Browsing by Issue Date, starting with "2004-08-01"

Now showing 1 - 20 of 69745

Improved method for measuring small optical rotation angle of chiral medium
(2004-08-01)
Lin, JY
;
Chen, KH
;
Su, DC
;
光電工程學系
;
Department of Photonics
Based on the principle of Feng et al., an improved optical method for measuring small rotational angle in chiral medium is proposed. When a quarter-wave plate and two analyzers with proper azimuth angles are arranged in the two outputs of a Mach-Zehnder interferometer (with sample been inserted in one of the light passages), the final phase difference of the two interference signals used to determine the rotational angle is greatly enhanced, which is found to be a about 15x the result obtained with the Feng et al.'s method. The feasibility of the measuring method was demonstrated by our experimental results. This method should bear the merits of high accuracy, short sample medium length, and simpler operational endeavor. (C) 2004 Elsevier B.V. All rights reserved.
Distinction between dry and raw milk using monoclonal antibodies prepared against dry milk proteins
(2004-08-01)
Chen, WL
;
Huang, MT
;
Liu, HC
;
Li, CW
;
Mao, SJT
It is well established that the heating process during the preparation of dry milk (DMLK) causes structural changes in some milk proteins. However, because such changes are subtle, whether they can be detected by an immunochemical approach remains questionable. The present study attempted to develop a sensitive mAb that might distinguish the DMLK from freshly prepared raw milk. To test this possibility, we immunized mice with commercially prepared DMLK and produced a panel of mAb. From 900 hybridomas screened using an ELISA, 4 clones were found to be specific to DMLK; the other 68 clones recognized both DMLK and raw milk. In contrast to polyclonal antibodies, only the specific mAb could detect the DMLK spiked into the raw milk at as low as 5% in concentration (vol/vol). Western blot analysis shows that these specific mAb were all directed against beta-lactoglobulin (LG) and LG-milk protein conjugates. These mAb reacted with raw milk heated at 95 for 15 min; the reaction with LG-conjugates, however, was abolished when treated with reducing reagent. Thus, results suggests that a new antigenic epitope was exposed in a heating process, and the thio group of LG cross linked with other protein moiety played a provocative role in mAb recognition. A hypothetical model with respect to the interaction between the mAb and DMLK is proposed and discussed.
A two-tier heterogeneous mobile ad hoc network architecture and its load-balance routing problem
(2004-08-01)
Huang, CF
;
Lee, HW
;
Tseng, YC
;
資訊工程學系
;
Department of Computer Science
The mobile ad hoc network (MANET) has attracted a lot of interest recently. However, most of the existing works have assumed a stand-alone MANET. In this paper, we propose a two-tier, heterogeneous MANET architecture which can support Internet access. The low tier of the network consists of a set of mobile hosts each equipped with a IEEE 802.11 wireless LAN card. In order to connect to the Internet and handle the network partitioning problem, we propose that the high tier is comprised of a subset of the mobile hosts, called gateways, which can access to cellular/infrastructure networks. The high tier is heterogeneous in the sense that the network interfaces in the gateway hosts could be IEEE 802.11 cards, PHS handsets, or GPRS handsets characterized by different bandwidths and latencies. Observing that the gateways could become the bottlenecks of the two-tier network, we propose a set of solutions, namely boundary-moving, host-partitioning, and probabilistic solutions, to solve the load-balance routing issue. Implementation issues/concerns of these schemes are discussed. Simulation results are presented to compare these load-balance routing schemes.
Cytochrome P450c17 alpha 5'-untranslated region T/C polymorphism in endometriosis
(2004-08-01)
Hsieh, YY
;
Chang, CC
;
Tsai, FJ
;
Lini, CC
;
Tsai, CH
Estrogen plays a role in the pathogenesis of endometriosis. The CYP17 gene codes for the cytochrome P450cl7alpha enzyme that is involved in the estrogen biosynthesis. We aimed to investigate if CYP 17 polymorphism could be used as marker to predict the susceptibility of endometriosis. Women were divided into two groups: (1) severe endometriosis (n= 119); (2) non-endometriosis groups (n=1 28). A 169-bp fragment encompassing the T/C polymorphic site in 5'-untranslated promoter region (5'-UTR) of the CYP17 was amplified by the polymerase chain reaction, treated with restriction enzyme MspA1I, and electrophoresis. The polymorphism was divided into restriction- enzyme indigestible (T homozygote), T/C heterozygote, and digestible (C homozygote). Genotypes and allelic frequencies for this polymorphism in both groups were compared. We observed a higher but non-significant percentage of T homozygote in the endometriosis women compared with the non-endometriosis women. Proportions of T homozygote/heterozygote/C homozygote for CYP17 in both groups were: (1) 26.1/46.2/27.7% and (2) 17.2/45.3/37.5% (p- value=0.13 1). T allele was related with higher susceptibility of endometriosis. T and C allele frequencies in both groups were: (1) 49.2/50.8%; (2) 39.8/60.2% (p- value=0.046). Despite the CYP17* T allele Appearing to be asscoiated with a trend of increased risk of endometriosis, CYP17 5'-UTR gene polymorphism might not be a useful marker for prediction of endometriosis susceptibility.
