Functional anthology of intrinsic disorder. 1. Biological processes and functions of proteins with long disordered regions.

PubMed

Xie, Hongbo; Vucetic, Slobodan; Iakoucheva, Lilia M; Oldfield, Christopher J; Dunker, A Keith; Uversky, Vladimir N; Obradovic, Zoran

2007-05-01

Identifying relationships between function, amino acid sequence, and protein structure represents a major challenge. In this study, we propose a bioinformatics approach that identifies functional keywords in the Swiss-Prot database that correlate with intrinsic disorder. A statistical evaluation is employed to rank the significance of these correlations. Protein sequence data redundancy and the relationship between protein length and protein structure were taken into consideration to ensure the quality of the statistical inferences. Over 200,000 proteins from the Swiss-Prot database were analyzed using this approach. The predictions of intrinsic disorder were carried out using PONDR VL3E predictor of long disordered regions that achieves an accuracy of above 86%. Overall, out of the 710 Swiss-Prot functional keywords that were each associated with at least 20 proteins, 238 were found to be strongly positively correlated with predicted long intrinsically disordered regions, whereas 302 were strongly negatively correlated with such regions. The remaining 170 keywords were ambiguous without strong positive or negative correlation with the disorder predictions. These functions cover a large variety of biological activities and imply that disordered regions are characterized by a wide functional repertoire. Our results agree well with literature findings, as we were able to find at least one illustrative example of functional disorder or order shown experimentally for the vast majority of keywords showing the strongest positive or negative correlation with intrinsic disorder. This work opens a series of three papers, which enriches the current view of protein structure-function relationships, especially with regards to functionalities of intrinsically disordered proteins, and provides researchers with a novel tool that could be used to improve the understanding of the relationships between protein structure and function. The first paper of the series describes our statistical approach, outlines the major findings, and provides illustrative examples of biological processes and functions positively and negatively correlated with intrinsic disorder.

Imprints of magnetic power and helicity spectra on radio polarimetry statistics

NASA Astrophysics Data System (ADS)

Junklewitz, H.; Enßlin, T. A.

2011-06-01

The statistical properties of turbulent magnetic fields in radio-synchrotron sources should be imprinted on the statistics of polarimetric observables. In search of these imprints, i.e. characteristic modifications of the polarimetry statistics caused by magnetic field properties, we calculate correlation and cross-correlation functions from a set of observables that contain total intensity I, polarized intensity P, and Faraday depth φ. The correlation functions are evaluated for all combinations of observables up to fourth order in magnetic field B. We derive these analytically as far as possible and from first principles using only some basic assumptions, such as Gaussian statistics for the underlying magnetic field in the observed region and statistical homogeneity. We further assume some simplifications to reduce the complexity of the calculations, because for a start we were interested in a proof of concept. Using this statistical approach, we show that it is possible to gain information about the helical part of the magnetic power spectrum via the correlation functions < P(kperp) φ(k'_{perp)φ(k''perp)>B} and < I(kperp) φ(k'_{perp)φ(k''perp)>B}. Using this insight, we construct an easy-to-use test for helicity called LITMUS (Local Inference Test for Magnetic fields which Uncovers heliceS), which gives a spectrally integrated measure of helicity. For now, all calculations are given in a Faraday-free case, but set up so that Faraday rotational effects can be included later.

Statistics of time delay and scattering correlation functions in chaotic systems. I. Random matrix theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Novaes, Marcel

2015-06-15

We consider the statistics of time delay in a chaotic cavity having M open channels, in the absence of time-reversal invariance. In the random matrix theory approach, we compute the average value of polynomial functions of the time delay matrix Q = − iħS{sup †}dS/dE, where S is the scattering matrix. Our results do not assume M to be large. In a companion paper, we develop a semiclassical approximation to S-matrix correlation functions, from which the statistics of Q can also be derived. Together, these papers contribute to establishing the conjectured equivalence between the random matrix and the semiclassical approaches.

A general statistical test for correlations in a finite-length time series.

PubMed

Hanson, Jeffery A; Yang, Haw

2008-06-07

The statistical properties of the autocorrelation function from a time series composed of independently and identically distributed stochastic variables has been studied. Analytical expressions for the autocorrelation function's variance have been derived. It has been found that two common ways of calculating the autocorrelation, moving-average and Fourier transform, exhibit different uncertainty characteristics. For periodic time series, the Fourier transform method is preferred because it gives smaller uncertainties that are uniform through all time lags. Based on these analytical results, a statistically robust method has been proposed to test the existence of correlations in a time series. The statistical test is verified by computer simulations and an application to single-molecule fluorescence spectroscopy is discussed.

Life Outside the Golden Window: Statistical Angles on the Signal-to-Noise Problem

NASA Astrophysics Data System (ADS)

Wagman, Michael

2018-03-01

Lattice QCD simulations of multi-baryon correlation functions can predict the structure and reactions of nuclei without encountering the baryon chemical potential sign problem. However, they suffer from a signal-to-noise problem where Monte Carlo estimates of observables have quantum fluctuations that are exponentially larger than their average values. Recent lattice QCD results demonstrate that the complex phase of baryon correlations functions relates the baryon signal-to-noise problem to a sign problem and exhibits unexpected statistical behavior resembling a heavy-tailed random walk on the unit circle. Estimators based on differences of correlation function phases evaluated at different Euclidean times are discussed that avoid the usual signal-to-noise problem, instead facing a signal-to-noise problem as the time interval associated with the phase difference is increased, and allow hadronic observables to be determined from arbitrarily large-time correlation functions.

Flaxseed oil supplementation manipulates correlations between serum individual mol % free fatty acid levels and insulin resistance in type 2 diabetics. Insulin resistance and percent remaining pancreatic β-cell function are unaffected.

PubMed

Barre, D E; Mizier-Barre, K A; Griscti, O; Hafez, K

2016-10-01

Elevated total serum free fatty acids (FFAs) concentrations have been suggested, controversially, to enhance insulin resistance and decrease percent remaining β-cell function. However, concentrations of individual serum FFAs have never been published in terms of their relationship (correlation) to homeostatic model assessment-insulin resistance (HOMA-IR) and percent remaining β-cell function (HOMA-%β) in the type 2 diabetics (T2Ds). Alpha-linolenic acid consumption has a negative correlation with the insulin resistance, which in turn is negatively correlated with the remaining β-cell function. The primary objective was to test the hypothesis that there would be different relationship (correlation) between the blood serum individual free FFA mol % levels and HOMA-IR and/or HOMA-%β in T2D. The secondary objective was to test the hypothesis that flaxseed oil, previously being shown to be ineffective in the glycemic control in T2Ds, may alter these correlations in a statistically significant manner as well as HOMA-IR and/or HOMA-%β. Patients were recruited via a newspaper advertisement and two physicians have been employed. All the patients came to visit one and three months later for a second visit. At the second visit, the subjects were randomly assigned (double blind) to flaxseed or safflower oil treatment for three months, until the third visit. Different statistically significant correlations or trends towards among some serum individual free FFA mol % levels and HOMA-IR and HOMA-%β, pre- and post-flaxseed and safflower oil supplementation were found. However, flaxseed oil had no impact on HOMA-IR or HOMA-%β despite statistically significant alterations in correlations compared to baseline HOMA-IR. The obtained data indicate that high doses of flaxseed oil have no statistically significant effect on HOMA-IR or HOMA-%β in T2Ds, probably due to the additive effects of negative and positive correlations.

An asymptotic theory for cross-correlation between auto-correlated sequences and its application on neuroimaging data.

PubMed

Zhou, Yunyi; Tao, Chenyang; Lu, Wenlian; Feng, Jianfeng

2018-04-20

Functional connectivity is among the most important tools to study brain. The correlation coefficient, between time series of different brain areas, is the most popular method to quantify functional connectivity. Correlation coefficient in practical use assumes the data to be temporally independent. However, the time series data of brain can manifest significant temporal auto-correlation. A widely applicable method is proposed for correcting temporal auto-correlation. We considered two types of time series models: (1) auto-regressive-moving-average model, (2) nonlinear dynamical system model with noisy fluctuations, and derived their respective asymptotic distributions of correlation coefficient. These two types of models are most commonly used in neuroscience studies. We show the respective asymptotic distributions share a unified expression. We have verified the validity of our method, and shown our method exhibited sufficient statistical power for detecting true correlation on numerical experiments. Employing our method on real dataset yields more robust functional network and higher classification accuracy than conventional methods. Our method robustly controls the type I error while maintaining sufficient statistical power for detecting true correlation in numerical experiments, where existing methods measuring association (linear and nonlinear) fail. In this work, we proposed a widely applicable approach for correcting the effect of temporal auto-correlation on functional connectivity. Empirical results favor the use of our method in functional network analysis. Copyright © 2018. Published by Elsevier B.V.

Theory of nonstationary Hawkes processes

NASA Astrophysics Data System (ADS)

Tannenbaum, Neta Ravid; Burak, Yoram

2017-12-01

We expand the theory of Hawkes processes to the nonstationary case, in which the mutually exciting point processes receive time-dependent inputs. We derive an analytical expression for the time-dependent correlations, which can be applied to networks with arbitrary connectivity, and inputs with arbitrary statistics. The expression shows how the network correlations are determined by the interplay between the network topology, the transfer functions relating units within the network, and the pattern and statistics of the external inputs. We illustrate the correlation structure using several examples in which neural network dynamics are modeled as a Hawkes process. In particular, we focus on the interplay between internally and externally generated oscillations and their signatures in the spike and rate correlation functions.

The large-scale correlations of multicell densities and profiles: implications for cosmic variance estimates

NASA Astrophysics Data System (ADS)

Codis, Sandrine; Bernardeau, Francis; Pichon, Christophe

2016-08-01

In order to quantify the error budget in the measured probability distribution functions of cell densities, the two-point statistics of cosmic densities in concentric spheres is investigated. Bias functions are introduced as the ratio of their two-point correlation function to the two-point correlation of the underlying dark matter distribution. They describe how cell densities are spatially correlated. They are computed here via the so-called large deviation principle in the quasi-linear regime. Their large-separation limit is presented and successfully compared to simulations for density and density slopes: this regime is shown to be rapidly reached allowing to get sub-percent precision for a wide range of densities and variances. The corresponding asymptotic limit provides an estimate of the cosmic variance of standard concentric cell statistics applied to finite surveys. More generally, no assumption on the separation is required for some specific moments of the two-point statistics, for instance when predicting the generating function of cumulants containing any powers of concentric densities in one location and one power of density at some arbitrary distance from the rest. This exact `one external leg' cumulant generating function is used in particular to probe the rate of convergence of the large-separation approximation.

Structuring Stokes correlation functions using vector-vortex beam

NASA Astrophysics Data System (ADS)

Kumar, Vijay; Anwar, Ali; Singh, R. P.

2018-01-01

Higher order statistical correlations of the optical vector speckle field, formed due to scattering of a vector-vortex beam, are explored. Here, we report on the experimental construction of the Stokes parameters covariance matrix, consisting of all possible spatial Stokes parameters correlation functions. We also propose and experimentally realize a new Stokes correlation functions called Stokes field auto correlation functions. It is observed that the Stokes correlation functions of the vector-vortex beam will be reflected in the respective Stokes correlation functions of the corresponding vector speckle field. The major advantage of proposing Stokes correlation functions is that the Stokes correlation function can be easily tuned by manipulating the polarization of vector-vortex beam used to generate vector speckle field and to get the phase information directly from the intensity measurements. Moreover, this approach leads to a complete experimental Stokes characterization of a broad range of random fields.

Correlation techniques and measurements of wave-height statistics

NASA Technical Reports Server (NTRS)

Guthart, H.; Taylor, W. C.; Graf, K. A.; Douglas, D. G.

1972-01-01

Statistical measurements of wave height fluctuations have been made in a wind wave tank. The power spectral density function of temporal wave height fluctuations evidenced second-harmonic components and an f to the minus 5th power law decay beyond the second harmonic. The observations of second harmonic effects agreed very well with a theoretical prediction. From the wave statistics, surface drift currents were inferred and compared to experimental measurements with satisfactory agreement. Measurements were made of the two dimensional correlation coefficient at 15 deg increments in angle with respect to the wind vector. An estimate of the two-dimensional spatial power spectral density function was also made.

Data Analysis Techniques for Physical Scientists

NASA Astrophysics Data System (ADS)

Pruneau, Claude A.

2017-10-01

Preface; How to read this book; 1. The scientific method; Part I. Foundation in Probability and Statistics: 2. Probability; 3. Probability models; 4. Classical inference I: estimators; 5. Classical inference II: optimization; 6. Classical inference III: confidence intervals and statistical tests; 7. Bayesian inference; Part II. Measurement Techniques: 8. Basic measurements; 9. Event reconstruction; 10. Correlation functions; 11. The multiple facets of correlation functions; 12. Data correction methods; Part III. Simulation Techniques: 13. Monte Carlo methods; 14. Collision and detector modeling; List of references; Index.

Quantitative evaluation of cross correlation between two finite-length time series with applications to single-molecule FRET.

PubMed

Hanson, Jeffery A; Yang, Haw

2008-11-06

The statistical properties of the cross correlation between two time series has been studied. An analytical expression for the cross correlation function's variance has been derived. On the basis of these results, a statistically robust method has been proposed to detect the existence and determine the direction of cross correlation between two time series. The proposed method has been characterized by computer simulations. Applications to single-molecule fluorescence spectroscopy are discussed. The results may also find immediate applications in fluorescence correlation spectroscopy (FCS) and its variants.

Statistics of baryon correlation functions in lattice QCD

NASA Astrophysics Data System (ADS)

Wagman, Michael L.; Savage, Martin J.; Nplqcd Collaboration

2017-12-01

A systematic analysis of the structure of single-baryon correlation functions calculated with lattice QCD is performed, with a particular focus on characterizing the structure of the noise associated with quantum fluctuations. The signal-to-noise problem in these correlation functions is shown, as long suspected, to result from a sign problem. The log-magnitude and complex phase are found to be approximately described by normal and wrapped normal distributions respectively. Properties of circular statistics are used to understand the emergence of a large time noise region where standard energy measurements are unreliable. Power-law tails in the distribution of baryon correlation functions, associated with stable distributions and "Lévy flights," are found to play a central role in their time evolution. A new method of analyzing correlation functions is considered for which the signal-to-noise ratio of energy measurements is constant, rather than exponentially degrading, with increasing source-sink separation time. This new method includes an additional systematic uncertainty that can be removed by performing an extrapolation, and the signal-to-noise problem reemerges in the statistics of this extrapolation. It is demonstrated that this new method allows accurate results for the nucleon mass to be extracted from the large-time noise region inaccessible to standard methods. The observations presented here are expected to apply to quantum Monte Carlo calculations more generally. Similar methods to those introduced here may lead to practical improvements in analysis of noisier systems.

Statistics of Stokes variables for correlated Gaussian fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eliyahu, D.

1994-09-01

The joint and marginal probability distribution functions of the Stokes variables are derived for correlated Gaussian fields [an extension of D. Eliyahu, Phys. Rev. E 47, 2881 (1993)]. The statistics depend only on the first moment (averaged) Stokes variables and have a universal form for [ital S][sub 1], [ital S][sub 2], and [ital S][sub 3]. The statistics of the variables describing the Cartesian coordinates of the Poincare sphere are given also.

Statistical power as a function of Cronbach alpha of instrument questionnaire items.

PubMed

Heo, Moonseong; Kim, Namhee; Faith, Myles S

2015-10-14

In countless number of clinical trials, measurements of outcomes rely on instrument questionnaire items which however often suffer measurement error problems which in turn affect statistical power of study designs. The Cronbach alpha or coefficient alpha, here denoted by C(α), can be used as a measure of internal consistency of parallel instrument items that are developed to measure a target unidimensional outcome construct. Scale score for the target construct is often represented by the sum of the item scores. However, power functions based on C(α) have been lacking for various study designs. We formulate a statistical model for parallel items to derive power functions as a function of C(α) under several study designs. To this end, we assume fixed true score variance assumption as opposed to usual fixed total variance assumption. That assumption is critical and practically relevant to show that smaller measurement errors are inversely associated with higher inter-item correlations, and thus that greater C(α) is associated with greater statistical power. We compare the derived theoretical statistical power with empirical power obtained through Monte Carlo simulations for the following comparisons: one-sample comparison of pre- and post-treatment mean differences, two-sample comparison of pre-post mean differences between groups, and two-sample comparison of mean differences between groups. It is shown that C(α) is the same as a test-retest correlation of the scale scores of parallel items, which enables testing significance of C(α). Closed-form power functions and samples size determination formulas are derived in terms of C(α), for all of the aforementioned comparisons. Power functions are shown to be an increasing function of C(α), regardless of comparison of interest. The derived power functions are well validated by simulation studies that show that the magnitudes of theoretical power are virtually identical to those of the empirical power. Regardless of research designs or settings, in order to increase statistical power, development and use of instruments with greater C(α), or equivalently with greater inter-item correlations, is crucial for trials that intend to use questionnaire items for measuring research outcomes. Further development of the power functions for binary or ordinal item scores and under more general item correlation strutures reflecting more real world situations would be a valuable future study.

Correlations of occupation numbers in the canonical ensemble and application to a Bose-Einstein condensate in a one-dimensional harmonic trap

NASA Astrophysics Data System (ADS)

Giraud, Olivier; Grabsch, Aurélien; Texier, Christophe

2018-05-01

We study statistical properties of N noninteracting identical bosons or fermions in the canonical ensemble. We derive several general representations for the p -point correlation function of occupation numbers n1⋯np ¯. We demonstrate that it can be expressed as a ratio of two p ×p determinants involving the (canonical) mean occupations n1¯, ..., np¯, which can themselves be conveniently expressed in terms of the k -body partition functions (with k ≤N ). We draw some connection with the theory of symmetric functions and obtain an expression of the correlation function in terms of Schur functions. Our findings are illustrated by revisiting the problem of Bose-Einstein condensation in a one-dimensional harmonic trap, for which we get analytical results. We get the moments of the occupation numbers and the correlation between ground-state and excited-state occupancies. In the temperature regime dominated by quantum correlations, the distribution of the ground-state occupancy is shown to be a truncated Gumbel law. The Gumbel law, describing extreme-value statistics, is obtained when the temperature is much smaller than the Bose-Einstein temperature.

Pelvic floor muscle strength of women consulting at the gynecology outpatient clinics and its correlation with sexual dysfunction: A cross-sectional study.

PubMed

Ozdemir, Filiz Ciledag; Pehlivan, Erkan; Melekoglu, Rauf

2017-01-01

To investigate the pelvic floor muscle strength of the women andevaluateits possible correlation with sexual dysfunction. In this cross-sectional type study, stratified clusters were used for the sampling method. Index of Female Sexual Function (IFSF) worksheetwere used for questions on sexual function. The pelvic floor muscle strength of subjects was assessed byperineometer. The chi-squared test, logistic regression and Pearson's correlation analysis were used for the statistical analysis. Four hundred thirty primiparous women, mean age 38.5 participated in this study. The average pelvic floor muscle strength value was found 31.4±9.6 cm H 2 O and the average Index of Female Sexual Function (IFSF) score was found 26.5±6.9. Parity (odds ratio OR=5.546) and age 40 or higher (OR=3.484) were found correlated with pelvic floor muscle weakness (p<0.05). The factors directly correlated with sexual dysfunction were found being overweight (OR=2.105) and age 40 or higher (OR=2.451) (p<0.05). Pearson's correlation analysis showed that there was a statistically significantlinear correlation between the muscular strength of the pelvic floor and sexual function (p=0.001). The results suggested subjects with decreased pelvic floor muscle strength value had higher frequency of sexual dysfunction.

Gaussian statistics of the cosmic microwave background: Correlation of temperature extrema in the COBE DMR two-year sky maps

NASA Technical Reports Server (NTRS)

Kogut, A.; Banday, A. J.; Bennett, C. L.; Hinshaw, G.; Lubin, P. M.; Smoot, G. F.

1995-01-01

We use the two-point correlation function of the extrema points (peaks and valleys) in the Cosmic Background Explorer (COBE) Differential Microwave Radiometers (DMR) 2 year sky maps as a test for non-Gaussian temperature distribution in the cosmic microwave background anisotropy. A maximum-likelihood analysis compares the DMR data to n = 1 toy models whose random-phase spherical harmonic components a(sub lm) are drawn from either Gaussian, chi-square, or log-normal parent populations. The likelihood of the 53 GHz (A+B)/2 data is greatest for the exact Gaussian model. There is less than 10% chance that the non-Gaussian models tested describe the DMR data, limited primarily by type II errors in the statistical inference. The extrema correlation function is a stronger test for this class of non-Gaussian models than topological statistics such as the genus.

Dynamics of EEG functional connectivity during statistical learning.

PubMed

Tóth, Brigitta; Janacsek, Karolina; Takács, Ádám; Kóbor, Andrea; Zavecz, Zsófia; Nemeth, Dezso

2017-10-01

Statistical learning is a fundamental mechanism of the brain, which extracts and represents regularities of our environment. Statistical learning is crucial in predictive processing, and in the acquisition of perceptual, motor, cognitive, and social skills. Although previous studies have revealed competitive neurocognitive processes underlying statistical learning, the neural communication of the related brain regions (functional connectivity, FC) has not yet been investigated. The present study aimed to fill this gap by investigating FC networks that promote statistical learning in humans. Young adults (N=28) performed a statistical learning task while 128-channels EEG was acquired. The task involved probabilistic sequences, which enabled to measure incidental/implicit learning of conditional probabilities. Phase synchronization in seven frequency bands was used to quantify FC between cortical regions during the first, second, and third periods of the learning task, respectively. Here we show that statistical learning is negatively correlated with FC of the anterior brain regions in slow (theta) and fast (beta) oscillations. These negative correlations increased as the learning progressed. Our findings provide evidence that dynamic antagonist brain networks serve a hallmark of statistical learning. Copyright © 2017 Elsevier Inc. All rights reserved.

Associations between results of post-stroke NDT-Bobath rehabilitation in gait parameters, ADL and hand functions.

PubMed

Mikołajewska, Emilia

2013-01-01

In patients after a stroke there are variable disorders. These patients often need rehabilitation in more than one area beceause of multiple limitations of the ability to perform everyday activities. The aim of the study was to assess correlations - statistical relationships between observed gait parameters, ADL and hand functions - results of rehabilitation of patients after ischaemic stroke according to the NDTBobath method for adults. The investigated group consisted of 60 patients after ischaemic stroke, who participated in the rehabilitation programme. 10 sessions of the NDT-Bobath therapy were provided in 2 weeks (10 days of the therapy). The calculation of correlations was made based on changes of parameters: Bobath Scale (to assess hand functions), Barthel Index (to assess ADL), gait velocity, cadence and stride lenght. Measurements were performed in every patient twice: on admission (before the therapy) and after last session of the therapy to assess rehabilitation effects. The main statistically relevant corellations observed in the study were as follows: in the whole group of patients: poor and moderate (negative) correlation between changes of gait parameters and Bobath Scale and Barthel Index, moderate and severe (negative) correlation between changes of gait parameters and Bobath Scale and Barthel Index in the group of women, correlation between changes in Bobath Scale and Barthel Index in the group of patients with left side of paresis, (negative) correlation between changes of gait parameters and Bobath Scale in group of patients younger than 68 years, moderate, high and very high correlations between changes in gait parameters in groups of women, men, younger than 68 years and older than 68 years. There have been observed statistically significant and favourable changes in the health status of patients, described by gait parameters, changes in hand functions and ADL. Based on the presented correlations there is an assumption that it is hard to achieve simultaneous recovery in all areas: gait parameters, hand functions and ADLs in two weeks of rehabilitation.

Factors associated with frailty in chronically ill older adults.

PubMed

Hackstaff, Lynn

2009-01-01

An ex post facto analysis of a secondary dataset examined relationships between physical frailty, depression, and the self-perceived domains of health status and quality-of-life in older adults. The randomized sample included 992 community-dwelling, chronically ill, and functionally impaired adults age 65 and older who received care from a Southern California Kaiser Permanente medical center between 1998 and 2002. Physical frailty represents a level of physiologic vulnerability and functional loss that results in dependence on others for basic, daily living needs (Fried et al., 2001). The purpose of the study was to identify possible intervention junctures related to self-efficacy of older adults in order to help optimize their functionality. Multivariate correlation analyses showed statistically significant positive correlations between frailty level and depression (r = .18; p = < .05), number of medical conditions (r = .09; p = < .05), and self-rated quality-of-life (r = .24; p = < .05). Frailty level showed a statistically significant negative correlation with self-perceived health status (r = -.25; p = < .05). Notably, no statistically significant correlation was found between age and frailty level (r = -.03; p = < .05). In linear regression, self-perceived health status had a partial variance with frailty level (part r = -.18). The significant correlations found support further research to identify interventions to help vulnerable, older adults challenge self-perceived capabilities so that they may achieve optimum functionality through increased physical activity earlier on, and increased self-efficacy to support successful adaptation to aging-related losses.

ESTIMATION OF FUNCTIONALS OF SPARSE COVARIANCE MATRICES.

PubMed

Fan, Jianqing; Rigollet, Philippe; Wang, Weichen

High-dimensional statistical tests often ignore correlations to gain simplicity and stability leading to null distributions that depend on functionals of correlation matrices such as their Frobenius norm and other ℓ r norms. Motivated by the computation of critical values of such tests, we investigate the difficulty of estimation the functionals of sparse correlation matrices. Specifically, we show that simple plug-in procedures based on thresholded estimators of correlation matrices are sparsity-adaptive and minimax optimal over a large class of correlation matrices. Akin to previous results on functional estimation, the minimax rates exhibit an elbow phenomenon. Our results are further illustrated in simulated data as well as an empirical study of data arising in financial econometrics.

ESTIMATION OF FUNCTIONALS OF SPARSE COVARIANCE MATRICES

PubMed Central

Fan, Jianqing; Rigollet, Philippe; Wang, Weichen

2016-01-01

High-dimensional statistical tests often ignore correlations to gain simplicity and stability leading to null distributions that depend on functionals of correlation matrices such as their Frobenius norm and other ℓr norms. Motivated by the computation of critical values of such tests, we investigate the difficulty of estimation the functionals of sparse correlation matrices. Specifically, we show that simple plug-in procedures based on thresholded estimators of correlation matrices are sparsity-adaptive and minimax optimal over a large class of correlation matrices. Akin to previous results on functional estimation, the minimax rates exhibit an elbow phenomenon. Our results are further illustrated in simulated data as well as an empirical study of data arising in financial econometrics. PMID:26806986

A quadratically regularized functional canonical correlation analysis for identifying the global structure of pleiotropy with NGS data

PubMed Central

Zhu, Yun; Fan, Ruzong; Xiong, Momiao

2017-01-01

Investigating the pleiotropic effects of genetic variants can increase statistical power, provide important information to achieve deep understanding of the complex genetic structures of disease, and offer powerful tools for designing effective treatments with fewer side effects. However, the current multiple phenotype association analysis paradigm lacks breadth (number of phenotypes and genetic variants jointly analyzed at the same time) and depth (hierarchical structure of phenotype and genotypes). A key issue for high dimensional pleiotropic analysis is to effectively extract informative internal representation and features from high dimensional genotype and phenotype data. To explore correlation information of genetic variants, effectively reduce data dimensions, and overcome critical barriers in advancing the development of novel statistical methods and computational algorithms for genetic pleiotropic analysis, we proposed a new statistic method referred to as a quadratically regularized functional CCA (QRFCCA) for association analysis which combines three approaches: (1) quadratically regularized matrix factorization, (2) functional data analysis and (3) canonical correlation analysis (CCA). Large-scale simulations show that the QRFCCA has a much higher power than that of the ten competing statistics while retaining the appropriate type 1 errors. To further evaluate performance, the QRFCCA and ten other statistics are applied to the whole genome sequencing dataset from the TwinsUK study. We identify a total of 79 genes with rare variants and 67 genes with common variants significantly associated with the 46 traits using QRFCCA. The results show that the QRFCCA substantially outperforms the ten other statistics. PMID:29040274

Statistical Approach To Extraction Of Texture In SAR

NASA Technical Reports Server (NTRS)

Rignot, Eric J.; Kwok, Ronald

1992-01-01

Improved statistical method of extraction of textural features in synthetic-aperture-radar (SAR) images takes account of effects of scheme used to sample raw SAR data, system noise, resolution of radar equipment, and speckle. Treatment of speckle incorporated into overall statistical treatment of speckle, system noise, and natural variations in texture. One computes speckle auto-correlation function from system transfer function that expresses effect of radar aperature and incorporates range and azimuth resolutions.

Statistical indicators of collective behavior and functional clusters in gene networks of yeast

NASA Astrophysics Data System (ADS)

Živković, J.; Tadić, B.; Wick, N.; Thurner, S.

2006-03-01

We analyze gene expression time-series data of yeast (S. cerevisiae) measured along two full cell-cycles. We quantify these data by using q-exponentials, gene expression ranking and a temporal mean-variance analysis. We construct gene interaction networks based on correlation coefficients and study the formation of the corresponding giant components and minimum spanning trees. By coloring genes according to their cell function we find functional clusters in the correlation networks and functional branches in the associated trees. Our results suggest that a percolation point of functional clusters can be identified on these gene expression correlation networks.

Impulse oscillometry at preschool age is a strong predictor of lung function by flow-volume spirometry in adolescence.

PubMed

Lauhkonen, Eero; Riikonen, Riikka; Törmänen, Sari; Koponen, Petri; Nuolivirta, Kirsi; Helminen, Merja; Toikka, Jyri; Korppi, Matti

2018-05-01

The transition from early childhood wheezing to persistent asthma is linked to lung function impairment over time. Little is known how the methods used to study lung function at different ages correlate longitudinally. Sixty-four children with a history of hospitalization for bronchiolitis before 6 months of age were prospectively studied with impulse oscillometry (IOS) at the mean age of 6.3 years and these preschool IOS results were compared with flow-volume spirometry (FVS) measurements at mean age of 11.4 years. The baseline respiratory system resistance at 5 Hz (Rrs5) showed a modest statistically significant correlation with all baseline FVS parameters except FVC. The post-bronchodilator (post-BD) Rrs5 showed a modest statistically significant correlation with post-BD FEV 1 and FEV 1 /FVC. The bronchodilator-induced decrease in Rrs5 showed a modest statistically significant correlation with the percent increase in FEV 1 . Baseline and post-BD respiratory reactance at 5 Hz (Xrs5) showed a modest statistically significant correlation with baseline and post-BD FVS parameters except post-BD FEV 1 /FVC, respectively, and post-BD Xrs5 showed a strong correlation with post-BD FVC (ρ = 0.61) and post-BD FEV 1 (ρ = 0.59). In adjusted linear regression, preschool Xrs5 remained as a statistically significant independent predictor of FVS parameters in adolescence; the one-unit decrease in the Z-score of preschool post-BD Xrs5 predicted 9.6% lower post-BD FEV 1 , 9.3% lower post-BD FVC, and 9.7% lower post-BD MEF 50 when expressed as %-predicted parameters. Persistent post-BD small airway impairment in children with a history of bronchiolitis detected with IOS at preschool age predicted FVS results measured in early adolescence. © 2018 Wiley Periodicals, Inc.

Rotational Invariance of the 2d Spin - Spin Correlation Function

NASA Astrophysics Data System (ADS)

Pinson, Haru

2012-09-01

At the critical temperature in the 2d Ising model on the square lattice, we establish the rotational invariance of the spin-spin correlation function using the asymptotics of the spin-spin correlation function along special directions (McCoy and Wu in the two dimensional Ising model. Harvard University Press, Cambridge, 1973) and the finite difference Hirota equation for which the spin-spin correlation function is shown to satisfy (Perk in Phys Lett A 79:3-5, 1980; Perk in Proceedings of III international symposium on selected topics in statistical mechanics, Dubna, August 22-26, 1984, JINR, vol II, pp 138-151, 1985).

Testing modified gravity using a marked correlation function

NASA Astrophysics Data System (ADS)

Armijo, Joaquí n.; Cai, Yan-Chuan; Padilla, Nelson; Li, Baojiu; Peacock, John A.

2018-05-01

In theories of modified gravity with the chameleon screening mechanism, the strength of the fifth force depends on environment. This induces an environment dependence of structure formation, which differs from ΛCDM. We show that these differences can be captured by the marked correlation function. With the galaxy correlation functions and number densities calibrated to match between f(R) and ΛCDM models in simulations, we show that the marked correlation functions from using either the local galaxy number density or halo mass as the marks encode extra information, which can be used to test these theories. We discuss possible applications of these statistics in observations.

Statistical measures of Planck scale signal correlations in interferometers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hogan, Craig J.; Kwon, Ohkyung

2015-06-22

A model-independent statistical framework is presented to interpret data from systems where the mean time derivative of positional cross correlation between world lines, a measure of spreading in a quantum geometrical wave function, is measured with a precision smaller than the Planck time. The framework provides a general way to constrain possible departures from perfect independence of classical world lines, associated with Planck scale bounds on positional information. A parametrized candidate set of possible correlation functions is shown to be consistent with the known causal structure of the classical geometry measured by an apparatus, and the holographic scaling of informationmore » suggested by gravity. Frequency-domain power spectra are derived that can be compared with interferometer data. As a result, simple projections of sensitivity for specific experimental set-ups suggests that measurements will directly yield constraints on a universal time derivative of the correlation function, and thereby confirm or rule out a class of Planck scale departures from classical geometry.« less

Statistical against dynamical PLF fission as seen by the IMF-IMF correlation functions and comparisons with CoMD model

NASA Astrophysics Data System (ADS)

Pagano, E. V.; Acosta, L.; Auditore, L.; Cap, T.; Cardella, G.; Colonna, M.; De Filippo, E.; Geraci, E.; Gnoffo, B.; Lanzalone, G.; Maiolino, C.; Martorana, N.; Pagano, A.; Papa, M.; Piasecki, E.; Pirrone, S.; Politi, G.; Porto, F.; Quattrocchi, L.; Rizzo, F.; Russotto, P.; Trifiro’, A.; Trimarchi, M.; Siwek-Wilczynska, K.

2018-05-01

In nuclear reactions at Fermi energies two and multi particles intensity interferometry correlation methods are powerful tools in order to pin down the characteristic time scale of the emission processes. In this paper we summarize an improved application of the fragment-fragment correlation function in the specific physics case of heavy projectile-like (PLF) binary massive splitting in two fragments of intermediate mass(IMF). Results are shown for the reverse kinematics reaction 124 Sn+64 Ni at 35 AMeV that has been investigated by using the forward part of CHIMERA multi-detector. The analysis was performed as a function of the charge asymmetry of the observed couples of IMF. We show a coexistence of dynamical and statistical components as a function of the charge asymmetry. Transport CoMD simulations are compared with the data in order to pin down the timescale of the fragments production and the relevant ingredients of the in medium effective interaction used in the transport calculations.

Asymptotic coincidence of the statistics for degenerate and non-degenerate correlated real Wishart ensembles

NASA Astrophysics Data System (ADS)

Wirtz, Tim; Kieburg, Mario; Guhr, Thomas

2017-06-01

The correlated Wishart model provides the standard benchmark when analyzing time series of any kind. Unfortunately, the real case, which is the most relevant one in applications, poses serious challenges for analytical calculations. Often these challenges are due to square root singularities which cannot be handled using common random matrix techniques. We present a new way to tackle this issue. Using supersymmetry, we carry out an anlaytical study which we support by numerical simulations. For large but finite matrix dimensions, we show that statistical properties of the fully correlated real Wishart model generically approach those of a correlated real Wishart model with doubled matrix dimensions and doubly degenerate empirical eigenvalues. This holds for the local and global spectral statistics. With Monte Carlo simulations we show that this is even approximately true for small matrix dimensions. We explicitly investigate the k-point correlation function as well as the distribution of the largest eigenvalue for which we find a surprisingly compact formula in the doubly degenerate case. Moreover we show that on the local scale the k-point correlation function exhibits the sine and the Airy kernel in the bulk and at the soft edges, respectively. We also address the positions and the fluctuations of the possible outliers in the data.

Surface temperature statistics over Los Angeles - The influence of land use

NASA Technical Reports Server (NTRS)

Dousset, Benedicte

1991-01-01

Surface temperature statistics from 84 NOAA AVHRR (Advanced Very High Resolution Radiometer) satellite images of the Los Angeles basin are interpreted as functions of the corresponding urban land-cover classified from a multispectral SPOT image. Urban heat islands observed in the temperature statistics correlate well with the distribution of industrial and fully built areas. Small cool islands coincide with highly watered parks and golf courses. There is a significant negative correlation between the afternoon surface temperature and a vegetation index computed from the SPOT image.

Joint statistics of strongly correlated neurons via dimensionality reduction

NASA Astrophysics Data System (ADS)

Deniz, Taşkın; Rotter, Stefan

2017-06-01

The relative timing of action potentials in neurons recorded from local cortical networks often shows a non-trivial dependence, which is then quantified by cross-correlation functions. Theoretical models emphasize that such spike train correlations are an inevitable consequence of two neurons being part of the same network and sharing some synaptic input. For non-linear neuron models, however, explicit correlation functions are difficult to compute analytically, and perturbative methods work only for weak shared input. In order to treat strong correlations, we suggest here an alternative non-perturbative method. Specifically, we study the case of two leaky integrate-and-fire neurons with strong shared input. Correlation functions derived from simulated spike trains fit our theoretical predictions very accurately. Using our method, we computed the non-linear correlation transfer as well as correlation functions that are asymmetric due to inhomogeneous intrinsic parameters or unequal input.

Constructing a bivariate distribution function with given marginals and correlation: application to the galaxy luminosity function

NASA Astrophysics Data System (ADS)

Takeuchi, Tsutomu T.

2010-08-01

We provide an analytic method to construct a bivariate distribution function (DF) with given marginal distributions and correlation coefficient. We introduce a convenient mathematical tool, called a copula, to connect two DFs with any prescribed dependence structure. If the correlation of two variables is weak (Pearson's correlation coefficient |ρ| < 1/3), the Farlie-Gumbel-Morgenstern (FGM) copula provides an intuitive and natural way to construct such a bivariate DF. When the linear correlation is stronger, the FGM copula cannot work anymore. In this case, we propose using a Gaussian copula, which connects two given marginals and is directly related to the linear correlation coefficient between two variables. Using the copulas, we construct the bivariate luminosity function (BLF) and discuss its statistical properties. We focus especially on the far-infrared-far-ulatraviolet (FUV-FIR) BLF, since these two wavelength regions are related to star-formation (SF) activity. Though both the FUV and FIR are related to SF activity, the univariate LFs have a very different functional form: the former is well described by the Schechter function whilst the latter has a much more extended power-law-like luminous end. We construct the FUV-FIR BLFs using the FGM and Gaussian copulas with different strengths of correlation, and examine their statistical properties. We then discuss some further possible applications of the BLF: the problem of a multiband flux-limited sample selection, the construction of the star-formation rate (SFR) function, and the construction of the stellar mass of galaxies (M*)-specific SFR (SFR/M*) relation. The copulas turn out to be a very useful tool to investigate all these issues, especially for including complicated selection effects.

Probability distributions of molecular observables computed from Markov models. II. Uncertainties in observables and their time-evolution

NASA Astrophysics Data System (ADS)

Chodera, John D.; Noé, Frank

2010-09-01

Discrete-state Markov (or master equation) models provide a useful simplified representation for characterizing the long-time statistical evolution of biomolecules in a manner that allows direct comparison with experiments as well as the elucidation of mechanistic pathways for an inherently stochastic process. A vital part of meaningful comparison with experiment is the characterization of the statistical uncertainty in the predicted experimental measurement, which may take the form of an equilibrium measurement of some spectroscopic signal, the time-evolution of this signal following a perturbation, or the observation of some statistic (such as the correlation function) of the equilibrium dynamics of a single molecule. Without meaningful error bars (which arise from both approximation and statistical error), there is no way to determine whether the deviations between model and experiment are statistically meaningful. Previous work has demonstrated that a Bayesian method that enforces microscopic reversibility can be used to characterize the statistical component of correlated uncertainties in state-to-state transition probabilities (and functions thereof) for a model inferred from molecular simulation data. Here, we extend this approach to include the uncertainty in observables that are functions of molecular conformation (such as surrogate spectroscopic signals) characterizing each state, permitting the full statistical uncertainty in computed spectroscopic experiments to be assessed. We test the approach in a simple model system to demonstrate that the computed uncertainties provide a useful indicator of statistical variation, and then apply it to the computation of the fluorescence autocorrelation function measured for a dye-labeled peptide previously studied by both experiment and simulation.

Statistical Learning Effects in Musicians and Non-Musicians: An MEG Study

ERIC Educational Resources Information Center

Paraskevopoulos, Evangelos; Kuchenbuch, Anja; Herholz, Sibylle C.; Pantev, Christo

2012-01-01

This study aimed to assess the effect of musical training in statistical learning of tone sequences using Magnetoencephalography (MEG). Specifically, MEG recordings were used to investigate the neural and functional correlates of the pre-attentive ability for detection of deviance, from a statistically learned tone sequence. The effect of…

Cosmological Constraints from Fourier Phase Statistics

NASA Astrophysics Data System (ADS)

Ali, Kamran; Obreschkow, Danail; Howlett, Cullan; Bonvin, Camille; Llinares, Claudio; Oliveira Franco, Felipe; Power, Chris

2018-06-01

Most statistical inference from cosmic large-scale structure relies on two-point statistics, i.e. on the galaxy-galaxy correlation function (2PCF) or the power spectrum. These statistics capture the full information encoded in the Fourier amplitudes of the galaxy density field but do not describe the Fourier phases of the field. Here, we quantify the information contained in the line correlation function (LCF), a three-point Fourier phase correlation function. Using cosmological simulations, we estimate the Fisher information (at redshift z = 0) of the 2PCF, LCF and their combination, regarding the cosmological parameters of the standard ΛCDM model, as well as a Warm Dark Matter (WDM) model and the f(R) and Symmetron modified gravity models. The galaxy bias is accounted for at the level of a linear bias. The relative information of the 2PCF and the LCF depends on the survey volume, sampling density (shot noise) and the bias uncertainty. For a volume of 1h^{-3}Gpc^3, sampled with points of mean density \\bar{n} = 2× 10^{-3} h3 Mpc^{-3} and a bias uncertainty of 13%, the LCF improves the parameter constraints by about 20% in the ΛCDM cosmology and potentially even more in alternative models. Finally, since a linear bias only affects the Fourier amplitudes (2PCF), but not the phases (LCF), the combination of the 2PCF and the LCF can be used to break the degeneracy between the linear bias and σ8, present in 2-point statistics.

Lattice QCD Thermodynamics and RHIC-BES Particle Production within Generic Nonextensive Statistics

NASA Astrophysics Data System (ADS)

Tawfik, Abdel Nasser

2018-05-01

The current status of implementing Tsallis (nonextensive) statistics on high-energy physics is briefly reviewed. The remarkably low freezeout-temperature, which apparently fails to reproduce the firstprinciple lattice QCD thermodynamics and the measured particle ratios, etc. is discussed. The present work suggests a novel interpretation for the so-called " Tsallis-temperature". It is proposed that the low Tsallis-temperature is due to incomplete implementation of Tsallis algebra though exponential and logarithmic functions to the high-energy particle-production. Substituting Tsallis algebra into grand-canonical partition-function of the hadron resonance gas model seems not assuring full incorporation of nonextensivity or correlations in that model. The statistics describing the phase-space volume, the number of states and the possible changes in the elementary cells should be rather modified due to interacting correlated subsystems, of which the phase-space is consisting. Alternatively, two asymptotic properties, each is associated with a scaling function, are utilized to classify a generalized entropy for such a system with large ensemble (produced particles) and strong correlations. Both scaling exponents define equivalence classes for all interacting and noninteracting systems and unambiguously characterize any statistical system in its thermodynamic limit. We conclude that the nature of lattice QCD simulations is apparently extensive and accordingly the Boltzmann-Gibbs statistics is fully fulfilled. Furthermore, we found that the ratios of various particle yields at extreme high and extreme low energies of RHIC-BES is likely nonextensive but not necessarily of Tsallis type.

Physique and Performance of Young Wheelchair Basketball Players in Relation with Classification

PubMed Central

Zancanaro, Carlo

2015-01-01

The relationships among physical characteristics, performance, and functional ability classification of younger wheelchair basketball players have been barely investigated to date. The purpose of this work was to assess anthropometry, body composition, and performance in sport-specific field tests in a national sample of Italian younger wheelchair basketball players as well as to evaluate the association of these variables with the players’ functional ability classification and game-related statistics. Several anthropometric measurements were obtained for 52 out of 91 eligible players nationwide. Performance was assessed in seven sport-specific field tests (5m sprint, 20m sprint with ball, suicide, maximal pass, pass for accuracy, spot shot and lay-ups) and game-related statistics (free-throw points scored per match, two- and three-point field-goals scored per match, and their sum). Association between variables, and predictivity was assessed by correlation and regression analysis, respectively. Players were grouped into four Classes of increasing functional ability (A-D). One-way ANOVA with Bonferroni’s correction for multiple comparisons was used to assess differences between Classes. Sitting height and functional ability Class especially correlated with performance outcomes, but wheelchair basketball experience and skinfolds did not. Game-related statistics and sport-specific field-test scores all showed significant correlation with each other. Upper arm circumference and/or maximal pass and lay-ups test scores were able to explain 42 to 59% of variance in game-related statistics (P<0.001). A clear difference in performance was only found for functional ability Class A and D. Conclusion: In younger wheelchair basketball players, sitting height positively contributes to performance. The maximal pass and lay-ups test should be carefully considered in younger wheelchair basketball training plans. Functional ability Class reflects to a limited extent the actual differences in performance. PMID:26606681

Phase dependence of the unnormalized second-order photon correlation function

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ciornea, V.; Bardetski, P.; Macovei, M. A., E-mail: macovei@phys.asm.md

2016-10-15

We investigate the resonant quantum dynamics of a multi-qubit ensemble in a microcavity. Both the quantum-dot subsystem and the microcavity mode are pumped coherently. We find that the microcavity photon statistics depends on the phase difference of the driving lasers, which is not the case for the photon intensity at resonant driving. This way, one can manipulate the two-photon correlations. In particular, higher degrees of photon correlations and, eventually, stronger intensities are obtained. Furthermore, the microcavity photon statistics exhibits steady-state oscillatory behaviors as well as asymmetries.

Modeling of two-particle femtoscopic correlations at top RHIC energy

NASA Astrophysics Data System (ADS)

Ermakov, N.; Nigmatkulov, G.

2017-01-01

The spatial and temporal characteristics of particle emitting source produced in particle and/or nuclear collisions can be measured by using two-particle femtoscopic correlations. These correlations arise due to quantum statistics, Coulomb and strong final state interactions. In this paper we report on the calculations of like-sign pion femtoscopic correlations produced in p+p, p+Au, d+Au, Au+Au at top RHIC energy using Ultra Relativistic Quantum Molecular Dynamics Model (UrQMD). Three-dimensional correlation functions are constructed using the Bertsch-Pratt parametrization of the two-particle relative momentum. The correlation functions are studied in several transverse mass ranges. The emitting source radii of charged pions, Rout, Rside, Rlong , are obtained from Gaussian fit to the correlation functions and compared to data from the STAR and PHENIX experiments.

Correlation between urodynamic function and 3D cat scan anatomy in neobladders: does it exist?

PubMed

Crivellaro, S; Mami, E; Wald, C; Smith, J J; Kocjancic, E; Stoffel, J; Bresette, J; Libertino, J A

2009-01-01

We compared the functional and anatomical differences among three different orthotopic neobladders, utilizing video urodynamics and 3D CT to determine what parameters, if any, correlate to function. Thirty-four patients were able to participate in the evaluation of their neobladder by 3D CT and video urodynamics. Three different orthotopic neobladders were identified (12 ileal, 7 ileocecal, 15 sigmoid). Multiple measurements, observations and functional data have been obtained. Statistical analysis for this study employed a linear regression test and an odds ratio calculation (using StatSoft V. 5.1). In comparing three different neobladders, no significant differences were noted. Looking at the entire population, the following association was statistically significant in linear correlation: the maximal capacity and the neobladder volume; the pressure at the maximal capacity and the distance from the symphysis, the pressure at maximal flow and both the distance from the symphysis and the thickness of the neobladder. The distance from the left femoral head was directly correlated with the post void residual and inversely correlated with the maximal flow. The Odds ratio calculation revealed (with significant P < 0.05) that the further the center of the neobladder is from the right femoral head, the higher risk of incontinence. The study seems to show no significant anatomical or functional difference among the three different types of neobladders. A possible correlation between the position of the neobladder and urinary incontinence is suggested, recognizing further study in a larger population is required.

Report on 3 and 4-point correlation statistics in the COBE DMR anisotrophy maps

NASA Technical Reports Server (NTRS)

Hinshaw, Gary (Principal Investigator); Gorski, Krzystof M.; Banday, Anthony J.; Bennett, Charles L.

1996-01-01

As part of the work performed under NASA contract # NAS5-32648, we have computed the 3-point and 4-point correlation functions of the COBE-DNIR 2-year and 4-year anisotropy maps. The motivation for this study was to search for evidence of non-Gaussian statistical fluctuations in the temperature maps: skewness or asymmetry in the case of the 3-point function, kurtosis in the case of the 4-point function. Such behavior would have very significant implications for our understanding of the processes of galaxy formation, because our current models of galaxy formation predict that non-Gaussian features should not be present in the DMR maps. The results of our work showed that the 3-point correlation function is consistent with zero and that the 4-point function is not a very sensitive probe of non-Gaussian behavior in the COBE-DMR data. Our computation and analysis of 3-point correlations in the 2-year DMR maps was published in the Astrophysical Journal Letters, volume 446, page L67, 1995. Our computation and analysis of 3-point correlations in the 4-year DMR maps will be published, together with some additional tests, in the June 10, 1996 issue of the Astrophysical Journal Letters. Copies of both of these papers are attached as an appendix to this report.

The Relationship between Family Functioning and Academic Achievement in Female High School Students of Isfahan, Iran, in 2013-2014.

PubMed

Rezaei-Dehaghani, Abdollah; Keshvari, Mahrokh; Paki, Somayeh

2018-01-01

Nowadays, the most important problem of the educational system is the vast spread of school failure. Therefore, detection of the factors leading to or preventing students' academic achievement is of utmost importance. Family function is considered to be a critical component of academic success. This study aimed to investigate the relationship between family functioning and academic achievement in high school female students in Isfahan. This descriptive correlational study was conducted through random sampling among 237 female high school students in Isfahan during school year 2013-2014. Data were collected by participants' personal characteristics and Bloom family function questionnaires. To analyze the data, descriptive statistics (mean and standard deviation) and inferential statistics (Pearson correlation and linear regression analysis) were adopted and computed using SPSS software. The results showed a significant correlation between family function (except lack of independence) and students' academic achievement ( p < 0.05). Further, among family function dimensions, expressiveness ( β = 0.235, p < 0.001), family socialization ( β = 0.219, p = 0.001), and cohesion ( β = 0.211, p = 0.001) were more reliable predictors of academic achievement. The results of this study showed that students' academic achievement is highly correlated with the performance of their families. Therefore, to improve students' educational status in cultural and educational programs, which are specified for them, family function centered plans should be at the heart of attention.

Statistical properties of cross-correlation in the Korean stock market

NASA Astrophysics Data System (ADS)

Oh, G.; Eom, C.; Wang, F.; Jung, W.-S.; Stanley, H. E.; Kim, S.

2011-01-01

We investigate the statistical properties of the cross-correlation matrix between individual stocks traded in the Korean stock market using the random matrix theory (RMT) and observe how these affect the portfolio weights in the Markowitz portfolio theory. We find that the distribution of the cross-correlation matrix is positively skewed and changes over time. We find that the eigenvalue distribution of original cross-correlation matrix deviates from the eigenvalues predicted by the RMT, and the largest eigenvalue is 52 times larger than the maximum value among the eigenvalues predicted by the RMT. The β_{473} coefficient, which reflect the largest eigenvalue property, is 0.8, while one of the eigenvalues in the RMT is approximately zero. Notably, we show that the entropy function E(σ) with the portfolio risk σ for the original and filtered cross-correlation matrices are consistent with a power-law function, E( σ) σ^{-γ}, with the exponent γ 2.92 and those for Asian currency crisis decreases significantly.

Neuronal Correlation Parameter and the Idea of Thermodynamic Entropy of an N-Body Gravitationally Bounded System.

PubMed

Haranas, Ioannis; Gkigkitzis, Ioannis; Kotsireas, Ilias; Austerlitz, Carlos

2017-01-01

Understanding how the brain encodes information and performs computation requires statistical and functional analysis. Given the complexity of the human brain, simple methods that facilitate the interpretation of statistical correlations among different brain regions can be very useful. In this report we introduce a numerical correlation measure that may serve the interpretation of correlational neuronal data, and may assist in the evaluation of different brain states. The description of the dynamical brain system, through a global numerical measure may indicate the presence of an action principle which may facilitate a application of physics principles in the study of the human brain and cognition.

A simple microstructure return model explaining microstructure noise and Epps effects

NASA Astrophysics Data System (ADS)

Saichev, A.; Sornette, D.

2014-01-01

We present a novel simple microstructure model of financial returns that combines (i) the well-known ARFIMA process applied to tick-by-tick returns, (ii) the bid-ask bounce effect, (iii) the fat tail structure of the distribution of returns and (iv) the non-Poissonian statistics of inter-trade intervals. This model allows us to explain both qualitatively and quantitatively important stylized facts observed in the statistics of both microstructure and macrostructure returns, including the short-ranged correlation of returns, the long-ranged correlations of absolute returns, the microstructure noise and Epps effects. According to the microstructure noise effect, volatility is a decreasing function of the time-scale used to estimate it. The Epps effect states that cross correlations between asset returns are increasing functions of the time-scale at which the returns are estimated. The microstructure noise is explained as the result of the negative return correlations inherent in the definition of the bid-ask bounce component (ii). In the presence of a genuine correlation between the returns of two assets, the Epps effect is due to an average statistical overlap of the momentum of the returns of the two assets defined over a finite time-scale in the presence of the long memory process (i).

Statistical tests for power-law cross-correlated processes

NASA Astrophysics Data System (ADS)

Podobnik, Boris; Jiang, Zhi-Qiang; Zhou, Wei-Xing; Stanley, H. Eugene

2011-12-01

For stationary time series, the cross-covariance and the cross-correlation as functions of time lag n serve to quantify the similarity of two time series. The latter measure is also used to assess whether the cross-correlations are statistically significant. For nonstationary time series, the analogous measures are detrended cross-correlations analysis (DCCA) and the recently proposed detrended cross-correlation coefficient, ρDCCA(T,n), where T is the total length of the time series and n the window size. For ρDCCA(T,n), we numerically calculated the Cauchy inequality -1≤ρDCCA(T,n)≤1. Here we derive -1≤ρDCCA(T,n)≤1 for a standard variance-covariance approach and for a detrending approach. For overlapping windows, we find the range of ρDCCA within which the cross-correlations become statistically significant. For overlapping windows we numerically determine—and for nonoverlapping windows we derive—that the standard deviation of ρDCCA(T,n) tends with increasing T to 1/T. Using ρDCCA(T,n) we show that the Chinese financial market's tendency to follow the U.S. market is extremely weak. We also propose an additional statistical test that can be used to quantify the existence of cross-correlations between two power-law correlated time series.

Mapping the Structure-Function Relationship in Glaucoma and Healthy Patients Measured with Spectralis OCT and Humphrey Perimetry

PubMed Central

Muñoz–Negrete, Francisco J.; Oblanca, Noelia; Rebolleda, Gema

2018-01-01

Purpose To study the structure-function relationship in glaucoma and healthy patients assessed with Spectralis OCT and Humphrey perimetry using new statistical approaches. Materials and Methods Eighty-five eyes were prospectively selected and divided into 2 groups: glaucoma (44) and healthy patients (41). Three different statistical approaches were carried out: (1) factor analysis of the threshold sensitivities (dB) (automated perimetry) and the macular thickness (μm) (Spectralis OCT), subsequently applying Pearson's correlation to the obtained regions, (2) nonparametric regression analysis relating the values in each pair of regions that showed significant correlation, and (3) nonparametric spatial regressions using three models designed for the purpose of this study. Results In the glaucoma group, a map that relates structural and functional damage was drawn. The strongest correlation with visual fields was observed in the peripheral nasal region of both superior and inferior hemigrids (r = 0.602 and r = 0.458, resp.). The estimated functions obtained with the nonparametric regressions provided the mean sensitivity that corresponds to each given macular thickness. These functions allowed for accurate characterization of the structure-function relationship. Conclusions Both maps and point-to-point functions obtained linking structure and function damage contribute to a better understanding of this relationship and may help in the future to improve glaucoma diagnosis. PMID:29850196

Analysis of Anatomic and Functional Measures in X-Linked Retinoschisis

PubMed Central

Cukras, Catherine A.; Huryn, Laryssa A.; Jeffrey, Brett P.; Turriff, Amy; Sieving, Paul A.

2018-01-01

Purpose To examine the symmetry of structural and functional parameters between eyes in patients with X-linked retinoschisis (XLRS), as well as changes in visual acuity and electrophysiology over time. Methods This is a single-center observational study of 120 males with XLRS who were evaluated at the National Eye Institute. Examinations included best-corrected visual acuity for all participants, as well as ERG recording and optical coherence tomography (OCT) on a subset of participants. Statistical analyses were performed using nonparametric Spearman correlations and linear regression. Results Our analyses demonstrated a statistically significant correlation of structural and functional measures between the two eyes of XLRS patients for all parameters. OCT central macular thickness (n = 78; Spearman r = 0.83, P < 0.0001) and ERG b/a ratio (n = 78; Spearman r = 0.82, P < 0.0001) were the most strongly correlated between a participant's eyes, whereas visual acuity was less strongly correlated (n = 120; Spearman r = 0.47, P < 0.0001). Stability of visual acuity was observed with an average change of less than one letter (n = 74; OD −0.66 and OS −0.70 letters) in a mean follow-up time of 6.8 years. There was no statistically significant change in the ERG b/a ratio within eyes over time. Conclusions Although a broad spectrum of clinical phenotypes is observed across individuals with XLRS, our study demonstrates a significant correlation of structural and functional findings between the two eyes and stability of measures of acuity and ERG parameters over time. These results highlight the utility of the fellow eye as a useful reference for monocular interventional trials.

Properties of permutation-based gene tests and controlling type 1 error using a summary statistic based gene test

PubMed Central

2013-01-01

Background The advent of genome-wide association studies has led to many novel disease-SNP associations, opening the door to focused study on their biological underpinnings. Because of the importance of analyzing these associations, numerous statistical methods have been devoted to them. However, fewer methods have attempted to associate entire genes or genomic regions with outcomes, which is potentially more useful knowledge from a biological perspective and those methods currently implemented are often permutation-based. Results One property of some permutation-based tests is that their power varies as a function of whether significant markers are in regions of linkage disequilibrium (LD) or not, which we show from a theoretical perspective. We therefore develop two methods for quantifying the degree of association between a genomic region and outcome, both of whose power does not vary as a function of LD structure. One method uses dimension reduction to “filter” redundant information when significant LD exists in the region, while the other, called the summary-statistic test, controls for LD by scaling marker Z-statistics using knowledge of the correlation matrix of markers. An advantage of this latter test is that it does not require the original data, but only their Z-statistics from univariate regressions and an estimate of the correlation structure of markers, and we show how to modify the test to protect the type 1 error rate when the correlation structure of markers is misspecified. We apply these methods to sequence data of oral cleft and compare our results to previously proposed gene tests, in particular permutation-based ones. We evaluate the versatility of the modification of the summary-statistic test since the specification of correlation structure between markers can be inaccurate. Conclusion We find a significant association in the sequence data between the 8q24 region and oral cleft using our dimension reduction approach and a borderline significant association using the summary-statistic based approach. We also implement the summary-statistic test using Z-statistics from an already-published GWAS of Chronic Obstructive Pulmonary Disorder (COPD) and correlation structure obtained from HapMap. We experiment with the modification of this test because the correlation structure is assumed imperfectly known. PMID:24199751

Properties of permutation-based gene tests and controlling type 1 error using a summary statistic based gene test.

PubMed

Swanson, David M; Blacker, Deborah; Alchawa, Taofik; Ludwig, Kerstin U; Mangold, Elisabeth; Lange, Christoph

2013-11-07

The advent of genome-wide association studies has led to many novel disease-SNP associations, opening the door to focused study on their biological underpinnings. Because of the importance of analyzing these associations, numerous statistical methods have been devoted to them. However, fewer methods have attempted to associate entire genes or genomic regions with outcomes, which is potentially more useful knowledge from a biological perspective and those methods currently implemented are often permutation-based. One property of some permutation-based tests is that their power varies as a function of whether significant markers are in regions of linkage disequilibrium (LD) or not, which we show from a theoretical perspective. We therefore develop two methods for quantifying the degree of association between a genomic region and outcome, both of whose power does not vary as a function of LD structure. One method uses dimension reduction to "filter" redundant information when significant LD exists in the region, while the other, called the summary-statistic test, controls for LD by scaling marker Z-statistics using knowledge of the correlation matrix of markers. An advantage of this latter test is that it does not require the original data, but only their Z-statistics from univariate regressions and an estimate of the correlation structure of markers, and we show how to modify the test to protect the type 1 error rate when the correlation structure of markers is misspecified. We apply these methods to sequence data of oral cleft and compare our results to previously proposed gene tests, in particular permutation-based ones. We evaluate the versatility of the modification of the summary-statistic test since the specification of correlation structure between markers can be inaccurate. We find a significant association in the sequence data between the 8q24 region and oral cleft using our dimension reduction approach and a borderline significant association using the summary-statistic based approach. We also implement the summary-statistic test using Z-statistics from an already-published GWAS of Chronic Obstructive Pulmonary Disorder (COPD) and correlation structure obtained from HapMap. We experiment with the modification of this test because the correlation structure is assumed imperfectly known.

Bacterial genomes lacking long-range correlations may not be modeled by low-order Markov chains: the role of mixing statistics and frame shift of neighboring genes.

PubMed

Cocho, Germinal; Miramontes, Pedro; Mansilla, Ricardo; Li, Wentian

2014-12-01

We examine the relationship between exponential correlation functions and Markov models in a bacterial genome in detail. Despite the well known fact that Markov models generate sequences with correlation function that decays exponentially, simply constructed Markov models based on nearest-neighbor dimer (first-order), trimer (second-order), up to hexamer (fifth-order), and treating the DNA sequence as being homogeneous all fail to predict the value of exponential decay rate. Even reading-frame-specific Markov models (both first- and fifth-order) could not explain the fact that the exponential decay is very slow. Starting with the in-phase coding-DNA-sequence (CDS), we investigated correlation within a fixed-codon-position subsequence, and in artificially constructed sequences by packing CDSs with out-of-phase spacers, as well as altering CDS length distribution by imposing an upper limit. From these targeted analyses, we conclude that the correlation in the bacterial genomic sequence is mainly due to a mixing of heterogeneous statistics at different codon positions, and the decay of correlation is due to the possible out-of-phase between neighboring CDSs. There are also small contributions to the correlation from bases at the same codon position, as well as by non-coding sequences. These show that the seemingly simple exponential correlation functions in bacterial genome hide a complexity in correlation structure which is not suitable for a modeling by Markov chain in a homogeneous sequence. Other results include: use of the (absolute value) second largest eigenvalue to represent the 16 correlation functions and the prediction of a 10-11 base periodicity from the hexamer frequencies. Copyright © 2014 Elsevier Ltd. All rights reserved.

Arterial spin labeling fMRI measurements of decreased blood flow in primary visual cortex correlates with decreased visual function in human glaucoma.

PubMed

Duncan, Robert O; Sample, Pamela A; Bowd, Christopher; Weinreb, Robert N; Zangwill, Linda M

2012-05-01

Altered metabolic activity has been identified as a potential contributing factor to the neurodegeneration associated with primary open angle glaucoma (POAG). Consequently, we sought to determine whether there is a relationship between the loss of visual function in human glaucoma and resting blood perfusion within primary visual cortex (V1). Arterial spin labeling (ASL) functional magnetic resonance imaging (fMRI) was conducted in 10 participants with POAG. Resting cerebral blood flow (CBF) was measured from dorsal and ventral V1. Behavioral measurements of visual function were obtained using standard automated perimetry (SAP), short-wavelength automated perimetry (SWAP), and frequency-doubling technology perimetry (FDT). Measurements of CBF were compared to differences in visual function for the superior and inferior hemifield. Differences in CBF between ventral and dorsal V1 were correlated with differences in visual function for the superior versus inferior visual field. A statistical bootstrapping analysis indicated that the observed correlations between fMRI responses and measurements of visual function for SAP (r=0.49), SWAP (r=0.63), and FDT (r=0.43) were statistically significant (all p<0.05). Resting blood perfusion in human V1 is correlated with the loss of visual function in POAG. Altered CBF may be a contributing factor to glaucomatous optic neuropathy, or it may be an indication of post-retinal glaucomatous neurodegeneration caused by damage to the retinal ganglion cells. Copyright © 2012 Elsevier Ltd. All rights reserved.

Statistical microeconomics and commodity prices: theory and empirical results.

PubMed

Baaquie, Belal E

2016-01-13

A review is made of the statistical generalization of microeconomics by Baaquie (Baaquie 2013 Phys. A 392, 4400-4416. (doi:10.1016/j.physa.2013.05.008)), where the market price of every traded commodity, at each instant of time, is considered to be an independent random variable. The dynamics of commodity market prices is given by the unequal time correlation function and is modelled by the Feynman path integral based on an action functional. The correlation functions of the model are defined using the path integral. The existence of the action functional for commodity prices that was postulated to exist in Baaquie (Baaquie 2013 Phys. A 392, 4400-4416. (doi:10.1016/j.physa.2013.05.008)) has been empirically ascertained in Baaquie et al. (Baaquie et al. 2015 Phys. A 428, 19-37. (doi:10.1016/j.physa.2015.02.030)). The model's action functionals for different commodities has been empirically determined and calibrated using the unequal time correlation functions of the market commodity prices using a perturbation expansion (Baaquie et al. 2015 Phys. A 428, 19-37. (doi:10.1016/j.physa.2015.02.030)). Nine commodities drawn from the energy, metal and grain sectors are empirically studied and their auto-correlation for up to 300 days is described by the model to an accuracy of R(2)>0.90-using only six parameters. © 2015 The Author(s).

Interatomic potentials in condensed matter via the maximum-entropy principle

NASA Astrophysics Data System (ADS)

Carlsson, A. E.

1987-09-01

A general method is described for the calculation of interatomic potentials in condensed-matter systems by use of a maximum-entropy Ansatz for the interatomic correlation functions. The interatomic potentials are given explicitly in terms of statistical correlation functions involving the potential energy and the structure factor of a ``reference medium.'' Illustrations are given for Al-Cu alloys and a model transition metal.

Colorectal cancer mutational profiles correlate with defined microbial communities in the tumor microenvironment.

PubMed

Burns, Michael B; Montassier, Emmanuel; Abrahante, Juan; Priya, Sambhawa; Niccum, David E; Khoruts, Alexander; Starr, Timothy K; Knights, Dan; Blekhman, Ran

2018-06-20

Variation in the gut microbiome has been linked to colorectal cancer (CRC), as well as to host genetic variation. However, we do not know whether, in addition to baseline host genetics, somatic mutational profiles in CRC tumors interact with the surrounding tumor microbiome, and if so, whether these changes can be used to understand microbe-host interactions with potential functional biological relevance. Here, we characterized the association between CRC microbial communities and tumor mutations using microbiome profiling and whole-exome sequencing in 44 pairs of tumors and matched normal tissues. We found statistically significant associations between loss-of-function mutations in tumor genes and shifts in the abundances of specific sets of bacterial taxa, suggestive of potential functional interaction. This correlation allows us to statistically predict interactions between loss-of-function tumor mutations in cancer-related genes and pathways, including MAPK and Wnt signaling, solely based on the composition of the microbiome. In conclusion, our study shows that CRC microbiomes are correlated with tumor mutational profiles, pointing towards possible mechanisms of molecular interaction.

THREE-POINT PHASE CORRELATIONS: A NEW MEASURE OF NONLINEAR LARGE-SCALE STRUCTURE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolstenhulme, Richard; Bonvin, Camille; Obreschkow, Danail

2015-05-10

We derive an analytical expression for a novel large-scale structure observable: the line correlation function. The line correlation function, which is constructed from the three-point correlation function of the phase of the density field, is a robust statistical measure allowing the extraction of information in the nonlinear and non-Gaussian regime. We show that, in perturbation theory, the line correlation is sensitive to the coupling kernel F{sub 2}, which governs the nonlinear gravitational evolution of the density field. We compare our analytical expression with results from numerical simulations and find a 1σ agreement for separations r ≳ 30 h{sup −1} Mpc.more » Fitting formulae for the power spectrum and the nonlinear coupling kernel at small scales allow us to extend our prediction into the strongly nonlinear regime, where we find a 1σ agreement with the simulations for r ≳ 2 h{sup −1} Mpc. We discuss the advantages of the line correlation relative to standard statistical measures like the bispectrum. Unlike the latter, the line correlation is independent of the bias, in the regime where the bias is local and linear. Furthermore, the variance of the line correlation is independent of the Gaussian variance on the modulus of the density field. This suggests that the line correlation can probe more precisely the nonlinear regime of gravity, with less contamination from the power spectrum variance.« less

Analysis/forecast experiments with a flow-dependent correlation function using FGGE data

NASA Technical Reports Server (NTRS)

Baker, W. E.; Bloom, S. C.; Carus, H.; Nestler, M. S.

1986-01-01

The use of a flow-dependent correlation function to improve the accuracy of an optimum interpolation (OI) scheme is examined. The development of the correlation function for the OI analysis scheme used for numerical weather prediction is described. The scheme uses a multivariate surface analysis over the oceans to model the pressure-wind error cross-correlation and it has the ability to use an error correlation function that is flow- and geographically-dependent. A series of four-day data assimilation experiments, conducted from January 5-9, 1979, were used to investigate the effect of the different features of the OI scheme (error correlation) on forecast skill for the barotropic lows and highs. The skill of the OI was compared with that of a successive correlation method (SCM) of analysis. It is observed that the largest difference in the correlation statistics occurred in barotropic and baroclinic lows and highs. The comparison reveals that the OI forecasts were more accurate than the SCM forecasts.

An Efficient and Reliable Statistical Method for Estimating Functional Connectivity in Large Scale Brain Networks Using Partial Correlation

PubMed Central

Wang, Yikai; Kang, Jian; Kemmer, Phebe B.; Guo, Ying

2016-01-01

Currently, network-oriented analysis of fMRI data has become an important tool for understanding brain organization and brain networks. Among the range of network modeling methods, partial correlation has shown great promises in accurately detecting true brain network connections. However, the application of partial correlation in investigating brain connectivity, especially in large-scale brain networks, has been limited so far due to the technical challenges in its estimation. In this paper, we propose an efficient and reliable statistical method for estimating partial correlation in large-scale brain network modeling. Our method derives partial correlation based on the precision matrix estimated via Constrained L1-minimization Approach (CLIME), which is a recently developed statistical method that is more efficient and demonstrates better performance than the existing methods. To help select an appropriate tuning parameter for sparsity control in the network estimation, we propose a new Dens-based selection method that provides a more informative and flexible tool to allow the users to select the tuning parameter based on the desired sparsity level. Another appealing feature of the Dens-based method is that it is much faster than the existing methods, which provides an important advantage in neuroimaging applications. Simulation studies show that the Dens-based method demonstrates comparable or better performance with respect to the existing methods in network estimation. We applied the proposed partial correlation method to investigate resting state functional connectivity using rs-fMRI data from the Philadelphia Neurodevelopmental Cohort (PNC) study. Our results show that partial correlation analysis removed considerable between-module marginal connections identified by full correlation analysis, suggesting these connections were likely caused by global effects or common connection to other nodes. Based on partial correlation, we find that the most significant direct connections are between homologous brain locations in the left and right hemisphere. When comparing partial correlation derived under different sparse tuning parameters, an important finding is that the sparse regularization has more shrinkage effects on negative functional connections than on positive connections, which supports previous findings that many of the negative brain connections are due to non-neurophysiological effects. An R package “DensParcorr” can be downloaded from CRAN for implementing the proposed statistical methods. PMID:27242395

An Efficient and Reliable Statistical Method for Estimating Functional Connectivity in Large Scale Brain Networks Using Partial Correlation.

PubMed

Wang, Yikai; Kang, Jian; Kemmer, Phebe B; Guo, Ying

2016-01-01

Currently, network-oriented analysis of fMRI data has become an important tool for understanding brain organization and brain networks. Among the range of network modeling methods, partial correlation has shown great promises in accurately detecting true brain network connections. However, the application of partial correlation in investigating brain connectivity, especially in large-scale brain networks, has been limited so far due to the technical challenges in its estimation. In this paper, we propose an efficient and reliable statistical method for estimating partial correlation in large-scale brain network modeling. Our method derives partial correlation based on the precision matrix estimated via Constrained L1-minimization Approach (CLIME), which is a recently developed statistical method that is more efficient and demonstrates better performance than the existing methods. To help select an appropriate tuning parameter for sparsity control in the network estimation, we propose a new Dens-based selection method that provides a more informative and flexible tool to allow the users to select the tuning parameter based on the desired sparsity level. Another appealing feature of the Dens-based method is that it is much faster than the existing methods, which provides an important advantage in neuroimaging applications. Simulation studies show that the Dens-based method demonstrates comparable or better performance with respect to the existing methods in network estimation. We applied the proposed partial correlation method to investigate resting state functional connectivity using rs-fMRI data from the Philadelphia Neurodevelopmental Cohort (PNC) study. Our results show that partial correlation analysis removed considerable between-module marginal connections identified by full correlation analysis, suggesting these connections were likely caused by global effects or common connection to other nodes. Based on partial correlation, we find that the most significant direct connections are between homologous brain locations in the left and right hemisphere. When comparing partial correlation derived under different sparse tuning parameters, an important finding is that the sparse regularization has more shrinkage effects on negative functional connections than on positive connections, which supports previous findings that many of the negative brain connections are due to non-neurophysiological effects. An R package "DensParcorr" can be downloaded from CRAN for implementing the proposed statistical methods.

Statistical inference of dynamic resting-state functional connectivity using hierarchical observation modeling.

