19,271 research outputs found
Gluon GPDs and Exclusive Photoproduction of a Quarkonium in Forward Region
Forward photoproduction of 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 is transversely polarized. We find that at
twist-3 the produced 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
can have a sizeable effect. We have also derived the amplitude of the
production of 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 -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 1 kpc. The component at the jet base
showing an inverted spectrum is identified as the core, with a mean brightness
temperature of ~K. The jet bends at about 600 pc (in
projection) away from the core, from a position angle of to
. Based on the available VLBI data, we inferred the proper motion
speed of the inner jet as mas yr (), corresponding to a jet speed of about at an inclination
angle of 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 -ray-emitting blazars, implying that the pc-scale jet in 3C~286 is
mildly relativistic. Unlike blazars in which -ray emission is in
general thought to originate from the beamed innermost jet, the location and
mechanism of -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 -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
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