Showing papers by "National Cheng Kung University published in 2002"

Low-temperature growth of well-aligned zno nanorods by chemical vapor deposition

Abstract: PPV, F8BT shows considerable anisotropy, with a birefringence of 0.19 at 633 nm. As with OC1C10±PPV there is a slight blue shift in the absorption peaks for the extraordinary direction with respect to the ordinary direction, again indicating a decreased conjugation length for chains lying out of the plane of the film. In conclusion, we have shown that a combination of reflection and transmission ellipsometry can be reliably employed to determine the ordinary and extraordinary optical constants in conjugated polymer films in both the absorbing and transparent regions. We have presented optical constants for two commonly used electroluminescent polymers, which will be useful in optical modeling of LEDs and photovoltaic devices. The technique provides structural information about the degree of chain alignment, and will in the future be applied to study the effects of annealing on optical properties, and to investigate possible variation of anisotropy with film thickness in thinner films than were studied here.

Tumours of histiocytes and accessory dendritic cells: an immunohistochemical approach to classification from the International Lymphoma Study Group based on 61 cases

Abstract: Neoplasms of histiocytes and dendritic cells are rare, and their phenotypic and biological definition is incomplete. Seeking to identify antigens detectable in paraffin-embedded sections that might allow a more complete, rational immunophenotypic classification of histiocytic/dendritic cell neoplasms, the International Lymphoma Study Group (ILSG) stained 61 tumours of suspected histiocytic/dendritic cell type with a panel of 15 antibodies including those reactive with histiocytes (CD68, lysozyme (LYS)), Langerhans cells (CD1a), follicular dendritic cells (FDC: CD21, CD35) and S100 protein. This analysis revealed that 57 cases (93%) fit into four major immunophenotypic groups (one histiocytic and three dendritic cell types) utilizing six markers: CD68, LYS, CD1a, S100, CD21, and CD35. The four (7%) unclassified cases were further classifiable into the above four groups using additional morphological and ultrastructural features. The four groups then included: (i) histiocytic sarcoma (n =18) with the following phenotype: CD68 (100%), LYS (94%), CD1a (0%), S100 (33%), CD21/35 (0%). The median age was 46 years. Presentation was predominantly extranodal (72%) with high mortality (58% dead of disease (DOD)). Three had systemic involvement consistent with `malignant histiocytosis'; (ii) Langerhans cell tumour (LCT) (n =26) which expressed: CD68 (96%), LYS (42%), CD1a (100%), S100 (100%), CD21/35 (0%). There were two morphological variants: cytologically typical (n =17) designated LCT; and cytologically malignant (n =9) designated Langerhans cell sarcoma (LCS). The LCS were often not easily recognized morphologically as LC-derived, but were diagnosed based on CD1a staining. LCT and LCS differed in median age (33 versus 41 years), male:female ratio (3.7:1 versus 1:2), and death rate (31% versus 50% DOD). Four LCT patients had systemic involvement typical of Letterer-Siwe disease; (iii) follicular dendritic cell tumour/sarcoma (FDCT) (n =13) which expressed: CD68 (54%), LYS (8%), CD1a (0%), S100 (16%), FDC markers CD21/35 (100%), EMA (40%). These patients were adults (median age 65 years) with predominantly localized nodal disease (75%) and low mortality (9% DOD); (iv) interdigitating dendritic cell tumour/sarcoma (IDCT) (n =4) which expressed: CD68 (50%), LYS (25%), CD1a (0%), S100 (100%), CD21/35 (0%). The patients were adults (median 71 years) with localized nodal disease (75%) without mortality (0% DOD). In conclusion, definitive immunophenotypic classification of histiocytic and accessory cell neoplasms into four categories was possible in 93% of the cases using six antigens detected in paraffin-embedded sections. Exceptional cases (7%) were resolvable when added morphological and ultrastructural features were considered. We propose a classification combining immunophenotype and morphology with five categories, including Langerhans cell sarcoma. This simplified scheme is practical for everyday diagnostic use and should provide a framework for additional investigation of these unusual neoplasms.

Community-acquired Klebsiella pneumoniae bacteremia: global differences in clinical patterns.

