Bulletin of the American Physical Society
2015 Annual Fall Meeting of the APS Ohio-Region Section
Volume 60, Number 12
Friday–Saturday, October 16–17, 2015; Cleveland, Ohio
Session B1: Poster Session (4:00 pm - 6:00 pm) |
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Chair: Petru S. Fodor, Cleveland State University Room: Atrium |
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B1.00001: Time-resolved UV-IR Pump-stimulated Emission Pump Spectroscopy: Probing Collisional Relaxation of $8p^{2}P_{3/2}$ Cs I MD SALAH UDDIN We describe and use a time-resolved pump-stimulated emission pump spectroscopic technique to measure collisional relaxation in a high-lying energy level of atomic cesium. Aligned $8p^{2}P_{3/2}$ cesium atoms were produced by a pump laser. A second laser, the stimulated emission pump, promoted the population exclusively to the $5d^{2}D_{5/2}$ level. The intensity of the $5d^{2}D_{5/2}\rightarrow6s^{2}S_{1/2}$ cascade fluorescence at $852.12\: nm$ was monitored. The linear polarization dependence of the $6s^{2}S_{1/2}\rightarrow8p^{2}P_{3/2}\rightarrow5d^{2}D_{5/2}$ transition was measured in the presence of argon gas at various pressures. From the measurement, we obtained the disalignment cross section value for the $8p^{2}P_{3/2}$ level due to collisions with ground-level argon atoms. [Preview Abstract] |
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B1.00002: Evolutionary trends in the humeral bone strength of theropod dinosaurs. Scott Lee, Zachary Richards The strength of the humerus bone is evaluated for 28 different theropod dinosaurs. These results are used to examine evolutionary trends in humeral bone strength for Tyrannosauroidea, Allosauroidea, and Ornithomimosauroidea dinosaurs. Humeral bone strength is also examined for carnivorous, piscivorous, omnivorous and herbivorous theropod dinosaurs. In general, the largest carnivorous theropod dinosaurs had the strongest humera while the herbivorous dinosaurs had the weakest humera. Based on these results, a determination of the humeral section modulus is sufficient to predict if a theropod dinosaur was herbivorous. This would be useful for newly discovered species for which no cranial elements are recovered. The possible uses of the forelimbs of \textit{Tyrannosaurus rex} are also discussed. [Preview Abstract] |
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B1.00003: Study of the softening of infra-red active vibrational modes in crystalline cytidine as a function of pressure. Carl Starkey, Scott Lee, Anthony Anderson DNA double helices are known to undergo conformational transitions when exposed to different conditions. The origins of these transitions are of great interest. It is possible that these transitions are driven by a weakening in the restoring forces associated with particular vibrational modes. We report the pressure dependences of the infrared-active vibrational modes of crystalline cytidine up to pressures above 4 GPa. Modes near 503, 758, 795, 3093, and 3351 cm$^{\mathrm{-1}}$ have negative pressure derivatives, indicating that the restoring forces of these modes are weakening with applied pressure. The two modes above 3000 cm$^{\mathrm{-1}}$ are hydrogen-bond stretching modes and their decrease in frequency with pressure shows the expected transfer of electrons from the molecular bond to the hydrogen bond as pressure is applied. The electronic wave function associated with the three modes below 800 cm$^{\mathrm{-1}}$ is changing in unexpected ways and indicates that the associated molecular components are losing electronic wave function. [Preview Abstract] |
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B1.00004: Dynamics of an Optically Trapped Particle Modeled with the Fokker-Planck Equation Justin Flaherty, Andrew Resnick Particles trapped in a laser experience a linear restoring force that keeps them centered in the trap and will undergo constrained Brownian motion. The particle's motion causes a change in the scattered laser light. The scattered light is projected onto a Quadrant Photodiode and is used to obtain the Mean Squared Displacement of the particle, as well as the linear spring constant of the laser trap. The spring constant can be used to obtain the force applied by the laser trap, which is in the realm of piconewtons. We present our work modeling this process in terms of the Fokker-Planck equation. [Preview Abstract] |
