3,997 research outputs found

    Renormalized Landau Levels and Particle-Hole Symmetry in Graphene

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    In this proceedings paper we report on a calculation of graphene's Landau levels in a magnetic field. Our calculations are based on a self-consistent Hartree-Fock approximation for graphene's massless-Dirac continuum model. We find that because of graphene's chiral band structure interactions not only shift Landau-level energies, as in a non-relativistic electron gas, but also alter Landau level wavefunctions. We comment on the subtle continuum model regularization procedure necessary to correctly maintain the lattice-model's particle hole symmetry properties

    Some Notes on Rational Spaces

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    Set constraints are inclusions between expressions denoting set of ground terms over a finitely ranked alphabet ÎŁ\Sigma. Rational spaces are topological spaces obtained as spaces of runs of topological ÎŁ\Sigma-hypergraphs. They were introduced by Kozen in \cite{K95a}, where the topological structure of the spaces of solutions to systems of set constraints was given in terms of rational spaces. In this paper we continue the investigation of rational spaces. We give a Myhill-Nerode like characterization of rational points, which in turn is used to re-derive results about the rational points of finitary rational spaces. We define congruences on ÎŁ\Sigma-hypergraphs, investigate their interplay with the Myhill-Nerode characterization, and finally we determine the computational complexity of some decision problems related to rational spaces

    Realism of procedural task trainers in a pediatric emergency medicine procedures course

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    Background: Pediatric emergency medicine (PEM) physicians have minimal experience in life saving procedures and have turned to task trainers to learn these skills. Realism of these models is an important consideration that has received little study.Method: PEM physicians and trainees participated in a day long procedural training course that utilized commercially available and homemade task trainers to teach pericardiocentesis, chest tube insertion, cricothyroidotomy and central line insertion. Participants rated the realism of the task trainers as part of a post-course survey.Results: The homemade task trainers received variable realism ratings, with 91% of participants rating the pork rib chest tube model as realistic, 82% rating the gelatin pericardiocentesis mold as realistic and 36% rating the ventilator tubing cricothyroidotomy model as realistic. Commercial trainers also received variable ratings, with 45% rating the chest drain and pericardiocentesis simulator as realistic, 74% rating the crichotracheotomy trainer as realistic and 80% rating the central line insertion trainer as realistic.Conclusions: Task training models utilized in our course received variable realism ratings. When deciding what type of task trainer to use future courses should carefully consider the desired aspect of realism, and how it aligns with the procedural skill, balanced with cost considerations

    Ab-initio study of the energy competition between \Gamma and K valleys in bilayer transition metal dichalcogenides

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    Moir\'e engineering in two-dimensional van der Waals bilayer crystals has emerged as a flexible platform for controlling strongly correlated electron systems. The competition between valleys for the band extremum energy position in the parent layers is crucial in deciding the qualitative nature of the moir\'e Hamiltonian since it controls the physics of the moir\'e minibands. Here we use density functional theory to examine the competition between K and Γ\Gamma for the valence band maximum in homo- and hetero-bilayers formed from the transition metal dichalcogenides (TMD), MX\{_2} where M=Mo,W and X=S,Se,Te. We shed light on how the competition is influenced by interlayer separation, which can be modified by applying pressure, by external gate-defined electric fields, and by transition metal atom d-orbital correlations. Our findings are related to several recent experiments, and contribute to the development of design rules for moir\'{e} materials

    The Democracy Cube as a Framework for Guiding Participatory Planning for Community-based IT Initiatives

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    Literature suggests there is a need to build more theoretically-informed understandings of the social processes implicated in participatory IT planning and implementation (Jakku & Thorburn, 2010). In this study, we explore the value of Archon Fung’s (2006) “democracy cube” as a framework for qualitatively examining the process we undertook for planning a community-based IT strategy. Our planning process involved consultations with multiple stakeholder groups across five different communities, as well as from other entities involved in disaster management, with the aim of surfacing factors that shaped local communities’ abilities to participate in disaster management activities. These factors, drawn from qualitative interviews and categorized using a SWOT framework, were subsequently translated into an IT strategy. In this paper, we revisit this process and examine it using Fung’s (2006) three dimensions of democratic participation as a lens: participant selection (our use of multiple stakeholder groups); communication and decision (our consultation process); and authority and power (how participant input drove our strategy). We use the framework to identify the specific practices that made IT planning participative, as well as those that made it nonparticipative. We also use our empirical data to explore ways that the framework can be enhanced

