Near-Surface Velocimetry Using Evanescent Wave Illumination

2003 ◽  
Author(s):  
Songwan Jin ◽  
Peter Huang ◽  
Jinil Park ◽  
Jung Yul Yoo ◽  
Kenneth S. Breuer
Keyword(s):  
Slip Velocity ◽  
Finite Thickness ◽  
Fluorescent Microscopy ◽  
Direct Consequence ◽  
Microfluidic System ◽  
Wall Region ◽  
Near Surface ◽  
Shear Rates ◽  
Seed Particles ◽  
Apparent Slip

Total internal reflection fluorescent microscopy (TIRFM) is used to measure particle motion in the near wall region of a microfluidic system. TIRFM images have minimum background noise and contain only particles that are very close to channel surface, where slip velocities may be present. Submicron sized fluorescent particles suspended in water are used as seed particles and images are analyzed with a PTV algorithm to extract information about apparent slip velocity. At relatively low shear rates (less than 2500 sec−1), an apparent slip velocity, proportional to the shear rate was observed. However, numerical simulations show that this observation is a direct consequence of the small, but finite thickness of the illuminated region, and most likely not due to physical slip at the surface. The statistical difference in apparent slip velocities measured over hydrophilic and hydrophobic surfaces is found to be minimal. Issues associated with the experimental technique and the interpretation of the experimental results are also discussed.

Flow at the interface of a model fibrous porous medium

2001 ◽  
Vol 426 ◽  
pp. 47-72 ◽  
Author(s):  
DAVID F. JAMES ◽  
ANTHONY M. J. DAVIS
Keyword(s):  
Porous Medium ◽  
Slip Velocity ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Circular Cylinders ◽  
Interfacial Region ◽  
Filling Fraction ◽  
Apparent Slip ◽  
Square Array ◽  
Pressure Driven Flow

Planar flow in the interfacial region of an open porous medium is investigated by finding solutions for Stokes flow in a channel partially filled with an array of circular cylinders beside one wall. The cylinders are in a square array oriented across the flow and are widely spaced, so that the solid volume fraction ϕ is 0.1 or less. For this spacing, singularity methods are appropriate and so they are used to find solutions for both planar Couette flow and Poiseuille flow in the open portion of the channel. The solutions, accurate to O(ϕ), are used to calculate the apparent slip velocity at the interface, Us, and results obtained for Us are presented in terms of a dimensionless slip velocity. For shear-driven flow, this dimensionless quantity is found to depend only weakly on ϕ and to be independent of the height of the array relative to the height of the channel and independent of the cylinder size relative to the height of the channel. For pressure-driven flow, Us is found to be less than that under comparable shear-flow conditions, and dependent on cylinder size and filling fraction in this case. Calculations also show that the external flow penetrates the porous medium very little, even for sparse arrays, and that Us is about one quarter of the velocity predicted by the Brinkman model.

Apparent slip velocity of paper coatings in viscometric flows

2000 ◽  
Vol 15 (5) ◽  
pp. 502-508 ◽  
Author(s):  
Annaleena Kokko ◽  
Tom Grankvist ◽  
Nick Triantafillopoulos
Keyword(s):  
Slip Velocity ◽  
Paper Coatings ◽  
Apparent Slip

scholarly journals Exploring Hidden Local Ordering in Microemulsions with a Weak Directive Second Order Parameter

2020 ◽  
Vol 3 (3) ◽  
pp. 703-709 ◽  
Author(s):  
Michael Kerscher ◽  
Frederik Lipfert ◽  
Henrich Frielinghaus
Keyword(s):  
Order Parameter ◽  
Capillary Condensation ◽  
Grazing Incidence ◽  
Near Surface ◽  
Correlation Lengths ◽  
Shear Rates ◽  
Surface Ordering ◽  
Scalar Order Parameter ◽  
Solid Liquid Interface ◽  
Solid Liquid

Abstract So far, the near-surface ordering of microemulsions was focused on lamellar ordering while the bulk microemulsion was bicontinuous. In a series of different non-ionic surfactants the near-surface ordering of microemulsions at a hydrophilic silicon surface was studied using grazing incidence small angle neutron scattering. For the surfactant C8E3, most likely a gyroid structure was found at the solid–liquid interface, while the more efficient surfactants find lamellar ordering up to lamellar capillary condensation. The ranges for near-surface ordering are deeper than the bulk correlation lengths. These findings point towards theories that use directional order parameters that would lead to deeper near-surface ordering than simple theories with a single scalar order parameter would predict. Rheology experiments display high viscosities at very low shear rates and, therefore, support the existence of a directional order parameter.