Magnetic field dependence of low-temperature specific heat of the spinel oxide superconductor LiTi2O4
(2004-08-01)
Sun, CP
;
Lin, JY
;
Mollah, S
;
Ho, PL
;
Yang, HD
Magnetic field dependence of low temperature specific heat of spinel oxide superconductor LiTi2O4 has been elaborately investigated. In the normal state, the obtained electronic coefficient of specific heat gamma(n)=19.15 mJ/mol K-2, the Debye temperature Theta(D)=657 K and some other parameters are compared with those reported earlier. The superconducting transition at T(c)similar to11.4 K is very sharp (DeltaT(c)similar to0.3 K) and the estimated deltaC/gamma(n)T(c) is similar to1.78. In the superconducting state, the best fit of data leads to the electronic specific heat C-es/gamma(n)T(c)=9.87 exp(-1.58 T-c/T) without field and gamma(H)proportional toH(0.95) with fields. In addition, H-c2(0)similar to11.7 T, H-c(0)similar to0.32 T, xi(GL)(0)similar to55 A, lambda(GL)(0)similar to1600 Angstrom, and H-c1(0)similar to26 mT are estimated from the Werthamer-Helfand-Hohenberg (WHH) theory or other relevant relations. All results from the present study indicate that LiTi2O4 can be well described by a typical type-II, BCS-like, moderate coupling, and fully gapped superconductor in the dirty limit. It is further suggested that LiTi2O4 is a moderately electron-electron correlated system.
Quantization noise reduction for DCT coded images
(2004-08-01)
Kuo, CC
;
Chang, WT
;
電信工程研究所
;
Institute of Communications Engineering
By modelling the quantization error as additive white noise in the transform domain, Wiener filter is used to reduce quantization noise for DCT coded images in DCT domain. Instead of deriving the spectrum of the transform coefficient, a DPCM loop is used to whiten the quantized DCT coefficients. The DPCM loop predicts the mean for each coefficient. By subtracting the mean, the quantized DCT coefficient is converted into the sum of prediction error and quantization noise. After the DPCM loop, the prediction error can be assumed uncorrelated to make the design of the subsequent Wiener filter easy. The Wiener filter is applied to remove the quantization noise to restore the prediction error. The original coefficient is reconstructed by adding the DPCM predicted mean with the restored prediction error. To increase the prediction accuracy, the decimated DCT coefficients in each subband are interpolated from the overlapped blocks.
High-efficiency wide-band SOA-based wavelength converters by using dual-pumped four-wave mixing and an assist beam
(2004-08-01)
Hsu, DZ
;
Lee, SL
;
Gong, PM
;
Lin, YM
;
Lee, SSW
Wavelength conversion with a high efficiency and wide conversion range can easily be realized by applying an assist beam of short wavelength to a dual-pumped semiconductor optical amplifier (SOA). Experimental results reveal that an assist beam can improve the conversion efficiency and signal-to-background ratio by up to 8.5 and 4.1 dB, respectively, when the SOA is biased at the current that makes the SOA transparent to the assist beam. The efficiency can exceed -10 dB over an 80-nm wavelength conversion range using a 23-dB gain SOA. The assist beam increases the system power budget because it simultaneously improves the conversion efficiency and reduces the receiver power penalty. The power penalties for up-converting and down-converting 10-Gb/s signals to 25 nm of wavelength range are less than 0.5 and 2.5 dB, respectively.
