Noncyclic covers of knot complements

Hempel has shown that the fundamental groups of knot complements are residually finite. This implies that every nontrivial knot must have a finite-sheeted, noncyclic cover. We give an explicit bound, $\Phi (c)$, such that if $K$ is a nontrivial knot in the three-sphere with a diagram with $c$ crossings and a particularly simple JSJ decomposition then the complement of $K$ has a finite-sheeted, noncyclic cover with at most $\Phi (c)$ sheets.Comment: 29 pages, 8 figures, from Ph.D. thesis at Columbia University; Acknowledgments added; Content correcte

Two-sided combinatorial volume bounds for non-obtuse hyperbolic polyhedra

We give a method for computing upper and lower bounds for the volume of a non-obtuse hyperbolic polyhedron in terms of the combinatorics of the 1-skeleton. We introduce an algorithm that detects the geometric decomposition of good 3-orbifolds with planar singular locus and underlying manifold the 3-sphere. The volume bounds follow from techniques related to the proof of Thurston's Orbifold Theorem, Schl\"afli's formula, and previous results of the author giving volume bounds for right-angled hyperbolic polyhedra.Comment: 36 pages, 19 figure

"Not wishing to be the white rhino in the crowd" : disability-disclosure at University

This article reports on a qualitative study identifying the drivers for and boundaries to disability-disclosure in interability interactions as experienced by 13 students with physical impairments at five Belgian higher education institutions. Through surveys and in-depth interviews, the study explored whether the students experience, prefer, and expect differences in communication about their impairments with temporarily able-bodied peers, instructors, and staff. Interviews provided insight into the nuances of disclosure and topic avoidance decisions that differ by disclosure target: disabilitydisclosure is mainly a balancing act between fulfilling physical needs and maintaining a normal, positive identity. The visibility of impairments seems to play a minor role in the students’ initial orientation toward disclosing. The functions of disability-disclosure as posited by the Communication Predicament of Disability Model and the CARE-keys to effective interability communication (i.e., Contact, Ask, Respect, Empathy) are discussed as well as the implications of the findings for Communication Accommodation Theory

Latest advances in the use of double stranded RNA as a tool for viral protection in tomato plants.

Lately, great attention has been diverted to elucidating the mechanisms underlining plant gene silencing and the action of non-coding RNA in plants. Concomitantly, knowledge about the interactions between plants and pathogens has evolved greatly, bringing to the spotlight the importance of double-stranded RNA (dsRNA) as a tool to generate or improve resistance against plant pathogens

Triangulated Surfaces in Twistor Space: A Kinematical Set up for Open/Closed String Duality

We exploit the properties of the three-dimensional hyperbolic space to discuss a simplicial setting for open/closed string duality based on (random) Regge triangulations decorated with null twistorial fields. We explicitly show that the twistorial N-points function, describing Dirichlet correlations over the moduli space of open N-bordered genus g surfaces, is naturally mapped into the Witten-Kontsevich intersection theory over the moduli space of N-pointed closed Riemann surfaces of the same genus. We also discuss various aspects of the geometrical setting which connects this model to PSL(2,C) Chern-Simons theory.Comment: 35 pages, references added, slightly revised introductio

Últimos avanços no uso de RNA de fita dupla como ferramenta para proteção viral em plantas de tomate.

Latest advances in the use of double-stranded RNA as tool for viral protection in tomato plants. Lately, great attention has been diverted to elucidating the mechanisms underlining plant gene silencing and the action of non-coding RNA in plants. Concomitantly, knowledge about the interactions between plants and pathogens has evolved greatly, bringing to the spotlight the importance of double-stranded RNA (dsRNA) as a tool to generate or improve resistance against plant pathogens. Plant viruses are responsible for important losses in the yield of several commodities. Viruses are very diverse, and to date, no products available in the market allow effective control of viral infections. The use of dsRNA molecules as a tool is based on the plant gene-silencing pathways (GS). After being topically applied, the dsRNA can activate GS, which uses it as a template for synthesizing small RNAs, leading to the degradation of specific RNA molecules present in the plant cell

Implementing a privacy-enhanced attribute-based credential system for online social networks with co-ownership management

Online social network (OSN) users are exhibiting an increased privacy-protective behaviour especially since multimedia sharing has emerged as a popular activity over most OSN sites. Popular OSN applications could reveal much of the users' personal information or let it easily derived, hence favouring different types of misbehaviour. In this article the authors deal with these privacy concerns by applying fine-grained access control and co-ownership management over the shared data. This proposal defines access policy as any linear boolean formula that is collectively determined by all users being exposed in that data collection namely the co-owners. All co-owners are empowered to take part in the process of data sharing by expressing (secretly) their privacy preferences and, as a result, jointly agreeing on the access policy. Access policies are built upon the concept of secret sharing systems. A number of predicates such as gender, affiliation or postal code can define a particular privacy setting. User attributes are then used as predicate values. In addition, by the deployment of privacy-enhanced attribute-based credential technologies, users satisfying the access policy will gain access without disclosing their real identities. The authors have implemented this system as a Facebook application demonstrating its viability, and procuring reasonable performance costs

Incidence, predictors and clinical impact of permanent pacemaker insertion in women following transcatheter aortic valve implantation: insights from a prospective multinational registry

To describe the incidence, predictors, and clinical impact of permanent pacemaker insertion (PPI) following transcatheter aortic valve replacement (TAVR) in women. Background: Data on pacemaker insertion complicating TAVR in women are scarce. Methods: The Women''s International Transcatheter Aortic Valve implantation (WIN-TAVI) is a prospective registry evaluating the safety and efficacy of TAVR in women. We included patients without preprocedural pacemakers and divided them into two groups: (1) PPI and (2) no-PPI. We identified PPI predictors using logistic regression and studied its clinical impact on the Valve Academic Research Consortium (VARC)-2 efficacy and safety endpoints. Results: Out of 1019 patients, 922 were included in the analysis. Post-TAVR PPI occurred in 132 (14.3%) patients. Clinical and procedural characteristics were similar in both groups. Pre-existing right bundle branch block (RBBB) was associated with a high risk of post-TAVR PPI (OR 3.62, 95% CI 1.85–7.06, p < 0.001), while implantation of balloon-expandable prosthesis was associated with a lower risk (OR 0.47, 95% CI 0.30–0.74, p < 0.001). Post-TAVR PPI prolonged in-hospital stay by a median of 2 days (11 [9–16] days in PPI vs. 9 [7–14] days in no-PPI, p = 0.005), yet risks of VARC-2 efficacy and safety endpoints at 1 year were similar in both groups (adjHR 0.95, 95% CI 0.60–1.52, p = 0.84 and adjHR 1.22, 95% CI 0.83–1.79, p = 0.31, respectively). Conclusion: Pacemaker implantation following TAVR is frequent among women and is associated with pre-existing RBBB and valve type. PPI prolongs hospital stay, albeit without any significant impact on 1-year outcomes