Browsing by Issue Date, starting with "2017-08-04"

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Palladium-Catalyzed C-H Bond Activation by Using Iminoquinone as a Directing Group and an Internal Oxidant or a Co-oxidant: Production of Dihydrophenanthridines, Phenanthridines, and Carbazoles
(2017-08-04)
Raju, Selvam
;
Annamalai, Pratheepkumar
;
Chen, Pei-Ling
;
Liu, Yi-Hung
;
Chuang, Shih-Ching
A palladium-catalyzed C-H bond activation reaction, via a redox-neutral pathway, for the preparation of dihydrophenanthridine, phenanthridine, and carbazole derivatives from biaryl 2-iminoquinones is developed. The preinstalled iminoquinone was designed to act as a directing group for ortho C-H activation and an internal oxidant or a co-oxidant. This catalysis proceeded through the following sequence: C-H bond activation, coordination and insertion of activated olefins, beta-hydride elimination, H-shift, insertion, and protonation or beta-hydride elimination. using this method without the addition of external oxidants. In addition, carbazoles can be prepared efficiently by
Rewritable ferroelectric vortex pairs in BiFeO3
(2017-08-04)
Li, Yang
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Jin, Yaming
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Lu, Xiaomei
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Yang, Jan-Chi
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Chu, Ying-Hao
Ferroelectric vortex in multiferroic materials has been considered as a promising alternative to current memory cells for the merit of high storage density. However, the formation of regular natural ferroelectric vortex is difficult, restricting the achievement of vortex memory device. Here, we demonstrated the creation of ferroelectric vortex-antivortex pairs in BiFeO3 thin films by using local electric field. The evolution of the polar vortex structure is studied by piezoresponse force microscopy at nanoscale. The results reveal that the patterns and stability of vortex structures are sensitive to the poling position. Consecutive writing and erasing processes cause no influence on the original domain configuration. The Z4 proper coloring vortex-antivortex network is then analyzed by graph theory, which verifies the rationality of artificial vortex-antivortex pairs. This study paves a foundation for artificial regulation of vortex, which provides a possible pathway for the design and realization of non-volatile vortex memory devices and logical devices.
Structural and spectroscopic characterizations of a new near-UV-converting cyan-emitting RbBaScSi3O9:Eu2+ phosphor with robust thermal performance
(2017-08-05)
Ray, Sudeshna
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Tadge, Prachi
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Dhoble, S. J.
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Nair, Govind B.
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Singh, Akash
To facilitate the next generation of White Light Emitting Diodes (WLEDs) with higher color rendering and warm lighting, the development of inorganic phosphor for efficient conversion of photons from blue/near-UV light to other visible wavelengths is essential. In this regard, we demonstrate a systematic, cost effective, solution-processable, easily scalable and fully controllable synthesis of a series of RbBaScSi3O9:xEu(2+) (x = 0.2, 0.5, 2, 5, 7), a new cyan emitting scandium silicate based phosphor with 79% internal quantum efficiency under n-UV excitation with robust thermal performance. The concept as well as the methodology of using a "Mineral Inspired Approach" emerges as a new blueprint for the rational design of novel phosphor for phosphor converted WLEDs. The structural refinement, electronic structural calculation using "Density Functional Theory", characteristic photoluminescence study, lifetime measurement as well as the thermal quenching properties of the phosphor has been investigated in detail. Owing to the highly efficient cyan emission at lambda(max) similar to 492 nm a full-width at half-maximum of 63 cm(-1) that shows only very low thermal quenching (89.28% relative to the PL intensity at 150 degrees C with respect to that of measured at room temperature), reflects the great potential for the industrial application of this particular phosphor. (C) 2017 Elsevier B.V. All rights reserved.
