Bulletin of the American Physical Society
Fall 2012 Meeting of the APS Ohio-Region Section
Volume 57, Number 6
Friday–Saturday, October 5–6, 2012; Detroit, Michigan
Session CA: Poster Session (4:00-6:00 PM) |
Hide Abstracts |
Chair: Gavin Lawes, Wayne State University Room: McGregor Conference Center J |
|
CA.00001: Stability of the Euler integration method in coupled two-domain diffusive systems Steffan Puwal, Bradley Roth Owing to its simplicity, the Euler integration method is widely used for modeling diffusive systems. The method involves approximating the derivative with a finite difference. The size of the space and time steps used cannot be considered independently. For the solution to converge, the time step can be no larger than a quantity proportional to the square of the space step; this is the well-known stability condition of the parabolic differential (heat) equation. In cardiac electrodynamics, the action potential reaction diffuses and one must separately consider the diffusive characteristics of the intracellular and extracellular spaces (a bidomain model). We derive the stability relation for this coupled two-domain diffusive system in the case of anisotropic, homogeneous electrical conductivity. We find that stability is uniquely determined only if the electrical conductivity tensors of the two spaces are symmetric (a condition related to the nature of the derivative) and are positive definite (a condition related to entropy). [Preview Abstract] |
|
CA.00002: Hyperfine Structure Measurement in the 8p$^{2}$P$_{3/2}$ Level of Cesium by Quantum Beat Spectroscopy Burcin Bayram, Oleg Popov, Stephen Kelly, Andrew Salsman Using the delayed- detection method in conjunction with pump-stimulated emission probe excitation, we have measured atomic polarization quantum beats in the 8p$^{2}$P$_{3/2}$ level of atomic cesium. According to the observed evolution of hyperfine structure dependent parameters, e.g. alignment and atomic polarization, by delaying the arrival time of the probe laser, the magnetic dipole A and electric quadrupole B coefficients are obtained. We will present our unique method, applied the first time to the 8p$^{2}$P$_{3/2}$ level of atomic cesium, and the results which are in good agreement with the previous determination within the error limits. [Preview Abstract] |
|
CA.00003: Comparison of mechanism of break up and cycle length in defibrillation success Natalya Melkus, Steffan Puwal Heart fibrillation is an often fatal condition which can be modeled by chaotic electrical activity; spiral waves of electrical activity rotate, break-up, and meander on tissue. As they do, they produce a chaotic distribution of electrical activity, negatively affecting physical contraction (blood pumping). Fenton, \textit{et al.} studied several mechanisms of this wave breakup, including ``far from tip'' and ``Doppler shift.'' We used Fenton \textit{et al.}'s mathematical model and the different modes of breakup proposed by Fenton to simulate fibrillation and to determine if the cycle length of the activity or the type of mechanism was more significant in defibrillation. Our data supports the conclusion that the cycle length is the more important factor in defibrillation. [Preview Abstract] |
|
CA.00004: Bone strength and athletic ability in hominids: \textit{Ardipithecus ramidus} to \textit{Homo sapiens} Scott Lee A methodology for the evaluation of the athletic ability of animals based on the strength of their femur and their body mass is developed. The ability of the femur to resist bending stresses is determined by its midlength cross-sectional geometry, its length and the elastic properties of the mineral part of the bone. The animal's athletic ability, determined by a ``bone strength index,'' is limited by this femoral bending strength in relation to the loads on the femur. This analysis is applied to the fossil record for \textit{Homo sapiens, Homo neanderthalensis, Homo erectus, Homo habilis, Australopithecus afarensis} and\textit{ Ardipithecus ramidus}. Evidence that the femoral bone strength index of modern \textit{Homo sapiens} has weakened over the last 50,000 years is found. [Preview Abstract] |
|
