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71.
A phenomenological approach was used to characterize the cure processes of epoxy resins (a diglycidyl ether of bisphenol A and its modifier CTBN) from dynamic experiments by DSC. Various kinetic parameters were obtained by using a modified Avrami expression. The resulting overall activation energies for the two systems agreed very well with the published data in the whole cure temperature range. In contrast with the isothermal results and the general dynamic models, a change in the exponent and the non-linear temperature dependence of the rate constant were also observed.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
72.
Abstract— Bioluminescence from the oxidation of acetaldehyde by bacterial luciferase of Photobacterium fischeri has been demonstrated for the first time and its efficiency has been compared with that of nonanal and other short chain aldehydes. 相似文献
73.
Woo‐Hyung Lee Hoyoul Kong Se‐Young Oh Hong‐Ku Shim In‐Nam Kang 《Journal of polymer science. Part A, Polymer chemistry》2009,47(1):111-120
A series of modified thiophene groups containing PPV‐based semiconducting materials, poly[(2,5‐bis(octyloxy)‐1,4‐phenylenevinylene)‐alt‐(2,2′bithienylenevinylene)] ( PPBT ), poly[(2,5‐bis(octyloxy)‐1,4‐phenylenevinylene)‐alt‐(5,5‐thiostilylenevinylene)] ( PPTVT ), have been synthesized through a Horner coupling reaction. From the FTIR and 1H NMR spectroscopy, the configuration of the vinylene groups in the polymers was all trans (E) geometry. The weight‐average molecular weights (Mw) of PPBT and PPTVT were found to be 11,700 and 11,800, with polydispersity indices of 2.51 and 2.53, respectively. PPBT and PPTVT thin films exhibit UV–visible absorption maxima at 538 and 558 nm, respectively, and the strong absorption shoulder peaks at 578 and 602 nm, respectively. Solution processed field‐effect transistors (FET) fabricated using all the polymers showed p‐type OTFT characteristics. The field‐effect mobility of the PPTVT was obtained up to 2.3 × 10?3 cm2 V?1 s?1, an on/off ratio of 1.0 × 105 with ambient air stability. Studies of the atomic force microscopy (AFM) and X‐ray diffraction (XRD) analysis of the polymer thin films revealed that all the polymers were amorphous structure. The greater planarity and rigidity of PPTVT compared to PPBT results in elongation of conjugation length and better π–π stacking of polymer chains in amorphous region, which leads to improved FET performance. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 111–120, 2009 相似文献
74.
Soo Kyung Bae Min‐Jung Kim Eon‐Jeong Shim Doo‐Yeoun Cho Ji‐Hong Shon Kwang‐Hyeon Liu Eun‐Young Kim Jae‐Gook Shin 《Biomedical chromatography : BMC》2009,23(6):568-572
A simple and rapid HPLC method using fluorescence detection was developed for determination of irbesartan in human plasma. Sample preparation was accomplished through a simple deproteinization procedure with 0.4 mL of acetonitrile containing 800 ng/mL of losartan (internal standard), and to a 0.1 mL plasma sample. Chromatographic separation was performed on a Zorbax Xclipse XDB C18 column (150 × 4.6 mm, i.d., 5 µm) at 40°C. An isocratic mobile phase, acetonitrile:0.1% formic acid (37:63, v/v), was run at a flow‐rate of 1.0 mL/min, and the column eluent was monitored using a fluorescence detector set at excitation and emission wavelengths of 250 and 370 nm, respectively. The retention times of irbesartan and losartan were 4.4 and 5.9 min, respectively. This assay was linear over a concentration range of 10–5000 ng/mL with a lower limit of quantification of 10 ng/mL. The coefficient of variation for this assay precision was less than 8.48%, and the accuracy exceeded 94.4%. The mean relative recoveries of irbesartan and losartan were 98.4 and 99.1%, respectively. This method was successfully applied for pharmacokinetic study after oral administration of irbesartan (300 mg) to 23 Korean healthy male volunteers. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
75.
