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A mechanism for isotonic fluid flow through the tight junctions of Necturus gallbladder epithelium (1993)

Hill, A. E. ; Shachar-Hill, B.

Springer

The journal of membrane biology 136 (1993), S. 253-262

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ISSN: 1432-1424

Keywords: Pore sizes ; Epithelial junctions ; Necturus gallbladder ; Fluid transport ; Convective channels ; Reflexion coefficient

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Abstract During isotonic fluid flow, Necturus gallbladder epithelium mediates net fluxes of paracellular probes by a convective process. We show here that the paracellular system is modeled by permeation through three populations of channels: (i) convective parallel-sided ones of width 7.7 nm (ii) small diffusive ones of radius ∼0.6 nm, and (ii) large diffusive ones of radius exceeding 50 nm. The reflexion coefficient of the convective channels is very low and the calculated osmotic flow rate is close to zero when compared with the observed fluid absorptive rate of 2 x 10−6 cm/sec. Analysis reveals that the convective channels behave as though closed to back-diffusion of probes; if this is due to solvent drag then very high fluid velocities are required, acting through minute areas. There are no transjunctional gradients that could drive the flow, and so the fluid must be propelled through the channel by components of the junction. We propose a mechanism based upon an active junctional peristalsis which allows discrimination on the basis of molecular size, in which the channels are always occluded at some point and so back-diffusion cannot occur. There is no local gradient of salt distal to the junctions and therefore the osmotic permeability of the membranes is irrelevant. High fluid velocities are not required, and the flow can occur over a substantial fraction of the junction. The mechanism must involve motile and contractile elements associated with the junction for which there is already considerable evidence.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00233664

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A comparative study of pulsed laser deposition and flash evaporation of Culn0.75Ga0.25Se2 thin films (1994)

Ahmed, E. ; Hill, A. E. ; Pilkington, R. D. ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Advanced Materials for Optics and Electronics 4 (1994), S. 423-429

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ISSN: 1057-9257

Keywords: Pulsed laser deposition ; CIGS ; Flash evaporation ; Thin films ; Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Electrical Engineering, Measurement and Control Technology , Physics

Notes: In this paper initial results are presented for the growth and characterisation of polycrystalline Culn0.75Ga0.25Se2 thin films prepared by pulsed laser deposition and flash evaporation. Analogies are drawn between these two important deposition technologies. The deposited films were characterised using a veriety of analytical techniques, including energy-dispersive analysis of X-rays and Rutherford-backscattering spectroscopy for compositional evaluation, X-ray diffreaction and Raman spectroscopy for structural evaluation, scanning electron microscopy for surface examination and the four-point and hot-point probe techniques for electrical characterisation. The comparison of films produced by these two deposition methods revealed that, in terms of their stochiometry, electrical and physical characteristics, good-quality GIGS thin films could be produced by both techniques.

Additional Material: 5 Ill.