10,254 research outputs found
Evolution of cooperation in multilevel public goods games with community structures
In a community-structured population, public goods games (PGG) occur both
within and between communities. Such type of PGG is referred as multilevel
public goods games (MPGG). We propose a minimalist evolutionary model of the
MPGG and analytically study the evolution of cooperation. We demonstrate that
in the case of sufficiently large community size and community number, if the
imitation strength within community is weak, i.e., an individual imitates
another one in the same community almost randomly, cooperation as well as
punishment are more abundant than defection in the long run; if the imitation
strength between communities is strong, i.e., the more successful strategy in
two individuals from distinct communities is always imitated, cooperation and
punishment are also more abundant. However, when both of the two imitation
intensities are strong, defection becomes the most abundant strategy in the
population. Our model provides insight into the investigation of the
large-scale cooperation in public social dilemma among contemporary
communities.Comment: 6 pages, 4 figures, Accepted by EP
Comparison of Millimeter-wave and X-Ray Emission in Seyfert Galaxies
We compare the emission at multiple wavelengths of an extended Seyfert galaxy
sample, including both types of Seyfert nuclei. We use the Caltech
Submillimeter Observatory to observe the CO J = 2-1 transition line in a sample
of 45 Seyfert galaxies and detect 35 of them. The galaxies are selected by
their joint soft X-ray (0.1-2.4 keV) and far-infrared ({\lambda} = 60-100
{\mu}m) emission from the ROSAT/IRAS sample. Since the CO line widths (W CO)
reflect the orbital motion in the gravitational potential of the host galaxy,
we study how the kinematics are affected by the central massive black hole
(BH), using the X-ray luminosity. A significant correlation is found between
the CO line width and hard (0.3-8 keV from Chandra and XMM-Newton) X-ray
luminosity for both types of Seyfert nuclei. Assuming an Eddington accretion to
estimate the BH mass (M BH) from the X-ray luminosity, the W CO-L X relation
establishes a direct connection between the kinematics of the molecular gas of
the host galaxy and the nuclear activity, and corroborates the previous studies
that show that the CO is a good surrogate for the bulge mass. We also find a
tight correlation between the (soft and hard) X-ray and the CO luminosities for
both Seyfert types. These results indicate a direct relation between the
molecular gas (i.e., star formation activity) of the host galaxy and the
nuclear activity. To establish a clear causal connection between molecular gas
and the fueling of nuclear activity, high-resolution maps (<100 pc) of the CO
emission of our sample will be required and provided in a forthcoming Atacama
Large Millimeter Array observation
Adaptive Genetic Algorithm for Crystal Structure Prediction
We present a genetic algorithm (GA) for structural search that combines the
speed of structure exploration by classical potentials with the accuracy of
density functional theory (DFT) calculations in an adaptive and iterative way.
This strategy increases the efficiency of the DFT-based GA by several orders of
magnitude. This gain allows considerable increase in size and complexity of
systems that can be studied by first principles. The method's performance is
illustrated by successful structure identifications of complex binary and
ternary inter-metallic compounds with 36 and 54 atoms per cell, respectively.
The discovery of a multi-TPa Mg-silicate phase with unit cell containing up to
56 atoms is also reported. Such phase is likely to be an essential component of
terrestrial exoplanetary mantles.Comment: 14 pages, 4 figure
The braking indices in pulsar emission models
Using the method proposed in a previous paper, we calculate pulsar braking
indices in the models with torque contributions from both inner and outer
accelerating regions, assuming that the interaction between them is negligible.
We suggest that it is likely that the inverse Compton scattering induced polar
vacuum gap and the outer gap coexist in the pulsar magnetosphere. We include
the new near threshold vacuum gap models with curvature-radiation and inverse
Compton scattering induced cascades, respectively; and find that these models
can well reproduce the measured values of the braking indices.Comment: A&Ap accepted, or at
http://vega.bac.pku.edu.cn/~rxxu/publications/index_P.ht
Specialization and selective social attention establishes the balance between individual and social learning (Version posted online May 11, 2021)
Highly ionized Fe K emission lines from the LINER galaxy M 81
We present spectral and timing results from a long (130 ks) XMM-NEWTON EPIC
observation of the nucleus of the Seyfert/LINER galaxy M 81. During the
observation the X-ray flux varied by 20%, but there was no significant change
in spectral shape. The 2-10 keV spectrum is well described by a power law
continuum and three narrow Fe K emission lines at 6.4, 6.7 and 6.96 keV. The
three emission lines have equivalent widths of 39, 47, and 37 eV respectively.
The ratios of the three lines are thus more similar to those observed from the
Galactic Centre region than to those typically observed from Seyfert galaxies.
The high ionization lines most likely originate either from photoionized gas
within 0.1 pc of the nucleus of M 81, or from a non-thermal distribution of
cosmic-ray electrons interacting with the 0.2-0.6 keV thermal plasma which is
found in the bulge of M 81.Comment: Accepted for publication in A&
Interventions for post-stroke fatigue
BACKGROUND: Post-stroke fatigue (PSF) is a common and distressing problem after stroke. The best ways to prevent or treat PSF are uncertain. Several different interventions can be argued to have a rational basis.