Fluorescent coumarin-based probe for cysteine and homocysteine with live cell application
(2017-08-05)
Wei, Ling-Fang
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Thirumalaivasan, Natesan
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Liao, Yu-Cheng
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Wu, Shu-Pao
;
應用化學系
Cysteine (Cys) and homocysteine (Hcy) are two of important biological thiols and function as important roles in several biological processes. The development of Cys and Hcy probes will help to explore the functions of biothiols in biological systems. In this work, a new coumarin-based probe AC, containing an acryloyl moiety, was developed for Cys and Hcy detection in cells. Cys and Hcy undergo a nucleophilic addition and subsequent cyclization reaction to remove to the acryloyl group and yield a fluorescent product, 7-hydroxylcomuarin. The probe AC showed good selectivity for cysteine and homocysteine over glutathione and other amino acids and had low detection limits of 65 nM for Cys and 79 nM for Hcy, respectively. Additionally, confocal imaging experiments demonstrated that the probe AC can be applied to visualize Cys and Hcy in living cells. (C) 2017 Elsevier B.V. All rights reserved.
Intermediate-Valence Ytterbium Compound Yb4Ga24Pt9: Synthesis, Crystal Structure, and Physical Properties
(2017-08-07)
Sichevych, Olga
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Prots, Yurii
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Utsumi, Yuki
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Akselrud, Lev
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Schmidt, Marcus
The title compound was synthesized by a reaction of the elemental educts in a corundum crucible at 1200 degrees C under an Ar atmosphere. The excess of Ga used in the initial mixture served as a flux for the subsequent crystal growth at 600 degrees C. The crystal structure of Yb4Ga24Pt9 was determined from single-crystal X-ray diffraction data: new prototype of crystal structure, space group C2/m, Pearson symbol mS74, a = 7.4809(1) angstrom, b = 12.9546(2) angstrom, c = 13.2479(2) angstrom, beta = 100.879(1)degrees, V = 1260.82(6) angstrom(3), R-F = 0.039 for 1781 observed reflections and 107 variable parameters. The structure is described as an ABABB stacking of two slabs with trigonal symmetry and compositions Yb4Ga6 (A) and Ga12Pt6 (B). The hard. X-ray photoelectron spectrum (HAXPES) of Yb4Ga24Pt9 shows both Yb2+ and Yb3+ contributions as evidence of an intermediate valence state of ytterbium The evaluated Yb valence of similar to 2.5 is in good agreement with the results obtained from the magnetic susceptibility measurements. The compound is, a bad metallic conductor.
交大e-News第237期-交大生助「紙飛機計畫」起飛翻譯程式教案供線上下載
(2017-08-07)
國立交通大學秘書室
;
Secretariat
Identifying the miRNA signature associated with survival time in patients with lung adenocarcinoma using miRNA expression profiles
(2017-08-08)
Sathipati, Srinivasulu Yerukala
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Ho, Shinn-Ying
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生物科技學系
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生物資訊及系統生物研究所
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Department of Biological Science and Technology
Lung adenocarcinoma is a multifactorial disease. MicroRNA (miRNA) expression profiles are extensively used for discovering potential theranostic biomarkers of lung cancer. This work proposes an optimized support vector regression (SVR) method called SVR-LUAD to simultaneously identify a set of miRNAs referred to the miRNA signature for estimating the survival time of lung adenocarcinoma patients using their miRNA expression profiles. SVR-LUAD uses an inheritable bi-objective combinatorial genetic algorithm to identify a small set of informative miRNAs cooperating with SVR by maximizing estimation accuracy. SVR-LUAD identified 18 out of 332 miRNAs using 10-fold cross-validation and achieved a correlation coefficient of 0.88 +/- 0.01 and mean absolute error of 0.56 +/- 0.03 year between real and estimated survival time. SVR-LUAD performs well compared to some well-recognized regression methods. The miRNA signature consists of the 18 miRNAs which strongly correlates with lung adenocarcinoma: hsa-let-7f-1, hsa-miR-16-1, hsa-miR-152, hsa-miR-217, hsa-miR-18a, hsa-miR- 193b, hsa-miR-3136, hsa-let-7g, hsa-miR-155, hsa-miR-3199-1, hsa-miR-219-2, hsa-miR-1254, hsa-miR-1291, hsa-miR-192, hsa-miR-3653, hsa-miR-3934, hsa-miR-342, and hsa-miR-141. Gene ontology annotation and pathway analysis of the miRNA signature revealed its biological significance in cancer and cellular pathways. This miRNA signature could aid in the development of novel therapeutic approaches to the treatment of lung adenocarcinoma.
