1,565 research outputs found
Statistical Analysis of the Metropolitan Seoul Subway System: Network Structure and Passenger Flows
The Metropolitan Seoul Subway system, consisting of 380 stations, provides
the major transportation mode in the metropolitan Seoul area. Focusing on the
network structure, we analyze statistical properties and topological
consequences of the subway system. We further study the passenger flows on the
system, and find that the flow weight distribution exhibits a power-law
behavior. In addition, the degree distribution of the spanning tree of the
flows also follows a power law.Comment: 10 pages, 4 figure
Sleepless in Seoul: `The Ant and the Metrohopper'
One of Aesop's (La Fontain's) famous fables `The Ant and the Grasshopper' is
widely known to give a moral lesson through comparison between the hard working
ant and the party-loving grasshopper. Here we show a slightly different version
of this fable, namely, "The Ant and the Metrohopper," which describes human
mobility patterns in modern urban life. Numerous real transportation networks
and the trajectory data have been studied in order to understand mobility
patterns. We study trajectories of commuters on the public transportation of
Metropolitan Seoul, Korea. Smart cards (Integrated Circuit Cards; ICCs) are
used in the public transportation system, which allow collection of transit
transaction data, including departure and arrival stations and time. This
empirical analysis provides human mobility patterns, which impact traffic
forecasting and transportation optimization, as well as urban planning.Comment: to be appeared in Journal of the Korean Physical Societ
Prediction of Giant Spin Motive Force due to Rashba Spin-Orbit Coupling
Magnetization dynamics in a ferromagnet can induce a spin-dependent electric
field through spin motive force. Spin current generated by the spin-dependent
electric field can in turn modify the magnetization dynamics through
spin-transfer torque. While this feedback effect is usually weak and thus
ignored, we predict that in Rashba spin-orbit coupling systems with large
Rashba parameter , the coupling generates the spin-dependent
electric field [\pm(\alpha_{\rm R}m_e/e\hbar) (\vhat{z}\times \partial
\vec{m}/\partial t)], which can be large enough to modify the magnetization
dynamics significantly. This effect should be relevant for device applications
based on ultrathin magnetic layers with strong Rashba spin-orbit coupling.Comment: 4+ pages, 2 figure
Microscopic Theory of Rashba Interaction in Magnetic Metal
Theory of Rashba spin-orbit coupling in magnetic metals is worked out from
microscopic Hamiltonian describing d-orbitals. When structural inversion
symmetry is broken, electron hopping between -orbitals generates chiral
ordering of orbital angular momentum, which combines with atomic spin-orbit
coupling to result in the Rashba interaction. Rashba parameter characterizing
the interaction is band-specific, even reversing its sign from band to band.
Large enhancement of the Rashba parameter found in recent experiments is
attributed to the orbital mixing of 3d magnetic atoms with non-magnetic heavy
elements as we demonstrate by first-principles and tight-binding calculations.Comment: 5 pages, 2 figure
Optical conductivity in the normal state fullerene superconductors
We calculate the optical conductivity, , in the normal state
fullerene superconductors by self-consistently including the impurity
scatterings, the electron-phonon and electron-electron Coulomb interactions.
The finite bandwidth of the fullerenes is explicitely considered, and the
vertex corection is included Nambu in calculating the renormalized
Green's function. is obtained by calculating the
current-current correlation function with the renormalized Green's function in
the Matsubara frequency and then performing analytic continuation to the real
frequency at finite temperature. The Drude weight in is
strongly suppressed due to the interactions and transfered to the mid-infrared
region around and above 0.06 eV which is somewhat less pronounced and much
broader compared with the expermental observation by DeGiorgi .Comment: 6 pages, 4 figures. To be published in Physical Review B, July 1
Changes in inorganic aerosol compositions over the Yellow Sea area from impact of Chinese emissions mitigation
Substantial mitigation of air pollutants emissions has been performed since 2013 around Beijing, and changes in the atmospheric characteristics have been expected over the downstream area of Beijing. In this study, both WRF-Chem simulation and on-site measurements were utilized for the Baengnyeong (island) supersite, one of the representative regional background sites located in the Yellow Sea, the entrance area of the long-range transport process in Korea. The changes in the chemical compositions of inorganic aerosols were examined for spring-time during the Chinese emission mitigation period from 2014 to 2016.
