Studies on La2-xPrxCayBa2Cu4+yOz (0.1 < x < 0.5) type mixed oxide superconductors

The La2-xPrxCayBa2Cu4+yOz (LaPrCaBCO) mixed oxides have been studied for their structural and superconducting properties using X-ray diffraction (XRD), d. c. resistivity, d. c. susceptibility and iodometric double titration. All the LaPrCaBCO samples for x = 0.1 - 0.5, exhibit tetragonal crystalline structure with P 4/mmm space group as determined by Rietveld analysis of the X-ray diffraction data. With increasing x, enhancement in Tc is observed, which is quite interesting for Pr substituted high Tc oxides. Maximum Tc ~ 58 K has been observed for x = 0.5(La-2125 stoichiometry). The results of structural studies and superconducting property measurements are presented in light of increase in Tc in LaPrCaBCO system with increasing Pr concentration.Comment: 6 pages including 5 figures and 1 tabl

Critical current density and flux pinning in La2-xPrxCa2xBa2Cu4+2xOz (x = 0.1 - 0.5) superconductors

Polycrystalline La2-xPrxCa2xBa2Cu4+2xOz (LPCaBCO) compounds with x = 0.1 - 0.5 were synthesized by solid-state reaction method and studied by room temperature X-ray diffraction, dc resistivity, dc magnetization and iodometry. The superconducting transition temperatures in these tetragonal triple perovskite compounds increases from 32 to 62 K (Tconset values) with increasing dopant concentration. The mixing of rare earth La3+ and Pr3+/4+ ions at rare earth site (La3+) along with substitution of divalent Ca2+ results in the shrinkage of unit cell volume. The contraction of unit cell volume due to larger ion being substituted by smaller ions, gives rise to creation of pinning centers in the unit cell leading to increase in critical current density and flux pinningComment: To be published in Solid State Communications (2004

Supplementation with omega-3 polyunsaturated fatty acids and effects on reproductive performance of sows

In studies of both humans and farm animals, the inclusion of omega-3 polyunsaturated fatty acids in the diet have been shown to have beneficial effects on many physiological processes including reproduction. The aim of this study was to examine the effects of supplementary omega-3 on sow reproductive performance and piglet survival. Salmon oil (1 %) was fed to sows throughout gestation and lactation as a source of omega-3 and sows were followed through their subsequent parity when returned to a commercial gestation and lactation diet. It was hypothesised that sows fed omega-3 would show improved piglet survivability (+2 %) and an increased litter size (one extra piglet born alive per litter) in the second experimental period compared with a soya oil supplemented control. Supplementation of 1 % salmon oil across one parity increased the body weight of sows at weaning (p = 0.01) and these sows maintained on average 4 kg ± 2.3 more over the lactation period than soya oil supplemented controls. Sows that were followed across a second un-supplemented reproductive period were heavier at farrowing (p < 0.01) and weaning (p < 0.05), had a higher condition score at farrowing and tended to have a higher condition score (p = 0.063) and back fat at weaning (p = 0.073) when they had received salmon oil in the previous reproductive cycle. However, salmon oil increased pre-weaning mortality by 2.4 % in the first reproductive period (p < 0.05) and significantly reduced litter weight at birth (ca 600 g; p < 0.05). Pre-weaning mortality was reduced by 3.4 % in the second experimental period when supplementation of both salmon oil and the soya oil control had ceased (p < 0.001). This effect tended to be greater for sows previously supplemented with omega-3. There was no effect on litter size, or the number of piglets born alive. Supplementation of 1 % salmon oil improved sow body weight at weaning and increased maternal stores across a second, un-supplemented reproductive cycle perhaps through effects on maternal nutrient partitioning. The increased mortality in the first experimental period and reduced mortality (across both treatment groups) when returned to a commercial diet suggests a negative effect of omega 3 fatty acid supplementation on piglet survival when fed throughout gestation and lactation