Log in

Relevant bibliographies by topics / DIFFERENTIAL MOLECULAR DIFFUSION / Journal articles

Journal articles on the topic 'DIFFERENTIAL MOLECULAR DIFFUSION'

To see the other types of publications on this topic, follow the link: DIFFERENTIAL MOLECULAR DIFFUSION.

Author: Grafiati

Published: 10 December 2022

Last updated: 28 January 2023

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the top 50 journal articles for your research on the topic 'DIFFERENTIAL MOLECULAR DIFFUSION.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.

1

Torga, Jorge R., Mario C. Marconi, R. Martı́n Negri, and Pedro F. Aramendı́a. "Molecular rotational diffusion detected by differential fluorescence energy." Chemical Physics 253, no. 2-3 (March 2000): 249–57. http://dx.doi.org/10.1016/s0301-0104(99)00398-5.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Sannan, Sigurd, and Alan R. Kerstein. "Differential Molecular Diffusion in a Hydrogen-Rich Jet." Energy Procedia 86 (January 2016): 304–14. http://dx.doi.org/10.1016/j.egypro.2016.01.031.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Chen, Yung-Cheng, and Jyh-Yuan Chen. "Fuel-dilution effect on differential molecular diffusion in laminar hydrogen diffusion flames." Combustion Theory and Modelling 2, no. 4 (December 1998): 497–514. http://dx.doi.org/10.1088/1364-7830/2/4/009.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Kerstein, A. R., M. A. Cremer, and P. A. McMurtry. "Scaling properties of differential molecular diffusion effects in turbulence." Physics of Fluids 7, no. 8 (August 1995): 1999–2007. http://dx.doi.org/10.1063/1.868511.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Vrbik, Jan, Daniel A. Legare, and Stuart M. Rothstein. "Infinitesimal differential diffusion quantum Monte Carlo: Diatomic molecular properties." Journal of Chemical Physics 92, no. 2 (January 15, 1990): 1221–27. http://dx.doi.org/10.1063/1.458130.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

JACKSON, P. RYAN, and CHRIS R. REHMANN. "Theory for differential transport of scalars in sheared stratified turbulence." Journal of Fluid Mechanics 621 (February 12, 2009): 1–21. http://dx.doi.org/10.1017/s0022112008004308.

Full text

Abstract:

Scalars with different molecular diffusivities can be transported at different rates in a strongly stratified, weakly turbulent flow. Rapid distortion theory (RDT) is used to examine the mechanisms responsible for differential diffusion of scalars in a sheared stratified flow. The theory, which applies when the flow is strongly stratified, predicts upgradient flux and its wavenumber dependence, which previous direct numerical simulations have shown to be important in differential diffusion. The net effect of shear on differential diffusion depends on the Grashof number, or the relative importance of buoyancy and viscous effects. RDT also allows the effects of the density ratio, Schmidt number, Lewis number, scalar activity and mean shear to be examined without the high computational cost of direct numerical simulation. RDT predicts that differential diffusion will increase with increasing density ratio, but only at low Grashof number. When the Lewis number is fixed, the Grashof number below which differential diffusion occurs decreases with increasing Schmidt number, and when one of the Schmidt numbers is fixed, differential diffusion decreases with increasing Lewis number. Also, differential transport of passive scalars increases when the Schmidt number of the scalar stratifying the flow increases.

APA, Harvard, Vancouver, ISO, and other styles

7

TANAKA, Atsushi, Susumu NODA, and Yoshiaki ONUMA. "211 On modelling of differential molecular diffusion in nonreacting turbulent jets." Proceedings of Conference of Tokai Branch 2000.49 (2000): 79–80. http://dx.doi.org/10.1299/jsmetokai.2000.49.79.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Chen, Andy, Ping Zhang, Zhiyao Duan, Guofeng Wang, and Hiroki Yokota. "Modelling the Molecular Transportation of Subcutaneously Injected Salubrinal." Biomedical Engineering and Computational Biology 3 (January 2011): BECB.S7050. http://dx.doi.org/10.4137/becb.s7050.

Full text

Abstract:

For the subcutaneous administration of a chemical agent (salubrinal), we constructed a mathematical model of molecule transportation and subsequently evaluated the kinetics of diffusion, convection, and molecular turnover. Salubrinal is a potential therapeutic agent that can reduce cellular damage and death. The understanding of its temporal profiles in local tissue as well as in a whole body is important to develop a proper strategy for its administration. Here, the diffusion and convection kinetics was formulated using partial and ordinary differential equations in one- and three-dimensional (semi-spherical) coordinates. Several key parameters including an injection velocity, a diffusion coefficient, thickness of subcutaneous tissue, and a permeability factor at the tissue-blood boundary were estimated from experimental data in rats. With reference to analytical solutions in a simplified model without convection, numerical solutions revealed that the diffusion coefficient and thickness of subcutaneous tissue determined the timing of the peak concentration in the plasma, and its magnitude was dictated by the permeability factor. Furthermore, the initial velocity, induced by needle injection, elevated an immediate transport of salubrinal at t < 1h. The described analysis with a combination of partial and ordinary differential equations contributes to the prediction of local and systemic effects and the understanding of the transportation mechanism of salubrinal and other agents.

APA, Harvard, Vancouver, ISO, and other styles

9

Pai, T. Y., C. F. Ouyang, Y. C. Liao, and H. G. Leu. "Qxygen transfer in gravity flow sewers." Water Science and Technology 42, no. 3-4 (August 1, 2000): 417–22. http://dx.doi.org/10.2166/wst.2000.0412.

