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How to trap a gradient flow [article]

Sébastien Bubeck, Dan Mikulincer
2020 arXiv   pre-print
Our main contribution is an algorithm, which we call gradient flow trapping (GFT), and the analysis of its oracle complexity.  ...  Moreover for d=2 he also proved a lower bound of Ω(1/√(ε)) for deterministic algorithms (we extend this result to randomized algorithms).  ...  In Section 2 we make a basic "local to global" observation about gradient flow which forms the basis of our "trapping" strategy.  ... 
arXiv:2001.02968v3 fatcat:segica6bubegfnv4rrspupx2oe

Optofluidic Particle Manipulation: Optical Trapping in a Thin-Membrane Microchannel

Zachary J. Walker, Tanner Wells, Ethan Belliston, Seth B. Walker, Carson Zeller, Mohammad Julker Neyen Sampad, S. M. Saiduzzaman, Holger Schmidt, Aaron R. Hawkins
2022 Biosensors  
On-chip waveguides are used to direct light into microfluidic trapping channels. Radiation pressure is used to push particles into a protrusion cavity, isolating the particles from liquid flow.  ...  Trapping performance is modeled for both cases. The first design, referred to as the orthogonal force design, is shown to have a 80% capture efficiency under typical operating conditions.  ...  For a fluid moving at a given speed, it is desirable to know how far up the channel in the z direction the particle would travel before becoming susceptible to the gradient force and centralizing as shown  ... 
doi:10.3390/bios12090690 pmid:36140075 fatcat:rj3pfge45baplkzm7fqo5ghx7y

Optothermal Molecule Trapping by Opposing Fluid Flow with Thermophoretic Drift

Stefan Duhr, Dieter Braun
2006 Physical Review Letters  
Thermophoresis moves molecules along temperature gradients, typically from hot to cold.  ...  As an application, we show how a radially converging temperature field confines short DNA into a 10 m small spot.  ...  This result illustrates how optically triggered thermophoretic traps can accumulate molecules in a variety of geometries.  ... 
doi:10.1103/physrevlett.97.038103 pmid:16907547 fatcat:wqv5a5u3s5e53kufzt7uiyuhsq

Fluido-Dynamic and Electromagnetic Characterization of 3D Carbon Dielectrophoresis with Finite Element Analysis

Rodrigo Martinez-Duarte, Salvatore Cito, Esther Collado-Arredondo,, Sergio O. Martinez, Marc J. Madou
2008 Sensors & Transducers  
Results demonstrate correlation between a decreasing flow velocity gradient and an increasing electric field gradient toward electrodes' surfaces which is optimal for selected CarbonDEP applications.  ...  in a water-based medium.  ...  Thanks to members of the Madou BIOMEMS research group and INRF at UCI for valuable discussions and support.  ... 
doaj:26d3fcb244094d46a204fb3a646c5246 fatcat:crkys3qjqja7ppun74aulcp6pq

Spatiotemporal Analysis of Cell Response to a Rigidity Gradient: A Quantitative Study Using Multiple Optical Tweezers

Myriam Allioux-Guérin, Delphine Icard-Arcizet, Christiane Durieux, Sylvie Hénon, François Gallet, Jean-Claude Mevel, Marie-Jo Masse, Marc Tramier, Maïté Coppey-Moisan
2009 Biophysical Journal  
Our results show that the strengthening of extracellular matrix-cytoskeleton linkages along a rigidity gradient is regulated by controlling adhesion area and actomyosin recruitment, to maintain a constant  ...  The rate at which force increases is proportional to trap stiffness.  ...  This work was supported by a grant from the Association pour la Recherche sur le Cancer, from Gefluc, and from the Agence National pour le Recherche (contracts 5A0631 and 5A0614).  ... 
doi:10.1529/biophysj.108.134627 pmid:18931254 pmcid:PMC2710016 fatcat:yl65xdhs7zh7xastcqab4tojje

A simple but rigorous model for calculating CO2 storage capacity in deep saline aquifers at the basin scale

Michael Szulczewski, Ruben Juanes
2009 Energy Procedia  
In this study, we explain a new model to calculate basin-scale storage capacity that is derived from flow dynamics and captures the dynamic phenomena of gravity override and capillary trapping.  ...  The only method to calculate storage capacity at the basin scale, however, is not derived from multiphase flow dynamics, which play a critical role in CO 2 storage.  ...  We calculate pressure to be 15 MPa using a hydrostatic gradient.  ... 
doi:10.1016/j.egypro.2009.02.117 fatcat:xs3gqw4iwvdmdkz4fbgz53tm6i

Design and Fabrication of a Dielectrophoretic Cell Trap Array

Logeeshan Velmanickam, Dharmakeerthi Nawarathna
2017 Advances in Science, Technology and Engineering Systems  
We present a design and fabrication of an integrated micro-fabricated dielectrophoretic (DEP) cell trap array in a microfluidic channel.  ...  In this work, we have used commercially available polystyrene beads to show the concept. Bead clusters of various sizes were successfully produced using DEP force (attractive or repulsive).  ...  We would like to thank Vidura Jayasooriya, Bharat Verma, Darrin Laudenbach and Jenna Pender in the Department of Electrical and Computer Engineering at the North Dakota State University for their help  ... 
doi:10.25046/aj020110 fatcat:vyg5ys7dkzgwfpxk64uk6o352u

Microscopic Investigation of Vortex Breakdown in a Dividing T-Junction Flow [article]

