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971.
Starting from cyclohexanecarboxylic acid, a combination of an Ireland ester Claisen rearrangement and RCM reactions was exploited for an efficient construction of spiro[5.5]undecanes containing a quaternary carbon atom adjacent to the spirocentre and the methodology was extended to complete total syntheses of three chamigrenes. 相似文献
972.
Ion synthesis and laser annealing of Cu nanoparticles in Al2O3 总被引:1,自引:0,他引:1
A.L. Stepanov V.N. Popok D.E. Hole I.B. Khaibullin 《Applied Physics A: Materials Science & Processing》2002,74(3):441-446
Al2O3 samples with Cu nanoparticles, synthesised by ion implantation at 40 keV with a dose of 1×1017 ion/cm2 and a current density from 2.5 to 12.5 μA/cm2, were annealed using ten pulses from a KrF excimer laser with a single pulse fluence of 0.3 J/cm2. The copper depth distribution, formation and modification of metal nanoparticles under the ion implantation and laser treatment
were studied by Rutherford backscattering (RBS), energy dispersive X-ray (EDX) analysis, atomic force microscopy (AFM) and
optical spectroscopy. It was found that laser annealing leads to a reduction in the nanoparticle size without diffusion of
metal atoms into the bulk. The change in particle size and the possibility for oxidation of the copper particles are examined
in the framework of Mie theory. Calculations presented show that under excimer laser treatment, Cu nanoparticles are more
likely to be reduced in size than to undergo oxidation.
Received: 19 April 2001 / Accepted: 7 November 2001 / Published online: 23 January 2002 相似文献
973.
Ph. Hägler B. Pire L. Szymanowski O.V. Teryaev 《The European Physical Journal C - Particles and Fields》2002,24(2):261-270
We study Pomeron-Odderon interference effects giving rise to charge and single-spin asymmetries in diffractive electroproduction
of a pair. We calculate these asymmetries, originating from both longitudinal and transverse polarizations of the virtual photon,
in the framework of QCD and in the Born approximation, in a kinematical domain accessible to HERA experiments. We predict
a sizable charge asymmetry with a characteristic dependence on the invariant mass of the pair, which makes this observable very important for establishing the magnitude of the Odderon exchange in hard processes.
The single-spin asymmetry turns out to be rather small. We briefly discuss future improvements of our calculations and their
possible effects on the results.
Received: 18 July 2002 / Published online: 25 October 2002 相似文献
974.
975.
Magnus B. Landstad 《Journal of Functional Analysis》2002,191(2):211-223
We study properties of C*-algebraic deformations of homogeneous spaces G/Γ which are equivariant in the sense that they preserve the natural action of G by left translation. The center is shown to be isomorphic to C(G/G0ρ) for a certain subgroup G0ρ of G, and there is a 1-1 correspondence between normalised traces and probability measures on G/G0ρ. This makes it possible to represent the deformed algebra as operators over L2(G/Γ). Applications to K-theory are also mentioned. 相似文献
976.
977.
R. A. Wind P. D. Majors K. R. Minard E. J. Ackerman D. S. Daly G. R. Holtom B. D. Thrall T. J. Weber 《Applied magnetic resonance》2002,22(2):145-158
Confocal fluorescence optical microscopy and magnetic resonance microscopy are each used to study live cells in a minimally invasive way. Both techniques provide complementary information. Therefore, by examining cells simultaneously with both methodologies, more detailed information is obtained than is possible with each microscope individually. In this paper two configurations of a combined confocal and magnetic resonance microscope are described. The first configuration is capable of studying large single cells or three-dimensional cell agglomerates, whereas the second configuration is designed for the investigation of monolayers of mammalian cells. In both cases the sample compartment is part of a temperature regulated perfusion system. Images obtained with the combined system are shown forXenopus laevis oocytes, model JB6 tumor spheroids, and a single layer of Chinese hamster ovary cells. Finally, potential applications of the combined microscope are discussed. 相似文献
978.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 50, No. 1, pp. 158–162, January, 1989. 相似文献
979.
The spectral structure of two parameter unbounded operator pencils of waveguide type is studied. Theorems on discreteness
of the spectrum for a fixed parameter are proved. Variational principles for real eigenvalues in some parts of the root zones
are established. In the case of n = 1 (quadratic pencils) domains containing the spectrum are described (see Fig. 1–3). Conditions in the definition of the
pencils of waveguide type arise naturally from physical problems and each of them has a physical meaning. In particular a
connection between the energetic stability condition and a perturbation problem for the coefficients is given. 相似文献
980.
Z. B. Alfassi F. Groppi M. L. Bonardi O. Presler U. German 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(3):639-640
Summary The paper deals with the common mistake of interpolating calculation of the efficiency of gamma-detectors by the inverse square
law of the distance of the source from the detector cap and suggests the use of the distance from the virtual point detector
instead. 相似文献