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  • Articles  (18)
  • diffusion  (18)
  • Springer  (18)
  • American Chemical Society
  • American Geophysical Union
  • De Gruyter
  • Emerald
  • 2000-2004  (15)
  • 1970-1974  (3)
  • 1930-1934
  • Physics  (17)
  • Geosciences  (1)
  • Technology  (1)
  • Education
  • 1
    Electronic Resource
    Electronic Resource
    Analysis of Diffusion in Hollow Geometries (2000)
    Springer
    Adsorption 6 (2000), S. 125-136 
    Details
    ISSN: 1572-8757
    Keywords: diffusion ; mathematical model ; analytical solution ; hollow material ; composite material ; mass transfer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The diffusion in hollow particles of solid adsorbent materials was analyzed based on analytical solutions to the basic diffusion equation. Three geometric shapes (plane sheet, cylinder, and sphere) of sorbent material were considered for two kinds of boundary conditions. The equations for determining the equivalent sizes compared to their corresponding solid particles were obtained directly from the theoretical expressions of sorption uptake curves. Among the three hollow particles of impermeable inner surface, the sphere gives the highest gain in effective diffusion rate compared to the corresponding solid particle. For permeable inner surface, at lower hollow volume fractions, the plane sheet shows the highest gain, while at higher hollow volume fractions, the sphere shows the highest gain in effective diffusion rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008913301145
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  • 2
    Electronic Resource
    Electronic Resource
    Fundamental Study on Near-Axis Scattered Light and Its Application to Optical Computed Tomography (2000)
    Springer
    Optical review 7 (2000), S. 383-388 
    Details
    ISSN: 1349-9432
    Keywords: near-axis scattered light ; optical computed tomography ; time-resolved measurement ; scattering ; diffusion ; random media ; visibility ; photon migration ; computed tomography ; biomedical optics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract To find a basic principle of optical computed tomography (optical CT), a fundamental study was conducted on the use of scattered light in diffuse random media. We call the scattered light that propagates along the optical axis of the incident light beam near-axis scattered light (NASL). The use of NASL for the imaging through a diffuse medium was proposed and its basic characteristics were analyzed. The existence and measurability of NASL were confirmed in the simulation and measurement. To detect NASL efficiently, a technique called the scattering angle differential technique was developed. In CT imaging with a model phantom, the feasibility and effectiveness of the proposed technique were verified. We found that this technique alone was not sufficient to obtain the cross sectional image of an animal body, therefore a technique called the contact technique was devised to overcome the problems of reflection and refraction at the air-tissue interface. Finally, a prototype system was developed which integrated all the proposed techniques. With this system, we could obtain the CT images of a living mouse, in which the blood-rich organs such as liver and kidneys were clearly recognizable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10043-000-0383-4
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  • 3
    Electronic Resource
    Electronic Resource
    The Rectangular Isotherm Model for Adsorption Kinetics (2000)
    Springer
    Adsorption 6 (2000), S. 287-291 
    Details
    ISSN: 1572-8757
    Keywords: diffusion ; shrinking core ; rectangular isotherm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The transient uptake response of an adsorbent particle, subjected to a step change in surface concentration, is considered. It is shown that, when the isotherm is highly favorable, the theoretical curves derived for a Langmuirian system reduce asymptotically to the much simpler form for a rectangular isotherm. The simple rectangular model provides a useful approximation even when the form of the actual isotherm is quite far from the rectangular limit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026504730443
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  • 4
    Electronic Resource
    Electronic Resource
    Film Model Approximation for Multicomponent Adsorption (2000)
    Springer
    Adsorption 6 (2000), S. 5-13 
    Details
    ISSN: 1572-8757
