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141.
Brigitte Schmieder Nicole Mein Yuanyong Deng Cristiana Dumitrache Jean-Marie Malherbe Joachim Staiger E. E. Deluca 《Solar physics》2004,223(1-2):119-141
This paper is focused on the formation of two filaments in a complex center of decaying active regions (AR 8329 and AR 8326), located in the northern hemisphere. The observations were obtained in Hα by the Multi-channel Subtractive Double Pass spectrograph (MSDP mounted on the German telescope VTT in Tenerife) and EUV lines with TRACE (Transition Region And Corona Explorer). High Doppler shifts are found to be related to the ends of filament segments where canceling magnetic fields are also located (as seen on magnetograms from Big Bear Solar Observatory). At these locations, velocities along the line of sight, derived by using a cloud model method reach −20 km s−1, the segments of filaments merge and frequently a time-related sub-flare is observed by TRACE. The chirality of the filament segments has been determined by different methods: the segments of dextral chirality join together and form a long dextral filament, and a single filament of sinistral chirality forms end to end with the dextral filament but does not merge with it. Assuming a model of twisted flux tube for filament material, we suggest that the dextral filament has negative helicity and a relationship between its formation and the close by sunspot with the same sign of helicity. 相似文献
142.
Jacques M. Beckers 《Solar physics》1993,144(2):399-402
In a recent article Seykora (1993) compares measurements of scintillation in the solar irradiance with solar seeing measurements. In this article I interpret the close linear relation which he found in terms of the common theory of atmospheric optics in the presence of turbulence. 相似文献
143.
Karolien Vermeiren Matthias Vanmaercke Joris Beckers 《International journal of geographical information science》2016,30(12):2377-2400
Numerous cities in developing regions worldwide are expanding at a tremendous rate. This requires adequate strategies to address the needs of these growing cities with diverse populations. Nonetheless, the development of urban policies is often hampered by the lack of reliable data or insight in the socio-spatial dynamics of this urban expansion. This paper therefore presents ASSURE, a spatially and temporally explicit model that can simulate urban growth and intra-urban social segregation, taking into account alternative policy strategies and expected social dynamics. The model has a flexible structure that allows incorporating specific city conditions that influence residential decision-making and adapting the simulation to the data available. This, in combination with the transparent model structure, makes ASSURE a potentially valuable decision support tool for urban planning. The potential is demonstrated with an example where the urban growth of and social segregation in Kampala (Uganda) is simulated based on (semi-)quantitative and qualitative data for ca. 800 households collected through interviews. The results of the simulations show that depending on the scenario, the spatial segregation and accessibility problems will evolve highly differently. 相似文献
144.
Aurélia Mouret Pierre Anschutz Pascal Lecroart Gwénaëlle Chaillou Christelle Hyacinthe Jonathan Deborde Frans J. Jorissen Bruno Deflandre Sabine Schmidt Jean-Marie Jouanneau 《Geo-Marine Letters》2009,29(3):133-149
Manganese is a major redox reactive element of benthic metabolism. We have built a database of existing knowledge on the benthic
geochemistry of Mn in the Bay of Biscay, in order to comprehensively assess the behaviour of Mn in a variety of environments
during early diagenesis. The database contains vertical profiles of particulate and dissolved Mn species of 59 cores collected
during 17 cruises between 1997 and 2006 at nine stations positioned between 140 and 4,800 m water depths. At all studied stations,
Mn species follow the conventional distribution, where Mn(III,IV) species are enriched in the oxic layer, and dissolved Mn
is present in the anoxic sediments. A minor part of Mn-oxides originates from sedimenting particles. The major part is of
diagenetic origin, and derives from the oxidation of upward-diffusing dissolved Mn(II). Mn-oxide inventories are higher at
the deeper stations than at the shallower ones. This difference cannot be attributed to different sources of sedimenting particles,
but it must depend on sedimentation rate and diagenetic processes. At depth, dissolved Mn(II) concentrations are constant.
This probably reflects equilibrium with an authigenic Mn(II) phase, which is the ultimate phase into which Mn is fossilized.
The Mn content of deeper anoxic sediments is similarly low in all the cores studied, associated with corresponding trends
of Mn content in sedimenting particles of the Bay of Biscay. Bioturbation, rather than redox oscillations, can convey Mn(III,IV)
species downwards into the anoxic sediments where they are reduced, associated with a peak of dissolved Mn. Because dissolved
Mn(II) is re-oxidized when it diffuses towards the oxic layer, the inventory of the diagenetic Mn(III,IV) phase remains at
steady state, especially at stations where the oxic layer is thick. It then becomes possible to calculate the residence time
of diagenetic Mn(III,IV) particles within the oxic layer, using the upward-directed flux of pore water Mn(II). By applying
this residence time to the accumulation of sediments within the oxic layer, we obtain the sediment mass accumulation rate.
The values calculated for the sediments of the Bay of Biscay fit well with accumulation rates obtained from radionuclides
or sediment traps. The method has also been validated with data collected in other marine sedimentary environments.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
145.
146.
