Correlation and prediction of gaseous diffusion coefficients.
NASA Technical Reports Server (NTRS)
Marrero, T. R.; Mason, E. A.
1973-01-01
A new correlation method for binary gaseous diffusion coefficients from very low temperatures to 10,000 K is proposed based on an extended principle of corresponding states, and having greater range and accuracy than previous correlations. There are two correlation parameters that are related to other physical quantities and that are predictable in the absence of diffusion measurements. Quantum effects and composition dependence are included, but high-pressure effects are not. The results are directly applicable to multicomponent mixtures.
NASA Astrophysics Data System (ADS)
Somers, Marcel A. J.; Mittemeijer, Eric J.
1995-01-01
Models were derived for monolayer and bilayer growth into a substrate in which diffusion of the solute governs the growth kinetics, as in gas-solid reactions, for example. In the models, the composition dependence of the solute diffusivity in the phases constituting the layers was accounted for by appropriate definition of an effective diffusion coefficient for a (sub)layer. This effective diffusion coefficient is the intrinsic diffusion coefficient weighted over the composition range of the (sub)layer. The models were applied for analyzing the growth kinetics of a γ'-Fe4N1-x monolayer on an α-Fe substrate and the growth kinetics of an ɛ-Fe2N1-z/γ'-Fe4N1-x bilayer on an α-Fe substrate, as observed by gaseous nitriding in an NH3/H2-gas mixture at 843 K. The kinetics of layer development and the evolution of the microstructure were investigated by means of thermogravimetry, layer-thickness measurements, light microscopy, and electron probe X-ray microanalysis (EPMA). The effective and self-diffusion coefficients were determined for each of the nitride layers. The composition dependence of the intrinsic (and effective) diffusion coefficients was established. Re-evaluating literature data for diffusion in γ'-Fe4N1-x on the basis of the present model, it followed that the previous and present data are consistent. The activation energy for diffusion of nitrogen in γ'-Fe4N1-x was determined from the temperature dependence of the self-diffusion coefficient. The self-diffusion coefficient for nitrogen in ɛ-Fe2N1-z was significantly larger than that for γ'-Fe4N1-x. This was explained qualitatively, considering the possible mechanisms for interstitial diffusion of nitrogen atoms in the close-packed iron lattices of the ɛ and γ' iron nitrides.
Garrett, George A.; Shacter, John
1978-01-01
1. A gaseous diffusion system comprising a plurality of diffusers connected in cascade to form a series of stages, each of said diffusers having a porous partition dividing it into a high pressure chamber and a low pressure chamber, and means for combining a portion of the enriched gas from a succeeding stage with a portion of the enriched gas from the low pressure chamber of each stage and feeding it into one extremity of the high pressure chamber thereof.
Turbulent diffusion of chemically reacting gaseous admixtures.
Elperin, T; Kleeorin, N; Liberman, M; Rogachevskii, I
2014-11-01
We study turbulent diffusion of chemically reacting gaseous admixtures in a developed turbulence. In our previous study [Phys. Rev. Lett. 80, 69 (1998)PRLTAO0031-900710.1103/PhysRevLett.80.69] using a path-integral approach for a delta-correlated in a time random velocity field, we demonstrated a strong modification of turbulent transport in fluid flows with chemical reactions or phase transitions. In the present study we use the spectral τ approximation that is valid for large Reynolds and Peclet numbers and show that turbulent diffusion of the reacting species can be strongly depleted by a large factor that is the ratio of turbulent and chemical times (turbulent Damköhler number). We have demonstrated that the derived theoretical dependence of a turbulent diffusion coefficient versus the turbulent Damköhler number is in good agreement with that obtained previously in the numerical modeling of a reactive front propagating in a turbulent flow and described by the Kolmogorov-Petrovskii-Piskunov-Fisher equation. We have found that turbulent cross-effects, e.g., turbulent mutual diffusion of gaseous admixtures and turbulent Dufour effect of the chemically reacting gaseous admixtures, are less sensitive to the values of stoichiometric coefficients. The mechanisms of the turbulent cross-effects differ from the molecular cross-effects known in irreversible thermodynamics. In a fully developed turbulence and at large Peclet numbers the turbulent cross-effects are much larger than the molecular ones. The obtained results are applicable also to heterogeneous phase transitions. PMID:25493875
Studies of Gaseous Multiplication Coefficient in Isobutane
Lima, Iara B.; Vivaldini, Tulio C.; Goncalves, Josemary A. C.; Botelho, Suzana; Bueno Tobias, Carmen C.; Ridenti, Marco A.; Pascholati, Paulo R.; Fonte, Paulo; Mangiarotti, Alessio
2010-05-21
This work presents the studies of gaseous multiplication coefficient behavior for isobutane, as function of the reduced electric field, by means of signal amplitude analysis. The experimental method used is based on the Pulsed Townsend technique, which follows from Townsend equation solution for a uniform electric field. In our configuration, the anode is made of a high resistivity (2.10{sup 12} OMEGA.cm) glass, while the cathode is of aluminium. In order to validate the technique and to analyze effects of non-uniformity, results for nitrogen, which has well-established data available in literature, are also presented.
Studies of Gaseous Multiplication Coefficient in Isobutane
NASA Astrophysics Data System (ADS)
Lima, Iara B.; Vivaldini, Túlio C.; Gonçalves, Josemary A. C.; Botelho, Suzana; Ridenti, Marco A.; Fonte, Paulo; Mangiarotti, Alessio; Pascholati, Paulo R.; Bueno Tobias, Carmen C.
2010-05-01
This work presents the studies of gaseous multiplication coefficient behavior for isobutane, as function of the reduced electric field, by means of signal amplitude analysis. The experimental method used is based on the Pulsed Townsend technique, which follows from Townsend equation solution for a uniform electric field. In our configuration, the anode is made of a high resistivity (2.1012 Ω.cm) glass, while the cathode is of aluminium. In order to validate the technique and to analyze effects of non-uniformity, results for nitrogen, which has well-established data available in literature, are also presented.
Portable vapor diffusion coefficient meter
Ho, Clifford K.
2007-06-12
An apparatus for measuring the effective vapor diffusion coefficient of a test vapor diffusing through a sample of porous media contained within a test chamber. A chemical sensor measures the time-varying concentration of vapor that has diffused a known distance through the porous media. A data processor contained within the apparatus compares the measured sensor data with analytical predictions of the response curve based on the transient diffusion equation using Fick's Law, iterating on the choice of an effective vapor diffusion coefficient until the difference between the predicted and measured curves is minimized. Optionally, a purge fluid can forced through the porous media, permitting the apparatus to also measure a gas-phase permeability. The apparatus can be made lightweight, self-powered, and portable for use in the field.
Uranium enrichment export control guide: Gaseous diffusion
Not Available
1989-09-01
This document was prepared to serve as a guide for export control officials in their interpretation, understanding, and implementation of export laws that relate to the Zangger International Trigger List for gaseous diffusion uranium enrichment process components, equipment, and materials. Particular emphasis is focused on items that are especially designed or prepared since export controls are required for these by States that are party to the International Nuclear Nonproliferation Treaty.
Diffusion method of seperating gaseous mixtures
Pontius, Rex B.
1976-01-01
A method of effecting a relatively large change in the relative concentrations of the components of a gaseous mixture by diffusion which comprises separating the mixture into heavier and lighter portions according to major fraction mass recycle procedure, further separating the heavier portions into still heavier subportions according to a major fraction mass recycle procedure, and further separating the lighter portions into still lighter subportions according to a major fraction equilibrium recycle procedure.
Radiant Extinction Of Gaseous Diffusion Flames
NASA Technical Reports Server (NTRS)
Berhan, S.; Chernovsky, M.; Atreya, A.; Baum, Howard R.; Sacksteder, Kurt R.
2003-01-01
The absence of buoyancy-induced flows in microgravity (mu:g) and the resulting increase in the reactant residence time significantly alters the fundamentals of many combustion processes. Substantial differences between normal gravity (ng) and :g flames have been reported in experiments on candle flames [1, 2], flame spread over solids [3, 4], droplet combustion [5,6], and others. These differences are more basic than just in the visible flame shape. Longer residence times and higher concentration of combustion products in the flame zone create a thermochemical environment that changes the flame chemistry and the heat and mass transfer processes. Processes such as flame radiation, that are often ignored in ng, become very important and sometimes even controlling. Furthermore, microgravity conditions considerably enhance flame radiation by: (i) the build-up of combustion products in the high-temperature reaction zone which increases the gas radiation, and (ii) longer residence times make conditions appropriate for substantial amounts of soot to form which is also responsible for radiative heat loss. Thus, it is anticipated that radiative heat loss may eventually extinguish the Aweak@ (low burning rate per unit flame area) :g diffusion flame. Yet, space shuttle experiments on candle flames show that in an infinite ambient atmosphere, the hemispherical candle flame in :g will burn indefinitely [1]. This may be because of the coupling between the fuel production rate and the flame via the heat-feedback mechanism for candle flames, flames over solids and fuel droplet flames. Thus, to focus only on the gas-phase phenomena leading to radiative extinction, aerodynamically stabilized gaseous diffusion flames are examined. This enables independent control of the fuel flow rate to help identify conditions under which radiative extinction occurs. Also, spherical geometry is chosen for the :g experiments and modeling because: (i) It reduces the complexity by making the problem
Simulating Isotope Enrichment by Gaseous Diffusion
NASA Astrophysics Data System (ADS)
Reed, Cameron
2015-04-01
A desktop-computer simulation of isotope enrichment by gaseous diffusion has been developed. The simulation incorporates two non-interacting point-mass species whose members pass through a cascade of cells containing porous membranes and retain constant speeds as they reflect off the walls of the cells and the spaces between holes in the membranes. A particular feature is periodic forward recycling of enriched material to cells further along the cascade along with simultaneous return of depleted material to preceding cells. The number of particles, the mass ratio, the initial fractional abundance of the lighter species, and the time between recycling operations can be chosen by the user. The simulation is simple enough to be understood on the basis of two-dimensional kinematics, and demonstrates that the fractional abundance of the lighter-isotope species increases along the cascade. The logic of the simulation will be described and results of some typical runs will be presented and discussed.
Viscosity and thermal conductivity coefficients of gaseous and liquid oxygen
NASA Technical Reports Server (NTRS)
Hanley, H. J. M.; Mccarty, R. D.; Sengers, J. V.
1974-01-01
Equations and tables are presented for the viscosity and thermal conductivity coefficients of gaseous and liquid oxygen at temperatures between 80 K and 400 K for pressures up to 200 atm. and at temperatures between 80 K and 2000 K for the dilute gas. A description of the anomalous behavior of the thermal conductivity in the critical region is included. The tabulated coefficients are reliable to within about 15% except for a region in the immediate vicinity of the critical point. Some possibilities for future improvements of this reliability are discussed.
Diffusion coefficients of several aqueous alkanolamine solutions
Snijder, E.D.; Riele, M.J.M. te; Versteeg, G.F.; Swaaij, W.P.M. van . Dept. of Chemical Engineering)
1993-07-01
In absorption processes of acid gases (H[sub 2]S, CO[sub 2], COS) in alkanolamine solutions, diffusion coefficients are used for the calculation of the mass transfer rate. The Taylor dispersion technique was applied for the determination of diffusion coefficients of various systems. Experiments with the system KCl in water showed that the experimental setup provides accurate data. For the alkanolamines monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA), and di-2-propanolamine (DIPA), correlations for the diffusion coefficient as a function of temperature at different concentrations are given. A single relation for every amine has been derived which correlates the diffusion coefficients as a function of temperature and concentration. The temperature was varied between 298 and 348 K, and the concentration between 0 and 4000-5000 mol/m[sup 3]. Furthermore, a modified Stokes-Einstein relation is presented for the prediction of the diffusion coefficients in the alkanolamines in relation to the viscosity of the solvent and the diffusion coefficient at infinite dilution. The diffusion coefficients at low concentrations are compared with some available relations for the estimation of diffusion coefficients at infinite dilution, and it appears that the agreement is fairly good.
Favorite Demonstrations: Gaseous Diffusion: A Demonstration of Graham's Law.
ERIC Educational Resources Information Center
Kauffman, George B.; Ebner, Ronald D.
1985-01-01
Describes a demonstration in which gaseous ammonia and hydrochloric acid are used to illustrate rates of diffusion (Graham's Law). Simple equipment needed for the demonstration include a long tube, rubber stoppes, and cotton. Two related demonstrations are also explained. (DH)
Feasibility of gas-phase decontamination of gaseous diffusion equipment
Munday, E.B.; Simmons, D.W.
1993-02-01
The five buildings at the K-25 Site formerly involved in the gaseous diffusion process contain 5000 gaseous diffusion stages as well as support facilities that are internally contaminated with uranium deposits. The gaseous diffusion facilities located at the Portsmouth Gaseous Diffusion Plant and the Paducah Gaseous Diffusion Plant also contain similar equipment and will eventually close. The decontamination of these facilities will require the most cost-effective technology consistent with the criticality, health physics, industrial hygiene, and environmental concerns; the technology must keep exposures to hazardous substances to levels as low as reasonably achievable (ALARA). This report documents recent laboratory experiments that were conducted to determine the feasibility of gas-phase decontamination of the internal surfaces of the gaseous diffusion equipment that is contaminated with uranium deposits. A gaseous fluorinating agent is used to fluorinate the solid uranium deposits to gaseous uranium hexafluoride (UF{sub 6}), which can be recovered by chemical trapping or freezing. The lab results regarding the feasibility of the gas-phase process are encouraging. These results especially showed promise for a novel decontamination approach called the long-term, low-temperature (LTLT) process. In the LTLT process: The equipment is rendered leak tight, evacuated, leak tested, and pretreated, charged with chlorine trifluoride (ClF{sub 3}) to subatmospheric pressure, left for an extended period, possibly > 4 months, while processing other items. Then the UF{sub 6} and other gases are evacuated. The UF{sub 6} is recovered by chemical trapping. The lab results demonstrated that ClF{sub 3} gas at subatmospheric pressure and at {approx} 75{degree}F is capable of volatilizing heavy deposits of uranyl fluoride from copper metal surfaces sufficiently that the remaining radioactive emissions are below limits.
Molecular Diffusion Coefficients: Experimental Determination and Demonstration.
ERIC Educational Resources Information Center
Fate, Gwendolyn; Lynn, David G.
1990-01-01
Presented are laboratory methods which allow the demonstration and determination of the diffusion coefficients of compounds ranging in size from water to small proteins. Included are the procedures involving the use of a spectrometer, UV cell, triterated agar, and oxygen diffusion. Results including quantification are described. (CW)
Diffuse reflection coefficient of a stratified sea.
Haltrin, V I
1999-02-20
A differential equation of a Riccati type for the diffuse reflection coefficient of a stratified sea is proposed. For a homogeneous sea with arbitrary inherent optical properties this equation is solved analytically. For an inhomogeneous sea it is solved approximately for any arbitrary stratification. The resulting equation expresses the diffuse reflection coefficient of the sea through vertical profiles of absorption and backscattering coefficients, bottom albedo, and sea depth. The results of calculations with this equation are compared with Monte Carlo computations. It was found that the precision of this approach is in the range of 15%. PMID:18305694
Diffusion and transport coefficients in synthetic opals
Sofo, J. O.; Mahan, G. D.
2000-07-15
Opals are structures composed of close-packed spheres in the size range of nano to micrometers. They are sintered to create small necks at the points of contact. We have solved the diffusion problem in such structures. The relation between the diffusion coefficient and the thermal and electrical conductivity is used to estimate the transport coefficients of opal structures as a function of the neck size and the mean free path of the carriers. The theory presented is also applicable to the diffusion problem in other periodic structures. (c) 2000 The American Physical Society.
NASA Astrophysics Data System (ADS)
Chau, J. F.; Or, D.; Jones, S.; Sukop, M.
2004-05-01
Liquid distribution in unsaturated porous media under different gravitational forces and resulting gaseous diffusion coefficients were investigated to enhance understanding of plant growth conditions in microgravity. Different fluid behavior in plant growth media under microgravity conditions as compared to earth presents a challenge to plant growth in long duration space exploration missions. Our primary objective was to provide qualitative description and quantitative measures of the role of reduced gravity on hydraulic and gaseous transport properties in simulated porous media. We implemented a multi-phase lattice Boltzmann code for equilibrium distribution of liquid in an idealized two-dimensional porous medium under microgravity and "normal" gravity conditions. The information was then used to provide boundary conditions for simulation of gaseous diffusion through the equilibrium domains (considering diffusion through liquid phase negligibly small). The models were tested by comparison with several analytical solutions to the diffusion equation, with excellent results. The relative diffusion coefficient for both series of simulations (with and without gravity) as functions of air-filled porosity was in good agreement with established models of Millington-Quirk. Liquid distribution under earth's gravity featured increased water content at the lower part of the medium relative to the distribution in reduced gravity, which resulted in decreased gas diffusion through a vertically oriented column of a porous medium. Simulation results for larger domains under various orientations will be presented.
Improved Diffusion Coefficients for Stellar Plasmas
NASA Astrophysics Data System (ADS)
Brassard, P.; Fontaine, G.
2014-04-01
We are currently working on the fourth generation of our codes for building evolutionary and static models of hot subdwarf and white dwarf stars. One of the improvements of these codes consists in an update of all the microphysics involved in the computations. As part of our efforts, we have taken a look at possible improvements for the diffusion coefficients. Since the publication of the widely used diffusion coefficients of Paquette et al. (1986), the number-crunching power of computers has immensely increased, allowing more accurate computations of the triple collision integrals. We have thus produced new tables of diffusion coefficients with higher accuracy and higher resolution than before, of general use in stellar astrophysics.
Radiant extinction of gaseous diffusion flames
NASA Technical Reports Server (NTRS)
Atreya, Arvind; Agrawal, Sanjay; Shamim, Tariq; Pickett, Kent; Sacksteder, Kurt R.; Baum, Howard R.
1995-01-01
The absence of buoyancy-induced flows in microgravity significantly alters the fundamentals of many combustion processes. Substantial differences between normal-gravity and microgravity flames have been reported during droplet combustion, flame spread over solids, candle flames, and others. These differences are more basic than just in the visible flame shape. Longer residence time and higher concentration of combustion products create a thermochemical environment which changes the flame chemistry. Processes such as flame radiation, that are often ignored under normal gravity, become very important and sometimes even controlling. This is particularly true for conditions at extinction of a microgravity diffusion flame. Under normal-gravity, the buoyant flow, which may be characterized by the strain rate, assists the diffusion process to transport the fuel and oxidizer to the combustion zone and remove the hot combustion products from it. These are essential functions for the survival of the flame which needs fuel and oxidizer. Thus, as the strain rate is increased, the diffusion flame which is 'weak' (reduced burning rate per unit flame area) at low strain rates is initially 'strengthened' and eventually it may be 'blown-out'. Most of the previous research on diffusion flame extinction has been conducted at the high strain rate 'blow-off' limit. The literature substantially lacks information on low strain rate, radiation-induced, extinction of diffusion flames. At the low strain rates encountered in microgravity, flame radiation is enhanced due to: (1) build-up of combustion products in the flame zone which increases the gas radiation, and (2) low strain rates provide sufficient residence time for substantial amounts of soot to form which further increases the flame radiation. It is expected that this radiative heat loss will extinguish the already 'weak' diffusion flame under certain conditions. Identifying these conditions (ambient atmosphere, fuel flow rate, fuel
Numerical investigations of gaseous spherical diffusion flames
NASA Astrophysics Data System (ADS)
Lecoustre, Vivien R.
Spherical diffusion flames have several unique characteristics that make them attractive from experimental and theoretical perspectives. They can be modeled with one spatial dimension, which frees computational resources for detailed chemistry, transport, and radiative loss models. This dissertation is a numerical study of two classes of spherical diffusion flames: hydrogen micro-diffusion flames, emphasizing kinetic extinction, and ethylene diffusion flames, emphasizing sooting limits. The flames were modeled using a one-dimensional, time-accurate diffusion flame code with detailed chemistry and transport. Radiative losses from products were modeled using a detailed absorption/emission statistical narrow band model and the discrete ordinates method. During this work the code has been enhanced by the implementation of a soot formation/oxidation model using the method of moments. Hydrogen micro-diffusion flames were studied experimentally and numerically. The experiments involved gas jets of hydrogen. At their quenching limits, these flames had heat release rates of 0.46 and 0.25 W in air and in oxygen, respectively. These are the weakest flames ever observed. The modeling results confirmed the quenching limits and revealed high rates of reactant leakage near the limits. The effects of the burner size and mass flow rate were predicted to have a significant impact on the flame chemistry and species distribution profiles, favoring kinetic extinction. Spherical ethylene diffusion flames at their sooting limits were also examined. Seventeen normal and inverse spherical flames were considered. Initially sooty, these flames were experimentally observed to reach their sooting limits 2 s after ignition. Structure of the flames at 2 s was considered, with an emphasis on the relationships among local temperature, carbon to oxygen atom ratio (C/O), and scalar dissipation rate. A critical C/O ratio was identified, along with two different sooting limit regimes. Diffusion flames
An introduction to technetium in the gaseous diffusion cascades
Simmons, D.W.
1996-09-01
The radioisotope technetium-99 ({sup 99}Tc) was introduced into the gaseous diffusion plants (GDP) as a contaminant in uranium that had been reprocessed from spent nuclear reactor fuel. {sup 99}Tc is a product of the nuclear fission of uranium-235 ({sup 235}U). The significantly higher emitted radioactivity of {sup 99}Tc generates concern in the enrichment complex and warrants increased attention (1) to the control of all site emissions, (2) to worker exposures and contamination control when process equipment requires disassembly and decontamination, and (3) to product purity when the enriched uranium hexafluoride (UF{sub 6}) product is marketed to the private sector. A total of 101,268 metric tons of RU ({approximately}96% of the total) was fed at the Paducah Gaseous Diffusion Plant (PGDP) between FY1953 and FY1976. An additional 5600 metric tons of RU from the government reactors were fed at the Oak Ridge Gaseous Diffusion Plant (ORGDP), plus an approximate 500 tons of foreign reactor returns. Only a small amount of RU was fed directly at the Portsmouth Gaseous Diffusion Plant (PORTS). The slightly enriched PGDP product was then fed to either the ORGDP or PORTS cascades for final enrichment. Bailey estimated in 1988 that of the 606 kg of Tc received at PGDP from RU, 121 kg was subsequently re-fed to ORGDP and 85 kg re-fed to PORTS.
The electron diffusion coefficient in Jupiter's magnetosphere
NASA Technical Reports Server (NTRS)
Birmingham, T.; Northrop, T.; Baxter, R.; Hess, W.; Lojko, M.
1974-01-01
A steady-state model of Jupiter's electron radiation belt is developed. The model includes injection from the solar wind, radial diffusion, energy degradation by synchrotron radiation, and absorption at Jupiter's surface. A diffusion coefficient of the form D sub RR/R sub J squared = k times R to the m-th power is assumed, and then observed data on synchrotron radiation are used to fit the model. The free parameters determined from this fit are m = 1.95 plus or minus 0.5, k = 1.7 plus or minus 0.5 x 10 to the 9th power per sec, and the magnetic moment of injected particles equals 770 plus or minus 300 MeV/G. The value of m shows quite clearly that the diffusion is not caused by magnetic pumping by a variable solar wind or by a fluctuating convection electric field. The process might be field line exchange driven by atmospheric-ionospheric winds; our diffusion coefficient has roughly the same radial dependence but is considerably smaller in magnitude than the upper bound diffusion coefficients recently suggested for this process by Brice and McDonough (1973) and Jacques and Davis (1972).
Micro-Fluidic Diffusion Coefficient Measurement
Forster, F.K.; Galambos, P.
1998-10-06
A new method for diffusion coefficient measurement applicable to micro-fluidics is pre- sented. The method Iltilizes an analytical model describing laminar dispersion in rect- anglllar ~llicro_channe]s. The Illethod ~vas verified throllgh measllremen~ of fllloresceill diffusivity in water and aqueolls polymer solutions of differing concentration. The diffll- sivity of flllorescein was measlmed as 0.64 x 10-gm2/s in water, 0.49 x 10-gm2/s in the 4 gm/dl dextran solution and 0.38 x 10-9n12/s in the 8 gnl/dl dextran solution.
Paducah Gaseous Diffusion Plant environmental report for 1992
Horak, C.M.
1993-09-01
This two-part report, Paducah Gaseous Diffusion Plant Environmental Report for 1992, is published annually. It reflects the results of an environmental monitoring program designed to quantify potential increases in the concentration of contaminants and potential doses to the resident human population. The Paducah Gaseous Diffusion Plant (PGDP) overall goal for environmental management is to protect the environment and PGDP`s neighbors and to maintain full compliance with all current regulations. The current environmental strategy is to identify any deficiencies and to develop a system to resolve them. The long-range goal of environmental management is to minimize the source of pollutants, reduce the generation of waste, and minimize hazardous waste by substitution of materials.
Paducah Gaseous Diffusion Plant Environmental report for 1990
Counce-Brown, D.
1991-09-01
This two-part report, Paducah Gaseous Diffusion Plant Site Environmental Report for 1990, is published annually. It reflects the results of a comprehensive, year-round program to monitor the impact of operations at Paducah Gaseous Diffusion Plant (PGDP) on the area's groundwater and surface waters, soil, air quality, vegetation, and wildlife. In addition, an assessment of the effect of PGDP effluents on the resident human population is made. PGDP's overall goal for environmental management is to protect the environment and PGDP's neighbors and to maintain full compliance with all current regulations. The current environmental strategy is to identify any deficiencies and to develop a system to resolve them. The long-range goal of environmental management is to minimize the source of pollutants, to reduce the formation of waste, and to minimize hazardous waste by substitution of materials.
Overview of seismic considerations at the Paducah Gaseous Diffusion Plant
Hunt, R.J.; Stoddart, W.C.; Burnett, W.A.; Beavers, J.E.
1992-10-01
This paper presents an overview of seismic considerations at the Paducah Gaseous Diffusion Plant (PGDP), which is managed by Martin Marietta Energy Systems, Inc., for the Department of Energy (DOE). The overview describes the original design, the seismic evaluations performed for the Safety Analysis Report (SAR) issued in 1985, and current evaluations and designs to address revised DOE requirements. Future plans to ensure changes in requirements and knowledge are addressed.
Transport coefficients of gaseous ions in an electric field
NASA Technical Reports Server (NTRS)
Whealton, J. H.; Mason, E. A.
1974-01-01
A general theory of ion mobility formulated by Kihara (1953) is extended to ion diffusion and to mixtures of neutral gases. The theory assumes that only binary collisions between ions and neutral particles need to be taken into account and that the velocity distribution function of the neutral particles is Maxwellian. These assumptions make it possible to use a linearized Boltzmann equation. Questions of mobility are considered along with aspects of diffusion and deviations from Fick's law of diffusion.
NASA Technical Reports Server (NTRS)
Chau, Jessica Furrer; Or, Dani; Sukop, Michael C.; Steinberg, S. L. (Principal Investigator)
2005-01-01
Liquid distributions in unsaturated porous media under different gravitational accelerations and corresponding macroscopic gaseous diffusion coefficients were investigated to enhance understanding of plant growth conditions in microgravity. We used a single-component, multiphase lattice Boltzmann code to simulate liquid configurations in two-dimensional porous media at varying water contents for different gravity conditions and measured gas diffusion through the media using a multicomponent lattice Boltzmann code. The relative diffusion coefficients (D rel) for simulations with and without gravity as functions of air-filled porosity were in good agreement with measured data and established models. We found significant differences in liquid configuration in porous media, leading to reductions in D rel of up to 25% under zero gravity. The study highlights potential applications of the lattice Boltzmann method for rapid and cost-effective evaluation of alternative plant growth media designs under variable gravity.
Gas phase decontamination of gaseous diffusion process equipment
Bundy, R.D.; Munday, E.B.; Simmons, D.W.; Neiswander, D.W.
1994-03-01
D&D of the process facilities at the gaseous diffusion plants (GDPs) will be an enormous task. The EBASCO estimate places the cost of D&D of the GDP at the K-25 Site at approximately $7.5 billion. Of this sum, nearly $4 billion is associated with the construction and operation of decontamination facilities and the dismantlement and transport of contaminated process equipment to these facilities. In situ long-term low-temperature (LTLT) gas phase decontamination is being developed and demonstrated at the K-25 site as a technology that has the potential to substantially lower these costs while reducing criticality and safeguards concerns and worker exposure to hazardous and radioactive materials. The objective of gas phase decontamination is to employ a gaseous reagent to fluorinate nonvolatile uranium deposits to form volatile LJF6, which can be recovered by chemical trapping or freezing. The LTLT process permits the decontamination of the inside of gas-tight GDP process equipment at room temperature by substituting a long exposure to subatmospheric C1F for higher reaction rates at higher temperatures. This paper outlines the concept for applying LTLT gas phase decontamination, reports encouraging laboratory experiments, and presents the status of the design of a prototype mobile system. Plans for demonstrating the LTLT process on full-size gaseous diffusion equipment are also outlined briefly.
Chau, Jessica Furrer; Or, Dani
2006-11-01
The effect of drainage front morphology on gaseous diffusion through partially saturated porous media is analyzed using the lattice Boltzmann method (LBM). Flow regimes for immiscible displacement in porous media have been characterized as stable displacement, capillary fingering, and viscous fingering. The dominance of a flow regime is associated with the relative magnitudes of gravity, viscous, and capillary forces, quantifiable via the Bond number Bo, capillary number Ca, and their difference, Bo-Ca . Forced drainage from an initially saturated two-dimensional (2D) porous medium was simulated and the resulting flow patterns were analyzed and compared with theoretical predictions and experimental results. The LBM simulations reproduced expected flow morphologies for a range of drainage velocities and gravitational forces (i.e., a range of capillary and Bond numbers). Furthermore, measures of drainage front width as a function of the dimensionless difference Bo-Ca correspond well with scaling laws derived from percolation theory. Effects of flow morphology on residual fluid entrapment and gaseous diffusion were assessed by running LBM diffusion simulations through the partially saturated domain for a range of water contents. The effective diffusion coefficient as a function of water content was estimated for three regimes: stable drainage front, capillary fingering, and viscous fingering. Significant reductions in gaseous diffusion coefficient were found for viscous fingering relative to stable displacement, and to a lesser extent for capillary fingering, indicating that wetting phase distribution with a high degree of fingering in the 2D domain severely restricts connectivity of gas diffusion pathways through the medium. The study lends support for the use of LBM in design and management of fluids in porous media under variable gravity, and enhances the understanding of the role of dynamic fluid behavior on macroscopic transport properties of partially saturated
Paducah Gaseous Diffusion Plant Annual Site Environmental Report for 1993
Not Available
1994-10-01
The purpose of this document is to summarize effluent monitoring and environmental surveillance results and compliance with environmental laws, regulations, and orders at the Paducah Gaseous Diffusion Plant (PGDP). Environmental monitoring at PGDP consists of two major activities: effluent monitoring and environmental surveillance. Effluent monitoring is direct measurement or the collection and analysis of samples of liquid and gaseous discharges to the environment. Environmental surveillance is direct measurement or the collection and analysis of samples of air, water, soil, foodstuff, biota, and other media. Environmental monitoring is performed to characterize and quantify contaminants, assess radiation exposures of members of the public, demonstrate compliance with applicable standards and permit requirements, and detect and assess the effects (if any) on the local environment. Multiple samples are collected throughout the year and are analyzed for radioactivity, chemical content, and various physical attributes.
Laminar and Turbulent Gaseous Diffusion Flames. Appendix C
NASA Technical Reports Server (NTRS)
Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)
2001-01-01
Recent measurements and predictions of the properties of homogeneous (gaseous) laminar and turbulent non-premixed (diffusion) flames are discussed, emphasizing results from both ground- and space-based studies at microgravity conditions. Initial considerations show that effects of buoyancy not only complicate the interpretation of observations of diffusion flames but at times mislead when such results are applied to the non-buoyant diffusion flame conditions of greatest practical interest. This behavior motivates consideration of experiments where effects of buoyancy are minimized; therefore, methods of controlling the intrusion of buoyancy during observations of non-premixed flames are described, considering approaches suitable for both normal laboratory conditions as well as classical microgravity techniques. Studies of laminar flames at low-gravity and microgravity conditions are emphasized in view of the computational tractability of such flames for developing methods of predicting flame structure as well as the relevance of such flames to more practical turbulent flames by exploiting laminar flamelet concepts.
Portsmouth Gaseous Diffusion Plant Environmental report for 1990
Counce-Brown, D.
1991-09-01
This calendar year 1990 annual report on environmental surveillance of the US Department of Energy's (DOE's) Portsmouth Gaseous Diffusion Plant (PORTS) and its environs consists of two parts: the summary, discussion, and conclusions (Part 1) and the data presentation (Part 2). The objectives of this report are as follows: report 1990 monitoring data for the installation and its environs that may have been affected by operations on the plant site, provide reasonably detailed information about the plant site and plant operations, provide detailed information on input and assumptions used in all calculations, provide trend analyses (when appropriate) to indicate increases and decreases in environmental impact, and provide general information on plant quality assurance.
Fractional diffusions with time-varying coefficients
NASA Astrophysics Data System (ADS)
Garra, Roberto; Orsingher, Enzo; Polito, Federico
2015-09-01
This paper is concerned with the fractionalized diffusion equations governing the law of the fractional Brownian motion BH(t). We obtain solutions of these equations which are probability laws extending that of BH(t). Our analysis is based on McBride fractional operators generalizing the hyper-Bessel operators L and converting their fractional power Lα into Erdélyi-Kober fractional integrals. We study also probabilistic properties of the random variables whose distributions satisfy space-time fractional equations involving Caputo and Riesz fractional derivatives. Some results emerging from the analysis of fractional equations with time-varying coefficients have the form of distributions of time-changed random variables.
Calculation and application of combined diffusion coefficients in thermal plasmas.
Murphy, Anthony B
2014-01-01
The combined diffusion coefficient method is widely used to treat the mixing and demixing of different plasma gases and vapours in thermal plasmas, such as welding arcs and plasma jets. It greatly simplifies the treatment of diffusion for many gas mixtures without sacrificing accuracy. Here, three subjects that are important in the implementation of the combined diffusion coefficient method are considered. First, it is shown that different expressions for the combined diffusion coefficients, arising from different definitions for the stoichiometric coefficients that assign the electrons to the two gases, are equivalent. Second, an approach is presented for calculating certain partial differential terms in the combined temperature and pressure diffusion coefficients that can cause difficulties. Finally, a method for applying the combined diffusion coefficients in computational models, which typically require diffusion to be expressed in terms of mass fraction gradients, is given. PMID:24603457
Calculation and application of combined diffusion coefficients in thermal plasmas
Murphy, Anthony B.
2014-01-01
The combined diffusion coefficient method is widely used to treat the mixing and demixing of different plasma gases and vapours in thermal plasmas, such as welding arcs and plasma jets. It greatly simplifies the treatment of diffusion for many gas mixtures without sacrificing accuracy. Here, three subjects that are important in the implementation of the combined diffusion coefficient method are considered. First, it is shown that different expressions for the combined diffusion coefficients, arising from different definitions for the stoichiometric coefficients that assign the electrons to the two gases, are equivalent. Second, an approach is presented for calculating certain partial differential terms in the combined temperature and pressure diffusion coefficients that can cause difficulties. Finally, a method for applying the combined diffusion coefficients in computational models, which typically require diffusion to be expressed in terms of mass fraction gradients, is given. PMID:24603457
ANALYTIC FORMS OF THE PERPENDICULAR DIFFUSION COEFFICIENT IN NRMHD TURBULENCE
Shalchi, A.
2015-02-01
In the past different analytic limits for the perpendicular diffusion coefficient of energetic particles interacting with magnetic turbulence were discussed. These different limits or cases correspond to different transport modes describing how the particles are diffusing across the large-scale magnetic field. In the current paper we describe a new transport regime by considering the model of noisy reduced magnetohydrodynamic turbulence. We derive different analytic forms of the perpendicular diffusion coefficient, and while we do this, we focus on the aforementioned new transport mode. We show that for this turbulence model a small perpendicular diffusion coefficient can be obtained so that the latter diffusion coefficient is more than hundred times smaller than the parallel diffusion coefficient. This result is relevant to explain observations in the solar system where such small perpendicular diffusion coefficients have been reported.
Portsmouth Gaseous Diffusion Plant annual site environmental report for 1993
Horak, C.M.
1994-11-01
This calendar year (CY) 1993 annual report on environmental monitoring of the US Department of Energy`s (DOE`s) Portsmouth Gaseous Diffusion Plant (Portsmouth) and its environs consists of three separate documents: a summary pamphlet for the general public; a more detail discussion and of compliance status, data, and environmental impacts (this document); and a volume of detailed data that is available on request. The objectives of this report are to report compliance status during 1993; provide information about the plant site and plant operations; report 1993 monitoring data for the installation and its environs that may have been affected by operations on the plant site; document information on input and assumptions used in calculations; provide trend analyses (where appropriate) to indicate increases and decreases in environmental impact, and provide general information on quality assurance for the environmental monitoring program.
Paducah Gaseous Diffusion Plant environmental report for 1989
Turner, J.W. )
1990-10-01
This two-part environmental report is published annually. It reflects the results of a comprehensive, year-round program to monitor the impact of operations at Paducah Gaseous Diffusion Plant (PGDP) on the area's groundwater and surface waters, soil, air quality, vegetation, and wildlife. In addition, an assessment of the effect of PGDP effluents on the resident human population is made. PGDP's overall goal for environmental management is to protect the environment and PGDP's neighbors and to maintain full compliance with all current regulations. The current environmental strategy is to identify any deficiencies and to develop a system to resolve them. The long-range goal of environmental management is to minimize the source of pollutants, to reduce the formation of waste, and to minimize hazardous waste by substitution of materials. 36 refs.
Seismic issues at the Paducah Gaseous Diffusion Plant
Fricke, K.E. )
1989-11-01
A seismic expert workshop was held at the Paducah Gaseous Diffusion Plant (PGDP) on March 13--15, 1989. the PGDP is operated by Martin Marietta Energy Systems, Inc. for the United States Department of Energy (DOE). During the last twenty years the design criteria for natural phenomenon hazards has steadily become more demanding at all of the DOE Oak Ridge Operations (ORO) sites. The purpose of the two-day workshop was to review the seismic vulnerability issues of the PGDP facilities. Participants to the workshop included recognized experts in the fields of seismic engineering, seismology and geosciences, and probabilistic analysis, along with engineers and other personnel from Energy Systems. A complete list of the workshop participants is included in the front of this report. 29 refs.
Paducah Gaseous Diffusion Plant environmental report for 1991. Volume 3
Williams, M.F.
1992-10-01
This two-part report is published annually. It reflects the results of an environmental monitoring program designed to quantify potential increases in the concentration of contaminants and potential doses to the resident human population from the Paducah Gaseous Diffusion Plant (PGDP). PGDP`s overall goal for environmental management is to protect the environment and PGDP`s neighbors and to maintain full compliance with all current regulations. The current environmental strategy is to identify any deficiencies and to develop a system to resolve them. The long-range goal of environmental management is to minimize the source of pollutants, to reduce the generation of waste, and to minimize hazardous waste by substitution of materials. Environmental-monitoring systems at PGDP include emission-monitoring networks for airborne and aqueous discharges, groundwater monitoring, solid waste characterization, and ambient-sampling networks for air, surface water, groundwater, vegetation, food crops, fish, wildlife, soil, and surface stream sediments.
Gaseous diffusion plant transition from DOE to external regulation
Dann, R.K.; Crites, T.R.; Rahm-Crites, L.K.
1997-12-01
After many years of operation as government-owned/contractor-operated facilities, large portions of the gaseous diffusion plants (GDPs) at Portsmouth, Ohio, and Paducah, Kentucky, were leased to the United States Enrichment Corporation (USEC). These facilities are now certified by the U.S. Nuclear Regulatory Commission (NRC) and subject to oversight by the Occupational Safety and Health Administration (OSHA). The transition from DOE to NRC regulation was more difficult than expected. The original commitment was to achieve NRC certification in October 1995; however, considerably more time was required and transition-related costs escalated. The Oak Ridge Operations Office originally estimated the cost of transition at $60 million; $240 million has been spent to date. The DOE`s experience in transitioning the GDPs to USEC operation with NRC oversight provides valuable lessons (both positive and negative) that could be applied to future transitions.
Paducah Gaseous Diffusion Plant environmental report for 1991
Williams, M.F. )
1992-10-01
This two-part report is published annually. It reflects the results of an environmental monitoring program designed to quantify potential increases in the concentration of contaminants and potential doses to the resident human population from the Paducah Gaseous Diffusion Plant (PGDP). PGDP's overall goal for environmental management is to protect the environment and PGDP's neighbors and to maintain full compliance with all current regulations. The current environmental strategy is to identify any deficiencies and to develop a system to resolve them. The long-range goal of environmental management is to minimize the source of pollutants, to reduce the generation of waste, and to minimize hazardous waste by substitution of materials. Environmental-monitoring systems at PGDP include emission-monitoring networks for airborne and aqueous discharges, groundwater monitoring, solid waste characterization, and ambient-sampling networks for air, surface water, groundwater, vegetation, food crops, fish, wildlife, soil, and surface stream sediments.
Tiger Team Assessment of the Paducah Gaseous Diffusion Plant
Not Available
1990-07-01
This document contains findings and concerns identified during the Tiger Team Assessment of the Department of Energy's (DOE) Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky. The assessment was directed by the Department's Office of Environment, Safety and Health (ES H) and was conducted from June 18 to July 20, 1990. The PGDP Tiger Team Assessment is comprehensive in scope. It covers the Environmental, Safety and Health (including OSHA Compliance), and Management areas and determines the site's compliance with applicable federal (including DOE), state, and local regulations and requirements. The objective of the assessment program is to provide the Secretary with information on the current ES H compliance status of DOE facilities, root causation for noncompliance, adequacy of DOE and site contractor ES H management programs, response actions to address the identified problem areas, and DOE-wide ES H compliance trends and root causes.
Tiger Team Assessment of the Paducah Gaseous Diffusion Plant
Not Available
1990-07-01
This document contains findings and concerns identified during the Tiger Team Assessment of the Department of Energy's (DOE's) Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky. The assessment was directed by the Department's Office of Environment, Safety and Health (ES H) and was conducted from June 18 to July 20, 1990. The PGDP Tiger Team Assessment is comprehensive in scope. It covers the Environmental, Safety and Health (including OSHA Compliance), and Management areas and determines the site's compliance with applicable federal (including DOE), state, and local regulations and requirements. The objective of the assessment program is to provide the Secretary with information on the current ES H compliance status of DOE facilities, root causation for noncompliance, adequacy of DOE and site contractor ES H management programs, response actions to address the identified problem areas, and DOE-wide ES H compliance trends and root causes. This volume contains appendices.
Measurement of the Portsmouth Gaseous Diffusion Plant criticality accident alarm
Tayloe, R.W. Jr. ); McGinnis, B. )
1990-08-31
Measurements of the Portsmouth Gaseous Diffusion Plant's nuclear criticality accident radiation alarm signal response time, sound wave frequency, and sound volume levels were made to demonstrate compliance with ANSI/ANS-8.3-1986. A steady-state alarm signal is produced within one-half second of obtaining a two-out-of-three detector trip. The fundamental alarm sound wave frequency is 440 hertz. The sound volume levels are greater than 10 decibels above background and ranged from 100 to 125 A-weighted decibels. The requirements of the standard were met; however the recommended maximum sound volume level of 115 dBA was exceeded. Emergency procedures require immediate evacuation upon initiation of a facility's radiation alarm. Comparison with standards for allowable time of exposure at different noise levels indicate that the elevated noise level at this location does not represent an occupational injury hazard. 8 refs., 5 figs.
Diffusion coefficient of three-dimensional Yukawa liquids
NASA Astrophysics Data System (ADS)
Dzhumagulova, K. N.; Ramazanov, T. S.; Masheeva, R. U.
2013-11-01
The purpose of this work is an investigation of the diffusion coefficient of the dust component in complex plasma. The computer simulation of the Yukawa liquids was made on the basis of the Langevin equation, which takes into account the influence of buffer plasma on the dust particles dynamics. The Green-Kubo relation was used to calculate the diffusion coefficient. Calculations of the diffusion coefficient for a wide range of the system parameters were performed. Using obtained numerical data, we constructed the interpolation formula for the diffusion coefficient. We also show that the interpolation formula correctly describes experimental data obtained under microgravity conditions.
Diffusion coefficient of three-dimensional Yukawa liquids
Dzhumagulova, K. N.; Ramazanov, T. S.; Masheeva, R. U.
2013-11-15
The purpose of this work is an investigation of the diffusion coefficient of the dust component in complex plasma. The computer simulation of the Yukawa liquids was made on the basis of the Langevin equation, which takes into account the influence of buffer plasma on the dust particles dynamics. The Green–Kubo relation was used to calculate the diffusion coefficient. Calculations of the diffusion coefficient for a wide range of the system parameters were performed. Using obtained numerical data, we constructed the interpolation formula for the diffusion coefficient. We also show that the interpolation formula correctly describes experimental data obtained under microgravity conditions.
78 FR 30342 - United States Enrichment Corporation, Paducah Gaseous Diffusion Plant
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2013-05-22
... COMMISSION United States Enrichment Corporation, Paducah Gaseous Diffusion Plant AGENCY: Nuclear Regulatory... Renewal of its Certificate of Compliance (CoC) for the Paducah Gaseous Diffusion Plant (PGDP). The... compliance for PGDP on November 26, 1996, and assumed regulatory oversight for the plant on March 3,...
Federal Register 2010, 2011, 2012, 2013, 2014
2013-11-06
... (78 FR 47780). At the request of the company official, the Department reviewed the certification for... Employment and Training Administration United States Enrichment Corporation, Paducah Gaseous Diffusion Plant... Corporation, Paducah Gaseous Diffusion Plant, including on-site leased workers from Diversified...
Combined diffusion coefficients for a mixture of three ionized gases
NASA Astrophysics Data System (ADS)
Zhang, X. N.; Murphy, A. B.; Li, H. P.; Xia, W. D.
2014-12-01
The combined diffusion coefficient method has been demonstrated to greatly simplify the treatment of diffusion in the modelling of thermal plasmas in gas mixtures without loss of accuracy. In this paper, an extension of this method to allow treatment of diffusion of a three-gas mixture has been achieved, provided that the gases are homonuclear and do not react with each other, and satisfy local chemical equilibrium. Formulas for the combined diffusion coefficients are presented, and combined diffusion coefficients for different mixtures of helium, argon and carbon at temperatures up to 30 000 K and at atmosphere pressure are calculated as an example.
Diffusion of gaseous and supercritical CO2 through polycarbonate
NASA Astrophysics Data System (ADS)
Goodman, Michael; Ozisik, Rahmi
2013-03-01
The design of polymeric materials for applications such as separation membranes and nanostructured foams requires prediction of gas transport properties under a wide range of pressures. In the current study, transport of CO2 both in gaseous and supercritical state through samples of polycarbonate at 51 °C and pressures from 15 to 2000 psi was measured using an asymptotic time lag apparatus. Through volumetric calibration, the traditional analysis was extended to yield permeability (P) and solubility (S), in addition to the usual asymptotic diffusivity (Da). Nonlinear least squares fitting to a truncated series solution then provided an alternative measurement of the (transient) diffusivity (Dt), as well as the surface concentration (Co) of adsorbed gas. At 1 atm, Da and Dt were within a factor of 2 from selected handbook values; and with increasing pressure, both exhibited an overall downward trend, consistent with other studies, but an unexpected dropoff occurred between 1350 and 1500 psi. As expected, Co showed an overall increase with pressure, but as with P and S, displayed a peculiar drop between 1350 and 1500 psi. Measurement of Co in polycarbonate has never been done before and constitutes a novel feature of this study. This work was partially supported by DUE-1003574.
Gaseous Diffusion and Pore Structure in Nuclear Graphites.
NASA Astrophysics Data System (ADS)
Mays, Timothy John
Available from UMI in association with The British Library. With the incentive of providing more information for oxidation and safety studies of graphite components in thermal nuclear reactors, a new method has been developed to determine the gas transport pore structure in nuclear graphites. It involves an analysis of the dependence on pressure of the isobaric, isothermal (room temperature) diffusivity ratios of components in a binary gas mixture flowing through annular graphite samples. A Wicke-Kallenbach apparatus was specially built to measure He-Ar diffusivity ratios at pressures below 100 Torr. The new apparatus incorporates capacitance manometers and servovalves for pressure measurement and control, hot wire meters for flow rate measurements, and a mass spectrometer for gas analysis. As pressure decreased, the diffusivity ratios were observed to decrease non-linearly, indicating that the mechanism of flow in the materials was in the transition region between molecular and Knudsen diffusion. A mathematical model was derived to relate the pressure dependence of the transition diffusivity ratio to gas transport pore structure, and a statistical analysis based on Tikhonov regularisation was developed which gave a good fit of the model to the data, and optimal estimates of the number of model capillary pores, and the distribution of pore sizes. In comparison, the established methods of molecular diffusion and permeation (flow of pure gases) only give mean data on the pore size distribution. Pore structure data from the new method accurately predicted CO_2-Ar molecular diffusivity ratios, but overestimated N_2 permeability coefficients, due, it was assumed, to differences between diffusion and permeation pore structure. The cumulative volume distributions for transport pores from the transition diffusion data were similar in shape to those for open pores from mercury porosimetry, but shifted towards higher pore radii, indicating that diffusion is not so influenced
Bounce resonance diffusion coefficients for spatially confined waves
NASA Astrophysics Data System (ADS)
Li, Xinxin; Tao, Xin; Lu, Quanmin; Dai, Lei
2015-11-01
Theoretical bounce resonance diffusion coefficients from interactions between electrons and spatially confined waves are derived and validated. Roberts and Schulz bounce resonance diffusion coefficients assume waves to be present on the whole bounce trajectory of particles; therefore, they are not directly applicable to waves that have a finite spatial extent. We theoretically derive and numerically validate a new set of bounce resonance diffusion coefficients for spatially confined waves. We apply our analysis to magnetosonic waves, which are confined to equatorial regions, using a previously published magnetosonic wave model. We find that the bounce resonance diffusion coefficients are comparable to the gyroresonance diffusion coefficients. We conclude that bounce resonance diffusion with magnetosonic waves might play an important role in relativistic electron dynamics.
Temperature dependence of the diffusion coefficient of nanoparticles
NASA Astrophysics Data System (ADS)
Rudyak, V. Ya.; Dubtsov, S. N.; Baklanov, A. M.
2008-06-01
The temperature dependence of the diffusion coefficient of nanoparticles in gases has been experimentally studied. It is established that this dependence significantly differs from that predicted by various correlations, in particular, by the Cunningham-Millikan-Davies correlation that is used as an instrumental basis for virtually all methods of measurement of the diffusion coefficient in aerosols.
Innovative Decontamination Technology for Use in Gaseous Diffusion Plant Decommissioning
Peters, M.J.; Norton, C.J.; Fraikor, G.B.; Potter, G.L.; Chang, K.C.
2006-07-01
The results of bench scale tests demonstrated that TechXtract{sup R} RadPro{sup TM} technology (hereinafter referred to as RadPro{sup R}) can provide 100% coverage of complex mockup gaseous diffusion plant (GDP) equipment and can decontaminate uranium (U) deposits with 98% to 99.99% efficiency. Deployment tests demonstrated RadPro{sup R} can be applied as foam, mist/fog, or steam, and fully cover the internal surfaces of complex mockup equipment, including large piping. Decontamination tests demonstrated that two formulations of RadPro{sup R}, one with neutron attenuators and one without neutron attenuators, could remove up to 99.99% of uranyl fluoride deposits, one of the most difficult to remove deposits in GDP equipment. These results were supplemented by results from previous tests conducted in 1994 that showed RadPro{sup R} could remove >97% of U and Tc-99 contamination from actual GDP components. Operational use of RadPro{sup R} at other DOE and commercial facilities also support these data. (authors)
Bioavailability study for the Paducah Gaseous Diffusion Plant
Phipps, T.L.; Kszos, L.A.
1996-08-01
The overall purpose of this plan is to assess the bioavailability of metals in the continuous and intermittent outfalls. The results may be used to determine alternative metal limits that more appropriately measure the portion of metal present necessary for toxicity to aquatic life. These limits must remain protective of in-stream aquatic life; thus, the highest concentration of metal in the water will be determined concurrently with an assessment of acute or chronic toxicity on laboratory tests. Using the method developed by the Kentucky Division of Water (KDOW), biomonitoring results and chemical data will be used to recommend alternative metal limits for the outfalls of concern. The data will be used to meet the objectives of the study: (1) evaluate the toxicity of continuous outfalls and intermittent outfalls at Paducah Gaseous Diffusion Plant; (2) determine the mean ratio of dissolved to Total Recoverable metal for Cd, Cr, Cu, Pb, Ni, and Zn in the continuous and intermittent outfalls; (3) determine whether the concentration of total recoverable metal discharged causes toxicity to fathead minnows and /or Ceriodaphnia; and (4) determine alternative metal limits for each metal of concern (Cd, Cr, Cu, Pb, Ni, and Zn).
Partnering efforts at the Paducah Gaseous Diffusion Plant
Warren, C.B.
1995-12-31
Before individuals or agencies can effectively work together to solve common problems, they must first agree on exactly what those problems are and establish common goals and methods that will lead to mutually acceptable solutions. Then, they must make a conscientious effort to form a cohesive team that focuses on the established goals and deemphasize traditional roles, which may in some instances be considered adversarial. This kind of teamwork/partnering process can be more difficult, though not impossible, to achieve in cases where there are traditional (real or imagined) adversarial relationships between the parties, i.e. regulator vs. regulated. The US Department of Energy Site Office (DOE) at Paducah, Kentucky, the Kentucky Department of Environmental Protection (KDEP) and the US Environmental Protection Agency, Region IV (EPA) have made t strides toward teamwork and partnering at DOE`s Paducah Gaseous Diffusion Plant. They have accomplished this in a number of ways, which will be discussed in greater detail but first and foremost, the agencies agreed up front that they had mutual goals and interests. These goals are to protect public health and the environment in a cost-effective and timely manner, taking care to make the wisest use of public resources (tax dollars); to evaluate and minimize risks, and to achieve ``Win-Win`` for all parties concerned.
Paducah Gaseous Diffusion Plant Northwest Plume interceptor system evaluation
Laase, A.D.; Clausen, J.L.
1998-07-01
The Paducah Gaseous Diffusion Plant (PGDP) recently installed an interceptor system consisting of four wells, evenly divided between two well fields, to contain the Northwest Plume. As stated in the Northwest Plume Record of Decision (ROD), groundwater will be pumped at a rate to reduce further contamination and initiate control of the northwest contaminant plume. The objective of this evaluation was to determine the optimum (minimal) well field pumping rates required for plume hotspot containment. Plume hotspot, as defined in the Northwest Plume ROD and throughout this report, is that portion of the plume with trichloroethene (TCE) concentrations greater than 1,000 {micro}g/L. An existing 3-dimensional groundwater model was modified and used to perform capture zone analyses of the north and south interceptor system well fields. Model results suggest that the plume hotspot is not contained at the system design pumping rate of 100 gallons per minute (gal/min) per well field. Rather, the modeling determined that north and south well field pumping rates of 400 and 150 gal/min, respectively, are necessary for plume hotspot containment. The difference between the design and optimal pumping rates required for containment can be attributed to the discovery of a highly transmissive zone in the vicinity of the two well fields.
Portsmouth Gaseous Diffusion Plant environmental report for 1989
Turner, J.W. )
1990-10-01
This calendar year 1989 annual report on environmental surveillance of the US Department of Energy's (DOE) Portsmouth Gaseous Diffusion Plant (PORTS) and its environs consists of two parts: the Summary, Discussion, and Conclusions (Part 1) and the Data Presentation (Part 2). The objectives of this report are the following: report 1989 monitoring data for the installation and its environs that may have been affected by operations on the plant site, provide reasonably detailed information about the plant site and plant operations, provide detailed information on input and assumptions used in all calculations, provide trend analyses (where appropriate) to indicate increases and decreases in environmental impact, and provide general information on plant quality assurance. Routine monitoring and sampling for radiation, radioactive materials, and chemical substances on and off the DOE site are used to document compliance with appropriate standards, to identify trends, to provide information for the public, and to contribute to general environmental knowledge. The surveillance program assists in fulfilling the DOE policy of protecting the public, employees, and environment from harm that could be caused by its activities and reducing negative environmental impacts to the greatest degree practicable. Environmental-monitoring information complements data on specific releases, trends, and summaries. 26 refs.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 10 Energy 2 2013-01-01 2013-01-01 false Illustrative List of Gaseous Diffusion Enrichment Plant... Appendix C to Part 110—Illustrative List of Gaseous Diffusion Enrichment Plant Assemblies and Components... for gaseous diffusion enrichment plants are the systems of plant needed to feed UF6 to the...
Code of Federal Regulations, 2014 CFR
2014-01-01
... 10 Energy 2 2014-01-01 2014-01-01 false Illustrative List of Gaseous Diffusion Enrichment Plant... Appendix C to Part 110—Illustrative List of Gaseous Diffusion Enrichment Plant Assemblies and Components... for gaseous diffusion enrichment plants are the systems of plant needed to feed UF6 to the...
1998-08-01
This report consists of two papers reviewing the waste storage facility and the landfill projects proposed for the Paducah Gaseous Diffusion Plant complex. The first paper is a review of DOE`s conceptual design report for a mixed waste storage facility. This evaluation is to review the necessity of constructing a separate mixed waste storage facility. The structure is to be capable of receiving, weighing, sampling and the interim storage of wastes for a five year period beginning in 1996. The estimated cost is assessed at approximately $18 million. The review is to help comprehend and decide whether a new storage building is a feasible approach to the PGDP mixed waste storage problem or should some alternate approach be considered. The second paper reviews DOE`s conceptual design report for a solid waste landfill. This solid waste landfill evaluation is to compare costs and the necessity to provide a new landfill that would meet State of Kentucky regulations. The assessment considered funding for a ten year storage facility, but includes a review of other facility needs such as a radiation detection building, compactor/baler machinery, material handling equipment, along with other personnel and equipment storage buildings at a cost of approximately $4.1 million. The review is to help discern whether a landfill only or the addition of compaction equipment is prudent.
Analytic expressions for ULF wave radiation belt radial diffusion coefficients
Ozeke, Louis G; Mann, Ian R; Murphy, Kyle R; Jonathan Rae, I; Milling, David K
2014-01-01
We present analytic expressions for ULF wave-derived radiation belt radial diffusion coefficients, as a function of L and Kp, which can easily be incorporated into global radiation belt transport models. The diffusion coefficients are derived from statistical representations of ULF wave power, electric field power mapped from ground magnetometer data, and compressional magnetic field power from in situ measurements. We show that the overall electric and magnetic diffusion coefficients are to a good approximation both independent of energy. We present example 1-D radial diffusion results from simulations driven by CRRES-observed time-dependent energy spectra at the outer boundary, under the action of radial diffusion driven by the new ULF wave radial diffusion coefficients and with empirical chorus wave loss terms (as a function of energy, Kp and L). There is excellent agreement between the differential flux produced by the 1-D, Kp-driven, radial diffusion model and CRRES observations of differential electron flux at 0.976 MeV—even though the model does not include the effects of local internal acceleration sources. Our results highlight not only the importance of correct specification of radial diffusion coefficients for developing accurate models but also show significant promise for belt specification based on relatively simple models driven by solar wind parameters such as solar wind speed or geomagnetic indices such as Kp. Key Points Analytic expressions for the radial diffusion coefficients are presented The coefficients do not dependent on energy or wave m value The electric field diffusion coefficient dominates over the magnetic PMID:26167440
Improved diffusion coefficients generated from Monte Carlo codes
Herman, B. R.; Forget, B.; Smith, K.; Aviles, B. N.
2013-07-01
Monte Carlo codes are becoming more widely used for reactor analysis. Some of these applications involve the generation of diffusion theory parameters including macroscopic cross sections and diffusion coefficients. Two approximations used to generate diffusion coefficients are assessed using the Monte Carlo code MC21. The first is the method of homogenization; whether to weight either fine-group transport cross sections or fine-group diffusion coefficients when collapsing to few-group diffusion coefficients. The second is a fundamental approximation made to the energy-dependent P1 equations to derive the energy-dependent diffusion equations. Standard Monte Carlo codes usually generate a flux-weighted transport cross section with no correction to the diffusion approximation. Results indicate that this causes noticeable tilting in reconstructed pin powers in simple test lattices with L2 norm error of 3.6%. This error is reduced significantly to 0.27% when weighting fine-group diffusion coefficients by the flux and applying a correction to the diffusion approximation. Noticeable tilting in reconstructed fluxes and pin powers was reduced when applying these corrections. (authors)
Derivation of anisotropic diffusion coefficients in a large annular cavity
Eiichi Suetomi; Hiroshi Sekimoto )
1993-06-01
A small reactor for a spacecraft or a small liquid-metal reactor for urban siting, decentralized electrical units, or seawater desalination is designed for a large leakage of neutrons from the reactor core. In these reactors, a movable annular reflector is used for reactivity control. Therefore, a large annular cavity exists between the core and the shielding materials. In this paper, anisotropic diffusion coefficients for a large annular cavity are derived by equating the neutron currents obtained by the diffusion equation and by the transport equation. These diffusion coefficients depend only on the geometrical configuration of the cavity. A numerical comparison of diffusion calculations using these diffusion coefficients and transport calculations shows good agreement.
The temperature variation of hydrogen diffusion coefficients in metal alloys
NASA Technical Reports Server (NTRS)
Danford, M. D.
1990-01-01
Hydrogen diffusion coefficients were measured as a function of temperature for a few metal alloys using an electrochemical evolution technique. Results from these measurements are compared to those obtained by the time-lag method. In all cases, diffusion coefficients obtained by the electrochemical method are larger than those by the time-lag method by an order of magnitude or more. These differences are attributed mainly to hydrogen trapping.
Experimental measurements of the diffusion coefficient of 212Pb.
Su, Y F; Newton, G J; Cheng, Y S; Yeh, H C
1989-03-01
Knowledge of the diffusion coefficient of Rn progeny is necessary for assessing the radiation exposure resulting from exposure to Rn and its progeny. The diffusion coefficient for 220Rn progeny was determined in ambient air by two independent methods, measuring deposition using a cylindrical tube or screens. A sampling train consisting of a diffusion tube and a screen-type diffusion battery was used for the experimental study. A range of flow rates and relative humidities was investigated. For 35% less than or equal to RH less than or equal to 85%, results from the two systems agree with each other. The diffusion coefficient of 212Pb was 0.036 +/- 0.002 cm2 s-1 and 0.037 +/- 0.004 cm2 s-1 for the tube and screen penetration methods, respectively. In low humidity air (RH less than 30%), a linear relationship between the diffusion coefficient of 212Pb and relative humidity was observed. The observed diffusion coefficient is strongly affected by the amount of material agglomerated onto the 212Pb atom. Further studies on the effects of trace gases and organics are required to fully understand the results. PMID:2537267
Experimental measurements of the diffusion coefficient of /sup 212/Pb
Su, Y.F.; Newton, G.J.; Cheng, Y.S.; Yeh, H.C.
1989-03-01
Knowledge of the diffusion coefficient of Rn progeny is necessary for assessing the radiation exposure resulting from exposure to Rn and its progeny. The diffusion coefficient for 220Rn progeny was determined in ambient air by two independent methods, measuring deposition using a cylindrical tube or screens. A sampling train consisting of a diffusion tube and a screen-type diffusion battery was used for the experimental study. A range of flow rates and relative humidities was investigated. For 35% less than or equal to RH less than or equal to 85%, results from the two systems agree with each other. The diffusion coefficient of 212Pb was 0.036 +/- 0.002 cm2 s-1 and 0.037 +/- 0.004 cm2 s-1 for the tube and screen penetration methods, respectively. In low humidity air (RH less than 30%), a linear relationship between the diffusion coefficient of 212Pb and relative humidity was observed. The observed diffusion coefficient is strongly affected by the amount of material agglomerated onto the 212Pb atom. Further studies on the effects of trace gases and organics are required to fully understand the results.
Calculation of Diffusion Coefficients from Bounce Resonance with Magnetosonic Waves
NASA Astrophysics Data System (ADS)
Tao, X.; Li, X.; Lu, Q.; Dai, L.
2015-12-01
Theoretical bounce resonance diffusion coefficients for interactions between electrons and magnetosonic waves are calculated and validated using guiding-center test particle simulations. First, we compare the theoretical diffusion coefficients of Roberts and Schulz with test particle simulations and find perfect agreement. However, the theoretical diffusion coefficients of Roberts and Schulz assume waves to be present on the whole trajectories of particles; therefore, they are not directly applicable to magnetosonic waves, which are found to be confined to equatorial regions from observations. Second, we derive a new set of bounce-resonance diffusion coefficients, taking into consideration the equatorial confinement of magnetosonic waves. These new diffusion coefficients are also validated by test particle simulations. Using a previously published magnetosonic wave model, our results demonstrate that bounce-resonance diffusion mainly results in strong pitch angle scattering of energetic electrons even with a moderate wave amplitude of 50 pT. We conclude that bounce-resonance diffusion plays an important role in relativistic electron dynamics and should be incorporated into global radiation belt modeling.
Empirical determination of diffusion coefficients and geospeedometry
NASA Astrophysics Data System (ADS)
Jaoul, Olivier; Béjina, Frédéric
2005-02-01
Geospeedometry allows to estimate the cooling rate (s init) of metamorphic rocks at the beginning of the cooling history using diffusion data. But the choice of a diffusion activation energy (E) and a preexponential factor (D 0) from experimental results can be difficult. We propose a method to obtain E directly from the rock itself by studying the variation of the average concentration of elements or isotopes (
Calculation of self-diffusion coefficients in iron
Zhang, Baohua
2014-01-15
On the basis of available P-V-T equation of state of iron, the temperature and pressure dependence of self-diffusion coefficients in iron polymorphs (α, δ, γ and ε phases) have been successfully reproduced in terms of the bulk elastic and expansivity data by means of a thermodynamical model that interconnects point defects parameters with bulk properties. The calculated diffusion parameters, such as self-diffusion coefficient, activation energy and activation volume over a broad temperature range (500-2500 K) and pressure range (0-100 GPa), compare favorably well with experimental or theoretical ones when the uncertainties are considered.
Diffusion coefficient and shear viscosity of rigid water models.
Tazi, Sami; Boţan, Alexandru; Salanne, Mathieu; Marry, Virginie; Turq, Pierre; Rotenberg, Benjamin
2012-07-18
We report the diffusion coefficient and viscosity of popular rigid water models: two non-polarizable ones (SPC/E with three sites, and TIP4P/2005 with four sites) and a polarizable one (Dang-Chang, four sites). We exploit the dependence of the diffusion coefficient on the system size (Yeh and Hummer 2004 J. Phys. Chem. B 108 15873) to obtain the size-independent value. This also provides an estimate of the viscosity of all water models, which we compare to the Green-Kubo result. In all cases, a good agreement is found. The TIP4P/2005 model is in better agreement with the experimental data for both diffusion and viscosity. The SPC/E and Dang-Chang models overestimate the diffusion coefficient and underestimate the viscosity. PMID:22739097
Ion diffusion coefficient measurements in nanochannels at various concentrations.
