Atomistic insights into the mixed-alkali effect in phosphosilicate glasses

Oxide glasses have proven useful as bioactive materials, owing to their fast degradation kinetics and tunable properties. Hence, in recent years tailoring the properties of bioactive glasses through compositional design have become the subject of widespread interest for their use in medical application, e.g., tissue regeneration. Understanding the mixed alkali effect (MAE) in oxide glasses is of fundamental importance for tailoring the glass compositions to control the mobility of ions and, therefore, the glass properties that depend on it, such as ion release, glass transition temperature, and ionic conductivity. However, most of the previously designed bioactive glasses were based on trial-and-error, which is due to the complex glass structure that is nontrivial to analyze and, thus, the lack of a clear picture of the glass structure at short- and medium-range order. Accordingly, we use molecular dynamics simulations to study whether using the MAE can control the bioactivity and properties of 45S5 glass and its structural origins. We showed that the network connectivity, a structural parameter often used to access the bioactivity of silicate glasses, does not change with Na substitution with Li or K. On the contrary, the elastic moduli showed a strong dependence on the type of the modifier as they increased with increasing mean field strength. Similarly, the mobility of the glass elements was significantly affected by the type of modifier used to substitute Na. The change of the properties is further discussed and explained using changes at the short- and medium-range structure by giving evidence of previous experimental findings. Finally, we highlight the origin of the nonexistence of the MAE, the effect of the modifier on the bioactivity of the glasses, the importance of dynamical descriptors in predicting the bioactivity of oxide glasses, and we provide the necessary insights, at the atomic scale, needed for further development of bioactive glasses

Les Surdites Brusques Idiopathiques Facteurs Pronostiques

Introduction : Les surdités brusques idiopathiques (SBI) constituent l\'un des sujets les plus débattus en otologie. Plusieurs problèmes d\'ordre physiopathologiques, thérapeutiques et pronostiques restent non résolus. But : Identifier les facteurs pronostiques, cliniques et audiométriques de récupération auditive après traitement d\'une SBI. Malades : Etude rétrospective portée sur 27 malades (29 cas de SBI) traités dans le service d\'ORL et chirurgie cervicofaciale du CHU Habib Bourguiba Sfax durant la période comprise entre les années 1990 et 2005. Méthodes : C\'est une étude statistique recherchant une corrélation significative entre certains facteurs cliniques et audiométriques et la récupération auditive. Les facteurs étudiés étaient : l\'âge, l\'aspect de la courbe audiométrique, la perte auditive initiale et le délai de prise en charge thérapeutique. Résultats : L\'âge inférieur à 50 ans, la courbe ascendante et la perte auditive inférieure à 70 dB étaient les facteurs de meilleur pronostic. Le délai de prise en charge thérapeutique semble avoir peu de rôle dans la récupération auditive. Discussion : La majorité des auteurs ont signalé que l\'âge jeune, les surdités légères ou moyennes, la courbe ascendante et la précocité de la prise en charge sont associés à un meilleur pronostic. Nos résultats rejoignent ceux de Tran Ba Huy qui ne trouve pas de corrélation entre le délai de prise en charge thérapeutique et le pronostic de récupération auditive.Introduction : Idiopathic Sudden Sensorineural Hearing Loss (ISSHL) remains one of the major otologic debates. Many etiopathogenic, therapeutic and prognostic problems are still unsolved. Purpose : Identify some clinical and audiometric factors influencing the recovery prognostic after treatment of ISSHL. Patients : Retrospective study of 27 patients (29 cases of ISSHL) treated in the department of Oto-Rhino-Laryngology and Head and Neck Surgery of Habib Bourguiba Hospital during the period from 1990 to 2005. Method: We underwent a statistical data to search a significant correlation between some clinical, audiometric factors and hearing recovery. The factors studied are: age of patient, the type of the tonal audiogram shape, the degree of the initial hearing loss and the therapeutic delay. Results: The age under 50 years, the ascending audiogram shape and initial hearing loss under 70dB involve a better prognostic. The therapeutic delay seems have a little role in the hearing recovery. Discussion: The majority of authors concluded that the young age, the mild and moderate hearing loss, the ascending audiogram shape and the precocity of treatment are correlated to a better prognostic. We, as Tran Ba Huy, don\'t find a significant correlation between the therapeutic delay and the quality of hearing recovery. Journal Tunisien d\'ORL et de chirurgie cervico-faciale Vol. 18 2007: pp. 7-1

