16 research outputs found
Active Brownian Particles. From Individual to Collective Stochastic Dynamics
We review theoretical models of individual motility as well as collective
dynamics and pattern formation of active particles. We focus on simple models
of active dynamics with a particular emphasis on nonlinear and stochastic
dynamics of such self-propelled entities in the framework of statistical
mechanics. Examples of such active units in complex physico-chemical and
biological systems are chemically powered nano-rods, localized patterns in
reaction-diffusion system, motile cells or macroscopic animals. Based on the
description of individual motion of point-like active particles by stochastic
differential equations, we discuss different velocity-dependent friction
functions, the impact of various types of fluctuations and calculate
characteristic observables such as stationary velocity distributions or
diffusion coefficients. Finally, we consider not only the free and confined
individual active dynamics but also different types of interaction between
active particles. The resulting collective dynamical behavior of large
assemblies and aggregates of active units is discussed and an overview over
some recent results on spatiotemporal pattern formation in such systems is
given.Comment: 161 pages, Review, Eur Phys J Special-Topics, accepte
Inter-rater reliability of the assessment of adverse drug reactions in the hospitalised elderly
BACKGROUND
The identification and assessment of adverse drug reactions (ADRs) is very challenging especially among the older person. Inter observer reliability of an ADR classification system by different healthcare providers is vital to establish the validity of the reaction.
OBJECTIVE
To assess the inter-rater reliability of an ADR classification system in hospitalised elderly patients and to investigate the differences in reliability by different professions.
METHODS
From a cohort of 330 elderly patients, patients who experienced a suspected medication related incident (n=87) were selected. The data were analysed by four healthcare professionals (2 pharmacists and 2 physicians) who independently classified the events into event type, types of adverse drug reactions, severity and preventability after a standardised induction based on previously published criteria. Fleiss' kappa was used to assess the level of agreement between the four raters. The difference in level of agreement between the professions was assessed using the weighted least-squares approach for comparing correlated kappa of Barnhart et al.
RESULTS
Pharmacists and physicians showed high agreement in the identification and on the type and causality of ADRs. However there was lower (moderate) agreement for the severity (kappa = 0.61) and preventability of ADR (kappa = 0.48). Statistically significant differences were also noted between the professions; pharmacists have higher agreement in the classification of preventability (p=0.03) whereas the physicians pairs showed stronger agreement for classifying severity (p<0.001).
CONCLUSION
Despite the high agreement in the identification, type and causality of ADRs, physicians and pharmacists have difficulties in classifying preventability and severity in a reliable way. A multi-disciplinary approach would enable each profession to share their expert knowledge in order to facilitate better or safer patient care
Crawling motility through the analysis of model locomotors: Two case studies
We study model locomotors on a substrate, which derive their propulsive capabilities from the tangential (viscous or frictional) resistance offered by the substrate. Our aim is to develop new tools and insight for future studies of cellular motility by crawling and of collective bacterial motion. The purely viscous case (worm) is relevant for cellular motility by crawling of individual cells. We re-examine some recent results on snail locomotion in order to assess the role of finely regulated adhesion mechanisms in crawling motility. Our main conclusion is that such regulation, although well documented in several biological systems, is not indispensable to accomplish locomotion driven by internal deformations, provided that the crawler may execute sufficiently large body deformations. Thus, there is no snail theorem. Namely, the crawling analog of the scallop theorem of low Reynolds number hydrodynamics does not hold for snail-like crawlers. The frictional case is obtained by assuming that the viscous coefficient governing tangential resistance forces, which act parallel and in the direction opposite to the velocity of the point to which they are applied, depends on the normal force acting at that point. We combine these surface interactions with inertial effects in order to investigate the mechanisms governing the motility of a bristle-robot. This model locomotor is easily manufactured and has been proposed as an effective tool to replicate and study collective bacterial motility. \ua9 EDP Sciences/Societ\ue0 Italiana di Fisica/Springer-Verlag 2012