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991.
In pursuit of photo‐curable adhesive for optical communication, dual‐curable acrylic oligomers (AOs) having alkoxy silane group, fluorine atoms and vinyl group as a pendent group were synthesized by two‐stage reactions. The isocyanate group containing oligomers were firstly synthesized via radical polymerization of acrylic monomers, and followed by urethane reaction with 2‐hydroxy ethyl methacrylate. The dual curing behaviors, e.g. thermal and photo‐cure, were studied by using photo‐differential scanning calorimetry (DSC) and real‐time IR. An optimum adhesive formulation, based on AO (15 g), epoxy acrylate (80 g), isobonyl methacrylate (17 g) and photo‐initiator (3 g), was obtained. As the content of AO was increased in the optical adhesive formulation, refractive index decreased but transmittance increased due to the increase in fluorine content. The optical transmittance at the range of 1.3 to 1.55 μm was higher than 90%. The addition of colloidal silica with the earlier mentioned formulation was helpful in decreasing crosslinking volume shrinkage and the increasing of glass fiber adhesion. The required properties for the optical adhesive, including chemical resistance and thermal resistance, dimension stability, etc. were also investigated. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
992.
Synthesis, photophysical, and complexation properties of fluorescent chemosensors, L1 and L2, with ‘receptor-spacer-fluorophore’ motif (L1: NS2O2-cyclic receptor, L2: acyclic analogue receptor) are described. Maximum chelation-enhanced fluorescence effect (TURN-ON type) was observed in the presence of Ag+ for both fluoroionophores in a 1:1 (v/v) aqueous ethanol solution: remarkably superior selectivity of L1 (150-fold) with cyclic receptor than that of the L2 (50-fold) with acyclic analogue was found. According to the fluorescence and NMR titrations, the excellent selectivity of L1 is attributed to its topology-based higher affinity in complexation. 相似文献
993.
H. C. Eun H. C. Yang Y. Z. Cho H. S. Lee 《Journal of Radioanalytical and Nuclear Chemistry》2009,281(3):585-590
This paper is a study on a stable destruction method of radioactive waste ion exchange resins. According to the resin TGA
results, its decomposition occurred through three stages. And a sufficient retention time of the resins and an effective retention
capacity of SO2 gases and the doped metal compounds were required to destruct resins doped with radioactive metals stably. The resins doped
with radioactive metal surrogates were effectively destructed in the lab-scale MCO system. CO and SO2 emissions were below 100 and 1 ppm, respectively. And the surrogates were collected more than 99.9% in the molten carbonate.
Thus, the resins can be destructed stably in the MCO process. 相似文献
994.
K. Y. Lee Y. Y. Yoon S. Y. Cho K. S. Ko Y. Kim 《Journal of Radioanalytical and Nuclear Chemistry》2009,281(2):287-290
Naturally occurring radionuclides (NORN) such as 40K, 226Ra and 232Th from 44 surface sediment samples collected from four desert regions of Chinese were determined to investigate the regional
characteristics of the source areas of Asian dust. The radionuclides for 41 surface sediment samples collected from seven
sites of the Keum River area in Korea were also determined to compare the regional characteristics with the Chinese desert
area. The specific activities (SA) and the specific activity ratios (SAR) of the radionuclides were investigated for distinguishing
the source region of Asian dust. The SA of 226Ra and 232Th as well as the SAR of 226Ra/40K and 232Th/40K were found to be useful to characterize source area and tracing Asian dust. 相似文献
995.
Shanmugam Easwaramoorthi Dr. Jae‐Yoon Shin Sung Cho Dr. Pyosang Kim Yasuhide Inokuma Eiji Tsurumaki Atsuhiro Osuka Prof. Dr. Dongho Kim Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(44):12005-12017
Donor–acceptor systems based on subporphyrins with nitro and amino substituents at meta and para positions of the meso‐phenyl groups were synthesized and their photophysical properties have been systematically investigated. These molecules show two types of charge‐transfer interactions, that is, from center to periphery and periphery to center depending on the peripheral substitution, in which the subporphyrin moiety plays a dual role as both donor and acceptor. Based on the solvent‐polarity‐dependent photophysical properties, we have shown that the fluorescence emission of para isomers originates from the solvatochromic, dipolar, symmetry‐broken, and relaxed excited states, whereas the non‐solvatochromic fluorescence of meta isomers is of the octupolar type with false symmetry breaking. The restricted meso‐(4‐aminophenyl) rotation at low temperature prevents the intramolecular charge‐transfer (ICT)‐forming process. The two‐photon absorption (TPA) cross‐section values were determined by photoexcitation at 800 nm in nonpolar toluene and polar acetonitrile solvents to see the effect of ICT on the TPA processes. The large enhancement in the TPA cross‐section value of approximately 3200 GM (1 GM=10?50 cm4 s photon?1) with donor–acceptor substitution has been attributed to the octupolar effect and ICT interactions. A correlation was found between the electron‐donating/‐withdrawing abilities of the peripheral groups and the TPA cross‐section values, that is, p‐aminophenyl>m‐aminophenyl>nitrophenyl. The increased stability of octupolar ICT interactions in highly polar solvents enhances the TPA cross‐section value by a factor of approximately 2 and 4, respectively, for p‐amino‐ and m‐nitrophenyl‐substituted subporphyrins. On the other hand, the stabilization of the symmetry‐broken, dipolar ICT state gives rise to a negligible impact on the TPA processes. 相似文献
996.
