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Electric modulation of conduction in multiferroic Ca-doped BiFeO<sub>3</sub> films
Yang, C.-H.,Seidel, J.,Kim, S. Y.,Rossen, P. B.,Yu, P.,Gajek, M.,Chu, Y. H.,Martin, L. W.,Holcomb, M. B.,He, Q.,Maksymovych, P.,Balke, N.,Kalinin, S. V.,Baddorf, A. P.,Basu, S. R.,Scullin, M. L.,Rames Nature Publishing Group 2009 Nature materials Vol.8 No.6
Many interesting materials phenomena such as the emergence of high-Tc superconductivity in the cuprates and colossal magnetoresistance in the manganites arise out of a doping-driven competition between energetically similar ground states. Doped multiferroics present a tantalizing evolution of this generic concept of phase competition. Here, we present the observation of an electronic conductor–insulator transition by control of band-filling in the model antiferromagnetic ferroelectric BiFeO<SUB>3</SUB> through Ca doping. Application of electric field enables us to control and manipulate this electronic transition to the extent that a p–n junction can be created, erased and inverted in this material. A ‘dome-like’ feature in the doping dependence of the ferroelectric transition is observed around a Ca concentration of ∼1/8, where a new pseudo-tetragonal phase appears and the electric modulation of conduction is optimized. Possible mechanisms for the observed effects are discussed on the basis of the interplay of ionic and electronic conduction. This observation opens the door to merging magnetoelectrics and magnetoelectronics at room temperature by combining electronic conduction with electric and magnetic degrees of freedom already present in the multiferroic BiFeO<SUB>3</SUB>.
Interface control of bulk ferroelectric polarization.
Yu, P,Luo, W,Yi, D,Zhang, J X,Rossell, M D,Yang, C-H,You, L,Singh-Bhalla, G,Yang, S Y,He, Q,Ramasse, Q M,Erni, R,Martin, L W,Chu, Y H,Pantelides, S T,Pennycook, S J,Ramesh, R National Academy of Sciences 2012 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.109 No.25
<P>The control of material interfaces at the atomic level has led to novel interfacial properties and functionalities. In particular, the study of polar discontinuities at interfaces between complex oxides lies at the frontier of modern condensed matter research. Here we employ a combination of experimental measurements and theoretical calculations to demonstrate the control of a bulk property, namely ferroelectric polarization, of a heteroepitaxial bilayer by precise atomic-scale interface engineering. More specifically, the control is achieved by exploiting the interfacial valence mismatch to influence the electrostatic potential step across the interface, which manifests itself as the biased-voltage in ferroelectric hysteresis loops and determines the ferroelectric state. A broad study of diverse systems comprising different ferroelectrics and conducting perovskite underlayers extends the generality of this phenomenon.</P>
The effect of surfactant on SrTiO3 particles synthesized by a microwave hydrothermal method
H. Y. He,W. P. Lao,J. F. Huang 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.4
SrTiO3 particles with different morphologies were successfully synthesized by a microwave hydrothermal method. The effect of different surfactants on the morphology, the crystal structure and the optical property of particles were investigated. Polyvinyl alcohol-derived particles had a rodlike morphology, a large ratio of c/a > 1 and small band gap energy (2.60 eV). Polyethylene glycol-derived particles had a shorter rodlike morphology, smaller ratio of c/a > 1 and a bigger band gap energy (3.25 eV). In contrast, the carboxymethyl cellulose-derived particles had a platelike morphology, a small ratio of c/a ~1, and a broad band gap (3.34 eV). Raman analysis revealed that the either polyethylene glycol- or polyvinyl alcohol-derived SrTiO3particles were tetragonal, while another particle was cubic.
He, X.,Bonaparte, N.,Kim, S.,Acharya, B.,Lee, J.Y.,Chi, L.,Lee, H.J.,Paik, Y.K.,Moon, P.G.,Baek, M.C.,Lee, E.K.,Kim, J.H.,Kim, I.S.,Lee, B.H. Elsevier Science Publishers 2012 Journal of controlled release Vol.162 No.3
Chemotherapy-induced apoptosis of tumor cells enhances the antigen presentation and sensitizes tumor cells to T cell-mediated cytotoxicity. Here we harnessed the apoptosis of tumor cells as a homing signal for the delivery of T cells to tumor. Jurkat T cells were anchored with ApoPep-1, an apoptosis-targeted peptide ligand, using the biocompatible anchor for membrane (BAM), an oleyl acid derivative. The ApoPep-1-BAM conjugate was efficiently anchored to cell membrane, while little anchoring was obtained with ApoPep-1 alone. The retention period of the ApoPep-1-BAM conjugate on cell membrane was approximately 80 and 40min in the absence and presence of serum, respectively. ApoPep-1 was resistant to degradation in serum until 2h. The apoptosis-targeted T cells that were anchored with the ApoPep-1-BAM preferentially bound to apoptotic tumor cells over living cells. When intravenously injected into tumor-bearing mice, the number of apoptosis-targeted T cells and in vivo fluorescence signals by the homing of the cells to doxorubicin-treated tumor were higher than those of untargeted T cells. Accumulation of apoptosis-targeted T cells at other organs such as liver was not detected. These results suggest that the chemotherapy-induced apoptosis and subsequent enhancement of T cell delivery to tumor by the membrane anchoring of the apoptosis-targeted peptide could be a novel strategy for cancer immunotherapy.