PubMed

Sojoudi, Alireza; Goodyear, Bradley G

2016-12-01

Spontaneous fluctuations of blood-oxygenation level-dependent functional magnetic resonance imaging (BOLD fMRI) signals are highly synchronous between brain regions that serve similar functions. This provides a means to investigate functional networks; however, most analysis techniques assume functional connections are constant over time. This may be problematic in the case of neurological disease, where functional connections may be highly variable. Recently, several methods have been proposed to determine moment-to-moment changes in the strength of functional connections over an imaging session (so called dynamic connectivity). Here a novel analysis framework based on a hierarchical observation modeling approach was proposed, to permit statistical inference of the presence of dynamic connectivity. A two-level linear model composed of overlapping sliding windows of fMRI signals, incorporating the fact that overlapping windows are not independent was described. To test this approach, datasets were synthesized whereby functional connectivity was either constant (significant or insignificant) or modulated by an external input. The method successfully determines the statistical significance of a functional connection in phase with the modulation, and it exhibits greater sensitivity and specificity in detecting regions with variable connectivity, when compared with sliding-window correlation analysis. For real data, this technique possesses greater reproducibility and provides a more discriminative estimate of dynamic connectivity than sliding-window correlation analysis. Hum Brain Mapp 37:4566-4580, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Machine learning classifier using abnormal brain network topological metrics in major depressive disorder.

PubMed

Guo, Hao; Cao, Xiaohua; Liu, Zhifen; Li, Haifang; Chen, Junjie; Zhang, Kerang

2012-12-05

Resting state functional brain networks have been widely studied in brain disease research. However, it is currently unclear whether abnormal resting state functional brain network metrics can be used with machine learning for the classification of brain diseases. Resting state functional brain networks were constructed for 28 healthy controls and 38 major depressive disorder patients by thresholding partial correlation matrices of 90 regions. Three nodal metrics were calculated using graph theory-based approaches. Nonparametric permutation tests were then used for group comparisons of topological metrics, which were used as classified features in six different algorithms. We used statistical significance as the threshold for selecting features and measured the accuracies of six classifiers with different number of features. A sensitivity analysis method was used to evaluate the importance of different features. The result indicated that some of the regions exhibited significantly abnormal nodal centralities, including the limbic system, basal ganglia, medial temporal, and prefrontal regions. Support vector machine with radial basis kernel function algorithm and neural network algorithm exhibited the highest average accuracy (79.27 and 78.22%, respectively) with 28 features (P<0.05). Correlation analysis between feature importance and the statistical significance of metrics was investigated, and the results revealed a strong positive correlation between them. Overall, the current study demonstrated that major depressive disorder is associated with abnormal functional brain network topological metrics and statistically significant nodal metrics can be successfully used for feature selection in classification algorithms.

[Vulnerability to atmospheric and geomagnetic factors of the body functions in healthy male dwellers of the Russian North].

PubMed

Markov, A L; Zenchenko, T A; Solonin, Iu G; Boĭko, E R

2013-01-01

In April 2009 through to November 2011, a Mars-500 satellite study of Russian Northerners (Syktyvkar citizens) was performed using the standard ECOSAN-2007 procedure evaluating the atmospheric and geomagnetic susceptibility of the main body functional parameters. Seventeen essentially healthy men at the age of 25 to 46 years were investigated. Statistical data treatment included correlation and single-factor analysis of variance. Comparison of the number of statistical correlations of the sum of all functional parameters for participants showed that most often they were sensitive to atmospheric pressure, temperature, relative humidity and oxygen partial pressure (29-35 %), and geomagnetic activity (28 %). Dependence of the functional parameters on the rate of temperature and pressure change was weak and comparable with random coincidence (11 %). Among the hemodynamic parameters, systolic pressure was particularly sensitive to space and terrestrial weather variations (29 %); sensitivity of heart rate and diastolic pressure were determined in 25 % and 21 % of participants, respectively. Among the heart rate variability parameters (HRV) the largest number of statistically reliable correlations was determined for the centralization index (32 %) and high-frequency HRV spectrum (31 %); index of the regulatory systems activity was least dependable (19 %). Life index, maximal breath-holding and Ckibinskaya's cardiorespiratory index are also susceptible. Individual responses of the functional parameters to terrestrial and space weather changes varied with partidpants which points to the necessity of individual approach to evaluation of person's reactions to environmental changes.

Statistics of voids in hierarchical universes

NASA Technical Reports Server (NTRS)

Fry, J. N.

1986-01-01

As one alternative to the N-point galaxy correlation function statistics, the distribution of holes or the probability that a volume of given size and shape be empty of galaxies can be considered. The probability of voids resulting from a variety of hierarchical patterns of clustering is considered, and these are compared with the results of numerical simulations and with observations. A scaling relation required by the hierarchical pattern of higher order correlation functions is seen to be obeyed in the simulations, and the numerical results show a clear difference between neutrino models and cold-particle models; voids are more likely in neutrino universes. Observational data do not yet distinguish but are close to being able to distinguish between models.

Modulational Instability of Cylindrical and Spherical NLS Equations. Statistical Approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grecu, A. T.; Grecu, D.; Visinescu, Anca

2010-01-21

The modulational (Benjamin-Feir) instability for cylindrical and spherical NLS equations (c/s NLS equations) is studied using a statistical approach (SAMI). A kinetic equation for a two-point correlation function is written and analyzed using the Wigner-Moyal transform. The linear stability of the Fourier transform of the two-point correlation function is studied and an implicit integral form for the dispersion relation is found. This is solved for different expressions of the initial spectrum (delta-spectrum, Lorentzian, Gaussian), and in the case of a Lorentzian spectrum the total growth of the instability is calculated. The similarities and differences with the usual one-dimensional NLS equationmore » are emphasized.« less

Pilot Study on the Effect of Botanical Medicine (Tribulus terrestris) on Serum Testosterone Level and Erectile Function in Aging Males With Partial Androgen Deficiency (PADAM).

PubMed

Roaiah, Mohamed Farid; El Khayat, Yasser Ibrahim; GamalEl Din, Sameh Fayek; Abd El Salam, Mohamed Ahmed

2016-05-18

This study was conducted on 30 consecutive male patients presenting to Kasr-Al Ainy Andrology outpatient clinic complaining of manifestations of partial androgen deficiency in aging males (PADAM). In this study (750 mg/day) of Tribulus terrestris in 3 divided doses, each of 250 mg, as an endogenous testosterone enhancer had been tried for a duration of 3 months and the evaluation of its effect had been monitored for each patient concerning its effect on serum testosterone (total and free) and luteinizing hormone (LH), as well as its impact on erectile function, which was evaluated by the International Index of Erectile Function-5 (IIEF-5) questionnaire for those patients. Results showed a statistically significant difference in the level of testosterone (total and free) and IIEF-5, but no statistically significant difference in the level of LH before and after treatment. Also, the study showed statistically significant correlation between testosterone (total and free) and IIEF-5, but no statistically significant correlation between the level of LH and the IIEF-5 before and after treatment.

Best Phd thesis Prize: Statistical analysis of ALFALFA galaxies: insights in galaxy

NASA Astrophysics Data System (ADS)

Papastergis, E.

2013-09-01

We use the rich dataset of local universe galaxies detected by the ALFALFA 21cm survey to study the statistical properties of gas-bearing galaxies. In particular, we measure the number density of galaxies as a function of their baryonic mass ("baryonic mass function") and rotational velocity ("velocity width function"), and we characterize their clustering properties ("two-point correlation function"). These statistical distributions are determined by both the properties of dark matter on small scales, as well as by the complex baryonic processes through which galaxies form over cosmic time. We interpret the ALFALFA measurements with the aid of publicly available cosmological N-body simulations and we present some key results related to galaxy formation and small-scale cosmology.

Protein Sectors: Statistical Coupling Analysis versus Conservation

PubMed Central

Teşileanu, Tiberiu; Colwell, Lucy J.; Leibler, Stanislas

2015-01-01

Statistical coupling analysis (SCA) is a method for analyzing multiple sequence alignments that was used to identify groups of coevolving residues termed “sectors”. The method applies spectral analysis to a matrix obtained by combining correlation information with sequence conservation. It has been asserted that the protein sectors identified by SCA are functionally significant, with different sectors controlling different biochemical properties of the protein. Here we reconsider the available experimental data and note that it involves almost exclusively proteins with a single sector. We show that in this case sequence conservation is the dominating factor in SCA, and can alone be used to make statistically equivalent functional predictions. Therefore, we suggest shifting the experimental focus to proteins for which SCA identifies several sectors. Correlations in protein alignments, which have been shown to be informative in a number of independent studies, would then be less dominated by sequence conservation. PMID:25723535

A novel coefficient for detecting and quantifying asymmetry of California electricity market based on asymmetric detrended cross-correlation analysis.

PubMed

Wang, Fang

2016-06-01

In order to detect and quantify asymmetry of two time series, a novel cross-correlation coefficient is proposed based on recent asymmetric detrended cross-correlation analysis (A-DXA), which we called A-DXA coefficient. The A-DXA coefficient, as an important extension of DXA coefficient ρDXA, contains two directional asymmetric cross-correlated indexes, describing upwards and downwards asymmetric cross-correlations, respectively. By using the information of directional covariance function of two time series and directional variance function of each series itself instead of power-law between the covariance function and time scale, the proposed A-DXA coefficient can well detect asymmetry between the two series no matter whether the cross-correlation is significant or not. By means of the proposed A-DXA coefficient conducted over the asymmetry for California electricity market, we found that the asymmetry between the prices and loads is not significant for daily average data in 1999 yr market (before electricity crisis) but extremely significant for those in 2000 yr market (during the crisis). To further uncover the difference of asymmetry between the years 1999 and 2000, a modified H statistic (MH) and ΔMH statistic are proposed. One of the present contributions is that the high MH values calculated for hourly data exist in majority months in 2000 market. Another important conclusion is that the cross-correlation with downwards dominates over the whole 1999 yr in contrast to the cross-correlation with upwards dominates over the 2000 yr.

Diffusion-weighted MRI of the pancreas: correlation with secretin endoscopic pancreatic function test (ePFT).

PubMed

Balci, N Cem; Momtahen, Amir Javad; Akduman, E Isin; Alkaade, Samer; Bilgin, Mehmet; Burton, Frank R

2008-10-01

To evaluate the correlation between apparent diffusion coefficient (ADC) values of the pancreas on diffusion-weighted imaging (DWI) and pancreatic exocrine function determined by HCO(3) concentration in the secretin endoscopic pancreatic function test (ePFT). Mean ADC values derived from 10 different points of the pancreatic gland on DWI were reviewed in 14 patients with normal (peak HCO(3) > or = 80 mEq/L) and 14 patients with abnormal (peak HCO(3) < 80 mEq/L) ePFT results. Magnetic resonance cholangiopancreatography (MRCP) images of the same patients were evaluated for the diagnosis of chronic pancreatitis. Correlation between ADC values and HCO(3) concentration as well as Cambridge scores in MRCP was performed using Spearman's correlation test. Mean ADC value of the pancreas was 1.52 +/- 0.13 x 10(-3) mm(2)/s in patients with abnormal ePFT results and 1.78 +/- 0.07 x 10(-3) mm(2)/s in the normal group. There was a significant statistical difference between the ADC values of the pancreas in the two groups (P < .0001). There was also a statistically significant correlation between HCO(3) level and ADC value of the pancreas in the study patients (r = 0.771, P < .0001). Morphologic changes of the pancreas according to the Cambridge classification were also well correlated with the mean ADC values (r = -0.763, P < .0001). Strong correlation between ADC value and pancreatic exocrine function as well as Cambridge score for chronic pancreatitis exists. Further studies are needed to determine the cut off ADC value for chronic pancreatitis.

Probing the statistics of primordial fluctuations and their evolution

NASA Technical Reports Server (NTRS)

Gaztanaga, Enrique; Yokoyama, Jun'ichi

1993-01-01

The statistical distribution of fluctuations on various scales is analyzed in terms of the counts in cells of smoothed density fields, using volume-limited samples of galaxy redshift catalogs. It is shown that the distribution on large scales, with volume average of the two-point correlation function of the smoothed field less than about 0.05, is consistent with Gaussian. Statistics are shown to agree remarkably well with the negative binomial distribution, which has hierarchial correlations and a Gaussian behavior at large scales. If these observed properties correspond to the matter distribution, they suggest that our universe started with Gaussian fluctuations and evolved keeping hierarchial form.

Anthropometrics related to the performance of a sample of male swimmers.

PubMed

Perciavalle, Valentina; Di Corrado, Donatella; Scuto, Claudia; Perciavalle, Vincenzo; Coco, Marinella

2014-06-01

The main purpose of the present investigation of 21 elite male swimmers was to assess whether the Ape Index (the ratio between the individual's arm span and height) and/or the second-to-fourth digit length ratio (2D:4D), i.e., the ratio between the length of the second and the fourth fingers of the right hand, are associated with the performance of high-level swimmers, when mood and/or executive function are covaried. The results showed no statistically significant correlation between the Ape Index and 2D:4D ratio, performance, executive function, or mood. In contrast, statistically significant correlations were found between 2D:4D ratio and performance, executive function, and mood. Regressions indicated that 2D:4D ratio and not Ape Index is related to the performances of a sample of male swimmers.

Wave Propagation in Non-Stationary Statistical Mantle Models at the Global Scale

NASA Astrophysics Data System (ADS)

Meschede, M.; Romanowicz, B. A.

2014-12-01

We study the effect of statistically distributed heterogeneities that are smaller than the resolution of current tomographic models on seismic waves that propagate through the Earth's mantle at teleseismic distances. Current global tomographic models are missing small-scale structure as evidenced by the failure of even accurate numerical synthetics to explain enhanced coda in observed body and surface waveforms. One way to characterize small scale heterogeneity is to construct random models and confront observed coda waveforms with predictions from these models. Statistical studies of the coda typically rely on models with simplified isotropic and stationary correlation functions in Cartesian geometries. We show how to construct more complex random models for the mantle that can account for arbitrary non-stationary and anisotropic correlation functions as well as for complex geometries. Although this method is computationally heavy, model characteristics such as translational, cylindrical or spherical symmetries can be used to greatly reduce the complexity such that this method becomes practical. With this approach, we can create 3D models of the full spherical Earth that can be radially anisotropic, i.e. with different horizontal and radial correlation functions, and radially non-stationary, i.e. with radially varying model power and correlation functions. Both of these features are crucial for a statistical description of the mantle in which structure depends to first order on the spherical geometry of the Earth. We combine different random model realizations of S velocity with current global tomographic models that are robust at long wavelengths (e.g. Meschede and Romanowicz, 2014, GJI submitted), and compute the effects of these hybrid models on the wavefield with a spectral element code (SPECFEM3D_GLOBE). We finally analyze the resulting coda waves for our model selection and compare our computations with observations. Based on these observations, we make predictions about the strength of unresolved small-scale structure and extrinsic attenuation.

A wavelet-based estimator of the degrees of freedom in denoised fMRI time series for probabilistic testing of functional connectivity and brain graphs.

PubMed

Patel, Ameera X; Bullmore, Edward T

2016-11-15

Connectome mapping using techniques such as functional magnetic resonance imaging (fMRI) has become a focus of systems neuroscience. There remain many statistical challenges in analysis of functional connectivity and network architecture from BOLD fMRI multivariate time series. One key statistic for any time series is its (effective) degrees of freedom, df, which will generally be less than the number of time points (or nominal degrees of freedom, N). If we know the df, then probabilistic inference on other fMRI statistics, such as the correlation between two voxel or regional time series, is feasible. However, we currently lack good estimators of df in fMRI time series, especially after the degrees of freedom of the "raw" data have been modified substantially by denoising algorithms for head movement. Here, we used a wavelet-based method both to denoise fMRI data and to estimate the (effective) df of the denoised process. We show that seed voxel correlations corrected for locally variable df could be tested for false positive connectivity with better control over Type I error and greater specificity of anatomical mapping than probabilistic connectivity maps using the nominal degrees of freedom. We also show that wavelet despiked statistics can be used to estimate all pairwise correlations between a set of regional nodes, assign a P value to each edge, and then iteratively add edges to the graph in order of increasing P. These probabilistically thresholded graphs are likely more robust to regional variation in head movement effects than comparable graphs constructed by thresholding correlations. Finally, we show that time-windowed estimates of df can be used for probabilistic connectivity testing or dynamic network analysis so that apparent changes in the functional connectome are appropriately corrected for the effects of transient noise bursts. Wavelet despiking is both an algorithm for fMRI time series denoising and an estimator of the (effective) df of denoised fMRI time series. Accurate estimation of df offers many potential advantages for probabilistically thresholding functional connectivity and network statistics tested in the context of spatially variant and non-stationary noise. Code for wavelet despiking, seed correlational testing and probabilistic graph construction is freely available to download as part of the BrainWavelet Toolbox at www.brainwavelet.org. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Uniform quantized electron gas

NASA Astrophysics Data System (ADS)

Høye, Johan S.; Lomba, Enrique

2016-10-01

In this work we study the correlation energy of the quantized electron gas of uniform density at temperature T  =  0. To do so we utilize methods from classical statistical mechanics. The basis for this is the Feynman path integral for the partition function of quantized systems. With this representation the quantum mechanical problem can be interpreted as, and is equivalent to, a classical polymer problem in four dimensions where the fourth dimension is imaginary time. Thus methods, results, and properties obtained in the statistical mechanics of classical fluids can be utilized. From this viewpoint we recover the well known RPA (random phase approximation). Then to improve it we modify the RPA by requiring the corresponding correlation function to be such that electrons with equal spins can not be on the same position. Numerical evaluations are compared with well known results of a standard parameterization of Monte Carlo correlation energies.

Schramm-Loewner evolution and perimeter of percolation clusters of correlated random landscapes.

PubMed

de Castro, C P; Luković, M; Pompanin, G; Andrade, R F S; Herrmann, H J

2018-03-27

Motivated by the fact that many physical landscapes are characterized by long-range height-height correlations that are quantified by the Hurst exponent H, we investigate the statistical properties of the iso-height lines of correlated surfaces in the framework of Schramm-Loewner evolution (SLE). We show numerically that in the continuum limit the external perimeter of a percolating cluster of correlated surfaces with H ∈ [-1, 0] is statistically equivalent to SLE curves. Our results suggest that the external perimeter also retains the Markovian properties, confirmed by the absence of time correlations in the driving function and the fact that the latter is Gaussian distributed for any specific time. We also confirm that for all H the variance of the winding angle grows logarithmically with size.

Minimum Bayes risk image correlation

NASA Technical Reports Server (NTRS)

Minter, T. C., Jr.

1980-01-01

In this paper, the problem of designing a matched filter for image correlation will be treated as a statistical pattern recognition problem. It is shown that, by minimizing a suitable criterion, a matched filter can be estimated which approximates the optimum Bayes discriminant function in a least-squares sense. It is well known that the use of the Bayes discriminant function in target classification minimizes the Bayes risk, which in turn directly minimizes the probability of a false fix. A fast Fourier implementation of the minimum Bayes risk correlation procedure is described.

Mineral element correlation with adenohypophyseal-adrenal cortex function and stress.

PubMed

Flynn, A; Pories, W J; Strain, W H; Hill, O A

1971-09-10

A statistical correlationl was made between adrenocorticotropin (ACTH) and four elements in rats under control, stress, and stress-recovery conditions. Blood serum zinc showed a strong positive correlation with the rise in ACTH during stress and its decline in stress recovery. Serum calcium, copper, and magnesium demonstrated little correlation with ACTH changes. The strong ACTH-zinc correlation points to an as yet undefined interaction between ACTH and zinc

Bose--Einstein Correlations and Thermal Cluster Formation in High-energy Collisions

NASA Astrophysics Data System (ADS)

Bialas, A.; Florkowski, W.; Zalewski, K.

The blast wave model is generalized to include the production of thermal clusters, as suggested by the apparent success of the statistical model of particle production at high energies. The formulae for the HBT correlation functions and the corresponding HBT radii are derived.

Partial Correlation-Based Retinotopically Organized Resting-State Functional Connectivity Within and Between Areas of the Visual Cortex Reflects More Than Cortical Distance

PubMed Central

Dawson, Debra Ann; Lam, Jack; Lewis, Lindsay B.; Carbonell, Felix; Mendola, Janine D.

2016-01-01

Abstract Numerous studies have demonstrated functional magnetic resonance imaging (fMRI)-based resting-state functional connectivity (RSFC) between cortical areas. Recent evidence suggests that synchronous fluctuations in blood oxygenation level-dependent fMRI reflect functional organization at a scale finer than that of visual areas. In this study, we investigated whether RSFCs within and between lower visual areas are retinotopically organized and whether retinotopically organized RSFC merely reflects cortical distance. Subjects underwent retinotopic mapping and separately resting-state fMRI. Visual areas V1, V2, and V3, were subdivided into regions of interest (ROIs) according to quadrants and visual field eccentricity. Functional connectivity (FC) was computed based on Pearson's linear correlation (correlation), and Pearson's linear partial correlation (correlation between two time courses after the time courses from all other regions in the network are regressed out). Within a quadrant, within visual areas, all correlation and nearly all partial correlation FC measures showed statistical significance. Consistently in V1, V2, and to a lesser extent in V3, correlation decreased with increasing eccentricity separation. Consistent with previously reported monkey anatomical connectivity, correlation/partial correlation values between regions from adjacent areas (V1-V2 and V2-V3) were higher than those between nonadjacent areas (V1-V3). Within a quadrant, partial correlation showed consistent significance between regions from two different areas with the same or adjacent eccentricities. Pairs of ROIs with similar eccentricity showed higher correlation/partial correlation than pairs distant in eccentricity. Between dorsal and ventral quadrants, partial correlation between common and adjacent eccentricity regions within a visual area showed statistical significance; this extended to more distant eccentricity regions in V1. Within and between quadrants, correlation decreased approximately linearly with increasing distances separating the tested ROIs. Partial correlation showed a more complex dependence on cortical distance: it decreased exponentially with increasing distance within a quadrant, but was best fit by a quadratic function between quadrants. We conclude that RSFCs within and between lower visual areas are retinotopically organized. Correlation-based FC is nonselectively high across lower visual areas, even between regions that do not share direct anatomical connections. The mechanisms likely involve network effects caused by the dense anatomical connectivity within this network and projections from higher visual areas. FC based on partial correlation, which minimizes network effects, follows expectations based on direct anatomical connections in the monkey visual cortex better than correlation. Last, partial correlation-based retinotopically organized RSFC reflects more than cortical distance effects. PMID:26415043

Partial Correlation-Based Retinotopically Organized Resting-State Functional Connectivity Within and Between Areas of the Visual Cortex Reflects More Than Cortical Distance.

PubMed

Dawson, Debra Ann; Lam, Jack; Lewis, Lindsay B; Carbonell, Felix; Mendola, Janine D; Shmuel, Amir

2016-02-01

Numerous studies have demonstrated functional magnetic resonance imaging (fMRI)-based resting-state functional connectivity (RSFC) between cortical areas. Recent evidence suggests that synchronous fluctuations in blood oxygenation level-dependent fMRI reflect functional organization at a scale finer than that of visual areas. In this study, we investigated whether RSFCs within and between lower visual areas are retinotopically organized and whether retinotopically organized RSFC merely reflects cortical distance. Subjects underwent retinotopic mapping and separately resting-state fMRI. Visual areas V1, V2, and V3, were subdivided into regions of interest (ROIs) according to quadrants and visual field eccentricity. Functional connectivity (FC) was computed based on Pearson's linear correlation (correlation), and Pearson's linear partial correlation (correlation between two time courses after the time courses from all other regions in the network are regressed out). Within a quadrant, within visual areas, all correlation and nearly all partial correlation FC measures showed statistical significance. Consistently in V1, V2, and to a lesser extent in V3, correlation decreased with increasing eccentricity separation. Consistent with previously reported monkey anatomical connectivity, correlation/partial correlation values between regions from adjacent areas (V1-V2 and V2-V3) were higher than those between nonadjacent areas (V1-V3). Within a quadrant, partial correlation showed consistent significance between regions from two different areas with the same or adjacent eccentricities. Pairs of ROIs with similar eccentricity showed higher correlation/partial correlation than pairs distant in eccentricity. Between dorsal and ventral quadrants, partial correlation between common and adjacent eccentricity regions within a visual area showed statistical significance; this extended to more distant eccentricity regions in V1. Within and between quadrants, correlation decreased approximately linearly with increasing distances separating the tested ROIs. Partial correlation showed a more complex dependence on cortical distance: it decreased exponentially with increasing distance within a quadrant, but was best fit by a quadratic function between quadrants. We conclude that RSFCs within and between lower visual areas are retinotopically organized. Correlation-based FC is nonselectively high across lower visual areas, even between regions that do not share direct anatomical connections. The mechanisms likely involve network effects caused by the dense anatomical connectivity within this network and projections from higher visual areas. FC based on partial correlation, which minimizes network effects, follows expectations based on direct anatomical connections in the monkey visual cortex better than correlation. Last, partial correlation-based retinotopically organized RSFC reflects more than cortical distance effects.

Investigating the role of background and observation error correlations in improving a model forecast of forest carbon balance using four dimensional variational data assimilation.

NASA Astrophysics Data System (ADS)

Pinnington, Ewan; Casella, Eric; Dance, Sarah; Lawless, Amos; Morison, James; Nichols, Nancy; Wilkinson, Matthew; Quaife, Tristan

2016-04-01

Forest ecosystems play an important role in sequestering human emitted carbon-dioxide from the atmosphere and therefore greatly reduce the effect of anthropogenic induced climate change. For that reason understanding their response to climate change is of great importance. Efforts to implement variational data assimilation routines with functional ecology models and land surface models have been limited, with sequential and Markov chain Monte Carlo data assimilation methods being prevalent. When data assimilation has been used with models of carbon balance, background "prior" errors and observation errors have largely been treated as independent and uncorrelated. Correlations between background errors have long been known to be a key aspect of data assimilation in numerical weather prediction. More recently, it has been shown that accounting for correlated observation errors in the assimilation algorithm can considerably improve data assimilation results and forecasts. In this paper we implement a 4D-Var scheme with a simple model of forest carbon balance, for joint parameter and state estimation and assimilate daily observations of Net Ecosystem CO2 Exchange (NEE) taken at the Alice Holt forest CO2 flux site in Hampshire, UK. We then investigate the effect of specifying correlations between parameter and state variables in background error statistics and the effect of specifying correlations in time between observation error statistics. The idea of including these correlations in time is new and has not been previously explored in carbon balance model data assimilation. In data assimilation, background and observation error statistics are often described by the background error covariance matrix and the observation error covariance matrix. We outline novel methods for creating correlated versions of these matrices, using a set of previously postulated dynamical constraints to include correlations in the background error statistics and a Gaussian correlation function to include time correlations in the observation error statistics. The methods used in this paper will allow the inclusion of time correlations between many different observation types in the assimilation algorithm, meaning that previously neglected information can be accounted for. In our experiments we compared the results using our new correlated background and observation error covariance matrices and those using diagonal covariance matrices. We found that using the new correlated matrices reduced the root mean square error in the 14 year forecast of daily NEE by 44 % decreasing from 4.22 g C m-2 day-1 to 2.38 g C m-2 day-1.

Development and validation of the Vellore Occupational Therapy Evaluation Scale to assess functioning in people with mental illness.

PubMed

Samuel, Reema; Russell, Paul Ss; Paraseth, Tapan Kumar; Ernest, Sharmila; Jacob, K S

2016-08-26

Available occupational therapy assessment scales focus on specific areas of functioning. There is a need for comprehensive evaluation of diverse aspects of functioning in people with mental illness. To develop a comprehensive assessment scale to evaluate diverse aspects of functioning among people with mental illness and to assess its validity and reliability. Available instruments, which evaluate diverse aspects of functioning in people with mental illness, were retrieved. Relevant items, which evaluate specific functions, were selected by a committee of mental health experts and combined to form a comprehensive instrument. Face and content validity and feasibility were assessed and the new instrument was piloted among 60 patients with mental illness. The final version of the instrument was employed in 151 consecutive clients, between 18 and 60 years of age, who were also assessed using Global Assessment of Functioning (GAF), Occupational Therapy Task Observation Scale (OTTOS), Social Functioning Questionnaire (SFQ), Rosenberg Self Esteem Scale (RSES) and Pai and Kapur Family Burden Interview Schedule (FBIS) by two therapists. The inter-rater reliability and test-retest reliability of the new instrument (Vellore Occupational Therapy Evaluation Scale (VOTES)) were also evaluated. The new scale had good internal consistency (Cronbach's alpha = .817), inter-rater reliability .928 (.877-.958) and test-retest reliability .928 (.868-.961). The correlation between the general behaviour domain (Pearson's Correlation Coefficient [PCC] = -.763, p = .000), task behaviour (PCC = -.829, p = .000), social skills (PCC = -.351, p = .000), intrapersonal skills (PCC = -.208, p = .010), instrumental activities of daily living (IADL) (PCC = -.329, p = .038) and leisure activities (PCC = -.433, p = .005) scores of VOTES with the corresponding domains in the scales used for comparison was statistically significant. The correlation between the total score of VOTES and the total scores of OTTOS, SFQ and RSES was also statistically significant suggesting convergent validity. The correlation between the total score of VOTES with the total score of FBI is not statistically significant, implying good divergent validity. VOTES seems to be a promising tool to assess overall functioning of people with mental illness. © The Author(s) 2016.

A radial map of multi-whisker correlation selectivity in the rat barrel cortex

PubMed Central

Estebanez, Luc; Bertherat, Julien; Shulz, Daniel E.; Bourdieu, Laurent; Léger, Jean- François

2016-01-01

In the barrel cortex, several features of single-whisker stimuli are organized in functional maps. The barrel cortex also encodes spatio-temporal correlation patterns of multi-whisker inputs, but so far the cortical mapping of neurons tuned to such input statistics is unknown. Here we report that layer 2/3 of the rat barrel cortex contains an additional functional map based on neuronal tuning to correlated versus uncorrelated multi-whisker stimuli: neuron responses to uncorrelated multi-whisker stimulation are strongest above barrel centres, whereas neuron responses to correlated and anti-correlated multi-whisker stimulation peak above the barrel–septal borders, forming rings of multi-whisker synchrony-preferring cells. PMID:27869114

A radial map of multi-whisker correlation selectivity in the rat barrel cortex.

PubMed

Estebanez, Luc; Bertherat, Julien; Shulz, Daniel E; Bourdieu, Laurent; Léger, Jean-François

2016-11-21

In the barrel cortex, several features of single-whisker stimuli are organized in functional maps. The barrel cortex also encodes spatio-temporal correlation patterns of multi-whisker inputs, but so far the cortical mapping of neurons tuned to such input statistics is unknown. Here we report that layer 2/3 of the rat barrel cortex contains an additional functional map based on neuronal tuning to correlated versus uncorrelated multi-whisker stimuli: neuron responses to uncorrelated multi-whisker stimulation are strongest above barrel centres, whereas neuron responses to correlated and anti-correlated multi-whisker stimulation peak above the barrel-septal borders, forming rings of multi-whisker synchrony-preferring cells.

Variational Method in the Statistical Theory of Turbulence

DTIC Science & Technology

1991-01-01

3.1.4) where 6 and c are the Kronecker and Levi - Civita tensors, respectively. Th u AB AB functions Z1, Z 2 and Z3 are invariant under rotations around...flow profide and certain two point correlation functions of a cylindrically syrametric free jet were carried out using the Rayleigh-Ritz method. A...reasonable agreement with experimental data. 14. SUBJECT TERMS 15. NUMBER OF PAGES 33 Two Phase Flow, Turbulence, Statistical Turbulence 16. PRICE CODE 17

Robustness of Type I Error and Power in Set Correlation Analysis of Contingency Tables.

ERIC Educational Resources Information Center

Cohen, Jacob; Nee, John C. M.

1990-01-01

The analysis of contingency tables via set correlation allows the assessment of subhypotheses involving contrast functions of the categories of the nominal scales. The robustness of such methods with regard to Type I error and statistical power was studied via a Monte Carlo experiment. (TJH)

Macular Thickness Assessment in Patients with Glaucoma and Its Correlation with Visual Fields

PubMed Central

Vaz, Fernando T; Ramalho, Mário; Pedrosa, Catarina; Lisboa, Maria; Kaku, Paulo; Esperancinha, Florindo

2016-01-01

Aim To determine the relationship between macular thickness (MT) and visual field (VF) parameters, as well as with changes in the retinal nerve fiber layer (RNFL) thickness in patients with glaucoma and ocular hypertension (OH). Materials and methods Cross-sectional statistical analysis of spectral domain optical coherence tomography (SD-OCT) compared with several VF parameters (mean defect - MD and loss variance - LV), in a nonrandom sample of 70 eyes from patients with glaucoma or OH. Statistical analysis was performed using Statistical Package for Social Sciences®. The correlation coefficient used was determined by Spearman correlation and the value of p < 0.05 was considered statistically significant. Results A significant correlation was seen between VF parameters and decrease in MT (MD: r = –0.363, p = 0.002; LV: r=–0.378, p = 0.001). The results were more significant when we compared the LV in the group with average MT 270 to 300 μm (r = –0.413, p = 0.015). Asymmetry between the superior macula and inferior macula correlated with LV (r = 0.432, p = 0.019) in the group with MT < 270 μm. There was also a significant correlation between thinning of superior-temporal and inferior-temporal RNFL and the decrease of the superior and inferior MT respectively (p < 0.001). Conclusion Spectral domain optical coherence tomography measurements of retinal thickness in the macula correlate with VF parameters and RNFL parameters in glaucoma patients. This relationship was first demonstrated with static computerized perimetry made with Octopus 101®. These results can be a valuable aid for evaluating and monitoring of glaucoma patients, establishing a correlation between structure and function. Measurements of retinal thickness in the macula may be an additional instrument for early detection of structural changes and its correlation with functional defects. How to cite this article Mota M, Vaz FT, Ramalho M, Pedrosa C, Lisboa M, Kaku P, Esperancinha F. Macular Thickness Assessment in Patients with Glaucoma and Its Correlation with Visual Fields. J Curr Glaucoma Pract 2016;10(3):85-90. PMID:27857487

Averages of ratios of the Riemann zeta-function and correlations of divisor sums

NASA Astrophysics Data System (ADS)

Conrey, Brian; Keating, Jonathan P.

2017-10-01

Nonlinearity has published articles containing a significant number-theoretic component since the journal was first established. We examine one thread, concerning the statistics of the zeros of the Riemann zeta function. We extend this by establishing a connection between the ratios conjecture for the Riemann zeta-function and a conjecture concerning correlations of convolutions of Möbius and divisor functions. Specifically, we prove that the ratios conjecture and an arithmetic correlations conjecture imply the same result. This provides new support for the ratios conjecture, which previously had been motivated by analogy with formulae in random matrix theory and by a heuristic recipe. Our main theorem generalises a recent calculation pertaining to the special case of two-over-two ratios.

Search for Correlated Fluctuations in the Beta+ Decay of Na-22

NASA Astrophysics Data System (ADS)

Silverman, M. P.; Strange, W.

2008-10-01

Claims for a ``cosmogenic'' force that correlates otherwise independent stochastic events have been made for at least 10 years, based largely on visual inspection of time series of histograms whose shapes were interpreted as suggestive of recurrent patterns with semi-diurnal, diurnal, and monthly periods. Building on our earlier work to test randomness of different nuclear decay processes, we have searched for correlations in the time-series of coincident positron-electron annihilations deriving from beta+ decay of Na-22. Disintegrations were counted within a narrow time window over a period of 7 days, leading to a time series of more than 1 million events. Statistical tests were performed on the raw time series, its correlation function, and its Fourier transform to search for cyclic correlations indicative of quantum-mechanical violating deviations from Poisson statistics. The time series was then partitioned into a sequence of 167 ``bags'' each of 8192 events. A histogram was made of the events of each bag, where contiguous frequency classes differed by a single count. The chronological sequence of histograms was then tested for correlations within classes. In all cases the results of the tests were in accord with statistical control, giving no evidence of correlated fluctuations.

Relation of intelligence to ego functioning in an adult psychiatric population.

PubMed

Allen, J G; Coyne, L; David, E

1986-01-01

Wechsler Adult Intelligence Scale-Revised (WAIS-R) IQs and clinical ratings of 10 ego functions in a diagnostically heterogeneous sample of 60 adult psychiatric inpatients were correlated. With severity of pathology statistically controlled, higher intelligence was associated with more adequate ego functioning in several spheres: primary autonomous functions, thought processes, object relations, and mastery-competence. There were also some clinically meaningful differences between the Verbal and Performance IQs in the pattern of correlations. Extending Hartmann's original views, the authors employ an ethological framework to conceptualize intelligence in relation to the ego's role in adaptation, emphasizing that intelligence is an important-albeit neglected-aspect of ego functioning.

An Introduction to Macro- Level Spatial Nonstationarity: a Geographically Weighted Regression Analysis of Diabetes and Poverty

PubMed Central

Siordia, Carlos; Saenz, Joseph; Tom, Sarah E.

2014-01-01

Type II diabetes is a growing health problem in the United States. Understanding geographic variation in diabetes prevalence will inform where resources for management and prevention should be allocated. Investigations of the correlates of diabetes prevalence have largely ignored how spatial nonstationarity might play a role in the macro-level distribution of diabetes. This paper introduces the reader to the concept of spatial nonstationarity—variance in statistical relationships as a function of geographical location. Since spatial nonstationarity means different predictors can have varying effects on model outcomes, we make use of a geographically weighed regression to calculate correlates of diabetes as a function of geographic location. By doing so, we demonstrate an exploratory example in which the diabetes-poverty macro-level statistical relationship varies as a function of location. In particular, we provide evidence that when predicting macro-level diabetes prevalence, poverty is not always positively associated with diabetes PMID:25414731

An Introduction to Macro- Level Spatial Nonstationarity: a Geographically Weighted Regression Analysis of Diabetes and Poverty.

PubMed

Siordia, Carlos; Saenz, Joseph; Tom, Sarah E

2012-01-01

Type II diabetes is a growing health problem in the United States. Understanding geographic variation in diabetes prevalence will inform where resources for management and prevention should be allocated. Investigations of the correlates of diabetes prevalence have largely ignored how spatial nonstationarity might play a role in the macro-level distribution of diabetes. This paper introduces the reader to the concept of spatial nonstationarity-variance in statistical relationships as a function of geographical location. Since spatial nonstationarity means different predictors can have varying effects on model outcomes, we make use of a geographically weighed regression to calculate correlates of diabetes as a function of geographic location. By doing so, we demonstrate an exploratory example in which the diabetes-poverty macro-level statistical relationship varies as a function of location. In particular, we provide evidence that when predicting macro-level diabetes prevalence, poverty is not always positively associated with diabetes.

A novel coefficient for detecting and quantifying asymmetry of California electricity market based on asymmetric detrended cross-correlation analysis

NASA Astrophysics Data System (ADS)

Wang, Fang

2016-06-01

In order to detect and quantify asymmetry of two time series, a novel cross-correlation coefficient is proposed based on recent asymmetric detrended cross-correlation analysis (A-DXA), which we called A-DXA coefficient. The A-DXA coefficient, as an important extension of DXA coefficient ρ D X A , contains two directional asymmetric cross-correlated indexes, describing upwards and downwards asymmetric cross-correlations, respectively. By using the information of directional covariance function of two time series and directional variance function of each series itself instead of power-law between the covariance function and time scale, the proposed A-DXA coefficient can well detect asymmetry between the two series no matter whether the cross-correlation is significant or not. By means of the proposed A-DXA coefficient conducted over the asymmetry for California electricity market, we found that the asymmetry between the prices and loads is not significant for daily average data in 1999 yr market (before electricity crisis) but extremely significant for those in 2000 yr market (during the crisis). To further uncover the difference of asymmetry between the years 1999 and 2000, a modified H statistic (MH) and ΔMH statistic are proposed. One of the present contributions is that the high MH values calculated for hourly data exist in majority months in 2000 market. Another important conclusion is that the cross-correlation with downwards dominates over the whole 1999 yr in contrast to the cross-correlation with upwards dominates over the 2000 yr.

A statistically compiled test battery for feasible evaluation of knee function after rupture of the Anterior Cruciate Ligament - derived from long-term follow-up data.

PubMed

Schelin, Lina; Tengman, Eva; Ryden, Patrik; Häger, Charlotte

2017-01-01

Clinical test batteries for evaluation of knee function after injury to the Anterior Cruciate Ligament (ACL) should be valid and feasible, while reliably capturing the outcome of rehabilitation. There is currently a lack of consensus as to which of the many available assessment tools for knee function that should be included. The present aim was to use a statistical approach to investigate the contribution of frequently used tests to avoid redundancy, and filter them down to a proposed comprehensive and yet feasible test battery for long-term evaluation after ACL injury. In total 48 outcome variables related to knee function, all potentially relevant for a long-term follow-up, were included from a cross-sectional study where 70 ACL-injured (17-28 years post injury) individuals were compared to 33 controls. Cluster analysis and logistic regression were used to group variables and identify an optimal test battery, from which a summarized estimator of knee function representing various functional aspects was derived. As expected, several variables were strongly correlated, and the variables also fell into logical clusters with higher within-correlation (max ρ = 0.61) than between clusters (max ρ = 0.19). An extracted test battery with just four variables assessing one-leg balance, isokinetic knee extension strength and hop performance (one-leg hop, side hop) were mathematically combined to an estimator of knee function, which acceptably classified ACL-injured individuals and controls. This estimator, derived from objective measures, correlated significantly with self-reported function, e.g. Lysholm score (ρ = 0.66; p<0.001). The proposed test battery, based on a solid statistical approach, includes assessments which are all clinically feasible, while also covering complementary aspects of knee function. Similar test batteries could be determined for earlier phases of ACL rehabilitation or to enable longitudinal monitoring. Such developments, established on a well-grounded consensus of measurements, would facilitate comparisons of studies and enable evidence-based rehabilitation.

The relationship between procrastination, learning strategies and statistics anxiety among Iranian college students: a canonical correlation analysis.

PubMed

Vahedi, Shahrum; Farrokhi, Farahman; Gahramani, Farahnaz; Issazadegan, Ali

2012-01-01

Approximately 66-80%of graduate students experience statistics anxiety and some researchers propose that many students identify statistics courses as the most anxiety-inducing courses in their academic curriculums. As such, it is likely that statistics anxiety is, in part, responsible for many students delaying enrollment in these courses for as long as possible. This paper proposes a canonical model by treating academic procrastination (AP), learning strategies (LS) as predictor variables and statistics anxiety (SA) as explained variables. A questionnaire survey was used for data collection and 246-college female student participated in this study. To examine the mutually independent relations between procrastination, learning strategies and statistics anxiety variables, a canonical correlation analysis was computed. Findings show that two canonical functions were statistically significant. The set of variables (metacognitive self-regulation, source management, preparing homework, preparing for test and preparing term papers) helped predict changes of statistics anxiety with respect to fearful behavior, Attitude towards math and class, Performance, but not Anxiety. These findings could be used in educational and psychological interventions in the context of statistics anxiety reduction.

Fast Computation of the Two-Point Correlation Function in the Age of Big Data

NASA Astrophysics Data System (ADS)

Pellegrino, Andrew; Timlin, John

2018-01-01

We present a new code which quickly computes the two-point correlation function for large sets of astronomical data. This code combines the ease of use of Python with the speed of parallel shared libraries written in C. We include the capability to compute the auto- and cross-correlation statistics, and allow the user to calculate the three-dimensional and angular correlation functions. Additionally, the code automatically divides the user-provided sky masks into contiguous subsamples of similar size, using the HEALPix pixelization scheme, for the purpose of resampling. Errors are computed using jackknife and bootstrap resampling in a way that adds negligible extra runtime, even with many subsamples. We demonstrate comparable speed with other clustering codes, and code accuracy compared to known and analytic results.

Removing the Impact of Correlated PSF Uncertainties in Weak Lensing

NASA Astrophysics Data System (ADS)

Lu, Tianhuan; Zhang, Jun; Dong, Fuyu; Li, Yingke; Liu, Dezi; Fu, Liping; Li, Guoliang; Fan, Zuhui

2018-05-01

Accurate reconstruction of the spatial distributions of the point-spread function (PSF) is crucial for high precision cosmic shear measurements. Nevertheless, current methods are not good at recovering the PSF fluctuations of high spatial frequencies. In general, the residual PSF fluctuations are spatially correlated, and therefore can significantly contaminate the correlation functions of the weak lensing signals. We propose a method to correct for this contamination statistically, without any assumptions on the PSF and galaxy morphologies or their spatial distribution. We demonstrate our idea with the data from the W2 field of CFHTLenS.

Phase transitions in the first-passage time of scale-invariant correlated processes

PubMed Central

Carretero-Campos, Concepción; Bernaola-Galván, Pedro; Ch. Ivanov, Plamen

2012-01-01

A key quantity describing the dynamics of complex systems is the first-passage time (FPT). The statistical properties of FPT depend on the specifics of the underlying system dynamics. We present a unified approach to account for the diversity of statistical behaviors of FPT observed in real-world systems. We find three distinct regimes, separated by two transition points, with fundamentally different behavior for FPT as a function of increasing strength of the correlations in the system dynamics: stretched exponential, power-law, and saturation regimes. In the saturation regime, the average length of FPT diverges proportionally to the system size, with important implications for understanding electronic delocalization in one-dimensional correlated-disordered systems. PMID:22400544

Outcome of transforaminal lumbar interbody fusion in spondylolisthesis-A clinico-radiological correlation.

PubMed

Balasubramanian, Vijay Anand; Douraiswami, Balaji; Subramani, Suresh

2018-06-01

Lumbar spondylolisthesis is a common cause of morbidity in middle aged individuals. Spinal fusion with instrumentation has become the gold standard for lumbar segmental instability. Studies which correlate the improvement in radiology postoperatively with functional outcome show contrasting reports. This study is aimed at finding the correlation between clinical and radiological outcomes after surgery with transforaminal lumbar interbody fusion. A retrospective study in 35 patients who underwent transforaminal lumbar interbody fusion in a period of 1 year was done. Preoperative pain (VAS Score), functional ability (ODI), radiological parameters (slip angle, slip grade, disc height, foraminal height, lumbar lordosis) were compared with postoperative recordings at the last followup. Functional improvement (Macnab's criteria) and fusion (Lee's fusion criteria) were assessed. Statistical analysis was done with student's paired t -test and Pearson's correlation coefficient. VAS score, ODI improved from 8 to 2 and 70 to 15 respectively. Slip angle improved from 23°to 5° on an average. 80% patients showed fusion and 85% showed good clinical outcome at 1 year followup. Analyzing with Pearson correlation coefficient showed no significant relation between pain scores and radiological parameters. But there was statistically significant relation between radiological fusion and the final clinical outcome. TLIF produces spinal fusion in most individuals. Strong spinal fusion is essential for good clinical outcome in spondylolisthesis patients who undergo TLIF. Reduction in slip is not necessary for all patients with listhesis.

Influence of super-horizon modes on correlation functions during inflation

NASA Astrophysics Data System (ADS)

Deutsch, Anne-Sylvie

2018-05-01

Coupling between sub- and super-Hubble modes can affect the locally observed statistics of our universe. In the context of Quasi-Single Field Inflation, we can compute correlation functions and derive the influence of those unobservable modes on observed correlation functions as well as on the inferred cosmological parameters. We study how different classes of diagrams affect the bispectrum in the squeezed limit; in particular, while contact-like diagrams leave the scaling between the long and short modes unchanged, exchange-like diagrams do modify the shape of the bispectrum. We show that the mass of the hidden sector field can hence be biased by an unavoidable cosmic variance that can reach a 1-σ uncertainty of Script O(10%) for a weakly non-Gaussian universe. Finally, we go beyond the bispectrum and show how couplings between unobservable and observable modes can affect generic correlation functions with arbitrary order non-derivative self-interactions.

The use of copula functions for predictive analysis of correlations between extreme storm tides

NASA Astrophysics Data System (ADS)

Domino, Krzysztof; Błachowicz, Tomasz; Ciupak, Maurycy

2014-11-01

In this paper we present a method used in quantitative description of weakly predictable hydrological, extreme events at inland sea. Investigations for correlations between variations of individual measuring points, employing combined statistical methods, were carried out. As a main tool for this analysis we used a two-dimensional copula function sensitive for correlated extreme effects. Additionally, a new proposed methodology, based on Detrended Fluctuations Analysis (DFA) and Anomalous Diffusion (AD), was used for the prediction of negative and positive auto-correlations and associated optimum choice of copula functions. As a practical example we analysed maximum storm tides data recorded at five spatially separated places at the Baltic Sea. For the analysis we used Gumbel, Clayton, and Frank copula functions and introduced the reversed Clayton copula. The application of our research model is associated with modelling the risk of high storm tides and possible storm flooding.

On the Power of Multivariate Latent Growth Curve Models to Detect Correlated Change

ERIC Educational Resources Information Center

Hertzog, Christopher; Lindenberger, Ulman; Ghisletta, Paolo; Oertzen, Timo von

2006-01-01

We evaluated the statistical power of single-indicator latent growth curve models (LGCMs) to detect correlated change between two variables (covariance of slopes) as a function of sample size, number of longitudinal measurement occasions, and reliability (measurement error variance). Power approximations following the method of Satorra and Saris…

Cross-section fluctuations in chaotic scattering systems.

PubMed

Ericson, Torleif E O; Dietz, Barbara; Richter, Achim

2016-10-01

Exact analytical expressions for the cross-section correlation functions of chaotic scattering systems have hitherto been derived only under special conditions. The objective of the present article is to provide expressions that are applicable beyond these restrictions. The derivation is based on a statistical model of Breit-Wigner type for chaotic scattering amplitudes which has been shown to describe the exact analytical results for the scattering (S)-matrix correlation functions accurately. Our results are given in the energy and in the time representations and apply in the whole range from isolated to overlapping resonances. The S-matrix contributions to the cross-section correlations are obtained in terms of explicit irreducible and reducible correlation functions. Consequently, the model can be used for a detailed exploration of the key features of the cross-section correlations and the underlying physical mechanisms. In the region of isolated resonances, the cross-section correlations contain a dominant contribution from the self-correlation term. For narrow states the self-correlations originate predominantly from widely spaced states with exceptionally large partial width. In the asymptotic region of well-overlapping resonances, the cross-section autocorrelation functions are given in terms of the S-matrix autocorrelation functions. For inelastic correlations, in particular, the Ericson fluctuations rapidly dominate in that region. Agreement with known analytical and experimental results is excellent.

Nonlinear Curve-Fitting Program

NASA Technical Reports Server (NTRS)

Everhart, Joel L.; Badavi, Forooz F.

1989-01-01

Nonlinear optimization algorithm helps in finding best-fit curve. Nonlinear Curve Fitting Program, NLINEAR, interactive curve-fitting routine based on description of quadratic expansion of X(sup 2) statistic. Utilizes nonlinear optimization algorithm calculating best statistically weighted values of parameters of fitting function and X(sup 2) minimized. Provides user with such statistical information as goodness of fit and estimated values of parameters producing highest degree of correlation between experimental data and mathematical model. Written in FORTRAN 77.

Group entropies, correlation laws, and zeta functions.

PubMed

Tempesta, Piergiulio

2011-08-01

The notion of group entropy is proposed. It enables the unification and generaliztion of many different definitions of entropy known in the literature, such as those of Boltzmann-Gibbs, Tsallis, Abe, and Kaniadakis. Other entropic functionals are introduced, related to nontrivial correlation laws characterizing universality classes of systems out of equilibrium when the dynamics is weakly chaotic. The associated thermostatistics are discussed. The mathematical structure underlying our construction is that of formal group theory, which provides the general structure of the correlations among particles and dictates the associated entropic functionals. As an example of application, the role of group entropies in information theory is illustrated and generalizations of the Kullback-Leibler divergence are proposed. A new connection between statistical mechanics and zeta functions is established. In particular, Tsallis entropy is related to the classical Riemann zeta function.

Revealing time bunching effect in single-molecule enzyme conformational dynamics.

PubMed

Lu, H Peter

2011-04-21

In this perspective, we focus our discussion on how the single-molecule spectroscopy and statistical analysis are able to reveal enzyme hidden properties, taking the study of T4 lysozyme as an example. Protein conformational fluctuations and dynamics play a crucial role in biomolecular functions, such as in enzymatic reactions. Single-molecule spectroscopy is a powerful approach to analyze protein conformational dynamics under physiological conditions, providing dynamic perspectives on a molecular-level understanding of protein structure-function mechanisms. Using single-molecule fluorescence spectroscopy, we have probed T4 lysozyme conformational motions under the hydrolysis reaction of a polysaccharide of E. coli B cell walls by monitoring the fluorescence resonant energy transfer (FRET) between a donor-acceptor probe pair tethered to T4 lysozyme domains involving open-close hinge-bending motions. Based on the single-molecule spectroscopic results, molecular dynamics simulation, a random walk model analysis, and a novel 2D statistical correlation analysis, we have revealed a time bunching effect in protein conformational motion dynamics that is critical to enzymatic functions. Bunching effect implies that conformational motion times tend to bunch in a finite and narrow time window. We show that convoluted multiple Poisson rate processes give rise to the bunching effect in the enzymatic reaction dynamics. Evidently, the bunching effect is likely common in protein conformational dynamics involving in conformation-gated protein functions. In this perspective, we will also discuss a new approach of 2D regional correlation analysis capable of analyzing fluctuation dynamics of complex multiple correlated and anti-correlated fluctuations under a non-correlated noise background. Using this new method, we are able to map out any defined segments along the fluctuation trajectories and determine whether they are correlated, anti-correlated, or non-correlated; after which, a cross correlation analysis can be applied for each specific segment to obtain a detailed fluctuation dynamics analysis.

Counting statistics of many-particle quantum walks

NASA Astrophysics Data System (ADS)

Mayer, Klaus; Tichy, Malte C.; Mintert, Florian; Konrad, Thomas; Buchleitner, Andreas

2011-06-01

We study quantum walks of many noninteracting particles on a beam splitter array as a paradigmatic testing ground for the competition of single- and many-particle interference in a multimode system. We derive a general expression for multimode particle-number correlation functions, valid for bosons and fermions, and infer pronounced signatures of many-particle interferences in the counting statistics.

Linearised and non-linearised isotherm models optimization analysis by error functions and statistical means

PubMed Central

2014-01-01

In adsorption study, to describe sorption process and evaluation of best-fitting isotherm model is a key analysis to investigate the theoretical hypothesis. Hence, numerous statistically analysis have been extensively used to estimate validity of the experimental equilibrium adsorption values with the predicted equilibrium values. Several statistical error analysis were carried out. In the present study, the following statistical analysis were carried out to evaluate the adsorption isotherm model fitness, like the Pearson correlation, the coefficient of determination and the Chi-square test, have been used. The ANOVA test was carried out for evaluating significance of various error functions and also coefficient of dispersion were evaluated for linearised and non-linearised models. The adsorption of phenol onto natural soil (Local name Kalathur soil) was carried out, in batch mode at 30 ± 20 C. For estimating the isotherm parameters, to get a holistic view of the analysis the models were compared between linear and non-linear isotherm models. The result reveled that, among above mentioned error functions and statistical functions were designed to determine the best fitting isotherm. PMID:25018878

Efficacy of isokinetic exercise on functional capacity and pain in patellofemoral pain syndrome.

PubMed

Alaca, Ridvan; Yilmaz, Bilge; Goktepe, A Salim; Mohur, Haydar; Kalyon, Tunc Alp

2002-11-01

To assess the effect of an isokinetic exercise program on symptoms and functions of patients with patellofemoral pain syndrome. A total of 22 consecutive patients with the complaint of anterior knee pain who met the inclusion criteria were recruited to assess the efficacy of isokinetic exercise on functional capacity, isokinetic parameters, and pain scores in patients with patellofemoral pain syndrome. A total of 37 knees were examined. Six-meter hopping, three-step hopping, and single-limb hopping course tests were performed for each patient with the measurements of the Lysholm scale and visual analog scale. Tested parameters were peak torque, total work, average power, and endurance ratios. Statistical analyses revealed that at the end of the 6-wk treatment period, functional and isokinetic parameters improved significantly, as did pain scores. There was not statistically significant correlation between different groups of parameters. The isokinetic exercise treatment program used in this study prevented the extensor power loss due to patellofemoral pain syndrome, but the improvement in the functional capacity was not correlated with the gained power.

Modeling clustered activity increase in amyloid-beta positron emission tomographic images with statistical descriptors.

PubMed

Shokouhi, Sepideh; Rogers, Baxter P; Kang, Hakmook; Ding, Zhaohua; Claassen, Daniel O; Mckay, John W; Riddle, William R

2015-01-01

Amyloid-beta (Aβ) imaging with positron emission tomography (PET) holds promise for detecting the presence of Aβ plaques in the cortical gray matter. Many image analyses focus on regional average measurements of tracer activity distribution; however, considerable additional information is available in the images. Metrics that describe the statistical properties of images, such as the two-point correlation function (S2), have found wide applications in astronomy and materials science. S2 provides a detailed characterization of spatial patterns in images typically referred to as clustering or flocculence. The objective of this study was to translate the two-point correlation method into Aβ-PET of the human brain using 11C-Pittsburgh compound B (11C-PiB) to characterize longitudinal changes in the tracer distribution that may reflect changes in Aβ plaque accumulation. We modified the conventional S2 metric, which is primarily used for binary images and formulated a weighted two-point correlation function (wS2) to describe nonbinary, real-valued PET images with a single statistical function. Using serial 11C-PiB scans, we calculated wS2 functions from two-dimensional PET images of different cortical regions as well as three-dimensional data from the whole brain. The area under the wS2 functions was calculated and compared with the mean/median of the standardized uptake value ratio (SUVR). For three-dimensional data, we compared the area under the wS2 curves with the subjects' cerebrospinal fluid measures. Overall, the longitudinal changes in wS2 correlated with the increase in mean SUVR but showed lower variance. The whole brain results showed a higher inverse correlation between the cerebrospinal Aβ and wS2 than between the cerebrospinal Aβ and SUVR mean/median. We did not observe any confounding of wS2 by region size or injected dose. The wS2 detects subtle changes and provides additional information about the binding characteristics of radiotracers and Aβ accumulation that are difficult to verify with mean SUVR alone.

Local image statistics: maximum-entropy constructions and perceptual salience

PubMed Central

Victor, Jonathan D.; Conte, Mary M.

2012-01-01

The space of visual signals is high-dimensional and natural visual images have a highly complex statistical structure. While many studies suggest that only a limited number of image statistics are used for perceptual judgments, a full understanding of visual function requires analysis not only of the impact of individual image statistics, but also, how they interact. In natural images, these statistical elements (luminance distributions, correlations of low and high order, edges, occlusions, etc.) are intermixed, and their effects are difficult to disentangle. Thus, there is a need for construction of stimuli in which one or more statistical elements are introduced in a controlled fashion, so that their individual and joint contributions can be analyzed. With this as motivation, we present algorithms to construct synthetic images in which local image statistics—including luminance distributions, pair-wise correlations, and higher-order correlations—are explicitly specified and all other statistics are determined implicitly by maximum-entropy. We then apply this approach to measure the sensitivity of the human visual system to local image statistics and to sample their interactions. PMID:22751397

Polychlorinated biphenyl exposure and effects in transformer repair workers.

PubMed Central

Emmett, E A

1985-01-01

Fifty-five present and past transformer repair workers exposed to polychlorinated biphenyls (PCBs) and 56 unexposed comparison workers were evaluated in a clinical-epidemiologic study. The groups were similar in most demographic variables. Adipose tissue lipid and serum PCBs concentrations were higher in current exposed workers (geometric means adipose 2.1 ppm, serum 12.2 ppb). Concentrations in comparison (0.6 ppm and 4.6 ppb) and previously exposed (0.83 ppm and 5.9 ppb) workers were lower. Statistically significant differences in serum albumin and lactic dehydrogenase, but not in other liver function tests, were seen between the exposed and comparison groups; however, after adjustment for confounding variables, no correlations were observed between liver function tests and either adipose or serum PCBs concentrations. Statistically significant correlation both before and after adjustment for confounding variables were seen with adipose PCBs and 24-hr urinary 17-hydroxycorticosteroid excretion and with serum PCBs and serum gamma-glutamyl transpeptidase. Both associations could reflect microsomal enzyme induction among other possibilities. No differences were seen in fasting serum triglycerides, total cholesterol, LDL, HDL or VLDL cholesterol between the two exposure groups. A statistically significant correlation between serum PCBs and serum triglycerides, total cholesterol, and VLDL cholesterol was removed by adjusting for confounding variables. No correlation was seen between adipose PCBs concentrations and any serum lipid component. Partition phenomena could account for these findings.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2863134

Scale-dependent cyclone-anticyclone asymmetry in a forced rotating turbulence experiment

NASA Astrophysics Data System (ADS)

Gallet, B.; Campagne, A.; Cortet, P.-P.; Moisy, F.

2014-03-01

We characterize the statistical and geometrical properties of the cyclone-anticyclone asymmetry in a statistically steady forced rotating turbulence experiment. Turbulence is generated by a set of vertical flaps which continuously inject velocity fluctuations towards the center of a tank mounted on a rotating platform. We first characterize the cyclone-anticyclone asymmetry from conventional single-point vorticity statistics. We propose a phenomenological model to explain the emergence of the asymmetry in the experiment, from which we predict scaling laws for the root-mean-square velocity in good agreement with the experimental data. We further quantify the cyclone-anticyclone asymmetry using a set of third-order two-point velocity correlations. We focus on the correlations which are nonzero only if the cyclone-anticyclone symmetry is broken. They offer two advantages over single-point vorticity statistics: first, they are defined from velocity measurements only, so an accurate resolution of the Kolmogorov scale is not required; second, they provide information on the scale-dependence of the cyclone-anticyclone asymmetry. We compute these correlation functions analytically for a random distribution of independent identical vortices. These model correlations describe well the experimental ones, indicating that the cyclone-anticyclone asymmetry is dominated by the large-scale long-lived cyclones.

The neuronal correlates of intranasal trigeminal function – An ALE meta-analysis of human functional brain imaging data

PubMed Central

Albrecht, Jessica; Kopietz, Rainer; Frasnelli, Johannes; Wiesmann, Martin; Hummel, Thomas; Lundström, Johan N.

2009-01-01

Almost every odor we encounter in daily life has the capacity to produce a trigeminal sensation. Surprisingly, few functional imaging studies exploring human neuronal correlates of intranasal trigeminal function exist, and results are to some degree inconsistent. We utilized activation likelihood estimation (ALE), a quantitative voxel-based meta-analysis tool, to analyze functional imaging data (fMRI/PET) following intranasal trigeminal stimulation with carbon dioxide (CO2), a stimulus known to exclusively activate the trigeminal system. Meta-analysis tools are able to identify activations common across studies, thereby enabling activation mapping with higher certainty. Activation foci of nine studies utilizing trigeminal stimulation were included in the meta-analysis. We found significant ALE scores, thus indicating consistent activation across studies, in the brainstem, ventrolateral posterior thalamic nucleus, anterior cingulate cortex, insula, precentral gyrus, as well as in primary and secondary somatosensory cortices – a network known for the processing of intranasal nociceptive stimuli. Significant ALE values were also observed in the piriform cortex, insula, and the orbitofrontal cortex, areas known to process chemosensory stimuli, and in association cortices. Additionally, the trigeminal ALE statistics were directly compared with ALE statistics originating from olfactory stimulation, demonstrating considerable overlap in activation. In conclusion, the results of this meta-analysis map the human neuronal correlates of intranasal trigeminal stimulation with high statistical certainty and demonstrate that the cortical areas recruited during the processing of intranasal CO2 stimuli include those outside traditional trigeminal areas. Moreover, through illustrations of the considerable overlap between brain areas that process trigeminal and olfactory information; these results demonstrate the interconnectivity of flavor processing. PMID:19913573

Handling of computational in vitro/in vivo correlation problems by Microsoft Excel II. Distribution functions and moments.

PubMed

Langenbucher, Frieder

2003-01-01

MS Excel is a useful tool to handle in vitro/in vivo correlation (IVIVC) distribution functions, with emphasis on the Weibull and the biexponential distribution, which are most useful for the presentation of cumulative profiles, e.g. release in vitro or urinary excretion in vivo, and differential profiles such as the plasma response in vivo. The discussion includes moments (AUC and mean) as summarizing statistics, and data-fitting algorithms for parameter estimation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ko, L.F.

Calculations for the two-point correlation functions in the scaling limit for two statistical models are presented. In Part I, the Ising model with a linear defect is studied for T < T/sub c/ and T > T/sub c/. The transfer matrix method of Onsager and Kaufman is used. The energy-density correlation is given by functions related to the modified Bessel functions. The dispersion expansion for the spin-spin correlation functions are derived. The dominant behavior for large separations at T not equal to T/sub c/ is extracted. It is shown that these expansions lead to systems of Fredholm integral equations. Inmore » Part II, the electric correlation function of the eight-vertex model for T < T/sub c/ is studied. The eight vertex model decouples to two independent Ising models when the four spin coupling vanishes. To first order in the four-spin coupling, the electric correlation function is related to a three-point function of the Ising model. This relation is systematically investigated and the full dispersion expansion (to first order in four-spin coupling) is obtained. The results is a new kind of structure which, unlike those of many solvable models, is apparently not expressible in terms of linear integral equations.« less

Hemispheric Asymmetry of Visual Cortical Response by Means of Functional Transcranial Doppler

PubMed Central

Roje-Bedeković, Marina; Lovrenčić-Huzjan, Arijana; Bosnar-Puretić, Marijana; Šerić, Vesna; Demarin, Vida

2012-01-01

We assessed the visual evoked response and investigated side-to-side differences in mean blood flow velocities (MBFVs) by means of functional transcranial Doppler (fTCD) in 49 right-handed patients with severe internal carotid artery (ICA) stenosis and 30 healthy volunteers, simultaneously in both posterior cerebral arteries (PCAs) using 2 MHz probes, successively in the dark and during the white light stimulation. Statistically significant correlation (P = 0.001) was shown in healthy and in patients (P < 0.05) between MBFV in right PCA in physiological conditions and MBFV in right PCA during the white light stimulation and in the dark. The correlation between MBVF in right PCA and contralateral left PCA was not statistically significant (P > 0.05). The correlation between ipsilateral left PCA was significantly higher than the one with contralateral right PCA (P < 0.05). There is a clear trend towards the lateralisation of the visual evoked response in the right PCA. PMID:22135771

Complex polarization-phase and spatial-frequency selections of laser images of blood-plasma films in diagnostics of changes in their polycrystalline structure

NASA Astrophysics Data System (ADS)

Ushenko, Yu. A.; Angelskii, P. O.; Dubolazov, A. V.; Karachevtsev, A. O.; Sidor, M. I.; Mintser, O. P.; Oleinichenko, B. P.; Bizer, L. I.

2013-10-01

We present a theoretical formalism of correlation phase analysis of laser images of human blood plasma with spatial-frequency selection of manifestations of mechanisms of linear and circular birefringence of albumin and globulin polycrystalline networks. Comparative results of the measurement of coordinate distributions of the correlation parameter—the modulus of the degree of local correlation of amplitudes—of laser images of blood plasma taken from patients of three groups—healthy patients (donors), rheumatoid-arthritis patients, and breast-cancer patients—are presented. We investigate values and ranges of change of statistical (the first to fourth statistical moments), correlation (excess of autocorrelation functions), and fractal (slopes of approximating curves and dispersion of extrema of logarithmic dependences of power spectra) parameters of coordinate distributions of the degree of local correlation of amplitudes. Objective criteria for diagnostics of occurrence and differentiation of inflammatory and oncological states are determined.

Wavelet analysis of polarization maps of polycrystalline biological fluids networks

NASA Astrophysics Data System (ADS)

Ushenko, Y. A.

2011-12-01

The optical model of human joints synovial fluid is proposed. The statistic (statistic moments), correlation (autocorrelation function) and self-similar (Log-Log dependencies of power spectrum) structure of polarization two-dimensional distributions (polarization maps) of synovial fluid has been analyzed. It has been shown that differentiation of polarization maps of joint synovial fluid with different physiological state samples is expected of scale-discriminative analysis. To mark out of small-scale domain structure of synovial fluid polarization maps, the wavelet analysis has been used. The set of parameters, which characterize statistic, correlation and self-similar structure of wavelet coefficients' distributions of different scales of polarization domains for diagnostics and differentiation of polycrystalline network transformation connected with the pathological processes, has been determined.

Predictive value of plasma β2-microglobulin on human body function and senescence.

PubMed

Dong, X-M; Cai, R; Yang, F; Zhang, Y-Y; Wang, X-G; Fu, S-L; Zhang, J-R

2016-06-01

To explore the correlation between plasma β2-microglobulin (β2-MG) as senescence factor with age, heart, liver and kidney function as well as the predictive value of β2-MG in human metabolism function and senescence. 387 cases of healthy people of different ages were selected and the automatic biochemical analyzer was used to test β2-MG in plasma based on immunoturbidimetry and also all biochemical indexes. The correlation between β2-MG and age, gender and all biochemical indexes was analyzed. β2-MG was positively correlated to age, r = 0.373; and the difference was of statistical significance (p < 0.010). It was significantly negative correlated to HDL-C but positively correlated to LP (a), BUN, CREA, UA, CYS-C, LDH, CK-MB, HBDH, AST, GLB and HCY. β2-MG was closely correlated to age, heart, kidney and liver biochemical indexes, which can be taken as an important biomarker for human body function and anti-senescence and have significant basic research and clinical guidance values.

New Statistics for Testing Differential Expression of Pathways from Microarray Data

NASA Astrophysics Data System (ADS)

Siu, Hoicheong; Dong, Hua; Jin, Li; Xiong, Momiao

Exploring biological meaning from microarray data is very important but remains a great challenge. Here, we developed three new statistics: linear combination test, quadratic test and de-correlation test to identify differentially expressed pathways from gene expression profile. We apply our statistics to two rheumatoid arthritis datasets. Notably, our results reveal three significant pathways and 275 genes in common in two datasets. The pathways we found are meaningful to uncover the disease mechanisms of rheumatoid arthritis, which implies that our statistics are a powerful tool in functional analysis of gene expression data.

Functional network-based statistics in depression: Theory of mind subnetwork and importance of parietal region.

PubMed

Lai, Chien-Han; Wu, Yu-Te; Hou, Yuh-Ming

2017-08-01

The functional network analysis of whole brain is an emerging field for research in depression. We initiated this study to investigate which subnetwork is significantly altered within the functional connectome in major depressive disorder (MDD). The study enrolled 52 first-episode medication-naïve patients with MDD and 40 controls for functional network analysis. All participants received the resting-state functional imaging using a 3-Tesla magnetic resonance scanner. After preprocessing, we calculated the connectivity matrix of functional connectivity in whole brain for each subject. The network-based statistics of connectome was used to perform group comparisons between patients and controls. The correlations between functional connectivity and clinical parameters were also performed. MDD patients had significant alterations in the network involving "theory of mind" regions, such as the left precentral gyrus, left angular gyrus, bilateral rolandic operculums and left inferior frontal gyrus. The center node of significant network was the left angular gyrus. No significant correlations of functional connectivity within the subnetwork and clinical parameters were noted. Functional connectivity of "theory of mind" subnetwork may be the core issue for pathophysiology in MDD. In addition, the center role of parietal region should be emphasized in future study. Copyright © 2017. Published by Elsevier B.V.

Under What Circumstances Does External Knowledge about the Correlation Structure Improve Power in Cluster Randomized Designs?

ERIC Educational Resources Information Center

Rhoads, Christopher

2014-01-01

Recent publications have drawn attention to the idea of utilizing prior information about the correlation structure to improve statistical power in cluster randomized experiments. Because power in cluster randomized designs is a function of many different parameters, it has been difficult for applied researchers to discern a simple rule explaining…

The deficit of joint position sense in the chronic unstable ankle as measured by inversion angle replication error.

PubMed

Nakasa, Tomoyuki; Fukuhara, Kohei; Adachi, Nobuo; Ochi, Mitsuo

2008-05-01

Functional instability is defined as a repeated ankle inversion sprain and a giving way sensation. Previous studies have described the damage of sensori-motor control in ankle sprain as being a possible cause of functional instability. The aim of this study was to evaluate the inversion angle replication errors in patients with functional instability after ankle sprain. The difference between the index angle and replication angle was measured in 12 subjects with functional instability, with the aim of evaluating the replication error. As a control group, the replication errors of 17 healthy volunteers were investigated. The side-to-side differences of the replication errors were compared between both the groups, and the relationship between the side-to-side differences of the replication errors and the mechanical instability were statistically analyzed in the unstable group. The side-to-side difference of the replication errors was 1.0 +/- 0.7 degrees in the unstable group and 0.2 +/- 0.7 degrees in the control group. There was a statistically significant difference between both the groups. The side-to-side differences of the replication errors in the unstable group did not statistically correlate to the anterior talar translation and talar tilt. The patients with functional instability had the deficit of joint position sense in comparison with healthy volunteers. The replication error did not correlate to the mechanical instability. The patients with functional instability should be treated appropriately in spite of having less mechanical instability.

Memory Effects and Nonequilibrium Correlations in the Dynamics of Open Quantum Systems

NASA Astrophysics Data System (ADS)

Morozov, V. G.

2018-01-01

We propose a systematic approach to the dynamics of open quantum systems in the framework of Zubarev's nonequilibrium statistical operator method. The approach is based on the relation between ensemble means of the Hubbard operators and the matrix elements of the reduced statistical operator of an open quantum system. This key relation allows deriving master equations for open systems following a scheme conceptually identical to the scheme used to derive kinetic equations for distribution functions. The advantage of the proposed formalism is that some relevant dynamical correlations between an open system and its environment can be taken into account. To illustrate the method, we derive a non-Markovian master equation containing the contribution of nonequilibrium correlations associated with energy conservation.

Photon statistics and polarization correlations at telecommunications wavelengths from a warm atomic ensemble.

PubMed

Willis, R T; Becerra, F E; Orozco, L A; Rolston, S L

2011-07-18

We present measurements of the polarization correlation and photon statistics of photon pairs that emerge from a laser-pumped warm rubidium vapor cell. The photon pairs occur at 780 nm and 1367 nm and are polarization entangled. We measure the autocorrelation of each of the generated fields as well as the cross-correlation function, and observe a strong violation of the two-beam Cauchy-Schwartz inequality. We evaluate the performance of the system as source of heralded single photons at a telecommunication wavelength. We measure the heralded autocorrelation and see that coincidences are suppressed by a factor of ≈ 20 from a Poissonian source at a generation rate of 1500 s(-1), a heralding efficiency of 10%, and a narrow spectral width.

Parametrically coupled fermionic oscillators: Correlation functions and phase-space description

NASA Astrophysics Data System (ADS)

Ghosh, Arnab

2015-01-01

A fermionic analog of a parametric amplifier is used to describe the joint quantum state of the two interacting fermionic modes. Based on a two-mode generalization of the time-dependent density operator, time evolution of the fermionic density operator is determined in terms of its two-mode Wigner and P function. It is shown that the equation of motion of the Wigner function corresponds to a fermionic analog of Liouville's equation. The equilibrium density operator for fermionic fields developed by Cahill and Glauber is thus extended to a dynamical context to show that the mathematical structures of both the correlation functions and the weight factors closely resemble their bosonic counterpart. It has been shown that the fermionic correlation functions are marked by a characteristic upper bound due to Fermi statistics, which can be verified in the matter wave counterpart of photon down-conversion experiments.

