Unique vortex and stripe domain structures in PbTiO 3 epitaxial nanodots

The domain structures of PbTiO 3 epitaxial nanodots under the influences of depolarization fields and mismatch strains have been studied using three dimensional phase field simulations. The single-vortex structure and mixed domain configuration, which consisted of zigzag stripe domain and closure dipole flux near the interfaces, were found to be effective in annihilating the depolarization fields in the isotropically tensile and compressive ferroelectric nanodots, respectively. These domain structures were produced by the combined effect of electrostatic and mismatch elastic energies. The width of stripe domain was found to be related to the volume percentage of polarization dipoles along the z-axis, which varied remarkably with the change of compressive mismatch strain. In the case of nanodots under anisotropic mismatch strains, double-vortex domain patterns and stripe domains with nearly straight domain walls were formed. Moreover, the domain structures with electrostatic energy neglected were also studied. © 2011 Elsevier Ltd. All rights reserved.postprin

Effects of film thickness and mismatch strains on magnetoelectric coupling in vertical heteroepitaxial nanocomposite thin films

The phase field model is adopted to study the magnetoelectric coupling effects in vertical heteroepitaxial nanocomposite thin films. Both the lateral epitaxial strains between the film and the substrate and the vertical epitaxial strains between the ferroelectric and ferromagnetic phases are accounted for in the model devised. The effects of the film thickness on the magnetic-field- induced electric polarization (MIEP) are investigated. The results obtained show that the MIEP is strongly dependent on the film thickness, as well as on the vertical and lateral epitaxial strains. © 2011 American Institute of Physics.published_or_final_versio

Interaction of O vacancies and domain structures in single crystal BaTi O3: Two-dimensional ferroelectric model

Two-dimensional simulations on the interactions of oxygen vacancies and different domain structures in barium titanate single crystal were carried out using the phase field method. The evolution of the spontaneous polarizations and oxygen vacancies was coupled through Maxwell's equation. The results showed that two barriers near the electrodes existed in both the 90°and 180°domain structures. It has also been observed that while an intrinsic electrostatic potential drop across the 90°domain wall created the electric fields which drove the electrons and oxygen vacancies aggregate on the different sides of the domain wall, the 180°domain wall had insignificant interaction with the potential, and no electron or vacancy accumulation in 180°domain structure was observed. Polarization charge density is believed to be the origin of this difference. © 2008 The American Physical Society.published_or_final_versio

Magnetic Resonance Imaging of Optic Nerve Traction During Adduction in Primary Open-Angle Glaucoma With Normal Intraocular Pressure.

PurposeWe used magnetic resonance imaging (MRI) to ascertain effects of optic nerve (ON) traction in adduction, a phenomenon proposed as neuropathic in primary open-angle glaucoma (POAG).MethodsSeventeen patients with POAG and maximal IOP ≤ 20 mm Hg, and 31 controls underwent MRI in central gaze and 20° to 30° abduction and adduction. Optic nerve and sheath area centroids permitted computation of midorbital lengths versus minimum paths.ResultsAverage mean deviation (±SEM) was -8.2 ± 1.2 dB in the 15 patients with POAG having interpretable perimetry. In central gaze, ON path length in POAG was significantly more redundant (104.5 ± 0.4% of geometric minimum) than in controls (102.9 ± 0.4%, P = 2.96 × 10-4). In both groups the ON became significantly straighter in adduction (28.6 ± 0.8° in POAG, 26.8 ± 1.1° in controls) than central gaze and abduction. In adduction, the ON in POAG straightened to 102.0% ± 0.2% of minimum path length versus 104.5% ± 0.4% in central gaze (P = 5.7 × 10-7), compared with controls who straightened to 101.6% ± 0.1% from 102.9% ± 0.3% in central gaze (P = 8.7 × 10-6); and globes retracted 0.73 ± 0.09 mm in POAG, but only 0.07 ± 0.08 mm in controls (P = 8.8 × 10-7). Both effects were confirmed in age-matched controls, and remained significant after correction for significant effects of age and axial globe length (P = 0.005).ConclusionsAlthough tethering and elongation of ON and sheath are normal in adduction, adduction is associated with abnormally great globe retraction in POAG without elevated IOP. Traction in adduction may cause mechanical overloading of the ON head and peripapillary sclera, thus contributing to or resulting from the optic neuropathy of glaucoma independent of IOP

Mesoscale magnetism at the grain boundaries in colossal magnetoresistive films

We report the discovery of mesoscale regions with distinctive magnetic properties in epitaxial La$_{1-x}$Sr$_{x}$MnO$_{3}$ films which exhibit tunneling-like magnetoresistance across grain boundaries. By using temperature-dependent magnetic force microscopy we observe that the mesoscale regions are formed near the grain boundaries and have a different Curie temperature (up to 20 K {\it higher}) than the grain interiors. Our images provide direct evidence for previous speculations that the grain boundaries in thin films are not magnetically and electronically sharp interfaces. The size of the mesoscale regions varies with temperature and nature of the underlying defect.Comment: 4 pages of text, 4 figure

Remarks on Renormalization of Black Hole Entropy

We elaborate the renormalization process of entropy of a nonextremal and an extremal Reissner-Nordstr\"{o}m black hole by using the Pauli-Villars regularization method, in which the regulator fields obey either the Bose-Einstein or Fermi-Dirac distribution depending on their spin-statistics. The black hole entropy involves only two renormalization constants. We also discuss the entropy and temperature of the extremal black hole.Comment: 14 pages, revtex, no figure

Identifying Locations of Violent Injuries in Las Vegas to Implement the Cardiff Violence Prevention Model

Public violence in the United States is a major health concern. Incidents involving violent crimes are often not reported to law enforcement. The Cardiff Model is a violence prevention program developed in the UK to identify and enable data sharing of violent injury locations between Emergency Rooms (ER) and local law enforcement to help identify areas for community improvements. The model is now in use in several major cities in the US to reduce violence. Las Vegas has seen an increase in public violence in recent years. As a result, researchers from the Southern Nevada Health District (SNHD) and University of Las Vegas (UNLV) believe the Cardiff Model is a viable solution to address this public health crisis. This research explores natural language processing and machine learning models to extract violent injury location information from ER records in preparation for introducing the Cardiff Violence Prevention Model in Clark County, Nevada