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1,115 result(s) for "Kim, Tae-Hoon"
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Seismic Performance Assessment of Deteriorated Two-Span Reinforced Concrete Bridges
This paper presents a nonlinear analysis procedure for the seismic performance assessment of deteriorated reinforced concrete bridges using a modified damage index. A finite-element analysis program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), is used to analyze deteriorated two-span simply supported reinforced concrete bridges. The new nonlinear material models for deteriorated reinforced concrete behaviors were proposed, considering corrosion effects as shown in a reduction in reinforcement section and bond strength. A modified damage index aims to quantify the seismic performance level in deteriorated reinforced concrete bridges. Several parameters of two-span simply supported deteriorated reinforced concrete bridge have been studied to determine the seismic performance levels. The newly developed analytical method for assessing the seismic performance of deteriorated reinforced concrete bridges is verified by comparison with the experimental and analytical parameter results.
Intrinsic signal optoretinography of dark adaptation kinetics
Delayed dark adaptation due to impaired rod photoreceptor homeostasis has been reported as the earliest symptom of eye diseases such as age-related macular degeneration, diabetic retinopathy, and retinitis pigmentosa. Objective measurement of dark adaptation can facilitate early diagnosis to enable prompt intervention to prevent vision loss. However, there is a lack of noninvasive methods capable of spatiotemporal monitoring of photoreceptor changes during dark adaptation. Here we demonstrate functional optical coherence tomography (OCT) for in vivo intrinsic signal optoretinography (ORG) of dark adaptation kinetics in the C57BL/6J mouse retina. Functional OCT revealed a shortening of the outer retina, a rearrangement of the cone and rod photoreceptor interdigitation zone, and a reduction in intrinsic signal amplitude at the photoreceptor inner segment ellipsoid (ISe). A strong positive correlation between the outer retinal shortening and ISe intensity reduction was also confirmed. Functional OCT of dark adaptation kinetics promises an objective method for rapid ORG assessment of physiological integrity of retinal photoreceptors.
ARS2/MAGL signaling in glioblastoma stem cells promotes self-renewal and M2-like polarization of tumor-associated macrophages
The interplay between glioblastoma stem cells (GSCs) and tumor-associated macrophages (TAMs) promotes progression of glioblastoma multiforme (GBM). However, the detailed molecular mechanisms underlying the relationship between these two cell types remain unclear. Here, we demonstrate that ARS2 (arsenite-resistance protein 2), a zinc finger protein that is essential for early mammalian development, plays critical roles in GSC maintenance and M2-like TAM polarization. ARS2 directly activates its novel transcriptional target MGLL , encoding monoacylglycerol lipase (MAGL), to regulate the self-renewal and tumorigenicity of GSCs through production of prostaglandin E 2 (PGE 2 ), which stimulates β-catenin activation of GSC and M2-like TAM polarization. We identify M2-like signature downregulated by which MAGL-specific inhibitor, JZL184, increased survival rate significantly in the mouse xenograft model by blocking PGE 2 production. Taken together, our results suggest that blocking the interplay between GSCs and TAMs by targeting ARS2/MAGL signaling offers a potentially novel therapeutic option for GBM patients. How glioblastoma stem cells (GSCs) and tumor-associated macrophages (TAMs) interact to promote progression of glioblastoma multiforme (GBM) is currently unclear. Here, the authors demonstrate a role for the ARS2/MAGL signalling in regulating self-renewal and tumorigenicity of GSCs and M2-like TAM polarization.
Dirac electrons in a dodecagonal graphene quasicrystal
Quasicrystal lattices, which can have rotational order but lack translational symmetry, can be used to explore electronic properties of materials between crystals and disordered solids. Ahn et al. grew graphene bilayers rotated exactly 30° that have 12-fold rotational order. Electron diffraction and microscopy confirmed the formation of quasicrystals, and angle-resolved photoemission spectroscopy revealed anomalous interlayer electronic coupling that was quasi-periodic. The millimeter-scale layers can potentially be transferred to other substrates. Science , this issue p. 782 A Dirac fermion quasicrystal with 12-fold rotational symmetry results from twisted bilayer graphene rotated exactly 30°. Quantum states of quasiparticles in solids are dictated by symmetry. We have experimentally demonstrated quantum states of Dirac electrons in a two-dimensional quasicrystal without translational symmetry. A dodecagonal quasicrystalline order was realized by epitaxial growth of twisted bilayer graphene rotated exactly 30°. We grew the graphene quasicrystal up to a millimeter scale on a silicon carbide surface while maintaining the single rotation angle over an entire sample and successfully isolated the quasicrystal from a substrate, demonstrating its structural and chemical stability under ambient conditions. Multiple Dirac cones replicated with the 12-fold rotational symmetry were observed in angle-resolved photoemission spectra, which revealed anomalous strong interlayer coupling with quasi-periodicity. Our study provides a way to explore physical properties of relativistic fermions with controllable quasicrystalline orders.
