Browsing by Author "Cetin A."
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Item Optical properties of Cu implanted ZnO(2006) Cetin A.; Kibar R.; Ayvacikli M.; Can N.; Buchal Ch.; Townsend P.D.; Stepanov A.L.; Karali T.; Selvi S.Nanoparticles of Cu have been made in zinc oxide crystals by ion implantation. The Cu ions were implanted at 400 keV into the (0 0 0 1) face of a single crystal. After implantation and after post-irradiation annealing there are numerous changes in the luminescence responses which include a variety of green and yellow emission bands. Following annealing at temperatures up to 1000 °C a green luminescence near 525 nm was observed which has been associated with the isolated Cu ions. The changes between as implanted and annealed luminescence signals suggests that the implants generate clustering or nanoparticle formation of Cu but anneals dissociate them. © 2006 Elsevier B.V. All rights reserved.Item Leptin levels in thyroid cancer(Elsevier (Singapore) Pte Ltd, 2009) Akinci M.; Kosova F.; Cetin B.; Aslan S.; Ari Z.; Cetin A.BACKGROUND: Leptin has physiological roles in multiple systems, and has possible effects on several carcinogenesis steps. The aim of this study was to investigate the leptin levels in thyroid papillary carcinoma (TPC) patients. METHODS: Forty-three female TPC patients and 30 healthy female control subjects were recruited for the study. TPC was diagnosed by fine needle aspiration biopsy. TPC patients had a bilateral total thyroidectomy operation and their leptin levels were measured before and 20 days after the operation. RESULTS: Serum leptin levels of TPC patients were higher than in control group subjects (21.15 ± 14.12 ng/mL vs. 9.89 ±0.21 ng/mL, p< 0.05). The leptin levels decreased after total thyroidectomy (13.92 ± 10.55 ng/mL) compared to prethyroidectomy levels (22.94 ± 14.67 ng/mL) in 34 patients who came to the follow-up visit (p< 0.05). However, the decreased post-thyroidectomy levels of leptin were still statistically significantly higher than the control group levels. Multivariate regression analysis showed that the leptin levels in TPC patients were not related to age, menopausal status or pathologic occult status but were directly related to the cancer group. CONCLUSION: Leptin levels were elevated in thyroid cancer, decreased after total thyroidectomy, and might be associated with thyroid papillary carcinogenesis. © 2009 Elsevier. All rights reserved.Item Effects of different postmenopausal hormone therapy regimens on cerebral blood flow and cognitive functions(2009) Guvenal T.; Durna A.; Erden O.; Guvenal F.; Cetin M.; Cetin A.Introduction: The purpose of this study was to compare the effects of different postmenopausal hormone therapy regimens, namely conjugated equine estrogens (CEE), CEE plus medroxyprogesterone acetate (MPA), tibolone, and raloxifene on cerebral blood flow and cognitive functions. Methods: A total of 64 healthy postmenopausal women admitted to the Department of Obstetrics and Gynecology, Cumhuriyet University, Turkey were included in this study. Patients were divided into five groups with respect to the treatment protocols: CEE 0.625 mg/day (n=13); CEE 0.625 mg/day + MPA 2.5 mg/day (n=14); tibolone 2.5 mg/day (n=11); raloxifene 60 mg/day (n=9); and control (n=17). The CEE group included only women with surgical menopause. Those who were on hormonal therapy, who had previously used hormonal therapy, who had neurological disorders, or who did not accept the longterm follow-up were excluded from the study. Demographic and clinic characteristics were recorded. Before starting the therapy regimens, cerebral blood flow was evaluated by internal carotid artery and middle cerebral artery peak systolic velocity, and pulsatility index measurements via Doppler ultrasonography. Cognitive functions were evaluated by the Standardized Mini-Mental Test. The mean follow-up period was 10.9±2.4 months, ranging between 8 and 16 months. After the follow-up period, the cerebral blood flow, and cognitive function of each woman was re-evaluated. Results: Demographic and clinical characteristics of the women were not significantly different between the study groups (P>0.05). There were no significant differences between the pretreatment and posttreatment values for cerebral blood flow indices and cognitive function scores in any of the study groups (P>0.05). Conclusion: Different postmenopausal hormone therapy regimens have not revealed any significant effects on either cerebral blood flow or cognitive function. © 2009 Springer Healthcare Communications.Item Luminescence properties of Tb implanted ZnO(2009) Cetin A.; Kibar R.; Selvi S.; Townsend P.D.; Can N.ZnO [0 0 0 1] crystals were irradiated at room temperature with Tb+ ions of 400 keV with fluences from 1×1016 to 2×1017 cm-2. The implanted layer was examined by several methods, including radioluminescence (RL), Rutherford backscattering spectrometry (RBS) and optical spectroscopy. The optical extinction spectra were simulated using Mie scattering theory. Absorption spectra predicted by Mie theory for particles of decreasing diameter were compared with those obtained experimentally. Some qualitative agreement between theoretical and experimental data was achieved. It was also shown that the intensities of the characteristic green emission bands associated with Tb produced by 5 D4 → 7 Fj = 5, 