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871.
R. W. Lourie 《Zeitschrift fur Physik C Particles and Fields》1991,50(2):345-351
We calculate the recoil polarization observables for neutral pion electroproduction on the proton. In particular, for theN(938)→N *(1440) transition, we study these observables for several quark models of the resonant amplitudes. We find that the polarization response functions, unlike the unpolarized cross section, have encouragingly large sensitivity to the presence of the Roper. Furthermore, these observables can clearly reveal the presence of a longitudinal coupling. 相似文献
872.
An improved method including extraction procedures is presented for the analysis of nucleotides in suspension-cultivated animal cells. Quantification was performed by ion-pair high-performance liquid chromatography after perchloric acid extraction. It was found that the amount of perchloric acid taken for extraction influenced the yield and that cell washing procedures caused deterioration of the analysis results for triphosphates. More than thirty nucleotides and sugar-nucleotides were separated within 25 min using a Supelcosil reversed-phase column (3 microns) with tetrabutylammonium hydrogensulphate as pairing agent and methanol-pH gradient elution. Cultivated hybridoma cells showed variations in intracellular nucleotide concentrations as well as relative amounts during different growth phases, which could reflect the physiological state of a cell culture. 相似文献
873.
The length-distribution of stereoregular sequences in low-density polyethylene (LDPE) is determined by a computer-aided analysis of cp-melting curves within the framework of thermodynamics of eutectoid copolymers. Small-angle x-ray scattering patterns are then described by using the structure data derived. One of the results is that fluctuations of the mean electron-density are increasingly reduced with an increasing degree of crystallinity.Dedicated to Prof. Dr. W. Pechhold on the occasion of his 60th birthday 相似文献
874.
The paper describes the possibility of designing matched interacting semiconductor quantum wells. It is shown that for a given eigenstate of a quantum well (QW), it is always possible to find another QW in such a way that the coupling leaves the original eigenstate of the host QW unperturbed irrespective of the strength of interaction. For rectangular QWs, the condition is met with whenever the second QW has appropriate width and depth so that phase travelled by an electron wave through it is an integral multiple of π. 相似文献
875.
To Professor Guillermo Torres on the occasion of his 70th birthday. 相似文献
876.
C. S. Creaser M. R. S. McCoustra K. E. O'Neill 《Journal of mass spectrometry : JMS》1991,26(4):335-338
Two fibre-optic interfaces were constructed for laser photodissociation/tandem mass spectrometry using an ion trap spectrometer. These interfaces allow sample introduction from a liquid reservoir, solids probe and gas chromatograph. The laser/ion trap configuration was applied to the analysis of a mixture of alkylbenenes separated by gas chromatography using 573 nm photons. 相似文献
877.
R. M. Trigub 《Ukrainian Mathematical Journal》1991,43(12):1572-1578
New statements are proved regarding multipliers of trigonometric Fourier series in the space C of continuous periodic functions.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 12, pp. 1686–1693, December, 1991. 相似文献
878.
In this paper we prove the existence of a solution of a coupled system involving a two phase incompressible flow in the ground and the mechanical deformation of the porous medium where the porosity is a function of the global pressure. The model is strongly coupled and involves a nonlinear degenerate parabolic equation. In order to show the existence of a weak solution, we consider a sequence of related uniformly parabolic problems and apply the Schauder fixed point theorem to show that they possess a classical solution. We then prove the relative compactness of sequences of solutions by means of the Fréchet-Kolmogorov theorem; this yields the convergence of a subsequence to a weak solution of the parabolic system. 相似文献
879.
P.A. Postigo A.R. Alija L.J. Martínez M.L. Dotor D. Golmayo J. Snchez-Dehesa C. Seassal P. Viktorovitch M. Galli A. Politi M. Patrini L.C. Andreani 《Photonics and Nanostructures》2007,5(2-3):79-85
Two-dimensional photonic crystal lasers have been fabricated on III–V semiconductor slabs. Tuning of the spontaneous emission in micro and nanocavities has been achieved by accurate control of the slab thickness. Different structures, some of them of new application to photonic crystal lasers, have been fabricated like the Suzuki-phase or the coupled-cavity ring-like resonators. Laser emission has been obtained by pulsed optical pumping. Optical characterization of the lasing modes have been performed showing one or more laser peaks centred around 1.55 μm. Far field characterization of the emission pattern has been realized showing different patterns depending on the geometrical shape of the structures. These kinds of devices may be used as efficient nanolaser sources for optical communications or optical sensors. 相似文献
880.