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  • 1
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    On Determining the Zenith-Angle Dependence of the Martian Radiation Environment at Gale Crater Altitudes (2015)
    Wiley
    Details
    Publication Date: 2015-12-17
    Description: We report the zenith-angle dependence of the radiation environment at Gale Crater on Mars. This is the first determination of this dependence on another planet than Earth and is important for future human exploration of Mars and understanding radiation effects in the Martian regolith. Within the narrow range of tilt angles (0≤ θ 0 ≤15 ∘ ) experienced by Curiosity on Mars, we find a dependence with , which is not too different from an isotropic radiation field and quite different from that at sea level on Earth where .
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Measurements of the Neutron Spectrum on the Martian Surface with MSL/RAD (2014)
    Wiley
    Details
    Publication Date: 2014-02-26
    Description: [1]  The Radiation Assessment Detector (RAD), onboard the Mars Science Laboratory rover Curiosity, measures the energetic charged and neutral particles, and the radiation dose rate on the surface of Mars. An important factor for determining the biological impact of the Martian surface radiation is the specific contribution of neutrons, with their deeper penetration depth and ensuing high biological effectiveness. This is very difficult to measure quantitatively, resulting in considerable uncertainties in the total radiation dose. In contrast to charged particles, neutral particles (neutrons and gamma rays) are generally only measured indirectly. Measured spectra are a complex convolution of the incident particle spectrum with the detector response function, and must be unfolded. We apply an inversion method (based on a maximum-likelihood estimation) to calculate the neutron and gamma spectra from the RAD neutral particle measurements. Here we show the first measurements of neutron/gamma spectra from the surface of Mars and compare them to theoretical predictions. The measured neutron spectrum (ranging from 8 to 740 MeV) translates into a radiation dose rate of 14 ± 4 μ Gy/day and a dose equivalent rate of 61 ± 15 μ Sv/day. This corresponds to 7% of the measured total surface dose rate, and 10% of the biologically relevant surface dose equivalent rate on Mars. [2]  Measuring the Martian neutron and gamma spectra is an essential step for determining the mutagenic influences to past or present life at or beneath the Martian surface as well as the radiation hazard for future human exploration, including the shieldingdesign of a potential habitat.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Solar wind outflow and the chromospheric magnetic network (1999)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1999-02-05
    Description: Observations of outflow velocities in coronal holes (regions of open coronal magnetic field) have recently been obtained with the Solar and Heliospheric Observatory (SOHO) spacecraft. Velocity maps of Ne7+ from its bright resonance line at 770 angstroms, formed at the base of the corona, show a relationship between outflow velocity and chromospheric magnetic network structure, suggesting that the solar wind is rooted at its base to this structure, emanating from localized regions along boundaries and boundary intersections of magnetic network cells. This apparent relation to the chromospheric magnetic network and the relatively large outflow velocity signatures will improve understanding of the complex structure and dynamics at the base of the corona and the source region of the solar wind.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hassler -- Dammasch -- Lemaire -- Brekke -- Curdt -- Mason -- Vial -- Wilhelm -- New York, N.Y. -- Science. 1999 Feb 5;283(5403):810-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Southwest Research Institute, 1050 Walnut Street, Boulder, CO 80302, USA. Max-Planck-Institut fur Aeronomie, D-37191 Katlenburg-Lindau, Germany. Institut d'Astrophysique Spatiale, Unite Mixte CNRS- Universite Paris XI, 91405 Orsay, France. Ins.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9933156" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Comparisons of High‐Linear Energy Transfer Spectra on the ISS and in Deep Space (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract In deep space, personnel and equipment are exposed to the space radiation environment in the form of energetic particles, specifically Galactic Cosmic Rays and sporadic Solar Energetic Particle events. Radiation fields resulting from these particles are modified by shielding, but most radiation measurements in deep space have been made with detectors that were unshielded or very lightly shielded. In contrast, the space radiation environment on the International Space Station (ISS) is more complicated, with time‐dependent modification of the incident flux by the geomagnetic field and complex bulk shielding distributions; measured particle spectra inside the ISS are affected by both types of shielding. The geomagnetic field is also responsible for the existence of the South Atlantic Anomaly, a region of trapped energetic protons and electrons, and hence enhanced radiation dose, through which the ISS travels several times per day on average. Here, our primary aim is to compare charged particle spectra at high linear energy transfer (LET) obtained by the ALTEA (Anomalous Long‐Term Effects in Astronauts) instrument on ISS during high‐latitude portions of the orbit to data acquired at the same time by the Cosmic Ray Telescope for the Effects of Radiation and Radiation Assessment Detector instruments, both in deep space. The hypothesis being tested is that these spectra are the same, modulo shielding differences, since the effects of the geomagnetic field are expected to be minimal at high latitudes.
