The First Spectroscopically Resolved Sub-parsec Orbit of a Supermassive Binary Black Hole

One of the most intriguing scenarios proposed to explain how active galactic nuclei are triggered involves the existence of a supermassive binary black hole system in their cores. Here we present an observational evidence for the first spectroscopically resolved sub-parsec orbit of a such system in the core of Seyfert galaxy NGC 4151. Using a method similar to those typically applied for spectroscopic binary stars we obtained radial velocity curves of the supermassive binary system, from which we calculated orbital elements and made estimates about the masses of components. Our analysis shows that periodic variations in the light and radial velocity curves can be accounted for an eccentric, sub-parsec Keplerian orbit of a 15.9-year period. The flux maximum in the lightcurve correspond to the approaching phase of a secondary component towards the observer. According to the obtained results we speculate that the periodic variations in the observed H{\alpha} line shape and flux are due to shock waves generated by the supersonic motion of the components through the surrounding medium. Given the large observational effort needed to reveal this spectroscopically resolved binary orbital motion we suggest that many such systems may exist in similar objects even if they are hard to find. Detecting more of them will provide us with insight into black hole mass growth process.Comment: 29 pages, 10 figures, published in ApJ, 759, 11

The Line Emission Region in III Zw 2: Kinematics and Variability

We have studied the Ly-al, Hbeta, Halpha and Mg II2798 line profiles of the Seyfert 1 galaxy III Zw 2. The shapes of these broad emission lines show evidence of a multicomponent origin and also features which may be identified as the peaks due to a rotating disk. We have proposed a two-component Broad Line Region (BLR) model consisting of an inner Keplerian relativistic disk and an outer structure surrounding the disk. The results of the fitting of the four Broad Emission Lines (BELs) here considered, are highly consistent in both the inner and outer component parameters. Adopting a mass of approx. 2 E8 sollar masses for the central object we found that the outer radius of the disk is approximately equal for the four considered lines (approx 0.01 pc). However, the inner radius of the disk is not the same: 0.0018 pc for Ly-alpha, 0.0027 pc for Mg II, and 0.0038 pc for the Balmer lines. This as well as the relatively broad component present in the blue wings of the narrow [OIII] lines indicate stratification in the emission-line region. Using long-term Hbeta observations (1972-1990, 1998) we found a flux variation of the BEL with respect to the [OIII] lines.Comment: ApJ, accepted, 22 pages, 10 figure

Techniques à membranes appliquées à l'élimination des matières en suspension dans un circuit semi-fermé d'aquaculture

