Simultaneous estimation of aerosol cloud concentration and spectral backscatter from multiple-wavelength lidar data

We present a sequential algorithm for estimating both concentration dependence on range and time and backscatter coefficient spectral dependence of optically thin localized atmospheric aerosols using data from rapidly tuned lidar. The range dependence of the aerosol is modeled as an expansion of the concentration in an orthonormal basis set whose coefficients carry the time dependence. Two estimators are run in parallel: a Kalman filter for the concentration range and time dependence and a maximum-likelihood estimator for the aerosol backscatter wavelength and time dependence. These two estimators exchange information continuously over the data-processing stream. The state model parameters of the Kalman filter are also estimated sequentially together with the concentration and backscatter. Lidar data collected prior to the aerosol release are used to estimate the ambient lidar return. The approach is illustrated on atmospheric backscatter long-wave infrared (CO2) lidar data.     

The influence of radon measurement errors on the uncertainties of epidemiological case-control studies

To analyse the influence of the parameters of case and control groups and uncertainties of radon concentration assessments on the dose-effect dependence, a special computer program was designed. The influence of measurement errors on the uncertainties of radon case-control analysis is demonstrated on examples of hypothetical case and control groups with sizes from 250-500 to 7000-14,000 members. The modelling was conducted using a Monte Carlo technique for different values of measurement uncertainties. The random errors of radon assessment affect both the numerical value of the slope coefficient β of the linear dependence of relative risk of lung cancer incidence on indoor radon concentration and the accuracy of this value. The extrapolation of the dependence of the slope coefficient β on the total (initial plus additional) random error of radon concentration assessment is suggested for the assessment of an unbiased value of the slope coefficient β.     

The Thermophysical Properties of Solid Solutions of CaLa2S4-La2S3 System

The thermal conductivity coefficient in the temperature range from 275 to 450 K and the coefficient of thermal expansion in the range from 300 to 900 K are experimentally determined for solid solutions of the CaLa₂S₄-La₂S₃ system. The mechanisms of heat transfer in CaLa₂S₄- La₂S₃ samples in the investigated temperature range are discussed, as well as the factors which define the complex concentration dependence of thermal conductivity coefficient. The correlation is treated between the value and temperature dependence of the coefficient of thermal expansion and the variation of the interatomic bond force in the case of variation of the concentration of cation vacancies in the investigated crystals.     

A kinetic study of mass transfer in reversed-phase liquid chromatography on a C18-silica gel

The characteristic features of mass-transfer kinetics in a reversed-phase (RP) column packed with a C18-silica were studied. The relevant information on phase equilibrium thermodynamics and mass-transfer kinetics was obtained by frontal analysis and the pulse method, respectively. The equilibrium isotherm was accounted for by the simple Langmuir model. The ratio of the axial dispersion coefficient to the mobile-phase flow velocity increased almost linearly with increasing solute concentration. Similarly, the mass-transfer rate coefficient (km) showed a linear dependence on the solute concentration. The positive concentration dependence of km resulted from that of the surface diffusion coefficient, which was interpreted with the chemical potential driving force model. The contribution of axial dispersion to band broadening was predominant in the RP column packed with the medium-size packing material used (particle diameter, 12 microns) whereas that of the kinetics of adsorption/desorption was negligibly small. The results of this study demonstrate how an analysis of the dependence of the mass-transfer kinetics on the flow velocity and the solute concentration allows a better understanding of this kinetics.     

Influence of the coefficient of vaporization on the parameters of the gas near the surface

The dependence of the coefficient of concentration jump on the coefficient of vaporization for a diluted binary mixture, when the concentrations of the components are significantly different, has been investigated. The analytical expression of the concentration jump for the case where the frequency of collisions of molecules is in proportion to their velocity has been obtained. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 2, pp. 121–126, March–April, 2007.     

A mathematical model of extraction with a variable mass-transfer coefficient

Using the relationship between the sizes of particles and the characteristics of their layer, we obtain the dependence of the mass-transfer coefficient on time and concentration; the dependence is included in the third-kind boundary condition. Using this condition, we solve the boundary-value problem of extraction.     

