Joseph Maclennan - Academia.edu (original) (raw)
Papers by Joseph Maclennan
Ferroelectrics, Dec 1, 2006
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Ferroelectrics, 2004
ABSTRACT
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arXiv (Cornell University), Oct 18, 2021
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Bulletin of the American Physical Society, Mar 5, 2007
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Bulletin of the American Physical Society, Mar 5, 2015
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Physical Review E
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Proceedings of the National Academy of Sciences
We report the observation of the smectic A F , a liquid crystal phase of the ferroelectric nemati... more We report the observation of the smectic A F , a liquid crystal phase of the ferroelectric nematic realm. The smectic A F is a phase of small polar, rod-shaped molecules that form two-dimensional fluid layers spaced by approximately the mean molecular length. The phase is uniaxial, with the molecular director, the local average long-axis orientation, normal to the layer planes, and ferroelectric, with a spontaneous electric polarization parallel to the director. Polarization measurements indicate almost complete polar ordering of the ∼10 Debye longitudinal molecular dipoles, and hysteretic polarization reversal with a coercive field ∼2 × 10 5 V / m is observed. The SmA F phase appears upon cooling in two binary mixtures of partially fluorinated mesogens: 2N/DIO, exhibiting a nematic (N)–smectic Z A (SmZ A )–ferroelectric nematic (N F )–SmA F phase sequence, and 7N/DIO, exhibiting an N–SmZ A –SmA F phase sequence. The latter presents an opportunity to study a transition between two s...
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arXiv (Cornell University), Aug 6, 2018
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arXiv (Cornell University), Aug 20, 2022
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Physics of Fluids
Machine learning techniques have been developed to identify inclusions on the surface of freely s... more Machine learning techniques have been developed to identify inclusions on the surface of freely suspended smectic liquid crystal films imaged by reflected light microscopy. The experimental images are preprocessed using Canny edge detection and then passed to a radial kernel support vector machine (SVM) trained to recognize circular islands and droplets. The SVM is able to identify these objects of interest with an accuracy that far exceeds that of conventional tracking software, especially when the background image is non-uniform or when the target features are in close proximity to one another. This method could be applied to tracking objects in a variety of visually inhomogeneous biological and soft matter environments, in order to study growth dynamics, the development of spatial order, and hydrodynamic behavior.
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arXiv (Cornell University), Dec 28, 2021
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Bulletin of the American Physical Society, Mar 17, 2021
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arXiv: Soft Condensed Matter, 2015
Binary mixtures of the twist-bend nematic-forming liquid crystal CB7CB with the prototypical rod-... more Binary mixtures of the twist-bend nematic-forming liquid crystal CB7CB with the prototypical rod-like liquid crystal 5CB exhibit a twist-bend nematic phase with properties similar to those reported for neat CB7CB. The mixtures appear homogeneous, with no micron- or nano-scale segregation evident at any concentration. The linear dependence of the phase transition temperature on concentration indicates that these binary mixtures are nearly ideal. However, a decrease in the viscosity with the addition of 5CB allows the characteristic twist-bend stripe textures to relax into a state of uniform birefringence. We confirm the presence of nanoscale modulations of the molecular orientation in the mixtures by freeze-fracture transmission electron microscopy (FFTEM), further evidence of their twist-bend nature. We devise and implement a statistical approach to quantitatively measure the ground state pitch of the twist-bend phase and its mixtures using FFTEM. The addition of 5CB generally shift...
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Bulletin of the American Physical Society, 2016
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Bulletin of the American Physical Society, 2021
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Bulletin of the American Physical Society, 2014
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1Physics Department, U. of Colorado, 2000 Colorado Ave., Boulder, CO, 80309 USA., 2Universities S... more 1Physics Department, U. of Colorado, 2000 Colorado Ave., Boulder, CO, 80309 USA., 2Universities Space Research Association, 21000 Brookpark Rd MS 105–1, Cleveland, OH 44135, USA, 3University of Magdeburg, Universitätsplatz 2, Magdeburg 39106, Germany, 4NASA Glenn Research Center, 21000 Brookpark Rd MS 77–7, Cleveland, OH 44135, USA, 5ZIN Technologies, 6745 Engle Road, Middleburg Heights, Cleveland, OH 44130, USA.
