2,445 research outputs found
Análisis cinemático del viraje en el esquí alpino de competición
Esta comunicación trata sobre la aplicación de la Biomecánica Deportiva como perspectiva
científica, al análisis cinemático del esquí alpino como objeto de estudio, y ha sido realizada
basándose en una situación real de competición como fue el Campeonato del Mundo de 1996
celebrado en Sierra Nevada (Granada). Para el análisis de la muestra, utilizamos la metodología
y las tecnologías propias de la biomecánica Deportiva como son el método indirecto y las técnicas
fotogramétricas tridimensionales, basadas en la filmación del gesto deportivo utilizando el vídeo.
Los resultados obtenidos muestran la existencia de un patrón general de movimiento en la
muestra de esquiadoras analizadas en cuanto a las velocidades tangenciales medias del CG(S).del
sistema (esquiador más implementos). Entre las conclusiones, destacamos la existencia de una
reducción de la velocidad tangencial media resultante en el recorrido analizado que es mayor aún,
en el instante de paso del palo de viraje en particular y cuanto más curva es la trayectoria. Atendiendo
a la desviación típica del comportamiento de la velocidad media resultante, podemos decir
que en este tramo de paso de la puerta encontramos las diferencias entre la técnica individual de
las esquiadoras analizadas.
Este estudio nos confirma la importancia del entrenamiento en situación real de competición
(en cuanto a material, características pista de entrenamiento, etc.
Quasi-exact solvability beyond the SL(2) algebraization
We present evidence to suggest that the study of one dimensional
quasi-exactly solvable (QES) models in quantum mechanics should be extended
beyond the usual \sla(2) approach. The motivation is twofold: We first show
that certain quasi-exactly solvable potentials constructed with the \sla(2)
Lie algebraic method allow for a new larger portion of the spectrum to be
obtained algebraically. This is done via another algebraization in which the
algebraic hamiltonian cannot be expressed as a polynomial in the generators of
\sla(2). We then show an example of a new quasi-exactly solvable potential
which cannot be obtained within the Lie-algebraic approach.Comment: Submitted to the proceedings of the 2005 Dubna workshop on
superintegrabilit
870 micron continuum observations of the bubble-shaped nebula Gum 31
We are presenting here a study of the cold dust in the infrared ring nebula
Gum 31. We aim at deriving the physical properties of the molecular gas and
dust associated with the nebula, and investigating its correlation with the
star formation in the region, that was probably triggered by the expansion of
the ionization front. We use 870 micron data obtained with LABOCA to map the
dust emission. The obtained LABOCA image was compared to archival IR,radio
continuum, and optical images. The 870 micron emission follows the 8 micron
(Spitzer), 250 micron, and 500 micron (Herschel) emission distributions showing
the classical morphology of a spherical shell. We use the 870 micron and 250
micron images to identify 60 dust clumps in the collected layers of molecular
gas using the Gaussclumps algorithm. The clumps have effective deconvolved
radii between 0.16 pc and 1.35 pc, masses between 70 Mo and 2800 Mo, and volume
densities between 1.1x10^3 cm^-3 and 2.04x10^5 cm^-3. The total mass of the
clumps is 37600 Mo. The dust temperature of the clumps is in the range from 21
K to 32 K, while inside the HII region reaches ~ 40 K. The clump mass
distribution is well-fitted by a power law dN/dlog(M/Mo) proportional to
M^(-alpha), with alpha=0.93+/-0.28. The slope differs from those obtained for
the stellar IMF in the solar neighborhood, suggesting that the clumps are not
direct progenitors of single stars/protostars. The mass-radius relationship for
the 41 clumps detected in the 870 microns emission shows that only 37% of them
lie in or above the high-mass star formation threshold, most of them having
candidate YSOs projected inside. A comparison of the dynamical age of the HII
region with the fragmentation time, allowed us to conclude that the collect and
collapse mechanism may be important for the star formation at the edge of Gum
31, although other processes may also be acting.Comment: 15 pages, 10 figures. Accepted for publication in A&
New Algebraic Quantum Many-body Problems
We develop a systematic procedure for constructing quantum many-body problems
whose spectrum can be partially or totally computed by purely algebraic means.