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B1.00005: Synthesis of Optimal Polymeric Microgels {\&} their Characterization with Light Scattering Christian Gunder, Kiril Streletzky Polymeric microgels were synthesized in by chemically crosslinking hydroxypropylcellulose (HPC) chains with each other in aqueous solutions of sodium hydroxide at temperatures above the low critical solution temperature (LCST) of HPC. In order to create a narrower size distribution of HPC microgels, surfactant was added. It was found that the LCST of the solution moved from 40C up to 80C with an increase in surfactant concentration from 0 to 12 g/l. Formed microgels were characterized by dynamic light scattering (DLS). Microgel solutions synthesized so far resulted in reasonably monodispersed nanoparticles with Rh of 90-150 nm below the known LCST for HPC, and Rh of 50-90 nm above the known LCST for HPC. Surprisingly, some of the microgels revealed weak VH signal, indicating their potential geometric anisotropy. Further studies were done in an attempt to explore the effect of synthesis temperature and crosslinker concentration on microgel size, polydispersity, and swelling ratio. It was found that maintaining a pH of 12 for the aqueous sodium hydroxide solvent was critical to ensure reproducibility of synthesis. However, it was also found that the pH of the solvent had no effect on the overall LCST of the HPC in surfactant-free solutions. [Preview Abstract] |
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B1.00006: A Computationally Integrated Undergraduate Physics Curriculum: What in the World? Norman Chonacky During the past decade or two, a fundamental change in methods has occurred in the practice of sciences and engineering. Numerical computational methods and products have assumed an equal place, with analytical theory and laboratory experimentation, in these practices. Unlike this revolution in professional practice, there have been relatively meager changes in undergraduate physics courses that might challenge the predominance of analytical theory and laboratory experiment. There are many possible reasons for this, as our research has shown. However, at the base of this lacuna lie barriers faculty face when confronted with the prospect of initiating inclusion of computation into the physics they teach. I will report on our research work and resulting projects designed to jump-start and support a broader process of computational integration into undergraduate physics courses. Briefly I review the background work by the Partnership for Integration on Computation into Undergraduate Physics (PICUP) in this area for over a decade. There are currently three national projects conducted by the PICUP, of which I will especially focus on one: ``Fostering integration of computational practices in physics courses: A local communities approach.'' [Preview Abstract] |
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B1.00007: Circular arrangements of atoms: solving Schr\"{o}dinger's equation for the energy spectrum Matthew Golden, Mellita Caragiu Schr\"{o}dinger's equation is used for a quantum particle confined to move in a circle of radius R. the particle encounters a zero potential almost everywhere, except for when it comes across delta function potentials of strength p, situated symmetrically around the ring. The energy spectrum for this system is analyzed in various cases of attractive or repulsive potentials and positive or negative total energy of the particle. [Preview Abstract] |
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B1.00008: Light Beyond The Bulb -- Light Based Technologies Corneliu Rablau On 20 December 2013, the UN General Assembly 68$^{th}$ Session proclaimed 2015 as the International Year of Light and Light-based Technologies. In doing so, the UN has recognized the importance of raising global awareness about how light-based technologies are changing the landscape of our daily lives, promote sustainable development and provide solutions to global challenges. Indeed, from communications to energy, education to health care and life sciences, defense and security to agriculture and environment, there is virtually no area of economic and social activity that has not been impacted by the \textit{enabling} attribute of light-based technologies. This presentation is a summary of the most impactful applications of light and has been compiled as a tribute to light and the vital role it plays -- in more than the obvious way -- in our daily lives. [Preview Abstract] |
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B1.00009: Fiber-Optic Force Sensor for Robotic Surgery Corneliu Rablau, Brendan Acre We report on the design, mathematical modeling and preliminary development work for a fiber optic \textbf{\textit{force}} sensor for applications of force sensing and force-feedback in robotic surgery and in other systems where a small passive sensor immune to electromagnetic interference (EMI) may be needed. Some major technical merits of the proposed sensor are that it can be made small enough to fit the distal end (active tip) of typical surgical devices used in robotic laparoscopic surgery (cylindrical sensor of diameter 10 mm or less), that it can be assembled completely from glass/dielectric materials (RF magnetic fields compatible) and that it does not require active powering and local conditioning (filtering, amplification) of the response signal it produces to an applied external force. The last two characteristic make this sensor immune to EMI, unlike other sensors based on electric/electronic devices like strain gages, piezoelectric crystals or micro-electromechanical devices (MEMS), e.g. MEMS capacitors. The force sensor is based on an optical fiber $+$ four-quadrant-mirror \textbf{\textit{displacement }}sensor using a four-wavelength multiplexed interrogation scheme based on Gaussian beams. [Preview Abstract] |
