Bulletin of the American Physical Society
2018 Annual Meeting of the Far West Section
Volume 63, Number 17
Thursday–Saturday, October 18–20, 2018; Cal State Fullerton, Fullerton, California
Session E02: Poster Session 2 |
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Chair: Patricia Sparks, Harvey Mudd College Room: Titan Student Union Pavillion A |
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E02.00001: Encoding Arbitrary Phase and Amplitude Modes on Laser Light with A Digital Micro-Mirror Device Michael Doris Controlling the amplitude and phase structure of laser light is important for many applications in atomic, molecular, and optical physics where the ability to configure light has vastly improved probing and tailoring interactions between light and matter. The introduction of the liquid crystal spatial light modulator (LC-SLM) and the digital micro-mirror Device (DMD) have enabled programmable control of laser light in applications such as optical tweezers, trapping, and imaging. The DMD is a faster alternative to the LC-SLM that can configure the amplitude and phase structure of light at rates upwards of 4kHz via millions of binary controlled micro-mirrors. Commercially available DMDs, commonly used by projector systems, are an economical and robust tool for crafting laser light in the lab. We demonstrate the DMD’s ability to encode an arbitrary phase and amplitude mode on a laser beam via diffraction patterns, produce flat top probe beams, and generate a known reference for holographic imaging of cold atoms. Due to the programmable nature of the DMD, the beams engineered by these devices will improve the existing absorption imaging of atom clouds through real time stabilization of probe beam shaping, alignment, and positioning. |
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E02.00002: Development of a Transient Absorption Spectrometer to Analyze Molecular Dynamics Daniel Wheeler, Eddie Cruz, John Schad, Eddie Cruz, Paul Arpin Ultrafast dynamics contribute to photo-physical processes such as photosynthesis, where |
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E02.00003: Experimental Apparatus to Study the Spinor Dynamics of a Bose Thermal Gas Catherine A Crichton, Lauren M Gorman, John G Stone, Thomas Garcia, Daniel Wells, Hyewon K Pechkis, Michael Doris, Joseph A Pechkis We present our progress towards the construction of a cold atom apparatus to study the spinor dynamics of a Bose thermal gas. We have designed, constructed, and tested low-cost, external-cavity diode lasers (ECDLs) to operate below the rubidium D2 transition at 780 nm for use in an undergraduate-only research laboratory. Using these ECDLs, we performed saturated absorption spectroscopy (SAS) to measure and lock to the transition frequencies of 85 Rb and 87 Rb using a sub-Doppler dichroic atomic vapor laser lock (DAVLL). We injection lock a free-running diode laser (FRDL) to with seed light from the trap ECDL. The locking electronics, frequency stabilization, and vacuum chamber design will be discussed. |
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E02.00004: The experimental design of integrating scanning tunneling microscopy with Fourier-transform infrared spectroscopy Kristopher K Barr, Andrew Ira Guttentag, Paul S Weiss The scanning tunneling microscope (STM) has revolutionized our ability to observe surface features at the scale of atoms and molecules on a variety of conductive substrates. Conventional STM images contain limited chemical information, generally related to electronic structural variations of surfaces and adsorbates. We propose to expand the capabilities of the STM by simultaneously exciting the surface with an evanescent wave of infrared radiation and measuring the changes in apparent conductance with the probe tip. Due to the local nature of scanning probe microscopies, we investigate vibrational structure below the diffraction limit. An interferometer source allows us to probe the surface at a variety of frequencies simultaneously letting us differentiate between similar molecules with different functional groups. This methodology will serve as the framework for future experiments on a variety of systems. |
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E02.00005: Using FLASH to Simulate the Ablation of an Al foil into a Background Plasma Adam He, Fabio Conti, Nicholas Aybar We performed 1-D simulations of a planar shock interacting with a background plasma in the FLASH MHD code. The simulations modeled upcoming experiments that will be done on the 800 kA, 150 ns LTD pulse generator at UCSD. The current pulse is set to pass through a 5-micron thick planar aluminum foil, causing it to ablate and turn into a plasma. The J x B force and the thermal expansion of the foil accelerate it into a background hydrogen plasma at supersonic speed. In order to simulate the current drive, we placed a time-varying magnetic field on the left-hand boundary of the foil. We found that the resultant shock propagates with a Mach number of 1.43 and retains a planar configuration within the first 2 ns of the experiment. A considerable amount of species mixing was also observed at the shock front, which exhibited a 50% decrease in aluminum concentration over a span of 4 microns. This finding provides valuable insight on the behavior and dynamics of current-driven, multispecies planar shocks, an area that lacks significant research. Future work will attempt to produce results for the remainder of the experiment and will compare these with experimental results. Keywords: shock, plasma, multispecies, magnetohydrodynamics, Mach number |
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E02.00006: Study on the Spectral and Acoustical Features of the Clarinet Sound Using Physical and Computational Analysis Joshua Rhee, Richard Kyung Acoustically, the clarinet sound is not closely related to the sound generated by other woodwind instrument. In this paper, acoustics knowledge was used to carry out physical and spectral analysis. The wave forms and spectrums of the clarinet and a few other instruments were calculated to compare their sound properties. The research implemented the sound of a clarinet instrument using harmonic equations and computer programs such as Mixcraft and MATLAB. The sound properties that were investigated were wavelength, fundamental frequency, harmonics, and trigonometric functions used in a Fourier transformation. It was noticed that several instruments had much more energy in the second, and/or third harmonics than in the first frequency. Also, a certain instrument showed the purest tones until a certain frequency. After crossing the frequency threshold, the tone became fuzzy. In the spectra analysis, we determined how the harmonics and power or energy of the clarinet were changed over time, but the pitch did not change. The main objective of this research was to study a musical note of the clarinet sound using digital audio workstation (DAW) and computational simulations.
