462 research outputs found
The relentless variability of Mrk 421 from the TeV to the radio
The origin of the gamma-ray emission of the blazar Mrk 421 is still a matter
of debate. We used 5.5 years of unbiased observing campaign data, obtained
using the FACT telescope and the Fermi LAT detector at TeV and GeV energies,
the longest and densest so far, together with contemporaneous multi-wavelength
observations, to characterise the variability of Mrk 421 and to constrain the
underlying physical mechanisms. We studied and correlated light curves obtained
by ten different instruments and found two significant results. The TeV and
X-ray light curves are very well correlated with a lag of <0.6 days. The GeV
and radio (15 Ghz band) light curves are widely and strongly correlated.
Variations of the GeV light curve lead those in the radio. Lepto-hadronic and
purely hadronic models in the frame of shock acceleration predict proton
acceleration or cooling timescales that are ruled out by the short variability
timescales and delays observed in Mrk 421. Instead the observations match the
predictions of leptonic models.Comment: 10 pages, 8 figures, 1 tabl
Conceptualizing Psychological Performance Enhancement in a Music Domain
Contrary to sport, the study of performance enhancement in music is at an earlier stage of development in its research, practice, and performer acceptance (Pecen, Collins, & MacNamara, 2016). In the absence of music performance enhancement research, practitioners frequently utilize sport as a template to inform both research and applied practice with musicians to optimize performance (Hays, 2002, 2012). While sport provides an evidence-based framework for studying performance enhancement, musicians have unique performance considerations that differ from athletes (Pecen et al., 2016), and these divergences in domains are not well understood. Using the McLeroy framework (McLeroy, Bibeau, Steckler, & Glanz, 1988), the purpose of this research was to conceptualize psychological performance enhancement (PPE) in a music domain. This purpose was achieved by way of two studies as part of a sequential explanatory mixed-methods design (Creswell & Plano Clark, 2011). Study 1 (N = 459) used descriptive surveys to identify musicians’ psychosocial responses to performance, the psychological skills and strategies
that musicians use during practice/rehearsal and performance, and the professionals specialized in performance enhancement with whom musicians have worked. Building upon study 1, study 2 (N = 12) utilized interpretative phenomenological analysis (IPA; Smith, Flowers, & Larkin, 2009) to deeply explore musicians’ lived experiences of psychological performance enhancement. The results from descriptive and inferential statistical analyses revealed that the psychological skills musicians employ may not appropriately address their psychosocial responses to performance. Furthermore, musicians’ performance needs are limited by the psychological skills training (PST) model of practice (Hardy, Jones, & Gould, 1996), as musicians seem to benefit from more mindfulness and acceptance-based models of performance enhancement (Gardner & Moore, 2007) that consider the well-being of the total performer and the environmental context. Results from the IPA demonstrated that the musicians employed a plethora of general and music-specific coping strategies to optimize performance, and also discussed various health and wellness behaviors, the influence that “others” play in the performance process (e.g., instructors, family), the influence of the external environment (e.g., acoustics, audience), the role of the music community (e.g., supportive behaviors, unsupportive behaviors), as well as the perceived access to and utilization of support systems as they relate to PPE. Musicians also considered seeking a performance psychology professional, preferably one with a background in music performance, so long as an individualized person-centered approach was utilized. Results support a systems-based approach to evaluating PPE in a music domain. Recommendations for musicians, educators/instructors, and performance psychology professionals are discussed, in addition to concerns related to musicians’ access to psychological performance enhancement services
Analysis of sensitivity of parameters in an active orthosis assisting the human walking
Este trabajo servirá para estudiar la influencia de algunos parámetros de una órtesis en un ciclo de marcha humana, realizado por una persona con un cierto grado de lesión que lleva una órtesis activa. Partiendo de una solución de referencia correspondiente a una persona sana, se estudiará cómo los cambios introducidos en el exoesqueleto afectan al ciclo de marcha humana en términos de energía, desviación de la referencia y otros parámetros definidos como variables de diseño. El problema consiste en un algoritmo de optimización en el que la función de coste tiene en cuenta el coste metabólico y la desviación con respecto al patrón, mientras que las variables de diseño deben cumplir una serie de restricciones en los puntos de control. Estas variables de diseño se evalúan en los nodos, para buscar la solución más óptima.
