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Articles 31 - 60 of 880
Full-Text Articles in Physics
Utilizing Parity Violating Electron Scattering As A Probe To Measure The Neutron Radius Of 208-Pb, David Eric King
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 …
Direct Single Molecule Imaging Of Enhanced Diffusion For Enzymes And Enzyme-Conjugated Dna Origami, Mengqi Xu
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
First Measurement Of B(Ξc0 → Π−Λ+C ), Michael Kent Wilkinson
Dissertations - ALL
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
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
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
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
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
Multimode Circuit Quantum Electrodynamics With Superconducting Metamaterial Resonators, . Indrajeet
Dissertations - ALL
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
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 …
Effective Computational Cosmology, Eva Nesbit
Effective Computational Cosmology, Eva Nesbit
Dissertations - ALL
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 …
Eccentricity Of Merging Neutron Star Binaries: Searches, Parameter Estimation, And Future Prospects, Amber Kiana Lenon
Eccentricity Of Merging Neutron Star Binaries: Searches, Parameter Estimation, And Future Prospects, Amber Kiana Lenon
Dissertations - ALL
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 …
Photovoltages In Polycrystalline Mosaic Solar Cells, Steluta A. Dinca, Eric A. Schiff
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, Voc, under illumination declines logarithmically with increasing ratio D/θ2, where D is the …
Beyond The Standard Models Of Particle Physics And Cosmology, Gabriele Rigo
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
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
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
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
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
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
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
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, …
The Vimentin Cytoskeleton: When Polymer Physics Meets Cell Biology, Alison E. Patteson, Robert J. Carroll, Daniel V. Iwamoto, Paul A. Janmey
The Vimentin Cytoskeleton: When Polymer Physics Meets Cell Biology, Alison E. Patteson, Robert J. Carroll, Daniel V. Iwamoto, Paul A. Janmey
Physics - All Scholarship
The proper functions of tissues depend on the ability of cells to withstand stress and maintain shape. Central to this process is the cytoskeleton, comprised of three polymeric networks: F-actin, microtubules, and intermediate filaments (IFs). IF proteins are among the most abundant cytoskeletal proteins in cells; yet they remain some of the least understood. Their structure and function deviate from those of their cytoskeletal partners, F-actin and microtubules. IF networks show a unique combination of extensibility, flexibility and toughness that confers mechanical resilience to the cell. Vimentin is an IF protein expressed in mesenchymal cells. This review highlights exciting new …
Mechanical And Non-Mechanical Functions Of Filamentous And Non-Filamentous Vimentin, Alison E. Patteson, Amir Vahabikashi, Robert D. Goldman, Paul A. Janmey
Mechanical And Non-Mechanical Functions Of Filamentous And Non-Filamentous Vimentin, Alison E. Patteson, Amir Vahabikashi, Robert D. Goldman, Paul A. Janmey
Physics - All Scholarship
Intermediate filaments (IFs) formed by vimentin are less understood than their cytoskeletal partners, microtubules and F-actin, but the unique physical properties of IFs, especially their resistance to large deformations, initially suggest a mechanical function. Indeed, vimentin IFs help regulate cell mechanics and contractility, and in crowded 3D environments they protect the nucleus during cell migration. Recently, a multitude of studies, often using genetic or proteomic screenings show that vimentin has many non-mechanical functions within and outside of cells. These include signaling roles in wound healing, lipogenesis, sterol processing, and various functions related to extracellular and cell surface vimentin. Extracellular vimentin …
