12,470 research outputs found
The impact of effective participation in stopping misinformation: an approach based on branching processes
The emergence of research focused to understand the spreading and impact of
disinformation is increasing year over year. Most times, the purpose of those
who start the spreading of information intentionally false and designed to
cause harm is in catalyzing its fast transformation into misinformation, which
is the false content shared by people who do not realize it is false or
misleading. Our interest is in discussing the role of people who decide to
adopt an active role in stopping the propagation of an information when they
realize that it is false. For this, we formulate two simple probabilistic
models to compare misinformation spreading in the possible scenarios for which
there is a passive or an active environment of aware individuals. With aware
individuals we mean those individuals who realize that a given information is
false or misleading. In the passive environment we assume that if one of an
aware individual is exposed to the misinformation then he/she will not spread
it. In the active environment we assume that if one of an aware individual is
exposed to the misinformation then he/she will not spread it but also he/she
will stop the propagation to other individuals from the individual who
contacted him/her. We appeal to the theory of branching processes to analyse
propagation in both scenarios and we discuss the role and the impact of
effective participation in stopping misinformation. We show that the
propagation reduces drastically provided we assume an active environment, and
we obtain theoretical and computational results to measure such a reduction,
which in turns depends on the proportion of aware individuals and the number of
potential contacts of each individual which is assumed to be random.Comment: 27 pages, 11 figures, revised version accepted for publication at
Journal of Statistical Mechanics: Theory and Experimen
Galactic Angular Momentum in the Illustris Simulation: Feedback and the Hubble Sequence
We study the stellar angular momentum of thousands of galaxies in the
Illustris cosmological simulation, which captures gravitational and gas
dynamics within galaxies, as well as feedback from stars and black holes. We
find that the angular momentum of the simulated galaxies matches observations
well, and in particular two distinct relations are found for late-type versus
early-type galaxies. The relation for late-type galaxies corresponds to the
value expected from full conservation of the specific angular momentum
generated by cosmological tidal torques. The relation for early-type galaxies
corresponds to retention of only ~30% of that, but we find that those
early-type galaxies with low angular momentum at z=0 nevertheless reside at
high redshift on the late-type relation. Some of them abruptly lose angular
momentum during major mergers. To gain further insight, we explore the scaling
relations in simulations where the galaxy formation physics is modified with
respect to the fiducial model. We find that galactic winds with high
mass-loading factors are essential for obtaining the high angular momentum
relation typical for late-type galaxies, while AGN feedback largely operates in
the opposite direction. Hence, feedback controls the stellar angular momentum
of galaxies, and appears to be instrumental for establishing the Hubble
sequence
The stellar halos of ETGs in the IllustrisTNG simulations: II. Accretion, merger history, and dark halo connection
Stellar halos in early-type galaxies (ETGs) are shaped by their accretion and
merger histories. We use a sample of 1114 ETGs in the TNG100 simulation with
stellar masses , selected at z=0
within the range of g-r colour and lambda-ellipticity diagram populated by
observed ETGs. We study how the rotational support and intrinsic shapes of the
stellar halos depend on the fraction of stars accreted, overall and separately
by major, minor, and mini mergers. Accretion histories in TNG100 ETGs as well
as the radial distributions of ex-situ stars strongly correlate
with stellar mass. Low-mass ETGs have characteristic peaked rotation profiles
and near-oblate shapes with rounder halos that are completely driven by the
in-situ stars. At high major mergers decrease the in-situ peak in
rotation velocity, flatten the profiles, and increase the
triaxiality of the stellar halos. Kinematic transition radii do not trace the
transition between in-situ and ex-situ dominated regions, but for systems with
the local rotational support and triaxiality of the
stellar halos is anti-correlated with the local ex-situ fraction at
fixed . These correlations are followed by fast and slow rotators alike
with a continuous and overlapping sequence of properties. Merger events
dynamically couple stars and dark matter: in high mass ETGs and at large radii
where , both components tend to have similar intrinsic shapes
and rotational support, and nearly aligned principal axes and spin directions.
Based on these results we suggest that extended photometry and kinematics of
massive ETGs () can be used to estimate the local
fraction of ex-situ stars and to approximate the intrinsic shapes and
rotational support of the co-spatial dark matter component. [abridged]Comment: 22 pages, 17 figures, submitted to A&
Modeling Galactic Conformity with the Color-Halo Age Relation in the Illustris Simulation
Comparisons between observational surveys and galaxy formation models find
that the mass of dark matter haloes can largely explain galaxies' stellar mass.
