Utilisation d'un microdébitmètre à haute résolution pour les mesures de turbulence par avion     

Aimé Druilhet  Henri Bardeau 《Pure and Applied Geophysics》1990,132(3):457-479

Résumé Nous avons décrit dansBardeau et al. (1987), la réalisation, le fonctionnement et les tests d'un microdébitmètre basé sur l'anémométrie à fil chaud. Il a été particulièrement montré que cet appareil était bien adapté aux mesures de pression et pression différentielle avec une grande sensibilité et une très faible constante de temps. Nous présentons ici les applications qui ont été faites de ce capteur aux mesures à haute résolution à bord d'avions instrumentés pour la recherche atmosphérique. L'avion utilisé était spécialement équipé pour les mesures de turbulence et permettait donc l'acquisition d'un grand nombre de paramètres indispensables à l'analyse des données de ce capteur. Dans les applications aéronautiques qui ont été faites, le capteur a surtout été utilisé en tant que variomètre. Les comparaisons avec les mesures standards d'altitude par pression et couplages pression-données inertielles montrent que cet instrument pourrait apporter une contribution intéressante dans le domaine de la mesure à haute fréquence des fluctuations de pression.  相似文献   

Effect of turbulence and inorganic carbon supply on growth ofDunaliella viridis Teodoresco     

Carlos Jiménez  Jesus Mercado  José Aguilera  J. M. rodriguez-Maroto  F. X. Niell 《International Journal of Salt Lake Research》1995,4(3):223-232

Turbulence is known to enhance growth in microalgae. We studied the possible effects of the extra inorganic carbon supplied to the cultures when air bubbling is the source of turbulence. A set of experiments was carried out to separate the effects of the subsidiary action of agitation on growth from those due to possible carbon enrichment from air CO₂ when air bubbling was the source of mixing. It was found that air bubbling does not induce an increase of the concentration of inorganic carbon in HCO ₃ ^– -enriched growth media, and that no differences appear between air-bubbled and CO₂-free air-bubbled cultures. On the other hand, photosynthetic O₂ was accumulated in the medium in non-mixed cultures, which showed higher respiration and lower photosynthetic rates, probably due to photoinhibition induced by oversaturation of O₂. Growth rate, maximal cell density and photosynthetic efficiency were higher in aerated cultures than in non-aerated ones.  相似文献   

High-resolution paleoenvironmental studies: an editorial note     

André F. Lotter  Michael Sturm 《Journal of Paleolimnology》1994,11(3):311-312

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Continental and marine paleoenvironments reflected by west Pacific clay sedimentation     

Dr. Hervé Chamley 《International Journal of Earth Sciences》1986,75(1):271-285

Various stratigraphic and paleoenvironmental results arise from mineralogical, geochemical and micromorpho logical investigations on Late Cretaceous and Cenozoic sediments recovered by the Deep Sea Drilling Project in the West Pacific:

Stratigraphic correlations. The deep pelagic red clays deposited on either side of the Shatsky Rise contain a variety of clay minerals, which point to the importance of eolian detrital supply and allow rough stratigraphic correlations.

Climate and paleocirculation. Neogene sediments of the Lord Howe Rise area reflect closely the relationship between the evolution of the Antarctic ice sheet and related aridification stages, and the atmospheric and oceanic circulation pattern since 14 my.

Regional and global tectonics. The post-Eocene deposits around New Zealand express a sequence of tectonic events and of relaxation stages, associated with changes in the circulation regime. Along the inner wall of the Japan Trench, clay mineral successions document the existence of an outer continental landmass until the late Oligocene, its collapse associated with volcanism close to the Paleogene-Neogene boundary, and an increased detrital influence from Japan since the early-middle Miocene.

Volcanism, diagenesis and detrital supply. The Aptian to Maastrichtian sediments in the Mariana Basin document a complex sequence of geochemical and geodynamical events: proximal volcanism and local supply from subaerial archipelagoes; early marine diagenesis during lithospheric subsidence and plate migration; and finally the occurrence and evolution of terrigenous input from distant sources distributed by marine currents.

