7,548 research outputs found

    Scattering Experiments with Microwave Billiards at an Exceptional Point under Broken Time Reversal Invariance

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    Scattering experiments with microwave cavities were performed and the effects of broken time-reversal invariance (TRI), induced by means of a magnetized ferrite placed inside the cavity, on an isolated doublet of nearly degenerate resonances were investigated. All elements of the effective Hamiltonian of this two-level system were extracted. As a function of two experimental parameters, the doublet and also the associated eigenvectors could be tuned to coalesce at a so-called exceptional point (EP). The behavior of the eigenvalues and eigenvectors when encircling the EP in parameter space was studied, including the geometric amplitude that builds up in the case of broken TRI. A one-dimensional subspace of parameters was found where the differences of the eigenvalues are either real or purely imaginary. There, the Hamiltonians were found PT-invariant under the combined operation of parity (P) and time reversal (T) in a generalized sense. The EP is the point of transition between both regions. There a spontaneous breaking of PT occurs

    Satellite power system: Concept development and evaluation program. Volume 3: Power transmission and reception. Technical summary and assessment

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    Efforts in the DOE/NASA concept development and evaluation program are discussed for the solar power satellite power transmission and reception system. A technical summary is provided together with a summary of system assessment activities. System options and system definition drivers are described. Major system assessment activities were in support of the reference system definition, solid state system studies, critical technology supporting investigations, and various system and subsystem tradeoffs. These activities are described together with reference system updates and alternative concepts for each of the subsystem areas. Conclusions reached as a result of the numerous analytical and experimental evaluations are presented. Remaining issues for a possible follow-on program are identified

    A Traffic Merging and Generation Framework for Realistic Synthesis of Network Traffic

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    The Internet is steadily growing and is of increasing importance for our economy and society. Due to this increased importance it is also in the focus of attacks, e.g. distributed denial of service (DDoS) attacks. As attackers dynamically change their attack behaviour, novel detection approaches that are able to automatically adjust to these dynamic attacks are needed. To train and test such network anomaly detection systems, it is necessary to provide realistic data. As of today, this area of research suffers from the lack of publicly available datasets that can be used to train and test anomaly detection systems and are exchangeable to allow reproducible research. Therefore, we propose a novel framework that enables researchers and developers to generate customizable synthetic datasets. It not only allows to generate fully-synthetic network traffic, but also to generate semi-synthetic network traffic by merging of multiple network captures from reallive environments. Further, it allows the mapping of IP addresses as well as the modi﬿cation of other header ﬿elds, if desired. This enables researchers and developers to exchange network traces from sensitive environments without revealing any sensitive end-user related information, while perceiving the relevant characteristics of the network(s) and attack(s). In the following, we provide a description of, the problem, our concept and the features of our solution, the architecture and functional model and ﬿nally provide a short summary together with an outlook for future work

    Likelihood-ratio ranking of gravitational-wave candidates in a non-Gaussian background

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    We describe a general approach to detection of transient gravitational-wave signals in the presence of non-Gaussian background noise. We prove that under quite general conditions, the ratio of the likelihood of observed data to contain a signal to the likelihood of it being a noise fluctuation provides optimal ranking for the candidate events found in an experiment. The likelihood-ratio ranking allows us to combine different kinds of data into a single analysis. We apply the general framework to the problem of unifying the results of independent experiments and the problem of accounting for non-Gaussian artifacts in the searches for gravitational waves from compact binary coalescence in LIGO data. We show analytically and confirm through simulations that in both cases the likelihood ratio statistic results in an improved analysis.Comment: 10 pages, 6 figure

    On determination of statistical properties of spectra from parametric level dynamics

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    We analyze an approach aiming at determining statistical properties of spectra of time-periodic quantum chaotic system based on the parameter dynamics of their quasienergies. In particular we show that application of the methods of statistical physics, proposed previously in the literature, taking into account appropriate integrals of motion of the parametric dynamics is fully justified, even if the used integrals of motion do not determine the invariant manifold in a unique way. The indetermination of the manifold is removed by applying Dirac's theory of constrained Hamiltonian systems and imposing appropriate primary, first-class constraints and a gauge transformation generated by them in the standard way. The obtained results close the gap in the whole reasoning aiming at understanding statistical properties of spectra in terms of parametric dynamics.Comment: 9 pages without figure

    Immunoproteomic identification and characterization of Ni2+-regulated proteins implicates Ni2+ in the induction of monocyte cell death

