Search

A new generation of ceramic on ceramic (BIOLOX ®delta) bearings has emerged more than 10 years ago proving a high resistance to wear and good clinical results. However, biological reactions to wear debris, particularly the nanoparticles, need to be evaluated. The first originality of this study is to start from real wear particles obtained by the hip walking simulator (CERsim). These particles were compared with particles obtained by usual methods to assess the biocompatibility of materials: press machine (CERpress). Two ranges of ceramic particles were thus observed: ceramic particles with micron (intergranular fractures) and nano sizes (intragranular fractures), and characterized compared to ultra-high molecular weight polyethylene (UHMWPE). The second originality of this work is to assess the cellular reaction using the primary joint chondrocyte cultures simulating the osteogenesis process and not the cell lines, which are used to simulate the biological reaction of osteolysis. The first results showed a significant difference in cell viability between the cells in contact with particles from the walking simulator and those obtained with the press machine. On the other hand, it was found that the way of extraction of the particles from the lubricant could significantly affect the biological reaction. More interestingly, nano-sized ceramic particles showed a significant impact on the secretion of functional inflammatory mediators, agreeing with recent results in vivo. These novel methods of characterizing the osteogenic impact of UHMWPE and ceramic wear debris can complement the conventional expertise method focusing previously on the osteolysis aspect.

This article presents an analysis of pension coverage based on contribution density. This approach is justified by the fact that coverage rates do not give a clear indication of effective contribut...

The complexity of osteoarticular pathologies means that currently there are no really effective treatments, apart from the placement of an implant (arthroplasty). Thus, 245,625 primary arthroplasties and 6,067 revision procedures were postponed in 2013-2018 [Annual report 2019 of the National Joint Replacement Register of the Australian Orthopedic Association] and the economic consequences of this demand on hospitals are serious. In this context, several friction couples have been developed over the years in order to reduce the wear of metal / polyethylene Total Hip Prostheses (THA); ceramic / polyethylene; metal / metal; ceramic / ceramic. The ex vivo wear estimate for these pairs shows very low wear for the metal / metal and ceramic / ceramic pairs. Nevertheless, some in vivo results are discordant: despite the low rate of wear, nanometric particles of metal and ceramic type can be bioactive for the organism, their biological reaction being able to be amplified for certain degenerative (osteoporosis) or inflammatory (polyarthritis). Therefore, the primary objective of this project is to understand and control the mechanical and physicochemical interactions between the biological environment (especially the lubricant) and the surfaces of ceramic / ceramic PTH implants. Thus in vivo expertises, ex vivo fatigue tests and in vitro wear particle toxicity tests are carried out in order to optimize the ceramic / periarticular tissue interaction and thus increase the in vivo lifespan of PTHs. ceramic., La complexité des pathologies ostéoarticulaires fait qu’actuellement il n'existe pas de traitements vraiment efficaces, hormis la pose d'un implant (arthroplastie). Ainsi, 245 625 arthroplasties primaires et 6 067 interventions de reprise ont été reportées en 2013-2018 [Rapport annuel 2019 du registre national de remplacement articulaire de l'Association australienne d'orthopédie] et les conséquences économiques de cette demande sur les hôpitaux sont lourdes. Dans ce contexte, plusieurs couple de frottement ont été développés au fil des années afin de diminuer l’usure des Prothèses Totale de Hanche (PTH) métal / polyéthylène ; céramique / polyéthylène ; métal / métal ; céramique / céramique. L’estimation ex vivo de l’usure pour ces couples montre une usure très faible pour les couples métal/métal et céramique/céramique. Néanmoins, certains résultats in vivo sont discordants : malgré le faible taux d’usure, les particules nanométriques de type métal et céramique peuvent être bioactives pour l’organisme, leur réaction biologique pouvant être amplifiée pour certaines milieux biologiques dégénératifs (ostéoporose) ou inflammatoires (polyarthrites). Par conséquent, ce projet a comme premier objectif de comprendre et de maîtriser les interactions mécaniques et physicochimiques entre l’environnement biologique (notamment le lubrifiant) et les surfaces d’implants PTH de type céramique/céramique. Ainsi des expertises in vivo, des tests de fatigue ex vivo et des tests de toxicité des particules d’usure in vitro sont réalisées afin d’optimiser l’interaction céramique / tissus periarticulaires et ainsi d’augmenter la durée de vie in vivo des PTH en céramique.