Antioxidant role of human haptoglobin
(2004-08-01)
Tseng, CF
;
Lin, CC
;
Huang, HY
;
Liu, HC
;
Mao, SJT
Human plasma haptoglobin (Hp) is classified according to three phenotypes: Hp 1-1, 2-1, and 2-2 attributed by their two common alleles 1 and 2. Clinically, the 2-2 phenotype is associated with the risk of cardiovascular diseases and diabetes mellitus in patients. In this study, we demonstrate that Hp is an extremely potent antioxidant, which directly protects low density lipoprotein from Cu2+-induced oxidation. Its potency was markedly superior to probucol (one of the most potent antioxidants). Ranking of the IC50 of antioxidant activity was as follows: Hp 1-1 > Hp 2-1 > Hp 2-2 > probucol > vitamin E. Blockage of disulfide linkages between Hp subunits, not only abolished the alpha-helical content but also diminished the ability of Hp to form a complex with hemoglobin. The modified Hp subunits exerted almost 4 times greater antioxidant activity than that of native Hp. To investigate the antioxidant role of Hp on the cellular level, the cDNA of Hp 1-1 was cloned, introduced into the pcDNA3.0 vector which contains the cytomega lovirus promoter and transfected into chinese hamster ovary (CHO)-K1 cells. Following transfection, CHO cells were able to express Hp 1-1 protein and significantly (p < 0.001) elevated cell tolerance against oxidative stress. Transfected cells showed 2-fold higher resistance to hydrogen peroxide exposure for 24 h compared to control cells. Thus, Hp plays a provocative antioxidant role as demonstrated by our in vitro and ex vivo studies.
Theoretical and experimental studies of tunable ultraviolet-blue femtosecond pulses in a 405-nm pumped type I beta-BaB2O4 noncollinear optical parametric amplifier and cascading sum-frequency generation
(2004-08-01)
Lee, CK
;
Zhang, JY
;
Huang, JYJ
;
Pan, CL
;
光電工程學系
Femtosecond laser pulses that are tunable from 380 to 460 nm were directly generated from a 405-nm-pumped type I beta-BaB2O4 noncollinear optical parametric amplifier (NOPA). A white-light supercontinuum from a CaF2 plate excited by 810-nm pulses was seeded into the NOPA. A theoretical analysis showed that the near-UV-to-blue radiation generated is attributable to cascaded sum-frequency generation (SFG) of the output of the NOPA and the residual fundamental beam at 810 nm. One can tune the blue-UV light by either changing the orientation of the NOPA crystal or adjusting the angle between the pump and the seeding pulse. The optical conversion efficiency from the 405-nm pump to the tunable SFG radiation is more than 5%. (C) 2004 Optical Society of America.
Finger-gate array quantum pumps: Pumping characteristics and mechanisms
(2004-08-01)
Chung, SW
;
Tang, CS
;
Chu, CS
;
Chang, CY
;
電子物理學系
We study the pumping effects, in both the adiabatic and nonadiabatic regimes, of a pair of finite finger-gate array (FGA) on a narrow channel. Connection between the pumping characteristics and associated mechanisms is established. The pumping potential is generated by ac biasing the FGA pair. For a single pair (N=1) of finger gates (FG's), the pumping mechanism is due to the coherent inelastic scattering of the traversing electron to its subband threshold. For a pair of FGA with pair number N>2, the dominant pumping mechanism becomes that of the time-dependent Bragg reflection. The contribution of the time-dependent Bragg reflection to the pumping is enabled by breaking the symmetry in the electron transmission when the pumping potential is of a predominant propagating type. This propagating wave condition can be achieved both by an appropriate choice of the FGA pair configuration and by the monitoring of a phase difference phi between the ac biases in the FGA pair. The robustness of such a pumping mechanism is demonstrated by considering a FGA pair with only pair number N=4.
Design on ESD protection scheme for IC with power-down-mode operation
(2004-08-01)
Ker, MD
;
Lin, KH
;
電機學院
;
College of Electrical and Computer Engineering
This paper presents a new electrostatic discharge (ESD) protection scheme for IC with power-down-mode operation. Adding a VDD ESD bus line and diodes into the proposed ESD protection scheme can block the leakage current from I/O pin to VDD power line and avoid malfunction during power-down operation. The whole-chip ESD protection design can be achieved by insertion of ESD clamp circuits between VSS power line and both the VDD power line and VDD ESD bus line. Experiment results show that the human-body model (HBM) ESD level of this new scheme can be greater than 7.5 kV in a 0.35-mum silicided CMOS process.
