1,363 research outputs found
The puzzle of anomalously large isospin violations in
The BES-III Collaboration recently report the observation of anomalously
large isospin violations in , where the in the invariant mass
spectrum appears to be much narrower ( 10 MeV) than the peak width
(50 MeV) measured in other processes. We show that a mechanism, named as
triangle singularity (TS), can produce a narrow enhancement between the charged
and neutral thresholds, i.e., . It can also
lead to different invariant mass spectra for
and , which can possibly explain the long-standing puzzle
about the need for two close states and in
and , respectively. The TS could be a key to our
understanding of the nature of and advance our knowledge
about the mixing between and .Comment: 4 pages and 7 eps figures; Journal-matched versio
Revised Constraints on the fast radio burst population from the first CHIME/FRB catalog
In this paper, we investigate the FRB population using the first CHIME/FRB
catalog. We first reconstruct the extragalactic dispersion measure -- redshift
relation ( relation) from well-localized FRBs, then use it
to infer redshift and isotropic energy of the first CHIME/FRB catalog. The
intrinsic energy distribution is modeled by the power law with an exponential
cutoff, and the selection effect of the CHIME telescope is modeled by a
two-parametric function of specific fluence. For the intrinsic redshift
distribution, the star formation history (SFH) model, as well as other five
SFH-related models are considered. We construct the joint likelihood of
fluence, energy and redshift, and all the free parameters are constrained
simultaneously using Bayesian inference method. The Bayesian information
criterion (BIC) is used to choose the model that best matches the observational
data. For comparison, we fit our models with two data samples, i.e. the Full
sample and the Gold sample. The power-law index and cutoff energy are tightly
constrained to be and , which are almost independent of the redshift distribution
model and the data sample we choose. The parameters involving the selection
effect strongly depends on the data sample, but are insensitive to the redshift
distribution model. According to BIC, the pure SFH model is strongly disfavored
by both the Full sample and Gold sample. For the rest five SFH-related redshift
distribution models, most of them can match the data well if the parameters are
properly chosen. Therefore, with the present data, it is still premature to
draw a conclusive conclusion on the FRB population.Comment: 13 pages, 16 figure
PEDF in Diabetic Retinopathy: A Protective Effect of Oxidative Stress
Diabetic retinopathy (DR) is a major cause of blindness in working age adults, and oxidative stress plays a vital role in the pathogenesis of DR. Pigment-epithelium-derived factor (PEDF), a multifunctional protein, has shown to inhibit the development of DR by accumulating evidence. This paper highlights the current understanding of probable mechanism about how PEDF blocks the deterioration of DR through its antioxidative properties and application prospects of PEDF as a novel therapeutic target in DR. Gene therapy of PEDF is becoming more and more acceptable and will widely be applied to the actual treatment in the near future
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
Orbital density wave induced by electron-lattice coupling in orthorhombic iron pnictides
In this paper we explore the magnetic and orbital properties closely related
to a tetragonal-orthorhombic structural phase transition in iron pnictides
based on both two- and five-orbital Hubbard models. The electron-lattice
coupling, which interplays with electronic interaction, is self-consistently
treated. Our results reveal that the orbital polarization stabilizes the spin
density wave (SDW) order in both tetragonal and orthorhombic phases. However,
the ferro-orbital density wave (F-ODW) only occurs in the orthorhombic phase
rather than in the tetragonal one. Magnetic moments of Fe are small in the
intermediate Coulomb interaction region for the striped antiferromangnetic
phase in the realistic five orbital model. The anisotropic Fermi surface in the
SDW/ODW orthorhombic phase is well in agreement with the recent angle-resolved
photoemission spectroscopy experiments. These results suggest a scenario that
the magnetic phase transition is driven by the ODW order mainly arising from
the electron-lattice coupling.Comment: 21 pages, 10 figure
Revised constraints on the photon mass from well-localized fast radio bursts
We constrain the photon mass from well-localized fast radio bursts (FRBs)
using Bayes inference method. The probability distributions of dispersion
measures (DM) of host galaxy and intergalactic medium are properly taken into
account. The photon mass is tightly constrained from 17 well-localized FRBs in
the redshift range . Assuming that there is no redshift evolution of
host DM, the and upper limits of photon mass are
constrained to be kg and kg, respectively. Monte Carlo simulations show that, even enlarging
the FRB sample to 200 and extending the redshift range to couldn't
significantly improve the constraining ability on photon mass. This is because
of the large uncertainty on the DM of intergalactic medium.Comment: 9 pages, 4 figure
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