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Casas-Flores, Sergio, Mauricio Rios-Momberg, Martha Bibbins, Patricia Ponce-Noyola i Alfredo Herrera-Estrella. "BLR-1 and BLR-2, key regulatory elements of photoconidiation and mycelial growth in Trichoderma atroviride". Microbiology 150, nr 11 (1.11.2004): 3561–69. http://dx.doi.org/10.1099/mic.0.27346-0.
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In fungi, phototropism, the induction of carotenogenesis and reproductive structures, and resetting of the circadian rhythm are controlled by blue light. Trichoderma atroviride, a fungus used in biological control, sporulates in a synchronized manner following a brief pulse of blue light. Due to its apparent simplicity, this response was chosen for pursuing photoreceptor isolation. Two genes were cloned, blue-light regulators 1 and 2 (blr-1 and blr-2), similar to the Neurospora crassa white-collar 1 and 2, respectively. The BLR-1 protein has all the characteristics of a blue-light photoreceptor, whereas the structure of the deduced BLR-2 protein suggests that it interacts with BLR-1 through PAS domains to form a complex. Disruption of the corresponding genes demonstrated that they are essential for blue-light-induced conidiation. blr-1 and blr-2 were also shown to be essential for the light-induced expression of the photolyase-encoding gene (phr-1). Mechanical injury of mycelia was found to trigger conidiation of T. atroviride, a response not described previously. This response was not altered in the mutants. A novel effect of both red and blue light on mycelial growth was found involving another light receptor, which is compensated by the BLR proteins.
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Sánchez-Arreguín, Alejandro, Ana Silvia Pérez-Martínez i Alfredo Herrera-Estrella. "Proteomic Analysis of Trichoderma atroviride Reveals Independent Roles for Transcription Factors BLR-1 and BLR-2 in Light and Darkness". Eukaryotic Cell 11, nr 1 (4.11.2011): 30–41. http://dx.doi.org/10.1128/ec.05263-11.
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ABSTRACT The genus Trichoderma is one of the most widely used biological control agents of plant-pathogenic fungi. The main mechanism for survival and dispersal of Trichoderma is through the production of asexual spores (conidia). The transition from filamentous growth to conidiation can be triggered by light, nutrient deprivation, and mechanical damage of the mycelium. We conducted proteomic profiling analyses of Trichoderma atroviride after a blue light pulse. The use of two-dimensional electrophoresis (2-DE) and mass spectrometry (MS) analysis allowed us to identify 72 proteins whose expression was affected by blue light. Functional category analysis showed that the various proteins are involved in metabolism, cell rescue, and protein synthesis. We determined the relationship between mRNA levels of selected genes 30 min after a light pulse and protein expression levels at different times after the pulse and found this correlation to be very weak. The correlation was highest when protein and mRNA levels were compared for the same time point. The transcription factors BLR-1 and BLR-2 are vital to the photoconidiation process; here we demonstrate that both BLR proteins are active in darkness and affect several elements at both the transcript and protein levels. Unexpectedly, in darkness, downregulation of proteins prevailed in the Δ blr-1 mutant, while upregulation of proteins predominated in the Δ blr-2 mutant. Our data demonstrate that the BLR proteins play roles individually and as a complex.
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Cohen, Joshua L., Matthew E. Glover, Phyllis C. Pugh, Andrew D. Fant, Rebecca K. Simmons, Huda Akil, Ilan A. Kerman i Sarah M. Clinton. "Maternal Style Selectively Shapes Amygdalar Development and Social Behavior in Rats Genetically Prone to High Anxiety". Developmental Neuroscience 37, nr 3 (2015): 203–14. http://dx.doi.org/10.1159/000374108.
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The early-life environment critically influences neurodevelopment and later psychological health. To elucidate neural and environmental elements that shape emotional behavior, we developed a rat model of individual differences in temperament and environmental reactivity. We selectively bred rats for high versus low behavioral response to novelty and found that high-reactive (bred high-responder, bHR) rats displayed greater risk-taking, impulsivity and aggression relative to low-reactive (bred low-responder, bLR) rats, which showed high levels of anxiety/depression-like behavior and certain stress vulnerability. The bHR/bLR traits are heritable, but prior work revealed bHR/bLR maternal style differences, with bLR dams showing more maternal attention than bHRs. The present study implemented a cross-fostering paradigm to examine the contribution of maternal behavior to the brain development and emotional behavior of bLR offspring. bLR offspring were reared by biological bLR mothers or fostered to a bLR or bHR mother and then evaluated to determine the effects on the following: (1) developmental gene expression in the hippocampus and amygdala and (2) adult anxiety/depression-like behavior. Genome-wide expression profiling showed that cross-fostering bLR rats to bHR mothers shifted developmental gene expression in the amygdala (but not hippocampus), reduced adult anxiety and enhanced social interaction. Our findings illustrate how an early-life manipulation such as cross-fostering changes the brain's developmental trajectory and ultimately impacts adult behavior. Moreover, while earlier studies highlighted hippocampal differences contributing to the bHR/bLR phenotypes, our results point to a role of the amygdala as well. Future work will pursue genetic and cellular mechanisms within the amygdala that contribute to bHR/bLR behavior either at baseline or following environmental manipulations.
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Casas-Flores, Sergio, Mauricio Rios-Momberg, Teresa Rosales-Saavedra, Pedro Martínez-Hernández, Vianey Olmedo-Monfil i Alfredo Herrera-Estrella. "Cross Talk between a Fungal Blue-Light Perception System and the Cyclic AMP Signaling Pathway". Eukaryotic Cell 5, nr 3 (marzec 2006): 499–506. http://dx.doi.org/10.1128/ec.5.3.499-506.2006.
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ABSTRACT Blue light regulates many physiological and developmental processes in fungi. In Trichoderma atroviride the complex formed by the BLR-1 and BLR-2 proteins appears to play an essential role as a sensor and transcriptional regulator in photoconidiation. Here we demonstrate that the BLR proteins are necessary for carbon deprivation induced conidiation, even in the absence of light, pointing to the existence of an unprecedented cross talk between light and carbon sensing. Further, in contrast to what has been found in all other fungal systems, clear BLR-independent blue-light responses, including the activation of protein kinase A (PKA) and the regulation of gene expression, were found. Expression of an antisense version of the pkr-1 gene, encoding the regulatory subunit of PKA, resulted in a nonsporulating phenotype, whereas overexpression of the gene produced colonies that conidiate even in the dark. In addition, overexpression of pkr-1 blocked the induction of early light response genes. Thus, our data demonstrate that PKA plays an important role in the regulation of light responses in Trichoderma. Together, these observations suggest that the BLR complex plays a general role in sensing environmental cues that trigger conidiation and that such a role can be separated from its function as a transcription factor.
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Lee, Jong-Gi, Jin-Soo Bae, Yeo-Hoon Yoon, Jun-Ho Lee i Kang-Young Cho. "Enhancement of Board Level Reliability on Automotive DRAM Package by Optimized Thermal & Mechanical Properties". International Symposium on Microelectronics 2020, nr 1 (1.09.2020): 000073–77. http://dx.doi.org/10.4071/2380-4505-2020.1.000073.
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Abstract As increased in demand for using memory devices in automotive applications, board level reliability (BLR) has been the one of the critical issue for using FBGA type packages in automotive. The required specification of BLR is listed in various standards (AEC-Q100, Q104 etc) and it is varied by automotive application customers. Most of customers are targeting grade from 1 to 3, however, requirement to memory package is grade 1 (−40°C~125°C). Currently low power (LP) memory device is widely adopted in automotive applications due to its wide bandwidth and high density capability. From package reliability point of view, it is challenge to satisfy the required BLR for target package by 1) dimension optimization, 2) selection of material, 3) mount condition, and 4) work around method. In this paper, the best combination to achieve the highest BLR life time was investigated compared with current mobile application LP4 package. Large pad size with large ball, high content of Ag in solder ball and Ni/Au pad finish were the best combination to result in the longest life time. Various density of LP4 package BLR were also estimated by mechanical simulation based from actual thermal cycling test on the highest Si volume LP4 package.
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Friedl, Martina A., Christian P. Kubicek i Irina S. Druzhinina. "Carbon Source Dependence and Photostimulation of Conidiation in Hypocrea atroviridis". Applied and Environmental Microbiology 74, nr 1 (2.11.2007): 245–50. http://dx.doi.org/10.1128/aem.02068-07.
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ABSTRACT Hypocrea atroviridis is frequently used as a photomorphogenetic model due to its ability to conidiate upon exposure to light. Light is thereby believed to be the primary trigger for spore formation. In contrast, we show here that conidiation is primarily carbon source dependent and that illumination plays a catalytic role; of a total of 95 tested carbon sources, only a small set of carbohydrates, polyols, and sugar acids allowed conidiation in darkness, and on most of them, conidiation was significantly more strongly expressed in light. In addition, there are also a number of carbon sources on which H. atroviridis conidiates in darkness, but light does not further stimulate the process. Yet on another small set of carbon sources (l-sorbitol, d-fucose, d- and l-arabinose, and erythritol), H. atroviridis shows better sporulation in darkness than in light. No sporulation was observed on organic acids and amino acids. Mutants with deletions in the two blue-light receptor proteins BLR-1 and BLR-2 generally showed weaker conidiation on a smaller number of carbon sources than did the parental strain, yet they clearly sporulated on 15 and 27 of the 95 carbon sources tested, respectively. Of the carbon sources supporting sporulation, only 11 supported the conidiation of both mutants, suggesting that the BLR-1 and BLR-2 receptors are variously involved in the carbon source-dependent regulation of spore formation. The addition of cyclic AMP, which has been reported to lead to conidiation in darkness, both positively and negatively affected sporulation and resulted in different effects in the parental strain and the two Δblr mutants. Our data show that the carbon source is the prime determinant for conidiation and that it influences the organism's regulation of conidiation by means of BLR-1 and BLR-2 and their cross talk with cyclic AMP.
