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Effect of microwave irradiation on the electrical and optical properties of SnO2 thin films
No full textWe report the electrical and optical characteristics of SnO2 thin films irradiated by microwaves (MWs) and grown using atomic layer deposition in a commercial MW oven operating at a frequency of 2.45���GHz. The properties of the MW-irradiated SnO2 thin films were compared with those of the as-deposited SnO2 thin films. After MW irradiation, the conductivity and transparency of the thin films were enhanced. In addition, the samples irradiated for 5���min showed optimal carrier concentration, Hall mobility, resistivity, and transmittance values of 1.5���×���1020 cm−3, 4.6���cm2/V���s, 8���×���10−3 Ω���cm, and 95.77%, respectively. The improved properties of the MW-irradiated samples were attributed mainly to the formation of an oxygen vacancy in the SnO2 lattice during MW irradiation. Our results can be applied for the fabrication of pure SnO2-based transparent conductive oxides; these oxides are generally doped with other elements.This research was supported by the National Research Foundation (NRF) funded by the Ministry of Education (2016R1A6A1A03013422). This work was also supported by Nano Material Technology Development Program (2014M3A7B4049367) through the National Research Foundation (NRF) of Korea funded by the Ministry of Science and ICT(MSIT), Korea
Effect of hydrogen peroxide on properties of graphene oxide in Hummers method
No full textAmong the several methods to prepare graphene oxide (GO) from graphite by oxidation, Hummers method has been the most widely used. Since Hummers method was first introduced about 60 years ago, many researches have tried to reveal the effect of each reagent on the final properties of GO. In all Hummers methods including the modified ones, sulfuric acid and potassium permanganate are used for oxidizing graphite and exfoliating oxidized graphite, and water and hydrogen peroxide are used for removing the residual manganese ions. However, the effects of hydrogen peroxide have been sometimes ignored during synthesis since hydrogen peroxide has been understood as simply reducing the residual manganese ions such as permanganate and manganese dioxide. For this reason, the quantity of hydrogen peroxide used for Hummers method varies. Here we demonstrate that the quantity of hydrogen peroxide added in the final stage strongly affects the final properties of GO. Experimental evidence is introduced revealing that chemical decomposition of GO with slight reduction accompanies the addition of hydrogen peroxide. The possible degradation mechanism by hydrogen peroxide in Hummers method is proposed in the last part of this study. (C) 2018 Elsevier Ltd. All rights reserved.This work was supported by the Korea CCS R&D Center (Korea CCS 2020 Project) grant funded by the Korea government (Ministry of Science and ICT) in 2016 (2014M1A8A1049307)
Accelerated Small-World Property of Structural Brain Networks in Preterm Infants at Term-Equivalent Age
No full textBackground: The prediction of neurodevelopmental outcomes in preterm infants is one of the clinical challenges of pediatrics. Despite the recent interest in brain development and white matter connectivity using a network-based analysis, very little is known about the brain network of at term-equivalent age in preterm infants. Objective: We aimed to investigate the structural brain network using diffusion MRI following preterm delivery at term-equivalent age compared with term infants and explored the influence of gestational age (GA) and clinical factors. Method: Diffusion tensor imaging data were acquired prospectively from 55 preterm neonates without apparent brain abnormalities (mean gestational age: 29.43 weeks) and 21 full-term infants at term-equivalent age. The global structural brain networks were produced by probabilistic white matter tractography in combination with the Johns Hopkins University neonate atlas to quantify connectivity between different cortical regions. Results: Compared with full-term infants, preterm infants had significantly lower global efficiency (p = 0.048) and increased small worldness (p = 0.012) after correcting for sex and age at MRI scan. The increased small worldness in the brain network at term-equivalent age was significantly linearly correlated with lower GA after adjusting for sex and the effects of postmenstrual age at MRI scan on the data in preterm infants (beta = -0.020, p = 0.037). In multivariate analysis, infants with chronic lung disease had significantly decreased changes in clustering (p = 0.014) and local efficiency (p = 0.027). Conclusion: The accelerated small worldness in preterm infants suggests that the structural brain network after preterm birth is reorganized in maximizing integrated and segregated processing, implying resilience against prematurity-associated pathology. (c) 2018 S. Karger AG, BaselThis work was supported by a Korean Grant of the National Research Foundation funded by the Korean Government MSIT (NRF-2017-R1C1B5015046) and the research fund of the Hanyang University (HY-2015)
Mismatch Negativity and Cortical Thickness in Patients With Schizophrenia and Bipolar Disorder
No full textIntroduction Mismatch negativity (MMN) is a measure of automatic neurophysiological brain processes for detecting unexpected sensory stimuli. This study investigated MMN reduction in patients with schizophrenia and bipolar disorder and examined whether cortical thickness is associated with MMN, for exploratory purposes.
