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Smolarek T, Haff GG, Poon WCK, Nagatani T, Barley OR, Guppy SN. Dynamic and Isometric Force-Time Curve Characteristics Influencing Change of Direction Performance of State-Level Netball Players. J Strength Cond Res 2023; 37:2397-2404. [PMID: 37815246 DOI: 10.1519/jsc.0000000000004616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/11/2023]
Abstract
ABSTRACT Smolarek, T, Haff, GG, Poon, WCK, Nagatani, T, Barley, OR, and Guppy, SN. Dynamic and isometric force-time curve characteristics influencing change of direction performance of state-level netball players. J Strength Cond Res 37(12): 2397-2404, 2023-Although multiple lower-body strength capacities are required to change direction rapidly, there is limited knowledge about the relative importance of these factors. Therefore, the purpose of this study was to assess the relationship between dynamic and isometric lower-body strength capacities and change of direction (COD) time in state-league netball players. Seventeen female athletes completed maximal isometric midthigh pull (IMTP), countermovement jump (CMJ), and modified 5-0-5 COD tests. Pearson's product moment correlations were used to determine the relationship between COD time and several IMTP and CMJ force-time curve characteristics. To assess the level of contribution of each force-time curve characteristic to COD time, multivariate-linear stepwise regression analyses were performed. A significant moderate correlation was noted between net relative peak force (PF) during the IMTP and COD time ( r = 0.488, p = 0.047), accounting for 23.8% of the variance in COD time. Moreover, concentric relative impulse during the CMJ was strongly correlated with COD time ( r = 0.718; p = 0.001), explaining 81.9% of the variance in COD time when combined with net relative braking PF in a stepwise regression. Based on these findings, female netball players who display higher concentric and isometric strength, as well as the ability to express higher impulses during the concentric phase of the CMJ, are likely to perform CODs faster. This may occur because COD requires the generation of greater propulsive forces, as well as reduced braking and contact times, along with greater isometric strength enabling effective repositioning of center of mass during COD tasks.
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Affiliation(s)
- Tinka Smolarek
- Institute of Sport and Exercise Sciences, University of Münster, Münster, Germany
| | - G Gregory Haff
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Australia; and
- Directorate of Psychology and Sport, University of Salford, Salford, United Kingdom
| | - Wayne C K Poon
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Australia; and
| | - Tsuyoshi Nagatani
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Australia; and
| | - Oliver R Barley
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Australia; and
| | - Stuart N Guppy
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Australia; and
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Nagatani T, Kendall KL, Guppy SN, Poon WCK, Haff GG. Effect of 3 Different Set Configurations on Kinematic Variables and Internal Loads During a Power Snatch Session. J Strength Cond Res 2023; 37:1929-1938. [PMID: 37729510 DOI: 10.1519/jsc.0000000000004498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
ABSTRACT Nagatani, T, Kendall, KL, Guppy, SN, Poon, WCK, and Haff, GG. Effect of 3 different set configurations on kinematic variables and internal loads during a power snatch session. J Strength Cond Res 37(10): 1929-1938, 2023-The aim of this study was to investigate the effect of 3 different set configurations on kinematic variables and internal loads during multiple sets performed with the power snatch. Ten strength-power athletes with at least 6 months of training experience performing the power snatch participated in this study, which consisted of 3 experimental protocols performed in a randomized repeated-measures design. The 3 protocols involved performing the power snatch for 3 sets of 5 repetitions at an average load of 75% 1 repetition maximum with a traditional (TRAD), cluster (CLU), or ascending cluster (A-CLU) protocol, where the training load was progressively increased across the set. Kinematic variables and internal loads (heart rate, blood lactate, and rate of perceived exertion) were measured during each protocol. The athletes maintained peak velocity (PV) and peak power (PP) and exhibited lower internal loads during CLU sets when compared with TRAD sets, whereas they displayed significant decreases in PV during TRAD sets. However, there were no statistically significant differences in PV and PP responses between the TRAD and CLU protocol. The athletes exhibited a significant decrease in PV, whereas PP was increased across each set in the A-CLU protocol, with lower internal loads observed compared with the TRAD protocol. Overall, the training loads used in this study do not appear to maximize the benefits of using CLU set during 3 sets of power snatches performed for 5 repetitions. In addition, A-CLU sets may potentially be useful as a means of maximizing the power output of the athlete.
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Affiliation(s)
- Tsuyoshi Nagatani
- School of Medical and Health Science, Centre for Human Performance, Edith Cowan University, Western Australia, Australia; and
| | - Kristina L Kendall
- School of Medical and Health Science, Centre for Human Performance, Edith Cowan University, Western Australia, Australia; and
| | - Stuart N Guppy
- School of Medical and Health Science, Centre for Human Performance, Edith Cowan University, Western Australia, Australia; and
| | - Wayne C K Poon
- School of Medical and Health Science, Centre for Human Performance, Edith Cowan University, Western Australia, Australia; and
| | - G Gregory Haff
- School of Medical and Health Science, Centre for Human Performance, Edith Cowan University, Western Australia, Australia; and
- University of Salford, Salford, United Kingdom
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Brackley CA, Lips A, Morozov A, Poon WCK, Marenduzzo D. Mechanisms for destabilisation of RNA viruses at air-water and liquid-liquid interfaces. Nat Commun 2021; 12:6812. [PMID: 34819516 PMCID: PMC8613244 DOI: 10.1038/s41467-021-27052-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 10/22/2021] [Indexed: 11/19/2022] Open
Abstract
Understanding the interactions between viruses and surfaces or interfaces is important, as they provide the principles underpinning the cleaning and disinfection of contaminated surfaces. Yet, the physics of such interactions is currently poorly understood. For instance, there are longstanding experimental observations suggesting that the presence of air-water interfaces can generically inactivate and kill viruses, yet the mechanism underlying this phenomenon remains unknown. Here we use theory and simulations to show that electrostatics may provide one such mechanism, and that this is very general. Thus, we predict that the electrostatic free energy of an RNA virus should increase by several thousands of kBT as the virion breaches an air-water interface. We also show that the fate of a virus approaching a generic liquid-liquid interface depends strongly on the detailed balance between interfacial and electrostatic forces, which can be tuned, for instance, by choosing different media to contact a virus-laden respiratory droplet. Tunability arises because both the electrostatic and interfacial forces scale similarly with viral size. We propose that these results can be used to design effective strategies for surface disinfection. We know that air-water interfaces can generically inactivate viruses, but the mechanisms behind this observation are unclear. Here the authors use simulations to uncover those mechanisms and find that the electrostatic repulsive free energy of an RNA virus increases by several thousands of kBT as it approaches an air-water interface, providing a mechanism for viral destabilization which may induce inactivation.
