997 research outputs found
Association between agility and speed with changes of direction in young players
Identificar factores asociados al máximo rendimiento en el fútbol posibilitará mejorar el proceso de planificación deportiva en etapas tempranas. Este estudio tuvo como objetivo determinar la asociación entre la agilidad y la velocidad con cambios de dirección (VCD) en jóvenes futbolistas (JF). Participaron voluntariamente dieciocho hombres entre los 10 y 13 años los cuales aplicaron el test de 20 metros con cambios de dirección (T20CD) y el test de agilidad Illinois (TAI). El análisis estadístico se realizó en el IBM SPSS V.22 en el cual se fijó para la significancia un p0,05) y no normal en TAI (p<0,05), el coeficiente correlacional de Spearman (r = 0,06; p = 0,8) evidenció una relación poco significativa (p<0,05). Por lo tanto se concluye que no existe asociación significativa entre la agilidad y la VCD en JF
A Comprehensive View of the 2006 December 13 CME: From the Sun to Interplanetary Space
The biggest halo coronal mass ejection (CME) since the Halloween storm in
2003, which occurred on 2006 December 13, is studied in terms of its solar
source and heliospheric consequences. The CME is accompanied by an X3.4 flare,
EUV dimmings and coronal waves. It generated significant space weather effects
such as an interplanetary shock, radio bursts, major solar energetic particle
(SEP) events, and a magnetic cloud (MC) detected by a fleet of spacecraft
including STEREO, ACE, Wind and Ulysses. Reconstruction of the MC with the
Grad-Shafranov (GS) method yields an axis orientation oblique to the flare
ribbons. Observations of the SEP intensities and anisotropies show that the
particles can be trapped, deflected and reaccelerated by the large-scale
transient structures. The CME-driven shock is observed at both the Earth and
Ulysses when they are separated by 74 in latitude and 117
in longitude, the largest shock extent ever detected. The ejecta seems missed
at Ulysses. The shock arrival time at Ulysses is well predicted by an MHD model
which can propagate the 1 AU data outward. The CME/shock is tracked remarkably
well from the Sun all the way to Ulysses by coronagraph images, type II
frequency drift, in situ measurements and the MHD model. These results reveal a
technique which combines MHD propagation of the solar wind and type II
emissions to predict the shock arrival time at the Earth, a significant advance
for space weather forecasting especially when in situ data are available from
the Solar Orbiter and Sentinels.Comment: 26 pages, 10 figures. 2008, ApJ, in pres
Probing upper thermospheric neutral densities at Mars using electron reflectometry
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95666/1/grl20594.pd
Enhancement of optical absorption by modulation of the oxygen flow of TiO2 films deposited by reactive sputtering
Oxygen-deficient TiO2
films with enhanced visible and near-infrared optical absorption have been
deposited by reactive sputtering using a planar diode radio frequency magnetron configuration. It is
observed that the increase in the absorption coefficient is more effective when the O2 gas supply is
periodically interrupted rather than by a decrease of the partial O2 gas pressure in the deposition
plasma. The optical absorption coefficient at 1.5 eV increases from about 1 102
cm 1
to more than
4 103
cm 1
as a result of the gas flow discontinuity. A red-shift of 0.24 eV in the optical
absorption edge is also observed. High resolution transmission electron microscopy with
composition analysis shows that the films present a dense columnar morphology, with estimated
mean column width of 40 nm. Moreover, the interruptions of the O2 gas flow do not produce
detectable variations in the film composition along its growing direction. X-ray diffraction and
micro-Raman experiments indicate the presence of the TiO2
anatase, rutile, and brookite phases.