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    Nickel allergy is the most common cause of allergic reactions worldwide, with cutaneous and systemic effects potentially affecting multiple organs. Monocytes are precursors of not only macrophages but also dendritic cells, the most potent activators of nickel hypersensitivity. Monocytes are themselves important antigen-presenting cells, capable of nickel-specific T-cell activation in vivo and in vitro, in addition to being important for immediate innate immune inflammation. To elucidate early Ni2+-dependent inflammatory molecular mechanisms in human monocytes, a Ni2+-specific proteomic approach was applied. Quantitative two-dimensional (2D) differential gel electrophoresis and Delta2D software analyses coupled with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) revealed that Ni2+ significantly regulated 56 protein species, of which 36 were analyzed by MALDI-MS. Bioinformatics analyses of all identified proteins resulted in Ni2+-associated functional annotation clusters, such as cell death, metal ion binding, and cytoskeletal remodeling. The involvement of Ni2+ in the induction of monocyte cell death, but not T-cell death, was observed at Ni2+ concentrations at or above 250 µM. Examination of caspase activity during Ni2+-mediated cell death revealed monocytic cell death independent of caspase-3 and -7 activity. However, confocal microscopy analysis demonstrated Ni2+-triggered cytoskeletal remodeling and nuclear condensation, characteristic of cellular apoptosis. Thus, Ni2+-specific peripheral blood mononuclear cell stimulation suggests monocytic cell death at Ni2+ concentrations at or above 250 µM, and monocytic effects on immune regulation at lower Ni2+ concentrations

    The Mean Drift: Tailoring the Mean Field Theory of Markov Processes for Real-World Applications

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    The statement of the mean field approximation theorem in the mean field theory of Markov processes particularly targets the behaviour of population processes with an unbounded number of agents. However, in most real-world engineering applications one faces the problem of analysing middle-sized systems in which the number of agents is bounded. In this paper we build on previous work in this area and introduce the mean drift. We present the concept of population processes and the conditions under which the approximation theorems apply, and then show how the mean drift is derived through a systematic application of the propagation of chaos. We then use the mean drift to construct a new set of ordinary differential equations which address the analysis of population processes with an arbitrary size

    Promoting sustainability in quality improvement: an evaluation of a web-based continuing education program in blood pressure measurement.

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    BACKGROUND: The accuracy of blood pressure measurement is variable in office-based settings. Even when staff training programs are effective, knowledge and skills decay over time, supporting the need for ongoing staff training. We evaluated whether a web-based continuing education program in blood pressure measurement reinforced knowledge and skills among clinical staff and promoted sustainability of an existing quality improvement program. METHODS: Medical assistants and nurses at six primary care clinics within a health system enrolled in a 30-min online educational program designed to refresh their knowledge of blood pressure measurement. A 20-question pre- and post-intervention survey addressed learners\u27 knowledge and attitudes. Direct observation of blood pressure measurement technique before and after the intervention was performed. Differences in responses to pre- and post-module knowledge and attitudes questions and in observation data were analyzed using chi-square tests and simple logistic regression. RESULTS: All 88 clinical staff members participated in the program and completed the evaluation survey. Participants answered 80.6% of questions correctly before the module and 93.4% afterwards (p \u3c 0.01). Scores improved significantly among staff from all job types. Licensed practical nurses and staff who had been in their current job at least a year were more likely to answer questions correctly than registered nurses and those in their current job less than a year. Attitudes toward correct blood pressure measurement were high at baseline and did not improve significantly. Prior to the intervention, staff adhered to 9 of 18 elements of the recommended technique during at least 90% of observations. Following the program, staff was more likely to explain the protocol, provide a rest period, measure an average blood pressure, and record the average blood pressure, but less likely to measure blood pressure with the arm at heart level and use the right arm. CONCLUSIONS: We designed, implemented, and evaluated a web-based educational program to improve knowledge, skills, and attitudes in blood pressure measurement and use of an automated device among nurses and medical assistants in ambulatory care. The program reinforced knowledge related to recommended blood pressure measurement technique. TRIAL REGISTRATION: Retrospectively registered with ClincalTrials.gov on March 22, 2012; registration number NCT01566864

    DIGITAL HISTORY EDUCATION FOR PUPILS. FIRST STEPS TOWARDS A TEACHING LEARNING LAB

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    This paper explores digital education for pupils in a humanities teaching-learning lab. So far, digital humanities educational approaches have been primarily aimed at students. Teaching-learning labs, in which students design, implement and evaluate teaching offers for pupils, have so far almost exclusively existed in STEM subjects.Based on a classification in European frameworks and a literature analysis on teaching-learning labs of digital history education, the current state of the art on the topic is elucidated. Using concrete practical examples, the first results of involving students in digital history projects will be presented and suitable digital tools for teaching humanities content will be introduced.</p
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