ARE CATTLE ON FEED REPORT REVISIONS RANDOM AND DOES INDUSTRY ANTICIPATE THEM?

Cattle on Feed (COF) reports are an important source of beef supply information. This study investigates whether COF report revisions are unbiased, random, and anticipated. Initial COF reports are biased, but the bias is economically small. Revisions to COF estimates are not random. Market analysts do not correctly anticipate revisions.Livestock Production/Industries,

Crossover to Potential Energy Landscape Dominated Dynamics in a Model Glass-forming Liquid

An equilibrated model glass-forming liquid is studied by mapping successive configurations produced by molecular dynamics simulation onto a time series of inherent structures (local minima in the potential energy). Using this ``inherent dynamics'' approach we find direct numerical evidence for the long held view that below a crossover temperature, $T_x$, the liquid's dynamics can be separated into (i) vibrations around inherent structures and (ii) transitions between inherent structures (M. Goldstein, J. Chem. Phys. {\bf 51}, 3728 (1969)), i.e., the dynamics become ``dominated'' by the potential energy landscape. In agreement with previous proposals, we find that $T_x$ is within the vicinity of the mode-coupling critical temperature $T_c$. We further find that at the lowest temperature simulated (close to $T_x$), transitions between inherent structures involve cooperative, string like rearrangements of groups of particles moving distances substantially smaller than the average interparticle distance.Comment: Expanded from 4 to 7 page

Electromagnetic cascade in high energy electron, positron, and photon interactions with intense laser pulses

The interaction of high energy electrons, positrons, and photons with intense laser pulses is studied in head-on collision geometry. It is shown that electrons and/or positrons undergo a cascade-type process involving multiple emissions of photons. These photons can consequently convert into electron-positron pairs. As a result charged particles quickly lose their energy developing an exponentially decaying energy distribution, which suppresses the emission of high energy photons, thus reducing the number of electron-positron pairs being generated. Therefore, this type of interaction suppresses the development of the electromagnetic avalanche-type discharge, i.e., the exponential growth of the number of electrons, positrons, and photons does not occur in the course of interaction. The suppression will occur when 3D effects can be neglected in the transverse particle orbits, i.e., for sufficiently broad laser pulses with intensities that are not too extreme. The final distributions of electrons, positrons, and photons are calculated for the case of a high energy e-beam interacting with a counter-streaming, short intense laser pulse. The energy loss of the e-beam, which requires a self-consistent quantum description, plays an important role in this process, as well as provides a clear experimental observable for the transition from the classical to quantum regime of interaction.Comment: 13 pages, 7 figure

Optimized laser pulse profile for efficient radiation pressure acceleration of ions

The radiation pressure acceleration regime of laser ion acceleration requires high intensity laser pulses to function efficiently. Moreover the foil should be opaque for incident radiation during the interaction to ensure maximum momentum transfer from the pulse to the foil, which requires proper matching of the target to the laser pulse. However, in the ultrarelativistic regime, this leads to large acceleration distances, over which the high laser intensity for a Gaussian laser pulse must be maintained. It is shown that proper tailoring of the laser pulse profile can significantly reduce the acceleration distance, leading to a compact laser ion accelerator, requiring less energy to operate.Comment: 10 pages, 4 figure

New genera and species of batoid fishes

The trawling campaigns carried out by the research vessel ATLANTIS of the Woods Hole Oceanographic Institution along the north and south coasts of Cuba during the winter of 1938 and spring of 1939, under the joint auspices of the University of Havana and of Harvard University, brought to light along the 200-500 fathom zone an abundant population of small skates (Family Rajidae), the existence of which had not previously been suspected there...