scholarly journals Diffusion Barriers in the Squid Nerve Fiber

1962 ◽  
Vol 46 (2) ◽  
pp. 245-255 ◽  
Author(s):  
Raimundo Villegas ◽  
Carlo Caputo ◽  
Leopoldo Villegas
Keyword(s):  
Ethylene Glycol ◽  
Path Length ◽  
Diffusion Rate ◽  
Effective Diffusion ◽  
Effective Area ◽  
Mean Values ◽  
Cylindrical Pores ◽  
In Series ◽  
Unit Path Length ◽  
Diffusion Rates

The squid nerve barriers are formed by (a) the axolemma (membrane of the axon proper), a membrane 80 Å thick perforated by cylindrical pores 4.0 to 4.5 Å radius, and (b) the Schwann layer, constituted of numerous cells forming a layer one cell thick, crossed by 60 Å wide slit channels. If a molecule present in the axoplasm has to reach the extraneural space, it has to pass (a) the pores, and (b) the channels, in series, and the diffusion rate will depend on the effective diffusion areas per unit path length, Apd/Δx for the axolemma, and Acd/Δx for the Schwann layer. By addition, And/Δx, the transneural effective area for diffusion per unit path length is obtained. The diffusion rates of C14-ethylene glycol (2.2 Å radius), and C14-glycerol (2.8 Å radius) were measured. The diffusion rate of H3-labeled water (1.5 Å radius) has been previously determined. The results expressed in terms of And/Δx (mean values ± SD, referred to 1 cm2 of nerve surface) are 5.3 ± 1.4 cm for water, 2.5 ± 0.4 cm for ethylene glycol, and 0.29 ± 0.03 cm for glycerol. Theoretical values for And/Δx of 2.5 and 0.83 cm for ethylene glycol and glycerol have been calculated. The agreement between the theoretical values for And/Δx and the experimental ones supports the diffusion barrier model described above.

Investigation of interdiffusion in (SimGen)p superlattices and Gen buried layers by Raman and X-ray techniques

1992 ◽  
Vol 70 (10-11) ◽  
pp. 852-859 ◽  
Author(s):  
D. J. Lockwood ◽  
J.-M. Baribeau ◽  
H. J. Labbé
Keyword(s):  
Diffusion Coefficient ◽  
Molecular Beam ◽  
Diffusion Rate ◽  
Effective Diffusion ◽  
Atomic Diffusion ◽  
X Ray ◽  
Diffusion Rates ◽  
Buried Layers ◽  
Interface Mixing ◽  
Anneal Temperature

Two thin pseudomorphic (SimGen)p superlattices with m = n = 4 and p = 5 and vice versa were prepared at 350 °C by molecular beam epitaxy on (100) Si to investigate interdiffusion upon annealing. A Raman scattering and X-ray reflectometry study of the as-grown specimens indicated significant interdiffusion at the Si–Ge interfaces. The Raman investigations of specimens annealed for 20 s at temperatures up to 750 °C showed that atomic diffusion across the Si–Ge interfaces had occurred at an anneal temperature of 600 °C. After a 20 s 700 °C anneal. Raman and X-ray techniques showed that the superlattices modulation was destroyed consistent with a diffusion coefficient of about 10−21 m2/s. Both techniques revealed that 100 s anneals at temperatures of 750–950 °C introduced a slower diffusion rate (10−20 m2/s at 950 °C), but also strain relief, in Gen (n < 12) epilayers buried in Si. The differences in the effective diffusion rates for the two types of heterostructure are attributed to a different degree of interface mixing during growth.

scholarly journals The Steady-State Transport of Oxygen through Hemoglobin Solutions

1966 ◽  
Vol 49 (4) ◽  
pp. 663-679 ◽  
Author(s):  
K. H. Keller ◽  
S. K. Friedlander
Keyword(s):  
Diffusion Coefficient ◽  
Brownian Motion ◽  
Steady State ◽  
Effective Diffusion ◽  
Close Correlation ◽  
Oxygen Electrode ◽  
Low Oxygen ◽  
Diffusion Rates ◽  
Oxygen Tensions ◽  
Diffusion Coefficient Of Oxygen

The steady-state transport of oxygen through hemoglobin solutions was studied to identify the mechanism of the diffusion augmentation observed at low oxygen tensions. A novel technique employing a platinum-silver oxygen electrode was developed to measure the effective diffusion coefficient of oxygen in steady-state transport. The measurements were made over a wider range of hemoglobin and oxygen concentrations than previously reported. Values of the Brownian motion diffusion coefficient of oxygen in hemoglobin solution were obtained as well as measurements of facilitated transport at low oxygen tensions. Transport rates up to ten times greater than ordinary diffusion rates were found. Predictions of oxygen flux were made assuming that the oxyhemoglobin transport coefficient was equal to the Brownian motion diffusivity which was measured in a separate set of experiments. The close correlation between prediction and experiment indicates that the diffusion of oxyhemoglobin is the mechanism by which steady-state oxygen transport is facilitated.