Wang, Junrong; Zhang, Li; Xue, Jianming; Hu, Guoqing
2014-03-01
Diffusion is one of the most fundamental properties of ionic transport in solutions. Here, we present experimental studies and theoretical analysis on the ion diffusion in nanochannels. Based on Fick's second law, we develop a current monitoring method to measure ion diffusion coefficient of high solution concentrations in nanochannels. This method is further extended to the cases at medium and low concentrations. Through monitoring ionic current during diffusion, we obtain diffusion coefficients of potassium chloride solution at different concentrations in nanochannels. These diffusion coefficients within the confined space are close to theirs bulk values. It is also found that the apparent ion diffusion equilibrium in the present experiments is very slow at low concentration, which we attribute to the slow equilibrium of the nanochannel surface charge. Finally, we get a primary acknowledge of the equilibrium rate between the nanochannel surface charge and electrolyte solution. The results in this work have improved the understanding of nanoscale diffusion and nanochannel surface charge and may be useful in nanofluidic applications such as ion-selective transport, energy conversion, and nanopore biosensors. PMID:24803967
Ion diffusion coefficient measurements in nanochannels at various concentrations
Wang, Junrong; Zhang, Li; Xue, Jianming; Hu, Guoqing
2014-01-01
Diffusion is one of the most fundamental properties of ionic transport in solutions. Here, we present experimental studies and theoretical analysis on the ion diffusion in nanochannels. Based on Fick's second law, we develop a current monitoring method to measure ion diffusion coefficient of high solution concentrations in nanochannels. This method is further extended to the cases at medium and low concentrations. Through monitoring ionic current during diffusion, we obtain diffusion coefficients of potassium chloride solution at different concentrations in nanochannels. These diffusion coefficients within the confined space are close to theirs bulk values. It is also found that the apparent ion diffusion equilibrium in the present experiments is very slow at low concentration, which we attribute to the slow equilibrium of the nanochannel surface charge. Finally, we get a primary acknowledge of the equilibrium rate between the nanochannel surface charge and electrolyte solution. The results in this work have improved the understanding of nanoscale diffusion and nanochannel surface charge and may be useful in nanofluidic applications such as ion-selective transport, energy conversion, and nanopore biosensors. PMID:24803967
Divergent Diffusion Coefficients in Simulations of Fluids and Lipid Membranes.
Vögele, Martin; Hummer, Gerhard
2016-08-25
We investigate the dependence of single-particle diffusion coefficients on the size and shape of the simulation box in molecular dynamics simulations of fluids and lipid membranes. We find that the diffusion coefficients of lipids and a carbon nanotube embedded in a lipid membrane diverge with the logarithm of the box width. For a neat Lennard-Jones fluid in flat rectangular boxes, diffusion becomes anisotropic, diverging logarithmically in all three directions with increasing box width. In elongated boxes, the diffusion coefficients normal to the long axis diverge linearly with the height-to-width ratio. For both lipid membranes and neat fluids, this behavior is predicted quantitatively by hydrodynamic theory. Mean-square displacements in the neat fluid exhibit intermediate regimes of anomalous diffusion, with t ln t and t(3/2) components in flat and elongated boxes, respectively. For membranes, the large finite-size effects, and the apparent inability to determine a well-defined lipid diffusion coefficient from simulation, rationalize difficulties in comparing simulation results to each other and to those from experiments. PMID:27385207
Mutual diffusion coefficients in systems containing the nickel ion
NASA Astrophysics Data System (ADS)
Ribeiro, Ana C. F.; Veríssimo, Luis V. M. M.; Gomes, Joselaine C. S.; Santos, Cecilia I. A. V.; Barros, Marisa C. F.; Lobo, Victor M. M.; Sobral, Abílio J. F. N.; Esteso, Miguel A.; Leaist, Derek G.
2013-04-01
Mutual diffusion coefficients of nickel chloride in water have been measured at 293.15 K and 303.15 K and at concentrations between 0.020 mol dm-3 and 0.100 mol dm-3, using a conductimetric cell. The experimental mutual diffusion coefficients are discussed on the basis of the Onsager-Fuoss model. The equivalent conductances at infinitesimal concentration of the nickel ion in these solutions at those temperatures have been estimated using these results. In addition, from these data, we have estimated some transport and structural parameters, such as limiting diffusion coefficient, ionic conductance at infinitesimal concentration, hydrodynamic radii and activation energy, contributing this way to a better understanding of the structure of these systems and of their thermodynamic behavior in aqueous solution at different concentrations.
Intrinsic Diffusion Coefficient of Interstitial Copper in Silicon
Istratov, A.A.; Flink, C.; Hieslmair, H.; Weber, E.R.; Heiser, T.
1998-08-01
Transient ion drift experiments designed to obtain reliable values for the intrinsic copper diffusivity in silicon are reported. From these measurements, the diffusion barrier of Cu in Si is determined to be 0.18{plus_minus}0.01 eV . It is shown that the commonly used expression of Hall and Racette [J.thinspthinspAppl.thinspthinspPhys.thinspthinsp{bold 35}, 379 (1964)] actually gives an effective diffusion coefficient for heavily boron-doped silicon and can neither be used for other doping levels nor extrapolated to lower temperatures. A model is developed which predicts the effective diffusion coefficient as a function of temperature, doping level, and the type of dopant. {copyright} {ital 1998} {ital The American Physical Society}
Exact curvilinear diffusion coefficients in the repton model
NASA Astrophysics Data System (ADS)
Buhot, A.
2005-10-01
The Rubinstein-Duke or repton model is one of the simplest lattice model of reptation for the diffusion of a polymer in a gel or a melt. Recently, a slightly modified model with hardcore interactions between the reptons has been introduced. The curvilinear diffusion coefficients of both models are exactly determined for all chain lengths. The case of periodic boundary conditions is also considered.
NASA Astrophysics Data System (ADS)
Kugler, T.; Rausch, M. H.; Fröba, A. P.
2015-11-01
The paper reports on binary diffusion coefficient data for the gaseous systems argon-neon, krypton-helium, ammonia-helium, nitrous oxide-nitrogen, and propane-helium measured using a Loschmidt cell combined with holographic interferometry between (293.15 and 353.15) K as well as between (1 and 10) bar. The investigations on the noble gas systems aimed to validate the measurement apparatus by comparing the binary diffusion coefficients measured as a function of temperature and pressure with theoretical data. In previous studies, it was already shown that the raw concentration-dependent data measured with the applied setup are affected by systematic effects if pure gases are used prior to the diffusion process. Hence, the concentration-dependent measurement data were processed to obtain averaged binary diffusion coefficients at a mean mole fraction of 0.5. The data for the molecular gas systems complete literature data on little investigated systems of technical interest and point out the capabilities of the applied measurement apparatus. Further experimental data are reported for the systems argon-helium, krypton-argon, krypton-neon, xenon-helium, xenon-krypton, nitrous oxide-carbon dioxide, and propane-carbon dioxide at 293.15 K, 2 bar, and a mean mole fraction of 0.5.
SHETTY, ANIL N.; CHIANG, SHARON; MALETIC-SAVATIC, MIRJANA; KASPRIAN, GREGOR; VANNUCCI, MARINA; LEE, WESLEY
2016-01-01
In this article, we discuss the theoretical background for diffusion weighted imaging and diffusion tensor imaging. Molecular diffusion is a random process involving thermal Brownian motion. In biological tissues, the underlying microstructures restrict the diffusion of water molecules, making diffusion directionally dependent. Water diffusion in tissue is mathematically characterized by the diffusion tensor, the elements of which contain information about the magnitude and direction of diffusion and is a function of the coordinate system. Thus, it is possible to generate contrast in tissue based primarily on diffusion effects. Expressing diffusion in terms of the measured diffusion coefficient (eigenvalue) in any one direction can lead to errors. Nowhere is this more evident than in white matter, due to the preferential orientation of myelin fibers. The directional dependency is removed by diagonalization of the diffusion tensor, which then yields a set of three eigenvalues and eigenvectors, representing the magnitude and direction of the three orthogonal axes of the diffusion ellipsoid, respectively. For example, the eigenvalue corresponding to the eigenvector along the long axis of the fiber corresponds qualitatively to diffusion with least restriction. Determination of the principal values of the diffusion tensor and various anisotropic indices provides structural information. We review the use of diffusion measurements using the modified Stejskal–Tanner diffusion equation. The anisotropy is analyzed by decomposing the diffusion tensor based on symmetrical properties describing the geometry of diffusion tensor. We further describe diffusion tensor properties in visualizing fiber tract organization of the human brain.
Evaluation of the vertical turbulent diffusion coefficient of industrial emissions
NASA Astrophysics Data System (ADS)
Ryzhakova, N. K.; Pokrovskaya, E. A.; Babicheva, V. O.
2015-07-01
A method for determining the vertical turbulent diffusion coefficients of industrial emissions in complex terrain and with long exposure times has been considered. The method is based on the usage of the distribution of the polluting impurity measured along a certain direction from a point source. The measurements are carried out with moss-biomonitors for a CHP in Novosibirsk.
Temperature Dependence of the Particle Diffusion Coefficient in Dust Grains
NASA Astrophysics Data System (ADS)
Pechal, Radim; Richterova, Ivana; Pavlu, Jiri; Safrankova, Jana; Nemecek, Zdenek
2014-05-01
During the interaction of ions/neutrals with dust grains, some of the particles are implanted into the grain and, as a consequence, the density gradient induces their diffusion toward the grain surface. Their release can cause a transport of these particles over large distances in space. In our laboratory experiment, measurements of the diffusion coefficient of the particles implanted into the dust grain are carried out in an electrodynamic quadrupole trap. Although experimental setup does not allow an assessment of the dust grain temperature, it can be modified (e.g., by changing thermal radiation from the surrounding walls, laser irradiation, etc.). We present an upgraded laboratory set-up and the resulting temperature dependence of diffusion coefficient estimations and discuss implications for the space dust.
Optimal estimation of diffusion coefficients from single-particle trajectories
NASA Astrophysics Data System (ADS)
Vestergaard, Christian L.; Blainey, Paul C.; Flyvbjerg, Henrik
2014-02-01
How does one optimally determine the diffusion coefficient of a diffusing particle from a single-time-lapse recorded trajectory of the particle? We answer this question with an explicit, unbiased, and practically optimal covariance-based estimator (CVE). This estimator is regression-free and is far superior to commonly used methods based on measured mean squared displacements. In experimentally relevant parameter ranges, it also outperforms the analytically intractable and computationally more demanding maximum likelihood estimator (MLE). For the case of diffusion on a flexible and fluctuating substrate, the CVE is biased by substrate motion. However, given some long time series and a substrate under some tension, an extended MLE can separate particle diffusion on the substrate from substrate motion in the laboratory frame. This provides benchmarks that allow removal of bias caused by substrate fluctuations in CVE. The resulting unbiased CVE is optimal also for short time series on a fluctuating substrate. We have applied our estimators to human 8-oxoguanine DNA glycolase proteins diffusing on flow-stretched DNA, a fluctuating substrate, and found that diffusion coefficients are severely overestimated if substrate fluctuations are not accounted for.
The porous medium permeability and effective diffusion coefficient direct correlation
NASA Astrophysics Data System (ADS)
Markicevic, Bojan
2012-11-01
Dimensionless analysis of a momentum and mass transport in the homogeneous porous medium reveals that the permeability and effective to the molecular diffusion coefficient ratio can be expressed as a function of medium pore and throat sizes and two additional geometrical scales. These two scales, each one pertinent to the momentum and mass transport, respectively, are referred to as permeability and diffusivity characteristic scales. Based on these findings, it can be shown that the medium permeability and effective diffusivity can be correlated, and, at the same time, that one microscopic scale needs to be known in this correlation. The same is implied from the Katz-Thompson formula - which correlates the permeability, effective diffusivity, and breakthrough capillary pressure length scale. We recast the correlation developed into the Katz-Thompson formula form, showing how corresponding members are related. It turns out that the coefficient from the Katz-Thompson formula is equal to the ratio of the permeability to diffusivity characteristic length scales, and it is indeed constant for the homogeneous media. As porous media are heterogeneous materials, the analysis is extended onto such materials using heterogeneous capillary networks. The networks with the uniform, normal and log-normal pore size distribution functions are generated, where the networks are sufficiently large to obtain small variations in permeability and effective diffusivity for pore size distribution set. For such stochastically homogeneous media, the effective pore size averages are used in calculating the permeability and effective diffusivity showing the true nature of the coefficient in the Katz-Thompson formula.
Determination of thermal diffusion coefficient of nanofluid: Fullerene-toluene
NASA Astrophysics Data System (ADS)
Martin, Alain; Bou-Ali, M. Mounir
2011-05-01
Thermodiffusion coefficient at fullerene mass concentrations of 0.05%, 0.1%, 0.15%, and 0.2% was established for pure fullerene (C 60) diluted in toluene solutions. For this, the thermogravitational technique has been used in planar configuration with 4 extraction points. The determination of the concentration distribution along the column in steady state is determined by the method of analysis based on density measurements. In order to determine the thermal diffusion coefficient all thermophysical properties such as density, viscosity, thermal expansion coefficient and mass expansion coefficients were determined. All these studies coincide with the importance of the knowledge of the thermophysics and transport properties of the nanofluids to develop new applications and to optimize the existing ones.
Determination of diffusion coefficient in disordered organic semiconductors
NASA Astrophysics Data System (ADS)
Rani, Varsha; Sharma, Akanksha; Ghosh, Subhasis
2016-05-01
Charge carrier transport in organic semiconductors is dominated by positional and energetic disorder in Gaussian density of states (GDOS) and is characterized by hopping through localized states. Due to the immobilization of charge carriers in these localized states, significant non-uniform carrier distribution exists, resulting diffusive transport. A simple, nevertheless powerful technique to determine diffusion coefficient D in disordered organic semiconductors has been presented. Diffusion coefficients of charge carriers in two technologically important organic molecular semiconductors, Pentacene and copper phthalocyanine (CuPc) have been measured from current-voltage (J-V) characteristics of Al/Pentacene/Au and Al/CuPc/Au based Schottky diodes. Ideality factor g and carrier mobility μ have been calculated from the exponential and space charge limited region respectively of J-V characteristics. Classical Einstein relation is not valid in organic semiconductors due to energetic disorders in DOS. Using generalized Einstein relation, diffusion coefficients have been obtained to be 1.31×10-6 and 1.73×10-7 cm2/s for Pentacene and CuPc respectively.
On-line vibration and analysis system at the Paducah Gaseous Diffusion Plant
Herricks, D.M.; Strunk, W.D.
1988-02-01
The enrichment facility in Paducah, KY uses a unique hard-wired vibration monitoring and analysis system for gaseous diffusion equipment. The axial flow and centrifugal flow compressors used in uranium enrichment range in size from 6 feet in diameter to less than one foot in diameter. These compressors must operate smoothly and safely, without breech of containment, since the working fluid of gaseous diffusion is gaseous UF/sub 6/. The condition of 1925 compressors is monitored by use of the 2500 point vibration analysis system. Since the failure mechanisms of the compressors are well known and documented, only one accelerometer per machine is needed for most machines. The system is completely automated and can generate spectra or broadband levels in either acceleration or velocity units. Levels are stored for historical review. The analyst can, via a custom telecommunications link, view and analyze data from all monitored points with an office PC. 4 figs.
Calcium diffusion coefficient in rod photoreceptor outer segments.
Nakatani, Kei; Chen, Chunhe; Koutalos, Yiannis
2002-01-01
Calcium (Ca(2+)) modulates several of the enzymatic pathways that mediate phototransduction in the outer segments of vertebrate rod photoreceptors. Ca(2+) enters the rod outer segment through cationic channels kept open by cyclic GMP (cGMP) and is pumped out by a Na(+)/Ca(2+),K(+) exchanger. Light initiates a biochemical cascade, which leads to closure of the cGMP-gated channels, and a concomitant decline in the concentration of Ca(2+). This decline mediates the recovery from stimulation by light and underlies the adaptation of the cell to background light. The speed with which the decline in the Ca(2+) concentration propagates through the rod outer segment depends on the Ca(2+) diffusion coefficient. We have used the fluorescent Ca(2+) indicator fluo-3 and confocal microscopy to measure the profile of the Ca(2+) concentration after stimulation of the rod photoreceptor by light. From these measurements, we have obtained a value of 15 +/- 1 microm(2)s(-1) for the radial Ca(2+) diffusion coefficient. This value is consistent with the effect of a low-affinity, immobile buffer reported to be present in the rod outer segment (L.Lagnado, L. Cervetto, and P.A. McNaughton, 1992, J. Physiol. 455:111-142) and with a buffering capacity of approximately 20 for rods in darkness(S. Nikonov, N. Engheta, and E.N. Pugh, Jr., 1998, J. Gen. Physiol. 111:7-37). This value suggests that diffusion provides a significant delay for the radial propagation of the decline in the concentration of Ca(2+). Also, because of baffling by the disks, the longitudinal Ca(2+) diffusion coefficient will be in the order of 2 microm(2)s(-1), which is much smaller than the longitudinal cGMP diffusion coefficient (30-60 microm(2)s(-1); ). Therefore, the longitudinal decline of Ca(2+) lags behind the longitudinal spread of excitation by cGMP. PMID:11806915
Hahne, Susanne; Maass, Philipp
2014-03-27
Analysis of signal fluctuations of a locally fixed probe, caused by molecules diffusing under the probe, can be used to determine diffusion coefficients. Theoretical treatments so far have been limited to point-like particles or to molecules with circle-like shapes. Here we extend these treatments to molecules with rectangle-like shapes, for which also rotational diffusion needs to be taken into account. Focusing on the distribution of peak widths in the signal, we show how translational as well as rotational diffusion coefficients can be determined. We address also the question, how the distribution of interpeak time intervals and autocorrelation function can be employed for determining diffusion coefficients. Our approach is validated against kinetic Monte Carlo simulations. PMID:24640969
D&D of the French High Enrichment Gaseous Diffusion Plant
BEHAR, Christophe; GUIBERTEAU, Philippe; DUPERRET, Bernard; TAUZIN, Claude
2003-02-27
This paper describes the D&D program that is being implemented at France's High Enrichment Gaseous Diffusion Plant, which was designed to supply France's Military with Highly Enriched Uranium. This plant was definitively shut down in June 1996, following French President Jacques Chirac's decision to end production of Highly Enriched Uranium and dismantle the corresponding facilities.
Not Available
1992-09-01
An aerial radiological survey was conducted from July 11--20, 1990, over an 83-square-kilometer (32-square-mile) area surrounding the Portsmouth Gaseous Diffusion Plant located near Portsmouth, Ohio. The survey was conducted at a nominal altitude of 91 meters (300 feet) with line spacings of 122 meters (400 feet). A contour map of the terrestrial gamma exposure rate extrapolated to 1 meter above ground level (AGL) was prepared and overlaid on an aerial photograph and a set of United States Geological Survey (USGS) topographic maps of the area. The terrestrial exposure rates varied from about 7 to 14 microroentgens per hour ([mu]R/h) at 1 meter above the ground. Analysis of the data for man-made sources and for the uranium decay product, protactinium-234m ([sup 234m]Pa), showed five sites within the boundaries of the Portsmouth Gaseous Diffusion Plant with elevated readings. Spectra obtained in the vicinity of the buildings at the Portsmouth Gaseous Diffusion Plant showed the presence of [sup 234m]Pa, a uranium-238 ([sup 238]U) decay product. In addition, spectral analysis of the data obtained over the processing plant facility showed gamma activity indicative of uranium-235 ([sup 234]U). No other man-made gamma ray emitting radioactive material was detected, either on or off the Portsmouth Gaseous Diffusion Plant property. Soil samples and pressurized ion chamber measurements were obtained at five different locations within the survey boundlaries to support the aerial data.
Environmental Restoration Site-Specific Plan for the Portsmouth Gaseous Diffusion Plant, FY 93
Not Available
1993-01-15
The purpose of this Site-Specific Plan (SSP) is to describe past, present, and future activities undertaken to implement Environmental Restoration and Waste Management goals at the Portsmouth Gaseous Diffusion Plant (PORTS). The SSP is presented in sections emphasizing Environmental Restoration description of activities, resources, and milestones.
Johnson, Robert L
2008-04-03
This activity was undertaken to demonstrate the applicability of market-available XRF instruments to quantify metal concentrations relative to background and risk-based action and no action levels in Paducah Gaseous Diffusion Plant (PGDP) soils. As such, the analysis below demonstrates the capabilities of the instruments relative to soil characterization applications at the PGDP.
Not Available
1994-07-01
The decision document presents the selected interim action for the North-South Diversion Ditch (NSDD) at the Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky. The primary objective of this interim remedial action is to initiate control of the source of continued contaminant releases into the NSDD and mitigate the spread of contamination from the NSDD.
Vertical eddy diffusion coefficient from the LANDSAT imagery
NASA Technical Reports Server (NTRS)
Viswanadham, Y. (Principal Investigator); Torsani, J. A.
1982-01-01
Analysis of five stable cases of the smoke plumes that originated in eastern Cabo Frio (22 deg 59'S; 42 deg 02'W), Brazil using LANDSAT imagery is presented for different months and years. From these images the lateral standard deviation (sigma sub y) and the lateral eddy diffusion coefficient (K sub y) are obtained from the formula based on Taylor's theory of diffusion by continuous moment. The rate of kinetic energy dissipation (e) is evaluated from the diffusion parameters sigma sub y and K sub y. Then, the vertical diffusion coefficient (K sub z) is estimated using Weinstock's formulation. These results agree well with the previous experimental values obtained over water surfaces by various workers. Values of e and K sub z show the weaker mixing processes in the marine stable boundary layer. The data sample is apparently to small to include representative active turbulent regions because such regions are so intermittent in time and in space. These results form a data base for use in the development and validation of mesoscale atmospheric diffusion models.
Meryem Seferinolu; Yuda Yurum
2006-05-15
The aim of this study is to measure the diffusion coefficients of pyridine in Turkish Cayirhan lignite (C: 57.1 wt%, dmmf) at temperatures about 20-27{sup o}C and determine the type of transport mechanism of diffusion. The raw coal sample was demineralized with HCl and HF by standard methods, and the raw and demineralized coal samples were extracted with pyridine. To investigate the diffusion of pyridine vapor in coal samples, the mass of pyridine uptake per mass of coal sample (M{sub t}/M{sub {infinity}}) was calculated as a function of time. The diffusion coefficients were measured from the slope of graphs of M{sub t}/M{sub {infinity}} versus t{sup 1/2}. The diffusion coefficient of pyridine in the raw coal increased from 10.0 x 10{sup -15} to 11.9 x 10{sup -15} m{sup 2}/s when the temperature was elevated from 21.1 to 26.9{sup o}C, respectively. The diffusion coefficients of pyridine raw coal and of those treated with HCl and HF were 11.9 x 10{sup -15}, 4.3 x 10{sup -15}, and 4.8 x 10{sup -15} m{sup 2}/s at 26.9{sup o}C, respectively. The studies in the present work on pyridine vapor diffusion in raw coals have generally indicated that the diffusion obeyed the Fickian diffusion mechanism the temperatures 20.0-27.0{sup o}C. Generally, the diffusion exponent values increased when the temperature elevated from 20.0 to 27.0{sup o}C, but this rise placed the diffusion of pyridine between the Fickian diffusion and Case II diffusion mechanisms. 29 refs., 6 figs., 4 tabs.
Apparent diffusion coefficient map of a case of extramedullary plasmacytoma
Ramachandran, Amrutha; Inyang, Alero F; Subhawong, Ty K
2016-01-01
Plasmacytomas are rare tumors, which arise from the monoclonal proliferation of malignant plasma cells. They may affect either the bony skeleton or rarely the soft tissues, the latter being referred to as extramedullary or extraosseous. We report a case of an extramedullary plasmacytoma that presented as a soft tissue mass involving the muscles of the left leg, in a patient who was previously treated for multiple myeloma. We describe the MR Imaging characteristics of the tumor and highlight the usefulness of diffusion-weighted imaging with apparent diffusion coefficient mapping. PMID:27200157
Takeda, M.; Hiratsuka, T.; Ito, K.; Finsterle, S.
2011-02-01
Diffusion anisotropy is a critical property in predicting migration of substances in sedimentary formations with very low permeability. The diffusion anisotropy of sedimentary rocks has been evaluated mainly from laboratory diffusion experiments, in which the directional diffusivities are separately estimated by through-diffusion experiments using different rock samples, or concurrently by in-diffusion experiments in which only the tracer profile in a rock block is measured. To estimate the diffusion anisotropy from a single rock sample, this study proposes an axisymmetric diffusion test, in which tracer diffuses between a cylindrical rock sample and a surrounding solution reservoir. The tracer diffusion between the sample and reservoir can be monitored from the reservoir tracer concentrations, and the tracer profile could also be obtained after dismantling the sample. Semi-analytical solutions are derived for tracer concentrations in both the reservoir and sample, accounting for an anisotropic diffusion tensor of rank two as well as the dilution effects from sampling and replacement of reservoir solution. The transient and steady-state analyses were examined experimentally and numerically for different experimental configurations, but without the need for tracer profiling. These experimental configurations are tested for in- and out-diffusion experiments using Koetoi and Wakkanai mudstones and Shirahama sandstone, and are scrutinized by a numerical approach to identify favorable conditions for parameter estimation. The analysis reveals the difficulty in estimating diffusion anisotropy; test configurations are proposed for enhanced identifiability of diffusion anisotropy. Moreover, it is demonstrated that the axisymmetric diffusion test is efficient in obtaining the sorption parameter from both steady-state and transient data, and in determining the effective diffusion coefficient if isotropic diffusion is assumed. Moreover, measuring reservoir concentrations in an
Takeda, M; Hiratsuka, T; Ito, K; Finsterle, S
2011-04-25
Diffusion anisotropy is a critical property in predicting migration of substances in sedimentary formations with very low permeability. The diffusion anisotropy of sedimentary rocks has been evaluated mainly from laboratory diffusion experiments, in which the directional diffusivities are separately estimated by through-diffusion experiments using different rock samples, or concurrently by in-diffusion experiments in which only the tracer profile in a rock block is measured. To estimate the diffusion anisotropy from a single rock sample, this study proposes an axisymmetric diffusion test, in which tracer diffuses between a cylindrical rock sample and a surrounding solution reservoir. The tracer diffusion between the sample and reservoir can be monitored from the reservoir tracer concentrations, and the tracer profile could also be obtained after dismantling the sample. Semi-analytical solutions are derived for tracer concentrations in both the reservoir and sample, accounting for an anisotropic diffusion tensor of rank two as well as the dilution effects from sampling and replacement of reservoir solution. The transient and steady-state analyses were examined experimentally and numerically for different experimental configurations, but without the need for tracer profiling. These experimental configurations are tested for in- and out-diffusion experiments using Koetoi and Wakkanai mudstones and Shirahama sandstone, and are scrutinized by a numerical approach to identify favorable conditions for parameter estimation. The analysis reveals the difficulty in estimating diffusion anisotropy; test configurations are proposed for enhanced identifiability of diffusion anisotropy. Moreover, it is demonstrated that the axisymmetric diffusion test is efficient in obtaining the sorption parameter from both steady-state and transient data, and in determining the effective diffusion coefficient if isotropic diffusion is assumed. Moreover, measuring reservoir concentrations in an
Radiative Extinction of Gaseous Spherical Diffusion Flames in Microgravity
NASA Technical Reports Server (NTRS)
Santa, K. J.; Chao, B. H.; Sunderland, P. B.; Urban, D. L.; Stocker, D. P.; Axelbaum, R. L.
2007-01-01
Radiative extinction of spherical diffusion flames was investigated experimentally and numerically. The experiments involved microgravity spherical diffusion flames burning ethylene and propane at 0.98 bar. Both normal (fuel flowing into oxidizer) and inverse (oxidizer flowing into fuel) flames were studied, with nitrogen supplied to either the fuel or the oxygen. Flame conditions were chosen to ensure that the flames extinguished within the 2.2 s of available test time; thus extinction occurred during unsteady flame conditions. Diagnostics included color video and thin-filament pyrometry. The computations, which simulated flow from a porous sphere into a quiescent environment, included detailed chemistry, transport and radiation, and yielded transient results. Radiative extinction was observed experimentally and simulated numerically. Extinction time, peak temperature, and radiative loss fraction were found to be independent of flow rate except at very low flow rates. Radiative heat loss was dominated by the combustion products downstream of the flame and was found to scale with flame surface area, not volume. For large transient flames the heat release rate also scaled with surface area and thus the radiative loss fraction was largely independent of flow rate. Peak temperatures at extinction onset were about 1100 K, which is significantly lower than for kinetic extinction. One observation of this work is that while radiative heat losses can drive transient extinction, this is not because radiative losses are increasing with time (flame size) but rather because the heat release rate is falling off as the temperature drops.
Response of radiation belt simulations to different radial diffusion coefficients
NASA Astrophysics Data System (ADS)
Drozdov, A.; Shprits, Y.; Subbotin, D.; Kellerman, A. C.
2013-12-01
Resonant interactions between Ultra Low Frequency (ULF) waves and relativistic electrons may violate the third adiabatic invariant of motion, which produces radial diffusion in the electron radiation belts. This process plays an important role in the formation and structure of the outer electron radiation belt and is important for electron acceleration and losses in that region. Two parameterizations of the resonant wave-particle interaction of electrons with ULF waves in the magnetosphere by Brautigam and Albert [2000] and Ozeke et al. [2012] are evaluated using the Versatile Electron Radiation Belt (VERB) diffusion code to estimate their relative effect on the radiation belt simulation. The period of investigation includes quiet time and storm time geomagnetic activity and is compared to data based on satellite observations. Our calculations take into account wave-particle interactions represented by radial diffusion transport, local acceleration, losses due to pitch-angle diffusion, and mixed diffusion. We show that the results of the 3D diffusion simulations depend on the assumed parametrization of waves. The differences between the simulations and potential missing physical mechanisms are discussed. References Brautigam, D. H., and J. M. Albert (2000), Radial diffusion analysis of outer radiation belt electrons during the October 9, 1990, magnetic storm, J. Geophys. Res., 105(A1), 291-309, doi:10.1029/1999JA900344 Ozeke, L. G., I. R. Mann, K. R. Murphy, I. J. Rae, D. K. Milling, S. R. Elkington, A. A. Chan, and H. J. Singer (2012), ULF wave derived radiation belt radial diffusion coefficients, J. Geophys. Res., 117, A04222, doi:10.1029/2011JA017463.
Rowley, R.L.; Adams, M.E.; Marshall, T.L.; Oscarson, J.L.; Wilding, W.V.; Anderson, D.J.
1997-03-01
Natural gas processors use amine treating processes to remove the acid gases H{sub 2}S and CO{sub 2} from gas streams. Absorption rates of gaseous CO{sub 2} into aqueous N-methyldiethanolamine (MDEA) solutions were measured in a quiescent, inverted-tube diffusiometer by monitoring the rate of pressure drop. The absorption rate was found to be insensitive to the diffusion coefficient of CO{sub 2} in solution but very sensitive to the diffusion rate of bicarbonate and protonated MDEA ions. Evidence also suggested that chemical reaction equilibrium is rapid relative to diffusion. A numerical model was developed on the basis of these observations. The model was used to regress diffusion coefficients of bicarbonate and protonated amine, which must be equivalent by electroneutrality arguments, from measured absorption rates. Complete modeling of the absorption process also required data for the diffusion coefficient of MDEA in water. These were measured using a Taylor dispersion apparatus. CO{sub 2} absorption rates and diffusion coefficients of bicarbonate and protonated MDEA were obtained at 298.2 K and 318.2 K in solutions containing 20, 35, and 50 mass % MDEA in water.
NASA Technical Reports Server (NTRS)
Tenney, D. R.; Unnam, J.
1978-01-01
Diffusion calculations were performed to establish the conditions under which concentration dependence of the diffusion coefficient was important in single, two, and three phase binary alloy systems. Finite-difference solutions were obtained for each type of system using diffusion coefficient variations typical of those observed in real alloy systems. Solutions were also obtained using average diffusion coefficients determined by taking a logarithmic average of each diffusion coefficient variation considered. The constant diffusion coefficient solutions were used as reference in assessing diffusion coefficient variation effects. Calculations were performed for planar, cylindrical, and spherical geometries in order to compare the effect of diffusion coefficient variations with the effect of interface geometries. In most of the cases considered, the diffusion coefficient of the major-alloy phase was the key parameter that controlled the kinetics of interdiffusion.
Kalwarf, D.R.; Nielson, K.K.; Rich, D.C.; Rogers, V.C.
1982-11-01
A method was developed and used to determine radon diffusion coefficients in compacted soils by transient-diffusion measurements. A relative standard deviation of 12% was observed in repeated measurements with a dry soil by the transient-diffusion method, and a 40% uncertainty was determined for moistures exceeding 50% of saturation. Excellent agreement was also obtained between values of the diffusion coefficient for radon in air, as measured by the transient-diffusion method, and those in the published literature. Good agreement was also obtained with diffusion coefficients measured by a steady-state method on the same soils. The agreement was best at low moistures, averaging less than ten percent difference, but differences of up to a factor of two were observed at high moistures. The comparison of the transient-diffusion and steady-state methods at low moistures provides an excellent verification of the theoretical validity and technical accuracy of these approaches, which are based on completely independent experimental conditions, measurement methods and mathematical interpretations.
Radon diffusion coefficients in soils of varying moisture content
NASA Astrophysics Data System (ADS)
Papachristodoulou, C.; Ioannides, K.; Pavlides, S.
2009-04-01
Radon is a naturally occurring radioactive gas that is generated in the Earth's crust and is free to migrate through soil and be released to the atmosphere. Due to its unique properties, soil gas radon has been established as a powerful tracer used for a variety of purposes, such as exploring uranium ores, locating geothermal resources and hydrocarbon deposits, mapping geological faults, predicting seismic activity or volcanic eruptions and testing atmospheric transport models. Much attention has also been given to the radiological health hazard posed by increased radon concentrations in the living and working environment. In order to exploit radon profiles for geophysical purposes and also to predict its entry indoors, it is necessary to study its transport through soils. Among other factors, the importance of soil moisture in such studies has been largely highlighted and it is widely accepted that any measurement of radon transport parameters should be accompanied by a measurement of the soil moisture content. In principle, validation of transport models in the field is encountered by a large number of uncontrollable and varying parameters; laboratory methods are therefore preferred, allowing for experiments to be conducted under well-specified and uniform conditions. In this work, a laboratory technique has been applied for studying the effect of soil moisture content on radon diffusion. A vertical diffusion chamber was employed, in which radon was produced from a 226Ra source, was allowed to diffuse through a soil column and was finally monitored using a silicon surface barrier detector. By solving the steady-state radon diffusion equation, diffusion coefficients (D) were determined for soil samples of varying moisture content (m), from null (m=0) to saturation (m=1). For dry soil, a D value of 4.1×10-7 m2s-1 was determined, which increased moderately by a factor of ~3 for soil with low moisture content, i.e. up to m ~0.2. At higher water fractions, a decrease
Estimation of glucose diffusion coefficient in scleral tissue
NASA Astrophysics Data System (ADS)
Bashkatov, Alexey N.; Genina, Elina A.; Sinichkin, Yurii P.; Lakodina, Nina A.; Kochubey, Vyacheslav I.; Tuchin, Valery V.
2000-04-01
Results of experimental and theoretical study of the optical properties of the eye sclera controlled by administration of osmotically active chemical, such as glucose, are presented. Glucose administration induces the diffusion of matter and as a result the equalization of the refractive indices of collagen fibrils and base material, and corresponding changes of transmittance spectra of scleral tissue. Transmittance spectra of the human scleral samples impregnated by glucose were measured. The significant increase of transmittance under action of osmotic liquid was observed. The diffusion coefficient of glucose within scleral tissue was estimated; the average value is 3.45 X 10-6 +/- 4.59 X 10-7 cm2/sec. The results are general and can be used to describe many other fibrous tissues impregnated by osmotically active chemical agents.
Optimal diffusion coefficient estimation in single-particle tracking
Michalet, Xavier; Berglund, Andrew J.
2016-01-01
Single-particle tracking is increasingly used to extract quantitative parameters on single molecules and their environment, while advances in spatial and temporal resolution of tracking techniques inspire new questions and avenues of investigation. Correspondingly, sophisticated analytical methods are constantly developed to obtain more refined information from measured trajectories. Here we point out some fundamental limitations of these approaches due to the finite length of trajectories, the presence of localization error, and motion blur, focusing on the simplest motion regime of free diffusion in an isotropic medium (Brownian motion). We show that two recently proposed algorithms approach the theoretical limit of diffusion coefficient uncertainty. We discuss the practical performance of the algorithms as well as some important implications of these results for single-particle tracking. PMID:23005136
Diffusion Coefficient in an Electrophoretic Asymmetrically Tilting Ratchet
NASA Astrophysics Data System (ADS)
Pasciak, P.; Kulakowski, K.; Gudowska-Nowak, E.
2005-05-01
We use the cellular-automaton Duke--Rubinstein model to simulate gel electrophoresis of DNA in periodically changing electric field. The field is dichotomic and its time average is zero. We observe non-vanishing current of molecules, what is known as the ratchet effect. We calculate the drift velocity and the diffusion coefficient for large field amplitude, where nonlinear effects can be observed. The results indicate that tuning the amplitude and frequency of the applied field for a given range of the molecule length can improve the resolving power of the separation of DNA.
Tracer diffusion coefficients in a sheared inelastic Maxwell gas
NASA Astrophysics Data System (ADS)
Garzó, Vicente; Trizac, Emmanuel
2016-07-01
We study the transport properties of an impurity in a sheared granular gas, in the framework of the Boltzmann equation for inelastic Maxwell models. We investigate here the impact of a nonequilibrium phase transition found in such systems, where the tracer species carries a finite fraction of the total kinetic energy (ordered phase). To this end, the diffusion coefficients are first obtained for a granular binary mixture in spatially inhomogeneous states close to the simple shear flow. In this situation, the set of coupled Boltzmann equations are solved by means of a Chapman–Enskog-like expansion around the (local) shear flow distributions for each species, thereby retaining all the hydrodynamic orders in the shear rate a. Due to the anisotropy induced by the shear flow, three tensorial quantities D ij , D p,ij , and D T,ij are required to describe the mass transport process instead of the conventional scalar coefficients. These tensors are given in terms of the solutions of a set of coupled algebraic equations, which can be exactly solved as functions of the shear rate a, the coefficients of restitution {αsr} and the parameters of the mixture (masses and composition). Once the forms of D ij , D p,ij , and D T,ij are obtained for arbitrary mole fraction {{x}1}={{n}1}/≤ft({{n}1}+{{n}2}\\right) (where n r is the number density of species r), the tracer limit ({{x}1}\\to 0 ) is carefully considered for the above three diffusion tensors. Explicit forms for these coefficients are derived showing that their shear rate dependence is significantly affected by the order-disorder transition.
Measurements of uranium holdup in an operating gaseous diffusion enrichment plant
Augustson, R.H.; Walton, R.B.; Harris, R.; Harbarger, W.; Hicks, J.; Timmons, G.; Shissler, D.; Tayloe, R.; Jones, S.; Fields, L.
1983-01-01
Holdup of nuclear material in process equipment is one of the major sources of uncertainty in materials balances, particularly for high-throughput facilities with large equipment and extensive piping, such as gaseous diffusion uranium-enrichment plants. Locating and measuring the holdup while the plant is operating is a challenging problem because of background from the process material and the neighboring equipment. This paper reports NDA measurements performed at the Goodyear Atomic Gaseous Diffusion Plant, Portsmouth, Ohio, on enrichment equipment at the higher enrichment and (>10% /sup 235/U isotopic abundance) of the cascade. Both neutron and gamma-ray measurements were made to locate anomalously large deposits in converters and compressors and, within the limitations of the techniques, to quantify the amount of the deposit.
Singhal, M.K.; Kincaid, J.H.; Hammond, C.R.; Stockdale, B.I.; Walls, J.C.; Brock, W.R.; Denton, D.R.
1995-12-31
In support of the Gaseous Diffusion Plant Safety Analysis Report Upgrade program (GDP SARUP), a natural phenomena hazards evaluation was performed for the main process equipment and piping in the uranium enrichment buildings at Paducah and Portsmouth gaseous diffusion plants. In order to reduce the cost of rigorous analyses, the evaluation methodology utilized a graded approach based on an experience data base collected by SQUG/EPRI that contains information on the performance of industrial equipment and piping during past earthquakes. This method consisted of a screening walkthrough of the facility in combination with the use of engineering judgment and simple calculations. By using these screenings combined with evaluations that contain decreasing conservatism, reductions in the time and cost of the analyses were significant. A team of experienced seismic engineers who were trained in the use of the DOE SQUG/EPRI Walkdown Screening Material was essential to the success of this natural phenomena hazards evaluation.
NASA Astrophysics Data System (ADS)
Araruna, F. D.; Braz e Silva, P.; Carvalho, R. R.; Rojas-Medar, M. A.
2015-06-01
We consider the motion of a viscous incompressible fluid consisting of two components with a diffusion effect obeying Fick's law in ℝ3. We prove that there exists a small time interval where the fluid variables converge uniformly as the viscosity and the diffusion coefficient tend to zero. In the limit, we find a non-homogeneous, non-viscous, incompressible fluid governed by an Euler-like system.
Environmental Restoration Site-Specific Plan for the Paducah Gaseous Diffusion Plant, FY 93
Not Available
1993-01-15
This report provides an overview of the major Environmental Restoration (ER) concerns at Paducah Gaseous Diffusion Plant (PGDP). The identified solid waste management units at PGDP are listed. In the Department of Energy (DOE) Five Year Plan development process, one or more waste management units are addressed in a series of activity data sheets (ADSs) which identify planned scope, schedule, and cost objectives that are representative of the current state of planned technical development for individual or multiple sites.
Sheaffer, M.K.; Keeton, S.C.
1993-09-20
This report evaluates nuclear criticality safety for Spray Booth Operations in the Decontamination and Recovery Facility, X-705, at the Portsmouth Gaseous Diffusion Plant. A general description of current procedures and related hardware/equipment is presented. Control parameters relevant to nuclear criticality safety are explained, and a consolidated listing of administrative controls and safety systems is developed. Based on compliance with DOE Orders and MMES practices, the overall operation is evaluated, and recommendations for enhanced safety are suggested.
NASA Technical Reports Server (NTRS)
Ukanwa, A. O.
1974-01-01
This experiment was performed in Skylab 3 with two objectives in mind. First, the experimental self-diffusion coefficients for liquid zinc were to be determined in a convection-free environment. Secondly the reduction in convective mixing in earth gravity by going into the zero-gravity environment of space was to be estimated. The experiment was designed to utilize high temperatures and linear thermal gradients provided by the M518 Multipurpose Electric Furnace, and the radioactivity of zinc-65 of 245-day half-life to investigate self-diffusion in liquid zinc. The distribution of zinc-65 tracer, after melting, maintaining at soak temperature for 1 hour of soak time and then resolidifying, was obtained by sample sectioning. The concentration of activity of each section (microcurie-gram) was plotted against positions along the sample axial and radial position. Experimental data and theoretical results from solution of Fick's law of diffusion in one dimensional were compared. Samples tested on earth showed very rapid diffusion. Diffusion coefficient in unit gravity was 50 times the zero-gravity diffusion coefficient of Skylab.
Diffusion in multilayer media: Transient behavior of the lateral diffusion coefficient
NASA Astrophysics Data System (ADS)
Berezhkovskii, Alexander M.; Weiss, George H.
2006-04-01
A general formalism for treating lateral diffusion in a multilayer medium is developed. The formalism is based on the relation between the lateral diffusion and the distribution of the cumulative residence time, which the diffusing particle spends in different layers. We exploit this fact to derive general expressions which give the global and local time-dependent diffusion coefficients in terms of the average cumulative times spent by the particle in different layers and the probabilities of finding the particle in different layers, respectively. These expressions are used to generalize two recently obtained results: (a) A solution for the short-time behavior of the lateral diffusion coefficient in two layers separated by a permeable membrane obtained by a perturbation theory is extended to the entire range of time. (b) A solution for the time-dependent diffusion coefficient of a ligand, which repeatedly dissociates and rebinds to sites on a planar surface, obtained under the assumption that the medium above the surface is infinite, is generalized to allow for the medium layer of finite thickness. For the latter problem we derive an expression for the Fourier-Laplace transform of the propagator in terms of the double Laplace transform of the probability density of the cumulative residence time spent by the ligand in the medium layer.
NASA Astrophysics Data System (ADS)
Garzó, Vicente; Murray, J. Aaron; Vega Reyes, Francisco
2013-04-01
The mass flux of a low-density granular binary mixture obtained previously by solving the Boltzmann equation by means of the Chapman-Enskog method is considered further. As in the elastic case, the associated transport coefficients D, Dp, and D' are given in terms of the solutions of a set of coupled linear integral equations which are approximately solved by considering the first and second Sonine approximations. The diffusion coefficients are explicitly obtained as functions of the coefficients of restitution and the parameters of the mixture (masses, diameters, and concentration) and their expressions hold for an arbitrary number of dimensions. In order to check the accuracy of the second Sonine correction for highly inelastic collisions, the Boltzmann equation is also numerically solved by means of the direct simulation Monte Carlo (DSMC) method to determine the mutual diffusion coefficient D in some special situations (self-diffusion problem and tracer limit). The comparison with DSMC results reveals that the second Sonine approximation to D improves the predictions made from the first Sonine approximation. We also study the granular segregation driven by a uni-directional thermal gradient. The segregation criterion is obtained from the so-called thermal diffusion factor Λ, which measures the amount of segregation parallel to the temperature gradient. The factor Λ is determined here by considering the second-order Sonine forms of the diffusion coefficients and its dependence on the coefficients of restitution is widely analyzed across the parameter space of the system. The results obtained in this paper extend previous works carried out in the tracer limit (vanishing mole fraction of one of the species) by some of the authors of the present paper.
Comparison Actin- and Glass-Supported Phospholipid Bilayer Diffusion Coefficients
Sterling, Sarah M.; Dawes, Ryan; Allgeyer, Edward S.; Ashworth, Sharon L.; Neivandt, David J.
2015-01-01
The formation of biomimetic lipid membranes has the potential to provide insights into cellular lipid membrane dynamics. The construction of such membranes necessitates not only the utilization of appropriate lipids, but also physiologically relevant substrate/support materials. The substrate materials employed have been shown to have demonstrable effects on the behavior of the overlying lipid membrane, and thus must be studied before use as a model cushion support. To our knowledge, we report the formation and investigation of a novel actin protein-supported lipid membrane. Specifically, inner leaflet lateral mobility of globular actin-supported DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) bilayers, deposited via the Langmuir-Blodgett/Langmuir Schaefer methodology, was investigated by z-scan fluorescence correlation spectroscopy across a temperature range of 20–44°C. The actin substrate was found to decrease the diffusion coefficient when compared to an identical membrane supported on glass. The depression of the diffusion coefficient occurred across all measured temperatures. These results indicated that the actin substrate exerted a direct effect on the fluidity of the lipid membrane and highlighted the fact that the choice of substrate/support is critical in studies of model lipid membranes. PMID:25902434
A New Relationship Among Self- and Impurity Diffusion Coefficients in Binary Solution Phases
NASA Astrophysics Data System (ADS)
Xin, Jinghua; Du, Yong; Shang, Shunli; Cui, Senlin; Wang, Jianchuan; Huang, Baiyun; Liu, Zikui
2016-07-01
A new relationship among self- and impurity diffusion coefficients has been proposed for binary solution phases and verified via 30 solid solutions. In terms of this model, one impurity diffusion coefficient in a binary phase can be predicted once the other three diffusion coefficients are available. The application of the present model is exemplified in the Al-Mg system.
A New Relationship Among Self- and Impurity Diffusion Coefficients in Binary Solution Phases
NASA Astrophysics Data System (ADS)
Xin, Jinghua; Du, Yong; Shang, Shunli; Cui, Senlin; Wang, Jianchuan; Huang, Baiyun; Liu, Zikui
2016-05-01
A new relationship among self- and impurity diffusion coefficients has been proposed for binary solution phases and verified via 30 solid solutions. In terms of this model, one impurity diffusion coefficient in a binary phase can be predicted once the other three diffusion coefficients are available. The application of the present model is exemplified in the Al-Mg system.
Calculation of combined diffusion coefficients in SF{sub 6}-Cu mixtures
Zhong, Linlin; Wang, Xiaohua Rong, Mingzhe Wu, Yi; Murphy, Anthony B.
2014-10-15
Diffusion coefficients play an important role in the description of the transport of metal vapours in gas mixtures. This paper is devoted to the calculation of four combined diffusion coefficients, namely, the combined ordinary diffusion coefficient, combined electric field diffusion coefficient, combined temperature diffusion coefficient, and combined pressure diffusion coefficient in SF{sub 6}-Cu mixtures at temperatures up to 30 000 K. These four coefficients describe diffusion due to composition gradients, applied electric fields, temperature gradients, and pressure gradients, respectively. The influence of copper fluoride and sulfide species on the diffusion coefficients is shown to be negligible. The effect of copper proportion and gas pressures on these diffusion coefficients is investigated. It is shown that increasing the proportion of copper generally increases the magnitude of the four diffusion coefficients, except for copper mole fractions of 90% or more. It is further found that increasing the pressure reduces the magnitude of the coefficients, except for the combined temperature diffusion coefficient, and shifts the maximum of all four coefficients towards higher temperatures. The results presented in this paper can be applied to the simulation of high-voltage circuit breaker arcs.
Nonperturbative estimate of the heavy quark momentum diffusion coefficient
NASA Astrophysics Data System (ADS)
Francis, A.; Kaczmarek, O.; Laine, M.; Neuhaus, T.; Ohno, H.
2015-12-01
We estimate the momentum diffusion coefficient of a heavy quark within a pure SU(3) plasma at a temperature of about 1.5 Tc . Large-scale Monte Carlo simulations on a series of lattices extending up to 1923×48 permit us to carry out a continuum extrapolation of the so-called color-electric imaginary-time correlator. The extrapolated correlator is analyzed with the help of theoretically motivated models for the corresponding spectral function. Evidence for a nonzero transport coefficient is found and, incorporating systematic uncertainties reflecting model assumptions, we obtain κ =(1.8 - 3.4 )T3 . This implies that the "drag coefficient," characterizing the time scale at which heavy quarks adjust to hydrodynamic flow, is ηD-1=(1.8 - 3.4 )(Tc/T )2(M /1.5 GeV ) fm /c , where M is the heavy quark kinetic mass. The results apply to bottom and, with somewhat larger systematic uncertainties, to charm quarks.
Code of Federal Regulations, 2010 CFR
2010-01-01
... pipelines. Inasmuch as gaseous diffusion technology uses uranium hexafluoride (UF6), all equipment, pipeline... prepared vacuum seals, with seal feed and seal exhaust connections, for sealing the shaft connecting...
Perrino, C; Catrambone, M; Esposito, G; Lahav, D; Mamane, Y
2009-05-01
A field study aimed to characterize atmospheric pollutants in the gaseous and the particulate phases was conducted during the fall-winter of 2004 and the summer of 2005 in the Ashdod area, Israel. The site is influenced by both anthropogenic sources (power plants, refineries, chemical and metal industries, a cargo port, road traffic) and natural sources (sea-spray and desert dust). The use of diffusion lines--a series of annular diffusion denuders for sampling gaseous compounds followed by a cyclone and a filter pack for determining PM(2.5) composition--allowed a good daily characterization of the main inorganic compounds in both the gaseous (HCl, HNO(3), SO(2), NH(3)) and the particulate phase (Cl(-), NO(3)(-), SO(4)(=), NH(4)(+), and base cations). During the summer campaign two other activities were added: an intensive 3-h sampling period and the determination of PM(2.5) bulk composition. The results were interpreted on the basis of meteorological condition, especially the mixing properties of the lower atmosphere as determined by monitoring the natural radioactivity due to Radon progeny, a good proxy of the atmospheric ability to dilute pollutants. Several pollution episodes were identified and the predominance of different sources was highlighted (sea-spray, desert dust, secondary photochemical pollutants). During the summer period a considerable increase of nitric acid and particulate sulphate was observed. Secondary inorganic pollutants (nitrate, sulphate and ammonium) constituted, on the average, 57% of the fine particle fraction, organic compounds 20%, primary anthropogenic compounds 14%, natural components (sea-spray and crustal elements) 9%. The advantages of the diffusion lines in determining gaseous and particulate N- and S- inorganic compounds are discussed. PMID:18535917
NASA Technical Reports Server (NTRS)
Weinstein, H.; Lavan, Z.
1975-01-01
Analytical investigations of fluid dynamics problems of relevance to the gaseous core nuclear reactor program are presented. The vortex type flow which appears in the nuclear light bulb concept is analyzed along with the fluid flow in the fuel inlet region for the coaxial flow gaseous core nuclear reactor concept. The development of numerical methods for the solution of the Navier-Stokes equations for appropriate geometries is extended to the case of rotating flows and almost completes the gas core program requirements in this area. The investigations demonstrate that the conceptual design of the coaxial flow reactor needs further development.
Not Available
1984-05-01
Air, water, soil, sediments, grass, and groundwater in the vicinity of the Paducah Gaseous Diffusion Plant were continuously or periodically sampled during 1983. Analyses for materials known to be in plant effluents were made to provide effluent control information and to determine compliance with applicable environmental standards. Low sulfur coal is burned in the steam plant to meet Kentucky emission limits for sulfur dioxide. Air analyses for radioactivity indicated concentrations at each offsite sampling station averaged less than 1% of the applicable Radioactivity Concentration Guide. Offsite analyses for fluorides in grass met the Kentucky Air Quality Requirements. All onsite and offsite airborne fluoride samples met the Kentucky one-week and one-month standards for gaseous HF. Soil samples were analyzed for uranium and showed no significant deviation from normal background concentrations. There was no detectable change in chemical, physical, or radioactive characteristics of either the Ohio River or ground water attributable to Paducah Gaseous Diffusion Plant operations. The results of water sample analyses of the Ohio River show the chromium and fluoride concentrations to be in compliance with the requirements of the applicable Kentucky regulations. Algal activity resulted in an increase in pH violations during 1983. 7 references, 7 figures, 26 tables.
Not Available
1985-07-01
Air, water, soil, sediments, grass, and groundwater in the vicinity of the Paducah Gaseous Diffusion Plant were continuously or periodically sampled during 1984. Analyses for materials known to be in plant effluents were made to provide effluent control information and to determine compliance with applicable environmental standards. Low sulfur coal is burned in the steam plant to meet Kentucky emission limits for sulfur dioxide. Air analyses for radioactivity indicated concentrations at each off-site sampling station averaged less than 1% of the DOE Radioactivity Concentration Guide (RCG). Offsite analyses for fluorides in grass met the Kentucky Air Quality Requirements. All onsite and offsite airborne fluoride samples met the Kentucky one-week and one-month standards for gaseous HF. Soil samples were analyzed for uranium and showed no significant deviation from normal background concentrations. There was no detectable change in chemical, physical, or radioactive characteristics of the Ohio River attributable to Paducah Gaseous Diffusion Plant operations. The results of water sample analyses of the Ohio River show the chromium and fluoride concentrations to be in compliance with the requirements of the applicable Kentucky regulations. 7 figs., 26 tabs.
Rodriguez, L.M.; Floyd, L.M.; Carrier, R.F.
1992-09-01
The Portsmouth Gaseous Diffusion Plant (PORTS) is owned by the US Department of Energy (DOE) and managed by Martin Marietta Energy Systems, Inc. As shown in Fig. 1, the plant is located in sparsely populated, rural Pike County, Ohio. PORTS began in 1952 as part of the Atomic Energy Commission`s (AEC) proposed expansion of the gaseous diffusion program in order to increase the production of enriched uranium. The 3,708-acre site is about a half mile east of US Interstate 23 (Fig. 2) and approximately 1 mile east of the Scioto River Valley (Fig. 3). The current layout of the plant is shown on Fig. 4. The principal site process is the separation of uranium isotopes {sup 235}U and {sup 238}U through gaseous diffusion. This uranium enrichment process involves the more rapid diffusion of lighter molecules of UF{sub 6} (uranium hexaflouride) through the barrier walls of a porous tube. The end result is a UF{sub 6} stream that is slightly enriched in the {sup 235}U isotope. The separation process is repeated in a cascade arrangement until the desired concentration is reached. At the request of the PORTS Environmental Safety and Health Division, the Health and Safety Research Division (HASRD), Oak Ridge National Laboratory (ORNL), conducted a radiological survey of the outdoor surface environment of the PORTS site. The surveyed area covered approximately 150 acres of fenced ground consisting of dirt, asphalt, and concrete. The survey was performed between July 1990 and April 1991, and the results reported to PORTS, Health Physics Department. The survey purpose was to determine the extent of radiological contamination and to locate and prioritize areas of concern from both a worker health/safety and an environmental standpoint. Specifically, the objectives of the survey were to assess the areal radioactive status of the site and to analyze surface soil samples for the presence of selected radionuclides. The principal radionuclide of concern is uranium.
Rodriguez, L.M.; Floyd, L.M.; Carrier, R.F.
1992-09-01
The Portsmouth Gaseous Diffusion Plant (PORTS) is owned by the US Department of Energy (DOE) and managed by Martin Marietta Energy Systems, Inc. As shown in Fig. 1, the plant is located in sparsely populated, rural Pike County, Ohio. PORTS began in 1952 as part of the Atomic Energy Commission's (AEC) proposed expansion of the gaseous diffusion program in order to increase the production of enriched uranium. The 3,708-acre site is about a half mile east of US Interstate 23 (Fig. 2) and approximately 1 mile east of the Scioto River Valley (Fig. 3). The current layout of the plant is shown on Fig. 4. The principal site process is the separation of uranium isotopes [sup 235]U and [sup 238]U through gaseous diffusion. This uranium enrichment process involves the more rapid diffusion of lighter molecules of UF[sub 6] (uranium hexaflouride) through the barrier walls of a porous tube. The end result is a UF[sub 6] stream that is slightly enriched in the [sup 235]U isotope. The separation process is repeated in a cascade arrangement until the desired concentration is reached. At the request of the PORTS Environmental Safety and Health Division, the Health and Safety Research Division (HASRD), Oak Ridge National Laboratory (ORNL), conducted a radiological survey of the outdoor surface environment of the PORTS site. The surveyed area covered approximately 150 acres of fenced ground consisting of dirt, asphalt, and concrete. The survey was performed between July 1990 and April 1991, and the results reported to PORTS, Health Physics Department. The survey purpose was to determine the extent of radiological contamination and to locate and prioritize areas of concern from both a worker health/safety and an environmental standpoint. Specifically, the objectives of the survey were to assess the areal radioactive status of the site and to analyze surface soil samples for the presence of selected radionuclides. The principal radionuclide of concern is uranium.
Measurement of diffusion coefficient of propylene glycol in skin tissue
NASA Astrophysics Data System (ADS)
Genin, Vadim D.; Bashkatov, Alexey N.; Genina, Elina A.; Tuchin, Valery V.
2015-03-01
Optical clearing of the rat skin under the action of propylene glycol was studied ex vivo. It was found that collimated transmittance of skin samples increased, whereas weight and thickness of the samples decreased during propylene glycol penetration in skin tissue. A mechanism of the optical clearing under the action of propylene glycol is discussed. Diffusion coefficient of propylene glycol in skin tissue ex vivo has been estimated as (1.35±0.95)×10-7 cm2/s with the taking into account of kinetics of both weight and thickness of skin samples. The presented results can be useful for enhancement of many methods of laser therapy and optical diagnostics of skin diseases and localization of subcutaneous neoplasms.
Diffusion coefficient of hydrogen in a cast gamma titanium aluminide
Sundaram, P.A.; Wessel, E.; Ennis, P.J.; Quadakkers, W.J.; Singheiser, L.
1999-06-04
Gamma titanium aluminides have the potential for high temperature applications because of their high specific strength and specific modulus. Their oxidation resistance is good, especially at intermediate temperatures and with suitable alloying additions, good oxidation resistance can be obtained up to 800 C. One critical area of application is in combustion engines in aero-space vehicles such as hypersonic airplanes and high speed civil transport airplanes. This entails the use of hydrogen as a fuel component and hence the effect of hydrogen on the mechanical properties of gamma titanium aluminides is of significant scientific and technological utility. The purpose of this short investigation is to use an electrochemical method under galvanostatic conditions to determine the diffusion coefficient of hydrogen in a cast gamma titanium aluminide, a typical technical alloy with potential application in gas turbines under creep conditions. This result will be then compared with that obtained by microhardness profiling of electrolytically hydrogen precharged material.
Experimental study of advective-diffusive gaseous CO2 transport through porous media
NASA Astrophysics Data System (ADS)
Basirat, Farzad; Sharma, Prabhakar; Niemi, Auli; Fagerlund, Fritjof
2014-05-01
Leakage of gaseous CO2 into the shallow subsurface system is one of the main concerns associated with geologic storage resources. A better understanding of CO2 leakage in the shallow subsurface plays an important role for developing leakage monitoring programs. CO2 may reach the unsaturated zone by different leak mechanisms such as exsolution from CO2 supersaturated water and continuous bubbling or gas flow along a leakage path. In the unsaturated zone, the CO2 is heavier than air and may accumulate below the ground surface and move laterally. We developed a small-scale experiment setup to study the possible gaseous CO2 transport mechanisms with different controlled conditions. In this study, the experiment setup was applied to measure CO2 distributions in time and space through homogenous dry sand in which the CO2 concentrations through the domain were measured by sensitive gas sensors. The preliminary analysis of the result suggests that the transport and distribution of gaseous CO2 is spatially and temporally sensitive for the selected experimental conditions of gas flow rate and porous media. To better understand the advection and diffusion processes through the unsaturated zone, the experimental results are coupled with the dusty gas model (DGM) of Mason et al. (1967). The dusty gas model's constitutive relationships are integrated into a numerical model for multicomponent gas mixture flow and transport in porous media. The DGM considers interactions between all gaseous species and Knudsen diffusion which is important in fine grained soils. Results from the applied model were consistent with the experimental breakthrough curves obtained in this study.
Measurement of the diffusion coefficient of sulfur hexafluoride in water
King. D.B.; Saltzman, E.S.
1995-04-15
Sulfur hexafluoride has been widely used in field studies and laboratory experiments to develop a relationship between gas transfer and wind speed. The interpretation of the data from such studies requires the diffusion coefficient of SF{sub 6} (D{sub SF6}), which has not previously been measured. In this study, D{sub SF6} has been determined in pure water and in 35%NaCl over a temperature range of 5-25{degrees}C. The measurements were made using a continuous-flow diffusion cell where SF{sub 6} flows beneath an agar gel membrane while helium flows above the gel. The experimental data for pure water yielded the following equation: D{sub SF6}=0.029 exp ({minus}19.3/RT, where R is the gas constant and T is temperature in kelvins). Measurements of D{sub SF6} in 35% NaCl were not significantly different from the pure water values. On the basis of this data, the authors estimate the Schmidt numbers for seawater over the temperature range 5-25{degrees}C to be Sc=3016.1{minus}172.00t+4.4996t{sup 2}{minus}0.047965t{sup 3}, where t is temperature in degrees Celsius. 31 refs., 3 figs., 2 tabs.
Universal function for the diffusion coefficient of DNA fragment
NASA Astrophysics Data System (ADS)
Mercier, Jean-Francois
2005-03-01
The separation of DNA fragments by (gel or capillary) electrophoresis has been studied extensively. To characterize the separation achieved by such systems, one needs to understand the impact (and their dependency upon the experimental quantities) of two physical parameters: the electrophoresis mobility μ and the diffusion coefficient D. Three different regimes have been shown to exist for both μ and D: the Ogston regime, the reptation regime and the reptation-with orientation regime (note that separation is only possible for the first two regimes). Both μ and D are well described by theory for all three regimes. Unfortunatly this results in disjointed scaling regimes and no theory-based general equations can apply to all regimes. Recently, an empirical formula has been proposed that adequately fit the mobility μ of dsDNA fragments across all three regimes and is compatible with accepted theories. In this work we propose a similar formula for the diffusion coefficent D. With those two formulas, one could optimize any separation system quite easily for a wide range of DNA molecular sizes.
Sykora, D.W.; Davis, J.J.
1993-08-01
The Paducah Gaseous Diffusion Plant (PGDP), owned by the US Department of Energy (DOE) and operated under contract by Martin Marietta Energy systems, Inc., is located southwest of Paducah, Kentucky. An aerial photograph and an oblique sketch of the plant are shown in Figures 1 and 2, respectively. The fenced portion of the plant consists of 748 acres. This plant was constructed in the 1950`s and is one of only two gaseous diffusion plants in operation in the United States; the other is located near Portsmouth, Ohio. The facilities at PGDP are currently being evaluated for safety in response to natural seismic hazards. Design and evaluation guidelines to evaluate the effects of earthquakes and other natural hazards on DOE facilities follow probabilistic hazard models that have been outlined by Kennedy et al. (1990). Criteria also established by Kennedy et al. (1990) classify diffusion plants as ``moderate hazard`` facilities. The US Army Engineer Waterways Experiment Station (WES) was tasked to calculate the site response using site-specific design earthquake records developed by others and the results of previous geotechnical investigations. In all, six earthquake records at three hazard levels and four individual and one average soil columns were used.
Bundy, R.D.; Munday, E.B.
1991-01-01
Construction of the gaseous diffusion plants (GDPs) was begun during World War 2 to produce enriched uranium for defense purposes. These plants, which utilized UF{sub 6} gas, were used primarily for this purpose through 1964. From 1959 through 1968, production shifted primarily to uranium enrichment to supply the nuclear power industry. Additional UF{sub 6}-handling facilities were built in feed and fuel-processing plants associated with the uranium enrichment process. Two of the five process buildings at Oak ridge were shut down in 1964. Uranium enrichment activities at Oak Ridge were discontinued altogether in 1985. In 1987, the Department of Energy (DOE) decided to proceed with a permanent shutdown of the Oak Ridge Gaseous Diffusion Plant (ORGDP). DOE intends to begin decommissioning and decontamination (D D) of ORGDP early in the next century. The remaining two GDPs are expected to be shut down during the next 10 to 40 years and will also require D D, as will the other UF{sub 6}-handling facilities. This paper presents an investigation of gas- phase decontamination of internally radioactively contaminated gaseous diffusion process equipment and piping using powerful fluorinating reagents that convert nonvolatile uranium compounds to volatile UF{sub 6}. These reagents include ClF{sub 3}, F{sub 2}, and other compounds. The scope of D D at the GDPs, previous work of gas-phase decontamination, four concepts for using gas-phase decontamination, plans for further study of gas-phase decontamination, and the current status of this work are discussed. 13 refs., 15 figs.
Socolof, M.L.; Saylor, R.E.; McCold, L.N.
1994-06-01
The US Department of Energy (DOE) formerly operated two gaseous diffusion plants (GDPs) for enriching uranium and maintained a third shutdown GDP. These plants maintain a large inventory of dichlorotetrafluorethane (CFC-114), a cholorofluorocarbon (CFC), as a coolant. The paper evaluates the global impacts of four alternatives to modify GDP coolant system operations for a three-year period beginning in 1996. Interim modification of GDP coolant system operations has the potential to reduce stratospheric ozone depletion from GDP coolant releases while a permanent solution is studied.
1995-10-01
The US Department of Energy (DOE), Office of Waste Management, proposes to construct and operate a solid waste landfill within the boundary of the Portsmouth Gaseous Diffusion Plant (PORTS), Piketon, Ohio. The purpose of the proposed action is to provide PORTS with additional landfill capacity for non-hazardous and asbestos wastes. The proposed action is needed to support continued operation of PORTS, which generates non-hazardous wastes on a daily basis and asbestos wastes intermittently. Three alternatives are evaluated in this environmental assessment (EA): the proposed action (construction and operation of the X-737 landfill), no-action, and offsite shipment of industrial solid wastes for disposal.
