Browsing by Issue Date, starting with "2015-07-24"

Now showing 1 - 20 of 21321

Time-resolved magnetophotoluminescence studies of magnetic polaron dynamics in type-II quantum dots
(2015-07-24)
Barman, B.
;
Oszwaldowski, R.
;
Schweidenback, L.
;
Russ, A. H.
;
Pientka, J. M.
We used continuous wave photoluminescence (cw-PL) and time-resolved photoluminescence (TR-PL) spectroscopy to compare the properties of magnetic polarons (MP) in two related spatially indirect II-VI epitaxially grown quantum dot systems. In the ZnTe/(Zn, Mn)Se system the holes are confined in the nonmagnetic ZnTe quantum dots (QDs), and the electrons reside in the magnetic (Zn, Mn)Se matrix. On the other hand, in the (Zn, Mn)Te/ZnSe system, the holes are confined in the magnetic (Zn, Mn)Te QDs, while the electrons remain in the surrounding nonmagnetic ZnSe matrix. The magnetic polaron formation energies E-MP in both systems were measured from the temporal redshift of the band-edge emission. The magnetic polaron exhibits distinct characteristics depending on the location of the Mn ions. In the ZnTe/(Zn, Mn)Se system the magnetic polaron shows conventional behavior with E-MP decreasing with increasing temperature T and increasing magnetic field B. In contrast, E-MP in the (Zn, Mn)Te/ZnSe system has unconventional dependence on temperature T and magnetic field B; E-MP is weakly dependent on T as well as on B. We discuss a possible origin for such a striking difference in the MP properties in two closely related QD systems.
Synthesis, characterization and analysis of the acrylamide- and glycidamide-glutathione conjugates
(2015-07-25)
Luo, Yu-Syuan
;
Long, Tai-Ying
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Shen, Li-Ching
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Huang, Shou-Ling
;
Chiang, Su-Yin
Acrylamide (AA) is reported present in high-temperature-processed food and classified as a possible human carcinogen. In vivo metabolic activation of AA by CYP 2E1 to glycidamide (GA) may play an important role on AA carcinogenicity. AA and GA can be detoxified by glutathione-S-transferase to form AA and isomeric GA glutathione conjugates (M-, GA2- and GA3-GSH, respectively), which can be further metabolized to mercapturic acids (MAs). Although many studies analyzed MAs in urine of rodents and humans, few studies have characterized and analyzed the GSH conjugates. The objectives of this study were to synthesize, purify, and characterize AA-GSH, GA2-GSH, GA3-GSH, (C-13(3))-AA-GSH, (C-13(3))-GA2-GSH, and (C-13(3))-GA3-GSH to develop an isotope-dilution liquid chromatography tandem mass spectrometry (LC-MS/MS) method to analyze AA- and GA-GSHs in blood of rats treated with AA. After purification and characterization of these conjugates, the LC-MS/MS method was developed and validated. This method reveals a limit of detection (S/N= 3) at 0.017 and a limit of quantitation (S/N = 10) at 0.05 ng/mL of serum for AA-GSH, 0.075 and 0.25 ng/mL for GA2-GSH, and 0.15 and 0.5 ng/mL for GA3-GSH. Analyzed with this method, AA-GSH, GA2-GSH and GA3-GSH were 1651.1 +/- 374.5, 18.4 +/- 6.3 and 75.3 +/- 31.3 ng/mL in blood of male rats at 2 h after treatment with 5 mg/kg bw of AA by ip injection. These results showed that the LC-MS/MS method was successfully developed to analyze AA-GSH, GA2-GSH and GA3-GSH with satisfying sensitivity of AA and GA which were conjugated by glutathione in vivo. (C) 2015 Elsevier Ireland Ltd. All rights reserved.
