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Editors’ preface for the topical issue on Seven papers on Noncommutative Geometry and Operator Algebras
No full textA variational approach to Gibbs artifacts removal in MRI
Full text linkGibbs ringing is a feature of MR images caused by the finite sampling of the acquisition space (k-space). It manifests itself with ringing patterns around sharp edges which become increasingly significant for low-resolution acquisitions. In this paper, we model the Gibbs artefact removal as a constrained variational problem where the data discrepancy, represented in denoising and convolutive form, is balanced to sparsity-promoting regularization functions such as Total Variation, Total Generalized Variation and L1 norm of the Wavelet transform. The efficacy of such models is evaluated by running a set of numerical experiments both on synthetic data and real acquisitions of brain images. The Total Generalized Variation penalty coupled with the convolutive data discrepancy term yields, in general, the best results both on synthetic and real data
La bonifica dei siti inquinati
No full textUpon full implementation of art. 17 Decree 22/1997, the owner of a contaminated site is subject to significant duties if the polluter fails to comply with the obligations of site remediation ordered by the Authorities. However, the owner's position, from a legal viewpoint, remains very different from the one of the polluter who caused the contamination, particularly with regard to clean up obligations and related civil and criminal liabilities
Gauge groups and bialgebroids
Full text linkWe study the Ehresmann–Schauenburg bialgebroid of a noncommutative principal bundle as a quantization of the gauge groupoid of a classical principal bundle. We show that the gauge group of the noncommutative bundle is isomorphic to the group of bisections of the bialgebroid, and we give a crossed module structure for the bisections and the automorphisms of the bialgebroid. Examples include: Galois objects of Taft algebras, a monopole bundle over a quantum sphere and a not faithfully flat Hopf–Galois extension of commutative algebras. For each of the latter two examples, there is in fact a suitable invertible antipode for the bialgebroid making it a Hopf algebroid
RETRACTED ARTICLE: The coordinate algebra of a quantum symplectic sphere does not embed into any C*-Algebra
No full text
PROJECTIVE SYSTEMS OF NONCOMMUTATIVE LATTICE AS A PREGEOMETRIC SUBSTRATUM. DSM-QM-434 (Oct 1998) 30p.
No full textAtti del convegno all'ISI Guccia, Palermo, December 199
PROJECTIVE SYSTEMS OF NONCOMMUTATIVE LATTICE AS A PREGEOMETRIC SUBSTRATUM. DSM-QM-434 (Oct 1998) 30p.
No full textAtti del convegno all'ISI Guccia, Palermo, December 199
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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