Browsing by Issue Date, starting with "2006-03-20"

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High energy scattering amplitudes of superstring theory
(2006-03-20)
Chan, CT
;
Lee, JC
;
Yang, Y
;
電子物理學系
;
Department of Electrophysics
We use three different methods to calculate the proportionality constants among high-energy scattering amplitudes of different string states with polarizations on the scattering plane. These are the decoupling of high-energy zero-norm states (HZNS), the Virasoro constraints and the saddle-point calculation. These calculations are performed at arbitrary but fixed mass level for the NS sector of 10D open superstring. All three methods give the consistent results, which generalize the previous works on the high-energy 26D open bosonic string theory. In addition, we discover new leading order high-energy scattering amplitudes, which are still proportional to the previous ones, with polarizations orthogonal to the scattering plane. These scattering amplitudes are of subleading order in energy for the case of 26D open bosonic string theory. The existence of these new high-energy scattering amplitudes is due to the worldsheet fermion exchange in the correlation functions and is, presumably, related to the high-energy massive spacetime fermionic scattering amplitudes in the R-sector of the theory. (c) 2006 Elsevier B.V. All rights reserved.
Properties of photoluminescence in type-II ZnTe/ZnSe quantum dots
(2006-03-20)
Lin, TY
;
Lyu, DY
;
Chang, J
;
Shen, JL
;
Chou, WC
Temperature and time evolution of the photoluminescence (PL) intensity of bimodal ZnTe/ZnSe type-II quantum dots (QDs) were investigated. A particular temperature dependence of PL was observed in large QDs. PL decay of small QDs is composed of a faster initial component and a slower tail component whereas PL decay of large QDs simply comprises a fast component. All phenomena could be understood consistently by considering charge carrier transfer mechanism, band-bending effect, and the existence of nonradiative centers in the bimodal type-II QD array. We show that excitons play an important role in the emission properties of a self-assembled type-II QD system.
Facile synthesis toward the construction of an activity probe library for glycosidases
(2006-03-20)
Shie, TH
;
Chiang, YL
;
Lin, JJ
;
Li, YK
;
Lo, LC
Chemical probes that selectively label the glycoside hydrolase (GH) subfamilies have proven to be a powerful tool in GH-related research. We have previously demonstrated the design and synthesis of an activity probe for beta-glucosidase adopting a cassette-like design in a model study. Herein we report an improved synthetic route using (4-hydroxyphenyl)acetic acid 2-cyanoethyl ester as the precursor for the latent trapping device. Parallel syntheses were performed for the preparation of a library based oil the structure of a key intermediate. The recognition head of this library covers a series of six sugars, including alpha- and beta-D-Glc, alpha- and beta-D-Gal, alpha-D-Man and alpha-L-Fuc. Each member in this versatile intermediate library could serve as the building block in constructing an activity probe for GHs. As demonstrated in this study, three probes that have the 1,2-cis configuration were thus prepared for the first time to target alpha-D-glucosidase, alpha-D-galactosidase, and alpha-L-fucosidase, respectively. (c) 2006 Elsevier Ltd. All rights reserved.
Electrical properties of resistance switching V-doped SrZrO3 films on textured LaNiO3 bottom electrodes
(2006-03-21)
Liu, CY
;
Wang, A
;
Jang, WY
;
Tseng, TY
;
電子工程學系及電子研究所
Sputter-deposited V-doped SrZrO3 (SZO) films were deposited on textured LaNiO3 (LNO) bottom electrodes to investigate the resistance switching properties and reliabilities. The microstructures of the SZO and LNO films were characterized by x-ray diffraction. The resistance of the AI/V-doped SZO/LNO sandwich structures can be reversibly switched by operating with dc bias voltages or voltage pulses. The device with [100] orientated SZO film had better resistance switching properties and the resistance ratio was more than 1000. The effect of thermal treatment on resistance switching properties was investigated and different behaviour of the two leakage-states was found. Finally, the reliability of the device was also investigated. The device with the properties of reversible resistance switching and non-destructive readout is suitable for nonvolatile memory application.