CA.00005: A Raman Scattering Study of the Interactions of DNA with its Water of Hydration Scott Lee, Nong-Jian Tao, Allan Rupprecht Raman spectroscopy is used to probe the nature of the hydrogen bonds which hold the water of hydration to DNA. The $\sim $ 3450 cm$^{-1}$ molecular O-H stretching mode shows that the first 6 water molecules per base pair of the primary hydration shell are very strongly bound to the DNA. The observed shift in the peak position of this mode permits a determination of the length of the hydrogen bonds for these water molecules. These hydrogen bonds appear to be about 0.3 {\AA} shorter than the hydrogen bonds in bulk water. The linewidth of this mode shows no significant changes above water contents of about 15 water molecules per base pair. This technique of using a vibrational spectroscopy to obtain structural information about the hydration shells of DNA could be used to study the hydration shells of other biomolecules. [Preview Abstract] |
|
CA.00006: The Dip in the Anodal Strength-Interval Curve in Cardiac Tissue Sunil Kandel, Bradley J. Roth Heart disease -- specifically ventricular fibrillation -- is the leading cause of death in the United States. The most common treatment for this lethal arrhythmia is defibrillation: application of a strong electrical shock that resets the heart to its normal rhythm. The goal of this project is to obtain a better understanding of how anodal (hyperpolarizing) shocks affect the heart by using numerical simulations. To accomplish this goal, we will test four hypotheses to find the response of refractory tissue to an anodal shock. We will use bidomain model; the state-of-the-art mathematical description of how cardiac tissue responds to an electric shock. The innovative feature of this proposal is to integrate the bidomain model with an ion channel model (Luo-Rudy model, 1994) that includes intracellular calcium dynamics to get a detailed calculation of the mechanism of the excitation and to understand the electrical behavior of the heart, which is important for pacing and defibrillation. [Preview Abstract] |
|
CA.00007: The application of time-gated fluorescence spectroscopy to the real-time monitoring of biological metabolism Zachary Long, Paul Urayama A time-gated fluorescence spectroscopy system capable of nanosecond gating and picosecond control of gate delays is presented. Used in conjunction with pulsed excitation, the system is capable of tracking the temporal evolution of the fluorescence spectrum from solution samples. The system uses a nitrogen discharge laser as the excitation source and a time-gated intensified CCD detector coupled to a spectrograph. Precise synchronization between the laser pulse and ICCD gate is achieved using a constant-fraction optical discriminator. System characterizations are presented, for example, the ability to both spectrally and temporally resolve the content of fluorophore mixtures is confirmed. Biotechnological applications are highlighted, including gated spectroscopy for the real time monitoring of metabolic activity via measurement of endogenous cellular fluorescence. [Preview Abstract] |
|
CA.00008: Cell Adhesion Modification of Streptococcus viridians in the Presence of Xylitol Jason Esmacher, Blair Vidakovich, Michael Giangrande, Peter Hoffmann There is scientific documentation that those who chew gum sweetened by the sugar alcohol xylitol report a dramatically lower incident of both dental caries and otitis media compared to those who chew conventional gum sweetened by sucrose. An explanation contends that xylitol interferes with the ability of Streptococcus viridian (SV) to form biofilms which is a necessary precursor to the bacteria's ability to damage human tissues. We have used atomic force microscopy to study the cell wall/fimbria properties at the nanonewton level in both the presence and absence of xylitol. The first set of measurements used varying concentrations of xylitol incorporated within the incubation medium. The second used non-xylitol grown bacteria, the xylitol was added externally at various concentrations. Our study suggests that growing SV with xylitol reduces their ability to adhere together. Additionally, externally added xylitol showed grouping of cell adhesion to a relatively narrow nanonewton spread that is concentration dependent. Measurement of the adhesion properties of the bacterial cell wall have found that there is a dramatic increase in the cell wall's firmness which simultaneously accompanied a decrease in its ability to support adhesion, even at very low concentrations of xylitol. [Preview Abstract] |
|
