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Smith, Duncan Peter. "AGN jet-gas cloud interactions". Thesis, University of Bristol, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.761232.
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Omma, Henrik Nilsen. "Jet-powered cooling cores : reversing cooling flows through AGN activity". Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419330.
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Cielo, Salvatore [Verfasser], i Andrea Valerio [Akademischer Betreuer] Macciò. "Numerical Models of AGN Jet Feedback / Salvatore Cielo ; Betreuer: Andrea Valerio Macciò". Heidelberg : Universitätsbibliothek Heidelberg, 2015. http://d-nb.info/1180395263/34.
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Dhalla, Sarah M. "Analysis of Kepler Active Galactic Nuclei Using A Revised Kirk, Rieger, Mastichiadis (1998) Model". FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1521.
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Active Galactic Nuclei (AGN) are cores of distant protogalaxies, with a supermassive blackhole at the center surrounded by an accretion disk, and bipolar jets. Blazars, a subset of AGN, have their jets aligned with our line of sight. Emission from blazars is highly variable on all timescales and frequencies. Microvariability refers to rapid continuum variations that arise within the jet. Bhatta et al. (2013) suggest a modified Kirk, Rieger, \& Mastichiadis (1998) model (KRM) to explain microvariability. The KRM model assumes that when shock waves passes though the jet, each turbulent cell encountered produces a pulse of emission characterized by cell size, local density enhancement, and magnetic field strength. NASA's \kepler\ has monitored optical emission from four AGN. We use the modified KRM model to analyze micro-variations in these \kepler\ data. The distribution of cell sizes computed from these data is consistent with the distribution expected from a turbulent plasma.
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Su, Meng. "Discovery of Giant Gamma-ray Bubbles in the Milky Way". Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10429.
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Based on data from the Fermi Gamma-ray Space Telescope, we have discovered two gigantic gamma-ray emitting bubble structures in our Milky Way (known as the Fermi bubbles), extending \(\sim 50\) degrees above and below the Galactic center with a width of \(\sim 40\) degrees in longitude. The gamma-ray emission associated with these bubbles has a significantly harder spectrum \((dN/dE \sim E^{-2})\) than the inverse Compton emission from known cosmic ray electrons in the Galactic disk, or the gamma-rays produced by decay of pions from proton-ISM collisions. There is no significant difference in the spectrum or gamma-ray luminosity between the north and south bubbles. The bubbles are spatially correlated with the hard-spectrum microwave excess known as the WMAP haze; we also found features in the ROSAT soft X-ray maps at \(1.5 - 2 keV\) which line up with the edges of the bubbles. The Fermi bubbles are most likely created by some large episode of energy injection in the Galactic center, such as past accretion events onto the central massive black hole, or a nuclear starburst in the last \(\sim 10 Myr\). Study of the origin and evolution of the bubbles also has the potential to improve our understanding of recent energetic events in the inner Galaxy and the high-latitude cosmic ray population. Furthermore, we have recently identified a gamma-ray cocoon feature within the southern bubble, with a jet-like feature along the cocoon's axis of symmetry, and another directly opposite the Galactic center in the north. If confirmed, these jets are the first resolved gamma-ray jets ever seen.Astronomy
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Fransson, Emma. "High energy gamma ray emission and multi-wavelength view of the AGN PKS 0537-441". Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-66894.
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This thesis describes the analysis of Very High Energy (VHE) emission from the Active Galactic Nucleus PKS 0537-441. It also aims to put the results in a wider context by implementing previous work done on this source. The data chosen for the analysis is provided by the Fermi-LAT satellite and covers the energy range between 300 MeV and 300 GeV. Initially a lightcurve of the received flux from the source was generated, containing data from August 2008 to April 2017, with a mean flux of 4∗10−8 photons per second per squared centimeter. The lightcurve contained sections of different flux intensities giving periods of special interest, such as a flaring period at August 2008 to August 2011, an enormous flare at April 2010 and a less active period between April 2013 - January 2016 that could be identified for further investigations. The differences in observed flux over time was tested and PKS 0537-441 was found to be a significantly variable source. Spectral Energy Distribution (SED) analysis was performed over both the entire period as well as over the selected subperiods and fitted against models using the tools provided by the Fermi Science Support Center (FSSC). The models used in the fitting was PowerLaw2, LogParabola and PLSuperExpCutoff and the best fit for the data was obtained from the PLSuperExpCutoff, except for the less intense period where the LogParabola gave the best fit. The result from the SED analysis was integrated with results from previous work done on the source, ranging over multiple wavelengths in order to get a SED which spanned over the entire electromagnetic spectrum. Finally, modeling of this multi wavelength SED was performed in order to obtain parameters for the physical processes involved in the creation of the radiation received from PKS 0537-441.
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Macconi, Duccio. "Radio morphology-accretion mode link in FRII low-excitation radio galaxies". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/17756/.
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Questo lavoro di tesi consiste nello studio sistematico di una popolazione di radiogalassie con comportamenti apparentemente difformi tra banda radio e ottica. Si tratta di AGN radio-loud molto potenti, con emissione radio estesa tipica di radiogalassie. Gli oggetti analizzati in questo lavoro sono classificati in banda radio come FRII, essendo caratterizzate su larga scala dalla presenza di hot-spot e assenza di getti gemelli. Sono invece classificate come LERG (Low Excitation Galaxies) in banda ottica, per via della presenza di alcune righe di emissione che permettono di stabilire il grado di eccitazione delle regioni centrali. Il catalogo da cui queste sono estratte è il 3CR, imponendo un taglio in redshift per z<0.3.
Per quanto riguarda i dati ottici, radio e la classificazione di tutte le sorgenti, si è fatto riferimento agli articoli di Buttiglione et al. (2009).
L'analisi in banda X è stata svolta utilizzando i dati di archivio pubblici dei telescopi Chandra e XMM-Newton. Una volta estratto lo spettro di emissione, per ogni sorgente si è cercato di ricostruire e studiare il modello fisico che meglio ne descrivesse l'emissione.
La raccolta e unione di dati radio, ottici e X per un campione completo di FRII-LERGs costituisce un punto nodale per la comprensione complessiva delle proprietà ambientali, di emissione ed accrescimento delle radio galassie. Lo studio dei meccanismi che portano alla formazione di questa popolazione è infatti, allo stato attuale, lontano da una comprensione completa e univoca.
Una volta unite le informazioni provenienti dalle varie bande è stato possibile raggiungere una visione d'insieme e trarre alcune conclusioni.
Per alcune proprietà intrinseche questa popolazione di radiogalassie si trova a metà strada tra FRII-HERGs e FRI-LERGs, permettendo di avvalorare l'ipotesi secondo cui la popolazione delle FRII-LERGs stia sperimentando una fase di transizione.
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Bollström, Nadja. "A gamma-ray study of a highly variable blazar : The Fermi-LAT analysis and the modeling of the FSRQ PKS 1510–089". Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-104617.
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The subject of this thesis is the analysis and modeling of the active galactic nucleus PKS 1510-089. The aim is to present a thorough background of active galactic nuclei combined with the analysis and modeling of a specific active galactic nucleus. The results will then be linked to previous research and theories about active galactic nuclei. The data used in the analysis were retrieved from the Fermi Gamma-ray Space Telescope. A light curve analysis that extended over 12 years provided knowledge about variability and presented four interesting flaring periods. The four periods underwent a spectral analysis, and the results showed that a log parabolic curvature could best describe all four periods. The last step before the modeling was to create spectral energy distributions for all four periods to retrieve spectral points from wavelengths other than those available from Fermi. Unfortunately, there were only sufficient data for one period. That period was later used in the modeling and resulted in a well-fitted external Compton model, which was compared, with relatively good results, with previous research.
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Meliani, Zakaria. "Modélisation de vents et de jets relativistes". Phd thesis, Université Paris-Diderot - Paris VII, 2004. http://tel.archives-ouvertes.fr/tel-00008067.
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Les vents et les jets sont un des phénomènes les plus répandu et spectaculaire en astrophysique des hautes énergies. En effet, une variété d'objets astrophysiques exhibent des écoulements aussi bien sous forme de vents que de jets fortement collimatés. Ils sont observés dans les étoiles jeunes, les noyaux actifs de galaxies (AGN), les étoiles à neutrons et les étoiles de la séquence principale. Cependant, malgré l'abondance des jets en astrophysique, le problème de la formation et de la collimation de ces écoulements reste ouvert. Différents modèles sont proposés pour résoudre ce problème. La plupart de ces modèles sont développés dans la limite newtonienne. Nous avons, dans cette thèse, élaboré des modèles hydrodynamiques et magnétohydrodynamiques en relativité générale pour analyser les différents mécanismes d'accélération et de collimation des écoulements aussi bien relativistes que classiques. Nous avons étudié les solutions d'écoulements purement hydrodynamique sphérique avec une équation d'état polytropique généralisée. Nous nous sommes intéressés aux effets de changement de l'état de la matière dans les écoulements sur l'accélération thermique, lorsqu'elle subit des grandes variations de température. Nous avons montré qu'avec notre nouvelle équation d'état, les effets de la gravité et thermique sont couplés, permettant une plus grande efficacité de l'accélération du vent. Nous avons aussi montré la nécessité de l'utilisation de ce nouveau polytrope plus cohérent dans le traitement des écoulements relativistes polytropiques. Dans la deuxième partie de la thèse, nous avons développé un modèle d'écoulement axial magnétisé 2.5D. La température élevée du plasma dans la couronne centrale due à la gravité élevée et la proximité de l'axe de rotation nous ont permis de négliger, dans un premier temps, les effets du cylindre de lumière comparativement aux effets thermiques. Dans ce cadre, nous avons montré que les effets relativistes favorisent l'accélération thermique au détriment de la collimation magnétique. Nous avons aussi montré l'importance de l'expansion initiale du jet sur l'efficacité de l'accélération du jet dans la partie basse. D'autre part, nous avons étudié les effets de la rotation relativiste sur la collimation du jet. Nous avons aussi utilisé le modèle pour déduire quelques différences entres les propriétés intrinsèques des jets d'AGN de type FRI et de FRII. Nous avons trouvé que les jets des FRI se caractérisés par une faible vitesse de rotation à la base et qu'asymptotiquement, ils sont confinés par le milieu ambiant. Par contre, les jets des FRII sont caractérisés par une vitesse de rotation à la base plus élevée que celle des jets de FRI, qui reste cependant sub-keplerienne. De plus, les jets des FRII s'auto-collimatent par leur propre champ magnétique. Nous avons développé un troisième modèle de jet dans le cas des rotateurs relativistes. En premier lieu, ce modèle nous a permis de mieux traiter les jets accélérés par le flux de Poynting contrairement au modèle précédent. Nous avons aussi étudié les effets du cylindre de lumière sur la collimation du jet et confirmé qu'il tend à décollimater ce dernier. D'autre part, nous avons trouvé que, dans les solutions caractérisés par un cylindre de lumière proche de la surface d'Alfvén, la rotation relativiste dans ces jets limite l'accélération de ces derniers. En effet, dans les solutions que nous avons étudiées, les vitesses poloïdales obtenues restent faibles, de l'ordre de $0.6c$. Nous avons aussi amorcé un code de simulation numérique d'écoulements relativistes utilisant la bibliothèque LORENE. Dans la thèse nous avons commencé à tester le code dans le cas simple de vents purement hydrodynamiques sphériques.
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Powling, Alexander. "Jet substructure : an analytical approach". Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/jet-substructure-an-analytical-approach(e1e67bdc-ddda-41e6-a263-af9c0836f278).html.