4 transitions have increased about 8 times after annealing. Optical spectroscopy and radioluminescence data have revealed that the ion implantation is a promising tool for synthesizing Tb nanoparticles in the ZnO surface. The Tb nanoparticles exhibit a rather weak plasma resonance. © 2009 Elsevier B.V. All rights reserved.Item Effects of selective and non-selective cyclooxygenase (COX) inhibitors on postoperative adhesion formation in a rat uterine horn model(2010) Guvenal T.; Yanar O.; Timuroglu Y.; Cetin M.; Cetin A.Objective: To investigate the effects of cyclooxygenase (COX) inhibitors including celecoxib, indomethacin, and nimesulide on postoperative adhesion formation. Material and Methods: Forty-eight female Wistar-Albino rats were randomly divided into four groups: control (saline solution), celecoxib, indomethacin, and nimesulide groups. The uterine horns of rats were traumatized with unipolar electrocautery. Drugs of each group and saline in the control group were insillated on travmatized areas of horns as intraperitoneally. After three weeks, the extent and severity of adhesions with a standardized scoring system were evaluated. Results: The extent and severity of postoperative adhesions were significantly reduced in nimesulide group compared with the control group. The extent but not severity of adhesions in rats given indomethacin was significantly reduced. Celecoxib showed no significant reduction in the extent and severity of adhesions. Conclusion: Nimesulide is more effective than the other COX inhibitors in the prevention of postoperative adhesions in rats.Item Third-order optical nonlinearities of Cu and Tb nanoparticles in SrTiO3(2010) Cetin A.; Kibar R.; Hatipoglu M.; Karabulut Y.; Can N.Some results of optical and nonlinear-optical properties of Cu and Tb nanoparticles implanted in SrTiO3 (STO) crystal are presented. The non-resonant third-order optical nonlinearities have been investigated by degenerate four wave mixing (DFWM), pump-probe and Z-scan techniques using femtosecond laser pulses. © 2010 Elsevier B.V. All rights reserved.Item Luminescence behavior and Raman characterization of rhodonite from Turkey(2011) Can N.; Guinea J.J.G.; Kibar R.; Cetin A.Cathodoluminescence (CL) and optical absorption properties of rhodonite natural silicate mineral were investigated. CL spectra show an intense Mn 2+ luminescence band, which occurs as broad-band emission in the orange-to-red range. The broadness of the emission is explained by strong interaction of 3d ions with the surrounding crystal field, which is strongly affected by lattice and atomistic vibrations of the ligands. Rhodonite rock exhibits luminescence maxima at 310, 425, and 626 nm. The Raman spectrum of rhodonite (from Turkey) is characterized by an intense band at about 668 cm -1 assigned to ν4 bending mode and showed additional bands exhibiting loss of degeneracy of the SiO4 units. A strong band at 408 cm -1 is attributed to the ν2 bending bond. Copyright © Taylor & Francis Group, LLC.Item Luminescence behaviour and Raman characterization of dendritic agate in the Dereyalak village (Eskiehir), Turkey(2011) Paral L.; Garcia Guinea J.; Kibar R.; Cetin A.; Can N.Results are presented for the cathodoluminescence (CL), X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectrometry (ICP-AES) and simultaneously two thermal analyses of (DTA/TGA) spectroscopy of dendritic agate which occurs in the Pliocene polymictic conglomerates of the Höyüklü Formation, North West of the Dereyalak village (Eskisehir, Turkey). Micro-Raman measurements were performed on dendritic agate and then strong quartz and moganite peaks were identified at 465 and 501 cm -1, respectively. Thermal analysis shows the loss of water and hydroxyl units occurs in 2 distinct stages; at 796 and 808 °C. Spatially resolved CL results at room temperature were recorded for chosen 3 different areas. Grey area (100% SiO2) displays the lowest CL emission. Brown area (99.7% SiO2 and 0.3% Fe2O3) contains exsolved non-detected ironed phases such as goethite-lepidochrocite to explain the brown colour and the iron point substitutional defects attributed to the 643 nm CL emission. White outer (98.7% SiO2 and 1.3% Al 2O3) would be strongly disordered as observed in the amorphous Raman spectrum containing as inferred from the spectrum CL on the outer areas, particularly non-bridging oxygen hole centres (NBOHC) (317 nm) and [AlO4]°/H (380 nm) centres produced by large amounts of aluminium in the lattice (1.33% Al2O3). When it comes to collect the data in the time resolved CL spectrum, at least three broad emission bands were detected in: a green band of low intensity at about 496 nm, intense orange band at about 600 nm, and a red band at 670 nm. The CL emission at 670 nm shows some relationships between the hydroxyl or alkali content and the abundance of O2 (super 3-) centres and E′1 centres. Another conspicuous observed feature in the CL spectra of agates is the existence of an orange emission band centred at around 600 nm. The predominance of the yellow CL emission band and the high concentration of E′1 centres are typical for agates formed by acidic volcanism processes. © 2011 Elsevier B.V. All rights reserved.Item Effect of surgical staging on 539 patients with borderline ovarian tumors: A Turkish Gynecologic Oncology Group study(2013) Guvenal T.; Dursun P.; Hasdemir P.S.; Hanhan