Full text

Abstract:

Oxygen diffused to water in gravity sewer pipes was studied in a 21 m long, 0.15 m diameter model sewer. At first, the sodium sulfide was added into the clean water to deoxygenate, then the pump was started to recirculate the water and the deoxygenated water was reaerated. The dissolved oxygen microelectrode was installed to measure the dissolved oxygen concentrations varied with flow velocity, time and depth. The dissolved oxygen concentration profiles were constructed and observed. The partial differential equation diffusion model that considered Fick's law including the molecular diffusion term and eddy diffusion term were derived. The analytic solution of the partial differential equation was used to determine the diffusivities by the method of nonlinear regression. The diffusivity values for the oxygen transfer was found to be a function of molecular diffusion, eddy diffusion and flow velocity.

APA, Harvard, Vancouver, ISO, and other styles

10

Brownell, C. J., and L. K. Su. "Planar laser imaging of differential molecular diffusion in gas-phase turbulent jets." Physics of Fluids 20, no. 3 (March 2008): 035109. http://dx.doi.org/10.1063/1.2884465.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Wang, Haifeng. "Consistent flamelet modeling of differential molecular diffusion for turbulent non-premixed flames." Physics of Fluids 28, no. 3 (March 2016): 035102. http://dx.doi.org/10.1063/1.4942514.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Kerstein, Alan R. "Linear-eddy modelling of turbulent transport. Part 3. Mixing and differential molecular diffusion in round jets." Journal of Fluid Mechanics 216 (July 1990): 411–35. http://dx.doi.org/10.1017/s0022112090000489.

Full text

Abstract:

The linear-eddy model of turbulent mixing represents a spatially developing flow by simulating the time development along a comoving transverse line. Along this line, scalar quantities evolve by molecular diffusion and by randomly occurring spatial rearrangements, representing turbulent convection. The modelling approach, previously applied to homogeneous turbulence and to planar shear layers, is generalized to axisymmetric flows. This formulation captures many features of jet mixing, including differential molecular diffusion effects. A novel experiment involving two unmixed species in the nozzle fluid is proposed and analysed.

APA, Harvard, Vancouver, ISO, and other styles

13

Fa, Kwok Sau. "Integro-differential diffusion equation and neutron scattering experiment." Physica Scripta 90, no. 2 (January 28, 2015): 025003. http://dx.doi.org/10.1088/0031-8949/90/2/025003.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

ULITSKY, MARK, T. VAITHIANATHAN, and LANCE R. COLLINS. "A spectral study of differential diffusion of passive scalars in isotropic turbulence." Journal of Fluid Mechanics 460 (June 10, 2002): 1–38. http://dx.doi.org/10.1017/s0022112001006607.

Full text

Abstract:

In a companion paper, Ulitsky & Collins (2000) applied the eddy-damped quasi-normal Markovian (EDQNM) turbulence theory to the mixing of two inert passive scalars with different diffusivities in stationary isotropic turbulence. Their paper showed that a rigorous application of the EDQNM approximation leads to a scalar covariance spectrum that violates the Cauchy–Schwartz inequality over a range of wavenumbers. The violation results from the improper functionality of the inverse diffusive time scales that arise from the Markovianization of the time evolution of the triple correlations. The modified inverse time scale they proposed eliminates this problem and allows meaningful predictions of the scalar covariance spectrum both with and without a uniform mean gradient.This study uses the modified EDQNM model to investigate the spectral dynamics of differential diffusion. Consistent with recent DNS results by Yeung (1996), we observe that whereas spectral transfer is predominantly from low to high wavenumbers, spectral incoherence, being of molecular origin, originates at high wavenumbers and is transferred in the opposite direction by the advective terms. Quantitative comparisons between the EDQNM model and the DNS show good agreement. In addition, the model is shown to give excellent estimates for the dissipation coefficient defined by Yeung (1998).We show that the EDQNM scalar covariance spectrum for two scalars with different molecular diffusivities can be approximated by the EDQNM autocorrelation spectrum for a scalar with molecular diffusivity equal to the arithmetic mean of the first two scalars. The result is exact for the case of an isotropic scalar and is shown to be a very good approximation for the scalar with a uniform mean gradient. We then exploit this relationship to derive a simple formula for the correlation coefficient of two differentially diffusing scalars as a function of their two Schmidt numbers and the turbulent Reynolds number. A comparison of the formula with the EDQNM model shows the model predicts the correct Reynolds number scaling and qualitatively predicts the dependence on the Schmidt numbers.To investigate the degree of local versus non-local transfer of the scalar covariance spectrum, we divided the energy spectrum into three ranges corresponding to the energy-containing eddies, the inertial range, and the dissipation range. Then, by conditioning the scalar transfer on the energy contained within each of the three ranges, we have determined that the transfer process is dominated first by local interactions (local transfer) followed by non-local interactions leading to local transfer. Non-local interactions leading to non-local transfer are found to be significant at the higher wavenumbers. This result has important implications for defining simpler spectral models that potentially can be applied to more complex engineering flows.

APA, Harvard, Vancouver, ISO, and other styles

15

Khrennikov, Andrei, Sergei Kozyrev, and Alf Månsson. "Hierarchical model of the actomyosin molecular motor based on ultrametric diffusion with drift." Infinite Dimensional Analysis, Quantum Probability and Related Topics 18, no. 02 (June 2015): 1550013. http://dx.doi.org/10.1142/s0219025715500137.

Full text

Abstract:

We discuss the approach to investigate molecular machines using systems of integro–differential ultrametric (p-adic) reaction–diffusion equations with drift. This approach combines the features of continuous and discrete dynamic models. We apply this model to investigation of actomyosin molecular motor. The introduced system of equations is solved analytically using p-adic wavelet theory. We find explicit stationary solutions and behavior in the relaxation regime.

