Search results for " Física"
showing 10 items of 920 documents
Modulador acusto-óptico en amplitud de fibra óptica basado en ondas acústicas de flexión
2014
Se reporta un estudio experimental de la operación de un modulador acusto-óptico (MAO) de fibra óptica basado en la interacción acusto-óptica producida por ondas acústicas de flexión estacionarias. Concentramos nuestra atención en los efectos de reducir el diámetro en la fibra óptica como mecanismo para optimizar la respuesta espectral del MAO. Como caso particular reportamos un modulador de 70 ¹m de diametro con una alta profundidad de modulación (60 %), bajas perdidas por inserción (1.3 dB) y un ancho ancho de banda a 3 dB de 40 nm que opera en el rango de los megahertz. Los resultados obtenidos demuestran que el incluir fibras estrechadas se puede considerar como un grado extra de libert…
Persistencia de residuos de disparo en puños de prendas de vestir
2013
La detección de partículas de residuos de disparo (RDD) en las ropas de un sospechoso es una evidencia muy importante en los casos judiciales para determinar si la persona disparó o no un arma de fuego. Sin embargo, debido a simples roces con otras superficies, las partículas asociadas al disparo se pierden por la actividad física de una persona. En este estudio se analizó la permanencia de los RDD retenidos sobre puños de prendas de vestir, luego de disparar una pistola calibre 9mm. Valiéndose de la técnica de Microscopía Electrónica de Barrido (SEM) combinada con Espectrometría de Energía Dispersiva (EDS) se caracterizó la morfología, composición y densidad de los RDD recolectados, tenien…
A Pluto-like radius and a high albedo for the dwarf planet Eris from an occultation
2011
The dwarf planet Eris is a trans-Neptunian object with an orbital eccentricity of 0.44, an inclination of 44 degrees and a surface composition very similar to that of Pluto. It resides at present at 95.7 astronomical units (1ĝ€‰au is the Earth-Sun distance) from Earth, near its aphelion and more than three times farther than Pluto. Owing to this great distance, measuring its size or detecting a putative atmosphere is difficult. Here we report the observation of a multi-chord stellar occultation by Eris on 6 November 2010 ut. The event is consistent with a spherical shape for Eris, with radius 1,163±6 kilometres, density 2.52±0.05 grams per cm 3 and a high visible geometric albedo,. No nitro…
Lesión medular y ejercicio físico: revisión desde una perspectiva deportiva
2016
Una de cada 2000 personas en Europa tiene lesión medular (LM), es normalmente más sedentaria que el resto de la población y encuentra diferentes problemas para practicar ejercicio físico (EF), destacando la escasa formación específica de los profesionales del deporte. Con el objetivo de aportar información sobre la LM y su interacción con la práctica deportiva, se realizó una revisión de literatura científica que analiza sus alteraciones músculoesqueléticas, cardiovasculares, respiratorias, de termorregulación, genitourinarias e intestinales, las úlceras por presión, la disreflexia autonómica y los aspectos nutricionales, generando recomendaciones prácticas. Como conclusión, la práctica hab…
Construcción de puentes y avenidas fluviales: algunos debates técnicos en el academicismo ilustrado del Reino de Valencia
2020
Con el afianzamiento de las políticas reformistas y la consolidación de las academias de bellas artes, durante el último tercio del siglo XVIII se desarrolló una creciente polémica entre los arquitectos y los maestros de obra en torno a la proyección y diseño de obra civil, particularmente la relacionada con ambientes fluviales. En este artículo se valora, con diferentes ejemplos, la incidencia de este debate en la proyección de puentes y su capacidad de resistencia a las avenidas fluviales. During the last third of the 18th century, reformist policies and the consolidation of the fine arts academies were consolidated. This fact affected the architects and the master builders with a policy …
120 min/week of neuromotor multicomponent training are enough to improve executive function and functional fitness in older women.
2021
Purpose: The study aimed at comparing the effects of a neuromotor multicomponent training program (MCTP) on executive function, functional fitness, blood pressure, body composition and health-related quality of life (HRQOL), compared with a concurrent strength and endurance exercise training program (CONTROL-EXE) and a cognitive training program (CONTROL-COG). Methods: 56 older women (73 ± 6 years) completed the 30-weeks intervention. The three groups attended two 60-min sessions per week and they were assessed before and after the intervention. Results: MCTP showed a moderate improvement in Stroop C condition (28 ± 7 vs 32 ± 8 correct items; p = 0.001; d = 0.53) and Stroop interference sco…
Credibility to attract, trust to stay: the mediating role of trust in improving brand congruence in sports services
2021
This research aims to demonstrate the mediating role of brand trust in the relationship between credibility and users' congruence with a sports services brand. The analysis was carried out using EQS 6.3 to perform the four required steps of the analysis (and the Sobel test was conducted for a public sports service and a private sports service. The results confirm the full mediation effect of brand trust in the case of the private service and a partial mediation for the public service. Therefore, this study confirms that credibility, in the presence of trust, ceases to have an influence on the congruence of users with the brand, which suggests that credibility is important at an initial stag…
Kinetic evidence for interaction of TMPyP4 with two different G-quadruplex conformations of human telomeric DNA
2018
Background: Stabilization of G-quadruplex helices by small ligands has attracted growing attention because they inhibit the activity of the enzyme telomerase, which is overexpressed in> 80% cancer cells. TMPyP4, one of the most studied G-quadruplex ligands, is used as a model to show that the ligands can exhibit different binding features with different conformations of a human telomeric specific sequence. Methods: UV–Vis, FRET melting Assay, Isothermal Titration Calorimetry, Time-resolved Fluorescence lifetime, T-Jump and Molecular Dynamics. Results: TMPyP4 yields two different complexes with two Tel22 telomeric conformations in the presence of Na+ or K+. T-Jump kinetic experiments show th…
Validation of the Satisfaction Questionnaire with physical education classes (CSCEF) in the Latin American context
2020
The objective of this study was to validate the Satisfaction Questionnaire in Physical Education Classes (CSCEF) in the context of Latin America (Dominican Republic). 1298 students aged between 15 and 21 participated. The psychometric properties of the instrument were analysed. The results demonstrated that the best factor solution would be a multidimensional model represented by nine dimensions for the satisfaction construct, as well as a higher-order model. According to Cronbach's alpha and omega index, values between .66 and .99 were obtained. The Latin American version of the CSCEF was invariant with respect to gender. Although the results of this study support the validity and reliabil…
The effects of playing tactics on creating scoring opportunities in random matches from US Major League Soccer
2015
The aim of this study was to examine the effects of playing tactics on the creation of scoring opportunities in random matches from US Major League Soccer 2014, taking into account both contextual and defensive variables. The sample included 3253 team possessions corresponding to 30 randomly selected matches. Multidimensional qualitative data from 10 categorical variables was analysed by means of descriptive analysis and multiple logistic regression analysis. Contextual variables such as match location (p=0.049), match half (p=0.043) and match status (P=0.032) were associated with creating scoring opportunities. With regards playing tactics, set plays created a higher proportion of scoring …