1,559 research outputs found
Dose Calibration of the ISS-RAD Fast Neutron Detector
The ISS-RAD instrument has been fabricated by Southwest Research Institute and delivered to NASA for flight to the ISS in late 2015 or early 2016. ISS-RAD is essentially two instruments that share a common interface to ISS. The two instruments are the Charged Particle Detector (CPD), which is very similar to the MSL-RAD detector on Mars, and the Fast Neutron Detector (FND), which is a boron-loaded plastic scintillator with readout optimized for the 0.5 to 10 MeV energy range. As the FND is completely new, it has been necessary to develop methodology to allow it to be used to measure the neutron dose and dose equivalent. This talk will focus on the methods developed and their implementation using calibration data obtained in quasi-monoenergetic (QMN) neutron fields at the PTB facility in Braunschweig, Germany. The QMN data allow us to determine an approximate response function, from which we estimate dose and dose equivalent contributions per detected neutron as a function of the pulse height. We refer to these as the "pSv per count" curves for dose equivalent and the "pGy per count" curves for dose. The FND is required to provide a dose equivalent measurement with an accuracy of 10% of the known value in a calibrated AmBe field. Four variants of the analysis method were developed, corresponding to two different approximations of the pSv per count curve, and two different implementations, one for real-time analysis onboard ISS and one for ground analysis. We will show that the preferred method, when applied in either real-time or ground analysis, yields good accuracy for the AmBe field. We find that the real-time algorithm is more susceptible to chance-coincidence background than is the algorithm used in ground analysis, so that the best estimates will come from the latter
GCR access to the Moon as measured by the CRaTER instrument on LRO
[1] Recent modeling efforts have yielded varying and conflicting results regarding the possibility that Earth\u27s magnetosphere is able to shield energetic particles of \u3e10 MeV at lunar distances. This population of particles consists of galactic cosmic rays as well as energetic particles that are accelerated by solar flares and coronal mass ejections. The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) onboard the Lunar Reconnaissance Orbiter is in orbit about the Moon and is thus able to directly test these modeling results. Over the course of a month, CRaTER samples the upstream solar wind as well as various regions of Earth\u27s magnetotail. CRaTER data from multiple lunations demonstrate that Earth\u27s magnetosphere at lunar distances produces no measurable influence on energetic particle flux, even at the lowest energies (\u3e14 MeV protons) where any effect should be maximized. For particles with energies of 14â30 MeV, we calculate an upper limit (determined by counting statistics) on the amount of shielding caused by the magnetosphere of 1.7%. The high energy channel (\u3e500 MeV) provides an upper limit of 3.2%
A generalized approach to model the spectra and radiation dose rate of solar particle events on the surface of Mars
For future human missions to Mars, it is important to study the surface
radiation environment during extreme and elevated conditions. In the long term,
it is mainly Galactic Cosmic Rays (GCRs) modulated by solar activity that
contributes to the radiation on the surface of Mars, but intense solar
energetic particle (SEP) events may induce acute health effects. Such events
may enhance the radiation level significantly and should be detected as
immediately as possible to prevent severe damage to humans and equipment.
However, the energetic particle environment on the Martian surface is
significantly different from that in deep space due to the influence of the
Martian atmosphere. Depending on the intensity and shape of the original solar
particle spectra as well as particle types, the surface spectra may induce
entirely different radiation effects. In order to give immediate and accurate
alerts while avoiding unnecessary ones, it is important to model and well
understand the atmospheric effect on the incoming SEPs including both protons
and helium ions. In this paper, we have developed a generalized approach to
quickly model the surface response of any given incoming proton/helium ion
spectra and have applied it to a set of historical large solar events thus
providing insights into the possible variety of surface radiation environments
that may be induced during SEP events. Based on the statistical study of more
than 30 significant solar events, we have obtained an empirical model for
estimating the surface dose rate directly from the intensities of a power-law
SEP spectra
Prevalence and duration of breast milk feeding in very preterm infants: A 3-year follow-up study and a systematic literature review
Background: The World Health Organization recommends exclusive breast milk feeding until 6 months and continuing up to 2 years of age; little is known about whether very preterm infants are fed in accordance with these recommendations. We aimed to describe the prevalence and duration of breast milk feeding in very preterm children and to systematically review internationally published data.
Methods: We evaluated breast milk feeding initiation and duration in very preterm children born in 2 Portuguese regions (2011â2012) enrolled in the EPICE cohort and followedâup to the age of 3 (n = 466). We searched PubMedÂź from inception to January 2017 to identify original studies reporting the prevalence and/or duration of breast milk feeding in very preterm children.
Results: 91.0% of children received some breast milk feeding and 65.3% were exclusively breast fed with a median duration of 2 months for exclusive and 3 months for any breast milk; only 9.9% received exclusive breast milk for at least 6 months, 10.2% received any breast milk for 12 months or more, and 2.0% for up to 24 months. The literature review identified few studies on feeding after hospital discharge (n = 9); these also reported a low prevalence of exclusive breast milk feeding at 6 months (1.0% to 27.0%) and of any breast milk at 12 months (8.0% to 12.0%).
Conclusions: The duration of breast milk feeding among Portuguese very preterm infants was shorter than recommended. However, this appears to be common globally. Research is needed to inform strategies to promote continued breast milk feeding.This study was funded by the European Union Seventh Framework Programme (FP7/2007â2013) under grant agreement no. 259882. This study was also funded by FEDER through the Operational Programme Competitiveness and Internationalization and national funding from the Foundation for Science and TechnologyâFCT (Portuguese Ministry of Science, Technology and Higher Education), under the Unidade de Investigação em EpidemiologiaâInstituto de SaĂșde PĂșblica da Universidade do Porto (EPIUnit) (POCIâ01â0145âFEDERâ006862; Ref.UID/DTP/04750/2013); the PhD Grant SFRH/BD/111794/2015 (Carina Rodrigues) and the individual grant SFRH/BSAB/113778/2015 (Henrique Barros), coâfunded by the FCT and the POCH/FSE Program
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