APA, Harvard, Vancouver, ISO, and other styles

16

Gargett, Ann E., William J. Merryfield, and Greg Holloway. "Direct Numerical Simulation of Differential Scalar Diffusion in Three-Dimensional Stratified Turbulence." Journal of Physical Oceanography 33, no. 8 (August 1, 2003): 1758–82. http://dx.doi.org/10.1175/2403.1.

Full text

Abstract:

Abstract The potential for differential turbulent transport of oceanic temperature (T) and salinity (𝒮) is explored using three-dimensional direct numerical simulations of decaying stratified turbulence. The simulations employ a realistic molecular diffusion coefficient for T, and one for a “salt” scalar S that is 10 times smaller. Initially, a uniformly stratified medium is disturbed by a turbulent burst whose initial energy is assigned a range of values. In each instance, transports of T integrated over the subsequent decay of the burst exceed those of S. The more energetic cases occupy parameter ranges similar to, and exhibit spectral characteristics that are essentially indistinguishable from, those of direct observations of turbulence in the stratified ocean interior. In these cases, the turbulent diffusivity of T exceeds that of S by 6%–22%. These simulations underestimate the degree of differential diffusion between T and salinity 𝒮 (which has a molecular diffusivity 100 times less than T); thus at the Reynolds numbers attained by the simulations these results constitute lower bounds for differential diffusion associated with sporadic turbulence in the ocean. The simulation results are consistent with previous laboratory and two-dimensional numerical experiments and suggest that the assumption of equal turbulent diffusivities for T and 𝒮, commonly used in circulation modeling and in interpreting oceanic mixing measurements, should be reconsidered.

APA, Harvard, Vancouver, ISO, and other styles

17

Li, Chunmei, Min Chen, Ben Wan, Jingying Yu, Ming Liu, Wei Zhang, and Jianye Wang. "A comparative study of Gaussian and non-Gaussian diffusion models for differential diagnosis of prostate cancer with in-bore transrectal MR-guided biopsy as a pathological reference." Acta Radiologica 59, no. 11 (February 27, 2018): 1395–402. http://dx.doi.org/10.1177/0284185118760961.

Full text

Abstract:

Background Although several studies have been reported on evaluating the performance of Gaussian and different non-Gaussian diffusion models on prostate cancer, few studies have been reported on the comparison of different models on differential diagnosis for prostate cancer. Purpose To compare the utility of various metrics derived from monoexponential model (MEM), biexponential model (BEM), stretched-exponential model (SEM) based diffusion-weighted imaging (DWI) and diffusion kurtosis imaging (DKI) in the differential diagnosis of prostate cancer. Material and Methods Thirty-three patients underwent magnetic resonance imaging (MRI) examination. Multi-b value and multi-direction DWIs were performed. In-bore MR-guided biopsy was performed. Apparent diffusion coefficient (ADC), pure molecular diffusion (ADCslow), pseudo-diffusion coefficient (ADCfast), perfusion fraction (f), water molecular diffusion heterogeneity index (α), distributed diffusion coefficient (DDC), non-Gaussian diffusion coefficient (MD), and mean kurtosis (MK) values were calculated and compared between cancerous and non-cancerous groups. Receiver operating characteristic (ROC) analysis was performed for all parameters and models. Results ADC, ADCslow, DDC, and MD values were significantly lower while MK value was significantly higher in prostate cancer than those of prostatitis and benign prostatic hyperplasia. ADC, ADCslow, DDC, MD, and MK could discriminate between tumor and non-tumorous lesions (area under the curve, 0.856, 0.835, 0.866, 0.918, and 0.937, respectively). MK was superior to ADC in the discrimination of prostate cancer. DKI was superior to MEM in the discrimination of prostate cancer. Conclusions Parameters derived from both Gaussian and non-Gaussian models could characterize prostate cancer. DKI may be advantageous than DWI for detection of prostate cancer.

APA, Harvard, Vancouver, ISO, and other styles

18

Dibble, R. W., L. L. Smith, L. Talbot, R. S. Barlow, and C. D. Carter. "MEASUREMENTS OF DIFFERENTIAL MOLECULAR DIFFUSION IN TURBULENT NONPREMIXED JET FLAMES OF H2-CO2 FUEL." International Journal of Energetic Materials and Chemical Propulsion 3, no. 1-6 (1994): 479–97. http://dx.doi.org/10.1615/intjenergeticmaterialschemprop.v3.i1-6.500.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Han, Chao, Tejas Pant, Utsav Jain, and Haifeng Wang. "Consistent modeling of differential molecular diffusion to yield desired Reynolds-number power-law scaling." Physics of Fluids 30, no. 8 (August 2018): 085108. http://dx.doi.org/10.1063/1.5045336.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Huiszoon, C., and W. J. Briels. "The static dipole polarizabilities of helium and molecular hydrogen by differential diffusion Monte Carlo." Chemical Physics Letters 203, no. 1 (February 1993): 49–54. http://dx.doi.org/10.1016/0009-2614(93)89309-6.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Gad Elkareem, Ashraf M., Ben Willikens, Jean Marie Stassen, and Marc D. de Smet. "Differential Vitreous Dye Diffusion Following Microplasmin or Plasmin Pre-Treatment." Current Eye Research 35, no. 3 (March 2010): 235–41. http://dx.doi.org/10.3109/02713680903484259.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Gebauer, Christian, Olaf Klein, Ralf Schmidt, and Wolfhart Seidel. "Helium Atom Scattering from CF4, CF3Cl, CF2Cl2 and CFCl3 in Crossed Molecular Bejams." Zeitschrift für Naturforschung A 50, no. 4-5 (May 1, 1995): 468–74. http://dx.doi.org/10.1515/zna-1995-4-521.

