Browsing by Author "Wang, Chih-Wei"

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Biomechanical comparison of unilateral and bilateral pedicle screws fixation for transforaminal lumbar interbody fusion after decompressive surgery - a finite element analysis
(2012-05-16)
Chen, Shih-Hao
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Lin, Shang-Chih
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Tsai, Wen-Chi
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Wang, Chih-Wei
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Chao, Shih-Heng
Background: Little is known about the biomechanical effectiveness of transforaminal lumbar interbody fusion (TLIF) cages in different positioning and various posterior implants used after decompressive surgery. The use of the various implants will induce the kinematic and mechanical changes in range of motion (ROM) and stresses at the surgical and adjacent segments. Unilateral pedicle screw with or without supplementary facet screw fixation in the minimally invasive TLIF procedure has not been ascertained to provide adequate stability without the need to expose on the contralateral side. This study used finite element (FE) models to investigate biomechanical differences in ROM and stress on the neighboring structures after TLIF cages insertion in conjunction with posterior fixation. Methods: A validated finite-element (FE) model of L1-S1 was established to implant three types of cages (TLIF with a single moon-shaped cage in the anterior or middle portion of vertebral bodies, and TLIF with a left diagonally placed ogival-shaped cage) from the left L4-5 level after unilateral decompressive surgery. Further, the effects of unilateral versus bilateral pedicle screw fixation (UPSF vs. BPSF) in each TLIF cage model was compared to analyze parameters, including stresses and ROM on the neighboring annulus, cage-vertebral interface and pedicle screws. Results: All the TLIF cages positioned with BPSF showed similar ROM (<5%) at surgical and adjacent levels, except TLIF with an anterior cage in flexion (61% lower) and TLIF with a left diagonal cage in left lateral bending (33% lower) at surgical level. On the other hand, the TLIF cage models with left UPSF showed varying changes of ROM and annulus stress in extension, right lateral bending and right axial rotation at surgical level. In particular, the TLIF model with a diagonal cage, UPSF, and contralateral facet screw fixation stabilize segmental motion of the surgical level mostly in extension and contralaterally axial rotation. Prominent stress shielded to the contralateral annulus, cage-vertebral interface, and pedicle screw at surgical level. A supplementary facet screw fixation shared stresses around the neighboring tissues and revealed similar ROM and stress patterns to those models with BPSF. Conclusions: TLIF surgery is not favored for asymmetrical positioning of a diagonal cage and UPSF used in contralateral axial rotation or lateral bending. Supplementation of a contralateral facet screw is recommended for the TLIF construct.
FASTR3D: a fast and accurate search tool for similar RNA 3D structures
(2009-07-01)
Lai, Chin-En
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Tsai, Ming-Yuan
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Liu, Yun-Chen
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Wang, Chih-Wei
;
Chen, Kun-Tze
FASTR3D is a web-based search tool that allows the user to fast and accurately search the PDB database for structurally similar RNAs. Currently, it allows the user to input three types of queries: (i) a PDB code of an RNA tertiary structure (default), optionally with specified residue range, (ii) an RNA secondary structure, optionally with primary sequence, in the dot-bracket notation and (iii) an RNA primary sequence in the FASTA format. In addition, the user can run FASTR3D with specifying additional filtering options: (i) the released date of RNA structures in the PDB database, and (ii) the experimental methods used to determine RNA structures and their least resolutions. In the output page, FASTR3D will show the user-queried RNA molecule, as well as user-specified options, followed by a detailed list of identified structurally similar RNAs. Particularly, when queried with RNA tertiary structures, FASTR3D provides a graphical display to show the structural superposition of the query structure and each of identified structures. FASTR3D is now available online at http://bioalgorithm.life.nctu.edu.tw/FASTR3D/.
Have Domestic Institutional Investors Become as Market Savvy as Foreign Investors? Evidence from the Taiwan Options Market
(2014-06-01)
Chiu, Wan-Chien
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Lee, Han-Hsing
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Wang, Chih-Wei
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資訊管理與財務金融系註：原資管所+財金所
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Department of Information Management and Finance
Previous empirical studies indicate that informed investors can predict future index returns. In emerging markets like Taiwan, previous research documents that only foreign institutional investors can predict next-day index returns of the host country. Unlike previous empirical results, we find that in more recent periods, the put/call ratio of domestic institutional investors shows significant predictive power for daily TAIEX returns, except during the 2008 financial crisis. In contrast, the put/call ratio of foreign institutional investors has weak predictability for the TAIEX returns prior to the severe global market downturn in late 2008. We further explore the intraday lead-lag relationship among index returns and put/call ratios of different trader types. Our results show that only the trading of domestic institutional investors possesses predictive capability for intraday TAIEX returns prior to the 2008 financial crisis. During the 2008 financial crisis, intraday TAIEX returns significantly lead option trades of foreign and domestic institutional investors, suggesting that although institutional investors closely watch and react to market fluctuations, they are unable to predict market movement beforehand.
iPARTS: an improved tool of pairwise alignment of RNA tertiary structures
(2010-07-01)
Wang, Chih-Wei
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Chen, Kun-Tze
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Lu, Chin Lung
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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
iPARTS is an improved web server for aligning two RNA 3D structures based on a structural alphabet (SA)-based approach. In particular, we first derive a Ramachandran-like diagram of RNAs by plotting nucleotides on a 2D axis using their two pseudotorsion angles g and h. Next, we apply the affinity propagation clustering algorithm to this g-h plot to obtain an SA of 23-nt conformations. We finally use this SA to transform RNA 3D structures into 1D sequences of SA letters and continue to utilize classical sequence alignment methods to compare these 1D SA-encoded sequences and determine their structural similarities. iPARTS takes as input two RNA 3D structures in the PDB format and outputs their global alignment (for determining overall structural similarity), semiglobal alignments (for detecting structural motifs or substructures), local alignments (for finding locally similar substructures) and normalized local structural alignments (for identifying more similar local substructures without non-similar internal fragments), with graphical display that allows the user to visually view, rotate and enlarge the superposition of aligned RNA 3D structures. iPARTS is now available online at http://bioalgorithm.life.nctu.edu.tw/iPARTS/.
