Linoleic acid hydroperoxide concentration in relation to mutagenicity of repeatedly used deep-frying fats

A high-performance liquid chromatography procedure was developed to measure linoleic acid hydroperoxides (LAHPO) in 19 used, deep-frying fat samples that were screened for mutagenicity. The detection limit of the method was found to be 10 nmol of LAHPO/g of fat. In eight samples, LAHPO were not detected; levels in the other samples ranged from 17 to 267 nmol/g of fat. LAHPO were not detectable in unusued hydrogenated frying fat samples. Concentrations of LAHPO correlated positively with mutagenicity to Salmonella tester strains TA97 and TA100, in presence of S9 mix only; coefficients of correlation were, respectively, r=0.48 (p<0.05) and r=0.24 (n.s.). Without metabolic activation no significant associations were observed. These results suggest that metabolites or secondary autoxidation products of linoleic acid generated in presence of liver S9 mix may contribute to mutagenicity of some of the used deep-frying fat samples.     

Testing blocks of refractory concrete in the walls of soaking pits

Refractories and Industrial Ceramics - The use of refractory concrete in recuperative soaking pits is quite feasible. The use of block structures of refractory concrete cuts repair time by half and...     

The application of coherent optics to the study of adhesive joints. I. Speckle photography

A new technique of coherent optics, speckle photography, has been applied to the study of the behavior of adhesive joints under shear stress. This technique allows the determination of the in-plane motion by a point-by-point analysis with a sensitivity of about 3 μm. This property has been used to measure the interfacial displacement of model glass-glass joints bonded by different types of adhesive when submitted to shear. The experimental results permit direct verification of Volkersen's theory as well as the determination of the actual shear modull of the thin adhesive layer. The simplicity of use and interpretation of the technique of speckle photography should lead to significant application of this method in the future for the study of adhesive joints.     

Optimal inlet temperature control of reactors with catalyst decay

The constant conversion policy which has been shown to be optimal in certain classes of optimal control problems for reactors with decaying catalyst is examined here for the inlet temperature control in a tubular reactor where the catalyst decay is a function of the composition. A single irreversible reaction is considered where the rate expression is a product of separate functions of temperature, concentration or conversion and catalyst activity. The catalyst decay rate expression is also a product of separate functions of the same variables. A proof of the constant exit conversion property is given for problems where the decay rate is of first-order with respect to the catalyst activity.