31,399 research outputs found
Constraining the bulk Lorentz factor from the photosphere emission
We propose a direct and model-independent method to constrain the Lorentz
factor of a relativistically expanding object, like gamma-ray bursts. Only the
measurements, such as thermal component of the emission, the distance and the
variable time scale of the light curve, are used. If the uncertainties are
considered, we will obtain lower limits of the Lorentz factor instead. We apply
this method to GRB 090618 and get a lower limit of the Lorentz factor to be 22.
The method can be used to any relativistically moving object, such as gamma-ray
bursts, blazars, and soft gamma-ray repeaters, providing the thermal component
of the emission being observed.Comment: 10 pages, 1 figur
In-vitro cytotoxicity of biosynthesized gold nanoparticles against thyroid cancer cell lines
Purpose: To undertake the biosynthesis of gold nanoparticles (AuNPs) using Shorea tumbuggaia bark extract and to study their in-vitro cytotoxicity in thyroid cancer (SW579) cell lines.Methods: AuNPs were prepared by adding 10 mL of Shorea tumbuggaia extract to 5 mL of 2 × 10-3 M of chloroauric acid (HAuCl4) and stirred at room temperature for about 20 min. The AuNPs were evaluated by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible (UV–Vis) spectroscopy and transmission electron microscopy (TEM). They were also assessed for cytotoxicity against SW579 cells using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.Results: The reaction of Shorea tumbuggaia extract with HAuCl4 led to a change in the color of the reaction solution to ruby red after 20 min, indicating the formation of AuNPs. The results of various instrumental tests, including XRD, TEM, UV–vis spectroscopy and FT-IR spectroscopy confirmed the formation of AuNPs. TEM images showed spherical NPs with a mean particle size of 20 nM. Further, in vitro cytotoxicity results indicated concentration-dependent cytotoxicity against SW579 cell lines.Conclusions: A simple, green and low-cost method for the preparation of AuNPs using Shorea tumbuggaia extract has been achieved. The AuNPs exert cytotoxic activity against SW579 cell lines.Keywords: Shorea tumbuggaia, Polyphenols, Gold nanoparticles, Cytotoxicity, Thyroid cancer cel
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