Browsing by Issue Date, starting with "2015-01-28"

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ZnSe center dot 0.5N(2)H(4) Hybrid Nanostructures: A Promising Alternative Photocatalyst for Solar Conversion
(2015-01-28)
Chen, Yu-Chih
;
Liu, Tao-Cheng
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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
As the molecular precursor of ZnSe, ZnSe center dot 0.5N(2)H(4) inorganic-organic hybrids have received relatively less attention due to the feasibility of their further processing and decomposition into pure-phase ZnSe. Here we demonstrated that ZnSe center dot 0.5N(2)H(4) hybrid nanostructures, which were prepared using a facile hydrazine-assisted hydrothermal method, may practically harvest solar energy for photoconversion applications. By modulating the volume ratio of hydrazine hydrate to deionized water employed in the synthesis, the morphology of the grown ZnSe center dot 0.5N(2)H(4) can be varied, which included nanowires, nanobelts and nanoflakes. With the relatively long exciton lifetime and highly anisotropic structure, ZnSe center dot 0.5N(2)H(4) nanowires performed much better in the photodegradation of rhodamine B than the other two counterpart products. As compared to pure ZnSe nanoparticles and single-phase ZnSe nanowires obtained from further processing ZnSe center dot 0.5N(2)H(4), the ZnSe center dot 0.5N(2)H(4) hybrid nanowires exhibited superior photocatalytic performance under visible light illumination. The hybrid nanowires were further decorated with Au particles to endow them with structural and compositional diversities. Time-resolved photoluminescence spectra suggested that almost 40% of the photoexcited electrons in ZnSe center dot 0.5N(2)H(4) nanowires can be transported to the decorated Au, which enabled a fuller extent of participation of charge carriers in the photocatalytic process and thus conduced to a significant enhancement in the photocatalytic activity. The demonstrations from this work illustrate that ZnSe center dot 0.5N(2)H(4) hybrid nanostructures can serve as a versatile photocatalyst platform for advanced photocatalytic applications.
Revealing the flexoelectricity in the mixed-phase regions of epitaxial BiFeO3 thin films
(2015-01-28)
Cheng, Cheng-En
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Liu, Heng-Jui
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Dinelli, Franco
;
Chen, Yi-Chun
;
Chang, Chen-Shiung
Understanding the elastic response on the nanoscale phase boundaries of multiferroics is an essential issue in order to explain their exotic behaviour. Mixed-phase BiFeO3 films, epitaxially grown on LaAlO3 (001) substrates, have been investigated by means of scanning probe microscopy to characterize the elastic and piezoelectric responses in the mixed-phase region of rhombohedral-like monoclinic (M-I) and tilted tetragonal-like monoclinic (M-II,M-tilt) phases. Ultrasonic force microscopy reveal that the regions with low/ high stiffness values topologically coincide with the M-I/M-II,M-tilt phases. X-ray diffraction strain analysis confirms that the M-I phase is more compliant than the M-II,(tilt) one. Significantly, the correlation between elastic modulation and piezoresponse across the mixed-phase regions manifests that the flexoelectric effect results in the enhancement of the piezoresponse at the phase boundaries and in the M-I regions. This accounts for the giant electromechanical effect in strained mixed-phase BiFeO3 films.
A polarized bifocal switch based on liquid crystals operated electrically and optically
(2015-01-28)
Chen, Hung-Shan
;
Lin, Yi-Hsin
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Chang, Chia-Ming
;
Wang, Yu-Jen
;
Srivastava, Abhishek Kumar
A polarized bifocal switch based on liquid crystals (LC) operated electrically and optically is demonstrated. The bifocal switch mainly consists of two parts: a LC layer as a polarization switch and two polymeric layers for modulation of polarization dependent spatial phase difference which results in a positive or a negative lensing effect. The orientations of the LC molecules in the polarization switch are manipulated either in electrically switching (ES) mode or optically rewritten (ORW) mode. The bifocal switch with an aperture size of 10mm exhibits two discrete lens powers (-1.39 Diopter and +0.7 Diopter) with different polarization states no matter in ES mode or in ORW mode. ORW mode is also a bistable mode. The related mechanism and electro-optical performance are discussed and demonstrated. Such a versatile optical switch is capable of not only switching between a positive lens power and a negative lens power, but also switching between two linear polarization states which can be useful in optical systems. The potential applications are for optical systems, wearable devices and ophthalmic lenses. (C) 2015 AIP Publishing LLC.
