281 research outputs found
Universal features in the growth dynamics of complex organizations
We analyze the fluctuations in the gross domestic product (GDP) of 152
countries for the period 1950--1992. We find that (i) the distribution of
annual growth rates for countries of a given GDP decays with ``fatter'' tails
than for a Gaussian, and (ii) the width of the distribution scales as a power
law of GDP with a scaling exponent . Both findings are in
surprising agreement with results on firm growth. These results are consistent
with the hypothesis that the evolution of organizations with complex structure
is governed by similar growth mechanisms.Comment: 4 pages, 7 ps figures, using Latex2e with epsf rotate and multicol
style files. Submitted to PR
Carbon superatom thin films
Assembling clusters on surfaces has emerged as a novel way to grow thin films
with targeted properties. In particular, it has been proposed from experimental
findings that fullerenes deposited on surfaces could give rise to thin films
retaining the bonding properties of the incident clusters. However the
microscopic structure of such films is still unclear. By performing quantum
molecular dynamics simulations, we show that C_28 fullerenes can be deposited
on a surface to form a thin film of nearly defect free molecules, which act as
carbon superatoms. Our findings help clarify the structure of disordered small
fullerene films and also support the recently proposed hyperdiamond model for
solid C_28.Comment: 13 pages, RevTeX, 2 figures available as black and white PostScript
files; color PostScript and/or gif files available upon reques
Galaxy populations in the most distant SPT-SZ clusters II. Galaxy structural properties in massive clusters at 1.4 âČ z âČ 1.7
We investigate structural properties of massive galaxy populations in the central regions ( 4 Ă 1014 M ), high-redshift (1.4 . z . 1.7) galaxy clusters from the 2500 deg2 South Pole Telescope Sunyaev Zelâdovich effect (SPT-SZ) survey. We probe the connection between galaxy structure and broad stellar population properties at stellar masses of log(M/M ) > 10.85. We find that quiescent and star-forming cluster galaxy populations are largely dominated by bulge- and disk-dominated sources, respectively, with relative contributions being fully consistent with those of field counterparts. At the same time, the enhanced quiescent galaxy fraction observed in these clusters with respect to the coeval field is reflected in a significant morphology-density relation, with bulge-dominated galaxies already clearly dominating the massive galaxy population in these clusters at z ⌠1.5. At face value, these observations show no significant environmental signatures in the correlation between broad structural and stellar population properties. In particular, the Sersic index and axis ratio distribution of massive, quiescent sources are consistent with field counterparts, in spite of the enhanced quiescent galaxy fraction in clusters. This consistency suggests a tight connection between quenching and structural evolution towards a bulge-dominated morphology, at least in the probed cluster regions and galaxy stellar mass range, irrespective of environment-related processes affecting star formation in cluster galaxies. We also probe the stellar massâsize relation of cluster galaxies, and find that star-forming and quiescent sources populate the massâsize plane in a manner largely similar to their field counterparts, with no evidence of a significant size difference for any probed sub-population. In particular, both quiescent and bulge-dominated cluster galaxies have average sizes at fixed stellar mass consistent with their counterparts in the field
Complex type 4 structure changing dynamics of digital agents: Nash equilibria of a game with arms race in innovations
The new digital economy has renewed interest in how digital agents can innovate. This follows the legacy of John von Neumann dynamical systems theory on complex biological systems as computation. The Gödel-Turing-Post (GTP) logic is shown to be necessary to generate innovation based structure changing Type 4 dynamics of the Wolfram-Chomsky schema. Two syntactic procedures of GTP logic permit digital agents to exit from listable sets of digital technologies to produce novelty and surprises. The first is meta-analyses or offline simulations. The second is a fixed point with a two place encoding of negation or opposition, referred to as the Gödel sentence. It is postulated that in phenomena ranging from the genome to human proteanism, the Gödel sentence is a ubiquitous syntactic construction without which escape from hostile agents qua the Liar is impossible and digital agents become entrained within fixed repertoires. The only recursive best response function of a 2-person adversarial game that can implement strategic innovation in lock-step formation of an arms race is the productive function of the Emil Post [58] set theoretic proof of the Gödel incompleteness result. This overturns the view of game theorists that surprise and innovation cannot be a Nash equilibrium of a game
Quantum Cryptography
Quantum cryptography could well be the first application of quantum mechanics
at the individual quanta level. The very fast progress in both theory and
experiments over the recent years are reviewed, with emphasis on open questions
and technological issues.Comment: 55 pages, 32 figures; to appear in Reviews of Modern Physic
Comparing very low birth weight versus very low gestation cohort methods for outcome analysis of high risk preterm infants
© 2017 The Author(s). Background: Compared to very low gestational age (<32 weeks, VLGA) cohorts, very low birth weight (<1500 g; VLBW) cohorts are more prone to selection bias toward small-for-gestational age (SGA) infants, which may impact upon the validity of data for benchmarking purposes. Method: Data from all VLGA or VLBW infants admitted in the 3 Networks between 2008 and 2011 were used. Two-thirds of each network cohort was randomly selected to develop prediction models for mortality and composite adverse outcome (CAO: mortality or cerebral injuries, chronic lung disease, severe retinopathy or necrotizing enterocolitis) and the remaining for internal validation. Areas under the ROC curves (AUC) of the models were compared. Results: VLBW cohort (24,335 infants) had twice more SGA infants (20.4% vs. 9.3%) than the VLGA cohort (29,180 infants) and had a higher rate of CAO (36.5% vs. 32.6%). The two models had equal prediction power for mortality and CAO (AUC 0.83), and similarly for all other cross-cohort validations (AUC 0.81-0.85). Neither model performed well for the extremes of birth weight for gestation (<1500 g and â„32 weeks, AUC 0.50-0.65; â„1500 g and <32 weeks, AUC 0.60-0.62). Conclusion: There was no difference in prediction power for adverse outcome between cohorting VLGA or VLBW despite substantial bias in SGA population. Either cohorting practises are suitable for international benchmarking
