Bias stress effects on different dielectric surfaces of pentacene thin-film transistors

In this paper, it was demonstrated that pentacene thin-film transistors (TFTs) were fabricated with an organic adhesion layer between an organic semiconductor and a gate insulator. In order to form polymeric film as an adhesion layer, a vapor deposition polymerization (VDP) process was introduced to substitute for the usual spin-coating process. Field effect mobility, threshold voltage, and on/off current ratio in pentacene TFTs with a 15 nm thick organic adhesion layer were about 0.4 cm2/Vs, -1 V, and 10(6), respectively. We also demonstrated that threshold voltage strongly depends on the stress time when a gate voltage has been applied for bias stress test. We suggest that a polyimide adhesion layer fabricated by the VDP method can be applied to realize organic TFTs with long-term stability because of lower threshold voltage shifts due to reduced charge trapping at the interface between the pentacene semiconductor and the polyimide layer.     

Apta-biosensors for nonlabeled real time detection of human IgE based on carbon nanotube field effect transistors

In this study, we demonstrated the aptamer-based biosensor (apta-biosensor) using CNT-FET devices for label free detection of allergy diagnosis by IgE detection. In order to detect the IgE, two kinds of receptor (monoclonal IgE antibody and anti-IgE aptamer)-modified CNT-FET devices were fabricated. The binding event of the target IgE onto receptors was detected by monitoring the gating effect caused by the charges of the target proteins. Since the CNT-FET biosensors were used in buffer solution, it was crucial to use small-size receptors like aptamers than whole antibodies so that the charged target IgE could approach the CNT surface within the Debye length distance to give a large gating effect. The results show that CNT-FET biosensors using monoclonal IgE antibody had very low sensitivity (minimum detectable level 1000 ng/mL), while those based on anti-IgE aptamer could detect 50 ng/mL. Moreover, the aptamer-modified CNT-FET herein could successfully block non-target proteins and could selectively detect the target protein in an environment similar to human serum electrolyte. Therefore, aptamer-based CNT-FET devices enable the production of label-free ultrasensitive electronic biosensors to detect clinically important biomarkers for disease diagnosis.     

High-permittivity and low-loss dielectric tunable pyrochlore thin films deposited by radio frequency magnetron sputtering from a lead zinc niobate target

Since Bi₂O₃-ZnO-Nb₂O₅ (BZN) pyrochlore thin films have been introduced as a tunable dielectric, the substitution of Bi with Pb could be a reasonable choice. The PbO-ZnO-Nb₂O₅ (PZN) cubic pyrochlore thin films were produced by radio frequency sputtering, and their dielectric properties, in terms of tunability, were measured. Up to 33.4% of tunability and comparable K factors with BZN films were obtained. The effects of film crystallization, along with substrate heating and post-annealing on the dielectric properties, were similar to those of BZN. However, strong texturing developed in the PbO-ZnO-Nb₂O₅ (PZN) films deposited at a high substrate temperature, which caused degradation of the loss tangent and K factor.     

Development of rapid mask fabrication technology for micro-abrasive jet machining

