Système de codage de canal hièrarchique pour la télévision numérique

Les avantages de l'approche hiérarchique en matière de diffusion numérique de télévision poussent à étudier des systèmes de codage de canal offrant au moins deux niveaux de protection vis-à-vis du bruit. Cet article présente une méthode de codage de canal hiérarchique; bien qu'inspirée des constellations multirésolution, cette méthode utilise les propriétés du décodage sur décisions douces pour obtenir un bien meilleur compromis entre la robustesse de l'information haute priorité et l'inévitable fragilité de l'information basse priorité qui en découle

Etude par coupes a basse temperature de l'espace cranio-pharyngo-mandibulaire. [A study of the cranio-pharyngo-mandibular space by sections at low temperature]

After acrylic injections into the vessels and mandibular block anaesthesia the pterygo-mandibular space is studied in 38 anatomical pieces. 538 colour slides have been obtained from anatomical cuts at low temperature with the scannigraph system. The results point out that a cranio-pharyngo-mandibular space is clearly distinguished laterally, from a medial maxillo-pharyngeal space. There is no transversal communication between them. On the contrary, the cranio-pharyngo-mandibular space communicates, forward and upward, with the temporal space; forward and downward, with the sub-mandibular space. The cranio-pharyngo-mandibular space contains an interpterygoid space communicating with the oval foramen by a "chimney" largely filled by the emissary pterygoid veins. A pericondilar plexus of veins is also observed. The cranio-pharyngo-mandibular space is characterised by the cellulo-adipose tissue by which it is filled and which guides the diffusion of injected solutions to the oval foramen

A tridimensional study using cuts at a low temperature of the infratemporal region

Although the infratemporal region is well defined anatomically, its complex topography has been the subject of numerous, and sometimes, opposite works. That is the reason why it appeared necessary for the authors to re-evaluate this topic using the original method of Combelles and Boyer, allowing to define three referential planes, and thereby, a tridimensional shape and the volume of this region. This study allows to conclude that the infratemporal region is a triangular prism with an horizontal main axis 47 mm long. Its anterior base has a mean area of 733 mm2. The posterior top consists of the Juvara slot and has a mean area of 490 mm2. This infratemporal prism contains another one, the pterygomandibular space, prismatic too. It widens out from coronoid plane (93 mm2) to mandibular foramen plane (169 mm2) before ending as a narrow groove between the neck of the mandibular condyle and the interpterygoid fascia. The volume of the pterygomandibular space is quite superior to the value usually reported in the dental literature. It is of 4.8 ml to 5.8 ml according to denture. These results point out the opportunity to accomodate more important volumes of anesthesic solutions, than the 1.8 ml usually performed, without any leak out of the infratemporal region