Heat transfer at the base of a cylindrical cavity oriented perpendicular to a freestream flow

The average and local heat transfer at the base surface of a cylindrical cavity whose opening is perpendicular to an oncoming freestream have been determined experimentally. During the course of the experiments, the cavity depth was varied from zero to 65% of the diameter, while the freestream Reynolds number ranged between about 5000 and 50,000. The average heat transfer coefficient decreased sharply with increasing cavity depth, the reduction being slightly greater than 50% at a depth-diameter ratio of 0.10 and greater than 90% when the depth-diameter ratio was 0.65. For the finite-depth cavities, the local heat transfer coefficient attained its maximum value at the center of the base surface and decreased with increasing radial distance from the center until a minimum was reached, after which there was a moderate increase adjacent to the outer edge of the base. The minimum occurred at the location where the radial outflow along the base separated from the surface, and a toroidal-shaped recirculation zone occupied the corner region at the intersection of the cavity base and side wall. In contrast, for the zero-depth cavity (i.e. a free disk oriented perpendicular to the oncoming flow), the local coefficient attained its minimum at the center of the surface and increased with increasing radial distance from the center.     

Accuracy of portable chest radiography in the critical care setting. Diagnosis of pneumonia based on quantitative cultures obtained from protected brush catheter

Sixty-six supine portable chest radiographs done on the day of bronchoscopy in 62 critical care unit patients suspected of having pneumonia were examined in a blinded fashion by two radiologists. Quantitative culture results obtained from protected brush catheter (PBC) specimens were compared with chest radiograph scores. For one observer, the sensitivity of the chest radiograph for predicting the presence of positive culture results was 0.60, specificity was 0.29, overall agreement was 0.41, positive predictive value was 0.34, and negative predictive value was 0.55. For the second observer, the values were as follows: sensitivity, 0.64; specificity, 0.27; overall agreement, 0.41; positive predictive value, 0.35; and negative predictive value, 0.55. The kappa statistic was calculated at 0.27 indicating marginal interobserver reproducibility. We conclude the portable chest radiograph in the critical care setting is not accurate in predicting the presence of pneumonia when the diagnosis is based on quantitative cultures obtained from protected brush catheter specimens.     

Empirical equations for the thermodynamic properties of aqueous sodium chloride

Equations for the thermodynamic properties of aqueous sodium chloride near its vapour pressure are presented. The equations are functions of temperature and concentration, and may be used to estimate aqueous sodium chloride's solubility, density, vapour pressure, specific enthalpy and entropy. They are valid for temperatures from 0 to 300°C, and concentrations extending to saturation with suitable accuracy. The thermodynamic equations are represented graphically and compared with published experimental data. These equations should prove to be a useful tool for modeling desalination equipment, particularly distillation processes.     

A review of the unique features of HDL apoproteins

The human plasma high density lipoproteins (HDL) are a heterogeneous ensemble of five proteins associated with both neutral and polar lipids. The sequences of all five proteins are known. ApoA-I and apoA-II are the major protein components; apoC-I, apoC-II and apoC-III are the minor protein components. All these apoproteins spontaneously recombine with phospholipids to give stable lipid-protein complexes and freely exchange between the two major HDL subclasses, HDL₂ and HDL₃. In addition, ApoC-I, apoC-II, and apoC-III exchange between HDL and very low density lipoproteins. Furthermore, certain HDL apoproteins are activators for plasma enzymes that are important in lipid metabolism. ApoA-I and apoC-I activate lecithin/cholesterol acyltransferase; apoC-II is an activator of lipoprotein lipase. The regions of apoC-I and apoC-II that are involved in the activation of these enzymes have been localized with synthetic peptides. Studies of synthetic and native fragments of apoA-II, apoC-I, apoC-II, and apoC-III as well as model lipid-binding peptides have identified specific regions with structural features common to lipid-binding proteins. These special properties, which include helical potential, sequences with a critical amphipathic length, and high hydrophobicity of the nonpolar side of the amphipathic helix, are the determinants of HDL structure and metabolism.     

Internal flows which transist from turbulent through intermittent to laminar

A transition model for internal flows which enables the prediction of the change of flow regime from turbulent through intermittent to laminar has been implemented by numerical simulation. This model had previously been demonstrated to be effective for the prediction of the breakdown of an initially laminar internal flow and its subsequent transitions to either intermittent or turbulent states. The model was employed here to study a flow which is decelerated by passing through a conical diffuser. The flow enters the diffuser with a fully developed turbulent velocity profile and exhibits transitions either in the diffuser or in a pipe situated downstream of the diffuser exit. The presence or absence of flow separation affected the onset of laminarization. Proof that laminarization actually occurred is provided by the values of the fully developed friction factors in the pipe downstream of the exit of the diffuser. These friction factors spanned the range from pure laminar flow through intermittent flow to fully turbulent flow. Comparisons were made with established benchmarks for each of these three flow regimes.     

Mechanics of the extension of cotton fibers. I. Experimental studies of the effect of convolutions

Cotton fibers have structure at many levels. This paper is concerned with the effect of gross convolutions on tensile properties. Experiments with rubber tubes show that convolutions result from the collapse of a twisted hollow tube. In cotton, the convolutions will reverse at the helix reversals. Extension of cotton fibers and of nylon models shows that the initial easy extension is due to the untwisting of convolutions. If the amounts of S- and Z-twist are different, the lesser part will become completely untwisted. Fibers stretched in water and then dried are without convolutions and are stiffer. Optical and SEM observations illustrate the behavior.     

Assessing the performance of a waste characterization expert system

Scientists at the Mississippi State University Diagnostic Instrumentation and Analysis Laboratory and the Idaho National Engineering and Environmental Laboratory (INEEL) have developed an expert system for a noninvasive characterization of containerized radiological waste. The characterization of the containers is necessary for determining their proper disposition. Three prototypes were developed, with each using a different method of handling uncertainty - a fuzzy system, a Bayesian network system, and a neural network system. The performance of each expert system was assessed to determine how well it modeled the decisions made by the INEEL domain expert. The prototype systems were also analyzed to measure the agreement in their decisions, the domain expert's decisions, and the decisions made by two additional experts. The neural network prototype was further analyzed to determine how consistent it was in its assessments. This paper describes the analysis of the performance of the three expert system prototypes.