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B1.00010: Cellular Hokey Pokey: A Coarse-Grained Model of Lamellipodia Protrusion Dynamics Driven by Fluctuations in Actin Polymerization Gillian Ryan, Dimitrios Vavylonis, Naoki Watanabe Animal cells that spread onto a surface often rely on actin-rich cell extensions called lamellipodia to execute cell protrusion. XTC cells on a two-dimensional substrate exhibit regular protrusion and retraction of their lamellipodium, even though the cell is not translating. Travelling waves of protrusion have also been observed, similar to those observed in crawling cells. These periodic fluctuations in leading edge position have been linked to excitable actin dynamics near the cell edge using a one dimensional model of actin dynamics, as a function of arc-length along the cell. In this work we extend this earlier model of actin dynamics into two-dimensions (along the arc-length and radial directions of the cell) and include a model membrane that protrudes and retracts in response to the changing number of free barbed ends of actin filaments near the membrane. We show that if the polymerization rate of these barbed ends changes depending on their local concentration at the leading edge and the opposing force from the cell membrane, the model can reproduce the patterns of membrane protrusion and retraction seen in experiment. We investigate both Brownian ratchet and switch-like force-velocity relationships between the membrane load forces and actin polymerization rate. [Preview Abstract] |
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B1.00011: Assessing the Effectiveness of Gravitational Wave Outreach Video Games Jonathan Wheeler Students and faculty at the Gravitational Wave Group in Birmingham, UK developed a remake of the classic 1972 game of Pong. Black Hole Pong was developed to be used in events such as science fairs as a way to engage children and pique interest in black holes. I describe a proposed study to assess the utility of Black Hole Pong and its successors in raising awareness of gravitational wave research, and in fostering conceptual understanding of astrophysics and gravity. Of particular interest in this study is potential use in high school science classrooms during astrophysics units. [Preview Abstract] |
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B1.00012: Wearable Fluorescence Imaging System for Intraoperative Guidance. Christopher Mela, Frank Papay, Yang Liu Surgeons rely on pre-operative and intraoperative imaging technologies such as MRI, CT and ultrasound to guide medical procedures. Due to their cost, complexity, large size and potential risks associated with their long term use these technologies can be cumbersome to implement. Also, it can be difficult to correlate the surgical landscape with the pre-operative images during a surgery. Recently, significant efforts have been directed towards optical modalities, such as fluorescence imaging, due to their high sensitivity and small size. Wearable imaging systems are being developed to overcome challenges encountered during image guided surgeries by implementing a real-time, intraoperative imaging system that can delineate unhealthy lesions from healthy tissue at the surgical site. We present a wearable, intraoperative fluorescent imaging system which provides the surgeon with a real-time, line-of-sight view of the fluorescent information on the surgical landscape. The system is also the first of its kind to offer wide-field, stereoscopic imagery, providing the surgeon with depth perception. Additionally, our system incorporates both a hand-held fluorescence imaging microscope module for detailed site inspection and also a portable ultrasound module for added depth information. The relative low cost of our system, as well as its highly modifiable and modular design, provides for tremendous potential in a variety of surgical settings and applications. [Preview Abstract] |
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B1.00013: Structural Determination of Chelating Mn(II) Complexes at Variable pH using Electron Paramagnetic Resonance Spectroscopy Michael Petronek, Doros Petasis Chelating compounds are utilized in a variety applications due to their ability to bind around a metal complex at multiple sites. Studies have reported a hexadentate (six-point) coordinate structure when bound to Mn(II), which is the theoretical expectation for polydentate molecules. Previous results have also revealed both seven and five coordinate structures while doing similar EPR studies. This study focuses on the binding nature of EDTA, DTPA, and EGTA when bound to Mn(II). Each polydentate compound is bound to Mn(II) at pH$=$3,7, and 10-11 in order to determine the effects of pH on the structure on such chelating compounds. This study uses Electron Paramagnetic Resonance Spectroscopy (EPR) which utilizes the paramagnetic properties of Mn(II) to reveal the structural elements of the compounds. We have found that at an acidic pH, polydentate compound binding is inhibited which may lead to the production of lesser coordinate sites (i.e. 5-point compounds) which is due to the addition of excess H$^{\mathrm{-\thinspace }}$ions in an acidic solution. At both a basic and neutral pH, results appeared consistent with one another which are indicative of the expected hexadentate compound. These results are good indicators of the binding behavior of these polydentate compounds at various pH levels, but it would be prudent to study each of these compounds at a wider range of pH levels, taking advantage of intermediate ones. [Preview Abstract] |
