Normal Stress Differences and Yield Stresses in Attractive Particle Networks

Verrelli, David I.; Kilcullen, Adam R.

doi:10.1155/2016/1716598

Cited by 13 publications

(6 citation statements)

References 129 publications

(263 reference statements)

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“…1D and E , respectively). Normal force is characterised as a normal stress difference (Δ N = N 1 − N 2 ), where N 1 and N 2 are the primary and secondary normal stress differences, respectively (see definition in ‘Materials and methods’ 28 ). The fluid’s elasticity dominates the viscous flow properties for the wild-type biofilm matrix extracted by EMIM-Ac, whereby Δ N is an order of magnitude greater than shear stress (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Forty milligrams per millilitre solutions of lyophilised biofilms were added to 1 mL EMIM-Ac and incubated at 55 °C for 2 h. A Haake Mars 3 (Thermo Fisher Scientific) stress-controlled rotational rheometer with Peltier-controlled element at 25 °C was used for rheological measurements. Thirty-five-millimetre-diameter parallel plate geometry was used with smooth titanium plates to measure viscosity and normal stress difference ( N 1 − N 2 ), where N 1 is the difference between normal stresses in the direction of shearing and those oriented perpendicular to the shear plane, and N 2 the difference between normal stresses perpendicular to the shear plane and those in the neutral, traverse, direction 28 . Prior to measurement, the gap error was zeroed at 4 N and gap error calculated as previously described 62 – 64 .…”

Section: Methodsmentioning

confidence: 99%

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The biofilm matrix scaffold of Pseudomonas aeruginosa contains G-quadruplex extracellular DNA structures

Seviour

Winnerdy

Wong

et al. 2021

npj Biofilms Microbiomes

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Extracellular DNA, or eDNA, is recognised as a critical biofilm component; however, it is not understood how it forms networked matrix structures. Here, we isolate eDNA from static-culture Pseudomonas aeruginosa biofilms using ionic liquids to preserve its biophysical signatures of fluid viscoelasticity and the temperature dependency of DNA transitions. We describe a loss of eDNA network structure as resulting from a change in nucleic acid conformation, and propose that its ability to form viscoelastic structures is key to its role in building biofilm matrices. Solid-state analysis of isolated eDNA, as a proxy for eDNA structure in biofilms, reveals non-canonical Hoogsteen base pairs, triads or tetrads involving thymine or uracil, and guanine, suggesting that the eDNA forms G-quadruplex structures. These are less abundant in chromosomal DNA and disappear when eDNA undergoes conformation transition. We verify the occurrence of G-quadruplex structures in the extracellular matrix of intact static and flow-cell biofilms of P. aeruginosa, as displayed by the matrix to G-quadruplex-specific antibody binding, and validate the loss of G-quadruplex structures in vivo to occur coincident with the disappearance of eDNA fibres. Given their stability, understanding how extracellular G-quadruplex structures form will elucidate how P. aeruginosa eDNA builds viscoelastic networks, which are a foundational biofilm property.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

The biofilm matrix scaffold of Pseudomonas aeruginosa contains G-quadruplex extracellular DNA structures

Seviour

Winnerdy

Wong

et al. 2021

npj Biofilms Microbiomes

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show abstract

“…This represents the normal stress acting in the direction of the shearing/flow. [ 32 ] The higher the value of

(τ_{11}

–

τ_{22})

, the higher is the melt elasticity. Higher values of

(τ_{11}

–

τ_{22})

are due to the higher strength of flow when the molecules are increasingly aligned in the flow direction due to the presence of fibrous nanofillers.…”

Section: Resultsmentioning

confidence: 99%

Nanofiber‐Carbon black dual filler reinforced sustainable high‐performance Natural Rubber nanocomposites

Surya

Naskar

Bhowmick

2022

Polymer Engineering & Sci

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In the present work, uncured and cured properties of high-performance, sustainable Natural Rubber nanocomposites developed by leveraging the unique synergy between carbon black and fibrous nanofillers such as silicon carbide, carbon nanotubes, and aramid nanofibers were investigated. Reinforcement in these composites was analyzed using the properties of the unvulcanized compounds, which were then correlated with those of the vulcanized compounds. A 50% increment was recorded for the bound rubber content of the nanocomposites, which resulted in tremendous improvements in the reinforcement index and tensile strength of the unvulcanized nanocomposites. In contrast, the die swell index came down compared with the control compound. The formation of a percolating network due to the presence of high aspect ratio fibers resulted in a higher Payne effect in hybrid nanocomposites, which was confirmed from the scanning and transmission electron microscopy. The 100% modulus, 300% modulus, and tensile strength of the unvulcanized nanocomposites recorded an improvement of 80, 121, and 450%, respectively, by the incorporation of nanofibers. The molecular aspects of reinforcement were elucidated from theoretical calculations using Mooney-Rivlin plots. It was presumed that the improved reinforcing efficiency of the nanofibers resulted from restricted mobility of elastomer chains due to the presence of the dual filler system.

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“…Generally, these stresses occur as a direct result of the fluid motion and are not isotropic. 53 In polymer solutions or melts, the existence of normal…”

Section: Normal Stress Differencesmentioning

confidence: 99%

Analysis of nonlinear viscoelastic lubrication using Giesekus constitutive equation

Abbaspur

Norouzi

Akbarzadeh

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part J:

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Recent research has shown that adding polymeric materials to mineral oils and consequently changing the behavior of Newtonian lubricants into viscoelastic materials will enhance the lubrication performance. Therefore, in order to examine theoretically the actual behavior of such lubricants, a suitable viscoelastic model must be considered. Hence, in this paper, the solution of fluid film lubrication is presented analytically using the Giesekus viscoelastic model. This constitutive model is based on the concept of configuration-dependent molecular mobility and is suitable for predicting the nonlinear viscoelastic properties. Indeed, it can describe the power-law regions for viscosity, the normal-stress coefficients, the elongational viscosity, and also the complex viscosity. In order to linearize the momentum and constitutive equations and obtain the generalized Reynolds equation, the perturbation method is used and the mobility factor is considered as the perturbation parameter. Here, the effects of mobility factor, outlet-to-inlet height ratio, and Weissenberg number on fluid film pressure distribution, velocity profiles, load capacity, friction coefficient, and first normal stress difference are investigated in detail. Due to the normal stress difference in viscoelastic fluids, using a viscoelastic fluid in contrast a Newtonian fluid can significantly increase the load-carrying capacity of bearing. Another result is with increasing the value of mobility factor, the fluid viscosity decreases and consequently the pressure distribution decreases simultaneously while the lateral normal stress in the y-direction increases. The term pressure distribution is more negligible than the term lateral normal stress and as a result by increasing the mobility factor the load-carrying capacity increases too. It is also observed that, when the Weissenberg numbers tend to infinity regardless of the mobility factor, the friction coefficient tends towards a constant value and rubber-like elasticity is responses.

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Normal Stress Differences and Yield Stresses in Attractive Particle Networks

Cited by 13 publications

References 129 publications

The biofilm matrix scaffold of Pseudomonas aeruginosa contains G-quadruplex extracellular DNA structures

The biofilm matrix scaffold of Pseudomonas aeruginosa contains G-quadruplex extracellular DNA structures

Nanofiber‐Carbon black dual filler reinforced sustainable high‐performance Natural Rubber nanocomposites

Analysis of nonlinear viscoelastic lubrication using Giesekus constitutive equation

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