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G. Teowee J. M. Boulton C. D. Baertlein R. K. Wade D. R. Uhlmann 《Journal of Sol-Gel Science and Technology》1994,2(1-3):623-626
A series of monolithic Pt-PZT-Pt capacitors was prepared based on sol-gel derived PZT 53/47 films fired to 700 C. After deposition of top Pt electrodes, the capacitors were subjected to post-metallization annealing (PMA) temperatures of 100 C to 700 C. Dielectric and ferroelectric (FE) characterizations were performed. Increasing the PMA temperature produced lower values of spontaneous and remanent polarizations, dielectric constant and leakage currents. The observations are correlated with a proposed FE capacitor model. 相似文献
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Appleby I Boulton LT Cobley CJ Hill C Hughes ML de Koning PD Lennon IC Praquin C Ramsden JA Samuel HJ Willis N 《Organic letters》2005,7(10):1931-1934
Two methods to produce (2S)-5-amino-2-(1-n-propyl-1H-imidazol-4-ylmethyl)-pentanoic acid were investigated. Diastereoisomeric salt resolution, using the quinidine salt, gave the desired intermediate in 98% ee and 33% yield. Asymmetric hydrogenation of various substrates gave high conversions, with up to 83% ee. Integration of these two approaches via asymmetric hydrogenation of a quinidine salt substrate followed by crystallization provided the desired intermediate in 94% ee and 76% yield. 相似文献
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A new and experimental photodensitometer designed for quantitative chromatography is described. The principal features of the instrument were based upon the results of an extensive theoretical analysis and incorporate a mechanical arrangement for the production fo a flying spot and an optical path in which two beams of light are separated after interaction with the medium. The device is constructed so as to be suitable for operation in the three principal modes; in reflectance measurements only the ratio of the beam signals is formed, whilst in transmittance measurements the ratio is converted to logarithmic form, in the fluorescence mode only a single beam is used. The spectral range of the instrument extends from the red end of the visible spectrum to the medium ultraviolet, and quartz optics are utilized in most of the optic elements. A quartz halogen lamp and a xenon-mercury lamp may be used alternatively as the light source. Changeable interference filters are employed to determine the spectral position of the light beams and semiconductor photo-diodes with sensitivities extending into the ultraviolet are used as photo-detectors. In the determination of the sensitivity limits of the device the photo-diodes were replaced by photomultipliers and the apparatus was shown to fulfil most of the calculated thoeretical predictions. 相似文献
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A sensitive and convenient high-performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS) assay is described for the (5-HT(lB/lD)) receptor agonist sumatriptan in human plasma. Sumatriptan was recovered from plasma (81.8 +/- 6.8%) by liquid-liquid extraction. The mobile phase flow rate was 0.3 mL/min and consisted of methanol:water:formic acid (90:10:0.1, v/v/v). The analytical column (4.6 x 100 mm) was packed with Partisil C(8) (5 micro m). The standard curve was linear from 0.7 to 70.4 ng/mL (r(2) > 0.99). The lower limit of quantitation was 0.7 ng/mL. The assay was specific, accurate (percentage deviation from nominal concentrations were <15%), precise and reproducible (within- and between-day coefficients of variation <10.3%). Sumatriptan in plasma was stable over three freeze/thaw cycles and at room temperature for one day. The utility of the assay was demonstrated by following sumatriptan plasma concentrations in two healthy subjects for 8-12 h following a single 20 mg intranasal dose. 相似文献
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The asymmetric hydrogenation of a selectively crystallised (E)-4,4-diaryl-3-butenoate with a rhodium-PhanePhos catalyst is described, providing an intermediate to the antidepressant sertraline. 相似文献
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In this brief overview various neurochemical isolation procedures that can be adopted for the analysis of several monoamine neurotransmitters/neuromodulators and their principal oxidatively deaminated metabolites are outlined. With respect to the trace amines, they can be identified and quantitated as their so-called dansyl derivatives after thin-layer chromatographic separation by mass spectrometric (MS) electron-impact (EI) ionisation followed by selected-ion monitoring (SIM) of their molecular ions. Deuterated homologues are added as internal standards at the start of the analytical procedure. The MS-EI-SIM procedure offers a tissue extract or releasate sensitivity of about 100 pg/g of tissue or fluid. In the case of tryptamine or phenylethylamine, by utilising different derivatives (N-acetylpentafluoropropionyl or N-acetylpentafluorobenzoyl), which cyclise to form perfluorinated spirocyclic compounds, it is possible using MS negative chemical ionisation techniques coupled with monitoring of the (M-HF) ions to achieve sensitivities for tissue extracts of 1 pg/g or less. Acidic and neutral metabolites (up to twelve of them can be assayed simultaneously) can be detected and quantitated in tissue extracts, releasates or biological fluids as their methylpentafluoropropionyl or trifluoroethyl-pentafluoropropionyl derivatives in the 100-1000 pg range using gas chromatographic-MS-SIM procedures. 相似文献