1,748 research outputs found
Black-Hole Mass and Growth Rate at High Redshift
We present new H and K bands spectroscopy of 15 high luminosity active
galactic nuclei (AGNs) at redshifts 2.3-3.4 obtained on Gemini South. We
combined the data with spectra of additional 29 high-luminosity sources to
obtain a sample with 10^{45.2}<\lambda L_{\lambda}(5100A)<10^{47.3} ergs/sec
and black hole (BH) mass range, using reverberation mapping relationships based
on the H_beta method, of 10^{8.8}-10^{10.7} M_sun. We do not find a correlation
of L/L_Edd with M_BH but find a correlation with \lambda L_{\lambda}(5100A)
which might be due to selection effects. The L/L_Edd distribution is broad and
covers the range ~0.07-1.6, similar to what is observed in lower redshift,
lower luminosity AGNs. We suggest that this consistently measured and
calibrated sample gives the best representation of L/L_Edd at those redshifts
and note potential discrepancies with recent theoretical and observational
studies. The lower accretion rates are not in accord with growth scenarios for
BHs at such redshifts and the growth times of many of the sources are longer
than the age of the universe at the corresponding epochs. This suggests earlier
episodes of faster growth at z>~3 for those sources. The use of the C IV method
gives considerably different results and a larger scatter; this method seems to
be a poor M_BH and L/L_Edd estimator at very high luminosity.Comment: 8 pages (emulateapj), 4 figures. Accepted for publication in Ap
Environmental constraints and pelagic fisheries in upwelling areas: The Peruvian puzzle
Pelagic fish catch statistics are used as surrogates to evaluate the potential fish productivity in upwelling ecosystems. A comparison between 10 upwelling areas of the world shows that the Peruvian ecosystem is threeto ten-fold more productive than the others. The size of the ecosystem, estimated by the surface of the continental shelf, does not by itself explain the observed disparity. Upwelling systems are characterized by different combinations of two different environmental variables: the upwelling intensity and the mixing generated by the wind. Using generalized additive models, an exploratory analysis is performed in order to identify the environmental conditions that maximize the total pelagic fish catch productivity (mainly sardine, sardinella and anchovy). The analyses consider fish catch as the dependent variable and the two environmental factors as the independent variables. Optimal environmental conditions appear to be a combination of: a high upwelling index (~ 1.2 m3·s-1·m-1) and moderate wind-mixing (~250 m3·s-3). The Peruvian ecosystem is the only upwelling system that has these characteristics, making it unique and singularly productive. These empirical results stress the importance of considering a combination of nvironmental factors when explaining pelagic fish productivity inupwelling systems
Generalised verification of the observer property in discrete event systems
The observer property is an important condition to be satisfied by abstractions of Discrete Event Systems (DES) models. This paper presents a generalised version of a previous algorithm which tests if an abstraction of a DES obtained through natural projection has the observer property. The procedure called OP-verifier II overcomes the limitations of the previously proposed verifier while keeping its computational complexity. Results are illustrated by a case study of a transfer line system
Generalised verification of the observer property in discrete event systems
The observer property is an important condition to be satisfied by abstractions of Discrete Event Systems (DES) models. This paper presents a generalised version of a previous algorithm which tests if an abstraction of a DES obtained through natural projection has the observer property. The procedure called OP-verifier II overcomes the limitations of the previously proposed verifier while keeping its computational complexity. Results are illustrated by a case study of a transfer line system
Beam hardening artifact reduction using dual energy computed tomography: implications for myocardial perfusion studies
Background: Myocardial perfusion computed tomography (CTP) using conventional single energy (SE) imaging is influenced by the presence of beam hardening artifacts (BHA), occasionally resembling perfusion defects and commonly observed at the left ventricular posterobasal wall (PB). We therefore sought to explore the ability of dual energy (DE) CTP to attenuate the presence of BHA. Methods: Consecutive patients without history of coronary artery disease who were referred for computed tomography coronary angiography due to atypical chest pain and a normal stress-rest SPECT and had absence or mild coronary atherosclerosis constituted the study population. The study group was acquired using DE and the control group using SE imaging. Results: Demographical characteristics were similar between groups, as well as the heart rate and the effective radiation dose. Myocardial signal density (SD) levels were evaluated in 280 basal segments among the DE group (140 PB segments for each energy level from 40 keV to 100 keV; and 140 reference segments), and in 40 basal segments (at the same locations) among the SE group. Among the DE group, myocardial SD levels and myocardial SD ratio evaluated at the reference segment were higher at low energy levels, with significantly lower SD levels at increasing energy levels. Myocardial signal-to-noise ratio was not significantly influenced by the energy level applied, although 70 keV was identified as the energy level with the best overall signal-to-noise ratio. Significant differences were identified between the PB segment and the reference segment among the lower energy levels, whereas at ≥ 70 keV myocardial SD levels were similar. Compared to DE reconstructions at the best energy level (70 keV), SE acquisitions showed no significant differences overall regarding myocardial SD levels among the reference segments. Conclusions: Beam hardening artifacts that influence the assessment of myocardial perfusion can be attenuated using DE at 70 keV or higher.Fil: Rodriguez Granillo, Gaston Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Cardiológicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Cardiológicas; Argentina. Diagnóstico Maipú; ArgentinaFil: Carrascosa, Patricia. Diagnóstico Maipú; ArgentinaFil: Cipriano, Silvia. Diagnóstico Maipú; ArgentinaFil: De Zan, Macarena. Diagnóstico Maipú; ArgentinaFil: Deviggiano, Alejandro. Diagnóstico Maipú; ArgentinaFil: Capunay, Carlos. Diagnóstico Maipú; ArgentinaFil: Cury, Ricardo C.. Miami Cardiac and Vascular Institute and Baptist Health; Estados Unido
