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Precise control of surface oxygen vacancies in ZnO nanoparticles for extremely high acetone sensing response

Journal of Advanced Ceramics 2022年第5期11卷 769-783页

作者： Jihyun LEE Youngmoon choi Byoung Joon PARK Jeong woo HAN Hyun-Sook LEE Jong Hyeok PARK wooyoung LEE Department of Materials Science and Engineering Yonsei UniversitySeoul 03722Republic of Korea Department of Chemical and Biological Engineering Yonsei UniversitySeoul 03722Republic of Korea Department of Chemical Engineering Pohang University of Science and TechnologyPohang 37673Republic of Korea Institute for Convergence Research and Education in Advanced Technology Yonsei UniversitySeoul 03722Republic of Korea

ZnO has been studied intensely for chemical sensors due to its high sensitivity and fast ***,we present a simple approach to precisely control oxygen vacancy contents to provide significantly enhanced acetone sensing performance of commercial ZnO nanopowders.A combination of H_(2)O_(2)treatment and thermal annealing produces optimal surface defects with oxygen vacancies on the ZnO nanoparticles(NPs).The highest response of~27,562 was achieved for 10 ppm acetone in 0.125 MH_(2)O_(2)treated/annealed ZnO NPs at the optimal working temperature of 400℃,which is significantly higher than that of reported so far in various acetone sensors based on metal oxide semiconductors(MOSs).Furthermore,first-principles calculations indicate that pre-adsorbed O formed on the surface of H_(2)O_(2)treated ZnO NPs can provide favorable adsorption energy,especially for acetone detection,due to strong bidentate bonding between carbonyl C atom of acetone molecules and pre-adsorbed O on the ZnO *** study demonstrates that controlling surface oxygen vacancies by H_(2)O_(2)treatment and re-annealing at optimal temperature is an effective method to improve the sensing properties of commercial MOS materials.

关键词： gas sensors acetone metal oxide semiconductors(MOSs) ZnO nanoparticles(NPs) H_(2)O_(2)treatment

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Effects of methionine supplementation in a reduced protein diet on growth performance, oxidative status, intestinal health, oocyst shedding, and methionine and folate metabolism in broilers under Eimeria challenge

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Journal of Animal Science and Biotechnology 2024年第5期15卷 1951-1979页

作者： Guanchen Liu Venkata Sesha Reddy Choppa Milan Kumar Sharma Hanseo Ko Janghan choi woo Kyun Kim Department of Poultry Science University of GeorgiaAthensGA 30602USA

Background This study investigated effects of different methionine(Met)supplementation levels in a reduced protein diet on growth performance,intestinal health,and different physiological parameters in broilers under Eimeria challenge.A total of 600 fourteen-day-old Cobb500 male broilers were challenged with ***,***,and ***,and randomly allocated in a 2×5 factorial *** received normal protein diets(20%crude protein,NCP)or reduced protein diets(17%crude protein,LCP),containing 2.8,4.4,6.0,7.6,and 9.2 g/kg of *** On 6 and 9 days post inoculation(DPI),increasing Met level linearly improved the growth performance(P<0.05).Total oocyst shedding linearly increased as Met level increased(P<0.05).Duodenal villus height(VH):crypt depth(CD)in the LCP groups were higher on 6 DPI(P<0.01)while lower on 9 DPI(P<0.05)compared to the NCP *** CD and duodenal VH:CD changed quadratically as Met level increased(P<0.05).On 6 DPI,liver glutathione(GSH)and glutathione disulfide(GSSG)linearly increased as Met level increased(P<0.05).On 9 DPI,GSSG quadratically increased,whereas GSH:GSSG quadratically decreased as Met levels increased(P<0.05).The expression of amino acid transporters linearly decreased as Met level increased(P<0.05).The expression of zonula occludens 2 and claudin-1 linearly increased on 6 DPI whereas decreased on 9 DPI as Met level increased(P<0.05).The expressions of cytokines were lower in the LCP groups than the NCP groups(P<0.05).Interaction effects were found for the expression of IL-10 and TNFαon 6 DPI(P<0.05),where it only changed quadratically in the NCP group as Met level *** expression of Met and folate metabolism genes were lower in the LCP groups than the NCP groups on 9 DPI(P<0.05).The expression of these genes linearly or quadratically decreased as Met level increased(P<0.05).Conclusion These results revealed the regulatory roles of Met in different physiological parameters including oxidative stat

关键词： Broiler Coccidiosis Eimeria Intestinal health Methionine

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Estimating the instantaneous reproduction number(R_(t))by using particle filter

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Infectious Disease Modelling 2023年第4期8卷 1002-1014页

