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41.
42.
Djamel Tahtat Mohamed Mahlous Samah Benamer Assia Nacer Khodja Souad Larbi Youcef 《Radiation Physics and Chemistry》2012,81(6):659-665
Chitosan A1, A2 and A3 with molecular weight of 471, 207 and 100 kDa respectively, produced from squid pen chitin was degraded by gamma rays in the solid state and in aqueous solution with various doses in air at ambient temperature. Effect of molecular weight on radiation chemical degradation yield of chain scission and degradation rate constants of γ-irradiated chitosan in solid state and in aqueous solution was investigated. The radiation chemical degradation yield G(s) and degradation rate values were calculated. The molecular weight changes were monitored by capillary viscometry method and the chemical structure changes were followed by UV analysis. The results showed that, the degradation of chitosan was faster in solution, than in solid state. The values of G(s) in solid state and in aqueous solution were respectively 1.1×10?8 mol/J and 0.074×10?7 mol/J for A1, 4.42×10?8 mol/J and 0.28×10?7 mol/J for A2 and 6.08×10?8 mol/J and 0.38×10?7 mol/J for A3. Degradation rate constants values ranged from 0.41×10?5 to 2.1×10?5 kGy?1 in solid state, whereas in solution they ranged from 13×10?5 to 68×10?5 kGy?1. The chitosan A3 was more sensitive to radiolysis than A1 and A2. The chain scission yield, G(s) and degradation rate constants seems to be greatly influenced by the initial molecular weight of the chitosan. Structural changes in irradiated chitosan are revealed by the apparition of absorption peaks at 261 and 295 nm, which could be attributed to the formation of carbonyl groups. In both conditions the peak intensity was higher in chitosan A3 than in A1 and A2, the oxidative products decreased with increasing molecular weight of chitosan. 相似文献
43.
In reversed phase liquid chromatography, the retention indices of benzene and nine mono substituted benzenes with different functionality based on the alkan-2-ones and alkyl aryl ketones retention index standards have been determined by the application of two new mathematical adaptation methods, viz. a multiparametric least-squares regression iterative method based on the determination of the adjusted retention times and a local cubic interpolation method directly using the total retention times. The two methods were applied to two types of columns. The first group includes four octadecyl-C18 columns with different packing materials obtained from different manufacturers, while the second comprises an octyl-C8 column. The retention indices have been extensively studied using either methanol–water or acetonitrile–water mobile phase systems. The influences of the concentration of the organic modifier in the mobile phase (methanol or acetonitrile), the column temperature, and the column packing material on retention indices of the set of the ten monoaromatics studied were also investigated. The calculated multiparametric retention indices values, those obtained by the local cubic interpolation and Kováts’ methods are compared. Good agreement was observed between the retention indices calculated by the three methods. 相似文献
44.
Larbi Berrahmoune 《Rendiconti del Circolo Matematico di Palermo》2009,58(2):275-282
We consider bilinear control systems of the form y′(t) = Ay(t) + u(t)By(t) where A generates a strongly continuous semigroup of contraction (e
t A
)
t⩾0 on an infinite-dimensional Hilbert space Y whose scalar product is denoted by 〈.,.〉. The function u denotes the scalar control. We suppose that B is a linear bounded operator from the state Y into itself. Tacking into account the control saturation, we study the problem of stabilization by feedback of the form u(t)=−f(〈By(t), y(t)〉). Application to the heat equation is considered.
相似文献
45.
Günther Wernicke Larbi Bouamama Oliver Kruschke Nazif Demoli Hartmut Gruber Sven Krüger 《Optics and Lasers in Engineering》2001,36(5)
Holographic microscopy with conjugate reconstruction for the interferometric determination of three-dimensional displacement was used for the investigation of the mechanical behaviour of micromechanic and microelectronic components. An experimental set-up for the exposure of the holographic interferograms is described for the application of the spatial heterodyne technique, for the application of phase shifting, and for electro-optic holography. Three holograms for different illumination directions recorded on one holographic plate were reconstructed conjugately, and spatial-heterodyne technique as well as phase-shift technique were used to evaluate the interferograms. Only by conjugated reconstruction, it is possible to obtain a perfectly optimised interferometer for the static evaluation method. The evaluation of interferograms, which are strongly disturbed by speckle noise, can be performed successfully. A comparison of the results of the application of these techniques is given. The influence of the speckle effect on the resolution was investigated. 相似文献
46.
