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31.
G. E. Yefchak G. A. Schultz J. Allison C. G. Enke J. F. Holland 《Journal of the American Society for Mass Spectrometry》1990,1(6):440-447
The pulsed ion sources used in conventional time-of-flight mass spectrometry (TOFMS) generally do not provide adequate resolving power across the mass range required for applications such as gas chromatography combined with mass spectrometry (GC/MS). Theoretical and experimental aspects of beam deflection techniques, which provide time encoding for TOFMS with continuous ions sources, are explored here. In this approach, ion source conditions do not affect resolving power, allowing for a greater variety of ionization modes to be used. Theoretical predictions for the resolving power attainable with beam deflection, which are satisfactory for GC/MS applications, agree well with experimentally determined values. The combination of GC-beam deflection-TOFMS with time-array detection is evaluated, and the capabilities of this system are compared to those of scanning mass spectrometers. 相似文献
32.
Richard Gilardi Clifford George Jerome Karle Philip E. Eaton Allison M. Fisher 《Journal of heterocyclic chemistry》1993,30(5):1385-1388
Exploration of the reactions of the 9-azahomocubane system led to derivatives of two small-ring systems containing aza-bridging atoms, 5-azatetracyclo[4.2.0.03,8.04,7]octane and 9-azatetracyclo[4.3.0.02,5.04,7]nonane. The structures were characterized by X-ray diffraction analyses. There are no prior X-ray structural reports on these systems. 相似文献
33.
Résumé Nous avons étudié les complexes que forment les acides éthylèneglycolbis-(-aminoéthyléther)] Sr,N-tétracétique et ,-diaminodiéthylétherN,N-tétracétique, soit avec le thorium, soit avec les terres cériques et, à la suite de cette étude, nous avons pu établir une méthode d'analyse et une séparation du thorium d'avec les terres cériques qui nous a donné satisfaction.
Une communication de ce travail a été faite à Graz, lors de la commémoration du centenaire de la naissance deF. Emich. 相似文献
Summary A study has been conducted of the complexes formed by the ethyleneglycol-bis (-amino-ethylether)-N,N-tetraacetic acid and,-diaminodiethylether-N,N-tetraacetic acid with either thorium or the ceric earths. As a result of this investigation, it was possible to set up a method of analysis and a separation of thorium from the cerium earths. These procedures have proved satisfactory.
Zusammenfassung Die von Äthylenglykol-bis-(-aminoäthyläther)-N,N-tetraessigsäure bzw.von ,-Diaminodiäthyläther-N,N-tetraessigsäure mit Thorium bzw. mit den Cer-Erden gebildeten Komplexe wurden untersucht. Auf Grund der Ergebnisse konnte ein Analysenverfahren und eine Trennungsmethode für Thorium und Cer-Erden entwickelt werden.
Une communication de ce travail a été faite à Graz, lors de la commémoration du centenaire de la naissance deF. Emich. 相似文献
34.
35.
Henry AA Olsen AG Matsuda S Yu C Geierstanger BH Romesberg FE 《Journal of the American Chemical Society》2004,126(22):6923-6931
Six unnatural nucleotides featuring fluorine-substituted phenyl nucleobase analogues have been synthesized, incorporated into DNA, and characterized in terms of the structure and replication properties of the self-pairs they form. Each unnatural self-pair is accommodated in B-form DNA without detectable structural perturbation, and all are thermally stable and selective to roughly the same degree. Furthermore, the efficiency of polymerase-mediated mispair synthesis is similar for each unnatural nucleotide in the template. In contrast, the efficiency of polymerase-mediated self-pair extension is highly dependent on the specific fluorine substitution pattern. The most promising unnatural base pair candidate of this series is the 3-fluorobenzene self-pair, which is replicated with reasonable efficiency and selectivity. 相似文献
36.
Allison A. Calhoun Patrick D. Nicholson Alexander B. Barnes 《Polymer Degradation and Stability》2006,91(9):1964-1971
Thermo-oxidative effects on the surface energy of polypropylene were measured by inverse gas chromatography as a function of exposure time and temperature. Unaltered polypropylene had a surface energy of 33 mJ/m2. Oxidized polypropylene, after exposure to air at temperatures of 100 °C and 110 °C, had a range of maximum surface energies from 38 to 41 mJ/m2. Comparisons between FTIR carbonyl peak growth and the surface energy showed that both methods detect oxidation, though the increase in surface energy is detected before the carbonyl peak growth is noticeable. The work of adhesion predicted by the surface free energies obtained in this work between a coated calcium carbonate and polypropylene changes by 10% due to the oxidation of the polymer at 110 °C. 相似文献
37.
Allison M. Mills Daniel Brunling Michael Ruck 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(8):i70-i72
A redetermination of the structure of `La32.66Fe11S60' in the trigonal space group Rm led to the new formula La52Fe12S90 and to a redefinition of the structure type. In the structure, the Fe2+ cations occur in Fe2S9 dimers of face‐sharing octahedra (with 3m symmetry). The dimers are linked by face‐ and vertex‐sharing bi‐ and tricapped LaS6 trigonal prisms (with m symmetry) to form a three‐dimensional network containing two types of cuboctahedral cavities. The larger cavities remain empty, while the smaller ones accommodate alternative sites for disordered La3+ cations. 相似文献
38.
Sabine Wenger Zouhair Asfari Jacques Vicens 《Journal of inclusion phenomena and macrocyclic chemistry》1994,20(4):293-296
We report the synthesis of the first calix[4]arene constrained to a 1,3-alternate conformation by one crown ether and one di-aza-benzo crown ether bridgings. Preliminary binding properties are also given. 相似文献
39.