A Model of Producer Incentives for Livestock Disease Management

We examine the management of livestock diseases from the producers' perspective, incorporating information and incentive asymmetries between producers and regulators. Using a dynamic model, we examine responses to different policy options including indemnity payments, subsidies to report at-risk animals, monitoring, and regulatory approaches to decreasing infection risks when perverse incentives and multiple policies interact. This conceptual analysis illustrates the importance of designing efficient combinations of regulatory and incentive-based policies.livestock disease, asymmetric information, reporting, indemnities, risk management, Livestock Production/Industries, C61, D82, Q12, Q18, Q28,

Bisphosphonate-related bilateral atypical femoral fractures : be aware and beware

Although bisphosphonates have a well established therapeutic role in the prevention of osteoporosis-related fractures, several reports published over the past 5-6 years suggest a possible causative relationship between long-term use of bisphosphonates and development of ‘atypical’ subtrochanteric and femoral diaphyseal fractures. A high level of clinical suspicion and prompt imaging when these patients present with groin/thigh pain should lead to a timely diagnosis. Appropriate elective management to mitigate against the increased risks of these fractures becoming complete could then be instituted. We present a case of complete bilateral atypical subtrochanteric fractures in a patient on long-term bisphosphonates for osteoporosis. Our objective is to highlight the fracture risk of this patient population; present the current knowledge; and discuss the dilemmas in management of both femora.peer-reviewe

What Drives Land-Use Change in the United States? A National Analysis of Landowner Decisions

Land-use changes involve important economic and environmental effects with implications for international trade, global climate change, wildlife, and other policy issues. We use an econometric model to identify factors driving land-use change in the United States between 1982 and 1997. We quantify the effects of net returns to alternative land uses on private landowners’ decisions to allocate land among six major uses, drawing on detailed micro-data on land use and land quality that are comprehensive of the contiguous U.S. This analysis provides the first evidence of the relative historical importance of markets and Federal farm policies affecting land-use changes nationally.Land Use, Land-Use Change, Econometric Analysis, Simulations

On marginal deformation of WZNW model and PP-wave limit of deformed AdS3×S3AdS_{3}\times S^{3} string geometry

We discuss the Penrose limit of the classical string geometry obtained from a truly marginal deformation of $SL(2)\otimes SU(2)$ WZNW model.Comment: 10 pages, late

Extent, Location, and Characteristics of Land Cropped Due to Insurance Subsidies

We examine changes in land use caused by the large increase in crop insurance premium subsidies under the 1994 Federal Crop Insurance and Reform Act (FCIRA). We use a conditional logit model to estimate changes in six major land uses from 1992 and 1997 as a function of the change in expected return to crop insurance. Our data on individual land parcels across the entire coterminous United States enable identification of the extent, location, and physical characteristics of the land brought into and retained in production as a result of the crop insurance policies. Results indicate the additional crop insurance premium subsidies increased cultivated cropland area on the order of 1.9 million acres (0.6%), consistent with the lower range of previous estimates of crop insurance acreage effects. The estimated lands in production due to the subsidy increases are of lower quality than cropland overall in term of both Land Capability Classification and proneness to flooding, as well as more environmentally sensitive in terms of erodibility and proportion in wetlands.Land Economics/Use,

The 1996 Federal Agriculture Improvement and Reform Act: Correcting a Distortion?

This study makes use of farm-level data from the Agricultural Census to evaluate the effects of the 1996 Federal Agriculture Improvement and Reform (FAIR) Act, which intended to "decouple" commodity payments from production decisions. Prior to this Act, agricultural support payments were linked to production decisions via prices and a complex set of restrictions that acted to control the supply of agricultural commodities. We compare farm-level 1992-to-1997 changes in commodity crop plantings of farms that participated in government programs with farms that did not participate. We find that the growth rate of program-crop acreage of non-participants was 19 percentage points below that of participants. This estimated difference remains unchanged after we account for unobserved effects relating to farm size, type, location, and interactions of these factors using over 1900 fixed-effects variables. These results may imply that program participation rules associated with pre-1996 programs effectively acted to limit program acreage in 1992. An alternative explanation is that payments associated with decoupled programs instituted with the 1996 Act were in fact distortionary and induced farmers to produce more than they would have without the payments. Additional research would be needed to test these competing theories.Agricultural and Food Policy,

Prevention or Control: Optimal Government Policies for Invasive Species Management

We present a conceptual, but empirically applicable, model for determining the optimal allocation of resources between exclusion and control activities for managing an invasive species with an uncertain discovery time. This model is used to investigate how to allocate limited resources between activities before and after the first discovery of an invasive species and the effects of the characteristics of an invasive species on limited resource allocation. The optimality conditions show that it is economically efficient to spend a larger share of outlays for exclusion activities before, rather than after, a species is first discovered, up to a threshold point. We also find that, after discovery, more exclusionary measures and fewer control measures are optimal, when the pest population is less than a threshold. As the pest population increases beyond this threshold, the exclusionary measures are no longer optimal. Finally, a comparative dynamic analysis indicates that the efficient level of total expenditures on preventive and control measures decreases with the level of the invasive species stock and increases with the intrinsic population growth rate, the rate of additional discoveries avoided, and the maximum possible pest population.invasive species, exclusion, control, eradication, public expenditures, Environmental Economics and Policy, Resource /Energy Economics and Policy,

Negative compressibility

Rearch financed by the Malta Council for Science and Technology and CHISMACOMB (an EU FP6 STREP project).Structures made up from bi-material elements which can exhibit negative properties, in particular negative compressibility (negative bulk modulus, i.e. expand in size when the external pressure is increased and shrink when the external pressure is decreased) are proposed. This anomalous behaviour is confirmed through finite element modelling.peer-reviewe

Point-actuated feedback control of multidimensional interfaces

We consider the application of feedback control strategies with point actuators to stabilise desired interface shapes. We take a multidimensional Kuramoto--Sivashinsky equation as a test case; this equation arises in the study of thin liquid films, exhibiting a wide range of dynamics in different parameter regimes, including unbounded growth and full spatiotemporal chaos. In the case of limited observability, we utilise a proportional control strategy where forcing at a point depends only on the local observation. We find that point-actuated controls may inhibit unbounded growth of a solution, if they are sufficient in number and in strength, and can exponentially stabilise the desired state. We investigate actuator arrangements, and find that the equidistant case is optimal, with heavy penalties for poorly arranged actuators. We additionally consider the problem of synchronising two chaotic solutions using proportional controls. In the case when the full interface is observable, we construct feedback gain matrices using the linearised dynamics. Such controls improve on the proportional case, and are applied to stabilise non-trivial steady and travelling wave solutions