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B1.00014: Passively Mode-locked Holmium-doped Fiber Oscillators Optimized for Ho:YLF Amplifier Seeding Colleen Bransley, Peng Li, Axel Ruehl, Ingmar Hartl We present soliton operation of holmium-doped fiber oscillators with independently tunable central wavelengths from 2040nm to 2070nm and spectral widths from 5nm to 10nm, which can be matched to the requirements of Ho:YLF amplifiers. [Preview Abstract] |
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B1.00015: Investigations of a ring shaped sheath using a dusty plasma William Theisen, Andrew Kurtz, Terrance Sheridan Dusty plasma particles in a confining potential ring regularly form into a single layer dust ring that sits above the electrode. The ring shaped sheath is generated using an electrode consisting of a variable aperture with a center boss. The height of the ring above the electrode can be measured and depends on a number of variables including the radius of the aperture. Measurements showed that the smaller the aperture, the higher the dust ring sits above the electrode. Measurements of the confining potential were also performed using the vibrational modes of the trapped dust particles. [Preview Abstract] |
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B1.00016: Polymer phase transitions in a dense solvent Ryogo Suzuki, Mark Taylor In this research, we investigate the physics of a model polymer in explicit solvent using computer simulations. In particular, we examine how the presence of explicit solvent affects the conformational phase transitions of a polymer chain between expanded, collapsed, and folded states. We study a flexible 16-bead square-well-sphere chain with short-range interactions in a hard sphere solvent across a range of solvent densities. Using the Wang-Landau algorithm we compute the single chain density of states for this system and thus are able to construct the canonical partition function. From the partition function we can determine all thermodynamic properties, including average energy, specific heat, and energy probability distribution functions. We find the dense hard sphere solvent acts to slightly stabilize the folded state of the chain and suppresses the polymer collapse transition. [Preview Abstract] |
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B1.00017: Effects of confining a polymer chain in a cylindrical pore Christian O'Neil, Mark Taylor Polymers attached to a surface can change the properties of that surface drastically. These tethered polymers can undergo conformational transitions (e.g., change between expanded, collapsed or folded shapes) that provide additional control of surface properties. Tethering polymers inside pores in a surface might provide an on/off switch between a polymer coated surface (chains expanded) and a polymer free surface (chains folded and retracted into the pores). Here we study the effects of confinement in a cylindrical pore on the phase transitions of a single polymer chain. In particular, we study the all-or-none folding transition of a 32 bead square-well-sphere chain with a short-range interaction. We carry out Monte Carlo computer simulations using the Wang-Landau algorithm to obtain the single chain density of states for this system. These results allow us to determine phase transition temperatures and thus, investigate how confinement affects phase behavior. For narrow pores we find a small entropic stabilization of the folded chain with decreasing pore diameter. [Preview Abstract] |
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B1.00018: Folding transitions of a flexible/semi-flexible diblock or linked copolymer Christian Walker, Mark Taylor Many chain macromolecules, such as proteins, undergo a folding transition into an ordered three-dimensional configuration for appropriate solvent conditions. In this research, we study the protein-like folding transition of the diblock copolymer. The model diblock copolymer is built by connecting two different chain segments, which each consist of Nseg square-well beads but have different bond lengths and thus different flexibilities (which is set by the bond length). We also study the effects of connecting the two identical domains via a semi-flexible hard-sphere linker consisting of Nlnk beads. We use Wang-Landau computer simulations to compute the density of states of this model and from this we construct the canonical partition function which gives all thermodynamic information about the system. Under the right conditions, we find that these diblock copolymers can undergo an all-or-none freezing transition in which the chains abruptly fold into compact structures with varying degrees of crystalline order depending on flexibility of the domains. [Preview Abstract] |