Entanglement-free determination of pretilt angles of twisted nematic liquid-crystal cells by phase measurement
(2017-08-10)
Chiang, Che-Wen
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Lin, Ping-Chun
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Yang, Kei-Hsiung
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光電系統研究所
;
影像與生醫光電研究所
The pretilt angle of a twisted nematic (TN) liquid crystal display has a strong effect on viewing angles and response times of the display as well as shifting the light-leaking disclination lines into the black-matrix area within pixels of a thin-film-transistor driven TN panel for a high contrast ratio. In this Letter, we develop an optical method to determine the TN pretilt angle based on heterodyne measurements of the phase versus the incident angle of a thin TN cell subjected to out-of-plane rotations. We believe that our method of measuring phases has advantages of simpler setup and calculations, better stability, and less sensitive to ambient electromagnetic interference than the commonly used method of measuring intensities.
Nano assembly of N-doped graphene quantum dots anchored Fe3O4/halloysite nanotubes for high performance supercapacitor
(2017-08-10)
Ganganboina, Akhilesh Babu
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Chowdhury, Ankan Dutta
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Doong, Ruey-an
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環境工程研究所
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Institute of Environmental Engineering
The development of robust and low cost electrode materials with superior electrochemical properties has been a subject of focus on energy storage devices. Herein, the development of N-doped graphene quantum dots (N-GQDs) deposited on Fe3O4-halloysite nanotubes (Fe3O4-HNTs) as active anode materials has been established for supercapacitor applications. The Fe3O4 nanoparticles synthesised by coprecipitation have been in-situ deposited on HNT surfaces following by the coating of (3-aminopropyl)-triexthoxysilane to anchor 4-10 nm N-GQDs via the formation of amide linkage. The N-GQD@Fe3O4-HNTs exhibits a high specific capacitance of 418 F g(-1) and maintains good rate capability in neutral electrolyte solutions. In addition, the anode materials show excellent electrochemical performance with energy and power densities of 10.4-29 W h kg(-1) and 0.25-5.2 kW kg(-1), respectively. Such excellent electrochemical features can be attributed to the synergistic contribution from individual components. The Fe3O4-HNTs provide 1-dimensional matrix to shorten the diffusion path of electrons and electrolyte ions as well as to absorb the mechanical stress during cycling along with excess sites for charge storage, while N-GQDs offer abundantly accessible electroactive sites for rapid electrons and electrolyte ions transport as well as enhance electrical conductivity of Fe3O4-HNTs. Results obtained in this study clearly demonstrate that metal oxide-HNTs are promising support to anchor N-GQDs nanomaterials as the high performance anode materials for next generation of energy storage devices with high energy and power densities. (C) 2017 Elsevier Ltd. All rights reserved.
The origin and mitigation of volcano-like morphologies in micron-thick AlGaN/AlN heteroepitaxy
(2017-08-14)
Huang, Chia-Yen
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Chang, Kai-Shiang
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Huang, Cheng-Yao
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Lin, Yun-Hsiang
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Peng, Wei-Chih
We investigated the origin of morphological instability in 2 mu m thick Al0.6Ga0.4N/AlN heteroepitaxy. The primary morphology was driven by the residual epitaxial strain, forming hill-like morphologies via surface diffusion. The secondary morphology was driven by the interaction between the primary morphology and dislocation clusters in the epitaxial layers. The difference in the local growth rate yields volcano-like morphologies centering on deep pits. Insertion of multi-stack superlattice transition layers between AlGaN and GaN effectively suppressed the secondary morphologies by simultaneously pre-relaxing the template and filtering treading dislocations. Published by AIP Publishing.
