549 research outputs found
Power-law distribution and scale-invariant structure from the first CHIME/FRB Fast Radio Burst catalog
We study the statistical property of fast radio bursts (FRBs) based on a
selected sample of 190 one-off FRBs in the first CHIME/FRB catalog. Three power
law models are used in the analysis, and we find the cumulative distribution
functions of energy can be well fitted by bent power law and thresholded power
law models. And the distribution functions of fluctuations of energy well
follow the Tsallis -Gaussian distribution. The values in the Tsallis
-Gaussian distribution are constant with small fluctuations for different
temporal scale intervals, indicating a scale-invariant structure of the bursts.
The earthquakes and soft gamma repeaters show similar properties, which are
consistent with the predictions of self-organized criticality systems.Comment: 7 pages, 3 figures, 2 tables; accepted for publication in Research in
Astronomy and Astrophysic
Extended dissipaton equation of motion for electronic open quantum systems: Application to the Kondo impurity model
In this paper, we present an extended dissipaton equation of motion for
studying the dynamics of electronic impurity systems. Compared with the
original theoretical formalism, the quadratic couplings are introduced into the
Hamiltonian accounting for the interaction between the impurity and its
surrounding environment. By exploiting the quadratic dissipaton algebra, the
proposed extended dissipaton equation of motion offers a powerful tool for
studying the dynamical behaviors of electronic impurity systems, particularly
in situations where nonequilibrium and strongly correlated effects play
significant roles. Numerical demonstrations are carried out to investigate the
temperature dependence of the Kondo resonance in the Kondo impurity model.Comment: 6 pages, 1 figur
1,5-Dimethyl-4-[(E)-3-phenoxyÂbenzylÂideneamino]-2-phenyl-1H-pyrazol-3(2H)-one
The title Schiff base, C24H21N3O2, adopts an E configuration with respect to the central C=N bond. The pyrazole ring and the central benzene ring attached to the imino group are almost coplanar. The phenyl ring attached to the pyrazole unit is twisted by 39.3 (2)° with respect to the pyrazole ring plane. The phenÂoxy benzene ring makes a dihedral angle of 79.8 (2)° with the central benzene ring
Mechanical performance of 22SiMn2TiB steel welded with low-transformation-temperature filler wire and stainless steel filler wire
TX-80 low-transformation-temperature (LTT) welding wire was used to replace the traditional ER 307Si welding wire to realize the connection of 22SiMn2TiB armor steel in manual overlay welding. The previously existing issues, such as welding cracks, large welding deformation, and severe welding residual stress, were solved to ensure good strength and ductility requirements. In particular, with the same welding conditions, TX-80 LTT wire eliminates welding cracks. It reduces the welding deformation no matter the base pretreatment of pre-setting angle or no pre-setting angle. By comparison, it was found that the microstructure at the TX-80 weld is mainly composed of martensite and a small amount of retained austenite. In contrast, the microstructure of the ER 307Si weld consists of a large amount of austenite and a small amount of skeleton-like ferrite. The variation trend of residual stress and microhardness from the weld to the base were investigated and compared with the mechanical properties of base materials. The TX-80 and the ER 307Si tensile samples elongation is 6.76% and 6.01%, while the ultimate tensile strengths are 877 and 667Â MPa, respectively. The average impact toughness at room temperature of the ER 307Si weld is 143.9Â J/cm2, much higher than that of the TX-80 weld, which is only 36.7Â J/cm2. The relationship between impact and tensile properties with microstructure species and distribution was established. In addition, the fracture surface of the tensile and the impact samples was observed and analyzed. Deeper dimples, fewer pores, larger radiation zone, and shear lips of TX-80 samples indicate better tensile ductility and worse impact toughness than those of ER 307Si weld.</p
The small heat shock protein (sHSP) genes in the silkworm, Bombyx mori, and comparative analysis with other insect sHSP genes
<p>Abstract</p> <p>Background</p> <p>Small heat shock proteins (sHSPs) are products of heat shock response and of other stress responses, and ubiquitous in all three domains of life, archaea, bacteria, and eukarya. They mainly function as molecular chaperones to protect proteins from being denatured in extreme conditions. Study on insect sHSPs could provide some insights into evolution of insects that have adapted to diverse niches in the world.</p> <p>Results</p> <p>Taking advantage of the newly assembled genome sequence, we performed a genome-wide analysis of the candidate sHSP genes in the silkworm, <it>Bombyx mori</it>. Based on known silkworm sHSP sequences, we identified 16 silkworm sHSP genes. Most of them are distributed on two silkworm chromosomes 5 and 27, respectively. 15 of 16 silkworm sHSPs have expression evidence. The comparative analysis of insect sHSPs from <it>B. mori</it>, <it>Drosophila melanogaster</it>, <it>Apis mellifera</it>, <it>Tribolium castaneum</it>, and <it>Anopheles gambiae </it>revealed that there is only one orthologous cluster whereas remaining clusters are species-specific on the phylogenetic tree. This suggested that most of sHSPs might have diverged in function across insects investigated. In addition, the data presented in this study also revealed that sHSPs in the insect orthologous cluster are highly conserved in both sequence and expression pattern. In sum, insect sHSPs show a completely different evolutionary pattern from that found in vertebrate sHSPs.</p> <p>Conclusion</p> <p><it>B. mori </it>has the largest number of insect sHSP genes characterized to date, including 16 genes. The inference that most species-specific sHSPs might have diverged in function across insects investigated will help us understand the adaptability of these insects to diverse environments.</p
