Etude de l'influence des facteurs de formulation sur les propriétés viscoélastiques d'un gel à base de Carbopol

Le carbopol est un polymère souvent utilise comme agent viscosifiant et stabilisant clans la formulation des produits pharmaceutiques et cosmétiques. Il est introduit sous forme de gel, avec les autres excipients pour conférer au produit l'aspect semi-solide. Ses propriétés rhéologiques, en matière de consistance et de cohésion, sont très sensibles aux facteurs de formulation, à la concentration du carbopol et au procède de fabrication à savoir, la température et la vitesse d'agitation. Ainsi, on s'est propose clans le cadre de ce travail d'effectuer une étude de débroussaillage des différents facteurs de contrôle lies au procède de formulation, en déterminant leur influence sur les caractéristiques viscoélastiques.Mots clés: Carbopol- Gel-Formulation -Interactions- Viscoélasticité -Plans d'expériences. Carbopol is a polymer often used as viscosifying and stabilizing agent in the pharmaceutical and cosmetic product formulations. It is introduced in the form of a gel, with the others ingredients to confer a semi-solid aspect to the product. Its rheological properties, such as consistency and cohesion, are very sensitive to the formulation factors, carbopol concentration and manufacturing processes, such as temperature and stirring velocity. Thus, the aim of this work is to investigate the effects of controlling factors on the viscoelastic properties of a gel formulated with carbopol.Keywords: Carbopol - Gel - Formulation - Interactions - Viscoelasticity - Experimental design

Propriétés physicochimiques et rhéologiques d’un mélange aqueux de biopolymères et d’un tensioactif non ionique

Dans ce travail, on s‟intéresse à l‟effet des concentrations du xanthane, du caséinate de sodium et du tween 20 sur les propriétés rhéologiques, zétamétriques et de surface de leurs mélanges, dans un milieu aqueux à pH neutre. Il a été mis en évidence, à l‟issue de l‟utilisation de la méthodologie des plans d‟expériences, de l‟existence des interactions répulsives de ségrégation entre les biopolymères, générant un affaiblissement du module de conservation viscoélastique, G‟o et par la même une fragilisation de la structure du système colloïdal. Dans cette situation, il a été observé que le potentiel zêta diminue, ce qui laisse supposer que les interactions répulsives électrostatiques entre les deux espèces anioniques ne sont pas responsables du relâchement de la structure. Par ailleurs, il a été observé que la tension de surface du mélange dépend essentiellement de la concentration du tween 20.Mots clés :Biopolymères - Tween 20 – Rhéologie - Tension de surface - Potentiel zêta

Spring and winter water mass composition in the Brazil-Malvinas Confluence

Hydrographic data of the Confluence 1 cruise collected during austral spring (November 1988) have been analyzed to estimate relative mixing proportions of the various water masses of the Brazil-Malvinas Confluence region using a multiparameter analysis. Seven source water types (SWT) are identified in this region, and all are retained for the analysis: Thermocline Water (TW), Subantarctic Surface Water (SASW), Antarctic Intermediate Water (AAIW), Upper Circumpolar Deep Water (UCDW), North Atlantic Deep Water (NADW), Lower Circumpolar Deep Water (LCDW) and Weddell Sea Deep Water (WSDW). Tracers selected are temperature, salinity, dissolved oxygen and nutrients. Mixing proportions are quantified and plotted along five zonal sections at 35.4, 36.5, 37.9, 41 and 41.6S. The solution obtained during the springtime cruise is consistent with the wintertime (September 1989) data set (Maamaatuaiahutapu et al., 1992): both show the large local recirculation of AAIW and the separation of NADW from the coast south of the thermocline front. However, noticeable changes in water mass mixing proportions can be detected between the winter of 1989 and the preceding spring. The seasonal change for the upper layers of TW and SASW is related to temporal and spatial fluctuations of the thermohaline front. The marked differences in SWT proportions between the two seasons occur at the same location for TW, SASW and AAIW; suggesting that the upper waters have a large impact on the AAIW movement. The deep waters undergo great spatial changes between the two cruises. The variation of the deep convergence position (revealed by the variation of spatial occupancy of the CDW and NADW) seems influenced by the movement of the thermocline front

