6,238 research outputs found
Possible evidence that pulsars are quark stars
It is a pity that the real state of matter in pulsar-like stars is still not
determined confidently because of the uncertainty about cold matter at
supranuclear density, even 40 years after the discovery of pulsar. Nuclear
matter (related to neutron stars) is one of the speculations for the inner
constitution of pulsars even from the Landau's time more than 70 years ago, but
quark matter (related to quark stars) is an alternative due to the fact of
asymptotic freedom of interaction between quarks as the standard model of
particle physics develops since 1960s. Therefore, one has to focus on
astrophysical observations in order to answer what the nature of pulsars is. In
this presentation, I would like to summarize possible observational
evidence/hints that pulsar-like stars could be quark stars, and to address
achievable clear evidence for quark stars in the future experiments.Comment: 6 pages, 2 figures; a talk at the international conference
"Astrophysics of Compact Objects" (July 1-7, 2007; Huangshan, China);
http://vega.bac.pku.edu.cn/rxxu/publications/index_C.htm. A mistake in Fig.1
is corrected; Correction of typo
Control efficacy of complex networks
Acknowledgements W.-X.W. was supported by CNNSF under Grant No. 61573064, and No. 61074116 the Fundamental Research Funds for the Central Universities and Beijing Nova Programme, China. Y.-C.L. was supported by ARO under Grant W911NF-14-1-0504.Peer reviewedPublisher PD
Image Clustering with Contrastive Learning and Multi-scale Graph Convolutional Networks
Deep clustering has recently attracted significant attention. Despite the
remarkable progress, most of the previous deep clustering works still suffer
from two limitations. First, many of them focus on some distribution-based
clustering loss, lacking the ability to exploit sample-wise (or
augmentation-wise) relationships via contrastive learning. Second, they often
neglect the indirect sample-wise structure information, overlooking the rich
possibilities of multi-scale neighborhood structure learning. In view of this,
this paper presents a new deep clustering approach termed Image clustering with
contrastive learning and multi-scale Graph Convolutional Networks (IcicleGCN),
which bridges the gap between convolutional neural network (CNN) and graph
convolutional network (GCN) as well as the gap between contrastive learning and
multi-scale neighborhood structure learning for the image clustering task. The
proposed IcicleGCN framework consists of four main modules, namely, the
CNN-based backbone, the Instance Similarity Module (ISM), the Joint Cluster
Structure Learning and Instance reconstruction Module (JC-SLIM), and the
Multi-scale GCN module (M-GCN). Specifically, with two random augmentations
performed on each image, the backbone network with two weight-sharing views is
utilized to learn the representations for the augmented samples, which are then
fed to ISM and JC-SLIM for instance-level and cluster-level contrastive
learning, respectively. Further, to enforce multi-scale neighborhood structure
learning, two streams of GCNs and an auto-encoder are simultaneously trained
via (i) the layer-wise interaction with representation fusion and (ii) the
joint self-adaptive learning that ensures their last-layer output distributions
to be consistent. Experiments on multiple image datasets demonstrate the
superior clustering performance of IcicleGCN over the state-of-the-art
Wide binary stars formed in the turbulent interstellar medium
The ubiquitous interstellar turbulence regulates star formation and the
scaling relations between the initial velocity differences and the initial
separations of stars. We propose that the formation of wide binaries with
initial separations in the range AU is a natural consequence of star formation in the turbulent
interstellar medium. With the decrease of , the mean turbulent relative
velocity between a pair of stars decreases, while the largest
velocity at which they still may be gravitationally bound
increases. When , a wide binary can form. In this
formation scenario, we derive the eccentricity distribution of wide
binaries for an arbitrary relative velocity distribution. By adopting a
turbulent velocity distribution, we find that wide binaries at a given initial
