979 research outputs found
Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. III. Detection of Fe II Reverberation in Nine Narrow-Line Seyfert 1 Galaxies
This is the third in a series of papers reporting on a large
reverberation-mapping campaign aimed to study the properties of active galactic
nuclei (AGNs) with high accretion rates. We present new results on the
variability of the optical Fe II emission lines in 10 AGNs observed by the
Yunnan Observatory 2.4m telescope during 2012--2013. We detect statistically
significant time lags, relative to the AGN continuum, in nine of the sources.
This accurate measurement is achieved by using a sophisticated spectral fitting
scheme that allows for apparent flux variations of the host galaxy, and several
narrow lines, due to the changing observing conditions. Six of the newly
detected lags are indistinguishable from the Hbeta lags measured in the same
sources. Two are significantly longer and one is slightly shorter. Combining
with Fe II lags reported in previous studies, we find a Fe II
radius--luminosity relationship similar to the one for Hbeta, although our
sample by itself shows no clear correlation. The results support the idea that
Fe II emission lines originate in photoionized gas which, for the majority of
the newly reported objects, is indistinguishable from the Hbeta-emitting gas.
We also present a tentative correlation between the lag and intensity of Fe II
and Hbeta and comment on its possible origin.Comment: 14 pages, 10 figures, accepted for publication in The Astrophysical
Journa
galign: A Tool for Rapid Genome Polymorphism Discovery
BACKGROUND: Highly parallel sequencing technologies have become important tools in the analysis of sequence polymorphisms on a genomic scale. However, the development of customized software to analyze data produced by these methods has lagged behind. METHODS/PRINCIPAL FINDINGS: Here I describe a tool, 'galign', designed to identify polymorphisms between sequence reads obtained using Illumina/Solexa technology and a reference genome. The 'galign' alignment tool does not use Smith-Waterman matrices for sequence comparisons. Instead, a simple algorithm comparing parsed sequence reads to parsed reference genome sequences is used. 'galign' output is geared towards immediate user application, displaying polymorphism locations, nucleotide changes, and relevant predicted amino-acid changes for ease of information processing. To do so, 'galign' requires several accessory files easily derived from an annotated reference genome. Direct sequencing as well as in silico studies demonstrate that 'galign' provides lesion predictions comparable in accuracy to available prediction programs, accompanied by greater processing speed and more user-friendly output. We demonstrate the use of 'galign' to identify mutations leading to phenotypic consequences in C. elegans. CONCLUSION/SIGNIFICANCE: Our studies suggest that 'galign' is a useful tool for polymorphism discovery, and is of immediate utility for sequence mining in C. elegans
Characteristics of functionalized nano-hydroxyapatite and internalization by human epithelial cell
Hydroxyapatite is the main inorganic component of biological bone and tooth enamel, and synthetic hydroxyapatite has been widely used as biomaterials. In this study, a facile method has been developed for the fabrication of arginine-functionalized and europium-doped hydroxyapatite nanoparticles (Arg-Eu-HAP). The synthesized nanoparticles characterized by transmission electron microscopy, X-ray diffractometry, Fourier transform infrared, and Zeta potential analyzer. Its biological properties with DNA binding, cell toxicity, cell binding and intracellular distribution were tested by agarose gel electrophoresis assay, flow cytometry, and fluorescence microscope and laser scanning confocal microscope. The synthesized Arg-Eu-HAP could effectively bind DNA without any cytotoxicity and be internalized into the cytoplasm and perinuclear of human lung epithelial cells
A Cluster Method for the Ashkin--Teller Model
A cluster Monte Carlo algorithm for the Ashkin-Teller (AT) model is
constructed according to the guidelines of a general scheme for such
algorithms. Its dynamical behaviour is tested for the square lattice AT model.
We perform simulations on the line of critical points along which the exponents
vary continuously, and find that critical slowing down is significantly
reduced. We find continuous variation of the dynamical exponent along the
line, following the variation of the ratio , in a manner which
satisfies the Li-Sokal bound , that was so far
proved only for Potts models.Comment: 18 pages, Revtex, figures include
Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. IV. H Time Lags and Implications for Super-Eddington Accretion
We have completed two years of photometric and spectroscopic monitoring of a
large number of active galactic nuclei (AGNs) with very high accretion rates.