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E02.00007: Optical Tweezer Measurements in Biophysical Environments Mauricio Miguel Gomez, Corbyn Jones, Wylie Ahmed Recently, optical tweezers have been used to study force fluctuations in equilibrium systems and to determine the physical properties of complex materials. We are currently implementing two calibration methods, the photon-momentum method and the active-passive method, to measure displacements and forces at the nanometer and piconewton scales. Here, we study the force fluctuations of chlamydomonas microswimmers as well as the rheological properties of xylem sap. By locally trapping a chalmydomonas, we are able to measure its beating frequency as well as the force generated to beat at that frequency. We calculated the stochastic force spectrum by estimating the power spectral density of the fluctuating force signal. We are applying a theoretical framework to extract the non-equilibrium microswimmer forces from the total force spectrum. Xylem sap is a fluid found in plants that is vital to the plant's ability to transport nutrients throughout the plant's system. The xylem sap was analyzed through an active microrheological experiment (AMR). We are quantifying xylem sap rheology to investigate the physics of negative pressure and cavitation phenomena in plants. |
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E02.00008: Quantitative X-ray fluorescence measurements of Pb in plaster-of-Paris bone phantoms Mihai R Gherase, Summer Al-Hamdani X-ray fluorescence (XRF) is the emission of characteristic x-rays by an excited atom. An important XRF application is the in vivo human bone lead (Pb) concentration measurement. An established method uses the K-shell XRF emissions using the Pb excitation of the gamma rays from a Cd109 radionuclide. The alternative is the L-shell XRF (LXRF) method. The LXRF disadvantage is lower intensities of Pb x-rays at 10.5 and 12.6 keV; its advantage is using x-ray tube and detectors for large population studies. The unknown x-ray attenuation of the soft tissue affects the LXRF measurement. Cylindrical plaster-of-Paris (poP) bone phantoms doped with [Pb] of 0,8,16,29,59, and 74 µg/g and polyoxymethylene soft tissue phantoms of 1, 2, and 3 mm thickness were used to simulate the in vivo setting. Sr was present in the poP material and found in human bone in concentrations ~10 times higher than Pb. A new calibration method based on the XRF peak height ratio of strontium (Sr) x-rays was explored. The deviations between calculated and known Pb concentration values were within the three standard deviation interval for more than 90% of the data. |
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E02.00009: An optimal grazing-incidence position method for arsenic measurements in polyester resin skin phantoms Alex Lawson, Mihai Gherase Arsenic (As) is a well-known toxic element. The adverse health effects of long-term As human exposure are insidious and include cancer. The exposure occurs mostly via human consumption of As contaminated well water–a naturally occurring problem in many parts of the world. The excess of As intake leads to its accumulation in keratin-rich tissues such as skin, nails, and hair. The x-ray fluorescence (XRF) method identifies elements in trace concentrations via the detection of their characteristic x-rays emitted. Portable spectrometers can be used for in vivo XRF skin As assessment in remote locations. These devices, however, were not designed for the detection of the superficially distributed As in the skin. An x-ray optics system, an x-ray detector, and a positioning stage were used to find the optimal grazing-incidence position of skin phantoms doped with As in 0, 4, 6, 8, and 12 μg/g concentrations. Using the As Kα peak height measurements, the As calibration line and a detection limit of (0.334±0.009) µg/g were obtained. The result is superior to those obtained in past studies and can guide future XRF investigations of As in skin. |
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E02.00010: X-ray Backscatter Modelling for Quantitative X-ray Fluorescence Microscopy Studies Annette Lopez X-ray fluorescence (XRF) is a non-destructive method capable of detecting chemical elements (Z>10) in trace concentrations at the parts per million (ppm) level. Observed differences at the microscopic scale between normal and pathological tissues are linked to various human diseases such as cancer, Parkinson, or osteoporosis. The advent of commercial polycapillary x-ray lenses (PXLs) extended the realm of XRF microscopy from synchrotron to table-top units using x-ray tubes. In this study, a 50-kV x-ray tube integrated with a PXL unit irradiated for 5 minutes a polyester resin sample of 300 micrometers thickness. The sample was doped with arsenic (As) at the 12 ppm level to mimic the presence of a trace element in a soft tissue sample. A silicon detector was placed at the 137-degree backscattering angle to acquire the x-ray spectrum. Coherent and incoherent cross section calculations estimated the backscatter-to-incident ratio (BIR) as a function of the photon energy, experimental detection geometry, thickness, and bulk elemental composition (BEC). The fitting of the BIR model to the experimental data in the 15-25 keV photon energy range yielded the BEC and the thickness of the resin sample. |
