Derive Mean Values Research Articles

Raman tensors for AB3C molecules

AbstractExplicit expressions for the Raman tensor of AB3C molecules are reported in terms of the bond polarizability parameters. By considering Fermi resonance between the ν1, 2ν5 and 2ν2 modes of CH3Cl, CH3Cl, CH3Br, CH3I and CH3F molecules, the relationships between the mean values of the polarizability derivatives with respect to dimensionless normal coordinates of these modes have been found.

Sensitivity of bioelectrical impedance to detect changes in human body composition.

The purpose of this study was to compare the estimates of lean body mass (LBM) and percent body fat (%BF), as predicted by bioelectrical impedance (BIA) and sum of skinfolds (SF), with those derived by hydrostatic weighing (HW) obtained before and after a 10-wk diet and exercise regimen. The experimental (E) group consisted of 17 healthy male subjects; 20 healthy males served as the control (C) group. Post hoc Scheffé contrasts computed on E group data indicated that, for both LBM and %BF, the Lukaski and Segal BIA equations, as well as the Durnin SF equation, derived mean values that were not significantly different (0.05 significance level) from HW in both pre- and postregimen conditions. For LBM, the same equations derived the following significant (P less than 0.01) correlation coefficients for both pre- and postregimen data: Lukaski, 0.87 and 0.85; Segal, 0.89 and 0.87; and Durnin, 0.90 and 0.88. For %BF, the correlation coefficients were slightly lower but remained statistically significant (P less than 0.01). The findings of this study suggest that the BIA method, by use of either the Lukaski or Segal prediction equations, is a valid means of predicting changes in human body composition as measured by the Siri transformation of body density.

Laser Mie scattering measurement of mean mixture fraction density and temperature by conditional seeding in a turbulent diffusion flame

The laser Mie scattering technique is used to measure the mean distributions of seed partieles in a turbulent diffusion flame of a jet of hydrogen air issuing in a coflowing air stream. Experiments are successively performed by seeding only the fuel channel and then only the coflow air. The conditional data are used to derive mean values of mixture fraction, density and temperature in the mixing flow. This technique appears to be well suited for measurements in diffusion flames where turbulent mixing is the dominant process and would be a very powerful tool for turbulence study in such flows if the two conditional seeding data could be obtained simultaneously.

The Heat of Formation of Mercury Vacancies in Hg0.8Cd0.2Te

A modified mass loss measurement technique has been employed, for the first time, for the direct in situ determination of vacancy concentrations in at elevated temperatures. This technique can also be used to establish the pressure‐temperature phase diagram for this type of systems. The derived mean value for the heat of formation of mercury vacancies in the above alloy is 0.43 eV. Theoretical considerations concerning the vacancy formation in and in are in qualitative agreement with our experimental value.

A class of cubic splines obtained through minimum conditions

A class of cubic spline minimizing some special functional is investigated. This class is determined by the solution of a quadratic programming problem in which the minimizing function depends linearly on a parameter α > 2 \alpha > 2 . For α = 1 / 2 \alpha = 1/2 natural splines are obtained. For α = − 1 \alpha = - 1 the spline minimizing the mean value of the third derivative is obtained. It is shown that this spline has the best convergence order.

A Class of Cubic Splines Obtained Through Minimum Conditions

A class of cubic spline minimizing some special functional is investigated. This class is determined by the solution of a quadratic programming problem in which the minimizing function depends linearly on a parameter $\alpha < 2$. For $\alpha = 1/2$ natural splines are obtained. For $\alpha = - 1$ the spline minimizing the mean value of the third derivative is obtained. It is shown that this spline has the best convergence order.

Mast cell and histamine content of human bronchoalveolar lavage fluid.

Bronchoalveolar lavage was performed in 97 patients including control patients with bronchial carcinoma (24) and patients with sarcoidosis (20), cryptogenic fibrosing alveolitis (9), and asthma (4), and others. Cytocentrifuged slides were stained by two methods: May-Grünwald Giemsa and toluidine blue. In the last 32 subjects the bronchoalveolar lavage fluid was separated into supernatant and cell pellet for the subsequent assay of the performed mast cell mediator, histamine. Comparison of the two methods of staining showed a bias towards toluidine blue. Controls had a differential mean (SE) mast cell count of 0.07% (0.01%). Higher counts were noted in cryptogenic fibrosing alveolitis--0.61% (0.15%) (p less than 0.001)--and in sarcoidosis--0.14% (0.02%) (p less than 0.05). There was a strong correlation between absolute mast cell counts and cell lysate histamine concentration (r = 0.78, p less than 0.001). Less strong, significant, correlations between supernatant histamine concentration and absolute mast cell counts (r = 0.48, p less than 0.01) or cell lysate histamine concentration (r = 0.72, p less than 0.01) were also found. Derived mean values of histamine per mast cell ranged from 3.7 to 10.9 picograms. The mean histamine content of lavage fluid supernatant as a percentage of the total lavage fluid histamine was 24.9% (3.3%). The possible clinical significance of these findings is discussed.

