1,460 research outputs found
KSS unit root test of nonlinearity and nonstationarity in China’s agricultural futures markets
AbstractUnit root tests are the starting points of most economic time series analyses. Based on the nonlinear unit root test proposed by Kapetanios, Shin and Shell (KSS), this article propose a procedure to detect the presence of nonstationarity against nonlinear processes in 5 representative China’s agricultural futures markets. Our results illustrate that a unit root is rejected in favor of nonlinear trend stationary for these markets; therefore, the results in current literature based on the linear hypothesis may be spurious in understanding true market’s dynamics. We contribute to current literature in providing for the first time the empirical evidence of these facts in China’s agricultural futures markets, which is fundamentally important in relevant researches
A closer look at interacting dark energy with statefinder hierarchy and growth rate of structure
We investigate the interacting dark energy models by using the diagnostics of
statefinder hierarchy and growth rate of structure. We wish to explore the
deviations from CDM and to differentiate possible degeneracies in the
interacting dark energy models with the geometrical and structure growth
diagnostics. We consider two interacting forms for the models, i.e., and , with being the dimensionless
coupling parameter. Our focus is the ICDM model that is a
one-parameter extension to CDM by considering a direct coupling
between the vacuum energy () and cold dark matter (CDM), with the only
additional parameter . But we begin with a more general case by
considering the ICDM model in which dark energy has a constant
(equation-of-state parameter). For calculating the growth rate of structure, we
employ the "parametrized post-Friedmann" theoretical framework for interacting
dark energy to numerically obtain the values for the models. We
show that in both geometrical and structural diagnostics the impact of is
much stronger than that of in the ICDM model. We thus wish to have a
closer look at the ICDM model by combining the geometrical and
structural diagnostics. We find that the evolutionary trajectories in the
-- plane exhibit distinctive features and the departures
from CDM could be well evaluated, theoretically, indicating that the
composite null diagnostic is a promising tool for
investigating the interacting dark energy models.Comment: 17 pages, 4 figures; accepted for publication in JCA
Nature of the in partial wave decomposition of scattering
In this letter, we perform partial wave decomposition on coupled channel
scattering amplitudes, --,
to study the resonance appears in these processes. Effective Lagrangians are
used to describe the interactions of four charmed vector mesons, and the
scattering amplitudes are calculated up to the next-to-leading order. Partial
wave projections are performed, and unitarization is implemented by Pad\'e
approximation. Then we fit the amplitudes to the invariant mass
spectra measured by LHCb and determine the unknown couplings. The pole
parameters of the are extracted as ~MeV and
~MeV. Our analysis implies that its quantum number
prefers to be . The pole counting rule and phase shifts show that it is
a normal Breit-Wigner resonance and hence should be a compact tetraquark.Comment: 6 pages, 4 figure
Possible Role of PHD Inhibitors as Hypoxia-Mimicking Agents in the Maintenance of Neural Stem Cells’ Self-Renewal Properties
Hypoxia is the most critical factor for maintaining stemness. During embryonic development, neural stem cells (NSCs) reside in hypoxic niches, and different levels of oxygen pressure and time of hypoxia exposure play important roles in the development of NSCs. Such hypoxic niches exist in adult brain tissue, where the neural precursors originate. Hypoxia-inducible factors (HIFs) are key transcription heterodimers consisting of regulatory α-subunits (HIF-1α, HIF-2α, HIF-3α) and a constitutive β-subunit (HIF-β). Regulation of downstream targets determines the fate of NSCs. In turn, the stability of HIFs-α is regulated by prolyl hydroxylases (PHDs), whose activity is principally modulated by PHD substrates like oxygen (O2), α-ketoglutarate (α-KG), and the co-factors ascorbate (ASC) and ferrous iron (Fe2+). It follows that the transcriptional activity of HIFs is actually determined by the contents of O2, α-KG, ASC, and Fe2+. In normoxia, HIFs-α are rapidly degraded via the ubiquitin-proteasome pathway, in which PHDs, activated by O2, lead to hydroxylation of HIFs-α at residues 402 and 564, followed by recognition by the tumor suppressor protein von Hippel–Lindau (pVHL) as an E3 ligase and ubiquitin labeling. Conversely, in hypoxia, the activity of PHDs is inhibited by low O2 levels and HIFs-α can thus be stabilized. Hence, suppression of PHD activity in normoxic conditions, mimicking the effect of hypoxia, might be beneficial for preserving the stemness of NSCs, and it is clinically relevant as a therapeutic approach for enhancing the number of NSCs in vitro and for cerebral ischemia injury in vivo. This study will review the putative role of PHD inhibitors on the self-renewal of NSCs
New insights into the oscillation of the nucleon electromagnetic form factors
The electromagnetic form factors of the proton and the neutron in the
timelike region are investigated. The electron-positron annihilation into
antinucleon-nucleon () pairs is treated in distorted wave Born
approximation, including the final-state interaction in the system.
The latter is obtained by a Lippmann-Schwinger equation for
potentials derived within SU(3) chiral effective field theory. By fitting to
the phase shifts and (differential) cross section data, a high quality
description is achieved. With these amplitudes, the oscillations of the
electromagnetic form factors of the proton and the neutron are studied. It is
found that each of them can be described by two fractional oscillators. One is
characterized as \lq overdamped' and dominates near the threshold, while the
other is \lq underdamped' and plays an important role in the high-energy
region. These two oscillators are essential to understand the distributions of
polarized electric charges induced by hard photons for the nucleons.Comment: 5 pages, 3 figures, add some discussion
Geometry and optics calibration of WFCTA prototype telescopes using star light
The Large High Altitude Air Shower Observatory project is proposed to study
high energy gamma ray astronomy ( 40 GeV-1 PeV ) and cosmic ray physics ( 20
TeV-1 EeV ). The wide field of view Cherenkov telescope array, as a component
of the LHAASO project, will be used to study energy spectrum and compositions
of cosmic ray by measuring the total Cherenkov light generated by air showers
and shower maximum depth. Two prototype telescopes have been in operation since
2008. The pointing accuracy of each telescope is crucial to the direction
reconstruction of the primary particles. On the other hand the primary energy
reconstruction relies on the shape of the Cherenkov image on the camera and the
unrecorded photons due to the imperfect connections between photomultiplier
tubes. UV bright stars are used as point-like objects to calibrate the pointing
and to study the optical properties of the camera, the spot size and the
fractions of unrecorded photons in the insensitive areas of the camera.Comment: 5 pages, 6 figures, submitted to Chinese Physics
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