The flare of radiation from the tidal disruption and accretion of a star can be used as a marker for supermassive black holes that otherwise lie dormant and undetected in the centres of distant ...galaxies. Previous candidate flares have had declining light curves in good agreement with expectations, but with poor constraints on the time of disruption and the type of star disrupted, because the rising emission was not observed. Recently, two 'relativistic' candidate tidal disruption events were discovered, each of whose extreme X-ray luminosity and synchrotron radio emission were interpreted as the onset of emission from a relativistic jet. Here we report a luminous ultraviolet-optical flare from the nuclear region of an inactive galaxy at a redshift of 0.1696. The observed continuum is cooler than expected for a simple accreting debris disk, but the well-sampled rise and decay of the light curve follow the predicted mass accretion rate and can be modelled to determine the time of disruption to an accuracy of two days. The black hole has a mass of about two million solar masses, modulo a factor dependent on the mass and radius of the star disrupted. On the basis of the spectroscopic signature of ionized helium from the unbound debris, we determine that the disrupted star was a helium-rich stellar core.
Aims/hypothesis Evidence that the beta cells of human patients with type 1 diabetes can be infected with enterovirus is accumulating, but it remains unclear whether such infections occur at high ...frequency and are important in the disease process. We have now assessed the prevalence of enteroviral capsid protein vp1 (vp1) staining in a large cohort of autopsy pancreases of recent-onset type 1 diabetic patients and a range of controls. Methods Serial sections of paraffin-embedded pancreatic autopsy samples from 72 recent-onset type 1 diabetes patients and up to 161 controls were immunostained for insulin, glucagon, vp1, double-stranded RNA activated protein kinase R (PKR) and MHC class I. Results vp1-immunopositive cells were detected in multiple islets of 44 out of 72 young recent-onset type 1 diabetic patients, compared with a total of only three islets in three out of 50 neonatal and paediatric normal controls. vp1 staining was restricted to insulin-containing beta cells. Among the control pancreases, vp1 immunopositivity was also observed in some islets from ten out of 25 type 2 diabetic patients. A strong correlation was established between islet cell vp1 positivity and PKR production in insulin-containing islets of both type 1 and type 2 diabetic patients, consistent with a persistent viral infection of the islets. Conclusions/interpretation Immunoreactive vp1 is commonly found in the islets of recent-onset type 1 diabetes patients, but only rarely in normal paediatric controls. vp1 immunostaining was also observed in some islets of type 2 diabetes patients, suggesting that the phenomenon is not restricted to type 1 diabetes patients.
The high-frequency radio sky is bursting with synchrotron transients from massive stellar explosions and accretion events, but the low-frequency radio sky has, so far, been quiet beyond the Galactic ...pulsar population and the long-term scintillation of active galactic nuclei. The low-frequency band, however, is sensitive to exotic coherent and polarized radio-emission processes, such as electron-cyclotron maser emission from flaring M dwarfs
, stellar magnetospheric plasma interactions with exoplanets
and a population of steep-spectrum pulsars
, making Galactic-plane searches a prospect for blind-transient discovery. Here we report an analysis of archival low-frequency radio data that reveals a periodic, low-frequency radio transient. We find that the source pulses every 18.18 min, an unusual periodicity that has, to our knowledge, not been observed previously. The emission is highly linearly polarized, bright, persists for 30-60 s on each occurrence and is visible across a broad frequency range. At times, the pulses comprise short-duration (<0.5 s) bursts; at others, a smoother profile is observed. These profiles evolve on timescales of hours. By measuring the dispersion of the radio pulses with respect to frequency, we have localized the source to within our own Galaxy and suggest that it could be an ultra-long-period magnetar.
Individuals often avoid or delay seeking professional help for mental health problems. Stigma may be a key deterrent to help-seeking but this has not been reviewed systematically. Our systematic ...review addressed the overarching question: What is the impact of mental health-related stigma on help-seeking for mental health problems? Subquestions were: (a) What is the size and direction of any association between stigma and help-seeking? (b) To what extent is stigma identified as a barrier to help-seeking? (c) What processes underlie the relationship between stigma and help-seeking? (d) Are there population groups for which stigma disproportionately deters help-seeking?
