On large deviation regimes for random media models

The focus of this article is on the different behavior of large deviations of random subadditive functionals above the mean versus large deviations below the mean in two random media models. We consider the point-to-point first passage percolation time $a_n$ on $\mathbb{Z}^d$ and a last passage percolation time $Z_n$. For these functionals, we have $\lim_{n\to\infty}\frac{a_n}{n}=\nu$ and $\lim_{n\to\infty}\frac{Z_n}{n}=\mu$. Typically, the large deviations for such functionals exhibits a strong asymmetry, large deviations above the limiting value are radically different from large deviations below this quantity. We develop robust techniques to quantify and explain the differences.Comment: Published in at http://dx.doi.org/10.1214/08-AAP535 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Motivations and Experiences of Teachers in a Northern Manitoba Community

This paper utilizes an exploratory case study method to examine the factors that attract and motivate teachers to stay in a remote, northern Canadian community. Bakan’s (1966) framework of agency and communion, provides a lens for exploring and understanding teachers’ experiences of working in the north where the term “the North” is understood not simply as one of two geographical poles, but also represents a consciousness of place. Subsequently, this study expands the conceptualization of Bakan’s notion of communion to include both the effects of emotion, which can be understood specifically as public, social, and in relation to others; as well as socio-spatial factors that illustrate the ways in which space is conceived, perceived and lived. Given the amount of human and financial capital required to recruit and retain teachers, as well as the negative implications that high levels of teacher attrition have on student success and emotional well-being, it is important to understand teachers’ perspectives on their experiences working in communities that are perceived as hard to staff.Cet article adopte une méthodologie exploratoire reposant sur l’étude de cas pour examiner les facteurs qui attirent les enseignants vers une communauté isolée du Nord canadien, et les motivent à y rester. Le cadre de l’agentivité et de la communion de Bakan (1966) offre une perspective à partir de laquelle explorer et comprendre les expériences des enseignants qui travaillent dans le nord, où l’expression « le nord » ne désigne pas uniquement un des deux pôles géographiques, mais aussi la conscience d’un lieu. Par la suite, l’étude étend la conceptualisation de la notion de communion de Bakan pour inclure les effets de l’émotion (que l’on comprend comme étant publiques, sociales et par rapport aux autres) ainsi que les facteurs socio-spatiaux qui illustrent les façons dont les lieux sont conçus, perçus et vécus. Compte tenu du capital humain et financier nécessaire pour recruter les enseignants et les maintenir en poste, ainsi que des incidences négatives qu’a le taux élevé de départ volontaire des enseignants sur le rendement et le bienêtre émotionnel des élèves, il est important de comprendre les perspectives des enseignants sur leurs expériences de travail dans des communautés perçues comme étant difficiles à pourvoir en personnel.

On large deviations for the parabolic Anderson model

The focus of this article is on the different behavior of large deviations of random functionals associated with the parabolic Anderson model above the mean versus large deviations below the mean. The functionals we treat are the solution u(x, t) to the spatially discrete parabolic Anderson model and a functional A n which is used in analyzing the a.s. Lyapunov exponent for u(x, t). Both satisfy a “law of large numbers”, with $${\lim_{t\to \infty} \frac{1}{t} \log u(x,t)=\lambda (\kappa)}$$ and $${\lim_{n\to \infty} \frac{A_n}{n}=\alpha}$$ . We then think of αn and λ(κ)t as being the mean of the respective quantities A n and log u(t, x). Typically, the large deviations for such functionals exhibits a strong asymmetry; large deviations above the mean take on a different order of magnitude from large deviations below the mean. We develop robust techniques to quantify and explain the differences

Integrating direct messaging with flood alerts and warnings:insights into effectiveness from a registered public user population

Direct messaging involving simultaneous mass transmission of brief text or voice messages to large numbers of recipients has become a frontline method in flood hazard communications. Messages are intended to serve as cues, drawing recipients' attention to changing conditions, yet the actual effectiveness of direct messaging among recipient groups remains under-examined. This article considers direct messaging within the Floodline public flood warning service in Scotland, implemented by the Scottish Environment Protection Agency (SEPA). Within Floodline, messaging is integrated with alerting and warning information, termed straightforwardly ‘Flood Alerts’ and ‘Flood Warnings’. Collaborating with SEPA, we conducted an online questionnaire survey of registered Floodline direct messaging recipients. In this article, our analysis focusses specifically on responses to three open-ended questions included in this survey, with an iterative qualitative coding approach employed to interpret themes of meaning from the question responses. This analysis gives a clear indication that recipients value Floodline and direct messaging. However, there are also questions raised over the utility of Flood Alerts and related messaging, which we elaborate in the findings and discussion, along with the scope for adding content, linking to other information, and developing closer relationships. Changes being developed by SEPA align with several of these findings.</p

Integrating direct messaging with flood alerts and warnings:insights into effectiveness from a registered public user population

