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PubMedDate not supplied

[Radiobiologic basis of the quality factor of protons and helium ions].

Reported data and experimental results of measuring the relative biological effectiveness of protons of different energies and helium ions of 4 GeV/nuclon were analyzed to determine quality factors of the major components of cosmic radiations. It is recommended to use quality factors equal to 1.30-1.45 for 100-730 MeV protons and equal to 1.75 for 9 GeV protons and 4 GeV/nuclon helium ions. It is also suggested to employ them as standards for solving practical problems of radiation safety in space flights.

Animals↗
PubMed1977

[Morphologic and cytochemical research aboard the biosatellite "Cosmos-782"].

Organs of rats flown for 19.5 days on board the Cosmos-782 biosatellite were investigated morphologically and cytochemically. After flight, as a result of drastic decrease or loss of static load on the musculeskeletal system in zero-g, the rats developed mineral metabolism changes that morphologically appeared as osteoporosis of spongy bones, their periosteocytic osteolysis, as well as inhibition of red blood cell precursors in bone marrow, atrophy and dystrophy of skeletal muscles. The development of stress-reaction which seemed to increase at certain flight stages (launch and re-entry) and weightlessness--1 g transition brought about changes in the structure and cell composition of lymph organs, changes in the hypothalamic-pituitary-neurosecretory system, adrenals, gastro-intestinal tract and other organs and systems. Changes in the receptor system of the inner ear resulted, evidently, from weightlessness and acceleration effects, whereas retinal lesions were due to heavy charged particles of cosmic radiation. The changes noted were reversible and 25 days after flight returned, completely or partly, to the normal.

Adrenal Glands↗
PubMed1983

[Frequency of chromosome recombination, nondisjunction and breaks in Drosophila melanogaster males exposed during space flight].

Effects of space flight factors on chromosomal nondisjunctions, breaks and mitotic recombination in Drosophila melanogaster males were studied. It was shown that space flight conditions increased the frequencies of nondisjunctions, breaks and mitotic recombination in chromosomes. It was established that the vibration and acceleration effects could not serve to explain the data obtained. On the basis of these data, it may be suggested that weightlessness and cosmic radiation are the main factors which are responsible for the effects observed.

Animals↗
PubMedDate not supplied

Mechanisms of development of morphological changes in mammals aboard biological satellites.

After orbital space flights lasting 19.5--22.5 days, disturbances are observed in mineral metabolism in rats, which are morphologically manifested as osteoporosis of the spongy sections of long hollow skeletal bones, periosteocytic osteolysis of them, atrophy and dystrophy of skeletal muscles, and inhibition of erythroid growth of bone marrow, which occurred and developed in weightlessness as a result of deprivation of motor activity due to removal (or reduction) of static load from the musculoskeletal system. Development of stress reaction, which is apparently intensified at certain stages of flight (lift off and touchdown) and during transition from weightlessness to conditions of gravitational force on earth, leads to corresponding changes in the structure and cellular composition of lymphoid organs, and to changes in the hypothalamic-hypophyseal neurosecretory system, adrenal glands, and other organs. Changes in the receptor apparatus of the vestibular system are associated with local circulatory changes occurring during weightlessness and G forces, while retinal injuries are associated with the effect of heavy charged particles of cosmic radiation. All changes are reversible and disappear completely or to a substantial degree a month after completion of the flight.

Animals↗
PubMed1994

Embryonic effects transmitted by male mice irradiated with 512 MeV/u 56Fe nuclei.

High-energy, high-charge nuclei may contribute substantially to the yearly equivalent dose in space flight from galactic cosmic radiation (GCR) at solar minimum. The largest single heavy-ion component is 56Fe. We used the mouse embryo chimera assay to test 512 MeV/u 56Fe nuclei for effects on the rate of proliferation of embryonic cells transmitted by sperm from irradiated mice. Male CD1 mice were acutely irradiated with 0.01, 0.05 or 0.1 Gy (LET, 184 keV/micron; fluence, 3.5 x 10(4)-3.3 x 10(5) nuclei/cm2; average dose rate, 0.02 Gy/min) at the Lawrence Berkeley Laboratory BEVATRON/BEVALAC Facility in Berkeley, CA. Irradiated males were bred weekly for 7 weeks to nonirradiated females and their four-cell embryos were paired with control embryos, forming aggregation chimeras. After 30-35 h of culture, chimeras were dissociated to obtain "proliferation ratios" (number of cells contributed by the embryo from the irradiated male/total number of cells in the chimera). Significant dose-dependent decreases in proliferation ratios were obtained across all three dose groups for postirradiation week 2 (P < 0.05 to P < 0.003). The 0.01- and 0.05-Gy dose groups also produced significant decreases in proliferation ratios for postirradiation week 1 (P < 0.05 to P < 0.01) and the 0.05-Gy dose group produced significant decreases in proliferation ratios for postirradiation week 6 (P < 0.05). Postirradiation weeks 1, 2 and 6 correspond to irradiation of epididymal sperm, testicular spermatids and spermatogonia, respectively. We calculate that only about 5% of sperm in the 0.1-Gy, 2.5% in the 0.05-Gy and 0.5% in the 0.01-Gy dose groups sustained direct hits from 56Fe nuclei. However, up to 47% of sperm during postirradiation weeks 1 and 2 transmitted proliferation ratios that were at or below one standard deviation from control mean proliferation ratios. Morphometry on sectioned testes showed a significant log-linear dose response for cell killing of type B spermatogonia, which are the most radiosensitive stage of spermatogenesis and which would have been tested as mature sperm during postirradiation week 6. We conclude that amplification from secondary radiation produced in the mouse and/or from diffusible chemical products arising from hit sperm and adjacent cells contributed to the high incidence of transmitted effects on proliferation of embryonic cells.

