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Results for “performance”

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PubMed1999

Effects of previous grazing nutrition and management on feedlot performance of cattle.

Management strategies designed to improve grazing animal performance can influence feedlot performance and carcass traits both positively and negatively. In spite of the economic relevance of potential interactions between grazing and finishing performance, controlled experiments evaluating integrated production systems are limited in number. Effects of grazing treatments can result from, or be overshadowed by, changes in gut fill, thus making it difficult to assign precise costs to different phases of production. Published reports have considered the effects of stocking rate, duration of grazing, forage characteristics, supplementation, and growth-promoting implants on subsequent finishing performance. Improvements in cattle performance attributed to changes in stocking rate generally have been neutral to positive with respect to effects on finishing performance. Comparisons among forages have led to the suggestion that forage species may contribute to differences in gastrointestinal fill of grazing cattle, thereby influencing gain and efficiency during the subsequent finishing phase. Creep-feeding suckling calves generally has increased preweaning performance but has had relatively little influence on performance during the subsequent finishing phase. Grain supplementation of stocker cattle during the grazing period has improved grazing performance, but effects on subsequent feedlot performance have been inconsistent. Potential carryover effects from protein and mineral supplementation also have been inconclusive. Lack of congruence among studies is puzzling but may be the consequence of highly varied production systems, differences in experimental procedures, and changes in gut fill or mass of internal organs. Based on the studies reviewed, the expression or absence of compensatory growth during the finishing phase appears to be related to the nutritional quality of forages utilized in the grazing period, with higher quality forages tending to yield greater compensatory effects. The bulk of evidence with suckling cattle and stocker implants suggests that effects on subsequent finishing performance are minimal. Attention is drawn to the noticeable lack of research pertaining to integrated production systems. A more thorough understanding of the interactions among grazing nutrition and management, finishing performance, and carcass traits is needed to facilitate greater economic exploitation of these relationships.

Animal Feed↗

PubMed1990

Improving financial performance: a study of 50 hospitals.

This article provides an analysis of key differences between a small sample of high-performing and low-performing hospitals where performance was defined as return on equity. Some of the more significant findings were: (1) high-performing hospitals achieve their superior performance through cost control rather than higher prices; (2) high-performing hospitals minimize their investment in plant assets and accounts receivable. They are also likely to have a newer plant than low-performing hospitals; (3) high-performing hospitals are not afraid to use debt in their capital structure, but they use significantly less debt than low-performing hospitals; (4) high-performing hospitals have set aside greater reserves for future plant replacement, which helps them to keep their level of debt reasonable and generates significant amounts of investment income; and (5) high-performing hospitals have greater market share than low-performing hospitals.

Accounts Payable and Receivable↗

PubMed2002

The effects of knowledge of performance and cognitive strategies on motor skill learning in children with cerebral palsy.

PURPOSE: The purpose of this research was to examine the effects of presenting augmented information to children with cerebral palsy during practice of a novel motor skill. METHODS: Single-subject designs with nonconcurrent baselines were used to study improvements in performance. Thirteen children with cerebral palsy were randomly assigned to one of three practice protocols and performed 36 ten-second trials to learn to move a Pedalo, a therapeutic exercise vehicle, backward. Each protocol involved a variable mix of practice under the following conditions: no augmented information, knowledge of performance, and knowledge of performance enhanced by a cognitive strategy. Performance was measured by changes in backward displacement (cm) of the Pedalo across trials. RESULTS: All 13 subjects demonstrated improvement in performance across phases. However, only eight subjects (62%) demonstrated a significant improvement in performance when the baseline and retention phases were compared. Of these eight subjects, one demonstrated significant improvement in performance with practice alone, two when provided with knowledge of performance, and five when provided with knowledge of performance and a cognitive strategy. CONCLUSIONS: This study suggests that children with cerebral palsy benefit greatly from practice of motor tasks and that some of these children may benefit from the use of cognitive strategies to enhance the role of knowledge of performance during practice of motor skills. However, sufficient time is required to successfully integrate the feedback into performance.

Journal Article↗

PubMed1997

Performance contracting for substance abuse treatment.

