Physical Sciences and Mathematics Commons^™

3d Flow Field Measurements Outside Nanopores, Jeffrey Mc Hugh, Alice L. Thorneywork, Kurt Andresen, Ulrich F. Keyser

Physics and Astronomy Faculty Publications

We demonstrate a non-stereoscopic, video-based particle tracking system with optical tweezers to study fluid flow in 3D in the vicinity of glass nanopores. In particular, we used the quadrant interpolation algorithm to extend our video-based particle tracking to displacements out of the trapping plane of the tweezers. This permitted the study of flow from nanopores oriented at an angle to the trapping plane, enabling the mounting of nanopores on a micromanipulator with which it was then possible to automate the mapping procedure. Mapping of the voltage driven flow in 3D volumes outside nanopores revealed polarity dependent flow fields. This is …

Evidence For Electron Energization Accompanying Spontaneous Formation Of Ion Acceleration Regions In Expanding Plasmas, Evan M. Aguirre, Rikard Bodin, Neng Yin, Timothy N. Good, Earl E. Scime

Physics and Astronomy Faculty Publications

We report experiments conducted in an expanding argon plasma generated in the inductive mode of a helicon source in the Hot hELIcon eXperiment–Large Experiment on Instabilities and Anisotropies facility. As the neutral gas pressure increases, the supersonic ion acceleration weakens. Increasing neutral pressure also alters the radial profile of electron temperature, density, and plasma potential upstream of the plasma expansion region. Langmuir probe measurements of the electron energy probability function (EEPF) show that heating of electrons at the plasma edge by RF fields diminishes with increasing gas pressure, yielding a plasma with a centrally peaked electron temperature, and flat potential …

Testing A Thermodynamic Approach To Collective Animal Behavior In Laboratory Fish Schools, Julia A. Giannini, James G. Puckett

Physics and Astronomy Faculty Publications

Collective behaviors displayed by groups of social animals are observed frequently in nature. Understanding and predicting the behavior of complex biological systems is dependent on developing effective descriptions and models. While collective animal systems are characteristically nonequilibrium, we can employ concepts from equilibrium statistical mechanics to motivate the measurement of material-like properties in laboratory animal aggregates. Here, we present results from a new set of experiments that utilize high speed footage of two-dimensional schooling events, particle tracking, and projected static and dynamic light fields to observe and control the behavior of negatively phototaxic fish schools (Hemigrammus bleheri). First, …

Additive Modulation Of Dna-Dna Interactions By Interstitial Ions, Wei Meng, Raju Timsina, Abby Bull, Kurt Andresen, Xiangyun Qiu

Physics and Astronomy Faculty Publications

Quantitative understanding of biomolecular electrostatics, particularly involving multivalent ions and highly charged surfaces, remains lacking. Ion-modulated interactions between nucleic acids provide a model system in which electrostatics plays a dominant role. Using ordered DNA arrays neutralized by spherical cobalt3+ hexammine and Mg2+ ions, we investigate how the interstitial ions modulate DNA-DNA interactions. Using methods of ion counting, osmotic stress, and x-ray diffraction, we systematically determine thermodynamic quantities, including ion chemical potentials, ion partition, DNA osmotic pressure and force, and DNA-DNA spacing. Analyses of the multidimensional data provide quantitative insights into their interdependencies. The key finding of this study is that …

Similarities Between Insect Swarms And Isothermal Globular Clusters, Dan Gorbonos, Kasper Van Der Vaart, Michael Sinhuber, James G. Puckett, Andrew M. Reynolds, Nicholas T. Ouellette, Nir S. Gov

Physics and Astronomy Faculty Publications

Previous work has suggested that disordered swarms of flying insects can be well modeled as self-gravitating systems, as long as the “gravitational” interaction is adaptive. Motivated by this work, we compare the predictions of the classic, mean-field King model for isothermal globular clusters to observations of insect swarms. Detailed numerical simulations of regular and adaptive gravity allow us to expose the features of the swarms' density and velocity profiles that are due to long-range interactions and are captured by the King model phenomenology, and those that are due to adaptivity and short-range repulsion. Our results provide further support for adaptive …

Milky Way Morphology, Laurence A. Marschall

Physics and Astronomy Faculty Publications

From our limited perspective—living on a planet that orbits one of several hundred billion stars inside the Milky Way—the detailed structure of our home galaxy is difficult to determine. It has long been recognized by astronomers as a typical spiral galaxy, one of countless flattened pinwheels of stars seen throughout the universe. By mapping the distances to more than 2,400 stars, scientists have now created, with unprecedented precision, a three-dimensional map that shows the Milky Way has a twisted shape. [excerpt]

Lorentz And Cpt Tests Using Penning Traps, Yunhua Ding

Physics and Astronomy Faculty Publications

The theoretical prospects for quantum electrodynamics with Lorentz-violating operators of mass dimensions up to six are revisited in this work. The dominant effects due to Lorentz and CPT violation are studied in measurements of magnetic moments of particles confined in Penning traps. Using recently reported experimental results, new coefficients for Lorentz violation are constrained and existing bounds of various coefficients are improved.

