposure of astronauts to radiation from galactic cosmic rays, which contain heavy ions such as (56)Fe. To study the effects of such exposures, experiments were conducted at the Brookhaven National Laboratory by exposing Wistar rats to high-mass, high-Z, high-energy (HZE) particles using the Alternating Gradient Synchrotron (AGS). The biological effectiveness of (56)Fe ions (1000 MeV/nucleon) relative to low-LET gamma rays and high-LET alpha particles for the induction of chromosome damage and micronuclei was determined. The mitotic index and the frequency of chromosome aberrations were evaluated in bone marrow cells, and the frequency of micronuclei was measured in cells isolated from the trachea and the deep lung. A marked delay in the entry of cells into mitosis was induced in the bone marrow cells that decreased as a function of time after the exposure. The frequencies of chromatid aberrations and micronuclei increased as linear functions of dose. The frequency of chromosome aberrations induced by HZE particles was about 3.2 times higher than that observed after exposure to (60)Co gamma rays. The frequency of micronuclei in rat lung fibroblasts, lung epithelial cells, and tracheal epithelial cells increased linearly, with slopes of 7 x 10(-4), 12 x 10(-4), and 11 x 10(-4) micronuclei/binucleated cell cGy(-1), respectively. When genetic damage induced by radiation from (56)Fe ions was compared to that from exposure to (60)Co gamma rays, (56)Fe-ion radiation was between 0.9 and 3.3 times more effective than (60)Co gamma rays. However, the HZE-particle exposures were only 10-20% as effective as radon in producing micronuclei in either deep lung or tracheal epithelial cells. Using microdosimetric techniques, we estimated that 32 cells were hit by delta rays for each cell that was traversed by the primary HZE (56)Fe particle. These calculations and the observed low relative effectiveness of the exposure to HZE particles suggest that at least part of the cytogenetic damage measured was caused by the delta rays. Much of the energy deposited by the primary HZE particles may result in cell killing and may therefore be "wasted" as far as production of detectable micronuclei is concerned. The role of wasted energy in studies of cancer induction may be important in risk estimates for exposure to HZE particles.

Animals↗
PubMed2003

Predicting the response of a submillimeter bolometer to cosmic rays.

Bolometers designed to detect submillimeter radiation also respond to cosmic, gamma, and x rays. Because detectors cannot be fully shielded from such energy sources, it is necessary to understand the effect of a photon or cosmic-ray particle being absorbed. The resulting signal (known as a glitch) can then be removed from raw data. We present measurements using an Americium-241 gamma radiation source to irradiate a prototype bolometer for the High Frequency Instrument in the Planck Surveyor satellite. Our measurements showed no variation in response depending on where the radiation was absorbed, demonstrating that the bolometer absorber and thermistor thermalize quickly. The bolometer has previously been fully characterized both electrically and optically. We find that using optically measured time constants underestimates the time taken for the detector to recover from a radiation absorption event. However, a full thermal model for the bolometer, with parameters taken from electrical and optical measurements, provides accurate time constants. Slight deviations from the model were seen at high energies; these can be accounted for by use of an extended model.

Journal Article↗
PubMed1995

Space and radiation protection: scientific requirements for space research.

Ionizing radiation poses a significant risk to humans living and working in space. The major sources of radiation are solar disturbances and galactic cosmic rays. The components of this radiation are energetic charged particles, protons, as well as fully ionized nuclei of all elements. The biological effects of these particles cannot be extrapolated in a straightforward manner from available data on x-rays and gamma-rays. A radiation protection program that meets the needs of spacefaring nations must have a solid scientific basis, capable not only of predicting biological effects, but also of making reliable estimates of the uncertainty in these predictions. A strategy leading to such predictions is proposed, and scientific requirements arising from this strategy are discussed.

Astronauts↗
PubMed2002

Radiation doses of Swiss population from external sources.