Micro-machining of a brittle material such as glass or silicon is important in micro fabrication. Particularly, micro-abrasive jet machining (μ-AJM) has become a useful technique for micro-machining of such materials. The μ-AJM process is mainly based on the erosion of a mask which protects brittle substrate against high velocity of micro-particles. Therefore, fabrication of an adequate mask is very important. Generally, for the fabrication of a mask in the μ-AJM process, a photomask based on the semi-conductor fabrication process was used. In this research a rapid mask fabrication technology has been developed for the μ-AJM. By scanning the focused UV laser beam, a micro-mask pattern was fabricated directly without photolithography process and photomask. Therefore, rapid and economic mask fabrication can be possible for the micro-abrasive jet machining. Two kinds of mask patterns were fabricated by using SU-8 and photopolymer (Watershed 11110). Using fabricated mask patterns, abrasive-jet machining of Si wafer was conducted successfully. This paper was recommended for publication in revised form by Associate Editor Dae-Eun Kim Seung Pyo Lee is a research engineer of GM Daewoo Auto & Technology. He receives his Ms degree in Precision Mechanical Engineering at the Chungbuk National University in 2007. Hyun-Wook Kang is currently a Ph.D. candidate in the Department of Mechanical Engineering at POSTECH, Korea. He received his B.S. degree in the Department of Mechanical Engineering from POSTECH. His current research interests are in the solid freeform fabrication technology for the engineered tissue construction. Seung-Jae Lee received the M.S. degree from the Dept. of Me-chanical Engineering from the POSTECH in 2002, and his Ph.D. degree in Dept. of Mechanical Engineering from POSTECH in 2007. His Ph.D research is the study of Microfabrication and Tissue engineering. In Hwan Lee is a professor of School of Mechanical Engineering at Chungbuk National University, Korea. He receives his Ph.D. degree in Mechanical Engineering from the POSTECH in 2003. His research is focused on micro-manufacturing and bio-system. Tae Jo Ko is a professor of mechanical engineering at Yeungnam University, Korea. Also, he is responsible for the Gyoungbuk Hybrid Technology Institute that is regional research innovation center and initiates the idea for hybrid manufacturing. He earned Ph.D in mechanical engineering from POSTECH, Korea, in 1994. He worked for Doosan Infracore Co. Ltd. (formerly Daewoo) from 1985 to 1995. His research interests include machine tools, metal cutting as well as nontraditional machining. Dong-Woo Cho is a professor in the Department of Mechanical Engineering at the POSTECH. He received his Ph.D. degree in Mechanical Engineering from the University of Wisconsin-Madison in 1986. His research focuses on the manufacturing system for Tissue Engineering.     

Age-hardening and overaging mechanisms related to the metastable phase formation by the decomposition of Ag and Cu in a dental Au–Ag–Cu–Pd–Zn alloy

The age-hardening and overaging mechanisms related to the metastable phase formation by the decomposition of Ag and Cu in a dental casting gold alloy composed of 56Au–25Ag–11.8Cu–5Pd–1.7Zn–0.4Pt–0.1Ir (wt.%) were elucidated by characterizing the age-hardening behaviour, phase transformations, changes in microstructure and changes in element distribution. The fast and apparent increase in hardness at the initial stage of the aging process at 400°C was caused by the nucleation and growth of the metastable Ag–Au-rich phase and the Cu–Au-rich phase by the miscibility limit of Ag and Cu. The transformation of the metastable Ag–Au-rich phase into the stable Ag–Au-rich phase progressed concurrently with the ordering of the Cu–Au-rich phase into the AuCu I phase through the metastable state, which resulted in the subsequent increase in hardness. The further increase in hardness was restrained before complete decomposition of the parent α₀ phase due to the initiation of the lamellar-forming grain boundary reaction. The progress of the lamellar-forming grain boundary reaction was not directly connected with the phase transformation of the metastable phases into the final product phases. The heterogeneous expansion of the lamellar structure from the grain boundary caused greater softening than the subsequent further coarsening of the lamellar structure. The lamellar structure was composed of the Ag–Au-rich layer which was Cu-, Pd- and Zn-depleted and the AuCu I layer containing Pd and Zn.     

Selective,Green Synthesis of Six‐Membered Cyclic Carbonates by Lipase‐Catalyzed Chemospecific Transesterification of Diols with Dimethyl Carbonate

A facile and green synthesis of six‐membered cyclic carbonates, the potential monomers for isocyanate‐free polyurethanes and polycarbonates, was achieved by transesterification of diols with dimethyl carbonate catalyzed by immobilized Candida antarctica lipase B, Novozym®435, followed by thermal cyclization in a solvent‐free medium. The difference in the chemospecificity of the lipase for the primary, secondary and tertiary alcohols as acyl acceptors was utilized to obtain a highly chemoselective synthesis of the cyclic carbonate in high yield. In the lipase‐catalyzed reaction with diols, the product contained almost equal proportions of mono‐ and di‐carbonates with 1,3‐propanediol having two primary alcohols, a higher proportion of mono‐carbonate with 1,3‐butanediol having a primary and a secondary alcohol, and mainly mono‐carbonate with 3‐methyl‐1,3‐butanediol having a primary and a tertiary alcohol. The chemospecificity of cyclic carbonates formed by thermal treatment at 90 °C was closely related to the proportion of mono‐carbonate. The yield of cyclic carbonate was 99.3% with 3‐methyl‐1,3‐butanediol, 85.5% with 1,3‐butanediol, and 43.2% with 1,3‐propanediol.     

