125 research outputs found
Software Holography: Interferometric Data Analysis for the Challenges of Next Generation Observatories
Next generation radio observatories such as the MWA, LWA, LOFAR, CARMA and
SKA provide a number of challenges for interferometric data analysis. These
challenges include heterogeneous arrays, direction-dependent instrumental gain,
and refractive and scintillating atmospheric conditions. From the analysis
perspective, this means that calibration solutions can not be described using a
single complex gain per antenna. In this paper we use the optimal map-making
formalism developed for CMB analyses to extend traditional interferometric
radio analysis techniques--removing the assumption of a single complex gain per
antenna and allowing more complete descriptions of the instrumental and
atmospheric conditions. Due to the similarity with holographic mapping of radio
antenna surfaces, we call this extended analysis approach software holography.
The resulting analysis algorithms are computationally efficient, unbiased, and
optimally sensitive. We show how software holography can be used to solve some
of the challenges of next generation observations, and how more familiar
analysis techniques can be derived as limiting cases.Comment: in revie
XMM-Newton Observations of Two Candidate Supernova Remnants
Candidate supernova remnants G23.5+0.1 and G25.5+0.0 were observed by
XMM-Newton in the course of a snap-shot survey of plerionic and composite SNRs
in the Galactic plane. In the field of G23.5+0.1, we detected an extended
source, ~3' in diameter, which we tentatively interpret as a pulsar-wind nebula
(PWN) of the middle-aged radio pulsar B1830-08. Our analysis suggests an
association between PSR B1830-08 and the surrounding diffuse radio emission. If
the radio emission is due to the SNR, then the pulsar must be significantly
younger than its characteristic age. Alternatively, the radio emission may come
from a relic PWN. In the field of G25.5+0.0, which contains the extended TeV
source HESS J1837-069, we detected the recently discovered young high-energy
pulsar J1838-0655 embedded in a PWN with extent of 1.3'. We also detected
another PWN candidate (AX J1837.3-0652) with an extent of 2' and unabsorbed
luminosity L_(2-10 keV) ~ 4 x 10^33 erg/s at d=7 kpc. The third X-ray source,
located within the extent of the HESS J1837-069, has a peculiar extended radio
counterpart, possibly a radio galaxy with a double nucleus or a microquasar. We
did not find any evidence of the SNR emission in the G25.5+0.0 field. We
provide detailed multiwavelength analysis and identifications of other field
sources and discuss robustness of the G25.5+0.0 and G23.5+0.1 classifications
as SNRs. (abstract abridged)Comment: 37 pages, 9 figures, submitted to Ap
Adatom Fe(III) on the hematite surface: Observation of a key reactive surface species
The reactivity of a mineral surface is determined by the variety and population of different types of surface sites (e.g., step, kink, adatom, and defect sites). The concept of "adsorbed nutrient" has been built into crystal growth theories, and many other studies of mineral surface reactivity appeal to ill-defined "active sites." Despite their theoretical importance, there has been little direct experimental or analytical investigation of the structure and properties of such species. Here, we use ex-situ and in-situ scanning tunneling microcopy (STM) combined with calculated images based on a resonant tunneling model to show that observed nonperiodic protrusions and depressions on the hematite (001) surface can be explained as Fe in an adsorbed or adatom state occupying sites different from those that result from simple termination of the bulk mineral. The number of such sites varies with sample preparation history, consistent with their removal from the surface in low pH solutions
Effects of intrauterine exposure to synthetic glucocorticoids on fetal, newborn, and infant hypothalamic-pituitary-adrenal axis function in humans : a systematic review
BACKGROUND: Synthetic glucocorticoids are commonly used in reproductive medicine. Fetal organ systems are highly sensitive to changes in the intrauterine environment, including overexposure to glucocorticoids. Structural and functional alterations resulting from such changes may persist throughout life and have been associated with diverse diseases. One system that could be particularly sensitive to fetal glucocorticoid overexposure is the hypothalamic-pituitary-adrenal (hpa) axis. Many human studies have investigated this possibility, but a systematic review to identify consistent, emergent findings is lacking. METHODS: We systematically review 49 human studies, assessing the effects of intrauterine exposure to synthetic glucocorticoids on fetal, neonate, and infant hpa function. RESULTS: Study quality varied considerably, but the main findings held true after restricting the analyses to higher-quality studies: intrauterine exposure to synthetic glucocorticoids reduces offspring hpa activity under unstimulated conditions after pain but not pharmacological challenge. Although reduced unstimulated hpa function appears to recover within the first 2 wk postpartum, blunted hpa reactivity to pain is likely to persist throughout the first 4 months of life. There is some evidence that the magnitude of the effects is correlated with the total amount of glucocorticoids administered and varies with the time interval between glucocorticoid exposure and hpa assessment. CONCLUSIONS: This systematic review has allowed the demonstration of the way in which intrauterine exposure to various regimens of synthetic glucocorticoids affects various forms of hpa function. As such, it guides future studies in terms of which variables need to be focused on in order to further strengthen the understanding of such therapy, whilst continuing to profit from its clinical benefits
