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1.
John C. Baez 《Foundations of Physics》1989,19(1):91-95
E. P. Wigner's argument that the probability of the existence of self-reproducing units, e.g., organisms, is zero according to standard quantum theory is stated and analyzed. Theorems are presented which indicate that Wigner's mathematical result in fact should not be interpreted as asserting the improbability of self-reproducing units. 相似文献
2.
John C. Baez 《Communications in Mathematical Physics》1998,193(1):219-231
Working in the Palatini formalism, we describe a procedure for constructing degenerate solutions of general relativity on
4-manifold M from certain solutions of 2-dimensional $BF$ theory on any framed surface Σ embedded in M. In these solutions the cotetrad field e (and thus the metric) vanishes outside a neighborhood of Σ, while inside this neighborhood the connection A and the field satisfy the equations of 4-dimensional BF theory. Our construction works in any signature and with any value of the cosmological constant. If for some 3-manifold S, at fixed time our solutions typically describe “flux tubes of area”: the 3-metric vanishes outside a collection of thickened
links embedded in S, while inside these thickened links it is nondegenerate only
in the two transverse directions. We comment on the quantization of the theory of solutions of this form and its relation
to the loop representation of quantum gravity.
Received: 21 April 1997 / Accepted: 22 August 1997 相似文献
3.
López-Alarcón C Squella JA Núñez-Vergara LJ Baez H Camargo C 《Rapid communications in mass spectrometry : RCM》2002,16(24):2229-2238
A gas chromatography/mass spectrometry (GC/MS) method for the qualitative and quantitative determination of the calcium-channel antagonists C-4-substituted 1,4-dihydropyridines, and their corresponding N-ethyl derivatives, is presented. Also, the electrochemical oxidation and the reactivity of the compounds with alkyl radicals derived from 2,2'-azobis-(2-amidinopropane) were monitored by GC/MS. Mass spectral fragmentation patterns for the C-4-substituted 1,4-dihydropy-ridine parent drugs were significantly different from those of their oxidation products, generated either by electrochemical oxidation or by reaction with alkyl radicals. However, for N-ethyl-1,4-dihydropyridine compounds it was not possible to detect the final products (pyridinium salts) using these experimental conditions. 相似文献
4.
John C. Baez 《Letters in Mathematical Physics》1996,38(2):129-143
Starting from a Lie group G whose Lie algebra is equipped with an invariant nondegenerate symmetric bilinear form, we show that four-dimensional BF theory with cosmological term gives rise to a TQFT satisfying a generalization of Atiyah's axioms to manifolds equipped with principal G-bundle. The case G=GL(4,) is especially interesting because every 4-manifold is then naturally equipped with a principal G-bundle, namely its frame bundle. In this case, the partition function of a compact oriented 4-manifold is the exponential of its signature, and the resulting TQFT is isomorphic to that constructed by Crane and Yetter using a state sum model, or by Broda using a surgery presentation of four-manifolds. 相似文献
5.
Olson IA Bacon WA Baez Sosa YY Delaney KM Forte SA Guglielmo MA Hill AN Kiesow KH Langenbacher RE Xun Y Young RO Bowyer WJ 《The journal of physical chemistry. A》2011,115(40):11001-11007
We describe three new strategies for determining heterogeneous reaction rates using photomicroscopy to measure the rate of retreat of metal surfaces: (i) spheres in a stirred solution, (ii) microscopic powder in an unstirred solution, and (iii) spheres on a rotating shaft. The strategies are applied to indium-mediated allylation (IMA), which is a powerful tool for synthetic chemists because of its stereoselectivity, broad applicability, and high yields. The rate-limiting step of IMA, reaction of allyl halides at indium metal surfaces, is shown to be fast, with a minimum value of the heterogeneous rate constant of 1 × 10(-2) cm/s, an order of magnitude faster than the previously determined minimum value. The strategies described here can be applied to any reaction in which the surface is retreating or advancing, thereby broadening the applicability of photomicroscopy to measuring heterogeneous reaction kinetics. 相似文献
6.
Perez Gutierrez RM Rosario Vargas S Martinez Martinez F Garcia Baez E Figueroa Torres G 《Natural product research》2006,20(3):305-310
Antispasmodic activity-guided fractionation together with chemical analysis led to the isolation of one novel delta-lactone named oedogonolide from Oedogonium capillare. Identification was based on spectroscopic methods. The oedogonolide produces a significant antispasmodic effect on the contractions of the rat ileum induced by acetylcholine, histamine and barium chloride. 相似文献
7.
The cathodic reduction of oxygen in 1 mol dm−3 sodium hydroxide solutions has been investigated at several types of titanium oxide cathodes. Layers of TiO2 were prepared on titanium by spraying and thermal decomposition of solutions of titanium n-butoxide in 2-propanol and titanium tetrachloride in methanol+water and also by anodization; the reduction was also studied at Ebonex®, a conducting ceramic consisting mainly of Ti5O9. In all cases, the reduction of oxygen occurs largely by a 4e− reaction to water and the reaction occurs at potentials close to −1.0 V vs. SCE. Cyclic voltammetry in the absence of oxygen shows that, at these potentials, the surfaces undergo reduction and the electrochemistry of the Fe(CN)64− /Fe(CN)63− couple has been used to probe further the properties of the TiO2 surfaces. 相似文献
8.
John C. Baez 《Letters in Mathematical Physics》1991,21(2):117-121
Let denote the conformally invariant neutral free scalar field on ×S
n. The naive lightcone Hamiltonian for a p interaction is given by cp, where C denotes a lightcone in ×S
n, and the Wick power is relative to the free vacuum. We show that this sesquilinear form annihilates the free vacuum if n3 is odd, p>2, and p(n–1)0 mod 4. 相似文献
9.
John C. Baez 《Letters in Mathematical Physics》1991,23(2):133-141
From a vector spaceV equipped with a Yang-Baxter operatorR one may form the r-symmetric algebraS
R
V=TV/v w–R(v w), which is a quantum vector space in the sense of Manin, and the associated quantum matrix algebraM
R
V=T(End(V))/f g–R(f g)R
-1. In the case whenR satisfies a Hecke-type identityR
2=(1–q)R+q, we construct a differential calculus
R
V forS
R
V which agrees with that constructed by Pusz, Woronowicz, Wess, and Zumino whenR is essentially theR-matrix of GL
q
(n). Elements of
R
V may be regarded as differential forms on the quantum vector spaceS
R
V. We show that
R
V isM
R
V-covariant in the sense that there is a coaction *:
R
V M
R
V
R
V with *d=(1 d)* extending the natural coaction :S
R
V M
R
V S
R
V. 相似文献
10.
A new compound was elucidated as 9-acetyl-6-caryophyllen-15-ol. Iridoid glucosides including catalpol, methyl catalpol, 7-deoxy-8-epiloganic
acid, and aucubin, were isolated from leaves of Buddleia parviflora, while the known compounds were identified as dehydrobuddledin A and buddledin C. The structures was elucidated by extensive
1D-2D-NMR spectroscopy.
Published in Khimiya Prirodnykh Soedinenii, No. 1, pp. 29–31, January–February, 2008. 相似文献