Mixed convective boundary layer flow over a vertical wedge embedded in a porous medium saturated with a nanofluid: Natural Convection Dominated Regime

A boundary layer analysis is presented for the mixed convection past a vertical wedge in a porous medium saturated with a nano fluid. The governing partial differential equations are transformed into a set of non-similar equations and solved numerically by an efficient, implicit, iterative, finite-difference method. A parametric study illustrating the influence of various physical parameters is performed. Numerical results for the velocity, temperature, and nanoparticles volume fraction profiles, as well as the friction factor, surface heat and mass transfer rates have been presented for parametric variations of the buoyancy ratio parameter Nr, Brownian motion parameter Nb, thermophoresis parameter Nt, and Lewis number Le. The dependency of the friction factor, surface heat transfer rate (Nusselt number), and mass transfer rate (Sherwood number) on these parameters has been discussed

Optimizing the Extraction Conditions of Hydroxytyrosol from Olive Leaves Using a Modified Spherical Activated Carbon: A New Experimental Design

The purification of hydroxytyrosol from olive leaves extract by modified activated carbon was studied experimentally in a batch system and a column by adsorption and desorption processes. The extraction yield reached 90% of hydroxytyrosol, which is the major compound found in the extract. Despite the abundance of research on extracts of hydroxytyrosol from olive leaves, it seems that the applied methods can be further improved. In this study, several approaches were applied to optimize the extraction conditions of this molecule. Hence, the response surface method and the Box-Behnken design (BBD) were used to evaluate the effect of the temperature, time, and adsorbent dose on the hydroxytyrosol recovery. Moreover, adsorption isotherm, kinetics, and thermodynamic studies were also performed to clarify the nature of the process. The main finding was the obtainment of a maximum adsorption yield of 97.5% at an adsorbent/adsorbate ratio of 1 : 20, after a 6 h cycle and at a temperature of 30°C. Furthermore, adsorption process seemed to fit best with Freundlich model. In addition, the thermodynamic study describes a spontaneous and endothermic process. Desorption assay using ethanol helped to recover 73% of hydroxytyrosol. Furthermore, the HPLC analysis of fractions after column adsorption showed a simple peak of hydroxytyrosol with purity higher than 97% and a flavonoids-rich fraction. These findings would indicate that this separation method for the recovery of phenolic compounds with high antioxidant activity can be a very promising one.This work was supported by the CINEA FP7 Project titled: “EU-MED Cooperation to foster Innovation and Exploitation in the Agro-Food Domain” and the Ministry of Higher Education and Scientific Research, Tunisia

MHD natural convection in an inclined cavity filled with a fluid saturated porous medium with heat source in the solid phase

A numerical investigation of unsteady magnetohydrodynamic free convection in an inclined square cavity filled with a fluid-saturated porous medium and with internal heat generation has been performed. A uniform magnetic field inclined with the same angle of the inclination of the cavity is applied. The governing equations are formulated and solved by a direct explicit finite-difference method subject to appropriate initial and boundary conditions. Two cases were considered, the first case when all the cavity walls are cooled and the second case when the cavity vertical walls are kept adiabatic. A parametric study illustrating the influence of the Hartmann number, Rayliegh number, the inclination angle of the cavity and the dimensionless time parameter on the flow and heat transfer characteristics such as the streamlines, isotherms and the average Nusselt number is performed. The velocity components at mid section of the cavity as well as the temperature profiles are reported graphically. The values of average Nusselt number for various parametric conditions are presented in tabular form

Anaerobic Digestion of Olive MillWastewater and Process Derivatives—Biomethane Potential, Operation of a Continuous Fixed Bed Digester, and Germination Index

Olive mill wastewater (OMW) management is an economic and environmental challenge for olive oil-producing countries. The recovery of components with high added value, such as antioxidants, is a highly researched approach that could help refinance performant wastewater treatment systems. Anaerobic (co-)digestion is a suitable process to valorize the energetic and nutritional content of OMW and OMW-derived waste streams from resource recovery processes. Issues of process stability, operation, and yields discourage industrial application. Deepening the understanding of biomethane potential, continuous anaerobic digester operational parameters, and co-substrates is key to large-scale implementation. The biomethane potential of different OMWderived samples and organic solid market waste as co-substrate was 106–350 NL methane per kg volatile solids (VS). The highest yields were obtained with the co-substrate and depolyphenolized OMW mixed with retentate from an ultrafiltration pretreatment. Over 150 days, an anaerobic fixed-bed 300 L digester was operated with different OMW-derived substrates, including OMW with selectively reduced polyphenol concentrations. Different combinations of organic loading rate and hydraulic retention time were set. The biogas yields ranged from 0.97 to 0.99 L of biogas per g of volatile solids (VS) eliminated, with an average methane content in the produced biogas of 64%. Potential inhibition of the process due to high polyphenol concentrations or over-acidification through volatile fatty acids was avoided in the continuous process through process and substrate manipulation.The InnoVa research project (2nd German-African Innovation Promotion Prize: Prof. Sami Sayadi, Prof. Sven Geißen) was funded by the Bundesministerium für Bildung und Forschung, grant number 01DG20005, and managed by the Deutsche Luft-und Raumfahrtzentrum—Projektträger. This research was supported by the Ministry of Higher Education and Scientific Research-Tunisia under a contract program for the Laboratory of Environmental Bioprocesses (LR01CBS2015). We acknowledge support by the German Research Foundation and the Open Access Publication Fund of TU Berlin

