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 participants’ 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 $CP$-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 figure

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 scientists’ 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 participants’ attitudes about research openness and their actual sharing behaviors, highlighting the need to study the “barrier” in addition to the “incentive” of research data sharing

Bank Loan Covenants and Accrual Quality

We examine whether financial covenants in loan contracts motivate banks to monitor borrowers’ 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 analysts’ information environment. The evidence supports the view that bank monitoring improves accounting quality