269 research outputs found
Multi-wavelength Temporal Variability of the Blazar 3C 454.3 during 2014 Activity Phase
We present a multi-wavelength temporal analysis of the blazar 3C 454.3 during
the high -ray active period from May-December, 2014. Except for X-rays,
the period is well sampled at near-infrared (NIR)-optical by the \emph{SMARTS}
facility and the source is detected continuously on daily timescale in the
\emph{Fermi}-LAT -ray band. The source exhibits diverse levels of
variability with many flaring/active states in the continuously sampled
-ray light curve which are also reflected in the NIR-optical light
curves and the sparsely sampled X-ray light curve by the \emph{Swift}-XRT.
Multi-band correlation analysis of this continuous segment during different
activity periods shows a change of state from no lags between IR and
-ray, optical and -ray, and IR and optical to a state where
-ray lags the IR/optical by 3 days. The results are consistent
with the previous studies of the same during various -ray flaring and
active episodes of the source. This consistency, in turn, suggests an extended
localized emission region with almost similar conditions during various
-ray activity states. On the other hand, the delay of -ray with
respect to IR/optical and a trend similar to IR/optical in X-rays along with
strong broadband correlations favor magnetic field related origin with X-ray
and -ray being inverse Comptonized of IR/optical photons and external
radiation field, respectively.Comment: 15 pages, 5 figures, 1 table, MNRAS accepte
Intraventricular arachnoid cyst of lateral ventricle in an elderly patient
Arachnoid cysts are usually located in relation to the arachnoid cisterns. Intra-ventricular location is rare and its embryological emergence in this site is controversial. We report a large intra-ventricular cyst in a 61-year-old female who presented with decreased vision, headache and right hemiparesis. MRI was suggestive of cystic lesion in the lateral ventricle and was excised completely through a craniotomy
Correlations between QPO frequencies and spectral parameters of GRS 1915+105 using AstroSat observations
In this work, we study the correlation between Quasi-periodic Oscillation
(QPO) frequency and the spectral parameters during various X-ray states in the
black hole binary GRS 1915+105 which matches well with the predicted
relativistic dynamic frequency (i.e. the inverse of the sound crossing time) at
the truncated radii. We have used broadband data of LAXPC and SXT instruments
onboard AstroSat. Spectral fitting shows that the accretion rate varies from
to gm/s and the truncated radius changing
from the last stable orbit of an almost maximally spinning black hole,
1.2 to 19 Gravitational radii. For this wide range, the frequencies of
the C-type QPO (2 - 6 Hz) follow the trend predicted by the relativistic
dynamical frequency model and interestingly, the high-frequency QPO at
70 Hz also follows the same trend, suggesting they originate from the innermost
stable circular orbit with the same mechanism as the more commonly observed
C-type QPO. While the qualitative trend is as predicted, there are quantitative
deviations between the data and the theory, and the possible reasons for these
deviations are discussed
Characterization of Polylactic Acid Films for Food Packaging as Affected by Dielectric Barrier Discharge Atmospheric Plasma
Dielectric barrier discharge (DBD) air plasma is a novel technique for in-package decontamination of food, but it has not been yet applied to the packaging material. Characterization of commercial polylactic acid (PLA) films was done after in-package DBD plasma treatment at different voltage and treatment time to evaluate its suitability as food packaging material. DBD plasma increased the roughness of PLA film mainly at the site in contact with high voltage electrode at both the voltage levels of 70 and 80 kV. DBD plasma treatments did not induce any change in the glass transition temperature, but significant increase in the initial degradation temperature and maximum degradation temperature was observed. DBD plasma treatment did not adversely affect the oxygen and water vapor permeability of PLA. A very limited overall migration was observed in different food simulants and was much below the regulatory limits
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