A method for dense packing discovery

The problem of packing a system of particles as densely as possible is foundational in the field of discrete geometry and is a powerful model in the material and biological sciences. As packing problems retreat from the reach of solution by analytic constructions, the importance of an efficient numerical method for conducting \textit{de novo} (from-scratch) searches for dense packings becomes crucial. In this paper, we use the \textit{divide and concur} framework to develop a general search method for the solution of periodic constraint problems, and we apply it to the discovery of dense periodic packings. An important feature of the method is the integration of the unit cell parameters with the other packing variables in the definition of the configuration space. The method we present led to improvements in the densest-known tetrahedron packing which are reported in [arXiv:0910.5226]. Here, we use the method to reproduce the densest known lattice sphere packings and the best known lattice kissing arrangements in up to 14 and 11 dimensions respectively (the first such numerical evidence for their optimality in some of these dimensions). For non-spherical particles, we report a new dense packing of regular four-dimensional simplices with density $\phi=128/219\approx0.5845$ and with a similar structure to the densest known tetrahedron packing.Comment: 15 pages, 5 figure

The ethnic identity complexity of transculturally placed foster youth in the Netherlands

This study addresses the ethnic identity of transculturally placed adolescent foster youth with ethnic minority backgrounds in The Netherlands. We conducted qualitative interviews to provide insight into the lifeworlds of twenty foster youth. We found that constructing an ethnic identity was complex for these ethnic minority foster youth. The foster youth showed ethnic identity ambivalence, and contradictory messages about ethnicity by birth parents, foster parents, peers, and strangers contributed to this process. The foster youth also sometimes distanced themselves from their ethnic minority background whereby the intersection of their ethnic minority background and the background of being a foster child could play a role. Additionally, some foster youth told stories of longing for and belonging to their ethnic minority background, especially when birth parents and foster parents cooperated in ethnic socialization. Overall, contradictory and intersecting messages provided by birth parents, foster parents, and peers influenced the extent to which they experienced their ethnic identity as complex. Therefore, future studies should be conducted to provide more insight into these processes, so foster care agencies and foster parents can be trained to fulfill a more guiding role in the ethnic identity development of transculturally placed foster youth

The ethnic identity of transracially placed foster children with an ethnic minority background:A systematic literature review

BackgroundEthnic minority foster children are frequently placed in families with ethnic majority backgrounds. In the international literature these placements are most commonly called transracial placements.AimsWith this study, we aim to obtain an encompassing view of the empirical scientific literature on how transracial placements may affect the ethnic identity of foster children.Materials and methodsTo gain insight into the ethnic identity of transracially placed foster children and the way they are ethnically socialized, we conducted a systematic literature review. We thereby followed the guidelines of the PRISMA statement.ResultsTransracially placed foster children may experience higher fluctuations in their racial/ ethnic identity over time than adolescents with a minority background in the general population. They also seem to be prone to experience disconnection from, or on the contrary, connection with the birth network; and some transracially placed foster children struggle with societal messages they receive about minority ethnicity and race. They may have an increased awareness of their minority ethnic background because of different physical appearances between themselves and the foster family. Foster parents can play a pivotal role in these processes, since culturally competent foster parents may guide foster children in their ethnic identity development by being open towards children’s cultural minority background as well as being self‐reflective regarding their own cultural values and beliefs.DiscussionThe ethnic development of transracially placed foster children seems to be influenced by intersecting mechanisms of being in foster care and having a minority ethnicity. Although the selected articles assume that foster parents impact the ethnic identities of their ethnic minority foster children, none of them measured the impact of foster parents’ skills and knowledge on foster children’ s ethnic identity development directly.ConclusionBeing transracially placed impacts the ethnic identity of foster children. Foster parents need to be cultural competent to encourage their foster children’s ethnic identity development

Perceived discrimination against Dutch Muslim youths in the school context and its relation with externalising behavior

