Bulletin of the American Physical Society
2005 APS April Meeting
Saturday–Tuesday, April 16–19, 2005; Tampa, FL
Session C11: Society of Physics Students II |
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Chair: Gary White, AIP/SPS Room: Marriott Tampa Waterside Room 7 |
Saturday, April 16, 2005 1:30PM - 1:42PM |
C11.00001: Low Mass Stellar Objects: The Early Years Near to Mid Infrared Spectrographic Studies of Protostars and Protoplanetary Disks/Envelopes in Taurus-Auriga Gail Zasowski, Dan Watson, Joel Green, Ben Sargent, Bill Forrest The study of young stellar objects (YSOs), and their accompanying dust/gas envelopes and disks is a significant and rapidly growing area in the field of astrophysics. Using spectroscopic data from the new Spitzer Space Telescope, I analyzed several Class I protostellar sources to identify characteristics that could be used in modeling these objects. First, the spectra were extracted from the raw Spitzer data and put into usable format. Then each source was fitted with representations of the spectral continua; these were used to calculate optical depths of the major peaks and features. Plotting these data revealed several trends, such as the close correlation between H$_{2}$O and CH$_{3}$OH ices. Laboratory ice spectra were fit to the strong 15.2 $\mu $m CO$_{2}$ feature of some objects. The apparent crystalline structure of some of these CO$_{2}$ features was studied. Much work remains to be done before a comprehensive understanding of these sources is reached. [Preview Abstract] |
Saturday, April 16, 2005 1:42PM - 1:54PM |
C11.00002: Thermal Processing of Silicate Dust Grains in Class II YSOs Jarron Leisenring Working in conjunction with the IRS Disks Team, this project makes use of the hundreds of object recently observed using the Spitzer Space Telescope within the Taurus-Auriga star-forming region of the sky. This project focuses on analyzing the mid-infrared emission features indicative of Class II YSOs at 8-13 microns which relates to the processing of initially amorphous silicate grains into partially crystalline form. Questions that I attempt to examine include the crystalline versus amorphous silicate mass ratios in the disk surrounding the star along with the conditions that affect change in this relationship. From reduced spectra obtained using the Spitzer Space Telescope, I have attempted to discern any trends between relative crystalline-to-amorphous silicate mass ratios and other known properties such as luminosities, disk masses, accretion rates, and estimated ages. [Preview Abstract] |
Saturday, April 16, 2005 1:54PM - 2:06PM |
C11.00003: The Period of Rotation, Shape, Density, and Homogeneous Surface Color of the Centaur 5145 Pholus James Rall, S.C. Tegler, W. Romanishin, G.J. Consolmagno, R. Worhatch, M. Nelson, S. Weidenschilling We present optical photometry of the Centaur 5145 Pholus during 05/2003 and 04/2004 using the facility CCD camera on the 1.8-m VATT on Mt. Graham, Arizona. We derive a double-peaked lightcurve and a rotation period of 9.980 hr with amplitude of 0.60 magnitude. We derive four possible rotational pole positions as well as axial ratios of a/b=1.9 and c/b=0.9. If we assume Pholus is a strengthless rubble-pile and its non-spherical shape is due to rotational distortion, our axial ratios and period measurements indicate Pholus has a density of 0.5 g per cubic centimeter, suggestive of an ice-rich, porous interior. By combining B-band and R-band lightcurves, we find B-R=1.94 and any B-R color variation over the surface of Pholus must be smaller than 0.06 magnitudes. By combining our V-R measurements with values in the literature, we find no evidence for any color variegation between the northern and southern hemispheres of Pholus. Our observations add to the evidence that individual Centaurs and KBOs exhibit homogeneous surface colors and hence gray impact craters on radiation reddened crusts are probably not responsible for the colors seen among the Centaur and Kuiper belt object populations. [Preview Abstract] |
Saturday, April 16, 2005 2:06PM - 2:18PM |
C11.00004: A Study of Afterpulsing in 20'' and 17'' Phototubes For The KamLAND Neutrino Detector John Carruth Research was done on sample photomultiplier tubes identical to those used in the Super Kamiokande Neutrino Detector in order to determine the precise effects of afterpulsing in decreasing PMT accuracy. The experiment involved 20'' and 17'' PMTs shielded from external light sources and subjected to single-photon emissions from an LED. Data was acquired using NIM/CAMAC electronics with a gated TDC/ADC setup controlled by a computer running LabVIEW. Data was also acquired using a computer-based oscilloscope program. The number of photons emitted by the LED was changed to determine the effect on the PMTs. Three different types of pulsing were measured: late pulsing, induced afterpulsing, and delayed prompts. The 17'' and 20'' PMTs were compared to determine relative accuracy. It was determined that for low photon counts, afterpulsing increased linearly with the number of photons in both the 17'' and 20'' PMTs. However, when the number of photoelectrons in the 20'' tube became greater than about 1000, such as from a cosmic ray, the photoelectrons began to exponentially contribute to the afterpulsing effect. The conclusion reached is that large numbers of photoelectrons in the photomultiplier can cause an exponential, even self-sustaining afterpulsing effect. This effectively renders the PMT blind to further neutrino events, and necessitates new techniques for sensing and removing such problem events. [Preview Abstract] |
Saturday, April 16, 2005 2:18PM - 2:42PM |
C11.00005: Molecular Devices: A Potential Replacement for Semiconductors Anthony Moeller, John Suehle, Oleg Kirillov, Lauren Cohen, Eric Vogel, Christina Hacker, Curt Richter A test structure was developed to sandwich a monolayer of organic molecules (F-OPE and ODT) between two electrical contacts; Au and PDOT, a conducting polymer. It has been theorized that these molecules exhibit a switching behavior when a voltage is applied, which combined with the size of these molecules ($\sim $ 20 x 10 {\AA}), should allow the construction of devices much smaller than current semiconductor devices. Four test structures were developed, an unetched one to test the insulating layer, one to test PDOT as an electrical contact, and the remaining two to test the F-OPE and ODT. The current was measured through each of the different devices for 0 to 1 V. The unetched sample showed currents on the order of pA, the sample with no molecules had currents on the order of mA, and the sample containing the F-OPE showed currents similar to that with no molecules, suggesting F-OPE self-assembly problems. The current for the sample containing ODT was between that for the unetched sample and that with no molecules, although a wide range of current was seen ($\sim $ 6-7 orders of magnitude). [Preview Abstract] |
Saturday, April 16, 2005 2:42PM - 2:54PM |
C11.00006: Neutralino-Nucleon Scattering Rates with Realistic Form Factors from Electron Scattering Data Ann Kemper, Gintaras Duda Theoretical calculations of neutralino cross sections with various nuclei are of great interest to various direct detection dark matter searches such as CDMS, EDELWEISS, and others. However, these cross sections and direct detection rates are computed with standard nuclear form factors such as Woods-Saxon or exponential models, which may not fit the nucleus in question exactly. As well known, elastic electron scattering can allow for very precise determinations of nuclear form factors and hence nuclear charge densities for spin-zero, spherical nuclei. Using electron scattering data we extract form factors and charge densities for various spin-zero nuclei important in direct dark matter searches such as Si, Ge, and S. Using DarkSUSY, a publicly available dark matter code, we re-calculate neutralino-nucleon cross sections and detection rates using the form factors extracted from the data. We will show that the “realistic” form factors can alter the cross sections and rates significantly and will compare our calculations to those computed with standard form factors. [Preview Abstract] |
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