A SAS(®) macro implementation of a multiple comparison post hoc test for a Kruskal-Wallis analysis

The Kruskal-Wallis (KW) nonparametric analysis of variance is often used instead of a standard one-way ANOVA when data are from a suspected non-normal population. The KW omnibus procedure tests for some differences between groups, but provides no specific post hoc pair wise comparisons. This paper provides a SAS^® macro implementation of a multiple comparison test based on significant Kruskal-Wallis results from the SAS NPAR1WAY procedure. The implementation is designed for up to 20 groups at a user-specified alpha significance level. A Monte-Carlo simulation compared this nonparametric procedure to commonly used parametric multiple comparison tests.     

The course of geriatric depression with "reversible dementia": a controlled study

OBJECTIVE: The goals of this longitudinal investigation were 1) to study the rate of development of irreversible dementia in elderly depressed patients with a dementia syndrome that subsided after improvement of depression and 2) to compare it with that of depressed, never-demented patients. METHOD: The subjects were 57 elderly patients consecutively hospitalized for major depression. At entry into the study, 23 subjects also met criteria for "reversible dementia," while 34 were without dementia. After a systematic clinical evaluation, the subjects were followed up at approximately yearly intervals for an average of 33.8 months. RESULTS: Irreversible dementia developed significantly more frequently in the depressed group with reversible dementia (43%) than in the group with depression alone (12%). Survival analysis showed that the group with reversible dementia had a 4.69-times higher chance of having developed dementia at follow-up than the patients with depression alone. No clinical characteristics at entry into the study were found to discriminate the subjects who developed irreversible dementia during the follow-up period from those who remained nondemented. CONCLUSIONS: These findings suggest that geriatric depression with reversible dementia is a clinical entity that includes a group of patients with early-stage dementing disorders. Therefore, identification of a reversible dementia syndrome is an indication for a thorough diagnostic workup and frequent follow-ups in order to identify treatable neurological disorders.     

Combined infra-red and X-ray studies of β-silicon nitride and β′-sialons

Previous investigations of the replacement of silicon by aluminium and nitrogen by oxygen in -silicon nitride have been based primarily on X-ray powder diffraction studies. In the present work this technique is coupled with parallel infra-red studies. X-ray analyses of sialons over a wide composition range confirm previous observations that increasing substitution of aluminium for silicon and nitrogen for oxygen in -silicon nitride is accompanied by an increase in cell size, with no evidence of any other structural modification. Parallel infra-red analyses show shifts in certain of the infra-red absorption bands to lower wavenumbers as the degree of substitution increases. Changes in the infrared spectra at the composition Si₂Al₄N₄O₄ indicate structural modifications which are not apparent from the X-ray investigations. It is suggested that these changes are a result of the ordering of the different atom types at this composition.     

Plasma somatomedin activity in normal and scoliotic children

In a study of plasma somatomedin activity in childhood scoliosis a group of five patients with congenital scoliosis was found to have significantly lower plasma somatomedin levels compared with a group of 20 normal children. A group of 52 patients with "idiopathic" scoliosis had normal plasma somatomedin levels. There is no apparent difference in the plasma somatomedin activity between the sexes, and no change in plasma somatomedin activity with chronologic age in these children, suggesting that normal adult somatomedin levels have been reached.     

