The 5th Annual

NC State University

Undergraduate Summer Research Symposium

 

REU Physics


Abstracts are listed in alphabetical order by the last name of the corresponding author.

 

 

 

Student Author(s): 

Bell, Mozella

Home Institution:

Grambling State University

Program:

REU Physics

Department(s):

Physics

Research Mentor(s): 

Keith Weninger/Physics

Title of Presentation:

The Use of Infrared Lasers in the Detection of FRET

 

 

Fluorescence resonance energy transfer (FRET) is a distance-dependent interaction between the electronic excited states of two dye molecules in which excitation is transferred from a donor molecule to an acceptor molecule without emission of a photon.  The efficiency of FRET is dependent on the inverse sixth power of the intermolecular separation, making it useful over distances comparable with the dimensions of biological macromolecules. Thus, FRET is an important technique for investigating a variety of biological phenomena that produce changes in molecular proximity. When FRET is used as a contrast mechanism, co localization of proteins and other molecules can be imaged with spatial resolution beyond the limits of conventional optical microscopy. In our experiment we are using an fluorescence microscope to validate the use of FRET in the infrared to study proteins and DNA.

 

 

 

Student Author(s): 

Chisnell, Robin M.

Home Institution:

Washington

University in St Louis

Program:

REU Physics

Department(s):

Physics

Research Mentor(s): 

Jerry Bernholc/Physics

Title of Presentation:

Structural Properties of Prion-Cu2+ Complexes

 

 

A change in the structure of the prion protein (PrP) is responsible for a group of neurodegenerative diseases including mad cow disease and Creutzfeldt-Jakob disease. Despite much research, the normal function of the protein is still unknown. The octarepeat domain of PrP (which is made of up to four repeats of the sequence PHGGGWGQ) is known to efficiently bind Cu2+. Because of  this efficiency, it was suggested that binding Cu2+ may be related to the normal function of PrP. Depending on the Cu2+ concentration the octarepeat domain may bind between one and four Cu2+ ions. In this project, we are investigating structural differences between the free protein and the various Cu2+ complexes, which may provide insight about the normal function of the prion protein. First, using molecular visualization software we build the initial structure of PrP. Then, molecular dynamics software is used to determine the equilibrium structure of the protein. Since classical molecular dynamics provides a poor description of Cu2+, we use binding site geometries obtained from quantum mechanical calculations to build the initial structures of the Cu2+-PrP complexes. When equilibrating these structures, the binding sites are kept fixed to  their quantum mechanical geometries. These equilibrated models are then analyzed and compared for structural differences.

 

 

 

 

Student Author(s): 

Cundari, Audrey L.

Home Institution:

Davidson College

Program:

REU Physics

Department(s):

Physics

Research Mentor(s): 

Laura I. Clarke/Physics

Title of Presentation:

Measuring the Barrier to Rotation of the 3-APS molecule using Dielectric Spectroscopy

 

 

Corrosion and friction are serious problems in the everyday world; a direct result of the intricate arrangement, movement, and electrical properties of a materials’ surface molecules.  Self-assembled monolayers containing silane molecules have important applications with regards to reducing friction and corrosion in a cost-effective and eco-friendly way.  The presence of internal rotation in these molecules (defined as the top portion of a molecule rotating with respect to a fixed base) may affect the frictional properties of a surface coated with these self-assembled monolayers.  A direct measurement of how easily a portion of the molecule turns with respect to another is known as the “potential barrier to rotation”.  By using amine-modified molecules, we studied the barrier to rotation in silane monolayers using dielectric spectroscopy.  In my poster, I will discuss the fabrication procedure for the silica electrodes upon which the silane monolayer was placed, the preliminary dielectric spectroscopy results, and an extensive literature search on various silane molecules’ barrier to rotation values.  The theoretical values will then be compared to the experimental results.

 

 

 

 

 

Student Author(s): 

Howell, Kelly M.