Full text

Abstract:

Abstract Differential cross sections have been measured by scattering He atoms from CFnCl4-n (1≤n≤4) in crossed molecular beams. The damping of the diffraction oscillations was used to extract interaction potentials for these molecules which range from nearly isotropic to rather anisotropic. Macroscopic binary parameters, as second virial coefficients, diffusion coefficients and viscosities were calculated from these potentials

APA, Harvard, Vancouver, ISO, and other styles

23

Han, Chao, David O. Lignell, Evatt R. Hawkes, Jacqueline H. Chen, and Haifeng Wang. "Examination of the effect of differential molecular diffusion in DNS of turbulent non-premixed flames." International Journal of Hydrogen Energy 42, no. 16 (April 2017): 11879–92. http://dx.doi.org/10.1016/j.ijhydene.2017.01.094.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Sannan, Sigurd, and Alan R. Kerstein. "Numerical Simulation of Differential Molecular Diffusion Effects in a Hydrogen-rich Turbulent Jet Using LEM3D." Energy Procedia 51 (2014): 253–58. http://dx.doi.org/10.1016/j.egypro.2014.07.029.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Maisuradze, Mikhail V., and Alexandra A. Kuklina. "Numerical Solution of the Differential Diffusion Equation for a Steel Carburizing Process." Solid State Phenomena 284 (October 2018): 1230–34. http://dx.doi.org/10.4028/www.scientific.net/ssp.284.1230.

Full text

Abstract:

The simplified algorithm of the numerical solution of the differential diffusion equation is presented. The solution is based on the one-dimensional diffusion model with the third kind boundary conditions and the finite difference method. The proposed approach allows for the quick and precise assessment of the carburizing process parameters – temperature and time.

APA, Harvard, Vancouver, ISO, and other styles

26

Breer, Jörg, Klaus de Groot, and Hansjürgen Schönert. "Diffusion in the Diaphragm Cell: Continuous Monitoring of the Concentrations and Determination of the Differential Diffusion Coefficient." Journal of Solution Chemistry 43, no. 1 (July 9, 2013): 71–82. http://dx.doi.org/10.1007/s10953-013-0020-z.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Hammer, Markus, and Wolfhart Seidel. "Helium Atom Scattering from C2H6, F2HCCH3, F3CCH2F and C2F6 in Crossed Molecular Beams." Zeitschrift für Naturforschung A 52, no. 10 (October 1, 1997): 695–701. http://dx.doi.org/10.1515/zna-1997-1002.

Full text

Abstract:

Abstract Rotationally unresolved differential cross sections were measured in crossed molecular beam experiments by scattering Helium atoms from Ethane, 1,1-Difluoroethane, 1,1,1,2-Tetrafluoroethane and Hexafluoroethane. The damping of observed diffraction oscillations was used to extract anisotropic interaction potentials for these scattering systems applying the infinite order sudden approximation (IOSA). Binary macroscopic parameters such as second heterogeneous virial coefficients and the coefficients of diffusion and viscosity were computed from these potentials and compared to results from macroscopic experiments.

APA, Harvard, Vancouver, ISO, and other styles

28

Munir, Noor, Majid Khan, Iqtadar Hussain, and Muhammad Amin. "Differential cryptanalysis of diffusion and confusion based information confidentiality mechanism." Optik 259 (June 2022): 168989. http://dx.doi.org/10.1016/j.ijleo.2022.168989.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Yang, Yang, Jianhui Lan, Bo Liang, Di Wang, Liman Chen, Meng Zhang, Caishan Jiao, et al. "Molecular Dynamics Simulations of Metal Electrode/Molten LiCl-KCl-UCl₃ Mixtures Interface." Journal of The Electrochemical Society 169, no. 3 (March 1, 2022): 032503. http://dx.doi.org/10.1149/1945-7111/ac579a.

Full text

Abstract:

The structural and dynamical properties of the interface between metal electrode/molten LiCl-KCl-UCl3 mixtures were studied through constant charge molecular dynamics simulation. We observed a layered structure of the metal electrode/molten LiCl-KCl-UCl3 mixtures interface composed by multiple layers of anions and cations. The distribution of U3+ at the interface was ordered, and the increase of electrode charges promoted this ordered interfacial distribution. The differential capacitance curve was a flattened and bell-like shape with the maximum at a negative surface charge due to the characteristic adsorption of cations. Moreover, the interfacial dynamical properties were described qualitatively, and an additional barrier to the diffusion along z-direction caused by layered distribution was found to explain the limitation of diffusion in z-direction at the interface.

APA, Harvard, Vancouver, ISO, and other styles

30

Smith, L. L., R. W. Dibble, L. Talbot, R. S. Barlow, and C. D. Carter. "Laser Raman scattering measurements of differential molecular diffusion in turbulent nonpremixed jet flames of H2CO2 fuel." Combustion and Flame 100, no. 1-2 (January 1995): 153–60. http://dx.doi.org/10.1016/0010-2180(94)00066-2.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Yu, C., and U. Maas. "Implementation of the Scalar Dissipation Rate in the REDIM Concept and its Validation for the Piloted Non-Premixed Turbulent Jet Flames." Eurasian Chemico-Technological Journal 23, no. 3 (November 10, 2021): 169. http://dx.doi.org/10.18321/ectj1100.

Full text

Abstract:

In order to address the impact of the concentration gradients on the chemistry – turbulence interaction in turbulent flames, the REDIM reduced chemistry is constructed incorporating the scalar dissipation rate, which is a key quantity describing the turbulent mixing process. This is achieved by providing a variable gradient estimate in the REDIM evolution equation. In such case, the REDIM reduced chemistry is tabulated as a function of the reduced coordinates and the scalar dissipation rate as an additional progress variable. The constructed REDIM is based on a detailed transport model including the differential diffusion, and is validated for a piloted non-premixed turbulent jet flames (Sandia Flame D and E). The results show that the newly generated REDIM can reproduce the thermo-kinetic quantities very well, and the differential molecular diffusion effect can also be well captured.