End-to-End Evaluation in Simultaneous Translation

This paper presents the end-to-end evaluation of an automatic simultaneous translation system, built with state-of-the-art components. It shows whether, and for which situations, such a system might be advantageous when compared to a human interpreter. Using speeches in English translated into Spanish, we resent the evaluation procedure and we discuss the results both for the recognition and translation components as well as for the overall system. Even if the translation process remains the Achilles’ heel of the system, the results show that the system can keep at least half of the information, becoming potentially useful for final users

The Effect of Preventive Measures and Vaccination against SARS-CoV-2 on the Infection Risk, Treatment, and Hospitalization. A Cross-Sectional Study of Algeria

Coronavirus disease (COVID-19) caused by the SARS-CoV-2 virus continues to afflict many countries around the world. The resurgence of COVID-19 cases and deaths in many countries shows a complacency in adhering to preventive guidelines. Consequently, vaccination continues to be a crucial intervention to reduce the effects of this pandemic. This study investigated the impact of preventive measures and COVID-19 vaccination on the infection, medication, and hospitalization. A cross-sectional online survey was conducted between 23 December 2021 and 12 March 2022 in Algeria. To evaluate the effectiveness of strategies aimed at avoiding and minimizing SARS-CoV-2 infection and severity, a questionnaire was created and validated. Descriptive statistics and logistic regression analyses were computed to identify associations between dependent and independent variables. Variables with a p-value of < 0.05 were considered statistically significant. Our results indicated that out of 2294 answers received, only 16% of our sample was vaccinated, and more than 60% did not apply preventive guidelines. As a result, 45% were infected with SARS-CoV-2, 75% took treatment (even preventive), and 9% were hospitalized. The logistic regression showed that the impact of preventive measures on the unvaccinated is statistically not significant (OR: 0.764, 95% CI = 0. 555-1.052; p = 0.09). However, this relationship changes significantly for people who are vaccinated (OR: 0.108, 95% CI = 0.047-0.248; p < 0.0001). Our results also demonstrated that the impact of protective measures on non-vaccinated individuals is statistically significant in reducing the need to receive anti-COVID-19 treatments (OR: 0.447, 95% CI = 0.321-0.623; p < 0.0001). Furthermore, the results showed that the impact of preventive measures on the non-vaccinated population is also statistically significant in reducing the risk of hospitalization (OR: 0.211, 95% CI = 0.081-0.548; p < 0.0001). Moreover, vaccinated individuals who neglect preventive measures must take the COVID-19 medication at a rate of 3.77 times (OR: 3.77) higher than those who follow preventive measures and are vaccinated. In short, our findings demonstrate the importance of combining preventive measures and vaccination in order to fight against the pandemic. Therefore, we advise the Ministry of Health and relevant authorities to put more effort into enhancing public knowledge about the COVID-19 infection and vaccination through education and awareness initiatives. Parallel to implementing vaccination as additional preventive strategy, behavioral change initiatives must be improved to encourage adherence to COVID-19 prevention recommendations

Efficiency of Hydrogen Peroxide and Fenton Reagent for Polycyclic Aromatic Hydrocarbon Degradation in Contaminated Soil: Insights from Experimental and Predictive Modeling

