Diversity, Richness and Composition of Ant Communities (Hymenoptera: Formicidae) in the Pre-Saharan Steppe of Algeria

This paper describes the structure and composition of ant communities in the pre-Saharan steppe of Algeria. The study focused on three stations located in two regions with different climates: semi-arid (Aflou) and arid (Laghouat). Ants were collected between March 2013 and February 2014, using pitfall trap sampling over a four-season period and quadrat counting techniques. A total of 20 ant species have been identified, which belong to 8 genera in three subfamilies: Dolichoderinae, Myrmicinae and Formicinae. Moreover, it was noticed that the study areas, which can be characterized by their floristic nature, physiognomic and even edaphic aspects, directly influence the ant community ecology and distribution. We classified them in both eurytopic and stenotopic species. It was also observed, using a Correspondence Factorial Analysis (CFA), that the ants’ activity is seasonal and often correlated with temperature fluctuation and trophic availability

Etude de l’effet de deux champignons entomopathogenes Beauveria bassiana et Metarhizium anisopliae var acridum sur le comportement alimentaire de Schistocerca gregaria

Dans le présent travail il est noté que les deux champignons entomopa thogènes Beauvaria bassiana et Metarhizium anisopliae var acridum, traités par ingestion ont affecté l’évolution pondérale des larves L 5 de Schistocerca gregaria . L’examen des résultats montre de même que le gain de poids moye n après 9 jours de traitement chez les larves du lot témoin est de 0,4230g. Il est de 0,159g pour celles traitées au B. bassiana . Par contre chez les larves traitées avec le M. anisopliae leur gain de poids est très réduit, il est de 0,011g. Concernant la consommation initiale des L 5 de S. gregaria , elle débute au 1 er jour avec 0,716±0,086g pour les témoins contre 0,05±0,008g et 0,691±0,083g respectivement chez les traitées au B. bassiana et au M. anisopliae . Cette consommation augmente et diminue au cours du temps et atteint des valeurs soit supérieures ou inférieures aux valeurs initiales jusqu'à atteindre finalement au 9 ème jour 0,168±0,020g, 0,029±0,005g et 0,068±0,008g respectivement pour les témoins et les traitées au B. bassiana et au M. anisopliae . Les indices nutritionnels de consommation et d’utilisation de la nourriture Coefficient d’Utilisation Di gestive apparent (CUD a ), l’Efficacité de Conversion de la nourriture Digérée en matière corporelle (ECD) et l’Efficacité de Conversion de la nourriture Ingérée en matière corporelle (ECI) ont été aussi affectés par le traitement aux deux cryptogame

Study of the maturation of a ketaprofen B-cyclodextrin mixture assisted by supercritical fluid

International audienceSupercritical fluids have found many applications due to their versatile physicochemical properties. They can be used as media for the formation of inclusion complexes, for helping encapsulation of an active substance into cyclodextrin (CDs) cavities. In addition, several active pharmaceutical substances such as ketoprofen, are not very polar, thus not very water-soluble, and in order to increase their rate of dissolution, such drugs can be included in a molecular cage, such as CD with the aid of supercriticalfluid processing. Several inclusion processes in supercritical media have been developed and the maturation process, in which supercritical carbon dioxide (SC-CO 2) is generally used, is among the most recent. It consists of using supercritical CO 2 to bring the active substance, the cyclodextrin and a quantity of water in contact one with another over certain duration, in order to obtain an inclusion complex. We have also studied the influence of several operating parameters on the inclusion rate e.g pressure, temperature, duration of maturation, density of the SC-CO 2 , agitation and factors related to the physical mixture, the amount of water, the molar ratio-cyclodextrin/ketoprofen and the mass ratio SC-CO 2 /mixture, as well as the effect of the method of preparation of the physical mixture on inclusion. We found that pressure, temperature, duration of maturation, agitation and density of SC-CO 2 all had a positive effect on inclusion of ketoprofen (KP) in-cyclodextrin (-CD). The stoichiometry of inclusion of KP in-CD is 1:2. The method of preparation of the powder mixture and mass ratio SC-CO 2 /mixture has an effect on inclusion

