1,751 research outputs found

    The Swiss and Dutch Health Insurance Systems: Universal Coverage and Regulated Competitive Insurance Markets

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    Compares systems of universal insurance coverage based on individual mandates, consumer choice of health plans, and regulated insurance market competition in Switzerland and the Netherlands. Discusses insights and implications for U.S. reform efforts

    Measurement of Electric Conductivity of Hot Gas in a SF6-circuit Breaker Interrupting Fault Currents

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    The realization of a new measurement method to determine electric conductivity of hot SF6-gas during interruption fault currents in an original self-blast circuit breaker is presented. The method is based on evaluation of phase shift between sinusoidal kHz-high voltage and current, applied on a sensor. This needs a kHz-resonance voltage generator and adapted sensors as a part of an electromagnetic shielded measurement system to determine time dependent electric conductivity with high resolution

    Focusing of quantum gate interactions using dynamical decoupling

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    In 1995, Cirac and Zoller proposed the first concrete implementation of a small-scale quantum computer, using laser beams focused to micron spot sizes to address individual trapped ions in a linear crystal. Here we propose a method to focus entangling gate interactions, but driven by microwave fields, to micron-sized zones, corresponding to 10510^{-5} microwave wavelengths. We demonstrate the ability to suppress the spin-dependent force using a single ion, and find the required interaction introduces 3.7(4)×1043.7(4)\times 10^{-4} error per emulated gate in a single-qubit benchmarking sequence. We model the scheme for a 17-qubit ion crystal, and find that any pair of ions should be addressable with an average crosstalk error of 105\sim 10^{-5}

    In-situ characterization of qubit drive-phase distortions

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    Reducing errors in quantum gates is critical to the development of quantum computers. To do so, any distortions in the control signals should be identified, however, conventional tools are not always applicable when part of the system is under high vacuum, cryogenic, or microscopic. Here, we demonstrate a method to detect and compensate for amplitude-dependent phase changes, using the qubit itself as a probe. The technique is implemented using a microwave-driven trapped ion qubit, where correcting phase distortions leads to a three-fold improvement in single-qubit gate error, to attain state-of-the-art performance benchmarked at 1.6(4)×1061.6(4)\times 10^{-6} error per Clifford gate

    Diversity and origins of bacterial and archaeal viruses on sinking particles reaching the abyssal ocean

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    © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Luo, E., Leu, A. O., Eppley, J. M., Karl, D. M., & DeLong, E. F. Diversity and origins of bacterial and archaeal viruses on sinking particles reaching the abyssal ocean. ISME Journal, 16, : 1627–1635, https://doi.org/10.1038/s41396-022-01202-1.Sinking particles and particle-associated microbes influence global biogeochemistry through particulate matter export from the surface to the deep ocean. Despite ongoing studies of particle-associated microbes, viruses in these habitats remain largely unexplored. Whether, where, and which viruses might contribute to particle production and export remain open to investigation. In this study, we analyzed 857 virus population genomes associated with sinking particles collected over three years in sediment traps moored at 4000 m in the North Pacific Subtropical Gyre. Particle-associated viruses here were linked to cellular hosts through matches to bacterial and archaeal metagenome-assembled genome (MAG)-encoded prophages or CRISPR spacers, identifying novel viruses infecting presumptive deep-sea bacteria such as Colwellia, Moritella, and Shewanella. We also identified lytic viruses whose abundances correlated with particulate carbon flux and/or were exported from the photic to abyssal ocean, including cyanophages. Our data are consistent with some of the predicted outcomes of the viral shuttle hypothesis, and further suggest that viral lysis of both autotrophic and heterotrophic prokaryotes may play a role in carbon export. Our analyses revealed the diversity and origins of prevalent viruses found on deep-sea sinking particles and identified prospective viral groups for future investigation into processes that govern particle export in the open ocean.This project is funded by grants from the Simons Foundation (#329108 to EFD and DMK, #721223 to EFD, and #721252 to DMK) and the Gordon and Betty Moore Foundation (GBMF3777 to EFD and GBMF3794 to DMK). Partial support for EL was provided by the Natural Sciences and Engineering Research Council of Canada (PGSD3-487490-2016)

    Heterogeneous processes: Laboratory, field, and modeling studies

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    The efficiencies of chemical families such as ClO(x) and NO(x) for altering the total abundance and distribution of stratospheric ozone are controlled by a partitioning between reactive (active) and nonreactive (reservoir) compounds within each family. Gas phase thermodynamics, photochemistry, and kinetics would dictate, for example, that only about 1 percent of the chlorine resident in the lower stratosphere would be in the form of active Cl or ClO, the remainder existing in the reservoir compounds HCl and ClONO2. The consistency of this picture was recently challenged by the recognition that important chemical transformations take place on polar regions: the Airborne Antarctic Ozone Experiment (AAOE) and the Airborne Arctic Stratospheric Expedition (AASA). Following the discovery of the Antarctic ozone hole, Solomon et al. suggested that the heterogeneous chemical reaction: ClONO2(g)+HCl(s) yields Cl2(g)+HNO3(s) could play a key role in converting chlorine from inactive forms into a species (Cl2) that would rapidly dissociate in sunlight to liberate atomic chlorine and initiate ozone depletion. The symbols (s) and (g) denote solid phase, or adsorbed onto a solid surface, and gas phase, respectively, and represent the approach by which such a reaction is modeled rather than the microscopic details of the reaction. The reaction was expected to be most important at altitudes where PSC's were most prevalent (10 to 25 km), thereby extending the altitude range over which chlorine compounds can efficiently destroy ozone from the 35 to 45 km region (where concentrations of active chlorine are usually highest) to lower altitudes where the ozone concentration is at its peak. This chapter will briefly review the current state of knowledge of heterogeneous processes in the stratosphere, emphasizing those results obtained since the World Meteorological Organization (WMO) conference. Sections are included on laboratory investigations of heterogeneous reactions, the characteristics and climatology of PSC's, stratospheric sulfate aerosols, and evidence of heterogeneous chemical processing

    Validation of vessel size imaging (VSI) in high-grade human gliomas using magnetic resonance imaging, image-guided biopsies, and quantitative immunohistochemistry.

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    To evaluate the association between a vessel size index (VSIMRI) derived from dynamic susceptibility contrast (DSC) perfusion imaging using a custom spin-and-gradient echo echoplanar imaging (SAGE-EPI) sequence and quantitative estimates of vessel morphometry based on immunohistochemistry from image-guided biopsy samples. The current study evaluated both relative cerebral blood volume (rCBV) and VSIMRI in eleven patients with high-grade glioma (7 WHO grade III and 4 WHO grade IV). Following 26 MRI-guided glioma biopsies in these 11 patients, we evaluated tissue morphometry, including vessel density and average radius, using an automated procedure based on the endothelial cell marker CD31 to highlight tumor vasculature. Measures of rCBV and VSIMRI were then compared to histological measures. We demonstrate good agreement between VSI measured by MRI and histology; VSIMRI = 13.67 μm and VSIHistology = 12.60 μm, with slight overestimation of VSIMRI in grade III patients compared to histology. rCBV showed a moderate but significant correlation with vessel density (r = 0.42, p = 0.03), and a correlation was also observed between VSIMRI and VSIHistology (r = 0.49, p = 0.01). The current study supports the hypothesis that vessel size measures using MRI accurately reflect vessel caliber within high-grade gliomas, while traditional measures of rCBV are correlated with vessel density and not vessel caliber
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