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A model of the diagenetic evolution of coaly sedimentary organic matter     

Jean-Paul Boudou  Régis Pelet  René Letolle 《Geochimica et cosmochimica acta》1984,48(6):1357-1362

Elemental composition was used to calculate the amounts of compounds produced during the diagenetic evolution of a coal series from the Mahakam delta (Kalimantan, Indonesia). These calculations were based on the following hypotheses: organic nitrogen does not take part in reactions and remains unchanged in the residual organic matter, the only compounds produced are water, carbon dioxide and hydrocarbons.This approach shows that carbon loss during diagenesis is mainly as CO₂, and hydrogen loss is mainly as H₂O. Hydrocarbon production is negligible, in accordance with absence of bacterial methane accumulations in the Mahakam delta.The δ¹³C of coals in the sequence becomes about 2 per mil more positive over the diagenetic depth range of coal evolution. Accounting for the coal δ¹³C change in terms of CO₂ loss requires that the CO₂ given off have δ¹³C of about ?40%.. Such negative CO₂ has not been observed in natural systems, except when CH₄ is undergoing oxidation. Several plausible causes for this effect are discussed.  相似文献   

Variations and change in south American streamflow   总被引：4，自引：0，他引：4  

José A. Marengo 《Climatic change》1995,31(1):99-117

Long-term hydroclimatological records in tropical South America have been analyzed in order to determine whether or not there have been significant changes in the hydrological cycle. Streamflow data from several rivers in Peru, Brazil, Argentina and Venezuela, as well as rainfall in Northeast Brazil have been used here for the study of long-term and interannual variations on hydrological conditions in different regions of South America. The Mann-Kendall statistical test is applied to the historical streamflow annual series in order to detect trends or changes in the mean. The Studentt-test is also applied to study the relationship between interannual variability and the magnitude of change and length of data required to identify a statistically significant trend.It follows from the statistical analysis of the currently available historical river data set that there is no clear evidence of trend or change in the mean streamflow of South American rivers resulting from a climate change, even though significant trends towards drier conditions have been found for rivers in the Northwest coast of Peru and in eastern Brazil. Interannual variations characterized the hydrology of tropical South America, in association with the extreme phases of the Southern Oscillation. The change required to identify a statistically significant variation in the mean is directly proportional to the interannual variability. The effects of Amazon deforestation are not noticeable on the 1903-92 interannual variability of the Rio Negro series at Manaus nor in rainfall time series.  相似文献   

Health, Safety and Environmental Risks of Underground Co2 Storage – Overview of Mechanisms and Current Knowledge     

Kay Damen  André Faaij  Wim Turkenburg 《Climatic change》2006,74(1-3):289-318

CO₂ capture and storage (CCS) in geological reservoirs may be part of a strategy to reduce global anthropogenic CO₂ emissions. Insight in the risks associated with underground CO₂ storage is needed to ensure that it can be applied as safe and effective greenhouse mitigation option. This paper aims to give an overview of the current (gaps in) knowledge of risks associated with underground CO₂ storage and research areas that need to be addressed to increase our understanding in those risks. Risks caused by a failure in surface installations are understood and can be minimised by risk abatement technologies and safety measures. The risks caused by underground CO₂ storage (CO₂ and CH₄ leakage, seismicity, ground movement and brine displacement) are less well understood. Main R&D objective is to determine the processes controlling leakage through/along wells, faults and fractures to assess leakage rates and to assess the effects on (marine) ecosystems. Although R&D activities currently being undertaken are working on these issues, it is expected that further demonstration projects and experimental work is needed to provide data for more thorough risk assessment.  相似文献   

Tectonic framework and extensional pattern of the Malaguide Complex from Sierra Espuña (Internal Betic Zone) during Jurassic–Cretaceous: implications for the Westernmost Tethys geodynamic evolution     

Manuel Martín-Martín  Iván Martín-Rojas  Jesús E. Caracuel  Antonio Estévez-Rubio  Agustín Martín Algarra  José Sandoval 《International Journal of Earth Sciences》2006,95(5):815-826