Kinetics of pulmonary CO 2 transfer studied by using labeled carbon dioxide C 16O 18O

The kinetics of alveolar-capillary CO 2 transfer was investigated, using 18O-labeled carbon dioxide (C 16O 18O), in 21 experiments on 2 resting human subjects. Single-breath experiments were performed. After the subjects expired to residual volume, they inspired a gas mixture containing 20% O 2 and 2.8% CO 2 — a quarter of CO 2 was labeled with 18O. The breath-hold time ranged between 0.5 and 20 sec. After expiration the gas mixture was analysed by mass spectrometry. The C 16O 18O concentration of the end-expiratory gas decreased with the increasing breath-hold time. The relationship of both showed a biexponential characteristics with the two time constants 0.4 and 16 sec. The lower time constant characterizes the CO 2 transfer from the alveolar space to the capillary blood, as well as the isotopic equilibrium of the 18O within the blood. The higher time constant could result from small admixtures of the label from the dead spaces or the lung tissues. The diffusing capacity of C 16O 18O was calculated by using the first part of the indicator clearance curve. The derived mean value of862 ml·mm Hg −1·min −1 is considered to be a lower limit of the ‘membrane diffusing capacity’ for CO 2 (D m CO2).

Trace metals from coal-fired power plants: Derivation of an average data base for assessment studies of the situation in the European communities

There is a pressing need to produce more electrical energy in the European Communities (EC) from coal-fired power plants (CFPPs). This would result in an increased release of trace metals (TM) into the environment with a potential impact on the different parts of the ecosystem and man. In view of the predicted increase in coal usage, an estimation of the amounts of TM released into the atmosphere or precipitated into the ashes produced by CFPPs is of crucial importance. This requires knowledge of the TM content in coals burnt in the European CFPPs. Twenty-nine coal samples, as burnt in CFPPs operating in the EC and made available by different organizations, were analysed for their TM content by neutron activation analysis (NAA). The values determined were integrated and compared with the existing literature data on global mean values of TM in coals so that average TM contents of the coals burnt in each member state of the EC were derived. Using the derived mean values as well as taking into account the amount of coal to be burnt in power plants of the EC, the average total TM mobilisation was predicted for fifteen elements for the year 1990. The global releases so estimated range from 66.5 to 19,420 metric tons for Hg and Zn, respectively.

Correlation of optical propagation near the sea surface with bulk meteorological measurements

Observations of optical propagation and bulk meteorological measurements were made from a tower located off the entrance to Narragansett Bay, RI. Measurements of air and sea temperatures, wind speed, and dew point were used to derive mean values ofC n 2. Then an optical propagation formulation employingC n 2 (height) was used to predict mean values of the spreading of a narrow target line at ranges up to 5 km. Predicted line widths were compared with measured ones. Under conditions of strong instability, mean line-width values agreed to within about ±25%. Under neutral and stable conditions, observations were limited by instrumentation, but predicted and mean measured line-widths agreed within a factor of two. Ratios were formed ofC n 2 values obtained from line-width measurements to corresponding values derived from bulk meteorological measurements under unstable atmospheric conditions. The geometric mean of the set of ratios was 0.94.

