2,081 research outputs found
Global Patterns of Synchronization in Human Communications
Social media are transforming global communication and coordination. The data
derived from social media can reveal patterns of human behavior at all levels
and scales of society. Using geolocated Twitter data, we have quantified
collective behaviors across multiple scales, ranging from the commutes of
individuals, to the daily pulse of 50 major urban areas and global patterns of
human coordination. Human activity and mobility patterns manifest the synchrony
required for contingency of actions between individuals. Urban areas show
regular cycles of contraction and expansion that resembles heartbeats linked
primarily to social rather than natural cycles. Business hours and circadian
rhythms influence daily cycles of work, recreation, and sleep. Different urban
areas have characteristic signatures of daily collective activities. The
differences are consistent with a new emergent global synchrony that couples
behavior in distant regions across the world. A globally synchronized peak that
includes exchange of ideas and information across Europe, Africa, Asia and
Australasia. We propose a dynamical model to explain the emergence of global
synchrony in the context of increasing global communication and reproduce the
observed behavior. The collective patterns we observe show how social
interactions lead to interdependence of behavior manifest in the
synchronization of communication. The creation and maintenance of temporally
sensitive social relationships results in the emergence of complexity of the
larger scale behavior of the social system.Comment: 20 pages, 12 figures. arXiv admin note: substantial text overlap with
arXiv:1602.0621
Propiedades mecánicas de aerogeles híbridos de sílice
Se han obtenido aerogeles híbridos de sílice orgánico-inorgánico por aplicación de ultrasonidos de alta potencia en los precursores líquidos y posterior secado del gel húmedo en condiciones supercríticas en etanol. Las cadenas orgánicas no se degradan térmicamente y aceleran el proceso de contracción de la red por activación térmica. Los ultrasonidos inducen un entrecruzamiento de cadenas orgánicas que unen los cúmulos de sílice porosa y evitan su ciclidación. Los ensayos de ruptura en compresión uniaxial indicaron un aumento del módulo de ruptura, pasando de 8 MPa para el aerogel de sílice pura hasta 24 MPa para un aerogel de 50% en peso de contenido de polímero. Se observa asimismo una disminución continua en el módulo de Young con el contenido de polímero (de 100 a 56 MPa). Estos aerogeles híbridos se comportan como elastómeros con deformaciones de hasta el 50%, mostrando una disminución del módulo de relajación viscoelástica.Hybrids silica aerogels have been obtained by means the high power ultrasounds application in the precursor liquid and the drying of the wet gel under the supercritical condition of ethanol. The organic chains don't degrade thermally and accelerate the network shrinkage process by thermal activation. The ultrasounds induce an organic Chain crosslinking bonding to the porous silica clusters and avoid its cyclidation. The failure tests by uniaxial compression show an increase of the rupture modulus, passing from 8 MPa for a pure silica aerogel to 24 MPa for an aerogel with a 50 weight % of polymer content. It is also noted a continuous decrease of the Young's modulus with the polymer content (from 100 to 56 MPa). These hybrid aerogels behave as elastomers with up to a 50% strain, showing a decrease in the relaxation viscoelastic modulus.Ministerio de Ciencia y Tecnología MAT2002- 08
SN 2013df, a double-peaked IIb supernova from a compact progenitor and an extended H envelope
Optical observations of the type IIb SN 2013df from a few days to about 250
days after explosion are presented. These observations are complemented with UV
photometry taken by \textit{SWIFT} up to 60 days post-explosion. The
double-peak optical light curve is similar to those of SNe 1993J and 2011fu
although with different decline and rise rates. From the modelling of the
bolometric light curve, we have estimated that the total mass of synthesised
Ni in the explosion is M, while the ejecta mass is
M and the explosion energy erg. In
addition, we have estimated a lower limit to the progenitor radius ranging from
. The spectral evolution indicates that SN 2013df had a
hydrogen envelope similar to SN 1993J ( M). The line
profiles in nebular spectra suggest that the explosion was asymmetric with the
presence of clumps in the ejecta, while the [O\,{\sc i}]
, luminosities, may indicate that the progenitor
of SN 2013df was a relatively low mass star ( M).Comment: 18 pages, 11 figures, 9 tables, accepted for publication in MNRA
Enzymatic hydrolysis of hidrothermally pretreated agave bagasse
info:eu-repo/semantics/publishedVersio
The supernova impostor PSN J09132750+7627410 and its progenitor
We report the results of our follow-up campaign of the supernova impostor PSN
J09132750+7627410, based on optical data covering . From the
beginning, the transient shows prominent narrow Balmer lines with P-Cygni
profiles, with a blue-shifted absorption component becoming more prominent with
time. Along the of the spectroscopic monitoring, broad
components are never detected in the hydrogen lines, suggesting that these
features are produced in slowly expanding material. The transient reaches an
absolute magnitude at maximum, a typical
luminosity for supernova impostors. Amateur astronomers provided
of archival observations of the host galaxy, NGC 2748. The
detection of the quiescent progenitor star in archival images obtained with the
Hubble Space Telescope suggests it to be an \msun white-yellow
supergiant.Comment: 7 pages, 4 figures, supplemental material available in the source
file. Accepted for publication on Astrophysical Journal Letter
Depresión en adultos mayores y su relación con la actividad física y sedentarismo en Talca, Chile
