Edge-colouring of joins of regular graphs, I

We prove that the edges of every even graph G=G ₁+G ₂ that is the join of two regular graphs G _i =(V _i ,E _i ) can be coloured with Δ(G) colours, whenever Δ(G)=Δ(G ₂)+|V ₁|. The proof of this result yields a combinatorial algorithm to optimally colour the edges of this type of graphs.     

The effects of high HIV prevalence on orphanhood and living arrangements of children in Malawi, Tanzania, and South Africa

Using longitudinal data from three demographic surveillance systems (DSS) and a retrospective cohort study, we estimate levels and trends in the prevalence and incidence of orphanhood in South Africa, Tanzania, and Malawi in the period 1988-2004. The prevalence of maternal, paternal, and double orphans rose in all three populations. In South Africa - where the HIV epidemic started later, has been very severe, and has not yet stabilized - the incidence of orphanhood among children is double that of the other populations. The living arrangements of children vary considerably between the populations, particularly in relation to fathers. Patterns of marriage, migration, and adult mortality influence the living and care arrangements of orphans and non-orphans. DSS data provide new insights into the impact of adult mortality on children, challenging several widely held assumptions. For example, we find no evidence that the prevalence of child-headed households is significant or has increased in the three study areas.     

A Crisis-Driven Migration? Aspirations and Experiences of the Post-2008 South European Migrants in London

Since the 1990s young South Europeans have been attracted to London by the dynamic labour market and cultural radiance of the city, but also pushed by unfavourable conditions in the labour markets of their origin countries. Subsequently, the Eurozone crisis, austerity politics and their socio-political consequences have markedly intensified migration rates. But did they also signify a rupture in terms of the motivations, experiences and aspirations of the migrants? Drawing on in-depth interviews with Greek, Italian and Spanish migrants of different educational levels, we find that post-materialist motivations and pro-migration dispositions prevail among the “crisis-migrants”. Migration is seen and experienced as a step forward, rather than a disruptive force, signalling a positive message in defence of intra-EU free mobility. Yet at times of neoliberal deregulation and economic and political uncertainty, aspirations for socio-economic stability and settlement are also of growing importance, questioning mobility as the normative way of contemporary life.     

Edge-colouring of joins of regular graphs II

We prove that the edges of every even graph G=G ₁+G ₂ that is the join of two regular graphs G ₁ and G ₂ can be coloured with Δ(G) colours, whenever Δ(G)=Δ(G ₁)+|V ₂|. The proof of this result together with the results in De Simone and Galluccio (J. Comb. Optim. 18:417–428, 2009) states that every even graph G that is the join of two regular graphs is Class 1. The proof yields an efficient combinatorial algorithm to find a Δ(G)-edge-colouring of this type of graphs.     

Bayesian assessment of goodness of fit against nonparametric alternatives

The classical chi‐square test of goodness of fit compares the hypothesis that data arise from some parametric family of distributions, against the nonparametric alternative that they arise from some other distribution. However, the chi‐square test requires continuous data to be grouped into arbitrary categories. Furthermore, as the test is based upon an approximation, it can only be used if there are sufficient data. In practice, these requirements are often wasteful of information and overly restrictive. The authors explore the use of the fractional Bayes factor to obtain a Bayesian alternative to the chi‐square test when no specific prior information is available. They consider the extent to which their methodology can handle small data sets and continuous data without arbitrary grouping.     

Two-stage adaptive cluster sampling

Adaptive cluster sampling is usually applied when estimating the abundance of elusive, clustered biological populations. It is commonly supposed that all individuals in the selected area units are detected by the observer, but in many acutal situations this assumption may be highly unrealistic and some individuals may be missed. This paper deals with the problem of handling imperfect detectability in adaptive cluster sampling by using a pure design-based approach. A two-stage adaptive procedure is proposed where the abundance in the selected units is estimated by replicated counts.     

Quantity competition, endogenous motives and behavioral heterogeneity

The article shows that strategic quantity competition can be characterized by behavioral heterogeneity, once competing firms are allowed in a pre-market stage to optimally choose the behavioral rule they will follow in their strategic choice of quantities. In particular, partitions of the population of identical firms in which some of them are profit maximizers while others follow an alternative criterion, turn out to be deviation-proof equilibria both in simultaneous and sequential game structures. Our findings that in a strategic framework heterogeneous behavioral rules may be consistent with individual incentives is a first attempt to provide a game-theoretic microfoundation of heterogeneity.     

Prevention of Problematic Gambling Behavior Among Adolescents: Testing the Efficacy of an Integrative Intervention

This study aimed at testing the efficacy of an integrative intervention to prevent adolescent problem gambling acting on a multidimensional set of factors including gambling related knowledge and misconceptions, economic perception of gambling, and superstitious thinking. A pre- and post-test design was performed with 181 Italian adolescents (64 % boys; Mean age = 15.95) randomly assigned to two groups (Training and No Training). Results revealed that the intervention was effective in improving correct knowledge about gambling and reducing misconceptions, perception of gambling’s profitability, and superstitious thinking. Except for misconceptions, these effects were obtained both in participants who were classified as Non-problem and At-Risk/Problem gamblers at the beginning of the intervention. Findings attested also that the training effects were stable over time, and that some changes in gambling behavior were produced. Findings were discussed referring to indications for future research aiming at confirming and extending the present results.     

The estimation of wildlife ungulate abundance using sample area surveys: an application to Maremma Regional Park

Sample surveys for estimating the abundance of wildlife ungulate populations are considered in a design-based approach. On the basis of previous theoretical results, a two-stage sampling is proposed. In the first stage, some spatial units are selected using Lahiri-Midzuno sampling, while in the second stage, the animal abundance in the selected units is estimated by means of plot sampling performed on the faecal accumulation within the units. The statistical properties of the resulting ratio estimator of abundance are outlined. An application of the proposed method for estimating fallow-deer and roe-deer abundance in Maremma Regional Park is described.