De houding jegens klasgenoten: etnisch gekleurd? Een onderzoek naar factoren van invloed op de attitude van basisschoolleerlingen jegens klasgenoten van verschillende etnische herkomst

The existence of so-called ‘black schools’ is seen as a societal problem, not only because these schools are said to negatively affect student performance,but also because of the negative effects the existence of these schools is suggested to have on the integration of ethnic minorities in society. It has oftenbeen claimed that ethnically mixed schools promote the integration ofminority students. This claim is largely based on Allport’s well-known contacthypothesis, which states that contact stimulates mutual acceptanceand weakens prejudice. In the US there is a long tradition in research on students’ interethnic attitudes. In the Netherlands, research in this area is rather scarce. With our study, we aim to contribute to the understanding of the effects of ethnicclass composition and interethnic contact between students on students’ethnic attitudes. Our study concerned a sample of 1287 2nd to 6th grade students fromfourteen schools in the Rotterdam and Nijmegen city areas. The schoolsranged from mainly ‘white’ to mainly ‘black’ schools. The students were administered a questionnaire in order to assess the number of intra- as wellas inter-ethnic mutual contacts. They were also asked to rate friendships with students from varying ethnic backgrounds, in order to assess theirattitudestowards their own and towards other ethnic groups. The teachers provided information about the students’ ethnic background, the ethnic composition of the school class and whether they provided some form ofintercultural education. The results of our study showed students to have more positive attitudes towards children from their own ethnic group than towards children fromother groups. The ethnic composition of the school class did not seem to affect students’ attitudes; neither did the number of inter-ethnic contacts,nor the amount of intercultural education

Job-Shop Scheduling by Implicit Enumeration

The classical combinatorial optimization problem of minimizing maximum completion time in a general job-shop has been the subject of extensive research. In this paper we review and extend this work. A general bounding approach is developed which includes all previously presented lower bounds as special cases. The strongest bound obtainable in this way is combined with two enumeration schemes, the relative merits of which are discussed. The results of some computational experiments and a large bibliography are included as well.

X-linked adrenoleukodystrophy: biochemical diagnosis and enzyme defect

The adrenoleukodystrophies refer to three genetically distinct disorders all characterized by the accumulation of very long-chain fatty acids. In this paper we will review the biochemical aspects of these leukodystrophies with particular emphasis on the methods used to measure very long-chain fatty acid levels in plasma and their reliability. Furthermore, we will concentrate on the primary defect in the X-linked form of adrenoleukodystroph

Evaluation of bone mineralization in former preterm born children: Phalangeal quantitative ultrasound cannot replace dual-energy X-ray absorptiometry

Background: Preterm infants are at risk of impaired bone health in later life. Dual-energy X-ray absorptiometry-scan (DXA) is the gold standard to determine bone mineralization. Phalangeal quantitative ultrasound (pQUS) is an alternative technique that is inexpensive, easy to use and radiation-free. The aim of this study was to investigate whether both techniques reveal equivalent results. Materials and methods: Sixty former preterm infants (31 boys; 29 girls) received a DXA and pQUS at age 9 to 10 years. DXA measured bone mineral content (BMC) and bone mineral density (BMD) for total body and lumbar spine (L1-4), while pQUS measured the amplitude dependent speed of sound (AD-SoS) and bone transit time (BTT) at metacarpals II-IV providing continuous values and Z-scores based on age and sex. Four statistical methods evaluated the association between both techniques: Pearson's correlation coefficients, partial correlation coefficients adjusted for gestational age, height and BMI, Bland-Altman analysis and cross tabulation. Results: Both techniques showed a statistically significant weak correlation for continuous values as well as Z-scores (0.291–0.462, p < 0.05). Boys had significant and relatively high correlations (0.468–0.585, p < 0.05). In comparison, the correlations for girls were not significant. Correlation coefficients further decreased while calculating the partial correlations. The Bland-Altman plots showed poor agreement. Sensitivity ranged from 33% to 92% and specificity from 16% to 68%. Positive and negative predictive values ranged from 4% to 38% and 82% to 97%, respectively. Conclusions: We found statistically significant weak correlations and poor agreement between DXA and pQUS measurements. DXA is not equivalent to pQUS and therefore not replaceable by this technique in former preterm born children at the age of 9 to 10 years