119 results on '"Park WI"'
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2. Rapid streptococcal pharyngitis testing and antibiotic prescribing before and during the COVID-19 pandemic
- Author
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Allan Seibert, Eddie Stenehjem, Anthony Wallin, Park Willis, Kim Brunisholz, Naresh Kumar, Valoree Stanfield, Nora Fino, Daniel Shapiro, and Adam Hersh
- Subjects
Infectious and parasitic diseases ,RC109-216 ,Public aspects of medicine ,RA1-1270 - Abstract
Background: Pharyngitis is 1 of the most common conditions leading to inappropriate antibiotic prescriptions. When personal protective equipment (PPE) was at first constrained during the COVID-19 pandemic, Intermountain Healthcare recommended limiting rapid group A streptococcal pharyngitis (GAS) testing in urgent-care clinics to preserve PPE. Notably, the percentage of pharyngitis encounters prescribed an antibiotic and that underwent GAS testing is a key Healthcare Effectiveness Data and Information Set (HEDIS) measure. We have described our experience with urgent-care pharyngitis encounters and the impact of temporarily reducing GAS testing on antibiotic prescribing before and during the COVID19 pandemic. Method: We identified all urgent care encounters between July 2018 and August 2021 associated with a primary diagnosis of pharyngitis using ICD-10 CM codes and a validated methodology. Pharyngitis encounters were assessed for antibiotic prescriptions ordered through the electronic health record (EHR) and the use of point-of-care rapid GAS tests. Pharyngitis encounters were analyzed monthly. We assessed the percentage of encounters associated with an antibiotic prescription regardless of testing and the percentage of encounters associated with an antibiotic prescription when a GAS test was or was not performed. We examined 3 periods relating to COVID-19 and GAS testing recommendations: the prepandemic period (July 2018–March 2020), the pandemic onset period (April 2020–June 2020), and the pandemic period (July 2020–August 2021). Results: Prior to the pandemic, the monthly percentage of pharyngitis encounters for which rapid GAS testing was performed was nearly 90% (Fig. 1). The average monthly percentage of urgent-care pharyngitis encounters prescribed an antibiotic was 38.9%, and the average percentage of monthly pharyngitis encounters prescribed an antibiotic that also underwent GAS testing was 90.4%. This HEDIS measure declined from 90.4% during the prepandemic period to 29.8% in the pandemic onset period when GAS testing was limited. Following resumption of routine testing practices the monthly percentage of urgent-care pharyngitis encounters for which rapid GAS testing was performed returned to levels ≥80% by July 2020 (Fig. 1). The average percentage of monthly pharyngitis encounters prescribed an antibiotic that also underwent GAS testing rose to 87.3% during this period. Conclusions: Limited PPE in our urgent care centers during the initial months of the COVID-19 pandemic was associated with a mandated substantial decline in rapid GAS testing. As testing volume decreased, we noted a simultaneous relative increase of >30% in antibiotic prescribing for pharyngitis. These findings suggest that rapid streptococcal testing promotes appropriate antibiotic prescribing.
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- 2022
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3. Rapid streptococcal pharyngitis testing and antibiotic prescribing before and during the coronavirus disease 2019 (COVID-19) pandemic
- Author
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Allan M. Seibert, Edward Stenehjem, Anthony Wallin, Park Willis, Kim Brunisholz, Naresh Kumar, Valoree Stanfield, Nora Fino, Daniel J. Shapiro, and Adam Hersh
- Subjects
Infectious and parasitic diseases ,RC109-216 ,Public aspects of medicine ,RA1-1270 - Published
- 2022
- Full Text
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4. Compression-plate fixation in acute diaphyseal fractures of the radius and ulna
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Anderson, LD, Sisk, D, Tooms, RE, and Park, WI, 3rd
- Published
- 1975
5. Impact Damage of Honeycomb Sandwich Antenna Structures
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Kim, Cha-Gyeom, primary, Lee, Ra-Mi, additional, Park, Hyeon-Cheol, additional, Hwang, Un-Bong, additional, and Park, Wi-Sang, additional
- Published
- 2002
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6. Bifurcation Analysis of Plastic Deformation of Multilayered Cylindrical Pressure Vessel.
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Park, Wi-Gon, primary, Okamura, Hiroyuki, additional, and Kobayashi, Hideo, additional
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- 1994
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7. Physiological responses over the time course during sustained passive muscle stretch in prehypertensive individuals.
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Park WI, Lim K, So J, Kim J, and Nho H
- Published
- 2008
8. Direct Printing of Ultrathin Block Copolymer Film with Nano-in-Micro Pattern Structures.
- Author
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Park TW, Kang YL, Kang EB, Jung H, Lee SK, Hwang GT, Lee JW, Choi SY, Nahm S, Kwon SH, Kim KH, and Park WI
- Abstract
Nanotransfer printing (nTP) is one of the most promising nanopatterning methods given that it can be used to produce nano-to-micro patterns effectively with functionalities for electronic device applications. However, the nTP process is hindered by several critical obstacles, such as sub-20 nm mold technology, reliable large-area replication, and uniform transfer-printing of functional materials. Here, for the first time, a dual nanopatterning process is demonstrated that creates periodic sub-20 nm structures on the eight-inch wafer by the transfer-printing of patterned ultra-thin (<50 nm) block copolymer (BCP) film onto desired substrates. This study shows how to transfer self-assembled BCP patterns from the Si mold onto rigid and/or flexible substrates through a nanopatterning method of thermally assisted nTP (T-nTP) and directed self-assembly (DSA) of Si-containing BCPs. In particular, the successful microscale patternization of well-ordered sub-20 nm SiO
x patterns is systematically presented by controlling the self-assembly conditions of BCP and printing temperature. In addition, various complex pattern geometries of nano-in-micro structures are displayed over a large patterning area by T-nTP, such as angular line, wave line, ring, dot-in-hole, and dot-in-honeycomb structures. This advanced BCP-replicated nanopatterning technology is expected to be widely applicable to nanofabrication of nano-to-micro electronic devices with complex circuits., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)- Published
- 2023
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9. High-Resolution Nanotransfer Printing of Porous Crossbar Array Using Patterned Metal Molds by Extreme-Pressure Imprint Lithography.
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Park TW, Kang YL, Kim YN, and Park WI
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High-resolution nanotransfer printing (nTP) technologies have attracted a tremendous amount of attention due to their excellent patternability, high productivity, and cost-effectiveness. However, there is still a need to develop low-cost mold manufacturing methods, because most nTP techniques generally require the use of patterned molds fabricated by high-cost lithography technology. Here, we introduce a novel nTP strategy that uses imprinted metal molds to serve as an alternative to a Si stamp in the transfer printing process. We present a method by which to fabricate rigid surface-patterned metallic molds (Zn, Al, and Ni) based on the process of direct extreme-pressure imprint lithography (EPIL). We also demonstrate the nanoscale pattern formation of functional materials, in this case Au, TiO
2 , and GST, onto diverse surfaces of SiO2 /Si, polished metal, and slippery glass by the versatile nTP method using the imprinted metallic molds with nanopatterns. Furthermore, we show the patterning results of nanoporous crossbar arrays on colorless polyimide (CPI) by a repeated nTP process. We expect that this combined nanopatterning method of EPIL and nTP processes will be extendable to the fabrication of various nanodevices with complex circuits based on micro/nanostructures.- Published
- 2023
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10. Formation of Multiscale Pattern Structures by Combined Patterning of Nanotransfer Printing and Laser Micromachining.
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Park TW, Kang YL, Kang EB, Kim S, Kim YN, and Park WI
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Various lithography techniques have been widely used for the fabrication of next-generation device applications. Micro/nanoscale pattern structures formed by lithographic methods significantly improve the performance capabilities of the devices. Here, we introduce a novel method that combines the patterning of nanotransfer printing (nTP) and laser micromachining to fabricate multiscale pattern structures on a wide range of scales. Prior to the formation of various nano-in-micro-in-millimeter (NMM) patterns, the nTP process is employed to obtain periodic nanoscale patterns on the target substrates. Then, an optimum laser-based patterning that effectively engraves various nanopatterned surfaces, in this case, spin-cast soft polymer film, rigid polymer film, a stainless still plate, and a Si substrate, is established. We demonstrate the formation of well-defined square and dot-shaped multiscale NMM-patterned structures by the combined patterning method of nTP and laser processes. Furthermore, we present the generation of unusual text-shaped NMM pattern structures on colorless polyimide (CPI) film, showing optically excellent rainbow luminescence based on the configuration of multiscale patterns from nanoscale to milliscale. We expect that this combined patterning strategy will be extendable to other nano-to-micro fabrication processes for application to various nano/microdevices with complex multiscale pattern geometries.
