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Results from EDGES High-Band. III. New Constraints on Parameters of the Early Universe
We present new constraints on parameters of cosmic dawn and the epoch of
reionization derived from the EDGES High-Band spectrum ( MHz). The
parameters are probed by evaluating global cm signals generated with the
recently developed Global21cm tool. This tool uses neural networks trained and
tested on spectra produced with semi-numerical simulations that
assume the standard thermal evolution of the cosmic microwave background and
the intergalactic medium. From our analysis, we constrain at (1) the
minimum virial circular velocity of star-forming halos to km
s, (2) the X-ray heating efficiency of early sources to , and (3) the low-energy cutoff of the X-ray spectral energy
distribution to keV. We also constrain the star-formation
efficiency (), the electron scattering optical depth (), and
the mean-free path of ionizing photons (). We re-compute the
constraints after incorporating into the analysis four estimates for the
neutral hydrogen fraction from high- quasars and galaxies, and a prior on
from Planck . The largest impact of the external
observations is on the parameters that most directly characterize reionization.
Specifically, we derive the combined constraints
and Mpc. The external observations also have a significant
effect on due to its degeneracy with , while the
constraints on , , and , remain primarily
determined by EDGES
Genomic epidemiology of SARS-CoV-2 in a UK university identifies dynamics of transmission
Understanding SARS-CoV-2 transmission in higher education settings is important to limit spread between students, and into at-risk populations. In this study, we sequenced 482 SARS-CoV-2 isolates from the University of Cambridge from 5 October to 6 December 2020. We perform a detailed phylogenetic comparison with 972 isolates from the surrounding community, complemented with epidemiological and contact tracing data, to determine transmission dynamics. We observe limited viral introductions into the university; the majority of student cases were linked to a single genetic cluster, likely following social gatherings at a venue outside the university. We identify considerable onward transmission associated with student accommodation and courses; this was effectively contained using local infection control measures and following a national lockdown. Transmission clusters were largely segregated within the university or the community. Our study highlights key determinants of SARS-CoV-2 transmission and effective interventions in a higher education setting that will inform public health policy during pandemics