Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session D11: Undergraduate Research IVUndergrad Friendly
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Sponsoring Units: APS/SPS Chair: Chrisy Xiyu Du, Harvard University Room: 110 |
Monday, March 2, 2020 2:30PM - 2:42PM |
D11.00001: High-pressure pretreatment of rice straw for optimizing the fermentable sugar yield Pratham Gupta, Bahiru Tsegaye, Chandrajit Balomajumder
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Monday, March 2, 2020 2:42PM - 2:54PM |
D11.00002: NSF IRES: Exploring the Effect of Temperature on a Plant's Photocyle by Observing the Blue-Light Photoreceptor Protein Arabidopsis Cryptochrome Marootpong Pooam, Nykiera Dixon, Michael Hilvert, Peter Misko, Kristy Waters, Stephen Mills, Soria Drahy, Dorothy Engle, Justin Link, Margaret Ahmad Cryptochrome is a blue-light photoreceptor protein involved in both plant and animal circadian rhythms. When illuminated by blue light, the flavin cofactor of cryptochrome is photoreduced, thus yielding the active state of the protein. This photoreduction and subsequent reoxidation can be observed spectroscopically. However, the effect of temperature on the photoreduction has not been extensively studied. Here, using a UV-Vis spectrophotometer, we demonstrate the effects of temperature on the photoreduction and reoxidation of purified Arabidopsis cryptochrome 1 (AtCry1) and cryptochrome 2 (AtCry2) proteins. It was hypothesized that at higher temperature, an increase in the rate of photoreduction and reoxidation would occur. However, our experimental results demonstrated that when comparing the reactions at 15°C and 25°C, temperature had no effect on the photoreduction of the flavin, but the rate of reoxidation was increased at the higher temperature. These results suggest increased activation in AtCry1 and AtCry2 at lower temperatures. |
Monday, March 2, 2020 2:54PM - 3:06PM |
D11.00003: Temperature Dependence in Stochastic and Deterministic Models of the Circadian Rhythm of Cyanobacteria Thomas Baer, Orrin Shindell The chemical reactions that lead to circadian rhythms in organisms are deterministically described in the limit where the number of cells is large. However, for each individual cell these reactions are stochastic as the number of molecules involved in them is small. Here, the circadian rhythms of cyanobacteria are considered. Using mathematical models of biochemical oscillations, we analyze the characteristic behavior of the deterministic system near a non-equilibrium phase transition. The control parameter that drives the transition is the temperature, which must be high enough for any biochemical oscillations to occur. We analyze the same set of reactions near the transition temperature in the stochastic limit and discuss features that emerge in the probability distributions of oscillation amplitudes and frequencies. We also comment on the thermodynamic connection between the small and large scale descriptions. |
Monday, March 2, 2020 3:06PM - 3:18PM |
D11.00004: Nano-optical imaging of bacteria on 2D materials Liana Shpani, Sharad Ambardar, Dmitri Voronine Bacteria cause hazards via biofouling and develop resistance to antibiotic treatments. However, due to their small size, spectroscopic imaging and analyzing bacteria using conventional optical microscopy is challenging. Moreover, atomically thin 2D materials, especially transition metal dichalcogenides, with their wide range of applications in optoelectronics, have also shown promising biological applications. In this work, we developed a novel nanoscale imaging approach to characterize bacteria-substrate interactions. Untreated and antibiotic-treated bacteria were deposited on the junction of monolayer MoS2-WS2 materials on top of a Si substrate. The optical characterization with 532 nm laser excitation provided far-field photoluminescence (PL) and near-field tip-enhanced photoluminescence (TEPL) measurements. When the bacteria were placed on the 2D materials, a higher PL signal was observed compared to the pure material. The enhancement and the red shift of the PL signal can be accounted as strain caused by the bacteria on the 2D materials. These observations show promising results to prompt further studies to analyze interactions of different bacteria with TMDs. |
Monday, March 2, 2020 3:18PM - 3:30PM |
