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2011 SPS Outstanding Student Awards for Undergraduate Research
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Recipients:

2008 ICPSThe 2011 SPS Outstanding Students Award recipients will represent the United States and SPS and present their research at the 2011 International Conference of Physics Students (ICPS), August 11-18, 2011, in Budapest, Hungary. Expenses for transportation, room, board, and meeting registration will be paid by SPS and it's parent organization, the American Institute of Physics.

They will 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 2011-12.

Lauren Richey,Brigham Young University

Lauren Richey
Brigham Young University

Feature Article: ICPS 2011

The Photonic Beetle: Bio-inspired Photonic Crystals

Abstract

Lauren R Richey, John S Gardner, Michael D Standing, Matthew R Jorgensen, Michael H Bartl

Photonic crystals (PCs) are periodic structures that manipulate electromagnetic waves by defining allowed and forbidden frequency bands known as photonic band gaps. Despite satisfactory production at longer wavelengths, visible counterparts are difficult to fabricate. As part of an ongoing search for PC structures operating in the visible, a honeycomb-like array of cylinders and air holes were found in the iridescent beetle scales of L. augustus. Furthermore, nanoscopic spheres were found in the beetle scales of G. celestis and A. elegans.

Through SEM analysis, sequential focused ion beam slicing, and three-dimensional modeling, the beetle scale structures were analyzed. A face centered cubic arrangement was found in G. celestis while A. elegans is still under investigation. The structure of L. augustus, however, was found to be a diamond crystal lattice. Despite the possible usefulness of these structures, the index of refraction of the scale is not adequate to produce a PC.

Through a chemical replication technique, L. augustus was doubly inverted from the chitin of the insect scale into a titania replica, theoretically producing a PC with a full-three-dimensional band gap. The structures of G. celestis and A. elegans were also inverted into a silica lattice. We are currently testing our replicated structures with quantum dots to investigate how the emission of the dot is inhibited within the predicted band gaps.

Thomas Markovich, University of Houston
Thomas Markovich
University of Houston

Feature Article: 2011 ICPS

Supersymmetric Quantum Mechanics in Multiple Dimensions Using Variational Monte Carlo for Geometric Optimization of Excited State Electronic Structures

Abstract

Thomas Markovich, Eric R. Bittner, Donald J. Kouri

Abstract

Lena Bradley, Penn State University

Lena Bradley
Penn State University

Feature Article: ICPS 2011: Budapest

Digital Breast Tomosynthesis (DBT)

Abstract

Digital Breast Tomosynthesis (DBT) is an emerging imaging modality that combines tomographic imaging with conventional digital mammography in order to improve sensitivity and specificity for detecting breast cancers. In developing DBT dosimetry and quality assurance, a direct application of mammographic dosimetry has appeal. However, DBT introduces rotation of the x-ray tube relative to the dosimeter, thus raising questions about the angular dependence of mammographic dosimeters. To measure this dependence, two ionization chambers, two solid-stated detectors, and one photodiode were rotated relative to an incident Mo/Mo x-ray beam. In this isocentric DBT simulation, the signal of each dosimeter was studied over an angular range of 180° for tube voltages of 26 to 34 kV. The ionization chambers were then modeled numerically to verify the response. Angularly symmetric “pencil” ionization chambers of varying internal mylar window size were also constructed and studied under similar conditions.  Results show that all commercial mammographic dosimeters underestimate dose to varying degrees, with solid-state detectors showing the most error. Experimental results were further enforced by numerical models of commercial ionization chambers. Correction factors for commercial dosimeters were computed from the data for various isocentric DBT images using projection angles up to ±25°.  These factors ranged from 1.0014 to 1.1380 and the magnitude of the dependence generally decreased with increasing energy.  In general, the error accrued in measuring DBT dose with a mammographic dosimeter varies significantly and cannot always be disregarded. The use of correction factors may be possible but is largely impractical, as they are specific to the dosimeter, x-ray beam, and DBT geometry.  Results from constructed chambers show almost no angular dependence and, in some cases, energy dependence comparable to that of standard dosimeters applied in mammography.  Thus, an angle-independent dosimeter may be more suitable for DBT quality assurance and dosimetry.

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