585 research outputs found
Theory of the SrTiO3 Surface State Two-Dimensional Electron Gas
We present a theory of the quasi two-dimensional electron gas (2DEG) systems
which appear near the surface of SrTiO when a large external electric field
attracts carriers to the surface. We find that non-linear and non-local
screening by the strongly polarizable SrTiO lattice plays an essential role
in determining 2DEG properties. The electronic structure always includes weakly
bound bulk-like bands that extend over many SrTiO layers. At 2D
carrier-densities exceeding 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
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
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
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Complete Genomic Sequences of Three Salmonella enterica subsp. enterica Serovar Muenchen Strains from an Orchard in San Joaquin County, California.
We present here the complete genome sequences of three Salmonella enterica subsp. enterica serovar Muenchen strains, LG24, LG25, and LG26. All three strains were isolated from almond drupes grown in an orchard in San Joaquin County, California, in 2016. These genomic sequences are nonidentical and will contribute to our understanding of S. enterica genomics
Aircraft/island/ship/satellite intercomparison: Preliminary results from July 16, 1987
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
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
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>
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
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