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231.
As a contribution to the systematic study of iron oxide thermodynamics, this work reports enthalpies of formation of green rust, a double layered (FeII, FeIII) hydroxide with the ideal stoichiometry , with sulfate as the anion in the interlayer. Samples were characterized by X-ray powder diffraction, thermogravimetric analysis, infrared spectroscopy, and Mössbauer spectroscopy. Full chemical analysis was performed. Contents of FeII, FeIII, water, and sulfate were obtained. We report standard enthalpies of formation for green rust with different FeII/FeIII ratios. Enthalpies of formation from single cation compounds, namely, Fe(OH)2, Fe(OH)3, FeSO4 and H2O show reasonable agreement with Gibbs free energies of formation from single cation compounds recalculated from the reported literature values. These values show that green rust has little stabilization over a mechanical mixture of these single cation compounds and there is no thermodynamic preference for any particular FeII/FeIII ratio. 相似文献
232.
de Guenni Lelys B. García Mariangel Muñoz Ángel G. Santos José L. Cedeño Alexandra Perugachi Carlos Castillo José 《Theoretical and Applied Climatology》2017,129(3-4):1059-1073
Theoretical and Applied Climatology - It is well known that El Niño-Southern Oscillation (ENSO) modifies precipitation patterns in several parts of the world. One of the most impacted areas is... 相似文献
233.
Artur?P.?DeditiusEmail author Martin?Reich Adam?C.?Simon Alexandra?Suvorova Jaayke?Knipping Malcolm?P.?Roberts Sergey?Rubanov Aaron?Dodd Martin?Saunders 《Contributions to Mineralogy and Petrology》2018,173(6):46
Magnetite from hydrothermal ore deposits can contain up to tens of thousands of parts per million (ppm) of elements such as Ti, Si, V, Al, Ca, Mg, Na, which tend to either structurally incorporate into growth and sector zones or form mineral micro- to nano-sized particles. Here, we report micro- to nano-structural and chemical data of hydrothermal magnetite from the Los Colorados iron oxide–apatite deposit in Chile, where magnetite displays both types of trace element incorporation. Three generations of magnetites (X–Z) were identified with concentrations of minor and trace elements that vary significantly: SiO2, from below detection limit (bdl) to 3.1 wt%; Al2O3, 0.3–2.3 wt%; CaO, bdl–0.9 wt%; MgO, 0.02–2.5 wt%; TiO2, 0.1–0.4 wt%; MnO, 0.04–0.2 wt%; Na2O, bdl–0.4 wt%; and K2O, bdl–0.4 wt%. An exception is V2O3, which is remarkably constant, ranging from 0.3 to 0.4 wt%. Six types of crystalline nanoparticles (NPs) were identified by means of transmission electron microscopy in the trace element-rich zones, which are each a few micrometres wide: (1) diopside, (2) clinoenstatite; (3) amphibole, (4) mica, (5) ulvöspinel, and (6) Ti-rich magnetite. In addition, Al-rich nanodomains, which contain 2–3 wt% of Al, occur within a single crystal of magnetite. The accumulation of NPs in the trace element-rich zones suggest that they form owing to supersaturation from a hydrothermal fluid, followed by entrapment during continuous growth of the magnetite surface. It is also concluded that mineral NPs promote exsolution of new phases from the mineral host, otherwise preserved as structurally bound trace elements. The presence of abundant mineral NPs in magnetite points to a complex incorporation of trace elements during growth, and provides a cautionary note on the interpretation of micron-scale chemical data of magnetite. 相似文献
234.
Ménard A. Dana Houser Chris Brander Robert W. Trimble Sarah Scaman Alexandra 《Natural Hazards》2018,94(2):953-973
Natural Hazards - The rip current hazard on beaches is a global public health issue. While physical controls on rip current formation and flow behavior are relatively well understood, there has... 相似文献
235.