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Affiliation(s)
- C A Brackley
- SUPA, School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, Scotland, UK
| | - A Lips
- SUPA, School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, Scotland, UK
| | - A Morozov
- SUPA, School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, Scotland, UK
| | - W C K Poon
- SUPA, School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, Scotland, UK
| | - D Marenduzzo
- SUPA, School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, Scotland, UK.
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Richards JA, Royer JR, Liebchen B, Guy BM, Poon WCK. Competing Timescales Lead to Oscillations in Shear-Thickening Suspensions. Phys Rev Lett 2019; 123:038004. [PMID: 31386471 DOI: 10.1103/physrevlett.123.038004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Indexed: 06/10/2023]
Abstract
Competing timescales generate novelty. Here, we show that a coupling between the timescales imposed by instrument inertia and the formation of interparticle frictional contacts in shear-thickening suspensions leads to highly asymmetric shear-rate oscillations. Experiments tuning the presence of oscillations by varying the two timescales support our model. The observed oscillations give access to a shear-jamming portion of the flow curve that is forbidden in conventional rheometry. Moreover, the oscillation frequency allows us to quantify an intrinsic relaxation time for particle contacts. The coupling of fast contact network dynamics to a slower system variable should be generic to many other areas of dense suspension flow, with instrument inertia providing a paradigmatic example.
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Affiliation(s)
- J A Richards
- SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - J R Royer
- SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - B Liebchen
- SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany
| | - B M Guy
- SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - W C K Poon
- SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
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Dell'Arciprete D, Blow ML, Brown AT, Farrell FDC, Lintuvuori JS, McVey AF, Marenduzzo D, Poon WCK. A growing bacterial colony in two dimensions as an active nematic. Nat Commun 2018; 9:4190. [PMID: 30305618 PMCID: PMC6180060 DOI: 10.1038/s41467-018-06370-3] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 08/23/2018] [Indexed: 11/18/2022] Open
Abstract
How a single bacterium becomes a colony of many thousand cells is important in biomedicine and food safety. Much is known about the molecular and genetic bases of this process, but less about the underlying physical mechanisms. Here we study the growth of single-layer micro-colonies of rod-shaped Escherichiacoli bacteria confined to just under the surface of soft agarose by a glass slide. Analysing this system as a liquid crystal, we find that growth-induced activity fragments the colony into microdomains of well-defined size, whilst the associated flow orients it tangentially at the boundary. Topological defect pairs with charges \documentclass[12pt]{minimal}
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\begin{document}$$+ {\textstyle{1 \over 2}}$$\end{document}+12 defects being propelled to the periphery. Theoretical modelling suggests that these phenomena have different physical origins from similar observations in other extensile active nematics, and a growing bacterial colony belongs to a new universality class, with features reminiscent of the expanding universe. Rod-shaped bacteria are an example of active matter. Here the authors find that a growing bacterial colony harbours internal cellular flows affecting orientational ordering in its interior and at the boundary. Results suggest this system may belong to a new active matter universality class.
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Affiliation(s)
- D Dell'Arciprete
- SUPA, School of Physics and Astronomy, The University of Edinburgh, James Clerk Maxwell Building, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK.,Dipartimento di Fisica, Universita' di Roma La Sapienza, Piazzale Aldo Moro 5, 00185, Rome, Italy
| | - M L Blow
- SUPA, School of Physics and Astronomy, The University of Edinburgh, James Clerk Maxwell Building, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK
| | - A T Brown
- SUPA, School of Physics and Astronomy, The University of Edinburgh, James Clerk Maxwell Building, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK
| | - F D C Farrell
- SUPA, School of Physics and Astronomy, The University of Edinburgh, James Clerk Maxwell Building, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK.,Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - J S Lintuvuori
- Université Bordeaux, CNRS, LOMA, UMR 5798, 33400, Talence, France
| | - A F McVey
- SUPA, School of Physics and Astronomy, The University of Edinburgh, James Clerk Maxwell Building, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK
| | - D Marenduzzo
- SUPA, School of Physics and Astronomy, The University of Edinburgh, James Clerk Maxwell Building, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK.
| | - W C K Poon
- SUPA, School of Physics and Astronomy, The University of Edinburgh, James Clerk Maxwell Building, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK
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Guy BM, Richards JA, Hodgson DJM, Blanco E, Poon WCK. Constraint-Based Approach to Granular Dispersion Rheology. Phys Rev Lett 2018; 121:128001. [PMID: 30296154 DOI: 10.1103/physrevlett.121.128001] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Indexed: 05/27/2023]
Abstract
We present a phenomenological model for granular suspension rheology in which particle interactions enter as constraints to relative particle motion. By considering constraints that are formed and released by stress respectively, we derive a range of experimental flow curves in a single treatment and predict singularities in viscosity and yield stress consistent with literature data. Fundamentally, we offer a generic description of suspension flow that is independent of bespoke microphysics.
