Lithium in field Am and normal A-F-type stars

Preliminary abundances of lithium and a few other elements have been obtained for 31 field Am stars with good Hipparcos parallaxes, as well as for 36 normal A and F stars. Radial and projected rotational velocities were determined as well. We examine the Li abundance as a function of the stellar parameters: for normal stars, it is clearly bimodal for Teff < 7500 K, while Am-Fm stars are all somewhat Li-deficient in this range. The most Li-deficient stars - either Am or normal - tend to be at least slightly evolved, but the reverse is not true.Comment: 4 pages, 2 figures, poster presented at the conference "Element stratification in stars, 40 years of atomic diffusion", eds. G. Alecian, O. Richard and S. Vauclair, EAS Publication Series, in pres

Simulation of a Hybrid Optical/Radio/Acoustic Extension to IceCube for EeV Neutrino Detection

Astrophysical neutrinos at $\sim$EeV energies promise to be an interesting source for astrophysics and particle physics. Detecting the predicted cosmogenic (``GZK'') neutrinos at 10$^{16}$ - 10$^{20}$ eV would test models of cosmic ray production at these energies and probe particle physics at $\sim$100 TeV center-of-mass energy. While IceCube could detect $\sim$1 GZK event per year, it is necessary to detect 10 or more events per year in order to study temporal, angular, and spectral distributions. The IceCube observatory may be able to achieve such event rates with an extension including optical, radio, and acoustic receivers. We present results from simulating such a hybrid detector.Comment: 4 pages, 2 figures; to appear in the Proceedings of the 29th ICRC, Pune, Indi

Study of the flat to slant crack transition in ductile thin sheet material : simulations and experiments

International audienceFlat to slant crack transition can typically be observed in ductile thin sheet materials. The crack initiates perpendicularly to the loading direction from the notch and then turns to 45° with respect to the loading direction during crack propagation. This phenomenon is, however, still not well understood and, so far, attempts to simulate the transition in three dimensions often fail to predict macroscopic loads correctly. In this study an initial attempt has been made to reproduce the flat to slant transition performing an implicit 3D Finite Element simulation via adapting a Gurson-type model. A second void nucleation term for deformation under shear was introduced.The Lode parameter was used here to identify shear deformation. Using this modification the flat to slant transition has been reproduced successfully at loads similar to the experimental results. Further experimental investigations of void growth in the flat and slant crack propagation regime have been carried out. Cracks in Kahn tear test specimens have been arrested in the three regimes and subsequently been observed via Synchrotron Radiation Tomography of the crack tips 3D quantitative void growth analyses ahead of the crack tip in the flat and slant regimes have confirmed the change in fracture mechanisms: void growth in the flat region is substantially higher as compared to the slant crack propagation region

Stabilized Schemes for the Hydrostatic Stokes Equations

Some new stable finite element (FE) schemes are presented for the hydrostatic Stokes system or primitive equations of the ocean. It is known that the stability of the mixed formulation ap- proximation for primitive equations requires the well-known Ladyzhenskaya–Babuˇska–Brezzi condi- tion related to the Stokes problem and an extra inf-sup condition relating the pressure and the vertical velocity. The main goal of this paper is to avoid this extra condition by adding a residual stabilizing term to the vertical momentum equation. Then, the stability for Stokes-stable FE combinations is extended to the primitive equations and some error estimates are provided using Taylor–Hood P2 –P1 or miniele- ment (P1 +bubble)–P1 FE approximations, showing the optimal convergence rate in the P2 –P1 case. These results are also extended to the anisotropic (nonhydrostatic) problem. On the other hand, by adding another residual term to the continuity equation, a better approximation of the vertical derivative of pressure is obtained. In this case, stability and error estimates including this better approximation are deduced, where optimal convergence rate is deduced in the (P 1 +bubble)–P1 case. Finally, some numerical experiments are presented supporting previous results

Ecologic correlations of selected food groups with disease incidence and mortality in Switzerland.

