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

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 $\sim$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

Behaviour of the Absorptive Part of the W Electromagnetic Vertex

The absorptive part of the $WW\gamma$ vertex induced by massive fermion loops is considered for different kinematical configurations. We show that the axial part of this vertex is different from zero not only when massive fermions are involved but also for massless fermion loops, if one of the W bosons is space-like and the other is time-like. We also discuss in what sense Low's soft photon theorem is satisfied.Comment: 17 pages, 1 figure, LaTe

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&

Constant probe orientation for fast contact-based inspection of 3D free-form surfaces using (3+2)-axis inspection machines

A new probe optimization method for contact based (3+2)-axis inspection machines is proposed. Given an inspection path of a stylus on a free-form surface, an optimal orientation of the stylus is computed such that (i) the inclination angle of the stylus is within a given angular range with respect to the surface normal, (ii) the motion of the stylus is globally collision free, and (iii) the stylus remains constant in the coordinate system of the measuring machine. The last condition guarantees that the inspection motion requires only the involvement of the three translational axes of the measuring machine. The numerical simulations were validated through physical experiments on a testcase of a tooth of a bevel gear due to the surface complexity and probe accessibility. This optimized method was compared to 3-axis and 5-axis inspection strategies, showing that the fixed (3+2)-axis stylus returns more accurate inspection results compared to the traditional 3-axis approach and similar to 5-axis approach

Galactic Evolution of Nitrogen

We present detailed spectroscopic analysis of nitrogen abundances in 31 unevolved metal-poor stars analysed by spectral synthesis of the near-UV NH band at 3360 A observed at high resolution with various telescopes. We found that [N/Fe] scales with that of iron in the metallicity range -3.1 < [Fe/H] <0 with the slope 0.01+-0.02. Furthermore, we derive uniform and accurate (N/O) ratios using oxygen abundances from near-UV OH lines obtained in our previous studies. We find that a primary component of nitrogen is required to explain the observations. The NH lines are discovered in the VLT/UVES spectra of the very metal-poor subdwarfs G64-12 and LP815-43 indicating that these stars are N rich. The results are compared with theoretical models and observations of extragalactic HII regions and Damped Ly$\alpha$ systems. This is the first direct comparison of the (N/O) ratios in these objects with those in Galactic stars.Comment: 10 pages, 6 figures, to appear in Astronomy and Astrophysic

Coexistence of Two Rare Sarcomas: Primary Leiomyosarcoma of Bone and Epithelioid Hemangioendothelioma of the Liver

A 33-year-old woman sought medical attention for a painful swelling of the left ankle. Plain radiographs revealed an osteolytic lesion involving the left distal tibia. An excisional biopsy provided the diagnosis of leiomyosarcoma in the tibia. A staging work-up was performed and an abdominal CT showed 4 liver hypodense lesions in both lobes with peripheral contrast enhancement. A liver biopsy confirmed the diagnosis of epithelioid hemangioendothelioma of the liver. No association between these two entities has been described before. This case introduces the importance of the pathological confirmation of apparent metastatic lesions in low grade sarcomas and provides a review of the literature of both tumours

Chemical abundances of planet-host stars: Results for alpha and Fe-group elements

In this paper, we present a study of the abundances of Si, Ca, Sc, Ti, V, Cr, Mn, Co, and Ni in a large set of stars known to harbor giant planets, as well as in a comparison sample of stars not known to have any planet ary-mass companions. We have checked for possible chemical differences between planet hosts and field stars without known planets. Our results show that overall, and for a given value of [Fe/H], the abundance trends for the planet hosts are nearly indistinguishable from those of the field stars. In general, the trends show no discontinuities,and the abundance distributions of stars with giant planets are high [Fe/H] extensions to the curves traced by the field dwarfs without planets. The only elements that might present slight differences between the two groups of stars are V, Mn, and to a lesser extent Ti and Co. We also use the available data to describe galactic chemical evolution trends for the elements studied. When comparing the results with former studies, a few differences emerge for the high [Fe/H] tail of the distribution, a region that is sampled with unprecedented detail in our analysis.Comment: Accepted for publication in Astronomy & Astrophysic

The blaSHV-5 gene is encoded in a compound transposon duplicated in tandem in Enterobacter cloacae

AbstractThe presence of blaSHV-5 is described in a compound transposon, duplicated in tandem and flanked by IS26 copies on a 70-kb conjugative plasmid (pHNM1), in an Enterobacter cloacae strain associated with a nosocomial outbreak that occurred in Mexico