4,471 research outputs found
Parent population of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies
Flat-spectrum radio-loud Narrow-Line Seyfert 1 galaxies (NLS1s) are a
recently discovered class of -ray emitting Active Galactic Nuclei
(AGN), that exhibit some blazar-like properties which are explained with the
presence of a relativistic jet viewed at small angles. When blazars are
observed at larger angles they appear as radio-galaxies, and we expect to
observe an analogue parent population for beamed NLS1s. However, the number of
known NLS1s with the jet viewed at large angles is not enough. Therefore, we
tried to understand the origin of this deficit. Current hypotheses about the
nature of parent sources are steep-spectrum radio-loud NLS1s, radio-quiet NLS1s
and disk-hosted radio-galaxies. To test these hypotheses we built three samples
of candidate sources plus a control sample, and calculated their black hole
mass and Eddington ratio using their optical spectra. We then performed a
Kolmogorov-Smirnov statistical test to investigate the compatibility of our
different samples with a beamed population. Our results indicate that, when the
inclination angle increases, a beamed source appears as a steep-spectrum
radio-loud NLS1, or possibly even as a disk-hosted radio-galaxy with low black
hole mass and high Eddington ratio. Further investigations, involving larger
complete samples and observations at radio frequency, are needed to understand
the incidence of disk-hosted radio-galaxies in the parent population, and to
assess whether radio-quiet NLS1s can play a role, as well.Comment: 12 pages, 6 figures, accepted for publication by Astronomy and
Astrophysic
Balmer Emission Line Profiles and the Complex Properties of Broad Line Regions in Active Galactic Nuclei
In this work we analyze a sample of AGN spectra, selected from the 6th Data
Release of the Sloan Digital Sky Survey, exploiting a generalized technique of
line profile analysis, designed to take into account the whole profiles of
their broad emission lines. We find that the line profile broadening functions
result from a complex structure, but we may be able to infer some constraints
about the role of the geometrical factor, thus improving our ability to
estimate AGN properties and their relation with the host galaxy. Our results
suggest that flattening and inclination within the structure of the Broad Line
Region (BLR) must be taken into account. We detect low inclinations of the BLR
motion plane with respect to our line of sight, typically i < 20 degrees, with
a geometrical effect which generally decreases as the line profile becomes
broader.Comment: 13 pages, 11 figures, updated reference list. ApJ accepte
Structure, Atomistic Simulations, and Phase Transition of Stoichiometric Yeelimite
ABSTRACT: Yeelimite, Ca4[Al6O12]SO4, is outstanding as an aluminate
sodalite, being the framework of these type of materials flexible and dependent
on ion sizes and anion ordering/disordering. On the other hand, yeelimite is also
important from an applied perspective as it is the most important phase in
calcium sulfoaluminate cements. However, its crystal structure is not well
studied. Here, we characterize the room temperature crystal structure of
stoichiometric yeelimite through joint Rietveld refinement using neutron and Xray
powder diffraction data coupled with chemical soft-constraints. Our structural
study shows that yeelimite has a lower symmetry than that of the previously
reported tetragonal system, which we establish to likely be the acentric
orthorhombic space group Pcc2, with a √2a × √2a × a superstructure based on
the cubic sodalite structure. Final unit cell values were a = 13.0356(7) Å, b =
13.0350(7) Å, and c = 9.1677(2) Å. We determine several structures using
density functional theory calculations, with the lowest energy structure being Pcc2 in agreement with our experimental result.
Yeelimite undergoes a reversible phase transition to a higher-symmetry phase which has been characterized to occur at 470 °C by
thermodiffractometry. The higher-symmetry phase is likely cubic or pseudocubic possessing an incommensurate superstructure,
as suggested by our theoretical calculations which show a phase transition from an orthorhombic to a tetragonal structure. Our
theoretical study also predicts a pressure-induced phase transition to a cubic structure of space group I43m. Finally, we show that
our reported crystal structure of yeelimite enables better mineralogical phase analysis of commercial calcium sulfoaluminate
cements, as shown by RF values for this phase, 6.9% and 4.8% for the previously published orthorhombic structure and for the
one reported in this study, respectively.Universidad de Málaga. Campus de Excelencia Internacional. Andalucía Tech
Sympathy for the environment predicts green consumerism but not more important environmental behaviours related to domestic energy use
SUMMARY Household consumption is a major contributor to global greenhouse gas emissions. Some behaviours (for example energy use and vehicle use) may have far larger impacts than others (for example green consumerism of household products). Here, the driving forces of green consumerism and two domestic energy uses (electricity consumption and vehicle fuel use) are compared. This study found that environmental attitudes predicted green consumerism, but not electricity consumption or vehicle fuel use. Furthermore, green consumerism was correlated with income and individual level demographic factors, while energy consumption was primarily predicted by household size and structural constraints. Because household energy consumption has greater environmental impacts than green consumerism, policies that aim to improve pro-environmental attitudes may not be effective in mitigating greenhouse gas emissions. Policies should rather aim to change structural constraints influencing transportation and household energy decisions and improve the conspicuousness of household energy consumption
Elastic lever arm model for myosin V
We present a mechanochemical model for myosin V, a two-headed processive
motor protein. We derive the properties of a dimer from those of an individual
head, which we model both with a 4-state cycle (detached, attached with ADP.Pi,
attached with ADP and attached without nucleotide) and alternatively with a
5-state cycle (where the power stroke is not tightly coupled to the phosphate
release). In each state the lever arm leaves the head at a different, but
fixed, angle. The lever arm itself is described as an elastic rod. The chemical
cycles of both heads are coordinated exclusively by the mechanical connection
between the two lever arms. The model explains head coordination by showing
that the lead head only binds to actin after the power stroke in the trail head
and that it only undergoes its power stroke after the trail head unbinds from
actin. Both models (4- and 5-state) reproduce the observed hand-over-hand
motion and fit the measured force-velocity relations. The main difference
between the two models concerns the load dependence of the run length, which is
much weaker in the 5-state model. We show how systematic processivity
measurement under varying conditions could be used to distinguish between both
models and to determine the kinetic parameters.Comment: 15 pages, 15 figures, to appear in Biophys.
