Self-driven lattice-model Monte Carlo simulations of alloy thermodynamic

Monte Carlo (MC) simulations of lattice models are a widely used way to compute thermodynamic properties of substitutional alloys. A limitation to their more widespread use is the difficulty of driving a MC simulation in order to obtain the desired quantities. To address this problem, we have devised a variety of high-level algorithms that serve as an interface between the user and a traditional MC code. The user specifies the goals sought in a high-level form that our algorithms convert into elementary tasks to be performed by a standard MC code. For instance, our algorithms permit the determination of the free energy of an alloy phase over its entire region of stability within a specified accuracy, without requiring any user intervention during the calculations. Our algorithms also enable the direct determination of composition-temperature phase boundaries without requiring the calculation of the whole free energy surface of the alloy system

Caregiver perspectives on the continued impact of the COVID-19 pandemic on children with intellectual/developmental disabilities

The COVID-19 pandemic has significantly impacted caregivers, especially those raising a child with an intellectual/developmental disability (IDD). While research has shown substantial disruption to the family, school, and occupational lives of the IDD community, little is known about the long-term impacts of COVID-19. To address this question, 249 caregivers were surveyed via an online questionnaire, between April and August of 2022 (more than 2 years into the pandemic) about potential impacts of the COVID-19 pandemic on their child\u27s access to health- and school-based therapeutic services, caregiver mental health, and family life. The majority of caregivers reported disruptions in access to and quality of school-based therapeutic services for their child as well as a reduction in educational accommodations in the 2021-2022 academic year. Nearly half of caregivers reported feeling anxious and almost a quarter reported feeling depressed for the majority of their days. More than half of respondents reported decreased social support, and one-fifth reported employment disruptions and decreased access to food. These findings suggest that families of children with IDD are still experiencing ongoing negative impacts of the pandemic, emphasizing the critical need for continued support in the wake of the initial and more obvious disruptions caused by the COVID-19 outbreak

Intensity Distribution of Waves Transmitted Through a Multiple Scattering Medium

The distributions of the angular transmission coefficient and of the total transmission are calculated for multiple scattered waves. The calculation is based on a mapping to the distribution of eigenvalues of the transmission matrix. The distributions depend on the profile of the incoming beam. The distribution function of the angular transmission has a stretched exponential decay. The total-transmission distribution grows log-normally whereas it decays exponentially.Comment: 8 pages, revtex3.0, 3 postscript figures, NvR0

Anomalous Conductance Distribution in Quasi-One Dimension: Possible Violation of One-Parameter Scaling Hypothesis

We report measurements of conductance distribution in a set of quasi-one-dimensional gold wires. The distribution includes the second cumulant or the variance which describes the universal conductance fluctuations, and the third cumulant which denotes the leading deviation. We have observed an asymmetric contribution--or, a nonvanishing third cumulant--contrary to the expectation for quasi-one-dimensional systems in the noninteracting theories in the one-parameter scaling framework, which include the perturbative diagrammatic calculations and the random matrix theory.Comment: 5 PAGE

Three "universal" mesoscopic Josephson effects

1. Introduction 2. Supercurrent from Excitation Spectrum 3. Excitation Spectrum from Scattering Matrix 4. Short-Junction Limit 5. Universal Josephson Effects 5.1 Quantum Point Contact 5.2 Quantum Dot 5.3 Disordered Point Contact (Average supercurrent, Supercurrent fluctuations)Comment: 21 pages, 2 figures; legacy revie

Aharonov-Bohm effect and resonances in the circular quantum billiard with two leads

We calculate the conductance through a circular quantum billiard with two leads and a point magnetic flux at the center. The boundary element method is used to solve the Schrodinger equation of the scattering problem, and the Landauer formula is used to calculate the conductance from the transmission coefficients. We use two different shapes of leads, straight and conic, and find that the conductance is affected by lead geometry, the relative positions of the leads and the magnetic flux. The Aharonov-Bohm effect can be seen from shifts and splittings of fluctuations. When the flux is equal to (h/2e) and the angle between leads is 180 degree, the conductance tends to be suppressed to zero in the low energy range due to the Aharonov-Bohm effect.Comment: LaTeX2e, 8 pages, 6 figures, submitted to Phys. Rev. B (Two references added. A discussion on discrete symmetries removed.

Andreev Conductance of Chaotic and Integrable Quantum Dots

We examine the voltage V and magnetic field B dependent Andreev conductance of a chaotic quantum dot coupled via point contacts to a normal metal and a superconductor. In the case where the contact to the superconductor dominates, we find that the conductance is consistent with the dot itself behaving as a superconductor-- it appears as though Andreev reflections are occurring locally at the interface between the normal lead and the dot. This is contrasted against the behaviour of an integrable dot, where for a similar strong coupling to the superconductor, no such effect is seen. The voltage dependence of the Andreev conductance thus provides an extremely pronounced quantum signature of the nature of the dot's classical dynamics. For the chaotic dot, we also study non-monotonic re-entrance effects which occur in both V and B.Comment: 13 pages, 9 figure

Signatures of photon localization

Signatures of photon localization are observed in a constellation of transport phenomena which reflect the transition from diffusive to localized waves. The dimensionless conductance, g, and the ratio of the typical spectral width and spacing of quasimodes, \delta, are key indicators of electronic and classical wave localization when inelastic processes are absent. However, these can no longer serve as localization parameters in absorbing samples since the affect of absorption depends upon the length of the trajectories of partial waves traversing the sample, which are superposed to create the scattered field. A robust determination of localization in the presence of absorption is found, however, in steady-state measurements of the statistics of radiation transmitted through random samples. This is captured in a single parameter, the variance of the total transmission normalized to its ensemble average value, which is equal to the degree of intensity correlation of the transmitted wave, \kappa. The intertwined effects of localization and absorption can also be disentangled in the time domain since all waves emerging from the sample at a fixed time delay from an exciting pulse, t, are suppressed equally by absorption. As a result, the relative weights of partial waves emerging from the sample, and hence the statistics of intensity fluctuations and correlation, and the suppression of propagation by weak localization are not changed by absorption, and manifest the growing impact of weak localization with t.Comment: RevTex 16 pages, 12 figures; to appear in special issue of J. Phys. A on quantum chaotic scatterin

Stress in nurses : stress-related affect and its determinants examined over the nursing day

Peer reviewedPostprin

Generalized Fokker-Planck Equation For Multichannel Disordered Quantum Conductors

The Dorokhov-Mello-Pereyra-Kumar (DMPK) equation, which describes the distribution of transmission eigenvalues of multichannel disordered conductors, has been enormously successful in describing a variety of detailed transport properties of mesoscopic wires. However, it is limited to the regime of quasi one dimension only. We derive a one parameter generalization of the DMPK equation, which should broaden the scope of the equation beyond the limit of quasi one dimension.Comment: 8 pages, abstract, introduction and summary rewritten for broader readership. To be published in Phys. Rev. Let