Les piscicultures en circuits semi-fermés sont confrontées au problème de l'élimination permanente des matières en suspension (M.E.S.) et des substances azotées. Les procédés conventionnels utilisés pour retenir les M.E.S. (décantation, hydrocyclones, filtres mécaniques à tambour rotatif, filtration gravitaire) ne donnent par entière satisfaction. Par contre, la filtration sur membranes permet d'arrêter en totalité les particules en suspension et les bactéries.On montre d'abord que les teneurs en M.E.S. et leurs répartitions granulométriques mesurées sur des échantillons prélevés en bassins d'aquaculture varient avec la taille des poissons et l'heure du prélèvement et on met en évidence la présence en nombre important de particules submicroniques.Différents essais de filtration sur membranes sont ensuite présentés :- d'une part, avec des membranes d'ultrafiltration capillaires à peau interne utilisées en potabilisation des eaux : on examine l'influence des paramètres hydrodynamiques (pression transmembranaire, vitesse de recirculation) afin de rechercher les conditions optimales de fonctionnement. Le flux de perméat ne dépasse pas dans le meilleur des cas 100 l.h-1.m-2.- d'autre part, avec des membranes de microfiltration organiques planes en fluorure de polyvinylidène (PVDF) et tubulaires en céramique. Les flux obtenus avec les membranes organiques sont de l'ordre de 250 l.h-1.m-2Dans tous les cas, la rétention des M.E.S. est totale.Cependant l'estimation de l'investissement et des coûts de fonctionnement pour une pisciculture en circuit fermé de taille industrielle conduit à des prix trop élevés pour que l'utilisation des membranes dans ce domaine soit à ce jour économiquement envisageable.A problem confronting semi-closed circuit aquaculture is the need for continuous elimination of suspended matter (SM) and nitrogenous substances. Conventional processes used to retain SM (settling tanks, hydrocyclones, rotating-drum mechanical filters, gravity filtration) are not entirely satisfactory. However, membrane filtration has recently been shown to allow removal of suspended particles and bacteria. The present study evaluates the performance of different ultrafiltration and microfiltration membranes for water processing in a semi-closed aquaculture system. A brief economic analysis of treatment costs is proposed based on the results.The marine aquafarm studied produces about 5 tons of turbot per year with a plant volume of about 100 m3. The water processing line is fitted with a rotating-drum mechanical filter that stops the largest particles and ejects 1 m3 h-1 of loaded water into the surrounding environment. Another 2 m3 h-1 are cleared out by overflowing the pumping pit. These volumes are renewed at a rate of 3% per hour by pumping saltwater from an underground source. Crossflow filtration was performed on rejections from both the mechanical filter and pumping pit overflow. SM contents and granulometric distributions determined by laser diffractometry were found to vary with sample source and withdrawal time, and size of fish in the pens. A comparison of granulometric distributions in volume percent and numerical percent underscores the presence of a great number (> 98 %) of submicron particles.To limit the risk of mechanical-pore fouling due to blockage by particles, organic membranes in the form of internal-skin capillaries (pore diameters of about 10 to 20 nm) were initially employed. These membranes, used in drinking water production, are relatively inexpensive. The experimental device was fitted with an interchangeable volumetric pump (with gears or monoscrew). Adjustable parameters were transmembrane pressure and circulation velocity within the module. Analysis of the influence of these hydrodynamic parameters revealed that pressures higher than 1 bar were unnecessary, as beyond this point permeate flux no longer increased. Optimal flux did not exceed 100 L h-1 m-2 with the gear pump. Replacing the latter with a monoscrew pump improved permeate flux up to 70 %.Tests were also performed with flat microfiltration organic membranes of polyvinylidene fluoride (PVDF) with pore diameters ranging from 0.1 to 8 µm. The flux obtained with these membranes was roughly 250 L h-1 m-2 and presented little variation with varying pore diameter. Comparative tests carried out on tubular membranes showed lower fluxes than those obtained with organic membranes which, considering their much higher cost, makes them less attractive in this context. The use of membranes in aquafarming is without precedent. An economic analysis of the practice was carried out based on financial assessments of processing of surface waters into drinking water, for which outputs to be treated and SM contents were of the same order of magnitude. With operating costs from 0.35 to 0.95 FF per cubic meter of filtered water, expected investment for a fishfarm producing 100 tons of fish a year is currently 3 to 4 times too great to consider economically profitable the use of membranes for water treatment in closed-circuit aquafarming

A System Out of Breath: How Hypoxia Possibly Contributes to the Pathogenesis of Systemic Sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by vascular alterations and immunological disturbances and fibrosis, the order of which remains to be fully determined. Clinically, patients show clear signs of hypoxia in skin and internal organs. The low oxygen tension is potentially caused by a yet to be indentified circuitry involving the three features that typify SSc. In addition, once present, the hypoxia creates a vicious circle of ongoing pathology. In this paper, we provide an overview of the evidence that points towards the mechanisms causing hypoxia in SSc. In addition, data that suggest how hypoxia itself may orchestrate worsening of symptoms is presented. Altogether, it is clear that hypoxia is an important hallmark in SSc patients. By providing an overview of the mechanisms at play and the possible therapeutic avenues that have emerged, we hope to stimulate researchers to provide novel clues into the conundrum in SSc patients

