Relativistic Lagrange Formulation

It is well-known that the equations for a simple fluid can be cast into what is called their Lagrange formulation. We introduce a notion of a generalized Lagrange formulation, which is applicable to a wide variety of systems of partial differential equations. These include numerous systems of physical interest, in particular, those for various material media in general relativity. There is proved a key theorem, to the effect that, if the original (Euler) system admits an initial-value formulation, then so does its generalized Lagrange formulation.Comment: 34 pages, no figures, accepted in J. Math. Phy

Initial Conditions for Large Cosmological Simulations

This technical paper describes a software package that was designed to produce initial conditions for large cosmological simulations in the context of the Horizon collaboration. These tools generalize E. Bertschinger's Grafic1 software to distributed parallel architectures and offer a flexible alternative to the Grafic2 software for ``zoom'' initial conditions, at the price of large cumulated cpu and memory usage. The codes have been validated up to resolutions of 4096^3 and were used to generate the initial conditions of large hydrodynamical and dark matter simulations. They also provide means to generate constrained realisations for the purpose of generating initial conditions compatible with, e.g. the local group, or the SDSS catalog.Comment: 12 pages, 11 figures, submitted to ApJ

The distribution of nearby stars in phase space mapped by Hipparcos: I. The potential well and local dynamical mass

Hipparcos data provide the first, volume limited and absolute magnitude limited homogeneous tracer of stellar density and velocity distributions in the solar neighbourhood. The density of A-type stars more luminous than $M_v=2.5$ can be accurately mapped within a sphere of 125 pc radius, while proper motions in galactic latitude provide the vertical velocity distribution near the galactic plane. The potential well across the galactic plane is traced practically hypothesis-free and model-free. The local dynamical density comes out as \rho_{0}=0.076 \pm0.015~M_{\sun}~{pc}^{-3} a value well below all previous determinations leaving no room for any disk shaped component of dark matter.Comment: 24 pages, 13 figures, latex. To appear in A&A (main journal

On the kinematic deconvolution of the local neighbourhood luminosity function

A method for inverting the statistical star counts equation, including proper motions, is presented; in order to break the degeneracy in that equation it uses the supplementary constraints required by dynamical consistency. The inversion gives access to both the kinematics and the luminosity function of each population in three r\'egimes: the singular ellipsoid, the constant ratio Schwarzschild ellipsoid plane parallel models and the epicyclic model. This more realistic model is taylored to account for local neighbourhood density and velocity distribution. The first model is fully investigated both analytically and via means of a non-parametric inversion technique, while the second model is shown to be formally its equivalent. The effect of noise and incompleteness in apparent magnitude is investigated. The third model is investigated via a 5D+2D non-parametric inversion technique where positivity of the underlying luminosity function is explicitely accounted for. It is argued that its future application to data such as the Tycho catalogue (and in the upcoming satellite GAIA) could lead -- provided the vertical potential, and/or the asymmetric drift or w_0 are known -- to a non-parametric determination of the local neighbourhood luminosity function without any reference to stellar evolution tracks. It should also yield the proportion of stars for each kinematic component and a kinematic diagnostic to split the thin disk from the thick disk or the halo.Comment: 18 pages, LateX (or Latex, etc), mnras, accepted for publicatio

Stellar dynamics in the Galactic Centre: proper motions and anisotropy

We report a new analysis of the stellar dynamics in the Galactic Centre, based on improved sky and line-of-sight velocities for more than 100 stars in the central few arcseconds from the black hole candidate SgrA*. The main results are as follows. (1)Overall, the stellar motions do not deviate strongly from isotropy. For those 32 stars with a determination of all three velocity components, the absolute, line-of-sight and sky velocities are in good agreement, consistent with a spherical star cluster. Likewise the sky-projected radial and tangential velocities of all 104 proper motion stars in our sample are also consistent with overall isotropy. (2)However, the sky-projected velocity components of the young, early-type stars in our sample indicate significant deviations from isotropy, with a strong radial dependence. Most of the bright He i emission-line stars at separations from 1 to 10 arcsec from SgrA* are on tangential orbits. This tangential anisotropy of the He i stars and most of the brighter members of the IRS 16 complex is largely caused by a clockwise (on the sky) and counter-rotating (line of sight, compared to the Galaxy), coherent rotation pattern. The overall rotation of the young star cluster may be a remnant of the original angular momentum pattern in the interstellar cloud from which these stars were formed. (3)The fainter, fast-moving stars within ≈1 arcsec of SgrA* may be largely moving on radial or very elliptical orbits. We have so far not detected deviations from linear motion (i.e., acceleration) for any of them. Most of the SgrA* cluster members are also on clockwise orbits. Spectroscopy indicates that they are early-type stars. We propose that the SgrA* cluster stars are those members of the early-type cluster that happen to have small angular momentum, and thus can plunge to the immediate vicinity of SgrA*. (4)We derive an anisotropy-independent estimate of the Sun—Galactic Centre distance between 7.8 and 8.2 kpc, with a formal statistical uncertainty of ±0.9 kpc. (5)We explicitly include velocity anisotropy in estimating the central mass distribution. We show how Leonard—Merritt and Bahcall—Tremaine mass estimates give systematic offsets in the inferred mass of the central object when applied to finite concentric rings for power-law clusters. Corrected Leonard—Merritt projected mass estimators and Jeans equation modelling confirm previous conclusions (from isotropic models) that a compact central mass concentration (central density ≥1012.6 M⊙ pc−3) is present and dominates the potential between 0.01 and 1 pc. Depending on the modelling method used, the derived central mass ranges between 2.6×106 and 3.3×106 M⊙ for R⊙=8.0 kp

