1,551 research outputs found

    Counselor librarianship: a new departure.

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    "Select reading list on counseling and student personnel work": p.34-35. Bibliographical references included in "Footnotes" (p. 35-39)

    The geometry and topology of quantum entanglement in holography

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    In this thesis I explore the connection between geometry and quantum entanglement, in the context of holographic duality, where entanglement entropies in a quantum field theory are associated with the areas of surfaces in a dual gravitational theory. The first chapter looks at a phase transition in such systems in finite size and at finite temperature, associated with the properties of minimal surfaces in a static black hole background. This is followed by the related problem of extremal surfaces in a spacetime describing the dynamical process of black hole formation, with a view towards understanding the connections between bulk locality and various field theory observables including entanglement entropy. The third chapter looks at the simple case of pure gravity in three spacetime dimensions, where I show how evaluating the entanglement entropy can be reduced to a simple algebraic calculation, and apply it to some interesting examples. Finally, the role played by topology of surfaces in a proposed derivation of a holographic entanglement entropy formula is investigated. This makes it clear what assumptions are required in order to reproduce the ‘homology constraint’, a topological condition necessary for consistency with field theory

    A General Framework for Complex Time-Driven Simulations on Hypercubes

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    We describe a general framework for building and running complex time-driven simulations with several levels of concurrency. The framework has been implemented on the Caltech/JPL Mark IIIfp hypercube using the Centaur communications protocol. Our framework allows the programmer to break the hypercube up into one or more subcubes of arbitrary size (task parallelism). Each subcube runs a separate application using data parallelism and synchronous communications internal to the subcube. Communications between subcubes are performed with asynchronous messages. Subcubes can each define their own parameters and commands which drive their particular application. These are collected and organized by the Control Processor (CP) in order that the entire simulation can be driven from a single command-driven shell. This system allows several programmers to develop disjoint pieces of a large simulation in parallel and to then integrate them with little effort. Each programmer is, of course, also able to take advantage of the separate data and I/O processors on each hypercube node in order to overlap calculation and communication (on-board parallelism) as well as the pipelined floating point processor on each node (pipelined processor parallelism). We show, as an example of the framework, a large space defense simulation. Functions (sensing, tracking, etc.) each comprise a subcube; functions are collected into defense platforms (satellites); and many platforms comprise the defense architecture. Software in the CP uses simple input to determine the node allocation to each function based on the desired defense architecture and number of platforms simulated in the hypercube. This allows many different architectures to be simulated. The set of simulated platforms, the results, and the messages between them are shown on color graphics displays. The methods used herein can be generalized to other simulations of a similar nature in a straightforward manner

    Sequential Analysis: A Methodology for Monitoring Approval Plans

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    published or submitted for publicatio

    Excitability in autonomous Boolean networks

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    We demonstrate theoretically and experimentally that excitable systems can be built with autonomous Boolean networks. Their experimental implementation is realized with asynchronous logic gates on a reconfigurabe chip. When these excitable systems are assembled into time-delay networks, their dynamics display nanosecond time-scale spike synchronization patterns that are controllable in period and phase.Comment: 6 pages, 5 figures, accepted in Europhysics Letters (epljournal.edpsciences.org

    The effect of snow accumulation on imaging riometer performance

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    In January 1998 an imaging riometer system was deployed at Halley, Antarctica (76°S, 27°W), involving the construction of an array of 64 crossed-dipole antennas and a ground plane. Weather conditions at Halley mean that such an array will rapidly bury beneath the snow, so the system was tuned to operate efficiently when buried. Theoretical calculations indicate that because the distance between the ground plane and the array was scaled to be 1/4λ in the snow, as snow fills the gap the signal will increase by 0.6–2.5 dB. Similarly, the short antennas are resonant when operated in snow, not in air. Theoretical calculations show that the largest effect of this is the mismatch of their feed point impedance to the receiver network. As the signal for each riometer beam is composed of a contribution from all 64 antennas, for each antenna that buries the signal level will increase by 1/64 of ∼9 dB. The measured response of the system to burial showed significant changes as snow accumulated in and over the array during 1998. The changes are consistent with the magnitude of the effects predicted by the theoretical calculations. The Halley imaging riometer system, having now been buried completely, is operating more efficiently than if a standard air-tuned configuration had been deployed. The results are of considerable relevance to the ever-increasing community of imaging riometer users regarding both deployment and the subsequent interpretation of scientific data. Some systems will experience similar permanent burial, while others will be subject to significant annual variability as a result of becoming snow-covered during winter and clear during summer

