7,057 research outputs found
Effective charging energy for a regular granular metal array
We study the Ambegaokar-Eckern-Sch\"{o}n (AES) model for a regular array of
metallic grains coupled by tunnel junctions of conductance and calculate
both paramagnetic and diamagnetic terms in the Kubo formula for the
conductivity. We find analytically, and confirm by numerical path integral
Monte Carlo methods, that for the conductivity obeys an Arrhenius law
with an effective charging energy
when the temperature is sufficiently low, due to a subtle cancellation between
inelastic-cotunneling contributions in the paramagnetic and diamagnetic
terms. We present numerical results for the effective charging energy and
compare the results with recent theoretical analyses. We discuss the different
ways in which the experimentally observed
law could be attributed to disorder.Comment: 5 pages, 3 figures, ReVTeX; added estimates of effective charging
energies and discussion of effects of disorde
"Exact" Algorithm for Random-Bond Ising Models in 2D
We present an efficient algorithm for calculating the properties of Ising
models in two dimensions, directly in the spin basis, without the need for
mapping to fermion or dimer models. The algorithm gives numerically exact
results for the partition function and correlation functions at a single
temperature on any planar network of N Ising spins in O(N^{3/2}) time or less.
The method can handle continuous or discrete bond disorder and is especially
efficient in the case of bond or site dilution, where it executes in O(L^2 ln
L) time near the percolation threshold. We demonstrate its feasibility on the
ferromagnetic Ising model and the +/- J random-bond Ising model (RBIM) and
discuss the regime of applicability in cases of full frustration such as the
Ising antiferromagnet on a triangular lattice.Comment: 4.2 pages, 5 figures, accepted for publication in Phys. Rev. Let
Noise Predictions for STM in Systems with Local Electron Nematic Order
We propose that thermal noise in local stripe orientation should be readily
detectable via STM on systems in which local stripe orientations are strongly
affected by quenched disorder. Stripes, a unidirectional, nanoscale modulation
of electronic charge, are strongly affected by quenched disorder in
two-dimensional and quasi-two-dimensional systems. While stripe orientations
tend to lock to major lattice directions, dopant disorder locally breaks
rotational symmetry. In a host crystal with otherwise rotational
symmetry, stripe orientations in the presence of quenched disorder map to the
random field Ising model. While the low temperature state of such a system is
generally a stripe glass in two dimensional or strongly layered systems, as the
temperature is raised, stripe orientational fluctuations become more prevalent.
We propose that these thermally excited fluctuations should be readily
detectable in scanning tunneling spectroscopy as {\em telegraph noise} in the
high voltage part of the local curves. We predict the spatial, temporal,
and thermal evolution of such noise, including the circumstances under which
such noise is most likely to be observed. In addition, we propose an in-situ
test, amenable to any local scanning probe, for assessing whether such noise is
due to correlated fluctuations rather than independent switchers.Comment: 8 pages, 8 figure
The Use of Scheffe-Equivalent Equations to Predict Physical Properties of Neoprene
The goal of this study is to find a more organized and directed approach to build models for mixture systems. An attempt is made to generate and then compare Scheffe (mixture) models with those generated by McGee using the ‘conventional’ method for neoprene data. The models are judged on their ability to predict physical properties of neoprene by comparing the following: predicted and actual values by inspection; the calculated % error of prediction; the squared multiple correlation coefficients; adjusted squared multiple correlation coefficients; the Fisher statistic and significance probability. Scheffe models do not have an intercept term and test statistics which appear on the computer printout are inflated. Pseudocomponents and Scheffe-equivalent models are procedures used to obtain accurate test statistics to describe the selected Scheffe models. The effectiveness of these two procedures is evaluated. Results indicate that Scheffe models are better predictors for the physical properties of neoprene than those generated by McGee using the ‘conventional’ method in 1980. Scheffe-equivalent equations are found to be more reliable than pseudocomponents for generating accurate test statistics to describe the selected Scheffe models
Are Artificial Tans the New Cigarette? How Plaintiffs Can Use the Lessons of Tobacco Litigation in Bringing Claims Against the Indoor Tanning Industry
Indoor tanning salons have grown significantly in popularity during recent years. Scientific research has revealed a strong link between skin cancer and ultraviolet light exposure from indoor tanning lamps. Despite such dangers, federal regulations place minimal restrictions on the labeling of indoor tanning lamps. Indoor tanning salons work vigorously to dispel notions of a link to skin cancer, often falsely promoting various health benefits of indoor tanning. The first lawsuit for injuries resulting from indoor tanning was recently filed against an indoor tanning salon, and other such litigation is poised to follow. This Note examines three potential tort claims against indoor tanning manufacturers and salons, and suggests ways to formulate compelling arguments in each instance. In doing so it draws on cases finding liability in the context of cigarettes, identifying similarities between the indoor tanning and cigarette industries
- …