Aerodynamic investigations of ventilated brake discs.

The heat dissipation and performance of a ventilated brake disc strongly depends on the aerodynamic characteristics of the flow through the rotor passages. The aim of this investigation was to provide an improved understanding of ventilated brake rotor flow phenomena, with a view to improving heat dissipation, as well as providing a measurement data set for validation of computational fluid dynamics methods. The flow fields at the exit of four different brake rotor geometries, rotated in free air, were measured using a five-hole pressure probe and a hot-wire anemometry system. The principal measurements were taken using two-component hot-wire techniques and were used to determine mean and unsteady flow characteristics at the exit of the brake rotors. Using phase-locked data processing, it was possible to reveal the spatial and temporal flow variation within individual rotor passages. The effects of disc geometry and rotational speed on the mean flow, passage turbulence intensity, and mass flow were determined. The rotor exit jet and wake flow were clearly observed as characterized by the passage geometry as well as definite regions of high and low turbulence. The aerodynamic flow characteristics were found to be reasonably independent of rotational speed but highly dependent upon rotor geometry

Monitorage de la pression fontanellaire chez le nouveau-né et le nourrisson. Evaluation d'une nouvelle technique de mesure, détermination des valeurs normales et utilisation clinique.

The experience with 200 measurements of anterior fontanelle pressure with the Rotterdam Teletransducer in newborns and infants is reported. Statistical analysis of 25 comparative measurements between anterior fontanelle pressure and invasive cerebrospinal fluid pressure showed an excellent correlation (rs = 0.95). Measurements were reproducible and the plot quality allowed visualisation of pulse pressure and pressure waves. Normal values of the anterior fontanelle pressure, pulse pressure amplitude and pressure wave maximal amplitude were established in 15 prematures, 27 term newborns and 10 infants. Anterior fontanelle pressure monitoring was performed in 19 term newborns with post-asphyxial encephalopathy, 18 newborns and infants with hydrocephalus, 8 preterm and term newborns with respiratory distress and 19 patients with subdural haematomas, metabolic diseases, meningitis, subarachnoidal haemorrhage, head trauma, post cardiac arrest encephalopathy and abnormal head growth or bulging fontanelle. Abnormal patterns of anterior fontanelle pressure monitoring were found in moderate or severe neonatal post-asphyxial encephalopathy, evolutive hydrocephalus, subdural haematomas, metabolic diseases with hyperammoniemia and other clinical situations. In contrast, anterior fontanelle pressure monitoring yielded normal values in mild post-asphyxial encephalopathy, arrested hydrocephalus, well functioning ventriculo-peritoneal derivation, and in normal infants with rapid head growth or bulging fontanelle. The Rotterdam Teletransducer provides thus accurate and reproducible values of intracranial pressure. Anterior fontanelle pressure monitoring may be of value in many situations in clinical practice

Positron emission tomography for the early postsurgical evaluation of pediatric brain tumors.

OBJECT: The object was to study the value of postoperative positron emission tomography (PET) to assess the extension of brain tumor resection. METHODS: Twenty children operated on for total resection of a glial tumor (18 low-grade, 2 anaplastic) presented a signal on postoperative magnetic resonance (MR) images raising the question of a possible tumor residue. PET was performed early ((18)F-Fluoro-deoxyglucose in 1, (11)C-methionine in 16, both in 3) to further characterize the nature of the abnormal MR signal in order to consider second-look surgery. An increased tracer uptake found in 14 children led to reoperation on 11 of them, confirming the tumor histologically. No (11)C-methionine uptake led to a conservative attitude in 6 children in whom MR imaging follow-up showed no tumor progression. CONCLUSIONS: The early postoperative PET, especially with (11)C-methionine, appears to be a valid basis for complementary therapeutic decisions, especially second-look surgery, in glial tumors for which a radical resection is a key factor for prognosis