The Angular Correlation Function of Galaxies from Early Sloan Digital Sky Survey Data

NASA Astrophysics Data System (ADS)

Connolly, Andrew J.; Scranton, Ryan; Johnston, David; Dodelson, Scott; Eisenstein, Daniel J.; Frieman, Joshua A.; Gunn, James E.; Hui, Lam; Jain, Bhuvnesh; Kent, Stephen; Loveday, Jon; Nichol, Robert C.; O'Connell, Liam; Postman, Marc; Scoccimarro, Roman; Sheth, Ravi K.; Stebbins, Albert; Strauss, Michael A.; Szalay, Alexander S.; Szapudi, István; Tegmark, Max; Vogeley, Michael S.; Zehavi, Idit; Annis, James; Bahcall, Neta; Brinkmann, J.; Csabai, István; Doi, Mamoru; Fukugita, Masataka; Hennessy, G. S.; Hindsley, Robert; Ichikawa, Takashi; Ivezić, Željko; Kim, Rita S. J.; Knapp, Gillian R.; Kunszt, Peter; Lamb, D. Q.; Lee, Brian C.; Lupton, Robert H.; McKay, Timothy A.; Munn, Jeff; Peoples, John; Pier, Jeff; Rockosi, Constance; Schlegel, David; Stoughton, Christopher; Tucker, Douglas L.; Yanny, Brian; York, Donald G.

2002-11-01

The Sloan Digital Sky Survey is one of the first multicolor photometric and spectroscopic surveys designed to measure the statistical properties of galaxies within the local universe. In this paper we present some of the initial results on the angular two-point correlation function measured from the early SDSS galaxy data. The form of the correlation function, over the magnitude interval 18

Correlates of Sexual Functioning and Relationship Satisfaction Among Men and Women Experiencing Chronic Pain.

PubMed

Finn, Erica; Morrison, Todd G; McGuire, Brian E

2018-05-01

The aims of the study were to 1) examine the prevalence of sexual functioning difficulties in a chronic pain sample; 2) identify correlates of sexual functioning and relationship satisfaction utilizing pain variables (pain severity and pain interference) and psychological variables (mood, pain-related cognitions, self-efficacy, self-esteem, body-image); and 3) investigate possible sex differences in the correlates of sexual functioning and relationship satisfaction. Two hundred sixty-nine participants were recruited online from chronic pain organizations, websites, social media sites, and discussion forums. Those who met criteria for inclusion were presented with a variety of measures related to pain, sexual functioning, and relationship satisfaction (for those in a relationship), as well as cognitive and affective variables. Participant mean age was 37 years, and the majority were female, heterosexual, and currently in a relationship. High levels of pain severity and interference from pain, fatigue, depression, anxiety, stress, and body image concerns were reported, along with low levels of self-esteem and pain self-efficacy. In addition, substantial proportions of male (43%) and female (48%) respondents had scores indicative of sexual problems. Exploratory hierarchical regression analyses revealed that, for women, age and relationship satisfaction (which were both treated as covariates) as well as depression emerged as statistically significant correlates of sexual functioning (i.e., women who were older and reported greater levels of depression and less satisfaction with their current relationship indicated poorer sexual functioning). When relationship satisfaction was the criterion measure, age and sexual functioning (again, treated as covariates) and perceived stress emerged as significant (i.e., women who were older, reported poorer sexual functioning, and reported greater perceived stress also indicated being less satisfied with their current relationship). For male participants, age emerged as the only statistically significant correlate of sexual functioning (i.e., older men reported poorer functioning). In terms of relationship satisfaction, self-esteem was the lone significant correlate variable (men who reported lower self-esteem also were less satisfied with their current relationship). Some sex differences were evident in the variables that predict sexual difficulties and relationship satisfaction among those suffering from chronic pain. Of note is that when psychological variables were considered, pain-specific physical variables (e.g., pain severity and activity limitations) accounted for very little additional variance.

Determination of statistics for any rotation of axes of a bivariate normal elliptical distribution. [of wind vector components

NASA Technical Reports Server (NTRS)

Falls, L. W.; Crutcher, H. L.

1976-01-01

Transformation of statistics from a dimensional set to another dimensional set involves linear functions of the original set of statistics. Similarly, linear functions will transform statistics within a dimensional set such that the new statistics are relevant to a new set of coordinate axes. A restricted case of the latter is the rotation of axes in a coordinate system involving any two correlated random variables. A special case is the transformation for horizontal wind distributions. Wind statistics are usually provided in terms of wind speed and direction (measured clockwise from north) or in east-west and north-south components. A direct application of this technique allows the determination of appropriate wind statistics parallel and normal to any preselected flight path of a space vehicle. Among the constraints for launching space vehicles are critical values selected from the distribution of the expected winds parallel to and normal to the flight path. These procedures are applied to space vehicle launches at Cape Kennedy, Florida.

The Relationship Between Procrastination, Learning Strategies and Statistics Anxiety Among Iranian College Students: A Canonical Correlation Analysis

PubMed Central

Vahedi, Shahrum; Farrokhi, Farahman; Gahramani, Farahnaz; Issazadegan, Ali

2012-01-01

Objective: Approximately 66-80%of graduate students experience statistics anxiety and some researchers propose that many students identify statistics courses as the most anxiety-inducing courses in their academic curriculums. As such, it is likely that statistics anxiety is, in part, responsible for many students delaying enrollment in these courses for as long as possible. This paper proposes a canonical model by treating academic procrastination (AP), learning strategies (LS) as predictor variables and statistics anxiety (SA) as explained variables. Methods: A questionnaire survey was used for data collection and 246-college female student participated in this study. To examine the mutually independent relations between procrastination, learning strategies and statistics anxiety variables, a canonical correlation analysis was computed. Results: Findings show that two canonical functions were statistically significant. The set of variables (metacognitive self-regulation, source management, preparing homework, preparing for test and preparing term papers) helped predict changes of statistics anxiety with respect to fearful behavior, Attitude towards math and class, Performance, but not Anxiety. Conclusion: These findings could be used in educational and psychological interventions in the context of statistics anxiety reduction. PMID:24644468

A critical review of the neuroimaging literature on synesthesia

PubMed Central

Hupé, Jean-Michel; Dojat, Michel

2015-01-01

Synesthesia refers to additional sensations experienced by some people for specific stimulations, such as the systematic arbitrary association of colors to letters for the most studied type. Here, we review all the studies (based mostly on functional and structural magnetic resonance imaging) that have searched for the neural correlates of this subjective experience, as well as structural differences related to synesthesia. Most differences claimed for synesthetes are unsupported, due mainly to low statistical power, statistical errors, and methodological limitations. Our critical review therefore casts some doubts on whether any neural correlate of the synesthetic experience has been established yet. Rather than being a neurological condition (i.e., a structural or functional brain anomaly), synesthesia could be reconsidered as a special kind of childhood memory, whose signature in the brain may be out of reach with present brain imaging techniques. PMID:25873873

Image classification at low light levels

NASA Astrophysics Data System (ADS)

Wernick, Miles N.; Morris, G. Michael

1986-12-01

An imaging photon-counting detector is used to achieve automatic sorting of two image classes. The classification decision is formed on the basis of the cross correlation between a photon-limited input image and a reference function stored in computer memory. Expressions for the statistical parameters of the low-light-level correlation signal are given and are verified experimentally. To obtain a correlation-based system for two-class sorting, it is necessary to construct a reference function that produces useful information for class discrimination. An expression for such a reference function is derived using maximum-likelihood decision theory. Theoretically predicted results are used to compare on the basis of performance the maximum-likelihood reference function with Fukunaga-Koontz basis vectors and average filters. For each method, good class discrimination is found to result in milliseconds from a sparse sampling of the input image.

Photon statistics of pulse-pumped four-wave mixing in fiber with weak signal injection

NASA Astrophysics Data System (ADS)

Nan-Nan, Liu; Yu-Hong, Liu; Jia-Min, Li; Xiao-Ying, Li

2016-07-01

We study the photon statistics of pulse-pumped four-wave mixing in fibers with weak coherent signal injection by measuring the intensity correlation functions of individual signal and idler fields. The experimental results show that the intensity correlation function of individual signal (idler) field decreases with the intensity of signal injection. After applying narrow band filter in signal (idler) band, the value of decreases from 1.9 ± 0.02 (1.9 ± 0.02) to 1.03 ± 0.02 (1.05 ± 0.02) when the intensity of signal injection varies from 0 to 120 photons/pulse. The results indicate that the photon statistics changes from Bose-Einstein distribution to Poisson distribution. We calculate the intensity correlation functions by using the multi-mode theory of four-wave mixing in fibers. The theoretical curves well fit the experimental results. Our investigation will be useful for mitigating the crosstalk between quantum and classical channels in a dense wavelength division multiplexing network. Project supported by the National Natural Science Foundation of China (Grant No. 11527808), the State Key Development Program for Basic Research of China (Grant No. 2014CB340103), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120032110055), the Natural Science Foundation of Tianjin, China (Grant No. 14JCQNJC02300), the Program for Changjiang Scholars and Innovative Research Team in University, China, and the Program of Introducing Talents of Discipline to Universities, China (Grant No. B07014).

Predicting weak lensing statistics from halo mass reconstructions - Final Paper

DOE Office of Scientific and Technical Information (OSTI.GOV)

Everett, Spencer

2015-08-20

As dark matter does not absorb or emit light, its distribution in the universe must be inferred through indirect effects such as the gravitational lensing of distant galaxies. While most sources are only weakly lensed, the systematic alignment of background galaxies around a foreground lens can constrain the mass of the lens which is largely in the form of dark matter. In this paper, I have implemented a framework to reconstruct all of the mass along lines of sight using a best-case dark matter halo model in which the halo mass is known. This framework is then used to makemore » predictions of the weak lensing of 3,240 generated source galaxies through a 324 arcmin² field of the Millennium Simulation. The lensed source ellipticities are characterized by the ellipticity-ellipticity and galaxy-mass correlation functions and compared to the same statistic for the intrinsic and ray-traced ellipticities. In the ellipticity-ellipticity correlation function, I and that the framework systematically under predicts the shear power by an average factor of 2.2 and fails to capture correlation from dark matter structure at scales larger than 1 arcminute. The model predicted galaxy-mass correlation function is in agreement with the ray-traced statistic from scales 0.2 to 0.7 arcminutes, but systematically underpredicts shear power at scales larger than 0.7 arcminutes by an average factor of 1.2. Optimization of the framework code has reduced the mean CPU time per lensing prediction by 70% to 24 ± 5 ms. Physical and computational shortcomings of the framework are discussed, as well as potential improvements for upcoming work.« less

[Carotid intima-media thickness distribution according to the stratification of cardiovascular risk by means of Framingham-REGICOR and score function charts].

PubMed

Hermida-Ameijeiras, Á; López-Paz, J E; Riveiro-Cruz, M A; Calvo-Gómez, C

2016-01-01

Carotid intima-media thickness (cIMT) has been suggested as a further tool for risk function charts. The aim of this study was to describethe relationship between cIMT and cardiovascular risk (CVR) estimation according to Framingham-REGICOR and SCORE equations. Observational, cross-sectional cohort study from 362 hypertensive subjects. Demographic and clinical information were collected as well as laboratory, ultrasonographic and CVR estimation by the Framingham-REGICOR and SCORE functions. Statistical analysis was performed using SPSS software (version 20,0). To analyze the data, statistical tests such as Chi-square, T-test, ANOVA, and Pearson correlation coefficient were used. According to both functions, differences on mean cIMT were found between low CVR group and intermediate to high groups. No differences were found between intermediate and high risk groups (cIMT: 0,73mm low risk patients vs. 0,89 or 0,88mm respectively according to SCORE function and cIMT: 0,73 vs. 0,85 or 0,87mm respectively according to Framingham-REGICOR function). cIMT correlated positively with CVR estimation according to both SCORE (r=0,421; P<.01), and Framingham-REGICOR functions (r=0,363; P<.01). cIMT correlates positively with CVR estimated by SCORE and Framingham-REGICOR functions. cIMT in those subjects at intermediate risk is similar to those at high risk. Our findings highlight the importance of carotid ultrasound in identifying silent target-organ damage in those patients at intermediate CVR. Copyright © 2015 SEHLELHA. Published by Elsevier España, S.L.U. All rights reserved.

Effect of gender, facial dimensions, body mass index and type of functional occlusion on bite force.

PubMed

Koç, Duygu; Doğan, Arife; Bek, Bülent

2011-01-01

Some factors such as gender, age, craniofacial morphology, body structure, occlusal contact patterns may affect the maximum bite force. Thus, the purposes of this study were to determine the mean maximum bite force in individuals with normal occlusion, and to examine the effect of gender, facial dimensions, body mass index (BMI), type of functional occlusion (canine guidance and group function occlusion) and balancing side interferences on it. Thirty-four individuals aged 19-20 years-old were selected for this study. Maximum bite force was measured with strain-gauge transducers at first molar region. Facial dimensions were defined by standardized frontal photographs as follows: anterior total facial height (ATFH), bizygomathic facial width (BFW) and intergonial width (IGW). BMI was calculated using the equation weight/height². The type of functional occlusion and the balancing side interferences of the subjects were identified by clinical examination. Bite force was found to be significantly higher in men than women (p<0.05). While there was a negative correlation between the bite force and ATFH/BFW, ATFH/IGW ratios in men (p<0.05), women did not show any statistically significant correlation (p>0.05). BMI and bite force correlation was not statistically significant (p>0.05). The average bite force did not differ in subjects with canine guidance or group function occlusion and in the presence of balancing side interferences (p>0.05). Data suggest that bite force is affected by gender. However, BMI, type of functional occlusion and the presence of balancing side interferences did not exert a meaningful influence on bite force. In addition, transverse facial dimensions showed correlation with bite force in only men.

Simulation of spatially evolving turbulence and the applicability of Taylor's hypothesis in compressible flow

NASA Technical Reports Server (NTRS)

Lee, Sangsan; Lele, Sanjiva K.; Moin, Parviz

1992-01-01

For the numerical simulation of inhomogeneous turbulent flows, a method is developed for generating stochastic inflow boundary conditions with a prescribed power spectrum. Turbulence statistics from spatial simulations using this method with a low fluctuation Mach number are in excellent agreement with the experimental data, which validates the procedure. Turbulence statistics from spatial simulations are also compared to those from temporal simulations using Taylor's hypothesis. Statistics such as turbulence intensity, vorticity, and velocity derivative skewness compare favorably with the temporal simulation. However, the statistics of dilatation show a significant departure from those obtained in the temporal simulation. To directly check the applicability of Taylor's hypothesis, space-time correlations of fluctuations in velocity, vorticity, and dilatation are investigated. Convection velocities based on vorticity and velocity fluctuations are computed as functions of the spatial and temporal separations. The profile of the space-time correlation of dilatation fluctuations is explained via a wave propagation model.

Diagrammatic analysis of correlations in polymer fluids: Cluster diagrams via Edwards' field theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morse, David C.

2006-10-15

Edwards' functional integral approach to the statistical mechanics of polymer liquids is amenable to a diagrammatic analysis in which free energies and correlation functions are expanded as infinite sums of Feynman diagrams. This analysis is shown to lead naturally to a perturbative cluster expansion that is closely related to the Mayer cluster expansion developed for molecular liquids by Chandler and co-workers. Expansion of the functional integral representation of the grand-canonical partition function yields a perturbation theory in which all quantities of interest are expressed as functionals of a monomer-monomer pair potential, as functionals of intramolecular correlation functions of non-interacting molecules,more » and as functions of molecular activities. In different variants of the theory, the pair potential may be either a bare or a screened potential. A series of topological reductions yields a renormalized diagrammatic expansion in which collective correlation functions are instead expressed diagrammatically as functionals of the true single-molecule correlation functions in the interacting fluid, and as functions of molecular number density. Similar renormalized expansions are also obtained for a collective Ornstein-Zernicke direct correlation function, and for intramolecular correlation functions. A concise discussion is given of the corresponding Mayer cluster expansion, and of the relationship between the Mayer and perturbative cluster expansions for liquids of flexible molecules. The application of the perturbative cluster expansion to coarse-grained models of dense multi-component polymer liquids is discussed, and a justification is given for the use of a loop expansion. As an example, the formalism is used to derive a new expression for the wave-number dependent direct correlation function and recover known expressions for the intramolecular two-point correlation function to first-order in a renormalized loop expansion for coarse-grained models of binary homopolymer blends and diblock copolymer melts.« less

Oxidative stress markers, cognitive functions, and psychosocial functioning in bipolar disorder: an empirical cross-sectional study.

PubMed

Aydemir, Ömer; Çubukçuoğlu, Zeynep; Erdin, Soner; Taş, Cumhur; Onur, Ece; Berk, Michael

2014-01-01

This study aimed to evaluate the relationship between oxidative stress markers and cognitive functions and domains of psychosocial functioning in bipolar disorder. Oxidative stress markers, cognitive functions, and domains of psychosocial functioning were evaluated in 51 patients with bipolar disorder who were in remission. Correlation analyses between these parameters were calculated with data controlled for duration of illness and number of episodes. There was no statistically significant correlation between oxidative stress markers and cognitive functions. In terms of psychosocial functioning, significant correlations were found between malondialdehyde and sense of stigmatization (r = -0.502); household activities and superoxide dismutase (r = 0.501); participation in social activities and nitric oxide (r = 0.414); hobbies and leisure time activities and total glutathione (r = -0.567), superoxide dismutase (r = 0.667), and neurotrophin 4 (r = 0.450); and taking initiative and self-sufficiency and superoxide dismutase (r = 0.597). There was no correlation between other domains of psychosocial functioning and oxidative stress markers. These results imply that oxidative stress markers do not appear to correlate clearly with cognitive impairment and reduced psychosocial functioning. However, there were some associations between selected oxidative markers and activity-oriented functional markers. This may represent a true negative association, or may be an artifact of oxidative stress being a state rather than a trait marker.

Coherent light depolarization by multiple scattering media and tissues: some fundamentals and applications

NASA Astrophysics Data System (ADS)

Zimnyakov, Dmitry A.; Tuchin, Valery V.; Yodh, Arjun G.; Mishin, Alexey A.; Peretochkin, Igor S.

1998-04-01

Relationships between decorrelation and depolarization of coherent light scattered by disordered media are examined by using the conception of the photon paths distribution functions. Analysis of behavior of the autocorrelation functions of the scattered field fluctuations and their polarization properties allows us to introduce generalized parameter of scattering media such as specific correlation time. Determination of specific correlation time has been carried out for phantom scattering media (water suspensions of polystyrene spheres). Results of statistical, correlation and polarization analysis of static and dynamic speckle patterns carried out in the experiments with human sclera with artificially controlled optical transmittance are presented. Some possibilities of applications of such polarization- correlation technique for monitoring and visualization of non- single scattering tissue structures are discussed.

The Portuguese version of the Epilepsy Surgery Inventory (ESI-55): cross-cultural adaptation and evaluation of psychometric properties.

PubMed

Alonso, Neide Barreira; Ciconelli, Rozana Mesquita; da Silva, Tatiana Indelicato; Westphal-Guitti, Ana Carolina; Azevedo, Auro Mauro; da Silva Noffs, Maria Helena; Caboclo, Luís Otávio Sales Ferreira; Sakamoto, Américo Ceiki; Targas Yacubian, Elza Márcia

2006-08-01

The purpose of this study was to develop a Portuguese version of the Epilepsy Surgery Inventory (ESI-55) and to assess its psychometric properties. Sixty patients with temporal lobe epilepsy related to unilateral mesial temporal sclerosis who underwent presurgical evaluation at the Universidade Federal de São Paulo (UNIFESP) formed the sample for this study. The psychometric properties of the ESI-55 included: reliability, validity, and responsiveness. Internal consistency was high in all domains (Cronbach's alpha ranging from 0.76 for Social Function to 0.88 for Physical Function) except Overall Quality of Life (alpha=0.45). Test-retest reliability after 1 week was good, with the intraclass correlation coefficient ranging from 0.79 (Energy/Fatigue) to 0.92 (Role Limitations due to Emotional Problems). Interrater reliability ranged from 0.84 (Cognitive Function) to 0.94 (Role Limitations due to Physical Problems). For construct validity, we verified a high correlation between the ESI-55 and Health Assessment Questionnaire-8 for the Physical Function domain (Pearson linear correlation=-0.84), and a moderate correlation for the Pain domain (P=-0.58), but for the other subscales no correlation was detected. Beck Depression Inventory and ESI-55 domains were highly statistically correlated (ANOVA: P<0.005), but there was no association of the Cognitive Function and Role Limitations due to Memory Problems subscales with neuropsychological evaluation (Pearson coefficient: P>0.05). With respect to demographic characteristics, a statistically significant correlation was observed for the variable educational level (Student t, P<0.005) and ESI-55 scores. There was a high correlation between seizure frequency and ESI-55 domains for clinical variables (ANOVA, P<0.005). Surgical treatment in this series improved health-related quality of life in the seizure-free group in three domains--Health Perception (1.24), Emotional Well-Being (1.32), and Energy/Fatigue (1.48)-as reflected by the standard response mean and the effect size of the sample. Our results support the psychometric properties of the Portuguese version of the ESI-55 as a measure of health-related quality of life.

Condensate statistics in interacting and ideal dilute bose gases

PubMed

Kocharovsky; Kocharovsky; Scully

2000-03-13

We obtain analytical formulas for the statistics, in particular, for the characteristic function and all cumulants, of the Bose-Einstein condensate in dilute weakly interacting and ideal equilibrium gases in the canonical ensemble via the particle-number-conserving operator formalism of Girardeau and Arnowitt. We prove that the ground-state occupation statistics is not Gaussian even in the thermodynamic limit. We calculate the effect of Bogoliubov coupling on suppression of ground-state occupation fluctuations and show that they are governed by a pair-correlation, squeezing mechanism.

Influence of Cobb Angle and ISIS2 Surface Topography Volumetric Asymmetry on Scoliosis Research Society-22 Outcome Scores in Scoliosis.

PubMed

Brewer, Paul; Berryman, Fiona; Baker, De; Pynsent, Paul; Gardner, Adrian

2013-11-01

Retrospective sequential patient series. To establish the relationship between the magnitude of the deformity in scoliosis and patients' perception of their condition, as measured with Scoliosis Research Society-22 scores. A total of 93 untreated patients with adolescent idiopathic scoliosis were included retrospectively. The Cobb angle was measured from a plain radiograph, and volumetric asymmetry was measured by ISIS2 surface topography. The association between Scoliosis Research Society scores for function, pain, self-image, and mental health against Cobb angle and volumetric asymmetry was investigated using the Pearson correlation coefficient. Correlation of both Cobb angle and volumetric asymmetry with function and pain was weak (all < .23); these correlation values were not statistically significant. Correlation of Cobb angle and volumetric asymmetry with self-image, was higher, although still moderate (-.37 for Cobb angle and -.44 for volumetric asymmetry). Both were statistically significant (Cobb angle, p = .0002; volumetric asymmetry; p = .00001). Cobb angle contributed 13.8% to the linear relationship with self-image, whereas volumetric asymmetry contributed 19.3%. For mental health, correlation was statistically significant with Cobb angle (p = .011) and volumetric asymmetry (p = .0005), but the correlation was low to moderate (-.26 and -.35, respectively). Cobb angle contributed 6.9% to the linear relationship with mental health, whereas volumetric asymmetry contributed 12.4%. Volumetric asymmetry correlates better with both mental health and self-image compared with Cobb angle, but the correlation was only moderate. This study suggests that a patient's own perception of self-image and mental health is multifactorial and not completely explained through present objective measurements of the size of the deformity. This helps to explain the difficulties in any objective analysis of a problem with multifactorial perception issues. Further study is required to investigate other physical aspects of the deformity that may have a role in how patients view themselves. Copyright © 2013 Scoliosis Research Society. Published by Elsevier Inc. All rights reserved.

The Radial Bow following Square Nailing in Radius and Ulna Shaft Fractures in Adults and its Relation to Disability and Function.

PubMed

Dave, M B; Parmar, K D; Sachde, B A

2016-07-01

One of the points made against nailing in radius and ulna shaft fractures has been the loss of radial bow and its impact on function. The aims of the study were to assess the change in magnitude and location of the radial bow in radius and ulna shaft fractures treated with intramedullary square nails and to assess the impact of this change on functional outcome, patient reported disability and the range of motion of the forearm. We measured the magnitude of radial bow and its location in the operated extremity and compared it to the uninjured side in 32 adult patients treated with intramedullary square nailing for radius and ulna shaft fractures at our institute. The mean loss of magnitude of maximum radial bow was 2.18 mm which was statistically significant by both student-T test and Mann-Whitney U test with p value less than 0.01. The location of maximum radial bow shifted distally but was statistically insignificant. The magnitude of maximum radial bow had a negative correlation with DASH score that was statistically insignificant (R=- 0.22, p=0.21). It had a positive, statistically significant correlation to the extent of supination in the operated extremity (R = 0.66, p = 0.0004). A loss of up to 2mm of radial bow did not influence the functional outcome as assessed by criteria reported by Anderson et al. The magnitude of radial bow influenced the supination of the forearm but not the final disability as measured by DASH score. Intramedullary nailing did decrease the magnitude of radial bow but a reduction of up to 2mm did not influence the functional outcome.

Statistics of primordial density perturbations from discrete seed masses

NASA Technical Reports Server (NTRS)

Scherrer, Robert J.; Bertschinger, Edmund

1991-01-01

The statistics of density perturbations for general distributions of seed masses with arbitrary matter accretion is examined. Formal expressions for the power spectrum, the N-point correlation functions, and the density distribution function are derived. These results are applied to the case of uncorrelated seed masses, and power spectra are derived for accretion of both hot and cold dark matter plus baryons. The reduced moments (cumulants) of the density distribution are computed and used to obtain a series expansion for the density distribution function. Analytic results are obtained for the density distribution function in the case of a distribution of seed masses with a spherical top-hat accretion pattern. More generally, the formalism makes it possible to give a complete characterization of the statistical properties of any random field generated from a discrete linear superposition of kernels. In particular, the results can be applied to density fields derived by smoothing a discrete set of points with a window function.

Correlational signatures of time-reversal symmetry breaking in two-dimensional flow

NASA Astrophysics Data System (ADS)

Hogg, Charlie; Ouellette, Nicholas

2015-11-01

Classical turbulence theories posit that broken spatial symmetries should be (statistically) restored at small scales. But since turbulent flows are inherently dissipative, time reversal symmetry is expected to remain broken throughout the cascade. However, the precise dynamical signature of this broken symmetry is not well understood. Recent work has shed new light on this fundamental question by considering the Lagrangian structure functions of power. Here, we take a somewhat different approach by studying the Lagrangian correlation functions of velocity and acceleration. We measured these correlations using particle tracking velocimetry in a quasi-two-dimensional electromagnetically driven flow that displayed net inverse energy transfer. We show that the correlation functions of the velocity and acceleration magnitudes are not symmetric in time, and that the degree of asymmetry can be related to the flux of energy between scales, suggesting that the asymmetry has a dynamical origin.

Mental Task Classification Scheme Utilizing Correlation Coefficient Extracted from Interchannel Intrinsic Mode Function.

PubMed

Rahman, Md Mostafizur; Fattah, Shaikh Anowarul

2017-01-01

In view of recent increase of brain computer interface (BCI) based applications, the importance of efficient classification of various mental tasks has increased prodigiously nowadays. In order to obtain effective classification, efficient feature extraction scheme is necessary, for which, in the proposed method, the interchannel relationship among electroencephalogram (EEG) data is utilized. It is expected that the correlation obtained from different combination of channels will be different for different mental tasks, which can be exploited to extract distinctive feature. The empirical mode decomposition (EMD) technique is employed on a test EEG signal obtained from a channel, which provides a number of intrinsic mode functions (IMFs), and correlation coefficient is extracted from interchannel IMF data. Simultaneously, different statistical features are also obtained from each IMF. Finally, the feature matrix is formed utilizing interchannel correlation features and intrachannel statistical features of the selected IMFs of EEG signal. Different kernels of the support vector machine (SVM) classifier are used to carry out the classification task. An EEG dataset containing ten different combinations of five different mental tasks is utilized to demonstrate the classification performance and a very high level of accuracy is achieved by the proposed scheme compared to existing methods.

The Purine Bias of Coding Sequences is Determined by Physicochemical Constraints on Proteins.

PubMed

Ponce de Leon, Miguel; de Miranda, Antonio Basilio; Alvarez-Valin, Fernando; Carels, Nicolas

2014-01-01

For this report, we analyzed protein secondary structures in relation to the statistics of three nucleotide codon positions. The purpose of this investigation was to find which properties of the ribosome, tRNA or protein level, could explain the purine bias (Rrr) as it is observed in coding DNA. We found that the Rrr pattern is the consequence of a regularity (the codon structure) resulting from physicochemical constraints on proteins and thermodynamic constraints on ribosomal machinery. The physicochemical constraints on proteins mainly come from the hydropathy and molecular weight (MW) of secondary structures as well as the energy cost of amino acid synthesis. These constraints appear through a network of statistical correlations, such as (i) the cost of amino acid synthesis, which is in favor of a higher level of guanine in the first codon position, (ii) the constructive contribution of hydropathy alternation in proteins, (iii) the spatial organization of secondary structure in proteins according to solvent accessibility, (iv) the spatial organization of secondary structure according to amino acid hydropathy, (v) the statistical correlation of MW with protein secondary structures and their overall hydropathy, (vi) the statistical correlation of thymine in the second codon position with hydropathy and the energy cost of amino acid synthesis, and (vii) the statistical correlation of adenine in the second codon position with amino acid complexity and the MW of secondary protein structures. Amino acid physicochemical properties and functional constraints on proteins constitute a code that is translated into a purine bias within the coding DNA via tRNAs. In that sense, the Rrr pattern within coding DNA is the effect of information transfer on nucleotide composition from protein to DNA by selection according to the codon positions. Thus, coding DNA structure and ribosomal machinery co-evolved to minimize the energy cost of protein coding given the functional constraints on proteins.

Voronoi Tessellation for reducing the processing time of correlation functions

NASA Astrophysics Data System (ADS)

Cárdenas-Montes, Miguel; Sevilla-Noarbe, Ignacio

2018-01-01

The increase of data volume in Cosmology is motivating the search of new solutions for solving the difficulties associated with the large processing time and precision of calculations. This is specially true in the case of several relevant statistics of the galaxy distribution of the Large Scale Structure of the Universe, namely the two and three point angular correlation functions. For these, the processing time has critically grown with the increase of the size of the data sample. Beyond parallel implementations to overcome the barrier of processing time, space partitioning algorithms are necessary to reduce the computational load. These can delimit the elements involved in the correlation function estimation to those that can potentially contribute to the final result. In this work, Voronoi Tessellation is used to reduce the processing time of the two-point and three-point angular correlation functions. The results of this proof-of-concept show a significant reduction of the processing time when preprocessing the galaxy positions with Voronoi Tessellation.

A statistically compiled test battery for feasible evaluation of knee function after rupture of the Anterior Cruciate Ligament – derived from long-term follow-up data

PubMed Central

2017-01-01

Purpose Clinical test batteries for evaluation of knee function after injury to the Anterior Cruciate Ligament (ACL) should be valid and feasible, while reliably capturing the outcome of rehabilitation. There is currently a lack of consensus as to which of the many available assessment tools for knee function that should be included. The present aim was to use a statistical approach to investigate the contribution of frequently used tests to avoid redundancy, and filter them down to a proposed comprehensive and yet feasible test battery for long-term evaluation after ACL injury. Methods In total 48 outcome variables related to knee function, all potentially relevant for a long-term follow-up, were included from a cross-sectional study where 70 ACL-injured (17–28 years post injury) individuals were compared to 33 controls. Cluster analysis and logistic regression were used to group variables and identify an optimal test battery, from which a summarized estimator of knee function representing various functional aspects was derived. Results As expected, several variables were strongly correlated, and the variables also fell into logical clusters with higher within-correlation (max ρ = 0.61) than between clusters (max ρ = 0.19). An extracted test battery with just four variables assessing one-leg balance, isokinetic knee extension strength and hop performance (one-leg hop, side hop) were mathematically combined to an estimator of knee function, which acceptably classified ACL-injured individuals and controls. This estimator, derived from objective measures, correlated significantly with self-reported function, e.g. Lysholm score (ρ = 0.66; p<0.001). Conclusions The proposed test battery, based on a solid statistical approach, includes assessments which are all clinically feasible, while also covering complementary aspects of knee function. Similar test batteries could be determined for earlier phases of ACL rehabilitation or to enable longitudinal monitoring. Such developments, established on a well-grounded consensus of measurements, would facilitate comparisons of studies and enable evidence-based rehabilitation. PMID:28459885

Statistical procedures for evaluating daily and monthly hydrologic model predictions

USGS Publications Warehouse

Coffey, M.E.; Workman, S.R.; Taraba, J.L.; Fogle, A.W.

2004-01-01

The overall study objective was to evaluate the applicability of different qualitative and quantitative methods for comparing daily and monthly SWAT computer model hydrologic streamflow predictions to observed data, and to recommend statistical methods for use in future model evaluations. Statistical methods were tested using daily streamflows and monthly equivalent runoff depths. The statistical techniques included linear regression, Nash-Sutcliffe efficiency, nonparametric tests, t-test, objective functions, autocorrelation, and cross-correlation. None of the methods specifically applied to the non-normal distribution and dependence between data points for the daily predicted and observed data. Of the tested methods, median objective functions, sign test, autocorrelation, and cross-correlation were most applicable for the daily data. The robust coefficient of determination (CD*) and robust modeling efficiency (EF*) objective functions were the preferred methods for daily model results due to the ease of comparing these values with a fixed ideal reference value of one. Predicted and observed monthly totals were more normally distributed, and there was less dependence between individual monthly totals than was observed for the corresponding predicted and observed daily values. More statistical methods were available for comparing SWAT model-predicted and observed monthly totals. The 1995 monthly SWAT model predictions and observed data had a regression Rr2 of 0.70, a Nash-Sutcliffe efficiency of 0.41, and the t-test failed to reject the equal data means hypothesis. The Nash-Sutcliffe coefficient and the R r2 coefficient were the preferred methods for monthly results due to the ability to compare these coefficients to a set ideal value of one.

Topological signatures of interstellar magnetic fields - I. Betti numbers and persistence diagrams

NASA Astrophysics Data System (ADS)

Makarenko, Irina; Shukurov, Anvar; Henderson, Robin; Rodrigues, Luiz F. S.; Bushby, Paul; Fletcher, Andrew

2018-04-01

The interstellar medium (ISM) is a magnetized system in which transonic or supersonic turbulence is driven by supernova explosions. This leads to the production of intermittent, filamentary structures in the ISM gas density, whilst the associated dynamo action also produces intermittent magnetic fields. The traditional theory of random functions, restricted to second-order statistical moments (or power spectra), does not adequately describe such systems. We apply topological data analysis (TDA), sensitive to all statistical moments and independent of the assumption of Gaussian statistics, to the gas density fluctuations in a magnetohydrodynamic simulation of the multiphase ISM. This simulation admits dynamo action, so produces physically realistic magnetic fields. The topology of the gas distribution, with and without magnetic fields, is quantified in terms of Betti numbers and persistence diagrams. Like the more standard correlation analysis, TDA shows that the ISM gas density is sensitive to the presence of magnetic fields. However, TDA gives us important additional information that cannot be obtained from correlation functions. In particular, the Betti numbers per correlation cell are shown to be physically informative. Magnetic fields make the ISM more homogeneous, reducing the abundance of both isolated gas clouds and cavities, with a stronger effect on the cavities. Remarkably, the modification of the gas distribution by magnetic fields is captured by the Betti numbers even in regions more than 300 pc from the mid-plane, where the magnetic field is weaker and correlation analysis fails to detect any signatures of magnetic effects.

Exact Asymptotics of the Freezing Transition of a Logarithmically Correlated Random Energy Model

NASA Astrophysics Data System (ADS)

Webb, Christian

2011-12-01

We consider a logarithmically correlated random energy model, namely a model for directed polymers on a Cayley tree, which was introduced by Derrida and Spohn. We prove asymptotic properties of a generating function of the partition function of the model by studying a discrete time analogy of the KPP-equation—thus translating Bramson's work on the KPP-equation into a discrete time case. We also discuss connections to extreme value statistics of a branching random walk and a rescaled multiplicative cascade measure beyond the critical point.

Statistical Physics on the Eve of the 21st Century: in Honour of J B McGuire on the Occasion of His 65th Birthday

NASA Astrophysics Data System (ADS)

Batchelor, Murray T.; Wille, Luc T.

The Table of Contents for the book is as follows: * Preface * Modelling the Immune System - An Example of the Simulation of Complex Biological Systems * Brief Overview of Quantum Computation * Quantal Information in Statistical Physics * Modeling Economic Randomness: Statistical Mechanics of Market Phenomena * Essentially Singular Solutions of Feigenbaum- Type Functional Equations * Spatiotemporal Chaotic Dynamics in Coupled Map Lattices * Approach to Equilibrium of Chaotic Systems * From Level to Level in Brain and Behavior * Linear and Entropic Transformations of the Hydrophobic Free Energy Sequence Help Characterize a Novel Brain Polyprotein: CART's Protein * Dynamical Systems Response to Pulsed High-Frequency Fields * Bose-Einstein Condensates in the Light of Nonlinear Physics * Markov Superposition Expansion for the Entropy and Correlation Functions in Two and Three Dimensions * Calculation of Wave Center Deflection and Multifractal Analysis of Directed Waves Through the Study of su(1,1)Ferromagnets * Spectral Properties and Phases in Hierarchical Master Equations * Universality of the Distribution Functions of Random Matrix Theory * The Universal Chiral Partition Function for Exclusion Statistics * Continuous Space-Time Symmetries in a Lattice Field Theory * Quelques Cas Limites du Problème à N Corps Unidimensionnel * Integrable Models of Correlated Electrons * On the Riemann Surface of the Three-State Chiral Potts Model * Two Exactly Soluble Lattice Models in Three Dimensions * Competition of Ferromagnetic and Antiferromagnetic Order in the Spin-l/2 XXZ Chain at Finite Temperature * Extended Vertex Operator Algebras and Monomial Bases * Parity and Charge Conjugation Symmetries and S Matrix of the XXZ Chain * An Exactly Solvable Constrained XXZ Chain * Integrable Mixed Vertex Models Ftom the Braid-Monoid Algebra * From Yang-Baxter Equations to Dynamical Zeta Functions for Birational Tlansformations * Hexagonal Lattice Directed Site Animals * Direction in the Star-Triangle Relations * A Self-Avoiding Walk Through Exactly Solved Lattice Models in Statistical Mechanics

The Effect of Wood Aerosols and Bioaerosols on the Respiratory Systems of Wood Manufacturing Industry Workers in Golestan Province

PubMed Central

Badirdast, Phateme; Salehpour, Soussan; Ghadjari, Ali; Khodakarim, Soheila; Panahi, Davod; Fadaei, Moslem; Rahimi, Abolfazl

2017-01-01

Background: Occupational exposure to dust leads to acute and chronic respiratory diseases, occupational asthma, and depressed lung function. In the light of a lack of comprehensive studies on the exposure of Iranian workers to wood dusts, the objective of this study was to monitor the occupational exposure to wood dust and bioaerosol, and their correlation with the lung function parameters in chipboard manufacturing industry workers. Materials and Methods: A cross-sectional study was conducted on chipboard workers in Golestan Province; a total of 150 men (100 exposed cases and 50 controls) were assessed. Workers were monitored for inhalable wood dust and lung function parameters, i.e., FVC, FEV1, FEV1/FVC, and FEF25–75%. The workers’ exposure to bioaerosols was measured using a bacterial sampler; a total of 68 area samples were collected. The analysis was performed using the Mann-Whitney, Kruskal-Wallis, and regression statistical tests. Results: The geometric mean value and geometric standard deviation of inhalable wood dust for the exposed and control groups were 19 ± 2.00 mg/m3 and 0.008 ± 0.001 mg/m3, respectively. A statistically significant correlation was observed between the lung parameters and cumulative exposure to inhalable wood dust, whereas a statistically significant correlation was not observed between the lung parameters and bioaerosol exposure. However, the exposure of Iranian workers to bioaerosols was higher, compared to their foreign coworkers. Conclusion: Considering the high level of exposure among workers in this study along with their lung function results, long-term exposure to wood dust may be detrimental to the workers’ health and steps to limit their exposure should be considered seriously. PMID:28638425

Interaction between the macrophage system and IgA immune complexes in IgA nephropathy.

PubMed

Roccatello, D; Coppo, R; Basolo, B; Martina, G; Rollino, C; Cordonnier, D; Busquet, G; Picciotto, G; Sena, L M; Piccoli, G

1983-01-01

In nine patients with IgA nephropathy, the function of the mononuclear phagocyte system was assessed by measuring in vivo clearance of anti-D coated red blood cells (RBC) and in vitro phagocytosis of sensitised RBC by monocytes. A strict correlation was found between in vivo macrophage function and in vitro monocyte phagocytosis. Statistical correlations were also found between in vivo clearance values and IgAIC and C3d values. A defective macrophage and monocyte function affects patients with major signs of clinical activity, highest IgAIC values, signs of complement activation and the most unfavourable clinical course.

Fatigue reliability of deck structures subjected to correlated crack growth

NASA Astrophysics Data System (ADS)

Feng, G. Q.; Garbatov, Y.; Guedes Soares, C.

2013-12-01

The objective of this work is to analyse fatigue reliability of deck structures subjected to correlated crack growth. The stress intensity factors of the correlated cracks are obtained by finite element analysis and based on which the geometry correction functions are derived. The Monte Carlo simulations are applied to predict the statistical descriptors of correlated cracks based on the Paris-Erdogan equation. A probabilistic model of crack growth as a function of time is used to analyse the fatigue reliability of deck structures accounting for the crack propagation correlation. A deck structure is modelled as a series system of stiffened panels, where a stiffened panel is regarded as a parallel system composed of plates and are longitudinal. It has been proven that the method developed here can be conveniently applied to perform the fatigue reliability assessment of structures subjected to correlated crack growth.

A naturalistic study on the relationship among resilient factors, psychiatric symptoms, and psychosocial functioning in a sample of residential patients with psychosis.

PubMed

Poloni, Nicola; Zizolfi, Daniele; Ielmini, Marta; Pagani, Roberto; Caselli, Ivano; Diurni, Marcello; Milano, Anna; Callegari, Camilla

2018-01-01

Resilience is a multidimensional process of adaptation aimed to overcome stressful or traumatic life experiences; only in the last few years it has been considered as a personal resource in psychosis and schizophrenia. This study aimed to assess the relationship between intrapersonal and interpersonal resilience factors and schizophrenia, particularly whether and how resilience can improve the course of psychotic illness. In this observational study, all patients recruited had to fulfill the following inclusion criteria: diagnosis of schizophrenia spectrum disorder ( Diagnostic and Statistical Manual of Mental Disorders-5 ); aged between 18 and 65 years; provided written informed consent; to be clinically stable (Clinical Global Impression Scale <3); history of illness ≥5 years; to be compliant with antipsychotic therapy over the last year; and regular submission to periodic monthly psychiatric visits. Patients were evaluated through the following scales: Resilience Scale for Adults (RSA) for resilience; Brief Psychiatric Rating Scale-Anchored version (BPRS-A), Scale for the Assessment of Negative Symptoms (SANS), and Scale for the Assessment of Positive Symptoms (SAPS) for psychotic symptomatology; and Life Skills Profile (LSP) for psychosocial functioning. Statistical analysis was performed by SPSS. Partial correlations were evaluated to assess the relationship between RSA total scores and subscores and BPRS-A, SANS, SAPS, and LSP total scores, removing the common variance among variables. Then, a series of hierarchical multiple linear regression models were used to examine the association between resilience, psychopathology, and psychosocial functioning. A statistically significant negative correlation among intrapersonal resilience factors and BPRS-A total score emerged, predicting psychiatric symptoms severity and explaining approximately 31% of the BPRS-A variance; otherwise, only the interpersonal resilience factors associated with social support were statistically and positively correlated with LSP total score, predicting psychosocial functioning and explaining the 11% of LSP variance. The specific contribution that resilience factors may have in predicting the severity of symptoms and the extent of psychosocial functioning emphasizes the importance of personalizing treatment for patients affected by schizophrenia, promoting personal resources, and translating them into better outcomes.

Gravitational Lensing Effect on the Two-Point Correlation of Hot Spots in the Cosmic Microwave Background.

PubMed

Takada; Komatsu; Futamase

2000-04-20

We investigate the weak gravitational lensing effect that is due to the large-scale structure of the universe on two-point correlations of local maxima (hot spots) in the two-dimensional sky map of the cosmic microwave background (CMB) anisotropy. According to the Gaussian random statistics, as most inflationary scenarios predict, the hot spots are discretely distributed, with some characteristic angular separations on the last scattering surface that are due to oscillations of the CMB angular power spectrum. The weak lensing then causes pairs of hot spots, which are separated with the characteristic scale, to be observed with various separations. We found that the lensing fairly smooths out the oscillatory features of the two-point correlation function of hot spots. This indicates that the hot spot correlations can be a new statistical tool for measuring the shape and normalization of the power spectrum of matter fluctuations from the lensing signatures.

Statistical functions and relevant correlation coefficients of clearness index

NASA Astrophysics Data System (ADS)

Pavanello, Diego; Zaaiman, Willem; Colli, Alessandra; Heiser, John; Smith, Scott

2015-08-01

This article presents a statistical analysis of the sky conditions, during years from 2010 to 2012, for three different locations: the Joint Research Centre site in Ispra (Italy, European Solar Test Installation - ESTI laboratories), the site of National Renewable Energy Laboratory in Golden (Colorado, USA) and the site of Brookhaven National Laboratories in Upton (New York, USA). The key parameter is the clearness index kT, a dimensionless expression of the global irradiance impinging upon a horizontal surface at a given instant of time. In the first part, the sky conditions are characterized using daily averages, giving a general overview of the three sites. In the second part the analysis is performed using data sets with a short-term resolution of 1 sample per minute, demonstrating remarkable properties of the statistical distributions of the clearness index, reinforced by a proof using fuzzy logic methods. Successively some time-dependent correlations between different meteorological variables are presented in terms of Pearson and Spearman correlation coefficients, and introducing a new one.

Statistical correlation analysis for comparing vibration data from test and analysis

NASA Technical Reports Server (NTRS)

Butler, T. G.; Strang, R. F.; Purves, L. R.; Hershfeld, D. J.

1986-01-01

A theory was developed to compare vibration modes obtained by NASTRAN analysis with those obtained experimentally. Because many more analytical modes can be obtained than experimental modes, the analytical set was treated as expansion functions for putting both sources in comparative form. The dimensional symmetry was developed for three general cases: nonsymmetric whole model compared with a nonsymmetric whole structural test, symmetric analytical portion compared with a symmetric experimental portion, and analytical symmetric portion with a whole experimental test. The theory was coded and a statistical correlation program was installed as a utility. The theory is established with small classical structures.

MWASTools: an R/bioconductor package for metabolome-wide association studies.

PubMed

Rodriguez-Martinez, Andrea; Posma, Joram M; Ayala, Rafael; Neves, Ana L; Anwar, Maryam; Petretto, Enrico; Emanueli, Costanza; Gauguier, Dominique; Nicholson, Jeremy K; Dumas, Marc-Emmanuel

2018-03-01

MWASTools is an R package designed to provide an integrated pipeline to analyse metabonomic data in large-scale epidemiological studies. Key functionalities of our package include: quality control analysis; metabolome-wide association analysis using various models (partial correlations, generalized linear models); visualization of statistical outcomes; metabolite assignment using statistical total correlation spectroscopy (STOCSY); and biological interpretation of metabolome-wide association studies results. The MWASTools R package is implemented in R (version  > =3.4) and is available from Bioconductor: https://bioconductor.org/packages/MWASTools/. m.dumas@imperial.ac.uk. Supplementary data are available at Bioinformatics online. © The Author(s) 2017. Published by Oxford University Press.

FAST TRACK COMMUNICATION: Freezing and extreme-value statistics in a random energy model with logarithmically correlated potential

NASA Astrophysics Data System (ADS)

Fyodorov, Yan V.; Bouchaud, Jean-Philippe

2008-09-01

We investigate some implications of the freezing scenario proposed by Carpentier and Le Doussal (CLD) for a random energy model (REM) with logarithmically correlated random potential. We introduce a particular (circular) variant of the model, and show that the integer moments of the partition function in the high-temperature phase are given by the well-known Dyson Coulomb gas integrals. The CLD freezing scenario allows one to use those moments for extracting the distribution of the free energy in both high- and low-temperature phases. In particular, it yields the full distribution of the minimal value in the potential sequence. This provides an explicit new class of extreme-value statistics for strongly correlated variables, manifestly different from the standard Gumbel class.

Spherical disharmonics in the Earth sciences and the spatial solution: Ridges, hotspots, slabs, geochemistry and tomography correlations

NASA Technical Reports Server (NTRS)

Ray, Terrill W.; Anderson, Don L.

1994-01-01

There is increasing use of statistical correlations between geophysical fields and between geochemical and geophysical fields in attempts to understand how the Earth works. Typically, such correlations have been based on spherical harmonic expansions. The expression of functions on the sphere as spherical harmonic series has many pitfalls, especially if the data are nonuniformly and/or sparsely sampled. Many of the difficulties involved in the use of spherical harmonic expansion techniques can be avoided through the use of spatial domain correlations, but this introduces other complications, such as the choice of a sampling lattice. Additionally, many geophysical and geochemical fields fail to satisfy the assumptions of standard statistical significance tests. This is especially problematic when the data values to be correlated with a geophysical field were collected at sample locations which themselves correlate with that field. This paper examines many correlations which have been claimed in the past between geochemistry and mantle tomography and between hotspot, ridge, and slab locations and tomography using both spherical harmonic coefficient correlations and spatial domain correlations. No conclusively significant correlations are found between isotopic geochemistry and mantle tomography. The Crough and Jurdy (short) hotspot location list shows statistically significant correlation with lowermost mantle tomography for degree 2 of the spherical harmonic expansion, but there are no statistically significant correlations in the spatial case. The Vogt (long) hotspot location list does not correlate with tomography anywhere in the mantle using either technique. Both hotspot lists show a strong correlation between hotspot locations and geoid highs when spatially correlated, but no correlations are revealed by spherical harmonic techniques. Ridge locations do not show any statistically significant correlations with tomography, slab locations, or the geoid; the strongest correlation is with lowermost mantle tomography, which is probably spurious. The most striking correlations are between mantle tomography and post-Pangean subducted slabs. The integrated locations of slabs correlate strongly with fast areas near the transition zone and the core-mantle boundary and with slow regions from 1022-1248 km depth. This seems to be consistent with the 'avalanching' downwellings which have been indicated by models of the mantle which include an endothermic phase transition at the 670-km discontinuity, although this is not a unique interpretation. Taken as a whole, these results suggest that slabs and associated cold downwellings are the dominant feature of mantle convection. Hotspot locations are no better correlated with lower mantle tomography than are ridge locations.

Synthesis of geophysical data with space-acquired imagery: a review

USGS Publications Warehouse

Hastings, David A.

1983-01-01

Statistical correlation has been used to determine the applicability of specific data sets to the development of geologic or exploration models. Various arithmetic functions have proven useful in developing models from such data sets.

Electrical Conductivity of Charged Particle Systems and Zubarev's Nonequilibrium Statistical Operator Method

NASA Astrophysics Data System (ADS)

Röpke, G.

2018-01-01

One of the fundamental problems in physics that are not yet rigorously solved is the statistical mechanics of nonequilibrium processes. An important contribution to describing irreversible behavior starting from reversible Hamiltonian dynamics was given by D. N. Zubarev, who invented the method of the nonequilibrium statistical operator. We discuss this approach, in particular, the extended von Neumann equation, and as an example consider the electrical conductivity of a system of charged particles. We consider the selection of the set of relevant observables. We show the relation between kinetic theory and linear response theory. Using thermodynamic Green's functions, we present a systematic treatment of correlation functions, but the convergence needs investigation. We compare different expressions for the conductivity and list open questions.

Pair correlation functions for identifying spatial correlation in discrete domains

NASA Astrophysics Data System (ADS)

Gavagnin, Enrico; Owen, Jennifer P.; Yates, Christian A.

2018-06-01

Identifying and quantifying spatial correlation are important aspects of studying the collective behavior of multiagent systems. Pair correlation functions (PCFs) are powerful statistical tools that can provide qualitative and quantitative information about correlation between pairs of agents. Despite the numerous PCFs defined for off-lattice domains, only a few recent studies have considered a PCF for discrete domains. Our work extends the study of spatial correlation in discrete domains by defining a new set of PCFs using two natural and intuitive definitions of distance for a square lattice: the taxicab and uniform metric. We show how these PCFs improve upon previous attempts and compare between the quantitative data acquired. We also extend our definitions of the PCF to other types of regular tessellation that have not been studied before, including hexagonal, triangular, and cuboidal. Finally, we provide a comprehensive PCF for any tessellation and metric, allowing investigation of spatial correlation in irregular lattices for which recognizing correlation is less intuitive.

Pulmonary function derangements in isolated or predominant mitral stenosis - Preoperative evaluation with clinico-hemodynamic correlation.

PubMed

Parvathy, Usha T; Rajan, Rajesh; Faybushevich, Alexander Georgevich

2014-06-01

It is well known that mitral stenosis (MS) is complicated by pulmonary hypertension (PH) of varying degrees. The hemodynamic derangement is associated with structural changes in the pulmonary vessels and parenchyma and also functional derangements. This article analyzes the pulmonary function derangements in 25 patients with isolated/predominant mitral stenosis of varying severity. THE AIM OF THE STUDY WAS TO CORRELATE THE PULMONARY FUNCTION TEST (PFT) DERANGEMENTS (DONE BY SIMPLE METHODS) WITH: a) patient demographics and clinical profile, b) severity of the mitral stenosis, and c) severity of pulmonary artery hypertension (PAH) and d) to evaluate its significance in preoperative assessment. This cross-sectional study was conducted in 25 patients with mitral stenosis who were selected for mitral valve (MV) surgery. The patients were evaluated for clinical class, echocardiographic severity of mitral stenosis and pulmonary hypertension, and with simple methods of assessment of pulmonary function with spirometry and blood gas analysis. The diagnosis and classification were made on standardized criteria. The associations and correlations of parameters, and the difference in groups of severity were analyzed statistically with Statistical Package for Social Sciences (SPSS), using nonparametric measures. THE SPIROMETRIC PARAMETERS SHOWED SIGNIFICANT CORRELATION WITH INCREASING NEW YORK HEART ASSOCIATION (NYHA) FUNCTIONAL CLASS (FC): forced vital capacity (FVC, r = -0.4*, p = 0.04), forced expiratory volume in one second (FEV1, r = -0.5*, p = 0.01), FEV1/FVC (r = -0.44*, p = 0.02), and with pulmonary venous congestion (PVC): FVC (r = -0.41*, p = 0.04) and FEV1 (r = -0.41*, p = 0.04). Cardiothoracic ratio (CTR) correlated only with FEV1 (r = -0.461*, p = 0.02) and peripheral saturation of oxygen (SPO2, r = -0.401*, p = 0.04). There was no linear correlation to duration of symptoms, mitral valve orifice area, or pulmonary hypertension, except for MV gradient with PCO2 (r = 0.594**, p = 0.002). The decreased oxygenation status correlated significantly with FC, CTR, PVC, and with deranged spirometry (r = 0.495*, p = 0.02). PFT derangements are seen in all grades of severity of MS and correlate well with the functional class, though no significant linear correlation with grades of severity of stenosis or pulmonary hypertension. Even the early or mild derangements in pulmonary function such as small airway obstruction in the less severe cases of normal or mild PH can be detected by simple and inexpensive methods when the conventional parameters are normal. The supplementary data from baseline arterial blood gas analysis is informative and relevant. This reclassified pulmonary function status might be prognostically predictive.

Neurodegenerative cerebrospinal fluid biomarkers tau and amyloid beta predict functional, quality of life, and neuropsychological outcomes after aneurysmal subarachnoid hemorrhage.

PubMed

Joswig, Holger; Korte, Wolfgang; Früh, Severin; Epprecht, Lorenz; Hildebrandt, Gerhard; Fournier, Jean-Yves; Stienen, Martin Nikolaus

2018-04-01

Cerebrospinal fluid (CSF) biomarkers might be useful in predicting outcome after aneurysmal subarachnoid hemorrhage (aSAH). It was the aim to determine whether tau and amyloid beta CSF concentrations predict functional, health-related quality of life (hrQoL), and neuropsychological outcomes after aSAH. Ventricular CSF was obtained from n = 24 aSAH patients at admission (D0), day 2 (D2), and day 6 (D6). CSF total (t)Tau, phosphorylated (p)Tau (181P) , and amyloid beta (1-40 and 1-42) (Aβ40/Aβ42) levels were compared between patients with favorable and unfavorable functional (modified Rankin Scale (mRS)), hrQoL (Euro-Qol (EQ-5D)), and neuropsychological outcomes at 3 (3 m) and 12 months (12 m). Patients with unfavorable functional (mRS 4-6) and hrQoL outcome (EQ-5D z-score ≤ - 1.0) at 3 and 12 m had higher CSF tTau/pTau and lower Aβ40/Aβ42 at D0, D2, and D6 with varying degrees of statistical significance. In terms of predicting neuropsychological outcome, CSF pTau showed a statistically significant correlation with the z-scores of executive function (r = - 0.7486, p = 0.008), verbal memory (r = - 0.8101, p = 0.002), attention (r = - 0.6498, p = 0.030), and visuospatial functioning (r = - 0.6944, p = 0.017) at 3 m. At 12 m, CSF pTau had statistically significant correlations with the z-scores of verbal memory (r = - 0.7473, p = 0.008) and visuospatial functioning (r = - 0.6678, p = 0.024). In conclusion, higher tTau/pTau and lower Aβ40/Aβ42 CSF levels predict unfavorable long-term functional and hrQoL outcomes. Neuropsychological deficits correlate with increased CSF tTau and pTau concentrations.

A quantitative study of factors influencing quality of life in rural Mexican women diagnosed with HIV.

PubMed

Holtz, Carol; Sowell, Richard; VanBrackle, Lewis; Velasquez, Gabriela; Hernandez-Alonso, Virginia

2014-01-01

This quantitative study explored the level of Quality of Life (QoL) in indigenous Mexican women and identified psychosocial factors that significantly influenced their QoL, using face-to-face interviews with 101 women accessing care in an HIV clinic in Oaxaca, Mexico. Variables included demographic characteristics, levels of depression, coping style, family functioning, HIV-related beliefs, and QoL. Descriptive statistics were used to analyze participant characteristics, and women's scores on data collection instruments. Pearson's R correlational statistics were used to determine the level of significance between study variables. Multiple regression analysis examined all variables that were significantly related to QoL. Pearson's correlational analysis of relationships between Spirituality, Educating Self about HIV, Family Functioning, Emotional Support, Physical Care, and Staying Positive demonstrated positive correlation to QoL. Stigma, depression, and avoidance coping were significantly and negatively associated with QoL. The final regression model indicated that depression and avoidance coping were the best predictor variables for QoL. Copyright © 2014 Association of Nurses in AIDS Care. Published by Elsevier Inc. All rights reserved.

OnabotulinumtoxinA detrusor injection improves female sexual function in women with overactive bladder wet syndrome.

PubMed

Balzarro, Matteo; Rubilotta, Emanuele; Braga, Andrea; Bassi, Silvia; Processali, Tania; Artibani, Walter; Serati, Maurizio

2018-05-05

The correlation between changes in sexual function and improvements in LUTD in patients treated with OnabotulinumtoxinA (onaBoNT-A) detrusor injection is unclear and limited only to women with neurogenic OAB. The aim of this study was to evaluate the impact of OnabotulinumtoxinA (onaBoNT-A) injection on sexual function in women undergoing this treatment for idiopathic wet overactive bladder (OAB). This is a pilot three-center observational study including women affected by idiopathic wet overactive bladder refractory to standard conservative treatments and underwent onaBoNT-A injection. Sexuality was assessed using the Female Sexual Function Index (FSFI). A 3-day voiding diary, OAB screener questionnaire (OAB-S), and the international consultation on incontinence questionnaire short form (ICIQ-sf) were completed before and 3 months after onaBoNT-A injection to evaluate OAB symptoms. All the 32 enrolled patients were included for statistical analysis. These patients received 100U of onaBoNT-A. Significant improvement of many FSFI domains was found. Only desire and pain domains had no significant improvements. The FSFI total score showed a significant improvement (P 0.0008). Clinical efficacy has been documented by voiding diaries, OAB-S scores, and ICIQ-sf scores. Correlation between UUI episodes and FSFI total score was statistically significant (r = -0.73; p = 0.04) while no significant correlation was found between the number of micturition and FSFI total score. Women who underwent successful OnaBoNT-A detrusor injection to treat wet OAB, showed an improvement in sexual function due to the significant correlation between the improvement of urinary urge incontinence and a better gratification of sexuality. Copyright © 2018. Published by Elsevier B.V.

Quality of life assessment in facial palsy: validation of the Dutch Facial Clinimetric Evaluation Scale.

PubMed

Kleiss, Ingrid J; Beurskens, Carien H G; Stalmeier, Peep F M; Ingels, Koen J A O; Marres, Henri A M

2015-08-01

This study aimed at validating an existing health-related quality of life questionnaire for patients with facial palsy for implementation in the Dutch language and culture. The Facial Clinimetric Evaluation Scale was translated into the Dutch language using a forward-backward translation method. A pilot test with the translated questionnaire was performed in 10 patients with facial palsy and 10 normal subjects. Finally, cross-cultural adaption was accomplished at our outpatient clinic for facial palsy. Analyses for internal consistency, test-retest reliability, construct validity and responsiveness were performed. Ninety-three patients completed the Dutch Facial Clinimetric Evaluation Scale, the Dutch Facial Disability Index, and the Dutch Short Form (36) Health Survey. Cronbach's α, representing internal consistency, was 0.800. Test-retest reliability was shown by an intraclass correlation coefficient of 0.737. Correlations with the House-Brackmann score, Sunnybrook score, Facial Disability Index physical function, and social/well-being function were -0.292, 0.570, 0.713, and 0.575, respectively. The SF-36 domains correlate best with the FaCE social function domain, with the strongest correlation between the both social function domains (r = 0.576). The FaCE score did statistically significantly increase in 35 patients receiving botulinum toxin type A (P = 0.042, Student t test). The domains 'facial comfort' and 'social function' improved statistically significantly as well (P = 0.022 and P = 0.046, respectively, Student t-test). The Dutch Facial Clinimetric Evaluation Scale shows good psychometric values and can be implemented in the management of Dutch-speaking patients with facial palsy in the Netherlands. Translation of the instrument into other languages may lead to widespread use, making evaluation and comparison possible among different providers.

Reversibility of trapped air on chest computed tomography in cystic fibrosis patients.

PubMed

Loeve, Martine; Rosenow, Tim; Gorbunova, Vladlena; Hop, Wim C J; Tiddens, Harm A W M; de Bruijne, Marleen

2015-06-01

To investigate changes in trapped air volume and distribution over time and compare computed tomography (CT) with pulmonary function tests for determining trapped air. Thirty children contributed two CTs and pulmonary function tests over 2 years. Localized changes in trapped air on CT were assessed using image analysis software, by deforming the CT at timepoint 2 to match timepoint 1, and measuring the volume of stable (TAstable), disappeared (TAdisappeared) and new (TAnew) trapped air as a proportion of total lung volume. We used the difference between total lung capacity measured by plethysmography and helium dilution, residual volume to total lung capacity ratio, forced expiratory flow at 75% of vital capacity, and maximum mid-expiratory flow as pulmonary function test markers of trapped air. Statistical analysis included Wilcoxon's signed rank test and Spearman correlation coefficients. Median (range) age at baseline was 11.9 (5-17) years. Median (range) of trapped air was 9.5 (2-33)% at timepoint 1 and 9.0 (0-25)% at timepoint 2 (p=0.49). Median (range) TAstable, TAdisappeared and TAnew were respectively 3.0 (0-12)%, 5.0 (1-22)% and 7.0 (0-20)%. Trapped air on CT correlated statistically significantly with all pulmonary function measures (p<0.01), other than residual volume to total lung capacity ratio (p=0.37). Trapped air on CT did not significantly progress over 2 years, may have a substantial stable component, and is significantly correlated with pulmonary function markers. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Correlation between Visual Field Index and Other Functional and Structural Measures in Glaucoma Patients and Suspects.

PubMed

Iutaka, Natalia A; Grochowski, Rubens A; Kasahara, Niro

2017-01-01

To evaluate the correlation between visual field index (VFI) and both structural and functional measures of the optic disc in primary open angle glaucoma patients and suspects. In this retrospective study, 162 glaucoma patients and suspects underwent standard automated perimetry (SAP), retinography, and retinal nerve fiber layer (RNFL) measurement. The optic disc was stratified according to the vertical cup/disc ratio (C/D) and sorted by the disc damage likelihood scale (DDLS). RNFL was measured with the optical coherence tomography. The VFI perimetry was correlated with the mean deviation (MD) and pattern standard deviation (PSD) obtained by SAP, and structural parameters by Pearson's correlation coefficients. VFI displayed strong correlation with MD ( R = 0.959) and PSD ( R = -0.744). The linear correlations between VFI and structural measures including C/D ( R = -0.179, P = 0.012), DDLS ( R = -0.214, P = 0.006), and RNFL ( R = 0.416, P < 0.001) were weak but statistically significant. VFI showed a strong correlation with MD and PSD but demonstrated a weak correlation with structural measures. It can possibly be used as a marker for functional impairment severity in patients with glaucoma.

Interactions between different EEG frequency bands and their effect on alpha-fMRI correlations.

PubMed

de Munck, J C; Gonçalves, S I; Mammoliti, R; Heethaar, R M; Lopes da Silva, F H

2009-08-01

In EEG/fMRI correlation studies it is common to consider the fMRI BOLD as filtered version of the EEG alpha power. Here the question is addressed whether other EEG frequency components may affect the correlation between alpha and BOLD. This was done comparing the statistical parametric maps (SPMs) of three different filter models wherein either the free or the standard hemodynamic response functions (HRF) were used in combination with the full spectral bandwidth of the EEG. EEG and fMRI were co-registered in a 30 min resting state condition in 15 healthy young subjects. Power variations in the delta, theta, alpha, beta and gamma bands were extracted from the EEG and used as regressors in a general linear model. Statistical parametric maps (SPMs) were computed using three different filter models, wherein either the free or the standard hemodynamic response functions (HRF) were used in combination with the full spectral bandwidth of the EEG. Results show that the SPMs of different EEG frequency bands, when significant, are very similar to that of the alpha rhythm. This is true in particular for the beta band, despite the fact that the alpha harmonics were discarded. It is shown that inclusion of EEG frequency bands as confounder in the fMRI-alpha correlation model has a large effect on the resulting SPM, in particular when for each frequency band the HRF is extracted from the data. We conclude that power fluctuations of different EEG frequency bands are mutually highly correlated, and that a multi frequency model is required to extract the SPM of the frequency of interest from EEG/fMRI data. When no constraints are put on the shapes of the HRFs of the nuisance frequencies, the correlation model looses so much statistical power that no correlations can be detected.

Significance tests for functional data with complex dependence structure.

PubMed

Staicu, Ana-Maria; Lahiri, Soumen N; Carroll, Raymond J

2015-01-01

We propose an L 2 -norm based global testing procedure for the null hypothesis that multiple group mean functions are equal, for functional data with complex dependence structure. Specifically, we consider the setting of functional data with a multilevel structure of the form groups-clusters or subjects-units, where the unit-level profiles are spatially correlated within the cluster, and the cluster-level data are independent. Orthogonal series expansions are used to approximate the group mean functions and the test statistic is estimated using the basis coefficients. The asymptotic null distribution of the test statistic is developed, under mild regularity conditions. To our knowledge this is the first work that studies hypothesis testing, when data have such complex multilevel functional and spatial structure. Two small-sample alternatives, including a novel block bootstrap for functional data, are proposed, and their performance is examined in simulation studies. The paper concludes with an illustration of a motivating experiment.

Statistical model of a flexible inextensible polymer chain: The effect of kinetic energy.

PubMed

Pergamenshchik, V M; Vozniak, A B

2017-01-01

Because of the holonomic constraints, the kinetic energy contribution in the partition function of an inextensible polymer chain is difficult to find, and it has been systematically ignored. We present the first thermodynamic calculation incorporating the kinetic energy of an inextensible polymer chain with the bending energy. To explore the effect of the translation-rotation degrees of freedom, we propose and solve a statistical model of a fully flexible chain of N+1 linked beads which, in the limit of smooth bending, is equivalent to the well-known wormlike chain model. The partition function with the kinetic and bending energies and correlations between orientations of any pair of links and velocities of any pair of beads are found. This solution is precise in the limits of small and large rigidity-to-temperature ratio b/T. The last exact solution is essential as even very "harmless" approximation results in loss of the important effects when the chain is very rigid. For very high b/T, the orientations of different links become fully correlated. Nevertheless, the chain does not go over into a hard rod even in the limit b/T→∞: While the velocity correlation length diverges, the correlations themselves remain weak and tend to the value ∝T/(N+1). The N dependence of the partition function is essentially determined by the kinetic energy contribution. We demonstrate that to obtain the correct energy and entropy in a constrained system, the T derivative of the partition function has to be applied before integration over the constraint-setting variable.

Statistical model of a flexible inextensible polymer chain: The effect of kinetic energy

NASA Astrophysics Data System (ADS)

Pergamenshchik, V. M.; Vozniak, A. B.

2017-01-01

Because of the holonomic constraints, the kinetic energy contribution in the partition function of an inextensible polymer chain is difficult to find, and it has been systematically ignored. We present the first thermodynamic calculation incorporating the kinetic energy of an inextensible polymer chain with the bending energy. To explore the effect of the translation-rotation degrees of freedom, we propose and solve a statistical model of a fully flexible chain of N +1 linked beads which, in the limit of smooth bending, is equivalent to the well-known wormlike chain model. The partition function with the kinetic and bending energies and correlations between orientations of any pair of links and velocities of any pair of beads are found. This solution is precise in the limits of small and large rigidity-to-temperature ratio b /T . The last exact solution is essential as even very "harmless" approximation results in loss of the important effects when the chain is very rigid. For very high b /T , the orientations of different links become fully correlated. Nevertheless, the chain does not go over into a hard rod even in the limit b /T →∞ : While the velocity correlation length diverges, the correlations themselves remain weak and tend to the value ∝T /(N +1 ). The N dependence of the partition function is essentially determined by the kinetic energy contribution. We demonstrate that to obtain the correct energy and entropy in a constrained system, the T derivative of the partition function has to be applied before integration over the constraint-setting variable.

Atmospheric convective velocities and the Fourier phase spectrum

NASA Technical Reports Server (NTRS)

Cliff, W. C.

1974-01-01

The relationship between convective velocity and the Fourier phase spectrum of the cross correlation is developed. By examining the convective velocity as a function of frequency, one may determine if Taylor's conversion from time statistics to space statistics is valid. It is felt that the high shear regions of the atmospheric boundary layer need to be explored to determine the validity of the use of Taylor's hypothesis for this region.

Counting the peaks in the excitation function for precompound processes

NASA Astrophysics Data System (ADS)

Bonetti, R.; Hussein, M. S.; Mello, P. A.

1983-08-01

The "counting of maxima" method of Brink and Stephen, conventionally used for the extraction of the correlation width of statistical (compound nucleus) reactions, is generalized to include precompound processes as well. It is found that this method supplies an important independent check of the results obtained from autocorrelation studies. An application is made to the reaction 25Mg(3He,p). NUCLEAR REACTIONS Statistical multistep compound processes discussed.

KiDS-450: cosmological constraints from weak-lensing peak statistics - II: Inference from shear peaks using N-body simulations

NASA Astrophysics Data System (ADS)

Martinet, Nicolas; Schneider, Peter; Hildebrandt, Hendrik; Shan, HuanYuan; Asgari, Marika; Dietrich, Jörg P.; Harnois-Déraps, Joachim; Erben, Thomas; Grado, Aniello; Heymans, Catherine; Hoekstra, Henk; Klaes, Dominik; Kuijken, Konrad; Merten, Julian; Nakajima, Reiko

2018-02-01

We study the statistics of peaks in a weak-lensing reconstructed mass map of the first 450 deg2 of the Kilo Degree Survey (KiDS-450). The map is computed with aperture masses directly applied to the shear field with an NFW-like compensated filter. We compare the peak statistics in the observations with that of simulations for various cosmologies to constrain the cosmological parameter S_8 = σ _8 √{Ω _m/0.3}, which probes the (Ωm, σ8) plane perpendicularly to its main degeneracy. We estimate S8 = 0.750 ± 0.059, using peaks in the signal-to-noise range 0 ≤ S/N ≤ 4, and accounting for various systematics, such as multiplicative shear bias, mean redshift bias, baryon feedback, intrinsic alignment, and shear-position coupling. These constraints are ˜ 25 per cent tighter than the constraints from the high significance peaks alone (3 ≤ S/N ≤ 4) which typically trace single-massive haloes. This demonstrates the gain of information from low-S/N peaks. However, we find that including S/N < 0 peaks does not add further information. Our results are in good agreement with the tomographic shear two-point correlation function measurement in KiDS-450. Combining shear peaks with non-tomographic measurements of the shear two-point correlation functions yields a ˜20 per cent improvement in the uncertainty on S8 compared to the shear two-point correlation functions alone, highlighting the great potential of peaks as a cosmological probe.

Novel Assessment of Interstitial Lung Disease Using the "Computer-Aided Lung Informatics for Pathology Evaluation and Rating" (CALIPER) Software System in Idiopathic Inflammatory Myopathies.

PubMed

Ungprasert, Patompong; Wilton, Katelynn M; Ernste, Floranne C; Kalra, Sanjay; Crowson, Cynthia S; Rajagopalan, Srinivasan; Bartholmai, Brian J

2017-10-01

To evaluate the correlation between measurements from quantitative thoracic high-resolution CT (HRCT) analysis with "Computer-Aided Lung Informatics for Pathology Evaluation and Rating" (CALIPER) software and measurements from pulmonary function tests (PFTs) in patients with idiopathic inflammatory myopathies (IIM)-associated interstitial lung disease (ILD). A cohort of patients with IIM-associated ILD seen at Mayo Clinic was identified from medical record review. Retrospective analysis of HRCT data and PFTs at baseline and 1 year was performed. The abnormalities in HRCT were quantified using CALIPER software. A total of 110 patients were identified. At baseline, total interstitial abnormalities as measured by CALIPER, both by absolute volume and by percentage of total lung volume, had a significant negative correlation with diffusing capacity for carbon monoxide (DLCO), total lung capacity (TLC), and oxygen saturation. Analysis by subtype of interstitial abnormality revealed significant negative correlations between ground glass opacities (GGO) and reticular density (RD) with DLCO and TLC. At one year, changes of total interstitial abnormalities compared with baseline had a significant negative correlation with changes of TLC and oxygen saturation. A negative correlation between changes of total interstitial abnormalities and DLCO was also observed, but it was not statistically significant. Analysis by subtype of interstitial abnormality revealed negative correlations between changes of GGO and RD and changes of DLCO, TLC, and oxygen saturation, but most of the correlations did not achieve statistical significance. CALIPER measurements correlate well with functional measurements in patients with IIM-associated ILD.

