133,540 research outputs found

    Spatiotemporal dispersion and wave envelopes with relativistic and pseudorelativistic characteristics

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    A generic nonparaxial model for pulse envelopes is presented. Classic Schro¨dinger-type descriptions of wave propagation have their origins in slowly-varying envelopes combined with a Galilean boost to the local time frame. By abandoning these two simplifications, a picture of pulse evolution emerges in which frame-of-reference considerations and space-time transformations take center stage. A wide range of effects, analogous to those in special relativity, then follows for both linear and nonlinear systems. Explicit demonstration is presented through exact bright and dark soliton pulse solutions

    Renormalization approach to many-particle systems

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    This paper presents a renormalization approach to many-particle systems. By starting from a bare Hamiltonian H=H0+H1{\cal H}= {\cal H}_0 +{\cal H}_1 with an unperturbed part H0{\cal H}_0 and a perturbation H1{\cal H}_1,we define an effective Hamiltonian which has a band-diagonal shape with respect to the eigenbasis of H0{\cal H}_0. This means that all transition matrix elements are suppressed which have energy differences larger than a given cutoff λ\lambda that is smaller than the cutoff Λ\Lambda of the original Hamiltonian. This property resembles a recent flow equation approach on the basis of continuous unitary transformations. For demonstration of the method we discuss an exact solvable model, as well as the Anderson-lattice model where the well-known quasiparticle behavior of heavy fermions is derived.Comment: 11 pages, final version, to be published in Phys. Rev.

    Adding Rule-Based Model Transformation to Modelling Languages in MetaEdit+

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    MetaEdit+ is a commercial tool by MetaCase for creating domain-specific, syntax-directed visual modelling environments. MetaEdit+ synthesizes such environments from user-provided metamodels and contains a Generator Editor for code/report generation. An API is provided to allow external manipulation of models through SOAP. Currently, the MetaEdit+ tool does not natively support rule-based model-to-model transformation. Such transformations are useful as they allow domain experts to intuitively (using domain-specific notations) model either operational semantics (a simulator) or denotational semantics (through model-to-model transformation onto a model in a known formalism) of a modelling language. We will demonstrate how to add rule-based operational semantics to modelling languages in MetaEdit+. In our approach, transformation rules are visually created in MetaEdit+. The rule editor is synthesized using modified versions of the original language's metamodel. This modification is performed in a structured fashion using a process called RAMification. Both the model and the rules are exported from MetaEdit+ to Python code. This code is combined with Py-T-Core, our library of transformation language primitives, to apply the rules on the model. Our demonstration has a client-server architecture, with the MetaEdit+ visual modelling environment as the client and the transformation engine as the server. After each transformation step, in-place changes to the model are propagated to MetaEdit+ for visualization using the SOAP API. A simple (manufacturing) Production System modelling language is used as an example

    Practice transformations to optimize the delivery of HIV primary care in community healthcare settings in the United States: A program implementation study.

