30 research outputs found
Orbital Subband Structures and Chiral Orbital Angular Momentum in the (001) Surface States of SrTiO
We have performed angle resolved photoemission spectroscopy (ARPES)
experiments on the surface states of SrTiO(001) using linearly and
circularly polarized light to investigate the subband structures of
out-of-plane orbitals and chiral orbital angular momentum (OAM).
The data taken in the first Brillouin zone reveal new subbands for
orbitals with Fermi wave vectors of 0.25 and 0.45 in
addition to the previously reported ones. As a result, there are at least two
subbands for all the Ti 3d t orbitals. Our circular dichroism ARPES data
is suggestive of a chiral OAM structure in the surface states and may provide
clues to the origin of the linear Rashba-like surface band splitting.Comment: 7 pages, 3 figures, Journal pape
3D Trajectory Reconstruction of Drones using a Single Camera
Drones have been widely utilized in various fields, but the number of drones
being used illegally and for hazardous purposes has increased recently. To
prevent those illegal drones, in this work, we propose a novel framework for
reconstructing 3D trajectories of drones using a single camera. By leveraging
calibrated cameras, we exploit the relationship between 2D and 3D spaces. We
automatically track the drones in 2D images using the drone tracker and
estimate their 2D rotations. By combining the estimated 2D drone positions with
their actual length information and camera parameters, we geometrically infer
the 3D trajectories of the drones. To address the lack of public drone
datasets, we also create synthetic 2D and 3D drone datasets. The experimental
results show that the proposed methods accurately reconstruct drone
trajectories in 3D space, and demonstrate the potential of our framework for
single camera-based surveillance systems.Comment: 10 pages, 9 figure
Cerebral perfusion simulation using realistically generated synthetic trees for healthy and stroke patients
Background and objective
Cerebral vascular diseases are among the most burdensome diseases faced by society. However, investigating the pathophysiology of diseases as well as developing future treatments still relies heavily on expensive in-vivo and in-vitro studies. The generation of realistic, patient-specific models of the cerebrovascular system capable of simulating hemodynamics and perfusion promises the ability to simulate diseased states, therefore accelerating development cycles using in silico studies and opening opportunities for the individual assessment of diseased states, treatment planning, and the prediction of outcomes. By providing a patient-specific, anatomically detailed and validated model of the human cerebral vascular system, we aim to provide the basis for future in silico investigations of the cerebral physiology and pathology.
Methods
In this retrospective study, a processing pipeline for patient-specific quantification of cerebral perfusion was developed and applied to healthy individuals and a stroke patient. Major arteries are segmented from 3T MR angiography data. A synthetic tree generation algorithm titled tissue-growth based optimization (GBO) is used to extend vascular trees beyond the imaging resolution. To investigate the anatomical accuracy of the generated trees, morphological parameters are compared against those of 7 T MRI, 9.4 T MRI, and dissection data. Using the generated vessel model, hemodynamics and perfusion are simulated by solving one-dimensional blood flow equations combined with Darcy flow equations.
Results
Morphological data of three healthy individuals (mean age 47 years ± 15.9 [SD], 2 female) was analyzed. Bifurcation and physiological characteristics of the synthetically generated vessels are comparable to those of dissection data. The inability of MRI based segmentation to resolve small branches and the small volume investigated cause a mismatch in the comparison to MRI data. Cerebral perfusion was estimated for healthy individuals and a stroke patient. The simulated perfusion is compared against Arterial-Spin-Labeling MRI perfusion data. Good qualitative agreement is found between simulated and measured cerebral blood flow (CBF). Ischemic regions are predicted well, however ischemia severity is overestimated.