Cluster Cosmology Constraints from the 2500 deg SPT-SZ Survey: Inclusion of Weak Gravitational Lensing Data from Magellan and the Hubble Space Telescope
We derive cosmological constraints using a galaxy cluster sample selected
from the 2500~deg SPT-SZ survey. The sample spans the redshift range . The
sample is supplemented with optical weak gravitational lensing measurements of
32 clusters with (from Magellan and HST) and X-ray measurements
of 89 clusters with (from Chandra). We rely on minimal modeling
assumptions: i) weak lensing provides an accurate means of measuring halo
masses, ii) the mean SZ and X-ray observables are related to the true halo mass
through power-law relations in mass and dimensionless Hubble parameter
with a-priori unknown parameters, iii) there is (correlated, lognormal)
intrinsic scatter and measurement noise relating these observables to their
mean relations. We simultaneously fit for these astrophysical modeling
parameters and for cosmology. Assuming a flat CDM model, in which
the sum of neutrino masses is a free parameter, we measure
, , and
. The redshift evolution
of the X-ray -mass and -mass relations are both
consistent with self-similar evolution to within . The mass-slope of
the -mass relation shows a deviation from
self-similarity. Similarly, the mass-slope of the -mass
relation is steeper than self-similarity at the level. In a CDM cosmology, we measure the dark energy equation of state parameter
from the cluster data. We perform a measurement of the growth
of structure since redshift and find no evidence for tension with
the prediction from General Relativity. We provide updated redshift and mass
estimates for the SPT sample. (abridged)Comment: Accepted for publication in ApJ (v2 is accepted version), the catalog
can be found at https://pole.uchicago.edu/public/data/sptsz-clusters
SPT Clusters with DES and HST Weak Lensing. I. Cluster Lensing and Bayesian Population Modeling of Multi-Wavelength Cluster Datasets
We present a Bayesian population modeling method to analyze the abundance of
galaxy clusters identified by the South Pole Telescope (SPT) with a
simultaneous mass calibration using weak gravitational lensing data from the
Dark Energy Survey (DES) and the Hubble Space Telescope (HST). We discuss and
validate the modeling choices with a particular focus on a robust,
weak-lensing-based mass calibration using DES data. For the DES Year 3 data, we
report a systematic uncertainty in weak-lensing mass calibration that increases
from 1\% at to 10\% at , to which we add 2\% in quadrature to
account for uncertainties in the impact of baryonic effects. We implement an
analysis pipeline that joins the cluster abundance likelihood with a
multi-observable likelihood for the SZ, optical richness, and weak-lensing
measurements for each individual cluster. We validate that our analysis
pipeline can recover unbiased cosmological constraints by analyzing mocks that
closely resemble the cluster sample extracted from the SPT-SZ, SPTpol~ECS, and
SPTpol~500d surveys and the DES Year~3 and HST-39 weak-lensing datasets. This
work represents a crucial prerequisite for the subsequent cosmological analysis
of the real dataset.Comment: submitted to PR
Trends in Outcomes for Neonates Born Very Preterm and Very Low Birth Weight in 11 High-Income Countries
Objective
To evaluate outcome trends of neonates born very preterm in 11 high-income countries participating in the International Network for Evaluating Outcomes of neonates. Study design In a retrospective cohort study, we included 154 233 neonates admitted to 529 neonatal units between January 1, 2007, and December 31, 2015, at 24(0/7) to 31(6/7) weeks of gestational age and birth weight <1500 g. Composite outcomes were in-hospital mortality or any of severe neurologic injury, treated retinopathy of prematurity, and bronchopulmonary dysplasia (BPD); and same composite outcome excluding BPD. Secondary outcomes were mortality and individual morbidities. For each country, annual outcome trends and adjusted relative risks comparing epoch 2 (2012-2015) to epoch 1 (2007-2011) were analyzed.
Results
For composite outcome including BPD, the trend decreased in Canada and Israel but increased in Australia and New Zealand, Japan, Spain, Sweden, and the United Kingdom. For composite outcome excluding BPD, the trend decreased in all countries except Spain, Sweden, Tuscany, and the United Kingdom. The risk of composite outcome was lower in epoch 2 than epoch 1 in Canada (adjusted relative risks 0.78; 95% CI 0.74-0.82) only. The risk of composite outcome excluding BPD was significantly lower in epoch 2 compared with epoch 1 in Australia and New Zealand, Canada, Finland, Japan, and Switzerland. Mortality rates reduced in most countries in epoch 2. BPD rates increased significantly in all countries except Canada, Israel, Finland, and Tuscany.
Conclusions
In most countries, mortality decreased whereas BPD increased for neonates born very preterm
Neptune to the Common-wealth of England (1652): the republican Britannia and the continuity of interests
In the seventeenth century, John Kerrigan reminds us, âmodels of empire did not always turn on monarchyâ. In this essay, I trace a vision of âNeptuneâs empireâ shared by royalists and republicans, binding English national interest to British overseas expansion. I take as my text a poem entitled âNeptune to the Common-wealth of Englandâ, prefixed to Marchamont Nedhamâs 1652 English translation of Mare Clausum (1635), John Seldenâs response to Mare Liberum (1609) by Hugo Grotius. This minor work is read alongside some equally obscure and more familiar texts in order to point up the ways in which it speaks to persistent cultural and political interests. I trace the afterlife of this verse, its critical reception and its unique status as a fragment that exemplifies the crossover between colonial republic and imperial monarchy at a crucial moment in British history, a moment that, with Brexit, remains resonant
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