CA.00009: Viscosity characterization of polymer and polymer-nanocomposite materials with the AFM Edward Kramkowski, David Wilson, Ashis Mukhopadhyay, Peter Hoffmann Traditional methods for characterizing the viscosity of solutions, while accurate, require the use of a few grams of the material being investigated. As the production methods of these materials becomes more costly, devising techniques that can accurately measure their physical properties with a much smaller mass of material would prove useful in streamlining the development process. To this end, we aim to design a quick, reliable, and cost-effective method of measuring viscosity through the use of an atomic force microscope, which requires less than a gram of the sample being tested. Here we will introduce preliminary results, comparing the AFM-determined viscosity with values attained through the use of other commonly used measurement devices. [Preview Abstract] |
|
CA.00010: Phase Transitions and Helix Formation of a Fused Square-Well-Sphere Chain Michael Mroz, Mark Taylor This study involves observing phase transitions of a flexible polymer chain made of N = 20 square-well-sphere monomers, with the hard-core diameter $\sigma$ and square-well diameter $\lambda\sigma$, connected by bonds of fixed length $L < \sigma$. The density of states of the polymer is calculated using the Wang-Landau simulation technique. The density of states was then utilized to compute thermodynamic and average structural properties of the chain. A temperature-interaction range (T-$\lambda$) phase diagram was constructed for a chain of bond length $L = 0.625\sigma$. With decreasing temperature this chain undergoes a coil-globule (i.e., collapse) transition followed by one or more low temperature transitions to an ordered ground-state structure. For $\lambda > 1.25$ this ground state is a simple helix while for smaller $\lambda$ the ground state is a wrapped structure, in which one end of the chain forms a linear core about which the rest of the chain is helically wound. The low temperature transition takes on a first-order character for $\lambda<1.1$. [Preview Abstract] |
|
CA.00011: Thermodynamics of cellulose solvation in novel solvent mixtures Ritankar Das, Jhih-Wei Chu Biomass contains abundant amounts of cellulose as crystalline microfibrils. A limiting step to using cellulose as an alternative energy source, however, is the hydrolysis of the biomass and subsequent transformation into fuels. Cellulose is insoluble in most solvents including organic solvents and water, but it is soluble in some ionic liquids like BMIM-Cl. This project aims to find alternative solvents that are less expensive and are more environmentally benign than the ionic liquids. All-atom molecular dynamics simulations were performed on dissociated glucan chains separated by multiple (4-5) solvation shells, in the presence of several novel solvents and solvent mixtures. The solubility of the chains in each solvent was indicated by contacts calculations after the equilibration of the molecular dynamics. It was discovered that pyridine and imidazole acted as the best solvents because their aromatic electronic structure was able to effectively disrupt the inter-sheet interactions among the glucan chains in the axial direction, and because perturbation of the solvent interactions in the presence of glucan chains was minimal. [Preview Abstract] |
|
CA.00012: Low temperature glassy relaxation in rare earth doped Fe$_{3}$O$_{4}$ nanoparticles Suvra Laha, Gavin Lawes Magnetic nanoparticles typically exhibit glassy relaxation at low temperature, which can be affected by doping. Gadolinium and Lanthanum doped Fe$_{3}$O$_{4}$ nanoparticles were synthesized using a chemical co-precipitation method. The structural and optical properties of these nanoparticles were characterized by using Transmission Electron Microscope (TEM) and the Raman spectroscopy. The TEM images show the formation of nanoparticles of size ranging between 12-14 nm and Raman spectra are consistent with the formation of Fe$_{3}$O$_{4}$. AC magnetic measurements were also conducted on these nanoparticles. From the ac out-of-phase susceptibility ($\chi $//) vs temperature (T) graphs, it is observed that the doped nanoparticles show larger amplitude relaxation peaks at low temperature as compared to the undoped particles. These magnetic relaxation features develop roughly between 25K to 35K and show frequency dependence. The increased magnetic relaxation at low temperatures can be attributed to structural defects which may arise due to the doping of lanthanides in Fe$_{3}$O$_{4}$ nanoparticles. [Preview Abstract] |
|