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- 2023
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11. MoS 2 Passivated Multilayer Graphene Membranes for Li-Ion Extraction From Seawater.
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Chang WJ, Jang S, Kim M, Kim Y, Jeong DY, Kim B, Kim JM, Nam S, and Park WI
- Abstract
Abundant Li resources in the ocean are promising alternatives to refining ore, whose supplies are limited by the total amount and geopolitical imbalance of reserves in Earth's crust. Despite advances in Li
+ extraction using porous membranes, they require screening other cations on a large scale due to the lack in precise control of pore size and inborn defects. Herein, MoS2 nanoflakes on a multilayer graphene membrane (MFs-on-MGM) that possess ion channels comprising i) van der Waals interlayer gaps for optimal Li+ extraction and ii) negatively charged vertical inlets for cation attraction, are reported. Ion transport measurements across the membrane reveal ≈6- and 13-fold higher selectivity for Li+ compared to Na+ and Mg2+ , respectively. Furthermore, continuous, stable Li+ extraction from seawater is demonstrated by integrating the membrane into a H2 and Cl2 evolution system, enabling more than 104 -fold decrease in the Na+ concentration and near-complete elimination of other cations., (© 2023 Wiley-VCH GmbH.)- Published
- 2023
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12. Superhydrophobic Electrodeposited Copper Surface for Robust Condensation Heat Transfer.
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Park J, Kim D, Kim H, Park WI, Lee J, and Chung W
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Superhydrophobic surfaces have great potential for various applications owing to their superior dewetting and mobility of water droplets. However, the physical robustness of nano/microscale rough surface structures supporting superhydrophobicity is critical in real applications. In this study, to create a superhydrophobic surface on copper, we employed copper electrodeposition to create a nano/microscale rough surface structure as an alternative to the nanoneedle CuO structure. The rough electrodeposited copper surface with a thin Teflon coating shows superhydrophobicity. The enhancement of dewetting and mobility of water droplets on copper surfaces by electrodeposition and hydrophobization significantly improved the condensation heat transfer by up to approximately 78% compared to that of copper substrates. Moreover, the nano/microscale rough surface structure of the electrodeposited copper surface exhibits better tolerance to physical rubbing, which destroys the nanoneedle-structured CuO surface. Therefore, the condensation heat transfer of the superhydrophobic electrodeposited copper surface decreased by only less than 10%, while that of the nanoneedle-structured CuO surface decreased by approximately 40%. This suggests that an electrodeposited copper surface can lead to the stable performance of superhydrophobicity for real applications., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)
- Published
- 2022
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13. Switching-Modulated Phase Change Memory Realized by Si-Containing Block Copolymers.
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Park TW and Park WI
- Abstract
The phase change memory (PCM) is one of the key enabling memory technologies for next-generation non-volatile memory device applications due to its high writing speed, excellent endurance, long retention time, and good scalability. However, the high power consumption of PCM devices caused by the high switching current from a high resistive state to a low resistive state is a critical obstacle to be resolved before widespread commercialization can be realized. Here, a useful approach to reduce the writing current of PCM, which depends strongly on the contact area between the heater electrode and active layer, by employing self-assembly process of Si-containing block copolymers (BCPs) is presented. Self-assembled insulative BCP pattern geometries can locally block the current path of the contact between a high resistive film (TiN) and a phase-change material (Ge
2 Sb2 Te5 ), resulting in a significant reduction of the writing current. Compared to a conventional PCM cell, the BCP-modified PCM shows excellent switching power reduction up to 1/20 given its use of self-assembled hybrid SiFex Oy /SiOx dot-in-hole nanostructures. This BCP-based bottom-up process can be extended to various applications of other non-volatile memory devices, such as resistive switching memory and magnetic storage devices., (© 2021 Wiley-VCH GmbH.)- Published
- 2021
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14. Rotating Cylinder-Assisted Nanoimprint Lithography for Enhanced Chemisorbable Filtration Complemented by Molecularly Imprinted Polymers.
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Jeon S, Park R, Jeong J, Heo G, Lee J, Shin MC, Kwon YW, Yang JC, Park WI, Kim KS, Park J, and Hong SW
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- Printing, Molecularly Imprinted Polymers, Nanostructures
- Abstract
Rotating cylindrical stamp-based nanoimprint technique has many advantages, including the continuous fabrication of intriguing micro/nanostructures and rapid pattern transfer on a large scale. Despite these advantages, the previous nanoimprint lithography has rarely been used for producing sophisticated nanoscale patterns on a non-planar substrate that has many extended applications. Here, the simple integration of nanoimprinting process with a help of a transparent stamp wrapped on the cylindrical roll and UV optical source in the core to enable high-throughput pattern transfer, particularly on a fabric substrate is demonstrated. Moreover, as a functional resin material, this innovative strategy involves a synergistic approach on the synthesis of molecularly imprinted polymer, which are spatially organized free-standing perforated nanostructures such as nano/microscale lines, posts, and holes patterns on various woven or nonwoven blank substrates. The proposed materials can serve as a self-encoded filtration medium for selective separation of formaldehyde molecules. It is envisioned that the combinatorial fabrication process and attractive material paves the way for designing next-generation separation systems in use to capture industrial or household toxic substances., (© 2021 Wiley-VCH GmbH.)
- Published
- 2021
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15. Controlled self-assembly of block copolymers in printed sub-20 nm cross-bar structures.
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Park TW, Kang YL, Byun M, Hong SW, Ahn YS, Lee J, and Park WI
- Abstract
Directed self-assembly (DSA) of block copolymers (BCPs) has garnered much attention due to its excellent pattern resolution, simple process, and good compatibility with many other lithography methods for useful nanodevice applications. Here, we present a BCP-based multiple nanopatterning process to achieve three-dimensional (3D) pattern formation of metal/oxide hybrid nanostructures. We employed a self-assembled sub-20 nm SiO
x line pattern as a master mold for nanotransfer printing (nTP) to generate a cross-bar array. By using the transfer-printed cross-bar structures as BCP-guiding templates, we can obtain well-ordered BCP microdomains in the distinct spaces of the nanotemplates through a confined BCP self-assembly process. We also demonstrate the morphological evolution of a cylinder-forming BCP by controlling the BCP film thickness, showing a clear morphological transition from cylinders to spheres in the designated nanospaces. Furthermore, we demonstrate how to control the number of BCP spheres within the cross-bar 3D pattern by adjusting the printing angle of the multiple nTP process to provide a suitable area for spontaneous BCP accommodation. This multiple-patterning-based approach is applicable to useful 3D nanofabrication of various devices with complex hybrid nanostructures., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)- Published
- 2021
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16. Topographically designed hybrid nanostructures via nanotransfer printing and block copolymer self-assembly.
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Park TW, Jung H, Park J, Ahn YS, Hong SW, Lee J, Lee JH, and Park WI
- Abstract
Nanotransfer printing (nTP) has attracted much attention due to its high pattern resolution, simple process, and low processing cost for useful nanofabrication. Here, we introduce a thermally assisted nTP (T-nTP) process for the effective fabrication of various periodic three-dimensional (3D) nanosheets, such as concavo-convex lines, spine lines, square domes, and complex multi-line patterns. The T-nTP method allows continuous nanoscale 3D patterns with functionality to be transferred onto both rigid and flexible substrates by heat without any collapse of uniform convex nanostructures with nanochannels. We also show the pattern formation of multi-layered hybrid structures consisting of two or more materials by T-nTP. Furthermore, the formation of silicon oxide nanodots (0D) within a printed metallic nanowave structure (3D) can be achieved by the combined method of T-nTP and the self-assembly of poly(styrene-b-dimethylsiloxane) (PS-b-PDMS) block copolymers. Moreover, we demonstrate how to obtain well-defined oxide-metal hybrid nanostructures (0D-in-3D) through the spontaneous accommodation of PDMS spheres in the confined spaces of an Au-wave nanotemplate. This approach is applicable during the nanofabrication of various high-resolution devices with complex geometrical nanopatterns.
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- 2021
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17. Extreme-Pressure Imprint Lithography for Heat and Ultraviolet-Free Direct Patterning of Rigid Nanoscale Features.
