Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “statistical physics”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 721 records · Page 40Linked to original sources
PubMed1998

Worksite physical activity interventions.

BACKGROUND: National objectives for public health have targeted worksite as important settings for interventions to increase physical activity. However, expert reviews reveal no scientific consensus about the effectiveness of worksite interventions for increasing physical activity or fitness. METHODS: We judged the quantity and quality of existing evidence against scientific standards for the internal and external validity of the research design and the validity of measurements. Meta-analytic methods were used to quantify the size of effects expressed as Pearson correlation coefficients (r). Variation in effect was examined in relation to several features of the studies deemed important for implementing successful worksite interventions. Pre-experimental cohort studies were excluded because they are sensitive to secular trends in physical activity. RESULTS: Twenty-six studies involving nearly 9,000 subjects yielded 45 effects. The mean effect was heterogeneous and small, r = 0.11 (95% CI, -0.20 to 0.40), approximating 1/4 S.D., or an increase in binomial success rate from 50% to 56%. Although effects varied slightly according to some of the study features we examined, effects were heterogeneous within levels of these features. Hence, the moderating variables examined did not explain variation in the effects (P > 0.05). The exception was that effects were smaller in randomized studies compared with studies using quasi-experimental designs (P < 0.05). CONCLUSIONS: Our results indicate that the typical worksite intervention has yet to demonstrate a statistically significant increase in physical activity or fitness. The few studies that have used an exemplary sample, research design, and outcome measure have also yielded small or no effects. The generally poor scientific quality of the literature on this topic precludes the judgment that interventions at worksites cannot increase physical activity or fitness, but such an increase remains to be demonstrated by studies using valid research designs and measures.

Adolescent↗
PubMed1977

A field and circuit thermodynamics for integrative physiology. I. Introduction to the general notions.

In this first of three articles on a physical basis for integrative physiology, statistical mechanical concepts are developed into a field thermodynamics. The development begins by comparing the different ways change is viewed in biology compared to physics. The Hamiltonian field concept unites the two. The requirements of a thermostatic description are introduced; then those of nonequilibrium thermodynamics are added. Conditions suitable for continuum, near-equilibrium analysis of systems are given; then the role of physical forces in organization is discussed. The development returns to statistical mechanics, and introduces conservation principles and equations of change for ensembles of interacting units. A general notion of systems and thermodynamic engines is discussed next, and a narrative account of the explanatory scope of field thermodynamics is given. Its applications to living systems are the subject of the subsequent two articles of this series.

Biophysical Phenomena↗
PubMedDate not supplied

Utilization of lumbosacral spine radiographs for the evaluation of low back pain in the emergency department.

We sought to determine how often Emergency Physicians (EPs) order plain radiographs (XRs) of the lumbosacral spine in evaluating patients with low back pain (LBP). In addition, we sought to determine what history and physical examination findings were statistically associated with the use of an XR. Patients evaluated in our Emergency Department (ED) between April 1, 1995 and September 30, 1995 for LBP were identified retrospectively by their ICD-9 discharge code. The ED record was reviewed, and an odds ratio (OR) was calculated for each of several history and physical examination findings, to determine which of them increased the likelihood of having an XR. Forty of 214 patients (19%) with LBP had an XR done. Patient characteristics associated with the use of an XR were: a positive straight leg examination, age > 50 years, a history of trauma, and vertebral tenderness. In this series, only a small minority of patients with LBP had an XR done as part of their ED evaluation. The choice of which patients to image was determined by history and physical examination findings. We conclude that the EPs we studied are evaluating LBP as conservatively, if not more so, than physicians in other specialties.

Adolescent↗
PubMed1978

Increased urinary excretion of triiodothyronine (T3) and thyroxine (T4) and decreased serum thyreotropic hormone (TSH) induced by motion sickness.

We exposed 35 male subjects to a rotary chair and motion sickness was provoked by Coriolis effect. This stress caused an increased excretion of urinary T3 and T4 and a decrease of TSH levels in serum. The increment in urinary excretion of thyroid hormones may serve as a very useful measure for the quantitation of physical stress. Although no statistically significant change of T3, T4, and TBG levels in serum could be observed by the employed techniques, the hypothesis is favoured that motion sickness probably causes an immeasurably small increase of the free thyroid hormone fraction in serum, thereby increasing urinary excretion of T3 and T4 and, in turn, decreasing TSH secretion. Physical or psychological stress situations involve most of the endocrine systems. Contadictory results have been reported in the literature concerning the relationship between thyroid function and stress.

