The normal spectrum of mitral and aortic valve discontinuity

The relationship of the base of the left and noncoronary sinuses of the aortic valve and the adjacent aortic leaflet of the mitral valve was studied in 106 normal heart specimens and 184 specimens with isolated VSD. The results show a spectrum of persistence of the tissue along the inner curvature of the heart. This may help settle the recent controversy in the interpretation of echocardiograms of this area because the recorded mitral-aortic discontinuity may be due to this spectrum rather than to variations in technique.     

Anticonvulsant nature of marihuana smoking

Marihuana smoking, in conjunction with therapeutic doses of phenobarbital and diphenylhydantoin, was apparently necessary for controlling seizures in one 24-year-old epileptic patient.     

Effect of fabrication parameters on the thermophysical properties of sintered wicks for heat pipe applications

Porous wicks for use in a loop heat pipe were sintered from copper and Monel powder. These wicks are characterized in terms of their porosity, liquid permeability, capillary pressure and thermal conductivity. The effect of fabrication parameters (particle size and sintering conditions) on these properties is studied. The experimentally measured values of permeability and capillary pressure were compared with correlations available in the literature. The Kozeny–Carman correlation was found to overpredict the experimental values of permeability; while the modified Young–Laplace equation was found to predict within 5% of the measured capillary pressure. Additionally, a model for predicting the thermal conductivity of sintered wicks is developed. First, the ‘two-sphere model’ is used to relate the sintering conditions to the size of the connection (the ‘neck’) between two particles. Then, a finite element simulation is used to determine the thermal resistance of the bonded particles as a function of the neck between them. This thermal resistance is integrated in a random 3D resistor network as a means to model the multiple connections between spheres in a wick and to calculate the effective thermal conductivity of the wick. Results of the model are compared with experimental measurements of thermal conductivity of sintered copper wicks. Agreement between the model and the experimental measurements is good (within 15%) for sintering temperatures below 550 °C, and within 26% for sintering temperatures up to 950 °C. Finally, a generalized thermal conductivity chart is presented, which can be used to estimate the sintering temperature and time required to achieve the desired thermal conductivity.     

Development and validation of a mathematical model to describe the growth of Pseudomonas spp. in raw poultry stored under aerobic conditions

Poultry meat spoils quickly unless it is processed, stored, and distributed under refrigerated conditions. Research has shown that the microbial spoilage rate is predominantly controlled by temperature and the spoilage flora of refrigerated, aerobically-stored poultry meat is generally dominated by Pseudomonas spp.

The objective of our study was to develop and validate a mathematical model that predicts the growth of Pseudomonas in raw poultry stored under aerobic conditions over a variety of temperatures.

Thirty-seven Pseudomonas growth rates were extracted from 6 previously published studies. Objectives, methods and data presentation formats varied widely among the studies, but all the studies used either naturally contaminated meat or poultry or Pseudomonas isolated from meat or poultry grown in laboratory media. These extracted growth rates were used to develop a model relating growth rate of Pseudomonas to storage or incubation temperature. A square-root equation [Ratkowsky, D.A., Olley, J., McMeekin, T.A., and Ball, A., 1982. Relationship between temperature and growth rate of bacterial cultures. J. Appl. Bacteriol. 149, 1–5.] was used to model the data. Model predictions were then compared to 20 Pseudomonas and 20 total aerobes growth rate measurements collected in our laboratory. The growth rates were derived from more than 600 bacterial concentration measurements on raw poultry at 10 temperatures ranging from 0 to 25 °C. Visual inspection of the data and the indices of bias and accuracy factors proposed by Baranyi et al. [Baranyi, J., Pin, C., and Ross, T., 1999. Validating and comparing predictive models. Int. J. Food Micro. 48, 159–166.] were used to analyze the performance of the model.

The experimental data for Pseudomonas showed a 4.8% discrepancy with the predictions and a bias of + 3.6%. Percent discrepancies show close agreement between model predictions and observations, and the positive bias factor demonstrates that the proposed model over-predicts growth rate, thus, can be considered fail-safe. Both Pseudomonas spp. as well as total aerobes may be considered good indicators of poultry spoilage.

A properly constructed and validated model for Pseudomonas growth under aerobic conditions can provide a fast and cost-effective alternative to traditional microbiological techniques to estimate the effects of storage temperature on product shelf-life. The model developed here may be used to determine the effect of both initial Pseudomonas concentration and storage temperature on shelf-life of poultry meat under aerobic storage conditions over temperatures from 0 to 25 °C.