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In the past few years, detailed study of the internal structure of hadronic jets has become an active area of research. In particular, jet substructure information has been used to distinguish signal from QCD initiated jets, which constitute a significant background for many physics searches. Prior to the work undertaken in this thesis, theoretical research on jet substructure was largely Monte Carlo based, with limited analytical input. This work presents an analytical approach to the study of jet substructure techniques in the context of high-p_T heavy resonance searches at the LHC.In this thesis, we compute the mass distribution of QCD initiated jets after application of several jet substructure algorithms using approximate fixed-order perturbative QCD at leading and next-to-leading order. This is sufficient to extract the leading logarithmic structure for each technique, which we compare to exact fixed-order results. Using this analytical insight, we propose modifications to some of these algorithms and use our results to discuss the phenomenological impact of different parameter choices. We also perform analytical calculations and Monte Carlo studies to examine the impact of QCD radiation on jets that arise from boosted Higgs decay after application of several jet substructure algorithms. Understanding the action on signal jets is important when two techniques perform similarly on background jets. An example studied here is the Y-splitter and Y-pruning techniques, which both perform well at rejecting background; however, the former retains signal jets which are subject to significant radiative and non-perturbative corrections. We demonstrate that the combination of Y-splitter with trimming ameliorates the poor signal tagging efficiency of Y-splitter whilst retaining effective background rejection. Consequently, we find that this combination outperforms the other techniques studied here, at high p_T. We use our analytical expressions to perform an approximate optimisation of parameters for each algorithm and compare our results to Monte Carlo simulation. Finally, we undertake an analytical fixed-order and resummed study of the mass distribution for QCD jets for the combination of Y-splitter with trimming. We demonstrate that the trimming has a numerically subleading effect on the Y-splitter distribution for typical parameter choices and discuss why such techniques can prove to be superior when compared to the currently proposed individual methods.
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Memola, Elisabetta. "Magnetic jets from accretion disks field structure and X-ray emission /". Phd thesis, [S.l.] : [s.n.], 2002. http://pub.ub.uni-potsdam.de/2002/0014/memola.pdf.
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Butler, Andrew Michael. "Mass-resolved resonant two-photon ionisation spectroscopy of jet-cooled Cu2 and Ag2". Thesis, University of Edinburgh, 1990. http://hdl.handle.net/1842/27635.
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Clusters of the transition metals were generated by laser vaporisation of a sample of the metal into the throat of a pulsed supersonic expansion. This allowed clusters with internal temperatures as low as 5 K to be routinely prepared. Mass-selective detection was accomplished by multi-photon ionisation of the clusters within the ion source of a time - of - flight mass spectrometer. Use of a tunable laser to carry out electronic excitation, prior to ionisation, allowed mass - resolved resonant two - photon ionisation spectra of the clusters to be recorded. Real time control of the experiment and automated data logging was achieved using software developed to run on an IBM PC - AT microcomputer. This allowed multiple ion signals to be recorded simultaneously whilst carrying out R2PI or time-resolved studies on the metal cluster species in the beam. Resonant two - photon ionisation spectroscopic studies were carried out on the ( 0 - 0 ) and ( 1 - 0 ) bands of the J X system of Cu9 and the A X system of Ag->. The 0.04 cm-1 bandwidth of the tunable dye laser used allowed rotationally resolved spectra to be recorded. The spectra recorded for these systems showed them both to be AA = 0 ( or AS2 = 0 ) transitions. The J state of CU2 was assigned to the 1 Zj state derived from the ?P + atomic limit at Dg(X) + 45821 cm-1. Rotational analysis of the spectra yieldedl | lthe following constants for the Cu2 isotopomer: Bg = 0.1166(1) cm , ae = 0.0021(1) cm-1. This gave Rg = 2.138(1) A for the J state, shorter than the ground state bond length. Accordingly the transition was assigned to 3ditg -*?4piru, to give the above assignment. The rotational constants obtained, for the *?7Ag-, isotopomer, from analysisI _ | *of the spectra of the A X system of Ag-, were: Bg = 0.0447(3) cm , ae= 0.0004(2) cm'*, and Bq = 0.0490(18) cm"1. These gave bond lengths of Rg = 2.649(9) A and Rq = 2.530(46) A. The observed Ail = 0 transition agreed with the previous assignment of the A state as 0* arising from the 5sag -+ 5sau promotion.
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Mingo, Fernandez Beatriz. "X-Ray studies of radio-loud AGN". Thesis, University of Hertfordshire, 2013. http://hdl.handle.net/2299/10921.
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In this thesis I use X-ray observations to study the cores and extended structures of radio-loud AGN, to determine their structure, accretion properties and the impact they have on their surroundings. I use new Chandra data and archival XMM-Newton observations ofMarkarian 6 to look for evidence of emission from shocked gas around the external radio bubbles, using spatially resolved regions in Chandra and spectral analysis of the XMM data. The results show that the bubbles in Mrk 6 are indeed driving a shock into the halo of the host galaxy, with a Mach number of 3.9. I also find that the spectrum of the AGN has a variable absorbing column, which changes from 8 × 1021 atoms cm−2 to 3 × 1023 atoms cm−2 on short timescales (2-6 years). This is probably caused by a clump of gas close to the central AGN, passing in front of us at the moment of the observation. Using new and archival Chandra observations of the Circinus galaxy, I match them to pre-existing radio, infrared and optical data to study the kpc-scale emission. As for Mrk 6, I find that the radio bubbles in Circinus are driving a shock into the interstellar medium of the host galaxy, with Mach numbers M 2.7–3.6 and M 2.8–5.3 for the W and E shells respectively. Comparing the results with those we previously obtained for Centaurus A, NGC 3801 and Mrk 6, I show that the total energy in the lobes (thermal+kinetic) scales approximately with the radio power of the parent AGN. The spatial coincidence between the X-ray and edge-brightened radio emission in Circinus resembles the morphology of some SNR shocks, a parallel that has been expected for AGN, but has never been observed before. I investigate what underlying mechanisms both types of systems may have in common, arguing that, in Circinus, the edge-brightening in the shells may be accounted for by a B field enhancement caused by shock compression, but do not preclude some local particle acceleration. I also carry out a systematic study of the X-ray emission from the cores in the 0.02 < z < 0.7 2Jy sample, using Chandra and XMM-Newton observations. I combine the results with the mid-IR, optical emission line and radio luminosities, and compare them with those of the 3CRR sources, to show that the low-excitation objects in our sample show all the signs of radiatively inefficient accretion. I study the effect of the jet-related emission on the various luminosities, confirming that it is the main source of soft X-ray emission for our sources. I also find strong correlations between the accretion-related luminosities, and identify several sources whose optical classification is incompatible with their accretion properties. I derive the bolometric and jet kinetic luminosities for the sample and find a difference in the total Eddington rate between the low and high-excitation populations, with the former peaking at 1 per cent and the latter at 20 per cent Eddington. There is, however, an overlap between the two, indicating that a simple Eddington switch may not be possible. The apparent independence of jet kinetic power and radiative luminosity in the highexcitation population in our plots allows us to test the hypothesis in which jet production and radiatively efficient accretion are in fact independent processes that can coexist in high-excitation objects.
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Kalfountzou, Eleni. "The evolution of AGN and their host galaxies". Thesis, University of Hertfordshire, 2015. http://hdl.handle.net/2299/17004.
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Active galaxies have been in the forefront of astronomic research since their first discovery, at least 50 years ago (e.g. Schmidt, 1963; Matthews & Sandage, 1963). The putative supermassive black hole (SMBH) at their center characterizes their properties and regulates the evolution of these objects. In this thesis, I study the 'demographics' and 'ecology' of active galactic nuclei (AGN) in the context of their evolution and the interaction with their environments (mainly their host galaxy). The number density of AGN has been found to peak at 1 < z < 3 (e.g. Ueda et al., 2003; Hasinger et al., 2005; Richards et al., 2005; Aird et al., 2010), similar to the star formation history (e.g. Silverman et al., 2008a; Aird et al., 2010). However, when taking into account obscuration, faint AGN are found to peak at lower redshift (z ≤ 2) than that of bright AGN (z ≈ 2 - 3; e.g. Hasinger et al., 2005; Hopkins et al., 2007; Xue et al., 2011). This qualitative behaviour is also broadly seen in star-forming galaxies (e.g. Cowie et al., 1996) and is often referred to as 'cosmic downsizing', although this term has developed a number of usages with respect to galaxies (e.g. Bundy et al., 2006; Cimatti et al., 2006; Faber et al., 2007; Fontanot et al., 2009). Though this behaviour is well established up to z ≈ 3, the nature of how and when the initial seed of these AGNs were formed remains an open question. For this study, I use Chandra surveys to study some of the most distant AGN in the Universe (z > 3). The combination of two different size and depth Chandra surveys (Chandra-COSMOS and ChaMP) provides me with the largest to-date z > 3 AGN sample, over a wide range of rest-frame 2-10 keV luminosities [log (Lₓ/erg s⁻¹) = 43.3-46.0] and obscuration (NH = 10²⁰ - 10²³ cm⁻²). I find strong evidence about a strong decline in number density of X-ray AGN above z ≈ 3, and also the association of this decline with a luminosity-dependent density evolution (LDDE; e.g. Gilli et al., 2007). Especially at high redshifts, the different evolution models predict quite different numbers of AGNs. The large size and the wide X-ray luminosity range of this sample reduces the uncertainties of previous studies at similar redshifts making it possible to distinguish between the different models and suggest that observations appear to favour the LDDE model. The observed AGN downsizing behaviour seen via the measured X-ray luminosity function (XLF) could arise due to changes in the mass of the typical active SMBH and/or changes in the typical accretion rate. But how does the growth of SMBHs over cosmic time influence its environment? A powerful way to address this question is to compare the host galaxy properties over a wide range of AGN and accretion rate types. Radio-jets are one of the most prominent constituents of AGN as they can interact directly with the host galaxy. Although AGN with radio jets are rare (they make up to 10 per cent of the total AGN population) radio galaxies make up over 30 per cent of the massive galaxy population and it is likely that all massive galaxies go through a radio-loud phase, as the activity is expected to be cyclical (e.g Best et al., 2005). It is therefore, important to investigate the impact of radio jets on the host galaxy and particularly the star formation. The method I follow focuses on the comparison of the host galaxy properties between optically selected quasar samples, with and without strong radio emission associated with powerful radio-jets, matched in AGN luminosity. Herschel far-infrared observations are used to trace the star formation in the host galaxy, providing minimal AGN contamination. In my first approach, I have constructed a sample of radio-loud and radio-quiet quasars from the Faint Images Radio Sky at Twenty-one centimetres (FIRST) and the Sloan Digital Sky Survey Data Release 7 (SDSS DR7), over the H-ATLAS Phase 1 Area (9h, 12h and 14.5h). The main result of this work is that RLQs at lower AGN luminosities tend to have on average higher FIR and 250-μm luminosity with respect to RQQs matched in AGN luminosity and redshift. However, evolution effects could be strong as the quasars in this sample cover a wide range of redshifts (0.4 < z < 5). Therefore, I follow a second approach with the advantage of a QSO sample selection at a single redshift epoch, decomposing the evolution effects from the AGN/star-formation study. The results indicate that radio-jets in powerful QSOs can both suppress and enhance the star formation in their host galaxies. These fundings are consistent with a galaxy mass and jet-power dependence model. Then we expect more massive galaxies to have more star-formation for a given jet-power because their star-formation is more enhanced by the jet. Although radio-jets are the best candidates for a direct AGN impact to the host galaxy, many models refer to an AGN feedback associated with energetic AGN winds and outflows which are expected to suppress the star formation in powerful AGN when compared to the overall galaxy population. My results do not suggest star formation is suppressed in the hosts of optically selected QSOs at z ≈ 1, with more than 30 per cent of them being associated with strong star formation rates (SFR ≈ 350 M⊙ yr⁻¹). Although different interpretations are possible, this result can be explained through periods of enhanced AGN activity and star-forming bursts, possibly through major mergers. However, optical QSOs comprise only a small fraction of the total AGN population. Even if the 'unified model' predicts that the host galaxy properties should not be affected by the viewing angle (type-1 vs. type-2 AGN), several studies have shown results supporting a scenario departing from the basic model. Investigating star formation in the hosts of 24 μm selected type-1&2 AGN, I found that the type-2 AGNs display on average higher star-formation rate than type-1 AGNs. This result is in agreement with previous studies suggesting an undergoing transition between a hidden growth phase and an unobscured AGN phase.