Micro-heterogeneity versus clustering in binary mixtures of ethanol with water or alkanes.

PubMed

Požar, Martina; Lovrinčević, Bernarda; Zoranić, Larisa; Primorać, Tomislav; Sokolić, Franjo; Perera, Aurélien

2016-08-24

Ethanol is a hydrogen bonding liquid. When mixed in small concentrations with water or alkanes, it forms aggregate structures reminiscent of, respectively, the direct and inverse micellar aggregates found in emulsions, albeit at much smaller sizes. At higher concentrations, micro-heterogeneous mixing with segregated domains is found. We examine how different statistical methods, namely correlation function analysis, structure factor analysis and cluster distribution analysis, can describe efficiently these morphological changes in these mixtures. In particular, we explain how the neat alcohol pre-peak of the structure factor evolves into the domain pre-peak under mixing conditions, and how this evolution differs whether the co-solvent is water or alkane. This study clearly establishes the heuristic superiority of the correlation function/structure factor analysis to study the micro-heterogeneity, since cluster distribution analysis is insensitive to domain segregation. Correlation functions detect the domains, with a clear structure factor pre-peak signature, while the cluster techniques detect the cluster hierarchy within domains. The main conclusion is that, in micro-segregated mixtures, the domain structure is a more fundamental statistical entity than the underlying cluster structures. These findings could help better understand comparatively the radiation scattering experiments, which are sensitive to domains, versus the spectroscopy-NMR experiments, which are sensitive to clusters.

Characterization of the Spatial Structure of Local Functional Connectivity Using Multidistance Average Correlation Measures.

PubMed

Macià, Dídac; Pujol, Jesus; Blanco-Hinojo, Laura; Martínez-Vilavella, Gerard; Martín-Santos, Rocío; Deus, Joan

2018-06-01

There is ample evidence from basic research in neuroscience of the importance of local corticocortical networks. Millimetric resolution is achievable with current functional magnetic resonance imaging (fMRI) scanners and sequences, and consequently a number of "local" activity similarity measures have been defined to describe patterns of segregation and integration at this spatial scale. We have introduced the use of IsoDistant Average Correlation (IDAC), easily defined as the average fMRI temporal correlation of a given voxel with other voxels placed at increasingly separated isodistant intervals, to characterize the curve of local fMRI signal similarities. IDAC curves can be statistically compared using parametric multivariate statistics. Furthermore, by using red-green-blue color coding to display jointly IDAC values belonging to three different distance lags, IDAC curves can also be displayed as multidistance IDAC maps. We applied IDAC analysis to a sample of 41 subjects scanned under two different conditions, a resting state and an auditory-visual continuous stimulation. Multidistance IDAC mapping was able to discriminate between gross anatomofunctional cortical areas and, moreover, was sensitive to modulation between the two brain conditions in areas known to activate and deactivate during audiovisual tasks. Unlike previous fMRI local similarity measures already in use, our approach draws special attention to the continuous smooth pattern of local functional connectivity.

Information Entropy Production of Maximum Entropy Markov Chains from Spike Trains

NASA Astrophysics Data System (ADS)

Cofré, Rodrigo; Maldonado, Cesar

2018-01-01

We consider the maximum entropy Markov chain inference approach to characterize the collective statistics of neuronal spike trains, focusing on the statistical properties of the inferred model. We review large deviations techniques useful in this context to describe properties of accuracy and convergence in terms of sampling size. We use these results to study the statistical fluctuation of correlations, distinguishability and irreversibility of maximum entropy Markov chains. We illustrate these applications using simple examples where the large deviation rate function is explicitly obtained for maximum entropy models of relevance in this field.

Peculiarities of the momentum distribution functions of strongly correlated charged fermions

NASA Astrophysics Data System (ADS)

Larkin, A. S.; Filinov, V. S.; Fortov, V. E.

2018-01-01

New numerical version of the Wigner approach to quantum thermodynamics of strongly coupled systems of particles has been developed for extreme conditions, when analytical approximations based on different kinds of perturbation theories cannot be applied. An explicit analytical expression of the Wigner function has been obtained in linear and harmonic approximations. Fermi statistical effects are accounted for by effective pair pseudopotential depending on coordinates, momenta and degeneracy parameter of particles and taking into account Pauli blocking of fermions. A new quantum Monte-Carlo method for calculations of average values of arbitrary quantum operators has been developed. Calculations of the momentum distribution functions and the pair correlation functions of degenerate ideal Fermi gas have been carried out for testing the developed approach. Comparison of the obtained momentum distribution functions of strongly correlated Coulomb systems with the Maxwell-Boltzmann and the Fermi distributions shows the significant influence of interparticle interaction both at small momenta and in high energy quantum ‘tails’.

Impact of resistance exercise program on functional capacity and muscular strength of knee extensor in pre-frail community-dwelling older women: a randomized crossover trial.

PubMed

Lustosa, Lygia P; Silva, Juscélio P; Coelho, Fernanda M; Pereira, Daniele S; Parentoni, Adriana N; Pereira, Leani S M

2011-01-01

Frailty syndrome in elderly people is characterized by a reduction of energy reserves and also by a decreased of resistance to stressors, resulting in an increase of vulnerability. The aim of this study was to verify the effect of a muscle-strengthening program with load in pre-frail elder women with regards to the functional capacity, knee extensor muscle strength and their correlation. Thrity-two pre-frail community-dwelling women participated in this study. Potential participants with cognitive impairment (MEEM), lower extremities orthopedic surgery, fractures, inability to walk unaided, neurological diseases, acute inflammatory disease, tumor growth, regular physical activity and current use of immunomodulators were excluded. All partcipants were evaluated by a blinded assessor using: Timed up and go (TUG), 10-Meter Walk Test (10MWT) and knee extensor muscle strength (Byodex System 3 Pro® isokinetic dynamometer at angular speeds of 60 and 180(0)/s). The intervention consisted of strengthening exercises of the lower extremities at 70% of 1RM, three times/ week for ten weeks. The statistical analysis was performed using the ANOVA and Spearman tests After the intervention, it was observed statistical significance on the work at 180(0)/s (F=12.71, p=0.02), on the power at 180(0)/s (F=15.40, p=0.02) and on the functional capacity (TUG, F=9.54, p=0.01; TC10, F=3.80, p=0.01). There was a good negative and statistically significant correlation between the TUG and work at 60(0)/s, such as the TUG and work at 180(0)/s (r=-0.65, p=0.01; r=-0.72, p=0.01). The intervention improved the muscular power and the functional capacity. The increase of the power correlated with function, which is an important variable of the quality of life in the pre-frail elders. Article registered in the ISRCT register under number ISRCTN62824599.

Renal dysfunction in liver cirrhosis and its correlation with Child-Pugh score and MELD score

NASA Astrophysics Data System (ADS)

Siregar, G. A.; Gurning, M.

2018-03-01

Renal dysfunction (RD) is a serious and common complication in a patient with liver cirrhosis. It provides a poor prognosis. The aim of our study was to evaluate the renal function in liver cirrhosis, also to determine the correlation with the graduation of liver disease assessed by Child-Pugh Score (CPS) and MELD score. This was a cross-sectional study included patients with liver cirrhosis admitted to Adam Malik Hospital Medan in June - August 2016. We divided them into two groups as not having renal dysfunction (serum creatinine < 1.5 mg/dL) and having renal dysfunction (serum creatinine ≤ 1.5 mg/dL). For the processing of data, SPSS 22.0 was used. Statistical methods used: Chi-square, Fisher exact, one way ANOVA, Kruskal Wallis test and Pearson coefficient of correlation. The level of significance was p<0.05. 55 patients with presented with renal dysfunction were 16 (29.1 %). There was statistically significant inverse correlation between GFR and CPS (r = -0.308), GFR and MELD score (r = -0.278). There was a statistically significant correlation between creatinine and MELD score (r = 0.359), creatinine and CPS (r = 0.382). The increase of the degree of liver damage is related to the increase of renal dysfunction.

A statistical mechanical theory of proton transport kinetics in hydrogen-bonded networks based on population correlation functions with applications to acids and bases.

PubMed

Tuckerman, Mark E; Chandra, Amalendu; Marx, Dominik

2010-09-28

Extraction of relaxation times, lifetimes, and rates associated with the transport of topological charge defects in hydrogen-bonded networks from molecular dynamics simulations is a challenge because proton transfer reactions continually change the identity of the defect core. In this paper, we present a statistical mechanical theory that allows these quantities to be computed in an unbiased manner. The theory employs a set of suitably defined indicator or population functions for locating a defect structure and their associated correlation functions. These functions are then used to develop a chemical master equation framework from which the rates and lifetimes can be determined. Furthermore, we develop an integral equation formalism for connecting various types of population correlation functions and derive an iterative solution to the equation, which is given a graphical interpretation. The chemical master equation framework is applied to the problems of both hydronium and hydroxide transport in bulk water. For each case it is shown that the theory establishes direct links between the defect's dominant solvation structures, the kinetics of charge transfer, and the mechanism of structural diffusion. A detailed analysis is presented for aqueous hydroxide, examining both reorientational time scales and relaxation of the rotational anisotropy, which is correlated with recent experimental results for these quantities. Finally, for OH(-)(aq) it is demonstrated that the "dynamical hypercoordination mechanism" is consistent with available experimental data while other mechanistic proposals are shown to fail. As a means of going beyond the linear rate theory valid from short up to intermediate time scales, a fractional kinetic model is introduced in the Appendix in order to describe the nonexponential long-time behavior of time-correlation functions. Within the mathematical framework of fractional calculus the power law decay ∼t(-σ), where σ is a parameter of the model and depends on the dimensionality of the system, is obtained from Mittag-Leffler functions due to their long-time asymptotics, whereas (stretched) exponential behavior is found for short times.

Statistical theory of correlations in random packings of hard particles.

PubMed

Jin, Yuliang; Puckett, James G; Makse, Hernán A

2014-05-01

A random packing of hard particles represents a fundamental model for granular matter. Despite its importance, analytical modeling of random packings remains difficult due to the existence of strong correlations which preclude the development of a simple theory. Here, we take inspiration from liquid theories for the n-particle angular correlation function to develop a formalism of random packings of hard particles from the bottom up. A progressive expansion into a shell of particles converges in the large layer limit under a Kirkwood-like approximation of higher-order correlations. We apply the formalism to hard disks and predict the density of two-dimensional random close packing (RCP), ϕ(rcp) = 0.85 ± 0.01, and random loose packing (RLP), ϕ(rlp) = 0.67 ± 0.01. Our theory also predicts a phase diagram and angular correlation functions that are in good agreement with experimental and numerical data.

New statistical potential for quality assessment of protein models and a survey of energy functions

PubMed Central

2010-01-01

Background Scoring functions, such as molecular mechanic forcefields and statistical potentials are fundamentally important tools in protein structure modeling and quality assessment. Results The performances of a number of publicly available scoring functions are compared with a statistical rigor, with an emphasis on knowledge-based potentials. We explored the effect on accuracy of alternative choices for representing interaction center types and other features of scoring functions, such as using information on solvent accessibility, on torsion angles, accounting for secondary structure preferences and side chain orientation. Partially based on the observations made, we present a novel residue based statistical potential, which employs a shuffled reference state definition and takes into account the mutual orientation of residue side chains. Atom- and residue-level statistical potentials and Linux executables to calculate the energy of a given protein proposed in this work can be downloaded from http://www.fiserlab.org/potentials. Conclusions Among the most influential terms we observed a critical role of a proper reference state definition and the benefits of including information about the microenvironment of interaction centers. Molecular mechanical potentials were also tested and found to be over-sensitive to small local imperfections in a structure, requiring unfeasible long energy relaxation before energy scores started to correlate with model quality. PMID:20226048

Statistical theory for the Kardar-Parisi-Zhang equation in (1+1) dimensions.

PubMed

Masoudi, A A; Shahbazi, F; Davoudi, J; Tabar, M Reza Rahimi

2002-02-01

The Kardar-Parisi-Zhang (KPZ) equation in (1+1) dimensions dynamically develops sharply connected valley structures within which the height derivative is not continuous. We develop a statistical theory for the KPZ equation in (1+1) dimensions driven with a random forcing that is white in time and Gaussian-correlated in space. A master equation is derived for the joint probability density function of height difference and height gradient P(h-h*, partial differential(x)h,t) when the forcing correlation length is much smaller than the system size and much larger than the typical sharp valley width. In the time scales before the creation of the sharp valleys, we find the exact generating function of h-h* and partial differential(x)h. The time scale of the sharp valley formation is expressed in terms of the force characteristics. In the stationary state, when the sharp valleys are fully developed, finite-size corrections to the scaling laws of the structure functions left angle bracket(h-h*)(n)(partial differential(x)h)(m)right angle bracket are also obtained.

[Changes of brain function and cognitive function after carotid artery stenting].

PubMed

Lu, Z X; Deng, G; Wei, H L; Zhao, G F; Wen, L Z; Chen, X

2017-10-24

Objective: To investigate the effect of carotid artery stenting(CAS) on cognitive function and brain function based on changes of a battery of neuropsychological tests and magnetic resonance imaging. Methods: Thirty-three patients were included with 17 in the stent-placement group and 16 in the control group (receiving medical treatment), among whom, the unilateral or bilateral severe internal carotid artery stenosis was confirmed by cerebral vascular angiography in the department of Interventional Radiology and Vascular Surgery of Zhongda Hospital Southeast University from June 2015 to September 2016.Neuropsychological tests and rest-state blood oxygenation level dependent fMRI were performed at the baseline and six months follow-up.The baseline characteristics and follow-up changes were compared in each group. Results: The overall cognitive function of the stent-placement group was statistically significantly improved ( P <0.05) compared with control group, mainly in the executive function, memory, attention and other aspects.The value of amplitude of low-frequency fluctuation(ALFF) showed statistically significant increase ( P <0.05, Alphasim correction) in left prefrontal cortex ( t =5.861 3, P <0.05), the somatosensory association cortex in left superior parietal lobe( t =5.601 2, P <0.05) and bilateral motor cortical area in posterior frontal lobe ( t =5.288 5, P <0.05). The ALFF showed statistically significant decrease ( P <0.05, Alphasim correction) in left retrosplenial cingulate cortex( t =-5.590 4, P <0.05), left insular cortex ( t =-6.340 8, P <0.05), right insular cortex ( t =-8.129 9, P <0.05) and left dorsal anterior cingulate cortex ( t =-5.584 8, P <0.05). There was no statistically significant difference ( P >0.05, Alphasim correction)between baseline and follow-up results in control group.Besides, the ALFF changes of the left insular cortex ( r =-0.591, P =0.033) and bilateral motor cortical area ( r =-0.659, P =0.014) were negatively correlated with auditory verb learning test (AVLT) score changes.The ALFF change of bilateral motor cortical area was negatively correlated with the AVLT-delay score change ( r =-0.588, P =0.034). And the ALFF change on right insular cortex and the frontal assessment battery (FAB) score change was positively correlated ( r =0.638, P =0.025). Conclusions: The overall cognitive function of patients with carotid artery stenosis significantly improve after CAS compared with medical treatment.The change of ALFF value in related brain area is also statistically significant.ALFF Change most in area of Default Mode Network may suggest a mechanism of postoperative neurological recovery in patients with carotid artery stenosis.

Establishing the kinetics of ballistic-to-diffusive transition using directional statistics

NASA Astrophysics Data System (ADS)

Liu, Pai; Heinson, William R.; Sumlin, Benjamin J.; Shen, Kuan-Yu; Chakrabarty, Rajan K.

2018-04-01

We establish the kinetics of ballistic-to-diffusive (BD) transition observed in two-dimensional random walk using directional statistics. Directional correlation is parameterized using the walker's turning angle distribution, which follows the commonly adopted wrapped Cauchy distribution (WCD) function. During the BD transition, the concentration factor (ρ) governing the WCD shape is observed to decrease from its initial value. We next analytically derive the relationship between effective ρ and time, which essentially quantifies the BD transition rate. The prediction of our kinetic expression agrees well with the empirical datasets obtained from correlated random walk simulation. We further connect our formulation with the conventionally used scaling relationship between the walker's mean-square displacement and time.

Intercorrelations of Anthropometric Measurements: A Source Book for USA Data

DTIC Science & Technology

1978-05-01

and most important of the statistical measures after the arithmetic mean and standard devi- ation. The coefficient was devised and developed by Francis ... Galton and Karl Pearson in the last decades of the nineteenth century as a measure of the degree of interrelationship or concomitant variation of a...paragraphs--in a wide variety of formulas such as ones for tests of statistical significance and for discriminant functions. Correlation coefficients are

Mechanics and statistics of the worm-like chain

NASA Astrophysics Data System (ADS)

Marantan, Andrew; Mahadevan, L.

2018-02-01

The worm-like chain model is a simple continuum model for the statistical mechanics of a flexible polymer subject to an external force. We offer a tutorial introduction to it using three approaches. First, we use a mesoscopic view, treating a long polymer (in two dimensions) as though it were made of many groups of correlated links or "clinks," allowing us to calculate its average extension as a function of the external force via scaling arguments. We then provide a standard statistical mechanics approach, obtaining the average extension by two different means: the equipartition theorem and the partition function. Finally, we work in a probabilistic framework, taking advantage of the Gaussian properties of the chain in the large-force limit to improve upon the previous calculations of the average extension.

Muscle performance, body fat, pain and function in the elderly with arthritis.

PubMed

Dos Santos, Wagner Teixeira; Rodrigues, Erika de Carvalho; Mainenti, Míriam Raquel Meira

2014-01-01

To correlate muscule performance, body composition, pain and joint function in elderly people with gonarthrosis. 21 elderly patients were submitted to bioelectrical impedance analysis, dynamometry associated with electromyographic (EMG) evaluation of isometric knee extension, in addition to pain assessment by the Numeric Pain Intensity Scale and function assessment, by the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis (OA) questionnaire. Correlations were checked by the Pearson's correlation coefficient. The sample characteristics were mean age 67.36 ± 4.21 years old, body fat percentage 40.57±6.15%, total WOMAC score 43.27 ± 16.32%, and maximum strength 19.95 ± 6.99 kgF. Pain during movement showed a statistical association with WOMAC physical activity domain (r = 0.47) and its general score (r = 0.51); pain intensity at night presented association with WOMAC stiffness domain (r = 0.55), in addition to the negative correlation with the slope values of the Medium Frequency of the EMG signal (r = - 0.57). pain intensity is correlated to functional incapacity in elderly people with knee OA and to a greater expression of fatigue in EMG signal. Levels of Evidence III, Study of non consecutive patients.

Uncertainties in the cluster-cluster correlation function

NASA Astrophysics Data System (ADS)

Ling, E. N.; Frenk, C. S.; Barrow, J. D.

1986-12-01

The bootstrap resampling technique is applied to estimate sampling errors and significance levels of the two-point correlation functions determined for a subset of the CfA redshift survey of galaxies and a redshift sample of 104 Abell clusters. The angular correlation function for a sample of 1664 Abell clusters is also calculated. The standard errors in xi(r) for the Abell data are found to be considerably larger than quoted 'Poisson errors'. The best estimate for the ratio of the correlation length of Abell clusters (richness class R greater than or equal to 1, distance class D less than or equal to 4) to that of CfA galaxies is 4.2 + 1.4 or - 1.0 (68 percentile error). The enhancement of cluster clustering over galaxy clustering is statistically significant in the presence of resampling errors. The uncertainties found do not include the effects of possible systematic biases in the galaxy and cluster catalogs and could be regarded as lower bounds on the true uncertainty range.

Correlations and Functional Connections in a Population of Grid Cells

PubMed Central

Roudi, Yasser

2015-01-01

We study the statistics of spike trains of simultaneously recorded grid cells in freely behaving rats. We evaluate pairwise correlations between these cells and, using a maximum entropy kinetic pairwise model (kinetic Ising model), study their functional connectivity. Even when we account for the covariations in firing rates due to overlapping fields, both the pairwise correlations and functional connections decay as a function of the shortest distance between the vertices of the spatial firing pattern of pairs of grid cells, i.e. their phase difference. They take positive values between cells with nearby phases and approach zero or negative values for larger phase differences. We find similar results also when, in addition to correlations due to overlapping fields, we account for correlations due to theta oscillations and head directional inputs. The inferred connections between neurons in the same module and those from different modules can be both negative and positive, with a mean close to zero, but with the strongest inferred connections found between cells of the same module. Taken together, our results suggest that grid cells in the same module do indeed form a local network of interconnected neurons with a functional connectivity that supports a role for attractor dynamics in the generation of grid pattern. PMID:25714908

Correlation between T2* cardiovascular magnetic resonance with left ventricular function and mass in adolescent and adult major thalassemia patients with iron overload.

PubMed

Djer, Mulyadi M; Anggriawan, Shirley L; Gatot, Djajadiman; Amalia, Pustika; Sastroasmoro, Sudigdo; Widjaja, Patricia

2013-10-01

to assess for a correlation between T2*CMR with LV function and mass in thalassemic patients with iron overload. a cross-sectional study on thalassemic patients was conducted between July and September 2010 at Cipto Mangunkusumo and Premier Hospitals, Jakarta, Indonesia. Clinical examinations, review of medical charts, electrocardiography, echocardiography, and T2*CMR were performed. Cardiac siderosis was measured by T2*CMR conduction time. Left ventricle diastolic and systolic functions, as well as LV mass index were measured using echocardiography. Correlations between T2*CMR and echocardiography findings, as well as serum ferritin were determined using Pearson's and Spearman's tests. thirty patients aged 13-41 years were enrolled, of whom two-thirds had -thalassemia major and one-third had HbE/-thalassemia. Diastolic dysfunction was identified in 8 patients, whereas systolic function was normal in all patients. Increased LV mass index was found in 3 patients. T2*CMR conduction times ranged from 8.98 to 55.04 ms and a value below 20 ms was demonstrated in 14 patients. There was a statistically significant moderate positive correlation of T2*CMR conduction time with E/A ratio (r = 0.471, P = 0.009), but no correlation was found with LV mass index (r=0.097, P=0.608). A moderate negative correlation was found between T2*CMR and serum ferritin (r = -0.514, P = 0.004), while a moderate negative correlation was found between serum ferritin and E/A ratio (r = -0.425, P = 0.019). T2*CMR myocardial conduction time has a moderate positive correlation with diastolic function, moderate negative correlation with serum ferritin, but not with LV mass index and systolic function.

Sample size, confidence, and contingency judgement.

PubMed

Clément, Mélanie; Mercier, Pierre; Pastò, Luigi

2002-06-01

According to statistical models, the acquisition function of contingency judgement is due to confidence increasing with sample size. According to associative models, the function reflects the accumulation of associative strength on which the judgement is based. Which view is right? Thirty university students assessed the relation between a fictitious medication and a symptom of skin discoloration in conditions that varied sample size (4, 6, 8 or 40 trials) and contingency (delta P = .20, .40, .60 or .80). Confidence was also collected. Contingency judgement was lower for smaller samples, while confidence level correlated inversely with sample size. This dissociation between contingency judgement and confidence contradicts the statistical perspective.

[Family functionality regarding the elderly with cognitive impairments: the caretaker's perception].

PubMed

dos Santos, Ariene Angelini; Pavarini, Sofia Cristina Iost

2012-10-01

The objectives of this study were to characterize the caregivers of elderly individuals with cognitive impairment living in different contexts of social vulnerability, and assess the family functionality of the elderly as perceived by the caregivers. Family functionality was evaluated using the Family APGAR instrument, assessed during home interviews with 72 caretakers. All the ethical aspects were observed. Spearman's correlation and the Mann-Whitney test were used, with 5% significance level (p<0.05). Results show that 82% of caregivers reported a good family functionality, 14% reported moderate family dysfunction, and 4% reported high family dysfunction. A statistically significant correlation was found between Family APGAR and the number of people living in the house (p=0.048). Further studies could verify the relationship between family functionality and the caretaker's overload in the context of elderly persons with dementia.

[Liver and heart T2* measurement in secondary haemochromatosis].

PubMed

Barrera Portillo, M C; Uranga Uranga, M; Sánchez González, J; Alústiza Echeverría, J M; Gervás Wells, C; Guisasola Íñiguez, A

2013-01-01

To determine whether there is iron overload by calculating the T2* value in the liver and myocardium in patients with secondary haemochromatosis. To analyse the correlation of the values obtained with the iron levels in blood, with the liver iron concentration (LIC) calculated using magnetic resonance (MR) imaging, and the correlation between them. A total of 16 patients (13 males, 3 females), with a mean age of 61 years, were included and evaluated in the years 2008 and 2009. Fifteen of them had received multiple transfusions, and one was diagnosed with hereditary sideroblastic anaemia. The measurements included, blood ferritin, LIC by MRI, cardiac function using MRI and the T2* value by means of multi-echo sequences in the liver (TR/TE1/ΔTE/No of echos/α: 21/1,18/1.0/20/35°) and myocardium (26/1.04/0.8/30/60°). A correlation-regression analysis was performed by comparing the cardiac and liver T2* values with the ferritin, LIC and between each of them. A total of 13 patients had ferritin values greater than 1000ng/ml (median/minimum/maximum: 1762/294/3785ng/ml). An increased LIC greater than 80μmol/g (median/minimum/maximum: 125.4/41.2/241.5μmol/g) was observed in 13 patients. In all cases cardiac function was conserved, and in 15 cases the liver T2* value was less than 6.3ms. The myocardium T2* value was less than 20ms. in only one case. A high correlation was observed between the liver T2* values and the LIC (r:-0.912). The correlation was statistically significant between the liver T2* value and ferritin (r:-0.541). The correlations between myocardium T2* and ferritin, myocardium T2* and LIC, and myocardium T2* and liver T2* were not statistically significant. The liver T2* showed a high correlation with LIC and a statistically significant correlation with ferritin. No association was observed between the myocardium T2* values and ferritin in blood, the LIC or the liver T2* value. Copyright © 2011 SERAM. Published by Elsevier Espana. All rights reserved.

An Ultra-Wideband Cross-Correlation Radiometer for Mesoscopic Experiments

NASA Astrophysics Data System (ADS)

Toonen, Ryan; Haselby, Cyrus; Qin, Hua; Eriksson, Mark; Blick, Robert

2007-03-01

We have designed, built and tested a cross-correlation radiometer for detecting statistical order in the quantum fluctuations of mesoscopic experiments at sub-Kelvin temperatures. Our system utilizes a fully analog front-end--operating over the X- and Ku-bands (8 to 18 GHz)--for computing the cross-correlation function. Digital signal processing techniques are used to provide robustness against instrumentation drifts and offsets. The economized version of our instrument can measure, with sufficient correlation efficiency, noise signals having power levels as low as 10 fW. We show that, if desired, we can improve this performance by including cryogenic preamplifiers which boost the signal-to-noise ratio near the signal source. By adding a few extra components, we can measure both the real and imaginary parts of the cross-correlation function--improving the overall signal-to-noise ratio by a factor of sqrt[2]. We demonstrate the utility of our cross-correlator with noise power measurements from a quantum point contact.

Filtering genetic variants and placing informative priors based on putative biological function.

PubMed

Friedrichs, Stefanie; Malzahn, Dörthe; Pugh, Elizabeth W; Almeida, Marcio; Liu, Xiao Qing; Bailey, Julia N

2016-02-03

High-density genetic marker data, especially sequence data, imply an immense multiple testing burden. This can be ameliorated by filtering genetic variants, exploiting or accounting for correlations between variants, jointly testing variants, and by incorporating informative priors. Priors can be based on biological knowledge or predicted variant function, or even be used to integrate gene expression or other omics data. Based on Genetic Analysis Workshop (GAW) 19 data, this article discusses diversity and usefulness of functional variant scores provided, for example, by PolyPhen2, SIFT, or RegulomeDB annotations. Incorporating functional scores into variant filters or weights and adjusting the significance level for correlations between variants yielded significant associations with blood pressure traits in a large family study of Mexican Americans (GAW19 data set). Marker rs218966 in gene PHF14 and rs9836027 in MAP4 significantly associated with hypertension; additionally, rare variants in SNUPN significantly associated with systolic blood pressure. Variant weights strongly influenced the power of kernel methods and burden tests. Apart from variant weights in test statistics, prior weights may also be used when combining test statistics or to informatively weight p values while controlling false discovery rate (FDR). Indeed, power improved when gene expression data for FDR-controlled informative weighting of association test p values of genes was used. Finally, approaches exploiting variant correlations included identity-by-descent mapping and the optimal strategy for joint testing rare and common variants, which was observed to depend on linkage disequilibrium structure.

Fall Risk Factors in Community-Dwelling Elderly Depending on Their Physical Function, Cognitive Status and Symptoms of Depression

PubMed Central

Kamińska, Magdalena Sylwia; Brodowski, Jacek; Karakiewicz, Beata

2015-01-01

Falls are the leading cause of unintentional injuries and injury-related disability, morbidity and mortality in the geriatric population. Therefore, they may also lower quality of life. The aim of this study was to analyze the fall risk factors in the community-dwelling elderly depending on their physical function, cognitive status and symptoms of depression. The study involved 304 individuals aged 65–100 years with a mean age of 78.6 ± 7.4. This survey-based study was conducted using the Geriatric Environmental Inquiry, the Barthel Scale (BS), the Abbreviated Mental Test Score (AMTS), the Geriatric Depression Scale (GDS) and the Tinetti Test (TT). There was a statistically significant correlation between the BS, the TT and the incidence of falls (p < 0.05). The number of falls correlated significantly with the results of the BS (R = −0.39), the GDS (R = 0.18), and the TT (R = −0.40). A statistically significant correlation was also noted between the TT results and the results of the BS (R = 0.77), the AMTS (R = 0.40) and the GDS (R = −0.37). The incidence of falls may significantly increase in people with a lower functional status, which may be related to cognitive process disturbances and lower affective functioning. A comprehensive geriatric assessment, related to all aspects of advanced-age patients’ efficiency, is recommended. Fall prevention strategies should include actions undertaken to evaluate and treat depression and cognitive disturbances. PMID:25811765

Correlation between the Quality of Attention and Cognitive Competence with Motor Action in Stroke Patients.

PubMed

Arsic, S; Konstantinovic, Lj; Eminovic, F; Pavlovic, D; Popovic, M B; Arsic, V

2015-01-01

It is considered that cognitive function and attention could affect walking, motion control, and proper conduct during the walk. To determine whether there is a difference in the quality of attention and cognitive ability in stroke patients and patients without neurological damage of similar age and education and to determine whether the connection of attention and cognition affects motor skills, the sample consisted of 50 stroke patients tested with hemiparesis, involved in the process of rehabilitation, and 50 persons, randomly chosen, without neurological damage. The survey used the following tests: Trail Making (TMT A B) test for assessing the flexibility of attention; Mini-Mental State Examination (MMSE) for cognitive status; Functional Ambulation Category (FAC) test to assess the functional status and parameters of walk: speed, frequency, and length of stride; STEP test for assessing the precision of movement and balance. With stroke patients, relationship between age and performance on the MMSE test was marginally significant. The ratio of performance to TMT A B test and years does not indicate statistical significance, while statistical significance between the MMSE test performance and education exists. In stroke patients, performance on MMSE test is correlated with the frequency and length of stride walk. The quality of cognitive function and attention is associated with motor skills but differs in stroke patients and people without neurological damage of similar age. The significance of this correlation can supplement research in neurorehabilitation, improve the quality of medical rehabilitation, and contribute to efficient recovery of these patients.

Association of ED with chronic periodontal disease.

PubMed

Matsumoto, S; Matsuda, M; Takekawa, M; Okada, M; Hashizume, K; Wada, N; Hori, J; Tamaki, G; Kita, M; Iwata, T; Kakizaki, H

2014-01-01

To examine the relationship between chronic periodontal disease (CPD) and ED, the interview sheet including the CPD self-checklist (CPD score) and the five-item version of the International Index of Erectile Function (IIEF-5) was distributed to 300 adult men who received a comprehensive dental examination. Statistical analyses were performed by the Spearman's rank correlation coefficient and other methods. Statistical significance was accepted at the level of P<0.05. The interview sheets were collected from 88 men (response rate 29.3%, 50.9±16.6 years old). There was a statistically significant correlation between the CPD score and the presence of ED (P=0.0415). The results in the present study suggest that ED is related to the damage caused by endothelial dysfunction and the systematic inflammatory changes associated with CPD. The present study also suggests that dental health is important as a preventive medicine for ED.

Accurate Structural Correlations from Maximum Likelihood Superpositions

PubMed Central

Theobald, Douglas L; Wuttke, Deborah S

2008-01-01

The cores of globular proteins are densely packed, resulting in complicated networks of structural interactions. These interactions in turn give rise to dynamic structural correlations over a wide range of time scales. Accurate analysis of these complex correlations is crucial for understanding biomolecular mechanisms and for relating structure to function. Here we report a highly accurate technique for inferring the major modes of structural correlation in macromolecules using likelihood-based statistical analysis of sets of structures. This method is generally applicable to any ensemble of related molecules, including families of nuclear magnetic resonance (NMR) models, different crystal forms of a protein, and structural alignments of homologous proteins, as well as molecular dynamics trajectories. Dominant modes of structural correlation are determined using principal components analysis (PCA) of the maximum likelihood estimate of the correlation matrix. The correlations we identify are inherently independent of the statistical uncertainty and dynamic heterogeneity associated with the structural coordinates. We additionally present an easily interpretable method (“PCA plots”) for displaying these positional correlations by color-coding them onto a macromolecular structure. Maximum likelihood PCA of structural superpositions, and the structural PCA plots that illustrate the results, will facilitate the accurate determination of dynamic structural correlations analyzed in diverse fields of structural biology. PMID:18282091

What kind of noise is brain noise: anomalous scaling behavior of the resting brain activity fluctuations

PubMed Central

Fraiman, Daniel; Chialvo, Dante R.

2012-01-01

The study of spontaneous fluctuations of brain activity, often referred as brain noise, is getting increasing attention in functional magnetic resonance imaging (fMRI) studies. Despite important efforts, much of the statistical properties of such fluctuations remain largely unknown. This work scrutinizes these fluctuations looking at specific statistical properties which are relevant to clarify its dynamical origins. Here, three statistical features which clearly differentiate brain data from naive expectations for random processes are uncovered: First, the variance of the fMRI mean signal as a function of the number of averaged voxels remains constant across a wide range of observed clusters sizes. Second, the anomalous behavior of the variance is originated by bursts of synchronized activity across regions, regardless of their widely different sizes. Finally, the correlation length (i.e., the length at which the correlation strength between two regions vanishes) as well as mutual information diverges with the cluster's size considered, such that arbitrarily large clusters exhibit the same collective dynamics than smaller ones. These three properties are known to be exclusive of complex systems exhibiting critical dynamics, where the spatio-temporal dynamics show these peculiar type of fluctuations. Thus, these findings are fully consistent with previous reports of brain critical dynamics, and are relevant for the interpretation of the role of fluctuations and variability in brain function in health and disease. PMID:22934058

Long-range correlation in cosmic microwave background radiation.

PubMed

Movahed, M Sadegh; Ghasemi, F; Rahvar, Sohrab; Tabar, M Reza Rahimi

2011-08-01

We investigate the statistical anisotropy and gaussianity of temperature fluctuations of Cosmic Microwave Background (CMB) radiation data from the Wilkinson Microwave Anisotropy Probe survey, using the Multifractal Detrended Fluctuation Analysis, Rescaled Range, and Scaled Windowed Variance methods. Multifractal Detrended Fluctuation Analysis shows that CMB fluctuations has a long-range correlation function with a multifractal behavior. By comparing the shuffled and surrogate series of CMB data, we conclude that the multifractality nature of the temperature fluctuation of CMB radiation is mainly due to the long-range correlations, and the map is consistent with a gaussian distribution.

Correspondence between large-scale ictal and interictal epileptic networks revealed by single photon emission computed tomography (SPECT) and electroencephalography (EEG)-functional magnetic resonance imaging (fMRI).

PubMed

Tousseyn, Simon; Dupont, Patrick; Goffin, Karolien; Sunaert, Stefan; Van Paesschen, Wim

2015-03-01

Epilepsy is increasingly recognized as a network disorder, but the spatial relationship between ictal and interictal networks is still largely unexplored. In this work, we compared hemodynamic changes related to seizures and interictal spikes on a whole brain scale. Twenty-eight patients with refractory focal epilepsy (14 temporal and 14 extratemporal lobe) underwent both subtraction ictal single photon emission computed tomography (SPECT) coregistered to magnetic resonance imaging (MRI) (SISCOM) and spike-related electroencephalography (EEG-functional MRI (fMRI). SISCOM visualized relative perfusion changes during seizures, whereas EEG-fMRI mapped blood oxygen level-dependent (BOLD) changes related to spikes. Similarity between statistical maps of both modalities was analyzed per patient using the following two measures: (1) correlation between unthresholded statistical maps (Pearson's correlation coefficient) and (2) overlap between thresholded images (Dice coefficient). Overlap was evaluated at a regional level, for hyperperfusions and activations and for hypoperfusions and deactivations separately, using different thresholds. Nonparametric permutation tests were applied to assess statistical significance (p ≤ 0.05). We found significant and positive correlations between hemodynamic changes related to seizures and spikes in 27 (96%) of 28 cases (median correlation coefficient 0.29 [range -0.12 to 0.62]). In 20 (71%) of 28 cases, spatial overlap between hyperperfusion on SISCOM and activation on EEG-fMRI was significantly larger than expected by chance. Congruent changes were not restricted to the territory of the presumed epileptogenic zone, but could be seen at distant sites (e.g., cerebellum and basal ganglia). Overlap between ictal hypoperfusion and interictal deactivation was statistically significant in 22 (79%) of 28 patients. Despite the high rate of congruence, discrepancies were observed for both modalities. We conclude that hemodynamic changes related to seizures and spikes varied spatially with the same sign and within a common network. Overlap was present in regions nearby and distant from discharge origin. Wiley Periodicals, Inc. © 2015 International League Against Epilepsy.

Surveillance system and method having an adaptive sequential probability fault detection test

NASA Technical Reports Server (NTRS)

Herzog, James P. (Inventor); Bickford, Randall L. (Inventor)

2005-01-01

System and method providing surveillance of an asset such as a process and/or apparatus by providing training and surveillance procedures that numerically fit a probability density function to an observed residual error signal distribution that is correlative to normal asset operation and then utilizes the fitted probability density function in a dynamic statistical hypothesis test for providing improved asset surveillance.

Surveillance system and method having an adaptive sequential probability fault detection test

NASA Technical Reports Server (NTRS)

Bickford, Randall L. (Inventor); Herzog, James P. (Inventor)

2006-01-01

System and method providing surveillance of an asset such as a process and/or apparatus by providing training and surveillance procedures that numerically fit a probability density function to an observed residual error signal distribution that is correlative to normal asset operation and then utilizes the fitted probability density function in a dynamic statistical hypothesis test for providing improved asset surveillance.

Surveillance System and Method having an Adaptive Sequential Probability Fault Detection Test

NASA Technical Reports Server (NTRS)

Bickford, Randall L. (Inventor); Herzog, James P. (Inventor)

2008-01-01

System and method providing surveillance of an asset such as a process and/or apparatus by providing training and surveillance procedures that numerically fit a probability density function to an observed residual error signal distribution that is correlative to normal asset operation and then utilizes the fitted probability density function in a dynamic statistical hypothesis test for providing improved asset surveillance.

Ionospheric scintillation studies

NASA Technical Reports Server (NTRS)

Rino, C. L.; Freemouw, E. J.

1973-01-01

The diffracted field of a monochromatic plane wave was characterized by two complex correlation functions. For a Gaussian complex field, these quantities suffice to completely define the statistics of the field. Thus, one can in principle calculate the statistics of any measurable quantity in terms of the model parameters. The best data fits were achieved for intensity statistics derived under the Gaussian statistics hypothesis. The signal structure that achieved the best fit was nearly invariant with scintillation level and irregularity source (ionosphere or solar wind). It was characterized by the fact that more than 80% of the scattered signal power is in phase quadrature with the undeviated or coherent signal component. Thus, the Gaussian-statistics hypothesis is both convenient and accurate for channel modeling work.

R package to estimate intracluster correlation coefficient with confidence interval for binary data.

PubMed

Chakraborty, Hrishikesh; Hossain, Akhtar

2018-03-01

The Intracluster Correlation Coefficient (ICC) is a major parameter of interest in cluster randomized trials that measures the degree to which responses within the same cluster are correlated. There are several types of ICC estimators and its confidence intervals (CI) suggested in the literature for binary data. Studies have compared relative weaknesses and advantages of ICC estimators as well as its CI for binary data and suggested situations where one is advantageous in practical research. The commonly used statistical computing systems currently facilitate estimation of only a very few variants of ICC and its CI. To address the limitations of current statistical packages, we developed an R package, ICCbin, to facilitate estimating ICC and its CI for binary responses using different methods. The ICCbin package is designed to provide estimates of ICC in 16 different ways including analysis of variance methods, moments based estimation, direct probabilistic methods, correlation based estimation, and resampling method. CI of ICC is estimated using 5 different methods. It also generates cluster binary data using exchangeable correlation structure. ICCbin package provides two functions for users. The function rcbin() generates cluster binary data and the function iccbin() estimates ICC and it's CI. The users can choose appropriate ICC and its CI estimate from the wide selection of estimates from the outputs. The R package ICCbin presents very flexible and easy to use ways to generate cluster binary data and to estimate ICC and it's CI for binary response using different methods. The package ICCbin is freely available for use with R from the CRAN repository (https://cran.r-project.org/package=ICCbin). We believe that this package can be a very useful tool for researchers to design cluster randomized trials with binary outcome. Copyright © 2017 Elsevier B.V. All rights reserved.

Sporadic Inclusion Body Myositis: MRI Findings and Correlation With Clinical and Functional Parameters.

PubMed

Guimaraes, Julio Brandao; Zanoteli, Edmar; Link, Thomas M; de Camargo, Leonardo V; Facchetti, Luca; Nardo, Lorenzo; Fernandes, Artur da Rocha Correa

2017-12-01

The purpose of this prospective study is to assess MRI findings in patients with sporadic inclusion body myositis (IBM) and correlate them with clinical and functional parameters. This study included 12 patients with biopsy-proven sporadic IBM. All patients underwent MRI of the bilateral upper and lower extremities. The images were scored for muscle atrophy, fatty infiltration, and edema pattern. Clinical data included onset and duration of disease. Muscle strength was measured using the Medical Research Council (MRC) scale, and functional status was assessed using the Modified Rankin Scale. Correlation between MRI and different clinical and functional parameters was calculated using the Spearman rank test and Pearson correlation. All patients showed MRI abnormalities, which were more severe within the lower limbs and the distal segments. The most prevalent MRI finding was fat infiltration. There was a statistically significant correlation between disease duration and number of muscles infiltrated by fat (r = 0.65; p = 0.04). The number of muscles with fat infiltration correlated with the sum of the scores of MRC (r = -0.60; p = 0.04) and with the Modified Rankin Scale (r = 0.48; p = 0.03). Our findings suggest that most patients with biopsy-proven sporadic IBM present with a typical pattern of muscle involvement at MRI, more extensively in the lower extremities. Moreover, MRI findings strongly correlated with clinical and functional parameters, because both the extent and severity of muscle involvement assessed by MRI and clinical and functional parameters are associated with the early onset of the disease and its duration.

Dissociated functional connectivity profiles for motor and attention deficits in acute right-hemisphere stroke

PubMed Central

Ramsey, Lenny; Rengachary, Jennifer; Zinn, Kristi; Siegel, Joshua S.; Metcalf, Nicholas V.; Strube, Michael J.; Snyder, Abraham Z.; Corbetta, Maurizio; Shulman, Gordon L.

2016-01-01

Strokes often cause multiple behavioural deficits that are correlated at the population level. Here, we show that motor and attention deficits are selectively associated with abnormal patterns of resting state functional connectivity in the dorsal attention and motor networks. We measured attention and motor deficits in 44 right hemisphere-damaged patients with a first-time stroke at 1–2 weeks post-onset. The motor battery included tests that evaluated deficits in both upper and lower extremities. The attention battery assessed both spatial and non-spatial attention deficits. Summary measures for motor and attention deficits were identified through principal component analyses on the raw behavioural scores. Functional connectivity in structurally normal cortex was estimated based on the temporal correlation of blood oxygenation level-dependent signals measured at rest with functional magnetic resonance imaging. Any correlation between motor and attention deficits and between functional connectivity in the dorsal attention network and motor networks that might spuriously affect the relationship between each deficit and functional connectivity was statistically removed. We report a double dissociation between abnormal functional connectivity patterns and attention and motor deficits, respectively. Attention deficits were significantly more correlated with abnormal interhemispheric functional connectivity within the dorsal attention network than motor networks, while motor deficits were significantly more correlated with abnormal interhemispheric functional connectivity patterns within the motor networks than dorsal attention network. These findings indicate that functional connectivity patterns in structurally normal cortex following a stroke link abnormal physiology in brain networks to the corresponding behavioural deficits. PMID:27225794

Chaotic oscillations and noise transformations in a simple dissipative system with delayed feedback

NASA Astrophysics Data System (ADS)

Zverev, V. V.; Rubinstein, B. Ya.

1991-04-01

We analyze the statistical behavior of signals in nonlinear circuits with delayed feedback in the presence of external Markovian noise. For the special class of circuits with intense phase mixing we develop an approach for the computation of the probability distributions and multitime correlation functions based on the random phase approximation. Both Gaussian and Kubo-Andersen models of external noise statistics are analyzed and the existence of the stationary (asymptotic) random process in the long-time limit is shown. We demonstrate that a nonlinear system with chaotic behavior becomes a noise amplifier with specific statistical transformation properties.

A primer of statistical methods for correlating parameters and properties of electrospun poly(L-lactide) scaffolds for tissue engineering--PART 1: design of experiments.

PubMed

Seyedmahmoud, Rasoul; Rainer, Alberto; Mozetic, Pamela; Maria Giannitelli, Sara; Trombetta, Marcella; Traversa, Enrico; Licoccia, Silvia; Rinaldi, Antonio

2015-01-01

Tissue engineering scaffolds produced by electrospinning are of enormous interest, but still lack a true understanding about the fundamental connection between the outstanding functional properties, the architecture, the mechanical properties, and the process parameters. Fragmentary results from several parametric studies only render some partial insights that are hard to compare and generally miss the role of parameters interactions. To bridge this gap, this article (Part-1 of 2) features a case study on poly-L-lactide scaffolds to demonstrate how statistical methods such as design of experiments can quantitatively identify the correlations existing between key scaffold properties and control parameters, in a systematic, consistent, and comprehensive manner disentangling main effects from interactions. The morphological properties (i.e., fiber distribution and porosity) and mechanical properties (Young's modulus) are "charted" as a function of molecular weight (MW) and other electrospinning process parameters (the Xs), considering the single effect as well as interactions between Xs. For the first time, the major role of the MW emerges clearly in controlling all scaffold properties. The correlation between mechanical and morphological properties is also addressed. © 2014 Wiley Periodicals, Inc.

Fabry disease in children: correlation between ocular manifestations, genotype and systemic clinical severity.

PubMed

Allen, L E; Cosgrave, E M; Kersey, J P; Ramaswami, U

2010-12-01

Fabry disease is an X linked lysosomal disorder associated with severe multiorgan failure and premature death. This study aims to determine the prevalence of ophthalmic manifestations in children with the condition and investigate the correlation with genotype and systemic disease severity. The records of 26 children from 18 pedigrees with Fabry disease undergoing regular ophthalmic and systemic examination were reviewed. All pedigrees underwent GLA gene sequencing to determine genotype. Correlations between ocular and systemic phenotype and genotype were investigated. Corneal verticillata occurred in 50% of the children in this study (95% CI, 29% to 79%). Children with ophthalmic manifestations were more likely to have loss-of-function GLA mutations (p=0.003). Retinal vascular tortuosity was seen in seven children (27%), all of whom had systemic symptoms suggestive of autonomic neuropathy, such as diarrhoea and syncope. These symptoms seemed less prevalent in children without retinal vascular changes, although this did not reach statistical significance (p=0.134). Ophthalmic manifestations of Fabry disease are common even in young children with loss-of-function GLA gene mutations. Although the limited sample size possibly prevented statistical significance, systemic symptoms of autonomic neuropathy often coexist with retinal vascular changes and may share the same pathogenesis.

Statistical Description of Associative Memory

NASA Astrophysics Data System (ADS)

Samengo, Inés

2003-03-01

The storage of memories, in the brain, induces some kind of modification in the structural and functional properties of a neural network. Here, a few neuropsychological and neurophysiological experiments are reviewed, suggesting that the plastic changes taking place during memory storage are governed, among other things, by the correlations in the activity of a set of neurons. The Hopfield model is briefly described, showing the way the methods of statistical physics can be useful to describe the storage and retrieval of memories.

Towards a statistical mechanical theory of active fluids.

PubMed

Marini Bettolo Marconi, Umberto; Maggi, Claudio

2015-12-07

We present a stochastic description of a model of N mutually interacting active particles in the presence of external fields and characterize its steady state behavior in the absence of currents. To reproduce the effects of the experimentally observed persistence of the trajectories of the active particles we consider a Gaussian force having a non-vanishing correlation time τ, whose finiteness is a measure of the activity of the system. With these ingredients we show that it is possible to develop a statistical mechanical approach similar to the one employed in the study of equilibrium liquids and to obtain the explicit form of the many-particle distribution function by means of the multidimensional unified colored noise approximation. Such a distribution plays a role analogous to the Gibbs distribution in equilibrium statistical mechanics and provides complete information about the microscopic state of the system. From here we develop a method to determine the one- and two-particle distribution functions in the spirit of the Born-Green-Yvon (BGY) equations of equilibrium statistical mechanics. The resulting equations which contain extra-correlations induced by the activity allow us to determine the stationary density profiles in the presence of external fields, the pair correlations and the pressure of active fluids. In the low density regime we obtained the effective pair potential ϕ(r) acting between two isolated particles separated by a distance, r, showing the existence of an effective attraction between them induced by activity. Based on these results, in the second half of the paper we propose a mean field theory as an approach simpler than the BGY hierarchy and use it to derive a van der Waals expression of the equation of state.

Nonlinear dynamic analysis of voices before and after surgical excision of vocal polyps

NASA Astrophysics Data System (ADS)

Zhang, Yu; McGilligan, Clancy; Zhou, Liang; Vig, Mark; Jiang, Jack J.

2004-05-01

Phase space reconstruction, correlation dimension, and second-order entropy, methods from nonlinear dynamics, are used to analyze sustained vowels generated by patients before and after surgical excision of vocal polyps. Two conventional acoustic perturbation parameters, jitter and shimmer, are also employed to analyze voices before and after surgery. Presurgical and postsurgical analyses of jitter, shimmer, correlation dimension, and second-order entropy are statistically compared. Correlation dimension and second-order entropy show a statistically significant decrease after surgery, indicating reduced complexity and higher predictability of postsurgical voice dynamics. There is not a significant postsurgical difference in shimmer, although jitter shows a significant postsurgical decrease. The results suggest that jitter and shimmer should be applied to analyze disordered voices with caution; however, nonlinear dynamic methods may be useful for analyzing abnormal vocal function and quantitatively evaluating the effects of surgical excision of vocal polyps.

Correlation between Post-LASIK Starburst Symptom and Ocular Wavefront Aberrations

NASA Astrophysics Data System (ADS)

Liu, Yong-Ji; Mu, Guo-Guang; Wang, Zhao-Qi; Wang-Yan

2006-06-01

Monochromatic aberrations in post laser in-situ keratomileusis (LASIK) eyes are measured. The data are categorized into reference group and starburst group according to the visual symptoms. Statistic analysis has been made to find the correlation between the ocular wavefront aberrations and the starburst symptom. The rms aberrations of the 3rd and 4th orders for the starburst group are significantly larger than those for the reference group. The starburst symptom shows a strong correlation with vertical coma, total coma, spherical aberrations. For 3-mm pupil size and 5.8-mm pupil size, the modulation transfer function (MTF) of the starburst group are lower than those of the reference group, but their visual acuities are close. MTF and PSF analyses are made for two groups, and the results are consistent with the statistical analysis, which means the difference between the two groups is mainly due to the third- and fourth-order Zernike aberrations.

Density Functionals of Chemical Bonding

PubMed Central

Putz, Mihai V.

2008-01-01

The behavior of electrons in general many-electronic systems throughout the density functionals of energy is reviewed. The basic physico-chemical concepts of density functional theory are employed to highlight the energy role in chemical structure while its extended influence in electronic localization function helps in chemical bonding understanding. In this context the energy functionals accompanied by electronic localization functions may provide a comprehensive description of the global-local levels electronic structures in general and of chemical bonds in special. Becke-Edgecombe and author’s Markovian electronic localization functions are discussed at atomic, molecular and solid state levels. Then, the analytical survey of the main workable kinetic, exchange, and correlation density functionals within local and gradient density approximations is undertaken. The hierarchy of various energy functionals is formulated by employing both the parabolic and statistical correlation degree of them with the electronegativity and chemical hardness indices by means of quantitative structure-property relationship (QSPR) analysis for basic atomic and molecular systems. PMID:19325846

Effects of Heterogeniety on Spatial Pattern Analysis of Wild Pistachio Trees in Zagros Woodlands, Iran

NASA Astrophysics Data System (ADS)

Erfanifard, Y.; Rezayan, F.

2014-10-01

Vegetation heterogeneity biases second-order summary statistics, e.g., Ripley's K-function, applied for spatial pattern analysis in ecology. Second-order investigation based on Ripley's K-function and related statistics (i.e., L- and pair correlation function g) is widely used in ecology to develop hypothesis on underlying processes by characterizing spatial patterns of vegetation. The aim of this study was to demonstrate effects of underlying heterogeneity of wild pistachio (Pistacia atlantica Desf.) trees on the second-order summary statistics of point pattern analysis in a part of Zagros woodlands, Iran. The spatial distribution of 431 wild pistachio trees was accurately mapped in a 40 ha stand in the Wild Pistachio & Almond Research Site, Fars province, Iran. Three commonly used second-order summary statistics (i.e., K-, L-, and g-functions) were applied to analyse their spatial pattern. The two-sample Kolmogorov-Smirnov goodness-of-fit test showed that the observed pattern significantly followed an inhomogeneous Poisson process null model in the study region. The results also showed that heterogeneous pattern of wild pistachio trees biased the homogeneous form of K-, L-, and g-functions, demonstrating a stronger aggregation of the trees at the scales of 0-50 m than actually existed and an aggregation at scales of 150-200 m, while regularly distributed. Consequently, we showed that heterogeneity of point patterns may bias the results of homogeneous second-order summary statistics and we also suggested applying inhomogeneous summary statistics with related null models for spatial pattern analysis of heterogeneous vegetations.

Conformal correlation functions in the Brownian loop soup

NASA Astrophysics Data System (ADS)

Camia, Federico; Gandolfi, Alberto; Kleban, Matthew

2016-01-01

We define and study a set of operators that compute statistical properties of the Brownian loop soup, a conformally invariant gas of random Brownian loops (Brownian paths constrained to begin and end at the same point) in two dimensions. We prove that the correlation functions of these operators have many of the properties of conformal primaries in a conformal field theory, and compute their conformal dimension. The dimensions are real and positive, but have the novel feature that they vary continuously as a periodic function of a real parameter. We comment on the relation of the Brownian loop soup to the free field, and use this relation to establish that the central charge of the loop soup is twice its intensity.

Statistics of time delay and scattering correlation functions in chaotic systems. II. Semiclassical approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Novaes, Marcel

2015-06-15

We consider S-matrix correlation functions for a chaotic cavity having M open channels, in the absence of time-reversal invariance. Relying on a semiclassical approximation, we compute the average over E of the quantities Tr[S{sup †}(E − ϵ) S(E + ϵ)]{sup n}, for general positive integer n. Our result is an infinite series in ϵ, whose coefficients are rational functions of M. From this, we extract moments of the time delay matrix Q = − iħS{sup †}dS/dE and check that the first 8 of them agree with the random matrix theory prediction from our previous paper [M. Novaes, J. Math. Phys.more » 56, 062110 (2015)].« less

Genome-scale cluster analysis of replicated microarrays using shrinkage correlation coefficient.

PubMed

Yao, Jianchao; Chang, Chunqi; Salmi, Mari L; Hung, Yeung Sam; Loraine, Ann; Roux, Stanley J

2008-06-18

Currently, clustering with some form of correlation coefficient as the gene similarity metric has become a popular method for profiling genomic data. The Pearson correlation coefficient and the standard deviation (SD)-weighted correlation coefficient are the two most widely-used correlations as the similarity metrics in clustering microarray data. However, these two correlations are not optimal for analyzing replicated microarray data generated by most laboratories. An effective correlation coefficient is needed to provide statistically sufficient analysis of replicated microarray data. In this study, we describe a novel correlation coefficient, shrinkage correlation coefficient (SCC), that fully exploits the similarity between the replicated microarray experimental samples. The methodology considers both the number of replicates and the variance within each experimental group in clustering expression data, and provides a robust statistical estimation of the error of replicated microarray data. The value of SCC is revealed by its comparison with two other correlation coefficients that are currently the most widely-used (Pearson correlation coefficient and SD-weighted correlation coefficient) using statistical measures on both synthetic expression data as well as real gene expression data from Saccharomyces cerevisiae. Two leading clustering methods, hierarchical and k-means clustering were applied for the comparison. The comparison indicated that using SCC achieves better clustering performance. Applying SCC-based hierarchical clustering to the replicated microarray data obtained from germinating spores of the fern Ceratopteris richardii, we discovered two clusters of genes with shared expression patterns during spore germination. Functional analysis suggested that some of the genetic mechanisms that control germination in such diverse plant lineages as mosses and angiosperms are also conserved among ferns. This study shows that SCC is an alternative to the Pearson correlation coefficient and the SD-weighted correlation coefficient, and is particularly useful for clustering replicated microarray data. This computational approach should be generally useful for proteomic data or other high-throughput analysis methodology.

Calculations with the quasirelativistic local-spin-density-functional theory for high-Z atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Y.; Whitehead, M.A.

1988-10-01

The generalized-exchange local-spin-density-functional theory (LSD-GX) with relativistic corrections of the mass velocity and Darwin terms has been used to calculate statistical total energies for the neutral atoms, the positive ions, and the negative ions for high-Z elements. The effect of the correlation and relaxation correction on the statistical total energy is discussed. Comparing the calculated results for the ionization potentials and electron affinities for the atoms (atomic number Z from 37 to 56 and 72 to 80) with experiment, shows that for the atoms rubidium to barium both the LSD-GX and the quasirelativistic LSD-GX, with self-interaction correction, Gopinathan, Whitehead, andmore » Bogdanovic's Fermi-hole parameters (Phys. Rev. A 14, 1 (1976)), and Vosko, Wilk, and Nusair's correlation correction (Can. J. Phys. 58, 1200 (1980)), are very good methods for calculating ionization potentials and electron affinities. For the atoms hafnium to mercury the relativistic effect has to be considered.« less

Upside/Downside statistical mechanics of nonequilibrium Brownian motion. I. Distributions, moments, and correlation functions of a free particle.

PubMed

Craven, Galen T; Nitzan, Abraham

2018-01-28

Statistical properties of Brownian motion that arise by analyzing, separately, trajectories over which the system energy increases (upside) or decreases (downside) with respect to a threshold energy level are derived. This selective analysis is applied to examine transport properties of a nonequilibrium Brownian process that is coupled to multiple thermal sources characterized by different temperatures. Distributions, moments, and correlation functions of a free particle that occur during upside and downside events are investigated for energy activation and energy relaxation processes and also for positive and negative energy fluctuations from the average energy. The presented results are sufficiently general and can be applied without modification to the standard Brownian motion. This article focuses on the mathematical basis of this selective analysis. In subsequent articles in this series, we apply this general formalism to processes in which heat transfer between thermal reservoirs is mediated by activated rate processes that take place in a system bridging them.

Upside/Downside statistical mechanics of nonequilibrium Brownian motion. I. Distributions, moments, and correlation functions of a free particle

NASA Astrophysics Data System (ADS)

Craven, Galen T.; Nitzan, Abraham

2018-01-01

Statistical properties of Brownian motion that arise by analyzing, separately, trajectories over which the system energy increases (upside) or decreases (downside) with respect to a threshold energy level are derived. This selective analysis is applied to examine transport properties of a nonequilibrium Brownian process that is coupled to multiple thermal sources characterized by different temperatures. Distributions, moments, and correlation functions of a free particle that occur during upside and downside events are investigated for energy activation and energy relaxation processes and also for positive and negative energy fluctuations from the average energy. The presented results are sufficiently general and can be applied without modification to the standard Brownian motion. This article focuses on the mathematical basis of this selective analysis. In subsequent articles in this series, we apply this general formalism to processes in which heat transfer between thermal reservoirs is mediated by activated rate processes that take place in a system bridging them.

A marked correlation function for constraining modified gravity models

NASA Astrophysics Data System (ADS)

White, Martin

2016-11-01

Future large scale structure surveys will provide increasingly tight constraints on our cosmological model. These surveys will report results on the distance scale and growth rate of perturbations through measurements of Baryon Acoustic Oscillations and Redshift-Space Distortions. It is interesting to ask: what further analyses should become routine, so as to test as-yet-unknown models of cosmic acceleration? Models which aim to explain the accelerated expansion rate of the Universe by modifications to General Relativity often invoke screening mechanisms which can imprint a non-standard density dependence on their predictions. This suggests density-dependent clustering as a `generic' constraint. This paper argues that a density-marked correlation function provides a density-dependent statistic which is easy to compute and report and requires minimal additional infrastructure beyond what is routinely available to such survey analyses. We give one realization of this idea and study it using low order perturbation theory. We encourage groups developing modified gravity theories to see whether such statistics provide discriminatory power for their models.

[Relationship between status of physical and mental function and quality of life among the elderly people admitted from long-term care insurance].

PubMed

Kim, Hyeong Seon; Bae, Nam Kyou; Kwon, In Sun; Cho, Young Chae

2010-07-01

This study was performed to determine the levels of quality of life (QOL) according to the grade of long-term care service for the elderly people who were admitted from long-term care insurance, and to reveal its association with the physical and mental functioning such as the Activity of Daily Living (ADL), the Instrumental Activity of Daily Living (IADL), the Center for Epidemiologic Studies Depression Scale (CES-D), and the Mini-Mental State Examination-Korean version (MMSE-K). The interviews were performed during the period from March 1 to May 31, 2009, for 958 elderly people in urban and rural areas. The questionnaire items included various indices such as the ADL, IADL, CES-D, and MMSE-K, as independent variables and the index of QOL, as the dependent ones. For statistical analysis, t-tests were used for the mean scores of QOL according to gender and the grade of long-term care services, and Spearman's correlation was used for each variable. The effects of physical and mental functioning for QOL were assessed by covariance structure analysis. The statistical significance was set at p<0.05. The mean scores of QOL among all the subjects was 55.4 ± 15.62 (Grade I: 49.7 ± 14.17, Grade II: 56.8 ± 14.62, Grade III: 59.4 ± 16.36), and it was lower according to the higher grade of long-term care insurance. In terms of the correlation matrix of the QOL and the physical and mental function factors, the QOL showed positive correlation with the ADL, IADL and MMSE-K, while it had negative correlation with depression. On the analysis of covariance, mental functioning (depression and the MMSE-K) had a greater influence on the level of QOL than the physical functioning (ADL and IADL). The level of the QOL in the elderly people who were admitted from long-term care insurance was lower according to higher the grade of long-term care insurance. Also, the mental functioning (depression and MMSE-K) was more influential on the level of the QOL than the physical functioning (ADL and IADL).

Statistical and linguistic features of DNA sequences

NASA Technical Reports Server (NTRS)

Havlin, S.; Buldyrev, S. V.; Goldberger, A. L.; Mantegna, R. N.; Peng, C. K.; Simons, M.; Stanley, H. E.

1995-01-01

We present evidence supporting the idea that the DNA sequence in genes containing noncoding regions is correlated, and that the correlation is remarkably long range--indeed, base pairs thousands of base pairs distant are correlated. We do not find such a long-range correlation in the coding regions of the gene. We resolve the problem of the "non-stationary" feature of the sequence of base pairs by applying a new algorithm called Detrended Fluctuation Analysis (DFA). We address the claim of Voss that there is no difference in the statistical properties of coding and noncoding regions of DNA by systematically applying the DFA algorithm, as well as standard FFT analysis, to all eukaryotic DNA sequences (33 301 coding and 29 453 noncoding) in the entire GenBank database. We describe a simple model to account for the presence of long-range power-law correlations which is based upon a generalization of the classic Levy walk. Finally, we describe briefly some recent work showing that the noncoding sequences have certain statistical features in common with natural languages. Specifically, we adapt to DNA the Zipf approach to analyzing linguistic texts, and the Shannon approach to quantifying the "redundancy" of a linguistic text in terms of a measurable entropy function. We suggest that noncoding regions in plants and invertebrates may display a smaller entropy and larger redundancy than coding regions, further supporting the possibility that noncoding regions of DNA may carry biological information.

On the insufficiency of arbitrarily precise covariance matrices: non-Gaussian weak-lensing likelihoods

NASA Astrophysics Data System (ADS)

Sellentin, Elena; Heavens, Alan F.

2018-01-01

We investigate whether a Gaussian likelihood, as routinely assumed in the analysis of cosmological data, is supported by simulated survey data. We define test statistics, based on a novel method that first destroys Gaussian correlations in a data set, and then measures the non-Gaussian correlations that remain. This procedure flags pairs of data points that depend on each other in a non-Gaussian fashion, and thereby identifies where the assumption of a Gaussian likelihood breaks down. Using this diagnosis, we find that non-Gaussian correlations in the CFHTLenS cosmic shear correlation functions are significant. With a simple exclusion of the most contaminated data points, the posterior for s8 is shifted without broadening, but we find no significant reduction in the tension with s8 derived from Planck cosmic microwave background data. However, we also show that the one-point distributions of the correlation statistics are noticeably skewed, such that sound weak-lensing data sets are intrinsically likely to lead to a systematically low lensing amplitude being inferred. The detected non-Gaussianities get larger with increasing angular scale such that for future wide-angle surveys such as Euclid or LSST, with their very small statistical errors, the large-scale modes are expected to be increasingly affected. The shifts in posteriors may then not be negligible and we recommend that these diagnostic tests be run as part of future analyses.

The Two-Dimensional Gabor Function Adapted to Natural Image Statistics: A Model of Simple-Cell Receptive Fields and Sparse Structure in Images.

PubMed

Loxley, P N

2017-10-01

The two-dimensional Gabor function is adapted to natural image statistics, leading to a tractable probabilistic generative model that can be used to model simple cell receptive field profiles, or generate basis functions for sparse coding applications. Learning is found to be most pronounced in three Gabor function parameters representing the size and spatial frequency of the two-dimensional Gabor function and characterized by a nonuniform probability distribution with heavy tails. All three parameters are found to be strongly correlated, resulting in a basis of multiscale Gabor functions with similar aspect ratios and size-dependent spatial frequencies. A key finding is that the distribution of receptive-field sizes is scale invariant over a wide range of values, so there is no characteristic receptive field size selected by natural image statistics. The Gabor function aspect ratio is found to be approximately conserved by the learning rules and is therefore not well determined by natural image statistics. This allows for three distinct solutions: a basis of Gabor functions with sharp orientation resolution at the expense of spatial-frequency resolution, a basis of Gabor functions with sharp spatial-frequency resolution at the expense of orientation resolution, or a basis with unit aspect ratio. Arbitrary mixtures of all three cases are also possible. Two parameters controlling the shape of the marginal distributions in a probabilistic generative model fully account for all three solutions. The best-performing probabilistic generative model for sparse coding applications is found to be a gaussian copula with Pareto marginal probability density functions.

A correlational analysis of the effects of changing environmental conditions on the NR atomic hydrogen maser

NASA Technical Reports Server (NTRS)

Dragonette, Richard A.; Suter, Joseph J.

1992-01-01

An extensive statistical analysis has been undertaken to determine if a correlation exists between changes in an NR atomic hydrogen maser's frequency offset and changes in environmental conditions. Correlation analyses have been performed comparing barometric pressure, humidity, and temperature with maser frequency offset as a function of time for periods ranging from 5.5 to 17 days. Semipartial correlation coefficients as large as -0.9 have been found between barometric pressure and maser frequency offset. Correlation between maser frequency offset and humidity was small compared to barometric pressure and unpredictable. Analysis of temperature data indicates that in the most current design, temperature does not significantly affect maser frequency offset.

A stochastic-dynamic model for global atmospheric mass field statistics

NASA Technical Reports Server (NTRS)

Ghil, M.; Balgovind, R.; Kalnay-Rivas, E.

1981-01-01

A model that yields the spatial correlation structure of atmospheric mass field forecast errors was developed. The model is governed by the potential vorticity equation forced by random noise. Expansion in spherical harmonics and correlation function was computed analytically using the expansion coefficients. The finite difference equivalent was solved using a fast Poisson solver and the correlation function was computed using stratified sampling of the individual realization of F(omega) and hence of phi(omega). A higher order equation for gamma was derived and solved directly in finite differences by two successive applications of the fast Poisson solver. The methods were compared for accuracy and efficiency and the third method was chosen as clearly superior. The results agree well with the latitude dependence of observed atmospheric correlation data. The value of the parameter c sub o which gives the best fit to the data is close to the value expected from dynamical considerations.

Comparison of diagnostic capability of macular ganglion cell complex and retinal nerve fiber layer among primary open angle glaucoma, ocular hypertension, and normal population using Fourier-domain optical coherence tomography and determining their functional correlation in Indian population

PubMed Central

Barua, Nabanita; Sitaraman, Chitra; Goel, Sonu; Chakraborti, Chandana; Mukherjee, Sonai; Parashar, Hemandra

2016-01-01

Context: Analysis of diagnostic ability of macular ganglionic cell complex and retinal nerve fiber layer (RNFL) in glaucoma. Aim: To correlate functional and structural parameters and comparing predictive value of each of the structural parameters using Fourier-domain (FD) optical coherence tomography (OCT) among primary open angle glaucoma (POAG) and ocular hypertension (OHT) versus normal population. Setting and Design: Single centric, cross-sectional study done in 234 eyes. Materials and Methods: Patients were enrolled in three groups: POAG, ocular hypertensive and normal (40 patients in each group). After comprehensive ophthalmological examination, patients underwent standard automated perimetry and FD-OCT scan in optic nerve head and ganglion cell mode. The relationship was assessed by correlating ganglion cell complex (GCC) parameters with mean deviation. Results were compared with RNFL parameters. Statistical Analysis: Data were analyzed with SPSS, analysis of variance, t-test, Pearson's coefficient, and receiver operating curve. Results: All parameters showed strong correlation with visual field (P < 0.001). Inferior GCC had highest area under curve (AUC) for detecting glaucoma (0.827) in POAG from normal population. However, the difference was not statistically significant (P > 0.5) when compared with other parameters. None of the parameters showed significant diagnostic capability to detect OHT from normal population. In diagnosing early glaucoma from OHT and normal population, only inferior GCC had statistically significant AUC value (0.715). Conclusion: In this study, GCC and RNFL parameters showed equal predictive capability in perimetric versus normal group. In early stage, inferior GCC was the best parameter. In OHT population, single day cross-sectional imaging was not valuable. PMID:27221682

White matter correlates of cognitive domains in normal aging with diffusion tensor imaging.

PubMed

Sasson, Efrat; Doniger, Glen M; Pasternak, Ofer; Tarrasch, Ricardo; Assaf, Yaniv

2013-01-01

The ability to perform complex as well as simple cognitive tasks engages a network of brain regions that is mediated by the white matter fiber bundles connecting them. Different cognitive tasks employ distinctive white matter fiber bundles. The temporal lobe and its projections subserve a variety of key functions known to deteriorate during aging. In a cohort of 52 healthy subjects (ages 25-82 years), we performed voxel-wise regression analysis correlating performance in higher-order cognitive domains (executive function, information processing speed, and memory) with white matter integrity, as measured by diffusion tensor imaging (DTI) fiber tracking in the temporal lobe projections [uncinate fasciculus (UF), fornix, cingulum, inferior longitudinal fasciculus (ILF), and superior longitudinal fasciculus (SLF)]. The fiber tracts were spatially registered and statistical parametric maps were produced to spatially localize the significant correlations. Results showed that performance in the executive function domain is correlated with DTI parameters in the left SLF and right UF; performance in the information processing speed domain is correlated with fractional anisotropy (FA) in the left cingulum, left fornix, right and left ILF and SLF; and the memory domain shows significant correlations with DTI parameters in the right fornix, right cingulum, left ILF, left SLF and right UF. These findings suggest that DTI tractography enables anatomical definition of region of interest (ROI) for correlation of behavioral parameters with diffusion indices, and functionality can be correlated with white matter integrity.

Three-pion Hanbury Brown-Twiss correlations in relativistic heavy-ion collisions from the STAR experiment.