APA, Harvard, Vancouver, ISO, and other styles

32

Porion, Patrice, Ali Asaad, Thomas Dabat, Baptiste Dazas, Alfred Delville, Eric Ferrage, Fabien Hubert, et al. "Water and Ion Dynamics in Confined Media: A Multi-Scale Study of the Clay/Water Interface." Colloids and Interfaces 5, no. 2 (June 15, 2021): 34. http://dx.doi.org/10.3390/colloids5020034.

Full text

Abstract:

This review details a large panel of experimental studies (Inelastic Neutron Scattering, Quasi-Elastic Neutron Scattering, Nuclear Magnetic Resonance relaxometry, Pulsed-Gradient Spin-Echo attenuation, Nuclear Magnetic Resonance Imaging, macroscopic diffusion experiments) used recently to probe, over a large distribution of characteristic times (from pico-second up to days), the dynamical properties of water molecules and neutralizing cations diffusing within clay/water interfacial media. The purpose of this review is not to describe these various experimental methods in detail but, rather, to investigate the specific dynamical information obtained by each of them concerning these clay/water interfacial media. In addition, this review also illustrates the various numerical methods (quantum Density Functional Theory, classical Molecular Dynamics, Brownian Dynamics, macroscopic differential equations) used to interpret these various experimental data by analyzing the corresponding multi-scale dynamical processes. The purpose of this multi-scale study is to perform a bottom-up analysis of the dynamical properties of confined ions and water molecules, by using complementary experimental and numerical studies covering a broad range of diffusion times (between pico-seconds up to days) and corresponding diffusion lengths (between Angstroms and centimeters). In the context of such a bottom-up approach, the numerical modeling of the dynamical properties of the diffusing probes is based on experimental or numerical investigations performed on a smaller scale, thus avoiding the use of empirical or fitted parameters.

APA, Harvard, Vancouver, ISO, and other styles

33

Ojewumi, Modupe Elizabeth, Moses Eterigho Emetere, Damilola Elizabeth Babatunde, and Joshua Olusegun Okeniyi. "In Situ Bioremediation of Crude Petroleum Oil Polluted Soil Using Mathematical Experimentation." International Journal of Chemical Engineering 2017 (2017): 1–11. http://dx.doi.org/10.1155/2017/5184760.

Full text

Abstract:

Mathematical modelling of in situ (on site) bioremediation of crude petroleum polluted soil was investigated. An unsteady state mathematical model based on bulk flow of oil through the soil and molecular diffusion through the pores of the soil was developed. The parabolic partial differential equation developed was resolved into a system of ordinary differential equations (ODEs) by orthogonal collocation method and the necessary boundary condition was used. The resultant system of ODE was solved using fourth-order Runge-Kutta method. The simulated data gave a good agreement with experimental data.

APA, Harvard, Vancouver, ISO, and other styles

34

Тандоев, А. Г., Т. Т. Мнацаканов, and С. Н. Юрков. "Мощные диоды Шоттки с участком отрицательного дифференциального сопротивления на вольт-амперной характеристике." Физика и техника полупроводников 55, no. 1 (2021): 75. http://dx.doi.org/10.21883/ftp.2021.01.50390.9521.

Full text

Abstract:

It is shown that at high current densities the carrier transport in base layer of Schottky diodes in addition to commonly accepted diffusive and drift currents is defined by recently discovered diffusion stimulated by quasi-neutral drift (DSQD). The influence of this recently discovered component of current on current-voltage characteristics of Schottky diode has been investigated. It was shown that in case if the ratio of base width $W$ to ambipolar diffusive length $L$ is higher than 1 ($W/L>1$) a part with negative differential resistance appears on the current-voltage characteristics of Schottky diode. The results of analytical investigation are confirmed by numerical calculation using INVESTIGATION program.

APA, Harvard, Vancouver, ISO, and other styles

35

Peiffer, Ann M., Lei Shi, John Olson, and Judy K. Brunso-Bechtold. "Differential effects of radiation and age on diffusion tensor imaging in rats." Brain Research 1351 (September 2010): 23–31. http://dx.doi.org/10.1016/j.brainres.2010.06.049.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Maragkos, G., P. Rauwoens, D. Fauconnier, and B. Merci. "Large eddy simulations of differential molecular diffusion in non-reacting turbulent jets of H2/CO2mixing with air." Physics of Fluids 26, no. 2 (February 2014): 025102. http://dx.doi.org/10.1063/1.4864097.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Lanzano, Luca, Tim Lei, Kayo Okamura, Hector Giral, Yupanqui Caldas, Omid Masihzadeh, Enrico Gratton, Moshe Levi, and Judith Blaine. "Differential modulation of the molecular dynamics of the type IIa and IIc sodium phosphate cotransporters by parathyroid hormone." American Journal of Physiology-Cell Physiology 301, no. 4 (October 2011): C850—C861. http://dx.doi.org/10.1152/ajpcell.00412.2010.

Full text

Abstract:

The kidney is a key regulator of phosphate homeostasis. There are two predominant renal sodium phosphate cotransporters, NaPi2a and NaPi2c. Both are regulated by parathyroid hormone (PTH), which decreases the abundance of the NaPi cotransporters in the apical membrane of renal proximal tubule cells. The time course of PTH-induced removal of the two cotransporters from the apical membrane, however, is markedly different for NaPi2a compared with NaPi2c. In animals and in cell culture, PTH treatment results in almost complete removal of NaPi2a from the brush border (BB) within 1 h whereas for NaPi2c this process in not complete until 4 to 8 h after PTH treatment. The reason for this is poorly understood. We have previously shown that the unconventional myosin motor myosin VI is required for PTH-induced removal of NaPi2a from the proximal tubule BB. Here we demonstrate that myosin VI is also necessary for PTH-induced removal of NaPi2c from the apical membrane. In addition, we show that, while at baseline the two cotransporters have similar diffusion coefficients within the membrane, after PTH addition the diffusion coefficient for NaPi2a initially exceeds that for NaPi2c. Thus NaPi2c appears to remain “tethered” in the apical membrane for longer periods of time after PTH treatment, accounting, at least in part, for the difference in response times to PTH of NaPi2a versus NaPi2c.