Novel methods of processing cement gel to examine and control microstructure and properties

1983 ◽  
Vol 310 (1511) ◽  
pp. 155-166 ◽  
Keyword(s):  
Surface Tension ◽  
Compressive Strength ◽  
Pore Water ◽  
Diffusion Rate ◽  
Exchange Process ◽  
Hydrated Cement ◽  
Diffusion Rates ◽  
And Control ◽  
Kinetics Of ◽  
Counter Diffusion

The microstructure of the gel produced by hydrating cement is sensitive to the manner in which the original pore water is removed. Exchange of the pore water with a miscible, low surface-tension fluid by a process of counter-diffusion is examined. Diffusion rates in the hydrated cement can be assessed from the kinetics of the exchange process. Evaporation of the low surface-tension fluid from the pores caused less alteration to the microstructure than direct removal of the original pore water. The sensitivity of the microstructure of hydrated cement to normal environmental drying is industrially significant because it is associated with increases in diffusion rates that could affect the durability of concrete. Drying lowered the correlation between diffusion rate and compressive strength. Possible methods of processing the cement gel to make it more resistant to the disruptive effects of drying are discussed.

A spatial SIS model with Holling II incidence rate

2019 ◽  
Vol 12 (08) ◽  
pp. 1950092 ◽  
Author(s):  
Wenhao Xie ◽  
Gongqian Liang ◽  
Wei Wang ◽  
Yanhong She
Keyword(s):  
Incidence Rate ◽  
Total Population ◽  
Diffusion Rate ◽  
Reproduction Number ◽  
Sis Model ◽  
Sis Epidemic Model ◽  
Asymptotic Profile ◽  
Number Formula ◽  
Diffusion Rates ◽  
Two Populations

A diffusive SIS epidemic model with Holling II incidence rate is studied in this paper. We introduce the basic reproduction number [Formula: see text] first. Then the existence of endemic equilibrium (EE) can be determined by the sizes of [Formula: see text] as well as the diffusion rates of susceptible and infected individuals. We also investigate the effect of diffusion rates on asymptotic profile of EE. Our results conclude that the infected population will die out if the diffusion rate of susceptible individuals is small and the total population [Formula: see text] is below a certain level; while the two populations persist eventually if at least one of the diffusion rates of the susceptible and infected individuals is large.

Diffusion of alkali and alkaline earth chlorides through a parchment-supported silver iodide membrane

1972 ◽  
Vol 25 (9) ◽  
pp. 1837 ◽  
Author(s):  
Beg M Aijaz ◽  
S Pratap
Keyword(s):  
Silver Iodide ◽  
Alkaline Earth ◽  
Diffusion Rate ◽  
Activation Parameters ◽  
Weak Field ◽  
Thermodynamic Quantities ◽  
Constant Flow ◽  
Ion Hydration ◽  
Diffusion Rates ◽  
Alkaline Earth Chlorides

Diffusion rates of KCl, NaCl, LiCl, BaCl2, CaCl2, and MgCl2 through a parchment-supported silver iodide membrane have been measured at various temperatures using a constant flow method. Activation energies and various Eyring activation parameters for the diffusion of these electrolytes have also been evaluated. The diffusion rate sequences obtained are KCl > NaCl > LiCl and BaCl2 > CaCl2 > MgCl2 and they point towards the weak field strength of the membrane fixed charged groups. Diffusion coefficients and the various Eyring activation parameters have been related to the ionic hydrated sizes and the various thermodynamic quantities of ionic hydration thus emphasizing the importance of ion hydration in diffusion across the membrane.

