Browsing by Issue Date, starting with "2019-12-06"

Now showing 1 - 20 of 6183

Palladium-Catalyzed Cascade Arylation of Vinylogous Esters Enabled by Tris(1-adamantyl)phosphine
(2019-12-06)
Yang, Yi-Chi
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Lin, Yi-Ching
;
Wu, Yen-Ku
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應用化學系
;
Department of Applied Chemistry
Described is a method for the transformation of a cyclic vinylogous ester to the corresponding polyarylated product. We found a catalytic system comprising palladium diacetate and tris(1-adamantyl)phosphine is quite effective in promoting a set of controlled cascade arylations. As a result, a range of novel (hetero)aryl-containing scaffolds was synthesized with a high level of efficiency.
Anisotropic superconductivity induced by periodic multiferroic domain patterns
(2019-12-06)
Huang, Yen-Lin
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Huang, Bo-Chao
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Wang, Yan-Ting
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Xue, Fei
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Lin, Jheng-Cyuan
The competition between order parameters, such as ferroelectricity, ferromagnetism, and superconductivity, is one of the most fascinating topics in condensed matter physics. Here, we report intriguing anisotropic superconductivity in YBa2Cu3O7-x films induced by a multiferroic, BiFeO3, with periodic domain patterns. The anisotropic superconductivity was investigated by transport measurements and supported by phase-field simulations, and then the detailed local electronic structures were revealed by cross-sectional scanning tunneling microscopy. We found that the oxygen redistribution in YBa2Cu3O7-x modulated by the ferroelectric polarization in BiFeO3 was the key mechanism driving this anisotropic superconductivity. The presented heteroarchitecture of a high-temperature superconductor and a domain-engineered multiferroic provides a new approach to tune superconductivity and offers potential advantages for the design of future multifunctional devices.
Selective catalytic oxidation of benzene to phenol by a vanadium oxide nanorod (V-nr) catalyst in CH3CN using H2O2(aq) and pyrazine-2-carboxylic acid (PCA)
(2019-12-07)
Wanna, Wondemagegn Hailemichael
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Janmanchi, Damodar
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Thiyagarajan, Natarajan
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Ramu, Ravirala
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Tsai, Yi-Fang
Vanadium based catalysts are known to be highly efficient for oxidation reactions using O-2 and/or H2O2. In this study, we developed a vanadium catalyst that can be prepared by a reaction of VCl3 in acetonitrile with the addition of 35% hydrogen peroxide (H2O2). The catalyst was further characterized by a variety of methods including V-51 NMR, XRD, XPS, XAS, EA, ICP-AES, BET, SEM and TEM. Based on the results obtained, the catalyst was identified as a vanadium oxide material (V-nr) with the morphology and shape of a nanorod with dimensions of similar to 40 nm x 450 nm (width x length). The porosity of a material can be essential for small molecule activation on a heterogeneous surface. This material exhibits exceptional catalytic performance for the selective oxidation of benzene to phenol (PhOH) at room temperature using H2O2 as an oxidant in acetonitrile. The addition of pyrazine-2-carboxylic acid (PCA) as a co-catalyst can efficiently enhance the catalytic activity with a percentage selectivity of 87-99% phenol, producing p-benzoquinone (p-BQ) as a minor product. With the deployment of (H2O2)-O-18, we observed the product phenol to be highly enriched by O-18, indicating that the hydroperoxovanadium intermediate is essential for its catalytic conversion. Together with its high NIH shift ratio (80% deuterium remained) observed with the mechanistic probe of 4-[H-2(0,1)] toluene, the results suggested that the catalytic oxidation reaction mediated by Vnr may involve metal based oxygenated intermediates for its highly selective catalytic oxidation of benzene to phenol.
減肥照過來！人一天到底要吃多少？
(2019-12-08)
陳千柔
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Department of Communication and Technology
;
傳播與科技學系
【You are what you eat】專題

健康必須從飲食做起，但究竟人的一天需要攝取多少熱量呢？哪些物質的攝取會提高罹患心血管疾病的風險？
對戰科技冷漠　體驗經濟是什麼？
(2019-12-08)
王會瑄
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Department of Communication and Technology
;
傳播與科技學系
【滑世代的體驗經濟】專題

在科技產品的不斷迭代之下，人與人的直接接觸已不再是學習、娛樂甚至社交活動的必要條件。在此同時，體驗經濟卻以一種看似對立，而又相輔相成的微妙關係崛起且持續發燒中。
停頓流浪貓生命旅途之中
(2019-12-08)
曾弘碩
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Department of Communication and Technology
;
傳播與科技學系
【那些貓兒與人類】專題

