Physics Commons^™

A Solid-State Phase Camera For Advanced Gravitational Wave Detectors, Erik Muniz

Dissertations - ALL

I present a novel way of wavefront sensing using a commercially available, continuouswavetime-of- ight camera with QVGA-resolution. This CMOS phase camera is capable of sensing externally modulated light sources with frequencies up to 100 MHz. The high-spatial-resolution of the sensor, combined with our integrated control electronics, allows the camera to image power modulation index as low as -62 dBc/second/pixel. The phase camera is applicable to problems where alignment and mode-mismatch sensing is needed and suited for diagnostic and control applications in gravitationalwave detectors. Specically, I explore the use of the phase camera in sensing the beat signals due to thermal …

Observation Of Ω Contribution In The C1(3872) → Π+Π−J/Ψ Decays, Baasansuren Batsukh

Dissertations - ALL

Resonant structure in the dipion mass spectrum produced via \decay{\Bu}{\X\Kp}, \decay{\X}{\jpsi \pip \pim}, with \decay{\jpsi}{\mu^+\mu^-} is analyzed using Run 1 and Run 2 data samples from the LHCb experiment. The spectrum is dominated by $\rhoz\to\pi^+\pi^-$, but cannot be described by this contribution alone. A significant $\omega\to\pi^+\pi^-$ contribution, interfering with $\rhoz$, is observed for the first time. This is a more significant observation ($>7.1\sigma$) of $\X\to\omega\jpsi$ decays, than previously achieved with $\omega\to\pi^+\pi^-\pi^0$ decays. The relative contribution of $\omega$ to the total $\X\to\pi^+\pi^-\jpsi$ rate is at the level expected from the measured $\X\to(\omega\to\pi^+\pi^-\pi^0)\jpsi$ rate, if the interference between the $\rho^0$ and …

Utilizing Parity Violating Electron Scattering As A Probe To Measure The Neutron Radius Of 208-Pb, David Eric King

Dissertations - ALL

The Lead Radius Experiment 2 (PREX-II) and Calcium Radius Experiment (CREX) carried out in Hall A of the Thomas Jefferson National Accelerator Facility were designed to measure the neutron skins of 208-Pb and 48-Ca nuclei by measuring the parity-violating asymmetry APV of the elastic scattering of polarized electrons on 208-Pb and 48-Ca targets. In order to achieve a precision measurement of the neutron skins of 208-Pb and 48-Ca it is imperative to maintain precise control over many experimental parameters–one of which is a precision measurement of the electron beam polarization (which is the largest contributor to experimental error making control …

Buckling Patterns And Mechanics Of Thin Interfacial Polymer Films, Monica M. Ripp

Dissertations - ALL

Thin elastic solids are easily deformed and will readily collapse into complex buckling modes. They can also transition between distinct buckling modes when the confining forces evolve over time, forming a variety of robust and striking patterns. Here we explore how thin interfacial films and the buckling modes they present couple with evolving macroscopic forces and how multi-scale features of the systems give rise to patterns.

In the indentation of a circular film floating on a liquid bath three buckling modes arise: wrinkling, crumpling, and folding. This work shows that striking transitions between these states accompany four regimes in the …

Direct Single Molecule Imaging Of Enhanced Diffusion For Enzymes And Enzyme-Conjugated Dna Origami, Mengqi Xu

Dissertations - ALL

Enzymes have been shown to diffuse faster in the presence of their substrates. Recently, we revealed new insights into this process of enhanced diffusion using single-particle tracking (SPT) with total internal reflection fluorescence (TIRF) microscopy. We found that the mobility of individual enzymes was enhanced three-fold in the presence of the substrate, and the motion remained Brownian. We showed that the relative increase in diffusion is independent of the total enzyme concentrations; and the oligomerization state of enzymes did not change during the catalytic turnover. These experiments ruled out the possibility that the enhanced enzyme diffusion was caused by the …

First Measurement Of B(Ξc0 → Π−Λ+C ), Michael Kent Wilkinson

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The first measurement of the branching fraction of the Ξc0 baryon in its decay to π− and Λ+c hadrons, B(Ξc0 → π−Λ+c ), is presented. This measurement was conducted with the LHCb detector, located on the Large Hadron Collider, using 13 TeV proton-proton collisions. There have been a number of theoretical predictions for the size of this branching fraction, spanning more than an order of magnitude; this large difference is primarily due to differing assumptions about the internal interactions contributing to the decay. The branching fraction measured here provides the first experimental evidence for the nature of these interactions; it …

