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—We propose NM landscapes as a new class of tunably rugged benchmark problems. NM landscapes are well-defined on alphabets of any arity, including both discrete and real-valued alphabets, include epistasis in a natural and transparent manner, are proven to have known value and location of the global maximum and, with some additional constraints, are proven(More)
OBJECTIVE To test a multifaceted collaborative quality improvement intervention designed to promote evidence based surfactant treatment for preterm infants of 23-29 weeks' gestation. DESIGN Cluster randomised controlled trial. SETTING AND PARTICIPANTS 114 neonatal intensive care units (which treated 6039 infants of 23-29 weeks gestation born in 2001).(More)
OBJECTIVE To identify changes in mortality and neonatal morbidities for infants with birth weight 501 to 1500 g born from 2000 to 2009. METHODS There were 355806 infants weighing 501 to 1500 g who were born in 2000-2009. Mortality during initial hospitalization and major neonatal morbidity in survivors (early and late infection, chronic lung disease,(More)
OBJECTIVE To identify changes in clinical practices for infants with birth weights of 501 to 1500 g born from 2000 to 2009. METHODS We used prospectively collected registry data for 355,806 infants born from 2000 to 2009 and cared for at 669 North American hospitals in the Vermont Oxford Network. Main outcome measures included obstetric and neonatal(More)
Covariate measurement error is often a feature of scientific data used for regression modelling. The consequences of such errors include a loss of power of tests of significance for the regression parameters corresponding to the true covariates. Power and sample size calculations that ignore covariate measurement error tend to overestimate power and(More)
BACKGROUND Fractionated electrograms are used by some as targets for ablation in atrial and ventricular arrhythmias. Fractionation has been demonstrated to result when there is repetitive or asynchronous activation of separate groups of cells within the recording region of a mapping electrode(s). METHODS AND RESULTS Using a computer model, we generated(More)
OBJECTIVE To describe the timing of initial surfactant treatment for high-risk preterm infants in routine practice and compare these findings with evidence from randomized trials and published guidelines. METHODS Data from the Vermont Oxford Network Database for infants who were born from 1998 to 2000 and had birth weights 401 to 1500 g and gestational(More)
Widespread unexplained variations in clinical practices and patient outcomes suggest major opportunities for improving the quality and safety of medical care. However, there is little consensus regarding how to best identify and disseminate healthcare improvements and a dearth of theory to guide the debate. Many consider multicenter randomized controlled(More)
BACKGROUND Very low birth weight infants often gain weight poorly and demonstrate growth failure during the initial hospitalization. Although many of the major morbidities experienced by these infants during their initial NICU stays have decreased in recent years, it is unclear whether growth has improved. METHODS We studied 362 833 infants weighing 501(More)
—Simulated landscapes have been used for decades to evaluate search strategies whose goal is to find the landscape location with maximum fitness. Understanding properties of landscapes is important for understanding search difficulty. This paper presents a novel and transparent characterization of NK landscapes and derives an analytic expression(More)