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Park WI, Park TW, Choi YJ, Lee S, Ryu S, Liang X, and Jung YS
- Abstract
Nanoimprint lithography (NIL) is typically performed by filling up of molds by heated polymers or UV-curable liquid resists, inevitably requiring subsequent pattern-transfer processes. Although direct NIL techniques have been suggested alternatively, they usually require precursors or ink-type resists containing undesired organic components. Here, we demonstrate extreme-pressure imprint lithography (EPIL) that effectively produces well-defined multiscale structures with a wide range from 10 nm to 10 mm on diverse surfaces even including pure or alloy metals without using any precursors, heating, UV exposure, or pattern transfer. In particular, EPIL is accomplished through precise control of room-temperature plastic deformation in nanoscale volumes, which is elucidated by finite element analyses and molecular dynamics simulations. In addition to scalability to macroscopic areas, we confirm the outstanding versatility of EPIL via its successful applications to Ni, Cu, steel, and organics. We expect that the state-of-the-art EPIL process combined with other emerging nanopatterning technologies will be extendable to the future large-area nanofabrication of various devices.
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- 2021
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18. Folic Acid Functionalized Carbon Dot/Polypyrrole Nanoparticles for Specific Bioimaging and Photothermal Therapy.
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Kim TE, Jang HJ, Park SW, Wei J, Cho S, Park WI, Lee BR, Yang CD, and Jung YK
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- Biocompatible Materials chemistry, Carbon chemistry, Cell Line, Cell Survival drug effects, Folic Acid chemistry, Humans, Materials Testing, Molecular Structure, Particle Size, Photothermal Therapy, Polymers chemistry, Pyrroles chemistry, Biocompatible Materials pharmacology, Carbon pharmacology, Folic Acid pharmacology, Nanoparticles chemistry, Optical Imaging, Polymers pharmacology, Pyrroles pharmacology, Quantum Dots chemistry
- Abstract
Polypyrrole nanoparticles (PPy-NPs) with excellent near-infrared absorption are commonly used as photothermal therapy (PTT) agents; however, PTT using PPy-NPs has a limitation in that it is difficult to maximize their therapeutic effect because of the lack of specific targeting. In this study, to overcome the difficulty of targeting, folic acid functionalized carbon dots (FA-CDs) with bright green fluorescence properties were combined with carboxylated PPy-NPs via the EDC/NHS coupling reaction to yield a PTT imaging agent. The synthesized FA-CD/PPy-NPs with excellent photostability performed folate receptor (FR) positive HeLa cancer cell imaging by green fluorescence signals of FA-CDs and exhibited high cell viability (above 90%) even at 500 μg/mL. The viability of HeLa cells incubated with 200 μg/mL FA-CD/PPy-NPs was dramatically decreased to 25.02 ± 1.85% by NIR laser irradiation, through photothermal therapeutic effects of FA-CD/PPy-NPs with high photothermal conversion efficiency (η = 40.80 ± 1.54%). The cancer cell death by FA-CD/PPy-NPs was confirmed by fluorescence imaging of FA-CDs as well as live/dead cell staining assay (calcein-AM/PI). These results demonstrate that the FA-CD/PPy-NPs can be utilized as multifunctional theranostic agents for specific bioimaging and treatment of FR-positive cancer cells.
- Published
- 2021
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19. Enabling the Selective Detection of Endocrine-Disrupting Chemicals via Molecularly Surface-Imprinted "Coffee Rings".
- Author
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Lee J, Yang JC, Lone S, Park WI, Lin Z, Park J, and Hong SW
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- Coffee, Polymerization, Polymers, Endocrine Disruptors, Molecular Imprinting
- Abstract
Molecularly imprinted polymers (MIPs) represent an intriguing class of synthetic materials that can selectively recognize and bind chemical or biological molecules in a variety of value-added applications in sensors, catalysis, drug delivery, antibodies, and receptors. In this context, many advanced methods of implementing functional MIP materials have been actively studied. Herein, we report a robust strategy to produce highly ordered arrays of surface-imprinted polymer patterns with unprecedented regularity for MIP-based sensor platform, which involves the controlled evaporative self-assembly process of MIP precursor solution in a confined geometry consisting of a spherical lens on a flat Si substrate (i.e., sphere-on-flat geometry) to synergistically utilize the "coffee-ring" effect and repetitive stick-slip motions of the three-phase contact line simply by solvent evaporation. Highly ordered arrays of the ring-patterned MIP films are then polymerized under UV irradiation to achieve semi-interpenetrating polymer networks. The extraction of templated target molecules from the surface-imprinted ring-patterned MIP films leaves behind copious cavities for the recognizable specific "memory sites" to efficiently detect small molecules. As a result, the elaborated surface structuring effect, sensitivity, and specific selectivity of the coffee-ring-based MIP sensors are scrutinized by capitalizing on an endocrine-disrupting chemical, 2,4-dichlorophenoxyacetic acid (2,4-D), as an example. Clearly, the evaporative self-assembly of nonvolatile solutes in a confined geometry renders the creation of familiar yet ordered coffee-ring-like patterns for a wide range of applications, including sensors, scaffolds for cell motility, templates, substrates for neuron guidance, etc., thereby dispensing with the need of multistep lithography techniques and external fields.
- Published
- 2021
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20. Formation of Li 2 CO 3 Nanostructures for Lithium-Ion Battery Anode Application by Nanotransfer Printing.
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Park TW, Kang YL, Lee SH, No GW, Park ES, Park C, Lee J, and Park WI
- Abstract
Various high-performance anode and cathode materials, such as lithium carbonate, lithium titanate, cobalt oxides, silicon, graphite, germanium, and tin, have been widely investigated in an effort to enhance the energy density storage properties of lithium-ion batteries (LIBs). However, the structural manipulation of anode materials to improve the battery performance remains a challenging issue. In LIBs, optimization of the anode material is a key technology affecting not only the power density but also the lifetime of the device. Here, we introduce a novel method by which to obtain nanostructures for LIB anode application on various surfaces via nanotransfer printing (nTP) process. We used a spark plasma sintering (SPS) process to fabricate a sputter target made of Li
2 CO3 , which is used as an anode material for LIBs. Using the nTP process, various Li2 CO3 nanoscale patterns, such as line, wave, and dot patterns on a SiO2 /Si substrate, were successfully obtained. Furthermore, we show highly ordered Li2 CO3 nanostructures on a variety of substrates, such as Al, Al2 O3 , flexible PET, and 2-Hydroxylethyl Methacrylate (HEMA) contact lens substrates. It is expected that the approach demonstrated here can provide new pathway to generate many other designable structures of various LIB anode materials.- Published
- 2021
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21. Direct nanofluidic channels via hardening and wrinkling of thin polymer films.
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Lee JH, Chang WJ, Choi WY, Park JM, Jang JI, and Park WI
- Abstract
In this study, we propose a rational route to create wrinkling patterns with individually controllable location and direction in thin polymer films. Optical and atomic force microscopy analysis confirmed the formation of straight wrinkles with a typical width of 1.51 to 1.55 μm and a height of 60 to 65 nm. Confocal fluorescence microscopy revealed that each wrinkle produces a continuous hollow channel that interconnects neighboring holes in the polymer film, demonstrating potential applications as nanoscale fluidic channel and reactor. Moreover, we propose a mechanism that considers the elastic deformation energy and interface energies as crucial parameters that govern the mechanical instabilities, which provides scaling relationships between the height, width, and thickness of the wrinkles. This offers additional opportunities for control over the size and aspect ratio of the wrinkles and channels.
- Published
- 2020
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22. Thermally assisted nanotransfer printing with sub-20-nm resolution and 8-inch wafer scalability.
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Park TW, Byun M, Jung H, Lee GR, Park JH, Jang HI, Lee JW, Kwon SH, Hong S, Lee JH, Jung YS, Kim KH, and Park WI
- Abstract
Nanotransfer printing (nTP) has attracted considerable attention due to its good pattern resolution, process simplicity, and cost-effectiveness. However, the development of a large-area nTP process has been hampered by critical reliability issues related to the uniform replication and regular transfer printing of functional nanomaterials. Here, we present a very practical thermally assisted nanotransfer printing (T-nTP) process that can easily produce well-ordered nanostructures on an 8-inch wafer via the use of a heat-rolling press system that provides both uniform pressure and heat. We also demonstrate various complex pattern geometries, such as wave, square, nut, zigzag, and elliptical nanostructures, on diverse substrates via T-nTP. Furthermore, we demonstrate how to obtain a high-density crossbar metal-insulator-metal memristive array using a combined method of T-nTP and directed self-assembly. We expect that the state-of-the-art T-nTP process presented here combined with other emerging patterning techniques will be especially useful for the large-area nanofabrication of various devices., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).)
