9,123 research outputs found

    Quantum criticality in a generalized Dicke model

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    We employ a generalized Dicke model to study theoretically the quantum criticality of an extended two-level atomic ensemble interacting with a single-mode quantized light field. Effective Hamiltonians are derived and diagonalized to investigate numerically their eigenfrequencies for different quantum phases in the system. Based on the analysis of the eigenfrequencies, an intriguing quantum-phase transition from a normal phase to a superradiant phase is revealed clearly, which is quite different from that observed with a standard Dicke model.Comment: 6 pages, 3 figure

    Determination of the magnetization profile of Co/Mg periodic multilayers by magneto-optic Kerr effect and X-ray magnetic resonant reflectivity

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    The resonant magnetic reflectivity of Co/Mg multilayers around the Co L2,3 absorption edge is simulated then measured on a specifically designed sample. The dichroic signal is obtained when making the difference between the two reflectivities measured with the magnetic field applied in two opposite directions parallel to the sample surface. The simulations show that the existence of magnetic dead layers at the interfaces between the Co and Mg layers leads to an important increase of the dichroic signal measured in the vicinity of the third Bragg peak that otherwise should be negligible. The measurements are in agreement with the model introducing 0.25 nm thick dead layers. This is attributed to the Co atoms in contact with the Mg layers and thus we conclude that the Co-Mg interfaces are abrupt from the magnetic point of view.Comment: 8 page

    Leaf-Encapsulated Vaccines: Agroinfiltration and Transient Expression of the Antigen Staphylococcal Endotoxin B in Radish Leaves.

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    Transgene introgression is a major concern associated with transgenic plant-based vaccines. Agroinfiltration can be used to selectively transform nonreproductive organs and avoid introgression. Here, we introduce a new vaccine modality in which Staphylococcal enterotoxin B (SEB) genes are agroinfiltrated into radishes (Raphanw sativus L.), resulting in transient expression and accumulation of SEB in planta. This approach can simultaneously express multiple antigens in a single leaf. Furthermore, the potential of high-throughput vaccine production was demonstrated by simultaneously agroinfiltrating multiple radish leaves using a multichannel pipette. The expression of SEB was detectable in two leaf cell types (epidermal and guard cells) in agroinfiltrated leaves. ICR mice intranasally immunized with homogenized leaves agroinfiltrated with SEB elicited detectable antibody to SEB and displayed protection against SEB-induced interferon-gamma (IFN-γ) production. The concept of encapsulating antigens in leaves rather than purifying them for immunization may facilitate rapid vaccine production during an epidemic disease

    Undecidable properties of self-affine sets and multi-tape automata

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    We study the decidability of the topological properties of some objects coming from fractal geometry. We prove that having empty interior is undecidable for the sets defined by two-dimensional graph-directed iterated function systems. These results are obtained by studying a particular class of self-affine sets associated with multi-tape automata. We first establish the undecidability of some language-theoretical properties of such automata, which then translate into undecidability results about their associated self-affine sets.Comment: 10 pages, v2 includes some corrections to match the published versio

    Mass and dust in the disk of a spiral lens galaxy

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    Gravitational lensing is a potentially important probe of spiral galaxy structure, but only a few cases of lensing by spiral galaxies are known. We present Hubble Space Telescope and Magellan observations of the two-image quasar PMN J2004-1349, revealing that the lens galaxy is a spiral galaxy. One of the quasar images passes through a spiral arm of the galaxy and suffers 3 magnitudes of V-band extinction. Using simple lens models, we show that the mass quadrupole is well-aligned with the observed galaxy disk. A more detailed model with components representing the bulge and disk gives a bulge-to-disk mass ratio of 0.16 +/- 0.05. The addition of a spherical dark halo, tailored to produce an overall flat rotation curve, does not change this conclusion.Comment: ApJ, in press [9pp, 7 figs

    Systems intervention to promote colon cancer screening in safety net settings: Protocol for a community-based participatory randomized controlled trial

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    BACKGROUND: Colorectal cancer is a leading cause of cancer mortality. Screening can be effective but is underutilized. System- or multi-level interventions could be effective at increasing screening, but most have been implemented and evaluated in higher-resource settings such as health maintenance organizations. Given the disparities evident for colorectal cancer and the potential for screening to improve outcomes, there is a need to expand this work to include diverse settings, including those who treat economically disadvantaged patients. This paper describes the study protocol for a trial designed to increase colorectal cancer screening in those ‘safety-net’ health centers that serve underinsured and uninsured patients. This trial was designed and is being implemented using a community-based participatory approach. METHODS/DESIGN: We developed a practical clinical cluster-randomized controlled trial. We will recruit 16 community health centers to this trial. This systems-level intervention consists of a menu of evidence-based implementation strategies for increasing colorectal cancer screening. Health centers in the intervention arm then collaborate with the study team to tailor strategies to their own setting in order to maximize fit and acceptability. Data are collected at the organizational level through interviews, and at the provider and patient levels through surveys. Patients complete a survey about their healthcare and screening utilization at baseline, six months, and twelve months. OUTCOMES: The primary outcome is colorectal cancer screening by patient self-report, supplemented by a chart-audit in a subsample of patients. Implementation outcomes informed by the Reach, Efficacy/Effectiveness, Adoption, Implementation, and Maintenance (RE-AIM) conceptual framework will be measured at patient, provider, and practice levels. DISCUSSION: Our study is one of the first to integrate community participatory strategies to a randomized controlled trial in a healthcare setting. The multi-level approach will support the ability of the intervention to affect screening through multiple avenues. The participatory approach will strengthen the chance that implementation strategies will be maintained after study completion and, supports external validity by increasing health center interest and willingness to participate. TRIAL REGISTRATION: NCT0129949

    Possible large phase in psi(2S) -> 1-0- Decays

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    The strong and the electromagnetic amplitudes are analyzed on the basis of the measurements of J/psi, psi(2S) -> 1-0- in e+e- experiments. The currently available experimental information is revised with inclusion of the contribution from e+e- -> gamma * -> 1-0- . The study shows that a large phase around minus 90 degree between the strong and the electromagnetic amplitudes could not be ruled out by the experimental data for psi(2S).Comment: 4 page
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