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Vila Real de Santo António, Portugal

Castro A.,University of Porto | Bressan N.,University of Porto | Antunes L.,CECAV UTAD | Nunes C.S.,University of Porto
2007 European Control Conference, ECC 2007

Because of the difficulty in analyzing raw electroencephalographic signal, several electroencephalographic monitors have been developed to aid anaesthetists on their task to maintain adequate anaesthesia. Spectral Entropy is used as a measure of electroencefalographic effects of drugs in human patients, and is a valuable tool to predict depth of anaesthesia. Monitors with implemented entropy algorithms, process the electroencephalogram (EEG) and are in current use at the operating room. In this study we used the EEG collected in rats and applied the Shannon entropy over the signal. The information obtained was used as an indicator of depth of anaesthesia. The main objective was to model the relation between the depth of anaesthesia in rats (entropy) and the propofol infusion rates, with the purpose of obtaining a closed-loop control for propofol infusions. Five adult rats were sedated with isoflurane, cannulated and equipped for the EEG collection. After the preparation, anaesthesia was induced with propofol infusions, using different infusion rates on each rat. The collected EEG (125Hz) was processed using an entropy algorithm developed in MATLAB® 7 that determined the entropy value at each second using the preceding 15s of signal. Pharmacokinetic models were fitted for each rat using bi and tri-compartmental models; the pharmacodynamic phase was also modelled for each rat. The relation between obtained propofol effect-site concentrations and the entropy values was modelled by a Hill Equation. The model obtained for the relation between infusion rates and entropy values was evaluated using the mean absolute deviation (MAD) and the relative mean square error (RMSE) for models comparative analysis. © 2007 EUCA. Source

Morais J.J.L.,CITAB UTAD | de Moura M.F.S.F.,University of Porto | Pereira F.A.M.,CITAB UTAD | Xavier J.,CITAB UTAD | And 3 more authors.
Journal of the Mechanical Behavior of Biomedical Materials

The primary objective of this work was to analyse the adequacy of the Double Cantilever Beam (DCB) test in determining fracture toughness under pure mode I loading of cortical bone tissue. A new data reduction scheme based on specimen compliance and the crack equivalent concept was used to overcome the difficulties inherent in crack monitoring during its growth. It provides a complete resistance curve, which is fundamental in estimating the fracture energy. A cohesive zone model was used to simulate damage initiation and propagation, thus assessing the efficacy of the proposed testing method and data reduction scheme. Subsequently, the DCB test was applied to evaluate the mode I fracture energy of hydrated and thermally dehydrated cortical bone tissue from young bovine femur, in the tangential-longitudinal propagation system. The results obtained demonstrate the efficacy of the DCB test and the proposed data reduction scheme on the bone fracture characterization under mode I loading. © 2010 Elsevier Ltd. Source

Lourenco A.L.,CECAV UTAD | Dias-da-Silva A.,CECAV UTAD | Santos A.S.,CECAV UTAD | Santos A.S.,University of Coimbra | And 4 more authors.
Journal of Animal Physiology and Animal Nutrition

The digestive capacity of the Portuguese native breed of Barrosão cattle and the Holstein-Friesian breed was measured when fed meadow hay (72-74 g CP and 641-671 g NDF/kg dry matter), offered either alone or supplemented with soya bean meal (150 g/kg dry matter), at maintenance level. Four mature cows of each breed were used. Average initial live weight (LW) was 457 and 635 kg for the Barrosão and the Holstein-Friesian cows respectively. The organic matter digestibility (OMD) of the meadow hay was higher in Holstein-Friesian than in Barrosão cows (p < 0.08) whether supplemented or not. The neutral detergent fibre digestibility of the hay was also higher in Holstein-Frisian when the hay was fed alone (p < 0.08). The soya bean meal supplementation increased the OMD and the NDFD digestibility of the total diet (p < 0.05), but not the OMD digestibility of the hay (p > 0.05). The results obtained in this study suggest a higher ability to digest fibre in the large dairy breed than in the small native breed. This suggestion is also supported by previous findings with sheep breeds largely differing in mature live weight. © 2013 Blackwell Verlag GmbH. Source

