A continuous process for the glycerolysis of soybean oil

A continuous process for the glycerolysis of soybean oil with pure and crude glycerol, the co-product from the transesterification of soybean oil, was investigated in a pilot plant. The process was equipped with a static and a high-shear mixer. The experimental studies explored the effects of variations in mixing intensity, temperature, reactant flow rates, and reactant stoichiometry on the formation of MG and DG. The developed process resulted in high conversion of TG to MG. The most favorable conditions were 230°C, 40 mL/min total flow, 25 min of reaction time, 2.5∶1 molar ratio of glycerol/soybean oil, and 3600 rpm for the reactions involving crude glycerol where the concentrations of MG and DG in the product were about 56 and 36 wt%, respectively. Under similar conditions, glycerolysis of pure glycerol resulted in 58% MG and 33% DG. In general, higher temperatures and mixing intensities favored the conversion of TG to MG and DG. Reaction temperature had a greater influence on the extent of the reaction than mixing. The formation of MG approached equilibrium for nearly all cases under investigation.     

Metabolism of 4-methylaminorex ("EU4EA") in the rat

Metabolism studies were conducted on 4-methylaminorex (4,5-dihydro-4-methyl-5-phenyl-2-oxazolamine [4-MAX]), a potent central nervous system stimulant that has emerged as a drug of abuse under the name "EU4EA", "EU4Euh", and "Ice". Tritiated norephedrine was cyclized with cyanogen bromide to form 3H-4-MAX, which was administered to rats at a dose of 10 mg/kg orally and intravenously. Radioactivity was excreted almost entirely in urine (40% of the dose was excreted by 24 h), primarily as the parent drug (60% of the total excretions were as the parent compound). Three metabolites were identified by high-performance liquid chromatography-tandem mass spectrometry with thermospray ionization: norephedrine, 5-phenyl-4-methyl-2-oxazolidinone, and 2-amino-5-(p-hydroxyphenyl)-4-methyl-2-oxazoline. Stability studies showed that 4-MAX in aqueous solution degraded very slightly to norephedrine upon standing. There was no evidence for glucuronide or sulfate conjugation. These results suggest that the metabolic fate of 4-MAX is similar to that of the amphetamines in that it is eliminated primarily unchanged but undergoes some slight oxidative deamination and aromatic hydroxylation. Hydrolytic degradation back to the synthetic precursor can also occur. There was no evidence for the hydrolysis of the oxazolamine ring to form a urea that has been reported for the demethylated congener aminorex. This suggests that 4-methyl substitution of the oxazoline ring may inhibit metabolism similar to the alpha-methyl substitution of beta-phenylethylamines.     

A continuous process for the conversion of vegetable oils into methyl esters of fatty acids

A continuous process for the transesterification of triglycerides to methyl esters was investigated in a pilot plant. The process was equipped with a motionless and a high-shear mixer. The experimental studies explored variations in the mixing intensity, stoichiometry, and catalyst concentration on the overall conversion. The combined as well as individual effect of mixers was examined. The developed process resulted in high conversions of vegetable oils into methyl esters. Conversion of triglycerides to methyl esters in excess of 98% was achieved. Larger excess amounts of alcohol favored higher conversions. The motionless and high-shear mixers each provided adequate mixing for the process. Higher catalyst concentrations resulted in higher conversions but increased the solubility of methyl esters in the glycerol layer. This reduced the amount of methyl esters separated by gravity settling. Presented in part at the Third Liquid Fuel Conference, Nashville, September 15–17, 1996.     

1/f noise considerations for the design and process optimization ofpiezoresistive cantilevers

Piezoresistive cantilevers are limited by two major noise sources: Johnson noise, which is independent of frequency, and conductance fluctuation noise, which has a 1/f spectrum. The 1/f fluctuations of piezoresistive cantilevers are shown to vary inversely with the total number of carriers in the piezoresistor, as formulated by Hooge in 1969. Therefore, while 1/f noise is reduced for large heavily doped cantilevers, sensitivity considerations favor thin lightly doped cantilevers. Balancing these conflicting constraints produces optima for many design and processing parameters. For a cantilever with specified spring constant and bandwidth requirements, optima are identified for the beam thickness and length, and it is shown that the legs should be between 1/3 and 2/3 of the total length with a doping depth that is 1/3 of the beam thickness. Additionally, an optimal doping concentration is identified as a function of the cantilever volume and the measurement bandwidth. Annealing reduces 1/f noise, but causes a loss in sensitivity due to dopant diffusion, and an optimal anneal is computed with a typical diffusion length 10^-8 cm. The analysis, methods, and some of the conclusions of this paper are also applicable to other types of piezoresistive sensors