Measurements of secondary neutrons from cosmic radiation with a Bonner sphere spectrometer at 79°N

Air crew members and airline passengers are continuously exposed to cosmic radiation during their flights. Particles ejected by the sun during so-called solar particle events (SPEs) in periods of high solar activity can contribute to this exposure. In rare cases the dose from a single SPE might even exceed the annual dose limit of 1 mSv above which dose monitoring of air crews is legally required in Germany. Measurements performed by means of neutron monitors have already shown that the relative intensity of secondary neutrons from cosmic radiation is enhanced during an SPE, particularly at regions close to the magnetic poles of the Earth where shielding of the cosmic radiation by the geomagnetic field is low. Here we describe a Bonner sphere spectrometer installed at the Koldewey station at 79°N, i.e. about 1,000 km from the geographic North pole, which is designed to provide first experimental data on the time-dependent energy spectrum of neutrons produced in the atmosphere during an SPE. This will be important to calculate doses from these neutrons to air crew members. The system is described in detail and first results are shown that were obtained during quiet periods of sun activity.     

A model method for testing cosmic radiation

The experiments showed that after gamma irradiation as well as after irradiation by secondary cosmic rays (hard component)Equisetum arvense spores produce in the first developmental phases prothalia at a changed rate,i.e. in favour of the females. This effect being specific for radiation cannot be produced by heat, pressure or changes of electric and magnetic field (i.e. factors appearing in higher sea levels with a stronger intensity of cosmic rays). It will be possible to apply the sensitivity of the mentioned method for investigating the problems of testing cosmic ray variations. The possibility of its application in spontaneous variability research is not less important.     

Computational study of radiation chemical processing in comet nuclei.

Cometary nuclei have been exposed to high levels of ionizing radiation since their formation. We present here some results of a computer model calculation of the effect of ionizing radiation on cometary material. The external (cosmic rays) and internal (embedded radionuclides) contributions in the processing of cometary nuclei are considered. As a first approximation we have used the available kinetic data of the liquid water system to model the radiation effects in a frozen cometary environment. Our [correction of out] data suggest that massive radiation chemical processing due to cosmic rays may have taken place only in the outer layers of comets. The internal contribution of radionuclides to the radiation processing of comet cores seems to be modest. Therefore, comets could be carriers of intact homochiral biomolecules.     

Computational study of radiation chemical processing in comet nuclei

Cometary nuclei have been exposed to high levels of ionizing radiation since their formation. We present here some results of a computer model calculation of the effect of ionizing radiation on cometary material. The external (cosmic rays) and internal (embedded radionuclides) contributions in the processing of cometary nuclei are considered. As a first approximation we have used the available kinetic data of the liquid water system to model the radiation effects in a frozen cometary environment. Out data suggest that massive radiation chemical processing due to cosmic rays may have taken place only in the outer layers of comets. The internal contribution of radionuclides to the radiation processing of comet cores seems to be modest. Therefore, comets could be carriers of intact homochiral biomolecules.Part of this work was carried out during a leave at the Laboratory of Chemical Evolution.     

Analytical Model for Estimating Terrestrial Cosmic Ray Fluxes Nearly Anytime and Anywhere in the World: Extension of PARMA/EXPACS

By extending our previously established model, here we present a new model called “PHITS-based Analytical Radiation Model in the Atmosphere (PARMA) version 3.0,” which can instantaneously estimate terrestrial cosmic ray fluxes of neutrons, protons, ions with charge up to 28 (Ni), muons, electrons, positrons, and photons nearly anytime and anywhere in the Earth’s atmosphere. The model comprises numerous analytical functions with parameters whose numerical values were fitted to reproduce the results of the extensive air shower (EAS) simulation performed by Particle and Heavy Ion Transport code System (PHITS). The accuracy of the EAS simulation was well verified using various experimental data, while that of PARMA3.0 was confirmed by the high R ² values of the fit. The models to be used for estimating radiation doses due to cosmic ray exposure, cosmic ray induced ionization rates, and count rates of neutron monitors were validated by investigating their capability to reproduce those quantities measured under various conditions. PARMA3.0 is available freely and is easy to use, as implemented in an open-access software program EXcel-based Program for Calculating Atmospheric Cosmic ray Spectrum (EXPACS). Because of these features, the new version of PARMA/EXPACS can be an important tool in various research fields such as geosciences, cosmic ray physics, and radiation research.     

