The Mars Science Laboratory spacecraft, containing the Curiosity rover, was launched to Mars on 26 November 2011, and for most of the 253-day, 560-million-kilometer cruise to Mars, the Radiation ...Assessment Detector made detailed measurements of the energetic particle radiation environment inside the spacecraft. These data provide insights into the radiation hazards that would be associated with a human mission to Mars. We report measurements of the radiation dose, dose equivalent, and linear energy transfer spectra. The dose equivalent for even the shortest round-trip with current propulsion systems and comparable shielding is found to be 0.66 ± 0.12 sievert.
The Radiation Assessment Detector (RAD) on the Mars Science Laboratory (MSL) is an energetic particle detector designed to measure a broad spectrum of energetic particle radiation. It will make the ...first-ever direct radiation measurements on the surface of Mars, detecting galactic cosmic rays, solar energetic particles, secondary neutrons, and other secondary particles created both in the atmosphere and in the Martian regolith. The radiation environment on Mars, both past and present, may have implications for habitability and the ability to sustain life. Radiation exposure is also a major concern for future human missions. The RAD instrument combines charged- and neutral-particle detection capability over a wide dynamic range in a compact, low-mass, low-power instrument. These capabilities are required in order to measure all the important components of the radiation environment.
RAD consists of the RAD Sensor Head (RSH) and the RAD Electronics Box (REB) integrated together in a small, compact volume. The RSH contains a solid-state detector telescope with three silicon PIN diodes for charged particle detection, a thallium doped Cesium Iodide scintillator, plastic scintillators for neutron detection and anti-coincidence shielding, and the front-end electronics. The REB contains three circuit boards, one with a novel mixed-signal ASIC for processing analog signals and an associated control FPGA, another with a second FPGA to communicate with the rover and perform onboard analysis of science data, and a third board with power supplies and power cycling or “sleep”-control electronics. The latter enables autonomous operation, independent of commands from the rover. RAD is a highly capable and highly configurable instrument that paves the way for future compact energetic particle detectors in space.
Canada's experience with immigration has been comparatively positive and mass immigration has considerable popular support within the country. The distinctive Canadian policy model-including large ...numbers with skill-based selection, multiculturalism and other policies aimed at promoting integration, and provincial autonomy-deserves international attention. However, Canada's success with immigration is only partly related to its policies and these may not be easily transferable to other contexts. Skill-based immigrant selection may be the most important feature of the Canadian model contributing to its success, and the effectiveness of this policy is clearly contingent on border control, which in the case of Canada is facilitated by geographical isolation. Canada's symbolic commitment to multiculturalism emphasizes the social integration of immigrants and this goal is also served by significant social services supporting settlement and language acquisition. The most significant distinctive feature of the Canadian approach to immigration may be the belief that immigration represents a positive opportunity to build the economy and develop the country. This belief represents a resource helping the country address some of the current problems confronting immigration, including reduced employment success of immigrants and evidence that racial divisions have significance particularly for certain groups. The belief in mass immigration as a positive resource and development opportunity underlies much of the positive discourse on immigration in Canada.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The European Space Agency (ESA) is currently expanding its efforts in identifying requirements and promoting research towards optimizing radiation protection of astronauts. Space agencies use common ...limits for tissue (deterministic) effects on the International Space Station. However, the agencies have in place different career radiation exposure limits (for stochastic effects) for astronauts in low-Earth orbit missions. Moreover, no specific limits for interplanetary missions are issued. Harmonization of risk models and dose limits for exploratory-class missions are now operational priorities, in view of the short-term plans for international exploratory-class human missions. The purpose of this paper is to report on the activity of the ESA Topical Team on space radiation research, whose task was to identify the most pertinent research requirements for improved space radiation protection and to develop a European space radiation risk model, to contribute to the efforts to reach international consensus on dose limits for deep space. The Topical Team recommended ESA to promote the development of a space radiation risk model based on European-specific expertise in: transport codes, radiobiological modelling, risk assessment, and uncertainty analysis. The model should provide cancer and non-cancer radiation risks for crews implementing exploratory missions. ESA should then support the International Commission on Radiological Protection to harmonize international models and dose limits in deep space, and guarantee continuous support in Europe for accelerator-based research configured to improve the models and develop risk mitigation strategies.