Direct measurement of site-specific rates of reactions of H with C3H8, i-C4H10, and n-C4H10
(2017-08-14)
Lin, Chia-Chieh
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Chen, Wei-Yu
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Matsui, Hiroyuki
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Wang, Niann-Shiah
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應用化學系
We measured the rates of abstraction of a hydrogen atom from specific sites in propane C3H8, 2-methyl propane (i-C4H10), and butane (n-C4H10); the sites are a primary hydrogen of C3H8 and i-C4H10 and a secondary hydrogen of n-C4H10. The excellent reproducibility of conditions of a diaphragm-less shock tube enabled us to conduct comparative measurements of the evolution of H atoms in three mixtures-(i) 0.5 ppm C2H5I + Ar, (ii) 0.5 ppm C2H5I + 50-100 ppm alkane as C3H8 or i-C4H10 or n-C4H10 + Ar, and (iii) the same concentrations of alkane + Ar without C2H5I-in the temperature range 1000-1200 K and at a pressure of 2.0 bars. The net profile of rise and decay of H atoms in the C2H5I + alkane mixture was derived on subtracting the absorbance of (iii) from that of (ii). Measurements of the mixture (iii) are important because the absorption of alkanes at 121.6 nm is not negligible. In the temperature range 1000-1100 K, the rate of decomposition of C2H5I was evaluated directly on analyzing the exponential growth of H atoms in the mixture (i). The rate of decomposition of C2H5I is summarized as ln(k/s(-1)) = (33.12 +/- 1.4) - (25.23 +/- 1.5) 10(3)/T (T = 1000-1100 K, P = 2.0 bars); the broadening factor F(T) in the Lindemann-Hinshelwood formula was evaluated in the fall-off region. The site-specific rates of H + (C-3-C-4) alkanes are summarized as follows: H + C3H8 -> H-2 + 1-C3H7, ln(k(1a)) = -(21.34 +/- 0.86) - (5.39 +/- 0.93) 10(3)/T, H + i-C4H10 -> H-2 + i-C4H9, ln(k(2a)) = -(20.50 +/- 1.36) - (6.14 +/- 0.13) 10(3)/T, H + n-C4H10 -> H-2 + 2-C4H9, ln(k(3b)) = - (21.37 +/- 1.15) - (4.83 +/- 1.26) 10(3)/T. The present experimental results are compared with published results from quantum-chemical calculations of potential-energy surfaces and transition-state theory. The present experiments are consistent with those calculations for the reaction rates for the attack at the primary site for H + C3H8 and H + i-C4H10, but for the attack at the secondary site of n-C4H10, our results are substantially smaller than the computational prediction, which might indicate a hindrance by the C-H bonds of the primary sites that serves to decrease the rate of abstraction from the secondary site of n-C4H10. The influence on the total rates of reactions H + alkane and the group additivity rule are discussed. Published by AIP Publishing.
Bubbling solutions for a skew-symmetric Chern-Simons system in a torus
(2017-08-15)
Han, Xiaosen
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Huang, Hsin-Yuan
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Lin, Chang-Shou
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應用數學系
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Department of Applied Mathematics
We establish the existence of bubbling solutions for the following skew-symmetric Chern Simons system Delta u(1) + 1/epsilon(2) e(u2) (1 - e(u1)) = 4 pi Sigma N-1 i=1 delta p(1/i) { Delta u(2) + 1/epsilon(2) e(u1) (1 - e(u2)) = 4 pi Sigma N-2 i=1 delta p(2/i) over a parallelogram Omega with doubly periodic boundary condition, where epsilon > 0 is a coupling parameter, and delta(p) denotes the Dirac measure concentrated at p. We obtain that if (N-1 - 1)(N-2 - 1) > 1, there exists an epsilon(o) > 0 such that, for any epsilon is an element of(0, epsilon(o)), the above system admits a solution (u(1),(epsilon), u(2),(epsilon)) satisfying u1,(epsilon) and u(2),(epsilon) blow up simultaneously at the point p*, and 1/epsilon(2) e(uj,k) (1 - e(ui,epsilon)) -> 4 pi N-i delta(p*) , 1 <= i, j <= 2 , i not equal j as epsilon -> 0, where the location of the point p* defined by (1.12) satisfies the condition (1.13). (C) 2017 Elsevier: Inc. All rights reserved.
