Host-guest inclusion complex between β-cyclodextrin and paeonol: A theoretical approach

Host-guest interactions of β-cyclodextrin (β-CD) with paeonol (PAE) were simulated using semi-empirical PM3 and both ONIOM2 [(B3LYP/6-31G*:PM3), (HF/6-31G*:PM3)] methods. The results obtained with PM3 method clearly indicate that the complexes formed are energetically favored with or without solvent, the model 1 (PAE entering into the cavity of β-CD from its wide side by OCH3 group) is found more favored than the model 2 (PAE entering into the cavity of β-CD from its wide side by COCH3 group). Finally, natural bonding orbital (NBO) analysis was performed based on ONIOM2 optimized complexes to quantify the donor–acceptor interactions between PAE and β-CD.     

Volumetric,Ultrasonic and Viscosimetric Studies for the Binary Mixture (1, 4-Dioxane + Water) at T = (295.15, 298.15, 301.15, 304.15, 307.15, 310.15 and 313.15) K

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...     

Biodiesel Production by Single and Mixed Immobilized Lipases Using Waste Cooking Oil

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.     

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).     

The anodic reactivity of 4,4′-dimethoxychalcone: a synthetic and mechanistic investigation

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.     

Antioxidative and DNA Protective Effects of Bacillomycin D-Like Lipopeptides Produced by B38 Strain

In the present study, we evaluated the antioxidant and the scavenging ability of C14, C15 and C16 bacillomycin D-like lipopeptides produced by B38 strain. They all displayed strong reducing power activity, hydroxyl and superoxide anion radicals scavenging activities and inhibition of lipid peroxidation. In addition, they were found to protect plasmid DNA damage from hydroxyl radical oxidation. Data suggested that their antioxidant potency can be attributed to the hydrophobic and aromatic side-chain groups of their amino acids as well as to the aliphatic chain of their beta amino fatty acids. Note that the hydrocarbon chain length did not interfere with the antioxidant power. Overall, such bacillomycin D lipopeptides which exhibit antioxidant and radical scavenging activities may be useful for cosmetic, therapeutic or pharmaceutical purposes in order to delay or prevent oxidative deterioration of manufactured products.     

A note on the Hausdorff dimension of general sums of pulses graphs

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).     

Convergence and decay estimates for a class of second order dissipative equations involving a non-negative potential energy

We estimate the rate of decay of the difference between a solution and its limiting equilibrium for the following abstract second order problem

     

Representation of type I heterostructure junctionless tunnel field effect transistor for high-performance logic application

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 Ga_1?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.