The linear autoregressive (AR) model is often used to investigate the pathophysiologic mechanisms controlling heart rate (HR) dynamics. This study implemented parametric models new to this field to determine if a more appropriate HR dynamics modeling structure exists. The linear AR and autoregressive-moving average (ARMA) models, and the nonlinear polynomial autoregressive (PAR) and bilinear (BL) models were fit to instantaneous HR time series obtained from nine subjects in the supine position. Model orders were determined by the Akaike Information Criteria (AIC). Model residual variance was used as the primary intermodel comparison criterion, with significance evaluated by a chi 2 distributed statistic. The BL model best represented the HR dynamics, as its residual variance was significantly (p < 0.05) smaller than that of the corresponding AR model for nine out of nine data sets. In all cases, the BL model had a smaller residual variance than either the ARMA or PAR models. The bilinear model was ineffective at data forecasting, however, we show that this cannot reflect BL model validity because poor prediction is inherent to the BL model structure. The apparent superiority of the nonlinear bilinear model suggests that future heart rate dynamics studies should put greater emphasis on nonlinear analyses.
Virtually all numerical techniques for elementary function generation share the common property of avoiding multiplication by iteratively performing shift operations. However, with the advent of VLSI, multiplier economics are considerably less formidible than before. We propose combining multipliers with these multiplication free algorithms to construct fast methods of elementary function generation. We demonstrate our idea by combining multipliers with the CORDIC algorithm to achieve fast vector rotation.
Celiac plexus neurolysis (CPN) has been used to treat pancreatic cancer pain for decades. Endoscopic ultrasound (EUS) has improved the safety of CPN, and has allowed its increased use for chronic pancreatitis pain relief [1]. We present a patient who developed end-organ ischemia following EUS-guided CPN, and believe this is the first report of this type of side effect stemming from this procedure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.