Methods Electroencephalograms were recorded in 38 patients with schizophrenia, 37 patients with bipolar disorder, and 32 healthy controls (HCs) performing a passive auditory oddball paradigm. All participants underwent T1 structural magnetic resonance imaging scanning to investigate the cortical thickness of MMN-generating regions. Average MMN amplitudes from the frontocentral electrodes were analyzed.
Results Patients with schizophrenia and bipolar disorder exhibited significantly reduced MMN amplitude compared with HCs. In bipolar disorder, we found intermediate MMN amplitude among the groups. Average MMN and cortical thickness of the right superior temporal gyrus (STG) were significantly negatively correlated in patients with schizophrenia. In patients with bipolar disorder, average MMN was significantly correlated with cortical thickness of the left anterior cingulate cortex and the right STG. MMN showed negative correlations with social and occupational functioning in schizophrenia, and with the Korean auditory verbal learning test for delayed recall in bipolar disorder.
Conclusions MMN reduction was associated with cortical thinning in frontal and temporal areas in patients, particularly with an auditory verbal hallucination-related region in schizophrenia and emotion-related regions in bipolar disorder. MMN was associated with functional outcomes in schizophrenia, whereas it was associated with neurocognition in bipolar disorder.This work was supported by a grant from the Korea Science and Engineering Foundation (KOSEF), funded by the Korean government (NRF-2018R1A2A2A05018505), and by the Ministry of Science, ICT & Future Planning (NRF-2015M3C7A1028252)
A novel estimation approach for the solar radiation potential with its complex spatial pattern via machine-learning techniques
No full textAs a clean and sustainable energy resource with lower environmental impact, the Chinese government encourages the application of solar energy system. The global solar radiation on the horizontal surface in the specific site should be investigated in advance so that the solar energy system could be implemented properly and efficiently. However, the monthly average daily solar radiation (MADSR) in China has complex spatial patterns, and its observation stations are still lacking due to the high cost of equipment. To address these challenges, this study aimed to develop a novel estimation approach for the MADSR with its complex spatial pattern over a vast area in China via machine-learning techniques (i.e. a clustering method (k-means) and an advanced case-based reasoning (A-CBR) model). The MADSR and the relevant information were collected from 97 cities in China for 10 years (from 2006 to 2015). The average prediction accuracy of the proposed approach was determined at 93.23%, showing a promising way. The proposed novel approach is expected to be generalized via the interpolation methods (e.g. kriging method in a geographical information system) so that decision-makers (e.g. construction manager or facility manager) can determine the appropriate location, size and form in implementing the solar energy system. (C) 2018 Elsevier Ltd. All rights reserved.This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT; Ministry of Science and ICT) (NRF-2018R1C1B4A02022690)
Increasing myosin light chain 3f (MLC3f) protects against a decline in contractile velocity
