Helena Cristina da Gama Leitão

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The necessary information to reproduce and keep an organism is codified in acid nucleic molecules. Deepening the knowledge about how the information is stored in these bio-sequences can lead to more efficient methods of comparing genomic sequences. In the present study, we analyzed the quantity of information contained in a DNA sequence that can be useful(More)
We describe an ongoing research project on efficient methods for reconstruction of objects from large collections of irregular fragments, such as ancient pottery, collapsed murals, etc.. Our solution for flat objects uses multiscale matching and constrained dynamic programming, and we are now extending it to curved pottery fragments. We seek collaborative(More)
We describe here an efficient algorithm for reassembling one or more unknown objects that have been broken or torn into a large number AE of irregular fragments—a problem that often arises in achaeology, art restoration , forensics, and other disciplines. The algorithm compares the curvature-encoded fragment outlines, using a modified dynamic programming(More)
Reassembling unknown broken objects from a large collection of fragments is a common problem in archaeology and other fields. Computer tools have recently been developed, by the authors and by others, which try to help by identifying pairs of fragments with matching outline shapes. Those tools have been successfully tested on small collections of fragments;(More)
We describe a robust method to recover the depth coordinate from a normal or slope map of a scene, obtained e.g. through photometric stereo or interferometry. The key feature of our method is the fast solution of the Poisson-like integration equations by a multi-scale iterative technique. The method accepts a weight map that can be used to exclude regions(More)
In this paper, we show how to speed up the table lookup step in gauge-based multi-image photometric stereo. In that step, one must find a pixel of a gauge object, of known shape and color, whose appearance under m different illumination fields is similar to that of a given scene pixel. This search reduces to finding the closest match to a given m- vector in(More)
We describe a procedure to solve the basic problem of variable lighting photometric stereo - namely, recovering the normal directions and intrinsic albedos at all visible points of an opaque object, by analyzing three or more photos of the same taken with different illuminations. We follow the gauge-based approach, where the lighting conditions and light(More)
The recognition of splice sites plays an important role in the annotation of the eukaryotic genes structure. The detection of such sites is a highly imbalanced classification task because the number of negatives examples found in the DNA sequences is much higher than the number of positive ones. One possible strategy to deal with this particularity is to(More)