Omar Benazzouz Luis M. Pinheiro Luis M. A. Matias Alexandra Afilhado Daniel Herold Seth S. Haines 《Mathematical Geosciences》2018,50(5):569-584
The positioning of ocean bottom seismometers (OBS) is a key step in the processing flow of OBS data, especially in the case of self popup types of OBS instruments. The use of first arrivals from airgun shots, rather than relying on the acoustic transponders mounted in the OBS, is becoming a trend and generally leads to more accurate positioning due to the statistics from a large number of shots. In this paper, a linearization of the OBS positioning problem via the multilateration technique is discussed. The discussed linear solution solves jointly for the average water layer velocity and the OBS position using only shot locations and first arrival times as input data. 相似文献
236.
A novel toxicity method to determine sublethal and lethal effects of manmade contaminants on the bioluminescence output from marine dinoflagellates has been developed and tested over the course of 16 years. The toxicity system, QwikLite™, was developed for the sole purpose of evaluating the potential toxicity of various materials used in bay sediments, storm water discharges, industrial discharges from Naval facilities, and antifoulant paints. Bioluminescence inhibition was observed in the following dinoflagellates: Lingulodinium polyedrum (formerly known as Gonyaulax polyedra), Ceratocorys horrida, Pyrocystis noctiluca, Pyrocystis lunula, Pyrocystis fusiformis, and Pyrophacus steinii. Cultured cells were exposed to various concentrations of contaminants from hours through 10 days. Further application with bioluminescent dinoflagellates in a variety of toxicity testing schemes have shown that these species can be used as a screening assay organism in lieu of the more costly, labor intensive bioassays presently in use. 相似文献
237.
Alfred S. McEwen Maria E. Banks Kris Becker James W. Bergstrom Edward Bortolini Shane Byrne Frank C. Chuang Ingrid Daubar Donald G. Deardorff W. Alan Delamere Colin M. Dundas Yisrael Espinoza Kathryn E. Fishbaugh Paul E. Geissler Jennifer L. Griffes Virginia C. Gulick Kenneth E. Herkenhoff Windy L. Jaeger Bob Kanefsky Robert King Kelly J. Kolb Alexandra Lefort Kevin W. Lewis Sarah Mattson Michael T. Mellon Moses P. Milazzo Tahirih Motazedian Albert Ortiz Joseph Plassmann Patrick S. Russell Mindi L. Searls Steven W. Squyres Nicolas Thomas Livio L. Tornabene Circe Verba James J. Wray 《Icarus》2010,205(1):2-216
The High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO) acquired 8 terapixels of data in 9137 images of Mars between October 2006 and December 2008, covering ∼0.55% of the surface. Images are typically 5-6 km wide with 3-color coverage over the central 20% of the swath, and their scales usually range from 25 to 60 cm/pixel. Nine hundred and sixty stereo pairs were acquired and more than 50 digital terrain models (DTMs) completed; these data have led to some of the most significant science results. New methods to measure and correct distortions due to pointing jitter facilitate topographic and change-detection studies at sub-meter scales. Recent results address Noachian bedrock stratigraphy, fluvially deposited fans in craters and in or near Valles Marineris, groundwater flow in fractures and porous media, quasi-periodic layering in polar and non-polar deposits, tectonic history of west Candor Chasma, geometry of clay-rich deposits near and within Mawrth Vallis, dynamics of flood lavas in the Cerberus Palus region, evidence for pyroclastic deposits, columnar jointing in lava flows, recent collapse pits, evidence for water in well-preserved impact craters, newly discovered large rayed craters, and glacial and periglacial processes. Of particular interest are ongoing processes such as those driven by the wind, impact cratering, avalanches of dust and/or frost, relatively bright deposits on steep gullied slopes, and the dynamic seasonal processes over polar regions. HiRISE has acquired hundreds of large images of past, present and potential future landing sites and has contributed to scientific and engineering studies of those sites. Warming the focal-plane electronics prior to imaging has mitigated an instrument anomaly that produces bad data under cold operating conditions. 相似文献
238.
