Dielectric properties and microstructures of (CaxSr1-x) ZrO3 ceramics

Yu-De Li,Jian-Ming Chen,Ying-Chieh Lee 한양대학교 세라믹연구소 2018 Journal of Ceramic Processing Research Vol.19 No.6

The effects of Ca/Sr ratio and the sintering temperature on the properties of (CaxSr(1-x))ZrO3 (CSZ) ceramics were investigatedin this study. CSZ ceramics were prepared using solid-state reaction process, which were sintered in air at temperaturesranging from 1350 oC to 1450 oC. Their structures were characterized by X-ray Diffraction (XRD), Scanning ElectronMicroscopy (SEM), and Transmission Electron Microscopy (TEM). The change in Ca/Sr ratio significantly affected thecrystalline phase and the dielectric properties of the (CaxSr(1-x))ZrO3 ceramics. The secondary phase, Ca0.15Zr0.85O1.85, wasobserved and increased correspondingly with the rising of sintering temperatures. In order to understand the effects ofsecondary phase on the dielectric properties of CSZ ceramics, the Ca0.15Zr0.85O1.85 phase was prepared individually using solidstatemethod. The Ca0.15Zr0.85O1.85 ceramics sintered at 1500 oC for 2 hours possessed a dielectric constant (εr) of 21.7, adielectric loss (tanδ) of 49.510−4 and an Insulation Resistance (IR) of 2.1 × 1010 Ω. The (Ca0.7Sr0.3)ZrO3 ceramics exhibited thebest dielectric properties, with a permittivity of 29, a dielectric loss (tanδ) of 2.7 × 10−4, and an Insulation Resistance (IR) of2.6 × 1012 Ω.

A study on microstructural and dielectric properties of Ba0.5-xZnxSr0.45Ca0.05TiO3 ceramics

Ying-Chieh Lee,Hui-Ju Hsu,I-Yu Huang,Huei-Jyun Shih,Christian Pithan 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.6

reaction process and sintered at temperatures ranging from 1150 °C to 1250 °C. The properties of these ceramics werefound to be significantly affected by variations in the Zn content. Densification of the BZSCT ceramics was observed to occurat sintering temperatures exceeding 1225 °C. Notably, the crystalline phases and dielectric properties of these ceramics werestrongly influenced by the Zn content. Three distinct secondary phases were identified in the BZSCT ceramics, includingBaZn2.03Ti3.93O10.89, Ba2ZnTi5O13 and Zn2TiO4. The addition of Zn resulted in a shift of the Curie point to lower temperatures. Specifically, with Zn substitution (up to 15 at.%), a Curie point of -60 °C was observed in the BZSCT ceramics. Theseceramics exhibited a high dielectric constant of 1035, a low dielectric loss of 0.017%, and an impressive Q value of 442 whensintered at 1225 °C. Moreover, when comparing the dielectric constants of BZSCT ceramics at 1 MHz and 1 GHz, it wasnoted that the permittivity was only slightly reduced by less than 30% at lower frequencies. In contrast, the permittivity ofBST ceramics decreased significantly, by approximately 70%, at microwave frequencies. These findings highlight the uniqueproperties and potential applications of BZSCT ceramics, particularly in microwave applications where they outperformtraditional BST ceramics.

Longevity, tumor, and physical vitality in rats consuming ginsenoside Rg1

Chao-Chieh Hsieh,Chiung-Yun Chang,Tania Xu Yar Lee,Jinfu Wu,Suchada Saovieng,Yu-Wen Hsieh,Maijian Zhu,Chih-Yang Huang,Chia-Hua Kuo The Korean Society of Ginseng 2023 Journal of Ginseng Research Vol.47 No.2

Background: Effects of the major ginsenoside Rg1 on mammalian longevity and physical vitality are rarely reported. Purpose: To examine longevity, tumor, and spontaneous locomotor activity in rats consuming Rg1. Methods: A total of 138 Wistar rats were randomized into 2 groups: control (N = 69) and Rg1 (N = 69). Rg1 (0.1 mg/kg per day) were orally supplemented from 6 months of age until natural death. Spontaneous mobility was measured by video-tracking together with body composition (dual energy x-ray absorptiometry) and inflammation markers at 5, 14, 21, and 28 months of age. Results: No significant differences in longevity (control: 706 days; Rg1: 651 days, p = 0.77) and tumor incidence (control: 19%; Rg1: 12%, p = 0.24) were observed between the two groups. Movement distance in the control group declined significantly by ~60% at 21 months of age, together with decreased TNF-α (p = 0.01) and increased IL-10 (p = 0.02). However, the movement distance in the Rg1 group was maintained ~50% above the control groups (p = 0.01) at 21 months of age with greater magnitudes of TNF-α decreases and IL-10 increases. Glucose, insulin, and body composition (bone, muscle and fat percentages) were similar for both groups during the entire observation period. Conclusion: The results of the study suggest a delay age-dependent decline in physical vitality during late life by lifelong Rg1 consumption. This improvement is associated with inflammatory modulation. Significant effects of Rg1 on longevity and tumorigenesis were not observed.

