Browsing by Author "Chen, Wei-Ta"

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Altered near-infrared spectroscopy response to breath-holding in patients with fibromyalgia
(2019-01-01)
Chen, Wei-Ta
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Yu, Chuan-Hsiang
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Sun, Chia-Wei
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交大名義發表
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National Chiao Tung University
Fibromyalgia (FM) is a complex syndrome characterized by chronic widespread pain and a heightened response to pressure. Most medical researches pointed out that FM patients with endothelial dysfunction and arterial stiffness. A continuous-wave near-infrared spectroscopy (NIRS) system is used in present study to measure the hemodynamic changes elicited by breath-holding task in patients with FM. Each patient completed a questionnaire survey including demographics, characteristics of body pain, associated symptoms, headache profiles and Hospital Anxiety and Depression Scale. A total of 27 FM patients and 26 health controls were enrolled. In comparison with healthy controls, patients with FM showed lower maximal and averaged change of oxyhemoglobin concentration in both the left (1.634 +/- 0.890 and 0.810 +/- 0.525 mu M) and the right (1.576 +/- 0.897 and 0.811 +/- 0.601 mu M) prefrontal cortex than healthy controls (P < .05 for both sides) during the breath-holding task. In conclusion, FM is associated with altered cerebrovascular reactivity measured by NIRS and breath-holding task, which may reflect endothelial dysfunction or arterial stiffness. Oxygenated hemoglobin concentration changes of healthy controls and FM patients.
Au-Cd1-xZnxS core-alloyed shell nanocrystals: boosting the interfacial charge dynamics by adjusting the shell composition
(2018-09-28)
Pu, Ying-Chih
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Chen, Wei-Ta
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Fang, Mei-Jing
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Chen, Yu-Lin
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Tsai, Kai-An
Au-Cd1-xZnxS core-shell nanocrystals (NCs) with controllable shell compositions (from x = 0 to x = 0.37) were synthesized by using the hot-injection method. By increasing the mole fraction of ZnS in the Cd1-xZnxS shell, the conduction band of Cd1-xZnxS can be cathodically shifted to cause an increase of energy difference between the conduction band level of the Cd1-xZnxS shell and the Fermi level of the Au core, thereby enlarging the driving force of interfacial electron transfer to enhance the photoelectrochemical (PEC) efficiency. The interfacial charge dynamics of the samples were examined by time-resolved photoluminescence (TRPL) spectroscopy. The results showed that the interfacial electron transfer rate constant (k(et)) from the Cd1-xZnxS shell to the Au core was increased by 2 orders of magnitude, from 2.41 x 10(7) to 4.91 x 10(9) s(-1) as the mole fraction of ZnS increased from 0 to 0.37. Furthermore, PEC characterization, including Mott-Schottky analysis and photovoltage decay measurements, illustrated that gradually introducing ZnS into the shell composition of Au-Cd1-xZnxS NCs can modify the band structure and enhance the effectiveness of interfacial ET for advancing the PEC properties. The practical use of Au-Cd1-xZnxS NCs in PEC methanol oxidation was also demonstrated, revealing their promising potential as viable photoelectrodes for various PEC applications. The present study delivers an alternative approach of modulating the interfacial ET dynamics of core-shell MSNs by means of shell composition adjustment. The illustrations provide an empirical guideline to the intelligent design of core-shell metal-semiconductor nanoheterostructures (MSNs) for the desired PEC applications.
Au-CdS Core-Shell Nanocrystals with Controllable Shell Thickness and Photoinduced Charge Separation Property
(2008-12-09)
Chen, Wei-Ta
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Yang, Ting-Ting
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Hsu, Yung-Jung
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材料科學與工程學系
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Department of Materials Science and Engineering
Au/ZnS core/shell nanocrystals as an efficient anode photocatalyst in direct methanol fuel cells
(2013)
Chen, Wei-Ta
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Lin, Yin-Kai
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Yang, Ting-Ting
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Pu, Ying-Chih
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Hsu, Yung-Jung
Au/ZnS core/shell nanocrystals with controllable shell thicknesses were synthesized using a cysteine-assisted hydrothermal method. Incorporating Au/ZnS nanocrystals into the traditional Pt-catalyzed half-cell reaction led to a 43.3% increase in methanol oxidation current under light illumination, demonstrating their promising potential for metal/semiconductor hybrid nanocrystals as the anode photocatalyst in direct methanol fuel cells.