Exploring the parent population of beamed NLS1s: from the black hole to the jet
The aim of this work is to understand the nature of the parent population of
beamed narrow-line Seyfert 1 galaxies (NLS1s), by studying the physical
properties of three parent candidates samples: steep-spectrum radio-loud NLS1s,
radio-quiet NLS1s and disk-hosted radio-galaxies. In particular, we focused on
the black hole mass and Eddington ratio distribution and on the interactions
between the jet and the narrow-line region.Comment: 6 pages, 2 figures, to appear in Proceedings of High Energy Phenomena
in Relativistic Outflows (HEPRO) V, Workshop Series of the Argentinian
Astronomical Societ
Chemical Recycling of a Textile Blend from Polyester and Viscose, Part II: Mechanism and Reactivity during Alkaline Hydrolysis of Textile Polyester
Chemical recycling of textiles holds the potential to yield materials of equal quality and value as products from virgin feedstock. Selective depolymerization of textile polyester (PET) from regenerated cellulose/PET blends, by means of alkaline hydrolysis, renders the monomers of PET while cellulose remains in fiber form. Here, we present the mechanism and reactivity of textile PET during alkaline hydrolysis. Part I of this article series focuses on the cellulose part and a possible industrialization of such a process. The kinetics and reaction mechanism for alkaline hydrolysis of polyester packaging materials or virgin bulk polyester are well described in the scientific literature; however, information on depolymerization of PET from textiles is sparse. We find that the reaction rate of hydrolysis is not affected by disintegrating the fabric to increase its surface area. We ascribe this to the yarn structure, where texturing and a low density assures a high accessibility even without disintegration. The reaction, similar to bulk polyester, is shown to be surface specific and proceeds via endwise peeling. Finally, we show that the reaction product terephthalic acid is pure and obtained in high yields
How children talk about events:Implications for eliciting and analyzing eyewitness reports
Legal and social service professionals often question whether various features of young witnesses’ responses during interviews are characteristic of children’s event reports or whether these features are concerning findings that reflect degraded memory, outside influence, or other phenomena. To assist helping professionals and researchers who collect data through interviews, we aggregated findings from child eyewitness studies and revisited transcript sets to construct fifteen principles that capture how children talk about events. These principles address children’s earliest event narratives, how children report information as interviews unfold and typical features of their narratives, threats to the accuracy of answers, the influence of interviewers’ language on children’s styles of reporting, how testimonies compare across multiple interviews and multiple witnesses to the same event, and the structure of accurate and inaccurate reports. A summary table highlights the implications of these principles for interviewers and the decision-makers who analyze children’s reports
Spectral optical monitoring of 3C390.3 in 1995-2007: I. Light curves and flux variation of the continuum and broad lines
Here we present the results of the long-term (1995-2007) spectral monitoring
of the broad line radio galaxy \object{3C~390.3}, a well known AGN with the
double peaked broad emission lines, usually assumed to be emitted from an
accretion disk. To explore dimensions and structure of the BLR, we analyze the
light curves of the broad H and H line fluxes and the continuum
flux. In order to find changes in the BLR, we analyze the H and
H line profiles, as well as the change in the line profiles during the
monitoring period. First we try to find a periodicity in the continuum and
H light curves, finding that there is a good chance for quasi-periodical
oscillations. Using the line shapes and their characteristics (as e.g. peaks
separation and their intensity ratio, or FWHM) of broad H and H
lines, we discuss the structure of the BLR. Also, we cross-correlate the
continuum flux with H and H lines to find dimensions of the BLR.
We found that during the monitoring period the broad emission component of the
H and H lines, and the continuum flux varied by a factor of
4-5. Also, we detected different structure in the line profiles of
H and H. It seems that an additional central component is
present and superposed to the disk emission. In the period of high activity
(after 2002), H became broader than H and red wing of H
was higher than the one of H. We found time lags of 95 days
between the continuum and H flux, and about 120 days between the
continuum and H flux. Variation in the line profiles, as well as
correlation between the line and continuum flux during the monitoring period is
in the favor of the disk origin of the broad lines with the possible
contribution of some additional region and/or some kind of perturbation in the
disk.Comment: 32 pages, accepted to A&A, typos correcte
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