5,959 research outputs found
Radio source evolution on galactic scales
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
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
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.
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
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
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
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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