Het meten van concentratie in (luchtvaart)netwerken : een analyse van verschillende indices

This paper analyzes to what extent different indices are able to measure the concentration in air transport networks. First, we illustrate the theoretical characteristics of the concentration ratio, Herfindahl-Hirschman index, network concentration index and Theilindex by applying these to socalled toy networks with known parameters. Second, the practical applicability of these indices is assessed by calculating them for three domestic airline networks (France, Germany and the United States). The dimensions of the concentration in each of these three networks as a proxy for the city systems are intuitively clear so that the results provide us with an appropriate touchstone for assessing the advantages and drawbacks of each of the indices. Based on the analyses of both the ideal-typical and the actually existing networks, the main implications for future research on concentration indices are discussed

Providing polyurethane foams with functionality: a kinetic comparison of different 'click' and coupling reaction pathways

For high-tech applications, polyurethane (PU) materials require additional surface properties and functionality, which can be achieved by incorporation of "clickable" groups in the PU structure, allowing for polymer post-modification via chemical coupling with desired molecules. Therefore, in this study, various "click" and coupling reactions, consisting of the copper(I) catalyzed Huisgen 1,3-dipolar alkyne-azide, thermally and photo-initiated thiol-ene/thiol-yne and Diels-Alder reactions, have been used for surface functionalization of PU foams. As a result of diffusional effects, the reaction rate was considerably depressed and thus, the reaction parameters, including the temperature and the concentration of reagents and the "click" compound, were optimized for each click/coupling approach to obtain high functionalization yields. As such, a kinetic comparison study of the different chemistries used was performed, using in situ FT-IR and offline H-1 NMR methods. This work not only reveals kinetic trends but also compares promising and limiting aspects of the different click/coupling pathways employed, which is envisaged to be also useful for functionalizing other cross-linked polymeric materials

Myhre syndrome : broadening the phenotypic spectrum

C

Gastric dysmotility following orthopaedic scoliosis surgery in patients with cerebral palsy: a case series

Scoliosis is a common complication in children with cerebral palsy (CP). In these patients, surgical correction carries a high risk of complications. CP is also associated with gastrointestinal dysmotility such as delayed gastric emptying and gastro-oesophageal refl ux. We describe 5 patients with CP in whom symptoms of gastric dysmotility clearly exacerbated after orthopaedic scoliosis surgery. They all showed persisting vomiting, nausea, bloating, weight loss, and anorexia necessitating total parental nutrition and / or jejunal feeding. This intensifi ed nutritional support resulted in weight gain. Symptoms, however, persisted in half of the patients. The aetiology of these gastro-intestinal motility problems following scoliosis surgery remains unclear. Mechanical obstruction needs to be ruled out. Delayed gastric emptying may be due to postprandial antral hypomotility as a consequence of sympathic stimulation. Malnutrition could further aggravate gastrointestinal dysmotility. This complication should be taken into account when surgery for spinal deformities in CP patients is planned, especially in patients with pre-existing gastrointestinal motility problems

Myhre syndrome : a first familial recurrence and broadening of the phenotypic spectrum

Myhre syndrome is a rare multisystem connective tissue disorder, characterized by short stature, facial dysmorphology, variable intellectual disability, skeletal abnormalities, arthropathy, cardiopathy, laryngotracheal anomalies, and stiff skin. So far, all molecularly confirmed cases harbored a de novo heterozygous gain-of-function mutation in SMAD4, encoding the SMAD4 transducer protein required for both transforming growth factor-beta and bone morphogenic proteins signaling. We report on four novel patients (one female proband and her two affected children, and one male proband) with Myhre syndrome harboring the recurrent c.1486C>T (p.Arg496Cys) mutation in SMAD4. The female proband presented with a congenital heart defect, vertebral anomalies, and facial dysmorphic features. She developed severe tracheal stenosis requiring a total laryngectomy. With assisted reproductive treatment, she gave birth to two affected children. The second proband presented with visual impairment following lensectomy in childhood, short stature, brachydactyly, stiff skin, and decreased peripheral sensitivity. Transmission electron microscopy (TEM) of the dermis shows irregular elastin cores with globular deposits and almost absent surrounding microfibrils and suggests age-related increased collagen deposition. We report on the first familial case of Myhre syndrome and illustrate the variable clinical spectrum of the disorder. Despite the primarily fibrotic nature of the disease, TEM analysis mainly indicates elastic fiber anomalies