Modeling of Read-Disturb-Induced SET-State Current Degradation in a Tungsten Oxide Resistive Switching Memory
(2018-11-01)
Su, Po-Cheng
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Jiang, Cheng-Min
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Wang, Chih-Wei
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Wang, Tahui
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電子工程學系及電子研究所
We characterize SET-state current degradation induced by read operations in a tungsten oxide resistive memory cell. The current degradation exhibits a two-stage evolution. In the second stage, the current decline follows inverse power-law dependence on cumulative read-disturb time. We present an analytical model to derive the inverse power law. Our model includes oxygen ion activation, mobile oxygen ion hopping, and the reduction of oxygen vacancy density by re-oxidation. Voltage and temperature effects on read-disturb-induced degradation are characterized for comparison with the model. Our results show that the power factor in the inverse power law has exponential dependence on a read voltage.
Non-lethal Candida albicans cph1/cph1 efg1/efg1 mutant partially protects mice from systemic infections by lethal wild-type cells
(2009-03-01)
Yang, Yun-Liang
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Wang, Chih-Wei
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Chen, Chiung-Tony
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Wang, Min-Hsien
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Hsiao, Chin-Fu
Although Candida albicans cph1/cph1 efg1/efg1 mutant cells are not lethal to mice, they proliferated in infected mice instead of simply being cleared by the host immune system. Here, we have shown that the cph1/cph1 efg1/efg1 mutant partially protects mice from systemic infections by the lethal wild-type Candida albicans cells. Our results further indicate that a second dose of the cph1/cph1 efg1/efg1 mutant did not boost the degree of protection. (c) 2008 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.
On-panel electrostatic discharge (ESD) protection design with thin-film transistor in LTPS process
(2007)
Ker, Ming-Dou
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Chuang, Jie-Yao
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Deng, Chih-Kang
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Kuo, Chung-Hong
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Li, Chun-Huai
The electrostatic discharge (ESD) robustness of diode-connected n-type thin-film transistors (N-TFTs) and diode-connected p-type thin-film transistors (P-TFTs) with different layout structures in a given low-temperature polycrystalline silicon (LTPS) process is investigated. By using the wafer-level transmission line pulsing (TLP) system, the high-current transient characteristics and the secondary breakdown current (It2) levels of the diode-connected TFTs under different device parameters and layout structures are directly measured on the glass substrate. Finally, one set of design rules for on-panel ESD protection design is suggested.
Susceptibilities to amphotericin B and fluconazole of Candida species in Taiwan Surveillance of Antimicrobial Resistance of Yeasts 2006
(2008-06-01)
Yang, Yun-Liang
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Wang, An-Huei
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Wang, Chih-Wei
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Cheng, Wei-Ting
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Li, Shu-Ying
Susceptibilities to amphotericin B and fluconazole of 964 Candida isolates collected in Taiwan Surveillance of Antimicrobial Resistance of Yeasts in 2006 were determined. There were 419 (43.5%) Candida albicans, 246 (25.5%) Candida tropicalis, 211 (21.9%) Candida glabrata, 62 (6.4%) Candida parapsilosis, 14 (1.5%) Candida krusei, and 12 (1.2%) others. Interestingly, 16 of the 17 amphotericin B-resistant isolates were non-albicans Candida species. The resistant rate to amphotericin B has decreased from 2.5% in 2002 to 1.8% in 2006. On the other hand, there were 132 C. tropicalis, 14 C. krusei, 10 C. albicans, and 9 C. glabrata isolates that had MICs to fluconazole >= 64 mu g/mL. The prevalence of isolates with such high MICs was significantly higher than that in 2002 (17.1% versus 1.9%). Our results further indicate that most of the isolates with MICs to fluconazole >= 64 mu g/mL exhibited the "trailing" phenomenon. (C) 2008 Elsevier Inc. All rights reserved.
Two Closely Related Fluconazole-Resistant Candida tropicalis Clones Circulating in Taiwan from 1999 to 2006
(2009-09-01)
Li, Shu-Ying
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Yang, Yun-Liang
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Lin, Yu-Hsin
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Ko, Hui-Ching
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Wang, An-Huei
Recently, we reported that diploid sequence type (DST) 140 was a predominant type of Candida tropicalis among isolates with fluconazole minimum inhibitory concentrations (MICs) >= 64 mu g/ml collected in the Taiwan Surveillance of Antimicrobial Resistance of Yeasts (TSARY) in 1999. To determine if DST140 persists in Taiwan, we have used multilocus sequence typing to characterize the genetic profiles of 31 resistant isolates (MICs >= 64 mu g/ml), together with 19 susceptible isolates (MICs <= 16 mu g/ml) collected in TSARY 2006. Among the 50 isolates, 33 distinct DSTs were detected. Of the 31 resistant isolates, 11 (35.5%) belonged to two closely related DSTs (140 and 98), whereas none of the 19 susceptible isolates did (p = 0.004). The isolates belonging to DST140 and 98 were from different geographic regions instead of a restricted area. Thus, our data show temporal and spatial transmission of C. tropicalis clones with high fluconazole MICs in Taiwan from 1999 to 2006.