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Affiliation(s)
- B M Guy
- SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - J A Richards
- SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - D J M Hodgson
- SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - E Blanco
- SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - W C K Poon
- SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
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7
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Brooks NJ, Cates ME, Clegg PS, Lips A, Poon WCK, Seddon JM. Soft interfacial materials: from fundamentals to formulation. Philos Trans A Math Phys Eng Sci 2016; 374:rsta.2015.0135. [PMID: 27298436 PMCID: PMC4920283 DOI: 10.1098/rsta.2015.0135] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 04/25/2016] [Indexed: 05/22/2023]
Abstract
This article is part of the themed issue ‘Soft interfacial materials: from fundamentals to formulation’.
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Affiliation(s)
- N J Brooks
- Department of Chemistry, Imperial College of Science Technology and Medicine, London SW7 2AZ, UK
| | - M E Cates
- DAMTP, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, UK
| | - P S Clegg
- School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK
| | - A Lips
- School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK
| | - W C K Poon
- School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK
| | - J M Seddon
- Department of Chemistry, Imperial College of Science Technology and Medicine, London SW7 2AZ, UK
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Harich R, Blythe TW, Hermes M, Zaccarelli E, Sederman AJ, Gladden LF, Poon WCK. Gravitational collapse of depletion-induced colloidal gels. Soft Matter 2016; 12:4300-8. [PMID: 27001686 DOI: 10.1039/c5sm02651b] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We study the ageing and ultimate gravitational collapse of colloidal gels in which the interparticle attraction is induced by non-adsorbing polymers via the depletion effect. The gels are formed through arrested spinodal decomposition, whereby the dense phase arrests into an attractive glass. We map the experimental state diagram onto a theoretical one obtained from computer simulations and theoretical calculations. Discrepancies between the experimental and simulated gel regions in the state diagram can be explained by the particle size and density dependence of the boundary below which the gel is not strong enough to resist gravitational stress. Visual observations show that gravitational collapse of the gels falls into two distinct regimes as the colloid and polymer concentrations are varied, with gels at low colloid concentrations showing the onset of rapid collapse after a delay time. Magnetic resonance imaging (MRI) was used to provide quantitative, spatio-temporally resolved measurements of the solid volume fraction in these rapidly collapsing gels. We find that during the delay time, a dense region builds up at the top of the sample. The rapid collapse is initiated when the gel structure is no longer able to support this dense layer.
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Affiliation(s)
- R Harich
- SUPA and School of Physics & Astronomy, The University of Edinburgh, JCMB, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK.
| | - T W Blythe
- Magnetic Resonance Research Centre, Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, UK
| | - M Hermes
- SUPA and School of Physics & Astronomy, The University of Edinburgh, JCMB, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK.
| | - E Zaccarelli
- CNR-ISC Uos Sapienza and Dipartimento di Fisica, Sapienza Università di Roma, P.le A. Moro 2, I-00185, Roma, Italy
| | - A J Sederman
- Magnetic Resonance Research Centre, Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, UK
| | - L F Gladden
- Magnetic Resonance Research Centre, Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, UK
| | - W C K Poon
- SUPA and School of Physics & Astronomy, The University of Edinburgh, JCMB, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK.
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9
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Guy BM, Hermes M, Poon WCK. Erratum: Towards a Unified Description of the Rheology of Hard-Particle Suspensions [Phys. Rev. Lett. 115, 088304 (2015)]. Phys Rev Lett 2016; 116:059901. [PMID: 26894742 DOI: 10.1103/physrevlett.116.059901] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Indexed: 06/05/2023]
Abstract
This corrects the article DOI: 10.1103/PhysRevLett.115.088304.
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Guy BM, Hermes M, Poon WCK. Towards a Unified Description of the Rheology of Hard-Particle Suspensions. Phys Rev Lett 2015; 115:088304. [PMID: 26340217 DOI: 10.1103/physrevlett.115.088304] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Indexed: 05/11/2023]
Abstract
The rheology of suspensions of Brownian, or colloidal, particles (diameter d≲1 μm) differs markedly from that of larger grains (d≳50 μm). Each of these two regimes has been separately studied, but the flow of suspensions with intermediate particle sizes (1 μm≲d≲50 μm), which occur ubiquitously in applications, remains poorly understood. By measuring the rheology of suspensions of hard spheres with a wide range of sizes, we show experimentally that shear thickening drives the transition from colloidal to granular flow across the intermediate size regime. This insight makes possible a unified description of the (noninertial) rheology of hard spheres over the full size spectrum. Moreover, we are able to test a new theory of friction-induced shear thickening, showing that our data can be well fitted using expressions derived from it.
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Affiliation(s)
- B M Guy
- SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - M Hermes
- SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
| | - W C K Poon
- SUPA, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Peter Guthrie Tait Road, Edinburgh EH9 3FD, United Kingdom
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11
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Vladescu ID, Marsden EJ, Schwarz-Linek J, Martinez VA, Arlt J, Morozov AN, Marenduzzo D, Cates ME, Poon WCK. Filling an emulsion drop with motile bacteria. Phys Rev Lett 2014; 113:268101. [PMID: 25615389 DOI: 10.1103/physrevlett.113.268101] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Indexed: 06/04/2023]
Abstract
We have measured the spatial distribution of motile Escherichia coli inside spherical water droplets emulsified in oil. At low cell concentrations, the cell density peaks at the water-oil interface; at increasing concentration, the bulk of each droplet fills up uniformly while the surface peak remains. Simulations and theory show that the bulk density results from a "traffic" of cells leaving the surface layer, increasingly due to cell-cell scattering as the surface coverage rises above ∼10%. Our findings show similarities with the physics of a rarefied gas in a spherical cavity with attractive walls.
