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Notes: A comprehensive study of the stress release and structural changes caused by postdeposition thermal annealing of tetrahedral amorphous carbon (ta-C) on Si has been carried out. Complete stress relief occurs at 600–700 °C and is accompanied by minimal structural modifications, as indicated by electron energy loss spectroscopy, Raman spectroscopy, and optical gap measurements. Further annealing in vacuum converts sp3 sites to sp2 with a drastic change occurring after 1100 °C. The field emitting behavior is substantially retained up to the complete stress relief, confirming that ta-C is a robust emitting material. © 1999 American Institute of Physics.

Notes: To understand the mechanism of electron field emission from diamond-like carbon, tetrahedral amorphous carbon (ta-C) films were subjected to Ar, H2, and O2 plasma treatments to change their surface condition and were deposited on substrates of different work function. The threshold fields and current densities for undoped ta-C are found to be significantly improved by the plasma treatments, largely due to an increase in emission site density, while little dependence was found on work function of substrate. This suggests that the main barrier to emission from ta-C is at the front surface. © 1999 American Institute of Physics.

Notes: Eight experiments aimed at improving methods for the village-based farming of giant clams were conducted in the Solomon Islands. The experiments focused on either improving the fitness of seed clams delivered to village farmers, assessing whether differential growth rates of seed clams in nursery tanks persisted during grow-out at farms, or testing the effects of alterations to the design of grow-out cages on the growth and survival of clams. We found that Tridacna squamosa (Lamarck) ‘seed’ transferred from land-based nursery tanks to a floating ocean nursery (FON) for ≈ 3 months at the end of the nursery phase were significantly larger than seed reared only in land-based nursery tanks. Similarly, T. maxima (Röding) placed in a FON for 2–5 months generally grew at a significantly greater rate than tank-reared ‘seed’. However, the use of FONs did not improve survival. There were no consistent differences in the growth and survival of fast- and slow-growing seed of T. derasa (Röding) at village sites when slow-growing seed were retained in the nursery until reaching a larger size. The survival of T. maxima was enhanced significantly by placing an insert of smaller mesh (a ‘settlement ring’) in grow-out cages for the first 2 months after delivery of seed to farmers. The settlement ring retained clams in cages until they found a suitable place to attach their byssal threads. Attempts to remove the sediment which impedes the attachment of T. maxima to the base of grow-out cages by perforating the substrate did not improve survival: the perforated substrate resulted in poor attachment of clams and harboured predators (Cymatium spp.). The survival of T. crocea (Lamarck) was not improved by ‘softening’ the concrete base of grow-out cages to simulate dead coral rock and to encourage the clams to burrow in the substrate. The survival of T. crocea in grow-out cages was enhanced significantly by enclosing the cages in fine mesh after the delivery of the seed clams to prevent predation and disturbance by juvenile wrasse, Thalassoma spp. The experiments indicate that the critical stage for village farming of giant clams is during the initial weeks following distribution of seed. Further research is needed to improve the survival of T. crocea and T. maxima during this phase.

Notes: Abstract. Fonofos is a highly toxic insecticide to birds that, when used as a cereal seed treatment, has caused mortality of free-living feral pigeons (Columba livia). Pigeons kept individually under ad libitum feeding conditions in the laboratory do not suffer lethal poisoning because they develop a strong avoidance response to fonofos-treated seed, which restricts consumption to below lethal levels. Two laboratory experiments were conducted to assess the role of avoidance in reducing the risk of acute poisoning of captive birds under food stress. In the first experiment, pigeons acclimatized to feed on untreated wheat seeds for 6 h/day were presented with fonofos-treated seeds for 6 h on a testing day, following normal food surplus in one experimental group (eight birds) and 6 days of deprivation in another (eight birds). In the second experiment, different pigeons were acclimatized to a feeding regime of 2 h/day and treated seeds were offered without previous restriction (eight birds) or after 6 days of food restriction in which birds were given 15% of normal intake (eight birds). In the second experiment, six birds in each experimental group were videotaped to study their feeding behavior. Survivors at the end of the testing day were killed, and all birds were dissected and analyzed to determine carcass and pectoral muscle composition. Food-stressed birds lost ∼11% of their initial body weight during 6 days of total or partial food restriction, but they still had visible fat deposits and a high body fat content, indicating that they were in good body condition in terms of energy reserves. Consumption of treated seeds on the testing day was reduced in comparison with normal intake of untreated seed in all birds, but there were differences between experimental groups. In ad libitum–fed birds, consumption of treated seed in each experiment averaged 12% and 19% of normal levels, exposure to fonofos was below lethal levels, and no bird died. In food-stressed birds, consumption was higher (34% or 56% of normal levels for the first and second experiments, respectively) and led to the ingestion of seed containing lethal doses of pesticide. Two birds in the first experiment and three in the second died of acute poisoning within around 2 h of initial exposure. The avoidance response developed quickly in both ad libitum–fed and food-stressed birds. Feeding took place in most birds almost exclusively in the first 9 min of the testing day. Within this interval, birds of the two experimental groups stopped ingesting treated seeds around 6 min after the onset of feeding. The differences between experimental groups in consumption of treated seed were due to the higher feeding rate and effective feeding time in food-stressed birds. It is concluded that although feral pigeons under severe food stress develop an early and strong conditioned food aversion to fonofos-treated seeds, avoidance does not always prevent mortality. The need for including hunger stress as a factor in avian dietary toxicity tests to make testing conditions more representative of those experienced by wild birds is discussed.