Unipolar resistive switching behaviors and mechanisms in an annealed Ni/ZrO2/TaN memory device
(2015-01-28)
Tsai, Tsung-Ling
;
Ho, Tsung-Han
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Tseng, Tseung-Yuen
;
電子物理學系
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Department of Electrophysics
The effects of Ni/ZrO2/TaN resistive switching memory devices without and with a 400 degrees C annealing process on switching properties are investigated. The devices exhibit unipolar resistive switching behaviors with low set and reset voltages because of a large amount of Ni diffusion with no reaction with ZrO2 after the annealing process, which is confirmed by ToF-SIMS and XPS analyses. A physical model based on a Ni filament is constructed to explain such phenomena. The device that undergoes the 400 degrees C annealing process exhibits an excellent endurance of more than 1.5 x 10(4) cycles. The improvement can be attributed to the enhancement of oxygen ion migration along grain boundaries, which result in less oxygen ion consumption during the reset process. The device also performs good retention up to 10(5) s at 150 degrees C. Therefore, it has great potential for high-density nonvolatile memory applications.
RNAcentral: an international database of ncRNA sequences
(2015-01-28)
Petrov, Anton I.
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Kay, Simon J. E.
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Gibson, Richard
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Kulesha, Eugene
;
Staines, Dan
The field of non-coding RNA biology has been hampered by the lack of availability of a comprehensive, up-to-date collection of accessioned RNA sequences. Here we present the first release of RNAcentral, a database that collates and integrates information from an international consortium of established RNA sequence databases. The initial release contains over 8.1 million sequences, including representatives of all major functional classes. A web portal (http://rnacentral.org) provides free access to data, search functionality, cross-references, source code and an integrated genome browser for selected species.
Asymmetric Engagement of Amygdala and Its Gamma Connectivity in Early Emotional Face Processing
(2015-01-28)
Liu, Tai-Ying
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Chen, Yong-Sheng
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Hsieh, Jen-Chuen
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Chen, Li-Fen
;
資訊工程學系
The amygdala has been regarded as a key substrate for emotion processing. However, the engagement of the left and right amygdala during the early perceptual processing of different emotional faces remains unclear. We investigated the temporal profiles of oscillatory gamma activity in the amygdala and effective connectivity of the amygdala with the thalamus and cortical areas during implicit emotion-perceptual tasks using event-related magnetoencephalography (MEG). We found that within 100 ms after stimulus onset the right amygdala habituated to emotional faces rapidly (with duration around 20-30 ms), whereas activity in the left amygdala (with duration around 50-60 ms) sustained longer than that in the right. Our data suggest that the right amygdala could be linked to autonomic arousal generated by facial emotions and the left amygdala might be involved in decoding or evaluating expressive faces in the early perceptual emotion processing. The results of effective connectivity provide evidence that only negative emotional processing engages both cortical and subcortical pathways connected to the right amygdala, representing its evolutional significance (survival). These findings demonstrate the asymmetric engagement of bilateral amygdala in emotional face processing as well as the capability of MEG for assessing tha-lamo-cortico-limbic circuitry.