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Shardell, Michelle, Neeta Parimi, Lisa Langsetmo, Toshiko Tanaka, Lingjing Jiang, Eric Orwoll, James M. Shikany, Deborah M. Kado i Peggy M. Cawthon. "Comparing Analytical Methods for the Gut Microbiome and Aging: Gut Microbial Communities and Body Weight in the Osteoporotic Fractures in Men (MrOS) Study". Journals of Gerontology: Series A 75, nr 7 (6.02.2020): 1267–75. http://dx.doi.org/10.1093/gerona/glaa034.
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Abstract Determining the role of gut microbial communities in aging-related phenotypes, including weight loss, is an emerging gerontology research priority. Gut microbiome datasets comprise relative abundances of microbial taxa that necessarily sum to 1; analysis ignoring this feature may produce misleading results. Using data from the Osteoporotic Fractures in Men (MrOS) study (n = 530; mean [SD] age = 84.3 [4.1] years), we assessed 163 genera from stool samples and body weight. We compared conventional analysis, which does not address the sum-to-1 constraint, to compositional analysis, which does. Specifically, we compared elastic net regression (for variable selection) and conventional Bayesian linear regression (BLR) and network analysis to compositional BLR and network analysis; adjusting for past weight, height, and other covariates. Conventional BLR identified Roseburia and Dialister (higher weight) and Coprococcus-1 (lower weight) after multiple comparisons adjustment (p < .0125); plus Sutterella and Ruminococcus-1 (p < .05). No conventional network module was associated with weight. Using compositional BLR, Coprococcus-2 and Acidaminococcus were most strongly associated with higher adjusted weight; Coprococcus-1 and Ruminococcus-1 were most strongly associated with lower adjusted weight (p < .05), but nonsignificant after multiple comparisons adjustment. Two compositional network modules with respective hub taxa Blautia and Faecalibacterium were associated with adjusted weight (p < .01). Findings depended on analytical workflow. Compositional analysis is advocated to appropriately handle the sum-to-1 constraint.
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McCreary, Erin K., Lloyd Clarke, Rachel V. Marini, Minh-Hong Nguyen, Cornelius J. Clancy i Ryan K. Shields. "656. Prioritizing Gram-Negative Bacteremia (GNB) Cases for Rapid Detection by β-Lactam Resistance (BLR) and Patient Outcomes". Open Forum Infectious Diseases 6, Supplement_2 (październik 2019): S301—S302. http://dx.doi.org/10.1093/ofid/ofz360.724.
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Abstract Background GNB is associated with significant morbidity and mortality. The availability of rapid diagnostic tests (RDTs) provides an opportunity to improve outcomes. Our goal was to review GNB and its empiric treatment at our center in order to devise rational approaches to diagnostic stewardship and use of RDTs. Methods All patients with GNB from 2010 to 2018 were evaluated. BLR was defined by 2019 CLSI breakpoints; phenotypes are shown in Table 1. Results A total of 2795 GNB cases were included (Table 2); 57% occurred within the first 24 hours of hospitalization and 29.3% in the ICU. The median length of stay (LOS) was 12 days; 17.2% of patients were re-admitted within 30 days. Fourteen- and 30-day mortality rates were 13.7% and 19.5%, respectively. Rates of death were higher (30 days; 26.3% vs. 17.1%; P < 0.001) and median LOS longer (17 vs. 11 days; P < 0.001) among patients with BLR compared with susceptible GNB. Thirty-day mortality rates were highest for CRE (30.1%) and BLR P. aeruginosa (BLR-Pa; 32.8%, Figure 1). 47.7% of BLR GNB were non-CRE/ESBL, which demonstrated higher mortality rates than CRE/ESBL (30 days; 27.6% vs. 21.2%; P = 0.048). Most common empiric regimens prescribed were piperacillin–tazobactam (TZP; 50.3%), cefepime (FEP; 24.2%), carbapenem (9.3%), or other agents (16.2%). 21.6% of GNB patients received inactive empiric treatment (IET). Empiric TZP (21.9%) was more likely to be inactive than FEP (17.5%; P = 0.05), but not a carbapenem (20.7%; P = NS). 57.6% of patients with inhibitor-resistant Enterobacteriaceae (IRE) received TZP empirically. Receipt of IET was associated with higher rates of death (30 days; 22.5% vs. 16.7, P = 0.03) and longer LOS (14 vs. 11 days; P < 0.001) than receipt of active ET. Rates of IET varied by pathogen (Figure 1). Conclusion IET is common against BLR GNB and associated with poor pt outcomes, highlighting the potential for RDTs and diagnostic stewardship teams (DSTs) to improve care. Genotypic RDTs detect most CRE/ESBL, but may miss nearly 50% of BLR GNB cases at our center. BLR-Pa and IRE are pathogens associated with prolonged LOS, and high rates of IET and death. These pathogens could be detected earlier by phenotypic RDTs and prioritized by DSTs to optimize early treatment regimens. Disclosures All authors: No reported disclosures.
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Capetti, Alessandro, Ari Laor, Ranieri D. Baldi, Andrew Robinson i Alessandro Marconi. "Spectropolarimetry of low redshift quasars: origin of the polarization and implications for black hole mass estimates". Monthly Notices of the Royal Astronomical Society 502, nr 4 (3.02.2021): 5086–103. http://dx.doi.org/10.1093/mnras/stab279.
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ABSTRACT We present the results of high signal-to-noise ratio VLT spectropolarimetry of a representative sample of 25 bright type 1 AGN at z < 0.37, of which nine are radio-loud. The sample covers uniformly the 5100 Å optical luminosity at L5100 ∼ 1044−1046 erg s−1, and H α width at FWHM ∼ 1000−10 000 $\rm {\, km \, s}^{-1}$. We derive the continuum and the H α polarization amplitude, polarization angle, and angle swing across the line, together with the radio properties. We find the following: (1) The broad line region (BLR) and continuum polarization are both produced by a single scattering medium. (2) The scattering medium is equatorial and at right angle to the system axis. (3) The scattering medium is located at or just outside the BLR. The continuum polarization and the H α polarization angle swing, can both serve as an inclination indicator. The observed line width is found to be affected by inclination, which can lead to an underestimate of the black hole mass by a factor of ∼5 for a close-to face-on view. The line width measured in the polarized flux overcomes the inclination bias and provides a close-to equatorial view of the BLR in all AGN, which allows to reduce the inclination bias in the BLR based black hole mass estimates.
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Rosales-Saavedra, T., E. U. Esquivel-Naranjo, S. Casas-Flores, P. Martínez-Hernández, E. Ibarra-Laclette, C. Cortes-Penagos i A. Herrera-Estrella. "Novel light-regulated genes in Trichoderma atroviride: a dissection by cDNA microarrays". Microbiology 152, nr 11 (1.11.2006): 3305–17. http://dx.doi.org/10.1099/mic.0.29000-0.
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The influence of light on living organisms is critical, not only because of its importance as the main source of energy for the biosphere, but also due to its capacity to induce changes in the behaviour and morphology of nearly all forms of life. The common soil fungus Trichoderma atroviride responds to blue light in a synchronized manner, in time and space, by forming a ring of green conidia at what had been the colony perimeter at the time of exposure (photoconidiation). A putative complex formed by the BLR-1 and BLR-2 proteins in T. atroviride appears to play an essential role as a sensor and transcriptional regulator in photoconidiation. Expression analyses using microarrays containing 1438 unigenes were carried out in order to identify early light response genes. It was found that 2.8 % of the genes were light responsive: 2 % induced and 0.8 % repressed. Expression analysis in blr deletion mutants allowed the demonstration of the occurrence of two types of light responses, a blr-independent response in addition to the expected blr-dependent one, as well as a new role of the BLR proteins in repression of transcription. Exposure of T. atroviride to continuous light helped to establish that the light-responsive genes are subject to photoadaptation. Finally, evidence is provided of red-light-regulated gene expression and a possible crosstalk between the blue and red light signalling pathways.
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Shardell, Michelle, Neeta Parimi, Lisa Langsetmo, Eric Orwoll, James Shikany, Deborah Kado i Peggy Cawthon. "Comparing Analytical Methods for Gut Microbiome and Aging: Gut Microbiota and Body Weight in the MrOS". Innovation in Aging 4, Supplement_1 (1.12.2020): 839. http://dx.doi.org/10.1093/geroni/igaa057.3074.
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Abstract Gut microbiome datasets comprise microbial taxa relative abundances that necessarily sum to 1; analysis ignoring this feature may produce misleading results. We assessed 163 genera from the first batch of Microbiome Ancillary Study (n=530) stool samples and examined associations between microbiota and body weight. We compared conventional Bayesian linear regression (BLR) and network analysis to their compositional counterparts, adjusting for past weight and other covariates. Conventional BLR identified Roseburia and Dialister (positive association) and Coprococcus-1 (negative association) after multiple comparisons adjustment(P<.0125). No conventional network module was associated with weight. Using compositional BLR, men with higher Coprococcus-2 and Acidaminococcus had higher weight, whereas men with higher Coprococcus-1 and Ruminococcus-1 had lower weight (P<.05), but findings were non-significant after multiple comparisons adjustment. Two compositional network modules with respective hub taxa Blautia and Faecalibacterium were associated with weight(P<.01). Findings depended on analytical workflow; compositional analysis is advocated to appropriately handle the sum-to-1 constraint.
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Devereux, Nick. "The dynamics of the broad-line region in NGC 3227". Monthly Notices of the Royal Astronomical Society 500, nr 1 (1.10.2020): 786–94. http://dx.doi.org/10.1093/mnras/staa3005.
