Order, chaos and complexity in discrete dynamical systems

A method for analyzing discrete dynamical systems is presented that provides a unified quantitative description of order, chaos and complexity in terms of information flow across system boundaries. Complexity is identified with variability in the relative dominance of order and chaos as systems evolve in time; therefore, purely ordered or purely chaotic behavior is considered simple. This notion of complexity is quantitatively expressed as fluctuation in net information gain. The method is applied to one-dimensional cellular automata, which are spatially and temporally discrete systems. Evidence is presented for a correlation between information fluctuation and the existence of internally complex propagating structures known as gliders. Gliders have been used in the construction of computing machines within cellular automata. This indicates that information variables may provide a connection between dynamical and computational notions of complexity. The method is also applied to one-dimensional maps, which are temporally discrete but spatially continuous, by partitioning the spatial dimension. For the logistic map, information fluctuation is maximum at the threshold between ordered and chaotic behavior, in agreement with the results of other researchers

Properties of real metallic surfaces: Effects of density functional semilocality and van der Waals nonlocality

We have computed the surface energies, work functions, and interlayer surface relaxations of clean (111), (110), and (100) surfaces of Al, Cu, Ru, Rh, Pd, Ag, Pt, and Au. Many of these metallic surfaces have technological or catalytic applications. We compare experimental reference values to those of the local density approximation (LDA), the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA), the PBEsol (PBE for solids) GGA, the SCAN meta-GGA, and SCAN+rVV10 (SCAN with a long-range van der Waals or vdW correction). The closest agreement with uncertain experimental values is achieved by the simplest density functional (LDA) and by the most sophisticated general-purpose one (SCAN+rVV10). The long-range vdW interaction increases the surface energies by about 10%, and the work functions by about 1%. LDA works for metal surfaces through a stronger-than-usual error cancellation. PBE yields the most-underestimated and presumably least accurate surface energies and work functions. Surface energies within the random phase approximation (RPA) are also reported. Interlayer relaxations from different functionals are in reasonable agreement with one another, and usually with experiment

A bibliography of publications by Albert Bates Lord

Note: [at time of printing] All items listed here can be found in Ellis Library at the University of Missouri, Columbia, either in Special Collections (Ellis 401) or in open stacks (see the affixed call numbers below). Many journals are available online to University of Missouri faculty, staff, and students, and of course through other institutions as well. A full collection of article-length items is maintained in hard copy and on CD in Special Collections

Mothers\u27 Sleep Deficits and Cognitive Performance: Moderation by Stress and Age

There are well-known associations between stress, poor sleep, and cognitive deficits, but little is known about their interactive effects, which the present study explored in a sample of mothers of toddlers. Since certain types of cognitive decline start during the 20s and continue into later ages, we also explored whether mothers\u27 age interacted with stress and sleep in the prediction of cognitive functioning. We hypothesized that poorer sleep [measured using one week of 24-hour wrist actigraphy data] and having more chronic stressors [e.g., life events, household chaos, work/family role conflict] would be linked with poorer cognitive performance [both executive function and standardized cognitive ability tasks], and that the interactive combination of poorer sleep and more stressors would account for the effect. We also explored whether this process operated differently for younger versus older women. In a socioeconomically and geographically diverse community sample of 227 women with toddler-age children [age, M = 32.73 yrs, SD = 5.15 yrs], poorer cognitive performance was predicted by greater activity during the sleep period, shorter sleep duration, and lower night-to-night consistency in sleep; it was not associated with higher levels of stress. The interactive effects hypothesis was supported for sleep activity [fragmented sleep] and sleep timing [when mothers went to bed]. The combination of more exposure to stressors and frequent night waking was particularly deleterious for older women\u27s performance. For younger women, going to bed late was associated with poorer performance if they were experiencing high levels of stress; for those experiencing low levels of stress, going to bed late was associated with better performance