Loops Versus Lines And The Compression Stiffening Of Cells, Mahesh C. Gandikota, Katarzyna Pogoda, Anne Van Oosten, Tyler A. Engstrom, Alison E. Patteson, Paul E. Janmey, J. M. Schwarz
Loops Versus Lines And The Compression Stiffening Of Cells, Mahesh C. Gandikota, Katarzyna Pogoda, Anne Van Oosten, Tyler A. Engstrom, Alison E. Patteson, Paul E. Janmey, J. M. Schwarz
Physics - All Scholarship
Both animal and plant tissue exhibit a nonlinear rheological phenomenon known as compression stiffening, or an increase in moduli with increasing uniaxial compressive strain. Does such a phenomenon exist in single cells, which are the building blocks of tissues? One expects an individual cell to compression soften since the semiflexible biopolymer-based cytoskeletal network maintains the mechanical integrity of the cell and in vitro semiflexible biopolymer networks typically compression soften. To the contrary, we find that mouse embryonic fibroblasts (mEFs) compression stiffen under uniaxial compression via atomic force microscopy studies. To understand this finding, we uncover several potential mechanisms for compression …
Loss Of Vimentin Enhances Cell Motility Through Small Confining Spaces, Alison E. Patteson, Katarzyna Pogoda, Fitzroy J. Byfield, Kalpana Mandal, Zofia Ostrowska-Podhorodecka, Elisabeth E. Charrier, Peter A. Galie, Piotr Deptuła, Robert Bucki, Christopher A. Mcculloch, Paul A. Janmey
Loss Of Vimentin Enhances Cell Motility Through Small Confining Spaces, Alison E. Patteson, Katarzyna Pogoda, Fitzroy J. Byfield, Kalpana Mandal, Zofia Ostrowska-Podhorodecka, Elisabeth E. Charrier, Peter A. Galie, Piotr Deptuła, Robert Bucki, Christopher A. Mcculloch, Paul A. Janmey
Physics - All Scholarship
The migration of cells through constricting spaces or along fibrous tracks in tissues is important for many biological processes and depends on the mechanical properties of a cytoskeleton made up of three different filaments: F-actin, microtubules, and intermediate filaments. The signaling pathways and cytoskeletal structures that control cell motility on 2D are often very different from those that control motility in 3D. Previous studies have shown that intermediate filaments can promote actin-driven protrusions at the cell edge, but have little effect on overall motility of cells on flat surfaces. They are however important for cells to maintain resistance to repeated …
Vimentin Protects Cells Against Nuclear Rupture And Dna Damage During Migration, Alison E. Patteson, Amir Vahabikashi, Katarzyna Pogoda, Stephen A. Adam, Kalpana Mandal, Mark Kittisopikul, Suganya Sivagurunathan, Anne Goldman, Robert D. Goldman, Paul A. Janmey
Vimentin Protects Cells Against Nuclear Rupture And Dna Damage During Migration, Alison E. Patteson, Amir Vahabikashi, Katarzyna Pogoda, Stephen A. Adam, Kalpana Mandal, Mark Kittisopikul, Suganya Sivagurunathan, Anne Goldman, Robert D. Goldman, Paul A. Janmey
Physics - All Scholarship
Mammalian cells frequently migrate through tight spaces during normal embryogenesis, wound healing, diapedesis, or in pathological situations such as metastasis. Nuclear size and shape are important factors in regulating the mechanical properties of cells during their migration through such tight spaces. At the onset of migratory behavior, cells often initiate the expression of vimentin, an intermediate filament protein that polymerizes into networks extending from a juxtanuclear cage to the cell periphery. However, the role of vimentin intermediate filaments (VIFs) in regulating nuclear shape and mechanics remains unknown. Here, we use wild-type and vimentin-null mouse embryonic fibroblasts to show that VIFs …
Emergence Of Tissue-Like Mechanics From Fibrous Networks Confined By Close-Packed Cells, Anne Van Oosten, Xingyu Chen, Likang Chin, Katrina Cruz, Alison E. Patteson, Katarzyna Pogoda, Vivek B. Shenoy, Paul A. Janmey
Emergence Of Tissue-Like Mechanics From Fibrous Networks Confined By Close-Packed Cells, Anne Van Oosten, Xingyu Chen, Likang Chin, Katrina Cruz, Alison E. Patteson, Katarzyna Pogoda, Vivek B. Shenoy, Paul A. Janmey
Physics - All Scholarship