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ABSTRACT Archival Hubble Space Telescope (HST) observations of the Seyfert 1 nucleus of NGC 3227 obtained with the Space Telescope Imaging Spectrograph (STIS) are re-examined in order to constrain a viable photoionization model for the broad-line region (BLR). The results imply that the BLR is a partially ionized, dust-free, spherical shell that is collapsing, supersonically, at the free-fall velocity due to its proximity to a supermassive black hole. The BLR is ionization bounded at the outer radius, coincident with the dust reverberation radius, and transforms into an X-ray emitting plasma inside the Balmer reverberation radius as the central UV–X-ray source is approached. Only 40 M⊙ of Hydrogen are required to explain the Balmer emission-line luminosity, but it is compressed by gravity into a column measuring 5.5 × 1024 atoms cm−2. Assuming radiatively inefficient accretion, the X-ray luminosity requires ∼10−2 M⊙ yr−1. However, the mass inflow rate required to explain the luminosity of the broad H α emission line is ∼1 M⊙ yr−1. The very large disparity between these two estimates indicates that 99 per cent of the inflowing gas must be re-directed into an outflow, and on a very short time-scale corresponding to ∼40 yr. Alternatively, the radiative efficiency of the inflow has been overestimated, or the X-ray luminosity has been underestimated, a distinct possibility if the BLR is indeed Compton-thick.
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Panda, Swayamtrupta. "The CaFe project: Optical Fe II and near-infrared Ca II triplet emission in active galaxies: simulated EWs and the co-dependence of cloud size and metal content". Astronomy & Astrophysics 650 (czerwiec 2021): A154. http://dx.doi.org/10.1051/0004-6361/202140393.
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Aims. Modelling the low-ionisation lines (LILs) in active galactic nuclei (AGNs) still faces problems in explaining the observed equivalent widths (EWs) when realistic covering factors are used and the distance of the broad-line region (BLR) from the centre is assumed to be consistent with the reverberation mapping measurements. We re-emphasise this problem and suggest that the BLR ‘sees’ a different continuum from that seen by a distant observer. This change in the continuum reflected in the change in the net bolometric luminosity from the AGN is then able to resolve the above problem. Methods. We carefully examine the optical Fe II and near-infrared (NIR) Ca II triplet (CaT) emission strengths with respect to Hβ emission using the photoionisation code CLOUDY and a range of physical parameters. Prominent among these parameters are (a) the ionisation parameter (U), (b) the local BLR cloud density (nH), (c) the metal content in the BLR cloud, and (d) the cloud column density. Using an incident continuum for I Zw 1 –a prototypical Type-1 narrow-line Seyfert galaxy– our basic setup is able to recover the line ratios for the optical Fe II (i.e. RFeII) and for the NIR CaT (i.e. RCaT) in agreement with the observed estimates. Nevertheless, the pairs of (U,nH) that reproduce the conforming line ratios do not relate to agreeable line EWs. We therefore propose a way to mitigate this issue. The LIL region of the BLR cloud does not see the same continuum emitted by the accretion disc as that seen by a distant observer; rather it sees a filtered version of the original continuum which brings the radial sizes into agreement with the reverberation mapped estimates for the extension of the BLR. This is achieved by scaling the radial distance of the emitting regions from the central continuum source using the photoionisation method in correspondence with the reverberation mapping estimates for I Zw 1. Taking inspiration from past studies, we suggest that this collimation of the incident continuum can be explained by the anisotropic emission from the accretion disc, which modifies the spectral energy distribution such that the BLR receives a much cooler continuum with a reduced number of line-ionising photons, allowing reconciliation in the modelling with the line EWs. Results. (1) The assumption of the filtered continuum as the source of BLR irradiation recovers realistic EWs for the LIL species, such as the Hβ, Fe II, and CaT. However, our study finds that to account for the adequate RFeII (Fe II/Hβ flux ratio) emission, the BLR needs to be selectively overabundant in iron. On the other hand, the RCaT (CaT/Hβ flux ratio) emission spans a broader range from solar to super-solar metallicities. In all these models, the BLR cloud density is found to be consistent with our conclusions from prior studies, that is, nH ∼ 1012 cm−3 is required for the sufficient emission of Fe II and CaT. (2) We extend our modelling to test and confirm the co-dependence between metallicity and cloud column density for these two ionic species (Fe II and CaT), further allowing us to constrain the physical parameter space for the emission of these LILs. Adopting the estimates from line ratios that diagnose the metallicity in these gas-rich media –which suggest super-solar values (≳5−10 Z⊙)–, we arrive at cloud columns that are of the order of 1024 cm−2. (3) Finally, we test the effect of inclusion of a micro-turbulent velocity within the BLR cloud and find that the Fe II emission is positively affected. An interesting result obtained here is the reduction in the value of the metallicity by up to a factor of ten for the RFeII cases when the microturbulence is invoked, suggesting that microturbulence can act as an apparent metallicity controller for the Fe II. On the contrary, the RCaT cases are relatively unaffected by the inclusion of microturbulence.
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Ramolla, Michael, Martin Haas, Christian Westhues, Francisco Pozo Nuñez, Catalina Sobrino Figaredo, Julia Blex, Matthias Zetzl i in. "Simultaneous Hα and dust reverberation mapping of 3C 120: Testing the bowl-shaped torus geometry". Astronomy & Astrophysics 620 (grudzień 2018): A137. http://dx.doi.org/10.1051/0004-6361/201732081.
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We monitored the Seyfert-1 galaxy 3C 120 between September 2014 and March 2015 at the Universitätssternwarte Bochum near Cerro Armazones in BVRIJK and a narrowband filter covering the redshifted Hα line. In addition we obtained a single contemporary spectrum with the spectrograph FAST at Mt. Hopkins. Compared to earlier epochs 3C 120 is about a factor of three brighter, allowing us to study the shape of the broad line region (BLR) and the dust torus in a high luminosity phase. The analysis of the light curves yields that the dust echo is rather sharp and symmetric in contrast to the more complex broad Hα BLR echo. We investigated how far this supports an optically thick bowl-shaped BLR and dust torus geometry. The comparison with several parameterizations of these models supports the following geometry: The BLR clouds lie inside the bowl closely above the bowl rim up to a halfcovering angle 0° < θ < 40° (measured against the equatorial plane). Then the BLR is spread over many isodelay surfaces, yielding a smeared and structured echo as observed. Furthermore, if the BLR clouds shield the bottom of the bowl rim against radiation from the nucleus, the hot dust emission comes essentially from the top edge of the bowl (40° < θ < 45°). Then, for small inclinations as for 3C120, the top dust edge forms a ring that largely coincides with a narrow range of isodelay surfaces, yielding the observed sharp dust echo. The scale height of the BLR increases with radial distance from the black hole (BH). This leads to luminosity dependent foreshortening effects of the lag. We discuss the implications and possible corrections of the foreshortening for the BH mass determination and consequences for the lag (size)–luminosity relationships and the difference from interferometric torus sizes.
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Hermosa Muñoz, Laura, Sara Cazzoli, Isabel Márquez i Josefa Masegosa. "Optical spectroscopy of type-2 LINERs". Proceedings of the International Astronomical Union 15, S356 (październik 2019): 317–19. http://dx.doi.org/10.1017/s174392132000321x.
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AbstractLow-Ionisation Nuclear Emission-line Regions (LINERs) are the least luminous and the most numerous among the local population of Active Galactic Nuclei (AGN). They can be classified as type-1 or type-2 if their optical spectra show or do not show, respectively, a broad component. It is associated with the presence of a Broad Line Region (BLR) in these systems. However, recent studies have proven that the classification of type-1 LINERs may be controversial, since space- and ground-based spectroscopy provide contradicting results on the presence of very broad components (Cazzoli et al.2018). We have studied the nuclear spectra of 9 type-2 LINERs with intermediate spectral resolution HST/STIS data. We present the results on our analysis of the different spectral components, and discuss the eventual presence of BLR components in type-2 LINER galaxies, together with the possible presence of outflows, both in comparison with type-1 LINERs. We have found a BLR component in 7 out of the 9 analysed objects within the HST/STIS data.
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Korista, K. T., i M. R. Goad. "Quantifying the impact of variable BLR diffuse continuum contributions on measured continuum interband delays". Monthly Notices of the Royal Astronomical Society 489, nr 4 (23.08.2019): 5284–300. http://dx.doi.org/10.1093/mnras/stz2330.
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ABSTRACT We investigate the contribution of reprocessed continuum emission (1000–10 000 Å) originating in broad-line region (BLR) gas, the diffuse continuum (DC), to the wavelength-dependent continuum delays measured in AGN disc reverberation mapping experiments. Assuming a spherical BLR geometry, we adopt a Local Optimally emitting Cloud (LOC) model for the BLR that approximately reproduces the broad emission-line strengths of the strongest UV lines (Ly α and C iv) in NGC 5548. Within this LOC framework, we explore how assumptions about the gas hydrogen density and column density distributions influence flux and delay spectra of the DC. We find that: (i) models which match well measured emission-line luminosities and time delays also produce a significant DC component, (ii) increased $\rm {\mathit{ n}_H}$ and/or $\rm {\mathit{ N}_H}$, particularly at smaller BLR radii, result in larger DC luminosities and reduced DC delays, (iii) in a given continuum band the relative importance of the DC component to the measured interband delays is proportional (though not 1:1) to its fractional contribution to the total light in that band, (iv) the measured DC delays and DC variability amplitude depend also on the variability amplitude and characteristic variability time-scale of the driving continuum, (v) the DC radial surface emissivity distributions F(r) approximate power laws in radius with indices close to −2 (≈1:1 response to variations in the driving continuum flux), thus their physics is relatively simple and less sensitive to the unknown geometry and uncertainties in radiative transfer. Finally, we provide a simple recipe for estimating the DC contribution in disc reverberation mapping experiments.
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Nguyen, Dieu D., Takuma Izumi, Sabine Thater, Masatoshi Imanishi, Taiki Kawamuro, Shunsuke Baba, Suzuka Nakano i in. "Black hole mass measurement using ALMA observations of [CI] and CO emissions in the Seyfert 1 galaxy NGC 7469". Monthly Notices of the Royal Astronomical Society 504, nr 3 (21.04.2021): 4123–42. http://dx.doi.org/10.1093/mnras/stab1002.
