Diffusive Component

2016 ◽  
Author(s):  
Masahide Terazima ◽  
Noboru Hirota ◽  
Silvia E. Braslavsky ◽  
Andreas Mandelis ◽  
Stephen E. Bialkowski ◽  
...  
Keyword(s):  
Diffusive Component

Tetraethylammonium transport by isolated perfused snake renal tubules

1984 ◽  
Vol 246 (4) ◽  
pp. F476-F487 ◽  
Author(s):  
C. T. Hawk ◽  
W. H. Dantzler
Keyword(s):  
Transepithelial Transport ◽  
Renal Tubules ◽  
Chemical Gradient ◽  
Saturation Kinetics ◽  
Sodium Dependency ◽  
Diffusive Component

Tetraethylammonium (TEA) transport was studied in isolated perfused snake (Thamnophis spp.) proximal renal tubules. Unidirectional lumen-to-bath (J1----bTEA) and bath-to-lumen (J1----bTEA) fluxes exhibited saturation kinetics, but Jb----1TEA also exhibited an apparent diffusive component and J1----bTEA did not. Jb----1TEA exceeded J1----bTEA at all concentrations studied, resulting in net TEA secretion. Transport into cells across both luminal and peritubular membranes was apparently against an electro-chemical gradient and was inhibited by cyanide. Km for J1----bTEA (5.9 microM) was about one-third Km for Jb----1TEA (19.9 microM), indicating greater affinity of the luminal transporter for TEA; but Vmax for Jb----1TEA (153 fmol X min-1 X mm-1) was about six times Vmax for J1----bTEA (27 fmol X min-1 X mm-1), indicating a greater capacity of the peritubular transporter for TEA, which could account for net TEA secretion. Jb----1TEA was inhibited by N-methylnicotinamide (NMN) in the bath, but J1----bTEA was inhibited initially and then apparently transstimulated by NMN in the lumen, indicating possible countertransport. J1----bTEA, but not Jb----1TEA, was significantly reduced by replacement of sodium with sucrose, indicating possible sodium dependency of the luminal transporter. All data indicate active (either primary or secondary) TEA transport at both luminal and peritubular membranes but net transepithelial transport in the bath-to-lumen direction.

LED Backlight Module by a Lightguide-Diffusive Component With Tetrahedron Reflector Array

2012 ◽  
Vol 8 (6) ◽  
pp. 321-328 ◽  
Author(s):  
Jang-Zern Tsai ◽  
Rong-Seng Chang ◽  
Tung-Yen Li ◽  
Thomas Chiang Chuang
Keyword(s):  
Led Backlight ◽  
Diffusive Component

Kinetics of potassium uptake in red spruce seedlings

1985 ◽  
Vol 63 (3) ◽  
pp. 512-516
Author(s):  
J. R. Cumming ◽  
R. T. Eckert ◽  
L. S. Evans
Keyword(s):  
Nonlinear Least Squares ◽  
Theoretical Models ◽  
Potassium Uptake ◽  
Red Spruce ◽  
Saturation Kinetics ◽  
Potassium Absorption ◽  
Parameter Values ◽  
Kinetics Of ◽  
Diffusive Component ◽  
Nutrient Solutions

Potassium uptake by roots of 3-week-old red spruce (Picea rubens Sarg.) seedlings was measured in nutrient solutions ranging in K+ concentration from 0.01 to 10.0 mM. Nonlinear least squares analysis was used to estimate uptake parameters Vmax and Km. Analyses of residuals generated by several theoretical models of ion uptake were undertaken to choose the best mechanistic uptake model. Potassium absorption by red spruce seedlings was characterized by Michaelis–Menten behavior from K+ solutions in the range 0.01 to 1.0 mM. Above 1.0 mM, accumulation of potassium was most readily accounted for by a linear diffusive component superimposed on saturation kinetics. Uptake parameter values of Vmax = 1.17 μmol K∙g fresh weight−1∙h−1 and Km = 0.083 mM were similar to those reported for other species. The culture of seedlings in full-strength nutrient solution did not reduce the ability to resolve these uptake parameters in short-term experiments.

LED Backlight Module by Lightguide-Diffusive Component

2012 ◽  
Vol 8 (2) ◽  
pp. 79-86 ◽  
Author(s):  
Rong-Seng Chang ◽  
Jang-Zern Tsai ◽  
Tung-Yen Li ◽  
Hsiang-Lin Liao
Keyword(s):  
Led Backlight ◽  
Diffusive Component

Base secretion in rat distal colon: ionic requirements

1990 ◽  
Vol 258 (6) ◽  
pp. G825-G832 ◽  
Author(s):  
G. M. Feldman ◽  
J. D. Koethe ◽  
R. L. Stephenson
Keyword(s):  
Permeability Coefficient ◽  
Distal Colon ◽  
Secretory Component ◽  
Bathing Solution ◽  
Apical Surface ◽  
Apparent Permeability ◽  
Rat Distal Colon ◽  
Apparent Permeability Coefficient ◽  
Diffusive Component ◽  
Active Base

To evaluate the ionic requirements of colonic base secretion, segments of rat distal colon were studied under short-circuited conditions. Net base flux was composed of an active secretory component and a diffusive component. Studied in the absence of a transepithelial HCO3- concentration gradient, active base secretion was dependent on the HCO3- concentration of the bathing solution but was not influenced by the CO2 tension or pH. Base secretion appeared to saturate with a Km of 33 +/- 9 mM and was inhibited by ouabain. The diffusive component was characterized by an apparent permeability coefficient to HCO3- of 8.9 +/- 0.9 x 10(-6) cm/s. In addition to requiring HCO3- on the serosal surface, net base secretion was inhibited by reducing the Na+ concentration in the serosal medium and the Cl- concentration in the mucosal medium. These data suggest that colonic base secretion involves HCO3- entry across the basolateral surface, energized by the Na+ gradient, and HCO3- exit across the apical surface in exchange for Cl-.

