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排序方式: 共有86条查询结果,搜索用时 125 毫秒
61.
Hanène M Ameur E Larbi KM Piras A Porcedda S Falconieri D Marongiu B Farhat F Chemli R 《Natural product research》2012,26(9):810-820
This study is outlined to probe the chemical composition of essential oil and in vitro antioxidant activity of Juniperus oxycedrus ssp. macrocarpa (S. & m.) Ball. and Juniperus oxycedrus L. ssp. rufescens (L. K.) berries, collected from four sites, according to their maturity phase. The chemical composition of the hydrodistilled essential oil was analysed by GC-MS. Forty-eight compounds were identified, accounting for approximately 79.8-98.9% of the oil. The main constituents were α-pinene, germacrene D, myrcene, abietadiene and cis-calamenene, their mean percentage vary according to their phenological stage. The antioxidant activity of the samples was determined by the ABTS and DPPH radical scavenging activities. Hawaria essential oil extracted from mature berries showed the highest antioxidant capacity. 相似文献
62.
Abdelkader Belfedal Yahya Bouizem Jamal Dine Sib Larbi Chahed 《Journal of Non》2012,358(11):1404-1409
Thin films of hydrogenated amorphous germanium (a-Ge:H) deposited at high growth rate by radiofrequency (RF) glow discharge with 1 sccm GeH4 diluted in 40 sccm H2 have been studied. The effect of the films thicknesses on the defect density and on the structural parameters was carefully investigated by means of infrared spectroscopy, optical transmission measurements, and the photothermal deflection spectroscopy (PDS) technique. The results of this investigation show that when the films thicknesses increase, the total hydrogen content (CH) decreases and the hydrogen-bonding configuration changes. The results of these changes appear clearly on the defects density and on the microstructure parameter of the films, while the disorder parameter EOV and the optical gap ET remain practically constant (EOV ≈ 45 ± 2 meV, ET = 1.08 ± 0.02 eV). The improvement of these parameters is mainly due to the incorporation of the hydrogen in the bulk of the material as the monohydride groups (Ge-H) rather than the polyhydride groups (Ge-H2 and Ge-H2n) when the films thicknesses increase. 相似文献
63.
Rachid Amrani Frederic Pichot Jean Podlecki Alain Foucaran Larbi Chahed Yvan Cuminal 《Journal of Non》2012,358(17):1978-1982
Using argon as a diluent of Silane, hydrogenated amorphous and nanorocrystalline silicon films Si:H were prepared by radio-frequency (13.56 MHz) plasma enhanced chemical vapor deposition (rf-PECVD). The deposition rate and crystallinity varying with the deposition pressure and rf power, were systematically studied. Structural analysis (Raman scattering spectroscopy and X-ray diffraction), combined with optical measurements spectroscopy were used to characterize the films. The argon dilution of silane for all samples studied was 95% by volume, and the substrate temperature was 200 °C. The deposition pressure was varied from 400 mTorr to 1400 mTorr and varying rf power from 50 to 250 W. The structural evolution studies, shows that beyond 200 W of rf power, an amorphous-nanocrystalline transition was observed, with an increase in crystalline fraction by increasing rf power and working pressure. The films were grown at high deposition rates. The deposition rates of the films near the amorphous-nanocrystalline phase transition region were found in the range 6–10 Å/s. A correlation between structural and optical properties has been found and discussed. 相似文献
64.
65.
Ali Ghoumaid Farid Benamira Larbi Guechi Zohra Khiat 《Central European Journal of Physics》2013,11(1):78-88
We present a rigorous path integral treatment of a dynamical system in the axially symmetric potential $V(r,\theta ) = V(r) + \tfrac{1} {{r^2 }}V(\theta ) $ . It is shown that the Green’s function can be calculated in spherical coordinate system for $V(\theta ) = \frac{{\hbar ^2 }} {{2\mu }}\frac{{\gamma + \beta \sin ^2 \theta + \alpha \sin ^4 \theta }} {{\sin ^2 \theta \cos ^2 \theta }} $ . As an illustration, we have chosen the example of a spherical harmonic oscillator and also the Coulomb potential for the radial dependence of this noncentral potential. The ring-shaped oscillator and the Hartmann ring-shaped potential are considered as particular cases. When α = β = γ = 0, the discrete energy spectrum, the normalized wave function of the spherical oscillator and the Coulomb potential of a hydrogen-like ion, for a state of orbital quantum number l ≥ 0, are recovered. 相似文献
66.
Azzouzi F Lyazidi SA Haddad M El Messaoudi M Hasnaoui A Larbi NB 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(4-5):875-879
Room temperature UV-vis absorption spectra of the tautomeric system 3,5-dithio-2,7-dimethyl-[1,2,4]-triazepine in solution, in acetonitrile (CH3CN), are measured at different water volume percentages. The comparison of the obtained measures to the calculated allowed absorption transitions, using ZINDO/S package, reveals the coexistence of all the tautomeric forms in aprotic polar solution with a high dominance of the dithione form. The solute-water hydrogen bond, which seems to be of 1:n-type, favours the dithiol and monothiol conformers to the detriment of the dithione one. Further experimental investigations lead to the result that standing at ambient Laboratory conditions in the dark favours the dithione tautomeric isomer, while standing at indirect sunlight shifts the tautomeric equilibrium away from this species. 相似文献
67.
Larbi Berrahmoune 《Rendiconti del Circolo Matematico di Palermo》2000,49(3):575-600
The stability of second order abstract distributed systems with damping and nonlinear perturbations is considered. Sufficient
conditions, including unique continuation property assumptions, are formulated to obtain (local, non-uniform and uniform)
exponential stability. Applications to the wave and Euler-Bernoulli equations are given. 相似文献
68.
Sofia Benamirouche Abderrezak Abdi Larbi Hemmouche Alberto Mejias Mohamed El Amine Belouchrani Didier Chicot Abdelwaheb Amrouche Mohamed Trari 《印度化学会志》2022,99(1):100307
This study has been conducted to investigate the effects of plastic deformation of an AA2024 aluminium alloy by cold rolling to 25%, 50% and 75% and then heat-treating and naturally ageing for 20 days to T4 on the microstructure and the electrochemical behavior. To characterize the microstructural modifications different techniques have been applied such as X-ray Diffraction (XRD) to demonstrate the intermetallic phases formed, Optical Microscopy (OM) and Scanning Electronic Microscopy (SEM) to evaluate their microstructures and grain size. Moreover, the surface topography has been measured to establish the roughness effect on the mechanical response when subjected to tensile, fatigue and micro-indentation tests. The corrosion behaviour was evaluated by Potentiodynamic Polarization Scanning, Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The results revealed that cold-rolled samples with 50% plastic deformation show a smoother topography and exhibit the best compromise between mechanical and corrosion resistance. 相似文献
69.
70.
Larbi Daho Bachir Nadjet Belasri Ahmed Guillot Philippe Caillier Bruno 《Plasma Chemistry and Plasma Processing》2019,39(5):1243-1254
Plasma Chemistry and Plasma Processing - The paper presents an experimental and theoretical study of the radiative emission in the pure krypton lamp excited by dielectric barrier discharge.... 相似文献