Extended system-bath entanglement theorem for multiple bosonic or fermionic environments
The system-bath entanglement theorem (SBET) was established in terms of
linear response functions [J. Chem. Phys. 152, 034102 (2020)] and generalized
to correlation functions [arXiv: 2312.13618 (2023)] in our previous works. This
theorem connects the entangled system-bath properties to the local system and
bare bath ones. In this work, firstly we extend the SBET to field-dressed
conditions with multiple bosonic Gaussian environments at different
temperatures. Not only the system but also environments are considered to be of
optical polarizability, as in reality. With the aid of the extended SBET
developed here, for the evaluation of the nonlinear spectroscopy such as the
pump-probe, the entangled system-bath contributions can be obtained upon
reduced system evolutions via certain quantum dissipative methods. The extended
SBET in the field-free condition and its counterpart in the classical limit is
also presented. The SBET for fermionic environments is elaborated within the
transport scenarios for completeness.Comment: 10 page
Robust Counterfactual Explanations on Graph Neural Networks
Massive deployment of Graph Neural Networks (GNNs) in high-stake applications
generates a strong demand for explanations that are robust to noise and align
well with human intuition. Most existing methods generate explanations by
identifying a subgraph of an input graph that has a strong correlation with the
prediction. These explanations are not robust to noise because independently
optimizing the correlation for a single input can easily overfit noise.
Moreover, they do not align well with human intuition because removing an
identified subgraph from an input graph does not necessarily change the
prediction result. In this paper, we propose a novel method to generate robust
counterfactual explanations on GNNs by explicitly modelling the common decision
logic of GNNs on similar input graphs. Our explanations are naturally robust to
noise because they are produced from the common decision boundaries of a GNN
that govern the predictions of many similar input graphs. The explanations also
align well with human intuition because removing the set of edges identified by
an explanation from the input graph changes the prediction significantly.
Exhaustive experiments on many public datasets demonstrate the superior
performance of our method
Elevated plasma pyruvate kinase M2 concentrations are associated with the clinical severity and prognosis of coronary artery disease
Graphical abstract
Highlights
Pyruvate kinase M2 is a predictor of clinical severity of coronary artery disease
Pyruvate kinase M2 predicts the incidence of major adverse cardiovascular events
Pyruvate kinase M2 showed additional prognostic value in coronary artery disease
IntroductionPyruvate kinase M2 (PKM2) was involved in the pathophysiology of atherosclerosis and coronary artery disease (CAD). We tested whether plasma PKM2 concentrations were correlated with clinical severity and major adverse cardiovascular events (MACEs) in CAD patients.
Materials and methodsA total of 2443 CAD patients and 238 controls were enrolled. The follow-up time was two years. Plasma PKM2 concentrations were detected by enzyme-linked immunosorbent assay (ELISA) kits (Cloud-Clone, Wuhan, China) using SpectraMax i3x Multi-Mode Microplate Reader (Molecular Devices, San Jose, USA). The predictors of acute coronary syndrome (ACS) were assessed by logistic regression analysis. The association between PKM2 concentration in different quartiles and MACEs was evaluated by Kaplan-Meier (KM) curves with log-rank test and Cox proportional hazard models. The predictive value of PKM2 and a cluster of conventional risk factors was determined by Receiver operating characteristic (ROC) curves. The net reclassification improvement (NRI) and the integrated discrimination improvement (IDI) were utilized to evaluate the enhancement in risk prediction when PKM2 was added to a predictive model containing a cluster of conventional risk factors.
ResultsIn CAD patients, PKM2 concentration was the independent predictor of ACS (P < 0.001). Kaplan-Meier cumulative survival curves and Cox proportional hazards analyses revealed that patients with a higher PKM2 concentration had higher incidence of MACEs compared to those with a lower PKM2 concentration (P < 0.001). The addition of PKM2 to a cluster of conventional risk factors significantly increased its prognostic value of MACEs.
ConclusionBaseline plasma PKM2 concentrations predict the clinical severity and prognosis of CAD
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