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Search Results: 1 - 10 of 62226 matches for " Tzu-Ching Yang "
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Core-Shell Structure of a Silicon Nanorod/Carbon Nanotube Field Emission Cathode
Bohr-Ran Huang,Ying-Kan Yang,Tzu-Ching Lin,Wen-Luh Yang
Journal of Nanomaterials , 2012, DOI: 10.1155/2012/369763
Abstract: A novel core-shell structure of silicon nanorods/carbon nanotubes (SiNRs/CNTs) is developed for use in field emission cathodes. The CNTs were synthesized on SiNRs, using the Ag-assisted electroless etching technique to form the SiNRs/CNT core-shell structure. This resulting SiNRs/CNT field emission cathode demonstrated improved field emission properties including a lower turn-on electric field on (1.3 V/μm, 1 μA/cm2), a lower threshold electric field th (1.8 V/μm, 1 mA/cm2), and a higher enhancement factor (2347). These superior properties indicate that this core-shell structure of SiNRs/CNTs has good potential in field emission cathode applications.
Nkx2.7 and Nkx2.5 Function Redundantly and Are Required for Cardiac Morphogenesis of Zebrafish Embryos
Chi-Tang Tu, Tzu-Ching Yang, Huai-Jen Tsai
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0004249
Abstract: Background Nkx2.7 is the tinman-related gene, as well as orthologs of Nkx2.5 and Nkx-2.3. Nkx2.7 and Nkx2.5 express in zebrafish heart fields of lateral plate mesoderm. The temporal and spatial expression patterns of Nkx2.7 are similar to those of Nkx2.5, but their functions during cardiogenesis remain unclear. Methodology/Principal Findings Here, Nkx2.7 is demonstrated to compensate for Nkx2.5 loss of function and play a predominant role in the lateral development of the heart, including normal cardiac looping and chamber formation. Knocking down Nkx2.5 showed that heart development was normal from 24 to 72 hpf. However, when knocking down either Nkx2.7 or Nkx2.5 together with Nkx2.7, it appeared that the heart failed to undergo looping and showed defective chambers, although embryos developed normally before the early heart tube stage. Decreased ventricular myocardium proliferation and defective myocardial differentiation appeared to result from late-stage up-regulation of bmp4, versican, tbx5 and tbx20, which were all expressed normally in hearts at an early stage. We also found that tbx5 and tbx20 were modulated by Nkx2.7 through the heart maturation stage because an inducible overexpression of Nkx2.7 in the heart caused down-regulation of tbx5 and tbx20. Although heart defects were induced by overexpression of an injection of 150-pg Nkx2.5 or 5-pg Nkx2.7 mRNA, either Nkx2.5 or Nkx2.7 mRNA rescued the defects induced by Nkx2.7-morpholino(MO) and Nkx2.5-MO with Nkx2.7-MO. Conclusions and Significance Therefore, we conclude that redundant activities of Nkx2.5 and Nkx2.7 are required for cardiac morphogenesis, but that Nkx2.7 plays a more critical function, specifically indicated by the gain-of-function and loss-of- function experiments where Nkx2.7 is observed to regulate the expressions of tbx5 and tbx20 through the maturation stage.
Zebrafish arl6ip1 Is Required for Neural Crest Development during Embryogenesis
Chi-Tang Tu, Tzu-Ching Yang, Hsing-Yen Huang, Huai-Jen Tsai
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0032899
Abstract: Background Although the embryonic expression pattern of ADP ribosylation factor-like 6 interacting protein 1 (Arl6ip1) has been reported, its function in neural crest development is unclear. Methods/Principal Findings We found that knockdown of Arl6ip1 caused defective embryonic neural crest derivatives that were particularly severe in craniofacial cartilages. Expressions of the ectodermal patterning factors msxb, dlx3b, and pax3 were normal, but the expressions of the neural crest specifier genes foxd3, snai1b, and sox10 were greatly reduced. These findings suggest that arl6ip1 is essential for specification of neural crest derivatives, but not neural crest induction. Furthermore, we revealed that the streams of crestin- and sox10-expressing neural crest cells, which migrate ventrally from neural tube into trunk, were disrupted in arl6ip1 morphants. This migration defect was not only in the trunk neural crest, but also in the enteric tract where the vagal-derived neural crest cells failed to populate the enteric nervous system. We found that this migration defect was induced by dampened Shh signaling, which may have resulted from defective cilia. These data further suggested that arl6ip1 is required for neural crest migration. Finally, by double-staining of TUNEL and crestin, we confirmed that the loss of neural crest cells could not be attributed to apoptosis. Conclusions/Significance Therefore, we concluded that arl6ip1 is required for neural crest migration and sublineage specification.
