排序方式: 共有69条查询结果,搜索用时 250 毫秒
21.
22.
Bouchoux G Guillemin JC Lemahieu N McMahon TB 《Rapid communications in mass spectrometry : RCM》2006,20(8):1187-1191
The gas-phase basicity (GB) of aminoacetonitrile (NH2CH2CN, 1) has been determined from measurement of proton transfer equilibrium constants in an ion cyclotron resonance mass spectrometer (GB(1) = 789.3 +/- 1.0 kJ x mol(-1)). Molecular orbital calculations up to the G2 level demonstrate that protonation occurs preferentially on the nitrogen atom of the NH2 group, and provide a theoretical proton affinity (PA(1)) of 824.0 kJ x mol(-1). Exact calculation of the entropy associated with hindered rotations and consideration of Boltzman distribution of conformers allow a theoretical estimate of the molar protonation entropy S degrees (1H+) - S degrees (1) = 8.6 J x mol(-1) x K(-1). Combining this value with experimental GB(1) leads to an 'experimental' proton affinity of 819.2 kJ x mol(-1), in close agreement with the G2 expectation. 相似文献
23.
24.
The behavior of the dielectric susceptibility of a semiconductor is studied in the case where the exciton state is probed by weak-pulse photons in the presence of a high-power laser pulse in the region of the M band of CuCl luminescence. A pronounced Autler-Townes effect for the exciton transition is shown to occur. The absorption peak position is determined by the amplitude and frequency of the pump field. 相似文献
25.
Nadège Handké Thomas Trimaille Elsa Luciani Marion Rollet Thierry Delair Bernard Verrier Denis Bertin Didier Gigmes 《Journal of polymer science. Part A, Polymer chemistry》2011,49(6):1341-1350
Poly(N‐acryloxysuccinimide) (PNAS) and poly(N‐acryloxysuccinimide‐co‐N‐vinylpyrrolidone) (P(NAS‐co‐NVP)) of adjustable molecular weights and narrow polydispersities were prepared by nitroxide‐mediated polymerization (NMP) in N,N‐dimethylformamide in the presence of free SG1 (N‐tert‐butyl‐N‐1‐diethylphosphono‐(2,2‐dimethylpropyl) nitroxide), with MAMA‐SG1 (N‐(2‐methylpropyl)‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl)‐O‐(2‐carboxylprop‐2‐yl)hydroxylamine) alkoxyamine as initiator. The reactivity ratios of NAS and NVP were determined to be rNAS = 0.12 and rNVP = 0, indicating a strong alternating tendency for the P(NAS‐co‐NVP) copolymer. NAS/NVP copolymerization was then performed from a SG1‐functionalized poly(D ,L ‐lactide) (PLA‐SG1) macro‐alkoxyamine as initiator, leading to the corresponding PLA‐b‐P(NAS‐co‐NVP) block copolymer, with similar NAS and NVP reactivity ratios as mentioned above. The copolymer was used as a surface modifier for the PLA diafiltration and nanoprecipitation processes to achieve nanoparticles in the range of 450 and 150 nm, respectively. The presence of the functional/hydrophilic P(NAS‐co‐NVP) block, and particularly the N‐succinimidyl (NS) ester moieties at the particle surface, was evidenced by ethanolamine derivatization and zeta potential measurements. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
26.
27.
28.
29.
30.
de Souza Nadábia A. B. de Souza F. S. Basílio I. D. Medeiros Ana C. D. Oliveira E. J. Santos Ana F. O. Macwdo R. O. Macędo R. O. 《Journal of Thermal Analysis and Calorimetry》2003,72(2):535-538
TG and DSC data were used to determine the thermal parameters of metronidazole drug and tablets. Three tablets A, B and C
were analysed. The TG curves of metronidazole drug and tablets A and B displayed five and C four thermal decomposition processes,
respectively. Analysis of the DSC data pointed to chemical interactions between metronidazole drug and the excipients of tablets,
suggested by alterations in the melting point of metronidazole. The rate constants obtained from the isothermal TG data presents
following sequence of the thermal stability: tablet A>tablet C>metronidazole drug>tablet B.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献