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Affiliation(s)
- I D Vladescu
- SUPA and The School of Physics & Astronomy, The University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
| | - E J Marsden
- SUPA and The School of Physics & Astronomy, The University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
| | - J Schwarz-Linek
- SUPA and The School of Physics & Astronomy, The University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
| | - V A Martinez
- SUPA and The School of Physics & Astronomy, The University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
| | - J Arlt
- SUPA and The School of Physics & Astronomy, The University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
| | - A N Morozov
- SUPA and The School of Physics & Astronomy, The University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
| | - D Marenduzzo
- SUPA and The School of Physics & Astronomy, The University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
| | - M E Cates
- SUPA and The School of Physics & Astronomy, The University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
| | - W C K Poon
- SUPA and The School of Physics & Astronomy, The University of Edinburgh, King's Buildings, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
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Sentjabrskaja T, Hermes M, Poon WCK, Estrada CD, Castañeda-Priego R, Egelhaaf SU, Laurati M. Transient dynamics during stress overshoots in binary colloidal glasses. Soft Matter 2014; 10:6546-6555. [PMID: 24988071 DOI: 10.1039/c4sm00577e] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We investigate, using simultaneous rheology and confocal microscopy, the time-dependent stress response and transient single-particle dynamics following a step change in shear rate in binary colloidal glasses with large dynamical asymmetry and different mixing ratios. The transition from solid-like response to flow is characterised by a stress overshoot, whose magnitude is linked to transient superdiffusive dynamics as well as cage compression effects. These and the yield strain at which the overshoot occurs vary with the mixing ratio, and hence the prevailing caging mechanism. The yielding and stress storage are dominated by dynamics on different time and length scales, the short-time in-cage dynamics and the long-time structural relaxation respectively. These time scales and their relation to the characteristic time associated with the applied shear, namely the inverse shear rate, result in two different and distinct regimes of the shear rate dependencies of the yield strain and the magnitude of the stress overshoot.
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Affiliation(s)
- T Sentjabrskaja
- Condensed Matter Physics Laboratory, Heinrich Heine University, Universitätsstraße 1, 40225 Düsseldorf, Germany.
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Reufer M, Besseling R, Schwarz-Linek J, Martinez VA, Morozov AN, Arlt J, Trubitsyn D, Ward FB, Poon WCK. Switching of Swimming Modes in Magnetospirillium gryphiswaldense. Biophys J 2014; 106:37-46. [PMID: 24411235 DOI: 10.1016/j.bpj.2013.10.038] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 10/16/2013] [Accepted: 10/28/2013] [Indexed: 10/25/2022] Open
Abstract
The microaerophilic magnetotactic bacterium Magnetospirillum gryphiswaldense swims along magnetic field lines using a single flagellum at each cell pole. It is believed that this magnetotactic behavior enables cells to seek optimal oxygen concentration with maximal efficiency. We analyze the trajectories of swimming M. gryphiswaldense cells in external magnetic fields larger than the earth's field, and show that each cell can switch very rapidly (in <0.2 s) between a fast and a slow swimming mode. Close to a glass surface, a variety of trajectories were observed, from straight swimming that systematically deviates from field lines to various helices. A model in which fast (slow) swimming is solely due to the rotation of the trailing (leading) flagellum can account for these observations. We determined the magnetic moment of this bacterium using a to our knowledge new method, and obtained a value of (2.0±0.6) × 10(-16) A · m(2). This value is found to be consistent with parameters emerging from quantitative fitting of trajectories to our model.
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Affiliation(s)
- M Reufer
- SUPA and COSMIC, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Edinburgh, United Kingdom.
| | - R Besseling
- SUPA and COSMIC, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Edinburgh, United Kingdom
| | - J Schwarz-Linek
- SUPA and COSMIC, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Edinburgh, United Kingdom
| | - V A Martinez
- SUPA and COSMIC, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Edinburgh, United Kingdom
| | - A N Morozov
- SUPA and COSMIC, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Edinburgh, United Kingdom
| | - J Arlt
- SUPA and COSMIC, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Edinburgh, United Kingdom
| | - D Trubitsyn
- SUPA and COSMIC, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Edinburgh, United Kingdom; Institute of Cell Biology, The University of Edinburgh, King's Buildings, Edinburgh, United Kingdom
| | - F B Ward
- Institute of Cell Biology, The University of Edinburgh, King's Buildings, Edinburgh, United Kingdom
| | - W C K Poon
- SUPA and COSMIC, School of Physics and Astronomy, The University of Edinburgh, King's Buildings, Edinburgh, United Kingdom
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14
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Jenkins MC, Haw MD, Barker GC, Poon WCK, Egelhaaf SU. Does gravity cause load-bearing bridges in colloidal and granular systems? Phys Rev Lett 2011; 107:038302. [PMID: 21838408 DOI: 10.1103/physrevlett.107.038302] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Indexed: 05/31/2023]
Abstract
We study structures which can bear loads, "bridges", in particulate packings. To investigate the relationship between bridges and gravity, we experimentally determine bridge statistics in colloidal packings. We vary the effective magnitude and direction of gravity, volume fraction, and interactions, and find that the bridge size distributions depend only on the mean number of neighbors. We identify a universal distribution, in agreement with simulation results for granulars, suggesting that applied loads merely exploit preexisting bridges, which are inherent in dense packings.
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Affiliation(s)
- M C Jenkins
- SUPA and The School of Physics & Astronomy, The University of Edinburgh, Kings Buildings, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
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15
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Sanz E, Valeriani C, Zaccarelli E, Poon WCK, Pusey PN, Cates ME. Crystallization mechanism of hard sphere glasses. Phys Rev Lett 2011; 106:215701. [PMID: 21699317 DOI: 10.1103/physrevlett.106.215701] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Indexed: 05/31/2023]
Abstract
In supercooled liquids, vitrification generally suppresses crystallization. Yet some glasses can still crystallize despite the arrest of diffusive motion. This ill-understood process may limit the stability of glasses, but its microscopic mechanism is not yet known. Here we present extensive computer simulations addressing the crystallization of monodisperse hard-sphere glasses at constant volume (as in a colloid experiment). Multiple crystalline patches appear without particles having to diffuse more than one diameter. As these patches grow, the mobility in neighboring areas is enhanced, creating dynamic heterogeneity with positive feedback. The future crystallization pattern cannot be predicted from the coordinates alone: Crystallization proceeds by a sequence of stochastic micronucleation events, correlated in space by emergent dynamic heterogeneity.
