8,659 research outputs found
Serve profile of male and female professional tennis players at the 2015 Roland Garros Grand Slam tournament
The aim of this study was to compare the serve statistics profile of male and female high-level tennis players. In all, 111 tennis singles matches of the Roland Garros 2015 tennis tournament were collected and 10 variables related to first and second serve were analyzed according to service box (deuce and advantage sides) and landing location (wide, body and T-areas). The results show: (a) men served faster than women; (b) men served a higher percentage of serves at T-area on deuce side (35.0 vs 27.7%) and at the wide zone on advantage side (44.1 vs 36.7%) with first serves, while women hit more to the body on both sides; (c) men won a higher percentage of points with their first serve compared to women at any zone on both sides, except for the T-area on deuce side; (d) with their second serve, men placed a greater percentage of serves in the T-area on deuce side (28.0 vs 21.8%) and wide on the advantage side, whereas women directed more to the body on the advantage side (41.4 vs 33.5%); (e) men won a higher percentage of points with their second serve when they placed it to the body zone on deuce side (54.1 vs 47.1%) and at the T-area on the advantage side (64.4% vs 44.1%). Our conclusions are that with respect to gender, players showed differing serve patterns. Men served faster, with higher success and placed their serves more frequently to the external areas of the service boxes, while women directed a higher percentage of serves to the body of their opponent
Svq: a proposal for still image coding in mpeg 4 - snhc
A technique for efficient coding of homogeneous textures is presented here. The technique is based on the use of Stochastic Vector Quantization and provides very high compression with graceful degradation. To encode the image, a linear prediction filter is computed. Then, the prediction error is encoded using a Stochastic Vector Quantization approach. To decode the image, the prediction error is decoded first and then filtered as a whole using the prediction filter, thus avoiding the block effect found in conventional VQ. The approach has been proposed as a still image coding technique in MPEG 4 SNHC. Comparisons with the Video VM of MPEG 4 are also presentedPeer ReviewedPostprint (published version
White dwarf constraints on a varying
A secular variation of modifies the structure and evolutionary time
scales of white dwarfs. Using an state-of-the-art stellar evolutionary code, an
up-to-date pulsational code, and a detailed population synthesis code we
demonstrate that the effects of a running are obvious both in the
properties of individual white dwarfs, and in those of the white dwarf
populations in clusters. Specifically, we show that the white dwarf
evolutionary sequences depend on both the value of , and on the value
of when the white dwarf was born. We show as well that the pulsational
properties of variable white dwarfs can be used to constrain .
Finally, we also show that the ensemble properties of of white dwarfs in
clusters can also be used to set upper bounds to . Precisely, the
tightest bound --- yr --- is obtained
studying the population of the old, metal-rich, well populated, open cluster
NGC 6791. Less stringent upper limits can be obtained comparing the theoretical
results obtained taking into account the effects of a running with the
measured rates of change of the periods of two well studied pulsating white
dwarfs, G117--B15A and R548. Using these white dwarfs we obtain yr, and
yr, respectively, which although less restrictive than the previous
bound, can be improved measuring the rate of change of the period of massive
white dwarfs.Comment: 6 pages, 3 figures. To be published in the proceedings of the
conference "Varying fundamental constants and dynamical dark energy" (8 - 13
July 2013, Sexten Center for Astrophysics
New objects in old structures: The Iron Age hoard of the Palacio III megalithic funerary complex (Almadén de la Plata, Seville, Spain)
