Technetium-99 content in some marine organisms collected near La Hague,France     

Lucien Jeanmaire  Michel Masson  Francois Patti  Pierre Germain  Liliane Cappellini 《Marine pollution bulletin》1981,12(1):29-32

Analyses for ⁹⁹Tc in some marine biological samples taken near the outlet of the low level radioactive effluent pipeline of the nuclear reprocessing plant of La Hague, France, gave positive results. From 500 to 3500 pCi kg^?1 wet weight of ⁹⁹Tc were observed in brown algae; Fucus sp. appeared to be a good indicator of this long-lived radionuclide in a marine environment.  相似文献   

The bi-decadal rainfall cycle,Southern Annular Mode and tropical cyclones over the Limpopo River Basin,southern Africa     

Johan Malherbe  Willem A. Landman  Francois A. Engelbrecht 《Climate Dynamics》2014,42(11-12):3121-3138

The association between bi-decadal rainfall variability over southern Africa and the rainfall contributed by tropical cyclonic systems from the Southwest Indian Ocean (SWIO) provides a potential means towards understanding decadal-scale variability over parts of the region. A multi-decadal period is considered, focusing on the anomalous tropospheric patterns that induced a particularly wet 8-year long sub-period over the Limpopo River Basin. The wet sub-period was also characterized by a larger contribution to rainfall by tropical cyclones and depressions. The findings suggest that a broadening of the Hadley circulation underpinned by an anomalous anticyclonic pattern to the east of southern Africa altered tropospheric steering flow, relative vorticity and moisture contents spatially during the sub-period of 8 years. These circulation modulations induced enhanced potential for tropical systems from the SWIO to cause precipitation over the Limpopo River Basin. The same patterns are also conducive to increasing rainfall over the larger subcontinent, therefore explaining the positive association in the bi-decadal rainfall cycle and rainfall contributed by tropical cyclonic systems from the SWIO. An overview of regional circulation anomlies during alternating near-decadal wet and dry epochs is given. The regional circulation anomalies are also explained in hemispheric context, specifically in relation to the Southern Annular Mode, towards understanding variation over other parts of the Southern Hemisphere at this time scale.  相似文献   

Simulations of an isolated two-dimensional thunderstorm: Sensitivity to cloud droplet size and the presence of graupel     

Mary-Jane Morongwa Bopape  Francois Alwyn Engelbrecht  David A. Randall  Willem Adolf Landman 《Asia-Pacific Journal of Atmospheric Sciences》2014,50(2):139-151

Cloud Resolving Models (CRMs) which are used increasingly to make operational forecasts, employ Bulk Microphysics Schemes (BMSs) to describe cloud microphysical processes. In this study two BMSs are employed in a new Nonhydrostatic σ-coordinate Model to perform two hour simulations of convection initiated by a warm bubble, using a horizontal grid resolution of 500 m. Different configurations of the two BMSs are applied, to test the effects of the presence of graupel with one scheme (2-configurations) and of changing the cloud droplet sizes in the second scheme (4-configurations), on the simulation of idealised thunderstorms. Maximum updrafts in all the simulations are similar over the first 40 minutes, but start to differ beyond this point. The first scheme simulates the development of a second convective cell that is triggered by the cold pool that develops from the outflow of the first storm. The cold pool is more intense in the simulation with graupel because of melting of graupel particles, which results in relatively large raindrops, decreases the temperature through latent heat absorption, causing stronger downdrafts, which all contribute to the formation of a more intense cold pool. The second scheme simulates the development of a second cell in two of its configurations, while two other configurations do not simulate the redevelopment. Two configurations that simulate the secondary redevelopment produce a slightly stronger cold pool just before redevelopment. Our results show that small differences in the microphysics formulations result in simulations of storm dynamics that diverge, possibly due nonlinearities in the model.  相似文献   

Relations between stellar mass and electron temperature-based metallicity for star-forming galaxies in a wide mass range     

Wei-Bin Shi  ;Yan-Chun Liang  ;Xu Shao  ;Xiao-Wei Liu  ;Gang Zhao  ;Francois Hammer  ;Yong Zhang  ;Hector Flores  ;Gui-Ping Ruan  ;Li Zhou 《中国天文和天体物理学报》2014,(7):875-890

