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Negative regulation of SEK1 signaling by serum- and glucocorticoid-inducible protein kinase 1
Kim, Myung Jin,Chae, Ji Soo,Kim, Kwang Je,Hwang, Sang Gil,Yoon, Kyoung Wan,Kim, Eun Kyung,Yun, Hee Jae,Cho, Jun-Ho,Kim, Jeehyun,Kim, Bong-Woo,Kim, Hyung-chul,Kang, Sang Sun,Lang, Florian,Cho, Ssang-Go Wiley (John WileySons) 2007 The EMBO journal Vol.26 No.13
<P>Serum- and glucocorticoid-inducible protein kinase 1 (SGK1) has been implicated in diverse cellular activities including the promotion of cell survival. The molecular mechanism of the role of SGK1 in protection against cellular stress has remained unclear, however. We have now shown that SGK1 inhibits the activation of SEK1 and thereby negatively regulates the JNK signaling pathway. SGK1 was found to physically associate with SEK1 in intact cells. Furthermore, activated SGK1 mediated the phosphorylation of SEK1 on serine 78, resulting in inhibition of the binding of SEK1 to JNK1, as well as to MEKK1. Replacement of serine 78 of SEK1 with alanine abolished SGK1-mediated SEK1 inhibition. Oxidative stress upregulated SGK1 expression, and depletion of SGK1 by RNA interference potentiated the activation of SEK1 induced by oxidative stress in Rat2 fibroblasts. Moreover, such SGK1 depletion prevented the dexamethasone-induced increase in SGK1 expression, as well as the inhibitory effects of dexamethasone on paclitaxel-induced SEK1-JNK signaling and apoptosis in MDA-MB-231 breast cancer cells. Together, our results suggest that SGK1 negatively regulates stress-activated signaling through inhibition of SEK1 function.</P>
Kim, Hyung-Jin,Kim, Pil Un,Hyeon, Min Gyu,Choi, Youngwoon,Kim, Jeehyun,Kim, Beop-Min The Optical Society 2016 Applied Optics Vol.55 No.26
<P>Dual-depth spectral-domain optical coherence tomography (SD-OCT) enables high-resolution in vivo whole-eye imaging. Two orthogonally polarized beams from a source are focused simultaneously on two axial positions of the anterior segment and the retina. For the detector arm, a 1 x 2 ultrafast optical switch sequentially delivers two spectral interference signals to a single spectrometer, which extends the in-air axial depth range up to 9.44 mm. An off-pivot complex conjugate removal technique doubles the depth range for all anterior segment imaging. The graphics-processing-unit-based parallel signal processing algorithm supports fast two-and three-dimensional image displays. The obtained high-resolution anterior and retinal images are measured biometrically. The dual-depth SD-OCT system has an axial resolution of similar to 6.4 mu m in air, and the sensitivity is 91.79 dB at 150 mu m from the zero-delay line. (C) 2016 Optical Society of America</P>
Skin pore imaging using spectral‑domain optical coherence tomography: a case report
Hyunmo Kim,Dongwan Kang,Daewoon Seong,Sm Abu Saleah,Jannat Amrin Luna,Yoonseok Kim,Hayoung Kim,Sangyeob Han,Mansik Jeon,Jeehyun Kim 대한의용생체공학회 2023 Biomedical Engineering Letters (BMEL) Vol.13 No.4
Sebum is an important component of the skin that has attracted attention in many fields, including dermatology and cosmetics. Pore expansion due to sebum on the skin can lead to various problems. Therefore, it is necessary to analyze the morphologicalcharacteristics of sebum. In this study, we used optical coherence tomography (OCT) to evaluate facial sebum areas. Weobtained the OCT maximum amplitude projection (MAP) image and a cross-sectional image of skin pores in the facial area. Subsequently, we detected the sebum in skin pores using the detection algorithm of the ImageJ software to quantitativelydetermine the size of randomly selected pores in the proposed MAP images. Additionally, the pore size was analyzed byacquiring images before and after facial sebum extraction. According to our research, facial sebum can be morphologicallydescribed using the OCT system. Since OCT imaging enables specific analysis of skin parameters, including pores andsebum, skin analysis employing OCT could be an effective method for further research.