隨著養貓人士與日俱增，對於貓咪的認知，不能侷限在網路上的影音，而是關懷貓咪的生命歷程，以及照顧機制的問題。
地方創生讓青年提升台灣「鄉村力」
(2019-12-08)
林怡恩
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Department of Communication and Technology
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傳播與科技學系
【地方創生：年輕人，回家吧】專題

政府將2019年訂定為地方創生元年，大力推動青年返鄉工作。希望藉此為鄉下村落創造新生機，也為台灣鄉村人口問題找到舒緩出口。
總編的話
(2019-12-08)
陳炘瑜
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Department of Communication and Technology
;
傳播與科技學系
本期為喀報327期，共計11篇文章，包含十篇文化現象、一篇社會議題。本篇頭題為陳姝芸的〈用數據看移工在台現況〉，探討被大眾忽視的台灣移工權益問題。本期專題題材多元，以時下熱門話題撰寫獨特的見解，或介紹鮮為人知的新知識，讓喀報的內容煥然一新，值得深讀。
ASMR旋風－席捲全球！
(2019-12-08)
李芝謙
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Department of Communication and Technology
;
傳播與科技學系
【具有療癒魔力的輕聲呢喃】專題

ASMR影片從YouTube發跡，逐漸形成一種次文化。透過數據及圖表，帶你來看看ASMR文化在全球的分佈，台灣又能夠如何利用這波熱潮呢？
Theoretical investigation of the vertical dielectric screening dependence on defects for few-layered van der Waals materials
(2019-12-08)
Singh, Amit
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Lee, Seunghan
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Bae, Hyeonhu
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Koo, Jahyun
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Yang, Li
First-principle calculations were employed to analyze the effects induced by vacancies of molybdenum (Mo) and sulfur (S) on the dielectric properties of few-layered MoS2. We explored the combined effects of vacancies and dipole interactions on the dielectric properties of few-layered MoS2. In the presence of dielectric screening, we investigated uniformly distributed Mo and S vacancies, and then considered the case of concentrated vacancies. Our results show that the dielectric screening remarkably depends on the distribution of vacancies owing to the polarization induced by the vacancies and on the interlayer distances. This conclusion was validated for a wide range of wide-gap semiconductors with different positions and distributions of vacancies, providing an effective and reliable method for calculating and predicting electrostatic screening of dimensionally reduced materials. We further provided a method for engineering the dielectric constant by changing the interlayer distance, tuning the number of vacancies and the distribution of vacancies in few-layered van der Waals materials for their application in nanodevices and supercapacitors.
電子鴉片？吸了幾片？
(2019-12-08)
李金福
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Department of Communication and Technology
;
傳播與科技學系
「電子鴉片抬頭不見低頭見」專題

只要你手邊有一臺能連接到網際網路的設備，你就會去用它上網。面對「電子鴉片」現代人該如何應對呢？
潛進大海自由潛水的技術
(2019-12-08)
曾冠霖
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Department of Communication and Technology
;
傳播與科技學系
【屏息之間的自由】專題

用簡單的圖示，比較不同潛水的形式，並整理自潛相關的基本技能與概念，讓你不再畏懼自由潛水。
用數據看移工在台現況
(2019-12-08)
陳姝芸
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Department of Communication and Technology
;
傳播與科技學系
【移生移世去除歧視與不公】專題

2019年台灣移工人數已超過七十萬，占了台灣一定人口數。然而，制度的不完善導致移工被嚴重剝削，究竟問題出在哪？
撕除酒精標籤
(2019-12-08)
吳宥芯
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Department of Communication and Technology
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傳播與科技學系
【撕除酒精標籤專題】

酒精在大多數人眼中被貼上負面的標籤，往往與負面詞彙相連，然而若撕除酒精標籤，認真研究其原貌，飲酒其實是一門於世界流傳千年的學問。
石虎與牠即將絕種的小夥伴
(2019-12-08)
李旻珊
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Department of Communication and Technology
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傳播與科技學系
【不是只有愛動物那麼簡單！保育知識面面觀】專題

