Liquid-Phase Sintering of TiC-Ni Composites

The sintering of TiC-Ni particle compacts was studied with specific attention to effects of processing conditions. Densification was progressively inhibited with the increasing additions of free carbon to the system. These results are explained on the basis of changes in the eutectic reactions in the system, reduced solubility of TiC in the Ni-rich liquid, and decreased wetting of the solid by the liquid. Presintering hydrogen heat treatment reduced the carbon content of the TiC-Ni compacts and led to reduction in sintering rates and elevated temperatures of liquid-phase formation. Wetting experiments with hydrogen-treated materials showed a time-dependent wetting angle. These results are discussed based on wetting theory and reactions predicted by the equilibrium ternary-phase diagram.     

Effectiveness of Chlortetracycline in Combination with Potassium Sorbate or Tetrasodium Ethylenediaminetetraacetate for Preservation of Vacuum Packed Rockfish Fillets

Rockfish fillets were dipped in either distilled deionized water (DDW), a solution of 1% Na₄EDTA plus 5 ppm chlortetracycline (CTC) or 1% K-sorbate plus 5 ppm CTC. After dipping, fliets were vacuum packed and stored at 2°C. Samples were evaluated after 0, 3, 7, 10, 14, and 21 days. The sorbate/CTC group differed less from fresh Filets than did the control (fillets dipped in DDW) for all indices measured (plate count, pH, redox potential, and TMA and NH₃ concentrations). Fillets treated with EDTA/CTC differed to a greater extent from fresh fillets than the sorbate/CTC group but less than the controls. Results were corroborated by sensory analyses which tested for color, flavor and odor. Fish fillets dipped in a solution of 1% K-sorbate plus 5 ppm CTC retained odor and flavor properties of fresh fillets better than the EDTA/CTC treated fillets after 14 days of storage.     

INFLUENCE OF THE INTRINSIC PROPERTIES OF FOOD ON THERMAL INACTTVATION OF SPORES OF NONPROTEOLYTIC CLOSTRIDIUM BOTULINUM: DEVELOPMENT OF A PREDICTIVE MODEL1

The effects and interactions of heating temperature (70–90C), pH (5–6.5), sodium chloride (0–3%), and sodium pyrophosphate (0–0.3%) on the heat resistance of a six strain mixture of spores of nonproteolytic Clostridium botulinum type B and type E in turkey were examined. Thermal death times were determined in submerged vials heated using a water bath. Heated spores were recovered on Reinforced Clostridial Medium (RCM) supplemented with lysozyme (10 μg/ml). Decimal reduction times (D-values) were calculated by fitting a survival model to the data with a curve fitting program. The D-values were analyzed by second order response surface regression for temperature, pH, salt (sodium chloride) and sodium pyrophosphate levels. The four variables interacted to effect the inactivation of spores. Confidence intervals (95%) predicted heat resistance of spores in turkey. The data suggest that the effect of reduced pH in increasing the inactivation was more pronounced at high temperatures and may provide an adequate degree of protection from nonproteolytic C. botulinum spores in minimally processed foods, particularly if employed in conjunction with combinations of salt and sodium pyrophosphate.     

Undergraduate Learning Portfolios for Institutional Assessment

Our objectives were to develop a model of student portfolios that simultaneously promotes student learning, provides useful outcomes assessment data, and is logistically feasible. From our pilot test of three portfolio models, we conclude that requiring students in selected courses to complete portfolio entries solves most of the logistics problems associated with a large‐scale portfolio plan. Such entries can promote learning by providing a focus for career and educational planning discussions between students and faculty academic advisors. Course faculty are probably in the best position to use the outcomes assessment data obtained from the entries.     

Effects of Feeding Elevated Levels of Monounsaturated Fats to Growing-finishing Swine on Acceptability of Low-fat Sausage

Sixty barrows and gilts were given one of five diets consisting of a control (corn and soybean meal), and four similar diets with a 10% replacement of animal fat, safflower oil, sunflower oil or canola oil. Pork trimmings, from carcasses of animals fed the five diets were used to formulate sausages at fat levels of 25 and 35% and water levels [4(% protein)+ 3% and 4(% protein)+ 11%]. Sensory panelists reported control sausages were springier than those from animal fat diets which were springier than those from all high oleate treatments. Sausages from high oleate treatments were more tender and less cohesive than the others. Sausage from canola oil treatment scored lowest flavor and palatability.     

Solubility of Oxygen in ZrC

Zirconium carbide specimens containing significant quantities of dissolved oxygen were synthesized using ZrO₂ and graphite as reactants in an atmosphere of CO. These specimens were studied by X-ray diffraction and analyzed chemically for C, O, and Zr. The data indicate that oxygen substitutes in the ZrC lattice, replacing more than 1 C atom/O atom, thus decreasing the lattice parameter. Under the conditions of the study, the reaction product is a solution of oxygen in the ZrC phase rather than a distinct oxycarbide phase.     

Clearance Regulation of Mechanical Gas Face Seals: Part II—Analysis and Control

This article presents the analysis and control of noncontacting mechanical gas face seals based on the state space model developed in Part I. Methods to analyze the controllability and observability of axial and tilt modes are described. The controllability analysis determines to what extent the dynamic response of the seal system modes can be shaped in a closed-loop feedback system, and the observability analysis determines if the seal system modes can be reconstructed from specific state measurements of the axial clearance and stator tilts. The error state-space method is employed to design a tracking controller to regulate the seal at a prescribed axial clearance. The control law is a function of all axial states; therefore, reduced order linear observers are designed to observe the unmeasured axial and tilt seal states. The axial clearance and tilt state estimates are used to reconstruct the gas film axial force and moments, which cannot be directly measured, for design and analysis. The analysis and control techniques are applied to the illustrative example presented in Part I. The results demonstrate that the gas film forces and moments can be estimated well and the seal system can be satisfactorily regulated with a sufficiently damped response that is within the bandwidth of today's electropneumatic actuators.     

ROLES OF CO-SURFACTANT AND CO-SOLVENT IN SURFACTANT WATERFLOODING

Residual oil displacement and surfactant retention were measured in Berea cores with well-characterized surfactant systems; phase and interfacial tension behavior was determined as well. The results, interpreted in terms of what is known about the different surfactant-rich microstructures present in aqueous sodium 4-(l'-heptylnonyl) benzenesulfonate (SHBS) alone or in conjunction with the co-surfactant sodium dodecylsulfate (SDS) or the co-solvent n-butanol (NBA), indicate that the large retention by Berea rock of liquid crystalline dispersions can be greatly reduced by sonicating them to produce tiny vesicles or by adding a suitable co-solvent or co-surfactant to dissolve the liquid crystallites.

The core tests show that high oil recovery with low retention can be achieved by injecting isotropic solutions of alcohol-solubilized surfactant or ultradispersions of vesicles, although the former performed better than the latter. These are able to form, in situ upon contact with residual oil, a surfactant-rich third phase with low interfacial tensions against both aqueous and oleic phases so that it can mobilize the oil.