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You searched for subject:( Confined suspensions). Showing records 1 – 3 of 3 total matches.

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Johannes Gutenberg Universität Mainz

1. Ricci, Andrea. Computer simulations of two-dimensional colloidal crystals in confinement.

Degree: 2006, Johannes Gutenberg Universität Mainz

Monte Carlo simulations are used to study the effect of confinement on a crystal of point particles interacting with an inverse power law potential in d=2 dimensions. This system can describe colloidal particles at the air-water interface, a model system for experimental study of two-dimensional melting. It is shown that the state of the system (a strip of width D) depends very sensitively on the precise boundary conditions at the two ``walls'' providing the confinement. If one uses a corrugated boundary commensurate with the order of the bulk triangular crystalline structure, both orientational order and positional order is enhanced, and such surface-induced order persists near the boundaries also at temperatures where the system in the bulk is in its fluid state. However, using smooth repulsive boundaries as walls providing the confinement, only the orientational order is enhanced, but positional (quasi-) long range order is destroyed: The mean-square displacement of two particles n lattice parameters apart in the y-direction along the walls then crosses over from the logarithmic increase (characteristic for d=2) to a linear increase (characteristic for d=1). The strip then exhibits a vanishing shear modulus. These results are interpreted in terms of a phenomenological harmonic theory. Also the effect of incommensurability of the strip width D with the triangular lattice structure is discussed, and a comparison with surface effects on phase transitions in simple Ising- and XY-models is made

Unter Verwendung von Monte Carlo Simulationen untersuchen wir, welchen Einfluss eine Beschränkung auf einen zweidimensionalen Kristall hat. Dieser besteht aus Punktteilchen, deren Wechselwirkungspotential eine inverse Potenzgesetzabhängigkeit zeigt. Das System kann kolloidale Teilchen modellieren, die sich in der Luft-Wasser Grenzfläche befinden.So können experimentell zweidimensionale Schmelzen untersucht werden. Wir zeigen, dass der Zustand des Systems (ein Streifen der Breite D) stark von den genauen Randbedingungen an den beschränkenden Wänden abhängt. Passen die Eigenschaften der Wände zu denen des dreieckigen Kristallgitters, so erhöht sich die Ordnung in den Positions- und Orientierungsfreiheitsgraden. Diese von den Oberflächen hervorgerufene Ordung bleibt an den Grenzflächen bestehen, insbesondere wenn sich das Bulk-System im flüssigen Zustand befindet. Wenn wir allerdings ein stetiges repulsives Potential als Wand verwenden, wird nur die Ordnung der Orientierungsfreiheitsgrade erhöht, während die der Positionsfreiheitsgrade("positional long range order") verschwindet: Dann geht das mittlere Verschiebungsquadrat zweier Teilchen, die in der zur Wand parallel verlaufenden y-Richtung n Gitter-Parameter voneinander entfernt sind, von einem logarithmischen Anstieg (charakteristisch für d=2) in einen linearen (charakteristisch für d=1) über. Der Schermodul des Streifens verschwindet in diesem Fall. Die Ergebnisse werden durch eine phänomenologisch harmonische Theorie interpretiert. Auch der Fall, bei dem die…

Subjects/Keywords: Colloidal Suspensions, Confined Systems; Physics

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APA (6th Edition):

Ricci, A. (2006). Computer simulations of two-dimensional colloidal crystals in confinement. (Doctoral Dissertation). Johannes Gutenberg Universität Mainz. Retrieved from http://ubm.opus.hbz-nrw.de/volltexte/2006/1134/

Chicago Manual of Style (16th Edition):

Ricci, Andrea. “Computer simulations of two-dimensional colloidal crystals in confinement.” 2006. Doctoral Dissertation, Johannes Gutenberg Universität Mainz. Accessed October 14, 2019. http://ubm.opus.hbz-nrw.de/volltexte/2006/1134/.