Abstract: We initiated a worldwide collaborative study, including 455 episodes of bacteremia, to elucidate the clinical patterns of Klebsiella pneumoniae. Historically, community-acquired pneumonia has been consistently associated with K. pneumoniae. Only four cases of community-acquired bacteremic K. pneumoniae pneumonia were seen in the 2-year study period in the United States, Argentina, Europe, or Australia; none were in alcoholics. In contrast, 53 cases of bacteremic K. pneumoniae pneumonia were observed in South Africa and Taiwan, where an association with alcoholism persisted (p=0.007). Twenty-five cases of a distinctive syndrome consisting of K. pneumoniae bacteremia in conjunction with community-acquired liver abscess, meningitis, or endophthalmitis were observed. A distinctive form of K. pneumoniae infection, often causing liver abscess, was identified, almost exclusively in Taiwan.

The effects of thickness and operation temperature on ZnO:Al thin film CO gas sensor

Abstract: Al-doped ZnO films were deposited onto SiO 2 /Si substrates by rf magnetron sputtering system as a CO gas sensor. The dependence of the thin film thickness on CO gas sensing properties was investigated, where the film thickness was varied by controlling the deposition time. The structure of the deposited ZnO:Al films was determined by X-ray diffraction, scanning electron microscopy and atomic force microscopy. The CO gas sensing properties were determined by in situ measurement for surface resistance of the thin film as a function of film thickness, different atmosphere, and operation temperature. It was shown that the films were flat and smooth with (0 0 0 1) preferred orientation. The grain size was increased as the film thickness was increased during deposition. Here, the CO gas sensing properties were relative to the structural characteristics where the maximum sensitivity of 61.6% was obtained at 65 nm film thickness for the operation temperature of 400 °C.

Discriminant waveletfaces and nearest feature classifiers for face recognition

Abstract: Feature extraction, discriminant analysis, and classification rules are three crucial issues for face recognition. We present hybrid approaches to handle three issues together. For feature extraction, we apply the multiresolution wavelet transform to extract the waveletface. We also perform the linear discriminant analysis on waveletfaces to reinforce discriminant power. During classification, the nearest feature plane (NFP) and nearest feature space (NFS) classifiers are explored for robust decisions in presence of wide facial variations. Their relationships to conventional nearest neighbor and nearest feature line classifiers are demonstrated. In the experiments, the discriminant waveletface incorporated with the NFS classifier achieves the best face recognition performance.

Catalyst-free growth and characterization of ZnO nanorods

Abstract: Highly oriented ZnO nanorods have been grown on various substrates, such as fused silica, Si(100), and sapphire (110), using a simple catalyst-free CVD method at low temperatures. TEM analyses indicate that epitaxial ZnO nanorods have been grown on sapphire (110) with the ZnO/sapphire orientational relationship [001]||[110] and [110]||[001]. In the Si(100) substrate, an amorphous SiOx interfacial layer exists between ZnO nanorods and Si(100). The well-aligned ZnO nanorods on fused silica substrates exhibit a strong UV emission and absorption at around 386 nm under room temperature. Photoluminescence and Raman spectra indicate that there is a very low concentration of oxygen vacancies in the highly oriented ZnO nanorods. Diameter control of the well-oriented and high-quality ZnO nanorods is achievable by variation of the growth conditions.

Dynamic Bus Arrival Time Prediction with Artificial Neural Networks

Abstract: Transit operations are interrupted frequently by stochastic variations in traffic and ridership conditions that deteriorate schedule or headway adherence and thus lengthen passenger wait times. Providing passengers with accurate vehicle arrival information through advanced traveler information systems is vital to reducing wait time. Two artificial neural networks (ANNs), trained by link-based and stop-based data, are applied to predict transit arrival times. To improve prediction accuracy, both are integrated with an adaptive algorithm to adapt to the prediction error in real time. The bus arrival times predicted by the ANNs are assessed with the microscopic simulation model CORSIM, which has been calibrated and validated with real-world data collected from route number 39 of the New Jersey Transit Corporation. Results show that the enhanced ANNs outperform the ones without integration of the adaptive algorithm.

