THE ROLE OF FARM OWNERSHIP IN OFF-FARM WORK PARTICIPATION

A labor supply model is used to examine the relationship between farm ownership and operators' participation in the off-farm labor market for the Northeast region. The results indicate that ownership significantly influences operators' off-farm employment participation. In particular, part-owners significantly allocate labor services to off-farm activities. The results also show that the participation rate among part-owner operators is high partly because the availability of other income sources accelerates the process of acquiring assets to become full-owner operators.Labor and Human Capital,

SEARCH THEORY RISK PREFERENCE AND FARMLAND PRESERVATION

This paper uses search theory to examine the role that risk preference (RP) plays in farmland preservation. Assuming that the distribution of the offer price is fixed, the analysis indicates that risk-averse agents have lower reservation prices than risk-neutral agents, and that agricultural land held by the former exits farming at a faster rate. The results also show that farmland preservation policies which increase reservation prices have a greater capitalization effect if agents are risk-loving, and that such policies, while effectively protecting the interest of land speculators, may be less effective in serving the needs of farming and farm-held open space.Risk and Uncertainty,

Validation of 3D Model-Based Maximum-Likelihood Estimation of Normalisation Factors for Partial Ring Positron Emission Tomography

The next generation of organ specific Positron Emission Tomography (PET) scanners, e.g. for breast imaging, will use partial ring geometries. We propose a component-based Maximum-Likelihood (ML) estimation of normalisation factors for 3D PET data reconstruction applicable to partial ring geometries. This method is based on the Software for Tomographic Image Reconstruction (STIR) for full ring PET and is validated for a stationary partial ring scanner. The model includes the estimation for crystal efficiencies and geometric factors. The algorithm is validated using Maximum Likelihood Estimation Method (MLEM) based 3D reconstruction in STIR using Geant4 Application for Tomographic Emission (GATE) simulation data for full and partial ring scanners and experimental data from a demonstrator with partial ring geometry. The uniformity of the reconstructed images of simulated cylindrical and NEMAIQ phantoms in both scanner geometries and the image of a line source in the partial ring demonstrator is assessed. The results have shown that uniform images in both axial and transaxial directions are obtained after applying the estimated normalisation factors. The accuracy of the algorithm is validated by comparing the normalisation factors between the full and partial ring systems in simulation. We have shown that the estimated normalisation factors are almost identical, even though the separate components are not. This proves that the ML estimation of the 3D normalisation factors is valid and can be applied to the partial ring scanner

Aspects of Two-Photon Physics at Linear e+e- Colliders

We discuss various reactions at future e+e- and gamma-gamma colliders involving real (beamstrahlung or backscattered laser) or quasi--real (bremsstrahlung) photons in the initial state and hadrons in the final state. The production of two central jets with large pT is described in some detail; we give distributions for the rapidity and pT of the jets as well as the di--jet invariant mass, and discuss the relative importance of various initial state configurations and the uncertainties in our predictions. We also present results for `mono--jet' production where one jet goes down a beam pipe, for the production of charm, bottom and top quarks, and for single production of W and Z bosons. Where appropriate, the two--photon processes are compared with annihilation reactions leading to similar final states. We also argue that the behaviour of the total inelastic gamma-gamma cross section at high energies will probably have little impact on the severity of background problems caused by soft and semi--hard (`minijet') two--photon reactions. We find very large differences in cross sections for all two--photon processes between existing designs for future e+e- colliders, due to the different beamstrahlung spectra; in particular, both designs with >1 events per bunch crossing exist.Comment: 51 pages, 13 figures(not included