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Kim, Youngsam,Jun, Taehong,Mulay, Sandip V.,Manjare, Sudesh T.,Kwak, Jinseong,Lee, Yunho,Churchill, David G. The Royal Society of Chemistry 2017 Dalton Transactions Vol.46 No.12
<▼1><P>A reversible fluorescent OFF–ON system displaying a novel <I>intramolecular</I> π–π interaction has been discovered and exploited for hypochlorite chemosensing.</P></▼1><▼2><P>A new BODIPY system displaying an intramolecular π–π-interaction was synthesized and studied. When the selenium center was oxidized, the substituted phenyl group undergoes π–π stacking with one side of the BODIPY core. The oxidized form showed, not only a down-field shift in the NMR peak, but also splitting due to geometrical changes that arise when going from <I>C</I>s to <I>C</I>1. The compound was characterized by X-ray diffraction; DFT methods helped elucidate the influence of the unexpected π–π stack and its connection to the photophysical properties imparted by the Se oxidation.</P></▼2>
Kim, Youngsam,Kang, Seonmi,Nam, Sunhwa,Yun, Seongjin,Seo, Kangmoon The Korean Society of Veterinary Science 2020 大韓獸醫學會誌 Vol.60 No.4
A 15-year-old, spayed, female American shorthair cat presented with recurrent corneal sequestrum in the right eye. The cat had undergone superficial keratectomy twice for corneal sequestrum treatment 5 and 11 months previously. Two layers of porcine small intestinal submucosa (SIS; Vetrix BioSIS®) were applied to the surgical corneal defect after keratectomy. Thereafter, clinical signs, such as lacrimation, blepharospasm, and corneal ulcer, disappeared 50 days postoperatively. Moreover, the application of SIS with keratectomy prevented recurrence until 651 days after surgery. SIS could be applied as an additional bioscaffold for surgical repair of corneal sequestrum recurring after superficial keratectomy alone in cats.
Kim, Youngsam,Mulay, Sandip V.,Choi, Minsuk,Yu, Seungyoon B.,Jon, Sangyong,Churchill, David G. Royal Society of Chemistry 2015 Chemical Science Vol.6 No.10
<▼1><P>Outstanding glutathione chemosensing selectivity with a new coumarin-based probe is reported and discussed in the context of live cell experiments; the point of attack is flanked by two proximal carbonyl groups.</P></▼1><▼2><P>A phenyl-selenium-substituted coumarin probe was synthesized for the purpose of achieving highly selective and extremely rapid detection of glutathione (GSH) over cysteine (Cys)/homocysteine (Hcy) without background fluorescence. The fluorescence intensity of the probe with GSH shows a ∼100-fold fluorescent enhancement compared with the signal generated for other closely related amino acids, including Cys and Hcy. Importantly, the substitution reaction with the sulfhydryl group of GSH at the 4-position of the probe, which is doubly-activated by two carbonyl groups, occurs extremely fast, showing subsecond maximum fluorescence intensity attainment; equilibrium was reached within 100 ms (UV-vis). The probe selectivity for GSH was confirmed in Hep3B cells by confocal microscopy imaging.</P></▼2>
Kim, Jaehyeon,Hyun, Younghoon,Park, Youngsam,Choi, Wonchul,Kim, Soojung,Jeon, Hyojin,Zyung, Taehyeong,Jang, Moongyu American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.9
<P>A silicon nanowire one-dimensional thermoelectric device is presented as a solution to enhance thermoelectric performance. A top-down process is adopted for the definition of 50 nm silicon nanowires (SiNWs) and the fabrication of the nano-structured thermoelectric devices on silicon on insulator (SOl) wafer. To measure the Seebeck coefficients of 50 nm width n- and p-type SiNWs, a thermoelectric test structure, containing SiNWs, micro-heaters and temperature sensors is fabricated. Doping concentration is 1.0 x 10(20) cm(-3) for both for n- and p-type SiNWs. To determine the temperature gradient, a temperature coefficient of resistance (TCR) analysis is done and the extracted TCR value is 1750-1800 PPM x K(-1). The measured Seebeck coefficients are -127.583 microV x K(-1) and 141.758 microV x K(-1) for n- and p-type SiNWs, respectively, at room temperature. Consequently, power factor values are 1.46 mW x m(-1) x K(-2) and 1.66 mW x m(-1) x K(-2) for n- and p-type SiNWs, respectively. Our results indicate that SiNWs based thermoelectric devices have a great potential for applications in future energy conversion systems.</P>
Finding Sentiment Dimension in Vector Space of Movie Reviews: An Unsupervised Approach
( Youngsam Kim ),( Hyopil Shin ) 서울대학교 인지과학연구소 2017 Journal of Cognitive Science Vol.18 No.1
This study suggests an unsupervised method to find sentiment orienations of the words in Korean movie reviews. The orientations are represented as real values on a sentiment domain, which is derived from high-dimensional vector space for the movie reviews. To search for the dimension, the Pointwise Mutual Information is first used to select a set of words that are close to common modifiers; The phrases comprised of these words often form good/ bad associations (e.g., “good acting”, “terrible acting”). A neural language model (Word2Vec) is then used to calculate the point-wise similarity distances between the chosen words and, dimensionality reduction algorithms (e.g., PCA, MDS) are employed to find the axis of the sentiment orientations. Finally, the performance of our method is measured by unsupervised classification of the two movie reviews based on the orientation values. According to the results, the best accuracy achieves 66% and 76% for the two datasets.