A new fabrication process for ultra-thick microfluidic microstructures utilizing SU-8 photoresist

Abstract: In this paper we describe a new process for fabricating ultra-thick microfluidic devices utilizing SU-8 50 negative photoresist (PR) by standard UV lithography. Instead of using a conventional spin coater, a simple 'constant-volume-injection' method is used to create a thick SU-8 PR film up to 1.5 mm with a single coating. The SU-8 PR is self-planarized during the modified soft-baking process and forms a highly-uniform surface without any edge bead effect, which commonly occurs while using a spin coater. Photomasks can be in close contact with the PR and a better lithographic image can be generated. Experimental data show that the average thickness is 494.32 ± 17.13 μm for a 500 μm thick film (n = 7) and the uniformity is less than 3.1% over a 10 × 10 cm2 area. In this study, the temperatures for the soft-baking process and post-exposure baking are 120 °C and 60 °C, respectively. These proved to be capable of reducing the processing time and of obtaining a better pattern definition of the SU-8 structures. We also report on an innovative photomask design for fabricating ultra-deep trenches, which prevents the structures from cracking and distorting during developing and hard-baking processes. In this paper, two microfluidic structures have been demonstrated using the developed novel methods, including a micronozzle for thruster applications and a microfluidic device with micropost arrays for bioanalytical applications.

All chronic rejection failures of kidney transplants were preceded by the development of HLA antibodies

Abstract: Background. Recent studies show that almost all patients who have rejected a kidney transplant had human leukocyte antigen (HLA) antibodies. In this study, we sought to determine whether patients develop HLA antibodies before chronic rejection. Methods. For the past 8 years, 139 patients who had undergone kidney transplantation were systematically examined, using an enzyme-linked immunosorbent assay-based method, for the development of class-I and class-II HLA antibodies 3 months, 6 months, and yearly after transplantation. Chronic rejection was diagnosed by biopsy. Results. Among 29 patients with chronic rejection, 100% of the patients had HLA antibodies before rejection. Of these patients, 14 patients developed antibodies de novo. In contrast, among 110 patients with stable function, 27% of the patients developed HLA antibodies posttransplant (P<0.001). Conclusions. HLA antibodies were found in 29 consecutive cases of chronic rejection failures as much as one year before the loss of grafts. We conclude that HLA antibodies may be a prerequisite for chronic immunologic rejection.

Formation and characterization of Au–Ag bimetallic nanoparticles in water-in-oil microemulsions

Abstract: Gold–silver bimetallic nanoparticles with varying mole fractions were synthesized in water-in-oil microemulsions of water/Aerosol OT/isooctane by the co-reduction of HAuCl4 and AgNO3 with hydrazine at 25 °C. TEM analysis revealed that the bimetallic nanoparticles were essentially monodisperse and had a mean diameter of 4–22 nm, increasing with an increase in the molar ratio of water to Aerosol OT (ω0) and Ag content. The UV/VIS absorption spectra of their solutions exhibited only one plasmon absorption and the absorption maximum of the plasmon band red-shifted almost linearly from 400 to 520 nm with increasing Au ∶ Ag molar ratio, revealing the formation of an alloy. Although the characteristic peaks for Au and Ag were too close to distinguish, the XRD analysis showed that the characteristic peaks for a Au–Ag bimetallic systems became broader and accordingly suggested the formation of bimetallic nanoparticles. The EDX analysis confirmed directly the formation of Au–Ag bimetallic nanoparticles. It showed that the composition of Au–Ag bimetallic nanoparticles was in good agreement with that of the feed solution but the outer layer of the particles was enriched in Ag. The HRTEM study indicated the resultant Au–Ag bimetallic nanoparticles contained single and multiple twins as well as stacking faults, and no mismatch was present. In addition, it was found that the formation rate of Au nanoparticles was much faster than that of Ag nanoparticles. This satisfactorily accounted for the composition distribution within a Au–Ag bimetallic nanoparticle.