We investigate a problem mentioned by Deleersnijder and Campin (Deleersnijder, E., & Campin, J. -M. (1993). Ocean Modelling 97, 2), who looked at the problem of the discretization of inertia–gravity waves in the staggered B-grid. We generalize this study by adding diffusion. General stability conditions are found with the help of Miller's theorem, and the paradox found in Deleersnijder and Campin (Deleersnijder, E., & Campin, J. -M. (1993). Ocean Modelling 97, 2) is discussed. It is argued that it stems from inappropriate application of boundary conditions in conjunction with a Coriolis force treatment which could produce mechanical work. 相似文献
147.
An investigation of trace metal distributions in the Western Mediterranean Sea was carried out during the RRS Discovery cruise (July 1993) in which a transect from the Strait of Gibraltar to the Strait of Sicily was conducted. Organically complexed dissolved trace metals and their total concentrations were measured to investigate the end-members and to predict the environmental capacity of the Mediterranean for potential toxic metals. The distribution of trace metals can be accounted for by the mixing of several end-members and by some atmospheric inputs to the surface water. For Pb and Fe, the effects of the atmospheric inputs are more pronounced than for the other metals. Due to the rapid exchange of water masses, the Western Mediterranean may have the ability to assimilate the increased external inputs for some trace metals such as Cu, Cd, Ni and Zn. But the external inputs for Pb and Fe exceed the removal capacity of the Western Mediterranean and these elements may accumulate in the water column of the western basin. The C18 Sep-Pak technique and direct determination by DPASV were used to determine the amount of trace metal–organic complexes. The C18 Sep-Pak column isolates only a small fraction of trace metals except for Cu. The maximum hydrophobic fractions for the studied trace metals, except for Cd and Pb, which are not detectable, were found in the subsurface layer at all stations. This maximum may well be linked to picoplankton activity and the picoplankton, prochlorophytes may have an important role in the speciation of dissolved Cu as well as Synechococcus. These organic ligands for Cu were produced at the maximum of biological activity in the Western Mediterranean basin and seem to be accumulated at halocline level by Mediterranean hydrodynamic characteristics. However, direct determination by DPASV showed that the major part of Cu, Cd and Pb, complexed by organic materials, was not isolated by C18 Sep-Pak technique. 相似文献
148.
Martine Mullet Sophie BoursiquotMustapha Abdelmoula Jean-Marie GéninJean-Jacques Ehrhardt 《Geochimica et cosmochimica acta》2002,66(5):829-836
Tetragonal FeS1−x mackinawite, has been synthesized by reacting metallic iron with a sodium sulfide solution and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), transmission Mössbauer spectroscopy (TMS) and X-ray photoelectron spectroscopy (XPS). Based on XRD and TEM analyses, synthetic mackinawite exhibits crystallization and is identical to the natural mineral. Unit cell parameters derived from XRD data are a = b = 0.3670 nm and c = 0.5049 nm. The bulk Fe:S ratio derived from the quantitative dispersive energy analysis is practically 1. XPS analyses, however, showed that mackinawite surface is composed of both Fe(II) and Fe(III) species bound to monosulfide. Accordingly, monosulfide is the dominant S species observed at the surface with lesser amount of polysulfides and elemental sulfur. TMS analysis revealed the presence of both Fe(II) and Fe(III) in the mackinawite structure, thus supporting the XPS analysis. We propose that the iron monosulfide phase synthesized by reacting metallic iron and dissolved sulfide is composed of Fe(II) and S(-II) atoms with the presence of a weathered thin layer covering the bulk material that consists of both Fe(II) and Fe(III) bound to S(-II) atoms and in a less extent of polysulfide and elemental sulfur. 相似文献
149.
Hossein Mehdizadeh Jean-Michel Liotard Jean-Marie Dautria 《Comptes Rendus Geoscience》2002,334(2):111-117
Lavas of the Quaternary Damavand volcano (Central Alborz, Northern Iran) have been analysed for major and trace elements. The shoshonitic character of this magmatic series is definitively confirmed and most samples correspond to banakites. The Nb, Ta and Ti negative anomalies observed in all lavas suggest that they derive from of a sub-continental lithosphere metasomatised in a subduction setting. Their variable trace element enrichments are explained both by mineral fractionation and by crustal contamination in a shallow magmatic chamber. To cite this article: H. Mehdizadeh et al., C. R. Geoscience 334 (2002) 111–117. 相似文献
150.
Élizabeth L. Simms Alvin E. Simms & Jean-Marie M. Dubois 《Geografiska Annaler: Series A, Physical Geography》1997,79(3):167-176
A method of analysis was developed to estimate wind-induced wave heights in the coastal zone. The analysis is based on a digital bathymetry model in raster format. The model uses wind characteristics such as direction, velocity, and fetch. In addition, underwater terrain slope magnitude and orientation, and water depth are used in the computation of the model to estimate wave heights. Two analyses are shown, taking into account waves built from short fetch wind and indefinite fetch wind. The analysis was applied to Hare Bay in northern Newfoundland. First, we take into account a northerly wind of 6.9 ms−1 where the fetch is 19 km or less. The estimated wave heights vary between 0 and 0.5 m. With the second application, we considered an indefinite ESE fetch wind of 17.8 ms−1 . In this case, the wave heights resulting from the application of the model vary between 0 and 11.8 m. We compared the modelling results based on ESE wind and the wave energy derived through visual analysis. Relationships were identified between the wave height classes and the wave energy categories. 相似文献