The Strait of Bonifacio is a long and narrow area between Corsica and Sardinia. To manage environmental emergencies related to the spill of oil from vessels, an innovative forecasting system was developed. This tool is capable of operationally predicting the dispersion of hydrocarbon spills in the coastal area of the Bonifacio Strait, either from an instantaneous or continuous spill and either in forward or backward mode. Experimental datasets, including ADCP water current measurements and the trajectories of drifter buoys released in the area, were used to evaluate the accuracy of this system. A comparison between the simulation results and experimental data revealed that both the water circulation and the surface transport processes are accurately reproduced by the model. The overall accuracy of the system in reproducing the transport of an oil spill at sea was estimated for both forward and backward prediction mode and in relation to different forecasting time lags. 相似文献
A fully time-dependent ionospheric convection model, in which electric potentials are derived by an analytic solution of Laplaces equation, is described. This model has been developed to replace the empirically derived average convection patterns currently used routinely in the Sheffield/SEL/UCL coupled thermosphere/ionosphere/plasmasphere model (CTIP) for modelling disturbed periods. Illustrative studies of such periods indicate that, for the electric field pulsation periods imposed, long-term averages of parameters such as Joule heating and plasma density have significantly different values in a time-dependent model compared to those derived under the same mean conditions in a steady-state model. These differences are indicative of the highly non-linear nature of the processes involved. 相似文献
We performed polarization observations of giant radio pulses from the millisecond pulsar B1937+21. The observations were carried out in July 2002 with the 64-m Kalyazin radio telescope at a frequency of 600 MHz in two polarization channels with left-and right-hand circular polarizations (RCP and LCP). We used the S2 data acquisition system with a time resolution of 125 ns. The duration of an observing session was 20 min. We detected twelve giant radio pulses with peak flux densities higher than 1000 Jy; five and seven of these pulses appeared in the RCP and LCP channels, respectively. We found no event that exceeded the established detection threshold simultaneously in the two polarization channels. Thus, we may conclude that the detected giant pulses have a high degree of circular polarization, with the frequency of occurrence of RCP and LCP pulses being the same. 相似文献
A mathematical model to predict the rhamnolipids production by Pseudomonas aeruginosa from oleic acid in a two phase liquid-liquid batch reaction system, was developed in this study. The model was based on two theoretical assumptions: 1) the convective oleic acid mass transfer is coupled to a bioreaction in the aqueous liquid bulk, and 2) the volume of the immiscible oleic acid drops and the saturation concentration at the interface are a function of rhamnolipids production. The model was able to accurately predict the experimental growth of the Pseudomonas aeruginosa strain, and the rhamnolipids production data with oleic acid as carbon source. This mathematical approach indicated a high correspondence between the saturation dimensionless profiles of oleic acid at the interface and the experimental profiles of surface tension difference. This modeling approach may constitute a useful tool in the design and scaling-up of bioreactors applied to the production of biosurfactants with immiscible carbon sources. 相似文献
Twenty-nine Rb-Sr whole-rock isotopic analyses and three U-Pb zircon analyses on foliated granites and largely unfoliated charnockitic rocks indicate that the central part of the Pan-African belt in west Africa was characterised by intense orogenic plutonism. These data and Rb-Sr analyses on muscovite books from late cross-cutting pegmatites indicate that the peak of magmatic activity occurred 610 ± 10 m.y. ago.Initial 87Sr/86Sr ratios for the granitic and charnockitic rocks are in the range 0.7065–0.7125, and indicate a significantly older crustal component in the magmas. 相似文献
This paper presents the calculated heavy metal (Fe, Mn, Zn, Ni, Cu, Cr, Co, Cd, and Pb) flows in suspended and dissolved forms in the main navigable branches of the Don and Kuban river deltas during the low-water period of 2013–2014. This work is based on the data of field studies in which water and suspended matter samples were collected and the turbidity and water discharge in deltas were measured. A quantitative estimate of heavy metal inflows into the deltas of the Don and Kuban rivers is provided. Transformation of flows of suspended and dissolved metal forms from the delta top to the sea edge is discussed. The influence of localities (Rostov-on-Don, Temryuk) on the increase in heavy metal flows downstream is shown, and the heavy metal flows in the deltas of the Don and Kuban rivers are compared.
