排序方式: 共有34条查询结果,搜索用时 15 毫秒
21.
Glass capillary gas chromatography with electron-capture detection. Separation of prostaglandins 总被引:1,自引:0,他引:1
Glass capillary gas chromatography of the prostaglandins was performed on a system including an all-glass, solventless injector; thermostable methylphenyl-polysiloxane glass capillary columns; and a conventional electron-capture detector fitted with a make-up gas tee. The principal stable metabolites of prostaglandin endoperoxide were separated as perfluorinated derivatives in 35 min. Detection limits equal or exceed those obtained for packed column separations and electron capture detection. Prostaglandin endoperoxide metabolic profiles from mammalian cell cultures were obtained using this system. These profiling studies are not possible with other chromatographic methods because of inferior resolution and sensitivity. 相似文献
22.
When a semiconductor host is doped by a foreign element, it is inevitable that a volume change will occur in the doped system. This volume change depends on both the size and charge state difference between the dopant and the host element. Unlike the "common expectation" that if the host is deformed to the same size as the dopant, then the formation energy of the dopant would reach a minimum, our first-principles calculations discovered that when an external hydrostatic strain is applied, the change of the impurity formation energy is monotonic: it decreases if the external hydrostatic strain is applied in the same direction as the volume change. This effect also exists when a biaxial strain is applied. A simple strain model is proposed to explain this unusual behavior, and we suggest that strain could be used to significantly improve the doping solubility in semiconductor systems. 相似文献
23.
AbstractA series of seven coumarinyl-amino acid ester conjugates have been synthesized and characterized by NMR (1H and 13C) and mass spectra. Further, the compounds were investigated for their therapeutic applications such as anti-inflammatory and antioxidant activities. Among the synthesized compounds most of the analogs showed good efficiency compared with the standard. 相似文献
24.
25.
Toulokhonova IS Stringfellow TC Ivanov SA Masunov A West R 《Journal of the American Chemical Society》2003,125(19):5767-5773
The reaction of 1,1-dilithio-2,3,4,5-tetraphenylsilole (1) with 1,1-dichloro-2,3-diphenylcyclopropene (2) leads to the novel 1,4-disila-1,4-dihydropentalene (4), as well as an exceptionally stable diradical for which the structure 3 is suggested. The diradical is unreactive toward water, methanol, and chloroform; upon heating it transforms into 4. Structure 3 for the paramagnetic species is proposed on the basis of EPR data and theoretical calculations. The trans-trans isomer of diradical 3 was calculated to be more stable than its cis-cis isomer. The strong and stable EPR signal in the reaction mixture is probably due to the trans-trans isomer of diradical 3 in the triplet state. A reaction scheme describing the formation of 3 and 4 is presented. 相似文献
26.
Myong K. Ahn Thomas C. Stringfellow Matthew Fasano Kenneth J. Bowles Michael A. Meador 《Journal of Polymer Science.Polymer Physics》1993,31(7):831-841
PMR-15 is a high-performance thermoset polyimide resin that is used in many high-temperature applications. Postcured PMR-15 produces room-temperature electron paramagnetic resonance (EPR) spectra from stable freeradical species that are formed during the postcuring stages. The variable-temperature EPR spectral intensities show a minimum at Tmin in the range ?60 to ?40°C, and a maximum at Tmax in the range 80–120°C. The EPR intensities follow the inverse temperature dependence of Curie's law below Tmin and are due to a stable free radical. The intensities then increase with increasing temperature between Tmin and Tmax. The free radical with such temperature dependence is not present below Tmin and is undetectable by EPR at temperatures above Tmax. These free radicals are generated during the postcuring process at elevated temperature above 310°C. The thermo-oxidative degradation involves free radicals generated during the postcuring process in the presence of oxygen gas. © 1993 John Wiley & Sons, Inc. 相似文献
27.
Roger W. Alder Paul Eastment Richard E. Moss Richard B. Sessions Martin A. Stringfellow 《Tetrahedron letters》1982,23(40):4181-4184
Condensation of 4-chlorobutanal and 5-chloropentanal with six cyclic diamines gave twelve α-aminoammonium salts; cleavage of these with LiAlH4 gave medium-ring bicyclic diamines. 相似文献
28.
G.B. Stringfellow 《Journal of Physics and Chemistry of Solids》1974,35(7):775-783
The techniques recently developed for the calculation of III-V ternary phase diagrams have been extended to the calculation of distribution coefficients of impurities in III-V semiconductors. The distribution coefficients are calculated with no adjustable parameters, the calculation requiring only the temperatures and entropies of fusion, binary phase diagrams and lattice parameters of the relevant III-V compounds, and the tetrahedral covalent radii, electronegativities, molar volumes and atomization energies of the donor impurities and group III and V elements concerned.The calculation is carried out for common donors S, Se, Te and Sn at the melting points of the III-V compounds GaP, GaAs, GaSb, InP, InAs and InSb, and the results compared with experimental results where available. In GaAs and GaP, the distribution coefficients are calculated vs temperature for solidification from the group III rich melt. 相似文献
29.
Alexopoulos T Allen C Anderson EW Balamurali V Banerjee S Beery PD Bhat P Biswas NN Bujak A Carmony DD Carter T Cole P Choi Y DeBonte R DeCarlo V Erwin AE Findeisen C Goshaw AT Gutay LJ Hirsch AS Hojvat C Jennings JR Kenney VP Lindsey CS Loomis C LoSecco JM McMahon T McManus AP Morgan N Nelson K Oh SH Porile NT Rimai A Reeves D Robertson WJ Scharenberg RP Stringfellow BC Stampke SR Thompson M Turkot F Walker WD Wang CH Warchol J Wesson DK Zhan Y 《Physical review D: Particles and fields》1992,46(7):2773-2786
30.
Alexopoulos T Allen C Anderson EW Balamurali V Banerjee S Beery PD Bhat P Bishop JM Biswas NN Bujak A Carmony DD Carter T Choi Y Cole P DeBonte R DeCarlo V Erwin AR Findeisen C Goshaw AT Gutay LJ Hirsch AS Hojvat C Jennings JR Kenney VP Lindsey CS Loomis C LoSecco JM McMahon T McManus AP Morgan NK Nelson K Oh SH Porile NT Reeves D Rimai A Robertson WR Scharenberg RP Stampke SR Stringfellow BC Thompson MA Turkot F Walker WD Wang CH Warchol J Wesson DK Zhan YH 《Physical review D: Particles and fields》1993,48(5):1931-1942