OBJECTIVE: To describe an innovation in performance contracting for substance abuse services in the State of Maine and examine data on measured performance by providers before and after the innovation. DATA SOURCES AND COLLECTION: From the Maine Addiction Treatment System (MATS), an admission and discharge data set collected by the Maine Office of Substance Abuse (OSA). The MATS data for this study include information on clients of programs receiving public funding from October 1, 1989 through June 30, 1994. Additional data are drawn from the contracts between the state and providers, and from service delivery reports submitted to OSA. STUDY DESIGN: Client-level performance measures were calculated directly from MATS using OSA's formulas and standards, and then aggregated to the treatment program level. Multivariate regression analysis was done for each performance indicator as a dependent variable with performance contracting, time, extent of state funding, and provider characteristics as independent variables. PRINCIPAL FINDINGS: Performance contracting is positively related to better performance for effectiveness indicators overall. Individual effectiveness indicators that showed improvement include drug use indicators (abstinence and reduction in use) and social functioning indicators. In addition, performance contracting is associated with an increase in efficiency performance, defined as delivery of the contracted amount of service, for agencies that depend heavily on OSA for funding. Finally, performance contracting appears unrelated to the special populations indicators that measure services to target populations that OSA considers harder to treat. CONCLUSIONS: There is tentative evidence of a relationship between provider performance and the introduction of performance contracting. More definite conclusions await more detailed analyses of client-level data.

Adult↗

PubMed1998

[Effect of noise on human mental rotation performance].

To investigate the effect of moderate level low frequency noise on human mental rotation performance, letter rotation and compass orientation tests were performed in 24 healthy young male subjects during 2 h exposure to 85-95dB (A), it was found that during 120 min exposure to noise of 85dB (A), the mean reaction time increased (P<0.05), performance of reaction time and total performance decreased (P<0.01) significantly as compared with control in letter rotation test, meanwhile, performance of reaction time and total performance at 120 min exposure were significantly higher than that at 30 min (P<0.05). During 120 min exposure to noise of 95dB (A), the mean reaction time increased (P<0.01), the performance of reaction time and total performance decreased (P<0.01) significantly as compared with control in compass orientation test, meanwhile, performance of reaction time at 120 min were significantly higher than that at 30 min(P<0.05). The results show that exposures to 85 dB(A) and 95 dB(A) noise for 2 h have certain effect on the performance of human mental rotation and may affect performance of complex tasks with a higher workload.

Adolescent↗

PubMed2005

The effect of caffeine on cognitive task performance and motor fatigue.

RATIONALE: In everyday life, people are usually capable of performing two tasks simultaneously. However, in a previous study we showed that during a fatiguing motor task, cognitive performance declined progressively. There is extensive literature on the (positive) effects of caffeine on cognitive and motor performance. These effects are most pronounced under suboptimal conditions, for example during fatigue. However, little is known about the effects of caffeine on cognitive performance during a fatiguing motor task. OBJECTIVE: This study was aimed to investigate whether a moderate dose of caffeine could attenuate the decline in cognitive performance during a fatiguing motor task. METHODS: The study consisted of a placebo and a caffeine (3 mg/kg) session. A total of 23 subjects completed these sessions in a semi-randomized and double-blind order. In each session, subjects performed maximal voluntary contractions of the index finger, a choice reaction time (CRT) task and a dual task consisting of a fatiguing motor task concomitantly with the same CRT task. After the fatiguing dual task, the CRT task was repeated. RESULTS: Caffeine improved cognitive task performance, in both the single and dual task, as shown by decreased reaction times together with unchanged accuracy. Cognitive performance in the dual task deteriorated with increasing fatigue. However, the decrease in cognitive performance in the beginning of the dual task, as observed in the placebo condition, was partly prevented by caffeine administration (i.e., no increase in reaction times). We found no effects of caffeine on motor parameters (absolute force, endurance time or electromyographic amplitude). CONCLUSIONS: Caffeine improved cognitive performance. This effect also extends under demanding situations, as was shown by the performance during the dual task, even during progressive motor fatigue.

Adolescent↗

PubMed2001

Maintaining alertness and performance during sleep deprivation: modafinil versus caffeine.

