Editorial

Ohne Zusammenfassung

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Editorial

     

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.     

Parent–Adolescent Sexual Communication and Its Association With Adolescent Sexual Behaviors: A Nationally Representative Analysis in the Netherlands

Sexual communication is a principal means of transmitting sexual values, beliefs, expectations, and knowledge from parents to children. Although this area has received considerable research attention, more studies with representative samples are needed to assure that findings are reflective of populations of interest. A nationally representative sample of parent–adolescent dyads (N = 2,965; mean adolescent age = 13.8 years) in the Netherlands was employed to examine the frequency of parent–adolescent sexual communication and its association with adolescent sexual behaviors (defined as sexual initiation, condom use, and contraceptive pill use). Nine communication topics in the areas of anatomy, relationships and rights, and protection and contraception were examined. In all, 75%of parents reported having discussed at least one topic multiple times with their adolescents. Romantic relationships were discussed most frequently. Hierarchical logistic regression analyses indicated that parent–adolescent sexual communication on protection and contraception was positively associated with adolescent sexual initiation and contraceptive pill use but not condom use. This may reflect that adolescents, when they become sexually active, are more likely to discuss sexuality with their parents. Findings are interpreted within the context of Dutch culture, which is generally accepting of adolescent sexuality and characterized by open sexual communication.     

An Ecological Model for Quantitative Risk Assessment for Schistosomiasis: The Case of a Patchy Environment in the Coastal Tropical Area of Northeastern Brazil

We developed a stochastic model for quantitative risk assessment for the Schistosoma mansoni (SM) parasite, which causes an endemic disease of public concern. The model provides answers in a useful format for public health decisions, uses data and expert opinion, and can be applied to any landscape where the snail Biomphalaria glabrata is the main intermediate host (South and Central America, the Caribbean, and Africa). It incorporates several realistic and case‐specific features: stage‐structured parasite populations, periodic praziquantel (PZQ) drug treatment for humans, density dependence, extreme events (prolonged rainfall), site‐specific sanitation quality, environmental stochasticity, monthly rainfall variation, uncertainty in parameters, and spatial dynamics. We parameterize the model through a real‐world application in the district of Porto de Galinhas (PG), one of the main touristic destinations in Brazil, where previous studies identified four parasite populations within the metapopulation. The results provide a good approximation of the dynamics of the system and are in agreement with our field observations, i.e., the lack of basic infrastructure (sanitation level and health programs) makes PG a suitable habitat for the persistence and growth of a parasite metapopulation. We quantify the risk of SM metapopulation explosion and quasi‐extinction and the time to metapopulation explosion and quasi‐extinction. We evaluate the sensitivity of the results under varying scenarios of future periodic PZQ treatment (based on the Brazilian Ministry of Health's plan) and sanitation quality. We conclude that the plan might be useful to slow SM metapopulation growth but not to control it. Additional investments in better sanitation are necessary.