PubMed Health⌕ Search

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.

At least 235 records · Page 13Linked to original sources
PubMed2005

Statistical aspects in physical mapping application to the genome of O. oeni strain GM.

This work addresses issues around physical maps, in particular, for circular genomes. The overlapping relationship between two fragments obtained by applying two different restriction enzymes, separately, is classified as nonoverlapping, partial overlapping, and total overlapping. A double partial overlapping can also appear in a particular situation. Taking into account DNA fragment lengths and under the assumption that the left-hand endpoints of the two restriction fragments are independent random variables, each of which with a uniform distribution along a circular genome, we present expressions for prior probabilities of those events. This information is combined with hybridization data via Bayes' theorem, in order to evaluate corresponding posterior probabilities. Additionally, we explore a sensitivity analysis to quantify the effect of length variation in the results.

Algorithms↗
PubMed1998

Protein fold recognition without Boltzmann statistics or explicit physical basis.

We present a fast method for finding optimal parameters for a low-resolution (threading) force field intended to distinguish correct from incorrect folds for a given protein sequence. In contrast to other methods, the parameterization uses information from >10(7) misfolded structures as well as a set of native sequence-structure pairs. In addition to testing the resulting force field's performance on the protein sequence threading problem, results are shown that characterize the number of parameters necessary for effective structure recognition.

Algorithms↗
PubMed2001

About some physical mechanisms of statistics of radiation-induced effects formation and non-linear cell response in low dose area.

A new cascade-stochastic approach to solve the direct and inverse problems of radiation-induced effect statistics in track biodetectors is presented in this paper. The analysis of the experimental data has made it possible to establish a non-linear nature of the "dose-effect" dependence in low dose area. For the first time, a new determination of the relative biological efficiency and quality coefficient of ionizing radiation in area of low doses are proposed.

Cell Nucleus↗
PubMed1994

A comprehensive study of physical parameters, biomechanical properties, and statistical correlations of iliac crest bone wedges used in spinal fusion surgery. I. Physical parameters and their correlations.

Iliac crest bone wedges are commonly used in spinal fusion procedures and must be capable of withstanding considerable mechanical stress during the healing process. The variability of "quality" of bone materials used in the production of bone wedges suggests that some bone materials may not be suitable for use in vertebral fusion procedures and some quantifiable means of predicting the suitability of bone wedges would be desirable. A total of 250 iliac crest wedges were used in this study. Physical parameters of iliac crest wedges, such as total cross-sectional area, cancellous cross-sectional area, cortical cross-sectional area, percentage of cortical cross-sectional area, "width," and apparent density were determined. The statistical correlations among physical parameters were investigated. These correlations revealed that the relative percentage of cortical and cancellous bone remained fairly constant at 41% and 59%, respectively, regardless of total cross-sectional area of a wedge, that apparent density did not appreciably change with donor age, and that ash (inorganic) and organic content (weight) correlated well with the apparent density.

Aging↗
PubMed2003

Stochastic phase resetting of stimulus-locked responses of two coupled oscillators: transient response clustering, synchronization, and desynchronization.

Transient phase dynamics, synchronization, and desynchronization which are stimulus-locked (i.e., tightly time-locked to a repetitively administered stimulus) are studied in two coupled phase oscillators in the presence of noise. The presented method makes it possible to detect such processes in numerical and experimental signals. The time resolution is enormous, since it is only restricted by the sampling rate. Stochastic stimulus locking of the phases or the n:m phase difference at a particular time t relative to stimulus onset is defined by the presence of one or more prominent peaks in the cross-trial distribution of the phases or the n:m phase difference at time t relative to stimulus onset in an ensemble of poststimulus responses. The oscillators' coupling may cause a transient cross-trial response clustering of the poststimulus responses. In particular, the mechanism by which intrinsic noise induces symmetric antiphase cross-trial response clustering in coupled detuned oscillators is a stochastic resonance. Unlike the presented approach, both cross-trial averaging (where an ensemble of poststimulus responses is simply averaged) and cross-trial cross correlation (CTCC) lead to severe misinterpretations: Triggered averaging cannot distinguish a cross-trial response clustering or decorrelation from a mean amplitude decrease of the single responses. CTCC not only depends on the oscillators' phase difference but also on their phases and, thus, inevitably displays "artificial" oscillations that are not related to synchronization or desynchronization.

Models, Statistical↗
PubMed2004

Observability of Rényi's entropy.

Despite recent claims we argue that Rényi's entropy is an observable quantity. It is shown that, contrary to popular belief, the reported domain of instability for Rényi entropies has zero measure (Bhattacharyya measure). In addition, we show that the instabilities can be easily emended by introducing a coarse graining into an actual measurement. We also clear up any doubts regarding the observability of Rényi's entropy in (multi)fractal systems and in systems with absolutely continuous probability density functions.

Entropy↗
PubMed2000

Does Acculturation Influence Physical Activity in Japanese American Older Adults?

PURPOSE: Despite the health benefits of physical activity, demographic and health factors as well as cultural backgrounds are thought to influence participation in physical activity. The aim of this study is to examine whether acculturation is associated with physical activity in a sample of Japanese American older adults living on the continental United States. METHODS: A survey was mailed to Japanese Americans identified from the mailing list of two community­based organizations. The survey included questions on physical activity, acculturation, demographics, health behaviors, and self­reported health status. Data were analyzed using bivariate and multiple regression techniques. FINDINGS: Acculturation was not a significant predictor of phsical activity in either community sample, or the pooled sample, after conrolling for other sociodemographic andhealth status variables. The models explained 23% to 2% of the variance in physical activity. Statistically significant predictors of physical activity included gender, work status, age, income, and health status. CONCLUSIONS: Our findings differ from studies of Japanese Americans in Hawaii and other racial/ethnic groups, suggesting that accultraion may have differential effects depending on the environment and the racial/ethnic group under study. KEY WORDS: Japanese American, physical activity, acculturation

Journal Article↗