Application of circular statistics in pulmonary diseases by blood gas analysis.
Explore the source record for details and available documents.
Blood Gas Analysis↗
SEARCH · PubMed Health
Results for “statistical physics”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Localization of a polymer in random media: relation to the localization of a quantum particle.
In this paper we consider in detail the connection between the problem of a polymer in a random medium and that of a quantum particle in a random potential. We are interested in a system of finite volume where the polymer is known to be localized inside a low minimum of the potential. We show how the end-to-end distance of a polymer that is free to move can be obtained from the density of states of the quantum particle using extreme value statistics. We give a physical interpretation to the recently discovered one-step replica-symmetry-breaking solution for the polymer [Phys. Rev. E 61, 1729 (2000)] in terms of the statistics of localized tail states. Numerical solutions of the variational equations for chains of different length are performed and compared with quenched averages computed directly by using the eigenfunctions and eigenenergies of the Schrödinger equation for a particle in a one-dimensional random potential. The quantities investigated are the radius of gyration of a free Gaussian chain, its mean square distance from the origin and the end-to-end distance of a tethered chain. The probability distribution for the position of the chain is also investigated. The glassiness of the system is explained and is estimated from the variance of the measured quantities.
Journal Article↗
Preliminary clinical results of two techniques for addressing graft tunnel mismatch in endoscopic anterior cruciate ligament reconstruction.
This study reports the initial clinical results of 540 degrees of graft rotation or free tibial bone block to address graft tunnel mismatch in endoscopic anterior cruciate ligament (ACL) reconstruction. The operative reports of patients who underwent endoscopic ACL reconstruction between 1999 and 2001 were reviewed. Nine of 11 patients treated with a free tibial bone block and 14 of 17 patients treated with 540 degrees of graft rotation were evaluated. Mean follow-up was 20 months (range: 13-40 months) for the bone block group and 34 months (range: 18-48 months) for the 540 degrees group. There were statistically significant improvements in physical examination test results postoperatively, and only one patient in the 540 degrees group had a grade one positive pivot shift test. KT-1000 arthrometer testing demonstrated a statistically significant decrease in manual maximum and side-to-side differences at final follow-up. Mean Lysholm and Noyes sports function scores were excellent or good for all patients. One patient required reoperation for flexion contracture, one patient required an arthroscopic irrigation and debridement for a minor infection, and one patient required arthroscopic subtotal medial meniscectomy for failed meniscal repair. No difference was noted between these results and previous results of patients undergoing conventional endoscopic ACL reconstruction. These results demonstrate graft rotation and free bone block techniques are effective in addressing graft tunnel mismatch in endoscopic ACL reconstruction.
Adolescent↗
[Quality of life in elderly patients with cerebral vascular disease and Parkinson's disease].
We developed a questionnaire for the study of background factors and quality of life (QOL) in elderly patients with cerebral vascular disease (CVD) and Parkinson's disease (PD). The questionnaire covered the background factors and four sections such as physical, functional, psychological and social health sections. Each section had 15 questions and disease-specific questions for CVD or PD were included in the physical health section. We analyzed 107 patients with CVD (76 elderly patients, aged 65 or more, 31 non-elderly patients under 65) and 136 patients with PD (91 elderly, 45 non-elderly). In the background section, of a total of 243 patients with CVD and PD, the elderly patients needed the assistance of their spouse and their sons wives more frequently than non-elderly patients. With regard to rehabilitation, non-elderly CVD patients had rehabilitation more frequently than the elderly CVD patients, while a higher percentage of elderly patients with PD had rehabilitation training more frequently than the non-elderly PD patients. In the QOL section, there was no difference between elderly and non-elderly CVD patients, while elderly PD patients were statistically more significantly disabled physically and weak-minded psychologically. The physical disabilities of the elderly PD patients in this statistical investigation included slow motion, stooped posture, frozen gait, difficulty in turning and standing up, constipation and dysuria. The psychological problems of elder PD patients included forgetfulness and a feeling of aging. These patients had significantly fewer consultations by family and relatives than the non-elderly PD patients. The overall tendency of QOL in patients with CVD and PD was similar to that of PD patients.
Aged↗
Analyzing bioassay data using Bayesian methods--a primer.
The classical statistics approach used in health physics for the interpretation of measurements is deficient in that it does not take into account "needle in a haystack" effects, that is, correct identification of events that are rare in a population. This is often the case in health physics measurements, and the false positive fraction (the fraction of results measuring positive that are actually zero) is often very large using the prescriptions of classical statistics. Bayesian statistics provides a methodology to minimize the number of incorrect decisions (wrong calls): false positives and false negatives. We present the basic method and a heuristic discussion. Examples are given using numerically generated and real bioassay data for tritium. Various analytical models are used to fit the prior probability distribution in order to test the sensitivity to choice of model. Parametric studies show that for typical situations involving rare events the normalized Bayesian decision level k(alpha) = Lc/sigma0, where sigma0 is the measurement uncertainty for zero true amount, is in the range of 3 to 5 depending on the true positive rate. Four times sigma0 rather than approximately two times sigma0, as in classical statistics, would seem a better choice for the decision level in these situations.
