6,695 research outputs found
Beryllium abundances in stars hosting giant planets
We have derived beryllium abundances in a wide sample of stars hosting
planets, with spectral types in the range F7V-K0V, aimed at studying in detail
the effects of the presence of planets on the structure and evolution of the
associated stars. Predictions from current models are compared with the derived
abundances and suggestions are provided to explain the observed
inconsistencies. We show that while still not clear, the results suggest that
theoretical models may have to be revised for stars with Teff<5500K. On the
other hand, a comparison between planet host and non-planet host stars shows no
clear difference between both populations. Although preliminary, this result
favors a ``primordial'' origin for the metallicity ``excess'' observed for the
planetary host stars. Under this assumption, i.e. that there would be no
differences between stars with and without giant planets, the light element
depletion pattern of our sample of stars may also be used to further
investigate and constraint Li and Be depletion mechanisms.Comment: A&A in press -- accepted on the 22/02/2002 (11 pages, 6 figures
included
Herida antebraquial infectada por Aeromonas hydrophila
Se presenta un caso de celulitis por Aeromonas hydrophila, en un paciente de
23 años, tras una herida antebraquial producida en el medio acuático. La celulitis se resolvió
mediante desbridamiento agresivo y quimioterapia. En los controles posteriores no se han
apreciado déficits funcionales tras la infección.A case of Aeromonas hidrophila cellulitis developped in a 23-year-old patient,
after aquatic environment forearm wound is presented. His cellulitis was effectively resolved
with aggressive debridement and chemotherapy. Follow-up examinations have shown no residual
functional deficits from the infection
Are beryllium abundances anomalous in stars with giant planets?
In this paper we present beryllium (Be) abundances in a large sample of 41
extra-solar planet host stars, and for 29 stars without any known
planetary-mass companion, spanning a large range of effective temperatures. The
Be abundances were derived through spectral synthesis done in standard Local
Thermodynamic Equilibrium, using spectra obtained with various instruments. The
results seem to confirm that overall, planet-host stars have ``normal'' Be
abundances, although a small, but not significant, difference might be present.
This result is discussed, and we show that this difference is probably not due
to any stellar ``pollution'' events. In other words, our results support the
idea that the high-metal content of planet-host stars has, overall, a
``primordial'' origin. However, we also find a small subset of planet-host
late-F and early-G dwarfs that might have higher than average Be abundances.
The reason for the offset is not clear, and might be related either to the
engulfment of planetary material, to galactic chemical evolution effects, or to
stellar-mass differences for stars of similar temperature.Comment: 15 pages, 9 figures, accepted for publication in Astronomy &
Astrophysic
Beryllium anomalies in solar-type field stars
We present a study of beryllium (Be) abundances in a large sample of field
solar-type dwarfs and sub-giants spanning a large range of effective
temperatures. The analysis shows that Be is severely depleted for F stars, as
expected by the light-element depletion models. However, we also show that
Beryllium abundances decrease with decreasing temperature for stars cooler than
6000 K, a result that cannot be explained by current theoretical models
including rotational mixing, but that is, at least in part, expected from the
models that take into account internal wave physics. In particular, the light
element abundances of the coolest and youngest stars in our sample suggest that
Be, as well as lithium (Li), has already been burned early during their
evolution. Furthermore, we find strong evidence for the existence of a Be-gap
for solar-temperature stars. The analysis of Li and Be abundances in the
sub-giants of our sample also shows the presence of one case that has still
detectable amounts of Li, while Be is severely depleted. Finally, we compare
the derived Be abundances with Li abundances derived using the same set of
stellar parameters. This gives us the possibility to explore the temperatures
for which the onset of Li and Be depletion occurs.Comment: 16 pages, 13 figures, accepted for publication in Astronomy &
Astrophysic
Spatial distribution of small hydrocarbons in the neighborhood of the Ultra Compact HII region Monoceros R2
We study the chemistry of small hydrocarbons in the photon-dominated regions
(PDRs) associated with the ultra-compact HII region Mon R2. Our goal is to
determine the variations of the abundance of small hydrocarbons in a high-UV
irradiated PDR and investigate their chemistry. We present an observational
study of CH, CCH and c-CH in Mon R2 combining data obtained with the
IRAM 30m telescope and Herschel. We determine the column densities of these
species, and compare their spatial distributions with that of polycyclic
aromatic hydrocarbon (PAH). We compare the observational results with different
chemical models to explore the relative importance of gas-phase, grain-surface
and time-dependent chemistry in these environments. The emission of the small
hydrocarbons show different patterns. The CCH emission is extended while CH and
c-CH are concentrated towards the more illuminated layers of the PDR.
The ratio of the column densities of c-CH and CCH shows spatial
variations up to a factor of a few, increasing from
_3_2 in the envelope to a maximum of
towards the 8m emission peak. Comparing these results
with other galactic PDRs, we find that the abundance of CCH is quite constant
over a wide range of G, whereas the abundance of c-CH is higher in
low-UV PDRs. In Mon R2, the gas-phase steady-state chemistry can account
relatively well for the abundances of CH and CCH in the most exposed layers of
the PDR, but falls short by a factor of 10 to reproduce c-CH.
