scholarly journals Two-Aperture Microfluidic Probes as Flow Dipoles: Theory and Applications

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Mohammadali Safavieh ◽  
Mohammad A. Qasaimeh ◽  
Ali Vakil ◽  
David Juncker ◽  
Thomas Gervais
Keyword(s):  
Open Space ◽  
Scaling Laws ◽  
Microfluidic System ◽  
Flow Rate Ratio ◽  
Published Data ◽  
Tissue Slices ◽  
Flow Parameters ◽  
Mobile Channel ◽  
Injection Flow ◽  
Organotypic Tissue

Abstract A microfluidic probe (MFP) is a mobile channel-less microfluidic system under which a fluid is injected from an aperture into an open space, hydrodynamically confined by a surrounding fluid and entirely re-aspirated into a second aperture. Various MFPs have been developed and have been used for applications ranging from surface patterning of photoresists to local perfusion of organotypic tissue slices. However, the hydrodynamic and mass transfer properties of the flow under the MFP have not been analyzed and the flow parameters are adjusted empirically. Here, we present an analytical model describing the key transport properties in MFP operation, including the dimensions of the hydrodynamic flow confinement (HFC) area, diffusion broadening and shear stress as a function of: (i) probe geometry (ii) aspiration-to-injection flow rate ratio (iii) gap between MFP and substrate and (iv) reagent diffusivity. Analytical results and scaling laws were validated against numerical simulations and experimental results from published data. These results will be useful to guide future MFP design and operation, notably to control the MFP “brush stroke” while preserving shear-sensitive cells and tissues.

scholarly journals Imaging of Intracellular ATP in Organotypic Tissue Slices of the Mouse Brain using the FRET-based Sensor ATeam1.03YEMK

10.3791/60294 ◽  
2019 ◽  
Author(s):  
Rodrigo Lerchundi ◽  
Karl W. Kafitz ◽  
Marcel Färfers ◽  
Felix Beyer ◽  
Na Huang ◽  
...  
Keyword(s):  
Mouse Brain ◽  
Tissue Slices ◽  
Intracellular Atp ◽  
Organotypic Tissue

Thermodynamic Scaling Near the Critical Point

2005 ◽  
Author(s):  
Eldred H. Chimowitz
Keyword(s):  
Thermal Conductivity ◽  
Thermodynamic Properties ◽  
Critical Point ◽  
Critical Phenomena ◽  
Isothermal Compressibility ◽  
Scaling Laws ◽  
Anomalous Behavior ◽  
Published Data ◽  
Limiting Behavior ◽  
Type Of Behavior

Thermodynamic scaling near the critical point is a signature of critical phenomena, and many useful applications of supercritical solvent fluids depend upon exploiting this behavior in some technologically interesting way. Near the critical point, many transport and thermodynamic properties show anomalous behavior which is usually linked to the divergence of certain thermodynamic properties, such as the fluid’s isothermal compressibility. In figures 3.1 and 3.2 we depict the near-critical behavior of both the density of xenon and the thermal conductivity of carbon dioxide, respectively, adapted from published data [1, 2]. The onset of what appear to be critical singularities in these properties is clearly evident in both instances. In this chapter, we focus upon the thermodynamic basis for this type of behavior. In the theory of critical phenomena, the limiting behavior of certain thermodynamic properties near the critical point assumes special significance. In particular, properties that diverge at the critical point are of interest, and this divergence is usually described in terms of scaling laws.

scholarly journals Scaling of myocardial mass to flow and morphometry of coronary arteries

2008 ◽  
Vol 104 (5) ◽  
pp. 1281-1286 ◽  
Author(s):  
Jenny Susana Choy ◽  
Ghassan S. Kassab
Keyword(s):  
Coronary Arteries ◽  
Scaling Laws ◽  
Myocardial Mass ◽  
Arterial Tree ◽  
Flow Parameters ◽  
Diffuse Coronary Artery Disease ◽  
Cumulative Length ◽  
Artery Disease ◽  
Function Relationship ◽  
Relationship Of