D11.00005: Human Gene Expression and the Protein-Protein Interaction Network: Identification of Potential Disease Module Association to Differential Gene Expression for Patient-to-Drug Matching Aydin Wells, Deisy Morselli Gysi, Albert L Barabasi The relationship between human gene expression (GE) and precision medicine applications is central in understanding how patients are affected by and how to better treat a disease. Even though it is of extreme importance, this knowledge is still absent from almost any disease analysis resulting in misdiagnosis and mistreatment based on symptomatic and physical observation criteria devoid of high throughput sequencing technologies. By detecting disease modules in the protein-protein interaction (PPI) network, along with the identification of patient differential GE sets (DGE), we can suggest effective individual treatment options. Here, we collect public RNA sequencing data for a diverse population and arrange unique GE patient profiles. DGEs are computed using machine learning techniques and are identified within the PPI network, where disease modules can be pinpointed. Those modules can be used for disease classification specific to expression levels and cohort phenotype. By elucidating these interactions using network approaches with an individual patient’s features, human diseases can be identified not by peripheral approaches, but by a personal genetic diagnosis; essentially redefining disease diagnostics from a “one size fits all” philosophy, to a “one size fits you” reality. |
Monday, March 2, 2020 3:30PM - 3:42PM |
D11.00006: Focused Ultrasound as a Replacement for Endodontic Therapy Talisi Meyer, Jennifer Canfield, Michael Jordan, Jason White Focused ultrasound has exhibited promising results as a therapeutic modality in its ability to minimize the invasiveness of a number of medical treatments that are physically and mentally traumatic to the patient. We propose the investigation of its use for non-invasive endodontic therapy (a.k.a. a “root canal”), with the ultimate goal of removing microbial infection from the root canal system of a contaminated tooth. |
Monday, March 2, 2020 3:42PM - 3:54PM |
D11.00007: Enhanced magnetic hyperthermia of copper ferrite nanoparticles for biomedical applications Enya Silva, J. Robles, Sarath Witanachchi, Anh-Tuan Le, Manh-Huong Phan Magnetic hyperthermia is a promising cancer treatment that has minimal side effects compared to chemotherapy and radiation therapy. The heating efficiency of magnetic nanoparticles is central to the effectiveness of magnetic hyperthermia as a treatment and, while Copper is a well-known thermal conductor, little research has been done regarding its ability to increase the heating efficiency of magnetic nanoparticles. In this experiment, the heating efficiency of different samples of Copper Ferrite nanoparticles was quantified by dispersing the nanoparticles in a solution and measuring the solution’s temperature change over time in an alternating magnetic field. This method is common in the study of magnetic hyperthermia because it best replicates the experiment’s clinical applications. This experiment yielded a value of about 300 W/g for the heating efficiency of Copper Ferrite, which is significantly higher than the value of about 80 W/g obtained for Iron Oxide nanoparticles from previous experiments. These results suggest that Copper is a viable option for increasing the heating efficiency of magnetic nanoparticles and that Copper Ferrite nanoparticles are viable candidates for magnetic hyperthermia therapy. |
Monday, March 2, 2020 3:54PM - 4:06PM |
D11.00008: Correlative photoluminescence and micro-Raman spectroscopy determining disorder from two-dimensional heterostructures to rare-earth minerals Joy J. Ma, Tao Jiang, Jun Yan, Molly A May, Markus B. Raschke Atomic composition and structural arrangement determine the correlation of electronic and lattice degrees of freedom in solids. With combined photoluminescence (PL) and Raman spectroscopy, simultaneous insight into electronic properties and structural disorder can be gained. Here, we use micro-Raman imaging to study spatial heterogeneity in structural disorder in the rare-earth mineral gadolinite as determined from correlative peak position and spectral linewidth analysis. We find the disorder associated with spatial variability in light and heavy rare earth element content. We then use micro-PL to investigate the effect of a plasmonic nano-slit on the excitonic landscape in a two-dimensional heterostructure of transition metal dichalcogenides and identify plasmonic enhancement of both intralayer and interlayer exciton emission as well as strain-induced spectral variations. In summary, this work demonstrates the combination of micro-PL and micro-Raman imaging to understand electronic and structural properties and disorder in crystal materials. |
Monday, March 2, 2020 4:06PM - 4:18PM |
D11.00009: Electron emission from randomly-oriented and vertically-aligned carbon nanotubes synthesized directly on conducting surface Matthew Kurilich, Arun Thapa, Wenzhi Li, Suman Neupane Field emission properties of carbon nanotubes (CNTs) have been intensively studied for various applications. It is desirable to synthesize CNTs directly on conducting substrates to develop field emission displays capable of operating at low voltages and at room temperature. As compared to the randomly-oriented CNTs, vertically-aligned CNTs demonstrate improved field emission properties with greater electric field enhancement and lower turn-on/threshold electric fields. In this work, we compare the electron emission between randomly-oriented and vertically-aligned CNT emitters synthesized directly on stainless steel substrates. The surface morphology of these CNTs has been studied with electron microscopy and the defects are analyzed by the Raman spectroscopy. The vertical alignment of the CNT emitters benefits the emission process by reducing the screening effect and by streamlining the path of ejected electrons directly onto the anode. |
