Is the heart preadapted to hypoxia? Evidence from fractal dynamics of heartbeat interval fluctuations at high altitude (5,050 m)

The dynamics of heartbeat interval time series over large time scales were studied by a modifed random walk analysis introduced recently asDetrended Fluctuation Analysis. In this analysis, the intrinsic fractal long-range power-law correlation properties of beat-to-beat fluctuations generated by the dynamical system (i.e., cardiac rhythm generator), after decomposition from extrinsic uncorrelated sources, can be quantified by the scaling exponent (α) which, in healthy subjects, for time scales of ∼10⁴ beats is ∼1.0. The effects of chronic hypoxia were determined from serial heartbeat interval time series of digitized twenty-four-hour ambulatory ECGs recorded in nine healthy subjects (mean age thirty-four years old) at sea level and during a sojourn at 5,050 m for thirty-four days (Ev-K2-CNR Pyramid Laboratory, Sagarmatha National Park, Nepal). The group averaged α exponent (±SD) was 0.99±0.04 (range 0.93–1.04). Longitudinal assessment of α in individual subjects did not reveal any effect of exposure to chronic high altitude hypoxia. The finding of α∼1 indicating scale-invariant long-range power-law correlations (1/f noise) of heartbeat fluctuations would reflect a genuinely self-similar fractal process that typically generates fluctuations on a wide range of time scales. Lack of a characteristic time scale along with the absence of any effect from exposure to chronic hypoxia on scaling properties suggests that the neuroautonomic cardiac control system is preadapted to hypoxia which helps prevent excessive mode-locking (error tolerance) that would restrict its functional responsiveness (plasticity) to hypoxic or other physiological stimuli. Editorial Note: A philosopher is, by definition, a lover of wisdom. In the following article, Dr. Dimitrov, as a philosopher, examines the principles that underlie being and thinking as performed by the structures of the brain. He reports his thoughts in a “virtual context.” Virtual, a word enjoying great popularity today, is derived from the Latin word for man; it describes manliness and implies apparent, but not actual, power. In his analysis of how information is dealt with by the human being, the author uses theoretical physics and mathematics that may seem arcane to some readers. A major aspect of his thesis declares that the effective performance of information systems relies not on the structures involved, but on the way they interact.     

Research as a counselling activity?: A discussion of some uses of counselling within the context of research on sensitive issues

The relationship between counselling and research strategies is examined tvithin the context of a qualitative study of people coping with the aftermath of child sexual abuse. Complementary aspects of both processes are explored within this context, and comparisons are made. The counselling potential of the research situation is identified. This is linked to the need for both researcher and research supervisor to develop additional skills.     

Self-other differences in children's perceptions about the causes of important events

Three studies examined differences between children's (ages 8-15) beliefs about the effectiveness of multiple internal and external causes for producing outcomes in their own lives versus in those of their peers. Differences specific to the school domain were found: Starting at age 11 or 12, children perceived internal causes as more important for others than for themselves; and only beliefs about the self related to perceived control. More strikingly, a sample of gifted children, who presumably receive social feedback that they are different from their peers, reported that (a) they exerted more control and possessed more ability than their peers and (b) other children knew less about the causes of school performance and had to rely more on effort and powerful others; only beliefs about the self correlated to cognitive performance. These results suggest that self-other differences are produced by both developmental change and environmental opportunities.     

Regression estimation and post-stratification in factor analysis

Regression estimation and poststratification are methods used in survey sampling to estimate a population mean, when additional information is available for some auxiliary variables. The extension of these methods to factor analysis is considered. These methods may be used either to improve the efficiency of estimation or to adjust for the effects of nonrandom selection. The estimation procedure may be formulated in a LISREL framework.The author is grateful to the referees for their comments.     

Skipping breakfast,sedentarism and overweight in children

To show by use of path analysis how in children of 9 and 10 years of age the known relationship between breakfast and high body mass index (BMI) is mediated by sedentary leisure time activities. A random sample of 291 9-year-old and 10-year-old school children from the Principality of Asturias (Spain) was taken. A transversal design was used, their weight and height were measured and an individual standardized interview was carried out in which they were asked about their breakfast habits and the time they spent each week on sedentary leisure activities. Using path analysis, a model was tested in which breakfast habits and leisure time were the independent variables and the BMI was the dependent variable. The results showed that there was an inverse correlation between number of breakfasts and BMI and a direct correlation between the time spent on sedentary leisure activities and BMI. Path analysis showed that the relationship between the frequency with which breakfast was eaten and BMI was mediated by the time spent on sedentary leisure activities. The above appears to confirm the direct role played by failing to have breakfast in the pandemic of obesity as this habit tends to increase children’s BMI. This relationship is, however, mediated by sedentary leisure. According to the data compiled, being overweight in children can only be prevented by modifying not just one of the habits that have been associated with it, but rather the whole group of habits as these appear to make up an obesogenic cluster in which sedentary leisure and not having breakfast are included.     

Assessing the role of alternative response rates and reinforcer rates in resistance to extinction of target responding when combining stimuli

Studies of behavioral momentum reveal that reinforcing an alternative response in the presence of a target response reduces the rate of target responding but increases its persistence, relative to training the target response on its own. Because of the parallels between these studies and differential‐reinforcement techniques to reduce problem behavior in clinical settings, alternative techniques to reduce problem behavior without enhancing its persistence are being explored. One potential solution is to train an alternative response in a separate stimulus context from problem behavior before combining the alternative stimulus with the target stimulus. The present study assessed how differences in reinforcement contingencies and rate for alternative responding influenced resistance to extinction of target responding when combining alternative and target stimuli in pigeons. Across three experiments, alternative stimuli signaling a response–reinforcer dependency and greater reinforcer rates more effectively decreased the persistence of target responding when combining alternative and target stimuli within the same extinction tests, but not when compared across separate extinction tests. Overall, these findings reveal that differences in competition between alternative and target responding produced by contingencies of alternative reinforcement could influence the effectiveness of treating problem behavior through combining stimulus contexts.     

The Effects of Two Taped-Words Interventions on Sight-Word Reading in Students with Mental Retardation

Multiple-baseline and alternating treatments design elements were combined to evaluate the effects of two taped-words (TW) interventions (rapid-paced and slow-paced) on sight-word reading accuracy levels in elementary students with mental retardation. During rapid TW, one word was presented every second via tape recorder and students were instructed to read aloud along with the tape. During slow TW, words were presented every 5s. Both TW interventions increased word reading accuracy but differences in learning rates between the two TW interventions were inconsistent across participants. Although no firm conclusions can be drawn regarding which pace is more effective, results show that regardless of pace, this efficient, self-managed intervention can be used to increase sight-word reading in students with mental retardation.     

The personal is the organizational in the ethics of hospital social workers

Understanding the social context of clinical ethics is vital for making ethical discourse central in professional practice and for preventing harm. In this paper, we present findings about clinical ethics from in-depth interviews and consultation with 7 members of a hospital social work department. Workers gave different accounts of ethical dilemmas and resources for ethical decision making than did their managers, whereas workers and managers agreed on core-guiding ethical principles and on ideal situations for ethical discourse. We discuss the research team's initial interpretations, the relevance of the extant ethics literature to organizational structures and dynamics, and alternative perspectives on clinical ethics.