6,140 research outputs found

    Sex differences in exercise-induced diaphragmatic fatigue in endurance-trained athletes

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    There is evidence that female athletes may be more susceptible to exercise-induced arterial hypoxemia and expiratory flow limitation and have greater increases in operational lung volumes during exercise relative to men. These pulmonary limitations may ultimately lead to greater levels of diaphragmatic fatigue in women. Accordingly, the purpose of this study was to determine whether there are sex differences in the prevalence and severity of exercise-induced diaphragmatic fatigue in 38 healthy endurance-trained men (n = 19; maximal aerobic capacity = 64.0 ± 1.9 ml·kg–1·min–1) and women (n = 19; maximal aerobic capacity = 57.1 ± 1.5 ml·kg–1·min–1). Transdiaphragmatic pressure (Pdi) was calculated as the difference between gastric and esophageal pressures. Inspiratory pressure-time products of the diaphragm and esophagus were calculated as the product of breathing frequency and the Pdi and esophageal pressure time integrals, respectively. Cervical magnetic stimulation was used to measure potentiated Pdi twitches (Pdi,tw) before and 10, 30, and 60 min after a constant-load cycling test performed at 90% of peak work rate until exhaustion. Diaphragm fatigue was considered present if there was a 15% reduction in Pdi,tw after exercise. Diaphragm fatigue occurred in 11 of 19 men (58%) and 8 of 19 women (42%). The percent drop in Pdi,tw at 10, 30, and 60 min after exercise in men (n = 11) was 30.6 ± 2.3, 20.7 ± 3.2, and 13.3 ± 4.5%, respectively, whereas results in women (n = 8) were 21.0 ± 2.1, 11.6 ± 2.9, and 9.7 ± 4.2%, respectively, with sex differences occurring at 10 and 30 min (P < 0.05). Men continued to have a reduced contribution of the diaphragm to total inspiratory force output (pressure-time product of the diaphragm/pressure-time product of the esophagus) during exercise, whereas diaphragmatic contribution in women changed very little over time. The findings from this study point to a female diaphragm that is more resistant to fatigue relative to their male counterparts

    Enantiomerically pure phosphonated carbocyclic 2'-oxa-3'-azanucleosides: synthesis and biological evaluation

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    Starting from enantiomeric pure 1-[(3S,5R)- and 1-[(3R,5S)-3-(hydroxymethyl)-2-methylisoxazolidin-5-yl]-5-methylpyrimidine-2,4(1H,3H)-diones (-)7a and (+)7b, obtained by lipase-catalyzed resolution, pure diethyl{[(3S,5R)-2-methyl-5-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)isoxazolidin-3-yl]methyl}phosphonate (-)12a and diethyl{[(3R,5S)-2-methyl-5-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)isoxazolidin-3-yl]methyl}phosphonate (+)12b have been synthesized. The obtained compounds showed no cytotoxic activity versus the U937 cell line in comparison with AZT, and were poorly able to inhibit HIV infection in vitro

    Quantum three-body system in D dimensions

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    The independent eigenstates of the total orbital angular momentum operators for a three-body system in an arbitrary D-dimensional space are presented by the method of group theory. The Schr\"{o}dinger equation is reduced to the generalized radial equations satisfied by the generalized radial functions with a given total orbital angular momentum denoted by a Young diagram [μ,ν,0,...,0][\mu,\nu,0,...,0] for the SO(D) group. Only three internal variables are involved in the functions and equations. The number of both the functions and the equations for the given angular momentum is finite and equal to (μν+1)(\mu-\nu+1).Comment: 16 pages, no figure, RevTex, Accepted by J. Math. Phy

    Quality indicators: developing 'MOOCs' in the European Higher Education Area

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    The objective of this research is to design an integrated system of evaluation of the quality of the Massive Open Online Courses (MOOC) taking into account the features of this type of courses. The criteria included in the evaluation of the quality of e-learning training in a broad sense are considered, and specifically those developed for the MOOCs. Using a quantitative, descriptive and sectional design, a team of experts have valued those indicators proposed by the scientific literature. To do this, eight courses, focusing on the field of entrepreneurship and innovation, were selected. Most of the analysed courses meet designated quality criteria by having a clear and organized academic structure. In addition, each course states clearly the timing and hours of dedication by the learner. However, only a few courses do that on the open Internet and on their own academic institutions' websites. None of the MOOCs establishes the admission requirements. The main contribution of the current research is that it gives MOOC developers some quality indicators, related to course design and platform, to better plan their applied design and implementation, which has a decisive positive impact on the educational quality of such e-learning platforms

    Gravitational collapse in an expanding background and the role of substructure II: Excess power at small scales and its effect of collapse of structures at larger scales

