Wyniki wyszukiwania - Biblioteka Nauki

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Evaluation of maxillary sinus anatomical variations and pathologies in elderly, young, posterior dentate and edentulous patient groups with cone-beam computed tomography

100%

Dedeoglu N. , Altun O.

Folia Morphologica

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2019

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tom 78

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nr 3

EN

Background: The aim of this study was to evaluate the frequency of maxillary sinus pathologies and anatomic variations in elderly and edentulous patients by using cone-beam computed tomography (CBCT). Materials and methods: The study included elderly and young patient groups. The elderly group involved posterior edentulous and dentate patients. CBCT images were assessed, and the presence of any pathological findings, septa, accessory maxillary ostium, and Haller cell in each maxillary sinus were recorded according to the groups. Chi-square test was used to analyse the intergroup differences (p < 0.05). Results: There was no statistically difference between the young and elderly groups regarding the presence of a pathology (p = 0.077) and septa (p = 0.37), whereas accessory ostium (p = 0.009) was more common and Haller cell (p = 0.000) was less common in the elderly group when compared to the young group. There was no significant difference between the edentulous and dentate group regarding the presence of a pathology (p = 0.39), septation (p = 0.69) and Haller cell (p = 0.75); accessory ostium rate was found to be increased (p = 0,015) in edentulous patients. Conclusions: It was observed that the frequency of accessory maxillary ostium was increased in elderly, especially in edentulism. And the frequency of Haller cell was found to be decreased in elderly patients. (Folia Morphol 2019; 78, 3: 595–599)

2

Effect of the microstructure of EB-PVD thermal barrier coatings on the thermal conductivity and the methods to reduce the thermal conductivity

100%

Altun O. , Boke Y. E.

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tom Vol. 29, nr 1-2

7-15

EN

Nowadays, the selection of the materials for usage aim is getting important because of the new high technologic developments. Especially for the parts operating at high temperatures, the materials which have low thermal conductivity and high mechanical resistance are preferred. Thermal Barrier Coatings (TBCs) are used in aerospace, diesel engine and power plant technologies due to porous structures and low thermal conductivity. Generally these coatings are applied by two methods, Electron Beam-Plasma Vapor Deposition (EB-PVD) and Atmospheric Plasma Spray (APS). EBPVD method provides the advantages of superior strain and thermal shock tolerant due to its columnar microsturucture. However this columnar structure increases the thermal conductivity of the coating, so this is an undesired property with regard to heat transfer. In this study, the effect of microstructure of the coating to the thermal conductivity of EB-PVD TBCs and the methods to reduce the thermal conductivity of these coatings have been investigated.

3

Problems for determining the thermal conductivity of TBCs by laser-flash method

80%

Altun O. , Erhan Boke Y. , Kalemtas A.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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tom Vol. 30, nr 2

115-120

EN

Purpose: The purpose of this paper was to investigate the parameters which effect the results of determining the thermal conductivity of thermal barrier coatings (TBCs) by laser-flash method. Design/methodology/approach: The air plasma-spray (APS) technique was used to deposition of two- and three-layered samples. Two-layered samples were composed of metal substrate (321 stainless steel), and ceramic top coat (8YSZ). Three-layered samples were composed of metal substrate (321 stainless steel), bond coat (NiCrAlY) and top coat (8YSZ). Thermal diffusivity of each layer have been measured in the temperature range from room temperature (RT) to 900° C by laser-flash method. The thermal conductivity was calculated with respect to density, specific heat and diffusivity of the materials. Findings: Obtained results show that the specific heat, density and thicknesses of metal substrate, bond coat and top coat play important role in the thermal conductivity measurement. Research limitations/implications: To obtain the correct results in laser-flash technique thickness, density, and cp of the materials are needed to be measured accurately and surface smoothness of samples should be provided sensitively. Errors in these parameters cause high deviations in measurements. Practical implications: It has been aimed offer an insight into the experimental determination of thermal conductivity of layered TBC system which are used in high technologic applications. Originality/value: Laser-flash method is the most widely used experimental technique to determine the thermal conductivity of APS TBCs at high temperatures. The research contributes to better understanding and recognition the importance of sample preparation in laser-flash method.

4

Determination of multiple antibiotic and heavy metal resistance of the bacteria isolated from the Kucukcekmece Lagoon, Turkey

80%

Kimiran-Erdem A. , Arslan-Aydogdu E. O. , Gurun S. , Altun O.

Polish Journal of Environmental Studies

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2015

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tom 24

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nr 3

EN

One hundred strains of Gram-negative bacteria were isolated from a brackish water Lagoon, Küçükçekmece in Istanbul-Turkey. Identification studies showed that 31% of the isolated bacteria were Escherichia coli, 28% were Citrobacter, and 12% were Enterobacter. Antibiotic and heavy metal resistances exhibited by these bacteria were evaluated. In antibiotic susceptibility tests, 68% of the isolates appeared to be resistant to vancomycin, while 38% was resistant to erythromycin, 23% to penicilin G, 19% to ampicillin, 13% to nalidixic acid and streptomycin, 7% to chloramphenicol, 5% to amikacin, 2% to gentamycin, and 1% to kanamycin. Most of the isolates tolerated various concentrations of heavy metals, and the minimum inhibitory concentrations (MIC) ranged from 20 μg/ml to >5000 μg/ml. In terms of heavy metal sensitivity, 98% of the isolates were resistant to Fe, 95% to Cd, 85% to Co, 83% to Cu and Zn, and 74% to Ni. When antibioticheavy metals multiresistance index was examined, it was determined that the multiple heavy metal resistance (MHMR) index was remarkably high for the bacteria, while the multiple antibiotic resistance (MAR) index was low according to heavy metal resistance. It was demonstrated that the bacteria isolated from Küçükçekmece Lagoon were highly resistant to antibiotics and heavy metals. It was concluded that if the wastewater discharge to the Lagoon is not regulated, resistance gene transfers into the bacteria hosted normally in human microbiota could create significant health issues.