- Published
- 2020
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23. Lithography-Free Route to Hierarchical Structuring of High-χ Block Copolymers on a Gradient Patterned Surface.
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Cho HR, Choe A, Park WI, Ko H, and Byun M
- Abstract
A chemically defined patterned surface was created via a combined process of controlled evaporative self-assembly of concentric polymer stripes and the selective surface modification of polymer brush. The former process involved physical adsorption of poly (methyl methacrylate) (PMMA) segments into silicon oxide surface, thus forming ultrathin PMMA stripes, whereas the latter process was based on the brush treatment of silicon native oxide surface using a hydroxyl-terminated polystyrene (PS-OH). The resulting alternating PMMA- and PS-rich stripes provided energetically favorable regions for self-assembly of high χ polystyrene- block -polydimethylsiloxane (PS- b -PDMS) in a simple and facile manner, dispensing the need for conventional lithography techniques. Subsequently, deep reactive ion etching and oxygen plasma treatment enabled the transition of the PDMS blocks into oxidized groove-shaped nanostructures.
- Published
- 2020
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24. Annual Fluctuation in Chigger Mite Populations and Orientia Tsutsugamushi Infections in Scrub Typhus Endemic Regions of South Korea.
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Kim SY, Gill B, Song BG, Chu H, Park WI, Lee HI, Shin EH, Cho SH, and Roh JY
- Abstract
Objectives: Chigger mites are vectors for scrub typhus. This study evaluated the annual fluctuations in chigger mite populations and Orientia tsutsugamushi infections in South Korea., Methods: During 2006 and 2007, chigger mites were collected monthly from wild rodents in 4 scrub typhus endemic regions of South Korea. The chigger mites were classified based on morphological characteristics, and analyzed using nested PCR for the detection of Orientia tsutsugamushi ., Results: During the surveillance period, the overall trapping rate for wild rodents was 10.8%. In total, 17,457 chigger mites (representing 5 genera and 15 species) were collected, and the average chigger index (representing the number of chigger mites per rodent), was 31.7. The monthly chigger index was consistently high (> 30) in Spring (March to April) and Autumn (October to November). The mite species included Leptotrombidium pallidum (43.5%), L. orientale (18.9%), L. scutellare (18.1%), L. palpale (10.6%), and L. zetum (3.6%). L. scutellare and L. palpale populations, were relatively higher in Autumn. Monthly O. tsutsugamushi infection rates in wild rodents (average: 4.8%) and chigger mites (average: 0.7%) peaked in Spring and Autumn., Conclusion: The findings demonstrated a bimodal pattern of the incidence of O. tsutsugamushi infections. Higher infection rates were observed in both wild rodents and chigger mites, in Spring and Autumn. However, this did not reflect the unimodal incidence of scrub typhus in Autumn. Further studies are needed to identify factors, such as human behavior and harvesting in Autumn that may explain this discordance., Competing Interests: Conflicts of Interest The authors have no conflicts of interest to declare., (Copyright ©2019, Korea Centers for Disease Control and Prevention.)
- Published
- 2019
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25. Direct Observation of Carboxymethyl Cellulose and Styrene-Butadiene Rubber Binder Distribution in Practical Graphite Anodes for Li-Ion Batteries.
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Chang WJ, Lee GH, Cheon YJ, Kim JT, Lee SI, Kim J, Kim M, Park WI, and Lee YJ
- Abstract
Despite the important role of carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) binders in graphite electrodes for Li-ion batteries, the direct analysis of these binders remains challenging, particularly at very low concentrations as in practical graphite anodes. In this paper, we report the systematic investigation of the physiochemical behavior of the CMC and SBR binders and direct observations of their distributions in practical graphite electrodes. The key to this unprecedented capability is combining the advantages of several analytic techniques, including laser-ablation laser-induced break-down spectroscopy, time of flight secondary ion mass spectrometry, and a surface and interfacial cutting analysis system. By correlating the vertical distribution with the adsorption behaviors of the CMC, our study reveals that the CMC migration toward the surface during the drying process depends on the degree of cross-linked binder-graphite network generation, which is determined by the surface property of graphite and CMC materials. The suggested analytical techniques enable the independent tracing of CMC and SBR, disclosing the different vertical distribution of SBR from that of the CMC binder in our practical graphite anodes. This achievement provides additional opportunity to analyze the correlation between the binder distribution and mechanical properties of the electrodes.
- Published
- 2019
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26. Pattern formation of metal-oxide hybrid nanostructures via the self-assembly of di-block copolymer blends.
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Jung DS, Bang J, Park TW, Lee SH, Jung YK, Byun M, Cho YR, Kim KH, Seong GH, and Park WI
- Abstract
The templated self-assembly of block copolymers (BCPs) with a high Flory-Huggins interaction parameter (χ) can effectively create ultrafine, well-ordered nanostructures in the range of 5-30 nm. However, the self-assembled BCP patterns remain limited to possible morphological geometries and materials. Here, we introduce a novel and useful self-assembly method of di-BCP blends capable of generating diverse hybrid nanostructures consisting of oxide and metal materials through the rapid microphase separation of A-B/B-C BCP blends. We successfully obtained various hybridized BCP morphologies which cannot be acquired from a single di-BCP, such as hexagonally arranged hybrid dot and dot-in-hole patterns by controlling the mixing ratios of the solvents with a binary solvent annealing process. Furthermore, we demonstrate how the binary solvent vapor annealing process can provide a wide range of pattern geometries to di-BCP blends, showing a well-defined spontaneous one-to-one accommodation in dot-in-hole nanostructures. Specifically, we show clearly how the self-assembled BCPs can be functionalized via selective reduction and/or an oxidation process, resulting in the excellent positioning of confined silica nanodots into each nanospace of a Pt mesh. These results suggest a new method to achieve the pattern formation of more diverse and complex hybrid nanostructures using various blended BCPs.
- Published
- 2019
- Full Text
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27. Electrical Double Layer of Supported Atomically Thin Materials.
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Kwon SS, Choi J, Heiranian M, Kim Y, Chang WJ, Knapp PM, Wang MC, Kim JM, Aluru NR, Park WI, and Nam S
- Abstract
The electrical double layer (EDL), consisting of two parallel layers of opposite charges, is foundational to many interfacial phenomena and unique in atomically thin materials. An important but unanswered question is how the "transparency" of atomically thin materials to their substrates influences the formation of the EDL. Here, we report that the EDL of graphene is directly affected by the surface energy of the underlying substrates. Cyclic voltammetry and electrochemical impedance spectroscopy measurements demonstrate that graphene on hydrophobic substrates exhibits an anomalously low EDL capacitance, much lower than what was previously measured for highly oriented pyrolytic graphite, suggesting disturbance of the EDL ("disordered EDL") formation due to the substrate-induced hydrophobicity to graphene. Similarly, electrostatic gating using EDL of graphene field-effect transistors shows much lower transconductance levels or even no gating for graphene on hydrophobic substrates, further supporting our hypothesis. Molecular dynamics simulations show that the EDL structure of graphene on a hydrophobic substrate is disordered, caused by the disruption of water dipole assemblies. Our study advances understanding of EDL in atomically thin limit.
- Published
- 2019
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28. Hierarchical multi-level block copolymer patterns by multiple self-assembly.
- Author
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Jung H, Shin WH, Park TW, Choi YJ, Yoon YJ, Park SH, Lim JH, Kwon JD, Lee JW, Kwon SH, Seong GH, Kim KH, and Park WI
- Abstract
Uniform, well-ordered sub-20 nm patterns can be generated by the templated self-assembly of block copolymers (BCPs) with a high Flory-Huggins interaction parameter (χ). However, the self-assembled BCP monolayers remain limited in the possible structural geometries. Here, we introduce a multiple self-assembly method which uses di-BCPs to produce diverse morphologies, such as dot, dot-in-honeycomb, line-on-dot, double-dot, pondering, dot-in-pondering, and line-on-pondering patterns. To improve the diversity of BCP morphological structures, we employed sphere-forming and cylinder-forming poly(styrene-block-dimethylsiloxane) (PS-b-PDMS) BCPs with a high χ. The self-assembled mono-layer and double-layer SiOx dot patterns were modified at a high temperature (∼800 °C), showing hexagonally arranged (dot) and double-hexagonally arranged (pondering) SiOx patterns, respectively. We successfully obtained additional new nanostructures (big-dot, dot-in-honeycomb, line-on-dot, pondering, dot-in-pondering, and line-on-pondering types) through a second self-assembly of cylinder-forming BCPs using the dot and pondering patterns as guiding templates. This simple approach can likely be extended to the multiple self-assembly of many other BCPs with good functionality, significantly contributing to the development of various nanodevices.
