Browsing by Issue Date, starting with "2015-07-14"

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Shape and Confinement Effects of Various Terminal Siloxane Groups on Supramolecular Interactions of Hydrogen-Bonded Bent-Core Liquid Crystals
(2015-07-14)
Chiang, I-Hung
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Chuang, Wei-Tsung
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Lu, Chia-Lin
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Lee, Ming-Tao
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Lin, Hong-Cheu
To investigate the shape and confinement effects of the terminal siloxane groups on the self-assembled behavior of molecular arrangements in hydrogen-bonded (H-bonded) bent-core complexes, four H-bonded bent-core complexes Si, P1, C4, and P8 with string-, ring-, and cagelike siloxane termini (i.e., linear siloxane unit -Si-O-Si-O-Si, cyclic siloxane unit (Si-O)(4), and silsesquioxane unit PUSS, respectively) were synthesized and investigated. By X-ray diffraction measurements, different types of SmCG (B8) phases and leaning angles were controlled by the shape effect of the string- and cage-like siloxane termini for Si and P1 (with only one arm of H-bonded bent-core), respectively. In addition, the confinement effect of Pi, C4, and P8 (accompanied by increasing the numbers of attached H-bonded bent-core arms) resulted in higher transition temperatures and the diminishing of mesophasic ranges (even the disappearance of mesophase in P8). Moreover, AFM images showed the bilayer smectic CG phases of Si and P1 were aligned to reveal highly ordered thread-like structures by a DC field. By spontaneous polarization measurements within the mesophasic ranges, Si and P1 showed ferroelectric transitions but C4 displayed antiferroelectricity. Finally, the electro-optical performance of B8 phases could be optimized through binary mixtures of Si and P1, and a well aligned modulated ribbon phase could be formed via specific molar ratios of the binary mixtures.
Tuning the functionalities of a mesocrystal via structural coupling
(2015-07-14)
Liu, Heng-Jui
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Liu, Yun-Ya
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Tsai, Chih-Ya
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Liao, Sheng-Chieh
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Chen, Ying-Jiun
In the past decades, mesocrystal, a kind of nanocrystals with specific crystallographic orientation, has drawn a lot of attention due to its intriguing functionalities. While the research community keeps searching for new mesocrystal systems, it is equally crucial to develop new approaches to tune the properties of mesocrystals. In this work, a self-organized two-dimensional mesocrystal composed of highly oriented CoFe2O4 (CFO) nano-crystals with assistance of different perovskite matrices is studied as a model system. We have demonstrated that the strain state and corresponding magnetic properties of the CFO mesocrystal can be modulated by changing the surrounding perovskite matrix through their intimate structural coupling. Interestingly, this controllability is more strongly correlated to the competition of bonding strength between the matrices and the CFO mesocrystals rather than the lattice mismatch. When embedded in a matrix with a higher melting point or stiffness, the CFO mesocrystal experiences higher out-of-plane compressive strain and shows a stronger magnetic anisotropy as well as cation site-exchange. Our study suggests a new pathway to tailor the functionalities of mesocrystals.
Perspective: Spectroscopy and kinetics of small gaseous Criegee intermediates
(2015-07-14)
Lee, Yuan-Pern
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應用化學系
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應用化學系分子科學碩博班
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Department of Applied Chemistry
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Institute of Molecular science
The Criegee intermediates, carbonyl oxides proposed by Criegee in 1949 as key intermediates in the ozonolysis of alkenes, play important roles in many aspects of atmospheric chemistry. Because direct detection of these gaseous intermediates was unavailable until recently, previous understanding of their reactions, derived from indirect experimental evidence, had great uncertainties. Recent laboratory detection of the simplest Criegee intermediate CH2OO and some larger members, produced from ultraviolet irradiation of corresponding diiodoalkanes in O-2, with various methods such as photoionization, ultraviolet absorption, infrared absorption, and microwave spectroscopy opens a new door to improved understanding of the roles of these Criegee intermediates. Their structures and spectral parameters have been characterized; their significant zwitterionic nature is hence confirmed. CH2OO, along with other products, has also been detected directly with microwave spectroscopy in gaseous ozonolysis reactions of ethene. The detailed kinetics of the source reaction, CH2I + O-2, which is critical to laboratory studies of CH2OO, are now understood satisfactorily. The kinetic investigations using direct detection identified some important atmospheric reactions, including reactions with NO2, SO2, water dimer, carboxylic acids, and carbonyl compounds. Efforts toward the characterization of larger Criegee intermediates and the investigation of related reactions are in progress. Some reactions of CH3CHOO are found to depend on conformation. This perspective examines progress toward the direct spectral characterization of Criegee intermediates and investigations of the associated reaction kinetics, and indicates some unresolved problems and prospective challenges for this exciting field of research. (C) 2015 AIP Publishing LLC.
