1,255 research outputs found

    Calculating invariants as coreflexive bisimulations

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    Invariants, bisimulations and assertions are the main ingredients of coalgebra theory applied to software systems. In this paper we reduce the first to a particular case of the second and show how both together pave the way to a theory of coalgebras which regards invariant predicates as types. An outcome of such a theory is a calculus of invariants’ proof obligation discharge, a fragment of which is presented in the paper. The approach has two main ingredients: one is that of adopting relations as “first class citizens” in a pointfree reasoning style; the other lies on a synergy found between a relational construct, Reynolds’ relation on functions involved in the abstraction theorem on parametric polymorphism and the coalgebraic account of bisimulations and invariants. This leads to an elegant proof of the equivalence between two different definitions of bisimulation found in coalgebra literature (due to B. Jacobs and Aczel & Mendler, respectively) and to their instantiation to the classical Park-Milner definition popular in process algebra.Partially supported by the Fundacao para a Ciencia e a Tecnologia, Portugal, under grant number SFRH/BD/27482/2006

    Generic Programming with Multiple Parameters

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    Which mathematics for the Information Society?

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    MathIS is a new project that aims to reinvigorate secondary- school mathematics by exploiting insights of the dynamics of algorithmic problem solving. This paper describes the main ideas that underpin the project. In summary, we propose a central role for formal logic, the development of a calculational style of reasoning, the emphasis on the algorithmic nature of mathematics, and the promotion of self-discovery by the students. These ideas are discussed and the case is made, through a number of examples that show the teaching style that we want to introduce, for their relevance in shaping mathematics training for the years to come. In our opinion, the education of software engineers that work effectively with formal methods and mathematical abstractions should start before university and would benefit from the ideas discussed here.Long-term collaboration with J. N. Oliveira on calculational approaches to mathematics is deeply acknowledged. We are also grateful to the anonymous referees for their valuable comments. This research was supported by FCT (the Portuguese Foundation for Science and Technology), in the context of the MATHIS Project under contract PTDC/EIA/73252/2006. The work of Joao F. Ferreira and AlexandraMendeswas further supported by FCT grants SFRH/BD/24269/2005 and SFRH/BD/29553/2006, respectively

    The role of the Self in assessing doping cognition: Implicit and explicit measures of athletes' doping-related prototype perceptions

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    Objectives: To examine athletes’ implicit and explicit prototype perceptions of performance enhancing substance (PES) users and non-users. Design: A cross-sectional mixed-method study. Methods: Competitive athletes from 39 sports (N=226; mean age= 27.66±9.74 years; 59% male) completed four self-report questions and two Brief Implicit Association Tests online, assessing prototype favourability and similarity of PES users and non-users. Results: Athletes explicitly associated themselves with a non-user (M= 3.13±0.92) more than a PES user (M= 0.56±0.88) and perceived a non-user (M= 89.92±14.98) more favourably than a PES user (M= 13.18±21.38). Indexing behaviour on self-reports, doping contemplators did not differ from ‘clean’ athletes in their perceptions of PES user prototypes while dopers perceived PES users favourably and similar to themselves. In comparison, doping contemplators paired the concept of 'dopers' easier with themselves than with others, while clean athletes and dopers had no preference for either pairing (D = -0.33, -0.08 and 0.01, respectively). All groups demonstrated some degree of preference for ‘good and doper’, moving from slight to moderate to strong preference in the groups of clean athletes, dopers and contemplators, respectively (D = -0.20, -0.37 and -0.80, respectively). Conclusions: Results suggest that doping contemplators may have a positive bias towards doping which is not endorsed in self-reports. Implicit preferences, along with the disparity between the implicit and explicit measures of athletes’ doping-related prototype perceptions advance understanding of doping behaviour and make a unique contribution to research methodology. Factors influencing the interplay between explicit and implicit endorsements of PES user prototypes warrant further research

    Study on Doping Prevention: A map of Legal, Regulatory and Prevention Practice Provisions in EU 28

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    Historically, anti-doping efforts have focused on the detection and deterrence of doping in elite and competitive sport. There is, however, a growing concern that doping is occurring outside the organised sporting system; giving rise to the belief that the misuse of doping agents in recreational sport has become a societal problem and a public health issue that must be addressed. The EU Commission awarded a contract (EAC/2013/0617) to a Consortium to undertake this Study with the aim of developing the evidence-base for policies designed to combat doping in recreational sport. Fourteen internationally recognised experts shaped the Study which comprised (i) the collection of primary data through a structured survey, and (ii) secondary data through literature searches and website analysis. All 28 Member States participated in the information-gathering process. Specifically, this involved a systematic study of the ethical considerations, legal position, prevention research landscape, and current practise in relation to the prevention of doping in recreational sport. The Study provides a comprehensive overview of current practice and legislation as it applies to the prevention of doping and promotes and supports the sharing of best practices in the EU regarding the fight against doping in recreational sport. It concludes with seven recommendations for future action that focus on the need for a coordinated response in relation to the problems arising from doping in recreational sport