This work deals with the development of a fiber laser generating high energy and width tunable square pulses and high-energy giant pulses. First, we have developed a numerical model to study the generation of rectangular pulses in a double amplifier fiber laser. The objective is to study the impact of the non-linear effect induced by the microstructured optical fiber on the control of the square pulse duration. A set of laser parameters allowed us to generate high energy square pulses in the dissipative soliton resonance (DSR) regime. In addition, several experiments have been set up to optimize the generation of the DSR pulse in terms of energy and duration. Experimentally, high energy giant pulses from a passively mode-locked fiber ring laser coupled to a long external cavity are obtained. This allowed us to generate a wide range of pulse duration of μs at a low repetition rate in cavities using artificial saturable absorbers.; Ce travail de thèse concerne le développement d’un laser à fibre générant des impulsions rectangulaires très énergétiques et accordables à l’échelle du temps et des impulsions géantes à haute énergie. En premier temps,nous avons développé un modèle numérique pour étudier la génération des impulsions rectangulaires dans un laser à fibre en forme de huit à double amplificateur.L’objectif est de montrer l’impact de l’effet non linéaire induit par la fibre micro structurée sur le contrôle de la durée d’impulsion rectangulaire générée par le laser. Un ensemble de paramètres laser nous a permis ainsi de générer des impulsions rectangulaires à haute énergie dans le régime de la résonance du soliton dissipatif (DSR). En plus, plusieurs expériences ont été mises en place pour optimiser la génération de l’impulsion DSR en termes d’énergie et de durée.Toujours sur le plan expérimental, des impulsions géantes à haute énergie à partir du laser à fibre verrouillé en phase couplé à un retard optique ont été obtenues. Cela nous a permis de générer une large plage de durée d’impulsion à l'échelle de μs à taux de répétition faible dans des cavités utilisant des absorbants saturables artificiels.

This work deals with the development of a fiber laser generating high energy and width tunable square pulses and high-energy giant pulses. First, we have developed a numerical model to study the generation of rectangular pulses in a double amplifier fiber laser. The objective is to study the impact of the non-linear effect induced by the microstructured optical fiber on the control of the square pulse duration. A set of laser parameters allowed us to generate high energy square pulses in the dissipative soliton resonance (DSR) regime. In addition, several experiments have been set up to optimize the generation of the DSR pulse in terms of energy and duration. Experimentally, high energy giant pulses from a passively mode-locked fiber ring laser coupled to a long external cavity are obtained. This allowed us to generate a wide range of pulse duration of μs at a low repetition rate in cavities using artificial saturable absorbers.; Ce travail de thèse concerne le développement d’un laser à fibre générant des impulsions rectangulaires très énergétiques et accordables à l’échelle du temps et des impulsions géantes à haute énergie. En premier temps,nous avons développé un modèle numérique pour étudier la génération des impulsions rectangulaires dans un laser à fibre en forme de huit à double amplificateur.L’objectif est de montrer l’impact de l’effet non linéaire induit par la fibre micro structurée sur le contrôle de la durée d’impulsion rectangulaire générée par le laser. Un ensemble de paramètres laser nous a permis ainsi de générer des impulsions rectangulaires à haute énergie dans le régime de la résonance du soliton dissipatif (DSR). En plus, plusieurs expériences ont été mises en place pour optimiser la génération de l’impulsion DSR en termes d’énergie et de durée.Toujours sur le plan expérimental, des impulsions géantes à haute énergie à partir du laser à fibre verrouillé en phase couplé à un retard optique ont été obtenues. Cela nous a permis de générer une large plage de durée d’impulsion à l'échelle de μs à taux de répétition faible dans des cavités utilisant des absorbants saturables artificiels.

