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A Surfactant-based Method for Carbon Coating of LiNi0.8Co0.15Al0.05O2 Cathode in Li Ion Batteries
Youngmin Chung,Seong-Hyeon Ryu,Jeong-Hun Ju,Yu-Rim Bak,황문진,Ki-Won Kim,조권구,Kwang-Sun Ryu 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.8
A LiNi0.8Co0.15Al0.05O2 (LNCAO/C) active material composite cathode was coated with carbon. The conductive carbon coating was obtained by addition of surfactant during synthesis. The addition of surfactant led to the formation of an amorphous carbon coating layer on the pristine LNCAO surface. The layer of carbon coating was clearly detected by FE-TEM analysis. In electrochemical performance, although the LNCAO/C showed similar capacity at low C-rate conditions, the rate capability was improved by the form of the carbon coating at high current discharge state. After 40cycles of charge-discharge processes, the capacity retention of LNCAO/C was better than that of LNCAO. The carbon coating is effectively protected the surface structure of the pristine LNCAO during Li insertion-extraction.
( Youngmin Yoon ),( Hyumwoo Kim ),( Sunae Han ),( Hyungnam Kim ),( Donghyun Kim ),( Ran Hong ),( Hyunlee Kim ),( Jonghoon Chung ),( Byungchul Shin ) 대한내과학회 2014 대한내과학회 추계학술대회 Vol.2014 No.1
Acute tubular necrosis (ATN) is a syndrome of intrinsic renal injury secondary to ischemic or toxic causes without parenchymal damages and usually non-oliguira. A 20- year old man presented with acute anuric renal failure preceded by 2 days of watery diarrhea. He had been anuria for 36hr with intravenous fiuid therapy. Oliguria persisted for 10 days and he required hemodialysis support for 6 days before renal recovery. He denied the use of any regular medication and any intravenous drug use. Renal biopsy revealed severe ATN. Histopathologic findings were marked desquamation of proximal tubular epithelial cells with intact distal tubules and normal glomeruli. We report an unusual case of ATN with anuria and clinically severe features.
Chung, Jong Won,You, Youngmin,Huh, Hyun Sue,An, Byeong-Kwan,Yoon, Seong-Jun,Kim, Se Hun,Lee, Soon W.,Park, Soo Young American Chemical Society 2009 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.131 No.23
<P>We have designed and synthesized asymmetric cyano-stilbene derivatives containing trifluoromethyl (-CF(3)) substituents with the aim of producing tightly packed pi-dimer systems that as crystals exhibit reversible [2 + 2] cycloaddition with characteristic fluorescence modulation. (Z)-3-(3',5'-Bis(trifluoromethyl)biphenyl-4-yl)-2-(4'-(trifluoromethyl)biphenyl-4-yl)acrylonitrile (CN(L)-TrFMBE) and its derivatives were found to form antiparallel pi-dimer stacks in crystals due to their specific intermolecular interactions, including C-F...H and C-F...pi interactions. The CN(L)-TrFMBE pi-dimer crystals (and powder) are not at all fluorescent initially but switch to a highly fluorescent state (Phi(PL) = 24%) when an external shear-strain and/or prolonged UV (365 nm) irradiation is applied. Our experimental and theoretical investigations show that the fluorescence modulation in this particular system is due to the external and/or internal (in the case of UV irradiation) shear-induced lateral displacement of the pi-dimer molecular pair, which effectively turns the fluorescence emission on at the cost of frustrated [2 + 2] cycloaddition. Further, the fluorescence 'off' state can be restored by thermal annealing, which regenerates the tightly packed pi-dimer by reverse displacement together with the thermal dissociation of the [2 + 2] cycloaddition product. This system provides a very rare example of high-contrast reversible fluorescence switching that is driven by a change in the molecular packing mode in the solid state, which enables piezochromic and photochromic responses.</P>
Depth-dependent seismicity and crustal heterogeneity in South Korea
Chung, Tae Woong,Iqbal, Muhammad Zafar,Lee, Youngmin,Yoshimoto, Kazuo,Jeong, Jina Elsevier 2018 Tectonophysics Vol.749 No.-
<P><B>Abstract</B></P> <P>Depth-dependent seismicity has been suggested in the seismogenic layer, which is divided into upper and lower layers by its seismicity boundary. Since large earthquakes tend to occur in the lower layer, the structure of the seismogenic layer, which includes the seismicity boundary, provides important information for seismic hazard assessment. Using 107 land-based earthquakes, the structure of the seismogenic layer in South Korea was studied with focal depth determination by identifying the minimum residuals between the observations and several models. The same procedure was done for the depth relocation of 138 events associated with the Gyeongju earthquake (M<SUB> <I>L</I> </SUB> 5.8), the largest event in South Korea in the last two centuries. The geothermal temperature at the focal depth was also estimated for all earthquakes, including the Gyeongju earthquake cluster and the Pohang earthquake (M<SUB> <I>L</I> </SUB> 5.4), which caused more damage than did the Gyeongju earthquake. As observed in a large-scale averaging of mainland China, a 12-km seismicity boundary was suggested due