Mapping, lithostratigraphic, biostratigraphic and structural detailed analyses in Sierra Espuña area (Internal Betic Zone, SE Spain) have allowed us to reconstruct the Jurassic–Cretaceous evolution of the Westernmost Mesomediterranean Microplate palaeomargin and, by correlation with other sectors (Northern Rift, central and western Internal Betic Zone), to propose a geodynamic evolution for the Westernmost Tethys. Extension began from Late Toarcian, when listric normal faults activated; these faults are arranged in three categories: large-scale faults, separating hectometric cortical blocks; main faults, dividing the former blocks into some kilometre-length blocks; and secondary faults, affecting the kilometric blocks. This fault ensemble, actually outcropping, in the Sierra Espuña area, broke the palaeomargin allowing the westerly Tethyan Oceanic aperture with an extension at about 17.2%. Extension was not homogeneous in time, being the Late Toarcian to the Dogger–Malm boundary the period when blocks underwent the greatest movement (rifting phase), leading to the drowning of the area (8.2% extension). During the Malm (drifting phase) extension followed (5.7%), while during the Cretaceous a change to pelagic facies is recorded with an extension of about 3.3% (post-drift stage). This evolution in the Westernmost Tethys seems to be related to areas out of the limit of significant crustal extension in the hanging wall block of the main cortical low-angle fault of the rifting.  相似文献   

Initial assessment of the infiltration and overland flow for different rainfall events in land constituted of sandstones of the Botucatu Formation (Guarani Aquifer), State of São Paulo, Brazil   总被引：1，自引：0，他引：1  

Lázaro Valentin Zuquette  Janaina Barrios Palma  Osni José Pejon 《Environmental Geology》2006,50(3):371-387

This study was carried out in the Córrego do Vaçununga basin constituted of eolic sandstones of Botucatu Formation and residual unconsolidated materials (>90%), considered the most important unconfined aquifer in Brazil, in the city of Luiz Antonio, State of São Paulo, Brazil. Laboratory and in situ tests were performed to characterize the unconsolidated materials in terms of basic physical properties, potential infiltration rate, suction and hydraulic conductivity. The results for infiltration and overland flow depths were obtained according to Morel-Seytoux and Khanji (Water Resour Res 10(4):795–800, 1976) and Chu (Water Resour Res 14(3):461–466, 1978) adaptation of the Green and Ampt [J Agr Sci 4(Part 1):1–24, 1911] model for steady and transient rainfalls, respectively. Rainfall data were collected from January of 2000 to December of 2002, and 12 scenarios were defined considering the intensity and durations. Rather than high homogeneity in terms of the texture of unconsolidated materials, the infiltration and overland flow ratio depends on the type of land use and associated management practices. The results showed that rainfall with high intensity and short duration do not produce high overland flow ratio as we have observed for transient scenarios with long duration and low intensities.  相似文献   

From granitoid to kyanite-bearing micaschist during fluid-assisted shearing (Ile d’Yeu, France)     

Caroline Sassier  Philippe Boulvais  Denis Gapais  Ramon Capdevila  Hervé Diot 《International Journal of Earth Sciences》2006,95(1):2-18

We describe amphibolite-facies shear zones affecting an orthogneiss from the Armorican Hercynian belt (Ile d’Yeu, western France). The deformation pattern is consistent with top-to-the-South thrusting followed by E–W extension, as documented elsewhere in the region. Shearing was accompanied by channelled fluid flow that transformed the orthogneiss into a peraluminous micaschist. Structural and mineralogical data indicate rather early strain localization. Then, temperature increase associated with crustal thickening favoured more distributed deformations marked by shear zone stretching and the development of a HT regional foliation. Chemical analyses made across five shear zones show mass transfers that mainly implied losses in Ca and Na, and gains in H₂O, Mg, and K. Most results indicate constant volume transformation, but some suggest records of either gains or losses of volume (between +20% and −30%). This might reflect variable records of fluid-rock interactions according to the timing of initiation and subsequent evolution of individual shear zones, early thrusting stages being marked by up-temperature flow, and late thrusting stages by down-temperature flow. δ¹⁸O analyses suggest that fluids experienced significant isotopic exchange with orthogneisses.  相似文献