Cloud computing in nanoHUB powering education and research

nanoHUB.org lets you access simulation/modeling tools online via an ordinary web browser. Where do the tools come from? From you—hundreds of you throughout the world who are developing simulation/modeling tools for research and education. Anyone can upload code onto nanoHUB and publish a tool. The tool can be restricted to a limited group of colleagues or open for the entire world to use. The source code can be kept protected or given out as open source. Learn from this overview how to contribute and publish a new tool on nanoHUB – starting with a tool registration form, then uploading code into a Subversion repository, developing and testing the code within the “workspace” tool, and finally, approving and publishing your tool. Learn how to use Rappture, the Rapid APPlication infrastrucTURE, a toolkit that makes it easy to develop graphical user interfaces for scientific tools in a variety of languages, including C/C++, Fortran, MATLAB, Octave, Java, Python, Perl, R, Ruby, and Tcl. See how your tool can be made available as a citable resource to thousands of users around the world, and use the built-in analytics of the nanoHUB platform to watch your user base grow

Quantum Transport with Dissipation: Linear and Non-Linear Response

We present a quantum transport equation derived under the simplifying assumption that the inelastic scattering is caused by uncorrelated point scatterers, such as magnetic impurities. While this assumption is not always realistic, we believe that the model can be used to describe much of the essential physics of quantum transport in mesoscopic systems. This assumption allows us to write a quantum transport equation that involves only the diagonal elements of the density matrix which we use to define a distribution function f(r; E). The kernel of this integral equation is calculated from the Schrodinger equation and contains all quantum interference effects. We show that at equilibrium the distribution function relaxes to the Fermi-Dirac function with a constant chemical potential everywhere in the structure. Assuming local thermodynamic equilibrium we then derive a linearized transport equation which has the appearance of a continuous version of the multiprobe Landauer formula. An alternative derivation is provided for the linearized transport equation starting from the multiprobe Landauer formula. Numerical results are presented for the conductivity of a disordered resistor with distributed inelastic scattering. A clear transition is observed from weak to strong localization as the inelastic scattering time is increased. In the present work we restrict ourselves to steady state transport and neglect many-body effects

An Integral Equation for Dissipative Quantum Transport

We present an integral equation derived under the simplifying assumption that the inelastic scattering is caused by uncorrelated point scatterers, such as magnetic impurities or impurities with internal degrees of freedom. While this assumption is not always realistic, we believe that the model can be used to describe much of the essential physics of quantum transport in mesoscopic systems. This assumption allows us to write a transport equation that involves only the electron density and not the spatial correlations of the wave function. The kernel of this integral equation is calculated from the Schrodinger equation and contains all quantum interference effects. We show that at equilibrium the electron density relaxes to the expected equilibrium value with a constant chemical potential everywhere in the structure. Assuming local thermodynamic equilibrium we then derive a linear-response transport equation which resembles the Landauer-Buttiker formula extended to include a continuous distribution of probes. An alternative derivation is provided in the appendix for the kernel of the linear-response transport equation, starting from the Kubo formula for the conductivity. We discuss the conditions under which this transport equation reduces to the well-known drift-diffusion equations describing classical Brownian motion. In the present work we restrict ourselves to steady state transport and neglect many-body effects beyond the Hartree term

Physicochemical properties of concentrated Martian surface waters

Understanding the processes controlling chemical sedimentation is an important step in deciphering paleoclimatic conditions from the rock records preserved on both Earth and Mars. Clear evidence for subaqueous sedimentation at Meridiani Planum, widespread saline mineral deposits in the Valles Marineris region, and the possible role of saline waters in forming recent geomorphologic features all underscore the need to understand the physical properties of highly concentrated solutions on Mars in addition to, and as a function of, their distinct chemistry. Using thermodynamic models predicting saline mineral solubility, we generate likely brine compositions ranging from bicarbonate-dominated to sulfate-dominated and predict their saline mineralogy. For each brine composition, we then estimate a number of thermal, transport, and colligative properties using established models that have been developed for highly concentrated multicomponent electrolyte solutions. The available experimental data and theoretical models that allow estimation of these physicochemical properties encompass, for the most part, much of the anticipated variation in chemistry for likely Martian brines. These estimates allow significant progress in building a detailed analysis of physical sedimentation at the ancient Martian surface and allow more accurate predictions of thermal behavior and the diffusive transport of matter through chemically distinct solutions under comparatively nonstandard conditions

Ageing validation of northern carp populations

The Carp is considered a threat to our native river fish and ecosystems by its ability to adapt to almost any fresh water body and through its feeding and breeding habits, change environmental parameters such as turbidity, light and water temperatures. This project forms part of the Invasive Animal CRC's freshwater program and is part of a strategy to develop control measures for carp. The age and size at maturity for carp in the northern part of their range (ie. Queensland) is currently unknown

SAMOD, a South African tax-benefit microsimulation model: Recent developments

This paper provides an account of a South African tax-benefit microsimulation model - SAMOD - which has been developed for use by government over the past ten years. The two datasets that underpin the current version of SAMOD are introduced, and the model's tax and benefit policies are described with discussion of the various data challenges and assumptions that had to be made in order to simulate them, with particular emphasis on the value-added tax policy. Simulations using the two different underpinning datasets are compared with reported administrative data. The paper concludes by highlighting three future developments for SAMOD

Updating NAMOD: A Namibian tax-benefit microsimulation model

This paper provides an account of a Nambian tax-benefit microsimulation model - NAMOD - which has been developed for use by government. Following a section on the importance of social security in Namibia and recent related studies, the paper outlines the tax-benefit policies that are included within NAMOD and describes the data challenges and assumptions that had to be made in order to simulate these policies. Results for 2015 are compared with reported administrative data. In spite of current data challenges, NAMOD can be used to help inform social security policy design

Why are fish oil supplements apparently failing to reproduce fish consumption epidemiology in RCT for cardiovascular disease?

Abstract of a presentation

Linear Response for Confined Particles

The dynamics of fluctuations is considered for electrons near a positive ion or for charges in a confining trap. The stationary nonuniform equilibrium densities are discussed and contrasted. The linear response function for small perturbations of this nonuniform state is calculated from a linear Markov kinetic theory whose generator for the dynamics is exact in the short time limit. The kinetic equation is solved in terms of an effective mean field single particle dynamics determined by the local density and dynamical screening by a dielectric function for the non-uniform system. The autocorrelation function for the total force on the charges is discussed.Comment: 4 pages, 1 figure. Results presented at the "International Conference on Strongly Coupled Coulomb Systems", Camerino, Italy, July 2008. Submitted for publication in the conference proceedings (special issue of Journal of Physics A