Correlated local distortions of the TlO layers in Tl2_2Ba2_2CuOy_{y}: An x-ray absorption study

We have used the XAFS (x-ray-absorption fine structure) technique to investigate the local structure about the Cu, Ba, and Tl atoms in orthorhombic Tl-2201 with a superconducting transition temperature T$_c$=60 K. Our results clearly show that the O(1), O(2), Cu, and Ba atoms are at their ideal sites as given by the diffraction measurements, while the Tl and O(3) atoms are more disordered than suggested by the average crystal structure. The Tl-Tl distance at 3.5 \AA{ } between the TlO layers does not change, but the Tl-Tl distance at 3.9 \AA{ } within the TlO layer is not observed and the Tl-Ba and Ba-Tl peaks are very broad. The shorter Tl-O(3) distance in the TlO layer is about 2.33 \AA, significantly shorter than the distance calculated with both the Tl and O(3) atoms at their ideal $4e$ sites ( $x=y=$0 or $\frac{1}{2}$). A model based on these results shows that the Tl atom is displaced along the directions from its ideal site by about 0.11 \AA; the displacements of neighboring Tl atoms are correlated. The O(3) atom is shifted from the $4e$ site by about 0.53 \AA{ } roughly along the directions. A comparison of the Tl L$_{III}$-edge XAFS spectra from three samples, with T$_c$=60 K, 76 K, and 89 K, shows that the O environment around the Tl atom is sensitive to T$_c$ while the Tl local displacement is insensitive to T$_c$ and the structural symmetry. These conclusions are compared with other experimental results and the implications for charge transfer and superconductivity are discussed. This paper has been submitted to Phys. Rev. B.Comment: 20 pages plus 14 ps figures, REVTEX 3.

The Portuguese Version of the Breastfeeding Self-Efficacy Scale—Short Form

The objective of this study was to translate and psychometrically assess a Portuguese version of the Breastfeeding Self-Efficacy Scale–Short Form (BSES-SF). The original English version of the BSES-SF was translated to Portuguese and tested among a sample of 89 mothers in southern Brazil from the 2nd to 12th postpartum week followed by face-to-face interviews. The mean total score of the Portuguese version of the BSES-SF was 63.6 ± 6.22. The reliability analysis of each item in the scale attained significant Cronbach’s alphas of 0.63 or superior. The Cronbach’s alpha generated by the entire range of 14 questions was 0.71. A factor analysis identified one factor that contributed to 20% of the variance. This study demonstrates that the original English version of the BSES-SF was successfully adapted to Portuguese. The Portuguese version of the BSES-SF constitutes a reliable research instrument for evaluating breastfeeding self-efficacy in Brazil