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B1.00019: Room-Temperature Microwave Power Detection from an Anharmonic Dipolar Resonance Nitin Parsa, Michael Gasper, Ryan Toonen, Mathew Ivill, Samuel Hirsch Electric-field-induced, anharmonic dipolar resonances of room-temperature, barium strontium titanate thin films [Appl. Phys. Lett. 100, 222908 (2012)] have been used to rectify and detect microwave signals with frequencies ranging from 2 GHz to 3GHz. The resonant frequency was shown to have strong dependence on film thickness with some amount of voltage-controlled tunability. Our experiments involved lock-in detection of an amplitude modulated microwave signal with power levels ranging from -20 dBm to $+$10 dBm. An on-resonant power detection sensitivity of 0.45 mV/mW was observed and shown to have built-in band-pass filtering corresponding to the resonant line shape. This characteristic could be exploited to eliminate the need for external filters that would be realized using traditional circuit components. Because the thin films were produced using a relatively inexpensive solution deposition method, we believe that our observed phenomena could be exploited for the purpose of reducing the cost and increasing the availability of biomedical instrumentation that relies on microwave power detection of industrial, scientific and medical (ISM) radio band frequencies ranging from 2.4 GHz to 2.5 GHz. [Preview Abstract] |
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B1.00020: Life Science Small Group Learning Lessons for Trigonometry Based General Physics Samantha Snelling The General Physics course at Andrews University has transitioned to a format that includes a Small Group Learning (SGL) problem solving period facilitated by Learning Assistants (LAs). Modeled in part after the University of Colorado Boulder's LA Program$[1]$ , this new format encourages active learning in problem-solving groups of three or four through discussion and synthesis. Motivated by the American Association of Medical Colleges and the large percentage of medical track students, the LA coordinator and lead professor have offered SGL lessons that show ``how current medical knowledge is scientifically [and physically] justified'', facilitate ``curiosity, skepticism, objectivity, and the use of scientific reasoning'' in understanding biological processes and medical procedures, and encourage ``the ability to synthesize information and collaborate across disciplines''.$[2]$ This poster will include examples of topics they have used: ballistocardiographs, motion and energy of kinesin, velocity and pressure in blood vessels, diffusion, electrophoresis used in DNA testing, ultrasound, axon conduction and resistance, x-ray diffraction used for determining the shape of DNA, PET and MRI scans and nuclear medicine. \\ $[1.]$ http://laa.colorado.edu/ \\ $[2.]$ American Association of Medical Colleges. AAMC-HHMI Committee. Scientific Foundations for Future Physicians. 2009. [Preview Abstract] |
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B1.00021: Room-Temperature Radio Frequency Bolometer based on Carbon Nanotube Thin Films Michael Gasper, Ryan Toonen, Samuel Hirsch, Mathew Ivill, Henning Richter, Ramesh Sivarajan Carbon nanotube (CNT) thin films deposited on sapphire substrates have been used to realize a microwave power sensor that operates at and above room temperature. The detector includes a power-sensitive resistor (provided by a CNT-based device) that has been incorporated into a voltage divider circuit. Using lock-in detection, experiments were performed with 915 MHz test signals that showed detection over the power range of -45 dBm to 0 dBm -- with 0 dBm being limited by the maximum level attainable from available equipment. A sensitivity of 0.36 mV/mW was achieved with a slightly-cooled device held at a temperature of 15 C. Additional experiments (which included static and pulsed current versus voltage measurements) indicate that the primary physical mechanism responsible for power detection near room temperature is Joule heating (a resistance change due to self-heating). Since the techniques involved in producing the CNT-based devices is relatively inexpensive, we believe that technology based on our observations could reduce the cost of biomedical instrumentation that relies on the detection of microwave power from the industrial, scientific and medical (ISM) radio frequency band of 902MHz to 928MHz. [Preview Abstract] |
