Defect Nucleation and Annihilation in Sheared Polymeric Liquid Crystals

ABSTRACTShear–induced nucleation and annihilation of topological defects due to hydrodynamic instability in nematic liquid crystals is a phenomenon of both scientific interest and practical importance. We use a complete generalized non-linear second order tensor Landau-de Gennes model that takes into account short range order elasticity, long-range elasticity and viscous effects, to simulate the nucleation and annihilation of twist inversion walls in flow-aligning nematic polymers subjected to shear flow. Shearing a homogeneous nematic sample perpendicular to the director results in an linear instability that maybe symmetric at low shear rates, and antisymmetric at higher shear rates. At even higher shear rates the onset of nonlinearities results in the nucleation of a parallel array of twist inversion walls, such that asymmetry prevails. By increasing the shear rate the following director symmetry transition cascade is observed: symmetric → antisymmetric → asymmetric → symmetric. The nucleation of the parallel array of twist inversion walls in the asymmetric mode is due to the degeneracy in reorientation towards the shear plane. The annihilation of twist walls is mediated by twist waves along the velocity gradient direction. Twist walls annihilate by three mechanisms: wall-wall annihilations, wall-wall coalescence, and wall-bounding surface coalescence. The annihilation rate increases with increasing shear rate and at sufficiently high rates the layered structure is replaced by a homogeneously aligned system. The role of short range and long range elasticity on defect nucleation and annihilation is characterized in terms of the Deborah and Ericksen numbers. Close form solutions to approximated equations are used to explain the numerical results of the full Landau-de Gennes equations of nematodynamics.

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The Competition Between Long-Range Antiferroelectric Order and Short-Range Antiferroelectric Forces as a Possible Cause of Reentrant Behavior in Polar Liquid Crystals

Molecular Crystals and Liquid Crystals Science and Technology Section A Molecular Crystals and Liquid Crystals ◽

10.1080/10587259308028795 ◽

1993 ◽

Vol 226 (1) ◽

pp. 123-136 ◽

Cited By ~ 3

Author(s):

L. V. Mirantsev

Keyword(s):

Liquid Crystals ◽

Long Range ◽

Short Range ◽

Polar Liquid ◽

Possible Cause

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INTERMOLECULAR POTENTIALS IN LIQUID CRYSTALS: COMPARISON BETWEEN SIMULATIONS AND NMR EXPERIMENTS

International Journal of Modern Physics C ◽

10.1142/s0129183199000309 ◽

1999 ◽

Vol 10 (02n03) ◽

pp. 403-413 ◽

Cited By ~ 12

Author(s):

RAYMOND T. SYVITSKI ◽

JAMES M. POLSON ◽

E. ELLIOTT BURNELL

Keyword(s):

Liquid Crystals ◽

Long Range ◽

Short Range ◽

Intermolecular Forces ◽

Order Parameters ◽

Intermolecular Potential ◽

Nmr Data ◽

Long Range Interactions ◽

Orientational Ordering ◽

Best Fit

The anisotropic intermolecular forces responsible for the orientational ordering in liquid crystals are probed by comparing Monte Carlo (MC) simulations with experimental nuclear magnetic resonance (NMR) results for solutes in nematic liquid crystals. In a special liquid crystal mixture where all long-range interactions are assumed to be minimized, the models for short-range interactions which best fit NMR experimental solute order parameters also best fit solute order parameters from MC simulations of hard ellipsoids. This is taken as an indication that in this special mixture the intermolecular potential is dominated by short-range forces. However, for liquid crystals where long-range interactions are important, simulations of hard ellipsoids with point quadrupoles cannot reproduce even the gross effects observed with experimental NMR data.

