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211.
Kevin Grove 《Geoforum》2009,40(2):207-216
The growing field of urban political ecology (UPE) has greatly advanced understandings of the socio-ecological transformations through which urban economies and environments are produced. However, this field has thus far failed to fully consider subjective (and subject-forming) dimensions of urban environmental struggle. I argue that this can be overcome through bringing urban political ecology into conversation with both post-structural political ecology and critical geopolitics. Bridging these literatures focuses attention on practices of socio-ecological exclusion and attachment through which environmental subjectivities are formed. This argument is drawn out through a case study of the politics of local economic development and conservation within the watershed of the Big Darby Creek near Columbus, Ohio. This struggle was driven by a preservationist movement that coalesced around a shared understanding of socio-ecological hybridity as a source of metaphysical insecurity. Hybridity appears here as a site of political and ethical struggle over social and ecological exclusions produced in the pursuit of security. This case study demonstrates a paradox of environmental politics: the non-human is at once a site of constituent possibilities for identity and subjectivity as well as forces which seek to foreclose this radical openness. Recognizing the paradoxical nature of environmental struggle allows for a more complex and nuanced account of the multifarious forces that shape the formation of environmental subjectivities. 相似文献
212.
Glenn J. MacPherson David W. Mittlefehldt Michael E. Lipschutz Robert N. Clayton Emma S. Bullock Andrei V. Ivanov Toshiko K. Mayeda Ming-Sheng Wang 《Geochimica et cosmochimica acta》2009,73(18):5493-5511
Oxygen isotope and trace element data for 13 samples of the Kaidun chondritic breccia reaffirm the complex polymict nature of this unique meteorite. Bulk Kaidun samples most closely resemble CR chondrites, but the matrix is CI-like. Two separated clasts are CR-like but have some properties that resemble CM, two clasts are enstatite chondrites (one EL and one EH), one clast is an aubrite-like metal-rich impact melt, and one clast is a unique layered olivine-bearing pyroxenite with the isotopic composition of an aubrite. Yet, although each clast resembles a known meteorite group, all deviate in some respect from the norms for those groups. Collectively, Kaidun has sampled materials not yet represented in the world meteorite collections and which greatly extend the definitions of known meteorite groups. Phyllosilicates in Kaidun span a very wide range in composition and vary from clast to clast, suggesting that the aqueous alteration experienced by the clasts predated assembly of the Kaidun parent body. 相似文献
213.
This study provides an experimental calibration of the equilibrium constant for AuPdFe alloys with Fe-bearing silicate melts.
The ideal metal capsules for H2O-bearing experiments are pure Au, because of its slow hydrogen diffusivity. However, above the melting point of Au, other
materials must be used. The solution to this problem is to use AuPd alloy capsules. However, under most relevant fO2 conditions, this alloy absorbs Fe from the coexisting silicate melt, thus changing the bulk composition of the experimental
charge. This study combines previous work on the Au–Pd, Pd–Fe, and Au–Fe binary systems to develop a ternary thermodynamic
solution model for AuPdFe. This solution model is used with experiments to calculate an equilibrium reaction coefficient for
the FeOmelt → Fealloy + 1/2O2 exchange reaction. Using a non-ideal ternary solution model, the fO2 conditions of hydrous, piston cylinder experiments can be estimated by analyzing the sample capsule alloy and the coexisting
liquid composition. 相似文献
214.
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
215.
216.
J. G. Barzyk M. R. Savina A. M. Davis R. Gallino F. Gyngard S. Amari E. Zinner M. J. Pellin R. S. Lewis R. N. Clayton 《Meteoritics & planetary science》2007,42(7-8):1103-1119
Abstract— Analyses of the isotopic compositions of multiple elements (Mo, Zr, and Ba) in individual mainstream presolar SiC grains were done by resonant ionization mass spectrometry (RIMS). While most heavy element compositions were consistent with model predictions for the slow neutron capture process (s‐process) in low‐mass (1.5–3 M⊙) asymptotic giant branch stars of solar metallicity when viewed on single‐element three‐isotope plots, grains with compositions deviating from model predictions were identified on multi‐element plots. These grains have compositions that cannot result from any neutron capture process but can be explained by contamination in some elements with solar system material. Previous work in which only one heavy element per grain was examined has been unable to identify contaminated grains. The multi‐element analyses of this study detected contaminated grains which were subsequently eliminated from consideration. The uncontaminated grains form a data set with a greatly reduced spread on the three‐isotope plots of each element measured, corresponding to a smaller range of 13C pocket efficiencies in parent AGB stars. Furthermore, due to this reduced spread, the nature of the stellar starting material, previously interpreted as having solar isotopic composition, is uncertain. The constraint on 13C pocket efficiencies in parent stars of these grains may help uncover the mechanism responsible for formation of 13C, the primary neutron source for s‐process nucleosynthesis in low‐mass stars. 相似文献
217.
