The present work is concerned with the determination of boron activation energy in theC35 steel and an estimation of the mass gain generated by the boriding treatment. Theboride layers are produced by the pack-boriding method on the C35 steel in the temperaturerange of 800−1000 °C for atreatment time ranging from 0.5 to 8 h. The presence of both FeB and Fe2B phases was confirmed by theX-ray diffraction technique and by a microscopic examination of the cross-sections ofborided samples. The boron activation energy was evaluated as 153.1 kJ mol-1 in the temperature range of800−1000 °C. This value ofenergy is in agreement with the literature data. The mass gain was measured by weighingthe samples before and after the boriding treatment by the weighing technique. Theevolution of mass gain as a function of temperature and time can be described by aparabolic law. Finally, an iso-thickness diagram was established to be used as a tool tooptimize the boride layers thicknesses according to the industrial application.

Growth in body mass in pups of the subantarctic fur seal Arctocephalus tropicalis was studied at Amsterdam Island, southern Indian Ocean during the rearing period between December 1995 and August 1996. We examined the change in the rates of mass gain and mass loss with pup age to explain the overall change in mass throughout the rearing period, when mothers alternate foraging trips at sea and attendance periods ashore. In the absence of their mothers, pups fast and lose mass. During the maternal attendance period ashore pups suck and gain mass. There was no significant difference in the rate of growth in mass between male and female pups. The rate of loss in mass during a fasting event was positively related to the initial body mass but negatively related to the age and duration of the fast of the pup. The rate of mass loss was best related to pup age by a quadratic relationship. The rate of mass loss increased until pups were 120 days old and then decreased until the end of the study period. The rate of gain in mass following a maternal foraging trip was positively related to the initial pup mass but negatively related to the foraging trip duration, and we found that the rate of mass gain decreased linearly with the age of the pup. The concomitant decrease in the rate of mass loss and mass gain for pups > 120 days old allowed pups to maintain a positive growth until they were 220 days old. After 220 days of age the rate of mass loss exceeded the rate of mass gain and the pups start to lose mass until weaning.