    Soil methane sink capacity response to a long-term wildfire chronosequence in Northern Sweden

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    Boreal forests occupy nearly one fifth of the terrestrial land surface and are recognised as globally important regulators of carbon (C) cycling and greenhouse gas emissions. Carbon sequestration processes in these forests include assimilation of CO2 into biomass and subsequently into soil organic matter, and soil microbial oxidation of methane (CH4). In this study we explored how ecosystem retrogression, which drives vegetation change, regulates the important process of soil CH4 oxidation in boreal forests. We measured soil CH4 oxidation processes on a group of 30 forested islands in northern Sweden differing greatly in fire history, and collectively representing a retrogressive chronosequence, spanning 5000 years. Across these islands the build-up of soil organic matter was observed to increase with time since fire disturbance, with a significant correlation between greater humus depth and increased net soil CH4 oxidation rates. We suggest that this increase in net CH4 oxidation rates, in the absence of disturbance, results as deeper humus stores accumulate and provide niches for methanotrophs to thrive. By using this gradient we have discovered important regulatory controls on the stability of soil CH4 oxidation processes that could not have not been explored through shorter-term experiments. Our findings indicate that in the absence of human interventions such as fire suppression, and with increased wildfire frequency, the globally important boreal CH4 sink could be diminished

    Improving stamina and mobility with preop walking in surgical patients with frailty traits -OASIS IV: randomized clinical trial study protocol

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    BACKGROUND: Frail older surgical patients face more than a two-fold increase in postoperative complications, including myocardial infarction, deep vein thrombosis, pulmonary embolism, pneumonia, ileus, and others. Many of these complications occur because of postoperative loss of stamina and poor mobility. Preoperative exercise may better prepare these vulnerable patients for surgery. We present the protocol for our ongoing randomized trial to assess the impact of a preoperative walking intervention with remote coaching and pedometer on outcomes of stamina (six-minute walk distance- 6MWD) and mobility (postoperative steps) in older adults with frailty traits. METHODS: We will be conducting a randomized clinical trial with a total of 120 patients permitting up to a 33% rate of attrition, to reach a final sample size of 80 (with 40 patients for each study arm). We will include patients who are age 60 or higher, score 4 or greater on the Edmonton Frailty Scale assessment, and will be undergoing a surgical operation that requires a 2 or more night hospital stay to be eligible for our trial. Using block randomization stratified on baseline 6MWD, we will assign patients to wear a pedometer. At the end of three baseline days, an athletic trainer (AT) will provide a daily step count goal reflecting a 10-20% increase from baseline. Subsequently, the AT will call weekly to further titrate the goal or calls more frequently if the patient is not meeting the prescribed goal. Controls will receive general walking advice. Our main outcome is change in 6MWD on postoperative day (POD) 2/3 vs. baseline. We will also collect 6MWD approximately 4 weeks after surgery and daily in-hospital steps. CONCLUSION: If changes in a 6MWD and step counts are significantly higher for the intervention group, we believe this will confirm our hypothesis that the intervention leads to decreased loss of stamina and mobility. Once confirmed, we anticipate expanding to multiple centers to assess the interventional impact on clinical endpoints. TRIAL REGISTRATION: The randomized clinical trial was registered on clinicaltrials.gov under the identifier NCT03892187 on March 27, 2019
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