3,934 research outputs found
Next-to-leading-order QCD corrections to
The associated production of Higgs boson with a hard photon at lepton
collider, i.e., , is known to bear a rather small cross
section in Standard Model, and can serve as a sensitive probe for the potential
new physics signals. Similar to the loop-induced Higgs decay channels , the process also starts at one-loop
order provided that the tiny electron mass is neglected. In this work, we
calculate the next-to-leading-order (NLO) QCD corrections to this associated
production process, which mainly stem from the gluonic dressing to
the top quark loop. The QCD corrections are found to be rather modest at lower
center-of-mass energy range ( GeV), thus of negligible impact on
Higgs factory such as CEPC. Nevertheless, when the energy is boosted to the ILC
energy range ( GeV), QCD corrections may enhance the
leading-order cross section by . In any event, the
process has a maximal production rate fb around
GeV, thus CEPC turns out to be the best place to look for this
rare Higgs production process. In the high energy limit, the effect of NLO QCD
corrections become completely negligible, which can be simply attributed to the
different asymptotic scaling behaviors of the LO and NLO cross sections, where
the former exhibits a milder decrement , but the latter undergoes
a much faster decrease .Comment: v4, 11 pages, 6 figures, 2 tables; errors in Appendix are fixed;
version accepted for publication at PL
Statistical Properties of Multiple Optical Emission Components in Gamma-Ray Bursts and Implications
Well-sampled optical lightcurves of 146 gamma-ray bursts (GRBs) are complied
from the literature. Multiple optical emission components are extracted with
power-law function fits to these lightcurves. We present a systematical
analysis for statistical properties and their relations to prompt gamma-ray
emission and X-ray afterglow for each component. We show that peak luminosity
in the prompt and late flares are correlated and the evolution of the peak
luminosity may signal the evolution of the accretion rate. No tight correlation
between the shallow decay phase/plateau and prompt gamma-ray emission is found.
Assuming that they are due to a long-lasting wind injected by a compact object,
we show that the injected behavior favors the scenarios of a long-lasting wind
after the main burst episode. The peak luminosity of the afterglow onset is
tightly correlated with Eiso, and it is dimmer as peaking later. Assuming that
the onset bump is due to the fireball deceleration by the external medium, we
examine the Gamma_0-Eiso relation and find that it is confirmed with the
current sample. Optical re-brightening is observed in 30 GRBs in our sample. It
shares the same relation between the width and the peak time as found in the
onset bump, but no clear correlation between the peak luminosity and Eiso as
observed in the onset bumps is found. Although its peak luminosity also decays
with time, the slope is much shallower than that of the onset peak. We get L
t^{-1}_{p}$, being consistent with off-axis observations to an expanding
external fireball in a wind-like circum medium. The late re-brightening may
signal another jet component. Mixing of different emission components may be
the reason for the observed chromatic breaks in different energy bands.Comment: 10 pages, 5 figures, to be published by IJMPD (Proceedings of "The
Third Galileo - Xu Guangqi meeting", Beijing, October 11-15, 2011
Half-titanocene 5-t-butyl-2-(1-(arylimino)methyl)quinolin-8-olate chlorides: Synthesis, characterization and ethylene (co-) polymerization behavior
A series of half-titanocene chloride complexes bearing 5-t-butyl-2-(1-(arylimino)methyl)quinolin-8-olate ligands (L), CpTiLCl₂, has been synthesized in acceptable yields by the stoichiometric reaction of CpTiCl₃ with the respective potassium 5-t-butyl-2-(1-(arylimino)methyl)quinolin-8-olate. All half-titanocene complexes were fully characterized by elemental analysis and NMR spectroscopy, and the molecular structures of the representative complexes C1 and C2 were confirmed as pseudo octahedral at titanium by single-crystal X-ray diffraction. When activated with methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all titanium complexes exhibited good activities (up to 4.8 × 10⁵ g mol⁻¹(Ti) h⁻¹) towards ethylene polymerization. The obtained polyethylene exhibited ultra-high molecular weight (up to 11.82 × 10⁵ g mol⁻¹) with narrow polydispersity. Furthermore, effective co-polymerization of ethylene with 1-hexene or 1-octene was achieved with several percentages of co-monomer incorporation in the resultant polyethylenes
LO-Net: Deep Real-time Lidar Odometry
We present a novel deep convolutional network pipeline, LO-Net, for real-time
lidar odometry estimation. Unlike most existing lidar odometry (LO) estimations
that go through individually designed feature selection, feature matching, and
pose estimation pipeline, LO-Net can be trained in an end-to-end manner. With a
new mask-weighted geometric constraint loss, LO-Net can effectively learn
feature representation for LO estimation, and can implicitly exploit the
sequential dependencies and dynamics in the data. We also design a scan-to-map
module, which uses the geometric and semantic information learned in LO-Net, to
improve the estimation accuracy. Experiments on benchmark datasets demonstrate
that LO-Net outperforms existing learning based approaches and has similar
accuracy with the state-of-the-art geometry-based approach, LOAM
Dimensionless ratios: characteristics of quantum liquids and their phase transitions
Dimensionless ratios of physical properties can characterize low-temperature
phases in a wide variety of materials. As such, the Wilson ratio (WR), the
Kadowaki-Woods ratio and the Wiedemann\--Franz law capture essential features
of Fermi liquids in metals, heavy fermions, etc. Here we prove that the phases
of many-body interacting multi-component quantum liquids in one dimension (1D)
can be described by WRs based on the compressibility, susceptibility and
specific heat associated with each component. These WRs arise due to additivity
rules within subsystems reminiscent of the rules for multi-resistor networks in
series and parallel --- a novel and useful characteristic of multi-component
Tomonaga-Luttinger liquids (TLL) independent of microscopic details of the
systems. Using experimentally realised multi-species cold atomic gases as
examples, we prove that the Wilson ratios uniquely identify phases of TLL,
while providing universal scaling relations at the boundaries between phases.