作者： Yong Sul Won woo-Sik Son Sunhwa choi Jong-Hoon Kim National Institute for Mathematical Sciences DaejeonSouth Korea International Vaccine Institute SeoulSouth Korea

Background:Monitoring the transmission of coronavirus disease 2019(COVID-19)requires accurate estimation of the effective reproduction number(Rt).However,existing methods for calculating Rt may yield biased estimates if important real-world factors,such as delays in confirmation,pre-symptomatic transmissions,or imperfect data observation,are not ***:To include real-world factors,we expanded the susceptible-exposed-infectiousrecovered(SEIR)model by incorporating pre-symptomatic(P)and asymptomatic(A)states,creating the SEPIAR *** utilizing both stochastic and deterministic versions of the model,and incorporating predetermined time series of Rt,we generated simulated datasets that simulate real-world challenges in estimating *** then compared the performance of our proposed particle filtering method for estimating Rt with the existing EpiEstim approach based on renewal ***:The particle filtering method accurately estimated Rt even in the presence of data with delays,pre-symptomatic transmission,and imperfect *** evaluating via the root mean square error(RMSE)metric,the performance of the particle filtering method was better in general and was comparable to the EpiEstim approach if perfectly deconvolved infection time series were provided,and substantially better when Rt exhibited short-term fluctuations and the data was right ***:The SEPIAR model,in conjunction with the particle filtering method,offers a reliable tool for predicting the transmission trend of COVID-19 and assessing the impact of intervention *** approach enables enhanced monitoring of COVID-19 transmission and can inform public health policies aimed at controlling the spread of the disease.

关键词： Particle filter Sequential Monte Carlo Effective reproduction number COVID-19 Transmission model Compartment model

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Strain-tunable optical microlens arrays with deformable wrinkles for spatially coordinated image projection on a security substrate

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Microsystems & Nanoengineering 2022年第5期8卷 225-237页

作者： In Sik choi Seongho Park Sangheon Jeon Young woo Kwon Rowoon Park Robert A.Taylor Kwangseuk Kyhm Suck Won Hong Department of Cogno-Mechatronics Engineering Department of Optics and Mechatronics EngineeringPusan National UniversityBusan 46241Republic of Korea Research Center for Dielectric and Advanced Matter Physics Pusan National UniversityBusan 46241Republic of Korea Department of Physics University of OxfordOxford OX13PUUK Department of Nano-Fusion Technology Pusan National UniversityBusan 46241Republic of Korea

As a new concept in materials design,a variety of strategies have been developed to fabricate optical microlens arrays(MLAs)that enable the miniaturization of optical systems on the micro/nanoscale to improve their characteristic performance with unique optical *** this paper,we introduce a cost-effective and facile fabrication process on a large scale up to~15 inches via sequential lithographic methods to produce thin and deformable hexagonally arranged MLAs consisting of polydimethylsiloxane(PDMS).Simple employment of oxygen plasma treatment on the prestrained MLAs effectively harnessed the spontaneous formation of highly uniform nanowrinkled structures all over the surface of the elastomeric *** strain-controlled tunability,unexpected optical diffraction patterns were characterized by the interference combination effect of the microlens and deformable ***,the hierarchically structured MLAs presented here have the potential to produce desirable spatial arrangements,which may provide easily accessible opportunities to realize microlens-based technology by tunable focal lengths for more advanced micro-optical devices and imaging projection elements on unconventional security substrates.

关键词： projection arrays spatially

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Graphene electrode with tunable charge transport in thin-film transistors

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Nano Research 2018年第1期11卷 274-286页

作者： Ick-Joon Park Tae In Kim In-Tak Cho Chang-woo Song Ji-woong Yang Hongkeun Park woo-Seok Cheong Sung Gap Im Jong-Ho Lee Sung-Yool choi School of Electrical Engineering GrapheneY2D Materials Research Center Korea Advanced Institute of Science and Technology (KAIST) Daejeon 34141 Republic of Korea Department of Electrical Engineering Seoul National University Seou108826 Republic of Korea Electronics and Telecommunications Research Institute Daejeon 34129 Republic of Korea Department of Chemical and Biomolecular Engineering Graphene/2D Materials Research Center Korea Advanced Institute of Science and Technology (KAIST) Daejeon 34141 Republic of Korea