Extracellular Vimentin As A Target Against Sars-Cov-2 Host Cell Invasion, Łukasz Suprewicz, Maxx Swoger, Sarthak Gupta, Ewelina Piktel, Fitzroy J. Byfield, Daniel V. Iwamoto, Danielle Germann, Joanna Reszeć, Natalia Marcińczyk, Robert J. Carroll, Paul A. Janmey, J. M. Schwarz, Robert Bucki, Alison E. Patteson

Physics - All Scholarship

Infection of human cells by pathogens, including SARS-CoV-2, typically proceeds by cell surface binding to a crucial receptor. The primary receptor for SARS-CoV-2 is the angiotensin-converting enzyme 2 (ACE2), yet new studies reveal the importance of additional extracellular co-receptors that mediate binding and host cell invasion by SARS-CoV-2. Vimentin is an intermediate filament protein that is increasingly recognized as being present on the extracellular surface of a subset of cell types, where it can bind to and facilitate pathogens’ cellular uptake. Biophysical and cell infection studies are done to determine whether vimentin might bind SARS-CoV-2 and facilitate its uptake. Dynamic …

A Data-Driven Statistical Description For The Hydrodynamics Of Active Matter, Ahmad Borzou, Alison E. Patteson, J. M. Schwarz

Physics - All Scholarship

Modeling living systems at the collective scale can be very challenging because the individual constituents can themselves be complex and the respective interactions between the constituents may not be fully understood. With the advent of high throughput experiments and in the age of big data, data-driven methods are on the rise to overcome these challenges. Although machine-learning approaches can help quantify correlations between the various players, they do not directly shed light on the underlying physical principles of such systems. Here, we present a data-driven method for obtaining the phase-space density of active matter systems such that the solution to …

The Role Of Vimentin–Nuclear Interactions In Persistent Cell Motility Through Confined Spaces, Sarthak Gupta, Alison E. Patteson, J. M. Schwarz

Physics - All Scholarship

The ability of cells to move through small spaces depends on the mechanical properties of the cellular cytoskeleton and on nuclear deformability. In mammalian cells, the cytoskeleton is composed of three interacting, semi-flexible polymer networks: actin, microtubules, and intermediate filaments (IF). Recent experiments of mouse embryonic fibroblasts with and without vimentin have shown that the IF vimentin plays a role in confined cell motility. Here, we develop a minimal model of a cell moving through a microchannel that incorporates explicit effects of actin and vimentin and implicit effects of microtubules. Specifically, the model consists of a cell with an actomyosin …

Self-Organization In Models Of Cyclically Sheared Suspensions, Jikai Wang

Dissertations - ALL

This thesis presents a study of random self-organized systems using computer-simulated models inspired by cyclically-sheared non-Brownian suspensions of monodisperse spherical particles in a density-matched fluid. When driven at low Reynolds number, such systems have vanishing thermal fluctuations and only short-range interactions between individual particles. Nevertheless, they show intriguing collective behaviors at large length scales, such as a strong suppression of fluctuations in the number density. Such self-organized "hyperuniform" states can useful in industrial applications where well-controlled states can ease the processing of such materials.In Chapter 2, we propose a new way of generating hyperuniform suspensions, by incorporating slow gravity-driven sedimentation …

Multimode Circuit Quantum Electrodynamics With Superconducting Metamaterial Resonators, . Indrajeet

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Superconducting devices in circuit quantum electrodynamics (cQED) systems are one of the leading approaches for realizing scalable quantum information processors. The combination of cQED architectures with multimode resonator systems can provide a flexible platform for performing analog quantum simulations, storing quantum information, and generating complex entangled states. Metamaterial resonant structures made from arrays of superconducting lumped circuit elements can exhibit microwave mode spectra with left-handed dispersion, resulting in a high density of modes in the same frequency range where superconducting qubits are typically operated, as well as a bandgap at lower frequencies that extends down to dc. In this thesis, …

Interplay Of Geometry And Mechanics: Disordered Spring Networks And Shape-Changing Cerebella, Mahesh Chandrasekhar Gandikota