San To Chan, Simon J. Haward, Amy Q. Shen
2018 arXiv   pre-print
3D-printed microfluidic devices offer new ways to study fluid dynamics. We present the first clear visualization of vortex breakdown in a dividing T-junction flow.  ...  Our results are summarized in a dimensionless phase diagram, which will guide the use of vortex breakdown in T-junctions to achieve specific flow manipulation.  ...  This provides a simple way to study how vorticity decay affects the vortex breakdown in a T-junction flow.  ... 
arXiv:1806.10754v1 fatcat:yeef4xc32zdhrdj2c7phia7z2u

Trapping Effects of Small Scale Sedimentary Heterogeneities

Peter Frykman, Carsten M. Nielsen, Niels Bech
2013 Energy Procedia  
The presented modeling study illustrates how even small-scale heterogeneity has implications for how the CO 2 is distributed and trapped in sedimentary sequences, and outlines a workflow for the study  ...  The initial flow simulation results show that in addition to the capillary trapped CO 2 which remains after an imbibition process and which is caused by well explained hysteresis, some is also arrested  ...  A digital version of the facies index model has kindly been supplied by Peter Bayer (ETH) who allowed access to the files from the study.  ... 
doi:10.1016/j.egypro.2013.06.453 fatcat:v5yejanzl5avlmhq7exomekbma

Global gyrokinetic turbulence simulations of MAST plasmas

S Saarelma, P Hill, A Bottino, G Colyer, A R Field, B McMillan, A Peeters, C M Roach
2012 Plasma Physics and Controlled Fusion  
In global simulations the flow shear stabilisation is found to be asymmetric with respect the direction of the flow: there is a small destabilising effect at low flow shear when the flow is in the co-direction  ...  When the electron response is assumed to be adiabatic, growth rates are found to be lower than the experimental E × B flow shearing rate.  ...  Figure 5 shows how the growth rates, with and without the experimental flow, vary as a function of the assumed ion temperature gradient.  ... 
doi:10.1088/0741-3335/54/8/085012 fatcat:bnozsbxnrzh3bhabsamyd3viru

Size and surface charge characterization of nanoparticles with a salt gradient

Martin K. Rasmussen, Jonas N. Pedersen, Rodolphe Marie
2020 Nature Communications  
The salt gradient causes oppositely directed particle and fluid transport that trap particles. Within minutes, the particle concentration increases more than two orders of magnitude.  ...  Here, we concentrate exosomes from a dilute solution and measure their size and zeta potential in a one-step measurement with a salt gradient in a capillary channel.  ...  The physical mechanism behind diffusiophoresis also gives rise to a diffusioosmotic fluid flow in the presence of a solute gradient near a charged plane 26 , for example, in a nanochannel 37 .  ... 
doi:10.1038/s41467-020-15889-3 pmid:32393750 fatcat:b7ezm6xujzgdbep3mo65tvyxeq

A microfluidic array for large-scale ordering and orientation of embryos

Kwanghun Chung, Yoosik Kim, Jitendra S Kanodia, Emily Gong, Stanislav Y Shvartsman, Hang Lu
2010 Nature Methods  
Based on passive hydrodynamics, we developed a microfluidic embryo trap array that rapidly orders and vertically orients hundreds of embryos.  ...  We describe the physical principles of the design and use this platform for the quantitative analysis of multiple morphogen gradients in the dorsoventral patterning system.  ...  In this paper, we describe the design and the physical principles of the embryo trap array and demonstrate how it can be used in to quantify morphogen gradients in fixed embryos and to monitor nuclear  ... 
doi:10.1038/nmeth.1548 pmid:21186361 pmcid:PMC4100329 fatcat:usvi44cnfbd6pfjcsrnkmly2eu

A mathematical model on the closing and opening mechanism for venus flytrap

Ruoting Yang, Scott C. Lenaghan, Mingjun Zhang, Lijin Xia
2010 Plant Signalling & Behavior  
Voltage-gated channels block water flow to the inner layer by maintaining a h + gradient, which leads to high elastic energy in the open state of the trap.  ...  on an osmotic gradient for flow. 7 If prey stimulates an AP, then the voltage gated channels open for a short time creating a gradient, which allows the aquaporin channels to open.  ... 
doi:10.4161/psb.5.8.12136 pmid:21460610 pmcid:PMC3115172 fatcat:vkzpthqa3zc4lbqsi4ywwvoywi

Unexpected trapping of particles at a T junction

Daniele Vigolo, Stefan Radl, Howard A. Stone
2014 Proceedings of the National Academy of Sciences of the United States of America  
Here we report experimental evidence and a theoretical description of a trapping mechanism for low-density particles in steady and pulsatile flows through Tshaped junctions.  ...  to industry and physiology. fluid dynamics | bubble trapping | vortex breakdown | 3D simulations  ...  In this paper we provide a more systematic understanding of how particles move through a simple bifurcation, i.e., a T junction.  ... 
doi:10.1073/pnas.1321585111 pmid:24639547 pmcid:PMC3977238 fatcat:pzlnnafvtng7tcbhduw7yxs4by

Whirl-enhanced continuous wave laser trapping of particles

S. Bartkiewicz, A. Miniewicz
2015 Physical Chemistry, Chemical Physics - PCCP  
This work highlights the role of the laser-induced whirl formation in a solvent–solute system for molecular trapping, liquid–liquid phase separation and controlled crystal growth under an optical microscope  ...  This work is dedicated to Dr Francois Kajzar (France) on the occasion of his 70 th birthday. Notes and references a Institute of Physical and Theoretical Chemistry, Department of  ...  The whirl in this case is formed preferably by trapping a gas/air bubble at its top to facilitate smooth flow of streams of liquid.  ... 
doi:10.1039/c4cp04008b pmid:25412568 fatcat:fvbcizsdnzecni2bt6k4m2ymfi
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