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1.
Some of the motivations for as well as the main points of the quantization of the Nappi-Witten string in the light-cone gauge are reviewed. 相似文献
2.
It is shown that in the one loop order of perturbation theory the coupling constant and parameter(s) of an (Abelian T) dual sigma model get renormalized in the same way as in the ‘original’ model. 相似文献
3.
L. Palla 《Zeitschrift fur Physik C Particles and Fields》1984,24(2):195-204
We compare the four-dimensional symmetric fields obtained by the coset space dimensional reduction scheme to the infinite tower of fields given by the harmonic expansion in a 4+N dimensional gauge theory coupled to fermions on a space-timeM 4 ×S/R. 相似文献
4.
The minimum energy path and the geometry of the transition state for the first stage of the reduction by LiBH4 of R2CO (RH, CH3) to alcohol have been determined by ab initio SCF calculations using a small basis set and subsequently confirmed by further calculations using a larger basis set and CI methods. Attention has been focused on the changes of electron distribution during the reaction, the nature of the bonding, and the effect of chemical substituents. The results lend support to one of the proposed reaction mechanisms. Some supplementary data concerning the role of the solvent are also discussed. 相似文献
5.
The electromagnetic mass shift of pions is discussed in unified gauge field theories of weak and electromagnetic interactions to second order of the electric charge and the pion mass, respectively. We calculate the contributions of the next to leading light-cone singularities (quark mass terms) and it is found that these do not contribute to the divergences in the mass shift provided the masses of the bare proton quark and neutron quark are equal. γ, Z, W, φ exchanges are taken into account. Different bare quark masses in general make the mass shift divergent. In the tadpole contribution, the Born term causes a divergence unless we extrapolate first to q2 = 0. 相似文献
6.
A family of 4n?1 parameter solutions corresponding to n monopoles is constructed by a three-dimensional “inverse scattering” method. Global regularity of the finitely separated two-monopole solution is shown. 相似文献
7.
Antonella Casoli Piero Mirti Gerardo Palla 《Fresenius' Journal of Analytical Chemistry》1995,352(3-4):372-379
Proteinaceous organic materials used as ancient painting media were investigated by capillary gas chromatography (GC) and capillary gas chromatography — mass spectrometry (GC/MS). Medieval wall paintings made by the tempera technique were considered and their binding media were studied by the characterization of their main chemical components. The basic methodology is based on the determination of amino acids in samples of paint layers after hydrolysis and derivatization and on the comparison with reference proteinaceous materials. Multivariate chemometric techniques were used to facilitate the recognition of the protein source from chromatographic data. To characterize the binders further, a method was developed for the determination of fatty acids, present as minor components, by GC/MS. The use of fused-silica capillary columns coated with selected stationary phases allowed the separation of amino acid and fatty acid derivatives in a single analytical run. 相似文献
8.
V. Dinca A. Palla?Papavlu A. Matei C. Luculescu M. Dinescu T. Lippert F. Di Pietrantonio D. Cannata M. Benetti E. Verona 《Applied Physics A: Materials Science & Processing》2010,98(2):429-434
This paper presents a comparative study of polymer pixel on sensors obtained by Laser Induced Forward Transfer (LIFT) assisted
by a triazene polymer as Dynamic Release Layer (DRL). Polyisobutylene (PIB) was selected as model for chemoselective polymers
which could be used as hydrogen-bond acidic polymer for vapor sensors. 相似文献
9.
One of the most remarkable social phenomena is the formation of communities in social networks corresponding to families, friendship circles, work teams, etc. Since people usually belong to several different communities at the same time, the induced overlaps result in an extremely complicated web of the communities themselves. Thus, uncovering the intricate community structure of social networks is a non-trivial task with great potential for practical applications, gaining a notable interest in the recent years. The Clique Percolation Method (CPM) is one of the earliest overlapping community finding methods, which was already used in the analysis of several different social networks. In this approach the communities correspond to k-clique percolation clusters, and the general heuristic for setting the parameters of the method is to tune the system just below the critical point of k-clique percolation. However, this rule is based on simple physical principles and its validity was never subject to quantitative analysis. Here we examine the quality of the partitioning in the vicinity of the critical point using recently introduced overlapping modularity measures. According to our results on real social and other networks, the overlapping modularities show a maximum close to the critical point, justifying the original criteria for the optimal parameter settings. 相似文献
10.
S. Giordano P. L. Palla L. Colombo 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(1):29-35
We prove a generic theorem stating the equivalence
between a graded dielectric ellipsoid (with gradation along a family of
internal confocal ellipsoids) and an anisotropic homogeneous ellipsoid. We then describe a procedure to obtain the three principal
permittivities of the effective ellipsoid for any given dielectric gradation profile. Finally, we apply a multiscale approach
to homogenize dispersions of ellipsoidal graded particles. 相似文献