1,514 research outputs found
The UV Excesses of Supernovae and the Implications for Studying Supernovae and Other Optical Transients
Supernovae (SNe), kilonovae (KNe), tidal disruption events (TDEs), optical
afterglows of gamma ray bursts (GRBs), and many other optical transients are
important phenomena in time-domain astronomy. Fitting the multi-band light
curves (LCs) or the synthesized (pseudo-)bolometric LCs can be used to
constrain the physical properties of optical transients. The (UV absorbed)
blackbody module is one of the most important modules used to fit the
multi-band LCs of optical transients having (UV absorbed) blackbody spectral
energy distributions (SEDs). We find, however, that the SEDs of some SNe show
UV excesses, which cannot be fitted by the model including a (UV absorbed)
blackbody module. We construct the bolometric LCs and employ the (cooling plus)
\Ni model to fit the constructed bolometric LCs, obtaining decent fits. Our
results demonstrate that the optical transients showing UV excesses cannot be
fitted by the multi-band models that include (UV-absorbed) blackbody module,
but can be well modeled by constructing and fitting their bolometric LCs.Comment: 9 pages, 4 figures, 1 table, submitted to Ap
Aquabis(5-butylpyridine-2-carboxylato)zinc monohydrate
In the title complex, [Zn(C10H12NO2)2(H2O)]·H2O, the ZnII ion is coordinated by two N and two O atoms from two 5-n-butylpyridine-2-carboxylato ligands and one O atom from a water molecule in a distorted square-pyramidal geometry. In the crystal, intermolecular O—H⋯O hydrogen bonds link molecules into a two-dimensional supramolecular structure parallel to (001)
SN 2018gk Revisited: the Photosphere, the Central Engine, And the Putative Dust
In this paper, we perform a comprehensive study for the physical properties
of SN 2018gk which is a luminous type IIb supernova (SN). We find that the
early-time photospheric velocity vary from a larger value to a smaller value
before the photosphere reach a temperature floor. We generalize the photosphere
modulus and fit the multi-band light curves (LCs) of SN 2018gk. We find that
the Ni mass model require M of Ni which is
larger than the derived ejecta mass ( M). Alternatively, we
use the magnetar plus Ni and the fallback plus Ni models to fit
the LCs of SN 2018gk, finding that the two models can fit the LCs. We favor the
magnetar plus Ni since the parameters are rather reasonable ( M, M which is smaller than the upper
limit of the value of the Ni mass can by synthesized by the
neutrino-powered core collapse SNe G which is comparable
to those of luminous and superluminous SNe studied in the literature, and
ms which is comparable to those of luminous SNe), while the
validity of the fallback plus Ni model depends on the accretion
efficiency (). Therefore, we suggest that SN 2018gk might be a SN IIb
mainly powered by a central engine. Finally, we confirm the NIR excesses of the
spectral energy distributions (SEDs) of SN 2018gk at some epochs and constrain
the physical properties of the putative dust using the blackbody plus dust
emission model.Comment: 26 pages, 11 figures, 5 tables, Accepted for publication in Ap
(Z)-1-[4-Fluoro-2-(pyrrolidin-1-yl)phenyl]-3-phenyl-2-(1H-1,2,4-triazol-1-yl)prop-2-en-1-one
In the title molecule, C21H19FN4O, the triazole ring forms dihedral angles of 67.0 (1) and 59.6 (1)° with the phenyl and fluoro-substituted benzene rings, respectively. The dihedral angle between the phenyl ring and the fluoro-substituted benzene ring is 79.1 (1)°. The pyrrolidine ring is in a half-chair conformation. In the crystal, weak C—H⋯O and C—H⋯N hydrogen bonds connect molecules into layers parallel to (001)
Eriodictyol modulates glioma cell autophagy and apoptosis by inhibition of PI3K/Akt/mTOR signaling pathway
Purpose: To investigate the effects of eriodictyol (ERD) on U251 human glioma cell cycle and viability, autophagy and apoptosis by modulation of PI3/Akt/mTOR signaling cascade. Methods: 740 Y-P was used to activate U251 human glioma cells. For exploring ERD effects, the U251 cells were treated with ERD and 740 Y-P together. MTT assay was used to elucidate cell viability and apoptosis. The expression of autophagic proteins (LC3B and Beclin-1), and apoptotic proteins (Bcl-2 and Bax) were quantified using Western blotting. To explore the role of PI3K/Akt/mTOR signaling pathway, their expression was measured in comparison to their respective phosphorylated derivatives by Western blotting. Results: ERD exposure downregulated p-PI3K and p-Akt protein expression. The results also indicate that ERD reduced cell viability and stimulated apoptosis in U251 cells (p < 0.05). Consequently, Bax expression was upregulated and the expression of Bcl-2 was downregulated. ERD enhanced the autophagy of glioma cells U251 by enhancing LC3B and Beclin-1 expression (p < 0.05). These effects were opposite to that revealed by 740 Y-P exposure alone. Conclusion: ERD reduces U251 human glioma cell viability, and triggers cell autophagy and apoptosis, which is significantly correlated to downregulation of PI3K/Akt/mTOR signalling cascade. Thus, the compound can potentially be used for the treatment of glioma
A terahertz polarization insensitive dual band metamaterial absorber
Metamaterial absorbers have attracted considerable attention for applications in the terahertz range. In this Letter, we report the design, fabrication, and characterization of a terahertz dual band metamaterial absorber that shows two distinct absorption peaks with high absorption. By manipulating the periodic patterned structures as well as the dielectric layer thickness of the metal–dielectric–metal structure, significantly high absorption can be obtained at specific resonance frequencies. Finite-difference time-domain modeling is used to design the structure of the absorber. The fabricated devices have been characterized using a Fourier transform IR spectrometer. The experimental results show two distinct absorption peaks at 2.7 and 5.2 THz, which are in good agreement with the simulation. The absorption magnitudes at 2.7 and 5.2 THz are 0.68 and 0.74, respectively
A Channel to Form Fast-spinning Black Hole-Neutron Star Binary Mergers as Multimessenger Sources. II. Accretion-induced Spin-up
In this work, we investigate an alternative channel for the formation of
fast-spinning black hole-neutron star (BHNS) binaries, in which super-Eddington
accretion is expected to occur in accreting BHs during the stable mass transfer
phase within BH-stripped helium (BH--He-rich) star binary systems. We evolve
intensive \texttt{MESA} grids of close-orbit BH--He-rich star systems to
systematically explore the projected aligned spins of BHs in BHNS binaries, as
well as the impact of different accretion limits on the tidal disruption
probability and electromagnetic (EM) signature of BHNS mergers. Most of the BHs
in BHNS mergers cannot be effectively spun up through accretion, if the
accretion rate is limited to , where
is the standard Eddington accretion limit. In order to
reach high spins (e.g., ), the BHs are required to
be born less massive (e.g., ) in binary systems with
initial periods of and accrete material at
. However, even under this high accretion limit,
BHs are typically challenging to significantly spin up and
generate detectable associated EM signals. Our population simulations suggest
that different accretion limits have a slight impact on the ratio of tidal
disruption events. However, as the accretion limit increases, the EM
counterparts from the cosmological BHNS population can become bright overall.Comment: 18 pages, 9 figures, 1 table, accepted for publication in Ap
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