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Abstract Background In children with severe generalized cerebral palsy, pneumonias are a major health issue. Malnutrition, dysphagia, gastro-oesophageal reflux, impaired respiratory function and constipation are hypothesized risk factors. Still, no data are available on the relative contribution of these possible risk factors in the described population. This paper describes the initiation of a study in 194 children with severe generalized cerebral palsy, on the prevalence and on the impact of these hypothesized risk factors of recurrent pneumonias. Methods/Design A nested case-control design with 18 months follow-up was chosen. Dysphagia, respiratory function and constipation will be assessed at baseline, malnutrition and gastro-oesophageal reflux at the end of the follow-up. The study population consists of a representative population sample of children with severe generalized cerebral palsy. Inclusion was done through care-centres in a predefined geographical area and not through hospitals. All measurements will be done on-site which sets high demands on all measurements. If these demands were not met in "gold standard" methods, other methods were chosen. Although the inclusion period was prolonged, the desired sample size of 300 children was not met. With a consent rate of 33%, nearly 10% of all eligible children in the Netherlands are included (n = 194). The study population is subtly different from the non-participants with regard to severity of dysphagia and prevalence rates of pneumonias and gastro-oesophageal reflux. Discussion Ethical issues complicated the study design. Assessment of malnutrition and gastro-oesophageal reflux at baseline was considered unethical, since these conditions can be easily treated. Therefore, we postponed these diagnostics until the end of the follow-up. In order to include a representative sample, all eligible children in a predefined geographical area had to be contacted. To increase the consent rate, on-site measurements are of first choice, but timely inclusion is jeopardised. The initiation of this first study among children with severe neurological impairment led to specific, unexpected problems. Despite small differences between participants and non-participating children, our sample is as representative as can be expected from any population-based study and will provide important, new information to bring us further towards effective interventions to prevent pneumonias in this population.

Abstract: This paper presents an experimental investigation on micromilling of fully sintered Zirconia ceramics by means of advanced cutting tools, including cBN and diamond coated mills. Zirconium oxide is selected because of its high hardness, resistance to wear, heat and chemicals. Two-flute end mills of nominal diameter 1mm and negative rake angle were used. The effect of the coating and tool material, along with the cutting parameters, were investigated by means of a one-factor variation experimental design; and the responses of interest, including tool wear and sample surface quality, were monitored over the machining time. The worn tools and the machined surfaces were also analyzed on a SEM to investigate the type of material removal mechanisms (MRM). The diamond coated tools provide the best performance in terms of life time, however delamination of the diamond coating followed by wear of the underlying hardmetal is identified as the prevailing tool wear mechanism. A ductile type of material removal mechanism could be observed, inducing an achievable surface roughness below 60nm. On the contrary, cBN tools exhibited fast breakage. A combined ductile-brittle material removal mechanism occurs, resulting in a surface roughness around 300nm. [Copyright &y& Elsevier]