A Theoretical Model for Water Flux Through the Artery Wall

1987 ◽  
Vol 109 (4) ◽  
pp. 311-317 ◽  
Author(s):  
R. Jain ◽  
G. Jayaraman
Keyword(s):  
Water Flux ◽  
Pressure Gradients ◽  
Artery Wall ◽  
Seepage Velocity ◽  
Heterogeneous Model ◽  
Large Pressure ◽  
The Matrix ◽  
Fluid Seepage ◽  
Two Layer Model ◽  
Water Saturated

A two layer model for water flux through the artery is studied using a matematical model based on the theory for the consolidation of water saturated soils. The matrix is considered to be constituted by two layers with different permeabilities and different elastic constants and the two systems of equations are coupled with the condition of continuity of pressure, total stress, solid displacement and fluid seepage velocity at the interface. The luminal pressure is considered to be harmonic in time. Exact solutions are obtained for displacements and pressures in both the layers. For large consolidation times, large pressure gradients are found to exist near the boundaries and at the interface. The heterogeneous model may not only be useful to understand the mechanics of transport in the physiological system but it will also help the bioengineers to choose proper implant materials to design artificial vascular organs for the purpose of prosthesis.

Pressure Gradients Affecting the Labyrinth during Hypobaric Pressure

1997 ◽  
Vol 106 (6) ◽  
pp. 495-502 ◽  
Author(s):  
Konrád S. Konrádsson ◽  
Björn I. R. Carlborg ◽  
Joseph C. Farmer
Keyword(s):  
Cerebrospinal Fluid ◽  
Eustachian Tube ◽  
Ambient Pressure ◽  
Pressure Gradients ◽  
Cochlear Aqueduct ◽  
Fluid Compartment ◽  
Large Pressure ◽  
Fluid Compartments ◽  
Pressure Changes ◽  
Considerable Pressure

Hypobaric effects on the perilymph pressure were investigated in 18 cats. The perilymph, tympanic cavity, cerebrospinal fluid, and systemic and ambient pressure changes were continuously recorded relative to the atmospheric pressure. The pressure equilibration of the eustachian tube and the cochlear aqueduct was studied, as well as the effects of blocking these channels. During ascent, the physiologic opening of the eustachian tube reduced the pressure gradients across the tympanic membrane. The patent cochlear aqueduct equilibrated perilymph pressure to cerebrospinal fluid compartment levels with a considerable pressure gradient across the oval and round windows. With the aqueduct blocked, the pressure decrease within the labyrinth and tympanic cavities was limited, resulting in large pressure gradients toward the chamber and the cerebrospinal fluid compartments, respectively. We conclude that closed cavities with limited pressure release capacities are the cause of the pressure gradients. The strain exerted by these pressure gradients is potentially harmful to the ear.

Intraventricular injection of antibodies to β1-integrins generates pressure gradients in the brain favoring hydrocephalus development in rats

2009 ◽  
Vol 297 (5) ◽  
pp. R1312-R1321 ◽  
Author(s):  
Gurjit Nagra ◽  
Lena Koh ◽  
Isabelle Aubert ◽  
Minhui Kim ◽  
Miles Johnston
Keyword(s):  
Fluid Pressure ◽  
Active Role ◽  
Intraventricular Injection ◽  
Pressure Gradients ◽  
Tissue Pressure ◽  
Before And After ◽  
The Matrix ◽  
System 2 ◽  
Periventricular Area ◽  
The Brain

In some tissues, the injection of antibodies to the β1-integrins leads to a reduction in interstitial fluid pressure, indicating an active role for the extracellular matrix in tissue pressure regulation. If perturbations of the matrix occur in the periventricular area of the brain, a comparable lowering of interstitial pressures may induce transparenchymal pressure gradients favoring ventricular expansion. To examine this concept, we measured periventricular (parenchymal) and ventricular pressures with a servo-null micropipette system (2-μm tip) in adult Wistar rats before and after anti-integrin antibodies or IgG/IgM isotype controls were injected into a lateral ventricle. In a second group, the animals were kept for 2 wk after similar injections and after euthanization, the brains were removed and assessed for hydrocephalus. In experiments in which antibodies to β1-integrins ( n = 10) but not isotype control IgG/IgM ( n = 7) were injected, we observed a decline in periventricular pressures relative to the preinjection values. Under similar circumstances, ventricular pressures were elevated ( n = 10) and were significantly greater than those in the periventricular interstitium. We estimated ventricular to periventricular pressure gradients of up to 4.3 cmH2O. In the chronic preparations, we observed enlarged ventricles in many of the animals that received injections of anti-integrin antibodies (21 of 29 animals; 72%) but not in any animal receiving the isotype controls. We conclude that modulation/disruption of β1-integrin-matrix interactions in the brain generates pressure gradients favoring ventricular expansion, suggesting a novel mechanism for hydrocephalus development.

scholarly journals Simulation Analysis on Water’s Micro Seepage Laws under Different Pressure Gradients Using Computed Tomography Method

