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101.
102.
Alistair Simon Bargery Alexander Barrett Lionel Wilson Jennie S. Gilbert 《Icarus》2010,210(1):488-506
Experiments have been performed to simulate the shallow ascent and surface release of water and brines under low atmospheric pressure. Atmospheric pressure was treated as an independent variable and water temperature and vapor pressure were examined as a function of total pressure variation down to low pressures. The physical and thermal responses of water to reducing pressure were monitored with pressure transducers, temperature sensors and visible imaging. Data were obtained for pure water and for solutions with dissolved NaCl or CO2. The experiments showed the pressure conditions under which the water remained liquid, underwent a rapid phase change to the gas state by boiling, and then solidified because of removal of latent heat. Liquid water is removed from phase equilibrium by decompression. Solid, liquid and gaseous water are present simultaneously, and not at the 611 Pa triple point, because dynamic interactions between the phases maintain unstable temperature gradients. After phase changes stop, the system reverts to equilibrium with its surroundings. Surface and shallow subsurface pressure conditions were simulated for Mars and the icy satellites of the outer Solar System. Freezing by evaporation in the absence of wind on Mars is shown to be unlikely for pure water at pressures greater than c. 670 Pa, and for saline solutions at pressures greater than c. 610 Pa. The physical nature of ice that forms depends on the salt content. Ice formed from saline water at pressures less than c. 610 Pa could be similar to terrestrial sea ice. Ice formed from pure water at pressures less than c. 100 Pa develops a low thermal conductivity and a ‘honeycomb’ structure created by sublimation. This ice could have a density as low as c. 450 kg m−3 and a thermal conductivity as low as 1.6 W m−1 K−1, and is highly reflective, more akin to snow than the clear ice from which it grew. The physical properties of ice formed from either pure or saline water at low pressures will act to reduce the surface temperature, and hence rate of sublimation, thereby prolonging the lifespan of any liquid water beneath. 相似文献
103.
Some things old, some things new: The spatial representations and politics of change of the peak oil relocalisation movement 总被引:1,自引:0,他引:1
Despite continued uncertainty about the physical realities and political, economic and social implications of peak oil, combined concerns about oil scarcity, climate change and globalisation has spawned an energetic relocalisation movement dedicated to achieving a comprehensive reduction in oil dependency through community-scale initiatives. This paper uses a discourse approach to examine the emergence, geographical spread and practices of the Transition Network, a UK-originated relocalisation movement now involving 186 local initiatives in the UK and other countries. We trace the movement’s drawing upon, and innovation from, discourses and techniques used by other grassroots environmental movements to promote a spatial representation of peak oil as an inevitable and geographically undiscriminating problem, and its use of addiction metaphors and participatory techniques to promote personal and community-scale energy descent initiatives as a viable and necessary alternative to globalisation. We also analyse the spatial representations and techniques used in the Network’s “rhizomic” spread across multiple localities around the world and embedding in communities where relocalisation initiatives are established. We conclude by examining the future challenges these spatial constructions of peak oil pose for the relocalisation movement. 相似文献
104.
Got green? addressing environmental justice in park provision 总被引:3,自引:0,他引:3
We present a pragmatic approach to assist planners in addressing racial inequities in park access. Utilizing the Los Angeles
metropolitan region as an example, we used Thiessen polygons to delineate a service area for each park, and described potential
park congestion or ‘pressure’ in each park service area. Results show that Latinos, African-Americans, and low-income groups
in general were likely to live close to parks with higher potential park congestion. On the other hand, predominantly White,
high-income areas were typically located close to parks with lower potential park congestion levels. The park service area
analysis presented here facilitates the identification of areas with greater park need and provides a pragmatic way to redress
existing disparities in park access. Built into a set of web-based decision support tools, the approach fosters greater community
participation and empowers local stakeholders in the process of park provision. 相似文献
105.