Background: There is little information regarding the impact of diet on disease incidence and mortality in Switzerland. We assessed ecologic correlations between food availability and disease.Methods: In this ecologic study for the period 1970-2009, food availability was measured using the food balance sheets of the Food and Agriculture Organization of the United Nations. Standardized mortality rates (SMRs) were obtained from the Swiss Federal Office of Statistics. Cancer incidence data were obtained from the World Health Organization Health For All database and the Vaud Cancer Registry. Associations between food availability and mortality/incidence were assessed at lags 0, 5, 10, and 15 years by multivariate regression adjusted for total caloric intake.Results: Alcoholic beverages and fruit availability were positively associated, and fish availability was inversely associated, with SMRs for cardiovascular diseases. Animal products, meat, and animal fats were positively associated with the SMR for ischemic heart disease only. For cancer, the results of analysis using SMRs and incidence rates were contradictory. Alcoholic beverages and fruits were positively associated with SMRs for all cancer but inversely associated with all-cancer incidence rates. Similar findings were obtained for all other foods except vegetables, which were weakly inversely associated with SMRs and incidence rates. Use of a 15-year lag reversed the associations with animal and vegetal products, weakened the association with alcohol and fruits, and strengthened the association with fish.Conclusions: Ecologic associations between food availability and disease vary considerably on the basis of whether mortality or incidence rates are used in the analysis. Great care is thus necessary when interpreting our results

Ductile rupture of prestrained X100 pipeline steel sheets

International audienceThe mechanical and damage behavior of a X100 steel after prestrain is studied in thiswork. Experimental results show both a plastic and rupture anisotropy: the T direction exhibits ahigher ultimate stress but the lowest ductility and toughness. Prestrain reduces ductility and crackgrowth resistance. A model able to represent the plastic and damage behaviour of the material beforeand after prestrain is proposed. The model incorporates plastic anisotropy, kinematic hardening, voidgrowth of the primary cavities, nucleation of secondary voids on carbides. Using the model afterimplementation in a FE software, allows to reproduce experimental trends

A generic framework for context-sensitive analysis of modular programs

Context-sensitive analysis provides information which is potentially more accurate than that provided by context-free analysis. Such information can then be applied in order to validate/debug the program and/or to specialize the program obtaining important improvements. Unfortunately, context-sensitive analysis of modular programs poses important theoretical and practical problems. One solution, used in several proposals, is to resort to context-free analysis. Other proposals do address context-sensitive analysis, but are only applicable when the description domain used satisfies rather restrictive properties. In this paper, we argüe that a general framework for context-sensitive analysis of modular programs, Le., one that allows using all the domains which have proved useful in practice in the non-modular setting, is indeed feasible and very useful. Driven by our experience in the design and implementation of analysis and specialization techniques in the context of CiaoPP, the Ciao system preprocessor, in this paper we discuss a number of design goals for context-sensitive analysis of modular programs as well as the problems which arise in trying to meet these goals. We also provide a high-level description of a framework for analysis of modular programs which does substantially meet these objectives. This framework is generic in that it can be instantiated in different ways in order to adapt to different contexts. Finally, the behavior of the different instantiations w.r.t. the design goals that motivate our work is also discussed

Experimental and computational analysis of toughness anisotropy in an AA2139 Al-alloy for aerospace applications

International audienceFracture toughness anisotropy of AA2139 (Al-Cu-Mg) in T351 and T8 conditions has been investigated via mechanical testing of smooth and notched specimens of different geometries, loaded in the rolling direction (L) or in the transverse direction (T). Fracture mechanisms were investigated via SEM and synchrotron radiation computed tomography (SRCT). Contributions to failure anisotropy are identified with: (i) anisotropic initial void shape and growth, (ii) plastic behaviour including isotropic/kinematic hardening and plastic anisotropy, and (iii) nucleation at a 2nd population of 2nd phase particles leading to coalescence via narrow crack regions. A model based in part on the Gurson-Tvergaard-Needleman approach is constructed to describe and predict deformation behaviour, crack propagation and, in particular, toughness anisotropy. Model parameters are fitted using microstructural data and data on deformation and crack propagation for a range of small test samples. Its transferability has been shown by simulating tests of large M(T) samples

Local approach of fracture on semi-crystalline polymers : contribution of X-ray laminography technique

International audienceDamage mechanisms in a PolyAmide 6 semi-crystalline polymer were characterized by using Synchrotron Radiation Laminography technique on CT like specimen. Damage appeared as multiple penny shaped crazes. The maximum damage occurred at mid-thickness and located at a small distance from the notch root. An attempt was made to apply local approach of fracture concept thanks to finite element analysis using damage-based constitutive model. FE simulation successfully captured the aforementioned micro-mechanisms of crack initiation, by void coalescence. Further work is carried out to determine the crack dimension corresponding to the maximum net stress: the criterion being used for the global approach of fracture

Z boson transverse momentum spectrum from the lepton angular distributions

In view of recent discussions concerning the possibly limiting energy resolution systematics on the measurement of the Z boson transverse momentum distribution at hadron colliders, we propose a novel measurement method based on the angular distributions of the decay leptons. We also introduce a phenomenological parametrization of the transverse momentum distribution that adapts well to all currently available predictions, a useful tool to quantify their differences.Comment: 12 pages, 6 figure