Reduction of the Yb valence in YbAl3 nanoparticles

Measurements of specific heat, dc magnetic susceptibility, and Yb LII and LIII x-ray absorption near-edge structure XANES and extended x-ray absorption fine structure EXAFS on YbAl3 milled alloys are reported. X-ray diffraction patterns are consistent with a reduction in particle size down to 10 nm and an increase in the lattice strain up to 0.4% for 120 h of milling time. A decrease in the mean valence from 2.86 for the unmilled alloy to 2.70 for 120 h milled YbAl3 is obtained from the analysis of XANES spectra. From the analysis of spectra in the EXAFS region, an increase in the mean-square disorder of neighbor distance with milling time is detected in good agreement with the results of x-ray diffraction. Size effects strongly influence the magnetic and thermal properties. The value for the maximum of the magnetic susceptibility decreases around 30% for 120 h milled alloy and an excess specific heat, with a peak around 40 K in the milled samples, is derived. These changes in the physical properties along the milled YbAl3 alloys are associated with the reduction in particle size. Such a reduction leads to the existence of a large number of Yb2+ atoms at the surface with respect to the bulk affecting the overall electronic state

MRI Bone Marrow Findings in 63 Patients with Type I Gaucher Disease

Purpose To determine whether MR bone marrow findings in Gaucher patients may help to identify patients at high risk of developing severe Gaucher bone complications exemplified by avascular necrosis (AVN) of the femoral head Materials and Methods MR images were obtained in 63 Type I Gaucher patients through a standard protocol using coronal Ti and T2-weighted sequences of the lower extremities The location and extent of infiltrated marrow was established using a semi-quantitative MRI scoring method (Dusseldorf Gaucher score DGS) and the morphological pattern of bone marrow involvement determined (whether homogeneous type A or non-homogeneous type B) The active marrow process with bone edema and AVN of the femoral head were also analyzed Results Bone marrow involvement was observed in femoral sites more than in tibial sites A high DGS was significantly correlated with type B morphology and femoral AVN (both p < 0 0001) Splenectomized patients showed a significantly higher Dusseldorf Gaucher score and type B morphology than non-splenectomized patients (both p < 0 05) AVN was seen in 46% of patients with type B morphology versus 3% in type A morphology (p < 0 0001) DGS and morphology of bone marrow involvement were not significantly correlated with active marrow processes Conclusion Type B marrow morphology and extensive marrow packing were significantly associated with AVN of the femoral head (both p < 0 0001) These patterns ale considered predictive and may be employed in a disease management context to alert physicians to the need for urgent therapeutic measure