RATIONALE: The performance and alertness effects of modafinil were evaluated to determine whether modafinil should replace caffeine for restoring performance and alertness during total sleep deprivation in otherwise healthy adults. OBJECTIVES: Study objectives were to determine (a) the relative efficacy of three doses of modafinil versus an active control dose of caffeine 600 mg; (b) whether modafinil effects are dose-dependent; and (c) the extent to which both agents maintain performance and alertness during the circadian trough. METHODS: Fifty healthy young adults remained awake for 54.5 h (from 6:30 a.m. day 1 to 1:00 p.m. on day 3) and performance and alertness tests were administered bi-hourly from 8:00 a.m. day 1 until 10:00 p.m. day 2. At 11:55 p.m. on day 2 (after 41.5 h awake), subjects received double blind administration of one of five drug doses: placebo; modafinil 100, 200, or 400 mg; or caffeine 600 mg ( n=10 per group), followed by hourly testing from midnight through 12:00 p.m. on day 3. RESULTS: Performance and alertness were significantly improved by modafinil 200 and 400 mg relative to placebo, and effects were comparable to those obtained with caffeine 600 mg. Although a trend toward better performance at higher modafinil doses suggested a dose-dependent effect, differences between modafinil doses were not significant. Performance enhancing effects were especially salient during the circadian nadir (6:00 a.m. through 10:00 a.m.). Few instances of adverse subjective side effects (nausea, heart pounding) were reported. CONCLUSIONS: Like caffeine, modafinil maintained performance and alertness during the early morning hours, when the combined effects of sleep loss and the circadian trough of performance and alertness trough were manifest. Thus, equivalent performance- and alertness-enhancing effects were obtained with drugs possessing different mechanisms of action. However, modafinil does not appear to offer advantages over caffeine (which is more readily available and less expensive) for improving performance and alertness during sleep loss in otherwise normal, healthy adults.

Administration, Oral↗

PubMedDate not supplied

Relationships between performance and skin resistance evolution involving various motor skills.

The aim of this article was to question the classical inverted-U curve relationship between activation and performance. It was hypothesized that changes in performance were related to both activation and the degree of skill difficulty, suggesting a more complex relation. Fifty-one subjects took part in one of three experiments requiring sensory and motor anticipation abilities. They were divided into three different groups, each performing one particular anticipation task. Skin resistance was continuously recorded during task performance. This autonomic variable is well known to be a reliable index in predicting activation variations. The first task, carried out in a seated position, was to intercept a moving spot on a computer screen by pressing the space bar on the keyboard. The second task, performed standing, required subjects to intercept a moving table tennis ball with palm of the hand, by extending the forearm and the arm. The third task, executed in movement was performed on a volley-ball ground. The aim was to hit a ball to reach a moving human target, using the forearm-blow technique. Results showed that 90.9% of subjects'performance in Experiment 1 was related to skin resistance tonic level variations, thus establishing a strong relationship between performance and arousal. Subjects' performance (43.8%) in Experiment 2 was related to skin resistance tonic level variations, whereas only 12.5% of performance was related to this variable in Experiment 3. In conclusion, tonic level variations can only account for success or failure in the first experiment. Conversely, success or failure were dependent upon information processing, decision making, and motor execution in the third experiment. The second experiment, requiring intermediate abilities, was found to show intermediate results. The role of skin resistance tonic level fluctuations and their use in the study of sporting performance are discussed, suggesting that arousal/performance relationships do not correspond to a simple inverted-U curve in complex motor skills requiring a steady level of arousal.

Adolescent↗

PubMed2004

Measuring physical performance via self-report in healthy young adults.

Discrepancies exist in literature as to what extent self-reporting can replace performance-based testing. To answer this question, self-reports and performance tests should measure identical constructs. Previous studies did not measure identical constructs. The objective of our study was to investigate to what extent self-reporting can replace performance-based testing. Seventy-two healthy subjects were tested. The constructs of the self-reports and the performance tests covered the same components to enable a comparison of self-reports and performance test results. Three different self-reports and a performance test were used to measure physical performance. Additionally, rating of perceived exertion was measured after the subjects lifted a reference weight to predict maximal lifting performance. The controls were age, gender, educational level, subject's participation in fitness, availability of reference data, motivation, attitude, general self-efficacy, and mood. Results showed that all lifting tasks could be predicted, though not solely via self-reporting. A prediction of the performance test results with a margin of +/-5 kg of error could be made for at least 79% of the subjects, via gender, self-reporting, and subject's participation in fitness. Self-reporting may not replace performance testing, although performance testing can be predicted with a margin of error of +/- 5 kg for at least 79% of the healthy subjects.

