Topological properties of spaces admitting free group actions

In 1992, David Wright proved a remarkable theorem about which contractible open manifolds are covering spaces. He showed that if a one-ended open manifold M has pro-monomorphic fundamental group at infinity which is not pro-trivial and is not stably Z, then M does not cover any manifold (except itself). In the non-manifold case, Wright's method showed that when a one-ended, simply connected, locally compact ANR X with pro-monomorphic fundamental group at infinity admits an action of Z by covering transformations then the fundamental group at infinity of X is (up to pro-isomorphism) an inverse sequence of finitely generated free groups. We improve upon this latter result, by showing that X must have a stable finitely generated free fundamental group at infinity. Simple examples show that a free group of any finite rank is possible. We also prove that if X (as above), admits a non-cocompact action of Z+Z by covering transformations, then X is simply connected at infinity. Corollary: Every finitely presented one-ended group G which contains an element of infinite order satisfies exactly one of the following: 1) G is simply connected at infinity; 2) G is virtually a surface group; 3) The fundamental group at infinity of G is not pro-monomorphic. Our methods also provide a quick new proof of Wright's open manifold theorem.Comment: Revised version with a shorter proof of the main theorem, plus numerous small corrections. To appear in the Journal of Topology. 31 pages, 4 figure

The global trade in (techno)corrections

Electronic monitoring (EM) of offender technologies developed as responses to the problem of prison overcrowding and the enhanced focus upon re-introducing market values to the criminal justice sector, incorporating advances in information and communication technological infrastructures into new modes of crime control. At first glance, EM technologies appear to be tools with the potential to stimulate criminal justice innovation: new modes of virtual regulation suited to the digital world that global citizens inhabit. Yet, closer scrutiny of the use of EM across the globe unveils a sprawling, amorphous industry in commercial techno-corrections that both stimulates penal growth in domestic markets and facilitates policy transfer across international jurisdictions. The pioneering EM markets of North America, the UK and Australasia act as testing stations for the next generation of developers across Europe, Latin America and South East Asia. Viewed more closely, EM appears indicative of an intensification of surveillance and electronic population governance that has emerged from neo-liberal states and dispersed across the globe in a myriad of shapes and forms

Creation of dense polymer brush layers by the controlled deposition of an amphiphilic responsive comb polymer

We introduce a copolymer with a comb topology that has been engineered to assemble in a brush configuration at an air-water interface. The molecule comprises a 6.1 kDa poly(methyl methacrylate) backbone with a statistical amount of poly[2-(dimethyl amino)ethyl methacrylate] polybase side chains averaging 2.43 per backbone.. Brush layers deposited with the hydrophobic PMMA backbone adsorbed to hydrophobized silicon are stable in water even when stored at pH values less than 2.0 for over 24 h. The use of a Langmuir trough allows a simple controlled deposition of the layers at a variety of grafting densities. Depth profiling of brush layers was performed using neutron reflectometry and reveals a significant shifting of the responsiveness of the layer upon changing the grafting density. The degree of swelling of the layers at a pH value of 4 (below the pK(b)) decreases as grafting density increases. Lowering the pH of the subphase during deposition causes the side chains to become charged and more hydrophilic extending to a brush-like configuration while at neutral pH the side chains lie in a "pancake" conformation at the interface. (C) 2009 Elsevier Ltd. All rights reserved

Perioperative thromboprophylaxis in digital replantation: a systematic review

Background There is no international consensus on the use of perioperative thromboprophylaxis in digital replantation. Suboptimal perioperative management may lead to replant failure which compromises extremity function, worsens psychosocial outcomes for patients and incurs significant cost. This systematic review evaluates and compares the efficacy and safety of perioperative antithrombotic protocols used in digital replantation. Methods A PRISMA-compliant prospectively registered (PROSPERO CRD42018108695) systematic review was conducted. Cochrane Central Register of Controlled Trials, Medline, EMBASE and Scopus were searched up until December 2019. Articles were assessed for eligibility in duplicate by two independent reviewers. All comparative studies which examined the use of perioperative thromboprophylaxis in digital replantation were eligible for inclusion. Results Collectively, 1,025 studies were identified of which 7 met full inclusion criteria reporting data from 635 patients (908 digital replants, 86% male, average age 37.3 years). Laceration was the most commonly reported mechanism of injury (68%) with 33% of replantation occurring in Tamai zone III. Fourteen distinct perioperative protocols were identified. One study reported significantly higher digital survival with continuous heparin infusion versus bolus heparin. Five studies demonstrated a significantly higher incidence of complications amongst patients treated with systemic heparin. Conclusions The clinical efficacy and safety of peri-operative antithrombotic therapy following digital replantation remains equivocal. The perceived benefits of improved digital survival must be tempered against the adverse systemic side effects of antithrombotic and anticoagulant therapies until further prospectively collected data sets become available