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B1.00022: Developing Affordable Wet-Sample Electron Microscopy Integrated with a Temperature Controlled Sample Holder Daniel Terrano, Petru Fodor, Kiril Streletzky Scanning electron microscopy (SEM) is widely used to analyze the size, shape and composition of material systems. However, using this tool for analyzing systems such as particles suspended in solution, requires drastic sample alterations, such as precipitation and fixation. Besides altering their environment, this exposes the particles to the harsh conditions within an electron microscope, such as high vacuum and electron beam exposure. To this end, the first goal of this study was to develop methodologies for imaging wet samples using electron microscopy. This is realized by creating a sandwich structure containing the solution of interest between a partially electron transparent window and a silicon substrate. The ability of the developed imaging cells to provide good imaging conditions is demonstrated with a variety of samples including polystyrene spheres, polymeric microgels and spindle shaped nanoparticles. As some of the systems investigated are temperature sensitive, the second goal of the project was to develop a temperature controlled stage that can be integrated with the SEM. In the future this heating stage will be used alongside the wet samples to image microgels above and below their critical solution temperature. [Preview Abstract] |
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B1.00023: Recombination lifetime measurements in GeSn alloys using transmission modulated photoconductive decay Matthew Mircovich, Emily Erdman, Jay Mathews Silicon photonics requires the development of Si-based lasers, modulators, waveguides, and detectors operating in the infrared beyond the band gap of silicon. GeSn alloys represent a possible solution to this problem. The band gap of GeSn is tunable with Sn concentration, and GeSn films are currently being grown on Si platforms. One important metric necessary for the realization of high-efficiency optoelectronic devices from semiconductor films is the recombination lifetime. Unfortunately, lifetime measurements can be quite difficult in thin films. A new system for lifetime measurement, called transmission modulated photoconductive decay (TMPCD) has been proven to be suitable for lifetime measurements in thin films. In this work, we will describe the fabrication of such a system and present preliminary results of measurements performed on GeSn thin film samples. [Preview Abstract] |
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B1.00024: How thick is human hair?$\backslash $f1 Eva Stanton, Traven Wood, Gabriela Popa In this experiment, we measured the thickness of human hair using two techniques. When the light from a laser beam falls on a single strand of hair, creates a diffraction pattern that we projected on a screen. Using the diffraction pattern, we calculated the width of the strand of hair. In the second method, we used a microscope connected to a computer. We analyzed different types of hair, including colored and not colored ones. We also measured rabbit and cat hair. We will present the analysis and precision of each method. [Preview Abstract] |
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B1.00025: Simulations of light propagation in dielectric materials with the finite difference time domain (FDTD) method Nathaniel Hawk, Jutta Luettmer-Strathmann Electromagnetic simulations allow for the study of light propagation in complex systems. There are many interesting optical geometries utilized today in the area of photovoltaics. By simulating material of various dielectric and conductive properties, we can experiment with geometries to “tune” optical systems. This is useful not only in the area of photovoltaics but in optical sensor design and many other areas. We have simulated materials using the finite difference time domain (FDTD) method in one, two and three dimensions. We created a simple one-dimensional simulation to validate the functionality of our finite difference calculations. We have simulated three dimensional dielectric sphere configurations as well as two dimensional parabolic mirror configurations at various frequencies. The results of the parabolic mirror simulations show that the intensity of the electric field in steady state forms unique interference patterns for each frequency near the focal point. This suggests that geometric structures may be tuned for specific frequencies and their harmonics by exploiting these interference geometries. [Preview Abstract] |
