Green spherules from Apollo 15: Inferences about their origin from inert gas measurements

The Moon ◽  
1973 ◽  
Vol 7 (1-2) ◽  
pp. 132-148 ◽  
Author(s):  
S. Lakatos ◽  
D. Heymann ◽  
A. Yaniv
Keyword(s):  
Inert Gas ◽  
Gas Measurements

Graphical analysis of multiple inert gas elimination data

1983 ◽  
Vol 55 (1) ◽  
pp. 32-36 ◽  
Author(s):  
W. E. Stewart ◽  
S. M. Mastenbrook
Keyword(s):  
Gas Exchange ◽  
Companion Paper ◽  
Graphical Analysis ◽  
Inert Gases ◽  
Inert Gas ◽  
Additional Test ◽  
Multicompartmental Model ◽  
Simple Rules ◽  
Gas Measurements ◽  
Mixed Venous

A plot of measured retention-excretion ratios [(Ri/Ei)obs] vs. reciprocal solubility (1/lambda i) for selected inert gases allows quick detection of shunt and ventilation-perfusion (V/Q) inhomogeneity in the lung. We derive simple rules for constructing a smooth R/E function from the data, using a multicompartmental model of the lung. If mixed venous inert gas measurements are available, the values [lambda i(1-Ri)/Ei]obs for the infused gases can be used to estimate the overall VT/QT ratio and provide an additional test of the consistency of the data. For any set of equilibrium compartments ventilated and perfused in parallel, we show that d(R/E)/d(1/lambda) cannot be negative, nor can d2(R/E)/d(1/lambda)2 be greater than zero. A rectilinear R/E function implies a narrow distribution of V/Q among the gas exchange compartments, whereas a downward-concave curve implies a broader distribution. The shunt perfusion and dead-space ventilation can be estimated from the asymptotes of the R/E function. The range of V/Q for the gas exchange compartments can also be bracketed if a well-defined region of curvature is present in the graph. Finally, from the R/E vs. 1/lambda graph and (if mixed venous data are available) from the lambda(1-R)/E values, we can determine quickly whether the data deserve the detailed numerical analysis outlined in our companion paper.

A simple model of VA/Q distribution for analysis of inert gas elimination data

1983 ◽  
Vol 55 (2) ◽  
pp. 562-568 ◽  
Author(s):  
P. Mertens
Keyword(s):  
General Procedure ◽  
Real Data ◽  
Compartment Model ◽  
Inert Gas ◽  
Logarithmic Scale ◽  
Fitting Procedure ◽  
Experimental Errors ◽  
Standard Deviations ◽  
Gas Measurements ◽  
Ventilation Perfusion Ratio

A general procedure for fitting compartments models of alveolar ventilation-perfusion ratio (VA/Q) distribution to inert gas elimination data is described. The method can be applied to any model consisting of a number of compartments ventilated and perfused in parallel, each compartment of the model having a fixed predetermined VA/Q ratio. The number of compartments and their VA/Q ratios required for adequately fitting real data have been examined. A 13-compartment model consisting of a shunt, a dead space, and 11 compartments equally spaced on a logarithmic scale from VA/Q of 0.01 to 100 was found to be suitable. The fitting procedure and the 13-compartment model form the basis of a method of analysis of inert gas elimination data. Essentially the method consists of calculating a sample of 30 distributions compatible with the data analyzed taking into account experimental errors in the inert gas measurements. From this sample, the averages and standard deviations of the flows to 13 zones on the VA/Q scale are estimated. The averages are estimates of the true flows to these zones, and the standard deviations give an indication of the range of flows compatible with the data. The method has some advantages over both the enforced-smoothing approach and the Monte Carlo linear programming scheme of Evans and Wagner (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 42: 889-898, 1977).

Inert gas measurements of coronary blood flow

1969 ◽  
Vol 23 (4) ◽  
pp. 548-555 ◽  
Author(s):  
Francis J. Klocke ◽  
Douglas R. Rosing ◽  
David E. Pittman
Keyword(s):  
Blood Flow ◽  
Coronary Blood Flow ◽  
Inert Gas ◽  
Gas Measurements

Information content of multiple inert gas elimination measurements

1987 ◽  
Vol 63 (2) ◽  
pp. 861-868 ◽  
Author(s):  
K. S. Kapitan ◽  
P. D. Wagner
Keyword(s):  
Information Content ◽  
Theoretical Basis ◽  
Experimental Error ◽  
Partition Coefficients ◽  
Data Interpretation ◽  
Inert Gases ◽  
Inert Gas ◽  
Logarithmic Scale ◽  
Independent Information ◽  
Gas Measurements

The multiple inert gas elimination technique provides a fundamental assessment of the distribution of ventilation-perfusion (VA/Q) ratios in the lung. The resolution of the finer structure of this distribution is limited however. This study examines the theoretical basis of this limitation and presents an objective method for evaluating the independence of inert gas measurements. It demonstrates the linear dependence of the inert gas kernels and their filtering characteristics to be the factors most limiting information content. The limited number of gases available for measurement and experimental error are lesser limitations. At usual levels of experimental error, no more than seven different inert gases having partition coefficients between those of SF6 and acetone will provide independent information, and information content will be maximized by choosing gases with partition coefficients spaced equally on a logarithmic scale. A fivefold reduction in experimental error will not significantly alter the information content of the measurements. The analysis applies equally to other methods of multiple inert gas elimination data interpretation.

Fission Gas Bubbles in Fractured UO2

1968 ◽  
Vol 26 ◽  
pp. 286-287
Author(s):  
O. M. Katz
Keyword(s):  
Electron Microscopy ◽  
Thermal Gradient ◽  
Gas Bubbles ◽  
Inert Gas ◽  
Thermal Gradients ◽  
Fission Gas ◽  
Beam Heating ◽  
Limited Application ◽  
Bubble Characteristics ◽  
Electron Beam Heating

The swelling of irradiated UO2 has been attributed to the migration and agglomeration of fission gas bubbles in a thermal gradient. High temperatures and thermal gradients obtained by electron beam heating simulate reactor behavior and lead to the postulation of swelling mechanisms. Although electron microscopy studies have been reported on UO2, two experimental procedures have limited application of the results: irradiation was achieved either with a stream of inert gas ions without fission or at depletions less than 2 x 1020 fissions/cm3 (∼3/4 at % burnup). This study was not limited either of these conditions and reports on the bubble characteristics observed by transmission and fractographic electron microscopy in high density (96% theoretical) UO2 irradiated between 3.5 and 31.3 x 1020 fissions/cm3 at temperatures below l600°F. Preliminary results from replicas of the as-polished and etched surfaces of these samples were published.

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