CA.00013: Diffusion of Nanoparticles in Semidilute Polymer Solutions: The Effect of Different Length Scales. Indermeet Kohli, Ashis Mukhopadhyay Gold nanoparticles (Au NPs) were used to investigate the length-scale dependent dynamics in semidilute poly(ethylene glycol) (PEG)-water solutions. Fluctuation correlation spectroscopy was used to measure the diffusion coefficients (D) of the NPs as a function of their radius, R$_{o}$ (2.5-10 nm), PEG volume fraction, $\phi $ (0-0.37) and molecular weight, M$_{w}$ (5 kg/mol and 35 kg/mol). Our results indicate that the radius of gyration, R$_{g}$ of the polymer chain is the crossover length scale for the NPs experiencing nanoviscosity or macroviscosity. The reduced diffusivity can be plotted on a single master curve as D$_{o}$/D$_{ }$= exp ($\alpha $(R$_{o}$/$\xi )^{\delta })$ for R$_{g} \quad >$ R$_{o}$ and as D$_{o}$/D$_{ }$= exp ($\alpha $(R$_{g}$/$\xi)^{\delta })$ for R$_{g} \quad \le $ R$_{o}$, where D$_{o}$ is diffusion coefficient in the neat solvent, $\xi $ is the correlation length, $\alpha $ = 1.63 and $\delta $ = 0.89. In the intermediate size regime, $\xi \quad <$ R$_{o} \quad <$ a($\phi )$, where `a($\phi )$' is the tube diameter for entangled polymer liquid, we found that D $\sim \quad \phi ^{-1.45}$ and independent of M$_{w}$. For R$_{o} \quad >$ a($\phi )$, D$\sim \phi ^{-4}$ was obtained. The results were compared with currently available theories. [Preview Abstract] |
|
CA.00014: Adsorption of Gold Nanoparticles from a Crowded Solution on Solid/Liquid Interface Sharmine Alam, Indermeet Kohli, Bhavdeep Patel, Ashis Mukhopadhyay Adsorption of nanoparticles at solid-liquid interface is of great importance in the field of colloidal science and biophysics. Protein adsorption is one of the most significant processes and can be mimicked by colloidal systems. We will present results of our studies of the kinetics of adsorption of gold nanoparticles from a crowded polyvinyl alcohol (PVA) polymer solution on a solid/liquid interface using phase-modulated ellipsometry and Fluctuation Correlation Spectroscopy (FCS). The experimental system mimics many biological processes, where the adsorption of particles or proteins takes place in the presence of many other components. [Preview Abstract] |
|
CA.00015: Effect of Surfactants on the Physical Properties and Electrochemical Performance of LiFePO$_{4}$ Cathode Material for Lithium Ion Batteries K. Bazzi, R. Naik, G.A. Nazri, M. Nazri, V. Naik, B.P. Mandal, P.P. Vaishnava Use of lithium iron phosphate in lithium ion battery is hampered by the poor electronic conductivity and slow lithium ion diffusion. Several methods have been tried to improve the conductivity. Carbon coating is found to be very suitable way to enhance the electronic conductivity. Here, we report synthesis of carbon coated LiFePO$_{4}$ composite materials using lauric, myristic, and oleic acid as source of carbon. The phase purity of these three LiFePO$_{4}$/C composites was confirmed by X-Ray Diffraction. The quality of carbon coating has been investigated by Raman spectroscopy. In all the samples, the carbon content is found to be approximately 10{\%}. SEM and TEM investigations reveal that the surfactants coat the LiFePO$_{4}$ particles uniformly with carbon and the coating reduces the particle size to approximately 30 nm. Due to high electrical conductivity, controlled particle size and suitable microstructure, among the three LiFePO$_{4}$ coated samples, the sample prepared in presence of lauric acid exhibited superior electrochemical performance in terms of specific capacity, the cycling stability and delivered high discharge capacity of $\sim $140 mAhg$^{-1}$ at C/2 rate. [Preview Abstract] |
|
CA.00016: Approaching the Intrinsic Bandgap in Suspended High-Mobility Graphene Nanoribbons Ming-Wei Lin, Cheng Ling, Luis Agapito, Nicholas Kioussis, Yiyang Zhang, Mark Ming-Cheng Cheng, Weili Wang, Efthimios Kaxiras, Zhixian Zhou We report electrical transport measurements on a suspended ultra-low-disorder graphene nanoribbon (GNR) with nearly atomically smooth edges that reveal a high mobility exceeding 3000 cm$^{2}$ V$^{-1}$ s$^{-1}$ and an intrinsic bandgap. The experimentally derived bandgap is in \textit{quantitative} agreement with the results of our electronic-structure calculations on chiral GNRs with comparable width taking into account the electron-electron interactions, indicating that the origin of the bandgap in non-armchair GNRs is partially due to the magnetic zigzag edges. [Preview Abstract] |
