260 research outputs found
Enabling Real-Time Ultrasound Imaging of Soft Tissue Mechanical Properties by Simplification of the Shear Wave Motion Equation
Ultrasound based shear wave elastography (SWE) is a technique used for non-invasive characterization and imaging of soft tissue mechanical properties. Robust estimation of shear wave propagation speed is essential for imaging of soft tissue mechanical properties. In this study we propose to estimate shear wave speed by inversion of the firstorder wave equation following directional filtering. This approach relies on estimation of first-order derivatives which allows for accurate estimations using smaller smoothing filters than when estimating second-order derivatives. The performance was compared to three current methods used to estimate shear wave propagation speed: direct inversion of the wave equation (DIWE), time-to-peak (TTP) and crosscorrelation (CC). The shear wave speed of three homogeneous phantoms of different elastic moduli (gelatin by weight of 5%, 7%, and 9%) were measured with each method. The proposed method was shown to produce shear speed estimates comparable to the conventional methods (standard deviation of measurements being 0.13 m/s, 0.05 m/s, and 0.12 m/s), but with simpler processing and usually less time (by a factor of 1, 13, and 20 for DIWE, CC, and TTP respectively). The proposed method was able to produce a 2-D speed estimate from a single direction of wave propagation in about four seconds using an off-the-shelf PC, showing the feasibility of performing real-time or near real-time elasticity imaging with dedicated hardware
Effects of Local Blood Flow on Muscle Stiffness
Muscle injuries, in the form of strains or even tears, affect millions of people each year through undue tension on muscles during everyday activities, work tasks, or physical activity including sports or working out. These injuries can take from a few weeks to even months to heal, with patients having to deal with inflammation, swelling, and pain throughout the healing process. Scar tissue also forms when the muscle is injured, which regenerates throughout the healing process, but never fully recovers to its state prior to injury. This scar tissue is thought to make the muscle more prone to subsequent injury, making it important to avoid muscle injuries to begin with so as to not lose overall strength and range of motion. Although there are currently certain activities identified to increase the probability of muscle injury, there is limited evidence as to what physiological components may make an individual more susceptible to injury. Therefore, the purpose of this study is to look at the association between two measures; blood flow velocity through muscle using Doppler ultrasound and the muscle\u27s stiffness, or Young\u27s modulus, using ultrasound elastography. A notable correlation between the two factors could allow clinicians to know if patients have a predisposition to muscle injury due to their rate of blood flow
Growth and characterization of -Sn thin films on In- and Sb-rich reconstructions of InSb(001)
-Sn thin films can exhibit a variety of topologically non-trivial
phases. Both studying the transitions between these phases and making use of
these phases in eventual applications requires good control over the electronic
and structural quality of -Sn thin films. -Sn growth on InSb
often results in out-diffusion of indium, a p-type dopant. By growing
-Sn via molecular beam epitaxy on the Sb-rich c(44) surface
reconstruction of InSb(001) rather than the In-rich c(82), we
demonstrate a route to substantially decrease and minimize this indium
incorporation. The reduction in indium concentration allows for the study of
the surface and bulk Dirac nodes in -Sn via angle-resolved
photoelectron spectroscopy without the common approaches of bulk doping or
surface dosing, simplifying topological phase identification. The lack of
indium incorporation is verified in angle-resolved and -integrated ultraviolet
photoelectron spectroscopy as well as in clear changes in the Hall response
First Principles Assessment of CdTe as a Tunnel Barrier at the -Sn/InSb Interface
Majorana zero modes, with prospective applications in topological quantum
computing, are expected to arise in superconductor/semiconductor interfaces,
such as -Sn and InSb. However, proximity to the superconductor may also
adversely affect the semiconductor's local properties. A tunnel barrier
inserted at the interface could resolve this issue. We assess the wide band gap
semiconductor, CdTe, as a candidate material to mediate the coupling at the
lattice-matched interface between -Sn and InSb. To this end, we use
density functional theory (DFT) with Hubbard U corrections, whose values are
machine-learned via Bayesian optimization (BO) [npj Computational Materials 6,
180 (2020)]. The results of DFT+U(BO) are validated against angle resolved
photoemission spectroscopy (ARPES) experiments for -Sn and CdTe. For
CdTe, the z-unfolding method [Advanced Quantum Technologies, 5, 2100033 (2022)]
is used to resolve the contributions of different values to the ARPES. We
then study the band offsets and the penetration depth of metal-induced gap
states (MIGS) in bilayer interfaces of InSb/-Sn, InSb/CdTe, and
CdTe/-Sn, as well as in tri-layer interfaces of InSb/CdTe/-Sn
with increasing thickness of CdTe. We find that 16 atomic layers (3.5 nm) of
CdTe can serve as a tunnel barrier, effectively shielding the InSb from MIGS
from the -Sn. This may guide the choice of dimensions of the CdTe
barrier to mediate the coupling in semiconductor-superconductor devices in
future Majorana zero modes experiments
Epitaxial growth, magnetoresistance, and electronic band structure of GdSb magnetic semimetal films
Motivated by observations of extreme magnetoresistance (XMR) in bulk crystals
of rare-earth monopnictide (RE-V) compounds and emerging applications in novel
spintronic and plasmonic devices based on thin-film semimetals, we have
investigated the electronic band structure and transport behavior of epitaxial
GdSb thin films grown on III-V semiconductor surfaces. The Gd3+ ion in GdSb has
a high spin S=7/2 and no orbital angular momentum, serving as a model system
for studying the effects of antiferromagnetic order and strong exchange
coupling on the resulting Fermi surface and magnetotransport properties of
RE-Vs. We present a surface and structural characterization study mapping the
optimal synthesis window of thin epitaxial GdSb films grown on III-V
lattice-matched buffer layers via molecular beam epitaxy. To determine the
factors limiting XMR in RE-V thin films and provide a benchmark for band
structure predictions of topological phases of RE-Vs, the electronic band
structure of GdSb thin films is studied, comparing carrier densities extracted
from magnetotransport, angle-resolved photoemission spectroscopy (ARPES), and
density functional theory (DFT) calculations. ARPES shows hole-carrier rich
topologically-trivial semi-metallic band structure close to complete
electron-hole compensation, with quantum confinement effects in the thin films
observed through the presence of quantum well states. DFT predicted Fermi
wavevectors are in excellent agreement with values obtained from quantum
oscillations observed in magnetic field-dependent resistivity measurements. An
electron-rich Hall coefficient is measured despite the higher hole carrier
density, attributed to the higher electron Hall mobility. The carrier
mobilities are limited by surface and interface scattering, resulting in lower
magnetoresistance than that measured for bulk crystals
Tuning the Band Topology of GdSb by Epitaxial Strain
Rare-earth monopnictide (RE-V) semimetal crystals subjected to hydrostatic
pressure have shown interesting trends in magnetoresistance, magnetic ordering,
and superconductivity, with theory predicting pressure-induced band inversion.
