Using deterioration modelling to simulate sewer rehabilitation strategy with low data availability.

Most cities face the problem of an aging infrastructure in need of extensive and ongoing repair, renovation or replacement. Since the 1980s, CCTV has been the industry standard for sewer system inspection and the main source of information for structural performance evaluation. Due to low inspection rates and the lack of information about sewer condition, deterioration models have been developed to simulate the condition of non-inspected sewers and assess the influence of several rehabilitation scenarios. This paper presents an innovative modelling tool for long-term sewer rehabilitation planning based on the integration of a deterioration and a rehabilitation model. The tool is demonstrated in full scale using CCTV and sewer data of the city of Sofia, in Bulgaria. Results provide tangible proofs of investment needs for sewer rehabilitation and support the utility in the negotiation of budgets with the municipality. Since age is one key variable for deterioration modelling, a new method is proposed to estimate missing construction years in the utility database with a prediction error of less than 7 years.

Effect of postconditioning on mitochondrial dysfunction in experimental aortic cross-clamping.

BACKGROUND: Cross-clamping of the aorta during abdominal aortic aneurysm surgery induces muscle ischaemia with resultant morbidity. This study tested whether ischaemic postconditioning would decrease mitochondrial dysfunction in skeletal muscle by reducing oxidative stress. METHODS: Three groups (9 rats each) underwent surgery, including a control group without ischaemia and an ischaemia-reperfusion group that had 3 h ischaemia induced by aortic clamping and collateral vessel ligation, followed by 2 h of reperfusion. The third group had ischaemia for 3 h then underwent postconditioning comprising three short intervals of ischaemia-reperfusion at the onset of reperfusion. Activity of complexes I, II, III and IV of the mitochondrial respiratory chain was monitored in gastrocnemius muscle, along with oxidative stress measured by dihydroethidium (DHE) staining and antioxidant defence determined by measurement of glutathione levels. RESULTS: Ischaemia-reperfusion alone caused a significant reduction in maximal oxidative capacity (-31.8 per cent; P = 0.002), activity of complexes II, III and IV (-34.5 per cent; P = 0.007) and complex IV activity (-30.6 per cent; P = 0.039). It also increased reactive oxygen species (DHE staining increased to 223.1 per cent of control value; P = 0.027) and reduced antioxidant defence (glutathione level -28.6 per cent; P = 0.039). Postconditioning counteracted these deleterious effects by increasing mitochondrial complex I, II, III and IV activities, restoring muscle DHE staining and preserving glutathione content. CONCLUSION: Ischaemic postconditioning protects skeletal muscle mitochondria against ischaemia-reperfusion injury by reducing oxidative stress and preserving antioxidant defence in an experimental model. Mitochondrial protection to reduce reperfusion injury in clinical vascular surgery may be warranted.