Single spin-torque vortex oscillator using combined bottom-up approach and e-beam lithography

A combined bottom-up assembly of electrodeposited nanowires and electron beam lithography technique has been developed to investigate the spin transfer torque and microwave emission on specially designed nanowires containing a single Co/Cu/Co pseudo spin valve. Microwave signals have been obtained even at zero magnetic field. Interestingly, high frequency vs. magnetic field tunability was demonstrated, in the range 0.4 - 2 MHz/Oe, depending on the orientation of the applied magnetic field relative to the magnetic layers of the pseudo spin valve. The frequency values and the emitted signal frequency as a function of the external magnetic field are in good quantitative agreement with the analytical vortex model as well as with micromagnetic simulations.Comment: 9 pages, 4 figure

On the formation of cyclones and anticyclones in a rotating fluid

It is commonly observed that the columnar vortices that dominate the large scales in homogeneous, rapidly rotating turbulence are predominantly cyclonic. This has prompted us to ask how this asymmetry arises. To provide a partial answer to this we look at the process of columnar vortex formation in a rotating fluid and, in particular, we examine how a localized region of swirl (an eddy) can convert itself into a columnar structure by inertial wave propagation. We show that, when the Rossby number (Ro) is small, the vortices evolve into columnar eddies through the radiation of linear inertial waves. When the Rossby number is large, on the other hand, no such column is formed. Rather, the eddy bursts radially outward under the action of the centrifugal force. There is no asymmetry between cyclonic and anticyclonic eddies for these two regimes. However, cyclones and anticyclones behave differently in the intermediate regime of Ro~1. Here we find that the transition from columnar vortex formation to radial bursting occurs at lower values of Ro for anticyclones, with the transition for anticyclones occurring at Ro~0.5, and that for cyclones at Ro~2. Thus, in a homogeneous turbulence experiment conducted at, say, Ro=1, we would expect to see more cyclones than anticyclones. The reason for this asymmetry at Ro~1 is explained

La vulnérabilité au stress induite par les situations managériales au sein des entreprises québécoises

RÉSUMÉ: Depuis la fin des années 1980, la gestion de projet s'est diffusée au sein de divers secteurs d'activité. Elle a révolutionné les pratiques managériales, elle a contribué au développement de l'activité par projet qui est nécessaire à l'essor économique des entreprises, et elle a fait progresser la recherche en gestion de projet depuis les années 2000. Néanmoins, la gestion de projet a entraîné différentes formes de malaises et de diffrcultés qui fragilisent les acteurs de projets et remettent en question leur bien-être. Incarnant jusqu'à présent le mythe de l'action heureuse (Loufrani-Fedida, 2012), elle devient alors responsable de vulnérabilités sur lesquelles il serait important de se pencher. L'objectif principal de cette étude exploratoire a été de déterminer les situations managériales qui induisent de la vulnérabilité au stress aux acteurs de projets. Lors de cette recherche, les notions de situation, de stress et de vulnérabilité ont été analysées et l'importance de la situation dans la vulnérabilité de l'individu au stress a été déterminée. Nous nous sommes également intéressée aux travaux des chercheurs Leroy (2006) et Leroy et al. (2012) selon lesquels les situations managériales sont porteuses de problématiques pour les acteurs de projets. Les contributions du Centre d'études sur le stress humain nous ont aussi permis de déterminer les variables qui prédisposent le plus l'individu aux situations de stress. Pour réaliser cette étude descriptive, les données ont été collectées suite à l'envoi d'un questionnaire en ligne à des acteurs de projets d'entreprises québécoises. Ceci nous a permis de collecter un échantillon de 78 répondants. L'analyse descriptive des principaux résultats a révélé que les situations managériales les plus porteuses de vulnérabilité au stress sont la gestion de réunion stratégique, la communication interne/externe, le Reporting, l'organisation/priorisation du temps, la gestion de réunion participative, la délégation. Par ailleurs, les variables Contrôle, Imprévisibilité, Nouveauté et Ego menacé influent le plus sur la vulnérabilité au stress induite par les situations managériales, et dépendent de dimensions spécifiques liées à l'individu et à l'organisation. Enfin, cette étude soumet des solutions d'accompagnement qui pourraient permettre de réduire la vulnérabilité au stress induite par certaines situations managériales aux acteurs de projets. -- Mot(s) clé(s) en français : situation, stress, vulnérabilité, situations managériales, gestion de projet,entreprise, Québec, acteurs de projets, solutions d'accompagnement. -- ABSTRACT: Since late 1980's, project management spread itself within various sectors of activity. It has revolutionized the managerial practices, it has contributed to the development of the project activity which is essential to the economic development of companies and it has advanced research in project management since the 2000's. Nevertheless, project management has brought different forms of discomforts and difficulties, weakening the projects' participants and questioning their well-being. Embodying the myth of the beneficient action up to now (Loufrani-Fedida, 2012), it is then becoming responsible of vulnerabilities which should be essential to address. The main goal of this exploratory study has been to determine the managerial situations which induce vuhlerability to stress to the projects' participants. During this research, the notions of situation, stress and vulnerability have been studied and the impor[ance of situation in the individual's vulnerability to stress has been determined. We also interested ourselves to researchers Leroy's (2006) and Leroy and al.'s (2012) works according to whom managerial situations imply difficulties to the projects' participants. The contributions of the Center for studies on human stress also allowed us to determine the variables which predisposed more the individual to stressful situations. To carry out this descriptive study, data were collected after the sending of an online questionnaire to projects participants of Quebec-based companies. This allowed us to gather a sample of 78 respondents. The descriptive analysis of the main results revealed that the managerial situations which carry more vulnerability to stress are strategic meeting management, internal/external communication, reporting, organization/prioritization of time, participatory meeting management, delegation. Besides, the Control, Unpredictability, Newness and Threatened ego variables exert more influence on vulnerability to the stress induced by the managerial situations and depend on specific dimensions linked to the individual and to the organization. Finally, this study offers support solutions which could alleviate vulnerability to stress that managerial situations induce to the projects' participants. -- Mot(s) clé(s) en anglais : situation, stress, vulnerability, managerial situations, project management, company, Quebec, projects' participants, support solutions

