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D M Ennis

Publications and source records attributed to D M Ennis.

13 recordsLinked to original sources
PubMed2001

A Thurstonian model for the dual pair (4IAX) discrimination method.

In the dual pair method, the subject is presented with two stimuli in two pairs: One pair is composed of two samples of the same stimulus; the other pair is composed of two samples of different stimuli, one being the same as that in the identical pair. The task of the judge is to select the most different pair. The psychometric function for the dual pair method is derived and expressed in terms of a singly noncentral beta distribution. A table is provided that connects a measure of the degree of difference, d, to the probability of a correct response. This table assumes an unbiased observer and differencing decision rule. A table is provided to give an estimate of the variance of d , the experimental estimate of d. The power of the dual pair method is also investigated, and a formula to determine the sample size required to meet Type I and Type II error specifications is given. The dual pair method appears to be slightly less powerful than the duo-trio and the triangular methods. Experimental investigation is needed to explore the dual pair in applied research work.

Decision Making↗
PubMed1999

Azithromycin compared with penicillin G benzathine for treatment of incubating syphilis.

BACKGROUND: Preventive therapy is an important element of syphilis control efforts. No currently recommended, single-dose alternatives to penicillin G benzathine are available for treatment of incubating syphilis. OBJECTIVE: To evaluate the use of a single 1.0-g dose of azithromycin for treatment of persons recently exposed to sexual partners with infectious syphilis. DESIGN: Single-center, open-label, randomized pilot study to compare azithromycin with penicillin G benzathine therapy. Participants were evaluated serologically for 3 months. SETTING: Sexually transmitted disease clinic in Birmingham, Alabama. PARTICIPANTS: 96 participants who in the preceding 30 days had been exposed to partners with infectious syphilis through sexual intercourse. MEASUREMENTS: Syphilis prevention, as indicated by nonreactive serologic tests (rapid plasma reagin and fluorescent treponemal antibody-absorbed), throughout the 3-month follow-up. RESULTS: Among 96 participants enrolled, none of 40 evaluable persons in the azithromycin group and none of 23 evaluable persons in the penicillin group developed evidence of syphilis. Significantly more penicillin-treated participants (21 of 44 [48%]) than azithromycin-treated participants (12 of 52 [23%]) became nonevaluable during follow-up (P = 0.01). CONCLUSION: A single 1.0-g dose of azithromycin seems to be efficacious for prevention of syphilis in persons exposed to infected sexual partners.

Administration, Oral↗
PubMed1997

Decreased fat and nitrogen losses in patients with AIDS receiving medium-chain-triglyceride-enriched formula vs those receiving long-chain-triglyceride-containing formula.

OBJECTIVE: The purpose of this study was to compare two enteral formulas, differing only in fat source, for product acceptance, tolerance, and effect on fat malabsorption and nutritional status in subjects with acquired immune deficiency syndrome (AIDS). DESIGN: The double-blind, randomized 15-day trial was divided into a 3-day period in which solid food was consumed followed by a 12-day experimental period in which liquid formulas were consumed. SETTING/SUBJECTS: Twenty-three men and one woman with AIDS and fat malabsorption completed the study. The study was conducted in the General Clinical Research Center, University of Alabama Hospital, University of Alabama at Birmingham. Laboratory assays were performed in the Department of Nutrition Sciences. INTERVENTIONS: After 3 days of consuming a controlled, solid food diet containing 100 g fat per day from mixed sources to document fat malabsorption, subjects were randomly assigned to one of two groups. Each group received a liquid formula containing 35% of energy as fat for 12 days. One group received a formula containing 85% medium-chain triglycerides (MCTs) and the control group received a formula containing 100% long-chain triglycerides. MAIN OUTCOME MEASURES: Determinations included stool number, consistency, weight, and fat and nitrogen content; urine nitrogen and creatinine levels; and body weight. STATISTICAL ANALYSIS PERFORMED: Subject demographic and other baseline characteristics were compared using two-sample t tests; stool and urine assessments were compared between groups at the initial experimental period using two-sample t tests; changes from initial to final experimental periods were assessed by means of analysis of covariance; changes in pooled intake, body weight, and the number and consistency of bowel movements were also assessed using analysis of covariance. All statistical tests were two-tailed and considered significant at P < .05. RESULTS: Within-group comparisons indicated that subjects fed the MCT formula showed significantly decreased stool fat and stool nitrogen content (P = .01 and P = .03, respectively) and increased fat absorption (P = .03), whereas those fed the control formula did not. Differences in stool fat between the groups were not statistically significant. However, the difference in fat absorption from the initial to final formula period was significant (P = .04). Subjects consuming the MCT formula also tended to have a decreased number of bowel movements and abdominal symptoms, whereas subjects fed the control formula showed no improvement. All subjects maintained their body weights. APPLICATIONS: There may be advantages to using an MCT-based formula in the treatment of AIDS-associated malabsorption.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Probabilistic models for sequential taste effects in triadic choice.

