5,575 research outputs found
Strangeness on the nucleon
Observables from parity violation in elastic electron-nucleon scattering and
neutral current quasi-elastic neutrino-nucleus scattering are employed as tools
to improve the current knowledge on the strangeness content in the nucleon.Comment: Proceedings of International Scientific Meeting on Nuclear Physics,
9-13th September 2012. La R\'abida, Huelva, Spai
Parity violation in quasielastic electron-nucleus scattering within the relativistic impulse approximation
We study parity violation in quasielastic (QE) electron-nucleus scattering
using the relativistic impulse approximation. Different fully relativistic
approaches have been considered to estimate the effects associated with the
final-state interactions. We have computed the parity-violating quasielastic
(PVQE) asymmetry and have analyzed its sensitivity to the different ingredients
that enter in the description of the reaction mechanism: final-state
interactions, nucleon off-shellness effects, current gauge ambiguities.
Particular attention has been paid to the description of the weak neutral
current form factors. The PVQE asymmetry is proven to be an excellent
observable when the goal is to get precise information on the axial-vector
sector of the weak neutral current. Specifically, from measurements of the
asymmetry at backward scattering angles good knowledge of the radiative
corrections entering in the isovector axial-vector sector can be gained.
Finally, scaling properties shown by the interference nuclear
responses are also analyzed.Comment: 15 pages, 11 figure
Parity violation and dynamical relativistic effects in reactions
It is well known that coincidence quasielastic reactions are
not appropriate to analyze effects linked to parity violation due the presence
of the fifth electromagnetic (EM) response . Nevertheless, in this
work we develop a fully relativistic approach to be applied to parity-violating
(PV) quasielastic processes. This is of importance as a
preliminary step in the subsequent study of inclusive quasielastic PV
reactions. Moreover, our present analysis allows us to
disentangle effects associated with the off-shell character of nucleons in
nuclei, gauge ambiguities and the role played by the lower components in the
nucleon wave functions, i.e., dynamical relativistic effects. This study can
help in getting clear information on PV effects. Particular attention is paid
to the relativistic plane-wave impulse approximation where the explicit
expressions for the PV single-nucleon responses are shown for the first time.Comment: 39 pages, 9 figure
Global analysis of parity-violating asymmetry data for elastic electron scattering
We perform a statistical analysis of the full set of parity-violating
asymmetry data for elastic electron scattering including the most recent high
precision measurement from -weak. Given the basis of the present analysis,
our estimates appear to favor non-zero vector strangeness, specifically,
positive (negative) values for the electric (magnetic) strange form factors. We
also provide an accurate estimate of the axial-vector nucleon form factor at
zero momentum transfer, . Our study shows to be
importantly reduced with respect to the currently accepted value. We also find
our analysis of data to be compatible with the Standard Model values for the
weak charges of the proton and neutron.Comment: 6 pages, 4 figures, 2 tables. Accepted for publication in PR
Spectrum of slow and super-slow (picosecond to nanosecond) water dynamics around organic and biological solutes
Water dynamics in the solvation shell of solutes plays a very important role in the interaction of biomolecules and in chemical reaction dynamics. However, a selective spectroscopic study of the solvation shell is difficult because of the interference of the solute dynamics. Here we report on the observation of heavily slowed down water dynamics in the solvation shell of different solutes by measuring the low-frequency spectrum of solvation water, free from the contribution of the solute. A slowdown factor of ~50 is observed even for relatively low concentrations of the solute. We go on to show that the effect can be generalized to different solutes including proteins
Mochila y carro escolar: análisis cinemático usando distintas cargas.
Premio Congreso SIBB 2016Introducción. El uso de los carros escolares es cada vez mayor en niños de educación primaria. Para clarificar las recomendaciones entre carro y/o mochila, en este estudio se ha realizado un análisis cinemático transportando distintas cargas con ambas opciones de transporte.Métodos. 14 sujetos fueron evaluados (9.6+1.8 años). Un sistema de captura de movimiento 3D fue utilizado para analizar la locomoción caminando sin carga, llevando una mochila y tirando del carro, ambas con el 10%, 15% y 20% peso corporal (BW) del sujeto. Los parámetros cinemáticos del tronco, pelvis, cadera y rodilla fueron analizados.Resultados. El tronco aumentó la flexión conforme aumentaba el peso del carro y la mochila. La pelvis y cadera aumentaron su flexión caminando con la mochila cargada comparado con caminar sin carga. La cadera aumentó su aducción usando la mochila con el 10% y el 20% BW con respecto al uso del carro, y disminuyó los movimientos de rotación (20% BW). La rodilla no mostró diferencias en ninguno de los planos, tampoco la pelvis ni el tronco en los planos frontal y lateral.Conclusiones. El uso del carro escolar requiere menos adaptaciones que la mochila con las mismas cargas y un comportamiento postural más próximo a caminar sin carga.Peer ReviewedAward-winnin
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