547 research outputs found
Matchings on infinite graphs
Elek and Lippner (2010) showed that the convergence of a sequence of
bounded-degree graphs implies the existence of a limit for the proportion of
vertices covered by a maximum matching. We provide a characterization of the
limiting parameter via a local recursion defined directly on the limit of the
graph sequence. Interestingly, the recursion may admit multiple solutions,
implying non-trivial long-range dependencies between the covered vertices. We
overcome this lack of correlation decay by introducing a perturbative parameter
(temperature), which we let progressively go to zero. This allows us to
uniquely identify the correct solution. In the important case where the graph
limit is a unimodular Galton-Watson tree, the recursion simplifies into a
distributional equation that can be solved explicitly, leading to a new
asymptotic formula that considerably extends the well-known one by Karp and
Sipser for Erd\"os-R\'enyi random graphs.Comment: 23 page
Expansive actions on uniform spaces and surjunctive maps
We present a uniform version of a result of M. Gromov on the surjunctivity of
maps commuting with expansive group actions and discuss several applications.
We prove in particular that for any group and any field \K, the
space of -marked groups such that the group algebra \K[G] is
stably finite is compact.Comment: 21 page
A Theory-Grounded Measure of Adolescents\u27 Response to Media Literacy Interventions
Media literacy interventions offer relatively new and promising avenues for the prevention of risky health behaviors among children and adolescents, but current literature remains largely equivocal about their efficacy. We propose that (a) much of this ambiguity stems from the lack of conceptual clarity in the literature regarding the cognitive process through which media literacy interventions influence their target audience, and (b) that the ability to track this cognitive process by means of valid and reliable measures is necessary to evaluating the effects of media literacy programs on their audience. Accordingly, the primary objective of this study was to develop and test theoretically-grounded measures of audiencesâ degree of engagement with the content of media literacy programs based on the recognition that engagement (and not participation per se) can better explain and predict individual variations in the effects of these programs. We tested the validity and reliability of this measure with two different samples of 10th grade high school students (Study I N = 294; Study II N = 171) who participated in a pilot and actual test of a brief media literacy curriculum. Responses to an inventory of items measuring evaluation of the media literacy program underwent an exploratory factor analysis for Study I. Four message evaluation factors (involvement, perceived novelty, critical thinking, personal reflection) emerged and were confirmed through CFA (Study II), demonstrating acceptable reliability as scales as well as item-level convergent validity and convergent and discriminant validity with other measures. We discuss the implications of including process of effect measures in the design and evaluation of media literacy interventions
Malignant Chondroblastoma of the Os Calcis
Patient. We describe a case of chondroblastoma of the os calcis which metastasized to the tibia, soft tissues and lung. A complete response of the lung lesions was noted with chemotherapy
How Cosmic Web Environment Affects Galaxy Quenching Across Cosmic Time
We investigate how cosmic web structures affect galaxy quenching in the
IllustrisTNG (TNG-100) cosmological simulations by reconstructing the cosmic
web in each snapshot using the DisPerSE framework. We measure the distance from
each galaxy with stellar mass log(M*/Msun)>=8 to the nearest node (dnode) and
the nearest filament spine (dfil) and study the dependence of both median
specific star formation rate () and median gas fraction () on these
distances. We find that of galaxies is only dependent on cosmic web
environment at z<2, with the dependence increasing with time. At z<=0.5,
8<=log(M*/Msun)<9 galaxies are quenched at dnode<1 Mpc, and significantly star
formation-suppressed at dfil<1 Mpc, trends which are driven mostly by satellite
galaxies. At z of
log(M*/Msun)=10 galaxies
actually experience an upturn in at dnode<0.2 Mpc (this is caused by
both satellites and centrals). Much of this cosmic web-dependence of star
formation activity can be explained by the evolution in . Our results
suggest that in the past ~10 Gyr, low-mass satellites are quenched by rapid gas
stripping in dense environments near nodes and gradual gas starvation in
intermediate-density environments near filaments, while at earlier times cosmic
web structures efficiently channeled cold gas into most galaxies.