There is no doubt that scaling relations exist between myocardial mass and morphometry of coronary vasculature. The purpose of this study is to quantify several morphological (diameter, length, and volume) and functional (flow) parameters of the coronary arterial tree in relation to myocardial mass. Eight normal porcine hearts of 117–244 g (mean of 177.5 ± 32.7) were used in this study. Various coronary subtrees of the left anterior descending, right coronary, and left circumflex arteries were perfused at pressure of 100 mmHg with different colors of a polymer (Microfil) to obtain rubber casts of arterial trees corresponding to different regions of myocardial mass. Volume, diameter, and cumulative length of coronary arteries were reconstructed from casts to analyze their relationship to the perfused myocardial mass. Volumetric flow was measured in relationship with perfused myocardial mass. Our results show that arterial volume is linearly related to regional myocardial mass, whereas the sum of coronary arterial branch lengths, vessel diameters, and volumetric flow show an ∼3/4, 3/8, and 3/4 power-law relationship, respectively, in relation to myocardial mass. These scaling laws suggest fundamental design principles underlying the structure-function relationship of the coronary arterial tree that may facilitate diagnosis and management of diffuse coronary artery disease.

scholarly journals Core mechanisms of drag enhancement on bodies settling in a stratified fluid

2019 ◽  
Vol 875 ◽  
pp. 622-656 ◽  
Author(s):  
Jie Zhang ◽  
Matthieu J. Mercier ◽  
Jacques Magnaudet
Keyword(s):  
Scaling Laws ◽  
Relative Magnitude ◽  
Stratified Fluid ◽  
The Body ◽  
Lower Atmosphere ◽  
Governing Equations ◽  
Flow Parameters ◽  
Induced Drag ◽  
Widespread Belief ◽  
Living Organisms

Stratification due to salt or heat gradients greatly affects the distribution of inert particles and living organisms in the ocean and the lower atmosphere. Laboratory studies considering the settling of a sphere in a linearly stratified fluid confirmed that stratification may dramatically enhance the drag on the body, but failed to identify the generic physical mechanism responsible for this increase. We present a rigorous splitting scheme of the various contributions to the drag on a settling body, which allows them to be properly disentangled whatever the relative magnitude of inertial, viscous, diffusive and buoyancy effects. We apply this splitting procedure to data obtained via direct numerical simulation of the flow past a settling sphere over a range of parameters covering a variety of situations of laboratory and geophysical interest. Contrary to widespread belief, we show that, in the parameter range covered by the simulations, the drag enhancement is generally not primarily due to the extra buoyancy force resulting from the dragging of light fluid by the body, but rather to the specific structure of the vorticity field set in by buoyancy effects. Simulations also reveal how the different buoyancy-induced contributions to the drag vary with the flow parameters. To unravel the origin of these variations, we analyse the different possible leading-order balances in the governing equations. Thanks to this procedure, we identify several distinct regimes which differ by the relative magnitude of length scales associated with stratification, viscosity and diffusivity. We derive the scaling laws of the buoyancy-induced drag contributions in each of these regimes. Considering tangible examples, we show how these scaling laws combined with numerical results may be used to obtain reliable predictions beyond the range of parameters covered by the simulations.

scholarly journals An organotypic slice model for ex vivo study of neural, immune, and microbial interactions of mouse intestine

2016 ◽  
Vol 310 (4) ◽  
pp. G240-G248 ◽  
Author(s):  
Luke A. Schwerdtfeger ◽  
Elizabeth P. Ryan ◽  
Stuart A. Tobet
Keyword(s):  
Ex Vivo ◽  
Three Dimensional ◽  
In Vitro Models ◽  
Microbial Interactions ◽  
Tissue Slices ◽  
Functional Investigation ◽  
Cells Of Cajal ◽  
Organotypic Tissue ◽  
Ex Vivo Study

