Digital demodulator-correlator

An apparatus for demodulation and correlation of a code modulated 10 MHz signal is presented. The apparatus is comprised of a sample and hold analog-to-digital converter synchronized by a frequency coherent 40 MHz pulse to obtain four evenly spaced samples of each of the signal. Each sample is added or subtracted to or from one of four accumulators to or from the separate sums. The correlation functions are then computed. As a further feature of the invention, multipliers are each multiplied by a squarewave chopper signal having a period that is long relative to the period of the received signal to foreclose contamination of the received signal by leakage from either of the other two terms of the multipliers

Intercropping as a disease management strategy

Non-Peer Reviewe

HyFlex pedagogy: six strategies supported by design-based research

Purpose–This study investigates the following research question: What pedagogical strategies are necessary for the success of the project? The findings to this question are based in new media literacies and help to further pedagogy in an emerging HyFlex model while also grounding in needed theorization. Design/methodology/approach–This study uses design-based research(DBR) across two iterations and four doctoral, higher education courses, using mixed methods of data collection and analysis. Findings–Six pedagogical strategies influential for HyFlex research are presented, each grounded in a new media literacy skill. Originality/value–These six pedagogical strategies help practitioners grappling with the HyFlex or blended learning model merge traditional pedagogy with how this might be tailored for students entrenched in a participatory culture

STEM EBIC Mapping of the Metal-Insulator Transition in Thin-film NbO 2

This article has been published in a revised form in Microscopy and Microanalysis https://doi.org/10.1017/S1431927617007802. This version is free to view and download for private research and study only. Not for re-distribution, re-sale or use in derivative works. © copyright holder

Differential electron yield imaging with STXM

Total electron yield (TEY) imaging is an established scanning transmission X-ray microscopy (STXM) technique that gives varying contrast based on a sample's geometry, elemental composition, and electrical conductivity. However, the TEY-STXM signal is determined solely by the electrons that the beam ejects from the sample. A related technique, X-ray beam-induced current (XBIC) imaging, is sensitive to electrons and holes independently, but requires electric fields in the sample. Here we report that multi-electrode devices can be wired to produce differential electron yield (DEY) contrast, which is also independently sensitive to electrons and holes, but does not require an electric field. Depending on whether the region illuminated by the focused STXM beam is better connected to one electrode or another, the DEY-STXM contrast changes sign. DEY-STXM images thus provide a vivid map of a device's connectivity landscape, which can be key to understanding device function and failure. To demonstrate an application in the area of failure analysis, we image a 100~nm, lithographically-defined aluminum nanowire that has failed after being stressed with a large current density.Comment: 8 pages, 6 figure

Demographic and Clinical Variation in Veterans Health Administration Provision of Assistive Technology Devices to Veterans Poststroke

Objectives: To examine variation in provision of assistive technology (AT) devices and the extent to which such variation may be explained by patient characteristics or Veterans Health Administration (VHA) administrative region. Design: Retrospective population-based study. Setting: VHA. Participants: Veterans poststroke in fiscal years 2001 and 2002 (N=12,046). Interventions: Not applicable. Main Outcome Measure: Provision of 8 categories of AT devices. Results: There was considerable regional variation in provision of AT. For example, differences across administrative regions in the VHA ranged from 5.1 to 28.1 standard manual wheelchairs per 100 veterans poststroke. Using logistic regression, with only demographic variables as predictors of standard manual wheelchair provision, the c statistic was .62, and the pseudo R2 was 2.5%. Adding disease severity increased the c statistic to .67 and the pseudo R2 to 6.2%, and adding Veteran Integrated Network System further increased the c statistic to .72 and pseudo R2 to 9.8%. Conclusions: Our research showed significant variation in the provision of AT devices to veterans poststroke, and it showed that patient characteristics accounted for only 6.2% of the variation. VHA administrative region and disability severity accounted for equivalent amounts of the variation

Dark-field transmission electron microscopy and the Debye-Waller factor of graphene

Graphene's structure bears on both the material's electronic properties and fundamental questions about long range order in two-dimensional crystals. We present an analytic calculation of selected area electron diffraction from multi-layer graphene and compare it with data from samples prepared by chemical vapor deposition and mechanical exfoliation. A single layer scatters only 0.5% of the incident electrons, so this kinematical calculation can be considered reliable for five or fewer layers. Dark-field transmission electron micrographs of multi-layer graphene illustrate how knowledge of the diffraction peak intensities can be applied for rapid mapping of thickness, stacking, and grain boundaries. The diffraction peak intensities also depend on the mean-square displacement of atoms from their ideal lattice locations, which is parameterized by a Debye-Waller factor. We measure the Debye-Waller factor of a suspended monolayer of exfoliated graphene and find a result consistent with an estimate based on the Debye model. For laboratory-scale graphene samples, finite size effects are sufficient to stabilize the graphene lattice against melting, indicating that ripples in the third dimension are not necessary.Comment: 10 pages, 4 figure

Periodic ground state for the charged massive Schwinger model

It is shown that the charged massive Schwinger model supports a periodic vacuum structure for arbitrary charge density, similar to the common crystalline layout known in solid state physics. The dynamical origin of the inhomogeneity is identified in the framework of the bozonized model and in terms of the original fermionic variables.Comment: 19 pages, 10 figures, revised version, accepted in Phys. Rev.