scholarly journals Combinational concentration gradient confinement through stagnation flow

Lab on a Chip ◽  
2016 ◽  
Vol 16 (2) ◽  
pp. 368-376 ◽  
Author(s):  
Toh G. G. Alicia ◽  
Chun Yang ◽  
Zhiping Wang ◽  
Nam-Trung Nguyen
Keyword(s):  
Shear Stress ◽  
Concentration Gradient ◽  
Stagnation Flow ◽  
Concentration Gradients ◽  
Stress Effects ◽  
Gradient Device

A concentration gradient device generates stagnation flows which confine combinational concentration gradients within velocity wells, thereby suppressing shear stress effects.

scholarly journals Studying dynamic stress effects on the behaviour of THP-1 cells by microfluidic channels

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Semra Zuhal Birol ◽  
Rana Fucucuoglu ◽  
Sertac Cadirci ◽  
Ayca Sayi-Yazgan ◽  
Levent Trabzon
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Vascular System ◽  
Circulatory System ◽  
Disease Process ◽  
Microfluidic Channels ◽  
Shear Stresses ◽  
Stress Effects ◽  
Adhesion Behavior ◽  
Cycling System

AbstractAtherosclerosis is a long-term disease process of the vascular system that is characterized by the formation of atherosclerotic plaques, which are inflammatory regions on medium and large-sized arteries. There are many factors contributing to plaque formation, such as changes in shear stress levels, rupture of endothelial cells, accumulation of lipids, and recruitment of leukocytes. Shear stress is one of the main factors that regulates the homeostasis of the circulatory system; therefore, sudden and chronic changes in shear stress may cause severe pathological conditions. In this study, microfluidic channels with cavitations were designed to mimic the shape of the atherosclerotic blood vessel, where the shear stress and pressure difference depend on design of the microchannels. Changes in the inflammatory-related molecules ICAM-1 and IL-8 were investigated in THP-1 cells in response to applied shear stresses in an continuous cycling system through microfluidic channels with periodic cavitations. ICAM-1 mRNA expression and IL-8 release were analyzed by qRT-PCR and ELISA, respectively. Additionally, the adhesion behavior of sheared THP-1 cells to endothelial cells was examined by fluorescence microscopy. The results showed that 15 Pa shear stress significantly increases expression of ICAM-1 gene and IL-8 release in THP-1 cells, whereas it decreases the adhesion between THP-1 cells and endothelial cells.

scholarly journals Soil irrigation frequencies, compaction, air porosity and shear stress effects on soybean root development

2015 ◽  
Vol 25 (1) ◽  
pp. 22-30 ◽  
Author(s):  
G. A. Hossne ◽  
J. Méndez ◽  
M. Trujillo ◽  
F. Parra
Keyword(s):  
Shear Stress ◽  
Root Development ◽  
Soybean Root ◽  
Stress Effects ◽  
Soil Irrigation

Experimental and Numerical Investigation of H2-Air Deflagration in the Presence of Concentration Gradients

2013 ◽  
Author(s):  
S. Kudriakov ◽  
E. Studer ◽  
M. Kuznetsov ◽  
J. Grune
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Hydrogen Concentration ◽  
Concentration Gradient ◽  
Large Scale ◽  
Gravity Concentration ◽  
Concentration Gradients ◽  
Flame Acceleration ◽  
Institute Of Technology ◽  
Karlsruhe Institute

A set of experiments performed at Karlsruhe Institute of Technology (KIT) in the framework of the LACOMECO European project is devoted to flame propagation in an obstructed large scale facility A3 (of 8 m height and 33 m3 volume) with initially vertical hydrogen concentration gradients. Almost linear positive and negative (relative to gravity) concentration gradients are created prior to ignition in the range from 4% to 13%, and the process of flame acceleration is investigated depending on hydrogen concentration gradient and ignition positions. In this paper we describe the A3 facility and analyse the experimental data obtained during the project. The results of numerical simulation performed using Europlexus code are presented together with the critical discussions and conclusions.

