Random Convex Hulls and Extreme Value Statistics

In this paper we study the statistical properties of convex hulls of $N$ random points in a plane chosen according to a given distribution. The points may be chosen independently or they may be correlated. After a non-exhaustive survey of the somewhat sporadic literature and diverse methods used in the random convex hull problem, we present a unifying approach, based on the notion of support function of a closed curve and the associated Cauchy's formulae, that allows us to compute exactly the mean perimeter and the mean area enclosed by the convex polygon both in case of independent as well as correlated points. Our method demonstrates a beautiful link between the random convex hull problem and the subject of extreme value statistics. As an example of correlated points, we study here in detail the case when the points represent the vertices of $n$ independent random walks. In the continuum time limit this reduces to $n$ independent planar Brownian trajectories for which we compute exactly, for all $n$, the mean perimeter and the mean area of their global convex hull. Our results have relevant applications in ecology in estimating the home range of a herd of animals. Some of these results were announced recently in a short communication [Phys. Rev. Lett. {\bf 103}, 140602 (2009)].Comment: 61 pages (pedagogical review); invited contribution to the special issue of J. Stat. Phys. celebrating the 50 years of Yeshiba/Rutgers meeting

Correlations and forecast of death tolls in the Syrian conflict

The Syrian armed conflict has been ongoing since 2011 and has already caused thousands of deaths. The analysis of death tolls helps to understand the dynamics of the conflict and to better allocate resources and aid to the affected areas. In this article, we use information on the daily number of deaths to study temporal and spatial correlations in the data, and exploit this information to forecast events of deaths. We found that the number of violent deaths per day in Syria varies more widely than that in England in which non-violent deaths dominate. We have identified strong positive auto-correlations in Syrian cities and non-trivial cross-correlations across some of them. The results indicate synchronization in the number of deaths at different times and locations, suggesting respectively that local attacks are followed by more attacks at subsequent days and that coordinated attacks may also take place across different locations. Thus the analysis of high temporal resolution data across multiple cities makes it possible to infer attack strategies, warn potential occurrence of future events, and hopefully avoid further deaths

Basic Income by Default: Lessons from Iran's 'Cash Subsidy' Programme

Karshenas and Tabatabai consider Iran’s nationwide, universal cash transfer programme, which was launched in December 2010 as compensation for massive cuts in subsidies that led to increased prices for energy and other basic products. The authors describe the unusual manner in which the programme emerged, and its potential lessons. Of particular interest is the impact on incomes and expenditures, labour supply, inflation, income distribution, and poverty, in the immediate aftermath of the launch of the programme, as well as its implications for similar schemes such as financing a UBI by carbon taxes. Given an extremely adverse broader environment however, the programme, while still continuing after eight years, has lost much of its lustre as the purchasing power of the transfers has been largely wiped out through inflation

Myopic Misery: Maternal Depression, Child Investments, and the Neurobiological Poverty Trap

In this paper, I explore in an overlapping generations framework, a mechanism motivating a neurobiological poverty trap. Poverty causes stress and depression in individuals susceptible to depression. Poor and depressed individuals discount the future at a higher rate and invest less in the human capital of their children than mentally healthy or rich individuals. This gene-environment interaction generates a vicious cycle in which poor individuals inherit not only susceptibility to depression but also stress and poverty. I show that a successful one-time intervention has the power to permanently eliminate the neurobiological poverty trap

Socioeconomic mobility and talent utilization of workers from poorer backgrounds: The overlooked importance of within-organization dynamics

Socioeconomic mobility, or the ability of individuals to improve their socioeconomic standing through merit-based contributions, is a fundamental ideal of modern societies. The key focus of societal efforts to ensure socioeconomic mobility has been on the provision of educational opportunities. We review evidence that even with the same education and job opportunities, being born into a poorer family undermines socioeconomic mobility due to processes occurring within organizations. The burden of poorer background might, ceteris paribus, be economically comparable to the gender gap. We argue that in the societal and scientific effort to promote socioeconomic mobility, the key context in which mobility is supposed to happen—organizations—as well as the key part of the life of people striving toward socioeconomic advancement—that as working adults—have been overlooked. We integrate the organizational literature pointing to key within-organizational processes impacting objective (socioeconomic) success with research, some emergent in organizational sciences and some disciplinary, on when, why, and how people from poorer backgrounds behave or are treated by others in the relevant situations. Integrating these literatures generates a novel and useful framework for identifying issues people born into poorer families face as employees, systematizes extant evidence and makes it more accessible to organizational scientists, and allows us to lay the agenda for future organizational scholarshi

La désadification des mouts et des vins par formation d'un sel double

Cet exposé donne un aperçu général du procédé de désacidification au moyen du sel double, mis au point par WURDIG et KIELHOFER pour les moûts et les vins. Il présente également les bases de calcul développées par REBELEIN et par l'auteur. Il traite en outre, de la possibilité d'augmenter l'effet de la désacidification par le sel double en ajoutant de l'acide tartrique