The viscoelasticity of the crosslinked semiflexible polymer networks—such as the internal cytoskeleton and the extracellular matrix—that provide shape and mechanical resistance against deformation is assumed to dominate tissue mechanics. However, the mechanical responses of soft tissues and semiflexible polymer gels differ in many respects. Tissues stiffen in compression but not in extension1,2,3,4,5, whereas semiflexible polymer networks soften in compression and stiffen in extension6,7. In shear deformation, semiflexible polymer gels stiffen with increasing strain, but tissues do not1,2,3,4,5 …
Quenching Active Swarms: Effects Of Light Exposure On Collective Motility In Swarming Serratia Marcescens, Junyi Yang, Paulo E. Arratia, Alison E. Patteson, Arvind Gopinath
Quenching Active Swarms: Effects Of Light Exposure On Collective Motility In Swarming Serratia Marcescens, Junyi Yang, Paulo E. Arratia, Alison E. Patteson, Arvind Gopinath
Physics - All Scholarship
Swarming colonies of the light-responsive bacteria Serratia marcescens grown on agar exhibit robust fluctuating large-scale flows that include arrayed vortices, jets and sinuous streamers. We study the immobilization and quenching of these collective flows when the moving swarm is exposed to intense wide-spectrum light with a substantial ultraviolet component. We map the emergent response of the swarm to light in terms of two parameters-light intensity and duration of exposure-and identify the conditions under which collective motility is impacted. For small exposure times and/or low intensities, we find collective motility to be negligibly affected. Increasing exposure times and/or intensity to higher …
Memory Formation In Matter, Joseph Paulsen, Nathan C. Keim, Zorana Zeravcic, Srikanth Sastry, Sidney R. Nagel
Memory Formation In Matter, Joseph Paulsen, Nathan C. Keim, Zorana Zeravcic, Srikanth Sastry, Sidney R. Nagel
Physics - All Scholarship
Memory formation in matter is a theme of broad intellectual relevance; it sits at the interdisciplinary crossroads of physics, biology, chemistry, and computer science. Memory connotes the ability to encode, access, and erase signatures of past history in the state of a system. Once the system has completely relaxed to thermal equilibrium, it is no longer able to recall aspects of its evolution. The memory of initial conditions or previous training protocols will be lost. Thus many forms of memory are intrinsically tied to far-from-equilibrium behavior and to transient response to a perturbation. This general behavior arises in diverse contexts …
The Propagation Of Active-Passive Interfaces In Bacterial Swarms, Alison E. Patteson, Arvind Gopinath, Paulo E. Arratia
The Propagation Of Active-Passive Interfaces In Bacterial Swarms, Alison E. Patteson, Arvind Gopinath, Paulo E. Arratia
Physics - All Scholarship
Propagating interfaces are ubiquitous in nature, underlying instabilities and pattern formation in biology and material science. Physical principles governing interface growth are well understood in passive settings; however, our understanding of interfaces in active systems is still in its infancy. Here, we study the evolution of an active-passive interface using a model active matter system, bacterial swarms. We use ultra-violet light exposure to create compact domains of passive bacteria within Serratia marcescens swarms, thereby creating interfaces separating motile and immotile cells. Post-exposure, the boundary re-shapes and erodes due to self-emergent collective flows. We demonstrate that the active-passive boundary acts as …
A Transparent Insulation Solar Façade Coupled With A Selective Absorber: An Experimentally Validated Building Energy Simulation Model, Miroslav Čekon, Jakub Čurpek
A Transparent Insulation Solar Façade Coupled With A Selective Absorber: An Experimentally Validated Building Energy Simulation Model, Miroslav Čekon, Jakub Čurpek
International Building Physics Conference 2018
The development of various advanced materials and their subsequent integration into innovative building envelope concepts has the potential to achieve energy savings. Additionally, their usability in practical applications can be enhanced via the use of building energy simulation (BES) methods. Experimental procedures in conjunction with numerical computations could enable the prediction of the future performance of solar thermal façade concepts. The presented study is focused on the thermal response of a transparent insulation material (TIM) incorporated in a façade structure. An experimental prototype of a solar façade element with both a selective and a nonselective absorber was developed for use …