187 research outputs found
FAST observations of an extremely active episode of FRB 20201124A: IV. Spin Period Search
We report the properties of more than 800 bursts detected from the repeating
fast radio burst (FRB) source FRB 20201124A with the Five-hundred-meter
Aperture Spherical radio telescope (FAST) during an extremely active episode on
UTC September 25th-28th, 2021 in a series of four papers. In this fourth paper
of the series, we present a systematic search of the spin period and linear
acceleration of the source object from both 996 individual pulse peaks and the
dedispersed time series. No credible spin period was found from this data set.
We rule out the presence of significant periodicity in the range between 1 ms
to 100 s with a pulse duty cycle (when the profile is defined
by a von-Mises function, not a boxcar function) and linear acceleration up to
m s in each of the four one-hour observing sessions, and up to
m s in all 4 days. These searches contest theoretical scenarios
involving a 1 ms to 100 s isolated magnetar/pulsar with surface magnetic field
G and a small duty cycle (such as in a polar-cap emission mode) or a
pulsar with a companion star or black hole up to 100 M and
hours. We also perform a periodicity search of the fine structures and
identify 53 unrelated millisecond-timescale "periods" in multi-components with
the highest significance of 3.9 . The "periods" recovered from the fine
structures are neither consistent nor harmonically related. Thus they are not
likely to come from a spin period. We caution against claiming spin periodicity
with significance below 4 with multi-components from one-off
FRBs. We discuss the implications of our results and the possible connections
between FRB multi-components and pulsar micro-structures.Comment: Accepted by Research in Astronomy and Astrophysics (RAA
Scintillation Arc from FRB 20220912A
We present the interstellar scintillation analysis of fast radio burst (FRB)
20220912A during its extremely active episode in 2022 using data from the
Five-hundred-meter Aperture Spherical Radio Telescope (FAST). We detect a
scintillation arc in the FRB's secondary spectrum, which describes the power in
terms of the scattered FRB signals' time delay and Doppler shift. The arc
indicates that the scintillation is caused by a highly localized region of the
ionized interstellar medium (IISM). Our analysis favors a Milky Way origin for
the localized scattering medium but cannot rule out a host galaxy origin. We
present our method for detecting the scintillation arc, which can be applied
generally to sources with irregularly spaced bursts or pulses. These methods
could help shed light on the complex interstellar environment surrounding the
FRBs and in our Galaxy.Comment: SCIENCE CHINA Physics, Mechanics & Astronomy , Volume 67, Issue 1:
219512 (2024
Total cucurbitacins from Herpetospermum pedunculosum pericarp do better than Hu-lu-su-pian (HLSP) in its safety and hepatoprotective efficacy
The pericarp of Herpetospermum pedunculosum (HPP) has traditionally been used for treating jaundice and hepatitis. However, the specific hepatoprotective components and their safety/efficacy profiles remain unclear. This study aimed to characterize the total cucurbitacins (TCs) extracted from HPP and evaluate their hepatoprotective potential. As a reference, Hu-lu-su-pian (HLSP), a known hepatoprotective drug containing cucurbitacins, was used for comparison of chemical composition, effects, and safety. Molecular networking based on UHPLC-MS/MS identified cucurbitacin B, isocucurbitacin B, and cucurbitacin E as the major components in TCs, comprising 70.3%, 26.1%, and 3.6% as determined by RP-HPLC, respectively. TCs treatment significantly reversed CCl4-induced metabolic changes associated with liver damage in a dose-dependent manner, impacting pathways including energy metabolism, oxidative stress and phenylalanine metabolism, and showed superior efficacy to HLSP. Safety evaluation also showed that TCs were safe, with higher LD50 and no observable adverse effect level (NOAEL) values than HLSP. The median lethal dose (LD50) and NOAEL values of TCs were 36.21 and 15Ā mg/kg body weight (BW), respectively, while the LD50 of HLSP was 14Ā mg/kg BW. In summary, TCs extracted from HPP demonstrated promising potential as a natural hepatoprotective agent, warranting further investigation into synergistic effects of individual cucurbitacin components
Constraint-Based Modeling and Kinetic Analysis of the Smad Dependent TGF-Ī² Signaling Pathway
Background
Investigation of dynamics and regulation of the TGF-Ī² signaling pathway is central to the understanding of complex cellular processes such as growth, apoptosis, and differentiation. In this study, we aim at using systems biology approach to provide dynamic analysis on this pathway.
Methodology/Principal Findings
We proposed a constraint-based modeling method to build a comprehensive mathematical model for the Smad dependent TGF-Ī² signaling pathway by fitting the experimental data and incorporating the qualitative constraints from the experimental analysis. The performance of the model generated by constraint-based modeling method is significantly improved compared to the model obtained by only fitting the quantitative data. The model agrees well with the experimental analysis of TGF-Ī² pathway, such as the time course of nuclear phosphorylated Smad, the subcellular location of Smad and signal response of Smad phosphorylation to different doses of TGF-Ī².
