Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session W21: Novel Imaging Techniques and Calorimetry |
Hide Abstracts |
Sponsoring Units: GIMS Chair: Wilhelmus Geerts, Texas State University Room: D161 |
Thursday, March 24, 2011 11:15AM - 11:27AM |
W21.00001: Particle distribution and dynamics in a complex fluid suspension studied by an image-analysis light-scattering technique Saad Algarni, H. Kashuri, Germano Iannacchione A relatively unique approach is described to analyze the scattered laser light from a complex fluid suspension for both static and dynamic behavior. Recent development of speckle analysis using CCD recorded direct imaging of the scattered coherent light has opened many new avenues for the application of static and dynamic light scattering experiments. The straightforward nature of this approach is somewhat offset by the constraints of the CCD chip size and placement to probe wide (or narrow) ranges of the wave vector. An alternative, and greatly simplified variation of this technique, is to convert the scattered light into diffuse scattering using a translucent screen placed at a desired location down beam then imaging the resulting pattern on the screen. A thru-beam stop and axis scales can be easily placed on the screen and recorded to improve the image quality and later analysis. One of many possible applications is the study of the particle (7nm diam aerosil SiO2 spheres) distribution and dynamics due to Brownian motion as well as sedimentation in a complex fluid (glycerol). [Preview Abstract] |
Thursday, March 24, 2011 11:27AM - 11:39AM |
W21.00002: ABSTRACT WITHDRAWN |
Thursday, March 24, 2011 11:39AM - 11:51AM |
W21.00003: 3D Optical Field Mapping of a Focused Cylindrical Vector Beam Using Rayleigh Nanoparticles Liangcheng Zhou, Qiwen Zhan, H. Daniel Ou-Yang We report a novel method of mapping the optical field distribution of a focused cylindrical vector beam (CVB) using optically trapped Rayleigh nanoparticles. By using an ensemble method to measure the potential energy of nanoparticles in a CVB trap, optical trapping energy as low as 0.05 k$_{B}$T was measured. We demonstrated that the absolute intensity of a highly localized optical field is measured \textit{in situ} using low concentration of polystyrene nanoparticles sized at 48 nm acting as optical nanoprobes. Their collective behavior in the focal volume gives very accurate reading of the optical field distribution, which shows excellent consistency with numerical simulations. [Preview Abstract] |
Thursday, March 24, 2011 11:51AM - 12:03PM |
W21.00004: High Resolution Micro-Optical Wall Shear Stress Sensor Based on Whispering Gallery Modes of Dielectric Microspheres Ulas Ayaz, Tindaro Ioppolo, Volkan Otugen We report the performance of a photonic wall shear stress sensor based on Whispering gallery mode (WGM) shifts of dielectric microsphere resonators. In particular, issues related to the sensitivity, resolution, frequency response and cross-axis sensitivity of the sensor are investigated experimentally. The sensor used in this prototype is a dielectric hollow microsphere made of Polydimethylsyloxane (PDMS). The wall shear stress acting on a sensing element of 125 $\mu $m diameter, is transmitted mechanically to the microsphere and the transmitted stress leads to shifts in the WGMs of the microsphere. By monitoring these WGM shifts, the magnitude as well as the direction of the wall shear stress are measured. Measurement resolutions better than 1 mPa have been observed. [Preview Abstract] |
Thursday, March 24, 2011 12:03PM - 12:15PM |
W21.00005: An effect of probe current on ADF image intensity of Si crystal Suhyun Kim, Yoshifumi Oshima, Yasumasa Tanishiro, Kunio Takayanagi Annular dark field (ADF) scanning transmission electron microscope has been used to identify elements in the crystal. To analyze ADF image intensity more quantitatively, simulation of ADF image is required. However, the simulation has been known to overestimate the intensity because source size used in the simulation is assumed to be a point. Therefore, finite effective source size has been taken into an account by convolving Gaussian function to simulation. And, the Gaussian convolution has been usefully used to solve the mismatch in intensity, providing us a way of quantitative analysis for ADF image. Here, we quantitatively estimated an effective size of the cold field emission source. We obtained different Gaussian convolution size for ADF image acquired with various probe current by comparing ADF image contrast between experiment and simulation. As a result, we found that the effective source size which is needed for explaining contrast of ADF image decreased with decreasing probe current. [Preview Abstract] |
Thursday, March 24, 2011 12:15PM - 12:27PM |
W21.00006: Fast and Computationally Efficient Boundary Detection Technique for Medical Images Arpita Das, Partha Goswami, Susanta Sen Detection of edge is a fundamental procedure of image processing. Many edge detection algorithms have been developed based on computation of the intensity gradient. In medical images, boundaries of the objects are vague for gradual change of intensities. Therefore need exists to develop a computationally efficient and accurate edge detection approach. We have presented such algorithm using modified global threshold technique. In our work, the boundaries are highlighted from the background by selecting a threshold (\textbf{T}) that separates object and background. In the image, where object to background or vice-verse transition occurs, pixel intensity either rises greater or equal to \textbf{T} (background to object transition) or falls less than \textbf{T} (object to background). We have marked these transition regions as object boundary and enhanced the corresponding intensity. The value of \textbf{T} may be specified heuristically or by following specific algorithm. Conventional global threshold algorithm computes the value of \textbf{T} automatically. But this approach is not computationally efficient and required a large memory. In this study, we have proposed a parameter for which computation of \textbf{T} is very easy and fast. We have also proved that a fixed size memory [256$\times $4Byte] is enough to compute this algorithm. [Preview Abstract] |
