2,754 research outputs found
The Diffuse Nature of Stromgren Spheres
In this Letter, we argue that the standard analytical derivations of
properties of HII regions, such as the speed, shape and asymptotic position of
ionisation fronts require a more precise treatment. These derivations use the
on the spot approximation, which in effect ignores the diffuse component of the
radiation field. We show that, in fact, HII regions are diffusion dominated.
This has as a result that the morphology of inhomogeneous HII regions will be
drastically different, because shadowing effects have a less profound impact on
the apparent shape. Moreover, it will have influence on the propagation speed
of ionisation fronts. We quantify our claims by analytically deriving the
internal radiation structure of HII regions, taking diffusion fully into
account for several different cosmologically relevant density distributions.Comment: 4 pages, 2 figures, accepted for publication in A&A Letter
Strength distribution of solar magnetic fields in photospheric quiet Sun regions
The magnetic topology of the solar photosphere in its quietest regions is
hidden by the difficulties to disentangle magnetic flux through the resolution
element from the field strength of unresolved structures. The observation of
spectral lines with strong coupling with hyperfine structure, like the observed
MnI line at 553.7 nm, allows such differentiation.
The main aim is to analyse the distribution of field strengths in the network
and intranetwork of the solar photosphere through inversion of the MnI line at
553.7 nm.
An inversion code for the magnetic field using the Principal Component
Analysis (PCA) has been developed. Statistical tests are run on the code to
validate it. The code has to draw information from the small-amplitude spectral
feature oppearing in the core of the Stokes V profile of the observed line for
field strengths below a certain threshold, coinciding with lower limit of the
Paschen-Back effect in the fine structure of the involved atomic levels.
The inversion of the observed profiles, using the circular polarization (V)
and the intensity (I), shows the presence of magnetic fields strengths in a
range from 0 to 2 kG, with predominant weak strength values. Mixed regions with
mean strength field values of 1130 and 435 Gauss are found associated with the
network and intranetwork respectively.
The MnI line at 553 nm probes the field strength distribution in the quiet
sun and shows the predominance of weak, hectoGauss fields in the intranetwork,
and strong, kiloGauss fields in the network. It also shows that both network
and intranetwork are to be understood at our present spatial resolutions as
field distributions of which we hint the mean properties.Comment: 10 pages, 6 figure
Physical activity practice and attitudes in canarian teenagers
En el presente estudio de la población adolescente de la Comunidad Autónoma de Canarias, se evidencia que aquellos adolescentes que cumplen con las recomendaciones de práctica de Actividad Física tanto de intensidad
moderada como vigorosa frente a los que no las cumplen, muestran a su vez mejores valores en la percepción del conjunto de actitudes que influyen en los niveles de práctica; competencia motriz, disfrute y valor-utilidad otorgada a la misma. Lo cual nos permite afirmar que este conjunto de factores pueden determinar el tipo y grado de participación en actividades físico-deportivas en este sector de la poblaciónIn this actual study of the adolescent population of the Autonomous Region of the Canary Islands, is evident, that teens who comply with the recommendations of practice of physical activity both of moderate intensity as vigorous intensity, compared with those which do not comply, show the best values in the perception of the set of attitudes that influence the levels of practice; perceived competence, enjoyment, perceived value. Which allows us to affirm that this set of factors can determine the type and degree of participation in physical-sport activities in this sector of the populatio
Chemical Abundance Study of One Red Giant Star in NGC 5694 : A Globular Cluster with Dwarf Spheroidals' Chemical Signature?
We report the abundance analysis of one red giant branch star in the
metal-poor outer halo globular cluster NGC 5694. We obtain [Fe/H] = -1.93,
based on the ionized lines, and our metallicity measurement is in good
agreement with previous estimates. We find that [Ca+Ti/2Fe] and [Cu/Fe] of NGC
5694 are about 0.3 -- 0.4 dex lower than other globular clusters with similar
metallicities, but similar to some LMC clusters and stars in some dwarf
spheroidal galaxies. Differences persist, however, in the abundances of neutron
capture elements. The unique chemical abundance pattern and the large
Galactocentric distance (30 kpc) and radial velocity (-138.6 +/- 1.0 km/sec)
indicate that NGC 5694 had an extragalactic origin.Comment: ApJL accepte
Hardware-software co-design of an iris recognition algorithm
This paper describes the implementation of an iris recognition algorithm based
on hardware-software co-design. The system architecture consists of a general-purpose 32-
bit microprocessor and several slave coprocessors that accelerate the most intensive
calculations. The whole iris recognition algorithm has been implemented on a low-cost
Spartan 3 FPGA, achieving significant reduction in execution time when compared to a
conventional software-based application. Experimental results show that with a clock
speed of 40 MHz, an IrisCode is obtained in less than 523 ms from an image of 640x480
pixels, which is just 20% of the total time needed by a software solution running on the
same microprocessor embedded in the architecture.Peer ReviewedPreprin
Estilos de trabajo e inteligencias múltiples
El objetivo del trabajo es determinarla validez yflabilidad del modelo dejos
estilos de trabajo, fundamentado en la teoría de las Inteligencias Múltiples
(IM). Primero, se analizan los componentes de dicha teoría y su incidencia
en el curriculum escolar. En segundo lugar, se estudia el procedimiento de
evaluación. Además, se presentan los resultados del estudio empírico realizado
con una muestra de 237 alumnos pertenecientes a Educación Infantil y
Primaria, escolarizados en centros públicos y privados de la Región de Murcia.
Del estudio realizado se desprende que los estilos están asociados a las
diferentes inteligencias; además, el inventario de estilos de trabajo arroja
una validez y fiabilidad altamente consistente.________________________________
The objective of this work is to determinate the validity and reliability of the
model of work styles, as set out In the theory of Multiple Intelligences (MI).
First, we analyze the components of this theory and their Incidence in the
school curriculum. Second, we study the evaluation procedure. Additionally,
we present the results of an empirical study carried out with a sample of 237
students in public and private nursery and primary schools in the province
of Murcia, Spain. The study carried out reveals that the styles are associated
with the different Intelligences. Furthermore, the inventory of styles shows a
highly consistent validity and reliability
On the classification and properties of noncommutative duplicates
We give an explicit description of the set of all factorization structures,
or twisting maps, existing between the algebras k^2 and k^2, and classify the
resulting algebras up to isomorphism. In the process we relate several
different approaches formerly taken to deal with this problem, filling a gap
that appeared in a recent paper by Cibils. We also provide a counterexample to
a result concerning the Hochschild (co)homology appeared in a paper by J.A.
Guccione and J.J. Guccione.Comment: 11 pages, no figure
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