2018 ◽  
Vol 2018 ◽  
pp. 1-26 ◽  
Author(s):  
Gang Zhou ◽  
Lei Qiu ◽  
Wenzheng Zhang ◽  
Jiao Xue
Keyword(s):  
Pressure Gradient ◽  
Mass Flow ◽  
Simulation Analysis ◽  
Effective Porosity ◽  
Pressure Gradients ◽  
Seepage Velocity ◽  
Average Mass ◽  
Depth Analysis ◽  
Tomography Method ◽  
Insight Into

The aim of this paper was to develop a model that can characterize the actual micropore structures in coal and gain an in-depth insight into water’s seepage rules in coal pores under different pressure gradients from a microscopic perspective. To achieve this goal, long-flame coals were first scanned by an X-ray 3D microscope; then, through a representative elementary volume (REV) analysis, the optimal side length was determined to be 60 μm; subsequently, by using Avizo software, the coal’s micropore structures were acquired. Considering that the porosity varies in the same coal sample, this study selected four regions in the sample for an in-depth analysis. Moreover, numerical simulations on water’s seepage behaviors in coal under 30 different pressure gradients were performed. The results show that (1) the variation of the simulated seepage velocity and pressure gradient accorded with Forchheimer’s high-velocity nonlinear seepage rules; (2) the permeability did not necessarily increase with the increase of the effective porosity; (3) in the same model, under different pressure gradients, the average seepage pressure decreased gradually, while the average seepage velocity and average mass flow varied greatly with the increase of the seepage length; and (4) under the same pressure gradient, the increase of the average mass flow from the inlet to the outlet became more significant under a higher inlet pressure.

scholarly journals Balloon-based drug coating delivery to the artery wall is dictated by coating micro-morphology and angioplasty pressure gradients

Biomaterials ◽  
2020 ◽  
Vol 260 ◽  
pp. 120337
Author(s):  
Abraham R. Tzafriri ◽  
Benny Muraj ◽  
Fernando Garcia-Polite ◽  
Antonio G. Salazar-Martín ◽  
Peter Markham ◽  
...  
Keyword(s):  
Pressure Gradients ◽  
Artery Wall ◽  
Micro Morphology ◽  
Drug Coating

scholarly journals Permeability and Antifouling Augmentation of a Hybrid PVDF-PEG Membrane Using Nano-Magnesium Oxide as a Powerful Mediator for POME Decolorization

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 549 ◽  
Author(s):  
Mohammed Abdulsalam ◽  
Hasfalina Che Man ◽  
Pei Sean Goh ◽  
Khairul Faezah Yunos ◽  
Zurina Zainal Abidin ◽  
...  
Keyword(s):  
Magnesium Oxide ◽  
Polyvinylidene Fluoride ◽  
Water Flux ◽  
Fouling Resistance ◽  
Hybrid Fibers ◽  
Total Period ◽  
Phase Inversion Technique ◽  
The Matrix ◽  
Palm Oil Mill ◽  
Agglomeration Of Nanoparticles

This study focused on developing a hydrophilic hybrid polyvinylidene fluoride (PVDF)-polyethylene glycol (PEG) hollow membrane by incorporating Nano-magnesium oxide (NMO) as a potent antifouling mediator. The Nano-hybrid hollow fibers with varied loading of NMO (0 g; 0.25 g; 0.50 g; 0.75 g and 1.25 g) were spun through phase inversion technique. The resultants Nano-hybrid fibers were characterized and compared based on SEM, EDX, contact angle, surface zeta-potential, permeability flux, fouling resistance and color rejection from palm oil mill effluent (POME). Noticeably, the permeability flux, fouling resistance and color rejection improved with the increase in NMO loading. PVDF-PEG with 0.50 g-NMO loading displayed an outstanding performance with 198.35 L/m2·h, 61.33 L/m2·h and 74.65% of water flux, POME flux and color rejection from POME, respectively. More so, a remarkable fouling resistance were obtained such that the flux recovery, reversible fouling percentage and irreversible fouling percentage remains relatively steady at 90.98%, 61.39% and 7.68%, respectively, even after 3 cycles of continuous filtrations for a total period of 9 h. However, at excess loading of 0.75 and 1.25 g-NMO, deterioration in the flux and fouling resistance was observed. This was due to the agglomeration of nanoparticles within the matrix structure at the excessive loading.

scholarly journals Investigating the impact of exit effects on solute transport in macroporous media

2021 ◽  
Vol 25 (2) ◽  
pp. 671-683
Author(s):  
Jérôme Raimbault ◽  
Pierre-Emmanuel Peyneau ◽  
Denis Courtier-Murias ◽  
Thomas Bigot ◽  
Jaime Gil Roca ◽  
...  
Keyword(s):  
Solute Transport ◽  
Finite Size ◽  
Breakthrough Curves ◽  
Macropore Flow ◽  
Reactive Solute Transport ◽  
The Matrix ◽  
Magnetic Resonance Imaging Mri ◽  
Breakthrough Experiments ◽  
Water Saturated ◽  
The Impact

