Higher Order Effects in the Dielectric Constant of Percolative Metal-Insulator Systems above the Critical Point

The dielectric constant of a conductor-insulator mixture shows a pronounced maximum above the critical volume concentration. Further experimental evidence is presented as well as a theoretical consideration based on a phenomenological equation. Explicit expressions are given for the position of the maximum in terms of scaling parameters and the (complex) conductances of the conductor and insulator. In order to fit some of the data, a volume fraction dependent expression for the conductivity of the more highly conductive component is introduced.Comment: 4 pages, Latex, 4 postscript (*.epsi) files submitted to Phys Rev.

Numerical description of discharge characteristics of the plasma needle

The plasma needle is a small atmospheric, nonthermal, radio-frequency discharge, generated at the tip of a needle, which can be used for localized disinfection of biological tissues. Although several experiments have characterized various qualities of the plasma needle, discharge characteristics and electrical properties are still not well known. In order to provide initial estimates on electrical properties and quantities such as particle densities, we employed a two-dimensional, time-dependent fluid model to describe the plasma needle. In this model the balance equation is solved in the drift-diffusion approach for various species and the electron energy, as well as Poisson's equation. We found that the plasma production occurs in the sheath region and results in a steady flux of reactive species outwards. Even at small (< 0.1%) admixtures of N-2 to the He background, N-2(+) is the dominant ion. The electron density is typically 10(11) cm(-3) and the dissipated power is in the order of 10 mW. These results are consistent with the experimental data available and can give direction to the practical development of the plasma needle. (c) 2005 American Institute of Physics

Risk factors for leaving employment due to multiple sclerosis and changes in risk over the past decades: using competing risk survival analysis

Background: No studies have assessed changes in employment survival in multiple sclerosis (MS) populations over recent decades, including the introduction of disease-modifying therapies (DMTs). Objectives: To evaluate factors associated with leaving employment due to MS; to assess whether the risk of leaving employment has changed over recent decades in Australia, stratified by MS phenotype. Methods: We included 1240 participants who were working before MS diagnosis. Information on employment status, reasons for leaving employment and year of leaving were collected. Data were analysed using competing risk survival analysis. Results: Males, progressive MS, lower education level and older age at diagnosis were associated with a higher sub-distribution hazard of leaving employment. Compared to the period before 2010, the sub-distribution hazard during 2010-2016 for relapsing-remitting multiple sclerosis (RRMS) was reduced by 43% (sub-distribution hazard ratio (sHR) 0.67, 95% confidence interval (CI): 0.50 to 0.90), while no significant reduction was seen for primary-progressive multiple sclerosis (PPMS) (sHR 1.25, 95% CI: 0.72 to 2.16) or secondary-progressive multiple sclerosis (SPMS) (sHR 1.37, 95% CI: 0.84 to 2.25). Conclusion: Males, people with progressive MS and those of lower education level were at higher risk of leaving employment. The differential changed risk of leaving employment between people with different MS phenotype after 2010 coincides with the increased usage of high-efficacy DMTs for RRMS

Minimal Model for Sand Dunes

We propose a minimal model for aeolian sand dunes. It combines an analytical description of the turbulent wind velocity field above the dune with a continuum saltation model that allows for saturation transients in the sand flux. The model provides a qualitative understanding of important features of real dunes, such as their longitudinal shape and aspect ratio, the formation of a slip face, the breaking of scale invariance, and the existence of a minimum dune size.Comment: 4 pages, 4 figures, replaced with publishd versio

Hippocampus-related effects of fluoxetine treatment under stressful vs enriched conditions

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Tracking poverty using satellite imagery and big data

Despite recent improvements in the availability and quality of socioeconomic data from developing countries, there are still persistent data gaps that are preventing comprehensive monitoring and evaluation of targets and indicators of the Sustainable Development Goals. Approaches are hampered by the inconsistent spatial and temporal coverage of census data and Demographic and Health Surveys, which serve as the primary source for population-level statistics in most developing countries. Traditional censuses are too expensive to be implemented in remote areas where population density is low and road networks are poor. However, the recent and rapid diffusion of high-resolution satellite imagery offers a new wealth of relatively untapped information that can be used to gain in-depth information on groups that have historically been left out by traditional surveys. Moreover, there are new data streams such as call detail records from mobile phone data networks can help to derive behavioral indicators and improve tracking of expenditure and wealth. This exploratory research conflates various data streams to derive spatially explicit poverty indicators for Senegal with immense scaling potential to other regions