14 research outputs found
The rapid assessment of aggregated wastewater samples for genomic surveillance of sars-cov-2 on a city-wide scale
Throughout the course of the ongoing SARS-CoV-2 pandemic there has been a need for approaches that enable rapid monitoring of public health using an unbiased and minimally invasive means. A major way this has been accomplished is through the regular assessment of wastewater samples by qRT-PCR to detect the prevalence of viral nucleic acid with respect to time and location. Further expansion of SARS-CoV-2 wastewater monitoring efforts to include the detection of variants of interest/concern through next-generation sequencing has enhanced the understanding of the SARS-CoV-2 outbreak. In this report, we detail the results of a collaborative effort between public health and metropolitan wastewater management authorities and the University of Louisville to monitor the SARS-CoV-2 pandemic through the monitoring of aggregate wastewater samples over a period of 28 weeks. Through the use of next-generation sequencing approaches the polymorphism signatures of Variants of Concern / Interest were evaluated to determine the likelihood of their prevalence within the community on the basis of their relative dominance within sequence datasets. Our data indicate that wastewater monitoring of water quality treatment centers and smaller neighbor-hood-scale catchment areas is a viable means by which the prevalence and genetic variation of SARS-CoV-2 within a metropolitan community of approximately one million individuals may be monitored, as our efforts detected the introduction and emergence of variants of concern in the city of Louisville. Importantly, these efforts confirm that regional emergence and spread of variants of interest/concern may be detected as readily in aggregate wastewater samples as compared to the individual wastewater sheds. Furthermore, the information gained from these efforts enabled targeted public health efforts including increased outreach to at-risk communities and the deployment of mobile or community-focused vaccination campaigns
The Sloan Digital Sky Survey Reverberation Mapping Project : how broad emission line widths change when luminosity changes
Funding: National Science Foundation of China (11721303, 11890693, 11991052) and the National Key R&D Program of China (2016YFA0400702, 2016YFA0400703). YS acknowledges support from an Alfred P. Sloan Research Fellowship and NSF grant AST-1715579. CJG, WNB, JRT, and DPS acknowledge support from NSF grants AST-1517113 and AST-1516784. KH acknowledges support from STFC grant ST/R000824/1. PBH acknowledges support from NSERC grant 2017-05983. YH acknowledges support from NASA grant HST-GO-15650.Quasar broad emission lines are largely powered by photoionization from the accretion continuum. Increased central luminosity will enhance line emissivity in more distant clouds, leading to increased average distance of the broad-line-emitting clouds and decreased averaged line width, known as the broad-line region (BLR) "breathing". However, different lines breathe differently, and some high-ionization lines, such as C IV, can even show "anti-breathing" where the line broadens when luminosity increases. Using multi-year photometric and spectroscopic monitoring data from the Sloan Digital Sky Survey Reverberation Mapping project, we quantify the breathing effect (Îlog W=αÎlog L) of broad Hα, HÎČ, Mg II, C IV,and C III] for statistical quasar samples over zâ0.1â2.5. We found that HÎČ displays the most consistent normal breathing expected from the virial relation (αâŒâ0.25), Mg II and Hα on average show no breathing (αâŒ0), and C IV (and similarly C III] and Si IV mostly shows anti-breathing (α>0). The anti-breathing of C IV can be well understood by the presence of a non-varying core component in addition to a reverberating broad-base component, consistent with earlier findings. The deviation from canonical breathing introduces extra scatter (aluminosity-dependent bias) in single-epoch virial BH mass estimates due to intrinsic quasar variability, which underlies the long argued caveats of C IV single-epoch masses. Using the line dispersion instead of FWHM leads to less, albeit still substantial, deviations from canonical breathing in most cases. Our results strengthen the need for reverberation mapping to provide reliable quasar BH masses, and quantify the level of variability-induced bias in single-epoch BH masses based on various lines.PostprintPeer reviewe
Citizenship and Identity: the self-image of secondary school students in England and Catalonia
© 2015 Society for Educational Studies We discuss the ways in which English and Catalan students perceive themselves as members of communities and as citizens and the role of schools in these perceptions. Questionnaire and interview data were collected and analysed from 583 secondary school students in a total of 9 schools that were known for their commitment to citizenship education in England and Catalonia. The research took place when issues of national and other identities were prominently discussed in the media and elsewhere and when significant changes were being introduced in both locations regarding citizenship education as a specific curriculum subject and also in the wider context of education and schooling. Our results suggest that while the English students in our sample understand citizenship in terms of a subjective identification, our Catalan students perceive citizenship as a legal and externally assigned status. We did not intend to obtain nationally representative samples but rather to gain in-depth knowledge of the data and to discuss the implications of these results for the differing purposes of citizenship education. We make recommendations for how school-based citizenship education may contribute to current challenges related to citizenship and identities
The Sloan Digital Sky Survey Reverberation Mapping project : photometric g and i light curves
Funding: P.H. acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), funding reference number 2017-05983. C.J.G., W.N.B., and D.P.S. acknowledge support from NSF grant AST-1517113. Y.S. acknowledges support from an Alfred P. Sloan Research Fellowship and NSF grant AST-1715579. L.C.H. acknowledges the National Key R&D Program of China (2016YFA0400702) and the National Science Foundation of China (11721303, 11991052). J.V.H.S. and K.H. acknowledge support from a STFC grant ST/R000824/1. C.S.K. is supported by NSF grants AST-1814440 and AST-1908570.The Sloan Digital Sky Survey (SDSS) Reverberation Mapping program monitors 849 active galactic nuclei (AGNs) both spectroscopically and photometrically. The photometric observations used in this work span over 4 yr and provide an excellent baseline for variability studies of these objects. We present the photometric light curves from 2014 to 2017 obtained by the Steward Observatory's Bok telescope and the Canada-France-Hawaii telescope with MegaCam. We provide details on the data acquisition and processing of the data from each telescope, the difference imaging photometry used to produce the light curves, and the calculation of a variability index to quantify each AGN's variability. We find that the Welch-Stetson J index provides a useful characterization of AGN variability and can be used to select AGNs for further study.PostprintPeer reviewe
UV/Optical disk reverberation lags despite a faint X-ray corona in the AGN Mrk 335
We present the first results from a 100-day Swift, NICER and ground-based
X-ray/UV/optical reverberation mapping campaign of the Narrow-Line Seyfert 1
Mrk 335, when it was in an unprecedented low X-ray flux state. Despite dramatic
suppression of the X-ray variability, we still observe UV/optical lags as
expected from disk reverberation. Moreover, the UV/optical lags are consistent
with archival observations when the X-ray luminosity was >10 times higher.
