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Choi, Dawoon,Lim, Yongjun,Roh, Sookyoung,Lee, Il-Min,Jung, Jaehoon,Lee, Byoungho The Optical Society 2010 Applied optics Vol.49 No.7
<P>A metal slit array arranged along a semicircular surface achieving subwavelength optical beam focusing along the lateral direction is proposed. Taking into consideration surface plasmon polaritons that pass through a metal slit array, we design the array with a curvature. By use of a genetic algorithm, the size of the metal slit and the corresponding curvature are to be determined. Based on our metal slit array configuration, the full width at half-maximum can be achieved on a subwavelength scale.</P>
Airy Beam Excitation Using a Subwavelength Metallic Slit Array
Dawoon Choi,Yongjun Lim,Il-Min Lee,Sookyoung Roh,Byoungho Lee IEEE 2012 IEEE photonics technology letters Vol.24 No.16
<P>A novel method for launching an Airy wave packet based on a metallic slit array with stepped-height is proposed. By appropriately adjusting the amplitude and phase of the transmittance from the metallic slit array, the Airy beam can be launched in a compact area. The method can be used in various applications, such as particle tweezing and trapping, without the need for any optical components or bulky structure.</P>
Metallic-Grating-Based Interconnector Between Surface Plasmon Polariton Waveguides
Dawoon Choi,Il-Min Lee,Jaehoon Jung,Junghyun Park,Jae-Hoon Han,Byoungho Lee IEEE 2009 Journal of Lightwave Technology Vol.27 No.24
<P>A metallic-grating-based interconnection scheme that interconnects two waveguide layers of surface plasmon polaritons (SPPs) is presented. We designed a diffraction grating for radiating light from the SPPs into free space or a homogeneous medium. An efficient receiver grating for receiving the light into SPPs is also explored. Using the well-established finite-element method, the appropriate grating geometry parameters are found. The directional interconnection efficiency is 32.4% for the best case in our numerical analysis.</P>
Effects of structurally stabilized EGF and bFGF on wound healing in type I and type II diabetic mice
Choi, Seong Mi,Lee, Kyoung-Mi,Kim, Hyun Jung,Park, Ik Kyu,Kang, Hwi Ju,Shin, Hang-Cheol,Baek, Dawoon,Choi, Yoorim,Park, Kwang Hwan,Lee, Jin Woo Elsevier 2018 Acta Biomaterialia: structure-property-function re Vol.66 No.-
<P><B>Abstract</B></P> <P>Diabetes mellitus comprises a multiple metabolic disorder that affects millions of people worldwide and consequentially poses challenges for clinical treatment. Among the various complications, diabetic ulcer constitutes the most prevalent associated disorder and leads to delayed wound healing. To enhance wound healing capacity, we developed structurally stabilized epidermal growth factor (ST-EGF) and basic fibroblast growth factor (ST-bFGF) to overcome limitations of commercially available EGF (CA-EGF) and bFGF (CA-bFGF), such as short half-life and loss of activity after loading onto a matrix. Neither ST-EGF nor ST-bFGF was toxic, and both were more stable at higher temperatures than CA-EGF and CA-bFGF. We loaded ST-EGF and ST-bFGF onto a hyaluronate-collagen dressing (HCD) matrix, a biocompatible carrier, and tested the effectiveness of this system in promoting wound healing in a mouse model of diabetes. Wounds treated with HCD matrix loaded with 0.3 μg/cm<SUP>2</SUP> ST-EGF or 1 μg/cm<SUP>2</SUP> ST-bFGF showed a more rapid rate of tissue repair as compared to the control in type I and II diabetes models. Our results indicate that an HDC matrix loaded with 0.3 μg/cm<SUP>2</SUP> ST-EGF or 1 μg/cm<SUP>2</SUP> ST-bFGF can promote wound healing in diabetic ulcers and are suitable for use in wound dressings owing to their stability for long periods at room temperature.</P> <P><B>Statement of Significance</B></P> <P>Various types of dressing materials loaded with growth factors, such as VEGF, EGF, and bFGF, are widely used to effect wound repair. However, such growth factor-loaded materials have several limitations for use as therapeutic agents in healing-impaired diabetic wounds. To overcome these limitations, we have developed new materials containing structurally stabilized EGF (ST-EGF) and bFGF (ST-bFGF). To confirm the wound healing capacity of newly developed materials (ST-EGF and ST-bFGF-loaded hyaluronate-collagen dressing [HCD] matrix), we applied these matrices in type I and type II diabetic wounds. Notably, these matrices were able to accelerate wound healing including re-epithelialization, neovascularization, and collagen deposition. Consequentially, these ST-EGF and ST-bFGF-loaded HCD matrix may be used as future therapeutic agents in patients with diabetic foot ulcers.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Choi Minseon,Lee Suyeon,Jang Dawoon,Park Sungjin 한국탄소학회 2022 Carbon Letters Vol.32 No.3
Electrochemical water splitting is an important process for next generation of eco-friendly energy systems. The oxygen evolution reaction (OER), which occurs at an anode during the process, requires efficient electrocatalysts to reduce activation energies. Although Ru- or Ir-containing materials show excellent electrocatalytic activities, their high cost is a critical drawback. Consequently, the development of efficient electrocatalysts composed of low-cost metal components is a great challenge. In this study, we develop a new route to produce a hybrid material (Fe–NC) containing Fe3C particles dispersed on the surface of N-doped carbon (NC) materials by heat treatment of a mixture of urea and Fe(II)Cl2(H2O)4. Microscopic analyses prove that the Fe3C particles are placed on the surfaces of thin NC materials. Additionally, various characterizations reveal that the particles contain Fe3C structure. Fe–NC shows good electrocatalytic properties with onset and overpotentials of 1.57 V and 545 mV, respectively, for OER in KOH electrolyte. This study suggests the possibility of the use of Fe3C-based composites as OER electrocatalysts.