Ground-state Properties of a Supersolid in RPA

We investigate the newly discovered supersolid phase by solving in random-phase approximation the anisotropic Heisenberg model of the hard-core boson ${}^4$He lattice at zero temperature. We include nearest and next-nearest neighbor interactions and calculate exactly all pair correlation functions in a cumulant decoupling scheme. We demonstrate the importance of vacancies and interstitials in the formation of the supersolid phase. The supersolid phase is characterised by strong quantum fluctuations which are taken into account rigorously. Furthermore we confirm that the superfluid to supersolid transition is triggered by a collapsing roton minimum however is stable against spontaneously induced superflow, i.e. vortex creation.Comment: 10 pages, 8 figure

RPA Green's Functions of the Anisotropic Heisenberg Model

We solve in random-phase approximation the anisotropic Heisenberg model, including nearest and next-nearest neighbour interactions by calculating all Green's functions and pair correlation functions in a cumulant decoupling scheme. The general exposition is pedagogic in tone and is intended to be accessible to any graduate student or physicist who is not an expert in the field.Comment: 26 pages, 4 figure

The brezis-ekeland-nayroles minimization principle with mixed finite element method for elastoplastic dynamic problems

We propose a modification of the Hamiltonian formalism which can be used for dissipative systems, the Brezis-Ekeland-Nayroles principle. The formalism is specialized to the standard plasticity in small strains and dynamics. We apply it to solve the classical problem of a thin tube in plane strain subjected to an internal pressure. The continuum is discretized with mixed finite elements

Solar Resource Measurements in Humboldt State University, Arcata, California: Cooperative Research and Development Final Report, CRADA Number CRD-08-262

Site-specific, long-term, continuous, and high-resolution measurements of solar irradiance are important for developing renewable resource data. These data are used for several research and development activities consistent with the NREL mission: establish a national 30-year climatological database of measured solar irradiances; provide high quality ground-truth data for satellite remote sensing validation; support development of radiative transfer models for estimating solar irradiance from available meteorological observations; provide solar resource information needed for technology deployment and operations. Data acquired under this agreement will be available to the public through NREL's Measurement & Instrumentation Data Center - MIDC (www.nrel.gov/midc) or the Renewable Resource Data Center - RReDC (http://rredc.nrel.gov). The MIDC offers a variety of standard data display, access, and analysis tools designed to address the needs of a wide user audience (e.g., industry, academia, and government interests)

partR2:partitioning R2 in generalized linear mixed models

The coefficient of determination R(2) quantifies the amount of variance explained by regression coefficients in a linear model. It can be seen as the fixed-effects complement to the repeatability R (intra-class correlation) for the variance explained by random effects and thus as a tool for variance decomposition. The R(2) of a model can be further partitioned into the variance explained by a particular predictor or a combination of predictors using semi-partial (part) R(2) and structure coefficients, but this is rarely done due to a lack of software implementing these statistics. Here, we introduce partR2, an R package that quantifies part R(2) for fixed effect predictors based on (generalized) linear mixed-effect model fits. The package iteratively removes predictors of interest from the model and monitors the change in the variance of the linear predictor. The difference to the full model gives a measure of the amount of variance explained uniquely by a particular predictor or a set of predictors. partR2 also estimates structure coefficients as the correlation between a predictor and fitted values, which provide an estimate of the total contribution of a fixed effect to the overall prediction, independent of other predictors. Structure coefficients can be converted to the total variance explained by a predictor, here called ‘inclusive’ R(2), as the square of the structure coefficients times total R(2). Furthermore, the package reports beta weights (standardized regression coefficients). Finally, partR2 implements parametric bootstrapping to quantify confidence intervals for each estimate. We illustrate the use of partR2 with real example datasets for Gaussian and binomial GLMMs and discuss interactions, which pose a specific challenge for partitioning the explained variance among predictors

Pneumococcal vaccination among adult risk patient with axial spondyloarthritis in Switzerland: Data from the survey of the ankylosing spondylitis association of Switzerland (SVMB)

While in Switzerland, pneumococcal vaccination is recommended for adult patients with axial spondyloarthritis (axSpA) treated with biological drugs, since 2014, little is known about the vaccination status of this specific patient population. This study assessed their vaccination status as part of a larger online survey by the ankylosing spondylitis association of Switzerland (SVMB). Out of 1560 who participated in the survey, 834 (53.5%) were eligible for the analysis. Vaccine coverage was low at 32.5% (271/834). Women and patients who got a flu shot every year were more likely to be covered. Age was negatively associated with being vaccinated. Most (54.2%; 147/271) were vaccinated by their general practitioner. Almost two-thirds of those who had not received the vaccine stated that it had not been offered to them (64.1%; 302/471). In summary, the vaccination coverage is low, but might be increased if the vaccine was offered systematically by general practitioners and specialists

Queer Worldmaking: Radical Sexual Politics in the Age of United States Hegemony

Queer struggles have radically contested the global social relations of the post-war American order. These struggles include most prominently the gay liberation movement of the sixties, the black lesbian feminist movement of the seventies, and the AIDS activist movement of the eighties. They responded to the successive regimes of accumulation that determined the organization and expansion of the American world system, forming extensive organizational structures, solidarity networks, and critical knowledges that traveled across the boundaries of nation, state, and territory. They were not intended primarily, or often even at all, as parodic citations of dominant gender norms within the public sphere, but rather as antagonistic practices that could transform and transcend the social relations of United States hegemony. This thesis is therefore about queer worldmaking in its most literal sense. It finds a connection between queer political formations and the American world system. The transnational connections, encounters, and ideological orientations of these queer social movements have been omitted within their nation-based narrative histories. This study asks the question: What appears when a reading of radical queer movements is pursued that resists an investment in nationally bounded chronologies? A transnational history of radical sexual politics is mobilized in the service of an alternative theory of queerness, revolutionary politics, and pleasure. It illuminates how queer social movements have deployed pleasure to validate their cause of revolutionary transformation on a transnational scale. Projects of queer worldmaking articulate queerness not only as a product of subordination and repression, but also as the site of pleasure, enjoyment, and sociality. What unites these social movements, it is argued, is their conviction that the pursuit of Eros could create openings for the supersession of the existing global order and the instantiation of egalitarian systems through which we can collectively and cooperatively determine our gender and sexual lives

Raman and photoluminescence spectroscopy of SiGe layer evolution on Si(100) induced by dewetting

International audienceHigh temperature annealing of thick (40-100 nm) Ge layers deposited on Si(100) at $400 C leads to the formation of continuous films prior to their transformation into porous-like films due to dewetting. The evolution of Si-Ge composition, lattice strain, and surface morphology caused by dewetting is analyzed using scanning electron microscopy, Raman, and photoluminescence (PL) spectroscopies. The Raman data reveal that the transformation from the continuous to porous film proceeds through strong Si-Ge interdiffusion, reducing the Ge content from 60% to about 20%, and changing the stress from compressive to tensile. We expect that Ge atoms migrate into the Si sub-strate occupying interstitial sites and providing thereby the compensation of the lattice mismatch. Annealing generates only one type of radiative recombination centers in SiGe resulting in a PL peak located at about 0.7 and 0.8 eV for continuous and porous film areas, respectively. Since annealing leads to the propagation of threading dislocations through the SiGe/Si interface, we can tentatively associate the observed PL peak to the well-known dislocation-related D1 band