311 research outputs found
Estudio del apoyo metatarsal en bipedestación mediante podoscopio electrónico de alta resolución.
Con el jin de estudiar el apoyo metatarsal en bipedestación se
han realizado 780 registros en la plataforma PDS 93, correspondientes
a 390 individuos, no seleccionados, sin patología de la
marcha, 234 varones y 156 mujeres, con edades comprendidas
entre 24 y 41 años (edad media de 29,9 años).
En cada registro se ha recogido la presión ejercida por cada metatarsiano,
relacionando la carga obtenida con el peso, conjiguración
mecánica del pie y huella plantar: Los resultados obtenidos se
han procesado estadísticamente por medio del programa SPSS.
El porcentaje de las cargas medias obtenidas para cada metatarsiano
han sido: 16,85, 21,25, 23,88, 20,24 y 17,78%, existiendo
dqerencias sign$cativas para el apoyo de los metatarsianos
centrales (p < 0,001).
Todos los metatarsianos soportan carga en bipedestación, de
acuerdo con las teorías actuales. Sin embargo, aunque la distribución
del peso para el primer metatarsiano se aproxima al doble
de los otros, la carga máxima en g/cm2 se realiza en los metatarsianos
centrales
Damping mechanisms for oscillations in solar prominences
Small amplitude oscillations are a commonly observed feature in
prominences/filaments. These oscillations appear to be of local nature, are
associated to the fine structure of prominence plasmas, and simultaneous flows
and counterflows are also present. The existing observational evidence reveals
that small amplitude oscillations, after excited, are damped in short spatial
and temporal scales by some as yet not well determined physical mechanism(s).
Commonly, these oscillations have been interpreted in terms of linear
magnetohydrodynamic (MHD) waves, and this paper reviews the theoretical damping
mechanisms that have been recently put forward in order to explain the observed
attenuation scales. These mechanisms include thermal effects, through
non-adiabatic processes, mass flows, resonant damping in non-uniform media, and
partial ionization effects. The relevance of each mechanism is assessed by
comparing the spatial and time scales produced by each of them with those
obtained from observations. Also, the application of the latest theoretical
results to perform prominence seismology is discussed, aiming to determine
physical parameters in prominence plasmas that are difficult to measure by
direct means.Comment: 36 pages, 16 figures, Space Science Reviews (accepted
Atmospheric Heating and Wind Acceleration: Results for Cool Evolved Stars based on Proposed Processes
A chromosphere is a universal attribute of stars of spectral type later than
~F5. Evolved (K and M) giants and supergiants (including the zeta Aurigae
binaries) show extended and highly turbulent chromospheres, which develop into
slow massive winds. The associated continuous mass loss has a significant
impact on stellar evolution, and thence on the chemical evolution of galaxies.
Yet despite the fundamental importance of those winds in astrophysics, the
question of their origin(s) remains unsolved. What sources heat a chromosphere?
What is the role of the chromosphere in the formation of stellar winds? This
chapter provides a review of the observational requirements and theoretical
approaches for modeling chromospheric heating and the acceleration of winds in
single cool, evolved stars and in eclipsing binary stars, including physical
models that have recently been proposed. It describes the successes that have
been achieved so far by invoking acoustic and MHD waves to provide a physical
description of plasma heating and wind acceleration, and discusses the
challenges that still remain.Comment: 46 pages, 9 figures, 1 table; modified and unedited manuscript;
accepted version to appear in: Giants of Eclipse, eds. E. Griffin and T. Ake
(Berlin: Springer
Atomic layering at the liquid silicon surface: a first- principles simulation
We simulate the liquid silicon surface with first-principles molecular
dynamics in a slab geometry. We find that the atom-density profile presents a
pronounced layering, similar to those observed in low-temperature liquid metals
like Ga and Hg. The depth-dependent pair correlation function shows that the
effect originates from directional bonding of Si atoms at the surface, and
propagates into the bulk. The layering has no major effects in the electronic
and dynamical properties of the system, that are very similar to those of bulk
liquid Si. To our knowledge, this is the first study of a liquid surface by
first-principles molecular dynamics.Comment: 4 pages, 4 figures, submitted to PR
SPIDER: Probing the Early Universe with a Suborbital Polarimeter
We evaluate the ability of SPIDER, a balloon-borne polarimeter, to detect a
