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31.
32.
Measurement of the de Haas-van Alphen frequencies of Hg3?δAsF6 as a function of pressure of up to 5 kbar shows that the Fermi surface of the linear chain mercury compound depends on changes of the tetragonal lattice constant with the intrachain mercury-mercury distance remaining independent of pressure. The incommensurability parameter δ increases from 0.21 to 0.23 between 0 and 5 kbar. An unusual result is that frequencies for different pressures in one day are locked to those of the initial pressure of the day. It is suggested that this results from the stabilization of the tetragonal lattice by the mercury-chain lattice at low temperatures. 相似文献
33.
34.
Differential elastic cross sections and polarizations are calculated in a multiple-scattering formalism for proton-4He scattering for energies in the range 0.6–24.0 GeV and for momentum transfers up to 4.0 fm?1. The calculations include Coulomb and spin effects. Corrections due to target-nucleon overlap and charge exchange are estimated. The results are compared with experimental data. 相似文献
35.
In the liquid sodium coolant of the Fast Reactor there are several measurements which may be performed using ultrasonic techniques. This paper gives a brief outline of one such measurement and then describes the design of an ultrasonic waveguide for the generation and detection of ultrasound in this hostile situation. The successful laboratory tests of the device are also reported. 相似文献
36.
In this article we obtain the boundedness of the periodic, discrete and ergodic
bilinear Hilbert transform, from
,
where
1$, and $p_3\ge 1$" align="middle" border="0">
. The main techniques are a bilinear version of the transference method of Coifman and Weiss and certain discretization of bilinear operators. In the periodic case, we also obtain the boundedness for
相似文献
37.
A general, unequivocal procedure for the preparation of specifically substituted 3-aryl-1-naphthaldehydes was developed. Benzylmagnesium bromides with 5-aryl-2, 2-dimethyl-4-pentene-3-ones (12) gave exclusively 1,4-addition products, 5,6-diaryl-2,2-dimethyl-3-hexanones (13). The hexanones on oxidation with peracetic acid gave 3,4-diarylbutanoic acids (14), which were cyclized to tetralones (15). The tetralones on treatment with MeMgI followed by dehydration and dehydrogenation gave 3-aryl-1-methylnaphthalenes (10), which were converted into corresponding aldehydes (11). When benzylmagnesium bromides were added to 4-aryl-3-butene-2-ones (1), mixtures of 1,2 and 1,4-addition products were formed. Further treatment of these mixtures also yielded the desired methylnaphthalenes along with various identified side products. 相似文献
38.
39.
Heteroarenes such as (aza and oxa)borines are increasingly important as synthetic targets and reagents. We map the intramolecular cyclization of saturated heterocyclic chains through dative bonding. A related set of planar unsaturated aza-, oxa-, and fluora-rings that feature dative σ bonding enhanced by π delocalization are identified. The systems have, in general, the formulae A′(CH2)mD′ and A′(CH)mD′, where m?=?3 and 4, and A′ and D′ are acceptor and donor sites, respectively. In each case, the ring isomers, achievable via A′←D' internal coordination (in the manner of Kekulé’s ouroboros), are more stable than chains. Unsaturated aromatic rings examined herein include a oxadiborine with a hypervalent oxygen center and a dioxadiborine. They are isoelectronic with an azaborine, which was synthesized more recently, and benzene. 相似文献
40.
Constant composition codes have been proposed as suitable coding schemes to solve the narrow band and impulse noise problems associated with powerline communication, while at the same time maintaining a constant power output. In particular, a certain class of constant composition codes called frequency permutation arrays have been suggested as ideal, in some sense, for these purposes. In this paper we characterise a family of neighbour transitive codes in Hamming graphs in which frequency permutation arrays play a central rode. We also classify all the permutation codes generated by groups in this family. 相似文献