The population is aging rapidly and Talca is not immune to this demographic phenomenon. Aging leads to a progressive deterioration of all systems such as cardiovascular, osteo-articular, muscular and nervous. The objective of this work is to relate depression with physical activity and other sociodemographic variables. This study is correlational and cross-sectional. Self-employed adults aged 65 years and over were recruited from the urban sector of the city of Talca. Face-to-face interviews were conducted to obtain sociodemographic data and apply the GDS questionnaires for depression and the IPAQ for physical activity. The statistical package SPSS version 25.0 was used. The sample is made up of 100 AM (N = 100), with a mean age of 73.2 years. A depression prevalence of 21% (N = 21) was found, in both men and women, which is related to physical activity (r = -0.229 and p = 0.004), and educational level (p = 0.035). Our results are consistent with previous studies. It is concluded that vigorous physical activity is related to low levels of depression and vice versa, as well, older adults with a low educational level tend to present more depression than those with a higher educational level.La población envejece rápidamente y Talca no escapa a este fenómeno demográfico. El envejecimiento conlleva un deterioro progresivo de todos los sistemas como cardiovascular, osteo-articular, muscular y nervioso. El objetivo de este trabajo es relacionar la depresión con la actividad física y otras variables sociodemográficas. Este estudio es de tipo correlacional y de corte transversal. Se reclutaron adultos mayores de 65 años y más, autovalentes del sector urbano de la ciudad de Talca. Se realizaron entrevistas cara a cara para obetner datos sociodemográficos y aplicar los cuestionarios GDS para depresión y el IPAQ para actividad física. Se utilizó el paquete estadístico SPSS versión 25.0. La muestra la conforman 100 AM (N=100), con una media de edad de 73,2 años. Se encontró una prevalencia de depresión de 21% (N=21), tanto en hombres como en mujeres, que se relaciona con la actividad física (r=-0,229 y p=0,004), y el nivel educacional (p=0,035). Nuestros resultados son coincidentes con estudios previos. Se concluye que una actividad física vigorosa se relaciona con bajos niveles de depresión y viceversa, así también, adultos mayores con bajo nivel educacional tienden a presentar más depresión que aquellos con nivel educacional más alto
Massive stars exploding in a He-rich circumstellar medium - VIII. PSN J07285387+3349106, a highly reddened supernova Ibn
We present spectroscopic and photometric observations for the Type Ibn
supernova (SN) dubbed PSN J07285387+3349106. Using data provided by amateur
astronomers, we monitored the photometric rise of the SN to maximum light,
occurred on 2015 February 18.8 UT (JD(max,V) = 2457072.0 +- 0.8). PSN
J07285387+3349106 exploded in the inner region of an infrared luminous galaxy,
and is the most reddened SN Ibn discovered so far. We apply multiple methods to
derive the total reddening to the SN, and determine a total colour excess
E(B-V)(tot) = 0.99 +- 0.48 mag. Accounting for the reddening correction, which
is affected by a large uncertainty, we estimate a peak absolute magnitude of
M(V) = -20.30 +- 1.50. The spectra are dominated by continuum emission at early
phases, and He I lines with narrow P-Cygni profiles are detected. We also
identify weak Fe III and N II features. All these lines show an absorption
component which is blue-shifted by about 900-1000 km/s. The spectra also show
relatively broad He I line wings with low contrast, which extend to above 3000
km/s. From about 2 weeks past maximum, broad lines of O I, Mg II and the Ca II
near-infrared triplet are identified. The composition and the expansion
velocity of the circumstellar material, and the presence of He I and
alpha-elements in the SN ejecta indicate that PSN J07285387+3349106 was
produced by the core-collapse of a stripped-envelope star. We suggest that the
precursor was WNE-type Wolf-Rayet star in its dense, He-rich circumstellar
cocoon.Comment: 12 pages, 7 figures, 2 tables. Accepted for publication in MNRA
Alpha-catenin-Dependent Recruitment of the Centrosomal Protein CAP350 to Adherens Junctions Allows Epithelial Cells to Acquire a Columnar Shape
Epithelial morphogenesis involves a dramatic reorganisation of the microtubule cytoskeleton. How this complex process is controlled at the molecular level is still largely unknown. Here, we report that the centrosomal microtubule (MT)-binding protein CAP350 localises at adherens junctions in epithelial cells. By two-hybrid screening, we identified a direct interaction of CAP350 with the adhesion protein α-catenin that was further confirmed by co-immunoprecipitation experiments. Block of epithelial cadherin (E-cadherin)-mediated cell-cell adhesion or α-catenin depletion prevented CAP350 localisation at cell-cell junctions. Knocking down junction-located CAP350 inhibited the establishment of an apico-basal array of microtubules and impaired the acquisition of columnar shape in Madin-Darby canine kidney II (MDCKII) cells grown as polarised epithelia. Furthermore, MDCKII cystogenesis was also defective in junctional CAP350-depleted cells. CAP350-depleted MDCKII cysts were smaller and contained either multiple lumens or no lumen. Membrane polarity was not affected, but cortical microtubule bundles did not properly form. Our results indicate that CAP350 may act as an adaptor between adherens junctions and microtubules, thus regulating epithelial differentiation and contributing to the definition of cell architecture. We also uncover a central role of α-catenin in global cytoskeleton remodelling, in which it acts not only on actin but also on MT reorganisation during epithelial morphogenesis.This work was supported by Ministerio de Economia y Competitividad, Spain (BFU2012-36717
and CSD2009-00016 to RMR and BFU2011-22916 to
JRM) and by Junta de Andalucia (CVI-7256 and
CTS-2071), and by a funding GenHomme Network
02490-6088 to Hybrigenics and the Institut Curie. MA
and AZ were supported by MEC–FPI Grants.Peer Reviewe
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