187,246 research outputs found

    Ubiquitination accomplished: E1 and E2 enzymes were not necessary

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    Qiu et al. (2016) show that a mono-ADP-ribosyltransferase, SdeA, from Legionella pneumophila catalyzes ADP-ribosylation of ubiquitin, allowing SdeA to modify substrate with ubiquitin in the absence of E1 and E2 enzymes

    Semileptonic B(Bs,Bc)B(B_s, B_c) decays in the light-cone QCD sum rules

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    Semileptonic BB(Bs,BcB_s, B_c) decays are investigated systematically in the light-cone QCD sum rules. Special emphasis is put on the LCSR calculation on weak form factors with an adequate chiral current correlator, which turns out to be particularly effective to control the pollution by higher twist components of spectator mesons. The result for each channel depends on the distribution amplitude of the the producing meson. The leading twist distribution amplitudes of the related heavy mesons and charmonium are worked out by a model approach in the reasonable way. A practical scenario is suggested to understand the behavior of weak form factors in the whole kinematically accessible ranges. The decay widths and branching ratios are estimated for several BB(BcB_c) decay modes of current interest.Comment: 8 pages, talk given by the first arthur at 4th International Conference on Flavor Physics (ICFP 2007), Beijing, China, Sept 24-28, 200

    Linear Precoding in Cooperative MIMO Cellular Networks with Limited Coordination Clusters

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    In a cooperative multiple-antenna downlink cellular network, maximization of a concave function of user rates is considered. A new linear precoding technique called soft interference nulling (SIN) is proposed, which performs at least as well as zero-forcing (ZF) beamforming. All base stations share channel state information, but each user's message is only routed to those that participate in the user's coordination cluster. SIN precoding is particularly useful when clusters of limited sizes overlap in the network, in which case traditional techniques such as dirty paper coding or ZF do not directly apply. The SIN precoder is computed by solving a sequence of convex optimization problems. SIN under partial network coordination can outperform ZF under full network coordination at moderate SNRs. Under overlapping coordination clusters, SIN precoding achieves considerably higher throughput compared to myopic ZF, especially when the clusters are large.Comment: 13 pages, 5 figure

    Decay of weak turbulence

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    Weak turbulence fields generated by single and multiple stage grids covering Reynolds numbers between 7 and 70 showing decay of energy spectr