RESUMEN
Cold heavy oil production with sand (CHOPS) is an extraction process for heavy oil in Canada, with the potential to lead to higher CH4 venting than conventional oil sites, that have not been adequately characterized. In order to quantify CH4 emissions from CHOPS activities, a focused aerial measurement campaign was conducted in the Canadian provinces of Alberta and Saskatchewan in June 2018. Total CH4 emissions from each of 10 clusters of CHOPS wells (containing 22-167 well sites per cluster) were derived using a mass balance computation algorithm that uses in situ wind data measurement on board aircraft. Results show that there is no statistically significant difference in CH4 emissions from CHOPS wells between the two provinces. Cluster-aggregated emission factors (EF) were determined using correspondingly aggregated production volumes. The average CH4 EF was 70.4 ± 36.9 kg/m3 produced oil for the Alberta wells and 55.1 ± 13.7 kg/m3 produced oil for the Saskatchewan wells. Using these EF and heavy oil production volumes reported to provincial regulators, the annual CH4 emissions from CHOPS were estimated to be 121% larger than CHOPS emissions extracted from Canada's National Inventory Report (NIR) for Saskatchewan. The EF were found to be positively correlated with the percentage of nonpiped production volumes in each cluster, indicating higher emissions for nonpiped wells while suggesting an avenue for methane emission reductions. A comparison with recent measurements indicates relatively limited effectiveness of regulations for Saskatchewan compared to those in Alberta. The results of this study indicate the substantial contribution of CHOPS operations to the underreporting observed in the NIR and provide measurement-based EF that can be used to develop improved emissions inventories for this sector and mitigate CH4 emissions from CHOPS operations.
RESUMEN
OBJECTIVE: To determine if choice of drug and ease of administration affect persistence of therapy with cholinesterase inhibitors (ChEIs) for treatment of dementia. METHODS: An observational administrative health database study was conducted in 5622 patients aged >or=65 years who received a new prescription for donepezil (DON), rivastigmine (RIV) or galantamine (GAL) from February to May 2006. Patients were followed for 1 year from initiation of therapy to determine percentage persistence and days of therapy. Once-daily galantamine extended release (GAL-ER) was compared with twice-daily galantamine immediate release (GAL-IR) to determine if ease of administration affected persistence. Previous treatment with ChEIs was also documented. RESULTS: One-year persistence rates were significantly different among the ChEIs: GAL-ER 54% (95% CI 51, 57), DON 46% (95% CI 43, 49) and RIV 40% (95% CI 37, 43). Average days of therapy were greater for GAL-ER (293) than for RIV (272), but there were no differences between DON (287) and GAL-ER or DON and RIV. One-year persistence was significantly greater for GAL-ER 54% (95% CI 48, 59) than for GAL-IR 44% (95% CI 39, 50), although there was no significant difference in days of therapy (293 vs 286, respectively). More patients currently treated with RIV (40.5%) or GAL-ER (32.3%) had received previous treatment with a different ChEI than with DON (21.9%). CONCLUSION: Among possible factors affecting persistence of ChEI therapy for dementia, choice of drug, ease of administration and previous treatment appear to be important.