Interestingly, both low- and high-flux states reveal UV/optical lags that are
6-11 times longer than expected from a thin disk. These long lags are often
interpreted as due to contamination from the broad line region, however the u
band excess lag (containing the Balmer jump from the diffuse continuum) is less
prevalent than in other AGN. The Swift campaign showed a low X-ray-to-optical
correlation (similar to previous campaigns), but NICER and ground-based
monitoring continued for another two weeks, during which the optical rose to
the highest level of the campaign, followed ~10 days later by a sharp rise in
X-rays. While the low X-ray countrate and relatively large systematic
uncertainties in the NICER background make this measurement challenging, if the
optical does lead X-rays in this flare, this indicates a departure from the
zeroth-order reprocessing picture. If the optical flare is due to an increase
in mass accretion rate, this occurs on much shorter than the viscous timescale.
Alternatively, the optical could be responding to an intrinsic rise in X-rays
that is initially hidden from our line-of-sight.Comment: Accepted for publication in the Astrophysical Journal. 15 pages, 8
figures, 3 table
AGN STORM 2. I. First results: A Change in the Weather of Mrk 817
We present the first results from the ongoing, intensive, multiwavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817. While this active galactic nucleus was, in part, selected for its historically unobscured nature, we discovered that the X-ray spectrum is highly absorbed, and there are new blueshifted, broad, and narrow UV absorption lines, which suggest that a dust-free, ionized obscurer located at the inner broad-line region partially covers the central source. Despite the obscuration, we measure UV and optical continuum reverberation lags consistent with a centrally illuminated ShakuraâSunyaev thin accretion disk, and measure reverberation lags associated with the optical broad-line region, as expected. However, in the first 55 days of the campaign, when the obscuration was becoming most extreme, we observe a de-coupling of the UV continuum and the UV broad emission-line variability. The correlation recovered in the next 42 days of the campaign, as Mrk 817 entered a less obscured state. The short C IV and Lyα lags suggest that the accretion disk extends beyond the UV broad-line region. Unified
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure
Trace metal distribution in the bed, bank and suspended sediment of the Ravensbourne River and its implication for sediment monitoring in an urban river
Purpose This study aims to identify a suitable sediment compartment for sediment quality monitoring by: (a) studying the concentration of trace metals (Cd, Cu, Ni, Pb and Zn) in the bed, bank and suspended sediment compartments of the Ravensbourne River to establish any differences in trace metal concentrations with compartment; (b) determining the influence of sediment particle size fractions (â0.05) in the concentrations of metals between the suspended sediment and the <â63 ÎŒm bed sediment fraction, but there was a significant difference (pâ<â0.05) between the suspended sediment and the <â63 ÎŒm bank sediment fraction. There were also significant differences between the concentrations of metals in the <â63 ÎŒm and the 63 ÎŒmâ2 mm fractions. Generally, the Ravensbourne River did not comply with the draft UK sediment quality guidelines for the metals analysed. Conclusions This study shows the importance of identifying a suitable sediment compartment to sample for compliance with sediment quality standards. The bed and suspended sediments are the most widely used sediment compartments for sediment monitoring, but collecting sufficient mass of the <â63 ÎŒm sediment fraction for monitoring presents a challenge for urban gravel bed rivers like the Ravensbourne River. It seems appropriate to establish individual monitoring regimes for different rivers
Quantifying the relationship between sub-population wastewater samples and community-wide SARS-CoV-2 seroprevalence
Robust epidemiological models relating wastewater to community disease prevalence are lacking. Assessments of SARS-CoV-2 infection rates have relied primarily on convenience sampling, which does not provide reliable estimates of community disease prevalence due to inherent biases. This study conducted serial stratified randomized samplings to estimate the prevalence of SARS-CoV-2 antibodies in 3717 participants, and obtained weekly samples of community wastewater for SARS-CoV-2 concentrations in Jefferson County, KY (USA) from August 2020 to February 2021. Using an expanded Susceptible-Infected-Recovered model, the longitudinal estimates of the disease prevalence were ob-tained and compared with the wastewater concentrations using regression analysis. The model analysis revealed sig-nificant temporal differences in epidemic peaks. The results showed that in some areas, the average incidence rate, based on serological sampling, was 50 % higher than the health department rate, which was based on convenience sampling. The model-estimated average prevalence rates correlated well with the wastewater (correlation = 0.63, CI (0.31,0.83)). In the regression analysis, a one copy per ml-unit increase in weekly average wastewater concentration of SARS-CoV-2 corresponded to an average increase of 1-1.3 cases of SARS-CoV-2 infection per 100,000 residents. The analysis indicates that wastewater may provide robust estimates of community spread of infection, in line with the modeled prevalence estimates obtained from stratified randomized sampling, and is therefore superior to publicly available health data.11Nsciescopu