Explore the Predictors of Fall Risk Factors for Residents in the Long-Term Care Facility

Hung-Chun Lee,Huei-Ru Lin,Chieh-Yu Liu,Chia-Jung Hsieh,Fang-Wun Cai 한국간호과학회 2015 한국간호과학회 학술대회 Vol.2015 No.10

An Evaluation of WRF Rainfall Forecasts in Taiwan during Three Mei-Yu Seasons from 2008 to 2010

Wang, Chung-Chieh,Chien, Fang-Ching,Paul, Sahana,Lee, Dong-In,Chuang, Π-Yu AMERICAN METEOROLOGICAL SOCIETY 2017 Weather and forecasting Vol.32 No.4

Thermoelectric Properties and Chemical Potential Tuning by K- and Se-Coalloying in (Pb0.5Sn0.5)1-xKxTe0.95Se0.05

Dianta Ginting,Chan-Chieh Lin,Gareoung Kim,Song Yi Back,Bora Won,조현용,Jae Hyun Yun,Hyeon Seob So,Hosun Lee,Byung-Kyu Yu,Sung-Jin Kim,Jong-Soo Rhyee 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.3

Topological crystal insulator (TCI) and topological Dirac semimetals have topologically nontrivial surface and bulk state,respectively. The parent compound of Pb 0.5 Sn 0.5 Te exhibiting TCI band inversion has particle-hole symmetry owing to thegapless Dirac band implying a strong electron–hole bipolar compensation in Seebeck coeffi cient. We recently reported thatweak perturbation of TCI state can enhance thermoelectric performance signifi cantly due to highly dispersive and degeneratedenergy bands. It is a great interest that the further increase of chemical potential has benefi ciary to thermoelectric performancein the vicinity of topological phase transition. Here we investigate the thermoelectric properties of the co-doping eff ect by Kand Se in (Pb 0.5 Sn 0.5 ) 1− x K x Te 0.95 Se 0.05 ( x = 0.0, 0.005, 0.010, 0.015, 0.02) compounds. K-doping increases the band gap from0.15 eV (Pb 0.5 Sn 0.5 Te) to 0.21 eV ( x = 0.05) as well as increasing chemical potential resulting in the suppression of bipolardiff usion eff ect. In spite of the suppression of bipolar diff usion eff ect by K-doping, the power factor in K-doped compoundis decreased signifi cantly than the one of non-doped Pb 0.5 Sn 0.5 Te 0.95 Se 0.05 compound. It indicates that when we increasechemical potential further on the breaking of topological band inversion, the thermoelectric performance is deterioratedbecause the chemical potential resides far from the linear band dispersions which become conventional material. The ZTfor the K-doped (Pb 0.5 Sn 0.5 ) 1− x K x Te 0.95 Se 0.05 is obtained as 0.91 at 750 K for x = 0.017 which is increased as much as 99%comparing to the pristine compound Pb 0.5 Sn 0.5 Te but it is reduced value (51.5%) comparing to those of Pb 0.5 Sn 0.5 Te 0.95 Se 0.05compound. We believe that this research is valuable on the confi rmation that the weak perturbation of topological state andappropriate chemical potential tuning are important criteria in high thermoelectric performance.

