Flesh and Peritoneal Lining Color of Gold, Bronze, and Black Tilapia mossambica

Flesh color of gold (homozygous recessive gg), bronze (heterozygous Gg), and black (homozygous dominant GG)Tilapia mossambica was evaluated sensorily (visually). Gold fish had white flesh, while black and bronze fish had flesh that had a grayish tint. Flesh color of gold fish was significantly lighter than that of both black and bronze fish (P = 0.001). Flesh color of bronze and black fish did not differ. Peritoneal lining of the abdominal cavity of black fish is black, that of gold fish is white, and that of bronze fish is spotted and quite variable. The peritoneal lining of black fish must be removed when they are marketed whole to remove the black pigmentation, but this is not necessary with gold fish.     

The A.C. impedance of polycrystalline CuInS2 thin films

The a.c. impedance of evaporated copper indium disulphide (CuInS2) thin films has been measured as a function of frequency and heat treatment. The frequency covered the range from 5 Hz up to 500 kHz and the temperature was varied from 433 K up to 513 K. The data was analysed in terms of the complex impedance, admittance and electric modulus planes. These plots are useful for the assignment of an appropriate equivalent electric circuit that deals easily with the polycrystalline thin layers. This revised version was published online in July 2006 with corrections to the Cover Date.     

Model for Ion-Exchanged Waveguides in Glass

An analytical model describing refractive index profiles in ion-exchanged glass waveguides is presented. Polarizability, volume, and stress-state changes are accounted for. Index distribution is given in terms of known or measurable physical parameters. Model predictions compare favorably with experimental results of field-assisted ion-exchanged waveguides fabricated in 7740 borosilicate glass. Experimental characterization of the index changes includes prism coupling, microprobe, and photoelastic measurements.     

THERMAL RESISTANCE, SURVIVAL AND INACTIVATION OF ENTEROBACTER SAKAZAKII (CRONOBACTER SPP.) IN POWDERED AND RECONSTITUTED INFANT FORMULA

Enterobacter sakazakii has recently been recognized as an opportunistic foodborne pathogen, and dry infant formula serves as the mode of transmission. The objectives of this study were to investigate the heat resistance, survival and inactivation under room and refrigeration temperatures storage of dry and reconstituted infant formula milk (IFM). E. sakazakii strains (eight strains) showed a wide variability in heat resistance at different temperatures (55, 60 and 63C). The D-values at 55C ranged from 1.51 to 14.83 min, at 60C from 0.17 to 2.71 min and at 63C from 0.05 to 0.88 min. The calculated z values for the studied E. sakazakii strains ranged from 3.76–10.11C. Microwave oven heating of 60-mL portions of reconstituted IFM for 40–50 s was effective in eradicating inoculated E. sakazakii. Storing powdered IFM for 15 days at 4C resulted in at least a 1-log reduction in E. sakazakii strains, whereas storing reconstituted IFM at 4C for 2 weeks resulted in more than a 2-log reduction in E. sakazakii.

PRACTICAL APPLICATIONS

This study shows that E. sakazakii strains differ widely in their heat resistance. No differences were observed between biofilm formers and nonformers in terms of heat-resistance in thermal inactivation kinetics experiments. Conventional high temperature short-time pasteurization processes are considered sufficient to inactivate all E. sakazakii strains, and a household microwave oven (40–50 s for 60-mL portions) can be used to inactivate E. sakazakii if present in reconstituted infant formula milk (IFM). Growth of E. sakazakii can be inhibited in powdered and reconstituted IFM by refrigeration. Also, it is recommended that reconstituted IFM be discarded or refrigerated if not immediately consumed. The probiotic L. acidophilus ATCC 4356 was not effective in inhibiting E. sakazakii in powdered or reconstituted IFM.     

Decentralized control for two time-scale discrete-time systems

Output feedback design of discrete-time decentralized systems with slow and fast modes is considered. Conditions for the complete separation of slow and fast subsystems are given. The slow and fast subsystem outputs, which are obtained by applying the slow and fast subcontrollers to the corresponding subsystems, will be shown to approximate those of the original system. Also, the composite control, when being applied to the original system, will place the eigenvalues sufficiently close to the desired locations.     

ANTIMUTAGENIC ACTIVITIES OF PHENOLIC PLANT FLAVONOIDS

Total phenolic plant flavonoids obtained from Thuia accidentalis L. and Cupressus sempevirens L. showed antimutagenic effects on benzo(a) pyrene [B(a)P] in Salmonella typhimurium strains TA100 and TA98. The n-butanol extract was more effective then chloroform and petrol eum-ether extracts, respectively. Aqueous extracts exhibited no inhibition in both strains. Total flavonoids from C. sempevirens showed more antimutagenic activity than flavonoids from T. accidentalis. None of the extracts revealed any cytotoxic or mutagenic activity on the bacterial tester strains.     

MATHEMATICAL MODELING OF FLUIDIZED BED HEAT REGENERATORS

Based on the two-phase theory of fluidization, a fairly rigorous model is developed to describe the dynamic behavior of fluidized-bed heat regenerators. This model takes into account the major hydrodynamic aspects of bubbling fluid beds. Based on the assumption that the gas leaves the bed in thermal equilibrium with the solids, a rather simplified model is presented. Exact analytical solutions are obtained for both models. The predictions of the more rigorous model are found to be in good agreement with many experimental observations. On the other hand, the simplified model gives satisfactory results only when the value of the parameter m₁is relatively large. Using the rigorous model, it has been shown that the bed thermal efficiency can be improved by reducing the time of operation, increasing the mass of solids or decreasing the bed aspect ratio. Also it has been found that when the gas flow-rate is increased, the amount of heat transferred to the solids displays a non-monotonic behavior and passes through a maximum.