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Öğe Ag-doped HfO2 thin films via sol–gel dip coating method(Springer Nature, 2019-10-01) Pakma, Osman; Kaval, Şehmus; Kari̇per, İshak AfşinIn this study, undoped and Ag-doped HfO2 thin films were deposited on glass substrates by means of sol–gel dip coating method. These films were then thermally annealed at 500 °C for 1 h. The structural and optical properties of undoped and Ag-doped HfO2 thin films were characterized by X-ray diffraction, UV–Vis spectrometry and scanning electron microscope. The results of this analysis were compared and interpreted with the results obtained in literature by various methods of coating with HfO2. The X-ray diffraction peaks of the films paired with monoclinic HfO2 crystalline peaks. The refractive indices of the films decreased with doping Ag, at 500 nm wavelengths. The optical band gap values of Ag-doped HfO2 thin films increased with doping Ag. The porous structures were observed on the surface films, especially with 5% Ag doping.Öğe Assessment of natural radiation exposure levels and mass attenuation coefficients of lime and gypsum samples used in Turkey(Springer Nature, 2009-11-17) Damla, Nevzat; Çevik, Uğur; Kobya, Ali İhsan; Çelik, Ahmet; Çelik, NecatiThe activity concentrations of 226Ra, 232Th, and 40K in lime and gypsum samples used as building materials in Turkey were measured using gamma spectrometry. The mean activity concentrations of 226Ra, 232Th, and 40K were found to be 38 ± 16, 20 ± 9, and 156 ± 54 Bq kg − 1 for lime and found to be 17 ± 6, 13 ± 5, and 429 ± 24 Bq kg − 1 for gypsum, respectively. The radiological hazards due to the natural radioactivity in the samples were inferred from calculations of radium equivalent activities (Raeq), indoor absorbed dose rate in the air, the annual effective dose, and gamma and alpha indices. These radiological parameters were evaluated and compared with the internationally recommended limits. The experimental mass attenuation coefficients (μ/ρ) of the samples were determined in the energy range 81–1,332 keV. The experimental mass attenuation coefficients were compared with theoretical values obtained using XCOM. It is found that the calculated values and the experimental results are in good agreement.Öğe Electrochemical determination of melatonin hormone using a boron-doped diamond electrode(Elsevier, 2012-01) Levent, AbdulkadirIn this study, a boron-doped diamond electrode was used for the electroanalytical determination of melatonin in the pharmaceutical tablet and urine samples by square-wave voltammetry. Melatonin yielded a well-defined voltammetric response in Britton-Robinson buffer, pH 3.0 at + 0.88 V (vs. Ag/AgCl). Using the optimal square-wave voltammetry conditions, the oxidation peak was used to determine melatonin in the concentration range of 5.0 × 107 M to 4.0 × 106 M (r = 0.998, n = 8), a detection limit of 1.1 × 107 M (0.025 μg/mL) and relative standard deviation was 2.06% at the 2.0 × 106 M level (n = 10). Recoveries of melatonin were in the range of 97.67–105%, for both tablet and spiked human urine samples.Öğe Preparation, spectral studies, theoretical, electrochemical and antibacterial investigation of a new Schiff base and its some metal complexes(Elsevier, 2014-10-05) İlhan, Salih; Baykara, Hacı; Seyitoğlu, Mehmet Salih; Levent, Abdulkadir; Özdemir, Sadin; Dündar, Abdurrahman; Öztomsuk, Abdussamet; Cornejo, MauricioA new Schiff base ligand, 1,6-Bis(2-(5-bromo-2-hydroxybenzylideneamino)-4-chlorophenoxy)hexane was synthesized. Some Schiff metal complexes of the new Schiff base were prepared by the reaction of some metal salts and the Schiff base. The complexes are non-electrolytes as shown by their molar conductivities (ΛM). The structures of metal complexes are proposed from elemental analysis, FT-IR, UV–vis, magnetic susceptibility measurements, molar conductivity measurements, mass spectra and thermal gravimetric analysis. In addition theoretical 1H NMR, HOMO–LUMO studies of the ligand; antimicrobial and cyclic voltammetric studies of the compounds were also carried out. In this study antioxidant and antibacterial activities of the compounds were examined via in vitro methods.