607 research outputs found

    Early Afterglows of Gamma-Ray Bursts in a Stratified Medium with a Power-Law Density Distribution

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    A long-duration gamma-ray burst (GRB) has been widely thought to arise from the collapse of a massive star, and it has been suggested that its ambient medium is a homogenous interstellar medium (ISM) or a stellar wind. There are two shocks when an ultra-relativistic fireball that has been ejected during the prompt gamma-ray emission phase sweeps up the circumburst medium: a reverse shock that propagates into the fireball, and a forward shock that propagates into the ambient medium. In this paper, we investigate the temporal evolution of the dynamics and emission of these two shocks in an environment with a general density distribution of n∝R−kn\propto R^{-k} (where RR is the radius) by considering thick-shell and thin-shell cases. A GRB afterglow with one smooth onset peak at early times is understood to result from such external shocks. Thus, we can determine the medium density distribution by fitting the onset peak appearing in the light curve of an early optical afterglow. We apply our model to 19 GRBs, and find that their kk values are in the range of 0.4 - 1.4, with a typical value of k∌1k\sim1, implying that this environment is neither a homogenous interstellar medium with k=0k=0 nor a typical stellar wind with k=2k=2. This shows that the progenitors of these GRBs might have undergone a new mass-loss evolution.Comment: 32 pages, 5 figures, 1 table, published in Ap

    Challenges and Countermeasures of Teachers’ Professional Development from the Perspective of Globalization

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    Under the influence of globalization, the intensification of international competition is in the final analysis the competition of education and talents. Teachers are the main body of teaching activities. Teachers’ professionalization is an important symbol to measure a country’s educational level. At present, the professional development of teachers in China is facing enormous challenges. In terms of concept, system and the allocation and utilization of educational resources, there are great problems. In order to meet the needs of teachers’ professional development in the perspective of globalization, the new era should promote the upgrading of teachers’ professional level from the aspects of renewal of ideas, improvement of system guarantee system, diversified development and integration and distribution of resources

    Injectable Self‐Healing Antibacterial Bioactive Polypeptide‐Based Hybrid Nanosystems for Efficiently Treating Multidrug Resistant Infection, Skin‐Tumor Therapy, and Enhancing Wound Healing

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    The surgical procedure in skin‐tumor therapy usually results in cutaneous defects, and multidrug‐resistant bacterial infection could cause chronic wounds. Here, for the first time, an injectable self‐healing antibacterial bioactive polypeptide‐based hybrid nanosystem is developed for treating multidrug resistant infection, skin‐tumor therapy, and wound healing. The multifunctional hydrogel is successfully prepared through incorporating monodispersed polydopamine functionalized bioactive glass nanoparticles (BGN@PDA) into an antibacterial F127‐Δ‐Poly‐L‐lysine hydrogel. The nanocomposites hydrogel displays excellent self‐healing and injectable ability, as well as robust antibacterial activity, especially against multidrug‐resistant bacteria in vitro and in vivo. The nanocomposites hydrogel also demonstrates outstanding photothermal performance with (near‐infrared laser irradiation) NIR irradiation, which could effectively kill the tumor cell (>90%) and inhibit tumor growth (inhibition rate up to 94%) in a subcutaneous skin‐tumor model. In addition, the nanocomposites hydrogel effectively accelerates wound healing in vivo. These results suggest that the BGN‐based nanocomposite hydrogel is a promising candidate for skin‐tumor therapy, wound healing, and anti‐infection. This work may offer a facile strategy to prepare multifunctional bioactive hydrogels for simultaneous tumor therapy, tissue regeneration, and anti‐infection.This paper reports an intrinsically multifunctional bioactive hybrid hydrogel for treating multidrug resistant infection, skin‐tumor therapy, and wound healing. The hybrid hydrogels display excellent self‐healing and injectable ability, as well as robust antibacterial activity, especially against multidrug‐resistant bacteria in vitro and in vivo, and also efficiently inhibits tumor growth and enhances wound healing.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149555/1/adfm201806883.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149555/2/adfm201806883-sup-0001-S1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149555/3/adfm201806883_am.pd

    Testing the Bell Inequality at Experiments of High Energy Physics

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    Besides using the laser beam, it is very tempting to directly testify the Bell inequality at high energy experiments where the spin correlation is exactly what the original Bell inequality investigates. In this work, we follow the proposal raised in literature and use the successive decays J/Ïˆâ†’ÎłÎ·c→ΛΛˉ→pπ−pˉπ+J/\psi\to\gamma\eta_c\to \Lambda\bar\Lambda\to p\pi^-\bar p\pi^+ to testify the Bell inequality. Our goal is twofold, namely, we first make a Monte-Carlo simulation of the processes based on the quantum field theory (QFT). Since the underlying theory is QFT, it implies that we pre-admit the validity of quantum picture. Even though the QFT is true, we need to find how big the database should be, so that we can clearly show deviations of the correlation from the Bell inequality determined by the local hidden variable theory. There have been some critiques on the proposed method, so in the second part, we suggest some improvements which may help to remedy the ambiguities indicated by the critiques. It may be realized at an updated facility of high energy physics, such as BES III.Comment: 16 pages, 5 figure