Cultural contact, exchange and interaction feature high in the list of challenging topics of current research on European Prehistory. Not far off is the issue of the changing role of monuments in the making and maintaining of key cultural devices such as memory and identity. Addressing both these highly-debated issues from a science-based perspective, in this paper we look at an unusual case study set in southern Iberia and illustrate how these archaeological questions can benefit from robust materials-science approaches.We present the contextual, morphological and analytical study of an exceptional Early Iron Age hoard composed of a number of different (and mostly exotic) materials such as amber, quartz, silver and ceramic. This hoard, found under the fallen orthostat of a megalithic structure built at least 2000 years earlier, throws new light on long-distance exchange networks and the effect they could have had on the cultural identities and social relations of local Iberian Early Iron Age communities. Moreover, the archaeometric study reveals how diverse and distant the sources of these item are (Northern Europe to Eastern and Western Mediterranean raw materials, as well as local and eastern technologies), therefore raising questions concerning the social mechanisms used to establish change and resistance in contexts of colonial encounter
Anderson Photon-Phonon Colocalization in Certain Random Superlattices
International audienceFundamental observations in physics ranging from gravitational wave detection to laser cooling of a nanomechanical oscillator into its quantum ground state rely on the interaction between the optical and the mechanical degrees of freedom. A key parameter to engineer this interaction is the spatial overlap between the two fields, optimized in carefully designed resonators on a case-by-case basis. Disorder is an alternative strategy to confine light and sound at the nanoscale. However, it lacks an a priori mechanism guaranteeing a high degree of colocalization due to the inherently complex nature of the underlying interference processes. Here, we propose a way to address this challenge by using GaAs=AlAs vertical distributed Bragg reflectors with embedded geometrical disorder. Because of a remarkable coincidence in the physical parameters governing light and motion propagation in these two materials, the equations for both longitudinal acoustic waves and normal-incidence light become practically equivalent for excitations of the same wavelength. This guarantees spatial overlap between the electromagnetic and displacement fields of specific photon-phonon pairs, leading to strong light-matter interaction. In particular, a statistical enhancement in the vacuum optomechanical coupling rate, g o , is found, making this system a promising candidate to explore Anderson localization of high frequency (∼20 GHz) phonons enabled by cavity optomechanics. The colocalization effect shown here unlocks the access to unexplored localization phenomena and the engineering of light-matter interactions mediated by Anderson-localized states
A white dwarf cooling age of 8 Gyr for NGC 6791 from physical separation processes
NGC 6791 is a well studied open cluster1 that it is so close to us that can
be imaged down to very faint luminosities. The main sequence turn-off age (~8
Gyr) and the age derived from the termination of the white dwarf cooling
sequence (~6 Gyr) are significantly different. One possible explanation is that
as white dwarfs cool, one of the ashes of helium burning, 22Ne, sinks in the
deep interior of these stars. At lower temperatures, white dwarfs are expected
to crystallise and phase separation of the main constituents of the core of a
typical white dwarf, 12C and 16O, is expected to occur. This sequence of events
is expected to introduce significant delays in the cooling times, but has not
hitherto been proven. Here we report that, as theoretically anticipated,
physical separation processes occur in the cores of white dwarfs, solving the
age discrepancy for NGC 6791.Comment: 3 pages, 2 figures, published in Natur
NIRS potential use for the determination of natural resources quality from dehesa (acorn and grass) in Montanera system for Iberian pigs.
NIRS technology has been used as an alternative to conventional methods to determinate the content of nutrients of acorns and grass from dehesa ecosystem. Dry matter (DM), crude fat (CF), crude protein (CP), starch, total phenolic compounds (TP), α-tocopherol, γ-tocopherol, fatty acids, neutral detergent fiber (NDF), total antioxidant activity (TAA) and total energy (TE) were determined by conventional methods for later development of NIRS predictive equations. The NIR spectrum of each sample was collected and for all studied parameters, a predictive model was obtained and external validated. Good prediction equations were obtained for moisture, crude fat, crude protein, total energy and γ-tocopherol in acorns samples, with high coefficients of correlation (1-VR) and low standard error of prediction (SEP) (1-VR=0.81, SEP=2.62; 1-VR=0.92, SEP=0.54; 1-VR=0.86, SEP=0.47; 1-VR=0.84, SEP=0.2; 1-VR=0.88, SEP=5.4, respectively) and crude protein, NDF, α-tocopherol and linolenic acid content in grass samples (1-VR=0.9, SEP=1.99; 1-VR=0.87, SEP=4.13; 1-VR=0.76, SEP=10.9; 1-VR=0.82, SEP=0.6, respectively). Therefore, these prediction models could be used to determinate the nutritional composition of Montanera natural resources