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Di, Federico Laura. "The kinematics and observable properties of AGN jets and cavities with cosmological simulations". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amslaurea.unibo.it/25346/.
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Most of the ordinary matter of Galaxy Clusters is in the form of a rarefied and ionized gas, called the Intra Cluster Medium (ICM). The ICM is believed to be constantly in motion, mainly due to turbulence. This thesis analyzes an highly resolved cosmological simulation of the gas dynamics of a single galaxy cluster, which included several dynamical effects for the realistic evolution of the ICM: gravity, matter accretions, shock waves, turbulence, magnetic fields and a central Active Galactic Nucleus (AGN). The AGN has been resimulated five different times by modifying the power of its jets. This promotes the onset of a different long-term dynamics of the ICM. Once the jets are injected, they release relativistic electrons. It is possible to follow the trajectories of such particles through tracers, that are tracked from the beginning to the end of the simulation to study the dynamics they are subject to throughout the life of the cluster.
The first purpose of this Thesis is to establish how much intracluster volume can be typically refilled by relativistic electrons expelled by jets, the electrons kinematics and the dependency between jet power and the kinematic of tracers.
The second purpose of this thesis is to produce a systematic comparison between observable-like estimates of the age and energetics of X-ray cavities produced by AGN in clusters, and their true value in the simulation. To this end, I analysed X-ray maps in a way that is as similar as possible to the procedure adopted in the real observations. The statistical results of cosmological simulations are also compared with the results obtained by analyzing a second fully idealized simulation, to assess to which extend can my result be affected by specific choices in the assumed numerical and physical setup.
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Migliori, Giulia. "High Energy Emission in Relativistic Jets of AGN: Theory predictions and gamma-ray view". Doctoral thesis, SISSA, 2010. http://hdl.handle.net/20.500.11767/4926.
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The last decade has been a golden epoch for the observations of extra-galactic jets. The extension of the observational window from the radio through infrared and optical up to the high energy band has provided us with a wealth of new data. The study of the jets by modeling their spectral energy distribution has become a very effective approach. Multi-band observations are determinant to constrain the model parameters and probe the radiative environment where the jets form and expand. The broadband fitting allows us to infer the main physical parameters
of the emitting plasma and to consequently estimate the total jet kinetic power.
In this thesis a simple leptonic synchrotron and inverse Compton model is adopted and generalized by taking into account the main local and external radiative fields which can act as seed photons. The model is used to derive constraints on the jet contribution to the total high energy emission in compact radio sources. These are supposed to be the young counterparts of the giant radio sources. Unveiling the origin of their high energy emission is crucial to understand their subsequent evolution and the nature of the feedback mechanism with the intergalactic medium. First, we discuss the modeled broadband emission of jets in low and high power young radio sources observed at increasing viewing angles. The role of the seed photons is investigated for different jet velocities and linear sizes. We then test the model on the spectral energy distribution of the compact quasar 3C 186.
The presence of a velocity structure internal to the jet appears to be a crucial requirement to ensure its radiative relevance at the high energies. The internal structure of the jet is the subject of a dedicated study carried out on the FR I radio galaxy NGC 6251. The two radiative models used to describe its non-thermal broadband nuclear mission
return back two deeply different pictures: a heavy and slow jet for the synchrotron self Compton model while a light but highly dissipative one for the structured jet model (spine-layer).
17
Douat, Claire. "Etude d'un micro-jet de plasma à pression atmosphérique". Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-00960400.
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Ces dernières années un nouveau type de décharges hors équilibre thermodynamique, aptes à générer des micro jets de plasma se propageant en atmosphère libre, a suscité beaucoup d'intérêt dans la communauté scientifique. Ces micro jets, produits dans des structures type décharge à barrière diélectrique, ont des propriétés particulièrement intéressantes, tant sur le plan de la physique des plasmas que sur celui des applications, en particulier pour des applications biomédicales ou de traitement de surface.Dans ce travail de thèse il est démontré que ces jets de plasma correspondent à la propagation à grande vitesse d'un front d'ionisation sans déplacement de matière. Une caractérisation des propriétés des jets (vitesse et distance de propagation) a été effectuée en fonction de la tension appliquée, du débit, de la composition du gaz, et de la géométrie de la décharge. La distribution spatio-temporelle des espèces réactives produites par le jet a été mesurée, et en particulier celle de l'état métastable He (2³S) mesuré par absorption laser. Des densités comprises entre 1.10¹² et 5.10¹³ cm-³ ont été obtenues pour l'état He (2³S). Sa distribution est annulaire à la sortie de la structure de la décharge et se referme le long du jet. La densité maximale est obtenue à une distance correspondant à la moitié de la zone où les atomes métastables sont présents, ce qui est en contradiction avec les modèles actuels. De plus, afin de mieux comprendre la physique des jets de plasma, nous avons fait interagir deux jets placés l'un en face de l'autre. L'étude de la contre propagation de deux jets révèle qu'il existe une distance minimale d'approche laissant entre eux une zone exempte de plasma. Après l'extinction des deux plasmas, une seconde décharge s'amorce exactement dans cette zone. Une étude détaillée couplant diagnostics électrique, imagerie ultra-rapide et spectroscopie d'émission nous a permis de montrer que cette décharge secondaire est due à une inversion de polarité conduisant à la création transitoire d'un piège à électrons.Dans le but d'aborder l'étude des applications des jets de plasma au domaine biologique, nous avons également étudié la dégradation de l'ADN plasmidique par un jet de plasma. Nous avons mis en évidence que ce type de plasma induit majoritairement des cassures simples et doubles brins, alors que très peu d'oxydations de base ou de sites abasiques sont observés, ceci même avec l'ajout de quelques pourcents d'oxygène dans le gaz.
18
Douat, Claire. "Etude d’un micro-jet de plasma à pression atmosphérique". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112028/document.
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Ces dernières années un nouveau type de décharges hors équilibre thermodynamique, aptes à générer des micro jets de plasma se propageant en atmosphère libre, a suscité beaucoup d’intérêt dans la communauté scientifique. Ces micro jets, produits dans des structures type décharge à barrière diélectrique, ont des propriétés particulièrement intéressantes, tant sur le plan de la physique des plasmas que sur celui des applications, en particulier pour des applications biomédicales ou de traitement de surface.Dans ce travail de thèse il est démontré que ces jets de plasma correspondent à la propagation à grande vitesse d'un front d'ionisation sans déplacement de matière. Une caractérisation des propriétés des jets (vitesse et distance de propagation) a été effectuée en fonction de la tension appliquée, du débit, de la composition du gaz, et de la géométrie de la décharge. La distribution spatio-temporelle des espèces réactives produites par le jet a été mesurée, et en particulier celle de l'état métastable He (2³S) mesuré par absorption laser. Des densités comprises entre 1.10¹² et 5.10¹³ cm-³ ont été obtenues pour l’état He (2³S). Sa distribution est annulaire à la sortie de la structure de la décharge et se referme le long du jet. La densité maximale est obtenue à une distance correspondant à la moitié de la zone où les atomes métastables sont présents, ce qui est en contradiction avec les modèles actuels. De plus, afin de mieux comprendre la physique des jets de plasma, nous avons fait interagir deux jets placés l’un en face de l’autre. L'étude de la contre propagation de deux jets révèle qu’il existe une distance minimale d'approche laissant entre eux une zone exempte de plasma. Après l’extinction des deux plasmas, une seconde décharge s’amorce exactement dans cette zone. Une étude détaillée couplant diagnostics électrique, imagerie ultra-rapide et spectroscopie d'émission nous a permis de montrer que cette décharge secondaire est due à une inversion de polarité conduisant à la création transitoire d'un piège à électrons.Dans le but d'aborder l'étude des applications des jets de plasma au domaine biologique, nous avons également étudié la dégradation de l’ADN plasmidique par un jet de plasma. Nous avons mis en évidence que ce type de plasma induit majoritairement des cassures simples et doubles brins, alors que très peu d’oxydations de base ou de sites abasiques sont observés, ceci même avec l’ajout de quelques pourcents d’oxygène dans le gazMicro plasma jets operating at atmospheric pressure in free atmosphere have recently attracted great attention because of their numerous advantages. In fact, micro plasma jets can be operated stably at atmospheric pressure and propagated over some centimeters in a free atmosphere. Moreover, these jets are non-thermal plasmas and create numerous reactive species. These properties allow to use this kind of plasma in many applications, such as surface treatment, decontamination, and plasma medicine.In this work it is shown that these micro plasma jets correspond to the fast propagation of an ionization front with no displacement of matter. A characterization of the plasma proprieties (e.g. distance and velocity of propagation) has been done as a function of the applied voltage, gas flow, gas composition and discharge geometry. The spatiotemporal distribution of the reactive species created by the plasma has been measured, with a special focus on the helium metastable atoms which have been measured by absorption laser spectroscopy. The helium metastable atom densities obtained are in the range of 1.10¹² to 5.10¹³ cm-³. Thanks to a very good spatiotemporal resolution, we have done a time-resolved full cartography of the plasma. This allowed us to show that the helium metastable atom distribution is annular near the nozzle and becomes circular as the plasma propagates. The maximum helium metastable atoms density has been measured at about half of the distance where the helium metastable atoms are present. This observation is in contradiction with results reported by numerical models. To gain further insight into the physical processes of the plasma, we have placed two micro plasma jets face to face. This study showed that both plasmas interact in such a way that they never come into contact, letting a space free of plasma between them. Moreover, we revealed that after the extinction of the plasmas, a second discharge is ignited in the previously free space. Fast imaging, spectroscopy diagnostics and electrical measurements showed that this second discharge is due to a polarity reversal, which creates an electron trap. Aiming the study of the application of micro plasma jets in the plasma medicine field, we have studied the degradation of plasmid DNA by our plasma jet. We observed that the plasma treatment leads mostly to single and double strands breaks, and to very little base oxidation and abasite site, even when oxygen is added into the gas mixture
19
O'Rourke, Brogan Roisín. "AGN Candidates for High Energy Neutrino Emission in IceCube". Thesis, Uppsala universitet, Högenergifysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-409739.
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Since the construction of the IceCube Neutrino Observatory was completed in 2010, many amazing discoveries have been made in the field of neutrino physics. Recently a neutrino event has been linked to an blazar-type active galactic nucleus source, bringing us one step closer to understanding the production of high-energy extragalactic neutrinos and ushering in a new era of multimessenger astronomy. This was found by linking the neutrino event to one of the Fermi Collaboration’s gamma ray sources which had a blazar counterpart. The quest to link other neutrino events to AGN (active galactic nuclei) sources through collaboration with the Fermi Large Area Telescope has turned up some interesting candidates. The fact that some of these potential sources are not blazars is curious and, although unconfirmed as neutrino sources, these objects merit further investigation due to their unusual nature.
20
Ruffa, Ilaria <1989>. "The AGN fuelling/feedback cycle in LERGs: the molecular gas component and its interplay with radio jets". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amsdottorato.unibo.it/9244/1/PhDThesis_IRuffa_finalversion.pdf.
