802 research outputs found
Clinical survey of neurosensory side-effects of mandibular parasymphyseal bone harvesting
The aim of the present survey was to assess neurosensory disturbances and/or tooth-pulp sensitivity losses after mandibular parasymphyseal bone-harvesting procedures. Twenty-eight harvesting areas in 16 patients were surveyed. Mucosal and skin sensitivity of the chin/lower lip, divided into four regions, were determined via Pointed-Blunt and Two-Point-Discrimination Tests. Pulp sensitivity of the mandibular teeth from the left second bicuspid to the right second bicuspid was tested by cold vitality preoperatively and 12 months postoperatively. Teeth were grouped according to sensitivity alterations and distance from the harvesting defects, as measured on CT scans, and statistically significant differences sought. At 12 months, 29% of preoperatively vital cuspids overlying the harvesting defects revealed pulp-sensitivity losses; no patient reported anaesthesia or analgesia; hypoaesthesia was present in 4% (8 sites; 2 patients), hypoalgesia was present in 3% (5 sites; 2 patients) and Two-Point-Discrimination Tests yielded pathologic responses in 5% of tested areas (10 sites; 4 patients). Teeth with and without pulp sensitivity changes were statistically indistinguishable regarding distances between root apices or mental foramen and the harvesting defect. The loss of pulp sensitivity in any tooth cannot be predicted simply on the basis of the distance between its apex and the harvesting osteotomy line
Globular Cluster Abundances and What They Can Tell Us About Galaxy Formation
We review the properties of globular clusters which make them useful for
studying the Galactic halo, Galactic chemical evolution, and the early stages
of the formation of the Milky Way. We review the evidence that GCs have a
chemical inventory similar to those of halo field stars. We discuss the
abundance ratios for dSph galaxies and show that it is possible to have formed
at least part the Galactic halo field stellar population by dissolving globular
clusters and/or accreting dSph galaxies but only if this occurred at an early
stage in the formation of the Galaxy. We review the constraints on halo
formation timescales deduced from the low Mg isotopic ratios in metal-poor halo
field dwarfs which indicate that AGB stars did not have time to contribute
significantly, while M71 contains two populations, one without and also one
with a substantial AGB contribution. We review the limited evidence for GCs
with a second population showing additional contributions from SNII, currently
confined to Omega Cen, M54, and M22, all of which may have been the nuclei or
central regions of accreted galaxies. We check our own data for additional such
GCs, and find preliminary indications that NGC 2419, a massive GC far in the
outer Galactic halo, may also belong to this group.Comment: Invited Talk: IAU Symp. 266, Star Clusters - Basic Building Blocks
Throughout Time and Space, proceedings to be published by Cambridge
University Pres
Clues on the Galactic evolution of sulphur from star clusters
(Abridged) The abundances of alpha-elements are a powerful diagnostic of the
star formation history and chemical evolution of a galaxy. Sulphur, being
moderately volatile, can be reliably measured in the interstellar medium (ISM)
of damped Ly-alpha galaxies and extragalactic HII regions. Measurements in
stars of different metallicity in our Galaxy can then be readily compared to
the abundances in external galaxies. Such a comparison is not possible for Si
or Ca that suffer depletion onto dust in the ISM. Furthermore, studying sulphur
is interesting because it probes nucleosynthetic conditions that are very
different from those of O or Mg. The measurements in star clusters are a
reliable tracers of the Galactic evolution of sulphur. We find
NLTE=6.11+/-0.04 for M 4, NLTE=7.17+/-0.02 for NGC 2477, and
NLTE=7.13+/-0.06 for NGC 5822. For the only star studied in Trumpler 5 we
find A(S)NLTE=6.43+/-0.03 and A(S)LTE=6.94+/-0.05. Our measurements show that,
by and large, the S abundances in Galactic clusters trace reliably those in
field stars. The only possible exception is Trumpler 5, for which the NLTE
sulphur abundance implies an [S/Fe] ratio lower by roughly 0.4 dex than
observed in field stars of comparable metallicity, even though its LTE sulphur
abundance is in line with abundances of field stars. Moreover the LTE sulphur
abundance is consistent only with the abundance of another alpha-element, Mg,
in the same star, while the low NLTE value is consistent with Si and Ca. The S
abundances in our sample of stars in clusters imply that the clusters are
