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We attempt to constrain the efficiency of additional transport or mixing processes that reduce the effect of atomic diffusion in stellar atmospheres. We apply spectral synthesis methods to spectra observed with the GIRAFFE spectrograph on the VLT to estimate abundances of Mg, Ti, Fe, and Ba in stars in the metal-poor globular cluster M30. To the abundances we fit trends of abundances predicted by stellar evolution models assuming different efficiencies of additional transport or mixing processes. The fitting procedure attempts to take into account the effects of parameter-dependent systematic errors in the derived abundances. We find that the parameter $T_0$, which describes the efficiency of additional transport or mixing processes, can almost certainly be constrained to the narrow range $\log_{10}{\left( T_0 / \left[ \mathrm{K} \right] \right)}$ between $6.09$ and $6.2$. This corresponds to decreased abundances for stars at the main sequence turn-off point compared to the red giant branch by $0.2\,\mathrm{dex}$ for Mg, $0.1\,\mathrm{dex}$ for Fe, and $0.07\,\mathrm{dex}$ for Ti. We also find that while our estimates do have non-negligible systematic errors stemming from the continuum placement and the assumed microturbulence, our method can take them into account. Our results partly amend the results of an earlier paper in this article series, that tentatively used a value of $\log_{10}{\left( T_0 / \left[ \mathrm{K} \right] \right)} = 6.0$ when modelling the Spite plateau of lithium. To more easily distinguish physical effects from systematic errors, we recommend that studies of this kind focus on elements for which the expected surface abundances as functions of effective temperature have a distinct structure and cover a wide range., Comment: 20 pages, 11 figures

It is clear that in order to explain many observed stellar phenomenae, atomic diffusion must be included in stellar models. Observed surface abundances allow us to constrain other transport pro- cesses which compete with atomic diffusion. We will focus on the effect of the flow of matter induced by mass-loss in stellar models.

Le sourire que recherchent les orthodontistes en fin de traitement repond generalement a des criteres objectifs, fonctionnels et des criteres esthetiques, plutot subjectifs.Il est clair que dans notre societe le sourire prend une place de choix, comme moyen de communication non verbale; la revalorisation de ce sourire est le principal motif de consultation orthodontique. La revue de litterature nous a permis de collecter les differents facteurs intervenant dans la perception du sourire, et de souligner le caractere interdependant de l’esthetique du sourire et de celle du visage. Existe-t-il une relation sourire/harmonie du visage ?Quels sont les criteres objectifs permettant de savoir si un sourire sera plaisant ou pas ?Notre etude a confirme, la correlation entre l’esthetique du visage et celle du sourire, ainsi que l’influence des facteurs retenus par la litterature. Elle a cependant permis de nuancer l’influence respective des differents facteurs, dans le cadre d’un sourire agreable, d’un sourire peu agreable et d’un sourire disgracieux. Elle a donc mis en evidence les criteres objectifs intervenant dans un rang totalement subjectif.

Aims. Atomic diffusion, including the effect of radiative accelerations on individual elements, leads to important variations of the chemical composition inside the stars. The accumulation in specific layers of the elements, which are the main contributors of the local opacity, leads to hydrodynamical instabilities that modify the internal stellar structure and surface abundances. Our aim is to study these effects and compare the resulting surface abundances with spectroscopic observations Methods. We computed the detailed structure of A-type stars including these effects. We used the Toulouse-Geneva Evolution Code (TGEC), where radiative accelerations are computed using the Single Valued Parameter (SVP) method, and we added double-diffusive convection with mixing coefficients deduced from three-dimensional (3D) simulations. Results. We show that the modification of the initial chemical composition has important effects on the internal stellar mixing and leads to different surface abundances of the elements. The results fit the observed surface chemical composition well if the layers, which are individually mixed by double-diffusive convection, are connected., Comment: 7 pages, 7 figures, accepted in A&A

la plupart des cliches de diffraction. Abstract. 2014 It is shown how electron microdiffraction connected with convergent beam electron diffraction can be used to identify unambiguously the space group of the 03B3,03B3' and 03B5 iron nitrides. The method involves the identification, from microdiffraction patterns, of a partial extinction symbol in agreement with a few possible space groups. The actual space group is then identified by means of the Tanaka "multibeam" method or from observation of the intensity of the diffracted beams on microdiffraction patterns. It is explained how to overcome the experimental difficulties connected with the small crystal size, the texture of the specimen and the absence of HOLZ reflections on most diffraction patterns.