Ferroelectric memory structure and fabrication method thereof
(2006-03-21)
Tseng
;
Tseung-Yuen
;
Lee
;
Shean Yiah
A ferroelectric memory structure is disclosed. The ferroelectric memory structure includes a substrate, an insulating layer formed on the substrate, a plurality of oxide electrodes formed on the insulating layer, a ferroelectric layer formed on the insulating layer and the plurality of oxide electrodes, and a plurality of metallic electrodes formed on the ferroelectric layer and corresponding to the plurality of the oxide electrodes.
On embed-ding cycles into faulty twisted cubes
(2006-03-22)
Yang, MC
;
Li, TK
;
Tan, JJM
;
Hsu, LH
;
資訊工程學系
The twisted cube TQ(n) is an alternative to the popular hypercube network. Recently, some interesting properties of TQ(n) were investigated. In this paper, we study the pancycle problem on faulty twisted cubes. Let f(e) and f(v) be the numbers of faulty edges and faulty vertices in TQ(n), respectively. We show that, with f(e) + f(v) <= n - 2, a faulty TQ(n) still contains a cycle of length l for every 4 <= l < V(TQ(n)) - f(v) and odd integer n >= 3. (C) 2005 Elsevier Inc. All rights reserved.
Simultaneous preparation of PI/POSS semi-IPN nanocomposites
(2006-03-24)
Chen, WY
;
Ko, SH
;
Hsieh, TH
;
Chang, FC
;
Wang, YZ
This investigation presents a simultaneous and convenient approach to produce a high-performance polyimide with a low dielectric constant by introducing the octa-acrylated polyhedral oligomeric silsesquioxane (methacrylated-POSS) into a polyimide matrix to form polyimide semi-interpenetrating polymer network (semi-IPN) nanocomposites. The differential scanning calorimetry (DSC) and Fourier-transform infrared (FT-IR) results indicate that the self-curing of methacrylated-POSS and the imidization of polyamic acid (PAA) occurs simultaneously. The morphology of a semi-IPN structure of polyimide[POSS-PI/POSS nanocomposites with POSS nanoparticles embedded inside the matrix is elucidated. The POSS particles are uniform and are aggregated to a size of approximately 50-60 nm inside the polyimide matrix. The interconnected POSS particles are observed at high POSS content. The structure is highly crosslinked, so the PI/POSS nanocomposites have an enhanced glass transition temperature. The high porosity of the PI/POSS nanocomposites markedly reduces the dielectric constant of PI because of the nanometer-scale porous structure of POSS.
Investigating photoluminescence and electroluminescence of iridium(III)-based blue-emitting phosphors
(2006-03-27)
Laskar, IR
;
Hsu, SF
;
Chen, TM
;
應用化學系
;
Department of Applied Chemistry
The syntheses of two new cyclometalated ligands [2-(2',4'-difluorophenyl)-4-tert-butylpyridine (F(2)(t)Buppy) and 2-(2',4'-difluorophenyl)-4-oxyhexylpyridine (F(2)HexOppy)] were carried out. Blue-light emitting iridium(III) complex dopants [Ir(F(2)Buppy)(2)(acac/pic)] (acac = acetylacetone; pic = picolinic acid) and [Ir(F(2)HeXOppy)(2)(acac/pic)] were prepared using these cyclometalated ligands with acetylacetone and picolinic acid as their ancillary ligands. The structure of the complexes, [Ir(F(2)(t)Buppy)(2)(acac)] and [Ir(F(2)(t)Buppy)(2)(pic)] were authenticated by X-ray single-crystal structure analysis and showed an octahedral geometry. Comparative absorption and emission spectra of thin-films as well as their solution samples were studied. The variation of the lowest emitting states to their corresponding unsubstituted complexes, [Ir(F(2)ppy)(2)(acac/pic)] was also discussed. The electroluminescent (EL) device was fabricated using [Ir(F(2)(t)Buppy)(2)(pic)] as the dopant (D-I) into the emitting layer and compared with two other EL devices where [Ir(F(2)MeOppy)(2)(acac)] (D-II) and FIrpic (D-III) dopants were used in the same device structure. The lower driving voltages obtained for D-I with respect to D-II and D-III devices were rationalized. The exceptional lowering of the luminance yield of the substituted dopants containing devices, D-I and D-II, to that of D-III which contains the unsubstituted dopant was also investigated. (c) 2005 Elsevier Ltd. All rights reserved.
