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| 22. |
- Broderick, Avery E., et al.
(författare)
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Characterizing and Mitigating Intraday Variability: Reconstructing Source Structure in Accreting Black Holes with mm-VLBI
- 2022
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
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Tidskriftsartikel (refereegranskat)abstract
- The extraordinary physical resolution afforded by the Event Horizon Telescope has opened a window onto the astrophysical phenomena unfolding on horizon scales in two known black holes, M87* and Sgr A*. However, with this leap in resolution has come a new set of practical complications. Sgr A* exhibits intraday variability that violates the assumptions underlying Earth aperture synthesis, limiting traditional image reconstruction methods to short timescales and data sets with very sparse (u, v) coverage. We present a new set of tools to detect and mitigate this variability. We develop a data-driven, model-agnostic procedure to detect and characterize the spatial structure of intraday variability. This method is calibrated against a large set of mock data sets, producing an empirical estimator of the spatial power spectrum of the brightness fluctuations. We present a novel Bayesian noise modeling algorithm that simultaneously reconstructs an average image and statistical measure of the fluctuations about it using a parameterized form for the excess variance in the complex visibilities not otherwise explained by the statistical errors. These methods are validated using a variety of simulated data, including general relativistic magnetohydrodynamic simulations appropriate for Sgr A* and M87*. We find that the reconstructed source structure and variability are robust to changes in the underlying image model. We apply these methods to the 2017 EHT observations of M87*, finding evidence for variability across the EHT observing campaign. The variability mitigation strategies presented are widely applicable to very long baseline interferometry observations of variable sources generally, for which they provide a data-informed averaging procedure and natural characterization of inter-epoch image consistency.
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| 23. |
- Cai, Jing, et al.
(författare)
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Elucidating the mechanisms of atmospheric new particle formation in the highly polluted Po Valley, Italy
- 2024
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Ingår i: Atmospheric Chemistry and Physics. - 1680-7316 .- 1680-7324. ; 24:4, s. 2423-2441
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Tidskriftsartikel (refereegranskat)abstract
- New particle formation (NPF) is a major source of aerosol particles and cloud condensation nuclei in the troposphere, playing an important role in both air quality and climate. Frequent NPF events have been observed in heavily polluted urban environments, contributing to the aerosol number concentration by a significant amount. The Po Valley region in northern Italy has been characterized as a hotspot for high aerosol loadings and frequent NPF events in southern Europe. However, the mechanisms of NPF and growth in this region are not completely understood. In this study, we conducted a continuous 2-month measurement campaign with state-of-the-art instruments to elucidate the NPF and growth mechanisms in northern Italy. Our results demonstrate that frequent NPF events (66% of all days during the measurement campaign) are primarily driven by abundant sulfuric acid (8.5×106cm-3) and basic molecules in this area. In contrast, oxygenated organic molecules from the atmospheric oxidation of volatile organic compounds (VOCs) appear to play a minor role in the initial cluster formation but contribute significantly to the consecutive growth process. Regarding alkaline molecules, amines are insufficient to stabilize all sulfuric acid clusters in the Po Valley. Ion cluster measurements and kinetic models suggest that ammonia (10ppb) must therefore also play a role in the nucleation process. Generally, the high formation rates of sub-2nm particles (87cm-3s-1) and nucleation-mode growth rates (5.1nmh-1) as well as the relatively low condensational sink (8.9×10-3s-1) will result in a high survival probability for newly formed particles, making NPF crucial for the springtime aerosol number budget. Our results also indicate that reducing key pollutants, such as SO2, amine and NH3, could help to substantially decrease the particle number concentrations in the Po Valley region.
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| 24. |
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| 25. |
- Cheng, Kaiyuan, et al.
(författare)
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Injectable tricalcium phosphate/calcium sulfate granule enhances bone repair by reversible setting reaction
- 2021
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier. - 0006-291X .- 1090-2104. ; 557, s. 151-158
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Tidskriftsartikel (refereegranskat)abstract
- Towards repairing bone defects, calcium sulfate and calcium phosphate cement have been recognized as promising bone grafts. However, the current bone cements are generally lack of proper porosity for cell migration and new tissue formation. On the other hand, porous scaffold cannot be delivered by injection, which limits its use its clinical use. Herein, we develop a novel tricalcium phosphate/calcium sulfate granule to overcome the limitations of injectable cements and traditional scaffolds. The biocompatible granule underwent in situ self-setting to form scaffold with porous structure after injection. It con-tributes to calcium deposition and upregulation of osteogenic genes of mesenchymal stem cells in a time-dependent manner. Within three months, cavitary bone defects of distal rabbit femurs implanted the granules exhibited better bone formation than those with those implanted with autologous bone.
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| 26. |
- Georgiev, Boris, et al.