    Print ISSN: 1539-4964
    Electronic ISSN: 1542-7390
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Measurements of energetic particle radiation in transit to Mars on the Mars Science Laboratory (2013)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2013-06-01
    Description: 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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zeitlin, C -- Hassler, D M -- Cucinotta, F A -- Ehresmann, B -- Wimmer-Schweingruber, R F -- Brinza, D E -- Kang, S -- Weigle, G -- Bottcher, S -- Bohm, E -- Burmeister, S -- Guo, J -- Kohler, J -- Martin, C -- Posner, A -- Rafkin, S -- Reitz, G -- New York, N.Y. -- Science. 2013 May 31;340(6136):1080-4. doi: 10.1126/science.1235989.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Southwest Research Institute, Boulder, CO, USA. zeitlin@boulder.swri.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23723233" target="_blank"〉PubMed〈/a〉
    Keywords: *Cosmic Radiation ; Humans ; *Mars ; *Radiation Dosage ; *Space Flight
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    In situ radiometric and exposure age dating of the martian surface (2013)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2013-12-11
    Description: We determined radiogenic and cosmogenic noble gases in a mudstone on the floor of Gale Crater. A K-Ar age of 4.21 +/- 0.35 billion years represents a mixture of detrital and authigenic components and confirms the expected antiquity of rocks comprising the crater rim. Cosmic-ray-produced (3)He, (21)Ne, and (36)Ar yield concordant surface exposure ages of 78 +/- 30 million years. Surface exposure occurred mainly in the present geomorphic setting rather than during primary erosion and transport. Our observations are consistent with mudstone deposition shortly after the Gale impact or possibly in a later event of rapid erosion and deposition. The mudstone remained buried until recent exposure by wind-driven scarp retreat. Sedimentary rocks exposed by this mechanism may thus offer the best potential for organic biomarker preservation against destruction by cosmic radiation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Farley, K A -- Malespin, C -- Mahaffy, P -- Grotzinger, J P -- Vasconcelos, P M -- Milliken, R E -- Malin, M -- Edgett, K S -- Pavlov, A A -- Hurowitz, J A -- Grant, J A -- Miller, H B -- Arvidson, R -- Beegle, L -- Calef, F -- Conrad, P G -- Dietrich, W E -- Eigenbrode, J -- Gellert, R -- Gupta, S -- Hamilton, V -- Hassler, D M -- Lewis, K W -- McLennan, S M -- Ming, D -- Navarro-Gonzalez, R -- Schwenzer, S P -- Steele, A -- Stolper, E M -- Sumner, D Y -- Vaniman, D -- Vasavada, A -- Williford, K -- Wimmer-Schweingruber, R F -- MSL Science Team -- New York, N.Y. -- Science. 2014 Jan 24;343(6169):1247166. doi: 10.1126/science.1247166. Epub 2013 Dec 9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24324273" target="_blank"〉PubMed〈/a〉
    Keywords: Biomarkers/analysis/chemistry ; *Cosmic Radiation ; *Evolution, Planetary ; *Exobiology ; Extraterrestrial Environment/*chemistry ; Geologic Sediments ; Isotopes/analysis/chemistry ; *Mars ; Noble Gases/*analysis ; Organic Chemicals/analysis/chemistry ; Radiation Dosage ; Radiometric Dating ; Surface Properties
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    Structural basis of histone H2A-H2B recognition by the essential chaperone FACT (2013)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2013-05-24
    Description: Facilitates chromatin transcription (FACT) is a conserved histone chaperone that reorganizes nucleosomes and ensures chromatin integrity during DNA transcription, replication and repair. Key to the broad functions of FACT is its recognition of histones H2A-H2B (ref. 2). However, the structural basis for how histones H2A-H2B are recognized and how this integrates with the other functions of FACT, including the recognition of histones H3-H4 and other nuclear factors, is unknown. Here we reveal the crystal structure of the evolutionarily conserved FACT chaperone domain Spt16M from Chaetomium thermophilum, in complex with the H2A-H2B heterodimer. A novel 'U-turn' motif scaffolded onto a Rtt106-like module embraces the alpha1 helix of H2B. Biochemical and in vivo assays validate the structure and dissect the contribution of histone tails and H3-H4 towards Spt16M binding. Furthermore, we report the structure of the FACT heterodimerization domain that connects FACT to replicative polymerases. Our results show that Spt16M makes several interactions with histones, which we suggest allow the module to invade the nucleosome gradually and block the strongest interaction of H2B with DNA. FACT would thus enhance 'nucleosome breathing' by re-organizing the first 30 base pairs of nucleosomal histone-DNA contacts. Our snapshot of the engagement of the chaperone with H2A-H2B and the structures of all globular FACT domains enable the high-resolution analysis of the vital chaperoning functions of FACT, shedding light on how the complex promotes the activity of enzymes that require nucleosome reorganization.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hondele, Maria -- Stuwe, Tobias -- Hassler, Markus -- Halbach, Felix -- Bowman, Andrew -- Zhang, Elisa T -- Nijmeijer, Bianca -- Kotthoff, Christiane -- Rybin, Vladimir -- Amlacher, Stefan -- Hurt, Ed -- Ladurner, Andreas G -- Howard Hughes Medical Institute/ -- England -- Nature. 