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211.
The onset of exhumation of the Canigou massif, related to the reactivation of the Têt Fault during the Gulf of Lion opening, is dated at 26–27 Ma, using apatite fission track method and lasts until the Aquitanian, at a rate of . The subsequent evolution is necessarily followed by a slower rate of exhumation to account for total exhumation. At the hanging-wall of this fault, the granite of Mont-Louis records an older exhumation history, where the crossing of the 110 °C isotherm at 40±4 Ma is related to the Pyrenean thrusting. To cite this article: O. Maurel et al., C. R. Geoscience 334 (2002) 941–948. 相似文献
212.
MUGABOWINDEKWE Maurice MUYIZERE Aline LI Fadong QIAO Yunfeng RWANYIZIRI Gaspard 《资源与生态学报(英文版)》2018,9(3):273-280
Crop calendar is an important tool providing relevant information on crops cycles in a specific area for effective agricultural management. Crop calendars vary in different areas given dissimilarities in agro-ecosystems’ characteristics. This research used multi-temporal MODIS NDVI stratification to assess differences in practiced maize crop calendars in various areas of Rwanda. Four (4) sample NDVI strata dominated by agriculture were purposively chosen, and 433 local farmers were randomly selected from the strata for interviews. The collected information helped to know about their maize planting as well as harvesting dates in order to generate maize calendars per NDVI strata. The generated crop calendars were later classified using k-means unsupervised classification, and produced 4 groupings of practiced maize calendars irrespective of NDVI strata. ANOVA results revealed significant differences between both the generated maize crop calendars by NDVI strata and the practiced crop calendars irrespective of NDVI strata, at p = 0.05. Moreover, chi-square tests and t-tests revealed not only a significant relationship between maize calendars and number of crop growing seasons, but also a significant relationship between maize calendars and NDVI strata, at p = 0.05. Finally, findings of this research contrasted the present conviction that there exist a single general maize calendar all over the country. Instead, the results were in accordance with the fact that Rwanda agro-ecosystems differ from East to West in terms of, mainly, altitude and rainfall patterns variations. 相似文献
213.
214.
A “Pingerprobe” is a system of echo sounding in which the sound source is placed near bottom to improve resolution by restricting the area investigated. It is demonstrated that a commercially available 12-kHz “pinger” with a synchronized shipboard receiver is useful not only in the monitoring of the positioning of a bottom or near-bottom instrument package (such as a corer) but also in making observations on the acoustic nature of the sea floor. In rough terrain the Pingerprobe has measured stratified sediments in some places where the PDR (Precision Depth Recorder) cannot. Observations on proximal abyssal plains indicate that the prolonged echo character common to these areas may result from small-scale roughness or inhomogeneity. When a suspended instrument is sent to the bottom in rough terrain, or in areas of intermittent subbottom reflections, use of a Pingerprobe improves information about the conditions at the point of contact and permits selection of the desired topographic setting. 相似文献
215.
Sorption of the trihydroxamate siderophores desferrioxamine-B and -D (DFOB and DFOD, respectively) and of the monohydroxamate ligand acetohydroxamic acid (aHA) to smectite were examined in batch sorption studies (pH 5.5, 0.1 M ionic strength) coupled with X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Both DFOB and DFOD, which have similar molecular structures but different charge properties (cationic versus neutral, respectively) showed a high affinity for smectite. In contrast, the smaller aHA molecule did not sorb appreciably. XRD analysis indicated that DFOB and DFOD each absorbed in the interlamellar region of the clay to give d-spacings of 13.4-13.7 Å at equilibrium solution concentrations <250 μM. FTIR spectra of sorbed DFOB and DFOD indicated that the conformation of each species was distinct from its conformation in the crystalline or dissolved states. At elevated initial solution concentrations of 500-1500 μM, DFOB formed a bilayer in the clay interlayer. Changes in the FTIR spectra of the DFOB-loaded clay samples at these higher surface loadings were consistent with the presence of a metal-siderophore complex in the interlayer. DFOB and DFOD both enhanced Fe and Al release from smectite, but aHA did not. Possible dissolution mechanisms are discussed in light of the FTIR and batch dissolution results. 相似文献
216.