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This Thesis has been carried out as part of an international collaboration overall aiming at a multi-component (stars, warm/cold gas, dust, radio jets) investigation of the AGN fuelling/feedback loop in the cores of a volume-limited (z<0.03) sample of eleven low excitation radio galaxies (LERGs). In this general context, this PhD Thesis mainly aimed at i) shedding light on the properties, kinematics and origin of the cold gas using ALMA CO(2-1) observations of nine sample members; ii) investigating the radio jets/cold ISM interplay on (sub-)kpc scales, coupling ALMA CO(2-1) and 230~GHz continuum observations with newly-acquired radio JVLA data at 10 GHz of five sample sources. Our work shows that rotating (sub-)kpc CO discs are very common in LERGs (six out of nine sources detected in CO). The 3D modelling of these discs demonstrates that the bulk of the gas is in ordered rotation (at least at the resolution of our ALMA observations). This may explain the relatively low accretion rate of LERGs. Nevertheless, low-level perturbations and/or non-circular motions are ubiquitous, indicating that the gas is not fully relaxed into the host galaxy potential. Whenever possible, we demonstrated that the observed CO discs are co-spatial with dust discs/lanes. In a couple of cases multi-wavelength constraints point towards an external origin of the gas. These evidence are difficult to reconcile with the chaotic cold accretion scenario, with implications for the powering mechanism of LERGs. The relative jet/CO disc inclination angles are found to span a wide range (27°-64°), with a marginal preference for angles around 45°. This is consistent with previous statistical 3D studies of the relative jet/dust disc orientation in radio galaxies. Hints of the presence of a jet/disc interaction are also observed in one case and tentatively found in the kinematics of other two sources.
21
Sauer, Petra. "The Role of Age and Gender in Education Expansion". WU Vienna University of Economics and Business, 2016. http://epub.wu.ac.at/5186/1/WP4_educineq_decomposition.pdf.
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Using the IIASA/VID dataset of populations by age, sex and level of education, I calculate education Gini coeffients and decompose the overall degree of educational inequality into age, sex and within-group components. I analyze the relative relevance of these components for inequality reduction and investigate the distributional outcomes of
education expansion. I find that, on average, equalization between males and females, younger and older cohorts as well as within these subgroups of the population
has significantly contributed to declining educational inequality over the observed sample period around the globe. But the relative role of these components fluctuates in the process of education expansion. First, as improvements are initiated by enhancing the educational
opportunities of the youth, the gap between cohorts widens in transition phases but vanishes thereafter. Second, gaps between sexes have been reduced but are predicted to widen
again if either males or females are the first to enter higher education levels. To a lesser extent, this is also true for gaps within population subgroups which can
be due to the ethnic background or the social and economic status of people.Series: INEQ Working Paper Series
22
Crespo, Cuaresma Jesus, C. Samir K i Petra Sauer. "Age-Specific Education Inequality, Education Mobility and Income Growth". European Commission, bmwfw, 2013. http://epub.wu.ac.at/4716/1/WWWforEurope_WPS_no006_MS15.pdf.
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We construct a new dataset of inequality in educational attainment by age and sex at the global level. The comparison of education inequality measures across age groups allows us to assess the effect of inter-generational education attainment trends on economic growth. Our results indicate that countries which are able to reduce the inequality of educational attainment of young cohorts over time tend to have higher growth rates of income per capita.
This effect is additional to that implied by the accumulation of human capital and implies that policies aiming at providing broad-based access to schooling
have returns in terms of economic growth that go beyond those achieved by increasing average educational attainment.Series: WWWforEurope
23
Crespo, Cuaresma Jesus, i Tapas Mishra. "Human Capital, Age Structure and Growth Fluctuations". Taylor & Francis, 2011. http://epub.wu.ac.at/3055/1/HCASGFOct07.pdf.
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This article assesses the empirical relationship between per capita income growth fluctuations and the age-structured human capital variations across four groups of geographically clustered developed and developing countries from spatial perspective. We estimate a spatial Vector Autoregressive (VAR) model of income dynamics where the distance between countries is defined on relational space based on their similarity in appropriation tendency of human capital in the production processes. These distances are computed using a newly developed human capital data set which fully characterizes the demographic structure of human capital, and thus underlines the joint relevance of demography and human capital in economic growth. Spatial effects on growth interdependence and complementarity are then explored with respect to the proposed distance metrics. Our results imply that significant cross-country growth interdependence based on human capital distances exists among defined country groups suggesting the need for a cooperative policy programme among them. We also find that the relationship between economic growth and human capital is highly nonlinear as a function of the proposed human capital distance.
24
Collet, Cédric. "Role of AGN feedback in galaxy evolution at high-redshift". Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01061155.
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There is growing evidence that supermassive black holes may play a crucial role for galaxy evolution, in particular during the formation of massive galaxies at high redshift (z ~ 2 - 3). Our work focuses on quantifying the effects of jets of radiogalaxies and of large bolometric luminosities of quasars on the interstellar gas in their host galaxies. To this end, we studied the kinematics of the ionized gas in 12 moderately powerful radio galaxies and 11 quasars (6 radio-loud and 5 radio-quiet) at high redshifts with rest-frame optical imaging spectroscopy obtained at the VLT with SINFONI. We searched for outflows and other signatures of feedback from the supermassive black holes in the centers of these galaxies to evaluate if the AGN may plausibly quench star formation. In our sample of moderately powerful radiogalaxies, we observe velocity dispersions nearly as large as those observed in the most powerful ones (with FWHM ~ 1000 km/s), but the quantity of ionized gas is decreased by one order of magnitude (Mion gas ~ 10^8 - 10^9 Msun) and velocity gradients tend to be less dramatic (Δv < 400 km/s), when they are observed. In our sample of quasars, we had to carefully subtract the broad spectral component of emission lines to have access to its narrow, and spatially extended, component. We detect truly extended emission line regions in 4/6 sources of our radio-loud subsample and in 1/5 source of our radio-quiet subsample. We estimate that masses of ionized gas in these sources are smaller than in our sample of high-redshift radiogalaxies (with Mion gas ~ 10^7 - 10^8 Msun) and kinematics tend to be more quiescent, akin to what is observed in local quasars. Finally, detailed observations of two outliers among our sample of high-redshift radiogalaxies revealed that one of them is closely surrounded by 14 companions galaxies, hence lying in an overdensity. We therefore interpret the presence and morphology of ionized gas around these galaxies as evidence for repeated cycles ouf AGN outbursts, akin to what can be observed in local clusters of galaxies, which are prime examples of AGN feedback in the nearby Universe.
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Crespo, Cuaresma Jesus, Martin Lábaj i Patrik Pruzinský. "Prospective Ageing and Economic Growth in Europe". WU Vienna University of Economics and Business, 2014. http://epub.wu.ac.at/4080/1/wp165.pdf.
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We assess empirically the role played by prospective ageing measures as a predictor of income growth in Europe. We show that prospective ageing measures which move beyond chronological age and incorporate changes in life expectancy are able to explain better the recent long-run growth experience of European economies. The improvement in explanatory power of prospective ageing indicators as compared to standard measures based on chronological age is particularly relevant for long-run economic growth horizons. (authors' abstract)Series: Department of Economics Working Paper Series
26
Berton, Marco. "Parent population of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies". Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424397.
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The aim of this thesis is to unveil the nature of the so-called parent population of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies (F-NLS1s). These sources are a subclass of active galactic nuclei which was recently identified as the third class of $\gamma$-ray emitting AGN. They likely harbor a relativistic jet directed toward the observer. The aim was to understand how do they appear when observed under a different inclination. To study their parent population I built four samples of parent candidates, that is steep-spectrum narrow-line Seyfert 1 galaxies (S-NLS1s), radio-quiet narrow-line Seyfert 1 (RQNLS1s), disk-hosted radio-galaxies (disk RGs) and finally compact steep-spectrum sources with high excitation spectrum (CSS/HERGs). For each sample I calculated the black hole mass and Eddington ratio, to compare them with those of F-NLS1s. I studied the differences in the narrow-line region of RQNLS1s and radio-loud NLS1s, to find traces of interactions with a relativistic jet. Finally, I built the first luminosity function of F-NLS1s, to compare it with that of CSS/HERGs. I concluded that a F-NLS1, when observed at large angles, appears as a S-NLS1s and later as a disk RGs. Both of them can be included in the larger group of CSS/HERGs. In general then F-NLS1s are CSS/HERGs observed inside their relativistic jet.Questa tesi si propone di svelare la natura della cosiddetta popolazione madre delle galassie narrow-line Seyfert 1 radio brillanti a spettro piatto (F-NLS1). Queste sorgenti sono una sottoclasse di nuclei galattici attivi che di recente è stata identificata come la terza classe degli AGN con emissione di raggi $\gamma$. Esse ospitano un getto relativistico diretto verso l'osservatore. Lo scopo era di comprendere come questi oggetti appaiono quando osservati da una diversa inclinazione. Per studiare ciò ho costruito quattro campioni di candidati, ossia narrow-line Seyfert 1 radio brillanti a spettro ripido (S-NLS1), narrow-line Seyfert 1 radio quiete (RQNLS1), radio-galassie ospitate in una galassia a disco (disk RG) e oggetti compatti a spettro ripido con spettro ad alta eccitazione (CSS/HERG). Per ciascun campione ho calcolato la massa del buco nero e il rapporto di Eddington, per confrontarlo con i valori già noti delle F-NLS1. Ho studiato le differenze fra le narrow-line region delle RQNLS1 e delle NLS1 radio brillanti, per trovare segni di interazione con il getto relativistico. Infine, ho costruito la prima funzione di luminosità delle F-NLS1, per confrontarla con quella dei CSS/HERG. Ho concluso che una F-NLS1, quando osservata ad angoli via via crescenti, appare prima come una S-NLS1 e dopodiché come una disk RG. Entrambe queste sorgenti possono essere incluse nella più vasta classe dei CSS/HERG. In generale quindi le F-NLS1 sono dei CSS/HERG osservate all'interno del loro getto relativistico.
27
Bessueille, François. "Contribution à l'élaboration et à la lecture des puces à ADN". Ecully, Ecole centrale de Lyon, 2001. http://www.theses.fr/2001ECDL0024.
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Dans le cadre de ce travail, différents procédés d'élaboration et de lecture de puces à ADN ont été mis au point. La méthode retenue pour l'élaboration des puces consiste à fonctionnaliser par silanisation des structures de type Si/SiO2 avec le chlorodiméthylsilylundécanoate de méthyle (CDSUM), puis après hydrolyse et activation des esters de méhtyle au n-hydroxysuccinimide (NHS), un aminopolyoxyde d'éthylène, lui-même greffé sur les esters activés, joue le rôle d'espaceur et assure une couverture de la surface par des terminaisons alcools primaires. Les substrats ainsi préparés permettent la synthèse d'oligonucléotides par la chimie des phosphoramidites. Des systèmes d'adressages, tels que la projection par jets et la fluidique, ont été réalisés pour localiser les réactions de synthèse à la surface des puces. Parallèlement aux systèmes d'adressage mécanique, une méthode de multifonctionnalisation par micro tamponnage a été développée, permettant d'optimiser la surface des substrats. Des travaux sur la lecture des puces ont été conduits selon différents procédés, tels que l'optoélectrochimie sur structure EDS ou la cartographie de fluorescence. Puis ces techniques ont été validées par radio-imagerie et XPS. Des puces réutilisables 20 fois, sans altération de réponse, hybridables par des oligonucléotides complémentaires et des fragments PCR doubles brins de 1. 5 kb, ayant une limite de détection de 10aM pour des hybridations oligonucléotides contre oligonucléotides, soit 5. 3 10-4 brins / ưm2 ont été obtenues, la sélectivité étant réalisée au mismatch près.
28
Lycos, Paul. "Technology and civil aviation: How popular attitudes and government policies shaped civil aviation and the air cargo industry from the early years of aviation through the jet age". Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=95179.