We select 947 star-forming galaxies from SDSS-DR7 with [O III]λ4363emission lines detected at a signal-to-noise ratio larger than 5σ. Their electron temperatures and direct oxygen abundances are then determined. We compare the results from different methods. t2, the electron temperature in the low ionization region, estimated from t3, that in the high ionization region, is compared using three analysis relations between t2- t3. These show obvious differences, which result in some different ionic oxygen abundances. The results of t3, t2, O++/H+and O+/H+derived by using methods from IRAF and literature are also compared. The ionic abundances O++/H+are higher than O+/H+for most cases. The different oxygen abundances derived from Teand the strong-line ratios show a clear discrepancy, which is more obvious following increasing stellar mass and strong-line ratio R23. The sample of galaxies from SDSS with detected [O III]λ4363 have lower metallicites and higher star formation rates, so they may not be typical representatives of the whole population of galaxies. Adopting data objects from Andrews Martini, Liang et al. and Lee et al. data, we derive new relations of stellar mass and metallicity for star-forming galaxies in a much wider stellar mass range: from 106 M to 1011 M.  相似文献   

Iron Distribution in Size‐Resolved Aerosols Generated by UV‐Femtosecond Laser Ablation: Influence of Cell Geometry and Implications for In Situ Isotopic Determination by LA‐MC‐ICP‐MS     

Francois‐Xavier d'Abzac  Andrew D. Czaja  Brian L. Beard  James J. Schauer  Clark M. Johnson 《Geostandards and Geoanalytical Research》2014,38(3):293-309

The influence of ablation cell geometry (Frames single‐ and HelEx two‐volume cells) and laser wavelength (198 and 266 nm) on aerosols produced by femtosecond laser ablation (fs‐LA) were evaluated. Morphologies, iron mass distribution (IMD) and ⁵⁶Fe/⁵⁴Fe ratios of particles generated from magnetite, pyrite, haematite and siderite were studied. The following two morphologies were identified: spherules (10–200 nm) and agglomerates (5–10 nm). Similarity in IMD and ablation rate at 198 and 266 nm indicates similar ablation mechanisms. ⁵⁶Fe/⁵⁴Fe ratios increased with aerodynamic particle size as a result of kinetic fractionation during laser plasma plume expansion, cooling and aerosol condensation. The HelEx cell produces smaller particles with a larger range of ⁵⁶Fe/⁵⁴Fe ratios (1.85‰) than particles from the Frames cell (1.16‰), but the bulk aerosol matches the bulk substrate for both cells, demonstrating stoichiometric fs‐LA sampling. IMD differences are the result of faster wash out of the HelEx cell allowing less time for agglomeration of small, low‐δ ⁵⁶Fe particles with larger, high‐δ ⁵⁶Fe particles in the cell. Even with a shorter ablation time, half the total Fe ion intensity, and half the ablation volume, the HelEx cell produced Fe isotope determinations for magnetite that were as precise as the Frames cell, even when the latter included an aerosol‐homogenising mixing chamber. The HelEx cell delivered a more constant stream of small particles to the ICP, producing a more stable Fe ion signal (0.7% vs. 1.5% RSE for ⁵⁶Fe in a forty‐cycle single analysis), constant instrumental mass bias and thus a more precise measurement.  相似文献   

Experimental investigation of reactions between two-mica granite and boron-rich fluids: Implications for the formation of tourmaline granite     

Lining CHENG  Chao ZHANG  Xiaosong YANG  Dongmei QI  Yongsheng ZHOU  Francois HOLTZ 《中国科学:地球科学(英文版)》2019,(10)

The genetic relationship between different types of granite is critical for understanding the formation and evolution of granitic magma. Fluid-rock interaction experiments between two-mica leucogranite and boron-rich fluids were carried out at 600–700°C and 200 MPa to investigate the effects of boron content in fluid and temperature on the reaction products. Our experimental results show that tourmaline granite can be produced by reactions between boron-rich fluid and two-mica granite.At 700°C, the addition of boron-rich fluid resulted in partial melting of two-mica granite and crystallization of tourmaline from the boron-rich partial melt. Increasing boron concentration in fluid promotes the melting of two-mica granite and the growth of tourmaline. No melt was produced in experiments at 600°C, in which Fe, Mg and Al released from biotite decomposition combined with boron from the fluid to form tourmaline under subsolidus conditions. The Na required for tourmaline crystallization derived from Na/K exchange between feldspar and the K released by biotite decomposition. The produced tourmaline generally has core-rim structures, indicating that the composition of melt or fluid evolved during tourmaline crystallization.Based on the experimental results, we propose that tourmaline granite veins or dikes can be formed by the reactions between boron-rich fluids, presumably produced by devolatilization of boron-bearing granitic magma, and incompletely crystallized granite at the top of the magma chamber. This "self-metasomatism" involving boron-rich fluid in the late stage of magma crystallization could be an important mechanism for the formation of tourmaline granite.  相似文献