Fire protection review revisit No. 2, Paducah Gaseous Diffusion Plant, Paducah, Kentucky
Dobson, P.H.; Keller, D.R.; Treece, S.D.
1990-02-01
A fire protection survey was conducted for the Department of Energy at the Paducah Gaseous Diffusion Plant, Paducah, Kentucky, from October 30--November 4, November 6--10, and December 4--8, 1989. The purpose of the survey was to review the facility fire protection program and to make recommendations. Surveys of other facilities resulted in a classification system for buildings which provide an indication of the importance of the building to the fulfillment of the mission of the facility. Recommendations in this report reflect to some degree the relative importance of the facility and the time to restore it to useful condition in the event a loss were to occur.
Divine, Craig E; McCray, John E
2004-03-15
Passive diffusion (PD) samplers offer several potential technical and cost-related advantages, particularly for measuring dissolved gases and volatile organic compounds (VOCs) in groundwater at contaminated sites. Sampler equilibration is a diffusion-type process; therefore, equilibration time is dependent on sampler dimensions, membrane thickness, and the temperature-dependent membrane diffusion coefficient (Dm) for the analyte of interest. Diffusion coefficients for low-density polyethylene membranes were measured for He, Ne, H2, O2, and N2 in laboratory experiments and ranged from 1.1 to 1.9 x 10(-7) cm2 sec(-1) (21 degrees C). Additionally, Dm values for several commonly occurring VOCs were estimated from empirical experimental data previously presented by others (Vroblesky, D. A.; Campbell, T. R. Adv. Environ. Res. 2001, 5(1), 1.), and estimated values ranged from 1.7 to 4.4 x 10(-7) cm2 sec(-1) (21 degrees C). On the basis of these Dm ranges, PD sampler equilibration time is predicted for various sampler dimensions, including dimensions consistent with simple constructed samplers used in this study and commercially available samplers. Additionally, a numerical model is presented that can be used to evaluate PD sampler concentration "lag time" for conditions in which in situ concentrations are temporally variable. The model adequately predicted lag time for laboratory experiments and is used to show that data obtained from appropriately designed PD samplers represent near-instantaneous measurement of in situ concentrations for most field conditions. PMID:15074699
The solid-phase diffusion coefficient (Dm) and material-air partition coefficient (Kma) are key parameters for characterizing the sources and transport of semivolatile organic compounds (SVOCs) in the indoor environment. In this work, a new experimental method was developed to es...
Inner zone electron radial diffusion coefficients - An update with Van Allen Probes MagEIS data
NASA Astrophysics Data System (ADS)
O'Brien, Paul; Fennell, Joseph; Guild, Timothy; Mazur, Joseph; Claudepierre, Seth; Clemmons, James; Turner, Drew; Blake, Bernard; Roeder, James
2016-07-01
Using MagEIS data from NASA's recent Van Allen Probes mission, we estimate the quiet-time radial diffusion coefficients for electrons in the inner radiation belt and slot, for energies up to ~700 keV. We provide observational evidence that energy diffusion is negligible. The main dynamic processes, then, are radial diffusion and elastic pitch angle scattering. We use a coordinate system in which these two modes of diffusion are separable. Then we integrate over pitch angle to obtain a field line content whose dynamics consist of radial diffusion and loss to the atmosphere. We estimate the loss timescale from periods of exponential decay in the time series. We then estimate the radial diffusion coefficient from the temporal and radial variation of the field line content. We show that our diffusion coefficients agree well with previously determined values. Our coefficients are consistent with diffusion by electrostatic impulses, whereas outer zone radial diffusion is thought to be dominated by electromagnetic fluctuations.
The diagnostic value of biexponential apparent diffusion coefficients in myopathy.
Ran, Jun; Liu, Yao; Sun, Dong; Morelli, John; Zhang, Ping; Wu, Gang; Sheng, Yuda; Xie, Ruyi; Zhang, Xiaoli; Li, Xiaoming
2016-07-01
To investigate the performance of a biexponential signal decay model using DWI in myopathies and to differentiate Polymyositis (PM)/Dermatomyositis (DM), Glycogen Storage Diseases (GSDs) and Muscular Dystrophies (MDs) utilizing diffusion-weighted imaging. 11 healthy volunteers (control group) and 46 patients with myopathy were enrolled in the retrospective study. 27 of 46 patients had PM/DM, 7 patients GSDs and 12 patients MDs. After conventional MR sequences, diffusion weighted imaging with a b-factor ranging from 0 to 1200 s/mm(2) was performed on both thighs. The intra-muscular signal-to-noise ratios (SNRs) on multiple-b DWI images were measured for 7 different muscles and compared among the different groups. The median T2 signal intensity and biexponential apparent diffusion coefficients (ADC), including standard ADC, fast ADC, and slow ADC values, were compared among the different groups. The intra-muscular SNRs were statistically significantly different depending on the b value, and also found among the 4 groups (p < 0.05). The median T2 signal intensity of the normal muscles in control group was statistically significantly lower than that of edematous muscles in the PM/DM, GSDs and MDs groups (p = 0.000), while there were no statistically significant differences among the PM/DM, GSDs, and MDs groups (p > 0.05). The median standard ADC value of the edematous muscles in GSDs was statistically significantly lower than that of normal muscles in the control group (p = 0.000) and the median ADC value of the edematous muscles in PM/DM patients was statistically significantly greater than that of the GSDs (p = 0.000) and MDs groups (p = 0.005). The median slow ADC value of the edematous muscles in MDs patients and PM/DM patients was statistically significantly greater than that of GSDs patients (p < 0.05). Intra-muscular SNR decay curves and biexponential ADC parameters are useful in distinguishing among PM/DM, GSDs, and MDs. PMID:27142711
Engle, Mark A.; Olea, Ricardo A.; O'Keefe, Jennifer M. K.; Hower, James C.; Geboy, Nicholas J.
2013-01-01
Coal fires occur in nature spontaneously, contribute to increases in greenhouse gases, and emit atmospheric toxicants. Increasing interest in quantifying coal fire emissions has resulted in the adaptation and development of specialized approaches and adoption of numerical modeling techniques. Overview of these methods for direct estimation of diffuse gas emissions from coal fires is presented in this paper. Here we take advantage of stochastic Gaussian simulation to interpolate CO2 fluxes measured using a dynamic closed chamber at the Ruth Mullins coal fire in Perry County, Kentucky. This approach allows for preparing a map of diffuse gas emissions, one of the two primary ways that gases emanate from coal fires, and establishing the reliability of the study both locally and for the entire fire. Future research directions include continuous and automated sampling to improve quantification of gaseous coal fire emissions.
On the structure of gaseous confined laminar diffusion flames: Numerical investigation
NASA Technical Reports Server (NTRS)
Mawid, M. A.; Bulzan, D. L.; Aggarwal, S. K.
1993-01-01
The structure and characteristics of gaseous confined laminar diffusion flames are investigated by numerically solving the time-dependent two-dimensional axisymmetric conservation equations. The numerical model accounts for the important chemical and physical processes involved, including axial diffusion, viscous effects, radial convection, and finite-rate chemistry. The numerical results clearly show that the flame has a finite thickness and leakage of fuel vapor into the flame zone is possible. The effect of heat release is found to induce some radial flow. Predicted flame shape and dimensions are compared to the classical Burke-Schumann flame. The numerically calculated flame is observed to be about 15 percent taller and 5 percent narrower than that of the Burke-Schumann solution under the same conditions.
High silicon self-diffusion coefficient in dry forsterite
NASA Astrophysics Data System (ADS)
Katsura, T.; Fei, H.; Hegoda, C.; Yamazaki, D.; Wiedenbeck, M.; Yurimoto, H.; Shcheka, S.
2012-12-01
Plastic deformation of mantle minerals is believed to be controlled by self-diffusion of the slowest species, which is silicon in silicate minerals. Olivine is the main constituent of upper mantle. Therefore, silicon self-diffusion coefficient (DSi) in olivine provides the basic information of upper mantle rheology. Dohmen et al. [1] and Jaoul et al. [2] measured the DSi at ambient pressure under dry conditions in natural olivine and iron-free forsterite, respectively. However, their results were ~2-3 orders of magnitude lower than that estimated from deformation experiments [3]. In this study, we revisited DSi in forsterite and resolved this discrepancy [4]. Forsterite single crystals were polished in colloidal silica solution, deposited with 300-500 nm of 29Si enriched Mg2SiO4 films, covered by 100 nm of ZrO2 films, and annealed at 1600-1800 K from ambient pressure up to 13 GPa using an ambient pressure furnace and multi-anvil apparatus. The surface roughness after diffusion were reduced to <50 nm by polishing again in colloidal silica solution. Diffusion profiles were obtained by SIMS. Water contents in the samples were <1 μg/g by FT-IR [4]. logDSi were determined to be -19.7±0.4 and -18.1±0.3 log[m2/s] under ambient pressure at 1600 and 1800 K, respectively. These values were 2.4 orders of magnitude higher than that determined by Jaoul et al. [2] in forsterite, as well as that reprted by Dohmen et al. [1] in natural olivine. Their low DSi could be obtained due to the bad contact of the coated films with the substrate. Our results well explain the high dislocation climb rates in deformation experiments [4]. We also determined a small negative pressure dependence of DSi with an activation volume of 1.7±0.4 cm3/mol, and an activation energy of ~410 kJ/mol. Calibratied to the same temperature, the nearly linear relationship of DSi against pressure in dry forsterite in this study, iron and water bearing wadsleyite and ringwoodite by Shimojuku et al. [5
A model for the diffuse attenuation coefficient of downwelling irradiance
NASA Astrophysics Data System (ADS)
Lee, Zhong-Ping; Du, Ke-Ping; Arnone, Robert
2005-02-01
The diffuse attenuation coefficient for downwelling irradiance (Kd) is an important parameter for ocean studies. For the vast ocean the only feasible means to get fine-scale measurements of Kd is by ocean color remote sensing. At present, values of Kd from remote sensing are estimated using empirical algorithms. Such an approach is insufficient to provide an understanding regarding the variation of Kd and contains large uncertainties in the derived values. In this study a semianalytical model for Kd is developed based on the radiative transfer equation, with values of the model parameters derived from Hydrolight simulations using the averaged particle phase function. The model is further tested with data simulated using significantly different particle phase functions, and the modeled Kd are found matching Hydrolight Kd very well (˜2% average error and ˜12% maximum error). Such a model provides an improved interpretation about the variation of Kd and a basis to more accurately determine Kd (especially using data from remote sensing).
On the Origin of Quantum Diffusion Coefficient and Quantum Potential
NASA Astrophysics Data System (ADS)
Gupta, Aseem
2016-03-01
Synchronizability of space and time experiences between different inhabitants of a spacetime is abstracted as a fundamental premise of Classical physics. Absence thereof i.e. desynchronization between space and time experiences of a system under study and the observer is then studied for a single dimension single particle system. Desynchronization fundamentally makes probability concepts enter physics ab-initio and not as secondary tools to deal with situations wherein incomplete information in situation following perfectly deterministic dynamics demands its introduction. Desynchronization model based on Poisson distribution of events vis-à-vis an observer, leads to expectation of particle's motion as a Brownian motion deriving Nelson's quantum diffusion coefficient naturally, without needing to postulate it. This model also incorporates physical effects akin to those of Bohm's Quantum Potential, again without needing any sub-quantum medium. Schrodinger's equation is shown to be derivable incorporating desynchronization only of space while Quantum Field Theory is shown to model desynchronization of time as well. Fundamental suggestion of the study is that it is desynchronization that is at the root of quantum phenomena rather than sub-micro scales of spacetime. Absence of possibility of synchronization between system's space and time and those of observer is studied. Mathematical modeling of desynchronized evolution explains some intriguing aspects of Quantum Mechanical theory.
The Blend Down Monitoring System Demonstration at the Paducah Gaseous Diffusion Plant
Benton, J.; Close, D.; Johnson, W., Jr.; Kerr, P.; March-Leuba, J.; Mastal, E.; Moss, C.; Powell, D.; Sumner, J.; Uckan, T.; Vines, R.; Wright, P.D.
1999-07-25
Agreements between the governments of the US and the Russian Federation for the US purchase of low enriched uranium (LEU) derived from highly enriched uranium (HEU) from dismantled Russian nuclear weapons calls for the establishment of transparency measures to provide confidence that nuclear nonproliferation goals are being met. To meet these transparency goals, the agreements call for the installation of nonintrusive US instruments to monitor the down blending of HEU to LEU. The Blend Down Monitoring System (BDMS) has been jointly developed by the Los Alamos National Laboratory (LANL) and the Oak Ridge National Laboratory (ORNL) to continuously monitor {sup 235}U enrichments and mass flow rates at Russian blending facilities. Prior to its installation in Russian facilities, the BDMS was installed and operated in a UF{sub 6} flow loop in the Paducah Gaseous Diffusion Plant simulating flow and enrichment conditions expected in a typical down-blending facility. A Russian delegation to the US witnessed the equipment demonstration in June, 1998. To conduct the demonstration in the Paducah Gaseous Diffusion Plant (PGDP), the BDMS was required to meet stringent Nuclear Regulatory Commission licensing, safety and operational requirements. The Paducah demonstration was an important milestone in achieving the operational certification for the BDMS use in Russian facilities.
1995-09-01
The Background Soils Project for the Paducah Gaseous Diffusion Plant (BSPP) will determine the background concentration levels of selected naturally occurring metals, other inorganics, and radionuclides in soils from uncontaminated areas in proximity to the Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky. The data will be used for comparison with characterization and compliance data for soils, with significant differences being indicative of contamination. All data collected as part of this project will be in addition to other background databases established for the PGDP. The BSPP will address the variability of surface and near-surface concentration levels with respect to (1) soil taxonomical types (series) and (2) soil sampling depths within a specific soil profile. The BSPP will also address the variability of concentration levels in deeper geologic formations by collecting samples of geologic materials. The BSPP will establish a database, with recommendations on how to use the data for contaminated site assessment, and provide data to estimate the potential human and health and ecological risk associated with background level concentrations of potentially hazardous constituents. BSPP data will be used or applied as follows.
Not Available
1991-06-01
Airborne multispectral scanner data of the Paducah Gaseous Diffusion Plant (PGDP) and surrounding area were acquired during late spring 1990. This survey was conducted by the Remote Sensing Laboratory (RSL) which is operated by EG G Energy Measurements (EG G/EM) for the US Department of Energy (DOE) Nevada Operations Office. It was requested by the US Department of Energy (DOE) Environmental Audit Team which was reviewing environmental conditions at the facility. The objectives of this survey were to: (1) Acquire 12-channel, multispectral scanner data of the PGDP from an altitude of 3000 feet above ground level (AGL); (2) Acquire predawn, digital thermal infrared (TIR) data of the site from the same altitude; (3) Collect color and color-infrared (CIR) aerial photographs over the facilities; and (4) Illustrate how the analyses of these data could benefit environmental monitoring at the PGDP. This report summarizes the two multispectral scanner and aerial photographic missions at the Paducah Gaseous Diffusion Plant. Selected examples of the multispectral data are presented to illustrate its potential for aiding environmental management at the site. 4 refs., 1 fig., 2 tabs.
Coordinate-dependent diffusion coefficients: Decay rate in open quantum systems
Sargsyan, V. V.; Palchikov, Yu. V.; Antonenko, N. V.; Kanokov, Z.; Adamian, G. G.
2007-06-15
Based on a master equation for the reduced density matrix of an open quantum collective system, the influence of coordinate-dependent microscopical diffusion coefficients on the decay rate from a metastable state is treated. For various frictions and temperatures larger than a crossover temperature, the quasistationary decay rates obtained with the coordinate-dependent microscopical set of diffusion coefficients are compared with those obtained with the coordinate-independent microscopical set of diffusion coefficients and coordinate-independent and -dependent phenomenological sets of diffusion coefficients. Neglecting the coordinate dependence of diffusion coefficients, one can strongly overestimate or underestimate the decay rate at low temperature. The coordinate-dependent phenomenological diffusion coefficient in momentum are shown to be suitable for applications.
NITRIC ACID-AIR DIFFUSION COEFFICIENT: EXPERIMENTAL DETERMINATION
Trace gaseous HNO3 in air is removed in a laminar flow nylon tube. The HNO3 deposition pattern was obtained by sectioning the tube, extracting with an aqueous solution, and measuring the concentration by ion chromatography. Mass transport analysis of the deposition pattern demons...
Miller, D.G.; Vitagliano, V.; Sartorio, R.
1986-04-10
Some interesting aspects of multicomponent diffusion in liquids are discussed. These include the existence of a negative main term diffusion coefficient; the utility of taking different components as the solvent; the change-of-solvent transformation for Fick's law coefficients and Onsager coefficients; the validity of the Onsager reciprocal relations on changing solvents; and the calculation of partial molar volumes from diffusion data. Previous work is surveyed on the irreversible thermodynamic basis for macroscopic diffusion; the importance of reference frames and transformations among them; and second law conditions on the volume-fixed diffusion coefficient matrix. Certain diffusion descriptions in other reference frames do not preserve these second law conditions. 78 references, 5 tables.
Spin Diffusion Coefficient of A1-PHASE of Superfluid 3He at Low Temperatures
NASA Astrophysics Data System (ADS)
Afzali, R.; Pashaee, F.
The spin diffusion coefficient tensor of the A1-phase of superfluid 3He at low temperatures and melting pressure is calculated using the Boltzmann equation approach and Pfitzner procedure. Then considering Bogoliubov-normal interaction, we show that the total spin diffusion is proportional to 1/T2, the spin diffusion coefficient of superfluid component D\\uparrowxzxz is proportional to T-2, and the spin diffusion coefficient of super-fluid component D\\uparrowxxxx (=D\\uarrowxyxy) is independent of temperature. Furthermore, it is seen that superfluid components play an important role in spin diffusion of the A1-phase.
Shalchi, A.
2013-09-01
We explore perpendicular diffusion based on the unified nonlinear transport theory. We derive simple analytical forms for the perpendicular mean free path and investigate the influence of different model spectra. We show that for cases where the field line random walk is normal diffusive, the perpendicular diffusion coefficient consists of only two transport regimes. Details of the spectral shape are less important, especially those of the inertial range. Only the macroscopic properties of the turbulence spectrum control the perpendicular diffusion coefficient. Simple formulae for the perpendicular diffusion coefficient are derived which can easily be implemented in solar modulation or shock acceleration codes.
Sykora, D.W.; Yule, D.E.
1996-04-01
This report documents a reassessment of liquefaction potential and estimation of earthquake-induced settlements for the U.S. Department of Energy (DOE), Paducah Gaseous Diffusion Plant (PGDP), located southwest of Paducah, KY. The U.S. Army Engineer Waterways Experiment Station (WES) was authorized to conduct this study from FY91 to FY94 by the DOE, Oak Ridge Operations (ORO), Oak Ridge, TN, through Inter- Agency Agreement (IAG) No. DE-AI05-91OR21971. The study was conducted under the Gaseous Diffusion Plant Safety Analysis Report (GDP SAR) Program.
NASA Astrophysics Data System (ADS)
Karatas, Ahmet Emre
High-pressure soot formation and flame stability characteristics were studied experimentally in laminar diffusion flames. For the former, radially resolved soot volume fraction and temperature profiles were measured in axisymmetric co-flow laminar diffusion flames of pre-vaporized n-heptane-air, undiluted ethylene-air, and nitrogen and carbon dioxide diluted ethylene-air at elevated pressures. Abel inversion was used to re-construct radially resolved data from the line-of-sight spectral soot emission measurements. For the latter, flame extinction strain rate was measured in counterflow laminar diffusion flames of C1-4 alcohols and hydrocarbon fuels of n-heptane, n-octane, iso-octane, toluene, Jet-A, and biodiesel. The luminous flame height, as marked by visible soot radiation, of the nitrogen- and helium-diluted n-heptane and nitrogen- and carbon dioxide-diluted ethylene flames stayed constant at all pressures. In pure ethylene flames, flame heights initially increased with pressure, but changed little above 5 atm. The maximum soot yield as a function of pressure in nitrogen-diluted n-heptane diffusion flames indicate that n-heptane flames are slightly more sensitive to pressure than gaseous alkane hydrocarbon flames at least up to 7 atm. Ethylene's maximum soot volume fractions were much higher than those of ethane and n-heptane diluted with nitrogen (fuel to nitrogen mass flow ratio is about 0.5). Pressure dependence of the peak carbon conversion to soot, defined as the percentage of fuel's carbon content converted to soot, was assessed and compared to previous measurements with other gaseous fuels. Maximum soot volume fractions were consistently lower in carbon dioxide-diluted flames between 5 and 15 atm but approached similar values to those in nitrogen-diluted flames at 20 atm. This observation implies that the chemical soot suppression effect of carbon dioxide, previously demonstrated at atmospheric pressure, is also present at elevated pressures up to 15 atm
Development of NF3 Deposit Removal Technology for the Portsmouth Gaseous Diffusion Plant
Scheele, R.D.; McNamara, B.K.; Rapko, B.M.; Edwards, M.K.; Kozelisky, A.E.; Daniel, R.C.; McSweeney, T.I.; Maharas, S.J.; Weaver, P.J.; Iwamasa, K.J.; Kefgen, R.B.
2006-07-01
This paper summarizes the Battelle, Stoller, and WASTREN (BSW) team's efforts, to date, in support of the United States Department of Energy's plans to remove uranium and technetium deposits before decommissioning the Portsmouth Gaseous Diffusion Plant. The BSW team investigated nitrogen trifluoride (NF{sub 3}) as a safer yet effective alternative gaseous treatment to the chlorine trifluoride (ClF{sub 3})-elemental fluorine (F{sub 2}) treatment currently used to remove uranium and technetium deposits from the uranium enrichment cascade. Both ClF{sub 3} and F{sub 2} are highly reactive, toxic, and hazardous gases, while NF{sub 3}, although toxic [1], is no more harmful than moth balls [2]. BSW's laboratory thermo-analytical and laboratory-scale prototype studies with NF{sub 3} established that thermal NF{sub 3} can effectively remove likely and potential uranium (UO{sub 2}F{sub 2} and UF{sub 4}) and technetium deposits (a surrogate deposit material, TcO{sub 2}, and pertechnetates) by conversion to volatile compounds. Our engineering evaluations suggest that NF{sub 3}'s effectiveness could be enhanced by combining with a lesser concentration of ClF{sub 3}. BSW's and other's studies indicate compatibility with Portsmouth materials of construction (aluminum, copper, and nickel). (authors)
Not Available
1986-05-01
Air, water, soil, sediments, grass, and groundwater in the vicinity of the Paducah Gaseous Diffusion Plant were continuously or periodically sampled during 1985. Analyses for materials known to be in plant effluents were made to provide effluent control information and to determine compliance with applicable environmental standards. Low sulfur coal is burned in the steam plant to meet Kentucky emission limits for sulfur dioxide. Air analyses for radioactivity indicated concentrations at each offsite sampling station continue to remain at low levels as indicated by calculations of potential radiation dose to the public. Off-site analyses for fluorides in grass met the Kentucky Air Quality Requirements. All on-site and off-site airborne fluoride samples met the Kentucky one-week and one-month standards for gaseous HF. Soil samples were analyzed for uranium and showed no significant deviation from normal background concentrations. The results of water sample analyses of the Ohio River show the chromium and fluoride concentrations to be in compliance with the requirements of the applicable Kentucky regulations.
A probabilistic safety analysis of UF{sub 6} handling at the Portsmouth Gaseous Diffusion Plant
Boyd, G.J.; Lewis, S.R.; Summitt, R.L.
1991-12-31
A probabilistic safety study of UF{sub 6} handling activities at the Portsmouth Gaseous Diffusion Plant has recently been completed. The analysis provides a unique perspective on the safety of UF{sub 6} handling activities. The estimated release frequencies provide an understanding of current risks, and the examination of individual contributors yields a ranking of important plant features and operations. Aside from the probabilistic results, however, there is an even more important benefit derived from a systematic modeling of all operations. The integrated approach employed in the analysis allows the interrelationships among the equipment and the required operations to be explored in depth. This paper summarizes the methods used in the study and provides an overview of some of the technical insights that were obtained. Specific areas of possible improvement in operations are described.
Kszos, L.A.; Hinzman, R.L.; Peterson, M.J.; Ryon, M.G.; Smith, J.G.; Southworth, G.R.
1995-06-01
On September 24, 1987, the Commonwealth of Kentucky Natural Resources and Environmental Protection Cabinet issued an Agreed Order that required the development of a Biological Monitoring Program (BMP) for the Paducah Gaseous Diffusion Plant (PGDP). The goals of BMP are to demonstrate that the effluent limitations established for PGDP protect and maintain the use of Little Bayou and Big Bayou creeks for growth and propagation of fish and other aquatic life, characterize potential health and environmental impacts, document the effects of pollution abatement facilities on stream biota, and recommend any program improvements that would increase effluent treatability. The BMP for PGDP consists of three major tasks: effluent and ambient toxicity monitoring, bioaccumulation studies, and ecological surveys of stream communities (i.e., benthic macroinvertebrates and fish). This report includes ESD activities occurring from December 1992 to December 1993, although activities conducted outside this time period are included as appropriate.
Kszos, L.A.
1994-03-01
On September 23, 1987, the Commonwealth of Kentucky Natural Resources and Environmental Protection Cabinet issued an Agreed Order that required the development of a Biological Monitoring Program (BMP) for the Paducah Gaseous Diffusion Plant (PGDP). Beginning in fall 1991, the Environmental Sciences Division (ESD) at Oak Ridge National Lab (ORNL) added data collection and report preparation to its responsibilities for the PGDP BMP. The BMP has been continued because it has proven to be extremely valuable in identifying those effluents with the potential for adversely affecting instream fauna, assessing the ecological health of receiving streams, guiding plans for remediation, and protecting human health. In September 1992, a renewed permit was issued which requires toxicity monitoring of continuous and intermittent outfalls on a quarterly basis. The BMP for PGDP consists of three major tasks: (1) effluent and ambient toxicity monitoring, (2) bioaccumulation studies, and (3) ecological surveys of stream communities. This report includes ESD/ORNL activities occurring from December 1990 to November 1992.
Not Available
1991-09-25
The Portsmouth Gaseous Diffusion Plant Security and Police Operations Department is responsible for protecting the US Department of Energy interests at the Portsmouth Plant from theft, sabotage, and other hostile acts that may adversely affect national security, the public health and safety, or property at the Department of Energy facility. This audit's purpose was to evaluate Martin Marietta Energy Systems, Inc.'s staff management at the Portsmouth Plant Security Department. The Portsmouth Plant Security Department could reduce operating cost up to an estimated $4.4 million over 5 years by: (1) Eliminating up to 14 unnecessary staff positions, and (2) reducing the length of relief breaks. These economies could be realized through implementing written operating procedures and negotiating removal of certain labor union restrictions. 2 tabs.
Regional flood hazard assessment of the Paducah and Portsmouth Gaseous Diffusion Plants
Johnson, R.O.; Wang, J.C.; Lee, D.W.
1991-01-01
Regional flood-hazard assessments performed for the Paducah and Portsmouth Gaseous Diffusion Plants are reviewed, compared, and contrasted to determine the relationship of probable maximum flood methodology with respect to US Department of Energy design and evaluation guidelines. The Paducah assessment was carried out using probable maximum flood methodology, while the Portsmouth assessment utilized probabilistic techniques. Results indicated that regional flooding along nearby rivers would not inundate either plant, and that the guidelines were satisfied. A comparison of results indicated that the probable maximum flood recurrence interval associated with the Paducah assessment exceeded the 10,000 years depending on the choice of the probabilistic model used to perform the assessment. It was concluded, based on an analysis of two data points, that smaller watersheds driven by single event storms could be assessed using probabilistic techniques, while probable maximum flood methodology could be applied to larger drainage basins flooded by storm sequences. 32 refs., 3 figs.
Portsmouth Gaseous Diffusion Plant Annual Site Environmental Report summary for 1993
Not Available
1994-11-01
This report contains summaries of the environmental programs at Paducah Gaseous Diffusion Plant, environmental monitoring and the results, and the impact of operations on the environment and the public for 1993. The environmental monitoring program at Paducah includes effluent monitoring and environmental surveillance. Effluent monitoring is measurement of releases as they occur. Contaminants are released through either airborne emissions or liquids discharged from the plant. These releases occur as part of normal site operations, such as cooling water discharged from the uranium enrichment cascade operations or airborne releases from ventilation systems. In the event of system failure, this monitoring provides timely warning so that corrective action can be taken before releases reach an unsafe level. Environmental surveillance tracks the dispersion of materials into the environment after they have been released. This involves the collection of samples from various media, such as water, soil, vegetation, and food crops, and the analysis of these samples for certain radionuclides, chemicals, and metals.
Paducah Gaseous Diffusion Plant Annual Site Environmental Report summary for 1993
Not Available
1994-11-01
This report contains summaries of the environmental programs at Paducah Gaseous Diffusion Plant, environmental monitoring and the results, and the impact of operations on the environment and the public for 1993. The environmental monitoring program at Paducah includes effluent monitoring and environmental surveillance. Effluent monitoring is measurement of releases as they occur. Contaminants are released through either airborne emissions or liquids discharged from the plant. These releases occur as part of normal site operations, such as cooling water discharged from the uranium enrichment cascade operations or airborne releases from ventilation systems. In the event of system failure, this monitoring provides timely warning so that corrective action can be taken before releases reach an unsafe level. Environmental surveillance tracks the dispersion of materials into the environment after they have been released. This involves the collection of samples from various media, such as water, soil, vegetation, and food crops, and the analysis of these samples for certain radionuclides, chemicals, and metals.
D`Aquila, D.M.; Holliday, R.T.; Dean, J.C.
1996-12-31
The Energy Policy Act of 1992 created the United States Enrichment Corporation (USEC) on July 1, 1993. The USEC is a government-owned business that leases those Gaseous Diffusion Plant (GDP) facilities at the Portsmouth, Ohio, and Paducah, Kentucky, sites from the U.S. Department of Energy (DOE) that are required for enriching uranium. Lockheed Martin Utility Services is the operating contractor for the USEC-leased facilities. The DOE has retained use of, and regulation over, some facilities and areas at the Portsmouth and Paducah sites for managing legacy wastes and environmental restoration activities. The USEC is regulated by the DOE, but is currently changing to regulation under the U.S. Nuclear Regulatory Commission (NRC). The USEC is also preparing for privatization of the uranium enrichment enterprise. These changes have significantly affected the nuclear criticality safety (NCS) programs at the sites.
Johnson, R.O.; Wang, J.C.; Lee, D.W.
1993-11-01
Local drainage analyses have been performed for the Paducah and Portsmouth Gaseous Diffusion Plants during an extreme storm having an approximate 10,000-yr recurrence interval. This review discusses the methods utilized to accomplish the analyses in accordance with US Department of Energy (DOE) design and evaluation guidelines, and summarizes trends, results, generalizations, and uncertainties applicable to other DOE facilities. Results indicate that some culverts may be undersized, and that the storm sewer system cannot drain the influx of precipitation from the base of buildings. Roofs have not been designed to sustain ponding when the primary drainage system is clogged. Some underground tunnels, building entrances, and ground level air intakes may require waterproofing.
Technology Transfer Automated Retrieval System (TEKTRAN)
Knowledge of the diffusion coefficient is necessary for modeling gas transport in soils and other porous media. This study was conducted to determine the relationship between the diffusion coefficient and pore structure parameters, such as the fractal dimension of pores (Dmp), the shortest path leng...
Surfactant-enhanced aquifer remediation at the Portsmouth Gaseous Diffusion Plant
Jackson, R.E.; Londergan, J.T.; Pickens, J.F.
1995-10-01
Many DOE facilities are situated in areas of sand and gravel which have become polluted with dense, non-aqueous phase liquids or DNAPLs, such as chlorinated solvents, from the various industrial operations at these facilities. The presence of such DNAPLs in sand and gravel aquifers is now recognized as the principal factor in the failure of standard ground-water remediation methods. The principal objective of this study, as stated in the Statement of Work of the contract (DE-AC21-92MC29111), is to demonstrate that multi-component DNAPLs can be readily solubilized in sand and gravel aquifers by dilute surfactant solutions. The specific objectives of the contract are: to identify dilute surfactants or blends of surfactants in the laboratory that will efficiently extract multi-component DNAPLs from sand and gravel aquifers by micellar solubilization (Phase 1); 2. to test the efficacy of the identified surfactants or blends of surfactants to solubilize in situ perchloroethylene (PCE) and trichloroethylene (TCE) DNAPLs by the injection and the subsequent extraction through an existing well or wells at a government-owned contaminated site (Phase 1); and 3. to demonstrate the full-scale operation of this remedial technology at a government-owned contaminated site (Phase 2). Specific objective number 1 has been completed and reported to DOE. However, the results of the test referred to in specific objective number 2, conducted at Paducah Gaseous Diffusion Plant in 1994, were inconclusive. Following this first test, it was decided by DOE and INTERA to move the test site elsewhere due to difficulties with obtaining core samples of the sand and gravel aquifer containing the DNAPL and with ascertaining the location of the DNAPL relative to the injection well. The solubilization test at the Portsmouth Gaseous Diffusion Plant (PORTS) will constitute the second test of Phase 1 of this contract.
Data set for diffusion coefficients of alloying elements in dilute Mg alloys from first-principles
Zhou, Bi-Cheng; Shang, Shun-Li; Wang, Yi; Liu, Zi-Kui
2015-01-01
Diffusion coefficients of alloying elements in Mg are critical for the development of new Mg alloys for lightweight applications. Here we present the data set of the temperature-dependent dilute tracer diffusion coefficients for 47 substitutional alloying elements in hexagonal closed packed (hcp) Mg calculated from first-principles calculations based on density functional theory (DFT) by combining transition state theory and an 8-frequency model. Benchmark for the DFT calculations and systematic comparison with experimental diffusion data are also presented. The data set refers to “Diffusion coefficients of alloying elements in dilute Mg alloys: A comprehensive first-principles study” by Zhou et al. [1]. PMID:26702419
NASA Astrophysics Data System (ADS)
Ilia Anisa, Nor; Azian, Noor; Sharizan, Mohd; Iwai, Yoshio
2014-04-01
6-gingerol and 6-shogaol are the main constituents as anti-inflammatory or bioactive compounds from zingiber officinale Roscoe. These bioactive compounds have been proven for inflammatory disease, antioxidatives and anticancer. The effect of temperature on diffusion coefficient for 6-gingerol and 6-shogaol were studied in subcritical water extraction. The diffusion coefficient was determined by Fick's second law. By neglecting external mass transfer and solid particle in spherical form, a linear portion of Ln (1-(Ct/Co)) versus time was plotted in determining the diffusion coefficient. 6-gingerol obtained the higher yield at 130°C with diffusion coefficient of 8.582x10-11 m2/s whilst for 6-shogaol, the higher yield and diffusion coefficient at 170°C and 19.417 × 10-11 m2/s.
Single-image diffusion coefficient measurements of proteins in free solution.
Zareh, Shannon Kian; DeSantis, Michael C; Kessler, Jonathan M; Li, Je-Luen; Wang, Y M
2012-04-01
Diffusion coefficient measurements are important for many biological and material investigations, such as studies of particle dynamics and kinetics, and size determinations. Among current measurement methods, single particle tracking (SPT) offers the unique ability to simultaneously obtain location and diffusion information about a molecule while using only femtomoles of sample. However, the temporal resolution of SPT is limited to seconds for single-color-labeled samples. By directly imaging three-dimensional diffusing fluorescent proteins and studying the widths of their intensity profiles, we were able to determine the proteins' diffusion coefficients using single protein images of submillisecond exposure times. This simple method improves the temporal resolution of diffusion coefficient measurements to submilliseconds, and can be readily applied to a range of particle sizes in SPT investigations and applications in which diffusion coefficient measurements are needed, such as reaction kinetics and particle size determinations. PMID:22500769
NMR measurements of solvent self-diffusion coefficients in polymer solutions
NASA Astrophysics Data System (ADS)
Blum, Frank D.; Pickup, Stephen; Waggoner, R. Allen
1989-11-01
The transport of solvents and other small molecules in polymer solutions is important in many areas such as reaction rates, drying of coatings, plasticizer loss, curing of resins, elimination of residual monomer, and controlled drug release. Some of the work done in our laboratory on the diffusion of small molecules in polymer solutions and dispersions is reviewed. The diffusion data was used to test the Vrentas and Duda's free-volume theory for self-diffusion coefficients; test the independence of the normalized solvent self-diffusion for several polymer-solvent systems; and predict the solvent loss curves for drying of coatings based on solvent self-diffusion coefficients.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 10 Energy 2 2011-01-01 2011-01-01 false Illustrative List of Gaseous Diffusion Enrichment Plant Assemblies and Components Under NRC Export Licensing Authority C Appendix C to Part 110 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) EXPORT AND IMPORT OF NUCLEAR EQUIPMENT AND MATERIAL Pt. 110, App. C Appendix C to Part 110—Illustrative List...
NASA Technical Reports Server (NTRS)
Goldman, H.; Wolf, M.
1979-01-01
The manufacturing methods for photovoltaic solar energy utilization are assessed. Economic and technical data on the current front junction formation processes of gaseous diffusion and ion implantation are presented. Future proposals, including modifying gaseous diffusion and using ion implantation, to decrease the cost of junction formation are studied. Technology developments in current processes and an economic evaluation of the processes are included.
Technology Transfer Automated Retrieval System (TEKTRAN)
The diffusion coefficient of water in biobased hydrogels were measured utilizing a simple NMR method. This method tracks the migration of deuterium oxide through imaging data that is fit to a diffusion equation. The results show that a 5 wt% soybean oil based hydrogel gives aqueous diffusion of 1.37...
Lober, Robert M; Cho, Yoon-Jae; Tang, Yujie; Barnes, Patrick D; Edwards, Michael S; Vogel, Hannes; Fisher, Paul G; Monje, Michelle; Yeom, Kristen W
2014-03-01
While pediatric diffuse intrinsic pontine gliomas (DIPG) remain fatal, recent data have shown subgroups with distinct molecular biology and clinical behavior. We hypothesized that diffusion-weighted MRI can be used as a prognostic marker to stratify DIPG subsets with distinct clinical behavior. Apparent diffusion coefficient (ADC) values derived from diffusion-weighted MRI were computed in 20 consecutive children with treatment-naïve DIPG tumors. The median ADC for the cohort was used to stratify the tumors into low and high ADC groups. Survival, gender, therapy, and potential steroid effects were compared between the ADC groups. Median age at diagnosis was 6.6 (range 2.3-13.2) years, with median follow-up seven (range 1-36) months. There were 14 boys and six girls. Seventeen patients received radiotherapy, five received chemotherapy, and six underwent cerebrospinal fluid diversion. The median ADC of 1,295 × 10(-6) mm(2)/s for the cohort partitioned tumors into low or high diffusion groups, which had distinct median survivals of 3 and 13 months, respectively (log-rank p < 0.001). Low ADC tumors were found only in boys, whereas high ADC tumors were found in both boys and girls. Available tissue specimens in three low ADC tumors demonstrated high-grade histology, whereas one high ADC tumor demonstrated low-grade histology with a histone H3.1 K27M mutation and high-grade metastatic lesion at autopsy. ADC derived from diffusion-weighted MRI may identify prognostically distinct subgroups of pediatric DIPG. PMID:24522717
Impurity Diffusion Coefficients of Al and Zn in Mg Determined from Solid-to-Solid Diffusion Couples
Kammerer, Catherine; Kulkarni, Nagraj S; Warmack, Robert J Bruce; Perry, Kelly A; Belova, Irina; Murch, Prof. Graeme; Sohn, Yong Ho
2013-08-01
Increasing use and development of lightweight Mgalloys have led to the desire for more fundamental research in and understanding of Mg-based systems. As property enhancing components, Al and Zn are two of the most important and common alloying elements for Mg-alloys. We have investigated the concentration dependent interdiffusion of Al and Zn in Mg using diffusion couples of pure polycrystalline Mg mated to Mg solid solutions containing either <9 at.% Al or <3 at.% Zn. Concentration profiles were determined by electron micro-probe microanalysis of the diffusion zone. The interdiffusion coefficients were determined by the classical Boltzmann-Matano method within the Mg solid solution. As the concentration of Al or Zn approaches the dilute ends, we employ an analytical approach based on the Hall method to estimate the impurity diffusion coefficients. Results of Al and Zn impurity diffusion in Mg are reported and compared to published impurity diffusion coefficients typically determined by thin film techniques.
Comparative study of methods used to estimate ionic diffusion coefficients using migration tests
Narsilio, G.A. Li, R. Pivonka, P. Smith, D.W.
2007-08-15
Ionic diffusion coefficients are estimated rapidly using electromigration tests. In this paper, electromigration tests are accurately simulated by numerically solving the Nernst-Planck (NP) equation (coupled with the electroneutrality condition (EN)) using the finite element method. Numerical simulations are validated against experimental data obtained elsewhere [E. Samson, J. Marchand, K.A. Snyder, Calculation of ionic diffusion coefficients on the basis of migration test results, Materials and Structures/Materiaux et Constructions 36 (257) (2003) 156-165., H. Friedmann, O. Amiri, A. Ait-Mokhtar, A direct method for determining chloride diffusion coefficient by using migration test, Cement and Concrete Research 34 (11) (2004) 1967-1973.]. It is shown that migration due to the non-linear electric potential completely overwhelms diffusion due to concentration gradients. The effects of different applied voltage differences and chloride source concentrations on estimations of chloride diffusion coefficients are explored. We show that the pore fluid within concrete and mortar specimens generally differs from the curing solution, lowering the apparent diffusion coefficient, primarily due to interactions of chloride ions with other ions in the pore fluid. We show that the variation of source chloride concentration strongly affects the estimation of diffusion coefficients in non-steady-state tests; however this effect vanishes under steady-state conditions. Most importantly, a comparison of diffusion coefficients obtained from sophisticated analyses (i.e., NP-EN) and a variety of commonly used simplifying methods to estimate chloride diffusion coefficients allows us to identify those methods and experimental conditions where both approaches deliver good estimates for chloride diffusion coefficients. Finally, we demonstrate why simultaneous use and monitoring of current density and fluxes are recommended for both the non-steady and steady-state migration tests.
Jacobs, Michael A; Ouwerkerk, Ronald; Petrowski, Kyle; Macura, Katarzyna J
2008-12-01
Prostate cancer is a major health problem, and the exploration of noninvasive imaging methods that have the potential to improve specificity while maintaining high sensitivity is still critically needed. Tissue changes induced by tumor growth can be visualized by magnetic resonance imaging (MRI) methods. Current MRI methods include conventional T2-weighted imaging, diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) mapping and magnetic resonance spectroscopy (MRS). Techniques such as DWI/ADC provide functional information about the behavior of water molecules in tissue; MRS can provide biochemical information about the presence or absence of certain metabolites, such as choline, creatine, and citrate. Finally, vascular parameters can be investigated using dynamic contrast-enhanced MRI. Moreover, with whole-body MRI and DWI, metastatic disease can be evaluated in 1 session and may provide a way to monitor treatment. Therefore, when combining these various methods, a multiparametric data set can be built to assist in the detection, localization, assessment of prostate cancer aggressiveness, and tumor staging. Such a comprehensive approach offers more power to evaluate prostate disease than any single measure alone. In this article, we focus on the role of DWI/ADC and MRS in the detection and characterization using both in vivo and ex vivo imaging of prostate pathology. PMID:19512848
Velocity-Space Diffusion Coefficients Due to Full-Wave ICRF Fields in Toroidal Geometry
Harvey, R.W.; Jaeger, F.; Berry, L.A.; Batchelor, D.B.; D'Azevedo, E.; Carter, M.D.; Ershov, N.M.; Smirnov, A.P.; Bonoli, P.; Wright, J.C.; Smithe, D.N.
2005-09-26
Jaeger et al. have calculated bounce-averaged QL diffusion coefficients from AORSA full-wave fields, based on non-Maxwellian distributions from CQL3D Fokker-Planck code. A zero banana-width approximation is employed. Complementing this calculation, a fully numerical calculation of ion velocity diffusion coefficients using the full-wave fields in numerical tokamak equilibria has been implemented to determine the finite orbit width effects. The un-approximated Lorentz equation of motion is integrated to obtain the change in velocity after one complete poloidal transit of the tokamak. Averaging velocity changes over initial starting gyro-phase and toroidal angle gives bounce-averaged diffusion coefficients. The coefficients from the full-wave and Lorentz orbit methods are compared for an ITER DT second harmonic tritium ICRF heating case: the diffusion coefficients are similar in magnitude but reveal substantial finite orbit effects.
Nonlinearity Effects of Lateral Density Diffusion Coefficient on Gain-Guided VCSEL Performance
NASA Technical Reports Server (NTRS)
Li, Jian-Zhong; Cheung, Samson H.; Ning, C. Z.; Biegel, Bryan (Technical Monitor)
2001-01-01
Electron and hole diffusions in the plane of semiconductor quantum wells play an important part in the static and dynamic operations of semiconductor lasers. In this paper, we apply a hydrodynamic model developed from the semiconductor Bloch equations to numerically study the effects of nonlinearity in the diffusion coefficient on single mode operation and direct modulation of a gain-guided InGaAs/GaAs multiple quantum well laser, operating not too far from threshold. We found that a small diffusion coefficient is advantageous for lowering the threshold current and increasing the modulation bandwidth. Most importantly, the effects of nonlinearity in the coefficient can be approximately reproduced by replacing the coefficient with an effective constant diffusion coefficient, which corresponds roughly to the half height density of the density distribution.
Miller, D.G.
1998-11-02
A procedure is developed for analyzing combined concentration profiles from multicomponent solid-state diffusion data obtained with free-diffusion boundary conditions. This procedure is exactly analogous to the analysis of liquid-state diffusion data obtained from free-diffusion refractive-index profiles (e.g. from Rayleigh interferometry). All data from all couples are least-squared together to characterize the diffusion coefficient matrix. Different profile weightings provide interesting alternatives, as well as diagnostics. Symmetric averagings are shown to eliminate or reduce effects of concentration dependence.
Measurement of effective air diffusion coefficients for trichloroethene in undisturbed soil cores
NASA Astrophysics Data System (ADS)
Bartelt-Hunt, Shannon L.; Smith, James A.
2002-06-01
In this study, we measure effective diffusion coefficients for trichloroethene in undisturbed soil samples taken from Picatinny Arsenal, New Jersey. The measured effective diffusion coefficients ranged from 0.0053 to 0.0609 cm 2/s over a range of air-filled porosity of 0.23-0.49. The experimental data were compared to several previously published relations that predict diffusion coefficients as a function of air-filled porosity and porosity. A multiple linear regression analysis was developed to determine if a modification of the exponents in Millington's [Science 130 (1959) 100] relation would better fit the experimental data. The literature relations appeared to generally underpredict the effective diffusion coefficient for the soil cores studied in this work. Inclusion of a particle-size distribution parameter, d10, did not significantly improve the fit of the linear regression equation. The effective diffusion coefficient and porosity data were used to recalculate estimates of diffusive flux through the subsurface made in a previous study performed at the field site. It was determined that the method of calculation used in the previous study resulted in an underprediction of diffusive flux from the subsurface. We conclude that although Millington's [Science 130 (1959) 100] relation works well to predict effective diffusion coefficients in homogeneous soils with relatively uniform particle-size distributions, it may be inaccurate for many natural soils with heterogeneous structure and/or non-uniform particle-size distributions.
Scale Dependence of Effective Matrix Diffusion Coefficient Evidence and Preliminary Interpertation
H.H. Liu; Y. Zhang
2006-06-20
The exchange of solute mass (through molecular diffusion) between fluid in fractures and fluid in the rock matrix is called matrix diffusion. Owing to the orders-of-magnitude slower flow velocity in the matrix compared to fractures, matrix diffusion can significantly retard solute transport in fractured rock, and therefore is an important process for a variety of problems, including remediation of subsurface contamination and geological disposal of nuclear waste. The effective matrix diffusion coefficient (molecular diffusion coefficient in free water multiplied by matrix tortuosity) is an important parameter for describing matrix diffusion, and in many cases largely determines overall solute transport behavior. While matrix diffusion coefficient values measured from small rock samples in the laboratory are generally used for modeling field-scale solute transport in fractured rock (Boving and Grathwohl, 2001), several research groups recently have independently found that effective matrix diffusion coefficients much larger than laboratory measurements are needed to match field-scale tracer-test data (Neretnieks, 2002; Becker and Shapiro, 2000; Shapiro, 2001; Liu et al., 2003,2004a). In addition to the observed enhancement, Liu et al. (2004b), based on a relatively small number of field-test results, reported that the effective matrix diffusion coefficient might be scale dependent, and, like permeability and dispersivity, it seems to increases with test scale. This scale-dependence has important implications for large-scale solute transport in fractured rock. Although a number of mechanisms have been proposed to explain the enhancement of the effective matrix diffusion coefficient, the potential scale dependence and its mechanisms are not fully investigated at this stage. The major objective of this study is to again demonstrate (based on more data published in the literature than those used in Liu et al. [2004b]) the potential scale dependence of the effective
Liu, Hui-Hai; Zhang, Yingqi; Molz, Fred J.
2006-04-30
The exchange of solute mass (through molecular diffusion) between fluid in fractures and fluid in the rock matrix is called matrix diffusion. Owing to the orders-of-magnitude slower flow velocity in the matrix compared to fractures, matrix diffusion can significantly retard solute transport in fractured rock, and therefore is an important process for a variety of problems, including remediation of subsurface contamination and geological disposal of nuclear waste. The effective matrix diffusion coefficient (molecular diffusion coefficient in free water multiplied by matrix tortuosity) is an important parameter for describing matrix diffusion, and in many cases largely determines overall solute transport behavior. While matrix diffusion coefficient values measured from small rock samples in the laboratory are generally used for modeling field-scale solute transport in fractured rock (Boving and Grathwohl, 2001), several research groups recently have independently found that effective matrix diffusion coefficients much larger than laboratory measurements are needed to match field-scale tracer-test data (Neretnieks, 2002; Becker and Shapiro, 2000; Shapiro, 2001; Liu et al., 2003, 2004a). In addition to the observed enhancement, Liu et al. (2004b), based on a relatively small number of field-test results, reported that the effective matrix diffusion coefficient might be scale dependent, and, like permeability and dispersivity, it seems to increases with test scale. This scale-dependence has important implications for large-scale solute transport in fractured rock. Although a number of mechanisms have been proposed to explain the enhancement of the effective matrix diffusion coefficient, the potential scale dependence and its mechanisms are not fully investigated at this stage. The major objective of this study is to again demonstrate (based on more data published in the literature than those used in Liu et al. [2004b]) the potential scale dependence of the effective
NASA Astrophysics Data System (ADS)
Tripathi, A. K.; Singhal, R. P.; Khazanov, G. V.; Avanov, L. A.
2016-04-01
Electron pitch angle (Dαα) and momentum (Dpp) diffusion coefficients have been calculated due to resonant interactions with electrostatic electron cyclotron harmonic (ECH) and whistler mode chorus waves. Calculations have been performed at two spatial locations L = 4.6 and 6.8 for electron energies ≤10 keV. Landau (n = 0) resonance and cyclotron harmonic resonances n = ±1, ±2, … ±5 have been included in the calculations. It is found that diffusion coefficient versus pitch angle (α) profiles show large dips and oscillations or banded structures. The structures are more pronounced for ECH and lower band chorus (LBC) and particularly at location 4.6. Calculations of diffusion coefficients have also been performed for individual resonances. It is noticed that the main contribution of ECH waves in pitch angle diffusion coefficient is due to resonances n = +1 and n = +2. A major contribution to momentum diffusion coefficients appears from n = +2. However, the banded structures in Dαα and Dpp coefficients appear only in the profile of diffusion coefficients for n = +2. The contribution of other resonances to diffusion coefficients is found to be, in general, quite small or even negligible. For LBC and upper band chorus waves, the banded structures appear only in Landau resonance. The Dpp diffusion coefficient for ECH waves is one to two orders smaller than Dαα coefficients. For chorus waves, Dpp coefficients are about an order of magnitude smaller than Dαα coefficients for the case n ≠ 0. In case of Landau resonance, the values of Dpp coefficient are generally larger than the values of Dαα coefficients particularly at lower energies. As an aid to the interpretation of results, we have also determined the resonant frequencies. For ECH waves, resonant frequencies have been estimated for wave normal angle 89° and harmonic resonances n = +1, +2, and +3, whereas for whistler mode waves, the frequencies have been calculated for angle 10° and Landau
NASA Astrophysics Data System (ADS)
Ray, E.; Bunton, P.; Pojman, J. A.
2007-10-01
A simple technique for determining the diffusion coefficient between two miscible liquids is presented based on observing concentration-dependent ultraviolet-excited fluorescence using a digital camera. The ultraviolet-excited visible fluorescence of corn syrup is proportional to the concentration of the syrup. The variation of fluorescence with distance from the transition zone between the fluids is fit by the Fick's law solution to the diffusion equation. By monitoring the concentration at successive times, the diffusion coefficient can be determined in otherwise transparent materials. The technique is quantitative and makes measurement of diffusion accessible in the advanced undergraduate physics laboratory.
Effective diffusion coefficient of a Brownian particle in a periodically expanded conical tube
Antipov, Anatoly E.; Barzykin, Alexander V.; Berezhkovskii, Alexander M.; Makhnovskii, Yurii A.; Zitserman, Vladimir Yu.; Aldoshin, Sergei M.
2016-01-01
Diffusion in a tube of periodically varying diameter occurs slower than that in a cylindrical tube because diffusing particles get trapped in wells of the periodic entropy potential which is due to variation of the tube cross-section area. To quantify the slowdown one has to establish a relation between the effective diffusion coefficient of the particle and the tube geometry, which is a very complicated problem. Here we show how to overcome the difficulties in the case of a periodically expanded conical tube, where we find an approximate solution for the effective diffusion coefficient as a function of the parameters determining the tube geometry. PMID:24329385
Garcia-Ratés, Miquel; de Hemptinne, Jean-Charles; Bonet Avalos, Josep; Nieto-Draghi, Carlos
2012-03-01
Mass diffusion coefficients of CO(2)/brine mixtures under thermodynamic conditions of deep saline aquifers have been investigated by molecular simulation. The objective of this work is to provide estimates of the diffusion coefficient of CO(2) in salty water to compensate the lack of experimental data on this property. We analyzed the influence of temperature, CO(2) concentration,and salinity on the diffusion coefficient, the rotational diffusion, as well as the electrical conductivity. We observe an increase of the mass diffusion coefficient with the temperature, but no clear dependence is identified with the salinity or with the CO(2) mole fraction, if the system is overall dilute. In this case, we notice an important dispersion on the values of the diffusion coefficient which impairs any conclusive statement about the effect of the gas concentration on the mobility of CO(2) molecules. Rotational relaxation times for water and CO(2) increase by decreasing temperature or increasing the salt concentration. We propose a correlation for the self-diffusion coefficient of CO(2) in terms of the rotational relaxation time which can ultimately be used to estimate the mutual diffusion coefficient of CO(2) in brine. The electrical conductivity of the CO(2)-brine mixtures was also calculated under different thermodynamic conditions. Electrical conductivity tends to increase with the temperature and salt concentration. However, we do not observe any influence of this property with the CO(2) concentration at the studied regimes. Our results give a first evaluation of the variation of the CO(2)-brine mass diffusion coefficient, rotational relaxation times, and electrical conductivity under the thermodynamic conditions typically encountered in deep saline aquifers. PMID:22292779
Quantitative mapping of the per‐axon diffusion coefficients in brain white matter
Kruggel, Frithjof; Alexander, Daniel C.
2015-01-01
Purpose This article presents a simple method for estimating the effective diffusion coefficients parallel and perpendicular to the axons unconfounded by the intravoxel fiber orientation distribution. We also call these parameters the per‐axon or microscopic diffusion coefficients. Theory and Methods Diffusion MR imaging is used to probe the underlying tissue material. The key observation is that for a fixed b‐value the spherical mean of the diffusion signal over the gradient directions does not depend on the axon orientation distribution. By exploiting this invariance property, we propose a simple, fast, and robust estimator of the per‐axon diffusion coefficients, which we refer to as the spherical mean technique. Results We demonstrate quantitative maps of the axon‐scale diffusion process, which has factored out the effects due to fiber dispersion and crossing, in human brain white matter. These microscopic diffusion coefficients are estimated in vivo using a widely available off‐the‐shelf pulse sequence featuring multiple b‐shells and high‐angular gradient resolution. Conclusion The estimation of the per‐axon diffusion coefficients is essential for the accurate recovery of the fiber orientation distribution. In addition, the spherical mean technique enables us to discriminate microscopic tissue features from fiber dispersion, which potentially improves the sensitivity and/or specificity to various neurological conditions. Magn Reson Med, 2015. Magn Reson Med 75:1752–1763, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. PMID:25974332
Parthasarathy, Ranganathan; Misra, Anil; Park, Jonggu; Ye, Qiang; Spencer, Paulette
2012-01-01
The diffusion of water into dentin adhesive polymers and leaching of unpolymerized monomer from the adhesive are linked to their mechanical softening and hydrolytic degradation. Therefore, diffusion coefficient data are critical for the mechanical design of these polymeric adhesives. In this study, diffusion coefficients of water and leachables were obtained for sixteen methacrylate-based crosslinked polymers using absorption experiments. The experimental mass change data was interpreted using numerical solution of the two-dimensional diffusion equations. The calculated diffusion coefficients varied from 1.05 × 10−8 cm2/sec (co-monomer TMTMA) to 3.15 × 10−8 cm2/sec (co-monomer T4EGDMA). Correlation of the diffusion coefficients with crosslink density and hydrophilicity showed an inverse trend (R2 = 0.41). The correlation of diffusion coefficient with crosslink density and hydrophilicity are closer for molecules differing by simple repeat units (R2 = 0.95). These differences in the trends reveal mechanisms of interaction of the diffusing water with the polymer structure. PMID:22430592
On the determinatino of high-pressure mass-diffusion coefficients for binary mixtures
NASA Technical Reports Server (NTRS)
Bellan, J.; Harstad, K.
2003-01-01
A model for high-pressure binary diffusion coefficient calculation is proposed based on considerations originating from recasting both the low pressure kinetic theory and the Stokes-Einstein infinite dilution expressions into forms consistent with corresponding states theory.
Manzini, Gianmarco; Cangiani, Andrea; Sutton, Oliver
2014-10-02
This document presents the results of a set of preliminary numerical experiments using several possible conforming virtual element approximations of the convection-reaction-diffusion equation with variable coefficients.
Lai, C.C.; Tan, C.S. . Dept. of Chemical Engineering)
1995-02-01
Molecular diffusion coefficients of ethyl acetate, toluene, phenol, and caffeine in supercritical carbon dioxide were measured by a chromatographic peak broadening technique in a coated capillary column at temperatures of 308, 318, and 328 K and pressures up to 145 bar. A linear adsorption in the polymer layer coated on the inner wall of the capillary column was observed. The experimentally determined diffusion coefficients showed substantial agreement with those reported in the literature. The diffusion coefficients were in the order of 10[sup [minus]4] cm[sup 2]/s and decreased with increasing carbon dioxide density. Based on the molecular diffusion coefficient data reported here and those published elsewhere, an empirically modified Wilke-Chang equation was proposed which was found to be more quantitative than some existing equations such as the Stokes-Einstein and Wilke-Chang equations.
Leahy-Dios, Alana; Zhuo, Lin; Firoozabadi, Abbas
2008-05-22
New thermal diffusion coefficients of binary mixtures are measured for n-decane-n-alkanes and 1-methylnaphthalene-n-alkanes with 25 and 75 wt % at 25 degrees C and 1 atm using the thermogravitational column technique. The alkanes range from n-pentane to n-eicosane. The new results confirm the recently observed nonmonotonic behavior of thermal diffusion coefficients with molecular weight for binary mixtures of n-decane- n-alkanes at the compositions studied. In this work, the mobility and disparity effects on thermal diffusion coefficients are quantified for binary mixtures. We also show for the binary mixtures studied that the thermal diffusion coefficients and mixture viscosity, both nonequilibrium properties, are closely related. PMID:18438988
Diffusion coefficients of articular cartilage for different CT and MRI contrast agents.
Kulmala, K A M; Korhonen, R K; Julkunen, P; Jurvelin, J S; Quinn, T M; Kröger, H; Töyräs, J
2010-10-01
In contrast enhanced magnetic resonance imaging (MRI) and computed tomography (CT), the equilibrium distribution of anionic contrast agent is expected to reflect the fixed charged density (FCD) of articular cartilage. Diffusion is mainly responsible for the transport of contrast agents into cartilage. In osteoarthritis, cartilage composition changes at early stages of disease, and solute diffusion is most likely affected. Thus, investigation of contrast agent diffusion could enable new methods for imaging of cartilage composition. The aim of this study was to determine the diffusion coefficient of four contrast agents (ioxaglate, gadopentetate, iodide, gadodiamide) in bovine articular cartilage. The contrast agents were different in molecular size and charge. In peripheral quantitative CT experiments, penetration of contrast agent into the tissue was allowed either through the articular surface or through deep cartilage. To determine diffusion coefficients, a finite element model based on Fick's law was fitted to experimental data. Diffusion through articular surface was faster than through deep cartilage with every contrast agent. Iodide, being of atomic size, diffused into the cartilage significantly faster (q<0.05) than the other three contrast agents, for either transport direction. The diffusion coefficients of all clinical contrast agents (ioxaglate, gadopentetate and gadodiamide) were relatively low (142.8-253.7 μm(2)/s). In clinical diagnostics, such slow diffusion may not reach equilibrium and this jeopardizes the determination of FCD by standard methods. However, differences between diffusion through articular surface and deep cartilage, that are characterized by different tissue composition, suggest that diffusion coefficients may correlate with cartilage composition. Present method could therefore enable image-based assessment of cartilage composition by determination of diffusion coefficients within cartilage tissue. PMID:20594900
Socolof, M.L.; McCold, L.N.; Saylor, R.E.
1997-01-01
Three gaseous diffusion plants (GDPs) for enriching uranium maintain a large inventory of chlorofluorocarbon-114 (CFC-114) as a coolant. To address the continued use of CFC-114, an ozone-depleting substance, the US Department of Energy (DOE) considered introducing perfluorocarbons (PFCs) by the end of 1995. These PFCs would not contribute to stratospheric ozone depletion but would be larger contributors to global warming than would CFC-114. The paper reports the results of an assessment of the global impacts of four alternatives for modifying GDP coolant system operations over a three-year period beginning in 1996. The overall contribution of GDP coolant releases to impacts on ozone depletion and global warming were quantified by parameters referred to as ozone-depletion impact and global-warming impact. The analysis showed that these parameters could be used as surrogates for predicting global impacts to all resources and could provide a framework for assessing environmental impacts of a permanent coolant replacement, eliminating the need for subsequent resource-specific analyses.
Kszos, L.A.; Peterson, M.J.; Ryon, M.G.; Smith, J.G.; Southworth, G.R.
1998-03-01
On September 24, 1987, the Commonwealth of Kentucky Natural Resources and Environmental Protection Cabinet issued an Agreed Order that required the development of a Biological Monitoring Program (BMP) for the Paducah Gaseous Diffusion Plant (PGDP). A plan for the biological monitoring of the receiving streams was implemented in 1987 and consisted of ecological surveys, toxicity monitoring of effluents and receiving streams, evaluation of bioaccumulation of trace contaminants in biota, and supplemental chemical characterization of effluents. Beginning in fall 1991, the Environmental Sciences Division (ESD) at Oak Ridge National Laboratory added data collection and report preparation to its responsibilities for the PGDP BMP. The BMP has been continued because it has proven to be extremely valuable in (1) identifying those effluents with the potential for adversely affecting instream fauna, (2) assessing the ecological health of receiving streams, and (3) guiding plans for remediation and protecting human health. The BMP for PGDP consists of three major tasks: (1) effluent toxicity monitoring, (2) bioaccumulation studies, and (3) ecological surveys of benthic macroinvertebrate communities and fish. With the exception of the benthic macroinvertebrate community surveys, this report focuses on activities from January to December 1997.
Kszos, L.A.; Konetsky, B.K.; Peterson, M.J.; Petrie, R.B.; Ryon, M.G.; Smith, J.G.; Southworth, G.R.
1997-06-01
On September 24, 1987, the Commonwealth of Kentucky Natural Resources and Environmental Protection Cabinet issued an Agreed Order that required the development of a Biological Monitoring Program (BMP) for the Paducah Gaseous diffusion Plant (PGDP). The PGDP BMP was conducted by the University of Kentucky Between 1987 and 1992 and by staff of the Environmental Sciences Division (ESD) at Oak Ridge National Laboratory (ORNL) from 1991 to present. The goals of BMP are to (1) demonstrate that the effluent limitations established for PGDP protect and maintain the use of Little Bayou and Big Bayou creeks for growth and propagation of fish and other aquatic life, (2) characterize potential environmental impacts, and (3) document the effects of pollution abatement facilities on stream. The BMP for PGDP consists of three major tasks: (1) effluent toxicity monitoring, (2) bioaccumulation studies, and (3) ecological surveys of stream communities (i.e., benthic macroinvertebrates and fish). This report focuses on ESD activities occurring from January 1996 to December 1996, although activities conducted outside this time period are included as appropriate.
Kszos, L.A.
1996-05-01
On September 24, 1987, the Commonwealth of Kentucky Natural Resources and Environmental Protection Cabinet issued an Agreed Order that required the development of a Biological Monitoring Program (BMP) for the Paducah Gaseous Diffusion Plant (PGDP). The PGDP BMP was implemented in 1987 by the University of Kentucky. Research staff of the Environmental Sciences Division (ESD) at Oak Ridge National Laboratory (ORNL) served as reviewers and advisers to the University of Kentucky. Beginning in fall 1991, ESD added data collection and report preparation to its responsibilities for the PGDP BMP. The goals of BMP are to (1) demonstrate that the effluent limitations established for PGDP protect and maintain the use of Little Bayou and Big Bayou creeks for growth and propagation of fish and other aquatic life, (2) characterize potential environmental impacts, (3) document the effects of pollution abatement facilities on stream biota, and (4) recommend any program improvements that would increase effluent treatability. In September 1992, a renewed Kentucky Pollutant Discharge Elimination System (KPDES) permit was issued to PGDP. The BMP for PGDP consists of three major tasks: (1) effluent and ambient toxicity monitoring, (2) bioaccumulation studies, and (3) ecological surveys of stream communities (i.e., benthic macroinvertebrates and fish). This report includes ESD activities occurring from December 1993 to December 1994, although activities conducted outside this time period are included as appropriate.
Oak Ridge Gaseous Diffusion Plant Biological Monitoring and Abatement Program for Mitchell Branch
Loar, J.M.; Adams, S.M.; Kszos, L.A.; Ryon, M.G.; Smith, J.G.; Southworth, G.R.; Stewart, A.J.