IL-19 Induces Production of IL-6 and TNF-α and Results in Cell Apoptosis Through TNF-α

Abstract: IL-10 is an immunosuppressive cytokine in the immune system. It was in clinical trial as an anti-inflammatory therapy for inflammatory bowel disease and various autoimmune diseases such as psoriasis, rheumatoid arthritis, and multiple sclerosis. IL-19 belongs to the IL-10 family, which includes IL-10, IL-19, IL-20, IL-22, melanoma differentiation-associated gene (MDA-7, IL-24), and AK155 (IL-26). Despite a partial homology in their amino acid sequences, they are dissimilar in their biologic functions. Little is known about the biologic function and gene regulation of IL-19. To understand the gene regulation of human IL-19, we identified a human IL-19 genomic clone and analyzed its promoter region. Five fusion genes containing different regions upstream of exon 1 linked to a luciferase reporter gene were expressed in the canine kidney epithelial-like Madin-Darby canine kidney cells. A fusion gene containing 394 bp showed luciferase activity 7- to 8-fold higher than the negative control of the promoterless fusion gene. We also isolated a full-length mouse cDNA clone. Mouse IL-19 shared 71% amino acid identity with human IL-19. Treatment of monocytes with mouse IL-19 induced the production of IL-6 and TNF-alpha. It also induced mouse monocyte apoptosis and the production of reactive oxygen species. Taken together, our results indicate that mouse IL-19 may play some important roles in inflammatory responses because it up-regulates IL-6 and TNF-alpha and induces apoptosis.

Structure-property relationship of cast Ti-Nb alloys.

Abstract: The present work is a study of the microstructure, mechanical properties and corrosion behaviour of a series of binary Ti-Nb alloys with Nb contents up to 35 wt%, with emphasis placed on the structure-property relationship of the alloys. The results indicate that crystal structure and morphology of the Ti-Nb alloys are sensitive to the Nb content. The cast c.p. Ti has a hexagonal alpha phase with a lath type morphology. The alloys containing 15 wt% or less Nb are dominated by a hexagonal alpha' phase with an acicular, martensitic structure. When containing 17.5-25 wt% Nb, the alloys are primarily comprised of an orthorhombic alpha" phase. With 27.5 wt% Nb, metastable beta phase starts to be retained. With Nb contents higher than 30 wt%, the equi-axed beta phase is almost entirely retained. Small amounts of omega phase are detected in alloys containing 27.5 and 30 wt% Nb. Among all present alloys, Ti-10Nb and Ti-27.5Nb exhibit the highest strengths, while the alpha"-dominated (17.5 and 20Nb) and beta-dominated (> 30Nb) alloys have the lowest moduli. All Ti-Nb alloys show excellent corrosion resistance in Hank's solution at 37 degrees C. From the present data, the microhardness, bending strength and modulus of the various phases in Ti-Nb alloys are compared and tentatively summarized as follows: Microhardness: omega > alpha' > alpha" > beta > alpha (c.p. Ti) Bending strength: omega > alpha' > alpha" > beta > alpha (c.p. Ti) Bending modulus: omega > alpha (c.p. Ti) > alpha' > alpha" > beta

Axial load behavior of stiffened concrete-filled steel columns

Abstract: This study investigates the axial load behavior of concrete-filled steel tubular (CFT) columns with the width-to-thickness ratios between 40 and 150, and proposes an effective stiffening scheme to improve the mechanical properties of square cross-sectional CFT columns. Seventeen specimens were tested to examine the effects of cross-sectional shapes, width-to-thickness ratios, and stiffening arrangements on the ultimate strength, stiffness, and ductility of CFT columns. Moreover, nonlinear finite element analysis was also conducted to investigate cross-sectional axial stress distribution at the ultimate strength. Comparing the measured ultimate strength with estimates by using some current specifications suggested that current specifications may considerably underestimate the ultimate strength of circular CFT columns, particularly for columns with a small width-to-thickness ratio. Results in this study demonstrate that the proposed stiffening scheme can significantly enhance the ultimate strength and ducti...

Effect of process parameters on the surface morphology and mechanical performance of silicon structures after deep reactive ion etching (DRIE)

Abstract: The ability to predict and control the influence of process parameters during silicon etching is vital for the success of most MEMS devices. In the case of deep reactive ion etching (DRIE) of silicon substrates, experimental results indicate that etch performance as well as surface morphology and post-etch mechanical behavior have a strong dependence on processing parameters. In order to understand the influence of these parameters, a set of experiments was designed and performed to fully characterize the sensitivity of surface morphology and mechanical behavior of silicon samples produced with different DRIE operating conditions. The designed experiment involved a matrix of 55 silicon wafers with radius hub flexure (RHF) specimens which were etched 10 min under varying DRIE processing conditions. Data collected by interferometry, atomic force microscopy (AFM), profilometry, and scanning electron microscopy (SEM), was used to determine the response of etching performance to operating conditions. The data collected for fracture strength was analyzed and modeled by finite element computation. The data was then fitted to response surfaces to model the dependence of response variables on dry processing conditions.