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ABSTRACT We present a supermassive black hole (SMBH) mass measurement in the Seyfert 1 galaxy NGC 7469 using Atacama Large Millimeter/submillimeter Array (ALMA) observations of the atomic-[CI](1–0) and molecular-12CO(1–0) emission lines at the spatial resolution of ≈0${_{.}^{\prime\prime}}$3 (or ≈100 pc). These emissions reveal that NGC 7469 hosts a circumnuclear gas disc (CND) with a ring-like structure and a two-arm/bi-symmetric spiral pattern within it, surrounded by a starbursting ring. The CND has a relatively low σgas/V ≈ 0.35 (r ≲ 0${_{.}^{\prime\prime}}$5) and ≈0.19 (r > 0${_{.}^{\prime\prime}}$5), suggesting that the gas is dynamically settled and suitable for dynamically deriving the mass of its central source. As is expected from X-ray dominated region (XDR) effects that dramatically increase an atomic carbon abundance by dissociating CO molecules, we suggest that the atomic [CI](1–0) emission is a better probe of SMBH masses than CO emission in active galactic nuclei (AGNs). Our dynamical model using the [CI](1–0) kinematics yields a $M_{\rm BH}=1.78^{+2.69}_{-1.10}\times 10^7$ M⊙ and $M/L_{\rm F547M}=2.25^{+0.40}_{-0.43}$ (M⊙/L⊙). The model using the 12CO(1–0) kinematics also gives a consistent MBH with a larger uncertainty, up to an order of magnitude, i.e. $M_{\rm BH}=1.60^{+11.52}_{-1.45}\times 10^7$ M⊙. This newly dynamical MBH is ≈2 times higher than the mass determined from the reverberation mapped (RM) method using emissions arising in the unresolved broad-line region (BLR). Given this new MBH, we are able to constrain the specific RM dimensionless scaling factor of $f=7.2^{+4.2}_{-3.4}$ for the AGN BLR in NGC 7469. The gas within the unresolved BLR thus has a Keplerian virial velocity component and the inclination of $i\approx {11.0^\circ }_{-2.5}^{+2.2}$, confirming its face-on orientation in a Seyfert 1 AGN by assuming a geometrically thin BLR model.
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Savić, D., R. Goosmann, L. Č. Popović, F. Marin i V. L. Afanasiev. "AGN black hole mass estimates using polarization in broad emission lines". Astronomy & Astrophysics 614 (czerwiec 2018): A120. http://dx.doi.org/10.1051/0004-6361/201732220.
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Context. The innermost regions in active galactic nuclei (AGNs) have not yet been spatially resolved, but spectropolarimetry can provide insight into their hidden physics and geometry. From spectropolarimetric observations in broad emission lines and assuming equatorial scattering as a dominant polarization mechanism, it is possible to estimate the mass of supermassive black holes (SMBHs) residing at the center of AGNs. Aims. We explore the possibilities and limits, and put constraints on the method for determining SMBH masses using polarization in broad emission lines by providing more in-depth theoretical modeling. Methods. We used the Monte Carlo radiative transfer code STOKES to explore polarization properties of Type-1 AGNs. We modeled equatorial scattering using flared-disk geometry for a set of different SMBH masses assuming Thomson scattering. In addition to the Keplerian motion, which is assumed to be dominant in the broad-line region (BLR), we also considered cases of additional radial inflows and vertical outflows. Results. We modeled the profiles of polarization plane position angle φ, degree of polarization, and total unpolarized lines for different BLR geometries and different SMBH masses. Our model confirms that the method can be widely used for Type-1 AGNs when viewing inclinations are between 25° and 45°. We show that the distance between the BLR and scattering region (SR) has a significant impact on the mass estimates and the best mass estimates are when the SR is situated at a distance 1.5–2.5 times larger than the outer BLR radius. Conclusions. Our models show that if Keplerian motion can be traced through the polarized line profile, then the direct estimation of the mass of the SMBH can be performed. When radial inflows or vertical outflows are present in the BLR, this method can still be applied if velocities of the inflow/outflow are less than 500 km s−1. We also find that models for NGC 4051, NGC 4151, 3C 273, and PG0844+349 are in good agreement with observations.
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Hermosa Muñoz, L., S. Cazzoli, I. Márquez i J. Masegosa. "Optical spectroscopy of type 2 LINERs". Astronomy & Astrophysics 635 (marzec 2020): A50. http://dx.doi.org/10.1051/0004-6361/201936680.
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Context. Type 2 Low-ionization Nuclear Emission-line Regions (LINERs) have been optically classified with the Palomar data as not presenting a broad component in the Balmer emission lines that are associated with the broad-line region (BLR) of the active galactic nuclei (AGN). Aims. We aim to unveil the presence of different kinematic components of emission lines in the nuclear region of a sample of local (z ≤ 0.022) type 2 LINERs. We focus on the analysis of the true nature of LINERs by means of the detection (or nondetection) of a broad component that originated in the BLR of the AGN. Additionally, we search for the possible presence of nonrotational motions such as outflows in these LINERs. Methods. We applied a decomposition of the nuclear emission lines using an spectroscopic analysis of the optical spectra of nine type 2 LINERs of intermediate-resolution spectroscopic data retrieved from the Hubble Space Telescope (HST) archive. The study is completed with archival spectra from the Double Spectrograph from the Palomar Observatory. Results. The emission line fitting reveals the presence of a broad component associated with the BLR in six out of the nine galaxies for the space-based data, and for two out of the eight from the ground-based spectra. The velocity dispersion for two galaxies (NGC 4486 and NGC 4594) measured in HST/STIS data suggest the presence of outflows. Conclusions. The results indicate that the spatial resolution plays a major role in the detection of the BLR, as it appears diluted in the ground-based data (even after removing stellar contribution). This is also true for the emission line diagnostics, as the contaminant light contributes to lower emission line ratios toward the star-forming area of standard BPTs. We propose to reclassify NGC 4594 as a type 1 LINER, since a BLR component is seen in both space- and ground-based spectra. We find ambiguous results for the BLR component of NGC 4486. The modest outflow detection in our sample may indicate that they are not as frequent as seen for type 1 LINERs.
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Vietri, G., V. Mainieri, D. Kakkad, H. Netzer, M. Perna, C. Circosta, C. M. Harrison i in. "SUPER". Astronomy & Astrophysics 644 (grudzień 2020): A175. http://dx.doi.org/10.1051/0004-6361/202039136.
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Aims. The SINFONI survey for Unveiling the Physics and Effect of Radiative feedback (SUPER) was designed to conduct a blind search for AGN-driven outflows on X-ray-selected AGNs at redshift z ∼ 2 with high (∼2 kpc) spatial resolution, and to correlate them with the properties of their host galaxy and central black hole. The main aims of this paper are: (a) to derive reliable estimates for the masses of the black holes and accretion rates for the Type-1 AGNs in this survey; and (b) to characterise the properties of the AGN-driven winds in the broad line region (BLR). Methods. We analysed rest-frame optical and UV spectra of 21 Type-1 AGNs. We used Hα, Hβ, and MgII line profiles to estimate the masses of the black holes. We used the blueshift of the CIV line profile to trace the presence of winds in the BLR. Results. We find that the Hα and Hβ line widths are strongly correlated, as is the line continuum luminosity at 5100 Å with Hα line luminosity, resulting in a well-defined correlation between black hole masses estimated from Hα and Hβ. Using these lines, we estimate that the black hole masses for our objects are in the range Log (MBH/M⊙) = 8.4–10.8 and are accreting at λEdd = 0.04–1.3. Furthermore, we confirm the well-known finding that the CIV line width does not correlate with the Balmer lines and the peak of the line profile is blueshifted with respect to the [OIII]-based systemic redshift. These findings support the idea that the CIV line is tracing outflowing gas in the BLR for which we estimated velocities up to ∼4700 km s−1. We confirm the strong dependence of the BLR wind velocity on the UV-to-X-ray continuum slope, the bolometric luminosity, and Eddington ratio. We infer BLR mass outflow rates in the range 0.005–3 M⊙ yr−1, revealing a correlation with the bolometric luminosity consistent with that observed for ionised winds in the narrow line region (NLR), and X-ray winds detected in local AGNs, and kinetic power ∼10−7 − 10−4 × LBol. The coupling efficiencies predicted by AGN-feedback models are much higher than the values reported for the BLR winds in the SUPER sample; although it should be noted that only a fraction of the energy injected by the AGN into the surrounding medium is expected to become kinetic power in the outflow. Finally, we find an anti-correlation between the equivalent width of the [OIII] line and the CIV velocity shift, and a positive correlation between this latter parameter and [OIII] outflow velocity. These findings, for the first time in an unbiased sample of AGNs at z ∼ 2, support a scenario where BLR winds are connected to galaxy-scale detected outflows, and are therefore capable of affecting the gas in the NLR located at kiloparsec scale distances.
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Kaspi, Shai. "Recent results of measuring black hole masses via reverberation mapping". Proceedings of the International Astronomical Union 15, S356 (październik 2019): 116–21. http://dx.doi.org/10.1017/s1743921320002707.
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AbstractOver the past three decades more than 100 Active Galactic Nuclei (AGNs) were measured using the reverberation mapping technique. This technique uses the response of the line emission in the Broad Line Region (BLR) to continuum emission variation and yields a measure for the distance of the BLR from the central Black Hole (BH). This in turn is used to measure the BH’s mass. Almost all of these measurements are of low-luminosity AGNs while for quasars with luminosities higher than 1046 rg s−1 there are hardly any attempts of reverberation mapping. This contribution reports on recent results from a two-decades campaigns to measure the BH mass in high-luminosity quasars using the reverberation mapping technique. BLR distance from the BH, BH mass, and AGN UV luminosity relations over eight orders of magnitude in luminosity are presented, pushing the luminosity limit to the highest point so far.
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Kaspi, Shai. "Results from Five Years of Spectrophotometric Monitoring of 28 Palomar-Green Quasars". International Astronomical Union Colloquium 159 (1997): 159–62. http://dx.doi.org/10.1017/s0252921100039877.