Efficiency Enhancement in InGaN Photovoltaic Cells With Inverted Textured Surface
(2017-08-15)
Wu, Ming-Hsien
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Horng, Ray-Hua
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Liao, Wen-Yih
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Chang, Sheng-Po
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Chang, Shoou-Jinn
We report on the improvement of conversion efficiency of InGaN photovoltaic (PV) cells with inverted textured surface (ITS). InGaN PV cells with ITS showed short-circuit current density and conversion efficiency of 0.63 mA/cm(2) and 1.01%, which are 68.17% and 73.33% higher than the characteristics of conventional InGaN PV cells, respectively. The improvement can be attributed to the reduction of both the shading effect of the electrode contact pad and surface reflection of the incident irradiation under one-sun air-mass 1.5-G illumination (100 mW/cm(2)).
Ammonium chiral borate salt catalyzed asymmetric Friedel-Crafts alkylation of indoles with alpha,beta-disubstituted enals
(2017-08-15)
Ueda, Mitsuhiro
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Yagyu, Yoshitaka
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Ryu, Ilhyong
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應用化學系
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Department of Applied Chemistry
In, the presence of a catalytic amount of ammonium chiral borate salt, asymmetric Friedel-Crafts alkylation of indoles with alpha,beta-disubstituted enals proceeded to give the corresponding 1,4-addition products with moderate enantioselectivities. (C) 2017 Elsevier Ltd. All rights reserved.
Oxygen Passivation Mediated Tunability of Trion and Excitons in MoS2
(2017-08-16)
Gogoi, Pranjal Kumar
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Hu, Zhenliang
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Wang, Qixing
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Carvalho, Alexandra
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Schmidt, Daniel
Using wide spectral range in situ spectroscopic ellipsometry with systematic ultrahigh vacuum annealing and in situ exposure to oxygen, we report the complex dielectric function of MoS2 isolating the environmental effects and revealing the crucial role of unpassivated and passivated sulphur vacancies. The spectral weights of the A (1.92 eV) and B (2.02 eV) exciton peaks in the dielectric function reduce significantly upon annealing, accompanied by spectral weight transfer in a broad energy range. Interestingly, the original spectral weights are recovered upon controlled oxygen exposure. This tunability of the excitonic effects is likely due to passivation and reemergence of the gap states in the band structure during oxygen adsorption and desorption, respectively, as indicated by ab initio density functional theory calculation results. This Letter unravels and emphasizes the important role of adsorbed oxygen in the optical spectra and many-body interactions of MoS2.
性別辨識系統及其方法
(2017-08-16)
范倫達
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吳宗翰
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曾煜棋
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荊宇泰
;
陳意翔
一種性別辨識方法包含以下步驟：藉由至少一影像深度擷取模組以擷取多個影像畫面並分析影像畫面中的多個人體骨架點資料，以取得對應人體骨架點資料的多個骨架點三維座標，藉由一伺服器依據骨架點三維座標計算至少一人體動態特徵及至少一人體靜態特徵，並依據人體動態特徵及人體靜態特徵以判斷一人體性別；其中，人體動態特徵包含至少一人體骨架點變異數，人體靜態特徵包含依據骨架點三維座標其中之二骨架點三維座標所計算出之至少一骨架寬度值。
阻抗至數位轉換器、阻抗至數位轉換裝置及方法
(2017-08-16)
邱俊誠
;
徐舜熙
一種阻抗至數位轉換器包含一偵測阻抗單元、一偏移阻抗單元、一參考阻抗單元、一積分單元及一電壓轉數碼單元。偵測阻抗單元將輸入信號轉換成一第一電荷。偏移阻抗單元將偏移信號轉換成一第二電荷。參考阻抗單元將參考信號轉換成一參考電荷，該參考電荷的正負相關於數位信號的邏輯準位。積分單元接收該第一電荷、該第二電荷及該參考電荷，並於每一週期時間據以加總轉換成一積分電壓。電壓轉數碼單元判斷積分電壓的大小以產生一數位信號。多個週期的數位信號的序列平均值正比於待偵測阻抗的阻抗值。阻抗值的偵測範圍的中心值是正比於類比信號的比例。阻抗值的靈敏度是正比於類比信號的比例。
Real-time observation of interfragment vibration and charge transfer within the TCNQF(4) dimer
(2017-08-17)
Hashimoto, Sena
;
Yabushita, Atsushi
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Iwakura, Izumi
;
電子物理學系
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Department of Electrophysics
The organic electron acceptors, 7,7,8,8-tetracyanoquinodimethane (TCNQ) and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (TCNQF(4)); are widely used to synthesize multivalent charge-transfer complexes. Their corresponding radical anion complexes have specific electronic, optical, and magnetic characters that have attracted attention in the field of materials development. In the present work,, we have performed time-resolved absorption spectroscopy of the (Na+)(2)(TCNQE(4)(center dot-))(2) radical anion complex to elucidate the reaction dynamics ([TCNQF(4)(center dot-)](2) -> TCNQF(4) + TCNQF(4)(2-)). A visible sub-10 fs laser pulse was used to observe the ultrafast dynamics of the charge transfer and real-time change of the molecular structure during the reaction. Unlike our previous work on the (Na+)(2)(TCNQ(.-))(2) radical anion complex, the interfragment vibrational mode was clearly observed for (Na+)(2)(TCNQP(4)(center dot-))(2). The difference in the intermolecular interaction is considered to reflect the difference in the pi-pi interaction and/or the difference in the flexibility of the molecular plane predicted by theoretical calculations. (C) 2017 Elsevier B.V. All rights reserved.
