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Jo, Yong-Ryun,Koo, Bonjae,Seo, Min-Ji,Kim, Jun Kyu,Lee, Siwon,Kim, Kyeounghak,Han, Jeong Woo,Jung, WooChul,Kim, Bong-Joong American Chemical Society 2019 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.141 No.16
<P>A precise control of the size, density, and distribution of metal nanoparticles dispersed on functional oxide supports is critical for promoting catalytic activity and stability in renewable energy and catalysis devices. Here, we measure the growth kinetics of individual Co particles ex-solved on SrTi<SUB>0.75</SUB>Co<SUB>0.25</SUB>O<SUB>3-δ</SUB> polycrystalline thin films under a high vacuum, and at various temperatures and grain sizes using in situ transmission electron microscopy. The ex-solution preferentially occurs at grain boundaries and corners which appear essential for controlling particle density and distribution, and enabling low temperature ex-solution. The particle reaches a saturated size after a few minutes, and the size depends on temperature. Quantitative measurements with a kinetic model determine the rate limiting step, vacancy formation enthalpy, ex-solution enthalpy, and activation energy for particle growth. The ex-solved particles are tightly socketed, preventing interactions among them over 800 °C. Furthermore, we obtain the first direct clarification of the active reaction site for CO oxidation-the Co-oxide interface, agreeing well with density functional theory calculations.</P> [FIG OMISSION]</BR>
Development of Parameters for Diagnosing Laryngeal Diseases
Kim, Yong Ju,Wang, Soo Geun,Kim, Gi Ryun,Kwon, Soon Bok,Jeon, Kye Rok,Back, Moo Jin,Yang, Byung Gon,Jo, Cheol Woo,Kim, Hyung Soon 한국음성과학회 2003 음성과학 Vol.10 No.1
Many people suffer from various laryngeal diseases. Since we can notice voice change easily, acoustic analysis can be helpful to diagnose the diseases. Several attempts have been made to clarify the relation between the parameters and the state of ssick vocal folds but any decisive parameters are not found yet. The purpose of this study was to select and develop those parameters useful for diagnosing and differentiating laryngeal diseases. We examined eight MDVP parameters, and two additional MFCC and LPC parameters obt ained from the production of an open vowel by 252 subjects with or without laryngeal diseases. Using a statistical procedure through the artificial neural networks, we attempted to differentiate laryngeal disease groups. Results showed that the LPC parameters indicated the highest differentiating rate by the networks followed by the MFCC and the MDVP parameters. In addition, Jita, Shim and NHR among the MDVP parameters came out better parameters in diagnosing laryngeal diseases.
석류 열수 추출물의 수면박탈을 유도한 Rat 모델에서의 항스트레스 효과
나주련(Ju-Ryun Na),김선오(Sunoh Kim),조아라(Ara Jo),배동혁(Donghyuck Bae),오교녀(Kyo-Nyeo Oh),김용재(Yong Jae Kim),이유현(Yoo-Hyun Lee),전우진(Woojin Jun) 한국식품영양과학회 2016 한국식품영양과학회지 Vol.45 No.11
수면은 하루의 약 3분의 1을 차지하며, 중추신경계의 항상성 회복, 에너지 저장, 체온조절, 불필요한 기억의 제거, 면역 기능, 에너지 보존 등의 기능을 수행하는 생리현상이다. 이러한 조건이 충족되지 않으면 삶의 질 저하뿐만 아니라 다양한 증상 및 질병이 야기된다. 현대인은 학업, 직장 등 다양한 요소로 인한 과도한 정신적 스트레스, 불안 또는 육체적 피로 등의 이유로 일시적 또는 장기적 수면장애가 증가하는 추세이다. 이렇게 많은 현대인들이 겪는 수면장애를 예방 및 개선하기 방안을 모색하기 위하여 전남 비교우위 특산자원인 석류의 수면, 특히 수면박탈 및 스트레스에 미치는 영향을 in vivo 및 in vitro 상에서 확인하였다. 석류(Punica granatum L.)는 부처꽃과에 속하는 낙엽활엽교목으로 인도, 페르시아가 원산지이다. 석류는 항산화, 항암, 항당뇨, 항통증, 항염증, 에스트로젠 효과 등이 알려져 있다. 석류 추출물을 전처리한 SH-SY5Y 세포에 H₂O₂/corticosterone에 의한 신경세포독성을 유발하여 보호 효과를 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide와 lactate dehydrogenase로 측정한 결과, 유의적인 보호 효과를 확인하였다. 또한, 수면박탈 동물모델에서 생존율, 몸무게, 꾸벅임에서 수면박탈군과 비교하여 모두 유의적인 보호 효과가 있는 것을 확인할 수 있었다. 석류 추출물의 수면박탈 스트레스에 대한 행동학적 보호 효과는 스트레스의 강도에 따라 행동학적 변화를 관찰한 결과, 운동능력 및 인지능력은 수면박탈이 지속되어도 보호 효과를 갖는 것을 확인하였다. 통각 효과는 hot hyperalgesia test를 통해 스트레스가 지속될수록 무뎌지는 경향을 확인할 수 있었다. 또한, Y maze는 변경행동력은 유의적인 차이는 없었으나 석류 추출물 투여군들의 움직임이 수면박탈군에 비하여 활발함을 확인하였다. 생화학적 변화를 확인한 결과 코티졸, 세로토닌 및 도파민, 테스토스테론 및 growth factor I의 함량은 수면박탈 스트레스에 의하여 증가하다가 석류 추출물 및 카페인에 의하여 유의적으로 감소하는 것을 확인할 수 있었다. 마지막으로 항산화 관련 인자인 catalase, glutathione, superoxide dismutase를 측정한 결과, 수면박탈군은 대조군에 비해 유의적으로 감소하는 경향을 보였으며, 석류 추출물에 의하여 회복되는 것을 확인할 수 있었다. 이러한 결과를 토대로 석류의 항스트레스 효과를 확인하였으며, 특히 동물실험에서는 석류 추출물에 의하여 수면박탈스트레스가 지속됨에 따라 감소하는 행동학적 결과들을 방지하는 것으로 나타났으며, 이러한 석류의 항스트레스 효과는 항산화적 측면과 연관이 있는 것으로 확인되었다. The anti-stress effects of Punica granatum L. (family Lythraceae, PG) on H₂O₂/corticosterone (CORT)-induced stress in cells and sleep-deprived rats were investigated. The PG extract showed neuroprotective effects in SH-SY5Y cells against H₂O₂/CORT-induced stress. Sleep deprivation led to behavioral, hormonal, and biochemical alterations in the animal model. The effects of P. granatum on physiological, behavioral, and biochemical parameters aggravated by sleep deprivation were investigated. Sleep deprivation impaired physiological (survival, body weight, and drowsiness scores) and behavioral (rotarod, passive avoidance, hot hyperalgesia, and Y maze) parameters as well as biochemical factors (cortisol, serotonin, dopamine, testosterone, and growth factor I contents in serum). These parameters were significantly recovered by PG extract in a concentration-dependent manner. The PG extract also enhanced catalase, superoxide dismutase, and non-enzymatic antioxidative activities such as glutathione compared to sleep-deprived rats. On the basis of these results, our findings suggest that Punica granatum prevents impairment of body functions induced by sleep deprivation and related oxidative damage.