Cinnamon zeylanicum bark extract and powder mediated green synthesis of nano-crystalline silver particles and its bactericidal activity 总被引:1,自引:0,他引:1
M. Sathishkumar K. Sneha S.W. Won C.-W. Cho S. Kim Y.-S. Yun 《Colloids and surfaces. B, Biointerfaces》2009,73(2):332-338
The exploitation of various plant materials for the biosynthesis of nanoparticles is considered a green technology as it does not involve any harmful chemicals. The present study reports the synthesis of silver (Ag) nanoparticles from silver precursor using the bark extract and powder of novel Cinnamon zeylanicum. Water-soluble organics present in the plant materials were mainly responsible for the reduction of silver ions to nano-sized Ag particles. TEM and XRD results confirmed the presence of nano-crystalline Ag particles. The pH played a major role in size control of the particles. Bark extract produced more Ag nanoparticles than the powder did, which was attributed to the large availability of the reducing agents in the extract. Zeta potential studies showed that the surface charge of the formed nanoparticles was highly negative. The EC50 value of the synthesized nanoparticles against Escherichia coli BL-21 strain was 11 ± 1.72 mg/L. ThusC. zeylanicum bark extract and powder are a good bio-resource/biomaterial for the synthesis of Ag nanoparticles with antimicrobial activity. 相似文献
997.
A chemiluminometric biosensor system for point-of-care testing has been developed using an immuno-chromatographic assay combined with an enzyme (e.g., horseradish peroxidase) tracer that produces a light signal measurable on a simple detector. Cross-flow chromatography, a method previously investigated by our laboratory, was utilized in order to accomplish sequential antigen-antibody binding and signal generation. This enzyme-linked immunosorbent assay (ELISA) was effectively carried out on a plastic chip that was redesigned to simplify the fabrication process. To enhance the sensitivity, biotin-streptavidin capture technology was employed in preparing an immuno-strip that was then incorporated onto the chip in order to generate the ELISA-on-a-chip (EOC) biosensor. Samples containing cardiac troponin I (cTnI) were analyzed using the EOC. A chemiluminescent signal proportional to the analyte concentration was produced by adding a luminogenic substrate to the tracer enzyme complexed with the analyte on the chip. The luminescent signal was detected in a dark chamber mounted with a cooled charge-coupled device and the signal was converted to optical density for quantification. This EOC biosensor system was capable of detecting cTnI present in serum at concentrations as low as 0.027 ng mL−1, 30 times lower than those measured using the conventional rapid test kit with colloidal gold as the tracer. In addition, the final data was acquired within 30 s after the addition of the enzyme substrate, which was faster than the detection time required when using a colorimetric substrate with the same tracer enzyme. 相似文献
998.
999.
Ji-Eun Lee Hyonchol Jang Eun-Jung Cho Hong-Duk Youn 《Experimental & molecular medicine》2009,41(7):471-477
Down syndrome critical region 1 (DSCR1), an oxidative stress-response gene, interacts with calcineurin and represses its phosphatase activity. Recently it was shown that hydrogen peroxide inactivates calcineurin by proteolytic cleavage. Based on these facts, we investigated whether oxidative stress affects DSCR1-mediated inactivation of calcineurin. We determined that overexpression of DSCR1 leads to increased proteolytic cleavage of calcineurin. Convertsely, knockdown of DSCR1 abolished calcineurin cleavage upon treatment with hydrogen peroxide. The PXIIXT motif in the COOH-terminus of DSCR1 is responsible for both binding and cleavage of calcineurin. The knockdown of overexpressed DSCR1 in DS fibroblast cells also abrogated calcineurin proteolysis by hydrogen peroxide. These results suggest that DSCR1 has the ability to inactivate calcineurin by inducing proteolytic cleavage of calcineurin upon oxidative stress. 相似文献
1000.
Sang-Bok Ma Kyung-Wan Nam Won-Sub Yoon Seong-Min Bak Xiao-Qing Yang Byung-Won Cho Kwang-Bum Kim 《Electrochemistry communications》2009,11(8):1575-1578
Nano-sized lithium manganese oxide (LMO) dispersed on carbon nanotubes (CNT) has been synthesized successfully via a microwave-assisted hydrothermal reaction at 200 °C for 30 min using MnO2-coated CNT and an aqueous LiOH solution. The initial specific capacity is 99.4 mAh/g at a 1.6 C-rate, and is maintained at 99.1 mAh/g even at a 16 C-rate. The initial specific capacity is also maintained up to the 50th cycle to give 97% capacity retention. The LMO/CNT nanocomposite shows excellent power performance and good structural reversibility as an electrode material in energy storage systems, such as lithium-ion batteries and electrochemical capacitors. This synthetic strategy opens a new avenue for the effective and facile synthesis of lithium transition metal oxide/CNT nanocomposite. 相似文献