8,500 research outputs found

    An Off-lattice Model for Br Electrodeposition on Au(100): from DFT to Experiment

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    Since Br adsorption on Au(100) displays an incommensurate ordered phase, a lattice-gas treatment of the adlayer configurations is not reliable. We therefore use density functional theory slab calculations to determine the parameters necessary for the construction of an off-lattice model. We compute and analyze the total energy and electron density as the lateral Br position and coverage are varied. This allows the calculation of the corrugation potential, the short-range lateral interactions, the dipole moment (long-range interactions), and the residence charge. From these parameters, we construct an off-lattice model with no freely adjustable parameters. The simulation results compare remarkably well with experimental results.Comment: 42 pages, 15 embedded figures, submitted to Surface Scienc

    'Heaf' multiple puncture tuberculin test

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    A comparison with intradermal tuberculin P.P.D. in the Cape coloured subjec

    Factors contributing to the ballistocardiographic wave form in healthy middle aged males

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    Factors contributing to ballistocardiographic waveform in healthy middle aged male

    Apparent Superluminal Behavior

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    The apparent superluminal propagation of electromagnetic signals seen in recent experiments is shown to be the result of simple and robust properties of relativistic field equations. Although the wave front of a signal passing through a classically forbidden region can never move faster than light, an attenuated replica of the signal is reproduced ``instantaneously'' on the other side of the barrier. The reconstructed signal, causally connected to the forerunner rather than the bulk of the input signal, appears to move through the barrier faster than light.Comment: 8 pages, no figure

    Meeting Reports

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    Student Voices: Recording the First-Generation Student Experience

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    In this session, an English instructor, digital initiatives librarian, and archivist will discuss an interdepartmental collaboration that integrates a digital story-telling project into first-generation undergraduate instruction. They will talk about the project goals, lesson plan, and learning outcomes; procedures for placing student-created oral histories in the digital repository; student reactions to the project; and lessons learned. This project focuses on first-generation students, a population that is growing at colleges and universities across the nation and receiving increased attention in the library and archives literature. At the University of Northern Colorado (UNC), approximately 40% of the undergraduate population is classified as first-generation. These students represent one of the most diverse populations on campus; many are minorities and/or come from underprivileged backgrounds. To enhance the success and retention of these students, the Center for Human Enrichment (CHE) program provides support through instruction, tutoring, and academic advising. First-year CHE participants follow a specialized curriculum of cohort courses, including College Composition and Introduction to Library Research, which are either taught or supported by faculty at UNC Libraries. The existing relationship between CHE and the Libraries has been strengthened in recent years by the development of the Student Voices project, an innovative collaboration that captures oral histories documenting the first-generation freshman experience and makes them available via the Libraries’ digital repository. The goal of the project is twofold: to document the perspectives and experiences of first-generation students, which have been largely absent within the university historical record, while simultaneously delivering instruction in primary sources and archival practice. The project is delivered as a classroom assignment, with the resulting oral history recordings collected by the UNC Archives and Special Collections and placed in the digital repository. Faculty from the UNC Libraries co-present a guest lecture to the CHE College Composition cohort classes, touching on such topics as the purpose of archives, digitization and copyright, and best practices for creating oral histories. Replicating the Story Corps model, students then interview each other in groups of two or three as part of an out-of-class assignment. They are asked to discuss topics such as their first impressions of campus, experiences adjusting to university life, and their expectations for college in addition to the expectations that others may have for them. Along with engaging with classmates to create a meaningful and substantive video or audio oral history, students learn to navigate technical issues of recording and submitting a digital file. While several substantive oral interviews have resulted from this project, it has not been without challenges. First–generation freshmen have unique needs, and challenges arose due to the presenter’s expectations about their experience and prior knowledge. The session will offer a case study that covers both digital initiatives in undergraduate instruction and interdisciplinary collaboration between campus units. Speakers will explore issues of teaching, engaging, and incorporating digital initiative concepts into first-generation education. Attendees will receive ideas for implementing similar collaborations at their institutions

    The COOH terminus of the c-Abl tyrosine kinase contains distinct F- and G-actin binding domains with bundling activity

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    The myristoylated form of c-Abl protein, as well as the P210bcr/abl protein, have been shown by indirect immunofluorescence to associate with F-actin stress fibers in fibroblasts. Analysis of deletion mutants of c-Abl stably expressed in fibroblasts maps the domain responsible for this interaction to the extreme COOH-terminus of Abl. This domain mediates the association of a heterologous protein with F-actin filaments after microinjection into NIH 3T3 cells, and directly binds to F-actin in a cosedimentation assay. Microinjection and cosedimentation assays localize the actin-binding domain to a 58 amino acid region, including a charged motif at the extreme COOH-terminus that is important for efficient binding. F-actin binding by Abl is calcium independent, and Abl competes with gelsolin for binding to F- actin. In addition to the F-actin binding domain, the COOH-terminus of Abl contains a proline-rich region that mediates binding and sequestration of G-actin, and the Abl F- and G-actin binding domains cooperate to bundle F-actin filaments in vitro. The COOH terminus of Abl thus confers several novel localizing functions upon the protein, including actin binding, nuclear localization, and DNA binding. Abl may modify and receive signals from the F-actin cytoskeleton in vivo, and is an ideal candidate to mediate signal transduction from the cell surface and cytoskeleton to the nucleus

    A Novel Method for Achieving SAR Imaging with a Pair of Micro-Satellites by Means of a Bi-Static Configuration

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    There is increasing interest in the potential capabilities and applications of micro -satellites in the field of Earth-observation (EO). Passive optical imaging is now well established on such platforms, however, an active imaging payload - a synthetic aperture radar (SAR) - would appear to be insupportable, due to its size, complexity and high -power requirements. A major driver of these requirements is that traditional SAR systems use backscatter - which is necessarily weak from most terrain types. If the forward scattered energy could be gathered, then the transmit-power requirements could drop significantly. We therefore propose a novel method by which two micro-satellites fly in formation to accomplish a SAR mission bi-statically. The transmitting satellite will be the “master”, with the receiver satellite “slaved” off it by means of a synchronization signal. The satellites image a swath of 30 km, at a ground resolution of 30 m from 700 km altitude. Our constellation geometry can image anywhere in a pre-selected latitude band, and requires minimal orbit-control resources. The viewing configuration resolves the left-right ambiguity that occurs in near nadir pointing bi-static radar. Applications to a polar ice-monitoring mission are discussed, although with minor changes any location on Earth can be viewed
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