Thursday, March 24, 2011 12:27PM - 12:39PM |
W21.00007: Integrated instrument for holographic optical trapping and multicolor holographic video microscopy Bhaskar Jyoti Krishnatreya, David G. Grier We designed and constructed an integrated holographic materials characterization and processing workstation that combines dynamical holographic optical trapping with multicolor holographic video microscopy. Unlike previously described systems, which are based on conventional light microscopes, our holographic workstation features a rigid, compact, adaptable, and modular design that can be replicated easily using standard off-the-shelf optical components. We demonstrate enhanced efficiency in micro-manipulation of colloidal materials using our instrument. By illuminating these colloidal particles with multiple laser wavelengths concurrently and analyzing the multicolor holograms independently for each color, we can acquire complementary information about the particles' size, position, and composition, and also gain insights into their material-dependent properties. [Preview Abstract] |
Thursday, March 24, 2011 12:39PM - 12:51PM |
W21.00008: Graded Index Lens Design for Aqueous Applications Theodore Martin, Michael Nicholas, Gregory Orris, Liang-Wu Cai, Daniel Torrent, Jose Sanchez-Dehesa A graded refractive index (GRIN) provides a means of controlling wave propagation within the bulk of a material without relying on curved interfaces between dissimilar materials. We report the design and experimental testing of a GRIN metamaterial that behaves as a lens for acoustic waves in water. The graded index is achieved using a regular array of cylindrical scatterers with an anisotropic distribution of sizes. The metamaterial lens operates at sonic frequencies and has flat interfaces. We demonstrate that this metamaterial design focuses acoustic signals in the same manner as an ideal optical lens. By comparing with calculations using multiple scattering theory and finite difference time domain methods we show that the elastic properties of the scatterers are important for achieving an accurate model of the transmitted signal. We consider perturbations of the metamaterial design and their impact on the transmission. [Preview Abstract] |
Thursday, March 24, 2011 12:51PM - 1:03PM |
W21.00009: WASTED at work: the Webcam Alpha Spectrometer Experiment Demonstrator Arthur Pallone, Nicole Newton Ion beam analysis (IBA) methods are commonly used to determine the composition or other properties of samples. The scanning of micrometer diameter and smaller ion beams across sample surfaces produces spatial distribution maps of those properties for the samples. Electron microscope providers offer radiation-hardened CMOS camera options to directly image sample areas as a complement to scanning the electron beam. A modified webcam operated in the radiographic mode of transmission ion microscopy (TIM), with alpha particles in place of electrons, has been shown to be an effective low-cost alternative to that camera for TIM. IBA under ambient pressure is still not commonly practiced. Even less common is the use of a radioactive source of ions, such as Po-210, in IBA. The synthesis of these three ideas -- the direct imaging by a modified webcam of Po-210 alpha particles that first pass through a sample under ambient pressure -- is explored with the Webcam Alpha Spectrometer Experiment Demonstrator (WASTED). A description of the experiment, first results, conclusions and future work will be presented. [Preview Abstract] |
Thursday, March 24, 2011 1:03PM - 1:15PM |
W21.00010: Fourier phase contrast microscopy technique for real time imaging of phase and fluorescence features simultaneously Chandra Yellleswarapu, Alexey Veraksa, Bhargab Das, Devulapalli Rao Understanding of biological cell response is facilitated by microscopy techniques, but has been limited by our ability to image cell structure and function at the same time. Current procedure is to obtain separate images, such as phase and fluorescence features, using different imaging techniques one after the other and digitally register the resulting images together. Mostly this procedure requires switching between the light sources and the associated optical paths, making it difficult to image biological events at short time scales. Recently we developed a novel optical Fourier phase contrast microscopy technique for real time display of phase and fluorescence features of biological specimens at the same time. We were able to image the brightfield+fluorescence, phase+fluorescence, and edge enhanced+fluorescence features of the \textit{Drosophila} embryo at once without the need for digital image registration and fusion. This comprehensive microscope has the capability of simultaneously providing both structural and functional information. [Preview Abstract] |
Thursday, March 24, 2011 1:15PM - 1:27PM |