The 10–12 September Solar Energetic Particle event produced the strongest increase of the radiation environment measured by the Radiation Assessment Detector on the surface of Mars since landing in ...August 2012. We report the details of the measurements of the energetic particle environment from Radiation Assessment Detector in Gale crater during this event. The Solar Energetic Particle event increased the low‐energy proton flux (below 100 MeV) by a factor of 30, and the higher‐energy proton flux by a factor of 4, above preevent levels. The 4He flux (below 100 MeV/nuc) rose by factors up to 10, and neutral particles by a factor of 2 above background. The increase started on 10 September around 19:50 UTC, peak‐level fluxes were reached on the morning of 11 September and prevailed for about 10 hr before decreasing toward background levels. The onset of a Forbush decrease on 13 September decreased the proton flux below preevent intensities.
Plain Language Summary
On 10 September 2017, increased solar activity produced a solar energetic particle (SEP)event. This SEP event arrived at Mars around UTC 20:00 the same day in form of energetic particles accelerated to high enough energies to reach the Martian surface. We report here measurements of the energetic particle environment during the event in Gale crater on Mars, made with the Radiation Assessment Detector on board NASA's Curiosity rover. The SEPs increased the Martian surface proton flux below 100‐MeV energy by a factor of 30, and by a factor of 4 at higher energies. The neutral particle environment doubled during the event, which is of particular interest for the planning of solar storm shelters, as the shielding is less effective against neutrons as it is against charged particles. The increase in proton flux was the highest so far observed by Radiation Assessment Detector since landing on Mars in August 2012. However, stronger SEP events are possible that can increase the Martian radiation environment by orders of magnitude more. This makes monitoring the effect of SEPs crucial as radiation remains one of the major health risks for astronauts on exploration missions.
Key Points
On 11 September 2017, RAD observed the strongest solar particle event on the Martian surface since landing
Proton fluxes at the Martian surface increased by factors of up to 30, helium fluxes by factors up to 10
Doubling of neutral particle counts is important for planning of future storm shelter shielding, which is not as effective against neutrons
Magnetic Resonance Imaging (MRI) is a reliable method, with a complementary role to Ultrasound (US) Echocardiography, that can be used to fully comprehend and precisely diagnose congenital cardiac ...malformations. Besides the anatomical study of the fetal cardiovascular system, it allows us to study the function of the fetal heart, remaining, at the same time, a safe adjunct to the classic fetal echocardiography. MRI also allows for the investigation of cardiac and placental diseases by providing information about hematocrit, oxygen saturation, and blood flow in fetal vessels. It is crucial for fetal medicine specialists and pediatric cardiologists to closely follow the advances of fetal cardiac MRI in order to provide the best possible care. In this review, we summarize the advance in techniques and their practical utility to date.
Solar radiation is among the most prominent stress factors organisms face during space travel and possibly on other planets. Our analysis of three different halophilic archaea, namely Halobacterium ...salinarum NRC-1, Halococcus morrhuae, and Halococcus hamelinensis, which were exposed to simulated solar radiation in either dried or liquid state, showed tremendous differences in tolerance and survivability. We found that Hcc. hamelinensis is not able to withstand high fluences of simulated solar radiation compared to the other tested organisms. These results can be correlated to significant differences in genomic integrity following exposure, as visualized by random amplified polymorphic DNA (RAPD)-PCR. In contrast to the other two tested strains, Hcc. hamelinensis accumulates compatible solutes such as trehalose for osmoprotection. The addition of 100 mM trehalose to the growth medium of Hcc. hamelinensis improved its survivability following exposure. Exposure of cells in liquid at different temperatures suggests that Hbt. salinarum NRC-1 is actively repairing cellular and DNA damage during exposure, whereas Hcc. morrhuae exhibits no difference in survival. For Hcc. morrhuae, the high resistance against simulated solar radiation may be explained with the formation of cell clusters. Our experiments showed that these clusters shield cells on the inside against simulated solar radiation, which results in better survival rates at higher fluences when compared to Hbt. salinarum NRC-1 and Hcc. hamelinensis. Overall, this study shows that some halophilic archaea are highly resistant to simulated solar radiation and that they are of high astrobiological significance.
