| 1. |
- Akrawy, Dashty T., et al.
(författare)
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New empirical formula for calculating (n, p) reaction cross-sections at 14.5 MeV neutrons
- 2020
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Ingår i: International Journal of Modern Physics E. - 0218-3013. ; 29:8
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Forskningsöversikt (refereegranskat)abstract
- An empirical formula to calculate the (n, p) reaction cross-sections for 14.5 MeV neutrons for 183 target nuclei in the range 44 ≤ A ≤ 212 is presented. Evaluated cross-section data from TENDL nuclear data library were used to test and benchmark the formula. In this new formula, the nonelastic cross-section term is replaced by the atomic number Z, while the asymmetry parameter-dependent exponential term has been retained. The calculated results are presented in comparison with the seven previously published formulae. We show that the new formula is significantly in better agreement with the measured values compared to previously published formulae.
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| 2. |
- Akrawy, Dashty T., et al.
(författare)
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α-decay half-lives new semi-empirical relationship including asymmetry, angular momentum and shell effects
- 2022
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 1021
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Tidskriftsartikel (refereegranskat)abstract
- We present a modified version of the semi-empirical formula SemFIS, which is based on the fission theory for predicting the alpha decay half-lives. The first version of SemFIS was found by D. N. Poenaru et al. and was at that time the best formula to predict the alpha-decay half-lives of superheavy nuclei among 18 different existing models. We compare a modified version of SemFIS against the old version and experimental data for four groups of alpha emitters: even-even; even-odd; odd-even, and odd-odd parent nuclei. Two sets of experimental values are used: set A, and set B. There are 356 nuclides in set A [137 e-e, 90 e-o, 66 o-e, and 63 o-o with Zmin, Zmax of (52,118); (52,112); (63,117), and (53,117), and Amin, Amax of (108,294); (107,281); (147,293), and (110,294), respectively]. Set B includes 420 α-emitters [144 e-e, 112 e-o, 84 o-e, and 80 o-o] with Zmin, Zmax of (52,118); (52,116); (53,117), and (53,117), and Amin, Amax of (106,294); (105,293);(111,293) and (110,294)]. Our study shows that the modified version of SemFIS gives better agreements with the experimental data than previously published versions.
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| 3. |
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| 4. |
- Luoni, F., et al.
(författare)
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Total nuclear reaction cross-section database for radiation protection in space and heavy-ion therapy applications
- 2021
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 23:10
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Forskningsöversikt (refereegranskat)abstract
- Realistic nuclear reaction cross-section models are an essential ingredient of reliable heavy-ion transport codes. Such codes are used for risk evaluation of manned space exploration missions as well as for ion-beam therapy dose calculations and treatment planning. Therefore, in this study, a collection of total nuclear reaction cross-section data has been generated within a GSI-ESA-NASA collaboration. The database includes the experimentally measured total nucleus-nucleus reaction cross-sections. The Tripathi, Kox, Shen, Kox-Shen, and Hybrid-Kurotama models are systematically compared with the collected data. Details about the implementation of the models are given. Literature gaps are pointed out and considerations are made about which models fit best the existing data for the most relevant systems to radiation protection in space and heavy-ion therapy.
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| 5. |
- Mortazavi, S. A.R., et al.
(författare)
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Can Reactivation of SARS-CoV-2 Decrease the Chance of Success of Future Deep Space Missions?
- 2021
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Ingår i: IEEE Aerospace Conference Proceedings. - 1095-323X. ; 2021-March
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Konferensbidrag (refereegranskat)abstract
- Korean CDC experts first reported the likelihood of reactivation in COVIOD-19 patients. They hypothesized that like childhood chicken pox infections which lie dormant for tens of years only to cause shingles in seniors, SARS-CoV-2 can reactivate. However, as testing for the virus had been flawed at that time, U.S. infectious disease experts were skeptical about the reports of second COVID-19 infections. New reports have addressed the urgent need to conduct large-scale studies to better understand the potential recurrence of SARS-CoV-2 in COVID-19 patients. Moreover, some case studies show possible reactivation of SARS-CoV-2 in a family cluster. Given this consideration, major space stressors such as microgravity and space radiation and their interactions which are not fully known, so far can increase the risk of reactivation of SARS-CoV-2 in future space missions, an event that can easily impact the success of any space mission. Since about 80% of infected people are either asymptomatic or show only mild symptoms, in a near future, it would be likely that astronauts who start their mission even after complex medical examinations, experience reactivation of the virus during their mission. Moreover, we have previously addressed the potential higher fatality of COVID-19 infections in space due to 1) uselessness of social distancing due to microgravity 2) immune system dysregulation 3) possibly higher mutation rates of the novel coronavirus (SARS-CoV-2) as a RNA virus 4) higher risk of reactivation of the virus 5) existence of strong selective pressure and 6) decreased maximum oxygen uptake.
