23,678 research outputs found

    Dendritic cells activated with products released by schistosome larvae drive Th2-type immune responses, which can be inhibited by manipulation of CD40 costimulation

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    The early immune events in response to infective larvae of the parasitic helminth Schistosoma mansoni are poorly understood, but here for the first time we report on the potential of products released by schistosome larvae (material released in the first 3 It after transformation [0-3hRP]) to stimulate the maturation of dendritic cells (DC) and alter their T-cell-polarizing function. This was performed in comparison with lipopolysaccharide (LPS) and zymosan A, which classically activate DC to prime for Th1- and Th2-type responses, respectively. In our study, immature bone marrow-derived DC stimulated in vitro with 0-3hRP exhibited up-regulated expression of major histocompatibility complex class II, CD40, and CD86 and increased production of interleukin 12p40 (IL-12p40) and IL-6, albeit at lower levels than in response to LPS or zymosan A. Using an in vitro ovalbumin peptide-restricted priming assay, DC matured with 0-3hRP exhibited a potent capacity to drive Th2 polarization of CD4(+) cells from DO11.10 transgenic mice. This was characterized by increased IL-4 production (but not gamma interferon) of a magnitude similar to that primed by DC matured with zymosan A. Inoculation of DO11.10 mice with 0-3hRP-activated DC pulsed with ovalbumin peptide also led to the development of a Th2-type polarized response in the skin-draining lymph nodes and spleen. However, ligation of CD40 on DC by anti-CD40 antibody treatment reversed the ability of 0-3hRP-activated DC to prime for Th2-type responses and instead caused the induction of a more Th1-type response

    Higher-Order Gravitational Lensing Reconstruction using Feynman Diagrams

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    We develop a method for calculating the correlation structure of the Cosmic Microwave Background (CMB) using Feynman diagrams, when the CMB has been modified by gravitational lensing, Faraday rotation, patchy reionization, or other distorting effects. This method is used to calculate the bias of the Hu-Okamoto quadratic estimator in reconstructing the lensing power spectrum up to O(\phi^4) in the lensing potential Ï•\phi. We consider both the diagonal noise TTTT, EBEB, etc. and, for the first time, the off-diagonal noise TTTE, TBEB, etc. The previously noted large O(\phi^4) term in the second order noise is identified to come from a particular class of diagrams. It can be significantly reduced by a reorganization of the Ï•\phi expansion. These improved estimators have almost no bias for the off-diagonal case involving only one BB component of the CMB, such as EEEB.Comment: 17 pages, 17 figure

    Effective field theory and the quark model

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    We analyze the connections between the quark model (QM) and the description of hadrons in the low-momentum limit of heavy-baryon effective field theory in QCD. By using a three-flavor-index representation for the effective baryon fields, we show that the ``nonrelativistic'' constituent QM for baryon masses and moments is completely equivalent through O(m_s) to a parametrization of the relativistic field theory in a general spin--flavor basis. The flavor and spin variables can be identified with those of effective valence quarks. Conversely, the spin-flavor description clarifies the structure and dynamical interpretation of the chiral expansion in effective field theory, and provides a direct connection between the field theory and the semirelativistic models for hadrons used in successful dynamical calculations. This allows dynamical information to be incorporated directly into the chiral expansion. We find, for example, that the striking success of the additive QM for baryon magnetic moments is a consequence of the relative smallness of the non-additive spin-dependent corrections.Comment: 25 pages, revtex, no figure

    Gravitational Lensing of the CMB: a Feynman Diagram Approach

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    We develop a Feynman diagram approach to calculating correlations of the Cosmic Microwave Background (CMB) in the presence of distortions. As one application, we focus on CMB distortions due to gravitational lensing by Large Scale Structure (LSS). We study the Hu-Okamoto quadratic estimator for extracting lensing from the CMB and derive the noise of the estimator up to O(Ï•4){\mathcal O}(\phi^4) in the lensing potential Ï•\phi. The previously noted large O(Ï•4){\mathcal O}(\phi^4) term can be significantly reduced by a reorganization of the Ï•\phi expansion. Our approach makes it simple to obtain expressions for quadratic estimators based on any CMB channel. We briefly discuss other applications to cosmology of this diagrammatic approach, such as distortions of the CMB due to patchy reionization, or due to Faraday rotation from primordial axion fields.Comment: 5 pages, 8 figures, v2: journal versio