Effect of Reaction Time on Optical Properties of CsPbBr₃ Perovskite Nanocrystals
Sung Hun Kim,Yong-Ryun Jo,Yong Bin Kim,Ju Seok Kim,Sang-Youp Yim,Hong Seok Lee 한국진공학회(ASCT) 2021 Applied Science and Convergence Technology Vol.30 No.5
We have studied the optical and structural properties of CsPbBr₃ perovskite nanocrystals (NCs) fabricated with various reaction times. The temporal evolution of the ensemble optical properties, such as absorption and fluorescence (FL) spectra and photoluminescence quantum yield (PLQY), was recorded under a set reaction temperature (170 ℃) and various amounts of time (5 s – 60 min). The FL intensity of the CsPbBr₃ NCs gradually decreased with increasing reaction time, and the observed PLQY of the CsPbBr₃ NCs ranged from less than 20% up to 35% because of the enlarged crystal size and the induced charge trap states. The FL peaks of as-obtained CsPbBr₃ NCs were tuned in the range of 516.8 to 526.8 nm with increasing reaction time as a result of the ripening phenomenon. Transmission electron microscopy and selected area electron diffraction analysis were performed to analyze the structural properties. The results revealed that the average edge length of CsPbBr₃ NCs with a reaction time of 5 s was 13.4 nm and confirmed that the cubic crystal structure was well ordered.
Lee, Sang Ho,Jo, Yong-Ryun,Noh, Yuseong,Kim, Bong-Joong,Kim, Won Bae Elsevier 2017 Journal of Power Sources Vol.367 No.-
<P><B>Abstract</B></P> <P>This paper reports hierarchically branched structures of tin dioxide nanowires for use in electrochemical energy conversion and storage electrode systems. The shallow tin dioxide branches are epitaxially grown on the tin dioxide nanowire backbones that are directly formed on current collectors. The branched tin dioxide nanowires are applied as anode electrodes for lithium-ion batteries, while palladium-incorporated branched nanowires are utilized as electrocatalysts for ethanol electrooxidation reactions. The structural benefits of these hierarchical platforms, such as enlarged electrochemical active surface area, void space formed between the branched structures, and conformal contact of the electroactive materials with current collectors, play important roles in improving the electrochemical Li-ion storage as well as electrocatalytic activity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hierarchically branched SnO<SUB>2</SUB> nanowires are proposed as new electrode platforms. </LI> <LI> Superior performances exhibited in applied energy conversion and storage systems. </LI> <LI> Structural advantages of the branched electrode led to the improved performances. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Lee, Seungchul,Song, Jaesun,Jo, Yong-Ryun,Choi, Kyoung Soon,Lee, Jongmin,Seo, Sehun,Kim, Taemin Ludvic,Jang, Ho Won,Jeon, Cheolho,Kim, Bong-Joong,Kim, Bongjae,Lee, Sanghan American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.47
<P>Nonequilibrium deposition is a remarkable method for the in situ growth of unique nanostructures and phases for the functionalization of thin films. We introduce a distinctive structure of a mixed-phase, composed of BiVO<SUB>4</SUB> and β-Bi<SUB>2</SUB>O<SUB>3</SUB>, for photoelectrochemical water splitting. The mixed-phase is fabricated via nonequilibrium deposition by adjusted oxygen partial pressure. According to density functional theory calculations, we find that vanadium exsolution can be facilitated by introducing oxygen vacancies, enabling the fabrication of a nanostructured mixed-phase. These unique structures enhance charge migration by increasing the interfacial area and properly aligning the band offset between two crystalline phases. Consequently, the photocurrent density of the nanostructured mixed-phase thin films is about twice that of pristine BiVO<SUB>4</SUB> thin films at 1.23 V<SUB>RHE</SUB>. Our work suggests that nonequilibrium deposition provides an innovative route for the structural engineering of photoelectrodes for the understanding of fundamental properties and improving the photocatalytic performance for solar water splitting.</P> [FIG OMISSION]</BR>