Bulletin of the American Physical Society
82nd Annual Meeting of the APS Southeastern Section
Volume 60, Number 18
Wednesday–Saturday, November 18–21, 2015; Mobile, Alabama
Session A3: Biophysics and Medical Physics |
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Chair: Mark Byrne, Spring Hill College Room: Riverview Plaza Hotel Mobile Bay Ballroom II |
Thursday, November 19, 2015 8:30AM - 9:06AM |
A3.00001: Sea-breezes in the Mobile Bay Area Invited Speaker: Sytske Kimball The sea-breeze is a warm season atmospheric phenomenon in coastal regions. A horizontal temperature gradient driven by the differential heat capacities of land and water drives this gravity current, which brings in cool and moist sea air. The passage of the sea-breeze front is accompanied by a sudden drop in temperature and dew-point temperature while the wind shifts from offshore to onshore. Sea breeze frontal passages from several local South Alabama Mesonet weather stations (\underline {http://chiliweb.southalabama.edu/}) are presented. The contrast between land- and sea-surface heating and the resulting horizontal pressure gradient is derived from buoy and Mesonet data. Sea breezes typically form under quiet synoptic conditions in opposing background flow. Upper air observations from the region demonstrate this. Dust and insects accumulate in the converging flow of the sea-breeze front, which is visible on WSR-88D Doppler radar. Under favorable atmospheric conditions, the converging flow at the sea-breeze front initiates thunderstorms. In Mobile and Baldwin counties (west and east of Mobile Bay) bay breezes can occur. Sometimes, both sea (Gulf) and bay breezes occur. Collison of these breezes can lead to the generation of thunderstorms. Radar images show this. Sometimes the sea-breeze can have significant impacts, including 1) severe thunderstorms with strong wind gusts, damaging hail, and/or dangerous lightning, 2) turbulence affecting air traffic, and 3) the concentration of ozone pollution. [Preview Abstract] |
Thursday, November 19, 2015 9:06AM - 9:18AM |
A3.00002: Study of Knee Joints with Spectral Analysis Uddhab Tiwari, Sanichiro Yoshida, Amanda Saladino, Brooklne Hadley, Maitram Nguyen, Jesse Hatchett, Daniel Hollander This research focuses on the explanation of the knee dynamics using the technique of spectral analysis. To understand the knee dynamics, a force plate, a stethoscope and an electromyography (EMG) are used which collects the data from the knee while performing different exercises at different rates. The data obtained is the measurement of the ground reaction force and torque from the feet, vibration of the knee joint, and electrical activity of the leg muscles. Thus obtained data is then used for analysis mainly using the idea of Fourier spectrum and transfer function. By observing the peak of the activity frequency, harmonics at the multiples of the activity frequency, and analyzing the transfer functions of the force and EMG signals in addition to acoustic signals, the knee dynamics can be understood. The analysis also allows for the detection of knee problems such as arthritis, injury, etc. to also be done. In future, we are planning to add accelerometer and goniometer for a better understanding of the knee dynamics. [Preview Abstract] |
Thursday, November 19, 2015 9:18AM - 9:30AM |
A3.00003: Membrane Pore Formation by Amyloid beta (25-35) Peptide Nabin Kandel, Suren Tatulian Amyloid (A?) peptide contributes to Alzheimer's disease by a yet unidentified mechanism. One of the possible mechanisms of A?toxicity is formation of pores in cellular membranes. We have characterized the formation of pores in phospholipid membranes by the A?$_{-35}$peptide (GSNKGAIIGLM) using fluorescence and circular dichroism (CD) techniques. CD identified formation of ?-sheet structure upon incubation of the peptide in aqueous buffer for 2 hours. Unilamellar vesicles composed of a zwitterionic lipid, 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC), and 70{\%} POPC plus 30{\%} of an acidic lipid, 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG), are made in 30 mM CaCl. Calcium is removed from the external medium by a desalting column. Quin-2, a fluorophore that displays increased fluorescence upon Ca$^{+}$binding, is added to the vesicles externally. Addition of the peptide results in increased Quin-2 fluorescence, which is interpreted by binding of the peptide to the vesicles, pore formation, and Ca$^{+}$leakage. The positive and negative control measurements involve addition of a detergent, Triton X-100, which causes vesicle rupture and release of total calcium, and blank buffer, respectively. The pore forming activity of A?$_{-35}$was dependent on the lipid composition of the vesicles. The effect of membrane cholesterol on A?pore formation may explain the role of cholesterol in AD pathogenesis. Furthermore, combined with FTIR analysis of the structure of membrane pores formed by A?$_{-35}$at various contents of cholesterol, we will provide an experimentally determined structure-function relationship for this highly neurotoxic peptide. [Preview Abstract] |
Thursday, November 19, 2015 9:30AM - 9:42AM |
A3.00004: Stress-strain measurements of aquatic snake lenses Nisha Lama, Dr. Cliff Fontenot, Dr. David Norwood, Dr. Rhett Allain Snakes may accommodate refractive error by lenticular displacement and deformation. The latter may be particularly useful for high refractive error, such as when semi-aquatic snakes dive, where refractive power of the cornea is lost because of refractive index similarity to water. We assessed the mechanical properties of snake lenses and how this might affect their ability to deform the lens and thus alter the lens power. We will present data taken with a force sensor and a rotary motion sensor to measure, in one shot, force versus displacement, from which we estimate the mechanical properties of stress and strain of the eye lens of a water snake. We will compare the results from lenses freshly removed from a snake to the lenses that were refrigerated 1-3 days before removal from the eye. We also compare results from semi-aquatic snakes to terrestrial snakes. [Preview Abstract] |
Thursday, November 19, 2015 9:42AM - 9:54AM |
A3.00005: New and simple post-translational circadian clock models Mark Byrne The first, and presently only known, protein-based circadian oscillator that functions outside cells (in a ``test-tube'') was discovered by Takao Kondo's lab in 2005 (Nakajima et al, Science 2005). There is evidence that other ``post-translational'' oscillators are operative in species other than the cyanobacterial species in which they were discovered (O'Neill and Reddy, Nature 2011; Edgar et al, Nature 2012). This raises the interesting experimental and theoretical question of the potential simplicity and ubiquity of protein-based clocks. I will describe some new and simple general designs (mathematical models) for protein-based post-translational circadian clocks. A protein with two modification sites can serve as a sustained limit cycle oscillator if two conditions are met. One condition is that there is a separation of timescales in the regulatory biochemical kinetics of the two sites (``fast'' vs ``slow'' regulation). The second condition is that one of the four possible protein states sequesters the molecules (cofactors) regulating the dynamics of site occupancy. [Preview Abstract] |
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