The risk concept in medicine — Statistical and epidemiological aspects: A case report for applied mathematics in cardiology

In this study the theory of risk factors is discussed. The risk-concept is essential in cardiology and is, furthermore, important not only in medicine in general, but also and particularly in ecology. Since environmental risk factors endanger our health, ecological risks have to be taken as medical problems. If a factor or a set of factors is a necessary but not a sufficient condition for a disease we speak of a risk factor or of risk factors. Statistical analysis of risk factors can be performed by multivariate methods. A method which is particularly useful for finding the most important of a set of risk factors, is discriminant analysis.     

Use of contextual information in the formation of cognitive maps

To investigate the importance of context and presentation of serial order of information in the formation of cognitive maps, subjects were shown slides of pairwise relationships between items and then asked to construct a map. Two context conditions were used: a spatial condition in which the item pairs appeared in the same location on the screen as they would appear in a slide of the entire map and a nonspatial condition in which all item pairs appeared centered on the screen. Information order was either chain, in which new information could be immediately added to the representation, or nonchain, in which brief storage was required. The results indicated that both spatial context and chain order enhance performance. In addition, spatial information reduces the effect of serial order, perhaps by allowing subjects to relate new information to the context itself if they cannot relate it to previous information.     

Self-esteem agreement in the marital relationship.

With the use of the circular-causal model of relationship development, this study examined the convergence of the self-esteem of marriage partners over four martial life stages. Three hundred thirty-six married couples in the United States were randomly selected and divided into four life stage groups: younger couples with a child (or children) under age 6; couples with children in school; empty nest couples, in which the wife is in the age range of 45-59 years; and retired couples. Measures of a partner's self-esteem and his or her evaluation of the spouse's self-esteem were taken. The findings demonstrated a convergence of the partners' self-esteem across life stages.     

INTERRELATING NATURE, HUMANITY, AND THE WORK OF GOD: SOME ISSUES FOR FUTURE REFLECTION

Abstract. This essay suggests some future items for an agenda about human viability, defined as survivability with meaning and purpose, by exploring interrelations between nature, humanity, and the work of God. It argues for intrinsic and creative value in nature, so there is a value kinship, as well as a factual kinship, between humans, nature, and God-working. It considers humans as "webs of culture, life, and cosmos" and suggests some implications of this notion of human nature for viability. And it asks what human fulfillment can be in light of the awesome creative-destroying-recreative activity that seems to be the ground of an evolving universe.     

Virtual Time-to-Collision and Human Postural Control

This article is a report on 3 experiments designed so that the role of virtual time-to-collision (VTC), which specifies the spatiotemporal proximity of the center of pressure to the postural stability boundary in the regulation of posture in upright stances, could be examined. Virtual time-to-collision was estimated for normal upright stance with different bases of support, and for postural oscillations in which the speed of movement and instructional constraints on the coordination mode used were manipulated. The results showed that virtual time-to-collision was predictably reduced as (a) the base of support was reduced, (b) the speed of the postural oscillation was increased, and (c) the number of biomechanical degrees of freedom regulated in the coordination mode increased. Over a range of task conditions, the coefficients of variation of the VTC time-series were significantly lower than the coefficients of variation for the velocity and acceleration time series of the center of pressure. The absolute values of VTC increased with the increment of the ground reaction forces a performer generated to avoid falling while approaching the stability boundary. These findings are consistent with the proposition that VTC may serve as an organizing informational control parameter for posture.     

The Ketamine Model of the Near-Death Experience: A Central Role for the N-Methyl-D-Aspartate Receptor

Near-death experiences (NDEs) can be reproduced by ketamine via blockade of receptors in the brain for the neurotransmitter glutamate, the N-methyl-D-aspartate (NMDA) receptors. Conditions that precipitate NDEs, such as hypoxia, ischemia, hypoglycemia, and temporal lobe epilepsy, have been shown to release a flood of glutamate, overactivating NMDA receptors and resulting in neurotoxicity. Ketamine prevents this neurotoxicity. There are substances in the brain that bind to the same receptor site as ketamine. Conditions that trigger a glutamate flood may also trigger a flood of neuroprotective agents that bind to NMDA receptors to protect cells, leading to an altered state of consciousness like that produced by ketamine.     

Visual control of discrete aiming movements

An experiment is reported which investigated the visual control of discrete rapid arm movements. Subjects were required to move as rapidly as possible to several target width-movement distance combinations under both visual and non-visual conditions. The movement time (MT) data were supportive of Fitts' Law in that MT was linearly related and highly correlated to the Index of Difficulty (ID). MT was also similar for different target width-distance combinations sharing the same ID value. The error rate analysis, which compared visual to non-visual perfromance, indicated that vision was only used, and to varying degrees, when MT exceeded 200 ms (3.58 ID level). There was some evidence that vision was differentially used within target width-distance combinations sharing the same ID. Estimates of endpoint variability generally reflected the results of the error rate analysis. These results do not support the discrete correction model of Fitts' Law proposed by Keele (1968).     

A 64-station computer-assisted teaching and research facility

A 64-subject computer-controlled laboratory for use in research and as a teaching aid is described. The laboratory hardware includes an 8K minicomputer, a 64-channel input multiplexor, and a video display generator. The software includes a complete operating system and an easy-to-use programming language. The entire laboratory, including the computer, was built for under $12,000.     

Signal identification: The comparison of two competitive theories

Attention, Perception, & Psychophysics - On each of a series of random trials, 10 observers had to identify which of two possible tones of different amplitude had been presented. Two theories...