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Intensive X-ray/UVOIR continuum reverberation mapping of the Seyfert AGN MCG+08-11-11
No full textWe present results from intensive (x3 daily), three-month-long X-ray, UV and optical monitoring of the bright Seyfert active galactic nucleus (AGN) MCG+08-11-11 with Swift, supported by optical-infrared ground-based monitoring. The 12 resultant, well-sampled, lightcurves are highly correlated; in particular, the X-ray to UV correlation r_max = 0.85 is, as far as we know, the highest yet recorded in a Seyfert galaxy. The lags increase with wavelength, as expected from reprocessing of central high-energy emission by surrounding material. Our lag spectrum is much shallower than that obtained from an optical monitoring campaign conducted a year earlier when MCG+08-11-11 was approximately 4 times brighter. After filtering out long-term trends in the earlier optical lightcurves we recover shorter lags consistent with our own - demonstrating concurrent reverberation signals from different spatial scales and the luminosity dependence of the measured lags. We use our lag spectrum to test several physical models, finding that disc reprocessing models cannot account for the observed 'excess' lags in the u and r-i-bands that are highly indicative of the Balmer and Paschen continua produced by reprocessing in the broad line region (BLR) gas. The structure seen in both the variable (rms) and lag spectra, and the large time delay between X-ray and UV variations (approximately 2 days) all suggest that the BLR is the dominant reprocessor. The hard X-ray spectrum (Gamma approximately 1.7) and faint, red, UV-optical spectrum both indicate that the Eddington accretion ratio is low: approximately 0.03. The bolometric luminosity then requires that the black hole mass is substantially greater than current reverberation mapping derived estimates
Towards generating discriminating instances for multi-agent pathfinding:a case study with shelf-based warehouse scenarios
No full textBenchmarking is central to the evaluation of multi-agent pathfinding (MAPF) solvers, yet benchmark instances are often manually designed and may not systematically expose differences between solving paradigms. Hence, gaining insight into the complementary strengths of different MAPF solving approaches is challenging. We present a preliminary study that explores the use of AutoIG, a constraint-based automated instance generation tool, as a means of generating MAPF benchmark instances that exhibit performance differences between solvers. We focus on a simple shelf based warehouse scenario and consider two representative MAPF solvers from the search-based and reduction-based paradigms, respectively. Our results indicate that, even in this restricted setting, AutoIG can identify instances with noticeable differences in solver performance. We also observe that the reduction-based solver (MAPF-encodings) tends to outperform the search-based solver (ICBS) on the generated instances, despite the latter paradigm being widely regarded as highly effective in many MAPF settings. Our work is an initial step toward a systematic understanding of the strengths and limitations of different MAPF solving paradigms through automated benchmark instance generation
Gaussian process modelling of infectious diseases using the Greta software package and GPUs
No full textGaussian process are a widely-used statistical tool for conducting non-parametric inference in applied sciences, with many computational packages available to fit to data and predict future observations. We study the use of the Greta software for Bayesian inference to apply Gaussian process regression to spatio-temporal data of infectious disease outbreaks and predict future outbreaks. Greta builds on Tensorflow, making it comparatively easy to take advantage of the significant gain in speed offered by GPUs. In these complex spatio-temporal models, we show a reduction of up to 70% in computational time relative to fitting the same models on CPUs. We show how the choice of covariance kernel impacts the ability to infer spread and extrapolate to unobserved spatial and temporal units. The inference pipeline is applied to weekly incidence data on tuberculosis in the East and West Midlands regions of England over a period of two years
Evolutionary influences of sexual signalling on protective colouring
No full textSexual signals can reduce survival, constraining their evolutionary elaboration. However, it is unclear whether these signals, once evolved, similarly impact the evolution of naturally selected adaptations. We argue that this dynamic could be important for protective colouration, an extensively studied suite of adaptations that can also be under sexual selection. Sexual signals sometimes coevolve positively with conspicuous warning colouration, promoting synergistic, dual-function associations. However, when coupled through shared structures or behaviours, sexual traits might constrain the evolution of concealment strategies, resulting in suboptimal camouflage. We suggest hypotheses, approaches, and study systems to distinguish these opposing causal roles of sexual selection in shaping naturally selected adaptations such as protective colouration
Chemoselectivity and enantioselectivity in the conjugate reduction of cinnamate esters and a tandem conjugate reduction-ester hydrogenation using manganese catalysts
No full textAn improved synthesis of manganese(I) tricarbonyl complexes of the Phosphino-Ferrocenyl-Amino-Methyl-Pyridine (PFAMPy) ligand family is reported. A comparison of both the neutral form [Mn(PFAMPy)(CO)2Br] and the cationic form [Mn(PFAMPy)(CO)3]Br was made for an enantioselective ketone hydrogenation, with both catalysts giving high yields and enantiomer ratios over 98:2. The [Mn(PFAMPy)(CO)3]Br catalyst was then applied in tandem conjugate reduction-ester hydrogenation to convert cinnamate esters into aryl propanols. This could be achieved for disubstituted cinnamates with the problematic inseparable allyl alcohol side products almost eliminated below 0.5%. A strategy to prevent C═O bond reduction preceding C═C reduction, and hence allylic alcohol side products, is to use a tert-butyl ester and mild conditions for the first few hours of reaction, prior to increasing temperature to promote ester hydrogenation. This approach is needed for trisubstituted cinnamate esters, which otherwise give mixtures. It is possible to carry out just conjugate reductions to saturated esters at lower temperatures without significant ester hydrogenation. Examples of manganese-catalyzed asymmetric hydrogenation of alkenes are presented in the form of an enantioselective and chemoselective conjugate reduction of trisubstituted cinnamate esters
Il ritorno del nucleare in Asia centrale: Kazakistan e Uzbekistan a confronto:The return of nuclear energy in Central Asia - A comparison between Kazakhstan and Uzbekistan
No full textAn interaction mechanism sustaining near-equilibrium shielded geophysical vortices
No full textWe investigate the interaction between two equally signed neutral vortices, namely vortices with a vanishing area integral of vorticity in inviscid non–divergent two-dimensional flows or a vanishing volume integral of potential vorticity anomaly in three-dimensional quasi-geostrophic (QG) flows. The vortices have a continuous (potential) vorticity distribution, and are linear combinations of appropriately normalised cylindrical (or spherical) Bessel functions of order 0, truncated at a zero of the Bessel function of order 1. Some pairs of neutral vortices reach an oscillating near-equilibrium state, attracting and repelling each other as a result of the exchange of small amounts of vorticity in their peripheries. This vorticity exchange generates a dipolar moment within each vortex which separates the vortices slightly, whereas the subsequent radial redistribution of the vorticity causes the vortices to come back closer again. The interaction is slower and weaker in three-dimensional QG flows, as the potential vorticity exchange primarily takes place close to the horizontal mid-plane of the vortices. These results have been corroborated using two radically different numerical models, namely a pseudo-spectral model and a high-resolution contour-advection model, both in two and in three dimensions. The observed oscillation mechanism could explain the persistence of geophysical vortices under the influence of other vortices and their ability to form stable vortex structures without experiencing vortex merging
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