- Published
- 2019
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29. Clinical Features and Management of "Phlebitis-like Abnormal Reaction" After Cyanoacrylate Closure for the Treatment of Incompetent Saphenous Veins.
- Author
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Park I, Jeong MH, Park CJ, Park WI, Park DW, and Joh JH
- Subjects
- Administration, Intravenous, Administration, Oral, Adult, Aged, Dexamethasone administration & dosage, Female, Foreign-Body Reaction diagnostic imaging, Foreign-Body Reaction drug therapy, Foreign-Body Reaction physiopathology, Glucocorticoids administration & dosage, Histamine Antagonists administration & dosage, Humans, Hypersensitivity, Delayed diagnostic imaging, Hypersensitivity, Delayed drug therapy, Hypersensitivity, Delayed physiopathology, Male, Middle Aged, Phlebitis diagnostic imaging, Phlebitis drug therapy, Phlebitis physiopathology, Prospective Studies, Risk Factors, Time Factors, Treatment Outcome, Venous Insufficiency diagnostic imaging, Venous Insufficiency physiopathology, Young Adult, Cyanoacrylates adverse effects, Foreign-Body Reaction chemically induced, Hypersensitivity, Delayed chemically induced, Phlebitis chemically induced, Saphenous Vein diagnostic imaging, Saphenous Vein physiopathology, Tissue Adhesives adverse effects, Venous Insufficiency therapy
- Abstract
Background: Cyanoacrylate closure for the treatment of incompetent saphenous veins does not cause thermal damage and demonstrates satisfactory outcomes with rapid recovery. However, the characteristics of phlebitis-like abnormal reaction (PLAR), the most common adverse event after cyanoacrylate closure, have not been clarified. Moreover, it differs from typical phlebitis after thermal ablation. The objective of our study is to investigate the clinical features of PLAR after cyanoacrylate closure and to report its management., Methods: A total of 160 patients with 271 incompetent saphenous veins (great saphenous veins, 201; small saphenous veins, 70) underwent cyanoacrylate closure with the VenaSeal™ system. We defined PLAR as any unusual skin condition that develops suddenly, such as erythema, itching, swelling, and pain/tenderness, over the treated veins several days after cyanoacrylate closure. Oral antihistamines and intravenous dexamethasone were administered to manage PLAR., Results: Of the 271 treated veins, 69 experienced PLAR (25.4%). The mean time of occurrence was 13.6 ± 4.6 days after treatment. The rate of occurrence of erythema, itching, swelling, and pain/tenderness were 92.2%, 91.2%, 66.2%, and 48.5%, respectively. The occurrence of PLAR was significantly higher for great saphenous veins than for small saphenous veins (P < 0.001). Occurrences were more frequent in cases with a suprafascial great saphenous vein of length >10 cm than in cases with a subfascial great saphenous vein (P = 0.001). The proportion of patients who reported swelling decreased by more than half after the administration of oral antihistamine. The pain score on the 10th day also decreased significantly after the administration of antihistamine (P = 0.006)., Conclusions: PLAR must be distinguished from classic phlebitis. We believe that PLAR is a type IV hypersensitivity reaction due to a foreign body, and in our experience, antihistamines or steroids are effective for the prevention and management of PLAR., (Copyright © 2018 Elsevier Inc. All rights reserved.)
- Published
- 2019
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30. Self-Powered Chemical Sensing Driven by Graphene-Based Photovoltaic Heterojunctions with Chemically Tunable Built-In Potentials.
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Lee D, Park H, Han SD, Kim SH, Huh W, Lee JY, Kim YS, Park MJ, Park WI, Kang CY, and Lee CH
- Abstract
Ultralow power chemical sensing is essential toward realizing the Internet of Things. However, electrically driven sensors must consume power to generate an electrical readout. Here, a different class of self-powered chemical sensing platform based on unconventional photovoltaic heterojunctions consisting of a top graphene (Gr) layer in contact with underlying photoactive semiconductors including bulk silicon and layered transition metal dichalcogenides is proposed. Owing to the chemically tunable electrochemical potential of Gr, the built-in potential at the junction is effectively modulated by absorbed gas molecules in a predictable manner depending on their redox characteristics. Such ability distinctive from bulk photovoltaic counterparts enables photovoltaic-driven chemical sensing without electric power consumption. Furthermore, it is demonstrated that the hydrogen (H
2 ) sensing properties are independent of the light intensity, but sensitive to the gas concentration down to the 1 ppm level at room temperature. These results present an innovative strategy to realize extremely energy-efficient sensors, providing an important advancement for future ubiquitous sensing., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)- Published
- 2019
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31. Controlled crystal facet of MAPbI 3 perovskite for highly efficient and stable solar cell via nucleation modulation.
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Ma Y, Hangoma PM, Park WI, Lim JH, Jung YK, Jeong JH, Park SH, and Kim KH
- Abstract
The crystallization of MAPbI3 perovskite films was purposefully engineered to investigate the governing factors which determine their morphological properties and moisture stability. By modulating nucleation, we obtained a single layer perovskite film with controlled crystal facet orientation and grain size. The lack of perovskite nucleation sites during crystallization allowed us to tailor the resulting crystallization phase. Theoretical calculations indicated that the nucleation sites for perovskite growth are related to the electron density around the oxygen atom (C[double bond, length as m-dash]O and S[double bond, length as m-dash]O) in a Lewis base. A single layer of micrometer-sized and (110)-oriented perovskite crystals was achieved in the optimized MAPbI3 films via suppressing the formation of nucleation sites. We fabricated inverted perovskite solar cells with the structure of glass/ITO/PEDOT:PSS/MAPbI3/PC61BM/Al which exhibited a high power conversion efficiency of 17.5% and a high fill factor over 83%. In addition, a study of the moisture stability indicated that the (110) facet orientation of the perovskite grains plays a more important role in film degradation than grain size.
- Published
- 2018
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32. Systematic review and meta-analysis of single-dose and non-single-dose methotrexate protocols in the treatment of ectopic pregnancy.
- Author
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Yuk JS, Lee JH, Park WI, Ahn HS, and Kim HJ
- Subjects
- Female, Humans, Pregnancy, Randomized Controlled Trials as Topic, Clinical Protocols, Methotrexate administration & dosage, Methotrexate therapeutic use, Pregnancy, Ectopic drug therapy
- Abstract
Background: It remains unclear which methotrexate protocol for the treatment of ectopic pregnancy has a higher success rate or a higher adverse effect rate., Objective: To compare the treatment success rates and adverse effect rates of single-dose and non-single-dose (two-dose and multi-dose) methotrexate protocols in the treatment of ectopic pregnancy., Search Strategy: Various databases including Medline, Embase, and the Cochrane Central Register of Controlled Trials were searched on July 1, 2017, using search terms including "methotrexate" and "pregnancy.", Selection Criteria: Randomized controlled trials comparing different methotrexate protocols for the treatment of ectopic pregnancy were included., Data Collection and Analysis: Relative risks (RRs) and 95% confidence intervals (CIs) were calculated to compare treatment success rates and adverse effect rates., Main Results: The single-dose and non-single-dose protocols had similar success rates (RR 1.00, 95% CI 0.96-1.04; 11 trials, 1121 patients, I
2 =18%). The non-single-dose protocols had a higher adverse effect rate than did the single-dose protocol (RR 0.73, 95% CI 0.59-0.91; nine trials, 934 patients, I2 =0%)., Conclusions: The single-dose methotrexate protocol was the optimal protocol for the medical treatment of ectopic pregnancy., (© 2018 International Federation of Gynecology and Obstetrics.)- Published
- 2018
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- View/download PDF
33. Synchronized-pressing fabrication of cost-efficient crystalline perovskite solar cells via intermediate engineering.
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Ma Y, Lee J, Liu Y, Hangoma PM, Park WI, Lim JH, Jung YK, Jeong JH, Park SH, and Kim K
- Abstract
A cost-effective fabrication method that can produce a remarkable enhancement in the device efficiency along with a reduction in the fabrication cost is one of the crucial requirements for the commercialization of perovskite-based solar cells. Here, we report a low-cost, printable, and highly effective synchronized-pressing annealing (SPA) method for inverted planar perovskite solar cells. In this method, two films are combined face-to-face for annealing, and separated as in a roll-to-roll process. Consequently, the SPA method provides two homogeneous highly crystalline MAPbI3 films with monolithic millimeter-scale crystalline grains by intermediate-induced crystallization engineering. The grains present a tendency of oriented growth along the <110> direction, parallel to the substrate, which leads to efficient charge transport. The IPSCs fabricated by the SPA method demonstrate a high efficiency of ∼17% with significantly enhanced photocurrents and fill factors. Moreover, the characteristics of both top and bottom devices are very similar, with nearly identical J-V curves and photoresponse spectra. As the SPA method is compatible with the printing technology for mass production, and as it can produce twin devices of high quality via one fabrication process, it can provide a remarkable reduction in the fabrication cost.
