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Biomedical subjects

C A Becker

Publications and source records attributed to C A Becker.

11 recordsLinked to original sources

Equilibrium adsorption at crystal-melt interfaces in Lennard-Jones alloys.

Although the properties of crystal-melt interfaces have been extensively studied in pure materials, effects of alloying on the interfacial free energy remain relatively poorly understood. In this work we make use of Monte Carlo computer simulations for model binary Lennard-Jones alloys to explore the effects which variations in atomic-size mismatch and the chemical contributions to mixing energies have upon density and composition profiles, as well as the resulting magnitudes of equilibrium adsorption coefficients in concentrated alloys. We study four different model systems covering a range of chemical and size mismatch, finding relatively small adsorption values which are nevertheless statistically different from zero.

Journal Article↗

A randomized trial of treatment options for alcohol-abusing workers.

BACKGROUND: Employee-assistance programs sponsored by companies or labor unions identify workers who abuse alcohol and refer them for care, often to inpatient rehabilitation programs. Yet the effectiveness of inpatient treatment, as compared with a variety of less intensive alternatives, has repeatedly been called into question. In this study, anchored in the work site, we compared the effectiveness of mandatory in-hospital treatment with that of required attendance at the meetings of a self-help group and a choice of treatment options. METHODS: We randomly assigned a series of 227 workers newly identified as abusing alcohol to one of three rehabilitation regimens: compulsory inpatient treatment, compulsory attendance at Alcoholics Anonymous (AA) meetings, and a choice of options. Inpatient backup was provided if needed. The groups were compared in terms of 12 job-performance variables and 12 measures of drinking and drug use during a two-year follow-up period. RESULTS: All three groups improved, and no significant differences were found among the groups in job-related outcome variables. On seven measures of drinking and drug use, however, we found significant differences at several follow-up assessments. The hospital group fared best and that assigned to AA the least well; those allowed to choose a program had intermediate outcomes. Additional inpatient treatment was required significantly more often (P less than 0.0001) by the AA group (63 percent) and the choice group (38 percent) than by subjects assigned to initial treatment in the hospital (23 percent). The differences among the groups were especially pronounced for workers who had used cocaine within six months before study entry. The estimated costs of inpatient treatment for the AA and choice groups averaged only 10 percent less than the costs for the hospital group because of their higher rates of additional treatment. CONCLUSIONS: Even for employed problem drinkers who are not abusing drugs and who have no serious medical problems, an initial referral to AA alone or a choice of programs, although less costly than inpatient care, involves more risk than compulsory inpatient treatment and should be accompanied by close monitoring for signs of incipient relapse.

Adult↗

Chronic antidepressant and clonidine treatment effects on conflict behavior in the rat.

The present studies examined the effects of chronic treatment with several antidepressants and clonidine on conflict behavior. In daily ten-minute sessions, water-deprived rats were trained to drink from a tube which was occasionally electrified (0.25 or 0.5 mA). Electrification was signalled by a tone. Chronic desipramine (5 mg/kg, IP, b.i.d.) or clonidine (40 micrograms/kg, b.i.d.) treatment resulted in time-dependent anticonflict effects, with a latency to onset of approximately 3-4 weeks. In contrast, chronic buproprion (up to 10 mg/kg, IP, b.i.d.), mianserin (up to 10 mg/kg, IP, b.i.d.) or trazodone (up to 40 mg/kg, IP, b.i.d.) treatment resulted in at best only a weak anticonflict effect. The efficacy of these antidepressants and clonidine to increase punished responding when administered chronically correlates well with their efficacy as antipanic agents in man.

Animals↗

Endothelial response to perfluorochemical perfusion.

The purpose of this study was to evaluate, in vivo, the effect of perfluorochemical (PFC) blood substitutes on arterial endothelium following total blood replacement. Conscious-female-Sprague-Dawley rats (150-200 gms) were isovolumically exchange perfused with 3 blood volumes of PFC emulsion in an oxygen chamber. The exchange was performed at 0.5 ml/min via an indwelling-intracardiac-double-lumen catheter. One hour after the exchange, the animal was sacrificed and the circulatory system flushed free of blood and PFC emulsion with Dulbecco's solution, followed by perfusion fixation with glutaraldehyde solution. The heart, lungs and thoracic aorta were excised. The pulmonary arterial endothelial cell response was determined by scanning electron microscopy (SEM) following acute exposure to PFC emulsions under conditions of varied pH, oncotic pressure and emulsion age. These endothelial surfaces exhibited increased microvilli, leukocyte adhesion, fibrin deposition and subendothelium exposure. The magnitude of these abnormal responses varied with the degree of alkalinity and reduced oncotic pressure of the perfusate.

Animals↗

Semantic context effects in visual word recognition, sentence processing, and reading: evidence for semantic strategies.

Earlier research studying the effects of semantic context on single words suggested that subjects may have two strategies for using a context (Becker, 1980). The present research finds that the semantic context strategies may be used in reading short sentences. Further, individual differences in context effects both in a word-level task and in a sentence-level task are related to individual differences in reading continuous text. These results are presented within the framework of the verification model (Becker, 1976, 1980), and the implications for two-process theory (Stanovich & West, 1979, 1981) are discussed.

Adult↗

Semantic context and word frequency effects in visual word recognition.

Semantic context and word frequency factors exert a strong influence on the time that it takes subjects to recognize words. Some of the explanations that have been offered for the effects of the two factors suggest that context and frequency should interact, and other explanations imply additivity. In a recent study, Schuberth and Eimas reported that context and frequency effects added to determine their subjects' reaction times in a lexical decision (word vs. nonword) task. The present experiment reexamines this question with improved procedures. The data show that context and frequency do interact, with a semantic context facilitating the processing of low-frequency words more than high-frequency words.

Discrimination Learning↗

Allocation of attention during visual word recognition.

A dual-task paradigm was used to assess attentional processing demands during visual word recognition. By manipulating the difficulty of each task, it is argued that the procedure estimates the attention demands of the memory-access component of word recognition. Specifically, the the complexity of the secondary task was varied from a simple reaction time task to a choice reaction time task, and the difficulty of a lexical decision (word vs. nonword) primary task was varied by manipulating word frequency. A comparison of the effect of secondary task complexity across levels of word frequency showed that the difference between the two secondary tasks was larger for low-frequency words than for high-frequency words. This result, supported by other characteristics of the data, suggests that the memory-access processing in one type of word recognition task does demand attention.

Acoustic Stimulation↗

Sound concept, unhealthy in practice ... but at great expense to providers and patients.

Those states considering implementation of a TennCare-type program should learn from Tennessee's mistakes. Enough lead time should be allowed for the development of the program and for patients and providers to learn about the new program. It should be actuarially should and have strong oversight with provider input. Finally, it should be done in an open forum to allow public accountability.

Actuarial Analysis↗