Deep learning assisted detection of glaucomatous optic neuropathy and potential designs for a generalizable model
(2020-05-14)
Ko, Yu-Chieh
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Wey, Shih-Yu
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Chen, Wei-Ta
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Chang, Yu-Fan
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Chen, Mei-Ju
Purpose To evaluate ways to improve the generalizability of a deep learning algorithm for identifying glaucomatous optic neuropathy (GON) using a limited number of fundus photographs, as well as the key features being used for classification. Methods A total of 944 fundus images from Taipei Veterans General Hospital (TVGH) were retrospectively collected. Clinical and demographic characteristics, including structural and functional measurements of the images with GON, were recorded. Transfer learning based on VGGNet was used to construct a convolutional neural network (CNN) to identify GON. To avoid missing cases with advanced GON, an ensemble model was adopted in which a support vector machine classifier would make final classification based on cup-to-disc ratio if the CNN classifier had low-confidence score. The CNN classifier was first established using TVGH dataset, and then fine-tuned by combining the training images of TVGH and DrishtiGS datasets. Class activation map (CAM) was used to identify key features used for CNN classification. Performance of each classifier was determined through area under receiver operating characteristic curve (AUC) and compared with the ensemble model by diagnostic accuracy. Results In 187 TVGH test images, the accuracy, sensitivity, and specificity of the CNN classifier were 95.0%, 95.7%, and 94.2%, respectively, and the AUC was 0.992 compared to the 92.8% accuracy rate of the ensemble model. For the Drishti-GS test images, the accuracy of the CNN, the fine-tuned CNN and ensemble model was 33.3%, 80.3%, and 80.3%, respectively. The CNN classifier did not misclassify images with moderate to severe diseases. Class-discriminative regions revealed by CAM co-localized with known characteristics of GON. Conclusions The ensemble model or a fine-tuned CNN classifier may be potential designs to build a generalizable deep learning model for glaucoma detection when large image databases are not available.
Enhanced catalytic activity of Ce(1-x)M(x)O(2) (M = Ti, Zr, and Hf) solid solution with controlled morphologies
(2010-01-01)
Chen, Wei-Ta
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Chen, Kuei-Bo
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Wang, Ming-Fang
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Weng, Sheng-Feng
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Lee, Chi-Shen
Ce(1-x)M(x)O(2) (M = Ti, Zr, and Hf) nanomaterials with controlled morphology and composition were synthesized by a two-step route for the first time. These nanomaterials exhibit high activities for hydrogen reduction and ethanol reforming reactions, and therefore, they may be useful for applications in catalysis and solid oxide fuel cells.
Enhanced catalytic activity of Ce1-xMxO2 (M = Ti, Zr, and Hf) solid solution with controlled morphologies
(2010-01-01)
Chen, Wei-Ta
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Chen, Kuei-Bo
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Wang, Ming-Fang
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Weng, Sheng-Feng
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Lee, Chi-Shen
Ce1-xMxO2 (M = Ti, Zr, and Hf) nanomaterials with controlled morphology and composition were synthesized by a two-step route for the first time. These nanomaterials exhibit high activities for hydrogen reduction and ethanol reforming reactions, and therefore, they may be useful for applications in catalysis and solid oxide fuel cells.
Interfacial Charge Carrier Dynamics in Core-Shell Au-CdS Nanocrystals
(2010-07-08)
Yang, Ting-Ting
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Chen, Wei-Ta
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Hsu, Yung-Jung
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Wei, Kung-Hwa
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Lin, Tai-Yuan
The interfacial charge carrier dynamics for core-shell Au-CdS nanocrystals with various shell thicknesses were investigated and presented. Due to the difference in band structures between Au and CdS, a pronounced photoinduced charge separation took place at the interface of Au and CdS, resulting in the electron-charged Au core and the hole-enriched CdS shell. The electron-charging of Au core in Au-CdS nanocrystals was revealed with the corresponding XPS analysis and photocurrent measurement. Time-resolved PL spectra were measured to quantitatively analyze the electron transfer event between CdS shell and Au core for Au-CdS nanocrystals. An increase in the electron-transfer rate constant was observed for Au-CdS nanocrystals with increasing shell thickness, probably due to the less pronounced electron hole interaction of thicker CdS, which enabled a fuller extent of participation of photoexcited electrons in the charge separation process. On the other hand, the hole-enriched CdS shell of Au-CdS nanocrystals upon light illumination was characterized with a photocatalytic process. The photocatalytic activity of Au-CdS nanocrystals was found to increase with increasing shell thickness, attributable to the greater capability of light absorption achieved by the extensive growth of the CdS shell. The correlation of photocatalytic activity with the shell thickness of Au-CdS nanocrystals corresponded well with that of the electron-transfer rate constant. As compared to the relevant commercial products like N-doped P-25 TiO(2), and CdS powders, the as-synthesized Au-CdS nanocrystals,exhibited superior photocatalytic performance under visible light illumination, demonstrating their potential as an effective visible-light-driven photocatalyst. Furthermore, the result of performance evaluation under natural sunlight shows that the present Au-CdS nanocrystals can be used as highly efficient photocatalysts which may practically harvest energy from sunlight.