La órtesis portada por la persona lesionada consiste en un exoesqueleto active SCKAFO, que contiene un actuador rotacional que aporta un par en cada una de las rodillas, así como un tobillo flexible Klenzak, que ayuda a flexionar el tobillo. Un encóder permite controlar el ángulo de flexión y corregir la posición si es necesario. Los resultados incluyen la evolución temporal a lo largo del ciclo de marcha de las coordenadas generalizadas, las fuerzas de reacción, los pares generados en las articulaciones y en los dispositivos de la órtesis (el motor y el tobillo Klenzak), la activación muscular y la excitación neuronal. Las conclusiones obtenidas servirán como guía para el diseño de futuras órtesis.This work will serve to study the influence of some parameters from an orthosis in a human walking cycle, performed by an injured person while wearing an active orthosis. Parting from a reference solution corresponding to an injured individual, it will be studied how the changes introduced in the exoskeleton affect to the walking cycle in terms of energy, deviation from the reference and other parameters defined as design variables. The problem consists on an optimization problem where the cost function bears the metabolical cost and the deviation from reference, while the design variables must fulfill a set of constraints in control points. These design variables are evaluated in node points, so as to look for the more optimal solution.
The orthosis worn by the injured individual consists on an SCKAFO active orthosis, which includes a rotational actuator in each knee that supplies a torque, and a flexible Klenzak ankle, that also helps to bend the ankle. An encoder serves to control the bending angle and correct the position if necessary. The results will include the temporary evolution through the walking cycle of generalized coordinates, reaction forces, torques generated both at the human body and the orthosis devices (motor and Klenzak ankle, muscle activation and neural excitation. The obtained conclusions will serve as a guide for future orthosis designing.Universidad de Sevilla. Grado en Ingeniería de Tecnologías Industriale
Enhancing community detection using a network weighting strategy
A community within a network is a group of vertices densely connected to each
other but less connected to the vertices outside. The problem of detecting
communities in large networks plays a key role in a wide range of research
areas, e.g. Computer Science, Biology and Sociology. Most of the existing
algorithms to find communities count on the topological features of the network
and often do not scale well on large, real-life instances.
In this article we propose a strategy to enhance existing community detection
algorithms by adding a pre-processing step in which edges are weighted
according to their centrality w.r.t. the network topology. In our approach, the
centrality of an edge reflects its contribute to making arbitrary graph
tranversals, i.e., spreading messages over the network, as short as possible.
Our strategy is able to effectively complements information about network
topology and it can be used as an additional tool to enhance community
detection. The computation of edge centralities is carried out by performing
multiple random walks of bounded length on the network. Our method makes the
computation of edge centralities feasible also on large-scale networks. It has
been tested in conjunction with three state-of-the-art community detection
algorithms, namely the Louvain method, COPRA and OSLOM. Experimental results
show that our method raises the accuracy of existing algorithms both on
synthetic and real-life datasets.Comment: 28 pages, 2 figure
Maniobrabilidad de vehículos de competición
[ES] El siguiente proyecto aborda de forma detallada la dinamica vehicular de coches de competicion y como afecta esta a la maniobrabilidad. La dinamica es uno de los aspectos mas importantes a tener en cuenta para el diseño de vehiculos de produccion, y mas aun, debido a la naturaleza competitiva y el alto ritmo de evolucion, en los vehiculos de competicion. Se comienza desarrollando un estudio sobre el comportamiento de los neumaticos, analizando las fuerzas que actuan sobre ellos y las distintas variables a tener en cuenta. A continuacion, nos encontramos con un capitulo en el que se explica la propia dinamica del vehiculo al completo, analizando las respuestas del vehiculo en estado estacionario y en estado transitorio. El siguiente capitulo trata sobre el frenado, en el que se indagan las formulas fundamentales para su entendimiento y algunos de los sistemas que se utilizan en la alta competicion. Siguiendo con la tematica, el apartado cinco es un estudio sobre la direccion y las geometrias utilizadas para optimizar el rendimiento. Para finalizar, se estudian las tecnicas de conduccion y los posibles reglajes que ayudan a bajar el tiempo por vuelta.[EN] The following project deals in detail with the vehicle dynamics of racing cars and how it affects handling. Dynamics is one of the most important aspects to be taken into account in the design of production vehicles, and even more so, due to the competitive nature and the high rate of evolution, in racing vehicles. We begin by developing a study on the behaviour of tyres, analysing the forces acting on them and the different variables to be taken into account. This is followed by a chapter in which the dynamics of the vehicle itself is explained in full, analysing the responses of the vehicle in steady and transient states. The next chapter deals with braking, in which the fundamental formulas for its understanding and some of the systems used in high competition are investigated. Continuing the theme, section five is a study of steering and the geometries used to optimise performance. Finally, driving techniques and possible settings to help lower lap times are examined
