High pressure–low flow remodeling of the rat saphenous vein wall

2017 ◽  
Vol 33 (2) ◽  
pp. 128-137 ◽  
Author(s):  
Judit R Hetthéssy ◽  
Anna-Mária Tőkés ◽  
Sándor Kérész ◽  
Petra Balla ◽  
Gabriella Dörnyei ◽  
...  
Keyword(s):  
Smooth Muscle Actin ◽  
Low Flow ◽  
Outer Diameter ◽  
Elastic Tissue ◽  
Vein Wall ◽  
Control Side ◽  
Combined Flow ◽  
Flow Pressure ◽  
Wall Mass ◽  
Histological Testing

Objective To better understand factors that may play a role in the development of varicosities. Methods We induced combined flow-pressure disturbance in the saphenous system of the rat by performing chronic partial clipping of the main branch. Biomechanical and quantitative histological testing was undertaken. Results A rich microvenous network developed. Bloodflow decreased to 0.65 ± 0.18 µl/s (control side, 3.5 ± 1.4 µl/s) and pressure elevated to 6.8 ± 0.7 mmHg (control side, 2.3 ± 0.2 mmHg, p < 0.05). Involution of the wall and lumen was observed (16.5%, 28.7% and 35.5% reduction in outer diameter, wall thickness and wall mass respectively, p < 0.05). Elevated macrophage (CD68) and cell division (Ki67) activity was observed. Elastic tissue and smooth muscle actin became less concentrated in the inner medial layers. Conclusions Low-flow induced morphological shrinking of the lumen in veins may override pressure-induced morphological distension. Loosening of the force-bearing elements during flow-induced wall remodeling may be an important pathological component in varicosity.

scholarly journals INVESTIGATION OF CRITICAL HEAT FLUX ON ABRADED INCONEL 625 TUBE

2020 ◽  
Vol 28 ◽  
pp. 15-22
Author(s):  
Ladislav Suk ◽  
Kamil Števanka ◽  
Taron Petrosyan ◽  
Daniel Vlček
Keyword(s):  
Surface Roughness ◽  
High Speed ◽  
Flow Boiling ◽  
Glass Tube ◽  
Annular Channel ◽  
Low Flow ◽  
Inconel 625 ◽  
Confocal Laser ◽  
Outer Diameter ◽  
Flow Parameters

Aim of this work was to study flow boiling in an annular channel at low pressure and low flow on a tube with modified surface roughness. The tube with the outer diameter of 9.14 mm and the heated length of 380 mm was made of Inconel 625 and was manually modified using 150 grit sandpaper. The tube was placed in a glass tube with an inner diameter of 14.8 mm. Outlet pressure was set to 120, 200 and 300 kPa with varying mass flow from 400 to 600 kg/(m2.s). A high speed camera was used to record several experiments to fully understand ongoing phenomena. Surface roughness was analysed using a confocal laser microscope and the effects of different mass flux and pressure on the CHF value were observed. Above all, the optimization of the flow parameters was done from the collected data and from the observed behaviour of the experimental loop.

scholarly journals EXPERIMENTAL INVESTIGATION OF CRITICAL HEAT FLUX IN ANNULUS AT LOW PRESSURE AND LOW FLOW PARAMETERS

2020 ◽  
Vol 28 ◽  
pp. 50-58
Author(s):  
Daniel Vlček ◽  
Ladislav Suk ◽  
Kamil Števanka ◽  
Taron Petrosyan
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Low Pressure ◽  
Low Flow ◽  
Inconel 625 ◽  
Outer Diameter ◽  
Flow Parameters ◽  
Low Mass ◽  
Vertically Aligned

Steady state flow boiling experiments were conducted on a technically smooth Inconel 625 tube with outer diameter 9.1 mm at inlet pressures 131, 220 and 323 kPa, inlet temperatures 62, 78 and 94 °C and approximately 400, 600 and 1000 kg/(m2.s) mass flow. Water of these parameters was entering into the vertically aligned annulus, where the uniformly heated tube was placed until the critical heat flux (CHF) appeared. The experimental data were compared to estimations of CHF by local PGT tube correlation and Groeneveld’s look-up tables for tubes. The results imply that in the region of low pressure and low mass flux, the differences between calculations and experiments are substantial (more than 50 % of CHF). The calculations further imply that look-up tables and tube correlations should be corrected to the annulus geometry. Here, the Doerffer’s approach was chosen and led to a substantial enhancement of CHF estimation. Yet, a new correlation for the region of low pressure and flow is needed.

scholarly journals Angiocrine FSTL1 insufficiency leads to atrial and vein wall fibrosis via SMAD3 activation