Adult↗

PubMed2004

Performance requirements of physically strenuous occupations: validating minimum standards for muscular strength and endurance.

Employment rights legislative mandates passed in the USA over the last three decades emphasize the importance of validating performance standards for physically strenuous occupations. This study validated minimally acceptable standards for the muscular strength and endurance necessary to perform fire suppression activities. Incumbent firefighters (n=153) selected for key demographic characteristics completed a simulated set of firefighting tasks (Fire Suppression Evolution) and then a Predictor Test Battery of physical abilities tests. Regression analysis revealed that three predictor test items (hose drag/high rise pack carry; arm lift; arm endurance) combined to significantly predict performance time of the Fire Suppression Evolution (p < or =0.01). Firefighters (n=41) rating videotaped performance times of the Fire Suppression Evolution determined that more than one-half a standard deviation slower than the mean time established by the incumbents reflected unacceptable performance. Approximately 80% of incumbent firefighters passed the minimally acceptable performance standard. Use of the 3-predictor test battery would correctly identify 89% of successful performers and 72% of unsuccessful performers. This study demonstrates that validation of minimal physical performance standards will identify a cohort of individuals with a high probability of not being able to perform critical fire suppression activities. This finding has important implications for examining the relationship between physical performance standards and medical and economic outcomes.

Adult↗

PubMed1996

Effect of divergent self-monitoring strategies on motor performance and emotion as a function of alternating task complexity.

The aim of this study was to determine the effectiveness of implementing different self-monitoring (SM) strategies as a function of varying task complexity on a computer game, 'Shufflepuck'. Self-monitoring theory suggests that positive self-monitoring (PSM) results in better performance for difficult tasks, whereas negative self-monitoring (NSM) is preferable for easy tasks. When SM was tested under easy and complex task conditions, it was found that performance effectiveness was a function of matching appropriate task difficulty with the SM strategy. Unpaired t-tests compared the first set of 100 trials (pre-task) with the second set of 100 trials (post-task) on a computer skills game requiring hand-eye coordination. The results showed that subjects who changed from the difficult task/PSM condition to the easy task/PSM condition (different task, same SM strategy) performed significantly poorer (P < 0.001) than subjects who changed from the difficult task/PSM condition to the easy task/NSM condition (different task, different SM strategy). A second unpaired t-test comparing the two sets of difference performance scores indicated that performance was significantly superior for subjects using the PSM than the NSM strategy while performing the difficult task (P < 0.05). That is, changing from the easy task/NSM condition to the difficult task/NSM condition produced poorer performance than changing from the easy task/NSM to the difficult task/PSM condition. In terms of subjects' emotions, the use of NSM and PSM when performing easy and difficult tasks, respectively, resulted in markedly less negative affect (P < 0.01), but did not influence positive affect, on pre- and post-task comparisons. Finally, correlations between affect and performance, based on pre- and post-performance and affect scores, were moderate to high. Implications of the present results for slumps in sport performance are offered.

Exercise↗

PubMed2005

Factors affecting resident performance: development of a theoretical model and a focused literature review.