MLA Handbook (7th Edition):

Ricci, Andrea. “Computer simulations of two-dimensional colloidal crystals in confinement.” 2006. Web. 14 Oct 2019.

Vancouver:

Ricci A. Computer simulations of two-dimensional colloidal crystals in confinement. [Internet] [Doctoral dissertation]. Johannes Gutenberg Universität Mainz; 2006. [cited 2019 Oct 14]. Available from: http://ubm.opus.hbz-nrw.de/volltexte/2006/1134/.

Council of Science Editors:

Ricci A. Computer simulations of two-dimensional colloidal crystals in confinement. [Doctoral Dissertation]. Johannes Gutenberg Universität Mainz; 2006. Available from: http://ubm.opus.hbz-nrw.de/volltexte/2006/1134/


Cornell University

2. Aponte Rivera, Christian Alberto. Spherically confined colloidal suspensions of hydrodynamically interacting particles: A model for intracellular transport.

Degree: 2017, Cornell University

The diffusion in and rheology of hydrodynamically interacting colloids confined by a spherical cavity via dynamic simulation is studied as a model for intracellular and other confined biophysical transport. The modeling of transport and rheology in such confined inhomogeneous soft materials requires an accurate description of the microscopic forces driving particle motion, such as entropic and hydrodynamic forces, and of particle interactions with nearby boundaries. Previous models of such micro-confined transport behavior had been limited primarily to a single particle inside a spherical cavity. Although attempts had been made prior to this work to extend such models to more than one confined particle, none had yet successfully accounted for the effects of hydrodynamics, owing to the difficulties of modeling many-body long-ranged interactions. To accurately model spherically confined suspensions, new far-field mobility functions are derived and, together with the appropriate near-field resistance functions, implemented in a Stokesian-dynamics like approach. The method fully accounts for all many-body far-field interactions and near-field interactions both between the particles themselves and between particles and the enclosing cavity. Utilizing the newly developed method, we study short- and long- time self-diffusion at equilibrium, with a focus on the dependence of the former on particle positions relative to the cavity, and of both on volume fraction and size ratio. It is found that the cavity exerts qualitative changes in transport behavior, such as a position dependent and anisotropic short-time self-diffusivity and anisotropic long-time transport behavior. Such qualitative changes suggest that careful interpretation of experimental measurements in 3D confined suspensions requires accounting for such confinement induced behaviors. To elucidate the effects of confinement on inter-particle hydrodynamic interactions, the method is utilized to determine the concentrated mobility of particles in the spherically confined domain. Confinement is found to induce qualitative changes in the functional dependence of particle entrainment with inter-particle separation. For widely separated particles, the functional dependence on inter-particle separation can be predicted via a Green's function. How this behavior can be utilized to develop a more accurate framework for two-point microrheology measurements near confining boundaries is discussed. Advisors/Committee Members: Kirby, Brian (committeeMember), Koch, Donald L. (committeeMember).

Subjects/Keywords: Colloidal dispersions; Confined suspensions; Intracellular transport; Fluid Mechanics; Transport Phenomena

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Aponte Rivera, C. A. (2017). Spherically confined colloidal suspensions of hydrodynamically interacting particles: A model for intracellular transport. (Thesis). Cornell University. Retrieved from http://hdl.handle.net/1813/59118

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Aponte Rivera, Christian Alberto. “Spherically confined colloidal suspensions of hydrodynamically interacting particles: A model for intracellular transport. ” 2017. Thesis, Cornell University. Accessed October 14, 2019. http://hdl.handle.net/1813/59118.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Aponte Rivera, Christian Alberto. “Spherically confined colloidal suspensions of hydrodynamically interacting particles: A model for intracellular transport. ” 2017. Web. 14 Oct 2019.

