Standard states for the activities of mineral surface sites and species     

Dimitri A Sverjensky 《Geochimica et cosmochimica acta》2003,67(1):17-28

A standard state commonly used for the activities of surface sites and surface species is the hypothetical 1.0 Molar standard state, which is implied by the use of molarity-based equilibrium constants. An undesirable practical consequence is that the magnitudes of such equilibrium constants are directly dependent on properties of the solid sorbent such as the site density and surface area. For reactions forming binuclear complexes, the magnitudes of the equilibrium constants even depend on the amount of solid. Although widely used, such equilibrium constants cannot be directly compared with each other without correction for differences in the properties or the amount of the solid. In the present study, new more general and useful standard states are proposed, leading to equilibrium constants independent of the surface area, site density, and the amount of the solid sorbent. Analytical relationships between the old and the new standard states enable conversion of equilibrium constants from one standard state to the other. These results have implications for several different types of surface complexation studies, including studies that correlate and compare equilibrium adsorption constants for different solids, sensitivity-analysis studies of the fitting of surface charge data as functions of pH and ionic strength, and studies employing correlations involving aqueous equilibrium constants for the purpose of predicting equilibrium constants for surface reactions.  相似文献   

Inorganic Water Quality Monitoring Using Specific Conductance in Mexico     

Luis E. Marín  B. Steinich  Oscar Escolero  Rosa María Leal  Braulio Silva  Susana Gutierrez 《Ground Water Monitoring & Remediation》1998,18(1):156-162

Five inorganic geochemical data sets with ion balances less than or equal to 5% (for different hydrogeologic basins in Mexico) were used to construct specific conductance (SC) vs. total dissolved solids (TDS) curves for each aquifer. These curves allow one to proxy the specific conductance for inorganic water quality. The data from these five curves were integrated to form a "global" curve for Mexico. The equation that defines the line is SC = 1.40 TDS + 18. We propose that, in addition to allowing ground water monitoring, establishing a SC vs. TDS curve may be implemented to monitor drinking water supplies such as wells and reservoirs. If anomalously high values are observed, this would warrant detailed geochemical sampling.  相似文献   

Spectral-element simulations of global seismic wave propagation—I. Validation     

Dimitri Komatitsch  Jeroen Tromp 《Geophysical Journal International》2002,149(2):390-412

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Implementation and Challenges of the Tsunami Warning System in the Western Mediterranean     

F. Schindelé  A. Gailler  H. Hébert  A. Loevenbruck  E. Gutierrez  A. Monnier  P. Roudil  D. Reymond  L. Rivera 《Pure and Applied Geophysics》2015,172(3-4):821-833

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Modeling level selection for seismic analysis of concrete‐filled steel tube/moment‐resisting frames by using fragility curves          下载免费PDF全文

Konstantinos A. Skalomenos  George D. Hatzigeorgiou  Dimitri E. Beskos 《地震工程与结构动力学》2015,44(2):199-220

The seismic behavior of plane moment‐resisting frames (MRFs) consisting of I steel beams and concrete‐filled steel tube (CFT) columns is investigated in this study. More specifically, the effect of modeling details of each individual component of CFT‐MRFs, such as the composite CFT columns, the beam‐column connections, the panel zones, and the steel I beams on their seismic behavior, is studied through comparisons against available experimental results. Then, fragility curves are constructed for three typical CFT‐MRFs, designed according to European codes, for various levels of modeling sophistication through nonlinear time‐history analyses. On the basis of these fragility curves, one can select the appropriate modeling level of sophistication that can lead to the desired seismic behavior for a given seismic intensity. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Numerical modeling of zero-offset laboratory data in a strong topographic environment: results for a spectral-element method and a discretized Kirchhoff integral method          下载免费PDF全文

Nathalie Favretto-Cristini  Anastasiya Tantsereva  Paul Cristini  Bjørn Ursin  Dimitri Komatitsch  Arkady M. Aizenberg 《地震科学（英文版）》2014,27(4):391-399

Accurate simulation of seismic wave propagation in complex geological structures is of particular interest nowadays. However conventional methods may fail to simulate realistic wavefields in environments with great and rapid structural changes, due for instance to the presence of shadow zones, diffractions and/or edge effects. Different methods, developed to improve seismic modeling, are typically tested on synthetic configurations against analytical solutions for simple canonical problems or reference methods, or via direct comparison with real data acquired in situ. Such approaches have limitations, especially if the propagation occurs in a complex environment with strong-contrast reflectors and surface irregularities, as it can be difficult to determine the method which gives the best approximation of the “real” solution, or to interpret the results obtained without an a priori knowledge of the geologic environment. An alternative approach for seismics consists in comparing the synthetic data with high-quality data collected in laboratory experiments under controlled conditions for a known configuration. In contrast with numerical experiments, laboratory data possess many of the characteristics of field data, as real waves propagate through models with no numerical approximations. We thus present a comparison of laboratory-scaled measurements of 3D zero-offset wave reflection of broadband pulses from a strong topographic environment immersed in a water tank with numerical data simulated by means of a spectral-element method and a discretized Kirchhoff integral method. The results indicate a good quantitative fit in terms of time arrivals and acceptable fit in amplitudes for all datasets.  相似文献   