Effect of space flight conditions on properties of hydrocarbon-oxidizing bacteria

Results of experiments on the Mir space station (EO-25 and EO-26) demonstrated that the conditions of orbital flight, primarily the cosmic radiation, was a mutagenic factor affecting both the genotype and phenotype of an oil-oxidizing bacterial strain, Mycobacterium flavescens EX-91. The emerging mutants differed from original culture by the rate of colony growth and the ability to ferment certain carbohydrates or synthesize beta-galactosidase. Changes in the rate of utilization of raw oil and individual hydrocarbon types (constituting model mixtures) suggest that cosmic radiation may serve as a means of obtaining mutant clones of microorganisms with new properties.     

Effects of space flight on the growth and some cytological characteristics of wheat seedlings.

Researchers report on the terrestrial growth of wheat seeds after exposure to microgravity and cosmic radiation in space. Some groups of experimental and control seeds were treated with cysteine before flight. The germination of space-flown seeds was not different from ground controls. Cysteine promoted growth in both experimental and control groups of seeds. Roots tips of seedlings grown from experimental seeds exhibited aberrant cells; preflight treatment with cysteine decreased the number of aberrant cells.     

Linking ‘10‐year’ herbivore cycles to the lunisolar oscillation: the cosmic ray hypothesis

The mean population cycle periods of the snowshoe hare Lepus americanus, the larch budmoth Zeiraphera diniana, and the autumnal moth Epirrita autumnata are 9.3 years, similar to the lunar nodal phase cycle. When the full/new Moon is situated close to the ecliptic plane at solstice, it interacts more strongly with the magnetosphere, which plays a crucial role in protecting the Earth against ionizing cosmic ray particles. Ionization by cosmic rays induces protein mobilization in plants, which may increase forage quality for herbivores. Series of hare/lynx population indices from Canadian provinces and an autumnal moth series from Fennoscandia correlated with the lunar nodal phase cycle with different time lags. Both the time lag and the impact of an active sun, which increases solar energetic particles, but decreases galactic cosmic ray particles, were related to radiation or the distance from the auroral oval. These insights improve our ability to explain and understand population peaks, and should also motivate further studies on the effects of cosmic rays on plant chemistry and herbivore performance.     

Mutation frequency of Dictyostelium discoideum spores exposed to the space environment.

Two strains of cellular slime mold Dictyostelium discoideum, a radiosensitive mutant and the parental wild-type strain, were used to investigate the effects of cosmic radiation on viability and mutation frequency at the spore stage for about 9 days in Space Shuttle of NASA. We measured little effect of space environment on viability and cell growth in the both strains as compared to ground controls. The mutation frequency of the flown spores were similar to that of ground control. These results suggest that there could be no effect of cosmic radiation, containing high linear energy transfer radiation at about 0.9 mSv/day as detected by real-time radiation monitoring device on the induction of mutation at the spore stage.     

The method based on generalized dosimetric function for estimation of cosmonauts' radiation hazard during long-term space missions

This paper presents a method of assessment of radiation hazard for cosmonauts. The method is based on a new dosimetric function, which enables a complicated nature of space radiation exposure to be reduced to the condition of a standard irradiation on Earth. It can be obtained on the basis of mean-tissue absorbed dose values calculated for each space radiation source, and transmission coefficients. The transmission coefficients define relative biological effectiveness of radiation and assess the influence on the radiobiological effects of the complex spatial and temporal distribution of the absorbed dose in the cosmonaut's body. The combination of cosmic ionizing radiation with other non-radiation nature factors in flight can be accounted.     

Proton irradiation suppresses angiogenic genes and impairs cell invasion and tumor growth

The energy deposition characteristics of proton radiation have attracted considerable attention in light of its implications for carcinogenesis risk in space travel, as well for application to cancer treatment. In space, it is the principle component of the galactic cosmic radiation to which astronauts will be exposed. For treatment, an increasing number of proton facilities are being established to exploit the physical advantages of this radiation type. However, the possibility that there may also be biologically based advantages to proton exposure has not been considered in either context. We demonstrate here that high-energy proton irradiation can inhibit expression of major pro-angiogenic factors and multiple angiogenesis-associated processes, including invasion and endothelial cell proliferation, which is prominent in cancer progression. Dose-dependent suppression of angiogenic signaling was demonstrated for both cancer and nontransformed cells. Pan-genomic microarray analysis and RT-PCR revealed that post-irradiation (0.5, 1.0 and 2.0 Gy), critical pro-angiogenic signaling factors including: vascular endothelial growth factor (VEGF), interleukin 6 and 8 (IL-6, IL-8) and hypoxia-inducible factor-1 alpha (HIF-1A), were significantly downregulated. Co-culture studies demonstrated that endothelial cell proliferation and invasion were inhibited by culturing with irradiated cancer or fibroblast cells, which suggests that proton irradiation may, in addition to direct action, contribute to angiogenesis suppression through modulation of paracrine signalings from targeted cells. Addition of recombinant IL-8 or VEGF partially restored these functions in vitro, while in vivo, an attenuated tumor growth rate was demonstrated for proton-irradiated human lung cancer cells. Taken together, these findings provide novel pre-clinical evidence that proton irradiation may, in addition to its physical targeting advantages, have important biological ramifications that should be a consideration in the optimization of proton therapy.     

