Browsing by Issue Date, starting with "2015-10-13"

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Hybridization of CMRP and ATRP: A Direct Living Chain Extension from Poly(vinyl acetate) to Poly(methyl methacrylate) and Polystyrene
(2015-10-13)
Chen, Ya-Jo
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Wu, Bing-Jyun
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Wang, Fu-Sheng
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Chi, Mu-Huan
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Chen, Jiun-Tai
Cobalt-mediated radical polymerization (CMRP) was used to prepare well-defined poly(vinyl acetate) (PVAc) as the macroinitiator in the reverse atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and styrene (Sty) for the synthesis of block copolymers of PVAc-b-PMMA and PVAc-b-PSty with linearly increased molecular weight and smoothly shifted gel permeation chromatography (GPC) traces. The chain extension from PVAc to PMMA or PSty via the hybridization of CMRP and ATRP required neither a difunctional initiator nor further chain-end modification and was as simple as regular chain extension in the reverse ATRP process. Because the cobalt complex bonded to the chain end of PVAc was dissociated during the ATRP process, this method also efficiently solved the issue of metal removal in the CMRP process.
Angular-Shaped 4,10-Dialkylanthradiselenophene and Its Donor-Acceptor Conjugated Polymers: Synthesis, Physical, Transistor, and Photovoltaic Properties
(2015-10-13)
Lai, Yu-Ying
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Chang, Huan-Hsuan
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Lai, Yun-Yu
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Liang, Wei-Wei
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Tsai, Che-En
An angular-shaped and isomerically pure 4,10-di(2-octyl)dodecylanthradiselenophene (aADS) was successfully developed. The expedient synthesis to form the framework of aADS with two lateral side chains regioseleclively at its 4,10-positions is via a base-induced propargyl-allenyl isomerization/6 pi-electrocyclization/aromatization protocol. This pentacyclic distannylated aADS unit was then copolymerized with dithienyldiketopyrrolopyrrole (DPP) and dithienyl-5,6-difluoro-2,1,3-benzothiadiazole (DTFBT) acceptors with different alkyl side chains to afford four donor-acceptor copolymers: PaADSDPP, PaADSDTFBT-C-4, PaADSDTFBT-C-8, and PaADSDTFBT-C8C12. UV-vis spectroscopy and cyclic voltammetry revealed that PaADSDPP has the narrowest energy band gap, and PaADSDTFBT-C8C12 has larger band gap than PaADSDTFBT-C-4 and PaADSDTFBT-C-8. Two layer ONIOM (our own n-layered integrated molecular orbital and molecular mechanics) calculations were implemented to investigate the disparity in optical, electrochemical, and device properties between these polymers. Both experimental and theoretical data suggest that the aliphatic side chains play a significant role in determining the physical, transistor, and photovoltaic properties of the polymers. PaADSDTFBT-C-4 and PaADSDTFBT-C-8 exhibited organic-field-effect-transistor hole mobilities of 2.7 x 10(-2) and 1.0 x 10(-2) cm(2) V-1 s(-1), greatly outperforming that of PaADSDTFBT-C8C12 with a mobility of 5.4 X 10(-6) cm(2) V-1 s(-1). Polymer solar cells were fabricated on the basis of ITO/PEDOT:PSS/polymer:PC71BM/Ca/Al configuration. The efficiency decreased as the increase of bulkiness of the aliphatic side chains installed on DTFBT units (4.4% for PaADSDTFBT-C-4, 3.5% for PaADSDTFBT-C-8, 0.3% for PaADSDTFBT-C8C12). Atomic force microscopy images reveal that the degree of aggregation for the polymer:fullerene blends is influenced significantly by the bulkiness of aliphatic side chain installed on DTFBT. Noticeable aggregation was found for the PaADSDTFBT-C8C12:PC71BM blend. These results are in good agreement with the computational results elucidating that the intermolecular interactions between the polymers and PC71BM are sterically hindered by the bulky 2-octyldodecyl groups. This work not only presents a promising selenophene-based aADS building block but also provides insights into the side-chain engineering for donor-acceptor conjugated copolymers.