Bobby M. Wilson 《GeoJournal》2010,75(3):273-281
A structural imperative of capital is to expand commodity exchange. To realize surplus value, capitalists not only have to
exploit workers in the production process, but also make workers buy what they produce. This paper examines how this imperative
of capital shaped race relations from the end of slavery through the Jim Crow era. The racism that sustained black slavery
was highly exclusionary––a fixed racism that undermined this imperative of capital to expand commodity exchange. A more flexible
racism would resolve this contradiction. Reconstruction was a move to erase all vestiges of the fixed racism that sustained
slavery from relations of commodity exchange. Jim Crow countered with a more flexible racism that maintained the racial status
quo but was less of a barrier to blacks participating in commodity exchange in the consumption process. 相似文献
106.
107.
L. Michaille A. D. Cañas J. C. Dainty J. Maxwell T. Gregory J. C. Quartel F. C. Reavell R. W. Wilson N. J. Wooder 《Monthly notices of the Royal Astronomical Society》2000,318(1):139-144
We report the results of the first laser beacon experiment at the astronomical site of La Palma (Canary Islands). A continuous wave low‐power laser (a few hundred mW) system has been set up. The laser, tuned on the sodium D2 line at 589 nm, is launched close to the zenith angle. The emission of the mesospheric sodium layer is observed from a telescope located 160 m away from the laser. The layer is therefore resolved in altitude and the different features of its dynamics are investigated. 相似文献
108.
C. J. N. Wilson B. F. Houghton B. J. Pillans S. D. Weaver 《Journal of Volcanology and Geothermal Research》1995,69(3-4)
Mayor Island is a peralkaline rhyolitic caldera volcano characterised by numerous, sector-confined pyroclastic deposits, together with lavas forming at least five composite shields. Correlation of sequences between sectors is difficult because of the scarcity of island-wide marker beds. However, eight distal calc-alkaline fall tephras (ca. 7.3 14C ka to 64 ka) from Okataina and Taupo volcanic centres in the nearby Taupo Volcanic Zone (TVZ) have been identified on the island. These “foreign” TVZ tephras provide marker planes to correlate activity in different sectors of Mayor Island volcano, and refine an eruptive chronology. At least seventeen pyroclastic eruptions and fourteen lava-producing events (including multiple, shield-forming events) have occurred in the past ca. 64 ka. Age controls provided by the calc-alkaline tephras confirm the extremely local dispersal characteristics of many of the Mayor Island eruptives and show that K/Ar ages as young as 25–33 ka on obsidians with 4.2–4.4% K2O are reliable. 相似文献
109.
J.J. Butler Jr S. Knobbe E.C. Reboulet D.O. Whittemore B.B. Wilson G.C. Bohling 《Ground water》2021,59(6):808-818
Many of the world's major aquifers are under severe stress as a result of intensive pumping to support irrigated agriculture and provide drinking water supplies for millions. The question of what the future holds for these aquifers is one of global importance. Without better information about subsurface conditions, it will be difficult to reliably assess an aquifer's response to management actions and climatic stresses. One important but underutilized source of information is the data from monitoring well networks that provide near-continuous records of water levels through time. Most organizations running these networks are, by necessity, primarily focused on network maintenance. The result is that relatively little attention is given to interpretation of the acquired hydrographs. However, embedded in those hydrographs is valuable information about subsurface conditions and aquifer responses to natural and anthropogenic stresses. We demonstrate the range of insights that can be gleaned from such hydrographs using data from the High Plains aquifer index well network of the Kansas Geological Survey. We show how information about an aquifer's hydraulic state and lateral extent, the nature of recharge, the hydraulic connection to the aquifer and nearby pumping wells, and the expected response to conservation-based pumping reductions can be extracted from these hydrographs. The value of this information is dependent on accurate water-level measurements; errors in those measurements can make it difficult to fully exploit the insights that water-well hydrographs can provide. We therefore conclude by presenting measures that can help reduce the potential for such errors. 相似文献
110.