Justin Flaherty

Justin Flaherty

he/him

CCAPP Affiliate Fellow

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publications

Primary cilia have a length-dependent persistence length

Published in Biomechanics and Modeling in Mechanobiology, 2019

The fluctuating position of an optically trapped cilium tip under untreated and Taxol-treated conditions was used to characterize mechanical properties of the cilium axoneme and its basal body by combining experimental, analytical, and computational tools. We provide, for the first time, evidence that the persistence length of a ciliary axoneme is length-dependent; longer cilia are stiffer than shorter cilia. We demonstrate that this apparent length dependence can be understood by a combination of modeling axonemal microtubules as anisotropic elastic shells and including actomyosin-driven stochastic basal body motion. Our results also demonstrate the possibility of using observable ciliary dynamics to probe interior cytoskeletal dynamics. It is hoped that our improved characterization of cilia will result in deeper understanding of the biological function of cellular flow sensing by this organelle.

Recommended citation: Flaherty, J., Feng, Z., Peng, Z. et al. Primary cilia have a length-dependent persistence length. Biomech Model Mechanobiol 19, 445–460 (2020). https://doi.org/10.1007/s10237-019-01220-7
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The Payload for Ultrahigh Energy Observations (PUEO): a white paper

Published in Journal of Instrumentation, 2021

The Payload for Ultrahigh Energy Observations (PUEO) long-duration balloon experiment is designed to have world-leading sensitivity to ultrahigh-energy neutrinos at energies above 1 EeV. Probing this energy region is essential for understanding the extreme-energy universe at all distance scales. PUEO leverages experience from and supersedes the successful Antarctic Impulsive Transient Antenna (ANITA) program, with an improved design that drastically improves sensitivity by more than an order of magnitude at energies below 30 EeV. PUEO will either make the first significant detection of or set the best limits on ultrahigh-energy neutrino fluxes.

Recommended citation: The PUEO Collaboration. The Payload for Ultrahigh Energy Observations (PUEO): a white paper. Journal of Instrumentation, 16, P08035 (2021). https://doi.org/10.1088/1748-0221/16/08/P08035
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Low-threshold ultrahigh-energy neutrino search with the Askaryan Radio

Published in Phys. Rev. D, 2022

In the pursuit of the measurement of the still-elusive ultrahigh-energy (UHE) neutrino flux at energies of order EeV, detectors using the in-ice Askaryan radio technique have increasingly targeted lower trigger thresholds. This has led to improved trigger-level sensitivity to UHE neutrinos. Working with data collected by the Askaryan Radio Array (ARA), we search for neutrino candidates at the lowest threshold achieved to date, leading to improved analysis-level sensitivities. A neutrino search on a data set with 208.7 days of livetime from the reduced-threshold fifth ARA station is performed, achieving a 68% analysis efficiency over all energies on a simulated mixed-composition neutrino flux with an expected background of \(0.10^{+0.06}_{−0.04}\) events passing the analysis. We observe one event passing our analysis and proceed to set a neutrino flux limit using a Feldman-Cousins construction. We show that the improved trigger-level sensitivity can be carried through an analysis, motivating the phased array triggering technique for use in future radio-detection experiments. We also include a projection using all available data from this detector. Finally, we find that future analyses will benefit from studies of events near the surface to fully understand the background expected for a large-scale detector.

Recommended citation: Allison, P et al. Low-threshold ultrahigh-energy neutrino search with the Askaryan Radio Array. Phys. Rev. D, 105, 122006 (2022). https://doi.org/10.1103/PhysRevD.105.122006
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Triboelectric backgrounds to radio-based polar ultra-high energy neutrino (UHEN) experiments

Published in Astroparticle Physics, 2023

In the hopes of observing the highest-energy neutrinos (E > 1 EeV) populating the Universe, both past (RICE, AURA, ANITA) and current (RNO-G, ARIANNA, ARA and TAROGE-M) polar-sited experiments exploit the impulsive radio emission produced by neutrino interactions. In such experiments, rare single event candidates must be unambiguously identified above backgrounds. Background rejection strategies to date primarily target thermal noise fluctuations and also impulsive radio-frequency signals of anthropogenic origin. In this paper, we consider the possibility that ‘fake’ neutrino signals may also be generated naturally via the ‘triboelectric effect.’ This broadly describes any process in which force applied at a boundary layer results in displacement of surface charge, leading to the production of an electrostatic potential difference V. Wind blowing over granular surfaces such as snow can induce such a potential difference, with subsequent coronal discharge. Discharges over timescales as short as nanoseconds can then lead to radio-frequency emissions at characteristic MHz–GHz frequencies. Using data from various past (RICE, AURA, SATRA, ANITA) and current (RNO-G, ARIANNA and ARA) neutrino experiments, we find evidence for such backgrounds, which are generally characterized by: (a) a threshold wind velocity which likely depends on the experimental trigger criteria and layout; for the experiments considered herein, this value is typically O(10 m/s), (b) frequency spectra generally shifted to the low-end of the frequency regime to which current radio experiments are typically sensitive (100–200 MHz), (c) for the strongest background signals, an apparent preference for discharges from above-surface structures, although the presence of more isotropic, lower amplitude triboelectric discharges cannot be excluded.

