Effect of Zinc Dialkyl Dithiophosphate Replenishment on Tribological Performance of Heavy-Duty Diesel Engine Oil.

Soot is the main contamination that affects oil performance and increases the frequency of oil changes in heavy-duty engine oil. Several studies discussed that additive concentration in engine oil can be influenced due to additive depletion over time and additive adsorption on soot particles. To extend oil drain intervals and improve oil performance, filter manufactures explore removing the soot to a certain level and replenishing the consumed additives. Zinc dialkyl dithiophosphate (ZDDP) is one of the most favored antiwear additives that react very rapidly with rubbing surfaces to form tribofilm that reduces wear. In this study, the experimental work aims to investigate the effect of ZDDP replenishment on tribological performance in the existence of soot and after removing soot from heavy-duty used oil. The study reveals that reclaiming the used oil can be achieved by removing the soot to a certain level. The results demonstrate that the reclaimed oil after removing soot is still not as good as the fresh oil. This study proves that additive depletion, additive adsorption on soot, and the decomposition of antiwear additive adversely influence the reclaimed oil performance. However, replenishing the consumed additive by adding a small amount of ZDDP helps to improve the reclaimed oil performance compared to a large amount of ZDDP which is required to re-gain the oil performance in the existence of soot.

Efficacy and safety of oral mega pulse methylprednisolone for severe therapy resistant Alopecia areata.

OBJECTIVE: To use intensive regimen of pulse steroid in the severe forms of Alopecia areata. METHODS: This prospective randomized study was conducted at King Khalid University Hospital, Riyadh, Kingdom of Saudi Arabia between 2003 to 2009. Patients with Alopecia universalis, Alopecia totalis, or Alopecia ophiasis were assigned to one of the 3 treatment groups: Group A received oral mega pulse methylprednisolone (MP) for 3 consecutive days once every 2 weeks for 24 weeks; Group B received 2 consecutive daily pulses every 3 weeks; and Group C received 3 consecutive daily pulses every 3 weeks. Patients who showed regrowth of 75% or more at 24 or 36 weeks continued their treatment, while intervals were increased gradually. RESULTS: Forty-two patients were included in this study, and 52.4% of them had atopic diathesis, while 35.7% had autoimmune thyroiditis. At 36 weeks, 12 (28.6%) patients had adequate response, 9 (21.4%) had inadequate response, and 21 (50%) patients had poor response. The response rate shows no statistically significant difference between treatment groups. There were statistically significant differences in age of onset, duration of the disease, and presence of subclinical hypothyroidism between different response groups. At follow-up: 13 (38.2%) patients relapsed; 5 (14.7%) patients developed moderate hair fall; 3 (8.8%) patients developed mild hair fall; 7 (20.1%) patients maintained their hair regrowth; and 6 (17.6%) patients were lost follow up. It was relatively well-tolerated among groups B and C. CONCLUSION: Oral mega pulse MP use in severe forms of Alopecia areata has relative efficacy and tolerance but with high relapse rate.