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| 6. |
- Mortazavi, S. M. J., et al.
(författare)
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Can Adaptive Response and Evolution Make Survival of Extremophile Bacteria Possible on Mars?
- 2020
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Ingår i: 2020 IEEE AEROSPACE CONFERENCE (AEROCONF 2020). - 1095-323X. - 9781728127347
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Konferensbidrag (refereegranskat)abstract
- The humidity on the surface of the red planet, Mars, drops steeply during the daytime as the temperature rises. In this situation, Martian microorganisms should have the capability to cope with desiccation. Extremophiles are microorganisms that are capable of surviving in extreme environmental conditions. It has previously been shown that a pre-exposure to low levels of either ionizing or non-ionizing radiation can induce resistance against subsequent exposure to high levels of different stressors (e.g. high doses of ionizing radiation) in a wide variety of living systems. Moreover, it has been shown that E. coli bacteria repeatedly exposed to a dose needed for 1% survival, and increasing the dose each time due to increased radioresistance for the same survival (1%), generates extremely radioresistant bacteria through directed evolution. Mortazavi et al. have warned that in a similar manner with extremophiles such as Deinococcus radiodurans, it would be very likely that this type of human-directed radioresistance makes E. coli bacteria resistant to all physical and chemical agents (generation of serious life-threatening micro-organisms). There are reports about the possibility of the existence of microbes in the salty puddles of Mars. On Mars, with its thin atmosphere and lack of the protective magnetic field, higher levels of space radiation cause more genetic mutations. Interestingly, these mutations in bacteria, which can make them resistant against radiation, can also make them resistant against desiccation. Moreover, the adaptive response to radiation in bacteria might play an important role in this process. As stated in a NASA report, the cells in the astronauts will be traversed by multiple protons before exposure to HZE particles. This sequential exposure might significantly increase the resistance against radiation. The same exposure in bacteria might not only induce resistance against the high levels of damage caused by HZEs, but also to other life-threatening factors for bacteria such as desiccation. In this paper, the current understanding of extremophiles and their capability of surviving in extreme environmental conditions as well as current findings about radioadaptive responses in bacteria will be discussed.
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| 7. |
- Mortazavi, S. M. J., et al.
(författare)
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Does Exposure of Astronauts' Brains to High-LET Radiation in Deep Space Threaten the Success of the Mission?
- 2020
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Ingår i: 2020 IEEE AEROSPACE CONFERENCE (AEROCONF 2020). - 1095-323X. - 9781728127347
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Konferensbidrag (refereegranskat)abstract
- Astronauts' exposure to radiation is different from exposure to radiation on Earth. Besides cancer, cardiovascular disease and acute radiation syndrome, there are concerns over the potential behavioral and cognitive impairments caused by exposure of the astronauts' central nervous system to high levels of space radiation. Therefore, potential behavioral and cognitive i mpairments caused by astronauts' brains exposure to high levels of space radiation and the possibility of developing dementia and other motor neuron diseases are getting more attention. As NASA is interested in studies on radium deposition in human brain, and exposure of the brain to high linear energy transfer (LET) alpha particles, we have assessed the cognitive effects of long-term exposure of human brain to alpha particles which partly mimics astronauts' exposure to high charge and energy (HZE) particles during upcoming mars missions. Dr. John Boice, President of NCRP, and his colleagues' have stated that human brain exposed for years to alpha particles on Earth may be more relevant to a Mars mission in contrast with the mouse brain exposed to heavy ions for a few minutes. Interestingly, both Boice and NASA did not pay enough attention to this fact that radium as well as many other alpha emitters tend to accumulate in the bone, and the alpha particles whose energies are typically -5 MeV have a very short range (maximum lOs of um), so the radiation dose due to the alpha emitters would be localized to volumes near the cranium rather than being uniformly distributed throughout the cerebral and cerebellar parenchyma. Extraordinary high levels of Ra-226 have previously been reported in high background radiation areas of Ramsar, where people are consuming locally grown foods. In this paper, we will present data which provide a human brain radiation exposure analogue for upcoming Mars missions. Normally the dose to the functional parts of the brain are not likely to be significant, even with higher uptakes of the radium or other alpha-emitting isotopes in the cranium. Therefore, only residents with calcium-rich diet were selected for the study. Measurements of background gamma radiation was performed in their bedrooms, dining rooms, vegetable yards and gardens with citrus fruit trees of the dwellings in areas with high levels of Ra-226 in the soil and at a nearby control area with the same socio-economic factors. Moreover, the food frequency, reaction time, working memory and computational abilities as well as the Radium Ingestion Index (RII) of 47 participants (22 males and 24 females) from the hot areas, where the annual radiation absorbed dose from background radiation is up to 260 mSv/y, were studied, and the same things were studied for 17 participants (4 males and 13 females) from a nearby normal background radiation area with the same socioeconomic factors as at the hot areas. Our study showed that exposure of human brain to high LET particles did not affect the working memory. However, individuals with higher levels of radium ingestion had significantly increased reaction times. The increased reaction time in individuals with higher exposure levels to alpha particles emitted from ingested Ra-226 is an important finding, since similar conditions might occur in deep space, when astronauts' brain cells are exposed to HZE particles. As the astronauts face numerous challenges in isolated and confined space environment, they should be able to respond quickly to different hazards. However, further studies are needed to verify if the fmdings in high radiation dose areas in Ramsar are relevant for deep space mission.
