Browsing by Issue Date, starting with "2017-07-11"

Now showing 1 - 20 of 13503

DNA Methyltransferases Modulate Hepatogenic Lineage Plasticity of Mesenchymal Stromal Cells
(2017-07-11)
Lee, Chien-Wei
;
Huang, Wei-Chih
;
Huang, Hsien-Da
;
Huang, Yi-Hsiang
;
Ho, Jennifer H.
The irreversibility of developmental processes in mammalian cells has been challenged by rising evidence that de-differentiation of hepatocytes occurs in adult liver. However, whether reversibility exists in mesenchymal stromal cell (MSC)-derived hepatocytes (dHeps) remains elusive. In this study, we find that hepatogenic differentiation (HD) of MSCs is a reversible process and is modulated by DNA methyltransferases (DNMTs). DNMTs are regulated by transforming growth factor beta 1 (TGF beta 1), which in turn controls hepatogenic differentiation and de-differentiation. In addition, a stepwise reduction in TGF beta 1 concentrations in culture media increases DNMT1 and decreases DNMT3 in primary hepatocytes (Heps) and confers Heps with multi-differentiation potentials similarly to MSCs. Hepatic lineage reversibility of MSCs and lineage conversion of Heps are regulated byDNMTs in response to TGF gamma 1. This previously unrecognized TGF beta 1-DNMTs-MSC-HD axis may further increase the understanding the normal and pathological processes in the liver, as well as functions of MSCs after transplantation to treat liver diseases.
Solvent On-Film Annealing (SOFA): Morphological Evolution of Polymer Particles on Polymer Films via Solvent Vapor Annealing
(2017-07-11)
Tseng, Hsiao-Fan
;
Cheng, Ming-Hsiang
;
Li, Jia-Wei
;
Chen, Jiun-Tai
;
應用化學系
Over the past few decades, anisotropic polymer particles are of significant interest because of their unique properties which can be applied in various areas, such as drug delivery, biotechnology, and electronics. Most approaches to synthesize anisotropic polymer particles, however, are complicated, and the three-dimensional shapes of the anisotropic particles are usually difficult to be controlled. In this work, we develop a solvent on-film annealing (SOFA) method to fabricate anisotropic polymer particles by studying the morphological evolution of polystyrene (PS) microspheres on poly(methyl methacrylate) (PMMA) films annealed in toluene vapor. At different annealing stages, the isotropic PS microspheres gradually transform to anisotropic PS particles with different morphologies, such as UFO-, cymbal-, peanut-, and bowl-shaped particles. The morphology evolution is driven by the surface and interfacial tensions during the annealing processes and can be confirmed by a selective removal technique. Acetic acid, a selective solvent for PMMA, and cyclohexane, a selective solvent for PS, are also used as the annealing solvents to further investigate the effect of the annealing solvent.
A study of electromigration behaviors of Ge2Sb2Te5 chalcogenide nano-strips subjected to pulse bias
(2017-07-12)
Huang, Yin-Hsien
;
Hsieh, Tsung-Eong
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Electromigration (EM) behaviors of pristine Ge2Sb2Te5 (GST) and cerium-doped GST (Ce-GST) nano-strips were investigated by the mean-time-to-failure (MTTF) tests under the pulse bias at the conditions of pulse frequency (f) ranging from 1 to 25 MHz and duty cycle ranging from 50% to 80%. Analytical results indicated that, at f greater than 10 MHz, the EM failure of GST nano-strips in pulse bias environment could be depicted by the 'average current model'. With the aid of Black's theory, the activation energies (Ea) of EM process under pulse bias were found to be 0.63 and 0.56 eV for GST and Ce-GST nano-strips, respectively. The Ea values were comparatively smaller than those observed in direct-current MTTF test of GST thin-film samples, implying the enhancement of surface diffusion and skin effect in GST nano-strips. The morphology and composition analyses indicated that the electrostatic and the electron-wind forces might simultaneously involve in the mass transport in GST nano-strips under the test conditions of this study. The composition analysis also revealed that doping could not effectively alleviate the element segregation in GST subjected to electrical bias.
Identifying the stiffness parameters of a structure using a subspace approach and the Gram-Schmidt process in a wavelet domain
(2017-07-13)
Su, Wei-Chih
;
Huang, Chiung-Shiann
;
Lien, Ho-Cheng
;
Le, Quang-Tuyen
;
土木工程學系
This article presents a procedure to improve the accuracy of calculated stiffness matrix of a structure based on the identified modal parameters from its measured responses. First, a continuous wavelet transform is applied to the measured responses of a structure, and the state-space model can be reconstructed by the wavelet coefficients of acceleration that can be obtained from the measured noisy responses. The modal parameters are identified using the subspace approach. Second, the identified mode shapes are corrected via Gram-Schmidt process. Finally, the identified natural frequencies and the corrected mode shapes in previous steps are utilized to build the stiffness matrix of structure. The accuracy of the proposed approach is numerically confirmed, and the noise effects on the ability to precisely identify the stiffness matrix are also investigated. The measured data of two eight-story steel frames in a shaking table test are analyzed to demonstrate the applicability of the procedure to real structures.