應用雙層寬邊耦合微帶線之平面式天線
(2004-08-01)
莊晴光
;
黃國
一種應用雙層寬邊耦合微帶線之平面式天線，包含：一上層饋入電路與一下層饋入電路，彼此電性絕緣；以及一上層寬邊耦合微帶線與一下層寬邊耦合微帶線，彼此電性絕緣且平行地延伸於同一方向上。該上層饋入電路係用以激發該上層寬邊耦合微帶線，而該下層饋入電路係用以激發該下層寬邊耦合微帶線。再者，藉由平行排列偶數個該應用雙層寬邊耦合微帶線之平面式天線，可形成一種平面式天線陣列，具有高指向性筆狀波束之輻射場型。
Experiments and calculations on photoionization and dissociative photoionization of CH2CO
(2004-08-01)
Chiang, SY
;
Fang, YS
;
Bahou, M
;
Sankaran, K
;
應用化學系
The dissociative photoionization of molecular-beam cooled CH2CO in a region of similar to10-20 eV was investigated with photoionization mass spectrometry using a synchrotron radiation as the light source. Photoionization efficiency curves of CH2CO+ and of observed fragment ions CH2+, CHCO+, HCO+ C2O+ CO+, and C2H2+ were measured to determine their appearance energies. Relative branching ratios as a function of photon energy were determined. Energies for formation of these observed fragment ions and their neutral counterparts upon ionization of CH2CO are computed with the Gaussian-3 method. Dissociative photoionization channels associated with six observed fragment ions are proposed based on comparison of determined appearance energies and predicted energies. The principal dissociative processes are direct breaking of C=C and C-H bonds to form CH2+ + CO and CHCO+ + H, respectively; at greater energies, dissociation involving H migration takes place.
Optical properties of Zn1-xCdxSe epilayers grown on (100)GaAs by molecular beam epitaxy
(2004-08-01)
Kuo, MC
;
Chiu, KC
;
Shih, TH
;
Lai, YJ
;
Yang, CS
Zn1-xCdxSe epilayers were grown on (100) GaAs substrates by molecular beam epitaxy. Lattice constants of the epilayers were measured by (004) rocking curve X-ray diffraction. A full width at half maximum of 475 to 2100 arcsec was obtained. The dependence of the energy gap on temperature, measured by the photoluminescence (PL) spectra, was fitted by Varshni's [Y. P. Varshni: Physica 34 149 (1967)] and O'Donnell's [R. P. O'Donnell and X. Chen: Appl. Phys. Lett. 58 2924 (1991)] models. The fitting parameters beta (161 K to 368K) and (hv) (13 meV to 24 meV), related to phonon energy, were obtained from Varshni and O'Donnell fits, respectively. The activation energies calculated from the integrated PL intensity versus inverse temperature decrease as the Cd content increases. The broadening of the PL linewidth with temperature was fitted by Gamma(T) = Gamma(0) + Gamma(a)T + Gamma(LOI)/[exp(homega(LOI)/kT) - 1] + Gamma(LO2)/[exp(homega(LO2)/kT) - 1] + Gamma(i)exp(-/kT). The impurity binding energy, (E-b), was found to decrease as the Cd composition increases.
Bioleaching of heavy metals from contaminated sediment by indigenous sulfur-oxidizing bacteria in an air-lift bioreactor: effects of sulfur concentration
(2004-08-01)
Chen, SY
;
Lin, JG
;
環境工程研究所
;
Institute of Environmental Engineering
The effects of sulfur concentration on the bioleaching of heavy metals from the sediment by indigenous sulfuroxidizing bacteria were investigated in an air-lift reactor. Increasing the sulfur concentration from 0.5 to 5 g/l enhanced the rates of pH reduction, sulfate production and metal solubilization. A Michaelis-Menten type equation was used to explain the relationships between sulfur concentration, sulfate production and metal solubilization in the bioleaching process. After 8 days of bioleaching, 97-99% of Cu, 96-98% of Zn, 62-68% of Mn, 73-87% of Ni and 31-50% of Pb were solubilized from the sediment, respectively. The efficiency of metal solubilization was found to be related to the speciation of metal in the sediment. From economical consideration, the recommended sulfur dosage for the bioleaching of metals from the sediment is 3 g/l. (C) 2004 Elsevier Ltd. All rights reserved.
Cryptanalysis of simple authenticated key agreement protocols
(2004-08-01)
Yang, CC
;
Chang, TY
;
Hwang, MS
;
資訊工程學系
;
Department of Computer Science
In this article, we will present a modification attack and a dictionary attack to subvert the security of the Tseng scheme and the Ku-Wang scheme. As we know, no existing schemes of simple authenticated key agreement protocols can successfully withstand our modification attack.