to the frequent seismicity in the upper layer. At 12-km depth at the Gyeongju earthquake site, the geothermal temperature reached 300 °C, and the occurrence of aftershocks was limited below that depth. Based on the rigorously estimated depth, we separated the scattering attenuation, <I>Q</I> <SUB> <I>s</I> </SUB> <SUP>−1</SUP>, by a multiple lapse time window analysis using individual earthquakes and found higher and lower values for events in the upper and lower layers, respectively. This depth-dependent observation suggests differences in heterogeneity between the upper and lower seismogenic layers and supports the hypothesis that the seismicity of a depth-dependent seismogenic layer is related to cracks, which diminish with depth. Our results suggest that the upper limit of the focal depth can be predicted from the depth of the seismicity boundary for normal large earthquakes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The seismicity boundary of seismogenic layer in South Korea was identified. </LI> <LI> Crustal seismic-wave scattering strength exhibits depth-dependent heterogeneity between the two layers. </LI> <LI> The upper limit of the focal depth of large earthquakes can be predicted from the depth of the seismicity boundary. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Focal depths versus number of earthquakes for South Korea, and the Gyeongju earthquake cluster. The seismogenic layer (<I>S.L.</I>) consists of upper and lower layers divided at 12-km depth. The histograms with orange fill denote focal depth temperatures higher than 300 °C. Red and blue stars denote the ML 5.8 and 5.1 events, respectively. In the right graph, the scattering Q<SUP>−1</SUP> values with frequencies are shown as connected lines of events exclusively included in the upper and lower layers, respectively.</P> <P>[DISPLAY OMISSION]</P>
Antibiotics-Associated Hemorrhagic Colitis Caused by Klebsiella oxytoca: Two Case Reports
Youngmin Youn,Sang Won Lee,Hyun-Hae Cho,Sanghui Park,Hae-Sun Chung,Jeong Wan Seo 대한소아소화기영양학회 2018 Pediatric gastroenterology, hepatology & nutrition Vol.21 No.2
Nowadays, Klebsiella oxytoca is described as a causative organism for antibiotic-associated hemorrhagic colitis (AAHC). Here we report two cases of pediatric AAHC, from which K. oxytoca was cultured after starting amox-icillin-clavulanate or amoxicillin treatment. The patients developed severe abdominal pain and a large amount of bloody diarrhea. K. oxytoca was obtained in intestinal fluid culture of a boy through the colonoscopy. On the other hand, colonic tissue culture and intestinal fluid culture were negative of the other patient. K. oxytoca was detected in stool culture when he was admitted. These cases showed characteristic endoscopic findings of segmental hemor-rhagic colitis, and both boys recovered spontaneously within 2-3 days after they stopped taking the antibiotics. Therefore, in children who develop relatively large amount of bloody diarrhea after antibiotic treatment, we should consider AAHC caused by K. oxytoca.
Chung Yuseong,Rahmat Endang,Nam Hyeon Hwa,Lee Ayeong,Park Jun Hong,Moon Byeong Cheol,Kang Youngmin 한국응용생명화학회 2023 Applied Biological Chemistry (Appl Biol Chem) Vol.66 No.-
Rehmannia glutinosa (Gaertn.) DC., belonging to the family Scrophulariaceae, is an important medicinal herb cultivated in East Asia. Traditionally, R. glutinosa is steam processed to increase its efficacy in treating various ailments such as diabetes, hematinic deficiencies and adrenal disorder. However, standardization of processed R. glutinosa is highly needed to increase its quality to fulfill global market demand that is safe and possess high level of efficacy. Therefore, this study aimed to optimize the R. glutinosa steam processing methods by evaluating some key parameters such as steaming temperature, number of steaming times, steaming duration, and additive supplementation. R. glutinosa samples were steam processed at different temperatures (100 °C, 110 °C, and 120 °C), various steaming times (1 to 5 times), several steaming duration (1 to 4 h), and additives supplementation (rice wine, 5% EtOH, 10% EtOH, 20% EtOH, 30% EtOH, and 40% EtOH). As the result, 2 h, 3 replications, and supplementation with 20% EtOH at 120 °C were identified as the optimal conditions for R. glutinosa steam processing. Optimized processed R. glutinosa (SPRR 20%EtOH) resulted in significantly higher content of 5-HMF (7648.60 ± 150.08 µg/g) and iso-verbacoside (203.80 ± 10.72 µg/g) compared with unprocessed R. glutinosa (UPR). Compared to those of other samples, SPRR 20% EtOH samples had higher total flavonoid (55.36 ± 1.68 mg/g) and phenolic (69.24 ± 4.56 mg/g) contents and stronger DPPH antioxidant activity (56%). Furthermore, SPRR 20% EtOH had excellent anti-inflammatory activity, as evidenced by the suppression of inducible nitric oxide synthase (iNOS) caused by activation of nuclear factor-κB (NF-κB) through p-p65 pathway in LPS-stimulated RAW 264.7 cells. These findings will provide a basis towards industrialization of R. glutinosa processing technology that will be very helpful for oriental medication field.