Interpretation of psychophysics response curves using statistical physics.

Experimental gustatory curves have been fitted for four sugars (sucrose, fructose, glucose and maltitol), using a double layer adsorption model. Three parameters of the model are fitted, namely the number of molecules per site n, the maximum response RM and the concentration at half saturation C1/2. The behaviours of these parameters are discussed in relationship to each molecule's characteristics. Starting from the double layer adsorption model, we determined (in addition) the adsorption energy of each molecule on taste receptor sites. The use of the threshold expression allowed us to gain information about the adsorption occupation rate of a receptor site which fires a minimal response at a gustatory nerve. Finally, by means of this model we could calculate the configurational entropy of the adsorption system, which can describe the order and disorder of the adsorbent surface.

Statistical thermodynamics of adsorption of dye DR75 onto natural materials and its modifications: double-layer model with two adsorption energies.

In this article, adsorption modelling was presented to describe the sorption of textile dye, Direct Red 75 (DR75), from coloured wastewater onto the natural and modified adsorbent, Posidonia oceanica. The formulation of the double-layer model with two energy levels was based on statistical physics and theoretical considerations. Thanks to the grand canonical ensemble in statistical physics some physico-chemical parameters related to the adsorption process were introduced in the analytical model expression. Fitting results show that the dye molecules are adsorbed in parallel position to the adsorbent surface. The magnitudes of the calculated adsorption energies show that the DR75 dye is physisorbed onto Posidonia. Both Van der Waals and hydrogen interactions are implicated in the adsorption process. Despite its simplicity, the model fits a wide range of experimental data, thereby supporting the underlying data that the grafted groups facilitate the parallel anchorage of the anionic dye molecule. Thermodynamic parameters, such as adsorption energy, entropy, Gibbs free adsorption energy and internal energy were calculated according to the double-layer model. Results suggested that the DR75 adsorption onto Posidonia was a spontaneous and exothermic process.

[Melitococcal psoas abscesses: study of three cases and review of the literature]. / Les abcès mélitococciques du psoas: etude de 3 cas et revue de la litterature.

Vertebral involvement is a common complication of brucellosis in adults. However psoas abscess related to brucellar spondylitis have rarely reported. The purpose of this report is to describe three cases of bilateral psoas abscess identified during workup for brucellar spondylitis. Medical imaging was helpful in confirming diagnosis of these fluid collections. Epidemiological, clinical, radiological and serological findings were consistent with melitococcal etiology. Treatment was based on a combination of antibiotics (rifampicine-doxycycline) and abscess evacuation by percutaneous drainage, needle aspiration or open surgery. Outcome was favourable. Brucellar psoas abscess is uncommon. Most caseare discovered coincidentally during investigation of melitococcal spondylitis. Management usually consists of fluid drainage and appropriate antibrucellar therapy. Prognosis is favourable.

Acid dye adsorption onto cationized polyamide fibres. Modeling and consequent interpretations of model parameter behaviours.

Experimental adsorption isotherms of four acid dyes named Acid Blue 25, Acid Yellow 99, Reactive Yellow 23, and Acid Blue 74 from aqueous solution onto cationized nylon-6,6 have been analyzed using a double layer adsorption model. The parameters involved in the analytical expression of this model such as the number or fraction of adsorbed dye molecule per site, n, the number of receptor sites per gram of adsorbent, N(M), and the concentration at half-saturation, c1/2, are determined from adsorption isotherms at four temperatures between 293 and 353 K. The evolution of these parameters with temperature is discussed in relation with adsorption process and the behaviours of the different dyes taking into account their particular structure. The results are compared with those already published dealing with the adsorption of these same dyes onto cationized cotton. The configurational entropy at various temperatures has been studied. This parameter allowed to deduce some results related to the evolution of the disorder during the adsorption process.

New theoretical expressions for the five adsorption type isotherms classified by BET based on statistical physics treatment.

New theoretical expressions to model the five adsorption isotherm types have been established. Using the grand canonical ensemble in statistical physics, we give an analytical expression to each of five physical adsorption isotherm types classified by Brunauer, Emett, and Teller, often called BET isotherms. The establishment of these expressions is based on statistical physics and theoretical considerations. This method allowed estimation of all the mathematical parameters in the models. The physicochemical parameters intervening in the adsorption process that the models present could be deduced directly from the experimental adsorption isotherms by numerical simulation. We determine the adequate model for each type of isotherm, which fixes by direct numerical simulation the monolayer, multilayer, or condensation character. New equations are discussed and results obtained are verified for experimental data from the literature. The new theoretical expressions that we have proposed, based on statistical physics treatment, are rather powerful to better understand and interpret the various five physical adsorption type isotherms at a microscopic level.

[Conditions of midwifery practice in Tunisia rural areas and maternal transfer]. / Conditions de pratique des sages-femmes en milieu rural tunisien et transfert maternel.

OBJECTIVES: This survey analyzed the conditions of midwife practice in rural maternity hospitals and their influence on maternal transfer in a sanitary region of northwestern Tunisia, an underprivileged region where transfer rate is the highest in the country. METHODS: The study concerned midwives in 8 rural maternity hospitals. The survey included the files of 1,065 women transferred to the regional maternity hospital over a one year period. RESULTS: The hospitals surveyed operated without a gynecologist. Conditions of practice varied from one hospital to another and had a clear influence on transfer rate. DISCUSSION: Our findings illustrated the importance of certain remediable insufficiencies including technical facilities, the level of midwife supervision, physician responsibility within the sanitary area, and assignment of gynecologists to the rural hospitals where a large volume of activity occurs. Improvements can be made in use of maternity hospitals to reassure women and midwives.