Three-Dimensional Time-Resolved Trajectories From Laboratory Insect Swarms, Michael Sinhuber, Kasper Van Der Vaart, Rui Ni, James G. Puckett, Douglas H. Kelley, Nicholas T. Ouellette

Physics and Astronomy Faculty Publications

Aggregations of animals display complex and dynamic behaviour, both at the individual level and on the level of the group as a whole. Often, this behaviour is collective, so that the group exhibits properties that are distinct from those of the individuals. In insect swarms, the motion of individuals is typically convoluted, and swarms display neither net polarization nor correlation. The swarms themselves, however, remain nearly stationary and maintain their cohesion even in noisy natural environments. This behaviour stands in contrast with other forms of collective animal behaviour, such as flocking, schooling, or herding, where the motion of individuals is …

The Limited Reign Of Saturn's Rings, Laurence A. Marschall

Physics and Astronomy Faculty Publications

Saturn’s rings—stretching tens of thousands of miles above its equator but no more than a few hundred yards thick—mark an ancient debris field of orbiting ice shards, the remains of a moon-sized object that strayed too close and was torn to pieces by Saturn’s intense gravitation. Astronomers have debated when the rings formed and how long they will stay in orbit. Recent observations from large, land-based telescopes and orbiting spacecraft reveal that Saturn’s rings are remarkably young and are dissipating at a rapid rate. [excerpt]

Collective Gradient Sensing In Fish Schools, James G. Puckett, Aawaz R. Pokhrel, Julia A. Giannini

Physics and Astronomy Faculty Publications

Throughout the animal kingdom, animals frequently benefit from living in groups. Models of collective behaviour show that simple local interactions are sufficient to generate group morphologies found in nature (swarms, flocks and mills). However, individuals also interact with the complex noisy environment in which they live. In this work, we experimentally investigate the group performance in navigating a noisy light gradient of two unrelated freshwater species: golden shiners (Notemigonuscrysoleucas) and rummy nose tetra (Hemigrammus bleheri). We find that tetras outperform shiners due to their innate individual ability to sense the environmental gradient. Using numerical simulations, we examine how group performance …

Ion Beams In Multi-Species Plasma, Evan M. Aguirre, Earl E. Scime, Timothy N. Good

Physics and Astronomy Faculty Publications

Argon and xenon ion velocity distribution functions are measured in Ar-He, Ar-Xe, and Xe-He expanding helicon plasmas to determine if ion beam velocity is enhanced by the presence of lighter ions. Contrary to observations in mixed gas sheath experiments, we find that adding a lighter ion does not increase the ion beam speed. The predominant effect is a reduction of ion beam velocity consistent with increased drag arising from increased gas pressure under all conditions: constant total gas pressure, equal plasma densities of different ions, and very different plasma densities of different ions. These results suggest that the physics responsible …

Slotted Rotatable Target Assembley And Systematic Error Analysis For A Search For Long Range Spin Dependent Interactions From Exotic Vector Boson Exchange Using Neutron Spin Rotation, C. Haddock, Bret E. Crawford, W. Fox, I. Francis, A. T. Holley, Scott W. Magers, M. Sarsour, W. M. Snow, J. Vanderwerp

Physics and Astronomy Faculty Publications

We discuss the design and construction of a novel target array of nonmagnetic test masses used in a neutron polarimetry measurement made in search for new possible exotic spin dependent neutron–atominteractions of Nature at sub-mm length scales. This target was designed to accept and efficiently transmit a transversely polarized slow neutron beam through a series of long open parallel slots bounded by flat rectangular plates. These openings possessed equal atom density gradients normal to the slots from the flat test masses with dimensions optimized to achieve maximum sensitivity to an exotic spin-dependent interaction from vector boson exchanges with ranges in …

Spatial Structure Of Ion Beams In An Expanding Plasma, Evan M. Aguirre, Earl E. Scime, Derek S. Thompson, Timothy N. Good