1992-01-01
A proposed Biological Monitoring and Abatement Program (BMAP) for the Oak Ridge Gaseous Diffusion Plant (ORGDP; currently the Oak Ridge K-25 Site) was prepared in December 1986, as required by the modified National Pollutant Discharge Elimination System (NPDES) permit that was issued on September 11, 1986. The effluent discharges to Mitchell Branch are complex, consisting of trace elements, organic chemicals, and radionuclides in addition to various conventional pollutants. Moreover, the composition of these effluent streams will be changing over time as various pollution abatement measures are implemented over the next several years. Although contaminant inputs to the stream originate primarily as point sources from existing plant operations, area sources, such as the classified burial grounds and the K-1407-C holding pond, can not be eliminated as potential sources of contaminants. The proposed BMAP consists of four tasks. These tasks include (1) ambient toxicity testing, (2) bioaccumulation studies, (3) biological indicator studies, and (4) ecological surveys of the benthic invertebrate and fish communities. BMAP will determine whether the effluent limits established for ORGDP protect the designated use of the receiving stream (Mitchell Branch) for growth and propagation of fish and aquatic life. Another objective of the program is to document the ecological effects resulting from various pollution abatement projects, such as the Central Neutralization Facility.
Not Available
1992-11-01
An aerial radiological survey of the Paducah Gaseous Diffusion Plant (PGDP) and surrounding area in Paducah, Kentucky, was conducted during May 15--25, 1990. The purpose of the survey was to measure and document the terrestrial radiological environment at the PGDP and surrounding area for use in effective environmental management and emergency response planning. The aerial survey was flown at an altitude of 61 meters (200 feet) along a series of parallel lines 107 meters (350 feet) apart. The survey encompassed an area of 62 square kilometers (24 square miles), bordered on the north by the Ohio River. The results of the aerial survey are reported as inferred exposure rates at 1 meter above ground level in the form of a gamma radiation contour map. Typical background exposure rates were found to vary from 5 to 12 microroentgens per hour ([mu]R/h). Protactinium-234m, a radioisotope indicative of uranium-238, was detected at several facilities at the PGDR. In support of the aerial survey, ground-based exposure rate and soil sample measurements were obtained at several sites within the survey perimeter. The results of the aerial and ground-based measurements were found to agree within [plus minus]15%.
Environmental Survey preliminary report, Oak Ridge Gaseous Diffusion Plant, Oak Ridge, Tennessee
Not Available
1989-02-01
This report presents the preliminary findings from the first phase of the Environmental Survey of the US Department of Energy's (DOE) Oak Ridge Gaseous Diffusion Plant (ORGDP) conducted March 14 through 25, 1988. The Survey is being conducted by an interdisciplinary team of environmental specialists, led and managed by the Office of Environment, Safety and Health's Office of Environmental Audit. Individual team components are being supplied by a private contractor. The objective of the Survey is to identify environmental risk associated with ORGDP. The Survey covers all environmental media and all areas of environmental regulation. It is being performed in accordance with the DOE Environmental Survey Manual. This phase of the Survey involves the review of existing site environmental data, observations of the operations carried on at ORGDP, and interviews with site personnel. The Survey team developed a Sampling and Analysis Plan to assist in further assessing certain of the environmental problems identified during is on-site activities. The Sampling and Analysis Plan will be executed by Idaho National Engineering Laboratory (INEL). When completed, the results will be incorporated into the ORGDP Survey findings for in inclusion into the Environmental Survey Summary Report. 120 refs., 41 figs., 74 tabs.
Internal exposure to uranium in a pooled cohort of gaseous diffusion plant workers.
Anderson, Jeri L; Apostoaei, A Iulian; Yiin, James H; Fleming, Donald A; Tseng, Chih-Yu; Chen, Pi-Hsueh
2016-03-01
Intakes and absorbed organ doses were estimated for 29 303 workers employed at three former US gaseous diffusion plants as part of a study of cause-specific mortality and cancer incidence in uranium enrichment workers. Uranium urinalysis data (>600 000 urine samples) were available for 58 % of the pooled cohort. Facility records provided uranium gravimetric and radioactivity concentration data and allowed estimation of enrichment levels of uranium to which workers may have been exposed. Urine data were generally recorded with facility department numbers, which were also available in study subjects' work histories. Bioassay data were imputed for study subjects with no recorded sample results (33 % of pooled cohort) by assigning department average urine uranium concentration. Gravimetric data were converted to 24-h uranium activity excretion using department average specific activities. Intakes and organ doses were calculated assuming chronic exposure by inhalation to a 5-µm activity median aerodynamic diameter aerosol of soluble uranium. Median intakes varied between 0.31 and 0.74 Bq d(-1) for the three facilities. Median organ doses for the three facilities varied between 0.019 and 0.051, 0.68 and 1.8, 0.078 and 0.22, 0.28 and 0.74, and 0.094 and 0.25 mGy for lung, bone surface, red bone marrow, kidneys, and liver, respectively. Estimated intakes and organ doses for study subjects with imputed bioassay data were similar in magnitude. PMID:26113578
Operating limit study for the proposed solid waste landfill at Paducah Gaseous Diffusion Plant
Lee, D.W.; Wang, J.C.; Kocher, D.C.
1995-06-01
A proposed solid waste landfill at Paducah Gaseous Diffusion Plant (PGDP) would accept wastes generated during normal operations that are identified as non-radioactive. These wastes may include small amounts of radioactive material from incidental contamination during plant operations. A site-specific analysis of the new solid waste landfill is presented to determine a proposed operating limit that will allow for waste disposal operations to occur such that protection of public health and the environment from the presence of incidentally contaminated waste materials can be assured. Performance objectives for disposal were defined from existing regulatory guidance to establish reasonable dose limits for protection of public health and the environment. Waste concentration limits were determined consistent with these performance objectives for the protection of off-site individuals and inadvertent intruders who might be directly exposed to disposed wastes. Exposures of off-site individuals were estimated using a conservative, site-specific model of the groundwater transport of contamination from the wastes. Direct intrusion was analyzed using an agricultural homesteader scenario. The most limiting concentrations from direct intrusion or groundwater transport were used to establish the concentration limits for radionuclides likely to be present in PGDP wastes.
Seismic hazard evaluation for the Paducah Gaseous Diffusion Plant, Paducah, Kentucky
Not Available
1991-07-01
The study presents the results of an investigation of seismic hazard at the site of the Paducah Gaseous Diffusion Plant. Paducah is located near the northern end of the Reelfoot Rift -- a large feature of the earth's crust that is believed to be associated with the New Madrid earthquakes of 1811 and 1812. Results from three separate seismic hazard analyses are presented here. The EPRI/SOG analysis uses the input data and methodology developed by the Electric Power Research Institute, under the sponsorship of several electric utilities, for the evaluation of seismic hazard in the central and eastern United States. Section 2 of this report documents the application of the EPRI/SOG methodology to the Paducah site (for both rock and soil conditions). The LLNL analysis uses the input data and methodology developed by the Lawrence Livermore National Laboratory for the Nuclear Regulatory Commission. This analysis was performed by LLNL and results were transmitted to us. Section 3 of this report contains a summary of LLNL inputs and results (for both rock and soil conditions, and considering 4 and 5 LLNL ground motion experts). 29 refs., 118 figs., 24 tabs.
Paducah Gaseous Diffusion Plant proposed pilot pump-and-treat project. Final report
Bodenstein, G.W.; Bonczek, R.R.; Early, T.O.; Huff, D.D.; Jones, K.S.; Nickelson, M.D.; Rightmire, C.T.
1994-01-01
On March 23, 1992, R.C. Sleeman of the Department of Energy, Oak Ridge Operations Office requested that a Groundwater Corrective Actions Team be assembled to evaluate the technical merit of and the need to implement a proposed groundwater pump-and-treat demonstration project for the Northwest contaminant plume at the Paducah Gaseous Diffusion Plant. In addition to other suggestions, the Team recommended that further characterization data be obtained for the plume. In the Fall of 1993 additional, temporary well points were installed so that groundwater samples from the shallow groundwater system and the Regional Gravel Aquifer (RGA) could be obtained to provide a three-dimensional view of groundwater contamination in the region of the plume. The results indicate that pure-phase DNAPL (trichloroethylene [TCE]) probably are present in the source area of the plume and extend in depth to the base of the RGA. Because the DNAPL likely will represent a source of a dissolved phase plume for decades it is essential that source containment take place. The Team recommends that although effective hydraulic containment can be achieved, other alternatives should be considered. For example, recent advances in emplacing low permeability barrier walls to depths of 100 to 150 ft make it possible to consider encirclement of the source of the Northwest plume.
Not Available
1990-02-28
Recognizing the value of a proactive, integrated approach to earthquake preparedness planning, Martin Marietta Energy Systems, Inc. initiated a contract in June 1989 with Murray State University, Murray, Kentucky, to develop a comprehensive earthquake management program for their Gaseous Diffusion Plant in Paducah, Kentucky (PGDP -- Subcontract No. 19P-JV649V). The overall purpose of the program is to mitigate the loss of life and property in the event of a major destructive earthquake. The program includes four distinct (yet integrated) components: an emergency management plan, with emphasis on the catastrophic earthquake; an Emergency Operations Center Duty Roster Manual; an Integrated Automated Emergency Management Information System (IAEMIS); and a series of five training program modules. The PLAN itself is comprised of four separate volumes: Volume I -- Chapters 1--3; Volume II -- Chapters 4--6, Volume III -- Chapter 7, and Volume IV -- 23 Appendices. The EOC Manual (which includes 15 mutual aid agreements) is designated as Chapter 7 in the PLAN and is a stand alone'' document numbered as Volume III. This document, Volume II, discusses methodology, engineering and environmental analyses, and operational procedures.
Wang, J.C.; Lee, D.W.; Ketelle, R.H.; Lee, R.R.; Kocher, D.C.
1994-12-31
The operating limits for radionuclides in sanitary and industrial wastes were determined for a proposed landfill at the Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky. These limits, which may be very small but nonzero, are not mandated by law or regulation but are needed for rational operation. The primary advantages of establishing such operating limits include (a) technically defensible screening criteria for landfill-destined solid wastes, (b) significant reductions in the required capacity of radioactive waste storage and disposal facilities, and (c) reductions in costs associated with storage and disposal of radioactive materials. The approach was based on analyses of potential contamination of groundwater at the plant boundary and the potential exposure to radioactivity of an intruder at the landfill after closure. The groundwater analysis includes (a) a source model describing the disposal of waste and the release of radionuclides from waste to groundwater, (b) site-specific groundwater flow and contaminant transport calculations, and (c) calculations of operating limits from the dose objective and conversion factors. The intruder analysis includes pathways through ingestion of contaminated vegetables and soil, external exposure to contaminated soil, and inhalation of suspended activity from contaminated soil particles. In both analyses, a limit on annual effective dose equivalent of 4 mrem (0.04 mSv) was adopted.
Wang, J.C.; Lee, D.W.; Ketelle, R.H.; Lee, R.R.; Kocher, D.C.
1994-05-24
The operating limits for radionuclides in sanitary and industrial wastes were determined for a proposed landfill at the Paducah Gaseous Diffusion Plant (PGDP), Kentucky. These limits, which may be very small but nonzero, are not mandated by law or regulation but are needed for rational operation. The approach was based on analyses of the potential contamination of groundwater at the plant boundary and the potential exposure to radioactivity of an intruder at the landfill after closure. The groundwater analysis includes (1) a source model describing the disposal of waste and the release of radionuclides from waste to the groundwater, (2) site-specific groundwater flow and contaminant transport calculations, and (3) calculations of operating limits from the dose limit and conversion factors. The intruder analysis includes pathways through ingestion of contaminated vegetables and soil, external exposure to contaminated soil, and inhalation of suspended activity from contaminated soil particles. In both analyses, a limit on annual effective dose equivalent of 4 mrem (0.04 mSv) was adopted. The intended application of the results is to refine the radiological monitoring standards employed by the PGDP Health Physics personnel to determine what constitutes radioactive wastes, with concurrence of the Commonwealth of Kentucky.
Not Available
1990-02-28
Recognizing the value of a proactive, integrated approach to earthquake preparedness planning, Martin Marietta Energy Systems, Inc. initiated a contract in June 1989 with Murray State University, Murray, Kentucky, to develop a comprehensive earthquake management program for their Gaseous Diffusion Plant in Paducah, Kentucky (PGDP -- Subcontract No. 19P-JV649V). The overall purpose of the program is to mitigate the loss of life and property in the event of a major destructive earthquake. The program includes four distinct (yet integrated) components: (1) an emergency management plan with emphasis on the catas trophic earthquake; (2) an Emergency Operations Center Duty Roster Manual; (3) an Integrated Automated Emergency Management Information System (IAEMIS); and (4) a series of five training program modules. The PLAN itself is comprised of four separate volumes: Volume I -- Chapters 1--3; Volume II -- Chapters 4--6; Volume III -- Chapter 7; and Volume IV -- 23 Appendices. The EOC Manual (which includes 15 mutual aid agreements) is designated as Chapter 7 in the PLAN and is this document numbered as Volume III.
Not Available
1990-02-28
Recognizing the value of a proactive, integrated approach to earthquake preparedness planning, Martin Marietta Energy Systems, Inc. initiated a contract in June 1989 with Murray State University, Murray, Kentucky, to develop a comprehensive earthquake management program for their Gaseous Diffusion Plant in Paducah, Kentucky. The overall purpose of the program is to mitigate the loss of life and property in the event of a major destructive earthquake. The program includes four distinct (yet integrated) components: an emergency management plan, with emphasis on the catastrophic earthquake; an Emergency Operations Center Duty Roster Manual; an Integrated Automated Emergency Management Information System (IAEMIS); and a series of five training program modules. The PLAN itself is comprised of four separate volumes: Volume I -- Chapters 1--3; Volume II -- Chapters 4--6, Volume III -- Chapter 7, and Volume IV -- 23 Appendices. The EOC Manual (which includes 15 mutual aid agreements) is designated as Chapter 7 in the PLAN and is a stand alone'' document numbered as Volume III. This document, Volume I, provides an introduction, summary and recommendations, and the emergency operations center direction and control.
Not Available
1990-02-28
Recognizing the value of a proactive, integrated approach to earthquake preparedness planning, Martin Marietta Energy Systems, Inc, initiated a contract in June 1989 with Murray State University, Murray, Kentucky, to develop a comprehensive earthquake management program for their Gaseous Diffusion Plant in Paducah, Kentucky (PGDP--Subcontract No. 19P-JV649V). The overall purpose of the program is to mitigate the loss of life and property in the event of a major destructive earthquake. The program includes four distinct (yet integrated) components: (1) an emergency management plan, with emphasis on the catas trophic earthquake, (2) an Emergency Operations Center Duty Roster Manual, (3) an Integrated Automated Emergency Management Information System (IAEMIS), and (4) a series of five training program modules. The PLAN itself is comprised of four separate volumes: Volume I--Chapters 1--3; Volume II--Chapters 4--6, Volume III--Chapter 7, and Volume IV--23 Appendices. The EOC Manual (which includes 15 mutual aid agreements) is designated as Chapter 7 in the PLAN and is a stand alone'' document numbered as Volume III. This document, Volume IV contains the appendices to this report.
Namdoo Moon
2007-12-01
An aerial radiological survey was conducted over the 16 square-mile (~41 square-kilometer) area surrounding the Portsmouth Gaseous Diffusion Plant. The survey was performed in August 2007 utilizing a large array of helicopter mounted sodium iodide detectors. The purpose of the survey was to update the previous radiological survey levels of the environment and surrounding areas of the plant. A search for a missing radium-226 source was also performed. Implied exposure rates, man-made activity, and excess bismuth-214 activity, as calculated from the aerial data are presented in the form of isopleth maps superimposed on imagery of the surveyed area. Ground level and implied aerial exposure rates for nine specific locations are compared. Detected radioisotopes and their associated gamma ray exposure rates were consistent with those expected from normal background emitters. At specific plant locations described in the report, man-made activity was consistent with the operational histories of the location. There was no spectral activity that would indicate the presence of the lost source.
Characteristics of Gaseous Diffusion Flames with High Temperature Combustion Air in Microgravity
NASA Technical Reports Server (NTRS)
Ghaderi, M.; Gupta, A. K.
2003-01-01
The characteristics of gaseous diffusion flames have been obtained using high temperature combustion air under microgravity conditions. The time resolved flame images under free fall microgravity conditions were obtained from the video images obtained. The tests results reported here were conducted using propane as the fuel and about 1000 C combustion air. The burner included a 0.686 mm diameter central fuel jet injected into the surrounding high temperature combustion air. The fuel jet exit Reynolds number was 63. Several measurements were taken at different air preheats and fuel jet exit Reynolds number. The resulting hybrid color flame was found to be blue at the base of the flame followed by a yellow color flame. The length and width of flame during the entire free fall conditions has been examined. Also the relative flame length and width for blue and yellow portion of the flame has been examined under microgravity conditions. The results show that the flame length decreases and width increases with high air preheats in microgravity condition. In microgravity conditions the flame length is larger with normal temperature combustion air than high temperature air.
NASA Astrophysics Data System (ADS)
Klyavin, O. V.; Fedorov, V. Yu.; Chernov, Yu. M.; Shpeizman, V. V.
2015-09-01
The load dependences of the microhardness of surface layers of NaCl and LiF ionic single crystals with juvenile surfaces and surfaces exposed to air for a long time measured in the air, nitrogen, and helium gaseous media have been investigated. It has been found that there is a change in the sign of the derivative of the microhardness as a function of the load for LiF crystals indented in helium and after their aging in air, as well as a weaker effect of the nitrogen and air gaseous media on the studied dependences as compared to NaCl crystals. It has also been found that, after the aging of the surface of NaCl crystals in air, there is a change in the sign of the derivative of the microhardness in the nitrogen and air gaseous media, as well as a pronounced change in the microhardness as a function of the time of aging the samples in air as compared to the weaker effect of the gaseous medium for LiF crystals. The obtained data have been analyzed in terms of the phenomenon of dislocation-dynamic diffusion of particles from the external medium into crystalline materials during their plastic deformation along the nucleating and moving dislocations. It has been shown that this phenomenon affects the microhardness through changes in the intensity of dislocation multiplication upon the formation of indentation rosettes in different gaseous media. The performed investigation of the microhardness of the juvenile surface of NaCl and LiF crystals in different gaseous media has revealed for the first time a different character of dislocation-dynamic diffusion of these media in a "pure" form.
Štefl, Martin; Kułakowska, Anna; Hof, Martin
2009-01-01
Abstract A new (to our knowledge) robust approach for the determination of lateral diffusion coefficients of weakly bound proteins is applied for the phosphatidylserine specific membrane interaction of bovine prothrombin. It is shown that z-scan fluorescence correlation spectroscopy in combination with pulsed interleaved dual excitation allows simultaneous monitoring of the lateral diffusion of labeled protein and phospholipids. Moreover, from the dependencies of the particle numbers on the axial sample positions at different protein concentrations phosphatidylserine-dependent equilibrium dissociation constants are derived confirming literature values. Increasing the amount of membrane-bound prothrombin retards the lateral protein and lipid diffusion, indicating coupling of both processes. The lateral diffusion coefficients of labeled lipids are considerably larger than the simultaneously determined lateral diffusion coefficients of prothrombin, which contradicts findings reported for the isolated N-terminus of prothrombin. PMID:19651025
Determination of the zincate diffusion coefficient and its application to alkaline battery problems
NASA Technical Reports Server (NTRS)
May, C. E.; Kautz, Harold E.
1978-01-01
The diffusion coefficient for the zincate ion at 24 C was found to be 9.9 X 10 to the minus 7th power squared cm per sec + or - 30 percent in 45 percent potassium hydroxide and 1.4 x 10 to the minus 7 squared cm per sec + or - 25 percent in 40 percent sodium hydroxide. Comparison of these values with literature values at different potassium hydroxide concentrations show that the Stokes-Einstein equation is obeyed. The diffusion coefficient is characteristic of the zincate ion (not the cation) and independent of its concentration. Calculations with the measured value of the diffusion coefficient show that the zinc concentration in an alkaline zincate half cell becomes uniform throughout in tens of hours by diffusion alone. Diffusion equations are derived which are applicable to finite size chambers. Details and discussion of the experimental method are also given.
Determination of the zincate diffusion coefficient and its application to alkaline battery problems
NASA Technical Reports Server (NTRS)
May, C. E.; Kautz, H. E.
1978-01-01
The diffusion coefficient for the zincate ion at 24 C was found to be 9.9 x 10 to the -7th power sq cm/sec + or - 30% in 45% potassium hydroxide and 1.4 x 10 to the -7th power sq cm/sec + or - 25% in 40% sodium hydroxide. Comparison of these values with literature values at different potassium hydroxide concentrations show that the Stokes-Einstein equation is obeyed. The diffusion coefficient is characteristic of the zincate ion (not the cation) and independent of its concentration. Calculations with the measured value of the diffusion coefficient show that the zinc concentration in an alkaline zincate half-cell becomes uniform throughout in tens of hours by diffusion alone. Diffusion equations are derived which are applicable to finite-size chambers. Details and discussion of the experimental method are also given.
NASA Astrophysics Data System (ADS)
Dietrich, Olaf; Hubert, Alexander; Heiland, Sabine
2014-06-01
The purpose of this study was to analyze and evaluate a model of restricted water diffusion between equidistant permeable membranes for cell-size and permeability measurements in biological tissue. Based on the known probability distribution of diffusion distances after the diffusion time τ in a system of permeable membranes characterized by three parameters (membrane permeability P, membrane distance L, and free diffusivity D0), an equivalent dimensionless model was derived with a probability distribution characterized by only a single (dimensionless) tissue parameter \\tilde{P}. Evaluating this proposed model function, the dimensionless diffusion coefficient \\tilde{D}_{eff}(\\tilde{\\tau };\\,\\tilde{P}) was numerically calculated for 60 values of the dimensionless diffusion time \\tilde{\\tau } and 35 values of \\tilde{P}. Diffusion coefficients were measured in a carrot by diffusion-weighted magnetic resonance imaging (MRI) at 18 diffusion times between 9.9 and 1022.7 ms and fitted to the simulation results \\tilde{D}_{eff}(\\tilde{\\tau };\\,\\tilde{P}) to determine L, P, and D0. The measured diffusivities followed the simulated dependence of \\tilde{D}_{eff}(\\tilde{\\tau };\\tilde{P}). Determined cell sizes varied from 21 to 76 μm, permeabilities from 0.007 to 0.039 μm-1, and the free diffusivities from 1354 to 1713 μm2 s-1. In conclusion, the proposed dimensionless tissue model can be used to determine tissue parameters (D0, L, P) based on diffusion MRI with multiple diffusion times. Measurements in a carrot showed a good agreement of the cell diameter, L, determined by diffusion MRI and by light microscopy.
FITTING OF THE DATA FOR DIFFUSION COEFFICIENTS IN UNSATURATED POROUS MEDIA
B. Bullard
1999-05-01
The purpose of this calculation is to evaluate diffusion coefficients in unsaturated porous media for use in the TSPA-VA analyses. Using experimental data, regression techniques were used to curve fit the diffusion coefficient in unsaturated porous media as a function of volumetric water content. This calculation substantiates the model fit used in Total System Performance Assessment-1995 An Evaluation of the Potential Yucca Mountain Repository (TSPA-1995), Section 6.5.4.
Note on coefficient matrices from stochastic Galerkin methods for random diffusion equations
Zhou Tao; Tang Tao
2010-11-01
In a recent work by Xiu and Shen [D. Xiu, J. Shen, Efficient stochastic Galerkin methods for random diffusion equations, J. Comput. Phys. 228 (2009) 266-281], the Galerkin methods are used to solve stochastic diffusion equations in random media, where some properties for the coefficient matrix of the resulting system are provided. They also posed an open question on the properties of the coefficient matrix. In this work, we will provide some results related to the open question.
Comparison of ICRF-Induced Ion Diffusion Coefficients Calculated with the DC and AORSA Codes
Harvey, R. W.; Petrov, Yu.; Jaeger, E. F.; Berry, L. A.; Batchelor, D. B.; Bonoli, P. T.; Wright, J. C.
2009-11-26
The DC (Diffusion Coefficient) code obtains RF diffusion coefficients by direct numerical integration of the Lorentz force equation for ion motion in the combined equilibrium fields and the RF full wave EM fields from the AORSA full-wave code. Suitable averaging over initial gyro- and toroidal-angle of coordinate 'kicks' after a bounce-period, gives noise-free bounce-averaged diffusion coefficients. For direct comparison with zero-banana-width coefficients from AORSA, perpendicular-drift terms in the Lorentz equation are subtracted off the integration. The DC code has been coupled to the CQL3D Fokker-Planck code. For a C-Mod minority ion ICRF heating test case, the total power absorption using the diffusion coefficients agree well, and the profiles are similarly close. This supports the DC calculation and the Kennel-Engelmann-based, no-correlations, coefficient calculation in AORSA. However, resonance correlations cause large differences in the pitch angle variations of the diffusion coefficients, and in the resulting evolution of the ion distribution functions.
Response of radiation belt simulations to different radial diffusion coefficients models
NASA Astrophysics Data System (ADS)
Drozdov, Alexander; Baker, Daniel N.; Shprits, Yuri; Kellerman, Adam
2016-07-01
Two parameterizations of the resonant wave-particle interactions of electrons with ultra-low frequency waves in the magnetosphere by Brautigam and Albert [2000] and Ozeke et al. [2014] are evaluated using the Versatile Electron Radiation Belt (VERB) diffusion code to estimate the effect of changing a diffusion coefficient on the radiation belt simulation. The period of investigation includes geomagnetically quiet and active time. The simulations take into account wave-particle interactions represented by radial diffusion transport, local acceleration, losses due to pitch-angle diffusion, and mixed diffusion.
NASA Astrophysics Data System (ADS)
Wu, Qiong; Li, Shu-Suo; Ma, Yue; Gong, Sheng-Kai
2012-10-01
The diffusion coefficients of several alloying elements (Al, Mo, Co, Ta, Ru, W, Cr, Re) in Ni are directly calculated using the five-frequency model and the first principles density functional theory. The correlation factors provided by the five-frequency model are explicitly calculated. The calculated diffusion coefficients show their excellent agreement with the available experimental data. Both the diffusion pre-factor (D0) and the activation energy (Q) of impurity diffusion are obtained. The diffusion coefficients above 700 K are sorted in the following order: DAl > DCr > DCo > DTa > DMo > DRu > DW > DRe. It is found that there is a positive correlation between the atomic radius of the solute and the jump energy of Ni that results in the rotation of the solute-vacancy pair (E1). The value of E2-E1 (E2 is the solute diffusion energy) and the correlation factor each also show a positive correlation. The larger atoms in the same series have lower diffusion activation energies and faster diffusion coefficients.
An alternative model for estimating liquid diffusion coefficients requiring no viscosity data
NASA Technical Reports Server (NTRS)
Morales, Wilfredo
1993-01-01
An equation, based on the free volume of a liquid solvent, was derived via dimensional analysis, to predict binary diffusion coefficients. The equation assumed that interaction between the solute and liquid solvent molecules followed a Lennard-Jones potential. The equation was compared to other diffusivity equations and was found to give good results over the temperature range examined.
NASA Astrophysics Data System (ADS)
Imel, Adam; Miller, Brad; Holley, Wade; Baskaran, Durairaj; Mays, Jimmy; Dadmun, Mark
2015-03-01
The diffusion properties of nanoparticles in polymer nanocomposites are largely unknown and depend intimately on the dispersion of the nanoparticles. We examine the diffusion of soft, organic nanoparticles, which disperse in a polymer matrix due to the interpenetration of polymer chains and particles and the reduction in the depletion of entropy in the system. The impact of the presence of soft nanoparticles on the diffusion coefficient of polystyrene chains has recently been determined with neutron reflectivity. This was completed by monitoring the interdiffusion of deuterated and protonated polystyrene nanocomposite bilayers with and without the soft nanoparticles dispersed throughout both layers and extracting the diffusion coefficient from the one-dimensional solution to Fick's second law of diffusion. In this work, we extend this method to bilayer systems with only the soft nanoparticles as one of the layers and a linear deuterated polystyrene as an adjacent layer. The development of this method allows us to determine the tracer diffusion coefficient of the soft polystyrene nanoparticles for the first time by analyzing the mutual diffusion coefficient from Fick's second law and the fast and slow modes theories for diffusion.
Not Available
1990-07-18
The Paducah Gaseous Diffusion Plant (PGDP) occupies 748 security-fenced acres located on a 3,400-acre tract in McCracken County, Kentucky, which was previously part of the Kentucky Ordnance Works. The principle objective on-site process at PGDP is the separation of uranium isotopes through gaseous diffusion. The process produces enriched uranium, which is used for nuclear fuel in commercial power plants and for military purposes. This document provides an overview of the major environmental and waste management concerns at PGDP, requirements for implementation, organization/management, corrective activities, environmental restoration, waste management options, compliance with National Environmental Policy Act (NEPA), reporting and data management, quality assurance and federal, state and local interactions. 12 refs., 6 figs., 5 tabs.
Temperature-Dependent Diffusion Coefficients from ab initio Computations: Hydrogen in Nickel
E Wimmer; W Wolf; J Sticht; P Saxe; C Geller; R Najafabadi; G Young
2006-03-16
The temperature-dependent mass diffusion coefficient is computed using transition state theory. Ab initio supercell phonon calculations of the entire system provide the attempt frequency, the activation enthalpy, and the activation entropy as a function of temperature. Effects due to thermal lattice expansion are included and found to be significant. Numerical results for the case of hydrogen in nickel demonstrate a strong temperature dependence of the migration enthalpy and entropy. Trapping in local minima along the diffusion path has a pronounced effect especially at low temperatures. The computed diffusion coefficients with and without trapping bracket the available experimental values over the entire temperature range between 0 and 1400 K.
Calculation of the coefficient and dynamics of water diffusion in graphite joints
NASA Astrophysics Data System (ADS)
Wang, Jun; Liu, Wen-Bin
2006-06-01
The coefficient and dynamics of water diffusion in adhesive-graphite joints were calculated insitu with energy dispersive X-ray (EDX) analysis, a method that is significantly simpler than elemental analysis. Water diffusion coefficient and dynamics of adhesive-graphite joints treated by different surface treatment menthods were also investigated. Calculation results indicated that the water diffusion rate in adhesive-graphite joints treated by sandpaper was higher than that treated by chemical oxidation or by silane couple agent. Also the durability of graphite joints treated by coupling agent is superior to that treated by chemical oxidation or sandpaper burnishing.
Franco, Luís F M; Castier, Marcelo; Economou, Ioannis G
2016-08-28
Applying classical molecular dynamics simulations, we calculate the parallel self-diffusion coefficients of different fluids (methane, nitrogen, and carbon dioxide) confined between two {101̄4} calcite crystal planes. We have observed that the molecules close to the calcite surface diffuse differently in distinct directions. This anisotropic behavior of the self-diffusion coefficient is investigated for different temperatures and pore sizes. The ion arrangement in the calcite crystal and the strong interactions between the fluid particles and the calcite surface may explain the anisotropy in this transport property. PMID:27586936
Narváez Valderrama, Jhon F; Baek, Kine; Molina, Francisco J; Allan, Ian J
2016-01-01
A film-stacking technique was used to estimate diffusion coefficients of polybrominated diphenyl ethers (PBDEs) in low density polyethylene (LDPE) and silicone rubber. Substantially higher PBDE diffusion coefficients were observed for silicone rubber (AlteSil™) than for LDPE. A much steeper decrease in LDPE diffusion coefficients was found with increasing PBDE molecular weight than that for silicone rubber. From a passive sampling point-of-view, this means that for equivalent polymer-water partition coefficients for these two materials, the mass transfer resistance for these substances in the LDPE will be significantly higher than that for silicone rubber. Boundary layer control of the uptake process for silicone rubber can be expected for PBDEs. With a microplastic perspective, the low diffusion coefficients of PBDEs and in particular of decabromo diphenyl ether (BDE 209) in LDPE imply that the polymer diffusion coefficients for these plastic additives used as flame retardants need to be taken into account when considering the risk posed by microplastic particle ingestion by marine organisms. PMID:26678428
Styszko, Katarzyna; Kupiec, Krzysztof
2016-10-01
In this study the diffusion coefficients of isoproturon, diuron and cybutryn in acrylate and silicone resin-based renders were determined. The diffusion coefficients were determined using measuring concentrations of biocides in the liquid phase after being in contact with renders for specific time intervals. The mathematical solution of the transient diffusion equation for an infinite plate contacted on one side with a limited volume of water was used to calculate the diffusion coefficient. The diffusion coefficients through the acrylate render were 8.10·10(-9) m(2) s(-1) for isoproturon, 1.96·10(-9) m(2) s(-1) for diuron and 1.53·10(-9) m(2) s(-1) for cybutryn. The results for the silicone render were lower by one order of magnitude. The compounds with a high diffusion coefficient for one polymer had likewise high values for the other polymer. PMID:27391050
Entropy-scaling laws for diffusion coefficients in liquid metals under high pressures
Cao, Qi-Long Shao, Ju-Xiang; Wang, Fan-Hou; Wang, Pan-Pan
2015-04-07
Molecular dynamic simulations on the liquid copper and tungsten are used to investigate the empirical entropy-scaling laws D{sup *}=A exp(BS{sub ex}), proposed independently by Rosenfeld and Dzugutov for diffusion coefficient, under high pressure conditions. We show that the scaling laws hold rather well for them under high pressure conditions. Furthermore, both the original diffusion coefficients and the reduced diffusion coefficients exhibit an Arrhenius relationship D{sub M}=D{sub M}{sup 0} exp(−E{sub M}/K{sub B}T), (M=un,R,D) and the activation energy E{sub M} increases with increasing pressure, the diffusion pre-exponential factors (D{sub R}{sup 0} and D{sub D}{sup 0}) are nearly independent of the pressure and element. The pair correlation entropy, S{sub 2}, depends linearly on the reciprocal temperature S{sub 2}=−E{sub S}/T, and the activation energy, E{sub S}, increases with increasing pressure. In particular, the ratios of the activation energies (E{sub un}, E{sub R}, and E{sub D}) obtained from diffusion coefficients to the activation energy, E{sub S}, obtained from the entropy keep constants in the whole pressure range. Therefore, the entropy-scaling laws for the diffusion coefficients and the Arrhenius law are linked via the temperature dependence of entropy.
Evaluation of Hamaker coefficients using Diffusion Monte Carlo method
NASA Astrophysics Data System (ADS)
Maezono, Ryo; Hongo, Kenta
We evaluated the Hamaker's constant for Cyclohexasilane to investigate its wettability, which is used as an ink of 'liquid silicon' in 'printed electronics'. Taking three representative geometries of the dimer coalescence (parallel, lined, and T-shaped), we evaluated these binding curves using diffusion Monte Carlo method. The parallel geometry gave the most long-ranged exponent, ~ 1 /r6 , in its asymptotic behavior. Evaluated binding lengths are fairly consistent with the experimental density of the molecule. The fitting of the asymptotic curve gave an estimation of Hamaker's constant being around 100 [zJ]. We also performed a CCSD(T) evaluation and got almost similar result. To check its justification, we applied the same scheme to Benzene and compared the estimation with those by other established methods, Lifshitz theory and SAPT (Symmetry-adopted perturbation theory). The result by the fitting scheme turned to be twice larger than those by Lifshitz and SAPT, both of which coincide with each other. It is hence implied that the present evaluation for Cyclohexasilane would be overestimated.
Bounce averaged diffusion coefficients in a physics based magnetic field geometry from RAM-SCB
NASA Astrophysics Data System (ADS)
Zhao, Lei; Yu, Yiqun; Delzanno, Gian Luca; Jordanova, Vania K.
2014-10-01
In this work we explore wave-particle interaction in the radiation belt. By applying quasilinear theory, we obtain the particle diffusion coefficients in both pitch angle and energy for different configurations of the Earth's magnetic field. We consider the Earth's magnetic dipole field as a reference, and compare the results against non-dipole field configurations corresponding to quiet and stormy conditions. The latter are obtained with RAM-SCB, a code that models the Earth's ring current and provide a realistic modeling of the Earth's magnetic field. The bounce averaged electron pitch angle diffusion coefficients are calculated for each magnetic field configuration. The equatorial pitch angle, wave frequency and spectral distribution of whistler waves are shown to affect the bounce averaged diffusion coefficients. In addition, wave-particle resonance is significantly influenced by the magnetic field configuration: in storm conditions, diffusion is strongly reduced for some equatorial pitch angles.
Carpenter, P.J. |; Doll, W.E.; Phillips, B.E.
1994-09-01
Ground penetrating radar (GPR) surveys were used to map shallow sands and gravels which are DNAPL migration pathways at the Paducah Gaseous Diffusion Plant in western Kentucky. The sands and gravels occur as paleochannel deposits, at depths of 17-25 ft, embedded in Pleistocene lacustrine clays. More than 30 GPR profiles were completed over the Drop Test Area (DTA) to map the top and base of the paleochannel deposits, and to assess their lateral continuity. A bistatic radar system was used with antenna frequencies of 25 and 50 MHz. An average velocity of 0.25 ft/ns for silty and clayey materials above the paleochannel deposits was established from radar walkaway tests, profiles over culverts of known depth, and comparison of radar sections with borings. In the south portion of the DTA, strong reflections corresponded to the water table at approximately 9-10 ft, the top of the paleochannel deposits at approximately 18 ft, and to gravel horizons within these deposits. The base of these deposits was not visible on the radar sections. Depth estimates for the top of the paleochannel deposits (from 50 records) were accurate to within 2 ft across the southern portion of the DTA. Continuity of these sands and gravels could not be assessed due to interference from air-wave reflections and lateral changes in signal penetration depth. However, the sands and gravels appear to extend across the entire southern portion of the DTA, at depths as shallow as 17 ft. Ringing, air-wave reflections and diffractions from powerlines, vehicles, well casings, and metal equipment severly degraded GPR profiles in the northern portion of the DTA; depths computed from reflection times (where visible) were accurate to within 4 ft in this area. The paleochannel deposits are deeper to the north and northeast where DNAPL has apparently pooled (DNAPL was not directly imaged by the GPR, however). Existing hydrogeological models of the DTA will be revised.
Becker, D.L.; Green, D.J.; Lindquist, M.R.
1993-12-31
The Portsmouth Gaseous Diffusion Plant (PORTS) conducts those operations that are necessary for the production, packaging, and shipment of enriched uranium hexafluoride (UF{sub 6}). Uranium hexafluoride enriched greater than 1.0 wt percent {sup 235}U shall be packaged in accordance with the US Department of Transportation (DOT) regulations of Title 49 CFR Parts 173 and 178, or in US Nuclear Regulatory Commission (NRC) or US Department of Energy (DOE) certified package designs. Concerns have been expressed regarding the various tiedown methods and condition of the trailers being used by some shippers/carriers for international transport of the UF{sub 6} cylinders/overpacks. The generally accepted method for securing the overpack during shipment is to bolt its base to the trailer bed. International shipments typically are not made using dedicated trailers, and numerous trailers have been received at PORTS with improperly and potentially dangerously secured overpacks. Also, many trailers have not been loaded at PORTS for international shipment because of mechanical problems, rotten flooring, bald tires, no brakes or brake lights, or broken springs. Because of the concerns about international shipments, the US Department of Energy-Headquarters (DOE-HQ) Office of Nuclear Energy, through DOE-HQ Transportation Management Division, requested Westinghouse Hanford Company to review UF{sub 6} packaging tiedown and shipping practices used by PORTS, and where possible and appropriate, provide recommendations for enhancing these practices. Consequently, a team of two individuals from Westinghouse Hanford visited PORTS on March 5 and 6, 1990, for the purpose of conducting this review. The paper provides a brief discussion of the review activities and a summary of the resulting findings and recommendations. A detailed reporting of the review is documented in Reference 4 [Report No. WHC-MR-0233].
Becker, D.L.; Green, D.J.; Lindquist, M.R.
1993-07-01
The Portsmouth Gaseous Diffusion Plant (PORTS) in Piketon, Ohio, is operated by Martin Marietta Energy Systems, Inc., through the US Department of Energy-Oak Ridge Operations Office (DOE-ORO) for the US Department of Energy-Headquarters, Office of Nuclear Energy. The PORTS conducts those operations that are necessary for the production, packaging, and shipment of uranium hexafluoride (UF{sub 6}). Uranium hexafluoride enriched uranium than 1.0 wt percent {sup 235}U shall be packaged in accordance with the US Department of Transportation (DOT) regulations of Title 49 CFR Parts 173 (Reference 1) and 178 (Reference 2), or in US Nuclear Regulatory Commission (NRC) or US Department of Energy (DOE) certified package designs. Concerns have been expressed regarding the various tiedown methods and condition of the trailers being used by some shippers/carriers for international transport of the UF{sub 6} cylinders/overpacks. Because of the concerns about international shipments, the US Department of Energy-Headquarters (DOE-HQ) Office of Nuclear Energy, through DOE-HQ Transportation Management Division, requested Westinghouse Hanford Company (Westinghouse Hanford) to review UF{sub 6} packaging tiedown and shipping practices used by PORTS, and where possible and appropriate, provide recommendations for enhancing these practices. Consequently, a team of two individuals from Westinghouse Hanford visited PORTS on March 5 and 6, 1990, for the purpose of conducting this review. The paper provides a brief discussion of the review activities and a summary of the resulting findings and recommendations. A detailed reporting of the is documented in Reference 4.
Martin, M.Z.
2003-05-01
In situ chemical oxidation through lance permeation (ISCO-LP) is an emerging remediation technology in which chemical oxidants (such as potassium or sodium permanganate) are delivered to the subsurface using vertical lance-like injectors. It is applicable to sites with oxidizable contaminants such as chlorinated solvents and fuel hydrocarbons. Because vertical lance injections can be deployed at relatively close spacing, ISCO-LP potentially can be used to clean-up contamination in low-permeability media. This document provides information that can help potential users determine whether ISCO-LP would apply to a particular environmental management problem. It contains a general description of the technology (Section 2), performance data from a field demonstration (Section 3), an assessment of technology applicability (Section 4), a summary of cost elements (Section 5), and a list of regulatory, environmental safety and health issues (Section 6). It is patterned after the Innovative Technology Summary Reports (ITSR) published by the Department of Energy's (DOE) Office of Science and Technology under the Subsurface Contaminants Focus Area (SCFA). As in the previously published ITSRs, the technology described in this report was developed through funding from SCFA. Most of the information contained in this report was obtained from a field demonstration of ISCO-LP conducted in July-August 2000 at DOE's Portsmouth Gaseous Diffusion Plant (PORTS). The field test was not completed due to an accident that caused a field worker serious injuries. Although performance assessment data are very limited, the field test highlighted important health and safety issues that must be considered by site managers and technology vendors interested in implementing ISCO-LP.
DeGarady, C J; Halbrook, R S
2003-11-01
Contamination at the Paducah Gaseous Diffusion Plant (PGDP), Paducah, Kentucky, has been under evaluation for many years. We studied amphibians in selected outfalls (drainage ditches) flowing from the PGDP to determine if PCBs were accumulating in their tissues and how this might affect local populations. We determined relative amphibian species richness and abundance among seven outfalls and three reference streams by listening to their calls during audio surveys. We also captured amphibians from each study site during the summers of 2000 and 2001 and analyzed their carcasses for PCBs (Aroclor 1260 and 34 congeners) and livers for ethoxyresorufin O-deethylase (EROD) activity, a biomarker of PCBs and other organic contamination. Ten species were heard across study sites, and abundance and richness at outfalls were similar to those observed at reference sites. However, there were significant differences in abundance (p = 0.001) and richness (p = 0.048) of amphibians between continuously flowing and intermittent outfalls. There were no significant differences in PCB concentrations (p = 0.113) in amphibians captured from study sites, although Aroclor 1260 concentrations tended to be higher in amphibians collected from one outfall (outfall 12) on the east side of the plant (x = 1260 microg/kg) compared with all other study sites (x = 489 microg/kg). EROD activity measured in the liver was not indicative of Aroclor 1260 concentrations in amphibians at the PGDP, and EROD did not differ by study site, species, age class, or gender. PCB concentrations measured in amphibians at the PGDP were similar to concentrations measured at reference sites and did not appear to negatively affect individual amphibians or abundance and richness. PMID:14708669
Evaluation of aqueous degreasers versus chlorinated solvents at the Paducah Gaseous Diffusion Plant
Gunn, D.
1988-10-31
Spent chlorinated solvents are produced mainly as a result of degreasing operations at several Paducah Gaseous Diffusion Plant (PGDP) locations. This waste is a listed hazardous waste under Resource Conservation and Recovery Act (RCRA) regulations (40 CFR 261). In addition, some of the solvents become contaminated with uranium which classifies the waste as a mixed waste for which no disposal method is currently available. Due to health and environmental concerns and the desire to minimize mixed and hazardous waste generation, degreasing operations in the plant were delineated and alternate nonhazardous solvents were evaluated for their suitability for replacing the chlorinated solvents. Metal cleanliness testing of eight aqueous degreasers using ultrasonic cleaning and immersion with agitation, and vapor degreasing with trichloroethylene (TCE) and 1,1,1-trichloroethane (TC-ane) was performed. Soils such as dust, fingerprints, lube oil, water-soluble oil, silicone grease, and petroleum-based grease were removed from Monel, copper, mild steel, aluminum, and phosphor bronze. Cleanliness was determined by estimating the surface energy of metal coupons before and after cleaning. A Kepner-Tregoe (KT) decision analysis was utilized to determine the three best multipurpose degreasers for the plant. Additional testing was performed on the top three selected degreasers to evaluate corrosive effects of the cleaning solutions (general surface corrosion and pitting), and to determine the compatability of any residual contamination with process gases. Corrosion testing was performed in an electrochemical corrosion tester. Cleaned coupons were exposed to uranium hexafluoride, fluorine, and chlorine trifluoride. In addition, metal cleanliness testing was conducted to evaluate the cleaning efficiency of parts cleaned in the field.
Bingham, Eula; Ringen, Knut; Dement, John; Cameron, Wilfrid; McGowan, William; Welch, Laura; Quinn, Patricia
2006-09-01
Construction workers were and are considered temporary workers at many construction sites. Since World War II, large numbers of construction workers were employed at U.S. Department of Energy nuclear weapons sites for periods ranging from a few days to over 30 years. These workers performed tasks during new construction and maintenance, repair, renovation, and demolition of existing facilities. Such tasks may involve emergency situations, and may entail opportunities for significant radiation exposures. This paper provides data from interviews with more than 750 construction workers at two gaseous diffusion plants (GDPs) at Paducah, Kentucky, and Portsmouth, Ohio regarding radiation monitoring practices. The aim was to determine the extent to which workers believed they were monitored during tasks involving potential radiation exposures. The adequacy of monitoring practices is important for two reasons: (a) Protecting workers from exposures: Construction workers were employed by sub-contractors, and may frequently been excluded from safety and health programs provided to permanent employees; and (b) Supporting claims for compensation: The Energy Employees Occupational Illness Compensation Program Act (EEOICPA) requires dose reconstruction of radiation exposures for most workers who file a claim regarding cancer. The use of monitoring data for radiation to qualify a worker means that there should be valid and complete monitoring during the work time at the various nuclear plants or workers may be unfairly denied compensation. The worker interviews from Paducah and Portsmouth were considered especially useful because these sites were designated as Special Exposure Cohorts (SECs) and the workers did not have to have a dose reconstruction to qualify for compensation for most cancers. Therefore, their responses were less likely to be affected by compensation concerns. Interview questions included asking for information regarding whether monitoring was performed, how
Prioritizing and scheduling Portsmouth Gaseous Diffusion Plant safeguards upgrades. Final report
Edmunds, T.; Saleh, R.; Zevanove, S.
1992-02-01
As part of the Site Safeguards and Security Plan (SSSP), facilities are required to develop a Resource Plan (RP). The Resource Plan provides documentation and justification for the facility`s planned upgrades, including the schedule, priority, and cost estimates for the safeguards and security upgrades. Portsmouth Gaseous Diffusion Plant (PORTS) management has identified and obtained funding approval for a number of safeguards and security upgrades, including line-item construction projects. These upgrade projects were selected to address a variety of concerns identified in the PORTS vulnerability assessments and other reviews performed in support of the SSSP process. However, budgeting and scheduling constraints do not make it possible to simultaneously begin implementation of all of the upgrade projects. A formal methodology and analysis are needed to explicitly address the trade-offs between competing safeguards objectives, and to prioritize and schedule the upgrade projects to ensure that the maximum benefit can be realized in the shortest possible time frame. The purpose of this report is to describe the methodology developed to support these upgrade project scheduling decisions. The report also presents the results obtained from applying the methodology to a set of the upgrade projects selected by PORTS S&S management. Data for the analysis are based on discussions with personnel familiar with the PORTS safeguards and security needs, the requirements for implementing these upgrades, and upgrade funding limitations. The analysis results presented here assume continued highly enriched uranium (HEU) operations at PORTS. However, the methodology developed is readily adaptable for the evaluation of other operational scenarios and other resource allocation issues relevant to PORTS.
1995-10-01
The U.S. Department of Energy (DOE) proposes to sell 8,500 radioactively contaminated nickel ingots (9.350 short tons), currently in open storage at the Paducah Gaseous Diffusion Plant (PGDP), to Scientific Ecology Group, Inc. (SEG) for decontamination and resale on the international market. SEG would take ownership of the ingots when they are loaded for transport by truck to its facility in Oak Ridge, Tennessee. SEG would receive approximately 200 short tons per month over approximately 48 months (an average of 180 ingots per month). The nickel decontamination process specified in SEG`s technical proposal is considered the best available technology and has been demonstrated in prototype at SEG. The resultant metal for resale would have contamination levels between 0.3 and 20 becquerel per gram (Bq/g). The health hazards associated with release of the decontaminated nickel are minimal. The activity concentration of the end product would be further reduced when the nickel is combined with other metals to make stainless steel. Low-level radioactive waste from the SEG decontamination process, estimated to be approximately 382 m{sup 3} (12,730 ft), would be shipped to a licensed commercial or DOE disposal facility. If the waste were packaged in 0.23 m{sup 3}-(7.5 ft{sup 3}-) capacity drums, approximately 1,500 to 1,900 drums would be transported over the 48-month contract period. Impacts from the construction of decontamination facilities and the selected site are minimal.
Inorganic soil and groundwater chemistry near Paducah Gaseous Diffusion Plant, Paducah, Kentucky
Moore, G.K.
1995-03-01
Near-surface soils, boreholes, and sediments near the Paducah Gaseous Diffusion Plant (PGDP) were sampled in 1989-91 as were monitoring wells, TVA wells, and privately-owned wells. Most wells were sampled two or three times. The resulting chemical analyses have been published in previous reports and have been previously described (CH2M HILL 1991, 1992; Clausen et al. 1992). The two reports by CH2M HILL are controversial, however, because, the concentrations of some constituents were reported to exceed background levels or drinking water standards and because both on-site (within the perimeter fence at PGDP) and off-site pollution was reported to have occurred. The groundwater samples upon which these interpretations were based may not be representative, however. The CH2M HILL findings are discussed in the report. The purpose of this report is to characterize the inorganic chemistry of groundwater and soils near PGDP, using data from the CH2M HILL reports (1991, 1992), and to determine whether or not any contamination has occurred. The scope is limited to analysis and interpretation of data in the CH2M HILL reports because previous interpretations of these data may not be valid, because samples were collected in a relatively short period of time at several hundred locations, and because the chemical analyses are nearly complete. Recent water samples from the same wells were not considered because the characterization of inorganic chemistry for groundwater and soil requirements only one representative sample and an accurate analysis from each location.
NASA Astrophysics Data System (ADS)
Liu, Xiaoyu; Guo, Zhishi; Roache, Nancy F.
2014-06-01
The solid-phase diffusion coefficient (Dm) and material/air partition coefficient (Kma) are key parameters for characterizing the sources and transport of semivolatile organic compounds (SVOCs) in the indoor environment. In this work, a new experimental method was developed to estimate parameters Dm and Kma. The SVOCs chosen for study were polychlorinated biphenyl (PCB) congeners, including PCB-52, PCB-66, PCB-101, PCB-110, and PCB-118. The test materials included polypropylene, high density polyethylene, low density polyethylene, polytetrafluoroethylene, polyether ether ketone, glass, stainless steel and concrete. Two 53-L environmental chambers were connected in series, with the relatively stable SVOCs source in the source chamber and the test materials, made as small “buttons”, in the test chamber. Prior to loading the test chamber with the test materials, the test chamber had been dosed with SVOCs for 12 days to “coat” the chamber walls. During the tests, the material buttons were removed from the test chamber at different exposure times to determine the amount of SVOC absorbed by the buttons. SVOC concentrations at the inlet and outlet of the test chamber were also monitored. The data were used to estimate the partition and diffusion coefficients by fitting a sink model to the experimental data. The parameters obtained were employed to predict the accumulation of SVOCs in the sink materials using an existing mass transfer model. The model prediction agreed reasonably well with the experimental data.
Balch, J; Guéguen, C
2015-01-01
In situ measurements of labile metal species using diffusive gradients in thin films (DGT) passive samplers are based on the diffusion rates of individual species. Although most studies have dealt with chemically isolated humic substances, the diffusion of dissolved organic matter (DOM) across the hydrogel is not well understood. In this study, the diffusion coefficient (D) and molecular weight (MW) of 11 aquatic DOM and 4 humic substances (HS) were determined. Natural, unaltered aquatic DOM was capable of diffusing across the diffusive gel membrane with D values ranging from 2.48×10(-6) to 5.31×10(-6) cm(2) s(-1). Humic substances had diffusion coefficient values ranging from 3.48×10(-6) to 6.05×10(-6) cm(2) s(-1), congruent with previous studies. Molecular weight of aquatic DOM and HS samples (∼500-1750 Da) measured using asymmetrical flow field-flow fractionation (AF4) strongly influenced D, with larger molecular weight DOM having lower D values. No noticeable changes in DOM size properties were observed during the diffusion process, suggesting that DOM remains intact following diffusion across the diffusive gel. The influence of molecular weight on DOM mobility will assist in further understanding and development of the DGT technique and the uptake and mobility of contaminants associated with DOM in aquatic environments. PMID:25112575
Annunziata, Onofrio; Vergara, Alessandro; Paduano, Luigi; Sartorio, Roberto; Miller, Donald G; Albright, John G
2009-10-01
We have experimentally investigated multicomponent diffusion in a protein-polymer-salt-water quaternary system. Specifically, we have measured the nine multicomponent diffusion coefficients, D(ij), for the lysozyme-poly(ethylene glycol)-NaCl-water system at pH 4.5 and 25 degrees C using precision Rayleigh interferometry. Lysozyme is a model protein for protein-crystallization and enzymology studies. We find that the protein diffusion coefficient, D(11), decreases as polymer concentration increases at a given salt concentration. This behavior can be quantitatively related to the corresponding increase in fluid viscosity only at low polymer concentration. However, at high polymer concentration (250 g/L), protein diffusion is enhanced compared to the corresponding viscosity prediction. We also find that a protein concentration gradient induces salt diffusion from high to low protein concentration. This effect increases in the presence of poly(ethylene glycol). Finally, we have evaluated systematic errors associated with measurements of protein diffusion coefficients by dynamic light scattering. This work overall helps characterize protein diffusion in crowded environments and may provide guidance for further theoretical developments in the field of protein crystallization and protein diffusion in such crowded systems, such as the cytoplasm of living cells. PMID:19746957
2014-01-01
Background Support vector regression (SVR) and Gaussian process regression (GPR) were used for the analysis of electroanalytical experimental data to estimate diffusion coefficients. Results For simulated cyclic voltammograms based on the EC, Eqr, and EqrC mechanisms these regression algorithms in combination with nonlinear kernel/covariance functions yielded diffusion coefficients with higher accuracy as compared to the standard approach of calculating diffusion coefficients relying on the Nicholson-Shain equation. The level of accuracy achieved by SVR and GPR is virtually independent of the rate constants governing the respective reaction steps. Further, the reduction of high-dimensional voltammetric signals by manual selection of typical voltammetric peak features decreased the performance of both regression algorithms compared to a reduction by downsampling or principal component analysis. After training on simulated data sets, diffusion coefficients were estimated by the regression algorithms for experimental data comprising voltammetric signals for three organometallic complexes. Conclusions Estimated diffusion coefficients closely matched the values determined by the parameter fitting method, but reduced the required computational time considerably for one of the reaction mechanisms. The automated processing of voltammograms according to the regression algorithms yields better results than the conventional analysis of peak-related data. PMID:24987463
Sublimation kinetics and diffusion coefficients of TNT, PETN, and RDX in air by thermogravimetry.
Hikal, Walid M; Weeks, Brandon L
2014-07-01
The diffusion coefficients of explosives are crucial in their trace detection and lifetime estimation. We report on the experimental values of diffusion coefficients of three of the most important explosives in both military and industry: TNT, PETN, and RDX. Thermogravimetric analysis (TGA) was used to determine the sublimation rates of TNT, PETN, and RDX powders in the form of cylindrical billets. The TGA was calibrated using ferrocene as a standard material of well-characterized sublimation rates and vapor pressures to determine the vapor pressures of TNT, PETN, and RDX. The determined sublimation rates and vapor pressures were used to indirectly determine the diffusion coefficients of TNT, PETN, and RDX for the first time. A linear log-log dependence of the diffusion coefficients on temperature is observed for the three materials. The diffusion coefficients of TNT, PETN, and RDX at 273 K were determined to be 5.76×10(-6)m(2)/sec, 4.94×10(-6)m(2)/s, and 5.89×10(-6)m(2)/s, respectively. Values are in excellent agreement with the theoretical values in literature. PMID:24840410
A first-principles methodology for diffusion coefficients in metals and dilute alloys
NASA Astrophysics Data System (ADS)
Mantina, Manjeera
This work is a study exploring the extent of suitability of static first-principles calculations for studying diffusion in metallic systems. Specifically, vacancy-mediated volume diffusion in pure elements and alloys with dilute concentration of impurities is studied. A novel procedure is discovered for predicting diffusion coefficients that overcomes the shortcomings of the well-known transition state theory, by Vineyard. The procedure that evolves from Eyring's reaction rate theory yields accurate diffusivity results that include anharmonic effects within the quasi-harmonic approximation. Alongside, the procedure is straightforward in its application within the conventional harmonic approximation, from the results of static first-principles calculations. To prove the extensibility of the procedure, diffusivities have been computed for a variety of systems. Over a wide temperature range, the calculated self-diffusion and impurity diffusion coefficients using local density approximation (LDA) of density functional theory (DFT) are seen to be in excellent match with experimental data. Self-diffusion coefficients have been calculated for: (i) fcc Al, Cu, Ni and Ag (ii) bcc W and Mo (v) hcp Mg, Ti and Zn. Impurity diffusion coefficients have been computed for: (i) Mg, Si, Cu, Li, Ag, Mo and 3d transition elements in fcc Al (ii) Mo, Ta in bcc W and Nb, Ta and W in bcc Mo (iii) Sn and Cd in hcp Mg and Al in hcp Ti. It is also an observation from this work, that LDA does not require surface correction for yielding energetics of vacancy-containing system in good comparison with experiments, unlike generalized gradient approximation (GGA). It is known that first-principles' energy minimization procedures based on electronic interactions are suited for metallic systems wherein the valence electrons are freely moving. In this thesis, research has been extended to study suitability of first-principles calculations within LDA/GGA including the localization parameter U, for Al
Yang, J; Köhler, K; Davis, D M; Burroughs, N J
2010-06-01
Fluorescence recovery after photobleaching is a widely established method for the estimation of diffusion coefficients, strip bleaching with an associated recovery curve analysis being one of the simplest techniques. However, its implementation requires near 100% bleaching in the region of interest with negligible fluorescence loss outside, both constraints being hard to achieve concomitantly for fast diffusing molecules. We demonstrate that when these requirements are not met there is an error in the estimation of the diffusion coefficient D, either an under- or overestimation depending on which assumption is violated the most. We propose a simple modification to the recovery curve analysis incorporating the concept of the relative bleached mass m giving a revised recovery time parametrization tau=m(2)w(2)/4piD for a strip of width w. This modified model removes the requirement of 100% bleaching in the region of interest and allows for limited diffusion of the fluorophore during bleaching. We validate our method by estimating the (volume) diffusion coefficient of FITC-labelled IgG in 60% glycerol solution, D= 4.09 +/- 0.21 microm(2) s(-1), and the (surface) diffusion coefficient of a green-fluorescent protein-tagged class I MHC protein expressed at the surface of a human B cell line, D= 0.32 +/- 0.03 microm(2) s(-1) for a population of cells. PMID:20579262
Liu, Fei; Kolesov, Grigory; Parkinson, Bruce A.
2014-09-26
A simple and straightforward method for measuring diffusion coefficients using interdigitated array (IDA) electrodes is reported. The method does not require that the exact electrode area be known but depends only the size of the gap between the IDA electrode pairs. Electroactive molecules produced at the generator electrode of the IDA by a voltage step or scan can diffuse to the collector electrode and the time delay before the current for the reverse electrochemical reaction is detected at the collector is used to calculate the diffusion coefficient. The measurement of the diffusion rate of Ru(NH3)6+2 in aqueous solution has been used as an example measuring diffusion coefficients using this method. Additionally, a digital simulation of the electrochemical response of the IDA electrodes was used to simulate the entire current/voltage/time behavior of the system and verify the experimentally measured diffusion coefficients. This work was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the Department of Energy, Office of Science, Office of Basic Energy Sciences.
Buffie, K.; Shalchi, A.; Heesen, V. E-mail: v.heesen@soton.ac.uk
2013-02-10
Diffusion coefficients are usually used to describe the propagation of cosmic rays through the universe. Whereas such transport parameters can be obtained from experiments in the solar system, it is difficult to determine diffusion coefficients in the Milky Way or in external galaxies. Recently, a value for the perpendicular diffusion coefficient in the nearby starburst galaxy NGC 253 has been proposed. In the present paper, we reproduce this value theoretically by using an advanced analytical theory for perpendicular diffusion.
Lee, Yugyung; Khemka, Alok; Yoo, Jin-Wook; Lee, Chi H
2008-03-01
This study is aimed to elucidate the physicodynamic phenomena governing diffusion coefficient (D) of the loaded drugs in a female controlled drug delivery system (FcDDS) and to find the most influencing variable on the diffusivity using artificial neural networks (ANN). The release profiles of sodium dodecyl sulphate (SDS), a topical microbicide used as a model drug, from FcDDS were obtained using in vitro apparatus, the Simulant Vaginal System (SVS), under various conditions. The effects of formulation and intrinsic/extrinsic variables on the diffusivity of SDS were assessed using artificial neural networks (ANN). The release profiles of SDS from FcDDS revealed a non-linear relationship between the diffusivity and formulation/physiological variables. Intrinsic variables (vaginal fluid pH, vaginal fluid secretion rate) have a more prominent role in defining the diffusion coefficient of SDS from FcDDS than formulation variables (formulation loading weight and loaded doses in the formulation) or extrinsic variables (inserting position). Among 5 variables, pH of vagina fluids is the most influencing factor in defining the diffusion coefficient (maximum value of 0.95+/-0.04) of SDS from FcDDS. The external exposure conditions clearly outweighed the effects of the formulation variables on the diffusion coefficient of SDS. A model-based approach can be used to assess the diffusion coefficient of loaded drugs in FcDDS under the given conditions, leading to a parameter-specific prevention strategy against sexually transmitted diseases (STD) with a high degree of confidence. PMID:17981411
Crack diffusion coefficient - A candidate fracture toughness parameter for short fiber composites
NASA Technical Reports Server (NTRS)
Mull, M. A.; Chudnovsky, A.; Moet, A.
1987-01-01
In brittle matrix composites, crack propagation occurs along random trajectories reflecting the heterogeneous nature of the strength field. Considering the crack trajectory as a diffusive process, the 'crack diffusion coefficient' is introduced. From fatigue crack propagation experiments on a set of identical SEN polyester composite specimens, the variance of the crack tip position along the loading axis is found to be a linear function of the effective 'time'. The latter is taken as the effective crack length. The coefficient of proportionality between variance of the crack trajectory and the effective crack length defines the crack diffusion coefficient D which is found in the present study to be 0.165 mm. This parameter reflects the ability of the composite to deviate the crack from the energetically most efficient path and thus links fracture toughness to the microstructure.
Excess entropy scaling for the diffusion coefficient in expanded liquid metals.
Bretonnet, J L
2004-06-15
Molecular-dynamics simulation is used to compute the pair correlation function and the velocity autocorrelation function of Cs and Rb along the liquid-vapor coexistence curve, from which the excess entropy S(ex) and the diffusion coefficient D are deduced. The numerical results of both physical properties are correlated and a scaling law between the excess entropy and the reduced diffusion coefficient D(*)(=D/D(0)) is investigated for different expressions of the reduction parameter D(0). The choice of thermodynamic states along the liquid--vapor coexistence curve gives us the possibility to extend the investigation of the relation between the reduced diffusion coefficient and the excess entropy over a wide area and to test the adequacy of the scaling law confidently. PMID:15268140
NASA Astrophysics Data System (ADS)
Ohsaka, K.; Rednikov, A.; Sadhal, S. S.
2003-02-01
We present a technique that can be used to determine the thermal diffusivity coefficient of undercooled liquids, which exist at temperatures below their freezing points. The technique involves levitation of a small amount of liquid in a flattened drop shape using an acoustic levitator and heating it with a laser beam. The heated drop is then subjected to natural cooling by heat loss from the surface. Due to acoustic streaming, the heat loss mainly occurs through the equator section of the drop. The measured cooling rate in combination with a radial heat conduction model allows us to calculate the thermal diffusivity coefficient of the drop. We demonstrate the feasibility of the technique using glycerin drops as a model liquid. The technique is well suited if the thermal diffusivity coefficient of the liquid in the normal state (i.e., above the freezing point) is known or can be measured by conventional techniques.
Studies on molten glass sealing in diffusion coefficient measurements using shear cell technique
NASA Astrophysics Data System (ADS)
Yu, Jianding; Natsuisaka, Makoto; Kato, Hirokazu; Matsumoto, Satoshi; Kinoshita, Kyoichi; Itami, Toshio; Yoda, Shinichi
2000-05-01
To develop a shear cell technique for measuring the diffusion coefficient of molten materials with high vapor pressure, molten silica glass was used to seal the vapor leak from the clearance between the cell and the rotating rod. An apparatus was designed to investigate the sealing ability of several molten silica glasses. Using Corning 0211, 7059, and 7740 silica glasses, Ar could be sealed under 150 kPa in the 1100-1500 K temperature range. The corresponding viscosities of the molten silica glasses in the sealing temperature range were 105.3-103.8 Pa s. Based on the results of Ar sealing experiments, the configuration of molten glass sealing was used to seal the As vapor leak in InxGa1-xAs diffusion coefficient measurement experiments. The As vapor leak was successfully sealed and excellent diffusion coefficient measurement data were obtained using the shear cell technique during microgravity experiments carried out on sounding rocket.
NASA Astrophysics Data System (ADS)
Shen, Jun; Zhou, Jianqin; Astrath, Nelson G. C.; Navessin, Titichai; Liu, Zhong-Sheng (Simon); Lei, Chao; Rohling, Jurandir H.; Bessarabov, Dmitri; Knights, Shanna; Ye, Siyu
In this work, using an in-house made Loschmidt diffusion cell, we measure the effective coefficient of dry gas (O 2-N 2) diffusion in cathode catalyst layers of PEM fuel cells at 25 °C and 1 atmosphere. The thicknesses of the catalyst layers under investigation are from 6 to 29 μm. Each catalyst layer is deposited on an Al 2O 3 membrane substrate by an automated spray coater. Diffusion signal processing procedure is developed to deduce the effective diffusion coefficient, which is found to be (1.47 ± 0.05) × 10 -7 m 2 s -1 for the catalyst layers. Porosity and pore size distribution of the catalyst layers are also measured using Hg porosimetry. The diffusion resistance of the interface between the catalyst layer and the substrate is found to be negligible. The experimental results show that the O 2-N 2 diffusion in the catalyst layers is dominated by the Knudsen effect.