Their values within a phase are solely determined by the stiffnesses and sound
velocities of subsystems and identify the internal degrees of freedom of said
phase such as its spin-degeneracy. This finding can be directly applied to a
wide range of 1D many-body systems and reveals deep physical insights into
recent experimental measurements of the universal thermodynamics in ultracold
atoms and spins.Comment: 12 pages (main paper), (6 figures
Role of ERK/MAPK in endothelin receptor signaling in human aortic smooth muscle cells
<p>Abstract</p> <p>Background</p> <p>Endothelin-1 (ET-1) is a potent vasoactive peptide, which induces vasoconstriction and proliferation in vascular smooth muscle cells (VSMCs) through activation of endothelin type A (ET<sub>A</sub>) and type B (ET<sub>B</sub>) receptors. The extracellular signal-regulated kinase 1 and 2 (ERK1/2) mitogen-activated protein kinases (MAPK) are involved in ET-1-induced VSMC contraction and proliferation. This study was designed to investigate the ET<sub>A </sub>and ET<sub>B </sub>receptor intracellular signaling in human VSMCs and used phosphorylation (activation) of ERK1/2 as a functional signal molecule for endothelin receptor activity.</p> <p>Results</p> <p>Subconfluent human VSMCs were stimulated by ET-1 at different concentrations (1 nM-1 μM). The activation of ERK1/2 was examined by immunofluorescence, Western blot and phosphoELISA using specific antibody against phosphorylated ERK1/2 protein. ET-1 induced a concentration- and time- dependent activation of ERK1/2 with a maximal effect at 10 min. It declined to baseline level at 30 min. The ET-1-induced activation of ERK1/2 was completely abolished by MEK1/2 inhibitors U0126 and SL327, and partially inhibited by the MEK1 inhibitor PD98059. A dual endothelin receptor antagonist bosentan or the ET<sub>A </sub>antagonist BQ123 blocked the ET-1 effect, while the ET<sub>B </sub>antagonist BQ788 had no significant effect. However, a selective ET<sub>B </sub>receptor agonist, Sarafotoxin 6c (S6c) caused a time-dependent ERK1/2 activation with a maximal effect by less than 20% of the ET-1-induced activation of ERK1/2. Increase in bosentan concentration up to 10 μM further inhibited ET-1-induced activation of ERK1/2 and had a stronger inhibitory effect than BQ123 or the combined use of BQ123 and BQ788. To further explore ET-1 intracellular signaling, PKC inhibitors (staurosporin and GF109203X), PKC-delta inhibitor (rottlerin), PKA inhibitor (H-89), and phosphatidylinositol 3-kinase (PI3K) inhibitor (wortmannin) were applied. The inhibitors showed significant inhibitory effects on ET-1-induced activation of ERK1/2. However, blockage of L-type Ca<sup>2+ </sup>channels or calcium/calmodulin-dependent protein kinase II, chelating extracellular Ca<sup>2+ </sup>or emptying internal Ca<sup>2+ </sup>stores, did not affect ET-1-induced activation of ERK1/2.</p> <p>Conclusion</p> <p>The ET<sub>A </sub>receptors predominate in the ET-1-induced activation of ERK1/2 in human VSMCs, which associates with increments in intracellular PKC, PKA and PI3K activities, but not Ca<sup>2+ </sup>signalling.</p
Enhance Primordial Black Hole Abundance through the Non-linear Processes around Bounce Point
The non-singular bouncing cosmology is an alternative paradigm to inflation,
wherein the background energy density vanishes at the bounce point, in the
context of Einstein gravity. Therefore, the non-linear effects in the evolution
of density fluctuations () may be strong in the bounce phase,
which potentially provides a mechanism to enhance the abundance of primordial
black holes (PBHs). This article presents a comprehensive illustration for PBH
enhancement due to the bounce phase. To calculate the non-linear evolution of
, the Raychaudhuri equation is numerically solved here. Since the
non-linear processes may lead to a non-Gaussian probability distribution
function for after the bounce point, the PBH abundance is
calculated in a modified Press-Schechter formalism. In this case, the criterion
of PBH formation is complicated, due to complicated non-linear evolutionary
behavior of during the bounce phase. Our results indicate that
the bounce phase indeed has potential to enhance the PBH abundance
sufficiently. Furthermore, the PBH abundance is applied to constrain the
parameters of bounce phase, providing a complementary to the surveys of cosmic
microwave background and large scale structure.Comment: 17 pages, 6 figure
- …