451 research outputs found
Diverse origins for non-repeating fast radio bursts: Rotational radio transient sources and cosmological compact binary merger remnants
A large number of fast radio bursts (FRBs) detected with the CHIME telescope
have enabled investigations of their energy distributions in different redshift
intervals, incorporating the consideration of the selection effects of CHIME.
As a result, we obtained a non-evolving energy function (EF) for the
high-energy FRBs (HEFRBs) of energies erg, which takes
the form of a power law with a low-energy exponential cutoff. On the contrary,
the energy distribution of the low-energy FRBs (LEFRBs) obviously cannot be
described by the same EF. Including the lowest dispersion measure (DM) samples,
the LEFRBs are concentrated towards the Galactic plane and their latitude
distribution is similar to that of Galactic rotational radio transients
(RRATs). These indications hint that LEFRBs might compose a special type of
RRATs, with relatively higher DMs and energies (i.e., erg for
a reference distance of kpc if they belong to the Milky Way). Finally,
we revisit the redshift-dependent event rate of HEFRBs and confirm that they
could be produced by the remnants of cosmological compact binary mergers.Comment: 8 pages, 7 figures. Accepted for publication in Astronomy &
Astrophysics. Comments are welcom
Unconventional superfluidity of superconductivity on Penrose lattice
We theoretically investigate the gap function, superfluid density and the
transition temperature of the superconductivity (SC) on semi-periodic Penrose
lattice, where an attractive Hubbard model is adopted as an example. Firstly,
we clarify that the gap function, density of states and superfluid density are
all positively correlate to the extended degree of single particle states
around the Fermi energy. Secondly, we identify that the paramagnetic component
of the superfluid density does not decay to zero in the thermodynamic limit,
which is completely different from the periodic system. The difference between
the diamagnetic and paramagnetic currents keeps stable with whatever scaling,
which is consistent with recent experimental results that although the
superfluid density is lower than that of the periodic system, the system has
bulk SC. Thirdly, we find that both the superfluid density and SC transition
temperature can be boosted with the increase of disorder strength, which should
be general to quasicrystal but unusual to periodic systems, reflecting the
interplay between the underlying geometry and disorder.Comment: 7 pages, 4 figures. version accepted by Sci. China-Phys. Mech. &
Astro
The regeneration of plantlets from culture anthers picked from anther culture derived plants in grape in vitro
Assessment of thyroid function during pregnancy: the advantage of self-sequential longitudinal reference intervals
Revisiting the Relationship between Scale of Fluctuation and Mean Cross Distance
Estimating scale of fluctuation is an intriguing issue, for which several methods have been developed, such as simple estimators (e.g., 0.8d¯-estimator) based on the mean cross distance d¯ of a soil property profile, sample autocorrelation function method, maximum likelihood method, Bayesian method, etc. Among these methods, the 0.8d¯-estimator is the simplest one and can be readily used by geotechnical practitioners whose training in probability theory and statistics is usually limited. It, however, shall be noted that the 0.8d¯-estimator was derived from the normal random field with squared exponential correlation function, which is largely ignored in its practical applications. Effects of the distribution type (e.g., normal or lognormal) and correlation function on the performance of the 0.8d¯-estimator remain unexplored and, hence, unknown to geotechnical practitioners, which potentially leads to misuse of the simple relationship. This paper aims to highlight the theoretical assumptions underlying the 0.8d¯-estimator and to, systematically, explore the effects of these theoretical assumptions on its performance (i.e., unbiasedness and variability). It is found that the 0.8d¯-estimator provides reasonably unbiased estimation of scale of fluctuation for the normal random field with squared exponential correlation function when there are, at least, two sampling data within a distance of scale of fluctuation. Whereas, results from the 0.8d¯-estimator for other cases violating the assumptions are biased, and may lead to a significant underestimation of scale of fluctuation. It is also found that the variability of the 0.8d¯-estimator increases as the sampling length decreases.The work described in this paper was supported by grants from National Key R&D Program of China (Project No. 2017YFC1501300), and the National Natural Science Foundation of China (Project Nos. 51528901, 51679174, 51779189), and an open fund from State Key Laboratory Hydraulics and Mountain River Engineering, Sichuan University (Project No. SKHL1619). The financial support is gratefully acknowledged
Spectroscopic Evidence for Multigap Superconductivity of Y at Megabar Pressures
The recent discovery of room-temperature superconductivity (RTSC) at
pressures of several megabars has led to intensive efforts to probe the origin
of superconducting (SC) electron pairs. Although the signatures of the SC phase
transition have been well established, few reports of the SC properties of
RTSCs have been published because of the diamond anvil cell (DAC) environments.