OBJECTIVES: To determine whether, among people with stroke, any intervention reduces the proportion of people with fatigue, fatigue severity, or both; and to determine the effect of intervention on health-related quality of life, disability, dependency and death, and whether such intervention is cost effective.
SEARCH METHODS: We searched the Cochrane Stroke Group Trials Register (last searched May 2014), Cochrane Central Register of Controlled Trials (The Cochrane Library, 2014, Issue 4), MEDLINE (1950 to May 2014), EMBASE (1980 to May 2014), CINAHL (1982 to May 2014), AMED (1985 to May 2014), PsycINFO (1967 to May 2014), Digital Dissertations (1861 to May 2014), British Nursing Index (1985 to May 2014), PEDro (searched May 2014) and PsycBITE (searched May 2014). We also searched four ongoing trials registries, scanned reference lists, performed citation tracking of included trials and contacted experts.
SELECTION CRITERIA: Two review authors independently scrutinised all titles and abstracts and excluded obviously irrelevant studies. We obtained the full texts for potentially relevant studies and three review authors independently applied the inclusion criteria. We included randomised controlled trials (RCTs) that compared an intervention with a control, or compared different interventions for PSF.
DATA COLLECTION AND ANALYSIS: Two review authors independently extracted data and assessed risk of bias for each included trial. The primary outcomes were severity of fatigue, or proportion of people with fatigue after treatment. We performed separate analyses for trials investigating efficacy in treating PSF, trials investigating efficacy in preventing PSF and trials not primarily investigating efficacy in PSF but which reported fatigue as an outcome. We pooled results from trials that had a control arm. For trials that compared different potentially active interventions without a control arm, we performed analyses for individual trials without pooling.We calculated standardised mean difference (SMD) as the effect size for continuous outcomes and risk ratio (RR) for dichotomous outcomes. We pooled the results using a random-effects model and assessed heterogeneity using the I(2) statistic. We performed separate subgroup analyses for pharmacological and non-pharmacological interventions. We also performed sensitivity analyses to assess the influence of methodological quality.
MAIN RESULTS: We retrieved 12,490 citations, obtained full texts for 58 studies and included 12 trials (three from the 2008 search and nine from the 2014 search) with 703 participants. Eight trials primarily investigated the efficacy in treating PSF, of which six trials with seven comparisons provided data suitable for meta-analysis (five pharmacological interventions: fluoxetine, enerion, (-)-OSU6162, citicoline and a combination of Chinese herbs; and two non-pharmacological interventions: a fatigue education programme and a mindfulness-based stress reduction programme). The fatigue severity was lower in the intervention groups than in the control groups (244 participants, pooled SMD -1.07, 95% confidence interval (CI) -1.93 to -0.21), with significant heterogeneity between trials (I(2) = 87%, degrees of freedom (df) = 6, P value < 0.00001). The beneficial effect was not seen in trials that had used adequate allocation concealment (two trials, 89 participants, SMD -0.38, 95% CI -0.80 to 0.04) or trials that had used adequate blinding of outcome assessors (four trials, 198 participants, SMD -1.10, 95% CI -2.31 to 0.11).No trial primarily investigated the efficacy in preventing PSF.Four trials (248 participants) did not primarily investigate the efficacy on fatigue but other symptoms after stroke. None of these interventions showed any benefit on reducing PSF, which included tirilazad mesylate, continuous positive airway pressure for sleep apnoea, antidepressants and a self management programme for recovery from chronic diseases. AUTHORS'
CONCLUSIONS: There was insufficient evidence on the efficacy of any intervention to treat or prevent fatigue after stroke. Trials to date have been small and heterogeneous, and some have had a high risk of bias. Some of the interventions described were feasible in people with stroke, but their efficacy should be investigated in RCTs with a more robust study design and adequate sample sizes
Insulating charge density wave for a half-filled SU(N) Hubbard model with an attractive on-site interaction in one dimension
We study a one-dimensional SU(N) Hubbard model with an attractive on-site
interaction and at half-filling on the bipartite lattice using
density-matrix renormalization-group method and a perturbation theory. We find
that the ground state of the SU(N) Hubbard model is a charge density wave state
with two-fold degeneracy. All the excitations are found to be gapful, resulting
in an insulating ground state, on contrary to that in the SU(2) case. Moreover,
the charge gap is equal to the Cooperon gap, which behaves as
in the strong coupling regime. However, the spin gap and the
quasiparticle gap as well open exponentially in the weak coupling
region, while in the strong coupling region, they linearly depend on such
that and .Comment: 7 pages, 7 figure
Weak convergence of Vervaat and Vervaat Error processes of long-range dependent sequences
Following Cs\"{o}rg\H{o}, Szyszkowicz and Wang (Ann. Statist. {\bf 34},
(2006), 1013--1044) we consider a long range dependent linear sequence. We
prove weak convergence of the uniform Vervaat and the uniform Vervaat error
processes, extending their results to distributions with unbounded support and
removing normality assumption
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