A phenomenological approach to the anisotropic magnetoresistance and planar Hall effect in tetragonal La(2/3)Ca(1/3)MnO3 thin films.

A La(2/3)Ca(1/3)MnO(3) Hall bar with its long dimension roughly along the hard axis [110] was fabricated on a single-crystal-like tensilely strained film on SrTiO(3)(001). The anisotropic magnetoresistance (AMR) and planar Hall effect (PHE) have been studied at various external magnetic fields and temperatures. A phenomenological model in the high field limit is developed, and the galvanomagnetic tensor based on a tetragonal symmetry 4/mmm (D(4h)), applicable to epitaxial films on a substrate, has been obtained by expanding the tensor to the sixth order. The derived in-plane transverse resistance R(xy) shows a sin2φ(M) angular dependence, while the longitudinal R(xx) is constituted by not only a two-fold cos2φ(M) term, but also a four-fold cos4φ(M) term due to the square symmetry of the lattice. The model is in good agreement with the experimental results in high fields, while deviations are observed near the {100} easy axis with the decreasing field. Close inspection of the fitting parameters reveals the evolution of these term weights with temperature and magnetic field, which is distinct from conventional ferromagnetic metals and cannot be explained by the phenomenological model. An alternative mechanism for AMR, stemming from the magnetization-induced local orbit deformation through spin-orbit interaction, as previously proposed by O'Donnell et al, may be prevalent in manganites and other systems of complicated crystal structure.

The role of magnetoelastic strain on orbital control and transport properties in an LaTiO(3)-CoFe(2)O(4) heterostructure.

Epitaxial heterostructures of CoFe(2)O(4)/LaTiO(3)/LaAlO(3) have been successfully prepared by using the pulsed laser deposition technique. The magnetoresistance (MR) of the samples is negative and linear with field at H≥2 T, exhibiting no dependence on field directions. Nevertheless, when H<2 T, the MR is negative in a field parallel to the sample plane, but positive in that along the film normal. This novel observed anisotropic MR is explained in terms of the magnetic anisotropy in the ferrimagnetic layer, as well as the magnetoelastic coupling between the two. In fields of different directions, the top CoFe(2)O(4) layer contracts or expands in the sample plane due to the significant magnetostriction effect, changing its resistance accordingly and exerting compressive or tensile strains on the bottom LaTiO(3) layer. Apparently the orbital status and the one-electron bandwidth in the LaTiO(3) layer are altered, which leads to a change in resistance.

Implementation of adiabatic geometric gates with superconducting phase qubits.

We present an adiabatic geometric quantum computation strategy based on the non-degenerate energy eigenstates in (but not limited to) superconducting phase qubit systems. The fidelity of the designed quantum gate was evaluated in the presence of simulated thermal fluctuations in a superconducting phase qubits circuit and was found to be quite robust against random errors. In addition, it was elucidated that the Berry phase in the designed adiabatic evolution may be detected directly via the quantum state tomography developed for superconducting qubits. We also analyze the effects of control parameter fluctuations on the experimental detection of the Berry phase.

Association of hospital and surgeon operation volume with the incidence of postoperative endophthalmitis: Taiwan experience.

PURPOSE: To determine the association between hospital and surgeon volume with the incidence of postoperative endophthalmitis. METHODS: A prospective cohort study was conducted to analyse the national health insurance claims data of those patients receiving cataract surgery in 2000 in Taiwan. A total of 108,705 patients who received cataract surgery by 1004 surgeons at 494 hospitals were followed to the end of 2002. Stepwise Cox regression was used to analyse the effects of hospital and surgeon volume of cataract surgery on postoperative endophthalmitis after adjustment for patient's age, gender, education, ophthalmic comorbidities, general comorbidities, and surgical factors including operative methods, different types of intraocular lenses, and surgeon's age. RESULTS: The 2-year incidence of postoperative endophthalmitis at high-volume hospitals (0.90%) was lower than low-volume hospitals (1.16%). The incidence of postoperative endophthalmitis by high-volume surgeons (0.59%) was lower than those by middle-high-volume (0.73%), middle-low-volume (0.80%), or low-volume surgeons (1.16%). After controlling for case mix, the risk of postoperative endophthalmitis of the low-volume hospitals (hazard ratio (HR) = 1.39) was higher than that of the high-volume hospitals. The risk of postoperative endophthalmitis of low-volume surgeons (HR = 1.67) was higher than that of the high-volume surgeons. CONCLUSIONS: The provider volume (hospital and surgeon volume) is associated with the risk of postoperative endophthalmitis. The patients who receive cataract surgery at low-volume hospitals or by low-volume surgeons have significantly higher risk of postoperative endophthalmitis than at high-volume hospitals or by high-volume surgeons. Provider volume can be considered in further postoperative endophthalmitis study as a risk factor.