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41.
A two-dimensional electrophoretic analysis of the total proteins was carried out in Vitis rupestris as model system in order to characterize the different developmental stages--from callus to plantlets--of somatic embryogenesis events in the grapevine. The patterns of callus, embryogenetic callus, somatic embryos and plantlets derived from leaf and petiole explants were compared. Each differentiation step was characterized by specific peptide spots. 相似文献
42.
T. G. G. Maffeïs G. T. Owen C. Malag G. Martinelli M. K. Kennedy F. E. Kruis S. P. Wilks 《Surface science》2004,550(1-3):21-25
In this work, we report a scanning tunnelling spectroscopy (STS) study of 30 and 10 nm tin dioxide nanoparticles. The STS spectra give a surface band gap of 2.5 eV for both samples and show that the density of surface states in the band gap is around 6 times higher for the 30 nm particles than for the 10 nm particles. This provides direct experimental evidence for our theoretical model, which predicts a decrease in the surface state density as the particle size decreases, and partly accounts for the improved sensitivity of gas sensing devices fabricated with nanoparticles. 相似文献
43.
V. T. Baranov S. Bellucci V. M. Biryukov G. I. Britvich C. Balasubramanian V. Guidi G. Giannini V. N. Zapolsky V. I. Kotov A. E. Kushnirenko V. A. Maisheev G. Martinelli E. Milan V. A. Pikalov V. I. Terekhov U. Uggerhoj V. N. Chepegin Yu. A. Chesnokov 《JETP Letters》2005,82(9):562-564
Radiation emitted by positrons moving in a periodically deformed crystal has been experimentally observed for the first time. Radiation spectra have been measured in a wide energy range. Experimental evidence has been obtained for an undulator peak in a radiation spectrum, which is qualitatively consistent with calculations. Crystalline undulators ensure an equivalent magnetic field of 1000 T and a period in the submillimeter range and can therefore be used to generate x-ray and gamma radiation that is a hundred times harder than radiation in usual undulators. 相似文献
44.
A. Jameson L. Martinelli N.A. Pierce 《Theoretical and Computational Fluid Dynamics》1998,10(1-4):213-237
This paper describes the formulation of optimization techniques based on control theory for aerodynamic shape design in viscous
compressible flow, modeled by the Navier–Stokes equations. It extends previous work on optimization for inviscid flow. The
theory is applied to a system defined by the partial differential equations of the flow, with the boundary shape acting as
the control. The Fréchet derivative of the cost function is determined via the solution of an adjoint partial differential
equation, and the boundary shape is then modified in a direction of descent. This process is repeated until an optimum solution
is approached. Each design cycle requires the numerical solution of both the flow and the adjoint equations, leading to a
computational cost roughly equal to the cost of two flow solutions. The cost is kept low by using multigrid techniques, in
conjunction with preconditioning to accelerate the convergence of the solutions. The power of the method is illustrated by
designs of wings and wing–body combinations for long range transport aircraft. Satisfactory designs are usually obtained with
20–40 design cycles.
Received 5 February 1997 and accepted 30 May 1997 相似文献
45.
M. Falcioni G. Martinelli M.L. Paciello B. Taglienti G. Parisi 《Nuclear Physics B》1983,225(3):313-325
We present the results of a Monte Carlo simulation for a lattice action improved à la Symanzik. The results seem to give a faster approach of the lattice physics to its continuum limit. 相似文献
46.
F. Fucito G. Martinelli C. Omero G. Parisi R. Petronzio F. Rapuano 《Nuclear Physics B》1982,210(3):407-421
A Monte Carlo computation of meson and hadron spectroscopy within lattice QCD is made. We give a detailed discussion of the statistical and systematic errors of the results and analyze the present limitations of our approach. The results are in agreement with the observed spectrum. We also estimate the values of up, down and strange quark masses. 相似文献
47.
From a culture broth of Actinoplanes ianthinogenes a red crystalline product was isolated displaying activity against bacteria and fungi. The structure of the new antibiotic, named purpuromycin, was established on the basis of chemico-physical evidences and chemical degradations. The product resulted to be structurally related to rubromycins, a group of antibiotics previously isolated from Streptomyces collinus. 相似文献
48.
The excited electron states in isolated rare-gas dimers are described by a model Hamiltonian with appropriate simplifications for the short-range terms. Then the energies of self-trapped excitons are obtained by including solid state effects. The results are compared with the available transient absorption spectroscopy measurements. 相似文献
49.
50.