THE IMPACT OF SELECTED HEDGING STRATEGIES ON THE CASH FLOW POSITION OF CATTLE FEEDERS

Agricultural Finance,

Canonical Models of Dielectric Response

The interaction of electromagnetic fields with a solid is characterized by several interconnected response functions: the dielectric function ε(ω), index of refraction N(ω), conductivity σ(ω), and optical impedance Z(ω). Here we utilize three canonical models of dielectric response -- the damped harmonic oscillator, Debye polarization response, and the Drude model -- to discuss these four optical response functions. Special emphasis is devoted to the response of a Drude metal. Our main focus is on electromagnetic wave propagation through a material. We also discuss the relaxation of charge fluctuations within the context of the three canonical models of response

Classical Fano Oscillator

Starting from the quantum-mechanical Fano-Anderson Hamiltonian, we derive classical equations of motion for coordinates associated with the discrete and continuum states. The frequency-dependent absorption spectrum associated with this classical system exhibits the same Fano line shape as the quantum-mechanical system when appropriate correspondences between classical and quantum variables are made. In the time domain, the response of this classical Fano oscillator depends upon the asymmetry parameter q that appears in the expression for the Fano line shape. In particular, under the influence of impulsive driving of the system, the discrete oscillator\u27s phase changes by ±π/2 as q increases from zero (maximum asymmetry in the frequency domain) to ∓∞ (minimum asymmetry). Previously published ultrafast-laser-pulse-driven coherent-phonon oscillations in degenerate p-type Si [ K. Kato et al. Jpn. J. Appl. Phys. 48 100205 (2009)] are discussed in light of these theoretical results

Temperature Dependence of Silicon Carrier Effective Masses with Application to FemtosecondReflectivity Measurements

The conductivity effective masses of electrons and holes in Si are calculated for carrier temperatures from 1 to 3000 K. The temperature dependence of the electron mass is calculated by use of a phenomenological model of conduction-band nonparabolicity that has been fitted to experimental measurements of the dependence of the electron conductivity effective mass on carrier concentration. The hole mass is investigated by tight-binding calculations of the valence bands, which have been adjusted to match experimental values of the valence-band curvature parameters at the top of the valence band. The calculations are in excellent agreement with femtosecond-laser reflectivity measurements of the change in optical effective mass as hot carriers cool from 1550 to 300 K

An Embedded-Atom-Method Model for Alkali-Metal Vibrations

We present an embedded-atom-method (EAM) model that accurately describes vibrational dynamics in the alkali metals Li, Na, K, Rb, and Cs. Bulk dispersion curves, frequency-moment Debye temperatures, and temperature-dependent entropy Debye temperatures are all in excellent agreement with experimental results. The model is also well suited for studying surface vibrational dynamics in these materials, as illustrated by calculations for the Na(110) surface

Ta(110) Surface and Subsurface Core-level Shifts and 4f7/2 Lineshapes

High-resolution 4f core-level spectra of the Ta(110) surface region have been obtained at 80 and 300 K with 70- and 100-eV synchrotron radiation. The data show that the subsurface core-level binding-energy shift (compared to deeper-lying atoms) for a close-packed bcc(110) surface can be substantial: 65±15 meV for the first underlayer atoms of Ta(110). The surface core-level shift is 360±12 meV at 80 K and decreases by 13±2 meV at 300 K. Final-state screening in both the bulk and surface layers is well described by a constant singularity index of 0.133±0.012. An enhanced phonon broadening at the surface corresponds to a reduced perpendicular Debye temperature for the surface atoms of 128±18 K compared to the bulk Debye temperature of 225 K

Surface Core-Level Phonon Broadening of Li(110)

High-resolution core-level photoemission data from the 1s level of Li(110) have been obtained between 77 and 280 K. Analysis of the data reveals a significant difference in the zero-temperature phonon broadening between the bulk and surface atoms but only a small difference in the effective surface and bulk Debye temperatures. This latter result is in good agreement with an embedded-atom-method calculation of the bulk and surface Debye temperatures of Li. Implications of these results to surface core-level phonon broadening and surface lattice dynamics of the heavier alkali metals are discussed

A Compact Rotating-Mirror Autocorrelator Design for Femtosecond and Picosecond LaserPulses

An interferometric rapid-scanning autocorrelator employing two antiparallel rotating mirrors in a variable arm is optimized for maximum optical path difference as a function of the separation of the two rotating mirrors. A very compact design (mirror separation≈mirror diameter) is possible without a reduction in the maximum pulse width that can be measured