Conclusions/Significance
The simulation results indicate that the signal response to TGF-Ī² is regulated by the balance between clathrin dependent endocytosis and non-clathrin mediated endocytosis. This model is useful to be built upon as new precise experimental data are emerging. The constraint-based modeling method can also be applied to quantitative modeling of other signaling pathways
FAST observations of an extremely active episode of FRB 20201124A: III. Polarimetry
As the third paper in the multiple-part series, we report the statistical
properties of radio bursts detected from the repeating fast radio burst (FRB)
source FRB 20201124A with the Five-hundred-meter Aperture Spherical radio
telescope (FAST) during an extremely active episode between the 25th and the
28th of September 2021 (UT). We focus on the polarisation properties of 536
bright bursts with . We found that the Faraday rotation
measures (RMs) monotonically dropped from to in the 4-day window. The RM values were compatible with
the values ( to ) reported 4 month ago (Xu et
al. 2022). However, the RM evolution rate in the current observation window was
at least an order of magnitude smaller than the one ($\sim 500\ {\rm rad \
m^{-2}\, day^{-1}}\le 1\ {\rm rad \ m^{-2} day^{-1}}L/IV/I\sigma$) were observed in 33% of
all bursts. The polarisation of single pulses seems to follow certain complex
trajectories on the Poincar\'e sphere, which may shed light on the radiation
mechanism at the source or the plasma properties along the path of FRB
propagation.Comment: 25 pages, 16 figures. Accepted by Research in Astronomy and
Astrophysics (RAA
Bogoliubov Quasiparticle on the Gossamer Fermi Surface in Electron-Doped Cuprates
In contrast to hole-doped cuprates, electron-doped cuprates consistently
exhibit strong antiferromagnetic correlations with a commensurate ({\pi},
{\pi}) ordering wave vector, leading to the prevalent belief that
antiferromagnetic spin fluctuations mediate Cooper pairing in these
unconventional superconductors. However, early investigations produced two
paradoxical findings: while antiferromagnetic spin fluctuations create the
largest pseudogap at "hot spots" in momentum space, Raman scattering and
angle-resolved photoemission spectroscopy measurements using the leading-edge
method seem to suggest the superconducting gap is also maximized at these
locations. This presented a dilemma for spin-fluctuation-mediated pairing:
Cooper pairing is strongest at momenta where normal state low energy spectral
weight is most suppressed. Here we investigate this dilemma in Nd2-xCexCuO4
using angle-resolved photoemission spectroscopy under significantly improved
experimental conditions. The unprecedented signal-to-noise ratio and resolution
allow us to directly observe the Bogoliubov quasiparticles, demonstrating the
existence and importance of two sectors of states: 1. The reconstructed main
band and the states gapped by the antiferromagnetic pseudogap around the hot
spots. 2. The gossamer Fermi surface states with distinct dispersion inside the
pseudogap, from which Bogoliubov quasiparticle coherence peaks emerge below Tc.
Supported by numerical results, we propose that the non-zero modulus of the
antiferromagnetic order parameter causes the former, while fluctuations in the
antiferromagnetic order parameter orientation are responsible for the latter.
Our revelations of the gossamer Fermi surface reconcile the paradoxical
observations, deepening our understanding of superconductivity in
electron-doped cuprates in particular, and unconventional superconductivity in
general.Comment: Submitted version 30 pages, 4 main figures, 8 extended data figures.
Accepted version in press at Nature Physic
The Litsea genome and the evolution of the laurel family
The laurel family within the Magnoliids has attracted attentions owing to its scents, variable inflorescences, and controversial phylogenetic position. Here, we present a chromosome-level assembly of the Litsea cubeba genome, together with low-coverage genomic and transcriptomic data for many other Lauraceae. Phylogenomic analyses show phylogenetic discordance at the position of Magnoliids, suggesting incomplete lineage sorting during the divergence of monocots, eudicots, and Magnoliids. An ancient whole-genome duplication (WGD) event occurred just before the divergence of Laurales and Magnoliales; subsequently, independent WGDs occurred almost simultaneously in the three Lauralean lineages. The phylogenetic relationships within Lauraceae correspond to the divergence of inflorescences, as evidenced by the phylogeny of FUWA, a conserved gene involved in determining panicle architecture in Lauraceae. Monoterpene synthases responsible for production of specific volatile compounds in Lauraceae are functionally verified. Our work sheds light on the evolution of the Lauraceae, the genetic basis for floral evolution and specific scents
Analysis on the pathogenic genes of 60 Chinese children with congenital hyperinsulinemia
This study aims to summarize and analyze the clinical manifestations, genetic characteristics, treatment modalities and long-term prognosis of congenital hyperinsulinemia (CHI) in Chinese children. Sixty children with CHI, who were treated at Beijing Childrenās Hospital from January 2014 to August 2017, and their families, were selected as subjects. The CHI-related causative genes in children were sequenced and analyzed using second-generation sequencing technology. Furthermore, the genetic pathogenesis and clinical characteristics of Chinese children with CHI were explored. Among the 60 CHI children, 27 children (27/60, 45%) carried known CHI-related gene mutations: 16 children (26.7%) carried ABCC8 gene mutations, seven children (11.7%) carried GLUD1 gene mutations, one child carried GCK gene mutations, two children carried HNF4Ī± gene mutations and one child carried HADH gene mutations. In these 60 patients, eight patients underwent 18F-L-DOPA PET scan for the pancreas, and five children were found to be focal type. The treatment of diazoxide was ineffective in these five patients, and hypoglycemia could be controlled after receiving partial pancreatectomy. In conclusion, ABCC8 gene mutation is the most common cause of CHI in Chinese children. The early genetic analysis of childrenās families has an important guiding significance for treatment planning and prognosis assessment
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