Field-Scale Effective Matrix Diffusion Coefficient for FracturedRock: Results From Literature Survey
Zhou, Quanlin; Liu, Hui Hai; Molz, Fred J.; Zhang, Yingqi; Bodvarsson, Gudmundur S.
2005-03-28
Matrix diffusion is an important mechanism for solutetransport in fractured rock. We recently conducted a literature survey onthe effective matrix diffusion coefficient, Dem, a key parameter fordescribing matrix diffusion processes at the field scale. Forty fieldtracer tests at 15 fractured geologic sites were surveyed and selectedfor study, based on data availability and quality. Field-scale Dem valueswere calculated, either directly using data reported in the literature orby reanalyzing the corresponding field tracer tests. Surveyed dataindicate that the effective-matrix-diffusion-coefficient factor FD(defined as the ratio of Dem to the lab-scale matrix diffusioncoefficient [Dem]of the same tracer) is generally larger than one,indicating that the effective matrix diffusion coefficient in the fieldis comparatively larger than the matrix diffusion coefficient at therock-core scale. This larger value could be attributed to the manymass-transfer processes at different scales in naturally heterogeneous,fractured rock systems. Furthermore, we observed a moderate trend towardsystematic increase in the emDFmDDF value with observation scale,indicating that the effective matrix diffusion coefficient is likely tobe statistically scale dependent. The FD value ranges from 1 to 10,000for observation scales from 5 to 2,000 m. At a given scale, the FD valuevaries by two orders of magnitude, reflecting the influence of differingdegrees of fractured rock heterogeneity at different sites. In addition,the surveyed data indicate that field-scale longitudinal dispersivitygenerally increases with observation scale, which is consistent withprevious studies. The scale-dependent field-scale matrix diffusioncoefficient (and dispersivity) may have significant implications forassessing long-term, large-scale radionuclide and contaminant transportevents in fractured rock, both for nuclear waste disposal and contaminantremediation.
Measurement of the local particle diffusion coefficient in a magnetized plasma
Meyerhofer, D.D.; Levinton, F.M.
1987-02-01
Local impurity particle diffusion coefficients have been measured in a low temperature plasma by the injection of test particles at the center of the plasma. The injection is accomplished by a high voltage discharge between two small graphite electrodes on a probe. The probe can be located anywhere in the plasma. The diffusion is observed spectroscopically. An analysis of the spatial and temporal evolution of the CII radiation from the carbon discharge can determine the parallel and perpendicular diffusion of the impurity ions. Results with the diagnostic have been obtained in the Proto S-1/C spheromak. The measured value of the diffusion coefficient in the afterglow plasma is in good agreement with classical predictions.
NASA Astrophysics Data System (ADS)
Salazar, Agustín; Fuente, Raquel; Apiñaniz, Estibaliz; Mendioroz, Arantza; Celorrio, R.
2011-08-01
The aim of this work is to analyze the ability of modulated photothermal radiometry to retrieve the thermal diffusivity and the optical absorption coefficient of layered materials simultaneously. First, we extend the thermal quadrupole method to calculate the surface temperature of semitransparent multilayered materials. Then, this matrix method is used to evaluate the influence of heat losses by convection and radiation, the influence of the use of thin paint layers on the accuracy of thermal diffusivity measurements, and the effect of lateral heat diffusion due to the use of Gaussian laser beams. Finally, we apply the quadrupole method to retrieve (a) the thermal contact resistance in glass stacks and (b) the thermal diffusivity and optical absorption coefficient depth profiles in heterogeneous materials with continuously varying physical properties, as is the case of functionally graded materials and partially cured dental resins.
ICP-MS measurement of diffusion coefficients of Cs in NBG-18 graphite
NASA Astrophysics Data System (ADS)
Carter, L. M.; Brockman, J. D.; Robertson, J. D.; Loyalka, S. K.
2015-11-01
Graphite is used in the HGTR/VHTR as moderator and it also functions as a barrier to fission product release. Therefore, an elucidation of transport of fission products in reactor-grade graphite is required. We have measured diffusion coefficients of Cs in graphite NBG-18 using the release method, wherein we infused spheres of NBG-18 with Cs and measured the release rates in the temperature range of 1090-1395 K. We have obtained: These seem to be the first reported values of Cs diffusion coefficients in NBG-18. The values are lower than those reported for other graphites in the literature.
NASA Astrophysics Data System (ADS)
Nasirabadi, P. Shojaee; Jabbari, M.; Hattel, J. H.
2016-06-01
Nowadays, many electronic systems are exposed to harsh conditions of relative humidity and temperature. Mass transport properties of electronic packaging materials are needed in order to investigate the influence of moisture and temperature on reliability of electronic devices. Polycarbonate (PC) is widely used in the electronics industry. Thus, in this work the water diffusion coefficient into PC is investigated. Furthermore, numerical methods used for estimation of the diffusion coefficient and their assumptions are discussed. 1D and 3D numerical solutions are compared and based on this, it is shown how the estimated value can be different depending on the choice of dimensionality in the model.
NASA Astrophysics Data System (ADS)
Hahne, Susanne; Ikonomov, Julian; Sokolowski, Moritz; Maass, Philipp
2013-02-01
Methods of determining surface diffusion coefficients of molecules from signal fluctuations of a locally fixed probe are revisited and refined. Particular emphasis is put on the influence of the molecule's extent. In addition to the formerly introduced autocorrelation method and residence time method, we develop a further method based on the distribution of intervals between successive peaks in the signal. The theoretical findings are applied to scanning tunneling microscopy measurements of copper phthalocyanine (CuPc) molecules on the Ag(100) surface. We discuss advantages and disadvantages of each method and suggest a combination to obtain accurate results for diffusion coefficients.
A New Method for the Calculation of Diffusion Coefficients with Monte Carlo
NASA Astrophysics Data System (ADS)
Dorval, Eric
2014-06-01
This paper presents a new Monte Carlo-based method for the calculation of diffusion coefficients. One distinctive feature of this method is that it does not resort to the computation of transport cross sections directly, although their functional form is retained. Instead, a special type of tally derived from a deterministic estimate of Fick's Law is used for tallying the total cross section, which is then combined with a set of other standard Monte Carlo tallies. Some properties of this method are presented by means of numerical examples for a multi-group 1-D implementation. Calculated diffusion coefficients are in general good agreement with values obtained by other methods.
NASA Technical Reports Server (NTRS)
Penner, Reginald M.; Vandyke, Leon S.; Martin, Charles R.
1987-01-01
The current pulse E sub oc relaxation method and its application to the determination of diffusion coefficients in electrochemically synthesized polypyrrole thin films is described. Diffusion coefficients for such films in Et4NBF4 and MeCN are determined for a series of submicron film thicknesses. Measurement of the double-layer capacitance, C sub dl, and the resistance, R sub u, of polypyrrole thin films as a function of potential obtained with the galvanostatic pulse method is reported. Measurements of the electrolyte concentration in reduced polypyrrole films are also presented to aid in the interpretation of the data.
Saripalli, Kanaka P.; Serne, R. Jeffrey; Meyer, Philip D.; McGrail, B. Peter
2002-08-01
Determination of aqueous phase diffusion coefficients of solutes through porous media is essential for understanding and modeling contaminant transport. Prediction of diffusion coefficients in both saturated and unsaturated zones requires knowledge of tortuosity and constrictivity factors. No methods are available for the direct measurement of these factors, which are empirical in their definition. In this paper, a new definition for the tortuosity factor is proposed, as the real to ideal interfacial area ratio. We define the tortuosity factor for saturated porous media (ts) as the ratio S/So (specific surface of real porous medium to that of an idealized capillary bundle). For unsaturated media, tortuosity factor (ta) is defined as aaw/aaw,o (ratio of the specific air-water interfacial area of real and the corresponding idealized porous medium). This tortuosity factor is suitably measured using sorptive tracers (e.g., nitrogen adsorption method) for saturated media and interfacial tracers for unsaturated media. A model based on this new definition of tortuosity factors, termed the Interfacial Area Ratio (IAR) model, is presented for the prediction of diffusion coefficients as a function of the degree of water saturation. Diffusion coefficients and diffusive resistances measured in a number of saturated and unsaturated granular porous media, for solutes in dilute aqueous solutions, agree well with the predictions of the IAR model. A comparison of permeability of saturated sands estimated based on ts and the same based on the Kozeny-Carman equation confirm the usefulness of the ts parameter as a measure of tortuosity.
Kruk, D; Meier, R; Rachocki, A; Korpała, A; Singh, R K; Rössler, E A
2014-06-28
Field Cycling Nuclear Magnetic Resonance (FC NMR) relaxation studies are reported for three ionic liquids: 1-ethyl-3- methylimidazolium thiocyanate (EMIM-SCN, 220-258 K), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4, 243-318 K), and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6, 258-323 K). The dispersion of (1)H spin-lattice relaxation rate R1(ω) is measured in the frequency range of 10 kHz-20 MHz, and the studies are complemented by (19)F spin-lattice relaxation measurements on BMIM-PF6 in the corresponding frequency range. From the (1)H relaxation results self-diffusion coefficients for the cation in EMIM-SCN, BMIM-BF4, and BMIM-PF6 are determined. This is done by performing an analysis considering all relevant intra- and intermolecular relaxation contributions to the (1)H spin-lattice relaxation as well as by benefiting from the universal low-frequency dispersion law characteristic of Fickian diffusion which yields, at low frequencies, a linear dependence of R1 on square root of frequency. From the (19)F relaxation both anion and cation diffusion coefficients are determined for BMIM-PF6. The diffusion coefficients obtained from FC NMR relaxometry are in good agreement with results reported from pulsed- field-gradient NMR. This shows that NMR relaxometry can be considered as an alternative route of determining diffusion coefficients of both cations and anions in ionic liquids. PMID:24985656
NASA Astrophysics Data System (ADS)
Kruk, D.; Meier, R.; Rachocki, A.; Korpała, A.; Singh, R. K.; Rössler, E. A.
2014-06-01
Field Cycling Nuclear Magnetic Resonance (FC NMR) relaxation studies are reported for three ionic liquids: 1-ethyl-3- methylimidazolium thiocyanate (EMIM-SCN, 220-258 K), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4, 243-318 K), and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6, 258-323 K). The dispersion of 1H spin-lattice relaxation rate R1(ω) is measured in the frequency range of 10 kHz-20 MHz, and the studies are complemented by 19F spin-lattice relaxation measurements on BMIM-PF6 in the corresponding frequency range. From the 1H relaxation results self-diffusion coefficients for the cation in EMIM-SCN, BMIM-BF4, and BMIM-PF6 are determined. This is done by performing an analysis considering all relevant intra- and intermolecular relaxation contributions to the 1H spin-lattice relaxation as well as by benefiting from the universal low-frequency dispersion law characteristic of Fickian diffusion which yields, at low frequencies, a linear dependence of R1 on square root of frequency. From the 19F relaxation both anion and cation diffusion coefficients are determined for BMIM-PF6. The diffusion coefficients obtained from FC NMR relaxometry are in good agreement with results reported from pulsed- field-gradient NMR. This shows that NMR relaxometry can be considered as an alternative route of determining diffusion coefficients of both cations and anions in ionic liquids.
FIELD-SCALE EFFECTIVE MATRIX DIFFUSION COEFFICIENT FOR FRACTURED ROCK:RESULTS FROM LITERATURE SURVEY
Q. Zhou; Hui-Hai Liu; F.J. Molz; Y. Zhang; G.S. Bodvarsson
2005-04-08
Matrix diffusion is an important mechanism for solute transport in fractured rock. We recently conducted a literature survey on the effective matrix diffusion coefficient, D{sub m}{sup e}, a key parameter for describing matrix diffusion processes at the field scale. Forty field tracer tests at 15 fractured geologic sites were surveyed and selected for the study, based on data availability and quality. Field-scale D{sub m}{sup e} values were calculated, either directly using data reported in the literature or by reanalyzing the corresponding field tracer tests. Surveyed data indicate that the effective-matrix-diffusion-coefficient factor F{sub D} (defined as the ratio of D{sub m}{sup e} to the lab-scale matrix diffusion coefficient [D{sub m}] of the same tracer) is generally larger than one, indicating that the effective matrix diffusion coefficient in the field is comparatively larger than the matrix diffusion coefficient at the rock-core scale. This larger value can be attributed to the many mass-transfer processes at different scales in naturally heterogeneous, fractured rock systems. Furthermore, we observed a moderate trend toward systematic increase in the F{sub D} value with observation scale, indicating that the effective matrix diffusion coefficient is likely to be statistically scale dependent. The F{sub D} value ranges from 1 to 10,000 for observation scales from 5 to 2,000 m. At a given scale, the F{sub D} value varies by two orders of magnitude, reflecting the influence of differing degrees of fractured rock heterogeneity at different sites. In addition, the surveyed data indicate that field-scale longitudinal dispersivity generally increases with observation scale, which is consistent with previous studies. The scale-dependent field-scale matrix diffusion coefficient (and dispersivity) may have significant implications for assessing long-term, large-scale radionuclide and contaminant transport events in fractured rock, both for nuclear waste disposal
Non-Fermi liquid behavior of the drag and diffusion coefficients in QED plasma
Sarkar, Sreemoyee; Dutt-Mazumder, Abhee K.
2011-11-01
We calculate the drag and diffusion coefficients in low temperature QED plasma and go beyond the leading order approximation. The non-Fermi-liquid behavior of these coefficients are clearly revealed. We observe that the subleading contributions due to the exchange of soft transverse photon in both cases are larger than the leading order terms coming from the longitudinal sector. The results are presented in closed form at zero and low temperature.
Correlation between the self-diffusion coefficient of lithium and the equation of state
NASA Astrophysics Data System (ADS)
Eftaxias, K.; Grammatikakis, J.; Varotsos, P.
1985-10-01
Anderson and Swenson [Phys. Rev. B 31, 668 (1985)] have recently presented new isothermal elastic data for lithium for temperatures up to 350 K. It is shown that these data are closely connected to the temperature variation of the self-diffusion coefficient D. Although the latter varies by six orders of magnitude (in the temperature region 195-350 K), however, the elastic data can successfully reproduce the self-diffusion curve without the use of any adjustable parameter.
Pc 5 Spectral Density at ULTIMA stataions and its Radial Diffusion Coefficients for REE
NASA Astrophysics Data System (ADS)
Fujimoto, A.; Tokunaga, T.; Abe, S.; Uozumi, T.; Yoshikawa, A.; Mann, I. R.; Chi, P. J.; Engebretson, M. J.; Yumoto, K.
2009-12-01
Pc 5 magnetic pulsations with frequencies between 1.67 and 6.67 mHz, are believed to contribute to the Relativistic Electron Enhancement (REE) in the outer radiation belt during magnetic storms. Ground-based observations suggested that high-speed solar wind and large-amplitude Pc 5 waves with a long duration during the storm recovery phase are closely associated with the production of relativistic electrons [Baker et al., 1998; Rostoker et al., 1998; Mathie and Mann, 2000; O’Brien et al., 2001, 2003]. On the other hand, many relativistic electron acceleration mechanisms have been proposed theoretically. They are separated roughly into two themes: in situ acceleration at L lower than 6.6 by wave particle interactions (as internal source acceleration mechanisms) [Liu et al., 1999; Summers et al., 1999; Summers and Ma, 2000] and acceleration by radial diffusion to transport and accelerate a source population of electrons from the outer to the inner magnetosphere (as external source acceleration mechanisms) [Elkington et al., 1999, 2003; Hudson et al., 2000; Kim et al., 2001]. One possible external source acceleration mechanism is the resonant interaction with ULF toroidal and poloidal waves. In order to verify which of the two mechanisms is more effective for the REE, we have to examine the time variation of electron phase space density. Electron phase space density is not directly measured, but we can estimate radial diffusion coefficients using observational electric and magnetic data. The goal of this paper is to get more reliable radial diffusion coefficient from ground-based observational magnetic field and to show reasonability of it for radial diffusion model. We use the global magnetometer data obtained from ULTIMA (Ultra Large Terrestrial International Magnetic Array, see http://www.serc.kyushu-u.ac.jp/ultima/ultima.html) stations, to precisely define the radial diffusion timescales. The ULTIMA includes McMAC, CARISAM, 210MM and MAGDAS/CPMN magnetometer
Mukhopadhyay, B; Bhattacharyya, R
2006-02-01
The paper is concerned with the effect of variable dispersal rates on Turing instability of a non-Lotka-Volterra reaction-diffusion system. In ecological applications, the dispersal rates of different species tends to oscillate in time. This oscillation is modeled by temporal variation in the diffusion coefficient with large as well as small periodicity. The case of large periodicity is analyzed using the theory of Floquet multipliers and that of the small periodicity by using Hill's equation. The effect of such variation on the resulting Turing space is studied. A comparative analysis of the Turing spaces with constant diffusivity and variable diffusivities is performed. Numerical simulations are carried out to support analytical findings. PMID:16794932
NASA Astrophysics Data System (ADS)
Jebaraj Johnley Muthuraj, Josiah
Cathodic protection is widely used for corrosion prevention. However, this process generates hydrogen at the protected metal surface, and diffusion of hydrogen through the metal may cause hydrogen embrittlement or hydrogen induced stress corrosion cracking. Thus the choice of a metal for use as fasteners depends upon its hydrogen uptake, permeation, diffusivity and trapping. The diffusivity of hydrogen through four high strength alloys (AISI 4340, alloy 718, alloy 686, and alloy 59) was analyzed by an electrochemical method developed by Devanathan and Stachurski. The effect of plasma nitriding and microstructure on hydrogen permeation through AISI 4340 was studied on six different specimens: as-received (AR) AISI 4340, nitrided samples with and without compound layer, samples quenched and tempered (Q&T) at 320° and 520°C, and nitrided samples Q&T 520°C. Studies on various nitrided specimens demonstrate that both the gamma'-Fe 4N rich compound surface layer and the deeper N diffusion layer that forms during plasma nitriding reduce the effective hydrogen diffusion coefficient, although the gamma'-Fe4N rich compound layer has a larger effect. Multiple permeation transients yield evidence for the presence of only reversible trap sites in as-received, Q&T 320 and 520 AISI 4340 specimens, and the presence of both reversible and irreversible trap sites in nitrided specimens. Moreover, the changes in microstructure during the quenching and tempering process result in a significant decrease in the diffusion coefficient of hydrogen compared to as-received specimens. In addition, density functional theory-based molecular dynamics simulations yield hydrogen diffusion coefficients through gamma'- Fe4N one order of magnitude lower than through α-Fe, which supports the experimental measurements of hydrogen permeation. The effect of microstructure and trapping was also studied in cold rolled, solutionized, and precipitation hardened Inconel 718 foils. The effective hydrogen
Kowsari, M H; Alavi, Saman; Ashrafizaadeh, Mahmud; Najafi, Bijan
2008-12-14
Molecular dynamics simulations are used to study the dynamics and transport properties of 12 room-temperature ionic liquids of the 1-alkyl-3-methylimidazolium [amim](+) (alkyl = methyl, ethyl, propyl, and butyl) family with PF(6)(-), NO(3)(-), and Cl(-) counterions. The explicit atom transferable force field of Canongia Lopes et al. [J. Phys. Chem. B 108, 2038 (2004)] is used in the simulations. In this first part, the dynamics of the ionic liquids are characterized by studying the mean-square displacement (MSD) and the velocity autocorrelation function (VACF) for the centers of mass of the ions at 400 K. Trajectory averaging was employed to evaluate the diffusion coefficients at two temperatures from the linear slope of MSD(t) functions in the range of 150-300 ps and from the integration of the VACF(t) functions at 400 K. Detailed comparisons are made between the diffusion results from the MSD and VACF methods. The diffusion coefficients from the integration of the VACFs are closer to experimental values than the diffusion coefficients calculated from the slope of MSDs. Both methods can show good agreement with experiment in predicting relative trends in the diffusion coefficients and determining the role of the cation and anion structures on the dynamical behavior of this family of ionic liquids. The MSD and self-diffusion of relatively heavier imidazolium cations are larger than those of the lighter anions from the Einstein results, except for the case of [bmim][Cl]. The cationic transference number generally decreases with temperature, in good agreement with experiments. For the same anion, the cationic transference numbers decrease with increasing length of the alkyl chain, and for the same cation, the trends in the cationic transference numbers are [NO(3)](-) < [Cl](-) < [PF(6)](-). The trends in the diffusion coefficient in the series of cations with identical anions are [emim](+) > [pmim](+) > [bmim](+) and those for anions with identical cations are [NO(3
Measurement and modeling of CO2 diffusion coefficient in Saline Aquifer at reservoir conditions
NASA Astrophysics Data System (ADS)
Azin, Reza; Mahmoudy, Mohamad; Raad, Seyed; Osfouri, Shahriar
2013-12-01
Storage of CO2 in deep saline aquifers is a promising techniques to mitigate global warming and reduce greenhouse gases (GHG). Correct measurement of diffusivity is essential for predicting rate of transfer and cumulative amount of trapped gas. Little information is available on diffusion of GHG in saline aquifers. In this study, diffusivity of CO2 into a saline aquifer taken from oil field was measured and modeled. Equilibrium concentration of CO2 at gas-liquid interface was determined using Henry's law. Experimental measurements were reported at temperature and pressure ranges of 32-50°C and 5900-6900 kPa, respectively. Results show that diffusivity of CO2 varies between 3.52-5.98×10-9 m2/s for 5900 kPa and 5.33-6.16×10-9 m2/s for 6900 kPa initial pressure. Also, it was found that both pressure and temperature have a positive impact on the measures of diffusion coefficient. Liquid swelling due to gas dissolution and variations in gas compressibility factor as a result of pressure decay was found negligible. Measured diffusivities were used model the physical model and develop concentration profile of dissolved gas in the liquid phase. Results of this study provide unique measures of CO2 diffusion coefficient in saline aquifer at high pressure and temperature conditions, which can be applied in full-field studies of carbon capture and sequestration projects.
Diffusion Coefficients from Molecular Dynamics Simulations in Binary and Ternary Mixtures
NASA Astrophysics Data System (ADS)
Liu, Xin; Schnell, Sondre K.; Simon, Jean-Marc; Krüger, Peter; Bedeaux, Dick; Kjelstrup, Signe; Bardow, André; Vlugt, Thijs J. H.
2013-07-01
Multicomponent diffusion in liquids is ubiquitous in (bio)chemical processes. It has gained considerable and increasing interest as it is often the rate limiting step in a process. In this paper, we review methods for calculating diffusion coefficients from molecular simulation and predictive engineering models. The main achievements of our research during the past years can be summarized as follows: (1) we introduced a consistent method for computing Fick diffusion coefficients using equilibrium molecular dynamics simulations; (2) we developed a multicomponent Darken equation for the description of the concentration dependence of Maxwell-Stefan diffusivities. In the case of infinite dilution, the multicomponent Darken equation provides an expression for [InlineEquation not available: see fulltext.] which can be used to parametrize the generalized Vignes equation; and (3) a predictive model for self-diffusivities was proposed for the parametrization of the multicomponent Darken equation. This equation accurately describes the concentration dependence of self-diffusivities in weakly associating systems. With these methods, a sound framework for the prediction of mutual diffusion in liquids is achieved.
Not Available
1993-07-01
This decision document presents the selected remedial action for the Northwest Plume at the Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky. The primary objective of this interim remedial action is to initiate a first phase remedial action, as an interim action to initiate control of the source and mitigate the spread of contamination in the Northwest plume. This operable unit addresses a portion of the contaminated ground water. Additional interim actions associated with this integrator operable unit are being considered, as well as for other areas of contaminated ground water.
1998-12-01
This decision document presents the remedial action for the Solid Waste Management Unit (SWMU) 91 of the Waste Area Group (WAG) 27 at the Paducah Gaseous Diffusion Plant (PGDP) near Paducah, Kentucky. The primary objective of this remedial action is to reduce the level of TCE-contaminated soil thereby reducing the potential future concentrations in ground water that could pose a threat to human health and the environment at the POE (i.e., the DOE property boundary). The potential for migration of the contamination from the soil of the off-site aquifer is the concern associated with the SWMU.
Health risk from earthquake caused releases of UF{sub 6} at the Paducah Gaseous Diffusion Plant
Brown, N.W; Lu, S.; Chen, J.C.; Roehnelt, R.; Lombardi, D.
1998-05-01
The health risk to the public and workers from potential exposure to the toxic materials from earthquake caused releases of uranium hexafluoride from the Paducah gaseous Diffusion Plant are evaluated. The results of the study show that the health risk from earthquake caused releases is small, and probably less than risks associated with the transportation of hydrogen fluoride and other similar chemicals used by industry. The probability of more than 30 people experiencing health consequences (injuries) from earthquake damage is less than 4xlO{sup 4}/yr.
Bounce averaged diffusion coefficients in a physics based magnetic field geometry from RAM-SCB
NASA Astrophysics Data System (ADS)
Zhao, L.; Yu, Y.; Delzanno, G. L.; Jordanova, V.
2014-12-01
Local acceleration via whistler wave and particle interaction plays an important role in particle dynamics in the radiation belt. In this work we explore wave-particle interaction in different magnetic field configurations related to the 17 March, 2013 storm. We consider the Earth's magnetic dipole field as a reference, and compare the results against non-dipole field configurations corresponding to quiet and stormy conditions. The latter are obtained with RAM-SCB, a code that models the Earth's ring current and provides a realistic modeling of the Earth's magnetic field. By applying quasi-linear theory, the bounce-averaged electron pitch angle, energy and mixed term diffusion coefficients are calculated for each magnetic field configuration. It is shown that the magnetic field can have a significant influence on the diffusion coefficients via the wave-particle resonance condition. In addition, the equatorial pitch angle, wave frequency and spectral distribution of whistler waves also affect the bounce-averaged diffusion coefficients in particle energy range from KeV to MeV. Part of the ongoing work will focus on the phase space density evolution based on the Fokker-Planck equation with the bounce-averaged diffusion coefficients previously calculated.
NASA Astrophysics Data System (ADS)
Chenyakin, Y.; Kamal, S.; Bertram, A. K.
2014-12-01
Secondary organic aerosol (SOA) particles are formed in the atmosphere via gas-to-particle conversion of low and semi volatile organic compounds. They are abundant in the atmosphere and can directly contribute to climate change by scattering solar radiation or indirectly by acting as cloud condensation nuclei or ice nuclei. There is also a health concern associated with SOA particles because they can make up a large fraction of suspended submicron particulate mass. In addition, a reduction in visibility in both polluted and rural areas can be due to SOA particles. Knowledge of diffusion coefficients of organic species within SOA particles is needed to predict the atmospheric behaviour and environmental impacts of these particles. Here we introduce a new method to determine diffusion coefficients of organic probes in particles made up of organic species as a function of relative humidity (RH). Our method involves using fluorescence recovery after photobleaching (FRAP) to measure the diffusion coefficients of organic fluorescent dyes in organic particles with dimensions of approximately 25 μm. We validated this method by measuring diffusion coefficients of organic dyes of varied size in sucrose-water solutions as a function of RH and comparing these results with data from the literature. In the future this method will be applied to SOA particles.
Although detailed thermodynamic analyses of the 2-pK diffuse layer surface complexation model generally specify bound site activity coefficients for the purpose of accounting for those non-ideal excess free energies contributing to bound site electrochemical potentials, in applic...
De Mezquia, D Alonso; Bou-Ali, M Mounir; Larrañaga, M; Madariaga, J A; Santamaría, C
2012-03-01
In this work we have measured the molecular diffusion coefficient of the n-alkane binary series nC(i)-nC(6), nC(i)-nC(10), and nC(i)-nC(12) at 298 K and 1 atm and a mass fraction of 0.5 by using the so-called sliding symmetric tubes technique. The results show that the diffusion coefficient at this concentration is proportional to the inverse viscosity of the mixture. In addition, we have also measured the diffusion coefficient of the systems nC(12)-nC(6), nC(12)-nC(7), and nC(12)-nC(8) as a function of concentration. From the data obtained, it is shown that the diffusion coefficient of the n-alkane binary mixtures at any concentration can be calculated from the molecular weight of the components and the dynamic viscosity of the corresponding mixture at 50% mass fraction. PMID:22263833
Bauer, Katharina Christin; Göbel, Mathias; Schwab, Marie-Luise; Schermeyer, Marie-Therese; Hubbuch, Jürgen
2016-09-10
The colloidal stability of a protein solution during downstream processing, formulation, and storage is a key issue for the biopharmaceutical production process. Thus, knowledge about colloidal solution characteristics, such as the tendency to form aggregates or high viscosity, at various processing conditions is of interest. This work correlates changes in the apparent diffusion coefficient as a parameter of protein interactions with observed protein aggregation and dynamic viscosity of the respective protein samples. For this purpose, the diffusion coefficient, the protein phase behavior, and the dynamic viscosity in various systems containing the model proteins α-lactalbumin, lysozyme, and glucose oxidase were studied. Each of these experiments revealed a wide range of variations in protein interactions depending on protein type, protein concentration, pH, and the NaCl concentration. All these variations showed to be mirrored by changes in the apparent diffusion coefficient in the respective samples. Whereas stable samples with relatively low viscosity showed an almost linear dependence, the deviation from the concentration-dependent linearity indicated both an increase in the sample viscosity and probability of protein aggregation. This deviation of the apparent diffusion coefficient from concentration-dependent linearity was independent of protein type and solution properties for this study. Thus, this single parameter shows the potential to act as a prognostic tool for colloidal stability of protein solutions. PMID:27421911
NASA Astrophysics Data System (ADS)
Poirier, David R.
2014-08-01
This article is a review of empirical and calculated data on density, viscosity, and diffusion coefficients in hypereutectic Al-Si liquid alloys. Many regressions of the data were effected in order to consolidate the data as functions, which can be used to calculate each property as a function of temperature and concentration of Si. The chemical diffusion coefficient in the alloys was derived based on the Sutherland model, which relates the diffusion coefficient to viscosity.
Diffusion coefficient of krypton atoms in helium gas at low and moderate temperatures
NASA Astrophysics Data System (ADS)
Bouazza, M. T.; Bouledroua, M.
In the present work, using the Chapman-Enskog method for dilute gases, the diffusion coefficients of ground krypton atoms in a very weakly ionized helium buffer gas are revisited. The calculations are carried out quantum mechanically in the range of low and moderate temperatures. The 1 Σ+ potential-energy curve via which Kr approaches He is constructed from the most recent ab initio energy points. The reliable data points used in the construction are smoothly connected to adequate long- and short-range forms. The calculations of the classical second virial coefficients and the Boyle temperature of the helium-krypton mixture are also discussed. These coefficients and their variations in terms of temperature are analysed by adopting the constructed HeKr potential and the Lennard-Jones form that fits it. The diffusion and elastic cross sections are also explored and the resonance features they exhibit are closely examined. The variation law of the diffusion coefficients with temperature is determined for typical values of density and pressure. The coefficients show excellent agreement with the available experimental data; the discrepancies do not exceed 5%.
Zarabadi, Atefeh S; Pawliszyn, Janusz
2015-02-17
Analysis in the frequency domain is considered a powerful tool to elicit precise information from spectroscopic signals. In this study, the Fourier transformation technique is employed to determine the diffusion coefficient (D) of a number of proteins in the frequency domain. Analytical approaches are investigated for determination of D from both experimental and data treatment viewpoints. The diffusion process is modeled to calculate diffusion coefficients based on the Fourier transformation solution to Fick's law equation, and its results are compared to time domain results. The simulations characterize optimum spatial and temporal conditions and demonstrate the noise tolerance of the method. The proposed model is validated by its application for the electropherograms from the diffusion path of a set of proteins. Real-time dynamic scanning is conducted to monitor dispersion by employing whole column imaging detection technology in combination with capillary isoelectric focusing (CIEF) and the imaging plug flow (iPF) experiment. These experimental techniques provide different peak shapes, which are utilized to demonstrate the Fourier transformation ability in extracting diffusion coefficients out of irregular shape signals. Experimental results confirmed that the Fourier transformation procedure substantially enhanced the accuracy of the determined values compared to those obtained in the time domain. PMID:25607375
Belova, Irina; Kulkarni, Nagraj S; Sohn, Yong Ho; Murch, Prof. Graeme
2013-01-01
In this paper, a new development of the classic Onsager phenomenological formalism is derived using relations based on linear response theory. The development concerns the correct description of the fluxes of the atomic isotopes. The resulting expressions in the laboratory frame are surprisingly simple and consist of terms coming from the standard interdiffusion expressions and from Fick s first law where the tracer diffusion coefficient is involved thus providing a better understanding of the relationship between the two approaches - Fick s first law and the Onsager phenomenological formalism. From an experimental application perspective, the new development is applied to the binary alloy case. The formalism provides the means to obtain the interdiffusion coefficient and tracer diffusion coefficients simultaneously from analysis of the interdiffusion concentration profiles in a single experiment.
Hydraulic Containment of TCE Contaminated Groundwater at the DOE Portsmouth Gaseous Diffusion Plant
Lewis, A.C.; Rieske, D.P.G.; Baird, D.R.P.E.
2008-07-01
This paper will describe the progress of a groundwater remedial action at the Portsmouth Gaseous Diffusion Plant (PORTS), a Department of Energy (DOE) facility that enriched uranium from the early 1950's until 2000. The X-749 southern boundary hydraulic containment system, combining a four-well extraction system with a previously constructed subsurface barrier wall, has been employed at PORTS. The hydraulic containment project has been implemented as part of containment and remediation of the X-749/X-120 area trichloroethylene (TCE) contaminant. The X-749/X-120 groundwater contaminant plume is located in the south central section (Quadrant I) of the PORTS facility. The plume is associated with the former X-120 Goodyear Training Facility and a landfill known as the X-749 Contaminated Materials Disposal Facility. The principal contaminants of concern are chlorinated solvents (primarily TCE) and technetium-99 (Tc-99). A subsurface barrier wall (X-749 South Barrier Wall) was completed in 1994 at the PORTS southern reservation boundary as an interim remedial measure to slow the advancement of the leading edge of the contaminated groundwater plume or to prevent the plume from migrating off DOE property. Remedial measures identified by Ohio Environmental Protection Agency (Ohio EPA) included installation of a barrier wall around the eastern and southern portions of the X-749 landfill to provide source control and installation of a phyto-remediation system to help contain groundwater flow and remove volatile organic compounds. Previous remedial measures that were implemented as elements of 'closures' on the X-749 landfill included a multimedia cap, barrier walls, and a groundwater collection system. Despite these measures, the X-749/X-120 groundwater plume has migrated beyond the southern DOE property boundary. Current TCE concentrations in off-site groundwater monitoring wells are below the preliminary remediation goal and drinking water maximum contaminant level for TCE
Swift, Barry D.; Tarantino, Joseph J., P. E.
2003-02-27
The Paducah Gaseous Diffusion Plant (PGDP), owned by the Department of Energy (DOE), has been enriching uranium since the early 1950s. The enrichment process involves electrical and mechanical components that require periodic cleaning. The primary cleaning agent was trichloroethene (TCE) until the late 1980s. Historical documentation indicates that a mixture of TCE and dry ice were used at PGDP for testing the integrity of steel cylinders, which stored depleted uranium. TCE and dry ice were contained in a below-ground pit and used during the integrity testing. TCE seeped from the pit and contaminated the surrounding soil. The Lasagna{trademark} technology was identified in the Record of Decision (ROD) as the selected alternative for remediation of the cylinder testing site. A public-private consortium formed in 1992 (including DOE, the U.S. Environmental Protection Agency, and the Kentucky Department for Environmental Protection, Monsanto, DuPont, and General Electric) developed the Lasagna{trademark} technology. This innovative technology employs electrokinetics to remediate soil contaminated with organics and is especially suited to sites with low permeability soils. This technology uses direct current to move water through the soil faster and more uniformly than hydraulic methods. Electrokinetics moves contaminants in soil pore water through treatment zones comprised of iron filings, where the contaminants are decomposed to basic chemical compounds such as ethane. After three years of development in the laboratory, the consortium field tested the Lasagna{trademark} process in several phases. CDM installed and operated Phase I, the trial installation and field test of a 150-square-foot area selected for a 120-day run in 1995. Approximately 98 percent of the TCE was removed. CDM then installed and operated the next phase (IIa), a year-long test on a 600-square-foot site. Completed in July 1997, this test removed 75 percent of the total volume of TCE down to a
Hermes, Helen E; Sitta, Christoph E; Schillinger, Burkhard; Löwen, Hartmut; Egelhaaf, Stefan U
2015-06-28
The dissolution of polyethylene oxide (PEO) tablets in water has been followed in situ by neutron radiography. When in contact with water, the crystalline phase of semi-crystalline PEO melts once a certain water content is attained. Polymer concentration profiles obtained from the neutron transmission images exhibited a pronounced kink which corresponds to a sharp front in the images and which is related to the melting transition. Sharp diffusion fronts and phase transitions are often linked to non-Fickian behaviour. However, by considering the time evolution of the complete concentration profiles in detail it is shown that the dissolution process can be explained using Fickian diffusion equations with a concentration-dependent diffusion coefficient. PMID:26018995
Estimating diffusion coefficients in low-permeability porous media using a macropore column
Young, D.F.; Ball, W.P.
1998-09-01
Diffusion coefficients in an aquitard material were measured by conducting miscible solute transport experiments through a specially constructed macropore column. Stainless steel HPLC columns were prepared in a manner that created an annular region of repacked aquitard material and a central core of medium-grained quartz sand. The column transport approach minimizes volatilization and sorption losses that can be problematic when measuring hydrophobic organic chemical diffusion with diffusion-cell methods or column-sectioning techniques. In the transport experiments, solutes (triated water, 1,2,4-trichlorobenzene, and tetrachloroethene) were transported through the central core by convection and hydrodynamic dispersion and through the low-permeability annulus by radial diffusion. All transport parameters were independently measured except for the effective diffusion coefficient in the aquitard material, which was obtained by model fitting. Batch-determined retardation factors agreed very closely with moment-derived retardation factors determined from the column experiments, and no evidence of pore exclusion was found. A model with retarded diffusion was found to apply, and the effective tortuosity factor of the aquitard material was estimated at an average value of 5.1.
Kuss, Joachim; Holzmann, Jörg; Ludwig, Ralf
2009-05-01
Mercury is a priority pollutant as its mobility between the hydrosphere and the atmosphere threatens the biosphere globally. The air-water gas transfer of elemental mercury (Hg0) is controlled by its diffusion through the water-side boundary layer and thus by its diffusion coefficient, D(Hg), the value of which, however, has not been established. Here, the diffusion of Hg0 in water was modeled by molecular dynamics (MD) simulation and the diffusion coefficient subsequently determined. Therefore the movement of either Hg(0) or xenon and 1000 model water molecules (TIP4P-Ew) were traced for time spans of 50 ns. The modeled D(Xe) of the monatomic noble gas agreed well with measured data; thus, MD simulation was assumed to be a reliable approach to determine D(Hg) for monatomic Hg(0) as well. Accordingly, Hg(0) diffusion was then simulated for freshwater and seawater, and the data were well-described by the equation of Eyring. The activation energies for the diffusion of Hg0 in freshwater was 17.0 kJ mol(-1) and in seawater 17.8 kJ mol(-1). The newly determined D(Hg) is clearly lower than the one previously used for an oceanic mercury budget. Thus, its incorporation into the model should lead to lower estimates of global ocean mercury emissions. PMID:19534132
Worth, H; Nüsse, W; Piiper, J
1978-01-01
In order to provide data required for quantitative analysis of gas diffusion in lung airways, diffusion of He, CO, O2, CO2 and SF6 in various gases used in respiratory physiology was studied in vitro at 37 degrees C and 25 degrees C. The gases were allowed to mix by diffusion in a closed cylindrical tube (length 2 m, internal diameter 1 cm), one half of which was initially filled with 1% test gas in a second gas and the other half of which was filled with the second gas only. Kinetics of diffusional equilibration was determined by withdrawal of spot samples analyzed by gas chromatography. The binary (mutual) diffusion coefficients (D) computed there from were in most cases in good agreement with values calculated on the basis of the Chapman-Enskog theory. PMID:625611
Method for the measurement of the diffusion coefficient of benzalkonium chloride.
Smith, M J; Flowers, T H; Cowling, M J; Duncan, H J
2002-03-01
Biofilm formation on the optical ports of cameras and underwater sensors is the primary cause of their reduced useful deployment time. The use of a transparent hydrogel coating containing the cationic surfactant benzalkonium chloride has been shown to extend the deployment times for up to 12 weeks for these instruments. In order to predict the effective lifetime of these coatings it was necessary to obtain the diffusion coefficient of the benzalkonium chloride used in the coatings. Benzalkonium chloride can have different alkyl chain lengths ranging from C8H17 to C18H37 with chain length greatly affecting its chemical properties. The benzalkonium chloride materials investigated here were mixtures of C12H25 and C14H29 as well as C14H29 on its own. These materials were selected for their proven biofilm resistant qualities. The diaphragm diffusion cell technique was investigated for its applicability to the measurement of diffusion coefficients of molecules with surfactant properties and the ability to form micelles. The method was found to be satisfactory for the cationic surfactant benzalkonium chloride. The average value of the membrane cell integral diffusion coefficient D was 7.78 x 10(-6) cm2 s(-1) at 25 degrees C and there was no significant effect of alkyl chain length on the measured value of D. PMID:11996332
NASA Astrophysics Data System (ADS)
Petruk, V. G.; Ivanov, A. P.; Kvaternyuk, S. M.; Barun, V. V.
2016-03-01
We have designed an experimental setup, based on two integrating spheres, that lets us measure the optical diffuse reflectance spectra (diffuse reflection coefficient vs. wavelength) of human skin quickly under clinical conditions in vivo. For the wavelength interval 520-1100 nm, we give the values of the diffuse reflection coefficient for healthy tissue, skin with a benign nevus, and skin with a malignant melanoma for a large group of test subjects. We experimentally established a number of wavelengths in the red-near IR region of the spectrum which can be used for early differential diagnosis of nevi and melanoma in patient cancer screening. According to the Kramer-Welch test, the probability of the diffuse reflection coefficient for skin with melanoma and a nevus having different distributions is >0.94, and at many wavelengths it is >0.999. By solving the inverse problem, we estimated the changes in a number of structural and biophysical parameters of the tissue on going from healthy skin to nevus and melanoma. The results obtained can provide a basis for developing a clinical approach to identifying the risk of malignant transformation of the skin before surgery and histological analysis of the tissue.
Sundaram, P.A.; Wessel, E.; Clemens, H.; Kestler, H.; Ennis, P.J.; Quadakkers, W.J.; Singheiser, L.
2000-03-14
The diffusion coefficient of hydrogen in some gamma based titanium aluminide alloys was determined at room temperature using an electrochemical techniques. A cast Ti-48Al-2Cr alloy as well as Ti-46.5Al-4(Cr,Nb,Ta,B) sheet material with primary annealed and designed fully lamellar microstructures were subjected to cathodic hydrogen charging at room temperature in the galvanostatic mode. The potential variation with time was monitored form which data the values of the diffusion coefficient of hydrogen, D were calculated form well known error function/infinite series solutions to Fick's second law. Very good correlation was obtained with respect to theoretical calculations. The diffusion coefficients appear to be in close agreement with those for the cast alloy calculated from microhardness measurements. The value of D can be overestimated for thick specimens. Results show that neither the microstructure in terms of grain/lamellar colony size, nor the charging current density, appear to have a significant effect on the value of D. Lattice diffusion appears to be rate controlling.
Yao, Shenggen; Babon, Jeffrey J; Norton, Raymond S
2008-08-01
Molecular rotational correlation times are of interest for many studies carried out in solution, including characterization of biomolecular structure and interactions. Here we have evaluated the estimates of protein effective rotational correlation times from their translational self-diffusion coefficients measured by pulsed-field gradient NMR against correlation times determined from both collective and residue-specific (15)N relaxation analyses and those derived from 3D structure-based hydrodynamic calculations. The results show that, provided the protein diffusive behavior is coherent with the Debye-Stokes-Einstein model, translational diffusion coefficients provide rapid estimates with reasonable accuracy of their effective rotational correlation times. Effective rotational correlation times estimated from translational diffusion coefficients may be particularly beneficial in cases where i) isotopically labelled material is not available, ii) collective backbone (15)N relaxation rates are difficult to interpret because of the presence of flexible termini or loops, or iii) a full relaxation analysis is practically difficult because of limited sensitivity owing to low protein concentration, high molecular mass or low temperatures. PMID:18583018
An interpretation of potential scale dependence of the effectivematrix diffusion coefficient
Liu, H.H.; Zhang, Y.Q.; Zhou, Q.; Molz, F.J.
2005-11-30
Matrix diffusion is an important process for solutetransport in fractured rock, and the matrix diffusion coefficient is akey parameter for describing this process. Previous studies indicatedthat the effective matrix diffusion coefficient values, obtained from alarge number of field tracer tests, are enhanced in comparison with localvalues and may increase with test scale. In this study, we have performednumerical experiments to investigate potential mechanisms behind possiblescale-dependent behavior. The focus of the experiments is on solutetransport in flow paths having geometries consistent with percolationtheories and characterized by local flow loops formed mainly bysmall-scale fractures. The water velocity distribution through a flowpath was determined using discrete fracture network flow simulations, andsolute transport was calculated using a previously derivedimpulse-response function and a particle-tracking scheme. Values foreffective (or up-scaled) transport parameters were obtained by matchingbreakthrough curves from numerical experiments with an analyticalsolution for solute transport along a single fracture. Results indicatethat a combination of local flow loops and the associated matrixdiffusion process, together with scaling properties in flow pathgeometry, seems to be the dominant mechanism causing the observed scaledependence of theeffective matrix diffusion coefficient (at a range ofscales).
Kruk, D.; Meier, R.; Rössler, E. A.; Rachocki, A.; Korpała, A.; Singh, R. K.
2014-06-28
Field Cycling Nuclear Magnetic Resonance (FC NMR) relaxation studies are reported for three ionic liquids: 1-ethyl-3- methylimidazolium thiocyanate (EMIM-SCN, 220–258 K), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF{sub 4}, 243–318 K), and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF{sub 6}, 258–323 K). The dispersion of {sup 1}H spin-lattice relaxation rate R{sub 1}(ω) is measured in the frequency range of 10 kHz–20 MHz, and the studies are complemented by {sup 19}F spin-lattice relaxation measurements on BMIM-PF{sub 6} in the corresponding frequency range. From the {sup 1}H relaxation results self-diffusion coefficients for the cation in EMIM-SCN, BMIM-BF{sub 4}, and BMIM-PF{sub 6} are determined. This is done by performing an analysis considering all relevant intra- and intermolecular relaxation contributions to the {sup 1}H spin-lattice relaxation as well as by benefiting from the universal low-frequency dispersion law characteristic of Fickian diffusion which yields, at low frequencies, a linear dependence of R{sub 1} on square root of frequency. From the {sup 19}F relaxation both anion and cation diffusion coefficients are determined for BMIM-PF{sub 6}. The diffusion coefficients obtained from FC NMR relaxometry are in good agreement with results reported from pulsed- field-gradient NMR. This shows that NMR relaxometry can be considered as an alternative route of determining diffusion coefficients of both cations and anions in ionic liquids.
NASA Astrophysics Data System (ADS)
Suzuki, S.; Itoh, H.
2016-05-01
The diffusion coefficient of the metastable excited Ne(3P2) atom in neon, the reflection coefficient of Ne(3P2) at the surface of an electrode and the rate coefficient of Ne(3P2) for collisional quenching by Ne(1S0) were determined from the gas pressure dependence of the effective lifetime of Ne(3P2). The effective lifetime of Ne(3P2) was measured from the transient current after turning off the Ultraviolet (UV) light in a Townsend discharge. The observed transient current waveform was analysed by solving the diffusion equation for the metastable excited Ne(3P2) atom using the third kind of boundary condition. The rate coefficient of Ne(3P2) for collisional quenching by Ne(1S0) and the reflection coefficient were determined by a nonspectroscopic method for the first time in neon to the best of our knowledge and were (3.2 ± 0.4) × 10‑16 cm3 s‑1 and 0.10 ± 0.04, respectively. The obtained diffusion coefficient at 1 Torr was 177 ± 17 cm2 s‑1, which is consistent with the value reported by Dixon and Grant. Moreover, the present results are compared with the results of Phelps and were found to be in good agreement. We also discuss the deexcitation rate of Ne(3P2) at pressures of up to 60 Torr in comparison with previously reported values.
A new in-situ method to determine the apparent gas diffusion coefficient of soils
NASA Astrophysics Data System (ADS)
Laemmel, Thomas; Paulus, Sinikka; Schack-Kirchner, Helmer; Maier, Martin
2015-04-01
Soil aeration is an important factor for the biological activity in the soil and soil respiration. Generally, gas exchange between soil and atmosphere is assumed to be governed by diffusion and Fick's Law is used to describe the fluxes in the soil. The "apparent soil gas diffusion coefficient" represents the proportional factor between the flux and the gas concentration gradient in the soil and reflects the ability of the soil to "transport passively" gases through the soil. One common way to determine this coefficient is to take core samples in the field and determine it in the lab. Unfortunately this method is destructive and needs laborious field work and can only reflect a small fraction of the whole soil. As a consequence insecurity about the resulting effective diffusivity on the profile scale must remain. We developed a new in-situ method using new gas sampling device, tracer gas and inverse soil gas modelling. The gas sampling device contains several sampling depths and can be easily installed into vertical holes of an auger, which allows for fast installation of the system. At the lower end of the device inert tracer gas is injected continuously. The tracer gas diffuses into the surrounding soil. The resulting distribution of the tracer gas concentrations is used to deduce the diffusivity profile of the soil. For Finite Element Modeling of the gas sampling device/soil system the program COMSOL is used. We will present the results of a field campaign comparing the new in-situ method with lab measurements on soil cores. The new sampling pole has several interesting advantages: it can be used in-situ and over a long time; so it allows following modifications of diffusion coefficients in interaction with rain but also vegetation cycle and wind.
Cleveland, G G; Chang, D C; Hazlewood, C F; Rorschach, H E
1976-01-01
The anisotropy of the spin-diffusion coefficient Ds of water protons in skeletal muscle has been studied by pulsed NMR methods. The mid-portion of the tibialis anterior muscle of mature male rats was placed in a special sample holder by means of which the muscle fiber orientation theta relative to the diffusion direction could be varied over the range 0 degrees less than or equal to theta less than or equal to 90 degrees. The value of Ds(theta) was determined for theta = 0 degrees, 45 degrees, and 90 degrees. The measured anisotropy Ds(0)/Ds(90) was 1.39, and the value of Ds(0) was 1.39 X 10(-5) cm2/s. These results are interpreted within the framework of a model calculation in which the diffusion equation is solved for a regular hexagonal network similar to the actin-myosin filament network. The large anisotropy, and the large reduction in the value of Ds measured parallel to the filament axes lead to two major conclusions: (a) interpretations in which the reduction in Ds is ascribed to the effect of geometrical obstructions on the diffusion of "free" water are ruled out; and, (b) there is a large fraction of the cellular water associated with the proteins in such a way that its diffusion coefficient is substantially reduced. PMID:963204
Celik, Azim
2016-01-01
PURPOSE We aimed to investigate the effect of key imaging parameters on the accuracy of apparent diffusion coefficient (ADC) maps using a phantom model combined with ADC calculation simulation and propose strategies to improve the accuracy of ADC quantification. METHODS Diffusion-weighted imaging (DWI) sequences were acquired on a phantom model using single-shot echo-planar imaging DWI at 1.5 T scanner by varying key imaging parameters including number of averages (NEX), repetition time (TR), echo time (TE), and diffusion preparation pulses. DWI signal simulations were performed for varying TR and TE. RESULTS Magnetic resonance diffusion signal and ADC maps were dependent on TR and TE imaging parameters as well as number of diffusion preparation pulses, but not on the NEX. However, the choice of a long TR and short TE could be used to minimize their effects on the resulting DWI sequences and ADC maps. CONCLUSION This study shows that TR and TE imaging parameters affect the diffusion images and ADC maps, but their effect can be minimized by utilizing diffusion preparation pulses. Another key imaging parameter, NEX, is less relevant to DWI and ADC quantification as long as DWI signal-to-noise ratio is above a certain level. Based on the phantom results and data simulations, DWI acquisition protocol can be optimized to obtain accurate ADC maps in routine clinical application for whole body imaging. PMID:26573977
Diffusion coefficients of Fokker-Planck equation for rotating dust grains in a fusion plasma
Bakhtiyari-Ramezani, M. Alinejad, N.; Mahmoodi, J.
2015-11-15
In the fusion devices, ions, H atoms, and H{sub 2} molecules collide with dust grains and exert stochastic torques which lead to small variations in angular momentum of the grain. By considering adsorption of the colliding particles, thermal desorption of H atoms and normal H{sub 2} molecules, and desorption of the recombined H{sub 2} molecules from the surface of an oblate spheroidal grain, we obtain diffusion coefficients of the Fokker-Planck equation for the distribution function of fluctuating angular momentum. Torque coefficients corresponding to the recombination mechanism show that the nonspherical dust grains may rotate with a suprathermal angular velocity.
Diffusion coefficients of Fokker-Planck equation for rotating dust grains in a fusion plasma
NASA Astrophysics Data System (ADS)
Bakhtiyari-Ramezani, M.; Mahmoodi, J.; Alinejad, N.
2015-11-01
In the fusion devices, ions, H atoms, and H2 molecules collide with dust grains and exert stochastic torques which lead to small variations in angular momentum of the grain. By considering adsorption of the colliding particles, thermal desorption of H atoms and normal H2 molecules, and desorption of the recombined H2 molecules from the surface of an oblate spheroidal grain, we obtain diffusion coefficients of the Fokker-Planck equation for the distribution function of fluctuating angular momentum. Torque coefficients corresponding to the recombination mechanism show that the nonspherical dust grains may rotate with a suprathermal angular velocity.
Zheng, Xiaobing; Dickey, Tommy; Chang, Grace
2002-10-20
In situ time-series measurements of spectral diffuse downwelling irradiance from the Bermuda Testbed Mooring are presented. Averaged diffuse attenuation coefficients of downwelling irradiance, Kd,and their elastic and inelastic components are investigated at seven wavelengths. At shorter wavelengths (<510 nm), Kd is weakly dependent on the solar zenith angle owing to the prevailing scattering effect and therefore can be considered a quasi-inherent optical property. At longer wavelengths (>510 nm), Kd shows a strong dependence on the solar zenith angle. As depth increases, inelastic scattering plays a greater role for the underwater light field at red wavelengths. PMID:12396201
Kernel-based regression of drift and diffusion coefficients of stochastic processes
NASA Astrophysics Data System (ADS)
Lamouroux, David; Lehnertz, Klaus
2009-09-01
To improve the estimation of drift and diffusion coefficients of stochastic processes in case of a limited amount of usable data due to e.g. non-stationarity of natural systems we suggest to use kernel-based instead of histogram-based regression. We propose a method for bandwidth selection and compare it to a widely used cross-validation method. Kernel-based regression reveals an enhanced ability to estimate drift and diffusion especially for a small amount of data. This allows one to improve resolvability of changes in complex dynamical systems as evidenced by an exemplary analysis of electroencephalographic data recorded from a human epileptic brain.
Thermal Expansion and Diffusion Coefficients of Carbon Nanotube-Polymer Composites
NASA Technical Reports Server (NTRS)
Wei, Chengyu; Srivastava, Deepak; Cho, Kyeongjae; Biegel, Bryan (Technical Monitor)
2001-01-01
Classical molecular dynamics (MD) simulations employing Brenner potential for intra-nanotube interactions and van der Waals forces for polymer-nanotube interface have been used to investigate thermal expansion and diffusion characteristics of carbon nanotube-polyethylene composites. Addition of carbon nanotubes to polymer matrix is found to significantly increase the glass transition temperature Tg, and thermal expansion and diffusion coefficients in the composite above Tg. The increase has been attributed to the temperature dependent increase of the excluded volume for the polymer chains, and the findings could have implications in the composite processing, coating and painting applications.
Integral formula for the effective diffusion coefficient in two-dimensional channels
NASA Astrophysics Data System (ADS)
Kalinay, Pavol
2016-07-01
The effective one-dimensional description of diffusion in two-dimensional channels of varying cross section is revisited. The effective diffusion coefficient D (x ) , extending Fick-Jacobs equation, depending on the longitudinal coordinate x , is derived here without use of scaling of the transverse coordinates. The result of the presented method is an integral formula for D (x ) , calculating its value at x as an integral of contributions from the neighboring positions x' depending on h (x') , a function shaping the channel. Unlike the standard formulas based on the scaling, the new proposed formula also describes D (x ) correctly near the cusps, or in wider channels.
NASA Astrophysics Data System (ADS)
Charsooghi, Mohammad A.; Akhlaghi, Ehsan A.; Tavaddod, Sharareh; Khalesifard, H. R.
2011-02-01
We developed a graphical user interface, MATLAB based program to calculate the translational diffusion coefficients in three dimensions for a single diffusing particle, suspended inside a fluid. When the particles are not spherical, in addition to their translational motion also a rotational freedom is considered for them and in addition to the previous translational diffusion coefficients a planar rotational diffusion coefficient can be calculated in this program. Time averaging and ensemble averaging over the particle displacements are taken to calculate the mean square displacement variations in time and so the diffusion coefficients. To monitor the random motion of non-spherical particles a reference frame is used that the particle just have translational motion in it. We call it the body frame that is just like the particle rotates about the z-axis of the lab frame. Some statistical analysis, such as velocity autocorrelation function and histogram of displacements for the particle either in the lab or body frames, are available in the program. Program also calculates theoretical values of the diffusion coefficients for particles of some basic geometrical shapes; sphere, spheroid and cylinder, when other diffusion parameters like temperature and fluid viscosity coefficient can be adjusted. Program summaryProgram title: KOJA Catalogue identifier: AEHK_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHK_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 48 021 No. of bytes in distributed program, including test data, etc.: 1 310 320 Distribution format: tar.gz Programming language: MatLab (MathWorks Inc.) version 7.6 or higher. Statistics Toolbox and Curve Fitting Toolbox required. Computer: Tested on windows and linux, but generally it would work on any
Drift tube measurements of mobilities and longitudinal diffusion coefficients of ions in gases
Chelf, R.D.
1982-01-01
The zero-field mobilities of Br/sup -/ and NH/sub 4//sup +/ in O/sub 2/ were determined as a function of gas temperature in a high pressure drift tube mass spectrometer. The mobilities and longitudinal diffusion coefficients of the ion-gas combinations Br/sup -/ in Ne and Kr, Li/sup +/ in Xe, and Tl//sup +/ in Kr and Xe were determined as a function of E/N, where E is the electric field strength and N is the gas number density in a low pressure drift tube mass spectrometer. The measured longitudinal diffusion coefficients were used for a test and comparison of the generalized Einstein relations of Viehland-Mason and Waldman-Mason theories. The measured mobilities of Br/sup -/ in Kr and Tl//sup +/ in Kr were used in an iterative-inversion scheme from which the ion-neutral interaction potentials were determined.
Diffusion coefficients of energetic water group ions near Comet Giacobini-Zinner
NASA Astrophysics Data System (ADS)
Tan, L. C.; Mason, G. M.; Richardson, I. G.; Ipavich, F. M.
1993-03-01
Data from the ultralow-energy charge analyzer and energetic particle anisotropy spectrometer sensors, acquired when the ICE spacecraft flew past Comet Giacobini-Zinner on September 11, 1985, are combined, and a single, self-consistent analysis technique is applied to derive a single-particle spectrum from about 200 to 1600 km/s. This information, together with the deduced bulk flow speed of the ions, is used to calculate a parallel diffusion coefficient in the transition region downstream of the bow wave (2.3 +/- 0.5) x 10 exp 17 sq cm/s; the corresponding scattering mean free path is (6 +/- 1) x 10 exp 4 km. The parallel diffusion coefficient is found to depend on the collision frequency of water group ions with Alfven waves, which are assumed to be propagating parallel (antiparallel) to the magnetic field.
A Monte Carlo model for determination of binary diffusion coefficients in gases
NASA Astrophysics Data System (ADS)
Panarese, A.; Bruno, D.; Colonna, G.; Diomede, P.; Laricchiuta, A.; Longo, S.; Capitelli, M.
2011-06-01
A Monte Carlo method has been developed for the calculation of binary diffusion coefficients in gas mixtures. The method is based on the stochastic solution of the linear Boltzmann equation obtained for the transport of one component in a thermal bath of the second one. Anisotropic scattering is included by calculating the classical deflection angle in binary collisions under isotropic potential. Model results are compared to accurate solutions of the Chapman-Enskog equation in the first and higher orders. We have selected two different cases, H 2 in H 2 and O in O 2, assuming rigid spheres or using a model phenomenological potential. Diffusion coefficients, calculated in the proposed approach, are found in close agreement with Chapman-Enskog results in all the cases considered, the deviations being reduced using higher order approximations.
Diffusion coefficients of energetic water group ions near Comet Giacobini-Zinner
NASA Technical Reports Server (NTRS)
Tan, L. C.; Mason, G. M.; Richardson, I. G.; Ipavich, F. M.
1993-01-01
Data from the ultralow-energy charge analyzer and energetic particle anisotropy spectrometer sensors, acquired when the ICE spacecraft flew past Comet Giacobini-Zinner on September 11, 1985, are combined, and a single, self-consistent analysis technique is applied to derive a single-particle spectrum from about 200 to 1600 km/s. This information, together with the deduced bulk flow speed of the ions, is used to calculate a parallel diffusion coefficient in the transition region downstream of the bow wave (2.3 +/- 0.5) x 10 exp 17 sq cm/s; the corresponding scattering mean free path is (6 +/- 1) x 10 exp 4 km. The parallel diffusion coefficient is found to depend on the collision frequency of water group ions with Alfven waves, which are assumed to be propagating parallel (antiparallel) to the magnetic field.
Oxygen diffusion coefficient and solubility in a new proton exchange membrane
Haug, A.T.; White, R.E.
2000-03-01
The electrochemical monitoring technique is used to measure the solubility and the diffusion coefficient of oxygen in a new proton exchange membrane that is being developed by Cape Cod Research, Inc., Using the method of least squares, the data were fit to an analytical solution of Fick's second law to determine D and c{sub 0}. Values of 0.40 x 10{sup {minus}6}cm{sup 2}/s and 4.98 x 10{sup {minus}6} mol/cm{sup 3} were obtained for the diffusion coefficient and solubility, respectively, of the Cape Cod membrane. These values are significantly less than those of Nafion 117 tested under identical conditions.
A Monte Carlo model for determination of binary diffusion coefficients in gases
Panarese, A.; Bruno, D.; Colonna, G.; Diomede, P.; Laricchiuta, A.; Longo, S.; Capitelli, M.
2011-06-20
A Monte Carlo method has been developed for the calculation of binary diffusion coefficients in gas mixtures. The method is based on the stochastic solution of the linear Boltzmann equation obtained for the transport of one component in a thermal bath of the second one. Anisotropic scattering is included by calculating the classical deflection angle in binary collisions under isotropic potential. Model results are compared to accurate solutions of the Chapman-Enskog equation in the first and higher orders. We have selected two different cases, H{sub 2} in H{sub 2} and O in O{sub 2}, assuming rigid spheres or using a model phenomenological potential. Diffusion coefficients, calculated in the proposed approach, are found in close agreement with Chapman-Enskog results in all the cases considered, the deviations being reduced using higher order approximations.
Rowley, R.L.; Oscarson, J.L.
1993-01-01
The objective of the work is to provide accurate data on diffusion coefficients and heats of absorption of acid gases in aqueous amine solutions to assist in the design of economical new amine treating systems and to improve the efficiency of existing plants. Specifically covered in the report are measurements of the mutual diffusion coefficient of methyldiethanolamine(MDEA) and diethanolamine in water. Measurements have been made at 25, 50 and 75C and at 0, 20, 35 and 50 wt% amine. Heats of absorption of CO2 into aqueous mixtures of MDEA have also been measured calorimetrically. Results are reported at temperatures of 120 and 260F and pressures of 500 and 1000 psia at total MDEA concentrations of 20, 35 and 50%.
Determination of the Solute Diffusion Coefficient by the Droplet Migration Method
Shan Liu; Jing Teng; Jeongyun Choi
2007-07-01
Further analysis of droplet migration in a temperature gradient field indicates that different terms can be used to evaluate the solute diffusion coefficient in liquid (D{sub L}) and that there exists a characteristic curve that can describe the motion of all the droplets for a given composition and temperature gradient. Critical experiments are subsequently conducted in succinonitrile (SCN)-salol and SCN-camphor transparent alloys in order to observe dynamic migration processes of a number of droplets. The derived diffusion coefficients from different terms are the same within experimental error. For SCN-salol alloys, D{sub L} = (0.69 {+-} 0.05) x 10{sup -3} mm{sup 2}/s, and for SCN-camphor alloys, D{sub L} = (0.24 {+-} 0.02) x 10{sup -3} mm{sup 2}/s.
Thermal diffusivity coefficient of glycerin determined on an acoustically levitated drop.
Ohsaka, K; Rednikov, A; Sadhal, S S
2002-10-01
We present a technique that can be used to determine the thermal diffusivity coefficient of undercooled liquids that exist at temperatures below their freezing points. The technique involves levitation of a small amount of liquid in the shape of a flattened drop using an acoustic levitator and heating it with a CO2 laser. The heated drop is then allowed to cool naturally by heat loss from the surface. Due to acoustic streaming, heat loss is highly non-uniform and appears to mainly occur at the drop circumference (equatorial region). This fact allows us to relate the heat loss rate with a heat transfer model to determine the thermal diffusion coefficient. We demonstrate the feasibility of the technique using glycerin drops as a model liquid. PMID:12446319
Diffusion coefficients of sodium fluoride in aqueous solutions at 298.15 k and 310.15 k.
Ribeiro, Ana C F; Lobo, Victor M M; Sobral, Abilio J F N; Soares, Helder T F C; Esteso, Ana R J; Esteso, Miguel A
2010-06-01
Mutual diffusion coefficients (interdiffusion coefficients) have been measured for sodium fluoride in water at 298.15 K and 310.15 K at concentrations between 0.003 mol dm-3 and 0.05 mol dm-3. The diffusion coefficients were measured using a conductimetric cell. The experimental mutual diffusion coefficients are discussed on the basis of the Onsager-Fuoss model. The limiting molar conductivity of the fluoride ion in these solutions at 310.15 K has been estimated using these results. PMID:24061738
NASA Astrophysics Data System (ADS)
Kujawa, Sebastian; Weres, Jerzy; Olek, Wiesław
2016-07-01
Uncertainties in mathematical modelling of water transport in cereal grain kernels during drying and storage are mainly due to implementing unreliable values of the water diffusion coefficient and simplifying the geometry of kernels. In the present study an attempt was made to reduce the uncertainties by developing a method for computer-aided identification of the water diffusion coefficient and more accurate 3D geometry modelling for individual kernels using original inverse finite element algorithms. The approach was exemplified by identifying the water diffusion coefficient for maize kernels subjected to drying. On the basis of the developed method, values of the water diffusion coefficient were estimated, 3D geometry of a maize kernel was represented by isoparametric finite elements, and the moisture content inside maize kernels dried in a thin layer was predicted. Validation of the results against experimental data showed significantly lower error values than in the case of results obtained for the water diffusion coefficient values available in the literature.
