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Long-Term Science Goals with In Situ Observations at the Sun-Earth Lagrange Point L4
Dae-Young Lee,김록순,Kyung-Eun Choi,서정준,Junga Hwang,Dooyoung Choi,유지현,이승욱,Sung Jun Noh,Jongho Seon,Kyung-Suk Cho,Kwangsun Ryu,김관혁,Jongdae Sohn,Jaeyoung Kwak,Peter H. Yoon 한국우주과학회 2024 Journal of Astronomy and Space Sciences Vol.41 No.1
The Korean heliospheric community, led by the Korea Astronomy and Space Science Institute (KASI), is currently assessing the viability of deploying a spacecraft at the Sun-Earth Lagrange Point L4 in collaboration with National Aeronautics and Space Administration (NASA). The aim of this mission is to utilize a combination of remote sensing and in situ instruments for comprehensive observations, complementing the capabilities of the L1 and L5 observatories. The paper outlines longterm scientific objectives, underscoring the significance of multi-point in-situ observations to better understand critical heliospheric phenomena. These include coronal mass ejections, magnetic flux ropes, heliospheric current sheets, kinetic waves and instabilities, suprathermal electrons and solar energetic particle events, as well as remote detection of solar radiation phenomena. Furthermore, the mission’s significance in advancing space weather prediction and space radiation exposure assessment models through the integration of L4 observations is discussed. This article is concluded with an emphasis on the potential of L4 observations to propel advancements in heliospheric science.
Structural and Optical Properties of Nitrogen-Ion-Implanted ZnO Nanorods
S.H. Park,Y.-B. Lee,C.H. Kwak,김선효,Yong-Dae Choi,한상욱 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.3
We present a study of the structural and the optical properties of nitrogen-ion-implanted ZnO nanorods. Vertically-aligned ZnO nanorods were synthesized on Al₂O₃. substrates by using a catalyst-free metal-organic chemical vapor deposition (MOCVD) procedure. Nitrogen ions with an energy of 120 keV and an ion flux of 1 × 10 16 particles/㎠ were implanted on the vertically-aligned ZnO nanorods. The structural properties were studied by using various techniques, including field emission transmission electron microscopy (FE-TEM), X-ray diffraction (XRD), and X-ray absorption fine structure (XAFS) analyses. The XRD measurements revealed that the crystalline properties of the nitrogen-ion-implanted ZnO nanorods were comparable with those of the as-grown ZnO nanorods. However, the XAFS analysis demonstrated that the bonding lengths of atomic pairs on the c-axis were slightly elongated and that the ion implantation caused an extra structural disorder of Zn-O pairs. The FE-TEM revealed that the nanorods had structurally-damaged spots along the entire length of the nanorods. From the photoluminescence (PL) spectra, we observed a considerably weak main donor-acceptor transition peak at 3.02 eV in the temperature range of 5 - 300 K. The blue shift and the intensity decrease of the main transition peak strongly suggest that the implanted nitrogen ions play a role in the optical property changes of the nanorods.
Ullah, H.M. Arif,Saba, Evelyn,Lee, Yuan Yee,Hong, Seung-Bok,Hyun, Sun-Hee,Kwak, Yi-Seong,Park, Chae-Kyu,Kim, Sung Dae,Rhee, Man Hee The Korean Society of Ginseng 2022 Journal of Ginseng Research Vol.46 No.5
Background: Ulcerative colitis (UC) is the large intestine disease that results in chronic inflammation and ulcers in the colon. Rg3-enriched Korean Red Ginseng extract (Rg3-RGE) is known for its pharmacological activities. Persicaria tinctoria (PT) is also used in the treatment of various inflammatory diseases. The aim of this study is to investigate the attenuating effects of Rg3-RGE with PT on oxazolone (OXA)-induced UC in mice. Methods: A total of six groups of mice including control group, OXA (as model group, 1.5%) group, sulfasalazine (75 mg/kg) group, Rg3-RGE (20 mg/kg) group, PT (300 mg/kg) group, and Rg3-RGE (10 mg/kg) with PT (150 mg/kg) group. Data on the colon length, body weight, disease activity index (DAI), histological changes, nitric oxide (NO) assay, Real-time PCR of inflammatory factors, ELISA of inflammatory factors, Western blot, and flow cytometry analysis were obtained. Results: Overall, the combination treatment of Rg3-RGE and PT significantly improved the colon length and body weight and decreased the DAI in mice compared with the treatment with OXA. Additionally, the histological injury was also reduced by the combination treatment. Moreover, the NO production level and inflammatory mediators and cytokines were significantly downregulated in the Rg3-RGE with the PT group compared with the model group. Also, NLR family pyrin domain containing 3 (NLRP3) inflammasome and nuclear factor kappa B (NF-𝛋B) were suppressed in the combination treatment group compared with the OXA group. Furthermore, the number of immune cell subtypes of CD4<sup>+</sup> T-helper cells, CD19<sup>+</sup> B-cells, and CD4<sup>+</sup> and CD25<sup>+</sup> regulatory T-cells (Tregs) was improved in the Rg3-RGE with the PT group compared with the OXA group. Conclusion: Overall, the mixture of Rg3-RGE and PT is an effective therapeutic treatment for UC.
The formation of hydroxyapatite on chemically-modified cellulose fibers
김덕준,Dae H. Kwak,Sung J. Hong,P. Greil 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.2
A direct bond between cellulose and calcium phosphate does not form under physiological conditions. In this study, NaOH was used to modify the surface of cellulose fibers in an attempt to form a template for hydroxyapatite growth. Surface modification of cellulose fibers with NaOH was used to accelerate the biomimetic formation of bone-like apatite. After surface modification,NaCl was produced on the surface of cellulose fibers that were immersed in simulated body fluid before the formation of calcium phosphate could occur. However, calcium phosphate nucleated on the surface of the NaOH-treated cellulose fibers in a simulated body fluid solution without NaCl. After calcium phosphate had nucleated on the cellulose fibers in the NaCl-free simulated body fluid, the resulting cellulose fibers were immersed in a normal simulated body fluid solution. The result was an increase in the thickness of the calcium phosphate layer on the cellulose fibers immersed in SBF, followed by the formation of hydroxyapatite on the cellulose fibers.
Space missions for astronomy and astrophysics in Korea: past, present, and future
Seon Kwang-Il,Han Wonyong,Lee Young-Wook,Lee Hyung Mok,Kim Min Bin,Park I. H.,Jeong Woong-Seob,Cho Kyung-Suk,Lee Jae Jin,Lee Dae-Hee,Kwak Kyujin 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.78 No.10
We review the history of space missions in Korea focusing on the field of astronomy and astrophysics. For each mission, scientific motivation and achievement are reviewed together with some technical details of the program, including mission schedule. This review includes ongoing and currently approved missions, as well as some planned ones. Within the admitted limitations of the authors’ perspectives, some comments on the future direction of the space program for astronomy and astrophysics in Korea are made at the end of this review.