Multivariate distributions defined in terms of contours

The paper deals with the problem of using contours as the basis for defining probability distributions. First, the most general probability densities with given contours are obtained and the particular cases of circular and elliptical contours are dealt with. It is shown that the so-called elliptically contoured distributions do not include all possible cases. Next, the case of contours defined by polar coordinates is analyzed including its simulation and parameter estimation. Finally, the case of cumulative distribution functions with given contours is discussed. Several examples are used for illustrative purposes.     

Framing Latina/o Immigration, Education, and Activism

Although Latinas/os have a long history in the USA and represent a growing percentage of the population, they remain largely invisible or stereotyped in dominant images and discourses. Such representations are often ahistorical, and they camouflage the effects of US power and inequality. However, the spring 2006 immigrant rights demonstrations disturbed dominant conceptions. The demonstrators called attention to the contradictory US practices that disrupt home countries, recruit labor migrants, and deny immigrants full participation. Likewise, the role of students in these demonstrations spurred reflections on why youth would walk out of their schools for immigrant rights. Inspired by these demonstrations, we combine materials from multiple disciplines to emphasize the significance of US imperialism, exploitation, and exclusion on Latina/o migration, education, and activism. Key to this article is a reframing of how the media, K-12 curriculum, and popular discourse often engage in a cultural cover-up that sustains inequality.     

Social Support Interventions in Migrant Populations

The phenomenon of immigration has led to an important increasein the number of social programmes and services for migrantpopulations in many European countries. However, some investigationshave shown that the use of formal resources is extremely lowin these groups. In contrast to the limited utilization of programmesand services, research in the field of social psychology hasrevealed that the primary source of help and support for immigrantsis their own informal social network. After analysing the characteristics,advantages and limitations of formal and informal support systems,this paper presents a typology of social support interventionswith migrant populations that integrates both types of support.Four levels are differentiated: dyadic interventions, socialnetwork interventions, mutual aid groups and community interventions.The development of programmes to strengthen the informal supportsystem is emphasized as an alternative to integrating formaland informal resources in social work practice with migrantpopulations.     

Improving flexibility and efficiency by adding parallelism to genetic algorithms

In this paper we develop a study on several types of parallel genetic algorithms (PGAs). Our motivation is to bring some uniformity to the proposal, comparison, and knowledge exchange among the traditionally opposite kinds of serial and parallel GAs. We comparatively analyze the properties of steady-state, generational, and cellular genetic algorithms. Afterwards, this study is extended to consider a distributed model consisting in a ring of GA islands. The analyzed features are the time complexity, selection pressure, schema processing rates, efficacy in finding an optimum, efficiency, speedup, and resistance to scalability. Besides that, we briefly discuss how the migration policy affects the search. Also, some of the search properties of cellular GAs are investigated. The selected benchmark is a representative subset of problems containing real world difficulties. We often conclude that parallel GAs are numerically better and faster than equivalent sequential GAs. Our aim is to shed some light on the advantages and drawbacks of various sequential and parallel GAs to help researchers using them in the very diverse application fields of the evolutionary computation.     

A team level investigation of the relationship between Leader–Member Exchange (LMX) differentiation,and commitment and performance

Although the differential treatment of team members by their leader is at the heart of Leader–Member Exchange (LMX) theory, empirical studies exploring the role of within-team LMX differentiation in relation to team outcomes are still relatively scarce. This study among 269 Dutch secondary school teachers from 33 different teams tested the hypotheses that the relationship between LMX differentiation and team commitment, and team performance is moderated by LMX-quality median. Moreover, we hypothesized that team members' perceived dissimilarity regarding work values and orientations would be positively related to within-team LMX differentiation. Teachers completed questionnaires on LMX-quality, dissimilarity, and team commitment, whereas team performance was rated by school principals. Results indeed showed that LMX differentiation is positively related to both outcome variables in teams with a low LMX-quality median only. As expected, more perceived dissimilarity between team members was related to more within-team variability in LMX-scores. These results contribute to knowledge on hypothetical antecedents and consequences of LMX differentiation at the team level.     