Small-Conductance Calcium-Activated Potassium Current Is Activated During Hypokalemia and Masks Short-Term Cardiac Memory Induced by Ventricular Pacing
(2015-10-13)
Chan, Yi-Hsin
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Tsai, Wei-Chung
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Ko, Jum-Suk
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Yin, Dechun
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Chang, Po-Cheng
Background-Hypokalemia increases the vulnerability to ventricular fibrillation. We hypothesize that the apamin-sensitive small-conductance calcium-activated potassium current (I-KAS) is activated during hypokalemia and that I-KAS blockade is proarrhythmic. Methods and Results-Optical mapping was performed in 23 Langendorff-perfused rabbit ventricles with atrioventricular block and either right or left ventricular pacing during normokalemia or hypokalemia. Apamin prolonged the action potential duration (APD) measured to 80% repolarization (APD(80)) by 26 milliseconds (95% confidence interval [CI], 14-37) during normokalemia and by 54 milliseconds (95% CI, 40-68) during hypokalemia (P=0.01) at a 1000-millisecond pacing cycle length. In hypokalemic ventricles, apamin increased the maximal slope of APD restitution, the pacing cycle length threshold of APD alternans, the pacing cycle length for wave-break induction, and the area of spatially discordant APD alternans. Apamin significantly facilitated the induction of sustained ventricular fibrillation (from 3 of 9 hearts to 9 of 9 hearts; P=0.009). Short-term cardiac memory was assessed by the slope of APD(80) versus activation time. The slope increased from 0.01 (95% CI, -0.09 to 0.12) at baseline to 0.34 (95% CI, 0.23-0.44) after apamin (P<0.001) during right ventricular pacing and from 0.07 (95% CI, -0.05 to 0.20) to 0.54 (95% CI, 0.06-1.03) after apamin infusion (P=0.045) during left ventricular pacing. Patch-clamp studies confirmed increased I-KAS in isolated rabbit ventricular myocytes during hypokalemia (P=0.038). Conclusions-Hypokalemia activates I-KAS to shorten APD and maintain repolarization reserve at late activation sites during ventricular pacing. I-KAS blockade prominently lengthens the APD at late activation sites and facilitates ventricular fibrillation induction.
Heterojunction of Zinc Blende/Wurtzite in Zn1-xCdxS Solid Solution for Efficient Solar Hydrogen Generation: X-ray Absorption/Diffraction Approaches
(2015-10-14)
Hsu, Ying-Ya
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Suen, Nian-Tzu
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Chang, Chung-Chieh
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Hung, Sung-Fu
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Chen, Chi-Liang
In the past decade, inorganic semiconductors have been successfully demonstrated as light absorbers in efficient solar water splitting to generate chemical fuels. Pseudobinary semiconductors Zn1-xCdxS (0 <= x <= 1) have exhibited a superior photocatalytic reactivity of H-2 production from splitting of water by artificial solar irradiation without any metal catalysts. However, most studies had revealed that the extremely high efficiency with an optimal content of Zn1-xCdxS solid solution was determined as a result of elevating the conduction band minimum (CBM) and the width of bandgap. In addition to corresponding band structure and bandgap, the local crystal structure should be taken into account as well to determine its photocatalytic performance. Herein, we demonstrated the correlations between the photocatalytic activity and structural properties that were first studied through synchrotron X-ray diffraction and X-ray absorption spectroscopy. The crystal structure transformed from zinc blende to coexisted phases of major zinc blende and minor wurtzite phases at a critical point. The heterojunction formed by coexistence of zinc blende and wurtzite phases in the Zn1-xCdxS solid solution can significantly improve the separation and migration of photoinduced electron hole pairs. Besides, X-ray absorption spectra and UV-vis spectra revealed that the bandgap of the Zn0.45Cd0.55S sample extended into the region of visible light because of the incorporation of Cd element in the sample. These results provided a significant progress toward the realization of the photoelectrochemical mechanism in heterojunction between zinc blende and wurtzite phases, which can effectively separate the charge-carriers and further suppress their recombination to enhance the photocatalytic reactivity.
