Uranium-bearing francolites present in organic-rich limestones of NW Greece: a preliminary study using synchrotron radiation and fission track techniques

Synchrotron radiation techniques (μ-XRF and μ-XANES) were applied to the study of organic-rich phosphatized limestones of NW Greece (Epirus). The results revealed uranium accumulation in areas of the material containing, among others, carbonate apatite (francolite) and organic matter. The UL ₃-edge of μ-XANES spectra showed that uranium was present in tetravalent form. U-bearing francolite crystals were separated from the rock and characterized by Raman spectroscopy and microprobe. The analysis of the crystals also indicated the presence of sodium and sulfur. The uranium presence in the crystals was also visualized, after neutron irradiation and etching, by the observation of the fission tracks.

     

The determination of zinc,copper and iron oxidation state in invasive ductal carcinoma of breast tissue and normal surrounding tissue using XANES

X‐ray absorption near‐edge structure (XANES) spectroscopy was used to examine the oxidation state of Zn, Fe and Cu in 22 normal and 23 tumour regions spread over 30 formalin‐fixed, paraffin‐embedded tissue samples of human primary invasive breast cancer. A micro‐mapping analysis of the metal distribution in the tissue was performed prior to the XANES analysis to identify and localise the metals in the tumour and normal tissue regions. The aim of this study was to identify the oxidation state of Zn, Fe and Cu in normal and tumour tissues of the breast, in order to correlate the oxidation state of these elements with the carcinogenesis process. The position of the Zn K‐edge in normal and tumour tissues suggests that Zn exists in a bounded form. The shape of the Cu K‐edge XANES spectra and the first derivative spectra of normal and tumour tissues shows that a significant portion of the total copper is present as Cu (I). Nevertheless, the position of the edges in the normal and tumour tissue spectra does not exclude the presence of Cu (II). The shape and position of both normal and tumour regions of the tissue suggest that they contain mixtures of Fe (II) and Fe (III) ions with a significant fraction being Fe (III). However, normal tissue regions were found to have a higher fraction of Fe (II) compared to the tumour tissues. In order to estimate the best target for therapy, more information is required about the relative abundance of Zn, Fe and Cu binding proteins, their oxidation state and their localisation at the subcellular level. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and crystal structure of low ferrialuminosilicate sanidine

Iron-containing potassium feldspar crystals are prepared using the hydrothermal synthesis in an alkaline medium at temperatures ranging from 500 to 52°C. The crystal structure of the synthetic potassium feldspar is refined [Ital Structures diffractometer, MoKαradiation, 1327 unique reflections with Fs>σ(F), anisotropic approximation, R(F) = 0.044]. It is established that, under the given preparation conditions, the synthesis leads to the formation of the monoclinic modification with the following unit-cell parameters: a = 8.655(7) Å, b = 13.101(9) Å, c = 7.250(8) Å, β = 116.02(2)°, space group C2/m, and Z = 4. The cation distribution over crystallographically inequivalent tetrahedral positions T(1) and T(2) is determined and justified using X-ray diffraction data. According to this distribution, the iron-containing potassium feldspar is assigned to the low ferrialuminosilicate sanidine. The proposed structural formula K _{A = 0.99}(Si_1.2Fe_0.5Al_0.3)_{ΣT(1) = 2}(Si_1.81Al_0.19)_{ΣT(2) = 2}O₈ agrees well with the data of the electron microprobe analysis. It is revealed that iron occupies the T(1) position and manifests itself as a majority rather than minority impurity element with respect to aluminum.     

Manganese speciation in Diplodon chilensis patagonicus shells: a XANES study

X‐ray absorption near‐edge spectroscopy (XANES) at the Mn K‐edge was used to investigate the environment of Mn in situ within the growth increments of the long‐lived freshwater bivalve species Diplodon chilensis patagonicus. Single XANES spectra and Mn Kα fluorescence distributions were acquired at submillimetre resolution (up to 100 µm × 50 µm), at Mn concentrations below the weight percent range (100–1000 µg g^?1) in a high Ca matrix. The position and intensity of the pre‐edge feature in the shell spectrum resembles best that of the Mn(II)‐bearing reference compounds, suggesting that this is the oxidation state of Mn in the bivalve shells. By comparison with the XANES spectra of selected standard compounds, hypotheses about Mn speciation in the shell are also reported. In particular, different factors, such as provenance, ontogenetic age, variable Mn‐concentrations or seasonal shell deposition seem not to influence the speciation of the metal in this bivalve species.