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At least 37 records · Page 2Linked to original sources
PubMed1999

Intraocular lens power prediction in a vietnamese population. A study to establish a limited set of intraocular lens powers that could be used in a vietnamese population.

AIM: To determine a range of dioptric powers for Intraocular Lenses (IOLs) that would cover at least 95% of the Vietnamese population attending hospital for cataract removal and IOL implantation. OBJECTIVE: To determine the ocular axial lengths and keratometric powers of people attending for cataract surgery at a hospital in Vietnam and hence predict the intraocular lens powers required for emmetropia for this population. HYPOTHESIS: 95% of the population attending a Vietnamese hospital for cataract and intraocular lens surgery would be within +/- 4.5 dioptres of the mean predicted emmetropic intraocular lens power. STUDY DESIGN: A case series. STUDY FACTORS: Axial length, keratometric power, age, sex, preoperative refractive status, preoperative vision, ethnicity. OUTCOME: Intraocular lens power for emmetropia. RESULTS: 346 adults attending for cataract surgery at the Hue Central Hospital, Vietnam were examined. The mean axial length was found to be 22.96 mm +/- 0. 99 (range 20.37-27.25), median 23.01 mm. The mean corneal power was 44.24 dioptres +/- 1.53 (range 39.50-49.00), median 44.5 dioptres. Using the SRK/T formula, with an "A" constant of 118.3, the mean predicted intraocular lens power required for emmetropia was 21.44 dioptres +/- 2.77 (range 10.87-27.25), median 21.56 dioptres. The mean predicted IOL power for females was 21.94 dioptres +/- 2.60 (range 13.84-29.68), median 22.13 dioptres. The mean predicted IOL power for males was 20.72 dioptres +/- 2.84 (range 10.87-28.95), median 20.66 dioptres. conclusion 95% of the population attending for cataract surgery were within 5.5 dioptres of the mean predicted emmetropic IOL power.

Adolescent↗
PubMed2005

Influence of different relative intensities on power output during the hang power clean: identification of the optimal load.

The influence of different relative intensities on power output was investigated in the present study in order to identify the optimal load that maximizes power output during the hang power clean. Fifteen men (age: 22.1 +/- 2.0 years, height: 180.1 +/- 6.3 cm, and body mass: 89.4 +/- 14.7 kg) performed the hang power cleans on a forceplate at 30-90% of one repetition maximum (1RM). Peak power was maximized at 70% 1RM, which was, however, not significantly different from peak power at 50, 60, 80, and 90% 1RM. Average power also was maximized at 70% 1RM, which was not significantly different from average power at 40, 50, 60, 80, and 90% 1RM. It was concluded that (a) the relative intensity had a significant influence on power output, and (b) power output can be maximized at a submaximal load during the hang power clean.

Adult↗
PubMed1999

Acoustically stimulated transient power scattering explains enhanced detection of the very low velocities in myocardial capillaries by power Doppler imaging: an in vitro study.

BACKGROUND: Although enhanced detection of myocardial perfusion signals by power Doppler imaging during contrast echocardiography has been noted, flow velocities in the coronary microvasculature should generally be below the threshold for Doppler motion detection. It has been suggested that in this situation nonlinear scattering related to acoustically stimulated microsphere oscillation or destruction may be responsible for the detected Doppler shift. METHODS AND RESULTS: This study examined the behavior of MRX 115 (ImaRx Pharmaceuticals) microbubbles during harmonic and nonharmonic power Doppler imaging at varying power outputs (mechanical indexes 0. 3, 0.5, 0.7, and 0.9) in a perfusion tube model under zero-flow conditions. Boluses of MRX 115 0.5-mL suspension were introduced into the model, and flow was halted during each imaging period. Once power Doppler imaging was implemented, a signal was detected as unique sparkling color pixels corresponding to individual bubble destruction events, even in the absence of contrast movement. This phenomenon continued until all contrast bubbles disappeared from the region subjected to power Doppler imaging, usually within 35 to 40 seconds. Off-line videointensity measurements showed that initial power Doppler signal intensity and maximum signal decay rates increased parallel to increasing power output and were substantially greater for nonharmonic than for harmonic imaging modes. CONCLUSION: This relationship between signal intensity and decay rate and acoustic power output suggests that transient scattering related to bubble destruction is responsible for generation of the power Doppler signal in the absence of flow. This would explain the enhanced detection of the very low velocity flows in the myocardial capillaries by power Doppler contrast imaging.