Radial Stagnation Flow on a Twisting Cylinder

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Patrick Weidman
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Shooting Method ◽  
Azimuthal Velocity ◽  
Shear Stresses ◽  
Torsional Motion ◽  
Stagnation Flow ◽  
Strong Function ◽  
Stress Parameter ◽  
Wall Shear

The problem of stagnation-point flow impinging radially on a linearly twisting cylinder is considered. This advances previous work on the motion outside a cylinder undergoing linear torsional motion. The problem is governed by a Reynolds number R and a dimensionless torsion rate σ. Numerical calculations are carried out using the ODEINT program, and convergence of the shooting method is obtained using the MNEWT program. The radial and azimuthal wall shear stresses are found over a range of R and σ, and radial and azimuthal velocity profiles at σ={0,1,2} are presented for various values of R. The interesting feature is that the axial wall shear stress parameter f″(1) is a very weak function of σ while the azimuthal wall shear stress parameter g′(1) is a strong function of σ although both stress parameters are a strong function of R.

Ammonia diffusion through Nalophan™ bags

2013 ◽  
Vol 69 (3) ◽  
pp. 486-494 ◽  
Author(s):  
Selena Sironi ◽  
Lidia Eusebio ◽  
Licinia Dentoni ◽  
Laura Capelli ◽  
Renato Del Rosso
Keyword(s):  
Concentration Gradient ◽  
Diffusion Rate ◽  
Water Concentration ◽  
Ammonia Concentration ◽  
Polymeric Film ◽  
Concentration Gradients ◽  
Storage Times ◽  
Film Interface ◽  
Over Time

The aim of the work is to verify the diffusion rate of ammonia through the Nalophan™ film that constitutes the sampling bag, considering storage times ranging from 1 to 26 h. The ammonia decay over time was evaluated using gas-chromatography for the quantification of ammonia concentration inside the bag. The research assesses the roles of both of ammonia and water concentration gradients at the polymeric film interface on the diffusion process. The results show that both the ammonia concentration gradient and, in a less pronounced way, the water concentration gradient are the main ‘engines’ of ammonia diffusion. Double bags seem to represent a simple solution for preventing ammonia losses during storage. Another interesting result concerns the role of the bag surface on the ammonia diffusion rate: the higher the surface/volume (S/V) ratio, the higher the ammonia diffusion rate through the polymeric film.

Time and Stress Effects in the Behavior of Rubber at Low Temperature

1950 ◽  
Vol 23 (1) ◽  
pp. 54-66 ◽  
Author(s):  
J. R. Beatty ◽  
J. M. Davies
Keyword(s):  
Shear Stress ◽  
Low Temperature ◽  
Natural Rubber ◽  
Applied Stress ◽  
Dynamic Modulus ◽  
Rate Of Change ◽  
Rate Process ◽  
X Ray ◽  
Stress Effects ◽  
Rubberlike Materials

Abstract The stiffening of rubberlike materials at low temperature involves several different phenomena, sometimes with their effects superimposed. One of these is crystallization. This is a rate process which is generally very fast at high stresses and very slow at zero stress. In these experiments at temperatures near −25° C and under a shear stress of about 148 lb. per sq. in. the dynamic modulus of the rubber increased at a rate convenient to study. Correlation with x-ray data showed that crystallization was very likely responsible for the increase in stiffness. The rate of change of stiffness increased rapidly with increase in applied stress, and there was no optimum rate at −25° C, as has been found for unstressed rubber. The degree of vulcanization influenced the rate of change, tighter cures giving smaller changes. Neoprene-FR, GR-S, and polybutadiene, which ordinarily show little evidence of crystallization, showed very definite, but small increases in stiffness. Mixing GR-S with natural rubber seems to limit the crystallization of the natural rubber rather effectively, but apparently Neoprene-FR does not mix intimately enough with natural rubber to affect the crystallization of the latter appreciably.

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