Direct messaging involving simultaneous mass transmission of brief text or voice messages to large numbers of recipients has become a frontline method in flood hazard communications. Messages are intended to serve as cues, drawing recipients' attention to changing conditions, yet the actual effectiveness of direct messaging among recipient groups remains under-examined. This article considers direct messaging within the Floodline public flood warning service in Scotland, implemented by the Scottish Environment Protection Agency (SEPA). Within Floodline, messaging is integrated with alerting and warning information, termed straightforwardly ‘Flood Alerts’ and ‘Flood Warnings’. Collaborating with SEPA, we conducted an online questionnaire survey of registered Floodline direct messaging recipients. In this article, our analysis focusses specifically on responses to three open-ended questions included in this survey, with an iterative qualitative coding approach employed to interpret themes of meaning from the question responses. This analysis gives a clear indication that recipients value Floodline and direct messaging. However, there are also questions raised over the utility of Flood Alerts and related messaging, which we elaborate in the findings and discussion, along with the scope for adding content, linking to other information, and developing closer relationships. Changes being developed by SEPA align with several of these findings.</p

Uniform shrinking and expansion under isotropic Brownian flows

We study some finite time transport properties of isotropic Brownian flows. Under a certain nondegeneracy condition on the potential spectral measure, we prove that uniform shrinking or expansion of balls under the flow over some bounded time interval can happen with positive probability. We also provide a control theorem for isotropic Brownian flows with drift. Finally, we apply the above results to show that under the nondegeneracy condition the length of a rectifiable curve evolving in an isotropic Brownian flow with strictly negative top Lyapunov exponent converges to zero as $t\to \infty$ with positive probability

The effect of cellulose nanocrystals on latex and adhesive properties in emulsion- based polymer nanocomposites

Pressure sensitive adhesives (PSAs) adhere quickly and firmly to surfaces with the application of light pressure, and can be removed without leaving a residue. Their mechanical performance is measured by tack, peel strength and shear strength. A balanced combination between the three mechanical performance measurements depends on the specific end-use application and is challenging to achieve. This is particularly so when replacing solvent-based technologies with more sustainable, water-based (i.e., emulsion polymerization) technologies. PSAs synthesized using emulsion polymerization tend to have a lower shear strength due to poor gel network formation. As a result, conventional emulsion-based PSAs suffer from the inability to increase certain adhesive properties (e.g., tack and peel strength) while simultaneously increasing shear strength. Nanomaterials are often used in polymer composites to improve polymer properties (e.g., tensile strength). They are particularly effective in low quantities (e.g., \u3c2 \u3ewt.%) because of their high surface area. Cellulose nanocrystals (CNCs) are a “green alternative” to common nanomaterials and are isolated from natural cellulose. CNCs have been used more commonly, in the past, as rheological modifiers and interface stabilizers.[1] Because CNCs form colloidally stable dispersions in water, they can be incorporated/processed in water-based systems, eliminating the need for organic solvents.[2] The most common method to produce CNCs is through acid hydrolysis with sulfuric acid; this process preferentially degrades the disordered cellulose regions and leaves behind the crystalline CNCs with grafted anionic sulfate half ester groups.[1] The resulting nanoparticles are whisker-shaped and have a high aspect ratio.[3] CNCs provide composite material reinforcement in the range of other nanomaterials. In the past, CNCs have been blended with polymers and significant strength improvements were noted.[4] Our studies demonstrate how to incorporate CNCs in a nanocomposite using an in situ semi-batch emulsion polymerization protocol.[5] PSA nanocomposite films were generated for a broad variety of copolymer systems including monomers such as iso-butyl acrylate, n-butyl acrylate, 2-ethyl hexyl acrylate, methyl methacrylate, styrene and vinyl acetate. In all cases, the monomer composition of the reaction formulations was manipulated to achieve a suitable range of polymer glass transition temperatures. CNC loadings were varied from 0 to 0.5 to 1 wt.% (based on monomer weight). The addition of CNC was shown to significantly and simultaneously increase tack, peel strength, and shear strength.[6] References [1] Dufresne, A., Nanocellulose, De Gruyter, Saint Martin D’Heres Cedex, France 2012. [2] Flauzino Neto, W. P., Mariano, M., da Silva, I. S. V., Silvério, H. A., Putaux, J.-L., Otaguro, H., Pasquini, D., Dufresne, A., Carbohydr. Polym. 2016, 153, 143. [3] Moon, R. J., Martini, A., Nairn, J., Simonsen, J., Youngblood, J., Chem. Soc. Rev., 2011, 40, 3941. [4] Rajisha, K. R., Maria, H. J., Pothan, L. A., Ahmad, Z., Thomas, S., Int. J. Biol. Macromol., 2014, 67, 147. [5] Dastjerdi, Z., Cranston, E. D., Dubé, M. A., Macromol. React. Eng., 2018, in press. [6] Dastjerdi, Z., Cranston, E. D., Dubé, M. A., Int. J. Adh. Adh. 2018, 81, 36-42

Species Trees from Highly Incongruent Gene Trees in Rice

Several methods have recently been developed to infer multilocus phylogenies by incorporating information from topological incongruence of the individual genes. In this study, we investigate 2 such methods, Bayesian concordance analysis and Bayesian estimation of species trees. Our test data are a collection of genes from cultivated rice (genus Oryza) and the most closely related wild species, generated using a high-throughput sequencing protocol and bioinformatics pipeline. Trees inferred from independent genes display levels of topological incongruence that far exceed that seen in previous data sets analyzed with these species tree methods. We identify differences in phylogenetic results between inference methods that incorporate gene tree incongruence. Finally, we discuss the challenges of scaling these analyses for data sets with thousands of gene trees and extensive levels of missing data