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Adenosine Diphosphate-Induced Aggregation of Human Platelets in Flow Through Tubes: III. Shear and Extrinsic Fibrinogen-Dependent Effects

Thrombosis and Haemostasis ◽

10.1055/s-0038-1642388 ◽

1994 ◽

Vol 71 (01) ◽

pp. 078-090 ◽

Cited By ~ 19

Author(s):

H L Goldsmith ◽

M M Frojmovic ◽

Susan Braovac ◽

Fiona McIntosh ◽

T Wong

Keyword(s):

Shear Rate ◽

Single Cells ◽

Adenosine Diphosphate ◽

Human Platelets ◽

Size Analysis ◽

Fibrinogen Concentration ◽

Human Fibrinogen ◽

Shear Rates ◽

Rate Dependent ◽

Induced Aggregation

SummaryThe effect of shear rate and fibrinogen concentration on adenosine diphosphate-induced aggregation of suspensions of washed human platelets in Poiseuille flow at 23°C was studied using a previously described double infusion technique and resistive particle counter size analysis (1). Using suspensions of multiple-centrifuged and -washed cells in Tyrodes-albumin [3 × 105 μl−1; (17)] with [fibrinogen] from 0 to 1.2μM, the, rate and extent of aggregation with 0.7 μM ADP in Tyrodes-albumin were measured over a range of mean transit times from 0.2 to 43 s, and at mean tube shear rates, Ḡ, = 41.9, 335 and 1,335 s−1. As measured by the decrease in singlet concentration, aggregation at 1.2 μM fibrinogen increased with increasing Ḡ up to 1,335 s1, in contrast to that previously reported in citratcd plasma, in which aggregation reached a maximum at Ḡ = 335 s−1. Without added fibrinogen, there was no aggregation at Ḡ = 41.9 s1; at Ḡ = 335 s1, there was significant aggregation but with an initial lag time, aggregation increasing further at Ḡ = 1,335 s−1. Without added fibrinogen, aggregation was abolished at all Ḡ upon incubation with the hexapeptide GRGDSP, but was almost unaffected by addition of an F(ab’)2 fragment of an antibody to human fibrinogen. Aggregation in the absence of added fibrinogen was also observed at 37°C. The activation of the multiple-washed platelets was tested using flow cytometry with the fluorescently labelled monoclonal antibodies FITC-PAC1 and FITC-9F9. It was shown that 57% of single cells in unactivated PRT expressed maximal GPIIb-IIIa fibrinogen receptors (MoAb PAC1) and 54% expressed pre-bound fibrinogen (MoAb 9F9), with further increases on ADP activation. However, incubation with GRGDSP and the F(ab’)2 fragment did not inhibit the prebound fibrinogen. Moreover, relatively unactivated cells (8% expressing receptor, 14% prebound fibrinogen), prepared from acidified cPRP by single centrifugation with 50 nM of the stable prostacyclin derivative, ZK 36 374, and resuspension in Tyrodes-albumin at 5 × 104 μl−1, aggregated with 2 and 5 μM ADP at Ḡ = 335 and 1,335 s−1 in the absence of added fibrinogen. We therefore postulate that a protein such as von Willebrand factor, secreted during platelet isolation or in flow at sufficiently high shear rates, may yield the observed shear-rate dependent aggregation without fibrinogen.

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Properties of twisted topological defects in 2D nematic liquid crystals

Soft Matter ◽

10.1039/d1sm00825k ◽

2021 ◽

Author(s):

Daniel Pearce ◽

Karsten Kruse

Keyword(s):

Liquid Crystals ◽

Nematic Liquid Crystals ◽

Topological Defects ◽

Two Dimensional

Topological defects are one of the most conspicuous features of liquid crystals. In two dimensional nematics, they have been shown to behave effectively as particles with both, charge and orientation,...

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Structural basis of long-range to short-range synaptic transition in NHEJ

Nature ◽

10.1038/s41586-021-03458-7 ◽

2021 ◽

Author(s):

Siyu Chen ◽

Linda Lee ◽

Tasmin Naila ◽

Susan Fishbain ◽

Annie Wang ◽

...

Keyword(s):

Long Range ◽

Short Range ◽

Structural Basis

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Shear-Induced and Nanofiber-Nucleated Crystallization of Novel Aliphatic–Aromatic Copolyesters Delineated for In Situ Generation of Biodegradable Nanocomposites

Polymers ◽

10.3390/polym13142315 ◽

2021 ◽

Vol 13 (14) ◽

pp. 2315

Author(s):

Ramin Hosseinnezhad

Keyword(s):