Simplified column shortening analysis of a multi‐storey reinforced concrete frame

An improved column shortening analysis method which can be used at the design stage of a tall building has been proposed. The proposed analysis method considers construction sequences, the restraining effect of horizontal members, as well as creep and shrinkage. The whole analysis period is divided into two phases: before completion and after completion, and correction factors are applied only to the before‐completion phase to consider the gradual nature of construction sequences. Age‐adjusted effective moduli of the horizontal members considering the long‐term behaviour of the members are used for more exact internal forces. Column shortenings of a 70‐storey reinforced concrete frame–shear wall building were investigated as a numerical example. It is shown that the proposed analysis method can be used effectively to evaluate the effects of the differential column shortening to the horizontal members at the design stage. Copyright © 2010 John Wiley & Sons, Ltd.     

MiR1885 Regulates Disease Tolerance Genes in Brassica rapa during Early Infection with Plasmodiophora brassicae

Clubroot caused by Plasmodiophora brassicae is a severe disease of cruciferous crops that decreases crop quality and productivity. Several clubroot resistance-related quantitative trait loci and candidate genes have been identified. However, the underlying regulatory mechanism, the interrelationships among genes, and how genes are regulated remain unexplored. MicroRNAs (miRNAs) are attracting attention as regulators of gene expression, including during biotic stress responses. The main objective of this study was to understand how miRNAs regulate clubroot resistance-related genes in P. brassicae-infected Brassica rapa. Two Brassica miRNAs, Bra-miR1885a and Bra-miR1885b, were revealed to target TIR-NBS genes. In non-infected plants, both miRNAs were expressed at low levels to maintain the balance between plant development and basal immunity. However, their expression levels increased in P. brassicae-infected plants. Both miRNAs down-regulated the expression of the TIR-NBS genes Bra019412 and Bra019410, which are located at a clubroot resistance-related quantitative trait locus. The Bra-miR1885-mediated down-regulation of both genes was detected for up to 15 days post-inoculation in the clubroot-resistant line CR Shinki and in the clubroot-susceptible line 94SK. A qRT-PCR analysis revealed Bra019412 expression was negatively regulated by miR1885. Both Bra019412 and Bra019410 were more highly expressed in CR Shinki than in 94SK; the same expression pattern was detected in multiple clubroot-resistant and clubroot-susceptible inbred lines. A 5′ rapid amplification of cDNA ends analysis confirmed the cleavage of Bra019412 by Bra-miR1885b. Thus, miR1885s potentially regulate TIR-NBS gene expression during P. brassicae infections of B. rapa.     

Determination of hyperoside and 2″-acetylhyperoside from Ligularia fischeri by high performance liquid chromatography

Ligularia fischeri and its main flavonoids, hyperoside and 2″-acetylhyperoside, posses antioxidant properties. This study was carried out to investigate the contents of hyperoside and 2″-acetylhyperoside in L. fischeri by using high performance liquid chromatography (HPLC). An HPLC–photodiode array (PDA) detection method was established for the simultaneous determination of hyperoside and 2″-acetylhyperoside in L. fischeri. Two flavonoids were successfully separated in less than 20 min using an YMC RP 18 column. The mobile phase was composed of water (A) and acetonitrile (B) with isocratic elution system (23% B) at a flow rate of 1 mL/min. Their calibration curves showed good linear regression (r > 0.9992) within the test ranges. The method was validated for specificity, accuracy, precision, and limits of detection. The determined two compounds were well separated with a linear range of 18–180 μg/mL. The contents of hyperoside and 2″-acetylhyperoside were 0.387 ± 0.002 and 0.526 ± 0.006 mg/g in L. fischeri, respectively.