Permeability in Relation to Viscosity and Structure of Rubber

1942 ◽  
Vol 15 (3) ◽  
pp. 537-544 ◽  
Author(s):  
Richard M. Barrer
Keyword(s):  
Viscous Flow ◽  
Thermal Energy ◽  
Diffusion Constant ◽  
The Self ◽  
Self Diffusion ◽  
Functional Relations ◽  
Diffusion Media ◽  
Entropy Of Activation ◽  
Arrhenius Energy ◽  
And Diffusion

Abstract Some properties of flow of solutes in and through rubbers are outlined. These properties indicate that, due to fluctuations of thermal energy, activated zones exist in certain polymers, of which viscous flow and diffusion are a consequence. A simple statistics of activated zones has been given, and from it equations are obtained for ΣN, D, Ds, and η, denoting respectively the total number of activated zones in rubber, the diffusion constant of simple solutes in the polymer, the self-diffusion constant of rubber, and its viscosity. Functional relations are predicted between log Do, log ηo, or ΔS* (the entropy of activation) and the Arrhenius energy of activation for diffusion or viscous flow. The available data clearly demonstrate this relationship. They also indicate no discontinuity between rubbers and liquids as diffusion media.

scholarly journals Water and Deuterium Oxide Permeability through Aquaporin 1: MD Predictions and Experimental Verification

2007 ◽  
Vol 130 (1) ◽  
pp. 111-116 ◽  
Author(s):  
Artem B. Mamonov ◽  
Rob D. Coalson ◽  
Mark L. Zeidel ◽  
John C. Mathai
Keyword(s):  
Deuterium Oxide ◽  
Diffusion Constant ◽  
Structural Data ◽  
Md Simulations ◽  
Water Model ◽  
Aquaporin 1 ◽  
Self Diffusion ◽  
Osmotic Permeability ◽  
Protein Channels ◽  
And Diffusion

Determining the mechanisms of flux through protein channels requires a combination of structural data, permeability measurement, and molecular dynamics (MD) simulations. To further clarify the mechanism of flux through aquaporin 1 (AQP1), osmotic pf (cm3/s/pore) and diffusion pd (cm3/s/pore) permeability coefficients per pore of H2O and D2O in AQP1 were calculated using MD simulations. We then compared the simulation results with experimental measurements of the osmotic AQP1 permeabilities of H2O and D2O. In this manner we evaluated the ability of MD simulations to predict actual flux results. For the MD simulations, the force field parameters of the D2O model were reparameterized from the TIP3P water model to reproduce the experimentally observed difference in the bulk self diffusion constants of H2O vs. D2O. Two MD systems (one for each solvent) were constructed, each containing explicit palmitoyl-oleoyl-phosphatidyl-ethanolamine (POPE) phospholipid molecules, solvent, and AQP1. It was found that the calculated value of pf for D2O is ∼15% smaller than for H2O. Bovine AQP1 was reconstituted into palmitoyl-oleoyl-phosphatidylcholine (POPC) liposomes, and it was found that the measured macroscopic osmotic permeability coefficient Pf (cm/s) of D2O is ∼21% lower than for H2O. The combined computational and experimental results suggest that deuterium oxide permeability through AQP1 is similar to that of water. The slightly lower observed osmotic permeability of D2O compared to H2O in AQP1 is most likely due to the lower self diffusion constant of D2O.

On The Melting of Amorphous Ge and Si

1981 ◽  
Vol 7 ◽  
Author(s):  
David Turnbull
Keyword(s):  
Glass Transition ◽  
External Surface ◽  
Rapid Heating ◽  
Diffusion Constant ◽  
Nucleation And Growth ◽  
The Self ◽  
Metallic State ◽  
Equilibrium Melting Temperature ◽  
Self Diffusion ◽  
Limiting Values

