5,959 research outputs found

    Radio source evolution on galactic scales

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    There is mounting evidence that mechanical radio source feedback is important in galaxy evolution and in order to quantify this feedback, detailed models of radio source evolution are required. We present an extension to current analytic models that encompasses young radio sources with physical sizes on sub-kiloparsec scales. This work builds on an existing young source dynamical model to include radiative losses in a flat environment, and as such, is the best physically-motivated Compact Symmetric Object model to date. Results predict that young radio sources experience significant radiative loss on length scales and spectral scales consistent with observed Compact Steep-Spectrum sources. We include full expressions for the transition to self-similar expansion and present this complete model of radio source evolution from first cocoon formation to end of source lifetime around 108 years within the context of a simplified King profile external atmosphere.T.M. thanks the Marshall Aid Commemoration Commission and St John’s College, Cambridge for PhD research funding.This is the final version of the article. It first appeared from Oxford University Press via http://dx.doi.org/10.1093/mnras/stu111

    A dual null formalism for the collapse of fluids in a cosmological background

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    In this work we revisit the definition of Matter Trapping Surfaces (MTS) introduced in previous investigations and show how it can be expressed in the so-called dual null formalism developed for Trapping Horizons (TH). With the aim of unifying both approaches, we construct a 2+2 threading from the 1+3 flow, and thus isolate one prefered spatial direction, that allows straightforward translation into a dual nul subbasis, and to deduce the geometric apparatus that follows. We remain as general as possible, reverting to spherical symmetry only when needed, and express the MTS conditions in terms of 2-expansion of the flow, then in purely geometric form of the dual null expansions. The Raychadhuri equations that describe both MTS and TH are written and interpreted using the previously defined gTOV (generalized Tolman-Oppenheimer-Volkov) functional introduced in previous work. Further using the Misner-Sharp mass and its previous perfect fluid definition, we relate the spatial 2-expansion to the fluid pressure, density and acceleration. The Raychaudhuri equations also allows us to define the MTS dynamic condition with first order differentials so the MTS conditions are now shown to be all first order differentials. This unified formalism allows one to realise that the MTS can only exist in normal regions, and so it can exist only between black hole horizons and cosmological horizons. Finally we obtain a relation yielding the sign, on a TH, of the non-vanishing null expansion which determines the nature of the TH from fluid content, and flow characteristics. The 2+2 unified formalism here investigated thus proves a powerful tool to reveal, in the future extensions, more of the very rich and subtle relations between MTS and TH.Comment: 10pp 1 fig. corrected for equation labels, cross listing correcte

    Viable entanglement detection of unknown mixed states in low dimensions

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    We explore procedures to detect entanglement of unknown mixed states, which can be experimentally viable. The heart of the method is a hierarchy of simple feasibility problems, which provides sufficient conditions to entanglement. Our numerical investigations indicate that the entanglement is detected with a cost which is much lower than full state tomography. The procedure is applicable to both free and bound entanglement, and involves only single copy measurements.Comment: 8 pages, 9 figures, 4 table

    Modeling electrodialysis and a photochemical process for their integration in saline wastewater treatment.

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    Oxidation processes can be used to treat industrial wastewater containing non-biodegradable organic compounds. However, the presence of dissolved salts may inhibit or retard the treatment process. In this study, wastewater desalination by electrodialysis (ED) associated with an advanced oxidation process (photo-Fenton) was applied to an aqueous NaCl solution containing phenol. The influence of process variables on the demineralization factor was investigated for ED in pilot scale and a correlation was obtained between the phenol, salt and water fluxes with the driving force. The oxidation process was investigated in a laboratory batch reactor and a model based on artificial neural networks was developed by fitting the experimental data describing the reaction rate as a function of the input variables. With the experimental parameters of both processes, a dynamic model was developed for ED and a continuous model, using a plug flow reactor approach, for the oxidation process. Finally, the hybrid model simulation could validate different scenarios of the integrated system and can be used for process optimization

    Moyens du bord: espaces en suspension, temps interstitiels et activités socioculturelles en prison