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As popular attitudes surrounding the place of a particular type of technology evolve, they spark advances and innovation as the technology grows in acceptance and use. This, in turn, attracts the attention of government interests. Agreeing on the technology's usefulness and rightful place in advancing the nation's welfare, government policies and regulation seek to encourage its optimum growth and reduce any perceived negative knock-on effects. These external forces influence the direction that technological innovation takes in a given space. Concurrently, the byproduct of such external forces is an adapting technology which itself exerts its due level of influence in the next wave of popular attitudes and government policies concerning it. The relationship between civil aviation and air cargo operations in the United States and the popular attitudes and government policies surrounding this space is one example of such a phenomenon. More specifically, that the prevailing level of civil aviation technology from 1903 to 1955 was a function of: (1) prevailing popular attitudes and (2) government policies (e.g. domestic U.S. and foreign government policies)themselves influenced by the technological advances in the field. Rather than offer an exhaustive account of the forces shaping civil aviation, this thesis offers a thoughtful analysis of the context in which aviation technology developed in the United States in order to better understand the interplay between these forces and the technological advances they inspired. This work traces the development of popular attitudes from a variety of perspectives, U.S. legislative efforts (e.g. Air Mail Act of 1925, Air Commerce Act of 1926, Civil Aeronautics Act of 1938), and international law (e.g. Warsaw Convention of 1929, Hague Protocol of 1955) as they relate to the advances made in civil aviation and air cargo. This is buttressed by a survey of selected technological changes over this period. Finally, the thesis concAu fur et a mesure que les attitudes populaires entourant un certain type de technologie évoluent et que cette industrie croit and approbation et utilisation, elles provoquent des étincelles de progrès et d'innovation dans ce secteur. Ceci, à son tour, attire l'attention des intérêts du gouvernement. Constatant l'utilité de cette technologie et de sa place légitime dans l'avancement du bien-être de la nation, les politiques et réglementations gouvernementales visent à stimuler sa croissance optimale et a réduire la perception négative de tout effet secondaire. Ces forces externes influencent la direction que prend l'innovation technologique dans un espace donné. Parallèlement, le sous-produit de telles forces est une technologie qui s'adapte et déploie son dû niveau d'influence dans la future vague d'attitudes populaires àvenir et les politiques gouvernementales le concernant. La relation entre l'aviation civile, les opérations de fret aérien aux Etats-Unis et les attitudes populaires jointes aux politiques gouvernementales encadrant cet espace est un exemple d'un tel phénomène. Plus précisément, que le niveau dominant la technologie de l'aviation civile de 1903 à 1955 a été une fonction : (1) des attitudes populaires dominantes et (2) des politiques gouvernementales (par exemple politiques nationales des États-Unis et politiques gouvernementales internationales) -elles mêmes influencées par les progrès technologiques dans ce domaine. Plutôt que d'offrir un compte rendu exhaustif des forces qui façonnent l'aviation civile, cette thèse propose une analyse approfondie du contexte dans lequel la technologie s'est développée dans l'aviation des États-Unis afin de mieux comprendre l'interaction entre ces forces et les avancées technologiques qu'elles ont inspiré. Cet ouvrage retrace l'évolution des attitudes populaires à partir d'une variété de perspectives, les efforts de la législation américaine (p.e. Air Mail Act$
29
Mahlberg, Bernhard, Inga Freund, Cuaresma Jesus Crespo i Alexia Prskawetz. "Ageing, productivity and wages in Austria". Elsevier, 2013. http://epub.wu.ac.at/3714/1/LABECO.pdf.
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Current demographic developments in industrialized countries and their consequences for workforce
ageing challenge the sustainability of intergenerational transfers and economic growth. A shrinking share
of the young workforce will have to support a growing share of elderly, non-working people. Therefore, the
productivity of the workforce is central to a sustainable economic future. Using a new matched employeremployee
panel dataset for Austrian firms for the period 2002-2005, we study the relationship between the
age structure of employees, labour productivity and wages. These data allow us to account, simultaneously,
for both socio-demographic characteristics of employees and firm heterogeneity, in order to explain labour
productivity and earnings. Our results indicate that firm productivity is not negatively related to the share of
older employees it employs. We also find no evidence for overpayment of older employees. Our results do not
show any association between wages and the share of older employees. Furthermore, we find a negative
relationship between the share of young employees and labour productivity as well as wages, which is more
prevalent in the industry and construction sector. (authors' abstract)
30
Crespo, Cuaresma Jesus, i Doris Anita Oberdabernig. "Education and the Transition to Sustained Democracy". WU Vienna University of Economics and Business, 2014. http://epub.wu.ac.at/4108/1/wp170.pdf.
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We study empirically the role of education, age structure and other socioeconomic factors as a determinant of the transition to stable democratic regimes. Our findings suggest that educational improvements (in particular in primary education) and policies towards reducing
inequalities in educational attainment play a particularly important role as a catalyst of sustainable democratization processes. (authors' abstract)Series: Department of Economics Working Paper Series
31
Walter, Philippe. "L'ordre et la memoire du temps : la fete et le calendrier dans les oeuvres narratives francaises de chretien de troyes a la mort artu". Paris 4, 1987. http://www.theses.fr/1987PA040176.
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L'etude des indices temporels et des mentions calendaires dans le recit francais de 1170 a 1230 permet la mise en evidence d'une esthetique narrative ou la fete et les deux notions d'ordre et de memoire essentielles dans le comput medieval jouent un role important. La fete ne sert pas seulement de repere dans la trame chronologique du recit ; sa distribution et sa place dans une oeuvre permet de comprendre les enjeux narratifs de celle-ci: au douzieme siecle, on ne trouve presque que des romans nuptiaux (conclus par des mariages), alors qu'au treizieme siecle, c'est le roman dynastique (destine a se conclure sur un couronnement) qui devient le modele dominant. L'analyse de la representation narrative des fetes calendaires (carnaval, fetes de mai, fete de la saint-jean, etc. ) et des fetes de cour (avec toutes leurs activites specifiques : jeux, rites, etc. ) permet de definir la culture courtoise comme une ere du jeu et du plaisir, par opposition a la culture de l'ordre symbolisee par la fete liturgique. Cette derniere cherche d'ailleurs de plus en plus a s'imposer tout comme elle investit les ceremonies sociales (mariages, couronnements, adoubements) que reflete la litterature. Le calendrier est en fait le lieu strategique d'affrontement de deux memoires au depart totalement distinctes voire antagonistes. L'hagiographie tente de les concilier en perpetuant de vieux substrats mythologiques du paganisme dans les saisons liturgiques. Un comparatisme attentif a la structure calendaire de l'imaginaire medieval et a la finalite differente des textes hagiographiques et litteraires permet d'eclairer certains themes courtois ainsi que certaines structures anthropologiques du conte populaire francais. L'histoire du calendrier permet de comprendre l'histoire des mentalites ainsi que les grands mythes dominant une epoque bien delimiteeThe study of temporal marks and calendar mentions in the french narrative from chretien de troyes to la mort artu (1170-1230) emphasizes an esthetical conception of the narrative where the theme of feast and the two concepts of order and memory (used in mmedieval comput) are essential. The analysis of calendar and courteos feasts shows that this literature promotes a culture based on play and pleasure, in opposition to a culture based on order (ordo) symbolized by liturgical feasts. In medieval societies, the calendar is a strategical space where two memories struggle for power. Medieval hagiography tries to conciliate them : it perpetuates old mythological substrata of paganism in the seasons of liturgical year. A comparative reading conscious of the calendar structure of medieval "imaginaire" explains several themes of courteosy and a few aspects of the french popykar tales
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Di, Filippo Laurent. "Du mythe au jeu : approche anthropo-communicationnelle du Nord : des récits médiévaux scandinaves au MMORPG Age of Conan : Hyborian Adventures". Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0213/document.
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Un rhinocéros Berserker, des hordes de Vanir déferlant sur la Cimmérie, le fils d’Ymir emprisonné... les références aux récits médiévaux scandinaves couramment désignés par les termes « mythes nordiques » sont nombreuses dans le jeu de rôle en ligne massivement multi-joueurs Age of Conan: Hyborian Adventures. Mais, comment des éléments issus de sources presque millénaires sont-ils devenus des composantes d’une production vidéoludique contemporaine ? À partir de ce cas d’étude, l’auteur de ce travail s’intéresse, de façon plus générale, aux phénomènes culturels et à leurs dynamiques à travers leurs processus de transmission, de manifestation et d’appropriation. Pour ce faire, il s’appuie sur une démarche qualitative et empirique à la croisée des Sciences de l’information et de la communication et des Études scandinaves afin de développer une approche anthropo-communicationnelle, fortement imprégnée par les travaux en Anthropologie. Celle-ci se fonde sur une méthodologie à la fois linguistique, socio-historique, d’observation participante sur le temps long et un suivi de veille sur le temps très long. Elle permet de constater que, des manuscrits médiévaux aux jeux vidéo en ligne, en passant par la littérature de fantasy américaine des années 1930, le sens donné aux références aux ressources culturelles du passé est sans cesse transformé et construit en fonction de la situation dans laquelle elles sont manifestées. Ces dynamiques culturelles s’inscrivent alors au cœur de la problématique du changement et de la permanence et mettent en lumière les constructions d’un imaginaire du commun tout en remettant au centre de la réflexion le travail des acteursA berserker rhinoceros, hordes of Vanir swarming upon Cimmeria, Ymir’s son imprisoned … references to the medieval scandinavian stories often designated as « Norse myths » are numerous in the massively multi-player online rôle playing game Age of Conan: Hyborian Adventures. But, how could elements coming from sources which are almost a thousand years old become parts of a contemporary videogame ? From this case study, the author of this work takes a more general interest in cultural phenomenons and their dynamics through their transmission, manifestation and appropriation processes. In order to do this, he leans on a qualitative and empirical research which articulates communication studies with scandinavian studies in order to build an anthropo-communicational approach, which is strongly influenced by Anthropology. This approach is based on a multi-layered methodology which includes linguistics, socio-historical method, long term participant observation and very long term information monitoring. It allows to observe that, from the medieval manuscripts to online video games, through american fantasy literature from the 1930’s, the significations which people give to past cultural ressources are always transformed and built according to the situation in which they are expressed. Such cultural dynamics fall within the heart of research questions about change and permanence and highlight the ways by which an imaginary of the common is built at the same time as it puts the work of the social actors at the center of the reflection
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Kiehlmann, Sebastian [Verfasser], A. J. [Akademischer Betreuer] Zensus i A. [Akademischer Betreuer] Eckart. "Origin of the gamma-ray emission in AGN jets - A multi-wavelength photometry and polarimetry data analysis of the quasar 3C 279 / Sebastian Kiehlmann. Gutachter: A.J. Zensus ; A. Eckart". Köln : Universitäts- und Stadtbibliothek Köln, 2015. http://d-nb.info/1074243269/34.
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Petutschnig, Matthias, i Silke Rünger. "The Effects of a Tax Allowance for Growth and Investment - Empirical Evidence from a Firm- Level Analysis". WU Vienna University of Economics and Business, Universität Wien, 2017. http://epub.wu.ac.at/5722/1/SSRN%2Did3024190.pdf.
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We contribute to the empirical literature on the debt bias of corporate income taxation through a firm-level evaluation of the European Commission's recent proposal of an Allowance for Growth and Investment (AGI). We use the introduction, the application and the repeal of a similar allowance in Austria during the early 2000s to evaluate the effects of the AGI on corporate equity and profit distribution. Our analysis provides evidence that such an allowance could increase corporate equity ratios by 5.5 percentage points and reduce profit distributions by 7.6 percentage points. These effects are stronger than those the previous literature for traditional Allowance for Corporate Equity (ACE) tax systems has identified.
Additionally, we contribute to the recently expanding literature on the influence of ownership on tax planning as we find significant differences in the utilization of the
AGI depending on individual specifics of the majority shareholder as well as depending on the number of shareholders of the respective firms.Series: WU International Taxation Research Paper Series
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Harwood, Jeremy James. "The dynamics and energetics of radio-loud active galaxies". Thesis, University of Hertfordshire, 2014. http://hdl.handle.net/2299/14409.
