186,231 research outputs found
A Markov theorem for plat closure of surface braids in Dunwoody and periodic Takahashi manifolds
No full textIn this article we deal with the problem of finding equivalence moves for links in
Dunwoody and periodic Takahashi manifolds. We represent these manifolds using
Heegaard splitting and we represent the embedded links as plat closure of elements
in the braid group of the corresponding Heegaard surfaces. More precisely, starting
from an open Heegaard diagram for such manifolds, we determine the plat slide
equivalence moves algorithmically and compute them explicitly in some cases
Hilden braid groups
No full textLet H g be a genus g handlebody and MCG 2n(T g) be the group of the isotopy classes of orientation preserving homeomorphisms of T g = ∂H g, fixing a given set of 2n points. In this paper we study two particular subgroups of MCG 2n(T g) which generalize Hilden groups defined by Hilden in [Generators for two groups related to the braid groups, Pacific J. Math. 59 (1975) 475486]. As well as Hilden groups are related to plat closures of braids, these generalizations are related to Heegaard splittings of manifolds and to bridge decompositions of links. Connections between these subgroups and motion groups of links in closed 3-manifolds are also provided. © 2012 World Scientific Publishing Company
[PtOTf(triphos)]OTf and [PtMe2(triphos-P,P′)] as versatile synthons of platinum(II)-triphos species
No full textThe new complex [PtOTf(triphos)]OTf (triphos = bis(2-diphenylphosphinoethyl)phenyl-phosphine, OTf = CF3SO3) (1) can be most efficiently prepared by adding triflic acid to the known complex [PtMe2(triphos-P,P′)] (5) where triphos acts as a bidentate ligand. The fluxional behaviours of 1 and 5 in solution and their reactivity have been investigated by NMR: [PtOTf(triphos)]OTf is a very electrophilic complex and its reactivity is dominated by the tendency of the labile ligand OTf to be replaced by a variety of nucleophiles, while the chemistry of [PtMe2(triphos-P,P′)] is controlled by the proclivity of the third phosphorus to coordinate to platinum, as soon as a vacancy is created via Pt-Me protonolysis. © 2001 Elsevier Science B.V
Assemblages/Decentralised
No full textThe concept of citizenship has traditionally been associated with privilege and the rules defined by nation-states. However, the increasing integration of digital technology calls for a reconsideration of the concept of citizenship as a system of relations rather than a static condition. The assemblage theory offers a way to understand citizenship as a dynamic, temporal, and spatial concept involving continuous transformation and networks of interdependent relationships. This shift from a fixed understanding of belonging to a more fluid and dynamic concept requires a reevaluation of the role of non-human actors and the importance of multiple, shifting narratives of time. Emerging digital technologies are enabling new forms of citizenship that are no longer tied to territorial jurisdictions, but instead are based on participation in distributed virtual communities. The development of decentralised technologies such as blockchain offers the potential for creating new institutions that enable a more agile and rapid recodification of citizenship status. However, the decentralisation of citizenship also raises concerns about the potential for centralised control and the need to protect decentralised activities. A key challenge is to imagine a strategy that can combine centralisation and decentralisation in a way that enables new forms of citizenship based on belonging to extraterritorial, distributed, and decentralised values and affinities
Risorse animali a Monte Bibele (Monterenzio – BO): l’abitato di Pianella di Monte Savino nel quadro dell’Italia settentrionale preromana
No full text
[PtOTf(triphos)]OTf and [PtMe2(triphos-P,P')] as versatile synthons of platinum(II)-triphos species
No full textVirtual quandle for links in lens spaces
No full textWe construct a virtual quandle for links in lens spaces L(p, 1). This invariant has two valuable advantages over an ordinary fundamental quandle for links in lens spaces: the virtual quandle is an essential invariant and the presentation of the virtual quandle can be easily written from the band diagram of a link
Diffeomorphic vs Isotopic Links in Lens Spaces
No full textLinks in lens spaces may be defined to be equivalent by ambient isotopy or by diffeomorphism of pairs. In the first case, for all the combinatorial representations of links, there is a set of Reidemeister-type moves on diagrams connecting isotopy equivalent links. In this paper, we provide a set of moves on disk, band and grid diagrams that connects diffeo-equivalent links: there are up to four isotopy equivalent links in each diffeo-equivalence class. Moreover, we investigate how the diffeo-equivalence relates to the lift of the link in the 3-sphere: in the particular case of oriented primitive-homologous knots, the lift completely determines the knot class in L(p, q) up to diffeo-equivalence, and thus only four possible knots up to isotopy equivalence can have the same lift
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