Incorporation of Fluorine onto Different Positions of Phenyl Substituted Benzo[1,2-b:4,5-b ']dithiophene Unit: Influence on Photovoltaic Properties
(2015-07-14)
Yuan, Jun
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Zou, Yingping
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Cui, Ruth
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Chao, Yi-Hsiang
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Wang, Zaiyu
We have designed and synthesized two low bandgap conjugated copolymers containing alternating meta-fluoro-p-alkoxyphenyl- (m-FPO-) or p-fluoro-m-alkoxyphenyl- (p-FPO-) substituted benzodithiophenes-co-benzooxadiazole (BO), named PBO-m-FPO and PBO-p-FPO. The properties, including UV-vis absorption, charge mobility and photovoltaic performance of the two polymers have been intensively investigated. The results indicated that the introduction of fluorine atom at m, p positions of phenyl substituted benzodithiophene unit hardly affected their absorption spectra and highest occupied molecular orbital (HOMO) level. However, the two polymers showed different photovoltaic properties. Power conversion efficiencies (PCEs) based on the device structure of ITO/PEDOT:PSS/polymer:PC71BM/Ca/Al demonstrated a large distinction (5.9% for PBO-m-FPO vs 2.8% for PBO-p-FPO) at optimal weight ratio. When replacing the Ca layer with zirconium acetylacetonate (ZrAcac), using 3% 1,8-diiodooctane (DIO) as the active layer additive, the PCEs of PBO-m-FPO and PBO-p-FPO increased by 36% (8.0% vs 5.9%) and 85% (5.1% vs 2.8%), respectively. The active layer\'s mobilities, morphology and molecular packing resulted in a significant difference in short-circuit current density (J(sc)) and fill factor (FF).
Analysis of Nonlinear Distortion and SSII Cancellation in EAM-Based IMDD OFDM Transmission
(2015-07-15)
Wei, Chia-Chien
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Cheng, Hsuan-Lin
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Chen, Hsing-Yu
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Chen, Yu-Chao
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Chu, Hsuan-Hao
In terms of second-order nonlinearity, nonlinear distortion in an EAM-based IMDD OFDM system is deterministically modeled as subcarrier-to-subcarrier intermixing interference ( SSII), such that DSP-based nonlinear compensation can be provided by decision-aided SSII cancellation at the receiver. The effectiveness of SSII cancellation heavily relies on the accuracy of SSII calculation, which is determined mainly by the modulation model adopted. This study made comprehensive comparisons of three small-signal models (constant-chirp, dynamic-chirp, and nonlinear-E/O models). We then combined theory and experiment results to examine the characteristics of SSII estimation and cancellation using various models, such as SSII spectra, regression coefficients, and correlation coefficients between the SSII and the total received errors, as well as the relationship between improvements in performance and the correlation coefficient. The nonlinear-E/O model is the most comprehensive, and as a result presents the flattest regression coefficient and highest correlation coefficient, which results in the most pronounced improvement in performance.
Structural, optical, and photoluminescence study of ZnO/IGZO thin film for thin film transistor application
(2015-07-15)
Tiwari, Nidhi
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Shieh, Han-Ping D.
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Liu, Po-Tsun
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光電工程學系
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顯示科技研究所
Highly transparent and c-axis oriented zinc oxide (ZnO)/indium gallium zinc oxide (IGZO) thin films have been fabricated by R.F. sputtering. The effect of annealing on physical properties of the films was investigated and compared with a-IGZO thin films. The films are wurtzite-type hexagonal structure similar to ZnO with [0 0 0 2] preferred direction and exhibit less density of defects. The TFTs fabricated with ZnO/IGZO films after annealing at 450 degrees C reveal smaller sub-threshold swing (SS similar to 0.52 V/dec) and threshold voltage (Vth similar to 1.3 V) than the TFTs (SS similar to 0.82 V/dec, Vth similar to 13.3 V) of a-IGZO thin film annealed at the same temperature. (C) 2015 Elsevier B.V. All rights reserved.
