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The discrete Fourier transform is considered as one of the most powerful tools in digital signal processing, which enable us to find the spectrum of finite-duration signals. In this article, we introduce the notion of discrete quadratic-phase Fourier transform, which encompasses a wider class of discrete Fourier transforms, including classical discrete Fourier transform, discrete fractional Fourier transform, discrete linear canonical transform, discrete Fresnal transform, and so on. To begin with, we examine the fundamental aspects of the discrete quadratic-phase Fourier transform, including the formulation of Parseval's and reconstruction formulae. To extend the scope of the present study, we establish weighted and non-weighted convolution and correlation structures associated with the discrete quadratic-phase Fourier transform.
RESUMO
BACKGROUND: The propensity of Ascaris lumbricoides to wander leads to varied surgical complications in the abdomen. Wandering A lumbricoides may sometimes reach the vermiform appendix and its presence there may remain silent or incite pathology. Our aim was to study ascariadial appendicitis. METHODS: Over a period of 3 years, we identified children who were found to have appendiceal ascariasis during surgery for different intestinal complications due to ascariasis. We studied the relationship between ascariasis and its lodgement inside the vermiform appendix in these patients. No preoperative diagnosis was made in this series. RESULTS: We found 11 patients with appendiceal ascariasis. It was incidentally found that 8/11 (72.7%) patients had worms inside their vermiform appendix but not appendicitis, whereas the remaining three patients (27.2%) were found to have Ascaris-associated appendicitis. The characteristic finding in Ascaris-infested vermiform appendix was that the worm is positioned with its head at the base and its tail at the tip of the appendix. CONCLUSION: Migration of A lumbrocoides inside the vermiform appendix is an incidental finding and tends to pursue a silent course in most patients. Only rarely does the presence of Ascaris inside the vermiform appendix cause appendicitis.