The exactly-solvable models include rational and hyperbolic potentials related
to root systems, in some cases with an additional external field. The
quasi-exactly solvable models can be considered as deformations of the previous
ones which share their algebraic character.Comment: LaTeX 2e with amstex package, 36 page
Numerical study of the aerodynamics of sound sources in a bass-reflex port
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.The aim of this paper is to study the aerodynamics phenomena of a bass-reflex port that causes noise in the audible frequency range. After discarding structural and mechanical vibration issues, the hypothesis considered is that vortex shedding is the source of the noise. Experimental and numerical evidences of the vortex, an analysis of its noise and the similarities between real and simulated performance are presented. The numerically simulated cases with the original geometry are excited at different frequencies and with modifications of the port geometry. Likewise, the internal performance of an enclosure with a closed port was simulated. The simulations have been performed with axisymmetrical geometries using the open-source OpenFOAM® toolbox. Moreover, experimental measurements were carried out. First, acoustic signal experiments were done to analyse the response of the bass-reflex ports. Secondly, a structure vibration measurement was conducted in order to exclude the cabinet structure vibration as a source of the noise in question. A good agreement was found between numerical and experimental results, especially in the frequency band of the detected noise, i.e. the 1000–1500 Hz range. Despite no remarkable improvement being made with the geometry changes explored, the presented CFD approach has proved a useful and cost-effective tool to address this kind of phenomenon.Peer ReviewedPostprint (published version
Failure analysis of prestressed anchor bars
Three broken steel bars from a sewed crack in a dam are reported. The inspection of the fracture surfaces of the prestressed bars suggests that fractures were triggered by small cracks and by the inherent brittleness of the bars, as fracture toughness was about 40 MPa m1/2. The analysis of the failures shows that the usual design requirements for prestressing bars fail to warn against brittle failures if some damage exists. Some recommendations, based on the concept of damage tolerance, are suggested to avoid similar unfortunate incidents
Additional restrictions on quasi-exactly solvable systems
In this paper we discuss constraints on two-dimensional quantum-mechanical
systems living in domains with boundaries. The constrains result from the
requirement of hermicity of corresponding Hamiltonians. We construct new
two-dimensional families of formally exactly solvable systems and applying such
constraints show that in real the systems are quasi-exactly solvable at best.
Nevertheless in the context of pseudo-Hermitian Hamiltonians some of the
constructed families are exactly solvable.Comment: 11 pages, 3 figures, extended version of talk given at the
International Workshop on Classical and Quantum Integrable Systems "CQIS-06",
Protvino, Russia, January 23-26, 200
Eficacia de un programa para el tratamiento del sobrepeso y la obesidad no mórbida en atención primaria y su influencia en la modificación de estilos de vida
Introducción y Objetivos: la modificación de conductas
no saludables es fundamental para tratar la obesidad. El
objetivo de este estudio fue evaluar los efectos de un
programa basado en dieta, ejercicio y apoyo psicológico
en la modificación conductual de pacientes con sobrepeso
y obesidad tratados en Atención Primaria.
Métodos: 60 pacientes con sobrepeso grado II y
obesidad grado I-II fueron incluidos en este ensayo piloto.
Edad entre 18-50 años. Los pacientes recibieron un
programa que combinaba educación nutricional, actividad
física y apoyo psicológico. Formato grupal, periodicidad
quincenal. Los principales resultados medidos al
inicio y 6 meses fueron parámetros antropométricos
(índice de masa corporal, porcentaje de masa grasa, perímetro
cintura) y de estilos de vida usando el Cuestionario
para la valoración de hábitos de vida relacionados con el
sobrepeso y la obesidad. Consta de 5 dimensiones: contenido
calórico de la dieta (CC), alimentación saludable
(AS), ejercicio físico (EF), comer por bienestar psicológico
(BP) y consumo de alcohol (CA). La mayor puntuación
indica mejores hábitos para CC, AS y EF y peores
para BP y CA.
Resultados: al final de la intervención mejoraron las
escalas CC (2,60± 0,5 vs 3,49± 0,7, p<0,001), EF (2,19± 0,9
vs 3,17± 1,0, p<0,001) y AS (3,04± 0,4 vs 3,43± 0,4, p<0,05)
del cuestionario; CA (3,98± 0,7 vs. 4,25± 0,7, p<0,05) y BP
(2,82± 1,0 vs. 3,34± 0,7, p<0,001) empeoraron.
Conclusión: el programa basado en moderada restricción
de la dieta, aumento de actividad física y apoyo psicológico
puede mejorar parámetros antropométricos y
estilos de vida en pacientes obesos tratados en un centro
de Atención PrimariaBackground: Lifestyle intervention is fundamental for
obesity treatment. The aim of this study was to evaluate the
effects of a program focused on diet, exercise and psychological
support on Lifestyle Modification in overweight and
obese patients treated in Primary Health Care setting.
Methods: 60 patients with grade II overweight and
non-morbid grade I-II obesity were included in this pilot
clinical trial. Ages ranged from18 to 50 years. They were
provided with a program combining nutritional education,
physical activity and psychological support.
Subjects attended group sessions every 2 weeks. The main
outcome measures at baseline and 6 months were body
composition parameters (BMI, body fat percentage, waist
circumference) and lifestyle intervention using the Questionnaire
for the assessment of overweight and obesity
related lifestyles at baseline and six months. This questionnaire
yields an five dimensions: diet caloric intake
(CC), healthy eating (AS), physical activity (EF), searching
for psychological well-being eating (BP) and
alcohol intake (CA). The higher score indicates better
lifestyles for CC, AS, EF and worse for BP y CA.
