Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session RR06: V: Materials Chemical PhysicsFocus
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Sponsoring Units: DCP Chair: Saravana Prakash Thirumuruganandham, Centro de Investigación de Ciencias Humanas y de la Educació Room: Virtual Room 6 |
Tuesday, March 21, 2023 11:30AM - 12:06PM |
RR06.00001: Particles at Membranes – Shape, Deformability, and Activity Invited Speaker: Gerhard Gompper Cell membranes interact with their environments in many ways. Endo- and exocytosis is used to shuttle large molecules and small vesicles in and out of the cell; harmful objects like viruses and nanoparticles invade the cell by passing the membrane barrier; cytoskele- tal filaments and bacteria push actively and can strongly deform the membrane [1]. In order to elucidate some basic physical mechanisms in this broad field of membrane remodelling and cell activity, I will focus on two topics: |
Tuesday, March 21, 2023 12:06PM - 12:18PM |
RR06.00002: Engineering of evanescent field in plasmonic nanostructure integrated tapered optical fibers Debanita Das, Anuj k singh, Alison Funston, ANSHUMAN KUMAR Tapered optical fibers (TOFs) have mitigated the issue of exponential decrement of the evanescent field across the diameter of the cladding in conventional optical fiber; thereby finding its promising application in optical fiber-based sensors. TOFs have shown to be highly sensitive to the refractive index of its environment. Integrating Au nanostructures (AuNS) on tapered fiber can result in coupling of the evanescent field (EF); thereby enhancing the localized surface plasmon resonance effect. |
Tuesday, March 21, 2023 12:18PM - 12:30PM |
RR06.00003: Measurement of entropy change of a half-cell electrochemical reaction using Multi-harmonic ElectroThermal Spectroscopy (METS) Divya Chalise, Ravi S Prasher, Venkat Srinivasan, Sean D Lubner, Sumanjeet Kaur In this work, we describe our newly established electrochemical method: Muti-harmonic Electrothermal Spectroscopy (METS) and explain how it can be used to resolve the entropy change at individual electrochemical electrodes. The entropy change of an electrochemical reaction can be related to the entropic coefficient, which is the temperature coefficient of the cell potential. Traditionally, this entropic coefficient is measured either through calorimetry or by measuring the cell potential as a function of temperature. However, these methods are limited to measuring the overall entropy change at both electrodes and cannot resolve the entropy change due to individual half-cell reactions at each electrode. With METS however, we are able to resolve the heat generation due to entropy change with a spatial resolution of a few microns, which allows attributing the change in entropy for half-cell reactions at individual electrodes, which are separated with each other by 10s of microns. |
Tuesday, March 21, 2023 12:30PM - 12:42PM |
RR06.00004: The origin of amphipathic nature of short and thin pristine carbon nanotubes - a fully recyclable 1D emulsion stabilizers for green chemistry applications Karolina Z Milowska, Slawomir Boncel, Anna W Kuziel, Mike C Payne, Heather F Greer, Artur P Terzyk, Aleksandra Cyganiuk, Emil Korczeniewski Short and thin pristine carbon nanotubes (CNTs) emerge as 1D emulsion stabilizers capable of replacing aquatoxic low-molecular surfactants. However, inconsistencies in understanding of water-solid interfaces for realistic CNTs hamper their individualization-driven functionalities, processability in benign media, and compatibility with a broad-scale of matrices. Pristine CNT processing based on water and inexpensive n-alkanes within a low energy regime would constitute an important step towards greener technologies. Therefore, we quantitatively assess structural CNT components, placing various CNTs on the scale from hydrophobicity to hydrophilicity. This structural interweave leads to amphipathicity enabling the formation of water-in-oil emulsions. Combining experiments with theoretical studies, we comprehensively characterize CNTs and CNT emulsions establishing descriptors of the emulsifying behavior of pristine and purified CNTs. They emerge as having hydrophilic open-ends, small number of oxygen-functionalized/vacancy surface areas, and hydrophobic sidewalls and full caps. The interplay of these regions allows short and thin CNTs to be utilized as fully recyclable 1D surfactants stabilizing water/oil emulsions which, as we demonstrate, can be applied as paints for flexible conductive coatings. We also show that their amphipathic strength depends on CNT size, the pristine-to-oxidized/vacancy domains and the oil-to-water ratios. |
Tuesday, March 21, 2023 12:42PM - 12:54PM |
RR06.00005: Image charge effects under metal and dielectric boundary conditions. (Edmond) Tingtao Zhou, Zhen-Gang Wang Image charge effect is a fundamental problem in electrostatics. However, a proper treatment at the continuum level |
Tuesday, March 21, 2023 12:54PM - 1:06PM |
RR06.00006: Nanoreactor active learning: Discovering chemistry with a general reactive machine learning potential Richard A Messerly, Justin Smith, Shuhao Zhang, Nick Lubbers, Olexandr Isayev, Sergei Tretiak, Ben T Nebgen, Kipton M Barros, Ryan B Jadrich Reactive chemistry atomistic simulation has a broad range of applications from drug design to energy to materials discovery. Machine learning interatomic potentials (MLIP) have become an efficient alternative to computationally expensive quantum chemistry simulations. In practice, reactive MLIPs require refitting to extensive datasets for each new application, and prior knowledge of reaction networks is required to generate fitting data. In this work, we develop a general reactive MLIP through unbiased active learning with a nanoreactor molecular dynamics inspired sampler. The resulting potential (ANI-nr) is then applied to study five distinct condensed phase reactive chemistry problems: carbon solid-phase nucleation, graphene ring formation from acetylene, biofuel additives, combustion of methane and the spontaneous formation of glycine from early-earth small molecules. In all studies, ANI-nr closely matches experiment and/or previous studies using traditional model chemistry methods, without needing to be refit for each application, which enables high-throughput in silico reactive chemistry experimentation. |
Tuesday, March 21, 2023 1:06PM - 1:18PM |
RR06.00007: Nonequilibrium free-energetics of confined active filaments from variational time reversal Jorge L Rosa-Raíces, David T Limmer Chromatin, a macromolecular filament packed inside the eukaryotic cell nucleus, dynamically mediates gene expression through conformational fluctuations and thereby controls essential biological functions including memory map formation in the brain and the mechanoelastic properties of musculoskeletal tissue throughout the body. Experimental observation and theoretical modeling link the epigenetic regulatory functions of chromatin to activity-driven processes operating far from thermodynamic equilibrium that carefully tailor the multiscale organization of chromatin. To elucidate a clearer picture of this interplay between activity and structure, we develop a quantitative understanding of how active forces drive the steady state nonequilibrium fluxes between metastable structural-dynamic motifs of a confined active filament. Combining stochastic thermodynamics and path-integral optimal control theory, we derive a method that variationally estimates the nonequilibrium free-energy density of an active diffusive polymeric system relative to its passive counterpart along an arbitrary order parameter. We show that the unique optimal control policy that saturates our variational bound for the free-energy density difference is that which achieves a non-dissipative time reversal of the driven process at its steady state, and we use this knowledge to design physically-motivated control policy parameterizations that converge rapidly in an online reinforcement learning implementation of our method. Applying our method to the active filament allows us to map out nonequilibrium free-energy profiles as functions of mean active force amplitude, nucleosome repeat length, and filament rigidity to quantify the relative populations of, and flux intensities between, structural-dynamic motifs that in qualitative agreement with those identified using previous coarse-grained polymer models of confined active chromatin. |
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