Here, we report the first direct evidence of two SC gaps in Y metal via
point-contact spectroscopy (PCS) in DAC environments, where a sharp peak at the
zero-bias voltage in the differential conductance is overlaid with a broad peak
owing to Andreev reflection. Analysis based on the Blonder-Tinkham-Klapwijk
(BTK) model reveals the existence of two SC gaps: the larger gap is 3.63 meV
and the smaller gap is 0.46 meV. The temperature dependence of the two SC gaps
is well explained by the BCS theory, indicating that two-band superconductivity
is realized in Y metal. The successful application of PCS to Y in DAC
environments is expected to guide future research on the SC gap in megabar
high-Tc superconductors.Comment: 17 pages, 4 figure
Single nonmagnetic impurity resonance in FeSe-based 122-type superconductors as a probe for pairing symmetry
We study the effect of a single non-magnetic impurity in
AFeSe (A=K, Rb, or Cs) superconductors by considering
various pairing states based on a three-orbital model consistent with the
photoemission experiments. The local density of states on and near the impurity
site has been calculated by solving the Bogoliubov-de Gennes equations
self-consistently. The impurity-induced in-gap bound states are found only for
attractive impurity scattering potential, as in the cases of doping of Co or
Ni, which is characterized by the strong particle-hole asymmetry, in the
nodeless wave pairing state. This property may be used to probe
the pairing symmetry of FeSe-based 122-type superconductors.Comment: 7 pages, 7 figure
Haplotype-based genome-wide association studies for carcass and growth traits in chicken
There have been several genome-wide association study (GWAS) reported for carcass, growth, and meat traits in chickens. Most of these studies have been based on single SNPs GWAS. In contrast, haplotype-based GWAS reports have been limited. In the present study, 2 Northeast Agricultural University broiler lines divergently selected for abdominal fat content (NEAUHLF) and genotyped with the chicken 60K SNP chip were used to perform a haplotype-based GWAS. The lean and fat chicken lines were selected for abdominal fat content for 11 yr. Abdominal fat weight was significantly different between the 2 lines; however, there was no difference for body weight between the lean and fat lines. A total of 132 haplotype windows were significantly associated with abdominal fat weight. These significantly associated haplotype windows were primarily located on chromosomes 2, 4, 8, 10, and 26. Seven candidate genes, including SHH, LMBR1, FGF7, IL16, PLIN1, IGF1R, and SLC16A1, were located within these associated regions. These genes may play important roles in the control of abdominal fat content. Two regions on chromosomes 3 and 10 were significantly associated with testis weight. These 2 regions were previously detected by the single SNP GWAS using this same resource population. TCF21 on chromosome 3 was identified as a potentially important candidate gene for testis growth and development based on gene expression analysis and the reported function of this gene. TCF12, which was previously detected in our SNP by SNP interaction analysis, was located in a region on chromosome 10 that was significantly associated with testis weight. Six candidate genes, including TNFRSF1B, PLOD1, NPPC, MTHFR, EPHB2, and SLC35A3, on chromosome 21 may play important roles in bone development based on the known function of these genes. In addition, several regions were significantly associated with other carcass and growth traits, but no candidate genes were identified. The results of the present study may be helpful in understanding the genetic mechanisms of carcass and growth traits in chickens
- …