Bandwidth control of forbidden transmission gaps in compound structures with subwavelength slits

Phase resonances in transmission compound structures with subwavelength slits produce sharp dips in the transmission response. For all equal slits, the wavelengths of these sharp transmission minima can be varied by changing the width or the length of all the slits. In this paper we show that the width of the dip, i.e., the frequency range of minimum transmittance, can be controlled by making at least one slit different from the rest within a compound unit cell. In particular, we investigate the effect that a change in the dielectric filling, or in the length of a single slit produces in the transmission response. We also analyze the scan angle behavior of these structures by means of band diagrams, and compare them with previous results for all-equal slit structures.Comment: 16 pages, 5 figures, submitted to Phys. Rev.

Proposal to the Ethics Education in Science and Engineering Program, National Science Foundation: Role-Play Scenarios for Teaching Responsible Conduct of Research

We propose to develop and assess role-play scenarios to teach central topics in the responsible conduct of research (RCR) to graduate students in science and engineering. Together the scenarios will cover plagiarism, authorship, conflict of interest, interpersonal conflicts in mentoring, and concerns about compliance with research regulations on human participants in research, animal subjects, or hazardous substances. Two scenarios will present potential whistleblowing situations. Intellectual merit: Few previous studies have carefully assessed the effectiveness of role-play in teaching ethics. We will conduct a rigorous, systematic assessment of role-play, using multiple methods, with a diverse group of graduate students. We will examine whether role-play helps students identify moral issues in research, understand multiple perspectives in ethical disputes, and negotiate practical solutions to moral problems. We will document how students’ conceptions of RCR change. We will determine whether students retain their new knowledge and skills. For this project, we will draw on our previous experience in the scholarship of teaching and learning. Broader impacts: Collaborating with both graduate and undergraduate students, we will develop educational materials that can be adopted by graduate programs in all science and engineering departments. These materials will be disseminated through professional meetings and archived online. We believe that by engaging students through the role-play scenarios, we would teach graduate students to handle ethical problems in RCR effectively. As an outcome of this project, we expect to find that long after students have participated in role-play sessions, they will recall the lessons of those sessions, and they will be able to apply those lessons to a wide range of ethical problems that they may encounter in their professional careers

A Qualitative Study of Emotions Experienced by First-year Engineering Students during Programming Tasks

In introductory computer programming courses, students experience a range of emotions. Students often experience anxiety and frustration when they encounter difficulties in writing programs. Continued frustration can discourage students from pursuing engineering and computing careers. Although prior research has shown how emotions affect students’ motivation and learning, little is known about students’ emotions in programming courses. In this qualitative study of first-year engineering students taking an introductory programming course, we examined the emotions that these students experienced during programming tasks and the reasons for experiencing those emotions. Our study was grounded in the control-value theory of achievement emotions. Each research participant came to two laboratory sessions: a programming session and a retrospective think-aloud interview session. In the programming session, each participant worked individually on programming problems. We collected screen capture, biometrics, and survey responses. In the interview session, each participant watched a video of their actions during the programming session. After every 2 minutes of viewing, the participants reported the emotions that they had experienced during this 2-minute period. We performed a thematic analysis of the interview data. Our results indicate that the participants experienced frustration most frequently. Sometimes they experienced multiple emotions. For example, one participant felt annoyed because she had made a mistake, but she felt joy and pride when she fixed the mistake. To promote student learning, educators should take students’ emotions into account in the design of curriculum and pedagogy for introductory programming courses

Structured Pairing in a First-Year Electrical and Computer Engineering Laboratory: The Effects on Student Retention, Attitudes, and Teamwork

This paper describes a simple technique, structured pairing, for organizing student teams in engineering instructional laboratories. This technique was adapted from pair programming, which was previously found to improve student confidence, satisfaction, and retention in computer science. A study of structured pairing was implemented in a large required course for first-year students in electrical and computer engineering. Six laboratory sections implemented structured pairing, and the other seven laboratory sections operated in a traditional way (i.e., unstructured team interactions). Data were collected from a student survey, two focus groups, and course enrollment records. Structured pairing students reported significantly higher confidence in laboratory tasks and satisfaction with the course and teamwork experiences. Focus group data indicated that structured pairing students experienced reciprocal scaffolding (i.e., students acknowledged that they learned from each other). Short-term retention in engineering did not differ significantly between structured pairing and traditional section students. These findings suggest that structured pairing is a more engaging and motivating alternative to traditional laboratory teaming methods

Role of the ArcAB two-component system in the resistance of Escherichia coli to reactive oxygen stress

<p>Abstract</p> <p>Background</p> <p>The global regulatory system ArcAB controls the anaerobic growth of <it>E. coli</it>, however, its role in aerobic conditions is not well characterized. We have previously reported that ArcA was necessary for <it>Salmonella </it>to resist reactive oxygen species (ROS) in aerobic conditions.</p> <p>Results</p> <p>To investigate the mechanism of ROS resistance mediated by ArcAB, we generated deletion mutants of ArcA and ArcB in <it>E. coli</it>. Our results demonstrated that both ArcA and ArcB were necessary for resistance to hydrogen peroxide (H₂O₂), a type of ROS, and their function in this resistance was independent from H₂O₂scavenge. Mutagenesis analysis of ArcA indicated that ROS resistance was mediated through a distinct signaling pathway from that used in anaerobic conditions. An abundant protein flagellin was elevated at both the protein and mRNA levels in the <it>ΔarcA </it>mutant as compared to the wild type <it>E. coli</it>, and deletion of flagellin restored the resistance of the <it>ΔarcA </it>mutant to H₂O₂. The resistance of the <it>ΔarcA </it>mutant <it>E. coli </it>to H₂O₂can also be restored by amino acid supplementation, suggesting that a deficiency in amino acid and/or protein synthesis in the mutant contributed to its susceptibility to H₂O₂, which is consistent with the notion that protein synthesis is necessary for ROS resistance.</p> <p>Conclusion</p> <p>Our results suggest that in addition to its role as a global regulator for anaerobic growth of bacteria, ArcAB system is also important for bacterial resistance to ROS in aerobic conditions, possibly through its influence on bacterial metabolism, especially amino acid and/or protein assimilation and synthesis.</p

What Do Students Experience as Peer Leaders of Learning Teams?

In a course for engineering freshmen, peer leaders facilitated optional study sessions, which implemented peer-led team learning workshops. Some leaders were paid teaching assistants, but most were undergraduate volunteers. To understand the experiences of the peer leaders, we asked them to keep weekly reflective journals. By performing a basic qualitative analysis of fourteen journals from two semesters, we developed a description of the experience of leading peer-led team learning workshops over the course of the semester. At the beginning of the semester, the leaders were apprehensive about teaching and concerned with correctly answering students’ questions. As the semester progressed, the leaders were often frustrated with the difficulty of teaching, and the leaders tried new ways of encouraging student participation. At the end of the semester, the leaders reported that they increased self-confidence, developed an appreciation for intellectual diversity, and gained an increased interest in teaching

Minimizing Access Pointer into Trees and Arrays

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryJoint Services Electronics Program / N00014-79-C-0424National Science Foundation / MCS-801070

Complexity Theory

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryNational Science Foundation / CCR-9315696Originally published July 1995; revision published November 1995 with the same tech report number

Optimal Dynamic Embedding of Trees into Arrays

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryJoint Services Electronics Program / N00014-79-C-042

The Complexity of Sorting on Distributed Systems

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryJoint Services Electronics Program / N00014-79-C-0424National Science Foundation / MCS-821744