717 research outputs found
J0041+3224: a new double-double radio galaxy
We report the discovery of a double-double radio galaxy (DDRG), J0041+3224,
with the Giant Metrewave Radio Telescope (GMRT) and subsequent high-frequency
observations with the Very Large Array (VLA). The inner and outer doubles are
aligned within about 4 deg and are reasonably collinear with the parent optical
galaxy. The outer double has a steeper radio spectrum compared with the inner
one. Using an estimated redshift of 0.45, the projected linear sizes of the
outer and inner doubles are 969 and 171 kpc respectively. The time scale of
interruption of jet activity has been estimated to be about 20 Myr, similar to
other known DDRGs. We have compiled a sample of known DDRGs, and have
re-examined the inverse correlation between the ratio of the luminosities of
the outer to the inner double and the size of the inner double, l_{in}. Unlike
the other DDRGs with l_{in} larger than about 50 kpc, the inner double of
J0041+3224 is marginally more luminous than the outer one. The two DDRGs with
l_{in} less than about a few kpc have a more luminous inner double than the
outer one, possibly due to a higher efficiency of conversion of beam energy as
the jets propagate through the dense interstellar medium. We have examined the
symmetry parameters and find that the inner doubles appear to be more
asymmetric in both its armlength and flux density ratios compared with the
outer doubles, although they appear marginally more collinear with the core
than the outer double. We discuss briefly possible implications of these
trends.Comment: Accepted for publication in MNRAS, 9 pages, 10 figure
Arp 65 interaction debris: massive HI displacement and star formation
Context: Pre-merger interactions between galaxies can induce significant
changes in the morphologies and kinematics of the stellar and ISM components.
Large amounts of gas and stars are often found to be disturbed or displaced as
tidal debris. This debris then evolves, sometimes forming stars and
occasionally tidal dwarf galaxies. Here we present results from our HI study of
Arp 65, an interacting pair hosting extended HI tidal debris. Aims: In an
effort to understand the evolution of tidal debris produced by interacting
pairs of galaxies, including in situ star and tidal dwarf galaxy formation, we
are mapping HI in a sample of interacting galaxy pairs. The Arp 65 pair is one
of them. Methods: Our resolved HI 21 cm line survey is being carried out using
the Giant Metrewave Radio Telescope (GMRT). We used our HI survey data as well
as available SDSS optical, Spitzer infra-red and GALEX UV data to study the
evolution of the tidal debris and the correlation of HI with the star-forming
regions within it. Results: In Arp 65 we see a high impact pre-merger
interaction involving a pair of massive galaxies (NGC 90 and NGC 93) that have
a stellar mass ratio of ~ 1:3. The interaction, which probably occurred ~ 1.0
-- 2.5 10 yr ago, appears to have displaced a large fraction of
the HI in NGC 90 (including the highest column density HI) beyond its optical
disk. We also find extended ongoing star formation in the outer disk of NGC 90.
In the major star-forming regions, we find the HI column densities to be ~ 4.7
10 cm or lower. But no signature of star formation was
found in the highest column density HI debris, SE of NGC 90. This indicates
conditions within the highest column density HI debris remain hostile to star
formation and it reaffirms that high HI column densities may be a necessary but
not sufficient criterion for star formation.Comment: Accepted in A&
Oxidative chemical beneficiation of low-quality coals under low-energy ultrasonic and microwave irradiation: an environmental-friendly approach
The present environmentally-friendly coal processing technology discussed herewith focuses on the combined effect of ultrasonic and microwave energy in the extent of mineral matter (ash yield) removal from high-sulfur, low-quality coals for their clean utilization. The novelty of this study is that the technique is very efficient instead of using drastic chemicals with less treatment time, less amount of reagent in comparison to the conventional method, and has the potential to adopt in large-scale commercial production of cleaner coals. The quality of the cleaner coal products was examined by using chemical analysis and advanced analytical techniques (electron beam analysis). The combined irradiation process of ultrasonic and microwave energy is observed to be the most effective for the beneficiation of high-sulfur coal than the single process. The result showed a maximum of 51.28% and 66.34% ash (mineral matter) removal from the coal samples by microwave followed by an ultrasonic process. The X-ray photoelectron spectroscopy (XPS) analysis revealed that both inorganic and organic sulfur is present in these Cenozoic low-rank, high-sulfur Indian coals. The high resolution-transmission electron microscopy (HR-TEM) image analysis of the treated coal samples showed nearly agglomerated collections of nanomaterials; carbon spheres/flacks with an irregular shape; and the elements such as oxygen, iron, silicon, sulfur, and aluminum in the beneficiated coal samples. The major mineral phases, including quartz, kaolinite, and gypsum, are found to be removed during the beneficiation process. The thermal analysis (TGA-DTG) also showed the suitability of the beneficiated coals for the power plant application
Time Domain Regional Discriminants
The time and frequency domains are equivalent displays of seismic trace, information, though
some qualities of the signal are more easily observed in one domain than the other. The relative
frequency excitation of Lg, for instance, is most easily viewed in the frequency domain, but such
waveform qualities as the sequence in which pulses arrive in the wave train or the sharpness of
pulse onset are most easily studied in the time domain (Murphy and Bennett, 1982, Blandford,
1981). Because of the tremendous complexity of high frequency regional data, most attempts at
using it for discrimination purposes have involved analysis of the frequency content of the various
arrivals either through transforming selected windows or through multiple bandpass filtering. We
report here on our initial attempts to explore the alternative and to discriminate events using those
waveform characteristics most easily observed in the time domain.