The outdoor radiation exposure of the population in Switzerland from external sources results from cosmic background as well as from natural and artificial ground radiation. The geographical distribution of these components and of the total dose rate are represented on maps consisting of 2 kmx2 km grid cells. The average dose rate on Swiss territory outdoors is 147 nSv/h (1.29 mSv/a). The distributions are then related to the population density distribution by GIS application. The population is exposed to an average dose rate of 108 nSv/h (0.95 mSv/a) per capita which is just below the threshold for man-made dose rate given by national regulation. The lower value (relative to the country average 147 nSv/h) arises from the fact that most of the population lives north of the Alps where the lithology is dominated by rocks of relatively low radioactivity and where the cosmic radiation is low relative to the Alps.

Environmental Exposure↗
PubMed1999

Biological dosimetry for astronauts: a real challenge.

Manned space missions recently increased in number and duration, thus it became important to estimate the biological risks encountered by astronauts. They are exposed to cosmic and galactic rays, a complex mixture of different radiations. In addition to the measurements realized by physical dosimeters, it becomes essential to estimate real biologically effective doses and compare them to physical doses. Biological dosimetry of radiation exposures has been widely performed using cytogenetic analysis of chromosomes. This approach has been used for many years in order to estimate absorbed doses in accidental or chronic overexposures of humans. In addition to conventional techniques (Giemsa or FPG staining, R- or G-banding), faster and accurate means of analysis have been developed (fluorescence in situ hybridization [FISH] painting). As results accumulate, it appears that strong interindividual variability exists in the basal level of aberrations. Moreover, some aberrations such as translocations exhibit a high background level. Radiation exposures seem to induce variability between individual responses. Its extent strongly differs with the mode of exposure, the doses delivered, the kind of radiation, and the cytogenetic method used. This paper aims to review the factors that may influence the reliability of cytogenetic dosimetry. The emphasis is on the exposure to high linear energy transfer (LET) particles in space as recent studies demonstrated interindividual variations in doses estimated from aberration analysis after long-term space missions. In addition to the problem of dose estimates, the heterogeneity of cosmic radiation raises questions relating to the real numbers of damaged cells in an individual, and potential long-term risks. Actually, densely ionizing particles are extremely potent to induce late chromosomal instability, and again, interindividual variability exists in the expression of damage.

Astronauts↗
PubMed2004

Sneutrino condensate source for density perturbations, leptogenesis, and low reheat temperature.

We bring together some known ingredients beyond the standard model physics that can explain the hot big bang model with the observed baryon asymmetry and also the fluctuations in the cosmic microwave background radiation with a minimal set of assumptions. We propose an interesting scenario where the inflaton energy density is dumped into an infinitely large extra dimension. Instead of the inflaton it is the right handed sneutrino condensate, which is acquiring a nonzero vacuum expectation value during inflation, whose fluctuations are responsible for the density perturbations seen in the cosmic microwave background radiation with a spectral index n(s) approximately 1. The decay of the condensate is explaining the reheating of the Universe with a temperature, T(rh)< or =10(9) GeV, and the baryon asymmetry of order one part in 10(10) with no baryon-isocurvature fluctuations.

Journal Article↗
PubMed1995

Ionizing radiation and cancer prevention.

Ionizing radiation long has been recognized as a cause of cancer. Among environmental cancer risks, radiation is unique in the variety of organs and tissues that it can affect. Numerous epidemiological studies with good dosimetry provide the basis for cancer risk estimation, including quantitative information derived from observed dose-response relationships. The amount of cancer attributable to ionizing radiation is difficult to estimate, but numbers such as 1 to 3% have been suggested. Some radiation-induced cancers attributable to naturally occurring exposures, such as cosmic and terrestrial radiation, are not preventable. The major natural radiation exposure, radon, can often be reduced, especially in the home, but not entirely eliminated. Medical use of radiation constitutes the other main category of exposure; because of the importance of its benefits to one's health, the appropriate prevention strategy is to simply work to minimize exposures.

Dose-Response Relationship, Radiation↗
PubMed2005

Estimated neutron dose to embryo and foetus during commercial flight.

