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排序方式: 共有759条查询结果,搜索用时 31 毫秒
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R. Centore P. Riccio S. Fusco A. Carella A. Quatela S. Schutzmann F. Stella F. De Matteis 《Journal of polymer science. Part A, Polymer chemistry》2007,45(13):2719-2725
We have prepared new polyesters containing quadratic, nonlinear optical (NLO) active chromophores covalently incorporated into the main chain. In these polymers, the sequence of the chromophore units along the main chain is rigorously head to tail. All the polyesters are processable, both in the melt and in solution. For one polyester, a full second‐order NLO characterization has been performed. An out‐of‐resonance d33 coefficient of 21 pm/V at 1368 nm has been measured. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2719–2725, 2007 相似文献
3.
Summary Complete Active-Space Self-Consistent-Field (CAS-SCF) calculations for cubic N8 are presented. We studied the N8↔4N2 reaction inD
4h
symmetry and found its energy release and activation barrier with three different atomic basis sets. The energy release for
this reaction is predicted to be around 526 kcal/mol, while the energy barrier to dissociation is estimated about 159 kcal/mol.
These results are in substantial agreement with previousab initio estimates.
The authors of this paper have agreed to not receive the proofs for correction. 相似文献
4.
Lucien Stella 《Angewandte Chemie (International ed. in English)》1983,22(5):337-350
Many N-chloroalkylamines with double bond(s) dissociate homolytically to give chlorine atoms and aminyl radicals which undergo intramolecular cyclization reactions. Here, the nature of the aminyl radicals (neutral, protonated, or complexed to metal salts) appears to be important. The reactivity varies strongly from one species to another, and their selectivities can be different towards addition, substitution, abstraction, or dimerization reactions. A good synthetic tool appears to be the “complexed radical”, which is generated under mild conditions. A variety of β-functionalized, substituted, fused, or bridged azaheterocycles with alkaloid part structures thus become easily accessible in high yields, in a regio- and, possibly, stereoselective manner. Many examples are discussed illustrating the synthetic possibilities, limitations, and mechanistic features of this cyclization process. 相似文献
5.
Dendritic molecular capsules for hydrophobic compounds 总被引:1,自引:0,他引:1
Morgan MT Carnahan MA Immoos CE Ribeiro AA Finkelstein S Lee SJ Grinstaff MW 《Journal of the American Chemical Society》2003,125(50):15485-15489
Reichardt's dye, a highly solvatochromic dye, was encapsulated within poly (glycerol succinic acid) ([Gn]-PGLSA-OH) dendrimers to investigate the interior environment of these dendritic macromolecules. The absorption maximum for the encapsulated Reichardt's dye in water was indicative of a relatively high dielectric constant present within the dye/dendrimer complex. (1)H NMR of the encapsulated complex showed the presence of aromatic protons from Reichardt's dye along with the aliphatic protons of the dendrimer. Additionally, there were substantial changes in T(1) and T(2) times of the encapsulated dye when compared with the free dye, and (1)H NOESY spectra for the complex showed a significant number of intermolecular NOE cross-peaks. These data reveal the close through-space proximity of the dye to the dendrimer and the restricted motion of the encapsulated dye. To demonstrate the potential use of these macromolecules as drug delivery vehicles, the poorly water-soluble anticancer drug 10-hydroxycamptothecin (10HCPT) was encapsulated within a carboxylated PGLSA dendrimer ([G4]-PGLSA-COONa). Cytotoxicity assays with human breast cancer cells showed a significant reduction of cell viability, demonstrating that 10HCPT retains activity upon encapsulation. 相似文献
6.
A method based on ior-pair reversed-phase liquid chromatography is reported for the determination of climbazol, a preservative used in cosmetic products. The column was packed wit LiChrosob RP-18, the mobile phase was acetonitrile-sodium perchlorate (0.05 M, pH 3.0) (40 + 60) and detection was at 224 nm. The method was applied to the analysis of commercial shampoos. The detection limit was 10 ng injected and calibration linearity was observed up to 6 μg. 相似文献
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Matteo Scampicchio Nathan S. Lawrence Alessandra Arecchi Stella Cosio Saverio Mannino 《Electroanalysis》2007,19(1):85-90
Cyclic voltammetry has been applied to the rapid measurement of free SH‐compounds in food flours samples. The protocol is based on the electrochemical adaptation of the Ellman's test, where the DTNB reacts with SH‐compounds present in food flour extracts, resulting in the equimolar production of the electroactive compound TNBA which, in turns, reacts with phenylendiamine. The reaction is found to provide an analytical signal from which to quantify indirectly free sulfhydryl compounds in flours extracts. 相似文献
10.
Heinz Günter Viehe Robert Mernyi Lucien Stella Zdenek Janousek 《Angewandte Chemie (International ed. in English)》1979,18(12):917-932
The 100 yers old Wurster's salts have long been recognized as compounds with redical cations. Their unusual stabilization derives partly form capto-dative (cd) substitution. This principle is now discussed as one factor of radical stabilization and it is applied to simple methine derivatives. cd-Substitution has synthetically useful applications: cd-substituents on a carbon atom allow its selective dehydrodimerization. Olefines with geminal and thus cross-conjugated cd-substituents are “radicophilic” and permit twofold carbon radical addition. cd-Substituted olefines are useful antioxidants, polymerization inhibitors and are promising agents in the control of biological radical reactions. Generally, many reactions of cd-substituted molecules appear to involve radicals. 相似文献