Etude du métabolisme de composés aromatiques par des bactéries anaérobies isolées de margines d'olives et de tourteaux de karité

Deux nouvelles souches anaérobies strictes, "Clostridium glycolicum CIN5" et "C. bifermentans TYR6" ont été isolées à partir d'un bassin de récupération de margines d'olives. La souche CIN5 et la souche type de "C. glycolicum" sont capables de réduire onze composés cinnamiques en leurs dérivés du 3-phénylpropionate correspondants. La souche TYR6 et la souche type de "C. bifermentans" transforment seulement le cinnamate en 3-phénylpropionate. La révision de la description des deux espèces est proposée. "Clostridium aerotolerans" et "C. xylanolyticum" transforment douze composés cinnamiques en leurs dérivés du 3-phénylpropionate correspondants. La souche type de "C. aerotolerans" est par contre , capable également de décarboxyler le p-coumarate en 4-vinylphénol, ultérieurement réduit en 4-éthylphénol. La souche type de "C. celerecrescens" réduit uniquement la double liaison de la chaîne acrylique des m- et p-méthoxycinnamates et du p-méthylcinnamate. La révision de la description de ces trois espèces est propsée. Deux nouvelles souches de bactéries anaérobies facultatives, "Streptococcus gallolyticus B7" et "E. coli C2", ont été isolées d'un digesteur anaérobie alimenté par des tourteaux de karité. La souche B7 et la souche type de "S. gallolyticus" sont capable d'hydrolyser l'acide tannique et libérer du gallate qui est ultérieurement décarboxylé en pyrogallol. Ces deux souches sont également capables de décarboxyler spécifiquement le protocatéchuate en catéchol, le p-coumarate, le caféate et le férulate en leurs dérivés vinylés correspondants. La révision de la description de "S. gallolyticus" est proposée. La souche C2 tolère l'acide tannique à 8,5 g/l et peut décarboxyler spécifiquement le p-hydroxybenzoate en phénol et le vanillate en guaïacol, que ce soit en anaérobiose ou en aérobiose. La souche type d' "E.coli" est par contre, incapable de métaboliser ces deux composés. Les deux activités 4-hydroxybenzoate et vanillate décarboxylases de la souche C2 sont intracellulaires, cytosolubles et inductibles. Il s'agit d'un complexe protéique d'environ 200 kDa, avec plus d'affinité pour le 4-hydroxybenzoate, sensible à l'O2, qui nécessite un agent réducteur comme l'ascorbate et qui fait intervenir une protéine chaperon.AIX-MARSEILLE1-BU Sci.St Charles (130552104) / SudocSudocFranceF

Protective effect of olive leaves phenolic compounds against neurodegenerative disorders: Promising alternative for Alzheimer and Parkinson diseases modulation

The main objective of this work was to review literature on compounds extracted from olive tree leaves, such as simple phenols (hydroxytyrosol) and flavonoids (Apigenin, apigenin-7-O-glucoside, luteolin.) and their diverse pharmacological activities as antioxidant, antimicrobial, anti-viral, anti-obesity, anti-inflammatory and neuroprotective properties. In addition, the study discussed the key mechanisms underlying their neuroprotective effects. This study adopted an approach of collecting data through the databases provided by ScienceDirect, SCOPUS, MEDLINE, PubMed and Google Scholar. This review revealed that there was an agreement on the great impact of olive tree leaves phenolic compounds on many metabolic syndromes as well as on the most prevalent neurodegenerative diseases such as Alzheimer and Parkinson. These findings would be of great importance for the use of olive tree leaves extracts as a food supplement and/or a source of drugs for many diseases. In addition, this review would of great help to beginning researchers in the field since it would offer them a general overview of the studies undertaken in the last two decades on the topic

MHD natural convection inside an inclined trapezoidal porous enclosure with internal heat generation or absorption subjected to isoflux heating

A steady laminar two-dimensional magneto-hydrodynamic natural convection flow in an inclined trapezoidal enclosure filled with a fluid-saturated porous medium is investigated numerically using a finite difference method. The left and right vertical sidewalls of the trapezoidal enclosure are maintained at a cold temperature. The horizontal top wall is considered adiabatic while the bottom wall is subjected to isoflux heating. A volumetric internal heat generation or absorption is embedded inside the trapezoidal enclosure while an external magnetic field is applied on the left sidewall of the enclosure. In the current work, the following parametric ranges of the non-dimensional groups are used: Hartmann number is varied as $0 = Ha = 50$, Darcy number is taken as $Da = 10 -3, 10 -4, and 8 × 10 -5, Rayleigh number is varied as$10 -3 = Ra = 10 -5, Prandtl number is considered constant at Pr = 0.7, the dimensionless internal heat generation or absorption parameter is varied as ? = -0.2, 0, 1, and 2.0, while the trapezoidal enclosure inclination angle is varied as 0°^ = ? = 90°. The results indicated a strong flow circulation occurs when the Darcy and the Rayleigh numbers are high. In addition, it is found that the Hartmann number, internal heat generation or absorption parameter and inclination angle have an important role on the flow and thermal characteristics. It is also found that when the enclosure inclination angle and Hartmann number increase the average Nusselt number along the hot bottom wall decreases

Isolation from a shea cake digester of a tannin-tolerant Escherichia coli strain decarboxylating penta-hydroxybenzoic and vanillic acids

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