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AbstractWe present 5 years of results from a spectrophotometric monitoring program of 28 quasars. The typical sampling intervals are several months. We show the light curves obtained for two quasars, PG 0804+762 and PG 0953+414. Both sources show Balmer emissionline variations which follow those of the continuum with a time lag of order 100 days. This is the first reliable measurement of such a lag in active galactic nuclei with luminosity L > 1045 erg s−1. The broad-line region (BLR) size that is implied is almost an order of magnitude larger than that measured in several Seyfert 1 galaxies and is consistent with the hypothesis that the BLR size grows as L0.5.
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Romano, P., M. Böttcher, L. Foschini, C. Boisson, S. Vercellone i M. Landoni. "Prospects for γ-ray observations of narrow-line Seyfert 1 galaxies with the Cherenkov Telescope Array – II. γ–γ absorption in the broad-line region radiation fields". Monthly Notices of the Royal Astronomical Society 494, nr 1 (3.03.2020): 411–24. http://dx.doi.org/10.1093/mnras/staa600.
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ABSTRACT Gamma-ray emitting narrow-line Seyfert 1 (γ-NLS1) galaxies possibly harbour relatively low-mass black holes (106–108 M⊙) accreting close to the Eddington limit, and share many characteristics with their sibling sources, flat-spectrum radio quasars. Although they have been detected in the MeV–GeV band with Fermi–LAT, they have never been seen in the very high energy band with current imaging atmospheric Cherenkov telescopes (IACTs). Thus, they are key targets for the next-generation IACT, the Cherenkov Telescope Array (CTA). In a previous work we selected, by means of extensive simulations, the best candidates for a prospective CTA detection (SBS 0846+513, PMN J0948+0022, and PKS 1502+036) taking into account the effects of both the intrinsic absorption (approximated with a cut-off at 30 GeV), and the extragalactic background light on the propagation of γ-rays. In this work, we simulate the spectra of these three sources by adopting more realistic broad-line region (BLR) absorption models. In particular, we consider the detailed treatment of γ–γ absorption in the radiation fields of the BLR as a function of the location of the γ-ray emission region with parameters inferred from observational constraints. We find that, due to the energy range extent and its sensitivity, CTA is particularly well suited to locate the γ-ray emitting region in γ-NLS1. In particular CTA will be able not only to distinguish whether the γ-ray emitting region is located inside or outside the BLR, but also where inside the BLR it may be.
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Laor, Ari, Buell T. Jannuzi, Richard F. Green i Todd A. Boroson. "The HST Spectrum of I Zw 1: Implications of the C III* λ1176 Emission Line". International Astronomical Union Colloquium 159 (1997): 116–17. http://dx.doi.org/10.1017/s0252921100039762.
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AbstractI Zw 1 is a well-known narrow-line quasar with very strong Fe II emission. High S/N spectra obtained with the HST FOS show a remarkably rich emission-line spectrum. The C III*λ1176 line is clearly detected in emission for the first time in AGNs. This line arises from radiative decay to the 2s2p3Pº0,1,2 metastable levels of C III. The observed flux is ~ 50 times larger than expected from collisional excitation or dielectronic recombination in photoionized gas. The most plausible mechanism for the large enhancement in the C III* λ1176 flux is resonance scattering of continuum photons by C III* ions. This mechanism requires large velocity gradients (~ 1000 km s−1) within each emitting cloud in the BLR. Such large velocity gradients can be induced by forces external to the gas in the BLR clouds, such as tidal disruption, or radiation pressure.
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Son, Dong-Hoon, i Siek Hyung. "IUE SPECTRA OF SEYEERT 1 GALAXY NGC 7469-BLR CHARACTERISTICS OF NGC 7469". Journal of Astronomy and Space Sciences 22, nr 3 (1.09.2005): 187–96. http://dx.doi.org/10.5140/jass.2005.22.3.187.
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Ilić, Dragana. "The BLR physics from the long-term optical monitoring of type-1 AGN". Proceedings of the International Astronomical Union 15, S356 (październik 2019): 144. http://dx.doi.org/10.1017/s1743921320002768.
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AbstractThe variation of optical continuum and broad emission lines is observed in all type 1 active galactic nuclei (AGN). In some cases even extreme variability is detected when broad-line profiles completely disappear as is the case in the co-called changing-look AGN, which raise new question on the theoretical model of AGN. This variability is an important tool to study the physics and geometry of the broad line region (BLR), e.g. it can be used to estimate its size through the reverberation mapping technique. Especially, long-term campaigns give new insights, like the detection of the periodic signals or discoveries of changing-look AGN. Here we will present the results of our long-term monitoring campaign of several well-known AGN, as e.g. NGC 3516 for which we confirm that it is the changing-look AGN, putting special attention of the applications for future large time-domain spectroscopic surveys, like the MaunaKea Spectroscopic Explorer project.
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Popović, Luka Č., Victor L. Afanasiev i Djordje Savić. "Black hole mass measurements in AGN: Polarization in broad emission lines". Proceedings of the International Astronomical Union 14, S342 (maj 2018): 1–4. http://dx.doi.org/10.1017/s1743921318007640.
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AbstractWe present a new method for supermassive black hole (SMBH) mass measurements in Type 1 active galactic nuclei (AGN) using polarization angle across broad lines. This method gives measured masses which are in a good agreement with reverberation estimates. Additionally, we explore the possibilities and limits of this method using the STOKES radiative transfer code taking a dominant Keplerian motion in the broad line region (BLR). We found that this method can be used for the direct SMBH mass estimation in the cases when in addition to the Kepler motion, radial inflows or vertical outflows are present in the BLR. Some advantages of the method are discussed.
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Panda, Swayamtrupta, Paola Marziani i Bożena Czerny. "Feii strength in NLS1s – dependence on the viewing angle and FWHM(Hβ)". Proceedings of the International Astronomical Union 15, S356 (październik 2019): 332–34. http://dx.doi.org/10.1017/s1743921320003269.
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AbstractWe address the effect of orientation of the accretion disk plane and the geometry of the broad line region (BLR) in the context of understanding the distribution of quasars along their Main Sequence. We utilize the photoionization code CLOUDY to model the BLR, incorporating the ‘un-constant’ virial factor. We show the preliminary results of the analysis to highlight the co-dependence of the Eigenvector 1 parameter, RFeII on the broad HβFWHM (i.e. the line dispersion) and the inclination angle (θ), assuming fixed values for the Eddington ratio (Lbol/ LEdd), black hole mass (MBH), spectral energy distribution (SED) shape, cloud density (nH) and composition.†
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Xue, S. J., i F. Z. Cheng. "Reverberation Mapping Analysis of the Broad-Line Region in Seyfert Galaxy NGC 4151". Symposium - International Astronomical Union 188 (1998): 424–25. http://dx.doi.org/10.1017/s0074180900115840.
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One of the primary goals of AGN variability studies has been to determine the size of broad-line region (BLR) through the reverberation mapping technique. In a recent international multiwavelength spectroscopic monitoring campaign, NGC 4151 has been observed intensively by ground-based telescopes for a period of over 2 months, with a typical temporal resolution of 1 day. The main result from this optical campaign is that finding the variation in the emission line flux (Hβ or Hα) lagging the continuum by 0-3 days (1993 campaign: Kaspi et al. 1996). This is in contrast to the past results in which a time lag of 9±2 days was found for the same emission line (1988 campaign: Maoz et al. 1991). Such a BLR “size problem” may be caused by a different variability timescale of the ionizing continuum or a real change in BLR gas distribution in the 5.5 yr interval between the two watch campaigns. In order to clarify which of the two possibilities is most likely the real case, we performed further reverberation analysis on both optical datasets.
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Sapitang, Michelle, Wanie M. Ridwan, Khairul Faizal Kushiar, Ali Najah Ahmed i Ahmed El-Shafie. "Machine Learning Application in Reservoir Water Level Forecasting for Sustainable Hydropower Generation Strategy". Sustainability 12, nr 15 (30.07.2020): 6121. http://dx.doi.org/10.3390/su12156121.
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The aim of this study is to accurately forecast the changes in water level of a reservoir located in Malaysia with two different scenarios; Scenario 1 (SC1) includes rainfall and water level as input and Scenario 2 (SC2) includes rainfall, water level, and sent out. Different time horizons (one day ahead to seven days) will be investigated to check the accuracy of the proposed models. In this study, four supervised machine learning algorithms for both scenarios were proposed such as Boosted Decision Tree Regression (BDTR), Decision Forest Regression (DFR), Bayesian Linear Regression (BLR) and Neural Network Regression (NNR). Eighty percent of the total data were used for training the datasets while 20% for the dataset used for testing. The models’ performance is evaluated using five statistical indexes; the Correlation Coefficient (R2), Mean Absolute Error (MAE), Root Mean Square Error (RMSE), Relative Absolute Error (RAE), and Relative Squared Error (RSE). The findings showed that among the four proposed models, the BLR model outperformed other models with R2 0.998952 (1-day ahead) for SC1 and BDTR for SC2 with R2 0.99992 (1-day ahead). With regards to the uncertainty analysis, 95PPU and d-factors were adopted to measure the uncertainties of the best models (BLR and BDTR). The results showed the value of 95PPU for both models in both scenarios (SC1 and SC2) fall into the range between 80% to 100%. As for the d-factor, all values in SC1 and SC2 fall below one.
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Nhu, Viet-Ha, Danesh Zandi, Himan Shahabi, Kamran Chapi, Ataollah Shirzadi, Nadhir Al-Ansari, Sushant K. Singh, Jie Dou i Hoang Nguyen. "Comparison of Support Vector Machine, Bayesian Logistic Regression, and Alternating Decision Tree Algorithms for Shallow Landslide Susceptibility Mapping along a Mountainous Road in the West of Iran". Applied Sciences 10, nr 15 (22.07.2020): 5047. http://dx.doi.org/10.3390/app10155047.
