排序方式： 共有39条查询结果，搜索用时 16 毫秒
11.
Josh N. Plant Kenneth S. Johnson Steve E. Fitzwater Carole M. Sakamoto Luke J. Coletti Hans W. Jannasch 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(12):1585-1595
An In Situ Ultraviolet Spectrophotometer (ISUS) was coupled to a benthic chamber to characterize the bisulfide flux emanating from a warm spring at the Extrovert Cliff locality within Monterey Bay, California. The chamber was periodically flushed with bottom seawater to reset chemical concentrations, which enabled deployments over multiple days. Data from several deployments, each lasting at least 10 days, were used to calculate flow rates, fluid concentrations, and fluxes over time. The bisulfide concentration of the fluid entering the chamber varied from 75 to 4500 μmol l?1. Positive temperature anomalies up to 3.5° were associated with these elevated concentrations. Linear flow rates ranged from 2 to >17 m day?1, while the bisulfide fluxes varied from 0.2 to 80 mol m?2 day?1. The bisulfide originated at depth and was not produced in the surface sediments via an anaerobic oxidation of methane coupled to sulfate reduction. Tides modulated the flow as well as the composition of the fluid entering the chamber. It appeared that a deep sourced fluid, which supplied the bisulfide, was mixed with a second, ambient seawater-like fluid before entering the flux chamber. At low tides, flow rates were at their highest and the contribution of the deep sourced fluid to the fluid entering the chamber was at a maximum. 相似文献
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Kelsey D. Hargrove Michael S. Kelley Humberto Campins Javier Licandro Josh Emery 《Icarus》2012,221(1):453-455
We find a clear diversity in the 3 μm and 10 μm features of three Cybele asteroids: (107) Camilla, (121) Hermione, and (65) Cybele. (121) Hermione exhibits a “check-like” 3 μm feature, which may be attributed to OH-dominated minerals and (107) Camilla shows a rounded “bowl” like feature closer to that of (65) Cybele, which may be attributed to H2O-dominated minerals. The 10 μm features of these three asteroids are also different from each other. 相似文献
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Josh Lepawsky 《Geoforum》2012,43(6):1194-1206
Electronic waste (e-waste) is thought to be the fastest growing segment of the overall solid waste stream in many countries. Between 2003 and 2010 more than half of all Canadian provinces and US states passed legislation specifically to govern the disposition of e-waste. The purpose of this research is to investigate the legal geographies of this legislation. The principle findings are that the work of jurisdiction around e-waste in Canada and the US places financial responsibility for waste management on consumers not producers. Thus, contra the explicit intent of e-waste legislation, a regime of extended consumer, rather than producer, responsibility is emerging and waste generated as a result of design and manufacturing decisions remains taboo. But the implications of the legislative governance of e-waste go beyond questions of regulatory success or failure. At stake in the legislative governance of e-waste is the assembling of the social in a legal way that generates distributions of action that are democratized only so long as they limit public decision making to waste already produced and marketized only so long as they extend the ability of manufacturers, e-waste recyclers, and paramarket organizations to appropriate value. The work of jurisdiction around e-waste suggests jurisdiction can be more multiple, distributed, and patchy than prevailing theory allows. 相似文献
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Arjun M. Heimsath Oliver A. Chadwick Josh J. Roering Shaun R. Levick 《地球表面变化过程与地形》2020,45(3):499-510
The textbook concept of an equilibrium landscape, which posits that soil production and erosion are balanced and equal channel incision, is rarely quantified for natural systems. In contrast to mountainous, rapidly eroding terrain, low relief and slow-eroding landscapes are poorly studied despite being widespread and densely inhabited. We use three field sites along a climosequence in South Africa to quantify very slow (2-5 m/My) soil production rates that do not vary across hillslopes or with climate. We show these rates to be indistinguishable from spatially invariant catchment-average erosion rates while soil depth and chemical weathering increase strongly with rainfall across our sites. Our analyses imply landscape-scale equilibrium although the dominant means of denudation varies from physical weathering in dry climates to chemical weathering in wet climates. In the two wetter sites, chemical weathering is so significant that clay translocates both vertically in soil columns and horizontally down hillslope catenas, resulting in particle size variation and the accumulation of buried stone lines at the clay-rich depth. We infer hundred-thousand-year residence times of these stone lines and suggest that bioturbation by termites plays a key role in exhuming sediment into the mobile soil layer from significant depths below the clay layer. Our results suggest how tradeoffs in physical and chemical weathering, potentially modulated by biological processes, shape slowly eroding, equilibrium landscapes. © 2019 John Wiley & Sons, Ltd. 相似文献