APA, Harvard, Vancouver, ISO, and other styles

38

Asle-Zaeem, M., and S. D. Mesarovic. "Investigation of Phase Transformation in Thin Film Using Finite Element Method." Solid State Phenomena 150 (January 2009): 29–41. http://dx.doi.org/10.4028/www.scientific.net/ssp.150.29.

Full text

Abstract:

Cahn-Hilliard type of phase field model coupled with elasticity is used to derive governing equations for the stress-mediated diffusion and phase transformation in thin films. To solve the resulting equations, a finite element (FE) model is presented. The partial differential equations governing diffusion and mechanical equilibrium are of different orders; Mixed-order finite elements, with C0 interpolation functions for displacement, and C1 interpolation functions for concentration are implemented. To validate this new numerical solver for such coupled problems, we test our implementation on thin film diffusion couples.

APA, Harvard, Vancouver, ISO, and other styles

39

Ostrikov, A. N., I. S. Bogomolov, and P. V. Filiptsov. "Mathematical modeling of the diffusion process of liquid additives into extruded pellets of feed stuff for prime fish species." Proceedings of the Voronezh State University of Engineering Technologies 82, no. 3 (October 19, 2020): 19–23. http://dx.doi.org/10.20914/2310-1202-2020-3-19-23.

Full text

Abstract:

A mathematical model of the diffusion process of liquid components into extruded pellets of feed stuff for prime fish species under vacuum spraying is considered. This will increase the fat content up to 40% and improve the digestibility and nutritive properties of the feed stuff. It is suggested to use the differential equation of molecular diffusion with boundary conditions of the third kind to describe the process of diffusion of liquid in porous pellets. For a mathematical description, the solution of the equation of unsteady molecular diffusion for bodies with the geometric shape of an unbounded cylinder (extruded pellets can be considered such bodies) was used. The studies carried out with values of the Bio criterion over 100 showed that the concentration of liquid additives inside the extruded pellets becomes equal to the concentration of liquid additives on their surface. Given a constant concentration of liquid additives on the surface of extruded pellets, this solution takes place in the form of a rapidly converging series. Considering that for Fourier numbers greater than 0.3 the series converges quickly, then all the members of the series can be discarded except the first one. Thus, the obtained solution of the equation of unsteady molecular diffusion at a constant concentration of liquid additives on the surface of pellets had the form of a rapidly converging series. Taking the logarithm of the obtained equation and solving its Fourier criterion, we attained the expression for determining the duration of the diffusion process. Comparison of the calculated curves and experimental data showed that the root mean square deviation did not exceed 14.3%. The use of vacuum spraying of liquid additives on the surface of pellets made it possible to increase the diffusion coefficient from 4.78?10e-4 to 6.112?10e-4 м2/с in comparison with the traditional technology of pelleting in a drum apparatus.

APA, Harvard, Vancouver, ISO, and other styles

40

Pantazaka, Evangelia, and Colin W. Taylor. "Differential Distribution, Clustering, and Lateral Diffusion of Subtypes of the Inositol 1,4,5-Trisphosphate Receptor." Journal of Biological Chemistry 286, no. 26 (May 5, 2011): 23378–87. http://dx.doi.org/10.1074/jbc.m111.236372.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Порцель, Л. М., В. Б. Шуман, А. А. Лаврентьев, А. Н. Лодыгин, Н. В. Абросимов, and Ю. А. Астров. "Исследование примеси магния в кремнии." Физика и техника полупроводников 54, no. 4 (2020): 321. http://dx.doi.org/10.21883/ftp.2020.04.49134.9318.

Full text

Abstract:

Profiles of both electrically active and total concentration of magnesium impurity in silicon were measured. Diffusion was performed into the floating zone dislocation-free n-type silicon at the temperatures Tdiff = 1000, 1100◦C and duration from 0.5 to 22.5 h. The depth profiles of the electrically active interstitial magnesium concentration NMgi (x) were determined by differential conductivity method, while the total concentration profile Ntotal(x) — with secondary ion mass spectroscopy. The total concentration of magnesium was found to be almost two orders higher than the concentration NMgi . It turned out that the effective diffusion coefficient DMgi decreases with the diffusion time. Possible physical processes responsible for formation of the electrically inactive component of magnesium impurity and the dependence of effective diffusion coefficient on time are discussed.

APA, Harvard, Vancouver, ISO, and other styles

42

Hayat, T., Z. Iqbal, M. Mustafa, and A. Alsaedi. "Stagnation-point flow of Jeffrey fluid with melting heat transfer and Soret and Dufour effects." International Journal of Numerical Methods for Heat & Fluid Flow 24, no. 2 (February 25, 2014): 402–18. http://dx.doi.org/10.1108/hff-02-2012-0023.