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    We study the interplay of clumping at small scales with the collapse and relaxation of perturbations at larger scales using N-Body simulations. We quantify the effect of collapsed haloes on perturbations at larger scales using two point correlation function, moments of counts in cells and mass function. The purpose of the study is twofold and the primary aim is to quantify the role played by collapsed low mass haloes in the evolution of perturbations at large scales, this is in view of the strong effect seen when the large scale perturbation is highly symmetric. Another reason for this study is to ask whether features or a cutoff in the initial power spectrum can be detected using measures of clustering at scales that are already non-linear. The final aim is to understand the effect of ignoring perturbations at scales smaller than the resolution of N-Body simulations. We find that these effects are ignorable if the scale of non-linearity is larger than the average inter-particle separation in simulations. Features in in the initial power spectrum can be detected easily if the scale of these features is in the linear regime, detecting such features becomes difficult as the relevant scales become non-linear. We find no effect of features in initial power spectra at small scales on the evolved power spectra at large scales. We may conclude that in general, the effect on evolution of perturbations at large scales of clumping on small scales is very small and may be ignored in most situations.Comment: Accepted for publication in MNRA

    Quantum four-body system in D dimensions

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    By the method of generalized spherical harmonic polynomials, the Schr\"{o}dinger equation for a four-body system in DD-dimensional space is reduced to the generalized radial equations where only six internal variables are involved. The problem on separating the rotational degrees of freedom from the internal ones for a quantum NN-body system in DD dimensions is generally discussed.Comment: 19 pages, no figure, RevTex, Submitted to J. Math. Phy

    Evaluando los Massive Open Online Courses (MOOCs): Un sistema integrado de calidad en el EEES

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    Comunicació presentada al Congrés Internacional de Docència Universitària i Innovació (CIDUI) 2016. Publicat a la Revista del CIDUIEl objetivo de esta investigación es el diseño de un sistema integrado de evaluación de la calidad de los MOOCs. Para ello se han considerado los criterios de evaluación empleados por diversas instituciones y autores (vg. REACU, ENQUA...). Metodológicamente, se ha aplicado un diseño cuantitativo, descriptivo y seccional para evaluar diversos cursos sobre emprendeduría e innovación. La principal contribución es establecer indicadores de calidad en el desarrollo e implementación de los MOOCs.Vicerrectorat de Política Docent i Lingüística. Programa de Millora i Innovació Docent de la Universitat de Barcelon

    Aprendre a emprendre en el sector audiovisual. El MOOC com a eina per millorar l’empleabilitat.

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    Es presenta la posada en marxa d’una acció d’innovació docent, promoguda des de l'ensenyament de Comunicació Audiovisual de la Facultat de Biblioteconomia i Documentació de la UB, i portada a terme pel Grup Consolidat d’Innovació Docent GIDC-CAV. Aquesta té com a objectius generals crear continguts i recursos digitals sobre l’emprenedoria en l'àmbit de la comunicació audiovisual en format MOOC i el desenvolupament i l’aplicació d’eines de seguiment del procés d’avaluació i d’aprenentatge.Programa de Millora i Innovació Docent de la Universitat de Barcelona - Vicerectorat de Política Docen

    Directrices académico-docentes en el grado de CAV: Un estudio exploratorio multifuente

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    En este artículo se presenta una experiencia de investigación en el marco de los estudios de Comunicación Audiovisual de la Universidad de Barcelona. El objetivo ha sido diseñar las directrices académico-docentes de la materia Proyectos del Grado de Comunicación Audiovisual. Durante los meses de octubre y noviembre de 2012, se realizó un estudio cualitativo descriptivo, de carácter exploratorio y con metodología multifuente para identificar aquellos aspectos que permiten el desarrollo de una propuesta didáctica caracterizada por el desarrollo de las competencias del estudiante. Se optó por realizar dos seminarios prospectivos como técnica de recogida de datos. Esta metodología es considerada especialmente útil para estudiar la generación de representaciones sociales, dado que a partir del debate grupal emerge el significado compartido acerca del tema de discusión. Los informantes fueron identificados como clave por el hecho de ser docentes, egresados y/o empleadores de Comunicación Audiovisual. El análisis de contenido muestra un cierto grado de consenso entre profesores, profesionales y egresados con respecto a los conocimientos/habilidades requeridos por los estudiantes y docentes para el desarrollo de un proyecto audiovisual. Se evidencia la conceptualización del proyecto como un proceso y un producto que requiere la puesta en práctica de conocimientos y habilidades, así como el papel relevante que estudiantes y profesores tienen frente a los empleadores. Así mismo se observa el gap existente entre las competencias descritas en la titulación y las expresadas en los seminarios prospectivos
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