Angular-Shaped 4,9-Dialkyl - and -Naphthodithiophene-Based Donor-Acceptor Copolymers: Investigation of Isomeric Structural Effects on Molecular Properties and Performance of Field-Effect Transistors and Photovoltaics
(2015-10-14)
Cheng, Sheng-Wen
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Chiou, De-Yang
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Tsai, Che-En
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Liang, Wei-Wei
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Lai, Yu-Ying
Two angular-shaped 4,9-didodecyl -aNDT and 4,9-didodecyl -aNDT isomeric structures have been regiospecifically designed and synthesized. The distannylated -aNDT and -aNDT monomers are copolymerized with the Br-DTNT monomer by the Stille coupling to furnish two isomeric copolymers, PNDTDTNT and PNDTDTNT, respectively. The geometric shape and coplanarity of the isomeric -aNDT and -aNDT segments in the polymers play a decisive role in determining their macroscopic device performance. Theoretical calculations show that PNDTDTNT possesses more linear polymeric backbone and higher coplanarity than PNDTDTNT. The less curved conjugated main chain facilitates stronger intermolecular - interactions, resulting in more redshifted absorption spectra of PNDTDTNT in both solution and thin film compared to the PNDTDTNT counterpart. 2D wide-angle X-ray diffraction analysis reveals that PNDTDTNT has more ordered -stacking and lamellar stacking than PNDTDTNT as a result of the lesser curvature of the PNDTDTNT backbone. Consistently, PNDTDTNT exhibits a greater field effect transistor hole mobility of 0.214 cm(2) V-1 s(-1) than PNDTDTNT with a mobility of 0.038 cm(2) V-1 s(-1). More significantly, the solar cell device incorporating the PNDTDTNT:PC71BM blend delivers a superior power conversion efficiency (PCE) of 8.01% that outperforms the PNDTDTNT:PC71BM-based device with a moderate PCE of 3.6%.
Evaluation of traumatic brain injury by optical technique
(2015-10-14)
Lin, Bor-Shyh
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Wang, Che-Chuan
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Chang, Ming-Hsien
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Chio, Chung-Ching
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光電系統研究所
Background: Traumatic brain injury (TBI), usually due to brain shaking or impact, affects the normal brain function and may lead to severe disability or even death. However, there is paucity of information regarding changes in the physiologic state of humans or animals after brain shaking. Methods: In this study, near-infrared spectroscopy (NIRS) was used to continuously monitor the concentration change of oxy-hemoglobin (HbO2) and deoxy-hemoglobin (HbR) to understand changes in the physiological state during and after brain shaking. Laser Doppler flowmetry was also used to monitor changes in cerebral blood flow under TBI to supplement the investigation. Triphenyltetrazolium chloride (TTC) staining was used to monitor changes of infarction volume corresponding to different impact strengths. Result: The experimental results indicated that concentration changes of HbO2 and total-hemoglobin (HbT) were significantly related to the impact strength. The infarction volume was also significantly related to the impact strength. Conclusion: Therefore, the non-invasive monitoring of concentration changes in HbO2, HbR, and HbT using NIRS may have a clinical application for the evaluation of TBI.
Feature Extraction from Human Gaiting Patterns using Principal Component Analysis and Multivariate Empirical Mode Decomposition
(2015-10-15)
ZAO JOHN KAR-KIN
;
LU CHIH-KAI
The present invention, in some embodiments thereof, relates to a technique for extracting one or more features of a person's gait from acceleration and velocity measurements collected by motion sensors associated with the person.