A Neuroprotective Action of Quercetin and Apigenin through Inhibiting Aggregation of Aβ and Activation of TRKB Signaling in a Cellular Experiment

Chiu Ya-Jen,Teng Yu-Shan,Chen Chiung-Mei,Sun Ying-Chieh,Hsieh-Li Hsiu Mei,Chang Kuo-Hsuan,Lee-Chen Guey-Jen 한국응용약물학회 2023 Biomolecules & Therapeutics(구 응용약물학회지) Vol.31 No.3

Alzheimer’s disease (AD) is a neurodegenerative disease with progressive memory loss and the cognitive decline. AD is mainly caused by abnormal accumulation of misfolded amyloid β (Aβ), which leads to neurodegeneration via a number of possible mechanisms such as down-regulation of brain-derived neurotrophic factor-tropomyosin-related kinase B (BDNF-TRKB) signaling pathway. 7,8-Dihydroxyflavone (7,8-DHF), a TRKB agonist, has demonstrated potential to enhance BDNF-TRKB pathway in various neurodegenerative diseases. To expand the capacity of flavones as TRKB agonists, two natural flavones quercetin and apigenin, were evaluated. With tryptophan fluorescence quenching assay, we illustrated the direct interaction between quercetin/ apigenin and TRKB extracellular domain. Employing Aβ folding reporter SH-SY5Y cells, we showed that quercetin and apigenin reduced Aβ-aggregation, oxidative stress, caspase-1 and acetylcholinesterase activities, as well as improved the neurite outgrowth. Treatments with quercetin and apigenin increased TRKB Tyr516 and Tyr817 and downstream cAMP-response-element binding protein (CREB) Ser133 to activate transcription of BDNF and BCL2 apoptosis regulator (BCL2), as well as reduced the expression of pro-apoptotic BCL2 associated X protein (BAX). Knockdown of TRKB counteracted the improvement of neurite outgrowth by quercetin and apigenin. Our results demonstrate that quercetin and apigenin are to work likely as a direct agonist on TRKB for their neuroprotective action, strengthening the therapeutic potential of quercetin and apigenin in treating AD.

Virtual Screening and Testing of GSK-3 Inhibitors Using Human SH-SY5Y Cells Expressing Tau Folding Reporter and Mouse Hippocampal Primary Culture under Tau Cytotoxicity

Lin Chih-Hsin,Hsieh Yu-Shao,Sun Ying-Chieh,Huang Wun-Han,Chen Shu-Ling,Weng Zheng-Kui,Lin Te-Hsien,Wu Yih-Ru,Chang Kuo-Hsuan,Huang Hei-Jen,Lee Guan-Chiun,Hsieh-Li Hsiu Mei,Lee-Chen Guey-Jen 한국응용약물학회 2023 Biomolecules & Therapeutics(구 응용약물학회지) Vol.31 No.1

Glycogen synthase kinase-3β (GSK-3β) is an important serine/threonine kinase that implicates in multiple cellular processes and links with the neurodegenerative diseases including Alzheimer’s disease (AD). In this study, structure-based virtual screening was performed to search database for compounds targeting GSK-3β from Enamine’s screening collection. Of the top-ranked compounds, 7 primary hits underwent a luminescent kinase assay and a cell assay using human neuroblastoma SH-SY5Y cells expressing Tau repeat domain (TauRD) with pro-aggregant mutation ΔK280. In the kinase assay for these 7 compounds, residual GSK-3β activities ranged from 36.1% to 90.0% were detected at the IC50 of SB-216763. In the cell assay, only compounds VB-030 and VB-037 reduced Tau aggregation in SH-SY5Y cells expressing ΔK280 TauRD-DsRed folding reporter. In SH-SY5Y cells expressing ΔK280 TauRD, neither VB-030 nor VB-037 increased expression of GSK-3α Ser21 or GSK-3β Ser9. Among extracellular signal-regulated kinase (ERK), AKT serine/threonine kinase 1 (AKT), mitogen-activated protein kinase 14 (P38) and mitogenactivated protein kinase 8 (JNK) which modulate Tau phosphorylation, VB-037 attenuated active phosphorylation of P38 Thr180/ Tyr182, whereas VB-030 had no effect on the phosphorylation status of ERK, AKT, P38 or JNK. However, both VB-030 and VB-037 reduced endogenous Tau phosphorylation at Ser202, Thr231, Ser396 and Ser404 in neuronally differentiated SH-SY5Y expressing ΔK280 TauRD. In addition, VB-030 and VB-037 further improved neuronal survival and/or neurite length and branch in mouse hippocampal primary culture under Tau cytotoxicity. Overall, through inhibiting GSK-3β kinase activity and/or p-P38 (Thr180/Tyr182), both compounds may serve as promising candidates to reduce Tau aggregation/cytotoxicity for AD treatment.