Activity patterns and temporal niche partitioning of dogs and medium-sized wild mammals in urban parks of Xalapa,Mexico

Urban Ecosystems - Free-ranging domestic dogs are the world most common exotic carnivore species that could negatively interact with the native wildlife as predators, competitors, and disease...     

From industrial restructuring to the financial crisis: Mainstream nationalism and minimum income in the Basque Country

The uneven development of minimum incomes in Spain is one of the factors that explain the significant differences in the poverty indicators that characterize the Spanish regions, generally in favour of the territories most committed to these policies (Basque Country, Navarra and Asturias). However, there are other aspects that deserve some consideration when interpreting the specific method of developing minimum incomes in southern Europe. One aspect has to do with the differing dynamics of countries, such as Spain and Italy, which have opted for a decentralized regional model. In this regard, the regional autonomous initiative of the Basque Country played a decisive role in promoting minimum income programs in the late 1980s. Without its leadership in the launch of the regional minimum income policy, Spanish trade unions would probably not have opted for this method as a mechanism for combating poverty in the 1990s. No Italian region went on to play this driving role at that time. This article analyses the ideological foundations of the Basque minimum income policy introduced in the late 1980s and which grew significantly before and during the crisis that started in 2007-2008. It examines the dominant political narrative on this issue by analysing the discourse of some of the key nationalist leaders involved in the birth and development of the minimum income scheme. The approach shows that the experience of social decline linked to industrial restructuring processes was instrumental in the construction of the nationalist narrative.     

Is Over-Education a Problem in Spain? Empirical Evidence Based on the EU-SILC

Spain is suffering an important economic slowdown which affects significantly to unemployment rises. For this reason, many individuals are considering to increase their educational level. However, this decision can lead to get worse labor market indicators. In this paper, we analyze the problem of over-education in Spain and its effect on earnings. Using the last four waves (2009–2012) of the European Union Statistics on Income and Living Conditions (EU-SILC, 2009–2012) this study analyses over-education situation of employed people and compares over-education rates and earnings of these individuals. Cross-sectional analysis (focused on a recent period of time) is performed. We apply different matching techniques based on propensity score methods to evaluate the impact of over-education on personal earnings. The results obtained in this paper add more empirical evidence supporting the effect of education on earnings together with occupational placement because over-education could be a great problem for many countries. In Spain, there exists a problem of over-education which varies among occupations. Overeducated workers are most likely to be found among “Service workers and shop and market sales workers” and “Elementary occupations”. Also, the majority of individuals working as “Professionals” are adequately educated. Besides, over-education has a significant negative impact on earnings. Although the results depend on the way we define over-education (interval or modal method), those individuals over-educated receive less earnings than they correspond to. In fact, the decrease can reach about 5000 euro per year.     

Campylobacter QMRA: A Bayesian Estimation of Prevalence and Concentration in Retail Foods Under Clustering and Heavy Censoring

A Bayesian statistical temporal‐prevalence‐concentration model (TPCM) was built to assess the prevalence and concentration of pathogenic campylobacter species in batches of fresh chicken and turkey meat at retail. The data set was collected from Finnish grocery stores in all the seasons of the year. Observations at low concentration levels are often censored due to the limit of determination of the microbiological methods. This model utilized the potential of Bayesian methods to borrow strength from related samples in order to perform under heavy censoring. In this extreme case the majority of the observed batch‐specific concentrations was below the limit of determination. The hierarchical structure was included in the model in order to take into account the within‐batch and between‐batch variability, which may have a significant impact on the sample outcome depending on the sampling plan. Temporal changes in the prevalence of campylobacter were modeled using a Markovian time series. The proposed model is adaptable for other pathogens if the same type of data set is available. The computation of the model was performed using OpenBUGS software.     

Paired comparisons analysis: an axiomatic approach to ranking methods

In this paper we present an axiomatic analysis of several ranking methods for general tournaments. We find that the ranking method obtained by applying maximum likelihood to the (Zermelo-)Bradley-Terry model, the most common method in statistics and psychology, is one of the ranking methods that perform best with respect to the set of properties under consideration. A less known ranking method, generalised row sum, performs well too. We also study, among others, the fair bets ranking method, widely studied in social choice, and the least squares method.