Some Open Points in Nonextensive Statistical Mechanics

We present and discuss a list of some interesting points that are currently open in nonextensive statistical mechanics. Their analytical, numerical, experimental or observational advancement would naturally be very welcome.Comment: 30 pages including 6 figures. Invited paper to appear in the International Journal of Bifurcation and Chao

A note on q-Gaussians and non-Gaussians in statistical mechanics

The sum of $N$ sufficiently strongly correlated random variables will not in general be Gaussian distributed in the limit N\to\infty. We revisit examples of sums x that have recently been put forward as instances of variables obeying a q-Gaussian law, that is, one of type (cst)\times[1-(1-q)x^2]^{1/(1-q)}. We show by explicit calculation that the probability distributions in the examples are actually analytically different from q-Gaussians, in spite of numerically resembling them very closely. Although q-Gaussians exhibit many interesting properties, the examples investigated do not support the idea that they play a special role as limit distributions of correlated sums.Comment: 17 pages including 3 figures. Introduction and references expande

Strictly and asymptotically scale-invariant probabilistic models of NN correlated binary random variables having {\em q}--Gaussians as N→∞N\to \infty limiting distributions

In order to physically enlighten the relationship between {\it $q$--independence} and {\it scale-invariance}, we introduce three types of asymptotically scale-invariant probabilistic models with binary random variables, namely (i) a family, characterized by an index $\nu=1,2,3,...$, unifying the Leibnitz triangle ($\nu=1$) and the case of independent variables ($\nu\to\infty$); (ii) two slightly different discretizations of $q$--Gaussians; (iii) a special family, characterized by the parameter $\chi$, which generalizes the usual case of independent variables (recovered for $\chi=1/2$). Models (i) and (iii) are in fact strictly scale-invariant. For models (i), we analytically show that the $N \to\infty$ probability distribution is a $q$--Gaussian with $q=(\nu -2)/(\nu-1)$. Models (ii) approach $q$--Gaussians by construction, and we numerically show that they do so with asymptotic scale-invariance. Models (iii), like two other strictly scale-invariant models recently discussed by Hilhorst and Schehr (2007), approach instead limiting distributions which are {\it not} $q$--Gaussians. The scenario which emerges is that asymptotic (or even strict) scale-invariance is not sufficient but it might be necessary for having strict (or asymptotic) $q$--independence, which, in turn, mandates $q$--Gaussian attractors.Comment: The present version is accepted for publication in JSTA

A realist evaluation of the role of communities of practice in changing healthcare practice

<p>Abstract</p> <p>Background</p> <p>Healthcare organisations seeking to manage knowledge and improve organisational performance are increasingly investing in communities of practice (CoPs). Such investments are being made in the absence of empirical evidence demonstrating the impact of CoPs in improving the delivery of healthcare. A realist evaluation is proposed to address this knowledge gap. Underpinned by the principle that outcomes are determined by the context in which an intervention is implemented, a realist evaluation is well suited to understand the role of CoPs in improving healthcare practice. By applying a realist approach, this study will explore the following questions: What outcomes do CoPs achieve in healthcare? Do these outcomes translate into improved practice in healthcare? What are the contexts and mechanisms by which CoPs improve healthcare?</p> <p>Methods</p> <p>The realist evaluation will be conducted by developing, testing, and refining theories on how, why, and when CoPs improve healthcare practice. When collecting data, context will be defined as the setting in which the CoP operates; mechanisms will be the factors and resources that the community offers to influence a change in behaviour or action; and outcomes will be defined as a change in behaviour or work practice that occurs as a result of accessing resources provided by the CoP.</p> <p>Discussion</p> <p>Realist evaluation is being used increasingly to study social interventions where context plays an important role in determining outcomes. This study further enhances the value of realist evaluations by incorporating a social network analysis component to quantify the structural context associated with CoPs. By identifying key mechanisms and contexts that optimise the effectiveness of CoPs, this study will contribute to creating a framework that will guide future establishment and evaluation of CoPs in healthcare.</p

Mango gall midges on Australia\u27s doorstep

Gall midges (Diptera: Cecidomyiidae) are common pests of mango trees in southern Asia. Currently, there are 21 described species from six genera and at least 10 undescribed species which are known to attack mango worldwide. All of the six described species known to attack mango in Southeast Asia and Australasia belong to the genus Procontarinia. Most mango gall midges cause leaf galls but some cause flower damage, others damage branches and shoots and one species attacks fruit. Few studies have quantified the economic impact of any of these species but considerable damage to leaves is commonly observed and, similar to direct damage by flower- and fruit-infesting species, is likely to affect fruit production. Studies of mango midges are hampered by difficulties in associating infestation symptoms with a particular species but techniques developed recently, such as gall histology and DNA barcoding, provide a means of accurately identifying known species without relying on rearing adults from galls. Surveys of mango trees in Australia, Cambodia, Myanmar, the Philippines, Timor-Leste, Solomon Islands and Papua New Guinea revealed the presence of eight species of gall midge, four of which appear to be new to science: Procontarinia sp. causing “high doughnut” leaf gall in Timor-Leste, Procontarinia sp. causing “low doughnut” leaf gall in Timor-Leste, Procontarinia sp. causing “blister” leaf gall in Timor-Leste and Cecidomyiidae sp. causing spherical leaf gall in Cambodia. Only a single species, Procontarinia pustulata, was present in Australia, having recently arrived onto Cape York Peninsula from Papua New Guinea via the Torres Strait. Furthermore, one of the undescribed species was detected recently near the Papua New Guinea/Indonesian border, indicating the possible presence of a pathway for the movement of midges from Asia into Australasia and continuing into Australia. The presence of a species on the Solomon Islands lends further support for an active pathway into Australasia. Procontarina echinogalliperda is reported for the first time from Myanmar. P. pustulata is reported for the first time from Timor-Leste and the Philippines and Procontarinia mangicola is reported for the first time from the Solomon Islands