Lee, Changho,Kim, Kyungun,Han, Seunghoon,Kim, Sehui,Lee, Jun Hoon,Kim, Hong Kyun,Kim, Chulhong,Jung, Woonggyu,Kim, Jeehyun SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS 2014 JOURNAL OF BIOMEDICAL OPTICS Vol.19 No.3
<P>An intraoperative surgical microscope is an essential tool in a neuro- or ophthalmological surgical environment. Yet, it has an inherent limitation to classify subsurface information because it only provides the surface images. To compensate for and assist in this problem, combining the surgical microscope with optical coherence tomography (OCT) has been adapted. We developed a real-time virtual intraoperative surgical OCT (VISOCT) system by adapting a spectral-domain OCT scanner with a commercial surgical microscope. Thanks to our custom-made beam splitting and image display subsystems, the OCT images and microscopic images are simultaneously visualized through an ocular lens or the eyepiece of the microscope. This improvement helps surgeons to focus on the operation without distraction to view OCT images on another separate display. Moreover, displaying the OCT live images on the eyepiece helps surgeon's depth perception during the surgeries. Finally, we successfully processed stimulated penetrating keratoplasty in live rabbits. We believe that these technical achievements are crucial to enhance the usability of the VISOCT system in a real surgical operating condition.</P>
Real-Time Retinal Imaging with a Parallel OCT Using a CMOS Smart Array Detector
jeehyun kim,Thomas Milner,Bong-Soo Sohn 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.5
We present a parallel optical coherence tomography(OCT) system using a complementary metal-oxide-semiconductor(CMOS) smart array detector. This paper includes descriptions of the CMOS smart array detector, and the experimental results of scattering surface targets including a wet tissue on an Air Force target, and {\it ex vivo} gold fish retina where the boundary between the vitreous humor and the ganglion cell layer could be identified in the acquired images. After three-dimensional volume rendering, several other layers between the ganglion cell layer and the choroid layer could be observed even though the contrast between the layers was weak. Control of the current version of the CMOS smart array detector requires significant time for maintenance. Although the current CMOS smart array detector needs improvement, the design is a promising ophthalmologic instrument and can provide fast retinal scanning and prompt display of the acquired images.
Design of mid-plane passive active multijunction antenna for 5-GHz KSTAR LHCD system
Kim, Jeehyun,Wang, Sonjong,Hillairet, Julien,Wi, Hyunho,Seon, Sangwon,Han, Jongwon,Delpech, Lena Elsevier 2017 Fusion engineering and design Vol.123 No.-
<P><B>Abstract</B></P> <P>The major upgrade of KSTAR LHCD system to 4MW is planned in 2021. 4-MW RF power will be provided by 8×0.5MW klystrons. Highly oversized circular waveguide transmitting TE<SUB>01</SUB>° mode will be adopted for the low loss transmission line longer than 50m. The design of the 4-MW mid-plane Passive Active Multijunction launcher has been performed. Considering parallel refractive index N<SUB>||</SUB> for the efficient current drive and the maximum power density at the launcher mouth, the launcher is composed of 256 active waveguides whose dimension is 58mm x 7mm and 18mm of spatial period for N<SUB>||0</SUB> =2.5. Multijunction with E<SUB>max <</SUB> 3.5kV/cm and high power waveguide components have been designed using HFSS code. The antenna properties were evaluated using ALOHA. Prototype PAM launcher with 32 active waveguides is under development for 0.5-MW pulsed operation.</P>
Study on rectangular-to-circular waveguide mode converter for KSTAR LHCD transmission line
Kim, Jeehyun,Seong, Taesik,Namkung, Won,Cho, Moohyun Elsevier 2018 Fusion engineering and design Vol.135 No.1
<P><B>Abstract</B></P> <P>A major upgrade of KSTAR LHCD system to 4 MW is planned for 2021. The system will be composed of eight 5-GHz 500-kW klystrons, low loss transmission lines with oversized circular waveguides, and a passive active multijunction launcher. Circular TE<SUB>01</SUB> mode will be adopted for transmission lines longer than 50 m because it has extremely low loss in oversized waveguide, but mode converters from rectangular TE<SUB>10</SUB> to circular TE<SUB>01</SUB> mode are not easy to design. Mock-ups of two types of mode converters were developed. One is serpentine type, and the other is symmetric sidewall coupling type. The TE<SUB>01</SUB> mode purities were demonstrated by measuring the transmission efficiencies between two identical mode converters at various angles between symmetric planes. A sidewall coupling mode converter with a refined design, which showed better circular symmetry and higher transmission efficiency than serpentine type, is under fabrication for prototype. The prototype mode converter is calculated to have 99.5% transmission efficiency, with 0.16% diffraction loss and 0.35% resistive loss, according to the simulation.</P>
Magnetomotive laser speckle imaging.
Kim, Jeehyun,Oh, Junghwan,Choi, Bernard SPIE--the International Society for Optical Engine 2010 JOURNAL OF BIOMEDICAL OPTICS Vol.15 No.1
<P>Laser speckle imaging (LSI) involves analysis of reflectance images collected during coherent optical excitation of an object to compute wide-field maps of tissue blood flow. An intrinsic limitation of LSI for resolving microvascular architecture is that its signal depends on relative motion of interrogated red blood cells. Hence, with LSI, small-diameter arterioles, venules, and capillaries are difficult to resolve due to the slow flow speeds associated with such vasculature. Furthermore, LSI characterization of subsurface blood flow is subject to blurring due to scattering, further limiting the ability of LSI to resolve or quantify blood flow in small vessels. Here, we show that magnetic activation of superparamagnetic iron oxide (SPIO) nanoparticles modulate the speckle flow index (SFI) values estimated from speckle contrast analysis of collected images. With application of an ac magnetic field to a solution of stagnant SPIO particles, an apparent increase in SFI is induced. Furthermore, with application of a focused dc magnetic field, a focal decrease in SFI values is induced. Magnetomotive LSI may enable wide-field mapping of suspicious tissue regions, enabling subsequent high-resolution optical interrogation of these regions. Similarly, subsequent photoactivation of intravascular SPIO nanoparticles could then be performed to induce selective photothermal destruction of unwanted vasculature.</P>