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B1.00026: MLC Optimization for VMAT Treatment Planning. Sarah Chamberlain, Daryl Nazareth, Samuel French In a linear accelerator used for radiation therapy, the Multi Leaf Collimator (MLC) is the final barrier that shapes the x-ray beam before the beam is incident on the patient anatomy. The MLC contains 120 leafs, that are able to slide independently in and out of the field during treatment delivery. In Volumetric-Modulated Arc Therapy (VMAT), a form of x-ray therapy, the gantry rotates almost 360 degrees about the patient, allowing the x-ray beam to be delivered continuously during motion. This complex mode of treatment is planned using sophisticated commercial clinical software which takes the organs at risk (OAR) constraints, the prescription dose, and the anatomical CT image as input, and uses optimization algorithms to determine the configuration of each leaf for an optimal treatment plan. In order to optimize the treatment plan further, we use a Monte Carlo software package, Electron Gamma Shower (EGS) with add-ons BEAMnrc and dosxyznrc, which calculate dose distributions by simulating the individual path of particles through the linear accelerator to a phantom or patient CT image. In order to use the BEAMnrc algorithms, software was developed in the Matlab environment that extracts the patient plan's data from Eclipse and performs dose calculations with BEAMnrc. The Matlab software will use Dose Volume Histograms to evaluate the plan, and then BEAMnrc will modify MLC leaf positions and recalculate dose in order to optimize a clinical objective function. This will result in a method that improves VMAT treatment plan quality. [Preview Abstract] |
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B1.00027: Deducing Shape of Anisotropic Particles in Solution from Light Scattering: Spindles and Nanorods. Ilona Tsuper, Daniel Terrano, Kiril Streletzky Depolarized Dynamic Light Scattering (DDLS) enables to measure in situ rotational and translational diffusion of nanoparticles suspended in solution. The particle size, shape, diffusion, and intermolecular interactions can then be interpreted from the DDLS data using various models of diffusion. Incorporating the technique of DDLS to analyze the dimensions of effortlessly imaged elongated particles, such as Iron (III) oxyhydroxide Spindles (FeOOH) and gold coated Nanorods, enables a further comprehension between rotational and translational diffusion, in conjunction with the size distribution of hard-to-image anisotropic wet systems such as micelles, microgels, and protein complexes. The emphasis of this study assessed an aged FeOOH Spindle sample, and explored the size distribution and modeling of the Nanorod particles. The light scattering results obtained from the basic model of non-interacting prolate ellipsoids offered dimensions similar (within 15%) to the size distribution from the Scanning Electron Microscope (SEM). The results, however, varied from the original particle size, potentially ensuing from sample aging and agglomeration of the FeOOH Spindles. Conversely, the Nanorod dimensions obtained from the Prolate Ellipsoid Model differed by a factor 1.2-2 from the value [Preview Abstract] |
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B1.00028: \textbf{Controlling ferrofluid droplets motion using surface tension gradients and magnetic fields} Mohan Panth, Khalid F. Eid, Andrew Sommeres, Ody Taylor Ferrofluids are suspensions of magnetic nanoparticles in carrier liquid and they exhibit interesting properties. With the application of external magnetic field, we can control the properties and flow of these liquids significantly. Ferrofluids have many potential biomedical and technological applications and are already used in sealing hard disc drives, x-ray tubes, controlling heat in loudspeakers. In our study, we prepare a hydrophobic copper surface with hydrophilic, wedge-shaped aluminum-covered areas. The surface tension gradients created on these surfaces facilitate the spontaneous motion of the ferrofluid droplets towards the more hydrophilic Al parts, due to a net capillary force exerted by the surface tension gradients. We observed that applying a magnetic field parallel to the surface tension gradient direction has little effect on the motion, while a strong perpendicular magnetic field can stop the motion. We observe a pinning of drops in perpendicular magnetic field of 250 Gauss (G) but there is motion in parallel fields up to 1500 G. We measure the maximum velocity when a ferrofluid droplet is placed on those wedges and the average velocity along the whole wedge. The contact angle at different magnetic fields (0, 500, 1000, and 1500 G) is also studied on both hydrophobic and hydrophilic surfaces. In perpendicular magnetic field, the field lines created by the electromagnet create nanoparticle chains that oppose the motion of the ferrofluid resulting in high viscosity and in parallel the field lines align with the direction of motion of ferrofluid and thus facilitate the motion by decreasing the viscosity. [Preview Abstract] |