He, P.,Li, Y.,Park, J.H. Pergamon Press [etc.] 2016 Journal of the Franklin Institute Vol.353 No.1
<P>This paper investigates the leader-following tracking consensus problem for high-order nonlinear dynamical multi-agent systems with switching topology and communication delay under noisy environments. In order to reflect a more realistic situation, we introduce a general multi-agent systems model and also further investigate its robust consensus under noisy environments, the topology of the network is assumed to be in a finite set of arbitrarily stochastic switching, the communication delay is also considered in the tracking control protocols. The mean square consensus sufficient conditions of multi-agent systems are explored via the common stochastic Lyapunov functional stability theory, in other words, can be solved by linear matrix inequality schemes. The mean square consensus condition is derived to provide a rigorous condition for leader-following of high-order nonlinear dynamical multi-agent systems with considerable scale. In particular, we prove that the proposed algorithm is robust against the bounded communication delay in noisy environments. On the other hand, when it involves many multi-agent systems, a more conservative but effective consensus protocol is also raised. The consensus protocols only require low-dimensional matrices, which are independent of the network size. In addition, the consensus criteria of two cases without communication delay or noisy environment are also proposed. A simple optimization program is also developed to determine the maximum allowable communication delay. Finally, in order to demonstrate the effectiveness and feasibility of the consensus protocol obtained in this paper, the numerical examples are given. (C) 2015 Published by Elsevier Ltd. on behalf of The Franklin Institute</P>
Shrestha, H.,Yuan, T.,He, Y.,Moon, P.G.,Shrestha, N.,Ryu, T.,Park, S.Y.,Cho, Y.C.,Lee, C.H.,Baek, M.C.,Cho, S.,Simkhada, S.,Kim, H.,Kim, K. Elsevier Biomedical Press 2016 Biochimica et biophysica acta, Molecular cell rese Vol.1863 No.9
Ubiquitination, a post-translational modification, involves the covalent attachment of ubiquitin to the target protein. The ubiquitin-proteasome pathway and the endosome-lysosome pathway control the degradation of the majority of eukaryotic proteins. Our previous study illustrated that δ-catenin ubiquitination occurs in a glycogen synthase kinase-3 (GSK-3) phosphorylation-dependent manner. However, the molecular mechanism of δ-catenin ubiquitination is still unknown. Here, we show that the lysine residues required for ubiquitination are located mainly in the C-terminal portion of δ-catenin. In addition, we provide evidence that β-TrCP-1 interacts with δ-catenin and functions as an E3 ligase, mediating δ-catenin ubiquitin-proteasome degradation. Furthermore, we prove that both the ubiquitin-proteasome pathway and the lysosome degradation pathway are involved in δ-catenin degradation. Our novel findings on the mechanism of δ-catenin ubiquitination will add a new perspective to δ-catenin degradation and the effects of δ-catenin on E-cadherin involved in epithelial cell-cell adhesion, which is implicated in prostate cancer progression.