State-of-the-art ongoing spectroscopic surveys such as SDSS and DESI, as well
as those planned with JWST and Roman are required to test our predictions
against observations.Comment: 5 Figures, 15 pages, submitted to ApJ Letter
Recording fineâscale movement of ground beetles by two methods: Potentials and methodological pitfalls
Movement trajectories are usually recorded as a sequence of discrete movement events described by two parameters: step length (distance) and turning angle (bearing). One of the most widespread methods to record the geocoordinates of each step is by a GPS device. Such devices have limited suitability for recording fine movements of species with low dispersal ability including flightless carabid beetles at small spatioâtemporal scales. As an alternative, the distanceâbearing approach can avoid the measurement error of GPS units since it uses directly measured distances and compass azimuths. As no quantification of measurement error between distanceâbearing and GPS approaches exists so far, we generated artificial fineâscale trajectories and in addition radioâtracked living carabids in a temperate forest and recorded each movement step by both methods. Trajectories obtained from distanceâbearing were compared to those obtained by a GPS device in terms of movement parameters. Consequently, both types of trajectories were segmented by stateâswitching modeling into two distinct movement stages typical for carabids: random walk and directed movement. We found that the measurement error of GPS compared to distanceâbearing was 1.878 m (SEM = 0.181 m) for distances and 31.330° (SEM = 2.066°) for bearings. Moreover, these errors increased under dense forest canopy and rainy weather. Distance error did not change with increasing distance recorded by distanceâbearing but bearings were significantly more sensitive to error at short distances. Stateâswitching models showed only slight, not significant, differences in movement states between the two methods in favor of the random walk in the distanceâbearing approach. However, the shape of the GPSâmeasured trajectories considerably differed from those recorded by distanceâbearing caused especially by bearing error at short distances. Our study showed that distanceâbearing could be more appropriate for recording movement steps not only of groundâdwelling beetles but also other small animals at fine spatioâtemporal scales
Filaments of The Slime Mold Cosmic Web And How They Affect Galaxy Evolution
We present a novel method for identifying cosmic web filaments using the
IllustrisTNG (TNG100) cosmological simulations and investigate the impact of
filaments on galaxies. We compare the use of cosmic density field estimates
from the Delaunay Tessellation Field Estimator (DTFE) and the Monte Carlo
Physarum Machine (MCPM), which is inspired by the slime mold organism, in the
DisPerSE structure identification framework. The MCPM-based reconstruction
identifies filaments with higher fidelity, finding more low-prominence/diffuse
filaments and better tracing the true underlying matter distribution than the
DTFE-based reconstruction. Using our new filament catalogs, we find that most
galaxies are located within 1.5-2.5 Mpc of a filamentary spine, with little
change in the median specific star formation rate and the median galactic gas
fraction with distance to the nearest filament. Instead, we introduce the
filament line density, {\Sigma}fil(MCPM), as the total MCPM overdensity per
unit length of a local filament segment, and find that this parameter is a
superior predictor of galactic gas supply and quenching. Our results indicate
that most galaxies are quenched and gas-poor near high-line density filaments
at z10.5 galaxies is mainly driven by
mass, while lower-mass galaxies are significantly affected by the filament line
density. In high-line density filaments, satellites are strongly quenched,
whereas centrals have reduced star formation, but not gas fraction, at z<=0.5.
