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11.
Nonlinear and multifractal approaches of the geomagnetic field 总被引:2,自引:0,他引:2
L. Hongre P. Sailhac M. Alexandrescu J. Dubois 《Physics of the Earth and Planetary Interiors》1999,110(3-4):157-190
Recent nonlinear dynamics techniques have been developed to analyse chaotic time series data. We first summarize the procedure which gives an appropriate reconstruction of the unknown dynamics from scalar measurements in a pseudophase space. It permits, firstly, the representation of the trajectories of the dynamical system—they define an attractor when the system is dissipative—by preserving its topological properties. We then present the invariant measures and ergodic quantities such as the multifractal spectrum and Lyapunov exponents which can be estimated on the reconstructed attractor. The multifractal analysis provides us with a characterization of the scaling energy of the process whereas the Lyapunov exponent gives another statistical measure of the stability of the dynamics. The estimation of these quantities was tested on synthetic data. The nonlinear and multifractal analyses were finally applied to the hourly mean values of the magnetic field recorded at the Eskdalemuir (ESK) observatory over 79 years (692,520 data measurements for each component). The estimations of a 5-dimensional pseudo-phase space and a positive Lyapunov exponent confirm the possibility of low-dimensional deterministic chaos in the magnetic field observations at ESK observatory. The correlation between the solar activity (the Wolf number), the unstable nature of the magnetic field, and the singularity spectrum points out the forcing of the solar cycles on the dynamics of the magnetic field at ESK observatory. 相似文献
12.
Nathalie Dubois Love Råman Vinnå Marvin Rabold Michael Hilbe Flavio S. Anselmetti Alfred Wüest Laetitia Meuriot Alice Jeannet Stéphanie Girardclos 《Sedimentology》2020,67(2):971-990
River engineering projects are developing rapidly across the globe, drastically modifying water courses and sediment transfer. Investigation of the impact of engineering works focuses usually on short-term impacts, thus a longer-term perspective is still missing on the effects that such projects have. The ‘Jura Water Corrections’ – the largest river engineering project ever undertaken in Switzerland – radically modified the hydrological system of Lake Biel in the 19th and 20th Century. The deviation of the Aare River into Lake Biel more than 140 years ago, in 1878, thus represents an ideal case study to investigate the long-term sedimentological impacts of such large-scale river rerouting. Sediment cores, along with new high-resolution bathymetric and seismic reflection datasets were acquired in Lake Biel to document the consequences of the Jura Water Corrections on the sedimentation history of Lake Biel. Numerous subaquatic mass transport structures were detected on all of the slopes of the lake. Notably, a relatively large mass transport complex (0·86 km2) was observed on the eastern shore, along the path of the Aare River intrusion. The large amount of sediment delivered by the Aare River since its deviation into the lake likely caused sediment overloading resulting in subaquatic mass transport. Alternatively, the dumping since 1963 in a subaquatic landfill of material excavated during the second phase of river engineering, when the channels flowing into and out of Lake Biel were widened and deepened, might have triggered the largest mass transport, dated to 1964 or 1965. Additional potential triggers include two nearby small earthquakes in 1964 and 1965 (MW 3·9 and 3·2, respectively). The data for this study indicate that relatively large mass transports have become recurrent in Lake Biel following the deviation of the Aare River, thus modifying hazard frequency for the neighbouring communities and infrastructure. 相似文献
13.
Mechanical isostasy of the lithosphere in the South Atlantic Ocean was studied using information on gravity anomalies and bathymetry with additional constraints imposed by the altimetric geoid. The isostatic responses (admittances) over the Walvis Ridge, Rio Grande Rise and Trindade Seamount Chain were computed using a three-dimensional algorithm. The eastern Walvis Ridge and the Rio Grande Rise have the same response, which is well explained by an Airy model of isostasy. The other features are regionally supported. A variation in the thickness of the elastic plate was found along the western Walvis Ridge. A high value of the elastic plate thickness (20 km) was found under the Trindade Chain. Geodynamic implications are discussed in the light of these results. 相似文献
14.
While the d.c. electrical properties of a rock, through the volume conductivity, provide information on pore space structure (Formation factor) and pore fluid, the frequency dependence of the electrical parameters allows the characterization of the pore-matrix interfaces. To illustrate these properties, we present here some results of measurements performed on sedimentary rocks (Vosges and Fontainebleau sandstones). These samples have a classical electrical response, i.e. a ‘Cole and Cole’ frequency behaviour near a certain relaxation frequency and a low-frequency dispersion. We discuss some of the models that have been proposed in the past to explain this behaviour. It appears that most of them are valid near and above the relaxation frequency, but only Dissado and Hill's model seems to be satisfactory over the whole frequency range. The fractal nature of the interfaces, assumed in two of these models but appropriate only for one of them, could also be a convenient explanation for the frequency dependence. 相似文献
15.
