The Experts below are selected from a list of 33171 Experts worldwide ranked by ideXlab platform
Wilson C K Poon - One of the best experts on this subject based on the ideXlab platform.
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on Polydispersity and the hard sphere glass transition
Soft Matter, 2015Co-Authors: Emanuela Zaccarelli, Siobhan M Liddle, Wilson C K PoonAbstract:We investigate the dynamics of polydisperse hard spheres at high packing fractions ϕ. We use extensive numerical simulations based on an experimentally-realistic particle size distribution (PSD) and compare to commonly-used PSDs such as Gaussian or top hat distribution. We find that the mode of kinetic arrest depends on the PSD's shape and not only on its variance. For the experimentally-realistic PSD we find ageing dynamics even though the density correlators decay fully to zero for ϕ ≥ 0.59. We observe substantial decoupling of the dynamics of the smallest and largest particles. While the smallest particles remain diffusive in all our simulations, a power-law describes the largest-particle diffusion, suggesting an ideal arrest at ϕc ∼ 0.588. The latter is however averted just before ϕc, due to the presence of the mobile smallest particles. In addition, we identify that a partial aging mechanism is at work, whose effects are most pronounced for the largest particles. By comparing our results with recent experimental observations of ergodic behavior up to ϕ ∼ 0.6 in a hard-sphere system, we argue that this is an effect of Polydispersity, which smears out the glass transition.
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on Polydispersity and the hard sphere glass transition
arXiv: Soft Condensed Matter, 2013Co-Authors: Emanuela Zaccarelli, Siobhan M Liddle, Wilson C K PoonAbstract:We simulate the dynamics of polydisperse hard spheres at high packing fractions, $\phi$, with an experimentally-realistic particle size distribution (PSD) and other commonly-used PSDs such as gaussian or top hat. We find that the mode of kinetic arrest depends on the PSD's shape and not only on its variance. For the experimentally-realistic PSD, the largest particles undergo an ideal glass transition at $\phi\sim 0.588$ while the smallest particles remain mobile. Such species-specific localisation was previously observed only in asymmetric binary mixtures. Our findings suggest that the recent observation of ergodic behavior up to $\phi \sim 0.6$ in a hard-sphere system is not evidence for activated dynamics, but an effect of Polydispersity.
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hard spheres crystallization and glass formation
Philosophical Transactions of the Royal Society A, 2009Co-Authors: P N Pusey, Emanuela Zaccarelli, Chantal Valeriani, Eduardo Sanz, Wilson C K Poon, Michael E CatesAbstract:Motivated by old experiments on colloidal suspensions, we report molecular dynamics simulations of assemblies of hard spheres, addressing crystallization and glass formation. The simulations cover wide ranges of Polydispersity s (standard deviation of the particle size distribution divided by its mean) and particle concentration. No crystallization is observed for s>0.07. For 0.02
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hard spheres crystallization and glass formation
arXiv: Materials Science, 2009Co-Authors: P N Pusey, Emanuela Zaccarelli, Chantal Valeriani, Eduardo Sanz, Wilson C K Poon, Michael E CatesAbstract:Motivated by old experiments on colloidal suspensions, we report molecular dynamics simulations of assemblies of hard spheres, addressing crystallization and glass formation. The simulations cover wide ranges of Polydispersity s (standard deviation of the particle size distribution divided by its mean) and particle concentration. No crystallization is observed for s > 0.07. For 0.02 < s < 0.07, we find that increasing the Polydispersity at a given concentration slows down crystal nucleation. The main effect here is that Polydispersity reduces the supersaturation since it tends to stabilise the fluid but to destabilise the crystal. At a given Polydispersity (< 0.07) we find three regimes of nucleation: standard nucleation and growth at concentrations in and slightly above the coexistence region; "spinodal nucleation", where the free energy barrier to nucleation appears to be negligible, at intermediate concentrations; and, at the highest concentrations, a new mechanism, still to be fully understood, which only requires small re-arrangement of the particle positions. The cross-over between the second and third regimes occurs at a concentration, around 58% by volume, where the colloid experiments show a marked change in the nature of the crystals formed and the particle dynamics indicate an "ideal" glass transition.
Thomas M Truskett - One of the best experts on this subject based on the ideXlab platform.
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communication from close packed to topologically close packed formation of laves phases in moderately polydisperse hard sphere mixtures
Journal of Chemical Physics, 2018Co-Authors: Beth A Lindquist, Ryan B Jadrich, Thomas M TruskettAbstract:Particle size Polydispersity can help to inhibit crystallization of the hard-sphere fluid into close-packed structures at high packing fractions and thus is often employed to create model glass-forming systems. Nonetheless, it is known that hard-sphere mixtures with modest Polydispersity still have ordered ground states. Here, we demonstrate by computer simulation that hard-sphere mixtures with increased Polydispersity fractionate on the basis of particle size and a bimodal subpopulation favors the formation of topologically close-packed C14 and C15 Laves phases in coexistence with a disordered phase. The generality of this result is supported by simulations of hard-sphere mixtures with particle-size distributions of four different forms.