Physics and Astronomy Faculty Publications

We report spatially resolved perpendicular and parallel, to the magnetic field, ion velocity distribution function (IVDF) measurements in an expanding argon helicon plasma. The parallel IVDFs, obtained through laser induced fluorescence (LIF), show an ion beam with v ≈ 8000 m/s flowing downstream and confined to the center of the discharge. The ion beam is measurable for tens of centimeters along the expansion axis before the LIF signal fades, likely a result of metastable quenching of the beam ions. The parallel ion beam velocity slows in agreement with expectations for the measured parallel electric field. The perpendicular IVDFs show an …

Confocal Laser Induced Fluorescence With Comparable Spatial Localization To The Conventional Method, Derek S. Thompson, Miguel F. Henriquez, Earl E. Scime, Timothy N. Good

Physics and Astronomy Faculty Publications

We present measurements of ion velocity distributions obtained by laser induced fluorescence (LIF) using a single viewport in an argon plasma. A patent pending design, which we refer to as the confocal fluorescence telescope, combines large objective lenses with a large central obscuration and a spatial filter to achieve high spatial localization along the laser injection direction. Models of the injection and collection optics of the two assemblies are used to provide a theoretical estimate of the spatial localization of the confocal arrangement, which is taken to be the full width at half maximum of the spatial optical response. The …

Catching Shadow Bands, Laurence A. Marschall

Physics and Astronomy Faculty Publications

Even though shadow bands are only visible for a few fleeting minutes, it is possible to catch them if you prepare in advance. Get a large piece of white cardboard or white-painted plywood to act as a screen--the bands are subtle and can be more easily seen against a clean, white surface. (excerpt)

Neutron-Unbound Excited States Of 23n, M. Jones, T. Baumann, J. Brett, J. Bullaro, P. A. Deyoung, J.E. Finck, N. Frank, K. Hammerton, J. Hinnefeld, Z. Kohley, A. N. Kuchera, J. Pereira, A. Rabeh, J. K. Smith, A. Spyrou, Sharon L. Stephenson, K. Stiefel, M. Tuttle-Timm, R. G.T. Zegers, M. Thoennessen

Physics and Astronomy Faculty Publications

Neutron unbound states in 23N were populated via proton knockout from an 83.4 MeV/nucleon 24O beam on a liquid deuterium target. The two-body decay energy displays two peaks at E1∼100keV and E2∼1MeV with respect to the neutron separation energy. The data are consistent with shell model calculations predicting resonances at excitation energies of ∼3.6MeV and ∼4.5MeV. The selectivity of the reaction implies that these states correspond to the first and second 3/2− states. The energy of the first state is about 1.3 MeV lower than the first excited 2+ in 24O. This decrease is largely due to coupling with the …

The Impact Of Base Stacking On The Conformations And Electrostatics Of Single-Stranded Dna, Alex Plumridge, Steve P. Meisburger, Kurt Andresen, Lois Pollack

Physics and Astronomy Faculty Publications

Single-stranded DNA (ssDNA) is notable for its interactions with ssDNA binding proteins (SSBs) during fundamentally important biological processes including DNA repair and replication. Previous work has begun to characterize the conformational and electrostatic properties of ssDNA in association with SSBs. However, the conformational distributions of free ssDNA have been difficult to determine. To capture the vast array of ssDNA conformations in solution, we pair small angle X-ray scattering with novel ensemble fitting methods, obtaining key parameters such as the size, shape and stacking character of strands with different sequences. Complementary ion counting measurements using inductively coupled plasma atomic emission spectroscopy …

On Marie Curie And Me, Sharon L. Stephenson

Physics and Astronomy Faculty Publications

When people discover I am a nuclear physicist, they often say, "Oh, like Marie Curie!" And yes, I am like Marie in that I have woman parts, I study nuclei, I have two children and a physicist husband. But had I lived in her time, I would not have been that rare female admitted to the Sorbonne. I could not have quietly made the top scores on the math and physics examinations. I am impulsive and thin-skinned, my occasional cleverness passing for deeper talent. I would probably have been a cleaning girl, pregnant at 15, unable to speak any language …

Neutron Correlations In The Decay Of The First Excited State Of 11li, Jenna K. Smith, Thomas J. Baumann, Daniel Bazin, James Brown, Paul A. Deyoung, Nathan H. Frank, Michael D. Jones, Zack Kohley, Bryan A. Luther, B. S. Marks, Artemis Spyrou, Sharon L. Stephenson, Michael R. Thoennessen, Alexander S. Volya

Physics and Astronomy Faculty Publications

The decay of unbound excited ¹¹Li was measured after being populated by a two-proton removal from a ¹³B beam at 71 MeV/nucleon. Decay energy spectra and Jacobi plots were obtained from measurements of the momentum vectors of the ⁹Li fragment and neutrons. A resonance at an excitation energy of ∼1.2 MeV was observed. The kinematics of the decay are equally well fit by a simple dineutron-like model or a phase-space model that includes final state interactions. A sequential decay model can be excluded.