10-year nationwide trends of the incidence, prevalence, and adverse outcomes of non-valvular atrial fibrillation nationwide health insurance data covering the entire Korean population
Most data on the clinical epidemiology of atrial fibrillation (AF) are reported from Western populations, and data for Asians are limited. We aimed to investigate the 10-year trends of the prevalence and incidence of non-valvular AF and provide prevalence projections till 2060 in Korea. We also investigated the annual risks of adverse outcomes among patients with AF. Using the Korean National Health Insurance Service database involving the entire Korean population, a total of 679,416 adults with newly diagnosed AF were identified from 2006 to 2015. The incidence and prevalence of AF and risk of adverse outcomes following AF onset were assessed. The prevalence of AF progressively increased by 2.10-fold from 0.73% in 2006 to 1.53% in 2015. The trend of its incidence was flat with a 10-year overall incidence of 1.77 per 1,000 person-years. The prevalence of AF is expected to reach 5.81% (2,290,591 patients with AF) in 2060. For a decade, the risk of all-cause mortality following AF declined by 30% (adjusted hazard ratio [HR]: 0.70, 95% confidence interval [CI]: 0.68–0.72), heart failure by 52% (adjusted HR: 0.48, 95% CI: 0.44–0.51), and ischemic stroke by 9% (adjusted HR: 0.91, 95% CI: 0.88–0.93). The burden of AF among Asian patients is increasing. Although the overall risks of cardiovascular events and death following AF onset have decreased over a decade, the event rates are still high. Optimized management of any associated comorbidities should be part of the holistic management approach for patients with AF.
Increasing trends in hospital care burden of atrial fibrillation in Korea, 2006 through 2015
ObjectiveTemporal changes in the healthcare burden of atrial fibrillation (AF) are less well known in rapidly ageing Asian countries. We examined trends in hospitalisations, costs, treatment patterns and outcomes related to AF in Korea.MethodsUsing the National Health Insurance Service (NHIS) database involving the entire adult Korean population (n=41 701 269 in 2015), we analysed a nationwide AF cohort representing 931 138 patients with AF. We studied all hospitalisations due to AF from 2006 to 2015.ResultsOverall, hospitalisations for AF increased by 420% from 767 to 3986 per 1 million Korean population from 2006 to 2015. Most admissions occurred in patients aged ≥70 years, and the most frequent coexisting conditions were hypertension, heart failure and chronic obstructive pulmonary disease. Hospitalisations mainly due to major bleeding and AF control increased, whereas hospitalisations mainly due to ischaemic stroke and myocardial infarction decreased. The total cost of care increased even after adjustment for inflation from €68.4 million in 2006 to €388.4 million in 2015, equivalent to 0.78% of the Korean NHIS total expenditure. Overall in-hospital mortality decreased from 7.5% in 2006 to 4.3% in 2015. The in-hospital mortality was highest in patients ≥80 years of age (7.7%) and in patients with chronic kidney disease (7.4%).ConclusionsAF hospitalisations have increased exponentially over the past 10 years in Korea, in association with an increase in comorbid chronic diseases. Mortality associated with AF hospitalisations decreased during the last decade, but hospitalisation costs have markedly increased.
Treatment timing and the effects of rhythm control strategy in patients with atrial fibrillation: nationwide cohort study
AbstractObjectiveTo investigate whether the results of a rhythm control strategy differ according to the duration between diagnosis of atrial fibrillation and treatment initiation.DesignLongitudinal observational cohort study.SettingPopulation based cohort from the Korean National Health Insurance Service database.Participants22 635 adults with atrial fibrillation and cardiovascular conditions, newly treated with rhythm control (antiarrhythmic drugs or ablation) or rate control strategies between 28 July 2011 and 31 December 2015.Main outcome measureA composite outcome of death from cardiovascular causes, ischaemic stroke, admission to hospital for heart failure, or acute myocardial infarction.ResultsOf the study population, 12 200 (53.9%) were male, the median age was 70, and the median follow-up duration was 2.1 years. Among patients with early treatment for atrial fibrillation (initiated within one year since diagnosis), compared with rate control, rhythm control was associated with a lower risk of the primary composite outcome (weighted incidence rate per 100 person years 7.42 in rhythm control v 9.25 in rate control; hazard ratio 0.81, 95% confidence interval 0.71 to 0.93; P=0.002). No difference in the risk of the primary composite outcome was found between rhythm and rate control (weighted incidence rate per 100 person years 8.67 in rhythm control v 8.99 in rate control; 0.97, 0.78 to 1.20; P=0.76) in patients with late treatment for atrial fibrillation (initiated after one year since diagnosis). No significant differences in safety outcomes were found between the rhythm and rate control strategies across different treatment timings. Earlier initiation of treatment was linearly associated with more favourable cardiovascular outcomes for rhythm control compared with rate control.ConclusionsEarly initiation of rhythm control treatment was associated with a lower risk of adverse cardiovascular outcomes than rate control treatment in patients with recently diagnosed atrial fibrillation. This association was not found in patients who had had atrial fibrillation for more than one year.
