Bulletin of the American Physical Society
Spring 2015 Meeting of the APS New England Section
Volume 60, Number 5
Friday–Saturday, April 24–25, 2015; Boston, Massachusetts
Session F2: Biological and Polymer Physics |
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Chair: Colin Howard, Boston University Room: Life Sciences and Engineering Building 103 |
Saturday, April 25, 2015 11:30AM - 11:42AM |
F2.00001: Cell Survivor: Teaching radiobiological intuition with a video game Melissa Spencer, Erno Sajo While new technologies use radiation for the benefit of society, whether in medicine, food irradiation, or nuclear power, public fear of these technologies is not influenced by their different potential to do harm, nor is this fear balanced by their potential benefits. Underlying this fear is a fundamental lack of understanding of the effects of radiation on the body. By modeling radiobiological experiments with a computer game, it is possible to enhance intuitive understanding of both the effects of different types of radiation as well as different factors that can enhance or suppress repair. A prototype game was developed where the player acts as the cell's enzymatic repair process. Cells are damaged by incident radiation, with either single or double strand breaks (SSB or DSB) occurring. The cells grow and reproduce, and are especially vulnerable during mitosis. Cell types display different radiosensitivity, which can be further altered by the addition of chemicals. Levels can be created to teach laypeople about certain types of radiation, for instance dental x-rays as compared to CT scans. As both a simulation and a video game, Cell Survivor shows promise as both an educational tool and a research tool. [Preview Abstract] |
Saturday, April 25, 2015 11:42AM - 11:54AM |
F2.00002: Effect of Chain Stiffness on the Glass Transition Temperature of Polymer Thin Film Kun Geng, Fei Chen, Ophelia Tsui The glass transition temperature ($T_{\mathrm{g}})$ of poly($\alpha $-methyl styrene) (PAMS) films supported by silica is studied as a function of film thicknesses from $\sim$17 to $\sim$168 nm at three molecular weights of 1.3, 20 and 420 kg/mol. For the 20 and 420 kg/mol films, the glass transition temperature decreases with decreasing film thickness, consistent with previous results. But for the 1.3 kg/mol films, it becomes independent of the film thickness. We tentatively suggest the $T_{\mathrm{g}}$ depression to be caused by free volume excess at the polymer-air interface and that its influence diminishes at low enough molecular weights because of a chain stiffness effect. Besides PAMS, we contemplate that silica-supported poly(methyl methacrylate) (PMMA) can be another potential candidate for such an effect since published data shows that chain stiffness also affects the $T_{\mathrm{g}}$ of this polymer. Preliminary results supporting this conjecture will be discussed. [Preview Abstract] |
Saturday, April 25, 2015 11:54AM - 12:06PM |
F2.00003: Mode-locking Behavior of Izhikevich Neurons under Periodic External Forcing AmirAli Farokhniaee, Edward Large Many neurons in the auditory system of the brain must encode amplitude variations of a periodic signal. These neurons under periodic stimulation display rich dynamical states including mode-locking and chaotic responses. Periodic stimuli such as sinusoidal waves and amplitude modulated (AM) sounds can lead to various forms of n:m mode-locked states, similar to the mode-locking phenomenon in a LASER resonance cavity. Obtaining Arnold tongues provides useful insight into the organization of mode-locking behavior of neurons under periodic forcing. In this study we obtained the regions of existence of various mode-locked states on the frequency-amplitude plane, which are called Arnold tongues, for Izhikevich neurons. This study is based on the model for neurons by Izhikevich (2003), which is a reduced model of a Hodgkin-Huxley neuron. This model is much simpler in terms of the dimension of the coupled non-linear differential equations compared to other existing models, but excellent for generating the complex spiking patterns observed in real neurons. Hence we can describe the construction of harmonic and sub-harmonic responses in the early processing stages of the auditory system, such as the auditory nerve and cochlear nucleus. [Preview Abstract] |
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