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Öğe Effect of different surface treatments on the shear bond strength of resin cement to zirconia ceramic and metal alloy(TAYLOR & FRANCIS LTD, 2018) Yucel, Munir Tolga; Kilic, Ismail; Okutan, Yener; Tobi, Elif Sumeyye; Kilic, Hamdi Sukur; Kepceoglu, Abdullah; Donmez, Mustafa BorgaThe bonding of resin cement to ceramic materials plays an important role in dentistry. The purpose of this study is to evaluate the effects of various surface treatments on the shear bond strength (SBS) of zirconia ceramic and metal alloy. A total of 60 specimens were prepared from Y-TZP ceramic and metal alloy. The specimens were divided into three subgroups (n=10) that received different surface treatments for each material. An Er:YAG laser (ER), a femtosecond laser (FS), and air-borne particle abrasion (A) were employed as surface treatments. One specimen from each group was analyzed using a scanning electron microscope (SEM) at 500 x magnification after surface treatments. The self-adhesive resin cement was then bonded to the treated surfaces using a Teflon mold. The specimens were thermocycled for 5,000 cycles at 5-55 degrees C, and then the SBS test was performed. Kruskal-Wallis and Mann-Whitney U tests were used to determine the differences between the groups (p=0.05), and failure modes were evaluated for each specimen. Statistical analyses revealed significant differences between the surface treatment methods. The mean SBS values of the air-borne particle-abraded groups were higher than those of the other groups. The femtosecond-irradiated groups of each material showed significantly higher SBS values than the Er:YAG-irradiated groups (p<0.05). Within the limitations of this study, air-borne particle abrasion and the femtosecond laser were more effective than Er:YAG laser treatment.Öğe An Experimental Investigation of Localised Surface Plasmon Resonance (LSPR) for Cu Nanoparticles Depending as a Function of Laser Pulse Number in Pulsed Laser Deposition(AMER INST PHYSICS, 2017) Gezgini, Serap Yigit; Kepceoglu, Abdullah; Kilic, Hamdi SukurCopper is a low cost metal and its nanoparticles have a unique optical properties such as LSPR. The location of LSPR wavelength can be tuned by controlling nanoparticles sizes and size distributions of nanoparticles, shapes and interparticle distances. This morphological changes are provided by controlling system parameters in PLD. For this work, 48000 and 36000 laser pulses from Nd:YAG laser were applied to produce Cu nanoparticle thin tilms. These thin films were characterised by performing-UV-VIS absorption spectroscopy, Atomic Force Microscopy (AFM) analysis. When the number of laser pulse decreases, the size of Cu nanoparticles and the number of nanoparticles arriving on the substrate are reduced, and LSPR peak of thin films are red shifted depending on the geometrical shapes of the Cu nanoparticles. We have driven a conclusion in this work that LSPR properties of Cu nanoparticles can be tuned by proposed method.Öğe Femtosecond laser induced photodynamic therapy on 5-ALA treated SKMEL-30 cells: An efficient theranostic strategy to combat melanoma(ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER, 2014) Kars, Meltem Demirel; Kara, Reyhan; Gundogdu, Yasemin; Kepceoglu, Abdullah; Kilic, Hamdi SukurPurpose: Photodynamic therapy (PDT) is a type of photo-chemotherapy that is based on the application of photosensitizer and irradiation of the region by laser sources. Photosensitizer and light interaction will develop reactive oxygen radicals ( O-1(2)) in the cells and elimination of cells by apoptosis or necrosis. Methods: Metastatic skin cancer cells SKMEL-30 were treated by 5-ALA in dark and then they were irradiated by 90-femtosecond (fs) laser with different pulse powers for different durations. The effects of 5-ALA mediated photodynamic therapy on the cells were determined by XTT proliferation kit and by flow cytometry measurements of Annexin V, 7-AAD and mitochondrial membrane potential alterations. Fluorescent accumulation of protoporphyrin IX was investigated by fluorometry and confocal laser microscope. Results: The viability tests for SKMEL-30 cells treated with different 5-ALA doses and femtosecond laser power and durations demonstrated that 635 nm, 45 mW pulse energy at 90 fs laser pulse applications for 60 sec to 1 mM 5-ALA exposed cells decreased the cell proliferation by 30%. Flow cytometric measurements exhibit that PDT caused 63% of mitochondria membrane potential alteration, 30% of cell death in the population by apoptosis and 39% of cells by necrosis. There was 1 mM 5-ALA exposure that also exhibited about 32% accumulation of fluorescence in the cells. Conclusion: The pretreatment of the cells with the precursor 5-ALA lets the imaging due to increased protoporphyrin IX fluorescence. This treatment method may be proposed as an effective theranostic strategy for melanoma because of its rapid and effective anticancer consequences. (C) 2014 Elsevier Masson SAS. All rights reserved.