Analysis of (sub-)Riemannian PDE-G-CNNs

Group equivariant convolutional neural networks (G-CNNs) have been successfully applied in geometric deep learning. Typically, G-CNNs have the advantage over CNNs that they do not waste network capacity on training symmetries that should have been hard-coded in the network. The recently introduced framework of PDE-based G-CNNs (PDE-G-CNNs) generalises G-CNNs. PDE-G-CNNs have the core advantages that they simultaneously 1) reduce network complexity, 2) increase classification performance, and 3) provide geometric interpretability. Their implementations primarily consist of linear and morphological convolutions with kernels. In this paper we show that the previously suggested approximative morphological kernels do not always accurately approximate the exact kernels accurately. More specifically, depending on the spatial anisotropy of the Riemannian metric, we argue that one must resort to sub-Riemannian approximations. We solve this problem by providing a new approximative kernel that works regardless of the anisotropy. We provide new theorems with better error estimates of the approximative kernels, and prove that they all carry the same reflectional symmetries as the exact ones. We test the effectiveness of multiple approximative kernels within the PDE-G-CNN framework on two datasets, and observe an improvement with the new approximative kernels. We report that the PDE-G-CNNs again allow for a considerable reduction of network complexity while having comparable or better performance than G-CNNs and CNNs on the two datasets. Moreover, PDE-G-CNNs have the advantage of better geometric interpretability over G-CNNs, as the morphological kernels are related to association fields from neurogeometry.Comment: 29 pages, 21 figure

A main sequence for quasars

The last 25 years saw a major step forward in the analysis of optical and UV spectroscopic data of large quasar samples. Multivariate statistical approaches have led to the definition of systematic trends in observational properties that are the basis of physical and dynamical modeling of quasar structure. We discuss the empirical correlates of the so-called "main sequence" associated with the quasar Eigenvector 1, its governing physical parameters and several implications on our view of the quasar structure, as well as some luminosity effects associated with the virialized component of the line emitting regions. We also briefly discuss quasars in a segment of the main sequence that includes the strongest FeII emitters. These sources show a small dispersion around a well-defined Eddington ratio value, a property which makes them potential Eddington standard candles.Comment: Invited talk presented at the Padova Conference on "Quasars at all cosmic epochs"; to appear in Frontiers of Astrophysics and Space Scienc

Governance of Offshore IT Outsourcing at Shell Global Functions IT-BAM Development and Application of a Governance Framework to Improve Outsourcing Relationships

The lack of effective IT governance is widely recognized as a key inhibitor to successful global IT outsourcing relationships. In this study we present the development and application of a governance framework to improve outsourcing relationships. The approach used to developing an IT governance framework includes a meta model and a customization process to fit the framework to the target organization. The IT governance framework consists of four different elements (1) organisational structures, (2) joint processes between in- and outsourcer, (3) responsibilities that link roles to processes and (4) a diverse set of control indicators to measure the success of the relationship. The IT governance framework is put in practice in Shell GFIT BAM, a part of Shell that concluded to have a lack of management control over at least one of their outsourcing relationships. In a workshop the governance framework was used to perform a gap analysis between the current and desired governance. Several gaps were identified in the way roles and responsibilities are assigned and joint processes are set-up. Moreover, this workshop also showed the usefulness and usability of the IT governance framework in structuring, providing input and managing stakeholders in the discussions around IT governance

Spectroscopy and spectropolarimetry of AGN: from observations to modelling

Active galactic nuclei (AGN) are one of the most luminous objects in the Universe, emitting powerful continuum and line emission across all wavelength bands. They represent an important link in the investigations of the galaxy evolution and cosmology. The resolving of the AGN inner structure is still a difficult task with current instruments, therefore the spectroscopy and spectropolarimetry are crucial tools to investigate these objects and their components, such as the properties of the supermassive black hole, the broad line region, and the dusty torus. In this review, we present the results of the project "Astrophysical spectroscopy of extragalactic objects", from the observations, data processing and analysis, to the modelling of different regions in AGN.Comment: Proceedings of the Serbian Astronomical Conference 201

The quasar main sequence and its potential for cosmology

The main sequence offers a method for the systematization of quasar spectral properties. Extreme FeII emitters (or extreme Population A, xA) are believed to be sources accreting matter at very high rates. They are easily identifiable along the quasar main sequence, in large spectroscopic surveys over a broad redshift range. The very high accretion rate makes it possible that massive black holes hosted in xA quasars radiate at a stable, extreme luminosity-to-mass ratio. After reviewing the basic interpretation of the main sequence, we report on the possibility of identifying virial broadening estimators from low-ionization line widths, and provide evidence of the conceptual validity of redshift-independent luminosities based on virial broadening for a known luminosity-to-mass ratio.Comment: 5 pages, 2 figures, contribution presented at the IAU Symposium 356, Nuclear Activity in Galaxies Across Cosmic Time, held in Addis Ababa, Ethiopia, on Oct. 7-11, 2019. M. Povic et al. (Eds.