Three-phase behavior-based detection and classification of known and unknown malware
(2015-07-25)
Lin, Ying-Dar
;
Lai, Yuan-Cheng
;
Lu, Chun-Nan
;
Hsu, Peng-Kai
;
Lee, Chia-Yin
To improve both accuracy and efficiency in detecting known and even unknown malware, we propose a three-phase behavior-based malware detection and classification approach, with a faster detector in the first phase to filter most samples, a slower detector in the second phase to observe remaining ambiguous samples, and then a classifier in the third phase to recognize their malware type. The faster detector executes programs in a sandbox to extract representative behaviors fed into a trained artificial neural network to evaluate their maliciousness, whereas the slower detector extracts and matches the LCSs of system call sequences fed into a trained Bayesian model to calculate their maliciousness. In the third phase, we define malware behavior vectors and calculate the cosine similarity to classify the malware. The experimental results show that the hybrid two-phase detection scheme outperforms the one-phase schemes and achieves 3.6% in false negative and 6.8% in false positive. The third-phase classifier also distinguishes the known-type malware with an accuracy of 85.8%. Copyright (c) 2015 John Wiley & Sons, Ltd.
Light extraction from electroluminescent devices using micro-rod array embedded within glass substrate
(2015-07-27)
Wang, Yi-Jun
;
Ouyang, Shi-Hong
;
Lu, Jian-Gang
;
Shieh, Han-Ping D.
;
光電工程學系
The total internal reflection (TIR) effect in conventional electroluminescent devices causes a large amount of light energy trapped in the devices and result in heat energy that adversely affects the performance of the device. In order to enhance the light out-coupling efficiency without sacrificing the electrical properties, a micro-rod array (MRA) structure fabricated by a femtosecond laser was demonstrated. Green, blue, and red organic light-emitting diodes were employed to verify the effect of the proposed method, which increases out-coupling efficiencies by a factor of 1.9, 1.7, and 1.82, respectively, compared with conventional devices. This highly effective method is compatible with current device fabrication processes and is applicable to full-color electroluminescent devices. (C) 2015 Optical Society of America
Synchronous-asynchronous laser mode-locking transition
(2015-07-27)
Wu, Shang-Ying
;
Hsiang, Wei-Wei
;
Lai, Yinchieh
;
光電工程學系
;
光電工程研究所
Synchronous-asynchronous mode-locking transition in a hybrid active and passive mode-locked laser is investigated theoretically. Three distinct mode-locking states are found and their transition diagram under varying detuning frequency and modulation strength is determined. By examining the steady-state lasing gain as a function of the detuning modulation frequency, we also clarify why the laser will become unstable near the transition points and why the nonlinear saturable absorption effect is crucial for the stable asynchronous mode-locking operation.
Mechanism study of 2-D laser array generation in a YAG crystal plate
(2015-07-27)
Zeng, Tao
;
He, Jinping
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Kobayashi, Takayoshi
;
Liu, Weiwei
;
電子物理學系
We have reproduced the process of two-dimensional array generation by using two crossing laser beams in a YAG crystal plate based on numerical simulation considering cross-phase modulation (XPM) and self-focusing. Furthermore, we come to the conclusion that both XPM and the cylindrical symmetry breaking in the initial beam profile contributes to the generation of two-dimensional array. In addition, we have studied the threshold input laser beam power for the two crossing beams splitting in a YAG crystal plate. Our study could be valuable in various applications, such as 2-D all-optical switching devices or multicolor pump-probe experiments. (C) 2015 Optical Society of America
Thermal stability and photoconductive properties of photosensors with an alternating multilayer structure of amorphous Se and AsxSe1-x
(2015-07-28)
Yu, Tung-Yuan
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Pan, Fu-Ming
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Chang, Cheng-Yi
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Lin, Jian-Siang
;
Huang, Wen-Hsien
In this study, we fabricated a-Se based photosensors with an alternating multilayer structure of a-Se and AsxSe1-x by rotational thermal evaporation deposition. During the deposition of the amorphous AsxSe1-x layers, As diffuses into the underlying a-Se component layers, thereby improving the thermal stability of the multilayer photosensor and thus increasing the breakdown electric field. Although the As doping introduces carrier traps in the a-Se layers, the multilayer photosensors demonstrate an effective quantum efficiency comparable to the single-layered a-Se sensor under the blue light illumination but are with a lower dark current density by two orders of magnitude. In addition to the top AsxSe1-x layer being functioning as an electron blocking layer, carrier traps present in the multilayer structure may decrease the drift mobility of charge carriers and disturb electric field distribution in the photosensors, thereby suppressing the dark current. (C) 2015 AIP Publishing LLC.
