397 research outputs found
Some possible sources of IceCube TeV-PeV neutrino events
The IceCube Collaboration has observed 37 neutrino events in the energy range
PeV and the sources of these neutrinos are
unknown. Here we have shown that positions of 12 high energy blazars and the
position of the FR-I galaxy Centaurus A, coincide within the error circles of
ten IceCube events, the later being in the error circle of the highest energy
event so far observed by IceCube. Two of the above blazars are simultaneously
within the error circles of the Telescope Array hotspot and one IceCube event.
We found that the blazar H2356-309 is within the error circles of three IceCube
events. We propose that photohadronic interaction of the Fermi accelerated high
energy protons with the synchrotron/SSC background photons in the nuclear
region of these high energy blazars and AGN are probably responsible for some
of the observed IceCube events.Comment: 14 pages, 3 figure, references adde
Multi-TeV flaring from blazars: Markarian 421 a case study
The TeV blazar Markarian 421 underwent multi-TeV flaring during April 2004
and simultaneously observed in x-ray and TeV energies. It was observed that the
TeV outbursts had no counterparts in the lower energies, which implies that
this might be an orphan flare. In the context of hadronic model, we have shown
that this multi-TeV flaring can be produced due to the interaction of
Fermi-accelerated protons of energy TeV with the background
photons in the low energy tail of the synchrotron self-Compton spectrum of the
blazar jet. We fit very well the flaring spectrum with this model. Based on
this study, we speculate that Mrk 501 and PG 1553+113 are possible candidates
for orphan flaring in the future.Comment: 8 pages, two columns, 3 figure
Photohadronic scenario in interpreting the February-March 2014 flare of 1ES 1011+496
The extraordinary multi-TeV flare from 1ES 1011 +496 during February-March
2014 was observed by MAGIC telescopes for 17 nights and the average spectrum of
the whole period has a non-trivial shape. We have used the photohadronic model
and a template EBL model to explain the average spectrum which fits well to the
flare data. The spectral index is the only free parameter in our
model. We have also shown that the non-trivial nature of the spectrum is due to
the change in the behavior of the optical depth above GeV
-ray energy accompanied with the high SSC flux.Comment: 11 pages, 3 figures, LaTe
Blazar origin of some IceCube events
Recently ANTARES collaboration presented a time dependent analysis to a
selected number of flaring blazars to look for upward going muon events
produced from the charge current interaction of the muon neutrinos. We use the
same list of flaring blazars to look for possible positional correlation with
the IceCube neutrino events. In the context of photohadronic model we propose
that the neutrinos are produced within the nuclear region of the blazar where
Fermi accelerated high energy protons interact with the background
synchrotron/SSC photons. Although we found that some objects from the ANTARES
list are within the error circles of few IceCube events, the statistical
analysis shows that none of these sources have a significant correlation.Comment: Latex file, 6 pages, two columns, 1 Figur
Very high-energy gamma-ray signature of ultrahigh-energy cosmic-ray acceleration in Centaurus A
The association of at least a dozen ultrahigh-energy cosmic-ray (UHECR)
events with energy EeV detected by the Pierre Auger Observatory
(PAO) from the direction of Centaurus-A, the nearest radio galaxy, supports the
scenario of UHECR acceleration in the jets of radio galaxies. In this work, we
model radio to very high energy (VHE, \rm GeV) -ray
emission from Cen A, including GeV hardness detected by Fermi-LAT and TeV
emission detected by HESS. We consider two scenarios: (i) Two zone synchrotron
self-Compton (SSC) and external-Compton (EC) models, (ii) Two zone SSC, EC and
photo-hadronic emission from cosmic ray interactions. The GeV hardness observed
by Fermi-LAT can be explained using these two scenarios, where zone 2 EC
emission is very important. Hadronic emission in scenario (ii) can explain VHE
data with the same spectral slope as obtained through fitting UHECRs from Cen
A. The peak luminosity in cosmic ray proton at 1 TeV, to explain the VHE
-ray data is erg/s. The bolometric
luminosity in cosmic ray protons is consistent with the luminosity required to
explain the origin of 13 UHECR signal events that are correlated with Cen A.Comment: 6 pages, 3 figures, Accepted for publication in MNRASL, Comments
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Revisiting constraints on 3+1 active-sterile neutrino mixing using IceCube data
Recent IceCube search results for sterile neutrino increased tension between
the combined appearance and disappearance experiments. On the other hand,
MiniBooNE latest data confirms at CL the short-baseline oscillation
anomaly. We analyze published IceCube data based on two different
active-sterile mixing schemes using one additional sterile neutrino flavor. We
present exclusion regions in the parameter ranges and for the
mass-mixing and flavor-mixing schemes. Under the more conservative mass-mixing
scheme, CL allowed regions for the appearance experiment and
MiniBooNE latest result are excluded at CL. In case of
less-restrictive flavor-mixing scheme, results from the appearance experiments
are excluded at CL. We also find that including prompt
component of the atmospheric neutrino flux relaxes constraints on sterile
mixing for .Comment: 15 pages and 5 figures. Accepted for publication in JHE
Searching for non-unitary neutrino oscillations in the present T2K and NOA data
The mixing of three active neutrino flavors is parameterized by the unitary
PMNS matrix. If there are more than three neutrino flavors and if the extra
generations are heavy isosinglets, the effective mixing matrix for
the three active neutrinos will be non-unitary. We have analyzed the latest T2K
and \nova data with the hypothesis of non-unitary mixing of the active
neutrinos. We found that the 2019 NOA data slightly (at
C.L.) prefer the non-unitary mixing over unitary mixing. In fact, allowing the
non-unitary mixing brings the \nova best-fit point in the
plane closer to the T2K best-fit point. The
2019 T2K data, on the other hand, cannot rule out any of the two mixing
schemes. A combined analysis of the NOA and T2K 2019 data prefers the
non-unitary mixing at C.L.. We derive constraints on the
non-unitary mixing parameters using the best-fit to the combined NOA and
T2K data. These constraints are weaker than previously found. The latest 2020
data from both the experiments prefer non-unitarity over unitary mixing at C.L. The combined analysis preferes non-unitarity at C.L.
The stronger tension, which exists between the latest 2020 data of the two
experiments, also gets reduced with non-unitary analysis.Comment: 30 pages, 19 figures, 3 tables. Results for 2020 data from NOvA and
T2K have been include
Programa de prácticas de bacteriología y micología
Conocer e identificar la morfología bacteriana y fungal, así como sus principios metabólicos, genéticos y taxonómicos
Hepatocyte Growth Factor Reduces Free Cholesterol-Mediated Lipotoxicity in Primary Hepatocytes by Countering Oxidative Stress
Cholesterol overload in the liver has shown toxic effects by inducing the aggravation of nonalcoholic fatty liver disease to steatohepatitis and sensitizing to damage. Although the mechanism of damage is complex, it has been demonstrated that oxidative stress plays a prominent role in the process. In addition, we have proved that hepatocyte growth factor induces an antioxidant response in hepatic cells; in the present work we aimed to figure out the protective effect of this growth factor in hepatocytes overloaded with free cholesterol. Hepatocytes from mice fed with a high-cholesterol diet were treated or not with HGF, reactive oxygen species present in cholesterol overloaded hepatocytes significantly decreased, and this effect was particularly associated with the increase in glutathione and related enzymes, such as γ-gamma glutamyl cysteine synthetase, GSH peroxidase, and GSH-S-transferase. Our data clearly indicate that HGF displays an antioxidant response by inducing the glutathione-related protection system
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