Bulletin of the American Physical Society
2015 Annual Meeting of the APS Mid-Atlantic Section
Volume 60, Number 14
Friday–Sunday, October 23–25, 2015; Morgantown, West Virginia
Session A1: Biological and Applied Physics |
Hide Abstracts |
Chair: Mohindar Seehra, West Virginia University Room: Waterfront Hotel Salon A |
Saturday, October 24, 2015 10:30AM - 11:06AM |
A1.00001: TBD Invited Speaker: Arjun Yohd . [Preview Abstract] |
Saturday, October 24, 2015 11:06AM - 11:18AM |
A1.00002: High Local Curvature Reduces Migration Rate in Multi-Layer Tissue. Holley Lynch, Shirley Yancy, Lance Davidson Both embryonic development and human disease, e.g. cancer metastasis, involve migration of tissues composed of multiple cell types. The mechanics of these movements remains largely unknown despite progress in understanding the migration of single cells and confluent monolayers. To expose these mechanics we study migration in amphibian embryonic tissues composed of mesenchymal and epithelial cells. Spreading rates in explants ranging in area from 0.12 to 2.63mm$^{\mathrm{2}}$ increase with explant size from 22$\pm $5 to 45$\pm $5 $\mu $m/hour. Possible explanations for these differences include edge curvature and cell count. Low curvature could lead to cooperative forces along the tissue edge, leading to a faster spreading rate. However, if spreading is driven by local cell rearrangement or shape change we would expect increased spreading rates in explants with more cells. To distinguish between these, we examined spreading in shaped explants with variable curvature, e.g. triangular explants. We found that regions of high curvature had lower spreading rates even with a greater distance between the edge and center of the explant. Thus, our results indicate that tissue migration rate depends on the local curvature. [Preview Abstract] |
(Author Not Attending)
|
A1.00003: Designing self-phoretic colloids and active swimmers Amir Nourhani, Paul E. Lammert The emerging field of powering at nanoscale began around 2004 with the discovery of self-phoretic swimmers such as electrocatalytic bimetallic nanomotors. While the field is still in its infancy, the last decade has witnessed a remarkable progress in designing different kinds of nanomotors. These autonomous movers typically harvest energy from their environment to sustain their deterministic locomotion. Within a unified formulation, encompassing self-electrophoresis, self-diffusiophoresis, and self-thermophoresis, generic performance characteristics of self-phoretic particles as a function of geometrical design --- particle shape and source/sink distribution --- are studied within the family of spheroids, both oblate and prolate. [Preview Abstract] |
Saturday, October 24, 2015 11:30AM - 11:42AM |
A1.00004: Spinodals in the Ising Model with Short-Ranged Interactions in the Hyperbolic Plane: True, Dynamic, and Thermodynamic Howard Richards In the Euclidean Plane, the short-ranged Ising model does not have true metastability -- the lifetime of the ``metastable'' state is always finite -- and therefore it has no true spinodal field. They do have, though, a ``thermodynamic spinodal'', in which the mode of decay switches from the nucleation and growth of one or more critical droplets to a subcritical fluctuation spanning the system and then growing in a quasi-one-dimensional fashion. They also have a ``dynamic spinodal'', which marks the transition from deterministic decay to stochastic decay. These two ``spinodals'' are distinct from each other and have different values. In contrast, the short-ranged Ising model in the hyperbolic plane \textbf{does} have true metastability, and, in the limit of large systems, its true spinodal, thermodynamic spinodal, and dynamic spinodal all coincide. [Preview Abstract] |
Saturday, October 24, 2015 11:42AM - 11:54AM |
A1.00005: Band Gap Narrowing in Nitrogen-Doped La$_{2}$Ti$_{2}$O$_{7}$ with Transient Absorption Spectroscopy for Hydrogen Generation Brandon Yost, Scott Cushing, Nianqiang Wu, Alan Bristow Nitrogen doping was found to extend lanthanum dititanate's (LTO), La$_{2}$Ti$_{2}$O$_{7}$, absorption from 380 nm to 550 nm giving a promising 2.3 eV bandgap for solar water splitting. The increased band gap in conjunction with a lack of mid-gap trap states allows for visible light photoactivity. In this presentation, transient absorption spectroscopy with both a supercontinuum and a THz probe confirm N-doping creates a continuum of states slightly above the valence band (VB) of intrinsic LTO without harming carrier lifetimes. Lifetimes are measured for carriers excited from the VB to the CB as well as from the dopant continuum to the CB. The measured lifetimes reveal lifetimes that are comparable to intrinsic LTO due to the minimal density of mid-gap states introduced by the nitrogen dopant. The THz probe confirms the visible light excited carriers are mobile and not trapped by measuring frequency dependent conductivity. Further, by adding reduced graphene oxide (RGO) and gold nanoparticles to the N-doped LTO, carrier extraction is further increased, tripling hydrogen generation. [Preview Abstract] |
Saturday, October 24, 2015 11:54AM - 12:06PM |