|
CA.00017: Mobility Enhancement and Highly Efficient Gating of Monolayer MoS$_{2}$ Transistors with Polymer Electrolyte Ming-Wei Lin, Lezhang Liu, Qing Lan, Xuebin Tan, Kulwinder Dhindsa, Peng Zeng, Vaman Naik, Mark Ming-Cheng Cheng, Zhixian Zhou We report electrical characterization of monolayer molybdenum disulfide (MoS$_{2})$ devices using a thin layer of polymer electrolyte consisting of poly(ethylene oxide) (PEO) and lithium perchlorate (LiClO$_{4})$ as both a contact-barrier reducer and channel mobility booster. We find that bare MoS$_{2}$ devices (without polymer electrolyte) fabricated on Si/SiO$_{2}$ have low channel mobility and large contact resistance, both of which severely limit the field-effect mobility of the devices. A thin layer of PEO/ LiClO$_{4}$ deposited on top of the devices not only substantially reduces the contact resistance but also boost the channel mobility, leading to dramatically enhancement of the field-effect mobility of the device. When the polymer electrolyte is used as a gate medium, the MoS$_{2}$ field-effect transistors exhibit excellent device characteristics such as a near ideal subthreshold swing and an on/off ratio of 10$^{6}$ as a result of the strong gate-channel coupling. [Preview Abstract] |
|
CA.00018: The effect of select non-structural parameters upon the intensity of calculated LEED I(E) curves Nathan Grieser The LEED investigation of the (5x5) structure formed by sulfur adsorbed on a clean Au(111) surface results in calculated I(E) curves which exhibit unexpectedly low intensity at high energies of the probing electrons. The present study investigates various parameters used in the dynamical LEED calculation these curves, which are predominantly responsible for the intensity of the curves. Parameters such as: the Debye temperature associated with the sulfur adsorbed layer, the imaginary part of the inner potential describing the inelastic energy losses of the probing electrons within the crystal, and the anisotropic vibrations of the sulfur layer (enhanced vibrations in a direction perpendicular to the surface) have been studied by monitoring their effect on the intensity of the calculated curves. Also, the phase shifts describing the scattering of the incoming electrons by the S and Au atoms have been calculated for different configurations of the sulfur atoms on the substrate, and their influence on the I(E) curves has been considered. It is concluded that even if a certain enhancement of the beams' features is possible by choosing a particular combination of the above mentioned parameters, the process of comparing the experimental and theoretical beams by mainly matching the peak positions (as done by the Pendry R factor) imposes certain values of these parameters, not necessarily the ones which would produce high intensity peaks. [Preview Abstract] |
|
CA.00019: Live cell imaging and determination of protein-protein rupture force with AFM Anwesha Sarkar, Edward Kramkowski, Elsa Varughese, Essa Mayyas, Peter Hoffmann Atomic Force Microscopy (AFM) provides superior imaging resolution and the ability to measure forces at the nanoscale. It is an important tool for studying a wide range of biomolecular samples from proteins, DNA to living cells. We are developing AFM measurement procedures to measure protein interactions on live cells at the single molecular level. To achieve this goal, a number of challenging problems need to be overcome. These include live cell imaging, lever functionalization, localizing single proteins on the cell surface, taking the effect of cell membrane deformation into account, developing data analysis methods to determine the protein-protein rupture force (subtracting out cell deformation) and determining bond characteristics and kinetic parameters for the protein interaction. This poster presents preliminary results obtained with AFM and addresses these various aspects. [Preview Abstract] |
|