我相信數學具有一種神秘的統一性 2005 年阿貝爾獎得主拉克斯訪談
(2015-07-15)
勞森（Martin Raussen）、史考（Christian Skau）
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趙學信
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Shing-Tung Yau Center
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丘成桐中心
事實上，我在 1949 年拿到博士學位後，又回洛沙拉摩斯待了一年，之後還有好幾個夏季在那兒擔任顧問。我在洛沙拉摩斯的第一次經歷，特別是後來那段期間，塑造了我的數學思路。首先，那是體驗如何成為科學團隊的一分子，團體的成員不只是數學家，而是有著不同視野的人，研究目的不是證明定理，而是做出產品。這是書本上學不到的，必須要親身參與，所以我鼓勵我的學生至少去洛沙拉摩斯訪問一個夏季。
20150715第五期目錄
(2015-07-15)
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] 3D改變未來 3D臉部形變的殺手級特效? [數] 馬航MH370失踪之謎 [理] 大自然，不自然？ [人] 我相信數學具有一種神秘的統一性學生的成就是我數學生涯的真正意義對《梅耶爾訪談》的回應 [文] 解釋「中國」的困境
解釋「中國」的困境從近世歷史看中國之「內」與「外」
(2015-07-15)
葛兆光
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Shing-Tung Yau Center
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丘成桐中心
2012 年底，我去韓國首爾演講，《朝鮮日報》的記者與兩位韓國教授來訪問我，他們看過我的《宅茲中國》這本書，於是，在訪談中提了幾個問題，第一是，中國現在是個傳統帝國，還是現代國家？第二，現在中國強大了，是否有恢復「朝貢體制」的想法，越來越膨脹的中國，將與韓國（等鄰國）如何相處？第三是，中國為什麼有國學熱，是否意味著要在文化上重新搞民族主義？他們質疑說，中國還有沒有真正的傳統文化（韓國保存了傳統文化）？
Optimization of mode numbers of VCSELs for small-cell backhaul applications
(2015-07-15)
Lu, I-Cheng
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Wei, Chia-Chien
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Shi, Jin-Wei
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Chen, Hsing-Yu
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Tsai, Sheng-Fan
This paper reports optical orthogonal frequency-division multiplexing (OFDM) transmission using 850 nm Zn-diffusion Vertical-Cavity Surface-Emitting Lasers (VCSELs) and multimode fiber (MMF) for small-cell backhaul applications. We also investigated the influence of side mode suppression ratio (SMSR) on the performance of OFDM modulation. By further optimizing the Zn-diffusion conditions and oxide aperture size, a high-power (6.7 mW) SM (SMSR > 30 dB) VCSEL is demonstrated. By using OFDM modulation and bit-loading algorithm, record-high BRDP (91 Gb/s km) at 26 Gb/s transmission under FEC threshold (bit error rate (BER) < 3.8 x 10(-3)) across 3.5 km OM4 fiber has been successfully demonstrated. (C) 2015 Elsevier B.V. All rights reserved.
Enhanced electromagnetic properties of Fe-Cr-Si alloy powders by sodium silicate treatment
(2015-07-15)
Chen, Shih Fan
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Chang, Hsuan Yao
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Wang, Shea Jue
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Chen, Shih Hsun
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Chen, Chien Chon
The Fe-Si-Cr alloy powders were successfully modified by using the phosphatizing and sodium silicate coating processes. The optimized surface pre-treatment for Fe-Si-Cr powder was phosphatized in 2 wt.% phosphoric solution and further treated with 4 wt.% sodium silicate solution at 75 degrees C for 30 min. These treatments increased the high-frequency stability for Fe-Si-Cr alloy powders, and the annealed cores further showed the enhanced performance of permeability, impedance, quality factor and anti-corrosion ability. Comparing with the Fe-Si-Al alloy, the Fe-Si-Cr also showed a superior performance in density, moldability and saturated magnetic induction. (C) 2015 Elsevier B.V. All rights reserved.