Prediction of Auto-Ignition Temperatures and Delays for Gas Turbine Applications

International audienceGas turbines burn a large variety of gaseous fuels under elevated pressure and temperature conditions. During transient operations like maintenance, start-ups or fuel transfers, variable gas/air mixtures are involved in the gas piping system. Therefore, in order to predict the risk of auto-ignition events and ensure a safe and optimal operation of gas turbines, it is of the essence to know the lowest temperature at which spontaneous ignition of fuels may happen. Experimental auto-ignition data of hydrocarbon-air mixtures at elevated pressures are scarce and often not applicable in specific industrial conditions. AIT data correspond to temperature ranges in which fuels display an incipient reactivity, with time scales amounting in seconds or even in minutes instead of milliseconds in flames. In these conditions, the critical reactions are most often different from the ones governing the reactivity in a flame or in high temperature ignition. Some of the critical paths for AIT, especially those involving peroxy radicals, are similar to those encountered in slow oxidation. Therefore, the main available kinetic models that have been developed for fast combustion, are unfortunately unable to represent properly these low temperature processes.In this context, a numerical approach addressing the influence of process conditions on the minimum auto-ignition temperature of different fuel/air mixtures has been developed. For that purpose, several chemical models available in the literature have been tested, in order to identify the most robust ones. Based on previous works of our group, a model covering a large temperature range has been developed, which offers a fair reconciliation between experimental and calculated AIT data through a wide range of fuel compositions. This model has been validated against experimental auto-ignition delay times (AID) corresponding to high temperature in order to ensure its relevance not only for AIT aspects but also for the reactivity of gaseous fuels over the wide range of gas turbine operation conditions. In addition, the AITs of methane, of pure light alkanes and of various blends representative of several natural gas and process-derived fuels were extensively covered. In particular, among alternative gas turbine fuels, hydrogen-rich gases are called to play an increasing part in the future so that their ignition characteristics have been addressed with particular care. Natural gas enriched with hydrogen, and different CO/H2 syngas fuels originating from a blast furnace (BFG) have namely been studied. Globally, the individual species covered are: H2, CO, CO2, N2, CH4, C2H6, C3H8, C4H10, and C5H12. AIT values have been evaluated in function of the equivalence ratio and pressure. All the results obtained have been fitted by means of a practical mathematical expression. The overall study leads to a simple correlation of AIT versus equivalence ratio/pressure that may be of fruitful use for the engineering community

Prediction of auto-ignition temperatures and delays for gas turbine applications

International audienceGas turbines burn a large variety of gaseous fuels under elevated pressure and temperature conditions. During transient operations, variable gas/air mixtures are involved in the gas piping system. In order to predict the risk of auto-ignition events and ensure a safe operation of gas turbines, it is of the essence to know the lowest temperature at which spontaneous ignition of fuels may happen. Experimental auto-ignition data of hydrocarbon–air mixtures at elevated pressures are scarce and often not applicable in specific industrial conditions. Auto-ignition temperature (AIT) data correspond to temperature ranges in which fuels display an incipient reactivity, with timescales amounting in seconds or even in minutes instead of milliseconds in flames. In these conditions, the critical reactions are most often different from the ones governing the reactivity in a flame or in high temperature ignition. Some of the critical paths for AIT are similar to those encountered in slow oxidation. Therefore, the main available kinetic models that have been developed for fast combustion are unfortunately unable to represent properly these low temperature processes. A numerical approach addressing the influence of process conditions on the minimum AIT of different fuel/air mixtures has been developed. Several chemical models available in the literature have been tested, in order to identify the most robust ones. Based on previous works of our group, a model has been developed, which offers a fair reconciliation between experimental and calculated AIT data through a wide range of fuel compositions. This model has been validated against experimental auto-ignition delay times corresponding to high temperature in order to ensure its relevance not only for AIT aspects but also for the reactivity of gaseous fuels over the wide range of gas turbine operation conditions. In addition, the AITs of methane, of pure light alkanes, and of various blends representative of several natural gas and process-derived fuels were extensively covered. In particular, among alternative gas turbine fuels, hydrogen-rich gases are called to play an increasing part in the future so that their ignition characteristics have been addressed with particular care. Natural gas enriched with hydrogen, and different syngas fuels have been studied. AIT values have been evaluated in function of the equivalence ratio and pressure. All the results obtained have been fitted by means of a practical mathematical expression. The overall study leads to a simple correlation of AIT versus equivalence ratio/pressure