KINETIC BEHAVIOR OF SOYBEAN LIPOXYGENASE: A COMPARATIVE STUDY OF THE FREE ENZYME AND THE ENZYME IMMOBILIZED IN AN ALGINATE SILICA SOL‐GEL MATRIX1

Lipoxygenase (LOX) is an enzyme that regioselectively introduces a hydroperoxide into polyunsaturated fatty acids (PUFA). We recently reported a procedure that immobilizes soybean LOX within an alginate sol‐gel matrix. In this study, the kinetic profile of free LOX was compared with that of the sol‐gel immobilized LOX. The temperature dependent activity profile of free LOX was optimal at 25C whereas immobilized LOX had optimal activity over the temperature range of 25–35C. Enzyme activity, measured in aqueous buffer, for both the free and immobilized LOX preparations had K_m values of 2.5 and 1.40 mmoles/L, respectively, and V_max values of 0.056 and 0.02 μmol/min, respectively. The relative rates of oxidation of linoleic acid and acylgfycerols containing linoleoyl residues catalyzed by free and immobilized LOX also were determined The results showed that both free and immobilized LOX favor linoleic acid as a substrate. Relative substrate preference for free LOX was linoleic acid >1‐monolinolein > 1,3‐dilinolein >trilinolein, and for immobilized LOX was linoleic acid >l, 3‐dilinolein >1‐monolinolein >trilinolein. In general, LOX immobilized in alginate silica sol‐gel matrix retained the physical and chemical characteristics of free LOX.     

Quantitative Analysis of Carotenoids and Carotenoid Esters in Fruits by HPLC: Red Bell Peppers

The carotenoids of red bell peppers were analyzed without saponifi-cation by high performance liquid chromatography using octadecyl silica as stationary and methanol-ethyl acetate as mobile phases. The red bell peppers contained 280 ug/gm total carotenoids. Capsanthin accounted for 60% of the total carotenoids. Also present were 11%beta-carotene and 20% capsorubin. Capsanthin was acylated with C₁₂ to C₁₈ saturated fatty acids.     

"Façadism" Returns, or the Advent of the "Duck-orated Shed"

Embedded in the culture of modern architecture is the directive that a façade ought to fit tightly around its building, like a well-fitting suit. "False façades,""façadism," and the "screen façade" have been derisive terms used by architects and critics to describe buildings whose façades appear either too big or too small for their buildings. Postmodernism changed this, so that façades relatively independent of their interiors were encouraged. The neo-modernism of the last two decades has integrated this "disconnected" façade into the practice of what otherwise is a revival of the system of the heroic period of the movement.     

SOLAR ABSORPTIVITY OF PEELED CASSAVA ROOT, YAM TUBER AND UNRIPE PLANTAIN FRUIT

Absorptivity is a property which governs the quantity of solar radiation absorbed by materials undergoing sun drying. A laboratory spectrophotometer was used to measure the spectral absorptivity of peeled cassava root, yam tuber, and unripe plantain fruit for wavelengths in the range 0.4–2.4 μm; 88% of solar radiation reaching the earth lies in this part of the electromagnetic spectrum. The total (i.e., integral) absorptivity calculated from the measured spectral absorptivity was 0.32 for fresh cassava which had a wet basis moisture content (M.C.) of 65%, 0.26 for fresh plantain (M.C. =61%) and 0.53 for fresh yam (M.C.=68%). Corresponding values for dried crops were 0.23 for cassava (M.C.=5%), 0.58 for plantain (M.C.=20%) and 0.77 for yam (M.C.=9%). Application of absorptivity data in evaluating heat transfer during sun drying of crops was discussed.     

Effect of Marination upon Mineral Content and Tenderness of Beef

This study compared marinated and nonmarinated beef to determine differences in semimembranosus muscle tenderness and selected mineral content. The minerals analyzed were iron, zinc, magnesium and sodium. Marination resulted in a significantly more tender muscle, as determined by shear values and trained panel evaluations. Mineral content was significantly affected by marination with substantial losses of iron, zinc, and magnesium and increased sodium. Marination would be a feasible method of enhancing tenderness of more economical cuts of beef; however, the subsequent loss and/or gain of minerals should be considered.     

Dry kiln scheduling in furniture production

In this paper, a dry kiln scheduling problem from the furniture manufacturing industry is considered. Factory-specified due dates for orders, kiln availability, kiln capacity, and travel time from the kilns to the factories are all incorporated in a model which is formulated as an integer linear program. The objective of the formulation is to minimize the maximum tardiness of orders arriving at the plants by solving a special case of scheduling n independent jobs on m non-identical parallel ciachines. Because of the computational complexity, and the fact that standard integer programming packages appear to perform very poorly on the problem, a heuristic approach is developed. Computational experience is provided which indicates that the heuristic gives very high quality solutions to problems in near real-time.     

INTERFEROMETRIC STUDIES OF INTERFACIAL MASS TRANSFER IN A LIQUID-LIQUID SYSTEM

Interfacial concentrations were found using a specially designed interferometer and a flowing junction cell. The relationship between refractive index and concentration was established by means of a new refractometer. Both optical instruments had a sensitivity of 1 × 10^?1.

Fringe patterns yielded concentration profiles and total solute transfer at any time. For the system water/acetic acid/carbon tetrachloride equilibrium was never reached at the interface at any solution strength. This indicates the presence of an interfacial resistance. In some cases density driven disturbances were initiated at the surface causing mixing effects.

Interfacial resistance to mass transfer was shown to exist. This resistance was evaluated for different initial concentrations of solution and is time dependent. An empirical relationship is proposed for predicting the value of the interfacial resistance at any exposure time.     

Modelling planting configuration and canopy architecture effects on diurnal light absorption changes in cotton

Abstract

A simplified model that accounts for diurnal solar zenith and azimuth angle illumination changes and plant geometry effects on photosynthetically active radiation (PAR) was developed, h was tested using diurnal absorbed PAR (APAR) measurements acquired for cotton (Gossvpium hirsuium L.) grown at Weslaco, Texas, during the 1984 and 1986 growing seasons. Diurnal canopy reflectance and transmittance measurements were automatically collected at 3-minute intervals from about 9.00 to 14.50 local standard time (LST) using radiometers mounted 3·7m above the soil surface and PAR light bar sensors located beneath the crop canopy perpendicular to the crop rows. Plant growth measurements estimated by the model were significantly correlated with observed measurements during crop development. Model-estimated heliotropic leaf elevation trends agreed with published results for cotton canopies. APAR, relative to incident PAR, was generally lower for east-west rows than for north-south rows during crop development. The APAR response of cotton canopies for both east-west and north-south rows were found to be essentially flat when solar azimuth was between 90° and 270° so one observation close to noon would probably be representative of the diurnal APAR measurements.     

ELECTROGENERATIVE OXIDATION OF ETHANOL TO ACETALDEHYDE

Ethanol enriched vapor streams from twenty-five volume percent ethanol-water mixtures can be selectively oxidized with porous platinum electrodes and sulfuric acid electrolyte in the elec-trogeneratice mode to give acetaldehyde. Acetaldehyde yield from ethanol depends on potential and feed rate of ethanol vapor in the carrier gas stream. Control of conversions of ethanol to acetaldehyde in the range of 3 to more than 60 percent in a single stage is demonstrated. It is shown that at moderate flow rates for selective conversion there is a preferred potential range at which to operate the electrogenerative reactor.