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In this thesis, I use the new generation of radio interferometer along with X-ray observations to investigate the dynamics and energetics of radio-loud active galaxies which are key to understanding AGN feedback and the evolution of galaxies as a whole. I present new JVLA observations of powerful radio source and use innovative techniques to undertake a detailed analysis of JVLA observations of powerful radio galaxies. I compare two of the most widely used models of spectral ageing, the Kardashev-Pacholczyk and Jaffe-Perola models and also results of the more complex, but potentially more realistic, Tribble model. I find that the Tribble model provides both a good fit to observations as well as providing a physically realistic description of the source. I present the first high-resolution spectral maps of the sources and find that the best-fitting injection indices across all models take higher values than has previously been assumed. I present characteristic hot spot advance speeds and compare them to those derived from dynamical ages, confirming that the previously known discrepancy in speed remains present in older radio sources even when ages are determined at high spectral and spatial resolutions. I show that some previously common assumptions made in determining spectral ages with narrow-band radio telescopes may not always hold. I present results from a study of the powerful radio galaxy 3C223 at low frequencies with LOFAR to determine its spectrum on spatially small scales and tightly constrain the injection index, which I find to be consistent with the high values found at GHz frequencies. Applying this new knowledge of the low energy electron population, I perform synchrotron / inverse-Compton model fitting and find that the total energy content of the radio galaxy lobes increases by a factor greater than 2 compared to previous studies. Using this result to provide revised estimates of the internal pressure, I find the northern lobe to be in pressure balance with the external medium and the southern lobe to be overpressured. I go on to present the first large sample investigation of the properties of jets in Fanaroff and Riley type I radio galaxies (FR-I) at X-ray energies based on data from the Chandra archive. I explore relations between the properties of the jets and the properties of host galaxies in which they reside. I find previously unknown correlations to exist, relating photon index, volume emissivity, jet volume and luminosity, and find that the previously held assumption of a relationship between luminosities at radio and X-ray wavelengths is linear in nature when bona fide FR-I radio galaxies are considered. In addition, I attempt to constrain properties which may play a key role in determination of the diffuse emission process. I test a simple model in which large-scale magnetic field variations are primarily responsible for determining jet properties; however, we find that this model is inconsistent with our best estimates of the relative magnetic field strengths in my sample.
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Charneau, Sébastien. "Approches moléculaires des mécanismes mis en jeu en fin de schizogonie intraérythrocytaire de Plasmodium falciparum (agent du paludisme) par hybridation soustractive suppressive et puces à ADN". Paris, Muséum national d'histoire naturelle, 2005. http://www.theses.fr/2005MNHN0001.
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Le propos de ce travail était d'étudier la différenciation des mérozoi͏̈tes de Plasmodium falciparum à travers son transcriptome. Premièrement, par hybridation soustractive suppressive, nous avons réalisé une banque d'ADNc spécifique de stade. Nous avons identifié 40 gènes exprimés spécifiquement lors de la morphogenèse des mérozoi͏̈tes, certains attendus car codant pour des protéines du mérozoi͏̈te (27,5%), les autres codant pour des protéines aux fonctions inconnues (72,5%). Nous avons caractérisé l'une de ces protéines, la dynamine 2 homologue. Exprimée uniquement lors de la schizogonie, elle pourrait être une molécule-clé de la différenciation des mérozoi͏̈tes et être impliquée dans la division mitochondriale. Deuxièmement, par puces à ADN, nous avons identifié dix gènes, encore non décrits, dont l'expression est significativement modulée par la rottlérine, un inhibiteur de protéines kinases qui stoppe la différenciation des mérozoi͏̈tes conduisant à la lyse du parasiteThe aim of this work was to study the differentiation of Plasmodium falciparum merozoite through its transcriptome. First, by suppression subtractive hybridization, we have realised a stage-specific cDNA library. We have identified 40 genes specifically expressed during merozoite morphogenesis, some expected as coding for merozoite proteins (27. 5%), the other coding for proteins of unknown function (72. 5%). We have characterized one of these proteins, the dynamin-2-like. Expressed only during schizogony, it could be a key-molecule of the merozoite differentiation and be involved in mitochondrial division. Second, by microarrays, we have identified 10 genes, as yet unreported, whose expression is significantly modulated by rottlerin, a protein kinase inhibitor that stops merozoite differentiation leading to the parasite lysis
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Valtonen-Mattila, Nora. "High Energy gamma-ray behavior of a potential astrophysical neutrino source : The case of TXS 0506+056". Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-90569.
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Blazars are a type of Active Galaxy that emit strong astrophysical jets. The association of a HE gamma-ray flare from the blazar TXS 0506+056 to the IceCube-170922A neutrino event in 2017, opened the possibility to a link between these two events. In this thesis, we will look at the HE gamma-ray behavior of TXS 0506+056 using data obtained from the Fermi-LAT by taking into account the other set of neutrino events associated with this source from 2014-2015. We will investigate whether both neutrino events present with comparable HE gamma-ray behavior by analyzing the lightcurves and the spectra for a quiet state, the 2014-2015 period, and the flare centered around the neutrino event from 2017. The results of the analysis performed in this thesis show no strong indication of a change in the gamma-ray behaviour in these potential neutrino detections.
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Glaub, Dominique. "La pratique New Age du tarot en Californie du Sud, une nouvelle forme de re-ligiosité : approche imaginaire et néo-tribale d'un jeu de cartes figurées". Paris 5, 1994. http://www.theses.fr/1994PA05H042.
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Objectif empirique : appréhender le tarot comme un objet culturel soumis à une acculturation dans l'espace et dans le temps. Présenter le visage éclate de la pratique divinatoire et son style baroque. Montrer que le tarot est, dans le cadre du new Age californien, un outil de transformation individuelle participant au projet collectif de l'avènement de l'ère du verseau et d'une nouvelle spiritualité objectif méthodologique : approche historique et imaginaire d'un projet culturel et d'une pratique sociale contemporaine (recours aux méthodes de recherche microsociologiques (entretiens, histoires de vie, observation participante)). Étudier "du-dedans" une forme sociale : "devenir le phénomène" objectif théorique : décrire une communauté de type néo-tribal organisée sous forme de réseau et dans laquelle l'informel, l'affectif, la proxémique et l'éphémère y sont les valeurs dominantes. Dégager dans la pratique new Age du tarot et dans ses contours, à la fois un mouvement de suradaptation à la modernité, une forme de contestation passive et une force sociale d'innovationEmpirical objective : To approach the tarot as a cultural object. To present the multi-facets of the modern divinatory practice and its "baroque style". To show that the tarot is, in a new age californien setting, a tool for individual transformation participating to the collective project of bringing the aquarion age and a new spirituality methodological objective : to use a historical and imaginary approach of a cultural object and a contemporary social practice (to use micro-sociological methods of research seen as (interviews, life histories observant participation)). To shedy "from the inside" a social form. To "become the phenomenon" theoretical objective :. To describe a neo-tribal community (organized as a social network) in which the "affect", the "informel", the "proxemique", and the "ephemenous" are the dominant values. To see in the tarot a "sur-adaptation" to modernity, a social contestation, and an social force of innovation
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Berry, Vincent. "Les cadres de l'expérience virtuelle : Jouer, vivre, apprendre dans un monde numérique : analyse des pratiques ludiques, sociales et communautaires des joueurs de jeux de rôles en ligne massivement multi-joueurs : Dark Age of Camelot et World of Warcraft". Paris 13, 2009. http://scbd-sto.univ-paris13.fr/secure/ederasme_th_2009_berry.pdf.
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Cette étude est une analyse de la pratique des joueurs francophones de Dark Age of Camelot et World of Warcraft. Qui sont-ils ? A quoi jouent-ils ?Quels sens donnent-ils à leurs pratiques ? A partir de données quantitatives (questionnaires) et qualitatives (entretiens et observations), la première partie décrit la population des joueurs en termes d’âge, de sexe, de milieu social. Que l’on soit homme ou femme, adolescent ou adulte, salarié, étudiant ou sans emploi, fan de fantasy, un ensemble de variables structurent les usages. . Dans un second temps, l’activité est analysée au regard des théories du jeu et du loisir. Espaces d’affrontements et de faire-semblant, les MMO sont aussi des univers « carnavalesques » permettant un certain relâchement du contrôle social. La troisième partie analyse la place du jeu dans l’espace social, familial, parental, amoureux. Pour certains, le MMO se pratique avec des « copains » dans un cybercafé, à sortie des cours. Pour d’autres, c’est une pratique solitaire, le soir en sortant »d’un boulot difficile ». Ailleurs, c’est une pratique de couple, le week-end. Contre la thèse postmoderne du cyberespace comme processus de déréalisation du monde, des sociabilités se développent dans le jeu et dans la « vraie vie ». Elles sont des moments de « socialisation par frottement » et d’ »expériences sociales » qui ne sont pas sans effets sur la construction de savoirs et de façon de penser le monde social. Cette étude montre ainsi comment en proposant « des carrières », ces « mondes du jeu » sont des espaces d’apprentissages informels mais aussi de (trans)formation d’habitus (vidéo)ludiques et de construction de nouveaux cadres de l’expérienceThis study analyzes the practice of French-speaking gamers of Dark Age of Camelot and World of Warcraft. Who are the players? What kind of game do they play? What meanings do they bring to their practices? Based on quantitative (questionnaires) and qualitative data (interviews and observations), the first part describes the gamer population in terms of age, gender and social class. Being a man or a woman, a teenager or an adult, being employed, a student or unemployed, being a fan of fantasy or not, a multitude of variables structure the gamers’ practices. Secondly, the activity is analyzed with respect to game and leisure theories. Being spaces of confrontations and make believe, MMOs are also “carnavalesque” universes allowing a certain loosening of social control. The third part analyzes the place of the game within social, family, parental and romantic life. For some gamers, the MMO is practised with "friends" in a cybercafe, after school. For others, it is a solitary practice, at night, upon finishing a “difficult day at work”. In other instances, it is a practice played by a couple, weekends only. Against the postmodern thesis of cyberspace as a process of “derealisation” of the world, social networks are constructed in the game and also in "real life". These social networks are moment of "socialization by friction" and "social experiences" which have effects on the construction of knowledge and the way that the gamers think of the social world. This study therefore shows how, by proposing "careers", these "game worlds" are spaces of informal learning but also of transformation of video-play habitus and of new frame analysis
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Huber, Peter, Harald Oberhofer i Michael Pfaffermayr. "Who Creates Jobs? Econometric Modeling and Evidence for Austrian Firm Level Data". WU Vienna University of Economics and Business, 2015. http://epub.wu.ac.at/4650/1/wp205.pdf.
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This paper offers an empirical analysis of net job creation patterns at the firm level for the Austrian economy between 1993 and 2013 focusing on the impact of firm size and age. We propose a new estimation strategy based on a two-part model. This allows to identify the structural parameters of interest and to decompose behavioral differences between exiting and surviving firms. Our findings suggest that conditional on survival, young Austrian firms experience the largest net job creation rates. Differences in firm size are not able to explain variation in net job creation rates among the group of continuing enterprises. Job destruction induced by market exit, however, is largest among the young and small firms with this effect being even more pronounced during the times of the Great Recession. In order to formulate sensible policy recommendations, a separate treatment of continuing versus exiting firms as proposed by the new two-part model estimation approach seems crucial.(authors' abstract)Series: Department of Economics Working Paper Series
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Grossard, Charline. "Evaluation et rééducation des expressions faciales émotionnelles chez l’enfant avec TSA : le projet JEMImE Serious games to teach social interactions and emotions to individuals with autism spectrum disorders (ASD) Children facial expression production : influence of age, gender, emotion subtype, elicitation condition and culture". Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS625.