Blood Flow Velocity↗
PubMed1996

Improved agreement of foot segmental power and rate of energy change during gait: inclusion of distal power terms and use of three-dimensional models.

Traditional models used to calculate foot segmental power have yielded poor agreement between foot power and the rate of energy change during the stance phase of gait and limited the applicability of foot segmental power analyses to swing phase only. The purpose of this study was to improve the agreement of foot segmental power and rate of energy change by using more inclusive models to calculate foot segmental power and energy. The gait of 15 adult subjects was studied and models were used to calculate foot segmental power that included either the proximal terms only (Model P, the most common method in the literature) or both proximal and distal terms (Model PD, a mathematically complete model). Power and energy terms were computed in two ways, from sagittal plane vector components only (two-dimensional condition) and from complete three-dimensional components (three-dimensional condition). Results revealed that the more inclusive the model, the higher the agreement of foot power and rate of energy change. During stance phase, Model P produced poor agreement (r(c) = 0.108) for both two-dimensional and three-dimensional conditions, Model PD-2D yielded higher agreement (r(c) = 0.645), and Model PD-3D exhibited nearly perfect agreement (r(c) = 0.956). The advantages of a segmental power analysis include the ability to identify the mechanisms of energy transfer into and out of the foot during movement. The results of this study suggest that foot power analyses are valid when using Model PD-3D to describe foot function during locomotion.

Adult↗
PubMed1975

Ventricular performance and energy of compression, power, and rate of change of power during isovolumic contraction.

During isovolumic contraction, there is a calculabe compression of the blood within the ventricle. Energy is expended by the ventricle during isovolumic contraction, and some of it is transferred to the blood in the form of elastic compression. The rate of energy transfer (power) and acceleration of energy transfer (rate of change of power) during isovolumic contraction were calculated based upon considerations of the energy of compression. In anaesthetized dogs, the isovolumic energy of compression was 42 plus or minus 6 (mean plus or minus SE) dyn cm; peak isovolumic power was 1,400 plus or minus 300 dyn cm sec-1; and peak rate of change of power was 56,000 plus or minus 15,000 dyn cm sec-2. During states of augmented contractility induced by isoproterenol, the peak acceleration of energy expeniditure (peak rate of change of power) increased to 126,000 plus or minus 33,000 dyn cm sec-2 (p smaller than 0.001). Conversely, with a reduction of contractility induced by propranolol, the peak isovolumic rate of change of power decreased to 30,000 plus or minus 5,700 dyn cm sec-2 (p smaller than 0.001). The peak rate of change of power was unaffected by changes of the afterload. A trend, however, suggests that it may be affected by preload. The derivations of the isovolumic energy of compression, power, and rate of change of power are based upon firm principles of fluid dynamics. No assumptions related to ventricular geometry, synergy of contraction, or characteristics of muscle fibers are implied. Because of its physiological meaning and the theoretical validity of its derivation, an expression such as the isovolumic peak rate of change of power, when utilized as an index of ventricular performance, would appear to be of value.

Animals↗
PubMed1975

The power struggle: definition and evaluation of power of muscular performance.

The authors define five different measurements of power of muscular performance. Using an isokinetic dynamometer, the velocity of motion is constant and thus can be controlled. Power, therefore, can be readily assessed. The speed of muscular contraction is of physiological and functional interest. The time it takes for muscles to develop force, the rate at which muscles can contract and sustain a force throughout the range of motion, and the relationship of speed to force are all facets of power. At least five terms which connote power of muscular performances are used today. These terms are power, peak power, average power, instantaneous power, and contractile power. The current misunderstanding of the terms and their misuses are discussed. Suggestions are offered for circumventing confusion in using power to describe motor performance.

Humans↗
PubMed1993

Theorizing about power: intersecting the ideas of Foucault with the "problem" of power in family therapy.

How to theorize about power has been a controversial issue in systemic family therapy, which, in its understanding of power, has shown the legacy of Gregory Bateson's ideas in terms of its earlier censorship of the concept of power as well as in the way in which the more recent challenges continue to be framed in relation to Bateson's position. This essay examines the work of the French philosopher, Michel Foucault, and his ideas on power in relation to family therapy themes. The main aim in intersecting Foucault's ideas with the "problem" of power in family therapy is to shed a different light on the way in which family therapy has theorized about power. A strong point of connection is made between Foucault's commitment to a relational analysis of power and family therapy's commitment to recursive analysis. However, a number of major contrasts are also identified. These contrasts are used to underline the need for family therapy to abandon the restrictions of Bateson's ideas on power, and to tackle the task of developing and using a recursive understanding of power.