Cross-talk induces bifurcations in nonlinear models of synaptic plasticity

Linear models of synaptic plasticity provide a useful starting-point for examining the dynamics of neuronal development and learning, but their inherent problems are well known. Models of synaptic plasticity that embrace the demands of biological realism are therefore typically nonlinear. Viewed from a more abstract perspective, nonlinear models of synaptic plasticity are a subset of nonlinear dynamical systems. As such, they may therefore exhibit bifurcations under the variation of control parameters, including noise and errors in synaptic updates. One source of noise or error is the cross-talk that occurs during otherwise Hebbian plasticity. Under cross-talk, stimulation of a set of synapses can induce or modify plasticity in adjacent, unstimulated synapses. Here, we analyze two nonlinear models of developmental synaptic plasticity and a model of independent component analysis in the presence of a simple model of cross-talk. We show that cross-talk does indeed induce bifurcations in these models, entirely destroying their ability to acquire either developmentally or learning-related patterns of fixed points. Importantly, the critical level of cross-talk required to induce bifurcations in these models is very sensitive to the statistics of the afferents' activities and the number of afferents synapsing on a postsynaptic cell. In particular, the critical level can be made arbitrarily small. Because bifurcations are inevitable in nonlinear models, our results likely apply to many nonlinear models of synaptic plasticity, although the precise details vary by model. Hence, many nonlinear models of synaptic plasticity are potentially fatally compromised by the toxic influence of cross-talk and other sources of noise and errors more generally. We conclude by arguing that biologically realistic models of synaptic plasticity must be robust against noise-induced bifurcations and that biological systems may have evolved strategies to circumvent their possible dangers.     

A criticism of the Flood-Grjotheim ionic treatment of slag-equilibria

The analysis by Flood and Grjotheim¹ of the equilibria between a metal and a fused slag utilizes the ionic behavior of the slag or salt, and it employs a reversible thermodynamic cycle. However, in the original analysis there appears to be an error in the use of free energy. A corrected treatment has been developed which involves a modest change and simplification in the original formulation. The revised analysis shows the importance of the thermodynamic behavior of ionic species in the slag, which may be nonideal. Data from the literature on slag-metal equilibria, for example: $$\left[ {Fe^{2 + } } \right] + \underline {Mn} = Fe\left( l \right) + \left[ {Mn^{2 + } } \right]$$ , are analyzed by the new formulation to obtain expressions for ratios of activity coefficients such as (γS^2?/γO^2?), (γMn²⁺/γFe²⁺) and [(γPO ₄ ^3? )²/(γO^2?)³] in terms of slag composition, the last two having been found to depend strongly on the oxygen-ion content of the slag.     

Psychophysiological studies in the pre-school children

The behavior of 24 children, aged 3-6 years, was recorded on video-tape. Simultaneously the ECG was recorded telemetrically. These observations were made during two pre-school educational programs lasting 90 minutes each: "Didactic games" and "Elementary music and movement program". For each child a scale was developed to show the correlation of mean heart-rate and well defined motor-activity. It was evident that the mean heart-rate was higher during the music program than during the didactic program, corresponding to the higher motor-activity. But it was found that in the didactic program the variation of the heart-rate within short intervals was higher due to the more frequent occurrence of respiratory arrhythmias. It was also seen that during the music program the children showed no signs of exertion as they did towards the end of the didactic program. Respiratory arrhythmias were not seen in children who according to the Schellong-test were classified as stable in their cardiovascular system. The arrhythmias occurred mainly when the children showed signs of fatigue.     

Development of the PenTile Matrix™ color AMLCD subpixel architecture and rendering algorithms

Abstract— Color subpixel rendering is enhanced by co‐optimizing the color subpixel architecture and algorithms with respect to human vision. This has resulted in the PenTile? display technology, which provides double the information content per subpixel when compared to a conventional RGB Stripe display. Output performance results from mathematical modeling, software simulations, and prototype AMLCDs displays demonstrate significant quality improvements to both text and full‐color images in comparison to images from RGB Stripe displays that have the same number of subpixels and column drivers.     

Adaptive control of linear systems with Markov perturbations

The stochastic model considered is a linear jump diffusion process X for which the coefficients and the jump processes depend on a Markov chain Z with finite state space. First, we study the optimal filtering and control problem for these systems with non-Gaussian initial conditions, given noisy observations of the state X and perfect measurements of Z. We derive a new sufficient condition which ensures the existence and the uniqueness of the solution of the nonlinear stochastic differential equations satisfied by the output of the filter. We study a quadratic control problem and show that the separation principle holds. Next, we investigate an adaptive control problem for a state process X defined by a linear diffusion for which the coefficients depend on a Markov chain, the processes X and Z being observed in independent white noises. Suboptimal estimates for the process X, Z and approximate control law are investigated for a large class of probability distributions of the initial state. Asymptotic properties of these filters and this control law are obtained. Upper bounds for the corresponding error are given