阿卡尼- 哈米德的願景巨型加速器與新自然律
(2015-10-15)
渥秋華 Natalie Wolchover
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周樹靜
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Shing-Tung Yau Center
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丘成桐中心
要讓尼瑪．阿卡尼-哈米德（Nima ArkaniHamed）持續談論宇宙的話題不是一件難事，他可以談上幾分鐘甚至數小時，把你傳送到人類理解力的邊緣，然後他會帶你跨越邊界，超越愛因斯坦，超越時空和量子力學以及所有對 20 世紀物理學的腐朽比喻，進入一個能解釋萬物既壯麗又新穎的願景，一切是那麼簡潔、那麼通透。然後他會提醒你，在 2015 年，這些都還是臆想，但是他確信某天這個願景將會成真。
黑洞動搖物理之本量子資訊認為黑洞蒸發會撼動物理學的基石
(2015-10-15)
基汀斯 Steven B. Giddings
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戴守煌
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Shing-Tung Yau Center
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丘成桐中心
量子資訊認為黑洞蒸發會撼動物理學的基石
廣義相對論中的數學 2015 年費爾茲研究所講辭
(2015-10-15)
丘成桐
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趙學信
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Shing-Tung Yau Center
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丘成桐中心
我們都知道，就在整整一百年前，愛因斯坦寫下了他統馭重力和動態時空的著名方程式。愛因斯坦的這項創造被認為是人類歷史上最偉大的成就之一，他的動機是要結合物理學上兩個重要但互不相容的理論：其一是行之已久的牛頓重力論，另一是剛發展出來的狹義相對論。
編輯曲線預約廣義相對論的下一個百年
(2015-10-15)
編輯室
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Shing-Tung Yau Center
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丘成桐中心
今年適逢廣義相對論提出的一百周年。為紀念這項重大突破，本刊特地推出「廣義相對論百年」專輯，挑了幾個比較不一樣的主題與讀者分享。
我像發現生命意義卻苦於無法言詮的人 2014 年京都獎得主韋頓訪談
(2015-10-15)
大栗博司
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戶田幸伸
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山崎雅人
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翁秉仁
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Shing-Tung Yau Center
事實上，我在幾天前的頒獎演說中也曾特別提及，我將這個獎視為對這整個領域的肯定，而不僅只於我個人。
Origin of metallic behavior in NiCo2O4 ferrimagnet
(2015-10-15)
Bitla, Yugandhar
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Chin, Yi-Ying
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Lin, Jheng-Cyuan
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Van, Chien Nguyen
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Liu, Ruirui
Predicting and understanding the cation distribution in spinels has been one of the most interesting problems in materials science. The present work investigates the effect of cation redistribution on the structural, electrical, optical and magnetic properties of mixed-valent inverse spinel NiCo2O4(NCO) thin films. It is observed that the films grown at low temperatures (T < 400 degrees C) exhibit metallic behavior while that grown at higher temperatures (T > 400 degrees C) are insulators with lower ferrimagnetic-paramagnetic phase transition temperature. So far, n-type Fe3O4 has been used as a conducting layer for the spinel thin films based devices and the search for a p-type counterpart still remains elusive. The inherent coexistence and coupling of ferrimagnetic order and the metallic nature in p-type NCO makes it a promising candidate for spintronic devices. Detailed X-ray Absorption and X-ray Magnetic Circular Dichroism studies revealed a strong correlation between the mixed-valent cation distribution and the resulting ferrimagnetic-metallic/insulating behavior. Our study clearly demonstrates that it is the concentration of Ni3+ ions and the Ni3+-O-2-Ni2+ double exchange interaction that is crucial in dictating the metallic behavior in NCO ferrimagnet. The metal-insulator and the associated magnetic order-disorder transitions can be tuned by the degree of cation site disorder via growth conditions.