Coteur G Danis B Fowler SW Teyssié JL Dubois P Warnau M 《Marine pollution bulletin》2001,42(8):667-672
The impact of four PCB congeners: 3,3',4,4'-tetrachlorobiphenyl (IUPAC congener #77), 3,3',4,4',5-pentachlorobiphenyl (IUPAC #126), 2,2',4,4',5,5'-hexachlorobiphenyl (IUPAC #153) and 3,3',4,4',5,5'-hexachlorobiphenyl (IUPAC #169) was investigated on the reactive oxygen species (ROS) production by coelomocytes of the echinoid Paracentrotus lividus, an important species in marine benthic ecosystems. PCBs were found to increase ROS production and to delay the time of peak production. These effects were stronger on bacteria-stimulated cells and were congener-specific: coplanar congeners (#77, 126 and 169) had more effect than the non-coplanar PCB #153. Among coplanar congeners, PCB #169 showed dose-dependent effects whereas PCB #77 and 126 were more toxic at high and low doses, respectively. The relative immunotoxicity of the different PCB congeners is discussed in the light of their structural properties and biological affinities. 相似文献
16.
J-Ph. Bernard P. Ade Y. André J. Aumont L. Bautista N. Bray P. de Bernardis O. Boulade F. Bousquet M. Bouzit V. Buttice A. Caillat M. Charra M. Chaigneau B. Crane J.-P. Crussaire F. Douchin E. Doumayrou J.-P. Dubois C. Engel P. Etcheto P. Gélot M. Griffin G. Foenard S. Grabarnik P. Hargrave A. Hughes R. Laureijs Y. Lepennec B. Leriche Y. Longval S. Maestre B. Maffei J. Martignac C. Marty W. Marty S. Masi F. Mirc R. Misawa J. Montel L. Montier B. Mot J. Narbonne J-M. Nicot F. Pajot G. Parot E. Pérot J. Pimentao G. Pisano N. Ponthieu I. Ristorcelli L. Rodriguez G. Roudil M. Salatino G. Savini O. Simonella M. Saccoccio P. Tapie J. Tauber J.-P. Torre C. Tucker 《Experimental Astronomy》2016,42(2):199-227
Future cosmology space missions will concentrate on measuring the polarization of the Cosmic Microwave Background, which potentially carries invaluable information about the earliest phases of the evolution of our universe. Such ambitious projects will ultimately be limited by the sensitivity of the instrument and by the accuracy at which polarized foreground emission from our own Galaxy can be subtracted out. We present the PILOT balloon project, which aims at characterizing one of these foreground sources, the polarized continuum emission by dust in the diffuse interstellar medium. The PILOT experiment also constitutes a test-bed for using multiplexed bolometer arrays for polarization measurements. This paper presents the instrument and its expected performances. Performance measured during ground calibrations of the instrument and in flight will be described in a forthcoming paper. 相似文献
17.
B.?LacroixEmail author D.?Charpentier M.?Buatier T.?Vennemann P.?Labaume T.?Adatte A.?Travé M.?Dubois 《Contributions to Mineralogy and Petrology》2012,163(6):1083-1102
The chemical and isotopic compositions of clay minerals such as illite and chlorite are commonly used to quantify diagenetic and low-grade metamorphic conditions, an approach that is also used in the present study of the Monte Perdido thrust fault from the South Pyrenean fold-and-thrust belt. The Monte Perdido thrust fault is a shallow thrust juxtaposing upper Cretaceous–Paleocene platform carbonates and Lower Eocene marls and turbidites from the Jaca basin. The core zone of the fault, about 6 m thick, consists of intensely deformed clay-bearing rocks bounded by major shear surfaces. Illite and chlorite are the main hydrous minerals in the fault zone. Illite is oriented along cleavage planes while chlorite formed along shear veins (<50 μm in thickness). Authigenic chlorite provides essential information about the origin of fluids and their temperature. δ18O and δD values of newly formed chlorite support equilibration with sedimentary interstitial water, directly derived from the local hanging wall and footwall during deformation. Given the absence of large-scale fluid flow, the mineralization observed in the thrust faults records the P–T conditions of thrust activity. Temperatures of chlorite formation of about 240°C are obtained via two independent methods: chlorite compositional thermometers and oxygen isotope fractionation between cogenetic chlorite and quartz. Burial depth conditions of 7 km are determined for the Monte Perdido thrust reactivation, coupling calculated temperature and fluid inclusion isochores. The present study demonstrates that both isotopic and thermodynamic methods applied to clay minerals formed in thrust fault are useful to help constrain diagenetic and low-grade metamorphic conditions. 相似文献
18.
