Equipoise among recanalization strategies

Modern acute ischemic stroke therapy is based on the premise that recanalization and subsequent reperfusion are essential for the preservation of brain tissue and favorable clinical outcomes. We outline key issues that we think underlie equipoise regarding the comparative clinical efficacy of IV recombinant tissue-type plasminogen activator (rt-PA) and intra-arterial (IA) reperfusion therapies for acute ischemic stroke. On the one hand, IV rt-PA therapy has the benefit of speed with presumed lower rates of recanalization of large artery occlusions as compared to IA methods. More recent reports of major arterial occlusions treated with IV rt-PA, as measured by transcranial Doppler and magnetic resonance angiography, demonstrate higher rates of recanalization. Conversely, IA therapies report higher recanalization rates, but are hampered by procedural delays and risks, even failing to be applied at all in occasional patients where time to reperfusion remains a critical factor. Higher rates of recanalization in IA trials using clot-removal devices have not translated into improved patient functional outcome as compared to trials of IV therapy. Combined IV-IA therapy promises to offer advantages of both, but perhaps only when applied in the timeliest of fashions, compared to IV therapy alone. Where equipoise exists, randomizing subjects to either IV rt-PA therapy or IV therapy followed by IA intervention, while incorporating new interventions into the study design, is a rational and appropriate research approach

Fitting a taper function to minimize the sum of absolute deviations Ajuste de uma função de afilamento via minimização da soma dos desvios absolutos

Multiple product inventories of forests require accurate estimates of the diameter, length and volume of each product. Taper functions have been used to precisely describe tree form, once they provide estimates for the diameter at any height or the height at any diameter. This study applied a goal programming technique to estimate the parameters of two taper functions to describe individual tree forms. The goal programming formulation generates parameters that minimize total absolute deviations (MOTAD). These parameters generated by the MOTAD method were compared to those of ordinary least squares (OLS) method. The analysis used a set of 178 trees cut from cloned eucalyptus plantations in the Southern part of the state of Bahia, Brazil. The values of the estimated parameters for the two taper functions resulted very similar when the two methods were compared. There was no significant difference between the two fitting methods according to the statistics used to evaluate the quality of the generated estimates. OLS and MOTAD resulted equally precise in the estimation of diameters and volumes outside and inside bark.<br>Os inventários florestais para múltiplos produtos requerem estimativas exatas do diâmetro, comprimento e volume de cada produto. As equações de afilamento têm sido usadas para descrever precisamente a forma da árvore uma vez que estas funções fornecem estimativas de diâmetro a qualquer altura ou de altura em qualquer diâmetro. Este trabalho aplica um modelo de programação por metas para estimar os parâmetros de duas equações de afilamento para descrever a forma do tronco de árvores individuais. O modelo de programação por metas gera parâmetros que minimizam a soma dos desvios absolutos (MOTAD). Esses parâmetros gerados pelo método MOTAD foram comparados aos parâmetros gerados pelo método dos mínimos quadrados ordinários (OLS). A análise se baseou em dados de cubagem de 178 árvores obtidas em plantios clonais de eucaliptos conduzidos na região sul da Bahia. Os valores dos parâmetros estimados por ambos os métodos de ajuste para as duas funções de afilamento mostraram-se muito semelhantes. Não houve diferença significativa entre os indicadores usados para avaliar a qualidade dos parâmetros estimados pelos dois métodos de ajuste. Os métodos OLS e MOTAD mostraram-se igualmente precisos na estimação de diâmetros e volumes com casca e sem casca