\ua9 2024 by the authors.This study investigates the degradation kinetics of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil using hydrogen peroxide (H2O2) and the Fenton process (H2O2/Fe2+). The effect of oxidant concentration and the Fenton molar ratio on PAH decomposition efficiency is examined. Results reveal that increasing H2O2 concentration above 25 mmol/samples leads to a slight increase in the rate constants for both first- and second-order reactions. The Fenton process demonstrates higher efficiency in PAH degradation compared to H2O2 alone, achieving decomposition yields ranging from 84.7% to 99.9%. pH evolution during the oxidation process influences PAH degradation, with alkaline conditions favoring lower elimination rates. Fourier-transform infrared (FTIR) spectroscopy analysis indicates significant elimination of PAHs after treatment, with both oxidants showing comparable efficacy in complete hydrocarbon degradation. The mechanisms of PAH degradation by H2O2 and the Fenton process involve hydroxyl radical formation, with the latter exhibiting greater efficiency due to Fe2+ catalysis. Gaussian process regression (GPR) modeling accurately predicts reduced concentration, with optimized ARD-Exponential kernel function demonstrating superior performance. The Improved Grey Wolf Optimizer algorithm facilitates optimization of reaction conditions, yielding a high degree of agreement between experimental and predicted values. A MATLAB 2022b interface is developed for efficient optimization and prediction of C/C0, a critical parameter in PAH degradation studies. This integrated approach offers insights into optimizing the efficiency of oxidant-based PAH remediation techniques, with potential applications in contaminated soil remediation

Formulation and Characterization of Double Emulsions W/O/W Stabilized by Two Natural Polymers with Two Manufacturing Processes (Comparative Study)

\ua9 2024 by the authors.Four distinct types of multiple emulsions were synthesized using xanthan gum and pectin through two distinct manufacturing processes. The assessment encompassed the examination of morphology, stability, and rheological properties for the resulting water-in-oil-in-water (W/O/W) double emulsions. Formulations were meticulously crafted with emulsifiers that were compatible with varying compositions. Remarkably stable multiple emulsions were achieved with a 0.5 wt% xanthan concentration, demonstrating resilience for nearly two months across diverse storage temperatures. In contrast, multiple emulsions formulated with a higher pectin concentration (2.75 wt%) exhibited instability within a mere three days. All multiple emulsions displayed shear-thinning behavior, characterized by a decline in apparent viscosity with escalating shear rates. Comparatively, multiple emulsions incorporating xanthan gum showcased elevated viscosity at low shear rates in contrast to those formulated with pectin. These results underscore the pivotal role of the stepwise process over the direct approach and emphasize the direct correlation between biopolymer concentration and emulsion stability. This present investigation demonstrated the potential use of pectin and xanthan gum as stabilizers of multiple emulsions with potential application in the pharmaceutical industry for the formulation of topical dosage forms

Effect of Co-60 gamma-ray irradiation on electrical properties of Ti/Au/GaAs1-xNx Schottky diodes

Current-voltage (I-V), capacitance-voltage-frequency (C-V-f) and conductance-voltage-frequency (G/ω-V-f) measurements at room temperature are used to study 50 kGy 60Co γ-ray electrical properties irradiation dependence of Ti/Au/GaAs1−xNx Schottky diodes with 0.2%; 0.4%; 0.8% and 1.2% nitrogen dilution. This γ-ray irradiation induces a permanent damage that has increased ideality factor and series resistance for all samples. It was accompanied by a decrease in Schottky barrier height with nitrogen content up to 0.4%N and remained constant thereafter. Radiation was also found to degrade the reverse leakage current. At high frequency (1 MHz), capacitance and conductance decreased after radiation due to a decrease in net doping concentration. Interface state density and series resistance were determined from C-V-f and G/ω-V-f characteristics using Hill-Coleman methods. Interface states density exponentially decreased with increasing frequency confirming the behavior of interface traps response to ac signal. Series resistance increases after irradiation is attributed to carrier's removal effect and mobility degradation. It has two peaks in the accumulation and inversion region for some diodes (0.4%N, 0.8%N). γ-ray irradiation produced traps levels and recombination centers that reduce relaxation time. An increase in %N content can impede irradiation damage with even some compensation when the percent of diluted nitrogen is high (1.2%N)