No full textDisuse induces adaptations in skeletal muscle, which lead to muscle deterioration. Hindlimb-unloading (HU) is a well-established model to investigate cellular mechanisms responsible for disuse-induced skeletal muscle dysfunction. In myosin heavy chain (MHC) type IIB fibers HU induces a reduction in contraction speed (Vo) and a reduction in the relative myosin light chain 3f (MLC3f) protein content compared with myosin light chain 1f (MLC1f) protein. This study tested the hypothesis that increasing the relative MLC3f protein content via rAd-MLC3f vector delivery would attenuate the HU-induced decline in Vo in single MHC type IIB fibers. Fischer-344 rats were randomly assigned to one of three groups: control, HU for 7 days, and HU for 7 days plus rAd-MLC3f. The semimembranosus muscles were injected with rAd-MLC3f (3.75 x 10(11)-5 x 10(11) ifu/ml) at four days after the initiation of HU. In single MHC type IIB fibers the relative MLC3f content decreased by 25% (12.00 +/- 0.60% to 9.06 +/- 0.66%) and Vo was reduced by 29% (3.22 +/- 0.14fl/s vs. 2.27 +/- 0.08fl/s) with HU compared to the control group. The rAd-MLC3f injection resulted in an increase in the relative MLC3f content (12.26 +/- 1.19%) and a concomitant increase in Vo (2.90 +/- 0.15fl/s) of MHC type IIB fibers. A positive relationship was observed between the percent of MLC3f content and Vo. Maximal isometric force and specific tension were reduced with HU by 49% (741.45 +/- 44.24 mu N to 379.09 +/- 23.77 mu N) and 33% (97.58 +/- 4.25kN/m(2) to 65.05 +/- 2.71kN/m(2)), respectively compared to the control group. The rAd-MLC3f injection did not change the HU-induced decline in force or specific tension. Collectively, these results indicate that rAd-MLC3f injection rescues hindlimb unloading-induced decline in Vo in MHC type IIB single muscle fibers.Funded by LVT, AG017768, National Institute on Aging/National Institutes of Health, https://www.nih.gov.JHK, HY-2016, Hanyang University, http://www.hanyang.ac.kr/web/eng.The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Fe3O4-ZnO Core-Shell Nanoparticles Fabricated by Ultra-Thin Atomic Layer Deposition Technique as a Drug Delivery Vehicle
No full textFe3O4-ZnO nanoparticles with core-shell structures were successfully fabricated by an atomic layer deposition method. The core-shell NPs consisted of superparamagnetic Fe3O4 cores of 100nm average size and conformal ZnO shells of 10nm thickness. The NPs showed a saturation magnetization of 23emu/g, which is suitable for magnetic delivery of the particles. Cytotoxicity testing revealed that the Fe3O4-ZnO NPs have high cell viability (over 90%) after 24h culture. Also, they exhibited a high ibuprofen-loading capacity (640g per mg of the particles) and good release ability (>90% after 72h in simulated body fluid). As a result, the Fe3O4-ZnO nanoparticles with conformal ultra-thin ZnO shell layers are anticipated as promising drug delivery vehicles with acceptable cell viability and high drug loading-release abilities.This work was supported by the Basic Science Research Program (2012R1A6A1029029) through the National Research Foundation of Korea (NRF) funded by the Ministry of Education and the Ministry of Science, ICT and Future Planning
Efficient Perovskite Light-Emitting Diodes using Polycrystalline Core-Shell-Mimicked Nanograins
No full textMaking small nanograins in polycrystalline organic-inorganic halide perovskite (OIHP) films is critical to improving the luminescent efficiency in perovskite light-emitting diodes (PeLEDs). 3D polycrystalline OIHPs have fundamental limitations related to exciton binding energy and exciton diffusion length. At the same time, passivating the defects at the grain boundaries is also critical when the grain size becomes smaller. Molecular additives can be incorporated to shield the nanograins to suppress defects at grain boundaries; however, unevenly distributed molecular additives can cause imbalanced charge distribution and inefficient local defect passivation in polycrystalline OIHP films. Here, a kinetically controlled polycrystalline organic-shielded nanograin (OSN) film with a uniformly distributed organic semiconducting additive (2,2 ',2 ''-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole), TPBI) is developed mimicking core-shell nanoparticles. The OSN film causes improved photophysical and electroluminescent properties with improved light out-coupling by possessing a