scholarly journals Quantifying Material Properties of Cell Monolayers by Analyzing Integer Topological Defects

2021 ◽  
Vol 126 (2) ◽  
Author(s):  
Carles Blanch-Mercader ◽  
Pau Guillamat ◽  
Aurélien Roux ◽  
Karsten Kruse
Keyword(s):  
Material Properties ◽  
Topological Defects ◽  
Cell Monolayers

Unifying polar and nematic active matter: Emergence and co-existence of half-integer and full-integer topological defects

2022 ◽  
Author(s):  
Aboutaleb Amiri ◽  
Romain Mueller ◽  
Amin Doostmohammadi
Keyword(s):  
Continuum Model ◽  
Topological Defect ◽  
Topological Defects ◽  
Active Matter ◽  
Defect States ◽  
Cell Monolayers ◽  
Half Integer ◽  
Generic Framework ◽  
Active Turbulence ◽  
The Continuum

Abstract The presence and significance of active topological defects is increasingly realised in diverse biological and biomimetic systems. We introduce a continuum model of polar active matter, based on conservation laws and symmetry arguments, that recapitulates both polar and apolar (nematic) features of topological defects in active turbulence. Using numerical simulations of the continuum model, we demonstrate the emergence of both half- and full-integer topological defects in polar active matter. Interestingly, we find that crossover from active turbulence with half- to full-integer defects can emerge with the coexistence region characterized by both defect types. These results put forward a minimal, generic framework for studying topological defect patterns in active matter which is capable of explaining the emergence of half-integer defects in polar systems such as bacteria and cell monolayers, as well as predicting the emergence of coexisting defect states in active matter.

scholarly journals Novel optofluidic concepts enabled by topological microfluidics-INVITED

2021 ◽  
Vol 255 ◽  
pp. 10002
Author(s):  
Anupam Sengupta
Keyword(s):  
Material Properties ◽  
Topological Defects ◽  
Optical Fields ◽  
Surface Anchoring ◽  
Micro Scale ◽  
Mechanical Responses ◽  
Non Invasive ◽  
The Rich ◽  
Director Orientation

The coupling between flow and director orientation of liquid crystals (LCs) has been long utilized to devise wide-ranging applications spanning modern displays, medical and environmental solutions, and bio-inspired designs and applications. LC-based optofluidic platforms offer a non-invasive handle to modulate light and material fields, both locally and dynamically. The flow-driven reorientation of the LC molecules can tailor distinct optical and mechanical responses in microfluidic confinements, and harness the coupling therein. Yet the synergy between traditional optofluidics with isotropic fluids and LC microfluidics remains at its infancy. Here, we discuss emerging optofluidic concepts based on Topological Microfluidics, leveraging microfluidic control of topological defects and defect landscapes. With a specific focus on the role of surface anchoring and microfluidic geometry, we present recent and ongoing works that harness flow-controlled director and defect configurations to modulate optical fields. The flow-induced optical attributes, and the corresponding feedback, is enhanced in the vicinity of the topological defects which geenerate distinct isotropic opto-material properties within an anisotropic matrix. By harnessing the rich interplay of confining geometry, anchoring and micro-scale nematodynamics, topological microfluidics offers a promising platform to ideate the next generation of optofluidic and optomechnical concepts.

scholarly journals Topological defects of integer charge in cell monolayers

Soft Matter ◽  
2021 ◽  
Author(s):  
Kirsten D. Endresen ◽  
MinSu Kim ◽  
Matthew Pittman ◽  
Yun Chen ◽  
Francesca Serra
Keyword(s):  
Epithelial Cells ◽  
Topological Charge ◽  
Topological Defects ◽  
Cell Type ◽  
Cell Monolayers

Using microscale topographic patterns to guide fibroblasts and epithelial cells to form topological defects in monolayers, we examine behaviors dependent on cell type as well as topological charge.

scholarly journals Cross-talk between topological defects in different fields revealed by nematic microfluidics

2017 ◽  
Vol 114 (29) ◽  
pp. E5771-E5777 ◽  
Author(s):  
Luca Giomi ◽  
Žiga Kos ◽  
Miha Ravnik ◽  
Anupam Sengupta
Keyword(s):  
Cross Talk ◽  
Material Properties ◽  
Topological Charge ◽  
Topological Defects ◽  
Vital Role ◽  
Microwave Background ◽  
Stagnation Points ◽  
Nematic Director ◽  
Cosmic Microwave Background Polarization ◽  
Topological Charges

Topological defects are singularities in material fields that play a vital role across a range of systems: from cosmic microwave background polarization to superconductors and biological materials. Although topological defects and their mutual interactions have been extensively studied, little is known about the interplay between defects in different fields—especially when they coevolve—within the same physical system. Here, using nematic microfluidics, we study the cross-talk of topological defects in two different material fields—the velocity field and the molecular orientational field. Specifically, we generate hydrodynamic stagnation points of different topological charges at the center of star-shaped microfluidic junctions, which then interact with emergent topological defects in the orientational field of the nematic director. We combine experiments and analytical and numerical calculations to show that a hydrodynamic singularity of a given topological charge can nucleate a nematic defect of equal topological charge and corroborate this by creating −1, −2, and −3 topological defects in four-, six-, and eight-arm junctions. Our work is an attempt toward understanding materials that are governed by distinctly multifield topology, where disparate topology-carrying fields are coupled and concertedly determine the material properties and response.

scholarly journals Integer topological defects of cell monolayers: Mechanics and flows