PubMed

Adams, J; Adler, C; Ahammed, Z; Allgower, C; Amonett, J; Anderson, B D; Anderson, M; Arkhipkin, D; Averichev, G S; Balewski, J; Barannikova, O; Barnby, L S; Baudot, J; Bekele, S; Belaga, V V; Bellwied, R; Berger, J; Bichsel, H; Billmeier, A; Bland, L C; Blyth, C O; Bonner, B E; Botje, M; Boucham, A; Brandin, A; Bravar, A; Cadman, R V; Cai, X Z; Caines, H; Calderón de la Barca Sánchez, M; Cardenas, A; Carroll, J; Castillo, J; Castro, M; Cebra, D; Chaloupka, P; Chattopadhyay, S; Chen, Y; Chernenko, S P; Cherney, M; Chikanian, A; Choi, B; Christie, W; Coffin, J P; Cormier, T M; Mora Corral, M; Cramer, J G; Crawford, H J; Derevschikov, A A; Didenko, L; Dietel, T; Draper, J E; Dunin, V B; Dunlop, J C; Eckardt, V; Efimov, L G; Emelianov, V; Engelage, J; Eppley, G; Erazmus, B; Fachini, P; Faine, V; Faivre, J; Fatemi, R; Filimonov, K; Finch, E; Fisyak, Y; Flierl, D; Foley, K J; Fu, J; Gagliardi, C A; Gagunashvili, N; Gans, J; Gaudichet, L; Germain, M; Geurts, F; Ghazikhanian, V; Grachov, O; Guedon, M; Guertin, S M; Gushin, E; Gutierrez, T D; Hallman, T J; Hardtke, D; Harris, J W; Heinz, M; Henry, T W; Heppelmann, S; Herston, T; Hippolyte, B; Hirsch, A; Hjort, E; Hoffmann, G W; Horsley, M; Huang, H Z; Humanic, T J; Igo, G; Ishihara, A; Jacobs, P; Jacobs, W W; Janik, M; Johnson, I; Jones, P G; Judd, E G; Kabana, S; Kaneta, M; Kaplan, M; Keane, D; Kiryluk, J; Kisiel, A; Klay, J; Klein, S R; Klyachko, A; Kollegger, T; Konstantinov, A S; Kopytine, M; Kotchenda, L; Kovalenko, A D; Kramer, M; Kravtsov, P; Krueger, K; Kuhn, C; Kulikov, A I; Kunde, G J; Kunz, C L; Kutuev, R Kh; Kuznetsov, A A; Lamont, M A C; Landgraf, J M; Lange, S; Lansdell, C P; Lasiuk, B; Laue, F; Lauret, J; Lebedev, A; Lednický, R; Leontiev, V M; LeVine, M J; Li, Q; Lindenbaum, S J; Lisa, M A; Liu, F; Liu, L; Liu, Z; Liu, Q J; Ljubicic, T; Llope, W J; Long, H; Longacre, R S; Lopez-Noriega, M; Love, W A; Ludlam, T; Lynn, D; Ma, J; Ma, Y G; Magestro, D; Majka, R; Margetis, S; Markert, C; Martin, L; Marx, J; Matis, H S; Matulenko, Yu A; McShane, T S; Meissner, F; Melnick, Yu; Meschanin, A; Messer, M; Miller, M L; Milosevich, Z; Minaev, N G; Mitchell, J; Molnar, L; Moore, C F; Morozov, V; de Moura, M M; Munhoz, M G; Nelson, J M; Nevski, P; Nikitin, V A; Nogach, L V; Norman, B; Nurushev, S B; Odyniec, G; Ogawa, A; Okorokov, V; Oldenburg, M; Olson, D; Paic, G; Pandey, S U; Panebratsev, Y; Panitkin, S Y; Pavlinov, A I; Pawlak, T; Perevoztchikov, V; Peryt, W; Petrov, V A; Picha, R; Planinic, M; Pluta, J; Porile, N; Porter, J; Poskanzer, A M; Potrebenikova, E; Prindle, D; Pruneau, C; Putschke, J; Rai, G; Rakness, G; Ravel, O; Ray, R L; Razin, S V; Reichhold, D; Reid, J G; Renault, G; Retiere, F; Ridiger, A; Ritter, H G; Roberts, J B; Rogachevski, O V; Romero, J L; Rose, A; Roy, C; Rykov, V; Sakrejda, I; Salur, S; Sandweiss, J; Savin, I; Schambach, J; Scharenberg, R P; Schmitz, N; Schroeder, L S; Schweda, K; Seger, J; Seyboth, P; Shahaliev, E; Shestermanov, K E; Shimanskii, S S; Simon, F; Skoro, G; Smirnov, N; Snellings, R; Sorensen, P; Sowinski, J; Spinka, H M; Srivastava, B; Stephenson, E J; Stock, R; Stolpovsky, A; Strikhanov, M; Stringfellow, B; Struck, C; Suaide, A A P; Sugarbaker, E; Suire, C; Sumbera, M; Surrow, B; Symons, T J M; Szanto de Toledo, A; Szarwas, P; Tai, A; Takahashi, J; Tang, A H; Thein, D; Thomas, J H; Thompson, M; Timoshenko, S; Tokarev, M; Tonjes, M B; Trainor, T A; Trentalange, S; Tribble, R E; Trofimov, V; Tsai, O; Ullrich, T; Underwood, D G; Van Buren, G; Vander Molen, A M; Vasiliev, A N; Vigdor, S E; Voloshin, S A; Vznuzdaev, M; Wang, F; Wang, Y; Ward, H; Watson, J W; Wells, R; Westfall, G D; Whitten, C; Wieman, H; Willson, R; Wissink, S W; Witt, R; Wood, J; Xu, N; Xu, Z; Yakutin, A E; Yamamoto, E; Yang, J; Yepes, P; Yurevich, V I; Zanevski, Y V; Zborovský, I; Zhang, H; Zhang, W M; Zoulkarneev, R; Zoulkarneeva, J; Zubarev, A N

2003-12-31

Data from the first physics run at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory, Au+Au collisions at sqrt[s(NN)]=130 GeV, have been analyzed by the STAR Collaboration using three-pion correlations with charged pions to study whether pions are emitted independently at freeze-out. We have made a high-statistics measurement of the three-pion correlation function and calculated the normalized three-particle correlator to obtain a quantitative measurement of the degree of chaoticity of the pion source. It is found that the degree of chaoticity seems to increase with increasing particle multiplicity.

Antenna systems for base station diversity in urban small and micro cells

NASA Astrophysics Data System (ADS)

Eggers, Patrick C. F.; Toftgard, Jorn; Oprea, Alex M.

1993-09-01

This paper describes cross-correlation properties for compact urban base station antenna configurations, nearly all resulting in very low envelope cross-correlation coefficients of about 0.1 to 0.3. A focus is set on polarization diversity systems for their potential in improving link quality when hand-held terminals are involved. An expression is given for the correlation function of compound space and polarization diversity systems. Dispersion and envelope dynamic statistics are presented for the measured environments. For microcell applications, it is found that systems such as GSM having a bandwidth of 200 MHz or less can use narrowband cross-correlation analysis directly.

On the Relation Between Soft Electron Precipitations in the Cusp Region and Solar Wind Coupling Functions

NASA Astrophysics Data System (ADS)

Dang, Tong; Zhang, Binzheng; Wiltberge, Michael; Wang, Wenbin; Varney, Roger; Dou, Xiankang; Wan, Weixing; Lei, Jiuhou

2018-01-01

In this study, the correlations between the fluxes of precipitating soft electrons in the cusp region and solar wind coupling functions are investigated utilizing the Lyon-Fedder-Mobarry global magnetosphere model simulations. We conduct two simulation runs during periods from 20 March 2008 to 16 April 2008 and from 15 to 24 December 2014, which are referred as "Equinox Case" and "Solstice Case," respectively. The simulation results of Equinox Case show that the plasma number density in the high-latitude cusp region scales well with the solar wind number density (ncusp/nsw=0.78), which agrees well with the statistical results from the Polar spacecraft measurements. For the Solstice Case, the plasma number density of high-latitude cusp in both hemispheres increases approximately linearly with upstream solar wind number density with prominent hemispheric asymmetry. Due to the dipole tilt effect, the average number density ratio ncusp/nsw in the Southern (summer) Hemisphere is nearly 3 times that in the Northern (winter) Hemisphere. In addition to the solar wind number density, 20 solar wind coupling functions are tested for the linear correlation with the fluxes of precipitating cusp soft electrons. The statistical results indicate that the solar wind dynamic pressure p exhibits the highest linear correlation with the cusp electron fluxes for both equinox and solstice conditions, with correlation coefficients greater than 0.75. The linear regression relations for equinox and solstice cases may provide an empirical calculation for the fluxes of cusp soft electron precipitation based on the upstream solar wind driving conditions.

Efficient 3D porous microstructure reconstruction via Gaussian random field and hybrid optimization.

PubMed

Jiang, Z; Chen, W; Burkhart, C

2013-11-01

Obtaining an accurate three-dimensional (3D) structure of a porous microstructure is important for assessing the material properties based on finite element analysis. Whereas directly obtaining 3D images of the microstructure is impractical under many circumstances, two sets of methods have been developed in literature to generate (reconstruct) 3D microstructure from its 2D images: one characterizes the microstructure based on certain statistical descriptors, typically two-point correlation function and cluster correlation function, and then performs an optimization process to build a 3D structure that matches those statistical descriptors; the other method models the microstructure using stochastic models like a Gaussian random field and generates a 3D structure directly from the function. The former obtains a relatively accurate 3D microstructure, but computationally the optimization process can be very intensive, especially for problems with large image size; the latter generates a 3D microstructure quickly but sacrifices the accuracy due to issues in numerical implementations. A hybrid optimization approach of modelling the 3D porous microstructure of random isotropic two-phase materials is proposed in this paper, which combines the two sets of methods and hence maintains the accuracy of the correlation-based method with improved efficiency. The proposed technique is verified for 3D reconstructions based on silica polymer composite images with different volume fractions. A comparison of the reconstructed microstructures and the optimization histories for both the original correlation-based method and our hybrid approach demonstrates the improved efficiency of the approach. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

Anismus as a cause of functional constipation--experience from Serbia.

PubMed

Jovanović, Igor; Jovanović, Dragana; Uglješić, Milenko; Milinić, Nikola; Cvetković, Mirjana; Branković, Marija; Nikolić, Goran

2015-01-01

BACKROUND/AIM: Anismus is paradoxal pressure increase or pressure decrease less than 20% of external anal sphincter during defecation straining. This study analyzed the presence of anismus as within a group of patients with the positive Rome III criteria for functional constipation. We used anorectal manometry as the determination method for anismus. We used anorectal water-perfused manometry in 60 patients with obstructive defecation defined by the Rome III criteria for functional constipation. We also analyzed anorectal function in 30 healthy subjects. The presence of anismus is more frequent in the group of patients with obstructive defecation compared to the control group (a highly statistically significant difference, p < 0.01). Furthermore, we found that the Rome III criteria for functional constipation showed 90% accuracy in predicting obstructive defecation. We analyzed the correlation of anismus with the presence of weak external anal sphincter, rectal sensibility disorders, enlarged piles, diverticular disease and anatomic variations of colon. We found no correlation between them in any of these cases. There is a significant correlation between anismus and positive Rome III criteria for functional constipation. Anorectal manometry should be performed in all patients with the positive Rome III criteria for functional constipation.

Statistical framework and noise sensitivity of the amplitude radial correlation contrast method.

PubMed

Kipervaser, Zeev Gideon; Pelled, Galit; Goelman, Gadi

2007-09-01

A statistical framework for the amplitude radial correlation contrast (RCC) method, which integrates a conventional pixel threshold approach with cluster-size statistics, is presented. The RCC method uses functional MRI (fMRI) data to group neighboring voxels in terms of their degree of temporal cross correlation and compares coherences in different brain states (e.g., stimulation OFF vs. ON). By defining the RCC correlation map as the difference between two RCC images, the map distribution of two OFF states is shown to be normal, enabling the definition of the pixel cutoff. The empirical cluster-size null distribution obtained after the application of the pixel cutoff is used to define a cluster-size cutoff that allows 5% false positives. Assuming that the fMRI signal equals the task-induced response plus noise, an analytical expression of amplitude-RCC dependency on noise is obtained and used to define the pixel threshold. In vivo and ex vivo data obtained during rat forepaw electric stimulation are used to fine-tune this threshold. Calculating the spatial coherences within in vivo and ex vivo images shows enhanced coherence in the in vivo data, but no dependency on the anesthesia method, magnetic field strength, or depth of anesthesia, strengthening the generality of the proposed cutoffs. Copyright (c) 2007 Wiley-Liss, Inc.

Impact of operator on determining functional parameters of nuclear medicine procedures.

PubMed

Mohammed, A M; Naddaf, S Y; Mahdi, F S; Al-Mutawa, Q I; Al-Dossary, H A; Elgazzar, A H

2006-01-01

The study was designed to assess the significance of the interoperator variability in the estimation of functional parameters for four nuclear medicine procedures. Three nuclear medicine technologists with varying years of experience processed the following randomly selected 20 cases with diverse functions of each study type: renography, renal cortical scans, myocardial perfusion gated single-photon emission computed tomography (MP-GSPECT) and gated blood pool ventriculography (GBPV). The technologists used the same standard processing routines and were blinded to the results of each other. The means of the values and the means of differences calculated case by case were statistically analyzed by one-way ANOVA. The values were further analyzed using Pearson correlation. The range of the mean values and standard deviation of relative renal function obtained by the three technologists were 50.65 +/- 3.9 to 50.92 +/- 4.4% for renography, 51.43 +/- 8.4 to 51.55 +/- 8.8% for renal cortical scans, 57.40 +/- 14.3 to 58.30 +/- 14.9% for left ventricular ejection fraction from MP-GSPECT and 54.80 +/- 12.8 to 55.10 +/- 13.1% for GBPV. The difference was not statistically significant, p > 0.9. The values showed a high correlation of more than 0.95. Calculated case by case, the mean of differences +/- SD was found to range from 0.42 +/- 0.36% in renal cortical scans to 1.35 +/- 0.87% in MP-GSPECT with a maximum difference of 4.00%. The difference was not statistically significant, p > 0.19. The estimated functional parameters were reproducible and operator independent as long as the standard processing instructions were followed. Copyright 2006 S. Karger AG, Basel.

Function of the parotid gland in juvenile recurrent parotitis: a case series.

PubMed

Xie, Li-song; Pu, Yi-ping; Zheng, Ling-yan; Yu, Chuang-qi; Wang, Zhi-jun; Shi, Huan

2016-04-01

Our aim was to find out how the parotid gland functions in 44 patients with juvenile recurrent parotitis, and to assess the value of measuring the serum amylase activity. Clinical and personal details were recorded, and all patients had their serum amylase activity measured together with sialography during the chronic phase. The function of the gland was classified by sialographic images. The chi square test and Spearman's rank correlation coefficient were used in the statistical analyses. There was a significant association between the degree of glandular function and serum amylase activity (p=0.014). The patients with unilateral and bilateral disease differed significantly in their degree of glandular function (p=0.020), those with bilateral disease having poorer function. There were no significant correlations between other clinical variables and glandular function. Serum amylase activity is an important diagnostic variable in juvenile recurrent parotitis, and poor parotid function reflects the severity of the disease. Copyright © 2016 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Noise correlation in PET, CT, SPECT and PET/CT data evaluated using autocorrelation function: a phantom study on data, reconstructed using FBP and OSEM.

PubMed

Razifar, Pasha; Sandström, Mattias; Schnieder, Harald; Långström, Bengt; Maripuu, Enn; Bengtsson, Ewert; Bergström, Mats

2005-08-25

Positron Emission Tomography (PET), Computed Tomography (CT), PET/CT and Single Photon Emission Tomography (SPECT) are non-invasive imaging tools used for creating two dimensional (2D) cross section images of three dimensional (3D) objects. PET and SPECT have the potential of providing functional or biochemical information by measuring distribution and kinetics of radiolabelled molecules, whereas CT visualizes X-ray density in tissues in the body. PET/CT provides fused images representing both functional and anatomical information with better precision in localization than PET alone. Images generated by these types of techniques are generally noisy, thereby impairing the imaging potential and affecting the precision in quantitative values derived from the images. It is crucial to explore and understand the properties of noise in these imaging techniques. Here we used autocorrelation function (ACF) specifically to describe noise correlation and its non-isotropic behaviour in experimentally generated images of PET, CT, PET/CT and SPECT. Experiments were performed using phantoms with different shapes. In PET and PET/CT studies, data were acquired in 2D acquisition mode and reconstructed by both analytical filter back projection (FBP) and iterative, ordered subsets expectation maximisation (OSEM) methods. In the PET/CT studies, different magnitudes of X-ray dose in the transmission were employed by using different mA settings for the X-ray tube. In the CT studies, data were acquired using different slice thickness with and without applied dose reduction function and the images were reconstructed by FBP. SPECT studies were performed in 2D, reconstructed using FBP and OSEM, using post 3D filtering. ACF images were generated from the primary images, and profiles across the ACF images were used to describe the noise correlation in different directions. The variance of noise across the images was visualised as images and with profiles across these images. The most important finding was that the pattern of noise correlation is rotation symmetric or isotropic, independent of object shape in PET and PET/CT images reconstructed using the iterative method. This is, however, not the case in FBP images when the shape of phantom is not circular. Also CT images reconstructed using FBP show the same non-isotropic pattern independent of slice thickness and utilization of care dose function. SPECT images show an isotropic correlation of the noise independent of object shape or applied reconstruction algorithm. Noise in PET/CT images was identical independent of the applied X-ray dose in the transmission part (CT), indicating that the noise from transmission with the applied doses does not propagate into the PET images showing that the noise from the emission part is dominant. The results indicate that in human studies it is possible to utilize a low dose in transmission part while maintaining the noise behaviour and the quality of the images. The combined effect of noise correlation for asymmetric objects and a varying noise variance across the image field significantly complicates the interpretation of the images when statistical methods are used, such as with statistical estimates of precision in average values, use of statistical parametric mapping methods and principal component analysis. Hence it is recommended that iterative reconstruction methods are used for such applications. However, it is possible to calculate the noise analytically in images reconstructed by FBP, while it is not possible to do the same calculation in images reconstructed by iterative methods. Therefore for performing statistical methods of analysis which depend on knowing the noise, FBP would be preferred.

The Junior College in International Perspective.

ERIC Educational Resources Information Center

Hall, Budd L.

The concept of the junior college is spreading rapidly throughout the world. Statistics show that educational development is positively correlated with economic development, yet educational systems often have not kept pace with technological, social, and economic developments since World War II. Junior colleges, with their flexibility of function,…

GOEAST: a web-based software toolkit for Gene Ontology enrichment analysis.

PubMed

Zheng, Qi; Wang, Xiu-Jie

2008-07-01

Gene Ontology (GO) analysis has become a commonly used approach for functional studies of large-scale genomic or transcriptomic data. Although there have been a lot of software with GO-related analysis functions, new tools are still needed to meet the requirements for data generated by newly developed technologies or for advanced analysis purpose. Here, we present a Gene Ontology Enrichment Analysis Software Toolkit (GOEAST), an easy-to-use web-based toolkit that identifies statistically overrepresented GO terms within given gene sets. Compared with available GO analysis tools, GOEAST has the following improved features: (i) GOEAST displays enriched GO terms in graphical format according to their relationships in the hierarchical tree of each GO category (biological process, molecular function and cellular component), therefore, provides better understanding of the correlations among enriched GO terms; (ii) GOEAST supports analysis for data from various sources (probe or probe set IDs of Affymetrix, Illumina, Agilent or customized microarrays, as well as different gene identifiers) and multiple species (about 60 prokaryote and eukaryote species); (iii) One unique feature of GOEAST is to allow cross comparison of the GO enrichment status of multiple experiments to identify functional correlations among them. GOEAST also provides rigorous statistical tests to enhance the reliability of analysis results. GOEAST is freely accessible at http://omicslab.genetics.ac.cn/GOEAST/

An attempt to determine the effect of increase of observation correlations on detectability and identifiability of a single gross error

NASA Astrophysics Data System (ADS)

Prószyński, Witold; Kwaśniak, Mieczysław

2016-12-01

The paper presents the results of investigating the effect of increase of observation correlations on detectability and identifiability of a single gross error, the outlier test sensitivity and also the response-based measures of internal reliability of networks. To reduce in a research a practically incomputable number of possible test options when considering all the non-diagonal elements of the correlation matrix as variables, its simplest representation was used being a matrix with all non-diagonal elements of equal values, termed uniform correlation. By raising the common correlation value incrementally, a sequence of matrix configurations could be obtained corresponding to the increasing level of observation correlations. For each of the measures characterizing the above mentioned features of network reliability the effect is presented in a diagram form as a function of the increasing level of observation correlations. The influence of observation correlations on sensitivity of the w-test for correlated observations (Förstner 1983, Teunissen 2006) is investigated in comparison with the original Baarda's w-test designated for uncorrelated observations, to determine the character of expected sensitivity degradation of the latter when used for correlated observations. The correlation effects obtained for different reliability measures exhibit mutual consistency in a satisfactory extent. As a by-product of the analyses, a simple formula valid for any arbitrary correlation matrix is proposed for transforming the Baarda's w-test statistics into the w-test statistics for correlated observations.

The relationship between dental aesthetic index (DAI) and perceptions of aesthetics, function and speech amongst secondary school children in Ibadan, Nigeria.

PubMed

Onyeaso, C O; Aderinokun, G A

2003-09-01

The purpose of the study was to investigate the relationship between a professionally derived index, the Dental Aesthetic Index, and some indications for orthodontic treatment as perceived by potential patients. An epidemiological survey of 614 secondary school students, 327 males (53.3%) and 287 females (46.7%) was carried out in Ibadan, Nigeria. Children aged 12-18 years (mean age, 14.9+/-2.9 SD) were randomly selected, none of them had received previous orthodontic treatment. One examiner assessed the students using the Dental Aesthetic Index (DAI). Subjects were also asked to complete a questionnaire consisting of three questions concerning appearance, function, and speech, using a 5-point Likert scale. Weak but statistically significant correlations were found for subjective assessments of appearance of teeth and the DAI (r=0.174; P<0.01) and between biting/chewing and appearance of teeth (r=0.095; P<0.05). Statistically significant correlations were found between appearance of teeth and speech (r=0.148; P<0.01) and biting/chewing and speech. The last showed the strongest correlation (r=0.268; P<0.01). The study has shown weak but significant correlation between DAI and children's perceptions of the appearance of their teeth. We recommend further study involving both DAI and Index of Orthodontic Treatment Need (IOTN) for comparison in the Nigerian population.

Parallel auto-correlative statistics with VTK.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pebay, Philippe Pierre; Bennett, Janine Camille

2013-08-01

This report summarizes existing statistical engines in VTK and presents both the serial and parallel auto-correlative statistics engines. It is a sequel to [PT08, BPRT09b, PT09, BPT09, PT10] which studied the parallel descriptive, correlative, multi-correlative, principal component analysis, contingency, k-means, and order statistics engines. The ease of use of the new parallel auto-correlative statistics engine is illustrated by the means of C++ code snippets and algorithm verification is provided. This report justifies the design of the statistics engines with parallel scalability in mind, and provides scalability and speed-up analysis results for the autocorrelative statistics engine.

Variety and volatility in financial markets

NASA Astrophysics Data System (ADS)

Lillo, Fabrizio; Mantegna, Rosario N.

2000-11-01

We study the price dynamics of stocks traded in a financial market by considering the statistical properties of both a single time series and an ensemble of stocks traded simultaneously. We use the n stocks traded on the New York Stock Exchange to form a statistical ensemble of daily stock returns. For each trading day of our database, we study the ensemble return distribution. We find that a typical ensemble return distribution exists in most of the trading days with the exception of crash and rally days and of the days following these extreme events. We analyze each ensemble return distribution by extracting its first two central moments. We observe that these moments fluctuate in time and are stochastic processes, themselves. We characterize the statistical properties of ensemble return distribution central moments by investigating their probability density functions and temporal correlation properties. In general, time-averaged and portfolio-averaged price returns have different statistical properties. We infer from these differences information about the relative strength of correlation between stocks and between different trading days. Last, we compare our empirical results with those predicted by the single-index model and we conclude that this simple model cannot explain the statistical properties of the second moment of the ensemble return distribution.

The ACS Survey of Galactic Globular Clusters. VIII. Effects of Environment on Globular Cluster Global Mass Functions

NASA Astrophysics Data System (ADS)

Paust, Nathaniel E. Q.; Reid, I. Neill; Piotto, Giampaolo; Aparicio, Antonio; Anderson, Jay; Sarajedini, Ata; Bedin, Luigi R.; Chaboyer, Brian; Dotter, Aaron; Hempel, Maren; Majewski, Steven; Marín-Franch, A.; Milone, Antonino; Rosenberg, Alfred; Siegel, Michael

2010-02-01

We have used observations obtained as part of the Hubble Space Telescope/ACS Survey of Galactic Globular Clusters to construct global present-day mass functions for 17 globular clusters utilizing multi-mass King models to extrapolate from our observations to the global cluster behavior. The global present-day mass functions for these clusters are well matched by power laws from the turnoff, ≈0.8 M sun, to 0.2-0.3 M sun on the lower main sequence. The slopes of those power-law fits, α, have been correlated with an extensive set of intrinsic and extrinsic cluster properties to investigate which parameters may influence the form of the present-day mass function. We do not confirm previous suggestions of correlations between α and either metallicity or Galactic location. However, we do find a strong statistical correlation with the related parameters central surface brightness, μ V , and inferred central density, ρ0. The correlation is such that clusters with denser cores (stronger binding energy) tend to have steeper mass functions (a higher proportion of low-mass stars), suggesting that dynamical evolution due to external interactions may have played a key role in determining α. Thus, the present-day mass function may owe more to nurture than to nature. Detailed modeling of external dynamical effects is therefore a requisite for determining the initial mass function for Galactic globular clusters.

Statistics of Dark Matter Halos from Gravitational Lensing.

PubMed

Jain; Van Waerbeke L

2000-02-10

We present a new approach to measure the mass function of dark matter halos and to discriminate models with differing values of Omega through weak gravitational lensing. We measure the distribution of peaks from simulated lensing surveys and show that the lensing signal due to dark matter halos can be detected for a wide range of peak heights. Even when the signal-to-noise ratio is well below the limit for detection of individual halos, projected halo statistics can be constrained for halo masses spanning galactic to cluster halos. The use of peak statistics relies on an analytical model of the noise due to the intrinsic ellipticities of source galaxies. The noise model has been shown to accurately describe simulated data for a variety of input ellipticity distributions. We show that the measured peak distribution has distinct signatures of gravitational lensing, and its non-Gaussian shape can be used to distinguish models with different values of Omega. The use of peak statistics is complementary to the measurement of field statistics, such as the ellipticity correlation function, and is possibly not susceptible to the same systematic errors.

Cell response to quasi-monochromatic light with different coherence

NASA Astrophysics Data System (ADS)

Budagovsky, A. V.; Solovykh, N. V.; Budagovskaya, O. N.; Budagovsky, I. A.

2015-04-01

The problem of the light coherence effect on the magnitude of the photoinduced cell response is discussed. The origins of ambiguous interpretation of the known experimental results are considered. Using the biological models, essentially differing in anatomy, morphology and biological functions (acrospires of radish, blackberry microsprouts cultivated in vitro, plum pollen), the effect of statistical properties of quasi-monochromatic light (λmax = 633 nm) on the magnitude of the photoinduced cell response is shown. It is found that for relatively low spatial coherence, the cell functional activity changes insignificantly. The maximal enhancement of growing processes (stimulating effect) is observed when the coherence length Lcoh and the correlation radius rcor are greater than the cell size, i.e., the entire cell fits into the field coherence volume. In this case, the representative indicators (germination of seeds and pollen, the spears length) exceeds those of non-irradiated objects by 1.7 - 3.9 times. For more correct assessment of the effect of light statistical properties on photocontrol processes, it is proposed to replace the qualitative description (coherent - incoherent) with the quantitative one, using the determination of spatial and temporal correlation functions and comparing them with the characteristic dimensions of the biological structures, e.g., the cell size.

Inter-rater reliability of the Sødring Motor Evaluation of Stroke patients (SMES).

PubMed

Halsaa, K E; Sødring, K M; Bjelland, E; Finsrud, K; Bautz-Holter, E

1999-12-01

The Sødring Motor Evaluation of Stroke patients is an instrument for physiotherapists to evaluate motor function and activities in stroke patients. The rating reflects quality as well as quantity of the patient's unassisted performance within three domains: leg, arm and gross function. The inter-rater reliability of the method was studied in a sample of 30 patients admitted to a stroke rehabilitation unit. Three therapists were involved in the study; two therapists assessed the same patient on two consecutive days in a balanced design. Cohen's weighted kappa and McNemar's test of symmetry were used as measures of item reliability, and the intraclass correlation coefficient was used to express the reliability of the sumscores. For 24 out of 32 items the weighted kappa statistic was excellent (0.75-0.98), while 7 items had a kappa statistic within the range 0.53-0.74 (fair to good). The reliability of one item was poor (0.13). The intraclass correlation coefficient for the three sumscores was 0.97, 0.91 and 0.97. We conclude that the Sødring Motor Evaluation of Stroke patients is a reliable measure of motor function in stroke patients undergoing rehabilitation.

Robust biological parametric mapping: an improved technique for multimodal brain image analysis

NASA Astrophysics Data System (ADS)

Yang, Xue; Beason-Held, Lori; Resnick, Susan M.; Landman, Bennett A.

2011-03-01

Mapping the quantitative relationship between structure and function in the human brain is an important and challenging problem. Numerous volumetric, surface, region of interest and voxelwise image processing techniques have been developed to statistically assess potential correlations between imaging and non-imaging metrics. Recently, biological parametric mapping has extended the widely popular statistical parametric approach to enable application of the general linear model to multiple image modalities (both for regressors and regressands) along with scalar valued observations. This approach offers great promise for direct, voxelwise assessment of structural and functional relationships with multiple imaging modalities. However, as presented, the biological parametric mapping approach is not robust to outliers and may lead to invalid inferences (e.g., artifactual low p-values) due to slight mis-registration or variation in anatomy between subjects. To enable widespread application of this approach, we introduce robust regression and robust inference in the neuroimaging context of application of the general linear model. Through simulation and empirical studies, we demonstrate that our robust approach reduces sensitivity to outliers without substantial degradation in power. The robust approach and associated software package provides a reliable way to quantitatively assess voxelwise correlations between structural and functional neuroimaging modalities.

Probing the statistical properties of CMB B-mode polarization through Minkowski functionals

NASA Astrophysics Data System (ADS)

Santos, Larissa; Wang, Kai; Zhao, Wen

2016-07-01

The detection of the magnetic type B-mode polarization is the main goal of future cosmic microwave background (CMB) experiments. In the standard model, the B-mode map is a strong non-gaussian field due to the CMB lensing component. Besides the two-point correlation function, the other statistics are also very important to dig the information of the polarization map. In this paper, we employ the Minkowski functionals to study the morphological properties of the lensed B-mode maps. We find that the deviations from Gaussianity are very significant for both full and partial-sky surveys. As an application of the analysis, we investigate the morphological imprints of the foreground residuals in the B-mode map. We find that even for very tiny foreground residuals, the effects on the map can be detected by the Minkowski functional analysis. Therefore, it provides a complementary way to investigate the foreground contaminations in the CMB studies.

Human movement stochastic variability leads to diagnostic biomarkers In Autism Spectrum Disorders (ASD)

NASA Astrophysics Data System (ADS)

Wu, Di; Torres, Elizabeth B.; Jose, Jorge V.

2015-03-01

ASD is a spectrum of neurodevelopmental disorders. The high heterogeneity of the symptoms associated with the disorder impedes efficient diagnoses based on human observations. Recent advances with high-resolution MEM wearable sensors enable accurate movement measurements that may escape the naked eye. It calls for objective metrics to extract physiological relevant information from the rapidly accumulating data. In this talk we'll discuss the statistical analysis of movement data continuously collected with high-resolution sensors at 240Hz. We calculated statistical properties of speed fluctuations within the millisecond time range that closely correlate with the subjects' cognitive abilities. We computed the periodicity and synchronicity of the speed fluctuations' from their power spectrum and ensemble averaged two-point cross-correlation function. We built a two-parameter phase space from the temporal statistical analyses of the nearest neighbor fluctuations that provided a quantitative biomarker for ASD and adult normal subjects and further classified ASD severity. We also found age related developmental statistical signatures and potential ASD parental links in our movement dynamical studies. Our results may have direct clinical applications.

Density-dependent clustering: I. Pulling back the curtains on motions of the BAO peak

NASA Astrophysics Data System (ADS)

Neyrinck, Mark C.; Szapudi, István; McCullagh, Nuala; Szalay, Alexander S.; Falck, Bridget; Wang, Jie

2018-05-01

The most common statistic used to analyze large-scale structure surveys is the correlation function, or power spectrum. Here, we show how `slicing' the correlation function on local density brings sensitivity to interesting non-Gaussian features in the large-scale structure, such as the expansion or contraction of baryon acoustic oscillations (BAO) according to the local density. The sliced correlation function measures the large-scale flows that smear out the BAO, instead of just correcting them as reconstruction algorithms do. Thus, we expect the sliced correlation function to be useful in constraining the growth factor, and modified gravity theories that involve the local density. Out of the studied cases, we find that the run of the BAO peak location with density is best revealed when slicing on a ˜40 h-1 Mpc filtered density. But slicing on a ˜100 h-1 Mpc filtered density may be most useful in distinguishing between underdense and overdense regions, whose BAO peaks are separated by a substantial ˜5 h-1 Mpc at z = 0. We also introduce `curtain plots' showing how local densities drive particle motions toward or away from each other over the course of an N-body simulation.

Correlation between the dizziness handicap inventory and balance performance during the acute phase of unilateral vestibulopathy.

PubMed

Son, Eun Jin; Lee, Dong-Hee; Oh, Jeong-Hoon; Seo, Jae-Hyun; Jeon, Eun-Ju

2015-01-01

The dizziness handicap inventory (DHI) is widely used to evaluate self-perceived handicap due to dizziness, and is known to correlate with vestibular function tests in chronic dizziness. However, whether DHI reflects subjective symptoms during the acute phase has not been studied. This study aims to investigate the correlations of subjective and objective measurements to highlight parameters that reflect the severity of dizziness during the first week of acute unilateral vestibulopathy. Thirty-seven patients with acute unilateral vestibulopathy were examined. Patients' subjective perceptions of dizziness were measured using the DHI, Vertigo Visual Analog Scale (VVAS), Disability Scale (DS), and Activity-Specific Balance Scale (ABC). Additionally, the oculomotor tests, Romberg and sharpened Romberg tests, functional reach test, and dynamic visual acuity tests were performed. The correlation between the DHI and other tests was evaluated. DHI-total scores exhibited a moderately positive correlation with VVAS and DS, and a moderately negative correlation with ABC. However, DHI-total score did not correlate with results of the Romberg, sharpened Romberg, or functional reach tests. When compared among four groups divided according to DHI scores, VVAS and DS scores exhibited statistically significant differences, but no significant differences were detected for other test results. Our findings revealed that the DHI correlated significantly with self-perceived symptoms measured by VVAS and DS, but not ABC. There was no significant correlation with other balance function tests during the first week of acute vestibulopathy. The results suggest that DHI, VVAS and DS may be more useful to measure the severity of acute dizziness symptoms. Copyright © 2015 Elsevier Inc. All rights reserved.

Statistical Systems with Z

NASA Astrophysics Data System (ADS)

William, Peter

In this dissertation several two dimensional statistical systems exhibiting discrete Z(n) symmetries are studied. For this purpose a newly developed algorithm to compute the partition function of these models exactly is utilized. The zeros of the partition function are examined in order to obtain information about the observable quantities at the critical point. This occurs in the form of critical exponents of the order parameters which characterize phenomena at the critical point. The correlation length exponent is found to agree very well with those computed from strong coupling expansions for the mass gap and with Monte Carlo results. In Feynman's path integral formalism the partition function of a statistical system can be related to the vacuum expectation value of the time ordered product of the observable quantities of the corresponding field theoretic model. Hence a generalization of ordinary scale invariance in the form of conformal invariance is focussed upon. This principle is very suitably applicable, in the case of two dimensional statistical models undergoing second order phase transitions at criticality. The conformal anomaly specifies the universality class to which these models belong. From an evaluation of the partition function, the free energy at criticality is computed, to determine the conformal anomaly of these models. The conformal anomaly for all the models considered here are in good agreement with the predicted values.

Assessment of global and regional left ventricular function using 64-slice multislice computed tomography and 2D echocardiography: a comparison with cardiac magnetic resonance.

PubMed

Annuar, Bin Rapaee; Liew, Chee Khoon; Chin, Sze Piaw; Ong, Tiong Kiam; Seyfarth, M Tobias; Chan, Wei Ling; Fong, Yean Yip; Ang, Choon Kiat; Lin, Naing; Liew, Houng Bang; Sim, Kui Hian

2008-01-01

To compare the assessment of global and regional left ventricular (LV) function using 64-slice multislice computed tomography (MSCT), 2D echocardiography (2DE) and cardiac magnetic resonance (CMR). Thirty-two consecutive patients (mean age, 56.5+/-9.7 years) referred for evaluation of coronary artery using 64-slice MSCT also underwent 2DE and CMR within 48h. The global left ventricular function which include left ventricular ejection fraction (LVEF), left ventricular end diastolic volume (LVdV) and left ventricular end systolic volume (LVsV) were determine using the three modalities. Regional wall motion (RWM) was assessed visually in all three modalities. The CMR served as the gold standard for the comparison between 64-slice MSCT with CMR and 2DE with CMR. Statistical analysis included Pearson correlation coefficient, Bland-Altman plots and kappa-statistics. The 64-slice MSCT agreed well with CMR for assessment of LVEF (r=0.92; p<0.0001), LVdV (r=0.98; p<0.0001) and LVsV (r=0.98; p<0.0001). In comparison with 64-slice MSCT, 2DE showed moderate correlation with CMR for the assessment of LVEF (r=0.84; p<0.0001), LVdV (r=0.83; p<0.0001) and LVsV (r=0.80; p<0.0001). However in RWM analysis, 2DE showed better accuracy than 64-slice MSCT (94.3% versus 82.4%) and closer agreement (kappa=0.89 versus 0.63) with CMR. 64-Slice MSCT correlates strongly with CMR in global LV function however in regional LV function 2DE showed better agreement with CMR than 64-slice MSCT.

Co-variation of tests commonly used in stroke rehabilitation.

PubMed

Langhammer, Birgitta; Stanghelle, Johan Kvalvik

2006-12-01

The aim of the present study was to analyse the co-variation of different tests commonly used in stroke rehabilitation, and specifically used in a recent randomized, controlled study of two different physiotherapy models in stroke rehabilitation. Correlations of the performed tests and recordings from previous work were studied. The test results from three-month, one-year and four-year follow-up were analysed in an SPSS Version 11 statistical package with Pearson and Spearman correlations. There was an expected high correlation between the motor function tests, both based on partial and total scores. The correlations between Nottingham Health Profile Part 1 and Motor Assessment Scale (MAS), Sødring Motor Evaluation Scale (SMES), the Berg Balance Scale (BBS) and Barthel Activities of Daily Living (ADL) index were low for all items except physical condition. The correlations between registered living conditions, assistive devices, recurrent stroke, motor function (MAS, SMES), ADL (Barthel ADL index) and balance (BBS) were high. The same variables showed weak or poor correlation to the Nottingham Health Profile (NHP). The co-variations of motor function tests and functional tests were high, but the co-variations of motor, functional and self-reported life-quality tests were poor. The patients rated themselves on a higher functional level in the self-reported tests than was observed objectively in the performance-based tests. A possible reason for this is that the patients may have been unaware they modified their performance to adjust for physical decline, and consequently overestimate their physical condition. This result underlines the importance of both performance-based and self-reported tests as complementary tools in a rehabilitation process.

Modular structure of functional networks in olfactory memory.

PubMed

Meunier, David; Fonlupt, Pierre; Saive, Anne-Lise; Plailly, Jane; Ravel, Nadine; Royet, Jean-Pierre

2014-07-15

Graph theory enables the study of systems by describing those systems as a set of nodes and edges. Graph theory has been widely applied to characterize the overall structure of data sets in the social, technological, and biological sciences, including neuroscience. Modular structure decomposition enables the definition of sub-networks whose components are gathered in the same module and work together closely, while working weakly with components from other modules. This processing is of interest for studying memory, a cognitive process that is widely distributed. We propose a new method to identify modular structure in task-related functional magnetic resonance imaging (fMRI) networks. The modular structure was obtained directly from correlation coefficients and thus retained information about both signs and weights. The method was applied to functional data acquired during a yes-no odor recognition memory task performed by young and elderly adults. Four response categories were explored: correct (Hit) and incorrect (False alarm, FA) recognition and correct and incorrect rejection. We extracted time series data for 36 areas as a function of response categories and age groups and calculated condition-based weighted correlation matrices. Overall, condition-based modular partitions were more homogeneous in young than elderly subjects. Using partition similarity-based statistics and a posteriori statistical analyses, we demonstrated that several areas, including the hippocampus, caudate nucleus, and anterior cingulate gyrus, belonged to the same module more frequently during Hit than during all other conditions. Modularity values were negatively correlated with memory scores in the Hit condition and positively correlated with bias scores (liberal/conservative attitude) in the Hit and FA conditions. We further demonstrated that the proportion of positive and negative links between areas of different modules (i.e., the proportion of correlated and anti-correlated areas) accounted for most of the observed differences in signed modularity. Taken together, our results provided some evidence that the neural networks involved in odor recognition memory are organized into modules and that these modular partitions are linked to behavioral performance and individual strategies. Copyright © 2014 Elsevier Inc. All rights reserved.

Discriminating topology in galaxy distributions using network analysis

NASA Astrophysics Data System (ADS)

Hong, Sungryong; Coutinho, Bruno C.; Dey, Arjun; Barabási, Albert-L.; Vogelsberger, Mark; Hernquist, Lars; Gebhardt, Karl

2016-07-01

The large-scale distribution of galaxies is generally analysed using the two-point correlation function. However, this statistic does not capture the topology of the distribution, and it is necessary to resort to higher order correlations to break degeneracies. We demonstrate that an alternate approach using network analysis can discriminate between topologically different distributions that have similar two-point correlations. We investigate two galaxy point distributions, one produced by a cosmological simulation and the other by a Lévy walk. For the cosmological simulation, we adopt the redshift z = 0.58 slice from Illustris and select galaxies with stellar masses greater than 108 M⊙. The two-point correlation function of these simulated galaxies follows a single power law, ξ(r) ˜ r-1.5. Then, we generate Lévy walks matching the correlation function and abundance with the simulated galaxies. We find that, while the two simulated galaxy point distributions have the same abundance and two-point correlation function, their spatial distributions are very different; most prominently, filamentary structures, absent in Lévy fractals. To quantify these missing topologies, we adopt network analysis tools and measure diameter, giant component, and transitivity from networks built by a conventional friends-of-friends recipe with various linking lengths. Unlike the abundance and two-point correlation function, these network quantities reveal a clear separation between the two simulated distributions; therefore, the galaxy distribution simulated by Illustris is not a Lévy fractal quantitatively. We find that the described network quantities offer an efficient tool for discriminating topologies and for comparing observed and theoretical distributions.

Statistical scaling of pore-scale Lagrangian velocities in natural porous media.

PubMed

Siena, M; Guadagnini, A; Riva, M; Bijeljic, B; Pereira Nunes, J P; Blunt, M J

2014-08-01

We investigate the scaling behavior of sample statistics of pore-scale Lagrangian velocities in two different rock samples, Bentheimer sandstone and Estaillades limestone. The samples are imaged using x-ray computer tomography with micron-scale resolution. The scaling analysis relies on the study of the way qth-order sample structure functions (statistical moments of order q of absolute increments) of Lagrangian velocities depend on separation distances, or lags, traveled along the mean flow direction. In the sandstone block, sample structure functions of all orders exhibit a power-law scaling within a clearly identifiable intermediate range of lags. Sample structure functions associated with the limestone block display two diverse power-law regimes, which we infer to be related to two overlapping spatially correlated structures. In both rocks and for all orders q, we observe linear relationships between logarithmic structure functions of successive orders at all lags (a phenomenon that is typically known as extended power scaling, or extended self-similarity). The scaling behavior of Lagrangian velocities is compared with the one exhibited by porosity and specific surface area, which constitute two key pore-scale geometric observables. The statistical scaling of the local velocity field reflects the behavior of these geometric observables, with the occurrence of power-law-scaling regimes within the same range of lags for sample structure functions of Lagrangian velocity, porosity, and specific surface area.

Equivalence between Step Selection Functions and Biased Correlated Random Walks for Statistical Inference on Animal Movement.

PubMed

Duchesne, Thierry; Fortin, Daniel; Rivest, Louis-Paul

2015-01-01

Animal movement has a fundamental impact on population and community structure and dynamics. Biased correlated random walks (BCRW) and step selection functions (SSF) are commonly used to study movements. Because no studies have contrasted the parameters and the statistical properties of their estimators for models constructed under these two Lagrangian approaches, it remains unclear whether or not they allow for similar inference. First, we used the Weak Law of Large Numbers to demonstrate that the log-likelihood function for estimating the parameters of BCRW models can be approximated by the log-likelihood of SSFs. Second, we illustrated the link between the two approaches by fitting BCRW with maximum likelihood and with SSF to simulated movement data in virtual environments and to the trajectory of bison (Bison bison L.) trails in natural landscapes. Using simulated and empirical data, we found that the parameters of a BCRW estimated directly from maximum likelihood and by fitting an SSF were remarkably similar. Movement analysis is increasingly used as a tool for understanding the influence of landscape properties on animal distribution. In the rapidly developing field of movement ecology, management and conservation biologists must decide which method they should implement to accurately assess the determinants of animal movement. We showed that BCRW and SSF can provide similar insights into the environmental features influencing animal movements. Both techniques have advantages. BCRW has already been extended to allow for multi-state modeling. Unlike BCRW, however, SSF can be estimated using most statistical packages, it can simultaneously evaluate habitat selection and movement biases, and can easily integrate a large number of movement taxes at multiple scales. SSF thus offers a simple, yet effective, statistical technique to identify movement taxis.

Statistical dynamo theory: Mode excitation.

PubMed

Hoyng, P

2009-04-01

We compute statistical properties of the lowest-order multipole coefficients of the magnetic field generated by a dynamo of arbitrary shape. To this end we expand the field in a complete biorthogonal set of base functions, viz. B= summation operator_{k}a;{k}(t)b;{k}(r) . The properties of these biorthogonal function sets are treated in detail. We consider a linear problem and the statistical properties of the fluid flow are supposed to be given. The turbulent convection may have an arbitrary distribution of spatial scales. The time evolution of the expansion coefficients a;{k} is governed by a stochastic differential equation from which we infer their averages a;{k} , autocorrelation functions a;{k}(t)a;{k *}(t+tau) , and an equation for the cross correlations a;{k}a;{l *} . The eigenfunctions of the dynamo equation (with eigenvalues lambda_{k} ) turn out to be a preferred set in terms of which our results assume their simplest form. The magnetic field of the dynamo is shown to consist of transiently excited eigenmodes whose frequency and coherence time is given by Ilambda_{k} and -1/Rlambda_{k} , respectively. The relative rms excitation level of the eigenmodes, and hence the distribution of magnetic energy over spatial scales, is determined by linear theory. An expression is derived for |a;{k}|;{2}/|a;{0}|;{2} in case the fundamental mode b;{0} has a dominant amplitude, and we outline how this expression may be evaluated. It is estimated that |a;{k}|;{2}/|a;{0}|;{2} approximately 1/N , where N is the number of convective cells in the dynamo. We show that the old problem of a short correlation time (or first-order smoothing approximation) has been partially eliminated. Finally we prove that for a simple statistically steady dynamo with finite resistivity all eigenvalues obey Rlambda_{k}<0 .

Anhedonia correlates with abnormal functional connectivity of the superior temporal gyrus and the caudate nucleus in patients with first-episode drug-naive major depressive disorder.

PubMed

Yang, Xin-Hua; Tian, Kai; Wang, Dong-Fang; Wang, Yi; Cheung, Eric F C; Xie, Guang-Rong; Chan, Raymond C K

2017-08-15

Recent empirical findings have suggested that imbalanced neural networks may underlie the pathophysiology of major depressive disorder (MDD). However, the contribution of the superior temporal gyrus (STG) and the caudate nucleus to its pathophysiology remains unclear. Functional magnetic resonance imaging (MRI) date were acquired from 40 patients with first-episode drug-naive MDD and 36 matched healthy controls during wakeful rest. We used whole-brain voxel-wise statistical maps to quantify within-group resting state functional connectivity (RSFC) and between-group differences of bilateral caudate and STG seeds. Compared with healthy controls, first-episode MDD patients were found to have reduced connectivity between the ventral caudate and several brain regions including the superior frontal gyrus (SFG), the superior parietal lobule (SPL) and the middle temporal gyrus (MTG), as well as increased connectivity with the cuneus. We also found increased connectivity between the left STG and the precuneus, the angular gyrus and the cuneus. Moreover, we found that increased anhedonia severity was correlated with the magnitude of ventral caudate functional connectivity with the cuneus and the MTG in MDD patients. Due to our small sample size, we did not correct the statistical threshold in the correlation analyses between clinical variables and connectivity abnormalities. The present study suggests that anhedonia is mainly associated with altered ventral caudate-cortical connectivity and highlights the importance of the ventral caudate in the neurobiology of MDD. Copyright © 2017 Elsevier B.V. All rights reserved.

Ex-vivo perfusion machines in kidney transplantation. The significance of the resistivity index.

PubMed

Elec, Florin Ioan; Lucan, Ciprian; Ghervan, Liviu; Munteanu, Valentin; Moga, Silviu; Suciu, Mihai; Enache, Dan; Elec, Alina; Munteanu, Adriana; Barbos, Adrian; Iacob, Gheorghita; Lucan, Mihai

2014-01-01

With a growing shortage of organs for transplantation, finding ways of increasing the donor organ pool remains of utmost importance. Perfusion machines (PM) have been proven to enhance the potential for kidney transplants to function sooner, last longer, giving patients the opportunity for a better life quality. The aim of this study is to evaluate the relation between the resistance index provided by the PM, the postoperative resistance index measured by Doppler ultrasound and the initial graft outcome. Between January 2012-December 2012, clinical data obtained from 82 consecutive renal transplants from brain death donors (BDD) which underwent PM maintenance were analyzed in a transversal study. Prior transplantation we recorded the solution temperature, filtration rate and the resistance index provided by PM. After the surgical intervention, each patient had standard follow-up. Doppler ultrasound resistivity index (RI) was recorded on the first postoperative day. Out of 115 renal transplants, 98 (85.21%) were performed with grafts from BDD. The PM was used for 82 renal grafts. The Doppler resistance index in relation to the resistance index shows a highly statistical correlation by linear regression (R=0.813, p<0.0001). Primary graft function was recorded in 74 patients (90.24%) and it was highly statistically significant correlated with the resistance index measured by PM. Out of 8 patients with primary non-function, 6 patients recovered with normal graft function at one year. The resistivity index recorded by the life-port machine is correlated with the vascular resistivity index measured by Doppler ultrasound and thus it may predicts the primary graft outcome.

Relationship between diffusion tensor fractional anisotropy and motor outcome in patients with hemiparesis after corona radiata infarct.

PubMed

Koyama, Tetsuo; Marumoto, Kohei; Miyake, Hiroji; Domen, Kazuhisa

2013-11-01

This study examined the relationship between fractional anisotropy (FA) values of magnetic resonance-diffusion tensor imaging (DTI) and motor outcome (1 month after onset) in 15 patients with hemiparesis after ischemic stroke of corona radiata lesions. DTI data were obtained on days 14-18. FA values within the cerebral peduncle were analyzed using a computer-automated method. Motor outcome of hemiparesis was evaluated according to Brunnstrom stage (BRS; 6-point scale: severe to normal) for separate shoulder/elbow/forearm, wrist/hand, and lower extremity functions. The ratio of FA values in the affected hemisphere to those in the unaffected hemisphere (rFA) was assessed in relation to the BRS data (Spearman rank correlation test, P<.05). rFA values ranged from .715 to 1.002 (median=.924). BRS ranged from 1 to 6 (median=4) for shoulder/elbow/forearm, from 1 to 6 (median=5) for wrist/hand, and from 2 to 6 (median=4) for the lower extremities. Analysis revealed statistically significant relationships between rFA and upper extremity functions (correlation coefficient=.679 for shoulder/elbow/forearm and .706 for wrist/hand). Although slightly less evident, the relationship between rFA and lower extremity function was also statistically significant (correlation coefficient=.641). FA values within the cerebral peduncle are moderately associated with the outcome of both upper and lower extremity functions, suggesting that DTI may be applicable for outcome prediction in stroke patients with corona radiata infarct. Copyright © 2013 National Stroke Association. Published by Elsevier Inc. All rights reserved.

Tests of Mediation: Paradoxical Decline in Statistical Power as a Function of Mediator Collinearity

ERIC Educational Resources Information Center

Beasley, T. Mark

2014-01-01

Increasing the correlation between the independent variable and the mediator ("a" coefficient) increases the effect size ("ab") for mediation analysis; however, increasing a by definition increases collinearity in mediation models. As a result, the standard error of product tests increase. The variance inflation caused by…

Quantification of the impact of a confounding variable on functional connectivity confirms anti-correlated networks in the resting-state.

PubMed

Carbonell, F; Bellec, P; Shmuel, A

2014-02-01

The effect of regressing out the global average signal (GAS) in resting state fMRI data has become a concern for interpreting functional connectivity analyses. It is not clear whether the reported anti-correlations between the Default Mode and the Dorsal Attention Networks are intrinsic to the brain, or are artificially created by regressing out the GAS. Here we introduce a concept, Impact of the Global Average on Functional Connectivity (IGAFC), for quantifying the sensitivity of seed-based correlation analyses to the regression of the GAS. This voxel-wise IGAFC index is defined as the product of two correlation coefficients: the correlation between the GAS and the fMRI time course of a voxel, times the correlation between the GAS and the seed time course. This definition enables the calculation of a threshold at which the impact of regressing-out the GAS would be large enough to introduce spurious negative correlations. It also yields a post-hoc impact correction procedure via thresholding, which eliminates spurious correlations introduced by regressing out the GAS. In addition, we introduce an Artificial Negative Correlation Index (ANCI), defined as the absolute difference between the IGAFC index and the impact threshold. The ANCI allows a graded confidence scale for ranking voxels according to their likelihood of showing artificial correlations. By applying this method, we observed regions in the Default Mode and Dorsal Attention Networks that were anti-correlated. These findings confirm that the previously reported negative correlations between the Dorsal Attention and Default Mode Networks are intrinsic to the brain and not the result of statistical manipulations. Our proposed quantification of the impact that a confound may have on functional connectivity can be generalized to global effect estimators other than the GAS. It can be readily applied to other confounds, such as systemic physiological or head movement interferences, in order to quantify their impact on functional connectivity in the resting state. © 2013.

Radiation-induced functional connectivity alterations in nasopharyngeal carcinoma patients with radiotherapy.

PubMed

Ma, Qiongmin; Wu, Donglin; Zeng, Ling-Li; Shen, Hui; Hu, Dewen; Qiu, Shijun

2016-07-01

The study aims to investigate the radiation-induced brain functional alterations in nasopharyngeal carcinoma (NPC) patients who received radiotherapy (RT) using functional magnetic resonance imaging (fMRI) and statistic scale.The fMRI data of 35 NPC patients with RT and 24 demographically matched untreated NPC patients were acquired. Montreal Cognitive Assessment (MoCA) was also measured to evaluate their global cognition performance. Multivariate pattern analysis was performed to find the significantly altered functional connections between these 2 groups, while the linear correlation level was detected between the altered functional connections and the MoCA scores.Forty-five notably altered functional connections were found, which were mainly located between 3 brain networks, the cerebellum, sensorimotor, and cingulo-opercular. With strictly false discovery rate correction, 5 altered functional connections were shown to have significant linear correlations with the MoCA scores, that is, the connections between the vermis and hippocampus, cerebellum lobule VI and dorsolateral prefrontal cortex, precuneus and dorsal frontal cortex, cuneus and middle occipital lobe, and insula and cuneus. Besides, the connectivity between the vermis and hippocampus was also significantly correlated with the attention score, 1 of the 7 subscores of the MoCA.The present study provides new insights into the radiation-induced functional connectivity impairments in NPC patients. The results showed that the RT may induce the cognitive impairments, especially the attention alterations. The 45 altered functional connections, especially the 5 altered functional connections that were significantly correlated to the MoCA scores, may serve as the potential biomarkers of the RT-induced brain functional impairments and provide valuable targets for further functional recovery treatment.

Anisotropic Bispectrum of Curvature Perturbations from Primordial Non-Abelian Vector Fields

NASA Astrophysics Data System (ADS)

Bartolo, Nicola; Dimastrogiovanni, Emanuela; Matarrese, Sabino; Riotto, Antonio

2009-10-01

We consider a primordial SU(2) vector multiplet during inflation in models where quantum fluctuations of vector fields are involved in producing the curvature perturbation. Recently, a lot of attention has been paid to models populated by vector fields, given the interesting possibility of generating some level of statistical anisotropy in the cosmological perturbations. The scenario we propose is strongly motivated by the fact that, for non-Abelian gauge fields, self-interactions are responsible for generating extra terms in the cosmological correlation functions, which are naturally absent in the Abelian case. We compute these extra contributions to the bispectrum of the curvature perturbation, using the δN formula and the Schwinger-Keldysh formalism. The primordial violation of rotational invariance (due to the introduction of the SU(2) gauge multiplet) leaves its imprint on the correlation functions introducing, as expected, some degree of statistical anisotropy in our results. We calculate the non-Gaussianity parameter fNL, proving that the new contributions derived from gauge bosons self-interactions can be important, and in some cases the dominat ones. We study the shape of the bispectrum and we find that it turns out to peak in the local configuration, with an amplitude that is modulated by the preferred directions that break statistical isotropy.

Statistical Study of Turbulence: Spectral Functions and Correlation Coefficients

NASA Technical Reports Server (NTRS)

Frenkiel, Francois N.

1958-01-01

In reading the publications on turbulence of different authors, one often runs the risk of confusing the various correlation coefficients and turbulence spectra. We have made a point of defining, by appropriate concepts, the differences which exist between these functions. Besides, we introduce in the symbols a few new characteristics of turbulence. In the first chapter, we study some relations between the correlation coefficients and the different turbulence spectra. Certain relations are given by means of demonstrations which could be called intuitive rather than mathematical. In this way we demonstrate that the correlation coefficients between the simultaneous turbulent velocities at two points are identical, whether studied in Lagrange's or in Euler's systems. We then consider new spectra of turbulence, obtained by study of the simultaneous velocities along a straight line of given direction. We determine some relations between these spectra and the correlation coefficients. Examining the relation between the spectrum of the turbulence measured at a fixed point and the longitudinal-correlation curve given by G. I. Taylor, we find that this equation is exact only when the coefficient is very small.

Non-parametric model selection for subject-specific topological organization of resting-state functional connectivity.

PubMed

Ferrarini, Luca; Veer, Ilya M; van Lew, Baldur; Oei, Nicole Y L; van Buchem, Mark A; Reiber, Johan H C; Rombouts, Serge A R B; Milles, J

2011-06-01

In recent years, graph theory has been successfully applied to study functional and anatomical connectivity networks in the human brain. Most of these networks have shown small-world topological characteristics: high efficiency in long distance communication between nodes, combined with highly interconnected local clusters of nodes. Moreover, functional studies performed at high resolutions have presented convincing evidence that resting-state functional connectivity networks exhibits (exponentially truncated) scale-free behavior. Such evidence, however, was mostly presented qualitatively, in terms of linear regressions of the degree distributions on log-log plots. Even when quantitative measures were given, these were usually limited to the r(2) correlation coefficient. However, the r(2) statistic is not an optimal estimator of explained variance, when dealing with (truncated) power-law models. Recent developments in statistics have introduced new non-parametric approaches, based on the Kolmogorov-Smirnov test, for the problem of model selection. In this work, we have built on this idea to statistically tackle the issue of model selection for the degree distribution of functional connectivity at rest. The analysis, performed at voxel level and in a subject-specific fashion, confirmed the superiority of a truncated power-law model, showing high consistency across subjects. Moreover, the most highly connected voxels were found to be consistently part of the default mode network. Our results provide statistically sound support to the evidence previously presented in literature for a truncated power-law model of resting-state functional connectivity. Copyright © 2010 Elsevier Inc. All rights reserved.

Is there differences in cognitive and motor functioning between hemodialysis and peritoneal dialysis patients?

PubMed

Radić, Josipa; Ljutić, Dragan; Radić, Mislav; Kovačić, Vedran; Sain, Milenka; Dodig-Ćurković, Katarina

2011-01-01

Change in cognitive function is one of the well-known consequences of the end-stage renal disease (ESRD). The aim of this study was to determine the effect of hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD) on cognitive and motor functions. In this cross-sectional study, cognitive and motor functions were investigated in a selected population of 42 patients with ESRD (22 patients on chronic HD and 20 patients on CAPD, aged 50.31 ± 11.07 years). Assessment of cognitive and motor functions was performed by Symbol Digit Modalities Test (SDMT) and Complex Reactiometer Drenovac (CRD-series), a battery of computer-generated psychological tests to measure simple visual discrimination of signal location, short-term memory, simple convergent visual orientation, and convergent thinking. The statistically significant difference in cognitive-motor functions between HD and CAPD patients was not found in any of the time-related parameters in all CRD-series tests or SDMT score. Higher serum levels of albumin, creatinine, and calcium were correlated with better cognitive-motor performance among all patients regardless of dialysis modality. The significant correlation between ultrafiltration rate per HD and short-term memory actualization test score (CRD-324 MT) among HD patients was found (r = 0.434, p = 0.025). This study has demonstrated that well-nourished and medically stable HD and CAPD patients without clinical signs of dementia or cognitive impairment and without significant difference in age and level of education performed all tests of cognitive-motor abilities without statistically significant difference.

Multiple commodities in statistical microeconomics: Model and market

NASA Astrophysics Data System (ADS)

Baaquie, Belal E.; Yu, Miao; Du, Xin

2016-11-01

A statistical generalization of microeconomics has been made in Baaquie (2013). In Baaquie et al. (2015), the market behavior of single commodities was analyzed and it was shown that market data provides strong support for the statistical microeconomic description of commodity prices. The case of multiple commodities is studied and a parsimonious generalization of the single commodity model is made for the multiple commodities case. Market data shows that the generalization can accurately model the simultaneous correlation functions of up to four commodities. To accurately model five or more commodities, further terms have to be included in the model. This study shows that the statistical microeconomics approach is a comprehensive and complete formulation of microeconomics, and which is independent to the mainstream formulation of microeconomics.

Reconstructing temperatures from lake sediments in northern Europe: what do the biological proxies really tell us?

NASA Astrophysics Data System (ADS)

Cunningham, Laura; Holmes, Naomi; Bigler, Christian; Dadal, Anna; Bergman, Jonas; Eriksson, Lars; Brooks, Stephen; Langdon, Pete; Caseldine, Chris

2010-05-01

Over the past two decades considerable effort has been devoted to quantitatively reconstructing temperatures from biological proxies preserved in lake sediments, via transfer functions. Such transfer functions typically consist of modern sediment samples, collected over a broad environmental gradient. Correlations between the biological communities and environmental parameters observed over these broad gradients are assumed to be equally valid temporally. The predictive ability of such spatially based transfer functions has traditionally been assessed by comparisons of measured and inferred temperatures within the calibration sets, with little validation against historical data. Although statistical techniques such as bootstrapping may improve error estimation, this approach remains partly a circular argument. This raises the question of how reliable such reconstructions are for inferring past changes in temperature? In order to address this question, we used transfer functions to reconstruct July temperatures from diatoms and chironomids from several locations across northern Europe. The transfer functions used showed good internal calibration statistics (r2 = 0.66 - 0.91). The diatom and chironomid inferred July air temperatures were compared to local observational records. As the sediment records were non-annual, all data were first smoothed using a 15 yr moving average filter. None of the five biologically-inferred temperature records were correlated with the local meteorological records. Furthermore, diatom inferred temperatures did not agree with chironomid inferred temperatures from the same cores from the same sites. In an attempt to understand this poor performance the biological proxy data was compressed using principal component analysis (PCA), and the PCA axes compared to the local meteorological data. These analyses clearly demonstrated that July temperatures were not correlated with the biological data at these locations. Some correlations were observed between the biological proxies and autumn and spring temperatures, although this varied slightly between sites and proxies. For example, chironomid data from Iceland was most strongly correlated with temperatures in February, March and April whilst in northern Sweden, the chironomid data was most strongly correlated with temperatures in March, April and May. It is suggested that the biological data at these sites may be responding to changes in the length of the ice-free period or hydrological regimes (including snow melt), rather than temperature per se. Our findings demonstrate the need to validate inferred temperatures against local meteorological data. Where such validation cannot be undertaken, inferred temperature reconstructions should be treated cautiously.

Characterization of the Pathological and Biochemical Markers that Correlate to the Clinical Features of Autism

DTIC Science & Technology

2012-08-01

system in relation to its evolution, structure and function . New York: CRC Press 1997 American Psychiatric Association. Diagnostic and statistical...Hesslow G, Yeo CH. The functional anatomy of skeletal conditioning. In: Moore JW, Editor. A neuroscientist’s guide to classical conditioning. New ...1995; Selkoe, 2001). Aβ is generated and detected in the endoplasmic reticulum/ Golgi apparatus and endosomal-lysosomal pathway (Cook D.G. et al., 1997

{Phi}{sup 4} kinks: Statistical mechanics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Habib, S.

1995-12-31

Some recent investigations of the thermal equilibrium properties of kinks in a 1+1-dimensional, classical {phi}{sup 4} field theory are reviewed. The distribution function, kink density, correlation function, and certain thermodynamic quantities were studied both theoretically and via large scale simulations. A simple double Gaussian variational approach within the transfer operator formalism was shown to give good results in the intermediate temperature range where the dilute gas theory is known to fail.

Beyond δ : Tailoring marked statistics to reveal modified gravity

NASA Astrophysics Data System (ADS)

Valogiannis, Georgios; Bean, Rachel

2018-01-01

Models that seek to explain cosmic acceleration through modifications to general relativity (GR) evade stringent Solar System constraints through a restoring, screening mechanism. Down-weighting the high-density, screened regions in favor of the low density, unscreened ones offers the potential to enhance the amount of information carried in such modified gravity models. In this work, we assess the performance of a new "marked" transformation and perform a systematic comparison with the clipping and logarithmic transformations, in the context of Λ CDM and the symmetron and f (R ) modified gravity models. Performance is measured in terms of the fractional boost in the Fisher information and the signal-to-noise ratio (SNR) for these models relative to the statistics derived from the standard density distribution. We find that all three statistics provide improved Fisher boosts over the basic density statistics. The model parameters for the marked and clipped transformation that best enhance signals and the Fisher boosts are determined. We also show that the mark is useful both as a Fourier and real-space transformation; a marked correlation function also enhances the SNR relative to the standard correlation function, and can on mildly nonlinear scales show a significant difference between the Λ CDM and the modified gravity models. Our results demonstrate how a series of simple analytical transformations could dramatically increase the predicted information extracted on deviations from GR, from large-scale surveys, and give the prospect for a much more feasible potential detection.

Advanced correlation grid: Analysis and visualisation of functional connectivity among multiple spike trains.

PubMed

Masud, Mohammad Shahed; Borisyuk, Roman; Stuart, Liz

2017-07-15

This study analyses multiple spike trains (MST) data, defines its functional connectivity and subsequently visualises an accurate diagram of connections. This is a challenging problem. For example, it is difficult to distinguish the common input and the direct functional connection of two spike trains. The new method presented in this paper is based on the traditional pairwise cross-correlation function (CCF) and a new combination of statistical techniques. First, the CCF is used to create the Advanced Correlation Grid (ACG) correlation where both the significant peak of the CCF and the corresponding time delay are used for detailed analysis of connectivity. Second, these two features of functional connectivity are used to classify connections. Finally, the visualization technique is used to represent the topology of functional connections. Examples are presented in the paper to demonstrate the new Advanced Correlation Grid method and to show how it enables discrimination between (i) influence from one spike train to another through an intermediate spike train and (ii) influence from one common spike train to another pair of analysed spike trains. The ACG method enables scientists to automatically distinguish between direct connections from spurious connections such as common source connection and indirect connection whereas existing methods require in-depth analysis to identify such connections. The ACG is a new and effective method for studying functional connectivity of multiple spike trains. This method can identify accurately all the direct connections and can distinguish common source and indirect connections automatically. Copyright © 2017 Elsevier B.V. All rights reserved.

Separating non-diffuse component from ambient seismic noise cross-correlation in southern California­­

NASA Astrophysics Data System (ADS)

Liu, X.; Beroza, G. C.; Nakata, N.

2017-12-01

Cross-correlation of fully diffuse wavefields provides Green's function between receivers, although the ambient noise field in the real world contains both diffuse and non-diffuse fields. The non-diffuse field potentially degrades the correlation functions. We attempt to blindly separate the diffuse and the non-diffuse components from cross-correlations of ambient seismic noise and analyze the potential bias caused by the non-diffuse components. We compute the 9-component noise cross-correlations for 17 stations in southern California. For the Rayleigh wave components, we assume that the cross-correlation of multiply scattered waves (diffuse component) is independent from the cross-correlation of ocean microseismic quasi-point source responses (non-diffuse component), and the cross-correlation function of ambient seismic data is the sum of both components. Thus we can blindly separate the non-diffuse component due to physical point sources and the more diffuse component due to cross-correlation of multiply scattered noise based on their statistical independence. We also perform beamforming over different frequency bands for the cross-correlations before and after the separation, and we find that the decomposed Rayleigh wave represents more coherent features among all Rayleigh wave polarization cross-correlation components. We show that after separating the non-diffuse component, the Frequency-Time Analysis results are less ambiguous. In addition, we estimate the bias in phase velocity on the raw cross-correlation data due to the non-diffuse component. We also apply this technique to a few borehole stations in Groningen, the Netherlands, to demonstrate its applicability in different instrument/geology settings.

Speckle suppression by doubly scattering systems.

PubMed

Li, Dayan; Kelly, Damien P; Sheridan, John T

2013-12-10

Speckle suppression in a two-diffuser system is examined. An analytical expression for the speckle space-time correlation function is derived, so that the speckle suppression mechanism can be investigated statistically. The grain size of the speckle field illuminating the second diffuser has a major impact on the speckle contrast after temporal averaging. It is shown that, when both the diffusers are rotating, the one with the lower rotating speed determines the period of the speckle correlation function. The coherent length of the averaged speckle intensity is shown to equal the mean speckle size of the individual speckle pattern before averaging. Numerical and experimental results are presented to verify our analysis in the context of speckle reduction.

Estimated Accuracy of Three Common Trajectory Statistical Methods

NASA Technical Reports Server (NTRS)

Kabashnikov, Vitaliy P.; Chaikovsky, Anatoli P.; Kucsera, Tom L.; Metelskaya, Natalia S.

2011-01-01

Three well-known trajectory statistical methods (TSMs), namely concentration field (CF), concentration weighted trajectory (CWT), and potential source contribution function (PSCF) methods were tested using known sources and artificially generated data sets to determine the ability of TSMs to reproduce spatial distribution of the sources. In the works by other authors, the accuracy of the trajectory statistical methods was estimated for particular species and at specified receptor locations. We have obtained a more general statistical estimation of the accuracy of source reconstruction and have found optimum conditions to reconstruct source distributions of atmospheric trace substances. Only virtual pollutants of the primary type were considered. In real world experiments, TSMs are intended for application to a priori unknown sources. Therefore, the accuracy of TSMs has to be tested with all possible spatial distributions of sources. An ensemble of geographical distributions of virtual sources was generated. Spearman s rank order correlation coefficient between spatial distributions of the known virtual and the reconstructed sources was taken to be a quantitative measure of the accuracy. Statistical estimates of the mean correlation coefficient and a range of the most probable values of correlation coefficients were obtained. All the TSMs that were considered here showed similar close results. The maximum of the ratio of the mean correlation to the width of the correlation interval containing the most probable correlation values determines the optimum conditions for reconstruction. An optimal geographical domain roughly coincides with the area supplying most of the substance to the receptor. The optimal domain s size is dependent on the substance decay time. Under optimum reconstruction conditions, the mean correlation coefficients can reach 0.70 0.75. The boundaries of the interval with the most probable correlation values are 0.6 0.9 for the decay time of 240 h and 0.5 0.95 for the decay time of 12 h. The best results of source reconstruction can be expected for the trace substances with a decay time on the order of several days. Although the methods considered in this paper do not guarantee high accuracy they are computationally simple and fast. Using the TSMs in optimum conditions and taking into account the range of uncertainties, one can obtain a first hint on potential source areas.

PLASS: Protein-ligand affinity statistical score a knowledge-based force-field model of interaction derived from the PDB

NASA Astrophysics Data System (ADS)

Ozrin, V. D.; Subbotin, M. V.; Nikitin, S. M.

2004-04-01

We have developed PLASS (Protein-Ligand Affinity Statistical Score), a pair-wise potential of mean-force for rapid estimation of the binding affinity of a ligand molecule to a protein active site. This scoring function is derived from the frequency of occurrence of atom-type pairs in crystallographic complexes taken from the Protein Data Bank (PDB). Statistical distributions are converted into distance-dependent contributions to the Gibbs free interaction energy for 10 atomic types using the Boltzmann hypothesis, with only one adjustable parameter. For a representative set of 72 protein-ligand structures, PLASS scores correlate well with the experimentally measured dissociation constants: a correlation coefficient R of 0.82 and RMS error of 2.0 kcal/mol. Such high accuracy results from our novel treatment of the volume correction term, which takes into account the inhomogeneous properties of the protein-ligand complexes. PLASS is able to rank reliably the affinity of complexes which have as much diversity as in the PDB.

Peculiarities of the statistics of spectrally selected fluorescence radiation in laser-pumped dye-doped random media

NASA Astrophysics Data System (ADS)

Yuvchenko, S. A.; Ushakova, E. V.; Pavlova, M. V.; Alonova, M. V.; Zimnyakov, D. A.

2018-04-01

We consider the practical realization of a new optical probe method of the random media which is defined as the reference-free path length interferometry with the intensity moments analysis. A peculiarity in the statistics of the spectrally selected fluorescence radiation in laser-pumped dye-doped random medium is discussed. Previously established correlations between the second- and the third-order moments of the intensity fluctuations in the random interference patterns, the coherence function of the probe radiation, and the path difference probability density for the interfering partial waves in the medium are confirmed. The correlations were verified using the statistical analysis of the spectrally selected fluorescence radiation emitted by a laser-pumped dye-doped random medium. Water solution of Rhodamine 6G was applied as the doping fluorescent agent for the ensembles of the densely packed silica grains, which were pumped by the 532 nm radiation of a solid state laser. The spectrum of the mean path length for a random medium was reconstructed.

Real- and redshift-space halo clustering in f(R) cosmologies

NASA Astrophysics Data System (ADS)

Arnalte-Mur, Pablo; Hellwing, Wojciech A.; Norberg, Peder

2017-05-01

We present two-point correlation function statistics of the mass and the haloes in the chameleon f(R) modified gravity scenario using a series of large-volume N-body simulations. Three distinct variations of f(R) are considered (F4, F5 and F6) and compared to a fiducial Λ cold dark matter (ΛCDM) model in the redshift range z ∈ [0, 1]. We find that the matter clustering is indistinguishable for all models except for F4, which shows a significantly steeper slope. The ratio of the redshift- to real-space correlation function at scales >20 h-1 Mpc agrees with the linear General Relativity (GR) Kaiser formula for the viable f(R) models considered. We consider three halo populations characterized by spatial abundances comparable to that of luminous red galaxies and galaxy clusters. The redshift-space halo correlation functions of F4 and F5 deviate significantly from ΛCDM at intermediate and high redshift, as the f(R) halo bias is smaller than or equal to that of the ΛCDM case. Finally, we introduce a new model-independent clustering statistic to distinguish f(R) from GR: the relative halo clustering ratio - R. The sampling required to adequately reduce the scatter in R will be available with the advent of the next-generation galaxy redshift surveys. This will foster a prospective avenue to obtain largely model-independent cosmological constraints on this class of modified gravity models.