Biological Assay↗
[Statistical methods for the analysis and comprehensive evaluation of the physical development of a children's collective].
Explore the source record for details and available documents.
Age Factors↗
Efficiency and ambiguity in an adaptive neural code.
We examine the dynamics of a neural code in the context of stimuli whose statistical properties are themselves evolving dynamically. Adaptation to these statistics occurs over a wide range of timescales-from tens of milliseconds to minutes. Rapid components of adaptation serve to optimize the information that action potentials carry about rapid stimulus variations within the local statistical ensemble, while changes in the rate and statistics of action-potential firing encode information about the ensemble itself, thus resolving potential ambiguities. The speed with which information is optimized and ambiguities are resolved approaches the physical limit imposed by statistical sampling and noise.
Adaptation, Physiological↗
Lower extremity physical performance and use of compensatory strategies for mobility.
OBJECTIVES: To compare measured lower extremity physical performance in the clinic with the methods used to carry out mobility tasks at home and to identify key factors influencing day-to-day task performance. DESIGN: Cross-sectional analysis of the Women's Health and Aging Study I. SETTING: Community-dwelling female residents of Baltimore, Maryland. PARTICIPANTS: One thousand two cognitively intact women aged 65 and older with moderate to severe physical limitations. MEASUREMENTS: Compensatory strategies reportedly used for mobility in the home, distinguishing between use of no compensatory strategies, behavioral changes only, durable medical equipment (DME) with or without behavioral change, and human help; measured lower extremity (LE) physical performance (gait speed, timed chair stands, balance). RESULTS: There was a statistically significant difference in LE physical performance between women using the four types of compensatory strategy (P < .001). Women who used DME for mobility in the home had worse performance than those using human help who in turn had worse performance than those with behavioral changes only; women reporting no compensatory strategies for in-home mobility performed best. Sequential multivariate logistic regressions identified several factors other than LE physical performance that were associated with use of specific compensatory strategies. Medical conditions, education, and environmental barriers influenced whether compensatory strategies were used at all, whereas income, contact with health providers, and availability of help in the home influenced the type of compensatory strategy. CONCLUSION: Physical abilities are an important factor influencing use of compensatory strategies for mobility, but several other factors also influence the ways that women adapt to mobility limitations.
Activities of Daily Living↗
Physical therapy interventions for patients with stroke in inpatient rehabilitation facilities.
BACKGROUND AND PURPOSE: The purpose of this study was to describe physical therapy provided to patients with stroke in inpatient rehabilitation facilities. SUBJECTS AND METHODS: Data were collected from 972 patients with stroke receiving physical therapy services at 6 rehabilitation facilities in the United States. Descriptive statistics were derived to describe physical therapy sessions, including proportion of therapy time spent in specific functional activities and proportion of those activities that included any of 59 interventions. RESULTS: Mean length of stay was 18.7 days (SD=10.3), and patients received physical therapy, on average, 13.6 days (SD=7.8). Patients attended, on average, 1.5 (SD=0.3) physical therapy sessions per day, with each session lasting 38.1 minutes (SD=17.1). Gait and prefunctional activities were performed most frequently (31.3% and 19.7% of total treatment time, respectively). For gait activity, physical therapists used balance and postural awareness training in more than 50% of sessions and used strength training for more than 50% of sessions of prefunctional activities. Eighty-six percent of the patients received evaluation, and 84% of the patients and families received education. DISCUSSION AND CONCLUSION: Therapists selected an eclectic approach to intervention rather than specific intervention techniques. The approach to patients' care included interventions to remediate impairments and to compensate for functional limitations. Therapists also reported frequently using motor control and motor learning approaches to facilitate all activities. This approach to care is largely consistent with existing stroke care guidelines and advances in the scientific theories of motor control and motor learning.
Adolescent↗
Describing maltreatment: do child protective service reports and research definitions agree?
