Angular homeostasis: IV. Polygonal orbits

Some properties are discussed of regular polygons that may result from angular homeostatic processes in stable orbit. To characterize these homeostatic polygons we need to discuss the winding number, the sidedness (integer, fractional and irrational), multiplicity, envelopes, and density. A regular (i.e., equilateral, equiangular) polygon may be closed in one revolution about its unique center, in multiple revolutions, or not at all. A homeostatic polygon can be generated only if all vertices are included in a single polygon, which occurs if and only if the number of vertices and the number of revolutions required to complete the polygon are relatively prime. For the homeostatic polygon to have a finite number of sides (without repeating itself) the angle subtended by any two successive vertices at the center must be a rational multiple of 2. Biological implications of these properties are illustrated.     

A bayesian approach to confirmatory factor analysis

Confirmatory factor analysis is considered from a Bayesian viewpoint, in which prior information on parameter is incorporated in the analysis. An iterative algorithm is developed to obtain the Bayes estimates. A numerical example based on longitudinal data is presented. A simulation study is designed to compare the Bayesian approach with the maximum likelihood method.Computer facilities were provided by the Computer Services Center, The Chinese University of Hong Kong.     

Testing whether independent treatment groups have equal medians

The paper suggests new methods for comparing the medians corresponding to independent treatment groups. The procedures are based on the Harrell-Davis estimator in conjunction with a slight modification and extension of the bootstrap calibration technique suggested by Loh. Alternatives to the Harrell-Davis estimator are briefly discussed. For the special case of two treatment groups, the proposed procedure always had more power than the Fligner-Rust solution, as well as the procedure examined by Wilcox and Charlin. Included is an illustration, using real data, that comparing medians, rather than means, can yield a substantially different conclusion as to whether two distributions differ in terms of some measure of central location.     

Neuronal changes in normal human aging and Alzheimer's disease

This article discusses age-related changes in brain weight, total number of cortical neurons, cortical dendrites, spine, and synapse density. The conclusion is that the present outlook is less grim than it was 30 years ago. Age-related reduction appears to be specific to brain region and cortical layer rather than a general feature. In addition, we describe a different pattern of changes that occur in Alzheimer's disease patients. This review concludes that the association cortices in particular are affected in aging and Alzheimer's disease and that the primary visual and somatosensory cortices are relatively spared.     

Personality and Serum Lipids: Does Lifestyle Account for Their Concurrent and Long‐term Relationships

This study evaluates concurrent and over time associations of personality with measures of three serum lipids associated coronary heart disease morbidity, namely, high‐density lipoprotein cholesterol (HDL‐C), low‐density lipoprotein cholesterol and triglyceride (TRI). Participants were individuals who underwent a health examination at two points of time, T1 (N = 3835) and T2 (N = 2283), about 2.5 years apart. Personality was assessed by the Five‐Factor Model. Health, socioeconomic status and healthy lifestyle behaviours (smoking intensity, physical activity and body weight) were controlled. Regression analyses indicate that the personality factors of neuroticism, extraversion and conscientiousness are each significantly associated with HDL‐C and TRI, both concurrently and over time. However, most of these associations decreased to marginal significance when adjusted for body weight or physical activity as possible mediators. Both concurrent and over time associations of the openness personality trait with HDL‐C and TRI were significant and persisted after adjustment for measures of a healthy lifestyle. This study emphasizes the importance of collecting measures of a healthy lifestyle to better understand how personality might influence serum lipids. Copyright © 2013 European Association of Personality Psychology     

Statistical manifold as an affine space: A functional equation approach

A statistical manifold M_μ consists of positive functions f such that defines a probability measure. In order to define an atlas on the manifold, it is viewed as an affine space associated with a subspace of the Orlicz space L^Φ. This leads to a functional equation whose solution, after imposing the linearity constrain in line with the vector space assumption, gives rise to a general form of mappings between the affine probability manifold and the vector (Orlicz) space. These results generalize the exponential statistical manifold and clarify some foundational issues in non-parametric information geometry.     

Energy,Complexity, and Strategies of Evolution: As Illustrated by Maya Indians of Guatemala

Using free energy rate density (Φ_m) I differentiate two evolutionary strategies common to cosmic, biological, and cultural systems: the horizontal when energy increases proportional to mass, with no increase in complexity; and the vertical when it increases disproportionately to the mass and complexity increases. The vertical process is a continuing increase in complexity such that the system becomes vulnerable to collapse when energy sources fail. This is illustrated by a comparison of four Mayan Indian groups in Guatemala.     

Tracking the Time Course of Word‐Frequency Effects in Auditory Word Recognition With Event‐Related Potentials

Although the word‐frequency effect is one of the most established findings in spoken‐word recognition, the precise processing locus of this effect is still a topic of debate. In this study, we used event‐related potentials (ERPs) to track the time course of the word‐frequency effect. In addition, the neighborhood density effect, which is known to reflect mechanisms involved in word identification, was also examined. The ERP data showed a clear frequency effect as early as 350 ms from word onset on the P350, followed by a later effect at word offset on the late N400. A neighborhood density effect was also found at an early stage of spoken‐word processing on the PMN, and at word offset on the late N400. Overall, our ERP differences for word frequency suggest that frequency affects the core processes of word identification starting from the initial phase of lexical activation and including target word selection. They thus rule out any interpretation of the word frequency effect that is limited to a purely decisional locus after word identification has been completed.     

Psychological and behavioural effects of bone density screening for osteoporosis

Abstract

To examine the psychological effects of bone density measurement, 298 women were assessed two weeks before the bone density scan, immediately before the scan, after the results, a week later and three months later. For the group as a whole, ratings of anxiety and perceived vulnerability were lower at the three month follow-up than at the initial assessment. Women who received a low bone mineral density (BMD) result were more anxious and reported more osteoporosis-preventive behaviours at the three month follow-up than women who received a high BMD result; these differences had not been apparent at the initial assessment Women with low BMD results had higher ratings of perceived vulnerability after the scan, although for some of these ratings there were group differences before the scan. Women with a low BMD result showed a decrease in ratings of the seriousness of a below-average result, which may reflect minimization of the health threat