Conclusions
GBO successfully generates detailed cerebral vascular models with realistic morphological parameters. Simulations based on the resulting networks predict perfusion territories and ischemic regions successfully
Perception Study of Traditional Korean Medical Students on the Medical Education Using the Dundee Ready Educational Environment Measure
Background. In Korea, a few studies regarding traditional Korean medicine (TKM) education have been conducted. The aim of this study is to evaluate students’ perceptions regarding TKM education in Korea and compare them with those of other countries using a quantitative scale, Dundee Ready Educational Environment Measure (DREEM). Materials and Methods. We conducted a survey using DREEM in a TKM college. Totally, 325 students responded to this survey and we performed the descriptive statistics of scores in all items, subscales, and total. Additionally, subgroup comparisons according to gender, school year, and academic achievement were analyzed. Results. Mean overall DREEM score was 94.65 out of 200, which is relatively low compared to previous studies. Particularly, perceptions regarding subscales of learning, atmosphere, and self-perceptions were interpreted as problematic. There was no statistically significant difference between genders in spite of some differences among groups based on school year or academic achievement. Conclusions. We could examine students’ perceptions regarding TKM education at a TKM college using DREEM for which validity and reliability were verified. TKM education was perceived relatively poor, but these quantitative indicators suggested which parts of education need improvement. We expect DREEM to be used widely in TKM or traditional medical education field
Deep learning-based statistical noise reduction for multidimensional spectral data
In spectroscopic experiments, data acquisition in multi-dimensional phase
space may require long acquisition time, owing to the large phase space volume
to be covered. In such case, the limited time available for data acquisition
can be a serious constraint for experiments in which multidimensional spectral
data are acquired. Here, taking angle-resolved photoemission spectroscopy
(ARPES) as an example, we demonstrate a denoising method that utilizes deep
learning as an intelligent way to overcome the constraint. With readily
available ARPES data and random generation of training data set, we
successfully trained the denoising neural network without overfitting. The
denoising neural network can remove the noise in the data while preserving its
intrinsic information. We show that the denoising neural network allows us to
perform similar level of second-derivative and line shape analysis on data
taken with two orders of magnitude less acquisition time. The importance of our
method lies in its applicability to any multidimensional spectral data that are
susceptible to statistical noise.Comment: 8 pages, 8 figure
Sign-tunable anomalous Hall effect induced by two-dimensional symmetry-protected nodal structures in ferromagnetic perovskite oxide thin films
Magnetism and spin-orbit coupling (SOC) are two quintessential ingredients
underlying novel topological transport phenomena in itinerant ferromagnets.
When spin-polarized bands support nodal points/lines with band degeneracy that
can be lifted by SOC, the nodal structures become a source of Berry curvature;
this leads to a large anomalous Hall effect (AHE). Contrary to
three-dimensional systems that naturally host nodal points/lines,
two-dimensional (2D) systems can possess stable nodal structures only when
proper crystalline symmetry exists. Here we show that 2D spin-polarized band
structures of perovskite oxides generally support symmetry-protected nodal
lines and points that govern both the sign and the magnitude of the AHE. To
demonstrate this, we performed angle-resolved photoemission studies of
ultrathin films of SrRuO, a representative metallic ferromagnet with SOC.
We show that the sign-changing AHE upon variation in the film thickness,
magnetization, and chemical potential can be well explained by theoretical
models. Our study is the first to directly characterize the topological band
structure of 2D spin-polarized bands and the corresponding AHE, which could
facilitate new switchable devices based on ferromagnetic ultrathin films
Electronic band structure of (111) thin filman angle-resolved photoemission spectroscopy study
We studied the electronic band structure of pulsed laser deposition (PLD)
grown (111)-oriented SrRuO (SRO) thin films using \textit{in situ}
angle-resolved photoemission spectroscopy (ARPES) technique. We observed
previously unreported, light bands with a renormalized quasiparticle effective
mass of about 0.8. The electron-phonon coupling underlying this mass
renormalization yields a characteristic "kink" in the band dispersion. The
self-energy analysis using the Einstein model suggests five optical phonon
modes covering an energy range 44 to 90 meV contribute to the coupling.
Besides, we show that the quasiparticle spectral intensity at the Fermi level
is considerably suppressed, and two prominent peaks appear in the valance band
spectrum at binding energies of 0.8 eV and 1.4 eV, respectively. We discuss the
possible implications of these observations. Overall, our work demonstrates
that high-quality thin films of oxides with large spin-orbit coupling can be
grown along the polar (111) orientation by the PLD technique, enabling
\textit{in situ} electronic band structure study. This could allow for
characterizing the thickness-dependent evolution of band structure of (111)
heterostructuresa prerequisite for exploring possible topological quantum
states in the bilayer limit