Ramsey Spectroscopy of the 2S_{1/2} Hyperfine Interval in Atomic Hydrogen.

The 2S_{1/2} hyperfine interval in atomic hydrogen was measured using Ramsey spectroscopy with a thermal beam cooled to cryogenic temperatures. The measured value is 177 556 838.87(85) Hz, which represents the most precise determination of this interval to date. The 1S_{1/2} hyperfine interval f(1S_{1/2}) and the 2S_{1/2} hyperfine interval f(2S_{1/2}) can be combined to give the quantity D_{21}=8f(2S_{1/2})-f(1S_{1/2}), which mostly eliminates uncertainty due to nuclear structure effects and is well described by bound-state quantum electrodynamics. Using the value of f(2S_{1/2}) from this work gives a value of D_{21}^{expt}=48 959.2(6.8) Hz, which is in agreement with the theoretical value of D_{21}^{Theory}=48 954.1(2.3) Hz.

Time course of effective interventional left heart assist for limitation of evolving myocardial infarction.

Previous work has shown that if pulsatile left atrial-femoral artery bypass is instituted after occlusion of the left anterior descending coronary artery for from 15 minutes to 2 hours, it can significantly limit the size of the infarct resulting 4 hours later. This study investigated whether pulsatile left atrial-femoral artery bypass begun after more clinically pertinent periods of initial ischemia can still significantly limit infarct expansion. After baseline measurements of hemodynamics, tension-time index, and regional myocardial blood flow in 73 open-chest, adult dogs, the left anterior descending coronary artery was ligated for 15 minutes or 1, 2, 4, or 6 hours of unprotected ischemia. In the five control groups, the initial ischemic period was merely extended for another 4 hours. In the five experimental groups, the animals were placed on pulsatile left atrial-femoral artery bypass for another 4 hours after the initial ischemic period. At the end of each procedure, gentian violet was used to identify the area at risk of infarction, and triphenyltetrazolium chloride was used to delineate the area of infarct. The results showed a significant reduction in the area of infarct as a percentage of the area at risk in each bypass group compared with its control group for all ischemic periods of less than 6 hours. These findings suggest that the maximum permissible ischemic time delay for myocardial salvage by pulsatile left atrial-femoral artery bypass is one which is pertinent in a clinical setting. The results justify continued attempts to develop appropriate techniques for percutaneous application of this modality to patients with an evolving myocardial infarction.

Patient positioning and nasal intubation for carotid endarterectomy.

Exposure of a very rostral carotid bifurcation for endarterectomy may occasionally be difficult. We are reporting a simple yet effective way to gain several centimetres of exposure of the distal cervical portion of the internal carotid artery in this circumstance.

Effects of noise and noise reduction processing on the operation of the Nucleus-22 cochlear implant processor.

Cochlear implants, like other types of auditory sensory aids, become increasingly ineffective with increasing ambient noise levels. One method of signal processing to reduce additive random wideband noise, the INTEL method, has been used to good effect as an input preprocessor for the Nucleus-22 cochlear implant. The implant's own signal processor estimates and encodes pitch frequency and the frequencies of Formants 1 and 2. The study reported here shows that additive noise results in substantial deviations in formant frequency estimates from those that would be observed in the absence of noise. When noisy speech is preprocessed by the INTEL method to reduce noise intensity, the deviations in the frequency estimates for Formant 2 are substantially reduced.

Dropping in and dropping out: participation motives of current and former youth gymnasts.

This study examined motives for participating in and discontinuing sport for 106 competitive, recreational, and former youth gymnasts. Similar to previous studies on participation motives in children's sport, gymnasts cited multiple reasons for their attraction to sport with the most important being competence, fitness, and challenge for the competitive gymnasts; competence, fitness, fun and situational for the recreational gymnasts; and competence, action, challenge and fun for the former gymnasts. A factor analysis was conducted and revealed seven categories of motivational factors, similar to those found by Gill et al. (1983). No support was found for a relationship between motives for gymnastic participation and reasons for attrition. The most important reasons for leaving gymnastics were having other things to do, injuries, not liking the pressure, not having enough fun, and too time consuming.

