Carlos E. Valencia

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We study irreducible representations of Rees cones and characterize the max-flow min-cut property of clutters in terms of the normality of Rees algebras and the integrality of certain polyhedra. Then we present some applications to combinatorial optimization and commutative algebra. As a byproduct we obtain an effective method, based on the program Normaliz(More)
Involuntary movements are unusual during or after acute stroke, and alien hand sign has not been reported after single parietal infarction. We report on a woman who presented with involuntary movements and a sense of alienness of her left upper limb following a right parietal infarction. This combination, that can meet the criteria for the 'alien hand(More)
Let G be a graph without isolated vertices and let α(G) be its stability number and τ (G) its covering number. The σ v-cover number of a graph, denoted by σ v (G), is the maximum natural number m such that every vertex of G belongs to a maximal independent set with at least m vertices. In the first part of this paper we prove that α(G) ≤ τ (G)[1 + α(G) − σ(More)
For a bipartite graph G we are able to characterize the complete intersection property of the edge subring in terms of the multiplicity and we give optimal bounds for this number. We give a method to obtain a regular sequence for the atomic ideal of G, when G is embedded on an orientable surface. We also give a graph theoretical condition for the edge(More)
UNLABELLED We investigated whether there is a direct correlation between plasma fibrinogen levels and the amount of leukoaraiosis (LA) in patients with symptomatic small-vessel disease. The study included 28 patients: 12 with a first-ever lacunar infarction (LI) and 16 with Binswanger's disease (BD). The mean age was 71 years (SD 8.6), and 21 were men. For(More)
The statistical analysis of tree structured data is a new topic in statistics with wide application areas. Some Principal Component Analysis (PCA) ideas were previously developed for binary tree spaces. In this study, we extend these ideas to the more general space of rooted and labeled trees. We redefine concepts such as tree-line and forward principal(More)
OBJECTIVES To analyze the correlation between blood pressure (BP) variability and leukoaraiosis (LA) amount in patients with symptomatic cerebral small-vessel disease. MATERIALS AND METHODS We included 25 hypertensive patients: 13 with Binswanger's disease (BD) and 12 with a first-ever lacunar infarction (LI). Baseline office BP was obtained for 3(More)