Associations between constructs related to social relationships and mental health conditions and symptoms: an umbrella review
BACKGROUND: Loneliness and social isolation are increasingly recognised as prevalent among people with mental health problems, and as potential targets for interventions to improve quality of life and outcomes, as well as for preventive strategies. Understanding the relationship between quality and quantity of social relationships and a range of mental health conditions is a helpful step towards development of such interventions. PURPOSE: Our aim was to give an overview of associations between constructs related to social relationships (including loneliness and social isolation) and diagnosed mental conditions and mental health symptoms, as reported in systematic reviews of observational studies. METHODS: For this umbrella review (systematic review of systematic reviews) we searched five databases (PsycINFO, MEDLINE, EMBASE, CINAHL, Web of Science) and relevant online resources (PROSPERO, Campbell Collaboration, Joanna Briggs Institute Evidence Synthesis Journal). We included systematic reviews of studies of associations between constructs related to social relationships and mental health diagnoses or psychiatric symptom severity, in clinical or general population samples. We also included reviews of general population studies investigating the relationship between loneliness and risk of onset of mental health problems. RESULTS: We identified 53 relevant systematic reviews, including them in a narrative synthesis. We found evidence regarding associations between (i) loneliness, social isolation, social support, social network size and composition, and individual-level social capital and (ii) diagnoses of mental health conditions and severity of various mental health symptoms. Depression (including post-natal) and psychosis were most often reported on, with few systematic reviews on eating disorders or post-traumatic stress disorder (PTSD), and only four related to anxiety. Social support was the most commonly included social construct. Our findings were limited by low quality of reviews and their inclusion of mainly cross-sectional evidence. CONCLUSION: Good quality evidence is needed on a wider range of social constructs, on conditions other than depression, and on longitudinal relationships between social constructs and mental health symptoms and conditions
Differential expression of collectins in human placenta and role in inflammation during spontaneous Labor.
© 2014 Yadav et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Collectins, collagen-containing Ca2+ dependent C-type lectins and a class of secretory proteins including SP-A, SP-D and MBL, are integral to immunomodulation and innate immune defense. In the present study, we aimed to investigate their placental transcript synthesis, labor associated differential expression and localization at feto-maternal interface, and their functional implication in spontaneous labor. The study involved using feto-maternal interface (placental/decidual tissues) from two groups of healthy pregnant women at term (≥37 weeks of gestation), undergoing either elective C-section with no labor ('NLc' group, n = 5), or normal vaginal delivery with spontaneous labor ('SLv' group, n = 5). The immune function of SP-D, on term placental explants, was analyzed for cytokine profile using multiplexed cytokine array. SP-A, SP-D and MBL transcripts were observed in the term placenta. The 'SLv' group showed significant up-regulation of SP-D (p = 0.001), and down-regulation of SP-A (p = 0.005), transcripts and protein compared to the 'NLc' group. Significant increase in 43 kDa and 50 kDa SP-D forms in placental and decidual tissues was associated with the spontaneous labor (p<0.05). In addition, the MMP-9-cleaved form of SP-D (25 kDa) was significantly higher in the placentae of 'SLv' group compared to the 'NLc' group (p = 0.002). Labor associated cytokines IL-1α, IL-1β, IL-6, IL-8, IL-10, TNF-α and MCP-1 showed significant increase (p<0.05) in a dose dependent manner in the placental explants treated with nSP-D and rhSP-D. In conclusion, the study emphasizes that SP-A and SP-D proteins associate with the spontaneous labor and SP-D plausibly contributes to the pro-inflammatory immune milieu of feto-maternal tissues.Funding provided by BT/PR15227/BRB/10/906/2011) Department of Biotechnology (DBT), Government of India http://dbtindia.nic.in/index.asp (TM) and Indian Council of Medical Research (ICMR) Junior Research Fellowship (JRF)/Senior Research Fellowship (SRF), Government of India, www.icmr.nic.in (AKY)
