Engaging Students in Community

Vincent Tinto’s Schema for Dropout From College, posits “it is the individual\u27s integration into the academic and social systems of the college that most directly relates to his continuance in that college” (96). I have sought to improve student integration through group-centric, community-engaged learning classes, where we spend nearly half our class time serving in the community. These community-engaged learning courses entail a fair amount of group work. Students are assigned in groups that serve together, do in-class group assignments together, and work on multifaceted group projects. Their time spent outside the classroom serving together, be it driving to a school to read with elementary school kids, or pulling carrots from the campus farm, allows students to opportunity to form deep and meaningful connections with their peers, many of which may have very different beliefs and experiences. It feels radical to “give up” half our class time traditionally used for covering course content, but the things they are learning as they serve are equally as important as the things we learn when we talk about literature, linguistics, or composition. When I transitioned my ENGL205 Literature and the Moral Imagination class to a community-engaged learning course, we went from simply talking about inequity—particularly in regards to racial inequality—to doing work to improve outcomes for our community members by ensuring they have access to healthy foods. Service learning brings to life our student learning outcomes and allows us to fulfil Xavier’s mission of practicing service rooted in justice and love

Optical gain in DNA-DCM for lasing in photonic materials

We present a detailed study of the gain length in an active medium obtained by doping of DNA strands with DCM dye molecules. The superior thermal stability of the composite and its low quenching, permits to obtain optical gain coefficient larger than 300 cm^-1. We also show that such an active material is excellent for integration into photonic nano-structures, to achieve, for example, efficient random lasing emission, and fluorescent photonic crystals

Optical doping of nitrides by ion implantation

A series of rare earth elements (RE) were implanted in GaN epilayers to study the lattice site location and optical activity. Rutherford backscattering spectrometry in the channeling mode(RBS/C) was used to follow the damage behavior in the Ga sublattice and the site location of the RE. For all the implanted elements (Ce, Pr, Dy, Er, and Lu) the results indicate the complete substitutionality on Ga sites after rapid thermal annealing at 1000°C for 2 min. The only exception occurs for Eu, which occupies a Ga displaced site. Annealing at 1200°C in nitrogen atmosphere at a pressure of IGPa is necessary to achieve the complete recovery of the damage in the samples. After annealing the recombination processes of the implanted samples were studied by above and below band gap excitation. For Er implanted samples besides the 1.54 μm emission green and red emissions are also observed. Red emissions from 5D0→7F2 and 3P0→3F2 transitions were found in Eu and Pr implanted samples even at room temperature

p-type GaN grown by phase shift epitaxy

Phase shift epitaxy (PSE) is a periodic growth scheme, which desynchronizes host material growth process from dopant incorporation, allowing independent optimization. p-type doping of GaN with Mg by PSE is accomplished with molecular beam epitaxy by periodic shutter action (in order to iterate between Ga-and N-rich surface conditions) and by adjusting time delays between dopant and Ga shutters. Optimum PSE growth was obtained by turning on the Mg flux in the N-rich condition. This suppresses Mg self-compensation at high Mg concentration and produces fairly high hole concentrations (2.4 Â 10 18 cm À

Efficient visible luminescence of nanocrystalline silicon prepared from amorphous silicon films by thermal annealing and stain etching

Films of nanocrystalline silicon (nc-Si) were prepared from hydrogenated amorphous silicon (a-Si:H) by using rapid thermal annealing. The formed nc-Si films were subjected to stain etching in hydrofluoric acid solutions in order to passivate surfaces of nc-Si. The optical reflectance spectroscopy revealed the nc-Si formation as well as the high optical quality of the formed films. The Raman scattering spectroscopy was used to estimate the mean size and volume fraction of nc-Si in the annealed films, which were about 4 to 8 nm and 44 to 90%, respectively, depending on the annealing regime. In contrast to as-deposited a-Si:H films, the nc-Si films after stain etching exhibited efficient photoluminescence in the spectral range of 600 to 950 nm at room temperature. The photoluminescence intensity and lifetimes of the stain etched nc-Si films were similar to those for conventional porous Si formed by electrochemical etching. The obtained results indicate new possibilities to prepare luminescent thin films for Si-based optoelectronics

DNA-Controlled Excitonic Switches

Fluorescence resonance energy transfer (FRET) is a promising means of enabling information processing in nanoscale devices, but dynamic control over exciton pathways is required. Here, we demonstrate the operation of two complementary switches consisting of diffusive FRET transmission lines in which exciton flow is controlled by DNA. Repeatable switching is accomplished by the removal or addition of fluorophores through toehold-mediated strand invasion. In principle, these switches can be networked to implement any Boolean function