Atomic diffusion in stars can create systematic trends of surface abundances with evolutionary stage. Globular clusters offer useful laboratories to put observational constraints on this theory as one needs to compare abundances in unevolved and evolved stars, all drawn from the same stellar population. In this paper, we show the results of an abundance study of stars in the globular cluster NGC6752 which shows weak but systematic abundances trends with evolutionary phase for Fe, Sc, Ti and Ca. The trends are best explained by a stellar structure model including atomic diffusion with efficient additional mixing. The model allows to correct for sub-primordial stellar lithium abundances of the stars on the Spite plateau, and to match it to the WMAP-calibrated Big-Bang nucleosynthesis predictions to within the mutual 1-sigma errors., Comment: 15 pages, 4 figures and 8 tables

A deficiency in transverse basal development of the maxilla can lead to an arch length and/or a width discrepancy. Limited alveolus bone volume, which directly depends on the underlying basal bone, creates an upper dental arch that is too narrow in relation to the lower arch creating unilateral or bilateral posterior crossbite(s). The cause of this maxillary deficiency is often related to abnormal nasal breathing associated with abnormal tongue function that compromises the volume of expansion of the maxilla during the growth period. The two maxillary bones determine the volume of the alveolar bone, and also the volume of the inferior area of the nasal fossae due to their palatal processes, worsening nasal breathing, which is often already deficient. Treating this maxillary deficit can require a surgical-medical case management of malfunctions by an ENT which can possibly involve maxillary expansion performed orthopedically before the mid-palatal suture becomes ossified in children (synostosis at approximately 15 years of age), or done as a surgically-assisted procedure for adults. Classically, the expander transmits, by the intermediary of the dentition, horizontal forces which make it possible to progressively expand the two halves of the maxilla by distraction and thus progressively to create bone and soft tissue on the median zone of the palatal processes of the maxilla. This type of expander usually causes no problems for adults who receive orthodontic treatment using traditional dental brackets because the dental pressure of the expander uses the same braces that are supporting the brackets placed on the posterior teeth. It is a very different matter when using the lingual technique whose additional cost and complexity is justified when the patient demands esthetic treatment. The use of a classic expander that is attached to the palatal surfaces of first molars will interfere with the system of lingual bonding, which is located on these same surfaces. Therefore, it is difficult to simultaneously perform both treatments.

In general, the smile that orthodontists try to create at the end of treatment satisfies objective functional criteria as well as subjective esthetic criteria.It’s obvious that in today’s society, a smile plays an important role in nonverbal communication: restoring or enhancing this smile is, in fact, the main reason patients consult their orthodontists.After reviewing the literature, we were able to identify various factors involved in the perception of a smile and to underscore the esthetic connection between the smile and the face.Is there a relationship between the smile and facial harmony?What are the objective criteria that allow us to discern whether a smile is pleasant or not?Our study confirmed that the esthetics of the face correlates with the perception of the smile and that the factors discussed in the literature pertaining to this correlation are valid.However, the study has also made it possible to clarify the respective influence of various factors as they relate to a pleasant smile, an unattractive smile or an unsightly smile. Therefore, our study has shown that objective functional criteria are involved in the entirely subjective esthetic realm of a smile.

Context. Abundance anomalies have been observed in field sdB stars and in nearly all Horizontal Branch (HB) stars of globular clusters with Teff > 11 000K whatever be the cluster metallicity. Aims. The aim is to determine the abundance variations to be expected in sdB stars and in HB stars of metallicities Z \geq 0.0001 and what observed abundances teach us about hydrodynamical processes competing with atomic diffusion. Methods. Complete stellar evolution models, including the effects of atomic diffusion and radiative acceleration, have been computed from the zero age main-sequence for metallicities of Z0 = 0.0001, 0.001, 0.004 and 0.02. On the HB the masses were selected to cover the Teff interval from 7000 to 37000K. Some 60 evolutionary HB models were calculated. The calculations of surface abundance anomalies during the horizontal branch depend on one parameter, the surface mixed mass. Results. For sdB stars with Teff < 37000K and for HB stars with Teff > 11 000K in all observed clusters, independent of metallicity, it was found that most observed abundance anomalies (even up to ~ x 200) were compatible, within error bars, with expected abundances. A mixed mass of ~1.E-7 M\odot was determined by comparison with observations. Conclusions. Observations of globular cluster HB stars with Teff > 11 000K and of sdB stars with Teff < 37 000K suggest that most observed abundance anomalies can be explained by element separation driven by radiative acceleration occuring at a mass fraction of ~1.E-7 M\odot. Mass loss or turbulence appear to limit the separation between 1.E-7 M\odot and the surface., Accepted for publication by A&A

Context. Atomic diffusion has been found to play a role during most stellar evolution stages. Aims. Its effect is studied during the relatively rapid red giant (RG) phase to determine the concentration variations it leads to and at what accuracy level it can be safely neglected. Methods. A model calculated with atomic diffusion to the helium flash is compared to one calculated without any atomic diffusion and to one calculated with atomic diffusion up to a point on the subgiant branch well past the turnoff but without diffusion thereafter. Results. For stars with a metallicity of Z = 10 -4 , it was found that the mass of the helium core at which the He flash occurs is 0.0026 M ⊙ larger in the presence of atomic diffusion. The difference decreases to 0.0017 M ⊙ as metallicity is increased to Z = 0.02. Radiative accelerations are found to play an interesting role around the hydrogen burning shell. The atomic diffusion of 4 He is also shown to lead to a larger μ inversion than 3 He burning. Its potential role in mixing between the burning shell and the surface convection zone is investigated. Conclusions. Whether one may neglect atomic diffusion during the RG phase depends on the required accuracy. It is not so negligible as one may have expected but still only reduces by about 0.02 dex the luminosity of the RG branch bump. The way it modifies the mass of the core when the flash occurs depends on metallicity.