數理簡訊機器要取代我們的老師了嗎？
(國立交通大學丘成桐中心, 2017-07-15)
編輯室
科技不斷加速的時代還如何談百年樹人
Differential Feedback of Geometrical Mean Decomposition Precoder for Time-Correlated MIMO Systems
(2017-07-15)
Chen, Hung-Chun
;
Lin, Yuan-Pei
;
電機工程學系
;
Department of Electrical and Computer Engineering
For a time-correlated channel, we consider the differential feedback of the geometrical mean decomposition (GMD) precoder, which is known to be optimal for a number of criteria. When the channel varies slowly, we can expect the optimal GMD precoders of consecutive channel uses to be close. We consider the feedback of the so-called differential precoder and show that it lies in a neighborhood of the identity matrix using matrix perturbation theory. Furthermore, the radius of the neighborhood is shown to be proportional to a time-correlation parameter. Such a characterization allows for subsequent efficient quantization of the differential precoder. We show how to design codewords for the prescribed radius by perturbing the identity matrix and applying QR decomposition on the perturbed matrix. Simulations are given to demonstrate that, with a small feedback rate, the performance of the proposed differential GMD comes close to the case when perfect channel state information is available to the transmitter for slowly time-varying channels like those in indoor and microcellular environments.
編輯曲線混沌與複雜說不完的好故事
(國立交通大學丘成桐中心, 2017-07-15)
編輯室
本雜誌將從這一期開始恢復為半年刊，若造成讀者的不便，敬請海涵。專題《秩序與複雜的華爾滋》上期的重點在數學本身，本期則放在各種應用。
譯者與贊助人
(國立交通大學丘成桐中心, 2017-07-15)
楊承淑
以林獻堂為中心的譯者群體
數理簡訊數學明星踏入政治圈
(國立交通大學丘成桐中心, 2017-07-15)
編輯室
法國政治的左右方程真的有解嗎？
專題-秩序與複雜的華爾滋（下）花豹的斑紋是怎麼來的
(國立交通大學丘成桐中心, 2017-07-15)
廖思善
;
陳文翊
不得不用數學來說的故事
量子生物學的實與虛
(國立交通大學丘成桐中心, 2017-07-15)
鄭原忠
評論《解開生命之謎：運用量子生物學，揭開生命起源與真相的前衛科學》
專題-秩序與複雜的華爾滋（下）亂序同舞的液體世界
(國立交通大學丘成桐中心, 2017-07-15)
伊林
以微粒電漿模擬液體微觀尺度的結構與運動
大學之前的教育
(國立交通大學丘成桐中心, 2017-07-15)
丘成桐　
對於中國教育改革的幾點意見
甚麼是橢圓曲線？
(國立交通大學丘成桐中心, 2017-07-15)
王夏聲　
在數論、代數幾何、複分析、密碼學和物理等領域的研究裡，橢圓曲線（elliptic curve）無所不在。橢圓曲線也是算術幾何（arithmetic geometry）的研究前沿，出現在懷爾斯（Andrew Wiles）的費馬最後定理證明中（請參見本期〈2016 年阿貝爾獎得主懷爾斯訪談〉）。
數理人文第十二期中英文對照
(國立交通大學丘成桐中心, 2017-07-15)
編輯室
中英名詞對照
數理簡訊 2017 年數學大獎
(國立交通大學丘成桐中心, 2017-07-15)
編輯室
2017 年阿貝爾獎頒給法國沙克雷（原卡尚）高等師範學院的梅耶爾（Yves Meyer），得獎理由是基於「他在小波〔wavelet〕數學理論中的樞紐角色」，跨越了數學、計算科學和資訊科技領域。
從鳥眼看見大自然的隱藏秩序
(國立交通大學丘成桐中心, 2017-07-15)
作者:渥秋華（Natalie Wolchover）
;
譯者:紀露結
漫步於秩序與隨機之間的超均勻性
投資純數學就是投資我們的未來
(國立交通大學丘成桐中心, 2017-07-15)
翁秉仁　
2016 年阿貝爾獎得主懷爾斯訪談
專題-秩序與複雜的華爾滋（下）勞倫茲和蝴蝶共同掀起的混沌風暴
(國立交通大學丘成桐中心, 2017-07-15)
陳義裕
一提到混沌，人們第一個想到的可能就是著名的「蝴蝶效應」。但除了得感激科普作家的辛勤筆耕，真正讓蝴蝶效應這個混沌代名詞得以如此流傳、深入人心的，恐怕還是得拜幾部好萊塢電影所賜，其中尤以 1993 年的賣座電影《侏羅紀公園》最為著名。在該部電影中，數學家主角所述蝴蝶效應指的是：北京的一隻蝴蝶隨便搧個翅，結果竟為本來應該是大晴天的紐約帶來豪雨。
Widely wavelength tunable fast intensity-modulated light source for biophotonic applications
(2017-07-15)
Huang, Tzu-Feng
;
Tseng, Sheng-Hao
;
Wang, Hsien-Yi
;
Chan, Ming-Che
;
光電學院
High modulation depth, fast (megahertz to gigahertz), intensity-modulated light sources of various wavelengths within the 0.7-1.35 mu m bio-penetration window are highly desirable for many biophotonic diagnosis systems. In this Letter, we present a novel scheme of a wavelength tunable, ultra-broadband light source which simply consists of a pump laser, a nonlinear fiber, and demodulation circuits. The working wavelength range of the light source is from 0.7 to 1.35 mu m which covers a vast part of the bio-penetration window, and its modulation frequencies extends from tens of megahertz to gigahertz. The performances of the proposed light source in either working wavelength range or modulation frequency bandwidth are much superior to any typical laser diodes or solid state lasers currently employed in the frequency-domain or other biophotonic utilization. The wide applicability of this novel light source in diverse biophotonic applications can be observed from our carefully designed diffused optical spectroscopy phantom measurement. (C) 2017 Optical Society of America