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Le trouble du Spectre de l’Autisme (TSA) est caractérisé par des difficultés concernant les habiletés sociales dont l’utilisation des expressions faciales émotionnelles (EFE). Si de nombreuses études s’intéressent à leur reconnaissance, peu évaluent leur production chez l’enfant typique et avec TSA. Les nouvelles technologies sont plébiscitées pour travailler les habiletés sociales auprès des enfants avec TSA, or, peu d’études concernent leur utilisation pour le travail de la production des EFE. Au début de ce projet, nous retrouvions seulement 4 jeux la travaillant. Notre objectif a été la création du jeu sérieux JEMImE travaillant la production des EFE chez l’enfant avec TSA grâce à un feedback automatisé. Nous avons d’abord constitué une base de données d’EFE d’enfants typiques et avec TSA pour créer un algorithme de reconnaissance des EFE et étudier leurs compétences de production. Plusieurs facteurs les influencent comme l’âge, le type d’émotion, la culture. Les EFE des enfants avec TSA sont jugées de moins bonne qualité par des juges humains et par l’algorithme de reconnaissance des EFE qui a besoin de plus de points repères sur leurs visages pour classer leurs EFE. L’algorithme ensuite intégré dans JEMImE donne un retour visuel en temps réel à l’enfant pour corriger ses productions. Une étude pilote auprès de 23 enfants avec TSA met en avant une bonne adaptation des enfants aux retours de l’algorithme ainsi qu’une bonne expérience dans l’utilisation du jeu. Ces résultats prometteurs ouvrent la voie à un développement plus poussé du jeu pour augmenter le temps de jeu et ainsi évaluer l’effet de cet entraînement sur la production des EFE chez les enfants avec TSAThe autism spectrum disorder (ASD) is characterized by difficulties in socials skills, as emotion recognition and production. Several studies focused on emotional facial expressions (EFE) recognition, but few worked on its production, either in typical children or in children with ASD. Nowadays, information and communication technologies are used to work on social skills in ASD but few studies using these technologies focus on EFE production. After a literature review, we found only 4 games regarding EFE production. Our final goal was to create the serious game JEMImE to work on EFE production with children with ASD using an automatic feedback. We first created a dataset of EFE of typical children and children with ASD to train an EFE recognition algorithm and to study their production skills. Several factors modulate them, such as age, type of emotion or culture. We observed that human judges and the algorithm assess the quality of the EFE of children with ASD as poorer than the EFE of typical children. Also, the EFE recognition algorithm needs more features to classify their EFE. We then integrated the algorithm in JEMImE to give the child a visual feedback in real time to correct his/her productions. A pilot study including 23 children with ASD showed that children are able to adapt their productions thanks to the feedback given by the algorithm and illustrated an overall good subjective experience with JEMImE. The beta version of JEMImE shows promising potential and encourages further development of the game in order to offer longer game exposure to children with ASD and so allow a reliable assessment of the effect of this training on their production of EFE
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Meyer, Eileen. "The Blazar Envelope and the Relativistic Jet Dichotomy: Unification of Radio-Loud AGN". Thesis, 2012. http://hdl.handle.net/1911/71676.
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Motivated by recent successes in linking the kinetic power of
relativistic jets in active galactic nuclei (AGN) to the
low-frequency, isotropic lobe emission, I have re-examined the blazar
and radio-loud AGN unification scheme through careful analysis of the
four parameters we believe to be fundamental in producing a particular
jet spectral energy distribution (SED): the kinetic power, accretion
power, accretion mode, and orientation. In particular, I have compiled
a multi-wavelength database for hundreds of jet SEDs in order to
characterize the jet spectrum by the synchrotron peak output, and have
conducted an analysis of the steep lobe emission in blazars in order
to determine the intrinsic jet power. This study of the link between
power and isotropic emission is likely to have a wider applicability
to other types or relativistic jet phenomena, such as
microquasars. Based on a well-characterized sample of over 200
sources, I suggest a new unification scheme for radio-loud AGN (Meyer
et al. 2011) which compliments evidence that a transition in jet
power at a few percent of the Eddington luminosity produces two types
of relativistic jet (Ghisellini, et al., 2009). The `broken power
sequence' addresses a series of recent findings severely at odds with
the previous unification scheme. This scheme makes many testable
predictions which will can be addressed with a larger body of data,
including a way to determine whether the coupling between accretion
and jet power is the currently presumed one-to-one correspondence, or
whether accretion power forms an upper bound, as very recent
observations suggest (Fernandes et al. 2011). This work is a first
step toward a unified understanding of the relativistic jets found in
radio-loud active galactic nuclei (AGN) and their connection to
accretion onto the super-massive black holes from which they emanate.
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Deovrat, *. "AGN Feedback in Galaxy Clisters - Controlling Cooling Flows in Galaxy Clusters by Momentum-driven AGN Jets". Thesis, 2017. http://etd.iisc.ac.in/handle/2005/4219.
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Synopsis
According to the hierarchical structure formation model, massive structures like galaxy clusters are formed due to the gravitational collapse of initial density perturbations and their subsequent mergers. As the formation of galaxy clusters is driven by gravity, they are expected to follow self-similar profiles for density, temperature, entropy etc (Kaiser 1986). However, observations show that self-similarity assumption is not followed in clusters due to the presence of cooling and other such non-gravitational processes (Markevitch et al. 1998; Ponman et al. 1999). More than a third of galaxy clusters have cooling time of the hot diffuse gas in the intra-cluster medium (ICM) in their core smaller than their lifetime (Cavagnolo et al. 2009). As a result, the hot gas in cluster core is expected to cool down catastrophically with total cold gas mass deposition in the core greater than 1012 M⊙ during their lifetime and a star formation rate of several 100 M⊙yr−1. However, lack of observational support of these cooling flow signatures (Peterson et al. 2003) in clusters with short cooling time (cool core clusters) point to the presence of some heating mechanism to compensate the cooling loses and prevent the runway cooling. Among many possible candidates, AGN jets associated with the supermassive black hole present in member central galaxy of the cluster has emerged as the principle heating source (McNamara and Nulsen 2007). Observations show that the energy required to form the structures in the ICM as a result of AGN outbursts, are sufficient to overcome the radiative losses of the ICM. However, the details of AGN feedback to control the cooling flow remains sketchy. My thesis is based on numerical study of AGN feedback in galaxy clusters and trying to answer some important questions related to it.
In chapter 1, we discuss the process of galaxy cluster formation and how self-similarity arises naturally in such systems. We then discuss the observational evidences of the breaking of self-similarity in galaxy clusters. We look at the early history of X-ray observations of galaxy clusters and the quest to find signatures of cooling flow as predicted by theoretical models. The non-detection of cooling flow signatures like absence of line emissions below 0.5 keV in several cool core clusters gave rise to the possibility of presence of some heating mechanism to control the cooling flow. We discuss the observational evidences pointing to AGN jets being the possible heating source to compensate for the cooling losses of the ICM. We discuss the different modes of AGN feedback in galaxy clusters and their role in the evolution of these systems. We finally give a brief history of the numerical work done in the area of AGN feedback in galaxy clusters. This chapter ends with the big questions in AGN feedback model that needed investigation.
In chapter 2, using high-resolution 3-D and 2-D (axisymmetric) hydrodynamic simulations in spherical geometry, we study the evolution of cool cluster cores heated by feedback-driven bipolar active galactic nuclei (AGN) jets. Condensation of cold gas, and the consequent en-hanced accretion, is required for AGN feedback to balance radiative cooling with reasonable efficiencies, and to match the observed cool core properties. A feedback efficiency (mechanical luminosity ≈ ǫM˙accc2; where M˙acc is the mass accretion rate at 1 kpc) as small as 6 × 10−5 is sufficient to reduce the cooling/accretion rate by ∼ 10 compared to a pure cooling flow in clusters (with M200 � 7 × 1014 M⊙). This value is much smaller compared to the ones consid-ered earlier, and is consistent with the jet efficiency and the fact that only a small fraction of gas at 1 kpc is accreted on to the super-massive black hole (SMBH). The feedback efficiency in earlier works was so high that the cluster core reached equilibrium in a hot state without much precipitation, unlike what is observed in cool-core clusters. We find hysteresis cycles in all our simulations with cold mode feedback: condensation of cold gas when the ratio of the cooling-time to the free-fall time (tcool/tff ) is � 10 leads to a sudden enhancement in the accretion rate; a large accretion rate causes strong jets and overheating of the hot ICM such that tcool/tff > 10; further condensation of cold gas is suppressed and the accretion rate falls, leading to slow cooling of the core and condensation of cold gas, restarting the cycle. Therefore, there is a spread in core properties, such as the jet power, accretion rate, for the same value of core entropy or tcool/tff . A fewer number of cycles are observed for higher efficiencies and for lower mass halos because the core is overheated to a longer cooling time. The 3-D simulations show the formation of a few-kpc scale, rotationally-supported, massive (∼ 1011M⊙) cold gas torus. Since the torus gas is not accreted on to the SMBH, it is largely decoupled from the feedback cycle. The radially dominant cold gas (T < 5 × 104 K; |vr| > |vφ|) consists of fast cold gas uplifted by AGN jets and freely-infalling cold gas condensing out of the core. The radially dominant cold gas extends out to 25 kpc for the fiducial run (halo mass 7 × 1014M⊙ and feedback efficiency 6 × 10−5), with the average mass inflow rate dominating the outflow rate by a factor of ≈ 2. We compare our simulation results with recent observations.
In chapter 3, we investigate the stochastic condensation of cold gas and its accretion onto the central super-massive black hole (SMBH) which is essential for active galactic nuclei (AGN) feedback to work in the most massive galaxies that lie at the centres of galaxy clusters. Our 3-D hydrodynamic AGN jet-ICM (intracluster medium) simulations, looking at the detailed angular momentum distribution of cold gas and its time variability for the first time, show that the angular momentum of the cold gas crossing � 1 kpc is essentially isotropic. With almost equal mass in clockwise and counter-clockwise orientations, we expect a cancellation of angular momentum on roughly the dynamical time. This means that a compact accretion flow with a short viscous time ought to form, through which enough accretion power can be channeled into jet mechanical energy sufficiently quickly to prevent a cooling flow. The inherent stochasticity, expected in feedback cycles driven by cold gas condensation, gives rise to a large variation in the cold gas mass at the centres of galaxy clusters, for similar cluster and SMBH masses, in agreement with the observations. Such correlations are expected to be much tighter for the smoother hot/Bondi accretion. The weak correlation between cavity power and Bondi power obtained from our simulations also match observations.
Recent analysis shows that it is important to explicitly include the gravitational potential of the central brightest central galaxy (BCG) to infer the acceleration due to gravity (g) and the free-fall time (tff ≡ [2r/g]1/2 ) in cool cluster cores. Accurately measuring tff is crucial because according to numerical simulations cold gas condensation and strong feedback occur in cluster cores with min(tcool/tff ) below a threshold value close to 10. Recent observations which include the BCG gravity show that the observed threshold in min(tcool/tff ) lies at a somewhat higher value, close to 10-30; there are only a few clusters in which this ratio falls much below
10. In chapter 4, we compare numerical simulations of feedback AGN (Active Galactic Nuclei) jets interacting with the intracluster medium (ICM), with and without a BCG potential. We find that, for a fixed feedback efficiency, the presence of a BCG does not significantly affect the temperature but increases (decreases) the core density (entropy) on average. Most importantly, min(tcool/tff ) is only affected slightly by the inclusion of the BCG gravity. Also notable is that the lowest value of min(tcool/tff ) in the NFW+BCG runs are about twice larger than in the NFW runs because of a shorter time for feedback heating (which scales with the free-fall time) in the former. We also look at the role of depletion of cold gas due to star formation and show that it only affects the rotationally dominant component (torus), while the radially dominant component (which regulates the feedback cycle) remains largely unaffected. Stellar gas depletion also increases the duty cycle of AGN jets. The distribution of metals due to AGN jets in our simulations is predominantly along the jet direction and the radial spread of metals is less compared to the observations. We also show that the turbulence in cool core clusters is weak, consistent with recent Hitomi results on Perseus cluster.
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Rieger, Frank Michael. "Rotating jet phenomena in Active Galactic Nuclei". 2001. http://hdl.handle.net/11858/00-1735-0000-0006-B413-D.
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Movassaghi, Jorshari Razzi. "A case for an ultra massive black hole in the galaxy cluster MS0735.6+7421". Thesis, 2012. http://hdl.handle.net/1828/4032.