The Lady Bountiful granitoid-hosted lode gold deposit, located in the mid-greenschist facies metamorphosed Ora Banda greenstone
sequence, is hosted predominantly by the late-tectonic Liberty Granodiorite. Gold mineralisation is localised along quartz-veined,
sinistral, brittle fault-zone(s) that transect the boundary between the Liberty Granodiorite and Mt Pleasant sill. Quartz
vein textures indicate two stages of a single gold-related vein-development event, with high-grade gold mineralisation restricted
to the second stage. Ore minerals include pyrite, chalcopyrite, pyrrhotite, galena, sphalerite, Au−Ag−Bi−Pb-tellurides, and
native gold. Fluid infitration has resulted in narrow (<1 m) bleached wallrock alteration envelopes to the fault zones comprising
albite-K-mica ±chlorite±calcite±rutile assemblages. Temperature-pressure conditions varied from Stage I (300°±50°C, ≈2 kbar)
to Stage II (250°±50°C, ≈0.5 to 2 kbar), with the hydrothermal fluid in both stages characterised by X(CO2)≤0.15 and moderate salinity (≈1.28 m NaCl). Intermittent phase separation of Stage II mineralising fluids, initiated by pressure
fluctuations in dilational sites, and/or fluid-dominated fluid: wallrock interaction, are invoked as the dominant depositional
mechanisms. The granitoid-hosted Lady Bountiful lode gold deposit shares many features with other granitoid-hosted lode gold
deposits in the Yilgarn Craton and the Superior Province. Granitoid-hosted lode gold deposits, such as the Lady Bountiful
deposit, provide additional evidence that the dominant control on the localisation of gold mineralisation within a granitoid
host is structure, with competency contrasts playing a significant role. Furthermore, the hydrothermal wallrock alteraction
and orefluid chemistry characteristics of the granitoid-hosted lode gold deposits are comparable to those established for
greenstone-hosted lode gold mineralisation. 相似文献
Summary The formation of the Madjarovo polymetallic ore deposit is closely related to Paleogene magmatism of intermediate character represented by subvolcanic and volcanic rocks. Six stages of vein type mineralization were established: 1. quartz-pyrite-chalcopyrite with Bi-sulphosalts; 2. quartz-hematite-chlorite with gold; 3. quartz-galena-sphalerite; 4. quartz-barite-chalcedony with Sb-sulphosalts; 5. quartz-arsenic sulphosalts; 6. calcite-siderite. Ag-bearing galena and Fe-poor sphalerite are the main minerals. Galena of early formation is Bi-bearing, while in late stages it carries more Sb. Gold was found in two generations in different parageneses. The early gold is Ag-poor and related to hematite, while the late one is Ag-rich and closely associated with quartz and sulphosalts. Three groups of sulphosalts were established: Se-bearing Bi-sulphosalts; Sb-sulphosalts, a part of them Cl-bearing, and As-sulphosalts with more or less Ag. Fluid inclusion data obtained in quartz, amethyst, sphalerite and barite from several representative ore veins show formation temperatures in the range of 370° to 150°C for different stages of mineralization. Evidence of boiling fluids suggests pressures of 70 to 180 bars which correspond to an average depth of mineralization near 1.000 m. The low salinities of the fluids (a/v 3.5 eq. wt% NaCI) indicate influx of meteoric waters during mineralization. On the basis of mineralogical and fluid inclusion data physicochemical conditions and source of the ore forming fluids are discussed.
Mineralogie und Flüssigkeitseinschlüsse in polymetallischen Erzgngen der Lagerstätte Madjarovo, Ost-Rhodopen, Bulgarien
Zusammenfassung Die Bildung der polymetallischen Lagerstätte Madjarovo war eng verknüpft mit einem Paläogenen Magmatismus von intermediärem Charakter, der durch Subvulkanite und Vulkanite repräsentiert wird. Es wurden sechs Bildungsstadien der Gangvererzung festgestellt: 1. Quarz-Pyrit-Chalcopyrit mit Bi-Sulfosalzen; 2. Quarz-Hämatit-Chlorit mit Gold; 3. Quarz-Galenit-Sphalerit; 4. Quarz-Baryt-Chalzedon mit Sb-Sulfosalzen; 5. Quarz-As-Sulfosalze; 6. Calcit-Siderit. Ag-führender Galenit und Fe-armer Sphalerit sind die Hauptminerale. Früh gebildeter Galenit is Bi-haltig, während Galenite der späteren Bildungsstadien mehr Sb führen. Gold wurde in zwei Generationen in unterschiedlichen Paragenesen gefunden. Das Früh-Gold (Ag-arm) ist verknüpft mit Hämatit, während das Spät-Gold (Ag-reich) mit Quarz und Sulfosalzen eng assoziiert ist. Es wurden drei Gruppen von Sulfosalzen festgestellt: Se-führende Bi-Sulfosalze; Sb-Sulfosalze, die z.T. Cl-führend sind, und As-Sulfosalze mit mehr oder weniger Ag-Gehalten. Flüssigkeitseinschlüsse in Quarz, Amethyst, Sphalerit und Baryt aus mehreren repräsentativen Erzgängen zeigen Bildungtemperaturen von 370°–150°C für unterschiedliche Mineralisationsstadien. Siedende Lösungen weisen auf einen Druckbereich von 70–180 Bar hin, der einer durchschnittlichen Bildungstiefe von 1.000 m entspricht. Die durchweg niedrige Salinität der Lösungen (durchschnittlich 3.5. Gew.% NaCl äq.) wird auf einen Zufluß von meteorischen Wässern während der Mineralisation zurückgeführt. Auf der Basis der mineralogischen Ergebnisse und der Daten fluider Einschlüse werden die physikochemischen Bedingungen und die Herkunft der Erzlösungen diskutiert.