Potent Antibacterial Nanoparticles for Pathogenic Bacteria
(2015-01-28)
Lai, Hong-Zheng
;
Chen, Wei-Yu
;
Wu, Ching-Yi
;
Chen, Yu-Chie
;
應用化學系
Antibiotic-resistant bacteria have emerged because of the prevalent use of antibacterial agents. Thus, new antibacterial agents and therapeutics that can treat bacterial infections are necessary. Vancomycin is a potent antibiotic. Unfortunately, some bacterial strains have developed their resistance toward vancomycin. Nevertheless, it has been demonstrated that vancomycin-immobilized nanoparticles (NPs) are capable to be used in inhibition of the cell growth of vancomycin-resistant bacterial strains through multivalent interactions. However, multistep syntheses are usually necessary to generate vancomycin-immobilized NPs. Thus, maintaining the antibiotic activity of vancomycin when the drug is immobilized on the surface of NPs is challenging. In this study, a facile approach to generate vancomycin immobilized gold (Van-Au) NPs through one-pot stirring of vancomycin with aqueous tetrachloroauric acid at pH 12 and 25 degrees C for 24 h was demonstrated. Van-Au NPs (8.4 +/- 1.3 nm in size) were readily generated. The generated Van-Au NPs maintained their antibiotic activities and inhibited the cell growth of pathogens, which included Gram-positive and Gram-negative bacteria as well as antibiotic-resistant bacterial strains. Furthermore, the minimum inhibitory concentration of the Van-Au NPs against bacteria was lower than that of free-form vancomycin. Staphylococcus aureus-infected macrophages were used as the model samples to examine the antibacterial activity of the Van-Au NPs. Macrophages have the tendency to engulf Van-Au NPs through endocytosis. The results showed that the cell growth of S. aureus in the macrophages was effectively inhibited, suggesting the potential of using the generated Van-Au NPs as antibacterial agents for bacterial infectious diseases.
Ambient-Stable, Annealing-Free, and Ambipolar Organic Field-Effect Transistors Based on Solution-Processable Poly(2,2 \'-bis(trifluoromethyl)biphenyl-alt-2,5-divinylthiophene) without Long Alkyl Side Chains
(2015-01-28)
Chiang, Chi-Jui
;
Chen, Jyh-Chien
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Tsao, Hsiang-Yen
;
Wu, Kuan-Yi
;
Wang, Chien-Lung
An ambipolar conjugated polymer CF3-PBTV, poly(2,2-bis(trifluoromethyl)biphenyl-alt-2,5-divinylthiophene), consisting of thienylenevinylene as the donor and trifluoromethyl-substituted biphenyl as the acceptor has been successfully synthesized. CF3-PBTV shows solution-processability without electrically insulating long alkyl side chains. Grazing incidence X-ray diffraction results suggest a nearly equal population of flat-on and end-on domains in CF3-PBTV thin film. The excellent ambipolarity of CF3-PBTV is demonstrated by well-equivalent charge mobilities of 0.065 and 0.078 cm(2) V-1 s(-1) for p- and n-channel, respectively. The organic field-effect transistors (OFET) also shows very high on/off ratio (approximate to 10(7)) which is attributed to the relatively large bandgap and low-lying highest occupied molecular orbital (HOMO) of CF3-PBTV. The OFET performance barely changes after the device is stored in ambient conditions for 90 days. The ambient-stability is attributed to the enhanced oxidative stability from its low-lying HOMO and the better moisture resistance from its fluorine contents. The performance of CF3-PBTV based OFET is annealing independent. It is noteworthy that the solution-processable, ambipolar, and thienylenevinylene-containing conjugated polymer without any long alkyl side chains is reported for the first time. And to the best of our knowledge, it is the first ambient-stable, annealing-free OFET with well-equivalent ambipolarity.
MethHC: a database of DNA methylation and gene expression in human cancer
(2015-01-28)
Huang, Wei-Yun
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Hsu, Sheng-Da
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Huang, Hsi-Yuan
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Sun, Yi-Ming
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Chou, Chih-Hung
We present MethHC (http://MethHC.mbc.nctu.edu.tw), a database comprising a systematic integration of a large collection of DNA methylation data and mRNA/microRNA expression profiles in human cancer. DNA methylation is an important epigenetic regulator of gene transcription, and genes with high levels of DNA methylation in their promoter regions are transcriptionally silent. Increasing numbers of DNA methylation and mRNA/microRNA expression profiles are being published in different public repositories. These data can help researchers to identify epigenetic patterns that are important for carcinogenesis. MethHC integrates data such as DNA methylation, mRNA expression, DNA methylation of microRNA gene and microRNA expression to identify correlations between DNA methylation and mRNA/microRNA expression from TCGA (The Cancer Genome Atlas), which includes 18 human cancers in more than 6000 samples, 6548 microarrays and 12 567 RNA sequencing data.