However, it remains uncertain whether additional environmental variables,
generally referred to as assembly bias, are necessary to explain other galaxy
properties. We use the Illustris Simulation to investigate the role of assembly
bias in producing galactic conformity by considering 18,000 galaxies with
> . We find a significant signal of
galactic conformity: out to distances of about 10 Mpc, the mean red fraction of
galaxies around redder galaxies is higher than around bluer galaxies at fixed
stellar mass. Dark matter haloes exhibit an analogous conformity signal, in
which the fraction of haloes formed at earlier times (old haloes) is higher
around old haloes than around younger ones at fixed halo mass. A plausible
interpretation of galactic conformity can be given as a combination of the halo
conformity signal with the galaxy color-halo age relation: at fixed stellar
mass, particularly toward the low-mass end, Illustris' galaxy colors correlate
with halo age, with the reddest galaxies (often satellites) being
preferentially found in the oldest haloes. In fact, we can explain the galactic
conformity effect with a simple semi-empirical model, by assigning stellar mass
based on halo mass (abundance matching) and by assigning galaxy color based on
halo age (age matching). We investigate other interpretations for the galactic
conformity, particularly its dependence on the isolation criterion and on the
central-satellite information. Regarding comparison to observations, we
conclude that the adopted selection/isolation criteria, projection effects, and
stacking techniques can have a significant impact on the measured amplitude of
the conformity signal.Comment: 15 pages, 8 figures; accepted for publication in MNRAS (minor
revisions to match accepted version
The progenitors of the intra-cluster light and intra-cluster globular clusters in galaxy groups and clusters
We use the IllustrisTNG50 cosmological hydrodynamical simulation,
complemented by a catalog of tagged globular clusters, to investigate the
properties and build up of two extended luminous components: the intra-cluster
light (ICL) and the intra-cluster globular clusters (ICGC). We select the 39
most massive groups and clusters in the box, spanning the range of virial
masses . We
find good agreement between predictions from the simulations and current
observational estimates of the fraction of mass in the ICL and its radial
extension. The stellar mass of the ICL is only of the stellar
mass in the central galaxy but encodes useful information on the assembly
history of the group or cluster. About half the ICL in all our systems is
brought in by galaxies in a narrow stellar mass range,
. However, the contribution of low-mass galaxies (
) to the build-up of the ICL varies broadly from system to
system, , a feature that might be recovered from the observable
properties of the ICL at . At fixed virial mass, systems where the
accretion of dwarf galaxies plays an important role have shallower metallicity
profiles, less metal content and a lower stellar mass in the ICL than systems
where the main contributors are more massive galaxies. We show that
intra-cluster GCs are also good tracers of this history, representing a
valuable alternative when diffuse light is not detectable
Cryptic genetic structure in an Argentinian population of Anastrepha fraterculus (Diptera: Tephritidae) evidenced by SSR markers and quantitative traits
In some regions of Argentina and Brazil, the South American fruit fly Anastrepha fraterculus (Wied.) (Diptera: Tephritidae) causes significant damage to crops. An efficient integrated management program requires knowledge of pest population dynamics, dispersion patterns, sexual and oviposition behaviour, and adaptive landscape. The present study combined simple sequence repeat (SSR) molecular markers and morphometric datasets in order to analyse the population structure and infer the oviposition resource use strategy of the females. Infested guava fruits were collected from nine wild trees in Tucumán, Argentina, and a total of 140 adult A. fraterculus were recovered. These were then measured for six morphometric traits and 89 of them were genotyped for eight SSR loci. Genetic variability estimates were high (expected heterozygosity = 0.71, allelic richness = 12.5), with 8 to 20 alleles per locus. According to Wright's F-statistics estimates, the highest proportion (83%) of genetic variation occurred within individuals while variance between and within fruits were similar (≈ 8.5%). Analysis of the cryptic genetic structure based on SSR using different approaches, namely discriminant analysis of principal components (DAPC) and sparse non-negative matrix factorization (SNMF), yielded results consistent with the occurrence of two clusters with virtually no admixture. Average kinship between individuals which had emerged from the same fruit (0.07) was lower than that expected for full-sib families. Univariate and multivariate analyses of phenotypic data showed 54-66% of variance among individuals within fruits and 34-46% among fruits. The comparison between phenotypic (PST) and molecular (FST) differentiation identified wing width and length as possible target of positive selection. The average kinship and high genetic variation within fruits, together with the highly significant genetic differentiation among fruits, supports the hypothesis that each fruit was colonised by about three ovipositing females. The results also indicate that females were able to disperse widely from the emergence site before mating and starting oviposition activity.Instituto de GenéticaFil: Rodriguez, Angeles I. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Ferreyra, Laura Ines. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Lanzavecchia, Silvia Beatriz. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética. Laboratorio de Genética de Insectos de Importancia Económica; ArgentinaFil: Gomez Cendra, Paula V. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vilardi, Juan Cesar. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Mental Health Patients' Expectations about the Non-Medical Care They Receive in Primary Care: A Cross-Sectional Descriptive Study