Full text

Abstract:

Purpose – This investigation has been carried out for thermal-diffusion (Dufour) and diffusion-thermo (Soret) effects on the boundary layer flow of Jeffrey fluid in the region of stagnation-point towards a stretching sheet. Heat transfer occurring during the melting process due to a stretching sheet is considered. The paper aims to discuss these issues. Design/methodology/approach – The authors convert governing partial differential equations into ordinary differential equations by using suitable transformations. Analytic solutions of velocity and temperature are found by using homotopy analysis method (HAM). Further graphs are displayed to study the salient features of embedding parameters. Expressions of skin friction coefficient, local Nusselt number and local Sherwood number have also been derived and examined. Findings – It is found that velocity and the boundary layer thickness are increasing functions of viscoelastic parameter (Deborah number). An increase in the melting process enhances the fluid velocity. An opposite effect of melting heat process is noticed on velocity and skin friction. Practical implications – The boundary layer flow in non-Newtonian fluids is very important in many applications including polymer and food processing, transpiration cooling, drag reduction, thermal oil recovery and ice and magma flows. Further, the thermal diffusion effect is employed for isotope separation and in mixtures between gases with very light and medium molecular weight. Originality/value – Very scarce literature is available on thermal-diffusion (Dufour) and diffusion-thermo (Soret) effects on the boundary layer flow of Jeffrey fluid in the region of stagnation-point towards a stretching sheet with melting heat transfer. Series solution is developed using HAM. Further, the authors compare the present results with the existing in literature and found excellent agreement.

APA, Harvard, Vancouver, ISO, and other styles

43

Yeung, P. K. "Multi-scalar triadic interactions in differential diffusion with and without mean scalar gradients." Journal of Fluid Mechanics 321 (August 25, 1996): 235–78. http://dx.doi.org/10.1017/s0022112096007719.

Full text

Abstract:

The spectral mechanisms of the differential diffusion of pairs of passive scalars with different molecular diffusivities are studied in stationary isotropic turbulence, using direct numerical simulation data at Taylor-scale Reynolds number up to 160 on 1283 and 2563 grids. Of greatest interest are the roles of nonlinear triadic interactions between different scale ranges of the velocity and scalar fields in the evolution of spectral coherency between the scalars, and the effects of mean scalar gradients.Analysis of single-scalar spectral transfer (extending the results of a previous study) indicates a robust local forward cascade behaviour at high wavenumbers, which is strengthened by both high diffusivity and mean gradients. This cascade is driven primarily by moderately non-local interactions in which two small-scale scalar modes are coupled via a lower-wavenumber velocity mode near the peak of the energy dissipation spectrum. This forward cascade is coherent, tending to increase the coherency between different scalars at high wavenumbers but to decrease it at lower wavenumbers. However, at early times coherency evolution at high wavenumbers is dominated by de-correlating effects due to a different type of non-local triad consisting of two scalar modes with a moderate scale separation and a relatively high-wavenumber velocity mode. Consequently, although the small-scale motions play little role in spectral transfer, they are responsible for the rapid de-correlation observed at early times. At later times both types of competing triadic interactions become important over a wider wavenumber range, with increased relative strength of the coherent cascade, so that the coherency becomes slow-changing. When uniform mean scalar gradients are present, a stationary state develops in the coherency spectrum as a result of a balance between a coherent mean gradient contribution (felt within about 1 eddy-turnover time) and the net contribution from scale interactions. The latter is made less de-correlating because of a strengthened coherent forward cascade, which is in turn caused by uniform mean gradients acting as a primarily low-wavenumber source of scalar fluctuations with the same spectral content as the velocity field.

APA, Harvard, Vancouver, ISO, and other styles

44

Sikora, Antonín, Bedřich Porsch, and Julius Pouchlý. "Effect of Temperature History upon Stability and Melting of Poly(ethylene oxide)." Collection of Czechoslovak Chemical Communications 58, no. 11 (1993): 2595–604. http://dx.doi.org/10.1135/cccc19932595.

Full text

Abstract:

The effect of temperature history upon the distribution of molecular weights and melting points has been investigated with high-molecular poly(ethylene oxides). The results obtained by the size exclusion chromatography (SEC) and differential scanning calorimetry (DSC) have shown that a long-term annealing of high-molecular poly(ethylene oxides) results in a distinct degradation of polymeric chains. The change in distribution of molecular weights and the presence of oligomers formed by degradation markedly affect the melting points of poly(ethylene oxide). The diffusion of oligomers from crystalline into amorphous regions is manifested by a time change of melting point and crystallinity degree of poly(ethylene oxide). The degradation is also observed during X-ray measurements.

APA, Harvard, Vancouver, ISO, and other styles

45

Smith, L. L., R. W. Dibble, L. Talbot, R. S. Barlow, and C. D. Carter. "Laser Raman scattering measurements of differential molecular diffusion in nonreacting turbulent jets of H2/CO2 mixing with air." Physics of Fluids 7, no. 6 (June 1995): 1455–66. http://dx.doi.org/10.1063/1.868532.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Taheri-Afarani, Hajar, Eugene Mamontov, William R. Carroll, and Joseph J. Biernacki. "A Molecular Description of Hydrogel Forming Polymers for Cement-Based Printing Paste Applications." Gels 8, no. 9 (September 16, 2022): 592. http://dx.doi.org/10.3390/gels8090592.

Full text

Abstract:

This research endeavors to link the physical and chemical characteristics of select polymer hydrogels to differences in printability when used as printing aids in cement-based printing pastes. A variety of experimental probes including differential scanning calorimetry (DSC), NMR-diffusion ordered spectroscopy (DOSY), quasi-elastic neutron scattering (QENS) using neutron backscattering spectroscopy, and X-ray powder diffraction (XRD), along with molecular dynamic simulations, were used. Conjectures based on objective measures of printability and physical and chemical-molecular characteristics of the polymer gels are emerging that should help target printing aid selection and design, and mix formulation. Molecular simulations were shown to link higher hydrogen bond probability and larger radius of gyration to higher viscosity gels. Furthermore, the higher viscosity gels also produced higher elastic properties, as measured by neutron backscattering spectroscopy.