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This paper aims to apply and compare the performance of the three machine learning algorithms–support vector machine (SVM), bayesian logistic regression (BLR), and alternating decision tree (ADTree)–to map landslide susceptibility along the mountainous road of the Salavat Abad saddle, Kurdistan province, Iran. We identified 66 shallow landslide locations, based on field surveys, by recording the locations of the landslides by a global position System (GPS), Google Earth imagery and black-and-white aerial photographs (scale 1: 20,000) and 19 landslide conditioning factors, then tested these factors using the information gain ratio (IGR) technique. We checked the validity of the models using statistical metrics, including sensitivity, specificity, accuracy, kappa, root mean square error (RMSE), and area under the receiver operating characteristic curve (AUC). We found that, although all three machine learning algorithms yielded excellent performance, the SVM algorithm (AUC = 0.984) slightly outperformed the BLR (AUC = 0.980), and ADTree (AUC = 0.977) algorithms. We observed that not only all three algorithms are useful and effective tools for identifying shallow landslide-prone areas but also the BLR algorithm can be used such as the SVM algorithm as a soft computing benchmark algorithm to check the performance of the models in future.
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Müller, A. L., i G. E. Romero. "Radiation from the impact of broad-line region clouds onto AGN accretion disks". Astronomy & Astrophysics 636 (kwiecień 2020): A92. http://dx.doi.org/10.1051/0004-6361/202037639.
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Context. Active galactic nuclei are supermassive black holes surrounded by an accretion disk, two populations of clouds, bipolar jets, and a dusty torus. The clouds move in Keplerian orbits at high velocities. In particular, the broad-line region (BLR) clouds have velocities ranging from 1000 to 10 000 km s−1. Given the extreme proximity of these clouds to the supermassive black hole, frequent collisions with the accretion disk should occur. Aims. The impact of BLR clouds onto the accretion disk can produce strong shock waves where particles might be accelerated. The goal of this work is to investigate the production of relativistic particles, and the associated non-thermal radiation in these events. In particular, we apply the model we develop to the Seyfert galaxy NGC 1068. Methods. We analyze the efficiency of diffusive shock acceleration in the shock of colliding clouds of the BLR with the accretion disk. We calculate the spectral energy distribution of photons generated by the relativistic particles and estimate the number of simultaneous impacts needed to explain the gamma radiation observed by Fermi in Seyfert galaxies. Results. We find that is possible to understand the measured gamma emission in terms of the interaction of clouds with the disk if the hard X-ray emission of the source is at least obscured between 20% and 40%. The total number of clouds contained in the BLR region might be between 3 × 108 and 6 × 108, which are values in good agreement with the observational evidence. The maximum energy achieved by the protons (∼PeV) in this context allows the production of neutrinos in the observing range of IceCube.
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Amorim, A., M. Bauböck, W. Brandner, M. Bolzer, Y. Clénet, R. Davies, P. T. de Zeeuw i in. "The central parsec of NGC 3783: a rotating broad emission line region, asymmetric hot dust structure, and compact coronal line region". Astronomy & Astrophysics 648 (kwiecień 2021): A117. http://dx.doi.org/10.1051/0004-6361/202040061.
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Using VLTI/GRAVITY and SINFONI data, we investigate the subparsec gas and dust structure around the nearby type 1 active galactic nucleus (AGN) hosted by NGC 3783. The K-band coverage of GRAVITY uniquely allows simultaneous analysis of the size and kinematics of the broad line region (BLR), the size and structure of the near-infrared(near-IR)-continuum-emitting hot dust, and the size of the coronal line region (CLR). We find the BLR, probed through broad Brγ emission, to be well described by a rotating, thick disc with a radial distribution of clouds peaking in the inner region. In our BLR model, the physical mean radius of 16 light-days is nearly twice the ten-day time-lag that would be measured, which closely matches the ten-day time-lag that has been measured by reverberation mapping. We measure a hot dust full-width at half-maximum (FWHM) size of 0.74 mas (0.14 pc) and further reconstruct an image of the hot dust, which reveals a faint (5% of the total flux) offset cloud that we interpret as an accreting or outflowing cloud heated by the central AGN. Finally, we directly measure the FWHM size of the nuclear CLR as traced by the [Ca VIII] and narrow Brγ line. We find a FWHM size of 2.2 mas (0.4 pc), fully in line with the expectation of the CLR located between the BLR and narrow line region. Combining all of these measurements together with larger scale near-IR integral field unit and mid-IR interferometry data, we are able to comprehensively map the structure and dynamics of gas and dust from 0.01 to 100 pc.
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Steyaert, Johanna M., Richard J. Weld, Artemio Mendoza-Mendoza i Alison Stewart. "Reproduction without sex: conidiation in the filamentous fungus Trichoderma". Microbiology 156, nr 10 (1.10.2010): 2887–900. http://dx.doi.org/10.1099/mic.0.041715-0.
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Trichoderma spp. have served as models for asexual reproduction in filamentous fungi for over 50 years. Physical stimuli, such as light exposure and mechanical injury to the mycelium, trigger conidiation; however, conidiogenesis itself is a holistic response determined by the cell's metabolic state, as influenced by the environment and endogenous biological rhythms. Key environmental parameters are the carbon and nitrogen status and the C : N ratio, the ambient pH and the level of calcium ions. Recent advances in our understanding of the molecular biology of this fungus have revealed a conserved mechanism of environmental perception through the White Collar orthologues BLR-1 and BLR-2. Also implicated in the molecular regulation are the PacC pathways and the conidial regulator VELVET. Signal transduction cascades which link environmental signals to physiological outputs have also been revealed.
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Gosalbes, M. J., Y. Vallès, N. Jiménez-Hernández, C. Balle, P. Riva, S. Miravet-Verde, L. E. de Vries i in. "High frequencies of antibiotic resistance genes in infants’ meconium and early fecal samples". Journal of Developmental Origins of Health and Disease 7, nr 1 (10.09.2015): 35–44. http://dx.doi.org/10.1017/s2040174415001506.
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The gastrointestinal tract (GIT) microbiota has been identified as an important reservoir of antibiotic resistance genes (ARGs) that can be horizontally transferred to pathogenic species. Maternal GIT microbes can be transmitted to the offspring, and recent work indicates that such transfer starts before birth. We have used culture-independent genetic screenings to explore whether ARGs are already present in the meconium accumulated in the GIT during fetal life and in feces of 1-week-old infants. We have analyzed resistance to β-lactam antibiotics (BLr) and tetracycline (Tcr), screening for a variety of genes conferring each. To evaluate whether ARGs could have been inherited by maternal transmission, we have screened perinatal fecal samples of the 1-week-old babies’ mothers, as well as a mother–infant series including meconium, fecal samples collected through the infant’s 1st year, maternal fecal samples and colostrum. Our results reveal a high prevalence of BLr and Tcr in both meconium and early fecal samples, implying that the GIT resistance reservoir starts to accumulate even before birth. We show that ARGs present in the mother may reach the meconium and colostrum and establish in the infant GIT, but also that some ARGs were likely acquired from other sources. Alarmingly, we identified in both meconium and 1-week-olds’ samples a particularly elevated prevalence of mecA (>45%), six-fold higher than that detected in the mothers. The mecA gene confers BLr to methicillin-resistant Staphylococcus aureus, and although its detection does not imply the presence of this pathogen, it does implicate the young infant’s GIT as a noteworthy reservoir of this gene.
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Raiteri, C. M., J. A. Acosta Pulido, M. Villata, M. I. Carnerero, P. Romano i S. Vercellone. "Unveiling the monster heart: unbeamed properties of blazar 4C 71.07". Monthly Notices of the Royal Astronomical Society 493, nr 2 (17.02.2020): 2793–804. http://dx.doi.org/10.1093/mnras/staa453.
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ABSTRACT 4C 71.07 is a high-redshift blazar whose optical radiation is dominated by quasar-like nuclear emission. We here present the results of a spectroscopic monitoring of the source to study its unbeamed properties. We obtained 24 optical spectra at the Nordic Optical Telescope and William Herschel Telescope and 3 near-infrared spectra at the Telescopio Nazionale Galileo. They show no evidence of narrow emission lines. The estimate of the systemic redshift from the Hβ and Hα broad emission lines leads to zsys = 2.2130 ± 0.0004. Notwithstanding the nearly face-on orientation of the accretion disc, the high-ionization emission lines present large broadening as well as noticeable blueshifts, which increase with the ionizing energy of the corresponding species. This is a clear indication of strong ionized outflows. Line broadening and blueshift appear correlated. We applied scaling relationships to estimate the mass of the supermassive black hole from the Balmer and C iv lines, taking into account the prescriptions to correct for outflow. They give $M_{\rm BH} \sim 2 \times 10^9 \, M_\odot$. We derived an Eddington luminosity $L_{\rm Edd} \sim 2.5 \times 10^{47} \rm \, erg \, s^{-1}$ ∼ Ldisc, and a broad-line region (BLR) luminosity of $L_{\rm BLR} \sim 1.5 \times 10^{46} \rm \, erg \, s^{-1}$. The line fluxes do not show significant variability in time. In particular, there is no line reaction to the jet flaring activity detected in 2015 October and November. This implies that the jet gives no contribution to the photoionization of the BLR in the considered period.
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Amorim, A., M. Bauböck, W. Brandner, Y. Clénet, R. Davies, P. T. de Zeeuw, J. Dexter i in. "The spatially resolved broad line region of IRAS 09149−6206". Astronomy & Astrophysics 643 (listopad 2020): A154. http://dx.doi.org/10.1051/0004-6361/202039067.
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We present new near-infrared VLTI/GRAVITY interferometric spectra that spatially resolve the broad Brγ emission line in the nucleus of the active galaxy IRAS 09149−6206. We use these data to measure the size of the broad line region (BLR) and estimate the mass of the central black hole. Using an improved phase calibration method that reduces the differential phase uncertainty to 0.05° per baseline across the spectrum, we detect a differential phase signal that reaches a maximum of ∼0.5° between the line and continuum. This represents an offset of ∼120 μas (0.14 pc) between the BLR and the centroid of the hot dust distribution traced by the 2.3 μm continuum. The offset is well within the dust sublimation region, which matches the measured ∼0.6 mas (0.7 pc) diameter of the continuum. A clear velocity gradient, almost perpendicular to the offset, is traced by the reconstructed photocentres of the spectral channels of the Brγ line. We infer the radius of the BLR to be ∼65 μas (0.075 pc), which is consistent with the radius–luminosity relation of nearby active galactic nuclei derived based on the time lag of the Hβ line from reverberation mapping campaigns. Our dynamical modelling indicates the black hole mass is ∼1 × 108 M⊙, which is a little below, but consistent with, the standard MBH–σ* relation.
