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121.
Simultaneous writing and probing of photoinduced second-order susceptibility chi((2)) in an azo-dye polymer thin film is demonstrated. The method is based on the fact that tensor properties of chi((2)) provide different planes of polarization for seeding and signal second harmonics. Our technique allows the chi((2)) value to be monitored in real time, completely eliminating the distortion of optical poling that can occur in traditional probing configurations. The possibility of attaining high values of chi((2)) in a DR1-PMMA guest?host system under low seeding intensities is shown. 相似文献
122.
Ching Hsuan Lin Hung Tse Lin Yu Wei Tian Shenghong A. Dai Wen Chiung Su 《Journal of polymer science. Part A, Polymer chemistry》2011,49(22):4851-4860
We reveal a route for the preparation of phosphinated bisphenol, 1,1‐bis(4‐hydroxyphenyl)‐1‐(6‐oxido‐6H‐dibenz <c,e> <1,2> oxaphosphorin‐6‐yl)ethane (2) , via a one‐pot reaction of 1,1,1‐tris(4‐hydroxyphenyl)ethane and 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene 10‐oxide (DOPO) in the catalysis of p‐toluenesulfonic acid. A two‐step reaction mechanism, acid‐fragmentation of 1,1,1‐tris(4‐hydroxyphenyl)ethane followed by nucleophilic addition of DOPO, is proposed for the synthesis. Based on (2) , a dicyanate ester derivative, 1,1‐bis(4‐cyanatophenyl)‐1‐(6‐oxido‐6H‐dibenz <c,e> <1,2> oxaphosphorin‐6‐yl)ethane (3) was prepared and co‐cured with a commercially available dicyanate ester, the dicyanate ester of bisphenol A (BACY). Experimental data show that incorporating (3) into BACY enhances the flame retardancy and dielectric properties with little penalty to the thermal properties. A thermoset with Tg 274 °C, coefficient of thermal expansion (CTE) 49 ppm/°C, Dk 3.04 (1 GHz), Td (5%,) N2: 435 °C, air: 424 °C, and UL‐94 V‐0 rating can be achieved via this approach. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011. 相似文献
123.
124.
A direct‐forcing immersed boundary‐lattice Boltzmann method (IB–LBM) is developed to simulate fluid–particle interaction problems. This method uses the pressure‐based LBM to solve the incompressible flow field and the immersed boundary method to handle the fluid–particle interactions. The pressure‐based LBM uses the pressure distribution functions instead of the density distribution functions as the independent dynamic variables. The main idea is to explicitly eliminate the compressible effect due to the density fluctuation. In the IB method, a direct‐forcing method is introduced to capture the particle motion. It directly computes an IB force density at each lattice grid from the differences between the pressure distribution functions obtained by the LBM and the equilibrium pressure distribution functions computed from the particle velocity. By applying this direct‐forcing method, the IB–LBM becomes a purely LBM version. Also, by applying the Gauss theorem, the formulas for computing the force and the torque acting on the particle from the flows are derived from the volume integrals over the particle volume instead of from the surface integrals over the particle surface. The order of accuracy of the IB–LBM is demonstrated on the errors of velocity field, wall stress, and gradients of velocity and pressure. As a demonstration of the efficiency and capabilities of the new method, sedimentation of a large number of spherical particles in an enclosure is simulated. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
125.
An ion pair HPLC method which can simultaneously detect the major metabolites of an exocrine pancreatic function testing agent (NBT-PABA) in plasma and urine has been developed. This assay has been applied to a pharmacokinetic study of PABA and its metabolites in 3 healthy adult volunteers following the oral administration of 1 g NBT-PABA. The 6 h testing period currently used to collect urine following the NBT-PABA ingestion is adequate for the recovery of PABA and its metabolites. Plasma determination of these compounds may provide an improved evaluation of the pancreatic performance in patients with abnormal liver or kidney function. 相似文献
126.
20-Deoxoluteone has been synthesized from sclareol. Sclareol was brominated with phosphorus tribromide to form a mixture of
primary allyl bromides, from which, by the malonic synthesis, a mixture of bicyclogeranylgeranylacetic acids was obtained
which was cyclized with fluorosulfonic acid to form a mixture of two diastereomeric δ-lactones. The predominating lactone
was converted by successive reduction with lithium tetrahydroaluminate, oxidation with oxalyl chloride in dimethyl sulfoxide,
reaction with methylmagnesium iodide, and oxidation by the chromium trioxide/pyridine complex into 20-deoxyluteone.
Institute of Chemistry, Moldavian SSR Academy of Science, Kishinev. Translated from Khimiya Prirodnykh Soedinenii, No. 3,
pp. 346–353, May–June, 1990. 相似文献
127.
128.
Guey‐Sheng Liou Po‐Han Lin Hung‐Ju Yen Yang‐Yen Yu Wen‐Chang Chen 《Journal of polymer science. Part A, Polymer chemistry》2010,48(6):1433-1440
In this study, a novel synthetic route was developed to prepare polyimide–nanocrystalline–titania hybrid optical films with a relatively high titania content (up to 50 wt %) and thickness (20–30 μm) from soluble polyimides containing hydroxyl groups. Two series of newly soluble polyimides were synthesized from the hydroxy‐substituted diamines with various commercial tetracarboxylic dianhydrides. The hydroxyl groups on the backbone of the polyimides could provide the organic–inorganic bonding and resulted in homogeneous hybrid solutions by controlling the mole ratio of titanium butoxide/hydroxyl group. AFM, SEM, TEM, and XRD results indicated the formation of well‐dispersed nanocrystalline‐titania. The flexible hybrid films could be successfully obtained and revealed relatively good surface planarity, thermal dimensional stability, tunable refractive index, and high optical transparency. A three‐layer antireflection coating based on the hybrid films was prepared and showed a reflectance of less than 0.5% in the visible range indicated its potential optical applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1433–1440, 2010 相似文献
129.
130.
We consider asymptotic expansions of solutions of the first initial boundary-value problem for strong Schr?dinger systems
near a conical point of the boundary of a domain. 相似文献