We discuss the prospect of applying our new filament identification method to
galaxy surveys with SDSS, DESI, Subaru PFS, etc. to elucidate the effect of
large-scale structure on galaxy formation.Comment: Submitted to ApJ, comments welcome. Data available at
https://github.com/farhantasy/CosmicWeb-Galaxies
Extensive Spectroscopy and Photometry of the Type IIP Supernova 2013ej
We present extensive optical (, , and open CCD) and
near-infrared () photometry for the very nearby Type IIP SN ~2013ej
extending from +1 to +461 days after shock breakout, estimated to be MJD
. Substantial time series ultraviolet and optical spectroscopy
obtained from +8 to +135 days are also presented. Considering well-observed SNe
IIP from the literature, we derive bolometric calibrations from
and unfiltered measurements that potentially reach 2\% precision with a
color-dependent correction. We observe moderately strong Si II
as early as +8 days. The photospheric velocity () is
determined by modeling the spectra in the vicinity of Fe II
whenever observed, and interpolating at photometric epochs based on a
semianalytic method. This gives km s at +50
days. We also observe spectral homogeneity of ultraviolet spectra at +10--12
days for SNe IIP, while variations are evident a week after explosion. Using
the expanding photosphere method, from combined analysis of SN 2013ej and SN
2002ap, we estimate the distance to the host galaxy to be
Mpc, consistent with distance estimates from other methods. Photometric and
spectroscopic analysis during the plateau phase, which we estimated to be
days long, yields an explosion energy of
ergs, a final pre-explosion progenitor mass of ~M and a
radius of ~R. We observe a broken exponential profile beyond
+120 days, with a break point at + days. Measurements beyond this
break time yield a Ni mass of ~M.Comment: 29 pages, 23 figures, 15 tables, Published in The Astrophisical
Journa
Testing SNe Ia distance measurement methods with SN 2011fe
The nearby, bright, almost completely unreddened Type Ia supernova 2011fe in
M101 provides a unique opportunity to test both the precision and the accuracy
of the extragalactic distances derived from SNe Ia light curve fitters. We
apply the current, public versions of the independent light curve fitting codes
MLCS2k2 and SALT2 to compute the distance modulus of SN 2011fe from
high-precision, multi-color (BVRI) light curves. The results from the two
fitting codes confirm that 2011fe is a "normal" (not peculiar) and only
slightly reddened SN Ia. New unreddened distance moduli are derived as 29.21
+/- 0.07 mag (D ~ 6.95 +/- 0.23$ Mpc, MLCS2k2), and 29.05 +/- 0.07 mag (6.46
+/- 0.21 Mpc, SALT2). Despite the very good fitting quality achieved with both
light curve fitters, the resulting distance moduli are inconsistent by 2 sigma.
Both are marginally consistent (at ~1 sigma) with the HST Key Project distance
modulus for M101. The SALT2 distance is in good agreement with the recently
revised Cepheid- and TRGB-distance to M101. Averaging all SN- and Cepheid-based
estimates, the absolute distance to M101 is ~6.6 +/- 0.5 Mpc.Comment: 8 pages, 7 figures, accepted for publication in A&
DIMBOA levels in hexaploid Brazilian wheat are not associated with antibiosis against the cereal aphids Rhopalosiphum padi and Sitobion avenae.
The objective of this study was to evaluate the natural levels of the plant defence compound DIMBOA in young leaves of eight hexaploid Brazilian wheat genotypes and the impact of the genotypes upon development of cereal aphids, Rhopalosiphum padi and Sitobion avenae. HPLC Analysis revealed that the DIMBOA levels varied from 5.376 (in BRS Guabiju) to 30.651 mmol/kgFW (in BRS TimbaĂșva) with two genotypes outperforming Solstice, a UK variety used as reference. Bioassays were conducted to evaluate the development and fecundity of both aphids when grown on the wheat genotypes. Although BRS Guabiju and BRS TimbaĂșva were among the genotypes showing the highest and lowest susceptibility respectively, against both aphids, no correlation could be found between DIMBOA levels and antibiosis effects. The cultivar BRS 327 that was among the genotypes showing lower intrinsic rate of population increase for the two aphid species. Elucidating the role of secondary metabolites in plant resistance to aphids and the characterisation of the genotypes that allowed reduced aphid development are important steps to achieve a better natural resistance in hexaploid Brazilian wheat
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