Öğe Identification of the Isomers Using Principal Component Analysis (PCA) Method(AMER INST PHYSICS, 2016) Kepceoglu, Abdullah; Gundogdu, Yasemin; Ledingham, Kenneth William David; Kilic, Hamdi SukurIn this work, we have carried out a detailed statistical analysis for experimental data of mass spectra from xylene isomers. Principle Component Analysis (PCA) was used to identify the isomers which cannot be distinguished using conventional statistical methods for interpretation of their mass spectra. Experiments have been carried out using a linear TOF-MS coupled to a femtosecond laser system as an energy source for the ionisation processes. We have performed experiments and collected data which has been analysed and interpreted using PCA as a multivariate analysis of these spectra. This demonstrates the strength of the method to get an insight for distinguishing the isomers which cannot be identified using conventional mass analysis obtained through dissociative ionisation processes on these molecules. The PCA results dependending on the laser pulse energy and the background pressure in the spectrometers have been presented in this work.Öğe An Investigation of Localised Surface Plasmon Resonance (LSPR) of Ag Nanoparticles Produced by Pulsed Laser Deposition (PLD) Technique(AMER INST PHYSICS, 2017) Gezgin, Serap Yigit; Kepceoglu, Abdullah; Kilic, Hamdi SukurNoble metal nano-structures such as Ag, Cu, Au are used commonly to increase power conversion efficiency of the solar cell by using their surface plasmons. The plasmonic metal nanoparticles of Ag among others that have strong LSPR in near-UV range. They increase photon absorbance via embedding in the active semiconductor of the solar cell. Thin films of Ag are grown in the desired particle size and interparticle distance easily and at low cost by PLD technique. Ag nanoparticle thin films were grown on micro slide glass at 25-36 mJ laser pulse energies under by PLD using nsNd:YAG laser. The result of this work have been presented by carrying out UV-VIS and AFM analysis. It was concluded that a laser energy increases, the density and size of Ag-NPs arriving on the substrate increases, and the interparticle distance was decreases. Therefore, LSPR wavelength shifts towards to longer wavelength region.Öğe Molecular Structure and TD-DFT Study of the Xylene Isomers(GAZI UNIV, 2019) Kepceoglu, Abdullah; Gundogdu, Yasemin; Dereli, Omer; Kilic, Hamdi SukurIn this work, we have investigated the xylene isomers in concepts of vertical and adiabatic ionization energy parameters and molecular orbital (HOMO-1, HOMO/SOMO, LUMO, LUMO+1) energies of the neutrals and singly charged cation radicals. As a first step of the calculations, conformational analysis has been performed for all isomers using the semi-empirical method with PM3 core type Hamiltonian. Geometry optimization and frequency calculations were performed by using Density Functional Theory (DFT) with Becke, three-parameter, Lee-Yang-Parr (B3LYP) exchange-correlation functional and 6-311++G(d,p) basis sets. UV-Vis electronic spectra of the neutral xylene isomers were calculated by using the TD-DFT method with cam-B3LYP functional and 6-311++G(2d,2p) basis set.Öğe Plasmonic Tuning of Gold Doped Thin Films for Layers of Photovoltaic Devices(AMER INST PHYSICS, 2016) Gezgin, Serap Yigit; Kilic, Hamdi Sukur; Kepceoglu, Abdullah; Bayir, Sercan; Nalbantoglu, Izzet Ercan; Toprak, AhmetIn order to increase the absorption rates in solar cells, increasing research activities on the plasmonic nanostructures are followed carefully. The plasmonic nanoparticles provides an important enhancement in the trapping of photons in the active layer of the solar cells by means of interaction between incident light and plasmonic nanoparticles. In order to obtain this approach, under of 5x10(-4) mbar and 1x10(-2) mbar ambient argon gas pressure, gold thin film was deposited on the silicon substrate by applying PLD system. The morphology of thin films obtained was investigated by AFM and SEM considering the effect of Ar gas pressure on the plasma plume. SPR peaks for Au nanoparticles deposited under 5x10(-4) mbar and 1x10(-2) mbar Ar gas pressure were observed at 756 nm and 658 nm wavelengths respectively. It has been stated that the SPR peak in the infrared is depend on the near field interaction between Au nanoparticles. Furthermore, when the pressure is increased to 1x10(-2) mbar Ar, it has been observed that the SPR peak for thin film is shifted towards to shorter wavelengths, and it has also been observed that the intensity of absorption peak is decreased.Öğe Production and Characterization of Titanium (Ti), Platinum (Pt) and Tantalum (Ta) Thin Films for Native DNA Biosensors(AMER INST PHYSICS, 2017) Genc, Eminegul; Kepceoglu, Abdullah; Gezgin, Serap Yigit; Kars, Meltem Demirel; Kilic, Hamdi SukurThe use of the femtosecond (fs) laser pulses for ablation applications have several advantageous and Laser Induced Forward Transfer (LIFT) is an ablation-driven transfer process. The use of fs laser pulses for LIFT is gaining a great attraction nowadays. The most of the Direct Writing (DW) methods are laser based techniques and the LIFT technique is the one of them. This spectacular technique allows high resolution without lithographic processes. In this study, we have grown Ti, Pt and Ta thin films on the microscope slides by Pulse Laser Deposition (PLD) teclmique using Nd:YAG laser in the high vacuum condition. As a result, thin films produced in this work is a good candidate to produce native DNA biosensors based on LIFT teclmique.
