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41.
Anne-Marie Aucour Pierre Faure Bernard Gomez Yann Hautevelle Raymond Michels Frédéric Thévenard 《Organic Geochemistry》2009,40(7):784-794
The chemical composition of Cretaceous leaf remains showing exceptionally well preserved cuticles was investigated using pyrolysis gas chromatography–mass spectrometry (Py-GC–MS) and thermally assisted hydrolysis methylation (THM)-GC–MS. Samples of Coniferales (Frenelopsis) and Ginkgoales (Nehvizdya penalveri) leaf remains were collected from freshwater and coastal marine depositional environments. Material for pyrolysis included (i) untreated leaves and cuticles obtained after extraction from mineral rock matrix and bleaching, (ii) kerogen fraction from both materials, (iii) non-hydrolysable fraction from kerogen. The THM-GC–MS data from untreated leaves and bleached cuticles show that the fossil cuticle geopolymer essentially released aliphatic components upon thermal treatment, with a dominance of fatty acids (FAs) and n-alkanes/n-alkenes. The FAs are essentially resistant to bleaching and remain after solvent extraction. They occur mainly as short chain compounds ranging from C6 to C16 and with maximum abundance at C8–C9. The n-alkanes/n-alkenes from kerogen and the non-hydrolysable residue occur mainly as short chain compounds in the range C10–C16, with the highest abundance at C9–C12. The THM-GC–MS pyrograms of the fossil cuticles differ from those of cutan from fresh living plants. They support the preservation model via polymerization of monomers derived from cutin or from unsaturated cell FAs. 相似文献
42.
Stratification and water mass formation in the Arctic Ocean: some implications for the nutrient distribution 总被引:1,自引:1,他引:0
The mixing processes and the water formations (transformations) in the Arctic Ocean are reviewed and their influence on the stratification discussed. The relations between the stratification and the nutrient distribution are examined. The interactions between drifting sea ice and advected warmer and nutrient-rich waters favour an early biological activity. By contrast, in the central Arctic Ocean and over comparably deep shelf areas such as the northern Barents Sea, the possibilities for large productivity are more limited because of late melting, less nutrient supply, and in the central Arctic, less available light. The sedimentation of organic matter on the shelves and the remineralisation into cold, dense waters formed by brine rejection and draining off the shelves lead to a loss of nutrients to the deep waters, which must be compensated for by advection of nutrient rich waters to the Arctic Ocean.
Possible effects of a reduction of the river run-off on the stratification and the nutrient distribution are discussed. 相似文献
Possible effects of a reduction of the river run-off on the stratification and the nutrient distribution are discussed. 相似文献
43.
Anne-Marie d'Hauteserre 《New Zealand geographer》2005,61(2):102-109
Abstract: This paper acknowledges Dame Evelyn Stokes’ introduction of postcolonial critical analysis of Māori/Pākehā relationships before postcolonialism was established as a field of theoretical enquiry. The paper reviews research I have done on some of the issues faced by the Mashantucket Pequots in the wider context of the contribution Dame Evelyn Stokes was making to similar debates in New Zealand. She emphasized that Māori research and knowledge provide a different world view and that this world view needs to be taken into account in any geographical study of New Zealand. Only in this way will it be possible to avoid the continued marginalization of Māoris from nation building in their own country. 相似文献
44.
Seismic Microzonation: A Comparison between Geotechnical and Seismological Approaches in Pointe-à-Pitre (French West Indies) 总被引:1,自引:0,他引:1
Benoit LeBrun Anne-Marie Duval Pierre-Yves Bard Olivier Monge Myriam Bour Sylvain Vidal Hubert Fabriol 《Bulletin of Earthquake Engineering》2004,2(1):27-50
Pointe-à-Pitre, the main city of Guadeloupe in the French West Indies, has on several occasions been partially destroyed by
major historical earthquakes. Moreover, a post-seismic assessment of the damage from the 1985 Montserrat earthquake indicates
that the town is prone to site effects. Consequently, from 1996 to 1998, BRGM conducted a seismic microzonation study based
on geotechnical and geological data. At the same time, three seismological studies were being conducted – two based on earthquake
recordings using a time-series analysis and the classical spectral ratio (CSR) method (CETE/LCPC and BRGM), and the third
based on noise measurement at 400 points using the horizontal-to-vertical noise ratio (HVNR) method (CETE/LCPC). The objective
of this paper is not to carry out a new microzonation study by taking into account all the results, but rather to show in
what respects the results of these different methods are in agreement or not. A comparison of the results of the seismological
studies with the geotechnical microzonation shows that they are in fairly good agreement, albeit with some discrepancies.
The results indicate that the seismological methods and the geotechnical data are highly complementary and should be used
together in compiling seismic transfer-function microzonation maps.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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48.
Eric Tabacchi Johannes Steiger Dov Corenblit Michael T. Monaghan Anne-Marie Planty-Tabacchi 《Aquatic Sciences - Research Across Boundaries》2009,71(3):279-289
The structure and function of alluvial Highly Dynamic River Systems (HDRS) are driven by highly variable hydrological disturbance
regimes, and alternate between resistant, metastable states and resilient, transitional states. These are in turn subject
to influences of feedback loops within hydrogeomorphic and biological processes. Here we consider how resistance and resilience
largely determine HDRS ecosystem trajectories and how these characteristics can be modified by natural and anthropogenic processes.
We review the mechanisms by which biodiversity can affect both resistance and resilience and introduce a conceptual framework
that incorporates some unique HDRS characteristics. We suggest that resilient and resistant patterns frequently coexist in
the active tract of these river systems, and that this coexistance promotes the return of metastable states after major disturbances.
In contrast, highly resistant and poorly resilient patterns dominate at their external boundaries. The loss of these natural
dynamics resulting from direct and indirect human impacts causes deviations to resistance and resilience patterns and therefore
to HDRS trajectory. We propose that understanding the role of interactions between biological and physical processes that
control resistance and resilience is crucial for system restoration and management. 相似文献
49.
50.
Gabriela Athi Frdric Marin Anne-Marie Treguier Bernard Bourls Catherine Guiavarch 《Ocean Modelling》2009,30(4):241-255
This study demonstrates the sensitivity of the near-surface properties in the tropical Atlantic Ocean to the high-frequency of the winds in numerical simulations. At intra-seasonal timescales (2–50 days), two distinct period ranges dominate the variability in the upper ocean: periods between 2 and 20 days, which are essentially wind-forced and periods between 20 and 50 days, due mostly to Tropical Instability Waves (TIWs). Using a numerical model forced by different wind fields, it is shown that the characteristics of the intra-seasonal variability in the ocean surface mixed-layer are strongly dependent on the wind forcing. Submonthly winds are shown to force large variability in the upper ocean that can strikingly decrease the amplitude of the TIWs in the mixed-layer and their imprint on the horizontal distribution of sea surface temperatures. Wind products containing too much energy at submonthly periods thus prevent wind-forced simulations from reproducing a realistic surface signature of TIWs, when compared to satellite observations of sea surface temperature. In addition, submonthly wind variability may be responsible for part of the observed interannual variability of the TIW signature in the temperature. The impact of submonthly winds is strongest in the mixed-layer: beneath the mixed-layer, all simulations show similar characteristics of the TIWs. 相似文献