2,669 research outputs found
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 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
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
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
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Association of acculturation with cardiac structure and function among Hispanics/Latinos: a cross-sectional analysis of the echocardiographic study of Latinos.
OBJECTIVE:Hispanics/Latinos, the largest immigrant population in the USA, undergo the process of acculturation and have a large burden of heart failure risk. Few studies have examined the association of acculturation on cardiac structure and function. DESIGN:Cross-sectional. SETTING:The Echocardiographic Study of Latinos. PARTICIPANTS:1818 Hispanic adult participants with baseline echocardiographic assessment and acculturation measured by the Short Acculturation Scale, nativity, age at immigration, length of US residence, generational status and language. PRIMARY AND SECONDARY OUTCOME MEASURES:Echocardiographic assessment of left atrial volume index (LAVI), left ventricular mass index (LVMI), early diastolic transmitral inflow and mitral annular velocities. RESULTS:The study population was predominantly Spanish-speaking and foreign-born with mean residence in the US of 22.7 years, mean age of 56.4 years; 50% had hypertension, 28% had diabetes and 44% had a body mass index >30 kg/m2. Multivariable analyses demonstrated higher LAVI with increasing years of US residence. Foreign-born and first-generation participants had higher E/e' but lower LAVI and e' velocities compared with the second generation. Higher acculturation and income >20K were associated with higher LVMI, LAVI and E/e' but lower e' velocities. Preferential Spanish-speakers with an income <20K had a higher E/e'. CONCLUSIONS:Acculturation was associated with abnormal cardiac structure and function, with some effect modification by socioeconomic status
Effectiveness of polyhexamethylene biguanide dressings vs. platelet-rich plasma in diabetic foot ulcer: a pilot study of case series
Diverse treatments, including polyhexamethylene biguanide dressings, have been explored for managing diabetic foot ulcers. Platelet-rich plasma, known for its potential in chronic wound healing, has demonstrated efficacy both in vivo and in vitro, with possible intralesional or topical application. However, research on the production costs of PRP is scarce. This study compares the effectiveness and financial implications of polyhexamethylene biguanide dressings versus Platelet-rich Plasma in the treatment of diabetic foot ulcers. Conducted at the General Hospital of Mexico from July to August 2019, this case series involved 8 patients, split equally between the two treatment groups. Weekly assessments showed consistent reductions in wound size in both groups. By the fourth week, 75% of patients achieved clinical healing. The PHMB group demonstrated a 75.13% reduction in wound size, compared to a 37.38% reduction in the PRP group. However, due to the small sample size, no statistical significance was found between wound size, healing time, and dressing type. This report suggests no clear relationship between treatment, healing duration, and wound diameter. Additionally, PRP did not show a clear financial advantage over PHMB dressings. Randomized control trials with sufficient sample sizes are required to demonstrate overall advantage for each therapy choice
Valoración del efecto de la calcitonina en la consolidación de la fractura de Colles
Se estudian cuarenta pacientes en que se ha producido una Fractura
de Epífisis Distal de Radio (Fractura de POUTEAU-COLLES) en pacientes
mayores de cincuenta años, con signos de osteoroporosis. Se han hecho
dos grupos aleatorios de veinte pacientes.
El grupo A se ha tratado con un programa de calcitonina y calcio que
cubre los tres primeros meses. El grupo B es tratado exclusivamente con
calcio, por igual período.
En ambos la reducción e inmovilización sigue los mismos criterios.
Se evalúan los resultados, observando que el grupo A presenta menos
secuelas dolorosas.The authors have studied 40 patients with fracture of distal
epiphysis of radius (POUTEAU-COLLES' fracture) all of them fifty
years old with signs of osteoporosis.
They have made two groups of patients (20 every one).
The group A has been treated with a program of calcitonin and
calcium during three months. The group B has been treated only
with calcium, three months, as well as the other group.
Both groups have the same criterion of reduction and inmovilization.
The evaluation of results in the first group showed less painful
consequences
Nitrogen abundances in Planet-harbouring stars
We present a detailed spectroscopic analysis of nitrogen abundances in 91
solar-type stars, 66 with and 25 without known planetary mass companions. All
comparison sample stars and 28 planet hosts were analysed by spectral synthesis
of the near-UV NH band at 3360 \AA observed at high resolution with the
VLT/UVES,while the near-IR NI 7468 \AA was measured in 31 objects. These two
abundance indicators are in good agreement. We found that nitrogen abundance
scales with that of iron in the metallicity range -0.6 <[Fe/H]< +0.4 with the
slope 1.08 \pm 0.05. Our results show that the bulk of nitrogen production at
high metallicities was coupled with iron. We found that the nitrogen abundance
distribution in stars with exoplanets is the high [Fe/H] extension of the curve
traced by the comparison sample of stars with no known planets. A comparison of
our nitrogen abundances with those available in the literature shows a good
agreement.Comment: 15 pages, 7 figures, Accepted for publication in A&
Conceptual design of the ITER fast-ion loss detector
et al.A conceptual design of a reciprocating fast-ion loss detector for ITER has been developed and is presented here. Fast-ion orbit simulations in a 3D magnetic equilibrium and up-to-date first wall have been carried out to revise the measurement requirements for the lost alpha monitor in ITER. In agreement with recent observations, the simulations presented here suggest that a pitch-angle resolution of ∼5° might be necessary to identify the loss mechanisms. Synthetic measurements including realistic lost alpha-particle as well as neutron and gamma fluxes predict scintillator signal-to-noise levels measurable with standard light acquisition systems with the detector aperture at ∼11 cm outside of the diagnostic first wall. At measurement position, heat load on detector head is comparable to that in present devices.This research was supported in part by the Spanish Ministry of Economy and Competitiveness (Grant Nos. RYC2011-09152, FIS2015-69362-P, and ENE2012- 31087) and the Marie Curie FP7 Integration Grant (No. PCIG11-GA2012-321455).Peer Reviewe
Oral administration of zein-based nanoparticles reduces glycemia and improves glucose tolerance in rats
The aim was to evaluate the effect of zein-based nanoparticles on the glucose homeostasis, following oral
administration to Wistar rats. For this purpose, bare nanoparticles (NP, with tropism for the upper intestinal
regions) and poly(ethylene glycol)-coated nanoparticles (NP-PEG), with the capability to reach the ileum and
cecum of animals, were evaluated. Both formulations were spherical in shape, displaying sizes around 200 nm
and a negative surface zeta potential. The oral administration of a single dose of these nanoparticles to animals
(50 mg/kg) induced a significant decrease of the glycemia, compared control rats and in animals treated with the
free protein (p < 0.001). Moreover, these nanoparticles improved the glycemic control against an intraperitoneal
glucose tolerance test; particularly NP-PEG. These findings would be due to an increased release of glucagon-like
peptide-1 (GLP-1) by L-cells, which are more abundant in distal regions of the intestine. In fact, the GLP-1 blood
levels of animals treated with nanoparticles were significantly higher than controls (about 40 % and 60 % for NP
and NP-PEG groups, respectively). This higher capability of NP-PEG, with respect to NP, to increase the release of
GLP-1 and control glycemia would be related to its ability to reach the distal areas of the small intestine
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