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Finite groups acting on hyperelliptic 3-manifolds
Full text linkWe consider 3-manifolds admitting the action of an involution such that its space of orbits is homeomorphic to S3. Such involutions are called hyperelliptic as the manifolds admitting such an action. We consider finite groups acting on 3-manifolds and containing hyperelliptic involutions whose fixed-point set has r > 2 components. In particular we prove that a simple group containing such an involution is isomorphic to PSL(2,q) for some odd prime power q, or to one of four other small simple groups
Involutions of spherical 3-manifolds
No full textWe classify involutions acting on spherical 3-manifolds up to conjugacy. Our geometric approach provides insights into numerous topological properties of these involutions
Preliminary notes on the karst of Sierra Mixteca-Zapoteca, South Tehuacan, Oxaca, Mexico
No full textfor the first time a karstologic study of the Sierra Mixteca-Zapoteca has been carreid out. The direct exploration of some deep canyons led to the discovery of several caves the morphologies of which are here discusse
The 2-rank of finite groups acting on hyperelliptic 3-manifolds
Full text linkWe consider 3-manifolds admitting the action of an involution such that its space of orbits is homeomorphic to S3. Such involutions are called hyperelliptic as the manifolds admitting such an action. We prove that the sectional 2-rank of a finite group acting on a 3-manifold and containing a hyperelliptic involution whose fixed-point set has two components has sectional 2-rank at most four; this upper bound is sharp. The cases where the hyperelliptic involution has a fixed-point set with a number of components different from 2 have been already considered in the literature. Our result completes the analysis and we obtain general results where the number of the components of the fixed-point set is not fixed. In particular, we obtain that a finite group acting on a 3-manifold and containing a hyperelliptic involution has 2-rank at most four, and four is the best possible upper bound. Finally, we restrict to the basic case of simple groups acting on hyperelliptic 3-manifolds: we use our result about the sectional 2-rank to prove that a simple group containing a hyperelliptic involution is isomorphic to PSL(2, q) for some odd prime power q, or to one of four other small simple groups
Efficacia della sonoisterosalpingografia nella valutazione della cavità uterina e della pervietà tubarica
No full text
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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