WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Conference Object Citation - WoS: 16Thermal Characterization of Ag and Ag Plus N Ion Implanted Ultra-High Molecular Weight Polyethylene (uhmwpe)(Elsevier Ltd., 2007) Urkaç, Emel Sokullu; Oztarhan, A.; Tıhmınlıoğlu, Funda; Kaya, N.; Ila, D.; Muntele, C.; Tek, Z.Most of total hip joints are composed of ultra-high molecular weight polyethylene (UHMWPE). However, as ultra-high molecular weight polyethylene is too stable in a body, wear debris may accumulate and cause biological response such as bone absorption and loosening of prosthesis. In this study, ultra-high molecular weight polyethylene samples were Ag and Ag + N hybrid ion implanted by using MEVVA ion implantation technique to improve its surface properties. Samples were implanted with a fluence of 10(17) ion/cm(2) and extraction voltage of 30 kV. Implanted and unimplanted samples were investigated by thermo-gravimetry analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), optical microscopy (OM) and contact Angle measurement. Thermal characterization results showed that the ion bombardment induced an increase in the % crystallinity, onset and termination degradation temperatures of UHMWPE. (c) 2007 Elsevier B.V. All rights reserved.Article Citation - WoS: 8Citation - Scopus: 9Polymeric Thermal Analysis of C+h and C+h+ar Ion Implanted Uhmwpe Samples(Elsevier Ltd., 2007) Kaya, N.; Öztarhan, Ahmet M.; Urkaç, Emel Sokullu; Ila, D.; Budak, S.; Oks, E.; Tıhmınlıoğlu, Funda; Muntele, C.Chemical surface characterization of C + H hybrid ion implanted UHMWPE samples were carried out using DSC (differential scanning calorimeter) and TGA (thermal gravimetric analysis) techniques. Samples were implanted with a fluence of 10(17) ion/cm(2) and an extraction voltage of 30 kV. The study of TGA and DSC curves showed that: (1) Polymeric decomposition temperature increased, (2) T-m, Delta C-p and Delta H-m values changed while Delta C-p and Delta H-m increased. T-g value could not be measured, because of some experimental limitations. However, the increase in Delta H-m values showed that T-g values increased, (3) the branch density which indicated the increase in number of cross-link (M-c) decreased in ion implanted samples and (4) increase in Delta H-m values indicated increase in crystallinity of implanted surface of UHMWPE samples.Conference Object The Cytoprotective Effects of Zinc on Cyclophosphamide Induced Hematoxicity(Elsevier Ltd., 2007) Ayhancı, Adnan; Doğan, Sevgi Zeynep; Appak, Sıla; Doğan, Sevgi[No abstract available]Article Citation - WoS: 2Reduction of Carbon Dioxide During the Synthesis of Metal Nano-Particles in Water(Elsevier Ltd., 2003) Polat, Hürriyet; Cohen, H; Meyerstein, D; Rusonik, I.An effort was made to synthesize "carbon-free" metal (Fe-0, Co-0, Ni-0) nano-particles via the reduction of their salts with BH4- in aqueous solutions. Surprisingly it was found that when the synthesis is carried out in the presence of CO2, e.g., in aerated solutions, the CO2 is catalytically reduced by BH(4)(-)on the surface of the metal particles. Carbon-free metals can be prepared by reduction under an inert atmosphere. Thus metal surfaces might have acted as catalysts for CO2 fixation, probably via the initial formation of carbon clusters, in the reductive atmosphere in the prebiotic era. (C) 2003 Elsevier B.V. All rights reserved.Article Citation - WoS: 4Asymptotic Formulae for the Schrodinger Operator With Dirichlet and Neumann Boundary Conditions(Elsevier Ltd., 2005) Karakilic, S; Atılgan, Şirin; Veliev, OAIn this paper, we consider the Schrodinger operators defined by the differential expression Lu = -Delta u+q(x)u in d-dimensional parallelepiped F, with the Dirichlet and Neumann boundary conditions, and obtain the asymptotic formulae for the eigenvalues of these operators.Article Citation - WoS: 20Synthesis, Structural Characterization, and Magnetic Properties of Nare9(geo4)(6)o-2 (re=nd, Pr)(Elsevier Ltd., 2004) Eanes, Mehtap; Pennington, WT; Kolis, JWThe new compounds NaRE9(GeO4)(6)O-2 (RE = Nd, Pr) have been synthesized at 500 and 524 degreesC, respectively, via the hydrothermal method. The compounds crystallize with an oxyapatite structure in the hexagonal space group P6(3)/m with one formula unit in a cell of dimensions a = 9.782(1) Angstrom, c = 7.083(1) Angstrom (T = 293 K), V = 587.0(2) Angstrom(3) for RE = Nd and a = 9.802(1) Angstrom, c = 7.116(1) Angstrom (T = 293 K), V = 592.1(2) Angstrom(3) for RE = Pr. Each structure is composed of REO7 and REO9 polyhedra as well as GeO4 tetrahedra. The magnetic susceptibility data indicates paramagnetic behavior for both compounds at temperatures between 60-300 K for Nd and 2-300 K for Pr with a Weiss constant of theta = 44.8 and 33.5 K for Nd and Pr, respectively. (C) 2003 Elsevier B.V. All rights reserved.Article On the Stability of the Residual-Free Bubbles for the Navier-Stokes Equations(Elsevier Ltd., 2005) Neslitürk, Ali İhsanThis paper considers the Galerkin finite element method for the incompressible Navier-Stokes equations in two dimensions, where the finite-dimensional spaces employed consist of piecewise polynomials enriched with residual-free bubble (RFB) functions. The stability features of the residual-free bubble functions for the linearized Navier-Stokes equations are analyzed in this work. It is shown that the enrichment of the velocity space by bubble functions stabilizes the numerical method for any value of the