Determining Predictor Importance in Multilevel Models for Longitudinal Data: An Extension of Dominance Analysis

Longitudinal models are used not only to analyze the change of an outcome over time but also to describe what person-level and time-varying factors might influence this trend. Whenever a researcher is interested in the factors or predictors impacting an outcome, a common follow-up question asked is that of the relative importance of such factors. Hence, this study aimed to extend and evaluate Dominance Analysis (DA), a method used to determine the relative importance of predictors in various linear models (Budescu, 1993; Azen & Budescu, 2003; Azen, 2013), for use with longitudinal multilevel models. A simulation study was conducted to investigate the effect of number of measurement occasions (level-1 units), number of subjects (level-2 units), different levels of model complexity (i.e., number of predictors at level-1 and level-2), size of predictor coefficients, predictor collinearity levels, misspecification of the covariance structure, and measures of model fit on DA results and provide recommendations to researchers who wish to determine the relative importance of predictors in longitudinal multilevel models. Results indicated that number of subjects was the most important factor influencing the accuracy of DA in rank-ordering the model predictors, and that more than 50 subjects are needed to obtain adequate power and confidence in the reproducibility of DA results. The McFadden pseudo R² is recommended as the standard measure of fit to use when performing DA in multilevel longitudinal models. Finally, asymptotic standard error and percentile confidence intervals constructed through bootstrapping can be used to determine if one predictor significantly dominates another but might not provide sufficient power unless there are at least 200 subjects in the sample or the magnitude of the general dominance difference measure is greater than 0.01 using McFadden’s R²

Response Elimination, Reinforcement Rate and Resurgence of Operant Behavior

The effects of reinforcement rates of alternative responding on resurgence were studied in six experiments with pigeons. In Experiment 1A, key pecking was maintained on a multiple variable-interval (VI) VI schedule during the first, Training, phase. In the second, Response-Elimination, phase, variable differential-reinforcement-of-other-behavior (DRO) schedules were in effect in each component and reinforcement rates were equal and then, higher in one (rich) component, and lower in the other (lean), than in the Training phase. In the third, Resurgence, phase, reinforcers were discontinued and more resurgence occurred in the lean than in the rich component. Differences in Training-phase response rates between components also could have produced these results. In subsequent experiments, rich and lean components were those in which higher and lower response rates occurred in the Training phase, respectively. These experiments differed in how reinforcement rates were programmed during the Response-Elimination phase. Experiment 1B was a replication of Experiment 1A with experimentally-naive pigeons. In Experiment 2, reinforcement rates were equal in one component and lower or higher in the other, relative to those programmed in the Training phase. In Experiment 3, reinforcers were discontinued in each component before differential reinforcement rates were in effect. In Experiment 4, differential reinforcement rates were in effect initially and, then, reinforcement rates in each component were equal to those in the Training phase. In Experiment 5, differential reinforcement rates were arranged by a fixed-DRO in each component and, in Experiment 6, alternative responding consisted of pecking a different key under VI schedules arranging higher and lower reinforcement rates than in the Training phase. Little to no resurgence occurred in each experiment, and differential resurgence was not systematically related to reinforcement rates of alternative responding. Schedule differences, topography of alternative responding, order of exposure to conditions or the length of Training and Response-Elimination phases could not explain these results, nor did current theoretical models of resurgence predict them. Reinforcement rates of alternative responding did not affect resurgence according to the schedule parameters in each experiment. Studies in which reinforcement rates of alternative responding were manipulated parametrically would clarify the present results and the effects of this variable on resurgence

Resurgence of temporal patterns of responding

The resurgence of temporal patterns of key pecking by pigeons was studied in two experiments. In Experiment 1, positively accelerated and linear patterns of responding were established under a discrete-trial multiple fixed-interval (FI) variable-interval (VI) schedule. Subsequently, responding on a different key produced reinforcers according to a VI schedule. When extinction was in effect, resurgence of previously established temporal patterns was observed for each pigeon. That is, positively accelerated and linear patterns recurred in the presence of the stimuli previously correlated with the FI and VI components of the multiple schedule, respectively---suggesting that these temporal patterns, although not directly reinforced, functioned as behavioral units. In Experiment 2, resurgence was assessed after positively accelerated patterns of responding were directly reinforced. Responding was reinforced only if the patterns approximated a predetermined temporal distribution of responses. Resurgence of previously reinforced patterns occurred for each pigeon and for 2 of 3 pigeons during a replication of the procedure. Although variability in patterns increased during the resurgence phases in Experiment 2, those patterns that occurred most frequently when reinforcement was in effect occurred at a higher relative frequency during extinction. These results (a) demonstrate the resurgence of temporally defined complex operants, (b) replicate and extend previous findings on resurgence of spatially defined operants, and (c) are discussed as they contribute to understanding the selection and recurrence of more complex behavioral units

Common Asset Impact on Default Contagion

In this work we present a simulation study to show that a shock in a common asset can be very impactful to default contagion, and we extend some analytic concepts to this scenario with common assets. We use an inhomogeneous random graph to represent the banking network, and, based on the possible exposures between banks, we define a minimum amount of capital each bank must hold in order to make the system stable to a shock that affects only a few banks. Then, we consider the case when a shock hits all banks at the same time, making them weaker and some of them initially in default. We analyze the final fraction of banks in default and compare it with other cases when the shock hits only a small proportion of banks. We show that a common shock can cause severe damage to the system