Variabilités des descripteurs physiques, chimiques et biologiques d'un réservoir de stokage (lagunage mixte, en Slimane - Maroc)

L'étude des variations des descripteurs physiques, chimiques et biologiques des eaux d'un réservoir de maturation du lagunage mixte (Ben Slimane, Maroc), a montré une augmentation des valeurs de certaines variables (oxygène dissous, transparence) après le 36ème jour de rétention en raison d'une remise en solution.A 36 jours de rétention, la chute des teneurs de la DBO5, de la DCO, des composés azotés (NH4+, NO3-, NTK) et phosphorés (PO43-, PT), et l'augmentation du pH, de l'oxygène dissous et de la transparence laissent présager une maturation à cette date de mesure. Les densités planctoniques enregistrées à ce niveau sont les plus basses.Au-delà de ce stade de maturation, le phytoplancton prolifère avec dominance d'Euglena viridis qui montre un pic de densité (4,1.106 Individus/m3) le 81ème jour. Le début de sa phase exponentielle de croissance est observé à partir du 18ème jour de maturation. La densité cellulaire est ensuite atténuée vraisemblablement en raison de la diminution de la charge organique (DBO5 et DCO) après le 81ème jour et de l'intensité de broutage par le zooplancton herbivore surtout Acanthocyclops robustus qui montre son maximum de croissance le 138ème jour.Après le 81ème jour de maturation, Euglena viridis est remplacée par deux espèces de Chlorophycées (Pediastrum boryanum et Ankyra judai) dont le maximum de densité (91% de la densité algale totale) est atteint le 138ème jour. La prolifération de ces espèces coïncide avec des valeurs en nitrates dépassant 10,6 mg N/L.A la fin de cette période d'étude (le 138ème jour), le zooplancton est à sa prolifération maximale (106 individus/m3). Il est dominé par Acanthocyclops robustus avec présence de Nauplii et de Daphnia magna. Les Rotifères présents depuis le début de la maturation disparaissent à 138 jours de rétention. L'étude bactériologique a révélé un rendement épuratoire remarquable atteignant 100% pour les coliformes fécaux et les streptocoques fécaux.A study of physical, chemical and biological descriptors of the water in the storage reservoir of a combined stabilization pond (Ben Slimane, Morocco), during maturation, showed an improvement of the purification output for some variables after 36 days of retention. Such an environment, rich with a range of different nutrients, allowed an optimal development of plankton characterized by a high species diversity that decreased with time. Zooplankton development seemed to be limited by poor phytoplankton biomass. However, trophic factors such as nutrients and temperature affected the evolution of planktonic species.After 36 days of retention, the decrease in BOD5, COD, NH4+, NO3-, total Kjeldahl nitrogen (TNK), PO43-, total phosphorus (TP), and the increase in pH, dissolved oxygen and transparency, suggested that maturation had been reached at this level. Simultaneously, phyto- and zooplankton were present in low densities. Nevertheless, beyond this stage of maturation, phytoplankton proliferation occurred, dominated by Euglena viridis whose exponential phase of growth began at the 18th day of maturation and reached a maximum density after 81 days (4.1x106 individus/m3). A low proportion of Chlorophyte species was observed, represented by Pediastrum boryanum and Ankyra judai. The zooplankton community was dominated by two species of Cladocera (Daphnia magna and Diaphanosoma sp).The increase in Euglena viridis density up to 81 days coincided with zooplanktonic proliferation constituted exclusively by Rotifers (Brachionus calyciflorus and Polyarthra remata). At 111 days of retention, the zooplankton community consisted of Copepods (Acanthocyclops robustus), which reappeared at this stage, as well as Nauplii Cladocera (Daphnia magna) and residual Rotifers (Brachionus calyciflorus and Polyarthra remata). The remarkable decrease in Euglena density on day 111 and their complete disappearance on day 138 was probably linked to grazing by herbivorous zooplankton and to low organic matter concentrations. Euglena viridis was replaced by two Chlorophytes (Pediastrum boryanum and Ankyra judai) reaching their maximum density (91% of total algal density) on day 138. The proliferation of these species coincided with values exceeding 10.6 mg N/L. Zooplankton were dominated by Acanthocyclops robustus with the presence of Nauplii and Daphnia magna (106individuals/m3). Rotifers were present since the beginning of the maturation, but were absent by 138 days of retention.The qualitative and quantitative changes in phyto- and zooplankton result from factors that control the growth and the loss of these populations. A low growth rate can lead to biomass accumulation if the growth exceeds loss. On the other hand, a low and stable biomass can result from a high growth rate that is compensated by important losses. Zooplankton grazing and algal sedimentation, which are the two main mechanisms related to phytoplankton decline, are two selective processes (POURRIOT et al., 1982). In stabilization ponds, food chains are established that allow water clarity and minimize algal proliferation. The bacteriological study showed a remarkable purification, with reductions reaching 100% for faecal coliforms and faecal Streptococcus