Shear Rate ◽

Cooling Rate ◽

Isothermal Crystallization ◽

Cellulose Nanofibers ◽

Crystallization Time ◽

Nucleation Density ◽

Shear Rates ◽

Biodegradable Nanocomposites ◽

In Situ Generation

The shear-induced and cellulose-nanofiber nucleated crystallization of two novel aliphatic–aromatic copolyesters is outlined due to its significance for the in situ generation of biodegradable nanocomposites, which require the crystallization of nanofibrous sheared inclusions at higher temperatures. The shear-induced non-isothermal crystallization of two copolyesters, namely, poly(butylene adipate-co-succinate-co-glutarate-co-terephthalate) (PBASGT) and poly(butylene adipate-co-terephthalate) (PBAT), was studied following a light depolarization technique. To have a deep insight into the process, the effects of the shear rate, shear time, shearing temperature and cooling rate on the initiation, kinetics, growth and termination of crystals were investigated. Films of 60 μm were subjected to various shear rates (100–800 s−1) for different time intervals during cooling. The effects of the shearing time and increasing the shear rate were found to be an elevated crystallization temperature, increased nucleation density, reduced growth size of lamella stacks and decreased crystallization time. Due to the boosted nucleation sites, the nuclei impinged with each other quickly and growth was hindered. The effect of the cooling rate was more significant at lower shear rates. Shearing the samples at lower temperatures, but still above the nominal melting point, further shifted the non-isothermal crystallization to higher temperatures. As a result of cellulose nanofibers’ presence, the crystallization of PBAT, analyzed by DSC, was shifted to higher temperatures.

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Comparison of short-range order in irradiated dysprosium titanates

npj Materials Degradation ◽

10.1038/s41529-021-00165-6 ◽

2021 ◽

Vol 5 (1) ◽

Author(s):

Roman Sherrod ◽

Eric C. O’Quinn ◽

Igor M. Gussev ◽

Cale Overstreet ◽

Joerg Neuefeind ◽

...

Keyword(s):

Long Range ◽

Short Range ◽

Structural Model ◽

Ion Irradiation ◽

Function Analysis ◽

Ion Beam ◽

Structural Response ◽

Heavy Ion ◽

Range Order ◽

Radiation Resistant

AbstractThe structural response of Dy2TiO5 oxide under swift heavy ion irradiation (2.2 GeV Au ions) was studied over a range of structural length scales utilizing neutron total scattering experiments. Refinement of diffraction data confirms that the long-range orthorhombic structure is susceptible to ion beam-induced amorphization with limited crystalline fraction remaining after irradiation to 8 × 1012 ions/cm2. In contrast, the local atomic arrangement, examined through pair distribution function analysis, shows only subtle changes after irradiation and is still described best by the original orthorhombic structural model. A comparison to Dy2Ti2O7 pyrochlore oxide under the same irradiation conditions reveals a different behavior: while the dysprosium titanate pyrochlore is more radiation resistant over the long-range with smaller degree of amorphization as compared to Dy2TiO5, the former involves more local atomic rearrangements, best described by a pyrochlore-to-weberite-type transformation. These results highlight the importance of short-range and medium-range order analysis for a comprehensive description of radiation behavior.

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Mobile and immobile boundaries in ferroelectric films

Scientific Reports ◽

10.1038/s41598-021-81516-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

P. Yudin ◽

K. Shapovalov ◽

T. Sluka ◽

J. Peräntie ◽

H. Jantunen ◽

...

Keyword(s):

Long Range ◽

Domain Walls ◽

Ferroelectric Properties ◽

Practical Importance ◽

Dynamic Responses ◽

Ferroelectric Films ◽

Domain Structures ◽

Mobile Interfaces ◽

Ferroelastic Domains ◽

Viable Method

AbstractThe intrinsic mobile interfaces in ferroelectrics—the domain walls can drive and enhance diverse ferroelectric properties, essential for modern applications. Control over the motion of domain walls is of high practical importance. Here we analyse theoretically and show experimentally epitaxial ferroelectric films, where mobile domain walls coexist and interact with immobile growth-induced interfaces—columnar boundaries. Whereas these boundaries do not disturb the long-range crystal order, they affect the behaviour of domain walls in a peculiar selective manner. The columnar boundaries substantially modify the behaviour of non-ferroelastic domains walls, but have negligible impact on the ferroelastic ones. The results suggest that introduction of immobile boundaries into ferroelectric films is a viable method to modify domain structures and dynamic responses at nano-scale that may serve to functionalization of a broader range of ferroelectric films where columnar boundaries naturally appear as a result of the 3D growth.

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