Dissertations - ALL

This thesis reports work in three topics - I) isotropic strain-induced rigidity transitions in under-constrained spring networks II) uniaxial strain-induced stiffening transitions in semiflexible networks with area-conserving inclusions and III) non-linearities in the buckling without bending morphogenesis model for growing cerebella. All models are two dimensional and we employ either discrete and continuum models to study these systems.In I), motivated by the rigidity transitions in isotropically strained disordered spring networks, we study rigidity transitions in isotropically strained area-conserving random polygonal loops. We find a crossover transition in these loops. We also provide arguments towards showing convexity as a necessary condition …

Eccentricity Of Merging Neutron Star Binaries: Searches, Parameter Estimation, And Future Prospects, Amber Kiana Lenon

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Since the start of the first observing run the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Advanced Virgo observatory have detected 48 binary black hole mergers and two binary neutron star mergers. Knowledge about the properties of the binary can be gained from the gravitational-wave observations. Binary neutron star systems can form with significant orbital eccentricity. Gravitational radiation efficiently removes this eccentricity from the binary's orbit as the star's inspiral together. This thesis describes a search for neutron star binaries that have an eccentric orbits when their gravitational waves enter the sensitive band of Advanced LIGO and Virgo. For …

Effective Computational Cosmology, Eva Nesbit

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Effective Field Theories (EFTs) provide a unique framework in which to attempt to answer outstanding questions in cosmology (and all field of physics, for that matter). This work investigates how the use of both EFTs and computational tools can help us to advance our knowledge of how the universe evolved and formed over time. Specifically, we review the successful EFT of Inflation, the EFT of Dark Energy (EFTDE), and introduce the EFT of Reheating as a generalized model of particle formation after inflation. In this way, we show how effective EFTs are at quantifying physical phenomenology at many different energy …

Photovoltages In Polycrystalline Mosaic Solar Cells, Steluta A. Dinca, Eric A. Schiff

Chemistry - All Scholarship

In some thin-film solar cells the light-absorbing layer is a mosaic of crystalline grains whose boundaries run from the back to the front of the cell. We used the semiconductor modeling software Sesame to do numerical calculations of the optoelectronic properties of such cells assuming that recombination of minority photocarriers occurs primarily at the grain boundaries. The work complements analytical results for diffusion-limited recombination at grain boundaries and dislocations. We chose idealized n-CdS/p-CdTe solar cells for illustration. We find that the open-circuit voltage, V_oc, under illumination declines logarithmically with increasing ratio D/θ², where D is the …

Beyond The Standard Models Of Particle Physics And Cosmology, Gabriele Rigo

Dissertations - ALL

Despite their numerous successes both from the theoretical and experimental point of view, conceptual and observational evidence suggests the Standard Models of Particle Physics and Cosmology should be considered incomplete theories, reliable only within their well-defined regime of validity. This dissertation covers various possible extensions of those models from the theoretical, phenomenological and model-building perspective. The topics analyzed range from extra-dimensional approaches to the hierarchy problem, to the AdS/CFT description of perturbative anomaly inflow, and new probes of vacuum energy in neutron stars and gravitational waves.

Beyond The Standard Models Of Particle Physics And Cosmology, Gabriele Rigo

Dissertations - ALL

Despite their numerous successes both from the theoretical and experimental point of view, conceptual and observational evidence suggests the Standard Models of Particle Physics and Cosmology should be considered incomplete theories, reliable only within their well-defined regime of validity. This dissertation covers various possible extensions of those models from the theoretical, phenomenological and model-building perspective. The topics analyzed range from extra-dimensional approaches to the hierarchy problem, to the AdS/CFT description of perturbative anomaly inflow, and new probes of vacuum energy in neutron stars and gravitational waves.

Dynamic Nuclear Structure Emerges From Chromatin Cross-Links And Motors, Kuang Liu, Alison E. Patteson, Edward J. Banigan, J. M. Schwarz

Physics - All Scholarship

The cell nucleus houses the chromosomes, which are linked to a soft shell of lamin protein filaments. Experiments indicate that correlated chromosome dynamics and nuclear shape fluctuations arise from motor activity. To identify the physical mechanisms, we develop a model of an active, cross-linked Rouse chain bound to a polymeric shell. System-sized correlated motions occur but require both motor activity and cross-links. Contractile motors, in particular, enhance chromosome dynamics by driving anomalous density fluctuations. Nuclear shape fluctuations depend on motor strength, cross-linking, and chromosome-lamina binding. Therefore, complex chromosome dynamics and nuclear shape emerge from a minimal, active chromosome-lamina system.