Charged Scalar-Tensor Boson Stars: Equilibrium, Stability and Evolution
We study charged boson stars in scalar-tensor (ST) gravitational theories. We
analyse the weak field limit of the solutions and analytically show that there
is a maximum charge to mass ratio for the bosons above which the weak field
solutions are not stable. This charge limit can be greater than the GR limit
for a wide class of ST theories. We numerically investigate strong field
solutions in both the Brans Dicke and power law ST theories. We find that the
charge limit decreases with increasing central boson density. We discuss the
gravitational evolution of charged and uncharged boson stars in a cosmological
setting and show how, at any point in its evolution, the physical properties of
the star may be calculated by a rescaling of a solution whose asymptotic value
of the scalar field is equal to its initial asymptotic value. We focus on
evolution in which the particle number of the star is conserved and we find
that the energy and central density of the star decreases as the cosmological
time increases. We also analyse the appearance of the scalarization phenomenon
recently discovered for neutron stars configurations and, finally, we give a
short discussion on how making the correct choice of mass influences the
argument over which conformal frame, the Einstein frame or the Jordan frame, is
physical.Comment: RevTeX, 27 pages, 9 postscript figures. Minor revisions and updated
references. Accepted for publication in Phys. Rev.
Estudio comparativo de los parámetros calidad de la leche, características tecnológicas y producción quesera de la Raza Merina de Grazalema frente al cruce con razas foráneas
En los últimos años se están incorporando masivamente
en España, en general, y en Andalucía, en
particular, razas ovinas foráneas de aptitud lechera,
fundamentalmente las razas Assaf, Awassi y Lacaune.
Su introducción está fomentando, asimismo, la realización
de cruces indiscriminados con nuestras razas
ovinas autóctonas, de aptitud lechera pero de menor
especialización, al menos cuantitativamente (Casas et
al., 2005).
El objetivo de este estudio ha sido analizar en dos
grupos de animales de un mismo rebaño (ovejas puras
de raza Merina de Grazalema, y ovejas cruzadas
Merina de Grazalema x Awassi) las características de
la producción lechera, y proceder a la elaboración de
quesos para estudiar las posibles diferencias tecnológicas
de los quesos derivados de ambas elaboraciones.
A través del mismo se ha comprobado una mayor producción
lechera de las ovejas cruzadas (167.35±13.20
kg frente a 136.84±4.25 kg) pero con un porcentaje de
grasa (6.25±0.34 % frente a 8.27±0.22 %), proteína
(4.71±0.14 % frente a 5.80±0.09 %) y extracto seco
(10.97±0.46 % frente a 14.07±0.28 %), estadísticamente
inferior. En cuanto a los parámetros de aptitud tecnológica,
los valores de tiempo de coagulación medio (24.70±0.77
minutos), dureza media (dureza del coágulo a los 30 minutos)
de 25.03±2.27 mm, y el rendimiento en cuajada
(327.50±5.70 g/l), mostraron cifras inferiores a las referenciadas
por Casas et al. (2005) para la raza ovina Merina de
Grazalema. Finalmente, la velocidad de endurecimiento
resultó mayor a los valores obtenidos en el trabajo citado
anteriormente (4.59±0.54 min.). Por otro lado, estos mismos
parámetros mostraron valores inferiores en el tiempo
de coagulación (19.60±0.62 minutos), velocidad de endurecimiento
(3.97±0.38 min.) y rendimiento en cuajada
(290.55±6.67), mientras que la dureza media (32.85±2.03
mm) fue superior en las ovejas cruzadas, respecto a los
valores encontrados en esta misma explotación para los
animales puros.
Como consecuencia de todo ello, el rendimiento quesero
real fue del 30.25 % para las ovejas puras frente al
23.70 % de las cruzadas.
Esto determina que la producción quesera real que
se obtiene por oveja pura, sea superior al de la cruzada
(41.38 kg queso fresco/lactación frente a los 39.70 de la
cruzada)
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