2,016 research outputs found

    Structure and Composition of Molecular Clouds with CN Zeeman Detections I: W3OH

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    We have carried out a multi-species study of a region which has had previous measurements of strong magnetic fields through the CN Zeeman effect in order to to explore the relationship between CN and N2_2H+^+, both of which have evidence that they remain in the gas phase at densities of 105^5 - 106^6 cm−3^{-3}. To achieve this we map the 1 arcmin2^2 region around the UCHII region of W3(OH) using the Combined Array for Millimeter-wave Astronomy (CARMA). Approximately 105 hours of data were collected in multiple array configurations to produce maps with an effective resolution of ∼\sim 2.5\arcsec at high signal-to-noise in CN, C18^{18}O, HCN, HCO+^+, N2_2H+^+, and two continuum bands (91.2 GHz and 112 GHz). These data allow us to compare tracer molecules associated with both low and high density regions to infer gas properties. We determine that CARMA resolves out approximately 35% of the CN emission around W3(OH) when compared with spectra obtained from the IRAM-30 meter telescope. The presence of strong absorption lines towards the continuum source in three of the molecular transitions infers the presence of a cold, dark, optically thick region in front of the continuum source. In addition, the presence of high-velocity emission lines near the continuum source shows the presence of hot clumpy emission behind the continuum source. These data determine that future high-resolution interferometric CN Zeeman measurements which cannot currently be performed (due to technical limitations of current telescopes) are feasible. We confirm that CN is indeed a good tracer for high density regions; with certain objects such as W3(OH) it appears to be a more accurate tracer than N2_2H+^+.Comment: 33 pages, 16 figures. Accepted by Ap

    Dictionary Learning and Sparse Coding-based Denoising for High-Resolution Task Functional Connectivity MRI Analysis

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    We propose a novel denoising framework for task functional Magnetic Resonance Imaging (tfMRI) data to delineate the high-resolution spatial pattern of the brain functional connectivity via dictionary learning and sparse coding (DLSC). In order to address the limitations of the unsupervised DLSC-based fMRI studies, we utilize the prior knowledge of task paradigm in the learning step to train a data-driven dictionary and to model the sparse representation. We apply the proposed DLSC-based method to Human Connectome Project (HCP) motor tfMRI dataset. Studies on the functional connectivity of cerebrocerebellar circuits in somatomotor networks show that the DLSC-based denoising framework can significantly improve the prominent connectivity patterns, in comparison to the temporal non-local means (tNLM)-based denoising method as well as the case without denoising, which is consistent and neuroscientifically meaningful within motor area. The promising results show that the proposed method can provide an important foundation for the high-resolution functional connectivity analysis, and provide a better approach for fMRI preprocessing.Comment: 8 pages, 3 figures, MLMI201

    Cosmetic colouring by Bearded Vultures Gypaetus barbatus: still no evidence for an antibacterial function

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    Bearded Vultures regularly visit ferruginous springs for cosmetic purposes to obtain their reddish plumage colouration. Different hypotheses have been proposed to explain this deliberate application of adventitious colouration: (1) to signal individual dominance status; (2) to exploit an anti-bacterial effect of iron oxides or ochre to reduce feather degradation by bacteria and, in parallel (3) to enable incubating birds to transfer this protection to their developing embryos to increase hatching success. Here, we re-evaluate the antibacterial hypothesis using three experimental approaches: (a) by applying feather-degrading bacteria to stained and unstained bearded vulture feathers; (b) by assessing the antibacterial activity of ochre; and (c) by comparing the breeding success of orange individuals with pale ones. Our findings suggest that the in vitro addition of feather degrading Bacillus licheniformis to naturally stained Bearded Vulture feathers did not retard feather degradation compared to controls. Iron particles from red soil (ochre) or iron salts had no antibacterial effect on the growth of three species of bacteria (Escherichia coli, Kocuria rhizophila and Bacillus licheniformis), incubated either in the dark or under visible light. Finally, breeding success did not differ between territories occupied by pale individuals versus orange ones. These results run counter to the hypothesis that iron oxides have an antibacterial role in Bearded Vultures. The use of red soils by Bearded Vultures may function as a territorial status signal, but may also be involved in other processes, such as pair formation and the long-term maintenance of the pair bond, as suggested for the closely related Egyptian vulture Neophron percnopterus

    Yang-Mills glueball masses from spectral reconstruction

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    We compute masses of the two lightest glueballs from spectral reconstructions of timelike interaction channels of the four-gluon vertex in Landau gauge Yang-Mills theory. The Euclidean spacelike dressings of the vertex are calculated with the functional renormalisation group. For the spectral reconstruction of these Euclidean data, we employ Gaussian process regression. The glueball resonances can be identified straightforwardly and we obtain msc=1870(75) m_{sc} = 1870(75)~ MeV as well as mps=2700(120) m_{ps} = 2700(120)~ MeV, in accordance with functional bound state and lattice calculations.Comment: 10 pages, 6 figure

    Fostering Preservice Teacher Identity in Science through a Student-Selected Project

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    This article addresses the problem of authentic student engagement in the science classroom by incorporating a semester long research and writing assignment that enables students to investigate scientific topics related to strong personal, career, or health interests

    A multi-particle model of the 3C 48 host

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    The first successful multi-particle model for the host of the well-known quasi-stellar object (QSO) 3C 48 is reported. It shows that the morphology and the stellar velocity field of the 3C 48 host can be reproduced by the merger of two disk galaxies. The conditions of the interaction are similar to those used for interpreting the appearance of the ''Antennae'' (NGC 4038/39) but seen from a different viewing angle. The model supports the controversial hypothesis that 3C 48A is the second nucleus of a merging galaxy, and it suggests a simple solution for the problem of the missing counter tidal tail.Comment: 5 pages, 5 figures, accepted for publication in A&
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