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2014 SPS Awards for Outstanding Undergraduate Research

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2014 International Conference of Physics StudentsThe 2014 SPS Award for Outstanding Undergraduate Research recipients represented the United States and SPS and presented their research at the 2014 International Conference of Physics Students (ICPS), August 10-17, 2014, in Heidelberg, Germany.

Expenses for transportation, room, board, and meeting registration are paid by SPS and it's parent organization, the American Institute of Physics. The recipients also receive a $500 honorarium and a $500 award for their SPS Chapter. In addition, they will be invited to give their research presentation at a SPS Research Session at a national meeting in 2014-2015.

Patrick Donnan

Helen Meskhidze
Elon University

Feature Article: International Conference of Physics Students 2014

Modeling the Composition and Emissions of Gamma-Ray Burst Jet Cocoons


Massive stars end their lives with powerful supernova explosions that, in extreme cases, may produce a gamma-ray burst. The driving mechanisms of these bursts are relativistic jets that propagate through the dense, rapidly rotating star. Previous studies have examined the general formation and photospheric emissions of the cocoons of these jets. However, the structure of the cocoon and the effect of cocoon composition on the creation of the gamma-ray burst have not yet been determined. In this study, we present the results of numerical simulations aimed at determining the composition and mixing of the cocoon material in gamma-ray burst progenitors and study how mixing affects the emitted radiation. We do so by adding tracer particles to special relativistic hydrodynamic simulations of collapsars to follow the mixing of matter within the cocoon as it evolves. Using this data, we compute the radiation signatures of cocoons from different progenitor stars with varying cocoon mixing. These simulations will enable us to understand the luminosity and radiation properties of the cocoon. When compared to observations, our calculations may put constraints on the progenitor stars structure that produces gamma-ray bursts.

Zoey Warecki

Zoey Warecki
Towson University

Feature Article: International Conference of Physics Students 2014

Structural and Electrical Properties of Electron-doped CaMnO3 Thin Films


Perovskite metal oxides are materials that are predicted to play as big a role in future electronic technologies as silicon does in today's semiconductor based electronic technologies. Mixed valent rare earth manganites are perovskite metal oxides containing rare earth/alkaline earth atoms, manganese and oxygen. Research in thin films of manganites in the past has largely been focused on the hole-doped compositions that exhibit the phenomenon of colossal magnetoresistance. Hole-doped manganites are derived from rare earth manganese oxides (such as LaMnO3) by partial substitution of the trivalent rare earth site (such as La3+) by a divalent alkaline earth element (such as Ca2+) which leads to the formation of Mn4+ ions to replace some of the Mn3+ ions. In contrast, electron-doped manganites can be obtained from alkaline earth manganese oxide (such as CaMnO3) by introducing Mn3+ ions to replace Mn4+ ions, which can be achieved either by partially substituting Ca with elements of higher valency, or by introducing oxygen vacancies. CaMnO3 as well as its electron doped derivatives have potential applications in several energy technologies.

We are currently investigating the properties of thin films of these electron-doped manganites. We use the technique of Pulsed Laser Deposition to grow the thin films. The films are grown epitaxially on LaAlO3 substrates, whose lattice parameters are larger than that of CaMnO3, thus causing the films to be under tensile stress. By decreasing the film thickness we can increase the tensile strain. We have studied structural and electrical properties of CaMnO3 films under tensile strain, by means of X-ray diffraction, temperature dependent resistivity measurements, and characterization of the film surface morphology using atomic force microscopy. Our results indicate that tensile strain causes CaMnO3 to be more susceptible to the formation of oxygen vacancies, thus reducing electrical resistivity. This result agrees with recent theoretical predictions correlating strain and oxygen vacancies, and has important implications for technological applications.

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