A1.00006: On the electronic and structural properties of thiolate protected gold nano-particles $Au_{25-x}Ag_{x}(SCH_{3})_{18}$ (For x $=$ 6,7,8) Gihan Panapitiya, Hong Wang, James P. Lewis Thiolate protected gold nanoparticles are among the highly studied nano-structures due to their extraordinary stability and possible applications in catalysis, bio-labeling, chemical sensing and molecular electronics. Doping these nanoparticles with a second metal like Ag have been found to alter optical absorption and chemical properties. In this study, we explore the structural, electronic and chemical properties of a bi-metalic nanoparticle of the form $Au_{25-x}Ag_{x}(SCH_{3})_{18}$ (For x $=$ 6,7,8). Due to the enormity of the number of different doped structures, we choose 500 random configurations for each doping level and energetically optimize them using DFT methods as implemented in Fireball. The lowest energy structures selected thereby are used to study the density of states and to determine the most favorable Ag doping sites. We also calculate the Fukui functions to analyze the chemical selectiveness of different sites of these structures to reactants used in catalytic processes. [Preview Abstract] |
Saturday, October 24, 2015 12:06PM - 12:18PM |
A1.00007: \textbf{Nature of magnetism in the molecular semiconductor Cobalt Phthalocyanine (C}$_{\mathrm{\mathbf{16}}}$\textbf{H}$_{\mathrm{\mathbf{32}}}$\textbf{CoN}$_{\mathrm{\mathbf{8}}}$\textbf{): Low temperature, high magnetic field investigations} Z. Wang, M. Lee, E.S. Choi, J. Poston, M.S. Seehra Transition metal doped phthalocyanines (MPc, M $=$ Mn, Fe, Co, Ni and Cu) are molecular semiconductors with many potential applications in which the M atoms form linear chains along the b-axis [1]. A recent report [2] on $\beta $-CoPc based on the temperature dependence (8 K to 310 K) of magnetization (M) in magnetic field H $=$ 70 kOe suggested it to be a linear chain magnet. Here we report results from detailed investigations of the magnetic properties of two powder samples of $\beta $-CoPc covering wider temperature range of 0.4 K to 300 K and in H up to 90 kOe. X-ray diffraction confirmed the $\beta $-phase and SEM showed needle-like (plate-like) morphology for the samples from Sigma-Aldrich (Alfa-Aesar). Magnetically, both samples are quite similar, the M vs. T data in H $=$ 10 kOe fitting the Curie-Weiss (CW) law above T \textgreater 3 K yielding $\theta \quad =$ 2.5 K, \textmu $=$ 2.16 \textmu $_{\mathrm{B}}$ per Co$^{\mathrm{2+}}$ and g $=$ 2.49 for S $=$ 1/2. Below 3 K, the data deviates from the CW law yielding a peak in M near 2 K, but the data from 0.4 K to 300 K fits well with the prediction of the Bonner-Fisher model for S $=$ 1/2 AFM Heisenberg chain [3] yielding the Co$^{\mathrm{2+}}$-Co$^{\mathrm{2+}}$ exchange constant J/k$_{\mathrm{B}}$ $=$ 3 K (\textbf{H} $=$ J $\Sigma $ \textbf{S}$_{\mathrm{\mathbf{i}}}$\textbullet \textbf{S}$_{\mathrm{\mathbf{i+1}}})$. [1] A. Mugarza et al, Phys. Rev. B. 85, 155437, (2012); [2] M. Serri et al, Nature. Commun. \textbf{5, }3079 (2014); [3] J. Bonner and M. Fisher, Phys. Rev. 135, A640 (1964). [Preview Abstract] |
Saturday, October 24, 2015 12:18PM - 12:30PM |
A1.00008: Physics of Untied Rotating Space Elevators Steven Knudsen, Leonardo Golubovic We explore fundamental aspects of the physics of a novel class of dynamical systems, Rotating Space Elevators (RSE) [L. Golubovi\'{c} and S. Knudsen, Europhys. Lett. 86\textbf{\textit{, }}34001 (2009); S. Knudsen and L. Golubovi\'{c}, Eur. Phys. J. Plus 129, 242 (2014)]. An RSE is a loopy string reaching deep into outer space. The floppy RSE loop executes a double rotating motion due to which the objects sliding along the RSE string (climbers) can be transported far away from the Earth's surface without using internal engines or propulsion. By extensive numerical simulations and analytic calculations, this study addresses an interesting and provocative question at the very heart of the RSE physics: What will happen if one \textit{unties} the rotating space elevator from the Earth? We find that the untied RSE exhibits rich nonlinear dynamics. In particular, strikingly, we find that the untied RSE may still behave as if it were tied to the planet. Such a quasi-tied yet untied RSE remains close to the Earth and exhibits persistent shape and enduring double rotating motion. Moreover, the climbers sliding along such a quasi-tied RSE move in much the same way as they do along a tied RSE. Under some conditions however we find that the untied RSE may undergo an instability leading it to a dynamical state in which the RSE hops well above the Earth surface. By changing the untied RSE parameters, the maximum height reached during hopping may be made to diverge. Such an untied RSE unbinds from the Earth to infinity, i.e., to interplanetary space. [Preview Abstract] |
Saturday, October 24, 2015 12:30PM - 12:42PM |
A1.00009: Potential Nanoparticle Exposure during Consumer Use of a Nano-enabled Product Vincent Castranova Development of nano-enabled printer toner leads to possible aerosolization of nanoparticles and inhalation exposure during printer operation. The goals of the present study were to: 1) develop a generation system for printer-emitted particles (PEPs), which reflects emissions measured during actual use of laser printers; 2) characterize the generated aerosol (number concentration, size distribution and composition of the PEPs); and 3) determine the bioactivity of PEPs in an in vitro, \quad co-culture system of small airway epithelial cells and microvascular endothelial cells, which mimics the air/blood barrier in the lung. Results indicate that laser printers using nano-enabled toner generate PEPs (as high as 1.3 million particles/cc with a mode diameter of 49-208 nm, containing nano-metals). In a transwell co-culture system, exposure of lung epithelial cells to PEPs results in particle uptake and secretion of pro-inflammatory mediators, which significantly alter endothelial cell function (increase production of oxidants, actin filament remodeling, gap formation, and mediator release). These responses could result in pulmonary edema and systemic inflammation in those operating laser printers in a poorly ventilated space for an extended period of time. [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