W21.00011: Atomic Resolution imaging with non-contact Atomic Force Microscope (nc-AFM) in a closed liquid cell Umit Celik, Demet Catcat, H. Ozgur Ozer, Ahmet Oral We have designed a non-contact Atomic Force Microscope, which can achieve true atomic resolution in a closed liquid cell, which does not suffer from evaporation of fluids during imaging. We have designed a closed liquid cell, where we can flow the fluid using a syringe or a peristaltic pump. The AFM cantilever holder was designed to eliminate acoustical resonances. We can obtain resonance curves without spurious acoustic peaks in liquid using a piezoactuator. We have used an RF modulated 635 nm low noise diode laser. RF modulation is effective to reduce the optical feedback noise and the optical interference noise. Deflection noise density of designed system is $\sim $20 fm/$\surd $Hz in air and $\sim $25 fm/$\surd $Hz in water. The observed frequency noise at the PLL output was $\sim $1Hz$_{pp}$ in water using a 300kHz, 32N/m cantilever oscillated at 0.9nm amplitude with Q$\sim $11. Force sensitivity of our system is demonstrated by imaging cleaved mica surface in water environment with atomic resolution. [Preview Abstract] |
Thursday, March 24, 2011 1:27PM - 1:39PM |
W21.00012: Scanning Tunneling Microscope Study of Atomic Steps in Gold Films on Muscovite Mica Olesya Sitnikova, Ramesh Mani We are carrying Scanning Tunneling Microscope (STM) studies of gold on Muscovite mica to observe the atomic step migration and test the functionality of our STM. The experiment was performed by using a RHK ultra-high-vacuum STM. The gold sample was prepared in low pressure vacuum chamber, and the films were grown at constant rate of 0.1 nm/sec to the desired thickness. After deposition, the films were thermally annealed to produce flat terraces which are being studied. The migration of atomic steps over time is being observed and the results are presented. [Preview Abstract] |
Thursday, March 24, 2011 1:39PM - 1:51PM |
W21.00013: X-Ray Fluorescence Imaging of Ancient Artifacts Robert Thorne, Ethan Geil, Kathryn Hudson, Charles Crowther Many archaeological artifacts feature inscribed and/or painted text or figures which, through erosion and aging, have become difficult or impossible to read with conventional methods. Often, however, the pigments in paints contain metallic elements, and traces may remain even after visible markings are gone. A promising non-destructive technique for revealing these remnants is X-ray fluorescence (XRF) imaging, in which a tightly focused beam of monochromatic synchrotron radiation is raster scanned across a sample. At each pixel, an energy-dispersive detector records a fluorescence spectrum, which is then analyzed to determine element concentrations. In this way, a map of various elements is made across a region of interest. We have succesfully XRF imaged ancient Greek, Roman, and Mayan artifacts, and in many cases, the element maps have revealed significant new information, including previously invisible painted lines and traces of iron from tools used to carve stone tablets. X-ray imaging can be used to determine an object's provenance, including the region where it was produced and whether it is authentic or a copy. [Preview Abstract] |
Thursday, March 24, 2011 1:51PM - 2:03PM |
W21.00014: Measuring the Imaginary Part of the Permittivity Using Calorimetry Hektor Kashuri, Krishna Sigdel, Klaida Kashuri, Germano S. Iannacchione Modulated or AC calorimetry is a well established technique for measuring the temperature dependence of the heat capacity of many complex fluids. Employing a dielectric or RF heating method, the heat capacity, thermal conductivity, and the dielectric properties of the sample are all probed simultaneously. Combining the results obtained by this technique for the liquid crystal 4-n-pentyl-4-cyanophenyl (5CB) with those obtained by our novel AC calorimetric technique employing RF (dielectric) heating, we have been able to directly measure the temperature dependence of the imaginary part of the permittivity of this liquid crystal. Measurements were performed over a temperature range from 303 to 313 K, spanning the nematic to isotropic phase transition, as well as radio frequencies from 10 to 30 MHz [Preview Abstract] |
Thursday, March 24, 2011 2:03PM - 2:15PM |
W21.00015: Calorimetry of epitaxial thin films Frances Hellman, David Cooke, James Groves, Bruce Clemens Thin film growth allows for the manipulation of material on the nanoscale, allowing for the creation of metastable phases not seen in the bulk. Heat capacity provides a direct way of measuring thermodynamic properties of these new materials, but traditional bulk calorimetric techniques are inappropriate for such a small amount of material. Micro- and nanocalorimetry techniques exist for the measurements of thin films but rely on an amorphous membrane platform, limiting the types of films which can be measured. In this work, ion-beam-assisted deposition is used to provide a biaxially-oriented MgO template on a suspended membrane microcalorimeter. Synchrotron X-ray diffraction was used to successfully assess the biaxial order of the MgO template. X-ray diffraction was also used to prove the high level of epitaxy of a film grown onto this MgO template. The contribution of the MgO layer to the technique will be discussed. An Fe$_{.49}$Rh$_{.51}$ film grown epitaxially onto the device was measured, comparing favorably to literature data on bulk crystals. This shows the viability of the MgO microcalorimeter as a way of measuring the thermodynamic properties of epitaxial thin films. [Preview Abstract] |
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