    Yallalie: a Buried Structure of Possible Impact Origin in the Perth Basin, Western Australia

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    An enigmatic buried structure, located in Mesozoic sedimentary rocks in the Perth Basin, Western Australia, was discovered in 1990 by Ampol Exploration. The basin-like Yallalie structure (centred on 30 26' 40.3'' S, 115 46' 16.4'' E) is circular in plan view and about 12 km in diameter. High resolution,seismic-reflection profiles across the structure show a basin-shaped area of chaotic reflections that extend to a depth of approximately 2 km below the surface. The structure has sharp boundaries with surrounding faulted, but otherwise relatively undisturbed, rocks. In the centre of the structure there is an uplifted area approximately 3?4 km across, similar to those described from complex meteorite impact structures. The seismically defined structure coincides with a circular topographic depression, and image processing of digital elevation data has allowed recognition of concentric and radial structures extending as far as 40 km from the centre of the depression. Gravity surveys show the structure to be associated with a positive gravity anomaly of about 30 gu. Aeromagnetic surveys have defined annular anomalies associated with the central uplifted section, and possibly margins, of the structure. A search for siderophile element enrichments (by neutron activation analysis) in the rocks of the structure, which would indicate the presence of a meteorite component, proved negative. Quartz grains in cores that penetrate the structure show the development of prismatic cleavage fractures and irregular, slightly curved planes formed by brittle fracture. An allochthonous breccia of Late Cretaceous rocks occurs a few kilometres west of the western margin of the structure. Quartz grains from a thin veneer of Tertiary sediments that drape the structure are essentially undeformed. However, multiple sets of closely spaced planar deformation features in quartz, characteristic of highly shocked rocks, have yet to be observed in the rocks of the Yallalie structure and the allochthonous breccia. The morphology of the Yallalie structure determined from topographic and geophysical data suggests strongly that it is of impact origin. Geological and geochemical evidence is equivocal, but is not inconsistent with this interpretation

    String cosmology from Poisson-Lie T-dual sigma models on supermanifolds

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    We generalize the formulation of Poisson-Lie T-dual sigma models on manifolds to supermanifolds. In this respect, we formulate 1+1 dimensional string cosmological models on the Lie supergroup C^3 and its dual (A_1,1 + 2A)^0_(1,0,0), which are coupled to two fermionic fields. Then, we solve the equations of motion of the models and show that there is a essential singularity for the metric of the original model and its dual.Comment: 17 pages, Appendix and three references have adde

    Super Poisson-Lie symmetry of the GL(1|1) WZNW model and worldsheet boundary conditions

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    We show that the WZNW model on the Lie supergroup GL(1|1) has super Poisson-Lie symmetry with the dual Lie supergroup B + A + A1;1|.i. Then, we discuss about D-branes and worldsheet boundary conditions on supermanifolds, in general, and obtain the algebraic relations on the gluing supermatrix for the Lie supergroup case. Finally, using the supercanonical transformation description of the super Poisson-Lie T-duality transformation, we obtain formula for the description of the dual gluing supermatrix, then, we find the gluing supermatrix for the WZNW model on GL(1|1) and its dual model. We also discuss about different boundary conditions.Comment: 19 pages, two Refs. have adde

    Capturing accelerometer outputs in healthy volunteers under normal and simulated-pathological conditions using ML classifiers

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    Wearable devices offer a possible solution for acquiring objective measurements of physical activity. Most current algorithms are derived using data from healthy volunteers. It is unclear whether such algorithms are suitable in specific clinical scenarios, such as when an individual has altered gait. We hypothesized that algorithms trained on healthy population will result in less accurate results when tested in individuals with altered gait. We further hypothesized that algorithms trained on simulated-pathological gait would prove better at classifying abnormal activity.We studied healthy volunteers to assess whether activity classification accuracy differed for those with healthy and simulated-pathological conditions. Healthy participants (n=30) were recruited from the University of Leeds to perform nine predefined activities under healthy and simulated-pathological conditions. Activities were captured using a wrist-worn MOX accelerometer (Maastricht Instruments, NL). Data were analyzed based on the Activity-Recognition-Chain process. We trained a Neural-Network, Random-Forests, k-Nearest-Neighbors (k-NN), Support-Vector-Machines (SVM) and Naive Bayes models to classify activity. Algorithms were trained four times; once with 'healthy' data, and once with 'simulated-pathological data' for each of activity-type and activity-task classification. In activity-type instances, the SVM provided the best results; the accuracy was 98.4% when the algorithm was trained and then tested with unseen data from the same group of healthy individuals. Accuracy dropped to 52.8% when tested on simulated-pathological data. When the model was retrained with simulated-pathological data, prediction accuracy for the corresponding test set was 96.7%. Algorithms developed on healthy data are less accurate for pathological conditions. When evaluating pathological conditions, classifier algorithms developed using data from a target sub-population can restore accuracy to above 95%.Clinical Relevance - This method remotely establishes health-related data of objective outcome measures of activities of daily living
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