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[en] Concentration of 210Pb has been measured in water and sediment trap samples collected on 7 experimental sites representative of the Gulf of Lion's continental margin. This marine system is characterised by a major continental input through the Rhone river and a powerful along-slope cyclonic current (Northern Current). From the distribution of bulk 210Pb activities, it was intended to gain some information on the processes controlling the transport of trace metals at the ocean/continent boundary. Residence times of 210Pb relative to scavenging in surface waters (0-100 m) showed a constant along-slope (i.e., downstream) decrease that can be related to increasing concentrations in suspended particles. Annual time-series of 210Pb activities in settling particles were determined on samples collected by traps at 500 and 1000 m depth. From this data set, a budget for 210Pb on this margin was established which permitted to determine the flux of 210Pb theoretically adsorbed onto particles. This theoretical flux was compared, at each site, with fluxes effectively measured by traps and revealed that exchange processes - mainly in the form of large inputs of this nuclide (import of 47 to 93% of measured flux) - largely affect the 210Pb distribution on this continental margin. (author)
[en] The natural radionuclides 210Po and 210Pb, members of the 238U decay chain, are particularly helpful to the understanding of particle transport processes in the ocean. These isotopes were analysed on sediment trap particles collected during 3 one-year experiments on continental margins. In the Bay of Biscay (Northeastern Atlantic) and in the Gulf of Lion (Northwestern Mediterranean Sea) both as part of the French ECOMARGE programme, and in the Middle Atlantic Bight (Northwestern Atlantic) as part of the SEEP programme. They yielded great insights into scenarios of particle transfer at each site, mainly based on the spatial and temporal distribution of 210Pb particulate concentrations and fluxes. (author)
[en] Electrical and dielectric properties of a polycrystalline La0.6Nd0.1Sr0.3Mn0.7Ti0.3O3 sample prepared by standard solid state reaction technique are presented. FTIR studies have showed the vibration of (Mn/Ti)O6 octahedra. The complex impedance is investigated in a temperature range 120-340 K and in frequency range 40 Hz-10 MHz. The impedance spectra have indicated that the electrical properties are strongly dependent on temperature and frequency, showing a good correlation with the sample microstructure. Ac conductivity is found to obey Jonscher power law. The value of activation energy estimated from the conductivity analysis is slightly higher than that deduced from relaxation analysis. (author)
[en] In this study, empirical K-shell fluorescence yields (ωK) from the available experimental data for elements with 6≤Z≤99 were calculated. The experimental data are fitted using the quantity (ωK/(1-ωK))1/q (where q=3, 3.5 and 4) vs. Z to deduce the empirical fluorescence yields. A comparison is made between the results of the procedures followed here and the literature theoretical and empirical values.
[en] In this study, interpolations (empirical and semi-empirical) of L sub-shell fluorescence yield and L shell Coster–Kronig transition probability values and the measured L X-ray production cross-sections, intensity ratios and L sub-shell fluorescence yield values of elements have been performed in the range of 50≤Z≤92. In this experimental setup, two sources (50 mCi 55Fe and 50 mCi 241Am) were used. L X-rays emitted by samples were counted by an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. - Highlights: • This work was performed for the elements having the atomic numbers between 50 and 92. • Experimental L-shell fluorescence parameters were investigated. • New fit values of L subshell fluorescence and Coster–Kronig yield were presented