Dissipative soliton resonance (DSR) is an efficient way to achieve high energetic pulses without wave breaking. In fiber laser, DSR operation manifests as square pulses emission. Based on this principle, we have experimentally demonstrated pulses in the micro joule range. Experiments have been conducted using double-clad Er:Yb-doped fiber lasers in different optical configurations. In particular, we demonstrate 10 μJ DSR emission in an optimized cavity and also the possibility to observe wave breaking in DSR regime. In the latter case, harmonic mode-locking of square pulses is demonstrated.

Le chapitre montre que les recommandations d'analystes sur le marché tunisien ont un impact sur les cours boursiers. Bien que faible, cet impact atteste d'une contribution à l'amélioration de l'efficience informationnelle. Ensuite, on montre que des portefeuilles suivant les recommandations ont des rentabilités excédentaires positives. Là encore l'ordre de grandeur est faible, mais il montre néanmoins que suivre les recommandations permet d'obtenir un profit supérieur à celui issu d'un suivi passif de l'indice de marché.

International audience; We experimentally demonstrate a broadlytunable dissipative soliton resonancedual-amplifier figure-of-eight fiber laseremission.The peak power is tuned continuously from 8.8to 41.4Wby the first amplifier andpulse width from 84 to 416 nsby the second one.

Colloque avec actes et comité de lecture. Internationale.; International audience; L'arthroplastie totale de la hanche représente une solution efficace pour les maladies osseuses et ostéo-articulaires. Plusieurs biomatériaux sont actuellement utilisés comme les aciers inoxydables, les polymères, les céramiques... Un nouveau composite est récemment introduit en orthopédie afin de réunir les avantages de l'alumine (Al2O3) et de la zircone (ZrO2). Notre étude consiste à l'amélioration de la durée de vie des prothèses. Cette amélioration commence par la caractérisation des origines du dysfonctionnement, le phénomène d'usure, la résistance à la fatigue et principalement le « squeaking » dans le cas des prothèses en biocéramiques. Cette étude porte sur une expertise d'une PTH fabriquées avec un couple céramique-céramique en particulier la composite BIOLOX delta. Cette prothèse est étudiée dans les conditions in vivo et récupérée d'un patient très actif après six mois de pose. La caractérisation des surfaces de contact est effectuée à l'aide de la Microscopie Electronique à Balayage (MEB) et la microscopie numérique VHX. Ces observations ont permis d'identifier les zones d'endommagement et/ou l'usure sous forme des stries et arrachement des particules dans le cas de la tête et dépôt de matière sur la cupule des PTH.

Tuberculosis (TB) infects one third of the world population. Its economic impact is important, affecting the global economy in the World.To determine the economic costs related to tuberculosis in Tunisia.Calculations were made for the reference year 2013; we covered all cost components of the disease, which are related to program management, BCG vaccination, health workers training, social mobilization, screening, chemoprophylaxis, and tuberculosis care. With the exception of costs related to care, which were the subject of a specific survey, the costs of other categories were obtained from the National TB Control Program.The cost of the different components related to the management, prevention, screening and tuberculosis care in 2013 amounted 504688,000DT. The cost of care represented 80.0% of total costs (6807 808,000DT) ; cost related to program management represented 13.2% (1 121 580,00 DT) and the BCG vaccination 6.0% e (512 300,00DT) The average cost per patient was 1447,360 DTin 2013.Reducing the cost of tuberculosis, would involve reducing diagnostic delay. It is also recommended to reduce hospitalization recourse, and prevent multidrug resistance which lead to additional expenditures.

In this article, we experimentally investigate the dynamics of dissipative soliton resonance (DSR) square pulses in different all-anomalous passively mode-locked double-clad Er:Yb fiber laser setups. In the figure-of-eight configuration, the aim of employing an amplifier in each loop is to control the output pulse's amplitude and width, which depend on the pumping power. At a maximum total pumping power of 4.7 W and a fundamental frequency of 133 kHz, 10 µJ DSR square pulses with a signal-to-noise ratio of 60 dB, are generated without observing any wave-breaking. In the fiber ring configuration, by fixing the pumping power to 1.18 W and carefully adjusting the polarization controllers, we obtain a DSR square pulse that can be split in a series of equally spaced smaller square pulses up to the 4th harmonic order at a fundamental frequency of 672 kHz.