Home Institution:

Davidson College

Program:

REU Physics

Department(s):

Physics

Research Mentor(s): 

Laura I. Clarke/Physics

Jason Bochinski/Physics

Title of Presentation:

Rotational and Fluorescent Properties of Quinizarin in Well-Characterized Thin Films

 

 

Quinizarin (1,4-dihydroxyanthraquinone), a fluorescent molecule, has uses as a dye, as a fuel marker, in anticancer

drugs, and in persistent spectral hole burning. However, few experiments investigate thin films, in particular, monolayers, of quinizarin. This experiment, through the deposition on glass and silicon slides of a 4.625 mM solution of quinizarin in methylene chloride, reveals the time dependence for growing a monolayer of quinizarin. The film thickness was measured using ellipsometry and the samples were further characterized by measuring the contact angle of water on the slides. The goal of this project was to measure the fluorescence polarization anisotropy of these films to detect changes in rotational motion for varying temperatures. In order to see whether quinizarin rotates, polarized 475 nm diode laser light was shined on the samples and the intensity of the  resulting fluorescent light parallel and perpendicular to the excitation polarization was measured for temperatures from 8 K to 500 K.  This poster will show the results from the thin film growth and the preliminary data for fluorescence and anisotropy.

 

 

 

 

Student Author(s): 

Koepke, Matt E.

Home Institution:

West Virginia University

Program:

REU Physics

Department(s):

Physics

Research Mentor(s): 

Thomas P. Pearl//Physics

Title of Presentation:

Study of Chiral Thin Films: Tartaric Acid Deposited on Ag(111)

 

 

Scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) have been used to study the characteristics of tartaric acid deposited on Ag(111).  Since Ag(111) is an achiral surface, we chose to deposit chiral tartaric acid, both (R, R) and (S, S) enantiomers, to see if the molecule imposes chirality onto the surface.  This molecule helps us understand the role of hydrogen bonding in the formation of molecular domains.  First, to ensure an atomically smooth surface, the substrate is prepared inside an ultra-high vacuum chamber by ion sputtering and then annealed.  Tartaric acid was  then dosed by vapor phase exposure to Ag(111) at room temperature by heating the acid to 380K.  STM was performed at 17 K and 83 K to limit thermal excitations.  We found the tartaric to absorb near the step edges of metallic surface as well as form chiral domains.  Once we obtain a coherent understanding of the surface chemistry and its characteristics, we will be able to improve our ability to manipulate and image molecules deposited on the surface.

 

 

 

 

Student Author(s): 

Stampe, S.

Perkins, J.

Hanson, J.

Home Institution:

University of Rochester

Program:

REU Physics

Department(s):

Physics

Research Mentor(s): 

Robert Nemanich/Physics

Title of Presentation:

Position Dependent Periodic SERS of  Pyridine Adsorbed onto a Silver Nanopatterned Surface

 

         

Surface Enhanced Raman Spectroscopy (SERS) was employed to study pyridine absorbed onto a sample of LiNbO3 known to be covered with silver nanowires. Raman Spectroscopy is a technique in which laser light is inelastically scattered from a sample and the changes in frequency of the light are measured by a spectrometer.  Changes in the vibrational or rotational energy states of the molecules in the sample result in distinct bands of scattered light known as Raman bands; these bands can often be used to identify the molecules that are present.  SERS is an enhancement of the intensity of the Raman bands by greater than 106 which results when the molecule is close to a rough metal surface, usually silver or gold.  The samples used were prepared by covering the polarity patterned LiNbO3 substrate with 0.01M AgNO3 and exposing it to a mercury lamp. The presence of nanowires was determined using Atomic Force Microscopy (AFM); the images show wires that are approximately 100nm wide, several millimeters long, and spaced 10-15 ěm apart.  The samples were then covered with 0.1M pyridine and  employed for the SERS measurements.  As the laser was scanned across the sample in the direction perpendicular to the nanowires a periodic change in the strength of the SERS signal was observed.  Further investigation is required to confirm that the observed SERS signal originates from  the nanowires.  Possible applications of this technique include the identification of proteins or genetic material in solution as they move across the location of the wires. 

 

 

 

 

Student Author(s): 

Sulock, David L.

Home Institution:

North Carolina State University

Program:

REU Physics

Department(s):

Physics

Research Mentor(s): 

Lubos Mitas/Physics

Lucas Wagner/Physics

Title of Presentation:

Electronic Structure Calculations of BiFeO3

 

 

Ferroelectrics are materials that exhibit spontaneous polarization when an electric field is applied to them.  Antiferromagnetic materials have alternating spin up and spin down electron orbitals.  Bismuth Ferrite (BiFeO3) is a potentially interesting  and useful material because it exhibits both ferroelectricity and antiferromagnetism.  On top of having applications resulting from either  phenomena, the interaction between magnetic and ferroelectric effects in the same material could prove more useful than either effect used separately.