An orthogonal simulated annealing algorithm for large floorplanning problems
(2004-08-01)
Ho, SY
;
Ho, SJ
;
Lin, YK
;
Chu, WCC
;
生物科技學系
The conventional simulated annealing with some random generation mechanism using the sequence-pair topological representation in block placement and floorplanning is effective for a very small number of modules (40-50). This paper proposes an orthogonal simulated annealing algorithm (OSA) with an efficient generation mechanism (EGM) for solving large floorplanning problems. EGM samples a small number of representative floorplans and then efficiently derives a high-performance floorplan by using a systematic reasoning method for the next move of OSA based on orthogonal experimental design. Furthermore, an improved swap operation is proposed which cooperates with EGM to make OSA efficient. Excellent experimental results using the Microelectronics Center of North Carolina and the Gigascale Sysems Research Center benchmarks show that OSA performs better than existing methods for large floorplanning problems.
Gold nanoparticles as selective and concentrating probes for samples in MALDI MS analysis
(2004-08-01)
Teng, CH
;
Ho, KC
;
Lin, YS
;
Chen, YC
;
應用化學系
MALDI mass spectrometry is used widely in various fields because it has the characteristics of speed, ease of use, high sensitivity, and wide detectable mass range, but suppression effects between analyte molecules and interference from the sample matrix frequently arise during MALDI analysis. The suppression effects can be avoided if target species are isolated from complicated matrix solutions in advance. Herein, we proposed a novel method for achieving such a goal. We describe a strategy that uses gold nanoparticles to capture charged species from a sample solution. Generally, ionic agents, such as anionic or cationic stabilizers, encapsulate gold nanoparticles to prevent their aggregation in solution. These charged stabilizers at the surface of the gold particles are capable of attracting oppositely charged species from a sample solution through electrostatic interactions. We have employed this concept to develop nanoparticle-based probes that selectively trap and concentrate target species in sample solutions. Additionally, to readily isolate them from solution after attracting their target species, we used gold nanoparticles that are adhered to the surface of magnetic particles through S-Au bonding. A magnet can then be employed to isolate the Au@magnetic particles from the solution. The species trapped by the isolated particles were then characterized by MALDI MS after a simple washing. We demonstrate that Au@magnetic particles having negatively charged surfaces are suitable probes for selectively trapping positively charged proteins from aqueous solutions. In addition, we have employed Au@magnetic particle-based probes successfully to concentrate low amounts of peptide residues from the tryptic digest products of cytochrome c (10(-7) M).
Mode beating noise reduction of mutually injection-locked erbium-doped fiber laser and laser diode link
(2004-08-01)
Lin, YH
;
Lin, GR
;
光電工程學系
;
Department of Photonics
We report a mutually injection-locked Erbium-doped fiber amplifier (or laser) and Fabry-Perot laser diode link (EDFA-FPLD or EDFL-FPLD) for single longitudinal mode lasing with linewidth of 0.012 nm and sidemode suppression ratio of 42 dB. The 3-dB linewidths of < 20 MHz and 350 kHz for the EDFL-FPLD and EDFA-FPLD links, respectively, are reported using interferometric determination., The mode-beating noise can be completely eliminated in the EDFA-FPLD link.
The effects of hydrogen plasma treatment on the plasma-enhanced chemical vapor deposition a-SiC : H films
(2004-08-01)
Chen, CF
;
Li, YW
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Amorphous hydrogenated silicon carbide (a-SiC:H) films were deposited using plasma-enhanced chemical vapor deposition (PECVD) process. Reducing silane flow rate increased the carbon concentration and optical band gap in the a-SiC:H films, but decreased the refractive index and dielectric constant. X-ray photoelectron spectroscopy (XPS) data revealed that the carbon concentration decreased as the methane flow rate increased, but the silicon concentration increased. Increasing the carbon concentration in the a-SiC:H film reduces the dielectric constant of the film. The carbon-rich a-Si0.24C0.68:H,, films treated with hydrogen plasma for various periods, were converted into films with more silicon content. Increasing the hydrogen plasma treatment period gradually roughened the surface even though the original film had a smooth surface, with a roughness <0.231 nm. The leakage current density of the hydrogen plasma treated a-Si0.24C0.68:1-1, films declined as the duration of the hydrogen plasma treatment period decreased.