Regular modes of a mixed dynamical based optical fiber

A multimode optical fiber with a truncated transverse cross section acts as a powerful versatile support to investigate the wave features of complex ray dynamics. In this paper, we concentrate on the case of a geometry inducing a mixed dynamics. We highlight the properties of regular modes associated to stable periodic orbits such as an enhanced intensity localization and report unexpected attributes such as the statistics of the Inverse Participation Ratio that present features analogous to those of Anderson localized modes. Our study is supported by both numerical and experimental results.Comment: 12 pages, 13 figure

Grammaire stratégique

La méthode présentée dans cet article a pour but d'aider les managers d'une entreprise à écrire et à lire les textes stratégiques et à parler entre eux de stratégie. Nous l'appelons une "grammaire stratégique". Elle vise à définir des propositions stratégiques types qui représentent des engagements à agir stratégiquement dans un contexte d'action donné. Le modèle théorique qui sous-tend cette méthode est présenté. Il s'appuie sur la sociologie de l'action de Habermas, et intègre les logiques stratégiques formalisées par Martinet. La méthode a été implémentée grâce à un outil de cartographie (logiciel See-K de Trivium) pour fournir une représentation cartographique de l'ensemble des documents stratégiques des régions du Groupe EDF. La pertinence des énoncés produits automatiquement sur ce corpus conduit à valider le mode d'indexation proposé. Ce travail débouche en outre sur des propositions de déploiement d'une telle approche au sein de EDF, afin de régénérer la production de discours stratégiques, aussi bien sur le fond que sur la forme, et de favoriser le partage de connaissances entre les managers autour de problématiques stratégiques communes.Management stratégique, discours stratégiques, conversations stratégiques, knowledge management, cartographie.

Reducing Ammonia Losses By Adding FeCI3 During Composting Of Sewage Sludge

The release of ammonia nitrogen during composting of sewage sludge mixed with a lignocellulosic bulking agent leads to a reduction in the agronomic value of the final compost and to harmful effects on the environment. We propose adding a cheap salt FeCl3 which can be used without special precaution to reduce ammonia losses by decreasing pH conditions. An in-vessel co-composting experiment was conducted in a large reactor (100 L) in which FeCl3 was added to sludge mixed with a bulking agent (pine shavings and sawdust) and compared with a control mixture without FeCl3. Temperature, oxygen consumption and pH were monitored throughout the composting of both mixtures. The final balance of organic matter, organic and inorganic nitrogen permitted to conclude that the addition of FeCl3 reduced nitrogen loss (by a factor of 2.4 in relation to the control) and increased mineralisation of the organic nitrogen by 1.6

Analysis of the molecular mobility of collagen and elastin in safe, atheromatous and aneurysmal aortas

Aim of the study : In this study, we propose to use a thermal technique, Differential Scanning Calorimetry (DSC) to follow the evolution of elastin and collagen in safe and pathological cardiovascular tissues. Patients and methods : The first part of this study deals with the analysis of the elastin network and associated proteins during ageing (from children to old persons) in aortic walls. The second part is devoted to the characterization of the collagenic phase in aneurysms. In both cases, physical data are correlated with biochemical analyses. Results and conclusion : For old persons aortas with atheromatous stades, elastin and associated proteins are found to interpenetrate to form a homogenous phase. Abdominal aortic aneurysms (AAA) are characterized by structural alterations of the aortic wall resulting from the degradation of elastic fibers and an increase of collagen/elastin ratio. Notable modifications are evidenced between collagen from control tissue and collagen from AAA, particularly concerning the thermal denaturation. Biochemical and thermal results are compatible with the increase of new collagen deposition and/or impairment of the collagen phase stability in the extracellular matrix of AAAs

