Physical Sciences and Mathematics Commons^™

Superlinear Increase Of Photoluminescence With Excitation Intensity In Zn-Doped Gan, Michael A. Reshchikov, Anita J. Olsen, Marilyn F. Bishop, Tom Mcmullen

Physics Publications

We have observed a superlinear increase of photoluminescence (PL) intensity in a narrow range of excitation intensities for Zn-doped GaN. The characteristic intensity at which the abrupt increase occurs increases with increasing temperature. This is unlike the usual observations for defects in semiconductors in which the PL intensity increases linearly with excitation intensity, saturating at high intensity because defects become saturated with photogenerated charge carriers. The observed phenomenon is attributed to a redirection of electron and hole flow from nonradiative centers at low excitation intensity to a recombination path via the Zn-Ga acceptor at high excitation intensity. This is the …

Contents

Journal of Mathematics and Science: Collaborative Explorations

No abstract provided.

Title Page, Coordinating Editor's Remarks

Journal of Mathematics and Science: Collaborative Explorations

No abstract provided.

Challenging Pre-Service Students' Teaching Perspectives In An Inquiry-Focused Program, J. L. Pecore, A. Shelton

Journal of Mathematics and Science: Collaborative Explorations

Inquiry teaching based on constructivist learning theory has been an emphasis in pre-service education for over a decade. In general, a developmental teaching perspective supports inquiry-based instruction where teachers view learners as constructors of knowledge and teaching as providing questions, problems, and challenges that form a bridge from the learners' prior knowledge to a new, more sophisticated form of reasoning. Since teaching perspectives influence student learning, teacher effectiveness, and teacher attrition, challenging pre-service teachers to overcome experience-based convictions of a transmission perspective is necessary in teacher education. In this study, we examined the teaching perspectives of secondary, pre-service methods students …

How Does Leadership Matter? Developing And Teaching A Definition Of Hands-On Science, A Prerequisite For Effective Inquiry Teaching, D. R. Sterling

Journal of Mathematics and Science: Collaborative Explorations

This descriptive case study describes leadership skills and planning for setting clear directions by program leaders for a statewide professional development initiative to extend improvement in science teaching and learning. For science teachers and leaders in Virginia, a critical part of setting clear goals that everyone can understand is defining key science terms. One of the four key terms, "hands-on science," is defined here. Materials to develop teachers' understanding of the term for effective implementation of classroom inquiry activities are shared, along with a rubric for evaluation by and for teachers. Understanding of the term "hands-on science" is necessary before …

Understanding Mathematics And Science Advice Networks Of Middle School Teachers, D. White, A. Ruff

Journal of Mathematics and Science: Collaborative Explorations

We report findings from a research project designed to examine the mathematics and science advice networks of teachers who participated in professional development under the auspices of the NSF-funded Rocky Mountain-Middle School Math and Science Partnership. We provide descriptive statistics of results. Additionally, we reflect on the research process and discuss some of the practical challenges involved.

Unlocking Undergraduate Problem Solving, D. Cline, K. Peterson

Journal of Mathematics and Science: Collaborative Explorations

It is difficult to find good problems for undergraduates. In this article, we explore an interesting problem that can be used in virtually any mathematics course. We then offer natural generalizations, state and prove some related results, and ultimately end with several open problems suitable for undergraduate research. Finally, we attempt to shed some light on what makes a problem interesting.

Aims & Scope

Journal of Mathematics and Science: Collaborative Explorations

No abstract provided.

Analysis Of Polyethylene Glycol In The Α-Hemolysin Nanopore, David M. Dancho

Theses and Dissertations

Nanopores have been shown to be a useful analytical tool for single molecule detection. They have been used to study the composition of DNA and other molecules of interest. These pores are usually α-hemolysin which is a toxin from Staphylococcus aureus or more recently nanoscale synthetic solid state pores. Now we are beginning to look at other molecules or proteins by sending them into the nanopores and measuring a characteristic partial current blockade. In this thesis we look at polyethylene glycol (PEG) as it enters and blocks current through a single alpha hemolysin pore. We report the effects of ionic …

Land Of The Ley, Grace Huddleston

AUCTUS: The Journal of Undergraduate Research and Creative Scholarship

The line separating phenomenon and science has become blurred in the investigation of ley lines. Ley lines can be described as “invisible” lines that link different places of interest and significance, either historical or geographical. This is a very loose definition, but it must remain vague, as it has to account for the various understandings of the lines. These individual interpretations are noted by Atkins Webster in his introduction to “Do Quasar Ley Lines Really Exist,” in which he states that “one supposition is that these ley lines were intended for some practical purpose, perhaps to mark a track or …

Methods In Visual Mathematics: Reductionism In Researching Mathematical Principles In Art, Lauren N. Colie

AUCTUS: The Journal of Undergraduate Research and Creative Scholarship

People traditionally rely on visual arts as an effective communication tool and medium of self-expression for when words fail to convey abstract concepts. Thera Mjaaland, anthropologist and professional photographer, writes, “Art is capable of negotiating conceptual gaps caused by a dichotomized epistemology” (393). In essence, Mjaaland asserts that art helps relate different modes of thinking by illustrating the abstract and difficult to grasp—privileging the communicative value of an image over that of text. Within this method of communication is a collection of works acknowledged by public consensus to be of an elevated status or value. The art world is deeply …

Enhanced Biocidal Activity Of Au Nanoparticles Synthesized In One Pot Using 2, 4-Dihydroxybenzene Carbodithioic Acid As A Reducing And Stabilizing Agent, Syeda Sohaila Naz, Nazar Ul Islam, Muhammad Raza Shah, Syed Sartaj Alam, Zafar Iqbal, Massimo Bertino, Louis Franzel, Afifa Ahmed