Epinephrine↗
PubMed2001

Physical activity and bone measures in young children: the Iowa bone development study.

OBJECTIVES: Physical activity has a beneficial effect on bone development in circumpubertal children, although its effect on younger children is uncertain. In this cross-sectional study, we examined associations between physical activity and bone measures in 368 preschool children (mean age: 5.2 years, range: 4-6 years). DESIGN: Physical activity was measured using 4-day accelerometry readings, parental report of children's usual physical activity, and parental report of children's hours of daily television viewing. Total body and site-specific bone mineral content and area bone mineral density (BMD) were measured by dual energy radiograph absorptiometry. RESULTS: After adjustment for age and body size, accelerometry measures of physical activity and parental report of usual physical activity were consistently and positively associated with bone mineral content and BMD in both boys and girls (r = 0.15-0.28). Television viewing was inversely associated with hip BMD in girls (r = -0.15). The proportion of variance in bone measures explained by physical activity in linear regression models ranged from r(2) = 1.5% to 9.0%. In all of these models except total body BMD, at least 1 and often several of the physical activity variables entered as independent predictors. Activity variables most likely to enter the regression models were vigorous physical activity (as determined by accelerometry) and parental ranking of child's usual physical activity. CONCLUSIONS: Findings indicate that there are statistically significant and, perhaps important, associations between physical activity and bone measures during early childhood, well ahead of the onset of peak bone mass. This would suggest that intervention strategies to increase physical activity in young children could contribute to optimal bone development.

Absorptiometry, Photon↗
PubMed2004

Comment on "Critique of q-entropy for thermal statistics".

It was recently argued [M. Nauenberg, Phys. Rev. E 67, 036114 (2003)] that the theory sometimes referred to as nonextensive statistical mechanics has no physical basis, for a considerable variety of reasons, including the impossibility of measuring the temperature out of the Boltzmann-Gibbs (BG) theory. We comment here on virtually all the physically and mathematically relevant issues, and point out what we consider to be severe inadvertences contained in that paper. In particular, we factually argue, through computer simulations, the validity of the zeroth principle of thermodynamics, and of the basic rules of thermometry for nonextensive systems. This fact further supports the possible connection with the thermodynamics of nonextensive statistical mechanics, which is already known to be consistent with the first, second, and third principles. All the foundational steps (e.g., the uniqueness of the entropy and the stationary state distribution) have already been established for nonextensive thermostatistics on similar grounds than those long known for BG statistics, the former corresponding to power laws (expected for long-range interactions when size N diverges before time t), and the latter correspond to the BG exponential law (expected for long-range interactions when N diverges after t, as well as for short-range interactions in any diverging order for N and t). We conclude that the invalidating arguments made by Nauenberg by no means apply.

Comment↗
PubMed2006

Psychological pain treatment in fibromyalgia syndrome: efficacy of operant behavioural and cognitive behavioural treatments.

The present study focused on the evaluation of the effects of operant behavioural (OBT) and cognitive behavioural (CBT) treatments for fibromyalgia syndrome (FMS). One hundred and twenty-five patients who fulfilled the American College of Rheumatology criteria for FMS were randomly assigned to OBT (n = 43), CBT (n = 42), or an attention-placebo (AP) treatment (n = 40) that consisted of discussions of FMS-related problems. Assessments of physical functioning, pain, affective distress, and cognitive and behavioural variables were performed pre-treatment and post-treatment as well as 6 and 12 months post-treatment. Patients receiving the OBT or CBT reported a significant reduction in pain intensity post-treatment (all Fs > 3.89, all Ps < 0.01). In addition, the CBT group reported statistically significant improvements in cognitive (all Fs > 7.95, all P < 0.01) and affective variables (all Fs > 2.99, all Ps < 0.02), and the OBT group demonstrated statistically significant improvements in physical functioning and behavioural variables (all Fs > 5.99, all Ps < 0.001) compared with AP. The AP group reported no significant improvement but actually deterioration in the outcome variables. The post-treatment effects for the OBT and CBT groups were maintained at both the 6- and 12-month follow-ups. These results suggest that both OBT and CBT are effective in treating patients with FMS with some differences in the outcome measures specifically targeted by the individual treatments compared with an unstructured discussion group. The AP group showed that unstructured discussion of FMS-related problems may be detrimental.

Adult↗
PubMed2003

Naturalistic auditory contrast improves spectrotemporal coding in the cat inferior colliculus.