CA.00020: Study of Quark Compositeness using the Dimuon Mass Distribution in a Helicity Non-Conserving Model in High Energy p-p Collisions Chamath Kottachchi Kankanamge Don, Sowjanya Gollapinni, Pramod Lamichhane, Paul Karchin, Leonard Spiegel The Standard Model (SM) of particle physics predicts and explains the nature of particle processes at very high accuracy, but it does not explain everything. The SM does not predict the mass spectra of quarks {\&} leptons as well as the number of family members in each group. A possible explanation is the existence of more fundamental particles in nature. The 4-fermion contact interaction is used to understand the compositeness of quarks and leptons with more basic constituents called preons. Using contact interactions in the helicity non-conserving model of quark compositeness, the predicted dimuon mass distribution is studied at a center of mass energy of 8 TeV for proton-proton collisions with compositeness energy scales ranging from 3 TeV to 30 TeV. Dimuon events are generated using the Monte Carlo generator Pythia 6.4. We have shown that the mean dimuon mass in contact interactions decreases with increasing compositeness energy scale. The results are compared with the mean dimuon mass distribution of the Drell Yan process. [Preview Abstract] |
|
CA.00021: Enhanced electrochemical performance of graphene modified LiFePO$_{4}$ as a cathode material for lithium ion batteries K.S. Dhindsa, B.P. Mandal, M.W. Lin, M. Nazri, G.A. Nazri, V.M. Naik, P. Vaishnava, R. Naik, Z.X. Zhou We have synthesized LiFePO$_{4}$/graphene nano-composites using a sol-gel method by adding water dispersed graphene oxide to the LiFePO$_{4}$ precursors during the synthesis. The graphene oxide was reduced by annealing the composite at 600$^{\circ}$C for 5h in flowing forming gas (90{\%} Ar and 10{\%} H$_{2})$. The phase purity of the product was characterized by X-Ray diffraction and Raman spectroscopy. The reduction of graphene oxide was verified by Raman spectroscopy and X-ray Photoelectron spectroscopy. The electronic conductivity of LiFePO$_{4}$/graphene composite was found to be six orders of magnitude higher than that of pure LiFePO$_{4}$ synthesized following otherwise the same procedure except that no graphene oxide was added. SEM and TEM images show that LiFePO$_{4}$ particles are wrapped in uniformly distributed graphene sheets throughout the material forming a three dimensional conducting network. At low currents, the capacity of the composite cathode reaches 160 mAh/g, which is very close to the theoretical limit. More significantly, the graphene wrapped LiFePO$_{4}$ shows a dramatically improved rate capability and excellent charge-discharge cycle stability in comparison with the LiFePO$_{4}$ without graphene. [Preview Abstract] |
|
CA.00022: Ionic-Liquid Gated Bilayer MoS$_{2}$ Field-Effect Transistors Meeghage Madusanka Perera, Hsun-Jen Chuang, Ming-Wei Lin, Bhim Chamlagain, Xuebin Tan, Mark Ming-Cheng Cheng, Zhixian Zhou We report the electrical characterization of ionic-liquid-gated bilayer MoS$_{2}$ field-effect transistors. An On-Off current ratio greater than 10$^{6}$ is achieved for hole transport, while that for electron transport exceeds 10$^{8}$. The subthreshold swing of our bilayer MoS$_{2}$ devices reaches as low as 47 mV/dec at 230 K, approaching the theoretical limit. We also demonstrate that 1) the extrinsic mobility of back-gated MoS$_{2}$ field-effect transistors is largely limited by the contact resistance; and 2) the extremely large electrical-double-layer capacitance of ionic liquid significantly reduces the Schottky contact barrier leading up to three orders of magnitude mobility increase for electron transport. [Preview Abstract] |
|
CA.00023: Few-layer MoSe$_{2}$ Ambipolar Field-Effect Transistors Bhim Chamlagain, Hsun-Jen Chuang, Meeghage Madusanka Perera, Ming-Wei Lin, Jiaqiang Yan, Nirmal Jeevi Ghimire, David Mandrus, Zhixian Zhou Field-effect transistors were fabricated from few-layer MoSe$_{2}$ quasi-two dimensional flakes produced by mechanically exfoliating high quality MoSe$_{2}$ crystals synthesized using a vapor transport method. Electrical transport measurement on back-gated MoSe$_{2}$ devices shows that they are n-type and their extrinsic mobility is in the range of 0.1 - 10 cm$^{2}$ V$^{1}$S$^{-1}$, similar to few-layer MoS$_{2}$ field-effect transistors. Ambipolar behavior is observed in ionic-liquid-gated MoSe$_{2}$ devices, with the On/Off current ratio exceeding 10$^{6}$ for both electrons and holes. For the electron channel, the extrinsic mobility measured in the ionic-liquid-gate configuration increases by over an order of magnitude, which can be attributed to the reduction of Schottky barrier by the more efficient gating. In addition, the electron mobility increases with decreasing temperature above 250 K, suggesting that the phonon scattering is a significant contributor to the channel resistance. On the other hand, the hole mobility is substantially lower and does not show significant temperature dependence, which is likely due to the higher contact resistance for holes. [Preview Abstract] |