Physics Publications

Background

The conjugation of gold nanoparticles with biocides such as natural products, oligosaccharides, DNA, proteins has attracted great attention of scientists recently. Gold NPs covered with biologically important molecules showed significant enhancement in biological activity in comparison with the activity of the free biocides. However, these reports are not very systematic and do not allow to draw definitive conclusions. We therefore embarked in a systematic study related to the synthesis and characterization of biocidal activities of Au nanoparticles conjugated to a wide variety of synthetic and natural biomolecules. In this specific report, we investigated the activity of a synthetic biocide, …

Blue Luminescence And Zn Acceptor In Gan, Denis Demchenko, Michael A. Reshchikov

Physics Publications

In this paper, we present a comparison of exchange-tuned hybrid density functional calculations with experimental data obtained for the Zn acceptor in GaN. Since this acceptor is one of the few reliably identified defects in GaN, we use Zn-doped GaN as a test case for the widely used HSE06 hybrid functional method of calculations of defect properties in semiconductors. Here, we present the experimental results of luminescence measurements in Zn-doped GaN from which we obtain Zn acceptor defect levels. They are compared with theoretically calculated defect thermodynamic and optical transition levels as well as the zero-phonon line associated with this …

Tunable Thermal Quenching Of Photoluminescence In Mg-Doped P-Type Gan, Michael A. Reshchikov, J. D. Mcnamara, S. Fernández-Garrido, R. Calarco

Physics Publications

We have studied the thermal quenching of the ultraviolet luminescence band with a maximum at about 3.25 eV in p-type Mg-doped GaN. The characteristic temperature of the thermal quenching of photoluminescence (PL) gradually shifted to higher temperatures with increasing excitation intensity. This effect is explained by a population inversion of charge carriers at low temperatures, which suddenly converts into a quasiequilibrium population as the temperature increases above the characteristic value. Tunable quenching of PL has been observed only in some of the GaN:Mg samples. The absence of the tunable quenching of PL in another group of GaN:Mg samples is preliminarily …

Unusually Large Spin Polarization And Magnetoresistance In A Femg8-Femg8 Superatomic Dimer, Lin Zhu, Meichun Qian, Shiv N. Khanna

Physics Publications

Electronic transport across a FeMg8 magnetic superatom and its dimer has been investigated using a density functional theory combined with Keldysh nonequilibrium Green's-function formalism. For a single cluster, our studies for the cluster supported in various orientations on a Au(100) surface show that the transport is sensitive to the contact geometry. Investigations covering the cases where the axes of Mg square antiprism are 45°, perpendicular, and parallel to the transport direction, show that the equilibrium conductance, transferred charge, and currentpolarizations can all change significantly with orientation. Our studies on the transport across a magnetic superatom dimer FeMg8–FeMg8 focus on the …

Magnetic Hollow Cages With Colossal Moments, Menghao Wu, Puru Jena

Physics Publications

A comprehensive study of the interaction of transition metal clusters with B, C, N, O, and Si reveal novel structure and properties: Co12C6, Mn12C6, and Mn24C18 clusters form stable ferromagnetic hollow cages with total magnetic moments of 14 μB, 38 μB, and 70 μB, respectively. Replacement of C with B, N, O, or Si has significant impact on their structure and magnetic properties. For example, Mn20Si12 cluster forms a ferrimagnetic dodecahedral hollow cage with a total magnetic moment of 36 μB while Mn12N6, X12C6 (X = Ni, Cu, Pd, Pt), and Cu12O6 possess no magnetic moment, although they retain hollow …

Scientific Inquiry And The Nature Of Science Task Force Report: Preface

Journal of Mathematics and Science: Collaborative Explorations

No abstract provided.

Teaching About Scientific Inquiry And The Nature Of Science: Toward A More Complete View Of Science

Journal of Mathematics and Science: Collaborative Explorations

No abstract provided.

Building A Case For Mathematics Specialist Programs, D. Blount, J. Singleton

Journal of Mathematics and Science: Collaborative Explorations

No abstract provided.

Right Triangles Of Gian Francesco Malfatti, J. Boyd

Journal of Mathematics and Science: Collaborative Explorations

No abstract provided.

Grappling With Issues Of Learning Science From Everyday Experiences: An Illustrative Case Study, A.-L. Tan, M. Kim, F. Talaue

Journal of Mathematics and Science: Collaborative Explorations

There are different perceptions among researchers with regard to the infusion of everyday experience in the teaching of science: 1) it hinders the learning of science concepts; or, 2) it increases the participation and motivation of students in science learning. This article attempts to contemplate those different perspectives of everyday knowledge in science classrooms by using everyday contexts to teach grade 3 science in Singapore. In this study, two groups of grade 3 students were presented with a scenario that required them to apply the concept of properties of materials to design a shoe. Subsequently, the transcripts of classroom discussions …

A Lesson Plan With An Arc Midpoint, G. V. Akulov, O. G. Akulov

Journal of Mathematics and Science: Collaborative Explorations

The article introduces an explicit way of locating the arc midpoint in the Cartesian plane, which is consistent for both x- and y-coordinates and is technically accessible for students starting as young as fifteen. The authors give the proof of the statement using two trigonometry identities, and discuss some materials for innovative lessons on the arc midpoint computation that could enrich and enhance curriculum.

Reform Teaching In Mathematics And Science Courses — A Follow-Up Evaluation, G. M. Bass Jr.

Journal of Mathematics and Science: Collaborative Explorations

No abstract provided.