            Experimentally BiFeO3 has been reported to have a spontaneous polarization ranging from .06 C/m^2 to 1.50 C/m^2.  This is an extremely wide range of values, the highest of which is over twice as large as the industry standard ferroelectric material PZT. BiFeO3 could therefore be useful for applications such as ferroelectric RAM if the large experimental values are correct.  Theoretical efforts thus far within Density Functional Theory in the LDA approximation have settled on a value of around 0.95 C/m2; however, it is not clear that LDA provides a sufficient description of the material as it significantly mispredicts the lattice constant by ~.2 Angstroms and predicts a conducting state for some  atomic configurations which we know to be insulating.  To go beyond the results provided by LDA we use Diffusion Monte Carlo (DMC), which allows  us to treat the system more accurately but at a higher computational cost.  In order to obtain accurate results we simulate the motion of 400 interacting electrons in a realistic crystal, effectively enabling us to predict the energy barrier between the positive and negative polarization phases.  This is the first step towards understanding the potential energy surface which is necessary for accurate first principles simulations of the material and eventually a complete grasp of BiFeO3's polarization.

 

 

 

 

Student Author(s): 

Taylor, Courtney D.

Home Institution:

North Carolina State University

Program:

REU Physics

Department(s):

Physics

Research Mentor(s): 

Paul R. Huffman/Physics

Title of Presentation:

EPICS Data Acquisition System in the Search for a Non-Zero Neutron Dipole Moment

 

 

The measurement of a nonzero electric dipole moment (EDM) of the neutron would significantly impact our understanding of the nature of the electro-weak and strong interactions. The goal of the current experiment is to improve the measurement sensitivity of the EDM by two orders of magnitude.  The experiment is based on the magnetic-resonance technique of rotating a magnetic dipole moment in a magnetic field. The measurement of the neutron EDM comes from a measurement of the difference in the precession frequencies of neutrons when a strong electric field parallel to the magnetic field is reversed.

            This construction project is divided into a number of subsystems, five of which require automated control.  The Experimental Physics and Industrial Control System (EPICS) is a slow-controls data acquisition (DAQ) system and is the system of choice for this experiment.  It was selected for both its ease of use and ability to act as a total control system for large systems.  As part of the initial research and development for the EDM project, we are setting up a prototype system that will eventually be copied and sent to the subsystem managers.  This prototype consists of a VME crate housing a single board computer and DAQ modules.  EPICS, running on a PC with CentOS Linux-x86, interfaces with the VME single board computer and provides a graphical user interface for the control system. The details on building this prototype DAQ system will be presented.

 

 

 

 

Student Author(s): 

Warren, Donald C.

Home Institution:

North Carolina State University

Program:

REU Physics

Department(s):

Physics

Research Mentor(s): 

Don Ellison/Physics

John Blondin/Physics

Title of Presentation:

Hydrodynamic Simulation of Supernova Remnants with Cosmic Ray Acceleration

 

 

                  

Supernovae, violent explosions associated with the deaths of massive stars, leave supernova remnants (SNRs) that are visible for thousands of years after the event.  SNRs are thought to be the primary source of Galactic cosmic rays (very-high-energy particles with origins inside the Milky Way, observed at Earth), but the efficiency of this process (the percentage of the supernova's energy that goes into producing cosmic rays) is unknown.  If the SNR very  efficiently produces cosmic rays, the gas in the remnant is highly compressible, which creates observable differences in the shape of the SNR.   Blast waves from supernovae typically have a “contact discontinuity” where ejecta from the star meet the surrounding medium, with a forward shock ahead and a reverse shock behind the discontinuity; additionally, in multiple dimensions instabilities arise in the contact discontinuity, making it asymmetric.  As cosmic ray production in the blast wave becomes more efficient, the material becomes more compressible, and the widths of the two shocked areas become smaller.  At high enough compressibilities, the instabilities in the contact discontinuity may reach up to or beyond the forward shock; such a structure has already been observed in, for example, Tycho's supernova remnant.  This project involves  simulating SNRs with hydrodynamic code, varying the efficiency of cosmic ray production, and calculating how the simulated remnants would look to modern telescopes.  Since many observations of the relative positions of the contact discontinuity and the forward shock have been made, it is then possible to estimate the efficiency of cosmic ray production of  well-known SNRs using these predicted morphologies.

 

 

 

 

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