Non-equilibrium transitions in multiscale systems with a bifurcating slow manifold

Noise-induced transitions between metastable fixed points in systems evolving on multiple time scales are analyzed in situations where the time scale separation gives rise to a slow manifold with bifurcation. This analysis is performed within the realm of large deviation theory. It is shown that these non-equilibrium transitions make use of a reaction channel created by the bifurcation structure of the slow manifold, leading to vastly increased transition rates. Several examples are used to illustrate these findings, including an insect outbreak model, a system modeling phase separation in the presence of evaporation, and a system modeling transitions in active matter self-assembly. The last example involves a spatially extended system modeled by a stochastic partial differential equation

Asymptotic properties of the maximum likelihood estimator in autoregressive models with Markov regime

An autoregressive process with Markov regime is an autoregressive process for which the regression function at each time point is given by a nonobservable Markov chain. In this paper we consider the asymptotic properties of the maximum likelihood estimator in a possibly nonstationary process of this kind for which the hidden state space is compact but not necessarily finite. Consistency and asymptotic normality are shown to follow from uniform exponential forgetting of the initial distribution for the hidden Markov chain conditional on the observations.Comment: Published at http://dx.doi.org/10.1214/009053604000000021 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Retirement and Subjective Well-Being

We provide an explanation for the common finding that the effect of retirement on life satisfaction is negligible. For this we use subjective well-being measures for life and domains of life satisfaction that are available in the German Socio-Economic Panel (GSOEP) and show that the effect of voluntary retirement on satisfaction with current household income is negative, while the effect on satisfaction with leisure is positive. At the same time, the effect on health satisfaction is positive but small. Following the life domain approach we then argue that these effects offset each other for an average individual and that therefore the overall effect is negligible. Furthermore, we show that it is important to distinguish between voluntary and involuntary retirement. The effect of involuntary retirement is negative because the adverse effect on satisfaction with household income is bigger, the favorable effect on satisfaction with leisure is smaller, and the effect on satisfaction with health is not significantly different from zero. These results turn out to be robust to using different identification strategies such as fixed effects and first differences estimation, as well as instrumental variables estimation using eligibility ages and plant closures as instruments for voluntary and involuntary retirement.retirement, subjective well-being, satisfaction measurement

Retirement and Subjective Well-Being

We provide an explanation for the common finding that the effect of retirement on life satisfaction is negligible. For this we use subjective well-being measures for life and domains of life satisfaction that are available in the German Socio-Economic Panel (GSOEP) and show that the effect of voluntary retirement on satisfaction with current household income is negative, while the effect on satisfaction with leisure is positive. At the same time, the effect on health satisfaction is positive but small. Following the life domain approach we then argue that these effects offset each other for an average individual and that therefore the overall effect is negligible. Furthermore, we show that it is important to distinguish between voluntary and involuntary retirement. The effect of involuntary retirement is negative because the adverse effect on satisfaction with household income is bigger, the favorable effect on satisfaction with leisure is smaller, and the effect on satisfaction with health is not significantly different from zero. These results turn out to be robust to using different identification strategies such as fixed effects and first differences estimation, as well as instrumental variables estimation using eligibility ages and plant closures as instruments for voluntary and involuntary retirement.labour economics ;

Extreme event quantification in dynamical systems with random components

A central problem in uncertainty quantification is how to characterize the impact that our incomplete knowledge about models has on the predictions we make from them. This question naturally lends itself to a probabilistic formulation, by making the unknown model parameters random with given statistics. Here this approach is used in concert with tools from large deviation theory (LDT) and optimal control to estimate the probability that some observables in a dynamical system go above a large threshold after some time, given the prior statistical information about the system's parameters and/or its initial conditions. Specifically, it is established under which conditions such extreme events occur in a predictable way, as the minimizer of the LDT action functional. It is also shown how this minimization can be numerically performed in an efficient way using tools from optimal control. These findings are illustrated on the examples of a rod with random elasticity pulled by a time-dependent force, and the nonlinear Schr\"odinger equation (NLSE) with random initial conditions

Effects of World Trade Center Particulate Matter From September 11, 2001 on Biochemical Pathways Associated with Apoptosis and Cell Viability

The dust that resulted from the collapse of the World Trade Center (WTC) towers on September 11th, 2001 contained organic and inorganic compounds. The survivors and first responders were breathing these compounds while fleeing and rescuing others. Some of the particles that were inhaled were small enough to affect the alveolar region of the lungs. This study looks at the effect that World Trade Center dust has on MRC-5 human lung fibroblasts. Cell viability is observed over time using an alamarBlue® assay. Previous studies have shown that MRC-5 cells that are exposed to WTC dust lose viability after 24 hours (Hernandez, Choi, & DiLorenzo, 2012). However, these studies only observed the viability of the cells at one time point. This study is different in that it shows that some viability of the cells that were exposed to WTC dust is regained at 48 hours. Western blots are performed to determine if the cells are producing proteins that would indicate apoptosis due to exposure to the dust. Western blots are performed to also observe the effect that the dust is having on the mitogen-activated protein kinases (MAPKs) c-Jun N-terminal protein kinase (JNK), p38, and extracellular signal-related kinase 1/2 (ERK1/2). The effect of the WTC dust on the MAPKs will be observed because these three proteins are involved in cell growth and apoptosis. ERK1/2 is also involved in survival and cell cycle progression. ERK1/2 is also known to have a part in cancer cell proliferation. JNK and p38 are involved also involved in inflammation. If these proteins are being expressed it could mean that survivors or first responders could be experiencing, or have experienced, one or more of these effects. Further studies should be performed to determine what immunological responses the MRC-5 human lung fibroblasts are having after being exposed to the WTC dust