divergence-free polarization pattern ("B-modes") in the Cosmic Microwave
Background (CMB). In the inflationary scenario, the amplitude of this signal is
proportional to that of the primordial scalar perturbations through the
tensor-to-scalar ratio r. We show that the expected level of systematic error
in the SPIDER instrument is significantly below the amplitude of an interesting
cosmological signal with r=0.03. We present a scanning strategy that enables us
to minimize uncertainty in the reconstruction of the Stokes parameters used to
characterize the CMB, while accessing a relatively wide range of angular
scales. Evaluating the amplitude of the polarized Galactic emission in the
SPIDER field, we conclude that the polarized emission from interstellar dust is
as bright or brighter than the cosmological signal at all SPIDER frequencies
(90 GHz, 150 GHz, and 280 GHz), a situation similar to that found in the
"Southern Hole." We show that two ~20-day flights of the SPIDER instrument can
constrain the amplitude of the B-mode signal to r<0.03 (99% CL) even when
foreground contamination is taken into account. In the absence of foregrounds,
the same limit can be reached after one 20-day flight.Comment: 29 pages, 8 figures, 4 tables; v2: matches published version, flight
schedule updated, two typos fixed in Table 2, references and minor
clarifications added, results unchange
Mesophyll porosity is modulated by the presence of functional stomata
The formation of stomata and leaf mesophyll airspace must be coordinated to establish an efficient and robust network that facilitates gas exchange for photosynthesis, however the mechanism by which this coordinated development occurs remains unclear. Here, we combine microCT and gas exchange analyses with measures of stomatal size and patterning in a range of wild, domesticated and transgenic lines of wheat and Arabidopsis to show that mesophyll airspace formation is linked to stomatal function in both monocots and eudicots. Our results support the hypothesis that gas flux via stomatal pores influences the degree and spatial patterning of mesophyll airspace formation, and indicate that this relationship has been selected for during the evolution of modern wheat. We propose that the coordination of stomata and mesophyll airspace pattern underpins water use efficiency in crops, providing a target for future improvement
Physics of Solar Prominences: II - Magnetic Structure and Dynamics
Observations and models of solar prominences are reviewed. We focus on
non-eruptive prominences, and describe recent progress in four areas of
prominence research: (1) magnetic structure deduced from observations and
models, (2) the dynamics of prominence plasmas (formation and flows), (3)
Magneto-hydrodynamic (MHD) waves in prominences and (4) the formation and
large-scale patterns of the filament channels in which prominences are located.
Finally, several outstanding issues in prominence research are discussed, along
with observations and models required to resolve them.Comment: 75 pages, 31 pictures, review pape
La Cueva de El Sidrón (Piloña Asturias)
Estado de las excavaciones y estudios en la Cueva de El Sidrón (PIloña, Asturias)
Model-independent search for CP violation in D0→K−K+π−π+ and D0→π−π+π+π− decays
A search for CP violation in the phase-space structures of D0 and View the MathML source decays to the final states K−K+π−π+ and π−π+π+π− is presented. The search is carried out with a data set corresponding to an integrated luminosity of 1.0 fb−1 collected in 2011 by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. For the K−K+π−π+ final state, the four-body phase space is divided into 32 bins, each bin with approximately 1800 decays. The p-value under the hypothesis of no CP violation is 9.1%, and in no bin is a CP asymmetry greater than 6.5% observed. The phase space of the π−π+π+π− final state is partitioned into 128 bins, each bin with approximately 2500 decays. The p-value under the hypothesis of no CP violation is 41%, and in no bin is a CP asymmetry greater than 5.5% observed. All results are consistent with the hypothesis of no CP violation at the current sensitivity
Search for the lepton-flavor-violating decays Bs0→e±μ∓ and B0→e±μ∓
A search for the lepton-flavor-violating decays Bs0→e±μ∓ and B0→e±μ∓ is performed with a data sample, corresponding to an integrated luminosity of 1.0 fb-1 of pp collisions at √s=7 TeV, collected by the LHCb experiment. The observed number of Bs0→e±μ∓ and B0→e±μ∓ candidates is consistent with background expectations. Upper limits on the branching fractions of both decays are determined to be B(Bs0→e±μ∓)101 TeV/c2 and MLQ(B0→e±μ∓)>126 TeV/c2 at 95% C.L., and are a factor of 2 higher than the previous bounds
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