Adler-Kostant-Symes systems as Lagrangian gauge theories

It is well known that the integrable Hamiltonian systems defined by the Adler-Kostant-Symes construction correspond via Hamiltonian reduction to systems on cotangent bundles of Lie groups. Generalizing previous results on Toda systems, here a Lagrangian version of the reduction procedure is exhibited for those cases for which the underlying Lie algebra admits an invariant scalar product. This is achieved by constructing a Lagrangian with gauge symmetry in such a way that, by means of the Dirac algorithm, this Lagrangian reproduces the Adler-Kostant-Symes system whose Hamiltonian is the quadratic form associated with the scalar product on the Lie algebra.Comment: 10 pages, LaTeX2

The role of ecolabeling in fisheries management and conservation

Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Blackwell for personal use, not for redistribution. The definitive version was published in Conservation Biology 20 (2006): 392-398, doi:10.1111/j.1523-1739.2006.00319.x.The Marine Stewardship Council (MSC) regulate the ecolabeling of products from fisheries with the aim of promoting sustainable fishery practices. To date 11 fisheries have attained full certification and a further 7 are under review. Together these fisheries offer 220 ecolabeled marine products to consumers. Despite great potential to encourage sustainable fisheries, and thereby bring conservation benefits to marine systems, there are a range of issues that may serve to limit the wider uptake of MSC ecolabeled products. These include a general lack of consumer concern for marine fish and sustainable fisheries, an absence of guaranteed continued financial benefits to participating fishers and difficulties of quality assurance which are related to the complexities in monitoring compliance of marine fisheries. In addition, it is apparent that property-rights over the fishery seem to be an essential prerequisite for engagement in MSC and this is one major impediment to wider uptake of the scheme in current marine fisheries, which tend to be open access. Some modifications to the current scheme may be needed if wider participation of marine fishers is to be achieved. These may include a tiered approach to certification, certification of fishers rather than fisheries, governmental facilitation to assist the latter, and greater engagement with retailers and buyers rather than individual consumers. None of these changes will occur without constructive engagement of Government, retailers and the fishing industry.MJK was part funded through a Marine Policy Center Senior Research Fellowship

Testing Tablet Computers in Nursing Education: A Comprehensive Evaluation Framework

Background: Tablet Computers (TCs) and other mobile digital devices are rapidly changing the way we communicate and access information in our personal and professional lives. Scarce research exists regarding their effectiveness in promoting the learning of health professionals. This paper describes the evaluation framework used in a study to test TCs in a post-diploma baccalaureate nursing program in the Gulf Cooperation Council (GCC) state of Qatar.Purpose: The evaluation framework was structured around 10 objectives designed to assess the impact of TC integration into the evidence-based practice (EBP) and reflective practice (RP) components of a scholarship course. Evaluation variables included perceptions of knowledge, confidence, comfort, satisfaction and technical skill before and after the 7-week TC implementation; students’ usage patterns and attitudes about the usefulness of TCs in promoting their learning related to EBP and RP were also examined; in addition, students’ views about the impact of TCs on the learning environment and their engagement in the learning process were sought.Methods: A mixed method descriptive design was used to assess outcomes of interest. Qualitative methods (focus groups, participant observation, field notes and reflective journals) were used to capture subjective perspectives of TC users. Quantitative methods (pre-test/posttest, activity logs and skills labs) were used to assess change in knowledge, attitude and technical proficiency over time.Results: The evaluation framework used to assess process and outcome variables in this study combined structural, philosophical, theoretical, pedagogical and methodological elements. These included the logic model, participatory action, theory-based course concepts, as well as a learning taxonomy involving cognitive, affective and psychomotor competencies.Conclusion: The value of a comprehensive evaluation plan executed in tandem with TC implementation is highlighted

Inverse problem for wave equation with sources and observations on disjoint sets

We consider an inverse problem for a hyperbolic partial differential equation on a compact Riemannian manifold. Assuming that $\Gamma_1$ and $\Gamma_2$ are two disjoint open subsets of the boundary of the manifold we define the restricted Dirichlet-to-Neumann operator $\Lambda_{\Gamma_1,\Gamma_2}$. This operator corresponds the boundary measurements when we have smooth sources supported on $\Gamma_1$ and the fields produced by these sources are observed on $\Gamma_2$. We show that when $\Gamma_1$ and $\Gamma_2$ are disjoint but their closures intersect at least at one point, then the restricted Dirichlet-to-Neumann operator $\Lambda_{\Gamma_1,\Gamma_2}$ determines the Riemannian manifold and the metric on it up to an isometry. In the Euclidian space, the result yields that an anisotropic wave speed inside a compact body is determined, up to a natural coordinate transformations, by measurements on the boundary of the body even when wave sources are kept away from receivers. Moreover, we show that if we have three arbitrary non-empty open subsets $\Gamma_1,\Gamma_2$, and $\Gamma_3$ of the boundary, then the restricted Dirichlet-to-Neumann operators $\Lambda_{\Gamma_j,\Gamma_k}$ for $1\leq j<k\leq 3$ determine the Riemannian manifold to an isometry. Similar result is proven also for the finite-time boundary measurements when the hyperbolic equation satisfies an exact controllability condition

Diversification under sexual selection: the relative roles of mate preference strength and the degree of divergence in mate preferences

The contribution of sexual selection to diversification remains poorly understood after decades of research. This may be in part because studies have focused predominantly on the strength of sexual selection, which offers an incomplete view of selection regimes. By contrast, students of natural selection focus on environmental differences that help compare selection regimes across populations. To ask how this disparity in focus may affect the conclusions of evolutionary research, we relate the amount of diversification in mating displays to quantitative descriptions of the strength and the amount of divergence in mate preferences across a diverse set of case studies of mate choice. We find that display diversification is better explained by preference divergence rather than preference strength; the effect of the latter is more subtle, and is best revealed as an interaction with the former. Our findings cast the action of sexual selection (and selection in general) in a novel light: the strength of selection influences the rate of evolution, and how divergent selection is determines how much diversification can occur. Adopting this view will enhance tests of the relative role of natural and sexual selection in processes such as speciation