Polymer Nanocomposites Based on Poly(ε-caprolactone), Hydroxyapatite and Graphene Oxide

Standard and hybrid polymer nanocomposites based on poly(ɛ-caprolactone) (PCL), hydroxyapatite (HAp) and graphene oxide (GO). The GO synthetized here is made up of multilayer graphene oxide (mGO), in which up to five layers are stacked and lateral size around of 1 µm. The nanocomposites (PCL/Hap, PCL/mGO and PCL/HAp/mGO) were prepared by melt mixing in a twin-screw extruder and characterized by mechanical test, transmission electron microscopy (TEM), infrared spectroscopy (FTIR), X-ray diffraction (XRD), contact angle (CA), surface zeta potential by streaming and cell proliferation. The HAp content was maintained at 20% (w/w) while mGO was used at three levels of content (0.05, 0.1, and 0.3 w/w). In terms of bulk properties, the presence of mGO even in very low content (0.05 to 0.3%) was very effective in order to increase mechanical properties of PCL (stress and strain at beak and tenacity) while HAp tends to decrease them. When the two fillers are inserted mGO act to recover the properties lost by the presence of HAp. TEM images showed single GO sheets very well dispersed alone or combined with HAp. For surface properties, significant changes have been achieved by the presence of mGO, HAp and mGO/HAp. The water contact angle drops to values below 90° for all nanocomposites making the material hydrophilic, but again by the presence of only 0.05% of mGO it was reached easily. Surface ξ-potential for all nanocomposite was lower than neat PCL. As a consequence of surface modifications improvements in cell proliferation ability could be also observed. All modification by the presence of GO point out these materials as excellent candidates to resorbable suture, drug delivery system, and bone graft substitutes.28331342COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP88887.310339/2018–002014/22840–3; 2012/50259–8; 2015/16591–

Bands of respiratory rate and cloacal temperature for different broiler chicken strains

The objective of this investigation was to estimate ideal bands of respiratory rate and cloacal temperature for broiler chicken strains during the rearing period and to evaluate the influence of time of exposure on bird physiological variables under different thermal stress conditions. The research was conducted in a climatic chamber during the six weeks of the rearing period, with Avian and Cobb strains exposed to two climatic conditions (comfort and stress), in three distinct times of exposure, in three conditions (before going to the chamber; at the end of exposure time; 30 minutes after the end of exposure), in four treatments: comfort with 60 minutes of exposure; stress with 30 minutes of exposure; stress with 60 minutes of exposure; stress with 90 minutes of exposure. Bands of respiratory rate and cloacal temperature were elaborated for both strains, for each one of the weeks of the rearing period. Strains differed, regardless of treatments and conditions adopted in the research on the third, fifth and sixth weeks of life in relation to the cloacal temperature. The Cobb strain is more tolerant to thermal stress in comparison with the Avian. There was difference for both variables between comfort and stress, but time of exposure to stress did not influence the physiological response of birds, except for cloacal temperature on the second week of life