The Cyclic Carburization Process by Bi-velocity Method

2015 ◽  
Vol 34 (4) ◽  
Author(s):  
Bartek Wierzba ◽  
Jolanta Romanowska ◽  
Krzysztof Kubiak ◽  
Jan Sieniawski
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
Stress Distribution ◽  
Stress Field ◽  
Diffusion Coefficients ◽  
Numerical Solutions ◽  
Concentration Profiles ◽  
Controlled Processes ◽  
Diffusion Controlled ◽  
Diffusive Component

AbstractThe paper presents numerical analysis of the cyclic external fluxes on diffusion process. It is shown, that the cycles characteristics strongly affects the concentration profiles and stress distribution in material. Calculations were performed using the bi-velocity method with the stress field factor. Moreover, the more general model describing the cyclic carburization process influenced by self stress was formulated. Numerical solutions were obtained assuming composition dependent diffusion coefficients. The results of simulation were compared with the experimental data. The model proposed in this paper may be applied to other diffusion controlled processes with the external flux of the diffusive component.

Diffusive Component

2016 ◽  
Author(s):  
Masahide Terazima ◽  
Noboru Hirota ◽  
Silvia E. Braslavsky ◽  
Andreas Mandelis ◽  
Stephen E. Bialkowski ◽  
...  
Keyword(s):  
Diffusive Component

scholarly journals Isopycnal Averaging at Constant Height. Part II: Relating to the Residual Streamfunction in Eulerian Space

2004 ◽  
Vol 34 (12) ◽  
pp. 2740-2755 ◽  
Author(s):  
A. J. George Nurser ◽  
Mei-Man Lee
Keyword(s):  
Taylor Expansion ◽  
Boundary Surface ◽  
Diffusive Flux ◽  
Eddy Flux ◽  
Advective Flow ◽  
Constant Height ◽  
The Relationship ◽  
Transformed Eulerian Mean ◽  
Vertical Eddy ◽  
Diffusive Component

Abstract In Part I, the “vertical” transport streamfunction was defined as resulting from isopycnic averaging at constant height in the same way that the meridional streamfunction results from averaging at constant latitude. Part II here discusses the relationship between these two isopycnic streamfunctions and the Eulerian residual streamfunction that arises from the transformed Eulerian mean (TEM). It is known that the meridional isopycnic streamfunction can be approximated by a Taylor expansion to give an Eulerian residual streamfunction involving the horizontal eddy flux. This Taylor expansion approximation works well in the interior, removing the spurious mixing associated with the simple Eulerian-averaged streamfunction. However, it fails near the surface where isopycnals outcrop to the surface. It can be shown in a similar way that the vertical isopycnic streamfunction can formally be approximated by a residual streamfunction involving the vertical eddy flux. However, if horizontal isopycnal displacements are large, this approximation fails even in the ocean interior. Inspired by the two different residual streamfunctions, a more general form of TEM formulation is explored. It is shown that the different TEM residual streamfunctions arise from decomposing the eddy flux into a component along isopycnals, which leads to advective flow, and a remaining diffusive component, which is oriented either vertically or horizontally. In theory the diffusive flux can be oriented in any direction, although in practice the orientation should be such that neither the advective flow nor the diffusive flux cross any boundary (surface, sidewalls, and bottom). However, it is not clear how to merge the continuously changing orientation in a physically meaningful way. A variety of approaches are discussed.

Generalized Ballistic-Diffusive Formulation and Hybrid SN-PN Solution of the Boltzmann Transport Equation for Phonons for Nonequilibrium Heat Conduction

2011 ◽  
Vol 133 (9) ◽  
Author(s):  
Arpit Mittal ◽  
Sandip Mazumder
Keyword(s):  
Heat Conduction ◽  
Transport Equation ◽  
Large Scale ◽  
A Priori ◽  
Boltzmann Transport Equation ◽  
Transient Heat Conduction ◽  
Discrete Ordinates ◽  
Boltzmann Transport ◽  
Discrete Ordinates Method ◽  
Diffusive Component

A generalized form of the ballistic-diffusive equations (BDEs) for approximate solution of the Boltzmann Transport equation (BTE) for phonons is formulated. The formulation presented here is new and general in the sense that, unlike previously published formulations of the BDE, it does not require a priori knowledge of the specific heat capacity of the material. Furthermore, it does not introduce artifacts such as media and ballistic temperatures. As a consequence, the boundary conditions have clear physical meaning. In formulating the BDE, the phonon intensity is split into two components: ballistic and diffusive. The ballistic component is traditionally determined using a viewfactor formulation, while the diffusive component is solved by invoking spherical harmonics expansions. Use of the viewfactor approach for the ballistic component is prohibitive for complex large-scale geometries. Instead, in this work, the ballistic equation is solved using two different established methods that are appropriate for use in complex geometries, namely the discrete ordinates method (DOM) and the control angle discrete ordinates method (CADOM). Results of each method for solving the BDE are compared against benchmark Monte Carlo results, as well as solutions of the BTE using standalone DOM and CADOM for two different two-dimensional transient heat conduction problems at various Knudsen numbers. It is found that standalone CADOM (for BTE) and hybrid CADOM-P1 (for BDE) yield the best accuracy. The hybrid CADOM-P1 is found to be the best method in terms of computational efficiency.

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