In the molecular envelope, time-dependent effects and grain surface chemistry
play a dominant role in determining the hydrocarbons abundances. Our study
shows that CCH and c-CH present a complex chemistry in which UV
photons, grain-surface chemistry and time dependent effects contribute to
determine their abundances.Comment: 18 pages, 11 figures, 7 tables. Proposed for acceptance in A&A.
Abstract abridge
Measurement of cooling and warming rates in vitrification-based plant cryopreservation protocols
Cryopreservation protocols include the use of additives and pre-treatments aimed to reduce the probability of ice nucleation at all temperatures, mainly through micro-viscosity increase. Still, there is a risk of ice formation in the temperature region comprised between the equilibrium freezing (Tf) and the glass transition (TG) temperatures. Consequently, fast cooling and warming, especially in this region, is a must to avoid ice-derived damage. Vitrification and droplet-vitrification techniques, frequently used cryopreservation protocols based in fast cooling, were studied, alongside with the corresponding warming procedures. A very fast data acquisition system, able to read very low temperatures, down to that of liquid nitrogen, was employed. Cooling rates, measured between -20 and -120 ºC, ranged from ca. 5 ºC s-1 to 400 ºC s-1, while warming rates spanned from ca. 2 ºC s-1 to 280 ºC s-1, for the different protocols and conditions studied. A wider measuring window (0 ºC to -150 ºC) produced lower rates for all cases. The cooling and warming rates were also related to the survival observed after the different procedures. Those protocols with the faster rates yielded the highest survival percentages.Centro de Investigación y Desarrollo en Criotecnología de Alimento
Influencia del origen del haba sobre el valor nutricional de la harina de soja
La harina de soja (HS) es la principal fuente de proteína en piensos para animales monogástricos. La mayor parte de las HS utilizadas en Europa proceden del continente Americano, en particular de Argentina (ARG), Brasil (BRA) y Estados Unidos (USA). Aunque la composición y valor nutricional de las HS varía entre países de origen (Grieshop et al., 2003; De Coca et al., 2008; 2010; Valencia et al., 2008), las tablas de composición de alimentos (NRC, 1998; FEDNA, 2010) clasifican las HS en función de su contenido en PB, sin tener en cuenta ni el origen ni las condiciones del procesado. En un trabajo anterior Mateos et al. (2009) se presentaron los resultados obtenidos de una colección de 262 muestras de HS recolectadas en las cosechas de los años 2007 y 2008 procedentes de estos tres países. Dependiendo de la variable considerada, el número de muestras analizadas varió entre 50 y 262. El presente trabajo tuvo como objetivo completar los análisis y complementar los resultados anteriores en relación con la composición química, el valor nutricional y la calidad de la PB de la HS con nuevas muestras procedentes de las cosechas de los años 2009 y 2010
Differences among origins on nutritional and quality parameters of soybean meal
Soybean meal (SBM) is the main protein source in livestock feeds. United States (USA), Brazil (BRA), and Argentine (ARG) are the major SBM exporter countries. The nutritive value of SBM varies because genetics, environment, farming conditions, and processing of the beans influence strongly the content and availability of major nutrients. The present research was conducted to determine the influence of origin (USA, BRA and ARG) on nutritive value and protein quality of SBM
Factors associated with compliance with physical activity recommendations among adolescents in Huesca.
BACKGROUND: Schools have been identified as environments of choice for physical activity promotion. This study examines factors associated with compliance with objectively assessed physical activity recommendations for early adolescents taking part in “Sigue la Huella”, a school-based intervention guided by a social ecological framework and Self-Determination Theory (Deci & Ryan, 2002). METHODS: A total of 200 students (108 boys) aged 12-13 years (M = 12.16; SD = ± 0.51), wore accelerometers during a 7-day period and completed a questionnaire. Participants were considered compliant to the recommendations if their moderate to vigorous physical activity, averaged over 7 days, was =60 minutes a day. RESULTS: 57.4% of boys and 9.9% of girls met recommendations. In a mixed logistic regression model, compliance was higher among boys and students attending private schools, and lower for obese students. Compliance was also associated with higher perceptions of physical competence, higher perceptions of autonomy in physical education, greater importance attached to physical education and less sedentary behavior. CONCLUSIONS: Assessed objectively, gender differences in compliance with physical activity recommendations were greater than expected. Self-Determination Theory emerged as a useful framework to identify motivational factors that can be addressed in school-based physical activity interventions and programs for early adolescents
Lessons from the operation of the "Penning-Fluorescent" TPC and prospects
We have recently reported the development of a new type of high-pressure
Xenon time projection chamber operated with an ultra-low diffusion mixture and
that simultaneously displays Penning effect and fluorescence in the
near-visible region (300 nm). The concept, dubbed `Penning-Fluorescent' TPC,
allows the simultaneous reconstruction of primary charge and scintillation with
high topological and calorimetric fidelity
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