Bulletin of the American Physical Society
Joint Fall 2017 Meeting of the Texas Section of the APS, Texas Section of the AAPT, and Zone 13 of the Society of Physics Students
Volume 62, Number 16
Friday–Saturday, October 20–21, 2017; The University of Texas at Dallas, Richardson, Texas
Session K4: Biophysics and Soft Matter Physics I |
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Chair: Wei Chen, University of Texas at Arlington Room: DGAC 1.128 |
Saturday, October 21, 2017 10:30AM - 10:42AM |
K4.00001: Contrast-enhanced imaging at earth's magnetic field Alan Zanders, Qing Wang, Peter Niedbalski, Lloyd Lumata Magnetic resonance imaging (MRI) is a non-invasive imaging modality that exploits the magnetic properties of nuclei and their response to magnetic field gradients to encode the spatial information of objects. One of the requirement for high-resolution MRI is the high homogeneity of magnetic field to produce the images. Homogeneous field strengths of 1 Tesla (T) or more are commonly used for clinical purposes. Another source of homogeneous field is the Earth's magnetic field, but its strength is only about 0.00003 T. Moreover, the slow rate of data acquisition in EFMRI, which is associated with the low field makes contrast imaging challenging. In this work, we explore the possibilities of generating image contrast with EFMRI at 0.3 Gauss using an established procedure that is common in clinical setting, namely by doping with trace concentrations of Gd-DOTA. Various images were acquired using common imaging techniques such as Gradient Echo (GE) and Filtered Back Projection (FBP). The echo time (TE) was varied for T2 contrast, and repetition time (TR) was varied for T1 contrast. These MRI results will be discussed in relation to the effectiveness of generating contrast in MRI at earth's magnetic field. [Preview Abstract] |
Saturday, October 21, 2017 10:42AM - 10:54AM |
K4.00002: The stability and reactivity of the DNP-NMR polarizing agents galvinoxyl, DPPH, 4-oxo-TEMPO, and trityl OX063 Luke Jeremiah Davis, Peter Niedbalski, Lloyd Lumata The organic free radicals galvinoxyl, DPPH, 4-oxo-TEMPO, and trityl OX063 are efficient polarizing agents used for fast dissolution dynamic nuclear polarization (DNP) NMR spectroscopy. In this study, ultraviolet-visible (UV-Vis) spectroscopy was used to estimate the molecular stability of these free radicals with respect to time, across varying temperatures, and in the setting of the naturally-occurring antioxidants glutathione or ascorbic acid. ESR spectroscopy was then used to investigate the degree of reactivity of each polarizing agent in the setting of various concentrations of either glutathione or ascorbic acid. Our time-dependent UV-Vis results show slight degradation of the $\pi $-conjugated system of galvinoxyl but, otherwise, no appreciable decay of the other molecules' conjugated system(s) or functional group(s). Overall, these results and other relevant findings of this study supplement prior research on these polarizing agents and may thereby facilitate further optimization of DNP-NMR bioimaging. [Preview Abstract] |
Saturday, October 21, 2017 10:54AM - 11:06AM |
K4.00003: Development of Instrumentation and Metrology for Low Magnetic Field Bio-Imaging Susana Beltran, Joshua Biller, Karl Stupic, John Moreland Because of the weak interaction of the proton magnetic moment with applied field, large applied static fields are necessary for adequate signal to noise ratios (SNR). An alternative route to increasing the SNR in a NMR or MRI experiment is to hyperpolarize the spins by placing them close to stable paramagnetic centers. For the same field strength, the paramagnetic centers are polarized 658x more than the protons, and some of this polarization can be transferred to the protons in a process called dynamic nuclear polarization (DNP). Solution state DNP can be applied to enhance NMR and MRI signals at low fields (\textless 0.3T); however, the process is still not understood well enough to make quantitative measurements. Recently a digital NMR was constructed at NIST2 and has been extended to include DNP operation programmed with LabVIEW. Along with the DNP experiment, the instrument can measure T1H with a simple single pulse saturation recovery experiment (SPSR). However, the SPSR suffers from a larger measurement error (\textpm 10{\%}) than the more commonly used inversion recovery sequence. To reduce error in the T1H measurement, work was undertaken to program in an inversion recovery sequence with composite pulses and an eight-step phase cycle. [Preview Abstract] |
Saturday, October 21, 2017 11:06AM - 11:18AM |
