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This paper reports results of an international comparison of one-dimensional (1D) grating pitch calibration by optical diffraction. Comparison results are analysed and discussed following the recommended guidelines for the analysis of CIPM key comparisons. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by SIM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

We have studied oxygen deficient GdBa 2 Cu 3 O 7− y samples by heating cycle technique and correlated the resistivity data with the oxygen deficiency derived from TGA. An orthorthombic to tetragonal phase transformation was found at about 720 K and it is consistent with that derived from the X-ray data. The resistivity is hysteretic cooling and shows semiconducting behavior for y ⩾0.7. Localization was found for samples with semiconductive properties. The electron-phonon coupling constant derived from the electric and magnetic measurements is λ tr =0.31 which suggests a weak electron-phonon coupling in high - T c oxides.