Enhancement of Thermoelectric Performance in Na-Doped Pb_0.6Sn_0.4Te_{0.95-<i>x</i>}Se_<i>x</i>S_0.05 via Breaking the Inversion Symmetry, Band Convergence, and Nanostructuring by Multiple Elements Doping

Ginting, Dianta,Lin, Chan-Chieh,Rathnam, Lydia,Kim, Gareoung,Yun, Jae Hyun,So, Hyeon Seob,Lee, Hosun,Yu, Byung-Kyu,Kim, Sung-Jin,Ahn, Kyunghan,Rhyee, Jong-Soo American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.14

<P>Topological insulators have attracted much interest in topological states of matter featuring unusual electrical conduction behaviors. It has been recently reported that a topological crystalline insulator could exhibit a high thermoelectric performance by breaking its crystal symmetry via chemical doping. Here, we investigate the multiple effects of Na, Se, and S alloying on thermoelectric properties of a topological crystalline insulator Pb<SUB>0.6</SUB>Sn<SUB>0.4</SUB>Te. The Na doping is known to be effective for breaking the crystalline mirror symmetry of Pb<SUB>0.6</SUB>Sn<SUB>0.4</SUB>Te. We demonstrate that simultaneous emergence of band convergence by Se alloying and nanostructuring by S doping enhance the power factor and decrease lattice thermal conductivity, respectively. Remarkably, the high power factor of 22.3 μW cm<SUP>-1</SUP> K<SUP>-2</SUP> at 800 K is achieved for Na 1%-doped Pb<SUB>0.6</SUB>Sn<SUB>0.4</SUB>Te<SUB>0.90</SUB>Se<SUB>0.05</SUB>S<SUB>0.05</SUB> mainly due to a relatively high Seebeck coefficient via band convergence by Se alloying as well as the suppression of bipolar conduction at high temperatures by the increase of energy band gap. Furthermore, the lattice thermal conductivity is significantly suppressed by PbS nanoprecipitates without deteriorating the hole carrier mobility, ranging from 0.80 W m<SUP>-1</SUP> K<SUP>-1</SUP> for Pb<SUB>0.6</SUB>Sn<SUB>0.4</SUB>Te to 0.17 W m<SUP>-1</SUP> K<SUP>-1</SUP> at 300 K for Pb<SUB>0.6</SUB>Sn<SUB>0.4</SUB>Te<SUB>0.85</SUB>Se<SUB>0.10</SUB>S<SUB>0.05</SUB>. As a result, the synergistically combined effects of breaking the crystalline mirror symmetry of topological crystalline insulator, band convergence, and nanostructuring for Pb<SUB>0.6</SUB>Sn<SUB>0.4</SUB>Te<SUB>0.95-<I>x</I></SUB>Se<SUB><I>x</I></SUB>S<SUB>0.05</SUB> (<I>x</I> = 0, 0.05, 0.1, 0.2, and 0.95) give rise to an impressively high <I>ZT</I> of 1.59 at 800 K for <I>x</I> = 0.05. We suggest that the multiple doping in topological crystalline insulators is effective for improving the thermoelectric performance.</P> [FIG OMISSION]</BR>

Theoretical study of the ammonia nitridation rate on an Fe (100) surface: A combined density functional theory and kinetic Monte Carlo study

Yeo, Sang Chul,Lo, Yu Chieh,Li, Ju,Lee, Hyuck Mo American Institute of Physics 2014 The Journal of chemical physics Vol.141 No.13

<P>Ammonia (NH3) nitridation on an Fe surface was studied by combining density functional theory (DFT) and kinetic Monte Carlo (kMC) calculations. A DFT calculation was performed to obtain the energy barriers (Eb) of the relevant elementary processes. The full mechanism of the exact reaction path was divided into five steps (adsorption, dissociation, surface migration, penetration, and diffusion) on an Fe (100) surface pre-covered with nitrogen. The energy barrier (Eb) depended on the N surface coverage. The DFT results were subsequently employed as a database for the kMC simulations. We then evaluated the NH3 nitridation rate on the N pre-covered Fe surface. To determine the conditions necessary for a rapid NH3 nitridation rate, the eight reaction events were considered in the kMC simulations: adsorption, desorption, dissociation, reverse dissociation, surface migration, penetration, reverse penetration, and diffusion. This study provides a real-time-scale simulation of NH3 nitridation influenced by nitrogen surface coverage that allowed us to theoretically determine a nitrogen coverage (0.56?ML) suitable for rapid NH3 nitridation. In this way, we were able to reveal the coverage dependence of the nitridation reaction using the combined DFT and kMC simulations.</P>