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Affiliation(s)
- Eduardo Sanz
- SUPA, School of Physics and Astronomy, University of Edinburgh, Mayfield Road, Edinburgh, EH9 3JZ, Scotland, United Kingdom.
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16
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Abstract
We report new results from our programme of molecular dynamics simulation of hard-sphere systems, focusing on crystallization and glass formation at high concentrations. First we consider a much larger system than hitherto, N = 86 400 equal-sized particles. The results are similar to those obtained with a smaller system, studied previously, showing conventional nucleation and growth of crystals at concentrations near melting and crossing over to a spinodal-like regime at higher concentrations where the free energy barrier to nucleation appears to be negligible. Second, we investigate the dependence on the initial state of the system. We have devised a Monte Carlo 'constrained aging' method to move the particles in such a way that crystallization is discouraged. After a period of such aging, the standard molecular dynamics programme is run. For a system of N = 3200, we find that constrained aging encourages caging of the particles and slows crystallization somewhat. Nevertheless, both aged and unaged systems crystallize at volume fraction φ = 0.61 whereas neither system shows full crystallization in the duration of the simulation at φ = 0.62, a concentration still significantly below that of random close packing.
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Affiliation(s)
- C Valeriani
- SUPA, School of Physics and Astronomy, The University of Edinburgh, Edinburgh, UK.
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17
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Abstract
We study phase separation and transient gelation experimentally in a mixture consisting of polydisperse colloids (polydispersity: ≈ 6%) and non-adsorbing polymers, where the ratio of the average size of the polymer to that of the colloid is ≈ 0.062. Unlike what has been reported previously for mixtures with somewhat lower colloid polydispersity (≈ 5%), the addition of polymers does not expand the fluid-solid coexistence region. Instead, we find a region of fluid-solid coexistence which has an approximately constant width but an unexpected re-entrant shape. We detect the presence of a metastable gas-liquid binodal, which gives rise to two-stepped crystallization kinetics that can be rationalized as the effect of fractionation. Finally, we find that the separation into multiple coexisting solid phases at high colloid volume fractions predicted by equilibrium statistical mechanics is kinetically suppressed before the system reaches dynamical arrest.
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Affiliation(s)
- S M Liddle
- SUPA and School of Physics and Astronomy, The University of Edinburgh, Edinburgh, UK.
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18
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Wilson LG, Martinez VA, Schwarz-Linek J, Tailleur J, Bryant G, Pusey PN, Poon WCK. Differential dynamic microscopy of bacterial motility. Phys Rev Lett 2011; 106:018101. [PMID: 21231772 DOI: 10.1103/physrevlett.106.018101] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Indexed: 05/09/2023]
Abstract
We demonstrate a method for the fast, high-throughput characterization of the dynamics of active particles. Specifically, we measure the swimming speed distribution and motile cell fraction in Escherichia coli suspensions. By averaging over ∼10(4) cells, our method is highly accurate compared to conventional tracking, yielding a routine tool for motility characterization. We find that the diffusivity of nonmotile cells is enhanced in proportion to the concentration of motile cells.
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Affiliation(s)
- L G Wilson
- SUPA and COSMIC, School of Physics & Astronomy, The University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
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19
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Besseling R, Isa L, Ballesta P, Petekidis G, Cates ME, Poon WCK. Shear banding and flow-concentration coupling in colloidal glasses. Phys Rev Lett 2010; 105:268301. [PMID: 21231717 DOI: 10.1103/physrevlett.105.268301] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Indexed: 05/30/2023]
Abstract
We report experiments on hard-sphere colloidal glasses that show a type of shear banding hitherto unobserved in soft glasses. We present a scenario that relates this to an instability due to shear-concentration coupling, a mechanism previously thought unimportant in these materials. Below a characteristic shear rate γ(c) we observe increasingly nonlinear and localized velocity profiles. We attribute this to very slight concentration gradients in the unstable flow regime. A simple model accounts for both the observed increase of γ(c) with concentration, and the fluctuations in the flow.
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Affiliation(s)
- R Besseling
- SUPA, School of Physics & Astronomy, The University of Edinburgh, Edinburgh, United Kingdom
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20
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Zaccarelli E, Valeriani C, Sanz E, Poon WCK, Cates ME, Pusey PN. Crystallization of hard-sphere glasses. Phys Rev Lett 2009; 103:135704. [PMID: 19905525 DOI: 10.1103/physrevlett.103.135704] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Indexed: 05/28/2023]
Abstract
We study by molecular dynamics the interplay between arrest and crystallization in hard spheres. For state points in the plane of volume fraction (0.54 <or= varphi <or= 0.63) and polydispersity (0 <or= s <or= 0.085), we delineate states that spontaneously crystallize from those that do not. For noncrystallizing (or precrystallization) samples we find isodiffusivity lines consistent with an ideal glass transition at varphi_{g} approximately 0.585, independent of s. Despite this, for s < 0.05, crystallization occurs at varphi > varphi_{g}. This happens on time scales for which the system is aging, and a diffusive regime in the mean square displacement is not reached; by those criteria, the system is a glass. Hence, contrary to a widespread assumption in the colloid literature, the occurrence of spontaneous crystallization within a bulk amorphous state does not prove that this state was an ergodic fluid rather than a glass.
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Affiliation(s)
- E Zaccarelli
- Dipartimento di Fisica and CNR-INFM-SOFT, Universitá di Roma La Sapienza, 00185, Roma, Italy
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21
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Abstract
We study the flow of concentrated hard-sphere colloidal suspensions along smooth, nonstick walls using cone-plate rheometry and simultaneous confocal microscopy. In the glass regime, the global flow shows a transition from Herschel-Bulkley behavior at large shear rate to a characteristic Bingham slip response at small rates, absent for ergodic colloidal fluids. Imaging reveals both the "solid" microstructure during full slip and the local nature of the "slip to shear" transition. Both the local and global flow are described by a phenomenological model, and the associated Bingham slip parameters exhibit characteristic scaling with size and concentration of the hard spheres.
