Yelken, Gülnihal
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Yelken, G.
Yelken, G
Yelken, Gulnihal Ozek
Yelken, Gülnihal Özek
Yelken Özek, Gülnihal
Yelken, Gulnihal
Yelken, Gulnihal O.
Yelken, Gülnihal Ö.
Yelken, G
Yelken, Gulnihal Ozek
Yelken, Gülnihal Özek
Yelken Özek, Gülnihal
Yelken, Gulnihal
Yelken, Gulnihal O.
Yelken, Gülnihal Ö.
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Email Address
gulnihalyelken@iyte.edu.tr
Main Affiliation
03.02. Department of Chemical Engineering
Status
Current Staff
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Sustainable Development Goals
1NO POVERTY
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2ZERO HUNGER
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3GOOD HEALTH AND WELL-BEING
1
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4QUALITY EDUCATION
1
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5GENDER EQUALITY
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6CLEAN WATER AND SANITATION
1
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7AFFORDABLE AND CLEAN ENERGY
3
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8DECENT WORK AND ECONOMIC GROWTH
1
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9INDUSTRY, INNOVATION AND INFRASTRUCTURE
2
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10REDUCED INEQUALITIES
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11SUSTAINABLE CITIES AND COMMUNITIES
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12RESPONSIBLE CONSUMPTION AND PRODUCTION
2
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13CLIMATE ACTION
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14LIFE BELOW WATER
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15LIFE ON LAND
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16PEACE, JUSTICE AND STRONG INSTITUTIONS
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Documents
3
Citations
11
h-index
2
Documents
3
Citations
11
Scholarly Output
4
Articles
1
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2886/1513
Supervised MSc Theses
1
Supervised PhD Theses
1
WoS Citation Count
5
Scopus Citation Count
5
Patents
0
Projects
1
WoS Citations per Publication
1.25
Scopus Citations per Publication
1.25
Open Access Source
4
Supervised Theses
2
| Journal | Count |
|---|---|
| 2014 18th National Biomedical Engineering Meeting, BIYOMUT 2014 | 1 |
| Applied Surface Science | 1 |
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Conference Object Effect of Ceria Nanoparticles Synthesis on Their Cytotoxicity Against Caco2 Cells in Vitro(Institute of Electrical and Electronics Engineers, 2014) Yelken, GülnihalIn recent year's cerium oxide has been used productively in various engineering and biological applications, such as solid oxide fuel cells, catalytic materials, solar cells and biomedical applications as biological antioxidants [1-4]. Aim of this study is to investigate effects of synthesis conditionsof nanoceria on cytotoxicity against CaCo2 (human colon adenocar-cinoma) Cells in vitro. The morphological and structural characterization of ceria nanopowders were performed by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectra (FTIR), size distribution, electrokinetic analysis (zeta potential measurements), surface area. Cytotoxicity test using colon cancer cells showed that nanoceria have no cytotoxic effect against Caco-2 cells at low concentration and cytotoxicity change with respect to synthesis conditions. © 2014 IEEE.Doctoral Thesis Estimation of the Surface Charge Distribution of Solids in Liquids by Using Atomic Force Microscopy(Izmir Institute of Technology, 2011) Yelken Özek, Gülnihal; Polat, MehmetColloidal systems are widely encountered in minerals, ceramics, environment, biology, pharmaceuticals and cosmetics industries. These systems consist of micronsized particulates dispersed in a solvent. Homogeneity, dispersibility, stability of colloidal systems determines the economy and success of the final product in these applications. Control and manipulation of these properties depend on detailed analysis of the interactions among the particles. Electrophoretic potential measurements or colloidal titration methods are widely employed to characterize the charging of colloidal systems. However these methods only yield average charging information, not the charge distribution on the surface. Atomic Force Microscope (AFM) allows topographic surface analysis at nanometer level resolutions. Though it is widely used to obtain derived information AFM directly measures the forces