Lourenco A.L.,CECAV UTAD | Cone J.W.,Wageningen University | Fontes P.,CECAV UTAD | Dias-Da-Silva A.A.,CECAV UTAD
NJAS - Wageningen Journal of Life Sciences

The aim of this study was to evaluate if the in vivo digestibility and intake differences, observed in previous studies, between Ile-de-France (IF) and Churra-da-Terra-Quente (CTQ) sheep breeds, were due to rumen environment and degradability differences. The intake, digestibility, rumen environment and degradability and urinary allantoin-nitrogen excretion were evaluated in 8 adult cannulated ewes (4 CTQ and 4 IF ewes). The animals were fed ad libitum hay - with and without a soybean meal supplementation (150 g/kg ingested hay, dry matter basis). The organic matter intake per kg of body weight was higher (P < 0.05) and the NDF and hay organic matter digestibility was lower in CTQ ewes (P < 0.05), irrespective of supplementation. The rumen pH remained above 6.35 in all treatments, and the difference between the breeds was not biologically relevant. The ammonia nitrogen rumen content and the urinary allantoin-nitrogen excretion were similar (P > 0.05), whether the breeds where fed hay or hay supplemented with soybean meal. The volatile fatty acid concentrations in the rumen were similar (P > 0.05) for both genotypes. There was no breed effect (P > 0.05) on the rumen protozoa population, although supplementation increased its number (P < 0.001). As a result of the absence of differences in rumen content characteristics, there were no differences between the breeds (P > 0.05) on rumen in sacco degradation results. Thus, the effective rumen degradation was lower in the CTQ breed, when its inherit lower outflow rate was used to calculate it. This study suggests that the native CTQ breed and the IF breed exhibit similar rumen conditions for the microbial degradation of fibrous feeds. Thus the higher intake and lower digestibility of the CTQ breed can only result from its inherit faster flow through the gastrointestinal tract. © 2013 Royal Netherlands Society for Agricultural Sciences. Source

Lourenco A.L.,CECAV UTAD | Cone J.W.,Wageningen University | Fontes P.,CECAV UTAD | Dias-da-Silva A.A.,CECAV UTAD
Journal of Animal Physiology and Animal Nutrition

The aim of this study was to compare the intake and digestive physiology of mature ewes of two breeds - Ile-de-France (mature weight: 75-80 kg) and Churra-da-Terra-Quente (CTQ; mature weight: 45-50 kg) - and evaluate the effects of ambient temperature and protein supplementation in the comparison. The temperature (25 °C vs. 11 °C) and soybean meal supplementation (150 g/kg of ingested hay on dry matter basis vs. unsupplemented control) were evaluated in 48 adult ewes of two breeds fed hay ad libitum and at a restricted level of intake. The intake, digestibility, rumen pH and NH3-N, rumen outflow rates, faeces particle size and thyroid hormones levels were measured. These hormones can be related with gastrointestinal motility, thus explaining rumen outflow rate patterns. Dry matter intake per kg of body weight was higher in CTQ ewes (p < 0.05). This breed also exhibited lower organic matter and neutral detergent fibre digestibility (p < 0.001) and higher solid (p < 0.001) and liquid (p < 0.01) rumen outflow rates irrespective of intake level, supplementation or temperature. Rumen pH remained above 6.6 in all treatments. NH3-N rumen content was similar (p > 0.05) when breeds were fed only hay. There was no breed effect (p > 0.05) on faeces particle size. Triiodothyronine was not affected (p > 0.05) by breed and thyroxine was higher (p < 0.10) in the CTQ breed but only at the lower temperatures (breed × temperature, p < 0.05). Ile-de-France sheep showed a lack of adaptation to lower temperatures. This study suggests that the native CTQ breed fulfils its metabolic needs by having a higher intake and inherits faster flow through the gastrointestinal tract, as a result, its digestive ability is diminished. © 2009 The Authors. Journal of Animal Physiology and Animal Nutrition © 2009 Blackwell Verlag GmbH. Source

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