Non-invasive Scanning Raman Spectroscopy and Tomography for Graphene Membrane Characterization

Graphene has extraordinary mechanical and electronic properties, making it a promising material for membrane based nanoelectromechanical systems (NEMS). Here, chemical-vapor-deposited graphene is transferred onto target substrates to suspend it over cavities and trenches for pressure-sensor applications. The development of such devices requires suitable metrology methods, i.e., large-scale characterization techniques, to confirm and analyze successful graphene transfer with intact suspended graphene membranes. We propose fast and noninvasive Raman spectroscopy mapping to distinguish between freestanding and substrate-supported graphene, utilizing the different strain and doping levels. The technique is expanded to combine two-dimensional area scans with cross-sectional Raman spectroscopy, resulting in three-dimensional Raman tomography of membrane-based graphene NEMS. The potential of Raman tomography for in-line monitoring is further demonstrated with a methodology for automated data analysis to spatially resolve the material composition in micrometer-scale integrated devices, including free-standing and substrate-supported graphene. Raman tomography may be applied to devices composed of other two-dimensional materials as well as silicon micro- and nanoelectromechanical systems.Comment: 23 pages, 5 figure

An Interactive Power System Analyzer With Graphics Display For Educational Use

The paper presents a student-oriented power-system analyzer with an interactive graphics display. Its capabilities include studies of (1) load flow, (2) load and generation, (3) voltage level control, (4) economic dispatch, and (5) contingency and planning analysis. Power network configurations of up to 30 buses can be presented clearly on one screen. The interactive nature of this program makes such studies effective and easy to use. With the support of a computer with graphics software and many graphics terminals, this program can be a useful teaching tool for power system studies. Copyright © 1986 by The Institute of Electrical and Electronics Engineers, Inc

A Graphene-based Hot Electron Transistor

We experimentally demonstrate DC functionality of graphene-based hot electron transistors, which we call Graphene Base Transistors (GBT). The fabrication scheme is potentially compatible with silicon technology and can be carried out at the wafer scale with standard silicon technology. The state of the GBTs can be switched by a potential applied to the transistor base, which is made of graphene. Transfer characteristics of the GBTs show ON/OFF current ratios exceeding 50.000.Comment: 18 pages, 6 figure

The Role of Using Formative Assessments in Problem-based Learning: A Health Sciences Education Perspective

Practitioners in the field of pharmacy are often confronted with ill-structured problems. Specifically, pharmacists are tasked with making patient-specific recommendations that are both safe and effective, which requires combining knowledge from the biomedical, behavioral, and pharmaceutical sciences. Given the dynamic nature of pharmacy as a profession, the field has begun to explore learning strategies that go beyond mere content coverage to strategies that better support higher-order learning outcomes. One of these approaches is problem-based learning (PBL). While studies have focused on how to support PBL to improve learning outcomes, the role of assessment is often overlooked. Further exploration is thus needed since assessment plays a pivotal role in teaching and learning. This Voices paper will explore this idea within a larger context; we will also share the experience of how a subject matter expert (SME) worked with a team of instructional designers (IDs) to revise an existing course to more explicitly employ PBL and thus adopt an inquiry-based mindset needed for complex clinical decision making. Given the inherent challenges of assessment in PBL, further discussion will be focused on how to (a) design ill-structured problems, (b) align assessments to the PBL curriculum, and (c) how to hold students accountable in cases where a traditional grade is not attached

A new regime of anomalous penetration of relativistically strong laser radiation into an overdense plasma

It is shown that penetration of relativistically intense laser light into an overdense plasma, accessible by self-induced transparency, occurs over a finite length only. The penetration length depends crucially on the overdense plasma parameter and increases with increasing incident intensity after exceeding the threshold for self-induced transparency. Exact analytical solutions describing the plasma-field distributions are presented.Comment: 6 pages, 2 figures in 2 separate eps files; submitted to JETP Letter

