1,185 research outputs found
Tidal Interaction between the UX Tauri A/C Disk System Revealed by ALMA
We present sensitive and high angular-resolution (âŒ0.âł2-0.âł3) (sub)millimeter (230 and 345 GHz) continuum and CO(2-1)/CO(3-2) line archive observations of the disk star system in UX Tauri carried out with the Atacama Large Millimeter/Submillimeter Array. These observations reveal the gas and dusty disk surrounding the young star UX Tauri A with a large signal-to-noise ratio (>400 in the continuum and >50 in the line), and for the first time we detect the molecular gas emission associated with the disk of UX Tauri C (with a size for the disk of <56 au). No (sub)millimeter continuum emission is detected at the 5Ï level (0.2 mJy at 0.85 mm) associated with UX Tauri C. For the component UX Tauri C, we estimate a dust disk mass of â€0.05 M â. Additionally, we report a strong tidal disk interaction between both disks, UX Tauri A/C, separated 360 au in projected distance. The CO line observations reveal marked spiral arms in the disk of UX Tauri A and an extended redshifted stream of gas associated with the UX Tauri C disk. No spiral arms are observed in the dust continuum emission of UX Tauri A. Assuming a Keplerian rotation we estimate the enclosed masses (disk+star) from their radial velocities in 1.4 ± 0.6 M oË for UX Tauri A, and 70 ± 30/sin i Jupiter masses for UX Tauri C (the latter coincides with the mass upper limit value for a brown dwarf). The observational evidence presented here lead us to propose that UX Tauri C has a close approach of a possible wide, evolving, and eccentric orbit around the disk of UX Tauri A, causing the formation of spiral arms and a stream of molecular gas falling toward UX Tauri C.Fil: Zapata, Luis A.. Instituto de RadioastronomĂa y AstrofĂsica; MĂ©xicoFil: RodrĂguez, Luis F.. Instituto de RadioastronomĂa y AstrofĂsica; MĂ©xico. Universidad AutĂłnoma de Chiapas; MĂ©xicoFil: Fernandez Lopez, Manuel. Provincia de Buenos Aires. GobernaciĂłn. ComisiĂłn de Investigaciones CientĂficas. Instituto Argentino de RadioastronomĂa. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto Argentino de RadioastronomĂa; ArgentinaFil: Palau, Aina. Instituto de RadioastronomĂa y AstrofĂsica; MĂ©xicoFil: Estalella, Robert. Universidad de Barcelona; EspañaFil: Osorio, Mayra. Instituto de AstrofĂsica de AndalucĂa; EspañaFil: Anglada, Guillem. Instituto de AstrofĂsica de AndalucĂa; EspañaFil: Huelamo, Nuria. Centro de AstrobiologĂa (csic-inta); Españ
Recurring adaptive introgression of a supergene variant that determines social organization
Introgression has been proposed as an essential source of adaptive genetic variation. However, a key barrier to adaptive introgression is that recombination can break down combinations of alleles that underpin many traits. This barrier might be overcome in supergene regions, where suppressed recombination leads to joint inheritance across many loci. Here, we study the evolution of a large supergene region that determines a major social and ecological trait in Solenopsis fire ants: whether colonies have one queen or multiple queens. Using coalescent-based phylogenies built from the genomes of 365 haploid fire ant males, we show that the supergene variant responsible for multiple-queen colonies evolved in one species and repeatedly spread to other species through introgressive hybridization. This finding highlights how supergene architecture can enable a complex adaptive phenotype to recurrently permeate species boundaries
Influence Diffusion in Social Networks under Time Window Constraints
We study a combinatorial model of the spread of influence in networks that
generalizes existing schemata recently proposed in the literature. In our
model, agents change behaviors/opinions on the basis of information collected
from their neighbors in a time interval of bounded size whereas agents are
assumed to have unbounded memory in previously studied scenarios. In our
mathematical framework, one is given a network , an integer value
for each node , and a time window size . The goal is to
determine a small set of nodes (target set) that influences the whole graph.
