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21.
Abir Ben Bacha Mona Alonazi Mona G. Alharbi Habib Horchani Imen Ben Abdelmalek 《Molecules (Basel, Switzerland)》2022,27(24)
Biodiesel is one of the important biofuels as an alternative to petroleum-based diesel fuels. In the current study, enzymatic transesterification reaction was carried out for the production of biodiesel from waste cooking oil (WCO) and experimental conditions were optimized, in order to reach maximum biodiesel yield. Bacillus stearothermophilus and Staphylococcus aureus lipase enzymes were individually immobilized on CaCO3 to be used as environmentally friendly catalysts for biodiesel production. The immobilized lipases exhibited better stability than free ones and were almost fully active after 60 days of storage at 4 °C. A significant biodiesel yield of 97.66 ± 0.57% was achieved without any pre-treatment and at 1:6 oil/methanol molar ratio, 1% of the enzyme mixture (a 1:1 ratio mixture of both lipase), 1% water content, after 24 h at 55 °C reaction temperature. The biocatalysts retained 93% of their initial activities after six cycles. The fuel and chemical properties such as the cloud point, viscosity at 40 °C and density at 15 °C of the produced biodiesel complied with international specifications (EN 14214) and, therefore, were comparable to those of other diesels/biodiesels. Interestingly, the resulting biodiesel revealed a linolenic methyl ester content of 0.55 ± 0.02% and an ester content of 97.7 ± 0.21% which is in good agreement with EN14214 requirements. Overall, using mixed CaCO3-immobilized lipases to obtain an environmentally friendly biodiesel from WCO is a promising and effective alternative for biodiesel production catalysis. 相似文献
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Approximation of the distribution of excesses using a generalized probability weighted moment method
The POT (Peaks-Over-Threshold) approach consists of using the generalized Pareto distribution (GPD) to approximate the distribution of excesses over a threshold. In this Note, we consider this approximation using a generalized probability weighted moment (GPWM) method. We study the asymptotic behaviour of our new estimators and also the functional bias of the GPD as an estimate of the distribution function of the excesses. To cite this article: J. Diebolt et al., C. R. Acad. Sci. Paris, Ser. I 340 (2005). 相似文献
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Rouzbeh Molaei Imen Abadi Seyed Ali Sedigh Ziabari 《Applied Physics A: Materials Science & Processing》2016,122(6):616
In this paper, a gate-all-around junctionless tunnel field effect transistor (JLTFET) based on heterostructure of compound and group III–V semiconductors is introduced and simulated. In order to blend the high tunneling efficiency of narrow band gap material JLTFETs and the high electron mobility of III–V JLTFETs, a type I heterostructure junctionless TFET adopting Ge–Al x Ga1?x As–Ge system has been optimized by numerical simulation in terms of aluminum (Al) composition. To improve device performance, we considered a nanowire structure, and it was illustrated that high-performance logic technology can be achieved by the proposed device. The optimal Al composition founded to be around 20 % (x = 0.2). The numerical simulation results demonstrate that the proposed device has low leakage current I OFF of ~1.9 × 10?17, I ON of 4 µA/µm, I ON/I OFF current ratio of 1.7 × 1011 and subthreshold swing SS of 12.6 mV/decade at the 40 nm gate length and temperature of 300 K. 相似文献
24.
Imen Aribi Sahbi Ayachi Kamel Alimi Sadok Roudesli Ayoub Haj Said 《Research on Chemical Intermediates》2017,43(1):73-89
The anodic oxidation of the 4,4′-dimethoxychalcone (DMC) was investigated by different electrochemical methods at a platinum working electrode and in acetonitrile as a solvent. The DMC exhibited a single irreversible anodic peak around 1.6 V versus Ag/AgCl. On the time scale of cyclic voltammetry experiments, the highly reactive radical cation issued from the first electron transfer underwent a second order rate-limiting reaction. The potential imposed electrolyses of DMC led to the formation of a semi-conducting oligomer with 40 % yield. Using different physico-chemicals methods, the structural study confirmed the formation of an o-phenylenevinylene oligomer. The values of the corresponding optical and electrochemical band gaps were calculated to be 3.15 and 2.86 eV, respectively. Finally, a mechanism for the DMC electro-oligomerization was proposed on the basis of the obtained results. 相似文献
25.
Enrique de Amo Imen Bhouri Juan Fernández-Sánchez 《Rendiconti del Circolo Matematico di Palermo》2011,60(3):469-476
In this work we study the some general fractal sums of pulses defined in ? by: $$F(t) =\sum^{+\infty}_{n=1}a_nG(\lambda_n^{-1}(t-X_n))$$ where (a n ), (λ n ) two positive scalar sequences such that ∑a n is divergent, and (λ n ) is non-increasing to 0, G is an elementary bump and X n are independent random variables uniformly distributed on a sufficiently large domain Ω. We investigate the Hausdorff dimension of the graph of G and in particular we answer a question given by Tricot in (Courbes et dimensions fractales, Springer, Berlin, 1995). 相似文献
26.
Imen Ben Hassen 《Journal of Functional Analysis》2011,260(10):2933-2963
We estimate the rate of decay of the difference between a solution and its limiting equilibrium for the following abstract second order problem
27.
Tabbene O Karkouch I Slimene IB Elfeddy N Cosette P Mangoni ML Jouenne T Limam F 《Applied biochemistry and biotechnology》2011,164(1):34-44
When cultured in minimal growth medium, the B38 strain of Bacillus subtilis did not exhibit any antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) clinical isolate. Coculturing B38 strain with viable MRSA cells weakly increased antibacterial activity production
(20 AU/ml). Addition of dead MRSA cells in a B38 culture, increased by 8-fold the B. subtilis strain antibacterial activity reaching 160 AU/ml against MRSA strain. This antibacterial activity recovered from cell-free
supernatants was stimulated by an autoinducing compound which is sensitive to the action of proteinase K suggesting a proteinaceous
nature. This compound was heat-stable till 80 °C and showed a molecular mass around 20 kDa as determined by SDS-PAGE. These
results suggest that the production of antibacterial compounds by B38 strain is dependent on the amount of the autoinducing
compound. 相似文献
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Mejri Imen Kouissi Taoufik Toumi Adel Ouerfelli Noureddine Bounaz Moncef 《Journal of solution chemistry》2021,50(9-10):1131-1168
Journal of Solution Chemistry - Density, speed of sound and viscosity data for the binary mixtures (1,4-dioxane (1)?+?water (2)), were measured over the whole composition range at... 相似文献