Influence of physico-chemical characteristics of limestone fillers on fresch and hardened mortar performances

peer reviewedIn order to meet the specific requirements for fresh Self-Compacting Concrete (SCC), i.e. a high workability together with a good resistance to segregation, the amount of coarse aggregates has to be reduced and replaced by fine material. Since cement is quite expensive and can develop a high heat of hydration with possible problems for thermal cracks in massive concrete, mineral fillers are usually used. In Belgium, local available materials are limestone fillers; they are very well-adapted for the optimisation of particle packing and flow behaviour of cementitious paste in SCC mixes. These by-products are issued from different sectors, such as the aggregate and lime production industry (quarrying operations) and the ornamental stones industry (sawing operations). The suitability of these fillers for use in SCC or conventional concrete production was investigated. This paper reports the effect of the nature and the substitution rate of the fillers on the properties of mortars. Some relationship between the physico-chemical properties of the fillers and the properties of mortars were brought forward

Seuils d'absorption des rayons X : un outil de caractérisation indispensable en chimie de coordination.

National audienceSynchrotron radiation allows to perform spectroscopic experiments in an energy range from infra-red to hard X-rays. The paper shows, through particular examples (role of the geometry, of the oxidation and spin state of the absorber ...) how it is possible to extract unique informations from X-ray absorption edges to characterize the electronic structure of the absorbing elements whatever the state of the sample (crystalline, amorphous, liquid, solution, gaseous). The interpretation of the data is proposed at a double level : qualitative, thanks to symmetry theory and more quantitative, thanks to quantum calculations

Correlations between stacked structures and weak itinerant magnetic properties of La2−x_{2-x} Yx_x Ni7_7 compounds

Hexagonal La$_2$Ni$_7$ and rhombohedral Y$_2$Ni$_7$ are weak itinerant antiferromagnet (wAFM) and ferromagnet (wFM), respectively. The crystal structure and magnetic properties of $A_2B_7$ intermetallic compounds ($A$ = La, Y, $B$ = Ni) have been investigated combining X-ray powder diffraction and magnetic measurements. The La$_{2-x}$Y$_x$Ni$_7$ intermetallic compounds with $0 \leq x \leq 1$ crystallize in the Ce$_{2}$Ni$_7$-type hexagonal structure with Y preferentially located in the [$AB_2$] units. The compounds with larger Y content ($1.2 \leq x < 2$) crystallize in both hexagonal and rhombohedral (Gd$_2$Co$_7$-type) structures with a progressive substitution of Y for La in the $A$ sites belonging to the [$AB_5$] units. Y$_2$Ni$_7$ crystallizes in the rhombohedral structure only. The average cell volume decreases linearly versus Y content, whereas the c/a ratio presents a minimum at $x = 1$ due to geometric constrains. The magnetic properties are strongly dependent on the structure type and the Y content. La$_{2}$Ni$_7$ displays a complex metamagnetic behavior with split AFM peaks. Compounds with x = 0.25 and 0.5 display a wAFM ground state and two metamagnetic transitions, the first one towards an intermediate wAFM state and the second one towards a FM state.T$_N$ and the second critical field increase with the Y content, indicating a stabilization of the AFM state. LaYNi$_7$, which is as the boundary between the two structure types, presents a very wFM state at low field and an AFM state as the applied field increases. All the compounds with $x > 1$ and containing a rhombohedral phase are wFM with $T_C$ = 53(2) K. In addition to the experimental studies, first principles calculations using spin polarization have been performed to interpret the evolution of both structural phase stability and magnetic ordering for $0 \leq x < 2$.Comment: 26 pages (7 for supplementary material), 4 tables, 9 main figures and 8 figures in supplementary materia

Optical Scar in a chaotic fibre

We propose to use a multimode optical fiber with a D-shaped cross section as a privileged system to image wavefunctions of a chaotic system. Scar modes are in particular the sub ject of our investigations. We study their imprints on the statistics of intensity and we show how the introduction of a localized gain region in the fiber is used to perform a selective excitation of scar modes.Comment: 13 page