Image decomposition of barred galaxies and AGN hosts     

Dimitri Alexei Gadotti 《Monthly notices of the Royal Astronomical Society》2008,384(1):420-439

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The growth of supermassive black holes in pseudo-bulges, classical bulges and elliptical galaxies     

Dimitri A. Gadotti  Guinevere Kauffmann 《Monthly notices of the Royal Astronomical Society》2009,399(2):621-627

Using results from structural analysis of a sample of nearly 1000 local galaxies from the Sloan Digital Sky Survey, we estimate how the mass in central black holes is distributed amongst elliptical galaxies, classical bulges and pseudo-bulges, and investigate the relation between their stellar masses and central stellar velocity dispersion σ. Assuming a single relation between elliptical galaxy/bulge mass, M _Bulge, and central black hole mass, M _BH, we find that  55⁺⁸₋₄  per cent of the mass in black holes in the local universe is in the centres of elliptical galaxies,  41⁺⁴₋₂  per cent in classical bulges and  4^+0.9_−0.4  per cent in pseudo-bulges. We find that ellipticals, classical bulges and pseudo-bulges follow different relations between their stellar masses and σ, and the most significant offset occurs for pseudo-bulges in barred galaxies. This structural dissimilarity leads to discrepant black hole masses if single   M _BH– M _Bulge  and   M _BH–σ  relations are used. Adopting relations from the literature, we find that the   M _BH–σ  relation yields an estimate of the total mass density in black holes that is roughly 55 per cent larger than if the   M _BH– M _Bulge  relation is used.  相似文献   

Diagenetic controls on the isotopic composition of carbonate‐associated sulphate in the Permian Capitan Reef Complex,West Texas     

Theodore M. Present  Melissa Gutierrez  Guillaume Paris  Charles Kerans  John P. Grotzinger  Jess F. Adkins 《Sedimentology》2019,66(7):2605-2626

Late Palaeozoic‐age strata from the Capitan Reef in west Texas show facies‐dependent heterogeneity in the sulphur isotopic composition of carbonate‐associated sulphate, which is trace sulphate incorporated into carbonate minerals that is often used to reconstruct the sulphur isotopic composition of ancient seawater. However, diagenetic pore fluid processes may influence the sulphur isotopic composition of carbonate‐associated sulphate. These processes variously modify the sulphur isotopic composition of incorporated sulphate from syndepositional seawater in shelf crest, outer shelf, shelf margin and slope depositional settings. This study used a new multicollector inductively‐coupled plasma mass spectrometry technique to determine the sulphur isotopic composition of samples of individual depositional and diagenetic textures. Carbonate rocks representing peritidal facies in the Yates and Tansill formations preserve the sulphur isotopic composition of Guadalupian seawater sulphate despite alteration of the carbon and oxygen isotopic compositions by meteoric and dolomitizing diagenetic processes. However, sulphur isotopic data indicate that limestones deposited in reef and slope facies in the Capitan and Bell Canyon formations largely incorporate sulphate from anoxic marine‐phreatic pore fluids isotopically modified from seawater by microbial sulphate reduction, despite generally preserving the carbon and oxygen isotopic compositions of Permian seawater. Some early and all late meteoric calcite cements have carbonate‐associated sulphate with a sulphur isotopic composition distinct from that of Permian seawater. Detailed petrographic and sedimentary context for carbonate‐associated sulphate analyses will allow for improved reconstructions of ancient seawater composition and diagenetic conditions in ancient carbonate platforms. The results of this study indicate that carbonate rocks that diagenetically stabilize in high‐energy environments without pore fluid sulphate gradients can provide a robust archive of ancient seawater's sulphur isotopic composition.  相似文献   

Comparison of short-term seacliff retreat measurement methods in Del Mar, California   总被引：1，自引：0，他引：1  

Adam P. Young  R.E. Flick  R. Gutierrez  R.T. Guza 《Geomorphology》2009,112(3-4):318-323

Seacliff retreat has been variously characterized as the recession rate of the cliff top, of the cliff base, and as the bulk recession rate based on volumetric changes of the entire cliff face. Here, these measures of retreat are compared using nine semi-annual airborne LiDAR (Light Detection And Ranging) surveys of southern California seacliffs. Changes in the cliff base location (where the steeply sloping cliff face intersects the beach) include cliff retreat owing to basal erosion, but also reflect changes in beach sand level and basal talus deposits. Averaged over the 2.5 km alongshore study span, the cliff base actually prograded seaward about 12 cm during the 4-year study. Cliff top change was dominated by few, relatively large (several meters) localized retreats. Cliff face changes, that include failures and deposits anywhere on the cliff profile, had a relatively small mean magnitude compared to cliff top changes and were more widely distributed alongshore. However, the similar alongshore averaged, cumulative cliff top and net bulk cliff face end-point retreat (14 and 19 cm, respectively) suggest that mean cumulative cliff top retreat can potentially be a viable surrogate for mean net cumulative cliff-wide erosion (and vice versa) over relatively short time periods. Cliff face erosion occurred repeatedly at some locations, confirming the presence of seacliff erosion hot-spots during the study period.  相似文献