Goal orientation and the modeling process: an individual's focus on form and outcome.

One's achievement goal orientation (e.g., task, ego) is suggested to reflect a differential focus on skill mastery and performance outcome (Duda, 1992). Goal orientation has further been suggested to be an important observer characteristic in the observational learning of motor skills (McCullagh, Weiss, & Ross, 1989). This study assessed the relationship between goal orientation and a focus on form and outcome aspects of a motor skill demonstration with college students (N = 30) having low perceived ability, knowledge, and experience in tennis. Participants viewed several videotaped demonstrations of a correctly performed tennis forehand and then visual recognition and verbal recall accuracy of form and outcome task characteristics were assessed. A canonical correlation analysis revealed a nonsignificant relationship between goal orientation and recall and recognition of form and outcome task characteristics. These results provide preliminary evidence to suggest that goal orientation may not be an important observer characteristic in the learning phase of the modeling process. Also, achievement goal orientations may not be associated with a differential focus on skill mastery or performance outcome but instead remain a reflection of divergent processes of success evaluation.

Returning injured athletes to competition: a role and ethical dilemma.

This study investigated the extent to which decisions by coaches and athletic trainers concerning the return of injured athletes to competition were influenced by the player's status and the game situation. Samples were drawn from Oregon high school and Canadian university basketball teams. Coaches and athletic trainers completed a questionnaire in which they decided whether an injured player should be returned to competition. The scenarios included winning, losing, or close games and involved a starter, first substitute, or bench player. Chi-square analyses revealed that coaches made decisions based on both a player's status and the game situation. In contrast, athletic trainers' decisions were not significantly influenced by these variables. Since the role of the coach seemingly makes it difficult to make health related decisions concerning injured players, athletic trainers should be responsible for such decisions.

A comparison of hearing-aid array processing techniques.

Microphone arrays have proven effective in improving speech intelligibility in noise for hearing-impaired listeners, and several array processing techniques have been proposed for hearing aids. Among the signal-processing approaches are classical delay-and-sum beamforming, superdirective arrays, and adaptive arrays. To directly compare the effectiveness of these different processing strategies, a 10-cm-long linear array was built using five uniformly spaced omnidirectional microphones. This array was used in the end-fire orientation to acquire speech and noise signals for a variety of array placements in two representative rooms. Both digital and simulated analog processing techniques were considered, with the array processing implemented in the frequency domain. The performance metric was the steady-state array gain weighted to represent the relative importance of the different frequency regions in understanding speech. The processing comparison indicates that digital systems are more effective than the simulated analog processing, and that both superdirective and adaptive digital array processing can provide more than 9 dB of weighted array gain.

Calorimetric studies of the haemoglobin-haptoglobin reaction.

Haptoglobin binds haemoglobin so firmly that there is practically no dissociation. It would be expected that the heat of the reaction would be relatively large. The development of the microcalorimeter by Benzinger offered the opportunity to measure the heat of reaction. The experiments were carried out in the Beckman 190B Microcalorimeter in two ways: (1) a constant amount of haptoglobin (Kabi; 65mg.) with different amounts of haemoglobin, and (2) a constant amount of haemoglobin (32.5mg.) with different amounts of haptoglobin. The proteins, each in 5ml. of 0.15m-phosphate buffer, pH7.4, were placed in equal-volume calorimeter cells. The heat produced/mg. of haemoglobin was calculated from the slope of the curve for a constant amount of haptoglobin and from the maximum heat for a constant amount of haemoglobin. This heat is about 70kcal./mole at 37 degrees . DeltaH varies with temperature, being -70.2 at 37 degrees , -29.7 at 20 degrees and 7.2 at 4 degrees . From the amount of haptoglobin required to attain maximum heat with 32.5mg. of haemoglobin and the amount of haemoglobin required to attain maximum heat with 65mg. of haptoglobin, it appears that at excess of haptoglobin there is competition between the reactions of 2moles of haptoglobin with 1mole of haemoglobin (or 2 alphabeta-chains) and 1mole of haptoglobin with 1mole of haemoglobin.

