A Tale of Two Populations: The Contribution of Merger and Secular Processes to the Evolution of Active Galactic Nuclei

Due to the co-evolution of supermassive black holes and their host galaxies, understanding the mechanisms that trigger active galactic nuclei (AGN) are imperative to understanding galaxy evolution and the formation of massive galaxies. It is observationally difficult to determine the trigger of a given AGN due to the difference between the AGN lifetime and triggering timescales. Here, we utilize AGN population synthesis modeling to determine the importance of different AGN triggering mechanisms. An AGN population model is computed by combining an observationally motivated AGN triggering rate and a theoretical AGN light curve. The free parameters of the AGN light curve are constrained by minimizing a \chi squared test with respect to the observed AGN hard X-ray luminosity function. The observed black hole space density, AGN number counts, and X-ray background spectrum are also considered as observational constraints. It is found that major mergers are not able to account for the entire AGN population. Therefore, non-merger processes, such as secular mechanisms, must also trigger AGN. Indeed, non-merger processes are the dominant AGN triggering mechanism at z \lesssim 1--1.5. Furthermore, the shape and evolution of the black hole mass function of AGN triggered by major mergers is intrinsically different from the shape and evolution of the black hole mass function of AGN triggered by secular processes.Comment: Accepted Ap

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Understanding the connection between active galactic nuclei and host star formation through multi-wavelength population synthesis modeling

Supermassive black holes, black holes with masses 1. I found that this is likely due to the dominant triggering mechanism of AGN switching from major mergers at z > 1.5 to secular processes by z ~ 1.PhDCommittee Chair: Ballantyne, David; Committee Member: Crenshaw, D. Michael; Committee Member: Laguna, Pablo; Committee Member: Taboada, Ignacio; Committee Member: Wise, Joh

Economic costs at age five associated with very preterm birth: multinational European cohort study

Background This study aims to estimate the economic costs of care provided to children born very preterm and extremely preterm across 11 European countries, and to understand what perinatal and socioeconomic factors contribute to higher costs. Methods Generalised linear modelling was used to explore the association between perinatal and sociodemographic characteristics and total economic costs (€, 2016 prices) during the fifth year of life. Results Lower gestational age was associated with increased mean societal costs of €2755 (p < 0.001), €752 (p < 0.01) and €657 (p < 0.01) for children born at < 26, 26–27 and 28–29 weeks, respectively, in comparison to the reference group born at 30–31 weeks. A sensitivity analyses that excluded variables (BPD, any neonatal morbidity and presence of congenital anomaly) plausibly lying on the causal pathway between gestational age at birth and economic outcomes elevated incremental societal costs by €1482, €763 and €144 at < 26, 26–27 and 28–29 weeks, respectively, in comparison to the baseline model. Conclusion This study provides new evidence about the main cost drivers associated with preterm birth in European countries. Evidence identified by this study can act as inputs within cost-effectiveness models for preventive or treatment interventions for preterm birth. Impact - What is the key message of your article? This study provides new evidence about the magnitude and drivers of economic costs associated with preterm birth in European countries. - What does it add to the existing literature? Lower gestational age is associated with increased mean societal costs during mid-childhood with indirect costs representing a key driver of increased costs. - What is the impact? For policy makers, this study adds to sparse evidence about the main cost drivers associated with preterm birth in European countries beyond the first 2 years of life

Health-related quality of life of children born very preterm: a multinational European cohort study

Purpose This study aims to (1) describe the health-related quality of life (HRQoL) outcomes experienced by children born very preterm (28–31 weeks’ gestation) and extremely preterm (< 28 weeks’ gestation) at five years of age and (2) explore the mediation effects of bronchopulmonary dysplasia (BPD) and severe non-respiratory neonatal morbidity on those outcomes. Methods This investigation was based on data for 3687 children born at < 32 weeks’ gestation that contributed to the EPICE and SHIPS studies conducted in 19 regions across 11 European countries. Descriptive statistics and multi-level ordinary linear squares (OLS) regression were used to explore the association between perinatal and sociodemographic characteristics and PedsQL™ GCS scores. A mediation analysis that applied generalised structural equation modelling explored the association between potential mediators and PedsQL™ GCS scores. Results The multi-level OLS regression (fully adjusted model) revealed that birth at < 26 weeks’ gestation, BPD status and experience of severe non-respiratory morbidity were associated with mean decrements in the total PedsQL™ GCS score of 0.35, 3.71 and 5.87, respectively. The mediation analysis revealed that the indirect effects of BPD and severe non-respiratory morbidity on the total PedsQL™ GCS score translated into decrements of 1.73 and 17.56, respectively, at < 26 weeks’ gestation; 0.99 and 10.95, respectively, at 26–27 weeks’ gestation; and 0.34 and 4.80, respectively, at 28–29 weeks’ gestation (referent: birth at 30–31 weeks’ gestation). Conclusion The findings suggest that HRQoL is particularly impaired by extremely preterm birth and the concomitant complications of preterm birth such as BPD and severe non-respiratory morbidity