The role of the source of discrimination in relation to minority Muslim youths’ psychosocial well-being has received remarkably little attention in the post-9/11 climate. We have examined one of the aspects of psychosocial well-being that is given prominent attention in the media and public discourse, namely externalising behaviour. The article reports whether perceived discrimination by four sources (school peers and teachers, peers, and adults outside the school) is related to externalising behaviour. Links between perceived discrimination sources and externalising behaviour among Dutch Muslim youths (n = 308, ages 14–18) were examined through surveys. The quantitative findings guided our qualitative analyses of interviews with 10 Muslim Dutch youths on their accounts of discrimination in the school context. When comparing different discrimination sources, only teacher discrimination was found to predict externalising behaviour significantly (explaining 15% of the variance). The qualitative follow-up illustrated the significance of teacher discrimination: Some Muslim youths felt that their teachers held back their school progress, while others reported receiving insults from teachers about their parents’ native country and their religion. We argue that students’ perceived powerlessness within the teacher-student relationship deserves further attention, as some Dutch Muslim youths reported painful experiences, with perceived teacher discrimination linked to higher levels of externalising behaviour

Hanging Out in the Past: Looking for Trouble or Romance? An Exploration of the Practice and Meaning of Hanging Out for Young Dutch People in 1930–60

Young people’s ‘hanging out’ has had different meanings in the recent and distant past in various countries and cultures, including delinquency or a common social phenomenon. Although there is evidence for hanging out as social behaviour in various countries, Dutch research on hanging out as a common social phenomenon is scarce. This article retrospectively explores the practice and meaning of hanging out for young people in the Netherlands between 1930 and 1960. Semi-structured qualitative interviews (n = 60) were analysed using the Constant Comparative Method, resulting in three key themes: familiarity, features and the meanings assigned to hanging out. Results indicate that hanging out was practised and known by most respondents, and included particular features (time, location, gender and routines). Meet, flirt with and date other young people was the most frequently mentioned meaning associated with hanging out. Accordingly, hanging out can indeed be considered to have been a common social phenomenon

“We Say ‘Mothers’ But Mean ‘Parents’”:Qualitative Perceptions and Experiences With Father Absence Among Curaçaoan, Curaçaoan-Dutch, and Dutch Young People

Perceptions and experiences with biological father absence might vary depending on the extent to which father absence constitutes a common family form, like it does in many Caribbean countries. The goal of this qualitative study was to better understand what it means to grow up without a father for Curaçaoan (n = 19; 15–24 years), Curaçaoan-Dutch (n = 15; 14–29 years), and Dutch (n = 16; 16–26 years) young men and women. Findings from thematic analyses of ethically approved in-depth interviews revealed that most interviewees from all three cultural groups perceived no bond with and upbringing from their absent father. The interviewees noted emotional pain, but also mentioned that (m)others compensated for their father’s absence. Dutch interviewees were more negative about their absent father, and both Dutch and Curaçaoan-Dutch interviewees experienced more difficulties with respect to their father’s absence compared with Curaçaoan interviewees. Studying the similarities and differences between perceptions and experiences with father absence enriches our knowledge of what it means to grow up without a father. Doing so from young people’s point of view and across cultures has important practical value by providing a fuller understanding of the meaning of father absence for young people across cultures

“We Say ‘Mothers’ But Mean ‘Parents’”:Qualitative Perceptions and Experiences With Father Absence Among Curaçaoan, Curaçaoan-Dutch, and Dutch Young People

Perceptions and experiences with biological father absence might vary depending on the extent to which father absence constitutes a common family form, like it does in many Caribbean countries. The goal of this qualitative study was to better understand what it means to grow up without a father for Curaçaoan (n = 19; 15–24 years), Curaçaoan-Dutch (n = 15; 14–29 years), and Dutch (n = 16; 16–26 years) young men and women. Findings from thematic analyses of ethically approved in-depth interviews revealed that most interviewees from all three cultural groups perceived no bond with and upbringing from their absent father. The interviewees noted emotional pain, but also mentioned that (m)others compensated for their father’s absence. Dutch interviewees were more negative about their absent father, and both Dutch and Curaçaoan-Dutch interviewees experienced more difficulties with respect to their father’s absence compared with Curaçaoan interviewees. Studying the similarities and differences between perceptions and experiences with father absence enriches our knowledge of what it means to grow up without a father. Doing so from young people’s point of view and across cultures has important practical value by providing a fuller understanding of the meaning of father absence for young people across cultures