Organotypic tissue slices provide seminatural, three-dimensional microenvironments for use in ex vivo study of specific organs and have advanced investigative capabilities compared with isolated cell cultures. Several characteristics of the gastrointestinal tract have made in vitro models for studying the intestine challenging, such as maintaining the intricate structure of microvilli, the intrinsic enteric nervous system, Peyer's patches, the microbiome, and the active contraction of gut muscles. In the present study, an organotypic intestinal slice model was developed that allows for functional investigation across regions of the intestine. Intestinal tissue slices were maintained ex vivo for several days in a physiologically relevant environment that preserved normal enterocyte structure, intact and proliferating crypt cells, submucosal organization, and muscle wall composure. Cell death was measured by a membrane-impermeable DNA binding indicator, ethidium homodimer, and less than 5% of cells were labeled in all regions of the villi and crypt epithelia at 24 h ex vivo. This tissue slice model demonstrated intact myenteric and submucosal neuronal plexuses and functional interstitial cells of Cajal to the extent that nonstimulated, segmental contractions occurred for up to 48 h ex vivo. To detect changes in physiological responses, slices were also assessed for segmental contractions in the presence and absence of antibiotic treatment, which resulted in slices with lesser or greater amounts of commensal bacteria, respectively. Segmental contractions were significantly greater in slices without antibiotics and increased native microbiota. This model renders mechanisms of neuroimmune-microbiome interactions in a complex gut environment available to direct observation and controlled perturbation.

scholarly journals Relationship between placental surface area and fetal growth rate in artiodactyls and perissodactyls

Mammalia ◽  
2017 ◽  
Vol 81 (4) ◽  
Author(s):  
Karl Klisch ◽  
Lea Carisch ◽  
Marcus Clauss
Keyword(s):  
Growth Rate ◽  
Surface Area ◽  
Fetal Growth ◽  
Scaling Laws ◽  
Gestation Period ◽  
Published Data ◽  
Gestation Length ◽  
Significant Difference

AbstractGestation periods in mammals are generally in line with scaling laws. There are several exceptions in which species of relatively similar size and degree of neonatal maturation show a significant difference in gestation length. For example the giraffids have a very long gestation period, compared to bovids of similar size. By using published data about the placental surface area at term, we show that in ungulates this surface area is more tightly correlated to the average fetal growth rate than to fetal and placenta weight. These data suggest that, within one type of placenta, gestation length and placental surface area are associated parameters.

Swelling characterization of photo-cross-linked gelatin methacrylate spherical microgels for bioencapsulation

e-Polymers ◽  
2014 ◽  
Vol 14 (3) ◽  
pp. 161-168 ◽  
Author(s):  
Jinmu Jung ◽  
Jonghyun Oh
Keyword(s):  
Flow Rate ◽  
Rate Ratio ◽  
Axial Flow ◽  
Microfluidic System ◽  
Low Flow ◽  
Flow Rate Ratio ◽  
Swelling Characteristics ◽  
Irradiation Apparatus ◽  
Proportional Relationship

AbstractThe swelling behavior of biocompatible and biodegradable polymers is important for the delivery and release of cells and drugs in biomedical applications. This study reported the swelling characteristics of photo-cross-linked gelatin methacrylate (GelMa) spherical microgels. Spherical microgels were generated in a microfluidic system consisting of a co-axial flow-focusing device for microdroplet generation and an ultraviolet (UV) irradiation apparatus for polymerization. At a low flow rate ratio (<0.14), the 9 wt.% GelMa spherical microgels were smaller than the 6 wt.% ones. In contrast, at a high flow rate ratio (>0.14), the results were reversed. Overall, a proportional relationship was observed between the flow rate ratio and the droplet size. The increased GelMa concentration improved the mechanical properties and increased the swelling ratios. The possibility of bioencapsulation was demonstrated, with good viability of 3T3 cells encapsulated in the spherical microgels.

A film flow in a drop catcher in space conditions

2007 ◽  
Vol 5 ◽  
pp. 235-240
Author(s):  
A.A. Koroteev ◽  
A.N. Osiptsov ◽  
E.S. Popushina
Keyword(s):  
Steady State ◽  
Open Space ◽  
Film Flow ◽  
Numerical Study ◽  
Film Surface ◽  
Inlet Section ◽  
Outlet Channel ◽  
Flow Parameters ◽  
State Regime ◽  
Space Conditions