We present a widely adjustable high energy square pulse laser operating in DSR in a passively mode-locked F8L using dual Er:Yb co-doped double clad amplifiers. By manually controlling the power of each amplifier, the pulse width can be varied in a range of 360 ns without generating multi-pulsing instabilities. To ensure that DSR would dominate the modelocking mechanism, we use a 1.5 km standard single-mode fiber in the cavity. At a maximum pumping power, the laser generated square pulses with 416 ns duration and an average output power of about 1.33 W with a repetition frequency of 133 KHz corresponding to a record pulse energy of 10 μJ.

We report the generation of square pulses operating in dissipative soliton resonance region from a dual-amplifier figure-of-eight fiber laser. Pulses with tunable width in a range of 360 ns and energy up to 10 μJ are obtained.

We use a unique database, collected by aggregating analysts’ reports on the Tunisian Stock Exchange. We study the price impact and the excess returns following analysts’ recommendations. Results are qualitatively in line with the literature. However, although often significant, the results are not as bold as one expects in a frontier market. We hypothesize that the market is not liquid enough for trades to fully convey the information content of recommendations. Moreover, we find that reiterated recommendations have more impact than revised recommendations. Studying reiterated recommendations provides original results. This is important, as it suggests that it could be more profitable for investors to follow reiterations on emerging markets

We describe the implementation of echo dynamic light scattering in a cross-correlation detection scheme, which enables the study of slow dynamics in moderately turbid colloidal systems by adapting a commercial light scattering device. Our setup combines a 3D cross-correlation detection scheme (3DDLS), which allows for suppression of multiple scattering, with the speckle echo technique for dynamic light scattering. The recorded cross-correlation echoes provide precise ensemble-averaged results that appropriately describe sample dynamics of ergodic and non-ergodic colloidal systems of different turbidities. Additionally, the high mechanical stability achieved in our setup makes possible an absolute estimation of the scattering intensity correlation function (ICF) directly from the height of echoes, thus making unnecessary any correction for imperfect rotation of the sample or of any ad hoc assumption regarding the correspondence between the absolute values of echo height and ICF. Furthermore, we find that zeroth-order echo height represents the coherence factor of the 3DDLS experiment.

Based on the dissipative soliton resonance occurring in highly anomalous dispersion regime, we have demonstrated the emission of highly energetic square-wave pulses from the Er:Yb doped double clad fiber laser passively mode-locked through nonlinear polarization evolution. In contrast with the classical soliton regime, when the pumping power increases the pulse broadens and its energy increases, both linearly. Experimental results exhibit a stable mode-locking with single pulse energy as high as 2.27 µJ, a pulse duration of about 200 ns and an average output power of 850 mW.

This article aims at measuring recommendation value on the Tunisian market and uses a database of 6646 recommendations (2005-2009). We apply the methodology of calendar-time portfolio analysis. This consists in simulating a portfolio that would include stocks depending on the recommendations issued. In order to measure abnormal (or “excess”) returns, the raw return of the portfolio is then compared to the evolution of the stock index and to the prediction of the Capital Asset Pricing Model. Portfolios following buy recommendations have raw monthly returns around 2% to 3%, but their excess return is not statistically different from zero. The portfolios following sell recommendations have a positive raw return but a significant negative excess return, which is explained mainly by the strong uprising trend of the Tunisian market on the sample period. Furthermore, although portfolios that follow upgraded recommendation have a positive raw return, the abnormal returns of upgrade or downgrade portfolios are not significantly different from zero. We build long-short portfolios, some of which earn a positive significant excess risk-adjusted return of 1.19% per month. Finally, the fact that “sell” signals are largely more informative than “buy” signals suggests that the market trend on a five years scale probably influences the ability of analysts to pick stocks that evolves reversely from the trend

International audience; We have experimentally demonstrated square pulses emission from a co-doped Er:Yb double-clad fiber laser operating in anomalous dispersion DSR regime using the nonlinear polarization evolution technique. Stable mode-locked pulses have a repetition rate of 373 kHz with 2.27 µJ energy per pulse under a pumping power of 30 W in cavity. With the increase of pump power, both the duration and the energy of the output square pulses broaden. The experimental results demonstrate that the passively mode-locked fiber laser operating in the anomalous regime can also realize a high-energy pulse, which is different from the conventional low-energy soliton pulse.

