Line-broadening effects in the powder infrared spectrum of apatite     

Etienne Balan  Simon Delattre  Damien Roche  Loïc Segalen  Guillaume Morin  Maxime Guillaumet  Marc Blanchard  Michele Lazzeri  Christian Brouder  Ekhard K. H. Salje 《Physics and Chemistry of Minerals》2011,38(2):111-122

The crystallinity of natural and synthetic apatite samples is often determined from the broadening of ν ₄ PO₄ infrared absorption bands. However, various physical mechanisms contribute to the observed linewidth. In the present study, the factors determining the linewidth in the powder spectrum of synthetic fluorapatite and hydroxyapatite samples are investigated. The temperature dependence of the infrared spectrum (10–270 K) is used to assess the respective contributions of homogeneous broadening, related to the decay of phonons through anharmonic coupling, and heterogeneous broadening related to elastic strain and macroscopic electrostatic effects. This latter contribution is dominant in the investigated samples and depends on the shape of powder particles. It is discussed under the light of the theoretical modeling of the low-frequency dielectric properties of apatite based on first-principles density functional theory calculations. The linewidth of the weak ν ₁ PO₄ absorption band provides a reliable information on microscopic sources of broadening, i.e., apatite crystallinity. In comparison, the other more intense PO₄ bands are more sensitive to long-range electrostatic effects.  相似文献   

Transport and distribution of bacteria and diatoms in the aqueous surface microlayer of a salt marsh     

Ronald W. Harvey  Leonard W. Lion  Lily Y. Young 《Estuarine, Coastal and Shelf Science》1983,16(5):543-547

The effects of tide and wind upon the distribution and transport of bacteria and diatoms in the aqueous surface microlayers of a Massachusetts and San Francisco Bay salt marsh were examined. The compression of the surface films by both tide and wind resulted in significant enrichments of bacterioneuston. At the San Francisco Bay site, significant numbers of diatoms were transported within the microlayer over a tidal cycle.  相似文献   

Chemical speciation of trace metals at the air-sea interface: The application of an equilibrium model     

Leonard W. Lion  James O. Leckie 《Environmental Geology》1981,3(5):293-314

Air-sea interfacial solutions have characteristically high concentrations of trace metals, microorganisms, organic compounds, and solids relative to bulk solutions. The potential for the chemical interaction of an array of trace metals in the interfacial regions with complexing organic ligands and adsorbing solid surfaces has been evaluated through the use of an equilibrium computer model. Computations suggest that higher interfacial accumulations of copper and lead may occur relative to cadmium and mercury. These results are found to be generally compatible with available field data describing trace metal interfacial accumulation. The forms of metals found to be partitioned between bulk and interfacial solutions are consistent with the hypothesis that solid surface adsorption and dissolved organic complexation reactions bring about metal enrichment at the surface microlayer.  相似文献   

Optimal deterministic guidance for bounded-thrust spacecrafts     

Kornhauser  Alain L.  Lion  Paul M. 《Celestial Mechanics and Dynamical Astronomy》1972,5(3):261-281

The minimum-propellant deterministic guidance law for bounded-thrust, constant jetexhaust velocity, spacecrafts is developed using the neighboring extremal theory. Minimization of the first-order variation in cost between a multi-burn nominal extremal and the perturbed trajectory eliminates all correction strategies except small changes in the nominal thrust-on, thrust-off times and small rotations of the thrust vector. Optimal values of these corrective controls for fixed values of initial state deviations, x ₀, are found by minimizing the second variation in cost subject to the variational state and adjoint equations — an accessory minimum problem. The solution takes the linear feedback form u=A ^–1 ₂₂ A ₂₁x ₀, where the matricesA ₂₂ andA ₂₁ are functions only of transition matrices calculated along the nominal trajectory. The solution is applied to a three-burn Earth-Mars transfer.  相似文献   

Hierarchical modelling of archaeomagnetic data and curve estimation by moving average technique     

Philippe Lanos  Maxime Le Goff  Mary Kovacheva  Elisabeth Schnepp 《Geophysical Journal International》2005,160(2):440-476

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Distortion of the geomagnetic field in volcanic terrains: an experimental study of the Mount Etna stratovolcano     

Jean-Claude Tanguy  Maxime Le Goff 《Physics of the Earth and Planetary Interiors》2004,141(1):59-70