2019 ◽  
Author(s):  
Haijuan Jiang ◽  
Luqing Zhang ◽  
Xuelian Liu ◽  
Wei Sun ◽  
Katsuhiro Kato ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Heart Valves ◽  
Smooth Muscle Actin ◽  
Vascular Wall ◽  
Cell Interaction ◽  
Alpha Smooth Muscle Actin ◽  
Vein Wall ◽  
Mural Cell ◽  
Smad3 Phosphorylation ◽  
Cardiovascular Fibrosis

AbstractAngiocrine factors, mediating the endothelial-mural cell interaction in vascular wall construction as well as maintenance, are incompletely characterized. Here we show that loss of follistatin-like protein 1 (FSTL1) in endothelial cells (Fstl1ECKO) led to an increase of pulmonary vascular resistance, resulting in the heart regurgitation especially with tricuspid valves. However, this abnormality was not detected in mutant mice with Fstl1 deletion in smooth muscle cells or hematopoietic cells. We further showed that there was excessive alpha-smooth muscle actin (αSMA) associated with atrial endocardia, heart valves, veins and microvessels after the endothelial FSTL1 deletion. Consistently, there was an increase of collagen deposition as demonstrated in livers of Fstl1ECKO mutants. The SMAD3 phosphorylation was significantly enhanced and pSMAD3 staining was colocalized with αSMA in vein walls, suggesting the activation of TGFβ signaling in vascular mural cells of Fstl1ECKO mice. The findings imply that endothelial FSTL1 is critical for the homeostasis of atria and veins and its insufficiency may favor cardiovascular fibrosis leading to heart failure.

Neovascularization in Recurrence of the Varicose Great Saphenous Vein following Transection

1987 ◽  
Vol 2 (2) ◽  
pp. 81-91 ◽  
Author(s):  
G.M. Glass
Keyword(s):  
Smooth Muscle ◽  
Saphenous Vein ◽  
Great Saphenous Vein ◽  
Varicose Veins ◽  
Elastic Tissue ◽  
Local Analgesia ◽  
Vascular Changes ◽  
Vein Wall ◽  
Surgical Exploration ◽  
Haemodynamic Changes

Recurrence of varicose veins after surgical treatment is widely attributed to morphological and haemodynamic changes in pre-existing collateral veins. Transection of the great saphenous vein in the thigh under local analgesia was used to promote healing of varicose ulceration. When healing was complete, saphenofemoral ligation combined with stripping or multiple ligation was performed. At the same time the vascular changes at the site of transection were investigated in 10 patients by phlebography, surgical exploration and examination of the excised vessels by radiographic and histological methods. The results showed that the continuity of the vein was restored by growth of new vessels in the surrounding tissues and vein wall. Some vessels increased in size, developing smooth muscle and elastic tissue in their walls, while the majority underwent regression. It was concluded that the theory of recurrence through pre-existing veins requires revision.

Hydraulic Behavior in Cased and Open Hole Sections in Highly Deviated Wellbores

2019 ◽  
Author(s):  
Jan David Ytrehus ◽  
Bjørnar Lund ◽  
Ali Taghipour ◽  
Birgitte Ruud Kosberg ◽  
Luca Carazza ◽  
...  
Keyword(s):  
Drilling Fluid ◽  
Transition To Turbulence ◽  
Low Flow ◽  
Wall Material ◽  
Outer Diameter ◽  
Flow Loop ◽  
Hole Cleaning ◽  
Hydraulic Behaviour ◽  
Lower Viscosity ◽  
Open Hole

Abstract In this paper we present results from flow loop experiments with an oil-based drilling fluid with micronized barite as weight materials. The use of micronized barite allows using lower viscosity drilling fluid, providing non-laminar flow, which is advantageous for particle transport in near-horizontal sections. While transition to turbulence and turbulent flow of non-Newtonian fluids has been well studied both theoretically and experimentally, there are very few published results on the effect of wellbore wall properties on flow regime transition and turbulence. This is relevant because horizontal sections are often open-hole with less well-defined surfaces than a steel casing surface. We have conducted a series of flow experiments with and without cuttings size particles in a 10 m long annular test section using steel and concrete material to represent the wellbore wall of a cased and open hole section. In both cases the annulus was formed by a freely rotating steel pipe of 2” outer diameter inside a 4” diameter wellbore. Experiments were conducted at 48°, 60° and 90° wellbore inclination from vertical. The two materials result in different hydraulic behaviour without particles with stronger turbulence when using concrete wellbore wall material than when using steel casing. While there is negligible difference at low flow rates, at 0.8 m/s and below, there is an increasing difference as the flow rate increases and becomes transitional to turbulence. Hole cleaning is found to differ dependent on the wall material. However, the effect on hole cleaning is less clear than for the pressure loss.

