Digital Signal Processing 13 (2003) 172--197

A careful comparison of three numeric techniques for estimation of the curvature along spatially quantized contours is reported. Two of the considered techniques are based on the Fourier transform (operating over 1D and 2D signals) and Gaussian regularization required to attenuate the spatial quantization noise. While the 1D approach has been reported before and used in a series of applications, the 2D Fourier transform-based method is reported in this article for the first time. The third approach, based on splines, represents a more traditional alternative. Three classes of parametric curves are investigated: analytical, B-splines, and synthesized in the Fourier domain. Four quantization schemes are considered: grid intersect quantization, square box quantization, a table scanner, and a video camera. The performances of the methods are evaluated in terms of their execution speed, curvature error, and sensitivity to the involved parameters. The third approach resulted the fastest, but implied larger errors; the Fourier methods allowed higher accuracy and were robust to parameter configurations. The 2D Fourier method provides the curvature values along the whole image, but exhibits interference in some situations. Such results are important not only for characterizing the relative performance of the considered methods, but also for providing practical guidelines for those interested in applying those techniques to real problems

A viagem científica de Neiva e Penna: roteiro para os estudos das doenças do sertão The scientific journey taken by Neiva and Penna: a blueprint for studies of diseases from the Brazilian hinterland

Analisa o relatório de Arthur Neiva e Belisario Penna , focalizando a contribuição dos autores ao estudo de uma das doenças endêmicas por eles encontrada ao longo de todo o trajeto percorrido, de longa data conhecida popularmente por 'mal de engasgo'. Observaram e descreveram com minúcia os sintomas apresentados pelos doentes e a associação frequente do mal de engasgo com outro mal endêmico conhecido por 'vexame' ou 'vexame do coração', que consistia em crises de palpitações. Os estudos epidemiológicos e clínicos de Neiva e Penna sobre o mal de engasgo muito contribuíram para o conhecimento dessa afecção e representaram um incentivo para todos os pesquisadores que se dedicaram ao seu estudo, especialmente quanto a sua relação com a doença de Chagas.<br>Analyze the report by Neiva and Penna, focusing on the contribution these authors made to the study of one of the endemic diseases encountered throughout their journey, which had been long known under the popular name of mal de engasgo (choking disease). They recorded their observations and detailed descriptions of the patients' symptoms and the association frequently encountered between mal de engasgo and another endemic disease, known as vexame or vexame do coração, characterized by bouts of palpitations. Neiva and Penna's epidemiological and clinical observations of mal de engasgo were crucial for all the researchers interested in the disease, especially its relationship with Chagas disease