Cell-Induced Confinement Effects In Soft Tissue Mechanics, Dawei Song, Jordan L. Shivers, Fred C. Mackintosh, Alison E. Patteson, Paul A. Janmey

Physics - All Scholarship

The mechanical properties of tissues play a critical role in their normal and pathophysiological functions such as tissue development, aging, injury, and disease. Understanding tissue mechanics is important not only for designing realistic biomimetic materials for tissue engineering and drug testing but also for developing novel diagnostic techniques and medical interventions. Tissues are heterogeneous materials consisting of cells confined within extracellular matrices (ECMs), both of which derive their structural integrity, at least in part, from networks of biopolymers. However, the rheology of purified reconstituted biopolymer networks fails to explain many key aspects of tissue mechanics. Notably, purified networks typically soften …

Vimentin Tunes Cell Migration On Collagen By Controlling Β1 Integrin Activation And Clustering, Zofia Ostrowska-Podhorodecka, Isabel Ding, Wilson Lee, Jelena Tanic, Sevil Abbasi, Pamma D. Arora, Richard S. Liu, Alison E. Patteson, Paul A. Janmey, Christopher A. Mcculloch

Physics - All Scholarship

Vimentin is a structural protein that is required for mesenchymal cell migration and directly interacts with actin, β1 integrin and paxillin. We examined how these interactions enable vimentin to regulate cell migration on collagen. In fibroblasts, depletion of vimentin increased talin-dependent activation of β1 integrin by more than 2-fold. Loss of vimentin was associated with reduction of β1 integrin clustering by 50% and inhibition of paxillin recruitment to focal adhesions by more than 60%, which was restored by vimentin expression. This reduction of paxillin was associated with 65% lower Cdc42 activation, a 60% reduction of cell extension formation and a …

Bacterial Activity Hinders Particle Sedimentation, Jaspreet Singh, Alison E. Patteson, Bryan O. Torres Maldonado, Prashant K. Purohit, Paulo E. Arratia

Physics - All Scholarship

Sedimentation in active fluids has come into focus due to the ubiquity of swimming micro-organisms in natural and industrial processes. Here, we investigate sedimentation dynamics of passive particles in a fluid as a function of bacteria E. coli concentration. Results show that the presence of swimming bacteria significantly reduces the speed of the sedimentation front even in the dilute regime, in which the sedimentation speed is expected to be independent of particle concentration. Furthermore, bacteria increase the dispersion of the passive particles, which determines the width of the sedimentation front. For short times, particle sedimentation speed has a linear dependence …

Cell Nuclei As Cytoplasmic Rheometers, Alison E. Patteson, J. M. Schwarz

Physics - All Scholarship

Some researchers probe the mechanics of cells by perturbing them from the outside, such as using an atomic force microscope probe to record the amount of deformation of the cell in response to applying a prescribed force at a defined speed. Other researchers probe the mechanics of cells by perturbing them from the inside, an example of which is particle-tracking microrheology, in which the spontaneous motion of submicron, passive fluorescent beads ballistically injected earlier into the cell decodes the cell moduli. Both types of probes are typically composed of nonliving material. In this issue of Biophysical Journal, Moradi and …

A Tissue-Engineered Human Trabecular Meshwork Hydrogel For Advanced Glaucoma Disease Modeling, Haiyan Li, Tyler Bagué, Alexander Kirschner, Ana N. Strat, Haven Roberts, Robert W. Weisenthal, Alison E. Patteson, Nasim Annabi, W. Daniel Stamer, Preethi S. Ganapathy, Samuel Herberg

Physics - All Scholarship

Abnormal human trabecular meshwork (HTM) cell function and extracellular matrix(ECM) remodeling contribute to HTM stiffening in primary open-angle glaucoma (POAG). Most current cellular HTM model systems do not sufficiently replicate the complex native three dimensional (3D) cell-ECM interface, limiting their use for investigating POAG pathology. Tissue-engineered hydrogels are ideally positioned to overcome shortcomings of current models. Here, we report a novel biomimetic HTM hydrogel and test its utility as a POAG disease model. HTM hydrogels were engineered by mixing normal donor-derived HTM cells with collagen type I, elastin-like polypeptide and hyaluronic acid, each containing photoactive functional groups, …