Abstract. The effect of macropore flow on solute transport has spurred much research over the last forty years. In this study, non-reactive solute transport in water-saturated columns filled with porous media crossed by a macropore was experimentally and numerically investigated. The emphasis was put on the study of exit effects, whose very existence is inherent to the finite size of any experimental column. We specifically investigated the impact of a filter at the column outlet on water flow and solute transport in macroporous systems. Experiments involving breakthrough measurements and magnetic resonance imaging (MRI) showed that solute transport displayed some significant non-unidirectional features, with a strong mass exchange at the interface between the macropore and the matrix. Fluid dynamics and transport simulations indicated that this was due to the non-unidirectional nature of the flow field close to the outlet filter. The flow near the exit of the column was shown to be strongly impacted by the presence of the outlet filter, which acts as a barrier and redistributes water from the macropore to the matrix. This impact was apparent on the breakthrough curves and the MRI images. It was also confirmed by computer simulations and could, if not properly taken into account, impede the accurate inference of the transport properties of macroporous media from breakthrough experiments.

scholarly journals Performance of Turbulence Models in Simulating Wind Loads on Photovoltaics Modules

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3290 ◽  
Author(s):  
Mireille B. Tadie Fogaing ◽  
Arman Hemmati ◽  
Carlos F. Lange ◽  
Brian A. Fleck
Keyword(s):  
Energy Transport ◽  
Turbulence Models ◽  
Wind Loads ◽  
Turbulence Energy ◽  
Pressure Gradients ◽  
Mean Flow ◽  
Velocity Gradients ◽  
Large Pressure ◽  
The Mean ◽  
Recirculation Length

The performance of five conventional turbulence models, commonly used in the wind industry, are examined in predicting the complex wake of an infinite span thin normal flat plate with large pressure gradients at Reynolds number of 1200. This body represents a large array of Photovoltaics modules, where two edges of the plate dominate the flow. This study provided a benchmark for capabilities of conventional turbulence models that are commonly used for wind forecasting in the wind energy industry. The results obtained from Reynolds Averaged Navier-Stokes (RANS) k - ε , Reynolds Normalization Group (RNG) k - ε , RANS k - ω Shear Stress Transport (SST) and Reynolds Stress Model (RSM) were compared with existing Direct Numerical Simulations (DNS). The mean flow features and unsteady wake characteristics were used as testing criteria amongst these models. All turbulence models over-predicted the mean recirculation length and under-predicted the mean drag coefficient. The major differences between numerical results in predicting the mean recirculation length, mean drag and velocity gradients, leading to deficits in turbulence kinetic energy production and diffusion, hint at major difficulties in modeling velocity gradients and thus turbulence energy transport terms, by traditional turbulence models. Unsteadiness of flow physics and nature of eddy viscosity approximations are potential reasons. This hints at the deficiencies of these models to predict complex flows with large pressure gradients, which are commonly observed in wind and solar farms. The under-prediction of wind loads on PV modules and over-estimation of the recirculation length behind them significantly affects the efficiency and operational feasibility of solar energy systems.

Design Considerations for a Small Bore Vascular Prosthesis

1988 ◽  
Vol 11 (4) ◽  
pp. 272-276 ◽  
Author(s):  
C.J. Underwood ◽  
W.F. Tait ◽  
D. Charlesworth
Keyword(s):  
Vascular Prosthesis ◽  
Elastic Behaviour ◽  
Internal Diameter ◽  
Pressure Gradients ◽  
Low Friction ◽  
Flow Disturbances ◽  
Flow Surface ◽  
Large Pressure ◽  
Good Potential

No synthetic prosthesis has yet been found which can satisfactorily be used as a substitute for saphenous veins in vascular surgery. One explanation for the lack of success is that their properties and behaviour do not mimic those of the arteries they replace. The essential features for a successful vascular prosthesis, over and above biocompatibility, are a low friction non-thrombogenic flow surface, mechanical (elastic) behaviour that matches natural artery and dimensions that approximate the host vessels. This will allow a high velocity of flow with low impedance. A prosthesis with this specification would avoid the problems of flow disturbances and reflection at the anastomoses, pulse wave damping and large pressure gradients, all of which reduce pulsatile energy. We have designed a vascular prosthesis based upon the above criteria. It has an internal diameter of 4 mm and a wall thickness of 1 mm. Its geometry makes it kink resistant and a good match for tibial and coronary arteries. The prosthesis is made from Polyurethane and its mechanical properties, which approximate to those of peripheral arteries, are achieved via a mechanism of internal wall compression rather than external circumferential expansion. To assess the in-vivo potential of this prosthesis, 21 grafts were implanted in 11 sheep, replacing a section of carotid artery with a 6 cm long prosthesis. All 21 grafts were patent after 3 months. One graft was removed for histological examination. 16 of the remaining 20 grafts were patent after 7 months. Problems associated with thrombosis were not encountered and we conclude that this prosthesis shows good potential as a small bore vascular substitute.

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