L'influence des variables psychosociales sur la décision de communication volontaire : cas des dirigeants tunisiens

International audienceDisclosure decisions are made based on managerial choice (Williams, 2008). But the question of their motives remains always posed. This research proposes to be centred on the behaviors of the managers explaining the voluntary disclosure of information. Taking root in the conceptual model of the theory of planned behavior (Ajzen, 1991), the developed model proposes 3 variables namely: the attitude, the subjective norm as well as the perceived behavioral control. Based on an investigation with the managers of 39 listed Tunisian firms (rate of answer of 70.9%), the results show that the attitude of the manager toward the communication on the future strategy of the company, its earnings forecasts and the reasons of the decrease of its dividends significantly predicts its intention to disclose this information. On the other hand, neither the subjective norm and nor its perception of control influence its decision to disclose.Les décisions de divulgations sont prises sur la base d'un choix managérial (Williams, 2008). Mais la question de leurs motivations reste toujours posée. Cette recherche se propose de se centrer sur les comportements des dirigeants expliquant la divulgation volontaire d'informations. Prenant racine dans le modèle conceptuel de la théorie du comportement planifié (Ajzen, 1991), le modèle développé met en avant 3 variables à savoir : l'attitude, la norme subjective ainsi que la perception du contrôle. Basés sur une enquête auprès des dirigeants de 39 entreprises tunisiennes cotées (taux de réponse de 70,9%), les résultats montrent que l'attitude du dirigeant à l'égard de la communication sur la stratégie future de l'entreprise, ses résultats prévisionnels et les raisons de la baisse de ses dividendes prédit significativement son intention de divulguer ces informations. Par contre, ni la norme subjective et ni sa perception du contrôle n'influencent sa décision de divulguer

Kinetic study of hydromagnesite thermolysis by constant rate thermal analysis

The present work is focused on the kinetic study of hydromagnesite thermal decomposition carried out by constant rate thermal analysis technique at 5 hPa partial pressure. The apparent activation energies were measured experimentally all along the decomposition without any assumption about the rate law of the determining step. Under these conditions the decomposition of hydromagnesite occurs in two steps. The first step is a dehydration which occurs with apparent activation energy of 60 kJ.mol-1 and D4 kinetic model. The second step is essentially decarbonatation, which occurs according to an F1 kinetic model and activation energy equal to 95 kJ.mol-1.Â

Towards the Electrochemical Diagnostic of Influenza Virus: Development of Graphene-Au Hybrid Nanocomposite Modified Influenza Virus Biosensor Based on Neuraminidase Activity

International audienceAn effective electrochemical influenza A biosensor based on a graphene-gold (Au) hybrid nanocomposite modified Au-screen printed electrode has been developed. The working principle of the developed biosensor relies on the measurement of neuraminidase (N) activity. After the optimization of experimental parameters like the effect of bovine serum albumin addition and immobilization times of fetuin A and PNA lectin, the analytical characteristics of the influenza A biosensor were investigated. As a result, a linear range between 10-8 U mL-1 and 10-1 U mL-1 was found with a relative standard deviation value of 3.23% (for 10-5 U mL-1 of N, n:3) and a limit of detection value of 10-8 U mL-1 N. The developed biosensor was applied for real influenza virus A (H9N2) detection and very successful results were obtained

Defining the operating conditions of the attrition-leaching process using thermodynamic process modelling

The attrition-leaching process aims at improving leaching performance when formation of passivation layers at the surface of leached particles is a severe limiting factor, as discussed recently by Julcour and coworkers (Julcour et al., 2015). This paper proposes a geochemistry-based modelling scheme for deriving the window of possible operating conditions for the attrition-leaching process to match the properties of the processed ore. The rationale is that the attrition-leaching process maintains the surface of reacting particles in an unpassivated state by continuous mechanical removal of surface leach layers, so that the process reactions can be modelled from thermodynamic equilibria throughout the duration of the process. The strength of the proposed modelling approach is that it bridges the gap between the properties of the ore and the process operating conditions. The present paper exemplifies the proposed process modelling route for derivation of the attrition-leaching process operating conditions in the context of the leaching of silicate ores, matching model predictions against controlled laboratory experiments. It is shown how thermodynamic modelling, when used in conjunction with a solid knowledge of the phases present in the system, can assist with deciding upon suitable process operating conditions. As an example, this firstprinciple modelling approach predicted that steel grinding medium would be converted into siderite (FeCO3) under a wide range of operating conditions, which led to questioning this initial choice of grinding medium for the attrition-leaching process under mineral carbonation conditions. It is emphasised that the same approach could be applied to ores of greater economic significance

