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131.
Jacques Barrau 《Heteroatom Chemistry》1991,2(6):601-611
The present review describes recent work on the synthesis, spectroscopic analysis, and investigation of the chemical behaviors of new polynuclear heterocyclic complexes 1–7 having M–M′–M catenation. Various CO substitution, cleavage, expansion, and adducts decomposition reactions are described. 相似文献
132.
Jacques Bastide Eduardo Mendes Franois Bou Martine Buzier Peter Lindner 《Macromolecular Symposia》1990,40(1):81-99
In this paper, it is shown how a percolation process can be used to describe the inhomogeneities of polymer concentration, appearing in gels prepared by random crosslinking of a semi-dilute solution, and how they are modified by swelling or stretching of the network. Neutron scattering experimental data are compared to the predictions of this model in the isotropic and anisotropic cases. A good agreement is found. In particular, “abnormal” butterfly patterns in the iso-intensity curves have been detected, as expected from the model. 相似文献
133.
Jacques R. Chrtien 《Trends in analytical chemistry : TRAC》1987,6(10):275-278
The impact of chemometrics in chromatography is presented. The development of systematic experiments is encouraged to exploit simultaneously the richness of teh chromatographic data and the possibilities of complementary data processing techniques. 相似文献
134.
Recently it has been suggested that zero quantum coherence in scalar coupled spin systems at thermal equilibrium can be created by a single non-selective pulse. In this note, it is shown that the proposed effect will be masked as a consequence of the failure of the conventional high-temperature approximation normally applied to the equilibrium spin density operator. For exacting experiments, its appears that the approximation (eq) ≈ 1-H
/kT may not suffice. 相似文献
135.
Mathieu Albini Catherine Taillier Vincent Dalla Jérôme Blanchet Jacques Rouden 《Tetrahedron letters》2014
A dramatic improvement of our previous methodology based on a Suzuki–Miyaura cross-coupling to access 3,3′-disubstituted H8-BINOLs using microwave heating is reported herein. These new conditions represent a large gain in term of atom-economy, reaction time, catalyst loading, and excess of reagents employed. 相似文献
136.
Martin L. Kaplan Robert C. Haddon Krishnan Raghavachari Shalini Menezes Frederic C. Schilling Jacques J. Hauser 《Molecular Crystals and Liquid Crystals》2013,570(1):51-66
Four compounds, N,N,N',N'-tetramethyl-p-phenylene diamine, N,N,N',N'-tetramethyl-benzidine, 4,4'-bis(dimethylamino)azobenzene and bis(4-dimethylaminophenylimino)sulfur (BAPIS) were examined electrochemically and spectroscopically. Each was shown to be a fairly good donor forming in its first oxidation state a radical-cation. The latter two materials surprisingly exhibited only single one-electron oxidations. Conformational flexibility about the -NSN- unit was studied by NMR spectroscopy and ab initio molecular orbital theory. The experimental ΔG* for a cis-trans to trans-cis interconversion in BAPIS was found to be 11.9 kcal/mole. The four donors all form 1:1 adducts with TCNQ. The compaction resistances of the complexes have been measured as a function of temperature. Of the four, (BAPIS)(TCNQ) appears to be a one-dimensional material. The other three complexes behave as typical mixed stack organic semiconductors. 相似文献
137.
This paper describes several combinatorial models for Laguerre, Charlier, and Hermite polynomials, and uses them to prove combinatorially some classical formulas. The so-called “Italian limit formula” (from Laguerre to Hermite), the Appel identity for Hermite polynomials, and the two Sheffer identities for Laguerre and Charlier polynomials are proved. We also give bijective proofs of the three-term recurrences. These three families form the bottom triangle in R. Askey's chart classifying hypergeometric orthogonal polynomials. 相似文献
138.
Electroreflectance spectra at normal incidence of (100) and (110) faces of gold and copper monocrystals are given, in the spectral range from 0.22–0.7 μm. The fractional change in reflectance is different with (110) faces when light is polarized parallel to the [001] direction and parallel to the [] direction while no anisotropy is seen on (100) faces. This shows that electroreflectance is a powerful tool to investigate metal surfaces where the optical electrons are sensitive to the distribution of the surface atoms. 相似文献
139.
Jacques Layssac Bernard Pire John P. Ralston 《Zeitschrift fur Physik C Particles and Fields》1984,25(1):49-54
We isolate final state interactions not parametrized by fragmentation functions and yet present in QCDO(α s ) corrections to two-jet production in photon-longitudinally polarized electron scattering. Our calculation focuses on dynamical imaginary (absorptive) corrections that are absent in any tree diagrams. We explicitly demonstrate cancellation of imaginary infinities in the sum over graphs. The resulting asymmetry is predicted to be small. Such a quantity should be soon measured in experiments exploiting the naturally large electron polarization occurring in standard high energy storage rings. 相似文献
140.
We study particle decay in de Sitter space–time as given by first-order perturbation theory in a Lagrangian interacting quantum
field theory. We study in detail the adiabatic limit of the perturbative amplitude and compute the “phase space” coefficient
exactly in the case of two equal particles produced in the disintegration. We show that for fields with masses above a critical
mass m
c there is no such thing as particle stability, so that decays forbidden in flat space–time do occur here. The lifetime of
such a particle also turns out to be independent of its velocity when that lifetime is comparable with de Sitter radius. Particles
with mass lower than critical have a completely different behavior: the masses of their decay products must obey quantification
rules, and their lifetime is zero. 相似文献