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B1.00029: A reliable method for sample loading during metabolic monitoring under high pressure MILLICENT GIKUNDA, Paul Urayama In previous publications, we presented a system for monitoring cellular metabolism under pressure, designed around a simple-to-construct, capillary-based spectroscopic/imaging chamber coupled to a microliter-flow perfusion system. The millimeter-sized capillary chamber functions up to 100 MPa, spanning most of the biosphere's pressure range. The perfusion system consists of two screw pump generators with one generator being compressed while the other is retracted, maintaining pressurization during flow. Although metabolic transitions can be controllably induced and monitored using the system (validated under pressure by monitoring the cyanide-induced response of UV-excited autofluorescence from \textit{Saccharomyces cerevisiae}), the previous sample-loading protocol was not well controlled. Here, we present a reliable approach for loading cellular samples, using a secondary capillary into which the sample is loaded, which is then inserted into the chamber. As validation, we demonstrate the ability to measure fluorescence from labeled microspheres, and to observe the cyanide-induced autofluorescence response in \textit{S. cerevisiae}. This study contributes to the development of monitoring approaches for studies involving the interaction between the physical environment with cellular metabolism. [Preview Abstract] |
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B1.00030: Using spectral-phasor analysis to assess NADH conformation under pressure Laxmi Risal, Paul Urayama Reduced nicotinamide adenine dinucleotide (NADH) plays an important role in cellular metabolism, serving as an electron carrier in energy-related metabolic pathways. NADH conformational state -- whether it is folded or unfolded -- has physiological and biophysical significance because NADH is largely folded in solution and unfolded when protein bound. Previously, we presented measurements of UV-excited NADH fluorescence under pressure up to 50 MPa, observing that the emission spectrum shifts to longer wavelengths upon pressurization. In order to separate shifts due to a conformational change from shift due to changes in solvent coupling, we applied a two-state solvent denaturation model, allowing us to estimate the thermodynamic volume change of the folding-unfolding transition. Here, we further assess this two-state assumption using spectral phasor analysis. A spectral phasor is the first harmonic of a spectrum's Fourier transform; a plot of the phasor's imaginary versus real components is useful for the analytical assessment of a fluorescent sample because phasors from a two-component system lay along a line. We discuss the validity of the two-state model and the volume change estimate in the context of spectral-phasor analysis results. [Preview Abstract] |
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B1.00031: Ti-based Catalysts for the Methanol Conversion as an Alternative Energy Source DoWoon Yoon, Byeongyeon Cho, Richard Kyung The United States has more natural gas than petroleum. If we are able to exploit that abundance by converting it to methanol, then the dependency on foreign fuel would be reduced. Prior research results have been controversial regarding the efficiencies of each catalyst. However, the contradictory results are due to inconsistencies of the theoretical and computational models, which we reconcile in our model. Places for oil production are becoming more and more costly, therefore, alternatives need to be considered before they run out. At the end of the study, the catalytic efficiency of TiCl$_{\mathrm{2}}$O, TiO, and TiClO will be modeled and explained based on the compound's electron structure and how the catalytic efficiency could be improved even more by forcing the catalyst to react with methane in different ways. The Density Functional Theory will be used to prove that TiCl$_{\mathrm{2}}$O is the best catalyst for the conversion of methanol, which will advocate the methanol~economy. [Preview Abstract] |
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B1.00032: Biomechanical Fracture Analysis on the Human Bone Jinyoung Lim, Jae Hoon Choi, Haban Weon Bone fractures occur from low-energy or high-energy injuries. At the time of the fracture, soft tissue injuries may also occur. Individuals who have an increased risk of developing stress fractures are those who participate in training that is of high-intensity and repetition. Through understanding bone mechanics, the causes of bone injuries can be understood. The purpose of this research is to evaluate stress and fracture conditions in the tibia by using biomechanical analysis. Two procedures are included in this research: the examination of biomechanical properties of bones, and the development of biomechanical and mathematical modeling of bones. By utilizing both of the procedures together with the technique of bone remodeling, the impact conditions that cause bone fractures and the physiological solutions (maximum stress) of the bones can be found. The results can be compared to the empirical results, and the data could help improve the surgical treatment of knee arthroplasty. It is suggested in the simulation for the tibia that a higher level of stress is distributed and exhibited to those proximal tibial sites; compared to the middle portion of the shank, or to the distal tibia-fibula junction. [Preview Abstract] |
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