6,095 research outputs found

    Progress report on a new search for free e/3 quarks in the cores of 10(15) - 10(16) eV air showers

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    The Leeds 3 sq m Wilson cloud chamber is being used in a new search for free e/3 quarks close to the axes of 10 to the 15th power - 10 to the 16th power eV air showers. A ratio trigger circuit is used to detect the incidence of air shower cores; the position of the shower center and the axis direction are determined from photographs of current-limited spark chambers. It is thus possible, for the first time, to know where we have looked for quarks in air showers and to select for scanning only those cloud chamber photographs where we have good evidence that the shower axis was close to the chamber. 250 g/sq cm of lead/concrete absorber above the cloud chamber serve to reduce particle densities and make a quark search possible very close to the shower axes. The current status of the search is given

    Progressor: Social navigation support through open social student modeling

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    The increased volumes of online learning content have produced two problems: how to help students to find the most appropriate resources and how to engage them in using these resources. Personalized and social learning have been suggested as potential ways to address these problems. Our work presented in this paper combines the ideas of personalized and social learning in the context of educational hypermedia. We introduce Progressor, an innovative Web-based tool based on the concepts of social navigation and open student modeling that helps students to find the most relevant resources in a large collection of parameterized self-assessment questions on Java programming. We have evaluated Progressor in a semester-long classroom study, the results of which are presented in this paper. The study confirmed the impact of personalized social navigation support provided by the system in the target context. The interface encouraged students to explore more topics attempting more questions and achieving higher success rates in answering them. A deeper analysis of the social navigation support mechanism revealed that the top students successfully led the way to discovering most relevant resources by creating clear pathways for weaker students. © 2013 Taylor and Francis Group, LLC

    Current status of MCNP6 as a simulation tool useful for space and accelerator applications

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    For the past several years, a major effort has been undertaken at Los Alamos National Laboratory (LANL) to develop the transport code MCNP6, the latest LANL Monte-Carlo transport code representing a merger and improvement of MCNP5 and MCNPX. We emphasize a description of the latest developments of MCNP6 at higher energies to improve its reliability in calculating rare-isotope production, high-energy cumulative particle production, and a gamut of reactions important for space-radiation shielding, cosmic-ray propagation, and accelerator applications. We present several examples of validation and verification of MCNP6 compared to a wide variety of intermediate- and high-energy experimental data on reactions induced by photons, mesons, nucleons, and nuclei at energies from tens of MeV to about 1 TeV/nucleon, and compare to results from other modern simulation tools.Comment: 4 pages, 3 figures, Proc. 11th Conference on the Intersections of Particle and Nuclear Physics (CIPANP 2012), St. Petersburg, FL, May 28 - June 3, 201

    QuizMap: Open social student modeling and adaptive navigation support with TreeMaps

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    In this paper, we present a novel approach to integrate social adaptive navigation support for self-assessment questions with an open student model using QuizMap, a TreeMap-based interface. By exposing student model in contrast to student peers and the whole class, QuizMap attempts to provide social guidance and increase student performance. The paper explains the nature of the QuizMap approach and its implementation in the context of self-assessment questions for Java programming. It also presents the design of a semester-long classroom study that we ran to evaluate QuizMap and reports the evaluation results. © 2011 Springer-Verlag Berlin Heidelberg

    MODELLING SCAPULAR BIOMECHANICS TO ENHANCE INTERPRETATION OF KINEMATICS AND PERFORMANCE DATA IN ROWING

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    Rowing involves repetitive, high intensity loading on the glenohumeral joint. Shoulder pain is associated with muscle weakness and imbalance, resulting in long-lasting overuse injuries. The goal of this study was to explore three-dimensional shoulder biomechanics during rowing to identify parameters that influence technique. Eleven athletes had their movement recorded by motion capture while using an instrumented ergometer. Kinetics and kinematics drove a computational model which output joint and muscle forces across the shoulder. Results suggest that subtle muscular changes identified by the model can be sensitively mapped to performance variables. When evaluated alongside ergometer-derived power metrics, biomechanics parameters can provide athletes and coaches a fuller picture of performance potential, injury risk, and training program efficacy

    FATIGUE LEADS TO ALTERED SPINAL KINEMATICS DURING HIGH PERFORMANCE ERGOMETER ROWING

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    Low back injuries in rowing are attributed to intense, repetitive, loading through the spine. Good technique and postural control are essential to maximize performance and minimize injury risk. This motion capture study recorded 3D spinal kinematics of 14 athletes during rowing at varying speeds on an instrumented ergometer and correlated motion with power metrics and athlete demographics. Sagittal plane rotation decreases in the lumbar spine and increases in the thoracic spine as speed increases. Transverse and frontal planes have little influence on force output. Declining postural control can be seen within each trial and worsened with higher rate. Assessments of form differences across athletes using relative motion between spine segments at critical stroke points show greater lumbar flexion (compared to thoracic) at the catch and neutral alignment at max handle force

    Ultrasound image reconstruction from compressed measurements using approximate message passing

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    Stereoselective palladium-catalyzed C(sp3)–H mono-arylation of piperidines and tetrahydropyrans with a C(4) directing group

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    A selective Pd-catalyzed C(3)–H cis-functionalization of piperidine and tetrahydropyran carboxylic acids is achieved using a C(4) aminoquinoline amide auxiliary. High mono- and cis-selectivity is attained by using mesityl carboxylic acid as an additive. Conditions are developed with significantly lower reaction temperatures (≀50 °C) than other reported heterocycle C(sp3)–H functionalization reactions, which is facilitated by a DoE optimization. A one-pot C–H functionalization-epimerization procedure provides the trans-3,4-disubstituted isomers directly. Divergent aminoquinoline removal is accomplished with the installation of carboxylic acid, alcohol, amide and nitrile functional groups. Overall fragment compounds suitable for screening are generated in 3-4 steps from readily-available heterocyclic carboxylic acids
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