15,973 research outputs found
Nature of Mathematical Modeling Tasks for Secondary Mathematics Preservice Teachers
This study investigated the nature of written modeling tasks reported by instructors of required courses in five secondary mathematics teacher education programs. These tasks were analyzed based on a framework addressing potential cognitive orientation (simple procedures, complex procedures, and rich tasks) and purpose (epistemological, educational, contextual, and socio-critical modeling) of the tasks. Our analysis suggests that most tasks included questions of more than one cognitive orientation and more than half of the tasks were coded as contextual modeling. We also found that tasks that were coded as contextual modeling offered opportunities for future teachers to engage with questions at all levels of cognitive orientation. The nature of several modeling tasks, along with the ideas for refining the current frameworks, are presented for future implications of analyzing and developing modeling tasks
Learning About Modeling in Teacher Preparation Programs
This study explores opportunities that secondary mathematics teacher preparation programs provide to learn about modeling in algebra. Forty-eight course instructors and ten focus groups at five universities were interviewed to answer questions related to modeling. With the analysis of the interview transcripts and related course materials, we found few opportunities for PSTs to engage with the full modeling cycle. Examples of opportunities to learn about algebraic modeling and the participantsâ perspectives on the opportunities can contribute to the study of modeling and algebra in teacher education
Fermion EDMs with Minimal Flavor Violation
We study the electric dipole moments (EDMs) of fermions in the standard model
supplemented with right-handed neutrinos and its extension including neutrino
seesaw mechanism under the framework of minimal flavor violation (MFV). In the
quark sector, we find that the current experimental bound on the neutron EDM
does not yield a significant restriction on the scale of MFV. In addition, we
consider how MFV may affect the contribution of the strong theta-term to the
neutron EDM. For the leptons, the existing EDM data also do not lead to strict
limits if neutrinos are Dirac particles. On the other hand, if neutrinos are
Majorana in nature, we find that the constraints become substantially stronger.
Moreover, the results of the latest search for the electron EDM by the ACME
Collaboration are sensitive to the MFV scale of order a few hundred GeV or
higher. We also look at constraints from -violating electron-nucleon
interactions that have been probed in atomic and molecular EDM searches.Comment: 27 pages, 6 figures. New materials adde
Detailed Studies of Pixelated CZT Detectors Grown with the Modified Horizontal Bridgman Method
The detector material Cadmium Zinc Telluride (CZT), known for its high
resolution over a broad energy range, is produced mainly by two methods: the
Modified High-Pressure Bridgman (MHB) and the High-Pressure Bridgman (HPB)
process. This study is based on MHB CZT substrates from the company Orbotech
Medical Solutions Ltd. with a detector size of 2.0x2.0x0.5 cm^3, 8x8 pixels and
a pitch of 2.46 mm. Former studies have emphasized only on the cathode material
showing that high-work-function improve the energy resolution at lower
energies. Therfore, we studied the influence of the anode material while
keeping the cathode material constant. We used four different materials:
Indium, Titanium, Chromium and Gold with work-functions between 4.1 eV and 5.1
eV. The low work-function materials Indium and Titanium achieved the best
performance with energy resolutions: 2.0 keV (at 59 keV) and 1.9 keV (at 122
keV) for Titanium; 2.1 keV (at 59 keV) and 2.9 keV (at 122 keV) for Indium.
These detectors are very competitive compared with the more expensive ones
based on HPB material if one takes the large pixel pitch of 2.46 mm into
account. We present a detailed comparison of our detector response with 3-D
simulations, from which we determined the mobility-lifetime-products for
electrons and holes. Finally, we evaluated the temperature dependency of the
detector performance and mobility-lifetime-products, which is important for
many applications. With decreasing temperature down to -30C the breakdown
voltage increases and the electron mobility-lifetime-product decreases by about
30% over a range from 20C to -30C. This causes the energy resolution to
deteriorate, but the concomitantly increasing breakdown voltage makes it
possible to increase the applied bias voltage and restore the full performance.Comment: Accepted for publication in Astroparticle Physics, 25 pages, 13
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Toward a conceptual framework for data sharing practices in social sciences: A profile approach. In the proceedings of the ASIS&T 2016 Annual Meeting
This paper investigates the landscape of data-sharing practices in social sciences via the data sharing profile approach. Guided by two pre-existing conceptual frameworks, Knowledge Infrastructure (KI) and the Theory of Remote Scientific Collaboration (TORSC), we design and test a profile tool that consists of four overarching dimensions for capturing social scientistsâ data practices, namely: 1) data characteristics, 2) perceived technical infrastructure, 3) perceived organizational context, and 4) individual characteristics. To ensure that the instrument can be applied in real and practical terms, we conduct a case study by collecting responses from 93 early-career social scientists at two research universities in the Pittsburgh Area, U.S. The results suggest that there is no significant difference, in general, among scholars who prefer quantitative, mixed method, or qualitative research methods in terms of research activities and data-sharing practices. We also confirm that there is a gap between participantsâ attitudes about research openness and their actual sharing behaviors, highlighting the need to study the âbarrierâ in addition to the âincentiveâ of research data sharing
The comparison and validity and reliability study of bilateral innominate vertical length measurements using innovative digital radiographic imaging software in assessing scoliotic leg length discrepancy
Bank Loan Covenants and Accrual Quality
We examine whether financial covenants in loan contracts motivate banks to monitor borrowersâ financial reporting practices and result in a higher quality of reported accruals. We document that, relative to loans without financial covenants, loans with financial covenants lead to a significant improvement in accrual quality measured by the extent to which accruals can be mapped into cash flows. The effect of loan covenants on accrual quality is stronger when external monitoring by non-bank stakeholders (i.e., institutional investors and financial analysts) is weaker. Furthermore, initiations of bank loans with financial covenants are related to subsequent improvements in analystsâ information environment. The evidence supports the view that bank monitoring improves accounting quality
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