Belmesnaoui Aqzzouz Redouane Nouira Larbi Zraoula 《Journal of Mathematical Analysis and Applications》2006,324(1):49-59
We give several characterizations of Banach lattices on which each positive Dunford-Pettis operator is compact. As consequences, we obtain new sufficient and necessary conditions under which a norm of a Banach lattice is order continuous, a positive weakly compact operator is compact and the dual operator of a positive Dunford-Pettis operator is Dunford-Pettis. 相似文献
47.
Chemical composition and antioxidant activity of the essential oil of Juniperus phoenicea L. berries
Medini H Elaissi A Larbi Khouja M Piras A Porcedda S Falconieri D Marongiu B Chemli R 《Natural product research》2011,25(18):1695-1706
This study is designed to examine the chemical composition and antioxidant activity of the essential oil of Juniperus phoenicea L. ripe and unripe berries. GC and GC/MS analyses resulted in the detection of 42 components representing approximately 96.50-99.57% of the oils. Major components of the oils were α-pinene (58.61-77.39%), camphene (0.67-9.31%), δ-3-carene (0-10.01%) and trans-verbenol (0-5.24%). Antioxidant activities were determined by two different test systems, DPPH and ABTS radical scavenging activities. In both systems ripe berries exhibited better activity potential than the unripe ones. 相似文献
48.
Benstâali W. Larbi Daho Bachir N. Bendella S. Belasri A. Harrache Z. Caillier B. 《Plasma Chemistry and Plasma Processing》2020,40(6):1585-1603
Plasma Chemistry and Plasma Processing - This work presents an electric and kinetic study of homogeneous dielectric barrier discharge (DBD) in pure krypton (Kr). The electrical characterization and... 相似文献
49.
Abdallah Larbi Doukara 《Tetrahedron》2010,66(10):1852-1858
A new route to S-alkylcarbamothioates is disclosed. In a first step, N-(2-aminophenyl)-4-methyl-thiazolin-2-thione is transformed into a mono- or disubstituted urea at nitrogen, and then in a second step, alkylated at sulfur. The resulting salts, after treatment with a base, gave S-alkylcarbamothioates in high isolated yields together with 3-methyl[1,3]thiazolo[3,2-a]benzimidazole under very mild conditions. 相似文献
50.
Larbi Filali Yamina Brahmi Jamal Dine Sib Fatiha Kail Yahya Bouizem Djamel Benlakehal Kacem Zellama Ahmed Bouhekka Aissa Kebab Larbi Chahed 《Surface and interface analysis : SIA》2019,51(5):531-540
Highly crystallized hydrogenated silicon layers were obtained via the treatment of hydrogenated polymorphous silicon films in a molecular hydrogen ambient. This contrasts other postdeposition studies that obtained nanocrystalline silicon films but necessitated either a plasma activation or high-temperature annealing. The structure of the samples was analyzed by Raman spectroscopy to determine the crystallite volume fraction, which was found to increase up to 80% within 1 hour of treatment. Atomic force microscopy (AFM) showed that the roughness of the surfaces was found to increase after the H2 treatment. Optical transmission and spectroscopic ellipsometry revealed the pronounced porosity of the films characterized by a static refractive index that is below three, which is a low value for hydrogenated silicon films and a void fraction that is around 15% in the bulk of the films. The effect of the hydrogen molecules on the structure of the films was discussed in terms of the compressive stress exerted by the molecules, trapped in structural inhomogeneities, on the amorphous tissue. It is suggested that for this process to take effect, the films need to be porous and that the amorphous network needs to be in a “relaxed” state. 相似文献