OPTICAL SYSTEM AND METHOD FOR ACTIVE IMAGE ACQUISITION
(2015-01-29)
TIEN CHUNG-HAO
;
HSIEH SHENG-HSUN
;
HUANG SHAO-HUNG
An active image acquisition system and method are introduced. The active image acquisition system retrieves light information of an object for creating an object model. The active image acquisition system includes a processing unit, a light-emitting unit and a capturing unit. The processing unit generates a plurality of modulating signals and a plurality of synchronous signals seriatim. The light emitting unit modulates a first light beam by the modulating signals, and the first light beam is emitted to the object. The object reflects a second light beam after the first light beam incident into the object with the light information. The capturing unit generates an image after capturing the second light beam in each modulating signals modulating the first light beam. The processing unit performs a first algorithm for calculating a plurality of the images and the modulating signals, and creating the object model.
Cisplatin-selected resistance is associated with increased motility and stem-like properties via activation of STAT3/Snail axis in atypical teratoid/rhabdoid tumor cells
(2015-01-30)
Liu, Wei-Hsiu
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Chen, Ming-Teh
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Wang, Mong-Lien
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Lee, Yi-Yen
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Chiou, Guang-Yuh
Atypical teratoid/rhabdoid tumor (ATRT) is a malignant pediatric brain tumor with great recurrence after complete surgery and chemotherapy. Here, we demonstrate that cisplatin treatment selects not only for resistance but also for a more oncogenic phenotype characterized by high self-renewal and invasive capabilities. These phenomena are likely due to STAT3 upregulatoin which occurred simultaneously with higher expression of Snail, an activator of epithelial-mesenchymal transition (EMT), in ATRT-CisR cells. STAT3 knockdown effectively suppressed Snail expression and blocked motility and invasion in ATRT-CisR cells, while overexpressing Snail reversed these effects. Chromatin immunoprecipitation assay indicated that STAT3 directly bound to Snail promoter. Moreover, STAT3 knockdown effectively suppressed cancer stem-like properties, synergistically enhanced the chemotherapeutic effect, and significantly improved survival rate in ATRT-CisR-transplanted immunocompromised mice. Finally, immunohistochemistrical analysis showed that STAT3 and Snail were coexpressed at high levels in recurrent ATRT tissues. Thus, the STAT3/Snail pathway plays an important role in oncogenic resistance, rendering cells not only drug-resistant but also increasingly oncogenic (invasion, EMT and recurrence). Therefore, the STAT3/Snail could be a target for ATRT treatment.
Microcontroller-Assisted Compensation of Adenosine Triphosphate Levels: Instrument and Method Development
(2015-01-30)
Hu, Jie-Bi
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Chen, Ting-Ru
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Chen, Yu-Chie
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Urban, Pawel L.
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應用化學系
In order to ascertain optimum conditions for biocatalytic processes carried out in vitro, we have designed a bio-opto-electronic system which ensures real-time compensation for depletion of adenosine triphosphate (ATP) in reactions involving transfer of phosphate groups. The system covers ATP concentration range of 2-48 mu M. The report demonstrates feasibility of the device operation using apyrase as the ATP-depleting enzyme.
Evaluating and comparing the university performance in knowledge utilization for patented inventions
(2015-02-01)
Hung, Wen-Chi
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Ding, Cherng G.
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Wang, Hung-Jui
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Lee, Meng-Che
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Lin, Chieh-Peng
Although universities have played an important role in knowledge creation, it is also of concern to see how universities perform in knowledge utilization. In the present article, an effective approach is proposed to evaluate and compare university performance in knowledge utilization for patented inventions. Growth trajectories of the cumulative patent citations to scientific publications produced by individual universities are analyzed by using latent growth modeling. Moreover, we examine how the utilization of scientific knowledge created in 1995 and 2005 is affected by research impact and university-industry collaboration among the universities in Europe, North America, and East Asia. The results indicate that not all top 300 research universities in the world perform well in knowledge utilization for patented inventions. Some policy implications are discussed.