20151015第六期目錄
(2015-10-15)
編輯室
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Shing-Tung Yau Center
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丘成桐中心
編輯曲線數理簡訊 [專題] 廣義相對論中的數學黑洞動搖物理之本星空中的重力透鏡 [數] 淺談動力系統中的禍福相倚 [理] 阿卡尼- 哈米德的願景 [人] 我像發現生命意義卻苦於無法言詮的人 [文] 時間感、歷史觀、思想與社會 [書評] 美是均衡中有錯愕
數理簡訊
(2015-10-15)
編輯室
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Shing-Tung Yau Center
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丘成桐中心
廣義相對論一百年屬於臺灣的愛因斯坦嘉年華從 2005 年開始，世界就進入愛因斯坦的十年。1905 年這位世上最有想法的物理學家發明了狹義相對論，打破了時空的傳統觀念，隨著運動，長度會收縮，時間會變慢，也從原子中找到前所未見的能源。中國的下一個長城？巨型對撞機的命運即將揭曉今年 9 月 25 日，就在中國國家主席習近平訪美期間，《華爾街日報》刊登了由重量級物理學家格羅斯（D. Gross）和韋頓（E. Witten）共同撰寫的文章〈中國的科學大躍進〉（China’s Great Scientific Leap Forward），呼籲美國應與中國加強科研合作，特別是在粒子物理學方面。由於此文，原本不太為人所知的中國巨型對撞機計畫一時引起了關注。解決艾狄胥的差異性猜想多工 vs. 單工電腦 vs. 大腦今年 9 月，UCLA 數學家陶哲軒在他的部落格及預印本網站 arXiv，以兩篇論文提出「艾狄胥差異性問題」（Erdös discrepancy problem，簡稱EDP）的證明，也為他和艾狄胥的老少交誼再添佳話。這是艾狄胥早在1930 年代即提出、但卻始終無法解答的組合數論問題，他在晚年經常把它列為個人最喜歡的問題之一，並提供 500 美元的懸賞獎金。
EEG correlates of spatial orientation in the human retrosplenial complex
(2015-10-15)
Lin, C-T.
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Chiu, T-C.
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Gramann, K.
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資訊工程學系
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腦科學研究中心
Studies on spatial navigation reliably demonstrate that the retrosplenial complex (RSC) plays a pivotal role for allocentric spatial information processing by transforming egocentric and allocentric spatial information into the respective other spatial reference frame (SRF). While more and more imaging studies investigate the role of the RSC in spatial tasks, high temporal resolution measures such as electroencephalography (EEG) are missing. To investigate the function of the RSC in spatial navigation with high temporal resolution we used EEG to analyze spectral perturbations during navigation based on allocentric and egocentric SRF. Participants performed a path integration task in a clearly structured virtual environment providing allothetic information. Continuous EEG recordings were decomposed by independent component analysis (ICA) with subsequent source reconstruction of independent time source series using equivalent dipole modeling. Time-frequency transformation was used to investigate reference frame-specific orientation processes during navigation as compared to a control condition with identical visual input but no orientation task. Our results demonstrate that navigation based on an egocentric reference frame recruited a network including the parietal, motor, and occipital cortices with dominant perturbations in the alpha band and theta modulation in frontal cortex. Allocentric navigation was accompanied by performance-related desynchronization of the 8-13 Hz frequency band and synchronization in the 12-14 Hz band in the RSC. The results support the claim that the retrosplenial complex is central to translating egocentric spatial information into allocentric reference frames. Modulations in different frequencies with different time courses in the RSC further provide first evidence of two distinct neural processes reflecting translation of spatial information based on distinct reference frames and the computation of heading changes. (C) 2015 Elsevier Inc. All rights reserved.
