40Ar-39Ar ages of biotites from Corsica and arguments for Permian age of alkaline granitic intrusion     

Henri Maluski 《Contributions to Mineralogy and Petrology》1976,58(3):305-317

The Western part of Corsica is underlain by Variscan calcalkaline granites which intrude the pre-Variscan basement. These granites and their basement are also intruded by Permian hyperalkaline granites. Overprinted biotites of the basement and the calcalkaline granites show only one plateau age at about 250 m.y., except for a sample of calcalkaline granite from the Cargèse region which has a high temperature plateau age of 330 m.y. related to the emplacement and a low temperature plateau age of 230 m.y. Plateau ages around 250 m.y. due to the intrusion of hyperalkaline granites whose biotites give plateau ages between 250 and 280 m.y. reflect this important thermal event.  相似文献   

Groundwater fluctuations and footslope ferricrete soils in the humid tropical zone of southern Cameroon     

Emile Temgoua  Henri‐Bosko Djeuda Tchapnga  Emile Tanawa  Claire Guenat  Hans‐Rudolf Pfeifer 《水文研究》2005,19(16):3097-3111

This paper discusses the relationship between the differentiation of ferruginous accumulations and the variable water saturation of footslope soil patterns. An analysis of the slope morphology of a typical hill in the forest zone of southern Cameroon and a seasonal survey of the levels of groundwaters, springs and rivers were considered in relation to the petrology of different soil patterns. The study site is a tabular hillock whose slopes present a progressive development from steep to gentle slopes. The variable residence time of water within the soil, creating an alternation of reducing and oxidizing conditions, affects soil chemistry, structure and lateral extension of the soil patterns. The ferruginous soil patterns, being formed on the footslopes, gradually increase in extent with decreasing slope angle and the relative rise of the groundwater level. The steep footslopes, where groundwater has a shorter residence time, show a soft mottled clay pattern, restricted to the bottom part of the slope. The moderate footslopes exhibit a deep permanent and a temporary perched groundwater table. The latter, with its regular capillary fringe, contributes to more reducing conditions within isolated domains in the soil patterns, and thus to the alternation with oxidizing conditions, generating a continuous hard soil pattern (massive carapace). The more gently dipping footslopes exhibit groundwater levels near the surface and also a significant amplitude of groundwater fluctuation. Iron, previously accumulated in moderate footslope patterns, is reduced, remobilized, and leached. The soil patterns formed develop into a variegated carapace, more extended along the slope, containing less iron, but nevertheless more hardened, due to the important fluctuations of the groundwater table. These patterns are limited to the zone of groundwater fluctuation and deteriorate as the water fluctuation zone recedes. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Truly isotropic biaxial hysteresis with arbitrary knee sharpness          下载免费PDF全文

P. Scott Harvey Jr.  Henri P. Gavin 《地震工程与结构动力学》2014,43(13):2051-2057

The inelastic responses of framed structures and seismic isolation systems undergoing biaxial (horizontal) shaking are coupled. In existing models for biaxial coupling of hysteretic behavior, the smoothness (or ‘knee') of the transition from elastic to yielding behavior cannot be modified without affecting the shape of the yield surface. This paper presents a model for coupled biaxial hysteretic behavior in which the knee from pre‐yield to post‐yield can be adjusted while maintaining an isotropic yield surface. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

In Memoriam: David le Sueur     

Henri EZ Tonnang  Richard YM Kangalawe  Pius Z Yanda 《Global Change & Human Health》2002,3(1):74-74

Biography

In Memoriam: David le Sueur  相似文献   

In situ Measurement of H2O and CH4 with Telecommunication Laser Diodes in the Lower Stratosphere: Dehydration and Indication of a Tropical Air Intrusion at Mid-Latitudes     

Georges Durry  Alain Hauchecorne  Joelle Ovarlez  Henri Ovarlez  Ivan Pouchet  Virginie Zeninari  Bertrand Parvitte 《Journal of Atmospheric Chemistry》2002,43(3):175-194

Telecommunication laser diodes emitting near 1.39 m and 1.65 m in combination with direct-differential absorption spectroscopy are efficient tools to monitor in situ stratospheric H₂O andCH₄ with a good precision error (a few percents), a high temporal resolution (ranging from 10 ms to 1 s), a large dynamic range in the concentration measurements (four orders of magnitude) and a high selectivity in the analyte species. To illustrate the capability of laser probing technique, we report balloonborne H₂Oand CH₄ simultaneous measurements obtained on October 2001 atmidlatitudes (43° N). The H₂O vertical profile achieved with the lasersensor in the lower stratosphere is compared with the H₂O data yielded by a balloonborne frost-point hygrometer. The total hydrogen mixing ratio in the lower stratosphere, 2[CH₄] + [H₂O], appears to beconstant at 7.5 ± 0.1 ppmv. Nevertheless, an unexpected largedehydration of 0.5 ppmv was detected by both the laser sensor and thehygrometer between 16 km and 23 km. We suspect the occurrence of a tropicalair intrusion into mid-latitudes. We support this interpretation using a high-resolution advection model for potential vorticity.  相似文献   