The effects of high altitude cosmic radiation on some members ofAcanthaceae

To study the effect of high altitude cosmic radiation the seed material of 15 species ofAcanthaceae was subjected to 3 types of exposures in balloon flights at an altitude of 30 900 to 38 100 metres. Germination behaviour was recorded and cytological studies were made. In the material subjected to one exposure, no detectable cytological or morphological change could be recorded. Material subjected to two exposures showed a 1 1/2 to 2 fold increase in cellular dimensions. A fragmented chromosome was observed inRostellularia procumbens. Flowering inJusticia betonica was advanced by 3 weeks. Among the species subjected to 3 exposures, two species showed diminution in height, and entered into flowering earlier than the controls. A study of germination behaviour showed, in general, that the decrease in germination percentage was directly proportional to the amount of radiation. The results indicate that the treatment with cosmic radiation may be helpful in reducing the period between sowing and harvesting. Therefore, if similar experiments be conducted on crop plants, they might yiled interesting and important results from the agricultural point of view.     

An estimation of Canadian population exposure to cosmic rays

The worldwide average exposure to cosmic rays contributes to about 16% of the annual effective dose from natural radiation sources. At ground level, doses from cosmic ray exposure depend strongly on altitude, and weakly on geographical location and solar activity. With the analytical model PARMA developed by the Japan Atomic Energy Agency, annual effective doses due to cosmic ray exposure at ground level were calculated for more than 1,500 communities across Canada which cover more than 85% of the Canadian population. The annual effective doses from cosmic ray exposure in the year 2000 during solar maximum ranged from 0.27 to 0.72 mSv with the population-weighted national average of 0.30 mSv. For the year 2006 during solar minimum, the doses varied between 0.30 and 0.84 mSv, and the population-weighted national average was 0.33 mSv. Averaged over solar activity, the Canadian population-weighted average annual effective dose due to cosmic ray exposure at ground level is estimated to be 0.31 mSv.     

Biological effects of weightlessness at the cellular level. Comparative study of cultures of Paramecia aboard the orbital station Salyut-6 and a stratospheric balloon

In order to distinguish the effects of cosmic rays from those of weightlessness at the cellular level, we performed experiments aboard stratospheric balloon, where gravity is equal to 1 g and cosmic radiation roughly equal to that aboard Salyut-6. The results suggest that the stimulation of cell proliferation is probably due to cosmic rays, metabolic changes being related to microgravity.     

Effect of Space Flight Conditions on the Properties of Hydrocarbon-Oxidizing Bacteria

Results of experiments on the Mir space station (EO-25 and EO-26) demonstrated that the conditions of orbital flight, primarily cosmic radiation, were a mutagenic factor affecting both the genotype and phenotype of an oil-oxidizing bacterial strain, Mycobacterium flavescensEX-91. The emerging mutants differed from the original culture by the rate of colony growth and the ability to ferment certain carbohydrates or synthesize -galactosidase. Changes in the rate of utilization of raw oil and individual hydrocarbon types (constituting model mixtures) suggest that cosmic radiation may serve as a means of obtaining mutant clones of microorganisms with new properties.     

Potential impacts of radon, terrestrial gamma and cosmic rays on childhood leukemia in France: a quantitative risk assessment

Previous epidemiological studies and quantitative risk assessments (QRA) have suggested that natural background radiation may be a cause of childhood leukemia. The present work uses a QRA approach to predict the excess risk of childhood leukemia in France related to three components of natural radiation: radon, cosmic rays and terrestrial gamma rays, using excess relative and absolute risk models proposed by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Both models were developed from the Life Span Study (LSS) of Japanese A-bomb survivors. Previous risk assessments were extended by considering uncertainties in radiation-related leukemia risk model parameters as part of this process, within a Bayesian framework. Estimated red bone marrow doses cumulated during childhood by the average French child due to radon, terrestrial gamma and cosmic rays are 4.4, 7.5 and 4.3 mSv, respectively. The excess fractions of cases (expressed as percentages) associated with these sources of natural radiation are 20 % [95 % credible interval (CI) 0–68 %] and 4 % (95 % CI 0–11 %) under the excess relative and excess absolute risk models, respectively. The large CIs, as well as the different point estimates obtained under these two models, highlight the uncertainties in predictions of radiation-related childhood leukemia risks. These results are only valid provided that models developed from the LSS can be transferred to the population of French children and to chronic natural radiation exposures, and must be considered in view of the currently limited knowledge concerning other potential risk factors for childhood leukemia. Last, they emphasize the need for further epidemiological investigations of the effects of natural radiation on childhood leukemia to reduce uncertainties and help refine radiation protection standards.     