separation generally exhibit a superthermal . This provides a natural
explanation for the observed superthermal of the wide binaries in the
Solar neighborhood.Comment: 7 pages, 4 figures, submitted to ApJ
Protective Effect of Anthocyanins Extract from Blueberry on TNBS-Induced IBD Model of Mice
This study was carried out to evaluate the protective effect of anthocyanins extract of blueberry on trinitrobenzene sulfonic acid (TNBS)-induced inflammatory bowel disease (IBD) model of mice. The study employed female C57BL/6 mice (n = 50), and colitis was induced by intracolonic injection of 0.5âmg of TNBS dissolved in 50% ethanolâphosphate buffered solution. The mice were divided into five groups (n = 10): vehicle, TNBS control and anthocyanins groups that received different doses of anthocyanins extract (10, 20 and 40âmgâkgâ1) daily for 6 days. Both increase in body weight and diarrhea symptoms were monitored each day. After 6 days, the animals were killed, and the following parameters were assessed: colon length, morphological score, histological score and biochemical assay (NO, myeloperoxidase (MPO), interleukin (IL)-12, IL-10, tumor necrosis factor (TNF)-α and interferon (IFN)-Îł). The results showed that the anthocyanins extract of blueberry rendered strong protection against TNBS-induced colonic damage at a dosage of 40âmgâkgâ1. When compared with the control, anthocyanins extract significantly prevented loss of body weight and ameliorated the scores of diarrhea, morphology and histology. Treatment with anthocyanins extract restored IL-10 excretion, as well as caused reduction in the levels of NO, MPO, IL-12, TNF-α and IFN-Îł. Our research revealed the protective effect of anthocyanins extract from blueberry on TNBS-induced experimental colitis in mice, as well as examined whether high levels of dietary blueberries would lower the risk or have protective effects on human IBD, which may require further investigation
Effect of beraprost sodium on renal function and p38MAPK signaling pathway in rats with diabetic nephropathy
Purpose: To investigate the effect of beraprost sodium (BPS) on renal function and P38MAPK pathway in diabetic nephropathy (DN) rats.Methods: Sprague Dawley (SD) rats (n = 30) were randomly divided into three groups, viz, normal control (NC), diabetic nephropathy (DN) and beraprost sodium (BPS). Creatinine (Cr), blood urea nitrogen (BUN) and fasting blood glucose (FBG), were determined by Hitachi 7020 automatic biochemical analyzer, while low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG) and total cholesterol (TC) were measured by Olympus 400 automatic biochemical analyzer. Western blot analysis was performed to examine protein expression. Interleukin-6 (IL-6), hs-CRP, and TNF-α levels were evaluated using enzyme linked immunosorbent assay (ELISA).Results: After 8 weeks of treatment, renal function indices (urine output, KW/BW, UAlb/24 h, Cr and BUN), blood lipid indices (FBG, LDL-C, TG and TC) and inflammatory factors levels (IL-6, hs-CRP and TNF-α) in DN group were higher than NC group (p < 0.05). In BPS group, renal function and blood lipid indices and inflammatory factor levels decreased when compared to DN group (p < 0.05). Furthermore, BPS inhibited the protein expression of p-P38MAPK, TGF-ÎČ1 and COX-2.Conclusion: Beraprost sodium improves renal function in DN rats by inhibiting P38MAPK signalingpathway
Kinetically Controlled Synthesis of Cefaclor with Immobilized Penicillin Acylase in the Presence of Organic Cosolvents
Enzymatic syntheses of cefaclor with immobilized penicillin acylase in organic cosolvents under kinetic control were carried out. KcPGA from Kluyvera citrophila was selected as the best catalyst among the three species of immobilized penicillin acylase. Ethylene glycol, glycerol, methanol, ethyl estate and polyethyleneglycol (PEG) were selected accordingly and cefaclor syntheses were preformed respectively. Best results in terms of yield were obtained in ethylene glycol, with which further studies were investigated and the maximum yield was Y = 93.5 %. The optimal conditions were pH 6.5, temperature Ξ = 5 °C, 3 mol D-phenylglycine methyl ester (PGME) per mol 7-aminodesacetoxymehtyl-3-chlorocephalosporin acid (7ACCA) and x = 30 % ethylene glycol fraction. Under above mentioned conditions, the yield was Y = 91.1 %
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