Scaling Limits of a Tagged Particle in the Exclusion Process with Variable Diffusion Coefficient
NASA Astrophysics Data System (ADS)
Gonçalves, Patrícia; Jara, Milton
2008-09-01
We prove a law of large numbers and a central limit theorem for a tagged particle in a symmetric simple exclusion process in ℤ with variable diffusion coefficient. The scaling limits are obtained from a similar result for the current through -1/2 for a zero-range process with bond disorder. For the CLT, we prove convergence to a fractional Brownian motion of Hurst exponent 1/4.
Measurement of the diffusion coefficient of acetone in succinonitrile at its melting point
NASA Technical Reports Server (NTRS)
Chopra, M. A.; Glicksman, M. E.; Singh, N. B.
1988-01-01
The diffusion coefficient of acetone in liquid succinonitrile at 331.1 K was determined using the method of McBain and Dawson (1935). Only dilute mixtures of SCN-acetone were studied. The interdiffusion constant was determined to be 0.0000127 sq cm/s and was essentially independent of the acetone concentration over the range investigated (0.5 to 18 mol pct acetone).
NASA Technical Reports Server (NTRS)
Gage, K. S.; Jasperson, W. H.
1977-01-01
An analysis is presented of the tropospheric turbulence data obtained by the Metrac positioning system, a radio location system which employs the Doppler principle to track inexpensive expendable balloon-borne transmitters. A Minneapolis field test of the Metrac system provided one-second samples of transmitter frequency from balloons tracked by four ground stations for more than an hour. The derivation of diffusion coefficients from the turbulence data was conducted by two methods, yielding highly consistent results.
NASA Technical Reports Server (NTRS)
Chow, M.; Houska, C. R.
1980-01-01
Solutions are given for one-dimensional diffusion problems with a time varying surface composition and also a composition dependent diffusion coefficient. The most general solution does not require special mathematical functions to fit the variation in surface composition or D(C). In another solution, a series expansion may be used to fit the time dependent surface concentration. These solutions make use of iterative calculations that converge rapidly and are highly stable. Computer times are much shorter than that required for finite difference calculations and can efficiently make use of interactive graphics terminals. Existing gas carburization data were used to provide an illustration of an iterative approach with a time varying carbon composition at the free surface.
Aguilar-Mendez, M A; Martin-Martinez, E San; Morales, J E; Cruz-Orea, A; Jaime-Fonseca, M R
2007-04-01
Water vapor diffusion coefficient (WVDC) and thermal diffusivity (alpha) were determined in gelatin-starch films through photothermal techniques. The effect of different variables in the elaboration of these films, such as starch and glycerol concentrations and pH, were evaluated through the response surface methodology. The results indicated that an increase in the glycerol concentration and pH favored the WVDC of the films. On the other hand, alpha was influenced principally by the starch content and pH of the film-forming solution. The minimum alpha value was 4.5 x 10(-4) cm2/s, which is compared with alpha values reported for commercial synthetic polymers. PMID:17420552
Smyre, J.L.; Moll, B.W.; King, A.L.
1996-06-01
Three gamma radiological surveys have been conducted under auspices of the ER Remote Sensing Program: (1) Oak Ridge Reservation (ORR) (1992), (2) Clinch River (1992), and (3) Portsmouth Gaseous Diffusion Plant (PORTS) (1993). In addition, the Remote Sensing Program has acquired the results of earlier surveys at Paducah Gaseous Diffusion Plant (PGDP) (1990) and PORTS (1990). These radiological surveys provide data for characterization and long-term monitoring of U.S. Department of Energy (DOE) contamination areas since many of the radioactive materials processed or handled on the ORR, PGDP, and PORTS are direct gamma radiation emitters or have gamma emitting daughter radionuclides. High resolution airborne gamma radiation surveys require a helicopter outfitted with one or two detector pods, a computer-based data acquisition system, and an accurate navigational positioning system for relating collected data to ground location. Sensors measure the ground-level gamma energy spectrum in the 38 to 3,026 KeV range. Analysis can provide gamma emission strength in counts per second for either gross or total man-made gamma emissions. Gross count gamma radiation includes natural background radiation from terrestrial sources (radionuclides present in small amounts in the earth`s soil and bedrock), from radon gas, and from cosmic rays from outer space as well as radiation from man-made radionuclides. Man-made count gamma data include only the portion of the gross count that can be directly attributed to gamma rays from man-made radionuclides. Interpretation of the gamma energy spectra can make possible the determination of which specific radioisotopes contribute to the observed man-made gamma radiation, either as direct or as indirect (i.e., daughter) gamma energy from specific radionuclides (e.g., cesium-137, cobalt-60, uranium-238).
Method for Calculating the Optical Diffuse Reflection Coefficient for the Ocular Fundus
NASA Astrophysics Data System (ADS)
Lisenko, S. A.; Kugeiko, M. M.
2016-07-01
We have developed a method for calculating the optical diffuse reflection coefficient for the ocular fundus, taking into account multiple scattering of light in its layers (retina, epithelium, choroid) and multiple refl ection of light between layers. The method is based on the formulas for optical "combination" of the layers of the medium, in which the optical parameters of the layers (absorption and scattering coefficients) are replaced by some effective values, different for cases of directional and diffuse illumination of the layer. Coefficients relating the effective optical parameters of the layers and the actual values were established based on the results of a Monte Carlo numerical simulation of radiation transport in the medium. We estimate the uncertainties in retrieval of the structural and morphological parameters for the fundus from its diffuse reflectance spectrum using our method. We show that the simulated spectra correspond to the experimental data and that the estimates of the fundus parameters obtained as a result of solving the inverse problem are reasonable.
Computing quasi-linear diffusion coefficients using the delta-f particle-in-cell method
Austin, T. M.; Smithe, D. N.; Ranjbar, V.
2009-11-26
Linear wave codes AORSA and TORIC couple to the bounce-averaged nonlinear Fokker-Planck code CQL3D through quasi-linear diffusion coefficients. Both linear wave codes rely on the quasi-local approximation that includes only first-order parallel and perpendicular gradient variations of cyclotron frequency and ignores field line curvature along with temperature and density gradient effects. The delta-f particle-in-cell (DFPIC) method has been successfully used for simulating ion-cyclotron fast wave behavior. This method also permits particle behavior such as multiple pass resonance, banana orbits, and superadiabaticity. We present new work on generating quasi-linear diffusion coefficients using the DFPIC method that will permit the electromagnetic particle-in-cell (EMPIC) code, VORPAL, to couple to CQL3D and to compare to AORSA and TORIC. A new multiple weight delta-f approach will be presented that converts velocity derivatives to action derivatives and yields a full tensor quasi-linear diffusion coefficient.
Renslow, Ryan S.; Majors, Paul D.; McLean, Jeffrey S.; Fredrickson, Jim K.; Ahmed, Bulbul; Beyenal, Haluk
2010-01-01
Diffusive mass transfer in biofilms is characterized by the effective diffusion coefficient. It is well-documented that the effective diffusion coefficient can vary by location in a biofilm. The current literature is dominated by effective diffusion coefficient measurements for distinct cell clusters and stratified biofilms showing this spatial variation. Regardless of whether distinct cell clusters or surface-averaging methods are used, position-dependent measurements of the effective diffusion coefficient are currently: 1) invasive to the biofilm, 2) performed under unnatural conditions, 3) lethal to cells, and/or 4) spatially restricted to only certain regions of the biofilm. Invasive measurements can lead to inaccurate results and prohibit further (time-dependent) measurements which are important for the mathematical modeling of biofilms. In this study our goals were to: 1) measure the effective diffusion coefficient for water in live biofilms, 2) monitor how the effective diffusion coefficient changes over time under growth conditions, and 3) correlate the effective diffusion coefficient with depth in the biofilm. We measured in situ two-dimensional effective diffusion coefficient maps within Shewanella oneidensis MR-1 biofilms using pulsed-field gradient nuclear magnetic resonance methods, and used them to calculate surface-averaged relative effective diffusion coefficient (Drs) profiles. We found that 1) Drs decreased from the top of the biofilm to the bottom, 2) Drs profiles differed for biofilms of different ages, 3) Drs profiles changed over time and generally decreased with time, 4) all the biofilms showed very similar Drs profiles near the top of the biofilm, and 5) the Drs profile near the bottom of the biofilm was different for each biofilm. Practically, our results demonstrate that advanced biofilm models should use a variable effective diffusivity which changes with time and location in the biofilm. PMID:20589671
Renslow, Ryan S.; Majors, Paul D.; McLean, Jeffrey S.; Fredrickson, Jim K.; Ahmed, B.; Beyenal, Haluk
2010-08-15
Diffusive mass transfer in biofilms is characterized by the effective diffusion coefficient. It is well-documented that the effective diffusion coefficient can vary by location in a biofilm. The current literature is dominated by effective diffusion coefficient measurements for distinct cell clusters and stratified biofilms showing this spatial variation. Regardless of whether distinct cell clusters or surface-averaging methods are used, position-dependent measurements of the effective diffusion coefficient are currently: 1) invasive to the biofilm, 2) performed under unnatural conditions, 3) lethal to cells, and/or 4) spatially restricted to only certain regions of the biofilm. Invasive measurements can lead to inaccurate results and prohibit further (time dependent) measurements which are important for the mathematical modeling of biofilms. In this study our goals were to: 1) measure the effective diffusion coefficient for water in live biofilms, 2) monitor how the effective diffusion coefficient changes over time under growth conditions, and 3) correlate the effective diffusion coefficient with depth in the biofilm. We measured in situ two-dimensional effective diffusion coefficient maps within Shewanella oneidensis MR-1biofilms using pulsed-field gradient nuclear magnetic resonance methods, and used them to calculate surface-averaged relative effective diffusion coefficient (Drs) profiles. We found that 1) Drs decreased from the top of the biofilm to the bottom, 2) Drs profiles differed for biofilms of different ages, 3) Drs profiles changed over time and generally decreased with time, 4) all the biofilms showed very similar Drs profiles near the top of the biofilm, and 5) the Drs profile near the bottom of the biofilm was different for each biofilm. Practically, our results demonstrate that advanced biofilm models should use a variable effective diffusivity which changes with time and location in the biofilm.
Shcherbak, L.; Kopach, O.; Fochuk, P.; James, R. B.; Bolotnikov, A. E.
2015-01-21
Understanding of self- and dopant-diffusion in semiconductor devices is essential to our being able to assure the formation of well-defined doped regions. In this paper, we compare obtained in the literature up to date the Arrhenius’ parameters (D=D_{0}exp(–ΔE_{a}/kT)) of point-defect diffusion coefficients and the I-VII groups impurities in CdTe crystals and films. We found that in the diffusion process there was a linear dependence between the pre-exponential factor, D_{0}, and the activation energy, ΔE_{a}, of different species: This was evident in the self-diffusivity and isovalent impurity Hg diffusivity as well as for the dominant IIIA and IVA groups impurities and Chlorine, except for the fast diffusing elements (e.g., Cu and Ag), chalcogens O, S, and Se, halogens I and Br as well as the transit impurities Mn, Co, Fe. As a result, reasons of the lack of correspondence of the data to compensative dependence are discussed.
Shcherbak, L.; Kopach, O.; Fochuk, P.; James, R. B.; Bolotnikov, A. E.
2015-01-21
Understanding of self- and dopant-diffusion in semiconductor devices is essential to our being able to assure the formation of well-defined doped regions. In this paper, we compare obtained in the literature up to date the Arrhenius’ parameters (D=D0exp(–ΔEa/kT)) of point-defect diffusion coefficients and the I-VII groups impurities in CdTe crystals and films. We found that in the diffusion process there was a linear dependence between the pre-exponential factor, D0, and the activation energy, ΔEa, of different species: This was evident in the self-diffusivity and isovalent impurity Hg diffusivity as well as for the dominant IIIA and IVA groups impurities andmore » Chlorine, except for the fast diffusing elements (e.g., Cu and Ag), chalcogens O, S, and Se, halogens I and Br as well as the transit impurities Mn, Co, Fe. As a result, reasons of the lack of correspondence of the data to compensative dependence are discussed.« less
Minority carrier diffusion lengths and absorption coefficients in silicon sheet material
NASA Technical Reports Server (NTRS)
Dumas, K. A.; Swimm, R. T.
1980-01-01
Most of the methods which have been developed for the measurement of the minority carrier diffusion length of silicon wafers require that the material have either a Schottky or an ohmic contact. The surface photovoltage (SPV) technique is an exception. The SPV technique could, therefore, become a valuable diagnostic tool in connection with current efforts to develop low-cost processes for the production of solar cells. The technique depends on a knowledge of the optical absorption coefficient. The considered investigation is concerned with a reevaluation of the absorption coefficient as a function of silicon processing. A comparison of absorption coefficient values showed these values to be relatively consistent from sample to sample, and independent of the sample growth method.
Molecular dynamics calculation of rotational diffusion coefficient of a carbon nanotube in fluid.
Cao, Bing-Yang; Dong, Ruo-Yu
2014-01-21
Rotational diffusion processes are correlated with nanoparticle visualization and manipulation techniques, widely used in nanocomposites, nanofluids, bioscience, and so on. However, a systematical methodology of deriving this diffusivity is still lacking. In the current work, three molecular dynamics (MD) schemes, including equilibrium (Green-Kubo formula and Einstein relation) and nonequilibrium (Einstein-Smoluchowski relation) methods, are developed to calculate the rotational diffusion coefficient, taking a single rigid carbon nanotube in fluid argon as a case. We can conclude that the three methods produce same results on the basis of plenty of data with variation of the calculation parameters (tube length, diameter, fluid temperature, density, and viscosity), indicative of the validity and accuracy of the MD simulations. However, these results have a non-negligible deviation from the theoretical predictions of Tirado et al. [J. Chem. Phys. 81, 2047 (1984)], which may come from several unrevealed factors of the theory. The three MD methods proposed in this paper can also be applied to other situations of calculating rotational diffusion coefficient. PMID:25669403
NASA Astrophysics Data System (ADS)
Kim, Changho; Borodin, Oleg; Karniadakis, George Em
2015-12-01
We analyze two standard methods to compute the diffusion coefficient of a tracer particle in a medium from molecular dynamics (MD) simulation, the velocity autocorrelation function (VACF) method, and the mean-squared displacement (MSD) method. We show that they are equivalent in the sense that they provide the same mean values with the same level of statistical errors. We obtain analytic expressions for the level of the statistical errors present in the time-dependent diffusion coefficient as well as the VACF and the MSD. Under the assumption that the velocity of the tracer particle is a Gaussian process, all results are expressed in terms of the VACF. Hence, the standard errors of all relevant quantities are computable once the VACF is obtained from MD simulation. By using analytic models described by the Langevin equations driven by Gaussian white noise and Poissonian white shot noise, we verify our theoretical error estimates and discuss the non-Gaussianity effect in the error estimates when the Gaussian process approximation does not hold exactly. For validation, we perform MD simulations for the self-diffusion of a Lennard-Jones fluid and the diffusion of a large and massive colloid particle suspended in the fluid. Our theoretical framework is also applicable to mesoscopic simulations, e.g., Langevin dynamics and dissipative particle dynamics.
A novel grating-imaging method to measure carrier diffusion coefficient in graphene
NASA Astrophysics Data System (ADS)
Chen, Ke; Wang, Yaguo; Akinwande, Deji; Bank, Seth; Lin, Jung-Fu
Similar to carrier mobility, carrier diffusion coefficient in graphene determines the response rate of future graphene-based electronics. Here we present a simple, sensitive and non-destructive technique integrated with ultrafast pump-probe spectroscopy to measure carrier diffusion in CVD-grown graphene. In the method, the pump and the probe beams pass through the same area of a photomask with metal strips i.e. a transmission amplitude grating, and get diffracted. The diffracted light is collected by an objective lens and focused onto the sample to generate carrier density grating. Relaxation of this carrier density grating is governed by both carrier recombination and carrier diffusion in the sample. Transient transmission change of the probe beams, which reflects this relaxation process, is recorded. The measured diffusion coefficients of multilayer and monolayer CVD-grown graphene are 2000cm2/s and 10000cm2/s, respectively, comparable with the reported values of epitaxial graphene and reduced graphene. This transmission grating technique can be used to measure carrier dynamics in versatile 2D materials.
Molecular dynamics calculation of rotational diffusion coefficient of a carbon nanotube in fluid
NASA Astrophysics Data System (ADS)
Cao, Bing-Yang; Dong, Ruo-Yu
2014-01-01
Rotational diffusion processes are correlated with nanoparticle visualization and manipulation techniques, widely used in nanocomposites, nanofluids, bioscience, and so on. However, a systematical methodology of deriving this diffusivity is still lacking. In the current work, three molecular dynamics (MD) schemes, including equilibrium (Green-Kubo formula and Einstein relation) and nonequilibrium (Einstein-Smoluchowski relation) methods, are developed to calculate the rotational diffusion coefficient, taking a single rigid carbon nanotube in fluid argon as a case. We can conclude that the three methods produce same results on the basis of plenty of data with variation of the calculation parameters (tube length, diameter, fluid temperature, density, and viscosity), indicative of the validity and accuracy of the MD simulations. However, these results have a non-negligible deviation from the theoretical predictions of Tirado et al. [J. Chem. Phys. 81, 2047 (1984)], which may come from several unrevealed factors of the theory. The three MD methods proposed in this paper can also be applied to other situations of calculating rotational diffusion coefficient.
Mialdun, A; Shevtsova, V
2015-12-14
We report on the measurement of diffusion (D), Soret (S(T)), and thermodiffusion (D(T)) coefficients in toluene-cyclohexane mixture with mass fraction of toluene 0.40 onboard of the International Space Station. The coefficients were measured in the range of the mean temperatures between 20 °C and 34 °C. The Soret coefficient is negative within the investigated temperature range and its absolute value |S(T)| decreases with increasing temperature. The diffusion coefficient for this system increases with temperature rising. For comparison, the temperature dependence of diffusion coefficient was measured in ground laboratory using counter-flow cell technique and revealed a good agreement with microgravity results. A non-direct comparison of the measured onboard Soret coefficients with different systems indicated a similar trend for the temperature dependent behavior. Unexpected experimental finding is that for this system the thermodiffusion coefficient D(T) does not depend on temperature. PMID:26671399
NASA Astrophysics Data System (ADS)
Mialdun, A.; Shevtsova, V.
2015-12-01
We report on the measurement of diffusion (D), Soret (ST), and thermodiffusion (DT) coefficients in toluene-cyclohexane mixture with mass fraction of toluene 0.40 onboard of the International Space Station. The coefficients were measured in the range of the mean temperatures between 20 °C and 34 °C. The Soret coefficient is negative within the investigated temperature range and its absolute value |ST| decreases with increasing temperature. The diffusion coefficient for this system increases with temperature rising. For comparison, the temperature dependence of diffusion coefficient was measured in ground laboratory using counter-flow cell technique and revealed a good agreement with microgravity results. A non-direct comparison of the measured onboard Soret coefficients with different systems indicated a similar trend for the temperature dependent behavior. Unexpected experimental finding is that for this system the thermodiffusion coefficient DT does not depend on temperature.
NASA Astrophysics Data System (ADS)
Lu, Yong; Zhang, Ping
2013-05-01
We report the prediction of temperature-dependent diffusion coefficients of interstitial hydrogen, deuterium, and tritium atoms in α-Ti using transition state theory. The microscopic parameters in the pre-factor and activation energy of the impurity diffusion coefficients are obtained from first-principles total energy and phonon calculations including the full coupling between the vibrational modes of the diffusing atom with the host lattice. The dual occupancy case of impurity atom in the hcp matrix is considered, and four diffusion paths are combined to obtain the final diffusion coefficients. The calculated diffusion parameters show good agreement with experiments. Our numerical results indicate that the diffusions of deuterium and tritium atoms are slower than that of the hydrogen atom at temperatures above 425 K and 390 K, respectively.
Jackson, G.D.
1987-10-01
The Paducah Environmental Advisory Committee was formed as: (1) an outgrowth of other Environmental Advisory Committees already in existence at Oak Ridge and other Martin Marietta Energy Systems plants; (2) a result of public concern following significant nuclear incidents at Bhopal and Chernobyl; (3) a result of the new direction and commitment of the management of the Paducah Gaseous Diffusion Plant following contract acquisition by Martin Marietta Energy Systems; and (4) a means of reducing and/or preventing local and/or public concern regarding the activities of and potential risks created by PGDP. This report discusses the following issues and concerns of the Committee arrived at through a series of meetings: (1) groundwater monitoring; (2) long-range tails storage; C-404, scrap yrads, and PCB and TCE cleanup; nuclear criticality plan and alarm systems; documentation of historical data regarding hazardous waste burial grounds; dosimeter badges; and asbestos handling and removal.
Brindley, T. L.; Tarantino, J. J.; Locke, A. L.; Dollins, D. W.
2006-07-01
This paper describes how 4-Dimensional (4D) Data Visualization Modeling was used to evaluate historical data and to help guide the decisions for the sampling necessary to complete a Remedial Investigation/Feasibility Study (RI/FS) for the burial ground sites at the Department of Energy (DOE) Paducah Gaseous Diffusion Plant (PGDP). DOE at the Paducah Site is primarily involved in environmental cleanup and landlord activities. The scope of this project was to prepare a work plan for identifying the data available and the data required to conduct an RI/FS for the Burial Ground Operable Unit (BGOU) located within and near PGDP. The work plan focuses on collecting existing information about contamination in and around the burial grounds and determining what additional data are required to support an assessment of risks to human health and the environment and to support future decisions regarding actions to reduce these risks. (authors)
Yu, Shuangying; Halbrook, Richard S; Sparling, Donald W
2013-10-01
Reptiles are declining globally, and environmental contamination has been suggested as a contributing factor; however, few studies have investigated the relationship between contamination and reptile populations. We performed a mark-recapture study at ponds near the Paducah Gaseous Diffusion Plant (PGDP), Kentucky, to determine if heavy metals had an impact on turtle populations. We measured concentrations of cadmium, chromium, copper, lead, and mercury in red-eared slider turtle (Trachemys scripta elegans) tissues and pond sediment and determined the correlation between metal concentrations and red-eared slider density. Metal concentrations measured in the current study were low, and turtle density was not significantly correlated with metal concentrations in tissues or sediment. However, we observed a trend of decreasing turtle density in ponds that had greater metal concentrations. Sex ratio and proportion of juveniles were significantly different among ponds, but it is unclear if these differences are related to contamination associated with the PGDP. PMID:23644581
Aronson, A.L.; Gordon, D.M.
2000-07-31
IN APRIL 1996, THE UNITED STATES (US) ADDED THE PORTSMOUTH GASEOUS DIFFUSION PLANT TO THE LIST OF FACILITIES ELIGIBLE FOR THE APPLICATION OF INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA) SAFEGUARDS. AT THAT TIME, THE US PROPOSED THAT THE IAEA CARRY OUT A ''VERIFICATION EXPERIMENT'' AT THE PLANT WITH RESPECT TO DOOWNBLENDING OF ABOUT 13 METRIC TONS OF HIGHLY ENRICHED URANIUM (HEU) IN THE FORM OF URANIUM HEXAFLUROIDE (UF6). DURING THE PERIOD DECEMBER 1997 THROUGH JULY 1998, THE IAEA CARRIED OUT THE REQUESTED VERIFICATION EXPERIMENT. THE VERIFICATION APPROACH USED FOR THIS EXPERIMENT INCLUDED, AMONG OTHER MEASURES, THE ENTRY OF PROCESS-OPERATIONAL DATA BY THE FACILITY OPERATOR ON A NEAR-REAL-TIME BASIS INTO A ''MAILBOX'' COMPUTER LOCATED WITHIN A TAMPER-INDICATING ENCLOSURE SEALED BY THE IAEA.
NASA Astrophysics Data System (ADS)
Hirao, Akiko; Nishizawa, Hideyuki; Tsukamoto, Takayuki; Matsumoto, Kazuki
1999-10-01
A new easy method for obtaining a drift mobility and a diffusion coefficient from a nondispersive time-of-flight transient has been developed. Nondispersive transients are described well in the theoretical photocurrent equation (PTE) based on the fact that a carrier packet drifts at a constant velocity and is spread by diffusion, the top electrode acts as a reflecting and partially absorbing wall, and the counter electrode acts as an absorbing wall. The fitting of the PTE to photocurrent transients gives the mobility and the diffusion coefficient (D) simultaneously. These are suitable characteristic values for descriptions of carriers transport because they do not show the thickness dependence and the negative field dependence in a low electric field. The mobility that sometimes shows the thickness dependence and the negative field dependence in a low electric field, however, has usually been measured from the time of the intersection of the asymptotes to the plateau and trailing edge of the transients. In order to obtain (mu) a from photocurrent transients by a simple method, we have tried to describe t0 and tail-broadening parameter W as functions of (mu) a and D, where W is defined as (t1/2 - t0)/t1/2 and t1/2 is the time at which the current is a half of that in the plateau region. The dependences of calculated (mu) k and W on the electric field and the sample thickness agreed well with those of the experimental data. These results verify the PTE and suggest that (mu) a and D can be calculated from t0 and W. We also report that the diffusion coefficient is proportional to the power of 2 of the mobility. This result agrees with a theory based on the Langevin equation which describes motions of carriers in a fluctuated field.
Dynamic properties and third order diffusion coefficients of ions in electrostatic fields
NASA Astrophysics Data System (ADS)
Koutselos, Andreas D.
1997-05-01
Velocity correlation functions and third order diffusion coefficients of ions moving in a buffer gas under the influence of an electrostatic field are determined via molecular dynamics simulation. For the closed shell system of K+ in Ar using a universal interaction model potential, the general form of the third order correlation functions is found to be monotonically decaying in time except in the cases of <ΔvZ(0)ΔvX(t)2>, <ΔvZ(0)ΔvY(t)2>, and <ΔvZ(0)ΔvZ(t)2>, with Δv(t)=v(t) -
Adams, M.E.; Marshall, T.L.; Rowley, R.L.
1998-07-01
Absorption rates of gaseous CO{sub 2} into aqueous blends of N-methyldiethanolamine (MDEA) and diethanolamine (DEA) and of gaseous H{sub 2}S into aqueous MDEA were measured in a quiescent, inverted-tube diffusiometer by monitoring the rate of pressure drop. A numerical model for absorption, diffusion, and reaction of CO{sub 2} and H{sub 2}S in blends of MDEA, DEA, and water was developed. The model was used to regress diffusion coefficients of bicarbonate, carbamate, and MDEAH{sub 2}CO{sub 3} for the case of CO{sub 2} absorption and of bisulfide ion for the case of H{sub 2}S absorption from measured absorption rates. CO{sub 2} absorption rates and diffusion coefficients of bicarbonate, carbamate, and MDEAH{sub 2}CO{sub 3} were obtained at 298.2 K and 318.2 K in aqueous solutions containing 50 mass % total amine at DEA:MDEA mole ratios of 1:20, 1:4, 1L3, and 2:3. H{sub 2}S absorption rates and diffusion coefficients of bisulfide ion were obtained at 298.2 K and 318.2 K in aqueous solutions containing 20, 35, and 50 mass % MDEA.
NASA Astrophysics Data System (ADS)
Szyszkiewicz-Warzecha, Krzysztof; Jasielec, Jerzy J.; Fausek, Janusz; Filipek, Robert
2016-06-01
Transport properties of ions have significant impact on the possibility of rebars corrosion thus the knowledge of a diffusion coefficient is important for reinforced concrete durability. Numerous tests for the determination of diffusion coefficients have been proposed but analysis of some of these tests show that they are too simplistic or even not valid. Hence, more rigorous models to calculate the coefficients should be employed. Here we propose the Nernst-Planck and Poisson equations, which take into account the concentration and electric potential field. Based on this model a special inverse method is presented for determination of a chloride diffusion coefficient. It requires the measurement of concentration profiles or flux on the boundary and solution of the NPP model to define the goal function. Finding the global minimum is equivalent to the determination of diffusion coefficients. Typical examples of the application of the presented method are given.
Provenzale, James M.; Isaacson, Jared; Chen, Steven; Stinnett, Sandra; Liu, Chunlei
2013-01-01
OBJECTIVE The purpose of our study was to correlate decrease in apparent diffusion coefficient (ADC) and increase in fractional anisotropy (FA) in various white matter (WM) regions using diffusion tenor imaging (DTI) within the first year of life. MATERIALS AND METHODS We performed DTI on 53 infants and measured FA and ADC within 10 WM regions important in brain development. For each region, we calculated the slope of ADC as a function of FA, the correlation coefficient (r) and correlation of determination (r2). We performed a group analysis of r values and r2 values for six WM regions primarily composed of crossing fibers and four regions primarily having parallel fibers. Upon finding that a strong correlation of FA with age existed, we adjusted for age and calculated partial correlation coefficients. RESULTS Slopes of FA versus ADC ranged from −1.00711 to −1.67592 (p < 0.05); r values ranged from −0.81 to −0.50 and r2 values from 0.25 to 0.66. The four greatest r2 values were within WM regions having large numbers of crossing fibers and the three lowest r2 values were in regions having predominantly parallel fibers. After adjusting for age, slopes ranged from −1.08095 to 0.09612 (p < 0.05 in five cases); partial correlation coefficients ranged from −0.49 to 0.03 and r2 values from 0.31 to 0.79. The highest partial correlation coefficients were then relatively equally distributed between the two types of WM regions. CONCLUSION In various regions, FA and ADC evolved with differing degrees of correlation. We found a strong influence of age on the relationship between FA and ADC. PMID:21098179
Evolution of the Magnetic Field Line Diffusion Coefficient and Non-Gaussian Statistics
NASA Astrophysics Data System (ADS)
Snodin, A. P.; Ruffolo, D.; Matthaeus, W. H.
2016-08-01
The magnetic field line random walk (FLRW) plays an important role in the transport of energy and particles in turbulent plasmas. For magnetic fluctuations that are transverse or almost transverse to a large-scale mean magnetic field, theories describing the FLRW usually predict asymptotic diffusion of magnetic field lines perpendicular to the mean field. Such theories often depend on the assumption that one can relate the Lagrangian and Eulerian statistics of the magnetic field via Corrsin’s hypothesis, and additionally take the distribution of magnetic field line displacements to be Gaussian. Here we take an ordinary differential equation (ODE) model with these underlying assumptions and test how well it describes the evolution of the magnetic field line diffusion coefficient in 2D+slab magnetic turbulence, by comparisons to computer simulations that do not involve such assumptions. In addition, we directly test the accuracy of the Corrsin approximation to the Lagrangian correlation. Over much of the studied parameter space we find that the ODE model is in fairly good agreement with computer simulations, in terms of both the evolution and asymptotic values of the diffusion coefficient. When there is poor agreement, we show that this can be largely attributed to the failure of Corrsin’s hypothesis rather than the assumption of Gaussian statistics of field line displacements. The degree of non-Gaussianity, which we measure in terms of the kurtosis, appears to be an indicator of how well Corrsin’s approximation works.
Optimal estimation of the diffusion coefficient from non-averaged and averaged noisy magnitude data
NASA Astrophysics Data System (ADS)
Kristoffersen, Anders
2007-08-01
The magnitude operation changes the signal distribution in MRI images from Gaussian to Rician. This introduces a bias that must be taken into account when estimating the apparent diffusion coefficient. Several estimators are known in the literature. In the present paper, two novel schemes are proposed. Both are based on simple least squares fitting of the measured signal, either to the median (MD) or to the maximum probability (MP) value of the Probability Density Function (PDF). Fitting to the mean (MN) or a high signal-to-noise ratio approximation to the mean (HS) is also possible. Special attention is paid to the case of averaged magnitude images. The PDF, which cannot be expressed in closed form, is analyzed numerically. A scheme for performing maximum likelihood (ML) estimation from averaged magnitude images is proposed. The performance of several estimators is evaluated by Monte Carlo (MC) simulations. We focus on typical clinical situations, where the number of acquisitions is limited. For non-averaged data the optimal choice is found to be MP or HS, whereas uncorrected schemes and the power image (PI) method should be avoided. For averaged data MD and ML perform equally well, whereas uncorrected schemes and HS are inadequate. MD provides easier implementation and higher computational efficiency than ML. Unbiased estimation of the diffusion coefficient allows high resolution diffusion tensor imaging (DTI) and may therefore help solving the problem of crossing fibers encountered in white matter tractography.
Ab initio calculation of oxygen self-diffusion coefficient in uranium dioxide UO2
NASA Astrophysics Data System (ADS)
Dorado, Boris; Garcia, Philippe; Torrent, Marc
Uranium dioxide UO2 is the most widely used nuclear fuel worldwide and its atomic transport properties are relevant to practically all engineering aspects of the material. Although transport properties have already been studied in UO2 by means of first-principles calculations, the ab initio determination of self-diffusion coefficients has up to now remained unreachable because the relevant computational tools were neither available or adapted. The present work reports our results related to the ab initio calculation of the oxygen self-diffusion coefficient in UO2. We first determine the Gibbs free energies of formation of oxygen charged defects by calculating both the electronic and vibrational (hence entropic) contributions. Then, we use the transition state theory in order to compute the effective jump frequency of the defects, which in turn provides us with the value of the pre-exponential factor. The results are compared to self-diffusion data obtained experimentally with a careful monitoring of the relevant thermodynamic conditions (oxygen partial pressure, temperature, impurity content).
Measuring partition and diffusion coefficients for volatile organic compounds in vinyl flooring
NASA Astrophysics Data System (ADS)
Cox, Steven S.; Zhao, Dongye; Little, John C.
Interactions between volatile organic compounds (VOCs) and vinyl flooring (VF), a relatively homogenous, diffusion-controlled building material, were characterized. The sorption/desorption behavior of VF was investigated using single-component and binary systems of seven common VOCs ranging in molecular weight from n-butanol to n-pentadecane. The simultaneous sorption of VOCs and water vapor by VF was also investigated. Rapid determination of the material/air partition coefficient ( K) and the material-phase diffusion coefficient ( D) for each VOC was achieved by placing thin VF slabs in a dynamic microbalance and subjecting them to controlled sorption/desorption cycles. K and D are shown to be independent of concentration for all of the VOCs and water vapor. For the four alkane VOCs studied, K correlates well with vapor pressure and D correlates well with molecular weight, providing a means to estimate these parameters for other alkane VOCs. While the simultaneous sorption of a binary mixture of VOCs is non-competitive, the presence of water vapor increases the uptake of VOCs by VF. This approach can be applied to other diffusion-controlled materials and should facilitate the prediction of their source/sink behavior using physically-based models.
The measurement of self-diffusion coefficients in liquid metals with quasielastic neutron scattering
NASA Astrophysics Data System (ADS)
Meyer, Andreas
2015-01-01
Quasielastic incoherent neutron scattering (QENS) has proven to be a versatile tool to study self diffusion of atoms in liquid metals. Here it is shown, that coherent contributions to the signal in the small q limit appear as a flat and energy independent constant to the QENS signal in single-component liquid metals even for systems with a small incoherent scattering cross section, like aluminum. Container-less processing via electromagnetic or electrostatic levitation devices, especially designed for QENS, enables the in-situ measurement on liquid metallic droplets of sizes between 5 mm to 10 mm in diameter. This gives access to the study of chemically reactive, refractory metallic melts and extends the accessible temperature range to undercoolings of several hundred Kelvin below the respective melting point. Compared to experiments using a thin-walled crucible giving hollow-cylindrical sample geometry it is shown that multiple scattering on levitated droplets is negligible for the analysis of the self-diffusion coefficient. QENS results of liquid germanium and 73germanium isotope mixtures, titanium, nickel, copper and aluminum are reviewed. The self-diffusion coefficients of these systems are best described by an Arrhenius-type temperature dependence around their respective melting points.
Measurement of Retinalamin diffusion coefficient in human sclera by optical spectroscopy
NASA Astrophysics Data System (ADS)
Genina, Elina A.; Bashkatov, Alexey N.; Zubkova, Elena A.; Kamenskikh, Tatiana G.; Tuchin, Valery V.
2008-12-01
The use of cytomedines (such as Retinalamin) in clinical practice has shown high effectiveness of the medicaments in ophthalmology. The study of diffusion of Retinalamin in scleral tissue is important for estimation of a drug dose delivered into inner tissue of eye, time of drug action, etc. In vitro measurements of spectral reflectance of sclera interacting with aqueous solution of Retinalamin have been carried out. Ten human sclera samples were included in the study. The results of the experiments have shown that penetration of Retinalamin into scleral tissue leads to the decrease of scleral reflectance due to optical immersion. Estimation of diffusion coefficient of studied solution has been made on the basis of analysis of optical reflectance dynamics of the sclera samples. The diffusion coefficient of Retinalamin in human scleral tissue was evaluated as (1.82±0.14)×10 -6 cm 2/s. The results are important for treatment of partial optic atrophy observed at primary open-angle glaucoma and others eye diseases.
Measuring diffusion coefficients via two-photon fluorescence recovery after photobleaching.
Sullivan, Kelley D; Brown, Edward B
2010-01-01
Multi-fluorescence recovery after photobleaching is a microscopy technique used to measure the diffusion coefficient (or analogous transport parameters) of macromolecules, and can be applied to both in vitro and in vivo biological systems. Multi-fluorescence recovery after photobleaching is performed by photobleaching a region of interest within a fluorescent sample using an intense laser flash, then attenuating the beam and monitoring the fluorescence as still-fluorescent molecules from outside the region of interest diffuse in to replace the photobleached molecules. We will begin our demonstration by aligning the laser beam through the Pockels Cell (laser modulator) and along the optical path through the laser scan box and objective lens to the sample. For simplicity, we will use a sample of aqueous fluorescent dye. We will then determine the proper experimental parameters for our sample including, monitor and bleaching powers, bleach duration, bin widths (for photon counting), and fluorescence recovery time. Next, we will describe the procedure for taking recovery curves, a process that can be largely automated via LabVIEW (National Instruments, Austin, TX) for enhanced throughput. Finally, the diffusion coefficient is determined by fitting the recovery data to the appropriate mathematical model using a least-squares fitting algorithm, readily programmable using software such as MATLAB (The Mathworks, Natick, MA). PMID:20190730
NASA Astrophysics Data System (ADS)
Deb Nath, S. K.
2014-05-01
Diffusion of perfluoropolyethers (PFPEs) lubricants on a hard disk surface is an important self healing characteristic to replenish PFPEs lubricants on their uncovered surface. In the present paper, we study the diffusion coefficients of non-functional PFPE Z and PFPE Zdol with functional end groups as a function of lubricant film thickness on a thin DLC (diamond-like) film. Diffusion coefficients of PFPE Z and PFPE Zdol molecules on a DLC film are calculated using the equation of Einstein's law of diffusion (Guo et al. J. Appl. Phys 93:8707, 2003; Guo Ph.D. thesis, 2006; Chung et al. IEEE Trans. Magn. 45:3644, 2009) considering the movement of their center of mass to reach their equilibrium positions from their original configurations. And it is averaged with the film thickness to show the thickness dependence on the diffusion of PFPEs lubricants on a DLC substrate. Firstly diffusion coefficients of sub-monolayer of partially coverage PFPE Z and PFPE Zdol on a DLC substrate are studied briefly and secondly the diffusion coefficient of monolayer PFPE Zdol on a DLC substrate is also studied elaborately. To support our results, we compare our thickness-dependent diffusion coefficients of PFPE Z and PFPE Zdol with those of published theoretical (Guo Ph.D. thesis, 2006; Chung et al. IEEE Trans. Magn. 45:3644, 2009) and experimental results (Chung et al. Tribol. Lett. 32:35, 2008; Ma et al. Tribol. Lett. 10:203, 2001). Here we study how lubricant film thickness plays an important role on its diffusion. Effects of polar end bead functionality, lubricant film thickness enhance the anisotropic behavior of diffusion coefficients of PFPE Zdol on the DLC substrate. But in the present analysis we consider hard disk carbon overcoat as a thin DLC film and we include all of their atoms within the force cut-off distance with PFPEs lubricant molecules for the interactions to study the thickness dependence on their diffusion coefficients.
Dissolved and gas-phase concentrations of nine polycyclic aromatic hydrocarbons and 46 polychlorinated biphenyl congeners were measured at eight sites on the Chesapeake Bay at four different times of the year to estimate net diffusive air-water gas exchange rates. Gaseous PAHs ar...
Kim, S.H.; Chen, N.C.J.; Taleyarkhan, R.P.; Keith, K.D.; Schmidt, R.W.; Carter, J.C.
1996-12-30
The gaseous diffusion process is currently employed at two plants in the US: the Paducah Gaseous Diffusion Plant and the Portsmouth Gaseous Diffusion Plant. As part of a facility-wide safety evaluation, a postulated design basis accident involving large line-rupture induced releases of uranium hexafluoride (UF{sub 6}) into the process building of a gaseous diffusion plant (GDP) is evaluated. When UF{sub 6} is released into the atmosphere, it undergoes an exothermic chemical reaction with moisture (H{sub 2}O) in the air to form vaporized hydrogen fluoride (HF) and aerosolized uranyl fluoride (UO{sub 2}F{sub 2}). These reactants disperse in the process building and transport through the building ventilation system. The ventilation system draws outside air into the process building, distributes it evenly throughout the building, and discharges it to the atmosphere at an elevated temperature. Since air is recirculated from the cell floor area to the operating floor, issues concerning in-building worker safety and evacuation need to be addressed. Therefore, the objective of this study is to evaluate the transport of HF vapor and UO{sub 2}F{sub 2} aerosols throughout the operating floor area following B-line break accident in the cell floor area.
NASA Astrophysics Data System (ADS)
Silva, Matthew D.; Helmer, Karl G.; Lee, Jing-Huei; Han, Sam S.; Springer, Charles S.; Sotak, Christopher H.
2002-05-01
An NMR method is presented for measuring compartment-specific water diffusion coefficient (D) values. It uses relaxography, employing an extracellular contrast reagent (CR) to distinguish intracellular (IC) and extracellular (EC) 1H2O signals by differences in their respective longitudinal (T1) relaxation times. A diffusion-weighted inversion-recovery spin-echo (DW-IRSE) pulse sequence was used to acquire IR data sets with systematically and independently varying inversion time (TI) and diffusion-attenuation gradient amplitude (g) values. Implementation of the DW-IRSE technique was demonstrated and validated using yeast cells suspended in 3 mM Gd-DTPA2- with a wet/dry mass ratio of 3.25:1.0. Two-dimensional (2D) NMR data were acquired at 2.0 T and analyzed using numerical inverse Laplace transformation (2D- and sequential 1D-ILT) and sequential exponential fitting to yield T1 and water D values. All three methods gave substantial agreement. Exponential fitting, deemed the most accurate and time efficient, yielded T1:D (relative contribution) values of 304 ms:0.023×10-5 cm2/s (47%) and 65 ms:1.24×10-5 cm2/s (53%) for the IC and EC components, respectively. The compartment-specific D values derived from direct biexponential fitting of diffusion-attenuation data were also in good agreement. Extension of the DW-IRSE method to in vivo models should provide valuable insights into compartment-specific water D changes in response to injury or disease.
Autrey, S Thomas ); Camaioni, Donald M. ); Kandanarachchi, Pramod H.; Franz, James A. )
2000-12-01
The diffusion coefficients of a benzyl-, sec-phenethyl-, and diphenylmethyl alcohol and the corresponding aryl carbonyls (benzaldehyde, acetophenone and benzophenone) were measured by Taylor's dispersion method in both ethyl and isopropyl alcohol. The experimental values are compared to published transient grating measurements of the corresponding aryl ketyl radicals (benzyl-, sec-phenethyl-, and diphenylmethyl-ketyl radical). In general, the diffusion coefficient of the aryl alcohols and the corresponding aryl ketyl radicals are equivalent within experimental error. This work shows that the diffusion of ketyl radicals is not anomalously slow and that aryl alcohols are significantly better models than the corresponding aryl ketones for analyzing the diffusion of aryl ketyl radicals in both ethyl and isopropyl alcohol. Empirical estimates of the diffusion coefficients of aryl alcohols using the Spernol-Wirtz and Wilke-Chang modifications to the Stokes-Einstein diffusion equation do not adequately account for the interactions between the aryl ketyl radicals or aryl alcohols with the hydroxylic solvents ethyl and isopropyl alcohol. The excellent agreement between the experimental diffusion coefficients of the aryl alcohols and the corresponding ketyl radicals show that the transient grating method can provide accurate estimates for the diffusion coefficients of transient species. This is especially important when a stable model is not available, for example the pyranyl radical.
Miyoshi, Hirofumi
1999-01-01
Donnan dialysis with ion-exchange membranes was studied under various kinds of experimental conditions using ions of different valences. The diffusion coefficients (D{sub d}) of various kinds of ions in the ion-exchange membrane were obtained by curve fitting an equation derived from the mass balance to three kinds of Donnan dialytic experiments. It was found that the value of D{sub d}/D{sub s} using D{sub d} of monovalent ions in Donnan dialysis with a set of monovalent feed ions and bivalent driving ions was 1/175, where D{sub s} represents a diffusion coefficient in solution. D{sub s} was calculated from the Nernst-Einstein equation substituted by the ionic conductance of ions at infinite dilution in water. Using D{sub d} of bivalent ions in Donnan dialysis with the same set led to a D{sub d}/D{sub s} value of 1/438. Moreover, using D{sub d} in Donnan dialysis with the same set, the value of D{sub d}/D{sub e} was kept constant at 0.4 (D{sub e} expresses the diffusion coefficient in the membrane when the valences of the feed and driving ions are equal). On the other hand, both D{sub d}/D{sub s} and D{sub d}/D{sub e} using D{sub d} in Donnan dialysis with a set of bivalent feed ions and monovalent driving ions were not constant.
NASA Technical Reports Server (NTRS)
Goldstein, M. L.
1977-01-01
In a study of cosmic ray propagation in interstellar and interplanetary space, a perturbed orbit resonant scattering theory for pitch angle diffusion in a slab model of magnetostatic turbulence is slightly generalized and used to compute the diffusion coefficient for spatial propagation parallel to the mean magnetic field. This diffusion coefficient has been useful for describing the solar modulation of the galactic cosmic rays, and for explaining the diffusive phase in solar flares in which the initial anisotropy of the particle distribution decays to isotropy.
Thomas, Franziska A; Visco, Ilaria; Petrášek, Zdeněk; Heinemann, Fabian; Schwille, Petra
2015-12-01
Recently, a new and versatile assay to determine the partitioning coefficient [Formula: see text] as a measure for the affinity of peripheral membrane proteins for lipid bilayers was presented in the research article entitled, "Introducing a fluorescence-based standard to quantify protein partitioning into membranes" [1]. Here, the well-characterized binding of hexahistidine-tag (His6) to NTA(Ni) was utilized. Complementarily, this data article reports the average diffusion coefficient [Formula: see text] of His6-tagged enhanced green fluorescent protein (eGFP-His6) and the fluorescent lipid analog ATTO-647N-DOPE in giant unilamellar vesicles (GUVs) containing different amounts of NTA(Ni) lipids. In addition, dissociation constants [Formula: see text] of the NTA(Ni)/eGFP-His6 system are reported. Further, a conversion between [Formula: see text] and [Formula: see text] is provided. PMID:26587560
Integral formula for the effective diffusion coefficient in two-dimensional channels.
Kalinay, Pavol
2016-07-01
The effective one-dimensional description of diffusion in two-dimensional channels of varying cross section is revisited. The effective diffusion coefficient D(x), extending Fick-Jacobs equation, depending on the longitudinal coordinate x, is derived here without use of scaling of the transverse coordinates. The result of the presented method is an integral formula for D(x), calculating its value at x as an integral of contributions from the neighboring positions x^{'} depending on h(x^{'}), a function shaping the channel. Unlike the standard formulas based on the scaling, the new proposed formula also describes D(x) correctly near the cusps, or in wider channels. PMID:27575072
Results of a monte carlo investigation of the diffuse attenuation coefficient.
Concannon, B M; Davis, J P
1999-08-20
There has been a large effort to relate the apparent optical properties of ocean water to the inherent optical properties, which are the absorption coefficient a, the scattering coefficient b, and the scattering phase function rho(theta). The diffuse attenuation coefficient kdiff' has most often been considered an apparent optical property. However, kdiff' can be considered a quasi-inherent property kdiff' when defined as a steady-state light distribution attenuation coefficient. The Honey-Wilson research empirically relates kdiff' to a and b. The Honey-Wilson relation most likely applies to a limited range of water types because it does not include dependence on rho(theta). A series of Monte Carlo simulations were initiated to calculate kdiff' in an unstratified water column. The calculations, which reflected open ocean water types, used ranges of the single-scattering albedo omega(0) and the mean forward-scattering angle theta(m) for two analytic phase functions with different shapes. It was found that kdiff' is nearly independent of the shape of rho(theta) and can be easily parameterized in terms of a, b, and theta(m) for 0.11
NASA Astrophysics Data System (ADS)
Wu, Yan; Duan, Guosheng; Zhao, Xiang
2015-03-01
Effects of magnetic field intensity on carbon diffusion coefficient in pure iron in the γ-Fe temperature region were investigated using carburizing technology. The carbon penetration profiles from the iron surface to interior were measured by field emission electron probe microanalyzer. The carbon diffusion coefficient in pure iron carburized with different magnetic field intensities was calculated according to the Fick's second law. It was found that the magnetic field intensity could obviously affect the carbon diffusion coefficient in pure iron in the γ-Fe temperature region, and the carbon diffusion coefficient decreased obviously with the enhancement of magnetic field intensity, when the magnetic field intensity was higher than 1 T, the carbon diffusion coefficient in field annealed specimen was less than half of that of the nonfield annealed specimen, further enhancing the magnetic field intensity, the carbon diffusion coefficient basically remains unchanged. The stiffening of lattice due to field-induced magnetic ordering was responsible for an increase in activation barrier for jumping carbon atoms. The greater the magnetic field intensity, the stronger the inhibiting effect of magnetic field on carbon diffusion.
Sanford, R.F.
1982-01-01
Geological examples of binary diffusion are numerous. They are potential indicators of the duration and rates of geological processes. Analytical solutions to the diffusion equations generally do not allow for variable diffusion coefficients, changing boundary conditions, and impingement of diffusion fields. The three programs presented here are based on Crank-Nicholson finite-difference approximations, which can take into account these complicating factors. Program 1 describes the diffusion of a component into an initially homogeneous phase that has a constant surface composition. Specifically it is written for Fe-Mg exchange in olivine at oxygen fugacities appropriate for the lunar crust, but other components, phases, or fugacities may be substituted by changing the values of the diffusion coefficient. Program 2 simulates the growth of exsolution lamellae. Program 3 describes the growth of reaction rims. These two programs are written for pseudobinary Ca-(Mg, Fe) exchange in pyroxenes. In all three programs, the diffusion coefficients and boundary conditions can be varied systematically with time. To enable users to employ widely different numerical values for diffusion coefficients and diffusion distance, the grid spacing in the space dimension and the increment by which the grid spacing in the time dimension is increased at each time step are input constants that can be varied each time the programs are run to yield a solution of the desired accuracy. ?? 1982.
The diffusive logistic equation with a free boundary and sign-changing coefficient
NASA Astrophysics Data System (ADS)
Wang, Mingxin
2015-02-01
This short paper concerns a diffusive logistic equation with a free boundary and sign-changing coefficient, which is formulated to study the spread of an invasive species, where the free boundary represents the expanding front. A spreading-vanishing dichotomy is derived, namely the species either successfully spreads to the right-half-space as time t → ∞ and survives (persists) in the new environment, or it fails to establish itself and will extinct in the long run. The sharp criteria for spreading and vanishing are also obtained. When spreading happens, we estimate the asymptotic spreading speed of the free boundary.
Sterling, Sarah M.; Allgeyer, Edward S.; Fick, Jörg; Prudovsky, Igor; Mason, Michael D.; Neivandt, David J.
2013-01-01
Model cellular membranes enable the study of biological processes in a controlled environment and reduce the traditional challenges associated with live or fixed cell studies. However, model membrane systems based on the air/water or oil/solution interface do not allow for incorporation of transmembrane proteins, or for the study of protein transport mechanisms. Conversely, a phospholipid bilayer deposited via the Langmuir-Blodgett/Langmuir Schaefer method on a hydrogel layer is potentially an effective mimic of the cross-section of a biological membrane, and facilitates both protein incorporation and transport studies. Prior to application, however, such membranes must be fully characterized, particularly with respect to the phospholipid bilayer phase transition temperature. Here we present a detailed characterization of the phase transition temperature of the inner and outer leaflets of a chitosan supported model membrane system. Specifically, the lateral diffusion coefficient of each individual leaflet has been determined as a function of temperature. Measurements were performed utilizing z-scan fluorescence correlation spectroscopy (FCS), a technique that yields calibration-free diffusion information. Analysis via the method of Wawrezinieck and coworkers, revealed that phospholipid diffusion changes from raft-like to free diffusion as the temperature is increased; an insight into the dynamic behavior of hydrogel supported membranes not previously reported. PMID:23705855
Xu, Jing; Zhang, Jianshun S; Liu, Xiaoyu; Gao, Zhi
2012-06-01
The partition and effective diffusion coefficients of formaldehyde were measured for three materials (conventional gypsum wallboard, "green" gypsum wallboard, and "green" carpet) under three relative humidity (RH) conditions (20%, 50%, and 70% RH). The "green" materials contained recycled materials and were friendly to environment. A dynamic dual-chamber test method was used. Results showed that a higher relative humidity led to a larger effective diffusion coefficient for two kinds of wallboards and carpet. The carpet was also found to be very permeable resulting in an effective diffusion coefficient at the same order of magnitude with the formaldehyde diffusion coefficient in air. The partition coefficient (K(ma)) of formaldehyde in conventional wallboard was 1.52 times larger at 50% RH than at 20% RH, whereas it decreased slightly from 50% to 70% RH, presumably due to the combined effects of water solubility of formaldehyde and micro-pore blocking by condensed moisture at the high RH level. The partition coefficient of formaldehyde increased slightly with the increase of relative humidity in "green" wallboard and "green" carpet. At the same relative humidity level, the "green" wallboard had larger partition coefficient and effective diffusion coefficient than the conventional wallboard, presumably due to the micro-pore structure differences between the two materials. The data generated could be used to assess the sorption effects of formaldehyde on building materials and to evaluate its impact on the formaldehyde concentration in buildings. PMID:22788105
Lateral diffusivity coefficients from the dynamics of a SF6 patch in a coastal environment
NASA Astrophysics Data System (ADS)
Kersalé, M.; Petrenko, A. A.; Doglioli, A. M.; Nencioli, F.; Bouffard, J.; Blain, S.; Diaz, F.; Labasque, T.; Quéguiner, B.; Dekeyser, I.
2016-01-01
The dispersion of a patch of the tracer sulfur hexafluoride (SF6) is used to assess the lateral diffusivity in the coastal waters of the western part of the Gulf of Lion (GoL), northwestern Mediterranean Sea, during the Latex10 experiment (September 2010). Immediately after the release, the spreading of the patch is associated with a strong decrease of the SF6 concentrations due to the gas exchange from the ocean to the atmosphere. This has been accurately quantified, evidencing the impact of the strong wind conditions during the first days of this campaign. Few days after the release, as the atmospheric loss of SF6 decreased, lateral diffusivity coefficient at spatial scales of 10 km has been computed using two approaches. First, the evolution of the patch with time was combined with a diffusion-strain model to obtain estimates of the strain rate (γ = 2.5 10- 6 s- 1) and of the lateral diffusivity coefficient (Kh = 23.2 m2 s- 1). Second, a steady state model was applied, showing Kh values similar to the previous method after a period of adjustment between 2 and 4.5 days. This implies that after such period, our computation of Kh becomes insensitive to the inclusion of further straining of the patch. Analysis of sea surface temperature satellite imagery shows the presence of a strong front in the study area. The front clearly affected the dynamics within the region and thus the temporal evolution of the patch. Our results are consistent with previous studies in open ocean and demonstrate the success and feasibility of those methods also under small-scale, rapidly-evolving dynamics typical of coastal environments.
Retrieval of diffuse attenuation coefficient in the China seas from surface reflectance.
Qiu, Zhongfeng; Wu, Tingting; Su, Yuanyuan
2013-07-01
Accurate estimation of the diffuse attenuation coefficient is important for our understanding the availability of light to underwater communities, which provide critical information for the China seas ecosystem. However, algorithm developments and validations of the diffuse attenuation coefficient in the China seas have been seldom performed before and therefore our knowledge on the quality of retrieval of the diffuse attenuate coefficient is poor. In this paper optical data at 306 sites collected in coastal waters of the China seas between July 2000 and February 2004 are used to evaluate three typical existing Kd(490) models. The in situ Kd(490) varied greatly among different sites from 0.029 m(-1) to 10.3 m(-1), with a mean of 0.92 ± 1.59 m(-1). Results show that the empirical model and the semi-analytical model significantly underestimate the Kd(490) value, with estimated mean values of 0.24 m(-1) and 0.5 m(-1), respectively. The combined model also shows significant differences when the in situ Kd(490) range from 0.2 m(-1) to 1 m(-1). Thus, the present study proposes that the three algorithms cannot be directly used to appropriately estimate Kd(490) in the turbid coastal waters of the China seas without a fine tuning for regional applications. In this paper, new Kd(490) algorithms are developed based on the semi-analytical retrieval of the absorption coefficient a(m(-1)) and the backscattering coefficient bb(m(-1)) from the reflectance at two wavelengths, 488 and 667 nm for the Moderate Resolution Imaging Spectroradiometer (MODIS) and 490 and 705 nm for the Medium Resolution Imaging Spectrometer (MERIS) applications, respectively. With the new approaches, the mean ratio and the relative percentage difference are 1.05 and 4.6%, respectively, based on an independent in situ data set. Furthermore, the estimates are reliable within a factor of 1.9 (95% confidence interval). Comparisons also show that the Kd(490) derived with the new algorithms are well correlated
Shiva, Amir Houshang; Teasdale, Peter R; Bennett, William W; Welsh, David T
2015-08-12
A systematic comparison of the diffusion coefficients of cations (Al, Cd, Co, Cu, Mn, Ni, Pb, Zn) and oxyanions (Al, As, Mo, Sb, V, W) in open (ODL) and restricted (RDL) diffusive layers used by the DGT technique was undertaken. Diffusion coefficients were measured using both the diffusion cell (Dcell) method at pH 4.00 and the DGT time-series (D(DGT)) method at pH 4.01 and 7.04 (pH 8.30 was used instead of 7.04 for Al) using the Chelex-Metsorb mixed binding layer. The performance of Chelex-Metsorb as a new DGT binding layer for Al uptake was also evaluated for the first time. Reasonable agreement was observed between D(cell) and D(DGT) measurements for both ODL and RDL, except for V and W. The ratios of D(cell)/D(DGT) for V of 0.44 and 0.39, and for W of 0.66 and 0.63 with ODL and RDL respectively, were much lower due to the formation of a high proportion of polyoxometalate species at the higher concentrations required with the D(cell) measurements. This is the first time that D values have been reported for several oxyanions using RDL. Except for Al at pH 8.30 with ODL, all D(DGT) measurements were retarded relative to diffusion coefficients in water (DW) for both diffusive hydrogels. Diffusion in RDL was further retarded compared with ODL, for all elements (0.66-0.78) with both methods. However, the degree of retardation observed changed for cations and anions at each pH. At pH 7.04 cations had a slightly higher D(DGT) and oxyanions had a slightly lower D(DGT) than at pH 4.01 for both ODL and RDL. It is proposed that this is due to partial formation of acrylic acid functional groups (pKa ≈4.5), which would be fully deprotonated at pH 7.04 (negative) and mostly protonated at pH 4.01 (neutral). As Al changes from being cationic at pH 4.01 to anionic at pH 8.30 the results were more complex. PMID:26320970
Bentley, Fiona K; Melis, Anastasios
2012-01-01
Photosynthesis for the generation of fuels and chemicals from cyanobacteria and microalgae offers the promise of a single host organism acting both as photocatalyst and processor, performing sunlight absorption and utilization, as well as CO(2) assimilation and conversion into product. However, there is a need to develop methods for generating, sequestering, and trapping such bio-products in an efficient and cost-effective manner that is suitable for industrial scale-up and exploitation. A sealed gaseous/aqueous two-phase photobioreactor was designed and applied for the photosynthetic generation of volatile isoprene (C(5)H(8)) hydrocarbons, which operates on the principle of spontaneous diffusion of CO(2) from the gaseous headspace into the microalgal or cyanobacterial-containing aqueous phase, followed by photosynthetic CO(2) assimilation and isoprene production by the transgenic microorganisms. Volatile isoprene hydrocarbons were emitted from the aqueous phase and were sequestered into the gaseous headspace. Periodic replacement (flushing) of the isoprene (C(5)H(8)) and oxygen (O(2)) content of the gaseous headspace with CO(2) allowed for the simultaneous harvesting of the photoproducts and replenishment of the CO(2) supply in the gaseous headspace. Reduction in practice of the gaseous/aqueous two-phase photobioreactor is offered in this work with a fed-batch and a semi-continuous culturing system using Synechocystis sp. PCC 6803 heterologously expressing the Pueraria montana (kudzu) isoprene synthase (IspS) gene. Constitutive isoprene production was observed over 192 h of experimentation, coupled with cyanobacterial biomass accumulation. The diffusion-based process in gaseous/aqueous two-phase photobioreactors has the potential to be applied to other high-value photosynthetically derived volatile molecules, emanating from a variety of photosynthetic microorganisms. PMID:21830206
Alonso de Mezquia, David; Wang, Zilin; Lapeira, Estela; Klein, Michael; Wiegand, Simone; Mounir Bou-Ali, M
2014-11-01
In this study, the thermodiffusion, molecular diffusion, and Soret coefficients of 12 binary mixtures composed of toluene, n-hexane and n-dodecane in the whole range of concentrations at atmospheric pressure and temperatures of 298.15 K and 308.15 K have been determined. The experimental measurements have been carried out using the Thermogravitational Column, the Sliding Symmetric Tubes and the Thermal Diffusion Forced Rayleigh Scattering techniques. The results obtained using the different techniques show a maximum deviation of 9% for the thermodiffusion coefficient, 8% for the molecular diffusion coefficient and 2% for the Soret coefficient. For the first time we report a decrease of the thermodiffusion coefficient with increasing ratio of the thermal expansion coefficient and viscosity for a binary mixture of an organic ring compound with a short n-alkane. This observation is discussed in terms of interactions between the different components. Additionally, the thermogravitational technique has been used to measure the thermodiffusion coefficients of four ternary mixtures consisting of toluene, n-hexane and n-dodecane at 298.15 K. In order to complete the study, the values obtained for the molecular diffusion coefficient in binary mixtures, and the thermodiffusion coefficient of binary and ternary mixtures have been compared with recently derived correlations. PMID:25376978
The partition and effective diffusion coefficients of formaldehyde were measured for three materials (conventional gypsum wallboard, "green" gypsum wallboard, and "green" carpet) under three relative humidity (RH) conditions (20%, 50% and 70% RH). A dynamic dual-chamber test meth...
The partition and effective diffusion coefficients of formaldehyde were measured for three materials (conventional gypsum wallboard, "green" gypsum wallboard, and "green" carpet) under three relative humidity (RH) conditions (20%, 50% and 70% RH). A dynamic dual-chamber test meth...
Energy Science and Technology Software Center (ESTSC)
1985-10-10
MARCOPOLO calculates the radial and axial diffusion coefficients in one-group and multi-group theory for a cylinderized cell (Wigner-Seitz theory) with several concentric zones according to the isotropic shock or linear anisotropic shock hypotheses.
NASA Astrophysics Data System (ADS)
Yoshida, Masayuki; Morooka, Masami; Takahashi, Manabu; Tomokage, Hajime
2000-05-01
Based on the pair diffusion models of vacancy and interstitial (V and I) mechanisms, the V and I components of effective P diffusion coefficient, DP^+,Veff and DP^+,Ieff, and the controlling process of P diffusion in Si are obtained. Assuming that the I mechanism is dominant, not only the I- concentration, CI^-, but also its gradient, d CI^-/d λ , is effective on DP^+,Ieff at high CP^+. DP^+,Ieff is large at d CI^-/d λ <0 and small at d CI^-/d λ >0. P+ and I- are generated by the dissociation of P-I pair. When excess I- thus generated is removed, d CI^-/d λ <0 is obtained. d CI^-/d λ <0 is also obtained by the decrease in quasi self-interstitial formation energy. Several diffusion models simulate the P diffusion profile well under an inert atmosphere. Applying the controlling process to them, the reason why they simulate the P profile well is investigated. Because all of them simulate the P profile well, it is difficult to conclude which model is correct. It is suggested that it is possible to conclude which model is correct from the P profile under oxidation at CP^+s >1× 1020 cm-3 (s: surface).
NASA Astrophysics Data System (ADS)
Farajnezhad, Arsalan; Asef Afshar, Orang; Asgarpour Khansary, Milad; Shirazian, Saeed
2016-07-01
The free volume theory has found practical application for prediction of diffusional behavior of polymer/solvent systems. In this paper, reviewing free volume theory, binary mutual diffusion coefficients in some polymer/solvent systems have been systematically presented through chemical thermodynamic modeling in terms of both activity coefficients and fugacity coefficients models. Here chemical thermodynamic model of compressible regular solution (CRS) was used for evaluation of diffusion coefficients calculations as the pure component properties would be required only. Four binary polymeric solutions of cyclohexane/polyisobutylene, n-pentane/polyisobutylene, toluene/polyisobutylene and chloroform/polyisobutylene were considered. The agreement between calculated data and the experimentally collected data was desirable and no considerable error propagation in approximating mutual diffusion coefficients has been observed.
Shalchi, A.; Danos, R. J.
2013-03-10
A spatially varying mean magnetic field gives rise to so-called adiabatic focusing of energetic particles propagating through the universe. In the past, different analytical approaches have been proposed to calculate the particle diffusion coefficient along the mean field with focusing. In the present paper, we show how these different results are related to each other. New results for the parallel diffusion coefficient that are more general than previous results are also presented.
NASA Astrophysics Data System (ADS)
Wu, Dan; Lu, Wanjun
2015-04-01
Injecting CO2 into lean-oil reservoirs is not only a way to geological storage but also enhanced oil recovery. In the secondary displacements of oil reservoir by CO2-injection, diffusion coefficients and solubility of CO2 are key parameters to calculate the volume of CO2 injected and the time to achieve the desired viscosity in the numerical simulation. Unfortunately, the experimental data on the CO2 diffusion coefficient and solubility in liquid hydrocarbons under high pressure conditions are scarce. Hexadecane has properties similar to the average properties of Brazilian heavy oil. Experimental data on the diffusion coefficients and solubility of CO2 in hexadecane were reviewed by Nieuwoudt and Rand (2002), Rincon and Trejo (2001) and Breman et al (1994), indicating that the data in the literature were limited at relatively low temperatures and/or low pressures. In this paper, the diffusion coefficients of carbon dioxide in hexadecane at different temperature and pressure were determined with in situ Raman spectroscopy. A model was established to describe relationship among diffusion coefficients, temperature, and pressure. The solubility of CO2 in hexadecane was obtained from 298.15 to 473.15 K and 10 to 45 MPa. The experimental results show that:(1) Solubility of CO2 decreases with increasing temperature.(2) Increasing pressure increases the CO2 solubility. in terms of the degree of influence,100K is similar with 10MPa.(3) Diffusion coefficients of CO2 increases with increasing temperature. (4) Increasing pressure decreases the CO2 diffusion coefficients, whereas the pressure effect on CO2 diffusion coefficients is very weak. Compared with traditional sampling and analytical methods, the advantages of our method include: (1) the use of in situ Raman signals for solubility measurements eliminates possible uncertainty caused by sampling and ex situ analysis. (2) it is simple and efficient, and (3) high-pressure data can be obtained safely.