Dopant profile engineering by near-infrared femtosecond laser activation
(2006-03-27)
Wang, YC
;
Pan, CL
;
Shieh, JM
;
Dai, BT
;
光電工程學系
Femtosecond laser annealing (FLA) was employed for activation of phosphorus (P)- and boron (B)-implanted silicons with negligible dopant diffusion. Preamorphizing implantation is not required. We found that the dopant profiles in FLA-activated samples essentially duplicate those of as-implanted ones even for junctions as deep as 100 nm below the surface. The measured sheet resistances and activation efficiencies of P- and B-implanted samples were in the range of 100-400 Omega/square and 28%-35%, respectively. Moreover, thermal-energy-assisted dopant diffusion by heating was observed for substrate temperature as low as 100 degrees C. The shallow activated-depth feature associated with FLA reduces the separation between end-of-range defects and high-concentration portion of dopants. This generates a steep interstitial gradient responsible for observed B and P uphill diffusions at a depth of about 60 nm below the surface. (c) 2006 American Institute of Physics.
InGaN self-assembled quantum dots grown by metal-organic chemical vapour deposition with growth interruption
(2006-03-28)
Yao, HH
;
Lu, TC
;
Huang, GS
;
Chen, CY
;
Liang, WD
Self-assembled InGaN quantum dots (QDs) were grown by metal-organic chemical vapour deposition with growth interruption at low V/III ratio and low growth temperature on sapphire substrates. The effects of the interruption time on the morphological and optical properties of InGaN QDs were studied. The results show that the growth interruption can modify the dimension and distribution of InGaN QDs, and cause the QD emission wavelength to blue shift with increasing interruption time. A density of InGaN QDs of about 4.5 x 10(10) cm(-2) with an average lateral size of 11.5 nm and an average height of 1.6 nm can be obtained by using a growth interruption time of 60 s.
Method and apparatus for motion estimation with all binary representation
(2006-03-28)
Luo
;
Jeng-Hung
;
Lee
;
Gen-Ming
;
Wang
A method of motion estimation for video encoding constructs a binary pyramid structure having three binary layers. A state update module registers and updates repeat occurrence of final motion vectors and a static-state checking module determines if the method is in a static mode or a normal mode based on the repeat occurrence. In a normal mode, the first binary layer is searched within a ±3 pixel refinement window to determine a first level motion vector. In the second binary layer, a search range is computed based on six motion vector candidates. By checking every point within in the search range, a second binary layer search generates a second level motion vector. Finally, a third binary layer search within a ±2 pixel refinement window generates a final motion vector according to the second level motion vector. In a static mode, a fine tuning module performs search within a ±1 pixel refinement window and generates a final motion vector.
Tryptophan 232 within oxidosqualene-lanosterol cyclase from Saccharomyces cerevisiae influences rearrangement and deprotonation but not cyclization reactions
(2006-03-30)
Wu, TK
;
Yu, MT
;
Liu, YT
;
Chang, CH
;
Wang, HJ
Oxidosqualene-lanosterol cyclases convert oxidosqualene to lanosterol in yeast and mammals. Site-saturated mutants' construction of Saccharomyces cerevisiae oxidosqualene-lanosterol cyclase, at Trp232 exchanges against proteinogenic amino acids, and product profiles are shown. All mutants, except Lys and Arg, produced protosta-12,24-dien-3 beta-ol, lanosterol, and parkeol. Overall, Trp232 plays a catalytic role in the influence of rearrangement process and determination of deprotonation position but does not involve intervention in the cyclization steps.