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Bulletin of the American Physical Society, 2020
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Optics Express, 2019
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Ferroelectrics, Dec 1, 2006
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Ferroelectrics, 2004
ABSTRACT
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arXiv (Cornell University), Oct 18, 2021
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Bulletin of the American Physical Society, Mar 5, 2007
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Bulletin of the American Physical Society, Mar 5, 2015
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Physical Review E
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Proceedings of the National Academy of Sciences
We report the observation of the smectic A F , a liquid crystal phase of the ferroelectric nemati... more We report the observation of the smectic A F , a liquid crystal phase of the ferroelectric nematic realm. The smectic A F is a phase of small polar, rod-shaped molecules that form two-dimensional fluid layers spaced by approximately the mean molecular length. The phase is uniaxial, with the molecular director, the local average long-axis orientation, normal to the layer planes, and ferroelectric, with a spontaneous electric polarization parallel to the director. Polarization measurements indicate almost complete polar ordering of the ∼10 Debye longitudinal molecular dipoles, and hysteretic polarization reversal with a coercive field ∼2 × 10 5 V / m is observed. The SmA F phase appears upon cooling in two binary mixtures of partially fluorinated mesogens: 2N/DIO, exhibiting a nematic (N)–smectic Z A (SmZ A )–ferroelectric nematic (N F )–SmA F phase sequence, and 7N/DIO, exhibiting an N–SmZ A –SmA F phase sequence. The latter presents an opportunity to study a transition between two s...
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arXiv (Cornell University), Aug 6, 2018
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arXiv (Cornell University), Aug 20, 2022
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Physics of Fluids
Machine learning techniques have been developed to identify inclusions on the surface of freely s... more Machine learning techniques have been developed to identify inclusions on the surface of freely suspended smectic liquid crystal films imaged by reflected light microscopy. The experimental images are preprocessed using Canny edge detection and then passed to a radial kernel support vector machine (SVM) trained to recognize circular islands and droplets. The SVM is able to identify these objects of interest with an accuracy that far exceeds that of conventional tracking software, especially when the background image is non-uniform or when the target features are in close proximity to one another. This method could be applied to tracking objects in a variety of visually inhomogeneous biological and soft matter environments, in order to study growth dynamics, the development of spatial order, and hydrodynamic behavior.
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arXiv (Cornell University), Dec 28, 2021
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Bulletin of the American Physical Society, Mar 17, 2021
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arXiv: Soft Condensed Matter, 2015
Binary mixtures of the twist-bend nematic-forming liquid crystal CB7CB with the prototypical rod-... more Binary mixtures of the twist-bend nematic-forming liquid crystal CB7CB with the prototypical rod-like liquid crystal 5CB exhibit a twist-bend nematic phase with properties similar to those reported for neat CB7CB. The mixtures appear homogeneous, with no micron- or nano-scale segregation evident at any concentration. The linear dependence of the phase transition temperature on concentration indicates that these binary mixtures are nearly ideal. However, a decrease in the viscosity with the addition of 5CB allows the characteristic twist-bend stripe textures to relax into a state of uniform birefringence. We confirm the presence of nanoscale modulations of the molecular orientation in the mixtures by freeze-fracture transmission electron microscopy (FFTEM), further evidence of their twist-bend nature. We devise and implement a statistical approach to quantitatively measure the ground state pitch of the twist-bend phase and its mixtures using FFTEM. The addition of 5CB generally shift...
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Bulletin of the American Physical Society, 2016
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Bulletin of the American Physical Society, 2021
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Bulletin of the American Physical Society, 2014
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1Physics Department, U. of Colorado, 2000 Colorado Ave., Boulder, CO, 80309 USA., 2Universities S... more 1Physics Department, U. of Colorado, 2000 Colorado Ave., Boulder, CO, 80309 USA., 2Universities Space Research Association, 21000 Brookpark Rd MS 105–1, Cleveland, OH 44135, USA, 3University of Magdeburg, Universitätsplatz 2, Magdeburg 39106, Germany, 4NASA Glenn Research Center, 21000 Brookpark Rd MS 77–7, Cleveland, OH 44135, USA, 5ZIN Technologies, 6745 Engle Road, Middleburg Heights, Cleveland, OH 44130, USA.
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Bulletin of the American Physical Society, 2020
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Optics Express, 2019
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