Kim, Youngsam,Jang, Yoon Jeong,Lee, Dongyoul,Kim, Byung-Sup,Churchill, David G. Elsevier 2017 Sensors and actuators. B, Chemical Vol.238 No.-
<P><B>Abstract</B></P> <P>Herein, a chemical probe is tested with live agents for the purpose of benchmarking fluorescent pyridyl-containing systems with actual nerve agents and simulants together. The molecule showed selective fluorogenic and colorimetric detection of Soman (GD) and its simulant over other G-series nerve agents and their simulants. <SUP>1</SUP>H and <SUP>31</SUP>P NMR spectroscopy and TD-DFT calculations help reveal the origin of the colorimetric and fluorogenic changes in the reacted system.</P>
Reference values for selected dry eye tests in normal Beagle dogs: a pilot study
Youngsam Kim,Seonmi Kang,Sunhyo Kim,Jaeho Shim,Seokmin Go,Kangmoon Seo 대한수의학회 2022 Journal of Veterinary Science Vol.23 No.1
Background: Dry eye disease (DED) cannot be diagnosed by a single test because it is a multifactorial disorder of the ocular surface. Although studies on various dry eye tests (DETs) in dogs have been reported, standard criteria have not been established except for the Schirmer tear test 1 (STT-1). Objectives: To establish reference values for DETs in dogs with normal STT-1 values (≥ 15 mm/min) and to analyze the correlation between DETs. Methods: The STT-1 was performed in 10 healthy Beagle dogs (20 eyes). After 20 min, interferometry (IF) for estimating the lipid layer thickness (LLT) of the tear film, tear meniscus height (TMH), non-invasive tear breakup time (NIBUT), and meibomian gland loss rate of the upper eyelid (MGLRU) and lower eyelid (MGLRL), were measured using an ocular surface analyzer. Results: Mean values for STT-1, TMH, and NIBUT were as follows: 21.7 ± 3.4 mm/min, 0.41 ± 0.21 mm, and 19.1 ± 9.5 sec, respectively. The most frequent LLT range, measured by IF, was 30–80 nm (11 eyes), followed by 80 nm (5 eyes) and 80–140 nm (4 eyes). MGLRU ≤ 25% was measured in 11 eyes and 26%–50% in 9 eyes; MGLRL ≤ 25% in 8 eyes and 26%–50% in 12 eyes. Besides positive correlation between TMH and NIBUT (P = 0.038), there were no significant associations between DETs. Conclusions: Data obtained in this study provided normative references that could be useful for diagnosing DED and for further research into correlation between DETs in dogs with DED.
Influence of Glycogen on the performance of dye-sensitized solar cells
Youngsam Jung(정영삼),Chunghee Kwak(곽정희),Youngbin Oh(오영빈),Yousub Bang(방유섭),Seowang Park(박서왕),Inhyeok Jeong(정인혁),Jaehyuk Lee(이재혁),Younghun Kim(김영훈),Seokhyeon Hong(홍석현),Taehyun Kim(김태현),Uiseok You(유의석),Seo 한국신재생에너지학회 2013 한국신재생에너지학회 학술대회논문집 Vol.2013 No.05
Youngsam Kim,Baesun Dong,Jaewon Jo,Kwang W. Kim 한국도로학회 2018 한국도로학회 학술대회 발표논문 초록집 Vol.2018 No.05
When there is a significant stripping in asphalt pavement, it is common practice to use a hydrated lime (HL) as an anti-stripping additive (ASA). However, since many asphalt plants do not have facilities for weighing and casting HL, they prefer to use of a liquid-type ASA (LA). Therefore, various brands of LAs which show proper anti-stripping function are currently developed, imported, and marketed in Korea. In addition to the anti-stripping effect, the HL has been known to give a significant age-retarding effect on paved asphalt in the field. Therefore, there was a question about whether or not the LA provides the same anti-aging effect as The HL. This study investigated anti-aging effect of the asphalt mixes which were prepared using both ASAs and short-term aged and long-term aged in the laboratory. The absolute viscosity was measured as an aging index from the binder recovered from the mixes after short-term aging (STA) and long-term aging (LTA) processes. The results showed that there was a significant higher aging found from the LA-added mix than the normal mix without any ASA. On the other hands, the mix with HL showed significantly lower ageing level than the LA-added mix and normal mix. The retardation of age-hardening by using HL was more effectively observed when the STA condition was stronger.
Soft‐wall ion transfer channel accurately predicts sterically hindered ion channel permeability
Kim Youngsam,Song Suhwan,Kim Min‐Cheol,Sim Eunji 대한화학회 2022 Bulletin of the Korean Chemical Society Vol.43 No.4
We provide a simple and systematic computational model to study ion channel permeability using density functional theory. While existing permeability models with a hard-wall steric hindrance factor work reasonably well for large ions, they severely inhibit the permeation of small ions through channel pores. Here, by introducing a steric hindrance factor that allows pore expansion due to intrinsically soft ion transfer channel walls, the new permeability model accurately describes the effect of steric hindrance stemming from the soft and flexible ion channel wall. Most importantly, the soft-wall ion transfer channel model works for a wide range of ionic radii from fluoride to gluconate. In addition, we show that strong local electrostatic interaction between densely charged ions such as fluoride and bicarbonate and ion channels with ion binding sites significantly promotes the permeation processes.