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In this work, we study the galaxy cluster MS0735.6+7421 that hosts the most energetic observed active galactic nucleus (AGN) outburst so far. Explaining this very energetic AGN outburst is found to be challenging. McNamara et al. 2009 grappled with this problem and proposed two possible solutions: either the black hole (BH) must be an ultra massive one (with mass $> 10^{10} \ \text{M}_\odot$), or the efficiency of the mass to energy conversion ($\epsilon$) should be higher than the generally assumed value of $\epsilon \sim 0.1$. However, the efficiency of the mass to energy conversion depends on the BH's spin {Benson and Babul 2009}; higher $\epsilon$ can be achieved with a higher spinning BH. Here, we explore the second solution in detail, and ask the question: How did the BH spin up to the very high spins in advance of the outburst? We also explore the attendant physical processes, such as star formation, during the spin-up mode and investigate the associated observational implications. Comparing our results with what is generally expected from simulations and observational studies suggests that for all intents and purposes, the existence of an ultra massive BH is the simplest solution.Graduate
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(5929751), Mary A. Hodge. "Linear Polarization of AGN Jets". Thesis, 2019.
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Active galactic nuclei (AGN) jets are energetic phenomena where twin jets of plasma emerge perpendicular to the plane of the accretion disk surrounding supermassive black holes in galactic centers. Radio-loud jets are largely divided into classes based on the angle of observation (blazars versus radio galaxies), spectral line widths (Flat Spectrum Radio Quasars/FSRQs versus BL Lac objects/BL Lacs), and location of the synchrotron peak frequency in their spectral energy distribution (high-spectral peaked/HSP, intermediate-spectral peaked/ISP, or low-spectral peaked/LSP).The linear fractional polarization of the radio emission and the direction of the polarization plan (electric vector position angle, "EVPA'') can be measured, providing information on the properties of the jets' magnetic field. This study uses and describes some processing of data from the MOJAVE program, taken with the VLBA at 15 GHz, to investigate the polarization behavior of 387 AGN.
The most polarized jets have good alignment between the EVPA and the local jet direction, and higher stability in both fractional polarization and the EVPA. This characterization best describes BL Lacs, which are notably different from FSRQs. HSP BL Lacs have lower fractional polarization than LSP BL Lacs, with fractional polarization partially dependent on apparent jet speeds. These results have supported a scenario where HSP BL Lacs and LSP BL Lacs are similar objects with differing relativistic beaming factors, while FSRQs and BL Lacs as a class have inherent differences in the makeup of their magnetic fields.
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Yates-Jones, PM. "Dynamics and radio properties of AGN jets in complex environments". Thesis, 2021. https://eprints.utas.edu.au/38129/1/Yates_Jones_whole_thesis.pdf.
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Active Galactic Nuclei (AGN) feedback is a key ingredient in galaxy formation and evolution. A large portion of this feedback is done by radio jets in the form of shock-heating and uplifting gas. Both theory and observations show that jets are affected by their environment; therefore to understand jet feedback, a detailed understanding of jet-environment interaction is required. Analytic and semi-analytic models can predict jet dynamics and large-scale morphology but necessitate simple assumptions about both the environment and jet stability. These assumptions are contrary to observations,which show that radio jets exist in a range of environments,including both near and far from the centres of both relaxed and non-relaxed galaxies, groups and clusters. Numerical simulations of radio jets allow those assumptions to be relaxed. I have developed a jet simulation model based on the PLUTO code for (relativistic)-hydrodynamics that supports three-dimensional, relativistic, initially conical jets, which is the basis for the results presented in this thesis. Using this model, I focus on the dynamics, feedback, and radio properties of jets in non-idealised environments.
To begin with, I investigate the role environment richness and intermittency play in radio jet evolution, by simulating two-dimensional, non-relativistic jets in poor group and cluster environments with varying intermittency properties. I show that the environment into which a radio jet is propagating plays an important role in the resulting morphology, dynamics and observable properties of the radio source. The same jet collimates much later in a poor group compared to a cluster, which leads to pronounced differences in radio morphology. The intermittency of the jet also affects the observable properties of the radio source, and multiple hotspots are present for multiple outburst jets in the cluster environment. I quantify the detectability of active and quiescent phases and find this to be strongly environment-dependent, concluding that the dynamics and observational properties of jets depend strongly on the details of energy injection and environment.
Next, I present relativistic three-dimensional simulations of high-power radio sources propagating into asymmetric cluster environments, removing the spherically symmetric assumption typically used in the literature. I offset the environment by 0 or 1 core radii (equal to 144 kpc), and incline the jets by 0, 15, or 45∘ away from the environment centre. The different environment encountered by each radio lobe provides a unique opportunity to study the effect of environment on otherwise identical jets. Synthetic radio observables are derived from the purely hydrodynamic simulations assuming a constant departure from equipartition for the magnetic and thermal energy densities. I find that the jets propagating into denser environments have consistently shorter lobe lengths and brighter hotspots, while the axial ratio of the two lobes is similar. I also reproduce the observed anti-correlation between lobe length asymmetry and environment asymmetry at redshifts < 0.3, confirming that observed large-scale radio lobe asymmetry can be driven by differences in the underlying environment.
Simulations of radio jets are often used to make predictions for radio observables, providing the basis for observer interpretation. I have developed a method for calculating synthetic synchrotron emission from purely hydrodynamic simulations including both adiabatic and radiative losses, by incorporating Lagrangian tracer particles into the Eulerian jet fluid flow. These tracer particles are advected by the jet, and the local fluid history for each particle is recorded. In post-processing, this history is used as input to a lossy analytic emissivity model to calculate the emissivity as a function of frequency, redshift, and fluid history. Calculating the emission in post-processing provides increased flexibility for emissivity parameters like the source redshift and observing frequency. I apply this method to the three-dimensional relativistic simulations in asymmetric environments to investigate the effects of environment asymmetry on the observed broadband radio properties for each lobe.
Finally, I present the foundations of CosmoDRAGoN, a large-scale project that will simulate the largest ever suite of double-lobed radio AGN in cosmological environments. Using simulated galaxy clusters taken from the three hundred cosmological simulation collaboration as the initial conditions for these simulations, I propagate relativistic three-dimensional conical jets into these cosmological environments. I compare the different jet morphologies produced based on the initial parameters, and show the impact of large-scale environment and cluster weather on jet evolution and observable broadband radio spectra for both active and remnant radio sources.
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VIETRI, GIUSTINA. "The most luminous quasars of the universe: probing the AGN/galaxy co-evolution at its extremes". Doctoral thesis, 2018. http://hdl.handle.net/11573/1051847.
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The systematic, multi-frequency investigation of hyper-luminous quasars shining at the golden epoch of AGN activity offers the unique opportunity of studying the power and the effect of AGN feedback at its extreme. The WISE/SDSS- selected hyper-luminous quasar (WISSH) survey is an extensive multi-band observing program to investigate the role of nuclear activity in SMBH-galaxy self-regulated growth via extended outflows. We found that WISSH AGN are typically powered by highly accreting (0.3-3 Ledd), ten billion solar masses SMBHs, demonstrating that WISSH provides a simple and valuable tool to complete the census of the extreme SMBH population in the universe. We found that the 70% of quasars lacks [OIII] emission but shows strong winds traced by 3000-8000 km/s blueshifts of the high-ionization (CIV) with respect to low-ionization (HBeta) broad emission lines, revealing strong radiatively driven winds that dominate the BLR kinematics. We investigated about the possible origins of this intriguing dichotomy which involves fundamental parameters such as bolometric luminosity, SMBH mass, Eddington ratio and shape of the UV-X-ray spectrum.
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Yang, Chen-Han, i 楊成瀚. "The (Un)Admirable Auratic Ob-ject: Study on the Art in the Age of Digital Individuation". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/k898zc.
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博士國立交通大學
社會與文化研究所
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This thesis aims to explore the state, the destiny, and the possibility of art and art work in the age of digital individuation in which the individuated individuals transindividually and collectively differ themselves from the other individuated individuals by digitally operating the mobile digital devices such as the smartphone and the tablet. We discover the correspondence between the user experience the individuated individuals have when they make digital individuation possible by digitally operating the mobile digital devices and the logic of the experience of consciousness the philosopher Gilbert Simondon and G.W.F. Hegel provided. By applying the method of “transduction” Simondon provided and the mediation of the concept “perception” Maurice Merleau-Ponty presented, we can see the Hegelian logic which is composed of the spiritual movement from subjective logic to the absolute idea or absolute logic (via objective logic) and the system of phase and phase-shift which is constructed by three couples of phases such as “body-surface”, “forcer-gadget”, and “changer-place” the individuated individuals give to the digital technical object and themselves. Owing to this, art and art work are not only not considered as the “object without aura” Walter Benjamin mentioned, but also not considered as the “aura without object” Boris Groys presented. Art and art work are considered as the “admirable auratic ob-ject” in the age of digital individuation. What the contemporary artists such as James Terrell, Liu Ho-jang, Chen Chieh-jen, and Kao Chung-li face is exactly the situation of the “admirable auratic ob-ject”; they have created the real artistic aura in this situation. However, due to the fact that the condition of possibility of the birth of art and art work as the “admirable auratic ob-ject” is the digital individuation the individuated individuals transindividually and collectively undergo, the artistic creation James Terrell, Liu Ho-jang, Chen Chieh-jen, and Kao Chung-li presented are no use for the real becoming and transformation of the digitally individuated individuals. Henceforth, what we need is the artistic and aesthetic practices-to-come that takes the “unadmirable auratic ob-ject” as the goal, the against-the-intermittence “enmittence” as the method, and the “animachinism” or the “machanimism” as the strategy of practice.
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Ferreira, Bruno Emanuel Azevedo. "Fuel and operational hedging : evidence from the airline industry". Master's thesis, 2019. http://hdl.handle.net/10400.14/28784.
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A indústria da aviação é, hoje em dia, caraterizada por uma intensa competição global entre companhias aéreas. Os custos com combustível representam uma parte substancial das despesas operacionais e estão sempre sujeitos à volatilidade do mercado. Tanto a cobertura de risco financeiro como operacional estão ao dispor das companhias aéreas para contrariar a volatilidade e reduzir os custos em combustível. Sendo um dos poucos estudos a incluir companhias aéreas da Europa e da Ásia, esta investigação foca-se em 43 companhias ao longo do período 2007-2017 e conclui que as transportadoras aéreas Europeias têm menor exposição ao risco do preço do combustível, do que as companhias Asiáticas ou Norte-Americanas. Também é realizada uma comparação entre tipos de companhias e é possível concluir que a exposição média ao preço do querosene é maior em companhias-bandeira do que nas de baixo custo. Pensamos que este será o primeiro estudo global a incluir três medidas de cobertura de risco operacional, sendo estes a diversidade da frota, a eficiência de combustível, e a utilização de aviões em leasing operacional. Treanor, Carter, Rogers, & Simkins (2013) estudaram estas medidas mas apenas em companhias Norte-Americanas. Usando modelos de efeitos-fixos, os nossos resultados sugerem que a cobertura do risco financeiro acaba por aumentar a exposição. Adicionalmente, as nossas evidências apontam para uma rejeição da hipótese de que a cobertura de risco operacional leva a uma diminuição da exposição ao risco do preço do querosene, em todas as nossas três proxies.The airline industry is nowadays characterized by an intense competition among carriers around the globe. Jet fuel costs represent a substantial part of airlines’ operating expenses and are always subject to the market volatility. Both financial and operational hedging are at the disposal of airlines to offset the volatility and smooth these expenses across the years. Being one of the few studies to include airlines from Europe and Asia, this research focuses in 43 airlines over the period 2007-2017 and finds that European carriers are less exposed to fuel price than Asian or North American airlines. We also test for types of carriers and find evidence that the average fuel exposure is higher on premium airlines, when comparing to low-cost carriers. To our knowledge, this is the first study to include three measures of operational hedging on a global sample of airlines, namely fleet diversity, fuel-efficiency and operating leased aircrafts. Treanor, Carter, Rogers, & Simkins (2013) studied these but only on a sample of North American airlines. Using fixed-effects’ models, our results suggest that financial hedging increases fuel risk exposure. Furthermore, our results lead to a rejection of the hypothesis that operational hedging decreases airlines’ exposure, on all three proxies we consider.