Evolution Of Network Architecture In A Granular Material Under Compression, Lia Papadopoulous, James G. Puckett, Karen E. Daniels, Danielle S. Bassett

Physics and Astronomy Faculty Publications

As a granular material is compressed, the particles and forces within the system arrange to form complex and heterogeneous collective structures. Force chains are a prime example of such structures, and are thought to constrain bulk properties such as mechanical stability and acoustic transmission. However, capturing and characterizing the evolving nature of the intrinsic inhomogeneity and mesoscale architecture of granular systems can be challenging. A growing body of work has shown that graph theoretic approaches may provide a useful foundation for tackling these problems. Here, we extend the current approaches by utilizing multilayer networks as a framework for directly quantifying …

Long-Range Acoustic Interactions In Insect Swarms: An Adaptive Gravity Model, Dan Gorbonos, Reuven Ianconescu, James G. Puckett, Rui Ni, Nicholas T. Ouellette, Nir S. Gov

Physics and Astronomy Faculty Publications

The collective motion of groups of animals emerges from the net effect of the interactions between individual members of the group. In many cases, such as birds, fish, or ungulates, these interactions are mediated by sensory stimuli that predominantly arise from nearby neighbors. But not all stimuli in animal groups are short range. Here, we consider mating swarms of midges, which are thought to interact primarily via long-range acoustic stimuli. We exploit the similarity in form between the decay of acoustic and gravitational sources to build a model for swarm behavior. By accounting for the adaptive nature of the midges' …

Back Half Of The Year, Ian R. Clarke

Physics and Astronomy Faculty Publications

Here we are in the back half of 2016, and the days are getting shorter. We have, as of today, lost 18 minutes since the solstice on June 20, and the speed of that change is quickening. You may wonder why it is that we have our hottest weather after our longest day is behind us. The simple answer is that it takes time for land and water masses to warm up. That’s the reason that Sept. 21 is likely to be a lot warmer than March 21, even though they have the same amount of daylight. [excerpt]

Living In The Milky Way, Ian R. Clarke

Physics and Astronomy Faculty Publications

It’s finally here. Today, June 20 at 6:34 p.m., is the the summer solstice, also known as the first day of summer and, confusingly enough, midsummer’s eve. From a scientific perspective, it marks the moment the sun reaches its northernmost point in our sky. As a result of that position, it’s the shortest night and longest day if you live north of the equator. [excerpt]

Search For 4n Contributions In The Reaction 14be(Ch2,X)10he, Michael D. Jones, Zack Kohley, Thomas J. Baumann, Greg Christian, Paul A. Deyoung, Joseph E. Finck, Nathan H. Frank, Robert A. Haring-Kaye, A. N. Kuchera, Bryan A. Luther, Shea Mosby, Jenna K. Smith, J. Snyder, Artemis Spyrou, Sharon L. Stephenson, Michael R. Thoennessen

Physics and Astronomy Faculty Publications

A previously published measurement of the ground state resonance of ¹⁰He, populated by a reaction of a 59 MeV/u ¹⁴Be beam on a deuterated polyethylene target, was further analyzed to search for ⁴n emission resulting from 2p removal. No evidence for 4n events was found. A lower limit of about 1 MeV was determined for a possible resonance in ¹²He.

Two-Neutron Sequential Decay Of 24o, M. D. Jones, N. Frank, T. Baumann, J. Brett, J. Bullaro, P. A. Deyoung, J.E. Finck, K. Hammerton, J. Hinnefeld, Z. Kohley, A. N. Kuchera, J. Pereira, A. Rabeh, W. F. Rogers, J. K. Smith, A. Spyrou, Sharon L. Stephenson, K. Stiefel, M. Tuttle-Timm, R. G.T. Zegers, M. Thoennessen

Physics and Astronomy Faculty Publications

A two-neutron unbound excited state of 24O was populated through a (d,d ) reaction at 83.4 MeV/nucleon. A state at E = 715 ± 110 (stat) ± 45 (sys) keV with a width of < 2 MeV was observed above the two-neutron separation energy placing it at 7.65 ± 0.2 MeV with respect to the ground state. Three-body correlations for the decay of 24O → 22O + 2n show clear evidence of a sequential decay through an intermediate state in 23O. Neither a di-neutron nor phase-space model for the three-body breakup were able to describe these correlations.

