Vibrated Squares As Equilibrium And Active Matter, 2018 University of Massachusetts Amherst

#### Vibrated Squares As Equilibrium And Active Matter, Lee Askew Walsh

*Doctoral Dissertations*

We study the effects of particle shape and self-propulsion on the collective behaviors of a two-dimensional granular fluid, using an experimental system of hard square grains. We energize the system by vibration, which, depending on particle shape, induces either isotropic diffusion or persistent self-propulsion in the particles. We use specially designed grains as a model system to study (i) the equilibrium packing of hard squares in two dimensions, (ii) the dynamics of athermal self-propelled particles, and (iii) the melting kinetics of an unconfined granular crystallite.

The first study concerns the phase diagram of a two-dimensional fluid of hard squares, which ...

Geometry, Growth And Pattern Formation In Thin Elastic Structures, 2018 University of Massachusetts Amherst

#### Geometry, Growth And Pattern Formation In Thin Elastic Structures, Salem Al-Mosleh

*Doctoral Dissertations*

Thin shells are abundant in nature and industry, from atomic to planetary scales. The mechanical behavior of a thin shell depends crucially on its geometry and embedding in 3 dimensions (3D). In fact, the behavior of extremely thin shells becomes scale independent and only depends on geometry. That is why the crumpling of graphene will have similarities to the crumpling of paper. In this thesis, we start by discussing the static behavior of thin shells, highlighting the role of asymptotic curves (curves with zero normal curvature) in determining the possible deformations and in controlling the folding patterns. In particular, we ...

Swelling Induced Deformation Of Thermally Responsive Hydrogels, 2018 University of Massachusetts Amherst

#### Swelling Induced Deformation Of Thermally Responsive Hydrogels, Ying Zhou

*Doctoral Dissertations*

Hydrogels are crosslinked polymeric networks imbibed with aqueous solutions. They undertake dramatic volume changes through swelling and deswelling processes, which can be stimulated by factors like temperature, pH or different chemicals. These unique properties render hydrogels particularly interesting for shape morphing related applications.

In this thesis, we focus on the swelling induced deformation of thermally responsive hydrogels with lower critical solution temperatures (LCSTs), including poly(*N*-isopropylacrylamide) (PNIPAm) and poly(*N*,*N*-diethylacrylamide) (PDEAm). Particularly, benzophenone containing monomers are copolymerized with NIPAm or DEAm to create photocrosslinkable temperature-responsive polymers, which allows fabrication of hydrogels with controlled shapes and crosslinking densities ...

Preparation, Mechanics And Structure Of Sphere Packings Near The Random Loose Packing Limit, 2018 University of Massachusetts Amherst

#### Preparation, Mechanics And Structure Of Sphere Packings Near The Random Loose Packing Limit, Greg Robert Farrell

*Doctoral Dissertations*

Packings of monodisperse, hard spheres serve as an important model system in the understanding of granular materials which are ubiquitous in nature and industry from sedimented river beds, to construction aggregates, to pharmaceuticals. Unlike frictionless hard spheres which are only stable at densities near the random close packing volume fraction, packings of real spheres form stable packings over a range of volume fractions. We report experimental investigations of sedimented packings of noncohesive polymethyl-methacrylate spheres over a range of volume fractions near the lower limit of this range of volume fractions.

We create packings by slow sedimentation in a viscous fluid ...

Dynamics And Structure Of Polyelectrolyte Complexes, 2018 University of Massachusetts Amherst

#### Dynamics And Structure Of Polyelectrolyte Complexes, Hamidreza Shojaei-Mahib

*Doctoral Dissertations*

Interaction of charged macromolecules among themselves and with charged interfaces in salty aqueous medium is a common phenomenon prevalent in biology and synthetic systems. We have addressed several inter-related issues in this general context. First we present a theory of adsorption of polyelectrolytes on the interior and exterior surfaces of a charged spherical vesicle. We derive the critical adsorption condition and the density profile of the polymer in terms of various characteristics of the polymer, vesicle, and the solution, such as the length and charge density of polymer, the radius and charge of the vesicle, the salt concentration of the ...

Band Filling And Temperature Effects On Electrical Conductivity In Strongly Correlated Hybridized Electron Systems, 2018 Minnesota State University, Mankato

#### Band Filling And Temperature Effects On Electrical Conductivity In Strongly Correlated Hybridized Electron Systems, Dylan T. Meyer

*All Theses, Dissertations, and Other Capstone Projects*

We investigate the effects of band filling as well as temperature change on the electrical conductivity of materials with strong interelectron interaction as well as band hybridization. This is done by use of the irreducible two-particle Green function method applied to strongly correlated electron systems described by the Periodic Anderson Model. It was found that there is a definite peak in electrical conductivity at low band occupancy when the d-energy sub-band is half filled. Conductivity was found to have a sharp drop with an increase in temperature as a result of thermal dispersion as well as a change in the ...