Dissipative soliton resonance (DSR) is a soliton formation where the energy in a dissipative system becomes infinite. In the anomalous dispersion regime, this energy is not limited by the soliton area theorem. Since this phenomenon is wave breaking free, it can be useful in designing fiber lasers generating pulses with relatively high energies. Based on this principle, we have demonstrated the emission of high energetic square pulses from Er:Yb double-clad passively mode-locked fiber lasers using different mode-locking mechanisms. We first show the evolution of pulse width, energy and peak power by varying the pumping power of the amplifier, then we control separately the characteristic of the output square pulse by assigning each one to an amplifier. Experimental results exhibit record energies in fiber lasers up to 10 uJ. Full Text: PDF ReferencesW. Chang, A. Ankiewicz, J.M Soto Crespo and N. Akhmediev, " Dissipative soliton resonances", Phys. Rev. A 78, 023830 (2008). CrossRef P. Grelu, W. Chang, A. Ankiewicz, J. M. Soto-Crespo, and N. Akhmediev, "Dissipative soliton resonance as a guideline for high-energy pulse laser oscillators", J. Opt. Soc. Am. B 27, 2336 (2010). CrossRef X. Wu, D. Y. Tang, H. Zhang, and L. M. Zhao, "Dissipative soliton resonance in an all-normal-dispersion erbium-doped fiber laser", Opt. Express 17, 5580 (2009). CrossRef G. Semaan, F. Ben Braham, M. Salhi, Y. Meng, F. Bahloul, and F. Sanchez, "Generation of high energy square-wave pulses in all anomalous dispersion Er:Yb passive mode locked fiber ring laser", Opt. Express 24, 8399 (2016). CrossRef K. Krzempek, "Dissipative soliton resonances in all-fiber Er-Yb double clad figure-8 laser", Opt. Express 23, 30651 (2015). CrossRef L. Mei et al., "Width and amplitude tunable square-wave pulse in dual-pump passively mode-locked fiber laser", Opt. Lett. 39, 3235 (2014). CrossRef X. Zhang et al., "Square-wave pulse with ultra-wide tuning range in a passively mode-locked fiber laser", Opt. Lett. 37, 1334 (2012). CrossRef K. Krzempek, J. Sotor, and K. Abramski, "Compact all-fiber figure-9 dissipative soliton resonance mode-locked double-clad Er:Yb laser", Opt. Lett. 41, 4995-4998 (2016). CrossRef G. Semaan, F. Ben Braham, J. Fourmont, M. Salhi, F. Bahloul, and F. Sanchez, "10uJ dissipative soliton resonance square pulse in a dual amplifier figure-of-eight double-clad Er:Yb mode-locked fiber laser", Opt. Lett. 41, 4767 (2016). CrossRef K. Krzempek and K. Abramski, "Dissipative soliton resonance mode-locked double clad Er:Yb laser at different values of anomalous dispersion", Opt. Express 24, 22379-22386 (2016). CrossRef

International audience; We demonstrate experimentally a double-clad Er:Yb co-doped dual amplifier passive mode-locked figure-of-eight fiber laser that generates high energy, width, and amplitude tunable dissipative soliton resonance square pulses. In our laser system, each loop contains an amplifier that controls a characteristic of the output pulse. The amplitude and width of the output beam can be controlled continuously but, dependently, according to the pump power of each amplifier. The pulse width can be tuned in a range of almost 360ns while the peak power varies from 8 to 120W. On maximum possible pumping from both sides without having a pulse break, we report square pulses with 10μJ energy per pulse with a signal-to-noise ratio of 60dB.