Ethics, Medical↗
PubMed1996

[Nursing and power--use of the so-called poststructuralism theory for the analysis of the power-relationships in the "female" nursing professional].

Nursing and power. Poststructuralism and its application to the power-relationships in the "female" occupation of nursing The theory of Foucault is used to outline a "genealogy" of nursing, historically a female occupation, subordinate to medicine. Foucault's ideas about power, discourse and panopticon are analysed in relation to nursing. The concept of discourse enables the writer to see the "feminine ideology" of society as the effect of power on the identity, behaviour and expression of emotion of women in nursing. The hospital and the "Mutterhaus" can be understood as panoptical institutions. Hospital nurses are in a position in which they have powers of disciplining patients and at the same time are themselves subject to surveillance and normalisation. As a concrete example, the techniques of using power, which originate from monasteries, form "norm-traps" when applied to nursing. Finally, not only the question of power, but also that of resistance to power, is addressed. Professionalisation and the move towards science-based nursing can be seen as "counter discourse". This is meant to set up the nurses' own knowledge base, their understanding of the nurse-patient relationship and of nursing practice, against the view of nursing as a profession subordinate to medicine. Foucault's view of power and resistance leads the writer to align herself with "the other side", in this case professionalisation in nursing. But at the same time one is invited to take the offensive in the debate of old and new contradictions.

Existentialism↗
PubMed2002

Power dressing and meta-analysis: incorporating power analysis into meta-analysis.

AIMS: This paper highlights the lack of consideration that is given to power in the health and social sciences, which is a continuing problem with both single study research and more importantly for meta-analysis. BACKGROUND: The power of a study is the probability that it will lead to a statistically significant result. By ignoring power the single study researcher makes it difficult to get negative results published and therefore affects meta-analysis through publication bias. Researchers using meta-analysis, who also ignore power, then compound the problem by including studies with low power that are more likely to show significant effects. METHOD: A simple means of calculating an easily understood measure of effect size from a contingency table is demonstrated in this paper. A computer programme for determining the power of a study is recommended and a method of reflecting the adequacy of the power of the studies in a meta-analysis is suggested. An example of this calculation from a meta-analytic study on intravenous magnesium, which produced inaccurate results, is provided. CONCLUSION: It is demonstrated that incorporating power analysis into this meta-analysis would have prevented misleading conclusions being reached. Some suggestions are made for changes in the protocol of meta-analytic studies, which highlight the importance of power analysis.

Bias↗
PubMed2006

Assessment of maximal aerobic power and critical power in a single 90-s isokinetic all-out cycling test.

The purpose of this study was to establish the validity of a 90-s all-out test for the estimation of maximal oxygen uptake (V.O (2max)) and submaximal aerobic ability as represented by critical power. We hypothesized that the fall in power output by the end of the 90-s all-out test (end power) would represent the exhaustion of anaerobic work capability, and as such, would correspond with the critical power. Sixteen active individuals (mean +/- SD: 30 +/- 6 years; 69.6 +/- 9.9 kg) carried out a series of tests: (i) an incremental ramp test to determine V.O (2max), (ii) three fixed-work rate trials to exhaustion to determine critical power, and (iii) two 90-s all-out tests to measure end power and peak V.O (2). End power (292 +/- 65 W) was related to (r=0.89) but was significantly higher (p<0.01) than critical power (264 +/- 50 W). The mean +/- 95 % limits of agreement (29 +/- 65 W) were too low to use these variables interchangeably. The peak V.O (2) in the 90-s trial was significantly lower than the V.O (2max) (3435 +/- 682 ml x min (-1) vs. 3929 +/- 784 ml x min (-1); p<0.01); mean +/- 95 % limits of agreement was equal to 495 +/- 440 mL x min (-1). The 90-s all-out test cannot, therefore, assess both V.O (2max) and critical power in adult performers. The duration of all-out exercise required to allow V.O (2) to attain its maximum is longer than 90 s.

