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At least 253 records · Page 14Linked to original sources
PubMed1994

Estimation of physical work load by statistical analysis of the heart rate in a conveyor-belt worker.

Physical work load was estimated in a female conveyor-belt worker in a bottling plant. Estimation was based on continuous measurement and on calculation of average heart rate values in three-minute and one-hour periods and during the total measuring period. The thermal component of the heart rate was calculated by means of the corrected effective temperature, for the one-hour periods. The average heart rate at rest was also determined. The work component of the heart rate was calculated by subtraction of the resting heart rate and the heart rate measured at 50 W, using a regression equation. The average estimated gross energy expenditure during the work was 9.6 +/- 1.3 kJ/min corresponding to the category of light industrial work. The average estimated oxygen uptake was 0.42 +/- 0.06 L/min. The average performed mechanical work was 12.2 +/- 4.2 W, i.e. the energy expenditure was 8.3 +/- 1.5%.

Adult↗
PubMed1985

Statistical software packages for physical therapists. STATPAK for the IBM PC.

If you have modestly sized files, modest computing requirements, and only a modest budget, look into STATPAK. Despite the limitations of STATPAK's computational accuracy, data-entry capabilities, and file-size restrictions. It is a package that provides many of the more frequently required statistical routines in physical therapy research. Besides, who knows when you'll need Fourier-transformed nonlinear correlations! Be prepared to spend an evening or two getting used to the cryptic program descriptions. Perhaps a future version will contain a tutorial with sample data to help the beginner get started; a general linear-model routine to permit ANOVAs on unbalanced Ns, assess multivariate hypotheses, and test the compound-symmetry assumption of repeated measured ANOVA would also be welcome. I would first recommend, however, that the documentation problems be addressed; at least let us find "Graphics" or "Chart" in the index, without having to guess that we should look under "Plot"!

Computers↗
PubMed2006

Geometric thermodynamic fields and the generalized ensemble in colloidal physics.

The statistical geometry of hard-sphere mixtures, as defined by Speedy and Reiss, is found to lead to a sum rule that is identical in form to the fundamental equation of the generalized ensemble. This leads one to conjecture the specific form of a set of thermodynamic fields entirely defined by ensemble averages of geometric properties of the configurations. The potential for a direct physical understanding of these quantities is discussed and it is noted that they could, therefore, be of crucial significance to our future understanding of colloidal physics. In the presence of an ideal wall, an analogous sum rule is obtained in terms of interfacial geometric properties (the available surface area for insertions at the wall). For this case, which generalizes beyond hard-sphere models, there exists an obvious physical interpretation involving complete wetting at the ideal wall.

Journal Article↗
PubMed2000

A comparison of primary and proxy respondent reports of habitual physical activity, using kappa statistics and log-linear models.

BACKGROUND: Many epidemiological studies rely in part on proxy informants. There is little published information on the reliability of proxy-respondent reports of physical activity. METHODS: Self-reported data on vigorous and moderate physical activity, from a representative sub-sample of participants in a community-based case-control study of coronary heart disease, were compared with information collected from their next-of-kin. RESULTS: Relative to primary respondents, proxy respondents under-reported activity by approximately 10 percentage points, for both leisure and work-time activity. On a simple three point scale (inactivity/moderate activity/physical activity), 70% of primary-proxy pairs were in exact agreement with regard to leisure time activity and 67% of pairs were in exact agreement on work-time activity. The corresponding values for the weighted kappa statistic were 0.66 [95% confidence interval (CI) 0.59-0.72] and 0.62 (0.54-0.72). Log-linear modelling provided evidence for superior agreement on worktime activity when the proxy was not the primary respondent's spouse. DISCUSSION: Overall levels of primary-proxy respondent agreement on physical activity seem somewhat lower than has been reported for smoking and alcohol-drinking frequency. There seems little reason to prefer spouse proxies when endeavouring to elicit information on work-time physical activity. Log-linear modelling provides an efficient means of exploring covariate effects in observer-agreement studies.

Adult↗
PubMed1994

A comprehensive study of physical parameters, biomechanical properties, and statistical correlations of iliac crest bone wedges used in spinal fusion surgery. II. Mechanical properties and correlation with physical parameters.

Iliac crest wedges have been the most frequently used bone graft in spinal fusion procedures since the 1970s. Physical parameters and correlations among physical parameters of allogeneic iliac crest wedges have been described in part I of this series. This article discusses the mechanical properties, as well as their correlations with physical parameters, of iliac crest wedges. A total of 250 frozen-thawed, freeze-dried, and rehydrated iliac crest wedges were used in this study. The axial load-bearing capacities for wedges in the three subgroups showed no statistically significant differences, however, rehydrated wedges appeared to have the greatest load bearing capacity and compressive strength. In addition, rehydrated wedges were more deformable than either the frozen-thawed or freeze-dried wedges. Based on biomechanical properties, it is suggested that rehydrated (1 hour in vacuo), or frozen-thawed iliac crest wedge should be used in spinal fusion procedures, and the direct clinical application of nonrehydrated freeze-dried wedges should be avoided.

Aging↗
PubMed1990

[The effect of combined rehabilitation on the physical work capacity of patients who have had a myocardial infarct].