    Sand as Maxwell's demon

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    We consider a dilute gas of granular material inside a box, kept in a stationary state by shaking. A wall separates the box into two identical compartments, save for a small hole at some finite height hh. As the gas is cooled, a second order phase transition occurs, in which the particles preferentially occupy one side of the box. We develop a quantitative theory of this clustering phenomenon and find good agreement with numerical simulations

    Giant planets around two intermediate-mass evolved stars and confirmation of the planetary nature of HIP67851 c

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    Precision radial velocities are required to discover and characterize planets orbiting nearby stars. Optical and near infrared spectra that exhibit many hundreds of absorption lines can allow the m/s precision levels required for such work. However, this means that studies have generally focused on solar-type dwarf stars. After the main-sequence, intermediate-mass stars (former A-F stars) expand and rotate slower than their progenitors, thus thousands of narrow absorption lines appear in the optical region, permitting the search for planetary Doppler signals in the data for these types of stars. We present the discovery of two giant planets around the intermediate-mass evolved star HIP65891 and HIP107773. The best Keplerian fit to the HIP65891 and HIP107773 radial velocities leads to the following orbital parameters: P=1084.5 d; mb_bsinii = 6.0 Mjup_{jup}; ee=0.13 and P=144.3 d; mb_bsinii = 2.0 Mjup_{jup}; ee=0.09, respectively. In addition, we confirm the planetary nature of the outer object orbiting the giant star HIP67851. The orbital parameters of HIP67851c are: P=2131.8 d, mc_csinii = 6.0 Mjup_{jup} and ee=0.17. With masses of 2.5 M⊙_\odot and 2.4 M⊙_\odot HIP65891 and HIP107773 are two of the most massive stars known to host planets. Additionally, HIP67851 is one of five giant stars that are known to host a planetary system having a close-in planet (a<a < 0.7 AU). Based on the evolutionary states of those five stars, we conclude that close-in planets do exist in multiple systems around subgiants and slightly evolved giants stars, but probably they are subsequently destroyed by the stellar envelope during the ascent of the red giant branch phase. As a consequence, planetary systems with close-in objects are not found around horizontal branch stars.Comment: Accepted for publication in A&

    Observation of suppression of light scattering induced by dipole-dipole interactions in a cold atomic ensemble

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    We study the emergence of collective scattering in the presence of dipole-dipole interactions when we illuminate a cold cloud of rubidium atoms with a near-resonant and weak intensity laser. The size of the atomic sample is comparable to the wavelength of light. When we gradually increase the atom number from 1 to 450, we observe a broadening of the line, a small red shift and, consistently with these, a strong suppression of the scattered light with respect to the noninteracting atom case. Numerical simulations, which include the internal atomic level structure, agree with the data.Comment: 5 pages, 5 figure

    Improving driver behaviour by design : a cognitive work analysis methodology

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    Within the European Community both the environmental and safety costs of road transport are unacceptably high. ‘Foot-LITE’ is a UK project which aims to encourage drivers to adopt ‘greener’ and safer driving practices, with real-time and retrospective feedback being given both in-vehicle and off-line. This paper describes the early concept development of Foot-LITE, for which a Cognitive Work Analysis (CWA) was conducted. In this paper, we present the results of the first phase of CWA – the Work Domain Analysis, as well as some concept interface designs based on the WDA to illustrate its application. In summary, the CWA establishes a common framework for the project, and will ultimately contribute to the design of the in-vehicle interface
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