Social Security and Unsecured Debt

Most young households simultaneously hold both unsecured debt on which they pay an average of 10 percent interest and social security wealth on which they earn less than 2 percent. We document this fact using data from the Panel Study of Income Dynamics. We then consider a life-cycle model with optimizing and rule-of-thumb' households and explore ways to reduce this inefficiency. We show that both allowing households to use social security wealth to pay off debt and exempting young households from social security contributions (but in both cases requiring higher contributions later later in life) leads to increases in welfare for both types of households and significant increases in consumption and saving, and reductions in debt, for optimizing households.

An entero-mesenteric bridging operation for bypassing lymphatic obstruction

Imperial Users onl

Semiclassical Vlasov and fluid models for an electron gas with spin effects

We derive a four-component Vlasov equation for a system composed of spin-1/2 fermions (typically electrons). The orbital part of the motion is classical, whereas the spin degrees of freedom are treated in a completely quantum-mechanical way. The corresponding hydrodynamic equations are derived by taking velocity moments of the phase-space distribution function. This hydrodynamic model is closed using a maximum entropy principle in the case of three or four constraints on the fluid moments, both for Maxwell-Boltzmann and Fermi-Dirac statistics.Comment: To appear in the European Physical Journal D, Topical Issue "Theory and Applications of the Vlasov Equation

Magnetic moment generation in small gold nanoparticles via the plasmonic inverse Faraday effect

We theoretically investigate the creation of a magnetic moment in gold nanoparticles by circularly polarized laser light. To this end, we describe the collective electron dynamics in gold nanoparticles using a semiclassical approach based on a quantum hydrodynamic model that incorporates the prin- cipal quantum many-body and nonlocal effects, such as the electron spill-out, the Hartree potential, and the exchange and correlation effects. We use a variational approach to investigate the breathing and the dipole dynamics induced by an external electric field. We show that gold nanoparticles can build up a static magnetic moment through the interaction with a circularly polarized laser field. We analyze that the responsible physical mechanism is a plasmonic, orbital inverse Faraday effect, which can be understood from the time-averaged electron current that contains currents rotating on the nanoparticles surface. The computed laser-induced magnetic moments are sizeable, of about 0.35 muB/atom for a laser intensity of 450 GW/cm2 at plasmon resonance

Configurator--a configuation program for satellite dish hardware

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (p. 72-73).by Mark Paul Hurst.M.S

The Guidebook, the Friend, and the Room: Visitor Experience in a Historic House

In this paper, we describe an electronic guidebook prototype and report on a study of its use in a historic house. Supported by mechanisms in the guidebook, visitors constructed experiences that had a high degree of interaction with three entities: the guidebook, their companions, and the house and its contents. For example, we found that most visitors played audio descriptions played through speakers (rather than using headphones or reading textual descriptions) to facilitate communication with their companions

Spin current generation by ultrafast laser pulses in ferromagnetic nickel films

International audienceA semiclassical phase-space model is used to study the ultrafast charge and spin dynamics in thin ferromagnetic films. Both itinerant and localized magnetism are taken into account. It is shown that an oscillating spin current can be generated in the film via the application of a femtosecond laser pulse in the visible range