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| 8. |
- Mortazavi, S. M. J., et al.
(författare)
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Radioadaptation of Astronauts' Microbiome and Bodies in a Deep Space Mission to Mars and Beyond
- 2020
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Ingår i: 2020 IEEE AEROSPACE CONFERENCE (AEROCONF 2020). - 1095-323X. - 9781728127347
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Konferensbidrag (refereegranskat)abstract
- During manned space missions, humans will be accompanied by microorganisms. This prompts us to study the characteristics of bacteria grown in space [1]. It has been shown that a pre-exposure to low levels of either ionizing or non-ionizing radiation can make microorganisms more resistant not only to high doses of ionizing radiation but to any factor that threatens their survival (e.g. antibiotics) [2,3]. This phenomenon that is called "adaptive response" (i.e. increased resistance in living organisms pre-exposed to a low level stressor such as a low dose of ionizing radiation) [4] significantly increases the risk of serious infections in deep space missions. It's worth noting that both animal and human data confirm the disruption of the immune system during spaceflight [5]. In addition, the virulence of bacteria can also be increased significantly in space [4], hence this kind of adaptive response which increases the resistance of bacteria can endanger the astronauts' lives in space. On the other hand, A NASA report notes that as astronauts' cells will be exposed to multiple protons before being traversed by HZE particles, they can show adaptive responses. Given this consideration, it would be realistic to expect co-radioadaptation of astronauts' microbiome and their body in a deep space journey to Mars and beyond. The complexity of these phenomena and current uncertainties, which highlight the need for further studies before any long-term manned mission, will be discussed in this paper.
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| 9. |
- Norbury, John W., et al.
(författare)
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Are Further Cross Section Measurements Necessary for Space Radiation Protection or Ion Therapy Applications? Helium Projectiles
- 2020
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Ingår i: Frontiers in Physics. - : Frontiers Media SA. - 2296-424X. ; 8
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Forskningsöversikt (refereegranskat)abstract
- The helium ((Formula presented.) He) component of the primary particles in the galactic cosmic ray spectrum makes significant contributions to the total astronaut radiation exposure. (Formula presented.) He ions are also desirable for direct applications in ion therapy. They contribute smaller projectile fragmentation than carbon ((Formula presented.) C) ions and smaller lateral beam spreading than protons. Space radiation protection and ion therapy applications need reliable nuclear reaction models and transport codes for energetic particles in matter. Neutrons and light ions ((Formula presented.) H, (Formula presented.) H, (Formula presented.) H, (Formula presented.) He, and (Formula presented.) He) are the most important secondary particles produced in space radiation and ion therapy nuclear reactions; these particles penetrate deeply and make large contributions to dose equivalent. Since neutrons and light ions may scatter at large angles, double differential cross sections are required by transport codes that propagate radiation fields through radiation shielding and human tissue. This work will review the importance of (Formula presented.) He projectiles to space radiation and ion therapy, and outline the present status of neutron and light ion production cross section measurements and modeling, with recommendations for future needs.
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| 10. |
- Sihver, Lembit, 1962, et al.
(författare)
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Biological protection in deep space missions
- 2021
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Ingår i: Journal of Biomedical Physics and Engineering. - : Salvia Medical Sciences Ltd. - 2251-7200. ; 11:6, s. 663-674
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Forskningsöversikt (refereegranskat)abstract
- During deep space missions, astronauts are exposed to highly ionizing radiation, incl. neutrons, protons and heavy ions from galactic cosmic rays (GCR), solar wind (SW) and solar energetic particles (SEP). This increase the risks for cancerogenisis, damages in central nervous system (CNS), cardiovascular diseases, etc. Large SEP events can even cause acute radiation syndrome (ARS). Long term manned deep space missions will therefor require unique radiation protection strategies. Since it has been shown that physical shielding alone is not sufficient, this paper propose pre-flight screening of the aspirants for evaluation of their level of adaptive responses. Methods for boosting their immune system, should also be further investigated, and the possibility of using radiation effect modulators are discussed. In this paper, especially, the use of vitamin C as a promising non-toxic, cost-effective, easily available radiation mitigator (which can be used hours after irradiation), is described. Although it has previously been shown that vitamin C can decrease radiation-induced chromosomal damage in rodents, it must be further investigated before any conclusions about its radiation mitigating properties in humans can be concluded.
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