947 research outputs found
Heavy Pseudoscalar Twist-3 Distribution Amplitudes within QCD Theory in Background Fields
In this paper, we study the properties of the twist-3 distribution amplitude
(DA) of the heavy pseudo-scalars such as , and . New sum
rules for the twist-3 DA moments \left_{\rm HP} and
\left_{\rm HP} up to sixth orders and up to dimension-six
condensates are deduced under the framework of the background field theory.
Based on the sum rules for the twist-3 DA moments, we construct a new model for
the two twist-3 DAs of the heavy pseudo-scalar with the help of the
Brodsky-Huang-Lepage prescription. Furthermore, we apply them to the
transition form factor () within the
light-cone sum rules approach, and the results are comparable with other
approaches. It has been found that the twist-3 DAs and
are important for a reliable prediction of
. For example, at the maximum recoil region, we have
, in which those two twist-3 terms
provide and contributions. Also we calculate the
branching ratio of the semi-leptonic decay as .Comment: 12 pages, 16 figure
Bounds On Anomalous Magnetic And Electric Moments Of Tau Lepton From LEP And Lepton Flavor Violation
The most stringent bounds on the anomalous magnetic and electric dipole
moments of the tau lepton was derived by Escribano and Mass\'{o}[6] from the Z
width at LEP in an effective lagrangian approach to the new physics. In this
paper we point out that the higher dimensional operators introduced by
Escribano and Mass\'{o} not only modify the neutral currents of the tau lepton
to Z gauge boson and the photon, but also induce lepton flavor violation (LFV).
The size of the LFV effect depends crucially on the dynamics of the lepton mass
generation. Assuming the lepton mass matrices in the form of an Fritzsch
ansatz, we point out that the experimental limit on will
push the anomalous magnetic and electric dipole moments of the tau lepton down
to and respectively.Comment: 6 pages, latex, no figure
Renormalization-group improved predictions for Higgs boson production at large
We study the next-to-next-to-leading logarithmic order resummation for the
large Higgs boson production at the LHC in the framework of
soft-collinear effective theory. We find that the resummation effects reduce
the scale uncertainty significantly and decrease the QCD NLO results by about
in the large region. The finite top quark mass effects and the
effects of the NNLO singular terms are also discussed.Comment: 31 pages, 17 figures, version published in Phys.Rev.
Effects of Helicobacter pylori
Infection of Helicobacter pylori (H. pylori) changed the proliferation of gastric epithelial cells and decreased the expression of heat shock protein 70 (HSP70). However, the effects of H. pylori on the proliferation of gastric epithelial cells and the roles of HSP70 during the progress need further investigation. Objective. To investigate the effects of Helicobacter pylori (H. pylori) and heat shock protein 70 (HSP70) on the proliferation of human gastric epithelial cells. Methods. H. pylori and a human gastric epithelial cell line (AGS) were cocultured. The proliferation of AGS cells was quantitated by an MTT assay, and the expression of HSP70 in AGS cells was detected by Western blotting. HSP70 expression in AGS cells was silenced by small interfering RNA (siRNA) to investigate the role of HSP70. The siRNA-treated AGS cells were cocultured with H. pylori and cell proliferation was measured by an MTT assay. Results. The proliferation of AGS cells was accelerated by coculturing with H. pylori for 4 and 8 h, but was suppressed at 24 and 48 h. HSP70 expression was decreased in AGS cells infected by H. pylori for 48 h. The proliferation in HSP70-silenced AGS cells was inhibited after coculturing with H. pylori for 24 and 48 h compared with the control group. Conclusions. Coculture of H. pylori altered the proliferation of gastric epithelial cells and decreased HSP70 expression. HSP70 knockdown supplemented the inhibitory effect of H. pylori on proliferation of epithelial cells. These results indicate that the effects of H. pylori on the proliferation of gastric epithelial cells at least partially depend on the decreased expression of HSP70 induced by the bacterium
Revisiting the Pion Leading-Twist Distribution Amplitude within the QCD Background Field Theory
We study the pion leading-twist distribution amplitude (DA) within the
framework of SVZ sum rules under the background field theory. To improve the
accuracy of the sum rules, we expand both the quark propagator and the vertex
(z\cdot \tensor{D})^n of the correlator up to dimension-six operators in the
background field theory. The sum rules for the pion DA moments are obtained, in
which all condensates up to dimension-six have been taken into consideration.