Graphene, a single atomic layer of sp2-hybridized carbon, has immense potential as a transparent conducting material in electronic applications owing to its superior properties, including optical transparency and high conductivity. Particularly, the tunable work function of graphene enables the integration of graphene electrodes with various electronic devices. To achieve high performance in graphene-based devices, effective charge transport between the graphene electrode and the semiconducting material needs to be optimized; this is closely related to the modulation of the Schottky barrier （SB）. In this study, we investigate the ~nable charge transport properties as a function of graphene doping in n-channel thin-film transistors （TFTs） in terms of the electrical characteristics and low-frequency noise （LFN） behaviors. Alkali metal carbonates tuned the work function of graphene, resulting in a dramatic decrease in the SB and an improvement of the carrier injection in n-channel TFTs. The electrical performance of the TFTs was evaluated by extraction of the field-effect mobilities and ratio of contact resistance to total resistance. Furthermore, the level of contact noise created by the barrier height fluctuation and relative contribution of channel noise and contact noise in the TFTs was investigated by LFN measurements to demonstrate the ~nable charge transport. Our findings therefore provide new insights into the tunable charge transport mechanism in graphene-based devices and reveal the immense potential of graphene as electrodes in high performance flexible and transparent displays.

关键词： charge transport graphene doping Schottky barrier work function contact property low-frequency noise

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Deep learning for development of organic optoelectronic devices:efficient prescreening of hosts and emitters in deep-blue fluorescent OLEDs

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npj Computational Materials 2022年第1期8卷 1406-1416页

作者： Minseok Jeong Joonyoung F.Joung Jinhyo Hwang Minhi Han Chang woo Koh Dong Hoon choi Sungnam Park Department of Chemistry and Research Institute for Natural Science Korea UniversitySeoul02841Korea

The highest occupied molecular orbital(HOMO)and lowest unoccupied molecular orbital(LUMO)energies,which are key factors in optoelectronic devices,must be accurately estimated for newly designed ***,we developed a deep learning(DL)model that was trained with an experimental database containing the HOMO and LUMO energies of 3026 organic molecules in solvents or solids and was capable of predicting the HOMO and LUMO energies of molecules with the mean absolute errors of 0.058 ***,we demonstrated that our DL model was efficiently used to virtually screen optimal host and emitter molecules for organic light-emitting diodes(OLEDs).Deep-blue fluorescent OLEDs,which were fabricated with emitter and host molecules selected via DL prediction,exhibited narrow emission(bandwidth=36 nm)at 412 nm and an external quantum efficiency of 6.58%.Our DL-assisted virtual screening method can be further applied to the development of component materials in optoelectronics.

关键词： emitter optoelectronic OLEDs

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Formation of spherical alloy microparticles in a porous salt medium

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Journal of Materials Science & Technology 2020年第8期36卷 189-196页

作者： Hayk HNersisyan Suk Cheol Kwon Vladislav E.Ri Wan Bae Kim woo Seok choi Jong Hyeon Lee RASOM Chungnam National University99 Daehak-roYuseong-guDaejeon 34134Republic of Korea Graduate School of Materials Science and Engineering Chungnam National University99 Daehak-roYuseong-guDaejeon 34134Republic of Korea

This study describes the development of a one-pot strategy to produce spherical alloy microparticles for advanced near-net-shape manufacturing processes, including additive manufacturing and powder injection molding. The Al Si12 eutectic alloy(ca. 12 wt% Si) system was chosen as the model with which the main experiments were carried out. The proposed process synergistically integrates a few common,low-cost processing techniques including the mixing of Al micrometer size particles with silicon and sodium chloride, heat-treating the mixture at temperatures of 650–810°C, and the dissolution of salt in water to produce spherical Al Si12 alloy particles without the need to rely on costly melting and atomizing techniques. This new process can use laow-cost source Al and Si powders as the raw materials to produce10–200 um-sized spherical particles of Al Si12. The Ansys-CFX computational fluid dynamics software was used to analyze the flow behavior of Al Si12 liquid droplets and particle size refinement in the narrow voids of the sample.

关键词： AlSi(12)alloy Morphology evaluation Particle distribution Simulation Solid-liquid transition Spheroidization

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Generation of tumor spheroids using a droplet-based microfluidic device for photothermal therapy

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Microsystems & Nanoengineering 2020年第1期6卷 796-805页

作者： Jong Min Lee Ji wook choi Christian D.Ahrberg Hyung woo choi Jang Ho Ha Seok Gyu Mun Sung Joon Mo Bong Geun Chung Department of Mechanical Engineering Sogang UniversitySeoulKorea Division of Chemical Industry Yeungnam University CollegeDaeguRepublic of Korea Research Center Sogang UniversitySeoulKorea Department of Biomedical Engineering Sogang UniversitySeoulKorea

Despite their simplicity,monolayer cell cultures are not able to accurately predict drug behavior in vivo due to their inability to accurately mimic cell-cell and cell-matrix *** contrast,cell spheroids are able to reproduce these interactions and thus would be a viable tool for testing drug ***,the generation of homogenous and reproducible cell spheroids on a large scale is a labor intensive and slow process compared to monolayer cell ***,we present a droplet-based microfluidic device for the automated,large-scale generation of homogenous cell spheroids in a uniform *** the microfluidic system,the size of the spheroids can be tuned to between 100 and 130μm with generation frequencies of 70 *** demonstrated the photothermal therapy(PTT)application of brain tumor spheroids generated by the microfluidic device using a reduced graphene oxide-branched polyethyleneimine-polyethylene glycol(rGO-BPEI-PEG)nanocomposite as the PTT ***,we generated uniformly sized neural stem cell(NSC)-derived neurospheres in the droplet-based microfluidic *** also confirmed that the neurites were regulated by ***,this droplet-based microfluidic device could be a powerful tool for photothermal therapy and drug screening applications.

