Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Article Citation - WoS: 10Citation - Scopus: 9Bi̇yomalzemelerden İ̇zole Edi̇len Staphylococcus Epidermidis Suşlarinin Yüzey Özelli̇kleri̇ni̇n Beli̇rlenmesi̇(Ankara Mikrobiyoloji Derneği, 2010) Sudağıdan, Mert; Erdem, İlker; Çavuşoğlu, Cengiz; Çiftçioğlu, MuhsinThe surface properties of bacteria play an important role on adhesion to the biomaterial surface. In this study, the surface properties of Staphylococcus epidermidis strains isolated from clinically used polymeric biomaterial surfaces were investigated on the basis of zeta potential, hydrophobicity and surface topography. A total of 10 S.epidermidis strains isolated from intravenous catheters (n= 5), endotracheal tubes (n= 3) and central venous catheters (n= 2) which were used in the patients of pulmonary Intensive Care Unit, Ege University Medical Faculty Hospital, were included to the study. Seven of those isolates were biofilm producers, inhabiting biofilm genes, 2 were non-biofilm producers, however, inhabiting biofilm genes, and 1 was non-biofilm producer, inhabiting no biofilm genes. Zeta potential analysis have been performed in 3 different buffers (phosphate-buffered saline, 1 mM potassium chloride and 1 mM potassium phosphate buffer) and at different pH values (pH 4.1-8.2), in order to simulate in vivo environment of the biomaterials. Hydrophobicities of the strains were examined by bacterial adhesion to hydrocarbon (BATH) test and the surface topography of biofilms and slime layers were visualized by atomic force microscopy (AFM) and scanning electron microscopy (SEM) methods. It was found that all strains have negative zeta potential values (surface charge) in all buffers and pH values. In hydrophobicity analysis, the highest value (86%) was determined for non-biofilm forming S.epidermidis strain YT-169b (endotracheal tube isolate) and the lowest hydrophobicity (2.5%) was determined for biofilm forming S.epidermidis strain YT-212 (central venous catheter isolate). Biofilm and slime layers of the strains were imaginated by AFM and SEM analysis in ?m scale. SEM analysis showed that bacteria highly adhered to rough surfaces on biomaterial surfaces and the produced slime layers covered the surface of bacteria. In conclusion, elucidating the surface properties of opportunistic pathogens in different physiologic buffers will give important clues for the production of non-adhesive materials and antibacterial surfaces for those bacteria. It was also estimated that designing the surface of the biomaterial to have negative surface charge in the body and to be as smooth as possible will hamper biofilm formation.Article Citation - WoS: 34Citation - Scopus: 43Zinc Stearate Production by Precipitation and Fusion Processes(American Chemical Society, 2005) Gönen, Mehmet; Balköse, Devrim; İnal, Fikret; Ülkü, SemraIn this study, the production of ZnSt2 using sodium stearate and zinc sulfate in a precipitation process, and stearic acid and zinc oxide in a fusion process, was investigated with regard to product purity. In the fusion process, an increase in mixing rate decreased the induction time occurring at the beginning of the reaction. While the melting point of the zinc stearate prepared by the precipitation process was found to be about 122°C by optical microscopy, it was slightly lower than 122°C for zinc stearate produced by the fusion process. Differential scanning calorimetry (DSC) indicated onset of melting at 120°C and 118°C for samples prepared by precipitation and fusion processes, respectively. Characteristic peaks of ZnSt2 were present in XRD patterns of the products obtained by both processes. From SEM micrographs, it was seen that zinc stearate obtained by both processes had lamellar structure.Article Citation - WoS: 29Citation - Scopus: 32Visualization of the Equilibrium Fcc Catalyst Surface by Afm and Sem-Eds(Kluwer Academic Publishers, 2003) Bayraktar, Oğuz; Kugler, Edwin L.The deposition of metal contaminants (e.g., Ni, V, and Fe) from the hydrocarbon feed causes the deactivation of fluid catalytic cracking (FCC) catalyst used in petroleum refining. It is very important to understand the changes in the morphology and chemical composition on the catalyst surface and how these structural and chemical changes affect the catalyst performance. In this research, metal-contaminated FCC catalysts from a commercial unit have been characterized using AFM together with SEM-EDS. The AFM images showed the surface pores as well as the features that surround the pore's entrance on the catalyst surface. Catalyst surface contains debris that appear as bright spots in AFM images. SEM-EDS results have shown the presence of iron in these bright spots. Fe enrichment at the catalyst particle surface was also confirmed by XPS analyses.