AMPFLUID: Aggregation Magnified Post-Assay Fluorescence for Ultrasensitive Immunodetection on Digital Microfluidics
(2015-02-01)
Huang, Cheng-Yeh
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Shih, Po-Huai
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Tsai, Po-Yen
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Lee, I-Chin
;
Hsu, Hsin-Yun
Several strategies are currently employed to enhance the detection limit of bead-based assays, but all these approaches improve the sensitivity by varying the assay procedures chemically or biologically. In previous digital microfluidic setups for bead-based immunoassay, the magnetic beads were suspended for detection. We investigated the effect of bead aggregation in such an immunoassay system and propose the aggregation magnified post-assay fluorescence for ultrasensitive immunodetection on digital microfluidics (AMPFLUID). The detection signal and sensitivity are further enhanced even at the post-assay stage without altering the original assay protocol on employing magnetically triggered post-assay aggregation of beads in a digital microfluidic setup followed by processing of the fluorescent signal. This method is shown to enhance the fluorescent signal with increased consistency and sensitivity after appropriate charge-coupled device (CCD) calibration. This method of on-chip detection allows the fulfilment of consumption of a volume at the nanoliter level and a limit of detection in the range picogram/mL. In our sTNF-RI model immunoassay, only 2.5 nL of sample is required; a detection limit 15 pg/mL is achieved. The decreased uncertainty of the measure is indicated by the error bars and coefficient of variation.
Hysteresis-free polymer-stabilised blue phase liquid crystals comprising low surface tension monomers
(2015-02-01)
Hsieh, Pao-Ju
;
Chen, Huang-Ming Philip
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分子醫學與生物工程研究所
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光電工程學系
;
顯示科技研究所
Partial replacement of fluoroacrylates in the monomer composition is able to reduce the free energy of polymer-stabilised blue phase liquid crystal (PSBPLC) due to their low surface tension. The ease of blue phase platelet texture formation is observed under fast cooling and short annealing time before ultraviolet irradiation. The peak driving voltages are dramatically decreased from 9% to 16% in the resulting PSBPLCs. In addition, the hysteresis is completely suppressed in the PSBPLC containing 3FM-M1. The other PSBPLC containing fluoroacrylates retain very small hysteresis (oV<0.8V) regardless the fluorine atom numbers. In comparison with current PSBPLCs, the fluoroacrylates serve as mesophase enhancer not only to promote the blue phase formation but also to improve the electro-optical properties.
Investigation and comparison of analog figures-of-merit for TFET and FinFET considering work-function variation
(2015-02-01)
Lee, Ko-Chun
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Fan, Ming-Long
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Su, Pin
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
This paper investigates and compares the impacts of metal-gate work-function variation on important analog figures-of-merit (FOMs) for TFET and FinFET devices using 3-D atomistic TCAD simulations. Our study indicates that, at 0.6 V supply voltage and 0.2 V gate-voltage overdrive, TFET exhibits superior variation immunity regarding transconductance to drain-current ratio (g(m)/I-DS), output resistance (R-out) and intrinsic gain, and comparable variability in g(m) and cutoff frequency (f(T)) as compared with the FinFET counterparts. In addition, how the correlations between pertinent parameters (e.g., g(m) and R-out) impact the variation immunity of important analog FOMs are analyzed. Our study may provide insights for low-voltage analog design using TFET/FinFET technologies. (C) 2014 Elsevier Ltd. All rights reserved.
A 7.92 Gb/s 437.2 mW Stochastic LDPC Decoder Chip for IEEE 802.15.3c Applications
(2015-02-01)
Lee, Xin-Ru
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Chen, Chih-Lung
;
Chang, Hsie-Chia
;
Lee, Chen-Yi
;
電子工程學系及電子研究所
This paper presents the first silicon-proven stochastic LDPC decoder to support multiple code rates for IEEE 802.15.3c applications. The critical path is improved by a reconfigurable stochastic check node unit (CNU) and variable node unit (VNU); therefore, a high throughput scheme can be realized with 768 MHz clock frequency. To achieve higher hardware and energy efficiency, the reduced complexity architecture of tracking forecast memory is experimentally investigated to implement the variable node units for IEEE 802.15.3c applications. Based on the properties of parity check matrices and stochastic arithmetic, the optimized routing networks with re-permutation techniques are adopted to enhance chip utilization. Considering the measurement uncertainties, a delay-lock loop with isolated power domain and a test environment consisting of an encoder, an AWGN generator and bypass circuits are also designed for inner clock and information generation. With these features, our proposed fully parallel LDPC decoder chip fabricated in 90-nm CMOS process with 760.3 K gate count can achieve 7.92 Gb/s data rate and power consumption of 437.2 mW under 1.2 V supply voltage. Compared to the state-of-the-art IEEE 802.15.3c LDPC decoder chips, our proposed chip achieves over 90% reduction of routing wires, 73.8% and 11.5% enhancement of hardware and energy efficiency, respectively.