Quantitative Imaging of Nanoparticles and Intracellular Vesicle Trafficking Using Total Internal Reflection Fluorescent Microscopy (TIRFM)

2007 ◽  
Author(s):  
Charles H. Margraves ◽  
Chang K. Choi ◽  
Kenneth D. Kihm ◽  
Anthony English ◽  
Seong H. Lee ◽  
...  
Keyword(s):  
Total Internal Reflection ◽  
Fluorescent Protein ◽  
Quantitative Imaging ◽  
Fluorescent Microscopy ◽  
Dynamic Imaging ◽  
Internal Reflection ◽  
Wall Region ◽  
Viable Solution ◽  
Multiple Cell ◽  
Green Fluorescent

Total internal reflection fluorescent microscopy (TIRFM) is a relatively well known tool used to examine the near wall region (approximately 1 μm). For years, cellular biologists have used TIRFM in a variety of experiments to examine multiple cell lines. However, much of the research has been somewhat static in nature, considering only initial and final states. With the increased ability to stain specific organelles within cells through the use of green fluorescent protein (GFP), dynamic imaging is becoming a viable solution to previously difficult problems.

scholarly journals SPITFIR(e): A supermaneuverable algorithm for restoring 2D-3D fluorescence images and videos, and background subtraction

2022 ◽  
Author(s):  
Sylvain Prigent ◽  
Hoai-Nam Nguyen ◽  
Ludovic Leconte ◽  
Cesar Augusto Valades-Cruz ◽  
Bassam Hajj ◽  
...  
Keyword(s):  
Fluorescent Microscopy ◽  
Direct Consequence ◽  
Light Sheet ◽  
Stimulated Emission ◽  
Wide Field ◽  
Modern Biology ◽  
Microscopy Imaging ◽  
Cell Behaviors ◽  
Primal Dual ◽  
Restoration Algorithms

While fluorescent microscopy imaging has become the spearhead of modern biology as it is able to generate long-term videos depicting 4D nanoscale cell behaviors, it is still limited by the optical aberrations and the photon budget available in the specimen and to some extend to photo-toxicity. A direct consequence is the necessity to develop flexible and "off-road" algorithms in order to recover structural details and improve spatial resolution, which is critical when pushing the illumination to the low levels in order to limit photo-damages. Moreover, as the processing of very large temporal series of images considerably slows down the analysis, special attention must be paid to the feasibility and scalability of the developed restoration algorithms. To address these specifications, we present a very flexible method designed to restore 2D-3D+Time fluorescent images and subtract undesirable out-of-focus background. We assume that the images are sparse and piece-wise smooth, and are corrupted by mixed Poisson-Gaussian noise. To recover the unknown image, we consider a novel convex and non-quadratic regularizer Sparse Hessian Variation) defined as the mixed norms which gathers image intensity and spatial second-order derivatives. This resulting restoration algorithm named SPITFIR(e) (SParse fIT for Fluorescence Image Restoration) utilizes the primal-dual optimization principle for energy minimization and can be used to process large images acquired with varied fluorescence microscopy modalities. It is nearly parameter-free as the practitioner needs only to specify the amount of desired sparsity (weak, moderate, high). Experimental results in lattice light sheet, stimulated emission depletion, multifocus microscopy, spinning disk confocal, and wide-field microscopy demonstrate the generic ability of the SPITFIR(e) algorithm to efficiently reduce noise and blur, and to subtract undesirable fluorescent background, while avoiding the emergence of deconvolution artifacts.

scholarly journals A Monte Carlo Model of Gas-Liquid-Hydrate Three-phase Coexistence Constrained by Pore Geometry in Marine Sediments

2021 ◽  
Vol 8 ◽  
Author(s):  
Jiangzhi Chen ◽  
Alan W. Rempel ◽  
Shenghua Mei
Keyword(s):  
Marine Sediments ◽  
Finite Thickness ◽  
Gas Bubbles ◽  
Spherical Particles ◽  
Stability Field ◽  
Phase Zone ◽  
Sediment Grain Size ◽  
Near Surface ◽  
Three Phase ◽  
Hydrate Stability

Gas hydrates form at relatively high pressures in near-surface, organic-rich marine sediments, with the base of the hydrate stability field and the onset of partial gas saturation determined by temperature increases with depth. Because of pore-scale curvature and wetting effects, the transition between gas hydrate and free gas occurrence need not take place at a distinct depth or temperature boundary, but instead can be characterized by a zone of finite thickness in which methane gas bubbles and hydrate crystals coexist with the same aqueous solution. Previous treatments have idealized pores as spheres or cylinders, but real pores between sediment grains have irregular, largely convex walls that enable the highly curved surfaces of gas bubbles and/or hydrate crystals within a given pore to change with varying conditions. In partially hydrate-saturated sediments, for example, the gas–liquid surface energy perturbs the onset of gas–liquid equilibrium by an amount proportional to bubble-surface curvature, causing a commensurate change to the equilibrium methane solubility in the liquid phase. This solubility is also constrained by the curvature of coexisting hydrate crystals and hence the volume occupied by the hydrate phase. As a result, the thickness of the three-phase zone depends not only on the pore space geometry, but also on the saturation levels of the hydrate and gaseous phases. We evaluate local geometrical constraints in a synthetic 3D packing of spherical particles resembling real granular sediments, relate the changes in the relative proportions of the phases to the three-phase equilibrium conditions, and demonstrate how the boundaries of the three-phase zone at the base of the hydrate stability field are displaced as a function of pore size, while varying with saturation level. The predicted thickness of the three-phase zone varies from tens to hundreds of meters, is inversely dependent on host sediment grain size, and increases dramatically when pores near complete saturation with hydrate and gas, requiring that interfacial curvatures become large.

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