A contact process with mutations on a tree

Consider the following stochastic model for immune response. Each pathogen gives birth to a new pathogen at rate $\lambda$. When a new pathogen is born, it has the same type as its parent with probability $1 - r$. With probability $r$, a mutation occurs, and the new pathogen has a different type from all previously observed pathogens. When a new type appears in the population, it survives for an exponential amount of time with mean 1, independently of all the other types. All pathogens of that type are killed simultaneously. Schinazi and Schweinsberg (2006) have shown that this model on $\Z^d$ behaves rather differently from its non-spatial version. In this paper, we show that this model on a homogeneous tree captures features from both the non-spatial version and the $\Z^d$ version. We also obtain comparison results between this model and the basic contact process on general graphs

Australian news media framing of medical tourism in low- and middle-income countries: A content review

© 2013 Imison and Schweinsberg; licensee BioMed Central Ltd. Background: Medical tourism - travel across international borders for health care - appears to be growing globally, with patients from high-income nations increasingly visiting low- and middle-income countries to access such services. This paper analyses Australian television and newspaper news and current affairs coverage to examine how medical tourism and these destinations for the practice are represented to media audiences. Methods: Electronic copies of Australian television (n = 66) and newspaper (n = 65) items from 2005-2011 about medical care overseas were coded for patterns of reporting (year, format and type) and story characteristics (geographic and medical foci in the coverage, news actors featured and appeals, credibility and risks of the practice mentioned). Results: Australian media coverage of medical tourism was largely focused on Asia, featuring cosmetic surgery procedures and therapies unavailable domestically. Experts were the most frequently-appearing news actors, followed by patients. Common among the types of appeals mentioned were access to services and low cost. Factors lending credibility included personal testimony, while uncertainty and ethical dilemmas featured strongly among potential risks mentioned from medical tourism. Conclusions: The Australian media coverage of medical tourism was characterised by a narrow range of medical, geographic and ethical concerns, a focus on individual Australian patients and on content presented as being personally relevant for domestic audiences. Medical tourism was portrayed as an exercise of economically-rational consumer choice, but with no attention given to its consequences for the commodification of health or broader political, medical and ethical implications. In this picture, LMICs were no longer passive recipients of aid but providers of a beneficial service to Australian patients

A social licence for the sharing economy

© 2019 Elsevier Inc. The emergence of community concerns around a range of sharing economy platforms have led to calls for more research into the so-called “dark side” of the sharing economy, including the development and application of analytical frameworks. In this article, we present one such framework based around social licence to operate (SLO), a concept that has been applied most extensively in the mining, forestry and energy sectors. We argue that, despite requiring some adaptations and refinements for application to the sharing economy context, social licence is a relevant and suitable concept for analysing community acceptance of sharing economy platforms and provides an opportunity for mutual learning between different sectors. We present a Sharing Economy SLO Framework and outline a research agenda that includes defining communities of interest and place that are affected by sharing economy practices, analysing the complex relationships between social acceptance and regulatory requirements, identifying and measuring key variables that determine SLO, and developing strategies for building and maintaining SLO for sharing economy practices

The Nature of Aesthetics: How Consumer Culture has Changed our National Parks

Tourism is essentially a modern Western social and cultural phenomenon, the analysis of which has evolved from premodernism through to postmodernism. Tourism differs significantly from nonWestern and historical forms of travel, being closely related to the emergence of modernity with the emphasis on economic viability and consumer culture. The massive growth of tourism over the 20th century and the emergence of a multibillion dollar global tourist industry have impacted on national parks as tourists increasingly seek nature-based experiences. This has occurred in conjunction with increases in leisure time, disposable income, technological improvements in communication and transportation, demographic changes, and a shift in the axis of personal identity and meaningful social action from production to consumption. This article examines how aesthetics fits into this evolution and the current role of national parks with a focus on the emergence of their production through the mass media to a consumer market. Finally, we propose more reflexivity in regards to tourism and place image production

Effect of selection on ancestry: an exactly soluble case and its phenomenological generalization

