2,144 research outputs found
Fermions Tunneling from Higher-Dimensional Reissner-Nordstr\"om Black Hole: Semiclassical and Beyond Semiclassical Approximation
Based on semiclassical tunneling method, we focus on charged fermions
tunneling from higher-dimensional Reissner-Nordstr\"{o}m black hole. We first
simplify the Dirac equation by semiclassical approximation, and then a
semiclassical Hamilton-Jacobi equation is obtained. Using the Hamilton-Jacobi
equation, we study the Hawking temperature and fermions tunneling rate at the
event horizon of the higher-dimensional Reissner-Nordstr\"{o}m black hole
spacetime. Finally, the correct entropy is calculation by the method beyond
semiclassical approximation.Comment: 7 page
Neutron star phase transition as the origin for the fast radio bursts and soft gamma-ray repeaters of SGR J1935+2154
Magnetars are believed as neutron stars (NSs) with strong magnetic fields.
X-ray flares and fast radio bursts (FRBs) have been observed from the magnetar
(soft gamma-ray repeater, SGR J1935+2154). We propose that the phase transition
of the NS can power the FRBs and SGRs.Based on the equation of state provided
by the MIT bag model and the mean field approximation, we solve the
Tolman-Oppenheimer-Volkoff equations to get the NS structure. With spin-down of
the NS, the hadronic shell gradually transfers to the quark shell.The
gravitational potential energy released by one time of the phase transition can
be achieved. The released energy, time interval between two successive phase
transitions, and glitch are all consistent with the observations of the FRBs
and the X-ray flares from SGR J1935+2154. We conclude that the phase transition
of an NS is a plausible mechanism to power the SGRs as well as the repeating
FRBs.Comment: 11 pages, 3 figure
Spatial distribution of NH2D in massive star-forming regions
To understand the relation between NHD and its physical environment, we
mapped ortho-NHD at 85.9 GHz toward 24 Galactic
late-stage massive star-forming regions with Institut de Radioastronomie
Millimtrique (IRAM) 30-m telescope. Ortho-NHD was
detected in 18 of 24 sources. Comparing with the distribution of HCN 1-0
as a dense gas tracer and radio recombination line H42, ortho-NHD
present complex and diverse spatial distribution in these
targets. 11 of the 18 targets, present a different distribution between
ortho-NHD and HCN 1-0, while no significant
difference between these two lines can be found in the other 7 sources, mainly
due to limited spatial resolution and sensitivity. Moreover, with H42
tracing massive young stellar objects, ortho-NHD seems
to show a relatively weak emission near the massive young stellar objects.Comment: 30 pages, 20 figures, 4 tables. Accepted to MNRA
Novel Sphingomyelin Biomarkers for Brain Glioma and Associated Regulation Research on the PI3K/Akt Signaling Pathway
Glioma is one of the most common malignant tumor types of the central nervous system. It is necessary to identify biomarkers and novel therapeutic targets for glioma. The purpose of the present study was to distinguish lipid biomarkers with differential expression patterns in glioma tissues and normal brain tissues by matrix assisted laser desorption/ionization (MALDI)‑imaging and MALDI‑time of flight (TOF)‑mass spectrometry (MS). Additionally, identification of lipid biomarkers was performed to describe novel therapeutic targets for glioma treatment. A total of six tissues from three patients with glioma and three control patients with traumatic brain injury were analyzed using UltrafleXtreme MALDI‑TOF/TOF. The expression levels of 15 lipid peaks were higher in the TBT samples compared with in the GBT samples. The expression levels of another 16 lipid peaks were higher in the GBT samples compared with in the TBT samples. 14 peaks were identified as sphingomyelins using MS/MS. Additional results were also obtained from experiments using the glioma cell line U373‑MG. These results indicated that treatment with the drug desipramine (Desi) inhibited the accumulation of ceramide on the cell membranes of glioma U373‑MG cells. Treatment with Desi inhibited the activation of insulin‑like growth factor‑1 receptor and inhibited the activation of proteins in the PI3K/Akt signaling pathway
Imaging Molecular Outflow in Massive Star-forming Regions with HNCO Lines
Protostellar outflows are considered a signpost of star formation. These
outflows can cause shocks in the molecular gas and are typically traced by the
line wings of certain molecules. HNCO (4--3) has been regarded as a shock
tracer because of the high abundance in shocked regions. Here we present the
first imaging results of HNCO (4--3) line wings toward nine sources in a sample
of twenty three massive star-forming regions using the IRAM 30\,m telescope. We
adopt the velocity range of the full width of HCN (10--9) and
HCO (1--0) emissions as the central emission values, beyond which
the emission from HNCO (4--3) is considered to be from line wings. The spatial
distributions of the red- and/or blue-lobes of HNCO (4--3) emission nicely
associate with those lobes of HCO (1--0) in most of the sources. High
intensity ratios of HNCO (4--3) to HCO (1--0) are obtained in the line
wings. The derived column density ratios of HNCO to HCO are consistent with
those previously observed towards massive star-forming regions. These results
provide direct evidence that HNCO could trace outflow in massive star-forming
regions. This work also implies that the formation of some HNCO molecules is
related to shock, either on the grain surface or within the shocked gas.Comment: 18 pages, 4 tables, 4 figures, and accepted for publication in Ap
- …