A study has been carried out to assess the radiation exposure from cosmic-ray neutrons to the embryo and foetus of pregnant aircrew and air travellers in consideration of the radiation exposure from cosmic-ray neutrons to the embryo and foetus. A Monte Carlo analysis was performed to determine the equivalent dose from neutrons to the brain and body of an embryo at 8 weeks and to the foetus at the 3, 6 and 9 month periods. Neutron fluence-to-absorbed dose conversion coefficients for the foetal brain and for the entire foetal body (isotropic irradiation geometry) have been determined at the four developmental stages. The equivalent dose rate to the foetus during commercial flights has been further evaluated considering the fluence-to-absorbed dose conversion coefficients, a neutron spectrum measured at an altitude of 11.3 km and an ICRP-92 radiation-weighting factor for neutrons. This study indicates that the foetus can exceed the annual dose limit of 1 mSv for the general public after, for example, 15 round trips on commercial trans-Atlantic flights.

Aircraft↗
PubMedDate not supplied

[Evaluation of the radiation risk of determinate effects from space radiation in a piloted mission to Mars].

Solar cosmic rays (SCR) are one of the sources of radiation risk specific to space flights. On Earth, occupational exposure has a regular character and radiation risk is an attribute of nothing else but stochasticity of radiobiological effects. In space flight, SCR impart stochasticity to the radiation environment and, therefore, probability to all, including determinate, radiobiological effects. The most dangerous effect is radiation disease the dosimetric functional of which is an equivalent dose to the blood-forming organs. In addition, this radiation pathology is modulated by reparative processes in the blood-forming tissue which must be also taken into account during radiation risk evaluation. Using the speculated mission to Mars as an example, it was shown that radiation risk of determinate effects defined as probability of death by radiation disease in consequence of exposure to SCR can be comparable in value to the risk from stochastic effects.

Cosmic Radiation↗
PubMed2000

Cosmic ray hits in the central nervous system at solar maximum.

It has been suggested that a manned mission to Mars be launched at solar maximum rather than at solar minimum to minimize the radiation exposure to galactic cosmic rays. It is true that the number of hits from highly ionizing particles to critical regions in the brain will be less at solar maximum, and it is of interest to estimate how much less. We present here calculations for several sites within the brain from iron ions (z = 26) and from particles with charge, z, greater than or equal to 15. The same shielding configurations and sites in the brain used in an earlier paper for solar minimum are employed so that direct comparison of results between the two solar activity conditions can be made. A simple pressure-vessel wall and an equipment room onboard a spacecraft are chosen as shielding examples. In the equipment room, typical results for the thalamus are that the probability of any particles with 7 greater than or equal to 15 and from 2.3 percent to 1.3 percent for iron ions. The extra shielding provided in the equipment room makes little difference in these numbers. We conclude that this decrease in hit frequency (less than a factor of two) does not provide a compelling reason to avoid solar minimum for a manned mission to Mars. This conclusion could be revised, however, if a very small number of hits is found to cause critical malfunction within the brain.

Aerospace Medicine↗
PubMed1977

Satellite studies on the use of electric fields for shielding biological objects against cosmic rays.

The paper presents the results of measurements of conduction currents in strong electric fields of an electrostatic radiation shield apparatus aboard the Cosmos 690 artificial satellite. Power, dose and weight-size characteristics were calculated for an electrostatic shield and it was concluded that with available high-voltage technology it is possible to create an efficient low-weight electrostatic shield against cosmic radiation for biological objects. The development of an electric field system for in-flight radiation protection of biological objects could solve a number of other technological problems, such as protection of equipment and instruments against electric inductions, discharges and surface breakdowns.

Cosmic Radiation↗
PubMedDate not supplied

In-flight radiation: counseling patients about risk.

BACKGROUND: At the high altitudes, which are the domain of commercial airliners, cosmic-ray exposure rates are hundreds of times greater than at ground level. If this radiation originated at a regulated industrial or medical facility, many frequent flyers would receive annual exposures in excess of the present legal limit applicable to members of the public. For pregnant travelers, the fetus is also at risk, with a sensitivity that varies during the course of pregnancy. METHODS: Health risks from in-flight radiation exposure are analyzed specifically to calculate the likelihood of cancer, birth defects, and genetic damage. A literature review was conducted from 1985 to 1998, using the key words "cosmic radiation," "aviation medicine," "radiation risk," and "in-flight radiation." RESULTS AND CONCLUSIONS: The analysis shows that for the passenger who travels only occasionally, the risks are extremely small. For business frequent flyers the risks are still small, but not negligible.

Aerospace Medicine↗