Detrital thermochronologic record of burial heating and sediment recycling in the Magallanes foreland basin,Patagonian Andes
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Julie C. Fosdick Marty Grove Stephan A. Graham Jeremy K. Hourigan Oscar Lovera Brian W. Romans 《Basin Research》2015,27(4):546-572
The Patagonian Magallanes retroarc foreland basin affords an excellent case study of sediment burial recycling within a thrust belt setting. We report combined detrital zircon U–Pb geochronology and (U–Th)/He thermochronology data and thermal modelling results that confirm delivery of both rapidly cooled, first‐cycle volcanogenic sediments from the Patagonian magmatic arc and recycled sediment from deeply buried and exhumed Cretaceous foredeep strata to the Cenozoic depocentre of the Patagonian Magallanes basin. We have quantified the magnitude of Eocene heating with thermal models that simultaneously forward model detrital zircon (U–Th)/He dates for best‐fit thermal histories. Our results indicate that 54–45 Ma burial of the Maastrichtian Dorotea Formation produced 164–180 °C conditions and heating to within the zircon He partial retention zone. Such deep burial is unusual for Andean foreland basins and may have resulted from combined effects of high basal heat flow and high sediment accumulation within a rapidly subsiding foredeep that was floored by basement weakened by previous Late Jurassic rifting. In this interpretation, Cenozoic thrust‐related deformation deeply eroded the Dorotea Formation from ca. 5 km burial depths and may be responsible for the development of a basin‐wide Palaeogene unconformity. Results from the Cenozoic Río Turbio and Santa Cruz formations confirm that they contain both Cenozoic first‐cycle zircon from the Patagonian magmatic arc and highly outgassed zircon recycled from older basin strata that experienced burial histories similar to those of the Dorotea Formation. 相似文献
218.
219.
Christopher A.Tout 《中国天文和天体物理学报》2007,(2)
Based on previous works of OPAL, we construct a series of opacity tables for various metallicities Z=0, 0.000 01, 0.000 03, 0.000 1, 0.000 3, 0.001, 0.004, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08 and 0.1. These tables can be easily used in Eggleton's stellar evolution code in place of the old tables without changing the code. The OPAL tables are used for log10(T/K) > 3.95 and Alexander's for log10(T/K) < 3.95. At log10(T/K) = 3.95, the two groups' data fit well for all hydrogen mass fractions. Conductive opacities are included by reciprocal addition according to the formulae of Yakovlev and Urpin. A comparison of 1 and 5 M models constructed with the older OPAL tables of Iglesias and Rogers shows that the new opacities have most effect in the late stages of evolution, the extension of the blue loop during helium burning for intermediate-mass and massive stars. 相似文献
220.
Jeffrey Albano Steve D. Comfort Vitaly Zlotnik Todd Halihan Mark Burbach Chanat Chokejaroenrat Sathaporn Onanong Wilson Clayton 《Ground Water Monitoring & Remediation》2010,30(3):96-106
Groundwater beneath the former Nebraska Ordnance Plant (NOP) is contaminated with the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). The current pump and treat facility is preventing offsite migration but does not offer a short-term solution. Our objective was to quantify the effectiveness of permanganate to degrade RDX in situ. This was accomplished by performing laboratory treatability experiments, aquifer characterization, and a pilot-scale in situ chemical oxidation (ISCO) demonstration. Treatability experiments confirmed that permanganate could mineralize RDX in the presence of NOP aquifer solids. The pilot-scale ISCO demonstration was performed using an extraction-injection well configuration to create a curtain of permanganate between two injection wells. RDX destruction was then quantified as the RDX-permanganate plume migrated downgradient through a monitoring well field. Electrical resistivity imaging (ERI) was used to identify the subsurface distribution of permanganate after injection. Results showed that RDX concentrations temporally decreased in wells closest to the injection wells by 70% to 80%. Observed degradation rates (0.12 and 0.087/d) were lower than those observed under laboratory batch conditions at 11.5 °C (0.20/d) and resulted from lower than projected permanganate concentrations. Both ERI and spatial electrical conductivity measurements verified that permanganate distribution was not uniform throughout the 6.1-m (20 feet) well screens and that groundwater sampling captured both treated and nontreated groundwater during pumping. Although heterogeneous flow paths precluded a uniform permanganate distribution, pilot-scale results provided proof-of-concept that permanganate can degrade RDX in situ and support permanganate as a possible remedial treatment for RDX-contaminated groundwater. 相似文献