Statistical analysis of natural sounds and speech reveals logarithmically distributed spectrotemporal modulations that can cover several orders of magnitude. By contrast, most artificial stimuli used to probe auditory function, including pure tones and white noise, have linearly distributed amplitude fluctuations with a limited average dynamic range. Here we explore whether the operating range of the auditory system is physically matched to the statistical structure of natural sounds. We recorded single-unit and multi-unit neuronal activity from the central nucleus of the cat inferior colliculus (ICC) in response to dynamic spectrotemporal sound sequences to determine whether ICC neurons respond preferentially to linear or logarithmic spectrotemporal amplitudes. We varied the intensity, dynamic range, and contrast statistics of these sounds to mimic those of natural and artificial stimuli. ICC neurons exhibited monotonic and nonmonotonic contrast dependencies with increasing dynamic range that were independent of the stimulus intensity. Midbrain neurons had higher firing rates and higher receptive field energies and showed a net improvement in spectrotemporal encoding ability for logarithmic stimuli, with an increase in the mutual information rate of approximately 50% over linear amplitude sounds. This efficient use of logarithmic spectrotemporal modulations by auditory midbrain neurons reflects a neural adaptation to structural regularities in natural sounds and likely underlies human perceptual abilities.

Action Potentials↗
PubMed2000

Effect of blood pressure and physical activity on carotid artery intima-media thickness in stage 1 hypertensives and controls.

The aim of the study was to investigate whether hypertension and physical training induce parallel changes in the arterial wall. Ninety-seven never-treated stage 1 hypertensive patients (HT) (systolic blood pressure 140 to 159 mm Hg or diastolic blood pressure 90 to 99 mm Hg) aged 18 to 45 years taking part in the Hypertension and Ambulatory Recording Venetia Study and 27 normotensive volunteers (NT) aged 30 +/- 9 years were studied. Data on physical or sports activity were collected and scored, and target organ involvement was investigated by assessing microalbuminuria, echocardiography, and carotid ultrasound study. The carotid arteries were examined according to the Atherosclerosis Risk in Communities protocol. Mean (m-IMT) and maximal (M-IMT) carotid intima-media thickness were measured at end-diastole in the far wall common carotid artery, in the bulb and internal carotid artery, in the lateral and posterior projection, averaging the left and right sides. A comparable level of physical activity was present in HT patients and NT subjects. Twenty-four-hour blood pressure and blood lipid levels, as well as target organ damage, were similar in physically active and sedentary HT. The m-IMT of the common carotid was greater in sedentary HT than in sedentary NT, as well as in active than in sedentary NT. The m-IMT of the internal carotid artery was also greater in active HT than in active NT, as well as in active than in sedentary HT. In logistic regression, comparing the first and fourth quartile of m-IMT, scored physical activity was a predictor of m-IMT in the internal carotid artery. No statistical interaction was found between physical activity and hypertension, indicating that these two items have a cumulative effect and act independently of each other. Sedentary HT had significantly greater levels of M-IMT than sedentary NT in all sites but the bulbs; in the internal and common carotid arteries, HT exercisers had significantly greater M-IMT than NT exercisers. Therefore, physical activity appears to be an early independent predictor of carotid wall thickness. This factor should be taken into consideration in population-based studies aimed at investigating supraortic vessels as it can act as a confounder.

Adult↗
PubMed2005

Using factor analysis to evaluate checklist items.

BACKGROUND: Relatively little research has been published examining the use of factor analytic techniques to improve the psychometric qualities of performance assessments. The purpose of the current investigation is to illustrate the potential use of structural equation modeling (SEM) with scores from a standardized patient examination. METHOD: Checklist items for a single case were examined to compare two models within a SEM framework: a single, underlying "data gathering" construct and a two-factor model consisting of medical history interviewing and physical examination maneuvers. RESULTS: The chi2 statistics obtained were statistically significant for both the single factor (chi2=1645.8, p<.001) and the two-factor model, (chi2=1373.1; p<.001), indicating marginal model-data fit. A difference statistic was calculated (chi2=320.9; p<.001), suggesting that the two-factor model has better fit. CONCLUSIONS: The parameters estimated by each model could be used to evaluate checklist item performance. The results of this investigation illustrate the utility of this method in the analysis of checklist item data.

Clinical Competence↗
PubMed2001

Physical therapy outcomes for persons with bilateral vestibular loss.