125 patients with past myocardial infarction (basic group) have been treated for 5 years by a comprehensive rehabilitation program and their physical fitness was checked against 35 patients also with past myocardial infarction who did not take part in the rehabilitation program (control group). The rehabilitation program included physical exercises, measured walking and psychological rehabilitation. The results show that the physical fitness of the basic group was significantly higher than that of the control group and the patients could sustain physical load over 600 kgf/min. 88.7% of the basic group patients returned to their professional occupation against 71.2% for the control group. Highest mortality was recorded during the first year following the discharge from the hospital. At the end of the 5-year observation period 77.2% of the basic group patients were alive versus 72.8% of the control group and 70.4% of the basic group patients are working vs 50.8% of the control group. The patients who had taken part in the comprehensive physical rehabilitation are with improved physical fitness (statistically proved). The relation between the restored physical fitness and the real resuming of professional activity is proved.

Adult↗
PubMed1989

[Analysis of permanent accident-induced physical damage based on statistics of the federal insurance organization].

The changes in the occurrence of the accidents are continuously reflected in the computer statistics of the State Insurance Co. Comparing the date from 1970, 1975, 1984, 1986 it is evident the rapid increase in rate and number of the accidents happened at home and the decrease of the accidents in the working places. The pedestrian is run down on the road more often. The rate of the manual workers reaches the 90% among the injured. The most of the accidents at school happen on the physical training and during the break-time. The mortality ratio is 0.78%, the rate of the permanent damages of health 5.72%. 70% of all injuries are caused by mechanical trauma, falling in particular. 30% or higher permanent damage of health caused by accident was found in 3.047 injured persons in the year 1983. 74% male, 26% female, 80% of them were in working age. In 85% of the damaged persons the degree of the P.D.H. was 50% or less, only 15% of them became invalid. The traffic accidents has the leading role in provoking severe P.D.H.-s. In the distribution according the injured part of the body the extremities are leading with 62% of participation, the fractures of the leg, ankle and heel bone in particular. The therapeutic results of this letter group could be improved by better, more careful rehabilitation.

Accidents↗
PubMed2005

Time autocorrelation function analysis of master equation and its application to atomic clusters.

We derive the energy fluctuation Delta(2)E, and the time autocorrelation kappa(tau) and its Fourier transformation--the fluctuation spectra S(omega)--of the master-equation transition matrix. The contribution from each eigenmode of the transition matrix to these fluctuation quantities reveals the relevant importance of the individual mode in the relaxation processes. The time scales associated with these relaxation processes are determined by the corresponding eigenvalues. Unlike traditional time evolution analysis, the autocorrelation function and fluctuation spectra analysis does not involve an arbitrary initial population. It is also more suitable for analyzing the underlying dynamic, kinetic behavior near the equilibrium and the behavior of the long-time-scale rare events. We utilize our technique to analyze the solid-liquid phase coexistence of the 13-atom Morse cluster and the fcc-to-icosahedral structure transition of the 38-atom Lennard-Jones cluster. For the processes studied, the fluctuation spectra from the master equation simplify the analysis of the transition matrix, and the important relaxation modes are easily extracted.

Chemistry, Physical↗
PubMed2004

Principal-component-analysis eigenvalue spectra from data with symmetry-breaking structure.

Principal component analysis (PCA) is a ubiquitous method of multivariate statistics that focuses on the eigenvalues lambda and eigenvectors of the sample covariance matrix of a data set. We consider p, N-dimensional data vectors xi drawn from a distribution with covariance matrix C. We use the replica method to evaluate the expected eigenvalue distribution rho(lambda) as N--> infinity with p=alphaN for some fixed alpha. In contrast to existing studies we consider the case where C contains a number of symmetry-breaking directions, so that the sample data set contains some definite structure. Explicitly we set C=sigma2I+sigma(2)Sigma(S)(m=1)A(m)B(m)B(T)(m), with A(m)>0 for all m. We find that the bulk of the eigenvalues are distributed as for the case when the elements of xi are independent and identically distributed. With increasing alpha a series of phase transitions are observed, at alpha=A(-2)(m), m=1,2,..., S, each time a single delta function, delta(lambda-lambda(u)(A(m))), separates from the upper edge of the bulk distribution, where lambda(u)(A)=sigma(2)[1+A][1+(alphaA)(-1)]. We confirm the results of the replica analysis by studying the Stieltjes transform of rho(lambda). This suggests that the results obtained from the replica analysis are universal, irrespective of the distribution from which xi is drawn, provided the fourth moment of each element of xi exists.

Fourier Analysis↗
PubMed2001

Predictability, complexity, and learning.

We define predictive information I(pred)(T) as the mutual information between the past and the future of a time series. Three qualitatively different behaviors are found in the limit of large observation times T:I(pred)(T) can remain finite, grow logarithmically, or grow as a fractional power law. If the time series allows us to learn a model with a finite number of parameters, then I(pred)(T) grows logarithmically with a coefficient that counts the dimensionality of the model space. In contrast, power-law growth is associated, for example, with the learning of infinite parameter (or nonparametric) models such as continuous functions with smoothness constraints. There are connections between the predictive information and measures of complexity that have been defined both in learning theory and the analysis of physical systems through statistical mechanics and dynamical systems theory. Furthermore, in the same way that entropy provides the unique measure of available information consistent with some simple and plausible conditions, we argue that the divergent part of I(pred)(T) provides the unique measure for the complexity of dynamics underlying a time series. Finally, we discuss how these ideas may be useful in problems in physics, statistics, and biology.

Forecasting↗