Reflexive insensitive modal logics

We analyze a class of modal logics rendered insensitive to reflexivity by way of a modification to the semantic definition of the modal operator. We explore the extent to which these logics can be characterized, and prove a general completeness theorem on the basis of a translation between normal modal logics and their reflexive-insensitive counterparts. Lastly, we provide a sufficient semantic condition describing when a similarly general soundness result is also available

Use of a Simple Age-Structured Bioeconomic Model to Estimate Optimal Long-Run Surpluses

When the New Zealand government introduced individual transferable quotas for major commercial fish stocks, the initial allocation for some stocks exceeded their total allowable catches and made it necessary to buy back immediately some of the quota. Quota was offered back by tender. A simple age-structured bioeconomic model was used to estimate long-run optimal surpluses. From these, the maximum prices that should be paid by government for quota were derived. The use of an age-structured model proved convenient for this purpose as the necessary parameter estimates tend to arise naturally from literature sources and the population dynamics are transparent. If stocks were managed optimally, the long-run value of quota would be equivalent to the net present value of the surplus at the dynamic maximum economic yield. Long-run surpluses proved to be dependent on the relative changes in catch rates and costs of fishing which resulted from changes in stock biomass. Optimal surpluses of up to 45% of the greenweight revenues were obtained for heavily exploited, long-lived stocks. Only small long-run surpluses were obtained for short-lived or very lightly exploited stocks.Environmental Economics and Policy, Resource /Energy Economics and Policy,

Allocating Transmission to Mitigate Market Power in Electricity Networks

Allocating Transmission to Mitigate Market Power in Electricity Network

The Design of a Carbon Tax

We consider the design of a tax on greenhouse gas emissions for a developed country such as the United States. We consider three sets of issues: the optimal tax base, issues relating to the rate (including the use of the revenues and rate changes over time) and trade. We show that a well-designed carbon tax can capture about 80% of U.S. emissions by taxing fewer than 3,000 taxpayers and up to almost 90% with a modest additional cost. We recommend full or partial delegation of rate setting authority to an agency to ensure that rates reflect new information about the costs of carbon emissions and of abatement. Adjustments should be made to the income tax to ensure that a carbon tax is revenue neutral and distributionally neutral. Finally, we propose an origin-based system for trade with countries that have an adequate carbon tax and a system of border taxes for imports from countries without a carbon tax. We suggest a system that imposes presumptive border tax adjustments with the ability of an individual firm to prove that a different rate should apply. The presumptive tax could be based either on average emissions for production of the item by the exporting country or by the importing country.

Tahiti sea level : the last deglacial sea level rise in the South Pacific

Integrated Ocean Drilling Program (IODP) Expedition 310 to the reef terraces around Tahiti, French Polynesia, was the second expedition to utilize a mission-specific platform (MSP) and was conducted by the European Consortium for Ocean Research Drilling (ECORD) Science Operator (ESO). The objectives of Expedition 310 are to establish the course of postglacial sea level rise at Tahiti, to define sea-surface temperature (SST) variations for the region over the period 20–10 ka, and to analyze the impact of sea level changes on reef growth and geometry. To meet these objectives, the postglacial reef sequence, which consists of successive reef terraces seaward of the living barrier reef, was cored from a dynamically positioned vessel during October and November 2005. A total of 37 boreholes across 22 sites were cored in water depths ranging from 41.65 to 117.54 m. Borehole logging operations in 10 boreholes provided continuous geophysical information about the drilled strata. The cores were described during the Onshore Science Party at the IODP Bremen Core Repository during February and March 2006, where minimum and some standard measurements were made. Further postcruise research on samples taken during the Onshore Science Party are expected to fulfill the objectives of the expedition

Mediating Market Power in Electricity Networks

We ask under what conditions transmission contracts increase or mitigate market power. We show that the allocation process of transmission rights is crucial. In an efficiently arbitraged uniform price auction generators will only obtain contracts that mitigate their market power. However, if generators inherit transmission contracts or buy them in a 'pay-as-bid' auction, then these contracts can enhance market power. In the two-node network case banning generators from holding transmission contracts that do not correspond to delivery of their own energy mitigates market power. Meshed networks differ in important ways as constrained links no longer isolate prices in competitive markets from market manipulation. The paper suggests ways of minimizing market power considerations when designing transmission contracts.

Comparing distance education and conventional education: Observations from a comparative study of post‐registration nurses

This retrospective study presents a comparison of assessment results achieved by distance‐learning students and classroom‐based students undertaking the same module in a degree course. The purpose of the comparison is to provide some objective measurement of the quality of distance education in relation to conventional classroom‐based education. The authors have selected three groups of students, who have all undertaken the same module in the B. Sc Health Studies degree programme offered by the University of Paisley. One group (in Paisley) undertook their studies by means of conventional classroom‐based education, the second (in Hong Kong) by supported distance learning with face‐to‐face contact in the form of tutorials, and the third (in a geographically dispersed group in the United Kingdom and other countries) by supported distance learning with no face‐to‐face contact. The results obtained by these three groups of students were analysed. Because of the differences in the size of the groups, the Kruskal‐ Wallis 1‐ Way Anova test was applied to validate the face value findings. The authors include findings from the literature comparing distance education with conventional education and from cross‐cultural studies to present their data in context. Analysis of the assessment results showed that students from all three groups were successful in their studies, but the students studying by distance learning obtained significantly higher end‐of‐module results than their classroom‐based colleagues. This latter finding reflects the conclusion that other investigators have reached In their discussion the authors identify educational, cultural and personal factors that may help to explain their findings. A limitation in the study is that it concerns only one module in the degree programme. The research now moves on to comparing students who have undertaken the whole degree programme by the means describe

Measuring logarithmic corrections to normal diffusion in infinite-horizon billiards

We perform numerical measurements of the moments of the position of a tracer particle in a two-dimensional periodic billiard model (Lorentz gas) with infinite corridors. This model is known to exhibit a weak form of super-diffusion, in the sense that there is a logarithmic correction to the linear growth in time of the mean-squared displacement. We show numerically that this expected asymptotic behavior is easily overwhelmed by the subleading linear growth throughout the time-range accessible to numerical simulations. We compare our simulations to the known analytical results for the variance of the anomalously-rescaled limiting normal distributions.Comment: 10 pages, 4 figure