Gluon GPDs and Exclusive Photoproduction of a Quarkonium in Forward Region

Forward photoproduction of $J/\psi$ can be used to extract Generalized Parton Distributions(GPD's) of gluons. We analyze the process at twist-3 level and study relevant classifications of twist-3 gluon GPD's. At leading power or twist-2 level the produced $J/\psi$ is transversely polarized. We find that at twist-3 the produced $J/\psi$ is longitudinally polarized. Our study shows that in high energy limit the twist-3 amplitude is only suppressed by the inverse power of the heavy quark mass relatively to the twist-2 amplitude. This indicates that the power correction to the cross-section of unpolarized $J/\psi$ can have a sizeable effect. We have also derived the amplitude of the production of $h_c$ at twist-3, but the result contains end-point singularities. The production of other quarkonia has been briefly discussed.Comment: Discussions of results are adde

Parsec-scale jet properties of the gamma-ray quasar 3C 286

The quasar 3C~286 is one of two compact steep spectrum sources detected by the {\it Fermi}/LAT. Here, we investigate the radio properties of the parsec(pc)-scale jet and its (possible) association with the $\gamma$-ray emission in 3C~286. The Very Long Baseline Interferometry (VLBI) images at various frequencies reveal a one-sided core--jet structure extending to the southwest at a projected distance of $\sim$1 kpc. The component at the jet base showing an inverted spectrum is identified as the core, with a mean brightness temperature of $2.8\times 10^{9}$~K. The jet bends at about 600 pc (in projection) away from the core, from a position angle of $-135^\circ$ to $-115^\circ$. Based on the available VLBI data, we inferred the proper motion speed of the inner jet as $0.013 \pm 0.011$ mas yr$^{-1}$ ($\beta_{\rm app} = 0.6 \pm 0.5$), corresponding to a jet speed of about $0.5\,c$ at an inclination angle of $48^\circ$ between the jet and the line of sight of the observer. The brightness temperature, jet speed and Lorentz factor are much lower than those of $\gamma$-ray-emitting blazars, implying that the pc-scale jet in 3C~286 is mildly relativistic. Unlike blazars in which $\gamma$-ray emission is in general thought to originate from the beamed innermost jet, the location and mechanism of $\gamma$-ray emission in 3C~286 may be different as indicated by the current radio data. Multi-band spectrum fitting may offer a complementary diagnostic clue of the $\gamma$-ray production mechanism in this source.Comment: 9 pages, 4 figures, accept for publication in MNRA

Effects of AdR-siPTEN on learning capability, memory and extracellular signal-regulated kinase expression in hippocampus of rats with vascular dementia

This study investigated the effects of a recombinant adenovirus, AdR-siPTEN, on learning capability, memory and extracellular signal-regulated kinase (ERK) expression in the hippocampus of rats withvascular dementia (VD). VD was introduced via permanent bilateral common carotid artery ligation (2-VO) in rats. AdR-siPTEN recombinant adenovirus and unrelated control adenovirus AdRFP were independently injected into the hippocampus of VD rats. Four weeks later, Morris water maze test was performed to detect the cognition of rats. Hematoxylin and eosin (HE) and Nissl staining were used to observe cellular morphous and neuronal damage in the hippocampus CA1 region. The mRNA andprotein expression of a phosphatase and tensin homolog deleted on chromosome 10 (PTEN), phosphatidylinositol 3-kinase (PI3K), ERK and cAMP response element-binding (CREB) were detected by reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry, respectively. PTEN expression was reduced apparently in hippocampus after RNAi intervation in the AdR-siPTENgroup (P<0.05). Compared with the AdRFP group, rats in the AdR-siPTEN group had significantly shorter escape latency to the invisible platform (except on the first day of test) (P<0.05); and more neurons with regular shape and/or Nissl bodies in hippocampus were observed in the AdR-siPTEN group, suggesting attenuated neuronal damage and degeneration. Additionally, the expression of PI3K, ERK and CREB in hippocampus CA1 region of AdR-siPTEN treatment group was markedly higher than that in the AdRFP group (P < 0.05). However, compared with the normal group, the expression of PI3K, ERK and CREB was dramatically decreased in the AdRFP group (P < 0.05). AdR-siPTEN may improvethe cognition of VD rats, attenuate neuronal damage and promote expression of ERK and CREB, leading to the protective effects on neuronal synaptic plasticity in VD rats. These results suggest that PTEN down-regulation may exert potential therapeutic effects on VD