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21.
The effect of intramolecular dipole-dipole interaction on polarisation at frequencies from 0 – 1012 Hz in dipolar media is investigated using a numerical solution of the Sturm-Liouville eigenvalue problem to which the governing Smoluchowski equation reduces. The results of Budó for the long-wavelength limit are extended to all frequencies up to the far infrared, where the predominant inertial effects are treated using a preliminary first-order correction. The numerical method of Pryce may be used to investigate much more realistic interaction potentials than the simple harmonic and cosine form considered by Budó. These simple forms are, however, sufficient to indicate that the integrated absorption intensity per molecule in the far infrared is very sensitive to dipole-dipole interaction and relative hydrodynamic drag on both interacting groups. Applications of the theory to the disordered solid and nematic phases are considered. 相似文献
22.
Summary Inverse gas chromatography is shown to be suitable for the study of the oxidation of vegetable oils. With air as carrier gas
characteristic plots of retention index versus time are obtained for hydroxylic test solutes that are consistent with the
oxidation behaviour of vegetable oils. Shifts of retention are found to be accompanied by changes of column efficiency due
to the oxidative crosslinking of polyunsaturated vegetable oils. The technique also leads to useful information concerning
the oxidation of antioxidant inhibited systems.
Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984 相似文献
23.
24.
William J. Evans Ira Bloom Robert J. Doedens 《Journal of organometallic chemistry》1984,265(3):249-255
(C5H5)2VCl reacts with LiCCC(CH3)3 to form (C5H5)2VCCC(CH3)3 which was characterized by spectroscopic, analytical, and crystallographic methods. The complex crystallizes from pentane at 0°C as a monomer in the orthorhombic space group Pnma with four molecules in a unit cell of dimensions a 9.075(3), b 9.807(3), c 16.444(5) Å. Full-matrix least-squares refinement based upon 1300 nonzero intensity data converged to a final conventional R factor of 0.060. The molecule has a mean VC5H5-ring centroid distance of 1.941 Å with 146.6° ring centroid-V-ring centroid angle. The vanadium alkynide carbon distance is 2.075(5) Å. 相似文献
25.
Field-portable, high-speed GC/TOFMS 总被引:1,自引:0,他引:1
Syage JA Nies BJ Evans MD Hanold KA 《Journal of the American Society for Mass Spectrometry》2001,12(6):648-655
This work is focused on developing a fast gas chromatograph, time-of-flight mass spectrometer (GC/TOFMS) for man-portable field use. The goal is to achieve a total system solution for meeting performance, size, weight, power, cost, and ruggedness requirements for a laboratory in the field. The core technology will also be adaptable to specific applications including real-time point detection for hazardous chemical releases (e.g., chemical weapons), for biological agent signature identification, and for mobile monitoring platforms (e.g., air, ship, truck). Previously we presented results of a feasibility demonstration for a 30-lb field-portable TOFMS system. In this work we present recent progress in integrating a low-power, high-speed GC and show the capability for accurately recording fast GC transients for targeted compound detection using a quadrupole ion trap, time-of-flight instrument (QitTof). 相似文献
26.
Peter C. Cherry Derek N. Evans Christopher E. Newall Nigel S. Watson Peter Murray-Rust Judith Murray-Rust 《Tetrahedron letters》1980,21(6):561-564
1,4-Addition of sulphur nucleophiles to the diene () derived the pen-2-em () from clavulanic acid provides the thiadeoxa analogues (–). X-ray analysis of the ester () shows the thermodynamically stable isomers to have the same relative stereochemistry as clavulanic acid. 相似文献
27.
Myron Evans 《Chemical physics letters》1976,39(3):601-605
A theory of brownian motion where the friction coefficient is a finite correlation function of molecular torque is used to derive an expression for the angular velocity autocorrelation function, ψ(r). This is related to the orientational a.c.f., φ(t), using an analysis of bandshapes due to Kubo and extended by Shimizu. Both functions φ(t) and ψ(t) contain inherent weaknesses since ψ(t) has a MacLaurin expansion even up to t4 only, and π(t) does not reduce to the Kummer function for an ensemble of free rotors in the so-called limit of vanishing friction. Reasons for this behaviour are discussed. 相似文献
28.
J. C. Evans K. R. N. Rao S. K. Jackson C. C. Rowlands M. D. Barratt 《Journal of separation science》1985,8(12):829-830
Radicals generated in linoleic acid and deuterated linoleic acid have been trapped by the spin trap 2-methyl-2-nitroso-propane (MNP) and identified by electron spin resonance (ESR) and ENDOR spectroscopy. The formation of two distinct secondary alkyl radical adducts (one conjugated, the other non-conjugated, as shown by their UV absorption spectra) was demonstrated by 11, 11-dideuterio-9-cis-12-cis-linoleic acid using HPLC and ESR spectroscopy. 相似文献
29.
Jeffrey C. Evans Simon K. Jackson Christopher C. Rowlands Martin D. Barratt 《Tetrahedron》1985,41(22):5191-5194
Under acid conditions aqueous solutions of chloramine-T form nitrogen-centred radicals via loss of the chlorine atom. The nitrogen radicals produced have been studied by ESR spectroscopy using the spintrapping method. Adducts of the spin trap phenyl-t-butyl nitrone are oxidized by chloramine-T in acid media to give a paramagnetic product in which the unpaired electron interacts with two inequivalent nitrogen atoms. The spin trap 5,5-dimethyl-2-pyrrolidine-1 -oxide is oxidized rapidly to 5,5-dimethyl-2-pyrrolidone-1-oxyl by chloramine-T under acid onditions. The water soluble trap α-4-pyridyl-1-oxide-N-t-butyl nitrone forms a stable nitroxide adduct with a nitrogen radical of chloramine-T in acid solution. Identical results were obtained with chloramine-B (sodium salt of N-chlorobenzene sulfonamide), indicating the involvement of the N-chloramine group in radical formation. 相似文献
30.
The asymmetric syntheses of the C-1 sidechains of zaragozic acid A and C are described. Aldol reaction defines the chirality at C-4′and C-5′in two independent routes. Multigram preparation as well as a route amenable to derivatization are highlights of these approaches. 相似文献