Shape Reconstruction and Weak Lensing Measurement with Interferometers: A Shapelet Approach
Tzu-Ching Chang,Alexandre Refregier
Physics , 2001, DOI: 10.1086/339496
Abstract: We present a new approach for image reconstruction and weak lensing measurements with interferometers. Based on the shapelet formalism presented in Refregier (2001), object images are decomposed into orthonormal Hermite basis functions. The shapelet coefficients of a collection of sources are simultaneously fit on the uv plane, the Fourier transform of the sky brightness distribution observed by interferometers. The resulting chi-square fit is linear in its parameters and can thus be performed efficiently by simple matrix multiplications. We show how the complex effects of bandwidth smearing, time averaging and non-coplanarity of the array can be easily and fully corrected for in our method. Optimal image reconstruction, co-addition, astrometry, and photometry can all be achieved using weighted sums of the derived coefficients. As an example we consider the observing conditions of the FIRST radio survey (Becker et al. 1995; White et al. 1997). We find that our method accurately recovers the shapes of simulated images even for the sparse uv sampling of this snapshot survey. Using one of the FIRST pointings, we find our method compares well with CLEAN, the commonly used method for interferometric imaging. Our method has the advantage of being linear in the fit parameters, of fitting all sources simultaneously, and of providing the full covariance matrix of the coefficients, which allows us to quantify the errors and cross-talk in image shapes. It is therefore well-suited for quantitative shape measurements which require high-precision. In particular, we show how our method can be combined with the results of Refregier & Bacon (2001) to provide an accurate measurement of weak lensing from interferometric data.
Rho Kinases Regulate the Renewal and Neural Differentiation of Embryonic Stem Cells in a Cell Plating Density–Dependent Manner
Tzu-Ching Chang,Yen-Chung Chen,Ming-Hua Yang,Chien-Hung Chen,En-Wei Hsing,Bor-Sheng Ko,Jun-Yang Liou,Kenneth K. Wu
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0009187
Abstract: Rho kinases (ROCKs) mediate cell contraction, local adhesion, and cell motility, which are considered to be important in cell differentiation. We postulated that ROCKs are involved in controlling embryonic stem (ES) cell renewal and differentiation.
Numerical analysis of airflow alteration in central airways following tracheobronchial stent placement
Chien-Yi Ho, Hsiu-Mei Liao, Chih-Yen Tu, Chih-Yang Huang, Chuen-Ming Shih, Min-Ying Su, Jeon-Hor Chen, Tzu-Ching Shih
Experimental Hematology & Oncology , 2012, DOI: 10.1186/2162-3619-1-23
Abstract: Airway tumors related to central airway compression produces dyspnea, stridor, hemorrhage, obstructive pneumonia, or combinative syndromes. These patients branded with a poor prognosis may not benefit from surgery with a curative intent; however, they will require procedures for palliation with the hopes of being provided with an improved quality of life. In 1915, Brunings and Albrecht [1] raised the model of endoscopic tracheal stent placement for the therapy of airway strictures. As the development of material technology, the commercial silicon stent which could use rigid bronchoscopy to place the implants was proposed by Duman [2]. From that time, metallic airway stent insertion can achieve symptomatic relief in the majority of patients with airway obstruction, and mounting researches aimed at evaluating the effectiveness of metallic airway stents implants based on the change in lung function [3-8], clinical symptoms [9-12], comorbidity incidence [13,14], and survival rate [15-22], have been reported. However, it was difficult to examine or evaluate the efficacy in some patients with severe airway obstruction [23,24].Computer tomography (CT) with two-dimensional (2D) or three-dimensional (3D) reconstruction image study can help to evaluate the improvement of the anatomic structure. However, the real alteration of airflow and the spread of gas particles in central airway before and after airway stents placement could not be accurately accessed before the Computational Fluid Dynamics (CFD) software was applied to mimic the internal luminal 3D airflow alteration [16], and to imitate normal human airway internal alterations [25,26]. Xu and Liu [18,21] reported the change in airway flow and pressure during airway obstruction. Kabilan [22] also used the CFD software to record and analyze the sheep airway flow. In 2005, Chen [23] combined 3D computer tomography and CFD software to investigate the coronary artery disease after stent placement. However, there was no repor
Leisure Activities’Selection and Motivation
Tzu-Ching Lin,Tun-Pei Pao
International Journal of Academic Research in Business and Social Sciences , 2011,
Abstract: The recent academic interest in the youth population has shown a significant increase in research pertaining to leisure. Leisure is a vital lifestyle component to balance people’s lifestyle. Students incline to gain benefits from leisure activities not only to reduce academic stress but also to motivate academic achievement. The objective of this study was to explain the characteristics and motivations of leisure activities’ selection among high school students in Taiwan. A total of 380 questionnaires was collected from the target group. Descriptive statistics, t-test, chi-square test and cross comparison for surveyed students to the questionnaires were used to analyze the valid data by SPSS version 16.0. The results revealed that playing on Computer Internet, going to coffee or tea shops and listening music and broadcasts were the top three leisure activities. In addition, entertainment, exercise and leisure were the top three characteristics of leisure activities. Enjoyment, pressure relaxing and killing time were the top three motivation selections among the surveyed group. This research may suggest that the Taiwanese government should develop more appropriate leisure places for teenagers.