Sequential effects and positional response bias are accounted for in new models for triadic choice. These models were applied to data on distilled water and dilute NaCl solutions by use of the triangular and 3-alternative forced-choice methods with 4 participants. The concept of a "conditional stimulus" is introduced to describe stimuli that are created partially by prior oral environmental effects. The effects of 1 or 2 prior stimuli on triadic choice was evaluated. The triad models used were based on a Thurstonian variant of M. W. Richardson's (1938) method of triads and a Thurstonian model for first choice among 3 possibly different stimuli. Maximum likelihood estimates of the scale values for conditional stimuli and bias parameters showed that it was necessary only to consider 1 prior stimulus. It was also shown that salt concentration differences are not the physical analog of the mental representations for the conditional stimuli. The results strongly suggest a water taste to salt taste continuum.

Adult↗
PubMed1995

The newer cephalosporins. Aztreonam and imipenem.

Many of the antimicrobial agents described here exhibit great advances over older drugs in terms of antimicrobial spectrum, clinical utility, and, sometimes, safety. The newer cephalosporins are useful for treatment of many common outpatient and inpatient infections. Aztreonam provides excellent coverage against a broad range of aerobic gram-negative bacteria, without the toxicity associated with aminoglycosides. Imipenem exhibits activity against an impressive array of pathogens. These antimicrobials are expensive, however, and some offer no advantages over older agents. Finally, all--including imipenem--are faced with increasing resistance of bacteria.

Aztreonam↗
PubMed1994

Triadic discrimination testing: refinement of Thurstonian and sequential sensitivity analysis approaches.

The effect of cognitive search strategies and variations in the oral environment on discrimination test performance were investigated. Subjects were required to discriminate between low concentration NaCl solutions and water using the 3-AFC and triangle test protocols. As predicted by Thurstonian modeling, subjects obtained a higher proportion of correct tests for the 3-AFC protocol than for the triangle protocol. The d' values obtained from both protocols corresponded. As predicted by the Sequential Sensitivity Analysis Model, which is largely based on changes in the oral environment, subjects obtained a higher proportion of correct tests for triads containing one NaCl stimulus than for triads containing one water stimulus. Measurement of physical signal strengths of the stimuli, by analysing the Na cation concentration change in the oral environment on tasting, indicated that the classical Thurstone-Ura two-distribution model was insufficient. The strong carry-over effects in the chemical senses require a model based on more than two distributions. It was also noted that subjects did not always use the search strategy required for a given test protocol. The artifactual effects of strategy change during an experiment are discussed.

Adaptation, Physiological↗
PubMed1994

Preference gives more consistent judgments than oddity only if the task can be modeled as forced choice.

Earlier data showed that subjects presented with two samples of distilled water and one of tap water were significantly more consistent in choosing the tap water as preferred than in identifying it as the odd sample in the set. The results were sometimes interpreted as demonstrating greater sensitivity for hedonic judgments than for oddity judgments. They are now shown to be explained by the statistical properties of the decision rules followed in different judgment tasks. In a new experiment, oddity and preference judgements were obtained in a replication of the original task with extra conditions. In two of the new conditions, the decision structure of a preference task was the same as that for the oddity task; in these conditions, performance was no better than with explicit oddity responses. The Thurstone-Ura model of triangle judgments proposed by Frijters predicts the results as an outcome of the greater statistical power of three-alternative forced choice tests compared with triangular tests. An excellent fit to all the data is given by a model wherein all subjects have the same d' for the difference between the water types but 25% of them prefer distilled water to tap water.

Choice Behavior↗
PubMed1988

Models for the duo-trio and triangular methods.

Duo-trio and triangular method models by Ura (1960, Japanese Union of Scientists and Engineers 7, 107-119) and David and Trivedi (unpublished Technical Report #55, Department of Statistics, Virginia Polytechnic Institute, 1962) for examining perceptual processes have proven to be very useful, but are limited to univariate phenomena. Recent Monte Carlo studies by Ennis and Mullen (1985, Chemical Senses 10, 605-608; 1986, Journal of Mathematical Psychology 30, 206-219), on the probabilities of correct decisions for multivariate responses, showed how they depend on discriminal distance, variance-covariance structure, and orientation in n-space. Mathematical models for the triangular and duo-trio method in the bivariate case were developed by Mullen and Ennis (1987, Psychometrika 52, 235-249). Formulation of the n-dimensional triangular method model was accomplished and problems in numerical integration were resolved by Kapenga et al. (1987, in Numerical Integration, P. Keast and G. Fairweather (eds), 321-328; Dordrecht: Reidel). The n-dimensional duo-trio method model is given in this paper and previous work on the triangular method is reviewed briefly.

Biometry↗
PubMed1978

Structural factors influencing the biodegradation of imides.

Comparative studies on the biodegradability of amides and imides are presented. Low-molecular-weight imides of varying chain lengths (4, 6, 7, 8, 18, and 20 carbons) were biodegrable. N-alkyl substitution of amides and imides resulted in non-biodegrable derivatives when the amide portion was greater than two carbons in length. N-alkyl-substituted derivatives of acetamide or diacetamide, however, were biodegrable. Several soil isolates, including Aspergillus niger and species of Flavobacterium and Alcaligenes, were capable of growth with imides as sole N or C sources.

Alcaligenes↗