9,157 research outputs found
Modeling dust emission in PN IC 418
We investigated the infrared (IR) dust emission from PN IC 418, using a
detailed model controlled by a previous determination of the stellar properties
and the characteristics of the photoionized nebula, keeping as free parameters
the dust types, amounts and distributions relative to the distance of the
central star. The model includes the ionized region and the neutral region
beyond the recombination front (Photodissociation region, or PDR), where the
[OI] and [CII] IR lines are formed. We succeeded in reproducing the observed
infrared emission from 2 to 200~\mm. The global energy budget is fitted by
summing up contributions from big grains of amorphous carbon located in the
neutral region and small graphite grains located in the ionized region (closer
to the central star).
Two emission features seen at 11.5 and 30~\mm are also reproduced by assuming
them to be due to silicon carbide (SiC) and magnesium and iron sulfides
(MgFeS), respectively. For this, we needed to consider ellipsoidal
shapes for the grains to reproduce the wavelength distribution of the features.
Some elements are depleted in the gaseous phase: Mg, Si, and S have sub-solar
abundances (-0.5 dex below solar by mass), while the abundance of C+N+O+Ne by
mass is close to solar. Adding the abundances of the elements present in the
dusty and gaseous forms leads to values closer to but not higher than solar,
confirming that the identification of the feature carriers is plausible. Iron
is strongly depleted (3 dex below solar) and the small amount present in dust
in our model is far from being enough to recover the solar value. A remaining
feature is found as a residue of the fitting process, between 12 and 25~\mm,
for which we do not have identification.Comment: Accepted for publication in Astronomy & Astrophysics. V2: adding
reference
On the frequency dependence of p-mode frequency shifts induced by magnetic activity in Kepler solar-like stars
The variations of the frequencies of the low-degree acoustic oscillations in
the Sun induced by magnetic activity show a dependence with radial order. The
frequency shifts are observed to increase towards higher-order modes to reach a
maximum of about 0.8 muHz over the 11-yr solar cycle. A comparable frequency
dependence is also measured in two other main-sequence solar-like stars, the
F-star HD49933, and the young 1-Gyr-old solar analog KIC10644253, although with
different amplitudes of the shifts of about 2 muHz and 0.5 muHz respectively.
Our objective here is to extend this analysis to stars with different masses,
metallicities, and evolutionary stages. From an initial set of 87 Kepler
solar-like oscillating stars with already known individual p-mode frequencies,
we identify five stars showing frequency shifts that can be considered reliable
using selection criteria based on Monte Carlo simulations and on the
photospheric magnetic activity proxy Sph. The frequency dependence of the
frequency shifts of four of these stars could be measured for the l=0 and l=1
modes individually. Given the quality of the data, the results could indicate
that a different physical source of perturbation than in the Sun is dominating
in this sample of solar-like stars.Comment: Accepted for publication in A&
Spatial clustering of interacting bugs: Levy flights versus Gaussian jumps
A biological competition model where the individuals of the same species
perform a two-dimensional Markovian continuous-time random walk and undergo
reproduction and death is studied. The competition is introduced through the
assumption that the reproduction rate depends on the crowding in the
neighborhood. The spatial dynamics corresponds either to normal diffusion
characterized by Gaussian jumps or to superdiffusion characterized by L\'evy
flights. It is observed that in both cases periodic patterns occur for
appropriate parameters of the model, indicating that the general macroscopic
collective behavior of the system is more strongly influenced by the
competition for the resources than by the type of spatial dynamics. However,
some differences arise that are discussed.Comment: This version incorporates in the text the correction published as an
Erratum in Europhysics Letters (EPL) 95, 69902 (2011) [doi:
10.1209/0295-5075/95/69902
Clavo gamma en el tratamiento de las fracturas del macizo trocantérico: estudio comparativo entre el Clavo Gamma Trocantérico y el Gamma 3
El clavo Gamma es una técnica bien establecida en el tratamiento de las fracturas del macizo trocantéreo. Hemos realizado un estudio prospectivo en 40 pacientes para comparar dos tipos de clavos. En 20 se utilizó el clavo gamma trocantérico y en 20 un nuevo dispositivo llamado Gamma3 fabricado en titanio y con modificaciones en el diseño para permitir una menor incisión y mayor faciliad en su implante. De todos los parámetros estudiados tanto intra como postoperatorios sólo hemos encontrado diferencias en cuanto al tiempo del acto quirúrgico y al tamaño de la incisión, encontrando menor tiempo y menor tamaño de la incisión en el clavo gamma 3. No encontramos diferencias en cuanto a las complicaciones técnicas, ni en cuanto al dolor, tiempo transcurrido hasta la consolidación o grado de independencia obtenido. Consideramos el clavo Gamma3 como una técnica valiosa que disminuye el tiempo de cirugía y el traumatismo de las partes blandas.The nail Gamma is a well-established technique in
the treatment of the trochanteric fractures. We have made a
prospective study in 40 patients for compare two Gamma nail
types. In 20 we use the Trochanteric Gamma Nail and in 20 a
new device called Gamma 3 manufactured in titanium and
with modifications in the design to permit a less incision and
most facilities in his implantation. Of all of the parameters studied both intra and postoperative we have found differences
in the time of surgical act and in the size of the incision, finding less time and less size of the approach in the gamma 3
nail. We do not find differences about technical complications, neither as to the pain, time to the consolidation or independence grade obtained. We regard to the nail Gamma 3 as
a valuable technique that decreases the time of surgery and
the traumatism of the soft tissues
Measures to improve influenza vaccination coverage in spanish medical students
Objective: To find out what measures medical students believe could help improve their influenza vaccination coverage. Method: On 5 November, 2019, the Dean of the Zaragoza Medical School sent an e-mail to the students asking them to fill out a questionnaire through Google Forms, in which they were asked to describe, in an open field, the measures that they believed could contribute to improving their flu vaccination coverage. The content of the responses was analyzed in a classic way, extracting descriptors and selecting the most representative verbatim accounts. Results: The main measures proposed were to improve the training on influenza and its vaccine, to improve the accessibility of the vaccine in time and space, to provide incentives to get vaccinated, to create visible and positive attitudes towards the vaccine, and to increase the diffusion of information about the vaccination campaign. Conclusion: This qualitative study has found potential measures to be applied specifically to medical students to improve their vaccination coverage in our country
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