    Longitudinal evaluation of cognitive functioning in young children with type 1 diabetes over 18 months

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    OBJECTIVE: Decrements in cognitive function may already be evident in young children with type 1 diabetes (T1D). Here we report prospectively acquired cognitive results over 18 months in a large cohort of young children with and without T1D. METHODS: 144 children with T1D (mean HbA1c: 7.9%) and 70 age-matched healthy controls (mean age both groups 8.5 years; median diabetes duration 3.9 yrs; mean age of onset 4.1 yrs) underwent neuropsychological testing at baseline and after 18-months of follow-up. We hypothesized that group differences observed at baseline would be more pronounced after 18 months, particularly in those T1D patients with greatest exposure to glycemic extremes. RESULTS: Cognitive domain scores did not differ between groups at the 18 month testing session and did not change differently between groups over the follow-up period. However, within the T1D group, a history of diabetic ketoacidosis (DKA) was correlated with lower Verbal IQ and greater hyperglycemia exposure (HbA1c area under the curve) was inversely correlated to executive functions test performance. In addition, those with a history of both types of exposure performed most poorly on measures of executive function. CONCLUSIONS: The subtle cognitive differences between T1D children and nondiabetic controls observed at baseline were not observed 18 months later. Within the T1D group, as at baseline, relationships between cognition (VIQ and executive functions) and glycemic variables (chronic hyperglycemia and DKA history) were evident. Continued longitudinal study of this T1D cohort and their carefully matched healthy comparison group is planned

    The Blessing of Randomness: SDE Beats ODE in General Diffusion-based Image Editing

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    We present a unified probabilistic formulation for diffusion-based image editing, where a latent variable is edited in a task-specific manner and generally deviates from the corresponding marginal distribution induced by the original stochastic or ordinary differential equation (SDE or ODE). Instead, it defines a corresponding SDE or ODE for editing. In the formulation, we prove that the Kullback-Leibler divergence between the marginal distributions of the two SDEs gradually decreases while that for the ODEs remains as the time approaches zero, which shows the promise of SDE in image editing. Inspired by it, we provide the SDE counterparts for widely used ODE baselines in various tasks including inpainting and image-to-image translation, where SDE shows a consistent and substantial improvement. Moreover, we propose SDE-Drag -- a simple yet effective method built upon the SDE formulation for point-based content dragging. We build a challenging benchmark (termed DragBench) with open-set natural, art, and AI-generated images for evaluation. A user study on DragBench indicates that SDE-Drag significantly outperforms our ODE baseline, existing diffusion-based methods, and the renowned DragGAN. Our results demonstrate the superiority and versatility of SDE in image editing and push the boundary of diffusion-based editing methods

    Control Techniques for an Interior Permanent Magnet Synchronous Motor of an Electrified Vehicle

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    A system and method for controlling an interior permanent magnet sychronous motor (IPMSM) are presented. In an exemplary implementation, phase current ripple estimation techniques are utilized for variable frequency switching pulse-width modulation control of the IPMSM. In one implementation, the method includes controlling a three-phase inverter based on an initial switching frequency to generate a three-phase alternating current (AC) voltage for the IPMSM. Transformed voltages are determined in a rotating reference frame based on the three-phase AC voltage in the stationary reference frame. Current ripples are determined in the rotating reference frame based on the transformed voltages. Phase current ripples are determined in the stationary reference frame based on the current ripples in the rotating reference frame. A modified switching frequency for the three-phase inverter is determined based on the initial switching frequency and the phase current ripples. The three-phase inverter is then controlled based on the modified switching frequency
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