585 research outputs found

    Theory of the SrTiO3 Surface State Two-Dimensional Electron Gas

    Full text link
    We present a theory of the quasi two-dimensional electron gas (2DEG) systems which appear near the surface of SrTiO3_3 when a large external electric field attracts carriers to the surface. We find that non-linear and non-local screening by the strongly polarizable SrTiO3_3 lattice plays an essential role in determining 2DEG properties. The electronic structure always includes weakly bound bulk-like bands that extend over many SrTiO3_3 layers. At 2D carrier-densities exceeding 1014cm2\sim 10^{14} {\rm cm}^{-2} tightly bound bands emerge that are confined within a few layers of the surface.Comment: 10 pages, 9 figures, 1 tabl

    Resolution Properties in Regularized Dynamic MRI Reconstruction

    Full text link
    In dynamic MRI, one is constantly addressing the tradeoff between spatial and temporal resolution. Regularized reconstruction methods may offer benefits in terms of this tradeoff. However, selection of the regularization parameters is challenging. In this work we examine the spatial and temporal resolution of penalized-likelihood image reconstruction for dynamic MRI, and present an accelerated method for computing the local impulse response. This method may prove advantageous for regularization parameter selection.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85877/1/Fessler228.pd

    Ultrafast control of material optical properties via the infrared resonant Raman effect

    Full text link
    The Raman effect -- inelastic scattering of light by lattice vibrations (phonons) -- produces an optical response closely tied to a material's crystal structure. Here we show that resonant optical excitation of IR and Raman phonons gives rise to a Raman scattering effect that can induce giant shifts to the refractive index and induce new optical constants that are forbidden in the equilibrium crystal structure. We complete the description of light-matter interactions mediated by coupled IR and Raman phonons in crystalline insulators -- currently the focus of numerous experiments aiming to dynamically control material properties -- by including a forgotten pathway through the nonlinear lattice polarizability. Our work expands the toolset for control and development of new optical technologies by revealing that the absorption of light within the terahertz gap can enable control of optical properties of materials over a broad frequency range.Comment: 15 pages, 6 figure

    Aircraft/island/ship/satellite intercomparison: Preliminary results from July 16, 1987

    Get PDF
    The First ISCCP Regional Experiment (FIRE) objective of validating and improving satellite algorithms for inferring cloud properties from satellite radiances was one of the central motivating factors in the design of the specific field experimental strategies used in the July, 1987 marine stratocumulus intensive field observations (IFO). The in situ measuring platforms were deployed to take maximum advantage of redundant measurements (for intercomparison of the in situ sensors) and to provide optimal coverage within satellite images. One of the most ambitious of these strategies was the attempt to coordinate measurements from San Nicolas Island (SNI), the R/V Pt. Sur, the meteorological aircraft, and the satellites. For the most part, this attempt was frustrated by flight restrictions in the vicinity of SNI. The exception was the mission of July 16, 1987, which achieved remarkable success in the coordination of the platforms. This presentation concerns operations conducted by the National Center for Atmospheric Research (NCAR) Electra and how data from the Electra can be integrated with and compared to data from the Pt. Sur, SNI, and the satellites. The focus is on the large-scale, integrated picture of the conditions on July 16 from the perspective of the Electra's flight operations

    Sex-Specific Impacts of Exercise on Cardiovascular Remodeling

    Get PDF
    Cardiovascular diseases (CVD) remain the leading cause of death in men and women. Biological sex plays a major role in cardiovascular physiology and pathological cardiovascular remodeling. Traditionally, pathological remodeling of cardiovascular system refers to the molecular, cellular, and morphological changes that result from insults, such as myocardial infarction or hypertension. Regular exercise training is known to induce physiological cardiovascular remodeling and beneficial functional adaptation of the cardiovascular apparatus. However, impact of exercise-induced cardiovascular remodeling and functional adaptation varies between males and females. This review aims to compare and contrast sex-specific manifestations of exercise-induced cardiovascular remodeling and functional adaptation. Specifically, we review (1) sex disparities in cardiovascular function, (2) influence of biological sex on exercise-induced cardiovascular remodeling and functional adaptation, and (3) sex-specific impacts of various types, intensities, and durations of exercise training on cardiovascular apparatus. The review highlights both animal and human studies in order to give an all-encompassing view of the exercise-induced sex differences in cardiovascular system and addresses the gaps in knowledge in the field

    d0 Perovskite-Semiconductor Electronic Structure

    Full text link
    We address the low-energy effective Hamiltonian of electron doped d0 perovskite semiconductors in cubic and tetragonal phases using the k*p method. The Hamiltonian depends on the spin-orbit interaction strength, on the temperature-dependent tetragonal distortion, and on a set of effective-mass parameters whose number is determined by the symmetry of the crystal. We explain how these parameters can be extracted from angle resolved photo-emission, Raman spectroscopy, and magneto-transport measurements and estimate their values in SrTiO3

    Uniaxial strain induced band splitting in semiconducting SrTiO<sub>3</sub>

    Get PDF
    We use angle-resolved photoemission spectroscopy to study the influence of mechanically induced uniaxial strain on the electronic structure of the oxide semiconductor SrTiO3. We observe an orbital splitting between the Ti 3dyz and 3dxy bands, which are degenerate when unperturbed. Using the k·p method, we qualitatively explain the direction and the size of the observed energy splitting. Our comprehensive understanding of band splitting explains the strain induced mobility enhancement of electron-doped SrTiO33 in terms of band degeneracy breaking and reduced interband scattering. Our approach can be extended to differently strained oxide systems
    corecore