between the tip and the surface atoms. The objective of the present work is to assess the applicability of AFM to surface charge mapping, i.e., the detection of positive or negative charged regions on metal oxide surfaces. Hence, well defined tips were prepared and allowed to interact with well defined oxide surfaces under different pH conditions. The influence of solution ion concentration and pH on the forces measured was also investigated. These measured force-distance curves were analyzed using a new solution of the one dimensional Poisson-Boltzmann equation to isolate the electrical double layer force, hence the surface charge on each measurement point. The new solution in question provides analytical expressions for all charging conditions which are amenable to such analysis.Repetitive force measurements on a predefined grid on the solid surface ultimately yield the charge distribution of the surface. Such an analysis procedure is new and advances the charge measurements on solids in solution to a new level.Master Thesis Preparation and Characterization of Inorganic Membranes by Using Sol-Gel Techniques(01. Izmir Institute of Technology, 2000) Yelken, Gülnihal; Çiftçioğlu, MuhsinIn this research the preparation of ceramIC membranes for gas separation applications by using sol-gel techniques were investigated. The effects of water/alkoxide ratio, H+/alkoxide ratio on the catalysis of the hydrolysis-condensation reactions and the peptization process were investigated by using N2 adsorptiondesorption isotherms, thermogravimetric analysis and FfIR (Fourier Transform Infra Red). The performance and the potential use of these materials in gas separation applications depend mainly on the ability in controlling-designing the microstructurepore network in these materials.The alumina and silica sols were prepared by using aluminium isopropoxide and tetraethylorthosilicate. Sols with different H+/ AI+3 and H20 / AI+3 ratios were prepared.These peptized clear boehmite sols were used for the preparation of unsupported Ah03 membranes at 600°C. The similar ratios were varied for the preparation of clear silica sols and these sols were further dried and heat treated at 400 C.The thermogravimetric analjsis has shown that the weights of the unsupported membranes were stable at the above temperatures. The boehmite was observed to decompose to the y-Alz03 phase at about 425°C. The FfIR analysis have proved the formation of boehmite in the sols and all the organic solvent peaks disappeared upon heat treatment.The y-Alz03 membranes all displayed Type IV isothems typical of mesoporous materials. Hysteresis loops were present in all these isotherms and fast desorption took place in the 0.4-0.6 PlPo range. The BJH pore size distributions were sharp for all the samples.The desorption pore size distributions were found to become wider at an intermediate acid content membrane which also had the lowest BET surface area. The BET particle sizes of these membranes were estimated to be in the 70-100 A0 range.The throat and pore cavity sizes of monosize sphere packings for this particle size range were observed to be in close agreement with the experimentallly determined adsorptiondesorption pore sizes.The silica samples all displayed Type I isotherms with no hysteresis typical of microporous materials. The HK (Horvoath Kawazoe) pore sizes were in the 4-5 AO range. An effect of the water content of these acid-catalyzed sols on the pore size were also detected.Article Citation - WoS: 5Citation - Scopus: 5Determination of Electrostatic Potential Distribution by Atomic Force Microscopy (afm) on Model Silica and Alumina Surfaces in Aqueous Electrolyte Solutions(Elsevier Ltd., 2014) Yelken Özek, Gülnihal; Polat, MehmetAFM was employed as a physicochemical probe to determine the electrostatic potential distribution quantitatively on selected ideal oxide surfaces (quartz 0 0 0 1 and sapphire 0 0 0 1) in aqueous media. The force of interaction between a silicon nitride tip and the oxide surface was measured at a given point under well-defined solution conditions. Relevant theories were used to isolate the electrostatic component from the total force of interaction which was then employed to estimate the surface potential at that point. Repeating the procedure on selected locations generated a potential map of the surface. Comparison of these potentials with those obtained from independent electrokinetic measurements confirmed the validity of the approach. © 2014 Elsevier B.V. All rights reserved.