Nitric Acid Modification of Activated Carbon Electrodes for Improvement of Electrochemical Capacitance

Abstract: Nitric acid oxidation of activated carbon fabric in combination with calcination in at different temperatures was conducted to explore the influence of surface carbon-oxygen complexes on the performance of electrochemical capacitors fabricated with the carbon fabric. The performance of the capacitors was tested in 1 M within a potential range of and 0.6 V. The specific capacitance of the carbon was found to increase upon oxidation. Surface complex analysis using temperature programmed desorption showed that the double-layer capacitance was enhanced due to the presence of CO-desorbing complexes while -desorbing complexes exhibited a negative effect. The micropore resistance for ion migration was low for these carbons. The electrical connection resistance between the fabric and the backing plate as well as that between the carbon fibers accounted for the major proportion of the overall resistance and was shown to increase due to oxidation. A capacitance increase of more than 40% has been achieved, without increasing IR drop, by nitric acid oxidation followed by 450°C calcination that was shown to remove the majority of the -desorbing complexes while retaining the CO-desorbing complexes. © 2002 The Electrochemical Society. All rights reserved.

InGaN-GaN multiquantum-well blue and green light-emitting diodes

Abstract: InGaN-GaN multiquantum-well (MQW) blue and green light-emitting diodes (LEDs) were prepared by organometallic vapor phase epitaxy, and the properties of these LEDs were evaluated by photoluminescence (PL), double crystal X-ray diffraction, and electroluminescence (EL) measurements. It was found that there were only small shifts observed in PL and EL peak positions of the blue MQW LEDs when the number of quantum well (QW) increased. However, significant shifts in PL and EL peak positions were observed in green MQW LEDs when the number of QW increased. It was also found that there was a large blue shift in EL peak position under high current injection in blue MQW LEDs. However, the blue shift in green MQW LEDs was negligibly small when the injection current was large. These observations could all be attributed to the rapid relaxation in green MQW LEDs since the In composition ratio in the InGaN well was high for the green MQW LEDs. The forward voltage V/sub f/ of green MQW LEDs was also found to be larger than that of blue MQW LEDs due to the same reason.

Preparation and characterization of a novel magnetic nano-adsorbent

Abstract: A novel magnetic nano-adsorbent has been developed using Fe3O4 nanoparticles (13.2 nm) as cores and polyacrylic acid (PAA) as ionic exchange groups. The Fe3O4 magnetic nanoparticles were prepared by co-precipitating Fe2+ and Fe3+ ions in an ammonia solution and treating under hydrothermal conditions. PAA was covalently bound onto the magnetic nanoparticles via carbodiimide activation. Transmission electron micrographs showed that the magnetic nanoparticles remained discrete and had no significant change in size after binding the PAA. The X-ray diffraction patterns indicated the magnetic nanoparticles were pure Fe3O4 with a spinel structure, and the binding of PAA did not result in a phase change. Magnetic measurement revealed the magnetic nanoparticles were superparamagnetic, and their saturation magnetization was reduced only slightly after PAA binding. Fourier transform infrared spectroscopy, thermogravimetric and differential thermal analyses, and X-ray photoelectron spectroscopy confirmed the binding of PAA to the magnetic nanoparticles, suggested a binding mechanism for the PAA, and revealed the maximum weight ratio of PAA bound to the magnetic nanoparticles was 0.12. In addition, the ionic exchange capacity of the resultant magnetic nano-adsorbents was estimated to be 1.64 mequiv g−1, much higher than those of commercial ionic exchange resins. When the magnetic nano-adsorbents were used for the recovery of lysozyme, the adsorption/desorption of lysozyme was completed within 1 min due to the absence of pore-diffusion resistance. Also, the adsorption/desorption efficiency could reach almost 100% under appropriate conditions, and the recovered lysozyme retained 95% activity.