Cet article etudie l'impact des systemes de retraite sur le niveau de vie et la pauvrete des personnes âgees dans trois pays du Maghreb : l'Algerie, le Maroc et la Tunisie. Les systemes de retraite du Maghreb sont tous des systemes contributifs de type bismarckien. Il apparait que les taux de pension sont assez eleves dans les pays du Maghreb. Les retraites moyennes representent environ 50% du salaire moyen. Cependant les disparites sont fortes selon les secteurs d'activite et entre hommes et femmes. De plus, une forte proportion de la population n'est pas couverte par l'assurance vieillesse au Maghreb, ce qui reduit d'autant l'incidence des systemes de retraite sur le revenu des personnes âgees. En l'absence ou en complement d'une couverture retraite, quelles sont les ressources des personnes âgees ? Les donnees d'enquetes permettent d'estimer chacune des sources de revenu dans les trois pays. D'une maniere generale, elles apparaissent diversifiees, les revenus d'activite et l'aide des enfants et de la famille arrivant en tete. Mais de fortes differences existent entre les trois pays. La pauvrete des personnes âgees dans les pays du Maghreb est cependant moins marquee que dans le reste de la population, contrairement a ce qui est observe dans d'autres pays en developpement. La solidarite familiale y contribue pour beaucoup et probablement autant que les systemes de retraite. Face aux changements demographiques, economiques et culturels en cours, et en l'absence d'une extension de la couverture a une plus large population, le choix de prestations non contributives, mises en place par d'autres pays, pourrait etre une voie a suivre au Maghreb pour lutter contre cette pauvrete.

International audience; We demonstrate the possibility of generating wave-breaking-free optical pulses from a mode-locked fiber ring laser coupled to a long passive resonator. By adjusting the delay line length to match the temporal separation of two consecutive spiking pulses, we have successfully obtained large stable pulses in the microsecond range for any available pump power. Our experimental results demonstrate a new method for energy scaling in passively mode-locked fiber lasers.

Two-photon microscopy is a powerful method in biomedical research that allows functional and anatomical imaging at a subcellular resolution in vivo. The technique is seriously hampered by absorption and scattering of light by blood, which prevents imaging through large vessels. Here, we demonstrate in the rat cerebral cortex that blood replacement by perfluorocarbon emulsion, a compound also used in human critical care medicine, yields superior image quality, while preserving neuronal integrity. Shadows of large superficial vessels disappear completely and cells can be imaged underneath them. For the first time, it is possible to image complete populations of neurons and astrocytes in the upper layers of neocortex in vivo.

Los sistemas de pensiones de tres paises de Africa del Norte, Argelia, Marruecos y Tunez, atraviesan dificultades. En el presente articulo se identifican las particularidades y los problemas comunes de los sistemas de pensiones de estos paises mediante la presentacion de las caracteristicas y la estructura organizativa de cada uno de ellos. En lo referente a la legislacion habilitadora y las simulaciones de casos, se estudia y analiza el elevado nivel de generosidad de los distintos sistemas de pensiones. Se afirma que en un contexto de envejecimiento de la poblacion, no se pueden mantener los niveles actuales de generosidad y, por lo tanto, hace falta una reforma. En el articulo se estudian distintas opciones de reforma, los retos que plantea su aplicacion y sus posibles repercusiones sobre la macroeconomia.

Auszug Die Rentensysteme in den nordafrikanischen Landern Algerien, Marokko und Tunesien stehen zurzeit vor einer Reihe von Schwierigkeiten. Der vorliegende Artikel stellt die Merkmale und die organisatorische Struktur der Rentensysteme in den genannten Landern vor und kristallisiert die Besonderheiten heraus sowie die gemeinsamen Probleme, die sie bewaltigen mussen. Anhand der sie regulierende Gesetzgebung und von Fallsimulationen wird das hohe Niveau der Groszugigkeit der verschiedenen Rentensysteme diskutiert und eine Analyse prasentiert. In Anbetracht der alternden Bevolkerung lassen sich die aktuellen Niveaus an Groszugigkeit nicht aufrechterhalten, so wird argumentiert; eine Reform ist notig. Der Artikel diskutiert verschiedene Reformoptionen, die Probleme bei der Umsetzung und mogliche makrookonomische Auswirkungen der Reform.