K4.00004: Mechanical Feedback in the \textit{Drosophila melanogaster }Embryo: Robustness and Intercellular Coordination Michael Holcomb, Guo-Jie Gao, Jeffrey Thomas, Jerzy Blawzdziewicz Successful embryonic development hinges on morphogenetic processes working in concert and requires both cellular coordination and the ability to continue development in spite of perturbations. We believe that this coordination and robustness are largely accomplished through intricate intercellular communication via mechanical stress fields and associated feedback mechanisms. The importance of chemical signaling to biological development is undeniable; however, mechanical stress has been shown to play an important role in tissue development. Systematic methods of studying the harmonization of cellular activities through mechanical stress and feedback within a tissue have yet to be developed. Motivated by the need for such methods, we introduce two novel modeling platforms which capture different aspects of ventral furrow formation (VFF), the initiating morphogenetic process of gastrulation in the Drosophila embryo. Both platforms represent cells as mechanically excitable objects which experience pairwise interactions; however, the first considers cells to be fully three dimensional, soft, non-spherical objects while the second hones in on the outer surface by simplifying cells into discs. Using these models, we explore how mechanical feedback can facilitate the robustness of VFF. [Preview Abstract] |
Saturday, October 21, 2017 11:18AM - 11:30AM |
K4.00005: Modelling Spread of Oncolytic Viruses in Heterogeneous Cell Populations Hana Dobrovolny Oncolytic viruses, which possess the ability to destroy or neutralize cancer cells, offer a possible alternative treatment for cancer. Existing mathematical models are focused on the effects of virus infection on tumor cells, but do not consider possible spread of the virus to normal healthy cells. We have developed a mathematical model of oncolytic virus infections of tumors that includes both tumor cells and neighboring normal cells. We use mathematical analysis and computer simulation to examine the conditions which lead to eradication of the tumor without serious damage to normal cells. We find that differences in infection rate between the two cell types are necessary for eradication of tumors while leaving normal cells unharmed. Differences in production rate or infected cell lifespan are not sufficient to protect healthy cells from infection. [Preview Abstract] |
Saturday, October 21, 2017 11:30AM - 11:42AM |
K4.00006: Ultrasensitive Detection of Dopamine by Combined Theoretical and Experimental Raman Studies Felicia Manciu Detection of trace amounts of neurotransmitters has become significant in diagnostic applications. Theoretical and experimental analysis of dopamine (DA) at sub-nanomolar concentrations relevant to physiological levels is presented in this work. Surface-enhanced Raman spectroscopy (SERS) utilizing silver nanoparticles was used for experimental studies and quantum chemical density functional methods for calculations. The relatively good agreement between the simulated and experimental results suggests the possibility that different forms of the DA molecule, such as uncharged $DA^{\pm }$, anionic $DA^{-}$, and dopaminequinone are simultaneously present. All of these molecular configurations, in a SERS environment, lose the dominant DA Raman lines at 750 $cm^{-1}$and 790 $cm^{-1}$. The occurrence of these features would imply the potential presence of multilayer neutral $DA^{0}$, or that of cationic $DA^{+}$. From a redox reaction perspective, the dopaminequinone form is more likely detected during the oxidation process, while the $DA^{\pm }$ form probably occurs during reduction. The ultrasensitivity demonstrated in the experimental data, in combination with the theoretical analysis presented, provides valuable information for advancing the detection and monitoring of DA. [Preview Abstract] |
Saturday, October 21, 2017 11:42AM - 11:54AM |
K4.00007: Label-free Raman Imaging to Monitor Breast Tumor Signatures John Ciubuc, Giulio Francia, Karla Parra, Marian Manciu, Emma Sundin, Kevin Bennet, Felicia Manciu Methods built on Raman spectroscopy have shown major potential in describing and discriminating between malignant and benign specimens. Accurate, real-time medical diagnosis benefits from substantial improvements through this vibrational optical method. Not only is acquisition of data possible in milliseconds and analysis possible in minutes, but Raman allows concurrent detection and monitoring of all biological components. Besides validating a significant Raman signature distinction between non-tumorigenic (MCF-10A) and tumorigenic (MCF-7) breast epithelial cells, this study reveals a label-free method of assessing overexpression of epidermal growth factor receptors (EGFR) in tumor cells. EGFR overexpression gives rise to Raman features associated with phosphorylated threonine and serine, and modifications of DNA/RNA characteristics. Investigations by gel electrophoresis reveal EGF induction of phosphorylated Akt, agreeing with the Raman results. The analysis presented is a vital step toward Raman-based evaluation of EGF receptors in breast cancer cells. With the goal of clinically applying Raman-guided methods for diagnosis of breast tumors, the current results lay the basis for proving label-free optical alternatives for prognosis of the disease. [Preview Abstract] |
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