Recommended citation: Aguilar, J.A. et al. Triboelectric backgrounds to radio-based polar ultra-high energy neutrino (UHEN) experiments. Astroparticle Physics, 145, 102790 (2023). https://doi.org/10.1016/j.astropartphys.2022.102790
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Polarization Reconstruction of Askaryan Emission of Ultra-High Energy Neutrinos Using the Askaryan Radio Array

Published in Proceedings of Science, 2023

The Askaryan Radio Array (ARA) is an ultra-high energy (> 10 PeV) neutrino detector located in the Dark Sector of the South Pole. It consists of five in-ice stations of antennas that are designed to detect radiation emitted by relativistic particle showers that are byproducts of neutrino interactions in the ice, which generate a cone of Cherenkov radiation in the radio regime (known as Askaryan radiation). The neutrino direction can be reconstructed through a combination of the direction of the Askaryan radiation, its polarization, and its frequency content. Since neutrinos are unaffected by electromagnetic forces and virtually unaffected by gravity, they travel in a straight line through the universe. This allows us to point them back towards potential sources. Through the use of radio pulser measurements, which are controlled radio emissions with a known polarization signature, we can evaluate our reconstruction techniques. Here I will show our reconstruction resolution after applying our reconstruction methods to pulser measurements.

Recommended citation: Flaherty, J. for the ARA Collaboration. Polarization Reconstruction of Askaryan Emission of Ultra-High Energy Neutrinos Using the Askaryan Radio Array. Proceedings of Science, ICRC2023, 1164 (2023). https://doi.org/10.22323/1.444.1164
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Effects of Biaxial Birefringence on Polarization Reconstruction for the Askaryan Radio Array

Published in Proceedings of Science, 2024

Ultra-high energy (UHE) neutrinos, with energies exceeding \(10^{17}\) eV, offer unique insights into cosmic accelerators and the origins of ultra-high energy cosmic rays. The Askaryan Radio Array (ARA) is designed to detect UHE neutrinos by capturing radio signals generated by their interactions within Antarctic ice. Observations from the South Pole Ice Core Experiment (SPICE) pulsing campaign revealed unexpected polarization effects in detected radio pulses transmitted through polar ice. This paper explores the impact of biaxial birefringence in South Pole ice on the polarization of SPICE pulses. We present a model that accounts for biaxial birefringence effects, showing how signal polarization can rotate during propagation through the ice. We show that the biaxial birefringence model can potentially explain the unexpected polarization results observed in SPICE data and highlight the need to validate the model to enhance future analyses and detector designs.

Recommended citation: Alan Salcedo Gomez, Justin Flaherty, Amy Connolly, et al. Effects of Biaxial Birefringence on Polarization Reconstruction for the Askaryan Radio Array. PoS, ARENA2024:009, 2024
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talks

teaching

Physics 241 - University Physics I

Undergraduate Course, Cleveland State University, Department of Physics, 2013

Calculus-based physics, with laboratory. Topics include mechanics, thermodynamics, and acoustics.

Physics 242 - University Physics II

Undergraduate Course, Cleveland State University, Department of Physics, 2013

Calculus-based physics, with laboratory. Topics include electricity, magnetism, optics.

Physics 103 - Flying Circus of Physics Lab

Undergraduate Course, Cleveland State University, Department of Physics, 2016

Non-major conceptual physics laboratory. Practical and everyday aspects of physics concepts such as kitchen physics, walking on fire, mechanics of sports, and electricity; as well as waves, optics, and modern physics, how the eye and camera work, the laser, the theory of relativity, and some basic cosmology.

Physics 221 - College Physics I

Undergraduate Course, Cleveland State University, Department of Physics, 2016

Algebra-based physics, with laboratory. Topics include mechanics, thermodynamics, fluids, and acoustics.

Physics 222 - College Physics II

Undergraduate Course, Cleveland State University, Department of Physics, 2016

Topics include electricity, magnetism, optics, atoms, nuclei, and elementary particles.

Physics 1251 - E&M, Waves, Optics, Modern Physics

Undergraduate Course, Ohio State University, Department of Physics, 2018

Calculus-based introduction to electricity and magnetism, waves, simple optics, and quantum mechanics; for students in physical sciences, mathematics, engineering.

Physics 1250 - Mechanics, Work and Energy, Thermal Physics

Undergraduate Course, Ohio State University, Department of Physics, 2019

Calculus-based introduction to classical physics: Newton’s laws, work and energy, fluids, thermodynamics; for students in physical sciences, mathematics, and engineering.

Physics 2300 - Intermediate Mechanics I

Undergraduate Course, Ohio State University, Department of Physics, 2023

Vectors and kinematics; foundations of Newtonian mechanics; momentum, work, and energy; conservative and nonconservative forces; potentials; angular momentum; rotation about a fixed axis; rigid body motion; noninertial systems and fictitious forces.

Physics 5700 - Advanced Physics Laboratory

Undergraduate Course, Ohio State University, Department of Physics, 2024

Lab course for physics majors. Three advanced experiments from a variety of physics disciplines are carried out. Emphasis is on experimental techniques, analysis of collected data, and formal presentation of experimental results.