On the Optimization of the Species Separation in an Inclined Darcy-Brinkman Porous Cavity under the Effect of an External Magnetic Field

An investigation is conducted to study analytically and numerically the effect of a magnetic field on the species separation induced by the combined effects of convection and Soret phenomenon in an inclined porous cavity saturated by an electrically conductive binary mixture and provided with four impermeable walls. The long sides of the cavity are subject to uniform heat flux while its short ends are adiabatic. Uniform magnetic field is applied perpendicularly to the heated walls. The mixture satisfies the Boussinesq approximation and the porous medium, modeled according to Darcy-Brinkman’s law, is assumed homogeneous and isotropic .The relevant parameters for the problem are the thermal Rayleigh number (RT = 1 to 106), the Lewis number (Le = 10), the inclination angle of the cavity (θ = 0º to 180), the separation parameter (φ = 0.5), the Darcy number (Da = 10-5 to 103), the Hartmann number (Ha = 0 to 100) and the aspect ratio of the cavity (Ar = 12). The limiting cases (Darcy and pure fluid media) are recovered in this study. Optimum conditions leading to maximum separation of species are determined while varying the governing parameters in their respective ranges. Results show that the magnetic field can enhance the species separation in cases where the optimal coupling between thermosolutal diffusion and convection is not achieved in its absence. On the other hand, in cases where this optimal coupling is reached in the absence of the magnetic field, the application of the latter destroys the separation of species

Factors Affecting Efficiency of Biosorption of Fe (III) and Zn (II) by Ulva lactuca and Corallina officinalis and Their Activated Carbons

The removal of heavy metals from industrial waste has become crucial in order to maintain water quality levels that are suitable for environmental and species reproductive health. The biosorption of Zn+2 and Fe+3 ions from aqueous solution was investigated using Ulva lactuca green algal biomass and Corallina officinalis red algal biomass, as well as their activated carbons. The effects of biosorbent dosage, pH, contact time, initial metal concentration, and temperature on biosorption were evaluated. The maximum monolayer capacity of Ulva lactuca and Corallina officinalis dry algal powder and algal activated carbon was reached at pH 5 and 3 for Zn+2 and Fe+3, respectively, while the other factors were similar for both algae, which were: contact time 120 min, adsorbent dose 1 g, temperature 40 C and initial concentrations of metal ion 50 mgL1. The batch experimental data can be modelled using the Langmuir and Freundlich isotherm models. Thermodynamic characteristics revealed that the adsorption process occurs naturally and is endothermic and spontaneous. For the adsorption of Zn+2 and Fe+3 ions, the value of G was found to be negative, confirming the practicality of the spontaneous adsorption process, which could be helpful for remediation in the era of temperature increase