In this paper, we report on the result of the second phase of the campaign,
during 2013--2014, and the measurements of five new H time lags out of
eight monitored AGNs. All five objects were identified as super-Eddington
accreting massive black holes (SEAMBHs). The highest measured accretion rates
for the objects in this campaign are , where
,
is the mass accretion rates, is the Eddington luminosity and
is the speed of light. We find that the H time lags in SEAMBHs are
significantly shorter than those measured in sub-Eddington AGNs, and the
deviations increase with increasing accretion rates. Thus, the relationship
between broad-line region size () and optical luminosity at
5100\AA, , requires accretion rate as an additional
parameter. We propose that much of the effect may be due to the strong
anisotropy of the emitted slim-disk radiation. Scaling by
the gravitational radius of the black hole, we define a new radius-mass
parameter () and show that it saturates at a critical accretion rate of
, indicating a transition from thin to slim
accretion disk and a saturated luminosity of the slim disks. The parameter
is a very useful probe for understanding the various types of accretion onto
massive black holes. We briefly comment on implications to the general
population of super-Eddington AGNs in the universe and applications to
cosmology.Comment: 53 pages, 12 figures, 7 tables, accepted for publication in The
Astrophysical Journa
para-Selective C-H amidation of simple arenes with nitriles
A para-selective C-H amidation of simple arenes with nitriles has been developed. By increasing the amount of arenes, a further meta-selective C-H arylation of the produced amides occurred. Both steric and electronic effects are utilized to control the selectivity, resulting in only para-selective amidation products. The readily available nitriles as amidation reagents instead of amides makes the synthesis of N-arylamides more accessible
Video-based interventions to improve self-assessment accuracy among physicians: a systematic review
Purpose
Self-assessment of a physician’s performance in both procedure and non-procedural activities can be used to identify their deficiencies to allow for appropriate corrective measures. Physicians are inaccurate in their self-assessments, which may compromise opportunities for self- development. To improve this accuracy, video-based interventions of physicians watching their own performance, an experts’ performance or both, have been proposed to inform their self-assessment. We conducted a systematic review of the effectiveness of video-based interventions targeting improved self-assessment accuracy among physicians.
Materials and methods
The authors performed a systematic search of MEDLINE, Embase, EBM reviews, and Scopus databases from inception to August 23, 2022, using combinations of terms for “self-assessment”, “video-recording”, and “physician”. Eligible studies were empirical investigations assessing the effect of video-based interventions on physicians’ self-assessment accuracy with a comparison of self-assessment accuracy pre- and post- video intervention. We defined self-assessment accuracy as a “direct comparison between an external evaluator and self-assessment that was quantified using formal statistical analysis”. Two reviewers independently screened records, extracted data, assessed risk of bias, and evaluated quality of evidence. A narrative synthesis was conducted, as variable outcomes precluded a meta-analysis.
Results
A total of 2,376 papers were initially retrieved. Of these, 22 papers were selected for full-text review; a final 9 studies met inclusion criteria for data extraction. Across studies, 240 participants from 5 specialties were represented. Video-based interventions included self-video review (8/9), benchmark video review (3/9), and/or a combination of both types (1/9). Five out of nine studies reported that participants had inaccurate self-assessment at baseline. After the intervention, 5 of 9 studies found a statistically significant improvement in self-assessment accuracy.
Conclusions
Overall, current data suggests video-based interventions can improve self-assessment accuracy. Benchmark video review may enable physicians to improve self-assessment accuracy, especially for those with limited experience performing a particular clinical skill. In contrast, self-video review may be able to provide improvement in self-assessment accuracy for more experience physicians. Future research should use standardized methods of comparison for self-assessment accuracy, such as the Bland-Altman analysis, to facilitate meta-analytic summation
Global Protected Areas as refuges for amphibians and reptiles under climate change
Protected Areas (PAs) are the cornerstone of biodiversity conservation. Here, we collated distributional data for >14,000 (~70% of) species of amphibians and reptiles (herpetofauna) to perform a global assessment of the conservation effectiveness of PAs using species distribution models. Our analyses reveal that >91% of herpetofauna species are currently distributed in PAs, and that this proportion will remain unaltered under future climate change. Indeed, loss of species’ distributional ranges will be lower inside PAs than outside them. Therefore, the proportion of effectively protected species is predicted to increase. However, over 7.8% of species currently occur outside PAs, and large spatial conservation gaps remain, mainly across tropical and subtropical moist broadleaf forests, and across non-high-income countries. We also predict that more than 300 amphibian and 500 reptile species may go extinct under climate change over the course of the ongoing century. Our study highlights the importance of PAs in providing herpetofauna with refuge from climate change, and suggests ways to optimize PAs to better conserve biodiversity worldwide
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