Connecting free volume with shape memory properties in noncytotoxic gamma-irradiated polycyclooctene

The free volume holes of a shape memory polymer have been analysed considering that the empty space between molecules is necessary for the molecular motion, and the shape memory response is based on polymer segments acting as molecular switches through variable flexibility with temperature or other stimuli. Therefore, thermomechanical analysis (TMA) and positron annihilation lifetime spectroscopy (PALS) have been applied to analyse shape recovery and free volume hole sizes in gamma irradiated polycyclooctene (PCO) samples, as a non-cytotoxic alternative to more conventional PCO crosslinked via peroxide for future applications in medicine. Thus, a first approach relating structure, free volume holes and shape memory properties in gamma irradiated PCO is presented. The results suggest that free volume holes caused by gamma irradiation in PCO samples facilitate the recovery process by improving movement of polymer chains and open t possibilities for the design and control of the macroscopic response.

A 3D computer assisted Orthopedic Surgery Planning approach based on planar radiography

Dissertação de mestrado integrado em Engenharia Biomédica (área de especialização em Informática Médica)

Aflatoxins detoxification by gamma irradiation

[Excerpt] Mycotoxins are secondary toxic metabolites of filamentous fungi. Aflatoxins (AFs) are produced to Aspergillus species such as A. flavus and A. parasiticus. These fungi are ubiquitous in nature and usually found on agricultural commodities. Therefore, AFs are encountered in many important foodstuff, including wheat, rice, maize, peanuts, sorghum, pearl millet, spices, oilseeds, tree nuts and milk. Due to the high toxicity of AFs, many methods have been studied to reduce or eliminate these mycotoxins from food and feed. Gamma irradiation is one technology that has been investigated with promising results. The aims of this study were (I) to study the effect of gamma radiation on aflatoxin B1, aflatoxin B2, aflatoxin G1 and aflatoxin G2 (II) to evaluate the effect of the presence of water on AFs degradation during the irradiation process; and (IV) to evaluate the cytotoxicity of radiolytic products formed. (...)