Current update of cerebral embolic protection devices

Carotid artery stenting (CAS) has evolved into a viable alternative to carotid endarterectomy. Although CAS outcomes have improved during the last decade, the associated stroke rate remains higher when compared with carotid endarterectomy. Therefore, the pivotal role of embolic protection devices (EPDs) in minimizing stroke risk cannot be underestimated as a vital component of CAS. As technology advances, EPDs continue to be refined, and each device currently on the market has its own advantages and disadvantages. This review provides an overview of the current status of EPDs and highlights the unique features of each device, followed by suggestions for application in specific clinical scenarios

Primordial helium recombination III: Thomson scattering, isotope shifts, and cumulative results

Upcoming precision measurements of the temperature anisotropy of the cosmic microwave background (CMB) at high multipoles will need to be complemented by a more complete understanding of recombination, which determines the damping of anisotropies on these scales. This is the third in a series of papers describing an accurate theory of HeI and HeII recombination. Here we describe the effect of Thomson scattering, the $^3$He isotope shift, the contribution of rare decays, collisional processes, and peculiar motion. These effects are found to be negligible: Thomson and $^3$He scattering modify the free electron fraction $x_e$ at the level of several $\times 10^{-4}$. The uncertainty in the $2^3P^o-1^1S$ rate is significant, and for conservative estimates gives uncertainties in $x_e$ of order $10^{-3}$. We describe several convergence tests for the atomic level code and its inputs, derive an overall $C_\ell$ error budget, and relate shifts in $x_e(z)$ to the changes in $C_\ell$, which are at the level of 0.5% at $\ell =3000$. Finally, we summarize the main corrections developed thus far. The remaining uncertainty from known effects is $\sim 0.3$ in $x_e$.Comment: 19 pages, 15 figures, to be submitted to PR

Suppression of protein aggregation by chaperone modification of high molecular weight complexes

Protein misfolding and aggregation are associated with many neurodegenerative diseases, including Huntington's disease. The cellular machinery for maintaining proteostasis includes molecular chaperones that facilitate protein folding and reduce proteotoxicity. Increasing the protein folding capacity of cells through manipulation of DNAJ chaperones has been shown to suppress aggregation and ameliorate polyglutamine toxicity in cells and flies. However, to date these promising findings have not been translated to mammalian models of disease. To address this issue, we developed transgenic mice that over-express the neuronal chaperone HSJ1a (DNAJB2a) and crossed them with the R6/2 mouse model of Huntington's disease. Over-expression of HSJ1a significantly reduced mutant huntingtin aggregation and enhanced solubility. Surprisingly, this was mediated through specific association with K63 ubiquitylated, detergent insoluble, higher order mutant huntingtin assemblies that decreased their ability to nucleate further aggregation. This was dependent on HSJ1a client binding ability, ubiquitin interaction and functional co-operation with HSP70. Importantly, these changes in mutant huntingtin solubility and aggregation led to improved neurological performance in R6/2 mice. These data reveal that prevention of further aggregation of detergent insoluble mutant huntingtin is an additional level of quality control for late stage chaperone-mediated neuroprotection. Furthermore, our findings represent an important proof of principle that DNAJ manipulation is a valid therapeutic approach for intervention in Huntington's diseas

The developmental course of illicit substance use from age 12 to 22: links with depressive, anxiety, and behavior disorders at age 18

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72027/1/j.1469-7610.2008.01915.x.pd

Predicting long-term developmental outcomes from maternal perceptions of infant and toddler behavior

The purpose of this study was to examine the long-term developmental correlates of maternal perceptions of infant and toddler behavior. Maternal ratings of children's social behavior and developmental progress were obtained when the children were 13 and 24 months of age, using the Maternal Perceptions Questionnaire. These early perceptions measures were intercorrelated with follow-up measures of children's developmental competence and behavioral adjustment at age 6. Maternal evaluations of child characteristics in the 2nd year predicted not only their own ratings of child behavioral adjustment but also teacher, examiner, and laboratory performance measures of cognitive competence and social adjustment. Although predictive correlations were generally modest, maternal perceptions scales showed meaningful patterns of relationships with later child characteristics, pointing to the desirability of further research on this topic.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28125/1/0000575.pd