Andreev reflection in two-dimensional relativistic materials with realistic tunneling transparency in normal-metal/superconductor junctions
(2017-08-17)
Chang, Yung-Yeh
;
Mou, Chung-Yu
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Chung, Chung-Hou
;
電子物理學系
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Department of Electrophysics
The Andreev conductance across realistic two-dimensional (2D) normal-metal (N)/superconductor (SC) junctions with a relativistic Dirac spectrum is theoretically investigated within the Blonder-Tinkham-Klapwijk formalism with tunable tunneling transparency. It is known that due to the effect of Klein tunneling, impurity potentials at the interface of 2D relativistic materials will enhance (not suppress) the tunneling and therefore are not suitable to model a realistic tunnel junction of these materials. Here, we propose a way to construct a more realistic tunnel junction by adding a narrow, homogeneous local strain, which effectively generates a delta-gauge potential and variations of electron hopping at the interface, to adjust the transparency of the N/SC junction. Remarkable suppression of the Andreev conductance is indeed observed in the graphene N/SC junction as the strength of the local strain increases. We also explore the Andreev conductance in a topological N/SC junction at the two inequivalent Dirac points and predict the distinctive behaviors for the conductance across the chiral-to-helical topological phase transition. The relevance of our results for the adatom-doped graphene is discussed.
Musashi-1 Enhances Glioblastoma Cell Migration and Cytoskeletal Dynamics through Translational Inhibition of Tensin3
(2017-08-18)
Chen, Hsiao-Yun
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Lin, Liang-Ting
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Wang, Mong-Lien
;
Laurent, Benoit
;
Hsu, Chih-Hung
The RNA-binding protein Musashi-1 (MSI1) exerts essential roles in multiple cellular functions, such as maintenance of self-renewal and pluripotency of stem cells. MSI1 overexpression has been observed in several tumor tissues, including glioblastoma (GBM), and is considered as a well-established marker for tumor metastasis and recurrence. However, the molecular mechanisms by which MSI1 regulates cell migration are still undetermined. Here we reported that MSI1 alters cell morphology, promotes cell migration, and increases viscoelasticity of GBM cells. We also found that MSI1 directly binds to the 3'UTR of Tensin 3 (TNS3) mRNA, a negative regulator of cell migration, to inhibit its translation. Additionally, we identified that RhoA-GTP could be a potential regulator in MSI1/TNS3-mediated cell migration and morphological changes. In a xenograft animal model, high expression ratio of MSI1 to TNS3 enhanced GBM tumor migration. We also confirmed that MSI1 and TNS3 expressions are mutually exclusive in migratory tumor lesions, and GBM patients with MSI1(high)/TNS3(low) pattern tend to have poor clinical outcome. Taken together, our findings suggested a critical role of MSI1-TNS3 axis in regulating GBM migration and highlighted that the ratio of MSI1/TNS3 could predict metastatic and survival outcome of GBM patients.