Framing the Issues: Economic Research on Employment Policy for People with Disabilities

This paper is designed to serve as a vehicle to engage the broad policy community in a discussion about proposed research to be conducted at Cornell’s Rehabilitation Research and Training Center (RRTC) for Economic Research on Employment Policy for Persons with Disabilities. The paper provides a brief introduction of the purpose of RRTCs followed by a description of the research projects to be conducted over the next five years. Because the projects are in the formative stage, suggestions about information that is most useful to the policy community will aid in targeting the research

Dynamical Mean-Field Study of the Ferromagnetic Transition Temperature of a Two-Band Model for Colossal Magnetoresistance Materials

The ferromagnetic (FM) transition temperature (Tc) of a two-band Double-Exchange (DE) model for colossal magnetoresistance (CMR) materials is studied using dynamical mean-field theory (DMFT), in wide ranges of coupling constants, hopping parameters, and carrier densities. The results are shown to be in excellent agreement with Monte Carlo simulations. When the bands overlap, the value of Tc is found to be much larger than in the one-band case, for all values of the chemical potential within the energy overlap interval. A nonzero interband hopping produces an additional substantial increase of Tc, showing the importance of these nondiagonal terms, and the concomitant use of multiband models, to boost up the critical temperatures in DE-based theories.Comment: 4 pages, 4 eps figure

Spin Dynamics of Double-Exchange Manganites with Magnetic Frustration

This work examines the effects of magnetic frustration due to competing ferromagnetic and antiferromagnetic Heisenberg interactions on the spin dynamics of the double-exchange model. When the local moments are non-colinear, a charge-density wave forms because the electrons prefer to sit on lines of sites that are coupled ferromagnetically. With increasing hopping energy, the local spins become aligned and the average spin-wave stiffness increases. Phase separation is found only within a narrow range of hopping energies. Results of this work are applied to the field-induced jump in the spin-wave stiffness observed in the manganite Pr$_{1-x}$Ca$_x$MnO$_3$ with $0.3 \le x \le 0.4$.Comment: 10 pages, 3 figure

Semiclassical Accuracy in Phase Space for Regular and Chaotic Dynamics

A phase-space semiclassical approximation valid to $O(\hbar)$ at short times is used to compare semiclassical accuracy for long-time and stationary observables in chaotic, stable, and mixed systems. Given the same level of semiclassical accuracy for the short time behavior, the squared semiclassical error in the chaotic system grows linearly in time, in contrast with quadratic growth in the classically stable system. In the chaotic system, the relative squared error at the Heisenberg time scales linearly with $\hbar_{\rm eff}$, allowing for unambiguous semiclassical determination of the eigenvalues and wave functions in the high-energy limit, while in the stable case the eigenvalue error always remains of the order of a mean level spacing. For a mixed classical phase space, eigenvalues associated with the chaotic sea can be semiclassically computed with greater accuracy than the ones associated with stable islands.Comment: 9 pages, 6 figures; to appear in Physical Review

Oil vulnerability in Melbourne

Peak Oil and Climate Change present serious challenges to governments and planners. The sprawling auto based city, which is the model upon which Australian cities have grown is particularly unsuited to a situation of decreasing oil availability and a need to reduce carbon emissions. The aim of this study is to investigate and expose possible variations in the spatial distribution of oil vulnerability in Melbourne. This study assesses vehicle ownership and usage characteristics by local government area (LGA), using data collected by the Victorian Department of Transport's Victorian Integrated Survey of Travel and Activity (VISTA) analysis. An Oil Vulnerability Index has been created and its application suggests that the fast growing outer suburbs of Melbourne are particularly vulnerable to oil price rises. Outer Suburban LGAs were found to have lower average incomes and travel by car more frequently and for longer distances. Future petrol price increases are likely to place stress on household expenditure, mobility and even the long-term viability of some suburbs

Acceleration Mechanics in Relativistic Shocks by the Weibel Instability

Plasma instabilities (e.g., Buneman, Weibel and other two-stream instabilities) created in collisionless shocks may be responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated long-term particle acceleration associated with relativistic electron-ion or electron-positron jet fronts propagating into an unmagnetized ambient electron-ion or electron-positron plasma. These simulations have been performed with a longer simulation system than our previous simulations in order to investigate the nonlinear stage of the Weibel instability and its particle acceleration mechanism. The current channels generated by the Weibel instability are surrounded by toroidal magnetic fields and radial electric fields. This radial electric field is quasi stationary and accelerates particles which are then deflected by the magnetic field.Comment: 17 pages, 5 figures, accepted for publication in ApJ, A full resolution ot the paper can be found at http://gammaray.nsstc.nasa.gov/~nishikawa/accmec.pd

Thermodynamic Consistency of the Dynamical Mean-Field Theory of the Double-Exchange Model

Although diagrammatic perturbation theory fails for the dynamical-mean field theory of the double-exchange model, the theory is nevertheless Phi-derivable and hence thermodynamically consistent, meaning that the same thermodynamic properties are obtained from either the partition function or the Green's function. We verify this consistency by evaluating the magnetic susceptibility and Curie temperature for any Hund's coupling.Comment: 9 pages, 1 figur

The customer isn\u27t always right: Limitations of \u27customer service\u27 approaches to education or why Higher Ed is not Burger King

The increasingly popular trend of conceptualising education in terms of \u27customer service\u27 is, in some ways, attractive. It encourages educators to think in terms of meeting students\u27 needs and to develop innovative ways to deliver their product. In other ways, however, it fails to convey the essential collaborative, participatory, reciprocal relationship that is central to effective teaching and learning. With respect to academic integrity, the customer service model also obscures students\u27 roles and responsibilities. In this paper, we identify some of the ways this model provides an inappropriate metaphor for understanding the project of teaching and learning (i.e., education) and argue that, when embraced uncritically, the model has the potential both to undermine education and at the same time derail efforts to develop and sustain a culture of integrity. After identifying this model\u27s shortcomings, we suggest ways to develop and promote a more robust model in which faculty and students work together toward a shared purpose while recognising and embracing their interlocking responsibilities