High-efficiency polymer light-emitting diodes using neutral surfactant modified aluminum cathode
(2006-03-30)
Niu, YH
;
Jen, AKY
;
Shu, CF
;
應用化學系
;
Department of Applied Chemistry
High-efficiency polymer light-emitting diodes were fabricated by inserting a layer of nonionic neutral surfactant between the electroluminescent (EL) layer and the high-work-function aluminum cathode via spin coating. It was found that both the poly(ethylene glycol)- and poly(propylene glycol)-based surfactants as well as their copolymers can all demonstrate similar performance enhancement. Device performances comparable to or even better than those of the control devices using calcium as the cathode have been achieved for both poly(p-phenylene)-based and polyfluorene-based conjugated polymers with orange-red, green, and blue emission colors. It is possible that when both surfactant and aluminum are used as the cathode, the abundant hole injection through a hole-transporting layer and hole pile-up at the inner side of the EL/surfactant interface might cause an effective electric field to induce the realignment of the dipole moment of those polar surfactant molecules, thus lowering the barrier for electron injection. In addition, the coordination between the aluminum and oxygen atoms on the surfactant might cause n-type doping in the areas near surfactant in the EL polymer layer that causes the enhancement of electron injection.
Sweeping technique combined with micellar electrokinetic chromatography for the simultaneous determination of flunitrazepam and its major metabolites
(2006-03-31)
Huang, CW
;
Jen, HP
;
Wang, RD
;
Hsieh, YZ
;
應用化學系
A sweeping technique, in conjunction with micellar electrokinetic chromatography, for the simultaneous determination of flunitrazepam and its major metabolites, 7-aminoflunitrazepam and N-desmethylflunitrazepam, is described. The optimized conditions for the sweeping and separation were a pH 9.5 buffer, 25 mM borate, 50 mM cetyltrimethylammonium bromide, 30% MeOH (v/v), and a 151-mm injection length. The calibration functions were all linear with the coefficient of determination (r(2)) exceeding 0.996 for the three target compounds. Using the sweeping procedure, the limits of detection were determined to be 13.4, 5.6, and 12.0 ng/mL for flunitrazepam, 7-aminoflunitrazepam, and N-desmethylflunitrazepam, respectively, and the sensitivity enhancement for each compound was within the range of 110-200 fold. The RSDs for the retention time and the peak area were less than 4.10%. The optimized sweeping method was also used to examine a spiked urine sample. We conclude that sweeping with micellar electrokinetic chromatography has considerable potential use in clinical and forensic analyses of flunitrazepam and its metabolites. (c) 2006 Elsevier B.V. All rights reserved.
MBE growth and structural and magnetic properties of (In1-gamma Al gamma)(1-x)MnxAs-diluted magnetic semiconductors
(2006-04-01)
Lee, WN
;
Chen, YF
;
Huang, JH
;
Guo, XJ
;
Kuo, CT
A series of quaternary-diluted magnetic semiconductors, (In1-y,Al-y)(1-x)MnxAs, have been successfully grown on InP substrates by low-temperature molecular beam epitaxy. The (ln(0.52)Al(0.48))(1-x)MnxAs with x <= 0.11 were grown on a nearly lattice-matched In0.52Al0.48As buffer, while the (In1-y,Al-y)(1-x)MnxAs with a higher Mn content of 0.11 < x <= 0.18 were grown on a graded 3-layer In,-,,Al-y 'As buffer structure. The results of transmission electron microscopy and double-crystal X-ray diffraction reveal that all (In1-yAly)(1-x),Mn,As epilayers are single crystal with zincblende structure, and the lattice constant increases with increasing the Mn content. The magnetic measurements show that the (In1-y,Al-y)(1-x)MnxAs semiconductors exhibit a paramagnetic-like state for x <= 0.05 while a ferromagnetic state for x >= 0.05, and the Curie temperature of ferromagnetic (In1-yAly)(1-x) MnxAs increases with increasing Mn content. (c) 2006 Elsevier B.V. All rights reserved.
