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21.
Jin Kyu Park Dong Hun Lee Bok Ju Song Jae Buem Oh Hwan Kyu Kim 《Journal of polymer science. Part A, Polymer chemistry》2006,44(3):1326-1342
We have designed and synthesized novel perfluorinated polyimides with 3D controlled structure. At first, we successfully developed the new synthetic routes to diamines with pendant bulky perfluorinated aromatic units in a multi‐step synthetic procedure. Novel perfluorinated polyimides were prepared in a two‐step reaction in N‐methyl‐2‐pyrrolidinone (NMP) solution: The first step was for the synthesis of polyamic acids (PAAs) and the second reaction was for the imidization of PAA. The polymer yield was over 89% and the inherent viscosity of PAAs was in the range of 0.24–0.36 dL/g. The thin films were prepared by spin‐coating the PAA solution in NMP onto various substrates such as a Si wafer or a KBr pellet, dried at 80 °C and further cured at 230 °C. The resultant polyimides are thermally stable over 400 °C. The refractive index and birefringence of the resultant polyimides are 1.5858–1.6452 and 0.01–0.005, respectively. The refractive index of polyimide decreases with increasing the fluorine content. The copolymerization and the ether linkages into the backbone reduce the birefringence of polyimides. Surprisingly, the pendant ether linkage is not a crucial factor in reducing the polyimide birefringence. Their birefringence is comparatively very low, compared with that of previous polyimides. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1326–1342, 2006 相似文献
22.
23.
Hong Oh Kim Rae Young Kim Jae Kun Lim Zuowei Shen 《Journal of Approximation Theory》2007,147(2):196-204
We start with a characterization of a pair of frames to be orthogonal in a shift-invariant space and then give a simple construction of a pair of orthogonal shift-invariant frames. This is applied to obtain a construction of a pair of Gabor orthogonal frames as an example. This is also developed further to obtain constructions of a pair of orthogonal wavelet frames. 相似文献
24.
Alexopoulos T Allen C Anderson EW Areti H Banerjee S Beery PD Biswas NN Bujak A Carmony DD Carter T Cole P Choi Y De Bonte RJ Erwin AR Findeisen C Goshaw AT Gutay LJ Hirsch AS Hojvat C Kenney VP Lindsey CS LoSecco JM McMahon T McManus AP Morgan N Nelson KS Oh SH Piekarz J Porile NT Reeves D Scharenberg RP Stampke SR Stringfellow BC Thompson MA Turkot F Walker WD Wang CH Wesson DK 《Physical review letters》1990,64(9):991-994
25.
Brick DH Widgoff M Beilliere P Lutz P Narjoux JL Gelfand N Alyea ED Bloomer M Bober J Busza W Cole B Frank TA Fuess TA Grodzins L Hafen ES Haridas P Huang D Huang HZ Hulsizer R Kistiakowsky V Ledoux RJ Milstene C Noguchi S Oh SH Pless IA Steadman S Stoughton TB Suchorebrow V Tether S Trepagnier PC Wadsworth BF Wu Y Yamamoto RK Cohn HO Calligarich E Castoldi C Dolfini R Introzzi G Ratti S Badiak M DiMarco R Jacques PF Kalelkar M Plano RJ Stamer PE Brucker EB Koller EL Alexander G Grunhaus J 《Physical review D: Particles and fields》1990,41(3):765-773
26.
[formula: see text] A novel type of palladium-catalyzed cascade cyclization-coupling reaction that proceeds with suppressed beta-hydride elimination has been found. One of the N-sulfonyl oxygens is suggested to coordinatively stabilize an alkylpalladium intermediate, thus preventing the intermediate from the usual beta-elimination. This is the first sequential palladium-catalyzed coupling reaction where the Suzuki and Heck reactions can compete. The reaction provides an efficient synthetic route to 4-methylene-3-arylmethylpyrrolidines, which are not readily available by other routes. 相似文献
27.
Photodissociation at 266 nm of protonated synthetic polypeptides containing a tryptophanyl residue was investigated using a homebuilt tandem time-of-flight mass spectrometer equipped with a matrix-assisted laser desorption/ionization source. Efficient photodissociation of the protonated peptides was demonstrated. Most of the intense peaks in the laser-induced tandem mass spectra were sequence ions. Furthermore, sequence ions due to cleavages at all the peptide bonds were observed; this is a feature of the technique that is particularly useful for peptide sequencing. Fragmentations at both ends of the tryptophanyl residue were especially prevalent, which can be useful for location of the tryptophanyl chromophore in a peptide. 相似文献
28.
Carbon capsules with hollow cores and mesoporous shells (HCMS) containing entrapped Au particles were prepared by template replication from solid core/mesoporous shell silica spheres with encapsulated Au particles. The resulting HCMS carbon capsules were then nanocast one step further to generate Au-trapping hollow core silica capsules with nanostructured shells. 相似文献
29.
Osteoprotegerin (OPG), a member of the tumor necrosis factor receptor superfamily, is known to inhibit osteoclastogenesis by acting as a soluble decoy receptor for the receptor activator of NF-kappaB ligand (RANKL). We report the presence of OPG on the membrane of osteoclasts and the possibility of the direct action of OPG on them. Highly pure osteoclast precursors were isolated from mouse long bones and induced to differentiate into mature osteoclasts by M-CSF and soluble RANKL (sRANKL). The presence of OPG on the membrane of these cells was confirmed by western blotting and immunostaining. Furthermore, sRANKL was found to be bound to the OPG on the osteoclast precursors. These results suggest that OPG might have a new role during the differentiation of osteoclasts beyond its role as a soluble decoy receptor. The mechanism of the existence of OPG on osteoclast precursors remains to be found. 相似文献
30.
The kinetic analysis of the degradation of polystyrene (PS) in supercritical acetone has been studied using the nonisothermal weight loss technique with heating rates of 3, 5 and 7 °C/min. The weight loss data according to degradation temperature have been analyzed using the integral method based on Arrhenius form to obtain the kinetic parameters such as apparent activation energy and overall reaction order. The kinetic parameters obtained from this work were also compared with those of the thermal degradation of PS in nitrogen atmosphere. From this work, it was found that the activation energies of PS degradation in supercritical acetone were 73.3-200.7 kJ/mol and lower than those of the thermal degradation in nitrogen atmosphere. 相似文献