Primary vesicoureteral reflux: conservative therapy or surgical intervention

Introduction:The relationship between urinary tract infections and primary vesicoureteral reflux may lead to permanent renal damage. In the literature an increasing number of spontaneous cure of vesicoureteral reflux in children and the significant decrease in surgical therapy has been observed.Objective:To study the evolution of primary vesicoureteral reflux associated with recurring urinary tract infections settings in patients of the Pediatric Nephrology department of our institution, evaluating cases in which cure was achieved through conservative therapy only and those in which surgical intervention was required.Methods: We analyzed records and collected data refers to parameters: sex, age upon the diagnosis of primary urinary infection, age upon diagnosis of vesicoureteral reflux, number of urinary tract infections, vesicoureteral reflux grade; renal function, renal scaring, other malformation of urinary tract, and surgical or conservative intervention. Statistical analysis was descriptive and conducted with the SPSS program.Results:Within the subgroup of patients with grade IV and V, 63.6% of the cases evolved to surgical intervention and 36.4% to conservative intervention. In those with grades I, II, and III, 38.5% evolved to surgical treatment against 61.5% for conservative approach. Among those with bilateral vesicoureteral reflux, 72.7% had to undergo surgical intervention. No relationship was observed between the vesicoureteral reflux grade and the presence of renal scaring.Conclusion: Patients with low grade vesicoureteral reflux and recurring urinary tract infections tend to experience spontaneous reflux resolution with good renal evolution in the long term in a way that surgical intervention becomes limited to high grade reflux or when followed by other clinical issues.Introdução:A associação entre refluxo vesicoureteral primário e infecções do trato urinário pode acarretar em dano renal permanente. Há, na literatura, a tendência de cura espontânea deste refluxo em crianças e marcante declínio na indicação do tratamento cirúrgico.Objetivo:Estudar a evolução dos refluxos vesicoureterais primários associados a quadros de infecções urinárias de repetição, em pacientes do serviço de Nefrologia Pediátrica da nossa instituição, avaliando os casos nos quais houve cura mediante tratamento conservador apenas, e aqueles nos quais foi necessária a intervenção cirúrgica.Métodos:Analisamos os prontuários dos pacientes com infecções urinárias de repetição associadas ao diagnóstico de refluxo vesicoureteral primário. Os dados coletados diziam respeito aos parâmetros: sexo, idade do diagnóstico da primeira infecção urinária, idade do diagnóstico de RVU, número de infecções urinárias, grau de refluxo, resultado da urocultura, função renal, cicatrizes renais, outras malformações do trato urinário e intervenção cirúrgica ou conservadora. A Análise estatística foi descritiva e realizada com o programa SPSS.Resultados:Dentro do subgrupo de pacientes com graus IV e V, notou-se 63,6% dos casos evoluindo para intervenção cirúrgica e 36,4%, para resolução por intervenção conservadora. Naqueles com graus I, II e III, 38,5% evoluíram para tratamento cirúrgico, contra 61,5%, para resolução por conduta conservadora. Dentre os pacientes com presença de refluxo vesicoureteral bilateralmente,72,7% tiveram evolução cirúrgica. Não se observou relação entre o grau de refluxo e a presença de cicatrizes renais.Conclusão:Pacientes com refluxo vesicoureteral de baixo grau e infecções urinárias de repetição tendem à resolução espontânea do refluxo, com boa evolução renal a longo prazo, de forma que a indicação cirúrgica fica reservada aos refluxos de alto grau ou com outras complicações clínicas.Universidade Federal de São Paulo (UNIFESP) Escola Paulista de MedicinaUNIFESP, EPMSciEL

METHODOLOGY FOR AUTOMOTIVE AIR-CONDITIONING CONTROL OPTIMIZATION USING ARTIFICIAL NEURAL NETWORKS

The transient nature of automotive air conditioning systems control is generally achieved through proportional–integral–derivative controllers (PID’s) parameters tunning. Due to the vast database available from decades of automotive manufacturers design and expertise, Artificial Neural Networks (ANN) might be able to identify underlying patterns to predict and properly tune the air-conditioning PID control systems under different thermal requirements. Recently, advances in computational capability have enabled compact embarked systems to rapidly solve complex, multi-variable sets of equations, thus allowing for ANN to promptly calculate tunning parameters and act upon PID controllers. As any new application, technical literature is still scarce. On this research, a coupled PID and 6-layers perceptron ANN system was devised, programmed and used to simulate how an air-conditioning system performance can be optimized through proportional–integral–derivative controllers tuning. This proposed setup response was then compared to a conventional heuristic PID tunning method (Ziegler Nichols) to demonstrate how ANN’s can more rapidly stabilize the system output

Resistance of the stable fly, Stomoxys calcitrans (Diptera: Muscidae), to cypermethrin in outbreak areas in Midwestern Brazil.

Population explosions of the stable fly (Stomoxys calcitrans) have become a serious concern for livestock producers near sugarcane mills in some regions of Brazil due to the insect?s massive reproduction on sugarcane byproducts and waste. Despite the limited efficiency of insecticides for controlling stable fly outbreaks, producers still rely on chemical control to mitigate the alarming infestations in affected areas. This study evaluated the susceptibility of S. calcitrans populations to cypermethrin in the state of Mato Grosso do Sul, Brazil. Stable flies were tested from three field populations and two colonies, established from flies previously collected at sugarcane mills. Wild flies were collected with Nzi traps in areas of sugarcane plantations. Both wild and colonized flies were exposed to eleven concentrations of cypermethrin in impregnated filter paper bioassays. All the populations proved to be resistant to cypermethrin, with resistance factors among field populations ranging from 6.8 to 38.6. The intensive use of insecticides has led to the development of pyrethroid resistance in stable fly populations in the proximities of sugarcane mills in the state of Mato Grosso do Sul