L-Cysteine-Assisted Growth of Core-Satellite ZnS-Au Nanoassemblies with High Photocatalytic Efficiency
(2010-04-20)
Chen, Wei-Ta
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Hsu, Yung-Jung
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材料科學與工程學系
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Department of Materials Science and Engineering
Core-satellite ZnS-Au nanoassemblies, in which each of the ZnS nanospheres was surrounded by a few Au nanoparticles, have been successfully prepared with a facile L-cysteine-assisted hydrothermal approach. The density of Au nanoparticles encircling each ZnS nanosphere can he readily controlled through suitably modulating the concentration of Au added. Because or the difference in hand structures between ZnS and Au, a pronounced photoinduced charge separation was observed for the as-synthesized ZnS-Au nanoassemblies. As compared to the relevant commercial products like Au-loaded P-25 TiO(2) and ZnS powders, ZnS-Au nanoassemblies exhibited superior photocatalytic performance, demonstrating their potential as an efficient photocatalyst in relevant redox reactions. Furthermore, the recycling test revealed that core satellite nanoassemblies of ZnS-Au could be promisingly utilized in the long-term course of photocatalysis. The present study provides new paradigm for designing the highly efficient semiconductor/metal hybrid photocatalysts that can effectively produce chemical energy from light.
Modulation and Improvement on Separation of Photoinduced Charge Carriers in CdS-Metal Nanoheterostructures
(2009-10-08)
Cheng, Wei-Yun
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Chen, Wei-Ta
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Hsu, Yung-Jung
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Lu, Shih-Yuan
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材料科學與工程學系
We demonstrate the feasibility of modulating and improving the separation of photoinduced charge carriers of CdS-M nanoheterostructures through partial replacement of S with two group 16 elements of larger atomic size, Se and Te. With the incorporation of Se or Te into the US nanowires (NWs), the defect states of the US NWs were effectively passivated, enabling a fuller extent of participation of the photoinduced electrons in the charge separation process, thus resulting in a more pronounced photoluminescence quenching and photocurrent depression for the CdS(1-x)Se(x) and CdS(1-x)Te(x) NWs. The present study provides a facile way of improving the photocatalytic efficiency of US through the improvement in retarding the recombination of photoinduced charge carriers.
Near-Infrared Brain Volumetric Imaging Method: A Monte Carlo Study
(2012-05-01)
Chuang, Ching-Cheng
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Wang, Pei-Ning
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Chen, Wei-Ta
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Lan, Tsuo-Hung
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Chen, Chung-Ming
"The symptom of brain volumetric changes may provide significant biomarker to predict progressive dementia. The brain volumetric changes of prefrontal cortex are highly associated with many neurodegenerative diseases. Besides, brain atrophy reveals the expanded interhemispheric fissure and the concomitant increasing cerebrospinal fluid volume. Thus, the quantitative assessment of brain volumetric changes is an important consideration for clinical studies of neurodegenerative diseases. In this study, we first proposed an approach that uses near-infrared brain volumetric imaging to detect brain volumetric changes. The healthy, aged, and typical Alzheimer's disease (AD) brains were modeled with different characterization of brain volumetric changes from in vivo MRI data based on time-resolved 3-D Monte Carlo simulation. In the results, the significant difference of prefrontal cortex structure can be observed among healthy, aged, and AD brain with various source-detector separations in sagittal view. Our study shows that the near-infrared brain volumetric imaging can be an indicator of brain atrophy for clinical application of neurodegenerative diseases with patient-oriented measurement."