Cross-correlations as a cosmological carbon monoxide detector
Anthony Pullen,Tzu-Ching Chang,Olivier Dore,Adam Lidz
Physics , 2012, DOI: 10.1088/0004-637X/768/1/15
Abstract: We present a new procedure to measure the large-scale carbon monoxide (CO) emissions across cosmic history. As a tracer of large-scale structure (LSS), the CO gas content as a function of redshift can be quantified by its three-dimensional fluctuation power spectra. Furthermore, cross-correlating CO emission with other LSS tracers offers a way to measure the emission as a function of scale and redshift. Here we introduce the model relevant for such a cross-correlation measurement between CO and other LSS tracers, and between different CO rotational lines. We propose a novel use of Cosmic Microwave Background (CMB) data and attempt to extract redshifted CO emissions embedded in the Wilkinson Microwave Anisotropy Probe (WMAP) dataset. We cross-correlate the all-sky WMAP7 data with LSS data sets, namely, the photometric quasar sample and the luminous red galaxy sample from the Sloan Digital Sky Survey Data Release 6 and 7 respectively. We are unable to detect a cross-correlation signal with either CO(1-0) nor CO(2-1) lines, mainly due to the instrumental noise in the WMAP data. However, we are able to rule out models more than three times greater than our more optimistic model. We discuss the cross-correlation signal from the thermal Sunyaev-Zeldovich effect and dust as potential contaminants, and quantify their impact for our CO measurements. We discuss forecasts for current CMB experiments and a hypothetical future CO focused experiment, and propose to cross-correlate CO temperature data with the Hobby-Eberly Telescope Dark Energy Experiment Ly-alpha-emitter sample, for which a signal-to-noise ratio of 58 is possible.
The Weight of Emptiness: The Gravitational Lensing Signal of Stacked Voids
Elisabeth Krause,Tzu-Ching Chang,Olivier Doré,Keiichi Umetsu
Physics , 2012, DOI: 10.1088/2041-8205/762/2/L20
Abstract: The upcoming new generation of spectroscopic galaxy redshift surveys will provide large samples of cosmic voids, the distinct, large underdense structures in the universe. Combining these with future galaxy imaging surveys, we study the prospects of probing the underlying matter distribution in and around cosmic voids via the weak gravitational lensing effects of stacked voids, utilizing both shear and magnification information. The statistical precision is greatly improved by stacking together a large number of voids along different lines of sight, even when taking into account the impact of inherent miscentering and projection effects. We show that Dark Energy Task Force Stage IV surveys, such as the Euclid satellite and the Large Synoptic Survey Telescope, should be able to detect the void lensing signal with sufficient precision from stacking abundant medium-sized voids, thus providing direct constraints on the matter density profile of voids independent of assumptions on galaxy bias.
Shapelets: A New Method to Measure Galaxy Shapes
Alexandre Refregier,Tzu-Ching Chang,David Bacon
Physics , 2002,
Abstract: We present a new approach to measure the shapes of galaxies, a fundamental task in observational astronomy. This approach is based on the decomposition of a galaxy image into a series of orthogonal basis functions, or `shapelets'. Our choice of basis functions, namely the Gauss-Hermite series, has a number of remarkable properties under distortions, convolutions and noise, which makes them particularly well suited for astrophysical applications. In particular, we describe how they can be used to measure the shear induced by weak gravitational lensing, with the precision required for upcoming surveys. We also show how shapelets can be used to reconstruct images from interferometric observations. Other application of shapelets, such as image compression, PSF deconvolution, de-projection and the study of galaxy morphology, are also briefly discussed.
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