Relationship between fibre orientation and tensile strength of natural collagen membranes for heart valve leaflets

Heart valve prostheses are used to replace native heart valves which that are damaged because of congenital diseases or due to ageing. Biological prostheses made of bovine pericardium are similar to native valves and do not require any anticoagulation treatment, but are less durable than mechanical prostheses and usually fail by tearing. Researches are oriented in improving the resistance and durability of biological heart valve prostheses in order to increase their life expectancy. To understand the mechanical behaviour of bovine pericardium and relate it to its microstructure (mainly collagen fibres concentration and orientation) uniaxial tensile tests have been performed on a model material made of collagen fibres. Small Angle Light Scattering (SALS) has been also used to characterize the microstructure without damaging the material. Results with the model material allowed us to obtain the orientation of the fibres, relating the microstructure to mechanical performance

Partioning of dietary energy of chickens fed maize or wheat-based diets with and without a commercial blend of phytogenic feed additives

The aim of the study was to investigate the effects of a standardized mixture of a commercial blend of phytogenic feed additives containing 5% carvacrol, 3% cinnamaldehyde, and 2% capsicum on utilization of dietary energy and performance in broiler chickens. Four experimental diets were offered to the birds from 7 to 21 d of age. These included 2 basal control diets based on either wheat or maize that contained 215 g CP/kg and 12.13 MJ/kg ME and another 2 diets using the basal control diets supplemented with the plant extracts combination at 100 mg/kg diet. Each diet was fed to 16 individually penned birds following randomization. Dietary plant extracts improved feed intake and weight gain (P < 0.05) and slightly (P < 0.1) improved feed efficiency of birds fed the maize-based diet. Supplementary plant extracts did not change dietary ME (P > 0.05) but improved (P < 0.05) dietary NE by reducing the heat increment (P < 0.05) per kilogram feed intake. Feeding phytogenics improved (P < 0.05) total carcass energy retention and the efficiency of dietary ME for carcass energy retention. The number of interactions between type of diet and supplementary phytogenic feed additive suggest that the chemical composition and the energy to protein ratio of the diet may influence the efficiency of phytogenics when fed to chickens. The experiment showed that although supplementary phytogenic additives did not affect dietary ME, they caused a significant improvement in the utilization of dietary energy for carcass energy retention but this did not always relate to growth performance.

Binary metal oxides for composite ultrafiltration membranes

A new ultrafiltration membrane was developed by the incorporation of binary metal oxides inside polyethersulfone. Physico-chemical characterization of the binary metal oxides demonstrated that the presence of Ti in the TiO2?ZrO2 system results in an increase of the size of the oxides, and also their dispersity. The crystalline phases of the synthesized binary metal oxides were identified as srilankite and zirconium titanium oxide. The effect of the addition of ZrO2 can be expressed in terms of the inhibition of crystal growth of anocrystalline TiO2 during the synthesis process. For photocatalytic applications the band gap of the synthesized semiconductors was determined, confirming a gradual increase (blue shift) in the band gap as the amount of Zr loading increases. Distinct distributions of binary metal oxides were found along the permeation axis for the synthesized membranes. Particles with Ti are more uniformly dispersed throughout the membrane cross-section. The physico-chemical characterization of membranes showed a strong correlation between some key membrane properties and the spatial particle distribution in the membrane structure. The proximity of metal oxide fillers to the membrane surface determines the hydrophilicity and porosity of modified membranes. Membranes incorporating binary metal oxides were found to be promising candidates for wastewater treatment by ultrafiltration, considering the observed improvement influx and anti-fouling properties of doped membranes. Multi-run fouling tests of doped membranes confirmed the stability of permeation through membranes embedded with binary TiO2?ZrO2 particles.