A health system's responsiveness is the result of patient expectations for the non-medical care they receive. The objective of this study was to assess mental patients' responsiveness to the health system in primary care, as related to the domains of dignity, autonomy, confidentiality, and communication. Data were collected from 215 people over the age of 18 with mental disorders, using the Multi-Country Survey Study (MCSS) developed by the World Health Organization. Of them, 95% reported a good experience regarding the dignity, confidentiality, communication, and autonomy domains. Regarding responsiveness, patients valued the dignity domain as the most important one (25.1%). Among the patients who experienced poor confidentiality, five out of seven earned less than 900 euros per month (X-2 = 10.8, p = 0.004). Among those who experienced good autonomy, 85 out of 156 belonged to the working social class (90.4%), and among those who valued it as poor (16.1%), the highest proportion was for middle class people (X-2 = 13.1, p = 0.028). The two students and 87.5% of retirees experienced this dimension as good, and most patients who valued it as poor were unemployed (43.5%) (X-2 = 13.0, p = 0.011). Patients with a household income higher than 900 euros more frequently valued responsiveness as good, regarding those domains related to communication, with OR = 3.84, 95% CI = 1.05-14.09, and confidentiality, with OR = 10.48, 95% CI = 1.94-56.59. To conclude, as regards responsiveness in primary care, the dignity domain always obtained the best scores by people with mental disorders. Low economic income is related to a poor assessment of confidentiality. Working class patients, students, and retirees value autonomy as good
Carbon assimilating fungi from surface ocean to subseafloor revealed by coupled phylogenetic and stable isotope analysis
Fungi are ubiquitous in the ocean and hypothesized to be important members of marine ecosystems, but their roles in the marine carbon cycle are poorly understood. Here, we use 13C DNA stable isotope probing coupled with phylogenetic analyses to investigate carbon assimilation within diverse communities of planktonic and benthic fungi in the Benguela Upwelling System (Namibia). Across the redox stratified water column and in the underlying sediments, assimilation of 13C-labeled carbon from diatom extracellular polymeric substances (13C-dEPS) by fungi correlated with the expression of fungal genes encoding carbohydrate-active enzymes. Phylogenetic analysis of genes from 13C-labeled metagenomes revealed saprotrophic lineages related to the facultative yeast Malassezia were the main fungal foragers of pelagic dEPS. In contrast, fungi living in the underlying sulfidic sediments assimilated more 13C-labeled carbon from chemosynthetic bacteria compared to dEPS. This coincided with a unique seafloor fungal community and dissolved organic matter composition compared to the water column, and a 100-fold increased fungal abundance within the subseafloor sulfide-nitrate transition zone. The subseafloor fungi feeding on 13C-labeled chemolithoautotrophs under anoxic conditions were affiliated with Chytridiomycota and Mucoromycota that encode cellulolytic and proteolytic enzymes, revealing polysaccharide and protein-degrading fungi that can anaerobically decompose chemosynthetic necromass. These subseafloor fungi, therefore, appear to be specialized in organic matter that is produced in the sediments. Our findings reveal that the phylogenetic diversity of fungi across redox stratified marine ecosystems translates into functionally relevant mechanisms helping to structure carbon flow from primary producers in marine microbiomes from the surface ocean to the subseafloor
A KK-monopole giant graviton in AdS_5 x Y_5
We construct a new giant graviton solution in AdS_5 x Y_5, with Y_5 a
quasi-regular Sasaki-Einstein manifold, consisting on a Kaluza-Klein monopole
wrapped around the Y_5 and with its Taub-NUT direction in AdS_5. We find that
this configuration has minimal energy when put in the centre of AdS_5, where it
behaves as a massless particle. When we take Y_5 to be S^5, we provide a
microscopical description in terms of multiple gravitational waves expanding
into the fuzzy S^5 defined as an S^1 bundle over the fuzzy CP^2. Finally we
provide a possible field theory dual interpretation of the construction.Comment: 11 pages, published versio
Dynamical Processing of Geophysical Signatures based on SPOT-5 Remote Sensing Imagery
An intelligent post-processing computational paradigm based on the use of dynamical filtering techniques modified to enhance the quality of reconstruction of geophysical signatures based on Spot-5 imagery is proposed. As a matter of particular study, a robust algorithm is reported for the analysis of the dynamic behavior of geophysical indexes extracted from the real-world remotely sensed scenes. The simulation results verify the efficiency of the approach as required for decision support in resources management
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