Five electronic databases were searched from 1980 to 2011 and references of reviews checked. A meta-synthesis of quantitative and qualitative studies, comprising three parallel narrative syntheses and subgroup analyses, was conducted.
The review identified 144 studies with 90,189 participants meeting inclusion criteria. The median association between stigma and help-seeking was d = - 0.27, with internalized and treatment stigma being most often associated with reduced help-seeking. Stigma was the fourth highest ranked barrier to help-seeking, with disclosure concerns the most commonly reported stigma barrier. A detailed conceptual model was derived that describes the processes contributing to, and counteracting, the deterrent effect of stigma on help-seeking. Ethnic minorities, youth, men and those in military and health professions were disproportionately deterred by stigma.
Stigma has a small- to moderate-sized negative effect on help-seeking. Review findings can be used to help inform the design of interventions to increase help-seeking.
Aliment Pharmacol Ther 2011; 33: 739–747
Summary
Background The clinical classification of hepatic encephalopathy is largely subjective, which has led to difficulties in designing trials in this ...field.
Aims To review the current classification of hepatic encephalopathy and to develop consensus guidelines on the design and conduct of future clinical trials.
Methods A round table was convened at the 14th International Society for Hepatic Encephalopathy and Nitrogen Metabolism (ISHEN) meeting. Key discussion points were the nomenclature of hepatic encephalopathy and the selection of patients, standards of care and end‐points for assessing the treatment and secondary prevention of hepatic encephalopathy.
Results It was generally agreed that severity assessment of hepatic encephalopathy in patients with cirrhosis, whether made clinically or more objectively, should be continuous rather than categorical, and a system for assessing the SONIC (Spectrum of Neuro‐cognitive Impairment in Cirrhosis) was proposed. Within this system, patients currently classified as having minimal hepatic encephalopathy and Grade I hepatic encephalopathy would be classified as having Covert hepatic encephalopathy, whereas those with apparent clinical abnormalities would continue to be classified as overt hepatic encephalopathy. Some aspects of the terminology require further debate. Consensus was also reached on the patient populations, standards of care and endpoints to assess clinical trial outcomes. However, some compromises had to be made as there is considerable inter‐ and intravariability in the availability of some of the more objective surrogate performance markers.
Conclusions The objectives of the round table were met. Robust, defendable guidelines for the conduct of future studies into hepatic encephalopathy have been provided. Outstanding issues are few and will continue to be discussed.
We present a sample of 1483 sources that display spectral peaks between 72 MHz and 1.4 GHz, selected from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. The GLEAM ...survey is the widest fractional bandwidth all-sky survey to date, ideal for identifying peaked-spectrum sources at low radio frequencies. Our peaked-spectrum sources are the low-frequency analogs of gigahertz-peaked spectrum (GPS) and compact-steep spectrum (CSS) sources, which have been hypothesized to be the precursors to massive radio galaxies. Our sample more than doubles the number of known peaked-spectrum candidates, and 95% of our sample have a newly characterized spectral peak. We highlight that some GPS sources peaking above 5 GHz have had multiple epochs of nuclear activity, and we demonstrate the possibility of identifying high-redshift (z > 2) galaxies via steep optically thin spectral indices and low observed peak frequencies. The distribution of the optically thick spectral indices of our sample is consistent with past GPS/CSS samples but with a large dispersion, suggesting that the spectral peak is a product of an inhomogeneous environment that is individualistic. We find no dependence of observed peak frequency with redshift, consistent with the peaked-spectrum sample comprising both local CSS sources and high-redshift GPS sources. The 5 GHz luminosity distribution lacks the brightest GPS and CSS sources of previous samples, implying that a convolution of source evolution and redshift influences the type of peaked-spectrum sources identified below 1 GHz. Finally, we discuss sources with optically thick spectral indices that exceed the synchrotron self-absorption limit.