The anatase phase is dominant, with a slight increment of the rutile and brookite phases in films
deposited under discontinued O2 gas flow. The increase of optical absorption in the visible and
near-infrared regions has been attributed to a high density of defects in the TiO2
films, which is
consistent with density functional theory calculations that place oxygen-related vacancy states in the
upper third of the optical bandgap. The electronic structure calculation results, along with the
adopted deposition method and experimental data, have been used to propose a mechanism to
explain the formation of the observed oxygen-related defects in TiO2 thin films. The observed
increase in sub-bandgap absorption and the modeling of the corresponding changes in the electronic
structure are potentially useful concerning the optimization of efficiency of the photocatalytic
activity and the magnetic doping of TiO2
films
Bathyraja griseocauda, Graytail Skate
The Greytail Skate (Bathyraja griseocauda) is a large (to 157 cm total length) skate that occurs in the Southeast Pacific and Southwest Atlantic Oceans from Coquimbo, Chile south around Cape Horn and north to Uruguay, including the Falkland Islands (Malvinas), and is demersal on the mid-continental shelf and upper slope at depths of 30?1,010 m. It is captured in trawl and longline fisheries targeting skates, squid, shrimp, scallops, hake, and Patagonian Toothfish (Dissostichus eleginoides) that are inadequately managed and together operate throughout its range. Its large body size and relatively unproductive life history make it particularly vulnerable to overfishing. In the Southeast Pacific, this skate is captured and discarded dead in inadequately managed fisheries that operate throughout that portion of its range. In the Southwest Atlantic, where large skates are typically utilized or exported for human consumption, the catch-per-unit-effort (CPUE) for this skate in the Falkland Islands (Malvinas) multi-species skate fishery declined consistently and substantially from 120 to 23 kg/hr between 1994 and 2006, and increased to 70 kg/hr in 2013 due to a change in the area fished. Although no later data are available, this fishery continues and is still not managed at the species level. In Argentina, there are no species-specific data, but rays in general declined in CPUE in the 1990s and early 2000s. Overall, due to the level of inadequately managed fishing pressure it is exposed to across its range, its large size and relatively unproductive life history, the decline in CPUE of rays in general in some areas, and the noted decline in CPUE (although succeeded by an increase) of this species in the Falkland Islands, it is suspected that this skate has undergone a population reduction of 50?79% over the past three generations (69 years). Therefore, the Greytail Skate is assessed as Endangered A2bd.Fil: Pollom, R.. University Fraser Simon; CanadáFil: Dulvy, N. K.. University Fraser Simon; CanadáFil: Acuña, E.. Universidad Católica del Norte; ChileFil: Bustamante, C.. Universidad de Antofagasta; ChileFil: Chiaramonte, Gustavo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia". Estación Hidrobiológica de Puerto Quequén (sede Quequén); ArgentinaFil: Cuevas, J. M.. Wildlife Conservation Society; Estados UnidosFil: Herman, K.. Georgia Aquarium; Estados UnidosFil: Paesch, L.. Direccion Nacional de Recursos Acuaticos ; UruguayFil: Pompert, J.. No especifíca;Fil: Velez Zuazo, X.. No especifíca
Amblyraja doellojuradoi, Southern Thorny Skate
The Southern Thorny Skate (Amblyraja doellojuradoi) is a small (to 69 cm total length) deepwater skate that occurs in the Southeast Atlantic Ocean from Uruguay to Southern Argentina and the Burdwood Bank, including the Falkland Islands (Malvinas). It is demersal on the mid- and outer continental shelf and upper slope at depths of 50?1,000 m. This skate is captured as bycatch in demersal trawl fisheries and possibly on longlines targeting hake, squid, and Patagonian Toothfish (Dissostichus eleginoides), and is increasingly retained for human consumption. It has some refuge at depth and is not suspected to be undergoing a reduction in population size at this time. Therefore, the Southern Thorny Skate is assessed as Least Concern.Fil: Pollom, R.. University Fraser Simon; CanadáFil: Dulvy, N. K.. University Fraser Simon; CanadáFil: Acuña, E.. Universidad Católica del Norte; ChileFil: Bustamante, C.. Universidad de Antofagasta; ChileFil: Chiaramonte, Gustavo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia". Estación Hidrobiológica de Puerto Quequén (sede Quequén); ArgentinaFil: Cuevas, J. M.. Wildlife Conservation Society; Estados UnidosFil: Herman, K.. Georgia Aquarium; Estados UnidosFil: Paesch, L.. Direccion Nacional de Recursos Acuaticos ; UruguayFil: Pompert, J.. No especifíca;Fil: Velez Zuazo, X.. No especifíca
A theory of nonvertical triplet energy transfer in terms of accurate potential energy surfaces: The transfer reaction from π,π∗ triplet donors to 1,3,5,7-cyclooctatetraene
Triplet energy transfer (TET) from aromatic donors to 1,3,5,7-cyclooctatetraene (COT) is an extreme case of “nonvertical” behavior, where the transfer rate for low-energy donors is considerably faster than that predicted for a thermally activated (Arrhenius) process. To explain the anomalous TET of COT and other molecules, a new theoretical model based on transition state theory for nonadiabatic processes is proposed here, which makes use of the adiabatic potential energy surfaces (PES) of reactants and products, as computed from high-level quantum mechanical methods, and a nonadiabatic transfer rate constant. It is shown that the rate of transfer depends on a geometrical distortion parameter γ = (2g2/κ1)1/2 in which g stands for the norm of the energy gradient in the PES of the acceptor triplet state and κ1 is a combination of vibrational force constants of the ground-state acceptor in the gradient direction. The application of the model to existing experimental data for the triplet energy transfer reaction to COT from a series of π,π∗ triplet donors, provides a detailed interpretation of the parameters that determine the transfer rate constant. In addition, the model shows that the observed decrease of the acceptor electronic excitation energy is due to thermal activation of C�C bond stretchings and C–C bond torsions, which collectively change the ground-state COT bent conformation (D2d) toward a planar triplet state (D8h)[email protected]
On the origin of aurorae on Mars
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95268/1/grl20829.pd
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