A second advantage of time domain analysis approaches is that they permit a deeper insight
into the physical processes creating a seismic signal's character. For this reason, they can be more
e3silv used to evaluate the transportabilty of a discriminant to varying geophysical and tectonic
regimes. This is an especially important feature in the development of regional discriminants. The
most prominent and successful spectral regional discriminants have been empirically developed.
This means that they must be redeveloped and reverified in each new area. As we shall show in
the following, through rigorous time domain analysis such features as regional depth phases can
be identified and used to discriminate. Discriminants based on such simple physical features as
source depth should be transportable anywhere.
In work recently completed under the treaty verification program, we have proved that such
time domain discriminants do exist. In analyzing a test discrimination data set from the western
U. S., we have discovered that the onset of P_n is always very similar for explosions and that few
earthquakes have this unique waveform character. This information can be constructed into a
simple discrimination scheme by testing the correlation of observed P_n waveform onsets with
average waveforms observed from explosions. High correlations indicate explosions and low
correlations earthquakes. We have also discovered that the regional phase P_g is actually composed of a sequence of sub-arrivals which correspond to successively higher orders of reverberation in
the crust. In realistic crust models, the depth phases play an important role in the waveshapes of
these sub-arrivals. By selecting an appropriate frequency band to analyze, we have been able to
accurately model this type of data from explosions in the western United States. Over the very
relevant regional distance ranges of 200 to 600 km, it appears that a discrimination procedure very
similar to the one which is known to work for P_n will also be effective for P_g. We are investigating
whether similar discriminants can be constructed based on the phases S_n and S_g in areas where
those phases are prominent arrivals
The effect of comorbidities of preeclampsia and eclampsia on maternal and fetal outcome
Background: The aim of this study is to comparatively assess the maternal and fetal outcome in preeclampsia and eclampsia patients with and without comorbidities. The objectives are to assess the comorbidities associated with preeclampsia and eclampsia cases and to find out the effects of the comorbidities of preeclampsia and eclampsia on maternal and fetal outcome.
Methods:380 patients who had attended antenatal OPD and emergency labour room of Assam medical college and hospital, Dibrugarh during June 2020 to July 2021 with preeclampsia and eclampsia were selected for present study. Based on relevant history, clinical and laboratory findings, these patients were further evaluated for associated comorbidities. The cases were distributed in the respective comorbidity group. Then the outcome of the mother and the baby were analyzed till the day of discharge in patients without comorbidities and with comorbidities and the same was compared.
Results: The eventful maternal (44.1%) and fetal (50.92%) outcome was more in preeclampsia and eclampsia patients with comorbidities than in patients without comorbidities which is statistically significant, (p value=0.029), (p value=0.009) respectively.
Conclusions: The effect of preeclampsia and eclampsia itself would adversely affect the pregnancy outcome and the effect is worse when associated with comorbidities. Appropriate prenatal counselling and optimization of the comorbidities is critical for women who are planning pregnancy
Time Domain Regional Discriminants
The time and frequency domains are equivalent displays of seismic trace, information, though
some qualities of the signal are more easily observed in one domain than the other. The relative
frequency excitation of Lg, for instance, is most easily viewed in the frequency domain, but such
waveform qualities as the sequence in which pulses arrive in the wave train or the sharpness of
pulse onset are most easily studied in the time domain (Murphy and Bennett, 1982, Blandford,
1981). Because of the tremendous complexity of high frequency regional data, most attempts at
using it for discrimination purposes have involved analysis of the frequency content of the various
arrivals either through transforming selected windows or through multiple bandpass filtering. We
report here on our initial attempts to explore the alternative and to discriminate events using those
waveform characteristics most easily observed in the time domain.
