Bulletin of the American Physical Society
2013 Annual Fall Meeting of the APS Ohio-Region Section
Volume 58, Number 9
Friday–Saturday, October 4–5, 2013; Cincinnati, Ohio
Session E5: Biophysics, Chemical Physics, Material Sciences |
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Room: Braunstein Hall 312 |
Saturday, October 5, 2013 8:00AM - 8:12AM |
E5.00001: Electronic properties of DNA molecules including defects under elongation Sadeq Malakooti, Eric Hedin, Yong Joe DNA defects may explain the origin of many serious diseases in human body. A recently reported study of DNA flaws shows an increased blood cancer risk from type 2 diabetes [1]. It has also been shown that electrical charge transport properties of DNA molecules are dramatically changed by the presence of any structural defect, which makes an intriguing field of study for researchers. Therefore, we investigate quantum mechanical electron transport along DNA molecules of poly (dG) and poly (dC) base pairs with a single defect. In a tight-binding framework in conjunction with the theories of Slater-Koster and linear elasticity, electronic properties, such as the transmission spectrum and current-voltage characteristics, are studied for different defect locations and different molecular elongations. \\[4pt] [1] A. Bonnefond \textit{et al.}, Nature Genetics \textbf{45}, 1040 (2013) [Preview Abstract] |
Saturday, October 5, 2013 8:12AM - 8:24AM |
E5.00002: Magneto-optic properties and self-heating behavior of superparamagnetic Fe$_{3}$O$_{4}$ nanoparticles under alternating magnetic field and near infra-red (785 nm) excitation M.E. Sadat, Donglu Shi, David B. Mast The magnetic and optical properties and associated heating behavior in alternating magnetic field and electromagnetic radiation (optical) are investigated on the multifunctional superparamagnetic Fe$_{3}$O$_{4}$ nanoparticles (SPION) for biomedical applications. It is found that SPION can effectively convert energy into heat under magnetic field and near infra-red (NIR) radiation. A rise of local temperature to 43-45 $^{\circ}$C, above the physiological temperature of 37 $^{\circ}$C, is achieved by these external fields, which can effectively kill cancer cell. In this work, four different Fe$_{3}$O$_{4}$ nanoparticle (core diameter 10 nm) systems are investigated. These include: 1) uncoated Fe$_{3}$O$_{4}$; 2) polyacrylic acid (PAA) coated Fe$_{3}$O$_{4}$; 3) Fe$_{3}$O$_{4}$ nanoparticles embedded in the polystyrene nanosphere (NS), and and 4) Fe$_{3}$O$_{4}$ nanoparticles embedded in the polystyrene NS with silica coating. The PAA coated Fe$_{3}$O$_{4}$ nanoparticles are found to be more efficient in thermal energy conversion compared to the NS systems. However, the heating rates of these nanoparticle systems are comparable when exposed to NIR (785 nm) light. The different heating behaviors and associated mechanisms are discussed based on magnetic dipole interactions for magnetic hyperthermia and by considering the Drude theory in the case of photothermal effect. [Preview Abstract] |
Saturday, October 5, 2013 8:24AM - 8:36AM |
E5.00003: Frequency Dependent Regulation of Cell Behavior by Electrical Stimuli: a Theoretical-Experimental Approach Toloo Taghian, Abdul Sheikh, Daria Narmoneva, Andrei Kogan Ionic environment of extracellular matrix (ECM) and cell cytoplasm on both sides of the insulating cell membrane generates a trans-membrane electric field (EF) that has been shown to regulate cell functions. Therefore, application of external EF may provide a tool for alteration of this intrinsic EF to trigger desired cell responses. To achieve this, however, the induced EF distribution in the cell and the mechanisms for EF-cell interaction need to be known. We have developed a combined theoretical-experimental approach to predict and measure the cell responses to the external EF in a wide frequency range. The 3D theoretical model of cell interactions with EF in native configuration is based on numerical solutions of Maxwell's equations (ANSYS\textunderscore HFSS) and provides high resolution distribution of induced EF in the cell membrane, cytoplasm and the extracellular space. The model predicts that cell response to the EF strongly depends on the EF frequency, which is consistent with our experimental results of endothelial cell activation by high (but not low) frequency EF. Further, the model suggests that the mechanism for such response may involve differential regulation of membrane-dependent and intracellular pathways in low vs. high frequency regimes. [Preview Abstract] |
Saturday, October 5, 2013 8:36AM - 8:48AM |
E5.00004: Cathodoluminescent Study of Li$_{2}$B$_{4}$O$_{7}$ Doped with Cu, Mn, and Ag Zachary Hadfield, Robert Hengehold, Joshua Reding, David Turner Lithium tetraborate or LTB crystals are being developed for possible use in solid state neutron detectors. LTB is of interest due to its large cross section for neutron capture by lithium and boron. Furthermore, the crystal fluoresces in the presence of ionizing radiation, making it an attractive candidate for a scintillating detection device. However, there is a lack of fundamental knowledge about the material characteristics, particularly with regard to its fluorescent spectrum. Cathodoluminescence (CL) measurements were conducted on undoped and doped samples of lithium tetraborate in order to characterize the nature of its fluorescent spectra under different conditions. Measurements were made using a vacuum ultraviolet CL system specifically designed to detect high energy photons emitted in wide band gap materials. The CL spectra from 10 K to room temperature were characterized for six different lithium tetraborate crystals: three undoped crystals and one each doped with silver, copper, and manganese. In addition, thermoluminescence measurements were conducted using a Harshaw Model 3500 Manual TLD Reader. After electron irradiation from the cathodoluminescence experiment, the samples were heated from 50$^{\circ}$C to 250$^{\circ}$C at a heating rate of 1$^{\circ}$C per second. The thermoluminescence measurements provided insight into the carrier trapping ability of the crystals after electron irradiation. [Preview Abstract] |
Saturday, October 5, 2013 8:48AM - 9:00AM |
E5.00005: Cathodoluminescent Study of ThO$_{2}$ Michael Lee, Robert Hengehold, Tony Kelly, David Turner, Matt Mann Single crystal thorium dioxide (ThO$_{2})$ samples were hydrothermally grown and studied using depth-resolved cathodoluminescence (CL) to characterize the surface and bulk electronic states. X-ray diffraction (XRD) measurements confirmed that these crystals were ThO$_{2}$ in the fluorite structure. Understanding the chemical and structural quality of ThO$_{2}$ will aid in the fabrication of better neutron detectors as well as in commercial power production with thorium breeder reactors. Monte Carlo simulations were used to predict the expected energy-dependent electron interaction depths in the ThO$_{2}$ crystals. CL was conducted using 1.5 - 12 keV electrons at vacuums of 5x10$^{-7}$ to 1.2x10$^{-9\, }$Torr, and sample temperatures of 24 K -- 297 K. The CL measurements indicated that the as-grown sample exhibited definite surface effects. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) conducted on the samples appeared to partially clean the surface as indicated by CL spectra taken following TOF-SIMS. [Preview Abstract] |
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