Monday, March 2, 2020 4:18PM - 4:30PM |
D11.00010: Tunable 3D Photonic Crystal Cavity for Coherent Coupling between Microwave Fields and Solid State Spins Abhijatmedhi Chotrattanapituk, Hyeongrak Choi, Dirk R. Englund We present a theory and experiment of a three dimensional (3D) photonic crystal (PhC) cavity for the control of microwave fields with ultra-low loss. The cavity consists of an engineered defect in a woodpile photonic crystal made of low-loss alumina rods. We measure a large complete bandgap of 13% of the center frequency and a cavity quality factor exceeding 22,000. The architecture allows for easy mechanical tuning of the cavity and waveguide. Our design has a variety of applications including the coherent coupling of microwave photons with electron and nuclear spins in solids. |
Monday, March 2, 2020 4:30PM - 4:42PM |
D11.00011: Viscosity of a Crowding Medium Obtained Through Optical Trapping James Howard, Javier E Hasbun, Suvranta Tripathy The dynamic viscoelasticity a cellular medium is mainly due to the crowding of a large number of interacting and non-interacting proteins. Our research presents how the viscosity of a medium is altered in the presence of globular proteins. Using an optical trap paired with a 980 nm infrared laser and Nikon inverted microscope we have developed a synthetic approach to calculate the viscosity of a medium. The method involves comparison of Equipartition theorem and Passive power-spectrum technique to determine viscosity. This approach has enabled us to calculate the viscosity of several water and glycerol concentrations. The method has been extended to investigate the viscoelasticity of the medium with various concentrations of globular Polyethylene glycol proteins. |
Monday, March 2, 2020 4:42PM - 4:54PM |
D11.00012: Computation of Forces and Torques on Clusters of Micron-Sized Spheres in Optical Tweezers Wyatt Vigilante, Jerome Fung Optical tweezers are a focused laser beam that exerts forces and torques on micrometer-sized particles. Calculations of optical forces on non-spherical particles whose size is comparable to the wavelength of the trapping beam are challenging. Here, we use a T-matrix code to calculate how clusters of spheres scatter light. The resulting T-matrix is exported to a software package that calculates optical forces and torques. We present calculations of optical forces and torques on clusters of two and three spheres. We discuss how the forces and torques depend on the orientation, size, and refractive index of the clusters. |
Monday, March 2, 2020 4:54PM - 5:06PM |
D11.00013: Nano-Optical Imaging of CVD Grown Lateral Heterostructures Rana Kamh, Sharad Ambardar, Hana Hrim, Dmitri Voronine Transition Metal Dichalcogenides (TMDs) have attracted a lot of attention due to their properties such as direct band gap, photoluminescence, and applications in electronics. Several combinations of TMD monolayer heterostructures have been fabricated and studied for their unique optical and electrical properties. Here we explore CVD grown WSe2-MoSe2 heterostructures with the presence of telluride in order to observe the effects that arise from the integration of this material in CVD growth. We characterize the resulting material using techniques such as Kelvin Probe Force Microscopy (KPFM), Atomic Force Microscopy (AFM), and Tip Enhanced Photoluminescence (TEPL), revealing the optical properties and surface topographies of the 2D heterostructures after exposure to telluride during growth. We observe alloying and quenching of the near field PL in the 2D lateral heterostructures and propose reasons for these effects after the incorporated material. The integration of telluride to 2D materials can provide potential applications in optoelectronic devices. |
Monday, March 2, 2020 5:06PM - 5:18PM |
D11.00014: Computer generated holograms for optical trapping using a Spatial Light Modulator Anthony Hewitt, Koon Siang Gan, Rainer Dumke, Michael Lim The general experimental modeling of quantum behavior with a well-characterized and well-controlled quantum system is now a possibility using a Bose-Einstein condensate loaded into programmable optical potentials. Through the use of a spatial light modulator (SLM), these patterns can be dynamically modified in real time to further increase the scope of these modelling capabilities. Accurate focal-plane intensity patterns can be generated using an SLM with appropriate algorithms. We demonstrate that the Mixed Region Amplitude Freedom (MRAF) algorithm can generate a desired intensity ring in the focal plane of a lens. We plan to use the MRAF output as the initial guess for a second algorithm that uses Conjugate Gradient Minimization (CGM) to reduce convergence time and increase overall accuracy. |
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