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121.
C R Clark C L McMillian J F Hoke K D Campagna W R Ravis 《Journal of chromatographic science》1987,25(6):247-251
An improved liquid chromatographic procedure is described for the quantitative determination of sulindac, sulindac sulfone, and sulindac sulfide from serum. The procedure makes use of acetonitrile extraction of the compounds of interest from acidified serum samples. Under these conditions extraction efficiencies in the 85 percent range are obtained for each of the compounds. The liquid chromatographic separation of the compounds of interest and the internal standard (indomethacin) is accomplished in an isocratic elution procedure using a nitrile (CN) stationary phase. The HPLC separation procedure is completed in less than 10 minutes, giving excellent resolution and peak shape. 相似文献
122.
P. A. Clark 《Theoretical chemistry accounts》1972,28(1):75-80
CNDO/2 calculations of the electronic properties of the series of isomeric butenes and pentenes yield ionization potentials which reproduce the observed trends. These are interpreted in terms of the charge distribution effects of the alkyl groups.
Presented in part at the Eighth Theoretical Chemistry Symposium held at the Batelle Institute, Geneva, Switzerland; March 26–30, 1972. 相似文献
Zusammenfassung CNDO/2 Rechnungen für die Butan- und Penten-Isomeren ergeben die richtigen Trends für die Ionisierungspotentiale. Sie werden im Zusammenhang mit der Änderung der Ladungsverteilung infolge Methylsubstitution diskutiert.
Résumé Des calculs CNDO/2 des propriétés électroniques des séries d'isomères du butène et du pentène fournissent des potentiels d'ionisation qui reproduisent les tendances observées. Les distributions de charge calculées pour les molécules sont utilisées pour interpréter les propriétés observées en termes d'effet du substituant alkyle.
Presented in part at the Eighth Theoretical Chemistry Symposium held at the Batelle Institute, Geneva, Switzerland; March 26–30, 1972. 相似文献
123.
The natural atomic orbital/point (NAO-PC) model originally developed to calculate molecular electrostatic potentials (MEPs) and multiple moments based on the AM1 wave function has been extended to PM3. As for AM1, NAO-PC/PM3 reproduces dipole moments calculated by the standard PM3 method very well. There is also a surprisingly good correlation between experimental and calculated quadrupole moments. The MEPs calculated using PM3/NAO-PC are found to be in better agreement with those given by RHF/6-31G* than those obtained from the PM3 wave function using Coulson charges. On the other hand, the NAO-PC model is often slightly worse then the method implemented in MOPAC-ESP. The MEPs calculated using our model based on the PM3 wave function are often in better agreement with those given by RHF/6-31G* than those obtain with AM1. © 1994 by John Wiley & Sons, Inc. 相似文献
124.
R. M. Lindstrom R. Zeisler D. H. Vincent R. R. Greenberg C. A. Stone E. A. Mackey D. L. Anderson D. D. Clark 《Journal of Radioanalytical and Nuclear Chemistry》1993,167(1):121-126
An instrument for neutron capture prompt gamma-ray activation analysis (PGAA) has been constructed as part of the Cold Neutron Research Facility at the 20 MW National Institute of Standards and Technology Research Reactor. The neutron fluence rate (thermal equivalent) is 1.5·108 n ·cm–2·s–1, with negligible fast neutrons and gamma-rays. With compact geometry and hydrogen-free construction, the sensitivity is sevenfold better than an existing thermal instrument. Hydrogen background is thirtyfold lower. 相似文献
125.
Phase memory decays were obtained from the transient signals sampled within 50 ns of laser excitation by time resolved electron spin echo (ese) spectroscopy in normal protonated, deuterated, deuterated 15N photosynthetic algae and broken chloroplasts. Previously, it has been shown that application of time resolved ese to study these systems, in particular, gives rise to two kinds of signals (standard and special ese). The standard ese signal at g = 2.0023 and the special ese signal exhibit similar electron spin echo envelope modulation (eseem). The modulation frequency and pattern can be identified with that obtained from stable oxidized P700 in the same system. The two lower field resonances of the standard ese signal do not show eseem. The results support the proposed mechanism for formation of special ese and the notion that the standard ese is due to at least two radicals. It is also demonstrated that we can observe eseem of P+700 under ambient temperature conditions. 相似文献
126.
Clark TD Ferrigno R Tien J Paul KE Whitesides GM 《Journal of the American Chemical Society》2002,124(19):5419-5426
This article presents a strategy for the fabrication of ordered microstructures using concepts of design inspired by molecular self-assembly and template-directed synthesis. The self-assembling components are 4-microm-thick hexagonal metal plates having sides 10 microm in length ("hexagons"), and each template consists of a 4-microm-thick circular metal plate surrounding a central cavity, the perimeter of which is complementary in shape to the external edges of a two-dimensional, close-packed array of hexagons. The hexagons and templates (collectively, "pieces") were fabricated via standard procedures and patterned into hydrophobic and hydrophilic regions using self-assembled monolayers (SAMs). Templated self-assembly occurs in water through capillary interactions between thin films of a nonpolar liquid adhesive coating the hydrophobic faces of the pieces. The hexagons tile the cavities enclosed by the templates, and the boundaries of the cavities determine the sizes and shapes of the assemblies. Curing the adhesive with ultraviolet light furnishes mechanically stable arrays having well-defined morphologies. By allowing control over the structures of the resulting aggregates, this work represents a step toward the development of practical methods for microfabrication based on self-assembly. 相似文献
127.
James B. Clark Arthur L. Smirl Eric W. Van Stryland H.J. Mackey B.R. Russell 《Chemical physics letters》1981,78(3):456-460
The population kinetics and the rotational diffusion of the rhodamine B monomer and dimer were measured by using picosecond pulses from a mode-locked Nd : YAG laser to induce and time resolve the concentration-dependent transient absorption saturation of various aqueous solutions of this organic dye. 相似文献
128.
129.
Addition of an aldehyde and zinc chloride to a cyclobutanone enolate, prepared by the reaction of an α-chlorocyclobutanone with dimethylcopperlithium, gave an aldol adduct in good yield. 相似文献
130.
June E. Reitz W. Sean McGivern M. Clark Church Marc D. Wilson Simon W. North 《国际化学动力学杂志》2002,34(4):255-261
Rate constants for several intermediate steps in the OH‐initiated oxidation of isoprene were determined using laser‐photolysis/laser‐induced fluorescence of OH radicals at total pressures between 3 and 4 Torr at 295 K. The rate constant for decomposition of the hydroxyalkoxy radical was determined to be (3.0 ± 0.5) × 104 s?1 in this pressure range, which is in fair agreement with previous work. The presence of a prompt alkoxy decomposition pathway was also investigated and found to contribute less than 10% to the total hydroxyalkoxy radical decomposition. The rate constant for the reaction of the hydroxyperoxy radical with NO was determined to be (2.5 ± 0.5) × 10?11 cm3 molecule?1 s?1, which is moderately higher than previously reported. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 255–261, 2002 相似文献