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from close packed to topologically close packed formation of laves phases in moderately polydisperse hard sphere mixtures
arXiv: Soft Condensed Matter, 2018Co-Authors: Beth A Lindquist, Ryan B Jadrich, Thomas M TruskettAbstract:Particle size Polydispersity can help to inhibit crystallization of the hard-sphere fluid into close-packed structures at high packing fractions and thus is often employed to create model glass-forming systems. Nonetheless, it is known that hard-sphere mixtures with modest Polydispersity still have ordered ground states. Here, we demonstrate by computer simulation that hard-sphere mixtures with increased Polydispersity fractionate on the basis of particle size, and a bimodal subpopulation favors formation of topologically close-packed C14 and C15 Laves phases in coexistence with a disordered phase. The generality of this result is supported by simulations of hard-sphere mixtures with particle-size distributions of four different forms.
Emanuela Zaccarelli - One of the best experts on this subject based on the ideXlab platform.
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on Polydispersity and the hard sphere glass transition
Soft Matter, 2015Co-Authors: Emanuela Zaccarelli, Siobhan M Liddle, Wilson C K PoonAbstract:We investigate the dynamics of polydisperse hard spheres at high packing fractions ϕ. We use extensive numerical simulations based on an experimentally-realistic particle size distribution (PSD) and compare to commonly-used PSDs such as Gaussian or top hat distribution. We find that the mode of kinetic arrest depends on the PSD's shape and not only on its variance. For the experimentally-realistic PSD we find ageing dynamics even though the density correlators decay fully to zero for ϕ ≥ 0.59. We observe substantial decoupling of the dynamics of the smallest and largest particles. While the smallest particles remain diffusive in all our simulations, a power-law describes the largest-particle diffusion, suggesting an ideal arrest at ϕc ∼ 0.588. The latter is however averted just before ϕc, due to the presence of the mobile smallest particles. In addition, we identify that a partial aging mechanism is at work, whose effects are most pronounced for the largest particles. By comparing our results with recent experimental observations of ergodic behavior up to ϕ ∼ 0.6 in a hard-sphere system, we argue that this is an effect of Polydispersity, which smears out the glass transition.
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on Polydispersity and the hard sphere glass transition
arXiv: Soft Condensed Matter, 2013Co-Authors: Emanuela Zaccarelli, Siobhan M Liddle, Wilson C K PoonAbstract:We simulate the dynamics of polydisperse hard spheres at high packing fractions, $\phi$, with an experimentally-realistic particle size distribution (PSD) and other commonly-used PSDs such as gaussian or top hat. We find that the mode of kinetic arrest depends on the PSD's shape and not only on its variance. For the experimentally-realistic PSD, the largest particles undergo an ideal glass transition at $\phi\sim 0.588$ while the smallest particles remain mobile. Such species-specific localisation was previously observed only in asymmetric binary mixtures. Our findings suggest that the recent observation of ergodic behavior up to $\phi \sim 0.6$ in a hard-sphere system is not evidence for activated dynamics, but an effect of Polydispersity.
-
hard spheres crystallization and glass formation
Philosophical Transactions of the Royal Society A, 2009Co-Authors: P N Pusey, Emanuela Zaccarelli, Chantal Valeriani, Eduardo Sanz, Wilson C K Poon, Michael E CatesAbstract:Motivated by old experiments on colloidal suspensions, we report molecular dynamics simulations of assemblies of hard spheres, addressing crystallization and glass formation. The simulations cover wide ranges of Polydispersity s (standard deviation of the particle size distribution divided by its mean) and particle concentration. No crystallization is observed for s>0.07. For 0.02
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hard spheres crystallization and glass formation
arXiv: Materials Science, 2009Co-Authors: P N Pusey, Emanuela Zaccarelli, Chantal Valeriani, Eduardo Sanz, Wilson C K Poon, Michael E CatesAbstract:Motivated by old experiments on colloidal suspensions, we report molecular dynamics simulations of assemblies of hard spheres, addressing crystallization and glass formation. The simulations cover wide ranges of Polydispersity s (standard deviation of the particle size distribution divided by its mean) and particle concentration. No crystallization is observed for s > 0.07. For 0.02 < s < 0.07, we find that increasing the Polydispersity at a given concentration slows down crystal nucleation. The main effect here is that Polydispersity reduces the supersaturation since it tends to stabilise the fluid but to destabilise the crystal. At a given Polydispersity (< 0.07) we find three regimes of nucleation: standard nucleation and growth at concentrations in and slightly above the coexistence region; "spinodal nucleation", where the free energy barrier to nucleation appears to be negligible, at intermediate concentrations; and, at the highest concentrations, a new mechanism, still to be fully understood, which only requires small re-arrangement of the particle positions. The cross-over between the second and third regimes occurs at a concentration, around 58% by volume, where the colloid experiments show a marked change in the nature of the crystals formed and the particle dynamics indicate an "ideal" glass transition.