Diel variability of glycolate in the eastern tropical Atlantic Ocean     

Christophe Leboulanger  Louise Oriol  Henri Jupin  Chantal Desolas-gros 《Deep Sea Research Part I: Oceanographic Research Papers》1997,44(12):2131-2139

The concentration of dissolved glycolate in sea water was measured by high performance liquid chromatography in the eastern tropical Atlantic Ocean during the Eumeli 4 oceanographic cruise in June 1992. Diurnal concentrations of glycolate reached 74 kg 1⁻¹ 1⁻¹ in mesotrophic waters and 17 μg 1⁻¹ 1 in oligotrophic waters. At midday total dissolved glycolate exceeded 1 g of carbon per m² of ocean, decreasing strongly during the night (less than 0.1 g of carbon per m²). At the three stations studied, glycolate carbon difference between night and day in the water column was of the same order as the daily primary production estimated by incorporation of ¹⁴C0₂. Disappearance of this compound at night suggested a rapid consumption by heterotrophic organisms. These data suggest that glycolate excretion by phytoplankton may be important, and possibly influenced by ambient nutrient concentrations. Further, with glycolate representing up to 50% of daily productivity, our estimates of the total biological reduction of C0₂ need to be re-examined.  相似文献   

A unified formulation for the three-dimensional shallow water equations using orthogonal co-ordinates: theory and application     

Herman W. J. Kernkamp  Henri A. H. Petit  Herman Gerritsen  Erik D. de Goede 《Ocean Dynamics》2005,55(3-4):351-369

In this paper, the formulations of the primitive equations for shallow water flow in various horizontal co-ordinate systems and the associated finite difference grid options used in shallow water flow modelling are reviewed. It is observed that horizontal co-ordinate transformations do not affect the chosen co-ordinate system and representation in the vertical, and are the same for the three- and two-dimensional cases. A systematic derivation of the equations in tensor notation is presented, resulting in a unified formulation for the shallow water equations that covers all orthogonal horizontal grid types of practical interest. This includes spherical curvilinear orthogonal co-ordinate systems on the globe. Computational efficiency can be achieved in a single computer code. Furthermore, a single numerical algorithmic code implementation satisfies. All co-ordinate system specific metrics are determined as part of a computer-aided model grid design, which supports all four orthogonal grid types. Existing intuitive grid design and visual interpretation is conserved by appropriate conformal mappings, which conserve spherical orthogonality in planar representation. A spherical curvilinear co-ordinate solution of wind driven steady channel flow applying a strongly distorted grid is shown to give good agreement with a regular spherical co-ordinate model approach and the solution based on a β-plane approximation. Especially designed spherical curvilinear boundary fitted model grids are shown for typhoon surge propagation in the South China Sea and for ocean-driven flows through Malacca Straits. By using spherical curvilinear grids the number of grid points in these single model grid applications is reduced by a factor of 50–100 in comparison with regular spherical grids that have the same horizontal resolution in the area of interest. The spherical curvilinear approach combines the advantages of the various grid approaches, while the overall computational effort remains acceptable for very large model domains.  相似文献   

A case study of Kelvin-Helmholtz vortices on both flanks of the Earth's magnetotail     

Masaki N. Nishino  Hiroshi Hasegawa  Yoshifumi Saito  Iannis Dandouras  Henri Rème  Alessandro Retinò  Elizabeth Lucek 《Planetary and Space Science》2011,59(7):502-509

Kelvin-Helmholtz instability (KHI) is a fundamental fluid dynamical process that develops in a velocity shear layer. It is excited on the tail-flanks of the Earth's magnetosphere where the flowing magnetosheath plasma and the stagnant magnetospheric plasma sit adjacent to each other. This instability is thought to induce vortical structures and play an important role in plasma transport there. While KHI vortices have been detected, the earlier observations were performed only on one flank at a time and questions related to dawn-dusk asymmetry were not addressed. Here, we report a case where KHI vortices grow more or less simultaneously and symmetrically on both flanks, despite all the factors that may have broken the symmetry. Yet, energy distributions of ions in and around the vortices show a remarkable dawn-dusk asymmetry. Our results thus suggest that although the initiation and development of the KHI depend primarily on the macroscopic properties of the flow, the observed enhancement of ion energy transport around the dawn side vortices may be linked to microphysical processes including wave-particle interactions. Possible coupling between macro- and micro-scales, if it is at work, suggests a role for KHI not only within the Earth's magnetosphere (e.g., magnetopause and geomagnetic tail) but also in other regions where shear flows of magnetized plasma play important roles.  相似文献   

An Engineering Approach to Seismic Risk Management in Hardrock Mines     

Marty Hudyma  Yves Henri Potvin 《Rock Mechanics and Rock Engineering》2010,43(6):891-906

The problem of mining-induced seismicity in hardrock mines has become significant as underground mines from around the world are pushing production to deeper levels. At many mines, the risk associated with large seismic events and rockburst damage must be managed to ensure the safety of mine workers and minimise production losses. In this paper, an engineering approach to seismic risk management is described. It relies on accepted risk management techniques, which principally include the identification and understanding of hazards from which risk mitigation measures can be developed. This is achieved using simple but effective analysis techniques of high resolution microseismic data.  相似文献