The spread of influence proceeds in rounds as follows: initially all nodes in
the target set are influenced; subsequently, in each round, any uninfluenced
node becomes influenced if the number of its neighbors that have been
influenced in the previous rounds is greater than or equal to .
We prove that the problem of finding a minimum cardinality target set that
influences the whole network is hard to approximate within a
polylogarithmic factor. On the positive side, we design exact polynomial time
algorithms for paths, rings, trees, and complete graphs.Comment: An extended abstract of a preliminary version of this paper appeared
in: Proceedings of 20th International Colloquium on Structural Information
and Communication Complexity (Sirocco 2013), Lectures Notes in Computer
Science vol. 8179, T. Moscibroda and A.A. Rescigno (Eds.), pp. 141-152, 201
Unveiling a cluster of protostellar disks around the massive protostar GGD 27 MM1
Context. Most stars form in clusters and thus it is important to characterize the protostellar disk population in dense environments to assess whether the environment plays a role in the subsequent evolution. Specifically, it is critical to evaluate whether planet formation is altered with respect to more isolated stars formed in dark clouds. Aims. We seek to investigate the properties of the protostellar disks in the GGD 27 cluster and compare these with those obtained from disks formed in nearby regions. Methods. We used ALMA to observe the star-forming region GGD 27 at 1.14 mm with an unprecedented angular resolution, 40 mas (âŒ56 au), and sensitivity (âŒ0.002 M·). Results. We detected a cluster of 25 continuum sources, most of which likely trace disks around Class 0/I protostars. Excluding the two most massive objects, disks masses are in the range 0.003-0.05 M·. The analysis of the cluster properties indicates that GGD 27 displays moderate subclustering. This result, combined with the dynamical timescale of the radio jet (âŒ104 years), suggests the youthfulness of the cluster. The lack of disk mass segregation signatures may support this as well. We found a clear paucity of disks with Rdisk > 100 au. The median value of the radius is 34 au; this value is smaller than the median of 92 au for Taurus but comparable to the value found in Ophiuchus and in the Orion Nebula Cluster. In GGD 27 there is no evidence of a distance-dependent disk mass distribution (i.e., disk mass depletion due to external photoevaporation), most likely due to the cluster youth. There is a clear deficit of disks for distances 0.04 pc. This suggests that dynamical interactions far from the cluster center are weaker, although the small disks found could be the result of disk truncation. This work demonstrates the potential to characterize disks from low-mass young stellar objects in distant and massive (still deeply embedded) clustered environments.Fil: Busquet, G.. Instituto de Estudios Espaciales de Cataluña; España. Instituto de Ciencias del Espacio (ice); EspañaFil: Girart, J. M.. Instituto de Estudios Espaciales de Cataluña; España. Instituto de Ciencias del Espacio (ice); EspañaFil: Estalella, R.. Universidad de Barcelona; EspañaFil: Fernandez Lopez, Manuel. Provincia de Buenos Aires. GobernaciĂłn. ComisiĂłn de Investigaciones CientĂficas. Instituto Argentino de RadioastronomĂa. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto Argentino de RadioastronomĂa; ArgentinaFil: GalvĂĄn Madrid, R.. Universidad Nacional AutĂłnoma de MĂ©xico; MĂ©xicoFil: Anglada, G.. Instituto de AstrofĂsica de AndalucĂa; EspañaFil: Carrasco GonzĂĄlez, C.. Universidad Nacional AutĂłnoma de MĂ©xico; MĂ©xicoFil: Añez LĂłpez, N.. Instituto de Ciencias del Espacio (ice); EspañaFil: Curiel, S.. Universidad Nacional AutĂłnoma de MĂ©xico; MĂ©xicoFil: Osorio, M.. Instituto de AstrofĂsica de AndalucĂa; EspañaFil: RodrĂguez, L. F.. Universidad Nacional AutĂłnoma de MĂ©xico; MĂ©xicoFil: Torrelles, J. M.. Instituto de Estudios Espaciales de Cataluña; España. Instituto de Ciencias del Espacio (ice); Españ