AMP-Activated Protein Kinase Directly Phosphorylates and Destabilizes Hedgehog Pathway Transcription Factor GLI1 in Medulloblastoma
(2015-07-28)
Li, Yen-Hsing
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Luo, Jia
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Mosley, Yung-Yi C.
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Hedrick, Victoria E.
;
Paul, Lake N.
The Hedgehog (Hh) pathway regulates cell differentiation and proliferation during development by controlling the Gli transcription factors. Cell fate decisions and progression toward organ and tissue maturity must be coordinated, and how an energy sensor regulates the Hh pathway is not clear. AMP-activated protein kinase (AMPK) is an important sensor of energy stores and controls protein synthesis and other energy-intensive processes. AMPK is directly responsive to intracellular AMP levels, inhibiting a wide range of cell activities if ATP is low and AMP is high. Thus, AMPK can affect development by influencing protein synthesis and other processes needed for growth and differentiation. Activation of AMPK reduces GLI1 protein levels and stability, thus blocking Sonic-hedgehog-induced transcriptional activity. AMPK phosphorylates GLI1 at serines 102 and 408 and threonine 1074. Mutation of these three sites into alanine prevents phosphorylation by AMPK. This leads to increased GLI1 protein stability, transcriptional activity, and oncogenic potency.
Plasmon-enhanced phonon and ionized impurity scattering in doped silicon
(2015-07-28)
Chen, Ming-Jer
;
Hsieh, Shang-Hsun
;
Chen, Chuan-Li
;
電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Historically, two microscopic electron scattering calculation methods have been used to fit macroscopic electron mobility data in n-type silicon. The first method was performed using a static system that included long-range electron-plasmon scattering; however, the well-known Born approximation fails in this case when dealing with electron-impurity scattering. In the second method, sophisticated numerical simulations were developed around plasmon-excited potential fluctuations and successfully reproduced the mobility data at room temperature. In this paper, we propose a third method as an alternative to the first method. First, using a fluctuating system, which was characterized on the basis of our recently experimentally extracted plasmon-excited potential fluctuations, the microscopic calculations reveal enhanced short-range scattering of electrons by phonons and ionized impurities due to increased electron temperature and increased screening length, respectively. The increased hot electron population makes the Born approximation hold, which eases the overall calculation task substantially. Then, we return to the static system while incorporating plasmon-enhanced impurity scattering. The resulting macroscopic electron mobility shows fairly good agreement with data over wide ranges of temperatures (200-400 K) and doping concentrations (10(15) -10(20) cm(-3)). Application of the proposed method to strained silicon is also demonstrated. (C) 2015 AIP Publishing LLC.
Passivated graphene transistors fabricated on a millimeter-sized single-crystal graphene film prepared with chemical vapor deposition
(2015-07-29)
Lin, Meng-Yu
;
Wang, Cheng-Hung
;
Chang, Shu-Wei
;
Lee, Si-Chen
;
Lin, Shih-Yen
In this work, we first investigate the effects of partial pressures and flow rates of precursors on the single-crystal graphene growth using chemical vapor depositions on copper foils. These factors are shown to be critical to the growth rate, seeding density and size of graphene single crystals. The prepared graphene films in millimeter sizes are then bubbling transferred to silicon-dioxide/silicon substrates for high-mobility graphene transistor fabrications. After high-temperature annealing and hexamethyldisilazane passivation, the water attachment is removed from the graphene channel. The elimination of uncontrolled doping and enhancement of carrier mobility accompanied by these procedures indicate that they are promising for fabrications of graphene transistors.
CLEANING APPARATUS FOR INKJET PRINT HEAD
(2015-07-30)
HU Jwu-Sheng
;
JAO Hsien-Tang
In the present invention, an inkjet printing head cleaning device is provided, through droplet image information and feedback control technology in order to drive the nozzle without ejecting, the micro clogging technique is able to avoid the nozzle crimp and reduce the material cost.