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E02.00011: Guiding High Energy Laser Pulses Through Hollow Core Fibers Steven J Sheppard The purpose of our research is to study uncoated hollow fibers for their potential applications in medicine, manufacturing and scientific research. The goal is to characterize the efficiency, beam quality and polarization of the transmitted beam for uncoated hollow fibers with a core diameter of 750μm. Optimum results are obtained with proper fiber tip preparation and efficient beam coupling. Results for a straight 2m section of uncoated fiber show an attenuation of 3.35 db/m and conservation of linear polarization. In the future, investigation of the polarization and attenuation effect of bending as well as shorter lengths will be completed. |
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E02.00012: Cells Mechanotransduction: Geometrical Confinement for Cell Wave Control Monika Tadrous, Vanni Petrolli Organisms develop from a single cell through a complicated procedure with multiple factors. One of the factors that decide a role of a cell in an organism is the spatial patterning of cell behavior. Cells travel in a mechanical wave like pattern with a certain wave length. We investigate the characteristics of the mechanical waves by confining tissues to a certain geometry that interferes with the wave length of the cell, manipulate the environment of the cell, then analyze the tissue reaction using Particle Image Velocimetry (PIV) and Traction Force Microscopy (TFM). |
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E02.00013: Biochemical Stability and Safety Analysis of Nano-scaled Biochemical Compounds Used in Contrast Agents in MRI and Positron Emission Tomography(PET) Michelle Kung, Hyunjin Chang This project aims to determine the thermodynamic stability and safety of various nano-scaled biochemical compounds used in contrast agents in MRI and Positron Emission Tomography(PET) scanning. By using molecular editing computer programs and a computational chemistry method, this paper discovers the optimal form of the biochemical molecules used in bio-imaging and molecular diagnostics of Alzheimer's disease. Nanoparticles(NPs) are widely used for the purposes of fluorescent imaging, mainly of cells and tissues. For selective targeting of specific cells, surface functionalization has been developed using biochemical nanoparticles used in treatment of Alzheimer's and cancer disease. The Density Functional Theory (DFT), a computational chemistry modeling method, was used to model the electron properties of the compounds. Avogadro is an open-source molecular editing program with an auto-optimization feature which can determine the theoretical values of a structure's atomic properties. It allows users to build virtually any molecule with the optimized geometry according to various force field options. |
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E02.00014: Physical and Biochemical Study of the Antioxidants Used in Dental Bacteria Inhibitors Won Jun Lee, Sun Lee Cocoa beans contain various beneficial compounds including polyphenols and flavonoids, both of which positively impact dental health. Polyphenols benefit oral health primarily by preventing bacterial growth. The chemical structure of polyphenols allow the molecules to remove ROS, inhibit enzymes, and induce antioxidant activity. Periodontal disease is just one oral ailment that research has proven for polyphenols to be effective at preventing. Flavonoids such as catechin, epicatechin, and procyanidins are antioxidant-containing phytonutrients. In this paper, those antioxidants are studied to observe how they beneficially aid tooth health by delaying tooth decay. This paper also illustrates how the tricyclic structure of flavonoids are able to thermodynamically give rise to such beneficial properties. In this project, we assessed the thermodynamical and stereochemical safety of several types of biochemical molecules that can be used as a biological and dental antioxidant. |