Opportunities and conditions to learn (OCL): A conceptual framework

“Opportunity to learn” has evolved into an umbrella phrase for describing a large range of settings, resources, structures, and processes. The aim of this study is to develop a conceptual framework that can accommodate a wide range of opportunities to learn, not just those provided by teachers in classrooms. An inclusive framework can bring together diverse studies about opportunity to learn, increasing synergies and uncovering interconnections, and making more visible marginalized forms of learning. It can also be used as a framework for holding governments, education authorities, and policy makers accountable for providing equitable opportunities and conditions to learn. This article presents a three-dimensional conceptual framework of opportunities and conditions to learn (OCL) that captures (a) notions of what opportunities exist and where those opportunities exist and opportunities offered by whom, as well as (b) a spate of conditions that can shape those opportunities

Bilayer Insulator Tunnel Barriers for Graphene-Based Vertical Hot-electron Transistors

Vertical graphene-based device concepts that rely on quantum mechanical tunneling are intensely being discussed in literature for applications in electronics and optoelectronics. In this work, the carrier transport mechanisms in semiconductor-insulator-graphene (SIG) capacitors are investigated with respect to their suitability as the electron emitter in vertical graphene base transistors (GBTs). Several dielectric materials as tunnel barriers are compared, including dielectric double layers. Using bilayer dielectrics, we experimentally demonstrate significant improvements in the electron injection current by promoting Fowler-Nordheim tunneling (FNT) and step tunneling (ST) while suppressing defect mediated carrier transports. High injected tunneling current densities approaching 10$^3$ A/cm$^2$ (limited by series resistance), and excellent current-voltage nonlinearity and asymmetry are achieved using a 1 nm-thick high quality dielectric, thulium silicate (TmSiO), as the first insulator layer, and titanium dioxide (TiO$_2$) as a high electron affinity second layer insulator. We also confirm the feasibility and effectiveness of our approach in a full GBT structure which shows dramatic improvement in the collector on-state current density with respect to the previously reported GBTs. The device design and the fabrication scheme have been selected with future CMOS process compatibility in mind. This work proposes a bilayer tunnel barrier approach as a promising candidate to be used in high performance vertical graphene-based tunneling devices

Does the pain-protective GTP cyclohydrolase haplotype significantly alter the pattern or severity of pain in humans with chronic pancreatitis?

<p>Abstract</p> <p>Background</p> <p>Pain is often a dominant clinical feature of chronic pancreatitis but the frequency and severity is highly variable between subjects. We hypothesized that genetic polymorphisms contribute to variations in clinical pain patterns. Since genetic variations in the GTP cyclohydrolase (GCH1) gene have been reported to protect some patients from pain, we investigated the effect of the "pain protective haplotype" in well characterized patients with chronic pancreatitis (CP) or recurrent acute pancreatitis (RAP) from the North American Pancreatitis Study 2 (NAPS2).</p> <p>Results</p> <p>Subjects in the NAPS2 study were asked to rank their pain in one of 5 categories reflecting different levels of pain frequency and severity. All subjects were genotyped at rs8007267 and rs3783641 to determine the frequency of the GCH1 pain-protective haplotype. In Caucasian subjects the frequency of the pain-protective GCH1 haplotype was no different in the control group (n = 236), CP patients (n = 265), RAP patients (N = 131), or in CP patients subclassified by pain category compared to previously reported haplotype frequencies in the general Caucasian population.</p> <p>Conclusion</p> <p>The GCH1 pain-protective haplotype does not have a significant effect on pain patterns or severity in RAP or CP. These results are important for helping to define the regulators of visceral pain, and to distinguish different mechanisms of pain.</p

Considerations In Developing And Utilizing Operator Training Simulators

Effective electric system operation depends on strengthening the relationship between the system operator and the electrical system with its associated control system. This relationship can be developed through a training medium which increases the operator\u27s knowledge of the behavior of the power system under various operating conditions and contingencies, and its response to control actions. An Operator Training Simulator (OTS), which simulates the static and dynamic responses of the operator\u27s power system and his control system, can accomplish these training objectives. The concepts developed in this paper are based on the work of the project team through funding by the Electric Power Research Institute. Copyright © 1983 by The Institute of Electrical and Electronics Engineers, Inc