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- 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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- Agustin, Melissa B., et al.
(författare)
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Lignin nanoparticles as co-stabilizers and modifiers of nanocellulose-based Pickering emulsions and foams
- 2023
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Ingår i: Cellulose. - : Springer Nature. - 0969-0239 .- 1572-882X. ; 30:14, s. 8955-8971
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Tidskriftsartikel (refereegranskat)abstract
- Nanocellulose is very hydrophilic, preventing interactions with the oil phase in Pickering emulsions. This limitation is herein addressed by incorporating lignin nanoparticles (LNPs) as co-stabilizers of nanocellulose-based Pickering emulsions. LNP addition decreases the oil droplet size and slows creaming at pH 5 and 8 and with increasing LNP content. Emulsification at pH 3 and LNP cationization lead to droplet flocculation and rapid creaming. LNP application for emulsification, prior or simultaneously with nanocellulose, favors stability given the improved interactions with the oil phase. The Pickering emulsions can be freeze–dried, enabling the recovery of a solid macroporous foam that can act as adsorbent for pharmaceutical pollutants. Overall, the properties of nanocellulose-based Pickering emulsions and foams can be tailored by LNP addition. This strategy offers a unique, green approach to stabilize biphasic systems using bio-based nanomaterials without tedious and costly modification procedures.
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- Parsaei, S., et al.
(författare)
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Effect of test-caused degradation on the unavailability of standby safety components
- 2024
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Ingår i: Nuclear engineering and technology. - : Elsevier. - 1738-5733 .- 2234-358X. ; 56:2, s. 526-535
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a safety-critical standby component unavailability model that contains aging effects caused by the elapsed time from installation, component degradation due to surveillance tests, and imperfect maintenance actions. An application of the model to a Motor-Operated Valve and a Motor-Driven Pump involved in the HPIS of a VVER/1000-V446 nuclear power plant is demonstrated and compared with other existing models at component and system levels. In addition, the effects of different unavailability models are reflected in the NPP's risk criterion, i.e., core damage frequency, over five maintenance periods. The results show that, compared with other models that do not simultaneously consider the full effects of degradation and maintenance impacts, the proposed model realistically evaluates the unavailabilities of the safety-related components and the involved systems as a plant age function. Therefore, it can effectively reflect the age-dependent CDF impact of a given testing and maintenance policy in a specified time horizon.
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