繼台灣雲豹傳聞滅絕後，石虎的保育備受矚目。究竟在台灣的保育規範內，石虎屬於哪一類？又有哪些與石虎同病相憐的動物呢？就讓我們來一探究竟！
Photon recycling characteristics of InGaAs/GaAsP multiple quantum well solar cells incorporating a spectrally selective filter and distributed Bragg reflector
(2019-12-09)
Hong, Chung-Yu
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Wang, Yi-Chin
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Su, Yu-Chih
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Tsai, Jia-Ling
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Tung, Chao-Ming
Photon management plays a vital role in the power conversion efficiency of III-V semiconductor solar cells. However, the photon recycling characteristics of GaAs-based multi-quantum-well (MQW) solar cells employed different optical designs had yet been fully explored. In this work, we investigate the impact of the spectrally selective filter (SSF) and distributed Bragg reflector (DBR) on the photovoltaic characteristics of single-junction, strain-balanced In0.1Ga0.9As/ GaAs0.85P0.15 MQW solar cells. Specifically, the SSFs with cutoff wavelengths of 880, 910, and 940 nm are designed and implemented on MQW solar cells with and without the incorporation of a rear DBR. Photon confinement in the vertical direction is verified based on the characterizations of reflectance, electroluminescence, and external quantum efficiency. We show that the photon confinement reduces the saturation current density, up to 26 times and 3 times for the 880 nm SSF-MQW and SSF-MQW-DBR devices, respectively, compared to that of the 940 nm devices. Furthermore, by comparing the SSF-MQW-DBR solar cells under simulated one-sun and concentrated illumination conditions, the open-circuit voltage exhibits a maximal net increase for the 910 nm SSF due to tradeoff between the short-circuit and saturation current density. The proposed SSF design may offer a viable approach to boost the performance of GaAs-based MQW solar cells. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Heat dissipation in quasi-ballistic single-atom contacts at room temperature
(2019-12-10)
Tsutsui, Makusu
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Chen, Yu-Chang
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交大名義發表
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電子物理學系
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National Chiao Tung University
We report on evaluations of local heating in Au single-atom chains at room temperature. We performed onsite thermometry of atomic-scale Au junctions under applied sinusoidal voltage of variable amplitudes. The AC approach enabled to preclude electromigration effects for characterizing the influence of energy dissipations on the lifetime. We elucidated nonlinear increase in the effective temperature of the current-carrying single-atom chains with the voltage amplitudes, which was attributed to subtle interplay between electron-phonon scattering and electron-mediated thermal transport in the quasi-ballistic conductor. We also found that only 0.2% of the electric power contributed to local heating while the majority was consumed at the diffusive bank. The present findings can be used for thermal management of future integrated nanoelectronics.
Iron embedded magnetic nanodiamonds for in vivo MRI contrast enhancement
(2019-12-11)
Lin, Bo-Rong
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Chen, Chien-Hsu
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Chang, Chun-Hsiang
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Kunuku, Srinivasu
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Chen, Tzung-Yuang
Although nanodiamonds have long being considered as a potential tool for biomedical research, the practical in vivo magnetic resonance imaging (MRI) application of nanodiamonds remains relatively unexplored. In this paper, we present the first application of in vivo MRI contrast enhancement using only iron embedded magnetic nanodiamonds. An MR image enhancement was clearly demonstrated in the rendering of T2-weighted images of mice obtained using an unmodified commercial MRI scanner. The excellent contrast obtained using these nanodiamonds opens the door to the non-invasive in vivo tracking of nanodiamonds and image enhancement. In the future, one can apply these magnetic nanodiamonds together with surface modifications to facilitate drug delivery, targeted therapy, localized thermal treatment, and diagnostic imaging.
Antiferroelectric antiferromagnetic type-I multiferroic Cu9O2(SeO3)(4)Cl-6
(2019-12-11)
Wu, H. C.
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Denisova, K. N.
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Menzel, D.
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Kakarla, D. Chandrasekhar
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Maximova, O. V.
We report that Cu9O2(SeO3)(4)Cl-6 is a new multiferroic compound. Comprehensive studies of this compound have been carried out on single crystals as well as polycrystalline samples. Magnetic susceptibility chi and specific heat C with H parallel to c axis both reveal an anomaly at T-N = 37 K associated with the long-range antiferromagnetic order. However, no signature of this phase transition is seen with the H parallel to b axis, providing evidence of the anisotropic nature of its magnetic properties. The results of chi measurements are consistent with the temperature evolution of the intensity of magnetic reflections from the neutron diffraction experiments. The magnetic structure derived from neutron scattering measurements shows that half of the Cu(5) ions carry no moments. Furthermore, an anomaly in the dielectric constant near T-N and observable magnetoelectric coupling below T-N are found. At high temperatures, a dielectric peak at T-E = 267 K is identified with no measurable spontaneous polarization below T-E, thereby suggesting an antiferroelectric order. A steplike anomaly seen in chi(T) at T-E hints the weak spin-lattice coupling. Concomitantly, high-resolution temperature-dependent synchrotron x-ray diffraction experiments elucidate a local structural distortion at T-E.
【12月山腰電影院】
(國立陽明大學, 2019-12-13)
陽明電子報編輯小組