Thin film transistors fabricated by in-situ doped unhydrogenated polysilicon films obtained by solid phase crystallization

International audienceHigh mobility low temperature (≤ 600°C) unhydrogenated in-situ doped polysilicon thin film transistors are made. Polysilicon layers are grown by a LPCVD technique and crystallized in vacuum by a thermal annealing. Source and drain regions are in-situ doped. Gate insulator is made of an APCVD silicon dioxide. Hydrogen passivation is not performed on the transistors. One type of transistors is made of two polysilicon layers, the other one is constituted of a single polysilicon layer. The electrical properties are better for transistors made of single polysilicon layer: a low threshold voltage (1.2 V), a subthreshold slope S = 0.7 V/dec, a high field effect mobility (≈ 100 cm2/Vs) and a On/Off state current ratio higher than 107 for a drain voltage Vds = 1 V. At low drain voltage, for both transistors, the Off state current results from a pure thermal emission of trapped carriers. However, at high drain voltage, the electrical behavior is different: in the case of single polysilicon TFTs, the current obeys the field-assisted (Poole-Frenkel) thermal emission model of trapped carriers while for TFTs made of two polysilicon layers, the higher Off state current results from a field-enhanced thermal emission

Acyl-Imidazoles A Privileged Ester Surrogate for Enantioselective Synthesis

International audienceSince the first report by Evans in asymmetric Friedel‐Crafts reactions, the use of acyl‐imidazoles has blossomed as powerful ester/amide surrogates. The imidazole scaffold indeed displays stability and special activation features allowing both better reactivity and selectivity in traditional ester/amide functionalizations: α‐(enolate chemistry), β‐(conjugate additions), α,β‐(cycloadditions) or γ/δ‐(vinylogous). An overview of the contemporary and growing interest in acyl‐imidazoles in metal‐ and organo‐catalyzed transformations (bio‐hybrid catalytic systems will be fully described in a back‐to‐back Minireview) will be highlighted. Moreover, post‐functionalization expediencies are also going to be discussed in this Minireview

Antibiotic consumption in nursing homes of the Canton of Vaud: trends over the years 2009 - 2014

Background & Objectives: Excessive use of antibiotics in nursing homes was reported in several studies1-3. Surveillance of their use in nursing homes is essential to plan interventions fostering an appropriate use and to measure the impact of these interventions. The aims of the study were to describe the antibiotic consumption in nursing homes of the Canton of Vaud and to examine whether the antibiotic consumption was correlated to the urinary catheter use and to methicillin-resistant Staphylococcus aureus (MRSA) colonization. Methods: Data on the use of systemic antibiotics (class J01 of WHO Anatomical Therapeutic Chemical (ATC) system, 2015) were collected from the community pharmacies' annual invoice data including 13 nursing homes in 2009. The number of nursing homes in the database increased to 67 in 2014, representing 46% of all nursing homes of the Canton of Vaud and 54% of the available beds. Aggregated data were converted into defined daily doses (DDD) and antibiotic consumption expressed in number of defined daily doses per 1000 beds and per day (DDD/1000B/D). Proportion of urinary catheter use and MRSA colonization data were provided through a point prevalence study. Results: The total consumption of systemic antibiotics was 52.2 DDD/1000B/D in 2009 and 48.3 in 2014. Beta-lactam antibacterials other than penicillins, macrolides and other antibacterials (including nitrofurantoin) consumption increased resp. by 80%, 45% and 187% between 2009 and 2014, while the use of sulfonamides and trimethoprim decreased by 41%. Penicillin and quinolone use remained relatively stable between 2009 and 2014. Amoxicillin and clavulanic acid (oral) was the most common antibiotic prescribed (31% of the total use), followed by ciprofloxacin (oral) (20%) and nitrofurantoin (10%). Among nursing homes, we reported a large variation in antibiotic consumption from 6.8 to 164.6 DDD/1000B/D in 2014. No correlation was found between global antibiotic consumption and urinary catheter use and between quinolone consumption and proportion of MRSA in 2010 and 2011 (p>0.05). Discussion & Conclusions: This study is the first that analyzes longitudinal data of antibiotic consumption in nursing homes of the Canton of Vaud. The findings suggest that a large variation in antibiotic consumption exists among nursing homes. Thus, antibiotic stewardship programs should be implemented to promote a more accurate use