PACS photometer calibration block analysis

The absolute stability of the PACS bolometer response over the entire mission lifetime without applying any corrections is about 0.5% (standard deviation) or about 8% peak-to-peak. This fantastic stability allows us to calibrate all scientific measurements by a fixed and time-independent response file, without using any information from the PACS internal calibration sources. However, the analysis of calibration block observations revealed clear correlations of the internal source signals with the evaporator temperature and a signal drift during the first half hour after the cooler recycling. These effects are small, but can be seen in repeated measurements of standard stars. From our analysis we established corrections for both effects which push the stability of the PACS bolometer response to about 0.2% (stdev) or 2% in the blue, 3% in the green and 5% in the red channel (peak-to-peak). After both corrections we still see a correlation of the signals with PACS FPU temperatures, possibly caused by parasitic heat influences via the Kevlar wires which connect the bolometers with the PACS Focal Plane Unit. No aging effect or degradation of the photometric system during the mission lifetime has been found.Comment: 15 pages, accepted for publication in Experimental Astronom

Magnetic properties of Gd_{1-x}Pr_xBa_2Cu_3O_{7-y} single crystals

Magnetic properties were studied for the high quality Al-free orthorhombic Gd_{1-x}Pr_xBa_2Cu_3O_{7-y} single crystals (0<=x<=1.0) grown by the flux method. An indication on the interaction between the Pr and Cu(2) magnetic sublattices was found for Pr123. Different signs of magnetic anisotropy were established for the Pr and Gd ions at low temperatures. It was also shown that superconductivity reported by Zou et al. [Phys. Rev. Lett. 80 (1998) 1074] for Pr123 single crystals grown by TSZF method seems to be connected with partial substitution of Ba for the Pr-sites.Comment: 2 pages (LaTeX2e), 4 EPS figures, phbauth style file included. LT22 conference paper accepted to Physica

On the commutability of homogenization and linearization in finite elasticity

We study non-convex elastic energy functionals associated to (spatially) periodic, frame indifferent energy densities with a single non-degenerate energy well at SO(n). Under the assumption that the energy density admits a quadratic Taylor expansion at identity, we prove that the Gamma-limits associated to homogenization and linearization commute. Moreover, we show that the homogenized energy density, which is determined by a multi-cell homogenization formula, has a quadratic Taylor expansion with a quadratic term that is given by the homogenization of the quadratic term associated to the linearization of the initial energy density