(författare)
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A Universal Power-law Prescription for Variability from Synthetic Images of Black Hole Accretion Flows
- 2022
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
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Tidskriftsartikel (refereegranskat)abstract
- We present a framework for characterizing the spatiotemporal power spectrum of the variability expected from the horizon-scale emission structure around supermassive black holes, and we apply this framework to a library of general relativistic magnetohydrodynamic (GRMHD) simulations and associated general relativistic ray-traced images relevant for Event Horizon Telescope (EHT) observations of Sgr A*. We find that the variability power spectrum is generically a red-noise process in both the temporal and spatial dimensions, with the peak in power occurring on the longest timescales and largest spatial scales. When both the time-averaged source structure and the spatially integrated light-curve variability are removed, the residual power spectrum exhibits a universal broken power-law behavior. On small spatial frequencies, the residual power spectrum rises as the square of the spatial frequency and is proportional to the variance in the centroid of emission. Beyond some peak in variability power, the residual power spectrum falls as that of the time-averaged source structure, which is similar across simulations; this behavior can be naturally explained if the variability arises from a multiplicative random field that has a steeper high-frequency power-law index than that of the time-averaged source structure. We briefly explore the ability of power spectral variability studies to constrain physical parameters relevant for the GRMHD simulations, which can be scaled to provide predictions for black holes in a range of systems in the optically thin regime. We present specific expectations for the behavior of the M87* and Sgr A* accretion flows as observed by the EHT.
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| 27. |
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| 28. |
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| 29. |
- Han, Hedong, et al.
(författare)
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Prevalence, trends, and outcomes of atrial fibrillation in hospitalized patients with metastatic cancer : findings from a national sample
- 2021
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Ingår i: Cancer Medicine. - : John Wiley & Sons. - 2045-7634. ; 10:16, s. 5661-5670
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Tidskriftsartikel (refereegranskat)abstract
- Background: Epidemiological evidence regarding the link between cancer and atrial fibrillation (AF) are limited and outcomes of metastatic cancer comorbid with AF need to be elucidated.Objective: This study aims to evaluate the prevalence, temporal trends, and outcomes of AF in hospitalized metastatic cancer patients.Methods: The National Inpatient Sample (NIS) database was used to identify adult patients with metastatic tumors from 2003 to 2014. We analyzed the trends in AF prevalence, in-hospital mortality, total cost, length of stay (LOS), and comorbidities pertaining to metastatic cancer. Multivariable-adjusted models were used to evaluate the association of AF with clinical factors, in-hospital mortality, total cost, and LOS.Results: Among 2,478,598 patients with metastatic cancer, 8.74% (216,737) were diagnosed with AF. The proportion of comorbid AF increased from 8.28% in 2003 to 10.06% in 2014 (p < 0.0001). Older age, white race, male, Medicare, higher income, larger hospital bed size, and urban teaching hospital were associated with higher AF occurrence. Among primary tumor sites, lung cancer experienced the highest odds of AF compared to other cancers. Patients with metastasis to lymph node and respiratory organ had higher odds of AF. In metastatic cancer, AF was associated with higher in-hospital mortality (odds ratio: 1.48; 95% confidence interval: 1.43-1.54), 18% longer LOS, and 19% higher cost.Conclusions: AF prevalence in metastatic cancer continues to increase from 2003 to 2014. AF is linked to poorer prognosis and higher healthcare resource utilization. As the population ages, optimal preventive and treatment management strategies are needed for metastatic cancer comorbid with AF.
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| 30. |
- Han, Hedong, et al.
(författare)
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Temporary Trend, Characteristics and Clinical Outcomes of Acute Pancreatitis Patients Infected with Human Immunodeficiency Virus
- 2021
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Ingår i: Digestive Diseases and Sciences. - : Kluwer Academic/Plenum Publishers. - 0163-2116 .- 1573-2568. ; 66, s. 1683-1692
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Compared to general population, human immunodeficiency virus (HIV) infection may increase frequency of acute pancreatitis (AP); however, evidence regarding effects of HIV infection on AP-related outcomes is limited and controversial.AIMS: We aim to investigate the temporary trend, characteristics and clinical outcomes of AP infected with HIV.METHODS: We reviewed data from the 2003-2014 National Inpatient Sample to identify patients with a primary diagnosis of AP. The primary outcomes (in-hospital mortality, acute respiratory failure, acute kidney injury, and prolonged length of stay [LOS]) and secondary outcomes (gastrointestinal hemorrhage, sepsis and total cost) were compared between patients with and without HIV infection using univariate, multivariable and propensity score matching analyses.RESULTS: Of 594,106 patients diagnosed with AP, 6775 (1.14%) had HIV infection. Patients with HIV were more likely to be younger, black, male, less likely to be gallstone-related and had lower rate of interventions. Multivariable analyses based on multiple imputation revealed that HIV infection was associated with higher risk of mortality (odds ratio [OR]: 1.74; 95% confidence interval [CI] 1.34-2.25), acute kidney injury (OR: 1.13; 95% CI 1.19-1.44), prolonged LOS (OR: 1.26; 95% CI 1.15-1.37) and 6% higher cost. There were no differences in sepsis, gastrointestinal bleeding, and respiratory failure between groups.CONCLUSIONS: HIV infection is associated with adverse outcomes including increased mortality, acute kidney injury and more healthcare utilization in AP patients. More assertive management strategies like early intravenous fluid resuscitation in HIV patients hospitalized with AP to prevent acute kidney injury may be helpful to improve clinical outcomes.
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