Adult↗
PubMed1989

Comparison of maximum aerobic power, maximum anaerobic power, and skinfold thickness of elite and nonelite junior wrestlers.

The purpose of this investigation was to identify physiologic differences between elite high school-age wrestlers and nonelite wrestlers of comparable age, weight, and training experience. Two groups of junior wrestler, elite (n = 18) and nonelite (n = 18) were measured for maximum aerobic power (treadmill run), maximum anaerobic power of the arms and legs (Wingate test), and skinfold thickness. On the average (+/- SE) elite juniors had a VO2max of 52.6 +/- 2.0 ml/kg.min-1, 376 +/- 20 W for arm power, and 540 +/- 25 W for leg power. The nonelite group had a VO2max of 51.5 +/- 1.4 ml/kg.min-1 and 331 +/- 22 W and 467 +/- 29 W for arm and leg power, respectively. Ttests were computed to identify differences between the groups. The results revealed significant differences in four skinfold thicknesses, absolute anaerobic leg power, and relative anaerobic power of arms and legs. It was concluded that relative maximum anaerobic power is distinctly greater in elite high school wrestlers than less successful peers. In light of the results, it may be of benefit for wrestlers of lower caliber to decrease body fat, increase fat-free weight, and increase total body power through training.

Adolescent↗
PubMed1999

Thawing of foods in a microwave oven: I. Effect of power levels and power cycling.

Microwave thawing is faster than other methods, but it can produce significant non-uniformity of heating. The objective of this study was to perform comprehensive experimentation and heat transfer modeling to relate the time to thaw and the non-uniformity of thawing to power cycling, power level and the surface heat transfer coefficient. The governing energy equation was formulated with an exponential decay of the microwave flux from the surface. Surface microwave flux was obtained from the measured temperature rise using inverse heat transfer analysis. Gradual phase change was formulated as an apparent specific heat, and was obtained for the experimental material tylose from differential scanning calorimetry (DSC) measurements. The temperatures were measured immediately following heating with a fast response thermocouple. Dielectric properties were measured above freezing. Results show that the microwave flux at the surface and its decay are affected by the changes in the power level. Power cycling has an almost identical effect as continuous power at the reduced level of the average cycled power. As power level increases, the surface flux increases by the same fraction. At higher power levels, however, the outside thaws relatively faster. A "shield" develops due to a much reduced microwave penetration depth at the surface. This thawing time at higher power levels is reduced considerably. Temperature increases initially are non-uniform since the surface is heated at a faster rate than the interior. In keeping with the assumption that once the temperature reaches 100 degrees C, all energy absorbed goes into evaporation, and subsequent temperature is maintained at 100 degrees C. Thus, eventually, non-uniformity starts to decrease.

Food Handling↗
PubMed1997

Ramp and constant power trials produce equivalent critical power estimates.

The standard critical power test protocol on the cycle ergometer prescribes a series of trials to exhaustion, each at a different but constant power setting. Recently the protocol has been modified and applied to a series of trials to exhaustion each at a different ramp incremental rate. This study was undertaken to compare critical power and anaerobic work capacity estimates in the same group of subjects when derived from the two protocols. Ten male subjects of mixed athletic ability cycled to exhaustion on eight occasions in randomized order over a 3-wk period. Four trials were performed at differing constant power settings and four trials on differing ramp incremental rates. Both critical power and anaerobic work capacity were estimated for each subject by curve fitting of the ramp model and of three versions of the constant power model. After adjusting for inter-subject variability, no significant differences were detected between critical power estimates or between anaerobic work capacity estimates from any model formulation or from the two protocols. It is concluded that both the ramp and constant power protocols produce equivalent estimates for critical power and anaerobic work capacity.

Adult↗
PubMed2004

What makes women feel powerful? An exploratory study of relationship power and sexual decision-making with African Americans at risk for HIV/STDs.