A radio spectral index map and catalogue at 147-1400 MHz covering 80 per cent of the sky
The radio spectral index is a powerful probe for classifying cosmic radio sources and understanding the origin of the radio emission. Combining data at 147 MHz and 1.4 GHz from the TIFR GMRT Sky Survey (TGSS) and the NRAO VLA Sky Survey (NVSS), we produced a large-area radio spectral index map of ~80 per cent of the sky (Dec. > - 40 deg), as well as a radio spectral index catalogue containing 1396 515 sources, of which 503 647 are not upper or lower limits. Almost every TGSS source has a detected counterpart, while this is true only for 36 per cent of NVSS sources. We released both the map and the catalogue to the astronomical community. The catalogue is analysed to discover systematic behaviours in the cosmic radio population. We find a differential spectral behaviour between faint and bright sources as well as between compact and extended sources. These trends are explained in terms of radio galaxy evolution. We also confirm earlier reports of an excess of steep-spectrum sources along the galactic plane. This corresponds to 86 compact and steep-spectrum source in excess compared to expectations. The properties of this excess are consistent with normal non-recycled pulsars, which may have been missed by pulsation searches due to larger than average scattering along the line of sight
Near-infrared spectra of Galactic stellar clusters detected on Spitzer/GLIMPSE images
We present near-infrared spectroscopic observations of massive stars in three
stellar clusters located in the direction of the inner Galaxy. One of them, the
Quartet, is a new discovery while the other two were previously reported as
candidate clusters identified on mid-infrared Spitzer images (GLIMPSE20 and
GLIMPSE13). Using medium-resolution (R=900-1320) H and K spectroscopy, we
firmly establish the nature of the brightest stars in these clusters, yielding
new identifications of an early WC and two Ofpe/WN9 stars in the Quartet and an
early WC star in GLIMPSE20. We combine this information with the available
photometric measurements from 2MASS, to estimate cluster masses, ages, and
distances. The presence of several massive stars places the Quartet and
GLIMPSE20 among the small sample of known Galactic stellar clusters with masses
of a few 10^3 Msun, and ages from 3 to 8 Myr. We estimate a distance of about
3.5 kpc for Glimpse 20, and 6.0 kpc for Quartet. The large number of giant
stars identified in GLIMPSE13 indicates that it is another massive (~ 6500
Msun) cluster, but older, with an age between 30 and 100 Myr, at a distance of
about 3 kpc.Comment: aastex macro, 21 pages, 15 figures. ApJ, accepte
Gradient Optics of subwavelength nanofilms
Propagation and tunneling of light through subwavelength photonic barriers,
formed by dielectric layers with continuous spatial variations of dielectric
susceptibility across the film are considered. Effects of giant
heterogeneity-induced non-local dispersion, both normal and anomalous, are
examined by means of a series of exact analytical solutions of Maxwell
equations for gradient media. Generalized Fresnel formulae, visualizing a
profound influence of gradient and curvature of dielectric susceptibility
profiles on reflectance/transmittance of periodical photonic heterostructures
are presented. Depending on the cutoff frequency of the barrier, governed by
technologically managed spatial profile of its refractive index, propagation or
tunneling of light through these barriers are examined. Nonattenuative transfer
of EM energy by evanescent waves, tunneling through dielectric gradient
barriers, characterized by real values of refractive index, decreasing in the
depth of medium, is shown. Scaling of the obtained results for different
spectral ranges of visible, IR and THz waves is illustrated. Potential of
gradient optical structures for design of miniaturized filters, polarizers and
frequency-selective interfaces of subwavelength thickness is considered
Star forming dwarf galaxies
Star forming dwarf galaxies (SFDGs) have a high gas content and low
metallicities, reminiscent of the basic entities in hierarchical galaxy
formation scenarios. In the young universe they probably also played a major
role in the cosmic reionization. Their abundant presence in the local volume
and their youthful character make them ideal objects for detailed studies of
the initial stellar mass function (IMF), fundamental star formation processes
and its feedback to the interstellar medium. Occasionally we witness SFDGs
involved in extreme starbursts, giving rise to strongly elevated production of
super star clusters and global superwinds, mechanisms yet to be explored in
more detail. SFDGs is the initial state of all dwarf galaxies and the relation
to the environment provides us with a key to how different types of dwarf
galaxies are emerging. In this review we will put the emphasis on the exotic
starburst phase, as it seems less important for present day galaxy evolution
but perhaps fundamental in the initial phase of galaxy formation.Comment: To appear in JENAM Symposium "Dwarf Galaxies: Keys to Galaxy
Formation and Evolution", P. Papaderos, G. Hensler, S. Recchi (eds.). Lisbon,
September 2010, Springer Verlag, in pres
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