26 research outputs found
Surrogate light curve models for kilonovae with comprehensive wind ejecta outflows and parameter estimation for AT2017gfo
The electromagnetic emission resulting from neutron star mergers have been
shown to encode properties of the ejected material in their light curves. The
ejecta properties inferred from the kilonova emission has been in tension with
those calculated based on the gravitational wave signal and numerical
relativity models. Motivated by this tension, we construct a broad set of
surrogate light curve models derived for kilonova ejecta. The four-parameter
family of two-dimensional anisotropic simulations and its associated surrogate
explore different assumptions about the wind outflow morphology and outflow
composition, keeping the dynamical ejecta component consistent. We present the
capabilities of these surrogate models in interpolating kilonova light curves
across various ejecta parameters and perform parameter estimation for AT2017gfo
both without any assumptions on the outflow and under the assumption that the
outflow must be representative of solar r-process abundance patterns. Our
parameter estimation for AT2017gfo shows these surrogate models help alleviate
the ejecta property discrepancy while also illustrating the impact of
systematic modeling uncertainties on these properties, urging further
investigation.Comment: 15 pages, 6 figures, data available in Zenodo
(https://zenodo.org/record/7335961) and GitHub
(https://github.com/markoris/surrogate_kne
Quantitative multiparametric magnetic resonance imaging can aid non-alcoholic steatohepatitis diagnosis in a Japanese cohort
Axisymmetric Radiative Transfer Models of Kilonovae
The detailed observations of GW170817 proved for the first time directly that
neutron star mergers are a major production site of heavy elements. The
observations could be fit by a number of simulations that qualitatively agree,
but can quantitatively differ (e.g. in total r-process mass) by an order of
magnitude. We categorize kilonova ejecta into several typical morphologies
motivated by numerical simulations, and apply a radiative transfer Monte Carlo
code to study how the geometric distribution of the ejecta shapes the emitted
radiation. We find major impacts on both spectra and light curves. The peak
bolometric luminosity can vary by two orders of magnitude and the timing of its
peak by a factor of five. These findings provide the crucial implication that
the ejecta masses inferred from observations around the peak brightness are
uncertain by at least an order of magnitude. Mixed two-component models with
lanthanide-rich ejecta are particularly sensitive to geometric distribution. A
subset of mixed models shows very strong viewing angle dependence due to
lanthanide "curtaining," which persists even if the relative mass of
lanthanide-rich component is small. The angular dependence is weak in the rest
of our models, but different geometric combinations of the two components lead
to a highly diverse set of light curves. We identify geometry-dependent {P
Cygni} features in late spectra that directly map out strong lines in the
simulated opacity of neodymium, which can help to constrain the ejecta geometry
and to directly probe the r-process abundances.Comment: 23 pages, 18 figures; accepted to Ap
CD or not CD, that is the question - a digital interobserver agreement study in coeliac disease
OBJECTIVE: Coeliac disease (CD) diagnosis generally depends on histological examination of duodenal biopsies. We present the first study analysing the concordance in examination of duodenal biopsies using digitised whole-slide images (WSIs). We further investigate whether the inclusion of IgA tTG and haemoglobin (Hb) data improves the inter-observer agreement of diagnosis.DESIGN: We undertook a large study of the concordance in histological examination of duodenal biopsies using digitised WSIs in an entirely virtual reporting setting. Our study was organised in two phases: in phase one, 13 pathologists independently classified 100 duodenal biopsies (40 normal; 40 CD; 20 indeterminate enteropathy) in the absence of any clinical or laboratory data. In phase two, the same pathologists examined the (re-anonymised) WSIs with the inclusion of IgA tTG and Hb data.RESULTS: We found the mean probability of two observers agreeing in the absence of additional data to be 0.73 (±0.08) with a corresponding Cohen's kappa of 0.59 (±0.11). We further showed that the inclusion of additional data increased the concordance to 0.80 (±0.06) with a Cohen's kappa coefficient of 0.67 (±0.09).CONCLUSION: We showed that the addition of serological data significantly improves the quality of CD diagnosis. However, the limited inter-observer agreement in CD diagnosis using digitised WSIs, even after the inclusion of IgA tTG and Hb data, indicates the important of interpreting duodenal biopsy in the appropriate clinical context. It further highlights the unmet need for an objective means of reproducible duodenal biopsy diagnosis, such as the automated analysis of WSIs using AI.<br/
Role of digital pathology in diagnostic histopathology in the response to COVID-19: results from a survey of experience in a UK tertiary referral hospital
The COVID-19 pandemic has challenged our diagnostic
services at a time when many histopathology
departments already faced a diminishing workforce and
increasing workload. Digital pathology (DP) has been
hailed as a potential solution to at least some of the
challenges faced. We present a survey of pathologists
within a UK National Health Service cellular pathology
department with access to DP, in which we ascertain
the role of DP in clinical services during this current
pandemic and explore challenges encountered. This
survey indicates an increase in uptake of diagnostic DP
during this period, with increased remote access. Half of
respondents agreed that DP had facilitated maintenance
of diagnostic practice. While challenges have been
encountered, these are remediable, and none have
impacted on the uptake of DP during this period. We
conclude that in our institution, DP has demonstrated
current and future potential to increase resilience in
diagnostic practice and have highlighted some of the
challenges that need to be considered