Because of the importance of relationship power and cultural norms on women's ability to protect themselves from HIV/STDs, effective interventions must address power differentials among men and women. These programs need to be informed by and adapted to the cultural values of the target population. Accordingly, we conducted exploratory interviews with 22 young African American women at risk of HIV/ STDs and unintended pregnancy and their male partners regarding the meaning of power in heterosexual relationships, what makes a woman feel powerful in a relationship with a man, and who makes sexual and reproductive decisions in their relationships. Content analyses suggested that relationship power was linked to control and decision-making for most participants; yet, others appeared to associate power with positive relationship qualities such as respect and security. In addition, most participants reported that they shared decision-making about sexual and reproductive matters with their partners. Subsequently, interviews were conducted with another 40 women to explore and identify cultural beliefs regarding what makes women feel powerful in their relationships with their husbands or partners. Cultural consensus analysis was performed and results indicated that the participants comprise a cultural group with shared beliefs about what makes women feel powerful in their relationships. Participants believed that women's sense of power in their relationships came from (1) knowing what they want and having autonomy and control; (2) the quality of their relationships; (3) having resources to provide for their families; and (4) physical attractiveness and sexual factors.

Adult↗
PubMed1992

Output power and metabolic input power of skeletal muscle contracting linearly to compress a pouch in a mock circulatory system.

Output power and metabolic input power values were determined for unconditioned canine latissimus dorsi (two), gastrocnemius (seven), and triceps (three) muscles contracting linearly to cause compression of a doubly valved pouch in a hydraulic model of the circulation. The motor nerves to the muscles were stimulated tetanically with 450 msec trains of 0.1 msec pulses having a frequency of 50/sec. The muscles were contracted 10, 20, 30, and 40 times per minute and pouch output in milliliters per minute was measured directly for each muscle at each contraction (train) rate. The output power in milliwatts was determined by two methods: (1) by using the pouch output and the pressure rise imparted to the stroke volume (average power) and (2) by using the pressure-volume loop. Metabolic input power in milliwatts was determined from the oxygen consumption in milliliters per minute of the working muscle. It was found that as the pouch output was increased, the pouch output power and the metabolic input power both increased. The average power output was slightly less than that computed from the pressure-volume loop. The mean output power values, when pumping at L liters per minute, were 0.62 L (average) and 0.75 L mW/gm (pressure-volume loop) for the latissimus dorsi muscles; 0.83 L (average) and 1.16 L mW/gm (pressure-volume loop) for the gastrocnemius muscles; and 0.55 L (average) and 0.66 L mW/gm (pressure-volume loop) for the triceps muscles. The percent efficiency of energy conversion ranged from 9.2% to 17.8% for the latissimus dorsi muscles, from 5.1% to 19.5% for the gastrocnemius muscles, and from 10.5% to 27.3% for the triceps muscles. However, it should not be concluded that one muscle type is better than another on the basis of percent efficiency because efficiency does not take endurance into account. An important observation in this study relates to the large output obtained with the three linearly contracting muscle types. All were capable of pumping in excess of 1.5 L/min. A second observation relates to the absence of fatigue, although determination of endurance was not an objective in these studies.

Animals↗
PubMed2002

Nurse-patient power relationship: preliminary evidence of patients' power messages.

The interactive relationship that is based on sharing power and control is the goal of health counseling practice. This research examined the nurse-patient power relationship and emphasized the patient's perspective. Health counseling sessions, 38 in number, were videotaped, transcribed verbatim, and analyzed by using an adaptation of conversation analysis (CA). The purpose of this research was to describe in detail how patients' minimized power asymmetry during hospital counseling. The results indicate that power is a complex and polysemic phenomenon that can be created jointly. Nurses' power is associated with their medical knowledge, which also patients construct. However, patients have several options to construct their power and influence the flow of interaction, for example, directing the counseling with questions, interruptions, and extensive disclosure, in which also nurses participated. The results are discussed in terms of earlier research on power messages and implications for a future power sharing practice.

Adolescent↗
PubMed1993

Power and violence: the relation between communication patterns, power discrepancies, and domestic violence.

This study hypothesized that power discrepancies in the marital relationship, where the husband is subordinate, serve as risk factors for husband-to-wife violence. The construct of marital power was assessed from 3 power domains operationalized by discrepancies in economic status, decision-making power, communication patterns, and communication skill. Three groups of married couples (N = 95) were compared: domestically violent (DV), maritally distressed/nonviolent (DNV), and maritally happy/nonviolent (HNV). DV couples were more likely than the 2 nonviolent groups to engage in husband demand/wife withdraw interactions. Within the DV group, husbands who had less power were more physically abusive toward their wives. Thus, violence may be compensatory behavior to make up for husbands' lack of power in other arenas of marriage. Difficulties in assessing marital power and future direction for the study of power and violence are discussed.

Adult↗