The universal functorial equivariant Lefschetz invariant

We introduce the universal functorial equivariant Lefschetz invariant for endomorphisms of finite proper G-CW-complexes, where G is a discrete group. We use K_0 of the category of "phi-endomorphisms of finitely generated free RPi(G,X)-modules". We derive results about fixed points of equivariant endomorphisms of cocompact proper smooth G-manifolds.Comment: 33 pages; shortened version of the author's PhD thesis, supervised by Wolfgang Lueck, Westfaelische Wilhelms-Universitaet Muenster, 200

The Sigma invariants of Thompson's group F

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Thompson's group F is the group of all increasing dyadic PL homeomorphisms of the closed unit interval. We compute Sigma(m)(F) and Sigma(m)(F;Z), the homotopical and homological Bieri-Neumann-Strebel-Renz invariants of F, and show that Sigma(m)(F) = Sigma(m)(F;Z). As an application, we show that, for every m, F has subgroups of type F(m-1) which are not of type FP(m) (thus certainly not of type F(m)).42263273Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Análisis comparativo entre un tutor circular y uno monolateral en elongaciones óseas

El presente trabajo compara la funcionalidad de dos tutores externos utilizados para elongación: el del Dr. Ilizarov y el tutor HG, desarrollado en nuestra institución. De 131 pacientes tratados con elongación ósea en 147 huesos largos se seleccionaron al azar 25 huesos por cada aparato anteriormente mencionado. Para objetivar los resultados se registraron estadísticamente variables independientes y dependientes en sus características subjetivas y objetivas, tales como: edad, sexo, tipo de hueso elongado, tolerancia psíquica, sensación de confort, facilidad de higiene y control, las infecciones, las rigideces articulares por retracción músculo tendinosa, y la deformación ósea residual. El objetivo fue comparar y establecer si el cambio en la elección del sistema fue ventajoso para nuestros pacientes. En el intento comparativo se enfrentaron dos variables, que a nuestro criterio eran las más importantes para establecer diferencias: la calidad del callo del hueso sometido a elongación y la presencia de complicaciones tanto transitorias como definitivas.In this work we compare the results obtained with two different external fixation devices in patients undergoing bone lengthening. The devices studied were the Ilizarov type and the HG, an apparatons developed in our institution. Out of 131 patientes treated by bone lengthening in 147 long bones, 25 bones lengthened with each device were selected at random. Different subjective and objective variables were assessed: age, sex, type of bone, psichological tolerance, patients, confort, nursing, infections, joint stiffness due to musculotendinous retractions, and residual bone deformity. The aim of the study was to analyze if the monolateral frame entailed advantages for our patients. Two main factors were more deeply analysed, namely the quality of the bone callus subjected to lengthening and the presence of both transitory and definitive complications

Observation of the complete rupture of a buried polymer layer by off-specular neutron reflectometry

We have used off-specular neutron reflectometry to study the rupture of a thin, deuterated polystyrene layer confined between a silicon substrate and a thick poly(methyl methacrylate) upper layer. After total rupture of the buried layer, the resulting roughness at the interface that controls the total reflection edge gives rise to Yoneda off-specular scattering. This hypothesis is confirmed by specular reflectivity data that can be fitted to an effective error function subsequent to the rupture of the buried layer. The observed increase in the Yoneda peak intensities, integrated along the path of constant momentum transfer qz, can be directly related to the formation of an interdigitated structure upon rupture of the buried layer. A distorted-wave Born approximation is used to quantitatively simulate the form of the off-specular data in terms of an equivalent error function, with fitting parameters in good agreement with the physical properties of the samples and key experimental results