202 research outputs found
Comparison of accuracy of fibrosis degree classifications by liver biopsy and non-invasive tests in chronic hepatitis C
<p>Abstract</p> <p>Background</p> <p>Non-invasive tests have been constructed and evaluated mainly for binary diagnoses such as significant fibrosis. Recently, detailed fibrosis classifications for several non-invasive tests have been developed, but their accuracy has not been thoroughly evaluated in comparison to liver biopsy, especially in clinical practice and for Fibroscan. Therefore, the main aim of the present study was to evaluate the accuracy of detailed fibrosis classifications available for non-invasive tests and liver biopsy. The secondary aim was to validate these accuracies in independent populations.</p> <p>Methods</p> <p>Four HCV populations provided 2,068 patients with liver biopsy, four different pathologist skill-levels and non-invasive tests. Results were expressed as percentages of correctly classified patients.</p> <p>Results</p> <p>In population #1 including 205 patients and comparing liver biopsy (reference: consensus reading by two experts) and blood tests, Metavir fibrosis (F<sub>M</sub>) stage accuracy was 64.4% in local pathologists vs. 82.2% (p < 10<sup>-3</sup>) in single expert pathologist. Significant discrepancy (≥ 2F<sub>M </sub>vs reference histological result) rates were: Fibrotest: 17.2%, FibroMeter<sup>2G</sup>: 5.6%, local pathologists: 4.9%, FibroMeter<sup>3G</sup>: 0.5%, expert pathologist: 0% (p < 10<sup>-3</sup>). In population #2 including 1,056 patients and comparing blood tests, the discrepancy scores, taking into account the error magnitude, of detailed fibrosis classification were significantly different between FibroMeter<sup>2G </sup>(0.30 ± 0.55) and FibroMeter<sup>3G </sup>(0.14 ± 0.37, p < 10<sup>-3</sup>) or Fibrotest (0.84 ± 0.80, p < 10<sup>-3</sup>). In population #3 (and #4) including 458 (359) patients and comparing blood tests and Fibroscan, accuracies of detailed fibrosis classification were, respectively: Fibrotest: 42.5% (33.5%), Fibroscan: 64.9% (50.7%), FibroMeter<sup>2G</sup>: 68.7% (68.2%), FibroMeter<sup>3G</sup>: 77.1% (83.4%), p < 10<sup>-3 </sup>(p < 10<sup>-3</sup>). Significant discrepancy (≥ 2 F<sub>M</sub>) rates were, respectively: Fibrotest: 21.3% (22.2%), Fibroscan: 12.9% (12.3%), FibroMeter<sup>2G</sup>: 5.7% (6.0%), FibroMeter<sup>3G</sup>: 0.9% (0.9%), p < 10<sup>-3 </sup>(p < 10<sup>-3</sup>).</p> <p>Conclusions</p> <p>The accuracy in detailed fibrosis classification of the best-performing blood test outperforms liver biopsy read by a local pathologist, i.e., in clinical practice; however, the classification precision is apparently lesser. This detailed classification accuracy is much lower than that of significant fibrosis with Fibroscan and even Fibrotest but higher with FibroMeter<sup>3G</sup>. FibroMeter classification accuracy was significantly higher than those of other non-invasive tests. Finally, for hepatitis C evaluation in clinical practice, fibrosis degree can be evaluated using an accurate blood test.</p
Now You See It, Now You Don't: The Disappearing Central Engine of the Quasar J1011+5442
We report the discovery of a new "changing-look" quasar, SDSS
J101152.98+544206.4, through repeat spectroscopy from the Time Domain
Spectroscopic Survey. This is an addition to a small but growing set of quasars
whose blue continua and broad optical emission lines have been observed to
decline by a large factor on a time scale of approximately a decade. The 5100
Angstrom monochromatic continuum luminosity of this quasar drops by a factor of
> 9.8 in a rest-frame time interval of < 9.7 years, while the broad H-alpha
luminosity drops by a factor of 55 in the same amount of time. The width of the
broad H-alpha line increases in the dim state such that the black hole mass
derived from the appropriate single-epoch scaling relation agrees between the
two epochs within a factor of 3. The fluxes of the narrow emission lines do not
appear to change between epochs. The light curve obtained by the Catalina Sky
Survey suggests that the transition occurs within a rest-frame time interval of
approximately 500 days. We examine three possible mechanisms for this
transition suggested in the recent literature. An abrupt change in the
reddening towards the central engine is disfavored by the substantial
difference between the timescale to obscure the central engine and the observed
timescale of the transition. A decaying tidal disruption flare is consistent
with the decay rate of the light curve but not with the prolonged bright state
preceding the decay, nor can this scenario provide the power required by the
luminosities of the emission lines. An abrupt drop in the accretion rate onto
the supermassive black hole appears to be the most plausible explanation for
the rapid dimming.Comment: Submitted to MNRA
Towards an Understanding of Changing-Look Quasars: An Archival Spectroscopic Search in SDSS
The uncertain origin of the recently-discovered `changing-looking' quasar
phenomenon -- in which a luminous quasar dims significantly to a quiescent
state in repeat spectroscopy over ~10 year timescales -- may present unexpected
challenges to our understanding of quasar accretion. To better understand this