OBJECTIVE: The purpose of the study was to assess the efficacy of physical therapy for patients with bilateral vestibular loss. STUDY DESIGN: Retrospective case series. METHODS: Twenty-four patients with a diagnosis of bilateral vestibular loss were identified by a retrospective chart review. Thirteen of the 24 patients met the inclusion criteria of having a moderate or greater loss of vestibular function bilaterally as rated by an otoneurologist based on the patient's vestibular function tests. These patients were treated with a custom-designed physical therapy program for a mean of 4.6 visits over an average period of 3.8 months. Patients completed the Dizziness Handicap Inventory and the Activities-specific Balance Confidence Scale at initial evaluation and discharge. Patients were asked to perform the balance and gait tasks of the Dynamic Gait Index, Sensory Organization Test of computerized dynamic posturography, and the Timed "Up and Go" test at their first and last physical therapy sessions. The number of falls in the previous 4 weeks and the use of an assistive device at initial evaluation and discharge were reported. Composite score, an overall score of clinical outcome, was calculated to determine clinically significant changes in physical performance and subjective information. RESULTS: On a population basis, statistically significant improvement was observed after physical therapy for each of the outcome measures including the composite score (P < .05). Clinically significant changes were demonstrated by 33% to 55% of the patients on the various outcome measures. No change was noted in the patients' risk of falling, their number of falls, and the use of assistive devices. CONCLUSION: Many patients with bilateral vestibular loss benefit from an individualized vestibular physical therapy exercise program based on improved physical function and reduced self-perceived levels of handicap.

Accidental Falls↗
PubMed1996

Pain, disability, and physical functioning in subgroups of patients with fibromyalgia.

OBJECTIVE: To investigate (1) whether patients with fibromyalgia (FM) could be subgrouped on the basis of psychosocial and behavioral responses to pain, and (2) the relationships among pain severity, perceived disability, and observed physical functioning, as measured by cervical spinal mobility. METHODS: 117 patients with FM received a comprehensive examination, underwent physical performance tasks during the evaluation, and completed self-report inventories. RESULTS: About 87% of the patients could be classified into the Multidimensional Pain Inventory clustering groups identified and validated in patients with a range of chronic pain problems (Dysfunctional, Interpersonally Distressed, and Adaptive Copers). Although the 3 groups exhibited comparable levels of physical functioning, the Dysfunctional and Interpersonally Distressed patients reported higher levels of pain, disability, and depression. Interpersonally Distressed patients also reported significantly lower levels of marital satisfaction than the other 2 subgroups. There were significant associations between pain severity and perceived disability, and pain severity and physical functioning, defined by spinal mobility tests. The relationship between disability and physical functioning did not reach statistical significance. Correlational analyses by subgroups revealed a significant association between patient perceived disability and physical functioning in the Adaptive Copers, but not the Dysfunctional or Interpersonally Distressed patients. CONCLUSIONS: Patients with FM can be classified into 3 subgroups based on psychosocial and behavioral characteristics. These subgroups show substantial differences in clinical presentation of their symptoms. Although the results should be considered preliminary due to the narrow range of physical functioning, the differential relationships between perceived disability and physical functioning across cluster groups suggest the importance of FM syndrome as a heterogeneous disorder. Treating patients with FM as a homogeneous group may compromise research results, impede understanding of the mechanisms underlying this condition, and deter development of effective treatment.

Adult↗
PubMed1989

Interpretive and critical research in sport and physical education.

Qualitative research encompasses two distinct approaches, interpretive research and critical research. Locke has provided an excellent review of the assumptions and methods of interpretive research. His article provides an important service to the field by informing the broad range of scholars within physical education about this growing area of research. The one weakness of his review is that it may not emphasize sufficiently the need to ground qualitative research in an understanding of the social sciences so that the researcher can provide an adequate context for the interpretation of data. Locke limits his review primarily to the interpretive approach and mentions critical theory only briefly, a decision that seems appropriate in an introductory tutorial. Most of the qualitative research being done in sport and physical education is interpretive, not critical. However, a few of the researchers in this area seem to be moving toward a critical perspective. Therefore, this article attempted to provide a brief overview of critical qualitative research.

Data Interpretation, Statistical↗
PubMed2006

Australian Vascular Quality of Life Index (AUSVIQUOL): a pilot study of a disease-specific quality of life measure.

BACKGROUND: To develop and test a quality of life (QOL) index specific for patients with vascular disease and appropriate for patients with abdominal aortic aneurysm (AAA) in the clinical setting. METHODS: The questions and domains of the Australian Vascular Quality of Life Index (AUSVIQUOL) were determined by examination of a prospective database for frequency of symptoms and an in-depth interview of a sample population. The validity of the AUSVIQUOL was tested by comparing it with the Medical Outcomes Short Form Health Survey (SF-36) in a study involving 60 patients who underwent endovascular AAA repair and 48 open AAA repair. A subpopulation of 22 patients representative of the two groups was then reassessed using the SF-36 and the AUSVIQUOL, to compare the reliability of the two indices. RESULTS: Similar domains of the SF-36 and the AUSVIQUOL measured common QOL elements. The correlation between the two indices was moderate; the AUSVIQUOL measured additional disease-specific QOL factors. The AUSVIQUOL showed better reliability than the SF-36 in all domains and statistically better in the physical function domain (P < 0.05). CONCLUSION: The AUSVIQUOL is an appropriate tool for the QOL assessment of patients with AAA in the clinical setting.