Halophiles-Solar radiation-Stress resistance-Survival.
We report dosimetric quantities measured by the Mars Science Laboratory Radiation Assessment Detector (RAD) on the surface of Mars during the 10–12 September 2017 solar particle event. Despite ...23 g/cm2 of CO2 shielding provided by the atmosphere above RAD, dose rates rose above background galactic cosmic ray levels by factors of 2 to 3 over the course of several hours and leveled off at sustained peak rates for about 12 hr before declining over the following 36 hr. As the solar particle event flux was gradually declining, a shock front reached Mars and caused a sudden drop of about 15% in instantaneous dose rates. No solar particles followed the shock arrival, and the magnetic shielding of galactic cosmic rays by the shock reduced their intensity to levels below those seen before the start of the event. This event is the largest seen to date by RAD on Mars.
Plain Language Summary
We report the radiation dose rate on the surface of Mars measured by the Radiation Assessment Detector (RAD) aboard the Curiosity rover before, during, and after the solar energetic particle (SEP) event of 10–12 September 2017. Future astronauts exploring Mars will be at risk from SEP events, which occur sporadically and often with little warning, as well as from galactic cosmic rays, which are a continuous source of radiation dose and which generally have higher energies than SEPs. The event described here was the largest so far observed by RAD in more than five years on Mars. Although the atmosphere of Mars is only about 1–2% as thick as Earth's, it provides a measure of shielding against solar particles, most of which are protons with energies insufficient to penetrate Mars' atmosphere and reach the surface. But in this event, RAD saw a clear increase in dose rates; the peak dose rate was nearly three times above galactic cosmic ray levels measured prior to the event. Though the increase was rapid and lasted for three days, it was too small to represent a risk to the health of an astronaut receiving it. Much larger SEP events are possible and could cause problematic doses.
Key Points
Protons accelerated during the large solar particle event of September 2017 reached the surface of Mars and were observed by MSL‐RAD
Dose rates were seen to increase by factors of 2 to 3 above the background level of the galactic cosmic rays
Doses integrated over a 30‐day interval that included the event remained well below NASA radiation exposure limits for astronauts
Although previous studies have examined the role of religion in immigrant integration, little systematic knowledge is available on how much and through which mechanisms religion facilitates or ...hinders immigrant socioeconomic and cultural integration. The papers in this collection explore the role of religion in the socioeconomic and cultural integration of immigrants and minorities from a cross-national perspective, with a particular focus on the experiences of immigrant youth. The formative years of adolescence and early adulthood serve as the foundation for individuals' later integration trajectories. In this introductory editorial, we describe the methodological challenges associated with the study of the role of religion in minorities' integration, and then identify five mechanisms that are prominent in the literature on the effects of religion. We then summarise the key findings reported in the papers included in this collection, and show how they help us understand these mechanisms. These papers highlight variations in the impact of minority religions on facilitating or hampering integration, and help clarify inferences regarding the significance of discrimination against minorities who have certain religious affiliations, such as Muslims. They also underscore the role of social, cultural and economic contexts in determining how religious affiliation is associated with integration outcomes.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
An interdisciplinary synthesis of Canadian research on immigrant employment success points toward key research priorities. Four determinants of immigrant employment success are widely recognized as ...significant: immigration policy and settlement patterns, "entry" and assimilation over time, lower value of immigrant human capital, and origins of immigrants and the possibility of discrimination. Other determinants include labour market niches, social and cultural capital, and institutional contexts. Addressing key research priorities-and distinguishing individual and contextual causes-will require new analytic strategies and sources of data. A companion paper, Part II: Understanding the Decline, applies the framework presented here to research on declining employment success for immigrants. Adapted from the source document.
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