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171.
Fouad Sahraoui Melvyn L. Goldstein Alain Roux Patrick Canu Nicole Cornilleau-Wehrlin Thierry Dudok De Wit Khurom Kiyani 《Planetary and Space Science》2011,59(7):585-591
Investigating space plasma turbulence from single-point measurements is known to be characterized by unavoidable ambiguities in disentangling temporal and spatial variations. Solving this problem has been one of the major goals of the Cluster mission. For that purpose multipoint measurements techniques, such as the k-filtering, have been developed. Such techniques combine several time series recorded simultaneously at different points in space to estimate the corresponding energy density in the wavenumber space. Here we apply the technique to both simulated and Cluster magnetometer data in the solar wind (SW) and investigate the errors and limitations that arise due to the separation of the spacecraft and the quality of the tetrahedral configuration. Specifically, we provide an estimation of the minimum and maximum scales that can be accurately measured given a specific distance between the satellites and show the importance of the geometry of the tetrahedron and the relationship of that geometry to spatial aliasing. We also present recent results on characterizing small scale SW turbulence and provide scientific arguments supporting the need of new magnetometers having better sensitivity than the existing ones. Throughout the paper we emphasize technical challenges and their solutions that can be considered for a better preparation of the Cross-Scale mission. 相似文献
172.
Keith Chun Leem Lee Joshua Peter Newell Jennifer Wolch Nicole Schneider Pascale Joassart-Marcelli 《社会与自然资源》2014,27(9):948-963
Despite widespread media coverage of livestock-related issues and growing scientific evidence linking meat production and climate change, systematic content analysis of this relationship in media coverage has been surprisingly minimal. In this article, we combine actor-network theory with framing theory to develop the basis for “story-networks”—networks of actants and artifacts that shape how a media report or “story” is framed. We coded livestock-related articles from a major U.S. newspaper, the Los Angeles Times, over the 1999–2010 period to understand how various actants and artifacts shaped different story-networks. Just 5% of all livestock articles addressed connections with climate change; these articles focused on technology, lifestyle, or policy. Distinctive story-networks characterized each category, framing the livestock–climate change linkage as an issue to be addressed through either technological innovation, individual lifestyle choices, or policy action. In each story-network type, varying configurations of actants and artifacts were involved, including the cattle themselves. 相似文献
173.
174.
This article explores how participation in watershed groups creates a social space that mediates the relationship between biophysical places and place-protective action. We analyze qualitative data from a survey of more than 200 watershed group volunteers in the Appalachian region of the United States who were asked to describe experiences that encouraged or discouraged their participation. “Place” emerged as a key theme, with further delineations between made places (those highly affected by human activity, including coal extraction); natural places; and re-made places (those restored by the efforts of the watershed-group participants). Our findings suggest that the places themselves—and the natural, institutional, and social resources in these places—are more than a backdrop or setting for the volunteer activities; they also inspire, enhance, and are transformed by the act of volunteering. 相似文献
175.
Julie A. Winkler Suzanne Thornsbury Marco Artavia Frank-M. Chmielewski Dieter Kirschke Sangjun Lee Malgorzata Liszewska Scott Loveridge Pang-Ning Tan Sharon Zhong Jeffrey A. Andresen J. Roy Black Robert Kurlus Denys Nizalov Nicole Olynk Zbigniew Ustrnul Costanza Zavalloni Jeanne M. Bisanz Géza Bujdosó Lesley Fusina Yvonne Henniges Peter Hilsendegen Katarzyna Lar Lukasz Malarzewski Thordis Moeller Roman Murmylo Tadeusz Niedzwiedz Olena Nizalova Haryono Prawiranata Nikki Rothwell Jenni van Ravensway Harald von Witzke Mollie Woods 《Climatic change》2010,103(3-4):445-470
A conceptual framework for climate change assessments of international market systems that involve long-term investments is proposed. The framework is a hybrid of dynamic and static modeling. Dynamic modeling is used for those system components for which temporally continuous modeling is possible, while fixed time slices are used for other system components where it can be assumed that underlying assumptions are held constant within the time slices but allowed to vary between slices. An important component of the framework is the assessment of the “metauncertainty” arising from the structural uncertainties of a linked sequence of climate, production, trade and decision-making models. The impetus for proposing the framework is the paucity of industry-wide assessments for market systems with multiple production regions and long-term capital investments that are vulnerable to climate variations and change, especially climate extremes. The proposed framework is pragmatic, eschewing the ideal for the tractable. Even so, numerous implementation challenges are expected, which are illustrated using an example industry. The conceptual framework is offered as a starting point for further discussions of strategies and approaches for climate change impact, vulnerability and adaptation assessments for international market systems. 相似文献
176.