Aged↗
PubMed1997

Evaluation of a training program for persons with SCI paraplegia using the Parastep 1 ambulation system: part 4. Effect on physical self-concept and depression.

OBJECTIVE: To determine whether persons with spinal cord injury (SCI) paraplegia who participated in an electrical stimulation walking program experienced changes in measures of physical self-concept and depression. DESIGN: Before-after trial. SETTING: Human SCI applied research laboratory. PARTICIPANTS: Volunteer sample of 12 men and 3 women with SCI paraplegia, mean age 28.75 +/- 6.6yrs and mean duration of injury 3.8 +/- 3.2yrs. INTERVENTION: Thirty-two FNS ambulation training sessions using a commercially available system (Parastep 1). The hybrid system consists of a microprocessor-controlled stimulator and a modified walking frame with finger-operated switches that permit the user to control the stimulation parameters and activate the stepping. OUTCOME MEASURES: The Tennessee Self-Concept Scale (TSCS) and the Beck Depression Inventory (BDI) were administered before and after training. Only the Physical Self subscale of the TSCS was analyzed. After training, individual interviews were performed to assess participants' subjective reactions to the training program. RESULTS: A repeated measures analysis of variance indicated that desired directional and statistically significant changes occurred on the Physical Self subscale of the TSCS (F(1,14) = 8.54, p < .011) and on the BDI (F(1,14) = 5.42, p < .035). CONCLUSIONS: Subsequent to the ambulation training program there were statistically significant increases in physical self-concept scores and decreases in depression scores.

Adult↗
PubMed2006

[Comprehensive predictors of fatigue for cancer patients].

PURPOSE: This study was conducted to identify comprehensive predictors of fatigue in cancer patients. METHODS: One hundred ten cancer patients visiting in-patient or out-patient clinics of a university hospital located in Incheon participated in this study. RESULTS: The hematologic indicators (WBC and Hemoglobin) were significant for explaining fatigue. The psychological factors of fatigue were statistically significant. Both anxiety and depression, included as psychological factors, were significant in explaining fatigue in cancer patients. The influence of physical factors on fatigue was also statistically significant. Among the variables included as physical factors, pain, nausea/vomiting/anorexia, and sleep disturbance were significant whereas, dyspnea was not significant. The influence of the daily activity factor on fatigue was statistically significant. Among the variables included as daily activity factors, regular exercise or not and the usual activity level were significant in explaining fatigue of cancer patients, while the level of rest was not statistically significant. CONCLUSIONS: From the study results fatigue of cancer patients appeared to be influenced by multidimensional factors, such as physiological, physical, psychological, and activity related factors.

Activities of Daily Living↗
PubMed2006

Storytelling, statistics and hereditary thought: the narrative support of early statistics.

This paper's main contention is that some basically methodological developments in science which are apparently distant and unrelated can be seen as part of a sequential story. Focusing on general inferential and epistemological matters, the paper links occurrences separated by both in time and space, by formal and representational issues rather than social or disciplinary links. It focuses on a few limited aspects of several cognitive practices in medical and biological contexts separated by geography, disciplines and decades, but connected by long term transdisciplinary representational and inferential structures and constraints. The paper intends to show a given set of knowledge claims based on organizing statistically empirical data can be seen to have been underpinned by a previous, more familiar, and probably more natural, narrative handling of similar evidence. To achieve that this paper moves from medicine in France in the late eighteenth and early nineteenth century to the second half of the nineteenth century in England among gentleman naturalists, following its subject: the shift from narrative depiction of hereditary transmission of physical peculiarities to posterior statistical articulations of the same phenomena. Some early defenders of heredity as an important (if not the most important) causal presence in the understanding of life adopted singular narratives, in the form of case stories from medical and natural history traditions, to flesh out a special kind of causality peculiar to heredity. This work tries to reconstruct historically the rationale that drove the use of such narratives. It then shows that when this rationale was methodologically challenged, its basic narrative and probabilistic underpinings were transferred to the statistical quantificational tools that took their place.

England↗