Results: At the end of the intervention the program
achieved improvements in Questionnaire related
lifestyles subscales: CC (2,60± 0,5 vs. 3,49± 0,7, p<0,001),
EF (2,19± 0,9 vs. 3,17± 1,0, p<0,001) and AS (3,04± 0,4 vs.
3,43± 0,4, p<0,05); CA (3,98± 0,7 vs. 4,25± 0,7, p<0,05)
and BP (2,82± 1,0 vs. 3,34± 0,7, p<0,001) has got worse.
Conclusion: The Program focused on balanced and
moderate energy-restricted diets, increased physical activity
and psychological support may improve the anthropometric
parameters and the Lifestyle intervention in
obese patients treated in a primary healthcare center.Este proyecto ha sido becado por el Ministerio de
Ciencia e Innovación, a través del Instituto de Salud
Carlos III y la Subdirección General de Evaluación y
Fomento de la Investigación, en el marco del «Subprograma
de Proyectos de Investigación de Evaluación de
Tecnologías Sanitarias e Investigación en servicios de
salud». Convocatoria 2008 de ayudas de la Acción
Estratégica en Salud, en el marco del Plan Nacional de
I+D+I 2008-2011 (PI08/90357). Y por la Fundación
MAPFRE, a través del programa de Ayudas a la Investigación
(2009
The Potential Role of Everlasting Flower (Helichrysum stoechas Moench) as an Antihypertensive Agent: Vasorelaxant Effects in the Rat Aorta
Helichrysum stoechas (L.) Moench (H. stoechas) is a medicinal plant traditionally used in the Iberian Peninsula to treat different disorders such as arterial hypertension. The aim of this study was to investigate the vascular effects of a polyphenolic methanolic extract of H. stoechas, which has high antioxidant activity, and its mechanism of action. Isometric myography studies were performed in an organ bath with rat aortic rings with intact endothelium. The H. stoechas extract produced vasorelaxation in the aortic rings that were precontracted by phenylephrine or KCl. L-NAME and Rp-8-Br-PET-cGMPS but not indomethacin or H-89; it also reduced the relaxant response evoked by H. stoechas extract on the phenylephrine-induced contractions. H. stoechas extract reduced the response to CaCl2 similar to verapamil and reduced the phenylephrine-induced contractions comparable with heparin. TRAM-34, apamin and glibenclamide reduced relaxation induced by the H. stoechas extract. The combination of L-NAME+TRAM-34+apamin almost completely inhibited the H. stoechas-induced effect. In conclusion, the relaxant effect of the H. stoechas extract is partially mediated by endothelium through the activation of the NO/PKG/cGMP pathway and the opening of Ca2+-activated K+ channels. Furthermore, the decrease in the cytosolic Ca2+ by the inhibition of Ca2+ influx through the L-type Ca2+ channels and by the reduction of Ca2+ release from the sarcoplasmic reticulum via the IP3 pathway is also involved. © 2022 by the authors. Licensee MDPI, Basel, Switzerland
Differential hippocampal response to chronic alcohol consumption of young adult and mature adult rats
AIMS Early ethanol consumption could be a risk factor for young brain integrity and its maturation, and also for the development of addictive behaviors in adulthood. Neuronal nitric oxide synthase (nNOS) expressing neurons are specifically located in the subgranular layer (SGL) of dentate gyrus and may be relevant for hippocampal neurogenesis. The focus of this work is aimed to determine local changes in the nNOS-like immunoreactive (nNOS-LIR) cell populations of the SGL after chronic ethanol exposure in young adult and mature adult rats. METHODS We used the nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase (NADPH-d) reaction as a qualitative marker of nNOS enzyme activity. We also analyzed the nNOS-LIR cell density by the nNOS immunocytochemistry in order to compare these two methods of labeling. Dorsal striatum (CPu) was also analyzed in order to compare two neural areas with high nNOS-LIR cell density. RESULTS The young adult group showed less hippocampal NADPH-d(+) cell density than the mature adult group. Interestingly, the NADPH-d(+) cell density was increased in the SGL of the young adult ethanol-treated group, whereas it decreased in the mature adult ethanol-treated group, when compared with their respective controls. No change was observed in any of the groups for the hippocampal nNOS-LIR cell density and no differences could be established in CPu for nNOS-LIR and NADPH-d(+) cell densities in any of the groups studied. CONCLUSION The NADPH-d expression is affected by chronic ethanol exposure in opposite ways between both age groups studied. Further studies are needed to evaluate the relative importance of these findings, especially when considering human subject
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