The measured ratio of ionic species to PM2.5 at the Baengnyeong supersite showed changes in aerosol inorganic chemical compositions from sulfate in 2014 to nitrate in 2015–2016. The modeling results also showed that nitrate was low in 2014 and significantly increased in 2015 and 2016, and the acidic aerosol condition had also changed toward a more neutralized status in both the simulation and the observations. The WRF-Chem modeling study further indicated that the sulfur was not neutralized in 2014. However, in 2015 and 2016, SO2 was more sufficiently neutralized as sulfur emissions were substantially reduced in China, while at the same time nitrate had begun to increase in such a ‘SO2–poor’ condition in Beijing area in China, and thus approaching more enhanced neutralization over the Yellow Sea area. The causes of the higher nitrate based on the modeled characteristics of the ammonia-sulfate-nitrate aerosol formation in response to the SO2 emissions reduction in China are also discussed in this paper
Longitudinal Patterns in Antithrombotic Therapy in Patients with Atrial Fibrillation after Percutaneous Coronary Intervention in the Non-Vitamin K Oral Anticoagulant Era:A Nationwide Population-Based Study
We investigated whether longitudinal patterns in antithrombotic therapy have changed after the introduction of non-vitamin K oral anticoagulants (NOACs) in patients with atrial fibrillation (AF) who underwent percutaneous coronary intervention (PCI). Using a claims database of the Korean AF population who underwent PCI between 2012 and 2016 (n = 18,691), we analyzed prescription records of oral anticoagulants (OACs) and antiplatelets at 3-month intervals over 2 years after PCI. The study population was stratified (pre-NOAC, transition, and NOAC era) using time-periods of NOAC introduction in Korea and an expansion of reimbursement for NOAC in AF as indicators. The overall rates of OAC were low at baseline (24.9%, 26.9%, and 35.2% in pre-NOAC, transition, and NOAC era, respectively), contrary to high rates of dual antiplatelet therapy (DAPT) (73.3%, 71.4%, and 63.6%). However, OAC prescription rates were increased at 1-year (18.5%, 22.5%, and 31.6%), and 2-year follow-up (17.8%, 24.2%, and 31.8%) from pre-NOAC to NOAC era. In NOAC era, 63.5% of baseline OAC prescriptions comprised NOAC, of which 96.4% included triple therapy with DAPT. Over 2 years, we observed increasing rates of double therapy with a single antiplatelet (18.3% and 20.0% at 1- and 2-year follow-up) and OAC monotherapy (2.7% and 8.9% at 1- and 2-year follow-up)
Net clinical benefit of antithrombotic therapy for atrial fibrillation patients with stable coronary artery disease
OBJECTIVES: To compare the net clinical benefit of oral anticoagulant (OAC) monotherapy to OAC plus single antiplatelet therapy (SAPT) in patients with atrial fibrillation (AF) and stable coronary artery disease (CAD) at 1- and 3-year after percutaneous coronary intervention (PCI). BACKGROUND: It has not been studied whether the net clinical benefit of the antithrombotic treatment options differs depending on the elapsed time from the index PCI. METHODS: Using the Korean nationwide claims database, we included AF patients who underwent PCI from 2009 to 2019 and constructed two cohorts: 1- and 3-year after PCI. In each cohort, the baseline characteristics of two groups were balanced using propensity score weighting. Ischemic stroke, myocardial infarction, major bleeding, and composite clinical outcomes were analyzed. RESULTS: Among patients with 1-year after PCI, OAC monotherapy (n = 678), and OAC plus SAPT (n = 3,159) showed comparable results for all clinical outcomes. In patients with 3-year after PCI, OAC monotherapy (n = 1,038) and OAC plus SAPT (n = 2,128) showed comparable results for ischemic stroke and myocardial infarction, but OAC monotherapy was associated with a lower risk of composite clinical outcomes (HR 0.762, 95% CI 0.607–0.950), mainly driven by the reduction of major bleeding risk (HR 0.498, 95% CI 0.345–0.701). CONCLUSION: Oral anticoagulant monotherapy may be a comparable choice for patients with AF and stable CAD compared to OAC plus SAPT. In patients with stable CAD more than 3-year after index PCI, OAC monotherapy would be a better choice, being associated with less major bleeding and a positive net clinical benefit
Phaeophyscia esslingeri sp. nov. (Physciaceae, lichen-forming Ascomycota) – a new lichen species from Eastern Asia, with a world-wide key to the hairy species of the genus
Phaeophyscia esslingeri, a new species for science, is described from South Korea, Eastern
Asia, compared with closely related taxa and illustrated with photographs. It is similar to Phaeophyscia
hirtella, but diff ers by larger and light grey thallus, wider lobes, apothecia without a corona of
dark rhizines around the base, shorter cortical hairs, and wider ascospores. Status of the hairy taxa
of the genus Phaeophyscia from Eastern Asia is discussed. A world-wide key to hairy species of the
genus Phaeophyscia is also included
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