M.; Guven S.; Yetimalar H.; Goksedef B.P.; Sakarya D.K.; Doruk A.; Terek M.C.; Saatli B.; Guzin K.; Corakci A.; Deger E.; Celik H.; Cetin A.; Ozsaran A.; Ozbakkaloglu A.; Kolusari A.; Celik C.; Keles R.; Sagir F.G.; Dilek S.; Uslu T.; Dikmen Y.; Altundag O.; Ayhan A.Objective The objectives of this study were to examine demographic and clinicopathologic characteristics and to determine the effects of primary surgery, surgical staging and the extensiveness of staging. Methods In a retrospective Turkish multicenter study, 539 patients, from 14 institutions, with borderline ovarian tumors were investigated. Some of the demographic, clinical and surgical characteristics of the cases were evaluated. The effects of type of surgery, surgical staging; complete or incomplete staging on survival rates were calculated by using Kaplan-Meier method. Results The median age at diagnosis was 40 years (range 15-84) and 71.1% of patients were premenopausal. The most common histologic types were serous and mucinous. Majority of the staged cases were in Stage IA (73.5%). 242 patients underwent conservative surgery. Recurrence rates were significantly higher in conservative surgery group (8.3% vs. 3%). Of all patients in this study, 294 (54.5%) have undergone surgical staging procedures. Of the patients who underwent surgical staging, 228 (77.6%) had comprehensive staging including lymphadenectomy. Appendectomy was performed on 204 (37.8%) of the patients. The median follow-up time was 36 months (range 1-120 months). Five-year survival rate was 100% and median survival time was 120 months. Surgical staging, lymph node sampling or dissection and appendectomy didn't cause any difference on survival. Conclusion Comprehensive surgical staging, lymph node sampling or dissection and appendectomy are not beneficial in borderline ovarian tumors surgical management. © 2013 Elsevier Inc.Item The effects of the informed consent given for cesarean section on anxiety and knowledge(S.O.G. CANADA Inc., 2014) Yildirim G.; Cetin A.; Aksu M.; Altiparmak S.; Guler N.Purpose: To determine the effects of information given before cesarean section on women's anxiety levels and their knowledge about informed consent regarding it. Materials and Methods: Sixty women who elected to undergo cesarean section were included in the study. The data were collected using the pregnancy-related clinical information form, informed consent form, cesarean information form, and State and Trait Anxiety Inventory. Kruskal-Wallis test, Mann-Whitney U test, chi-square test and Pearson correlation were used as statistical methods. Results: The women's knowledge scores before and after they were informed about cesarean section were 14.8 ± 5.5 and 29.8 ± 2.6, respectively (p < 0.05). Their state anxiety scores before and after they were informed about cesarean section were 28.4 ± 6.6 and 28.0 ± 5.9, respectively (p > 0.05). Conclusion: It was determined that the participants' pre-training knowledge scores about cesarean section increased significantly after they were informed, and that their state and trait anxiety scores decreased very little after they were informed.Item Investigating pedestrian evacuation using ant algorithms(Springer, 2018) Gokce S.; Cetin A.; Kibar R.Ants communicate with each other by depositing a chemical called pheromone on the substrate while they crawl forward. By this way, they follow their predecessor and large trail systems are built. Inspired by the communication via chemical signals of ants, we have proposed a model to investigate the collective motion in humans during an emergency. It is considered that pedestrians use some kind of virtual chemotaxis to find the shortest way to the exit. This basic idea is implemented with the floor field model which is the most popular cellular automata model. The dependence of the evacuation from a room on the virtual chemotaxis evaporating rate f and the presence of the obstacle are investigated in this paper. The simulation results show that the increase in evaporation rate has been seen to slow down the evacuation. Moreover, it is found that positioning the obstacles in the room could lead to the phase transitions and decrease the evacuation time. © 2018, Indian Academy of Sciences.Item A Decision Support System for Role Assignment in Software Project Management with Evaluation of Personality Types(Springer Science and Business Media Deutschland GmbH, 2020) Celikten A.; Kurt E.; Cetin A.Recent studies show that personal factors in software engineering are effective on team performance, motivation and job quality. Forming team members or incorporation of a new member into the team that currently working on a software project directly affects the project team’s work performance and hence the progress of the project. In this study, a decision support system was developed to provide the ability to select team members according to personal characteristics in order to improve the performance of software project teams. The developed decision support system, determines the project roles that can be appropriate by analyzing the personality type of the project team members. The fuzzy c-means method, one of the fuzzy clustering methods, was used when the IPI personality inventory and personality type team members were determined to be appropriate to their personality type. © 2020, Springer Nature Switzerland AG.