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 (Mg$_x$Fe$_{1-x}$S), 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 index theorem for Wilson fermions

We consider a Wilson-Dirac operator with improved chiral properties. We show that, for arbitrarily rough gauge fields, it satisfies the index theorem if we identify the zero modes with the small real eigenvalues of the fermion operator and use the geometrical definition of topological charge. This is also confirmed in a numerical study of the quenched Schwinger model. These results suggest that integer definitions of the topological charge based on counting real modes of the Wilson operator are equivalent to the geometrical definition. The problem of exceptional configurations and the sign problem in simulations with an odd number of dynamical Wilson fermions are briefly discussed.Comment: Latex, 18 pages, 6 figure

A test for asymptotic giant branch evolution theories: Planetary Nebulae in the Large Magellanic Cloud

We used a new generation of asymptotic giant branch (AGB) stellar models that include dust formation in the stellar winds to find the links between evolutionary models and the observed properties of a homogeneous sample of Large Magellanic Cloud (LMC) planetary nebulae (PNe). Comparison between the evolutionary yields of elements such as CNO and the corresponding observed chemical abundances is a powerful tool to shed light on evolutionary processes such as hot bottom burning (HBB) and third dredge-up (TDU). We found that the occurrence of HBB is needed to interpret the nitrogen-enriched (log(N/H)+12>8) PNe. In particular, N-rich PNe with the lowest carbon content are nicely reproduced by AGB models of mass M >=6 Mo, whose surface chemistry reflects the pure effects of HBB. PNe with log(N/H)+12<7.5 correspond to ejecta of stars that have not experienced HBB, with initial mass below about 3 Mo. Some of these stars show very large carbon abundances, owing to the many TDU episodes experienced. We found from our LMC PN sample that there is a threshold to the amount of carbon accumulated at AGB surfaces, log(C/H)+12<9. Confirmation of this constraint would indicate that, after the C-star stage is reached,AGBs experience only a few thermal pulses, which suggests a rapid loss of the external mantle, probably owing to the effects of radiation pressure on carbonaceous dust particles present in the circumstellar envelope. The implications of these findings for AGB evolution theories and the need to extend the PN sample currently available are discussed.Comment: 12 pages, 4 figures, 1 table, accepted for publication in MNRAS (2015 July 13; in original form 2015 June 9

Planetary Nebulae in the Small Magellanic Cloud

We analyse the planetary nebulae (PNe) population of the Small Magellanic Cloud (SMC), based on evolutionary models of stars with metallicities in the range $10^{-3} \leq Z \leq 4\times 10^{-3}$ and mass $0.9 M\odot < M < 8M\odot$, evolved through the asymptotic giant branch (AGB) phase. The models used account for dust formation in the circumstellar envelope. To characterise the PNe sample of the SMC, we compare the observed abundances of the various species with the final chemical composition of the AGB models: this study allows us to identify the progenitors of the PNe observed, in terms of mass and chemical composition. According to our interpretation, most of the PNe descend from low-mass ($M < 2 M\odot$) stars, which become carbon rich, after experiencing repeated third dredge-up episodes, during the AGB phase. A fraction of the PNe showing the signature of advanced CNO processing are interpreted as the progeny of massive AGB stars, with mass above $\sim 6 M\odot$, undergoing strong hot bottom burning. The differences with the chemical composition of the PNe population of the Large Magellanic Cloud (LMC) is explained on the basis of the diverse star formation history and age-metallicity relation of the two galaxies. The implications of the present study for some still highly debated points regarding the AGB evolution are also commented.Comment: Accepted for publication in MNRAS, 11 pages, 4 figure

