ABSTRACT Recent empirical results show that forecast combinations and cross-learning schemes are winning approaches in the time series field. Although many competition-winning combination methods - with cross-learning or not - use static weights along the forecasting horizon, we could not find extensive work about the effects of using horizon-optimized weights. This paper proposes a forecast combination framework and provides a considerably sizeable empirical investigation into the use of horizon-optimized weights, i.e., weights that may vary over the forecasting horizon. We build on cross-learning, time series clustering and cross-validation to form Horizon-Optimized Convex Combinations (HOC2) of forecasts from five methods: Automated exponential smoothing, Automated ARIMA, Theta, TBATS, and Seasonal naïve. Our combinations were tested with data from the previous M1, M3 and M4 forecast competitions, comprising 104,004 time series with different frequencies and lengths. The results shall be helpful to support future research on how horizon-optimized weights can be used interchangeably with static ones.

Abstract In this study, we developed and validated a chromatographic method by High-performance Liquid Chromatography coupled to Diode-Array Ultraviolet Detector for quantification of acetaminophen in small volumes of plasma. This analytical method is particularly suitable for studies of gastric emptying time and pharmacokinetics in small rodents. Orally administered acetaminophen is promptly and completely absorbed in the intestines, with negligible absorption from the stomach. Owing to these kinetic features, acetaminophen can be used to study gastric emptying. The newly-validated analytical method was employed to investigate whether plants used as anti-dyspeptics in the Brazilian traditional medicine affect the gastric emptying. Lyophilized aqueous extracts from leaves of Baccharis trimera (Less) DC., Asteraceae (carqueja), Maytenus ilicifolia Mart. Ex Reissek, Celastraceae (espinheira-santa) and Lippia alba (Mill.) N.E.Br. ex Britton & P. Wilson, Verbenaceae (erva-cidreira) were administered by gavage to female Wistar rats 30 min before a single oral dose of acetaminophen (50 mg/kg). L. alba extract (50 mg/kg) did not alter acetaminophen plasma concentration versus time curve an indication that it has no effect on gastric emptying. Extracts of B. trimera (50 mg/kg) and M. ilicifolia (30 and 50 mg/kg, but not 10 mg/kg), however, slightly delayed gastric emptying. M. ilicifolia given by intraperitoneal route (30 mg/kg) also retarded gastric emptying. In conclusion, the newly-validated analytical method is adequate for studying the effects of medicinal plants on gastric emptying.