No abstract

Common optical absorption features are observed near 0.5 eV in four undoped single-crystal copper oxides: La2CuC>4, Nd2CuC>4, Pr2Cu04, and S^CuC^Ch. These absorption bands are shown to be weakly electric dipole allowed excitations of the Cu02 layers. The features are ascribed to an exciton near 0.4 eV, probably of crystal-field origin, with strong multimagnon sidebands. Our observations provide an important basis for understanding the doped materials.

The upper critical Seld H, q and fiuctuation conductivity were measured for highly oriented thin nlHls of YBa2Cu307 -. The H, 2 results demonstrate the intrinsic anisotropy in this layered su-

Pulse oximetry is an important diagnostic and patient monitoring tool. However, motion can induce considerable error into pulse oximetry accuracy, resulting in loss of data, inaccurate readings, and false alarms. We will discuss how motion artifact affects pulse oximetry accuracy, the clinical consequences of motion artifact, and the methods used by various technologies to minimize the impact of the motion noise.

We measure the longitudinal (p xx ) and Hall (p xv ) resistivities as a function of magnetic field and temperature in the mixed state of epitaxial YBa2Cu3C>7 films. We observe a striking power-law behavior p xy {T) oc [p xx (T)] a at fixed field, with a -1.7 ±0.2. Our results link the Hall behavior to collective behavior in the presence of pinning. In addition, this power-law dependence is consistent with new calculations for the vortex-glass transition, and therein may provide the first measurement of a new critical exponent.