33,934 research outputs found
Modifying Fragility and Collective Motion in Polymer Melts with Nanoparticles
We investigate the impact of nanoparticles (NP) on the fragility and
cooperative string-like motion in a model glass-forming polymer melt by
molecular dynamics simulation. The NP cause significant changes to both the
fragility and the average length of string-like motion, where the effect
depends on the NP-polymer interaction and the NP concentration. We interpret
these changes via the Adam-Gibbs (AG) theory, assuming the strings can be
identified with the "cooperatively rearranging regions" of AG. Our findings
indicate fragility is primarily a measure of the temperature dependence of the
cooperativity of molecular motion.Comment: To appear in Physical Review Letter
Financial asset returns, direction-of-change forecasting, and volatility dynamics
We consider three sets of phenomena that feature prominently - and separately - in the financial economics literature: conditional mean dependence (or lack thereof) in asset returns, dependence (and hence forecastability) in asset return signs, and dependence (and hence forecastability) in asset return volatilities. We show that they are very much interrelated, and we explore the relationships in detail. Among other things, we show that: (a) Volatility dependence produces sign dependence, so long as expected returns are nonzero, so that one should expect sign dependence, given the overwhelming evidence of volatility dependence; (b) The standard finding of little or no conditional mean dependence is entirely consistent with a significant degree of sign dependence and volatility dependence; (c) Sign dependence is not likely to be found via analysis of sign autocorrelations, runs tests, or traditional market timing tests, because of the special nonlinear nature of sign dependence; (d) Sign dependence is not likely to be found in very high-frequency (e.g., daily) or very low-frequency (e.g., annual) returns; instead, it is more likely to be found at intermediate return horizons; (e) Sign dependence is very much present in actual U.S. equity returns, and its properties match closely our theoretical predictions; (f) The link between volatility forecastability and sign forecastability remains intact in conditionally non-Gaussian environments, as for example with time-varying conditional skewness and/or kurtosis
The relationship of intrinsic, extrinsic, and quest religious orientations to Jungian psychological type among churchgoers in England and Wales
Employing the New Indices of Religious Orientation (NIRO), this study examines the theory that different religious orientations are related to individual differences in psychological type as developed by Carl Jung and operationalized by the Myers-Briggs Type Indicator (MBTI). Data provided by 481 weekly churchgoing Christians who completed the MBTI and the NIRO demonstrated that quest religious orientation scores were higher among intuitives than among sensers, but were unrelated to introversion and extraversion, thinking and feeling, or judging and perceiving; that intrinsic religious orientation scores were higher among extraverts than introverts, higher among sensers than intuitives and higher among feelers than thinkers, but unrelated to judging and perceiving; and that extrinsic religious orientation scores were unrelated to any of the four components of psychological type. The findings relating to Jungian psychological type differences are applied in order to elucidate the psychological significance of extrinsic, intrinsic, and quest orientations to religion
Fluctuations of the front in a stochastic combustion model
We consider an interacting particle system on the one dimensional lattice
modeling combustion. The process depends on two integer parameters
. Particles move independently as continuous time simple
symmetric random walks except that 1. When a particle jumps to a site which has
not been previously visited by any particle, it branches into particles; 2.
When a particle jumps to a site with particles, it is annihilated. We start
from a configuration where all sites to the left of the origin have been
previously visited and study the law of large numbers and central limit theorem
for , the rightmost visited site at time .
The proofs are based on the construction of a renewal structure leading to a
definition of regeneration times for which good tail estimates can be
performed.Comment: 19 page
Financial Asset Returns, Direction-of-Change Forecasting, and Volatility Dynamics
We consider three sets of phenomena that feature prominently - and separately - in the financial economics literature: conditional mean dependence (or lack thereof) in asset returns, dependence (and hence forecastability) in asset return signs, and dependence (and hence forecastability) in asset return volatilities. We show that they are very much interrelated, and we explore the relationships in detail. Among other things, we show that (a) Volatility dependence produces sign dependence, so long as expected returns are nonzero, so that one should expect sign dependence, given the overwhelming evidence of volatility dependence; (b) The standard finding of little or no conditional mean dependence is entirely consistent with a significant degree of sign dependence and volatility dependence; (c) Sign dependence is not likely to be found via analysis of sign autocorrelations, runs tests, or traditional market timing tests, because of the special nonlinear nature of sign dependence; (d) Sign dependence is not likely to be found in very high-frequency (e.g., daily) or very low-frequency (e.g., annual) returns; instead, it is more likely to be found at intermediate return horizons; (e) Sign dependence is very much present in actual U.S. equity returns, and its properties match closely our theoretical predictions; (f) The link between volatility forecastability and sign forecastability remains intact in conditionally non-Gaussian environments, as for example with time-varying conditional skewness and/or kurtosis.Conditional Mean Dependence, Conditional Volatility Dependence, Sign Dependence, VIX
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