Measurement of Binary Diffusion Coefficients for Neon–Argon Gas Mixtures Using a Loschmidt Cell Combined with Holographic Interferometry

The paper reports on experimental binary diffusion coefficient data of neon–argon gas mixtures. Measurements were performed in the temperature range between 293.15 K and 333.15 K and for pressures between 1 bar and 10 bar over almost the whole composition range using a Loschmidt diffusion cell combined with holographic interferometry. The thermostated Loschmidt cell is divided into two half-cells, which can be separated and connected by a sliding plate. Prior to the measurements, two different pure gases are filled into the two half-cells. After starting the diffusion process, the temporal change of the partial molar densities, or rather of the refractive index of the gases, is detected in both half-cells using two holographic interferometers. With this apparatus, the temperature, pressure, and concentration dependence of the binary diffusion coefficient can be determined. The relative uncertainty of a diffusion measurement is between 0.4 % and 1.4 % depending on the pressure. The experimental data are compared with data from the literature and with new theoretical data based on quantum-mechanical ab initio calculations combined with the kinetic theory of gases. Due to a systematic error, the concentration dependence determined in the upper half-cell shows deviations from the theoretical values and from most of the literature data. The concentration, temperature, and pressure dependence obtained from the data from the lower half-cell, however, are in very good agreement with available data. The product of the binary gas diffusion coefficient and the molar density of the gas mixture shows no significant dependence on pressure for the studied neon–argon noble gas system.     

The change of the diffusivity with the change of the concentration of the solvent in a solution

Summary We consider the convective mass transfer of drops and solid particles with a viscous liquid flow when the diffusion coefficient is arbitrarily dependent on the concentration. We discuss the exact solutions of this problem and we present such a solution for the special case of hyperbolic dependence of the diffusion coefficient on the concentration. The formula for the average Sherwood number is obtained.With 3 Figures     

Desired concentration-dependent ion exchange for micro-optic lenses

The required concentration-dependent diffusion coefficients for both ideal one-dimensional and ideal radial gradient-index profiles are determined. The modified quasi-chemical diffusion model is used to relate the diffusion coefficient to optimum glass composition. Adding aluminum to sodium silicate glasses facilitates the approach to the desired concentration dependence of the diffusion coefficient for silver-sodium ion exchange. A parabolic one-dimensional index profile is fabricated in one of the glasses. It deviates from ideal values by less than 2%.     

The effect of the size and packing of molecules on the thermodynamic properties of mixtures

The suggested approach explains the concentration dependence of density and of bulk-and-elastic properties of thermodynamically ideal mixture from the structural standpoint. It is demonstrated that the deviations of the concentration dependence of volumetric density and of the coefficient of isothermal compressibility from the mole-additive rule are caused by the difference between the structure parameters of pure liquids contained in the mixture (molecular volume, packing factors, and molecular densities). The contribution made by each one of the structure parameters to the deviation of the behavior of density of thermodynamically ideal mixture from the mole-additive rule is identified and estimated within suggested simulation for mixtures of different types.     

Temperature Dependence of Photothermal Displacement Signal in Silicon

Abstract

This letter presents the preliminary results of a study on the dependence of photothermal displacement signal on temperature in crystalline silicon wafers and coated silicon samples. The temperature enters indirectly into the signal as thermal conductivity, specific heat and thermal expansion coefficient of the material vary with temperature. The experimental results are consistent with that theoretically expected by taking into account the dependence of thermal conductivity from dopant concentration at low temperatures.     

Lipopolymer gradient diffusion in supported bilayer membranes

We measure the gradient diffusion coefficient of a model lipopolymer in supported lipid bilayer membranes from Fourier-transform post-electrophoresis relaxation. The experiments and accompanying quantitative interpretation furnish the concentration dependence of the gradient diffusion coefficient. In striking contrast to the recent measurements of the self-diffusion coefficient from fluorescence recovery after photobleaching, the lipopolymer gradient diffusion coefficient increases with concentration. We interpret the enhancement at small but finite concentrations using the Scalettar–Abney–Owicki (SAO) statistical mechanical theory (1988) and the Bussell–Koch–Hammer (BKH) hydrodynamic theory (1995), which are customarily adopted to model membrane protein dynamics. The SAO theory furnishes an effective disc radius and soft repulsive interaction radius that are comparable to the Flory radius of the unperturbed polyethylene glycol chains. On the other hand, the BKH theory predicts a gradient diffusion coefficient that decreases with disc/membrane protein concentration. Thus, in contrast to membrane proteins, we conclude that lipopolymer hydrodynamic interactions are weak because the principal disturbances are in the low-viscosity aqueous phase. Accordingly, lipopolymer interactions are dominated by thermodynamic interactions among polymer chains. Interestingly, our experiments suggest that increasing (decreasing) the polymer molecular weight should increase (decrease) the relaxation rate of lipopolymer concentration fluctuations.     

