Abstract
We report the first astrophysical application of the technique of wide-field interplanetary scintillation (IPS) with the Murchison Widefield Array (MWA). This powerful technique allows us to ...identify and measure sub-arcsecond compact components in low-frequency radio sources across large areas of sky without the need for long-baseline interferometry or ionospheric calibration. We present the results of a 5-min observation of a 30 × 30 deg2 MWA field at 162 MHz with 0.5 s time resolution. Of the 2550 continuum sources detected in this field, 302 (12 per cent) show rapid fluctuations caused by IPS. We find that at least 32 per cent of bright low-frequency radio sources contain a sub-arcsecond compact component that contributes over 40 per cent of the total flux density. Perhaps surprisingly, peaked-spectrum radio sources are the dominant population among the strongly scintillating, low-frequency sources in our sample. While gamma-ray active galactic nuclei are generally compact, flat-spectrum radio sources at higher frequencies (162 MHz), the properties of many of the Fermi blazars in our field are consistent with a compact component embedded within more extended low-frequency emission. The detection of a known pulsar in our field shows that the wide-field IPS technique is at the threshold of sensitivity needed to detect new pulsars using image plane analysis, and scaling the current MWA sensitivity to that expected for SKA-low implies that large IPS-based pulsar searches will be feasible with SKA. Calibration strategies for the SKA require a better knowledge of the space density of compact sources at low radio frequencies, which IPS observations can now provide.
The AT20G high-angular-resolution catalogue Chhetri, R.; Ekers, R. D.; Jones, P. A. ...
Monthly notices of the Royal Astronomical Society,
2013, Letnik:
434, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We present the high-angular-resolution catalogue for the Australia Telescope 20 GHz (AT20G) survey, using the high-angular-resolution 6-km antenna data at the baselines of ∼4500 m of the Australia ...Telescope Compact Array. We have used the data to produce the visibility catalogue that separates the compact active galactic nuclei (AGNs) from the extended radio sources at the 0.15 arcsec angular scale, corresponding to the linear size scale of 1 kpc at redshifts higher than 0.7. We find the radio population at 20 GHz to be dominated by compact AGNs constituting 77 per cent of the total sources in the AT20G. We introduce the visibility-spectra diagnostic plot, produced using the AT20G cross-matches with lower frequency radio surveys at 1 GHz the NRAO VLA Sky Survey (NVSS) and the Sydney University Molonglo Sky Survey (SUMSS), that separates the 20 GHz population into distinct sub-populations of the compact AGNs, the compact steep-spectrum (CSS) sources, the extended AGN-powered sources and extended flat-spectrum sources. The extended flat-spectrum sources include a local thermal emitting population of high-latitude planetary nebulae and also gravitational lens and binary black hole candidates among the AGNs. We find a smooth transition in properties between the CSS sources and the AGN populations. The visibility catalogue, together with the main AT20G survey, provides an estimate of angular size scales for sources in the AT20G and an estimate of the flux arising from central cores of extended radio sources. The identification of the compact AGNs in the AT20G survey provides high-quality calibrators for high-frequency radio telescope arrays and very large baseline interferometry observations.
Objectives
The present study aimed to explore the effect of umbilical cord mesenchymal stem cells (UC-MSCs) on the modulation of T lymphocytes from system lupus erythematosus (SLE) patients and the ...possible mechanism.
Methods
A total of 24 hospitalized SLE patients and 28 healthy individuals were enrolled. T lymphocytes were sorted using Miltenyi magnetic beads. After the addition of recombinant human interleukin (IL)-2 and CD3CD28 T-cell activator, cells were loaded onto six-well plates pre-inoculated or not with UC-MSCs for 1 week of culture. The supernatants were collected for testing inflammatory factors by enzyme-linked immunosorbent assay. Meanwhile, T lymphocytes were collected to assess the expression levels of genes, proteins in relation to SLE and miR-181a by polymerase chain reaction and Western blot.
Results
Compared with T lymphocytes cultured alone, interferon-γ, IL-4, IL-6 and IL-10 levels were significantly decreased in T lymphocytes from SLE patients co-cultured with UC-MSCs. In addition, the gene and protein expression levels of TNF alpha, osteopontin and nuclear factor-kappa B in T lymphocytes were significantly decreased, while miR-181a expression was markedly elevated (p < 0.05 or 0.008).
Conclusion
UC-MSCs have showed certain immunomodulatory and inhibitory effects in vitro on T lymphocytes from SLE patients, which could potentially be a beneficial treatment of the disease. UC-MSCs may up-regulate miR-181a and down-regulate inflammation-related gene expression.
ABSTRACT
Past studies of compact active galactic nuclei (AGNs), the dominant population at high radio frequencies, selected them using flat spectral index criteria. This biases the sample due to the ...steepening of AGN spectra at high radio frequencies. We improve upon this by selecting 3610 compact AGNs using their angular size information ($\lesssim$0.15 arcsec scale) from the Australia Telescope 20 GHz (AT20G) high-angular resolution catalogue. We cross-match these against the Wide-field Infrared Survey Explorer AllWISE catalogue and present a catalogue with 3300 (91 per cent) matches, 91 (3 per cent) rejects, and 219 (6 per cent) non-detections that are excellent high-redshift candidates. Of the matched compact AGNs, 92 per cent exhibit QSO mid-infrared colours (W1−W2 > 0.5). Therefore, our sample of high frequency compact sources has a very high rate of identification with mid-infrared QSOs. We find counterparts for 88 per cent of 387 compact steep-spectrum (CSS) sources in the AT20G survey, 82 ± 5 per cent of which exhibit QSO mid-infrared colours and have moderate redshifts (zmedian = 0.82), while those dominated by host galaxy colours in mid-infrared have lower redshifts (zmedian = 0.13). The latter classified into late- and early-type galaxies using their mid-infrared colours shows a majority (68 ± 4 per cent) have colours characteristic of late-type galaxies. Thus, we find that a larger fraction of these CSS sources are embedded in hosts with higher gas densities than average early-type galaxies. We compare mid-infrared colours of our AGNs against those reported for AGNs primarily selected using non-radio techniques. This shows that mid-infrared SED of high frequency selected compact radio AGN is comparatively less red, possibly due to contributions from their hosts.