Yet, thus far, there have been no direct experimental reports of interchanged
band order in RE-Vs due to strain. This work studies the evolution of band
topology in biaxially strained GdSb (001) epitaxial films using angle-resolved
photoemission spectroscopy (ARPES) and density functional theory (DFT). We find
that biaxial strain continuously tunes the electronic structure from
topologically trivial to nontrivial, reducing the gap between the hole and the
electron bands dispersing along the [001] direction. The conduction and valence
band shifts seen in DFT and ARPES measurements are explained by a tight-binding
model that accounts for the orbital symmetry of each band. Finally, we discuss
the effect of biaxial strain on carrier compensation and magnetic ordering
temperature
Dynamical coupled-channel approaches on a momentum lattice
Dynamical coupled-channel approaches are a widely used tool in hadronic
physics that allow to analyze different reactions and partial waves in a
consistent way. In such approaches the basic interactions are derived within an
effective Lagrangian framework and the resulting pseudo-potentials are then
unitarized in a coupled-channel scattering equation. We propose a scheme that
allows for a solution of the arising integral equation in discretized momentum
space for periodic as well as twisted boundary conditions. This permits to
study finite size effects as they appear in lattice QCD simulations. The new
formalism, at this stage with a restriction to S-waves, is applied to
coupled-channel models for the sigma(600), f0(980), and a0(980) mesons, and
also for the Lambda(1405) baryon. Lattice spectra are predicted.Comment: 7 pages, 4 figure
Tuning the band topology of GdSb by epitaxial strain
Rare-earth monopnictide (RE-V) semimetal crystals subjected to hydrostatic pressure have shown interesting trends in magnetoresistance, magnetic ordering, and superconductivity, with theory predicting pressure-induced band inversion. Yet, thus far, there have been no direct experimental reports of interchanged band order in RE-Vs due to strain. This work studies the evolution of band topology in biaxially strained GdSb(001) epitaxial films using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT). As biaxial strain is tuned from tensile to compressive strain, the gap between the hole and the electron bands dispersed along [001] decreases. The conduction and valence band shifts seen in DFT and ARPES measurements are explained by a tight-binding model that accounts for the orbital symmetry of each band. Finally, we discuss the effect of biaxial strain on carrier compensation and magnetic ordering temperature
Pan-Cancer Analysis of lncRNA Regulation Supports Their Targeting of Cancer Genes in Each Tumor Context
Long noncoding RNAs (lncRNAs) are commonly dys-regulated in tumors, but only a handful are known toplay pathophysiological roles in cancer. We inferredlncRNAs that dysregulate cancer pathways, onco-genes, and tumor suppressors (cancer genes) bymodeling their effects on the activity of transcriptionfactors, RNA-binding proteins, and microRNAs in5,185 TCGA tumors and 1,019 ENCODE assays.Our predictions included hundreds of candidateonco- and tumor-suppressor lncRNAs (cancerlncRNAs) whose somatic alterations account for thedysregulation of dozens of cancer genes and path-ways in each of 14 tumor contexts. To demonstrateproof of concept, we showed that perturbations tar-geting OIP5-AS1 (an inferred tumor suppressor) andTUG1 and WT1-AS (inferred onco-lncRNAs) dysre-gulated cancer genes and altered proliferation ofbreast and gynecologic cancer cells. Our analysis in-dicates that, although most lncRNAs are dysregu-lated in a tumor-specific manner, some, includingOIP5-AS1, TUG1, NEAT1, MEG3, and TSIX, synergis-tically dysregulate cancer pathways in multiple tumorcontexts
Genomic, Pathway Network, and Immunologic Features Distinguishing Squamous Carcinomas
This integrated, multiplatform PanCancer Atlas study co-mapped and identified distinguishing
molecular features of squamous cell carcinomas (SCCs) from five sites associated with smokin
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