Studying of salt diffusion behaviour in brick

In this paper, an analysis of the diffusion behaviour of salts in fully saturated brick is presented. This paper extends the previous work to including more salt types and measurement data. Dependence of diffusion coefficient on temperature and other factors is discussed. Starting from the mathematical model which has been verified before, the obtained results are 2-fold: first the diffusion coefficients for different types of salts are given which are evaluated from measurements; moreover, dependence of temperature and ambient salt concentration on diffusion coefficient is presented.     

Effect of the concentration dependence of the diffusion coefficient on the distribution and flow of hydrogen in palladium membranes

Results are presented from the calculation of steady-state profiles of the distribution and flow of hydrogen in palladium membranes. The distributions are obtained with allowance for features of the dependence of the diffusion coefficient on hydrogen concentration.Translated from Inzhenerno-fizicheskii Zhurnal, Vol. 59, No. 10, pp. 602–606, October, 1990.     

Mathematical Model of Magnetic Aftereffect in Hydrogenated Ferromagnets

We consider a mathematical model of magnetic aftereffect in ferromagnets saturated with hydrogen. The influence of the concentration of hydrogen on the magnetic aftereffect is taken into account by the dependence of the coefficient of relaxation of magnetization on the level of strains, which, in turn, depends on the concentration of hydrogen. The time dependence of the electromotive force in a contour enclosing a long cylinder is established for various values of the rate of magnetic relaxation. The obtained dependences can be used for the interpretation of the results of measurements aimed at the evaluation of the concentration of hydrogen.     

Frequency dependence of backscatter coefficient versus scatterervolume fraction

Various groups are using the frequency dependence of backscattering to characterize tissue. In most cases, sparse scatterer concentrations are assumed in relating scattering parameters to tissue properties. This study addresses the relationship between backscatter frequency dependence and scatterer volume fraction. Backscatter coefficients (BSC) in the 2.5 to 9.0 MHz frequency range were measured for agar-gel phantoms containing Sephadex scatterers (mean diameter 42 μm) at volume fractions ranging from 5 to 50%. The BSC increased with scatterer volume fraction at low scatterer concentrations; at higher concentrations, the BSC reached a maximum with concentration and then decreased with yet increasing scatterer concentrations, as has been noted by previous authors. In addition, the volume fraction for the maximum backscatter coefficient varied with frequency, generally being greater at higher frequencies than lower frequencies, and the frequency dependence of the backscatter coefficient was greater for the higher scatterer concentrations than for the lower concentrations. These results are predicted by continuum models, where the spatial autocorrelation function depends on scatterer volume fraction     

Integral transform “infixing” method for nonlinear transient mass-transfer problems

An approximate method is proposed for solving nonlinear problems of transient mass transfer between a wall and a motionless fluid for an arbitrary concentration dependence of the diffusion coefficient. Nonlinear problems compounded with a volume or surface chemical reaction are investigated.Notation a linear space scale - C concentration - C_s surface concentration on wall - C₀ concentration at initial time - c dimensionless concentration - D diffusion coefficient D=D(C) - j dimensionless diffusion flux onto wall - K_s rate constant of surface chemical reaction - K_v rate constant of volume chemical reaction - t time - X distance from wall Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 55, No. 4, pp. 638–643, October, 1988.     

Heat transfer on boiling a Freon-22-dibutyl phthalate solution

Experimental data on the boiling heat transfer of a Freon-22-dibutyl phthalate solution have been obtained on a special apparatus. The dependence of the heat-transfer coefficient on the heat load, pressure, and solution concentration has been established.     

Self-diffusion of poly (ethylene oxide) – modified paclitaxel in dilute aqueous solutions

In order to make the hydrophobic anti-cancer drug Paclitaxel watersoluble, it was coupled to highly uniform poly (ethylene oxide) (PEO) with the molar mass M_w = 5,000 g/mol with a self-immolating succinate linker. The concentration and temperature dependence of the unrestricted molecular mobility of the molecules (long-time self-diffusion) in homogeneous aqueous (D₂O) solution was studied by gradient field NMR around body temperature in the highly dilute region. The concentration dependence of the friction coefficient, and the self-diffusion coefficient is unexpectedly strong and probably caused by peculiarities of the shape and/or the flexibility of the molecules rather than their size. Dedicated to Prof. Dr. W. S. Veeman, Gerhard-Mercator-University, Duisburg, on the occasion of his 60th birthday