2013 Jul 4;499(7456):111-4. doi: 10.1038/nature12242. Epub 2013 May 22.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physiological Chemistry, Butenandt Institute and LMU Biomedical Center, Faculty of Medicine, Ludwig Maximilians University of Munich, Butenandtstrasse 5, 81377 Munich, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23698368" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Motifs ; Chaetomium/*chemistry ; Conserved Sequence ; Crystallography, X-Ray ; DNA/chemistry/metabolism ; DNA Replication ; Fungal Proteins/*chemistry/*metabolism ; Histones/chemistry/*metabolism ; Hydrophobic and Hydrophilic Interactions ; Models, Molecular ; Molecular Chaperones/*chemistry/*metabolism ; Nucleosomes/chemistry/metabolism ; Protein Binding ; Protein Multimerization ; Protein Structure, Secondary ; Protein Structure, Tertiary ; Substrate Specificity
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 8
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    Background levels of methane in Mars atmosphere show strong seasonal variations (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2018-06-08
    Description: Variable levels of methane in the martian atmosphere have eluded explanation partly because the measurements are not repeatable in time or location. We report in situ measurements at Gale crater made over a 5-year period by the Tunable Laser Spectrometer on the Curiosity rover. The background levels of methane have a mean value 0.41 ± 0.16 parts per billion by volume (ppbv) (95% confidence interval) and exhibit a strong, repeatable seasonal variation (0.24 to 0.65 ppbv). This variation is greater than that predicted from either ultraviolet degradation of impact-delivered organics on the surface or from the annual surface pressure cycle. The large seasonal variation in the background and occurrences of higher temporary spikes (~7 ppbv) are consistent with small localized sources of methane released from martian surface or subsurface reservoirs.
    Keywords: Geochemistry, Geophysics, Planetary Science
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    Mars' surface radiation environment measured with the Mars Science Laboratory's Curiosity rover (2013)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2013-12-11
    Description: The Radiation Assessment Detector (RAD) on the Mars Science Laboratory's Curiosity rover began making detailed measurements of the cosmic ray and energetic particle radiation environment on the surface of Mars on 7 August 2012. We report and discuss measurements of the absorbed dose and dose equivalent from galactic cosmic rays and solar energetic particles on the martian surface for ~300 days of observations during the current solar maximum. These measurements provide insight into the radiation hazards associated with a human mission to the surface of Mars and provide an anchor point with which to model the subsurface radiation environment, with implications for microbial survival times of any possible extant or past life, as well as for the preservation of potential organic biosignatures of the ancient martian environment.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hassler, Donald M -- Zeitlin, Cary -- Wimmer-Schweingruber, Robert F -- Ehresmann, Bent -- Rafkin, Scot -- Eigenbrode, Jennifer L -- Brinza, David E -- Weigle, Gerald -- Bottcher, Stephan -- Bohm, Eckart -- Burmeister, Soenke -- Guo, Jingnan -- Kohler, Jan -- Martin, Cesar -- Reitz, Guenther -- Cucinotta, Francis A -- Kim, Myung-Hee -- Grinspoon, David -- Bullock, Mark A -- Posner, Arik -- Gomez-Elvira, Javier -- Vasavada, Ashwin -- Grotzinger, John P -- MSL Science Team -- New York, N.Y. -- Science. 2014 Jan 24;343(6169):1244797. doi: 10.1126/science.1244797. Epub 2013 Dec 9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Southwest Research Institute, Boulder, CO 80302, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24324275" target="_blank"〉PubMed〈/a〉
    Keywords: *Cosmic Radiation ; Deinococcus/physiology/radiation effects ; *Exobiology ; *Extraterrestrial Environment ; Humans ; *Mars ; Organic Chemicals/analysis ; Radiation Dosage ; Space Flight ; Surface Properties/radiation effects
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
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    Characterization of cell cultures in contact with different orthopedic implants biomaterials (2016)
    Institute of Physics (IOP)
    Details
    Publication Date: 2016-09-03
    Description: The aim of this study is to identify the role of biological and mechanical constraints (at the cellular level) surrounding living tissues (cartilage and bone) in the presence of different joint implant biomaterials. In this fact, cells cultures in the presence of different types of biomaterials (pyrolytic carbon, cobalt-Chromium, titanium) has been performed. These cell cultures were subjected to biological characterization tests and mechanical characterization. The obtained results correlate with the in vivo observations (a promotion of the creation of a neocartilagical tissue in contact with the Pyrolytic Carbon implants).
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
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