Beth A Lindquist - One of the best experts on this subject based on the ideXlab platform.
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communication from close packed to topologically close packed formation of laves phases in moderately polydisperse hard sphere mixtures
Journal of Chemical Physics, 2018Co-Authors: Beth A Lindquist, Ryan B Jadrich, Thomas M TruskettAbstract:Particle size Polydispersity can help to inhibit crystallization of the hard-sphere fluid into close-packed structures at high packing fractions and thus is often employed to create model glass-forming systems. Nonetheless, it is known that hard-sphere mixtures with modest Polydispersity still have ordered ground states. Here, we demonstrate by computer simulation that hard-sphere mixtures with increased Polydispersity fractionate on the basis of particle size and a bimodal subpopulation favors the formation of topologically close-packed C14 and C15 Laves phases in coexistence with a disordered phase. The generality of this result is supported by simulations of hard-sphere mixtures with particle-size distributions of four different forms.
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from close packed to topologically close packed formation of laves phases in moderately polydisperse hard sphere mixtures
arXiv: Soft Condensed Matter, 2018Co-Authors: Beth A Lindquist, Ryan B Jadrich, Thomas M TruskettAbstract:Particle size Polydispersity can help to inhibit crystallization of the hard-sphere fluid into close-packed structures at high packing fractions and thus is often employed to create model glass-forming systems. Nonetheless, it is known that hard-sphere mixtures with modest Polydispersity still have ordered ground states. Here, we demonstrate by computer simulation that hard-sphere mixtures with increased Polydispersity fractionate on the basis of particle size, and a bimodal subpopulation favors formation of topologically close-packed C14 and C15 Laves phases in coexistence with a disordered phase. The generality of this result is supported by simulations of hard-sphere mixtures with particle-size distributions of four different forms.
Nurhidayah Sarifuddin 051624153003 - One of the best experts on this subject based on the ideXlab platform.
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PENGARUH KONSENTRASI ASAM HIALURONAT TERHADAP KARAKTERISTIK FISIK, STABILITAS FISIK DAN EFEKTIVITAS COENZYM Q10 DALAM SISTEM NANOSTRUCTURE LIPID CARRIER (NLC) SEBAGAI ANTI AGING
2019Co-Authors: Nurhidayah Sarifuddin 051624153003Abstract:Coenzyme Q10 is, often also known as ubiquinone, coenzyme Q10 or Q10, is fat soluble and naturally present in plants, animals and mitochondria. Coenzyme Q10 functions as an antioxidant that can protect the body from damage caused by free radicals. Hyaluronic acid is known as a hydrophilic polymer derived from polysaccharides which has the ability to increase percutaneous penetration by changing the composition of tightly arranged stratum corneum cells to increase skin permeability. Hyaluronic acid is also functions as a moisturizer. The Nanostructured Lipid Carrier is a modification of the SLN system, which consists of a mixture of solid and liquid lipids (oil), stabilized with aqueous surfactant solution, is one method to increase drug penetration through the stratum corneum because it has several advantages. The purpose of this study was to see the effect of adding hyaluronic acid to the characteristics, physical stability and effectiveness of the Nanostructure Lipid Carrier (NLC) as anti aging. Examination of characteristics including organoleptic, pH, viscosity, particle size, Polydispersity index, entrapment efficiency, morphology. The effectiveness is in vivo penetration, physical stability includes pH, particle size, polidispersity index and viscosity. pH measurements using pH meters, viscosity using brookfild, particle size and polidispersity index using Delsa Nano Particle Size Analyzer, examination of particle morphology using Transmission Electron Microscopy (TEM) and trapping effectiveness using centrifuge method then seen using UV spectrophotometer at 273 nm. Determination of penetration effectiveness was carried out in vivo using the back skin of male mice with Rhodamin B markers using a fluorosense microscope. In this study 4 formulas were used with different HA amounts: (F1) NLC coenzym Q10 without HA; (F2) NLC 0.5% coenzym Q10-HA; (F3) NLC 1% coenzym Q10-HA; (F4) 1.5% NLC coenzym Q10-HA. From the results of the additional characteristic test HA affects the coenzym Q10 NLC to the viscosity and particle size, where F4 produces greater viscosity 16.6 ± 1.385 cps, particle size 120.5 ± 8.69 nm. The penetration effectiveness test in vivo using the back skin of mice shows that all formulas are capable of penetrating from the 2nd hour. But F4 with the smallest particle size, shows the ability to penetrate deeper than other formulas. Physical stability test (pH, particle size and viscosity index polidispersity) performed by the storage for 30 days at room temperature. The measurement results showed that pH, particle size, Polydispersity index and viscosity were stable during storage