Group Partition and Dynamic Rate Adaptation for Scalable Capacity-Region-Aware Device-to-Device Communications
(2015-02-01)
Liou, Yi-Shing
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Gau, Rung-Hung
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Chang, Chung-Ju
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電機工程學系
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Department of Electrical and Computer Engineering
In this paper, we propose using group partition and dynamic rate adaptation for scalable throughput optimization of capacity-region-aware device-to-device communications. We adopt network information theory that allows a receiving device to simultaneously decode multiple packets from multiple transmitting devices, as long as the vector of transmitting rates is inside the capacity region. Based on graph theory, devices are first partitioned into subgroups. To optimize the throughput of a subgroup, instead of directly solving an integer-linear programming problem, we propose using a fast iterative algorithm to select active devices and using aggression levels for rate adaptation based on channel state information. Simulation results show that the proposed algorithm is scalable and could significantly outperform the greedy algorithm by more than 50%.
On the buckling and crushing of expanded honeycomb
(2015-02-01)
Jang, Wen-Yea
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Kyriakides, Stelios
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機械工程學系
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Department of Mechanical Engineering
Commonly used hexagonal honeycomb is manufactured by cold expansion of a laminate of thin metal foils that are bonded along periodically placed strips. The process results in nearly hexagonal cells with double walls in one direction, small rounding at the bent corners, and leaves behind residual stresses. This paper evaluates the effect of the expansion on the compressive response of the honeycomb. A finite element model of a characteristic cell is developed using shell elements and by applying to it the appropriate periodicity conditions. The model is first expanded mechanically producing the realistic geometry and changes to the mechanical properties of the material. The cell is subsequently compressed laterally leading first to buckling, followed by collapse by progressive folding, all similar to the behavior of ideal, stress free hexagonal honeycomb. The calculated buckling stress is about 10% higher than the ideal case, the collapse stress about 5% lower and the average crushing stress somewhat higher. In addition, the buckling and collapse stresses show some sensitivity to the size of periodic domain analyzed, as indeed was the case for the ideal case. (C) 2014 Elsevier Ltd. All rights reserved.
主動式影像擷取之光學系統及光學方法
(2015-02-01)
田仲豪
;
謝昇勲
;
黃少宏
一種主動式影像擷取之光學系統及光學方法，供擷取一物體的一光場資訊以建立一物體模型，該光學系統包含一處理單元、一光發射單元與一擷取單元。該處理單元依序地產生複數個調變訊號與複數個同步訊號。該光發射單元藉由該等調變訊號調變一第一光線並將該第一光線發射至該物體，以在該物體反射具有該物體之光場資訊一第二光線。該擷取單元藉由該等同步訊號，在每一調變訊號調變該第一光線的過程中，同步地擷取該第二光線以產生一影像。該處理單元執行一第一演算法計算複數個該影像與該等調變訊號以建立該物體模型。 The invention is related to an active image acquisition system and method. The active image acquisition system retrieves light information of an object for creating an object model. The active image acquisition system comprises a processing unit, a light emitting unit and a capturing unit. The processing unit generates a plurality of modulating signals and a plurality of synchronous signals seriatim. The light emitting unit modulates a first light beam by the modulating signals, and the first light beam is emitted to the object. The object reflects a second light beam after the first light beam incident into the object with the light information. The capturing unit generates an image after capturing the second light beam in each modulating signals modulating the first light beam. The processing unit performs a first algorithm for calculating a plurality of the images and the modulating signals, and creating the object model.