http://archives.univ-biskra.dz/handle/123456789/57 Mon, 06 Apr 2026 20:33:36 GMT 2026-04-06T20:33:36Z http://archives.univ-biskra.dz/handle/123456789/31693 Titre: Synthesis and study of the dielectric properties of a doped NBT type material Auteur(s): Rahal Rahima Résumé: The present study reports the fabrication of NBT-type ceramic materials with the general formula (Na0.5Bi0.5) 0.94 R 0.04Ti 0.95 (Ni0.2 Fe0.2 Sb0.6) 0.05O3 (abbreviated as NBT-RNFS), where R denotes the dopant elements La, Nd, Gd, and Y. The ceramics were synthesized via the conventional solid state reaction method. The main objective of this study was to investigate the effect of rare earth doping on the dielectric and photocatalytic properties of novel NBT-based ceramic materials. The NBT-RNFS samples were successfully synthesized at 1150°C. Undoped NBT-NFS samples had a single rhombohedral phase, while rare earth-doped NBT-NFS samples showed a rhombohedral phase along with a pyrochlore phase. Rietveld refinement of the XRD data showed a slight shrinkage of the unit cell volume with the substitution of rare earth elements, attributed to their relatively lower ionic radii compared to the host ions. Optical bandgap analysis revealed that the fabricated perovskite samples exhibited semiconducting behavior, with measured bandgap values ranging from 2.61 to 2.80 eV. The La-doped NBT-RNFS system exhibited an impressive 83% photocatalytic dye degradation rate, substantially outperforming the 23% dye removal efficiency of the undoped material. Similarly, the Nd-doped (62% dye removal) and Y-doped (66% dye removal) NBT-RNFS ceramics also displayed enhanced photocatalytic activities under broadband solar light exposure. The La-doped NBT-RNFS composition demonstrated an exceptionally high dielectric constant (εr) of 1151.87, while the Nd-doped NBT-RNFS exhibited a dielectric constant of 1122.31. These values significantly exceeded the dielectric constant of 951.02 obtained for the undoped NBT-NFS ceramic. Wed, 01 Jan 2025 00:00:00 GMT http://archives.univ-biskra.dz/handle/123456789/31693 2025-01-01T00:00:00Z http://archives.univ-biskra.dz/handle/123456789/31692 Titre: Études de différents modes d'interactions entre une cible neuro dégénérative et une nouvelle classe de molécules bioactives : Approches de Docking/Dynamique moléculaire, Replacement bioisostérique et ADME. Auteur(s): METTAI Merzaka Résumé: Monoamine oxidase B and adenosine A2A receptors are used as key targets in Parkinson's disease. The inhibitory power of a new series of phenylxanthine derivatives on two biological targets, the hMAO-B and hA2AR, has recently been demonstrated. Consequently, in our research work we carried out a study of the interactions established between 38 phenylxanthine derivatives with the biological targets hMAO-B and hA2AR. This study is based on the use of various molecular modeling techniques. A molecular docking study revealed that compounds L24 ((E)-3-(3-Chlorophenyl)-N-(4-(1,3-dimethyl-2,6- dioxo-2,3,6, 7-tetrahydro-1H-purin-8-yl) phenyl) acrylamide and L32 ((E)-3-(3-Chlorophenyl)-N-(3-(1,3 dimethyl-2,6-dioxo- 2,3,6,7-tetrahydro-1H-purin-8-yl)phenyl)acrylamide had a high affinity with the cavities of hMAO-B and hA2AR targets (S score: -10.160 and -7.344 kcal/mol respectively), and the stability of the complexes studied was confirmed through molecular dynamics simulations. A molecular electrostatic potential (MEP) analysis of compounds 24 and 32 was also carried out. In addition, the bioisosteric replacement approach was successfully applied to design two new analogues of each compound with low energy scores. Moreover, ADME-T and Drug-likeness results revealed promising pharmacokinetic properties and oral bioavailability for these compounds. Therefore, compounds L24, L32 and their analogues can be further analyzed and optimized to design new, more effective lead compounds for the treatment of Parkinson's disease. Wed, 01 Jan 2025 00:00:00 GMT http://archives.univ-biskra.dz/handle/123456789/31692 2025-01-01T00:00:00Z http://archives.univ-biskra.dz/handle/123456789/31691 Titre: Synthèse et propriétés catalytiques d’oxydes mixtes à base de Néodyme et métaux de transitions Résumé: The goal of the project is to create strong and efficient oxygen evolution reaction (OER) electrocatalysts in order to address environmental pollution and energy scarcity. The sol-gel method was used to produce the perovskite NdFe1-xNixO3, and its electrocatalytic activity towards OER was evaluated. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and electrochemical techniques like linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronopotentiometry were among the methods used to characterize the prepared catalysts. The outcomes demonstrated that the NdFe1-xNixO3 compounds had a roughly spherical morphology and a pure orthorhombic crystal structure over the whole substitution range. The compounds were calcined at 800 ◦C. The calculated average diameters of crystallites are 19–24 ± 0.5 nm. The NdFe0.8Ni0.2O3 electrode, in particular, showed remarkable electroactivity, displaying lowest over potential (310 mV vs RHE) required to achieve a current density of 10 mA.cm−2, the lowest Tafel slope (149 mV.dec-1), and good stability over a 60-hour period, the NdFe0.8Ni0.2O3 electrode stood out for its exceptional electroactivity. These results offer insightful information about the development and design of high-performance electrocatalysts for uses in sustainable energy conversion and storage. Wed, 01 Jan 2025 00:00:00 GMT http://archives.univ-biskra.dz/handle/123456789/31691 2025-01-01T00:00:00Z http://archives.univ-biskra.dz/handle/123456789/31690 Titre: Contribution à l’étude statistique des populations pour l’amélioration du gain des lasers à puits quantique à base de nitrures dilués. Auteur(s): Sara HANI Résumé: The present thesis investigates a quantum well laser GaSb1-xNx/GaSb emitting in the infrared spectral region. The active region is made of GaSb1-xNxand the cladding layers consist of GaSb. Several physical properties (electronic, optical and elastic) of GaSb1-xNx were calculated and used as input date for the simulation of our quantum well laser. The optical gain was thereafter addressed as a function of wavelength, the width of the active region and the concentration of charge carriers. The optical spectrum of the gain is calculated using the k.p method considering the parabolic model of conduction band and the subbands coupling between heavy holes and light holes in the conduction band. The effect of the strain was taken into consideration. Description: Physique Wed, 01 Jan 2025 00:00:00 GMT http://archives.univ-biskra.dz/handle/123456789/31690 2025-01-01T00:00:00Z