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Acciari, V. A., S. Ansoldi, L. A. Antonelli, A. Arbet Engels, C. Arcaro, D. Baack, A. Babić i in. "Detection of persistent VHE gamma-ray emission from PKS 1510–089 by the MAGIC telescopes during low states between 2012 and 2017". Astronomy & Astrophysics 619 (listopad 2018): A159. http://dx.doi.org/10.1051/0004-6361/201833618.
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Context. PKS 1510–089 is a flat spectrum radio quasar strongly variable in the optical and GeV range. To date, very high-energy (VHE, > 100 GeV) emission has been observed from this source either during long high states of optical and GeV activity or during short flares. Aims. We search for low-state VHE gamma-ray emission from PKS 1510–089. We characterize and model the source in a broadband context, which would provide a baseline over which high states and flares could be better understood. Methods. PKS 1510–089 has been monitored by the MAGIC telescopes since 2012. We use daily binned Fermi-LAT flux measurements of PKS 1510–089 to characterize the GeV emission and select the observation periods of MAGIC during low state of activity. For the selected times we compute the average radio, IR, optical, UV, X-ray, and gamma-ray emission to construct a low-state spectral energy distribution of the source. The broadband emission is modeled within an external Compton scenario with a stationary emission region through which plasma and magnetic fields are flowing. We also perform the emission-model-independent calculations of the maximum absorption in the broad line region (BLR) using two different models. Results. The MAGIC telescopes collected 75 hr of data during times when the Fermi-LAT flux measured above 1 GeV was below 3 × 10−8 cm−2 s−1, which is the threshold adopted for the definition of a low gamma-ray activity state. The data show a strongly significant (9.5σ) VHE gamma-ray emission at the level of (4.27 ± 0.61stat) × 10−12 cm−2 s−1 above 150 GeV, a factor of 80 lower than the highest flare observed so far from this object. Despite the lower flux, the spectral shape is consistent with earlier detections in the VHE band. The broadband emission is compatible with the external Compton scenario assuming a large emission region located beyond the BLR. For the first time the gamma-ray data allow us to place a limit on the location of the emission region during a low gamma-ray state of a FSRQ. For the used model of the BLR, the 95% confidence level on the location of the emission region allows us to place it at a distance > 74% of the outer radius of the BLR.
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Vercellone, Stefano, Luigi Foschini, Patrizia Romano, Markus Böttcher i Catherine Boisson. "High-Energy and Very High-Energy Constraints from Log-Parabolic Spectral Models in Narrow-Line Seyfert 1 Galaxies". Universe 6, nr 4 (16.04.2020): 54. http://dx.doi.org/10.3390/universe6040054.
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Narrow-line Seyfert 1 galaxies (NLSy1s) are a well established class of γ -ray sources, showing the presence of a jet like the more common flat-spectrum radio quasars. The evidence of γ -ray emission poses the issue of the location of the γ -ray emitting zone and of the contribution of the γ - γ absorption within the broad-line region (BLR), since such objects have been detected by Fermi-LAT in the MeV-GeV energy range but not by imaging atmospheric Cherenkov telescopes beyond 100 GeV. We discuss how the spectral properties of three NLSy1s (SBS 0846+513, PMN J0948+0022, and PKS 1502+036) derived from the Fermi Large Area Telescope Fourth Source Catalog (4FGL) compared with theoretical models based on the observed properties of the BLR. In particular, we focus on the question on how simple power-law spectral models and log-parabolic ones could be disentangled in γ -ray narrow-line Seyfert 1 galaxies by means of current Fermi-LAT or future imaging atmospheric Cherenkov telescopes data. We found that the only possibility for a log-parabolic model to mimic a power-law model in the energy band above E ∼ 100 GeV is to have a very small value of the curvature parameter β ∼ 0.05 .
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Esser, J., J. U. Pott, H. Landt i W. D. Vacca. "Analyzing temporal variations of AGN emission line profiles in the context of (dusty) cloud structure formation in the broad line region". Astronomy & Astrophysics 621 (styczeń 2019): A46. http://dx.doi.org/10.1051/0004-6361/201834291.
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The formation processes and the exact appearance of the dust torus and broad line region (BLR) of active galactic nuclei (AGN) are under debate. Theoretical studies show a possible connection between the dust torus and BLR through a common origin in the accretion disk. However observationally the dust torus and BLR are typically studied separately. NGC 4151 is possibly one of the best suited Seyfert 1 galaxies for simultaneous examinations because of its high number of both photometric and spectroscopic observations in the past. Here we compare changes of the dust radius to shape variations of broad emission lines (BEL). While the radius of the dust torus decreased by almost a factor of two from 2004 to 2006 shape variations can be seen in the red wing of BELs of NGC 4151. These simultaneous changes are discussed in a dust and BEL formation scheme. We also use the BEL shape variations to assess possible cloud distributions, especially in azimuthal direction, which could be responsible for the observed variations. Our findings can best be explained in the framework of a dust inflated accretion disk. The changes in the BELs suggest that this dusty cloud formation does not happen continuously, and over the whole accretion disk, but on the contrary in spatially confined areas over rather short amount of times. We derive limits to the azimuthal extension of the observed localized BEL flux enhancement event.
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Risaliti, Guido. "The Structure of AGNs from X-Ray Absorption Variability". Proceedings of the International Astronomical Union 5, S267 (sierpień 2009): 299–306. http://dx.doi.org/10.1017/s1743921310006514.
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AbstractWe present new evidence of X-ray absorption variability on time scales from a few hours to a few days for several nearby bright AGNs. The observed NH variations imply that the X-ray absorber is made of clouds eclipsing the X-ray source with velocities in excess of 103 km s−1, and densities, sizes and distances from the central black hole typical of BLR clouds. We conclude that the variable X-ray absorption is due to the same clouds emitting the broad emission lines in the optical/UV. We then concentrate on the two highest signal-to-noise spectra of eclipses, discovered in two long observations of NGC 1365 and Mrk 766, and we show that the obscuring clouds have a cometary shape, with a high density head followed by a tail with decreasing NH. Our results show that X-ray time resolved spectroscopy can be a powerful way to directly measure the physical and geometrical properties of BLR clouds.
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Panda, Swayamtrupta, Paola Marziani i Bożena Czerny. "Feii emission in NLS1s – originating from denser regions with higher abundances?" Proceedings of the International Astronomical Union 15, S356 (październik 2019): 77–81. http://dx.doi.org/10.1017/s1743921320002616.
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AbstractThe interpretation of the main sequence of quasars has become a frontier subject in the last years. This considers the effect of a highly flattened, axially symmetric geometry for the broad line region (BLR) on the parameters related to the distribution of quasars along their main sequence. We utilize the photoionization code CLOUDY to model the BLR, assuming ‘un-constant’ virial factor with a strong dependence on the viewing angle. We show the preliminary results of the analysis to highlight the co-dependence of the Eigenvector 1 parameter, RFeii on the broad Hβ FWHM (i.e. the line dispersion) and the inclination angle (θ), assuming fixed values for the Eddington ratio (Lbo1/LEdd), black hole mass (MBH) and spectral energy distribution (SED) shape. We consider four cases with changing cloud density (nH) and composition. Understanding the emitting region is crucial as this knowledge can be extended to the use of quasars as distance indicators for Cosmology.‡
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Luk, Abbie Sheung-Wan, Jason Cheuk-Sing Yam, Henry Hing-Wai Lau, Wilson Wai-Kuen Yip i Alvin Lerrmann Young. "Surgical Outcome of Medial Rectus Resection in Recurrent Exotropia: A Novel Surgical Formula". Journal of Ophthalmology 2015 (2015): 1–5. http://dx.doi.org/10.1155/2015/758463.
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Purpose. To evaluate the surgical outcomes of unilateral or bilateral medial rectus (MR) muscle resection for recurrent exotropia after bilateral lateral rectus (BLR) muscle recession based on a novel surgical formula.Methods. Forty-one consecutive patients with unilateral or bilateral MR muscle resection for recurrent exotropia after BLR muscle recession were included in this retrospective study. All surgeries were performed according to the formula: 1.0 mm MR muscle resection for every 5 prism dioptres (PD) of exotropia, with an addition of 0.5 mm to each MR muscle operated on.Results. The mean recurrent exotropia distant deviation was 28 PD ± 11.2 (range 14 to 55 PD). Overall at postoperative 1 month, 36 (88%) achieved successful outcomes, 4 (10%) had undercorrection, and 1 (2%) had overcorrection. At postoperative 6 months, 29 (71%) achieved successful outcomes, 12 (29%) had undercorrection, and none had overcorrection. Subgroup analysis showed no statistically significant difference in success rates between unilateral and bilateral MR groups.Conclusion. Unilateral or bilateral MR muscle resection using our surgical formula is a safe and effective method for calculating the amount of MR resection in moderate to large angle recurrent exotropia, with a low overcorrection rate.
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COLE, JOSHUA A., i STEPHEN G. SIMPSON. "MASS PROBLEMS AND HYPERARITHMETICITY". Journal of Mathematical Logic 07, nr 02 (grudzień 2007): 125–43. http://dx.doi.org/10.1142/s0219061307000652.