Gas-Solid Chromatographic Determination of Volatile Denaturants in Ethanol Solution

1974 ◽  
Vol 57 (1) ◽  
pp. 148-152
Author(s):  
Glenn E Martin ◽  
Donald M Figert
Keyword(s):  
Ethylene Glycol ◽  
Methyl Isobutyl Ketone ◽  
General Rule ◽  
Chromatographic Determination ◽  
Ethanol Solution ◽  
Isobutyl Ketone ◽  
Mean Values ◽  
Glycol Monoethyl Ether ◽  
The Mean

Abstract A gas-solid chromatographic determination of volatile denaturants in non-beverage alcohol samples was studied by 10 collaborators representing 6 laboratories. The mean values obtained by 10 collaborators for a concentration of 2.00% each in ethanol solution were: acetone 2.14, ethyl acetate 1.95, ethylene glycol monomethyJ ether 1.90, toluene 1.89, methanol 2.08, chloroform 1.89, n-butanol 1.95, ethylene glycol monoethyl ether 1.88, methyl isobutyl ketone 1.83, isopropanol 2.18, sec.-butanol 2.01, and benzene 2.03. The mean values obtained by the 10 collaborators for a concentration of 4.00% each were: 4.08, 3.94, 3.91, 3.94, 4.07, 4.04, 4.01, 3.99, 3.99, 4.12, 4.05, and 4.06%, respectively. Likewise, at a concentration of 8.00%, each of the results by these same collaborators were: 7.89, 7.94, 8.07, 8.03, 8.04, 8.19, 7.98, 7.97, 8.10, 7.99, 8.10, and 8.07%, respectively. As a general rule, as the precision improved so did the accuracy.

scholarly journals Hemodialysis Membrane Coated with a Polymer Having a Hydrophilic Blood-Contacting Layer can Enhance Diffusional Performance

2017 ◽  
Vol 40 (12) ◽  
pp. 665-669 ◽  
Author(s):  
Masashi Tagaya ◽  
Saki Nagoshi ◽  
Morihiro Matsuda ◽  
Shunsuke Takahashi ◽  
Shinya Okano ◽  
...  
Keyword(s):  
Diffusion Rate ◽  
Removal Rates ◽  
Coating Agent ◽  
Sieving Coefficient ◽  
Polyethersulfone Membrane ◽  
Wide Range ◽  
Coated Membranes ◽  
Preliminary Study ◽  
Diffusion Rates

Purpose Currently, the foreign surfaces of various extracorporeal circulation devices are coated with a biocompatible polymer coating agent (BPA), which creates a hydrophilic blood-contacting layer to reduce thrombogenicity, while the membranes in hemodialyzers are not. We aimed to clarify other side effects of BPA-coated membranes by examining the diffusion performance in in vitro experiments. Methods We used a polyethersulfone membrane (sieving coefficient of albumin is ≤0.01) coated with BPA product, SEC-1™ (Toyobo), in a hemodialyzer. To estimate the diffusion rates of a wide range of molecules, 2 L of saline containing vancomycin, lysozyme, and albumin were recirculated in the circuit configured with a hemodialyzer, and dialyzed continuously using water. The concentrations of sodium, vancomycin, lysozyme, and albumin were measured every 5 minutes for 30 minutes and compared in experiments with BPA-coated (n = 4) and BPA-noncoated (n = 4) membranes. Results The removal rates of sodium and vancomycin after 5 minutes of dialysis (n = 24) were significantly higher in BPA-coated than noncoated membranes, while those of lysozyme and albumin were not significantly different. The removal rates of sodium and vancomycin after 30 minutes of dialysis (n = 4) were significantly higher, and those of lysozyme were significantly lower in BPA-coated than noncoated membranes, while those of albumin were not significantly different. Conclusions The preliminary study suggests that BPA-coated membranes enhanced the diffusion rate of molecules with low and middle molecular weight without affecting the sieving coefficient of albumin. Thus, BPA coating can enhance the dialysis performance of membranes.

scholarly journals Diffusion of isotopes in the annual layers of ice sheets

1998 ◽  
Vol 44 (148) ◽  
pp. 467-468 ◽  
Author(s):  
J. F. Nye
Keyword(s):  
Liquid Water ◽  
Effective Diffusion ◽  
Diffusion Constant ◽  
Ice Sheets ◽  
Self Diffusion ◽  
Diffusion Rates ◽  
Antarctic Ice Sheets

Abstract The annual layering in the Greenland and Antarctic ice sheets revealed by the b 0 record becomes less distinct with depth because of self-diffusion. However, the calculated diffusion rates are loo slow to explain die observations. It is suggested that the presence of veins of liquid water increases the effective diffusion constant by a factor of about 20.

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