Statistical properties of a filtered Poisson process with additive random noise: distributions, correlations and moment estimation

NASA Astrophysics Data System (ADS)

Theodorsen, A.; E Garcia, O.; Rypdal, M.

2017-05-01

Filtered Poisson processes are often used as reference models for intermittent fluctuations in physical systems. Such a process is here extended by adding a noise term, either as a purely additive term to the process or as a dynamical term in a stochastic differential equation. The lowest order moments, probability density function, auto-correlation function and power spectral density are derived and used to identify and compare the effects of the two different noise terms. Monte-Carlo studies of synthetic time series are used to investigate the accuracy of model parameter estimation and to identify methods for distinguishing the noise types. It is shown that the probability density function and the three lowest order moments provide accurate estimations of the model parameters, but are unable to separate the noise types. The auto-correlation function and the power spectral density also provide methods for estimating the model parameters, as well as being capable of identifying the noise type. The number of times the signal crosses a prescribed threshold level in the positive direction also promises to be able to differentiate the noise type.

Understanding photon sideband statistics and correlation for determining phonon coherence

NASA Astrophysics Data System (ADS)

Ding, Ding; Yin, Xiaobo; Li, Baowen

2018-01-01

Generating and detecting coherent high-frequency heat-carrying phonons have been topics of great interest in recent years. Although there have been successful attempts in generating and observing coherent phonons, rigorous techniques to characterize and detect phonon coherence in a crystalline material have been lagging compared to what has been achieved for photons. One main challenge is a lack of detailed understanding of how detection signals for phonons can be related to coherence. The quantum theory of photoelectric detection has greatly advanced the ability to characterize photon coherence in the past century, and a similar theory for phonon detection is necessary. Here, we reexamine the optical sideband fluorescence technique that has been used to detect high-frequency phonons in materials with optically active defects. We propose a quantum theory of phonon detection using the sideband technique and found that there are distinct differences in sideband counting statistics between thermal and coherent phonons. We further propose a second-order correlation function unique to sideband signals that allows for a rigorous distinction between thermal and coherent phonons. Our theory is relevant to a correlation measurement with nontrivial response functions at the quantum level and can potentially bridge the gap of experimentally determining phonon coherence to be on par with that of photons.

Autonomic nervous system and lipid metabolism: findings in anxious-depressive spectrum and eating disorders.

PubMed

Pistorio, Elisabetta; Luca, Maria; Luca, Antonina; Messina, Vincenzo; Calandra, Carmela

2011-10-28

To correlate lipid metabolism and autonomic dysfunction with anxious-depressive spectrum and eating disorders. To propose the lipid index (LI) as a new possible biomarker. 95 patients and 60 controls were enrolled from the University Psychiatry Unit of Catania and from general practitioners (GPs). The patients were divided into four pathological groups: Anxiety, Depression, Anxious-Depressive Disorder and Eating Disorders [Diagnostic and Statistical Manual of Mental Disorders Fourth Edition Text Revision (DSM-IV-TR) official/appendix criteria]. The levels of the cholesterol, triglycerides and apolipoproteins A and B were determined. The LI, for each subject, was obtained through a mathematical operation on the values of the cholesterol and triglycerides levels compared with the maximum cut-off of the general population. The autonomic functioning was tested with Ewing battery tests. Particularly, the correlation between heart rate variability (HRV) and lipid metabolism has been investigated. Pathological and control groups, compared among each other, presented some peculiarities in the lipid metabolism and the autonomic dysfunction scores. In addition, a statistically significant correlation has been found between HRV and lipid metabolism. Lipid metabolism and autonomic functioning seem to be related to the discussed psychiatric disorders. LI, in addition, could represent a new possible biomarker to be considered.

Correlation between solar flare productivity and photospheric vector magnetic fields

NASA Astrophysics Data System (ADS)

Cui, Yanmei; Wang, Huaning

2008-11-01

Studying the statistical correlation between the solar flare productivity and photospheric magnetic fields is very important and necessary. It is helpful to set up a practical flare forecast model based on magnetic properties and improve the physical understanding of solar flare eruptions. In the previous study ([Cui, Y.M., Li, R., Zhang, L.Y., He, Y.L., Wang, H.N. Correlation between solar flare productivity and photospheric magnetic field properties 1. Maximum horizontal gradient, length of neutral line, number of singular points. Sol. Phys. 237, 45 59, 2006]; from now on we refer to this paper as ‘Paper I’), three measures of the maximum horizontal gradient, the length of the neutral line, and the number of singular points are computed from 23990 SOHO/MDI longitudinal magnetograms. The statistical relationship between the solar flare productivity and these three measures is well fitted with sigmoid functions. In the current work, the three measures of the length of strong-shear neutral line, total unsigned current, and total unsigned current helicity are computed from 1353 vector magnetograms observed at Huairou Solar Observing Station. The relationship between the solar flare productivity and the current three measures can also be well fitted with sigmoid functions. These results are expected to be beneficial to future operational flare forecasting models.

Random field assessment of nanoscopic inhomogeneity of bone

PubMed Central

Dong, X. Neil; Luo, Qing; Sparkman, Daniel M.; Millwater, Harry R.; Wang, Xiaodu

2010-01-01

Bone quality is significantly correlated with the inhomogeneous distribution of material and ultrastructural properties (e.g., modulus and mineralization) of the tissue. Current techniques for quantifying inhomogeneity consist of descriptive statistics such as mean, standard deviation and coefficient of variation. However, these parameters do not describe the spatial variations of bone properties. The objective of this study was to develop a novel statistical method to characterize and quantitatively describe the spatial variation of bone properties at ultrastructural levels. To do so, a random field defined by an exponential covariance function was used to present the spatial uncertainty of elastic modulus by delineating the correlation of the modulus at different locations in bone lamellae. The correlation length, a characteristic parameter of the covariance function, was employed to estimate the fluctuation of the elastic modulus in the random field. Using this approach, two distribution maps of the elastic modulus within bone lamellae were generated using simulation and compared with those obtained experimentally by a combination of atomic force microscopy and nanoindentation techniques. The simulation-generated maps of elastic modulus were in close agreement with the experimental ones, thus validating the random field approach in defining the inhomogeneity of elastic modulus in lamellae of bone. Indeed, generation of such random fields will facilitate multi-scale modeling of bone in more pragmatic details. PMID:20817128

On the Relationship between Molecular Hit Rates in High-Throughput Screening and Molecular Descriptors.

PubMed

Hansson, Mari; Pemberton, John; Engkvist, Ola; Feierberg, Isabella; Brive, Lars; Jarvis, Philip; Zander-Balderud, Linda; Chen, Hongming

2014-06-01

High-throughput screening (HTS) is widely used in the pharmaceutical industry to identify novel chemical starting points for drug discovery projects. The current study focuses on the relationship between molecular hit rate in recent in-house HTS and four common molecular descriptors: lipophilicity (ClogP), size (heavy atom count, HEV), fraction of sp(3)-hybridized carbons (Fsp3), and fraction of molecular framework (f(MF)). The molecular hit rate is defined as the fraction of times the molecule has been assigned as active in the HTS campaigns where it has been screened. Beta-binomial statistical models were built to model the molecular hit rate as a function of these descriptors. The advantage of the beta-binomial statistical models is that the correlation between the descriptors is taken into account. Higher degree polynomial terms of the descriptors were also added into the beta-binomial statistic model to improve the model quality. The relative influence of different molecular descriptors on molecular hit rate has been estimated, taking into account that the descriptors are correlated to each other through applying beta-binomial statistical modeling. The results show that ClogP has the largest influence on the molecular hit rate, followed by Fsp3 and HEV. f(MF) has only a minor influence besides its correlation with the other molecular descriptors. © 2013 Society for Laboratory Automation and Screening.

Maxillary sinus augmentation by crestal access: a retrospective study on cavity size and outcome correlation.

PubMed

Spinato, Sergio; Bernardello, Fabio; Galindo-Moreno, Pablo; Zaffe, Davide

2015-12-01

Cone-beam computed tomography (CBCT) and radiographic outcomes of crestal sinus elevation, performed using mineralized human bone allograft, were analyzed to correlate results with maxillary sinus size. A total of 60 sinus augmentations in 60 patients, with initial bone ≤5 mm, were performed. Digital radiographs were taken at surgical implant placement time up to post-prosthetic loading follow-up (12-72 months), when CBCT evaluation was carried out. Marginal bone loss (MBL) was radiographically analyzed at 6 months and follow-up time post-loading. Sinus size (BPD), implant distance from palatal (PID) and buccal wall (BID), and absence of bone coverage of implant (intra-sinus bone loss--IBL) were evaluated and statistically evaluated by ANOVA and linear regression analyses. MBL increased as a function of time. MBL at final follow-up was statistically associated with MBL at 6 months. A statistically significant correlation of IBL with wall distance and of IBL/mm with time was identified with greater values in wide sinuses (WS ≥ 13.27 mm) than in narrow sinuses (NS < 13.27 mm). This study is the first quantitative and statistically significant confirmation that crestal technique with residual ridge height <5 mm is more appropriate and predictable, in terms of intra-sinus bone coverage, in narrow than in WS. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

On the linearity of tracer bias around voids

NASA Astrophysics Data System (ADS)

Pollina, Giorgia; Hamaus, Nico; Dolag, Klaus; Weller, Jochen; Baldi, Marco; Moscardini, Lauro

2017-07-01

The large-scale structure of the Universe can be observed only via luminous tracers of the dark matter. However, the clustering statistics of tracers are biased and depend on various properties, such as their host-halo mass and assembly history. On very large scales, this tracer bias results in a constant offset in the clustering amplitude, known as linear bias. Towards smaller non-linear scales, this is no longer the case and tracer bias becomes a complicated function of scale and time. We focus on tracer bias centred on cosmic voids, I.e. depressions of the density field that spatially dominate the Universe. We consider three types of tracers: galaxies, galaxy clusters and active galactic nuclei, extracted from the hydrodynamical simulation Magneticum Pathfinder. In contrast to common clustering statistics that focus on auto-correlations of tracers, we find that void-tracer cross-correlations are successfully described by a linear bias relation. The tracer-density profile of voids can thus be related to their matter-density profile by a single number. We show that it coincides with the linear tracer bias extracted from the large-scale auto-correlation function and expectations from theory, if sufficiently large voids are considered. For smaller voids we observe a shift towards higher values. This has important consequences on cosmological parameter inference, as the problem of unknown tracer bias is alleviated up to a constant number. The smallest scales in existing data sets become accessible to simpler models, providing numerous modes of the density field that have been disregarded so far, but may help to further reduce statistical errors in constraining cosmology.

Handheld echocardiography during hospitalization for acute myocardial infarction.

PubMed

Cullen, Michael W; Geske, Jeffrey B; Anavekar, Nandan S; Askew, J Wells; Lewis, Bradley R; Oh, Jae K

2017-11-01

Handheld echocardiography (HHE) is concordant with standard transthoracic echocardiography (TTE) in a variety of settings but has not been thoroughly compared to traditional TTE in patients with acute myocardial infarction (AMI). Completed by experienced operators, HHE provides accurate diagnostic capabilities compared with standard TTE in AMI patients. This study prospectively enrolled patients admitted to the coronary care unit with AMI. Experienced sonographers performed HHE with a V-scan. All patients underwent clinical TTE. Each HHE was interpreted by 2 experts blinded to standard TTE. Agreement was assessed with κ statistics and concordance correlation coefficients. Analysis included 82 patients (mean age, 66 years; 74% male). On standard TTE, mean left ventricular (LV) ejection fraction was 46%. Correlation coefficients between HHE and TTE were 0.75 (95% confidence interval: 0.66 to 0.82) for LV ejection fraction and 0.69 (95% confidence interval: 0.58 to 0.77) for wall motion score index. The κ statistics ranged from 0.47 to 0.56 for LV enlargement, 0.55 to 0.79 for mitral regurgitation, and 0.44 to 0.57 for inferior vena cava dilatation. The κ statistics were highest for the anterior (0.81) and septal (0.71) apex and lowest for the mid inferolateral (0.36) and basal inferoseptal (0.36) walls. In patients with AMI, HHE and standard TTE demonstrate good correlation for LV function and wall motion. Agreement was less robust for structural abnormalities and specific wall segments. In experienced hands, HHE can provide a focused assessment of LV function in patients hospitalized with AMI; however, HHE should not substitute for comprehensive TTE. © 2017 Wiley Periodicals, Inc.

Correlation of gingival thickness with gingival width, probing depth, and papillary fill in maxillary anterior teeth in students of a dental college in Navi Mumbai

PubMed Central

Singh, Jyotsna; Rathod, Varsha J.; Rao, Prajakta R.; Patil, Aardra A.; Langade, Deepak G.; Singh, Roshan K.

2016-01-01

Context: The gingival biotype is of utmost importance for esthetics and biologic function. Anatomical characteristic of periodontium such as gingival thickness (GT), width of keratinized gingiva, and alveolar bone morphology will determine the behavior of periodontium when subjected to physical, chemical, or bacterial insult or during therapeutic procedure. Aims: The aim of this study was to correlate the GT with gingival width (GW), probing depth (PD), and papillary fill (PF) in relation to maxillary anterior region. Settings and Design: Undergraduate dental students and interns from a dental college in Navi Mumbai were enrolled in the study according to the inclusion criteria. Six teeth per subject were assessed; a total of 2178 maxillary anterior teeth were examined. Subjects and Methods: Subjects were examined clinically for GT, width of keratinized gingiva, pocket depth, and interdental PF. The data obtained was tabulated and subjected to statistical analysis. Statistical Analysis Used: Spearman's correlation analysis test was performed to find the correlation of GT with GW, PD, and PF. Results: Positive correlation was found between GT and GW (r = 0.241). No significant correlation could be found between GT and PD; and between GT and PF. Conclusions: The present study confirmed a positive correlation between GT and GW. A weak negative correlation was found between GT and PD. PMID:27994424

Drooling, saliva production, and swallowing in cerebral palsy.

PubMed

Senner, Jill E; Logemann, Jerilyn; Zecker, Steven; Gaebler-Spira, Deborah

2004-12-01

Fourteen participants (six females, eight males) ranging in age from 7 years 11 months to 18 years 2 months (mean 11y 7mo) with a confirmed diagnosis of spastic cerebral palsy (CP) were included in the study. Participants included those who drooled (CP+, n=14); age- and sex-matched children with spastic CP who were dry to mild and never to infrequent droolers (CP-, n=14) as well as typically developing peers (CTRL, n=14) served as controls. Frequency of swallowing was measured by using simultaneous cervical ausculation and videotaping of the head and neck. Saliva production was measured with the Saxon test, a simple gauze-chewing procedure. In addition, Pediatric Evaluation of Disability Inventory (PEDI), Test of Nonverbal Intelligence-3 (TONI-3), dysarthria severity scale, and Gross Motor Function Classification System (GMFCS) scores were obtained for each participant. Both groups of participants with CP tended to swallow less frequently than typically developing participants and tended to produce less saliva than typically developing controls; however, these differences were not statistically significant. No correlation was found between amount of saliva produced and amount drooled (r=0.245). An analysis of variance (ANOVA) conducted on the PEDI functional skills mean scores indicated significant differences between the three groups (F(2,39)=23.522,p<0.0001). Likewise, an ANOVA conducted on the TONI-3 scores revealed statistically significant differences between the three groups (F(2,39)=31.761, p<0.0001). A Spearman's rho correlation indicated that GMFCS scores were not significantly correlated with drooling severity (Spearman's rho correlation=0.3951,p=0.037). Drooling severity was found to be positively correlated with dysarthria severity (Spearman's rho correlation=0.82,p<0.0001). These findings suggest that drooling in patients with CP is related to swallowing difficulties rather than hypersalivation.

Correlation between the pain numeric rating scale and the 12-item WHO Disability Assessment Schedule 2.0 in patients with musculoskeletal pain.

PubMed

Saltychev, Mikhail; Bärlund, Esa; Laimi, Katri

2018-03-01

The aim of this study was to assess the correlation between pain severity measured on a numeric rating scale and restrictions of functioning measured with the WHO Disability Assessment Schedule (WHODAS 2.0). This was a cross-sectional study of 1207 patients with musculoskeletal pain conditions. Correlation was assessed using Spearman's and Pearson tests. Although all the Spearman's rank correlations between WHODAS 2.0 items and pain severity were statistically significant, they were mostly weak, with only a few moderate associations for 'S2 household responsibilities', 'S8 washing', 'S9 dressing', and 'S12 day-to-day work'. The correlation between the WHODAS 2.0 total score and pain severity was also moderate: 0.41 [95% confidence interval (CI): 0.36-0.45] for average pain and 0.42 (95% CI: 0.37-0.46) for worst pain. The correlation between the WHODAS 2.0 total score and pain level was also assessed using Pearson's product-moment correlation, yielding figures that were similar to Spearman's correlation: 0.42 (P<0.0001, 95% CI: 0.37-0.46) for average pain and 0.39 (P<0.0001, 95% CI: 0.34-0.44) for worst pain. Among patients with chronic musculoskeletal pain, the correlation between pain severity measured by numeric rating scale and functioning level measured by WHODAS 2.0 was weak to moderate, with slightly stronger associations in physical domains of functioning.

Quality of life of gestational trophoblastic neoplasia survivors: a study of patients at the Philippine General Hospital trophoblastic disease section.

PubMed

Cagayan, M Stephanie Fay S; Llarena, Raquel T

2010-01-01

To evaluate the quality of life (QOL) of patients who were diagnosed with gestational trophoblastic neoplasia (GTN) at the Philippine General Hospital Trophoblastic Disease Section and who were in remission at the time of this study. A cross-sectional descriptive study designed to measure the QOL of all patients diagnosed as having GTN in remission and following up at the Philippine General Hospital Trophoblastic Disease Outpatient Clinic from May-August 2008 (N = 46). This study used the short form 12-question (SF-12) survey forms to evaluate the QOL of patients diagnosed with GTN. Scores from the SF-12 were analyzed using Pearson's correlation. Statistical significance was assumed for p values < 0.05 and 0.01 for all statistical tests. Forty-six GTN survivors included in the study successfully answered all the questions. Using Pearson's correlation of demographic characteristic variables and SF-12 domains, it was found that there was better physical functioning among younger patients, and there was mild limitation in moderate activities during a typical day among older patients. There was a significant positive correlation between educational level and physical functioning. A negative correlation was found between the stage of GTN and patients' general health. In conclusion, the survivors' age, educational level and type of treatment had impact on the QOL among GTN survivors in terms of physical functioning. No relationship was established between the demographic variables and mental status. SF-12 appears to be a reliable instrument, suggesting its potential in measuring health status in GTN survivors. Age, educational attainment and type of treatment were shown to have an impact on the QOL of the surviving GTN patients.

The relationships between cognitive function and hearing loss among the elderly.

PubMed

Huh, MyungJin

2018-01-01

[Purpose] Research related to dementia has gained momentum in South Korea and studies have found that the auditory sense affects dementia. This study aims to examine the relationship between the decline in hearing function and the overall cognitive function among the elderly. [Subjects and Methods] Eighty-two older adults aged 65-90 years (mean age: 79.3, SD: 5.2) participated. The Korean Mini-Mental State Examination was used to assess cognitive function. Further, to assess the hearing function, pure-tone audiometry was performed prior to the cognitive function test. We used a paired t-test and Pearson's correlation test for the analysis. [Results] Generally, the higher the frequency band, the more hearing loss was identified among the elderly. In addition, the difference in hearing between both ears was significant; particularly, hearing loss in the right ear was significantly higher than that in the left. Cognitive function was not related to age, however, the correlation between cognitive function and hearing loss in the right ear was statistically significant. [Conclusion] Hearing loss influences cognitive function among the elderly.

Correlation of nerve ultrasound, electrophysiological and clinical findings in chronic inflammatory demyelinating polyneuropathy.

PubMed

Kerasnoudis, A; Pitarokoili, K; Behrendt, V; Gold, R; Yoon, M-S

2015-01-01

We present the nerve ultrasound findings in chronic inflammatory demyelinating polyneuropathy (CIDP) and examine their correlation with electrophysiology and functional disability. A total of 75 healthy controls and 48 CIDP patients underwent clinical, sonographic and electrophysiological evaluation a mean of 3.9 years(SD+/-2.7) after disease onset. Nerve ultrasound revealed statistically significant higher cross-sectional area (CSA) values of the median (P<.0001), ulnar (P<.0001), radial (P<.0001), tibial (P<.0001), fibular nerve(P<.0001) in most of the anatomic sites and brachial plexus (supraclavicular, P<.0001;interscalene space, P = .0118),when compared to controls. The electroneurography documented signs of permanent axonal loss in the majority of peripheral nerves. A correlation between sonographic and electrophysiological findings was found only between the motor conduction velocity and CSA of the tibial nerve at the ankle (r = -.451, P = .007). Neither nerve sonography nor electrophysiology correlated with functional disability. The CSA of the median nerve in carpal tunnel and the ulnar nerve in Guyon's canal correlated with disease duration (P = .036, P = .027 respectively). CIDP seems to show inhomogenous CSA enlargement in brachial plexus and peripheral nerves, with weak correlation to electrophysiological findings. Neither nerve sonography nor electrophysiology correlated with functional disability in CIDP patients. Multicenter, prospective studies are required to proof the applicability and diagnostic values of these findings. Copyright © 2014 by the American Society of Neuroimaging.

Identifying Dynamic Functional Connectivity Changes in Dementia with Lewy Bodies Based on Product Hidden Markov Models.

PubMed

Sourty, Marion; Thoraval, Laurent; Roquet, Daniel; Armspach, Jean-Paul; Foucher, Jack; Blanc, Frédéric

2016-01-01

Exploring time-varying connectivity networks in neurodegenerative disorders is a recent field of research in functional MRI. Dementia with Lewy bodies (DLB) represents 20% of the neurodegenerative forms of dementia. Fluctuations of cognition and vigilance are the key symptoms of DLB. To date, no dynamic functional connectivity (DFC) investigations of this disorder have been performed. In this paper, we refer to the concept of connectivity state as a piecewise stationary configuration of functional connectivity between brain networks. From this concept, we propose a new method for group-level as well as for subject-level studies to compare and characterize connectivity state changes between a set of resting-state networks (RSNs). Dynamic Bayesian networks, statistical and graph theory-based models, enable one to learn dependencies between interacting state-based processes. Product hidden Markov models (PHMM), an instance of dynamic Bayesian networks, are introduced here to capture both statistical and temporal aspects of DFC of a set of RSNs. This analysis was based on sliding-window cross-correlations between seven RSNs extracted from a group independent component analysis performed on 20 healthy elderly subjects and 16 patients with DLB. Statistical models of DFC differed in patients compared to healthy subjects for the occipito-parieto-frontal network, the medial occipital network and the right fronto-parietal network. In addition, pairwise comparisons of DFC of RSNs revealed a decrease of dependency between these two visual networks (occipito-parieto-frontal and medial occipital networks) and the right fronto-parietal control network. The analysis of DFC state changes thus pointed out networks related to the cognitive functions that are known to be impaired in DLB: visual processing as well as attentional and executive functions. Besides this context, product HMM applied to RSNs cross-correlations offers a promising new approach to investigate structural and temporal aspects of brain DFC.

Determination of Relevant Neuron–Neuron Connections for Neural Prosthetics Using Time-Delayed Mutual Information: Tutorial and Preliminary Results

PubMed Central

Taghva, Alexander; Song, Dong; Hampson, Robert E.; Deadwyler, Sam A.; Berger, Theodore W.

2013-01-01

BACKGROUND Identification of functional dependence among neurons is a necessary component in both the rational design of neural prostheses as well as in the characterization of network physiology. The objective of this article is to provide a tutorial for neurosurgeons regarding information theory, specifically time-delayed mutual information, and to compare time-delayed mutual information, an information theoretic quantity based on statistical dependence, with cross-correlation, a commonly used metric for this task in a preliminary analysis of rat hippocampal neurons. METHODS Spike trains were recorded from rats performing delayed nonmatch-to-sample task using an array of electrodes surgically implanted into the hippocampus of each hemisphere of the brain. In addition, spike train simulations of positively correlated neurons, negatively correlated neurons, and neurons correlated by nonlinear functions were generated. These were evaluated by time-delayed mutual information (MI) and cross-correlation. RESULTS Application of time-delayed MI to experimental data indicated the optimal bin size for information capture in the CA3-CA1 system was 40 ms, which may provide some insight into the spatiotemporal nature of encoding in the rat hippocampus. On simulated data, time-delayed MI showed peak values at appropriate time lags in positively correlated, negatively correlated, and complexly correlated data. Cross-correlation showed peak and troughs with positively correlated and negatively correlated data, but failed to capture some higher order correlations. CONCLUSIONS Comparison of time-delayed MI to cross-correlation in identification of functionally dependent neurons indicates that the methods are not equivalent. Time-delayed MI appeared to capture some interactions between CA3-CA1 neurons at physiologically plausible time delays missed by cross-correlation. It should be considered as a method for identification of functional dependence between neurons and may be useful in the development of neural prosthetics. PMID:22120279

Determination of relevant neuron-neuron connections for neural prosthetics using time-delayed mutual information: tutorial and preliminary results.

PubMed

Taghva, Alexander; Song, Dong; Hampson, Robert E; Deadwyler, Sam A; Berger, Theodore W

2012-12-01

Identification of functional dependence among neurons is a necessary component in both the rational design of neural prostheses as well as in the characterization of network physiology. The objective of this article is to provide a tutorial for neurosurgeons regarding information theory, specifically time-delayed mutual information, and to compare time-delayed mutual information, an information theoretic quantity based on statistical dependence, with cross-correlation, a commonly used metric for this task in a preliminary analysis of rat hippocampal neurons. Spike trains were recorded from rats performing delayed nonmatch-to-sample task using an array of electrodes surgically implanted into the hippocampus of each hemisphere of the brain. In addition, spike train simulations of positively correlated neurons, negatively correlated neurons, and neurons correlated by nonlinear functions were generated. These were evaluated by time-delayed mutual information (MI) and cross-correlation. Application of time-delayed MI to experimental data indicated the optimal bin size for information capture in the CA3-CA1 system was 40 ms, which may provide some insight into the spatiotemporal nature of encoding in the rat hippocampus. On simulated data, time-delayed MI showed peak values at appropriate time lags in positively correlated, negatively correlated, and complexly correlated data. Cross-correlation showed peak and troughs with positively correlated and negatively correlated data, but failed to capture some higher order correlations. Comparison of time-delayed MI to cross-correlation in identification of functionally dependent neurons indicates that the methods are not equivalent. Time-delayed MI appeared to capture some interactions between CA3-CA1 neurons at physiologically plausible time delays missed by cross-correlation. It should be considered as a method for identification of functional dependence between neurons and may be useful in the development of neural prosthetics. Copyright © 2012 Elsevier Inc. All rights reserved.

Correlation spectrometer for filtering of (quasi) elastic neutron scattering with variable resolution

NASA Astrophysics Data System (ADS)

Magazù, Salvatore; Mezei, Ferenc; Migliardo, Federica

2018-05-01

In a variety of applications of inelastic neutron scattering spectroscopy the goal is to single out the elastic scattering contribution from the total scattered spectrum as a function of momentum transfer and sample environment parameters. The elastic part of the spectrum is defined in such a case by the energy resolution of the spectrometer. Variable elastic energy resolution offers a way to distinguish between elastic and quasi-elastic intensities. Correlation spectroscopy lends itself as an efficient, high intensity approach for accomplishing this both at continuous and pulsed neutron sources. On the one hand, in beam modulation methods the Liouville theorem coupling between intensity and resolution is relaxed and time-of-flight velocity analysis of the neutron velocity distribution can be performed with 50 % duty factor exposure for all available resolutions. On the other hand, the (quasi)elastic part of the spectrum generally contains the major part of the integrated intensity at a given detector, and thus correlation spectroscopy can be applied with most favorable signal to statistical noise ratio. The novel spectrometer CORELLI at SNS is an example for this type of application of the correlation technique at a pulsed source. On a continuous neutron source a statistical chopper can be used for quasi-random time dependent beam modulation and the total time-of-flight of the neutron from the statistical chopper to detection is determined by the analysis of the correlation between the temporal fluctuation of the neutron detection rate and the statistical chopper beam modulation pattern. The correlation analysis can either be used for the determination of the incoming neutron velocity or for the scattered neutron velocity, depending of the position of the statistical chopper along the neutron trajectory. These two options are considered together with an evaluation of spectrometer performance compared to conventional spectroscopy, in particular for variable resolution elastic neutron scattering (RENS) studies of relaxation processes and the evolution of mean square displacements. A particular focus of our analysis is the unique feature of correlation spectroscopy of delivering high and resolution independent beam intensity, thus the same statistical chopper scan contains both high intensity and high resolution information at the same time, and can be evaluated both ways. This flexibility for variable resolution data handling represents an additional asset for correlation spectroscopy in variable resolution work. Changing the beam width for the same statistical chopper allows us to additionally trade resolution for intensity in two different experimental runs, similarly for conventional single slit chopper spectroscopy. The combination of these two approaches is a capability of particular value in neutron spectroscopy studies requiring variable energy resolution, such as the systematic study of quasi-elastic scattering and mean square displacement. Furthermore the statistical chopper approach is particularly advantageous for studying samples with low scattering intensity in the presence of a high, sample independent background.

Very High-Frequency (VHF) ionospheric scintillation fading measurements at Lima, Peru

NASA Technical Reports Server (NTRS)

Blank, H. A.; Golden, T. S.

1972-01-01

During the spring equinox of 1970, scintillating signals at VHF (136.4 MHz) were observed at Lima, Peru. The transmission originated from ATS 3 and was observed through a pair of antennas spaced 1200 feet apart on an east-west baseline. The empirical data were digitized, reduced, and analyzed. The results include amplitude probability density and distribution functions, time autocorrelation functions, cross correlation functions for the spaced antennas, and appropriate spectral density functions. Results show estimates of the statistics of the ground diffraction pattern to gain insight into gross ionospheric irregularity size, and irregularity velocity in the antenna planes.

Negative Correlations in Visual Cortical Networks

PubMed Central

Chelaru, Mircea I.; Dragoi, Valentin

2016-01-01

The amount of information encoded by cortical circuits depends critically on the capacity of nearby neurons to exhibit trial-to-trial (noise) correlations in their responses. Depending on their sign and relationship to signal correlations, noise correlations can either increase or decrease the population code accuracy relative to uncorrelated neuronal firing. Whereas positive noise correlations have been extensively studied using experimental and theoretical tools, the functional role of negative correlations in cortical circuits has remained elusive. We addressed this issue by performing multiple-electrode recording in the superficial layers of the primary visual cortex (V1) of alert monkey. Despite the fact that positive noise correlations decayed exponentially with the difference in the orientation preference between cells, negative correlations were uniformly distributed across the population. Using a statistical model for Fisher Information estimation, we found that a mild increase in negative correlations causes a sharp increase in network accuracy even when mean correlations were held constant. To examine the variables controlling the strength of negative correlations, we implemented a recurrent spiking network model of V1. We found that increasing local inhibition and reducing excitation causes a decrease in the firing rates of neurons while increasing the negative noise correlations, which in turn increase the population signal-to-noise ratio and network accuracy. Altogether, these results contribute to our understanding of the neuronal mechanism involved in the generation of negative correlations and their beneficial impact on cortical circuit function. PMID:25217468

Motor function outcomes of pediatric patients with hemiplegic cerebral palsy after rehabilitation treatment: a diffusion tensor imaging study

PubMed Central

Kim, Jin Hyun; Kwon, Yong Min; Son, Su Min

2015-01-01

Previous diffusion tensor imaging (DTI) studies regarding pediatric patients with motor dysfunction have confirmed the correlation between DTI parameters of the injured corticospinal tract and the severity of motor dysfunction. There is also evidence that DTI parameters can help predict the prognosis of motor function of patients with cerebral palsy. But few studies are reported on the DTI parameters that can reflect the motor function outcomes of pediatric patients with hemiplegic cerebral palsy after rehabilitation treatment. In the present study, 36 pediatric patients with hemiplegic cerebral palsy were included. Before and after rehabilitation treatment, DTI was used to measure the fiber number (FN), fractional anisotropy (FA) and apparent diffusion coefficient (ADC) of bilateral corticospinal tracts. Functional Level of Hemiplegia scale (FxL) was used to assess the therapeutic effect of rehabilitative therapy on clinical hemiplegia. Correlation analysis was performed to assess the statistical interrelationship between the change amount of DTI parameters and FxL. DTI findings obtained at the initial and follow-up evaluations demonstrated that more affected corticospinal tract yielded significantly decreased FN and FA values and significantly increased ADC value compared to the less affected corticospinal tract. Correlation analysis results showed that the change amount of FxL was positively correlated to FN and FA values, and the correlation to FN was stronger than the correlation to FA. The results suggest that FN and FA values can be used to evaluate the motor function outcomes of pediatric patients with hemiplegic cerebral palsy after rehabilitation treatment and FN is of more significance for evaluation. PMID:26170825

Evaluating a measure of social health derived from two mental health recovery measures: the California Quality of Life (CA-QOL) and Mental Health Statistics Improvement Program Consumer Survey (MHSIP).

PubMed

Carlson, Jordan A; Sarkin, Andrew J; Levack, Ashley E; Sklar, Marisa; Tally, Steven R; Gilmer, Todd P; Groessl, Erik J

2011-08-01

Social health is important to measure when assessing outcomes in community mental health. Our objective was to validate social health scales using items from two broader commonly used measures that assess mental health outcomes. Participants were 609 adults receiving psychological treatment services. Items were identified from the California Quality of Life (CA-QOL) and Mental Health Statistics Improvement Program (MHSIP) outcome measures by their conceptual correspondence with social health and compared to the Social Functioning Questionnaire (SFQ) using correlational analyses. Pearson correlations for the identified CA-QOL and MSHIP items with the SFQ ranged from .42 to .62, and the identified scale scores produced Pearson correlation coefficients of .56, .70, and, .70 with the SFQ. Concurrent validity with social health was supported for the identified scales. The current inclusion of these assessment tools allows community mental health programs to include social health in their assessments.

Statistical Characteristics of the Gaussian-Noise Spikes Exceeding the Specified Threshold as Applied to Discharges in a Thundercloud

NASA Astrophysics Data System (ADS)

Klimenko, V. V.

2017-12-01

We obtain expressions for the probabilities of the normal-noise spikes with the Gaussian correlation function and for the probability density of the inter-spike intervals. As distinct from the delta-correlated noise, in which the intervals are distributed by the exponential law, the probability of the subsequent spike depends on the previous spike and the interval-distribution law deviates from the exponential one for a finite noise-correlation time (frequency-bandwidth restriction). This deviation is the most pronounced for a low detection threshold. Similarity of the behaviors of the distributions of the inter-discharge intervals in a thundercloud and the noise spikes for the varying repetition rate of the discharges/spikes, which is determined by the ratio of the detection threshold to the root-mean-square value of noise, is observed. The results of this work can be useful for the quantitative description of the statistical characteristics of the noise spikes and studying the role of fluctuations for the discharge emergence in a thundercloud.

Covariance analyses of satellite-derived mesoscale wind fields

NASA Technical Reports Server (NTRS)

Maddox, R. A.; Vonder Haar, T. H.

1979-01-01

Statistical structure functions have been computed independently for nine satellite-derived mesoscale wind fields that were obtained on two different days. Small cumulus clouds were tracked at 5 min intervals, but since these clouds occurred primarily in the warm sectors of midlatitude cyclones the results cannot be considered representative of the circulations within cyclones in general. The field structure varied considerably with time and was especially affected if mesoscale features were observed. The wind fields on the 2 days studied were highly anisotropic with large gradients in structure occurring approximately normal to the mean flow. Structure function calculations for the combined set of satellite winds were used to estimate random error present in the fields. It is concluded for these data that the random error in vector winds derived from cumulus cloud tracking using high-frequency satellite data is less than 1.75 m/s. Spatial correlation functions were also computed for the nine data sets. Normalized correlation functions were considerably different for u and v components and decreased rapidly as data point separation increased for both components. The correlation functions for transverse and longitudinal components decreased less rapidly as data point separation increased.

Determination of the Wave Parameters from the Statistical Characteristics of the Image of a Linear Test Object

NASA Astrophysics Data System (ADS)

Weber, V. L.

2018-03-01

We statistically analyze the images of the objects of the "light-line" and "half-plane" types which are observed through a randomly irregular air-water interface. The expressions for the correlation function of fluctuations of the image of an object given in the form of a luminous half-plane are found. The possibility of determining the spatial and temporal correlation functions of the slopes of a rough water surface from these relationships is shown. The problem of the probability of intersection of a small arbitrarily oriented line segment by the contour image of a luminous straight line is solved. Using the results of solving this problem, we show the possibility of determining the values of the curvature variances of a rough water surface. A practical method for obtaining an image of a rectilinear luminous object in the light rays reflected from the rough surface is proposed. It is theoretically shown that such an object can be synthesized by temporal accumulation of the image of a point source of light rapidly moving in the horizontal plane with respect to the water surface.

Statistical properties and condensate fluctuation of attractive Bose gas with finite number of particles

NASA Astrophysics Data System (ADS)

Bera, Sangita; Lekala, Mantile Leslie; Chakrabarti, Barnali; Bhattacharyya, Satadal; Rampho, Gaotsiwe Joel

2017-09-01

'We study the condensate fluctuation and several statistics of weakly interacting attractive Bose gas of 7 Li atoms in harmonic trap. Using exact recursion relation we calculate canonical ensemble partition function and study the thermal evolution of the condensate. As 7 Li condensate is associated with collapse, the number of condensate atom is truly finite and it facilitates to study the condensate in mesoscopic region. Being highly correlated, we utilize the two-body correlated basis function to get the many-body effective potential which is further used to calculate the energy levels. Taking van der Waals interaction as interatomic interaction we calculate several quantities like condensate fraction N, root-mean-square fluctuation δn0 and different orders of central moments. We observe the effect of finite size on the calculation of condensate fluctuations and the effect of attractive interaction over the noninteracting limit. We observe the depletion of the condensate with increase in temperature. The calculated moments nicely exhibit the mesoscopic effect. The sharp fall in the root-mean-square fluctuation near the critical point signifies the possibility of phase transition.

Statistics of initial density perturbations in heavy ion collisions and their fluid dynamic response

NASA Astrophysics Data System (ADS)

Floerchinger, Stefan; Wiedemann, Urs Achim

2014-08-01

An interesting opportunity to determine thermodynamic and transport properties in more detail is to identify generic statistical properties of initial density perturbations. Here we study event-by-event fluctuations in terms of correlation functions for two models that can be solved analytically. The first assumes Gaussian fluctuations around a distribution that is fixed by the collision geometry but leads to non-Gaussian features after averaging over the reaction plane orientation at non-zero impact parameter. In this context, we derive a three-parameter extension of the commonly used Bessel-Gaussian event-by-event distribution of harmonic flow coefficients. Secondly, we study a model of N independent point sources for which connected n-point correlation functions of initial perturbations scale like 1 /N n-1. This scaling is violated for non-central collisions in a way that can be characterized by its impact parameter dependence. We discuss to what extent these are generic properties that can be expected to hold for any model of initial conditions, and how this can improve the fluid dynamical analysis of heavy ion collisions.

Propagation of radially polarized multi-cosine Gaussian Schell-model beams in non-Kolmogorov turbulence

NASA Astrophysics Data System (ADS)

Tang, Miaomiao; Zhao, Daomu; Li, Xinzhong; Wang, Jingge

2018-01-01

Recently, we introduced a new class of radially polarized beams with multi-cosine Gaussian Schell-model(MCGSM) correlation function based on the partially coherent theory (Tang et al., 2017). In this manuscript, we extend the work to study the statistical properties such as the spectral density, the degree of coherence, the degree of polarization, and the state of polarization of the beam propagating in isotropic turbulence with a non-Kolmogorov power spectrum. Analytical formulas for the cross-spectral density matrix elements of a radially polarized MCGSM beam in non-Kolmogorov turbulence are derived. Numerical results show that lattice-like intensity pattern of the beam, which keeps propagation-invariant in free space, is destroyed by the turbulence when it passes at sufficiently large distances from the source. It is also shown that the polarization properties are mainly affected by the source correlation functions, and change in the turbulent statistics plays a relatively small effect. In addition, the polarization state exhibits self-splitting property and each beamlet evolves into radially polarized structure upon propagation.

Inference of Functionally-Relevant N-acetyltransferase Residues Based on Statistical Correlations.

PubMed

Neuwald, Andrew F; Altschul, Stephen F

2016-12-01

Over evolutionary time, members of a superfamily of homologous proteins sharing a common structural core diverge into subgroups filling various functional niches. At the sequence level, such divergence appears as correlations that arise from residue patterns distinct to each subgroup. Such a superfamily may be viewed as a population of sequences corresponding to a complex, high-dimensional probability distribution. Here we model this distribution as hierarchical interrelated hidden Markov models (hiHMMs), which describe these sequence correlations implicitly. By characterizing such correlations one may hope to obtain information regarding functionally-relevant properties that have thus far evaded detection. To do so, we infer a hiHMM distribution from sequence data using Bayes' theorem and Markov chain Monte Carlo (MCMC) sampling, which is widely recognized as the most effective approach for characterizing a complex, high dimensional distribution. Other routines then map correlated residue patterns to available structures with a view to hypothesis generation. When applied to N-acetyltransferases, this reveals sequence and structural features indicative of functionally important, yet generally unknown biochemical properties. Even for sets of proteins for which nothing is known beyond unannotated sequences and structures, this can lead to helpful insights. We describe, for example, a putative coenzyme-A-induced-fit substrate binding mechanism mediated by arginine residue switching between salt bridge and π-π stacking interactions. A suite of programs implementing this approach is available (psed.igs.umaryland.edu).

Statistical-mechanics theory of active mode locking with noise.

PubMed

Gordon, Ariel; Fischer, Baruch

2004-05-01

Actively mode-locked lasers with noise are studied employing statistical mechanics. A mapping of the system to the spherical model (related to the Ising model) of ferromagnets in one dimension that has an exact solution is established. It gives basic features, such as analytical expressions for the correlation function between modes, and the widths and shapes of the pulses [different from the Kuizenga-Siegman expression; IEEE J. Quantum Electron. QE-6, 803 (1970)] and reveals the susceptibility to noise of mode ordering compared with passive mode locking.

A hybrid correlation analysis with application to imaging genetics

NASA Astrophysics Data System (ADS)

Hu, Wenxing; Fang, Jian; Calhoun, Vince D.; Wang, Yu-Ping

2018-03-01

Investigating the association between brain regions and genes continues to be a challenging topic in imaging genetics. Current brain region of interest (ROI)-gene association studies normally reduce data dimension by averaging the value of voxels in each ROI. This averaging may lead to a loss of information due to the existence of functional sub-regions. Pearson correlation is widely used for association analysis. However, it only detects linear correlation whereas nonlinear correlation may exist among ROIs. In this work, we introduced distance correlation to ROI-gene association analysis, which can detect both linear and nonlinear correlations and overcome the limitation of averaging operations by taking advantage of the information at each voxel. Nevertheless, distance correlation usually has a much lower value than Pearson correlation. To address this problem, we proposed a hybrid correlation analysis approach, by applying canonical correlation analysis (CCA) to the distance covariance matrix instead of directly computing distance correlation. Incorporating CCA into distance correlation approach may be more suitable for complex disease study because it can detect highly associated pairs of ROI and gene groups, and may improve the distance correlation level and statistical power. In addition, we developed a novel nonlinear CCA, called distance kernel CCA, which seeks the optimal combination of features with the most significant dependence. This approach was applied to imaging genetic data from the Philadelphia Neurodevelopmental Cohort (PNC). Experiments showed that our hybrid approach produced more consistent results than conventional CCA across resampling and both the correlation and statistical significance were increased compared to distance correlation analysis. Further gene enrichment analysis and region of interest (ROI) analysis confirmed the associations of the identified genes with brain ROIs. Therefore, our approach provides a powerful tool for finding the correlation between brain imaging and genomic data.

Unbiased estimators for spatial distribution functions of classical fluids

NASA Astrophysics Data System (ADS)

Adib, Artur B.; Jarzynski, Christopher

2005-01-01

We use a statistical-mechanical identity closely related to the familiar virial theorem, to derive unbiased estimators for spatial distribution functions of classical fluids. In particular, we obtain estimators for both the fluid density ρ(r) in the vicinity of a fixed solute and the pair correlation g(r) of a homogeneous classical fluid. We illustrate the utility of our estimators with numerical examples, which reveal advantages over traditional histogram-based methods of computing such distributions.

Siting stability in skeletally mature patients with scoliosis and myelomeningocele.

PubMed

Bartnicki, Bartłomiej; Synder, Marek; Kujawa, Jolanta; Stańczak, Katarzyna; Sibiński, Marcin

2012-01-01

The purpose of the study was to assess the influence of sitting stability in skeletally mature patients on their quality of life and general physical function. We also aimed to assess the relationship between sitting balance and the severity of scoliosis or other disorders of individuals with myelomeningocoele. The prospective study enrolled 19 patients with a mean age of 21.4 years (min. 13 years). Patients treated operatively for spinal deformity were excluded from the study. Different aspects of the quality of life were assessed with several questionnaires serving to measure overall quality of life, general physical function, self-perception and self-motivation as well as dysfunction related to spine deformity. Walking ability was assessed according to the Hoffer classification and the level of motor neuron injury was evaluated with the International Myelodysplasia Study Protocol. Statistical analysis showed that sitting stability assessed by examiners or parents positively correlated with overall quality of life, general physical function, pelvic obliquity measured by Osebold method, and the level of motor spine dysfunction. It was not related to self-perception and self-motivation of patients. There was no statistical correlation between sitting balance and the Cobb angle, walking ability, presence of pressure sores and age. The value of the Cobb angle is not a good indicator of sitting balance in patients with scoliosis and myelomeningocoele. Stabile sitting is related to better overall quality of life and physical function.

Lagrangian single-particle turbulent statistics through the Hilbert-Huang transform.

PubMed

Huang, Yongxiang; Biferale, Luca; Calzavarini, Enrico; Sun, Chao; Toschi, Federico

2013-04-01

The Hilbert-Huang transform is applied to analyze single-particle Lagrangian velocity data from numerical simulations of hydrodynamic turbulence. The velocity trajectory is described in terms of a set of intrinsic mode functions C(i)(t) and of their instantaneous frequency ω(i)(t). On the basis of this decomposition we define the ω-conditioned statistical moments of the C(i) modes, named q-order Hilbert spectra (HS). We show that such quantities have enhanced scaling properties as compared to traditional Fourier transform- or correlation-based (structure functions) statistical indicators, thus providing better insights into the turbulent energy transfer process. We present clear empirical evidence that the energylike quantity, i.e., the second-order HS, displays a linear scaling in time in the inertial range, as expected from a dimensional analysis. We also measure high-order moment scaling exponents in a direct way, without resorting to the extended self-similarity procedure. This leads to an estimate of the Lagrangian structure function exponents which are consistent with the multifractal prediction in the Lagrangian frame as proposed by Biferale et al. [Phys. Rev. Lett. 93, 064502 (2004)].

Radiation-induced functional connectivity alterations in nasopharyngeal carcinoma patients with radiotherapy

PubMed Central

Ma, Qiongmin; Wu, Donglin; Zeng, Ling-Li; Shen, Hui; Hu, Dewen; Qiu, Shijun

2016-01-01

Abstract The study aims to investigate the radiation-induced brain functional alterations in nasopharyngeal carcinoma (NPC) patients who received radiotherapy (RT) using functional magnetic resonance imaging (fMRI) and statistic scale. The fMRI data of 35 NPC patients with RT and 24 demographically matched untreated NPC patients were acquired. Montreal Cognitive Assessment (MoCA) was also measured to evaluate their global cognition performance. Multivariate pattern analysis was performed to find the significantly altered functional connections between these 2 groups, while the linear correlation level was detected between the altered functional connections and the MoCA scores. Forty-five notably altered functional connections were found, which were mainly located between 3 brain networks, the cerebellum, sensorimotor, and cingulo-opercular. With strictly false discovery rate correction, 5 altered functional connections were shown to have significant linear correlations with the MoCA scores, that is, the connections between the vermis and hippocampus, cerebellum lobule VI and dorsolateral prefrontal cortex, precuneus and dorsal frontal cortex, cuneus and middle occipital lobe, and insula and cuneus. Besides, the connectivity between the vermis and hippocampus was also significantly correlated with the attention score, 1 of the 7 subscores of the MoCA. The present study provides new insights into the radiation-induced functional connectivity impairments in NPC patients. The results showed that the RT may induce the cognitive impairments, especially the attention alterations. The 45 altered functional connections, especially the 5 altered functional connections that were significantly correlated to the MoCA scores, may serve as the potential biomarkers of the RT-induced brain functional impairments and provide valuable targets for further functional recovery treatment. PMID:27442663

RAPID3 scores and hand outcome measurements in RA patients: a preliminary study.

PubMed

Qorolli, Merita; Hundozi-Hysenaj, Hajrije; Rexhepi, Sylejman; Rehxepi, Blerta; Grazio, Simeon

2017-06-01

The Routine Assessment of Patient Index Data 3 (RAPID3) is a patient-reported disease activity measure used to assess physical function, pain, and global health in patients with rheumatoid arthritis (RA) without formal joint counts. Since hand involvement and its decreased function are hallmarks of RA, the aim of our study was to investigate the performance of RAPID3 scores with regard to hand function and to confirm previous findings that the RAPID3 score as a disease activity measure is strongly correlated with the DAS28 score. Sixty-eight consecutive patients with RA (85% female), aged 18-75 years, were included in the study and were recruited during their outpatient visit. Apart from demographic and clinical data, the obtained parameters of interest included RAPID3 scores and assessments of the function of the hand, namely, the signal of functional impairment (SOFI)-hand, grip strength, and pulp-to-palm distance, as well the Health Assessment Questionnaire- Disability Index (HAQ-DI) and DAS28 scores. Pearson's correlation coefficient, Student's t test and linear regression were used in the statistical analysis of the results. The significance was set to p < 0.05. A positive correlation was found between RAPID3 scores and HAQ-DI scores, SOFI-hand scores, and pulp-to-palm distance, and negative correlation was observed between RAPID3 scores and grip strength. The order regarding the strength of correlations between RAPID3 scores and other variables (from the strongest to the weakest) was as follows: HAQ-DI, grip strength, SOFI-hand and pulp-to-palm distance. The hand assessment variables had stronger correlations with RAPID3 scores than with DAS28 scores. Our preliminary study showed that RAPID3 scores were strongly correlated with measurements of the functional ability of the hand, demonstrating that RAPID3 can be used as a measure of disease activity in clinical practice and to characterize hand function. Further studies are needed to confirm this result.

Recurrence plot statistics and the effect of embedding

NASA Astrophysics Data System (ADS)

March, T. K.; Chapman, S. C.; Dendy, R. O.

2005-01-01

Recurrence plots provide a graphical representation of the recurrent patterns in a timeseries, the quantification of which is a relatively new field. Here we derive analytical expressions which relate the values of key statistics, notably determinism and entropy of line length distribution, to the correlation sum as a function of embedding dimension. These expressions are obtained by deriving the transformation which generates an embedded recurrence plot from an unembedded plot. A single unembedded recurrence plot thus provides the statistics of all possible embedded recurrence plots. If the correlation sum scales exponentially with embedding dimension, we show that these statistics are determined entirely by the exponent of the exponential. This explains the results of Iwanski and Bradley [J.S. Iwanski, E. Bradley, Recurrence plots of experimental data: to embed or not to embed? Chaos 8 (1998) 861-871] who found that certain recurrence plot statistics are apparently invariant to embedding dimension for certain low-dimensional systems. We also examine the relationship between the mutual information content of two timeseries and the common recurrent structure seen in their recurrence plots. This allows time-localized contributions to mutual information to be visualized. This technique is demonstrated using geomagnetic index data; we show that the AU and AL geomagnetic indices share half their information, and find the timescale on which mutual features appear.

Aggregation models on hypergraphs

NASA Astrophysics Data System (ADS)

Alberici, Diego; Contucci, Pierluigi; Mingione, Emanuele; Molari, Marco

2017-01-01

Following a newly introduced approach by Rasetti and Merelli we investigate the possibility to extract topological information about the space where interacting systems are modelled. From the statistical datum of their observable quantities, like the correlation functions, we show how to reconstruct the activities of their constitutive parts which embed the topological information. The procedure is implemented on a class of polymer models on hypergraphs with hard-core interactions. We show that the model fulfils a set of iterative relations for the partition function that generalise those introduced by Heilmann and Lieb for the monomer-dimer case. After translating those relations into structural identities for the correlation functions we use them to test the precision and the robustness of the inverse problem. Finally the possible presence of a further interaction of peer-to-peer type is considered and a criterion to discover it is identified.

Jet-Track Correlation Studies in PbPb and pp at 5.02 TeV

NASA Astrophysics Data System (ADS)

Trauger, Hallie Causey; CMS Collaboration

2017-11-01

Jet-track correlations are used to extend measurements of the properties of jets beyond classic fixed-R jet reconstruction. New measurements with PbPb and pp collision data at √{sNN} = 5.02 TeV, recorded by CMS, are carried out using a statistical approach that allows for a reliable subtraction of the underlying event beyond the typical distance parameters of jet reconstruction. Measurements of correlated particle densities are extended out to ±1.5 units of relative azimuth and pseudorapidity. Double-differential measurements of jet fragmentation functions and jet shapes are presented up to radial distance of R=1 from the jet axis.

Modelling nematode movement using time-fractional dynamics.

PubMed

Hapca, Simona; Crawford, John W; MacMillan, Keith; Wilson, Mike J; Young, Iain M

2007-09-07

We use a correlated random walk model in two dimensions to simulate the movement of the slug parasitic nematode Phasmarhabditis hermaphrodita in homogeneous environments. The model incorporates the observed statistical distributions of turning angle and speed derived from time-lapse studies of individual nematode trails. We identify strong temporal correlations between the turning angles and speed that preclude the case of a simple random walk in which successive steps are independent. These correlated random walks are appropriately modelled using an anomalous diffusion model, more precisely using a fractional sub-diffusion model for which the associated stochastic process is characterised by strong memory effects in the probability density function.

Central depression in nucleonic densities: Trend analysis in the nuclear density functional theory approach

NASA Astrophysics Data System (ADS)

Schuetrumpf, B.; Nazarewicz, W.; Reinhard, P.-G.

2017-08-01

Background: The central depression of nucleonic density, i.e., a reduction of density in the nuclear interior, has been attributed to many factors. For instance, bubble structures in superheavy nuclei are believed to be due to the electrostatic repulsion. In light nuclei, the mechanism behind the density reduction in the interior has been discussed in terms of shell effects associated with occupations of s orbits. Purpose: The main objective of this work is to reveal mechanisms behind the formation of central depression in nucleonic densities in light and heavy nuclei. To this end, we introduce several measures of the internal nucleonic density. Through the statistical analysis, we study the information content of these measures with respect to nuclear matter properties. Method: We apply nuclear density functional theory with Skyrme functionals. Using the statistical tools of linear least square regression, we inspect correlations between various measures of central depression and model parameters, including nuclear matter properties. We study bivariate correlations with selected quantities as well as multiple correlations with groups of parameters. Detailed correlation analysis is carried out for 34Si for which a bubble structure has been reported recently, 48Ca, and N =82 , 126, and 184 isotonic chains. Results: We show that the central depression in medium-mass nuclei is very sensitive to shell effects, whereas for superheavy systems it is firmly driven by the electrostatic repulsion. An appreciable semibubble structure in proton density is predicted for 294Og, which is currently the heaviest nucleus known experimentally. Conclusion: Our correlation analysis reveals that the central density indicators in nuclei below 208Pb carry little information on parameters of nuclear matter; they are predominantly driven by shell structure. On the other hand, in the superheavy nuclei there exists a clear relationship between the central nucleonic density and symmetry energy.

Findings regarding the relationships between sociodemographic, psychological, comorbidity factors, and functional status, in geriatric inpatients.

PubMed

Capisizu, Ana; Aurelian, Sorina; Zamfirescu, Andreea; Omer, Ioana; Haras, Monica; Ciobotaru, Camelia; Onose, Liliana; Spircu, Tiberiu; Onose, Gelu

2015-01-01

To assess the impact of socio-demographic and comorbidity factors, and quantified depressive symptoms on disability in inpatients. Observational cross-sectional study, including a number of 80 elderly (16 men, 64 women; mean age 72.48 years; standard deviation 9.95 years) admitted in the Geriatrics Clinic of "St. Luca" Hospital, Bucharest, between May-July, 2012. We used the Functional Independence Measure, Geriatric Depression Scale and an array of socio-demographic and poly-pathology parameters. Statistical analysis included Wilcoxon and Kruskal-Wallis tests for ordinal variables, linear bivariate correlations, general linear model analysis, ANOVA. FIM scores were negatively correlated with age (R=-0.301; 95%CI=-0.439 -0.163; p=0.007); GDS scores had a statistically significant negative correlation (R=-0.322; 95% CI=-0.324 -0.052; p=0.004) with FIM scores. A general linear model, including other variables (gender, age, provenance, matrimonial state, living conditions, education, respectively number of chronic illnesses) as factors, found living conditions (p=0.027) and the combination of matrimonial state and gender (p=0.004) to significantly influence FIM scores. ANOVA showed significant differences in FIM scores stratified by the number of chronic diseases (p=0.035). Our study objectified the negative impact of depression on functional status; interestingly, education had no influence on FIM scores; living conditions and a combination of matrimonial state and gender had an important impact: patients with living spouses showed better functional scores than divorced/widowers; the number of chronic diseases also affected the FIM scores: lower in patients with significant polypathology. These findings should be considered when designing geriatric rehabilitation programs, especially for home--including skilled--cares.

Relating resting-state fMRI and EEG whole-brain connectomes across frequency bands.

PubMed

Deligianni, Fani; Centeno, Maria; Carmichael, David W; Clayden, Jonathan D

2014-01-01

Whole brain functional connectomes hold promise for understanding human brain activity across a range of cognitive, developmental and pathological states. So called resting-state (rs) functional MRI studies have contributed to the brain being considered at a macroscopic scale as a set of interacting regions. Interactions are defined as correlation-based signal measurements driven by blood oxygenation level dependent (BOLD) contrast. Understanding the neurophysiological basis of these measurements is important in conveying useful information about brain function. Local coupling between BOLD fMRI and neurophysiological measurements is relatively well defined, with evidence that gamma (range) frequency EEG signals are the closest correlate of BOLD fMRI changes during cognitive processing. However, it is less clear how whole-brain network interactions relate during rest where lower frequency signals have been suggested to play a key role. Simultaneous EEG-fMRI offers the opportunity to observe brain network dynamics with high spatio-temporal resolution. We utilize these measurements to compare the connectomes derived from rs-fMRI and EEG band limited power (BLP). Merging this multi-modal information requires the development of an appropriate statistical framework. We relate the covariance matrices of the Hilbert envelope of the source localized EEG signal across bands to the covariance matrices derived from rs-fMRI with the means of statistical prediction based on sparse Canonical Correlation Analysis (sCCA). Subsequently, we identify the most prominent connections that contribute to this relationship. We compare whole-brain functional connectomes based on their geodesic distance to reliably estimate the performance of the prediction. The performance of predicting fMRI from EEG connectomes is considerably better than predicting EEG from fMRI across all bands, whereas the connectomes derived in low frequency EEG bands resemble best rs-fMRI connectivity.

Relating resting-state fMRI and EEG whole-brain connectomes across frequency bands

PubMed Central

Deligianni, Fani; Centeno, Maria; Carmichael, David W.; Clayden, Jonathan D.

2014-01-01

Whole brain functional connectomes hold promise for understanding human brain activity across a range of cognitive, developmental and pathological states. So called resting-state (rs) functional MRI studies have contributed to the brain being considered at a macroscopic scale as a set of interacting regions. Interactions are defined as correlation-based signal measurements driven by blood oxygenation level dependent (BOLD) contrast. Understanding the neurophysiological basis of these measurements is important in conveying useful information about brain function. Local coupling between BOLD fMRI and neurophysiological measurements is relatively well defined, with evidence that gamma (range) frequency EEG signals are the closest correlate of BOLD fMRI changes during cognitive processing. However, it is less clear how whole-brain network interactions relate during rest where lower frequency signals have been suggested to play a key role. Simultaneous EEG-fMRI offers the opportunity to observe brain network dynamics with high spatio-temporal resolution. We utilize these measurements to compare the connectomes derived from rs-fMRI and EEG band limited power (BLP). Merging this multi-modal information requires the development of an appropriate statistical framework. We relate the covariance matrices of the Hilbert envelope of the source localized EEG signal across bands to the covariance matrices derived from rs-fMRI with the means of statistical prediction based on sparse Canonical Correlation Analysis (sCCA). Subsequently, we identify the most prominent connections that contribute to this relationship. We compare whole-brain functional connectomes based on their geodesic distance to reliably estimate the performance of the prediction. The performance of predicting fMRI from EEG connectomes is considerably better than predicting EEG from fMRI across all bands, whereas the connectomes derived in low frequency EEG bands resemble best rs-fMRI connectivity. PMID:25221467

Plateletworks platelet function test compared to the thromboelastograph for prediction of postoperative outcomes.

PubMed

Ostrowsky, Jacob; Foes, Jennifer; Warchol, Mark; Tsarovsky, Gary; Blay, Jessica

2004-06-01

Approximately 3.5 million units of platelets are transfused in the United States each year to patients undergoing open-heart surgery with cardiopulmonary bypass (CPB). CPB is a known contributor to platelet loss and platelet dysfunction leading to disruption of hemostasis. Impaired hemostasis results in excess bleeding in 5-25% of all patients undergoing CPB. For this reason, it may be beneficial to measure platelet number and function in these patients. The purpose of this study was to compare the Plateletworks platelet function analyzer to the thromboelastograph (TEG) in predicting postoperatiave hemostatic outcomes as measured by blood product use and chest tube (CT) drainage. This study consisted of 35 adult patients undergoing cardiac surgery with cardiopulmonary bypass at Rush-Presbyterian-Saint Luke's Medical Center (RPSLMC). The Plateletworks and TEG tests were performed preoperatively, after protamine was given, and 24 hours postoperatively on all patients. Plateletworks demonstrated a statistically significant change in platelet function as shown by the adenosine diphosphate (ADP) reagent tube from the preoperative period to the removal of the aortic cross clamp (p = .011). The TEG did not demonstrate a significant change in the k-time and maximum amplitude (MA), but did show a significant change in the alpha-angle from the pre-operative to postoperatiave sample (p = .035). A correlation was found between Plateletworks collagen reagent tubes preoperatively and CT drainage (p = .048, r -0.324). No statistical correlation was established between TEG parameters and CT drainage at any time interval. TEG preoperative MA showed a correlation to receipt of blood products (p = .016). When comparing the Plateletworks to the TEG in this study, the Plateletworks system was a more useful predictor of blood product use and chest tube drainage.

Ex-vivo perfusion machines in kidney transplantation. The significance of the resistivity index

PubMed Central

ELEC, FLORIN IOAN; LUCAN, CIPRIAN; GHERVAN, LIVIU; MUNTEANU, VALENTIN; MOGA, SILVIU; SUCIU, MIHAI; ENACHE, DAN; ELEC, ALINA; MUNTEANU, ADRIANA; BARBOS, ADRIAN; IACOB, GHEORGHITA; LUCAN, MIHAI

2014-01-01

Introduction With a growing shortage of organs for transplantation, finding ways of increasing the donor organ pool remains of utmost importance. Perfusion machines (PM) have been proven to enhance the potential for kidney transplants to function sooner, last longer, giving patients the opportunity for a better life quality. Objective The aim of this study is to evaluate the relation between the resistance index provided by the PM, the postoperative resistance index measured by Doppler ultrasound and the initial graft outcome. Material and method Between January 2012-December 2012, clinical data obtained from 82 consecutive renal transplants from brain death donors (BDD) which underwent PM maintenance were analyzed in a transversal study. Prior transplantation we recorded the solution temperature, filtration rate and the resistance index provided by PM. After the surgical intervention, each patient had standard follow-up. Doppler ultrasound resistivity index (RI) was recorded on the first postoperative day. Results Out of 115 renal transplants, 98 (85.21%) were performed with grafts from BDD. The PM was used for 82 renal grafts. The Doppler resistance index in relation to the resistance index shows a highly statistical correlation by linear regression (R=0.813, p<0.0001). Primary graft function was recorded in 74 patients (90.24%) and it was highly statistically significant correlated with the resistance index measured by PM. Out of 8 patients with primary non-function, 6 patients recovered with normal graft function at one year. Conclusion The resistivity index recorded by the life-port machine is correlated with the vascular resistivity index measured by Doppler ultrasound and thus it may predicts the primary graft outcome. PMID:26527992

Application of Statistic Experimental Design to Assess the Effect of Gammairradiation Pre-Treatment on the Drying Characteristics and Qualities of Wheat

NASA Astrophysics Data System (ADS)

Yu, Yong; Wang, Jun

Wheat, pretreated by 60Co gamma irradiation, was dried by hot-air with irradiation dosage 0-3 kGy, drying temperature 40-60 °C, and initial moisture contents 19-25% (drying basis). The drying characteristics and dried qualities of wheat were evaluated based on drying time, average dehydration rate, wet gluten content (WGC), moisture content of wet gluten (MCWG)and titratable acidity (TA). A quadratic rotation-orthogonal composite experimental design, with three variables (at five levels) and five response functions, and analysis method were employed to study the effect of three variables on the individual response functions. The five response functions (drying time, average dehydration rate, WGC, MCWG, TA) correlated with these variables by second order polynomials consisting of linear, quadratic and interaction terms. A high correlation coefficient indicated the suitability of the second order polynomial to predict these response functions. The linear, interaction and quadratic effects of three variables on the five response functions were all studied.

An analysis of the AVE-SESAME I period using statistical structure and correlation functions. [Atmospheric Variability Experiment-Severe Environmental Storm and Mesoscale Experiment

NASA Technical Reports Server (NTRS)

Fuelberg, H. E.; Meyer, P. J.

1984-01-01

Structure and correlation functions are used to describe atmospheric variability during the 10-11 April day of AVE-SESAME 1979 that coincided with the Red River Valley tornado outbreak. The special mesoscale rawinsonde data are employed in calculations involving temperature, geopotential height, horizontal wind speed and mixing ratio. Functional analyses are performed in both the lower and upper troposphere for the composite 24 h experiment period and at individual 3 h observation times. Results show that mesoscale features are prominent during the composite period. Fields of mixing ratio and horizontal wind speed exhibit the greatest amounts of small-scale variance, whereas temperature and geopotential height contain the least. Results for the nine individual times show that small-scale variance is greatest during the convective outbreak. The functions also are used to estimate random errors in the rawinsonde data. Finally, sensitivity analyses are presented to quantify confidence limits of the structure functions.

Empirical microeconomics action functionals

NASA Astrophysics Data System (ADS)

Baaquie, Belal E.; Du, Xin; Tanputraman, Winson

2015-06-01

A statistical generalization of microeconomics has been made in Baaquie (2013), where the market price of every traded commodity, at each instant of time, is considered to be an independent random variable. The dynamics of commodity market prices is modeled by an action functional-and the focus of this paper is to empirically determine the action functionals for different commodities. The correlation functions of the model are defined using a Feynman path integral. The model is calibrated using the unequal time correlation of the market commodity prices as well as their cubic and quartic moments using a perturbation expansion. The consistency of the perturbation expansion is verified by a numerical evaluation of the path integral. Nine commodities drawn from the energy, metal and grain sectors are studied and their market behavior is described by the model to an accuracy of over 90% using only six parameters. The paper empirically establishes the existence of the action functional for commodity prices that was postulated to exist in Baaquie (2013).

How Volatilities Nonlocal in Time Affect the Price Dynamics in Complex Financial Systems

PubMed Central

Tan, Lei; Zheng, Bo; Chen, Jun-Jie; Jiang, Xiong-Fei

2015-01-01

What is the dominating mechanism of the price dynamics in financial systems is of great interest to scientists. The problem whether and how volatilities affect the price movement draws much attention. Although many efforts have been made, it remains challenging. Physicists usually apply the concepts and methods in statistical physics, such as temporal correlation functions, to study financial dynamics. However, the usual volatility-return correlation function, which is local in time, typically fluctuates around zero. Here we construct dynamic observables nonlocal in time to explore the volatility-return correlation, based on the empirical data of hundreds of individual stocks and 25 stock market indices in different countries. Strikingly, the correlation is discovered to be non-zero, with an amplitude of a few percent and a duration of over two weeks. This result provides compelling evidence that past volatilities nonlocal in time affect future returns. Further, we introduce an agent-based model with a novel mechanism, that is, the asymmetric trading preference in volatile and stable markets, to understand the microscopic origin of the volatility-return correlation nonlocal in time. PMID:25723154

Correlations between ultrasonographic characteristics of corpora lutea and systemic concentrations of progesterone during the discrete stages of corpora lutea lifespan and secretory activity in cyclic ewes.

PubMed

Gallienne, Jacqueline; Gregg, Caroline; LeBlanc, Evan; Yaakob, Norazlin; Wu, Di; Davies, Kate; Rawlings, Norman; Pierson, Roger; Deardon, Rob; Bartlewski, Pawel

2012-05-01

Associations between physical characteristics and functionality of corpora lutea (CL) have previously been reported in monovulatory species, albeit several studies in cattle and humans have refuted the existence of temporal relationships between CL size, echotexture and serum progesterone (P(4)) concentrations. The main objective of the present study was to examine whether or not there were correlations between ultrasonographic image attributes of CL and systemic concentrations of P(4) during the discrete stages of the luteal phase in two breeds of sheep differing in ovulation rates (non-prolific Western White Face [WWF] ewes and prolific Finn [F] sheep). Transrectal ovarian ultrasonography utilized a 7.5-MHz linear-array transducer connected to a portable scanner (Aloka SSD-500) and the images were analyzed using commercially available image analytical software (Image ProPlus(®)) validated for the present application in sheep. The correlations were assessed using the Pearson's Product Moment (PPM) analysis and also, to increase the accuracy of statistical tests, the analysis of covariance (ANCOVA), with the number of CL as a co-factor. In WWF ewes, serum concentrations of P(4) correlated significantly with the total luteal area (TLA) during the CL growth phase (days 3-6; day 0 = ovulation) and functional luteolysis (days 12-15), and with numerical pixel values (NPVs--pixel intensity) during luteolysis; the results obtained by using two different statistical methods were generally similar. In prolific F ewes, serum P(4) concentrations were directly correlated with TLA during CL growth (days 3-6; ANCOVA), functional luteolysis (days 13-14; PPM), and structural CL regression (days 11-14; PPM and ANCOVA), and with NPVs during functional luteolysis (PPM and ANCOVA). We concluded that systemic P(4) concentrations could only be accurately predicted from the changes in luteal area during CL growth and regression, and from NPVs during luteolysis, in both prolific and non-prolific ewes, but the changes in size and echotexture of the luteal glands at mid-cycle were not indicative of serum P(4) concentrations in sheep.

The effects of sex hormones on immune function: a meta-analysis.

PubMed

Foo, Yong Zhi; Nakagawa, Shinichi; Rhodes, Gillian; Simmons, Leigh W

2017-02-01

The effects of sex hormones on immune function have received much attention, especially following the proposal of the immunocompetence handicap hypothesis. Many studies, both experimental and correlational, have been conducted to test the relationship between immune function and the sex hormones testosterone in males and oestrogen in females. However, the results are mixed. We conducted four cross-species meta-analyses to investigate the relationship between sex hormones and immune function: (i) the effect of testosterone manipulation on immune function in males, (ii) the correlation between circulating testosterone level and immune function in males, (iii) the effect of oestrogen manipulation on immune function in females, and (iv) the correlation between circulating oestrogen level and immune function in females. The results from the experimental studies showed that testosterone had a medium-sized immunosuppressive effect on immune function. The effect of oestrogen, on the other hand, depended on the immune measure used. Oestrogen suppressed cell-mediated immune function while reducing parasite loads. The overall correlation (meta-analytic relationship) between circulating sex hormone level and immune function was not statistically significant for either testosterone or oestrogen despite the power of meta-analysis. These results suggest that correlational studies have limited value for testing the effects of sex hormones on immune function. We found little evidence of publication bias in the four data sets using indirect tests. There was a weak and positive relationship between year of publication and effect size for experimental studies of testosterone that became non-significant after we controlled for castration and immune measure, suggesting that the temporal trend was due to changes in these moderators over time. Graphical analyses suggest that the temporal trend was due to an increased use of cytokine measures across time. We found substantial heterogeneity in effect sizes, except in correlational studies of testosterone, even after we accounted for the relevant random and fixed factors. In conclusion, our results provide good evidence that testosterone suppresses immune function and that the effect of oestrogen varies depending on the immune measure used. © 2016 Cambridge Philosophical Society.

Cell response to quasi-monochromatic light with different coherence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Budagovsky, A V; Solovykh, N V; Budagovskaya, O N

The problem of the light coherence effect on the magnitude of the photoinduced cell response is discussed. The origins of ambiguous interpretation of the known experimental results are considered. Using the biological models, essentially differing in anatomy, morphology and biological functions (acrospires of radish, blackberry microsprouts cultivated in vitro, plum pollen), the effect of statistical properties of quasi-monochromatic light (λ{sub max} = 633 nm) on the magnitude of the photoinduced cell response is shown. It is found that for relatively low spatial coherence, the cell functional activity changes insignificantly. The maximal enhancement of growing processes (stimulating effect) is observed whenmore » the coherence length L{sub coh} and the correlation radius r{sub cor} are greater than the cell size, i.e., the entire cell fits into the field coherence volume. In this case, the representative indicators (germination of seeds and pollen, the spears length) exceeds those of non-irradiated objects by 1.7 – 3.9 times. For more correct assessment of the effect of light statistical properties on photocontrol processes, it is proposed to replace the qualitative description (coherent – incoherent) with the quantitative one, using the determination of spatial and temporal correlation functions and comparing them with the characteristic dimensions of the biological structures, e.g., the cell size. (biophotonics)« less

A statistical approach to develop a detailed soot growth model using PAH characteristics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raj, Abhijeet; Celnik, Matthew; Shirley, Raphael

A detailed PAH growth model is developed, which is solved using a kinetic Monte Carlo algorithm. The model describes the structure and growth of planar PAH molecules, and is referred to as the kinetic Monte Carlo-aromatic site (KMC-ARS) model. A detailed PAH growth mechanism based on reactions at radical sites available in the literature, and additional reactions obtained from quantum chemistry calculations are used to model the PAH growth processes. New rates for the reactions involved in the cyclodehydrogenation process for the formation of 6-member rings on PAHs are calculated in this work based on density functional theory simulations. Themore » KMC-ARS model is validated by comparing experimentally observed ensembles on PAHs with the computed ensembles for a C{sub 2}H{sub 2} and a C{sub 6}H{sub 6} flame at different heights above the burner. The motivation for this model is the development of a detailed soot particle population balance model which describes the evolution of an ensemble of soot particles based on their PAH structure. However, at present incorporating such a detailed model into a population balance is computationally unfeasible. Therefore, a simpler model referred to as the site-counting model has been developed, which replaces the structural information of the PAH molecules by their functional groups augmented with statistical closure expressions. This closure is obtained from the KMC-ARS model, which is used to develop correlations and statistics in different flame environments which describe such PAH structural information. These correlations and statistics are implemented in the site-counting model, and results from the site-counting model and the KMC-ARS model are in good agreement. Additionally the effect of steric hindrance in large PAH structures is investigated and correlations for sites unavailable for reaction are presented. (author)« less

Random-phase metasurfaces at optical wavelengths

NASA Astrophysics Data System (ADS)

Pors, Anders; Ding, Fei; Chen, Yiting; Radko, Ilya P.; Bozhevolnyi, Sergey I.