Using the sum rules, we obtain \left|_{\rm 1\;GeV} = 0.338 \pm
0.032, \left|_{\rm 1\;GeV} = 0.211 \pm 0.030 and
\left|_{\rm 1\;GeV} = 0.163 \pm 0.030. It is shown that the
dimension-six condensates shall provide sizable contributions to the pion DA
moments. We show that the first Gegenbauer moment of the pion leading-twist DA
is , which is consistent with those
obtained in the literature within errors but prefers a larger central value as
indicated by lattice QCD predictions.Comment: 13 pages, 7 figure
4-Chloro-N′-(4-methÂoxyÂbenzylÂidene)benzohydrazide methanol monosolvate
The title compound, C15H13ClN2O2·CH4O, consists of a 4-chloro-N′-(4-methÂoxyÂbenzylÂidene)benzohydrazide (CMB) molÂecule and a methanol molÂecule of crystallization. It was obtained by the condensation of 4-methÂoxyÂbenzaldehyde with 4-chloroÂbenzohydrazide. In the CMB molÂecule, the dihedral angle between the two benzene rings is 50.1 (3)°. The methanol molÂecule is linked to the CMB molÂecule through O—H⋯O and O—H⋯N hydrogen bonds. In the crystal, CMB molÂecules are linked through interÂmolecular N—H⋯O hydrogen bonds, involving the methanol molÂecule, forming chains propagating along [010]
Diagnostic Evaluation of Policy-Gradient-Based Ranking
Learning-to-rank has been intensively studied and has shown significantly increasing values in a wide range of domains, such as web search, recommender systems, dialogue systems, machine translation, and even computational biology, to name a few. In light of recent advances in neural networks, there has been a strong and continuing interest in exploring how to deploy popular techniques, such as reinforcement learning and adversarial learning, to solve ranking problems. However, armed with the aforesaid popular techniques, most studies tend to show how effective a new method is. A comprehensive comparison between techniques and an in-depth analysis of their deficiencies are somehow overlooked. This paper is motivated by the observation that recent ranking methods based on either reinforcement learning or adversarial learning boil down to policy-gradient-based optimization. Based on the widely used benchmark collections with complete information (where relevance labels are known for all items), such as MSLRWEB30K and Yahoo-Set1, we thoroughly investigate the extent to which policy-gradient-based ranking methods are effective. On one hand, we analytically identify the pitfalls of policy-gradient-based ranking. On the other hand, we experimentally compare a wide range of representative methods. The experimental results echo our analysis and show that policy-gradient-based ranking methods are, by a large margin, inferior to many conventional ranking methods. Regardless of whether we use reinforcement learning or adversarial learning, the failures are largely attributable to the gradient estimation based on sampled rankings, which significantly diverge from ideal rankings. In particular, the larger the number of documents per query and the more fine-grained the ground-truth labels, the greater the impact policy-gradient-based ranking suffers. Careful examination of this weakness is highly recommended for developing enhanced methods based on policy gradient
New fossil seeds of Eurya (Theaceae) from East Asia and their paleobiogeographic implications
AbstractEurya has an excellent fossil record in Europe, but it has only a few fossil occurrences in East Asia though this vast area houses the highest modern diversity of the genus. In this study, three-dimensionally preserved fossil seeds of Eurya stigmosa (Ludwig) Mai from the late Pliocene of northwestern Yunnan, southwestern China are described. The seeds are compressed and flattened, slightly campylotropous, and nearly circular to slightly angular in shape. The surface of the seeds is sculptured by a distinctive foveolate pattern, consisting of funnel-shaped and finely pitted cells. Each seed valve contains a reniform or horseshoe-shaped embryo cavity, a characteristic condyle structure and an internal raphe. These fossil seeds represent one of the few fossil records of Eurya in East Asia. This new finding therefore largely extends the distributional ranges of Eurya during Neogene. Fossil records summarized here show that Eurya persisted in Europe until the early Pleistocene, but disappeared thereafter. The genus might have first appeared in East Asia no later than the late Oligocene, and dispersed widely in regions such as Japan, Nepal, and southwestern China
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