A second advantage of time domain analysis approaches is that they permit a deeper insight
into the physical processes creating a seismic signal's character. For this reason, they can be more
e3silv used to evaluate the transportabilty of a discriminant to varying geophysical and tectonic
regimes. This is an especially important feature in the development of regional discriminants. The
most prominent and successful spectral regional discriminants have been empirically developed.
This means that they must be redeveloped and reverified in each new area. As we shall show in
the following, through rigorous time domain analysis such features as regional depth phases can
be identified and used to discriminate. Discriminants based on such simple physical features as
source depth should be transportable anywhere.
In work recently completed under the treaty verification program, we have proved that such
time domain discriminants do exist. In analyzing a test discrimination data set from the western
U. S., we have discovered that the onset of P_n is always very similar for explosions and that few
earthquakes have this unique waveform character. This information can be constructed into a
simple discrimination scheme by testing the correlation of observed P_n waveform onsets with
average waveforms observed from explosions. High correlations indicate explosions and low
correlations earthquakes. We have also discovered that the regional phase P_g is actually composed of a sequence of sub-arrivals which correspond to successively higher orders of reverberation in
the crust. In realistic crust models, the depth phases play an important role in the waveshapes of
these sub-arrivals. By selecting an appropriate frequency band to analyze, we have been able to
accurately model this type of data from explosions in the western United States. Over the very
relevant regional distance ranges of 200 to 600 km, it appears that a discrimination procedure very
similar to the one which is known to work for P_n will also be effective for P_g. We are investigating
whether similar discriminants can be constructed based on the phases S_n and S_g in areas where
those phases are prominent arrivals
A survey of extended radio jets with Chandra and HST
We present the results from an X-ray and optical survey of a sample of 17
radio jets in AGN performed with Chandra and HST. The sample was selected from
the radio and is unbiased toward detection at shorter wavelengths, but
preferentially it includes beamed sources. We find that X-ray emission is
common on kpc-scales, with over half radio jets exhibiting at least one X-ray
knot on the Chandra images. The distributions of the radio-to-X-ray and
radio-to-optical spectral indices for the detected jets are similar to the
limits for the non-detections,suggesting all bright radio jets have X-ray
counterparts which will be visible in longer observations. Comparing the radio
and X-ray morphologies shows that the majority of the X-ray jets have
structures that closely map the radio. Analysis of the SED of the jet knots
suggest the knots in which the X-ray and radio morphologies track each other
produce X-rays by IC scattering of the Cosmic Microwave Background. The
remaining knots produce X-rays by the synchrotron process. Spectral changes are
detected along the jets, with the ratio of the X-ray-to-radio and
optical-to-radio flux densities decreasing from the inner to the outer regions.
This suggests the presence of an additional contribution to the X-ray flux in
the jet's inner part, either from synchrotron or IC of the stellar light.
Alternatively, in a pure IC/CMB scenario, the plasma decelerates as it flows
from the inner to the outer regions. Finally, the X-ray spectral indices for
the brightest knots are flat, indicating that the bulk of the luminosity of the
jets is emitted at GeV energies, and raising the interesting possibility of
future detections with GLAST.Comment: 26 pages, 6 ps figures, 6 jpeg figures (1 replaced); accepted for
publication in Ap
Intermittent jet activity in the radio galaxy 4C29.30?
We present radio observations at frequencies ranging from 240 to 8460 MHz of
the radio galaxy 4C29.30 (J0840+2949) using the Giant Metrewave Radio Telescope
(GMRT), the Very Large Array (VLA) and the Effelsberg telescope. We report the
existence of weak extended emission with an angular size of 520 arcsec
(639 kpc) within which a compact edge-brightened double-lobed source with a
size of 29 arcsec (36 kpc) is embedded. We determine the spectrum of the inner
double from 240 to 8460 MHz and show that it has a single power-law spectrum
with a spectral index of 0.8. Its spectral age is estimated to be
\lapp33 Myr. The extended diffuse emission has a steep spectrum with a
spectral index of 1.3 and a break frequency \lapp240 MHz. The spectral
age is \gapp200 Myr, suggesting that the extended diffuse emission is due to
an earlier cycle of activity. We reanalyse archival x-ray data from Chandra and
suggest that the x-ray emission from the hotspots consists of a mixture of
nonthermal and thermal components, the latter being possibly due to gas which
is shock heated by the jets from the host galaxy.Comment: 14 pages, 11 figures, accepted for publication in MNRA
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