Validation of Geant4 10.3 simulation of proton interaction for space radiation effects     

Vladimir Ivanchenko  Paolo Dondero  Valentina Fioretti  Anton Ivantchenko  Fan Lei  Simone Lotti  Alfonso Mantero  Teresa Mineo 《Experimental Astronomy》2017,44(3):437-450

Monte Carlo simulation of space radiation effects induced by protons is important for design of space missions. Geant4 is a well established toolkit for Monte Carlo simulation focused on high energy physics applications. In this work, a set of new validation results versus data for Geant4 electromagnetic and hadronic interaction of protons is presented and discussed. Optimal configuration of Geant4 physics for space applications is proposed.  相似文献   

Deep-sea bacterial communities in sediments and guts of deposit-feeding holothurians in Portuguese canyons (NE Atlantic)     

Teresa Amaro  Harry Witte  Gerhard J. Herndl  Marina R. Cunha  David S.M. Billett 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(10):1834-1843

Deposit-feeding holothurians often dominate the megafauna in bathyal deep-sea settings, in terms of both abundance and biomass. Molpadia musculus is particularly abundant at about 3400 m depth in the Nazaré Canyon on the NE Atlantic Continental Margin. However, these high abundances are unusual for burrowing species at this depth. The objective of this research was to understand the reasons of the massive occurrence of these molpadiid holothurians in the Nazaré Canyon. To address this question we investigated possible trophic interactions with bacteria at sites where the organic content of the sediment was different (Setúbal and Cascais Canyons, NE Atlantic Continental Margin). The molecular fingerprinting technique of Denaturing Gradient Gel Electrophoresis (DGGE) with band sequencing, combined with non-metric multi-dimensional scaling and statistical analyses, was used to compare the bacterial community diversity in canyon sediments and holothurian gut contents. Our results suggest that M. musculus does not need to develop a specialised gut bacterial community to aid digestion where the sediment is rich in organic matter (Nazaré Canyon); in contrast, such a community may be developed where the sediment is poorer in organic matter (Cascais Canyon).  相似文献   

Spatial and seasonal variations of the macrobenthic community and metal contamination in the Douro estuary (Portugal)   总被引：3，自引：0，他引：3  

Mucha AP  Vasconcelos MT  Bordalo AA 《Marine environmental research》2005,60(5):531-550

The macrobenthic community structure and characteristics of sediments were studied in samples collected seasonally at five stations in the lower mesotidal Douro estuary, Portugal. Sediment characterisation included grain size distribution, total-recoverable metals (Al, Fe, Mn, Zn, Cu, Cr, Pb, Ni and Cd), acid-volatile sulphides (AVS) and simultaneously extracted metals (SEM) and total organic matter contents. Spatial variation surpassed temporal variation both in terms of environmental parameters and community structure. Clear anthropogenic contamination in terms of Zn, Cr, Cu and Pb, and a positive SEM-AVS, indicating the potential bioavailability of these metals, were detected on the north bank of the estuary. Multivariate analysis revealed that in addition to natural sediment characteristics, the anthropogenic metal contamination was influencing the macrobenthic community structure. In fact, greater concentrations of Zn, Cr, Cu and Pb were associated with lower number of species and/or diversity. Finally, the dry weight-normalised metal concentrations appeared as a more useful tool than the SEM-AVS model in predicting disturbance of the macrobenthic community in the studied area.  相似文献   

New Reference Materials,Analytical Procedures and Data Reduction Strategies for Sr Isotope Measurements in Geological Materials by LA-MC-ICP-MS     

Jacob Mulder  Graham Hagen-Peter  Teresa Ubide  Rasmus Andreasen  Ellen Kooijman  Melanie Kielman-Schmitt  Yue-Xing Feng  Bence Paul  Andreas Karlsson  Christian Tegner  Charles Lesher  Fidel Costa 《Geostandards and Geoanalytical Research》2023,47(2):311-336

Laser ablation multi-collector mass spectrometry (LA-MC-ICP-MS) has emerged as the technique of choice for in situ measurements of Sr isotopes in geological minerals. However, the method poses analytical challenges and there is no widely adopted standardised approach to collecting these data or correcting the numerous potential isobaric inferences. Here, we outline practical analytical procedures and data reduction strategies to help establish a consistent framework for collecting and correcting Sr isotope measurements in geological materials by LA-MC-ICP-MS. We characterise a new set of plagioclase reference materials, which are available for distribution to the community, and present a new data reduction scheme for the Iolite software package to correct isobaric interferences for different materials and analytical conditions. Our tests show that a combination of Kr-baseline subtraction, Rb-peak-stripping using βRb derived from a bracketing glass reference material, and a CaCa or CaAr correction for plagioclase and CaCa or CaAr + REE²⁺ correction for rock glasses, yields the most accurate and precise ⁸⁷Sr/⁸⁶Sr measurements for these materials. Using the analytical and correction procedures outlined herein, spot analyses using a beam diameter of 100 μm or rastering with a 50–65 μm diameter beam can readily achieve < 100 ppm 2SE repeatability ("internal") precision for ⁸⁷Sr/⁸⁶Sr measurements for materials with < 1000 μg g^-1 Sr.  相似文献