Search

On présente dans cet article les résultats d'une première série de recherches sur la dépollution des gaz d'échappement des moteurs diesel au moyen de pots catalytiques. L'efficacité des catalyseurs à base de platine pour l'oxydation du monoxyde de carbone et des hydrocarbures imbrûlés a pu être établie par des essais sur banc moteur et sur véhicule. L'emploi de certaines phases actives à base de métaux non nobles permet d'autre part d'abaisser la température de début d'oxydation des particules de suie de 380 à 250 °C environ, avec, entre 250 et 350 °C, élimination de 15 à 20 % des produits piégés. L'essai de divers media filtrants a mis en évidence l'importance des phénomènes d'adsorption des revêtements en alumine et a orienté la recherche vers de nouveaux supports pour filtres catalytiques. This article describes the results of a first series of research on the depollution of exhaust gases from diesel engines by catalytic mufflers. The effectiveness of platinum-base catalysts for the oxidation of carbon monoxide and unburned hydrocarbons was determined by test on an engine test bed and on vehicles on the road. The use of some active non-noble metal phases reduced on the other hand the starting oxidation temperature of soot particulates from 380°C to about 250°C, eliminating 15 to 20% of the trapped products between 250 and 350° C. Tests of different filtering media revealed the importance of adsorption phenomena on alumina coatings and directed research toward new supports for catalytic filters.

Cet article fait le point, sous forme résumée, des travaux de recherches et de développement menés par l'Institut Français du Pétrole (IFP) depuis vingt ans dans le domaine des piles à combustible : sélection des filières directes conduisant au choix de la pile hydrogène-air basse température à électrolyte basique, mise au point des générateurs à hydrogène alimentés en méthanol. On présente les résultats obtenus et les conclusions des enquêtes effectués dans le domaine des groupes électrogènes et des applications spéciales, dans celui de la traction automobile et dans celui de la production massive d'électricité. This article reviews and sums up the research and development done by Institut Français du Pétrole (IFP) in the last 20 years in the field of fuel cells, including the selection of direct methods leading to the choice of low-temperature basic-electrolyte hydrogen/air cells and the development of methanol-powered hydrogen generators. The results obtained are desceibed along with the conclusions of surveys made in the field of electric generators and special applications in the fields of automotive traction and massive electricity production.

A partir de l'examen des normes actuelles et envisagées dans le futur pour limiter les émissions de particules Diesel, et en considérant les propriétés physico-chimiques de ces particules, cet article expose les problèmes posés par la filtration des suies Diesel et leur élimination par combustion sur les différents types de filtres actuellement retenus. La régénération des filtres par combustion catalytique du dépôt est plus particulièrement discutée. From an examination of present regulations and ones being considered for the future to limit particle emissions by diesel engines, and considering the physicochemical properties of such particles, this article describes the problems raised by filtering soot from diesel engines and eliminating it by various types of filters now used. Filter regeneration by catalytic combustion of the deposit is considered in particular.

Recordings were made from 43 poor sleepers between the ages of 20 and 30 for at least 4 consecutive nights. Three subject groups were formed on the basis of the awakenings occurring up to the sixth hour of sleep. The first group, with an average of 61 min wakefulness, is characterized by the abundance of long-lasting waking periods. The second group, with 18 min average wakefulness, showed the highest absolute number of awakenings, almost all of which were very brief. The third group, with 6 min average wakefulness, showed a slightly lower number of awakenings, but these were almost exclusively micro-waking periods. The temporal distribution of the waking periods was also different in the first group, in which the longest waking periods occur during the first hour of sleep and remain elevated until the fifth hour of sleep. The latency for falling asleep is particularly high for this group. A correlation exists between the amount of time awake up until the sixth hour of the night and the subject's anxiety level and the neuroticism index. 65% of the subjects obtained pathological scores on one or more MMPI scales. According to the order of frequency these were scales Sc, Pd and Pt. No preferential profile was found.

Observation of the four cases reported and a review of the published literature suggest that spinal column lipomas can produce two entirely unrelated types of radiological image. 1. An image of cord-like appearance and variable width which joins the filum terminale to the sacrum, and is usually associated with enlargement of the spinal cord at the same level. This image can be demonstrated by both gas myelography and opaque myelography, and is produced by a lipoma of the filum terminale. The cord image is either that of an ectopic spinal cord or that of the lipomatous tumor itself, which joins the filum terminale to the sacrum. A spina bifida is often associated with these tumors, which can be intradural alone, which is very rare, or both intradural and epidural, and are often associated with enlargement of the spinal canal. 2. A fairly specific blocking-type of image which can be seen by opaque myelography, and consists of fringed bands which become progressively shorter from above downwards until being completely blocked. This appearance, which is extremely rare, is peculiar to intramedullary lipomas, the image probably corresponding to the dissociation of the medullary fiber bundles by the tumoral cords.