759 research outputs found

    Breathing New Life into Old Technological Infrastructure: Broadband Internet as a Means of Jump-Starting the Economy and Connecting the Country

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    This paper examines the current structure of universal service and the FCC’s Universal Service Fund, recent pushes to expand the definition of and funding for universal service to include broadband access, and how broadband internet can contribute to saving the ailing economy. This paper concludes by calling for the inclusion of broadband internet in the Universal Service Fund

    Ion-implanted epitaxially grown ZnSe

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    The use of ZnSe to obtain efficient, short wavelength injection luminescence was investigated. It was proposed that shorter wavelength emission and higher efficiency be achieved by employing a p-i-n diode structure rather than the normal p-n diode structure. The intervening i layer minimizes concentration quenching effects and the donor-acceptor pair states leading to long wavelength emission. The surface p layer was formed by ion implantation; implantation of the i layer rather than the n substrate permits higher, uncompensated p-type doping. An ion implanted p-n junction in ZnSe is efficiency-limited by high electron injection terminating in nonradiative recombination at the front surface, and by low hole injection resulting from the inability to obtain high conductivity p-type surface layers. While the injection ratio in p-n junctions was determined by the radio of majority carrier concentrations, the injection ratio in p-i-n structures was determined by the mobility ratios and/or space charge neutrality requirements in the i layer

    Solar cells for terrestrial applications

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    The power efficiency curves of photovoltaic solar cells were investigated as a function of the forbidden energy gap (E sub g) and the current-voltage characteristic of the diode. Minority carrier injection, depletion layer recombination, and interface recombination terms were considered in models for the I-V characteristic. The collection efficiency for photons with energy between (E sub g) and an upper energy cutoff (E sub w) was assumed to be 100% and zero otherwise. Results are presented in terms of a single parameter related to the ratio of depletion layer width and minority carrier diffusion length. It was found that increasing depletion layer recombination shifts the efficiency curves to larger values of the energy without changing the shape of the efficiency curve appreciably. It is believed that similar results would be obtained whenever the quality factors in the exponential energy gap and forward bias terms are equal

    Right To Appointed Counsel: The Outer Limits. Davis v. Page

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    Abandoned, abused, neglected, surrendered, run-away, truant, and uncontrollably disobedient children in Florida are neatly categorized by the law as dependent

    Watching the watchdog: Making self-regulation work in journalism

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    A new report from the Ethical Journalism Network (EJN) looks at how journalism is monitored in 16 countries across five continents and the impact this has on public trust. EJN Communications officer Stefanie Chernow and director Aidan White discuss how to make self-regulation work in the UK and elsewhere

    Designing core-shell 3D photonic crystal lattices for negative refraction

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    We use a plane wave expansion method to define parameters for the fabrication of 3-dimensional (3D) core-shell photonic crystals (PhCs) with lattice geometries that are capable of all-angle negative refraction (AANR) in the midinfrared centered around 8.0 μm. We discuss the dependence of the AANR frequency range on the volume fraction of solid within the lattice and on the ratio of the low index core material to the high index shell material. Following the constraints set by simulations, we fabricate two types of nanolattice PhCs: (1) polymer core-germanium shell and (2) amorphous carbon core-germanium shell to enable experimental observation of 3D negative refraction and related dispersion phenomena at infrared and eventually optical frequencies

    Design, Fabrication, and Characterization of 3D Nanolattice Photonic Crystals for Bandgap and Refractive Index Engineering

