The structure and stability of beta-Ta thin films

Ta films with tetragonal crystalline structure (beta-phase), deposited by magnetron sputtering on different substrates (steel, silicon and silicon dioxide), have been studied. In all cases, very highly preferred (001) orientation was observed in x-ray diffraction (XRD) measurements. All diffraction data revealed two weak reflections corresponding to d-spacing of 0.5272 and 0.1777 nm. The presence of the two peaks, attributed to (001) and (003) reflections, indicates that beta-Ta films exhibit a high preference for the space group of P-421m over P42/mnm, previously proposed for beta-Ta. Differences in relative intensities of (00l) reflections, calculated for single crystal beta-Ta sigma-type Frank-Kasper structure and those measured in the films, are attributed to defects in the films. Molecular dynamics simulations performed on tantalum clusters with six different initial configurations using the embedded-atom-method (EAM) potential revealed the stability of beta-Ta, which might explain its growth on many substrates under various deposition conditions.Comment: 27 pages, 6 figures,1 tabl

Effects of intravenous infusions of sodium bicarbonate on blood oxygen binding in calves with diarrhoea

Twelve diarrhoeic calves were treated intravenously with an isotonic solution containing sodium bicarbonate, and their oxygen equilibrium curves (OECs) were calculated under standard conditions and compared with those of a group of healthy calves. The relationships between the OECs for arterial and venous blood and the oxygen extraction ratio were investigated. in the diarrhoeic calves, the affinity of haemoglobin for oxygen, measured under standard conditions, was increased compared with the healthy animals. During the infusion, the standard partial oxygen pressure at 50 per cent saturation of haemoglobin (P50) values stayed below the values recorded in the healthy animals. At the end of the infusion the mean standard P50 of the diarrhoeic calves was lower than before the infusion. The combined effects of all the regulating factors on blood oxygen binding resulted in the OECS of the arterial and jugular venous blood of the diarrhoeic calves remaining unchanged compared with the healthy calves. However, the administration of the infusion decreased the P50 of both the arterial and venous blood to below the value recorded in the healthy calves. oxygen extraction by the tissues was impaired in the diarrhoeic calves throughout the infusion, and they remained dehydrated and depressed until 120 minutes after the infusion bega