- Published
- 2018
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34. Anomalous Photovoltaic Response of Graphene-on-GaN Schottky Photodiodes.
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Lee JH, Lee WW, Yang DW, Chang WJ, Kwon SS, and Park WI
- Abstract
Graphene has attracted great attention as an alternative to conventional metallic or transparent conducting electrodes. Despite its similarities with conventional electrodes, recent studies have shown that a single-atom layer of graphene possesses unique characteristics, such as a tunable work function and transparencies for electric potential, reactivity, and wetting. Nevertheless, a systematic analysis of graphene and semiconductor junction characteristics has not yet been carried out. Here, we report the photoresponse characteristics of graphene-on-GaN Schottky junction photodiodes (Gr-GaN SJPDs), showing a typical rectifying behavior and distinct photovoltaic and photoelectric responses. Following the initial abrupt response to UV illumination, the Gr-GaN SJPDs exhibited a distinct difference in photocarrier dynamics depending on the applied bias voltage, which is characterized by either a negative or positive change in photocurrent with time. We propose underlying mechanisms for the anomalous photocarrier dynamics based on the interplay between electrostatic molecular interactions over the one-atom-thick graphene and GaN junction and trapped photocarriers at the defect states in the GaN thin film.
- Published
- 2018
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35. Enhanced piezoresponse of highly aligned electrospun poly(vinylidene fluoride) nanofibers.
- Author
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Kang SB, Won SH, Im MJ, Kim CU, Park WI, Baik JM, and Choi KJ
- Abstract
Well-ordered nanostructure arrays with controlled densities can potentially improve material properties; however, their fabrication typically involves the use of complicated processing techniques. In this work, we demonstrate a uniaxial alignment procedure for fabricating poly(vinylidene fluoride) (PVDF) electrospun nanofibers (NFs) by introducing collectors with additional steps. The mechanism of the observed NF alignment, which occurs due to the concentration of lateral electric field lines around collector steps, has been elucidated via finite-difference time-domain simulations. The membranes composed of well-aligned PVDF NFs are characterized by a higher content of the PVDF β-phase, as compared to those manufactured from randomly orientated fibers. The piezoelectric energy harvester, which was fabricated by transferring well-aligned PVDF NFs onto flexible substrates with Ag electrodes attached to both sides, exhibited a 2-fold increase in the output voltage and a 3-fold increase in the output current as compared to the corresponding values obtained for the device manufactured from randomly oriented NFs. The enhanced piezoresponse observed for the aligned PVDF NFs is due to their higher β-phase content, denser structure, smaller effective radius of curvature during bending, greater applied strain, and higher fraction of contributing NFs.
- Published
- 2017
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36. 3D calcite heterostructures for dynamic and deformable mineralized matrices.
- Author
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Yi J, Wang Y, Jiang Y, Jung IW, Liu W, De Andrade V, Xu R, Parameswaran R, Peters IR, Divan R, Xiao X, Sun T, Lee Y, Park WI, and Tian B
- Abstract
Scales are rooted in soft tissues, and are regenerated by specialized cells. The realization of dynamic synthetic analogues with inorganic materials has been a significant challenge, because the abiological regeneration sites that could yield deterministic growth behavior are hard to form. Here we overcome this fundamental hurdle by constructing a mutable and deformable array of three-dimensional calcite heterostructures that are partially locked in silicone. Individual calcite crystals exhibit asymmetrical dumbbell shapes and are prepared by a parallel tectonic approach under ambient conditions. The silicone matrix immobilizes the epitaxial nucleation sites through self-templated cavities, which enables symmetry breaking in reaction dynamics and scalable manipulation of the mineral ensembles. With this platform, we devise several mineral-enabled dynamic surfaces and interfaces. For example, we show that the induced growth of minerals yields localized inorganic adhesion for biological tissue and reversible focal encapsulation for sensitive components in flexible electronics.Minerals are rarely explored as building blocks for dynamic inorganic materials. Here, the authors derive inspiration from fish scales to create mutable surfaces based on arrays of calcite crystals, in which one end of each crystal is immobilized in and regenerated from silicone, and the other functional end is left exposed.
- Published
- 2017
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37. Dual spectra band emissive Eu 2+ /Mn 2+ co-activated alkaline earth phosphates for indoor plant growth novel phosphor converted-LEDs.
- Author
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Yun YJ, Kim JK, Ju JY, Choi SK, Park WI, Suh JY, Jung HK, Kim Y, and Choi S
- Subjects
- Luminescence, Luminescent Agents chemical synthesis, Metals, Alkaline Earth chemistry, Phosphates chemical synthesis, Plant Development radiation effects, Europium chemistry, Lighting instrumentation, Luminescent Agents chemistry, Manganese chemistry, Phosphates chemistry
- Abstract
This paper reports designing a novel single composition blue/red color illuminating phosphor followed by fabricating "smart" agricultural/horticultural LED lighting. Color-tunable Eu
2+ /Mn2+ co-activated alkaline earth phosphates, Na(Sr,Ba)PO4 and Ca3 Mg3 (PO4 )4 , are considered, and the stable doping sites for the corresponding activators are identified by using first-principle DFT calculations. We can realize the designated color purity with stable thermal quenching preserved luminescence behavior is induced by the Eu2+ center positioned at different coordination states with intermixed Sr2+ /Ba2+ sites in Na(Sr,Ba)PO4 hosts. Moreover, we demonstrate that the resultant LED lighting adopting the proposed novel phosphor composition stimulates the enhanced photosynthesis reaction for indoor hydroponics plants, such as oats and onions, which is superior to the narrow line emission band induced by the mixture of conventional red/green/blue LEDs. Thus, using the color-tunable single composition luminescent material may produce an innovative energy-efficient artificial lighting for indoor plant growth.- Published
- 2017
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38. Levonorgestrel-Releasing Intrauterine Systems Versus Oral Cyclic Medroxyprogesterone Acetate in Endometrial Hyperplasia Therapy: A Meta-Analysis.
- Author
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Yuk JS, Song JY, Lee JH, Park WI, Ahn HS, and Kim HJ
- Subjects
- Administration, Oral, Antineoplastic Agents, Hormonal administration & dosage, Female, Humans, Medroxyprogesterone Acetate administration & dosage, Randomized Controlled Trials as Topic, Antineoplastic Agents, Hormonal therapeutic use, Endometrial Hyperplasia drug therapy, Intrauterine Devices, Medicated, Levonorgestrel therapeutic use, Medroxyprogesterone Acetate therapeutic use
- Abstract
Background: This study aimed to compare the levonorgestrel-releasing intrauterine system (LNG-IUS) with oral cyclic medroxyprogesterone acetate (MPA) in endometrial hyperplasia therapy using randomized controlled trials (RCTs)., Methods: The study searched MEDLINE, EMBASE, CENTRAL, and other databases. All regression outcomes were calculated for dichotomous outcomes in terms of relative risk (RR) and 95% confidence intervals (CIs) using a Mantel-Haenszel random effects model., Results: The search found 543 articles but selected 342 articles after the removal of duplicates. A meta-analysis found five RCTs (377 patients). The study did not analyze RR for total outcome because of high heterogeneity (I
2 = 87%). In a subgroup analysis of studies with non-obese women, the LNG-IUS treatment appeared to have a higher regression rate than oral MPA (RR 1.41; 95% CI 1.23-1.62; 4 trials, 265 patients; I2 = 0%). In a subgroup analysis of studies with obese women, LNG-IUS appeared to have a regression rate similar to that of oral MPA (RR 1.03; 95% CI 0.94-1.13; 1 trial, 60 patients). In a subgroup analysis according to histology in the non-obese group, the LNG-IUS treatment appeared to have a higher regression rate than oral cyclic MPA in a meta-analysis of women with non-atypical endometrial hyperplasia (RR 1.36; 95% CI 1.07-1.73; 2 trials, 92 patients; I2 = 6%) and mixed endometrial hyperplasia (atypical and non-atypical) (RR 1.44; 95% CI 1.21-1.71; 2 trials, 173 patients; I2 = 0%)., Conclusions: The LNG-IUS treatment has a higher regression rate than cyclic MPA in non-atypical endometrial hyperplasia and mixed endometrial hyperplasia therapy for non-obese women but has a similar regression rate, albeit limited, for obese women.- Published
- 2017
- Full Text
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39. Defect-Mediated Molecular Interaction and Charge Transfer in Graphene Mesh-Glucose Sensors.