AbstractThree large (kilometric-scale) caves were studied in the Buda hills and the main directions of cave corridors, fault planes and mineralized veins were measured. Different stages of mineralizations are recognised: calcite scaleno- hedrons, baryte, silica, gypsum. New investigations of fluid inclusions in the baryte suggest a crystallization temperature of 50 °C and a freshwater fluid source. Microtectonic analysis allows the reconstruction of the successive tectonic events: (1) a NE-SW extensional phase at the Late Eocene-Early Oligocene limit (phase I), (2) a strike-slip phase with NW-SE compression and NE-SW extension during the Late Oligocene-Early Miocene (phase II), (3) a NW-SE transten- sional phase (phase III) and finally (4) a NE-SW extensional phase of Quaternary age (phase IV). The major phase is the strike-slip one, characterized by an important dextral strike- slip zone: the Ferenc-hegy zone. © Elsevier, Paris 相似文献
19.
Sommaire La discussion de l'éclipse du 16.IX.1978 basée sur la comparaison des mesures photométriques de l'ombre avec la théorie basée sur l'atmosphère terrestre (pure). Les différences de la densité observée et de la densité calculée sont partiellement dues à l'absorption dans la couche d'ozone, mais le reste doit être attribué à l'absorption dans le milieu situé au-dessus de la couche d'ozone.
Décédé subitement le 2 décembre, 1979. 相似文献
The discussion of the eclipse 1978.IX.16 based on the comparison of the photometrical measurements of the shadow with the theory based on pure terrestrial atmosphere, is presented. The differences between the observed and computed density of the shadow are partly due to the absorption in the ozone layer, and the remainder can be attributed to the absorbing medium above the ozone layer.
Décédé subitement le 2 décembre, 1979. 相似文献
20.
Sébastien Lefebvre Julio César Marín Leal Stanislas Dubois Francis Orvain Jean-Louis Blin Marie-Paule Bataillé Alain Ourry Robert Galois 《Estuarine, Coastal and Shelf Science》2009
The temporal dynamics of carbon and nitrogen isotope values of co-occurring suspension-feeders in two shellfish culture areas (Normandy, France) were investigated over two years to evaluate the inter-specific trophic partitioning and relative contributions of organic matter sources to benthic suspension-feeders' diet. Oysters (Crassostrea gigas), mussels (Mytilus edulis), cockles (Cerastoderma edule), slipper limpets (Crepidula fornicata), and sand-mason worms (Lanice conchilega) were sampled in an estuarine environment (Baie des Veys, east Cotentin, Normandy), while oysters, mussels, slipper limpets, and honeycomb worms (Sabellaria alveolata) were sampled in an open-marine environment (Lingreville-sur-mer, west Cotentin, Normandy). Whatever the sampling period, the bivalves, C. gigas and M. edulis, exhibited the lowest values of δ13C and δ15N compared with the other species. Feeding relationships among suspension-feeders in both C. gigas culture areas exhibited temporal variations due to the marine/estuarine influence and seasonal changes in food supply. In the open-marine ecosystem, the contribution of phytoplankton remained the most important for all species except S. alveolata, while in the estuarine ecosystem, microphytobenthos and/or macroalgae detritus contributed a larger extent to the organisms' diets. During phytoplankton bloom periods (e.g. May and July) suspension-feeders, except for S. alveolata, relied strongly on phytoplankton; however, the majority of suspension-feeders exhibited different opportunistic behaviour in winter when phytoplankton biomass might be a limiting factor. We hypothesized that differences in particle capture and selection by the suspension-feeders influenced their isotopic values. Feeding ecology of suspension-feeders partly explained why competition was limited and why ecosystems can often support unexpectedly large numbers of suspension-feeders. We also showed that understanding ecosystem characteristics of the organic matter sources is of primary importance to determine the extent to which members of the suspension-feeding guild potentially compete for food. 相似文献