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E02.00015: Study on the Physical and Biochemical Properties of Fullerene Derivatives and CNTs (Carbon Nano Tubes) for Cancer Treatment Jaesang Noh, Amanda Kyung Nanotechnology is ever more frequently the star of biochemistry as it continually unlocks methods to cure disease. Among its clinical applications, fullerenes and CNTs (Carbon Nano Tubes), as well as metal oxides, are being utilized in therapy for cancer patients. These nano-scaled compounds exhibit anti-tumor properties that inhibit cancer from spreading throughout the body, and a wide variety of fullerenes and CNTs have the potential to be applied in the therapeutic process. Once a fullerene is absorbed by one's cells, its C60 derivatives react to light radiation by transforming molecular oxygen into reactive oxygen, thereby triggering apoptosis in the HeLa cells and other cancer cells that are able to absorb such molecules. In this project, physical and biochemical properties of the fullerenes and CNTs as tumor cell inhibitors were studied. Also the thermodynamic stability of all the derivatives were studied in the light of their promising role in treating tumor cells. The Avogadro software was used to measure the optimization energy of each compounds. Complexes with relatively low optimization energies were predicted to be more thermodynamically stable than those with relatively high energies. |
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E02.00016: Bio-mechanical Modeling and Analysis of Knee Joints Affected by Kyphosis Using Computational and Physical Calculations Minseo Lee, Amanda Kyung The physical and computational analysis can be used in cases where determining the clinical condition of patients is not easy. Kyphosis is one of the most well known disorders that elders suffer from the deformed thoracic vertebra causing incorrect postures and changing the center of mass of the body forward. In this paper, the effect of aging kyphosis on the patient 's use of stairs was experimentally investigated, and the most comfortable physical factors for kyphosis patients were suggested. Also, the effect of kyphosis on kinematics of knee joints and legs has been computationally performed. Using the free body of diagram of forces acting on the knee during loading and walking, bio-mechanical model depicting knee joint kinematics has been studied. Moment equilibrium and force equilibrium are also considered. Based on the fact that magnitude of the joint reaction force on knee joints can reach several times the body weight, the stability analysis of the knee and lower leg bone has been studied. This research includes two procedures: Study of mathematical modeling of the lower leg using bio-mechanics, and the development of mechanical analysis of the tibial bone.
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E02.00017: Study on the Abnormalities in the Genetic Sequence in DNA Causing Leber Congenital Amaurosis (LCA) Namju Kim, Richard Kyung RPE65 is a gene critical for the visual function. Its mutation disrupts the vertebrate visual cycle, resulting in eye disorders such as RP and LCA. The role of RPE65 in the visual cycle is to catalyze the transformation of all-trans-retinyl ester to 11-cis-retinol and to allow the eye to detect light. [1] In LCA, a defective RPE65 gene results in a decreased regeneration of 11-cis-retinal. This breaks the phototransduction pathway and photoreceptors are unable to respond to light. Although malfunction of RPE65 causes LCA and RP eye disorders, research has shown that partial inhibition of RPE65 may treat age-related macular degeneration (AMD). This paper identifies and analyzes abnormalities in the genetic sequence that lead to mutations in patients with genetic eye disorders. In this paper, computational analysis of Arg91Trp mutation was performed to determine its resulting pathogenesis. First, sequence abnormalities in the gene of RP and LCA patients were identified. Then, sterochemical analysis was performed via gene editing program and molecular geometry analysis to observe the effect of the mutation on the peptide’s thermodynamic stability. |
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E02.00018: Study on Bio-images to Enhance Resolutions Using Computational and Numerical Simulations Eunsuh Kim, Lauren Chung In this paper, an alternative algorithm for bio-image processing was mathematically and computationally studied. Generally, digital bio-image subtraction and numerical filtering process such as LPF(Low Pass Filter) and HPF(High Pass Filter) are used to enhance the quality of normal biological and anatomic details of image. The main purpose of this research was to develop a better algorithm that would enhance the quality of the final radiograph images of human organs and structures. An ideal low pass filter would be able to increase the resolution of image as well as decrease the Ringing Artifact. In this paper, through comparison with conventional techniques, a few trigonometric functions and specific algebraic functions were tested to reduce Artifact. Compared to those produced by using a unit step function, the presented scheme improved the resolution of the resulting bio-image. Different variables were applied on the full K-space in order to find a most efficient filter, which can be used to produce better bio-image. Depending on the width of the LPF functions, the resolution of the resulting image using the non-Gaussian behavior differed. When the domain over the frequency domain was narrow, it produced blurry images.
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