Parental knowledge and adolescents' risk behaviors
In this paper we study whether parental knowledge of adolescentsâ activities varies according to socio-demographic variables, and we analyze the possible association between parental knowledge patterns and certain risk behaviors among adolescents. A cross-sectional study was performed with representative samples of high-school students in Peru and El Salvador. A questionnaire assessed risk behaviors, as well as possible determinants, including parental knowledge. The questionnaire was answered by 6,208 adolescents. We observed that the greater the degree of knowledge, the lower the frequency of risk behaviors among youth. The degree of knowledge was inversely associated with childrenâs age, and we observed that being female was associated with a greater degree of parental knowledge. The study shows that parentsâ supervision criteria might be influenced by gender stereotypes, which would have a harmful effect on young males, as the lower degree of knowledge puts them at higher odds of risk behaviors
Study of and decays and determination of the CKM angle
We report a study of the suppressed and favored
decays, where the neutral meson is detected
through its decays to the and CP-even and
final states. The measurement is carried out using a proton-proton
collision data sample collected by the LHCb experiment, corresponding to an
integrated luminosity of 3.0~fb. We observe the first significant
signals in the CP-even final states of the meson for both the suppressed
and favored modes, as well as
in the doubly Cabibbo-suppressed final state of the decay. Evidence for the ADS suppressed decay , with , is also presented. From the observed
yields in the , and their
charge conjugate decay modes, we measure the value of the weak phase to be
. This is one of the most precise
single-measurement determinations of to date.Comment: 22 pages, 9 figures; All figures and tables, along with any
supplementary material and additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-020.htm
Quantum numbers of the state and orbital angular momentum in its decay
Angular correlations in decays, with , and , are used to measure
orbital angular momentum contributions and to determine the value of
the meson. The data correspond to an integrated luminosity of 3.0
fb of proton-proton collisions collected with the LHCb detector. This
determination, for the first time performed without assuming a value for the
orbital angular momentum, confirms the quantum numbers to be .
The is found to decay predominantly through S wave and an upper limit
of at C.L. is set on the fraction of D wave.Comment: 16 pages, 4 figure
Differential branching fraction and angular analysis of decays
The differential branching fraction of the rare decay is measured as a function of , the
square of the dimuon invariant mass. The analysis is performed using
proton-proton collision data, corresponding to an integrated luminosity of 3.0
\mbox{ fb}^{-1}, collected by the LHCb experiment. Evidence of signal is
observed in the region below the square of the mass. Integrating
over 15 < q^{2} < 20 \mbox{ GeV}^2/c^4 the branching fraction is measured as
d\mathcal{B}(\Lambda^{0}_{b} \rightarrow \Lambda \mu^+\mu^-)/dq^2 = (1.18 ^{+
0.09} _{-0.08} \pm 0.03 \pm 0.27) \times 10^{-7} ( \mbox{GeV}^{2}/c^{4})^{-1},
where the uncertainties are statistical, systematic and due to the
normalisation mode, , respectively.
In the intervals where the signal is observed, angular distributions are
studied and the forward-backward asymmetries in the dimuon ()
and hadron () systems are measured for the first time. In the
range 15 < q^2 < 20 \mbox{ GeV}^2/c^4 they are found to be A^{l}_{\rm FB} =
-0.05 \pm 0.09 \mbox{ (stat)} \pm 0.03 \mbox{ (syst)} and A^{h}_{\rm FB} =
-0.29 \pm 0.07 \mbox{ (stat)} \pm 0.03 \mbox{ (syst)}.Comment: 27 pages, 10 figures, Erratum adde
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