Search PubMed⌕ Search

Biomedical subjects

E A Thomas

Publications and source records attributed to E A Thomas.

At least 73 records · Page 4Linked to original sources
PubMed1987

Behavior-dependent contexts for repeated plays of the Prisoner's Dilemma: II. Dynamical aspects of the evolution of cooperation.

Iterated Prisoner's Dilemma models are proposed in which, at any trial, the probability of staying in the game depends on the outcome of the previous trial. If a player's choice depends on its own play (cooperate or defect) at the previous trial, it becomes possible for cooperative strategies to increase when rare in a population of egoists. A dynamic analysis is used to demonstrate that stable polymorphisms may result, and may involve more strategies than just Tit-for-Tat and all-Defect. The tendency for clustering among like strategists to enhance their initial increase when rare is also explored dynamically.

Behavior↗
PubMed1987

The accuracy of digital subtraction angiography for the quantification of atherosclerosis.

Digital subtraction angiography (DSA) allows the degree of arterial patency or stenosis to be rapidly quantified. We have assessed the accuracy with which a single-plane DSA system is able to quantify area patency by densitometric and geometric methods. Arterial phantoms were designed to test for systematic error; intra-arterial DSA images of critical lesions of the carotid bifurcation and the lower abdominal and peripheral vessels were used to determine intra- and interobserver reproducibility. The densitometric method, which was more accurate than the geometric method, had a mean systematic error of up to 4% and a mean intra-observer variability of about 15% (coefficient of variation). We have identified the principal sources of inaccuracy and ways in which it may be reduced.

Arteriosclerosis↗
PubMed1986

Strategic deworming for spring-calving beef cow/calf herds.

Strategic application of an anthelmintic was tested during the 1982 grazing season as part of the continued study of the epidemiology of beef cattle parasitism in central Missouri. Forty Hereford and Hereford X Simmental cow/calf pairs were assigned to 2 treatment groups. The 20 cow/calf pairs in group 1 were nonmedicated controls. After calving in mid-March, the 20 cows in group 2 were drenched with a 10% suspension of the anthelmintic fenbendazole (10 mg/kg of body weight). Ten cow/calf pairs were placed on each of four 20-acre fescue or orchard grass pastures in mid-May. Cows and calves in treatment group 2 were drenched with the 10% fenbendazole suspension (5 mg/kg) in mid-July. Body weights and fecal specimens were obtained monthly. Nematode egg counts in cow and calf fecal specimens collected monthly were significantly (P less than 0.05) lower in treatment group 2 than in treatment group 1. Numbers of larvae cultured for speciation revealed that Ostertagia ostertagi was the predominant nematode species. Developmental arrest of O ostertagi was found to be significantly (P less than 0.05) greater than zero from mid-May to mid-July. An important significant difference (P less than 0.01) was shown in body weights of calves, with the calves in treatment group 2 having a higher mean weight gain of 22.5 kg in adjusted 205-day weaning weights, and a higher mean daily gain of 0.11 kg. Weight maintenance of cows was not affected significantly by anthelmintic treatment. Nematode egg counts in monthly cow and calf fecal specimens were not significantly different between those animals on different pastures.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Training in geropsychology at the doctoral level: 1984.

To study type and amount of training in geropsychology available to students in APA-approved doctoral programs in clinical and counseling psychology, a questionnaire was mailed to all such programs in 1984. Response rate was 71 of 132 (59%) for clinical programs and 27 of 37 (73%) for counseling programs. Very little difference was found between responses of clinical and counseling programs and between this 1984 survey and one conducted in 1975-76. There seems to be a very small increase in training opportunities for psychology students in geropsychology in 1984 at the doctoral level.

Education, Graduate↗
PubMed1985

Maggot control.

Explore the source record for details and available documents.

Air Pressure↗
PubMed1985

Children's Rorschachs: description and prediction.

The temporal consistency for 23 Rorschach variables was examined in an 8-year longitudinal study which involved testing 57 subjects at 24-month intervals, beginning when the subjects were age 8 and administering the fourth retest when they were age 16. The objective was to compare these data with norms for the various age groups and to study the features of development as manifest in the Rorschach. Only one variable, the X+%, appears relatively stable from age 8 to age 16, and the majority do not manifest consistency until the interval between ages 14 and 16. The data suggest that long term descriptive predictions of children can only be formulated with great caution except when conditions of severe pathology exist.

Adolescent↗
PubMed1984

The short-term dynamics of social organization in preschool triads.

Sequential dependencies in solitary and interactive states of social organization were examined as a function of age, sex, and type of toy in 12 triads of 3 1/2- and 5-year-old children. Each triad was observed during 2 30-min sessions, one in which objects with highly specific functions (e.g., dolls, trucks) were available, and one in which objects with relatively ambiguous functions (e.g., pipe cleaners, cardboard cylinders) were present. The results indicated that, while old and young triads did not differ in the tendency to initiate triadic interaction when the preceding state was solitary, old triads were more likely than young triads to maintain the triadic state and to shift to that state from the dyadic state. Boy triads were more likely than girl triads to remain in a solitary state and less likely to shift to and remain in a dyadic state, though no sex difference was found in the transition probabilities when the preceding state was triadic. Triads were more likely to remain in a solitary state in the presence of high-specificity toys than in the presence of low-specificity toys. Verbal metacommunication was more frequent among old triads than young triads, and it facilitated maintenance, but not initiation, of interactive states. The distinction between initiation and maintenance tendencies was formalized in a Markov model of the dynamics of social organization, and the parameter estimates yielded by the model were used to provide a simplified description of the "main" effects of age, sex, and type of toy. It is argued that models such as this one are useful in circumventing certain restrictions on the possible interpretations of raw sequential statistics.

Child Development↗
PubMed1978

Response to 30 generations of selection for open-field activity in laboratory mice.

High and low lines resulting from 30 generations of bidirectional selection for open-field activity have nonoverlapping distributions and more than a thirtyfold difference in mean activity. Open-field defecation scores of low-active lines are approximately 7 times higher than those of high-active lines, substantiating earlier reports of a large, negative genetic correlation between these characters. Since the selection experiment is replicated, other variables which are found to be reliably different among the high, control, and low lines are likely to be causally related to open-field activity; thus these selected lines of mice may be of use to other investigators.

Albinism↗
PubMed1977

Control of attention in the processing of temporal and spatial information in complex visual patterns.

Eighteen stimuli were created by orthogonally varying the area (A), perimeter (P), and exposure duration of checkerboard patterns. Subjects judged either the area and duration of the presented shapes (area-time group) or the perimeter and duration (perimeter-time group) of the same figures. Perceived duration, area, and perimeter varied with changes in the uninstructed an the instructed stimulus dimensions. The discussion focuses on the ability of subjects to control the allocation of attention to instructed stimulus dimensions, as well as on the evidence in the data in favor of detailed sequential or fast holistic processing. It is suggested that the concept of stimulus complexity, defined as P2/A, is useful in describing the temporal and spatial illusions obtained in this study.

Attention↗