The Flow of Real Gases Through Porous Media

Abstract The effect of variations of pressure-dependent viscosity and gas lawdeviation factor on the flow of real gasses through porous media has beenconsidered. A rigorous gas flow equation was developed which is a second order, non-linear partial differential equation with variation coefficients. Thisequation was reduced by a change of variable to a form similar to thediffusivity equation, but with potential-dependent diffusivity. The change ofvariable can be used as a new pseudo-pressure for gas flow which replacespressure or pressure-squared as currently applied to gas flow. Substitution of the real gas pseudo-pressure has a number of importantconsequences. First, second degree pressure gradient terms which have commonlybeen neglected under the assumption that the pressure gradient is smalleverywhere in the flow system, are rigorously handled. Omission of seconddegree terms leads to serious errors in estimated pressure distributions fortight formations. Second, flow equations in terms of the real gaspseudo-pressure do not contain viscosity or gas law deviation factors, and thusavoid the need for selection of an average pressure to evaluate physicalproperties. Third, the real gas pseudo-pressure can be determined numericallyin terms of pseudo-reduced pressures and temperatures from existing physicalproperty correlations to provide generally useful information. The real gaspseudo-pressure was determined by numerical integration and is presented inboth tabular and graphical form in this paper. Finally, production of real gascan be correlated in terms of the real gas pseudo-pressure and shown to besimilar to liquid flow as described by diffusivity equation solutions. Application of the real gas pseudo-pressure to radial flow systems undertransient, steady-state or approximate pseudo-steady-state injection orproduction have been considered. Superposition of the linearized real gas flowsolutions to generate variable rate performance was investigated and foundsatisfactory. This provides justification for pressure build-up testing. It isbelieved that the concept of the real gas pseudo-pressure will lead to improvedinterpretation of results of current gas well testing procedures, both steadyand unsteady-state in nature, and improved forecasting of gas production. Introduction In recent years a considerable effort has been directed to the theory ofisothermal flow of gases through porous media. The present state of knowledgeis far from being fully developed. The difficulty lies in the non-linearity ofpartial differential equations which describe both real and ideal gas flow. Solutions which are available are approximate analytical solutions, graphicalsolutions, analogue solutions and numerical solutions. The earliest attempt to solve this problem involved the method ofsuccessions of steady states proposed by Muskat.1 Approximateanalytical solutions2 were obtained by linearizing the flow equationfor ideal gas to yield a diffusivity-type equation. Such solutions, thoughwidely used and easy to apply to engineering problems, are of limited valuebecause of idealized assumptions and restrictions imposed upon the flowequation. The validity of linearized equations and the conditions under whichtheir solutions apply have not been fully discussed in the literature. Approximate solutions are those of Heatherington et al.,2MacRoberts 4 and Janicek and Katz.5 A graphical solutionof the linearized equation was given by Cornell and Katz.6 Also, byusing the mean value of the time derivative in the flow equation, Rowan andClegg 7 gave several simple approximate solutions. All the solutionswere obtained assuming small pressure gradients and constant gas properties. Variation of gas properties with pressure has been neglected because ofanalytic difficulties, even in approximate analytic solutions. Green and Wilts8 used an electrical network for simulatingone-dimensional flow of an ideal gas. Numerical methods using finite differenceequations and digital computing techniques have been used extensively forsolving both ideal and real gas equations. Aronofsky and Jenkins9,10and Bruce et al.11 gave numerical solutions for linear andradial gas flow. Douglas et al.12 gave a solution for asquare drainage area. Aronofsky13 included the effect of slippage onideal gas flow. The most important contribution to the theory of flow of idealgases through porous media was the conclusion reached by Aronofsky andJenkins14 that solutions for the liquid flow case15 couldbe used to generate approximate solutions for constant rate production of idealgases.

Isotope effects in phase equilibria; a new tool for the study of intermolecular forces

The renascence of interest in isotope effects in phase equilibria during the past decade has provided a new body of experimental data pertaining to intermolecular forces. Concurrent advances in the quantum theory of the liquid and solid states have led to the formulation of the mass dependence of the quantum partition function and its temperature dependence. The theory shows that in the first approximation the isotope effects in phase equilibria are determined by the mean value of the second derivative of the intermolecular potential. For monatomic systems a new set of molecular parameters have been derived for neon, krypton, and xenon based on the WHALLEY-SCHNEIDER parameters for argon. For the condensed rare gases, it has been shown that independent particle models, e.g. anharmonic Einstein model of the crystal and quantum cell models in the liquid, cannot account for the observed isotope effects. The isotope effect on melting is discussed in terms of the structure of the solid and the nearest neighbor numbers of the liquid.For polyatomic molecules, a wealth of new information and a number of new phenomena associated with intermolecular forces have been discovered. It is found that in the first approximation the intermolecular potential appears as the sum of atomic interactions. A development of this method leads to a direct and quantitative explanation of a number of hitherto incomprehensible phenomena. Isotopic substitution provides a direct demonstration of hindered rotation in the liquid. Two new types of quantum effects associated with molecular rotation have been found. The first type is a coupling of the molecular rotation with the molecular translation in the field of the intermolecular force. The effect persists even for free rotation and is most pronounced for molecules with small moments of inertia. The effect has been quantitatively investigated through the phase equilibrium behaviour of the isotopic and rotational forms of hydrogen. The second effect is a coupling of the molecular rotation with the molecular vibration in the field associated with the hindered rotation. A quantitative investigation of this rotation-vibration interaction has been made by the study of the vapor pressures of the deuteroethylenes. Studies of isotopic phase equilibria together with molecular spectroscopy of the condensed state provide information concerning the perturbation of the intramolecular vibrations by the intermolecular forces.