OBJECTIVE: The National Research Council identified inadequate research definitions for abuse and neglect as barriers to research in child maltreatment. We examine the concordance between child protective services (CPS) classifications of maltreatment type with the determinations of type from two research coding systems. We contrast the two coding systems and the CPS classification, in their ability to predict subsequent difficulties in the psychological functioning of maltreated children at age 8. METHOD: The sample included 545 children who were enrolled in Longitudinal Studies of Child Abuse and Neglect (LONGSCAN) with a report of child maltreatment, had data collected at approximately 4 and 8 years of age, and had a lifetime review of CPS records to age 8. CPS Maltreatment reports were coded using LONGSCAN's modification of the Maltreatment Classification System (MMCS) and the Second National Incidence Study maltreatment coding system (NIS-2). The first analyses used reports as the unit of analysis to examine agreement between CPS and research determinations of allegation type. Validation analyses examined outcomes for each type of maltreatment experienced after age 4 under each coding system using the Child Behavior Checklist (CBCL), Trauma Symptom Checklist-Alternative form, and the Vineland Screener as the measures of outcome. Control variables were the CBCL and Battelle Developmental Screener, measured at age 4. RESULTS: There were a total of 1980 reports of maltreatment for 545 study children although only 1593 CPS reports specified at least one type of maltreatment. There were differences between the type of maltreatment recorded in child protective service records and the conclusions reached by either research classification system. CPS classifications were most discordant with the research systems for emotional abuse and neglect. Nearly 10% of physical and sexual abuse reports, as determined by the MMCS, were classified as neglect by the child protective service agencies. The NIS-2 system and the MMCS had very high Kappa statistics for agreement for physical and sexual abuse. The validity of the research definitions for physical and sexual abuse was demonstrated in models predicting children's functioning at age 8. Prediction of child functioning was significantly but modestly improved in several domains compared to the CPS classifications. CONCLUSION: Both research classification systems moderately improved on the prediction of the adverse effects of maltreatment compared to the characterization of a maltreatment exposure as recorded by CPS.
Child↗
The use of correlation integrals in the study of localized muscle fatigue of elbow flexors during maximal efforts.
Innovative applications of non-linear time series analysis have recently been used to investigate physiological phenomena. In this study, we investigated the feasibility of using the correlation integral to monitor the localized muscle fatigue process in the biceps brachii during sustained maximal efforts. The subjects performed isometric maximum contractions until failure in elbow flexion (90 degrees from neutral). The median and the 70th percentile frequency of the Surface electromyography (SEMG) power spectrum, the integrated SEMG, and the Correlation Integral (CI) were evaluated during the trials. The linear correlation between these variables and the elbow torque production was used to quantify the ability of a parameter to follow the fatiguing process. The CI had the highest linear correlation with torque (0.77 (0.12SD)), while the spectral indices correlations with torque were much lower. The decreasing trend of the torque production was followed by the spectral indices for only the beginning part of the contraction, while the CI increased sharply after the torque production fell to about 0.60 of the MVC. This suggests that the CI is sensitive to different changes of the SEMG signal during fatigue than the spectral variables.
Adult↗
Prevalence of childhood trauma in a community sample of substance-abusing women.
The purpose of this study was to estimate the prevalence of positive trauma histories in a community sample of intravenous drug using (IVDU) women for five subsets of childhood trauma (emotional abuse or neglect, physical abuse or neglect, and sexual abuse) and to compare demographic variables between the abused versus nonabused groups. Of the 181 women who completed the Childhood Trauma Questionnaire (CTQ), 109 (60.2%) were sexually abused, 100 (55.2%) were physically abused, 83 (45.9%) were emotionally abused, 151 (83.4%) were emotionally neglected, and 108 (59.7%) were physically neglected. There were no statistically significant findings for age, ethnicity, and educational level. Those subjects that were physically neglected were more likely not to be in a current relationship compared to those subjects that were not abused (p = .036). The findings suggest that the prevalence of all five childhood traumas was higher than what has been reported in the general population, and that physical neglect of individuals may predict lack of current significant relationships.
Adult↗
Accurate and efficient loop selections by the DFIRE-based all-atom statistical potential.
The conformations of loops are determined by the water-mediated interactions between amino acid residues. Energy functions that describe the interactions can be derived either from physical principles (physical-based energy function) or statistical analysis of known protein structures (knowledge-based statistical potentials). It is commonly believed that statistical potentials are appropriate for coarse-grained representation of proteins but are not as accurate as physical-based potentials when atomic resolution is required. Several recent applications of physical-based energy functions to loop selections appear to support this view. In this article, we apply a recently developed DFIRE-based statistical potential to three different loop decoy sets (RAPPER, Jacobson, and Forrest-Woolf sets). Together with a rotamer library for side-chain optimization, the performance of DFIRE-based potential in the RAPPER decoy set (385 loop targets) is comparable to that of AMBER/GBSA for short loops (two to eight residues). The DFIRE is more accurate for longer loops (9 to 12 residues). Similar trend is observed when comparing DFIRE with another physical-based OPLS/SGB-NP energy function in the large Jacobson decoy set (788 loop targets). In the Forrest-Woolf decoy set for the loops of membrane proteins, the DFIRE potential performs substantially better than the combination of the CHARMM force field with several solvation models. The results suggest that a single-term DFIRE-statistical energy function can provide an accurate loop prediction at a fraction of computing cost required for more complicate physical-based energy functions. A Web server for academic users is established for loop selection at the softwares/services section of the Web site http://theory.med.buffalo.edu/.