We consider a family of models describing the evolution under selection of a population whose dynamics can be related to the propagation of noisy traveling waves. For one particular model, that we shall call the exponential model, the properties of the traveling wave front can be calculated exactly, as well as the statistics of the genealogy of the population. One striking result is that, for this particular model, the genealogical trees have the same statistics as the trees of replicas in the Parisi mean-field theory of spin glasses. We also find that in the exponential model, the coalescence times along these trees grow like the logarithm of the population size. A phenomenological picture of the propagation of wave fronts that we introduced in a previous work, as well as our numerical data, suggest that these statistics remain valid for a larger class of models, while the coalescence times grow like the cube of the logarithm of the population size.Comment: 26 page

Wide-bandwidth, tunable, multiple-pulse-width optical delays using slow light in cesium vapor

We demonstrate an all-optical delay line in hot cesium vapor that tunably delays 275 ps input pulses up to 6.8 ns and 740 input ps pulses up to 59 ns (group index of approximately 200) with little pulse distortion. The delay is made tunable with a fast reconfiguration time (hundreds of ns) by optically pumping out of the atomic ground states.Comment: 4 pages, 6 figure

How genealogies are affected by the speed of evolution

In a series of recent works it has been shown that a class of simple models of evolving populations under selection leads to genealogical trees whose statistics are given by the Bolthausen-Sznitman coalescent rather than by the well known Kingman coalescent in the case of neutral evolution. Here we show that when conditioning the genealogies on the speed of evolution, one finds a one parameter family of tree statistics which interpolates between the Bolthausen-Sznitman and Kingman's coalescents. This interpolation can be calculated explicitly for one specific version of the model, the exponential model. Numerical simulations of another version of the model and a phenomenological theory indicate that this one-parameter family of tree statistics could be universal. We compare this tree structure with those appearing in other contexts, in particular in the mean field theory of spin glasses

Glacier maxima in Baffin Bay during the Medieval Warm Period coeval with Norse settlement

The climatic mechanisms driving the shift from the Medieval Warm Period (MWP) to the Little Ice Age (LIA) in the North Atlantic region are debated. We use cosmogenic beryllium-10 dating to develop a moraine chronology with century-scale resolution over the last millennium and show that alpine glaciers in Baffin Island and western Greenland were at or near their maximum LIA configurations during the proposed general timing of the MWP. Complimentary paleoclimate proxy data suggest that the western North Atlantic region remained cool, whereas the eastern North Atlantic region was comparatively warmer during the MWP—a dipole pattern compatible with a persistent positive phase of the North Atlantic Oscillation. These results demonstrate that over the last millennium, glaciers approached their eventual LIA maxima before what is considered the classic LIA in the Northern Hemisphere. Furthermore, a relatively cool western North Atlantic region during the MWP has implications for understanding Norse migration patterns during the MWP. Our results, paired with other regional climate records, point to nonclimatic factors as contributing to the Norse exodus from the western North Atlantic region

Survival of near-critical branching Brownian motion

Consider a system of particles performing branching Brownian motion with negative drift $\mu = \sqrt{2 - \epsilon}$ and killed upon hitting zero. Initially there is one particle at $x>0$. Kesten showed that the process survives with positive probability if and only if $\epsilon>0$. Here we are interested in the asymptotics as \eps\to 0 of the survival probability $Q_\mu(x)$. It is proved that if $L= \pi/\sqrt{\epsilon}$ then for all $x \in \R$, $\lim_{\epsilon \to 0} Q_\mu(L+x) = \theta(x) \in (0,1)$ exists and is a travelling wave solution of the Fisher-KPP equation. Furthermore, we obtain sharp asymptotics of the survival probability when $x<L$ and $L-x \to \infty$. The proofs rely on probabilistic methods developed by the authors in a previous work. This completes earlier work by Harris, Harris and Kyprianou and confirms predictions made by Derrida and Simon, which were obtained using nonrigorous PDE methods

Wide-Bandwidth, Tunable, Multiple-Pulse-Width Optical Delays Using Slow Light in Cesium Vapor

We demonstrate an all-optical delay line in hot cesium vapor that tunably delays 275 ps input pulses up to 6.8 ns and 740 input ps pulses up to 59 ns (group index of approximately 200) with little pulse distortion. The delay is made tunable with a fast reconfiguration time (hundreds of ns) by optically pumping out of the atomic ground states