學生的成就是我數學生涯的真正意義 2010 年高斯獎得主梅耶爾訪談
(2015-07-15)
普松 Ulf Persson
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周樹靜
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Shing-Tung Yau Center
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丘成桐中心
自有費爾茲獎以來，法國得獎者除了格羅騰迪克（Alexander Grothendieck）之外，全部出自巴黎高等師範學校（École Normale Supérieure，簡稱 ENS 或 ENS-Ulm）的畢業校友 1，這是無法忽視的事實。在法國還有幾所高等師範（Écoles Normales），像我現在任職的卡尚高等師範學校（École normale supérieure de Cachan，簡稱 ENSCachan），就沒有巴黎高等師範那麼傑出，主要的數學研究方向是應用數學。在法國，應用數學地位不如純數學，科技不如科學。這項主題我們會通篇見到。
3D改變未來泛談數學的 3D 應用
(2015-07-15)
丘成桐
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Shing-Tung Yau Center
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丘成桐中心
我從小就學習基礎科學，從純數學開始到現在，已經 40 多年了。我學習數學從微分幾何開始，再學微分方程，以後發展到物理的廣義相對論、高能物理和弦論。我學習這些學問，一貫帶著熱情，希望看到基礎科學的發展，能對人類有貢獻，對大自然有深入的了解。可是我也慢慢感覺到，基礎科學其實對工業技術和社會科學也有很重要的幫助。所以這二十年來，我參與了很多工程科學的研究。我不單研究幾何在 3D 科技上的發展，也參與過控制論等應用理論的研究。我今天的演講將以3D 科技為主。
馬航MH370失踪之謎計算數學的飛機迫降全攻略
(2015-07-15)
陳鞏
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顧聰
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摩里斯 Philip J. Morris
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佩特遜 Eric G. Paterson
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舍捷夫 Alexey Sergeev
撇開謀殺和陰謀這類人為因素不談，針對事故所做的任何科學調查，都必須考量工程方面的因素，譬如機件儀器故障、空中爆炸、天氣、導航系統等。不過，在數學家的好奇心以及我們從小對飛機的著迷的驅使下，這阻擋不了我們加入調查與重建工作，希望有所貢獻。事實上，數學與工程密不可分
大自然，不自然？近來實驗顯示宇宙可能沒有什麼道理
(2015-07-15)
渥秋華 Natalie Wolchover
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戴守煌
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Shing-Tung Yau Center
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丘成桐中心
在某個陰暗的四月天午後，一群物理學教授與學生擠在哥倫比亞大學一間木質壁板的演講廳裡，聆聽阿卡尼 - 哈米德（Nima Arkani-Hamed）的演講。他是來自附近普林斯頓高等研究院的知名理論物理學家。披著一頭及肩深色頭髮的阿卡尼 - 哈米德，所報告的是歐洲大型強子對撞機（Large Hadron Collider，簡稱 LHC）近期實驗得出兩個看似彼此矛盾的推論。
數理簡訊
(2015-07-15)
編輯室
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Shing-Tung Yau Center
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丘成桐中心
純數學和應用數學的畫界高斯獎的三位得主對於什麼才是正宗數學，純數學家和應用數學家之間曾經劍拔弩張，不過純數和應數的分野十分模糊，尤其好的純數和好的應數如何畫界就更微妙。個人主觀意向並不算數，因為「好」數學需要公評，基於數學的抽象性，最合理的評價方式之一或許是數學獎。我們以年輕的高斯獎來當參考。高斯獎可能是目前應用數學的最高獎，這個德國數學聯盟（DMV）和主辦世界數學家大會的國際數學聯盟（IMU）合辦的獎項，每四年在數學家大會上與費爾茲獎等其他獎項一起頒獎。從2006 年開始，到現在才第三屆。你不知道的費爾茲獎二三事隨著 2014 年新一屆費爾茲獎得主的出爐，數學難得在大眾媒體佔據版面。美國數學學會在 2015 年的《會訊》中也以兩篇文章呈現費爾茲獎少見的面向。其中之一是科學史學者巴瑞尼（Barany）的〈神話與獎章〉（The Myth and the Medal），探討費爾茲獎是如何成為「數學界的諾貝爾獎」。另一篇〈費爾茲獎是否帶來詛咒？〉（Is There a Curse of the Fields Medal?），則是數學家柯拉爾（Kollár）評述經濟學家所做的費爾茲獎研究。插手 3D 產業的數學家交大丘成桐中心特別成立 3D 影像研究群，致力於應用幾何學理論，進行高速和高解析度 3D 成像和 3D人臉的研究分析，並涉足醫學、計算流體動力學等新興的跨越學科領域。目前研究目標為 3D 幾何運算處理，包括曲面匹配、3D 人臉辨識、動態曲面跟蹤、形狀分析、表情類比等各種演算法，以厚植學術研發能量及培育人才。另外也規劃成立展覽廳，將備有3D 掃描儀、電腦、3D 列印之整合系統，透過「動手實做」的理念，讓參訪者能從做中學，玩中學，進而喜愛 3D 數學，推廣數學、科技與文創教育。
對《梅耶爾訪談》的回應
(2015-07-15)
大衛．盧埃勒 David Ruelle
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Shing-Tung Yau Center
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丘成桐中心
親愛的伊夫．梅耶爾，我很高興讀到你的歐洲數學學會訪談，登載於 IAMP 2011 年 6 月的News Bulletin 上，尤其是其中你談到法國高等學校的事。就像你一樣，我偏好像師範學校與綜合工科學校這種菁英系統，但反對他們賦與學生的終生特權。後者實際上相當於終生歧視非高等學校畢業的學生。有趣（或者令人感嘆）的是許多法國左翼知識份子，他們可以為各式各樣的歧視奮鬥，卻獨獨忽略這一塊。