2016-06-01

Random-phase metasurfaces, in which the constituents scatter light with random phases, have the property that an incident plane wave will diffusely scatter, hereby leading to a complex far-field response that is most suitably described by statistical means. In this work, we present and exemplify the statistical description of the far-field response, particularly highlighting how the response for polarised and unpolarised light might be alike or different depending on the correlation of scattering phases for two orthogonal polarisations. By utilizing gap plasmon-based metasurfaces, consisting of an optically thick gold film overlaid by a subwavelength thin glass spacer and an array of gold nanobricks, we design and realize random-phase metasurfaces at a wavelength of 800 nm. Optical characterisation of the fabricated samples convincingly demonstrates the diffuse scattering of reflected light, with statistics obeying the theoretical predictions. We foresee the use of random-phase metasurfaces for camouflage applications and as high-quality reference structures in dark-field microscopy, while the control of the statistics for polarised and unpolarised light might find usage in security applications. Finally, by incorporating a certain correlation between scattering by neighbouring metasurface constituents new types of functionalities can be realised, such as a Lambertian reflector.

Statistics of Optical Coherence Tomography Data From Human Retina

PubMed Central

de Juan, Joaquín; Ferrone, Claudia; Giannini, Daniela; Huang, David; Koch, Giorgio; Russo, Valentina; Tan, Ou; Bruni, Carlo

2010-01-01

Optical coherence tomography (OCT) has recently become one of the primary methods for noninvasive probing of the human retina. The pseudoimage formed by OCT (the so-called B-scan) varies probabilistically across pixels due to complexities in the measurement technique. Hence, sensitive automatic procedures of diagnosis using OCT may exploit statistical analysis of the spatial distribution of reflectance. In this paper, we perform a statistical study of retinal OCT data. We find that the stretched exponential probability density function can model well the distribution of intensities in OCT pseudoimages. Moreover, we show a small, but significant correlation between neighbor pixels when measuring OCT intensities with pixels of about 5 µm. We then develop a simple joint probability model for the OCT data consistent with known retinal features. This model fits well the stretched exponential distribution of intensities and their spatial correlation. In normal retinas, fit parameters of this model are relatively constant along retinal layers, but varies across layers. However, in retinas with diabetic retinopathy, large spikes of parameter modulation interrupt the constancy within layers, exactly where pathologies are visible. We argue that these results give hope for improvement in statistical pathology-detection methods even when the disease is in its early stages. PMID:20304733

Effects of Diabetic Ketoacidosis on Visual and Verbal Neurocognitive Function in Young Patients Presenting with New-Onset Type 1 Diabetes.

PubMed

Jessup, Ashley B; Grimley, Mary Beth; Meyer, Echo; Passmore, Gregory P; Belger, Ayşenil; Hoffman, William H; Çalıkoğlu, Ali S

2015-09-01

To evaluate the effects of diabetic ketoacidosis (DKA) on neurocognitive functions in children and adolescents presenting with new-onset type 1 diabetes. Newly diagnosed patients were divided into two groups: those with DKA and those without DKA (non-DKA). Following metabolic stabilization, the patients took a mini-mental status exam prior to undergoing a baseline battery of cognitive tests that evaluated visual and verbal cognitive tasks. Follow-up testing was performed 8-12 weeks after diagnosis. Patients completed an IQ test at follow-up. There was no statistical difference between the DKA and non-DKA groups neither in alertness at baseline testing nor in an IQ test at follow-up. The DKA group had significantly lower baseline scores than the non-DKA group for the visual cognitive tasks of design recognition, design memory and the composite visual memory index (VMI). At follow-up, Design Recognition remained statistically lower in the DKA group, but the design memory and the VMI tasks returned to statistical parity between the two groups. No significant differences were found in verbal cognitive tasks at baseline or follow-up between the two groups. Direct correlations were present for the admission CO2 and the visual cognitive tasks of VMI, design memory and design recognition. Direct correlations were also present for admission pH and VMI, design memory and picture memory. Pediatric patients presenting with newly diagnosed type 1 diabetes and severe but uncomplicated DKA showed a definite trend for lower cognitive functioning when compared to the age-matched patients without DKA.

Breaking of scale invariance in the time dependence of correlation functions in isotropic and homogeneous turbulence

NASA Astrophysics Data System (ADS)

Tarpin, Malo; Canet, Léonie; Wschebor, Nicolás

2018-05-01

In this paper, we present theoretical results on the statistical properties of stationary, homogeneous, and isotropic turbulence in incompressible flows in three dimensions. Within the framework of the non-perturbative renormalization group, we derive a closed renormalization flow equation for a generic n-point correlation (and response) function for large wave-numbers with respect to the inverse integral scale. The closure is obtained from a controlled expansion and relies on extended symmetries of the Navier-Stokes field theory. It yields the exact leading behavior of the flow equation at large wave-numbers |p→ i| and for arbitrary time differences ti in the stationary state. Furthermore, we obtain the form of the general solution of the corresponding fixed point equation, which yields the analytical form of the leading wave-number and time dependence of n-point correlation functions, for large wave-numbers and both for small ti and in the limit ti → ∞. At small ti, the leading contribution at large wave-numbers is logarithmically equivalent to -α (ɛL ) 2 /3|∑tip→ i|2, where α is a non-universal constant, L is the integral scale, and ɛ is the mean energy injection rate. For the 2-point function, the (tp)2 dependence is known to originate from the sweeping effect. The derived formula embodies the generalization of the effect of sweeping to n-point correlation functions. At large wave-numbers and large ti, we show that the ti2 dependence in the leading order contribution crosses over to a |ti| dependence. The expression of the correlation functions in this regime was not derived before, even for the 2-point function. Both predictions can be tested in direct numerical simulations and in experiments.

Functional parameter screening for predicting durability of rolling sliding contacts with different surface finishes

NASA Astrophysics Data System (ADS)

Dimkovski, Z.; Lööf, P.-J.; Rosén, B.-G.; Nilsson, P. H.

2018-06-01

The reliability and lifetime of machine elements such as gears and rolling bearings depend on their wear and fatigue resistance. In order to screen the wear and surface damage, three finishing processes: (i) brushing, (ii) manganese phosphating and (iii) shot peening were applied on three disc pairs and long-term tested on a twin-disc tribometer. In this paper, the elastic contact of the disc surfaces (measured after only few revolutions) was simulated and a number of functional and roughness parameters were correlated. The functional parameters consisted of subsurface stresses at different depths and a new parameter called ‘pressure spikes’ factor’. The new parameter is derived from the pressure distribution and takes into account the proximity and magnitude of the pressure spikes. Strong correlations were found among the pressure spikes’ factor and surface peak/height parameters. The orthogonal shear stresses and Von Mises stresses at the shallowest depths under the surface have shown the highest correlations but no good correlations were found when the statistics of the whole stress fields was analyzed. The use of the new parameter offers a fast way to screen the durability of the contacting surfaces operating at similar conditions.

Statistical Analysis of Large Scale Structure by the Discrete Wavelet Transform

NASA Astrophysics Data System (ADS)

Pando, Jesus

1997-10-01

The discrete wavelet transform (DWT) is developed as a general statistical tool for the study of large scale structures (LSS) in astrophysics. The DWT is used in all aspects of structure identification including cluster analysis, spectrum and two-point correlation studies, scale-scale correlation analysis and to measure deviations from Gaussian behavior. The techniques developed are demonstrated on 'academic' signals, on simulated models of the Lymanα (Lyα) forests, and on observational data of the Lyα forests. This technique can detect clustering in the Ly-α clouds where traditional techniques such as the two-point correlation function have failed. The position and strength of these clusters in both real and simulated data is determined and it is shown that clusters exist on scales as large as at least 20 h-1 Mpc at significance levels of 2-4 σ. Furthermore, it is found that the strength distribution of the clusters can be used to distinguish between real data and simulated samples even where other traditional methods have failed to detect differences. Second, a method for measuring the power spectrum of a density field using the DWT is developed. All common features determined by the usual Fourier power spectrum can be calculated by the DWT. These features, such as the index of a power law or typical scales, can be detected even when the samples are geometrically complex, the samples are incomplete, or the mean density on larger scales is not known (the infrared uncertainty). Using this method the spectra of Ly-α forests in both simulated and real samples is calculated. Third, a method for measuring hierarchical clustering is introduced. Because hierarchical evolution is characterized by a set of rules of how larger dark matter halos are formed by the merging of smaller halos, scale-scale correlations of the density field should be one of the most sensitive quantities in determining the merging history. We show that these correlations can be completely determined by the correlations between discrete wavelet coefficients on adjacent scales and at nearly the same spatial position, Cj,j+12/cdot2. Scale-scale correlations on two samples of the QSO Ly-α forests absorption spectra are computed. Lastly, higher order statistics are developed to detect deviations from Gaussian behavior. These higher order statistics are necessary to fully characterize the Ly-α forests because the usual 2nd order statistics, such as the two-point correlation function or power spectrum, give inconclusive results. It is shown how this technique takes advantage of the locality of the DWT to circumvent the central limit theorem. A non-Gaussian spectrum is defined and this spectrum reveals not only the magnitude, but the scales of non-Gaussianity. When applied to simulated and observational samples of the Ly-α clouds, it is found that different popular models of structure formation have different spectra while two, independent observational data sets, have the same spectra. Moreover, the non-Gaussian spectra of real data sets are significantly different from the spectra of various possible random samples. (Abstract shortened by UMI.)

Analysis of the two-point velocity correlations in turbulent boundary layer flows

NASA Technical Reports Server (NTRS)

Oberlack, M.

1995-01-01

The general objective of the present work is to explore the use of Rapid Distortion Theory (RDT) in analysis of the two-point statistics of the log-layer. RDT is applicable only to unsteady flows where the non-linear turbulence-turbulence interaction can be neglected in comparison to linear turbulence-mean interactions. Here we propose to use RDT to examine the structure of the large energy-containing scales and their interaction with the mean flow in the log-region. The contents of the work are twofold: First, two-point analysis methods will be used to derive the law-of-the-wall for the special case of zero mean pressure gradient. The basic assumptions needed are one-dimensionality in the mean flow and homogeneity of the fluctuations. It will be shown that a formal solution of the two-point correlation equation can be obtained as a power series in the von Karman constant, known to be on the order of 0.4. In the second part, a detailed analysis of the two-point correlation function in the log-layer will be given. The fundamental set of equations and a functional relation for the two-point correlation function will be derived. An asymptotic expansion procedure will be used in the log-layer to match Kolmogorov's universal range and the one-point correlations to the inviscid outer region valid for large correlation distances.

Novel application of windowed beamforming function imaging for FLGPR

NASA Astrophysics Data System (ADS)

Xique, Ismael J.; Burns, Joseph W.; Thelen, Brian J.; LaRose, Ryan M.

2018-04-01

Backprojection of cross-correlated array data, using algorithms such as coherent interferometric imaging (Borcea, et al., 2006), has been advanced as a method to improve the statistical stability of images of targets in an inhomogeneous medium. Recently, the Windowed Beamforming Energy (WBE) function algorithm has been introduced as a functionally equivalent approach, which is significantly less computationally burdensome (Borcea, et al., 2011). WBE produces similar results through the use of a quadratic function summing signals after beamforming in transmission and reception, and windowing in the time domain. We investigate the application of WBE to improve the detection of buried targets with forward looking ground penetrating MIMO radar (FLGPR) data. The formulation of WBE as well the software implementation of WBE for the FLGPR data collection will be discussed. WBE imaging results are compared to standard backprojection and Coherence Factor imaging. Additionally, the effectiveness of WBE on field-collected data is demonstrated qualitatively through images and quantitatively through the use of a CFAR statistic on buried targets of a variety of contrast levels.

Assessing dynamics, spatial scale, and uncertainty in task-related brain network analyses

PubMed Central

Stephen, Emily P.; Lepage, Kyle Q.; Eden, Uri T.; Brunner, Peter; Schalk, Gerwin; Brumberg, Jonathan S.; Guenther, Frank H.; Kramer, Mark A.

2014-01-01

The brain is a complex network of interconnected elements, whose interactions evolve dynamically in time to cooperatively perform specific functions. A common technique to probe these interactions involves multi-sensor recordings of brain activity during a repeated task. Many techniques exist to characterize the resulting task-related activity, including establishing functional networks, which represent the statistical associations between brain areas. Although functional network inference is commonly employed to analyze neural time series data, techniques to assess the uncertainty—both in the functional network edges and the corresponding aggregate measures of network topology—are lacking. To address this, we describe a statistically principled approach for computing uncertainty in functional networks and aggregate network measures in task-related data. The approach is based on a resampling procedure that utilizes the trial structure common in experimental recordings. We show in simulations that this approach successfully identifies functional networks and associated measures of confidence emergent during a task in a variety of scenarios, including dynamically evolving networks. In addition, we describe a principled technique for establishing functional networks based on predetermined regions of interest using canonical correlation. Doing so provides additional robustness to the functional network inference. Finally, we illustrate the use of these methods on example invasive brain voltage recordings collected during an overt speech task. The general strategy described here—appropriate for static and dynamic network inference and different statistical measures of coupling—permits the evaluation of confidence in network measures in a variety of settings common to neuroscience. PMID:24678295

Assessing dynamics, spatial scale, and uncertainty in task-related brain network analyses.

PubMed

Stephen, Emily P; Lepage, Kyle Q; Eden, Uri T; Brunner, Peter; Schalk, Gerwin; Brumberg, Jonathan S; Guenther, Frank H; Kramer, Mark A

2014-01-01

The brain is a complex network of interconnected elements, whose interactions evolve dynamically in time to cooperatively perform specific functions. A common technique to probe these interactions involves multi-sensor recordings of brain activity during a repeated task. Many techniques exist to characterize the resulting task-related activity, including establishing functional networks, which represent the statistical associations between brain areas. Although functional network inference is commonly employed to analyze neural time series data, techniques to assess the uncertainty-both in the functional network edges and the corresponding aggregate measures of network topology-are lacking. To address this, we describe a statistically principled approach for computing uncertainty in functional networks and aggregate network measures in task-related data. The approach is based on a resampling procedure that utilizes the trial structure common in experimental recordings. We show in simulations that this approach successfully identifies functional networks and associated measures of confidence emergent during a task in a variety of scenarios, including dynamically evolving networks. In addition, we describe a principled technique for establishing functional networks based on predetermined regions of interest using canonical correlation. Doing so provides additional robustness to the functional network inference. Finally, we illustrate the use of these methods on example invasive brain voltage recordings collected during an overt speech task. The general strategy described here-appropriate for static and dynamic network inference and different statistical measures of coupling-permits the evaluation of confidence in network measures in a variety of settings common to neuroscience.

Correlation between the single, high dose of ingested baclofen and clinical symptoms.

PubMed

Anand, Jacek Sein; Zając, Maciej; Waldman, Wojciech; Wojtyła, Andrzej; Biliński, Przemysław; Jaworska-Łuczak, Barbara

2017-12-23

Baclofen is a drug used mainly to treat muscle spasticity. Its overdose can lead to life-threatening clinical symptoms, including acute respiratory failure requiring mechanical ventilation. The aim of this study was to assess the prevalence of selected clinical symptoms associated with baclofen poisoning comparing to an ingested dose. 60 cases of oral baclofen poisoning were analyzed. Gender, age distribution, and correlation between the dose of ingested baclofen were studied, as well as and following clinical parameters: degree of altered consciousness, heart rate, blood pressure, presence of acute respiratory failure, duration of mechanical ventilation, and presence of psychotic symptoms. The study found statistically significant correlations between dosage of ingested baclofen and presence of acute respiratory failure, as well as duration of mechanical ventilation. No statistically significant correlations were found between the dose of ingested baclofen and presence of hypertension, bradycardia, acute psychotic symptoms, or level of consciousness disturbance. However, it was found that patients who suffered from hypertension, bradycardia, and altered mental status ingested a larger dose of baclofen. There is a statistically significant correlation between the dose of ingested baclofen and the presence of acute respiratory failure, and duration of mechanical ventilation. Patients who have taken a single dose of baclofen of 200 mg, or higher, should be managed in centres able to provide continuous monitoring of life functions. Those with a higher level of a single dose of baclofen ingestion (>500 mg), should be hospitalized in a Toxicology Unit or Intensive Care Unit able to provide airway support and mechanical ventilation.

Quantum noise of a Bose-Einstein condensate in an optical cavity, correlations, and entanglement

NASA Astrophysics Data System (ADS)

Szirmai, G.; Nagy, D.; Domokos, P.

2010-04-01

A Bose-Einstein condensate of ultracold atoms inside the field of a laser-driven optical cavity exhibits dispersive optical bistability. We describe this system by using mean-field approximation and by analyzing the correlation functions of the linearized quantum fluctuations around the mean-field solution. The entanglement and the statistics of the atom-field quadratures are given in the stationary state. It is shown that the mean-field solution, that is, the Bose-Einstein condensate, is robust against entanglement generation for most of the phase diagram.

Exploration of particle production mechanisms via angular correlations of π, K, p, Λ with ALICE in pp collisions at √S = 7 TeV

NASA Astrophysics Data System (ADS)

Janik, Małgorzata Anna

2018-02-01

Two-particle correlations as a function of Δη and Δφ are used in many colliding systems to study a wide range of physical phenomena. Examples include the collective behavior of the quark-gluon plasma medium, jets, quantum statistics or Coulomb effects, conservation laws, and resonance decays. In this work, measurements of the correlations of identified particles and their antiparticles (for π, K, p, Λ) are reported in pp collisions at √s = 7 TeV at low transverse momenta. The analysis reveals differences in particle production between baryons and mesons. The correlation functions for mesons exhibit the expected peak dominated by the effects of mini-jet fragmentation and are reproduced well by general purpose Monte Carlo generators. For baryon pairs where both particles have the same baryon number, an anti-correlation structure is observed instead of a peak centered at (Δη, Δφ) = (0, 0); an observation which presents a challenge to models typically used to describe pp data (PYTHIA, PHOJET). This baryon anti-correlation is further interpreted in the context of baryon production mechanisms in the fragmentation processes.

Body-mass dependence of age-related deterioration in human muscular function.

PubMed

Meltzer, D E

1996-04-01

Maximal anaerobic power of human muscles declines with increasing chronological age and is correlated with body mass. This study investigated whether the rate of deterioration in human muscular function among trained weight lifters is also correlated with body mass. Cross-sectional analysis of performance data of over 1,100 Masters competitors in Olympic-style weight lifting was carried out; eight body-weight classes and six age groups were represented. Two-lift total data (sum of snatch and clean and jerk lifts) were analyzed. Mean deterioration rates in the performance of athletes of widely diverse body masses were compared over the following age ranges: 42-57, 42-62, and 42-67 yr. No statistically significant correlation (P < 0.05) was found between rate of performance decline and body mass. The relationship between body mass and the magnitude of age-related variation of deterioration rate was also studied; no significant correlation was found. Previous studies have demonstrated that performance in Olympic-style weight lifting is correlated with maximal anaerobic muscular power. This leads us to suggest that the age-related deterioration rate of anaerobic power in trained subjects may not be correlated with the body mass of the individual.

Experiment design for pilot identification in compensatory tracking tasks

NASA Technical Reports Server (NTRS)

Wells, W. R.

1976-01-01

A design criterion for input functions in laboratory tracking tasks resulting in efficient parameter estimation is formulated. The criterion is that the statistical correlations between pairs of parameters be reduced in order to minimize the problem of nonuniqueness in the extraction process. The effectiveness of the method is demonstrated for a lower order dynamic system.

Evaluation of sexual functions of the pregnant women.

PubMed

Tosun Güleroğlu, Funda; Gördeles Beşer, Nalan

2014-01-01

Pregnant women may avoid sexual intercourse or may unavoidably undergo problems in their sexual lives because of various complaints they suffer from. The study aims to evaluate sexual functions of the pregnant women and to determine the factors that negatively affect their sexual health. This is a descriptive research study conducted to evaluate sexual functions of pregnant women. Three hundred six pregnant women admitted to the Women Birth Polyclinics within the Women Birth and Children's Hospital between October 1, 2010 and March 31, 2011 were included in the study. The data were gathered using a personal information form and the Female Sexual Function Index (FSFI). Kruskall-Wallis variance analysis and Mann-Whitney U-tests were used for the statistical analysis. The main outcome is an assessment of the FSFI domains in pregnancy and relationships between pregnancy complaints and sexual functions. The results indicated that the mean age of the pregnant women was 25.6 ± 5.4 and their length of marriage was 5.93 ± 5.4 years. The study revealed that 88.9% of the pregnant women had sexual desire disorders, 86.9% had sexual arousal disorder, 42.8% had lubrication disorders, 69.6% had orgasm disorders, and 48% had sexual satisfaction disorders. Statistically significant differences were found in correlations between FSFI medians and the characteristics of the pregnant women in terms of age, educational level, length and type of marriage, and gestational week. There were also statistically significant differences in correlations between the pregnancy characteristics in terms of backache, constipation, respiratory difficulty, leg ache, and cramp problems (P < 0.05). It was determined that the sexual lives of the pregnant women were negatively affected not only by factors such as old age, low educational status, arranged marriages lasting for more than 10 years, undesired pregnancy, and gestational week but also by health problems such as backache, constipation, respiratory difficulty, leg ache, and cramp problems. © 2013 International Society for Sexual Medicine.

Civil construction work: The unseen contributor to the occupational and global disease burden

PubMed Central

Sitalakshmi, R.; Saikumar, P.; Jeyachandran, P.; Manoharan; Thangavel; Thomas, Jayakar

2016-01-01

Background: Construction industry is the second largest employment giving industry in India with many semi-skilled or unskilled workers taking up the occupation for livelihood without any training and proper guidance. Aim: To evaluate the pathogenic association of cement exposure to occupational contact dermatoses as evidenced by immune markers and to correlate their pulmonary functions with years of exposure to cement. Setting and Design: This was a cross-sectional study conducted among randomly selected cement workers. Methods and material: Evaluation of socioeconomic status (SES) and years of exposure of cement workers was done using a questionnaire. Clinical examination of skin lesions and strip patch test with application of potassium dichromate on unexposed skin was performed. Results were interpreted after 48 hours. Absolute eosinophil count (AEC) and IgE levels measured, and spirometric evaluation was performed. Statistical Analysis: Analysis of variance and Pearson's correlation test were used for data analysis. P < 0.05 was considered to be statistically significant. Results: Clinically, skin lesions were noticed in 51%, elevated AEC in 47%, and raised Anti IgE in 73%. Two participants developed positive reactions to the skin strip patch test. Duration of exposure to cement and SES were compared with clinical skin lesions. Spirometry result was normal in 81%, obstruction in 8%, restriction in 10%, and mixed pattern in 1%. Forced expiratory volume at 1.0 second, forced expiratory flow (25–75%), and  (PEFR) Peak Expiratory Flow Rate were markedly reduced with years of exposure. Workers who had greater skin lesions and with increase in exposure had increased AEC and IgE levels, although statistically not significant. Conclusions: Exposure to cement and poor SES is strongly correlated to increased prevalence of skin lesions and reduced pulmonary functions. PMID:28194084

Can Retinal Ganglion Cell Dipoles Seed Iso-Orientation Domains in the Visual Cortex?

PubMed Central

Schottdorf, Manuel; Eglen, Stephen J.; Wolf, Fred; Keil, Wolfgang

2014-01-01

It has been argued that the emergence of roughly periodic orientation preference maps (OPMs) in the primary visual cortex (V1) of carnivores and primates can be explained by a so-called statistical connectivity model. This model assumes that input to V1 neurons is dominated by feed-forward projections originating from a small set of retinal ganglion cells (RGCs). The typical spacing between adjacent cortical orientation columns preferring the same orientation then arises via Moiré-Interference between hexagonal ON/OFF RGC mosaics. While this Moiré-Interference critically depends on long-range hexagonal order within the RGC mosaics, a recent statistical analysis of RGC receptive field positions found no evidence for such long-range positional order. Hexagonal order may be only one of several ways to obtain spatially repetitive OPMs in the statistical connectivity model. Here, we investigate a more general requirement on the spatial structure of RGC mosaics that can seed the emergence of spatially repetitive cortical OPMs, namely that angular correlations between so-called RGC dipoles exhibit a spatial structure similar to that of OPM autocorrelation functions. Both in cat beta cell mosaics as well as primate parasol receptive field mosaics we find that RGC dipole angles are spatially uncorrelated. To help assess the level of these correlations, we introduce a novel point process that generates mosaics with realistic nearest neighbor statistics and a tunable degree of spatial correlations of dipole angles. Using this process, we show that given the size of available data sets, the presence of even weak angular correlations in the data is very unlikely. We conclude that the layout of ON/OFF ganglion cell mosaics lacks the spatial structure necessary to seed iso-orientation domains in the primary visual cortex. PMID:24475081

Can retinal ganglion cell dipoles seed iso-orientation domains in the visual cortex?

PubMed

Schottdorf, Manuel; Eglen, Stephen J; Wolf, Fred; Keil, Wolfgang

2014-01-01

It has been argued that the emergence of roughly periodic orientation preference maps (OPMs) in the primary visual cortex (V1) of carnivores and primates can be explained by a so-called statistical connectivity model. This model assumes that input to V1 neurons is dominated by feed-forward projections originating from a small set of retinal ganglion cells (RGCs). The typical spacing between adjacent cortical orientation columns preferring the same orientation then arises via Moiré-Interference between hexagonal ON/OFF RGC mosaics. While this Moiré-Interference critically depends on long-range hexagonal order within the RGC mosaics, a recent statistical analysis of RGC receptive field positions found no evidence for such long-range positional order. Hexagonal order may be only one of several ways to obtain spatially repetitive OPMs in the statistical connectivity model. Here, we investigate a more general requirement on the spatial structure of RGC mosaics that can seed the emergence of spatially repetitive cortical OPMs, namely that angular correlations between so-called RGC dipoles exhibit a spatial structure similar to that of OPM autocorrelation functions. Both in cat beta cell mosaics as well as primate parasol receptive field mosaics we find that RGC dipole angles are spatially uncorrelated. To help assess the level of these correlations, we introduce a novel point process that generates mosaics with realistic nearest neighbor statistics and a tunable degree of spatial correlations of dipole angles. Using this process, we show that given the size of available data sets, the presence of even weak angular correlations in the data is very unlikely. We conclude that the layout of ON/OFF ganglion cell mosaics lacks the spatial structure necessary to seed iso-orientation domains in the primary visual cortex.

Validation of the DRAGON Score in a Chinese Population to Predict Functional Outcome of Intravenous Thrombolysis-Treated Stroke Patients.

PubMed

Zhang, Xinmiao; Liao, Xiaoling; Wang, Chunjuan; Liu, Liping; Wang, Chunxue; Zhao, Xingquan; Pan, Yuesong; Wang, Yilong; Wang, Yongjun

2015-08-01

The DRAGON score predicts functional outcome of ischemic stroke patients treated with intravenous thrombolysis. Our aim was to evaluate its utility in a Chinese stroke population. Patients with acute ischemic stroke treated with intravenous thrombolysis were prospectively registered in the Thrombolysis Implementation and Monitor of acute ischemic Stroke in China. We excluded patients with basilar artery occlusion and missing data, leaving 970 eligible patients. We calculated the DRAGON score, and the clinical outcome was measured by the modified Rankin Scale at 3 months. Model discrimination was quantified by calculating the C statistic. Calibration was assessed using Pearson correlation coefficient. The C statistic was .73 (.70-.76) for good outcome and .75 (.70-.79) for miserable outcome. Proportions of patients with good outcome were 94%, 83%, 70%, and 0% for 0 to 1, 2, 3, and 8 to 10 score points, respectively. Proportions of patients with miserable outcome were 0%, 3%, 9%, and 50% for 0 to 1, 2, 3, and 8 to 10 points, respectively. There was high correlation between predicted and observed probability of 3-month favorable and miserable outcome in the external validation cohort (Pearson correlation coefficient, .98 and .98, respectively, both P < .0001). The DRAGON score showed good performance to predict functional outcome after tissue-type plasminogen activator treatment in the Chinese population. This study demonstrated the accuracy and usability of the DRAGON score in the Chinese population in daily practice. Copyright © 2015 National Stroke Association. Published by Elsevier Inc. All rights reserved.

Correlation of the VEMP score, ambulation and upper extremity function in clinically isolated syndrome.

PubMed

Crnošija, Luka; Krbot Skorić, Magdalena; Gabelić, Tereza; Adamec, Ivan; Brinar, Vesna; Habek, Mario

2015-12-15

To investigate the correlation of the vestibular evoked myogenic potential (VEMP) score with Timed 25-Foot Walk (T25FW), 9-Hole Peg Test (9HPT), Paced Auditory Serial Addition Test (PASAT) and EDSS in patients with multiple sclerosis (MS). This prospective, cross sectional study included 52 patients with clinically isolated syndrome (CIS). Cervical VEMP (cVEMP) and ocular VEMP (oVEMP), analyzed in the form of the cVEMP, oVEMP and VEMP scores, T25FW, 9HPT, PASAT and Expanded Disability Status Scale (EDSS) were performed. The only predictor of walking impairment in this study was general disability as measured by the EDSS, after controlling for age, gender, PASAT and EDSS the effect of VEMP score was non-significant (p=0.419). 9HPT of the dominant hand did not correlate with the oVEMP score (rs=0.258, p=0.065), however after controlling for age, gender, PASAT and EDSS, the effect of the oVEMP score on 9HPT of the dominant hand was statistically significant (p=0.017). After controlling for age, gender and oVEMP score, the effect of the PASAT on 9HPT variable for the non-dominant hand was statistically significant (p=0.001). We found possible effects of brainstem dysfunction on walking impairment, however they were not seen after correction for EDSS and cognitive dysfunction. On the other hand, dominant hand function seems to be influenced by upper brainstem dysfunction measured with oVEMP, while cognitive dysfunction is related to non-dominant hand function. Copyright © 2015 Elsevier B.V. All rights reserved.

Whole-brain diffusion tensor imaging in correlation to visual-evoked potentials in multiple sclerosis: a tract-based spatial statistics analysis.

PubMed

Lobsien, D; Ettrich, B; Sotiriou, K; Classen, J; Then Bergh, F; Hoffmann, K-T

2014-01-01

Functional correlates of microstructural damage of the brain affected by MS are incompletely understood. The purpose of this study was to evaluate correlations of visual-evoked potentials with microstructural brain changes as determined by DTI in patients with demyelinating central nervous disease. Sixty-one patients with clinically isolated syndrome or MS were prospectively recruited. The mean P100 visual-evoked potential latencies of the right and left eyes of each patient were calculated and used for the analysis. For DTI acquisition, a single-shot echo-planar imaging pulse sequence with 80 diffusion directions was performed at 3T. Fractional anisotropy, radial diffusivity, and axial diffusivity were calculated and correlated with mean P100 visual-evoked potentials by tract-based spatial statistics. Significant negative correlations between mean P100 visual-evoked potentials and fractional anisotropy and significant positive correlations between mean P100 visual-evoked potentials and radial diffusivity were found widespread over the whole brain. The highest significance was found in the optic radiation, frontoparietal white matter, and corpus callosum. Significant positive correlations between mean P100 visual-evoked potentials and axial diffusivity were less widespread, notably sparing the optic radiation. Microstructural changes of the whole brain correlated significantly with mean P100 visual-evoked potentials. The distribution of the correlations showed clear differences among axial diffusivity, fractional anisotropy, and radial diffusivity, notably in the optic radiation. This finding suggests a stronger correlation of mean P100 visual-evoked potentials to demyelination than to axonal damage. © 2014 by American Journal of Neuroradiology.

Evaluation of bone mineral density and related parameters in patients with haemophilia: a single center cross-sectional study

PubMed Central

Kiper Unal, Hatice Demet; Comert Ozkan, Melda; Atilla, Fatos Dilan; Demirci, Zuhal; Soyer, Nur; Yildirim Simsir, Ilgin; Omur, Ozgur; Capaci, Kazim; Saydam, Guray; Sahin, Fahri

2017-01-01

Haemophilia has been associated with low bone mineral density (BMD) probably due to some predisposing factors. The aim of this study was to evaluate the relationship between BMD and potential clinical predictors in adult haemophilic patients. Fortynine patients with moderate and severe haemophilia were enrolled. BMD was measured by Dual Energy X-Ray Absorptiometry (DXA) and blood tests were performed for vitamin D, calcium, phosphore, alkaline phosphatase and parathormone levels. Functional Independence Score in Haemophilia (FISH) and Haemophilia Joint Health Score (HJHS) were used to assess musculoskeletal functions. Body mass index (BMI), Hepatitis C virus (HCV)/Human immunodeficiency virus (HIV) seropositivity and smoking status were also recorded. BMD was found lower than expected for reference age in 34.8% of patients of less than 50 years old. In patients older than 50 years, 66.6% of them had osteoporosis and 33.3% of them had normal BMD. FISH score was statistically significant correlated with BMD of total hip (TH) and femur neck (FN) but not with lumbar spine (LS). In eligible patients, there was also a statistically significant correlation between BMD of TH and HJHS. Vitamine D deficiency was common and found in 77.5% of patients, although there was no significant correlation with BMD. Also no correlation was found between BMD and blood tests, HCV/HIV status, BMI and smoking. This study confirmed that patients with haemophilia have an increased prevelance of low BMD even in younger group. Our results showed that there are significant correlations between FISH score and BMD of TH and FN and also between HJHS score and BMD of TH. Thus, using scoring systems may be beneficial as a simple predictors of BMD to reflect the severity of haemophilic arthropathy. PMID:29181264

Evaluation of bone mineral density and related parameters in patients with haemophilia: a single center cross-sectional study.

PubMed

Kiper Unal, Hatice Demet; Comert Ozkan, Melda; Atilla, Fatos Dilan; Demirci, Zuhal; Soyer, Nur; Yildirim Simsir, Ilgin; Omur, Ozgur; Capaci, Kazim; Saydam, Guray; Sahin, Fahri

2017-01-01

Haemophilia has been associated with low bone mineral density (BMD) probably due to some predisposing factors. The aim of this study was to evaluate the relationship between BMD and potential clinical predictors in adult haemophilic patients. Fortynine patients with moderate and severe haemophilia were enrolled. BMD was measured by Dual Energy X-Ray Absorptiometry (DXA) and blood tests were performed for vitamin D, calcium, phosphore, alkaline phosphatase and parathormone levels. Functional Independence Score in Haemophilia (FISH) and Haemophilia Joint Health Score (HJHS) were used to assess musculoskeletal functions. Body mass index (BMI), Hepatitis C virus (HCV)/Human immunodeficiency virus (HIV) seropositivity and smoking status were also recorded. BMD was found lower than expected for reference age in 34.8% of patients of less than 50 years old. In patients older than 50 years, 66.6% of them had osteoporosis and 33.3% of them had normal BMD. FISH score was statistically significant correlated with BMD of total hip (TH) and femur neck (FN) but not with lumbar spine (LS). In eligible patients, there was also a statistically significant correlation between BMD of TH and HJHS. Vitamine D deficiency was common and found in 77.5% of patients, although there was no significant correlation with BMD. Also no correlation was found between BMD and blood tests, HCV/HIV status, BMI and smoking. This study confirmed that patients with haemophilia have an increased prevelance of low BMD even in younger group. Our results showed that there are significant correlations between FISH score and BMD of TH and FN and also between HJHS score and BMD of TH. Thus, using scoring systems may be beneficial as a simple predictors of BMD to reflect the severity of haemophilic arthropathy.

Helicity statistics in homogeneous and isotropic turbulence and turbulence models

NASA Astrophysics Data System (ADS)

Sahoo, Ganapati; De Pietro, Massimo; Biferale, Luca

2017-02-01

We study the statistical properties of helicity in direct numerical simulations of fully developed homogeneous and isotropic turbulence and in a class of turbulence shell models. We consider correlation functions based on combinations of vorticity and velocity increments that are not invariant under mirror symmetry. We also study the scaling properties of high-order structure functions based on the moments of the velocity increments projected on a subset of modes with either positive or negative helicity (chirality). We show that mirror symmetry is recovered at small scales, i.e., chiral terms are subleading and they are well captured by a dimensional argument plus anomalous corrections. These findings are also supported by a high Reynolds numbers study of helical shell models with the same chiral symmetry of Navier-Stokes equations.

EvolQG - An R package for evolutionary quantitative genetics

PubMed Central

Melo, Diogo; Garcia, Guilherme; Hubbe, Alex; Assis, Ana Paula; Marroig, Gabriel

2016-01-01

We present an open source package for performing evolutionary quantitative genetics analyses in the R environment for statistical computing. Evolutionary theory shows that evolution depends critically on the available variation in a given population. When dealing with many quantitative traits this variation is expressed in the form of a covariance matrix, particularly the additive genetic covariance matrix or sometimes the phenotypic matrix, when the genetic matrix is unavailable and there is evidence the phenotypic matrix is sufficiently similar to the genetic matrix. Given this mathematical representation of available variation, the \\textbf{EvolQG} package provides functions for calculation of relevant evolutionary statistics; estimation of sampling error; corrections for this error; matrix comparison via correlations, distances and matrix decomposition; analysis of modularity patterns; and functions for testing evolutionary hypotheses on taxa diversification. PMID:27785352

Vision-related quality of life in patients with chronic central serous chorioretinopathy.

PubMed

Türkcü, Fatih Mehmet; Şahin, Alparslan; Bez, Yasin; Yüksel, Harun; Cinar, Yasin; Kürşat Cingü, Abdullah; Çaça, İhsan

2015-07-01

To evaluate vision-related quality of life in patients with chronic central serous chorioretinopathy (CSCR). Prospective, cross-sectional study. The interviewer-administered National Eye Institute visual function questionnaire (NEI-VFQ-25) was used in 30 adult consecutive patients with chronic CSCR patients. The controls were 30 gender- and age-matched people with normal visual function who came from the same socioeconomic and educational background as the participants. Patients with CSCR had statistically significant lower scores than controls for all the subscales, except for general health. In the study group, all subscale scores of vision-related quality of life, except general health, showed statistically significant negative correlations with the visual acuity. People with CSCR have worse vision-related quality of life than people without the condition.

Effects of a finite outer scale on the measurement of atmospheric-turbulence statistics with a Hartmann wave-front sensor.

PubMed

Feng, Shen; Wenhan, Jiang

2002-06-10

Phase-structure and aperture-averaged slope-correlated functions with a finite outer scale are derived based on the Taylor hypothesis and a generalized spectrum, such as the von Kármán modal. The effects of the finite outer scale on measuring and determining the character of atmospheric-turbulence statistics are shown especially for an approximately 4-m class telescope and subaperture. The phase structure function and atmospheric coherent length based on the Kolmogorov model are approximations of the formalism we have derived. The analysis shows that it cannot be determined whether the deviation from the power-law parameter of Kolmogorov turbulence is caused by real variations of the spectrum or by the effect of the finite outer scale.

Connection between two statistical approaches for the modelling of particle velocity and concentration distributions in turbulent flow: The mesoscopic Eulerian formalism and the two-point probability density function method

NASA Astrophysics Data System (ADS)

Simonin, Olivier; Zaichik, Leonid I.; Alipchenkov, Vladimir M.; Février, Pierre

2006-12-01

The objective of the paper is to elucidate a connection between two approaches that have been separately proposed for modelling the statistical spatial properties of inertial particles in turbulent fluid flows. One of the approaches proposed recently by Février, Simonin, and Squires [J. Fluid Mech. 533, 1 (2005)] is based on the partitioning of particle turbulent velocity field into spatially correlated (mesoscopic Eulerian) and random-uncorrelated (quasi-Brownian) components. The other approach stems from a kinetic equation for the two-point probability density function of the velocity distributions of two particles [Zaichik and Alipchenkov, Phys. Fluids 15, 1776 (2003)]. Comparisons between these approaches are performed for isotropic homogeneous turbulence and demonstrate encouraging agreement.

Information properties of morphologically complex words modulate brain activity during word reading

PubMed Central

Hultén, Annika; Lehtonen, Minna; Lagus, Krista; Salmelin, Riitta

2018-01-01

Abstract Neuroimaging studies of the reading process point to functionally distinct stages in word recognition. Yet, current understanding of the operations linked to those various stages is mainly descriptive in nature. Approaches developed in the field of computational linguistics may offer a more quantitative approach for understanding brain dynamics. Our aim was to evaluate whether a statistical model of morphology, with well‐defined computational principles, can capture the neural dynamics of reading, using the concept of surprisal from information theory as the common measure. The Morfessor model, created for unsupervised discovery of morphemes, is based on the minimum description length principle and attempts to find optimal units of representation for complex words. In a word recognition task, we correlated brain responses to word surprisal values derived from Morfessor and from other psycholinguistic variables that have been linked with various levels of linguistic abstraction. The magnetoencephalography data analysis focused on spatially, temporally and functionally distinct components of cortical activation observed in reading tasks. The early occipital and occipito‐temporal responses were correlated with parameters relating to visual complexity and orthographic properties, whereas the later bilateral superior temporal activation was correlated with whole‐word based and morphological models. The results show that the word processing costs estimated by the statistical Morfessor model are relevant for brain dynamics of reading during late processing stages. PMID:29524274

Weak lensing mass map and peak statistics in Canada-France-Hawaii Telescope Stripe 82 survey

NASA Astrophysics Data System (ADS)

Shan, Huan Yuan; Kneib, Jean-Paul; Comparat, Johan; Jullo, Eric; Charbonnier, Aldée; Erben, Thomas; Makler, Martin; Moraes, Bruno; Van Waerbeke, Ludovic; Courbin, Frédéric; Meylan, Georges; Tao, Charling; Taylor, James E.

2014-08-01

We present a weak lensing mass map covering ˜124 deg2 of the Canada-France-Hawaii Telescope Stripe 82 Survey (CS82). We study the statistics of rare peaks in the map, including peak abundance, the peak-peak correlation functions and the tangential-shear profiles around peaks. We find that the abundance of peaks detected in CS82 is consistent with predictions from a Λ cold dark matter cosmological model, once noise effects are properly included. The correlation functions of peaks with different signal-to-noise ratio (SNR) are well described by power laws, and there is a clear cross-correlation between the Sloan Digital Sky Survey III/Constant Mass galaxies and high SNR peaks. The tangential-shear profiles around peaks increase with peak SNR. We fit analytical models to the tangential-shear profiles, including a projected singular isothermal sphere (SIS) model and a projected Navarro, Frenk & White (NFW) model, plus a two-halo term. For the high SNR peaks, the SIS model is rejected at ˜3σ. The NFW model plus a two-halo term gives more acceptable fits to the data. Some peaks match the positions of optically detected clusters, while others are relatively dark. Comparing dark and matched peaks, we find a difference in lensing signal of a factor of 2, suggesting that about half of the dark peaks are false detections.

Experiments with a three-dimensional statistical objective analysis scheme using FGGE data

NASA Technical Reports Server (NTRS)

Baker, Wayman E.; Bloom, Stephen C.; Woollen, John S.; Nestler, Mark S.; Brin, Eugenia

1987-01-01

A three-dimensional (3D), multivariate, statistical objective analysis scheme (referred to as optimum interpolation or OI) has been developed for use in numerical weather prediction studies with the FGGE data. Some novel aspects of the present scheme include: (1) a multivariate surface analysis over the oceans, which employs an Ekman balance instead of the usual geostrophic relationship, to model the pressure-wind error cross correlations, and (2) the capability to use an error correlation function which is geographically dependent. A series of 4-day data assimilation experiments are conducted to examine the importance of some of the key features of the OI in terms of their effects on forecast skill, as well as to compare the forecast skill using the OI with that utilizing a successive correction method (SCM) of analysis developed earlier. For the three cases examined, the forecast skill is found to be rather insensitive to varying the error correlation function geographically. However, significant differences are noted between forecasts from a two-dimensional (2D) version of the OI and those from the 3D OI, with the 3D OI forecasts exhibiting better forecast skill. The 3D OI forecasts are also more accurate than those from the SCM initial conditions. The 3D OI with the multivariate oceanic surface analysis was found to produce forecasts which were slightly more accurate, on the average, than a univariate version.

Information properties of morphologically complex words modulate brain activity during word reading.

PubMed

Hakala, Tero; Hultén, Annika; Lehtonen, Minna; Lagus, Krista; Salmelin, Riitta

2018-06-01

Neuroimaging studies of the reading process point to functionally distinct stages in word recognition. Yet, current understanding of the operations linked to those various stages is mainly descriptive in nature. Approaches developed in the field of computational linguistics may offer a more quantitative approach for understanding brain dynamics. Our aim was to evaluate whether a statistical model of morphology, with well-defined computational principles, can capture the neural dynamics of reading, using the concept of surprisal from information theory as the common measure. The Morfessor model, created for unsupervised discovery of morphemes, is based on the minimum description length principle and attempts to find optimal units of representation for complex words. In a word recognition task, we correlated brain responses to word surprisal values derived from Morfessor and from other psycholinguistic variables that have been linked with various levels of linguistic abstraction. The magnetoencephalography data analysis focused on spatially, temporally and functionally distinct components of cortical activation observed in reading tasks. The early occipital and occipito-temporal responses were correlated with parameters relating to visual complexity and orthographic properties, whereas the later bilateral superior temporal activation was correlated with whole-word based and morphological models. The results show that the word processing costs estimated by the statistical Morfessor model are relevant for brain dynamics of reading during late processing stages. © 2018 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Random field assessment of nanoscopic inhomogeneity of bone.

PubMed

Dong, X Neil; Luo, Qing; Sparkman, Daniel M; Millwater, Harry R; Wang, Xiaodu

2010-12-01

Bone quality is significantly correlated with the inhomogeneous distribution of material and ultrastructural properties (e.g., modulus and mineralization) of the tissue. Current techniques for quantifying inhomogeneity consist of descriptive statistics such as mean, standard deviation and coefficient of variation. However, these parameters do not describe the spatial variations of bone properties. The objective of this study was to develop a novel statistical method to characterize and quantitatively describe the spatial variation of bone properties at ultrastructural levels. To do so, a random field defined by an exponential covariance function was used to represent the spatial uncertainty of elastic modulus by delineating the correlation of the modulus at different locations in bone lamellae. The correlation length, a characteristic parameter of the covariance function, was employed to estimate the fluctuation of the elastic modulus in the random field. Using this approach, two distribution maps of the elastic modulus within bone lamellae were generated using simulation and compared with those obtained experimentally by a combination of atomic force microscopy and nanoindentation techniques. The simulation-generated maps of elastic modulus were in close agreement with the experimental ones, thus validating the random field approach in defining the inhomogeneity of elastic modulus in lamellae of bone. Indeed, generation of such random fields will facilitate multi-scale modeling of bone in more pragmatic details. Copyright © 2010 Elsevier Inc. All rights reserved.

Estimating and Identifying Unspecified Correlation Structure for Longitudinal Data

PubMed Central

Hu, Jianhua; Wang, Peng; Qu, Annie

2014-01-01

Identifying correlation structure is important to achieving estimation efficiency in analyzing longitudinal data, and is also crucial for drawing valid statistical inference for large size clustered data. In this paper, we propose a nonparametric method to estimate the correlation structure, which is applicable for discrete longitudinal data. We utilize eigenvector-based basis matrices to approximate the inverse of the empirical correlation matrix and determine the number of basis matrices via model selection. A penalized objective function based on the difference between the empirical and model approximation of the correlation matrices is adopted to select an informative structure for the correlation matrix. The eigenvector representation of the correlation estimation is capable of reducing the risk of model misspecification, and also provides useful information on the specific within-cluster correlation pattern of the data. We show that the proposed method possesses the oracle property and selects the true correlation structure consistently. The proposed method is illustrated through simulations and two data examples on air pollution and sonar signal studies. PMID:26361433

A statistical analysis of the elastic distortion and dislocation density fields in deformed crystals

DOE PAGES

Mohamed, Mamdouh S.; Larson, Bennett C.; Tischler, Jonathan Z.; ...

2015-05-18

The statistical properties of the elastic distortion fields of dislocations in deforming crystals are investigated using the method of discrete dislocation dynamics to simulate dislocation structures and dislocation density evolution under tensile loading. Probability distribution functions (PDF) and pair correlation functions (PCF) of the simulated internal elastic strains and lattice rotations are generated for tensile strain levels up to 0.85%. The PDFs of simulated lattice rotation are compared with sub-micrometer resolution three-dimensional X-ray microscopy measurements of rotation magnitudes and deformation length scales in 1.0% and 2.3% compression strained Cu single crystals to explore the linkage between experiment and the theoreticalmore » analysis. The statistical properties of the deformation simulations are analyzed through determinations of the Nye and Kr ner dislocation density tensors. The significance of the magnitudes and the length scales of the elastic strain and the rotation parts of dislocation density tensors are demonstrated, and their relevance to understanding the fundamental aspects of deformation is discussed.« less

Lagrangian statistics in compressible isotropic homogeneous turbulence

NASA Astrophysics Data System (ADS)

Yang, Yantao; Wang, Jianchun; Shi, Yipeng; Chen, Shiyi

2011-11-01

In this work we conducted the Direct Numerical Simulation (DNS) of a forced compressible isotropic homogeneous turbulence and investigated the flow statistics from the Lagrangian point of view, namely the statistics is computed following the passive tracers trajectories. The numerical method combined the Eulerian field solver which was developed by Wang et al. (2010, J. Comp. Phys., 229, 5257-5279), and a Lagrangian module for tracking the tracers and recording the data. The Lagrangian probability density functions (p.d.f.'s) have then been calculated for both kinetic and thermodynamic quantities. In order to isolate the shearing part from the compressing part of the flow, we employed the Helmholtz decomposition to decompose the flow field (mainly the velocity field) into the solenoidal and compressive parts. The solenoidal part was compared with the incompressible case, while the compressibility effect showed up in the compressive part. The Lagrangian structure functions and cross-correlation between various quantities will also be discussed. This work was supported in part by the China's Turbulence Program under Grant No.2009CB724101.

New insights into time series analysis. II - Non-correlated observations

NASA Astrophysics Data System (ADS)

Ferreira Lopes, C. E.; Cross, N. J. G.

2017-08-01

Context. Statistical parameters are used to draw conclusions in a vast number of fields such as finance, weather, industrial, and science. These parameters are also used to identify variability patterns on photometric data to select non-stochastic variations that are indicative of astrophysical effects. New, more efficient, selection methods are mandatory to analyze the huge amount of astronomical data. Aims: We seek to improve the current methods used to select non-stochastic variations on non-correlated data. Methods: We used standard and new data-mining parameters to analyze non-correlated data to find the best way to discriminate between stochastic and non-stochastic variations. A new approach that includes a modified Strateva function was performed to select non-stochastic variations. Monte Carlo simulations and public time-domain data were used to estimate its accuracy and performance. Results: We introduce 16 modified statistical parameters covering different features of statistical distribution such as average, dispersion, and shape parameters. Many dispersion and shape parameters are unbound parameters, I.e. equations that do not require the calculation of average. Unbound parameters are computed with single loop and hence decreasing running time. Moreover, the majority of these parameters have lower errors than previous parameters, which is mainly observed for distributions with few measurements. A set of non-correlated variability indices, sample size corrections, and a new noise model along with tests of different apertures and cut-offs on the data (BAS approach) are introduced. The number of mis-selections are reduced by about 520% using a single waveband and 1200% combining all wavebands. On the other hand, the even-mean also improves the correlated indices introduced in Paper I. The mis-selection rate is reduced by about 18% if the even-mean is used instead of the mean to compute the correlated indices in the WFCAM database. Even-statistics allows us to improve the effectiveness of both correlated and non-correlated indices. Conclusions: The selection of non-stochastic variations is improved by non-correlated indices. The even-averages provide a better estimation of mean and median for almost all statistical distributions analyzed. The correlated variability indices, which are proposed in the first paper of this series, are also improved if the even-mean is used. The even-parameters will also be useful for classifying light curves in the last step of this project. We consider that the first step of this project, where we set new techniques and methods that provide a huge improvement on the efficiency of selection of variable stars, is now complete. Many of these techniques may be useful for a large number of fields. Next, we will commence a new step of this project regarding the analysis of period search methods.

Aggregation models on hypergraphs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alberici, Diego, E-mail: diego.alberici2@unibo.it; Contucci, Pierluigi, E-mail: pierluigi.contucci@unibo.it; Mingione, Emanuele, E-mail: emanuele.mingione2@unibo.it

2017-01-15

Following a newly introduced approach by Rasetti and Merelli we investigate the possibility to extract topological information about the space where interacting systems are modelled. From the statistical datum of their observable quantities, like the correlation functions, we show how to reconstruct the activities of their constitutive parts which embed the topological information. The procedure is implemented on a class of polymer models on hypergraphs with hard-core interactions. We show that the model fulfils a set of iterative relations for the partition function that generalise those introduced by Heilmann and Lieb for the monomer–dimer case. After translating those relations intomore » structural identities for the correlation functions we use them to test the precision and the robustness of the inverse problem. Finally the possible presence of a further interaction of peer-to-peer type is considered and a criterion to discover it is identified.« less

Blind channel estimation and deconvolution in colored noise using higher-order cumulants

NASA Astrophysics Data System (ADS)

Tugnait, Jitendra K.; Gummadavelli, Uma

1994-10-01

Existing approaches to blind channel estimation and deconvolution (equalization) focus exclusively on channel or inverse-channel impulse response estimation. It is well-known that the quality of the deconvolved output depends crucially upon the noise statistics also. Typically it is assumed that the noise is white and the signal-to-noise ratio is known. In this paper we remove these restrictions. Both the channel impulse response and the noise model are estimated from the higher-order (fourth, e.g.) cumulant function and the (second-order) correlation function of the received data via a least-squares cumulant/correlation matching criterion. It is assumed that the noise higher-order cumulant function vanishes (e.g., Gaussian noise, as is the case for digital communications). Consistency of the proposed approach is established under certain mild sufficient conditions. The approach is illustrated via simulation examples involving blind equalization of digital communications signals.

FGWAS: Functional genome wide association analysis.

PubMed

Huang, Chao; Thompson, Paul; Wang, Yalin; Yu, Yang; Zhang, Jingwen; Kong, Dehan; Colen, Rivka R; Knickmeyer, Rebecca C; Zhu, Hongtu

2017-10-01

Functional phenotypes (e.g., subcortical surface representation), which commonly arise in imaging genetic studies, have been used to detect putative genes for complexly inherited neuropsychiatric and neurodegenerative disorders. However, existing statistical methods largely ignore the functional features (e.g., functional smoothness and correlation). The aim of this paper is to develop a functional genome-wide association analysis (FGWAS) framework to efficiently carry out whole-genome analyses of functional phenotypes. FGWAS consists of three components: a multivariate varying coefficient model, a global sure independence screening procedure, and a test procedure. Compared with the standard multivariate regression model, the multivariate varying coefficient model explicitly models the functional features of functional phenotypes through the integration of smooth coefficient functions and functional principal component analysis. Statistically, compared with existing methods for genome-wide association studies (GWAS), FGWAS can substantially boost the detection power for discovering important genetic variants influencing brain structure and function. Simulation studies show that FGWAS outperforms existing GWAS methods for searching sparse signals in an extremely large search space, while controlling for the family-wise error rate. We have successfully applied FGWAS to large-scale analysis of data from the Alzheimer's Disease Neuroimaging Initiative for 708 subjects, 30,000 vertices on the left and right hippocampal surfaces, and 501,584 SNPs. Copyright © 2017 Elsevier Inc. All rights reserved.

Structures of Neural Correlation and How They Favor Coding

PubMed Central

Franke, Felix; Fiscella, Michele; Sevelev, Maksim; Roska, Botond; Hierlemann, Andreas; da Silveira, Rava Azeredo

2017-01-01

Summary The neural representation of information suffers from “noise”—the trial-to-trial variability in the response of neurons. The impact of correlated noise upon population coding has been debated, but a direct connection between theory and experiment remains tenuous. Here, we substantiate this connection and propose a refined theoretical picture. Using simultaneous recordings from a population of direction-selective retinal ganglion cells, we demonstrate that coding benefits from noise correlations. The effect is appreciable already in small populations, yet it is a collective phenomenon. Furthermore, the stimulus-dependent structure of correlation is key. We develop simple functional models that capture the stimulus-dependent statistics. We then use them to quantify the performance of population coding, which depends upon interplays of feature sensitivities and noise correlations in the population. Because favorable structures of correlation emerge robustly in circuits with noisy, nonlinear elements, they will arise and benefit coding beyond the confines of retina. PMID:26796692

The mechanics of state dependent neural correlations

PubMed Central

Doiron, Brent; Litwin-Kumar, Ashok; Rosenbaum, Robert; Ocker, Gabriel K.; Josić, Krešimir

2016-01-01

Simultaneous recordings from large neural populations are becoming increasingly common. An important feature of the population activity are the trial-to-trial correlated fluctuations of the spike train outputs of recorded neuron pairs. Like the firing rate of single neurons, correlated activity can be modulated by a number of factors, from changes in arousal and attentional state to learning and task engagement. However, the network mechanisms that underlie these changes are not fully understood. We review recent theoretical results that identify three separate biophysical mechanisms that modulate spike train correlations: changes in input correlations, internal fluctuations, and the transfer function of single neurons. We first examine these mechanisms in feedforward pathways, and then show how the same approach can explain the modulation of correlations in recurrent networks. Such mechanistic constraints on the modulation of population activity will be important in statistical analyses of high dimensional neural data. PMID:26906505

Entropy of the Bose-Einstein-condensate ground state: Correlation versus ground-state entropy

NASA Astrophysics Data System (ADS)

Kim, Moochan B.; Svidzinsky, Anatoly; Agarwal, Girish S.; Scully, Marlan O.

2018-01-01

Calculation of the entropy of an ideal Bose-Einstein condensate (BEC) in a three-dimensional trap reveals unusual, previously unrecognized, features of the canonical ensemble. It is found that, for any temperature, the entropy of the Bose gas is equal to the entropy of the excited particles although the entropy of the particles in the ground state is nonzero. We explain this by considering the correlations between the ground-state particles and particles in the excited states. These correlations lead to a correlation entropy which is exactly equal to the contribution from the ground state. The correlations themselves arise from the fact that we have a fixed number of particles obeying quantum statistics. We present results for correlation functions between the ground and excited states in a Bose gas, so as to clarify the role of fluctuations in the system. We also report the sub-Poissonian nature of the ground-state fluctuations.

Magnetic resonance spectroscopy of normal appearing white matter in early relapsing-remitting multiple sclerosis: correlations between disability and spectroscopy

PubMed Central

Ruiz-Peña, Juan Luis; Piñero, Pilar; Sellers, Guillermo; Argente, Joaquín; Casado, Alfredo; Foronda, Jesus; Uclés, Antonio; Izquierdo, Guillermo

2004-01-01

Background What currently appears to be irreversible axonal loss in normal appearing white matter, measured by proton magnetic resonance spectroscopy is of great interest in the study of Multiple Sclerosis. Our aim is to determine the axonal damage in normal appearing white matter measured by magnetic resonance spectroscopy and to correlate this with the functional disability measured by Multiple Sclerosis Functional Composite scale, Neurological Rating Scale, Ambulation Index scale, and Expanded Disability Scale Score. Methods Thirty one patients (9 male and 22 female) with relapsing remitting Multiple Sclerosis and a Kurtzke Expanded Disability Scale Score of 0–5.5 were recruited from four hospitals in Andalusia, Spain and included in the study. Magnetic resonance spectroscopy scans and neurological disability assessments were performed the same day. Results A statistically significant correlation was found (r = -0.38 p < 0.05) between disability (measured by Expanded Disability Scale Score) and N-Acetyl Aspartate (NAA/Cr ratio) levels in normal appearing white matter in these patients. No correlation was found between the NAA/Cr ratio and disability measured by any of the other disability assessment scales. Conclusions There is correlation between disability (measured by Expanded Disability Scale Score) and the NAA/Cr ratio in normal appearing white matter. The lack of correlation between the NAA/Cr ratio and the Multiple Sclerosis Functional Composite score indicates that the Multiple Sclerosis Functional Composite is not able to measure irreversible disability and would be more useful as a marker in stages where axonal damage is not a predominant factor. PMID:15191618

Accuracy Evaluation of the Unified P-Value from Combining Correlated P-Values

PubMed Central

Alves, Gelio; Yu, Yi-Kuo

2014-01-01

Meta-analysis methods that combine -values into a single unified -value are frequently employed to improve confidence in hypothesis testing. An assumption made by most meta-analysis methods is that the -values to be combined are independent, which may not always be true. To investigate the accuracy of the unified -value from combining correlated -values, we have evaluated a family of statistical methods that combine: independent, weighted independent, correlated, and weighted correlated -values. Statistical accuracy evaluation by combining simulated correlated -values showed that correlation among -values can have a significant effect on the accuracy of the combined -value obtained. Among the statistical methods evaluated those that weight -values compute more accurate combined -values than those that do not. Also, statistical methods that utilize the correlation information have the best performance, producing significantly more accurate combined -values. In our study we have demonstrated that statistical methods that combine -values based on the assumption of independence can produce inaccurate -values when combining correlated -values, even when the -values are only weakly correlated. Therefore, to prevent from drawing false conclusions during hypothesis testing, our study advises caution be used when interpreting the -value obtained from combining -values of unknown correlation. However, when the correlation information is available, the weighting-capable statistical method, first introduced by Brown and recently modified by Hou, seems to perform the best amongst the methods investigated. PMID:24663491

Correlation of RNA secondary structure statistics with thermodynamic stability and applications to folding.

PubMed

Wu, Johnny C; Gardner, David P; Ozer, Stuart; Gutell, Robin R; Ren, Pengyu

2009-08-28

The accurate prediction of the secondary and tertiary structure of an RNA with different folding algorithms is dependent on several factors, including the energy functions. However, an RNA higher-order structure cannot be predicted accurately from its sequence based on a limited set of energy parameters. The inter- and intramolecular forces between this RNA and other small molecules and macromolecules, in addition to other factors in the cell such as pH, ionic strength, and temperature, influence the complex dynamics associated with transition of a single stranded RNA to its secondary and tertiary structure. Since all of the factors that affect the formation of an RNAs 3D structure cannot be determined experimentally, statistically derived potential energy has been used in the prediction of protein structure. In the current work, we evaluate the statistical free energy of various secondary structure motifs, including base-pair stacks, hairpin loops, and internal loops, using their statistical frequency obtained from the comparative analysis of more than 50,000 RNA sequences stored in the RNA Comparative Analysis Database (rCAD) at the Comparative RNA Web (CRW) Site. Statistical energy was computed from the structural statistics for several datasets. While the statistical energy for a base-pair stack correlates with experimentally derived free energy values, suggesting a Boltzmann-like distribution, variation is observed between different molecules and their location on the phylogenetic tree of life. Our statistical energy values calculated for several structural elements were utilized in the Mfold RNA-folding algorithm. The combined statistical energy values for base-pair stacks, hairpins and internal loop flanks result in a significant improvement in the accuracy of secondary structure prediction; the hairpin flanks contribute the most.

Normalization methods in time series of platelet function assays

PubMed Central

Van Poucke, Sven; Zhang, Zhongheng; Roest, Mark; Vukicevic, Milan; Beran, Maud; Lauwereins, Bart; Zheng, Ming-Hua; Henskens, Yvonne; Lancé, Marcus; Marcus, Abraham

2016-01-01

Abstract Platelet function can be quantitatively assessed by specific assays such as light-transmission aggregometry, multiple-electrode aggregometry measuring the response to adenosine diphosphate (ADP), arachidonic acid, collagen, and thrombin-receptor activating peptide and viscoelastic tests such as rotational thromboelastometry (ROTEM). The task of extracting meaningful statistical and clinical information from high-dimensional data spaces in temporal multivariate clinical data represented in multivariate time series is complex. Building insightful visualizations for multivariate time series demands adequate usage of normalization techniques. In this article, various methods for data normalization (z-transformation, range transformation, proportion transformation, and interquartile range) are presented and visualized discussing the most suited approach for platelet function data series. Normalization was calculated per assay (test) for all time points and per time point for all tests. Interquartile range, range transformation, and z-transformation demonstrated the correlation as calculated by the Spearman correlation test, when normalized per assay (test) for all time points. When normalizing per time point for all tests, no correlation could be abstracted from the charts as was the case when using all data as 1 dataset for normalization. PMID:27428217

Influence of nonlinear effects on statistical properties of the radiation from SASE FEL

NASA Astrophysics Data System (ADS)

Saldin, E. L.; Schneidmiller, E. A.; Yurkov, M. V.

1998-02-01

The paper presents analysis of statistical properties of the radiation from self-amplified spontaneous emission (SASE) free-electron laser operating in nonlinear mode. The present approach allows one to calculate the following statistical properties of the SASE FEL radiation: time and spectral field correlation functions, distribution of the fluctuations of the instantaneous radiation power, distribution of the energy in the electron bunch, distribution of the radiation energy after monochromator installed at the FEL amplifier exit and the radiation spectrum. It has been observed that the statistics of the instantaneous radiation power from SASE FEL operating in the nonlinear regime changes significantly with respect to the linear regime. All numerical results presented in the paper have been calculated for the 70 nm SASE FEL at the TESLA Test Facility under construction at DESY.

Jordanian Men's and Women's Attitudes Toward Intimate Partner Violence and Its Correlates With Family Functioning and Demographics.

PubMed

Alzoubi, Fatmeh Ahmad; Ali, Reem Ahmad

2018-04-01

Jordan is a developing country in the Middle East and, much like other countries in the world, has high rates of intimate partner violence (IPV). Little information is available on Jordanian men's and women's attitudes toward IPV. The purpose of this study is to examine men's and women's attitudes toward IPV in Jordan and its relationship with some demographics and family functioning. A descriptive cross-sectional correlational design with a sample of 401 men and women was used. Descriptive statistics ( M, SD), Pearson r, t test, and ANOVA were used. The results indicated that Jordanian men and women have a lower score of IPVAS, 40.06 ( SD = 8.20), indicating lower acceptance of IPV compared with the literature. Family functioning was 3.12 ( SD = 0.46), indicating more healthy families. Family functioning was negatively correlated with IPVAS scores ( r = -.22, p = .00). All demographic variables showed small to moderate correlations with IPVAS. Education for both study participants and their spouses had a negative correlation with IPVAS ( r = -.27, p = .00) and ( r = -.20, p = .00), respectively. Male participants, individuals who were living with extended family, and those living in rural areas had significantly high IPVAS scores, indicating more accepting attitudes toward IPV. Practitioners should provide families with education on the methods of conflict resolution, effective communication within the family, problem-solving approaches, equal role distribution, and appropriate styles of establishing a family.

Cardiac magnetic resonance analysis of right ventricular function: comparison of quantification in the short-axis and 4-chamber planes.

PubMed

Souto Bayarri, M; Masip Capdevila, L; Remuiñan Pereira, C; Suárez-Cuenca, J J; Martínez Monzonís, A; Couto Pérez, M I; Carreira Villamor, J M

2015-01-01

To compare the methods of right ventricle segmentation in the short-axis and 4-chamber planes in cardiac magnetic resonance imaging and to correlate the findings with those of the tricuspid annular plane systolic excursion (TAPSE) method in echocardiography. We used a 1.5T MRI scanner to study 26 patients with diverse cardiovascular diseases. In all MRI studies, we obtained cine-mode images from the base to the apex in both the short-axis and 4-chamber planes using steady-state free precession sequences and 6mm thick slices. In all patients, we quantified the end-diastolic volume, end-systolic volume, and the ejection fraction of the right ventricle. On the same day as the cardiac magnetic resonance imaging study, 14 patients also underwent echocardiography with TAPSE calculation of right ventricular function. No statistically significant differences were found in the volumes and function of the right ventricle calculated using the 2 segmentation methods. The correlation between the volume estimations by the two segmentation methods was excellent (r=0,95); the correlation for the ejection fraction was slightly lower (r=0,8). The correlation between the cardiac magnetic resonance imaging estimate of right ventricular ejection fraction and TAPSE was very low (r=0,2, P<.01). Both ventricular segmentation methods quantify right ventricular function adequately. The correlation with the echocardiographic method is low. Copyright © 2012 SERAM. Published by Elsevier España, S.L.U. All rights reserved.

Applying the multivariate time-rescaling theorem to neural population models

PubMed Central

Gerhard, Felipe; Haslinger, Robert; Pipa, Gordon

2011-01-01

Statistical models of neural activity are integral to modern neuroscience. Recently, interest has grown in modeling the spiking activity of populations of simultaneously recorded neurons to study the effects of correlations and functional connectivity on neural information processing. However any statistical model must be validated by an appropriate goodness-of-fit test. Kolmogorov-Smirnov tests based upon the time-rescaling theorem have proven to be useful for evaluating point-process-based statistical models of single-neuron spike trains. Here we discuss the extension of the time-rescaling theorem to the multivariate (neural population) case. We show that even in the presence of strong correlations between spike trains, models which neglect couplings between neurons can be erroneously passed by the univariate time-rescaling test. We present the multivariate version of the time-rescaling theorem, and provide a practical step-by-step procedure for applying it towards testing the sufficiency of neural population models. Using several simple analytically tractable models and also more complex simulated and real data sets, we demonstrate that important features of the population activity can only be detected using the multivariate extension of the test. PMID:21395436

Searches for correlation between UHECR events and high-energy gamma-ray Fermi-LAT data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Álvarez, Ezequiel; Cuoco, Alessandro; Mirabal, Nestor

The astrophysical sources responsible for ultra high-energy cosmic rays (UHECRs) continue to be one of the most intriguing mysteries in astrophysics. We present a comprehensive search for correlations between high-energy (∼> 1 GeV) gamma-ray events from the Fermi Large Area Telescope (LAT) and UHECRs (∼> 60 EeV) detected by the Telescope Array and the Pierre Auger Observatory. We perform two separate searches. First, we conduct a standard cross-correlation analysis between the arrival directions of 148 UHECRs and 360 gamma-ray sources in the Second Catalog of Hard Fermi-LAT sources (2FHL). Second, we search for a possible correlation between UHECR directions andmore » unresolved Fermi -LAT gamma-ray emission. For the latter, we use three different methods: a stacking technique with both a model-dependent and model-independent background estimate, and a cross-correlation function analysis. We also test for statistically significant excesses in gamma rays from signal regions centered on Cen A and the Telescope Array hotspot. No significant correlation is found in any of the analyses performed, except a weak (∼< 2σ) hint of signal with the correlation function method on scales ∼ 1°. Upper limits on the flux of possible power-law gamma-ray sources of UHECRs are derived.« less

Searches for correlation between UHECR events and high-energy gamma-ray Fermi-LAT data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Álvarez, Ezequiel; Cuoco, Alessandro; Mirabal, Nestor

The astrophysical sources responsible for ultra high-energy cosmic rays (UHECRs) continue to be one of the most intriguing mysteries in astrophysics. Here, we present a comprehensive search for correlations between high-energy (≳ 1 GeV) gamma-ray events from the Fermi Large Area Telescope (LAT) and UHECRs (≳ 60 EeV) detected by the Telescope Array and the Pierre Auger Observatory. We perform two separate searches. First, we conduct a standard cross-correlation analysis between the arrival directions of 148 UHECRs and 360 gamma-ray sources in the Second Catalog of Hard Fermi-LAT sources (2FHL). Second, we search for a possible correlation between UHECR directionsmore » and unresolved Fermi-LAT gamma-ray emission. For the latter, we use three different methods: a stacking technique with both a model-dependent and model-independent background estimate, and a cross-correlation function analysis. We also test for statistically significant excesses in gamma rays from signal regions centered on Cen A and the Telescope Array hotspot. There was no significant correlation is found in any of the analyses performed, except a weak (≲ 2σ) hint of signal with the correlation function method on scales ~ 1°. Upper limits on the flux of possible power-law gamma-ray sources of UHECRs are derived.« less

Searches for correlation between UHECR events and high-energy gamma-ray Fermi-LAT data

DOE PAGES

Álvarez, Ezequiel; Cuoco, Alessandro; Mirabal, Nestor; ...