Statistical Biophysics Blog: Let’S Stop Being Sloppy About Uncertainty, 2017 Oregon Health & Science University

#### Statistical Biophysics Blog: Let’S Stop Being Sloppy About Uncertainty, Daniel M. Zuckerman

*Scholar Archive*

Molecular dynamics simulations often fail to reach timescales characteristic of equilibrum sampling, so great care must be taken in computing and reporting statistical uncertainty.

A Molecular Debye-Hückel Theory Of Solvation In Polar Fluids: An Extension Of The Born Model, 2017 Guizhou Education University

#### A Molecular Debye-Hückel Theory Of Solvation In Polar Fluids: An Extension Of The Born Model, Tiejun Xiao, Xueyu Song

*Ames Laboratory Accepted Manuscripts*

A dielectric response theory of solvation beyond the conventional Born model for polar fluids is presented. The dielectric response of a polar fluid is described by a Born response mode and a linear combination of Debye-Hückel-like response modes that capture the nonlocal response of polar fluids. The Born mode is characterized by a bulk dielectric constant, while a Debye-Hückel mode is characterized by its corresponding Debye screening length. Both the bulk dielectric constant and the Debye screening lengths are determined from the bulk dielectric function of the polar fluid. The linear combination coefficients of the response modes are evaluated in ...

Transport Of Water And Ions Through Single-Walled Armchair Carbon Nanotubes: A Molecular Dynamics Study, 2017 University of Tennessee, Knoxville

#### Transport Of Water And Ions Through Single-Walled Armchair Carbon Nanotubes: A Molecular Dynamics Study, Michelle Patricia Aranha

*Doctoral Dissertations*

The narrow hydrophobic interior of a carbon nanotube (CNT) poses a barrier to the transport of water and ions, and yet, unexpectedly, numerous experimental and simulation studies have confirmed fast water transport rates comparable to those seen in biological aquaporin channels. These outstanding features of high water permeability and high solute rejection of even dissolved ions that would typically require a lot of energy for separation in commercial processes makes carbon nanotubes an exciting candidate for desalination membranes. Extending ion exclusion beyond simple mechanical sieving by the inclusion of electrostatics via added functionality to the nanotube bears promise to not ...

Weak-Value Amplification And Optimal Parameter Estimation In The Presence Of Correlated Noise, 2017 University of Toronto

#### Weak-Value Amplification And Optimal Parameter Estimation In The Presence Of Correlated Noise, Josiah Sinclair, Matin Hallaji, Aephraim M. Steinberg, Jeff Tollaksen, Andrew N. Jordan

*Mathematics, Physics, and Computer Science Faculty Articles and Research*

We analytically and numerically investigate the performance of weak-value amplification (WVA) and related parameter estimation methods in the presence of temporally correlated noise. WVA is a special instance of a general measurement strategy that involves sorting data into separate subsets based on the outcome of a second “partitioning” measurement. Using a simplified correlated noise model that can be analyzed exactly together with optimal statistical estimators, we compare WVA to a conventional measurement method. We find that WVA indeed yields a much lower variance of the parameter of interest than the conventional technique does, optimized in the absence of any partitioning ...

Dynamic Self-Assembly And Self-Organized Transport Of Magnetic Micro-Swimmers, 2017 Argonne National Laboratory

#### Dynamic Self-Assembly And Self-Organized Transport Of Magnetic Micro-Swimmers, Gašper Kokot, German Kolmakov V, Igor S. Aranson, Alexey Snezhko

*Publications and Research*

We demonstrate experimentally and in computer simulations that magnetic microfloaters can self-organize into various functional structures while energized by an external alternating (ac) magnetic field. The structures exhibit self-propelled motion and an ability to carry a cargo along a pre-defined path. The morphology of the self-assembled swimmers is controlled by the frequency and amplitude of the magnetic field.

Electromagnetic Shielding Effectiveness Of 3d Printed Polymer Composites, 2017 Foundation for Research and Technology-Hellas

#### Electromagnetic Shielding Effectiveness Of 3d Printed Polymer Composites, Z. Viskadourakis, K. C. Vasilopoulos, E. N. Economou, Costas M. Soukoulis, G. Kenanakis

*Ames Laboratory Accepted Manuscripts*

We report on preliminary results regarding the electromagnetic shielding effectiveness of various 3D printed polymeric composite structures. All studied samples were fabricated using 3D printing technology, following the fused deposition modeling approach, using commercially available filaments as starting materials. The electromagnetic shielding performance of the fabricated 3D samples was investigated in the so called C-band of the electromagnetic spectrum (3.5–7.0 GHz), which is typically used for long-distance radio telecommunications. We provide evidence that 3D printing technology can be effectively utilized to prepare operational shields, making them promising candidates for electromagnetic shielding applications for electronic devices.

