The carbon balance of Africa: synthesis of recent research studies.

The African continent contributes one of the largest uncertainties to the global CO(2) budget, because very few long-term measurements are carried out in this region. The contribution of Africa to the global carbon cycle is characterized by its low fossil fuel emissions, a rapidly increasing population causing cropland expansion, and degradation and deforestation risk to extensive dryland and savannah ecosystems and to tropical forests in Central Africa. A synthesis of the carbon balance of African ecosystems is provided at different scales, including observations of land-atmosphere CO(2) flux and soil carbon and biomass carbon stocks. A review of the most recent estimates of the net long-term carbon balance of African ecosystems is provided, including losses from fire disturbance, based upon observations, giving a sink of the order of 0.2 Pg C yr(-1) with a large uncertainty around this number. By comparison, fossil fuel emissions are only of the order of 0.2 Pg C yr(-1) and land-use emissions are of the order of 0.24 Pg C yr(-1). The sources of year-to-year variations in the ecosystem carbon-balance are also discussed. Recommendations for the deployment of a coordinated carbon-monitoring system for African ecosystems are given.

[Located hinge-axis or conventional hinge-axis?]. / Axe-charnière localisé ou axe-charnière conventionnel?

The purpose of this study is first, to evaluate the influence of locating the horizontal transverse axis of rotation of the mandible, both kinematically and conventionally, and second, to determine the influence of the thickness of the wax check-bite, as obtained in the centric relation, upon the functional analysis of the occlusion. The results show that the influence of any displacement of the horizontal transverse axis of rotation of the mandible is smaller, within a circle with a 6-mm radius, than that of the thickness of the wax check-bite obtained in the centric relation.

[Presentation of a universal face-bow]. / Présentation d'un arc facial universel.

A universal face bow is reported for transferring an arbitary or located hinge axis on most articulators. Its use is simple and safe due to the rigidity of the assemblies during every step of the transfer.

[A new modular semi-adaptable articulator]. / Un nouvel articulateur semi-adaptable modulaire.

A new semi-adjustable Arcon articulator is reported. It is an evolutive device that can be set with two different types of condylar housings. - A Type: adjustable condylar guidance, preadjusted Bennett angle at 13 degrees - B Type: adjustable condylar guidance, adjustable Bennett angle. It is possible to set on this B type fossa assembly another Bennett wing with an adjustable immediate side shift This device has a double lock in centric relation and may be set with an arbitrary or localized hinge axis.

[Comparative clinical study of 3 technics of functional analysis of occlusion]. / Etude clinique comparative de trois techniques d'analyse fonctionelle de l'occlusion.

The object of our research is to compare clinically and objectively three articulators: -- the Dentatus, semiadjustable articulator which employs dynamico-static records -- the T.M.J., fully adjustable articulator which employs dynamico-cinematic stereographic endobuccal records -- the Denar, fully adjustable articulator which employs dynamico-cinematic pantographic extrabuccal records. We expressly avoided repeating the mechanical and mathematical analysis of the possibilities and limitations of the articulator and copying the previous researches which always imply quasi-perfection in the behaviour of the patient, in the manipulations of the dental surgeon and in the physical qualities of the articulator and materials used. Our comparative research claims to respect all the variables which occur in the carrying out of an actual case and which are inherent in the patient, the dental surgeon, the articulator and the materials used. In carrying out our research we followed two essential conditions: -- We decided to follow, first of all, a strictly clinical plan using successively the three articulators in the analysis of the occlusal function (carried out twice) for each of the six patients and comparing the results obtained for each articulator and for each patient. -- We decided, next, that this comparative research should be strictly objective. To this end, we did not set out to form an opinion, on the basis of clinical impressions, favourable or unfavourable to the different characteristics of the three articulators. We limited ourselves, on the contrary, to measuring, superposing and making a comparative analysis of the results obtained with the three articulators for the same analysis of the occlusal function.

[Bite plates and occlusal splints]. / Plaques et gouttières de libération occlusale.

Occlusal adjustments are often necessary in cases of masticatory muscle spasm, bruxism, traumatic occlusion and TMJ disturbancies. Before such occlusal adjustments are performed, the patient should either wear a bite plate or an occlusal splint which frees the occlusion for a certain time. The splint is fabricated on a semiadjustable articulator such as the Hanau H2-XPR which is also used for the functional analysis on the models prior to any adjustments. Advantages and disadvantages of different types of plates and occlusal splints are discussed. The authors conclude that an occlusal splint covering the entire dental arch, such freeing the occlusion, seems to be the most appropriate appliance available today.