Nanocrystalline PbWO4 phosphor powders, which have scheelite structure, were successfully synthesized at low temperatures via a modified citrate complex route assisted by microwave irradiation. Crystallization of the PbWO4 precursor were detected at 400 °C, and entirely completed at 500 °C. Prepared PbWO4 nanocrystallites showed primarily spherical and disperse morphology. The average crystallite sizes were between 18 and 29 nm, showing an ordinary tendency to increase with temperature. The nanocrytalline PbWO4 phosphor powders exhibited spread-eagle shape of blue luminescence. Especially the PbWO4 phosphor powders prepared at 600 °C showed the strongest luminescent intensity, which was due to the higher crystallinity and homogeneous particle morphology. 相似文献
76.
77.
Hui‐Bog Noh Pankaj Kumar Tapan Kumar Biswas Duk‐Soo Kim Yoon‐Bo Shim 《Electroanalysis》2010,22(6):632-638
The performance of an enzyme sensor fabricated through covalent bond formation on the HRP‐bonded poly(1,8‐diaminonaphthalene) (polyDAN) layer with gold nanoparticles (AuNPs) was applied to catalyze the electrochemical reduction of H2O2. The surface characteristics of the sensor probe were studied using cyclic voltammetry, SEM, XPS, QCM, and impedance spectroscopy. The AuNP‐deposited surface resulted in higher conductivity and sensitivity for H2O2 detection in phosphate buffer solution. A linear calibration plot was obtained in the H2O2 concentration range between 10.0 μM and 25.0 mM with detection limit 5.0±1.25 μM. The lifetime of HRP/polyDAN/AuNP/GC probe was over 70 days without response loss. 相似文献
78.
Junoh Kim Jongwon Shim Yong‐Jin Kim Kookheon Char Kyung‐Do Suh Jin‐Woong Kim 《Macromolecular bioscience》2010,10(10):1171-1176
This study reports a facile and practical means to non‐invasively deliver biologically active ingredients through the skin using polymer‐based nanocarriers. For this, polymer nanocapsules were fabricated with different surface charges as well as glass transition temperatures and we observed their ability to deliver the encapsulated active ingredient, coenzyme Q10, through the skin layer. Direct imaging of a probe molecule, Nile Red, and a matrix polymer labeled with fluorescence moiety, Lucifer Yellow, allowed us to demonstrate that the probe molecule readily permeates into the deep skin, while the matrix polymer stays in the stratum corneum layer due to electrostatic interactions. Quantitative characterization of the penetrating amount of coenzyme Q10 using the Frantz cell method proved that, to achieve improved delivery efficiency, the nanocapsule should have a low glass transition temperature as well as positive surface charges.
79.
Ha J Seo HY Shim YS Nam HJ Seog H Ito M Nakagawa H 《Journal of AOAC International》2010,93(6):1905-1911
A sensitive and specific heating block method coupled with ultra-HPLC (u-HPLC) was developed for the analysis of capsaicin in Gochujang and validated by comparing with a conventional HPLC (AOAC Method 995.03). The method validation parameters yielded good results, including linearity, precision, accuracy, and recovery. The u-HPLC separation was performed on a reversed C18 column (50 x 2 mm id, particle size 2 microm), followed by fluorescence detection (excitation 280 nm, emission 325 nm). Methanol was used as the extracting solvent, and the amount of sample taken was approximately 0.2 g; the optimum amount of extraction solvent and extraction time were 15 mL and 1 h, respectively. The recovery of capsaicin in Gochujang was more than 93%, and the LOD and LOQ of the u-HPLC analysis were 0.05 and 0.16 microg/g for capsaicin and 0.05 and 0.16 microg/g for dihydrocapsaicin. The calibration graphs for capsaicin and dihydrocapsaicin were linear from 0.2 to 10.0 microg/mL for u-HPLC. The interday and intraday precisions (RSD values) were < 6.27%. 相似文献
80.
Jo E Jhon YH Choi SB Shim JG Kim JH Lee JH Lee IY Jang KR Kim J 《Chemical communications (Cambridge, England)》2010,46(48):9158-9160
A crystal structure of a carbamate of 2-amino-2-methyl-1-propanol (AMP-carbamate) has been elucidated and its structural and electronic properties investigated by density functional theory calculations and natural bond orbital analyses. 相似文献