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    A dinamização do sector sociocultural é atualmente uma parte integrante da gestão das prisões portuguesas. Neste contexto, reclusos são incentivados a participar ativamente, fazendo uso das suas competências sociais e artísticas, e beneficiando de alívios na pressão disciplinar da prisão. Frequentadores destes “espaços suspensos” onde se organizam atividades lúdicas e artísticas, alguns reclusos tornam-se “prata da casa”, simultaneamente imagem pública da prisão e beneficiários de uma relação próxima com os técnicos. Propomos aqui a análise desta posição ambígua e das formas como a “prata da casa” nos permitem pensar sobre esta modalidade penal em que os reclusos assumem uma parte da administração da sua própria pena.The sociocultural sector has been in recent times an integral part of Portuguese prison management. Inmates are encouraged to proactively engage in these activities, to put their social and artistic skills to use, and to find in them some relief in the prison’s disciplinary pressure. As they participate in these “suspended spaces” wherein ludic and artistic activities are organized, certain inmates become “prata da casa” (homegrown pride), acting as the prison’s public image and benefiting from a close relationship with the prison staff. Drawing from this ambiguous status, we propose an analysis of a penal modality whereby inmates partly take charge of managing their own sentence.Moyens du bord: Espaces en suspension, temps interstitiels et activités socioculturelles en prison La dynamisation du secteur socioculturel fait actuellement partie intégrante de la gestion des prisons portugaises. Dans ce contexte, les détenus sont encouragés à y participer activement, en employant leurs compétences sociales et artistiques et en bénéficiant de soulagements par rapport à la pression disciplinaire de la prison. Dans ces « espaces en suspension », où des activités ludiques et artistiques sont organisées, certains des détenus deviennent « prata da casa » (moyens du bord), en agissant, en même temps, comme l’image publique de la prison et en bénéficiant d’une relation plus étroite avec le personnel. Cet article vise à analyser cette ambiguïté et la manière dont les « moyens du bord » nous permettent de réfléchir sur cette modalité pénale où les détenus prennent à leur compte une partie de l’administration de leurs propres peines.info:eu-repo/semantics/publishedVersio

    The Search for Intergalactic Hydrogen Clouds in Voids

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    I present the results of a search for intergalactic hydrogen clouds in voids. Clouds are detected by their HI LyA absorption lines in the HST spectra of low-redshift AGN. The parameter with which the environments of clouds are characterized is the tidal field, which places a lower limit on the cloud mass-density which is dynamically stable against disruption. Galaxy redshift catalogs are used to sum the tidal fields along the lines of sight, sorting clouds according to tidal field upper, or lower limits. The analytical methodology employed is designed to detect gas clouds whose expansion following reionization is restrained by dark matter perturbations. End-products are the cloud equivalent width distribution functions (EWDF) of catalogs formed by sorting clouds according to various tidal field upper, or lower limits. Cumulative EWDFs are steep in voids (S ~ -1.5 \pm 0.2), but flatter in high tidal field zones (S ~ -0.5 \pm 0.1). Most probable cloud Doppler parameters are ~30 km/s in voids and ~60 km/s in proximity to galaxies. In voids, the cumulative line density at low EW (~ 15 mA) is ~ 500 per unit redshift. The void filling factor is found to be 0.87 <= f_v <= 0.94. The void EWDF is remarkably uniform over this volume, with a possible tendency for more massive clouds to be in void centers. The size and nature of the void cloud population suggested by this study is completely unanticipated by the results of published 3-D simulations, which predict that most clouds are in filamentary structures around galaxy concentrations, and that very few observable absorbers would lie in voids. Strategies for modeling this population are briefly discussed.Comment: 21 pages, 19 figures, apjemulate style, to appear in ApJ vol. 57

    Recurrent copy number variations as risk factors for neurodevelopmental disorders: critical overview and analysis of clinical implications

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    Neurodevelopmental disorders (NDs) encompass a spectrum of neuropsychiatric manifestations. Chromosomal regions 1q21.1, 3q29, 15q11.2, 15q13.3, 16p11.2, 16p13.1 and 22q11 harbour rare but recurrent CNVs that have been uncovered as being important risk factors for several of these disorders. These rearrangements may underlie a broad phenotypical spectrum, ranging from normal development, to learning problems, intellectual disability (ID), epilepsy and psychiatric diseases, such as autism spectrum disorders (ASDs) and schizophrenia (SZ). The highly increased risk of developing neurodevelopmental phenotypes associated with some of these CNVs makes them an unavoidable element in the clinical context in paediatrics, neurology and psychiatry. However, and although finding these risk loci has been the goal of neuropsychiatric genetics for many years, the translation of this recent knowledge into clinical practice has not been trivial. In this article, we will: (1) review the state of the art on recurrent CNVs associated with NDs, namely ASD, ID, epilepsy and SZ; (2) discuss the models used to dissect the underlying neurobiology of disease, (3) discuss how this knowledge can be used in clinical practice.FEDER through the Programa Operacional Factores de Competitividade — COMPETE and by Portuguese national funds through Fundação para a Ciência e Tecnologi
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