Direct evaluation of dynamical large-deviation rate functions using a variational ansatz

We describe a simple form of importance sampling designed to bound and compute large-deviation rate functions for time-extensive dynamical observables in continuous-time Markov chains. We start with a model, defined by a set of rates, and a time-extensive dynamical observable. We construct a reference model, a variational ansatz for the behavior of the original model conditioned on atypical values of the observable. Direct simulation of the reference model provides an upper bound on the large-deviation rate function associated with the original model, an estimate of the tightness of the bound, and, if the ansatz is chosen well, the exact rate function. The exact rare behavior of the original model does not need to be known in advance. We use this method to calculate rate functions for currents and counting observables in a set of network- and lattice models taken from the literature. Straightforward ansatze yield bounds that are tighter than bounds obtained from Level 2.5 of large deviations via approximations that involve uniform scalings of rates. We show how to correct these bounds in order to recover the rate functions exactly. Our approach is complementary to more specialized methods, and offers a physically transparent framework for approximating and calculating the likelihood of dynamical large deviations

Role of cortisol in social and memory impairments in individuals with velocardiofacial syndrome (VCFS)

Velocardiofacial Syndrome (VCFS) is a genetic disorder characterized by numerous physiological and psychological symptoms. Little is known regarding the neuropsychological and hormonal substrates and the social functioning in individuals with VCFS. There is some evidence to suggest that the stress hormone cortisol contributes to social, cognitive, and communication deficits in related populations (Corbett, Schupp, Levine, & Mendoza, 2009). This study investigated the role that cortisol has on the social and cognitive impairments observed in children with VCFS. To this end, 11 children with confirmed VCFS were assessed for baseline cortisol levels and received neuropsychological testing that assessed attention, memory, language, and social functioning. These results were compared with the results from 11 controls that were matched according to age and sex. It was hypothesized that children with VCFS would have significantly higher baseline cortisol levels relative to control children. Additionally, these cortisol levels would be negatively correlated with measures of social functioning as measured by CBCL, ABAS-II, and RCMAS-2. Furthermore, it was hypothesized that cortisol levels would be negatively correlated with performance on cognitive tests. Specifically, it was hypothesized that cortisol levels in children with VCFS would be negatively correlated with tests of attention and memory as measured by the WRAML-2. Children with VCFS had significantly higher cortisol levels than control counterparts; F(1, 20) = 5.436, p \u3c .05. Cortisol levels in VCFS were not related to measures of social functioning or measures of cognitive functioning. That said, a significant negative correlation was observed between the General Memory and Attention/Concentration indices of the WRAML-2 and cortisol concentrations in the control population: r(11) = -.78,

Substrates of social functioning in individuals with VCFS

Velocardiofacial Syndrome (VCFS) is a genetic disorder characterized by numerous physiological and psychological symptoms. Little is known regarding the neuropsychological substrates of social functioning in individuals with VCFS. This study was a secondary data analysis investigating the relationship between various brain structure volumes and social deficits in individuals with VCFS. Volumetric measures of brain regions based on magnetic resonance imaging (MRI) were compared between 6 VCFS individuals and 6 controls. Controls were identically matched according to age and gender. It was hypothesized that after covarying for total brain volume, VCFS patients would exhibit larger amygdala and insula volumes and smaller prefrontal cortex (PFC), orbitofrontal cortex (OFC), dorsolateral prefrontal cortex (DLPFC), insula, superior temorpal sulcus (STS), and anterior cingulate cortex (ACC) volumes relative to controls. In addition, scores on the Child Behavior Checklist (CBCL), a measure assessing problematic behaviors and social competency, would be correlated with volumes of amygdala, PFC, OFC, DLPFC, STS, and ACC in patients with VCFS. Specifically, it was hypothesized that regional volumes in patients with VCFS will be associated with increased problem scores and decreased social competency as measured by the CBCL. Amygdala volumes were found to be enlarged in individuals with VCFS relative to controls t (10) = 4.01, p \u3c .05) and negatively correlated with the attention subscale of the CBCL r(6)= -.98, p \u3c .01. Contrary to expectations, DLPFC volumes were larger in individuals with VCFS relative to controls t(10)= 3.23, p \u3c .05)

Should we teach old dogs new tricks? the impact of community college retraining on older displaced workers

This paper estimates the returns to retraining for older displaced workers--those 35 or older--by estimating the impact that community college schooling has on their subsequent earnings. Our analysis relies on longitudinal administrative data covering workers who were displaced from jobs in Washington State during the first half of the 1990s and who subsequently remained attached to the state’s work force. Our database contains displaced workers' quarterly earnings records covering 14 years matched to the records of 25 of the state's community colleges. We find that older displaced workers participate in community college schooling at significantly lower rates than younger displaced workers. However, among those who participate in retraining, the per-period impact for older and younger displaced workers is similar. ; We estimate that one academic year of such schooling increases the long- term earnings by about 8 percent for older males and by about 10 percent for older females. These per-period impacts are in line with those reported in the schooling literature. These percentages do not necessarily imply that retraining older workers is a sound social investment. We find that the social internal rates of return from investments in older displaced workers' retraining are less than for younger displaced workers and likely less than those reported for schooling of children. However, our internal rate of return estimates are very sensitive to how we measure the opportunity cost of retraining. If we assume that these opportunity costs are zero, the internal rate of return from retraining older displaced workers is about 11 percent. By contrast, if we rely on our estimates of the opportunity cost of retraining, the internal rate of return may be less than 2 percent for older men and as low as 4 percent for older women.Displaced workers ; Education

Earnings Losses of Displaced Workers

The 1990-1991 recession has intensified concerns about the consequences of workers' job losses. To estimate the magnitude and temporal pattern of displaced workers' earnings losses, we exploit an unusual administrative data set that includes both employees' quarterly earnings histories and information about their firms. We find that when high-tenure workers separate from distressed firms their long-term losses average 25 percent per year. Further, their losses mount even prior to separation, are not limited to workers in a few industrial sectors, and are substantial even for those who find new jobs in similar firms. This evidence suggests that displaced workers' earnings losses result largely from the loss of some unidentified attribute of the employment relationship.earnings, wages, losses, displaced, dislocated, workers, Jacobson, LaLonde, Sullivan