Bulletin of the American Physical Society
Fall 2015 Joint Meeting of the Texas Section of the AAPT, Texas Section of the APS and Zone 13 of the Society of Physics Students
Volume 60, Number 15
Thursday–Saturday, October 29–31, 2015; Waco, Texas
Session J1: Atomic/Molecular Physics II |
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Chair: Ken Park, Baylor University Room: C.105 |
Friday, October 30, 2015 3:30PM - 3:42PM |
J1.00001: Dynamic nuclear polarization of $^{\mathrm{13}}$C-labeled amino acids. Christopher Parish, Peter Niedbalski, Sarah Ferguson, Andhika Kiswandhi, Lloyd Lumata Amino acids are targeted raw materials by cancers to sustain their rapid growth and proliferation. $^{\mathrm{13}}$C-enriched amino acids are important metabolic tracers for cancer diagnostics using nuclear magnetic resonance (NMR) spectroscopy. $^{\mathrm{13}}$C NMR of amino acids however is hampered by the inherently low NMR sensitivity of the $^{\mathrm{13}}$C nuclei. In this study, we have employed a physics technique known as dynamic nuclear polarization (DNP) to enhance the NMR signals of $^{\mathrm{13}}$C-enriched amino acids. DNP works by transferring the high polarization of electrons to the nuclear spins via microwave irradiation at low temperature and high magnetic field. Using a fast dissolution method in which the frozen polarized samples are dissolved rapidly with superheated water, injectable solutions of $^{\mathrm{13}}$C-amino acids with highly enhanced NMR signals (by at least 5,000-fold) were produced at room temperature. Factors that affect the NMR signal enhancement levels such as the choice of free radical polarizing agents and sample preparation will be discussed along with the thermal mixing physics model of DNP. [Preview Abstract] |
Friday, October 30, 2015 3:42PM - 3:54PM |
J1.00002: Dynamic nuclear polarization of carbonyl and methyl $^{13}$C spins: $^{13}$C acetate samples doped with trityl OX063 Peter Niedbalski, Christopher Parish, Lloyd Lumata Dynamic nuclear polarization (DNP) is a physics technique that amplifies magnetic resonance signals by several thousand-fold for NMR spectroscopy and imaging (MRI). Herein we have investigated the effect of carbon-13 isotopic location on the DNP of acetate (one of the biomolecules commonly used for metabolic imaging) at 3.35 T and 1.4 K using a narrow ESR linewidth free radical trityl OX063. We have found that the carbonyl $^{13}$C spins yielded about twice the polarization produced in methyl $^{13}$C spins. Deuteration of the methyl group, though beneficial in the liquid-state, did not produce an improvement in the polarization level at cryogenic conditions. Concurrently, the solid-state nuclear relaxation of these samples correlate with the polarization levels achieved. These results suggest that the location of the $^{13}$C isotopic labeling in acetate has a direct impact on the solid-state polarization achieved and that polarization efficiency is mainly governed by the nuclear relaxation leakage factor. [Preview Abstract] |
Friday, October 30, 2015 3:54PM - 4:06PM |
J1.00003: Electron relaxation of DNP free radical DPPH at W-band Armin Khamoshi, Pavanjeet Kaur, Peter Niedbalski, Likai Song, Lloyd Lumata Hyperpolarization via dissolution dynamic nuclear polarization (DNP) is a method of enhancing the nuclear spin alignment, hence the magnetic resonance signals, by up to four orders of magnitude. Central to the DNP process are the sources of free electrons, mainly provided by free radicals, where their high polarization is transferred to the nuclei via microwaves. The stable spin-1/2, organic free radical 2, 2-diphenyl-1-pycrylhydrazyl or DPPH is an efficient polarizing agent for dissolution DNP. In this study, we have investigated the temperature dependence of spin-lattice relaxation rate T1 of DPPH in W-band in temperatures ranging from 4K to 250K. Electron spin resonance (ESR) data at concentrations optimal for DNP (20 mM and 40 mM) show that the nitroxide-based DPPH has a relatively-wide ESR linewidth due to the hyperfine coupling of the free electron with nitrogen-14. W-band ESR data reveal in both concentrations the behavior is in accordance to high temperature limit of the one-phonon direct process prediction. These results and its implications in DNP efficiency will be discussed together with 13C DNP data taken at 3.35 T. [Preview Abstract] |
Friday, October 30, 2015 4:06PM - 4:18PM |
J1.00004: Analysis of Soils Using Laser-Induced Breakdown Spectroscopy Brian Ko, Dmitri Voronine, Jeremy Kunz, Zachary Liege, Alexei Sokolov, Marlan Scully Laser-induced breakdown spectroscopy is a useful technique in agriculture due to its ability to rapidly detect the elemental composition of the sample, such as soil. Using LIBS, qualitative analysis of elemental abundances and deficiencies can be quickly performed, increasing crop yields and reducing waste. In this experiment, soil samples enriched with different commercial fertilizers were analyzed using a picosecond laser system in order to detect changes in trace element concentrations. [Preview Abstract] |
Friday, October 30, 2015 4:18PM - 4:30PM |
J1.00005: High-Sensitivity and High-Resolution Magnetic Gradiometry and Thermometry with Nitrogen---Vacancy Diamond Tipped Fiber Probes Sean Blakley, Ilya Fedotov, Evgeniy Serebryannikov, Lyubov Doronina-Amitonova, Hector Perez, Joe Becker, Nikolai Safronov, Sergei Kilin, Vladimir Velichansky, Philip Hemmer, Marlan Scully, Aleksei Zheltikov This talk will demonstrate the performance of our high-sensitivity and high-resolution nitrogen---vacancy diamond (NVD) gradiometer and thermometer fiber probes. By employing an optically detected magnetic resonance (ODMR) technique involving through-fiber optical interrogation and readout of an NVD on a fiber tip with fiber integrated microwave excitation, we are able to assess the temperature and field gradient environment around the probe. We use multiple probe designs to achieve gradient sensitivities of 10$^{\mathrm{-7}}$ nT/nm(Hz)$^{\mathrm{1/2}}$, resolutions of 5 microns, and millikelvin accuracies in a package amenable to in situ measurements in challenging biological environments. [Preview Abstract] |
Friday, October 30, 2015 4:30PM - 4:42PM |
J1.00006: Construction and design of an apparatus to study the Z-dependence of bremsstrahlung produced by 5 keV electrons incident on thick targets Sean Czarnecki, Scott Williams, Ashton Short The design and construction of an apparatus to study the bremsstrahlung produced by 5 keV electrons incident on thick Al, Cu, Zn, Ag, Sn, W and Au targets is described. The purpose of the experiments is to measure the Z-dependence of bremsstrahlung for several photon energies in the range of 3 keV - 5 keV in order to determine whether or not polarizational bremsstrahlung (PB) contributes to the total bremsstrahlung spectrum in experiments involving thick, solid targets. Unlike ordinary bremsstrahlung (OB), which is emitted by a charged particle when it is accelerated in the Coulomb field of a target atom, PB (which theory predicts to have a different Z-dependence than OB) is emitted by a target atom's electrons as the Coulomb field of the incident charged particle polarizes the atom. The results of our experiments will be compared to the simulated results of the Monte Carlo code, PENELOPE, which is based on OB theory alone, and does not consider any PB contributions. If the comparison suggests that bremsstrahlung emitted in solid-target experiments includes a significant PB contribution, it means that the PENELOPE code (which is commonly used in medical physics for dosimetry) underestimates the intensity of radiation emitted by medical X-ray generators and needs to be corrected. [Preview Abstract] |
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