A non-isothermal film flow is considered, which is formed on the inner surface of a conical drop catcher on whose inlet a uniform stream of a droplet medium is supplied under open space conditions. For the regime of inertial deposition of droplets, under the assumption of small relative thickness of the film and the absence of droplets rebounced from the film surface asymptotic models of steady-state film flow are constructed and studied. For a slow isothermal flow, the shape and parameters of the film are found analytically. For a general case, a parameteric numerical study ща the velocity and temperature distributions, as well as the film thickness, is performed. The flow parameters in the inlet section of the outlet channel are determined, and the conditions required for the steady-state regime of drop catcher operation are found.

scholarly journals Fluid-driven cracks in an elastic matrix in the toughness-dominated limit

2016 ◽  
Vol 374 (2078) ◽  
pp. 20150425 ◽  
Author(s):  
Ching-Yao Lai ◽  
Zhong Zheng ◽  
Emilie Dressaire ◽  
Howard A. Stone
Keyword(s):  
Scaling Laws ◽  
Pressure Ratio ◽  
Elastic Matrix ◽  
Viscous Effects ◽  
Self Similarity ◽  
Injection Flow ◽  
Wide Range ◽  
Crack Dynamics ◽  
Maximum Crack ◽  
Good Agreement

The dynamics of fluid-driven cracks in an elastic matrix is studied experimentally. We report the crack radius R ( t ) as a function of time, as well as the crack shapes w ( r , t ) as a function of space and time. A dimensionless parameter, the pressure ratio Δ p f /Δ p v , is identified to gauge the relative importance between the toughness (Δ p f ) and viscous (Δ p v ) effects. In our previous paper (Lai et al. 2015 Proc. R. Soc. A 471 , 20150255. ( doi:10.1098/rspa.2015.0255 )), we investigated the viscous limit experimentally when the toughness-related stresses are negligible for the crack propagation. In this paper, the experimental parameters, i.e. Young’s modulus E of the gelatin, viscosity μ of the fracturing liquid and the injection flow rate Q , were chosen so that the viscous effects in the flow are negligible compared with the toughness effects, i.e. Δ p f /Δ p v ≫1. In this limit, the crack dynamics can be described by the toughness-dominated scaling laws, which give the crack radius R ( t )∝ t 2/5 and the half maximum crack thickness W ( t )∝ t 1/5 . The experimental results are in good agreement with the predictions of the toughness scaling laws: the experimental data for crack radius R ( t ) for a wide range of parameters ( E , μ , Q ) collapse after being rescaled by the toughness scaling laws, and the rescaled crack shapes w ( r , t ) also collapse to a dimensionless shape, which demonstrates the self-similarity of the crack shape. The appropriate choice of the viscous or toughness scaling laws is important to accurately describe the crack dynamics. This article is part of the themed issue ‘Energy and the subsurface’.

A Validated CFD Methodology to Obtain the Total Pressure Loss Coefficients in Internal Compressible Flow at Junctions

2006 ◽  
Author(s):  
J. Pe´rez-Garci´a ◽  
E. Sanmiguel-Rojas ◽  
J. Herna´ndez-Grau ◽  
A. Viedma
Keyword(s):  
Compressible Flow ◽  
Pressure Loss ◽  
Total Pressure ◽  
Simulation Models ◽  
Loss Coefficient ◽  
Total Pressure Loss ◽  
Flow Rate Ratio ◽  
Published Data ◽  
One Dimensional ◽  
Pressure Loss Coefficient

A global methodology has been developed and validated to obtain the total pressure loss coefficient in internal compressible flow at T-type junctions. This methodology is based on the calculation of the thermo-fluid properties extrapolated to the branch axes intersection, once the straight pipe friction losses numerically calculated have been subtracted from the total energy losses. For this purpose, a steady adiabatic compressible one-dimensional flow with friction mathematical model has been applied to the results obtained by numerical simulation using the commercial finite volume code FLUENT. A 90 degree T-type junction has been studied and the predicted loss coefficient has been related to the extrapolated Mach number in the common branch and to the mass flow rate ratio between branches at different flow configurations, in both combining and dividing flows. The numerical results have been compared with experimental results and published data in open literature. In general, a good agreement is obtained. The correlations obtained will be applied as boundary condition in one-dimensional global simulation models of fluid systems in which these components are present.

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