4,845 research outputs found

    MHD Wave Propagation in the Neighbourhood of Two Null Points

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    The nature of fast magnetoacoustic and Alfv\'en waves is investigated in a zero β\beta plasma in the neighbourhood of a pair of two-dimensional null points. This gives an indication of wave propagation in the low β\beta solar corona, for a more complicated magnetic configuration than that looked at by McLaughlin & Hood (2004). It is found that the fast wave is attracted to the null points and that the front of the wave slows down as it approaches the null point pair, with the wave splitting and part of the wave accumulating at one null and the rest at the other. Current density will then accumulate at these points and ohmic dissipation will then extract the energy in the wave at these points. This suggests locations where wave heating will occur in the corona. The Alfv\'en wave behaves in a different manner in that the wave accumulates along the separatrices. Hence, the current density will accumulate at this part of the topology and this is where wave heating will occur. However, the phenomenon of wave accumulation at a specific place is a feature of both wave types, and illustrates the importance of studying the topology of the corona when considering MHD wave propagation.Comment: 11 pages, 14 figure

    Multiple domestications of asian rice

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    In their recent Correspondence about our study showingthat there were three origins of Asian rice2, Huang and Han suggest that the methodology that we used to infer multiple domestications was flawed as it did not take account of the strong genetic bottleneck in japonica

    New Evidence for Homocysteine Lowering for Management of Treatment-Resistant Hypertension

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    Treatment-resistant hypertension is a topic of great importance and the subject of editorial comments in the American Journal of Hypertension. Homocysteine is an intermediate compound in the vitamin regulated One Carbon Methylation pathway which affects glutathione, methionine, and nitric oxide metabolism. Elevated homocysteine, triggered by genetic mutations or insufficient body stores of active vitamins B6, B12, folate, riboflavin, indicates oxidative stress and is associated with impaired nitric oxide synthesis causing small vessel vasoconstriction in the central nervous system. High homocysteine (defined later) is also a risk factor for hypertension

    Deep radio observations of the radio halo of the bullet cluster 1E 0657-55.8

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    We present deep 1.1-3.1 GHz Australia Telescope Compact Array observations of the radio halo of the bullet cluster, 1E 0657-55.8. In comparison to existing images of this radio halo the detection in our images is at higher significance. The radio halo is as extended as the X-ray emission in the direction of cluster merger but is significantly less extended than the X-ray emission in the perpendicular direction. At low significance we detect a faint second peak in the radio halo close to the X-ray centroid of the smaller sub-cluster (the bullet) suggesting that, similarly to the X-ray emission, the radio halo may consist of two components. Finally, we find that the distinctive shape of the western edge of the radio halo traces out the X-ray detected bow shock. The radio halo morphology and the lack of strong point-to-point correlations between radio, X-ray and weak-lensing properties suggests that the radio halo is still being formed. The colocation of the X-ray shock with a distinctive radio brightness edge illustrates that the shock is influencing the structure of the radio halo. These observations support the theory that shocks and turbulence influence the formation and evolution of radio halo synchrotron emission.Comment: 15 pages, 16 figures, 3 tables. Accepted by MNRA

    Increased risk donor criteria: The time for change is now

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155965/1/ctr13879.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155965/2/ctr13879_am.pd
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