- Author
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Kwon SS, Shin JH, Choi J, Nam S, and Park WI
- Abstract
We report the role of defects in enzymatic graphene field-effect transistor sensors by introducing engineered defects in graphene channels. Compared with conventional graphene sensors (Gr sensors), graphene mesh sensors (GM sensors), with an array of circular holes, initially exhibited a higher irreversible response to glucose, involving strong chemisorption to edge defects. However, after immobilization of glucose oxidase, the irreversibility of the responses was substantially diminished, without any reduction in the sensitivity of the GM sensors (i.e., -0.53 mV/mM for the GM sensor vs -0.37 mV/mM for Gr sensor). Furthermore, multiple cycle operation led to rapid sensing and improved the reversibility of GM sensors. In addition, control tests with sensors containing a linker showed that sensitivity was increased in Gr sensors but decreased in GM sensors. Our findings indicate that edge defects can be used to replace linkers for immobilization of glucose oxidase and improve charge transfer across glucose oxidase-graphene interfaces.
- Published
- 2017
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40. Area-Selective Lift-Off Mechanism Based on Dual-Triggered Interfacial Adhesion Switching: Highly Facile Fabrication of Flexible Nanomesh Electrode.
- Author
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Yu S, Han HJ, Kim JM, Yim S, Sim DM, Lim H, Lee JH, Park WI, Park JH, Kim KH, and Jung YS
- Abstract
With the recent emergence of flexible and wearable optoelectronic devices, the achievement of sufficient bendability and stretchability of transparent and conducting electrodes (TCEs) has become an important requirement. Although metal-mesh-based structures have been investigated for TCEs because of their excellent performances, the fabrication of mesh or grid structures with a submicron line width is still complex due to the requirements of laborious lithography and pattern transfer steps. Here, we introduce an extremely facile fabrication technique for metal patterns embedded in a flexible substrate based on submicron replication and an area-selective delamination (ASD) pattern. The high-yield, area-specific lift-off process is based on the principle of solvent-assisted delamination of deposited metal thin films and a mechanical triggering effect by soft wiping or ultrasonication. Our fabrication process is very simple, convenient, and cost-effective in that it does not require any lithography/etching steps or sophisticated facilities. Moreover, their outstanding optical and electrical properties (e.g., sheet resistances of 0.43 Ω sq
-1 at 94% transmittance), which are markedly superior to those of other flexible TCEs, are demonstrated. Furthermore, there is no significant change of resistance over 1000 repeated bending cycles, with a bending radius of 5 mm, and immersion in various solvents such as salt water and organic solvents. Finally, we demonstrate high-performance transparent heaters and flexible touch panels fabricated using the nanomesh electrode, confirming the long-range electrical conduction and reliability of the electrode.- Published
- 2017
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41. Switching of Photonic Crystal Lasers by Graphene.
- Author
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Hwang MS, Kim HR, Kim KH, Jeong KY, Park JS, Choi JH, Kang JH, Lee JM, Park WI, Song JH, Seo MK, and Park HG
- Abstract
Unique features of graphene have motivated the development of graphene-integrated photonic devices. In particular, the electrical tunability of graphene loss enables high-speed modulation of light and tuning of cavity resonances in graphene-integrated waveguides and cavities. However, efficient control of light emission such as lasing, using graphene, remains a challenge. In this work, we demonstrate on/off switching of single- and double-cavity photonic crystal lasers by electrical gating of a monolayer graphene sheet on top of photonic crystal cavities. The optical loss of graphene was controlled by varying the gate voltage V
g , with the ion gel atop the graphene sheet. First, the fundamental properties of graphene were investigated through the transmittance measurement and numerical simulations. Next, optically pumped lasing was demonstrated for a graphene-integrated single photonic crystal cavity at Vg below -0.6 V, exhibiting a low lasing threshold of ∼480 μW, whereas lasing was not observed at Vg above -0.6 V owing to the intrinsic optical loss of graphene. Changing quality factor of the graphene-integrated photonic crystal cavity enables or disables the lasing operation. Moreover, in the double-cavity photonic crystal lasers with graphene, switching of individual cavities with separate graphene sheets was achieved, and these two lasing actions were controlled independently despite the close distance of ∼2.2 μm between adjacent cavities. We believe that our simple and practical approach for switching in graphene-integrated active photonic devices will pave the way toward designing high-contrast and ultracompact photonic integrated circuits.- Published
- 2017
- Full Text
- View/download PDF
42. Comparison of Laparoscopic Cornual Resection and Cornuotomy for Interstitial Pregnancy.
- Author
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Lee MH, Im SY, Kim MK, Shin SY, and Park WI
- Subjects
- Adolescent, Adult, Female, Humans, Laparoscopy methods, Operative Time, Pregnancy, Pregnancy, Ectopic surgery, Retrospective Studies, Young Adult, Gynecologic Surgical Procedures methods, Pregnancy, Interstitial surgery
- Abstract
Study Objective: To compare the clinical efficacy and safety of laparoscopic cornuotomy and cornual resection in the treatment of interstitial pregnancy., Design: Retrospective chart review between 2006 and 2014 (Canadian Task Force classification II-2)., Setting: Two academic tertiary care hospitals., Patients: Seventy-five patients with interstitial pregnancy treated by laparoscopy., Measurement and Main Results: In the 75 patients, 53 who underwent cornual resection and 22 who underwent cornuotomy, we evaluated operating time, changes in hemoglobin levels after surgery, the rate of major complications, and the incidence of persistent interstitial pregnancy. The mean operating time was significantly shorter for cornuotomy than for cornual resection (59.36 ± 19.32 minutes vs. 77.11 ± 23.97 minutes, respectively). Changes in hemoglobin level after the operation, rates of major complications, and the incidence of persistent interstitial pregnancy were not significantly different in the 2 surgery groups., Conclusion: Laparoscopic cornuotomy yielded clinical results comparable to those of cornual resection. Laparoscopic cornuotomy may reduce the time of operation, and had the same incidence of persistent interstitial pregnancy as cornual resection., (Copyright © 2016 AAGL. Published by Elsevier Inc. All rights reserved.)
- Published
- 2017
- Full Text
- View/download PDF
43. Eu(2+)-Activated Phase-Pure Oxonitridosilicate Phosphor in a Ba-Si-O-N System via Facile Silicate-Assisted Routes Designed by First-Principles Thermodynamic Simulation.
- Author
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Yun YJ, Kim JK, Ju JY, Choi SK, Park WI, Jung HK, Kim Y, and Choi S
- Abstract
Eu(2+)-activated single phase Ba(2+)-oxonitridosilicate phosphors were prepared under a mild synthetic condition via silicate precursors, and their luminescent properties were investigated. Both the preferred oxonitridosilicate formation as for the available host compounds and thermodynamic stability within the Ba-Si-O-N system were elucidated in detail by the theoretical simulation based on the first-principles density functional theory. Those results can visualize the optimum synthetic conditions for Eu(2+)-activated highly luminescent Ba(2+)-oxonitridosilicates, especially Ba3Si6O12N2, as promising conversion phosphors for white LEDs, including Ba3Si6O9N4 and BaSi2O2N2 phases. To prove the simulated design rule, we synthesized the Ba3Si6O12N2:Eu(2+) phosphor using various silicate precursors, Ba2Si4O10, Ba2Si3O8, and BaSiO3, in a carbothermal reduction ambient and finally succeeded in obtaining a phase of pure highly luminescent oxonitridosilicate phosphor without using any solid-state nitride addition and/or high pressure synthetic procedures. Our study provides useful guidelines for robust synthetic procedures for developing thermally stable rare-earth-ion activated oxonitridosilicate phosphors and an established simulation method that can be effectively applied to other multigas systems.
- Published
- 2016
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44. Observation of Charge Separation and Space-Charge Region in Single-Crystal P3HT/C60 Heterojunction Nanowires.
