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841.
Mitchell Anthamatten Stephan A. Letts Katherine Day Robert C. Cook Anthony P. Gies Tracy P. Hamilton William K. Nonidez 《Journal of polymer science. Part A, Polymer chemistry》2004,42(23):5999-6010
The condensation polymerization of 4,4′‐oxydianiline with pyromellitic dianhydride for the formation of poly(amic acid) and the subsequent imidization for the formation of polyimides were investigated for films prepared with vapor‐deposition polymerization techniques. Fourier transform infrared spectroscopy, thermal analysis, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry of films at different temperatures indicated that additional solid‐state polymerization occurred before imidization. The experiments revealed that, upon vapor deposition, poly(amic acid) oligomers formed that had a number‐average molecular weight of about 1500 Da. Between 100–130 °C, these chains underwent an additional condensation reaction and formed slightly higher molecular weight oligomers. Calorimetry measurements showed that this reaction was exothermic [enthalpy of reaction (ΔH) ~ ?30 J/g] and had an activation energy of about 120 kJ/mol. The experimental ΔH values were compared with results from ab initio molecular modeling calculations to estimate the number of amide groups formed. At higher temperatures (150–300 °C), the imidization of amide linkages occurred as an endothermic reaction (ΔH ~ +120 J/g) with an activation energy of about 130 kJ/mol. The solid‐state kinetics depended on the reaction conversion as well as the processing conditions used to deposit the films. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5999–6010, 2004 相似文献
842.
A. F. Kluk Noah R. Johnson J. H. Hamilton 《Zeitschrift für Physik A Hadrons and Nuclei》1972,253(1):1-12
A detailed investigation of the energies and intensities of the γ-rays that depopulate the low spin levels of the β- and γ-vibrational bands of156Gd and the γ-vibrational band of158Gd has been conducted. Both singles and γ-γ coincidence measurements were made on sources of 15-d156Eu and 46-min158Eu by use of large volume, high resolution Ge(Li) detectors. In addition to the γ-band at 1154.09 keV, twoK π=0+ bands were observed in156Gd with band heads at 1049.45 and 1168.11 keV, respectively. The 2+ and 3+ members of the γ-vibrational band in158Gd were observed at 1187.12 and 1265.43 keV, respectively, as well as a newK π=0+ band at 1195.98 keV. A first order perturbational treatment of the branching ratios was applied to both nuclei. In addition, the mixing between the ground state, the β-, and the γ-vibrational bands of156Gd is considered from two approaches, but neither satisfactorily explains all the experimentalB(E2) ratios. 相似文献
843.
844.
J. B. Gupta N. C. Singhal J. H. Hamilton 《Zeitschrift für Physik A Hadrons and Nuclei》1973,261(2):137-142
The weak transitions in the decay of125Sb have been investigated through gamma ray measurements with high resolution X-ray and with large volume Ge(Li) detectors. The 172.6, 178.8 and 198.5 keV gamma rays are confirmed, while others previously reported were not. Accurate intensities were obtained for the stronger transitions. The weighted averages of these intensities which cover the range of 116 to 670 keV are useful for calibration of Ge(Li) systems. 相似文献
845.
846.
Greentree AD Schirmer SG Green F Hollenberg LC Hamilton AR Clark RG 《Physical review letters》2004,92(9):097901
Given a particular quantum computing architecture, how might one optimize its resources to maximize its computing power? We consider quantum computers with a number of distinguishable quantum states, and entangled particles shared between those states. Hilbert-space dimensionality is linked to nonclassicality and, hence, quantum computing power. We find that qutrit-based quantum computers optimize the Hilbert-space dimensionality and so are expected to be more powerful than other qudit implementations. In going beyond qudits, we identify structures with much higher Hilbert-space dimensionalities. 相似文献
847.
The coordination polymer Pb[B(Im)(4)](NO(3))(xH(2)O), constructed by using sodium tetrakis(imidazolyl)borate and lead(II) nitrate solutions, is a layered material with the metal centers facing the interlayer spacing. As in naturally occurring layered minerals, this compound can readily undergo anion exchange and reversible intercalation of solvent water in the solid state with retention of crystallinity. We observed changes in solvent intercalation by (207)Pb solid state NMR (SSNMR) and thermogravimetric analysis (TGA). Stoichiometric exchange of (15)N nitrate for nitrate and iodide for nitrate is monitored by (15)N and (207)Pb SSNMR, and single crystals of the iodide-exchanged material Pb[B(Im)(4)]I were isolated. While the iodide compound can be obtained through facile exchange from the nitrate parent compound, the organic anion benzoate is placed in the interlayer spacing for nitrate under self-assembly conditions and forms an alternating monolayer in Pb[B(Im)(4)](C(6)H(5)COO)(0.5H(2)O). The ion exchange versus self-assembly behavior correlates with the structural differences in the three compounds. In both Pb[B(Im)(4)]I and Pb[B(Im)(4)](C(6)H(5)COO)(0.5H(2)O), the lead sites act as Lewis acids for the iodide and benzoate, respectively. 相似文献
848.
849.
Mono-urea serine derivatives with low molecular weights were prepared in one step and show remarkable self-assembling and gelation properties in water. 相似文献
850.
Hamilton Patti Pollock Jane Englebright Mitchell De Ann F. Vicenzi Angela E. West Bruce J. 《Nonlinear dynamics, psychology, and life sciences》1997,1(4):237-261
In this article, the authors present an overview of the applications of chaos theory and nonlinear dynamics to problems of relevance not only to nurses, but to anyone dealing with human functioning and interaction. These applications have been in the areas of epidemiology, nursing management and physiological functioning. In some cases, the applications were successful in identifying information that would have been overlooked using traditional methods. In other cases, the problems of data collection and analysis, unique to nonlinear dynamics, are still being developed and tested. 相似文献