Evaluation of combustion by-products of MTBE as a component of reformulated gasoline.

Methyl tertiary-butyl ether (MTBE) is a gasoline oxygenate that is widely used throughout the US and Europe as an octane-booster and as a means of reducing automotive carbon monoxide (CO) emissions. The combustion by-products of pure MTBE have been evaluated in previous laboratory studies, but little attention has been paid to the combustion by-products of MTBE as a component of gasoline. MTBE is often used in reformulated gasoline (RFG), which has chemical and physical characteristics distinct from conventional gasoline. The formation of MTBE by-products in RFG is not well-understood, especially under "worst-case" vehicle emission scenarios such as fuel-rich operations, cold-starts or malfunctioning emission control systems, conditions which have not been studied extensively. Engine-out automotive dynamometer studies have compared RFG with MTBE to non-oxygenated RFG. Their findings suggest that adding MTBE to reformulated gasoline does not impact the high temperature flame chemistry in cylinder combustion processes. Comparison of tailpipe and exhaust emission studies indicate that reactions in the catalytic converter are quite effective in destroying most hydrocarbon MTBE by-product species. Since important reaction by-products are formed in the post-flame region, understanding changes in this region will contribute to the understanding of fuel-related changes in emissions.

The influence of diabetes mellitus upon peripheral vascular disease.

The treatment of 332 consecutive patients referred to a peripheral vascular unit with rest pain, ulceration or gangrene of the lower limb has been studied. Ninety-seven (20 per cent) of the patients had diabetes mellitus. Although diabetes was related to adverse limb salvage and patient survival rates, this could be accounted for by the influence of initial presenting clinical features and treatment upon survival time. The influence of these factors upon survival time was still strong even when the data were stratified for diabetric status. Thus, an extensive amputation carries the worse prognosis, with a less extensive amputation intermediate between an extensive amputation and any other form of therapy. Patients with both rest pain and ulceration or gangrene have a poor prognosis when assessed by either limb salvage or mortality. The majority of the patients with less extensive amputations are diabetic. This is related to the high incidence of localized ulceration among those in the diabetic group. In diabetics, a less extensive amputation, if clinically indicated, is worthwhile because of the low incidence of a subsequent extensive amputation after a less extensive amputation and the better survival rate for those patients with less extensive amputations as compared with those with extensive amputations.