2021 ◽  
Vol 103 (1) ◽  
Author(s):  
Carles Blanch-Mercader ◽  
Pau Guillamat ◽  
Aurélien Roux ◽  
Karsten Kruse
Keyword(s):  
Topological Defects ◽  
Cell Monolayers

scholarly journals Active forces in confluent cell monolayers

2021 ◽  
Author(s):  
Guanming Zhang ◽  
Julia Mary Yeomans
Keyword(s):  
Field Model ◽  
Collective Motion ◽  
Cell Monolayer ◽  
Phase Field Model ◽  
Topological Defects ◽  
Cellular Interactions ◽  
Cell Monolayers ◽  
Nematic Ordering ◽  
Active Turbulence ◽  
Confluent Cell

We use a computational phase-field model together with analytical analysis to study how inter-cellular active forces can mediate individual cell morphology and collective motion in a confluent cell monolayer. Contractile inter-cellular interactions lead to cell elongation, nematic ordering and active turbulence, characterised by motile topological defects. Extensile interactions result in frustration, and perpendicular cell orientations become more prevalent. Furthermore, we show that contractile behaviour can change to extensile behaviour if anisotropic fluctuations in cell shape are considered.

scholarly journals Chiral stresses in nematic cell monolayers

Soft Matter ◽  
2020 ◽  
Vol 16 (3) ◽  
pp. 764-774 ◽  
Author(s):  
Ludwig A. Hoffmann ◽  
Koen Schakenraad ◽  
Roeland M. H. Merks ◽  
Luca Giomi
Keyword(s):  
Collective Motion ◽  
Topological Defects ◽  
Cell Monolayers ◽  
Microscopic Origin

We discuss the microscopic origin of chiral stresses in nematic cell monolayers and investigate how chirality affects the motion of topological defects, as well as the collective motion in stripe-shaped domains.

A pre-embedding, protein a-gold immunolabelling technique for cytocentrifuged cell monolayers for lm and tem

1986 ◽  
Vol 44 ◽  
pp. 220-221
Author(s):  
K. Chien ◽  
I.P. Shintaku ◽  
A.F. Sassoon ◽  
R.L. Van de Velde ◽  
R. Heusser
Keyword(s):  
Cell Surface ◽  
Staining Method ◽  
Protein A ◽  
Surface Antigens ◽  
Cell Suspensions ◽  
Cellular Morphology ◽  
Cellular Phenotype ◽  
Cell Surface Antigens ◽  
Cell Monolayers ◽  
Diagnostic Histopathology

Identification of cellular phenotype by cell surface antigens in conjunction with ultrastructural analysis of cellular morphology can be a useful tool in the study of biologic processes as well as in diagnostic histopathology. In this abstract, we describe a simple pre-embedding, protein A-gold staining method which is designed for cell suspensions combining the handling convenience of slide-mounted cell monolayers and the ability to evaluate specimen staining specificity prior to EM embedding.

Grain boundary segregation in metals

1992 ◽  
Vol 50 (2) ◽  
pp. 1204-1205
Author(s):  
C.L. Briant
Keyword(s):  
Fracture Surface ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Material Properties ◽  
Electron Spectroscopy ◽  
High Vacuum ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Local Concentration ◽  
The One

Grain boundary segregation is the process by which solute elements in a material diffuse to the grain boundaries, become trapped there, and increase their local concentration at the boundary over that in the bulk. As a result of this process this local concentration of the segregant at the grain boundary can be many orders of magnitude greater than the bulk concentration of the segregant. The importance of this problem lies in the fact that grain boundary segregation can affect many material properties such as fracture, corrosion, and grain growth.One of the best ways to study grain boundary segregation is with Auger electron spectroscopy. This spectroscopy is an extremely surface sensitive technique. When it is used to study grain boundary segregation the sample must first be fractured intergranularly in the high vacuum spectrometer. This fracture surface is then the one that is analyzed. The development of scanning Auger spectrometers have allowed researchers to first image the fracture surface that is created and then to perform analyses on individual grain boundaries.

Processing Immunoperoxidase Labeled Cell Monolayers and Cryostat Sesctions For Electron Microscopy

1985 ◽  
Vol 43 ◽  
pp. 714-715
Author(s):  
K. Chien ◽  
R. Van de Velde ◽  
I.P. Shintaku ◽  
A.F. Sassoon
Keyword(s):  
Cell Monolayer ◽  
Cell Types ◽  
Surface Antigens ◽  
Immunoperoxidase Method ◽  
Reaction Step ◽  
Hot Plate ◽  
Air Drying ◽  
New Approach ◽  
Cell Monolayers ◽  
Glass Slides

Immunoelectron microscopy of neoplastic lymphoma cells is valuable for precise localization of surface antigens and identification of cell types. We have developed a new approach in which the immunohistochemical staining can be evaluated prior to embedding for EM and desired area subsequently selected for ultrathin sectioning.A freshly prepared lymphoma cell suspension is spun onto polylysine hydrobromide- coated glass slides by cytocentrifugation and immediately fixed without air drying in polylysine paraformaldehyde (PLP) fixative. After rinsing in PBS, slides are stained by a 3-step immunoperoxidase method. Cell monolayer is then fixed in buffered 3% glutaraldehyde prior to DAB reaction. After the DAB reaction step, wet monolayers can be examined under LM for presence of brown reaction product and selected monolayers then processed by routine methods for EM and embedded with the Chien Re-embedding Mold. After the polymerization, the epoxy blocks are easily separated from the glass slides by heatingon a 100°C hot plate for 20 seconds.

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