Corey A Cohn Steffen Mueller Eckard Wimmer Nicole Leifer Steven Greenbaum Daniel R Strongin Martin AA Schoonen 《Geochemical transactions》2006,7(1):3-11
Background
Pyrite, the most abundant metal sulphide on Earth, is known to spontaneously form hydrogen peroxide when exposed to water. In this study the hypothesis that pyrite-induced hydrogen peroxide is transformed to hydroxyl radicals is tested. 相似文献177.
Nicole C. Lautze Thomas W. Sisson Margaret T. Mangan Timothy L. Grove 《Contributions to Mineralogy and Petrology》2011,161(2):331-347
Diffusive coarsening (Ostwald ripening) of H2O and H2O-CO2 bubbles in rhyolite and basaltic andesite melts was studied with elevated temperature–pressure experiments to investigate
the rates and time spans over which vapor bubbles may enlarge and attain sufficient buoyancy to segregate in magmatic systems.
Bubble growth and segregation are also considered in terms of classical steady-state and transient (non-steady-state) ripening
theory. Experimental results are consistent with diffusive coarsening as the dominant mechanism of bubble growth. Ripening
is faster in experiments saturated with pure H2O than in those with a CO2-rich mixed vapor probably due to faster diffusion of H2O than CO2 through the melt. None of the experimental series followed the time1/3 increase in mean bubble radius and time−1 decrease in bubble number density predicted by classical steady-state ripening theory. Instead, products are interpreted
as resulting from transient regime ripening. Application of transient regime theory suggests that bubbly magmas may require
from days to 100 years to reach steady-state ripening conditions. Experimental results, as well as theory for steady-state
ripening of bubbles that are immobile or undergoing buoyant ascent, indicate that diffusive coarsening efficiently eliminates
micron-sized bubbles and would produce mm-sized bubbles in 102–104 years in crustal magma bodies. Once bubbles attain mm-sizes, their calculated ascent rates are sufficient that they could
transit multiple kilometers over hundreds to thousands of years through mafic and silicic melt, respectively. These results
show that diffusive coarsening can facilitate transfer of volatiles through, and from, magmatic systems by creating bubbles
sufficiently large for rapid ascent. 相似文献
178.
Benjamin Rotenberg Jean-Pierre Morel Pierre Turq Nicole Morel-Desrosiers 《Geochimica et cosmochimica acta》2009,73(14):4034-20527
We study the origin of the ionic exchange enthalpy in montmorillonite clays using microcalorimetry measurements and molecular simulation. We first determine the standard reaction enthalpy for well-defined interlayer water contents. We then show by a detailed analysis based on thermodynamic cycles that replacing Na+ ions by Cs+ in the interlayer of montmorillonite clays is an endothermic process, and that the overall exchange is exothermic only because it is dominated by the exothermic replacement of Cs+ by Na+ in the aqueous phase. This conclusion from ionic exchange enthalpies supports the one of a recent study of the ionic exchange free energy by Teppen and Miller [Teppen B. J. and Miller D. M. (2006) Hydration energy determines isovalent cation exchange selectivity by clay minerals. Soil Sci. Soc. Am. J.70(1), 31-40] and contradicts long-held views on the role of ion-clay interactions in determining the ionic exchange thermodynamics. This calls for a paradigm shift for the origin of this exchange: The driving force is the “hydrophobicity” of Cs+ compared to Na+ and not its affinity for clay surfaces. 相似文献
179.
180.
Revision and recalibration of existing shock classifications for quartzose rocks using low‐shock pressure (2.5–20 GPa) recovery experiments and mesoscale numerical modeling 下载免费PDF全文
Astrid Kowitz Nicole Güldemeister Ralf Thomas Schmitt Wolf‐Uwe Reimold Kai Wünnemann Andreas Holzwarth 《Meteoritics & planetary science》2016,51(10):1741-1761
A combination of shock recovery experiments and numerical modeling of shock deformation in the low‐shock pressure range from 2.5 to 20 GPa for two dry sandstone types of different porosity, a completely water‐saturated sandstone, and a well‐indurated quartzite provides new insights into strongly heterogeneous distribution of different shock features. (1) For nonporous quartzo‐feldspathic rocks, the traditional classification scheme (Stöffler 1984 ) is suitable with slight changes in pressure calibration. (2) For water‐saturated quartzose rocks, a cataclastic texture (microbreccia) seems to be typical for the shock pressure range up to 20 GPa. This microbreccia does not show formation of PDFs but diaplectic quartz glass/SiO2 melt is formed at 20 GPa (~1 vol%). (3) For porous quartzose rocks, the following sequence of shock features is observed with progressive increase in shock pressure (1) crushing of pores, (2) intense fracturing of quartz grains, and (3) increasing formation of diaplectic quartz glass/SiO2 melt replacing fracturing. The formation of diaplectic quartz glass/SiO2 melt, together with SiO2 high‐pressure phases, is a continuous process that strongly depends on porosity. This experimental observation is confirmed by our concomitant numerical modeling. Recalibration of the shock classification scheme results in a porosity versus shock pressure diagram illustrating distinct boundaries for the different shock stages. 相似文献