low refractive index. Finally, highly improved electroluminescent efficiencies of 21.81% ph el(-1) and 87.35 cd A(-1) are achieved with a half-sphere lens and four-time increased half-lifetime in polycrystalline PeLEDs. This strategy to make homogeneous, defect-healed polycrystalline core-shell-mimicked nanograin film with better optical out-coupling will provide a simple and efficient way to make highly efficient perovskite polycrystal films and their optoelectronics devices.This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (Ministry of Science, ICT & Future Planning) (NRF-2016R1A3B1908431)
Forkhead box O1 (FOXO1) controls the migratory response of Toll-like receptor (TLR3)-stimulated human mesenchymal stromalcells
No full textMesenchymal stromal cells (MSCs) can potently regulate the functions of immune cells and are being investigated for the management of inflammatory diseases. Toll-like receptor 3 (TLR3)-stimulated human MSCs (hMSCs) exhibit increased migration and chemotaxis within and toward damaged tissues. However, the regulatory mechanisms underlying these migratory activities are unclear. Therefore, we analyzed the migration capability and gene expression profiles of TLR3-stimulated hMSCs using RNA-Seq, wound healing, and transwell cell migration assay. Along with increased cell migration, the TLR3 stimulation also increased the expression of cytokines, chemokines, and cell migration-related genes. The promoter regions of the latter showed an enrichment of putative motifs for binding the transcription factors forkhead box O1 (FOXO1), FOXO3, NF-kB (NF-kB1), and RELA proto-oncogene and NF-kB subunit. Of note, FOXO1 inhibition by the FOXO1-selective inhibitor AS1842856 significantly reduced both migration and the expression of migration-related genes. In summary, our results indicate that TLR3 stimulation induces hMSC migration through the expression of FOXO1-activated genes. © 2019 American Society for Biochemistry and Molecular Biology Inc. All rights reserved.This work was supported by National Research Foundation of Korea (NRF) Grants 2017M3A9G7073033, 2017R1A2B4012905, and 2011-0030049 (to Y. G. C.) and 2016R1D1A1B04934970 (to K. H. J.) from the Korean govern-ment. The authors declare that they have no conflicts of interest with the contents of this article
Synthetic aperture imaging of contact acoustic nonlinearity to visualize the closing interfaces using tone-burst ultrasonic waves
No full textContact acoustic nonlinearity (CAN) effect was visualized by synthetic aperture focusing technique (SAFT) via a signal-processing method for acoustic nonlinearity imaging. The proposed signal-processing technique, named Synthetic Aperture Imaging of Acoustic Nonlinearity (SAIAN), allows the SAFT to visualize CAN that is difficult to be visualized by linear ultrasonic imaging. Using the SAIAN algorithm, the fundamental and second-order harmonic frequency components are extracted from the tone-burst wave signal and then these component signals are transformed into pulse-like signals. From the pulse-like signals, the CAN parameter signals can be obtained in the form of pulses, which allows CAN to be visualized by SAFT. In order to verify the effectiveness of the SAIAN, the nonlinear ultrasonic measurements using tone-burst waves were conducted to visualize closing interfaces. As a result, CAN effect appeared at partially closed part of a contacting interface in the images of the CAN signals converted by the SAIAN; on the contrary, the CAN feature was not shown in linear ultrasonic images based on the fundamental frequency component. These results support that the SAIAN is a useful signal processing for acoustic nonlinearity visualization that improves the probability of detection of closing interfaces and the accuracy in crack sizing. (C) 2018 Elsevier Ltd. All rights reserved.This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (NRF-2013M2A2A9043241)