    Keywords: multicomponent adsorption ; diffusion ; Maxwell-Stefan model ; linear driving force approximation ; Langmuir isotherm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An approximate rate equation based on a film-model representation of diffusional mass transfer is developed to describe the kinetics of multicomponent adsorption. The model describes mass transfer as a pseudo-steady state diffusion process through a flat film of thickness equal to one fifth of the particle radius. Starting with an irreversible thermodynamics description of multicomponent diffusion, the flux relationships are integrated across the film yielding analytical expressions for the rate of mass transfer in a multicomponent adsorption system, when adsorption equilibria are described by the extended Langmuir isotherm. The new approximate rate equation can be conveniently used in the numerical simulation of adsorption systems with concentration-dependent micropore or surface diffusivity, and describes the effects of diffusional flux coupling. Results of accuracy comparable with that obtained when using the classical linear-driving-force approximation for systems with constant diffusivities are obtained with this new rate equation for both batch and fixed-bed adsorption calculations. A generalization of the approach based on the Gibbs adsorption isotherm describes mass transfer rates in terms of the spreading-pressure gradient and provides an extension to other multicomponent isotherm forms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008927713530
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  • 5
    Electronic Resource
    Electronic Resource
    Phenomenological equations for multicomponent fluids (1972)
    Springer
    Journal of statistical physics 5 (1972), S. 113-125 
    Details
    ISSN: 1572-9613
    Keywords: Nonequilibrium thermodynamics ; electrolyte solution ; high-temperature plasma ; state variable ; forces and fluxes ; nonlocal linear relation ; Onsager reciprocity ; hydrodynamic equation of motion for component ; Navier-Stokes equation ; diffusion ; viscosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Ahydrodynamic equation of motion for each component of a multicomponent fluid is derived on the basis of nonequilibrium thermodynamics. Special care has been directed to the choice of state variables. In some limiting cases, this equation leads to customary phenomenological equations, such as the equation for diffusion and the Navier-Stokes equation. The viscosity is a consequence of nonlocal coupling of forces and fluxes. The reciprocity between the linear coefficients is examined closely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01008374
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  • 6
    Electronic Resource
    Electronic Resource
    Effective Potential for the Reaction-Diffusion-Decay System (2000)
    Springer
    Journal of statistical physics 99 (2000), S. 903-941 
    Details
    ISSN: 1572-9613
    Keywords: effective potential ; reaction ; diffusion ; decay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In previous work we have developed a general method for casting stochastic partial differential equations (SPDEs) into a functional integral formalism, and have derived the one-loop effective potential for these systems. In this paper we apply the same formalism to a specific field theory of considerable interest, the reaction-diffusion-decay system. When this field theory is subject to white noise we can calculate the one-loop effective potential (for arbitrary polynomial reaction kinetics) and show that it is one-loop ultraviolet renormalizable in 1, 2, and 3 space dimensions. For specific choices of interaction terms the one-loop renormalizability can be extended to higher dimensions. We also show how to include the effects of fluctuations in the study of pattern formation away from equilibrium, and conclude that noise affects the stability of the system in a way which is calculable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018699630306
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  • 7
    Electronic Resource
    Electronic Resource
    Dynamic Light Scattering Measurement of Nanometer Particles in Liquids (2000)
    Springer
    Journal of nanoparticle research 2 (2000), S. 123-131 
    Details
    ISSN: 1572-896X
    Keywords: nanoparticle ; characterization ; light scattering ; PCS ; interferometry ; diffusion ; polydispersivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics , Technology
    Notes: Abstract Dynamic light scattering (DLS) techniques for studying sizes and shapes of nanoparticles in liquids are reviewed. In photon correlation spectroscopy (PCS), the time fluctuations in the intensity of light scattered by the particle dispersion are monitored. For dilute dispersions of spherical nanoparticles, the decay rate of the time autocorrelation function of these intensity fluctuations is used to directly measure the particle translational diffusion coefficient, which is in turn related to the particle hydrodynamic radius. For a spherical particle, the hydrodynamic radius is essentially the same as the geometric particle radius (including any possible solvation layers). PCS is one of the most commonly used methods for measuring radii of submicron size particles in liquid dispersions. Depolarized Fabry-Perot interferometry (FPI) is a less common dynamic light scattering technique that is applicable to optically anisotropic nanoparticles. In FPI the frequency broadening of laser light scattered by the particles is analyzed. This broadening is proportional to the particle rotational diffusion coefficient, which is in turn related to the particle dimensions. The translational diffusion coefficient measured by PCS and the rotational diffusion coefficient measured by depolarized FPI may be combined to obtain the dimensions of non-spherical particles. DLS studies of liquid dispersions of nanometer-sized oligonucleotides in a water-based buffer are used as examples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010067107182