Population Of 13be In A Nucleon Exchange Reaction, B. R. Marks, P. A. Deyoung, J. K. Smith, T. Baumann, J. Brown, N. Frank, J. Hinnefeld, M. Hoffman, M. D. Jones, Z. Kohley, A. N. Kuchera, B. Luther, A. Spyrou, Sharon L. Stephenson, C. Sullivan, M. Thoennessen, N. Viscariello, S. J. Williams

Physics and Astronomy Faculty Publications

The neutron-unbound nucleus Be13 was populated with a nucleon exchange reaction from a 71 MeV/u secondary B13 beam. The decay-energy spectrum was reconstructed using invariant mass spectroscopy based on Be12 fragments in coincidence with neutrons. The data could be described with an s-wave resonance at Er=0.73(9)MeV with a width of Γr=1.98(34)MeVand a d-wave resonance at Er=2.56(13)MeV with a width of Γr=2.29(73)MeV. The observed spectral shape is consistent with previous one-proton removal reaction measurements from B14.

Intrinsic Fluctuations And Driven Response Of Insect Swarms, Rui Ni, James G. Puckett, Eric R. Dufresne, Nicholas T. Ouellette

Physics and Astronomy Faculty Publications

Animals of all sizes form groups, as acting together can convey advantages over acting alone; thus, collective animal behavior has been identified as a promising template for designing engineered systems. However, models and observations have focused predominantly on characterizing the overall group morphology, and often focus on highly ordered groups such as bird flocks. We instead study a disorganized aggregation (an insect mating swarm), and compare its natural fluctuations with the group-level response to an external stimulus. We quantify the swarm’s frequency-dependent linear response and its spectrum of intrinsic fluctuations, and show that the ratio of these two quantities has …

Time-Frequency Analysis Reveals Pairwise Interactions In Insect Swarms, James G. Puckett, Rui Ni, Nicholas T. Ouellette

Physics and Astronomy Faculty Publications

The macroscopic emergent behavior of social animal groups is a classic example of dynamical self-organization, and is thought to arise from the local interactions between individuals. Determining these interactions from empirical data sets of real animal groups, however, is challenging. Using multicamera imaging and tracking, we studied the motion of individual flying midges in laboratory mating swarms. By performing a time-frequency analysis of the midge trajectories, we show that the midge behavior can be segmented into two distinct modes: one that is independent and composed of low-frequency maneuvers, and one that consists of higher-frequency nearly harmonic oscillations conducted in synchrony …

Precise Mass And Radius Measurements For The Components Of The Bright Solar-Type Eclipsing Binary Star V1094 Tauri, P. F.L. Maxted, R. J. Hutcheon, G. Torres, C. H.S. Lacy, J. Southworth, B. Smalley, K. Pavlovski, Laurence A. Marschall, J. V. Clausen

Physics and Astronomy Faculty Publications

Context. V1094 Tau is a bright eclipsing binary star with an orbital period close to nine days that contains two stars similar to the Sun.

Aims. Our aim is to test models of Sun-like stars using precise and accurate mass and radius measurements for both stars in V1094 Tau.

Methods. We present new spectroscopy of V1094 Tau, which we use to estimate the effective temperatures of both stars and to refine their spectroscopic orbits. We also present new, high-quality photometry covering both eclipses of V1094 Tau in the Strömgren uvby system and in the Johnson V-band.

Results. The masses, …

A Slow Neutron Polarimeter For The Measurement Of Parity-Odd Neutron Rotary Power, W. M. Snow, E. Anderson, L. Barron-Palos, C. D. Bass, T. D. Bass, Bret E. Crawford, C. Crawford, J. M. Dawkins, D. Esposito, J. Fry, H. Gardiner, K. Gan, C. Haddock, B. R. Heckel, A. T. Holley, J. C. Horton, C. Huffer, J. Lieffers, D. Luo, M. Maldonado-Velazquez, D. M. Markoff, A. M. Micherdzinska, H. P. Mumm, J. S. Nico, M. Sarsour, S. Santra, E. I. Sharapov, H. E. Swanson, S. B. Walbridge, V. Zhumabekova

Physics and Astronomy Faculty Publications

We present the design, description, calibration procedure, and an analysis of systematic effects for an apparatus designed to measure the rotation of the plane of polarization of a transversely polarized slow neutron beam as it passes through unpolarized matter. This device is the neutronoptical equivalent of a crossed polarizer/analyzer pair familiar from light optics. This apparatus has been used to search for parity violation in the interaction of polarized slow neutrons in matter. Given the brightness of existing slow neutron sources, this apparatus is capable ofmeasuring a neutron rotary power of dϕ/dz = 1 × 10⁻⁷ rad/m.