phenomenon, we take a first step to building a sample of changing-look quasars
with a systematic but simple archival search for these objects in the Sloan
Digital Sky Survey Data Release 12. By leveraging the >10 year baselines for
objects with repeat spectroscopy, we uncover two new changing-look quasars, and
a third discovered previously. Decomposition of the multi-epoch spectra and
analysis of the broad emission lines suggest that the quasar accretion disk
emission dims due to rapidly decreasing accretion rates (by factors of >2.5),
while disfavoring changes in intrinsic dust extinction for the two objects
where these analyses are possible. Broad emission line energetics also support
intrinsic dimming of quasar emission as the origin for this phenomenon rather
than transient tidal disruption events or supernovae. Although our search
criteria included quasars at all redshifts and transitions from either
quasar-like to galaxy-like states or the reverse, all of the clear cases of
changing-look quasars discovered were at relatively low-redshift (z ~ 0.2 -
0.3) and only exhibit quasar-like to galaxy-like transitions.Comment: 15 pages, 8 figures. Updated to accepted versio
Welcome to the Twilight Zone: The Mid-Infrared Properties of Poststarburst Galaxies
We investigate the optical and Wide-field Survey Explorer (WISE) colors of
"E+A" identified post-starburst galaxies, including a deep analysis on 190
post-starbursts detected in the 2{\mu}m All Sky Survey Extended Source Catalog.
The post-starburst galaxies appear in both the optical green valley and the
WISE Infrared Transition Zone (IRTZ). Furthermore, we find that post-starbursts
occupy a distinct region [3.4]-[4.6] vs. [4.6]-[12] WISE colors, enabling the
identification of this class of transitioning galaxies through the use of
broad-band photometric criteria alone. We have investigated possible causes for
the WISE colors of post-starbursts by constructing a composite spectral energy
distribution (SED), finding that mid-infrared (4-12{\mu}m) properties of
post-starbursts are consistent with either 11.3{\mu}m polycyclic aromatic
hydrocarbon emission, or Thermally Pulsating Asymptotic Giant Branch (TP-AGB)
and post-AGB stars. The composite SED of extended post- starburst galaxies with
22{\mu}m emission detected with signal to noise >3 requires a hot dust
component to produce their observed rising mid-infrared SED between 12 and
22{\mu}m. The composite SED of WISE 22{\mu}m non-detections (S/N<3), created by
stacking 22{\mu}m images, is also flat, requiring a hot dust component. The
most likely source of this mid-infrared emission of these E+A galaxies is a
buried active galactic nucleus. The inferred upper limit to the Eddington
ratios of post-starbursts are 1e-2 to 1e-4, with an average of 1e-3. This
suggests that AGNs are not radiatively dominant in these systems. This could
mean that including selections able to identify active galactic nuclei as part
of a search for transitioning and post-starburst galaxies would create a more
complete census of the transition pathways taken as a galaxy quenches its star
formation.Comment: 13 pages, 11 figures, accepted for publication in the Astrophysical
Journa
SHOCKED POSTSTARBURST GALAXY SURVEY. II. the MOLECULAR GAS CONTENT and PROPERTIES of A SUBSET of SPOGs
We present CO(1–0) observations of objects within the Shocked POststarburst Galaxy Survey taken with the Institut de Radioastronomie Millimétrique 30 m single dish and the Combined Array for Research for Millimeter Astronomy interferometer. Shocked poststarburst galaxies (SPOGs) represent a transitioning population of galaxies, with deep Balmer absorption , consistent with an intermediate-age (A-star) stellar population, and ionized gas line ratios inconsistent with pure star formation. The CO(1–0) subsample was selected from SPOGs detected by the Wide-field Infrared Survey Explorer with 22 μm flux detected at a signal-to-noise ratio (S/N) > 3. Of the 52 objects observed in CO(1–0), 47 are detected with S/N > 3. A large fraction (37%–46% ± 7%) of our CO-SPOG sample were visually classified as morphologically disrupted. The H2 masses detected were between , consistent with the gas masses found in normal galaxies, though approximately an order of magnitude larger than the range seen in poststarburst galaxies. When comparing the 22 μm and CO(1–0) fluxes, SPOGs diverge from the normal star-forming relation, having 22 μm fluxes in excess of the relation by a factor of , suggestive of the presence of active galactic nuclei (AGNs). The Na i D characteristics of CO-SPOGs show that it is likely that many of these objects host interstellar winds. Objects with large Na i D enhancements also tend to emit in the radio, suggesting possible AGN driving of neutral winds
Suppression of Star Formation in NGC 1266
NGC1266 is a nearby lenticular galaxy that harbors a massive outflow of molecular gas powered by the mechanical energy of an active galactic nucleus (AGN). It has been speculated that such outflows hinder star formation (SF) in their host galaxies, providing a form of feedback to the process of galaxy formation. Previous studies, however, indicated that only jets from extremely rare, high power quasars or radio galaxies could impart significant feedback on their hosts. Here we present detailed observations of the gas and dust continuum of NGC1266 at millimeter wavelengths. Our observations show that molecular gas is being driven out of the