Vancouver:

Aponte Rivera CA. Spherically confined colloidal suspensions of hydrodynamically interacting particles: A model for intracellular transport. [Internet] [Thesis]. Cornell University; 2017. [cited 2019 Oct 14]. Available from: http://hdl.handle.net/1813/59118.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Aponte Rivera CA. Spherically confined colloidal suspensions of hydrodynamically interacting particles: A model for intracellular transport. [Thesis]. Cornell University; 2017. Available from: http://hdl.handle.net/1813/59118

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


University of Texas – Austin

3. -2728-5566. From confinement to clustering : decoding the structural and diffusive signatures of microscopic frustration.

Degree: PhD, Chemical engineering, 2016, University of Texas – Austin

There are diverse technological contexts where fluids and suspensions are perturbed by applied fields like interfaces or intrinsically governed by complex interparticle potentials. When these interactions act over lengthscales comparable to the fluid particle size and become strong enough to frustrate particle packing or rearrangements, they drive systems to exhibit microscopically inhomogeneous (i.e., position-dependent) structural and relaxation responses. We use computer simulations and statistical-mechanical tools to find connections between such frustrating interactions and inhomogeneous fluid responses, which can profoundly impact macroscopic material properties and processing requirements. We first consider how to measure and predict the position-dependent and average diffusion coefficients of particles along inhomogeneous free-energy landscapes (i.e., potentials of mean force). Characterizing diffusion in such inhomogeneous fluids is crucial for modeling, e.g., the transit of colloids across microfluidic devices and of solutes through biological membranes. We validate a practical technique based on the Fokker-Planck diffusion formalism that measures diffusivities based solely on particle trajectory data. We focus on hard-sphere fluids confined to thin channels or subjected to external fields that impose density fluctuations at various wavelengths. We find, for example, that hydrodynamic predictions of tracer diffusion in confinement are surprisingly robust given non-continuum solvents. We also demonstrate that correlations between fluid static structure and diffusivity can qualitatively depend on the lengthscale of density fluctuations or the onset of supercooling. We next examine fluids governed by competing short-range attractions and long-range repulsions that drive formation of equilibrium cluster phases, which comprise monodisperse aggregates of monomers. The formation of such morphologies greatly impacts, e.g., the manufacturing of therapeutic protein solutions. We first address a major challenge in probing the real-space structure of such suspensions: detecting and characterizing cluster phases based on the static structure factor accessible via scattering experiments. Using computer simulations and liquid-state theory, we validate rules for interpreting low-wavenumber features in the structure factor in terms of cluster emergence, size, spatial distribution, etc. We then validate a thermodynamic model that predicts cluster size based on the strengths of monomer interactions, adapting classical nucleation theory to incorporate new empirical scalings for the surface energies of small stable droplets. Advisors/Committee Members: Truskett, Thomas Michael, 1973- (advisor), Bonnecaze, Roger T. (committee member), Ganesan, Venkat (committee member), Lynd, Nathaniel A. (committee member), Makarov, Dmitrii E. (committee member).

Subjects/Keywords: Complex fluids; Colloidal suspensions; Diffusion coefficient; Fokker-Planck equation; Confined fluids; SALR fluids; Equilibrium clusters; Structure factor; Classical nucleation theory

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

-2728-5566. (2016). From confinement to clustering : decoding the structural and diffusive signatures of microscopic frustration. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/46440

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Chicago Manual of Style (16th Edition):

-2728-5566. “From confinement to clustering : decoding the structural and diffusive signatures of microscopic frustration.” 2016. Doctoral Dissertation, University of Texas – Austin. Accessed October 14, 2019. http://hdl.handle.net/2152/46440.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7th Edition):

-2728-5566. “From confinement to clustering : decoding the structural and diffusive signatures of microscopic frustration.” 2016. Web. 14 Oct 2019.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-2728-5566. From confinement to clustering : decoding the structural and diffusive signatures of microscopic frustration. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2016. [cited 2019 Oct 14]. Available from: http://hdl.handle.net/2152/46440.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-2728-5566. From confinement to clustering : decoding the structural and diffusive signatures of microscopic frustration. [Doctoral Dissertation]. University of Texas – Austin; 2016. Available from: http://hdl.handle.net/2152/46440

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

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