APA, Harvard, Vancouver, ISO, and other styles

47

Holden, Arun V. "Defibrillation in Models of Cardiac Muscle." Journal of Theoretical Medicine 1, no. 2 (1997): 91–102. http://dx.doi.org/10.1080/10273669708833010.

Full text

Abstract:

The propagation of electrical activity in cardiac tissue can be modelled by reaction diffusion equations, where a tensor of diffusion coefficients represents anisotropy due to fiber orintation, and excitation is represented by high-order, stiff differential systems. The effects of external electrical stimulation, as in artifical pacemakers, or in defibrillators, requires bidomain models, in wich intra- and extracellular currents are treated separately.simplified approaches are taken to this problem to illustrate two methods of defibrillation: by a sinhle large pulse, that eliminates all propagating activity, and by a series of smaller amplitude perturbations, that drive out re-entrant sources of excitation.

APA, Harvard, Vancouver, ISO, and other styles

48

Ouyang, Minhui, Tina Jeon, Aristeidis Sotiras, Qinmu Peng, Virendra Mishra, Cathy Halovanic, Min Chen, et al. "Differential cortical microstructural maturation in the preterm human brain with diffusion kurtosis and tensor imaging." Proceedings of the National Academy of Sciences 116, no. 10 (February 19, 2019): 4681–88. http://dx.doi.org/10.1073/pnas.1812156116.

Full text

Abstract:

During the third trimester, the human brain undergoes rapid cellular and molecular processes that reshape the structural architecture of the cerebral cortex. Knowledge of cortical differentiation obtained predominantly from histological studies is limited in localized and small cortical regions. How cortical microstructure is differentiated across cortical regions in this critical period is unknown. In this study, the cortical microstructural architecture across the entire cortex was delineated with non-Gaussian diffusion kurtosis imaging as well as conventional diffusion tensor imaging of 89 preterm neonates aged 31–42 postmenstrual weeks. The temporal changes of cortical mean kurtosis (MK) or fractional anisotropy (FA) were heterogeneous across the cortical regions. Cortical MK decreases were observed throughout the studied age period, while cortical FA decrease reached its plateau around 37 weeks. More rapid decreases in MK were found in the primary visual region, while faster FA declines were observed in the prefrontal cortex. We found that distinctive cortical microstructural changes were coupled with microstructural maturation of associated white matter tracts. Both cortical MK and FA measurements predicted the postmenstrual age of preterm infants accurately. This study revealed a differential 4D spatiotemporal cytoarchitectural signature inferred by non-Gaussian diffusion barriers inside the cortical plate during the third trimester. The cytoarchitectural processes, including dendritic arborization and neuronal density decreases, were inferred by regional cortical FA and MK measurements. The presented findings suggest that cortical MK and FA measurements could be used as effective imaging markers for cortical microstructural changes in typical and potentially atypical brain development.

APA, Harvard, Vancouver, ISO, and other styles

49

Bowers, Abigail, Jared Bunn, and Myles Kim. "Efficient Methods to Calculate Partial Sphere Surface Areas for a Higher Resolution Finite Volume Method for Diffusion-Reaction Systems in Biological Modeling." Mathematical and Computational Applications 25, no. 1 (December 23, 2019): 2. http://dx.doi.org/10.3390/mca25010002.

Full text

Abstract:

Computational models for multicellular biological systems, in both in vitro and in vivo environments, require solving systems of differential equations to incorporate molecular transport and their reactions such as release, uptake, or decay. Examples can be found from drugs, growth nutrients, and signaling factors. The systems of differential equations frequently fall into the category of the diffusion-reaction system due to the nature of the spatial and temporal change. Due to the complexity of equations and complexity of the modeled systems, an analytical solution for the systems of the differential equations is not possible. Therefore, numerical calculation schemes are required and have been used for multicellular biological systems such as bacterial population dynamics or cancer cell dynamics. Finite volume methods in conjunction with agent-based models have been popular choices to simulate such reaction-diffusion systems. In such implementations, the reaction occurs within each finite volume and finite volumes interact with one another following the law of diffusion. The characteristic of the reaction can be determined by the agents in the finite volume. In the case of cancer cell growth dynamics, it is observed that cell behavior can be different by a matter of a few cell size distances because of the chemical gradient. Therefore, in the modeling of such systems, the spatial resolution must be comparable to the cell size. Such spatial resolution poses an extra challenge in the development and execution of the computational model due to the agents sitting over multiple finite volumes. In this article, a few computational methods for cell surface-based reaction for the finite volume method will be introduced and tested for their performance in terms of accuracy and computation speed.

APA, Harvard, Vancouver, ISO, and other styles

50

Klus, Stefan, Feliks Nüske, and Boumediene Hamzi. "Kernel-Based Approximation of the Koopman Generator and Schrödinger Operator." Entropy 22, no. 7 (June 30, 2020): 722. http://dx.doi.org/10.3390/e22070722.

Full text

Abstract:

Many dimensionality and model reduction techniques rely on estimating dominant eigenfunctions of associated dynamical operators from data. Important examples include the Koopman operator and its generator, but also the Schrödinger operator. We propose a kernel-based method for the approximation of differential operators in reproducing kernel Hilbert spaces and show how eigenfunctions can be estimated by solving auxiliary matrix eigenvalue problems. The resulting algorithms are applied to molecular dynamics and quantum chemistry examples. Furthermore, we exploit that, under certain conditions, the Schrödinger operator can be transformed into a Kolmogorov backward operator corresponding to a drift-diffusion process and vice versa. This allows us to apply methods developed for the analysis of high-dimensional stochastic differential equations to quantum mechanical systems.

APA, Harvard, Vancouver, ISO, and other styles

We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!