PURPOSE: The clinical performances of physicians have come under scrutiny as greater public attention is paid to the quality of health care. However, determinants of physician performance have not been well elucidated. The authors sought to develop a theoretical model of physician performance, and explored the literature about factors affecting resident performance. METHOD: Using expert consensus panel, in 2002-03 the authors developed a hypothesis-generating model of resident performance. The developed model had three input factors (individual resident factors, health care infrastructure, and medical education infrastructure), intermediate process measures (knowledge, skills, attitudes, habits), and final health outcomes (affecting patient, community and population). The authors used factors from the model to focus a PubMed search (1967-2002) for all original articles related to the factors of individual resident performance. RESULTS: The authors found 52 original studies that examined factors of an individual resident's performance. They describe each study's measurement instrument, study design, major findings, and limitations. Studies were categorized into five domains: learning styles/personality, social/financial factors, practice preferences, personal health, and response to job environment. Few studies examined intermediate or final performance outcomes. Most were single-institution, cross-sectional, and survey-based studies. CONCLUSIONS: Attempting to understand resident performance without understanding factors that influence performance is analogous to examining patient adherence to medication regimens without understanding the individual patient and his or her environment. Based on a systematic review of the literature, the authors found few discrete associations between the factors of individual resident and the resident's actual job performance. Additionally, they identify and discuss major gaps in the educational literature.

Adult↗

PubMed2001

Comparing performance on a simulated 12 hour shift rotation in young and older subjects.

OBJECTIVES: To simulate a 12 hour shift rotation and measure the difference in performance if any, between older and younger subjects. Significant reductions in neurobehavioural performance during shift work and particularly night work have long been recognised. There are conflicting reports of the effects of 12 hour shifts on performance, alertness, and safety. Furthermore, research suggests that older shift workers have more sleep disruption and maladaption to shift work. When this is combined with longer hours at work there may be considerable reductions in performance for older compared with younger workers. METHODS: Thirty two subjects were allocated to groups according to age. Group one had 16 subjects with a mean (SD) age of 21.2 (2.7) years, and group two had 16 subjects with a mean (SD) age of 43.9 (6.8) years. Subjects came to the laboratory for six consecutive days and completed a simulated 12 hour shift rotation consisting of two 12 hour day shifts (0700-1900), followed by two 12 hour night shifts (1900-0700). During the work period subjects completed a computer administered neurobehavioural performance task every hour. RESULTS: Performance for the older subjects was consistently lower than for the younger subjects. There was a significant difference in performance across the shift between older and younger subjects. There was a significant change in performance across the shifts in the older subjects, such that performance significantly increased across the day shifts and decreased across the night shifts. By contrast, the younger subjects were able to maintain performance across both day shifts and the second night shift. CONCLUSIONS: There are significant differences in performance of older and younger subjects during a simulated 12 hour shift rotation. Future studies both in the field and the laboratory would be useful in determining whether this is typical and if there are any important consequences for the older worker on 12 hour shifts.

Adolescent↗

PubMed2003

The influence of subjective alertness and motivation on human performance independent of circadian and homeostatic regulation.

Endogenous circadian rhythmicity and sleep-wake homeostasis are robust regulators of human alertness and performance, yet few studies have examined how these regulatory processes affect motivation. Moreover, the influence of alertness and motivation on performance, independent of circadian phase and hours awake, has not been studied. Healthy subjects, 12 males and 3 females, ages 20 to 41, participated in a 2-week 28-h forced desynchrony protocol to address these issues. Subjects performed a battery of tests every 2 hours during scheduled wakefulness. Performance on a mathematical addition test and ratings of alertness and motivation on visual analog scales were analyzed. Performance scores were categorized as being associated with the highest or lowest alertness and motivation ratings for each circadian phase/hours awake bin to determine whether high levels of alertness and motivation resulted in higher performance scores above and beyond the effects of circadian and homeostatic regulation. Motivation varied significantly as a function of circadian phase and hours awake. Motivation and alertness were correlated. When circadian phase and hours awake were accounted for, performance was better when alertness and motivation ratings were highest and worse when those ratings were lowest. The present findings suggest that human performance is influenced by alertness and motivation independent of circadian phase and hours awake. Future studies examining the influence of circadian phase and sleep-wake homeostasis on human performance also should assess alertness and motivation to aid in the interpretation of performance data. Such studies also may aid in the development of countermeasures to improve human performance.

Adult↗

PubMed2003

Warm up II: performance changes following active warm up and how to structure the warm up.