The prevalence of playing-related musculoskeletal disorders in selected Western classical music students at the South African College of Music, University of Cape Town
The study aimed to ascertain the prevalence of playing-related musculoskeletal disorders (PRMDs) among Western classical instrumentalists at the South African College of Music. Seventy-two undergraduate string, woodwind and keyboard instrumental students were approached during classes or individually and asked to complete a specially designed questionnaire. Data were sent to a statistician at the University of Cape Town Statistics Consulting Unit and the statistical package SPSS (Version 22) was used to analyse the data. Seventy-one (71) of the 72 questionnaires were returned. The average respondent was a 20-year-old, right-handed female who had been playing her instrument for 10.8 years; 88.8% of the respondents had experienced a PRMD at some point in their lives, 82.1% within the preceding 12 months and 46.3% had a PRMD at the time of the study. No correlation was found between the prevalence of a PRMD and age, gender, instrument type, number of years of playing the instrument, playing another instrument or the university programme, stream or year. A significant relationship was found between the instrument level and the current prevalence of PRMDs. The most commonly affected area was the shoulder followed by the back, neck, hand or wrist and fingers. The most commonly indicated duration was 1 week (35.3%), though many PRMDs had lasted for more than 2 years (19.6%); 46.3% of the PRMDs had a severity of 3/5 or higher, and 34.2% of PRMDs were both 3/5 or higher for severity and frequency. Only 3.7% of the responses indicated that a body awareness technique was being used regularly, while 37.4% of the answers indicated that the techniques had "never been heard of". Over half (51.7%) of respondents had consulted a health professional. Physiotherapists and Alexander teachers were the most frequently consulted professionals. Treatment strategies were non-invasive and mostly self-reliant and though most respondents felt that the treatment strategies had helped temporarily, there was little long-term satisfaction. This study concludes that the prevalence of PRMDs in students at the South African College of music is high and around half of the PRMDs affect the students' ability to play or perform their instrument at an optimum level. Actions can and need to be taken to reduce these values in future
Classification of Urinary Calculi using Feed-Forward Neural Networks
Recent studies have shown that more than 80% of the analysed samples of urinary calculi in our laboratory were mainly composed of four types of calculi, consisting of the following substances: (1) whewellite and weddellite, (2) whewellite, weddellite and uric acid, (3) whewellite, weddellite and struvite and (4) whewellite, weddellite and carbonate apatite. In this work the results of classification of these types of calculi (using their infrared spectra in the region 1450–450 cm–1) by feed-forward neural networks are presented. Genetic algorithms were used for optimization of neural networks and for selection of the spectral regions most suitable for classification purposes. The generalization abilities of the neural networks were controlled by an early stopping procedure. The best network architecture and the most suitable spectral regions were chosen using twentyfold cross-validation. The cross-validation error for the real samples varies from 5.3% to 5.9% misclassifications, which makes the proposed method a promising tool for the identification of these types of calculi.KEY WORDS:Urinary calculi, infrared spectroscopy, classification, neural networks, variable selection, genetic algorithms
Viruses in the North Sea: viromics and prophage genomics
Despite their small size, viruses have an enormous influence on microbial population dynamics, due to lysis and horizontal gene transfer. Due the high abundance of their hosts, bacteriophages or phages comprise the majority of viruses and provide the largest reservoirs of unexplored genetic diversity in marine environments. The rise of Next Generation Sequencing (NGS) techniques brings new opportunities to investigate the marine virus community. However, there is no current statutory pipeline applied in marine phage ecology. Therefore, this thesis proposes a virus-specific pipeline based on the integration of existing tools and state of the art techniques. The developed pipeline was applied to accomplish the two research aims of this thesis: (1) to analyze the virus community in the North Sea with viromics(virus metagenomics), and (2) to characterize lysogenic phages from potentially pathogenic Vibrio species.
The results of the first part of this thesis show that the virus community is dominated by phages and they are not evenly distributed throughout the North Sea. In general, the coastal virus community was genetically more diverse than the open sea community. The influence of riverine inflow and currents affects the genetic virus diversity with the community carrying genes from a variety of metabolic pathways and other functions.
In the second part, lysogenic Vibrio phages from the North Sea were induced (ca. 40 % of tested isolates) and four phage genomes were characterized. The phages from V. parahaemolyticus (2 tailed phages, 1 filamentous phage) and V. cholerae (1 tailed phage) can integrate into their host genome and might have a role in pathogenicity.
This thesis represents an exemplary study of the virus community in the North Sea, with special emphasis on the marine phages. The settled virus-specific pipeline the obtained insights will contribute to extend the study of the virus diversity dynamics in other marine areas to characterize novel phage groups
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