The scope for biomanipulation in improving water quality

Biomanipulation is a form of biological engineering in which organisms are selectively removed or encouraged to alleviate the symptoms of eutrophication. Most examples involve fish and grazer zooplankton though mussels have also been used. The technique involves continuous management in many deeper lakes and is not a substitute for nutrient control. In some lakes, alterations to the lake environment have given longer-term positive effects. And in some shallow lakes, biomanipulation may be essential, alongside nutrient control, in re- establishing former aquatic-plant-dominated ecosystems which have been lost through severe eutrophication. The emergence of biomanipulation techniques emphasises that lake systems are not simply chemical reactors which respond simply to engineered chemical changes, but very complex and still very imperfectly understood ecosystems which require a yet profounder understanding before they can be restored with certainty

Beltway: Getting Around Garbage Collection Gridlock

We present the design and implementation of a new garbage collection framework that significantly generalizes existing copying collectors. The Beltway framework exploits and separates object age and incrementality. It groups objects in one or more increments on queues called belts, collects belts independently, and collects increments on a belt in first-in-first-out order. We show that Beltway configurations, selected by command line options, act and perform the same as semi-space, generational, and older-first collectors, and encompass all previous copying collectors of which we are aware. The increasing reliance on garbage collected languages such as Java requires that the collector perform well. We show that the generality of Beltway enables us to design and implement new collectors that are robust to variations in heap size and improve total execution time over the best generational copying collectors of which we are aware by up to 40%, and on average by 5 to 10%, for small to moderate heap sizes. New garbage collection algorithms are rare, and yet we define not just one, but a new family of collectors that subsumes previous work. This generality enables us to explore a larger design space and build better collectors

Gaugino condensation in an improved heterotic M-theory

Gaugino condensation is discussed in the context of a consistent new version of low energy heterotic M-theory. The four dimensional reduction of the theory is described, based on simple boson and fermion backgrounds. This is generalised to include gaugino condenstates and various background fluxes, some with non-trivial topology. It is found that condensate and quantised flux contributions to the four-dimensional superpotential contain no corrections due to the warping of the higher dimensional metric.Comment: 11 pages, 4 figures, LaTe

A HYPERBOLIC TANGENT YIELD FUNCTION OF FLORIDA CITRUS

This study models Florida citrus production as a function of the age profile of a given tree stock. The age relationship is estimated using a modified hyperbolic tangent function and the parameters is solved by Spatial Process Models and Maximum Likelihood approach. The estimation is based on the production data of four citrus varieties in 25 regions of Florida from 1992 to 2005. The results show smooth S-shaped yield curves of Florida citrus. This analysis offers yield function of citrus as the first step for statistical modeling of the risks associated with citrus cancers aimed at pricing insurance rates.yield function, citrus, hyperbolic tangent, insurance, spatial autoregressive, Demand and Price Analysis,

VERTICAL INTEGRATION AND TRADE POLICY: THE CASE OF SUGAR

The degree of vertical integration in the U.S. sugar industry between raw sugar processing and sugar refining cannot be explained using theories of vertical integration based on transaction costs (e.g. Williamson). We graphically decompose the economic rents accruing to each level in the marketing channel. Different strategies of several major sugar producing, processing and refining entities with regard to sugar quota policy are explored.Agribusiness, Industrial Organization,

The Effect of Consumption Based Taxes on Agriculture in the United States

Recently several proposals have arisen to replace the current income tax system in the United States with a consumption based or Fair Tax. This study investigates the effect of such a consumption based tax on agricultural investment decisions using stochastic optimal control to model the investment decision at the farm level. The results indicate that a consumption tax rate of 25.9 percent would be equivalent to the income tax rate paid by very large producers in the United States.Public Economics,

Using APT to Assess the Impact of Farm Policy on Agribusiness Stocks

This study investigates the impact of differing U. S. Farm Policy regimes on the stock prices of publicly traded agribusinesses. Following the Roll and Ross approach, we apply a two step Arbitrage Pricing Model (APM). We analyze the effect of agricultural policy on returns to agribusiness by applying a modified APM to agricultural returns to test for the presence of an agribusiness premium or discount. We further augment our analysis by dividing the sample into two time periods around the implementation of the 1996. The differences in agribusiness premium can then be tested using a paired t-test. The empirical evidence lends support to a switch from negative returns to agribusiness stocks pre-FAIR Act to positive returns to agribusiness stocks after its enactment.Agribusiness, Agricultural and Food Policy,

Rethinking the Role of History in Law & Economics: The Case of the Federal Radio Commission in 1927

In the study of law and economics, there is a danger that historical inferences from theory may infect historical tests of theory. It is imperative, therefore, that historical tests always involve a vigorous search not only for confirming evidence, but for disconfirming evidence as well. We undertake such a search in the context of a single well-known case: the Federal Radio Commission's (FRC's) 1927 decision not to expand the broadcast radio band. The standard account of this decision holds that incumbent broadcasters opposed expansion (to avoid increased competition) and succeeded in capturing the FRC. Although successful broadcaster opposition may be taken as confirming evidence for this interpretation, our review of the record reveals even stronger disconfirming evidence. In particular, we find that every major interest group, not just radio broadcasters, publicly opposed expansion of the band in 1927, and that broadcasters themselves were divided at the FRC's hearings.

QUANTIFYING GAINS TO RISK DIVERSIFICATION USING CERTAINTY EQUIVALENCE IN A MEAN-VARIANCE MODEL: AN APPLICATION TO FLORIDA CITRUS

The marginal benefit and cost of diversification for Florida orange producers is analyzed using certainty equivalents. Results indicate that for moderate and high levels of risk aversion, diversification into strawberry, grapefruit, or additional orange production is not optimal. However, moderately risk averse Florida orange producers can gain by diversifying into grapefruit production if the annual amortized fixed costs can be reduced by as little as 10 percent.Risk and Uncertainty,