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A mass problem is a set of Turing oracles. If P and Q are mass problems, we say that P is weakly reducible to Q if for all Y ∈ Q there exists X ∈ P such that X is Turing reducible to Y. A weak degree is an equivalence class of mass problems under mutual weak reducibility. Let [Formula: see text] be the lattice of weak degrees of mass problems associated with nonempty [Formula: see text] subsets of the Cantor space. The lattice [Formula: see text] has been studied in previous publications. The purpose of this paper is to show that [Formula: see text] partakes of hyperarithmeticity. We exhibit a family of specific, natural degrees in [Formula: see text] which are indexed by the ordinal numbers less than [Formula: see text] and which correspond to the hyperarithmetical hierarchy. Namely, for each [Formula: see text], let hα be the weak degree of 0(α), the αth Turing jump of 0. If p is the weak degree of any mass problem P, let p* be the weak degree of the mass problem P* = {Y | ∃X (X ∈ P and BLR (X) ⊆ BLR (Y))} where BLR (X) is the set of functions which are boundedly limit recursive in X. Let 1 be the top degree in [Formula: see text]. We prove that all of the weak degrees [Formula: see text], [Formula: see text], are distinct and belong to [Formula: see text]. In addition, we prove that certain index sets associated with [Formula: see text] are [Formula: see text] complete.
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del Palacio, S., V. Bosch-Ramon i G. E. Romero. "Gamma rays from jets interacting with BLR clouds in blazars". Astronomy & Astrophysics 623 (marzec 2019): A101. http://dx.doi.org/10.1051/0004-6361/201834231.
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Context. The innermost parts of powerful jets in active galactic nuclei are surrounded by dense, high-velocity clouds from the broad-line region, which may penetrate into the jet and lead to the formation of a strong shock. Such jet-cloud interactions are expected to have measurable effects on the γ-ray emission from blazars. Aims. We characterise the dynamics of a typical cloud-jet interaction scenario, and the evolution of its radiative output in the 0.1–30 GeV energy range, to assess to what extent these interactions can contribute to the γ-ray emission in blazars. Methods. We use semi-analytical descriptions of the jet-cloud dynamics, taking into account the expansion of the cloud inside the jet and its acceleration. Assuming that electrons are accelerated in the interaction and making use of the hydrodynamical information, we then compute the high-energy radiation from the cloud, including the absorption of γ-rays in the ambient photon field through pair creation. Results. Jet-cloud interactions can lead to significant γ-ray fluxes in blazars with a broad-line region (BLR), in particular when the cloud expansion and acceleration inside the jet are taken into account. This is caused by 1) the increased shocked area in the jet, which leads to an increase in the energy budget for the non-thermal emission; 2) a more efficient inverse Compton cooling with the boosted photon field of the BLR; and 3) an increased observer luminosity due to Doppler boosting effects. Conclusions. For typical broad-line region parameters, either (i) jet-cloud interactions contribute significantly to the persistent γ-ray emission from blazars or (ii) the BLR is far from spherical or the fraction of energy deposited in non-thermal electrons is small.
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Rodríguez-Pascual, P. M. "IUE Monitoring of the Bright Seyfert 1 Galaxy Fairall 9". International Astronomical Union Colloquium 159 (1997): 167–68. http://dx.doi.org/10.1017/s0252921100039907.
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AbstractAn eight-month spectrscopic monitoring campaign on the Seyfert 1 galaxy Fairall 9 has been carried out with the International Ultraviolet Explorer (IUE) in order to measure continuum-continuum and continuum-emission-line delays for a high-luminosity active galactic nucleus (AGN). The results are consistent with those of previous campaigns on lower luminosity AGNs: (i) there is no measurable time lag between different ultraviolet continuum bands, (ii) the measured time lags for the emission lines are relatively short, and (iii) the more rapid and stronger response to continuum changes of He II, as compared to C IV, is consistent with a stratified broad-line region (BLR) structure.
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Robertson, K. A., E. S. Colvin, M. R. Kelley i M. L. Fishel. "APX3330 inhibition of the redox function of ape-1/ref-1 (Ref-1) in promyelocytic leukemia cells enhances retinoic acid (ATRA) induced myeloid differentiation and limits cell proliferation as an approach to the prevention of the retinoic acid syndrome (RAS)". Journal of Clinical Oncology 27, nr 15_suppl (20.05.2009): e14613-e14613. http://dx.doi.org/10.1200/jco.2009.27.15_suppl.e14613.
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e14613 Background: ATRA + chemotherapy has improved the treatment of promyelocytic leukemia(APL). However, 25% of ATRA treated APL patients experience toxicities that comprise the RAS (life-threatening respiratory distress, edema, renal failure, hypotension, coagulopathy and rising blast count). One approach to prevent RAS is to limit blast proliferation and enhance myeloid differentiation. Ref-1 is a DNA repair protein that functions in redox regulation of cellular proteins, such as Fos, Jun, p53, and NFkB. HL60 myeloid leukemia cells are promyeloblasts that respond to ATRA with granulocytic differentiation/growth arrest. Prior studies suggest Ref-1 redox control is integral to ATRA-induced differentiation. To define the role of the redox function of Ref-1, we used the Ref-1 specific drug, APX3330, to block Ref-1 redox function and examined the response of HL60 cells to ATRA. Methods: Cell growth assessed using trypan blue. Differentiation was evaluated by morphology and expression of CD11b by flow cytometry. Apoptosis was assayed by annexin-PI staining on flow cytometry and cell cycle analysis assayed with propidium iodide flow cytometry. To assess activation of the MAPK pathway, BLR-1 expression was determined by real time PCR. Results: 1) APX3330 blockade of Ref-1 redox function resulted in limited cell growth yet a profound increase in differentiation and a moderate increase in apoptosis. 2) dose dependent studies with ATRA showed a similar degree of differentiation in cells treated with 10 μM ATRA to cells treated with APX3330 + 0.01 μM ATRA; allowing HL60 cells + APX3330 to give a similar response to a 1000 fold lower dose of ATRA. APX3330 alone did not induce differentiation and induced only minimal apoptosis but in combination with ATRA, increased the number of cells in G1/G0 phase significantly. 3) APX3330 + ATRA increased BLR-1 expression significantly by real time PCR suggesting enhanced activation of the MAPK pathway. Conclusions: APX3330 + ATRA limits HL60 growth and dramatically enhances terminal granulocytic differentiation. These finding may provide a therapeutic approach for prevention of the RAS. No significant financial relationships to disclose.
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Doddamani, Vijayakumar H., i P. Vedavathi. "Ultraviolet Line-Continuum properties of Seyfert 1 galaxies and quasars". Proceedings of the International Astronomical Union 9, S304 (październik 2013): 233–35. http://dx.doi.org/10.1017/s1743921314003883.
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AbstractActive galaxies are most luminous objects in the universe whose spectra are characterized by both permitted and forbidden emission line features. The spectra of Seyfert 1 galaxies and quasars contain strong and broad emission lines of wide ranging ionization potentials. The velocity widths of the lines range from a minimum of ≈ 500 km/s for narrow lines to a maximum of 20,000 km/sec for broad lines. The UV spectra of the active galaxies contain strong and broad emission lines such as Lyα, NV, SiIV, OIV], CIV, CIII] and MgII lines. The widths of the broad lines are attributed to the differential doppler shifts of the emission lines due to the bulk motions of individual clumpy gas clouds in the BLR region. We have anlysed UV spectra of Seyfert 1 galaxies and quasars from IUE satellite archival database to understand the nature of dependence of the emission line properties with the underlying UV continuum. We have undertaken line luminosity correlation studies for Lyα and CIV lines with their underlying UV continuum luminosity at 1125Å, 1425Å & 1625Å. The IUE archival spectra have been reduced for galactic reddening using the E(B-V) and NHI values published continuum luminosity has been observed at 1125Å, 1425Å & 1625Å. The Lyα line line has exhibited strongest linear correlation wavelengths while CIV line has shown at 1425Å and 2625Å wavelengths. These results are empirically consistent with the predictions of the general multi-component photo-ionization models suggesting that the central strong UV continuum has been reprocessed by the clumpy gas clouds of the broad emission region (BLR). A detailed account of the data reduction, UV flux measurement and the significance of line-luminosity correlations are discussed in this paper.
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Kartje, John F., Arieh Königl i Moshe Elitzur. "Water Maser Emission from Dusty Clouds in AGNs". International Astronomical Union Colloquium 163 (1997): 738–39. http://dx.doi.org/10.1017/s0252921100043712.
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AbstractA natural site for water maser emission in AGNs is provided by dusty gas with properties characteristic of broad line region (BLR) clouds. Radiation shielding by dust in the clouds is critical for allowing molecular gas to exist ≤ 1 pc from the central engine. Thus, the innermost radius at which such masers appear should correspond to the grain sublimation radius rsub. We suggest a dynamical model in which the masing clouds are embedded within a magnetized accretion disk wind.
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Denney, Kelly D., B. M. Peterson, R. W. Pogge, M. C. Bentz, C. M. Gaskell, T. Minezaki, C. A. Onken, S. G. Sergeev i M. Vestergaard. "Reverberation Mapping Results from MDM Observatory". Proceedings of the International Astronomical Union 5, S267 (sierpień 2009): 201. http://dx.doi.org/10.1017/s1743921310006216.
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Reverberation mapping takes advantage of the presence of a time delay or lag, τ, between continuum and emission line flux variations observed through spectroscopic monitoring campaigns to infer the radius of the broad-line region (BLR) and, subsequently, the central black hole mass in type 1 AGNs. We present results from a multi-month reverberation mapping campaign undertaken primarily at MDM Observatory with supporting observations from around the world. We measure BLR radii and black hole masses for six objects. The primary goal of this campaign was to obtain either new or improved Hβ reverberation lag measurements for several relatively low-luminosity AGNs. Using cross correlation techniques to measure the time delay between the mean optical continuum flux density around 5100 Å and the integrated Hβ flux, we determine the Hβ lags and black hole mass measurements listed in columns 2 and 3 of Table 1, respectively. Column 4 tells if this measurement is new, an improvement meant to replace a previous, less reliable measurement, or simply an additional measurement not used to replace a previous value. The complete results from this study are currently being prepared for publication. A subsequent velocity-resolved analysis of the Hβ response shows that three of the six primary targets demonstrate kinematic signatures (column 5) of infall, outflow, and non-radial virialized motions (see Denney et al. 2009).