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1.
Zouhaier Bouallagui Mohamed Bouaziz Salwa Lassoued Jean Marc Engasser Mohamed Ghoul Sami Sayadi 《Applied biochemistry and biotechnology》2011,163(5):592-599
We previously reported the production of high yields of hydroxytyrosol through the bioconversion of tyrosol. In the present
work, hydroxytyrosol was subjected to the lipase catalyzed acylation aiming for the recovery of more lipophilic esters that
might be easily incorporated in cosmetic and food preparations. Hydroxytyrosyl acetate and hydroxytyrosyl oleate were produced
with respective molar esterification yields of 98% and 78%. DPPH free radical quenching potency demonstrated that the acylation
of hydroxytyrosol did not alter its antioxidant activity. The acylated esters were shown to be more effective than the natural
antioxidant: caffeic acid and two synthetic ones as BHA and BHT. Antiproliferative activity on human cervical cells (HeLa)
resulted in IC50 values of 0.46, 0.42 and 0.33 mM for hydroxytyrosol and its acetyl and oleyl esters, respectively. Additionally, when used
at a non-cytotoxic concentration (100 μM), these compounds showed significant effectiveness in preventing iron-induced oxidative
stress, resulting in a reduction of 30%, 36% and 38% in thiobarbituric acid-reactive substance production, respectively. 相似文献
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Zouhaier Mehrez Mourad Bouterra Afif El Cafsi Ali Belghith Patrick Le Quere 《Heat and Mass Transfer》2009,46(1):107-112
A numerical study based on the large eddy simulation methodology was made of heat transfer in locally disturbed turbulent
separated and reattached flow over a backward facing step. The local disturbance was given to the flow by a sinusoidally blowing/suction
of the fluid into a separated shear layer. The Reynolds number was fixed at 33,000 and Richardson number at 0.5. The disturbance
frequency was varied in the range 0 ≤ St ≤ 2, where St is the Strouhal number of disturbance. The obtained results revealed the existence of an optimum perturbation frequency value,
St = 0.25, in terms of the reduced reattachment length. At this frequency the heat transfer is significantly enhanced in the
recirculation zone. The influence of the frequency and the amplitude of disturbance, in the maximum heat transfer positions
and the maximum local Nusselt number, is analysed. 相似文献
3.
Bensouilah Rahma Olivet Lilian Hammedi Tijani Pronier Stéphane Barbier Jacques Fontaine Céline Ghorbel Abdelhamid Ksibi Zouhaier 《Research on Chemical Intermediates》2021,47(2):813-834
Research on Chemical Intermediates - Formaldehyde has been successfully converted into CO2 and H2O at low temperature in the presence of CeO2x–TiO2(100?x) mixed oxides prepared by the... 相似文献
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The Lyapunov exponent is an important indicator of chaotic dynamics. Using wavelet analysis, we define a multiscale representation of this exponent which we demonstrate the scale-wise dependence for functions belonging to spaces. An empirical study involving simulated processes and financial time series corroborates the theoretical findings. 相似文献
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Mohamed Ksibi Elimam Elaloui Ammar Houas Noomen Moussa 《Applied Surface Science》2003,220(1-4):105-112
Physico-chemical analysis (X-ray, FTIR) and/or methanol oxidation reaction test were performed on fresh and deactivated vanadium catalysts used in H2SO4 manufacturing. It allowed the diagnosis of catalyst deactivation sources, as well as the processes of regenerating and recycling the worn out catalyst in converter. One of these processes is hydrometallurgical method. It consists in treating the deactivated catalyst with alkaline or acidic reagents and forming vanadate solution. A simple and non-costly operation of chemical attack permits the extraction of vanadium from silica in deactivated catalyst. The extracted vanadium can be used for the confection of regenerated catalysts or metallic tools. After optimization, this method can be used for industrial application. 相似文献
6.
Mohamed Triki Zouhaier Ksibi Abdelhamid Ghorbel Francisco Medina 《Journal of Sol-Gel Science and Technology》2011,59(1):1-6
Catalytic wet air oxidation of an aqueous solution of p-hydroxybenzoic acid was conducted over ruthenium catalysts (1 wt%)
supported on CeO2–Al2O3 aerogels mixed oxides at 140 °C and 50 bars of air. We study the effect of the amount of CeO2 in the catalyst. We found that the optimal cerium content in the Al2O3 support was 20 wt%. The activity of the Ru/Al2O3 and Ru/CeO2 was also tested for comparison. It was found that the addition of CeO2 on the alumina support improves the activity of Ru catalysts. The activity of the samples decreases in the following order:
Ru/Ce–Al (20) > Ru/Ce–Al (10) > Ru/Ce–Al (5) ≈ Ru/Al2O3 > Ru/CeO2. Samples characterization was performed by means of N2 adsorption–desorption, XRD, UV–Vis, TPR, SEM and TEM. 相似文献
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A series of tungsten‐doped Titania photocatalysts were synthesized using a low‐temperature method. The effects of dopant concentration and annealing temperature on the phase transitions, crystallinity, electronic, optical, and photocatalytic properties of the resulting material were studied. The X‐ray patterns revealed that the doping delays the transition of anatase to rutile to a high temperature. A new phase WyTi1‐yO2 appeared for 5.00 wt% W‐TiO2 annealed at 900 °C. Raman and diffuse reflectance UV–Vis spectroscopy showed that band gap values decreased slightly up to 700 °C. X‐ray photoelectron spectroscopy showed that surface species viz. Ti3+, Ti4+, O2?, oxygen‐vacancies, and adsorbed OH groups vary depending on the preparation conditions. The photocatalytic activity was evaluated via the degradation of methylene blue using LED white light. The degradation rate was affected by the percentage of dopants. The best photocatalytic activity was achieved with the sample labeled 5.00 wt% W‐TiO2 annealed at 700 °C. 相似文献