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Öğe Effects of sodium nitroprusside on ischemia-reperfusion injury(TIP ARASTIRMALARI DERNEGI, 2010) Yavuz C.; Çakir O.; Göz M.; Kale E.; Uzunlar A.K.Aim: The aim of this study was to investigate the effects of sodium nitroprussid (SNP) on ischemia-reperfusion injury in rats. Method: Twenty-four Sprague-Dawney rats were divided into four equal groups: group I without ischemia-reperfusion (I-R); group II with ischemia; group III with I-R; group IV with I-R and SNP. Complete bilateral hindlimb ischemia was produced by means of tourniquet occlusion of the upper thigh. Result: Blood creatine phosphokinase, lactate dehydrogenase, aspartate transaminase, urea, creatinine levels were not significantly different between groups 3 and 4. Malondialdehyde (MDA) levels were not significantly different between groups 3 and 4 in liver, soleus muscles and lung tissue. However, MDA levels were significantly lower in group 4 when compared with group 3 in renal tissue. Histological examination of the soleus muscles revealed that neutrophil leukocyte infiltration in group 3 was significantly less prominent than in group 4. Conclusion: These results have shown that SNP was not able to improve muscle ischemia-reperfusion injury in our study.Öğe Gases as coolant and lubricant in machining processes(2007) Çakir O.New approaches have been applied to solve many problems occurred in machining processes. One of these problems is the application of cutting fluids during machining operations due to new environmental legislations. The use of cutting fluids is no longer advantages due to their hazardous effects on environment and workers, although cutting fluids have still some advantages such as providing longer tool life. Industrially accepted new approaches have been examined to replace cutting fluids and various advancements have been reported. The aim of this study is to determine possible replacement of cutting fluids in machining operation and the applications of gases instead of cutting fluids in various machining processes. The reported results were promising; longer tool life and better surface finish quality were obtained. The present study discussed various gases application in machining processes and results of studies examined in detail.Öğe Review of etchants for copper and its alloys in wet etching processes(Trans Tech Publications Ltd, 2008) Çakir O.Wet etching processes have been widely used for producing micro-components for various applications. These processes are simple and easy to implement. The selection of suitable chemical solution which is called etchant is the most important factor in the wet etching processes. It affects etch rate and surface finish quality. Copper and its alloys are important commercial materials in various industries, especially in electronics industry. Their wide applications are due to their excellent electrical and thermal conductivity, ease of fabrication, good strength and fatigue properties. The present study examines the possible etchants for copper and its alloys and reviews studies in detail to find out optimum etchant and its application parameters. The study is also aimed to provide information about safety, health and environmental issues caused by using various etchants in wet etching processes of copper and copper alloys.Öğe Study of etch rate and surface roughness in chemical etching of stainless steel(Trans Tech Publications Ltd, 2008) Çakir O.In this study, stainless steel material (X5CrNi1810) was micromachined by chemical etching method. Ferric chloride was selected as etchant which is the most widely used etchant for iron-based materials. Four different etchant concentrations (32°Bé, 36°Bé, 40°Bé and 44°Bé) were used at various etching temperature. Moreover, the influence of the addition of hydrochloric acid to main etchant on etching performance was examined. The aim of this study was to investigate the depth of etch and surface roughness affected by etchant concentration, hydrochloric acid addition and etching temperature. It was observed that etching temperature for any etchant concentration is important factor in case of depth of etch and surface roughness. It was also noticed that the addition of hydrochloric acid to main etchant increased depth of etch value at any etching temperature. The optimum etching parameters were obtained for the chemical etching of stainless steel.Öğe Study of surface roughness in EDM(2007) Çakir O.Electrical discharge machining (EDM) is widely accepted standard nontraditional machining process in the production of dies and molds. EDM is based on removing material from a workpiece by means of series repetitive electrical discharges between an electrode (tool) and a machined part in dielectric medium. The present study is devoted to examine the influences of EDM parameters on surface roughness. The selected EDM parameters were pulsed current (8, 16 and 24 A), pulse time (2, 4, 6, 12, 24, 48 and 100 ?s) and pulse pause time (2 and 3 ?s). The workpiece material was AISI 1040 steel. Experimental investigation was based on surface roughness of machined workpiece surface and used electrode. It was observed that the combination of low values of pulsed current and pulse time, and high pulse pause time produced a better surface finish quality.