Sikkim and Darjeeling Himalayan region is characterized by a rich floral diversity and an equally rich ethnomedicinal tradition. Herbal medicine is the dominant system of medicine practiced by the ...local tribes of this region for the treatment of diabetes. During the course of the present studies it was found that 37 species of plants belonging to 28 families are used as antidiabetic agents in the folk medicinal practices in the region and 81% of these plants are hitherto unreported as hypoglycemic agents. This finding may lead to serious research towards developing new and efficient drugs for diabetes.
Abstract
Rapid land use change in urban areas creates a unique climate, which risks the health of its inhabitants. The unique urban climate is attributable to a phenomenon recognized as the Urban ...Heat Island (UHI). Under such circumstances, the urban regions become hotter than their rural surroundings, creating an island of higher temperatures. Human exposure to excessively warm heat islands, particularly in humid climates like India, is becoming an increasingly serious public health issue. This paper briefly analyses the formation of surface urban heat islands (SUHI), identified by estimating the Land Surface Temperature (LST) and also its potential impacts on the occurrence of heat-related Non-Communicable Diseases (NCD) within a city. Barasat city of India has been chosen to demonstrate this work. LST has been estimated from the Landsat data using a remote sensing platform. It has been observed that the high LST in Barasat city perfectly followed an emitting shape in descending order from the city center to the suburban areas. A primary household survey was conducted in 2018 in the month of March-April, where 200 samples were collected. The information has been collected from the samples regarding their occupation, average hours of exposure to high heat zones, and the NCDs they have suffered from. It has been found that heat cramps, heat stress, heat strokes, and respiratory diseases are common for people exposed to the high heat zone. Although NCDs increase the socioeconomic burden in developing cities, NCD surveillance is limited in India. This study will assist in formulating a better urban neighborhood considering the city’s population exposed to UHI.
We have shown previously that the Murchison Widefield Array (MWA), can detect 100s of Interplanetary Scintillation (IPS) sources simultaneously across a field of view (FoV) ∼30° in extent. To test if ...we can use this capability to track heliospheric structures, we undertook a search of 88 hr of MWA IPS data, and identified an observation likely to have a significant Coronal Mass Ejection (CME) in the FoV. We demonstrate that in a single 5‐min MWA observation we are able to localize and image a CME ∼33 hr after launch at an elongation of ∼37° from the Sun. We use IPS observables to constrain the kinematics of the CME, and describe how MWA IPS observations can be used in the future to make a unique contribution to heliospheric modeling efforts.
Plain Language Summary
Coronal Mass Ejections (CMEs) are the link between events on the surface of the Sun, and Geomagnetic Storms on Earth. Tracking them through space is therefore critical to forecasting these important events. However, while there are many ways of detecting the launch of a CME and watching it leave the Sun, and ways we can detect them in orbit shortly before they arrive at the Earth, tracking them on their way through interplanetary space is much more tricky. In this paper we report on a detection of a CME in interplanetary space using a technique called Interplanetary Scintillation. This technique is certainly not new, however, we use a Radio telescope in Australia called the Murchison Widefield Array (MWA) which allows us to map the detected CME in unprecedented detail. We show how we can use MWA observations to track the CME as it heads on a trajectory away from the Earth. We hope that in the future we can use the same instrument and technique to track an Earthbound CME.
Key Points
We are able to recover a Coronal Mass Ejection (CME) detected in coronagraph images in Interplanetary Scintillation (IPS) observations taken 33 hr later
The unprecedented number of lines of sight in our IPS observations allow us to image the CME and localize it to degree‐level accuracy
The CME's location in the IPS observation is consistent with fast CME‐propagation, and confirms a “broad‐side” (plane of sky) trajectory
We present polarization data for 180 extragalactic sources extracted from the Australia Telescope 20 GHz (AT20G) survey catalogue and observed with the Australia Telescope Compact Array during a ...dedicated, high sensitivity run (... 1 mJy). For the sake of completeness, we extracted the polarization information for seven extended sources from the 9 yr Wilkinson Microwave Anisotropy Probe co-added maps at 23 GHz. The full sample of 187 sources constitutes a ...99 per cent complete sample of extragalactic sources brighter than S20GHz = 500 mJy at the selection epoch with declination ... < -30... The sample has a 91.4 per cent detection rate in polarization at ...20 GHz (94 per cent if considering the subsample of point-like sources). We have measurements also at 4.8 and 8.6 GHz within ~1 month of the 20 GHz observations for 172 sources to reconstruct the spectral properties of the sample in total intensity and in polarization: 143 of them have a polarization detection at all three frequencies. (ProQuest: ... denotes formulae/symbols omitted.)
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