Pension systems in the North African countries of Algeria, Morocco and Tunisia are facing a certain number of difficulties. Presenting the characteristics and organizational structure of each, this article identifies the specificities of, as well as the common problems confronting, these countries' pension systems. With reference to authorizing legislation and case simulations, the high level of generosity of the different pension systems is discussed and an analysis presented. In a context of population ageing, it is argued that current levels of generosity cannot be maintained; reform is needed. The article discusses different reform options, the challenges of implementation and the possible macroeconomic impacts of reform.

Resume Les systemes de retraite de trois pays nord-africains — Algerie, Maroc et Tunisie — sont confrontes a un certain nombre de difficultes. En presentant les caracteristiques et la structure organisationnelle de chacun d'entre eux, cet article recense les particularites et les problemes qui leur sont communs. Se referant a la legislation pertinente et faisant appel a des simulations de cas, il examine le niveau —eleve— de generosite des differents systemes de retraite et en presente une analyse. Dans le contexte du vieillissement de la population, d'aucuns font valoir que les niveaux de generosite actuels ne peuvent pas etre maintenus, et qu'une reforme est necessaire. L'auteur etudie dans cet article differentes options de reforme, de meme que les problemes de mise en œuvre et les impacts macro-economiques eventuels de la reforme.

This paper discusses the impact of aging on the financial equilibrium of the Tunisian retirement system and the macroeconomic implications of reform, including a partial switch to pre-funding. We use a stylized , closed economy and an overlapping-generation model to analyze the impact of the introduction of a multi-pillar system combining the pay-as-you-go (PAYG) and pre-funded approaches (including temporarily and permanently pre-funded plans). The analysis focuses on (1) the response of saving to the reform at the aggregate level and (2) cohort-specific accumulation and consumption profiles. The reform generates a strong crowding-out effect, restraining capital accumulation. Our simulations also show that the burden of the reform is spread unevenly among cohorts., Nous présentons dans ce papier l’impact des évolutions démographiques sur l’équilibre financier du système de retraite en Tunisie. Il s’agit par la suite d’analyser, à l’aide d’un modèle à générations imbriquées en économie fermée, l’impact de deux types de réforme introduisant une dose de capitalisation, parallèlement au système par répartition existant. Le premier scénario de réforme correspond à l’introduction d’un fonds de réserve, le second à la mise en place d’un pilier capitalisé. Nous mesurons l’impact sur le niveau d’épargne et de consommation. Le modèle met en évidence un effet d’éviction important qui limite l’impact sur l’épargne. Les simulations montrent que le poids de la réforme est davantage supporté par certaines générations., Ben Braham Mehdi. Impact de l'introduction d'une dose de capitalisation en Tunisie : simulations à l'aide d'un modèle à générations imbriquées. In: Économie & prévision, n°180-181, 2007-4-5. pp. 189-199.

International audience; We investigate experimentally the operational boundaries of dissipative soliton resonance in a double-clad Er:Yb co-doped dual amplifier passively mode-locked figure-of-eight fiber laser. While mode-locking with a nonlinear amplifying loop mirror, we present an exhaustive series of experiments in order to optimize the pulse energy and pulse width tunability. In addition to the pumping power of the amplifiers, several key experimental parameters have been identified such as the net cavity dispersion, the coupling ratio between the two loops of the cavity and the exact position of the long fiber coils. Under optimized conditions, the laser delivers square pulses with an energy varying between 8.5 and 10.1 μJ while the pulse width ranges from 84-416 ns.