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    BackgroundThe United States HIV care workforce is shrinking, which could complicate service delivery to people living with HIV (PLWH). In this study, we examined the impact of practice transformations, defined as efficiencies in structures and delivery of care, on demonstration project sites within the Workforce Capacity Building Initiative, a Health Resources and Services Administration (HRSA) Ryan White HIV/AIDS Program Special Projects of National Significance (SPNS).Methods and findingsData were collected at 14 demonstration project sites in 7 states and the District of Columbia. Organizational assessments were completed at sites once before and 4 times after implementation. They captured 3 transformation approaches: maximizing the HIV care workforce (efforts to increase the number of existing healthcare workforce members involved in the care of PLWH), share-the-care (team-based care giving more responsibility to midlevel providers and staff), and enhancing client engagement in primary HIV care to reduce emergency and inpatient care (e.g., care coordination). We also obtained Ryan White HIV/AIDS Program Services Reports (RSRs) from sites for calendar years (CYs) 2014-2016, corresponding to before, during, and after transformation. The RSR include data on client retention in HIV care, prescription of antiretroviral therapy (ART), and viral suppression. We used generalized estimating equation (GEE) models to analyze changes among sites implementing each practice transformation approach. The demonstration projects had a mean of 18.5 prescribing providers (SD = 23.5). They reported data on more than 13,500 clients per year (mean = 969/site, SD = 1,351). Demographic characteristics remained similar over time. In 2014, a majority of clients were male (71% versus 28% female and 0.2% transgender), with a mean age of 47 (interquartile range [IQR] 37-54). Racial/ethnic characteristics (48% African American, 31% Hispanic/Latino, 14% white) and HIV risk varied (31% men who have sex with men; 31% heterosexual men and women; 7% injection drug use). A substantial minority was on Medicaid (41%). Across sites, there was significant uptake in practices consistent with maximizing the HIV care workforce (18% increase, p < 0.001), share-the-care (25% increase, p < 0.001), and facilitating patient engagement in HIV primary care (13% increase, p < 0.001). There were also significant improvements over time in retention in HIV care (adjusted odds ratio [aOR] = 1.03; 95% confidence interval [CI] 1.02-1.04; p < 0.001), ART prescription levels (aOR = 1.01; 95% CI 1.00-1.01; p < 0.001), and viral suppression (aOR = 1.03; 95% CI 1.02-1.04; p < 0.001). All outcomes improved at sites that implemented transformations to maximize the HIV care workforce or improve client engagement. At sites that implemented share-the-care practices, only retention in care and viral suppression outcomes improved. Study limitations included use of demonstration project sites funded by the Ryan White HIV/AIDS Program (RWHAP), which tend to have better HIV outcomes than other US clinics; varying practice transformation designs; lack of a true control condition; and a potential Hawthorne effect because site teams were aware of the evaluation.ConclusionsIn this study, we found that practice transformations are a potential strategy for addressing anticipated workforce challenges among those providing care to PLWH. They hold the promise of optimizing the use of personnel and ensuring the delivery of care to all in need while potentially enhancing HIV care continuum outcomes

    Information sharing performance management: a semantic interoperability assessment in the maritime surveillance domain

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    Information Sharing (IS) is essential for organizations to obtain information in a cost-effective way. If the existing information is not shared among the organizations that hold it, the alternative is to develop the necessary capabilities to acquire, store, process and manage it, which will lead to duplicated costs, especially unwanted if governmental organizations are concerned. The European Commission has elected IS among public administrations as a priority, has launched several IS initiatives, such as the EUCISE2020 project within the roadmap for developing the maritime Common Information Sharing Environment (CISE), and has defined the levels of interoperability essential for IS, which entail Semantic Interoperability (SI). An open question is how can IS performance be managed? Specifically, how can IS as-is, and to-be states and targets be defined, and how can organizations progress be monitored and controlled? In this paper, we propose 11 indicators for assessing SI that contribute to answering these questions. They have been demonstrated and evaluated with the data collected through a questionnaire, based on the CISE information model proposed during the CoopP project, which was answered by five public authorities that require maritime surveillance information and are committed to share information with each other.Postprint (published version

    Plasmonic catalysis with designer nanoparticles

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    Catalysis is central to a more sustainable future and a circular economy. If the energy required to drive catalytic processes could be harvested directly from sunlight, the possibility of replacing contemporary processes based on terrestrial fuels by the conversion of light into chemical energy could become a step closer to reality. Plasmonic catalysis is currently at the forefront of photocatalysis, enabling one to overcome the limitations of "classical" wide bandgap semiconductors for solar-driven chemistry. Plasmonic catalysis enables the acceleration and control of a variety of molecular transformations due to the localized surface plasmon resonance (LSPR) excitation. Studies in this area have often focused on the fundamental understanding of plasmonic catalysis and the demonstration of plasmonic catalytic activities towards different reactions. In this feature article, we discuss recent contributions from our group in this field by employing plasmonic nanoparticles (NPs) with controllable features as model systems to gain insights into structure-performance relationships in plasmonic catalysis. We start by discussing the effect of size, shape, and composition in plasmonic NPs over their activities towards LSPR-mediated molecular transformations. Then, we focus on the effect of metal support interactions over activities, reaction selectivity, and reaction pathways. Next, we shift to the control over the structure in hollow NPs and nanorattles. Inspired by the findings from these model systems, we demonstrate a design-driven strategy for the development of plasmonic catalysts based on plasmonic-catalytic multicomponent NPs for two types of molecular transformations: the selective hydrogenation of phenylacetylene and the oxygen evolution reaction. Finally, future directions, challenges, and perspectives in the field of plasmonic catalysis with designer NPs are discussed. We believe that the examples and concepts presented herein may inspire work and progress in plasmonic catalysis encompassing the design of plasmonic multicomponent materials, new strategies to control reaction selectivity, and the unraveling of stability and reaction mechanisms.Peer reviewe
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