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Nephrolithiasis in patients with inflammatory bowel disease in the community
Background: Inflammatory bowel disease (IBD) has been associated with renal stone formation. The objective of this study was to determine prospectively the prevalence of nephrolithiasis in a community-based population of patients with IBD and to analyze factors associated with renal calculus formation. Methods: Screening renal ultrasound was performed in a well characterized cohort of patients seen between 2009 and 2012 at an IBD clinic. We enrolled 168 patients, including 93 with Crohn’s disease and 75 with ulcerative colitis. Clinical and phenotypic variables associated with asymptomatic nephrolithiasis were determined. Results: Nephrolithiasis was detected in 36 patients with Crohn’s disease and in 28 patients with ulcerative colitis (38% for both). Although none of the patients had been previously hospitalized for symptomatic nephrolithiasis, nine with Crohn’s disease and five with ulcerative colitis had recurrent urinary tract infections or hydronephrosis. In patients with Crohn’s disease, ileocolonic (L3) disease was associated with a greater risk of nephrolithiasis than was ileal (L1) or colonic (L2) disease (odds ratio [OR] 2.3, 95% confidence interval [CI] 1.8–7). Active ulcerative colitis (regardless of severity) represented a significant risk factor for formation of renal calculi (OR 4.2, 95% CI 1.1–15, P = 0.02). Conclusion: In surgery-naïve patients with IBD in the community, asymptomatic nephrolithiasis is common and should be considered when renal dysfunction or infection is detected
Verification of the observer property in discrete event systems
The observer property is an important condition to be satisfied by abstractions of Discrete Event System (DES) models. This technical note presents a new algorithm that tests if an abstraction of a DES obtained through natural projection has the observer property. The procedure, called OP-Verifier, can be applied to (potentially nondeterministic) automata, with no restriction on the existence of cycles of 'non-relevant' events. This procedure has quadratic complexity in the number of states. The performance of the algorithm is illustrated by a set of experiments
Using Uppaal for the secure and optimal control of AGV fleets
The design and realization of an on line control system for automated guided vehicles (AGV) is addressed. A synthesis method is proposed based on the use of the model checking tool for timed automata Uppaal. This system has to route the vehicles while ensuring the system safeness, a good coordination between vehicles and the optimization of performance criteria.This problem is like synthesizing a Ramadge and Wonham supervisor combined with routing and optimizing functions, that is an ongoing problem within the supervisory control theory. The proposed concepts are validated through a software tool suite based on Uppaal in order to generate optimal traces and interact with an AGV system emulated with Arena
The Influence of Human-Milk Substitutes Marketing on Breastfeeding Intention and Practice among Native and Immigrant Brazilians
Background: The International Code of Marketing of Breast-Milk Substitutes is a global public health policy aiming to protect breastfeeding from the influence of human-milk substitutes marketing. Brazil is one of the few countries substantially implementing it. Most countries adopted selected provisions, including Portugal. Research Aim: To explore whether Brazilians’ perspectives about breastfeeding intention and practice are influenced by human-milk substitutes marketing upon migration to Portugal. Methods: A qualitative, prospective, cross-sectional survey design was conducted in Brazil and Portugal (2018–2019). Qualitative semi-structured interviews were performed with native (n = 16) and immigrant (n = 15) Brazilians. Women aged 18 or above, mothers of 0–12 month infants, and without contraindications to breastfeed, were eligible for the study. Heterogeneity sampling was employed based on socioeconomic status and infants’ age. Content analysis was conducted using NVivo. Results: Brazilian immigrants were more aware of the potential negative influence of human-milk substitutes marketing than natives. Sociocultural factors contributed to Brazilian immigrants being less permeable to the influence of human-milk substitutes marketing in the host country, where a less protective breastfeeding environment was perceived. Conclusions: Sociocultural factors including breastfeeding promotion strategies and a strong breastfeeding culture in the home country appear to play a protective role on breastfeeding intention and practice among Brazilians migrating to Portugal. © The Author(s) 2022.The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study is funded by FEDER funds through the Operational Programme for Competitiveness and Internationalization, and by national funding through the Foundation for Science and Technology (FCT; Portuguese Ministry of Science, Technology and Higher Education), under the scope of the project ‘‘Perinatal Health in Migrants: Barriers, Incentives and Outcomes’’ (POCI-01-0145-FEDER-016874; PTDC/DTPSAP/6384/2014), the projects UIDB/04750/2020 e LA/P/0064/2020, the PhD grant PD/BD/128082/2016 (C. L.) co-funded by the FCT and Human Potential Operating Program of the European Social Fund (POPH/FSE Program) and the contract DL57/2016/CP1336/CT0001 (C.F.). A. M. has a research scholarship from the Brazilian National Council for Scientific and Technological Development (CNPq)
EuroMarine Research Strategy Report: Deliverable 3.2. Seventh Framework Programme Project EuroMarine
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