10,563 research outputs found
The Great Wars, The Great Crash, and the Unit Root Hypothesis: Some New Evidence About an Old Stylized Fact
For decades, the prevailing sentiment among economists was that growth rates remain constant over the long run. Kaldor considered this to be one of the six important 'stylized facts' that theory should address, and until the emergence of endogenous growth models, this was a fundamental feature of growth theory. This paper uses an endogenous trend break model to investigate the unit root hypothesis for 16 countries, using annual GDP data spanning up to 130 years. Rejection of the unit root, which is facilitated by the inclusion of a trend break, introduces the possibility of examining the long run behavior of growth rates. We find that most countries exhibited fairly steady growth for a period lasting several decades. The termination of this period was usually characterized by a significant, and sudden, drop in GDP levels. But rather than simply returning to their previous steady state path, as predicted by the standard neoclassical growth model, most countries continued to grow at roughly double their prebreak rates for many decades, even after their original growth path had been surpassed.
Central limit theorems for the spectra of classes of random fractals
We discuss the spectral asymptotics of some open subsets of the real line
with random fractal boundary and of a random fractal, the continuum random
tree. In the case of open subsets with random fractal boundary we establish the
existence of the second order term in the asymptotics almost surely and then
determine when there will be a central limit theorem which captures the
fluctuations around this limit. We will show examples from a class of random
fractals generated from Dirichlet distributions as this is a relatively simple
setting in which there are sets where there will and will not be a central
limit theorem. The Brownian continuum random tree can also be viewed as a
random fractal generated by a Dirichlet distribution. The first order term in
the spectral asymptotics is known almost surely and here we show that there is
a central limit theorem describing the fluctuations about this, though the
positivity of the variance arising in the central limit theorem is left open.
In both cases these fractals can be described through a general
Crump-Mode-Jagers branching process and we exploit this connection to establish
our central limit theorems for the higher order terms in the spectral
asymptotics. Our main tool is a central limit theorem for such general
branching processes which we prove under conditions which are weaker than those
previously known
Upright time and sit-to-stand transition progression after total hip arthroplasty: an in-hospital longitudinal study
Social marketing: Immunizing against unethical practice
A simple approach for the catalytic conversion of primary alcohols into their corresponding esters and amides, with evolution of H2 gas using in situ formed ruthenium PNP- and PNN-pincer catalysts, is presented. The evaluation showed conversions for the esterification with turnover numbers as high as 4300, and 4400 for the amidation
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Deploying a microstructure profiler in Corpus Christi Bay
Center for Water and the Environmen
Adaptation Algorithm and Theory Based on Generalized Discrepancy
We present a new algorithm for domain adaptation improving upon a discrepancy
minimization algorithm previously shown to outperform a number of algorithms
for this task. Unlike many previous algorithms for domain adaptation, our
algorithm does not consist of a fixed reweighting of the losses over the
training sample. We show that our algorithm benefits from a solid theoretical
foundation and more favorable learning bounds than discrepancy minimization. We
present a detailed description of our algorithm and give several efficient
solutions for solving its optimization problem. We also report the results of
several experiments showing that it outperforms discrepancy minimization
Linking healthcare associated norovirus outbreaks: a molecular epidemiologic method for investigating transmission.
BACKGROUND: Noroviruses are highly infectious pathogens that cause gastroenteritis in the community and in semi-closed institutions such as hospitals. During outbreaks, multiple units within a hospital are often affected, and a major question for control programs is: are the affected units part of the same outbreak or are they unrelated transmission events? In practice, investigators often assume a transmission link based on epidemiological observations, rather than a systematic approach to tracing transmission.Here, we present a combined molecular and statistical method for assessing:1) whether observed clusters provide evidence of local transmission and2) the probability that anecdotally|linked outbreaks truly shared a transmission event. METHODS: 76 healthcare associated outbreaks were observed in an active and prospective surveillance scheme of 15 hospitals in the county of Avon, England from April 2002 to March 2003. Viral RNA from 64 out of 76 specimens from distinct outbreaks was amplified by reverse transcription-PCR and was sequenced in the polymerase (ORF 1) and capsid (ORF 2) regions. The genetic diversity, at the nucleotide level, was analysed in relation to the epidemiological patterns. RESULTS: Two out of four genetic and epidemiological clusters of outbreaks were unlikely to have occurred by chance alone, thus suggesting local transmission. There was anecdotal epidemiological evidence of a transmission link among 5 outbreaks pairs. By combining this epidemiological observation with viral sequence data, the evidence of a link remained convincing in 3 of these pairs. These results are sensitive to prior beliefs of the strength of epidemiological evidence especially when the outbreak strains are common in the background population. CONCLUSION: The evidence suggests that transmission between hospitals units does occur. Using the proposed criteria, certain hypothesized transmission links between outbreaks were supported while others were refuted. The combined molecular/epidemiologic approach presented here could be applied to other viral populations and potentially to other pathogens for a more thorough view of transmission
Superheating and solid-liquid phase coexistence in nanoparticles with non-melting surfaces
We present a phenomenological model of melting in nanoparticles with facets
that are only partially wet by their liquid phase. We show that in this model,
as the solid nanoparticle seeks to avoid coexistence with the liquid, the
microcanonical melting temperature can exceed the bulk melting point, and that
the onset of coexistence is a first-order transition. We show that these
results are consistent with molecular dynamics simulations of aluminum
nanoparticles which remain solid above the bulk melting temperature.Comment: 8 pages, 5 figure
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