Global convergence of a non-convex Douglas-Rachford iteration

We establish a region of convergence for the proto-typical non-convex Douglas-Rachford iteration which finds a point on the intersection of a line and a circle. Previous work on the non-convex iteration [2] was only able to establish local convergence, and was ineffective in that no explicit region of convergence could be given

Sapling age structure and growth series reveal a shift in recruitment dynamics of sugar maple and American beech over the last 40 years

Northern hardwoods have undergone a marked change in their dynamics, with American beech (Fagus grandifolia Ehrh.) increasing in abundance relative to sugar maple (Acer saccharum Marsh.). This study aims to better understand this sudden shift in recruitment dynamics. We performed an extensive analysis of the age structure, radial growth pattern, and release history on >700 saplings from 34 mature maple–beech stands of southern Quebec. We found (i) that the sapling age structures showed a progressive decrease in the establishment of maple relative to beech starting about 40 years ago, (ii) a change in the species growth hierarchy that started in the 1980s due to increasing radial growth of beech, (iii) that this growth trend is negligible for both maple and beech when we account for size and suppression status, and finally (iv) that the growth trend appears to be independent of present soil conditions. These results contrast with previous studies conducted at the adult stage that reported a growth decline for maple. We conclude that this change in recruitment dynamics is not related to growth, and consequently, further studies investigating this phenomenon should concentrate on establishment and survival

Divide and concur: A general approach to constraint satisfaction

Many difficult computational problems involve the simultaneous satisfaction of multiple constraints which are individually easy to satisfy. Such problems occur in diffractive imaging, protein folding, constrained optimization (e.g., spin glasses), and satisfiability testing. We present a simple geometric framework to express and solve such problems and apply it to two benchmarks. In the first application (3SAT, a boolean satisfaction problem), the resulting method exhibits similar performance scaling as a leading context-specific algorithm (walksat). In the second application (sphere packing), the method allowed us to find improved solutions to some old and well-studied optimization problems. Based upon its simplicity and observed efficiency, we argue that this framework provides a competitive alternative to stochastic methods such as simulated annealing.Comment: 4 pages, 2 figure

Serologic evidence for the presence in Pteropus bats of a paramyxovirus related to equine morbillivirus.

Two outbreaks of a previously unknown disease in horses and humans occurred in Queensland in 1994. The outbreaks occurred within 1 month of each other in Brisbane and Mackay, which are approximately 1000 km apart. In the Brisbane incident, 21 horses were infected of which 14 died or were euthanized after severe clinical signs of an acute respiratory disease. Two human cases were in patients with less well defined clinical signs; one patient died (1,2). In the Mackay incident two horses became seriously ill and died, and one person also died (3). Although it is now known that the two outbreaks occurred in August and September 1994, knowledge of the Mackay outbreak did not occur until late 1995 when the infected person died of a relapsing encephalitis. The name equine morbillivirus (EMV) has been proposed for a paramyxovirus isolated from four of the Brisbane horses and the first patient who died (2)

Arduous implementation: Does the Normalisation Process Model explain why it's so difficult to embed decision support technologies for patients in routine clinical practice

Background: decision support technologies (DSTs, also known as decision aids) help patients and professionals take part in collaborative decision-making processes. Trials have shown favorable impacts on patient knowledge, satisfaction, decisional conflict and confidence. However, they have not become routinely embedded in health care settings. Few studies have approached this issue using a theoretical framework. We explained problems of implementing DSTs using the Normalization Process Model, a conceptual model that focuses attention on how complex interventions become routinely embedded in practice.Methods: the Normalization Process Model was used as the basis of conceptual analysis of the outcomes of previous primary research and reviews. Using a virtual working environment we applied the model and its main concepts to examine: the 'workability' of DSTs in professional-patient interactions; how DSTs affect knowledge relations between their users; how DSTs impact on users' skills and performance; and the impact of DSTs on the allocation of organizational resources.Results: conceptual analysis using the Normalization Process Model provided insight on implementation problems for DSTs in routine settings. Current research focuses mainly on the interactional workability of these technologies, but factors related to divisions of labor and health care, and the organizational contexts in which DSTs are used, are poorly described and understood.Conclusion: the model successfully provided a framework for helping to identify factors that promote and inhibit the implementation of DSTs in healthcare and gave us insights into factors influencing the introduction of new technologies into contexts where negotiations are characterized by asymmetries of power and knowledge. Future research and development on the deployment of DSTs needs to take a more holistic approach and give emphasis to the structural conditions and social norms in which these technologies are enacte

Singularity confinement and algebraic integrability

Two important notions of integrability for discrete mappings are algebraic integrability and singularity confinement, have been used for discrete mappings. Algebraic integrability is related to the existence of sufficiently many conserved quantities whereas singularity confinement is associated with the local analysis of singularities. In this paper, the relationship between these two notions is explored for birational autonomous mappings. Two types of results are obtained: first, algebraically integrable mappings are shown to have the singularity confinement property. Second, a proof of the non-existence of algebraic conserved quantities of discrete systems based on the lack of confinement property is given.Comment: 18 pages, no figur

Remarks on the notion of quantum integrability

We discuss the notion of integrability in quantum mechanics. Starting from a review of some definitions commonly used in the literature, we propose a different set of criteria, leading to a classification of models in terms of different integrability classes. We end by highlighting some of the expected physical properties associated to models fulfilling the proposed criteria.Comment: 22 pages, no figures, Proceedings of Statphys 2