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The present study was conducted to investigate the effectiveness of new, less toxic, less harmful, and nonmetallic graphite (G) and metallic iron oxide (Fe2O3) nanofuel additives by analyzing experimentally their consequences on exhaust emissions and performance of an air cooled, single cylinder, 4-stroke gasoline engine. Fe2O3 and graphite nanoparticles at 40, 80, and 120 mg/l of gasoline concentrations were mixed with gasoline by means of a magnetic stirrer. Brake power (BP), brake-specific fuel consumption (BSFC), torque (T), brake thermal efficiency (BTE), nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons (HC), and carbon dioxide (CO2) emissions were the investigated parameters. Experimental results indicated that G-blends showed a higher rise in brake power, brake thermal efficiency and torque and a greater reduction in the brake-specific fuel consumption as compared to that of Fe2O3 fuel blends. Moreover, the G-blends produced less NOx and CO2 than Fe2O3 blends but produced more emissions of CO and HC than that of Fe2O3 blends. On average, G-blends produced 0.46%, 0.71%, and 1.71% more torque, power, and BTE and 2.43%, 1.87%, and 13.39% less brake-specific fuel consumption (BSFC), NOx, and CO2 than Fe2O3 blends, respectively. So, in terms of the eight parameters, four performance parameters (i.e., T, BP, BSFC, BTE), and four engine emission exhaust indicators (i.e., CO, NOx, HC, CO2), graphite nanoparticles showed more positive results for 6 parameters (T, BP, BSFC, BTE, NOx, CO2), while two parameters HC and CO showed negative results with graphite as compared to that of Fe2O3 nanoparticles. So, overall, we conclude that nanoparticles of graphite are more engine and environment friendly than that of iron oxide fuel additives.
RESUMO
OBJECTIVES: To determine the difference in patency and complication rates of arterio-venous fistula (AVF) constructed in pre-dialysis versus post-dialysis settings. STUDY DESIGN: Descriptive study. PLACE AND DURATION OF STUDY: The Department of Vascular Surgery, Shifa International Hospital, Islamabad from January 2014 to August 2020. METHODOLOGY: Computerised record of 726 patients, who had undergone vascular access surgery for haemodialysis, was collected. Patients were divided into two groups according to those who had undergone AVF surgery: a) prior to the commencement; or b) after the commencement of haemodialysis. Primary and secondary patency rates were determined clinically by using duplex scans. Complications and suitability of AV fistula were assessed in both the groups. Data was collected and analysed using SPSS version 25, considering p-value of less than 0.05 as statistically significant. RESULTS: Early fistula failure was significantly higher in post-dialysis group compared with pre-dialysis group, while primary patency was higher in pre-dialysis (78.2%) group comparing with post-dialysis (66.1%) group. Secondary patency was 88.9% and 75.8% in pre- and post-dialysis groups, respectively. Early dialysis suitability failure rates were 12.2% and 15.1%; and late suitability failure rates were 7.9% and 16.1% in the pre- and post-dialysis groups, respectively. Higher rates of complications like maturation failure, low flow AVF, stenosis, thrombosis, venous hypertension, AV aneurysm, and infections were encountered in post-dialysis group compared to pre-dialysis group. CONCLUSION: Surgical creation of AVF three months prior to commencement of haemodialysis is advantageous in terms of patient outcomes and healthcare resources. However, a multidisciplinary approach and timely referral of patients to a vascular clinic further enhances the outcome with respect to the suitability of vascular access for dialysis. KEY WORDS: Arterio-venous fistula, Dialysis, Patency, Complications, Suitability.
