RESUMEN
Biodiesel is increasingly being used in automotive and other engine applications because of its potential to contribute to the reduction of CO2 and other harmful emissions. However, biodiesel is known to be more corrosive in contact with metallic components than petroleum diesel. This work explores the corrosion of aluminium, steel, brass and copper metallic coupons exposed to B100 biodiesel at 25, 80, 90, 100, 110 and 120 °C. The metals that were chosen are commonly found in automotive engines. The B100 in each experiment was sampled at 48, 100, 150, 200 and 270 h and examined by GCMS to determine compositional changes. It was found that corrosion rates for copper were 10x faster than brass and approximately 100x faster than for mild steel, Al7075 and Al1050. Activation energies for corrosion were calculated from mass loss and ICP, with good correlation between the two methods for Cu containing samples. By mass loss, the activation energies for Cu, Brass, Al7075 and Al1050 were calculated to be -47.9 kJ mol-1, -85.4 kJ mol-1, -86.7 kJ mol-1 and -54.4 kJ mol-1, respectively. By ICP analysis, the activation energies for Cu, Brass, and Al7075 were calculated to be -57.9 kJ mol-1, -90 kJ mol-1 and -140 kJ mol-1, respectively. Corrosion rates in brass and copper samples were faster owing to the direct reaction of copper with the fatty acid. The copper was found to cause chain scission and greater degradation of the biodiesel.
RESUMEN
BACKGROUND: Previous studies have investigated the association between the use of bisphosphonates and the development of breast cancer, which presented controversial results. Thus, this meta-analysis was conducted to summarize the current evidence of the association of bisphosphonate use with breast cancer risk. METHODS: A comprehensive search was conducted in PubMed, ISI Web of Knowledge, the Cochrane Library, and Embase from inception to March 2019 by two researches, who independently selected trials, retrieved relevant data, and assessed study quality. The summary relative risk (RR) for the use of bisphosphonates on the risks of developing breast cancer was calculated using a random-effect model. RESULTS: The present meta-analysis, which included four case-control studies, involving 55052 breast cancer cases, and seven retrospective cohort studies, involving 14641 breast cancer cases, assessed the effect of bisphosphonates on breast cancer risk. The random-effect model meta-analysis found a reduced risk of breast cancer with exposure to bisphosphonates with pooled RR of 0.87 (95% confidence interval [CI]: 0.80 to 0.94). The short-term use of bisphosphonates (<1 year) did not render significant alteration (RR = 0.92, 95% CI: 0.82 to 1.03), while a significant 26% risk reduction of breast cancer was noted with long-term use (>1 year) (RR = 0.74, 95% CI: 0.62 to 0.90). A protective effect of bisphosphonates was shown in contralateral breast cancer (RR = 0.41, 95% CI: 0.20 to 0.84). In terms of the type of bisphosphonates, a significant inverse relationship was noted for etidronate, with pooled RR of 0.87 (95% CI: 0.80 to 0.96). CONCLUSION: This meta-analysis suggested that the use of bisphosphonates was associated with reduced risk of breast cancer, including contralateral breast cancer. Compared to other types of bisphosphonates, only etidronate showed a significant inverse relationship. Additionally, the long-term use (>1 year) of bisphosphonates was more significant in lowering breast cancer risk. Further randomized controlled trials are needed to verify this association. This trial is registered with PROSPERO (registration number: CRD42018105024) (registered on 29 August 2018).
