Les fontes au chrome sont bien connues pour leurs propriétés à l’usure. Elles sontutilisées dans les domaines miniers, cimentiers ainsi que tant d’autres. Leurs facultés derésister à l’usure sont principalement dues à leur microstructure qui est constituée d’unréseau de carbure eutectique du type M7C3 contenu dans une matriceausténitique ou martensitique. Plusieurs chercheurs ont exploré la possibilité d’améliorerles propriétés à l’usure de ces fontes en agissant sur la microstructure, la morphologiedes composants microstructuraux ainsi que sur leur distribution. Le présent travailconsiste à étudier l’effet du niobium sur le comportement à l’usure d’une fonte au chrome.Des caractérisations par microscopie optique, usure par abrasion et par frottement sontréalisées dans le but de déterminer la résistance à l’usure de cette fonte et le type demicrostructure ayant été à l’origine de cette amélioration. Les résultats obtenus montrentque la fonte étudiée est une fonte à 15 % de chrome. L’addition du niobium a eu un effetsur la microstructure ainsi que sur les résistances par abrasion et par frottement deséchantillons de fontes traitées. La résistance à l’usure augmente avec l’accroissement dela teneur en niobium.

The continual recruitment of new individuals makes it difficult to study both the survival of multivoltine mosquitoes, and the size of the infectious reservoir in narural populations of malaria vectors. During long-term surveillance of a population of Anopheles gambiae Giles sensu lato in a Tanzanian village by daily light trapping, a temporary dry spell resulted in the cessation of recruitment for a period of 33 days, and a decline in numbers of A. arabiensis Patton caught from over 2000 to less than 10 in a sentinel house. Traps placed elsewhere in the village indicated similar proportionate declines although numbers caught varied according to location. A survival rate of 83% per day was estimated from the rate of population decline. Survival was unrelated to the size of the mosquitoes. The infectious reservoir (the chance of a mosquito acquiring an infection) was estimated to be 2% per feed. The exploitation of fortuitous events which temporarily eliminate a single stage in the life cycle has general applicability in the study of the bionomics of multivoltine insects.

An audit of post-operative nausea and vomiting (PONV) was undertaken in 935 female patients who used morphine patient-controlled analgesia (PCA) for pain relief after major gynaecological operations in a district general hospital. We investigated retrospectively five different antiemetic policies and a reference group without policy from January 1993 to July 1995. The department’s computerized audit system was used to analyse the observations. At the beginning of the audit, the incidence of nausea and vomiting was as high as 71.5%. But as a consequence of this audit, a departmental policy was adopted 3 years later, which had an incidence of PONV of only 51.7%. During this time the compliance with antiemetic protocols increased from 41% to 76%. There was significantly less PONV if an antiemetic protocol was followed (P=0.002). This emphasizes the importance of corporate involvement in the development, formulation and evaluation of departmental protocols if compliance is to be high. We conclude that audit as a corporate effort improves the acceptance of departmental protocols. This reduces PONV significantly irrespective of the type of antiemetic drug used.