Membrane Proteins↗
Geometry of escort distributions.
Given an original distribution, its statistical and probabilistic attributes may be scanned using the associated escort distribution introduced by Beck and Schlögl and employed in the formulation of nonextensive statistical mechanics. Here, the geometric structure of the one-parameter family of the escort distributions is studied based on the Kullback-Leibler divergence and the relevant Fisher metric. It is shown that the Fisher metric is given in terms of the generalized bit variance, which measures fluctuations of the crowding index of a multifractal. The Cramér-Rao inequality leads to a fundamental limit for the precision of the statistical estimate of the order of the escort distribution. We also show quantitatively that it is inappropriate to use the original distribution instead of the escort distribution for calculating the expectation values of physical quantities in nonextensive statistical mechanics.
Journal Article↗
Quality of life of patients with chronic renal allograft rejection and anemia.
BACKGROUND: The treatment with recombinant human erythropoietin (rHuEPO) of anemia associated with renal insufficiency (RI) improves the health-related quality of life (HRQOL) of those patients. The objective of this study was to evaluate the HRQOL of patients with chronic allograft nephropathy (CAN) and anemia associated to RI, and the effect of rHuEPO treatment on the HRQOL. METHODS: This prospective study consisted of 17 kidney transplant patients with RI caused by CAN and anemia who received rHuEPO. The hemoglobin (Hb) target was 12 g/dL. Serum Hb, hematocrit (Hct) and creatinine clearance (CrCl) were collected. HRQOL was evaluated with the Kidney Disease Quality of Life Short-Form 36 (SF-36) questionnaire at the start, at the 3rd and 6th month and at the end of the follow-up. SF-36 scores (eight scales, physical component summary (PCS) and mental component summary (MCS) were standardized by age and gender using the Spanish population norms. The "effect size" was also calculated for each score. RESULTS: Hb and Hct statistically improved from the start to the 3rd month and to the end of the study (p<0.01). Although the CrCl remained stable during most of the follow-up, it worsened (p=0.002) around the 13th month. SF-36 scores at the beginning were worse than that of the general population. Three SF-36 scales statistically improved; role-physical, vitality and mental health. The effect size was moderate for pain (0.41), role-emotional (0.39) and MCS (0.42); and large for role-physical (0.65), vitality (0.81) and mental health (0.74). CONCLUSIONS: The poor HRQOL of patients with CAN and anemia improves with rHuEPO treatment, the effect size varying from moderate to large.
Adult↗
Relationship between physical fitness and susceptibility to cardiovascular disease.
Explore the source record for details and available documents.
Cardiovascular Diseases↗
Development of physical fitness test batteries by factor analysis techniques.
Explore the source record for details and available documents.
Factor Analysis, Statistical↗
C-peptide, insulin-like growth factor binding protein-1, glycosylated hemoglobin, and the risk of distal colorectal adenoma in women.
BACKGROUND: Determinants of insulin secretion and insulin-like growth factors (IGF) have been directly associated with risk for colorectal cancer. However, few studies have evaluated whether these factors are also associated with risk of colorectal adenoma, the main precursor lesion to colorectal cancer. METHODS: We identified 380 distal colorectal adenoma cases diagnosed between 1989 and 1998 and 380 controls among nondiabetic women from the cohort of 32,826 women, nested in the Nurses' Health Study, who provided blood samples in 1989 to 1990. Cases and controls were individually matched on year of birth, time period of and indication(s) for endoscopy, and date of blood draw. RESULTS: High concentrations of C-peptide, an indicator of insulin secretion, were statistically significantly associated with risk of distal colorectal adenoma [multivariable relative risk (MVRR) top versus bottom quartile, 1.63; 95% confidence interval (95% CI), 1.01-2.66; P = 0.01], even after including body mass index and physical activity in the statistical model. Fasting IGF binding protein-1 (IGFBP-1) concentrations did not show any clear association with risk for adenoma (MVRR top versus bottom quartile, 1.08; 95% CI, 0.56-2.07). These associations did not differ significantly by size/stage of adenoma. Glycosylated hemoglobin (HbA1c) was associated with a nonstatistically significant increased risk of colorectal adenoma (MVRR top versus bottom quartile, 1.47; 95% CI, 0.89-2.44). CONCLUSIONS: High HbA1c and low IGFBP-1 were not clearly associated with increased risk of distal colorectal adenoma. However, our current results and previous associations between C-peptide and colorectal cancer suggest that hyperinsulinemia may play a role throughout the development of colorectal neoplasia.
Adenoma↗