Interplay Of Quantum Size Effect, Anisotropy And Surface Stress Shapes The Instability Of Thin Metal Films, 2017 Western Kentucky University

#### Interplay Of Quantum Size Effect, Anisotropy And Surface Stress Shapes The Instability Of Thin Metal Films, Mikhail Khenner

*Mathematics Faculty Publications*

Morphological instability of a planar surface ([111], [011], or [001]) of an ultra-thin metal film is studied in a parameter space formed by three major effects (the quantum size effect, the surface energy anisotropy and the surface stress) that influence a film dewetting. The analysis is based on the extended Mullins equation, where the effects are cast as functions of the film thickness. The formulation of the quantum size effect (Z. Zhang et al., PRL 80, 5381 (1998)) includes the oscillation of the surface energy with thickness caused by electrons confinement. By systematically comparing the effects, their contributions into the ...

Interplay Of Quantum Size Effect, Anisotropy And Surface Stress Shapes The Instability Of Thin Metal Films, 2017 Western Kentucky University

#### Interplay Of Quantum Size Effect, Anisotropy And Surface Stress Shapes The Instability Of Thin Metal Films, Mikhail Khenner

*Mikhail Khenner*

Planar Granular Shear Flow Under External Vibration, 2017 Bucknell University

#### Planar Granular Shear Flow Under External Vibration, Brian Utter, Eric P. Hoppmann

*Faculty Journal Articles*

We present results from a planar shear experiment in which a two-dimensional horizontal granular assembly of pentagonal particles sheared between two parallel walls is subjected to external vibration. Particle tracking and photoelastic measurements are used to quantify both grain scale motion and interparticle stresses with and without imposed vibrations. We characterize the particle motion in planar shear and find that flow of these strongly interlocking particles consists of transient vortex motion with a mean flow given by the sum of exponential profiles imposed by the shearing walls. Vibration is applied either through the shearing surface or as bulk vertical vibration ...

Ion Size Effects On The Properties Of Charge Regulating Electric Double Layers, 2017 University of New Mexico

#### Ion Size Effects On The Properties Of Charge Regulating Electric Double Layers, Divya Jyoti Prakash

*Nanoscience and Microsystems ETDs*

The behavior of charged interfaces formed in various systems like colloidal solution, fuel cells, battery, electro-deposition, catalysis is governed by the properties of electrical double layer(EDL). Civilized model with charge regulation boundary condition determined by thermodynamic equilibrium at the interface has been used to model electrical double layer and shows that size of the solvent plays a critical role in characterizing the properties of EDL using classical density functional theory.This thesis investigates the impact of ion size in electrolyte solutions on the electrical double layer formed at the interface using a similar model. It is found that ion ...

Non-Hermitian Matter-Wave Mixing In Bose-Einstein Condensates: Dissipation-Induced Amplification, 2017 Bilkent University

#### Non-Hermitian Matter-Wave Mixing In Bose-Einstein Condensates: Dissipation-Induced Amplification, S. Wuster, Ramy El-Ganainy

*Department of Physics Publications*

We investigate the nonlinear scattering dynamics in interacting atomic Bose-Einstein condensates under non-Hermitian dissipative conditions. We show that, by carefully engineering a momentum-dependent atomic loss profile, one can achieve matter-wave amplification through four-wave mixing in a quasi-one-dimensional nearly-free-space setup—a process that is forbidden in the counterpart Hermitian systems due to energy mismatch. Additionally, we show that similar effects lead to rich nonlinear dynamics in higher dimensions. Finally, we propose a physical realization for selectively tailoring the momentum-dependent atomic dissipation. Our strategy is based on a two-step process: (i) exciting atoms to narrow Rydberg or metastable excited states, and (ii ...

Statistical Biophysics Blog: What I Have Against (Most) Pmf Calculations, 2017 Oregon Health & Science University

#### Statistical Biophysics Blog: What I Have Against (Most) Pmf Calculations, Daniel M. Zuckerman

*Scholar Archive*

The potential of mean force (PMF) is one of the most widely used characterizations of a biomolecular system computed from simulation, but calculating and interpreting a PMF both present challenges.

Overview Of Weighted Ensemble Simulation: Path-Sampling, Steady States, Equilibrium, 2017 Oregon Health & Science University

#### Overview Of Weighted Ensemble Simulation: Path-Sampling, Steady States, Equilibrium, Daniel M. Zuckerman

*Scholar Archive*

A concise overview of the weighted ensemble path sampling method for rare events is given, aimed at beginners.

Accuracy And Stability Of Integration Methods For Neutrino Transport In Core Collapse Supernovae, 2017 kgrego12

#### Accuracy And Stability Of Integration Methods For Neutrino Transport In Core Collapse Supernovae, Kyle A. Gregory

*Chancellor’s Honors Program Projects*

No abstract provided.