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531.
532.
Jonathan Ferreira 《Astrophysics and Space Science》2003,287(1-4):15-20
This paper is focused on the huge dynamical importance of the mass load in magnetized jet models. I will first review some `naive' questions (Why should jets be magnetized? What is the jet driving source?), then show why the jet mass load is so important and why numerical simulations are unable yet to deal with jet formation. I will afterwards briefly describe some results of the only accretion disc model addressing explicitely this question and present a possible star-disc magnetospheric interaction giving rise to time-dependent outbursts. 相似文献
533.
Capria Maria Teresa Coradini Angioletta De Sanctis Maria Cristina 《Earth, Moon, and Planets》2002,90(1-4):217-225
A theoretical model of the nucleus thermal evolutionand differentiation is used to simulatethe evolution along the orbit of
the gasand dust emissions of comet Hale–Bopp. The model was already applied to this comet (Capria et al., 2000b): At that
time only the results of the observations obtained shortly after the perihelion were available. Now much more data have been
published and we present more refined and complete results about the production rates of gasand dust along the orbit and the
internal stratigraphy. The results of our model on long distance activity and its explanation are also presented. 相似文献
534.
M. G. Santos A. Heavens A. Balbi J. Borrill P. G. Ferreira S. Hanany A. H. Jaffe A. T. Lee B. Rabii P. L. Richards G. F. Smoot R. Stompor C. D. Winant J. H. P. Wu 《Monthly notices of the Royal Astronomical Society》2003,341(2):623-643
We describe different methods for estimating the bispectrum of cosmic microwave background data. In particular, we construct a minimum-variance estimator for the flat-sky limit and compare results with previously studied frequentist methods. Application to the MAXIMA data set shows consistency with primordial Gaussianity. Weak quadratic non-Gaussianity is characterized by a tunable parameter f NL , corresponding to non-Gaussianity at a level of ∼10−5 f NL (the ratio of non-Gaussian to Gaussian terms), and we find limits of f NL = 1500 ± 950 for the minimum-variance estimator and f NL = 2700 ± 1650 for the usual frequentist estimator. These are the tightest limits on primordial non-Gaussianity, which include the full effects of the radiation transfer function. 相似文献
535.
C. Patinha E. Correia E. Ferreira da Silva A. Simes P. Reis F. Morgado E. Cardoso Fonseca 《Journal of Geochemical Exploration》2008,98(1-2):34
The aim of this study is to define geochemical and geological patterns, not only inside of Paul de Arzila natural reserve but in the surrounding area. The Correspondence Analysis was used as a discriminate technique to separate previously identified groups, in this case three types of soils (cambisols + luvisols + fluvisols). The purpose was to identify the main chemical association representative for the local types of soils. The results allow us to separate the chemical elements that are related to natural sources from the anthropogenic sources. 相似文献
536.
Eric H. Oelkers Jacques Schott Jean-Marie Gauthier Teresa Herrero-Roncal 《Geochimica et cosmochimica acta》2008,72(20):4948-4961
Steady-state muscovite dissolution rates have been measured at temperatures from 60 to 201 °C and 1 ? pH ? 10.3 as a function of reactive solution K, Si, and Al concentration. The pegmatitic muscovite used in these experiments has a composition consistent with (Na0.09, K0.86)Fe0.05Al2.92Si3.05O10(OH1.95, F0.06). All experiments were performed in titanium mixed-flow reactors. All experiments were performed at far-from-equilibrium conditions with respect to muscovite. All reactive solutions were undersaturated with respect to secondary product phases other than for some experiments which were supersaturated with respect to bohemite and diaspore; steady-state dissolution was stoichiometric for all experiments that were undersaturated with respect to these phases.The variation of rates with reactive solution composition depends on the solution pH. At pH ? 7 rates were found to decrease significantly with increasing reactive fluid Al activity but be independent of aqueous SiO2 activity. pH < 7 rates measured in the present study from 60 to 175 °C are consistent with
537.
Teresa Zahoransky Henrik Friis Michael A. W. Marks 《Physics and Chemistry of Minerals》2016,43(7):459-480
Sodalite (Na8Al6Si6O24Cl2) shows a wide range of colours and may exhibit a variety of optical properties including cathodoluminescence, photoluminescence and tenebrescence. These optical peculiarities are not yet fully understood but are of key interest for industry. We provide a detailed study on the photochromic properties of natural sodalite, and we show that S is crucially influencing luminescence of sodalites. A reduced intensity in cathodoluminescence was observed at high S contents for some samples, showing that S can act as cathodoluminescence quencher. Photoluminescent sodalites are generally enriched in S compared to non-photoluminescent samples, although few samples being very low in S still show photoluminescence. Additionally, S was found to enlarge the unit cell in natural sodalites which might have a crucial impact on their photochromic properties. The most efficient tenebrescent samples were found to be low in Fe, Mn and S. They showed the smallest unit-cell dimensions, and a strong link between the atomic structure and the formation of F-centres is proposed. Tenebrescence in natural sodalites appears to be enhanced (1) by S but saturated at too high S concentrations and (2) by a stoichiometry and structure close to the ideal sodalite composition. In contrast to the term self-quenching for luminescence, we propose a saturation of F-centres to explain tenebrescence at different S contents. 相似文献
538.
M. W. Pedersen A. Kokkalis H. Bardarson S. Bonanomi W. J. Boonstra W. E. Butler F. K. Diekert N. Fouzai M. Holma R. E. Holt K. Ø. Kvile E. Nieminen K. M. Ottosen A. Richter L. A. Rogers G. Romagnoni M. Snickars A. Törnroos B. Weigel J. D. Whittington P. Woods J. Yletyinen A. S. A. Ferreira 《Climatic change》2016,134(1-2):147-161
539.
Igor Oliveira Ribeiro Rodrigo Augusto Ferreira de Souza Rita Valéria Andreoli Mary Toshie Kayano Patrícia dos Santos Costa 《大气科学进展》2016,33(7):852-864
The spatiotemporal variability of the greenhouse gas methane(CH_4) in the atmosphere over the Amazon is studied using data from the space-borne measurements of the Atmospheric Infrared Sounder on board NASA's AQUA satellite for the period 2003–12. The results show a pronounced variability of this gas over the Amazon Basin lowlands region, where wetland areas occur. CH_4 has a well-defined seasonal behavior, with a progressive increase of its concentration during the dry season, followed by a decrease during the wet season. Concerning this variability, the present study indicates the important role of ENSO in modulating the variability of CH_4 emissions over the northern Amazon, where this association seems to be mostly linked to changes in flooded areas in response to ENSO-related precipitation changes. In this region, a CH_4 decrease(increase) is due to the El Nino-related(La Ni ?na-related) dryness(wetness). On the other hand, an increase(decrease) in the biomass burning over the southeastern Amazon during very dry(wet) years explains the increase(decrease) in CH_4 emissions in this region. The present analysis identifies the two main areas of the Amazon, its northern and southeastern sectors, with remarkable interannual variations of CH_4. This result might be useful for future monitoring of the variations in the concentration of CH_4, the second-most important greenhouse gas, in this area. 相似文献
540.