Centre of Statistics and its Applications

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Publications

A novel and simpler alkaline hydrolysis methodology for extraction of ferulic acid from brewer’s spent grain and its (partial) purification through adsorption in a synthetic resin

Publication . Ideia, Pedro; Sousa-Ferreira, Ivo; Castilho, Paula C.

This work aims to develop simpler methodologies of extracting ferulic acid (FA) from brewer’s spent grain (BSG). BSG is produced by brewing companies at high amounts all over the year and does not possess a direct application. Thus, its use as raw material for extraction of bioactive compounds has gained attention in the last years. FA has different interesting applications in cosmetics, food industry, and pharmaceutics. Several studies aim for its extraction from BSG by various methods, namely alkaline hydrolysis. In the present work, we suggest the use of autoclave to process higher amounts of BSG in a lab scale. A simplification of the regular post-hydrolysis procedures is also proposed to decrease the number of experimental steps and energy costs and to simultaneously increase the extraction yield (up to 470 mg of FA per 100 g of BSG). The adsorption of extracted FA in a synthetic resin is suggested as a partial purification method.

2020Journal article

Open access

Um olhar sobre o desenvolvimento de modelos de sobrevivência para acontecimentos recorrentes

Publication . Sousa-Ferreira, Ivo; Abreu, Ana Maria; Rocha, Cristina

2020Journal article

Open access

Modelos paramétricos flexíveis para acontecimentos recorrentes

Publication . Sousa-Ferreira, Ivo; Rocha, Cristina; Abreu, Ana Maria

Neste trabalho, s˜ao propostas duas classes de modelos pa ram´etricos para analisar o tempo entre acontecimentos recorrentes, utilizando splines c´ubicos restritos. As classes de modelos diferem no modo como se lida com a dependˆencia entre acontecimentos. Al´em disso, ambas as classes s˜ao caracterizadas por uma transforma¸c˜ao da fun¸c˜ao de sobrevivˆencia, atrav´es da fun¸c˜ao de liga¸c˜ao log-log ou −logit. De forma a ilustrar a metodologia proposta, efetua-se uma aplica¸c˜ao a um conjunto de dados reais sobre a recorrˆencia de cancro da bexiga. Os resultados revelam que o uso de splines c´ubicos res tritos permite modelar de forma flex´ıvel e adequada o tempo entre acontecimentos sucessivos.

2021Conference object

Open access