关键词： fluid viable simplicity

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Influence of the h TERT rs2736100 polymorphism on telomere length in gastric cancer

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World Journal of Gastroenterology 2015年第31期21卷 9328-9336页

作者： Byung Joon choi Jung Hwan Yoon Olga Kim Won Suk choi Suk woo Nam Jung Young Lee Won Sang Park Department of Pediatrics College of MedicineThe Catholic University of Korea Department of Pathology College of MedicineThe Catholic University of Korea Functional Rnomics Research Center College of MedicineThe Catholic University of Korea

AIM: To investigate the functional consequences of rs2736100 polymorphism in telomere length and examine its link to gastric cancer ***: Telomere length and human telomerase reverse transcriptase(h TERT) m RNA expression were measured in 35 gastric cancer tissues and 5 cell lines and correlated to rs2736100 polymorphism. The relationship between rs2736100 polymorphism and the risk of gastric cancer were examined in 243 gastric cancer patients and 246 healthy ***: The rs2736100 A allele carrier is closely associated with reduced h TERT m RNA expression and shortened telomere length in gastric cancer tissue and cell lines. When gastric cancers were stratified by histological subtype,telomere length and h TERT m RNA levels were significantly increased in those with the C/C genotype in intestinal-type gastric cancer,but not in diffuse-type gastric cancer. Interestingly,there was no significant difference in the genotype and allele frequencies of the rs2736100 polymorphism between the patients with gastric cancer and healthy ***: The rs2736100 polymorphism of the h TERT gene is involved in the regulation of h TERT expression and telomere length,but not in the risk of gastric cancer.

关键词： Human telomerase reverse transcriptase Telomere Ga

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Preclinical Long-term Magnetic Resonance Imaging Study of Silymarin Liver-protective Effects

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Journal of Clinical and Translational Hepatology 2022年第6期10卷 1167-1175页

作者： Yeon Ji Chae Hwon Heo Chul-woong woo Sang-Tae Kim Jae-Im Kwon Monica Young choi Yu Sub Sung Kyung Won Kim Jeong Kon Kim Yoonseok choi Dong-Cheol woo Department of Convergence Medicine Asan Medical CenterUniversity of Ulsan College of MedicineSeoulRepublic of Korea Convergence Medicine Research Center Asan Institute for Life SciencesAsan Medical CenterSeoulRepublic of Korea Clinical Research Center Asan Medical CenterSeoulRepublic of Korea Department of Radiology Asan Medical CenterUniversity of Ulsan College of MedicineSeoulRepublic of Korea Medical Research Institute Gangneung Asan HospitalGangneung-siGangwon-doRepublic of Korea

Background and Aims:Efficacy evaluations with preclini-cal magnetic resonance imaging(MRI)are uncommon,but MRI in the preclinical phase of drug development provides information that is useful for longitudinal *** study aim was to monitor the protective effectiveness of silymarin with multiparameter MRI and biomarkers in a thioacetamide(TAA)-induced model of liver injury in *** analysis was conducted to assess compare the monitoring of liver function by MRI and ***-ods:TAA was injected three times a week for 8 weeks to generate a disease model(TAA group).In the TAA and sily-marin-treated(TAA-SY)groups,silymarin was administered three times weekly from week *** images were acquired at 0,2,4,6,and 8 weeks in the control,TAA,and TAA-SY ***:The area under the curve to maximum time(AUCtmax)and T_(2)*values of the TAA group decreased over the study period,but the serological markers of liver abnormality increased significantly more than those in the control *** the TAA-SY group,MRI and serological biomarkers indicated attenuation of liver function as in the TAA ***,pattern changes were observed from week 6 to comparable levels in the control group with si-lymarin *** correlations between either AUCtmax or T_(2)*values and the serological biomarkers were ***:Silymarin had hepatoprotective effects on TAA-induced liver injury and demonstrated the usefulness of multiparametric MRI to evaluate efficacy in preclinical studies of liver drug development.

关键词： Liver fibrosis Magnetic resonance imaging Silymarin T1-weight-ed dynamic contrast-enhanced T_(2)*

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