scholarly journals Experimental Investigation of Critical Heat Flux on Different Surfaces at Low Pressure and Low Flow

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5205
Author(s):  
Ladislav Suk ◽  
Taron Petrosyan ◽  
Kamil Stevanka ◽  
Daniel Vlcek ◽  
Pavel Gejdos
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Surface Characteristic ◽  
Low Flow ◽  
Inconel 625 ◽  
Outer Diameter ◽  
Vertically Aligned ◽  
Experimental Runs ◽  
Effect Of Surface

Steady state flow boiling experiments were carried out on several heated tubes with outer diameter 9.14 mm at outlet pressures 120, 200 and 300 kPa, inlet temperatures 64, 78 and 91 °C and approximately 400, 500, 600 and 800 kg/(m2·s) mass flux entering the vertically aligned test annulus until critical heat flux (CHF) was reached. The tubes were made of Inconel 625 with a length of 400 mm. The Inconel tubes were tested in three different modifications as smooth, abraded with 150 grit sandpaper and bead blasted. Multiple experiments were repeated on the same specimen to investigate the effect of surface characteristic changes (i.e., wettability, roughness and oxide layer morphology) on the occurrence of CHF. Despite the changes in initial wettability, the CHF dependency was not clearly observed, however, the changes in roughness led to an increase in CHF. The total number of 115 experimental runs were collected and the results were also compared with other literature experimental data.

Mixed Convective Low Flow Pressure Drop in Vertical Rod Assemblies: II—Experimental Validation

1989 ◽  
Vol 111 (4) ◽  
pp. 966-973 ◽  
Author(s):  
K. Y. Suh ◽  
N. E. Todreas ◽  
W. M. Rohsenow
Keyword(s):  
Mixed Convection ◽  
Experimental Validation ◽  
Low Flow ◽  
Laminar Regime ◽  
Transition Flow ◽  
Rod Bundles ◽  
Number Range ◽  
Experimental Procedure ◽  
Proposed Model ◽  
Flow Pressure

An experimental study has been conducted to validate the predictive models and correlations for laminar and transition flow frictional pressure loss in vertical rod bundles under mixed convection conditions. An experimental procedure has been developed to measure low differential pressures under mixed convection conditions in 19 heated rod bare and wire-wrapped assemblies. The proposed model has been found successfully to predict the effects of wire wrapping, power skew, transition from laminar regime, developing and Interacting flow redistributions, and rod number on the friction loss characteristics in bundle geometries over the bundle average Grq/Re number range of 6 to 18,500.

Evaluation of the efficacy of foam sclerosant after addition of glycerine on human great saphenous vein: histological and immunohistochemical study

2021 ◽  
Author(s):  
A Sawaby ◽  
S Maklad ◽  
I Atta ◽  
A El Abd ◽  
MM Mady ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Smooth Muscle ◽  
Varicose Vein ◽  
Immunohistochemical Study ◽  
Smooth Muscle Actin ◽  
Treatment Modalities ◽  
Muscle Fibres ◽  
Vein Wall ◽  
Saphenous Veins ◽  
The Media

Introduction Several treatment modalities have been postulated to improve the efficacy of varicose vein treatment. Addition of glycerine to the sclerosing material has been documented to increase its viscosity and subsequently prolong the duration of stability, in addition to the direct sclerosing effect of glycerine. This histological and immunohistochemical study investigated the efficacy of addition of glycerine 72% to sclerotherapy on the human varicose vein. Methods After surgical stripping of great saphenous veins, three equal segments were resected between two clamps. Specimen 1 was injected with saline only, specimen 2 was exposed to foam sclerosant 2%, and specimen 3 was exposed to a mixture of foam sclerosant 2% and glycerine 72%. All segments were left for 5min. Vein segments were then processed for histological and immunohistochemical study. Results Microscopically, haematoxylin and eosin-stained specimen 1 showed endothelial swelling, cytoplasmic eosinophilia and pyknotic nuclei. The media showed sarcoplasm vacuolisation and necrosis. Specimen 3 showed hypereosinophilic sarcoplasm of the smooth muscle fibres. Oedema was less evident, with a relative decrease in the thickness of the wall compared with specimen 2. Immunohistochemically, the expression of smooth muscle actin was weak in specimen 3 compared with specimens 1 and 2. Expression of CD31 antibody was much reduced in specimen 2 which showed conserved islands of endothelial cells. By contrast, there was a complete loss of endothelial cells in specimen 3. Conclusion Addition of glycerine 72% to foam sclerosant has a more damaging effect on human vein wall.

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