The relation between children's accuracy estimates of their physical competence and achievement-related characteristics.

The relationship between perceptions of competence and control, achievement, and motivated behavior in youth sport has been a topic of considerable interest. The purpose of this study was to examine whether children who are under-, accurate, or overestimators of their physical competence differ in their achievement characteristics. Children (N = 133), 8 to 13 years of age, who were attending a summer sport program, completed a series of questionnaires designed to assess perceptions of competence and control, motivational orientation, and competitive trait anxiety. Measures of physical competence were obtained by teachers' ratings that paralleled the children's measure of perceived competence. Perceived competence and teachers' ratings were standardized by grade level, and an accuracy score was computed from the difference between these scores. Children were then categorized as underestimators, accurate raters, or overestimators according to upper and lower quartiles of this distribution. A 2 x 2 x 3 (age level by gender by accuracy) MANCOVA revealed a significant gender by accuracy interaction. Underestimating girls were lower in challenge motivation, higher in trait anxiety, and more external in their control perceptions than accurate or overestimators. Underestimating boys were higher in perceived unknown control than accurate and overestimating boys. It was concluded that children who seriously underestimate their perceived competence may be likely candidates for discontinuation of sport activities or low levels of physical achievement.

Predictors of intrinsic motivation among adolescent students in physical education.

This study examined the relationships among social factors, individual differences, intrinsic motivation, and effort and persistence in the physical education context using cognitive evaluation theory as a framework. Female (n = 201) and male (n = 206) high school students completed measures of motivational climate, teaching style, perceived competence, self-determination, goal orientations, and intrinsic motivation. Teachers rated the students on effort and persistence in the class activities. Hypothesized relationships among the variables were tested using structural equation modeling. Results revealed that perceived competence and goal orientations directly predicted intrinsic motivation and mediated the effects of motivational climate and teaching style on intrinsic motivation. Intrinsic motivation directly predicted effort and persistence. Task goal orientation mediated the effects of learning climate on perceived competence and self-determination. The strongest predictors of intrinsic motivation and effort and persistence were task goal orientation perceived competence, and learning climate.

Fair Play for Kids: effects on the moral development of children in physical education.

Commitment to the principles of sportspersonship is an acknowledged goal for school physical education. However, few programs have been implemented to investigate moral development changes in physical activity settings. A field experiment was designed to examine the effect of participation in educational activities selected from Fair Play for Kids (1990) on the moral judgment, reason, intention, and prosocial behavior of children (N = 452) in the 4th through 6th grades. Six intact classrooms at each grade level (N = 18) were randomly assigned to the following groups: (a) control, (b) Fair Play for Kids curriculum during physical education only, or (c) Fair Play for Kids curriculum during all school subjects. Experimental protocol extended for 7 months of an academic year, and moral development indicators were assessed prior to and following the intervention. Using class as the unit of analysis, 3 x 2 (Group x Time) repeated measures analyses of variance revealed that both treatment groups were significantly higher than the control group at posttest for moral judgment, reason, and intention scores. For students within classes, repeated measures analyses showed that treatment group participants had significantly higher posttest scores on all 4 measures as compared to students in the control group. Results provide initial validation of the Fair Play For Kids curriculum for effecting change in the moral development of elementary school students.

Developmental modeling effects on the quantitative and qualitative aspects of motor performance.

The purpose of the present experiment was to replicate and extend previous developmental modeling research by examining the qualitative as well as quantitative aspects of motor performance. Eighty females of two age groups (5-0 to 6-6 and 7-6 to 9-0 years) were randomly assigned to conditions within a 2 x 2 x 2 (Age x Model Type x Rehearsal) factorial design. Children received either verbal instructions only (no model) or a visual demonstration with experimenter-given verbal cues (verbal model) of a five-part dance skill sequence. Children were either prompted to verbally rehearse before skill execution or merely asked to reproduce the sequence without prompting. Both quantitative (order) and qualitative (form) performances were assessed. Results revealed a significant age main effect for both order and form performance, with older children performing better than younger children. A model type main effect was also found for both order and form performance. The verbal model condition produced better qualitative performance, whereas the no model condition resulted in better quantitative scores. These results are discussed in terms of differential coding strategies that may influence task components in modeling.