Financial analysts issue "buy", "sell" or "hold" recommendation about stocks. Recommendations have value if investors trade upon them, which should affect prices and trading volumes. We use the methodology of event study to analyze price and volume reaction to the recommendation release. With a database of 6646 recommendations about 55 companies on the Tunisian Stock Exchange (BVMT) from 2005 to 2009, we show that prices and volumes react significantly to recommendations level. However, we only provide a weak evidence of reaction to changes in recommendations. We explain this result by a special feature of this market place: the systematic release of monthly recommendations, in contrast to developed markets where new recommendations are issued only if new information is available. This can focus investors on the confirmation of the recommendation, rather than on their revisions. We also find a special feature of emerging stock markets, which is that volumes are abnormally low for most of the event period following a "sell" or "hold" recommendation, whereas in that case they are abnormally high in more liquid markets., Les analystes financiers émettent des recommandations d'achat, de vente ou neutre sur les actions. Les recommandations ont de la valeur si les investisseurs échangent sur cette base, affectant ainsi les prix et les volumes. On utilise la méthodologie de l'étude d'évènement pour analyser la réaction des prix et des volumes sur la Bourse des Valeurs Mobilières de Tunis (BVMT) à des recommandations sur 55 sociétés de 2055 à 2009. Nous montrons que les prix et les volumes réagissent significativement aux niveaux des recommandations ; cependant, ils ne réagissent que faiblement à une révision des recommandations. Ceci contraste avec les marchés financiers des pays développés. Nous l'expliquons par un trait particulier du marché tunisien : les recommandations sont issues tous les mois de manière systématique, alors que sur la plupart des autres places une recommandation nouvelle n'est publiée que lorsque l'analyste estime disposer d'information nouvelle. Cela peut focaliser les investisseurs tunisiens sur la confirmation d'une recommandation plutôt que sur sa révision.

This article aims at measuring recommendation value on the Tunisian market and uses a database of 6646 recommendations (2005-2009). We apply the methodology of calendar-time portfolio analysis. This consists in simulating a portfolio that would include stocks depending on the recommendations issued. In order to measure abnormal (or “excess”) returns, the raw return of the portfolio is then compared to the evolution of the stock index and to the prediction of the Capital Asset Pricing Model. Portfolios following buy recommendations have raw monthly returns around 2% to 3%, but their excess return is not statistically different from zero. The portfolios following sell recommendations have a positive raw return but a significant negative excess return, which is explained mainly by the strong uprising trend of the Tunisian market on the sample period. Furthermore, although portfolios that follow upgraded recommendation have a positive raw return, the abnormal returns of upgrade or downgrade portfolios are not significantly different from zero. We build long-short portfolios, some of which earn a positive significant excess risk-adjusted return of 1.19% per month. Finally, the fact that “sell” signals are largely more informative than “buy” signals suggests that the market trend on a five years scale probably influences the ability of analysts to pick stocks that evolves reversely from the trend.

The $ \beta^{{+}}_{}$ /EC decay of 185Tl was studied at the ISOLDE facility, the $ \gamma$ -rays belonging to 185Hg have been identified and a partial low-spin level scheme of 185Hg has been built. The decay of 185m+gHg was studied at the ISOCELE facility. Conversion electron lines of very low-energy transitions were observed for the first time. Electron data have been obtained for four transitions in 185Au and two transitions in 185Hg . From the analysis performed using an internal energy calibration procedure the energy location of the 185mHg has been determined to be $ E_{IS}= 103.7(4)$ keV. This $ E_{IS}$ value is consistent with that determined independently, $ E_{IS}=94(13)$ keV, using 185m+gHg $ \alpha$ -decay data from literature. New $ \alpha$ particles emitted from 189m+gPb have been detected and their origins determined by in-source laser spectroscopy at the ISOLDE facility. $ \alpha$ - $ \gamma$ coincidence results have served to locate the $ 13/2^{+}$ isomeric state of 189Pb at $ E_{IS}=40(4)$ keV. This latter $ E_{IS}$ value added to $ \alpha$ -decay data from literature have allowed the energy location of the $ 13/2^{+}$ isomeric states of 193Po and 197Rn at 95(7)keV and 194(12)keV, respectively. The nuclear structure of the isomeric and ground states in the nuclei of the three $ \alpha$ -emitter chains starting with 195m+g, 197m+g, 199m+gRn are discussed.