Öğe Parameter optimization of power system stabilizers via kidney-inspired algorithm(SAGE, 2018-06-25) Ekinci, Serdar; Demiroren, Aysen; Hekimoğlu, BaranThis article describes the application of a new population-based meta-heuristic optimization algorithm inspired by the kidney process in the human body for the tuning of power system stabilizers (PSSs) in a multi-machine power system. The tuning problem of PSS parameters is formulated as an optimization problem that aims at maximizing the damping ratio of the electromechanical modes and the kidney-inspired algorithm (KA) is used to search for the optimal parameters. The efficacy of the KA-based PSS design was successfully tested on a well-known 16-machine, 68-bus power system. The obtained results are evaluated and compared with the other results obtained by the original particle swarm optimization (PSO) and the bat algorithm (BA) methods. From the detailed eigenvalue analysis, the nonlinear simulation studies and some performance indices it has been found out that for damping oscillations, the performance of the proposed KA approach in this study is better than that obtained by other intelligent techniques (PSO and BA). Moreover, the efficiency and the superior performance of the proposed method over the other two algorithms in terms of computation time, convergence rate and solution quality are confirmed.Öğe Al-Makrizi’s Khitat and the markets in Cairo during the Mamluks era(Türk Tarih Kurumu, 2017-08) Ağır, Abdullah MesutThis study examines the markets in Cairo during the reign of the Mamlūks in the light of al-Makrīzī’s Chronicle al-Khitat. Besides those which were built during the Mamlūks era the commercial life were ongoing at the markets dating back to the Fatimids and the Ayyubids periods. The marketplaces generally occupied in al-Qasaba which was between Bāb al-Futūh in the north and Bāb al-Zuwayla in the south was the trading center of the city. Al-Qasaba is al-Mu’izz Street today which takes its name from the Fatimid Caliph al-Mu’izz li-Dinillah (341-364/953-975). The economic and social decline especially seen during the second half of the Mamlūks in the 15th century af-fected also the domestic markets stability and most of the sûqs disappeared depending on these conditions.Öğe Synthesis and characterization of 1,2-bis(2-(5-bromo-2-hydroxybenzilidenamino)-4-chlorophenoxy)ethane and its metal complexes: An experimental, theoretical, electrochemical, antioxidant and antibacterial study(Elsevier, 2014-01-24) İlhan, Salih; Baykara, Hacı; Öztomsuk, Abdussamet; Levent, Abdulkadir; Seyitoğlu, Mehmet Salih; Özdemir, SadinA new Schiff base ligand was synthesized by reaction of 5-bromosalicylaldehyde with 1,2-bis(4-chloro-2-aminophenoxy)ethane. Then the Schiff base complexes were synthesized by the reaction of metal salts and the novel Schiff base. The molar conductivity properties of the complexes were studied and found out that the complexes are nonelectrolytes. The structures of the ligand and its metal complexes were characterized by elemental analysis, FT-IR, UV–VIS, magnetic susceptibility measurements, molar conductivity measurements, and thermal gravimetric analysis. In addition antioxidant, theoretical NMR studies and cyclic voltammetry of the complexes were done. Two methods namely metal chelating activity and diphenylpicrylhydrazyl (DPPH) radical scavenging method were used to determine the antioxidant activity, and antibacterial properties of the compounds were also studied.Öğe Protective effect of Hypericum perforatum L. on serum and hair trace elements in rats 7,12-dimethylbenz[a]anthracene-induced oxidative stress(Elsevier, 2012-02-08) Ekin, Suat; Yardım, Yavuz; Oto, Gökhan; Levent, Abdulkadir; Özgökçe, Fevzi; Kusman, TubaThe study was designed to assess the effect of Hypericum perforatum L. (H.P) on serum and hair trace elements and mineral levels, oral administration of 7,12-dimethylbenz[a]anthracene (DMBA) induced oxidative stress in Sprague-Dawley female rats. Analysis of the trace element has been carried out using atomic absorption spectrophotometer method at end of 60th day. It has been found out that the DMBA group contained statistically lower Zn and Cr compared to the control group (p < 0.01) and (p < 0.05), Cu, Mg and Na contained higher than control group (p < 0.05), (p < 0.05) and (p < 0.05). In DMBA + H.P group, Zn higher and Na lower than DMBA group (p < 0.05), (p < 0.05), in hair samples Cd, K and Zn contained lower DMBA compared to the control group (p < 0.05), (p < 0.05) and (p < 0.05). In group DMBA + H.P, Cd was higher than DMBA group and Cr lowered accordance with control group (p < 0.05). The present study demonstrated significantly positive and beneficial effect of H.P on the concentration levels of Zn and Na in serum, also on Cd levels in hair between DMBA and DMBA + H.P groups.
