The convergence method to calculate particles fluxes in x rays spectrometry techniques. Application in nuclear compounds

A method to calculate particle fluxes applicable in most of the spectroscopy techniques is described. Flux intensities of backscattered or absorbed electrons and emitted photons are calculated using a method of convergence to solve the Invariant Embedding equations that are used to describe the particle trajectories inside a solid sample. Our results are found to be helpful to carry out a procedure for quantitative characterization using instrument such as Electron Probe Microanalysis or other probes. Examples of application to calculate the composition of ternary alloys are given and are compared with the same calculations using another procedure.Comment: 15 page

Electron Probe X-Ray Microanalysis Applied to Thin Surface Films and Stratified Specimens

The basic principles of X-ray microanalysis of thin surface films and stratified targets are summarized. The influence of the electron beam accelerating voltage on the analyzed depth is discussed. It is shown that in the field of soft X-rays, the effective depth of analysis is most often limited by the absorption of the radiation in the specimen itself. For high energy radiations, the importance of the secondary emission due to fluorescence excited by the continuous radiation and by the characteristic lines is outlined. The main concepts of the recent ø(ρz) models used for quantitation in the recent software packages are reminded. The performance of the technique for the simultaneous determination of the mass thicknesses and the compositions of the layers in a stratified target is illustrated with several examples. These examples also illustrate the capability and the limitations of the iterative procedure used in the recent software packages such as Strata or Multifilm

Fracture through cavitation in a metallic glass

The fracture surfaces of a Zr-based bulk metallic glass exhibit exotic multi-affine isotropic scaling properties. The study of the mismatch between the two facing fracture surfaces as a function of their distance shows that fracture occurs mostly through the growth and coalescence of damage cavities. The fractal nature of these damage cavities is shown to control the roughness of the fracture surfaces

Absolute values of the London penetration depth in YBa2Cu3O6+y measured by zero field ESR spectroscopy on Gd doped single crystals

Zero-field electron spin resonance (ESR) of dilute Gd ions substituted for Y in the cuprate superconductor YBa$_2$Cu$_3$O$_{\rm 6+y}$ is used as a novel technique for measuring the absolute value of the low temperature magnetic penetration depth $\lambda(T\to 0)$. The Gd ESR spectrum of samples with $\approx 1$ substitution was obtained with a broadband microwave technique that measures power absorption bolometrically from 0.5 GHz to 21 GHz. This ESR spectrum is determined by the crystal field that lifts the level degeneracy of the spin 7/2 Gd$^{3+}$ ion and details of this spectrum provide information concerning oxygen ordering in the samples. The magnetic penetration depth is obtained by relating the number of Gd ions exposed to the microwave magnetic field to the frequency-integrated intensity of the observed ESR transitions. This technique has allowed us to determine precise values of $\lambda$ for screening currents flowing in the three crystallographic orientations ($\hat a$, $\hat b$ and $\hat c$) in samples of Gd$_{\rm x}$Y$_{\rm 1-x}$Ba$_2$Cu$_3$O$_{6+{\rm y}}$ of three different oxygen contents ${\rm y}=0.993$ ($T_c = 89$ K), ${\rm y}=0.77$ ($T_c=75$ K) and ${\rm y}=0.52$ ($T_c=56$ K). The in-plane values are found to depart substantially from the widely reported relation $T_c\propto 1/\lambda^2$.Comment: 14 pages, 12 figures; version to appear in PR

Iron sulphides at the epithermal gold-copper deposit of Palai-Islica (Almería, SE of Spain)

El artículo original ha sido publicado por la Mineralogical Society disponible en: http://www.minersoc.org/pages/e_journals/minmag.htmlAu-Cu mineralisation at Palai-Islica occurs as disseminations in massive silicification and, more abundantly, in sulphide-bearing quartz veins. The major ore minerals in the deposit are pyrite ± chalcopyrite, sphalerite and galena and there are a great variety of accessory minerals, including Au-Ag alloys and native gold. Pyrite, the most abundant sulphide, is closely associated with gold. Seven different types of pyrite have been distinguished with a variable concentration of different trace elements. Among them only free of trace elements (type IV) is related to Au-Ag alloys. Pyrites associated with these Au-Ag alloys have a cubic and pentagonal dodecahedral habits whereas those with only the pentagonal dodecahedral habit are from barren zones. In addition, there is no significant invisible gold in pyrite, but there is relatively high Ag in collomorphic pyrite (up to 0.20 wt%) or type III pyrite (up to 1.47 wt%). As is the most abundant trace element in pyrite (up to 6.11 wt%), present as a metastable solid solution or as a non-stoichiometric element. Some kind of marcasite related with gold levels also have considerable amounts of trace elements (As, up to 1.15 wt%, Sb up to 0.40 wt%)Departamento de Mineralogía y Petrología. Grupo de Investigación de la Junta de Andalucía RNM-0131. Proyectos PB-97-1211 y BTE2001-330

Experimental and computational study of trace element distribution between orthopyroxene and anhydrous silicate melts: substitution mechanisms and the effect of iron

Although orthopyroxene (Opx) is present during a wide range of magmatic differentiation processes in the terrestrial and lunar mantle, its effect on melt trace element contents is not well quantified. We present results of a combined experimental and computational study of trace element partitioning between Opx and anhydrous silicate melts. Experiments were performed in air at atmospheric pressure and temperatures ranging from 1,326 to 1,420°C in the system CaO-MgO-A