|
CA.00024: Tomographic Reconstruction of Breast Characteristics Using Transmitted Ultrasound Signals Gursharan Sandhu, Cuiping Li, Neb Duric, Zhi-Feng Huang X-ray Mammography has been the standard technique for the detection of breast cancer. However, it uses ionizing radiation, and can cause severe discomfort. It also has low spatial resolution, and can be prone to misdiagnosis. Techniques such as X-ray CT and MRI alleviate some of these issues but are costly. Researchers at Karmanos Cancer Institute developed a tomographic ultrasound device which is able to reconstruct the reflectivity, attenuation, and sound speed characteristics of the breast. A patient places her breast into a ring array of transducers immersed in a water bath, and the device scanning the breast yields a 3d reconstruction. Our work focuses on improving algorithms for attenuation and sound speed imaging. Current time-of-flight tomography provides relatively low resolution images. Improvements are made by considering diffraction effects with the use of the low resolution image as a seed to the Born approximation. Ultimately, full waveform inversion will be used to obtain images with resolution comparable to MRI. [Preview Abstract] |
|
CA.00025: Nonspecific targeting of iron oxide nanoparticles to the liver, kidney and spleen: A novel approach to achieving specificity Maheshika Palihawadana Arachchige, Amanda Flack, Xuequn Chen, Jing Li, David Oupicky, Y.-C. Norman Cheng, Yimin Shen, Bhanu Jena, Gavin Lawes Recently there has been significant interest in developing Fe$_{3}$O$_{4}$ nanoparticles for biomedical applications including targeted drug delivery and magnetic resonance imaging. One of the major problems in applying these nanoparticles clinically is to minimize the undesirable filtration of these materials by the mononuclear phagocyte system. Preliminary MRI and magnetization studies on hyaluronic acid coated nanoparticles injected intravenously into mice confirm that the nanoparticles accumulate in the liver, spleen, and kidneys. To identify whether this nanoparticle accumulation are due to some certain specific proteins, we exposed hyaluronic acid coated nanoparticles to proteins extracted from these organs, together with blood plasma proteins, then used gel electrophoresis together with mass spectroscopy to identify the proteins binding to the nanoparticles. We find that the accumulation of nanoparticles in these organs can be due to specific binding by a small number of proteins. By appropriately functionalizing the Fe$_{3}$O$_{4}$ nanoparticles, possibly by blocking the binding sites of these specific proteins, we expect that the nanoparticles uptake in the liver, spleen, and kidneys will be reduced, which, in turn, could increase the concentration of nanoparticles at tumor sites. [Preview Abstract] |
|
CA.00026: Assessment of Pulmonary Artery Stiffness of Repaired Congenital Heart Disease Patients Namheon Lee, Rajit Banerjee, Michael Taylor, Kan Hor Surgical correction or palliation of congenital heart disease (CHD) often requires augmenting the main pulmonary artery (MPA) with non-native material or placing a cylindrical graft. The degree to which this intervention affects PA compliance is largely unknown. In this study, the MPA stiffness characteristics were assessed by its compliance, distensibility, and pressure-strain modulus. Coregistered velocity encoded phase-contrast MRI and cardiac catheterization data were available for a cohort of repaired CHD patients (n=8) and controls (n=3). All patients were repaired with either an RV-PA conduit or a RV outflow tract patch. We measured the MPA area change by MRI and MPA pressure during the cath. The measurements were taken through or just distal to the conduit. The MPA compliance and distensibility for the patients were significantly lower than the controls: compliance (9.8$\pm $10.8 vs 28.3$\pm $7.7mm$^{2}$/mmHg, p$<$0.05), distensibility (2.2$\pm $1.5 vs 6.6$\pm $2.1{\%}Area change/mmHg, p=0.05). The patients had a significantly higher pressure-strain modulus (152.3$\pm $116.4mmHg, p$<$0.05) than the controls (35.8$\pm $10.6mmHg). The abnormally elevated PA stiffness due to the rigidity of the conduit or patch material may cause a compliance mismatch resulting in high stress levels contributing to the observed progressive PA dilatation. This may be a factor in the progressive RV dilatation seen in this cohort of repaired CHD patients. [Preview Abstract] |
