Fully 2 D flow modeling of resin infusion under flexible tooling using unstructured meshes and wet and dry compaction properties

This article presents a model to simulate the RIFT process for complex 2 1/2D geometries in advance. Compaction and permeability experiments were carried out for two types of preform. A significant difference between dry and wet preform compaction was observed. The model takes both into account and by doing so, the general assumption, that the RIFT process can be modeled as a quasi-static process, becomes invalid. Therefore, a fully transient model is proposed, including the preform compaction flux. Experiments were carried out to validate the model. It was found that using the wet and dry preform properties leads to a good prediction of the height distributions, flow front positions and filling times

Optimising the flow pipe arrangement for resin infusion under flexible tooling

A method is presented to optimise the flow pipe arrangement for the RIFT process for complex 2 1/2D geometries. To this end, a mesh distance-based model is coupled to a genetic optimisation algorithm. The mesh distance-based model is based on the assumption that the resin fills the nodes closest to the inlets first. It was verified with cases known from literature and with the results from a physically based flow model. The genetic algorithm provides a stable and effective optimisation method. A variable crossover rate increased its effectiveness. Depending on the choice of fitness function, the method can be used to optimise the different production parameters such as flow pipe position and length, fill distance and number of vents

Spatial working memory and contextual cueing in patients with Korsakoff amnesia

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Reliability and validity of a qualitative and quantitative motor test for 5- to 6-year-old children

Reliability and validity of a qualitative and quantitative motor test for 5- to 6-year-old children. Kroes M, Vissers YL, Sleijpen FA, Feron FJ, Kessels AG, Bakker E, Kalff AC, Hendriksen JG, Troost J, Jolles J, Vles JS. Department of Neurology, University Hospital Maastricht, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands. Clumsiness in preschool children may be a precursor to impaired academic performance and psychological and developmental problems. It is assumed that in this age group especially the qualitative aspects (=pattern) of a movement reflect variations in motor development. Currently available motor tests for this age group, however, mostly objectify quantitative aspects of a movement alone and do not objectify qualitative aspects. The aim of this study was to develop a new, valid, and reliable tool (Maastricht's Motor Test (MMT)) to objectify qualitative and quantitative aspects of movement in 5- to 6-year-old children. The test covers Static Balance (14 items), Dynamic Balance (20 items), Ball Skills (eight items), and Diadochokinesis and Manual Dexterity (28 items). About 50% of the items measure qualitative aspects and 50% quantitative aspects of movements. In total 487 subjects were recruited from the first year of primary school. To validate the test, one school doctor's global judgment was used as a form of expert validity. Sensitivity and specificity were calculated for different cut-off points. Intra-class correlation coefficients (ICC) of inter-rater (N = 42), intra-rater (N = 24), and test-retest (N = 43) agreement were determined. ICCs of the qualitative total score ranged from 0.61 to 0.95 and were comparable with those of the total quantitative score. The MMT can be used to objectify both qualitative and quantitative aspects of movements. The additional value of the qualitative observations has to be determined in children with various developmental problems

Suitability of Pharmacokinetic Models for Dynamic Contrast-Enhanced MRI of Abdominal Aortic Aneurysm Vessel Wall: A Comparison

PURPOSE: Increased microvascularization of the abdominal aortic aneurysm (AAA) vessel wall has been related to AAA progression and rupture. The aim of this study was to compare the suitability of three pharmacokinetic models to describe AAA vessel wall enhancement using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). MATERIALS AND METHODS: Patients with AAA underwent DCE-MRI at 1.5 Tesla. The volume transfer constant (K(trans) ), which reflects microvascular flow, permeability and surface area, was calculated by fitting the blood and aneurysm vessel wall gadolinium concentration curves. The relative fit errors, parameter uncertainties and parameter reproducibilities for the Patlak, Tofts and Extended Tofts model were compared to find the most suitable model. Scan-rescan reproducibility was assessed using the interclass correlation coefficient and coefficient of variation (CV). Further, the relationship between K(trans) and AAA size was investigated. RESULTS: DCE-MRI examinations from thirty-nine patients (mean age+/-SD: 72+/-6 years; M/F: 35/4) with an mean AAA maximal diameter of 49+/-6 mm could be included for pharmacokinetic analysis. Relative fit uncertainties for K(trans) based on the Patlak model (17%) were significantly lower compared to the Tofts (37%) and Extended Tofts model (42%) (p<0.001). K(trans) scan-rescan reproducibility for the Patlak model (ICC = 0.61 and CV = 22%) was comparable with the Tofts (ICC = 0.61, CV = 23%) and Extended Tofts model (ICC = 0.76, CV = 22%). K(trans) was positively correlated with maximal AAA diameter (Spearman's rho = 0.38, p = 0.02) using the Patlak model. CONCLUSION: Using the presented imaging protocol, the Patlak model is most suited to describe DCE-MRI data of the AAA vessel wall with good K(trans) scan-rescan reproducibility

Contrast Material-induced Nephropathy in the Era of Hydration

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