Effect of cation on diffusion coefficient of ionic liquids at onion-like carbon electrodes.
Van Aken, Katherine L; McDonough, John K; Li, Song; Feng, Guang; Chathoth, Suresh M; Mamontov, Eugene; Fulvio, Pasquale F; Cummings, Peter T; Dai, Sheng; Gogotsi, Yury
2014-07-16
While most supercapacitors are limited in their performance by the stability of the electrolyte, using neat ionic liquids (ILs) as the electrolyte can expand the voltage window and temperature range of operation. In this study, ILs with bis(trifluoromethylsulfonyl)imide (Tf2N) as the anion were investigated as the electrolyte in onion-like carbon-based electrochemical capacitors. To probe the influence of cations on the electrochemical performance of supercapacitors, three different cations were used: 1-ethyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium and 1,6-bis(3-methylimidazolium-1-yl). A series of electrochemical characterization tests was performed using cyclic voltammetry (CV), galvanostatic cycling and electrochemical impedance spectroscopy (EIS). Diffusion coefficients were measured using EIS and correlated with quasielastic neutron scattering and molecular dynamics simulation. These three techniques were used in parallel to confirm a consistent trend between the three ILs. It was found that the IL with the smaller sized cation had a larger diffusion coefficient, leading to a higher capacitance at faster charge-discharge rates. Furthermore, the IL electrolyte performance was correlated with increasing temperature, which limited the voltage stability window and led to the formation of a solid electrolyte interphase on the carbon electrode surface, evident in both the CV and EIS experiments. PMID:24920163
Computing the blood brain barrier (BBB) diffusion coefficient: A molecular dynamics approach
NASA Astrophysics Data System (ADS)
Shamloo, Amir; Pedram, Maysam Z.; Heidari, Hossein; Alasty, Aria
2016-07-01
Various physical and biological aspects of the Blood Brain Barrier (BBB) structure still remain unfolded. Therefore, among the several mechanisms of drug delivery, only a few have succeeded in breaching this barrier, one of which is the use of Magnetic Nanoparticles (MNPs). However, a quantitative characterization of the BBB permeability is desirable to find an optimal magnetic force-field. In the present study, a molecular model of the BBB is introduced that precisely represents the interactions between MNPs and the membranes of Endothelial Cells (ECs) that form the BBB. Steered Molecular Dynamics (SMD) simulations of the BBB crossing phenomenon have been carried out. Mathematical modeling of the BBB as an input-output system has been considered from a system dynamics modeling viewpoint, enabling us to analyze the BBB behavior based on a robust model. From this model, the force profile required to overcome the barrier has been extracted for a single NP from the SMD simulations at a range of velocities. Using this data a transfer function model has been obtained and the diffusion coefficient is evaluated. This study is a novel approach to bridge the gap between nanoscale models and microscale models of the BBB. The characteristic diffusion coefficient has the nano-scale molecular effects inherent, furthermore reducing the computational costs of a nano-scale simulation model and enabling much more complex studies to be conducted.
Double obstacle phase field approach to an inverse problem for a discontinuous diffusion coefficient
NASA Astrophysics Data System (ADS)
Deckelnick, Klaus; Elliott, Charles M.; Styles, Vanessa
2016-04-01
We propose a double obstacle phase field approach to the recovery of piece-wise constant diffusion coefficients for elliptic partial differential equations. The approach to this inverse problem is that of optimal control in which we have a quadratic fidelity term to which we add a perimeter regularization weighted by a parameter σ. This yields a functional which is optimized over a set of diffusion coefficients subject to a state equation which is the underlying elliptic PDE. In order to derive a problem which is amenable to computation the perimeter functional is relaxed using a gradient energy functional together with an obstacle potential in which there is an interface parameter ɛ. This phase field approach is justified by proving {{Γ }}- convergence to the functional with perimeter regularization as ε \\to 0. The computational approach is based on a finite element approximation. This discretization is shown to converge in an appropriate way to the solution of the phase field problem. We derive an iterative method which is shown to yield an energy decreasing sequence converging to a discrete critical point. The efficacy of the approach is illustrated with numerical experiments.
A simple method for the determination of ionic diffusion coefficients in flooded soils
NASA Astrophysics Data System (ADS)
Gardner, P. J.; Flynn, N.; Maltby, E.
2001-02-01
Soil cores from river marginal wetlands from the Torridge and Severn catchments in the UK were collected to study rates of soil denitrification at different sites and at two stations (levee and backplain depression) at the river margin. Half the cores were sterilized prior to flooding to destroy the denitrifying bacteria. After flooding and equilibration, monitoring the concentration of amended nitrate in the supernatant of the sterile cores over a period of 7 days provided a simple procedure for the estimation of the diffusion coefficient of the nitrate ion in the flooded soils. An expression was developed that permitted this diffusion coefficient to be extracted from the slope of a plot of supernatant concentration versus (time)1/2. The values obtained, at 15 °C, varied from 2·4 to 6·8 × 10-10m2s-1. Sterile cores are usually treated as controls in denitrification experiments; this work develops a procedure whereby they may yield useful soil process information.
In-situ estimate of submesoscale horizontal eddy diffusion coefficients across a front
NASA Astrophysics Data System (ADS)
Nencioli, Francesco; d'Ovidio, Francesco; Doglioli, Andrea; Petrenko, Anne
2013-04-01
Fronts, jets and eddies are ubiquitous features of the world oceans, and play a key role in regulating energy budget, heat transfer, horizontal and vertical transport, and biogeochemical processes. Although recent advances in computational power have favored the analysis of mesoscale and submesoscale dynamics from high-resolution numerical simulations, studies from in-situ observations are still relatively scarce. The small dimensions and short duration of such structures still pose major challenges for fine-scale dedicated field experiments. As a consequence, in-situ quantitative estimates of key physical parameters for high-resolution numerical models, such as horizontal eddy diffusion coefficients, are still lacking. The Latex10 campaign (September 1-24, 2010), within the LAgrangian Transport EXperiment (LATEX), adopted an adaptive sampling strategy that included satellite data, ship-based current measurements, and iterative Lagrangian drifter releases to successfully map coherent transport structures in the western Gulf of Lion. Comparisons with AVHRR imagery evidenced that the detected structures were associated with an intense frontal feature, originated by the convergence and subsequent stirring of colder coastal waters with warmer open-sea waters. We present a method for computing horizontal eddy diffusion coefficients by combining the stirring rates estimated from the Lagrangian drifter trajectories with the shapes of the surface temperature and salinity gradient (assumed to be at the equilibrium) from the ship thermosalinograph. The average value we obtained from various sections across the front is 2.5 m2s-1, with horizontal scales (width of the front) ranging between 0.5 and 2.5 km. This is in line with the values commonly used for high-resolution numerical simulations. Further field experiment will be required to extend the results to different ocean regions and regimes, and to thoroughly test the robustness of the equilibrium hypothesis. Remote sensed
NASA Astrophysics Data System (ADS)
Frazer, E. J.; Thonstad, J.
2010-06-01
The solubility of alumina was measured by rotating an alumina cylinder (~500 rpm) in a high-purity melt for ~3 to 6 hours, crushing and sampling the frozen melt, and determining the oxygen content in a Leco analyzer. The alumina solubilities determined were as follows: (1) 3.2 ± 0.3 wt pct in NaF-AlF3 eutectic at 1023 K (750 °C); (2) 3.0 ± 0.3 wt pct in NaF-AlF3-CaF2 (5 wt pct) at 1023 K (750 °C); and (3) 5.2 ± 0.5 wt pct in a KF-AlF3 eutectic at 1003 K (730 °C). The alumina solubility in the KF-AlF3 eutectic was 2 wt pct more than in the sodium analogue, offering the possibility of operating a low-temperature aluminum smelting cell without the need for an alumina slurry. The diffusion coefficient of the dissolved alumina species was determined in the NaF-AlF3 eutectic at 1023 K (750 °C) using the rotating disc method and applying the Levich equation. Through a limited range of rotation rates, the system seemed to be mass-transfer controlled, and the diffusion coefficient was estimated to be in the range 1.8 to 2.2 × 10-6 cm2 s-1. This value is about five times lower than the values encountered at traditional aluminum smelting temperatures (~1233 K (960 °C)) and would result in relatively low mass transfer coefficients.
Hydraulic conductivity, albumin reflection and diffusion coefficients of pig mediastinal pleura.
Parameswaran, S; Brown, L V; Ibbott, G S; Lai-Fook, S J
1999-09-01
Hydraulic conductivity (L), albumin reflection coefficient (sigma), and albumin diffusion coefficient (D) were measured across pig mediastinal pleura. The tissue (7 mm diameter) was bonded between two chambers. Flow (Q) of lactated Ringer solution between the chambers was measured in turn at driving pressures (DeltaP) of 2, 4, and 6 cm H(2)O. Value of L was proportional to the slope of the Q-DeltaP curve. Then Q was measured in turn at three albumin osmotic pressure differences (Deltapi equivalent to -1, -2, and -3 g/dl albumin concentration difference, DeltaC) with DeltaP constant at either 2, 3, 4, or 6 cm H(2)O. From Starling's equation, magnitude of sigma was the slope of the Q-Deltapi curve divided by the slope of the Q-DeltaP curve. We measured the diffusion of 0, 2, 5, and 10 g/dl albumin with tracer (125)I-albumin. Tracer mass (M) that diffused across the pleura was measured for 10 h using a well-type NaI(T1) detector. D was calculated from the slope of the M-time curve. Values of L averaged 2.0 x 10(-8) cm(3). s(-1). dyne(-1) (n = 23). Values of sigma were small (0.02-0.05) and sigma increased as flow increased 20-fold. D (n = 24) increased 3-fold from 2.7 x 10(-8) cm(2)/s as DeltaC increased from 0 to 10 g/dl. The small values of sigma indicated that mediastinal pleura provided little restriction to the passage of protein. PMID:10458927
Measurement of the dimensionless extinction coefficient of soot within laminar diffusion flames.
Suo-Anttila, Jill Marie; Williams, Timothy C.; Shaddix, Christopher R.; Jensen, Kirk A.
2005-01-01
The dimensionless extinction coefficient (K{sub e}) of soot must be known to quantify laser extinction measurements of soot concentration and to predict optical attenuation through smoke clouds. Previous investigations have measured K{sub e} for post-flame soot emitted from laminar and turbulent diffusion flames and smoking laminar premixed flames. This paper presents the first measurements of soot K{sub e} from within laminar diffusion flames, using a small extractive probe to withdraw the soot from the flame. To measure K{sub e}, two laser sources (635 nm and 1310 nm) were coupled to a transmission cell, followed by gravimetric sampling. Coannular diffusion flames of methane, ethylene and nitrogen-diluted kerosene burning in air were studied, together with slot flames of methane and ethylene. K{sub e} was measured at the radial location of maximum soot volume fraction at several heights for each flame. Results for K{sub e} at both 635 nm and 1310 nm for ethylene and kerosene coannular flames were in the range of 9-10, consistent with the results from previous studies of post-flame soot. The ethylene slot flame and the methane flames have lower K{sub e} values, in some cases as low as 2.0. These lower values of K{sub e} are found to result from the contributions of (a) the condensation of PAH species during the sampling of soot, (b) the wavelength-dependent absorptivity of soot precursor particles, and, in the case of methane, (c) the negligible contribution of soot scattering to the extinction coefficient. RDG calculations of soot scattering, in combination with the measured K{sub e} values, imply that the soot refractive index is in the vicinity of 1.75-1.03i at 635 nm.
NASA Astrophysics Data System (ADS)
Yoshida, Ken; Matubayasi, Nobuyuki; Nakahara, Masaru
2008-12-01
The self-diffusion coefficients D for water, benzene, and cyclohexane are determined by using the pulsed-field-gradient spin echo method in high-temperature conditions along the liquid branch of the coexistence curve: 30-350 °C (1.0-0.58 g cm-3), 30-250 °C (0.87-0.56 g cm-3), and 30-250 °C (0.77-0.48 g cm-3) for water, benzene, and cyclohexane, respectively. The temperature and density effects are separated and their origins are discussed by examining the diffusion data over a wide range of thermodynamic states. The temperature dependence of the self-diffusion coefficient for water is larger than that for organic solvents due to the large contribution of the attractive hydrogen-bonding interaction in water. The density dependence is larger for organic solvents than for water. The difference is explained in terms of the van der Waals picture that the structure of nonpolar organic solvents is determined by the packing effect due to the repulsion or exclusion volumes. The dynamic solvation shell scheme [K. Yoshida et al., J. Chem. Phys. 127, 174509 (2007)] is applied for the molecular interpretation of the translational dynamics with the aid of molecular dynamics simulation. In water at high temperatures, the velocity relaxation is not completed before the relaxation of the solvation shell (mobile-shell type) as a result of the breakdown of the hydrogen-bonding network. In contrast, the velocity relaxation of benzene is rather confined within the solvation shell (in-shell type).
Drag and diffusion coefficient of a spherical particle attached to a fluid interface
NASA Astrophysics Data System (ADS)
Hardt, Steffen; Doerr, Aaron; Masoud, Hassan; Stone, Howard
2015-11-01
We consider a spherical particle attached to the interface between two immiscible fluids of large viscosity contrast. The degree of immersion in the two fluids is determined by the contact angle. For small enough particles and significant contact-angle hysteresis, it can be assumed that the three-phase contact line is pinned at the particle surface. We study the movement of such particles along the fluid interface for the case of small Reynolds and capillary numbers. We solve the Stokes equation based on two geometric perturbation expansions around contact angles of 90 degrees and 180 degrees, the latter corresponding to a particle completely immersed in the less viscous phase. Based on the Lorentz Reciprocity Theorem we obtain expressions for the drag coefficient of an interfacial particle which are analogs of the well-known Stokes drag coefficient for a particle moving in an unbounded medium. Interpolation of the two results gives a relationship which approximates the drag coefficient quite accurately over the entire range of contact angles. A comparison with previously published numerical results for contact angles below 90 degrees shows good agreement. Using the fluctuation-dissipation theorem, we also obtain expressions for the diffusion constant of a small particle attached to a fluid interface.
NASA Astrophysics Data System (ADS)
Asadian, M.; Saeedi, H.; Yadegari, M.; Shojaee, M.
2014-06-01
In this paper, a new mathematical model has been presented to determine the equilibrium segregation (k0) and effective segregation (keff) coefficients for neodymium (Nd) in YAG crystal grown by Czochralski (CZ) method. Determination of diffusion coefficient (DL) of Nd impurity in molten YAG is also investigated. In this model, utilizing Lambert W-function is a new idea to solve the Scheil equation for calculation of effective segregation coefficient. The Nd concentration in the crystal has been measured by optical absorption method to calculate keff. The analyses show that the keff is related to the growth parameters such as crystal growth rate (ug) and crystal rotation rate (ω), ( ug/√{ω}) but it is independent of the Nd concentration in the initial melt (C0). Based on obtained keff and experimental growth data, k0 and DL of Nd in molten YAG have been calculated. For all experiments, the average value of k0=0.216 and DL=1.4×10-6 (cm2/s) are obtained. Our results are corroborated by the theoretical and experimental data from the literature.
Apparent diffusion coefficient and fractional anisotropy of newly diagnosed grade II gliomas†
Khayal, Inas S.; McKnight, Tracy R.; McGue, Colleen; Vandenberg, Scott; Lamborn, Kathleen R.; Chang, Susan M.; Cha, Soonmee; Nelson, Sarah J.
2013-01-01
Distinguishing between low-grade oligodendrogliomas (ODs) and astrocytomas (AC) is of interest for defining prognosis and stratifying patients to specific treatment regimens. The purpose of this study was to determine if the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) from diffusion imaging can help to differentiate between newly diagnosed grade II OD and AC subtypes and to evaluate the ADC and FA values for the mixed population of oligoastrocytomas (OA). Fifty-three patients with newly diagnosed grade II gliomas were studied using a 1.5T whole body scanner (23 ODs, 16 ACs, and 14 OAs). The imaging protocol included post-gadolinium T1-weighted images, T2-weighted images, and either three and/or six directional diffusion imaging sequence with b = 1000 s/mm2. Diffusion-weighted images were analyzed using in-house software to calculate maps of ADC and for six directional acquisitions, FA. The intensity values were normalized by values from normal appearing white matter (NAWM) to generate maps of normalized apparent diffusion coefficient (nADC) and normalized fractional anisotropy (nFA). The hyperintense region in the T2 weighted image was defined as the T2All region. A Mann–Whitney rank-sum test was performed on the 25th, median, and 75th nADC and nFA among the three subtypes. Logistic regression was performed to determine how well the nADC and nFA predict subtype. Lesions diagnosed as being OD had significantly lower nADC and significantly higher nFA, compared to AC. The nADC and nFA values individually classified the data with an accuracy of 87%. Combining the two did not enhance the classification. The patients with OA had nADC and nFA values between those of OD and AC. This suggests that ADC and FA may be helpful in directing tissue sampling to the most appropriate regions for taking biopsies in order to make a definitive diagnosis. PMID:19125391
Apparent diffusion coefficient and fractional anisotropy of newly diagnosed grade II gliomas.
Khayal, Inas S; McKnight, Tracy R; McGue, Colleen; Vandenberg, Scott; Lamborn, Kathleen R; Chang, Susan M; Cha, Soonmee; Nelson, Sarah J
2009-05-01
Distinguishing between low-grade oligodendrogliomas (ODs) and astrocytomas (AC) is of interest for defining prognosis and stratifying patients to specific treatment regimens. The purpose of this study was to determine if the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) from diffusion imaging can help to differentiate between newly diagnosed grade II OD and AC subtypes and to evaluate the ADC and FA values for the mixed population of oligoastrocytomas (OA). Fifty-three patients with newly diagnosed grade II gliomas were studied using a 1.5T whole body scanner (23 ODs, 16 ACs, and 14 OAs). The imaging protocol included post-gadolinium T1-weighted images, T2-weighted images, and either three and/or six directional diffusion imaging sequence with b = 1000 s/mm(2). Diffusion-weighted images were analyzed using in-house software to calculate maps of ADC and for six directional acquisitions, FA. The intensity values were normalized by values from normal appearing white matter (NAWM) to generate maps of normalized apparent diffusion coefficient (nADC) and normalized fractional anisotropy (nFA). The hyperintense region in the T2 weighted image was defined as the T2All region. A Mann-Whitney rank-sum test was performed on the 25th, median, and 75th nADC and nFA among the three subtypes. Logistic regression was performed to determine how well the nADC and nFA predict subtype. Lesions diagnosed as being OD had significantly lower nADC and significantly higher nFA, compared to AC. The nADC and nFA values individually classified the data with an accuracy of 87%. Combining the two did not enhance the classification. The patients with OA had nADC and nFA values between those of OD and AC. This suggests that ADC and FA may be helpful in directing tissue sampling to the most appropriate regions for taking biopsies in order to make a definitive diagnosis. PMID:19125391
Demir, Senay; Altinkaya, Naime; Kocer, Nazim Emrah; Erbay, Ayse; Oguzkurt, Pelin
2015-01-01
PURPOSE In children the assessment of solid tumors’ response to chemotherapy is based primarily on size reduction, which can be unreliable and a late marker, in the presence of necrosis. We aimed to establish whether apparent diffusion coefficient (ADC) values of childhood neuroblastomas show proportional changes in relation to chemotherapy response. METHODS We evaluated 15 pediatric patients with abdominopelvic neuroblastomas, who had undergone MRI before and after chemotherapy. Two radiologists retrospectively analyzed all images by drawing a round uniform region-of-interest in the solid/contrast-enhancing portion of the lesions in consensus. The ADC values from pre- and postchemotherapy images were compared. RESULTS Postchemotherapy ADC values were significantly higher than those obtained before treatment (P < 0.05, for minimum, maximum, and median ADC values). CONCLUSION Our results support diffusion-weighted MRI as a promising noninvasive biomarker of therapeutic responses. To the best of our knowledge, this is the first report to compare diffusion-weighted imaging findings before and after chemotherapy in childhood neuroblastic tumors. PMID:25519453
Measurement and prediction of the oxygen diffusion coefficient in partly saturated media
NASA Astrophysics Data System (ADS)
Aachib, M.; Mbonimpa, M.; Aubertin, M.; Bussiere, B.
2004-05-01
Molecular diffusion is an important mechanism for gas transport in various natural and man-made systems. This is particularly the case with soil covers installed on acid generating mine tailings, where oxygen availability has to be controlled. One of the most important roles of such covers is to limit gas flux, which depends on the effective diffusion coefficient De of the cover materials. This paper presents an experimental procedure and results from oxygen diffusion tests performed on different types of materials, at various degrees of saturation. The determination of De in the laboratory from the test data is based on solutions to Fick's laws. The ensuing values of De are compared to values calculated from available models that relate De to basic material properties, including porosity and degree of saturation. Statistical indicators are used to evaluate the accuracy of selected models, individually and on a comparative basis. It is shown that modified versions of the Millington-Quirk and Millington-Shearer models provide De values close to the measured data. A semi-empirical expression, ensuing from these models and measurements, is proposed as a simple means of estimating De.
Measurement of 18O tracer diffusion coefficients in thin yttria stabilized zirconia films
Gerstl, M.; Frömling, T.; Schintlmeister, A.; Hutter, H.; Fleig, J.
2011-01-01
In this paper we present a method to measure oxygen tracer diffusion coefficients in thin ion conducting films without being limited by slow oxygen incorporation kinetics. The method is based on a two step process. In the first step a substantial amount of 18O tracer is locally incorporated for example into an yttria stabilized zirconia (YSZ) layer at low temperatures with the aid of an electric current, thus overcoming slow thermal oxygen exchange while still limiting lateral diffusion to a minimum. In the second step controlled diffusion takes place at elevated temperatures in ultra high vacuum (UHV) to impede loss of tracer due to oxygen exchange at the film surface. In this second step the surface of the thin film may additionally be modified compared to the oxygen incorporation step. This allows to easily investigate effects of interfaces on ion transport. The achieved in-plane concentration profiles are then measured by secondary ion mass spectrometry (SIMS). Comparison with electrical measurements on YSZ thin films proves the applicability of the method.
Determination of the diffusion length and the optical self absorption coefficient using EBIC model
NASA Astrophysics Data System (ADS)
Guermazi, S.; Guermazi, H.; Mlik, Y.; El Jani, B.; Grill, C.; Toureille, A.
2001-10-01
We have developed a model of calculation of the induced current due to an electron beam. The expression for the electron beam induced current (EBIC) with an extended generation profile is obtained via the resolution of a steady state continuity equation by the Green function method, satisfying appropriated boundary conditions to the physical model. The generation profile takes into account the lateral diffusion, the effect of defects, dislocations and recombination surfaces besides the number of absorbed electrons and that of diffuse electrons as a function of the depth. In the case of a Schottky diode Au/GaAs obtained by metalorganic vapour phase epitaxy (MOVPE) method, the theoretical induced current profile is compared to the experimental one and to theoretical profiles whose analytical expressions are given by van Roosbroeck and Bresse. The minority carriers diffusion length L_n = 2 μm and the optical self-absorption coefficient a=0.034 μm^{-1} can be deduced from the experimental current profile, measured by scanning electron microscopy. The theoretical curve, obtained from the proposed model is in a good agreement with the experimental one for surface recombination velocity 10^6 cm s^{-1} except for distances far from the depletion layer (x_0 > 2.3 μm) where the photocurrent produced by the multiple process of the reabsorbed recombination radiation is preponderant. Our results are in agreement with those obtained by other experimental techniques on the same samples.
Not Available
1982-09-01
A waste heat recovery system for the Portsmouth Gaseous Diffusion Plant (GDP) in Piketon, Ohio is under development. This project includes the design and capital cost estimate for utilizing large quantities of waste heat presently dissipated by the cooling towers. The amount of heat available is equivalent to 1200 MW per day. This project will use part of the waste heat for the Pike County Joint Vocational School, 3 miles north of the plant site. The design includes provisions for the heating of the existing 90,000-square-foot school, proposed expansion, and a future 3-acre teaching greenhouse. A portion of the remainder of the waste energy will be used to heat a proposed greenhouse complex. The balance will be used as a heat source for heat pumps to provide steam for various proposed process industries. The Department of Enegy specifies that the recirculating cooling water remain within the GDP battery limits. Therefore, separate water loops for the offsite waste heat piping complex must be provided. The project description, scope of work and phase description, alternates considered, design criteria, and drawing list are included.
Gunn, D.
1988-01-01
Spent trichloroethylene (TCE), 1,1,1-trichloroethane (TC-ane), and sludge are generated mainly as a result of vapor degreasing operations at the Paducah Gaseous Diffusion Plant (PGDP). Additionally, small quantities of spent chlorinated solvents are generated as a result of small parts cleanup. Additionally, some of the solvents become contaminated with uranium which classifies them as mixed waste for which no disposal method is currently available. Due to health and environmental concerns and the desire to minimize mixed and hazardous waste generation, a study was initiated to identify nonchlorinated, less toxic degreasers, perform laboratory testing of the most promising alternatives, and initiate field testing to determine if alternate degreasers present operational problems. The degreaser that cleaned and protected metal surfaces best was an all-purpose, water-based, hard surface cleaner consisting of biodegradable synthetic detergents, inorganic builders, and glycol either solvent. Additionally, this product was free-rinsing and did not leave any contaminants that would react with commonly used process gases. This product is recommended as a replacement for chlorinated solvents for many degreasing operations at PGDP.
Haire, M.J.; Jordan, W.C.; Jollay, L.J. III; Dahl, T.L.
1997-02-01
The US Department of Energy (DOE) Deputy Assistant Secretary of Energy for Environmental Management has issued a challenge to complete DOE environmental cleanup within a decade. The response for Oak Ridge facilities is in accordance with the DOE ten-year plan which calls for completion of > 95% of environmental management work by the year 2006. This will result in a 99% risk reduction and in a significant savings in base line costs in waste management (legacy waste); remedial action (groundwater, soil, etc.); and decontamination and decommissioning (D and D). It is assumed that there will be long-term institutional control of cascade equipment, i.e., there will be no walk away from sites, and that there will be firm radioactivity release limits by 1999 for recycle metals. An integral part of these plants is the removal of uranium deposits which pose nuclear criticality safety concerns in the shut down of the Oak Ridge Gaseous Diffusion Plant. DOE has initiated the Nuclear Criticality Stabilization Program to improve nuclear criticality safety by removing the larger uranium deposits from unfavorable geometry equipment. Nondestructive assay (NDA) measurements have identified the location of these deposits. The objective of the K-25 Site Nuclear Criticality Stabilization Program is to remove and place uranium deposits into safe geometry storage containers to meet the double contingency principle. Each step of the removal process results in safer conditions where multiple controls are present. Upon completion of the Program, nuclear criticality risks will be greatly reduced.
Source term evaluation for UF{sub 6} release event in feed facility at gaseous diffusion plants
Kim, S.H.; Taleyarkhan, R.P.
1997-01-30
An assessment of UF{sub 6} release accidents was conducted for the feed facility of a gaseous diffusion plant (GDP). Release rates from pig-tail connections were estimated from CYLIND code predictions, whereas, MELCOR was utilized for simulating reactions of UF{sub 6} with moisture and consequent transport of UO{sub 2}F{sub 2} aerosols and HF vapor through the building and to the environment. Two wind speeds were utilized. At the high end (Case 1) a wind speed of {approximately} 1 m/s (200 fpm) was assumed to flow parallel to the building length. At the low end (Case 2) to represent stagnant conditions a corresponding wind speed of 1 cm/s (2 fpm) was utilized. A further conservative assumption was made to specify no closure of crane and train doors at either end of the building. Relaxation of this assumption should provide for additional margins. Results indicated that, for the high (200 fpm) wind speed, close to 66% of the UO{sub 2}F{sub 2} aerosols and 100% of the HF gas get released to the environment over a 10-minute period. However, for the low (2 fpm) wind speed, negligible amount ({approximately} 1% UO{sub 2}F{sub 2}) of aerosols get released even over a 2 hour period.
1998-12-01
This Record of Decision (ROD) presents the final remedial action decisions selected for soils and sediments in each of the solid waste management units (SWMUs) of Waste Area Groups (WAGs) 1 and 7 at the Paducah Gaseous Diffusion Plant (PGDP) near Paducah, Kentucky. Waste Area Group 1 consists of SWMUs 100 and 136. Waste Area Group 7 consists of SWMUs 8 and 130 through 134. By mutual consent among the United States Environmental Protection Agency (EPA), the Kentucky Department for Environmental Protection (KDEP), the United States Department of Defense (DOD), the United States Army Corps of Engineers (COE), and the DOE, it was agreed that the evaluation and implementation of any remedial actions required for the Kentucky Ordnance Works (KOW) SWMUs (SWMU 94 (KOW Sewage Treatment Plant), SWMU 95 (KOW Burn Area), and SWMU 157 (KOW Toluene Spill Site)), formerly included in WAGs 1 and 7, would be the responsibility of the DOD and conducted on behalf of the DOD by the COE. Due to the agreements reached among these entities, remedial technologies for the KOW SWMUs are not discussed further in this ROD and will be evaluated as part of the WAG 10 investigation by the COE. Additionally, by written mutual consent, the EPA, the DKEP, and the DOE agreed that an evaluation of remedial alternatives for SWMU 38, the C-615 Sewage Treatment Plant, would be deferred until the unit ceases operation. Consequently, no remedial actions are discussed for these SWMUs in this ROD.
Lyon, B.F.
1996-02-01
During the summer of 1995, ultrasonic wall thickness data were collected for 100 steel cylinders containing depleted uranium (DU) hexafluoride located at Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky. The cylinders were selected for measurement to assess the condition of the more vulnerable portion of the cylinder inventory at PGDP. The purpose of this report is to apply the method used in Lyon to estimate the effects of corrosion for larger unsampled populations as a function of time. The scope of this report is limited and is not intended to represent the final analyses of available data. Future efforts will include continuing analyses of available data to investigate defensible deviations from the conservative assumptions made to date. For each cylinder population considered, two basic types of analyses were conducted: (1) estimates were made of the number of cylinders as a function of time that will have a minimum wall thickness of either 0 mils (1 mil = 0.00 1 in.) or 250 mils and (2) the current minimum wall thickness distributions across cylinders were estimated for each cylinder population considered. Additional analyses were also performed investigating comparisons of the results for F and G yards with the results presented in Lyon (1995).
Apparent diffusion coefficient measurements to support a diagnosis of intracranial hypotension
Fulwadhva, U; Dundmadappa, S K
2014-01-01
Objective: Intracranial hypotension (ICH) can be a challenging diagnosis, as cerebrospinal fluid leaks may be difficult to confirm, patients may have other causes for clinical symptoms and imaging findings can be non-specific, particularly in the setting of comorbidities. We investigate the use of brain diffusion measurements [apparent diffusion coefficient (ADC) values] in the assessment of ICH. Methods: 13 cases of ICH were identified retrospectively based on imaging findings and their clinical histories were compared with 13 control subjects. Regional ADC values and average diffusion constant (Dav) from brain slice ADC histograms were measured. Results: ADC values trended higher in all brain regions in patients with ICH than those in control subjects, with statistically significant differences in frontal white matter, mid-brain and deep grey structures. Dav determined by a single-slice ADC histogram was significantly higher in patients with ICH than in the control group (p = 0.008). In two cases followed longitudinally, Dav correlated with the patient's symptoms and decreased towards normal value with blood patch. In one case, decreased Dav correlated with the formation of subdural collections. Conclusion: Cerebral oedema as assessed by increased ADC is strongly correlated with ICH (10 of 13 cases). Histographic analysis of ADC values may offer increased accuracy of ADC measurement. ADC value assessment in the determination of ICH may be particularly useful in complex clinical cases, where treatment is followed over time or where gadolinium is not used and meningeal enhancement cannot be assessed. Advances in knowledge: This article investigates the use of brain diffusion measurements in the assessment of ICH in the clinical setting. PMID:24896198
Drabik, Dominik; Przybyło, Magda; Sikorski, Aleksander; Langner, Marek
2016-03-01
Fluorescence Correlation Spectroscopy (FCS) is a technique, which allows determination of the diffusion coefficient and concentration of fluorescent objects suspended in the solution. The measured parameter is the fluctuation of the fluorescence signal emitted by diffusing molecules. When 100 nm DOPC vesicles labeled with various fluorescent dyes (Fluorescein-PE, NBD-PE, Atto488 DOPE or βBodipy FL) were measured, different values of diffusion coefficients have been obtained. These diffusion coefficients were different from the expected values measured using the dynamic light scattering method (DLS). The FCS was initially developed for solutions containing small fluorescent molecules therefore the observed inconsistency may result from the nature of vesicle suspension itself. The duration of the fluorescence signal may depend on the following factors: the exposure time of the labeled object to the excitation beam, the photo-physical properties (e.g., stability) of a fluorophore, the theoretical model used for the calculations of the diffusion coefficient and optical properties of the vesicle suspension. The diffusion coefficients determined for differently labeled liposomes show that its dependence on vesicle size and quantity of fluorescent probed used for labeling was significant demonstrating that the fluorescence properties of the fluorophore itself (bleaching and/or blinking) were critical factors for a correct outcome of FCS experiment. The new, based on combined FCS and DLS measurements, method for the determination of the focal volume prove itself to be useful for the evaluation of a fluorescence dye with respect to its applicability for FCS experiment. PMID:26695945
NASA Astrophysics Data System (ADS)
Kikugawa, Gota; Ando, Shotaro; Suzuki, Jo; Naruke, Yoichi; Nakano, Takeo; Ohara, Taku
2015-01-01
In the present study, molecular dynamics (MD) simulations on the monatomic Lennard-Jones liquid in a periodic boundary system were performed in order to elucidate the effect of the computational domain size and shape on the self-diffusion coefficient measured by the system. So far, the system size dependence in cubic computational domains has been intensively investigated and these studies showed that the diffusion coefficient depends linearly on the inverse of the system size, which is theoretically predicted based on the hydrodynamic interaction. We examined the system size effect not only in the cubic cell systems but also in rectangular cell systems which were created by changing one side length of the cubic cell with the system density kept constant. As a result, the diffusion coefficient in the direction perpendicular to the long side of the rectangular cell significantly increases more or less linearly with the side length. On the other hand, the diffusion coefficient in the direction along the long side is almost constant or slightly decreases. Consequently, anisotropy of the diffusion coefficient emerges in a rectangular cell with periodic boundary conditions even in a bulk liquid simulation. This unexpected result is of critical importance because rectangular fluid systems confined in nanospace, which are present in realistic nanoscale technologies, have been widely studied in recent MD simulations. In order to elucidate the underlying mechanism for this serious system shape effect on the diffusion property, the correlation structures of particle velocities were examined.
NASA Astrophysics Data System (ADS)
Manouchehrian Fard, Manouchehr; Beiki, Hossein
2015-12-01
An experimental study was performed to measure benzoic acid diffusion coefficient in water-based γ-Al2O3 nanofluids at different temperatures. Measurements were carried out at 15, 20 and 25 °C. γ-Al2O3 nanoparticles with an average diameter of 10-20 nm were added into de-ionized water as the based fluid. Nanoparticles volume fractions used in the based fluid were 0.025, 0.05, 0.1, 0.2, 0.4 and 0.8 %. Measurements showed that the diffusion coefficients was not changed with nanoparticles concentration and no enhancement was found. Dependence of diffusion coefficients on nanoparticles concentration followed the same trend in all temperatures investigated in this work. Nano stirring and nano-obstacles could be regarded as two reasons for mass diffusivity changes in nanofluids.
Macarini, Luca; Stoppino, Luca Pio; Milillo, Paola; Ciuffreda, Pierpaolo; Fortunato, Francesca; Vinci, Roberta
2010-01-01
The purpose of the study was to assess the capability and the reliability of apparent diffusion coefficient (ADC) measurements in the evaluation of different benign renal abnormalities. Twenty-five healthy volunteers and 31 patients, divided into seven different groups (A-G) according to pathology, underwent diffusion-weighted magnetic resonance imaging (DW MRI) of the kidneys using 1.5-T system. DW images were obtained in the axial plane with a spin-echo echo planar imaging single-shot sequence with three b values (0, 300, and 600 s/mm²). Before acquisition of DW sequences, we performed in each patient a morphological study of the kidneys. ADC was 2.40±0.20×10⁻³ mm² s⁻¹ in volunteers. A significant difference was found between Groups A (cysts=3.39±0.51×10⁻³ mm² s⁻¹) and B (acute/chronic renal failure=1.38±0.40×10⁻³ mm² s⁻¹) and between Groups A and C (chronic pyelonephritis=1.53±0.21×10⁻³ mm² s⁻¹) (P<.05). An important difference was also observed among Group D (hydronephrosis=4.82±0.35×10⁻³ mm² s⁻¹) and Groups A, B, and C (P<.05), whereas no differences were found between Groups B and C (P>.05). A considerable correlation between glomerular filtration rate and ADC was found (P=.04). In conclusion, significant differences were detected among different patient groups, and this suggests that ADC measurements can be useful in differentiating normal renal parenchyma from most commonly encountered nonmalignant renal lesions. PMID:21092872
Yang, Yunjun; Gao, Lingyun; Fu, Jun; Zhang, Jun; Li, Yuxin; Yin, Bo; Chen, Weijian; Geng, Daoying
2013-11-01
Supratentorial cerebral infarction can cause functional inhibition of remote regions such as the cerebellum, which may be relevant to diaschisis. This phenomenon is often analyzed using positron emission tomography and single photon emission CT. However, these methods are expensive and radioactive. Thus, the present study quantified the changes of infarction core and remote regions after unilateral middle cerebral artery occlusion using apparent diffusion coefficient values. Diffusion-weighted imaging showed that the area of infarction core gradually increased to involve the cerebral cortex with increasing infarction time. Diffusion weighted imaging signals were initially increased and then stabilized by 24 hours. With increasing infarction time, the apparent diffusion coefficient value in the infarction core and remote bilateral cerebellum both gradually decreased, and then slightly increased 3-24 hours after infarction. Apparent diffusion coefficient values at remote regions (cerebellum) varied along with the change of supratentorial infarction core, suggesting that the phenomenon of diaschisis existed at the remote regions. Thus, apparent diffusion coefficient values and diffusion weighted imaging can be used to detect early diaschisis. PMID:25206615
Surface diffusion coefficient of Au atoms on single layer graphene grown on Cu
Ruffino, F. Cacciato, G.; Grimaldi, M. G.
2014-02-28
A 5 nm thick Au film was deposited on single layer graphene sheets grown on Cu. By thermal processes, the dewetting phenomenon of the Au film on the graphene was induced so to form Au nanoparticles. The mean radius, surface-to-surface distance, and surface density evolution of the nanoparticles on the graphene sheets as a function of the annealing temperature were quantified by scanning electron microscopy analyses. These quantitative data were analyzed within the classical mean-field nucleation theory so to obtain the temperature-dependent Au atoms surface diffusion coefficient on graphene: D{sub S}(T)=[(8.2±0.6)×10{sup −8}]exp[−(0.31±0.02(eV)/(at) )/kT] cm{sup 2}/s.
Gamma convolution models for self-diffusion coefficient distributions in PGSE NMR
NASA Astrophysics Data System (ADS)
Röding, Magnus; Williamson, Nathan H.; Nydén, Magnus
2015-12-01
We introduce a closed-form signal attenuation model for pulsed-field gradient spin echo (PGSE) NMR based on self-diffusion coefficient distributions that are convolutions of n gamma distributions, n ⩾ 1 . Gamma convolutions provide a general class of uni-modal distributions that includes the gamma distribution as a special case for n = 1 and the lognormal distribution among others as limit cases when n approaches infinity. We demonstrate the usefulness of the gamma convolution model by simulations and experimental data from samples of poly(vinyl alcohol) and polystyrene, showing that this model provides goodness of fit superior to both the gamma and lognormal distributions and comparable to the common inverse Laplace transform.
Varga, Agnes; Gyetvai, Gergely; Nagy, Lívia; Nagy, Géza
2009-08-01
The diffusion coefficient of glucose in different media is an important parameter in life sciences, as well as in biotechnology and microbiology. In this work a simple, fast method is proposed that is based on the electrochemical time of flight principle. In most of the earlier time of flight experiments performed, a constant flight distance was applied. In the present work a scanning electrochemical microscope (SECM) was applied as a measuring tool. With use of the SECM, the flying distance could be changed with high precision, making measurements with several flight distances more accurate and reliable values could be obtained for solutions as well as for gels. The conventional voltammetric methods are not applicable for glucose detection. In our work electrocatalytic copper oxide coated copper microelectrodes and micro-sized amperometric enzyme sensors were used as detectors, while microdroplet-ejecting pneumatically driven micropipettes were used as a source. PMID:19517100
Energetic particle diffusion coefficients upstream of quasi-parallel interplanetary shocks
NASA Technical Reports Server (NTRS)
Tan, L. C.; Mason, G. M.; Gloeckler, G.; Ipavich, F. M.
1989-01-01
The properties of about 30 to 130-keV/e protons and alpha particles upstream of six quasi-parallel interplanetary shocks that passed by the ISEE 3 spacecraft during 1978-1979 were analyzed, and the values for the upstream energegic particle diffusion coefficient, kappa, in these six events were deduced for a number of energies and upstream positions. These observations were compared with predictions of Lee's (1983) theory of shock acceleration. It was found that the observations verified the prediction of the A/Q dependence (where A and Q are the particle atomic mass and ionization state, respectively) of kappa for alpha and proton particles upstream of the quasi-parallel shocks.
Metin, Melike R.; Aydın, Hasan; Çetin, Hüseyin; Özmen, Evrim; Kayaçetin, Serra
2016-01-01
Objectives: To establish retrospectively the relation between the histopathologic grade of colorectal liver metastasis and apparent diffusion coefficient (ADC) values of hepatic metastases of colorectal adenocarcinomas. Methods: The diagnoses of liver metastases were confirmed with biopsy, surgery, and follow-up imaging findings. Twenty-six patients with 94 liver metastasis were included in the study. Of 94 masses, 59 were poorly-differentiated adenocarcinoma, 18 were moderately-differentiated adenocarcinoma, and 17 were well-differentiated regarding the diameters, ADC values, and ratio index (RI) values. Kolmogorov-smirnov normality test, Kruskal-wallis analysis of variance, Mann-Whitney U test with Bonferroni correction, Spearman correlation analysis, and receiver operating characteristics curve methods were applied to evaluate the statistical relations. Results: There was a statistically significant difference in terms of ADC values and RI between poorly-differentiated adenocarcinoma and moderately-differentiated adenocarcinoma plus well-differentiated adenocarcinomas. Poorly-differentiated adenocarcinomas have the lowest ADC values and highest RI values among other groups. Conclusion: Use of ADC values alone can be executed for the diagnosis of focal hepatic masses and also can aid in the differentiation of benign and malignant hepatic lesions. PMID:27052280
Remote sensing of the diffuse attenuation coefficient of ocean water. [coastal zone color scanner
NASA Technical Reports Server (NTRS)
Austin, R. W.
1981-01-01
A technique was devised which uses remotely sensed spectral radiances from the sea to assess the optical diffuse attenuation coefficient, K (lambda) of near-surface ocean water. With spectral image data from a sensor such as the coastal zone color scanner (CZCS) carried on NIMBUS-7, it is possible to rapidly compute the K (lambda) fields for large ocean areas and obtain K "images" which show synoptic, spatial distribution of this attenuation coefficient. The technique utilizes a relationship that has been determined between the value of K and the ratio of the upwelling radiances leaving the sea surface at two wavelengths. The relationship was developed to provide an algorithm for inferring K from the radiance images obtained by the CZCS, thus the wavelengths were selected from those used by this sensor, viz., 443, 520, 550 and 670 nm. The majority of the radiance arriving at the spacecraft is the result of scattering in the atmospheric and is unrelated to the radiance signal generated by the water. A necessary step in the processing of the data received by the sensor is, therefore, the effective removal of these atmospheric path radiance signals before the K algorithm is applied. Examples of the efficacy of these removal techniques are given together with examples of the spatial distributions of K in several ocean areas.
NASA Astrophysics Data System (ADS)
Fuente, Raquel; Apiñaniz, Estibaliz; Mendioroz, Arantza; Salazar, Agustín
2011-08-01
Modulated photothermal radiometry (PTR) has been widely used to measure the thermal diffusivity of bulk materials. The method is based on illuminating the sample with a plane light beam and measuring the infrared emission with an infrared detector. The amplitude and phase of the PTR voltage is recorded as a function of the modulation frequency and then fitted to the theoretical model. In this work, we test the ability of modulated PTR to retrieve simultaneously the thermal diffusivity and the optical absorption coefficient of homogeneous slabs. In order to eliminate the instrumental factor, self-normalization is used, i.e., the ratio of the PTR signal recorded at the rear and front surfaces. The influence of the multiple reflections of the light beam, the heat losses, and the transparency to infrared wavelengths are analyzed. Measurements performed on a wide variety of homogeneous materials, covering the whole range from transparent to opaque, confirm the validity of the method. In Part II of this work, the method is extended to multilayered materials.
Relationship Between Choline and Apparent Diffusion Coefficient in Patients With Gliomas
Khayal, Inas S.; Crawford, Forrest W.; Saraswathy, Suja; Lamborn, Kathleen R.; Chang, Susan M.; Cha, Soonmee; McKnight, Tracy R.; Nelson, Sarah J.
2011-01-01
Purpose To examine the relationship between apparent diffusion coefficients (ADC) from diffusion weighted imaging (DWI) and choline levels from proton magnetic resonance spectroscopic imaging (MRSI) in newly diagnosed Grade II and IV gliomas within distinct anatomic regions. Materials and Methods A total of 37 patients with Grade II and 28 patients with Grade IV glioma were scanned on a 1.5T system with 3D MRSI and DWI. Region level analysis included Spearman rank correlation between median normalized ADC and choline for each patient per grade within each distinct abnormal anatomical region. Voxel level analysis calculated a Spearman rank correlation per region, per patient. Results Grade II lesions showed no evidence of a correlation between normalized ADC and choline using either the region or voxel level analysis. Region level analysis of Grade IV lesions did not appear to correlate in the contrast enhancement or necrotic core, but did suggest a significant negative correlation in the more heterogeneous nonenhancing and combined regions. Conclusion There appears to be differences in the relationship between ADC and choline levels in Grade II and Grade IV gliomas. Correlation within these regions in Grade IV lesions was strongest when all regions were included, suggesting heterogeneity may be driving the relationship. PMID:18383265
Fat Confounds the Observed Apparent Diffusion Coefficient in Patients with Hepatic Steatosis
Hansmann, Jan; Hernando, Diego; Reeder, Scott B.
2013-01-01
Purpose Triglyceride signal contained in peaks near the water peak remain unsuppressed by conventional fat suppression techniques used in diffusion-weighted imaging (DWI). In this work we investigated the dependence of the apparent diffusion coefficient (ADC) on liver fat content and whether it is confounded by fat signal. Methods 43 patients underwent liver DWI (b=0,500s/mm2) and single-voxel MR-spectroscopy (MRS). Proton density fat-fraction (PDFF;range 0.23–34.5%) was measured from MRS. A theoretical model was developed to account for the effects of fat on observed ADC, and used to correct the ADC. Linear correlation analysis was performed to assess the relationship between PDFF and ADC before and after correction. Results Linear correlation analysis showed an inverse dependence between observed ADC and PDFF before correction (r2=0.132;p=0.017), and no dependence after correction (r2=0.033;p=0.24). Conclusion The observed decrease in ADC in patients with fatty liver is, at least in part, artifactual due to residual fat signal near the water peak. PMID:23161434
Small effect of water on upper-mantle rheology based on silicon self-diffusion coefficients.
Fei, Hongzhan; Wiedenbeck, Michael; Yamazaki, Daisuke; Katsura, Tomoo
2013-06-13
Water has been thought to affect the dynamical processes in the Earth's interior to a great extent. In particular, experimental deformation results suggest that even only a few tens of parts per million of water by weight enhances the creep rates in olivine by orders of magnitude. However, those deformation studies have limitations, such as considering only a limited range of water concentrations and very high stresses, which might affect the results. Rock deformation can also be understood as an effect of silicon self-diffusion, because the creep rates of minerals at temperatures as high as those in the Earth's interior are limited by self-diffusion of the slowest species. Here we experimentally determine the silicon self-diffusion coefficient DSi in forsterite at 8 GPa and 1,600 K to 1,800 K as a function of water content CH2O from less than 1 to about 800 parts per million of water by weight, yielding the relationship, DSi ≈ (CH2O)(1/3). This exponent is strikingly lower than that obtained by deformation experiments (1.2; ref. 7). The high nominal creep rates in the deformation studies under wet conditions may be caused by excess grain boundary water. We conclude that the effect of water on upper-mantle rheology is very small. Hence, the smooth motion of the Earth's tectonic plates cannot be caused by mineral hydration in the asthenosphere. Also, water cannot cause the viscosity minimum zone in the upper mantle. And finally, the dominant mechanism responsible for hotspot immobility cannot be water content differences between their source and surrounding regions. PMID:23765497
Arnspang, Eva C; Koffman, Jennifer S; Marlar, Saw; Wiseman, Paul W; Nejsum, Lene N
2014-01-01
Lateral diffusion and compartmentalization of plasma membrane proteins are tightly regulated in cells and thus, studying these processes will reveal new insights to plasma membrane protein function and regulation. Recently, k-Space Image Correlation Spectroscopy (kICS)(1) was developed to enable routine measurements of diffusion coefficients directly from images of fluorescently tagged plasma membrane proteins, that avoided systematic biases introduced by probe photophysics. Although the theoretical basis for the analysis is complex, the method can be implemented by nonexperts using a freely available code to measure diffusion coefficients of proteins. kICS calculates a time correlation function from a fluorescence microscopy image stack after Fourier transformation of each image to reciprocal (k-) space. Subsequently, circular averaging, natural logarithm transform and linear fits to the correlation function yields the diffusion coefficient. This paper provides a step-by-step guide to the image analysis and measurement of diffusion coefficients via kICS. First, a high frame rate image sequence of a fluorescently labeled plasma membrane protein is acquired using a fluorescence microscope. Then, a region of interest (ROI) avoiding intracellular organelles, moving vesicles or protruding membrane regions is selected. The ROI stack is imported into a freely available code and several defined parameters (see Method section) are set for kICS analysis. The program then generates a "slope of slopes" plot from the k-space time correlation functions, and the diffusion coefficient is calculated from the slope of the plot. Below is a step-by-step kICS procedure to measure the diffusion coefficient of a membrane protein using the renal water channel aquaporin-3 tagged with EGFP as a canonical example. PMID:24893770
Kimura, Y; Kida, Y; Matsushita, Y; Yasaka, Y; Ueno, M; Takahashi, K
2015-06-25
Translational diffusion coefficients of diphenylcyclopropenone (DPCP), diphenylacetylene (DPA), and carbon monoxide (CO) in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMIm][NTf2]) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIm][NTf2]) were determined by the transient grating (TG) spectroscopy under pressure from 0.1 to 200 MPa at 298 K and from 298 to 373 K under 0.1 MPa. Diffusion coefficients of these molecules at high temperatures in tributylmethylphosphonium bis(trifluoromethanesulfonyl)imide ([P4441][NTf2]), and tetraoctylphosphonium bis(trifluoromethanesulfonyl)imide ([P8888][NTf2]), and also in the mixtures of [BMIm][NTf2], N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide ([Pp13][NTf2]), and trihexyltetradecylphosphonium bis(trifluoromethanesulfonyl)imide ([P66614][NTf2]) with ethanol or chloroform have been determined. Diffusion coefficients except in ILs of phosphonium cations were well scaled by the power law of T/η, i.e., (T/η)(P), where T and η are the absolute temperature and the viscosity, irrespective of the solvent species, pressure and temperature, and the compositions of mixtures. The values of the exponent P were smaller for the smaller size of the molecules. On the other hand, the diffusion coefficients in ILs of phosphonium cations with longer alkyl chains were larger than the values expected from the correlation obtained by other ILs and conventional liquids. The deviation becomes larger with increasing the number of carbon atoms of alkyl-chain of cation, and with decreasing the molecular size of diffusing molecules. The molecular size dependence of the diffusion coefficient was correlated by the ratio of the volume of the solute to that of the solvent as demonstrated by the preceding work (Kaintz et al., J. Phys. Chem. B 2013 , 117 , 11697 ). Diffusion coefficients have been well correlated with the power laws of both T/η and the relative volume of the solute to the solvent
NASA Astrophysics Data System (ADS)
Xiong, Jianyin; Zhang, Yinping; Wang, Xinke; Chang, Dongwu
Through the observation of the pore structure and mercury intruding porosimetry (MIP) experiments of some typical porous building materials, we found that the diffusion coefficient of the material can be expressed by that of a representative elementary volume (REV) in which the pore structure can be simplified as a connection in series of macro and meso pores. Based upon that, a macro-meso two-scale model for predicting the diffusion coefficient of porous building materials is proposed. In contrast to the traditional porous mass transfer model for determining the diffusion coefficient described in the literature [Blondeau, P., Tiffonnet, A.L., Damian, A., Amiri, O., Molina, J.L., 2003. Assessment of contaminant diffusivities in building materials from porosimetry tests. Indoor Air 13, 302-310; Seo, J., Kato, S., Ataka, Y., Zhu, Q., 2005. Evaluation of effective diffusion coefficient in various building materials and absorbents by mercury intrusion porosimetry. In Proceedings of the Indoor Air, Beijing, China, pp. 1854-1859], the proposed model relates the volatile organic compound (VOC) diffusion coefficient of building material not only to the porosity of the building material, but also to the pore size distribution and pore connection modes. To verify the model, a series of experiments of VOC emissions of three types of medium-density board were conducted. The comparison of the model and experimental results shows that the proposed model agrees much better with the experimental results than the traditional models in the literature. More validation for other building materials is needed. The proposed model is useful for predicting the VOC diffusion coefficient of porous building materials and for developing low VOC emission building materials.
Yasuda, Isamu; Hikita, Tomoji . Fundamental Technology Research Lab.)
1994-05-01
Chemical relaxation experiments were conducted on sintered samples of calcium-doped lanthanum chromites by abruptly changing the oxygen partial pressure in the atmosphere and following the time change of conductivity. The re-equilibration kinetics was analyzed by fitting the relaxation data to the solutions of Fick's second law for appropriate boundary conditions. The diffusion equation ignoring the effect of surface reaction failed to describe the transient behavior especially for the initial stage, while that taking the surface effect into account gave a satisfactory interpretation of the overall relaxation process and allowed a precise determination of the two kinetic parameters: oxygen chemical diffusion coefficient and surface reaction rate constant. The chemical diffusion coefficients increased with a decrease of the oxygen partial pressure due to the corresponding change in the concentration of the moving species. The activation energy was similar to that of oxygen vacancy diffusion coefficients in other monocrystalline perovskites, suggesting that the measured diffusion coefficients were attributable to lattice diffusion. The surface reaction rate constant increased with a decrease of the oxygen partial pressure similarly to the reported oxygen nonstoichiometry, which implies that the presence of oxygen vacancies plays an important role in the surface reaction kinetics.
Olson, A; Pugh, E N
1993-01-01
Experiments have demonstrated that single photoisomerizations in amphibian and primate rods can cause the suppression of 3-5% of the dark circulating current at the response peak (Baylor, D. A., T. D. Lamb, and K. W. Yau. 1979. J. Physiol. (Lond.). 288:613-634; Baylor, D. A., B. J. Nunn, and J. L. Schnapf. 1984. J. Physiol. (Lond.). 357:575-607). These results indicate that the change in [cGMP] effected by a single isomerization must spread longitudinally over at least the corresponding fractional length of the outer segment. The effective longitudinal diffusion coefficient, Dx, of cGMP is thus an important determinant of rod sensitivity. We report here measurements of the effective longitudinal diffusion coefficients, Dx, of two fluorescently labeled molecules: 5/6-carboxyfluorescein and 8-(fluoresceinyl)thioguanosine 3',5'-cyclic monophosphate, introduced into detached outer segments via whole-cell patch electrodes. For these compounds, the average time for equilibration of the entire outer segment with the patch pipette was approximately 6 min. Fluorescence images of rods were analyzed with a one-dimensional diffusion model that included limitations on transfer between the electrode and outer segment and the effects of intracellular binding of the dyes. The analyses yielded estimates of Dx of 1.9 and 1.0 microns 2.s-1 for the two dyes. It is shown that these results place an upper limit on Dx for cGMP of 11 microns2.s-1. The actual value of Dx for cGMP in the rod will depend on the degree of intracellular binding of cGMP. Estimates of the effective buffering power for cGMP in the rod at rest range from two to six (Lamb and Pugh, 1992; Cote and Brunnock, 1993). When combined with these estimates, our results predict that for cGMP itself, Dx falls within the range of 1.4-5.5 microns 2.s-1. Images FIGURE 5 FIGURE 6 PMID:8241412
First-principles binary diffusion coefficients for H, H₂, and four normal alkanes + N₂.
Jasper, Ahren W; Kamarchik, Eugene; Miller, James A; Klippenstein, Stephen J
2014-09-28
Collision integrals related to binary (dilute gas) diffusion are calculated classically for six species colliding with N2. The most detailed calculations make no assumptions regarding the complexity of the potential energy surface, and the resulting classical collision integrals are in excellent agreement with previous semiclassical results for H + N2 and H2 + N2 and with recent experimental results for CnH(2n+2) + N2, n = 2-4. The detailed classical results are used to test the accuracy of three simplifying assumptions typically made when calculating collision integrals: (1) approximating the intermolecular potential as isotropic, (2) neglecting the internal structure of the colliders (i.e., neglecting inelasticity), and (3) employing unphysical R(-12) repulsive interactions. The effect of anisotropy is found to be negligible for H + N2 and H2 + N2 (in agreement with previous quantum mechanical and semiclassical results for systems involving atomic and diatomic species) but is more significant for larger species at low temperatures. For example, the neglect of anisotropy decreases the diffusion coefficient for butane + N2 by 15% at 300 K. The neglect of inelasticity, in contrast, introduces only very small errors. Approximating the repulsive wall as an unphysical R(-12) interaction is a significant source of error at all temperatures for the weakly interacting systems H + N2 and H2 + N2, with errors as large as 40%. For the normal alkanes in N2, which feature stronger interactions, the 12/6 Lennard-Jones approximation is found to be accurate, particularly at temperatures above ∼700 K where it predicts the full-dimensional result to within 5% (although with somewhat different temperature dependence). Overall, the typical practical approach of assuming isotropic 12/6 Lennard-Jones interactions is confirmed to be suitable for combustion applications except for weakly interacting systems, such as H + N2. For these systems, anisotropy and inelasticity can safely be
First-principles binary diffusion coefficients for H, H2 and four normal alkanes + N2
Jasper, Ahren W.; Kamarchik, Eugene; Miller, James A.; Klippenstein, Stephen J.
2014-09-30
Collision integrals related to binary (dilute gas) diffusion are calculated classically for six species colliding with N2. The most detailed calculations make no assumptions regarding the complexity of the potential energy surface, and the resulting classical collision integrals are in excellent agreement with previous semiclassical results for H + N2 and H2 + N2 and with recent experimental results for C n H2n+2 + N2, n = 2–4. The detailed classical results are used to test the accuracy of three simplifying assumptions typically made when calculating collision integrals: (1) approximating the intermolecular potential as isotropic, (2) neglecting the internal structuremore » of the colliders (i.e., neglecting inelasticity), and (3) employing unphysical R–12 repulsive interactions. The effect of anisotropy is found to be negligible for H + N2 and H2 + N2 (in agreement with previous quantum mechanical and semiclassical results for systems involving atomic and diatomic species) but is more significant for larger species at low temperatures. For example, the neglect of anisotropy decreases the diffusion coefficient for butane + N2 by 15% at 300 K. The neglect of inelasticity, in contrast, introduces only very small errors. Approximating the repulsive wall as an unphysical R–12 interaction is a significant source of error at all temperatures for the weakly interacting systems H + N2 and H2 + N2, with errors as large as 40%. For the normal alkanes in N2, which feature stronger interactions, the 12/6 Lennard–Jones approximation is found to be accurate, particularly at temperatures above –700 K where it predicts the full-dimensional result to within 5% (although with somewhat different temperature dependence). Overall, the typical practical approach of assuming isotropic 12/6 Lennard–Jones interactions is confirmed to be suitable for combustion applications except for weakly interacting systems, such as H + N2. For these systems, anisotropy and inelasticity
First-principles binary diffusion coefficients for H, H2, and four normal alkanes + N2
NASA Astrophysics Data System (ADS)
Jasper, Ahren W.; Kamarchik, Eugene; Miller, James A.; Klippenstein, Stephen J.
2014-09-01
Collision integrals related to binary (dilute gas) diffusion are calculated classically for six species colliding with N2. The most detailed calculations make no assumptions regarding the complexity of the potential energy surface, and the resulting classical collision integrals are in excellent agreement with previous semiclassical results for H + N2 and H2 + N2 and with recent experimental results for CnH2n+2 + N2, n = 2-4. The detailed classical results are used to test the accuracy of three simplifying assumptions typically made when calculating collision integrals: (1) approximating the intermolecular potential as isotropic, (2) neglecting the internal structure of the colliders (i.e., neglecting inelasticity), and (3) employing unphysical R-12 repulsive interactions. The effect of anisotropy is found to be negligible for H + N2 and H2 + N2 (in agreement with previous quantum mechanical and semiclassical results for systems involving atomic and diatomic species) but is more significant for larger species at low temperatures. For example, the neglect of anisotropy decreases the diffusion coefficient for butane + N2 by 15% at 300 K. The neglect of inelasticity, in contrast, introduces only very small errors. Approximating the repulsive wall as an unphysical R-12 interaction is a significant source of error at all temperatures for the weakly interacting systems H + N2 and H2 + N2, with errors as large as 40%. For the normal alkanes in N2, which feature stronger interactions, the 12/6 Lennard-Jones approximation is found to be accurate, particularly at temperatures above ˜700 K where it predicts the full-dimensional result to within 5% (although with somewhat different temperature dependence). Overall, the typical practical approach of assuming isotropic 12/6 Lennard-Jones interactions is confirmed to be suitable for combustion applications except for weakly interacting systems, such as H + N2. For these systems, anisotropy and inelasticity can safely be
Hasnain, Sabeeha; McClendon, Christopher L; Hsu, Monica T; Jacobson, Matthew P; Bandyopadhyay, Pradipta
2014-01-01
A new coarse-grained model of the E. coli cytoplasm is developed by describing the proteins of the cytoplasm as flexible units consisting of one or more spheres that follow Brownian dynamics (BD), with hydrodynamic interactions (HI) accounted for by a mean-field approach. Extensive BD simulations were performed to calculate the diffusion coefficients of three different proteins in the cellular environment. The results are in close agreement with experimental or previously simulated values, where available. Control simulations without HI showed that use of HI is essential to obtain accurate diffusion coefficients. Anomalous diffusion inside the crowded cellular medium was investigated with Fractional Brownian motion analysis, and found to be present in this model. By running a series of control simulations in which various forces were removed systematically, it was found that repulsive interactions (volume exclusion) are the main cause for anomalous diffusion, with a secondary contribution from HI. PMID:25180859
Jafar, Maysam M; Parsai, Arman; Miquel, Marc E
2016-01-01
There is considerable disparity in the published apparent diffusion coefficient (ADC) values across different anatomies. Institutions are increasingly assessing repeatability and reproducibility of the derived ADC to determine its variation, which could potentially be used as an indicator in determining tumour aggressiveness or assessing tumour response. In this manuscript, a review of selected articles published to date in healthy extra-cranial body diffusion-weighted magnetic resonance imaging is presented, detailing reported ADC values and discussing their variation across different studies. In total 115 studies were selected including 28 for liver parenchyma, 15 for kidney (renal parenchyma), 14 for spleen, 13 for pancreatic body, 6 for gallbladder, 13 for prostate, 13 for uterus (endometrium, myometrium, cervix) and 13 for fibroglandular breast tissue. Median ADC values in selected studies were found to be 1.28 × 10-3 mm2/s in liver, 1.94 × 10-3 mm2/s in kidney, 1.60 × 10-3 mm2/s in pancreatic body, 0.85 × 10-3 mm2/s in spleen, 2.73 × 10-3 mm2/s in gallbladder, 1.64 × 10-3 mm2/s and 1.31 × 10-3 mm2/s in prostate peripheral zone and central gland respectively (combined median value of 1.54×10-3 mm2/s), 1.44 × 10-3 mm2/s in endometrium, 1.53 × 10-3 mm2/s in myometrium, 1.71 × 10-3 mm2/s in cervix and 1.92 × 10-3 mm2/s in breast. In addition, six phantom studies and thirteen in vivo studies were summarized to compare repeatability and reproducibility of the measured ADC. All selected phantom studies demonstrated lower intra-scanner and inter-scanner variation compared to in vivo studies. Based on the findings of this manuscript, it is recommended that protocols need to be optimised for the body part studied and that system-induced variability must be established using a standardized phantom in any clinical study. Reproducibility of the measured ADC must also be assessed in a volunteer population, as variations are far more significant in vivo compared
Zheng, De-Xian; Meng, Shu-Chun; Liu, Qing-Jun; Li, Chuan-Ting; Shang, Xi-Dan; Zhu, Yu-Seng; Bai, Tian-Jun; Xu, Shi-Ming
2016-01-01
AIM: To determine if efficacy of chemotherapy on liver metastasis of gastrointestinal tract cancer can be predicted by apparent diffusion coefficient (ADC) values of diffusion-weighted imaging (DWI). METHODS: In total, 86 patients with liver metastasis of gastrointestinal tract cancer (156 metastatic lesions) diagnosed in our hospital were included in this study. The maximum diameters of these tumors were compared with each other before treatment, 2 wk after treatment, and 12 wk after treatment. Selected patients were classified as the effective group and the ineffective group, depending on the maximum diameter of the tumor after 12 wk of treatment; and the ADC values at different treatment times between the two groups were compared. Spearman rank correlation was used to analyze the relationship between ADC value and tumor diameter. Receiver operating characteristic curve (ROC curve) was used to analyze the ADC values before treatment to predict the patient’s sensitivity and specificity degree of efficacy to the chemotherapy. RESULTS: There was no difference in age between the two groups and in maximum tumor diameter before treatment and 2 wk after treatment. However, after 12 wk of treatment, maximum tumor diameter in the effective group was significantly lower than that in the ineffective group (P < 0.05). Before treatment, ADC values in the ineffective group were significantly higher than those in the effective group (P < 0.05). There was no difference in ADC values between the effective and ineffective groups after 2 and 12 wk of treatment. However, ADC values were significantly higher after 2 and 12 wk of treatment compared to before treatment in the effective group (P < 0.05). Spearman rank correlation analysis showed that ADC value before treatment and the reduced percentage of the maximum tumor diameter after 12 wk of treatment were negatively correlated, while the increase in the percentage of the ADC value 12 wk after treatment and the decrease in the
Park, Sung Yoon; Kim, Chan Kyo; Park, Byung Kwan; Park, Won; Park, Hee Chul; Han, Deok Hyun; Kim, Bohyun
2012-06-01
Purpose: To investigate the feasibility of diffusion-weighted MRI (DWI) as an early and reproducible change indicator in patients receiving radiotherapy for prostate cancer (PC). Methods and Materials: Eight consecutive patients with biopsy-proven PC underwent DWI at 3T. All patients who received external-beam radiotherapy had four serial MR scans, as follows: before therapy (PreTx); after 1 week of therapy (PostT1); after 3 weeks of therapy (PostT2); and 1 month after the completion of therapy (PostT3). At each time, the apparent diffusion coefficient (ADC) was measured in tumors and normal tissues. For reproducibility of the ADC measurement, five patients also had two separate pretreatment DWI scans at an interval of <2 weeks. Serum prostate-specific antigen (PSA) levels were evaluated at the same time as MR scans. Results: Thirteen tumors (peripheral zone = 10; transition zone = 3) were found. The mean ADC values for the tumors from PreTx to PostT3 were 0.86, 1.03, 1.15, and 1.26 Multiplication-Sign 10{sup -3} mm{sup 2}/s in sequence, respectively. Compared with PreTx, PostT1 (p = 0.005), PostT2 (p = 0.003), and PostT3 (p < 0.001) showed a significant increase in ADC values. The mean ADC values of the benign tissues from PreTx to PostT3 were 1.60, 1.58, 1.47, and 1.46 Multiplication-Sign 10{sup -3} mm{sup 2}/s in sequence, respectively. Reproducibility of ADC measurements was confirmed with a mean difference in ADC of -0.04 in peripheral zone and -0.017 in transition zone between two separate pretreatment MR scans. The mean PSA levels from PreTx to PostT3 were 9.05, 9.18, 9.25, and 4.11 ng/mL in sequence, respectively. Conclusions: DWI, as a reproducible biomarker, has the potential to evaluate the early therapeutic changes of PC to radiotherapy.