Polarization of electromagnetic radiation at the second harmonic of the electron gyrofrequency in a turbulent plasma

A study is made of the polarization of electromagnetic radiation at the second harmonic of the electron gyrofrequency. The radiation is emitted by a highly ionized collisionless plasma in which the turbulence is excited at electron gyrofrequencies in a strong magnetic field. The mechanism for the generation of electromagnetic waves during mergings of the gyrofrequency plasmons is analyzed. It is shown that, even in a strong magnetic field, the degree of circular polarization of electromagnetic radiation at the second harmonic of the electron gyrofrequency may be moderate or weak.     

Problems of ensuring human radiation safety during interplanetary flights

The work contains the analyses and discussion of the main sources of space radiation specified for interplanetary flights, the dosimetric functionals used for describing the processes of radiation lesions and reparation of the organism in the conditions of the complex radiation impact with a broad charge composition of cosmic rays and a peculiar spatial and temporal dose behavior. It represents the results of calculations of the radiation risks during the flight and the total lifelong radiation risk with taking into account all the delayed unfavorable biological consequences. The main uncertainties in the calculated values of radiation risk leading to its undervaluation are analyzed. In addition, also provided is the range of theoretical and experimental investigations necessary for the adjustment of coefficient values used in the algorithm of radiation risk calculations, as well as in the nomenclature of experiments for estimating the individual resistance of man to the extreme influence and investigations aimed at estimating and increasing the reliability of the operator activity of cosmonauts.     

Effects of reduced natural background radiation on Drosophila melanogaster growth and development as revealed by the FLYINGLOW program

Natural background radiation of Earth and cosmic rays played a relevant role during the evolution of living organisms. However, how chronic low doses of radiation can affect biological processes is still unclear. Previous data have indicated that cells grown at the Gran Sasso Underground Laboratory (LNGS, L'Aquila) of National Institute of Nuclear Physics (INFN) of Italy, where the dose rate of cosmic rays and neutrons is significantly reduced with respect to the external environment, elicited an impaired response against endogenous damage as compared to cells grown outside LNGS. This suggests that environmental radiation contributes to the development of defense mechanisms at cellular level. To further understand how environmental radiation affects metabolism of living organisms, we have recently launched the FLYINGLOW program that aims at exploiting Drosophila melanogaster as a model for evaluating the effects of low doses/dose rates of radiation at the organismal level. Here, we will present a comparative data set on lifespan, motility and fertility from different Drosophila strains grown in parallel at LNGS and in a reference laboratory at the University of L'Aquila. Our data suggest the reduced radiation environment can influence Drosophila development and, depending on the genetic background, may affect viability for several generations even when flies are moved back to normal background radiation. As flies are considered a valuable model for human biology, our results might shed some light on understanding the effect of low dose radiation also in humans.     

Time series analysis supporting the hypothesis that enhanced cosmic radiation during germ cell formation can increase breast cancer mortality in germ cell cohorts

 Techniques from cancer epidemiology and time series analysis were used to explore the hypothesis that cosmic radiation can induce germ cell changes leading to increases in future breast cancer mortality. A birth cohort time series for female breast cancer mortality was obtained using a model-independent, age-period-cohort analysis on age-specific mortality data for 1940–1990. The birth cohort series contained several oscillatory components, which were isolated and compared to the corresponding frequency components of a cosmic ray surrogate time series – Greenland ice-core ¹⁰Be concentrations. A technique, referred to as component wave-train alignment, was used to show that the breast cancer and cosmic ray oscillations were phase-locked approx. 25 years before the time of birth. This is consistent with the time of germ cell formation, which occurs during the fetal development stage of the preceding generation. Evidence is presented that the observable oscillations in the birth cohort series were residues of oscillations of much larger amplitude in the germ cell cohort, which were attenuated by the effect of the broad maternal age distribution. It is predicted that a minimum of 50% of breast cancer risk is associated with germ cell damage by cosmic radiation (priming event), which leads to the development of individuals with a higher risk of breast cancer. It is proposed that the priming event, by preceding other steps of carcinogenesis, works in concert with risk factor exposure during life. The priming event is consistent with epigenetic changes such as imprinting. Received: 10 June 1996 / Revised: 4 December 1996 / Accepted: 19 December 1996