chemically homogeneous for S within 0.05 dex.Comment: A&A in pres
3D molecular line formation in dwarf carbon-enhanced metal-poor stars
We present a detailed analysis of the carbon and nitrogen abundances of two
dwarf carbon-enhanced metal-poor (CEMP) stars: SDSS J1349-0229 and SDSS
J0912+0216. We also report the oxygen abundance of SDSS J1349-0229. These stars
are metal-poor, with [Fe/H] < -2.5, and were selected from our ongoing survey
of extremely metal-poor dwarf candidates from the Sloan Digital SkySurvey
(SDSS). The carbon, nitrogen and oxygen abundances rely on molecular lines
which form in the outer layers of the stellar atmosphere. It is known that
convection in metal-poor stars induces very low temperatures which are not
predicted by `classical' 1D stellar atmospheres. To obtain the correct
temperature structure, one needs full 3D hydrodynamical models. Using CO5BOLD
3D hydrodynamical model atmospheres and the Linfor3D line formation code,
molecular lines of CH, NH, OH and C2 were computed, and 3D carbon, nitrogen and
oxygen abundances were determined. The resulting carbon abundances were
compared to abundances derived using atomic CI lines in 1D LTE and NLTE. There
is not a good agreement between the carbon abundances determined from C2 bands
and from the CH band, and molecular lines do not agree with the atomic CI
lines. Although this may be partly due to uncertainties in the transition
probabilities of the molecular bands it certainly has to do with the
temperature structure of the outer layers of the adopted model atmosphere. We
explore the influence of the 3D model properties on the molecular abundance
determination. In particular, the choice of the number of opacity bins used in
the model calculations and its subsequent effects on the temperature structure
and molecular line formation is discussed. (Abridged)Comment: Poster presented at IAU JD 10, Rio de Janeiro, 10-11 August 2009,
published in Memorie della Societa' Astronomica Italiana, Vol. 80 n.3 P.735.
One reference corrected, matches the published versio
Three carbon-enhanced metal-poor dwarf stars from the SDSS - Chemical abundances from CO^5BOLD 3D hydrodynamical model atmospheres
The origin of carbon-enhanced metal-poor stars enriched with both s and r
elements is highly debated. Detailed abundances of these types of stars are
crucial to understand the nature of their progenitors. The aim of this
investigation is to study in detail the abundances of SDSS J1349-0229, SDSS
J0912+0216 and SDSS J1036+1212, three dwarf CEMP stars, selected from the Sloan
Digital Sky Survey. Using high resolution VLT/UVES spectra (R ~ 30 000) we
determine abundances for Li, C, N, O, Na, Mg, Al, Ca, Sc, Ti, Cr, Mn, Fe, Co,
Ni and 21 neutron-capture elements. We made use of CO^5BOLD 3D hydrodynamical
model atmospheres in the analysis of the carbon, nitrogen and oxygen
abundances. NLTE corrections for C I and O I lines were computed using the Kiel
code. We classify SDSS J1349-0229 and SDSS J0912+0216 as CEMP-r+s stars. SDSS
J1036+1212 belongs to the class CEMP-no/s, with enhanced Ba, but deficient Sr,
of which it is the third member discovered to date. Radial-velocity variations
have been observed in SDSS J1349-0229, providing evidence that it is a member
of a binary system. The chemical composition of the three stars is generally
compatible with mass transfer from an AGB companion. However, many details
remain difficult to explain. Most notably of those are the abundance of Li at
the level of the Spite plateau in SDSS J1036+1212 and the large over-abundance
of the pure r-process element Eu in all three stars.Comment: 12 pages, 15 figures. Accepted for publication in A&
Chemical composition of a sample of bright solar-metallicity stars
We present a detailed analysis of seven young stars observed with the
spectrograph SOPHIE at the Observatoire de Haute-Provence for which the
chemical composition was incomplete or absent in the literature. For five
stars, we derived the stellar parameters and chemical compositions using our
automatic pipeline optimized for F, G, and K stars, while for the other two
stars with high rotational velocity, we derived the stellar parameters by using
other information (parallax), and performed a line-by-line analysis.
Chromospheric emission-line fluxes from CaII are obtained for all targets. The
stellar parameters we derive are generally in good agreement with what is
available in the literature. We provide a chemical analysis of two of the stars
for the first time. The star HIP 80124 shows a strong Li feature at 670.8 nm
implying a high lithium abundance. Its chemical pattern is not consistent with
it being a solar sibling, as has been suggested.Comment: To be published on A
- …