viscosity parameter for triangular elements and for values of the viscosity parameter in the vanishing limit case for quadrilateral elements.Article Citation - WoS: 56Citation - Scopus: 63Processing, Characterization and Photocatalytic Properties of Cu Doped Tio2 Thin Films on Glass Substrate by Sol-Gel Technique(Elsevier Ltd., 2006) Çelik, Erdal; Gökçen, Z.; Azem, N. Funda Ak; Tanoğlu, Metin; Emrullahoğlu, O. F.The present paper describes processing, properties and photocatalytic application of Cu doped TiO2 thin films on glass substrate. Cu doped TiO2 coatings were successfully prepared on glass slide substrates using sol-gel method. The obtained solutions exhibit acidic characteristics. The phase structure, thermal, microstructure and surface properties of the coatings were characterized by using XRD, DTA/TG, SEM and AFM. Their adhesion properties and spectroscopic analysis were investigated by a scratch tester and UV-vis spectroscopy. Four different solutions were prepared by changing Cu/Ti ratios. Glass substrates were coated by solutions of Ti-alkoxide, Cu-chloride, glacial acetic acid and isopropanol. The obtained gel films were dried at 300 degrees C for 10 min and subsequently heat-treated at 500 degrees C for 5 min in air. The oxide thin films were annealed at 600 degrees C for 60min in air. TiO2, CuO, Cu4Ti, Ti3O5 and Cu3TiO4 phases were found in the coating. The organic matters were burned at temperatures between 200 and 350 degrees C and TiO2 crystallization was formed at 450 degrees C. The weight loss of the powder during process up to 600 degrees C is approximately 70%. The microstructural observations demonstrated that CuO content was led an improved surface morphology while thickness of the film and surface defects were increased in accordance with number of dipping. According to AFM results, it was found that as the Cu/Ti content increases the surface roughness of the films increases. In addition structural, thermal and microstructural results, it was found that the films of 0.73 ratio have better adhesion strength to the glass substrate among other coatings. The oxide films were found to be active for photocatalytic decomposition of metylene blue. (c) 2006 Published by Elsevier B.V.Article Citation - WoS: 171Characteristics of Brick Used as Aggregate in Historic Brick-Lime Mortars and Plasters(Elsevier Ltd., 2006) Böke, Hasan; Akkurt, Sedat; İpekoğlu, Başak; Uğurlu, ElifMortars and plasters composed of a mixture of brick powder and lime have been used since ancient times due to their hydraulic properties. In this study, raw material compositions, basic physical, mineralogical, microstructural and hydraulic properties of some historic Ottoman Bath brick-lime mortars and plasters were determined by XRD, SEM-EDS, AFM, TGA and chemical analyses. The mineralogical and chemical compositions, microstructures, morphologies and pozzolanicities of the brick powders and fragments used as aggregates in the mortars and plasters were examined to find out the relationship between hydraulic properties of the mortars and the bricks. The characteristics of bricks used in the bath domes were also determined to investigate whether the brick aggregates used in mortar and plasters were prepared from these bricks. The results indicated that the mortars and plasters were hydraulic owing to the presence of crushed brick powders that have good pozzolanicity. The brick powders bad high pozzolanicity because they contained high amounts of calcium-poor clay minerals in their raw materials that were fired at low temperatures. On the other hand, bricks used in the domes had poor pozzolanicity with different mineralogical and chemical compositions from bricks used in mortars and plasters. Based on the results of the analysis, it was thought that the bricks manufactured with high amounts of clays were consciously chosen in the preparation of hydraulic mortars and plasters. (C) 2006 Elsevier Ltd. All rights reserved.Article Citation - WoS: 4Citation - Scopus: 5Conductance Fluctuations in Undoped Hydrogenated Amorphous Silicon-Germanium Alloy Thin Films(Elsevier Ltd., 2002) Güneş, Mehmet; Johanson, Robert E.; Kasap, Safa O.; Yang, Jeffrey C.; Guha, SubhenduWe report coplanar conductance fluctuations of device quality, undoped hydrogenated amorphous silicon-germanium alloy thin films (a-SiGe:H) measured from 430 to 490 K. The a-SiGe:H alloys produce noise power spectra similar to coplanar undoped a-Si:H films in the same temperature range. The noise power spectrum S(n) does not fit a single 1/fα power law but rather has two distinct regions, each accurately fitted by a power law, but with different slopes. The low frequency slope α1 is similar to that observed in undoped a-Si:H films varying from 1.30 to 1.46 for different Ge concentrations and shows a slight temperature dependence. At higher frequencies, the slope α2 is less than unity and temperature independent but depends on the Ge content of the film. α2 decreases from 0.60 for no Ge (pure a-Si:H) to 0.15 for 40 at.% Ge. The noise power at lower frequencies increases and at higher frequencies decreases substantially as the temperature increases from 430 to 490 K. We infer that similar noise mechanisms are operating in undoped a-SiGe:H and a-Si:H films but that the Ge content is influencing the noise, particularly the slope at higher frequencies. In addition, the noise has the expected quadratic dependence on bias current and obeys Gaussian statistics.