Dark Energy: a Brief Review

The problem of dark energy is briefly reviewed in both theoretical and observational aspects. In the theoretical aspect, dark energy scenarios are classified into symmetry, anthropic principle, tuning mechanism, modified gravity, quantum cosmology, holographic principle, back-reaction and phenomenological types. In the observational aspect, we introduce cosmic probes, dark energy related projects, observational constraints on theoretical models and model independent reconstructions.Comment: 19 pages, invited review article to appear in the special issue of "Frontiers of Physics" dedicated to "High energy astrophysics", an shortened version of our previous article arXiv:1103.587

Discriminating 1D new physics solutions in b→sℓℓb\to s\ell\ell decays

The recent measurements of $R_{K^+}$, $R_{K_S^0}$, $R_{K^{*+}}$, $B_s\to\mu^+\mu^-$, a set of CP-averaged angular observables for the $B^0\to K^{*0}\mu^+\mu^-$ decay, and its isospin partner $B^+\to K^{*+}\mu^+\mu^-$ by the LHCb Collaboration, consistently hint at lepton universality violation in the $b\to s\ell\ell$ transitions. In this work, we first perform global fits to the $b\to s\ell\ell$ data and show that five one-dimensional scenarios, i.e, $\delta C_9^{\mu}$, $\delta C_{10}^{\mu}$, $\delta C_L^{\mu}$, $\delta C_9^{\mu}=C_{10}^{\mu\prime}$, and $\delta C_9^{\mu}=-C_9^{\mu\prime}$ can best explain the so-called B anamolies. Furthermore, we explore how these scenarios can be distinguished from each other. For this purpose, we first study the combinations of four angular asymmetries $A_i$~$(i=3,4,5,9)$ and find that they cannot distinguish the five new physics scenarios. We then show that a newly constructed ratio $R_{S}$ can uniquely discriminate the five new physics scenarios in proper intervals of $q^2$ if it can be measured with a percent level precision.Comment: 16 pages, 6 figures; latest $R_{K_S^0}$, $R_{K^{*+}}$ data include

Evidence for self-organized criticality phenomena in prompt phase of short gamma-ray bursts

The prompt phase of gamma-ray burst (GRB) contains essential information regarding the physical nature and central engine, which are as yet unknown. In this paper, we investigate the self-organized criticality (SOC) phenomena in GRB prompt phase as done in X-ray flares of GRBs. We obtain the differential and cumulative distributions of 243 short GRB pulses, such as peak flux, FWHM, rise time, decay time, and peak time in the fourth BATSE TTE Catalog with the Markov Chain Monte Carlo (MCMC) technique. It is found that these distributions can be well described by power-law models. In particular, comparisons are made in 182 short GRB pulses in the third Swift GRB Catalog from 2004 December to 2019 July. The results are essentially consistent with those in BATSE ones. We notice that there is no obvious power-law index evolution across different energy bands for either BATSE or Swift sGRBs. The joint analysis suggests that GRB prompt phase can be explained by a Fractal-Diffusive, Self-Organized Criticality (FD-SOC) system with the spatial dimension S = 3 and the classical diffusion ? = 1. Our findings show that GRB prompt phases and X-ray flares possess the very same magnetically dominated stochastic process and mechanism.Comment: 18 pages, 10 figures, accepted for publication in ApJ

Effects of Splenectomy on Spontaneously Chronic Pancreatitis in aly/aly Mice

Background and Aim. Mice with alymphoplasia (aly/aly) mutation characterized by a lack of lymph nodes, Peyer's patches, and well-defined lymphoid follicles in the spleen were found. In this study, we used splenectomized aly/aly mice to elucidate the effects of secondary lymphoid organs in the development of aly/aly autoimmune pancreatitis. Methods. Forty-eight 10-week-old aly/aly mice were divided into two groups for splenectomy and sham operation. Histological and immunohistochemical analyses of the pancreas were performed at the ages of 20, 30, and 40 weeks old after operation, respectively. Results. Our results showed that mononuclear cell infiltration was restricted to the interlobular connective tissues at the age of 20 weeks, and not increase obviously at the age of 30 and 40 weeks in splenectomized aly/aly mice. Furthermore, an apparent decrease in the expressions of CD4+ T, CD8+ T, and B cells was detected in the pancreatic tissues compared with sham aly/aly mice, however, no significant difference in macrophage expression between mice with and without a splenectomy. Conclusions. Inflammation infiltration and development of the pancreatitis in aly/aly mice were suppressed effectively after splenectomy, which was, at least partly, correlated to inhibition of the infiltration of T and B cells in pancreatic tissues but not to macrophages

Multivalent Polyanionic 2D Nanosheets Functionalized Nanofibrous Stem Cell-based Neural Scaffolds

Because developed neural cells are no longer regenerative and proliferative, achieving neural regenerations by using induced pluripotent stem cells (IPS cells) for nerve diseases have recently attracted much attention. Since the IPS cells' growth and differentiation can be manipulated by different physical and chemicals cues, scaffolds combining the beneficial nanostructures and extracellular matrix may become an ideal interface to promote IPS cells' neural differentiation. In this work, a biocompatible and multivalent polyanion, hyperbranched polyglycerol sulfate, is used to modify the graphene oxide to obtain bio-adhesive 2D nanosheets. After coating electrospinning nanofibers, the 2D nanosheets-functionalized nanofibrous scaffolds are applied to mediate the proliferation, lineage specification, and neural differentiation of IPS cells. The results suggest that the modified scaffolds can improve the adhesion and proliferation of IPS cells combined with high efficiency in maintaining their stemness. During the neural differentiation process, the scaffolds can promote neural differentiation and their maturity, meanwhile decreasing the lineage specification toward astrocyte. Overall, this study not only provides new multivalent/bio-adhesive nanofibrous scaffolds that integrate the chemical and physical cues to facilitate the targeted neural differentiation of IPS cells but also presents a novel pathway for the fabrication of carbon nanomaterials-based biocomposites in regenerative therapies