|
CA.00027: Development of a Laser Manipulation System for Dusty (Complex) Plasma Research Lisa Simpson, Jeremiah Williams A dusty (complex) plasma is a cloud of ionized gas containing small particles (i.e. dust). In the laboratory setting, the dust component typically consists of micron- to nanometer-sized dust grains which allows for the study of a wide range of physics at the kinetic level. Because of the relatively large size of the dust grains, it is possible to manipulate the dust component via the radiation pressure force. This poster presents work on the development of a laser manipulation system for use in dusty plasma research. Details of the laser manipulation system, as well as the studies that we plan to conduct in the future, will be discussed. [Preview Abstract] |
|
CA.00028: Numerical simulations of the particle image velocimetry technique applied to dusty plasmas Anya Weaver, Jeremiah Williams A dusty plasma is a system composed of ions, electrons, neutral particles, and charged microparticles. The dust component in this cloud of ionized gas consists of micron- to nanometer-sized dust grains, which allows for the study of physics on the kinetic level. Recent developments in stereoscopic and tomographic particle image velocimetry (stereo-PIV) techniques have been used to map the underlying distribution functions of the microparticles. This poster describes the numerical study of the PIV measurement technique and its application to the measured three-dimensional velocity space distribution function. [Preview Abstract] |
|
CA.00029: Mixing evaluation using an entropic measure in Dean flow micromixers Petru Fodor, Brian Vyhnalek, Miron Kaufman Promoting mixing in fluid systems at low Reynolds number, remains one of the problems of interest in the development of microreactors. In the laminar flow regime characteristic to these type of systems the mixing between different species needed for chemical reactions relies on diffusion, which is relatively slow. In order to circumvent this problem various methodologies exploiting appropriately chosen geometries or relying on external forces such as magnetic, electrokinetic, ultrasonic ones are used to either increase the interface between the chemical components and/or induce chaotic advection within the fluid stream. In this work we investigate computationally the use of curved channels at Reynolds numbers from 25 to 900, in which the centrifugal forces, experienced by the fluid as it travels along a curved trajectory, induce counter-rotating flows (Dean Vortices). The presence of these transversal flows promotes the mixing of chemical species which are introduced in the system at different position across the cross section of the channel. The mixing efficiency is evaluated using the Shannon entropy. We have found this measure to be useful in understanding mixing in the staggered herringbone mixer [Petru S. Fodor and Miron Kaufman, Modern Physics Letters B 25, 1111 (2011)]. [Preview Abstract] |
|
CA.00030: Light Scattering Study of Elongated Particles \textit{in situ}: From FeOOH Nanorice to Polypeptide Micelles Philip Dee, Kiril Streletzky Utilizing the powerful experimental technique of Dynamic Light Scattering (DLS) for size characterization of anisotropic particles can be extremely misleading. Unfortunately, this point is often not realized by researchers who strive for particle sizing of nanoparticles in suspensions. The first goal of this study was to highlight the ambiguities of the DLS experiment on elongated particles. The second goal was to demonstrate the power of Depolarized Dynamic Light Scattering (DDLS) in probing the anisotropy of different types of nanoparticles. Both goals were realized by studying two very different systems: inorganic FeOOH nanorice and elastin like polypeptide (ELP) micelles. The difference between the two systems is fundamental as FeOOH particles are solid, contain no water, and, therefore, are easily imaged using SEM, TEM, and AFM. Polypeptide micelles are soft particles filled with water, and, therefore, not easily imaged by abovementioned techniques. Perfecting DDLS on a system like FeOOH would allow less ambiguous interpretation of light scattering experiments on ELP micelles. We present a consistent analysis of DDLS results on FeOOH nanorice and outline the potential difficulties and challenges of DDLS application for polypeptide micelles. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700