Effects of Pt Decoration on the CO Sensing Reaction Mechanism of PdO Nanoflakes Thin Films
(2015-07-30)
Chiang, Yu-Ju
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Lee, Kuang-Chung
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Pan, Fu-Ming
;
材料科學與工程學系
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Department of Materials Science and Engineering
We sputter-deposited Pt nanopartides on a PdO nanoflake thin film and studied the CO sensing behavior of the Pt-decorated PdO (Pt-PdO) sensor at temperatures below 250 degrees C. According to X-ray photoelectron spectroscopy and temperature-programmed desorption, Pt nanoparticles can modify the electronic structure of the PdO thin film, thus improving the kinetics of PdO reduction by CO. The CO sensing response of the Pt-PdO sensor is greatly influenced by PdO reduction and reoxidation in the temperature range between 100 and 200 degrees C. The dramatic difference in the CO sensing behavior at 150 degrees C between the Pt-PdO and the bare PdO sensors is ascribed to the kinetic competition between PdO reduction and oxidation of growing Pd nanoislands on which dissociative oxygen adsorption takes place. On the other hand, the CO sensing characteristic of the Pt-PdO sensor at 100 degrees C and below is similar to that of the bare PdO sensor because PdO reduction is negligible in the temperature range. The Pt-PdO sensor exhibits a distinct delay in the recovery profile at 100 degrees C as a result of the sluggish replacement of CO adspecies by oxygen on Pt nanoparticles. At temperatures above 200 degrees C, the sensing behavior of the Pt-PdO sensor can be understood on the basis of the oxygen vacancy model. A highly CO-selective sensor based on the pattern recognition of the peculiar sensing response profile at 150 degrees C is suggested.
Epitaxial growth of a monolayer WSe2-MoS2 lateral p-n junction with an atomically sharp interface
(2015-07-31)
Li, Ming-Yang
;
Shi, Yumeng
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Cheng, Chia-Chin
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Lu, Li-Syuan
;
Lin, Yung-Chang
Two-dimensional transition metal dichalcogenides (TMDCs) such as molybdenum sulfide MoS2 and tungsten sulfide WSe2 have potential applications in electronics because they exhibit high on-off current ratios and distinctive electro-optical properties. Spatially connected TMDC lateral heterojunctions are key components for constructing monolayer p-n rectifying diodes, light-emitting diodes, photovoltaic devices, and bipolar junction transistors. However, such structures are not readily prepared via the layer-stacking techniques, and direct growth favors the thermodynamically preferred TMDC alloys. We report the two-step epitaxial growth of lateral WSe2-MoS2 heterojunction, where the edge of WSe2 induces the epitaxial MoS2 growth despite a large lattice mismatch. The epitaxial growth process offers a controllable method to obtain lateral heterojunction with an atomically sharp interface.
HCV NS5A Up-Regulates COX-2 Expression via IL-8-Mediated Activation of the ERK/JNK MAPK Pathway
(2015-07-31)
Chen, Wei-Chun
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Tseng, Chin-Kai
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Chen, Yen-Hsu
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Lin, Chun-Kuang
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Hsu, Shihhsien
Chronic hepatitis C virus (HCV) infection leads to intrahepatic inflammation and liver cell injury, which are considered a risk factor for virus-associated hepatitis, cirrhosis, and hepatocellular carcinoma worldwide. Inflammatory cytokines are critical components of the immune system and influence cellular signaling, and genetic imbalances. In this study, we found that cyclooxygenase-2 (COX-2) and interleukin-8 (IL-8) were significantly induced by HCV infection and HCV NS5A expression, and induction of COX-2 correlated with HCV-induced IL-8 production. We also found that the ERK and JNK signaling pathways were involved in the regulation of IL-8-mediated COX-2 induction in response to HCV infection. Using a promoter-linked reporter assay, we identified that the C/EBP regulatory element within the COX-2 promoter was the dominant factor responsible for the induction of COX-2 by HCV. Silencing C/EBP attenuated HCV-induced COX-2 expression. Our results revealed that HCV-induced inflammation promotes viral replication, providing new insights into the involvement of IL-8-mediated COX-2 induction in HCV replication.
