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1.
Molecular mechanics calculations on cycloheptadiene indicate that the molecule has a structure which undergoes a wide pseudorotational motion between two C1 forms, and a C1 form, and this structure is in equilibrium with the C2 form. It is shown that this equilibrium mixture is consistent with all of the available experimental data. 相似文献
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Alan P. Sprague 《Geometriae Dedicata》1984,16(2):149-156
A special Laguerre plane is a nondegenerate transversal 3-design such that the residue of each point is a dual affine plane. A special Laguerre plane is equivalent to an optimal code with three information digits and maximal length. An extended dual affine plane is an incidence structure (whose objects will be called points and blocks) such that the residue of each point is a dual affine plane, and each pair of points is in at least one block. Finite extended dual affine planes exist only of order 2, 4, and (dubiously) 10. We show that any finite incidence structure having the residue of each point a dual affine plane either is a transversal 3-design or has a block through each pair of points. Hence theorem: If a finite nondegenerate connected incidence structure has the residue of each point a dual affine plane, then is either an extended dual affine plane or a special Laguerre plane.
This research was partially supported by NSF Grant MCS-8102361. 相似文献
5.
Abstract— By means of in situ photolysis EPR of aqueous solutions of α-oxocarboxylic acids (RCO-CO2 H) at pH values above 5, semidione radical anions [RC(O- )=C(O')R] and α-hydroxy-α-carboxy alkyl radicals [RC(OH)CO2 -] were detected. C02 was identified as a reaction product. On photolysis of mixtures of α-oxocarboxylic acids (RCOCO2 H and R'COCC2 H), "mixed" semidione radical anions [RC(O- >=C(O)R'] were observed in addition to RC(O- )=C(O')R, R'C(O- )=C(O')R', RC(OH)CO2 - and R'C(OH)CO2 - . The experimental results are explained in terms of photodecarboxylation (α-clea-vage) of electronically excited RCOCOJ to yield RCO and CO2 . The radicals RC(OH)CO2 - are formed by reduction of RCOCO2 - by CO2 - . The semidione radicals are produced by addition of RCO to RCOCO2 - followed by decarboxylation of the intermediate adduct. This mechanism was confirmed by generating acyl radicals independently and reacting them with α-oxocarboxylic acids. Selected product studies support the mechanism suggested. 相似文献
6.
Liu JF Ye P Sprague K Sargent K Yohannes D Baldino CM Wilson CJ Ng SC 《Organic letters》2005,7(15):3363-3366
[reaction: see text]. Total syntheses of deoxyvasicinone (1), mackinazolinone (2), and 8-hydroxydeoxyvasicinone (3) via novel microwave-assisted domino reactions, as well as a novel three-component one-pot total synthesis of isaindigotone (5) promoted by microwave irradiation, are reported. The efficient reaction process enabled us to rapidly access related natural product derivatives and to identify a new class of cytotoxic agents. 相似文献
7.
Simultaneous audio and video were recorded of a silver perch Bairdiella chrysoura producing its characteristic drumming sound in the field. The background noise contribution to the total sound pressure level is estimated using sounds that occurred between the pulses of the silver perch sound. This background contribution is subtracted from the total sound to give an estimate of the sound pressure level of the individual fish. A silver perch source level in the range 128-135 dB (re: 1 microPa) is obtained using an estimate of the distance between the fish and the hydrophone. The maximum distance at which an individual silver perch could be detected depends on the background sound level as well as the propagation losses. Under the conditions recorded in this study, the maximum detection distance would be 1-7 m from the hydrophone. 相似文献
8.
We consider the contribution offermion–antifermion condensates to the anomalousmagnetic moment of a fermion in a vacuum in which suchcondensates exist. The real part of the condensatecontribution to the anomalous magnetic moment is shown to bezero. A nonzero imaginary part is obtained below thekinematic threshold for intermediatefermion–antifermion pairs. The calculation isshown to be gauge-parameter independent provided a single fermion masscharacterizes both the fermion propagator andcondensate-sensitive contributions, suggestive of adynamically generated fermion mass. The nonzeroimaginary part is then argued to correspond to the kinematicproduction of the intermediatestate Goldstone bosonsanticipated from a chiral-noninvariant vacuum. Finally,speculations are presented concerning the applicability of these results to quark electromagneticproperties. 相似文献
9.
Ruedi Gygax Jakob Wirz Joseph T. Sprague Norman L. Allinger 《Helvetica chimica acta》1977,60(8):2522-2529
The isodynamical interconversion between the quasiplanar equilibrium conformers 1b and 1c of 1,5-bisdehydro[12]annulene requires a free energy of activation ΔG# = 4.5 ± 0.2 kcal/mol (120 K) which was determined by line shape analysis of its temperature-dependent NMR. spectrum. Force field calculations indicate that this barrier reflects the energy needed to disrupt the cyclic π-conjugation in going to the nonplanar transition state 1a . 相似文献
10.
1,5-cyclooctadiene and the corresponding dibenzo derivatives have been studied by means of force-field calculations. The relative stabilities of the various conformations, and the energy surfaces which interconnect them found from the calculations are used to interpret the available experimental data. Differences between the parent diene and the dibenzo derivative are noted, and are attributed largely to the difference in torsional barriers of a saturated carbon bond when attached to a double bond, as opposed to being attached to an aromatic ring. 相似文献