Gas and dust from solar metallicity AGB stars

We study the asymptotic giant branch (AGB) evolution of stars with masses between $1~M_{\odot} - 8.5~M_{\odot}$. We focus on stars with a solar chemical composition, which allows us to interpret evolved stars in the Galaxy. We present a detailed comparison with models of the same chemistry, calculated with a different evolution code and based on a different set of physical assumptions. We find that stars of mass $\ge 3.5~M_{\odot}$ experience hot bottom burning at the base of the envelope. They have AGB lifetimes shorter than $\sim 3\times 10^5$ yr and eject into their surroundings gas contaminated by proton-capture nucleosynthesis, at an extent sensitive to the treatment of convection. Low mass stars with $1.5~M_{\odot} \le M \le 3~M_{\odot}$ become carbon stars. During the final phases the C/O ratio grows to $\sim 3$. We find a remarkable agreement between the two codes for the low-mass models and conclude that predictions for the physical and chemical properties of these stars, and the AGB lifetime, are not that sensitive to the modelling of the AGB phase. The dust produced is also dependent on the mass: low-mass stars produce mainly solid carbon and silicon carbide dust, whereas higher mass stars produce silicates and alumina dust. Possible future observations potentially able to add more robustness to the present results are also discussed.Comment: 27 pages, 24 figures; accepted for publication in MNRA

Effects of specific training applied to power in juniors football players for the improvement of power in the jump

El objetivo del presente estudio fue; a) comprobar los efectos de un entrenamiento especifico de potencia sobre la potencia de salto en jóvenes futbolistas b) conocer si la asociación de trabajos con cargas y pliometria está indicado para la potencia de salto. Para ello se reclutaron cuarenta jugadores juveniles españoles con una media de edad de (17.29 ± 0.791) pertenecientes a las categorías preferente y autonómica. Se formaron dos grupos, un grupo experimental GEX (P+F) asociaba un entrenamiento especial destinado a elevar los niveles de potencia junto al realizado habitualmente en su club. El programa se diseño con cargas especificas de carácter individual (después de realizar una evaluación para identificarlas mediante el mejor valor de potencia media con el dispositivo Isocontrol 5.2) y los ejercicios realizados fueron cargada de fuerza, media sentadilla, salto cargado y saltos continuos de 40 -50cm; se formo un segundo grupo denominado GC (F) que solo realizo su trabajo de futbol habitual en campo. Las variables evaluadas fueron; Salto CMJa y salto cargado (SC) se estableció un nivel de significación de p<0.05. Los resultados al final del estudio mostraron que el grupo el grupo GEX mejoro de manera estadísticamente significativa en CMJa y SC, mientras que en el grupo GC esos cambios no fueron significativos en ninguna de las variables. Estos resultados nos llevan a la conclusión que un entrenamiento específico de potencia asociado al entrenamiento habitual en el futbol en jugadores juveniles, mejora significativamente la potencia de salto con y sin carga

Effects of a strength training in Spanish football youth with the load express where the best value in the exercise of power loaded jump.

Con el presente estudio, se pretendió comprobar los efectos de un entrenamiento específico de potencia expresado en la curva de potencia carga, en jóvenes futbolistas. El ejercicio realizado es el salto cargado (SC). Para ello se reclutó a cuarenta jugadores juveniles españoles, con una media de edad de (17.29 ± 0.791), pertenecientes a las categorías preferente y autonómica. Se formaron dos grupos, un grupo experimental GEX (P+F) asociaba un entrenamiento especial, destinado a elevar los niveles de potencia junto al realizado habitualmente en su club. El programa se diseñó con cargas especificas de carácter individual (después de realizar una evaluación para identificarlas, mediante el mejor valor de potencia media con el dispositivo Isocontrol 5.2) y los ejercicios realizados, fueron: cargada colgado, media sentadilla, salto cargado y saltos continuos de 40 -50cm. Se formó un segundo grupo denominado GC (F) que solo realizó, su trabajo de fútbol habitual en campo. Las variables evaluadas en el (SC) fueron: la 1RM y la carga óptima, con la que el futbolista manifiesta la mejor potencia media en cinco repeticiones. Se estableció un nivel de significación de p≤0.05. Los resultados, tras ocho semanas mostraron, que el grupo el grupo GEX elevó de manera estadísticamente significativa el peso en el que el deportista manifiesta su máxima potencia, mientras que en el grupo GC esos cambios no fueron significativos. Estos resultados nos llevan a la conclusión, que un entrenamiento específico de potencia, asociado al entrenamiento habitual en el fútbol, en jugadores juveniles, mejora significativamente la carga óptima en relación con la 1RM en el SC y la carga optima donde se manifiesta la mejor potencia media en SC, se encuentra alrededor del 50% de 1RM. Finalmente el peso donde el jugador manifiesta su mejor valor de potencia se desplaza hacia la el punto de 1RM