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    Three-dimensional (3D) photonic crystals (PhCs) have been the focus of ever-increasing interest in the scientific community given their potential to impact areas spanning energy conversion to analyte sensing. These architected materials are defined by a refractive index that is spatially modulated with a period comparable to that of the electromagnetic wavelength. As a result, constructive and destructive interference due to multiple scattering gives rise to a band structure for photons which may contain gaps. Both bands and bandgaps can be engineered to specifically manipulate light propagation by 3D PhCs. In this work we explore the effect of lattice architecture, finite-size effects, and material constraints on stopband position and emergence of band dispersion phenomena like negative refraction. We show that uniaxial mechanical compression can be used to stably and reversibly tune stopband position in 3D polymer nanolattice PhCs with octahedron unit-cell geometry. We then explore how lattice architecture, namely the differences in 3D cubic space group and finite size effects impact experimentally observable stopbands, and assess the degree to which the stopband behavior of real PhCs can be adequately described by the photonic band structure for an infinite, ideal PhC. Finally, we discuss the design, fabrication, and characterization of a core-shell 3D nanolattice PhC which exhibits an effective negative refractive index in the mid-infrared range.</p

    Mount Carmel Downtown Inc. Vision 2020

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    The purpose of this document is to analyze research and provide suggestions to help Mount Carmel Downtown Inc. (MCDI) strategically plan change in Mount Carmel’s downtown district. The analysis is based on over 27 interviews, observations from visits to Mount Carmel, 250 responses to a community survey, a survey of 14 local businesses, and supplemental background research in order to determine MCDI and Mount Carmel’s assets, obstacles and areas for improvement. This report was developed by a group of Bucknell University Managing for Sustainability student researchers in a senior capstone course MSUS 400 taught by Prof. Eric Martin

    Polymer lattices as mechanically tunable 3-dimensional photonic crystals operating in the infrared

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    Broadly tunable photonic crystals in the near- to mid-infrared region could find use in spectroscopy, non-invasive medical diagnosis, chemical and biological sensing, and military applications, but so far have not been widely realized. We report the fabrication and characterization of three-dimensional tunable photonic crystals composed of polymer nanolattices with an octahedron unit-cell geometry. These photonic crystals exhibit a strong peak in reflection in the mid-infrared that shifts substantially and reversibly with application of compressive uniaxial strain. A strain of ∼40% results in a 2.2 μm wavelength shift in the pseudo-stop band, from 7.3 μm for the as-fabricated nanolattice to 5.1 μm when strained. We found a linear relationship between the overall compressive strain in the photonic crystal and the resulting stopband shift, with a ∼50 nm blueshift in the reflection peak position per percent increase in strain. These results suggest that architected nanolattices can serve as efficient three-dimensional mechanically tunable photonic crystals, providing a foundation for new opto-mechanical components and devices across infrared and possibly visible frequencies

    The Impact of Environmental Factors on Emergency Medicine Resident Career Choice

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    Objective: To evaluate the impact of environmental factors on emergency medicine (EM) resident career choice. Methods: Program directors of all U.S. EM residencies were surveyed in November 1997. A 22-item questionnaire assessed resources allocated to research, fellowship availability, academic productivity of faculty and residents, and career choices of residency graduates. Results: The response rate was 83%. The program director (mean ± SD) estimates of resident career choice were as follows: 27.8 ± 19.1% pursued academic positions with emphasis on teaching, 5.4 ± 9.8% pursued academic positions with emphasis on research, and 66.8 ± 23.1%, pursued private practice positions. In addition, 5.70 ± 6.13% of the residency graduates were estimated to seek felloship training. Univariate analyses demonstrated that increasing departmental funding for research, having substantial resource availability (defined as having at least two of the following: dedicated laboratory space; support for a laboratory research technician/assistant, a clinical research nurse or study coordinator, a statistician, or an assistant with a PhD degree), a greater number of peer-reviewed publications by residents (r = 0.22; p = 0.08), and a greater number of peer-reviewed publications by faculty (r = 0.26; p = 0.04) positively correlated with the percentage of graduates who pursue academic research careers. Using multiple regression, however, increasing intramural funding and the presence of substantial resource availability were the only variables predictive of resident pursuit of an academic research career. Conclusion: Modification of the EM training environment may influence the career choices of graduates. Specifically, greater commitment of departmental funds and support of resources for research may enhance the likelihood of a trainee's choosing an academic research career.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72940/1/j.1553-2712.1999.tb00387.x.pd
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