ABSTRACTThe amorphous semiconducting phase (a-sc) of Si or Ge is so resistant to crystallization that rapid heating may bring it into a temperature regime in which it melts. Such melting might occur in one or the other of two ways, either homogeneously, by the reverse of the glass transition, to a viscous semi-conducting melt (ℓ-sc) or by transition, probably by nucleation and growth, to the molten metallic state (ℓm). Using the self-diffusion constant of the crystalline elements in conjunction with the Stokes-Einstein equation, upper limiting values of the glass transition (a-sc→ℓ-sc) temperatures of Si and Ge were calculated. These were of the order 0.6 to 0.65 Tcℓ for slow and 1.1 Tcℓ for ultra rapid heating, where Tcℓ is the equilibrium melting temperature of the crystal. Arguments are given that superheating to a temperature 1.15 to 1.25 Taℓ (a-sc↔ℓm in equilibrium at temperature T = Taℓ< Tcℓ) may be required for copious internal nucleation of im in a-sc. At lesser superheating the transition must be initiated at internal flaws (e.g. voids) or at the external surface of the a-sc film. Therefore the superheating at perceptible onset of the transition during rapid heating can vary widely from specimen to specimen, depending on the flaw concentration and how the external surface of a-sc was treated.

scholarly journals Ultrafast Laplace NMR to study metal-ligand interactions in reversible polarisation transfer from parahydrogen

2021 ◽  
Author(s):  
Ben. J. Tickner ◽  
Vladimir V. Zhivonitko ◽  
Ville-Veikko Telkki
Keyword(s):  
Molecular Structure ◽  
Relaxation Times ◽  
The Self ◽  
Self Diffusion ◽  
Structure And Dynamics ◽  
Relaxation Parameters ◽  
Diffusion Constants ◽  
Ligand Interactions ◽  
And Diffusion ◽  
Metal Ligand

Laplace Nuclear Magnetic Resonance (NMR) can determine relaxation parameters and diffusion constants, giving valuable information about molecular structure and dynamics. Information about relaxation times (T1 and T2) and the self-diffusion...

scholarly journals Time-of-flight modulated intensity small-angle neutron scattering measurement of the self-diffusion constant of water

2021 ◽  
Vol 54 (3) ◽  
Author(s):  
Stephen J. Kuhn ◽  
Niels Geerits ◽  
Christian Franz ◽  
Jeroen Plomp ◽  
Robert M. Dalgliesh ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Spin Echo ◽  
Time Of Flight ◽  
Diffusion Constant ◽  
The Self ◽  
Neutron Resonance ◽  
High Energy Resolution ◽  
Self Diffusion

The modulated intensity by zero effort small-angle neutron scattering (MI-SANS) technique is used to measure scattering with a high energy resolution on samples normally ill-suited for neutron resonance spin echo. The self-diffusion constant of water is measured over a q–t range of 0.01–0.2 Å−1 and 70–500 ps. In addition to demonstrating the methodology of using time-of-flight MI-SANS instruments to observe diffusion in liquids, the results support previous measurements on water performed with different methods. This polarized neutron technique simultaneously measures the intermediate scattering function for a wide range of time and length scales. Two radio frequency flippers were used in a spin-echo setup with a 100 kHz frequency difference in order to create a high-resolution time measurement. The results are compared with self-diffusion measurements made by other techniques and the general applicability of MI-SANS at a pulsed source is assessed.

Point Defects and Diffusion in Ni3Ga

1998 ◽  
Vol 527 ◽  
Author(s):  
T. IKEDA ◽  
A. Almazouzi ◽  
A. Funao ◽  
H. Numakura ◽  
M. Koiwa ◽  
...  
Keyword(s):  
Point Defects ◽  
Positron Lifetime ◽  
Major Element ◽  
Tracer Diffusion ◽  
The Self ◽  
Self Diffusion ◽  
Order Of Magnitude ◽  
Constituent Elements ◽  
Tracer Diffusion Coefficients ◽  
And Diffusion

ABSTRACTThe properties of intrinsic point defects and the self-diffusion behaviour of the constituent elements in Ni3Ga have been studied by positron annihilation, tracer diffusion and interdiffusion experiments. Thermal vacancies have been detected by positron lifetime measurements for specimens quenched from high temperatures. The vacancy formation energy is in the range between 1.7 and 1.8 eV, and is not dependent strongly on the composition. The tracer diffusion coefficients of Ni and Ga are of the same order of magnitude, and the interdiffusion coefficient is about 10 times larger than the diffusion coefficient of Ni. The diffusion in Ni3Ga has been found to satisfy the Darken-Manning equation, as expected from the model of the self-diffusion in this type of materials, where both the species of atoms are assumed to migrate primarily in the sub-lattice of the major element via the ordinary vacancy mechanism.

Sign in / Sign up

Export Citation Format

Share Document