Tide gauge observations usually include temperature and density measurements. As an example of such data, a time series of sea surface temperature (SST) from 1855 to 1877 and from 1921 to 1993 at Fort Point, San Francisco, California (the longest U.S. record), and mean air temperature at Mission Dolores (San Francisco), California, from 1936 to 1990, were analyzed. Annual mean Fort Point SST increased at a rate of 0.3°C per century, but the coefficient of determination (r2) was below 0.06; for air temperature the results were 1.6°C per century and r2 = 0.16 respectively. Evidence of El Niño were found in the periodogram of the mean annual SST but not in the air temperature. The annual and semiannual peaks in the monthly time‐series analysis of SST and air temperature dominate their periodograms, and the cross‐correlation between them has r2 = 0.47. Of the 1.3 mmlyr sea level rise over the same time period. 0.003°C/yr accounts for 0.04 mmlyr in thermal expansion if the upper 100 m of the water column were uniformly warmed. 相似文献
239.
Multivariate statistics are used to investigate sensitivity of the tropical atmospheric circulation to scenario-based global
land cover change (LCC), with the largest changes occurring in the tropics. Three simulations performed with the fully coupled
Parallel Climate Model (PCM) are compared: (1) a present day control run; (2) a simulation with present day land cover and
Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES) A2 greenhouse gas (GHG) projections;
and (3) a simulation with SRES A2 land cover and GHG projections. Dimensionality of PCM data is reduced by projection onto
a priori specified eigenvectors, consisting of Rossby and Kelvin waves produced by a linearized, reduced gravity model of
the tropical circulation. A Hotelling T
2 test is performed on projection amplitudes. Effects of LCC evaluated by this method are limited to diabatic heating. A statistically
significant and recurrent signal is detected for 33% of all tests performed for various combinations of parameters. Taking
into account uncertainties and limitations of the present methodology, this signal can be interpreted as a Rossby wave response
to prescribed LCC. The Rossby waves are shallow, large-scale motions, trapped at the equator and most pronounced in boreal
summer. Differences in mass and flow fields indicate a shift of the tropical Walker circulation patterns with an anomalous
subsidence over tropical South America. 相似文献
240.
Alexandra Jahn Bruno Tremblay Lawrence A. Mysak Robert Newton 《Climate Dynamics》2010,34(2-3):201-222
Freshwater (FW) leaves the Arctic Ocean through sea-ice export and the outflow of low-salinity upper ocean water. Whereas the variability of the sea-ice export is known to be mainly caused by changes in the local wind and the thickness of the exported sea ice, the mechanisms that regulate the variability of the liquid FW export are still under investigation. To better understand these mechanisms, we present an analysis of the variability of the liquid FW export from the Arctic Ocean for the period 1950–2007, using a simulation from an energy and mass conserving global ocean–sea ice model, coupled to an Energy Moisture Balance Model of the atmosphere, and forced with daily winds from the NCEP reanalysis. Our results show that the simulated liquid FW exports through the Canadian Arctic Archipelago (CAA) and the Fram Strait lag changes in the large-scale atmospheric circulation over the Arctic by 1 and 6 years, respectively. The variability of the liquid FW exports is caused by changes in the cyclonicity of the atmospheric forcing, which cause a FW redistribution in the Arctic through changes in Ekman transport in the Beaufort Gyre. This in turn causes changes in the sea surface height (SSH) and salinity upstream of the CAA and Fram Strait, which affect the velocity and salinity of the outflow. The SSH changes induced by the large-scale atmospheric circulation are found to explain a large part of the variance of the liquid FW export, while the local wind plays a much smaller role. We also show that during periods of increased liquid FW export from the Arctic, the strength of the simulated Atlantic meridional overturning circulation is reduced and the ocean heat transport into the Arctic is increased. These results are particularly relevant in the context of global warming, as climate simulations predict an increase in the liquid FW export from the Arctic during the twenty-first century. 相似文献