Structural and optical properties of Zn3P2 thin films

Conditions have been developed for the deposition of a stoichiometric thin film of zinc phosphide (Zn₃P₂) using electron beam evaporation. Structural properties of as-deposited and annealed thin films of zinc phosphide have been studied using electron and X-ray diffraction. The as-deposited film is non-crystalline, structural ordering starts on annealing at 200° C and the film becomes crystalline at 300° C with the structure matching that of the bulk material. Optical absorption has been investigated over the range 1 to 3 eV with emphasis on the region of interband absorption. The thin film absorption edge is found to be exponential for lower values of absorption coefficient. Analysis of thin film data showed that Zn₃P₂ is a direct-band-gap material. On annealing there is a shift in the band edge towards higher energy. NCL Communication No. 3571.     

Signal processing in prolonged EEG recordings during intensive care

Methods for analyzing and displaying EEG signals are discussed. The increasing availability and affordability of powerful computer equipment makes possible the use of ever more sophisticated signal processing techniques, which extract relevant (but not readily discernible) information from long-term EEG recordings and can easily identify important features in the EEG. Whether these techniques are actually taken up in clinical practice is heavily dependent on how well they match clinical requirements. This article concentrates on requirements set in the context of long-term recordings in the ICU that demand the ability to process short-term discrete events as well as long-term trend information. A huge range of potentially useful signal processing techniques exists. This article illustrates the value of some of these techniques for ICU signals using the EEG recordings collected during the IMPROVE project     

A sorption rate hypothesis for the increase in H2 permeability of palladium-silver (Pd-Ag) membranes caused by air oxidation

Hydrogen permeation measurements were performed at 300 °C for 25-μm cold-rolled Pd-Ag 25 wt% membranes before and after air oxidation at the same temperature as permeation. The air oxidation resulted in enhanced H₂ permeation through the membrane, as well as a roughening of the surface with the formation of surface grains and defects. The protruding grains can be leveled off by exposure to H₂ but the surface defects cannot. These microstructure changes are only on the membrane surfaces and do not create transmembrane defects that would allow permeation for gas species other than H₂. The H₂ permeability of the oxidized membrane increased by 25-90% compared to that of the as-received film at the same permeation condition, and the membranes retained perfect H₂ selectivity over N₂. The percent improvement of H₂ permeability decreases with increasing H₂ feed pressure. A new sorption kinetics hypothesis is proposed to elucidate the increase in H₂ permeability of Pd-Ag membranes caused by oxidation. H₂ solubility and sorption rate results were presented to test the new hypothesis. It is found that air oxidation does not change the H₂ solubility in Pd-Ag membranes, but enhances the H₂ sorption kinetics significantly. The extent of kinetics enhancement also decreases with increasing H₂ pressures. The much faster sorption equilibrium implies higher effective H₂ diffusivity at the Pd-Ag membrane surface for the oxidized sample and a higher transfer rate of atomic hydrogen from surface/sub-surface to the membrane bulk that contributes to the increase of H₂ permeability observed in experiments.     

Effect of different stocking densities during transport on welfare and meat quality in Danish slaughter pigs

Four stocking densities (0.35, 0.39, 0.42 and 0.50 m² per 100 kg pig) were investigated under Danish early Autumn conditions (16–24 ° C) in a study of the effect of transport conditions on pig welfare and meat quality. Two transports were carried out for each stocking density, the two producers concerned delivering pigs to the upper and lower tiers, respectively, of a specialist pig transport vehicle. Total average journey time was 2 hr 39 min and total average transport time 1 hr 47 min. After arrival at the factory pigs were lairaged in groups of 15 for about hr and then slaughtered using minimal stress with group CO₂-stunning. Pig behaviour was monitored during transport in the front compartment of the lower tier. Blood samples were taken at slaughter for analysis of creatine phosphokinase, lactate and cortisol and carcasses were evaluated for skin damage and meat quality. Stocking density, as such, had relatively little effect on blood profile or meat quality. Creatine phosphokinase levels were lowest with a stocking density of 0.50 m² and the incidence of unacceptable skin damage was generally lowest with a stocking density of 0.35 m² and highest with 0.42 m². The main source of variation in this experiment was day of transport/slaughter within stocking density so that factors other than stocking density have affected the results obtained. Stocking density had a direct effect on pig behaviour during transport. Giving pigs more space during the short transport did not result in them lying down. On the contrary there was continuous disturbance from other pigs and at 0.42 and 0.50 m² pigs had difficulty maintaining balance, when the vehicle negotiated bends or poor road surfaces. Variations in pig behaviour during transport could account for the observed differences in skin damage.     

Effect of dimension on direct search methods for constrained optimization

A simple technique, involving a series of disjointed optimization problems, for finding the effect of the number of variables on direct search methods is described. The computational results obtained with this technique show that the dimension has a significant effect on the performance of direct search methods. Both the accuracy of the solution and the computational effort, which could increase by as much as sixteenfold when the number of variables is doubled, are affected.     

Correction of post burns contracture of wrist with Ilizarov method

A case of severe post burns contracture of the wrist, of 43 years duration resulting in recurrent ulceration of the skin was successfully treated by gradual distraction using the Ilizarov method. This method is superior to plaster of Paris cast and is more versatile than other forms of external fixation.     

Extraction and fractionation of proteins of sorghum kernels

Using multi-step extraction, sorghum flour was shown to contain 28 % albumin and globulin, 30 % pro-lamin and 12 % soluble glutelin. The remaining 30 % proteins are difficult to extract and may be bound. Alkaline copper sulphate and sodium sulphite were not very effective in extracting the protein, nor were dilute acetic acid and sodium pyrophosphate buffer. A virtually complete extraction of proteins could be achieved by 8 M urea with 0·1 M sodium dodecyl sulphate; 8M urea alone extracted 60% of the total protein. Sephadex gel (G 100) filtration showed that the normal solvent extracts contain three major fractions, one a low molecular weight, dialysable fraction, one of high molecular weight proteins elected around the void volume, and an intermediate fraction. 8 M urea extracts yielded three main peaks and six minor peaks. From a standard curve, approximate molecular weights of these main fractions were estimated as 82,000, 46,000 and 2000, respectively. Disc electrophoresis on polyacrylamide gel gave compatible results. Single bands were observed in dialysed aqueous, saline and alcoholic extracts, two sharp bands in the case of sodium hydroxide extracts. Extraction with 8 M urea gave three main and five minor bands on disc electrophoresis.