607 research outputs found
Early Afterglows of Gamma-Ray Bursts in a Stratified Medium with a Power-Law Density Distribution
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 (where 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 values are in the range of 0.4 - 1.4,
with a typical value of , implying that this environment is neither a
homogenous interstellar medium with nor a typical stellar wind with
. 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 Teachersâ Professional Development from the Perspective of Globalization
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. Teachersâ professionalization is an important symbol to measure a countryâs 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 teachersâ professional development in the perspective of globalization, the new era should promote the upgrading of teachersâ professional level from the aspects of renewal of ideas, improvement of system guarantee system, diversified development and integration and distribution of resources
Injectable SelfâHealing Antibacterial Bioactive PolypeptideâBased Hybrid Nanosystems for Efficiently Treating Multidrug Resistant Infection, SkinâTumor Therapy, and Enhancing Wound Healing
The surgical procedure in skinâtumor therapy usually results in cutaneous defects, and multidrugâresistant bacterial infection could cause chronic wounds. Here, for the first time, an injectable selfâhealing antibacterial bioactive polypeptideâbased hybrid nanosystem is developed for treating multidrug resistant infection, skinâtumor therapy, and wound healing. The multifunctional hydrogel is successfully prepared through incorporating monodispersed polydopamine functionalized bioactive glass nanoparticles (BGN@PDA) into an antibacterial F127âΔâPolyâLâlysine hydrogel. The nanocomposites hydrogel displays excellent selfâhealing and injectable ability, as well as robust antibacterial activity, especially against multidrugâresistant bacteria in vitro and in vivo. The nanocomposites hydrogel also demonstrates outstanding photothermal performance with (nearâinfrared laser irradiation) NIR irradiation, which could effectively kill the tumor cell (>90%) and inhibit tumor growth (inhibition rate up to 94%) in a subcutaneous skinâtumor model. In addition, the nanocomposites hydrogel effectively accelerates wound healing in vivo. These results suggest that the BGNâbased nanocomposite hydrogel is a promising candidate for skinâtumor therapy, wound healing, and antiâinfection. This work may offer a facile strategy to prepare multifunctional bioactive hydrogels for simultaneous tumor therapy, tissue regeneration, and antiâinfection.This paper reports an intrinsically multifunctional bioactive hybrid hydrogel for treating multidrug resistant infection, skinâtumor therapy, and wound healing. The hybrid hydrogels display excellent selfâhealing and injectable ability, as well as robust antibacterial activity, especially against multidrugâresistant 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
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
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
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