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The Schmidt hammer (SH) is widely used in geomorphology for relative- and calibrated-exposure age dating surfaces and deposits within landforms. This study employs a laboratory-based methodology to assess the effects of surface roughness, clast roundness, and clast volume on SH rebound values (R-values) by analyzing samples from three modern depositional environments (i.e. river, alluvial fan, talus). Each environment contains clasts of Torlesse supergroup greywacke sandstones with distinct roundness and micro-scale roughness characteristics. Roundness, surface roughness, and clast volume were all found to influence R-values significantly. The R-values from different deposit types are statistically significant and could potentially create an apparent age divergence of several thousand years for samples with the same exposure-age. © 2020 John Wiley & Sons, Ltd. 相似文献
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Philip C. Farese Giorgio Dall&#x;Oglio Josh Gundersen Brian Keating Slade Klawikowski Lloyd Knox Alan Levy Chris O&#x;Dell Alan Peel Lucio Piccirillo John Ruhl Peter Timbie 《New Astronomy Reviews》2003,47(11-12):1033
COMPASS is an on-axis 2.6-m telescope coupled to a correlation polarimeter. The entire instrument was built specifically for CMB polarization studies. Careful attention was given to receiver and optics design, stability of the pointing platform, avoidance of systematic offsets, and development of data analysis techniques. Here we describe the experiment, its strengths and weaknesses, and the various things we have learned that may benefit future efforts to measure the polarization of the CMB. 相似文献
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Brian Dzwonkowski B.L. Lipphardt Jr. Josh T. Kohut Xiao-Hai Yan Richard W. Garvine 《Continental Shelf Research》2010
Sub-inertial across-shelf flows over the central mid-Atlantic Bight were examined using long-range CODAR SeaSonde type HF-radar surface velocities for the period August 2002 through February 2004. Across-shelf flow in this region was found to be episodic, with offshore flow occurring six times more often than onshore flow. Several recurring spatial patterns in offshore flow are identified, and two of these patterns emerge as statistically significant using empirical orthogonal functions. The most common type of offshore flow was a shelf-wide flow with events occurring throughout the year. The most energetic and well-defined shelf-wide flow events occurred during October through April, when the water column was less stratified. Other offshore flow patterns were more localized, with a flow at the bend or ‘point’ in the New Jersey coast being most common and most energetic. The offshore flow events identified here are capable of driving significant offshore transport, with more than one-third of offshore flow episodes having potential transport distances of greater than 14 km. In addition, clusters of multiple offshore flow events are shown to be capable of transporting near-surface material across much of the continental shelf. 相似文献
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Josh Kohut Hugh Roarty Evan Randall-Goodwin Scott Glenn C. Sage Lichtenwalner 《Ocean Dynamics》2012,62(6):953-968
The National High Frequency (HF) Surface Current Mapping Radar Network is being developed as a backbone system within the U.S. Integrated Ocean Observing System. This paper focuses on the application of HF radar-derived surface current maps to U.S. Coast Guard Search and Rescue operations along the Mid-Atlantic coast of the USA. In that context, we evaluated two algorithms used to combine maps of radial currents into a single map of total vector currents. In situ data provided by seven drifter deployments and four bottom-mounted current meters were used to (1) evaluate the well-established unweighted least squares (UWLS) and the more recently adapted optimal interpolation (OI) algorithms and (2) quantify the sensitivity of the OI algorithm to varying decorrelation scales and error thresholds. Results with both algorithms were shown to depend on the location within the HF radar data footprint. The comparisons near the center of the HF radar coverage showed no significant difference between the two algorithms. The most significant distinction between the two was seen in the drifter trajectories. With these simulations, the weighting of radial velocities by distance in the OI implementation was very effective at reducing both the distance between the actual drifter and the cluster of simulated particles as well as the scale of the search area that encompasses them. In this study, the OI further reduced the already improved UWLS-based search areas by an additional factor of 2. The results also indicated that the OI output was relatively insensitive to the varying decorrelation scales and error thresholds tested. 相似文献