The inclination (I), declination (D) and total intensity (F) of the geomagnetic field were measured on Mount Etna in 1989-1991 at a dozen sites previously sampled for archeomagnetic studies. The purpose of the work was to determine the variations of these parameters at 30 cm above ground level, and how the distortion from the main field can affect the archeomagnetic record of volcanic rocks. Ten measurements were usually performed at each site with a three-component flux-gate magnetometer, whose estimated precision is ±0.2° on direction and ±50 nT on intensity. This was considered sufficient on volcanic areas with highly magnetized rocks and where the geomagnetic gradient may be in excess of 1000 nT/m. Results averaged for each site generally show small variations in intensity (±3% of the total field) and direction (±1.5°). The averaged values of the 12 sites (I=52.6°, D=0.3°, F=44010 nT) are very close to those measured in sedimentary terrain away from the volcano (I=52.9°, D=0.35°, F=44110 nT), themselves consistent with the interpolated IGRF in eastern Sicily. The largest deviations of the geomagnetic direction have been observed on four sites, three of them located on the South flank between 1900 and 700 m elevation. It is suggested that these anomalies are mainly related to dyke swarms which are common within the South Rift Zone of Mount Etna. Our findings show that reliable archeomagnetic results can be obtained from volcanic rocks, provided that lavas of the same eruption are sampled on several sites distributed over the largest possible area.  相似文献   

Structures in the Canyon Mountain Ophiolite indicate an island-arc intrusion     

Maxime Misseri  Franoise Boudier 《Tectonophysics》1985,120(3-4):191-209

Lithosphere created in an interarc basin is expected to be characterized by features distinguishing it from “normal” oceanic lithosphere. Apart from island-arc geochemical affinities and from the occurrence of hydrous high-T parageneses in the mantle and deep crustal sequences, it is expected that due to a low rate of spreading, vertical transport prevails over lateral drifting.

The Canyon Mountain complex located in an island-arc environment of Permo-Triassic age offers a remarkable illustration of these expected geological characteristics. In particular, mantle diapirism is deduced from the structural study. Smaller diapirs are formed in crustal formations. The intrusions took place at variable temperatures (1300°–800°C) and were accompanied by multistage melting in hydrous conditions.  相似文献   

Reply to the Comment on “Chronology of Vesuvius' activity from A.D. 79 to 1631 based on archeomagnetism of lavas and historical sources” by R. Lanza and E. Zanella     

Claudia Principe  Jean-Claude Tanguy  Simone Arrighi  Maxime Le Goff 《Bulletin of Volcanology》2006,68(4):397-398

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Organo-colloidal control on major- and trace-element partitioning in shallow groundwaters: Confronting ultrafiltration and modelling     

Olivier Pourret  Aline DiaMélanie Davranche  Gérard GruauOdile Hénin  Maxime Angée 《Applied Geochemistry》2007

Ultrafiltration experiments using new small ultracentifugal filter devices were performed at different pore size cut-offs to allow the study of organo-colloidal control on metal partitioning in water samples. Two shallow, circumneutral pH waters from the Mercy site wetland (western France) were sampled: one dissolved organic carbon (DOC)- and Fe-rich and a second DOC-rich and Fe-poor. Major- and trace-element cations and DOC concentrations were analysed and data treated using an ascendant hierarchical classification method. This reveals the presence of three groups: (i) a “truly” dissolved group (Na, K, Rb, Ca, Mg, Ba, Sr, Si and Ni); (ii) an inorganic colloidal group carrying Fe, Al and Th; and (iii) an organic colloidal group enriched in Cr, Mn, Co, Cu and U. However, REE and V have an ambivalent behaviour, being alternatively in the organic pool and in the inorganic pool depending on sample. Moreover, organic speciation calculation using Model VI were performed on both samples for elements for which binding constants were available (Ca, Mg, Ni, Fe, Al, Th, Cr, Cu, Dy, Eu). Calculation shows relatively the same partitioning of these elements as ultrafiltration does. However, some limitations appear such as (i) a direct use of ultrafiltration results which tends to overestimate the fraction of elements bound to humic material in the inorganic pool as regards to model calculations as well as, (ii) a direct use of speciation calculation results which tends to overestimate the fraction of elements bound to humic material in the organic pool with regard to ultrafiltration results. Beside these limitations, one can consider that both techniques, ultrafiltration and speciation calculation, give complementary information, especially for more complex samples where inorganic and organic colloids compete.  相似文献   

A transversely isotropic thermo-poroelastic model for claystone: parameter identification and application to a 3D underground structure     

Richard Giot  Sylvie Granet  Maxime Faivre  Nadia Massoussi  Julie Huang 《Geomechanics and Geoengineering》2018,13(4):246-263

A transversely isotropic thermo-poroelastic constitutive law is developed and implemented in the finite element code Code_Aster (EDF, France). It is then validated using an analytic solution for an inclined borehole in a transversely isotropic medium. A strategy for identifying the parameters of the transversely isotropic thermo-poroelastic model based on an inverse method is proposed on the basis of different laboratory tests. To demonstrate the efficiency and applicability of the model, it is then applied in a three-dimensional numerical model of an underground structure in a parameter sensitivity study. The results of the modelling highlight the importance of accounting for anisotropic phenomena when determining the dimensions of underground facilities. The whole approach is presented in the paper, from model development to application to 3D numerical modelling to an engineering case study.  相似文献