Comment on "Evidence for nontrivial ground-state structure of 3d +/- J spin glasses"

In a recent Letter [Europhys. Lett. 40, 429 (1997)], Hartmann presented results for the structure of the degenerate ground states of the three-dimensional +/- J spin glass model obtained using a genetic algorithm. In this Comment, I argue that the method does not produce the correct thermodynamic distribution of ground states and therefore gives erroneous results for the overlap distribution. I present results of simulated annealing calculations using different annealing rates for cubic lattices with N=4*4*4spins. The disorder-averaged overlap distribution exhibits a significant dependence on the annealing rate, even when the energy has converged. For fast annealing, moments of the distribution are similar to those presented by Hartmann. However, as the annealing rate is lowered, they approach the results previously obtained using a multi-canonical Monte Carlo method. This shows explicitly that care must be taken not only to reach states with the lowest energy but also to ensure that they obey the correct thermodynamic distribution, i.e., that the probability is the same for reaching any of the ground states.Comment: 2 pages, Revtex, 1 PostScript figur

Growth and structural characterization of pyramidal site-controlled quantum dots with high uniformity and spectral purity

This work presents some fundamental features of pyramidal site-controlled InGaAs Quantum Dots (QDs) grown by MetalOrganic Vapour Phase Epitaxy on patterned GaAs (111)B substrate. The dots self-form inside pyramidal recesses patterned on the wafer via pre-growth processing. The major advantage of this growth technique is the control it provides over the dot nucleation posi-tion and the dimensions of the confined structures onto the sub-strate. The fundamental steps of substrate patterning and the QD forma-tion mechanism are described together with a discussion of the structural particulars. The post-growth processes, including sur-face etching and substrate removal, which are required to facili-tate optical characterization, are discussed. With this approach extremely high uniformity and record spectral purity are both achieved

Direct sampling of complex landscapes at low temperatures: the three-dimensional +/-J Ising spin glass

A method is presented, which allows to sample directly low-temperature configurations of glassy systems, like spin glasses. The basic idea is to generate ground states and low lying excited configurations using a heuristic algorithm. Then, with the help of microcanonical Monte Carlo simulations, more configurations are found, clusters of configurations are determined and entropies evaluated. Finally equilibrium configuration are randomly sampled with proper Gibbs-Boltzmann weights. The method is applied to three-dimensional Ising spin glasses with +- J interactions and temperatures T<=0.5. The low-temperature behavior of this model is characterized by evaluating different overlap quantities, exhibiting a complex low-energy landscape for T>0, while the T=0 behavior appears to be less complex.Comment: 9 pages, 7 figures, revtex (one sentence changed compared to v2

School Bus Monitors in Western New York

The New York State Department of Education defines a “bus monitor” (also commonly referred to as a “bus aide”) as any person employed for the purpose of assisting children to safely embark and disembark from a school bus which is owned, leased or contracted for by a public school district or board of cooperative educational services, and for the purpose of assisting the school bus driver with maintaining proper student behavior on such school bus