Animals↗
PubMed1994

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.

Adolescent↗
PubMed2002

Intercomparison of radiation instruments for cosmic-ray with heavy ion beams at NIRS (ICCHIBAN project).

The first InterComparison for Cosmic-ray with Heavy Ion Beams At NIRS (ICCHIBAN) project is an ongoing, international collaboration organized at the National Institute of Radiological Sciences (NIRS), Japan, for the purpose of characterizing and comparing at a controlled, ground-based heavy ion facility the radiation response of instruments used aboard piloted spacecraft for crew and area dosimetry. We present preliminary results from the first set of ICCHIBAN exposures made at HIMAC heavy ion accelerator in February 2002. The initial series of exposures (1st ICCHIBAN run) was designed to establish the response of active detectors to two well-characterized heavy ion beams; 400 MeV/nucleon 12C and 400 MeV/nucleon 56Fe. These beams are representative in charge and energy of two of the most significant heavy ion components present in the galactic cosmic radiation spectrum. The properties of the incident beam, including intensity, profile, charge and total energy, were characterized using several different detector systems, including silicon detectors, CR-39 plastic nuclear track detectors and plastic scintillation counters. Once the response of each detector to heavy ion beams of known composition has been measured, results from on-orbit measurements made by the different instruments can be more meaningfully compared. We conclude by discussing plans for future ICCHIBAN runs, including next 2nd ICCHIBAN run for passive detectors in early summer 2002.

Cosmic Radiation↗
PubMed2003

Cosmic microwave background radiation anisotropies in brane worlds.

We propose a new formulation to calculate the cosmic microwave background (CMB) spectrum in the Randall-Sundrum two-brane model based on recent progress in solving the bulk geometry using a low energy approximation. The evolution of the anisotropic stress imprinted on the brane by the 5D Weyl tensor is calculated. An impact of the dark radiation perturbation on the CMB spectrum is investigated in a simple model assuming an initially scale-invariant adiabatic perturbation. The dark radiation perturbation induces isocurvature perturbations, but the resultant spectrum can be quite different from the prediction of simple mixtures of adiabatic and isocurvature perturbations due to Weyl anisotropic stress.

Journal Article↗
PubMed1999

Contribution of cosmic ray heavy ions to the radiation hazard in manned space flights.

Primary cosmic radiation arriving near the Earth may be classified into two general categories: the gamma component and the hadronic component. The hadronic component contains mainly protons, a small amount of alpha particles and a smaller amount of heavier charged nuclei (ions). Although the fluxes of these heavier ions are very small in comparison to those of protons, they are able to originate a huge linear energy transfer (LET). This work studies the contribution of heavy ions from cosmic rays to the radiation hazard to which the crew of a manned long duration space flight might be exposed. The geometry of the energy deposition by a heavy ion is studied, and it is found that energies of the order of up to 10(23) J kg-1 are deposited.

Cosmic Radiation↗
PubMed2000

A flat Universe from high-resolution maps of the cosmic microwave background radiation

The blackbody radiation left over from the Big Bang has been transformed by the expansion of the Universe into the nearly isotropic 2.73 K cosmic microwave background. Tiny inhomogeneities in the early Universe left their imprint on the microwave background in the form of small anisotropies in its temperature. These anisotropies contain information about basic cosmological parameters, particularly the total energy density and curvature of the Universe. Here we report the first images of resolved structure in the microwave background anisotropies over a significant part of the sky. Maps at four frequencies clearly distinguish the microwave background from foreground emission. We compute the angular power spectrum of the microwave background, and find a peak at Legendre multipole Ipeak = (197 +/- 6), with an amplitude delta T200 = (69 +/- 8) microK. This is consistent with that expected for cold dark matter models in a flat (euclidean) Universe, as favoured by standard inflationary models.

Journal Article↗