Structural and electrical characterization of hybrid metal-polypyrrole nanowires

We present here the synthesis and structural characterization of hybrid Au-polypyrrole-Au and Pt- polypyrrole-Au nanowires together with a study of their electrical properties from room-temperature down to very low temperature. A careful characterization of the metal-polymer interfaces by trans- mission electron microscopy revealed that the structure and mechanical strength of bottom and upper interfaces are very different. Variable temperature electrical transport measurements were performed on both multiple nanowires - contained within the polycarbonate template - and single nanowires. Our data show that the three-dimensional Mott variable-range-hopping model provides a complete framework for the understanding of transport in PPy nanowires, including non-linear current-voltage characteristics and magnetotransport at low temperatures.Comment: Phys. Rev. B Vol. 76 Issue 11 (2007

Couplage statistique entre vorticité et gradient de scalaire passif dans une turbulence statistiquement homogène et isotrope mise en rotation

International audienc

The Accuracy Of The Annual Financial Report Data: An Empirical Analysis Of GCC Firms

Company’s might try to enhance the picture of their income numbers (looks better than it should be) in the eyes of the reader of their annual financial reports.  These information could be used by investors and accounting researchers who their decisions depend on the information provided in financial reports.  When companies engage in income enhancement, investment decisions may be adversely affected.  The objective of this paper is to examine income numbers in a sample of the Gulf Cooperation Council (GCC) firms (UAE, Qatar, Oman, Saudi Arabia, Kuwait and, Bahrain) to determine if the frequency of the second digits conforms to the expected distribution.  The results indicate that the null hypothesis could be rejected, suggesting the annual financial data may not be as accurate as expected.  In other words, income enhancement at the second digit exists. We also discussed accounting standards that have been used by these companies.     &nbsp

Guideline for Optical Optimization of Planar Perovskite Solar Cells

Organometallic halide perovskite solar cells have emerged as a versatile photovoltaic technology with soaring efficiencies. Planar configuration in particular, has been a structure of choice thanks to its lower temperature processing, compatibility with tandem solar cells and potential in commercialization. Despite all the breakthroughs in the field, the optical mechanisms leading to highly efficient perovskite solar cells lack profound insight. In this paper, a comprehensive guideline is introduced involving semi-analytical equations for thickness optimization of the front and rear transport layers, perovskite, and transparent conductive oxides to improve the antireflection and light trapping properties, and therefore to maximize the photocurrent of perovskite solar cells. It is shown that a photocurrent enhancement above 2 mA/cm2 can be achieved by altering - reducing or increasing - the thicknesses of the layers constituting a CH3NH3PbI3 (MAPI) type perovskite solar cell. The proposed guideline is tested against experiments as well as previously published experimental and simulation results for MAPI. Additionally, the provided guideline for various types of perovskites can be extended to other direct band gap absorber-based solar cells in superstrate configuration

Regulation with a Risk-Averse Principal

We construct the optimal regulation contract between a risk-averse principal, such as a small municipality, and a risk-neutral private ''public service'' operator, such as a large multinational firm. With adverse selection, moral hazard and socially costly transfers, we show that the more risk-averse the principal, the more result oriented the contract. We also show that, for a given degree of the regulator's risk aversion, the larger the number of operators supervised by one regulator, the more high powered the incentive scheme. In a two period dynamic setting, we focus on the commitment issue. We define a measure of the social value of a regulator's ability to sign binding long term contracts, and we obtain that this increases with the degree of the principal's risk aversion. We discuss some political implications of these results in terms of regulatory institutions' design. Such issues like the efficiency of the contract, credibility or independence of the regulator are tackled with this concept of regulator's risk aversion.