Xiao, P; Wong, W; Cottenden, A M; Imhof, R E
2012-08-01
Skin over-hydration is a common problem that affects many people who wear incontinence pads or diapers. The aim of this study is to develop a new method for stratum corneum (SC) over-hydration and SC water diffusion coefficient measurements using opto-thermal transient emission radiometry (OTTER) and evaporimetry. With OTTER, we can measure the SC surface hydration and hydration gradient. With evaporimetry, we can measure the time-dependent evaporative drying curves of water vapour flux density (WVFD). The combination of hydration results and WVFD results can yield information on the SC water diffusion coefficient and how it depends on the SC surface hydration level. The results show that SC water diffusion coefficient is non-linearly proportional to the SC surface hydration level. The results also show strong correlations between evaporative drying flux measured using the Evaporimeter and surface hydration estimated from OTTER measurements. PMID:22515301
NASA Astrophysics Data System (ADS)
Ansari, Rafat R.; Suh, Kwang I.; Sebag, J.
2006-02-01
PURPOSE: Pharmacologic vitreolysis is a new approach to improve vitreo-retinal surgery. Ultimately, the development of drugs to liquefy and detach vitreous from retina should prevent disease by mitigating the contribution of vitreous to retinopathy and eliminate the need for surgery. However, the mechanism of action of pharmacologic vitreolysis remains unclear. The technique of Dynamic light scattering (DLS) was used to evaluate the effects of microplasmin by following the diffusion coefficients of spherical polystyrene nano-particles injected with microplasmin into the vitreous. METHODS: Diffusion coefficients in dissected (n=9) porcine eyes were measured in vitro. DLS was performed on all specimens at 37°C as often as every 10 minutes for up to 6 hours following injections of human recombinant microplasmin at doses ranging from 0.125 mg to 0.8 mg, with 20 nm diameter tracer nanospheres. RESULTS: DLS findings in untreated porcine vitreous were similar to the previously described findings in bovine and human vitreous, demonstrating a fast (early) component, resulting from the flexible hyaluronan molecules, and a slow (late) component, resulting form the stiff collagen molecules. Microplasmin increased porcine vitreous diffusion coefficients. A new approach was developed to use DLS measurements of vitreous diffusion coefficients to evaluate the effects of microplasmin in intact eyes. CONCLUSIONS: Pharmacologic vitreolysis with human recombinant microplasmin increases vitreous diffusion coefficients in vitro. The results of these studies indicate that this new approach using DLS to measure vitreous diffusion coefficients can be used to study the effects of pharmacologic vitreolysis using microplasmin and other agents in intact eyes and ultimately in vivo.
Danel, J-F; Kazandjian, L; Zérah, G
2012-06-01
Computations of the self-diffusion coefficient and viscosity in warm dense matter are presented with an emphasis on obtaining numerical convergence and a careful evaluation of the standard deviation. The transport coefficients are computed with the Green-Kubo relation and orbital-free molecular dynamics at the Thomas-Fermi-Dirac level. The numerical parameters are varied until the Green-Kubo integral is equal to a constant in the t→+∞ limit; the transport coefficients are deduced from this constant and not by extrapolation of the Green-Kubo integral. The latter method, which gives rise to an unknown error, is tested for the computation of viscosity; it appears that it should be used with caution. In the large domain of coupling constant considered, both the self-diffusion coefficient and viscosity turn out to be well approximated by simple analytical laws using a single effective atomic number calculated in the average-atom model. PMID:23005237
Goemans, M.G.E.; Gloyna, E.F.
1996-10-01
The potential of sub- and supercritical water as extraction solvents has been demonstrated for the (reactive) extraction of coals, used car tires, organic species from residual aqueous solutions, and class selective extraction of organic pollutants with different polarities from solids. In addition, the potential of extraction of coal with supercritical aqueous solutions has been studied. However, physical transport in water at elevated temperature and pressures- and their impact on heterogenous reactions and (reactive) extraction -are not adequately understood. This situation is largely due to the limited data that is available for diffusion in high temperature, high pressure water mixture. Only the molecular diffusion of Iodine ions and hydroquinone in near-critical subcritical water and the self diffusion of coefficient of compressed supercritical water have been reported. In this paper, we present molecular diffusion coefficients of benzophenone, acetone, naphthalene, and anthracene in water at infinite dilution. Pressures ranged from 250 to 500 bar at temperatures ranging from 50{degrees}C to 500{degrees}C resulting in water densities ranging from 1000 to 150 kg/m{sup 3}. Diffusion coefficients were determined by the Taylor-Aris dispersion technique. The effects of increased diffusion on the mass transfer coefficients for emulsions and packed beds were quantified. Molecular division coefficients were 10 to 20 times faster in supercritical water than in water at ambient conditions. Experimental results were correlated with hydrodynamic and kinetic theory. This study and results to be published elsewhere show that diffusion-limited conditions are much more likely to be encountered in supercritical water than is commonly acknowledged.
NASA Astrophysics Data System (ADS)
Bashkatov, Alexey N.; Genina, Elina A.; Kochubey, Vyacheslav I.; Tuchin, Valery V.; Chikina, Elena E.; Knyazev, Anatoly B.; Mareev, Oleg V.
2005-06-01
The optical properties of human maxillary sinus mucosa were measured in the wavelength range 400-2000 nm. The measurements were carried out using the commercially available spectrophotometer with the integrating sphere. The inverse adding-doubling method has been used to determine the absorption and reduced scattering coefficients from the measurements. Diffusion of Methylene Blue in the mucous tissue has been studied in vitro and value of the diffusion coefficient of Methylene Blue in the tissue has been estimated at 20°C as (4.77+/-2.9)x10-7 cm2/sec.
NASA Astrophysics Data System (ADS)
Ahadi, Amirhossein; Saghir, M. Ziad
2014-08-01
In this study, a Mach-Zehnder interferometer that is equipped with two lasers of different wavelengths was used to conduct high resolution measurements of concentration profiles of a ternary mixture inside a diffusion cell. Windowed Fourier transform along with an advanced unwrapping procedure was employed to extract the phase image from fringe images. Then the phase difference was obtained for a spatial resolution of 1920×1240. According to the measured refractive index profile, concentration contours of two components (out of three) were measured. Consequently, the concentration profile of the third components was calculated. Previously, the analytical solution for binary mixtures was used to estimate only the pure diffusion coefficients. In this study, for the first time, the refractive indices measured by two lasers along with the analytical solution for the ternary system, based on Fick's law, and an evolutionary algorithm (EA) known as a genetic algorithm (GA) were employed to measure the pure and cross diffusion coefficients of a transparent ternary mixture simultaneously. The optimization method to estimate diffusion coefficients was tested against various objective functions, and the best approach was that which was proposed herein. In order to validate the proposed measurement method, the experimental results of the Selectable Optical Diagnostics Instrument-Diffusion Coefficients in Mixtures (SODI-DCMIX1 project) on board the International Space Station (ISS) were analyzed using this technique and the obtained results were compared with previous techniques.
NASA Astrophysics Data System (ADS)
Unno, M.; Kawamoto, K.; Moldrup, P.; Komatsu, T.
2008-12-01
The soil-gas diffusion coefficient (Dp) and its dependency on air-filled porosity (ɛ) govern gas diffusion and reaction processes in soil. Accurate Dp(ɛ) prediction models for variably saturated peat soils are needed to evaluate vadose zone transport and fate of greenhouse gases such as methane in peaty wetlands. In this study, we measured Dp on undisturbed peat soil samples at different soil-water matric potentials, and developed new, linear and nonlinear expressions for describing and predicting Dp(ɛ). The new Dp(ɛ) models together with existing Dp(ɛ) models were tested against both measured data and independent data sets from literature. Twelve undisturbed 100cm3 peat soil cores were taken between the soil surface and down to 30-cm depth at Bibai wetland, Hokkaido, Japan. The soil cores were initially saturated with water, and drained at given matric potentials, pF=1.0, 1.5, 1.8, 2.0, 3.0, and 4.1 (where pF equals to log | Ψ | , Ψ: the soil-water matric potential in cm H2O), using the hanging water and pressure plate methods. At each matric potential, simultaneous measurements of volume shrinkage, soil-water retention, and Dp were conducted. Literature datasets of Dp(ɛ) for peat soil cores taken from different areas within the same wetland, specifically 12 samples from Iiyama and Hasegawa (2005) and 12 samples from Iiduka et al. (2008), were also used. A total of 191 measurements of Dp(ɛ) at pF ≤ 2.0 were applied for developing new Dp(ɛ) models for pF ≤ 2.0 where effects of shrinkage on Dp were assumed negligible. By modifying 3 existing Dp(ɛ) models, the Buckingham (1904) model, the Macroporosity-Dependent Model (MPD; Moldrup et al., 2000), and the Penman-Call model (Moldrup et al., 2005), we suggested 3 new Dp(ɛ) expressions for peat soil. In the Buckingham-based Dp(ɛ) model, a variable X(ɛ"w relationship (where X is the pore connectivity factor) derived from measurements was introduced in the Dp(ɛ) expression. In the Penman-Call-based Dp
2011-01-01
Background To study the rules that apparent diffusion coefficient (ADC) changes with time and space in cerebral infarction, and to provide the evidence in defining the infarction stages. Methods 117 work-ups in 98 patients with cerebral infarction (12 hyperacute, 43 acute, 29 subacute, 10 steady, and 23 chronic infarctions) were imaged with both conventional MRI and diffusion weighted imaging. The average ADC values, the relative ADC (rADC) values, and the ADC values or rADC values from the center to the periphery of the lesion were calculated. Results The average ADC values and the rADC values of hyperacute and acute infarction lesion depressed obviously. rADC values in hyperacute and acute stage was minimized, and increased progressively as time passed and appeared as "pseudonormal" values in approximately 8 to 14 days. Thereafter, rADC values became greater than normal in chronic stage. There was positive correlation between rADC values and time (P < 0.01). The ADC values and the rADC values in hyperacute and acute lesions had gradient signs that these lesions increased from the center to the periphery. The ADC values and the rADC values in subacute lesions had adverse gradient signs that these lesions decreased from the center to the periphery. Conclusion The ADC values of infarction lesions have evolution rules with time and space. The evolution rules with time and those in space can be helpful to decide the clinical stage, and to provide the evidence in guiding the treatment or judging the prognosis in infarction. PMID:21211049
Zhang, Lei; Rao, Sheng-Xiang; Xu, Xue-Feng; Wang, Dan-Song; Jin, Da-Yong; Zeng, Meng-Su
2016-01-01
PURPOSE We aimed to explore the potential value of the whole tumor apparent diffusion coefficient (ADC) for discriminating between benign and malignant intraductal papillary mucinous neoplasms (IPMNs) of the pancreas. METHODS Forty-two patients underwent 1.5 T magnetic resonance imaging that included diffusion-weighted imaging (DWI, b=0.500 s/mm2). The mean, minimum, and maximum ADC values were measured for the whole tumor. The differences between benign and malignant IPMNs were calculated for the mean ADC, ADC-min, and ADC-max values. Receiver operating characteristics (ROC) analysis was conducted to evaluate their potential diagnostic performance. RESULTS Fifteen of 25 benign IPMNs demonstrated low or iso-signal intensity on DWI with a b value of 500 s/mm2 compared with normal pancreatic parenchyma, whereas all malignant IPMNs demonstrated high signal intensity. The mean value of ADC was significantly higher in benign IPMNs compared with malignant IPMNs (3.39×10−3 mm2/s vs. 2.39×10−3 mm2/s, P < 0.001), with an area under the ROC curve (AUC) of 0.92 (95% confidence interval [CI], 0.79–0.98). The ADC-min value of malignant IPMNs was also significantly lower than that of benign IPMNs (1.24×10−3 mm2/s vs. 2.58×10−3 mm2/s, P < 0.001), with an AUC of 0.94 (95% CI, 0.82–0.99). No marked difference was found between benign and malignant IPMNs for the ADC-max value (3.89×10−3 mm2/s vs. 3.78×10−3 mm2/s, P = 0.299). CONCLUSION Lower mean and minimum ADC values of the whole tumor might be potential predictors of malignant IPMNs of the pancreas. PMID:27283593
Diffusion length damage coefficient and annealing studies in proton-irradiated InP
NASA Technical Reports Server (NTRS)
Hakimzadeh, Roshanak; Vargas-Aburto, Carlos; Bailey, Sheila G.; Williams, Wendell
1993-01-01
We report on the measurement of the diffusion length damage coefficient (K(sub L)) and the annealing characteristics of the minority carrier diffusion length (L(sub n)) in Czochralski-grown zinc-doped indium phosphide (InP), with a carrier concentration of 1 x 10(exp l8) cm(exp -3). In measuring K(sub L) irradiations were made with 0.5 MeV protons with fluences ranging from 1 x 10(exp 11) to 3 x 10(exp 13) cm(exp -2). Pre- and post-irradiation electron-beam induced current (EBIC) measurements allowed for the extraction of L(sub n) from which K(sub L) was determined. In studying the annealing characteristics of L(sub n) irradiations were made with 2 MeV protons with fluence of 5 x 10(exp 13) cm(exp -2). Post-irradiation studies of L(sub n) with time at room temperature, and with minority carrier photoinjection and forward-bias injection were carried out. The results showed that recovery under Air Mass Zero (AMO) photoinjection was complete. L(sub n) was also found to recover under forward-bias injection, where recovery was found to depend on the value of the injection current. However, no recovery of L(sub n) after proton irradiation was observed with time at room temperature, in contrast to the behavior of 1 MeV electron-irradiated InP solar cells reported previously.
Bozkurt Bostan, Tuğba; Koç, Gonca; Sezgin, Gülten; Altay, Canan; Fazıl Gelal, M.; Oyar, Orhan
2016-01-01
Background: Magnetic resonance imaging (MRI) has become a diagnostic and problem solving method for the breast examinations in addition to conventional breast examination methods. Diffusion-weighted imaging (DWI) adds valuable information to conventional MRI. Aims: Our aim was to show the impact of apparent diffusion coefficient (ADC) values acquired with DWI to differentiate benign and malignant breast lesions. Study Design: Diagnostic accuracy study. Methods: Forty-six women with 58 breast masses (35 malignant, 23 benign) were examined on a 1.5 T clinical MRI scanner. The morphologic characteristics of the lesions on conventional MRI sequences and contrast uptake pattern were assessed. ADC values of both lesions and normal breast parenchyma were measured. The ADC values obtained were statistically compared with the histopathologic results using Paired Samples t-Test. Results: Multiple lesions were detected in 12 (26%) of the patients, while only one lesion was detected in 34 (74%). Overall, 35 lesions out of 58 were histopathologically proven to be malignant. In the dynamic contrast-enhanced series, 5 of the malignant lesions were type 1, while 8 benign lesions revealed either type 2 or 3 time signal intensity curves (85% sensitivity, 56% spesifity). Mean ADC values were significantly different in malignant vs. benign lesions. (1.04±0.29×10−3 cm2/sec vs. 1.61±0.50×10−3 cm2/sec for the malignant and benign lesions, respectively, p=0.03). A cut-off value of 1.30×10−3 mm2/sec for ADC detected with receiver operating characteristic analysis yielded 89.1% sensitivity and 100% specificity for the differentiation between benign and malignant lesions. Conclusion: ADC values improve the diagnostic accuracy of solid breast lesions when evaluated with the conventional MRI sequences. Therefore, DWI should be incorporated to routine breast MRI protocol. PMID:27308073
Katirag, Ahmet; Beker-Acay, Mehtap; Unlu, Ebru; Demirbas, Hayri; Demirturk, Nese
2016-01-01
Objective: Our purpose was to reveal the efficiency of diffusion weighted imaging (DWI) in the diagnosis of encephalitis, and to determine the relation between the apparent diffusion coefficient (ADC) values, the onset of the clinical symptoms, and the lesion extent. Methods: Conventional magnetic resonance imaging (MRI) was performed in 17 patients with encephalitis diagnosed on the basis of laboratory, clinical and radiologic findings during 2009 and 2015. Based on the duration between the onset of the symptoms and the brain MRI findings, the patients were divided into three groups. ADC values of the encephalitis lesion, the lesions’ topographic analysis score, deep gray matter involvement, patients’ clinical situation and the duration of the arrival to the clinic was examined. Results: Mean ADC values were 0,988±0,335 x10-3 mm2/s in group I (0-2 days), 1,045±0,347 x10-3 mm2/s in Group-II (3-7 days), 1,451±0,225 x10-3 mm2/s in Group-III (8 days and over). The relation between the ADC values and the duration of the arrival, topographic analysis score, the relation between the patients’ clinical situation and the deep gray matter involvement were found to be statistically significant. The deep gray matter involvement was demonstrated more clearly by FLAIR images when compared with DWI. Conclusion: Conventional MRI sequences may be insufficient in showing the encephalitis lesion. DWI must be added to the imaging modalities immediately in the cases suspected of having encephalitis. PMID:27375722
Kopp, Joshua D
2007-06-01
To determine the future extent of the TCE contamination plume at PGDP, a groundwater and solute transport model has been developed by the Department of Energy (DOE). The model used to perform these calculations is MODFLOWT which is an enhanced groundwater transport model developed by the United States Geological Survey (USGS). MODFLOWT models groundwater movement as well as the transport of species that are subject to adsorption and decay by using a finite difference method (Duffield et al 2001). A significant limitation of MODFLOWT is that it requires large amounts of data. This data can be difficult and expensive to obtain. MODFLOWT also requires excessive computational time to perform one simulation. It is desirable to have a model that can predict the spatial extent of the contaminant plume without as much required data and that does not require excessive computational times. The purpose of this study is to develop and alternative model to MODFLOWT that can produce similar results for possible use in a companion management model. The alternative model used in this study is an artificial neural network (ANN).
Shalchi, A.
2014-01-10
We explore perpendicular diffusion based on the unified nonlinear transport theory. In Paper I, we focused on magnetostatic turbulence, whereas in the present article we include dynamical turbulence effects. For simplicity, we assume a constant correlation time. We show that there is now a nonvanishing contribution of the slab modes. We explore the parameter regimes in which the turbulence dynamics becomes important for perpendicular diffusion. Analytical forms for the perpendicular diffusion coefficient are derived, which can be implemented easily in solar modulation or shock acceleration codes.
Le, Cheng-Feng; Li, Yun-Mei; Zha, Yong; Sun, De-Yong; Wang, Li-Zhen
2009-02-01
The spectral and chemical analytical data of Taihu Lake water quality in Nov. 8-22, 2007 were used to analyze the spectral characteristics of diffuse attenuation coefficient (Kd) of the water body in autumn and related affecting factors. On the basis of this analysis, the Kd at band 490 nm, Kd (490), was used as a variable to build the relationship between Kd and remote sensing reflectance. The results indicated that within the scope of visible band, the Kd of the water body at most locations of Taihu Lake presented an exponent decreasing trend with the increase of wave length. Due to the higher concentration of phytoplankton in some locations, a peak value of Kd was presented at band 675 nm. Non-organic suspended particles, because of their higher content in suspended sediment, had larger effects on Kd than organic suspended ones. There was a good correlation between Kd and remote sensing reflectance. Taking Rrs (550), Rrs (675) and Rrs (731) as independent variables and doing regression analysis with Kd (490), a good linear relationship was found between Kd (490) and Rrs (731), and multi-variate linear regression analysis using variables Rrs (550), Rrs (675) and Rrs (731) could get better effect (R2 > 0.96) than the regression analysis using variable Rrs (731). PMID:19459373
Diffuse attenuation coefficient of downwelling irradiance: An evaluation of remote sensing methods
NASA Astrophysics Data System (ADS)
Lee, Zhong-Ping; Darecki, Miroslaw; Carder, Kendall L.; Davis, Curtiss O.; Stramski, Dariusz; Rhea, W. Joseph
2005-02-01
The propagation of downwelling irradiance at wavelength λ from surface to a depth (z) in the ocean is governed by the diffuse attenuation coefficient, ?(λ). There are two standard methods for the derivation of ?(λ) in remote sensing, which both are based on empirical relationships involving the blue-to-green ratio of ocean color. Recently, a semianalytical method to derive ?(λ) from reflectance has also been developed. In this study, using ?(490) and ?(443) as examples, we compare the ?(λ) values derived from the three methods using data collected in three different regions that cover oceanic and coastal waters, with ?(490) ranging from ˜0.04 to 4.0 m-1. The derived values are compared with the data calculated from in situ measurements of the vertical profiles of downwelling irradiance. The comparisons show that the two standard methods produced satisfactory estimates of ?(λ) in oceanic waters where attenuation is relatively low but resulted in significant errors in coastal waters. The newly developed semianalytical method appears to have no such limitation as it performed well for both oceanic and coastal waters. For all data in this study the average of absolute percentage difference between the in situ measured and the semianalytically derived ? is ˜14% for λ = 490 nm and ˜11% for λ = 443 nm.
Isotopic mass-dependence of metal cation diffusion coefficients in liquid water
Bourg, I.C.; Richter, F.M.; Christensen, J.N.; Sposito, G.
2009-01-11
Isotope distributions in natural systems can be highly sensitive to the mass (m) dependence of solute diffusion coefficients (D) in liquid water. Isotope geochemistry studies routinely have assumed that this mass dependence either is negligible (as predicted by hydrodynamic theories) or follows a kinetic-theory-like inverse square root relationship (D {proportional_to} m{sup -0.5}). However, our recent experimental results and molecular dynamics (MD) simulations showed that the mass dependence of D is intermediate between hydrodynamic and kinetic theory predictions (D {proportional_to} m{sup -{beta}} with 0 {<=} {beta} < 0.2 for Li{sup +}, Cl{sup -}, Mg{sup 2+}, and the noble gases). In this paper, we present new MD simulations and experimental results for Na{sup +}, K{sup +}, Cs{sup +}, and Ca{sup 2+} that confirm the generality of the inverse power-law relation D {proportional_to} m{sup -{beta}}. Our new findings allow us to develop a general description of the influence of solute valence and radius on the mass dependence of D for monatomic solutes in liquid water. This mass dependence decreases with solute radius and with the magnitude of solute valence. Molecular-scale analysis of our MD simulation results reveals that these trends derive from the exponent {beta} being smallest for those solutes whose motions are most strongly coupled to solvent hydrodynamic modes.
Marmer, G.J.; Dunn, C.P.; Filley, T.H.; Moeller, K.L.; Pfingston, J.M.; Policastro, A.J.; Cleland, J.H.
1991-09-01
Uranium enrichment in the United States has utilized a diffusion process to preferentially enrich the U-235 isotope in the uranium product. In the 1970s, the US Department of Energy (DOE) began investigating more efficient and cost-effective enrichment technologies. In January 1990, the Secretary of Energy approved a plan for the demonstration and deployment of the Uranium Atomic Vapor Laser isotope Separation (U-AVLIS) technology with the near-term goal to provide the necessary information to make a deployment decision by November 1992. Initial facility operation is anticipated for 1999. A programmatic document for use in screening DOE sites to locate a U-AVLIS production plant was developed and implemented in two parts. The first part consisted of a series of screening analyses, based on exclusionary and other criteria, that identified a reasonable number of candidate sites. The final evaluation, which included sensitivity studies, identified the Oak Ridge Gaseous Diffusion Plant (ORGDP) site, the Paducah Gaseous Diffusion Plant (PGDP) site, and the Portsmouth Gaseous Diffusion Plant (PORTS) site as having significant advantages over the other sites considered. This environmental site description (ESD) provides a detailed description of the PORTS site and vicinity suitable for use in an environmental impact statement (EIS). This report is based on existing literature, data collected at the site, and information collected by Argonne National Laboratory (ANL) staff during site visits. The organization of the ESD is as follows. Topics addressed in Sec. 2 include a general site description and the disciplines of geology, water resources, biotic resources, air resources, noise, cultural resources, land use. Socioeconomics, and waste management. Identification of any additional data that would be required for an EIS is presented in Sec. 3.
NASA Astrophysics Data System (ADS)
Drozdov, Alexander; Mann, Ian; Baker, Daniel N.; Subbotin, Dmitriy; Ozeke, Louis; Shprits, Yuri; Kellerman, Adam
Two parameterizations of the resonant wave-particle interactions of electrons with ULF waves in the magnetosphere by Brautigam and Albert [2000] and Ozeke et al. [2012] are evaluated using the Versatile Electron Radiation Belt (VERB) diffusion code to estimate the effect of changing a diffusion coefficient on the radiation belt simulation. The period of investigation includes geomagnetically quiet and active time. The simulations take into account wave-particle interactions represented by radial diffusion transport, local acceleration, losses due to pitch-angle diffusion, and mixed diffusion. 1. Brautigam, D. H., and J. M. Albert (2000), Radial diffusion analysis of outer radiation belt electrons during the October 9, 1990, magnetic storm, J. Geophys. Res., 105(A1), 291-309, doi:10.1029/1999JA900344 2. Ozeke, L. G., I. R. Mann, K. R. Murphy, I. J. Rae, D. K. Milling, S. R. Elkington, A. A. Chan, and H. J. Singer (2012), ULF wave derived radiation belt radial diffusion coefficients, J. Geophys. Res., 117, A04222, doi:10.1029/2011JA017463.
Sun, Licun; Pu, Xiaoyun
2016-01-01
A visualization and quantification optical method for measuring binary liquid diffusion coefficient (D) based on an asymmetric liquid-core cylindrical lens (ALCL) is introduced in this paper. Four groups of control experiments were performed to verify the influences of diffusing substance category, concentration and temperature on diffusion process, and the measured D values were well consistent with data measured by Holographic interferometry and Taylor dispersion methods. The drifting of the diffusion image recorded by CCD reflects the diffusion rate visually in an easily understandable way. This optical method for measuring D values based on the ALCL is characterized by visual measurement, simplified device, and easy operation, which provides a new way for measuring liquid D value visually. PMID:27325006
Sun, Licun; Pu, Xiaoyun
2016-01-01
A visualization and quantification optical method for measuring binary liquid diffusion coefficient (D) based on an asymmetric liquid-core cylindrical lens (ALCL) is introduced in this paper. Four groups of control experiments were performed to verify the influences of diffusing substance category, concentration and temperature on diffusion process, and the measured D values were well consistent with data measured by Holographic interferometry and Taylor dispersion methods. The drifting of the diffusion image recorded by CCD reflects the diffusion rate visually in an easily understandable way. This optical method for measuring D values based on the ALCL is characterized by visual measurement, simplified device, and easy operation, which provides a new way for measuring liquid D value visually. PMID:27325006
NASA Astrophysics Data System (ADS)
Masuda, Akiko; Ushida, Kiminori; Nishimura, Goro; Kinjo, Masataka; Tamura, Mamoru; Koshino, Hiroyuki; Yamashita, Koichi; Kluge, Thomas
2004-12-01
The distance dependence of the diffusion coefficient (DDDC) of a globular protein (cytchrome c) in aqueous hyaluronan (HA) solution, which is a model system for extracellular matrices (ECMs), was measured by a combination of three kinds of spectroscopic measurements of diffusion coefficients, the time and space samplings of which are different. The results of the three methods are plotted against the diffusion distance derived from the consideration of each experimental condition. Due to the characteristic morphology of HA with an effective mesh structure, the proteins showed two extreme diffusion modes: (1) short (<10 nm) diffusion with rare contact with polymer chains; (2) long (>100 nm) diffusion significantly disrupted by polymer chains showing an ≈30% reduction in diffusion coefficient. The transition from the short diffusion to the long one occurs in a very narrow range (10-100 nm) of diffusion distance and this unique character of HA realizing anomalous diffusion should provide suitable environments for various bioactivities when involved in ECM.
Estimation of CO2 diffusion coefficient at 0-10 cm depth in undisturbed and tilled soils
Technology Transfer Automated Retrieval System (TEKTRAN)
Diffusion coefficients (D) of CO2 at 0 – 10 cm layers in undisturbed and tilled soil conditions were estimated using Penman, Millington-Quirk, Ridgwell et al. (1999), Troeh et al., and Moldrup et al. models. Soil bulk density and volumetric soil water content ('v) at 0 – 10 cm were measured on April...
Goossens, Karel; Prior, Mira; Pacheco, Victor; Willbold, Dieter; Müllen, Klaus; Enderlein, Jörg; Hofkens, Johan; Gregor, Ingo
2015-07-28
Dual-focus fluorescence correlation spectroscopy (2fFCS) is a versatile method to determine accurate diffusion coefficients of fluorescent species in an absolute, reference-free manner. Whereas (either classical or dual-focus) FCS has been employed primarily in the life sciences and thus in aqueous environments, it is increasingly being used in materials chemistry, as well. These measurements are often performed in nonaqueous media such as organic solvents. However, the diffusion coefficients of reference dyes in organic solvents are not readily available. For this reason we determined the translational diffusion coefficients of several commercially available organosoluble fluorescent dyes by means of 2fFCS. The selected dyes and organic solvents span the visible spectrum and a broad range of refractive indices, respectively. The diffusion coefficients can be used as absolute reference values for the calibration of experimental FCS setups, allowing quantitative measurements to be performed. We show that reliable information about the hydrodynamic dimensions of the fluorescent species (including noncommercial compounds) within organic media can be extracted from the 2fFCS data. PMID:26144863
Dominé, F; Xueref, I
2001-09-01
Diffusion of gases in ice is involved in cloud, snow, and ice core chemistry, but few data exist on the relevant diffusion coefficients. A novel method to measure diffusion coefficients in ice has recently been proposed by Livingston et al. (Anal. Chem., 2000, 72, 5590-5599). It is based on depth profiling of doped ice crystals epitaxially grown on Ru(001) by laser resonant desorption (LRD). Using this method, Livingston et al. obtained a value of the diffusion coefficient of the HCl hydrate in ice at 190 K of about 5 x 10(-11) cm2/s. We argue here that this value is many orders of magnitude higher than what could be expected from literature values, which are not reported in sufficient detail by Livingston et al. We investigate the possibilities that their high value could be due to (1) diffusion in defects in the ice, which would be present in very high concentrations because of the ice growth method; and (2) the fact that diffusion of high concentrations of HCl in ice at 190 K forms an amorphous HCl:H2O solid mixture, where HCl diffusion is fast. We present new infrared spectroscopic data on solid HCl:H2O mixtures that confirm that such mixtures can indeed be formed in an amorphous state at 190 K. Our proposed interpretation is that by depositing large amounts of HCl on epitaxially grown ice, Livingston et al. created a superficial amorphous binary mixture and that fast diffusion of HCl in the ice, possibly accelerated by a high defect density, produced an amorphous HCl:H2O mixture. We conclude that the processes studied by Livingston et al. are different from those involved in the atmospheric and cryospheric sciences, and that their data, obtained by depth profiling using LRD, probably cannot be applied to those fields. PMID:11569830
Gebrekristos, R.A.; Shapiro, A.M.; Usher, B.H.
2008-01-01
An in situ method of estimating the effective diffusion coefficient for a chemical constituent that diffuses into the primary porosity of a rock is developed by abruptly changing the concentration of the dissolved constituent in a borehole in contact with the rock matrix and monitoring the time-varying concentration. The experiment was conducted in a borehole completed in mudstone on the campus of the University of the Free State in Bloemfontein, South Africa. Numerous tracer tests were conducted at this site, which left a residual concentration of sodium chloride in boreholes that diffused into the rock matrix over a period of years. Fresh water was introduced into a borehole in contact with the mudstone, and the time-varying increase of chloride was observed by monitoring the electrical conductivity (EC) at various depths in the borehole. Estimates of the effective diffusion coefficient were obtained by interpreting measurements of EC over 34 d. The effective diffusion coefficient at a depth of 36 m was approximately 7.8??10-6 m2/d, but was sensitive to the assumed matrix porosity. The formation factor and mass flux for the mudstone were also estimated from the experiment. ?? Springer-Verlag 2007.
Majer, G.; Melchior, J. P.
2014-03-07
Precise diffusion measurements of rhodamine 6G (Rh6G) dissolved in D{sub 2}O at concentrations between 50 and 200 μM were carried out in the temperature range from 280 to 320 K using pulsed field gradient nuclear magnetic resonance (PFG-NMR). The obtained diffusion coefficients can be used as a calibration reference in fluorescence correlation spectroscopy (FCS). Besides measuring the diffusivity of Rh6G, the diffusion coefficient of the solvent in the same system could be determined in parallel by PFG-NMR as the resonances of water and Rh6G are well separated in the {sup 1}H NMR spectrum. To analyze the differences due to the isotope effect of the solvent (D{sub 2}O vs. H{sub 2}O), the correlation time τ{sub D} of Rh6G was measured by FCS in both D{sub 2}O and H{sub 2}O. The obtained isotopic correction factor, τ{sub D}(D{sub 2}O)/τ{sub D}(H{sub 2}O) = 1.24, reflects the isotope effect of the solvent´s self-diffusion coefficients as determined previously by PFG-NMR.
Higaki, M.; Otsuka, T.; Hashizume, K.; Tokunaga, K.; Ezato, K.; Suzuki, S.; Enoeda, M.; Akiba, M.
2015-03-15
Hydrogen diffusion coefficients in a reduced activation ferritic/martensitic steel (F82H) and an oxide dispersion strengthened F82H (ODS-F82H) have been determined from depth profiles of plasma-loaded hydrogen with a tritium imaging plate technique (TIPT) in the temperature range from 298 K to 523 K. Data on hydrogen diffusion coefficients, D, in F82H, are summarized as D [m{sup 2}*s{sup -1}] =1.1*10{sup -7}exp(-16[kJ mol{sup -1}]/RT). The present data indicate almost no trapping effect on hydrogen diffusion due to an excess entry of energetic hydrogen by the plasma loading, which results in saturation of the trapping sites at the surface and even in the bulk. In the case of ODS-F82H, data of hydrogen diffusion coefficients are summarized as D [m{sup 2}*s{sup -1}] =2.2*10{sup -7}exp(-30[kJ mol{sup -1}]/RT) indicating a remarkable trapping effect on hydrogen diffusion caused by tiny oxide particles (Y{sub 2}O{sub 3}) in the bulk of F82H. Such oxide particles introduced in the bulk may play an effective role not only on enhancement of mechanical strength but also on suppression of hydrogen penetration by plasma loading.
NASA Technical Reports Server (NTRS)
Paillat, O.; Wasserburg, G. J.
1993-01-01
Experimental studies of self-diffusion isotopes in silicate melts often have quite large uncertainties when comparing one study to another. We designed an experiment in order to improve the precision of the results by simultaneously studying several elements (Mg, Ca, Sr, Ba) during the same experiment thereby greatly reducing the relative experimental uncertainties. Results show that the uncertainties on the diffusion coefficients can be reduced to 10 percent, allowing a more reliable comparison of differences of self-diffusion coefficients of the elements. This type of experiment permits us to study precisely and simultaneously several elements with no restriction on any element. We also designed an experiment to investigate the possible effects of multicomponent diffusion during Mg self-diffusion experiments by comparing cases where the concentrations of the elements and the isotopic compositions are different. The results suggest that there are differences between the effective means of transport. This approach should allow us to investigate the importance of multicomponent diffusion in silicate melts.
Mandal, A.B.; Nair, B.U. )
1991-10-31
Critical micelle concentrations (cmc) of cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC) surfactants in aqueous solution have been determined by using the cyclic voltammetric technique. (Co(en){sub 3})(ClO{sub 4}){sub 3} has been used as the redox-active electrochemical probe. The cmc values so obtained for the surfactants were found to be in good agreement with the literature values. The partition coefficient, K, of the electrochemical probe between water and surfactants in nonmicellar and micellar states was estimated using the peak current, i{sub p} and half-wave potential, E{sub 1/2} values. The self-diffusion coefficient, D{sub m}, interaction parameter, k{sub f}, and hydrodynamic radius of the micelles were also estimated. The results suggest that the probe is sensitive to the nature of surfactant as well as surfactant concentration.
NASA Astrophysics Data System (ADS)
Bologna, Mauro; Svenkeson, Adam; West, Bruce J.; Grigolini, Paolo
2015-07-01
Diffusion processes in heterogeneous media, and biological systems in particular, are riddled with the difficult theoretical issue of whether the true origin of anomalous behavior is renewal or memory, or a special combination of the two. Accounting for the possible mixture of renewal and memory sources of subdiffusion is challenging from a computational point of view as well. This problem is exacerbated by the limited number of techniques available for solving fractional diffusion equations with time-dependent coefficients. We propose an iterative scheme for solving fractional differential equations with time-dependent coefficients that is based on a parametric expansion in the fractional index. We demonstrate how this method can be used to predict the long-time behavior of nonautonomous fractional differential equations by studying the anomalous diffusion process arising from a mixture of renewal and memory sources.
NASA Astrophysics Data System (ADS)
Manapova, Aigul
2016-08-01
We consider optimal control problems for second order elliptic equations with non-self-adjoint operators-convection-diffusion problems. Control processes are described by semi-linear convection-diffusion equation with discontinuous data and solutions (states) subject to the boundary interface conditions of imperfect type (i.e., problems with a jump of the coefficients and the solution on the interface; the jump of the solution is proportional to the normal component of the flux). Controls are involved in the coefficients of diffusion and convective transfer. We prove differentiability and Lipshitz continuity of the cost functional, depending on a state of the system and a control. The calculation of the gradients uses the numerical solutions of direct problems for the state and adjoint problems.
NASA Astrophysics Data System (ADS)
Liu, Wenlong; Tu, Weichao; Li, Xinlin; Sarris, Theodore; Khotyaintsev, Yuri; Fu, Huishan; Zhang, Hui; Shi, Quanqi
2016-02-01
Based on 7 years' observations from Time History of Events and Macroscale Interactions during Substorms (THEMIS), we investigate the statistical distribution of electric field Pc5 ULF wave power under different geomagnetic activities and calculate the radial diffusion coefficient due to electric field, , for outer radiation belt electrons. A simple empirical expression of is also derived. Subsequently, we compare to previous DLL models and find similar Kp dependence with the model, which is also based on in situ electric field measurements. The absolute value of is constantly higher than , probably due to the limited orbital coverage of CRRES. The differences between and the commonly used and models are significant, especially in Kp dependence and energy dependence. Possible reasons for these differences and their implications are discussed. The diffusion coefficient provided in this paper, which also has energy dependence, will be an important contributor to quantify the radial diffusion process of radiation belt electrons.
Plata, Juan C.; Holbrook, Andrew B.; Marx, Michael; Salgaonkar, Vasant; Jones, Peter; Pascal-Tenorio, Aurea; Bouley, Donna; Diederich, Chris; Sommer, Graham; Pauly, Kim Butts
2015-01-01
Purpose: Evaluate whether a decrease in apparent diffusion coefficient (ADC), associated with loss of tissue viability (LOTV), can be observed during the course of thermal ablation of the prostate. Methods: Thermal ablation was performed in a healthy in vivo canine prostate model (N = 2, ages: 5 yr healthy, mixed breed, weights: 13–14 kg) using a transurethral high-intensity ultrasound catheter and was monitored using a strategy that interleaves diffusion weighted images and gradient-echo images. The two sequences were used to measure ADC and changes in temperature during the treatment. Changes in temperature were used to compute expected changes in ADC. The difference between expected and measured ADC, ADCDIFF, was analyzed in regions ranging from moderate hyperthermia to heat fixation. A receiver operator characteristic (ROC) curve analysis was used to select a threshold of detection of LOTV. Time of threshold activation, tLOTV, was compared with time to reach CEM43 = 240, tDOSE. Results: The observed relationship between temperature and ADC in vivo (2.2%/ °C, 1.94%–2.47%/ °C 95% confidence interval) was not significantly different than the previously reported value of 2.4%/ °C in phantom. ADCDIFF changes after correction for temperature showed a mean decrease of 25% in ADC 60 min post-treatment in regions where sufficient thermal dose (CEM43 > 240) was achieved. Following our ROC analysis, a threshold of 2.25% decrease in ADCDIFF for three consecutive time points was chosen as an indicator of LOTV. The ADCDIFF was found to decrease quickly (1–2 min) after reaching CEM43 = 240 in regions associated with heat fixation and more slowly (10–20 min) in regions that received slower heating. Conclusions: Simultaneous monitoring of ADC and temperature during treatment might allow for a more complete tissue viability assessment of ablative thermal treatments in the prostate. ADCDIFF decreases during the course of treatment may be interpreted as loss of
Wang, Hai-Yi; Wang, Jia; Tang, Ye-Huan; Ye, Hui-Yi; Ma, Lin
2015-01-01
Background: Coronal diffusion-weighted magnetic resonance imaging (DW-MRI) and apparent diffusion coefficient (ADC) values have gradually become applied (following conventional axial DW-MRI) in the renal analysis. To explore whether data obtained using coronal DW-MRI are comparable with those derived using axial DW-MRI, this preliminary study sought to assess the agreement in renal ADC values between coronal DW-MRI and axial DW-MRI. Methods: Thirty-four healthy volunteers were enrolled in the study; written consents were obtained. All subjects underwent respiratory-triggered axial and coronal DW-MRI using a 1.5-MR system with b values of 0 and 800 s/mm2. The signal-to-noise ratios (SNRs) of the two DW-MRI sequences were measured and statistically compared using the paired t-test. The extent of agreement of ADC values of the upper pole, mid-pole, and lower pole of the kidney; the mean ADC values of the left kidney and right kidney; and the mean ADC values of the bilateral kidneys were evaluated via calculation of intraclass correlation coefficients (ICCs) or Bland–Altman method between the two DW-MRI sequences. Results: The SNR of coronal DW-MR images was statistically inferior to that of axial DW-MR images (P < 0.001). The ICCs of the ADC values of each region of interest, and the mean ADC values of bilateral kidneys, between the two sequences, were greater than 0.5, and the mean ADCs of the bilateral kidneys demonstrated the highest ICC (0.869; 95% confidence interval: 0.739–0.935). In addition, 94.1% (32/34), 94.1% (32/34), and 97.1% (31/34) of the ADC bias was inside the limits of agreement in terms of the mean ADC values of the left kidneys, right kidneys, and bilateral kidneys when coronal and axial DWI-MRI were compared. Conclusions: ADC values derived using coronal DW-MRI exhibited moderate-to-good agreement to those of axial DW-MRI, rendering the former an additional useful DW-MRI method, and causing the ADC values derived using the two types of DW
Analysis of ligand-protein exchange by Clustering of Ligand Diffusion Coefficient Pairs (CoLD-CoP)
NASA Astrophysics Data System (ADS)
Snyder, David A.; Chantova, Mihaela; Chaudhry, Saadia
2015-06-01
NMR spectroscopy is a powerful tool in describing protein structures and protein activity for pharmaceutical and biochemical development. This study describes a method to determine weak binding ligands in biological systems by using hierarchic diffusion coefficient clustering of multidimensional data obtained with a 400 MHz Bruker NMR. Comparison of DOSY spectrums of ligands of the chemical library in the presence and absence of target proteins show translational diffusion rates for small molecules upon interaction with macromolecules. For weak binders such as compounds found in fragment libraries, changes in diffusion rates upon macromolecular binding are on the order of the precision of DOSY diffusion measurements, and identifying such subtle shifts in diffusion requires careful statistical analysis. The "CoLD-CoP" (Clustering of Ligand Diffusion Coefficient Pairs) method presented here uses SAHN clustering to identify protein-binders in a chemical library or even a not fully characterized metabolite mixture. We will show how DOSY NMR and the "CoLD-CoP" method complement each other in identifying the most suitable candidates for lysozyme and wheat germ acid phosphatase.
A first-principles study of the diffusion coefficients of alloying elements in dilute α-Ti alloys.
Xu, W W; Shang, S L; Zhou, B C; Wang, Y; Chen, L J; Wang, C P; Liu, X J; Liu, Z K
2016-06-22
Using first-principles calculations accompanied by the transition state theory and an 8-frequency model, we present a comprehensive investigation of the diffusion coefficients of substitutional alloying elements X in dilute α-Ti alloys, where X denotes Al, V, Nb, Ta, Mo, Zr, and Sn. The alloying elements Mo and Al exhibit a maximum and a minimum diffusion rate in dilute α-Ti alloys, respectively. It is found that the nearest-neighbor solute-vacancy binding energies and activation energies are roughly inversely proportional to the volume changes induced by solute atoms. There are two exceptions to this trend: Al and Mo. Besides the physical effect (i.e., solute size), two other key factors governing solute diffusion in dilute α-Ti are clarified: the chemical bonding characteristics and vibrational features of X-Ti pairs. It verifies that the ultrafast diffusivity of Mo arises from the interactions with Ti atoms by metallic bonds and its low-frequency contributions to lattice vibration, while the more covalent bonding nature and the high-frequency contributions to the lattice vibration of Al lead to its ultraslow diffusivity. In addition, the correlation effects of diffusion coefficients are non-negligible for the large solutes Ta, Nb, and Zr, in which the direct solute-vacancy migration barriers are much smaller than the solvent-vacancy migration barriers. PMID:27282515
Chen, Yuan-Gui; Chen, Ming-Qiu; Guo, Yu-Yan; Li, Si-Cong; Wu, Jun-Xin; Xu, Ben-Hua
2016-01-01
Objective To evaluate the predictive value of the apparent diffusion coefficient (ADC) for pathologic complete response (pCR) to neoadjuvant chemoradiotherapy (NCRT) in locally advanced rectal cancer. Methods A total of 265 patients with rectal adenocarcinoma, whole Diffusion-Weighted MRI (DWI-MRI) images, clinically stage II to III (cT3-4 and/or cN+) and treated with NCRT followed by TME were screened. Fifty patients with pCR and another 50 patients without pCR with similar clinical charcacters and treatment regimens were selected for statistical analysis. All the patients’ pre-CRT and post-CRT average ADC values were calculated from the coefficient maps created by DWI-MRI and recorded independently. The difference in the ADC values between the pCR and non-pCR was analyzed by the Mann-Whitney U test. The cut-off ADC value of the receiver operating characteristic (ROC) curve with pCR was then established. Results The mean pre- and post-ADC values in all patients, and in pCR patients and non-pCR patients were 0.879±0.06 and 1.383±0.11, 0.859±0.04 and 1.440±0.10, 0.899±0.07 and 1.325±0.09 (×10-3mm2/s), respectively. The difference between the pre- and post-ADC values in all patients, pCR patients, and non-pCR patients were considered to be statistically significant. The pre-ADC value was significantly lower in the pCR patients than in the non-pCR patients (p = 0.003), whereas the post-ADC values were significantly higher in the pCR patients than in the non-pCR patients. The percentage increase of the ADC value (ΔADC%) in the pCR and non-pCR patients were 68% and 48% respectively (p<0.001). The ROC curves of the cut-off value of the pre-CRT patient ADC value was 0.866×10-3mm2/s. The AUC, sensitivity, specificity, PPV, NPV, and accuracy of diagnosing pCR were 0.670 (95% CI 0.563–0.777), 0.600, 0.640, 60%, 60%, and 60%, respectively. The cut-off value of ΔADC% was 58%. The corresponding AUC, sensitivity, specificity, PPV, NPV, and accuracy of diagnosing p
Association of the apparent diffusion coefficient with maturity in adolescent sacroiliac joints
Vendhan, Kanimozhi; Roberts, James; Atkinson, David; Punwani, Shonit; Sen, Debajit; Ioannou, Yiannis; Hall‐Craggs, Margaret A.
2016-01-01
Purpose To determine the extent to which apparent diffusion coefficient (ADC) values vary with skeletal maturity in adolescent joints. Materials and Methods A retrospective study was performed with Institutional Review Board (IRB) approval. We used a picture archiving and communication system (PACS) search to identify and recruit all adolescents who had undergone 1.5T magnetic resonance imaging (MRI) of the sacroiliac joints (SIJs) between January 2010 and June 2015, and had no evidence of sacroiliitis and normal inflammatory markers. In all, 55 individuals were assessed. For each patient, coronal and sagittal images of the sacrum were visually analyzed to determine sacral maturity. Patients were divided into three groups depending on the degree of fusion of the sacral segmental apophyses: “Fused,” “Partial,” and “Unfused.” For each group, SIJ ADC was measured using a linear region‐of‐interest technique. Results Mean ADC values were 690 × 10−6 mm2/s in the fused group, 720 × 10−6 mm2/s in the partial group, and 842 × 10−6 mm2/s in the unfused group. ADC values were significantly higher in the unfused group than in the fused group (P = 0.046). ADC values were also higher in unfused subjects than partially fused subjects (P = 0.074). Conclusion Joint ADC values are higher in skeletally immature (unfused) patients than in skeletally more mature (fused) patients. ADC values measured in the unfused group overlap with those previously reported in sacroiliitis. These results suggest that ADC measurements in adolescent joints must be interpreted in light of joint maturity. Joint immaturity may lead to misdiagnosis of sacroiliitis, since immature juxta‐articular bone may appear similar to inflammation. J. Magn. Reson. Imaging 2016. J. Magn. Reson. Imaging 2016;44:556–564. PMID:26898474
A method for estimating the diffuse attenuation coefficient (KdPAR)from paired temperature sensors
Read, Jordan S.; Rose, Kevin C.; Winslow, Luke A.; Read, Emily Kara
2015-01-01
A new method for estimating the diffuse attenuation coefficient for photosynthetically active radiation (KdPAR) from paired temperature sensors was derived. We show that during cases where the attenuation of penetrating shortwave solar radiation is the dominant source of temperature changes, time series measurements of water temperatures at multiple depths (z1 and z2) are related to one another by a linear scaling factor (a). KdPAR can then be estimated by the simple equation KdPAR ln(a)/(z2/z1). A suggested workflow is presented that outlines procedures for calculating KdPAR according to this paired temperature sensor (PTS) method. This method is best suited for conditions when radiative temperature gains are large relative to physical noise. These conditions occur frequently on water bodies with low wind and/or high KdPARs but can be used for other types of lakes during time periods of low wind and/or where spatially redundant measurements of temperatures are available. The optimal vertical placement of temperature sensors according to a priori knowledge of KdPAR is also described. This information can be used to inform the design of future sensor deployments using the PTS method or for campaigns where characterizing sub-daily changes in temperatures is important. The PTS method provides a novel method to characterize light attenuation in aquatic ecosystems without expensive radiometric equipment or the user subjectivity inherent in Secchi depth measurements. This method also can enable the estimation of KdPAR at higher frequencies than many manual monitoring programs allow.
Lu, Yan; Li, Mingzhong
2016-01-01
The solubility and diffusion coefficient are two of the most important physicochemical properties of a drug compound. In practice, both have been measured separately, which is time consuming. This work utilizes a novel technique of UV imaging to determine the solubility and diffusion coefficients of poorly water-soluble drugs simultaneously. A 2-step optimal method is proposed to determine the solubility and diffusion coefficients of a poorly water-soluble pharmaceutical substance based on the Fick's second law of diffusion and UV imaging measurements. Experimental results demonstrate that the proposed method can be used to determine the solubility and diffusion coefficients of a drug with reasonable accuracy, indicating that UV imaging may provide a new opportunity to accurately measure the solubility and diffusion coefficients of a poorly water-soluble drug simultaneously and rapidly. PMID:26852848
Haas, O.; Velazquez, C.S.; Porat, Z.; Murray, R.W.
1995-10-12
Ferrocene labeled monomethoxy-poly(ethylene glycol)s (MPEG) with molecular weights of 1900 and 750 were used as redox probe solutes in poly(ethylene glycol) melt solvents of molecular weight 750, 2000, and 20000. Cyclic voltammetry and chronoamperometry at microdisk electrodes were employed to measure the diffusion coefficients of the redox probes, which were independent of the probe concentration and varied between 10{sup -7} and 10{sup -10} cm{sup 2}/s. Diffusional activation barrier results also suggest that the ferrocene label does not significantly influence the diffusivity of the probe molecule in the host solvent. Activation barrier, viscosity, and ionic conductivity results show that the LiClO{sub 4} electrolyte does not influence the diffusion barrier or viscosity as long as the ether O/Li{sup +} ratio is >=250 (ca. 0.1 M) which is still a sufficient electrolyte concentration to allow quantitative electrochemical diffusion measurements. 21 refs., 7 figs., 2 tabs.
Lee, Cheng-Kuang; Tsai, Meng-Tsan; Chang, Feng-Yu; Yang, Chih-Hsun; Shen, Su-Chin; Yuan, Ouyang; Yang, Chih-He
2013-01-01
In this study, time-resolved optical coherence tomography (OCT) scanning images of the process of water diffusion in the skin that illustrate the enhancement in the backscattered intensities due to the increased water concentration are presented. In our experiments, the water concentration in the skin was increased by soaking the hand in water, and the same region of the skin was scanned and measured with the OCT system and a commercial moisture monitor every three minutes. To quantitatively analyze the moisture-related optical properties and the velocity of water diffusion in human skin, the attenuation coefficients of the skin, including the epidermis and dermis layers, were evaluated. Furthermore, the evaluated attenuation coefficients were compared with the measurements made using the commercial moisture monitor. The results demonstrate that the attenuation coefficient increases as the water concentration increases. Furthermore, by evaluating the positions of center-of mass of the backscattered intensities from OCT images, the diffusion velocity can be estimated. In contrast to the commercial moisture monitor, OCT can provide three-dimensional structural images of the skin and characterize its optical property, which together can be used to observe morphological changes and quantitatively evaluate the moisture-related attenuation coefficients in different skin layers. PMID:23529149
de Oliveira, Lucas Nonato; Sampaio, Francisco Glaildo Almeida; Moreira, Marcos Vasques; de Almeida, Adelaide
2014-08-01
In Fricke dosimetry, optical density measurements are performed some time after dosimeter irradiation. Values of the diffusion coefficient of Fe(3+) in Fricke Xylenol gel (FXG) are necessary for determining the spatial distribution of the absorbed dose from measurements of the optical density. Five sets of FXG dosimeters, kept at different constant temperatures, were exposed to collimated 6 MV photons. The optical density profile, proportional to the Fe(3+) concentration, at the boundary between irradiated and non-irradiated parts of each dosimeter was measured periodically over a period of 60 h. By comparing the experimental data with a function that accounts for the unobserved initial concentration profile of Fe(3+) in the FXG, we obtained diffusion coefficients 0.30±0.05, 0.40±0.05, 0.50±0.05, 0.60±0.05 and 0.80±0.05 mm(2)/h for the temperatures 283.0±0.5, 286.0±0.5, 289.0±0.5, 292.0±0.5, and 296.0±0.5 K, respectively. The activation energy of Fe(3+) diffusion in the gel, 0.54±0.06 eV, was determined from the temperature dependence of the diffusion coefficients. PMID:24836903
NASA Technical Reports Server (NTRS)
Dean, D. C.; Goldstein, J. I.
1984-01-01
The interdiffusion coefficient of FeNi in fcc taenite (gamma) of Fe-Ni and Fe-Ni-0.2 P alloys was measured as a function of temperature between 600 and 900 C. This temperature range is directly applicable to the nucleation and growth of the Widmanstatten pattern in iron meteorites and metal regions of stony and stony-iron meteorites. Diffusion couples were made from FeNi or FeNiP alloys which ensured that the couples were in the taenite phase at the diffusion temperature. The presence or absence of grain boundary diffusion was determined by measuring the Ni profile normal to the existing grain boundaries with the AEM. Ignoring any variation of interdiffusion coefficient with composition, the measured data was plotted versus the reciprocal of the diffusion temperature. The FeNi data generally follow the extrapolated Goldstein, et al. (1965) data from high temperatures. The FeNiP data indicates that small additions of P (0.2 wt%) cause a 3 to 10 fold increase in the FeNi interdifussion coefficient increasing with decreasing temperature. This increase is about the same as that predicted by Narayan and Goldstein (1983) at the Widmanstatten growth temperature.
Torgersen, T.; Mathieu, G.; Hesslein, R.H.; Broecker, W.S.
1982-01-20
A direct field comparison was conducted to determine the dependency of gas exchange coefficient (k/sub x/) on the diffusion coefficient (D/sub x/). The study also sought to confirm the enhanced vertical exchange properties of limnocorrals and similar enclosures. Gas exchange coefficients for /sup 222/Rn and /sup 3/He were determined in a small northern Ontario lake, using a /sup 226/Ra and /sup 3/H spike to gain the necessary precision. The results indicate that the gas exchange coefficient is functionally dependent on the diffusion coefficient raised to the 1.22/sub -35//sup + > 12/ power (k/sub x/ = f(D/sub x//sup 1.22)), clearly supporting the stagnant film model of gas exchange. Limnocorrals were found to have gas exchange rates up to 1.7 times higher than the whole lake in spite of the observation of more calm surface conditions in the corral than in the open lake. 33 references, 6 figures, 8 tables.
Lewis, A.C.; Baird, D.R.
2006-07-01
This paper describes applications of phyto-remediation at the Portsmouth Gaseous Diffusion Plant (PORTS), a Department of Energy (DOE) Facility that enriched uranium from the early 1950's until 2000. Phyto-remediation has been implemented to assist in the removal of TCE (trichloroethylene) in the groundwater at two locations at the PORTS facility: the X-740 area and the X-749/X-120 area. Phyto-remediation technology is based on the ability of certain plants species (in this case hybrid poplar trees) and their associated rhizo-spheric microorganisms to remove, degrade, or contain chemical contaminants located in the soil, sediment, surface water, groundwater, and possibly even the atmosphere. Phyto-remediation technology is a promising clean-up solution for a wide variety of pollutants and sites. Mature trees, such as the hybrid poplar, can consume up to 3,000 gallons of groundwater per acre per day. Organic compounds are captured in the trees' root systems. These organic compounds are degraded by ultraviolet light as they are transpired along with the water vapor through the leaves of the trees. The phyto-remediation system at the X-740 area encompasses 766 one-year old hybrid poplar trees (Populus nigra x nigra, Populus nigra x maximowiczii, and Populus deltoides x nigra) that were planted 10 feet apart in rows 10 feet to 20 feet apart, over an area of 2.6 acres. The system was installed to manage the VOC contaminant plume. At the X749/X-120 area, a phyto-remediation system of 2,640 hybrid poplar trees (Populus nigra x maximowiczii) was planted in seven areas/zones to manage the VOC contaminant plume. The objectives of these systems are to remove contamination from the groundwater and to prevent further migration of contaminants. The goal of these remediation procedures is to achieve completely mature and functional phyto-remediation systems within two years of the initial planting of the hybrid poplar trees at each planting location. There is a direct
Miller, Peter T.; Starmer, R. John
2003-02-27
The primary objective of the investigation was to confirm the presence and determine the location of a cache of 30 to 60 buried 55-gallon drums that were allegedly dumped along the course of the pre-existing, northsouth diversion ditch (NSDD) adjacent to permitted landfills at the Paducah Gaseous Diffusion Plant, Kentucky. The ditch had been rerouted and was being filled and re-graded at the time of the alleged dumping. Historic information and interviews with individuals associated with alleged dumping activities indicated that the drums were dumped prior to the addition of other fill materials. In addition, materials alleged to have been dumped in the ditch, such as buried roofing materials, roof flashing, metal pins, tar substances, fly ash, and concrete rubble complicated data interpretation. Some clean fill materials have been placed over the site and graded. This is an environment that is extremely complicated in terms of past waste dumping activities, construction practices and miscellaneous landfill operations. The combination of site knowledge gained from interviews and research of existing site maps, variable frequency EM data, classical total magnetic field data and optimized GPR lead to success where a simpler less focused approach by other investigators using EM-31 and EM-61 electromagnetic methods and unfocused ground penetrating radar (GPR)did not produce results and defined no real anomalies. A variable frequency electromagnetic conductivity unit was used to collect the EM data at 3,030 Hz, 5,070 Hz, 8,430 Hz, and 14,010 Hz. Both in-phase and quadrature components were recorded at each station point. These results provided depth estimates for targets and some information on the subsurface conditions. A standard magnetometer was used to conduct the magnetic survey that showed the locations and extent of buried metal, the approximate volume of ferrous metal present within a particular area, and allowed estimation of approximate target depths. The GPR
Looney, B.; Eddy-Dilek, C.
2012-08-28
Evaluation of disposal records, soil data, and spatial/temporal groundwater data from the Paducah Gaseous Diffusion Plant (PGDP) Solid Waste Management Unit (SWMU) 7 indicate that the peak contaminant concentrations measured in monitoring well (MW) 66 result from the influence of the regional PGDP NW Plume, and does not support the presence of significant vertical transport from local contaminant sources in SWMU 7. This updated evaluation supports the 2006 conceptualization which suggested the high and low concentrations in MW66 represent different flow conditions (i.e., local versus regional influences). Incorporation of the additional lines of evidence from data collected since 2006 provide the basis to link high contaminant concentrations in MW66 (peaks) to the regional 'Northwest Plume' and to the upgradient source, specifically, the C400 Building Area. The conceptual model was further refined to demonstrate that groundwater and the various contaminant plumes respond to complex site conditions in predictable ways. This type of conceptualization bounds the expected system behavior and supports development of environmental cleanup strategies, providing a basis to support decisions even if it is not feasible to completely characterize all of the 'complexities' present in the system. We recommend that the site carefully consider the potential impacts to groundwater and contaminant plume migration as they plan and implement onsite production operations, remediation efforts, and reconfiguration activities. For example, this conceptual model suggests that rerouting drainage water, constructing ponds or basin, reconfiguring cooling water systems, capping sites, decommissioning buildings, fixing (or not fixing) water leaks, and other similar actions will potentially have a 'direct' impact on the groundwater contaminant plumes. Our conclusion that the peak concentrations in MW66 are linked to the regional PGDP NW Plume does not imply that there TCE is not present in SWMU
NASA Astrophysics Data System (ADS)
Montejo, Ludguier D.; Jia, Jingfei; Kim, Hyun K.; Hielscher, Andreas H.
2013-03-01
We apply the Fourier Transform to absorption and scattering coefficient images of proximal interphalangeal (PIP) joints and evaluate the performance of these coefficients as classifiers using receiver operator characteristic (ROC) curve analysis. We find 25 features that yield a Youden index over 0.7, 3 features that yield a Youden index over 0.8, and 1 feature that yields a Youden index over 0.9 (90.0% sensitivity and 100% specificity). In general, scattering coefficient images yield better one-dimensional classifiers compared to absorption coefficient images. Using features derived from scattering coefficient images we obtain an average Youden index of 0.58 +/- 0.16, and an average Youden index of 0.45 +/- 0.15 when using features from absorption coefficient images.
NASA Astrophysics Data System (ADS)
Gubar, Yu. I.
2015-11-01
A radial profile of the plasma mass distribution in Jupiter's magnetosphere in the region beyond Io's orbit up to ˜15 Jupiter radii R J constructed according to the results of measurements on the Voyager 1 and Galileo spacecraft is used to determine the radial dependence and radial diffusion coefficient D LL . The initial profile is approximated by a function decreasing as L -5 ± 1. For this radial mass distribution, radial ion diffusion outside of Io's orbit caused by centrifugal forces is possible. An estimate of (1.2-6.7)10-11 L 6 ± 1 for D LL was obtained.
NASA Technical Reports Server (NTRS)
Cao, Fang; Fichot, Cedric G.; Hooker, Stanford B.; Miller, William L.
2014-01-01
Photochemical processes driven by high-energy ultraviolet radiation (UVR) in inshore, estuarine, and coastal waters play an important role in global bio geochemical cycles and biological systems. A key to modeling photochemical processes in these optically complex waters is an accurate description of the vertical distribution of UVR in the water column which can be obtained using the diffuse attenuation coefficients of down welling irradiance (Kd()). The Sea UV Sea UVc algorithms (Fichot et al., 2008) can accurately retrieve Kd ( 320, 340, 380,412, 443 and 490 nm) in oceanic and coastal waters using multispectral remote sensing reflectances (Rrs(), Sea WiFS bands). However, SeaUVSeaUVc algorithms are currently not optimized for use in optically complex, inshore waters, where they tend to severely underestimate Kd(). Here, a new training data set of optical properties collected in optically complex, inshore waters was used to re-parameterize the published SeaUVSeaUVc algorithms, resulting in improved Kd() retrievals for turbid, estuarine waters. Although the updated SeaUVSeaUVc algorithms perform best in optically complex waters, the published SeaUVSeaUVc models still perform well in most coastal and oceanic waters. Therefore, we propose a composite set of SeaUVSeaUVc algorithms, optimized for Kd() retrieval in almost all marine systems, ranging from oceanic to inshore waters. The composite algorithm set can retrieve Kd from ocean color with good accuracy across this wide range of water types (e.g., within 13 mean relative error for Kd(340)). A validation step using three independent, in situ data sets indicates that the composite SeaUVSeaUVc can generate accurate Kd values from 320 490 nm using satellite imagery on a global scale. Taking advantage of the inherent benefits of our statistical methods, we pooled the validation data with the training set, obtaining an optimized composite model for estimating Kd() in UV wavelengths for almost all marine waters. This
Shynkaryk, Mykola V; Pyatkovskyy, Taras; Mohamed, Hussein M; Yousef, Ahmed E; Sastry, Sudhir K
2015-12-01
Produce safety has received much recent attention, with the emphasis being largely on discovery of how microbes invade produce. However, the sanitization operation deserves more attention than it has received. The ability of a sanitizer to reach the site of pathogens is a fundamental prerequisite for efficacy. This work addresses the transport processes of ozone (gaseous and liquid) sanitizer for decontamination of leafy greens. The liquid sanitizer was ineffective against Escherichia coli K-12 in situations where air bubbles may be trapped within cavities. A model was developed for diffusion of sanitizer into the interior of produce. The reaction rate of ozone with the surface of a lettuce leaf was determined experimentally and was used in a numerical simulation to evaluate ozone concentrations within the produce and to determine the time required to reach different locations. For aqueous ozone, the penetration depth was limited to several millimeters by ozone self-decomposition due to the significant time required for diffusion. In contrast, gaseous sanitizer was able to reach a depth of 100 mm in several minutes without depletion in the absence of reaction with surfaces. However, when the ozone gas reacted with the produce surface, gas concentration was significantly affected. Simulation data were validated experimentally by measuring ozone concentrations at the bottom of a cylinder made of lettuce leaf. The microbiological test confirmed the relationship between ozone transport, its self-decomposition, reaction with surrounding materials, and the degree of inactivation of E. coli K-12. Our study shows that decontamination of fresh produce, through direct contact with the sanitizer, is more feasible with gaseous than with aqueous sanitizers. Therefore, sanitization during a high-speed washing process is effective only for decontaminating the wash water. PMID:26613904