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Öğe Anderson localization in optical lattices with speckle disorder(Amer Physical Soc, 2011) Sucu, Serpil; Aktas, Saban; Okan, S. Erol; Akdeniz, Zehra; Vignolo, PatriziaWe study the localization properties of noninteracting waves propagating in a speckle-like potential superposed on a one-dimensional lattice. Using a combined decimation-renormalization procedure, we estimate the localization length for a tight-binding Hamiltonian where site energies are square-sinc-correlated random variables. By decreasing the width of the correlation function, the disorder patterns approach a delta-correlated disorder, and the localization length becomes almost energy independent in the strong disorder limit. We show that this regime can be reached for a size of the speckle grains on the order of (lower than) four lattice steps.Öğe The binding energy of hydrogenic impurity in multilayered spherical quantum dot(Elsevier Science Bv, 2008) Aktas, Saban; Boz, Figen KaracaThe binding energy of a hydrogenic impurity of a multilayered spherical GaAs-(Ga,Al)As quantum dot has been investigated as a function of the barrier thickness and the inner dot thickness for various barrier potentials in the effect of the band non-parabolicity. Within the effective mass approximation, the ground state energy has been calculated using the fourth-order Runge-Kutta method. The ground state binding energy of hydrogenic impurity located at the center of a quantum dot has been studied with a variational approach. We have found that a variation in the binding energy has depended on the geometry of the dot. (c) 2007 Elsevier B.V. All rights reserved.Öğe Characterization of dinaphthosulfoxide molecule(Elsevier Science Bv, 2015) Ulucam, Guhergul; Okan, S. Erol; Aktas, Saban; Ogretmen, Gul PenbeDinaphthosulfoxide has been synthesized, and confirmed by the experimental methods. The geometrical optimization of the two isomers of the molecule in their ground state was studied using density functional theory. Then, NMR and IR spectra were calculated for the optimized configurations. Analyzing the hydroxyl features in the NMR data and that of sulfoxide in IR spectra, the experimental observables are found to be in agreement with the properties of the syn isomer. (C) 2015 Elsevier B.V. All rights reserved.Öğe Double vanadyl-carrying phenanthroline complexes: template synthesis and DFT study(Springer International Publishing Ag, 2020) Ulucam, Guhergul; Yenturk, Busra; Okan, Sevket Erol; Aktas, SabanThree new Oxo vanadium(IV) complexes were synthesized by the template reactions of 1,10-phenanthroline-2-carboxyaldehyde and vanadium(IV) sulfate with three different diamines. The structures of complexes were elucidated by measuring their FT-IR, UV-Vis, LC/+ ESI MS spectra and thermogravimetric analysis and molar conductance. Meantime, the molecular configuration of complexes and their FT-IR spectra were calculated at B3LYP level with the density functional theory. The LanL2DZ basis set was used for the optimization of the complexes, whilst the 6-311G basis set was used for the calculation of infrared spectra. The length of the coordinate bonds of the complexes was obtained together with parameters such as the bond angles, the dihedral angles, and HOMO-LUMO level energies. The individual FT-IR spectrum for each complex obtained from the density functional theory was found to be in good agreement with that of the experimental FT-IR spectrum.Öğe Energy levels of GaAs/AlxGa1-xAs/AlAs spherical quantum dot with an impurity(Elsevier Science Bv, 2016) Boz, Figen Karaca; Nisanci, Beyza; Aktas, Saban; Okan, S. ErolWe have calculated the energy levels and the radial probability distributions of an electron with an impurity in a spherical quantum dot which is layered as GaAs/AlxGa1-xAs/AlAs. The numerical method used is the fourth-order Runge-Kutta method in the framework of the effective mass approximation. The variation of the energy levels have been calculated as functions of the radius of the GaAs sphere and the thickness of AlxGa1-xAs spherical layer considering effective mass and dielectric constant mismatches. The results have presented the importance of the geometry on the electronic properties of the spherical GaAs/AlxGa1-xAs/AlAs quantum dot. (C) 2016 Elsevier B.V. All rights reserved.Öğe Geometric effects on energy states of a hydrogenic impurity in multilayered spherical quantum dot(Elsevier Science Bv, 2009) Boz, Figen Karaca; Aktas, Saban; Bilekkaya, Abdullah; Okan, Sevket ErolThe energy states of a hydrogenic impurity, located at the center of a multilayered spherical quantum dot, are calculated as functions of the barrier thickness and the inner dot thickness by using a fourth-order Runge-Kutta method. It is shown that the method is able to calculate all the energy states for any potential pro. le in the dot. Also, the binding energies show dramatic changes in comparison with those of single spherical quantum dots. (C) 2009 Elsevier B.V. All rights reserved.Öğe New Schiff-base ligands containing thiophene terminals: Synthesis, characterization and biological activities(Elsevier, 2021) Ulucam, Guhergul; Okan, Sevket Erol; Aktas, Saban; Yenturk, BusraSchiffbase ligand C18H24N2S2 was synthesized in the reaction of aromatic aldehyde 4-methylthiophene-2-carbaldehyde with hexane-1,6-diamine. Also, C20H28N2S2 was obtained reacting 4-methylthiophene-2-carbaldehyde with octane-1,8-diamine. The ligands have been characterized by NMR (H-1, C-13), FT-IR and mass spectroscopy. The energies and the atomic configurations of the ligands have been optimized within Density Functional Theory. The NMR and FT-IR spectra of the compounds were calculated on their optimized molecular structures, and they were compared with their corresponding experimental NMR and FT-IR spectra. The antibacterial activities of synthesized compounds were investigated by using Broth Micro-Dilution method. They were effective on Staphylococcus aureus ATCC 25923 bacteria as much as the effect created by the antibiotic in the same dose. The cytotoxic effects the ligands were pronounced on the cancer cell lines while no harm of them was observed on the healthy cells. (C) 2021 Elsevier B.V. All rights reserved.Öğe Synthesis and characterization of new N-heterocyclic carbene ligands: 1,3-Bis(acetamide)imidazol-3-ium bromide and 3-(acetamide)-1-(3-aminopropy1)-1H-imidazol-3-ium bromide(Elsevier, 2017) Turkyilmaz, Murat; Ulucam, Guhergul; Aktas, Saban; Okan, S. ErolTwo new pincer type N-heterocyclic carbene ligands were synthesized. The compounds were characterized by FTIR, NMR (H-1, C-13) GC-MS and elemental analyses. They were also both modelled by DFT calculations as the crystal structure of 1,3-bis(acetamide)imidazol-3-ium bromide was determined by XRD which is an orthorhombic system with space group P2(1)2(1)2. The structural analyses in gas phase were realized by comparing the experimental NMR and IR spectra with those of the theoretical calculations. In vitro biological activities of the molecules were determined and found that one of them exhibits significant cytotoxic activity. (C) 2017 Elsevier B.V. All rights reserved.Öğe Theoretical suggestions of resonant tunneling diodes and laser field effects on their current-voltage characteristics(Academic Press Ltd- Elsevier Science Ltd, 2019) Okan, S. Erol; Boz, Figen Karaca; Aktas, SabanSeveral resonance-tunneling diodes are modelled for a fixed resonance energy. The theoretically suggested diodes are classified according to their local potentials differed by the doping concentrations. The electronic properties of the diodes are explored in the framework of numerical calculations. In addition, the laser field effects on the latter properties are reported. They show that the laser field application enriches the functionality of these devices in applications.