- Author
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Park KS, Lee KS, Baek J, Lee L, Son BH, Koo Lee YE, Ahn YH, Park WI, Kang Y, and Sung MM
- Abstract
We directly observed charge separation and a space-charge region in an organic single-crystal p-n heterojunction nanowire, by means of scanning photocurrent microscopy. The axial p-n heterojunction nanowire had a well-defined planar junction, consisted of P3HT (p-type) and C60 (n-type) single crystals and was fabricated by means of the recently developed inkjet-assisted nanotransfer printing technique. The depletion region formed at the p-n junction was directly observed by exploring the spatial distribution of photogenerated carriers along the heterojunction nanowire under various applied bias voltages. Our study provides a facile approach toward the precise characterization of charge transport in organic heterojunction systems as well as the design of efficient nanoscale organic optoelectronic devices., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2016
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45. Association between pregnancy and adnexal torsion: A population-based, matched case-control study.
- Author
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Yuk JS, Shin JY, Park WI, Kim DW, Shin JW, and Lee JH
- Subjects
- Adult, Female, Humans, Incidence, Odds Ratio, Ovarian Diseases diagnosis, Pregnancy, Pregnancy Complications diagnosis, Pregnancy Outcome, Republic of Korea epidemiology, Risk Factors, Torsion Abnormality diagnosis, Ovarian Diseases epidemiology, Population Surveillance, Pregnancy Complications epidemiology, Torsion Abnormality epidemiology
- Abstract
The purpose of this study was to determine the effect of pregnancy on adnexal torsion (AT). We conducted a matched case-control study using the Korean Health Insurance Review and Assessment Service-National Inpatients Sample (HIRA-NIS) from 2009 to 2011. AT patients were defined as women with both a diagnostic code (N835) and a surgical code for AT. The AT patients were randomly matched 1:4 with women without AT by age and year of claim. In total, 545 AT cases and 2180 controls were enrolled from a total of 1,843,451 women. After adjustment for such covariates as age, pregnancy was found to be associated with a lower rate of AT (adjusted odds ratio 0.314, 95% confidence interval [CI] 0.237-0.416, P value <0.01) and ovarian hyperstimulation syndrome was associated with a higher rate of AT (adjusted odds ratio 20.091, 95% CI 3.607-111.908, P value <0.01). We found that pregnancy is a negative risk factor for AT. However, a further study is needed to elucidate the mechanisms underlying these results., Competing Interests: The authors have no funding and conflicts of interest to disclose.
- Published
- 2016
- Full Text
- View/download PDF
46. Graves Disease Is Associated With Endometriosis: A 3-Year Population-Based Cross-Sectional Study.
- Author
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Yuk JS, Park EJ, Seo YS, Kim HJ, Kwon SY, and Park WI
- Subjects
- Adult, Case-Control Studies, Cross-Sectional Studies, Endometriosis complications, Female, Graves Disease complications, Humans, Prevalence, Republic of Korea epidemiology, Endometriosis epidemiology, Graves Disease epidemiology
- Abstract
The aim of this cross-sectional study was to compare the prevalence of thyroid diseases between women with and without endometriosis.We established the endometriosis group according to diagnosis codes, surgery codes, and gonadotropin-releasing hormone agonist codes using the Korean Health Insurance Review and Assessment Service-National Inpatients Sample (HIRA-NIS) from 2009 to 2011. Four controls were randomly matched to each endometriosis case. Thyroid disease cases were selected using the thyroid disease diagnosis code (E0X).Among the 1,843,451 women sampled, 5615 had endometriosis; 22,460 controls were matched to the endometriosis cases. After adjustment for age and sampling year, Graves disease was associated with endometriosis (odds ratio [OR]: 2.52; 95% CI: 1.30-4.88; P < 0.01), while hypothyroidism was not (OR: 1.17; 95% CI: 0.90-1.52; P = 0.25). Autoimmune hypothyroidism was also not associated with endometriosis (OR: 1.61; 95% CI: 0.88-2.94; P = 0.12).This study revealed an association between Graves disease and endometriosis., Competing Interests: The authors have no conflicts of interest to disclose.
- Published
- 2016
- Full Text
- View/download PDF
47. Reversible and Irreversible Responses of Defect-Engineered Graphene-Based Electrolyte-Gated pH Sensors.
- Author
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Kwon SS, Yi J, Lee WW, Shin JH, Kim SH, Cho SH, Nam S, and Park WI
- Abstract
We have studied the role of defects in electrolyte-gated graphene mesh (GM) field-effect transistors (FETs) by introducing engineered edge defects in graphene (Gr) channels. Compared with Gr-FETs, GM-FETs were characterized as having large increments of Dirac point shift (∼30-100 mV/pH) that even sometimes exceeded the Nernst limit (59 mV/pH) by means of electrostatic gating of H(+) ions. This feature was attributed to the defect-mediated chemisorptions of H(+) ions to the graphene edge, as supported by Raman measurements and observed cycling characteristics of the GM FETs. Although the H(+) ion binding to the defects increased the device response to pH change, this binding was found to be irreversible. However, the irreversible component showed relatively fast decay, almost disappearing after 5 cycles of exposure to solutions of decreasing pH value from 8.25 to 6.55. Similar behavior could be found in the Gr-FET, but the irreversible component of the response was much smaller. Finally, after complete passivation of the defects, both Gr-FETs and GM-FETs exhibited only reversible response to pH change, with similar magnitude in the range of 6-8 mV/pH.
- Published
- 2016
- Full Text
- View/download PDF
48. Chemical and biological sensors based on defect-engineered graphene mesh field-effect transistors.
- Author
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Cho SH, Kwon SS, Yi J, and Park WI
- Abstract
Graphene has been intensively studied for applications to high-performance sensors, but the sensing characteristics of graphene devices have varied from case to case, and the sensing mechanism has not been satisfactorily determined thus far. In this review, we describe recent progress in engineering of the defects in graphene grown by a silica-assisted chemical vapor deposition technique and elucidate the effect of the defects upon the electrical response of graphene sensors. This review provides guidelines for engineering and/or passivating defects to improve sensor performance and reliability.
- Published
- 2016
- Full Text
- View/download PDF
49. First Isolation of Severe Fever with Thrombocytopenia Syndrome Virus from Haemaphysalis longicornis Ticks Collected in Severe Fever with Thrombocytopenia Syndrome Outbreak Areas in the Republic of Korea.
- Author
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Yun SM, Song BG, Choi W, Roh JY, Lee YJ, Park WI, Han MG, Ju YR, and Lee WJ
- Subjects
- Animals, Disease Outbreaks, Humans, Phlebovirus genetics, Phylogeny, RNA, Viral genetics, Republic of Korea, Ixodidae virology, Phlebovirus isolation & purification
- Abstract
Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne infectious disease that is endemic to China, Japan, and the Republic of Korea (ROK). In this study, 8313 ticks collected from SFTS outbreak areas in the ROK in 2013 were used to detect the SFTS virus (SFTSV). A single SFTSV was isolated in cell culture from one pool of Haemaphysalis longicornis ticks collected from Samcheok-si, Gangwon Province, in the ROK. Phylogenetic analysis showed that the SFTSV isolate was clustered with the SFTSV strain from Japan, which was isolated from humans. To the best of our knowledge, this is the first isolation in the world of SFTSV in ticks collected from vegetation.
- Published
- 2016
- Full Text
- View/download PDF
50. Enhancing the Directed Self-assembly Kinetics of Block Copolymers Using Binary Solvent Mixtures.
- Author
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Park WI, Choi YJ, Yun JM, Hong SW, Jung YS, and Kim KH
- Abstract
The rapid pattern formation of well-ordered block copolymer (BCP) nanostructures is practical for next-generation nanolithography applications. However, there remain critical hurdles to achieve the rapid self-assembly of BCPs with a high Flory-Huggins interaction parameter (χ), owing to their slow kinetics. In this article, we report that a binary solvent vapor annealing methodology can significantly accelerate the self-assembly kinetics of poly(dimethylsiloxane-b-styrene) (PDMS-b-PS) BCPs with a high-χ. In particular, we systemically analyzed the effects of the mixing ratio of a binary solvent composed of a PDMS-selective solvent (heptane) and a PS-selective solvent (toluene), showing an ultrafast self-assembly time (≤1 min) to obtain a well-ordered nanostructure. Moreover, we successfully accomplished extremely fast generation of sub-20 nm dot patterns within an annealing time of 10 s in a 300 nm-wide trench by means of binary solvent annealing. We believe that these results are also applicable to other solvent-based annealing systems of BCPs and that they will contribute to the realization of next-generation ultrafine lithography applications.
- Published
- 2015
- Full Text
- View/download PDF
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