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Affiliation(s)
- P Ballesta
- Scottish Universities Physics Alliance (SUPA) and School of Physics, The University of Edinburgh, Kings Buildings, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
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22
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Barrett-Freeman C, Evans MR, Marenduzzo D, Poon WCK. Nonequilibrium phase transition in the sedimentation of reproducing particles. Phys Rev Lett 2008; 101:100602. [PMID: 18851200 DOI: 10.1103/physrevlett.101.100602] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Revised: 05/29/2008] [Indexed: 05/26/2023]
Abstract
We study numerically and analytically the dynamics of a sedimenting suspension of active, reproducing particles, such as growing bacteria in a gravitational field. In steady state we find a nonequilibrium phase transition between a "sedimentation" regime, analogous to the sedimentation equilibrium of passive colloids, and a "uniform" regime, in which the particle density is constant in all but the top and bottom of the sample. We discuss the importance of fluctuations in particle density in locating the phase-transition point, and report the kinetics of sedimentation at early times.
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Affiliation(s)
- C Barrett-Freeman
- SUPA and School of Physics, The University of Edinburgh, Mayfield Road, Edinburgh, EH9 3JZ, United Kingdom
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23
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Herzig EM, White KA, Schofield AB, Poon WCK, Clegg PS. Bicontinuous emulsions stabilized solely by colloidal particles. Nat Mater 2007; 6:966-971. [PMID: 17982465 DOI: 10.1038/nmat2055] [Citation(s) in RCA: 280] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Accepted: 09/28/2007] [Indexed: 05/25/2023]
Abstract
Recent large-scale computer simulations suggest that it may be possible to create a new class of soft solids, called 'bijels', by stabilizing and arresting the bicontinuous interface in a binary liquid demixing via spinodal decomposition using particles that are neutrally wetted by both liquids. The interfacial layer of particles is expected to be semi-permeable; hence, if realized, these new materials would have many potential applications, for example, as micro-reaction media. However, the creation of bijels in the laboratory faces serious obstacles. In general, fast quench rates are necessary to bypass nucleation, so that only samples with limited thickness can be produced, which destroys the three-dimensionality of the putative bicontinuous network. Moreover, even a small degree of unequal wettability of the particles by the two liquids can lead to ill-characterized, 'lumpy' interfacial layers and therefore irreproducible material properties. Here, we report a reproducible protocol for creating three-dimensional samples of bijel in which the interfaces are stabilized by essentially a single layer of particles. We demonstrate how to tune the mean interfacial separation in these bijels, and show that mechanically, they indeed behave as soft solids. These characteristics and their tunability will be of great value for microfluidic applications.
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Affiliation(s)
- E M Herzig
- SUPA, School of Physics, University of Edinburgh, Mayfield Road, Edinburgh, UK
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24
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Bailey AE, Poon WCK, Christianson RJ, Schofield AB, Gasser U, Prasad V, Manley S, Segre PN, Cipelletti L, Meyer WV, Doherty MP, Sankaran S, Jankovsky AL, Shiley WL, Bowen JP, Eggers JC, Kurta C, Lorik T, Pusey PN, Weitz DA. Spinodal decomposition in a model colloid-polymer mixture in microgravity. Phys Rev Lett 2007; 99:205701. [PMID: 18233160 DOI: 10.1103/physrevlett.99.205701] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2007] [Revised: 08/19/2007] [Indexed: 05/25/2023]
Abstract
We study phase separation in a deeply quenched colloid-polymer mixture in microgravity on the International Space Station using small-angle light scattering and direct imaging. We observe a clear crossover from early-stage spinodal decomposition to late-stage, interfacial-tension-driven coarsening. Data acquired over 5 orders of magnitude in time show more than 3 orders of magnitude increase in domain size, following nearly the same evolution as that in binary liquid mixtures. The late-stage growth approaches the expected linear growth rate quite slowly.
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Affiliation(s)
- A E Bailey
- Dept. of Physics & SEAS, Harvard University, Cambridge, Massachusetts 02138, USA
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25
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Smith PA, Petekidis G, Egelhaaf SU, Poon WCK. Yielding and crystallization of colloidal gels under oscillatory shear. Phys Rev E Stat Nonlin Soft Matter Phys 2007; 76:041402. [PMID: 17994983 DOI: 10.1103/physreve.76.041402] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2007] [Indexed: 05/25/2023]
Abstract
We have studied the behavior of a colloidal gel under oscillatory shear. The quiescent gel was an arrested structure formed by a 40% volume fraction hard-sphere suspension in which a "depletion" interparticle attraction was induced by adding nonadsorbing polymer. We applied progressively larger amplitude oscillatory shear to the sample, and observed its behavior using conventional and confocal microscopy as well as dynamic light scattering echo spectroscopy. We find that, to within experimental uncertainties, the point at which irreversible particle rearrangements (or yielding) occur coincides with the observation of crystallization. We summarize our findings in a "shear state diagram." The strain amplitude required for yielding/crystallization increases with decreasing oscillation frequency. We can quantitatively account for our observations by estimating the effect of shear on the probability for a particle to escape from the attractive potential of its neighbor using a Kramers approach.
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Affiliation(s)
- P A Smith
- SUPA, School of Physics, The University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
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26
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Abstract
Glycerol is widely used as an additive to stabilize proteins in aqueous solution. We have studied the effect of up to 40 wt % glycerol on the crystallization of lysozyme from brine. As the glycerol concentration increased, progressively larger amounts of salt were needed to crystallize the protein. Like previous authors, we interpret this as evidence for glycerol changing the interaction between lysozyme molecules. We quantitatively model the interprotein interaction using a Derjaguin-Landau-Verwey-Overbeek potential. We find that the effect of glycerol can be entirely accounted for by the way it modifies the dielectric constant and refractive index of the solvent. Quantifying the interprotein interaction by the second virial coefficient, B(2), we find a universal crystallization boundary for all glycerol concentrations.
