lunes, 9 de junio de 2014

Paper Nuevo: Deconvolución de señales isotópicas


En este paper publicado en Oecologia describimos el problema asociado al analizar múltiples pelos en un mechón, y como la señal isotópica de cada pelo se "mezcla" para generar una señal promedio dependiente de la etapa de crecimiento de cada pelo y de su tasa de crecimiento. Presentamos un modelo matemático de deconvolución para recuperar la señal "original" en equilibrio. Este modelo es aplicable a otros tipos de muestra, no solo pelos, y también a otros tipos de señales como la concentración de drogas y metabolitos, por ejemplo.

Este trabajo fue parte de la tesis doctoral de Chris Remien, dentro del programa de Doctorado de Matemática aplicada a la Biología (Graduate Studies in Mathematical Biology) de la Universidad de Utah, y representa una de las tantas colaboraciones multidisciplinarias del laboratorio del Dr. Jim Ehleringer.

Remien, Christopher H., Frederick R. Adler, Lesley A. Chesson, Luciano O. Valenzuela, James R. Ehleringer, and Thure E. Cerling. “Deconvolution of Isotope Signals from Bundles of Multiple Hairs.Oecologia, May 3, 2014, 1–9. doi:10.1007/s00442-014-2945-3.

Abstract
Segmental analysis of hair has been used in diverse fields ranging from forensics to ecology to measure the concentration of substances such as drugs and isotopes. Multiple hairs are typically combined into a bundle for segmental analysis to obtain a high-resolution series of measurements. Individual hair strands cycle through multiple phases of growth and grow at different rates when in the growth phase. Variation in growth of hair strands in a bundle can cause misalignment of substance concentration between hairs, attenuating the primary body signal. We developed a mathematical model based on the known physiology of hair growth to describe the signal averaging caused by bundling multiple hairs for segmental analysis. The model was used to form an inverse method to estimate the primary body signal from measurements of a hair bundle. The inverse method was applied to a previously described stable oxygen isotope chronology from the hair of a murder victim and provides a refined interpretation of the data. Aspects of the reconstruction were confirmed when the victim was later identified.

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