Opposite shifts in size at metamorphosis in response to larval and metamorph predators

Predation risk can cause organisms to alter the timing of life history switch points. Theory suggests that increased risk in an early life stage should select for switching earlier and smaller, while increased risk in the subsequent stage should select for switching later and larger. This framework has frequently been applied to metamorphosis in amphibians, with mixed results. Few studies examining the effect of larval predation risk on metamorphosis have observed the predicted pattern, and no studies, to our knowledge, have examined the effect of increased risk during and after metamorphosis on the timing of this switch point. Here we examine the effect of larval and post-metamorphic predation risk on metamorphosis in the red-eyed treefrog, Agalychnis callidryas. We raised tadpoles in the presence or absence of cues from caged water bugs fed larvae and cues from spiders fed emerging metamorphs. Water bugs are effective larval predators, while spiders are poor larval predators but prey on metamorphs. Furthermore, since spiders forage on the water surface it is possible that tadpoles could assess future risk from this predator. Predators induced opposite shifts in life history. Tadpoles emerged smaller and less developed in response to water bugs, but later and larger in response to spiders. Interestingly, predator effects on larval duration were not independent; tadpoles delayed emerging in response to spiders, but only in the absence of water bugs.     

Computer-based training for safety: comparing methods with older and younger workers

INTRODUCTION: Computer-based safety training is becoming more common and is being delivered to an increasingly aging workforce. Aging results in a number of changes that make it more difficult to learn from certain types of computer-based training. Instructional designs derived from cognitive learning theories may overcome some of these difficulties. METHODS: Three versions of computer-based respiratory safety training were shown to older and younger workers who then took a high and a low level learning test. RESULTS: Younger workers did better overall. Both older and younger workers did best with the version containing text with pictures and audio narration. DISCUSSION: Computer-based training with pictures and audio narration may be beneficial for workers over 45 years of age. IMPACT ON INDUSTRY: Computer-based safety training has advantages but workers of different ages may benefit differently. Computer-based safety programs should be designed and selected based on their ability to effectively train older as well as younger learners.     

Development and Application of Critical,Target and Monitoring Loads for the Management of Acid Deposition in Alberta,Canada

The Alberta, Canada acid deposition management framework, based upon the application of critical, target and monitoring loads, is described. This framework is the culmination of four years work by stakeholders brought together within Alberta's Clean Air Strategic Alliance (CASA). The elements of the framework include scientific aspects of measurement, model estimation, and monitoring of acid deposition, assessment of receptor sensitivity, and management processes to reduce emissions and deposition (should reductions become necessary). All loads are applied to grid cells measuring 1°latitude × 1° longitude, with each cell being categorized as sensitive, moderately sensitive or of low sensitivity on the basis of the sensitivities of the soil and water systems within the cell. Critical loads have been set at 0.25, 0.50 and 1.00 keq H⁺ ha^-1 yr^-1 for grid cells that are categorized as sensitive, moderately sensitive, and of low sensitivity, respectively. Target loads, the environmental management objectives, have been set at 0.22, 0.45, and 0.90 keq H⁺ ha^-1 yr^-1, and monitoring loads, a new concept in acid deposition management, have been set at 0.17, 0.35 and 0.70 keq H⁺ ha^-1 yr^-1 for the three sensitivity classes. When model prediction indicates that deposition may be exceeding the monitoring load, deposition monitoring and receptor sensitivity studies are to be initiated to confirm the deposition model prediction, and to ensure that the sensitivity of the recipient systems is understood. In this manner, management actions that occur in the event of a target load exceedance will be based upon receptor sensitivity and deposition data rather than upon model prediction alone. A process for stakeholder involvement in the evaluation of the framework and its application in long-term, long-range management of emissions and deposition is also included within the framework.     

Alum split applications strengthened phosphorus fixation and phosphate sorption in high legacy phosphorus calcareous soil

High phosphorus (P) saturation arising from historic P inputs to protected vegetable fields (PVFs) drives high P mobilisation to waterbodies. Amendment of soils with alum has shown potential in terms of fixing labile P and protecting water quality. The present 15 month pot experiment investigated P stabilisation across single alum application (Alum-1 treatment, 20 g alum/kg soil incorporated into soil before the maize was sown), alum split applications (Alum-4 treatment, 5 g alum/kg soil incorporated into soil before each crop was sown i.e. 4 × 5 g/kg) and soil only treatment (Control). Results showed that the Alum-1 treatment caused the strongest stabilisation of soil labile P after maize plant removal, whereas the P stabilisation effect was gradually weakened due to the transformation of soil non-labile P to labile P and the reduced active Al³⁺ in soil solution. For the Alum-4 treatment, soil labile P decreased gradually with each crop planting and was lower than the Alum-1 treatment at the end of the final crop removal, without any impairment on plant growth. The better P stabilisation at the end of Alum-4 treatment was closely correlated with a progressive supply of Al³⁺ and a gradual decrease of pH, which resulted in higher contents of poorly-crystalline Al, Fe and exchangeable Ca. These aspects were conducive to increasing the soil P stabilisation and phosphate sorption. In terms of management, growers in continuous cropping systems could utilise split alum applications as a strategy to alleviate P losses in high-P enriched calcareous soil.     

Pyrrhic victories: the cost to the board of ousting the CEO

Going against anecdotal evidence and common perception, the findings presented here show that boards who take action against their CEOs do so only at great cost to themselves, winning only a pyrrhic victory. Indeed, the findings presented show three distinct levels of board turnover. Normal attrition in periods of continuity produced a turnover of 10.99 per cent over two years; routine retirement exists (22.35 per cent) produced a similar turnover level to forced exits which did not imply a failure of the board to perform its monitoring function (25.36 per cent). However, forced CEO exits which implied a failure in the board's monitoring and advising roles caused a dramatically higher level of subsequent board turnover (40.55 per cent). These findings demonstrate that is not only the CEO that is forced to sacrifice his or her job when a company is in distress, but that the board is also accountable for its failure to perform its monitoring and advising duties adequately. Copyright © 1999 John Wiley & Sons, Ltd.     

Enhanced removal of mercury and lead by a novel and efficient surface-functionalized imogolite with nanoscale zero-valent iron material

Environmental Science and Pollution Research - A novel hybrid nanomaterial, nanoscale zero-valent iron (nZVI)-grafted imogolite nanotubes (Imo), was synthesized via a fast and straightforward...