While warm up is considered to be essential for optimum performance, there is little scientific evidence supporting its effectiveness in many situations. As a result, warm-up procedures are usually based on the trial and error experience of the athlete or coach, rather than on scientific study. Summarising the findings of the many warm-up studies conducted over the years is difficult. Many of the earlier studies were poorly controlled, contained few study participants and often omitted statistical analyses. Furthermore, over the years, warm up protocols consisting of different types (e.g. active, passive, specific) and structures (e.g. varied intensity, duration and recovery) have been used. Finally, while many studies have investigated the physiological responses to warm up, relatively few studies have reported changes in performance following warm up. The first part of this review critically analyses reported changes in performance following various active warm-up protocols. While there is a scarcity of well-controlled studies with large subject numbers and appropriate statistical analyses, a number of conclusions can be drawn regarding the effects of active warm up on performance. Active warm up tends to result in slightly larger improvements in short-term performance (<10 seconds) than those achieved by passive heating alone. However, short-term performance may be impaired if the warm-up protocol is too intense or does not allow sufficient recovery, and results in a decreased availability of high-energy phosphates before commencing the task. Active warm up appears to improve both long-term (>/=5 minutes) and intermediate performance (>10 seconds, but <5 minutes) if it allows the athlete to begin the subsequent task in a relatively non-fatigued state, but with an elevated baseline oxygen consumption (VO(2)). While active warm up has been reported to improve endurance performance, it may have a detrimental effect on endurance performance if it causes a significant increase in thermoregulatory strain. The addition of a brief, task-specific burst of activity has been reported to provide further ergogenic benefits for some tasks. By manipulating intensity, duration and recovery, many different warm-up protocols may be able to achieve similar physiological and performance changes. Finally, passive warm-up techniques may be important to supplement or maintain temperature increases produced by an active warm up, especially if there is an unavoidable delay between the warm up and the task and/or the weather is cold. Further research is required to investigate the role of warm up in different environmental conditions, especially for endurance events where a critical core temperature may limit performance.

Exercise↗

PubMed2000

Establishing stable test performance in tests from the Behavioral Assessment and Research System (BARS).

Research to identify adverse effects in humans chronically exposed to neurotoxic substances in the workplace or environment typically assesses people at one point in time in a cross-sectional study. The most widely used strategy employs performance measures taken from a single point in time and compares these with either performance of a control group or established normative data. However, multiple comparison points of the same people on the same test allow the dissection of acute--from chronic--exposure effects, among other important questions. When performance measures are used from multiple points in time, within-subject deviations are examined. For either research design, the goal is to minimize the effects of practice and to obtain stable performance on a test. Demographic variables such as age, education, and cultural background or ethnicity influence performance on neurobehavioral tests. These variables may also influence the development of stable performance. Different populations may have different learning curves so that stable performance on a test is achieved with different amounts of practice. This is especially important when making comparisons across groups that may not have equivalent backgrounds. The performance of three groups, English-speaking adults, Spanish-speaking adolescents, and Spanish-speaking migrant adolescents, was examined. Each group completed a battery of neurobehavioral tests from the Behavioral Assessment and Research System (BARS) during four sessions. Repeated measures ANOVAs were used to investigate performance across time. Tests measuring motor performance produced stable performance from the first session. More complex tasks that involved attention and memory showed a practice effect across sessions.

Adolescent↗

PubMedDate not supplied

Right and left handedness defined: a multivariate approach using hand preference and hand performance measures.

