Diffusion of multiple species with excluded-volume effects

Stochastic models of diffusion with excluded-volume effects are used to model many biological and physical systems at a discrete level. The average properties of the population may be described by a continuum model based on partial differential equations. In this paper we consider multiple interacting subpopulations/species and study how the inter-species competition emerges at the population level. Each individual is described as a finite-size hard core interacting particle undergoing Brownian motion. The link between the discrete stochastic equations of motion and the continuum model is considered systematically using the method of matched asymptotic expansions. The system for two species leads to a nonlinear cross-diffusion system for each subpopulation, which captures the enhancement of the effective diffusion rate due to excluded-volume interactions between particles of the same species, and the diminishment due to particles of the other species. This model can explain two alternative notions of the diffusion coefficient that are often confounded, namely collective diffusion and self-diffusion. Simulations of the discrete system show good agreement with the analytic results

Carrier mobility and scattering lifetime in electric double-layer gated few-layer graphene

We fabricate electric double-layer field-effect transistor (EDL-FET) devices on mechanically exfoliated few-layer graphene. We exploit the large capacitance of a polymeric electrolyte to study the transport properties of three, four and five-layer samples under a large induced surface charge density both above and below the glass transition temperature of the polymer. We find that the carrier mobility shows a strong asymmetry between the hole and electron doping regime. We then employ ab-initio density functional theory (DFT) calculations to determine the average scattering lifetime from the experimental data. We explain its peculiar dependence on the carrier density in terms of the specific properties of the electrolyte we used in our experiments.Comment: 6 pages, 3 figure

“Popping it” as family in Mosquitoes & Me: affective accumulation and Anzaldúan aesthetic consciousness in \u3ci\u3eCiencia Zurda\u3c/i\u3e

This article uses key concepts of Anzaldúan philosophy to describe the Mosquitoes & Me summer camp as ciencia zurda or left-handed science. It details a day-in-the-life portrait of Elena, a first-generation Latina middle schooler, as she experiences the opportunities that Mosquitoes & Me provided for self-other bridge crossing and radically relational, Nepantlan potential. Our discussion of Elena’s experiences in terms of Nepantlan principles of diversity, Affect, and spirit, as well as Affective accumulation and aesthetic consciousness, infuse an emotional and spiritual dimension to inquiry science- and responsive sciencecomplementarity and revisit a call for soul-centered, socially-transformative science. Este artículo utiliza conceptos clave de la filosofía de Anzaldúan para describir el campamento de verano Mosquitos & Me como ciencia zurda. Detalla un retrato del día a día en la vida de Elena, una estudiante de secundaria latinoamericana de primera generación, mientras experimenta las oportunidades que Mosquitoes & Me le brindó para cruzar el puente entre sí misma y el potencial Nepantla que es radicalmente relacional. Nuestra discusión sobre las experiencias de Elena en términos de los principios de Nepantla sobre diversidad, afecto y espíritu, así como la acumulación afectiva y la conciencia estética, infunden una dimensión emocional y espiritual a la complementariedad de la ciencia investigadora y la ciencia receptiva, y hacen un llamado por una ciencia centrada en el alma y socialmente transformadora

Effects of environmental, living space and climate variability on the utilization of impregnated bed nets in west Cameroon: A community based survey for policy implementation

Background: Despite the fact that Long Lasting Impregnated Mosquito Net (LLIN) represents one of the most effective tools in fighting malaria, its use remains limited. Our study aimed at determining how environmental, household characteristics and climate affect bed net use. Methodology: A cross sectional descriptive and analytic study was carried out from January to April 2014 in Mifi health district. Data collected were collected in households during a face to face interview with standard household questionnaires, entered and analyzed using Epi Info software version 3.5.3. Graphics and tables were obtained using MS Excel and Word. Results: Of the 317 participants interviewed, average age was 33.23 years (SD = 10.80) and female sex predominant (85.2%). Most participants had attended secondary education 53.6% (n= 170), married marital status was most represented (58.1%; n= 185).75.4% (n=239) of households had at least 1 LLIN and average district coverage estimated to 1 LLIN for 3.3 persons. 78% of occupants in households with at least one LLIN had slept under the night before the survey. The presence of a ceiling in a house reduced net usage by 2.5% (p = 0.67) compared to house lacking ceiling. Standing waters around the compound increased net utilization rate to 16.6% (p = 0.03), whereas the presence of a covered well decreased the rate by 1.4% (p = 0.86). The dry season was identified as the period during which 86.8% (n= 239) of respondents sleep less under a net. Heat (57.60% n = 138/239), increased choking (2.5%), reduction in vector breeding sites (39.90%; n = 95) were cited as main reasons. Conclusion: Although classified as zone of continuous transmission, our findings indicate that bed net usage by our study population depends on environmental, household characteristics and climate. There is therefore an urgent need to develop strategic communication and sensitization campaigns coupled to environmental management to help scale up and optimize malaria burden reductio

Reconstruction of Bandlimited Functions from Unsigned Samples

We consider the recovery of real-valued bandlimited functions from the absolute values of their samples, possibly spaced nonuniformly. We show that such a reconstruction is always possible if the function is sampled at more than twice its Nyquist rate, and may not necessarily be possible if the samples are taken at less than twice the Nyquist rate. In the case of uniform samples, we also describe an FFT-based algorithm to perform the reconstruction. We prove that it converges exponentially rapidly in the number of samples used and examine its numerical behavior on some test cases