Oscar Martinez-Rubi Maurice de Kleijn Stefan Verhoeven Niels Drost Jisk Attema Maarten van Meersbergen 《International Journal of Digital Earth》2016,9(12):1135-1152
This article discusses the use of 3D technologies in digital earth applications (DEAs) to study complex sites. These are large areas containing objects with heterogeneous shapes and semantic information. The study proposes that DEAs should be modular, have multi-tier architectures, and be developed as Free and Open Source Software if possible. In DEAs requiring high reliability in the 3D measurements, point clouds are proposed as basis for the 3D Digital digital earth representation. For the development of DEAs, we propose to follow a workflow with four components: data acquisition and processing, data management, data analysis and data visualization. For every component, technological challenges of using 3D technologies are identified and solutions applied for a case study are presented. The case study is a modular 3D DEA developed for the archaeological project Mapping the Via Appia. The 3D DEA allows archaeologists to virtually analyze a complex study area. 相似文献
217.
In a previous study we demonstrated the progressive disappearance of Escherichia coli populations upon contact with marine environment (Bianchi & Mircea, 1976). We have used the same experimental device to study the behaviour of other bacteria of enteric or terrigenous origin (Vibrio cholerae, Streptococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa) when rejected into the sea. 相似文献
218.
Maurice Danard 《Boundary-Layer Meteorology》1976,10(4):409-422
Methods have been designed to calculate orographic and frictional influences on precipitation in coastal regions. A model computes the vertical fluxes of water vapor at the top of the planetary boundary layer due to these two effects. The horizontal downwind displacement of falling precipitation is also allowed for. The procedures are applied over southwestern British Columbia to monthly amounts and maximum 24-h rainfalls for return periods of 2–50 yr. Correlation coefficients between observed and computed precipitation vary from 0.65 to 0.97, the average being 0.84. 相似文献
219.
Oldoinyo Lengai in the Tanzanian rift valley is the only active carbonatite volcano in the world and its natrocarbonatitic lavas are unique in composition. The characteristics of effusive natrocarbonatite activity in June 1988 were studied and fresh samples were directly collected from active carbonatitic lava lakes and flows. Analyses of these samples provide the first information on natrocarbonatites since these unusual volcanic rock type was first described from the 1960–1961 eruptions. The analytical results constrain the original chemistry of fresh natrocarbonatite. Temperatures in lava lakes and of carbonatite lava flows range 491–544°C. The natrocarbonatite lava is extremely fluid at these temperatures and reaches incandescence. The most common variety of natrocarbonatite is porphyritic with abundant phenocrysts of nyerereite (Na0.82K0.19)2(Ca, Sr, Ba)0.975(CO3)2 and gregoryite Na1.74K0.1(Ca, Sr, Ba)0.16CO3, with complex substitution of (CO3)2- by (SO4)2-, (PO4)3-, F-, and Cl-. A phenocryst-poor to aphyric natrocarbonatite variety reflects residual liquids separating from the crystal-rich porphyritic flows. Sylvite, fluorite, and Fe-alabandite (Mn0.7Fe0.3S) have been identified as additional primary magmatic phases. Rare phases in the matrix are witherite (BaCO3) and sellaite (MgF2). Sylvite and gregoryite, and to a lesser extent nyerereite, are water-soluble and are responsible for the immediate decomposition and chemical alteration of natrocarbonatites under atmospheric conditions. A peralkaline combeite-bearing nephelinite lava is closely related to the natrocarbonatite activity, and is isotopically indistinguishable. It is likely that these two magma compositions are related by liquid immiscibility. The unusual hyperalkaline composition of both magma types makes Oldoinyo Lengai an exotic volcano, and its carbonatites have extreme compositions, and are not representative of carbonatites in general. 相似文献
220.
C. Subbarao Maddukuri Peter R. Slawson Maurice B. Danard 《Boundary-Layer Meteorology》1978,15(2):163-179
A two-dimensional atmospheric boundary-layer model is applied to the Nanticoke region on the northern shore of Lake Erie (80 ° 03W and 42 ° 50N) to simulate numerically the observed wind and temperature profiles. In general, the profiles predicted by the model agree reasonably well with the observed profiles. 相似文献