nuclear region at Ṁ_(out) ≈ 110M_⊙ yr^(−1), of which the vast majority cannot escape the nucleus. Only 2M_⊙ yr^(−1)
is actually capable of escaping the galaxy. Most of the molecular gas that remains is very inefficient at forming
stars. The far-infrared emission is dominated by an ultra-compact (≾50 pc) source that could either be powered
by an AGN or by an ultra-compact starburst. The ratio of the SF surface density (Σ_(SFR)) to the gas surface
density (Σ_(H2)) indicates that SF is suppressed by a factor of ≈ 50 compared to normal star-forming galaxies if
all gas is forming stars, and ≈150 for the outskirt (98%) dense molecular gas if the central region is is powered
by an ultra-compact starburst. The AGN-driven bulk outflow could account for this extreme suppression by
hindering the fragmentation and gravitational collapse necessary to form stars through a process of turbulent
injection. This result suggests that even relatively common, low-power AGNs are able to alter the evolution of
their host galaxies as their black holes grow onto the M-σ relation
Determinants of parents' reticence toward vaccination in urban areas in Benin (West Africa)
Analysis of the data reveals those who are vaccination-reticent say it goes against the will of God, that it is a poison from the “white witch doctor,” and a sin. Members of the control group argued against this, but without conviction. They adhere to the principle of obedience to authority, a biblical precept invoked when the vaccinators oblige them to vaccinate their children. To limit the spread of this phenomenon among the religious population of the cities like Parakou and Cotonou in Benin, more detailed information and negotiation between health authorities and pastors of the churches are essential
Liver Stiffness Measurement and Biochemical Markers in Senegalese Chronic Hepatitis B Patients with Normal ALT and High Viral Load
Despite the high prevalence of chronic hepatitis B (CHB) in Africa, few studies have been performed among African patients. We sought to evaluate liver stiffness measurement by FibroScan® (LSM) and two biochemical scores (FibroTest®, Fibrometer®) to diagnose liver fibrosis in Senegalese CHB patients with HBV plasma DNA load ≥3.2 log(10) IU/mL and normal alanine aminotransferase (ALT) values.LSM and liver fibrosis biochemical markers were performed on 225 consecutive HBV infected Senegalese patients with high viral load. Patients with an LSM range between 7 and 13 kPa underwent liver biopsy (LB). Two experienced liver pathologists performed histological grading using Metavir and Ishak scoring.225 patients were evaluated (84% male) and LB was performed in 69 patients, showing F2 and F3 fibrosis in 17% and 10% respectively. In these patients with a 7-13 kPa range of LSM, accuracy for diagnosis of significant fibrosis according to LB was unsatisfactory for all non-invasive markers with AUROCs below 0.70. For patients with LSM values below 7 kPa, FibroTest® (FT), and Fibrometer® (FM) using the cut-offs recommended by the test promoters suggested a fibrosis in 18% of cases for FT (8% severe fibrosis) and 8% for FM. For patients with LSM values greater than 13 kPa, FT, FM suggested a possible fibrosis in 73% and 70%, respectively.In highly replicative HBV-infected African patients with normal ALT and LSM value below 13 kPa, FibroScan®, FibroTest® or Fibrometer® were unsuitable to predict the histological liver status of fibrosis
Future mmVLBI Research with ALMA: a European vision
Very long baseline interferometry at millimetre/submillimetre wavelengths (mmVLBI) offers the highest achievable spatial resolution at any wavelength in astronomy. The anticipated inclusion of ALMA as a phased array into a global VLBI network will bring unprecedented sensitivity and a transformational leap in capabilities for mmVLBI. Building on years of pioneering efforts in the US and Europe the ongoing ALMA Phasing Project (APP), a US-led international collaboration with MPIfR-led European contributions, is expected to deliver a beamformer and VLBI capability to ALMA by the end of 2014 (APP: Fish et al. 2013, arXiv:1309.3519). This report focuses on the future use of mmVLBI by the international users community from a European viewpoint. Firstly, it highlights the intense science interest in Europe in future mmVLBI observations as compiled from the responses to a general call to the European community for future research projects. A wide range of research is presented that includes, amongst others: - Imaging the event horizon of the black hole at the centre of the Galaxy - Testing the theory of General Relativity an/or searching for alternative theories - Studying the origin of AGN jets and jet formation - Cosmological evolution of galaxies and BHs, AGN feedback - Masers in the Milky Way (in stars and star-forming regions) - Extragalactic emission lines and astro-chemistry - Redshifted absorption lines in distant galaxies and study of the ISM and circumnuclear gas - Pulsars, neutron stars, X-ray binaries - Testing cosmology - Testing fundamental physical constant
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