The Red MSX Source (RMS) survey has identified a sample of ∼1200 massive young stellar objects (MYSOs), compact and ultra-compact H ii regions from a sample of ∼2000 MSX and Two Micron All Sky Survey ...(2MASS) colour-selected sources. We have used the 100-m Green Bank Telescope to search for 22-24 GHz water maser and ammonia (1,1), (2,2) and (3,3) emission towards ∼600 RMS sources located within the northern Galactic plane. We have identified 308 H2O masers which corresponds to an overall detection rate of ∼50 per cent. We find no significant difference in the detection rate for H ii regions and MYSOs which would suggest that the conditions required to produce maser emission are equally likely in both phases. Comparing the detection rates as a function of luminosity, we find the H2O detection rate has a positive dependence on the source luminosity, with the detection rate increasing with increasing luminosity.
We detect ammonia emission towards 479 of these massive young stars, which corresponds to ∼80 per cent. Ammonia is an excellent probe of high-density gas allowing us to measure key parameters such as gas temperatures, opacities and column densities, as well as providing an insight into the gas kinematics. The average kinetic temperature, full width at half-maximum linewidth and total NH3 column density for the sample are approximately 22 K, 2 km s−1 and 2 × 1015 cm−2, respectively. We find that the NH3 (1,1) linewidth and kinetic temperature are correlated with luminosity, and finding no underlying dependence of these parameters on the evolutionary phase of the embedded sources, we conclude that the observed trends in the derived parameters are more likely to be due to the energy output of the central source and/or the linewidth-clump mass relationship.
The velocities of the peak H2O masers and the NH3 emission are in excellent agreement with each other, which would strongly suggest an association between the dense gas and the maser emission. Moreover, we find the bolometric luminosity of the embedded source and the isotropic luminosity of the H2O maser are also correlated. We conclude from the correlations of the cloud and water maser velocities and the bolometric and maser luminosity that there is a strong dynamical relationship between the embedded young massive star and the H2O maser.
We present a detailed statistical study of massive star formation in the environment of 322 Spitzer mid-infrared bubbles by using the Red MSX Source (RMS) survey for massive young stellar objects ...(YSOs). Using a combination of simple surface density plots and a more sophisticated angular cross-correlation function analysis, we show that there is a statistically significant overdensity of RMS YSOs towards the bubbles. There is a clear peak in the surface density and angular cross-correlation function of YSOs projected against the rim of the bubbles. By investigating the autocorrelation function of the RMS YSOs, we show that this is not due to intrinsic clustering of the RMS YSO sample. RMS YSOs and Spitzer bubbles are essentially uncorrelated with each other beyond a normalized angular distance of two bubble radii. The bubbles associated with RMS YSOs tend to be both smaller and thinner than those that are not associated with YSOs. We interpret this tendency to be due to an age effect, with YSOs being preferentially found around smaller and younger bubbles. We find no evidence to suggest that the YSOs associated with the bubbles are any more luminous than the rest of the RMS YSO population, which suggests that the triggering process does not produce a top-heavy luminosity function or initial mass function. We suggest that it is likely that the YSOs were triggered by the expansion of the bubbles and estimate that the fraction of massive stars in the Milky Way formed by this process could be between 14 and 30 per cent.
In recent years, wide-field sky surveys providing deep multiband imaging have presented a new path for indirectly characterizing the progenitor populations of core-collapse supernovae (SNe): ...systematic light-curve studies. We assemble a set of 76 grizy-band Type IIP SN light curves from Pan-STARRS1, obtained over a constant survey program of 4 yr and classified using both spectroscopy and machine-learning-based photometric techniques. We develop and apply a new Bayesian model for the full multiband evolution of each light curve in the sample. We find no evidence of a subpopulation of fast-declining explosions (historically referred to as ''Type IIL'' SNe). However, we identify a highly significant relation between the plateau phase decay rate and peak luminosity among our SNe IIP. These results argue in favor of a single parameter, likely determined by initial stellar mass, predominantly controlling the explosions of red supergiants. This relation could also be applied for SN cosmology, offering a standardizable candle good to an intrinsic scatter of ≲ 0.2 mag. We compare each light curve to physical models from hydrodynamic simulations to estimate progenitor initial masses and other properties of the Pan-STARRS1 Type IIP SN sample. We show that correction of systematic discrepancies between modeled and observed SN IIP light-curve properties and an expanded grid of progenitor properties are needed to enable robust progenitor inferences from multiband light-curve samples of this kind. This work will serve as a pathfinder for photometric studies of core-collapse SNe to be conducted through future wide-field transient searches.
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