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Öğe Fast production of ZnO nanorods by arc discharge in de-ionized water and applications in dye-sensitized solar cells(ELSEVIER SCIENCE SA, 2014) Sonmezoglu, S.; Eskizeybek, V.; Toumiat, A.; Avci, A.Fast production of the ZnO nanorods by bottom up approach using arc discharge method in de-ionized water was carried out. Structural analysis showed that the obtained ZnO powder exhibits crystallize in the hexagonal wurtzite structure with (101) preferential orientation. Furthermore, transmission electron microscopy observations showed that rod-like structure is the abundant form with a bimodial grain size distribution around 10 and 30 nm. Optical characterization of the as-synthesized ZnO nanorods revealed the existence of the two absorption and photoluminescence (PL) bands both located at UV spectral region attributed to the two grain size distributions. In addition, the two additional visible bands PL spectrum located at 430 and 492 nm are attributed the interstitial zinc and oxygen vacancies; respectively. Dye sensitized solar cells (DSSCs) were successfully produced via different ruthenium based dyes and ferrocene liquid electrolyte by using of as synthesized ZnO nanorods modified photoanodes. It has been found that DSSCs made with N719 dye is the most efficient with photoconversion of approximately 7% compared to the other dyes. Such nanorod form of the ZnO nanostructures with ruthenium dyes resulted in significant improvements of the device performance in terms of electron transportation and UV light absorption. This work would explore feasible routes to synthesize efficient metal-oxide nanostructures for opto-electronic or other related applications. Published by Elsevier B. V.Öğe Impact of a type-D personality on clinical and psychometric properties of patients with a first myocardial infarction in a Turkish sample(ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER, 2016) Annagur, B.; Demir, K.; Avci, A.; Uygur, O.[Abstract not Available]Öğe Radiation dose and diagnostic accuracy of high-pitch dual-source coronary angiography in the evaluation of coronary artery stenoses(ELSEVIER MASSON, CORPORATION OFFICE, 2016) Koplay, M.; Erdogan, H.; Avci, A.; Sivri, M.; Demir, K.; Guler, I.; Demir, L. S.Purpose: "Flash Spiral'' imaging is a new prospective ECG-triggered spiral scan mode that uses a very high-pitch for coronary computed tomography angiography (CTA). This enables complete image acquisition within one cardiac cycle with a very low radiation exposure. The aim of this study was to investigate the diagnostic accuracy, image quality, and effective radiation dose of prospectively ECG-triggered high-pitch spiral method (Flash spiral mode) of coronary CTA using dual-source technology for the evaluation of coronary artery stenoses. Material and methods: The study included 186 consecutive patients (115 men, 71 women; mean age: 53.37 years) who underwent coronary CTA. Coronary CTA was performed with a 128 x 2-slice dual-source CT (Somatom Definition Flash, Siemens, Germany) using a prospectively ECG-triggered high-pitch spiral mode. Patients were divided into three groups according to heart rate (<= 65 bpm, 66-75 bpm, >= 76 bpm) and body mass index (BMI) (20-24 kg/m(2), 25-29 kg/m(2), 30-34 kg/m(2)) values. The correlation between heart rates, image quality and BMI values are investigated. A four-point scale (1 = excellent, 4 = poor/non-diagnostic) was used to rank the comparative image quality. Effective radiation doses were calculated. Also the correlation between radiation dose, sex and BMI values were investigated. In addition, diagnostic accuracy of CTA for detection of significant (= 50%) coronary artery stenoses was compared with invasive coronary angiography findings of 612 vessel segments in 38 patients. The sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy rate were calculated. Results: A total of 2976 coronary artery segments were present. Of all coronary artery segments, 2381 (80%) had an image quality score of 1, and 1.5% segments were rated as "poor/nondiagnostic". When the correlation between heart rate and image quality is investigated, there was a significant difference between < 65 bpm and > 76 bpm groups. However, there was no significant difference between < 65 bpm and 66-75 bpm groups. The mean effective dose was found as 1.3 mSv (min: 0.5, max: 2.4 mSv). The correlation between effective radiation dose and BMI was moderate. However, the correlation between gender and radiation dose was significant. Sensitivity, specificity, negative predictive value and accuracy of coronary CTA on a per -vessel segment were 90.1%, 97.4%, 98.6%, and 96.5%, respectively. Conclusions: Prospectively ECG -triggered high -pitch spiral mode coronary CTA provides high image quality and diagnostic accuracy, with very low radiation dose for evaluation and exclusion of coronary artery stenoses. (C) 2015 Editions franc aises de radiologie. Published by Elsevier Masson SAS. All rights reserved.Öğe Structural and optical properties of CdO nanowires synthesized from Cd(OH)(2) precursors by calcination(WILEY-V C H VERLAG GMBH, 2011) Eskizeybek, V.; Avci, A.; Chhowalla, M.CdO nanowires were produced by calcination process using Cd(OH)(2) nanowires as precursors. The Cd(OH)(2) nanowires were synthesized via arc discharge method submerged in de-ionized water. Transmission electron microscopy (TEM) analysis of the as-synthesized Cd(OH)(2) nanowires revealed that nanowire morphology was abundant form with the diameters range from 5 to 40 nm. In addition to the nanowire morphology, Cd(OH)(2) nanospheres and hexagonal shaped nanoparticles were also displayed. The Cd(OH)(2) nanostructures were used as precursors to produce CdO nanowires and calcinated in air at 400 degrees C for four hours. After calcination, the structural, morphological and optical properties of the as-synthesized CdO nanowires were characterized by means of TEM, selected area electron diffraction (SAED), X-ray diffraction (XRD) and UV-vis spectroscopy. The XRD and SAED techniques showed that the as-synthesized Cd(OH)(2) nanostructures could be transformed into CdO nanostructures after the calcination process. TEM results revealed that the as-synthesized CdO nanowires were 5-30 nm in diameter and shorter than corresponding Cd(OH)(2) nanowires. In addition, the diameters of the spherical or irregular CdO nanoparticles ranged from 20 nm to 50 nm. UV-vis spectroscopy analysis was showed that the direct gap of the CdO nanowires were found to be 2.60 eV which is slightly higher than the earlier reported values of the bulk CdO for direct band gaps (2.3 eV) due to quantum size effect. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimÖğe Synthesis of Carbon Nanostructures and CaCO3 Nanoparticles by Arc Discharge in Mineral Water(TRANS TECH PUBLICATIONS LTD, 2011) Eskizeybek, V.; Karabulut, E. S.; Avci, A.The synthesis of multi-walled carbon nanotubes MWCNTs, carbon nanoshells, carbon nanoonions (CNOs), different types of carbon nanostructures and CaCO3 nanoparticles were performed using an arc-discharge method in mineral water. The structures of the synthesized nanostructures were visualized by scanning electron microscopy and transmission electron microscopy (TEM). Furthermore, ultraviolet-visible spectroscopy and thermo-gravimetric analysis (TGA) were used to determine the optical and thermal properties of the synthesized nanostructures. The TEM observations revealed that as-synthesized MWCNTs and CNOs have nominal diameters in the range of 10-20 nm and 30-50 nm, respectively. The CaCO3 nanoparticles were directly synthesized using arc discharge due to the presence of Ca minerals in the mineral water. The production rate of synthesized MWCNTs decreased when the arc current increased above 50 A, and the production rate of different nanoparticles increased with increasing arc current. The thermal-oxidative stability of the carbon nanostructures using TGA was explored separately under argon and oxygen atmospheres.