"Show and tell" in the gymnasium revisited: developmental differences in modeling and verbal rehearsal effects on motor skill learning and performance.

Little research has investigated the observational learning process from a developmental perspective. The purpose of this study was to extend previous research by considering two factors: performance versus learning and sequencing versus form scores. Children (N = 60) comprising two age groups (5-0 to 6-11 and 8-0 to 9-11 years) were randomly assigned to verbal rehearsal only, model only, or model plus verbal rehearsal conditions. The task was a 6-part motor skill sequence in which proper sequencing and quality of form were assessed. A 2 x 3 x 4 (age group by model type by trial blocks) repeated measures MANOVA revealed a significant three-way interaction. Older children performed equally well under any of the model type conditions during both performance and learning. For younger children, a model plus rehearsal was superior to rehearsal only on sequence and form at performance and learning and superior to model only on sequence scores during the first two performance trial blocks. Model only and model plus rehearsal conditions were equally effective on form scores. These results suggest that age differences exist in the modeling of motor skills under conditions varying in model type, sequence and form scores, and performance and learning phases.

Modeling effects on children's form kinematics, performance outcome, and cognitive recognition of a sport skill: an integrated perspective.

This study examined the effectiveness of visual and verbal models during the initial phase of complex sport skill acquisition in children. Thirty-six girls between the ages of 7-0 and 8-11 years were randomly assigned to one of three experimental conditions in a 3 x 4 (Model Type x Trial Block) factorial design. A visual model performing an underhand modified softball pitch was viewed prior to each of four blocks of five practice trials. Verbal performance cues were added to the model at the second, third, or fourth trial block, according to the experimental condition. A multivariate repeated measures analysis of variance revealed a significant trial block main effect, with subjects showing improved matching of form kinematics to the model with increasing trials but no differences in performance outcome. More dramatic changes coincident with the addition of verbal cues were observed for some kinematic variables. Children exhibited better cognitive recognition of correct form as a function of increased exposure to the visual model.

Observational learning and the fearful child: influence of peer models on swimming skill performance and psychological responses.

This study examined the role of peer mastery and coping models on children's swimming skills, fear, and self-efficacy. Children (N = 24; M age = 6.2 years), who were identified as fearful of the water, were matched to control, peer-mastery, or peer-coping model conditions. Day 1 included a preintervention assessment. Days 2-4 included exposure to model conditions followed by a 20-min swimming lesson, Day 5 consisted of postintervention assessments, and a follow-up test was conducted 4 days later. Data were analyzed in a series of 3 x 3 (Model Type x Assessment Period) repeated measures analyses of variance on the dependent variables. Results revealed differences between modeling and control groups at postintervention and follow-up, but the small sample size and large within-group variability compromised many statistically significant findings. Calculation of effect sizes indicated moderate-to-large pre- to posintervention differences between control and modeling groups on skill, self-efficacy, and fear of swimming. These findings suggest that a modeling intervention combined with swimming lessons is a more effective behavior change agent for fearful children than swimming lessons alone.

Management of orbital-cranial trauma.

Orbital-cranial injuries have the greatest potential for death and disability of any condition treated by the ophthalmologist. An object that penetrates through the orbit into the brain may leave only a small entrance wound. Patients can have normal vision, neurologic exam, and plain x-rays despite trauma that may lead to meningitis, brain abscess, or pneumocephalus. The CT scan greatly aids in both the early and late management of blunt and penetrating orbital-cranial trauma. The detection of pneumocephalus may be the only clue that intracranial penetration has occurred. Blunt trauma can cause vision loss, ophthalmoplegia, ptosis, and intracranial injury. Management of orbital-cranial trauma frequently requires a team approach by the ophthalmologist and neurosurgeon due to the complexity of these injuries.