L. P. Zhu,X. Q. Gu,H. P. He,F. Huang,M. X. Qiu,Z. Z. Ye,Y. Z. Zhang,B. H. Zhao 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5
A ZnO/Zn0.85Mg0.15O single quantum well (SQW) was fabricated on a Si(111) substrate by using a pulsed laser deposition (PLD) technique. Photoluminescence (PL) measurements were carried out in the range of 10 − 290 K in order to investigate the mechanism of carrier dynamics. At 10 K, the sample exhibited two predominant ultraviolet emissions, one at 3.57 eV and the other at 3.38 eV, which were attributed to recombinations of localized excitons (LE band) in the barrier and the well layers, respectively. The quantum well emission showed a blue shift of nearly 20 meV with respect to the epitaxial ZnO films. We also observed that the carrier localization resulted in an “S-shaped” red-blue-red shift of the ∽3.38 eV emission with increasing temperature. A ZnO/Zn0.85Mg0.15O single quantum well (SQW) was fabricated on a Si(111) substrate by using a pulsed laser deposition (PLD) technique. Photoluminescence (PL) measurements were carried out in the range of 10 − 290 K in order to investigate the mechanism of carrier dynamics. At 10 K, the sample exhibited two predominant ultraviolet emissions, one at 3.57 eV and the other at 3.38 eV, which were attributed to recombinations of localized excitons (LE band) in the barrier and the well layers, respectively. The quantum well emission showed a blue shift of nearly 20 meV with respect to the epitaxial ZnO films. We also observed that the carrier localization resulted in an “S-shaped” red-blue-red shift of the ∽3.38 eV emission with increasing temperature.
적층된 Inconel 625 의 기계적 표면강화처리에 따른 수소취화 특성 분석
백승호(S. H. Baek),허산산(S. S. He),박준필(J. P. Park),장문석(M. S. Jang),백동현(D. H. Back),이동훈(D. H. Lee),이재선(J. S. Lee),박상후(S. H. Park) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월
지구온난화, 이상기후 등 환경오염의 부정적인 영향으로 인하여 화석에너지를 대체하기 위한 수소 에너지에 대한 관심이 높아지고 있으며, 자동차, 저장용기 등 산업 각계에서 수소를 사용하기 위한 기초기술개발이 요구되고 있다. 그러나 금속이 수소에 노출될 경우 수소 취성을 정도의 차이만 있을 뿐 필연적이며, 수소취성으로 인하여 금속 재료의 연성이 감소하기 때문에 현재 수소환경에서 금속 재료의 사용은 제한이 많은 상태이다. 이러한 문제를 해결하기 위하여 본 연구에서는 적층 제조와 기계적 표면 강화를 이용한 표면처리 방법인 UNSM (Ultrasonic Nanocrystal Surface Modification)을 이용하여 수소취화를 억제하고자 하였다. UNSM 이란, 초음파로 진동하는 혼을 이용하여 소재의 표면을 타격하여 표면을 강화하는 공정으로, 표면조도 개선, 결정구조 미세화, 표면 경도 증가 등의 효과가 있다. 특히, 결정구조 미세화는 수소분자의 침투를 억제하여 수소취화를 방지할 수 있다. 구체적으로 본 연구에서는 기계가공 및 적층제조된 Inconel 625 소재에 UNSM 표면처리를 한 후 한국 가스안전공사의 가스 수소 장입장치를 이용하여 수소압 70 MPa 환경에서 2 주간 수소를 장입하였을 때의 수소취성 특성을 SSRT (Slow Strain Rate Test) 실험, 마이크로 경도, SEM, 파단면 문석등을 이용하여 비교하였다. 결과적으로 UNSM 표면처리를 수행할 경우 기계 가공한 시편의 경우 강도가 2, 연성이 8% 증가하였으며, 적층제조된 시편에 대해서는 강도가 1%, 연성이 3% 증가하는 등 UNSM 표면처리가 수소취화 억제에 효과가 있음을 확인하였다. 향후 수소취화량에 따른 UNSM 처리의 효과 및 수소취화 상태에서의 다양한 물성들을 확인하고 이를 기계부품 설계에 적용할 예정이다.
Fungal diversity notes 603-708: taxonomic and phylogenetic notes on genera and species
Hyde, Kevin D.,Norphanphoun, Chada,Abreu, Vanessa P.,Bazzicalupo, Anna,Thilini Chethana, K. W.,Clericuzio, Marco,Dayarathne, Monika C.,Dissanayake, Asha J.,Ekanayaka, Anusha H.,He, Mao-Qiang,Hongsanan Springer Netherlands 2017 FUNGAL DIVERSITY Vol. No.
<P>We introduce the new basidiomycete species Agaricus purpurlesquameus, Agaricus rufusfibrillosus, Lactifluus holophyllus, Lactifluus luteolamellatus, Lactifluus pseudohygrophoroides, Russula benwooii, Russula hypofragilis, Russula obscurozelleri, Russula parapallens, Russula phoenicea, Russula pseudopelargonia, Russula pseudotsugarum, Russula rhodocephala, Russula salishensis, Steccherinum amapaense, Tephrocybella constrictospora, Tyromyces amazonicus and Tyromyces angulatus and provide updated trees to the genera. We also introduce Mortierella formicae in Mortierellales, Mucoromycota and provide an updated phylogenetic tree.</P>