3D臉部形變的殺手級特效? 計算保角幾何與 3D 動畫
(2015-07-15)
林文偉．樂美亨
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Shing-Tung Yau Center
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丘成桐中心
影像形變（morphing）是由一張影像流暢的變化成另一張影像的漸變過程。1991 年，流行音樂之王麥可．傑克森（Michael Jackson）在歌曲Black or White 的音樂影片結尾就使用了這種特效，接連將不同種族的人臉，從一張連續的變化成另一張，視覺感受令人驚豔。隨後許多廣告影片也紛紛開始模仿運用影像形變的特效。隨著電腦技術的快速發展，2D 影像形變特效的技術已近乎成熟，被廣泛應用於影片的製作中。然而，處理 3D 影像的形變特效仍有許多困難之處。隨著 3D 列印科技日漸進步，3D 影像影像處理的技術也隨之漸漸受到重視。
編輯曲線動畫也需要數學
(2015-07-15)
編輯室
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Shing-Tung Yau Center
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丘成桐中心
針對本期專題「數學與應用」，我們選擇一個特別角度切入：「數學與 3D 產業」。傳統上數學應用多與科學「發現」有關，但我們想關注數學在設計「發明」上的應用。
Incidence of Non-Traumatic Subconjunctival Hemorrhage in a Nationwide Study in Taiwan from 2000 to 2011
(2015-07-16)
Hu, Dan-Ning
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Mou, Chih-Hsin
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Chao, Shih-Chun
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Lin, Ching-Yang
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Nien, Chan-Wei
Objective To determine the nationwide incidence of non-traumatic subconjunctival hemorrhage (NTSCH) in Taiwan from 2000-2011 and to analyze the risk factors for NTSCH using a case-control analysis. Methods This is a population-based cohort administrative database study. Randomly selected 1,000,000 residents from the Taiwan National Health Insurance Research Database in 2000 and followed for 12 years to determine the population incidence of NTSCH. Individuals with the first diagnosis of subconjunctival hemorrhage were identified by the corresponding International Classification of Diseases code (ICD) 372.72. Traumatic subconjunctival hemorrhages (ICD-9 codes 921, 871, 850-854 and 959.01) were excluded. The association of NTSCH with various demographic factors, comorbidities and use of medications was studied by a population based case-control analysis using data of 2008-2011. Results A total of 67,720 patients with a first-time diagnosis of NTSCH were identified during the 12 years period. The mean annual incidence was 65 per 10,000 individuals (crude incidence) and 60 per 10,000 individuals (age-and sex-standardized incidence). The incidence rate of NTSCH was higher in women than in men, [men-women ratio: 0.80 (95% confidence interval: 0.78-0.81)]. The age-specific incidence decreased from childhood to the group of teenagers, after which it increased to a maximal value of 136.2 per 10,000 people in the age group of 60-69 years. Case-control analysis showed that comorbidities of hypertension, purpura and thrombocytopenia, and the use of aspirin were significantly associated with the risk of NTSCH. Conclusions This study indicates that NTSCH is a common eye disease that occurs once in 167 individuals in a general East Asian population per year. It occurs more often in women than in men and the age-specific incidence peaked in the age group of 60-69 years. Hypertension, purpura and thrombocytopenia, and the use of aspirin are the major risk factors for NTSCH.