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  • 8
    Electronic Resource
    Electronic Resource
    Fluxes of methane and carbon dioxide from a small productive lake to the atmosphere (2000)
    Springer
    Biogeochemistry 49 (2000), S. 1-19 
    Details
    ISSN: 1573-515X
    Keywords: carbon dioxide ; diffusion ; ebullition ; emission ; freshwater ; hypertrophic lakes ; methane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The fluxes of CH4 and CO2 to the atmosphere, and the relative contributions of ebullition and molecular diffusion, were determined for a small hypertrophic freshwater lake (Priest Pot, UK) over the period May to October 1997. The average total flux of CH4 and CO2 (estimated from 7 sites on the lake) was approximately 52 mmol m−2 d−1 and was apportioned 12 and 40 mmol m−2 d−1 toCH4 and CO2 respectively. Diffusion across the air-water interface accounted for the loss of 0.4and 40 mmol m−2 d−1 of CH4 and CO2 respectively whilst the corresponding figures for ebullition losses were 12.0 (CH4) and 0.23 (CO2) mmol m−2 d−1. Most CH4 (96%) was lost by ebullition, and most CO2 (99%) by diffusive processes. The ebullition of gas, measured at weekly intervals along a transect of the lake, showed high spatial and temporal variation. The CH4 content of the trapped gas varied between 44 and 88% (by volume) and was highest at the deepest points. Pulses of gas ebullition were detected during periods of rapidly falling barometric pressure. Therelevance of the measurements to global estimates ofcarbon emission from freshwaters are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006269900174
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  • 9
    Electronic Resource
    Electronic Resource
    Microscopic Chaos and Diffusion (2000)
    Springer
    Journal of statistical physics 101 (2000), S. 775-817 
    Details
    ISSN: 1572-9613
    Keywords: chaos ; diffusion ; Ehrenfest wind-tree model ; Lorentz gas ; statistical mechanics ; periodic orbits ; Brownian motion ; billiards ; time series analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We investigate the connections between microscopic chaos, defined on a dynamical level and arising from collisions between molecules, and diffusion, characterized by a mean square displacement proportional to the time. We use a number of models involving a single particle moving in two dimensions and colliding with fixed scatterers. We find that a number of microscopically nonchaotic models exhibit diffusion, and that the standard methods of chaotic time series analysis are ill suited to the problem of distinguishing between chaotic and nonchaotic microscopic dynamics. However, we show that periodic orbits play an important role in our models, in that their different properties in our chaotic and nonchaotic models can be used to distinguish them at the level of time series analysis, and in systems with absorbing boundaries. Our findings are relevant to experiments aimed at verifying the existence of chaoticity and related dynamical properties on a microscopic level in diffusive systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026477605331
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  • 10
    Electronic Resource
    Electronic Resource
    On the Convergence of the Boltzmann Equation for Semiconductors Toward the Energy Transport Model (2000)
    Springer
    Journal of statistical physics 98 (2000), S. 835-870 
    Details
    ISSN: 1572-9613
    Keywords: Boltzmann equation ; semiconductor ; diffusion ; energy transport model ; entropy dissipation rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The diffusion limit of the Boltzmann equation of semiconductors is analyzed. The dominant collisions are the elastic collisions on one hand and the electron–electron collisions with the Pauli exclusion terms on the other hand. Under a nondegeneracy hypothesis on the distribution function, a lower bound of the entropy dissipation rate of the leading term of the Boltzmann kernel for semiconductors in terms of a distance to the space of Fermi–Dirac functions is proved. This estimate and a mean compactness lemma are used to prove the convergence of the solution of the Boltzmann equation to a solution of the energy transport model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018635827617
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