7,105 research outputs found
The Milnor-Moore theorem for algebras in rational homotopy theory
We give a construction of the universal enveloping algebra of a given algebra, alternative to the already existing versions. As applications, we derive a higher homotopy algebras version of the classical Milnor-Moore theorem, proposing a new model for simply connected rational homotopy types, and uncovering a relationship between the higher order rational Whitehead products in homotopy groups and the Pontryagin-Massey products in the rational loop space homology algebra
Broadening of HO rotational lines by collision with He atoms at low temperature
We report pressure broadening coefficients for the 21 electric-dipole
transitions between the eight lowest rotational levels of ortho-HO and
para-HO molecules by collisions with He at temperatures from 20 to 120 K.
These coefficients are derived from recently published experimental
state-to-state rate coefficients for HO:He inelastic collisions, plus an
elastic contribution from close coupling calculations. The resulting
coefficients are compared to the available experimental data. Mostly due to the
elastic contribution, the pressure broadening coefficients differ much from
line to line, and increase markedly at low temperature. The present results are
meant as a guide for future experiments and astrophysical observations.Comment: 2 figures, 2 table
Variables predictors of the set in the defence complex in volleyball
El objetivo de la investigación fue conocer las variables predictoras de
la eficacia de colocación en el complejo de defensa (KII), en ambos géneros, en
categorías de formación. La muestra del estudio estuvo compuesta por 2.404
acciones de juego, 1.104 en género masculino y 1.300 en género femenino,
desarrolladas por los 34 equipos participantes en el Campeonato de España
Under 16. La variable dependiente fue la eficacia de colocación. Las variables
independientes se agruparon en: variables de defensa, de colocación en KII y de
bloqueo. Los resultados determinaron que, en ambos géneros, la eficacia de
defensa, la técnica de colocación y la participación en bloqueo predecían la
eficacia de la colocación; en género masculino, zona de defensa y tiempo de
colocación; ninguna variable fue predictora únicamente en género femenino.
Esta información puede ser relevante para el desarrollo del proceso de
entrenamiento en voleibolThe objective of the research was to analyse the variables predictors of the
setting efficacy in the defence complex (KII), in youth athlete, in both genders.
The study sample was comprised of 2404 game actions, 1104 in the male
gender and 1300 in the female gender. The actions were carried out by the 34
teams that participated in the Spanish Under-16 Championship. The dependant
variable was the setting efficacy. The results determined that, in both genders,
the dig efficacy, setting technique and the participation in block predicted the
setting efficacy; in male gender, the defence zone and tempo of set; no
predictor variables were exclusive to the female gender. This information may
be relevant when developing training processes in volleyballEste estudio se ha realizado gracias a la aportación de la Consejería de Economía e Infraestructuras de la Junta de Extremadura a través del Fondo Europeo de Desarrollo Regiona
Close encounters involving RAVE stars beyond the 47 Tucanae tidal radius
The most accurate 6D phase-space information from the Radial Velocity
Experiment (RAVE) was used to integrate the orbits of 105 stars around the
galactic globular cluster 47 Tucanae, to look for close encounters between them
in the past, with a minimum distance approach less than the cluster tidal
radius. The stars are currently over the distance range 3.0 kpc d 5.5
kpc. Using the uncertainties in the current position and velocity vector for
both, star and cluster, 105 pairs of star-cluster orbits were generated in a
Monte Carlo numerical scheme, integrated over 2 Gyr and considering an
axisymmetric and non-axisymmetric Milky-Way-like Galactic potential,
respectively. In this scheme, we identified 20 potential cluster members that
had close encounters with the globular cluster 47 Tucanae, all of which have a
relative velocity distribution (V) less than 200 km s at the
minimum distance approach. Among these potential members, 9 had close
encounters with the cluster with velocities less than the escape velocity of 47
Tucanae, therefore a scenario of tidal stripping seems likely. These stars have
been classified with a 93\% confidence level, leading to the identification of
extratidal cluster stars. For the other 11 stars, V exceeds the escape
velocity of the cluster, therefore they were likely ejected or are unassociated
interlopers.Comment: 10 pages, 6 figures, 2 table, Accepted for publication in MNRA
Threading Through Macrocycles Enhances the Performance of Carbon Nanotubes as Polymer Fillers
In this work we study the reinforcement of polymers by mechanically
interlocked derivatives of single-walled carbon nanotubes (SWNTs). We compare
the mechanical properties of fibers made of polymers and of composites with
pristine single-walled carbon nanotubes (SWNTs), mechanically interlocked
derivatives of SWNTs (MINTs) and the corresponding supramolecular models.
Improvements of both Young's modulus and tensile strength of up to 200 % were
observed for the polystyrene-MINTs samples with an optimized loading of just
0.01 wt.%, while the supramolecular models with identical chemical composition
and loading showed negligible or even detrimental influence. This behavior is
found for three different types of SWNTs and two types of macrocycles.
Molecular dynamics simulations show that the polymer adopts an elongated
conformation parallel to the SWNT when interacting with MINT fillers,
irrespective of the macrocycle chemical nature, whereas a more globular
structure is taken upon facing with either pristine SWNTs or supramolecular
models. The MINT composite architecture thus leads to a more efficient
exploitation of the axial properties of the SWNTs and of the polymer chain at
the interface, in agreement with experimental results. Our findings demonstrate
that the mechanical bond imparts distinctive advantageous properties to SWNT
derivatives as polymer fillers.Comment: 39 pages, 19 figure
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