Esra Dokumaci

In vitro comparison of epidural bacteria filters permeability and screening scanning electron microscopy

BACKGROUND AND OBJECTIVES Epidural catheter bacteria filters are barriers in the patient-controlled analgesia/anaesthesia for preventing contamination at the epidural insertion site. The efficiency of these filters varies according to pore sizes and materials. METHOD The bacterial adhesion capability of the two filters was measured in vitro experiment. Adhesion capacities for standard Staphylococcus aureus (ATCC 25923) and Pseudomonas aeruginosa (ATCC 27853) strains of the two different filters (Portex and Rusch) which have the same pore size were examined. Bacterial suspension of 0.5 Mc Farland was placed in the patient-controlled analgesia pump, was filtered at a speed of 5 mL/h. in continuous infusion for 48 h and accumulated in bottle. The two filters were compared with colony counts of bacteria in the filters and bottles. At the same time, the filters and adhered bacteria were monitored by scanning electron microscope. RESULTS Electron microscopic examination of filters showed that the Portex filter had a granular and the Rusch filter fibrillary structure. Colony counting from the catheter and bottle showed that both of the filters have significant bacterial adhesion capability (p<0.001). After the bacteria suspension infusion, colony countings showed that the Portex filter was more efficient (p<0.001). There was not any difference between S. aureus and P. aeruginosa bacteria adhesion. In the SEM monitoring after the infusion, it was physically shown that the bacteria were adhered efficiently by both of the filters. CONCLUSION The granular structured filter was found statistically and significantly more successful than the fibrial. Although the pore sizes of the filters were same - of which structural differences shown by SEM were the same - it would not be right to attribute the changes in the efficiencies to only structural differences. Using microbiological and physical proofs with regard to efficiency at the same time has been another important aspect of this experiment.

Oxidation Behavior of Mo Containing Alloys

In this study, high temperature (T>500oC) oxidation behavior of two commercial Ni-base alloys and two experimental alloys, all containing more than 10% Molybdenum, is investigated. Experimental alloys were prepared from high purity materials using an arc-melting furnace under a protective environment. During tests, samples were exposed to the stagnant air environment of a high temperature furnace for predetermined times. Extent of oxidation was determined from sample mass change measurements as well as morphological and chemical analyses of the oxidation products. For analyses, a scanning electron microscope (SEM) equipped with backscattered electron (BE) and energy dispersive spectroscopic (EDS) detectors was used. Crystalline phases formed in the product scales over the alloy samples were identified by an x-ray diffractometer (XRD). Preliminary results indicate that although Mo in the alloy prevents the development of a protective oxide scale at the alloy surface, presence of alloying elements such as Cr or Al can decrease this negative effect of Mo on oxide scale formation.

Comparação in vitro da permeabilidade de filtros epidurais antibacterianos e triagem por microscopia eletrônica de varredura

BACKGROUND AND OBJECTIVES Epidural catheter bacteria filters are barriers in the patient-controlled analgesia/anaesthesia for preventing contamination at the epidural insertion site. The efficiency of these filters varies according to pore sizes and materials. METHOD The bacterial adhesion capability of the two filters was measured in vitro experiment. Adhesion capacities for standard Staphylococcus aureus (ATCC 25923) and Pseudomonas aeruginosa (ATCC 27853) strains of the two different filters (Portex and Rusch) which have the same pore size were examined. Bacterial suspension of 0.5 Mc Farland was placed in the patient-controlled analgesia pump, was filtered at a speed of 5mL/h. in continuous infusion for 48h and accumulated in bottle. The two filters were compared with colony counts of bacteria in the filters and bottles. At the same time, the filters and adhered bacteria were monitored by scanning electron microscope. RESULTS Electron microscopic examination of filters showed that the Portex filter had a granular and the Rusch filter fibrillary structure. Colony counting from the catheter and bottle showed that both of the filters have significant bacterial adhesion capability (p<0.001). After the bacteria suspension infusion, colony countings showed that the Portex filter was more efficient (p<0.001). There was not any difference between S. aureus and P. aeruginosa bacteria adhesion. In the SEM monitoring after the infusion, it was physically shown that the bacteria were adhered efficiently by both of the filters. CONCLUSION The granular structured filter was found statistically and significantly more successful than the fibrial. Although the pore sizes of the filters were same - of which structural differences shown by SEM were the same - it would not be right to attribute the changes in the efficiencies to only structural differences. Using microbiological and physical proofs with regard to efficiency at the same time has been another important aspect of this experiment.

Effect of Vanadium and Zirconium Additions on Mechanical Properties and Microstructure of Gravity Die-Cast AlSi9Cu2 Alloy Cylinder Heads

Systematic work was performed in the present study to investigate the effect of V and Zr additions on microstructural evolution and mechanical properties of the gravity die-cast AlSi9Cu2 alloy in T6 temper. The equiaxed dendritic structure typical of AlSi9Cu2 alloy is replaced by a much finer columnar dendritic network when modified with V and Zr additions. This remarkable structural refinement is believed to be linked with the formation of the V- and Zr-containing phases that form during solidification. The co-addition of V and Zr affects the tensile properties and hardness more significantly than individual additions. While the increase in strength is accompanied by a decrease in elongation, the penalty to be paid, particularly in the case of co-addition of V and Zr, is rather small and thus could be tolerated for the superior strength in some applications.

Gözenekli ZrB2 Peletlerin Farklı Sıcaklıklardaki Oksidasyon Davranışları

1Dokuz Eylül Üniversitesi, Mühendislik Fakültesi, Metalurji ve Malzeme Mühendisliği Bölümü, 35390, İzmir (ORCID: 0000-0003-3886-3963) 2Dokuz Eylül Üniversitesi, Torbalı Meslek Yüksekokulu, Endüstriyel Cam ve Seramik Programı, 35860, İzmir (ORCID: 0000-0002-7506-5795) 3Dokuz Eylül Üniversitesi, Mühendislik Fakültesi, Metalurji ve Malzeme Mühendisliği Bölümü, 35390, İzmir (ORCID: 0000-0002-2830-1898)