星空中的重力透鏡偏折的光透露暗能量、暗物質與黑洞的祕密
(2015-10-15)
庫普曼斯 Leon V. E. Koopmans
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布蘭福特 Roger D. Blandford
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李沃龍
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Shing-Tung Yau Center
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丘成桐中心
愛因斯坦在 1915 年所完成的廣義相對論，為我們提供了描述宇宙結構所需的工具，並決定光在其中的傳播途徑。它指出，假若我們把時空當成是平坦的，會發現光行經重力勢阱（potential well）時彷彿受其吸引而產生偏折。這種偏折現象如今稱為重力透鏡（gravitational lensing），在 1919年 5 月 29 日的日全蝕期間，首度被位於巴西索布拉爾（Sobral）與西非外海普林西比島（Principe Island）的英國探險隊觀測到。兩支探險隊觀察靠近太陽邊緣的恆星，並測量它們的位移，發現此結果比較接近愛因斯坦預期的 1.7 角秒，而非只有一半大小的牛頓理論預測值。1919 年的觀測結果意謂著愛因斯坦理論的重大勝利。
A New D-A conjugated polymer P(PTQD-BDT) with PTQD acceptor and BDT donor units for BHJ polymer solar cells application
(2015-10-15)
Keshtov, M. L.
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Kuklin, S. A.
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Chen, F. C.
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Khokhlov, A. R.
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Kurchania, Rajnish
A novel donor-acceptor (D-A) copolymer comprising of weak electron donating BDT moiety and strong 9-(2-octyldodecyl)-8H-pyrrolo[3,4-b] bisthieno[2,3-f:3\',2\'-h] quinoxaline-8,10(9H)-dione (PTQD) unit denoted as P(PTQD-BDT) was synthesized as donor material for polymer solar cells. P(PTQD-BDT) shows a broad visible-near-infrared absorption band with an optical bandgap of 1.74 eV and possesses a relatively low-lying HOMO level at -5.28 eV. Bulk-heterojunction polymer solar cell with the optimized blend of 1:2 (weight ratio) P(PTQD-BDT):PC71BM (processed with chloroform) shows an open circuit voltage of 0.92 V, a short circuit current density of 7.84 mA/cm(2), and a fill factor of 0.50, achieving a power conversion efficiency (PCE) of 3.61%. The PCE has been further improved to 5.55% (J(sc) = 10.34 mA/cm(2), V-oc = 0.88V and FF = 0.61), when 3% vol 1,8-diio-dooctane (DIO) was used as solvent additive for the processing of P(PTQD-BDT):PC71BM blended film. The enhancement in J(sc) is as a result of the appropriate morphology and efficient exciton dissociation into free charge carrier. The increase in PCE has been attributed to the favorable nanoscale morphology for efficient exciton dissociation and charge transport (reduction in the electron to hole mobility ratio). (c) 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2390-2398
淺談動力系統中的禍福相倚由阿維拉的工作談起
(2015-10-15)
班榮超
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Shing-Tung Yau Center
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丘成桐中心
動力系統大致分為兩大類：連續型及離散型。連續型動力系統一般是透過微分方程來描述，而離散型動力系統主要是由差分方程（或稱變換或映射）所刻畫。本文將把重點放在後者。
時間感、歷史觀、思想與社會進化思想在近代中國
(2015-10-15)
王汎森
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Shing-Tung Yau Center
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丘成桐中心
.透過嚴復所譯的《天演論》，「進化」成為影響近代中國最重要的思想觀念之一。該書所譯並非達爾文的《物種原始》，而是對赫胥黎《進化與倫理》的譯述。 .「演化」、「進步」、「進化」是不同的概念，但演化論傳入中國後，各概念被不加批判的混用附會，形成線性的進步觀，滲透到各領域、層面。改變了人們的時間感、學術思路、道德尺度，擁有不可挑戰的正當性。當時許多即使是對立的思維，也得在進化論的架構下才能理解。 .對進化論的看法固非一成不變的。當有人對漸變感到不耐，而企求驟變或突變時，原先是進步動力的進化論，變成激進派如辯證唯物論者眼中的桎梏而遭受攻擊。