L'influence des variables psychosociales sur la décision de communication volontaire : cas des dirigeants tunisiens

Les décisions de divulgations sont prises sur la base d'un choix managérial (Williams, 2008). Mais la question de leurs motivations reste toujours posée. Cette recherche se propose de se centrer sur les comportements des dirigeants expliquant la divulgation volontaire d'informations. Prenant racine dans le modèle conceptuel de la théorie du comportement planifié (Ajzen, 1991), le modèle développé met en avant 3 variables à savoir : l'attitude, la norme subjective ainsi que la perception du contrôle. Basés sur une enquête auprès des dirigeants de 39 entreprises tunisiennes cotées (taux de réponse de 70,9%), les résultats montrent que l'attitude du dirigeant à l'égard de la communication sur la stratégie future de l'entreprise, ses résultats prévisionnels et les raisons de la baisse de ses dividendes prédit significativement son intention de divulguer ces informations. Par contre, ni la norme subjective et ni sa perception du contrôle n'influencent sa décision de divulguer.divulgation volontaire ; intention ; attitude ; dirigeant ; théorie du comportement planifié

Insights Into Nickel Slag Carbonation in a Stirred Bead Mill

This work is part of the ongoing development of the attrition-leaching carbonation process, a single-step aqueous carbonation technology that integrates a stirred bead mill. The principle of the attrition-leaching carbonation process is to continuously refresh the surfaces of reactive particles so that leaching can proceed unimpeded, yielding enhanced carbonation kinetics and yield. Invariably, attrition-leaching carbonation experiments carried out under controlled temperature and CO2 partial pressure conditions with different silicate-rich carbonation feedstocks - natural ores and nickel slags - show a carbonation yield that tends towards a plateau 20–50% below the stoichiometric yield. This repeatable behaviour raises the question as to whether the carbonation limitation is due to specific equilibrium side reactions of the carbonation feedstock or to a kinetic limitation of the attrition-leaching carbonation process. To try to provide some answers to this puzzling question, this reflexive paper implements a “thermo-kinetic” modelling methodology based upon geochemical equilibrium simulations and particle reaction models. The results obtained indicate that the observed slowing down of the carbonation process can be explained either by the formation of Mg- and/or Fe-rich silicates that precipitate at the expense of carbonates, or by a decrease in the efficiency of the attrition process over time. Indeed, either one of these mechanisms could explain the observed behaviour of the attrition-leaching carbonation process. However, the cross comparison of different data sources pleads in favour of the attrition-leaching carbonation performance being limited by the attrition process. Pending further confirmation, this tentative conclusion suggests that further development of the attrition-leaching carbonation process requires new knowledge about its inner workings, and that there may be ways to optimize the performance of this process beyond that based on standard stirred bead mill operating rules

An electrochemical immunosensor based on a 4,4′-thiobisbenzenethiol self-assembled monolayer for the detection of hemagglutinin from avian influenza virus H5N1

An electrochemical immunosensor for the detection of hemagglutinin from avian influenza virus H5N1 is presented in this paper. The following steps lead up to the construction of immunosensor: (i) modification of gold electrodes with 4,4′-thiobisbenzenethiol, (ii) modification of self-assembled monolayer of 4,4′-thiobisbenzenethiol with gold colloidal nanoparticles, (iii) immobilization of single chain variable fragments of antibodies (scFv) against hemagglutinin H5 via Ssingle bondAu covalent bonds, (iv) blocking of the remaining free space with bovine serum albumin. The interactions between the scFv and hemagglutinin variants have been explored with electrochemical impedance spectroscopy in the presence of [Fe(CN)6]3−/4− as an electroactive marker. The immunosensor was able to detect two different His-tagged variants of recombinant hemagglutinin from H5N1 viruses: the short fragment (17–340 residues) of A/swan/Poland/305-135V08/2006 and the long (17–530 residues) of A/Bar-headed Goose/Qinghai/12/2005. The strongest response has been observed for the long variant with a detection limit of 0.6 pg/mL and a dynamic range from 4.0 to 20.0 pg/mL. The recombinant hemagglutinin (17–527 residues) from A/chicken/Netherlands/1/03 (H7N7), used as the negative control generated a weak response. This confirms the selectivity of the immunsensor proposed. A miniaturized version of the immunosensor, based on screen-printed gold electrodes, was tested with the same set of recombinant hemagglutinins and it achieved a linear range from 1 to 8 pg/mL with a detection limit of 0.9 pg/mL for the long fragment of hemagglutinin