Expression and purification of human placenta lactogen in Escherichia coli
(2006-04-01)
Lan, PC
;
Tseng, CF
;
Lin, MC
;
Chang, CA
;
生物科技學系
There are many growth factors secreted by placenta including growth hormone, placenta lactogen (PL), prolactin, follicle stimulating hormone, luteinizing hormone, thyroid stimulating hormone, and chorionic gonadotropin. For a systematic study of how these growth factors work together to result in the various biological functions and future clinical applications, it is needed to produce enough quantities of each protein. In this paper, we report the cloning of human PL (hPL) and expression by Escherichia coli (E coli). Four kinds of expression vectors containing the hPL gene were transformed into several kinds of suitable host strains and grown at 37 and/or 30 degrees C. Determination of the yield of recombinant hPL by SDS-PAGE reveals that among the various conditions, pQE30-PL in E. coli strain M15[pREP4] expressed the largest amount of recombinant hPL at 37 degrees C. However, the expressed recombinant hPL was accumulated in inclusion body forms. The inclusion bodies were solubilized in 8 M urea and purified by a His(6) tagged affinity column under denaturing condition and the final yield of hPL was determined to be 48 mg/L. Intra-chain disulfide bonds could be formed either by oxidation in the refolding buffer or by air oxidation in the presence of urea. The biological activity was examined by the fact that hPL could stimulate erythroid maturation by the formation of hemoglobin in K-562 cells in the presence of erythropoietin. Initial optimization studies resulted in the production of 282.4 mg/L of hPL. (c) 2005 Elsevier Inc. All rights reserved.
A background timing-skew calibration technique for time-interleaved analog-to-digital converters
(2006-04-01)
Wang, CY
;
Wu, JT
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper presents a background timing-skew calibration technique for time-interleaved analog-to-digital converters (ADCs). The timing skew between any two adjacent analog-digital (AID) channels is detected by counting the number of zero crossings of the ADCs input while randomly alternating their sampling sequence. Digitally controlled delay units are adjusted to minimize the timing skews among the AID channels caused by the mismatches among the clock routes. The calibration behaviors, including converging speed and timing jitter, are theoretically analyzed and verified with simulations. A 6-bit 16-channel ADC is used as an example.
Ritter reaction of 1-aryl-1-fluoro-2-haloethanes
(2006-04-01)
Ho, TL
;
Chein, RJ
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應用化學系
;
Department of Applied Chemistry
Fluorinated phenethyl bromides 1, 2, and 3, prove to be totally inert under Ritter reaction conditions in the presence of either SnCl4 or AgNO3, due to the strong deactivation by the gem-difluoro unit. Subjecting 2-bromo-1-fluoro-1-phenylethane to SnCl4 in MeCN at elevated temperatures led to formation of 2-methyl-4-phenyl-4,5-dihydrooxazole.
Topological horseshoes for perturbations of singular difference equations
(2006-04-01)
Li, MC
;
Malkin, M
;
應用數學系
;
Department of Applied Mathematics
In this paper, we Study solutions of difference equations Phi(lambda)(y(n), y(n+1),...,y(n+m)) = 0, n is an element of Z, of order in with parameter lambda, and consider the case when Phi(lambda) has a singular limit depending on a single variable as lambda -> lambda(0), i.e. Phi(lambda 0)(y(0),...,y(m)) = phi(y(N)), where N is an integer with 0 <= N <= m and phi is a function. We prove that if phi has k simple zeros then for lambda close enough to lambda(0), the difference equation has a k-horseshoe among its solutions, that is, the dynamics is conjugate to the full shift with k symbols. Moreover, we show that these horseshoes change continuously in the uniform topology as lambda varies. As applications of these results, we establish the horseshoe structure in families of generalized Henon-like maps and of Arneodo-Coullet-Tresser maps near their anti-integrable limits as well as in steady states for certain lattice models.
Multiple-objective planning for a production and distribution model of the supply chain: Case of a bicycle manufacturer
(2006-04-01)
Tzeng, GH
;
Tang, TI
;
Huang, YM
;
Chang, ML
;
科技管理研究所
The bicycle industry is one of the most competitive industries in Taiwan. To construct multi-objective production and distribution models tor supply chain, following five methods are compared and discussed: (i) Multi-objective compromise programming; (ii) Fuzzy multi-objective programming (iii) Weighted multi-objective programming; (iv) Weighted fuzzy multi-objective programming; and (v) Two-phase fuzzy multi- objective programming. The weighted multi-objective model has been found better for considering the maximum profit for enterprises and the maximum quality for customer service. After raising the per-unit production cost in production processes, it was observed that the total profit would decrease in real empirical study. In addition, if the unit inventory cost increases due to improving the customer service level, then the total profit might increase, but not significantly.