Active skeleton for bacteria modeling

The investigation of spatio-temporal dynamics of bacterial cells and their molecular components requires automated image analysis tools to track cell shape properties and molecular component locations inside the cells. In the study of bacteria aging, the molecular components of interest are protein aggregates accumulated near bacteria boundaries. This particular location makes very ambiguous the correspondence between aggregates and cells, since computing accurately bacteria boundaries in phase-contrast time-lapse imaging is a challenging task. This paper proposes an active skeleton formulation for bacteria modeling which provides several advantages: an easy computation of shape properties (perimeter, length, thickness, orientation), an improved boundary accuracy in noisy images, and a natural bacteria-centered coordinate system that permits the intrinsic location of molecular components inside the cell. Starting from an initial skeleton estimate, the medial axis of the bacterium is obtained by minimizing an energy function which incorporates bacteria shape constraints. Experimental results on biological images and comparative evaluation of the performances validate the proposed approach for modeling cigar-shaped bacteria like Escherichia coli. The Image-J plugin of the proposed method can be found online at http://fluobactracker.inrialpes.fr.Comment: Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging and Visualizationto appear i

Particle detection and tracking in fluorescence time-lapse imaging: a contrario approach

This paper proposes a probabilistic approach for the detection and the tracking of particles in fluorescent time-lapse imaging. In the presence of a very noised and poor-quality data, particles and trajectories can be characterized by an a contrario model, that estimates the probability of observing the structures of interest in random data. This approach, first introduced in the modeling of human visual perception and then successfully applied in many image processing tasks, leads to algorithms that neither require a previous learning stage, nor a tedious parameter tuning and are very robust to noise. Comparative evaluations against a well-established baseline show that the proposed approach outperforms the state of the art.Comment: Published in Journal of Machine Vision and Application

Optimal Asymmetric Binary Quantization for Estimation Under Symmetrically Distributed Noise

Estimation of a location parameter based on noisy and binary quantized measurements is considered in this letter. We study the behavior of the Cramer-Rao bound as a function of the quantizer threshold for different symmetric unimodal noise distributions. We show that, in some cases, the intuitive choice of threshold position given by the symmetry of the problem, placing the threshold on the true parameter value, can lead to locally worst estimation performance.Comment: 4 pages, 5 figure

La révolution tranquille et les poétes de la parole au Québec (1960-1970)

Durante los años sesenta, la poesía de Québec era consciente de la existencia del pensamiento nacionalista, especialmente en esta importante transformación política denominada "the quiet Revolution". El lenguaje poético pervivió en antiguas figuras poéticas y sus orígenes se renovaron en la realidad contemporánea con el fin de encontrar una fuente de nueva inspiración. La poesía de Québec pasó a ser una forma de percibir las dificultades de la supervivencia, de la vida misma. Proporcionó su propia visión de la situación política, social y económica de los quebequeses, dentro de la sociedad y de la asunción de su alienación. En ese sentido, algunos poetas iban a la frontera de la poesía, al "nom-poem" (Gaston Miron), o a un "poem wihout image" (Paul Chamberland).Durante los años sesenta, la poesía de Québec era consciente de la existencia del pensamiento nacionalista, especialmente en esta importante transformación política denominada "the quiet Revolution". El lenguaje poético pervivió en antiguas figuras poéticas y sus orígenes se renovaron en la realidad contemporánea con el fin de encontrar una fuente de nueva inspiración. La poesía de Québec pasó a ser una forma de percibir las dificultades de la supervivencia, de la vida misma. Proporcionó su propia visión de la situación política, social y económica de los quebequeses, dentro de la sociedad y de la asunción de su alienación. En ese sentido, algunos poetas iban a la frontera de la poesía, al "nom-poem" (Gaston Miron), o a un "poem wihout image" (Paul Chamberland).notPeerReviewe