Carrier generation and recombination dynamics in type-II ZnSeTe/ZnMnSe quantum structures
(2015-07-31)
Lin, Yan-Cheng
;
Chou, Wu-Ching
;
電子物理學系
;
Department of Electrophysics
Type-II band alignment structure is coveted in the design of photovoltaic devices, since it is beneficial for the transport of photogenerated carriers. Here we study the generation and recombination dynamics of carriers in a type-II quantum structure composed of ZnSe0.92Te0.08 highly mismatched alloys (HMAs) and Zn0.97Mn0.03Se. The photoinduced holes at the ZnSe0.92Te0.08 HMAs firstly undergo rapid relaxation to the isoelectronic centers above the valence band edge and subsequently recombine with the free electrons in the Zn0.97Mn0.03Se. The long carrier lifetimes over 120 ns induced by spatially indirect excitons that are bound to isoelectronic Te trapping states further increase with increasing temperature.
編案：汙名連線的可能性
(深河出版有限公司, 2015-08-01)
人間思想編輯部
Homoepitaxial growth and stress analysis of (111) diamond film with embedded gold islands
(2015-08-01)
Chiu, Kim-An
;
Wu, Ping-Hsun
;
Peng, Chun-Yen
;
Tian, Jr-Sheng
;
Chang, Li
The internal stress in high-quality (111) homoepitaxial diamond film grown on high-pressure high temperature (HPHT) synthesized single crystal diamond substrate by chemical vapor deposition (CVD) can be reduced effectively by embedding Au islands in diamond. Au islands formed from an Au layer deposited on the diamond substrate by electron beam evaporation can be obtained after hydrogen plasma annealing. Transmission electron microscopy and X-ray diffraction results show that the Au islands covered with CVD diamond have a size in a few hundreds of nanometers and are oriented with diamond in the orientation relationship of {111}Au//{111}(Dia) and < 110 > Au//< 110 > Dia. The surfaces of the CVD diamond films grown on substrate with and without Au coating exhibit cracks when the film thickness reaches 3.5 mu m. As evaluated from the Raman peak shift, it is shown that the internal tensile stress in the film with Au islands is less than in the same thick film on substrate without Au coating. A crack-free (111) homoepitaxial diamond film in the same thickness can be obtained by insertion of multilayers of Au islands in CVD diamond. (c) 2015 Elsevier Ltd. All rights reserved.
Novel junctionless silicon-oxide-nitride-oxide-silicon memory devices with field-enhanced poly-Si nanowire structure
(2015-08-01)
Chou, Chia-Hsin
;
Chan, Wei-Sheng
;
Wu, Chun-Yu
;
Lee, I-Che
;
Liao, Ta-Chuan
In this work, a novel gate-all-around (GAA) low-temperature poly-Si (LTPS) junctionless (JL) silicon-oxide-nitride-oxide-silicon (SONOS) nonvolatile memory device with a field-enhanced nanowire (NW) structure has been proposed to improve the programing/erasing (P/E) performance. Each nanowire has three sharp corners fabricated by a sidewall spacer formation technique to obtain high local electrical fields. Owing to the higher carrier concentration in the channel and the high local electrical field from the three sharp corners, such a JL SONOS memory device exhibits a significantly enhanced P/E speed, a larger memory window, and better data retention properties than a conventional inversion mode NW-channel memory device. (C) 2015 The Japan Society of Applied Physics
MicroRNA-122 is a potential regulator of DNA methylation partly by affecting the global level profile of 5hmC
(2015-08-01)
Tsou, Ann-Ping
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Wang, Kuan-Hua
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Huang, Hsi-Yuan
;
Chen, Li-Jung
;
Liu, Tze-Tze
後記：重返馬來西亞
(深河出版有限公司, 2015-08-01)
蘇穎欣