A note on the span of Hadamard products of vectors

We give a new proof of Theorem 6 in [L. Qiu and X. Zhan, On the span of Hadamard products of vectors, Linear Algebra Appl. 422 (2007) 304--307].Comment: 2 page

Ubiquitination accomplished: E1 and E2 enzymes were not necessary

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

Nuclear absorption of Charmoniums in pA and AA collisions

We have analysed the latest NA50 data on $J/\psi$ production in pA and AA collisions. The $J/\psi$ production is assumed to be a two step process, (i) formation of $c\bar{c}$ pairs, perturbatively calculable, and (ii) formation of $J/\psi$ from the pair, a non-perturbative process, which is conviniently parametrized. In a nuclear medium, as the $c\bar{c}$ pair passes through the nuclear medium, it gain relative square momentum and some of the pairs can gain enough square momentum to cross the threshold for open charm meson, leading to suppression in nuclear medium. Few parameters of the model were fixed from the latest high statistics NA50 pA and NA38 SU total $J/\psi$ cross sectional data. The model then reproduces the centrality dependence of $J/\psi$ over Drell-Yan ration in 200 GeV/c S+U and 158 GeV/c Pb+Pb collisions. We also discuss the centrality dependence of $J/\psi$ suppression at RHIC energy.Comment: 4 pages including 3 figures, Revised version, to be published in Phys.Rev.

Book review : Goodbye iSlave : a manifesto for digital abolition

Review of the book Goodbye iSlave: A Manifesto for Digital Abolition, by Jack Linchuan Qiu. Urbana: University of Illinois Press, 2016, ISBN 978-0-252-08212-2Author’s OriginalPublishe

J/ψJ/\psi suppression in Pb+Pb collisions and pTp_T broadening

We have analysed the NA50 data, on the centrality dependence of $p_T$ broadening of $J/\psi$'s, in Pb+Pb collisions, at the CERN-SPS. The data were analysed in a QCD based model, where $J/\psi$'s are suppressed in 'nuclear' medium. Without any free parameter, the model could explain the NA50 $p_T$ broadening data. The data were also analysed in a QGP based threshold model, where $J/\psi$ suppression is 100% above a critical density. The QGP based model could not explain the NA50 $p_T$ broadening data. We have also predicted the centrality dependence of $J/\psi$ suppression and $p_T$ broadening at RHIC energy. Both the models, the QGP based threshold model and the QCD based nuclear absorption model, predict $p_T$ broadening very close to each other.Comment: The paper was completely revised. The conclusion is also changed. 5 pages, 4 figure