OBJECTIVE: The major aim of this study was to determine whether a combination of hand preference inventories and hand performance measures identifies distinct handedness groups. If distinct groups are identified, then these subgroupings can be used in future studies to learn more about the neurobiology of these distinct handedness groups. BACKGROUND: Although most individuals classify themselves as right- or left-handed, it is not entirely clear whether handedness should be determined based on preference inventories, hand performance tasks, or a combination of these measures. Given that hand preference is linked in part to hemispheric specialization of language, it is important to clearly define hand preference groups if lateralized differences between right- and left-handers are to be explored. Healthy adult right- and left-handers were examined from a multivariate perspective in an attempt to determine whether handedness subgroups exist within performance data. METHOD: Hand preference of 62 right- and left-handed male and female adults was assessed using items from Briggs and Nebes' and Oldfield's handedness inventories. Individuals were assigned to right- and left-hand preference groups, both by visually inspecting the distribution of preference scores and via cluster analysis. Asymmetries in performance of unimanual motor tasks (grooved pegboard, finger-tapping, and grip strength) were then examined using a multivariate approach. RESULTS: Sixteen items from the two-handedness inventories were used to determine preference-based handedness groups. Two non-overlapping groups, right- and left-hand preference, were identified. Writing hand was highly correlated with hand-preference group, as only three individuals in the entire sample wrote with the non-preferred hand. The expected unimodal distributions of performance asymmetry scores, known as laterality quotients (LQs), were seen. However, when those LQs were viewed from a multivariate perspective, distinct performance-based groups emerged. In more than 90% of the observed cases, the performance-based groups corresponded to preference-based groups. No sex differences were found; the relationship between preference and performance measures was not significantly different for men and women. CONCLUSIONS: Writing hand was highly correlated with scores from a hand preference inventory. In contrast, the use of a single hand performance measure, finger tapping or pegboard, did not always correctly classify an individual as right- or left-handed. However, when both of these hand performance measures were used together. individuals were correctly classified as right- or left-handed. Using this approach, two approximately non-overlapping groups, right- and left-handers, emerged. Thus, handedness is probably not a one-dimensional trait or behavior, and must be defined using multiple measures that assess different aspects of hand preference and performance. The implications for hemispheric specialization of language and neural asymmetry research are discussed.

Adult↗

PubMed2001

Evaluation of confocal microscopy system performance.

BACKGROUND: The confocal laser scanning microscope (CLSM) has been used by scientists to visualize three-dimensional (3D) biological samples. Although this system involves lasers, electronics, optics, and microscopes, there are few published tests that can be used to assess the performance of this equipment. Usually the CLSM is assessed by subjectively evaluating a biological/histological test slide for image quality. Although there is a use for the test slide, there are many other components in the CLSM that need to be assessed. It would be useful if tests existed that produced reference values for machine performance. The aim of this research was to develop quality assurance tests to ensure that the CLSM was stable while delivering reproducible intensity measurements with excellent image quality. METHODS: Our ultimate research objective was to quantify fluorescence using a CLSM. To achieve this goal, it is essential that the CLSM be stable while delivering known parameters of performance. Using Leica TCS-SP1 and TCS-4D systems, a number of tests have been devised to evaluate equipment performance. Tests measuring dichroic reflectivity, field illumination, lens performance, laser power output, spectral registration, axial resolution, laser stability, photomultiplier tube (PMT) reliability, and system noise were either incorporated from the literature or derived in our laboratory to measure performance. These tests are also applicable to other manufacturer's systems with minor modifications. RESULTS: A preliminary report from our laboratory has addressed a number of the QA issues necessary to achieve CLSM performance. This report extends our initial work on the evaluation of CLSM system performance. Tests that were described previously have been modified and new tests involved in laser stability and sensitivity are described. The QA tests on the CLSM measured laser power, PMT function, dichroic reflection, spectral registration, axial registration, system noise and sensitivity, lens performance, and laser stability. Laser power stability varied between 3% and 30% due to various factors, which may include incompatibility of the fiber-optic polarization with laser polarization, thermal instability of the acoustical optical transmission filter (AOTF), and laser noise. The sensitivity of the system was measured using a 10-microm Spherotech bead and the PMTs were assessed with the CV concept (image noise). The maximum sensitivity obtainable on our TCS-SP1 system measured on the 10-microm Spherotech beads was approximately 4% for 488 nm, 2.5% for 568 nm, 20% for 647 nm, and 19% for 365 nm laser light. The values serve as a comparison to test machine sensitivity from the same or different manufacturers. CONCLUSIONS: QA tests are described on the CLSM to assess performance and ensure that reproducing data are obtained. It is suggested strongly that these tests be used in place of a biological/histological sample to evaluate system performance. The tests are more specific and can recognize instrument functionality and problems better than a biological/histological sample. Utilization of this testing approach will eliminate the subjective assessment of the CLSM and may allow the data from different machines to be compared. These tests are essential if one is interested in making intensity measurements on experimental samples as well as obtaining the best signal detection and image resolution from a CLSM. Published 2001 Wiley-Liss, Inc.

Electric Power Supplies↗