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Affiliation(s)
- H Sedgwick
- Scottish Universities Physics Alliance (SUPA), School of Physics, The University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, Scotland
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27
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Besseling R, Weeks ER, Schofield AB, Poon WCK. Three-dimensional imaging of colloidal glasses under steady shear. Phys Rev Lett 2007; 99:028301. [PMID: 17678265 DOI: 10.1103/physrevlett.99.028301] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2006] [Revised: 02/27/2007] [Indexed: 05/16/2023]
Abstract
Using fast confocal microscopy we image the three-dimensional dynamics of particles in a yielded hard-sphere colloidal glass under steady shear. The structural relaxation, observed in regions with uniform shear, is nearly isotropic but is distinctly different from that of quiescent metastable colloidal fluids. The inverse relaxation time tau(alpha)(-1) and diffusion constant D, as functions of the local shear rate gamma*, show marked shear thinning with tau(alpha)(-1) proportional to D proportional to gamma*(0.8) over more than two decades in gamma*. In contrast, the global rheology of the system displays Herschel-Bulkley behavior. We discuss the possible role of large scale shear localization and other mechanisms in generating this difference.
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Affiliation(s)
- R Besseling
- Scottish Universities Physics Alliance (SUPA) and School of Physics, The University of Edinburgh, Kings Buildings, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
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28
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Sugden KEP, Evans MR, Poon WCK, Read ND. Model of hyphal tip growth involving microtubule-based transport. Phys Rev E Stat Nonlin Soft Matter Phys 2007; 75:031909. [PMID: 17500728 DOI: 10.1103/physreve.75.031909] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2006] [Revised: 11/09/2006] [Indexed: 05/15/2023]
Abstract
We propose a simple model for mass transport within a fungal hypha and its subsequent growth. Inspired by the role of microtubule-transported vesicles, we embody the internal dynamics of mass inside a hypha with mutually excluding particles progressing stochastically along a growing one-dimensional lattice. The connection between long-range transport of materials for growth and the resulting extension of the hyphal tip has not previously been addressed in the modeling literature to our knowledge. We derive and analyze mean-field equations for the model and present a phase diagram of its steady-state behavior, which we compare to simulations. We discuss our results in the context of the filamentous fungus Neurospora crassa.
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Affiliation(s)
- K E P Sugden
- SUPA, School of Physics, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
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29
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Gordon VD, Beales PA, Zhao Z, Blake C, Mackintosh FC, Olmsted PD, Cates ME, Egelhaaf SU, Poon WCK. Lipid organization and the morphology of solid-like domains in phase-separating binary lipid membranes. J Phys Condens Matter 2006; 18:L415-L420. [PMID: 21690854 DOI: 10.1088/0953-8984/18/32/l02] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In multi-component lipid membranes, phase separation can lead to the formation of domains. The morphology of fluid-like domains has been rationalized in terms of membrane elasticity and line tension. We show that the morphology of solid-like domains is governed by different physics, and instead reflects the molecular ordering of the lipids. An understanding of this link opens new possibilities for the rational design of patterned membranes.
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Affiliation(s)
- V D Gordon
- SUPA, School of Physics and Collaborative Optical Spectroscopy, Micromanipulation and Imaging Centre (COSMIC), The University of Edinburgh, James Clerk Maxwell Building, Kings Buildings, Mayfield Road, Edinburgh EH9 3JZ, UK
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30
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Isa L, Besseling R, Weeks ER, Poon WCK. Experimental studies of the flow of concentrated hard sphere suspensions into a constriction. ACTA ACUST UNITED AC 2006. [DOI: 10.1088/1742-6596/40/1/016] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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31
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Sedgwick H, Kroy K, Salonen A, Robertson MB, Egelhaaf SU, Poon WCK. Non-equilibrium behavior of sticky colloidal particles: beads, clusters and gels. Eur Phys J E Soft Matter 2005; 16:77-80. [PMID: 15688143 DOI: 10.1140/epje/e2005-00009-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2004] [Indexed: 05/24/2023]
Abstract
To understand the non-equilibrium behavior of colloidal particles with short-range attraction, we studied salt-induced aggregation of lysozyme. Optical microscopy revealed four regimes: bicontinuous texture, 'beads', large aggregates, and transient gelation. The interaction of a metastable liquid-liquid binodal and an ergodic to non-ergodic transition boundary inside the equilibrium crystallization region can explain our findings.
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Affiliation(s)
- H Sedgwick
- School of Physics, The University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, Scotland, UK
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32
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Abstract
Mode-coupling theory (MCT) predicts the arrest of colloids in terms of their volume fraction, and the range and depth of the interparticle attraction. We discuss how the effective values of these parameters evolve under cluster aggregation. We argue that weak gelation in colloids can be idealized as a two-stage ergodicity breaking: first at short scales (approximated by the bare MCT) and then at larger scales (governed by MCT applied to clusters). The competition between the arrest and phase separation is considered in relation to recent experiments. We predict a long-lived "semiergodic" phase of mobile clusters, showing logarithmic relaxation close to the gel line.
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Affiliation(s)
- K Kroy
- Hahn-Meitner Institut, Glienicker Strasse 100, 14109 Berlin, Germany
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33
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Abstract
We studied the crystallization of a globular protein, lysozyme, in the cubic phase of the lipid mono-olein. The solubility of lysozyme in salt solution decreased by a factor of approximately 4 when confined in cubic phase. Monte Carlo simulations and calculations show that this can be explained by the confinement of lysozyme molecules to the narrow water cells in the cubic phase.