Factors controlling the distributions of dissolved organic matter in the East China Sea during summer
To determine the distribution of dissolved organic matter (DOM) in the East China Sea (ECS) during the summer, we measured the dissolved organic carbon (DOC) and nitrogen (DON), fluorescent dissolved organic matter (FDOM), and chlorophyll a (Chl. a ) in the upper 100-m layer of this region during July and September 2015. The DOC (r 2  = 0.72 and 0.78 in July and September, respectively) and DON (r 2  = 0.43 and 0.33) were significantly correlated with salinity, suggesting that the river is the primary origin of DOM. However, we found that at a DOC “pulse” under a salinity ranging from 24 to 35, the extrapolating DOC values (304 ± 11 μM) were twice higher than those with a salinity of close to 0, as found in a previous study. The excess DOC concentration seemed to be attributed to the microbial metabolism during transport from the estuary based on the good relationships between DOC and marine humic-like FDOM (r 2  = 0.42 and 0.47), as well as the fluorescence, humification, and biological indexes, but showed no correlation with Chl. a . Thus, the results of our study indicate that microbial activities can be a significant factor controlling the distribution of DOM in the ECS during summer.
Tracing terrestrial versus marine sources of dissolved organic carbon in a coastal bay using stable carbon isotopes
The sources of dissolved organic matter (DOM) in coastal waters are diverse, and they play different roles in the biogeochemistry and ecosystems of the ocean. In this study, we measured dissolved organic carbon (DOC) and nitrogen (DON), the stable carbon isotopic composition of dissolved organic carbon (δ13C-DOC), and fluorescent dissolved organic matter (FDOM) in coastal bay waters surrounded by large cities (Masan Bay, Republic of Korea) to determine the different DOM sources in this region. The surface seawater samples were collected in two sampling campaigns (August 2011 and August 2016). The salinities were in the range of 10–21 in 2011 and 25–32 in 2016. In 2011, excess DOC was observed in high-salinity (16–21) waters; the excess DOC source was found to be mainly from marine autochthonous production according to the δ13C-DOC values (−23.7 ‰ to −20.6 ‰), the higher concentrations of protein-like FDOM, and the lower DOC∕DON (C∕N) ratios (8–15). In contrast, excess DOC observed in high-salinity waters in 2016 was characterized by low FDOM, more depleted δ13C values (−28.8 ‰ to −21.1 ‰), and high C∕N ratios (13–45), suggesting that the source of excess DOC is terrestrial C3 plants by direct land–seawater interactions. Our results show that multiple DOM tracers such as δ13C-DOC, FDOM, and C∕N ratios are powerful for determining different sources of DOM occurring in coastal waters.
Effect of contact number among graphene nanosheets on the conductivities of tunnels and polymer composites
Simple equations are expressed for tunnel conductivity, tunnel resistance and conductivity of a graphene-filled composite by the number of contacts and interphase part. More specially, the active filler amount is suggested by interphase depth, which changes the contact number. The conductivity of nanocomposite is presented by filler content, filler dimensions, tunneling length and interphase depth. The innovative model is surveyed by the experimented conductivity of real examples. Too, the impacts of numerous issues on the tunnel resistance, tunnel conductivity and conductivity of nanocomposite are discussed to validate the novel equations. The estimates agree with the experimented data and the impacts of several terms on the tunnel resistance, tunnel conductivity and conductivity of system are sensible. Thin and big nanosheets positively affect the nanocomposite’s conductivity, but thick nanosheets improve the tunnel conductivity. High conductivity is found at short tunnels, while the nanocomposite’s conductivity directly depends on the tunneling length. The dissimilar effects of these features on the tunneling properties and conductivity are described.