Sand transport over a barchan dune

The present work investigates an important and yet unsolved issue: the relationship between the sand flux and the fluid shear stress over a spatially varying bed of particles. It is now recognized that over such a bed, the particle flux is not in equilibrium with the shear stress: there is some lag related to the particle inertia or particle settling. A confident modelling of this relaxation phenomena and the corresponding length scales, is still lacking (Charru, Andreotti and Claudin 2013). This question is investigated here from experiments on barchan dunes in a closed-conduit water flow. From visualizations with a high-speed camera and a tracking algorithm, the particle motion over the whole dune surface is determined: particle trajectories, local velocity and surface density of the moving particles, and local particle flux. The relationship between the local particle flux and local shear stress (estimated from previous analyses) is investigated. Surprisingly, the particle flux appears to be out-ofequilibrium over the whole dune surface, with saturation length much larger than expected

Determination of the sand flux over a barchan dune under a water flow

The modelling of sand transport by uid ows is crucial in many environmental as well as industrial problems. The present work investigates an important and yet unsolved issue: the relationship between the particle ux and the shear stress exerted by the uid ow at the bed surface

Towards the measurement of Enterprise Information Systems agility to support EIS improving projects

International audienceEnterprise information systems (EIS) are directly implied in the global performance of an organisation. Nevertheless, their potential rigidity in comparison with the required fast evolution of the supported organisation remains an important open research question. The proposed research work aims to define and evaluate the agility of an EIS, in order to assist both software engineers and business managers in EIS improvement projects. In particular, a framework is proposed to structure the different existing metrics on agility according to the improvements needs and the intrinsic characteristics of an information system

Towards Assessment of information system agility

International audienceCurrently, the information systems agility and the satisfaction of the dynamic environment requirements is essential challenges for companies. The purpose of this paper is to represent the existing approaches for achieving agility in software development as well as in production system. The objective is to identify the relevant metrics for evaluating information system agility. Then, we propose an analysis model that contains these agile metrics, to observe their combination in information system

Influence de la gravité sur le transport granulaire en écoulement turbulent

Une étude expérimentale est menée afin de déterminer l'influence de la gravité sur les mécanismes de transport granulaire par un écoulement. Le dispositif est constitué d'un canal inclinable jusqu'à de fortes pentes. On s'intéressera aux notions de seuil de mise en mouvement et vitesses de dunes ainsi formées. Ceci permettra de constater que la pente impacte avant tout chose le nombre de Shields critique et ne modifie pas la vitesse des dunes, dépendante uniquement de l'écart au seuil malgré un changement dans leur morphologie

Synthesis and Radioprotective Activity of New Organosilicon and Germanium Compounds

Silathiazolidine and metalladithioacetals (M = Si, Ge) have been prepared by the interaction of dialkyldichloro- or bis(diethylamino)dialkylsilanes and -germanes with 3-[N-(2- thioethyl)]amino-propanamide (WR-2529) and [1-thioethyl-2-(1-naphtylmethyl)]-2- imidazoline. The study of these compounds in the field of chemical radioprotection has shown a notable decrease in the toxicity and a rather large increase in the radioprotective activity of these new derivatives in comparison with the starting organic compounds

A Review on the Radioprotective Activity of organogermanium and Organosilicon Compounds

The present review describes the work carried out during the last 20 years in the field of the radioprotective activity and toxicity of several classes of organosilicon and organogermanium compounds (i.e. metallathiazolidines, metalladithioacetals, metallatranes and germathianes)

Evaluation of the Housing First program in patients with severe mental disorders in France: study protocol for a randomized controlled trial.

International audienceBACKGROUND: Recent studies in North American contexts have suggested that the Housing First model is a promising strategy for providing effective services to homeless people with mental illness. In the context of the highly generous French national health and social care system, which is easily accessible and does not require out-of-pocket payment, the French Health Ministry insists on rigorous techniques, including randomized protocols, to evaluate the impact of Housing First approaches in France.Method and design: A prospective randomized trial was designed to assess the impact of a Housing First intervention on health outcomes and costs over a period of 24 months on homeless people with severe mental illness, compared to Treatment-As-Usual. The study is being conducted in four cities in France: Lille, Marseille, Paris and Toulouse. The inclusion criteria are as follows: over 18 years of age, absolutely homeless or in precarious housing, and possessing a 'high' level of need: diagnosis of schizophrenia or bipolar disorder and moderate to severe disability according to the Multnomah Community Ability Scale (score <= 62) and at least one of the following three criteria: 1) having been hospitalized for mental illness two or more times in any one year during the preceding five years; 2) co-morbid alcohol or substance use; and 3) having been recently arrested or incarcerated. Participants will be randomized to receiving the Housing First intervention or Treatment-As-Usual. The Housing First intervention provides immediate access to independent housing and community care. The primary outcome criterion is the use of high-cost health services (that is,, number of hospital admissions and number of emergency department visits) during the 24-month follow-up period. Secondary outcome measures include health outcomes, social functioning, housing stability and contact with police services. An evaluation of the cost-effectiveness and cost-utility of Housing First will also be conducted. A total of 300 individuals per group will be included. DISCUSSION: This is the first study to examine the impact of a Housing First intervention compared to Treatment-As-Usual in France. It should provide key information to policymakers concerning the cost-effectiveness and health outcomes of the Housing First model in the French context.Trial registration: The current clinical trial number is NCT01570712

Forced Stratified Turbulence: Successive Transitions with Reynolds Number

Numerical simulations are made for forced turbulence at a sequence of increasing values of Reynolds number, R, keeping fixed a strongly stable, volume-mean density stratification. At smaller values of R, the turbulent velocity is mainly horizontal, and the momentum balance is approximately cyclostrophic and hydrostatic. This is a regime dominated by so-called pancake vortices, with only a weak excitation of internal gravity waves and large values of the local Richardson number, Ri, everywhere. At higher values of R there are successive transitions to (a) overturning motions with local reversals in the density stratification and small or negative values of Ri; (b) growth of a horizontally uniform vertical shear flow component; and (c) growth of a large-scale vertical flow component. Throughout these transitions, pancake vortices continue to dominate the large-scale part of the turbulence, and the gravity wave component remains weak except at small scales.Comment: 8 pages, 5 figures (submitted to Phys. Rev. E