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Affiliation(s)
- S Tanaka
- School of Physics, The University of Edinburgh, JCMB, King's Buildings, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
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34
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Pham KN, Egelhaaf SU, Pusey PN, Poon WCK. Glasses in hard spheres with short-range attraction. Phys Rev E Stat Nonlin Soft Matter Phys 2004; 69:011503. [PMID: 14995624 DOI: 10.1103/physreve.69.011503] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2003] [Indexed: 05/24/2023]
Abstract
We report a detailed experimental study of the structure and dynamics of glassy states in hard spheres with short-range attraction. The system is a suspension of nearly hard-sphere colloidal particles and nonadsorbing linear polymer which induces a depletion attraction between the particles. Observation of crystallization reveals a reentrant glass transition. Static light scattering shows a continuous change in the static structure factors upon increasing attraction. Dynamic light scattering results, which cover 11 orders of magnitude in time, are consistent with the existence of two distinct kinds of glasses, those dominated by interparticle repulsion and caging, and those dominated by attraction. Samples close to the "A3 point" predicted by mode coupling theory for such systems show very slow, logarithmic dynamics.
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Affiliation(s)
- K N Pham
- School of Physics, The University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom
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35
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Auer S, Poon WCK, Frenkel D. Phase behavior and crystallization kinetics of poly-12-hydroxystearic-coated polymethylmethacrylate colloids. Phys Rev E Stat Nonlin Soft Matter Phys 2003; 67:020401. [PMID: 12636644 DOI: 10.1103/physreve.67.020401] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2002] [Indexed: 05/24/2023]
Abstract
Polymethylmethacrylate (PMMA) colloids sterically stabilized by a layer of chemically grafted poly-12-hydroxystearic (PHSA) are widely used in experiments as model hard spheres. However, due to the coating, the interaction between particles is slightly soft. Here we report a numerical study of the effect of the PHSA coating on the phase behavior and crystallization kinetics of PMMA colloids based on parameters determined from surface-force measurements on PHSA-PMMA-coated mica surfaces [B. A. de L. Costello and P. F. Luckham, J. Colloid Interface Sci. 156, 72 (1993); B. A. de L. Costello et al., Langmuir 8, 464 (1992)]. We find that the core volume fraction of particles at freezing measured by Pusey and van Megen [Nature 320, 340 (1986)] can only be reproduced by using a thickness of the PHSA layer that is considerably larger than literature values. This may indicate that the particles are in fact slightly charged. Compared to perfect hard spheres, the crystallization rate in these slightly soft particles was found to be increased by about two orders of magnitudes.
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Affiliation(s)
- S Auer
- FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam, The Netherlands
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36
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Martelozzo VC, Schofield AB, Poon WCK, Pusey PN. Structural aging of crystals of hard-sphere colloids. Phys Rev E Stat Nonlin Soft Matter Phys 2002; 66:021408. [PMID: 12241179 DOI: 10.1103/physreve.66.021408] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2001] [Revised: 06/24/2002] [Indexed: 05/23/2023]
Abstract
We report a detailed experimental study of the aging of the (initial) random hexagonal close-packed (rhcp) crystals formed in suspensions of hard-sphere colloids near the melting point. By suspending the same colloidal particles in two different mixtures of solvents we are able to tune the strength of the gravitational forces acting on the particles. The crystal structure is deduced from diffraction patterns measured by the light scattering equivalent of powder x-ray crystallography. A spontaneous aging of the structure is observed over long periods of time, consisting of a fraction of pure face-centered cubic (fcc) crystals growing at the expense of the randomly stacked crystallites. The rate of growth of the new crystals is small and consistent with the predictions by Pronk and Frenkel [13]. Gravity is also revealed to affect the crystals and favor fcc order but through a slow gradual rearrangement of the random stacking. An important new observation is that small mechanical perturbations can strongly affect the structure of the colloidal crystals, promoting fcc growth and interfering with the spontaneous aging process. Previous experimental results are also discussed in the light of these new findings.
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Affiliation(s)
- V C Martelozzo
- Department of Physics and Astronomy, The University of Edinburgh, Mayfield Road, Edinburgh, EH9 3JZ, Scotland, United Kingdom
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37
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Abstract
When a simple alcohol such as methanol or ethanol is mixed with water, the entropy of the system increases far less than expected for an ideal solution of randomly mixed molecules. This well-known effect has been attributed to hydrophobic headgroups creating ice-like or clathrate-like structures in the surrounding water, although experimental support for this hypothesis is scarce. In fact, an increasing amount of experimental and theoretical work suggests that the hydrophobic headgroups of alcohol molecules in aqueous solution cluster together. However, a consistent description of the details of this self-association is lacking. Here we use neutron diffraction with isotope substitution to probe the molecular-scale structure of a concentrated alcohol water mixture (7:3 molar ratio). Our data indicate that most of the water molecules exist as small hydrogen-bonded strings and clusters in a 'fluid' of close-packed methyl groups, with water clusters bridging neighbouring methanol hydroxyl groups through hydrogen bonding. This behaviour suggests that the anomalous thermodynamics of water alcohol systems arises from incomplete mixing at the molecular level and from retention of remnants of the three-dimensional hydrogen-bonded network structure of bulk water.
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Affiliation(s)
- S Dixit
- Department of Physics and Astronomy, The University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, UK
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Pham KN, Puertas AM, Bergenholtz J, Egelhaaf SU, Moussaïd A, Pusey PN, Schofield AB, Cates ME, Fuchs M, Poon WCK. Multiple glassy states in a simple model system. Science 2002; 296:104-6. [PMID: 11935020 DOI: 10.1126/science.1068238] [Citation(s) in RCA: 656] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Experiments, theory, and simulation were used to study glass formation in a simple model system composed of hard spheres with short-range attraction ("sticky hard spheres"). The experiments, using well-characterized colloids, revealed a reentrant glass transition line. Mode-coupling theory calculations and molecular dynamics simulations suggest that the reentrance is due to the existence of two qualitatively different glassy states: one dominated by repulsion (with structural arrest due to caging) and the other by attraction (with structural arrest due to bonding). This picture is consistent with a study of the particle dynamics in the colloid using dynamic light scattering.
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Affiliation(s)
- K N Pham
- Department of Physics and Astronomy, The University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, UK
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