The H− equilibrium using coupled rate equations for H−, H,H+, H2, and H2 +     

Bruce W. Lites  Dimitri Mihalas 《Solar physics》1984,93(1):23-35

We formulate rate equations for the reaction network coupling H, H^–, H⁺, H₂, and H₂ ⁺. We attempt to systematize the notation, and to write the equations in a form suitable for modern computational methods of handling the coupled rate equations and radiative transfer equations, for both dynamical and static atmospheres. We have accounted for more processes than are generally considered in most current work; some of these may have an impact on the equilibrium of H^– (hence its opacity) and on charge conservation (hence the proton density) in the atmospheres of solar-type stars.Operated by the Association of Universities for Research in Astronomy, Inc. under Contract AST 78-17292 with the National Science Foundation.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

Europium redox equilibria in aqueous solution   总被引：6，自引：0，他引：6  

Dimitri A. Sverjensky 《Earth and Planetary Science Letters》1984,67(1):70-78

Thermochemical data and recent advances in theoretical aqueous solution chemistry enable prediction of the relative stabilities of aqueous Eu²⁺ and Eu³⁺ over a wide range of temperatures and pressures. At low temperatures, near earth surface conditions, the aqueous geochemistry of europium should be dominated by the trivalent state, except possibly in the most reducing, alkaline pore waters of anoxic marine sediments. However, at temperatures greater than about 250°C and elevated pressures, divalent europium should predominate. Even with significant amounts of complexing, trivalent europium is not stable at elevated temperatures and pressures. Consequently, under most hydrothermal and metamorphic conditions, europium in aqueous solution should be divalent. At intermediate temperatures, around 100°C, significant activities of both Eu²⁺ and Eu³⁺, and related complexes, can occur in aqueous solutions, depending on the oxidation state and the pH of the solutions, and the activities of potential ligands such as sulfate, carbonate and chloride. The predicted stability of divalent europium in aqueous solution at elevated temperatures is consistent with the large positive europium anomalies in rare earth element patterns of high-temperature barites of hydrothermal and metamorphic origin reported by Guichard et al. [5] and with the observed depletion of europium as a result of high-temperature sericitization of feldspar-bearing assemblages discovered by Alderton et al. [1]. It is suggested that significant fractionation of europium relative to the other rare earth elements may take place during high-temperature hydrothermal alteration processes, such as in the mid-oceanic ridge systems, because of the expected stability of divalent europium during these processes.  相似文献   

Sensitive stages during embryonic development of wolffish, Anarhichas lupus L. determining the final numbers of rays in unpaired fins and skeletal abnormalities     

Pavlov  Dimitri A.; Moksness  Erlend 《ICES Journal of Marine Science》1996,53(4):731-740

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Glacial isostatic adjustment on 3-D Earth models: a finite-volume formulation   总被引：3，自引：0，他引：3  

Konstantin Latychev  Jerry X. Mitrovica  Jeroen Tromp  Mark E. Tamisiea  Dimitri Komatitsch  Christina C. Christara 《Geophysical Journal International》2005,161(2):421-444

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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   

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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250 years of sardine and anchovy scale deposition record in Mejillones Bay, northern Chile   总被引：2，自引：1，他引：1  

Jorge Valds  Luc Ortlieb  Dimitri Gutierrez  Luis Marinovic  Gabriel Vargas  Abdel Sifeddine 《Progress in Oceanography》2008,79(2-4):198

Marine oxygen-deficient environments with high sedimentation rates and high primary productivity can provide relevant information regarding variations of ocean–climatic conditions in the past. In the Humboldt current ecosystem, which now hosts huge populations of pelagic fishes (mainly anchovy and sardine), fish scale abundance in the sedimentary record may be useful indicators of environmental change. Here we assess such a proxy record in a 42 cm-long sedimentary core collected from 80 m in Mejillones Bay (23°S, northern Chile). We also analyse fish remains in surface sediment sampled along a bathymetric transect (from 10 to 110 m water depth) in the same bay. In the core-top record, the fluctuations of sardine and anchovy scale deposition rates (SDR) agreed with those of industrial catches for these two species in northern Chile, tending to validate the SDR as a proxy of local fish biomass when bottom anoxic conditions prevail. However, apparent SDR for records prior to 1820 have probably been influenced by dissolution processes linked to the oxygenation of the bottom environment of Mejillones Bay, as suggested by other proxy records. After 1820, the fluctuations in the relative abundance of sardine and anchovy scales point to alternating warm and cold conditions during about 30 years and then a progressively cooler period. Since ca. 1870, marked fluctuations of SDR of both species are observed, probably as a consequence of the onset of a different oceanographic regime characterized by intensified upwelling, stronger subsurface oxygen deficiency, higher primary productivity, and enhanced “ENSO-like” interdecadal variability. While anchovy SDR fluctuated in periods of 25–40 years, only two peak periods of sardine SDR occurred (late 19th century and late 20th century), suggesting that sardine abundance depends on other ocean–climatic factors.  相似文献   

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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