2016-12-13

The astrophysical sources responsible for ultra high-energy cosmic rays (UHECRs) continue to be one of the most intriguing mysteries in astrophysics. Here, we present a comprehensive search for correlations between high-energy (≳ 1 GeV) gamma-ray events from the Fermi Large Area Telescope (LAT) and UHECRs (≳ 60 EeV) detected by the Telescope Array and the Pierre Auger Observatory. We perform two separate searches. First, we conduct a standard cross-correlation analysis between the arrival directions of 148 UHECRs and 360 gamma-ray sources in the Second Catalog of Hard Fermi-LAT sources (2FHL). Second, we search for a possible correlation between UHECR directionsmore » and unresolved Fermi-LAT gamma-ray emission. For the latter, we use three different methods: a stacking technique with both a model-dependent and model-independent background estimate, and a cross-correlation function analysis. We also test for statistically significant excesses in gamma rays from signal regions centered on Cen A and the Telescope Array hotspot. There was no significant correlation is found in any of the analyses performed, except a weak (≲ 2σ) hint of signal with the correlation function method on scales ~ 1°. Upper limits on the flux of possible power-law gamma-ray sources of UHECRs are derived.« less

Impact of the calibration period on the conceptual rainfall-runoff model parameter estimates

NASA Astrophysics Data System (ADS)

Todorovic, Andrijana; Plavsic, Jasna

2015-04-01

A conceptual rainfall-runoff model is defined by its structure and parameters, which are commonly inferred through model calibration. Parameter estimates depend on objective function(s), optimisation method, and calibration period. Model calibration over different periods may result in dissimilar parameter estimates, while model efficiency decreases outside calibration period. Problem of model (parameter) transferability, which conditions reliability of hydrologic simulations, has been investigated for decades. In this paper, dependence of the parameter estimates and model performance on calibration period is analysed. The main question that is addressed is: are there any changes in optimised parameters and model efficiency that can be linked to the changes in hydrologic or meteorological variables (flow, precipitation and temperature)? Conceptual, semi-distributed HBV-light model is calibrated over five-year periods shifted by a year (sliding time windows). Length of the calibration periods is selected to enable identification of all parameters. One water year of model warm-up precedes every simulation, which starts with the beginning of a water year. The model is calibrated using the built-in GAP optimisation algorithm. The objective function used for calibration is composed of Nash-Sutcliffe coefficient for flows and logarithms of flows, and volumetric error, all of which participate in the composite objective function with approximately equal weights. Same prior parameter ranges are used in all simulations. The model is calibrated against flows observed at the Slovac stream gauge on the Kolubara River in Serbia (records from 1954 to 2013). There are no trends in precipitation nor in flows, however, there is a statistically significant increasing trend in temperatures at this catchment. Parameter variability across the calibration periods is quantified in terms of standard deviations of normalised parameters, enabling detection of the most variable parameters. Correlation coefficients among optimised model parameters and total precipitation P, mean temperature T and mean flow Q are calculated to give an insight into parameter dependence on the hydrometeorological drivers. The results reveal high sensitivity of almost all model parameters towards calibration period. The highest variability is displayed by the refreezing coefficient, water holding capacity, and temperature gradient. The only statistically significant (decreasing) trend is detected in the evapotranspiration reduction threshold. Statistically significant correlation is detected between the precipitation gradient and precipitation depth, and between the time-area histogram base and flows. All other correlations are not statistically significant, implying that changes in optimised parameters cannot generally be linked to the changes in P, T or Q. As for the model performance, the model reproduces the observed runoff satisfactorily, though the runoff is slightly overestimated in wet periods. The Nash-Sutcliffe efficiency coefficient (NSE) ranges from 0.44 to 0.79. Higher NSE values are obtained over wetter periods, what is supported by statistically significant correlation between NSE and flows. Overall, no systematic variations in parameters or in model performance are detected. Parameter variability may therefore rather be attributed to errors in data or inadequacies in the model structure. Further research is required to examine the impact of the calibration strategy or model structure on the variability in optimised parameters in time.

Correlation of ultra-low dose chest CT findings with physiologic measures of asbestosis.

PubMed

Manners, David; Wong, Patrick; Murray, Conor; Teh, Joelin; Kwok, Yi Jin; de Klerk, Nick; Alfonso, Helman; Franklin, Peter; Reid, Alison; Musk, A W Bill; Brims, Fraser J H

2017-08-01

The correlation between ultra low dose computed tomography (ULDCT)-detected parenchymal lung changes and pulmonary function abnormalities is not well described. This study aimed to determine the relationship between ULDCT-detected interstitial lung disease (ILD) and measures of pulmonary function in an asbestos-exposed population. Two thoracic radiologists independently categorised prone ULDCT scans from 143 participants for ILD appearances as absent (score 0), probable (1) or definite (2) without knowledge of asbestos exposure or lung function. Pulmonary function measures included spirometry and diffusing capacity to carbon monoxide (DLCO). Participants were 92% male with a median age of 73.0 years. CT dose index volume was between 0.6 and 1.8 mGy. Probable or definite ILD was reported in 63 (44.1%) participants. Inter-observer agreement was good (k = 0.613, p < 0.001). There was a statistically significant correlation between the ILD score and both forced expiratory volume in 1 second (FEV 1 ) and forced vital capacity (FVC) (r = -0.17, p = 0.04 and r = -0.20, p = 0.02). There was a strong correlation between ILD score and DLCO (r = -0.34, p < 0.0001). Changes consistent with ILD on ULDCT correlate well with corresponding reductions in gas transfer, similar to standard CT. In asbestos-exposed populations, ULDCT may be adequate to detect radiological changes consistent with asbestosis. • Interobserver agreement for the ILD score using prone ULDCT is good. • Prone ULDCT appearances of ILD correlate with changes in spirometric observations. • Prone ULDCT appearances of ILD correlate strongly with changes in gas transfer. • Prone ULDCT may provide sufficient radiological evidence to inform the diagnosis of asbestosis.

Statistics of velocity gradients in two-dimensional Navier-Stokes and ocean turbulence.

PubMed

Schorghofer, Norbert; Gille, Sarah T

2002-02-01

Probability density functions and conditional averages of velocity gradients derived from upper ocean observations are compared with results from forced simulations of the two-dimensional Navier-Stokes equations. Ocean data are derived from TOPEX satellite altimeter measurements. The simulations use rapid forcing on large scales, characteristic of surface winds. The probability distributions of transverse velocity derivatives from the ocean observations agree with the forced simulations, although they differ from unforced simulations reported elsewhere. The distribution and cross correlation of velocity derivatives provide clear evidence that large coherent eddies play only a minor role in generating the observed statistics.

Statistical analysis of experimental data for mathematical modeling of physical processes in the atmosphere

NASA Astrophysics Data System (ADS)

Karpushin, P. A.; Popov, Yu B.; Popova, A. I.; Popova, K. Yu; Krasnenko, N. P.; Lavrinenko, A. V.

2017-11-01

In this paper, the probabilities of faultless operation of aerologic stations are analyzed, the hypothesis of normality of the empirical data required for using the Kalman filter algorithms is tested, and the spatial correlation functions of distributions of meteorological parameters are determined. The results of a statistical analysis of two-term (0, 12 GMT) radiosonde observations of the temperature and wind velocity components at some preset altitude ranges in the troposphere in 2001-2016 are presented. These data can be used in mathematical modeling of physical processes in the atmosphere.

Neural Correlates of Phrase Rhythm: An EEG Study of Bipartite vs. Rondo Sonata Form.

PubMed

Martínez-Rodrigo, Arturo; Fernández-Sotos, Alicia; Latorre, José Miguel; Moncho-Bogani, José; Fernández-Caballero, Antonio

2017-01-01

This paper introduces the neural correlates of phrase rhythm. In short, phrase rhythm is the rhythmic aspect of phrase construction and the relationships between phrases. For the sake of establishing the neural correlates, a musical experiment has been designed to induce music-evoked stimuli related to phrase rhythm. Brain activity is monitored through electroencephalography (EEG) by using a brain-computer interface. The power spectral value of each EEG channel is estimated to obtain how power variance distributes as a function of frequency. Our experiment shows statistical differences in theta and alpha bands in the phrase rhythm variations of two classical sonatas, one in bipartite form and the other in rondo form.

Neural Correlates of Phrase Rhythm: An EEG Study of Bipartite vs. Rondo Sonata Form

PubMed Central

Martínez-Rodrigo, Arturo; Fernández-Sotos, Alicia; Latorre, José Miguel; Moncho-Bogani, José; Fernández-Caballero, Antonio

2017-01-01

This paper introduces the neural correlates of phrase rhythm. In short, phrase rhythm is the rhythmic aspect of phrase construction and the relationships between phrases. For the sake of establishing the neural correlates, a musical experiment has been designed to induce music-evoked stimuli related to phrase rhythm. Brain activity is monitored through electroencephalography (EEG) by using a brain–computer interface. The power spectral value of each EEG channel is estimated to obtain how power variance distributes as a function of frequency. Our experiment shows statistical differences in theta and alpha bands in the phrase rhythm variations of two classical sonatas, one in bipartite form and the other in rondo form. PMID:28496406

Tests of Mediation: Paradoxical Decline in Statistical Power as a Function of Mediator Collinearity

PubMed Central

Beasley, T. Mark

2013-01-01

Increasing the correlation between the independent variable and the mediator (a coefficient) increases the effect size (ab) for mediation analysis; however, increasing a by definition increases collinearity in mediation models. As a result, the standard error of product tests increase. The variance inflation due to increases in a at some point outweighs the increase of the effect size (ab) and results in a loss of statistical power. This phenomenon also occurs with nonparametric bootstrapping approaches because the variance of the bootstrap distribution of ab approximates the variance expected from normal theory. Both variances increase dramatically when a exceeds the b coefficient, thus explaining the power decline with increases in a. Implications for statistical analysis and applied researchers are discussed. PMID:24954952

Quantitative MRI in hypomyelinating disorders: Correlation with motor handicap.

PubMed

Steenweg, Marjan E; Wolf, Nicole I; van Wieringen, Wessel N; Barkhof, Frederik; van der Knaap, Marjo S; Pouwels, Petra J W

2016-08-23

To assess the correlation of tissue parameters estimated by quantitative magnetic resonance (MR) techniques and motor handicap in patients with hypomyelination. Twenty-eight patients with different causes of hypomyelination (12 males, 16 females; mean age 10 years) and 61 controls (33 males, 28 females; mean age 8 years) were prospectively investigated. We quantified T2 relaxation time, magnetization transfer ratio, fractional anisotropy, mean, axial, and radial diffusivities, and brain metabolites. We performed measurements in the splenium, parietal deep white matter, and corticospinal tracts in the centrum semiovale. We further analyzed diffusion measures using tract-based spatial statistics. We estimated severity of motor handicap by the gross motor function classification system. We evaluated correlation of handicap with MR measures by linear regression analyses. Fractional anisotropy, magnetization transfer ratio, choline, and N-acetylaspartate/creatine ratio were lower and diffusivities, T2 values, and inositol were higher in patients than in controls. Tract-based spatial statistics showed that these changes were widespread for fractional anisotropy (96% of the white matter skeleton), radial (93%) and mean (84%) diffusivity, and less so for axial diffusivity (20%). Correlation with handicap yielded radial diffusivity and N-acetylaspartate/creatine ratio as strongest independent explanatory variables. Gross motor function classification system grades are in part explained by MR measures. They indicate that mainly lack of myelin and, to a lesser degree, loss of axonal integrity codetermine the degree of motor handicap in patients with hypomyelinating disorders. These MR measures can be used to evaluate strategies that are aimed at promotion of myelination. © 2016 American Academy of Neurology.

Prevalence of malnutrition and its correlates in older adults living in long stay institutions situated in Beirut, Lebanon.

PubMed

El Zoghbi, Mohamad; Boulos, Christa; Awada, Sanaa; Rachidi, Samar; Al-Hajje, Amal; Bawab, Wafaa; Saleh, Nadine; Salameh, Pascale

2014-01-01

Malnutrition represents an important issue in older adults; unfortunately, there is lack of data concerning this topic in Lebanon. This paper aims to provide a description of nutritional status and its correlates in older adults living in long stay institutions situated in Beirut. This cross-sectional study was conducted in three long stay institutions in Beirut in 2012. The study population was composed of people aged 65 years and above, having a score of Folstein Mini Mental State Examination (MMSE) greater than 14 and without renal failure requiring dialysis. Subjects meeting inclusion criteria filled out a questionnaire consisting of nutritional status scale (Mini Nutritional Assessment: MNA) and several other parts (demographic, self-assessment of the state health, smoking and alcohol, physical dependence, quality of life, frailty, depression, social isolation and loneliness). Data were entered and analyzed using the statistical software SPSS (Statistical Package for Social Sciences), version 17.0 (Chicago, IL, USA). Among 111 older adults (55 men and 56 women), 14 (12.6%) were malnourished, 54 (48.7%) were at risk of malnutrition and 43 (38.7%) had an adequate nutritional status. Multivariate analysis showed that physical exercise, depression, frailty and cognitive function were independent correlates of nutritional status of older adults. This model explained 42.2% (adjusted R2 = 0.422) of the older adults nutritional status variability. We found a moderate percentage of malnutrition in older adults living in long stay institutions situated in Beirut, and the correlates of malnutrition in older adults were low physical exercise, depression, frailty and low cognitive function.

Columnar organization of orientation domains in V1

NASA Astrophysics Data System (ADS)

Liedtke, Joscha; Wolf, Fred

In the primary visual cortex (V1) of primates and carnivores, the functional architecture of basic stimulus selectivities appears similar across cortical layers (Hubel & Wiesel, 1962) justifying the use of two-dimensional cortical models and disregarding organization in the third dimension. Here we show theoretically that already small deviations from an exact columnar organization lead to non-trivial three-dimensional functional structures. We extend two-dimensional random field models (Schnabel et al., 2007) to a three-dimensional cortex by keeping a typical scale in each layer and introducing a correlation length in the third, columnar dimension. We examine in detail the three-dimensional functional architecture for different cortical geometries with different columnar correlation lengths. We find that (i) topological defect lines are generally curved and (ii) for large cortical curvatures closed loops and reconnecting topological defect lines appear. This theory extends the class of random field models by introducing a columnar dimension and provides a systematic statistical assessment of the three-dimensional functional architecture of V1 (see also (Tanaka et al., 2011)).

Statistical quantifiers of memory for an analysis of human brain and neuro-system diseases

NASA Astrophysics Data System (ADS)

Demin, S. A.; Yulmetyev, R. M.; Panischev, O. Yu.; Hänggi, Peter

2008-03-01

On the basis of a memory function formalism for correlation functions of time series we investigate statistical memory effects by the use of appropriate spectral and relaxation parameters of measured stochastic data for neuro-system diseases. In particular, we study the dynamics of the walk of a patient who suffers from Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), and compare against the data of healthy people (CO - control group). We employ an analytical method which is able to characterize the stochastic properties of stride-to-stride variations of gait cycle timing. Our results allow us to estimate quantitatively a few human locomotion function abnormalities occurring in the human brain and in the central nervous system (CNS). Particularly, the patient's gait dynamics are characterized by an increased memory behavior together with sizable fluctuations as compared with the locomotion dynamics of healthy patients. Moreover, we complement our findings with peculiar features as detected in phase-space portraits and spectral characteristics for the different data sets (PD, HD, ALS and healthy people). The evaluation of statistical quantifiers of the memory function is shown to provide a useful toolkit which can be put to work to identify various abnormalities of locomotion dynamics. Moreover, it allows one to diagnose qualitatively and quantitatively serious brain and central nervous system diseases.

Matrix metalloproteinase-14 is a biomarker of angiogenic activity in proliferative diabetic retinopathy

PubMed Central

Mohammad, Ghulam; Allegaert, Eef; Ahmad, Ajmal; Siddiquei, Mohammad Mairaj; Alam, Kaiser; Gikandi, Priscilla W.; De Hertogh, Gert; Opdenakker, Ghislain

2018-01-01

Purpose Matrix metalloproteinase-14 (MMP-14) is a transmembrane MMP that plays a critical role in promoting angiogenesis. We investigated the expression levels of MMP-14 and correlated the levels with clinical disease activity and with the levels of the angiogenic factors vascular endothelial growth factor (VEGF) and MMP-9 in proliferative diabetic retinopathy (PDR). To reinforce the findings at the functional level, we examined the expression of MMP-14 in the retinas of diabetic rats. Methods Vitreous samples from 34 patients with PDR and 18 nondiabetic patients and epiretinal membranes from 13 patients with PDR and the retinas of rats were studied with enzyme-linked immunosorbent assay, immunohistochemistry, western blotting, and real-time reverse transcription PCR (RT–PCR). Results The MMP-14, VEGF, and MMP-9 levels were statistically significantly higher in the vitreous samples from patients with PDR than in the samples from the nondiabetic controls (p<0.001 for all comparisons). The MMP-14 levels in patients with PDR with active neovascularization were statistically significantly higher than those in patients with inactive PDR (p<0.001). There were statistically significant positive correlations between levels of MMP-14 and levels of VEGF (r = 0.3; p = 0.032) and MMP-9 (r = 0.54; p<0.001). In the epiretinal membranes, MMP-14 was expressed in vascular endothelial cells, leukocytes, and myofibroblasts. Statistically significant positive correlations were detected between the numbers of blood vessels expressing CD31 and the numbers of blood vessels (r = 0.74; p = 0.004) and stromal cells (r = 0.72; p = 0.005) expressing MMP-14. Statistically significant increases of MMP-14 mRNA and protein were detected in rat retinas after induction of diabetes. Conclusions These results suggest that MMP-14 is involved in PDR angiogenesis. PMID:29853773

A Comparison between the WATCH Flare Data Statistical Properties and Predictions of the Statistical Flare Model

NASA Astrophysics Data System (ADS)

Crosby, N.; Georgoulis, M.; Vilmer, N.

1999-10-01

Solar burst observations in the deka-keV energy range originating from the WATCH experiment aboard the GRANAT spacecraft were used to perform frequency distributions built on measured X-ray flare parameters (Crosby et al., 1998). The results of the study show that: 1- the overall distribution functions are robust power laws extending over a number of decades. The typical parameters of events (total counts, peak count rates, duration) are all correlated to each other. 2- the overall distribution functions are the convolution of significantly different distribution functions built on parts of the whole data set filtered by the event duration. These "partial" frequency distributions are still power law distributions over several decades, with a slope systematically decreasing with increasing duration. 3- No correlation is found between the elapsed time interval between successive bursts arising from the same active region and the peak intensity of the flare. In this paper, we attempt a tentative comparison between the statistical properties of the self-organized critical (SOC) cellular automaton statistical flare models (see e.g. Lu and Hamilton (1991), Georgoulis and Vlahos (1996, 1998)) and the respective properties of the WATCH flare data. Despite the inherent weaknesses of the SOC models to simulate a number of physical processes in the active region, it is found that most of the observed statistical properties can be reproduced using the SOC models, including the various frequency distributions and scatter plots. We finally conclude that, even if SOC models must be refined to improve the physical links to MHD approaches, they nevertheless represent a good approach to describe the properties of rapid energy dissipation and magnetic field annihilation in complex and magnetized plasmas. Crosby N., Vilmer N., Lund N. and Sunyaev R., A&A; 334; 299-313; 1998 Crosby N., Lund N., Vilmer N. and Sunyaev R.; A&A Supplement Series; 130, 233, 1998 Georgoulis M. and Vlahos L., 1996, Astrophy. J. Letters, 469, L135 Georgoulis M. and Vlahos L., 1998, in preparation Lu E.T. and Hamilton R.J., 1991, Astroph. J., 380, L89

Statistical analysis of strait time index and a simple model for trend and trend reversal

NASA Astrophysics Data System (ADS)

Chen, Kan; Jayaprakash, C.

2003-06-01

We analyze the daily closing prices of the Strait Time Index (STI) as well as the individual stocks traded in Singapore's stock market from 1988 to 2001. We find that the Hurst exponent is approximately 0.6 for both the STI and individual stocks, while the normal correlation functions show the random walk exponent of 0.5. We also investigate the conditional average of the price change in an interval of length T given the price change in the previous interval. We find strong correlations for price changes larger than a threshold value proportional to T; this indicates that there is no uniform crossover to Gaussian behavior. A simple model based on short-time trend and trend reversal is constructed. We show that the model exhibits statistical properties and market swings similar to those of the real market.

Reaction of O2(+)(X 2Pi sub g) with H2, D2, and HD - Guided ion beam studies, MO correlations, and statistical theory calculations

NASA Technical Reports Server (NTRS)

Weber, M. E.; Dalleska, N. F.; Tjelta, B. L.; Fisher, E. R.; Armentrout, P. B.

1993-01-01

Guided ion-beam mass spectrometry is used to examined the reactions of vibrationally cold ground-state O2(+)(X 2Pi sub g) with H2, D2, and HD. The energy dependence of the absolute integral cross sections from thermal energy to over 4 eV are measured in the center-of-mass frame of reference. Results are also presented for internally excited O2(+) ions reacting with D2 and HD. The results are consistent with the dominant state being the a 4Pi sub u electronic state. The experimental excitation functions are analyzed in detail and interpreted by extending the molecular orbital correlation arguments of Mahan (1971) and by comparison with results of statistical phase space theory and with a theory that predicts a tight transition state.

Bayesian truncation errors in chiral effective field theory: model checking and accounting for correlations

NASA Astrophysics Data System (ADS)

Melendez, Jordan; Wesolowski, Sarah; Furnstahl, Dick

2017-09-01

Chiral effective field theory (EFT) predictions are necessarily truncated at some order in the EFT expansion, which induces an error that must be quantified for robust statistical comparisons to experiment. A Bayesian model yields posterior probability distribution functions for these errors based on expectations of naturalness encoded in Bayesian priors and the observed order-by-order convergence pattern of the EFT. As a general example of a statistical approach to truncation errors, the model was applied to chiral EFT for neutron-proton scattering using various semi-local potentials of Epelbaum, Krebs, and Meißner (EKM). Here we discuss how our model can learn correlation information from the data and how to perform Bayesian model checking to validate that the EFT is working as advertised. Supported in part by NSF PHY-1614460 and DOE NUCLEI SciDAC DE-SC0008533.

Analysis/forecast experiments with a multivariate statistical analysis scheme using FGGE data

NASA Technical Reports Server (NTRS)

Baker, W. E.; Bloom, S. C.; Nestler, M. S.

1985-01-01

A three-dimensional, multivariate, statistical analysis method, optimal interpolation (OI) is described for modeling meteorological data from widely dispersed sites. The model was developed to analyze FGGE data at the NASA-Goddard Laboratory of Atmospherics. The model features a multivariate surface analysis over the oceans, including maintenance of the Ekman balance and a geographically dependent correlation function. Preliminary comparisons are made between the OI model and similar schemes employed at the European Center for Medium Range Weather Forecasts and the National Meteorological Center. The OI scheme is used to provide input to a GCM, and model error correlations are calculated for forecasts of 500 mb vertical water mixing ratios and the wind profiles. Comparisons are made between the predictions and measured data. The model is shown to be as accurate as a successive corrections model out to 4.5 days.

A Solution Space for a System of Null-State Partial Differential Equations: Part 1

NASA Astrophysics Data System (ADS)

Flores, Steven M.; Kleban, Peter

2015-01-01

This article is the first of four that completely and rigorously characterize a solution space for a homogeneous system of 2 N + 3 linear partial differential equations (PDEs) in 2 N variables that arises in conformal field theory (CFT) and multiple Schramm-Löwner evolution (SLE). In CFT, these are null-state equations and conformal Ward identities. They govern partition functions for the continuum limit of a statistical cluster or loop-gas model, such as percolation, or more generally the Potts models and O( n) models, at the statistical mechanical critical point. (SLE partition functions also satisfy these equations.) For such a lattice model in a polygon with its 2 N sides exhibiting a free/fixed side-alternating boundary condition , this partition function is proportional to the CFT correlation function where the w i are the vertices of and where is a one-leg corner operator. (Partition functions for "crossing events" in which clusters join the fixed sides of in some specified connectivity are linear combinations of such correlation functions.) When conformally mapped onto the upper half-plane, methods of CFT show that this correlation function satisfies the system of PDEs that we consider. In this first article, we use methods of analysis to prove that the dimension of this solution space is no more than C N , the Nth Catalan number. While our motivations are based in CFT, our proofs are completely rigorous. This proof is contained entirely within this article, except for the proof of Lemma 14, which constitutes the second article (Flores and Kleban, in Commun Math Phys, arXiv:1404.0035, 2014). In the third article (Flores and Kleban, in Commun Math Phys, arXiv:1303.7182, 2013), we use the results of this article to prove that the solution space of this system of PDEs has dimension C N and is spanned by solutions constructed with the CFT Coulomb gas (contour integral) formalism. In the fourth article (Flores and Kleban, in Commun Math Phys, arXiv:1405.2747, 2014), we prove further CFT-related properties about these solutions, some useful for calculating cluster-crossing probabilities of critical lattice models in polygons.

A statistical physics view of pitch fluctuations in the classical music from Bach to Chopin: evidence for scaling.

PubMed

Liu, Lu; Wei, Jianrong; Zhang, Huishu; Xin, Jianhong; Huang, Jiping

2013-01-01

Because classical music has greatly affected our life and culture in its long history, it has attracted extensive attention from researchers to understand laws behind it. Based on statistical physics, here we use a different method to investigate classical music, namely, by analyzing cumulative distribution functions (CDFs) and autocorrelation functions of pitch fluctuations in compositions. We analyze 1,876 compositions of five representative classical music composers across 164 years from Bach, to Mozart, to Beethoven, to Mendelsohn, and to Chopin. We report that the biggest pitch fluctuations of a composer gradually increase as time evolves from Bach time to Mendelsohn/Chopin time. In particular, for the compositions of a composer, the positive and negative tails of a CDF of pitch fluctuations are distributed not only in power laws (with the scale-free property), but also in symmetry (namely, the probability of a treble following a bass and that of a bass following a treble are basically the same for each composer). The power-law exponent decreases as time elapses. Further, we also calculate the autocorrelation function of the pitch fluctuation. The autocorrelation function shows a power-law distribution for each composer. Especially, the power-law exponents vary with the composers, indicating their different levels of long-range correlation of notes. This work not only suggests a way to understand and develop music from a viewpoint of statistical physics, but also enriches the realm of traditional statistical physics by analyzing music.

Liver reserve function assessment by acoustic radiation force impulse imaging

PubMed Central

Sun, Xiao-Lan; Liang, Li-Wei; Cao, Hui; Men, Qiong; Hou, Ke-Zhu; Chen, Zhen; Zhao, Ya-E

2015-01-01

AIM: To evaluate the utility of liver reserve function by acoustic radiation force impulse (ARFI) imaging in patients with liver tumors. METHODS: Seventy-six patients with liver tumors were enrolled in this study. Serum biochemical indexes, such as aminotransferase (ALT), aspartate aminotransferase (AST), serum albumin (ALB), total bilirubin (T-Bil), and other indicators were observed. Liver stiffness (LS) was measured by ARFI imaging, measurements were repeated 10 times, and the average value of the results was taken as the final LS value. Indocyanine green (ICG) retention was performed, and ICG-K and ICG-R15 were recorded. Child-Pugh (CP) scores were carried out based on patient’s preoperative biochemical tests and physical condition. Correlations among CP scores, ICG-R15, ICG-K and LS values were observed and analyzed using either the Pearson correlation coefficient or the Spearman rank correlation coefficient. Kruskal-Wallis test was used to compare LS values of CP scores, and the receiver-operator characteristic (ROC) curve was used to analyze liver reserve function assessment accuracy. RESULTS: LS in the ICG-R15 10%-20% group was significantly higher than in the ICG-R15 < 10% group; and the difference was statistically significant (2.19 ± 0.27 vs 1.59 ± 0.32, P < 0.01). LS in the ICG-R15 > 20% group was significantly higher than in the ICG-R15 < 10% group; and the difference was statistically significant (2.92 ± 0.29 vs 1.59 ± 0.32, P < 0.01). The LS value in patients with CP class A was lower than in patients with CP class B (1.57 ± 0.34 vs 1.86 ± 0.27, P < 0.05), while the LS value in patients with CP class B was lower than in patients with CP class C (1.86 ± 0.27 vs 2.47 ± 0.33, P < 0.01). LS was positively correlated with ICG-R15 (r = 0.617, P < 0.01) and CP score (r = 0.772, P < 0.01). Meanwhile, LS was negatively correlated with ICG-K (r = -0.673, P < 0.01). AST, ALT and T-Bil were positively correlated with LS, while ALB was negatively correlated with LS (P < 0.05). The ROC curve revealed that the when the LS value was 2.34 m/s, the Youden index was at its highest point, sensitivity was 69.2% and specificity was 92.1%. CONCLUSION: For patients with liver tumors, ARFI imaging is a useful tool for assessing liver reserve function. PMID:26327773

Postoperative perceived health status in adolescent following idiopathic scoliosis surgical treatment: results using the adapted French version of Scoliosis Research Society Outcomes questionnaire (SRS-22).

PubMed

Chaib, Y; Bachy, M; Zakine, S; Mary, P; Khouri, N; Vialle, R

2013-06-01

Assessing functional outcome from patient-based outcomes questionnaires are essential to the evaluation of adolescent idiopathic scoliosis surgical treatment At the minimum follow-up of 2 years, 45 operated on adolescent idiopathic scoliosis patients were mailed the French version of the Scoliosis Research Society Outcome Instrument (SRS-22) questionnaires containing items on pain, activities of daily living, and satisfaction. Mean values of the SRS-22 domains were 3,66 for the Pain domain, 3,85 for the Self-perceived image domain, 4,32 for the Function domain, 3,52 for the Mental health domain and 4,12 for the Global satisfaction with management domain. Mean value of the global SRS-22 score was 3,88. We showed no differences in functional SRS-22 health status in patients according to the type of curve (Lenke classification). We showed statistically significant correlations between the gain of Cobb angle and Patients self-image and function domain scores. There was a statistically significant correlation between preoperative Cobb angle and patient satisfaction with management. Even if Function and Self-image scores in our patients are close to control group values, indicating good short to mid-term outcome of surgical treatment, scores for pain and mental health status were significantly lower in patients than controls. Long-term follow-up studies conducted by multiple surgeons over successive generations are mandatory to assess clinical significance of these differences. Level IV. Retrospective study. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Pulmonary MR imaging with ultra-short TEs: utility for disease severity assessment of connective tissue disease patients.

PubMed

Ohno, Yoshiharu; Nishio, Mizuho; Koyama, Hisanobu; Takenaka, Daisuke; Takahashi, Masaya; Yoshikawa, Takeshi; Matsumoto, Sumiaki; Obara, Makoto; van Cauteren, Marc; Sugimura, Kazuro

2013-08-01

To evaluate the utility of pulmonary magnetic resonance (MR) imaging with ultra-short echo times (UTEs) at a 3.0 T MR system for pulmonary functional loss and disease severity assessments of connective tissue disease (CTD) patients with interstitial lung disease (ILD). This prospective study was approved by the institutional review board, and written informed consent was obtained from 18 CTD patients (eight men and ten women) and eight normal subjects with suspected chest disease (three men and five women). All subjects underwent thin-section MDCT, pulmonary MR imaging with UTEs, pulmonary function test and serum KL-6. Regional T2 maps were generated from each MR data set, and mean T2 values were determined from ROI measurements. From each thin-section MDCT data set, CT-based disease severity was evaluated with a visual scoring system. Mean T2 values for normal and CTD subjects were statistically compared by using Student's t-test. To assess capability for pulmonary functional loss and disease severity assessments, mean T2 values were statistically correlated with pulmonary functional parameters, serum KL-6 and CT-based disease severity. Mean T2 values for normal and CTD subjects were significantly different (p=0.0019) and showed significant correlations with %VC, %DLCO, serum KL-6 and CT-based disease severity of CTD patients (p<0.05). Pulmonary MR imaging with UTEs is useful for pulmonary functional loss and disease severity assessments of CTD patients with ILD. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Explorations in Statistics: Correlation

ERIC Educational Resources Information Center

Curran-Everett, Douglas

2010-01-01

Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This sixth installment of "Explorations in Statistics" explores correlation, a familiar technique that estimates the magnitude of a straight-line relationship between two variables. Correlation is meaningful only when the…

Quantitative analysis of the correlations in the Boltzmann-Grad limit for hard spheres

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pulvirenti, M.

2014-12-09

In this contribution I consider the problem of the validity of the Boltzmann equation for a system of hard spheres in the Boltzmann-Grad limit. I briefly review the results available nowadays with a particular emphasis on the celebrated Lanford’s validity theorem. Finally I present some recent results, obtained in collaboration with S. Simonella, concerning a quantitative analysis of the propagation of chaos. More precisely we introduce a quantity (the correlation error) measuring how close a j-particle rescaled correlation function at time t (sufficiently small) is far from the full statistical independence. Roughly speaking, a correlation error of order k, measuresmore » (in the context of the BBKGY hierarchy) the event in which k tagged particles form a recolliding group.« less

Evaluating Cellular Polyfunctionality with a Novel Polyfunctionality Index

PubMed Central

Larsen, Martin; Sauce, Delphine; Arnaud, Laurent; Fastenackels, Solène; Appay, Victor; Gorochov, Guy

2012-01-01

Functional evaluation of naturally occurring or vaccination-induced T cell responses in mice, men and monkeys has in recent years advanced from single-parameter (e.g. IFN-γ-secretion) to much more complex multidimensional measurements. Co-secretion of multiple functional molecules (such as cytokines and chemokines) at the single-cell level is now measurable due primarily to major advances in multiparametric flow cytometry. The very extensive and complex datasets generated by this technology raise the demand for proper analytical tools that enable the analysis of combinatorial functional properties of T cells, hence polyfunctionality. Presently, multidimensional functional measures are analysed either by evaluating all combinations of parameters individually or by summing frequencies of combinations that include the same number of simultaneous functions. Often these evaluations are visualized as pie charts. Whereas pie charts effectively represent and compare average polyfunctionality profiles of particular T cell subsets or patient groups, they do not document the degree or variation of polyfunctionality within a group nor does it allow more sophisticated statistical analysis. Here we propose a novel polyfunctionality index that numerically evaluates the degree and variation of polyfuntionality, and enable comparative and correlative parametric and non-parametric statistical tests. Moreover, it allows the usage of more advanced statistical approaches, such as cluster analysis. We believe that the polyfunctionality index will render polyfunctionality an appropriate end-point measure in future studies of T cell responsiveness. PMID:22860124

Comparison of mean deviation with AGIS and CIGTS scores in association with structural parameters in glaucomatous eyes.

PubMed

Naka, Maiko; Kanamori, Akiyasu; Tatsumi, Yasuko; Fujioka, Miyuki; Nagai-Kusuhara, Azusa; Nakamura, Makoto; Negi, Akira

2009-01-01

To evaluate which of the 3 clinically used visual field indices including mean deviation (MD), Advanced Glaucoma Intervention Study (AGIS) score, and Collaborative Initial Glaucoma Treatment Study (CIGTS) score are best in evaluating functional damage of glaucomatous optic neuropathy. In 213 glaucomatous eyes, peripapillary retinal nerve fiber layer thickness (RNFLT) and optic disc configuration were measured with Stratus optical coherence tomography and Heidelberg Retina Tomograph-2, respectively. Visual field was measured with standard automated perimetry 30-2. Correlations of the structural parameters compared with the 3 VF indices using second polynomial regression were calculated. In addition, these correlations were analyzed among eyes of 3 different stages of glaucoma, as defined by MD score (early, MD> or =-6 dB; moderate, -12 dB< or =MD<-6 dB; advanced, MD<-12 dB). Among structure-function relationships in all subjects, the highest correlation determination (R) was MD with RNFLT (=0.298). CIGTS score showed better R than MD or AGIS score with rim area, but these values were not higher than any R with RNFLT. In analyses of 3 groups depending on MD, statistically significant structure-function correlations were observed only in patients with an advanced stage. No clear difference was found among MD and AGIS/CIGTS scores in expressing functional damage of glaucomatous eyes. MD is suggested to be no worse than others in monitoring glaucoma in clinical setting.

A Multiscale pipeline for the search of string-induced CMB anisotropies

NASA Astrophysics Data System (ADS)

Vafaei Sadr, A.; Movahed, S. M. S.; Farhang, M.; Ringeval, C.; Bouchet, F. R.

2018-03-01

We propose a multiscale edge-detection algorithm to search for the Gott-Kaiser-Stebbins imprints of a cosmic string (CS) network on the cosmic microwave background (CMB) anisotropies. Curvelet decomposition and extended Canny algorithm are used to enhance the string detectability. Various statistical tools are then applied to quantify the deviation of CMB maps having a CS contribution with respect to pure Gaussian anisotropies of inflationary origin. These statistical measures include the one-point probability density function, the weighted two-point correlation function (TPCF) of the anisotropies, the unweighted TPCF of the peaks and of the up-crossing map, as well as their cross-correlation. We use this algorithm on a hundred of simulated Nambu-Goto CMB flat sky maps, covering approximately 10 per cent of the sky, and for different string tensions Gμ. On noiseless sky maps with an angular resolution of 0.9 arcmin, we show that our pipeline detects CSs with Gμ as low as Gμ ≳ 4.3 × 10-10. At the same resolution, but with a noise level typical to a CMB-S4 phase II experiment, the detection threshold would be to Gμ ≳ 1.2 × 10-7.

On the role of structure-dynamic relationship in determining the excess entropy of mixing and chemical ordering in binary square-well liquid alloys

NASA Astrophysics Data System (ADS)

Lalneihpuii, R.; Shrivastava, Ruchi; Mishra, Raj Kumar

2018-05-01

Using statistical mechanical model with square-well (SW) interatomic potential within the frame work of mean spherical approximation, we determine the composition dependent microscopic correlation functions, interdiffusion coefficients, surface tension and chemical ordering in Ag-Cu melts. Further Dzugutov universal scaling law of normalized diffusion is verified with SW potential in binary mixtures. We find that the excess entropy scaling law is valid for SW binary melts. The partial and total structure factors in the attractive and repulsive regions of the interacting potential are evaluated and then Fourier transformed to get partial and total radial distribution functions. A good agreement between theoretical and experimental values for total structure factor and the reduced radial distribution function are observed, which consolidates our model calculations. The well-known Bhatia-Thornton correlation functions are also computed for Ag-Cu melts. The concentration-concentration correlations in the long wavelength limit in liquid Ag-Cu alloys have been analytically derived through the long wavelength limit of partial correlation functions and apply it to demonstrate the chemical ordering and interdiffusion coefficients in binary liquid alloys. We also investigate the concentration dependent viscosity coefficients and surface tension using the computed diffusion data in these alloys. Our computed results for structure, transport and surface properties of liquid Ag-Cu alloys obtained with square-well interatomic interaction are fully consistent with their corresponding experimental values.

Photon statistics and speckle visibility spectroscopy with partially coherent X-rays.

PubMed

Li, Luxi; Kwaśniewski, Paweł; Orsi, Davide; Wiegart, Lutz; Cristofolini, Luigi; Caronna, Chiara; Fluerasu, Andrei

2014-11-01

A new approach is proposed for measuring structural dynamics in materials from multi-speckle scattering patterns obtained with partially coherent X-rays. Coherent X-ray scattering is already widely used at high-brightness synchrotron lightsources to measure dynamics using X-ray photon correlation spectroscopy, but in many situations this experimental approach based on recording long series of images (i.e. movies) is either not adequate or not practical. Following the development of visible-light speckle visibility spectroscopy, the dynamic information is obtained instead by analyzing the photon statistics and calculating the speckle contrast in single scattering patterns. This quantity, also referred to as the speckle visibility, is determined by the properties of the partially coherent beam and other experimental parameters, as well as the internal motions in the sample (dynamics). As a case study, Brownian dynamics in a low-density colloidal suspension is measured and an excellent agreement is found between correlation functions measured by X-ray photon correlation spectroscopy and the decay in speckle visibility with integration time obtained from the analysis presented here.

Prevalence of upper airway obstruction in patients with apparently asymptomatic euthyroid multi nodular goitre

PubMed Central

Menon, Sunil K.; Jagtap, Varsha S.; Sarathi, Vijaya; Lila, Anurag R.; Bandgar, Tushar R.; Menon, Padmavathy S; Shah, Nalini S.

2011-01-01

Aims: To study the prevalence of upper airway obstruction (UAO) in “apparently asymptomatic” patients with euthyroid multinodular goitre (MNG) and find correlation between clinical features, UAO on pulmonary function test (PFT) and tracheal narrowing on computerised tomography (CT). Materials and Methods: Consecutive patients with apparently asymptomatic euthyroid MNG attending thyroid clinic in a tertiary centre underwent clinical examination to elicit features of UAO, PFT, and CT of neck and chest. Statistical Analysis Used: Statistical analysis was done with SPSS version 11.5 using paired t-test, Chi square test, and Fisher's exact test. P value of <0.05 was considered to be significant. Results: Fifty-six patients (52 females and four males) were studied. The prevalence of UAO (PFT) and significant tracheal narrowing (CT) was 14.3%. and 9.3%, respectively. Clinical features failed to predict UAO or significant tracheal narrowing. Tracheal narrowing (CT) did not correlate with UAO (PFT). Volume of goitre significantly correlated with degree of tracheal narrowing. Conclusions: Clinical features do not predict UAO on PFT or tracheal narrowing on CT in apparently asymptomatic patients with euthyroid MNG. PMID:21966649

Developing Matlab scripts for image analysis and quality assessment

NASA Astrophysics Data System (ADS)

Vaiopoulos, A. D.

2011-11-01

Image processing is a very helpful tool in many fields of modern sciences that involve digital imaging examination and interpretation. Processed images however, often need to be correlated with the original image, in order to ensure that the resulting image fulfills its purpose. Aside from the visual examination, which is mandatory, image quality indices (such as correlation coefficient, entropy and others) are very useful, when deciding which processed image is the most satisfactory. For this reason, a single program (script) was written in Matlab language, which automatically calculates eight indices by utilizing eight respective functions (independent function scripts). The program was tested in both fused hyperspectral (Hyperion-ALI) and multispectral (ALI, Landsat) imagery and proved to be efficient. Indices were found to be in agreement with visual examination and statistical observations.

Oral cancer associated with chronic mechanical irritation of the oral mucosa.

PubMed

Piemonte, E; Lazos, J; Belardinelli, P; Secchi, D; Brunotto, M; Lanfranchi-Tizeira, H

2018-03-01

Most of the studies dealing with Chronic Mechanical Irritation (CMI) and Oral Cancer (OC) only considered prosthetic and dental variables separately, and CMI functional factors are not registered. Thus, the aim of this study was to assess OC risk in individuals with dental, prosthetic and functional CMI. Also, we examined CMI presence in relation to tumor size. A case-control study was carried out from 2009 to 2013. Study group were squamous cell carcinoma cases; control group was patients seeking dental treatment in the same institution. 153 patients were studied (Study group n=53, Control group n=100). CMI reproducibility displayed a correlation coefficient of 1 (p<0.0001). Bivariate analysis showed statistically significant associations for all variables (age, gender, tobacco and alcohol consumption and CMI). Multivariate analysis exhibited statistical significance for age, alcohol, and CMI, but not for gender or tobacco. Relationship of CMI with tumor size showed no statistically significant differences. CMI could be regarded as a risk factor for oral cancer. In individuals with other OC risk factors, proper treatment of the mechanical injuring factors (dental, prosthetic and functional) could be an important measure to reduce the risk of oral cancer.

Testing the Difference of Correlated Agreement Coefficients for Statistical Significance

ERIC Educational Resources Information Center

Gwet, Kilem L.

2016-01-01

This article addresses the problem of testing the difference between two correlated agreement coefficients for statistical significance. A number of authors have proposed methods for testing the difference between two correlated kappa coefficients, which require either the use of resampling methods or the use of advanced statistical modeling…

Modeling of Dissipation Element Statistics in Turbulent Non-Premixed Jet Flames

NASA Astrophysics Data System (ADS)

Denker, Dominik; Attili, Antonio; Boschung, Jonas; Hennig, Fabian; Pitsch, Heinz

2017-11-01

The dissipation element (DE) analysis is a method for analyzing and compartmentalizing turbulent scalar fields. DEs can be described by two parameters, namely the Euclidean distance l between their extremal points and the scalar difference in the respective points Δϕ . The joint probability density function (jPDF) of these two parameters P(Δϕ , l) is expected to suffice for a statistical reconstruction of the scalar field. In addition, reacting scalars show a strong correlation with these DE parameters in both premixed and non-premixed flames. Normalized DE statistics show a remarkable invariance towards changes in Reynolds numbers. This feature of DE statistics was exploited in a Boltzmann-type evolution equation based model for the probability density function (PDF) of the distance between the extremal points P(l) in isotropic turbulence. Later, this model was extended for the jPDF P(Δϕ , l) and then adapted for the use in free shear flows. The effect of heat release on the scalar scales and DE statistics is investigated and an extended model for non-premixed jet flames is introduced, which accounts for the presence of chemical reactions. This new model is validated against a series of DNS of temporally evolving jet flames. European Research Council Project ``Milestone''.

Technical Note: Statistical dependences between channels in radiochromic film readings. Implications in multichannel dosimetry.

PubMed

González-López, Antonio; Vera-Sánchez, Juan Antonio; Ruiz-Morales, Carmen

2016-05-01

This note studies the statistical relationships between color channels in radiochromic film readings with flatbed scanners. The same relationships are studied for noise. Finally, their implications for multichannel film dosimetry are discussed. Radiochromic films exposed to wedged fields of 6 MV energy were read in a flatbed scanner. The joint histograms of pairs of color channels were used to obtain the joint and conditional probability density functions between channels. Then, the conditional expectations and variances of one channel given another channel were obtained. Noise was extracted from film readings by means of a multiresolution analysis. Two different dose ranges were analyzed, the first one ranging from 112 to 473 cGy and the second one from 52 to 1290 cGy. For the smallest dose range, the conditional expectations of one channel given another channel can be approximated by linear functions, while the conditional variances are fairly constant. The slopes of the linear relationships between channels can be used to simplify the expression that estimates the dose by means of the multichannel method. The slopes of the linear relationships between each channel and the red one can also be interpreted as weights in the final contribution to dose estimation. However, for the largest dose range, the conditional expectations of one channel given another channel are no longer linear functions. Finally, noises in different channels were found to correlate weakly. Signals present in different channels of radiochromic film readings show a strong statistical dependence. By contrast, noise correlates weakly between channels. For the smallest dose range analyzed, the linear behavior between the conditional expectation of one channel given another channel can be used to simplify calculations in multichannel film dosimetry.

Modeling Pair Distribution Functions of Rare-Earth Phosphate Glasses Using Principal Component Analysis.

PubMed

Cole, Jacqueline M; Cheng, Xie; Payne, Michael C

2016-11-07

The use of principal component analysis (PCA) to statistically infer features of local structure from experimental pair distribution function (PDF) data is assessed on a case study of rare-earth phosphate glasses (REPGs). Such glasses, codoped with two rare-earth ions (R and R') of different sizes and optical properties, are of interest to the laser industry. The determination of structure-property relationships in these materials is an important aspect of their technological development. Yet, realizing the local structure of codoped REPGs presents significant challenges relative to their singly doped counterparts; specifically, R and R' are difficult to distinguish in terms of establishing relative material compositions, identifying atomic pairwise correlation profiles in a PDF that are associated with each ion, and resolving peak overlap of such profiles in PDFs. This study demonstrates that PCA can be employed to help overcome these structural complications, by statistically inferring trends in PDFs that exist for a restricted set of experimental data on REPGs, and using these as training data to predict material compositions and PDF profiles in unknown codoped REPGs. The application of these PCA methods to resolve individual atomic pairwise correlations in t(r) signatures is also presented. The training methods developed for these structural predictions are prevalidated by testing their ability to reproduce known physical phenomena, such as the lanthanide contraction, on PDF signatures of the structurally simpler singly doped REPGs. The intrinsic limitations of applying PCA to analyze PDFs relative to the quality control of source data, data processing, and sample definition, are also considered. While this case study is limited to lanthanide-doped REPGs, this type of statistical inference may easily be extended to other inorganic solid-state materials and be exploited in large-scale data-mining efforts that probe many t(r) functions.

Technical Note: Statistical dependences between channels in radiochromic film readings. Implications in multichannel dosimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

González-López, Antonio, E-mail: antonio.gonzalez7@carm.es; Vera-Sánchez, Juan Antonio; Ruiz-Morales, Carmen

Purpose: This note studies the statistical relationships between color channels in radiochromic film readings with flatbed scanners. The same relationships are studied for noise. Finally, their implications for multichannel film dosimetry are discussed. Methods: Radiochromic films exposed to wedged fields of 6 MV energy were read in a flatbed scanner. The joint histograms of pairs of color channels were used to obtain the joint and conditional probability density functions between channels. Then, the conditional expectations and variances of one channel given another channel were obtained. Noise was extracted from film readings by means of a multiresolution analysis. Two different dosemore » ranges were analyzed, the first one ranging from 112 to 473 cGy and the second one from 52 to 1290 cGy. Results: For the smallest dose range, the conditional expectations of one channel given another channel can be approximated by linear functions, while the conditional variances are fairly constant. The slopes of the linear relationships between channels can be used to simplify the expression that estimates the dose by means of the multichannel method. The slopes of the linear relationships between each channel and the red one can also be interpreted as weights in the final contribution to dose estimation. However, for the largest dose range, the conditional expectations of one channel given another channel are no longer linear functions. Finally, noises in different channels were found to correlate weakly. Conclusions: Signals present in different channels of radiochromic film readings show a strong statistical dependence. By contrast, noise correlates weakly between channels. For the smallest dose range analyzed, the linear behavior between the conditional expectation of one channel given another channel can be used to simplify calculations in multichannel film dosimetry.« less

Clustering Coefficients for Correlation Networks.

PubMed

Masuda, Naoki; Sakaki, Michiko; Ezaki, Takahiro; Watanabe, Takamitsu

2018-01-01

Graph theory is a useful tool for deciphering structural and functional networks of the brain on various spatial and temporal scales. The clustering coefficient quantifies the abundance of connected triangles in a network and is a major descriptive statistics of networks. For example, it finds an application in the assessment of small-worldness of brain networks, which is affected by attentional and cognitive conditions, age, psychiatric disorders and so forth. However, it remains unclear how the clustering coefficient should be measured in a correlation-based network, which is among major representations of brain networks. In the present article, we propose clustering coefficients tailored to correlation matrices. The key idea is to use three-way partial correlation or partial mutual information to measure the strength of the association between the two neighboring nodes of a focal node relative to the amount of pseudo-correlation expected from indirect paths between the nodes. Our method avoids the difficulties of previous applications of clustering coefficient (and other) measures in defining correlational networks, i.e., thresholding on the correlation value, discarding of negative correlation values, the pseudo-correlation problem and full partial correlation matrices whose estimation is computationally difficult. For proof of concept, we apply the proposed clustering coefficient measures to functional magnetic resonance imaging data obtained from healthy participants of various ages and compare them with conventional clustering coefficients. We show that the clustering coefficients decline with the age. The proposed clustering coefficients are more strongly correlated with age than the conventional ones are. We also show that the local variants of the proposed clustering coefficients (i.e., abundance of triangles around a focal node) are useful in characterizing individual nodes. In contrast, the conventional local clustering coefficients were strongly correlated with and therefore may be confounded by the node's connectivity. The proposed methods are expected to help us to understand clustering and lack thereof in correlational brain networks, such as those derived from functional time series and across-participant correlation in neuroanatomical properties.

Clustering Coefficients for Correlation Networks

PubMed Central

Masuda, Naoki; Sakaki, Michiko; Ezaki, Takahiro; Watanabe, Takamitsu

2018-01-01

Graph theory is a useful tool for deciphering structural and functional networks of the brain on various spatial and temporal scales. The clustering coefficient quantifies the abundance of connected triangles in a network and is a major descriptive statistics of networks. For example, it finds an application in the assessment of small-worldness of brain networks, which is affected by attentional and cognitive conditions, age, psychiatric disorders and so forth. However, it remains unclear how the clustering coefficient should be measured in a correlation-based network, which is among major representations of brain networks. In the present article, we propose clustering coefficients tailored to correlation matrices. The key idea is to use three-way partial correlation or partial mutual information to measure the strength of the association between the two neighboring nodes of a focal node relative to the amount of pseudo-correlation expected from indirect paths between the nodes. Our method avoids the difficulties of previous applications of clustering coefficient (and other) measures in defining correlational networks, i.e., thresholding on the correlation value, discarding of negative correlation values, the pseudo-correlation problem and full partial correlation matrices whose estimation is computationally difficult. For proof of concept, we apply the proposed clustering coefficient measures to functional magnetic resonance imaging data obtained from healthy participants of various ages and compare them with conventional clustering coefficients. We show that the clustering coefficients decline with the age. The proposed clustering coefficients are more strongly correlated with age than the conventional ones are. We also show that the local variants of the proposed clustering coefficients (i.e., abundance of triangles around a focal node) are useful in characterizing individual nodes. In contrast, the conventional local clustering coefficients were strongly correlated with and therefore may be confounded by the node's connectivity. The proposed methods are expected to help us to understand clustering and lack thereof in correlational brain networks, such as those derived from functional time series and across-participant correlation in neuroanatomical properties. PMID:29599714

Microscopic Electron Variations Measured Simultaneously By The Cluster Spacecraft

NASA Astrophysics Data System (ADS)

Buckley, A. M.; Carozzi, T. D.; Gough, M. P.; Beloff, N.

Data is used from the Particle Correlator experiments running on each of the four Cluster spacecraft so as to determine common microscopic behaviour in the elec- tron population observed over the macroscopic Cluster separations. The Cluster par- ticle correlator experiments operate by forming on board Auto Correlation Functions (ACFs) generated from short time series of electron counts obtained, as a function of electron energy, from the PEACE HEEA sensor. The information on the microscopic variation of the electron flux covers the frequency range DC up to 41 kHz (encom- passing typical electron plasma frequencies and electron gyro frequencies and their harmonics), the electron energy range is that covered by the PEACE HEEA sensor (within the range 1 eV to 26 keV). Results are presented of coherent electron struc- tures observed simultaneously by the four spacecraft in the differing plasma interac- tion regions and boundaries encountered by Cluster. As an aid to understanding the plasma interactions, use is made of numerical simulations which model both the un- derlying statistical properties of the electrons and also the manner in which particle correlator experiments operate.

Electron-mediated relaxation following ultrafast pumping of strongly correlated materials: model evidence of a correlation-tuned crossover between thermal and nonthermal states.

PubMed

Moritz, B; Kemper, A F; Sentef, M; Devereaux, T P; Freericks, J K

2013-08-16

We examine electron-electron mediated relaxation following ultrafast electric field pump excitation of the fermionic degrees of freedom in the Falicov-Kimball model for correlated electrons. The results reveal a dichotomy in the temporal evolution of the system as one tunes through the Mott metal-to-insulator transition: in the metallic regime relaxation can be characterized by evolution toward a steady state well described by Fermi-Dirac statistics with an increased effective temperature; however, in the insulating regime this quasithermal paradigm breaks down with relaxation toward a nonthermal state with a complicated electronic distribution as a function of momentum. We characterize the behavior by studying changes in the energy, photoemission response, and electronic distribution as functions of time. This relaxation may be observable qualitatively on short enough time scales that the electrons behave like an isolated system not in contact with additional degrees of freedom which would act as a thermal bath, especially when using strong driving fields and studying materials whose physics may manifest the effects of correlations.

MODELING STATISTICAL PROPERTIES OF SOLAR ACTIVE REGIONS THROUGH DIRECT NUMERICAL SIMULATIONS OF 3D-MHD TURBULENCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malapaka, Shiva Kumar; Mueller, Wolf-Christian

Statistical properties of the Sun's photospheric turbulent magnetic field, especially those of the active regions (ARs), have been studied using the line-of-sight data from magnetograms taken by the Solar and Heliospheric Observatory and several other instruments. This includes structure functions and their exponents, flatness curves, and correlation functions. In these works, the dependence of structure function exponents ({zeta}{sub p}) of the order of the structure functions (p) was modeled using a non-intermittent K41 model. It is now well known that the ARs are highly turbulent and are associated with strong intermittent events. In this paper, we compare some of themore » observations from Abramenko et al. with the log-Poisson model used for modeling intermittent MHD turbulent flows. Next, we analyze the structure function data obtained from the direct numerical simulations (DNS) of homogeneous, incompressible 3D-MHD turbulence in three cases: sustained by forcing, freely decaying, and a flow initially driven and later allowed to decay (case 3). The respective DNS replicate the properties seen in the plots of {zeta}{sub p} against p of ARs. We also reproduce the trends and changes observed in intermittency in flatness and correlation functions of ARs. It is suggested from this analysis that an AR in the onset phase of a flare can be treated as a forced 3D-MHD turbulent system in its simplest form and that the flaring stage is representative of decaying 3D-MHD turbulence. It is also inferred that significant changes in intermittency from the initial onset phase of a flare to its final peak flaring phase are related to the time taken by the system to reach the initial onset phase.« less

Quantum formalism for classical statistics

NASA Astrophysics Data System (ADS)

Wetterich, C.

2018-06-01

In static classical statistical systems the problem of information transport from a boundary to the bulk finds a simple description in terms of wave functions or density matrices. While the transfer matrix formalism is a type of Heisenberg picture for this problem, we develop here the associated Schrödinger picture that keeps track of the local probabilistic information. The transport of the probabilistic information between neighboring hypersurfaces obeys a linear evolution equation, and therefore the superposition principle for the possible solutions. Operators are associated to local observables, with rules for the computation of expectation values similar to quantum mechanics. We discuss how non-commutativity naturally arises in this setting. Also other features characteristic of quantum mechanics, such as complex structure, change of basis or symmetry transformations, can be found in classical statistics once formulated in terms of wave functions or density matrices. We construct for every quantum system an equivalent classical statistical system, such that time in quantum mechanics corresponds to the location of hypersurfaces in the classical probabilistic ensemble. For suitable choices of local observables in the classical statistical system one can, in principle, compute all expectation values and correlations of observables in the quantum system from the local probabilistic information of the associated classical statistical system. Realizing a static memory material as a quantum simulator for a given quantum system is not a matter of principle, but rather of practical simplicity.

Detrended fluctuation analysis of short datasets: An application to fetal cardiac data

NASA Astrophysics Data System (ADS)

Govindan, R. B.; Wilson, J. D.; Preißl, H.; Eswaran, H.; Campbell, J. Q.; Lowery, C. L.

2007-02-01

Using detrended fluctuation analysis (DFA) we perform scaling analysis of short datasets of length 500-1500 data points. We quantify the long range correlation (exponent α) by computing the mean value of the local exponents αL (in the asymptotic regime). The local exponents are obtained as the (numerical) derivative of the logarithm of the fluctuation function F(s) with respect to the logarithm of the scale factor s:αL=dlog10F(s)/dlog10s. These local exponents display huge variations and complicate the correct quantification of the underlying correlations. We propose the use of the phase randomized surrogate (PRS), which preserves the long range correlations of the original data, to minimize the variations in the local exponents. Using the numerically generated uncorrelated and long range correlated data, we show that performing DFA on several realizations of PRS and estimating αL from the averaged fluctuation functions (of all realizations) can minimize the variations in αL. The application of this approach to the fetal cardiac data (RR intervals) is discussed and we show that there is a statistically significant correlation between α and the gestation age.

Altered brain functional connectivity induced by physical exercise may improve neuropsychological functions in patients with benign epilepsy.

PubMed

Koirala, Gyan Raj; Lee, Dongpyo; Eom, Soyong; Kim, Nam-Young; Kim, Heung Dong

2017-11-01

The objective of this study was to elucidate alteration in functional connectivity (FC) in patients with benign epilepsy with centrotemporal spikes (BECTS) as induced by physical exercise therapy and their correlation to the neuropsychological (NP) functions. We analyzed 115 artifact- and spike-free 2-second epochs extracted from resting state EEG recordings before and after 5weeks of physical exercise in eight patients with BECTS. The exact Low Resolution Electromagnetic Tomography (eLORETA) was used for source reconstruction. We evaluated the cortical current source density (CSD) power across five different frequency bands (delta, theta, alpha, beta, and gamma). Altered FC between 34 regions of interests (ROIs) was then examined using lagged phase synchronization (LPS) method. We further investigated the correlation between the altered FC measures and the changes in NP test scores. We observed changes in CSD power following the exercise for all frequency bands and statistically significant increases in the right temporal region for the alpha band. There were a number of altered FC between the cortical ROIs in all frequency bands of interest. Furthermore, significant correlations were observed between FC measures and NP test scores at theta and alpha bands. The increased localization power at alpha band may be an indication of the positive impact of exercise in patients with BECTS. Frequency band-specific alterations in FC among cortical regions were associated with the modulation of cognitive and NP functions. The significant correlation between FC and NP tests suggests that physical exercise may mitigate the severity of BECTS, thereby enhancing NP function. Copyright © 2017 Elsevier Inc. All rights reserved.

Orthotopic bladder substitution in men revisited: identification of continence predictors.

PubMed

Koraitim, M M; Atta, M A; Foda, M K

2006-11-01

We determined the impact of the functional characteristics of the neobladder and urethral sphincter on continence results, and determined the most significant predictors of continence. A total of 88 male patients 29 to 70 years old underwent orthotopic bladder substitution with tubularized ileocecal segment (40) and detubularized sigmoid (25) or ileum (23). Uroflowmetry, cystometry and urethral pressure profilometry were performed at 13 to 36 months (mean 19) postoperatively. The correlation between urinary continence and 28 urodynamic variables was assessed. Parameters that correlated significantly with continence were entered into a multivariate analysis using a logistic regression model to determine the most significant predictors of continence. Maximum urethral closure pressure was the only parameter that showed a statistically significant correlation with diurnal continence. Nocturnal continence had not only a statistically significant positive correlation with maximum urethral closure pressure, but also statistically significant negative correlations with maximum contraction amplitude, and baseline pressure at mid and maximum capacity. Three of these 4 parameters, including maximum urethral closure pressure, maximum contraction amplitude and baseline pressure at mid capacity, proved to be significant predictors of continence on multivariate analysis. While daytime continence is determined by maximum urethral closure pressure, during the night it is the net result of 2 forces that have about equal influence but in opposite directions, that is maximum urethral closure pressure vs maximum contraction amplitude plus baseline pressure at mid capacity. Two equations were derived from the logistic regression model to predict the probability of continence after orthotopic bladder substitution, including Z1 (diurnal) = 0.605 + 0.0085 maximum urethral closure pressure and Z2 (nocturnal) = 0.841 + 0.01 [maximum urethral closure pressure - (maximum contraction amplitude + baseline pressure at mid capacity)].

Multivariate two-part statistics for analysis of correlated mass spectrometry data from multiple biological specimens.

PubMed

Taylor, Sandra L; Ruhaak, L Renee; Weiss, Robert H; Kelly, Karen; Kim, Kyoungmi

2017-01-01

High through-put mass spectrometry (MS) is now being used to profile small molecular compounds across multiple biological sample types from the same subjects with the goal of leveraging information across biospecimens. Multivariate statistical methods that combine information from all biospecimens could be more powerful than the usual univariate analyses. However, missing values are common in MS data and imputation can impact between-biospecimen correlation and multivariate analysis results. We propose two multivariate two-part statistics that accommodate missing values and combine data from all biospecimens to identify differentially regulated compounds. Statistical significance is determined using a multivariate permutation null distribution. Relative to univariate tests, the multivariate procedures detected more significant compounds in three biological datasets. In a simulation study, we showed that multi-biospecimen testing procedures were more powerful than single-biospecimen methods when compounds are differentially regulated in multiple biospecimens but univariate methods can be more powerful if compounds are differentially regulated in only one biospecimen. We provide R functions to implement and illustrate our method as supplementary information CONTACT: sltaylor@ucdavis.eduSupplementary information: Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Cerebral correlates of delta waves during non-REM sleep revisited.

PubMed

Dang-Vu, Thien Thanh; Desseilles, Martin; Laureys, Steven; Degueldre, Christian; Perrin, Fabien; Phillips, Christophe; Maquet, Pierre; Peigneux, Philippe

2005-10-15

We aimed at characterizing the neural correlates of delta activity during Non Rapid Eye Movement (NREM) sleep in non-sleep-deprived normal young adults, based on the statistical analysis of a positron emission tomography (PET) sleep data set. One hundred fifteen PET scans were obtained using H(2)(15)O under continuous polygraphic monitoring during stages 2-4 of NREM sleep. Correlations between regional cerebral blood flow (rCBF) and delta power (1.5-4 Hz) spectral density were analyzed using statistical parametric mapping (SPM2). Delta power values obtained at central scalp locations negatively correlated during NREM sleep with rCBF in the ventromedial prefrontal cortex, the basal forebrain, the striatum, the anterior insula, and the precuneus. These regions embrace the set of brain areas in which rCBF decreases during slow wave sleep (SWS) as compared to Rapid Eye Movement (REM) sleep and wakefulness (Maquet, P., Degueldre, C., Delfiore, G., Aerts, J., Peters, J.M., Luxen, A., Franck, G., 1997. Functional neuroanatomy of human slow wave sleep. J. Neurosci. 17, 2807-S2812), supporting the notion that delta activity is a valuable prominent feature of NREM sleep. A strong association was observed between rCBF in the ventromedial prefrontal regions and delta power, in agreement with electrophysiological studies. In contrast to the results of a previous PET study investigating the brain correlates of delta activity (Hofle, N., Paus, T., Reutens, D., Fiset, P., Gotman, J., Evans, A.C., Jones, B.E., 1997. Regional cerebral blood flow changes as a function of delta and spindle activity during slow wave sleep in humans. J. Neurosci. 17, 4800-4808), in which waking scans were mixed with NREM sleep scans, no correlation was found with thalamus activity. This latter result stresses the importance of an extra-thalamic delta rhythm among the synchronous NREM sleep oscillations. Consequently, this rCBF distribution might preferentially reflect a particular modulation of the cellular processes involved in the generation of cortical delta waves during NREM sleep.

Atlasing the frontal lobe connections and their variability due to age and education: a spherical deconvolution tractography study.

PubMed

Rojkova, K; Volle, E; Urbanski, M; Humbert, F; Dell'Acqua, F; Thiebaut de Schotten, M

2016-04-01

In neuroscience, there is a growing consensus that higher cognitive functions may be supported by distributed networks involving different cerebral regions, rather than by single brain areas. Communication within these networks is mediated by white matter tracts and is particularly prominent in the frontal lobes for the control and integration of information. However, the detailed mapping of frontal connections remains incomplete, albeit crucial to an increased understanding of these cognitive functions. Based on 47 high-resolution diffusion-weighted imaging datasets (age range 22-71 years), we built a statistical normative atlas of the frontal lobe connections in stereotaxic space, using state-of-the-art spherical deconvolution tractography. We dissected 55 tracts including U-shaped fibers. We further characterized these tracts by measuring their correlation with age and education level. We reported age-related differences in the microstructural organization of several, specific frontal fiber tracts, but found no correlation with education level. Future voxel-based analyses, such as voxel-based morphometry or tract-based spatial statistics studies, may benefit from our atlas by identifying the tracts and networks involved in frontal functions. Our atlas will also build the capacity of clinicians to further understand the mechanisms involved in brain recovery and plasticity, as well as assist clinicians in the diagnosis of disconnection or abnormality within specific tracts of individual patients with various brain diseases.

Visual functions in amblyopia as determinants of response to treatment.

PubMed

Singh, Vinita; Agrawal, Siddharth

2013-01-01

To describe the visual functions in amblyopia as determinants of response to treatment. Sixty-nine patients with unilateral and bilateral amblyopia (114 amblyopic eyes) 3 to 15 years old (mean age: 8.80 ± 2.9 years), 40 males (58%) and 29 females (42%), were included in this study. All patients were treated by conventional occlusion 6 hours per day for mild to moderate amblyopia (visual acuity 0.70 or better) and full-time for 4 weeks followed by 6 hours per day for severe amblyopia (visual acuity 0.8 or worse). During occlusion, near activities requiring hand-eye coordination were advised. The follow-up examination was done at 3 and 6 months. Improvement in visual acuity was evaluated on the logMAR chart and correlated with the visual functions. Statistical analysis was done using Wilcoxon rank sum test (Mann-Whitney U test) and Kruskal-Wallis analysis. There was a statistically significant association of poor contrast sensitivity with the grade of amblyopia (P < .001). The grade of amblyopia (P < .01), accommodation (P < .01), stereopsis (P = .01), and mesopic visual acuity (P < .03) were found to have a correlation with response to amblyopia therapy. The grade of amblyopia (initial visual acuity) and accommodation are strong determinants of response to amblyopia therapy, whereas stereopsis and mesopic visual acuity have some value as determinants. Copyright 2013, SLACK Incorporated.

Strong coupling constant from Adler function in lattice QCD

NASA Astrophysics Data System (ADS)

Hudspith, Renwick J.; Lewis, Randy; Maltman, Kim; Shintani, Eigo

2016-09-01

We compute the QCD coupling constant, αs, from the Adler function with vector hadronic vacuum polarization (HVP) function. On the lattice, Adler function can be measured by the differential of HVP at two different momentum scales. HVP is measured from the conserved-local vector current correlator using nf = 2 + 1 flavor Domain Wall lattice data with three different lattice cutoffs, up to a-1 ≈ 3.14 GeV. To avoid the lattice artifact due to O(4) symmetry breaking, we set the cylinder cut on the lattice momentum with reflection projection onto vector current correlator, and it then provides smooth function of momentum scale for extracted HVP. We present a global fit of the lattice data at a justified momentum scale with three lattice cutoffs using continuum perturbation theory at 𝒪(αs4) to obtain the coupling in the continuum limit at arbitrary scale. We take the running to Z boson mass through the appropriate thresholds, and obtain αs(5)(MZ) = 0.1191(24)(37) where the first is statistical error and the second is systematic one.

Neuroanatomical Correlates of Theory of Mind Deficit in Parkinson’s Disease: A Multimodal Imaging Study

PubMed Central

Díez-Cirarda, María; Ojeda, Natalia; Peña, Javier; Cabrera-Zubizarreta, Alberto; Gómez-Beldarrain, María Ángeles; Gómez-Esteban, Juan Carlos; Ibarretxe-Bilbao, Naroa

2015-01-01

Background Parkinson’s disease (PD) patients show theory of mind (ToM) deficit since the early stages of the disease, and this deficit has been associated with working memory, executive functions and quality of life impairment. To date, neuroanatomical correlates of ToM have not been assessed with magnetic resonance imaging in PD. The main objective of this study was to assess cerebral correlates of ToM deficit in PD. The second objective was to explore the relationships between ToM, working memory and executive functions, and to analyse the neural correlates of ToM, controlling for both working memory and executive functions. Methods Thirty-seven PD patients (Hoehn and Yahr median = 2.0) and 15 healthy controls underwent a neuropsychological assessment and magnetic resonance images in a 3T-scanner were acquired. T1-weighted images were analysed with voxel-based morphometry, and white matter integrity and diffusivity measures were obtained from diffusion weighted images and analysed using tract-based spatial statistics. Results PD patients showed impairments in ToM, working memory and executive functions; grey matter loss and white matter reduction compared to healthy controls. Grey matter volume decrease in the precentral and postcentral gyrus, middle and inferior frontal gyrus correlated with ToM deficit in PD. White matter in the superior longitudinal fasciculus (adjacent to the parietal lobe) and white matter adjacent to the frontal lobe correlated with ToM impairment in PD. After controlling for executive functions, the relationship between ToM deficit and white matter remained significant for white matter areas adjacent to the precuneus and the parietal lobe. Conclusions Findings reinforce the existence of ToM impairment from the early Hoehn and Yahr stages in PD, and the findings suggest associations with white matter and grey matter volume decrease. This study contributes to better understand ToM deficit and its neural correlates in PD, which is a basic skill for development of healthy social relationships. PMID:26559669

Neuroanatomical Correlates of Theory of Mind Deficit in Parkinson's Disease: A Multimodal Imaging Study.

PubMed

Díez-Cirarda, María; Ojeda, Natalia; Peña, Javier; Cabrera-Zubizarreta, Alberto; Gómez-Beldarrain, María Ángeles; Gómez-Esteban, Juan Carlos; Ibarretxe-Bilbao, Naroa

2015-01-01

Parkinson's disease (PD) patients show theory of mind (ToM) deficit since the early stages of the disease, and this deficit has been associated with working memory, executive functions and quality of life impairment. To date, neuroanatomical correlates of ToM have not been assessed with magnetic resonance imaging in PD. The main objective of this study was to assess cerebral correlates of ToM deficit in PD. The second objective was to explore the relationships between ToM, working memory and executive functions, and to analyse the neural correlates of ToM, controlling for both working memory and executive functions. Thirty-seven PD patients (Hoehn and Yahr median = 2.0) and 15 healthy controls underwent a neuropsychological assessment and magnetic resonance images in a 3T-scanner were acquired. T1-weighted images were analysed with voxel-based morphometry, and white matter integrity and diffusivity measures were obtained from diffusion weighted images and analysed using tract-based spatial statistics. PD patients showed impairments in ToM, working memory and executive functions; grey matter loss and white matter reduction compared to healthy controls. Grey matter volume decrease in the precentral and postcentral gyrus, middle and inferior frontal gyrus correlated with ToM deficit in PD. White matter in the superior longitudinal fasciculus (adjacent to the parietal lobe) and white matter adjacent to the frontal lobe correlated with ToM impairment in PD. After controlling for executive functions, the relationship between ToM deficit and white matter remained significant for white matter areas adjacent to the precuneus and the parietal lobe. Findings reinforce the existence of ToM impairment from the early Hoehn and Yahr stages in PD, and the findings suggest associations with white matter and grey matter volume decrease. This study contributes to better understand ToM deficit and its neural correlates in PD, which is a basic skill for development of healthy social relationships.

Carrier Modulation Via Waveform Probability Density Function

NASA Technical Reports Server (NTRS)

Williams, Glenn L.

2006-01-01

Beyond the classic modes of carrier modulation by varying amplitude (AM), phase (PM), or frequency (FM), we extend the modulation domain of an analog carrier signal to include a class of general modulations which are distinguished by their probability density function histogram. Separate waveform states are easily created by varying the pdf of the transmitted waveform. Individual waveform states are assignable as proxies for digital one's or zero's. At the receiver, these states are easily detected by accumulating sampled waveform statistics and performing periodic pattern matching, correlation, or statistical filtering. No fundamental physical laws are broken in the detection process. We show how a typical modulation scheme would work in the digital domain and suggest how to build an analog version. We propose that clever variations of the modulating waveform (and thus the histogram) can provide simple steganographic encoding.

Carrier Modulation Via Waveform Probability Density Function

NASA Technical Reports Server (NTRS)

Williams, Glenn L.

2004-01-01

Beyond the classic modes of carrier modulation by varying amplitude (AM), phase (PM), or frequency (FM), we extend the modulation domain of an analog carrier signal to include a class of general modulations which are distinguished by their probability density function histogram. Separate waveform states are easily created by varying the pdf of the transmitted waveform. Individual waveform states are assignable as proxies for digital ONEs or ZEROs. At the receiver, these states are easily detected by accumulating sampled waveform statistics and performing periodic pattern matching, correlation, or statistical filtering. No fundamental natural laws are broken in the detection process. We show how a typical modulation scheme would work in the digital domain and suggest how to build an analog version. We propose that clever variations of the modulating waveform (and thus the histogram) can provide simple steganographic encoding.

[Comparative evaluation of the functional state of the respiratory system in workers exposed to asbestos and cotton dust].

PubMed

Izycki, J; Gielec, L

1979-01-01

63 spinners exposed to cotton dust and 75 spinners exposed to asbestos dust were examined. In the women working in asbestos spinning room chronic nonspecific respiratory tract diseases prevalence was found to amount to 30% and in the cotton exposed group it was 15%. Mean values of lungs' vital capacity remained within the due values, although they were statistically significantly lower in asbestos exposed spinners (p less than 0,001). On the other hand, the percentage ratio of the forced expiratory capacity of 1 second was statistically significantly lower (0,001 less than p less than 0,01) in those exposed to cotton dust. The authors point to the occurrence of functional disturbances of the respiratory tract prior to radiological symptoms of lung asbestosis and their correlation with clinical symptoms.

Electromagnetic Compatibility Testing Studies

NASA Technical Reports Server (NTRS)

Trost, Thomas F.; Mitra, Atindra K.

1996-01-01

This report discusses the results on analytical models and measurement and simulation of statistical properties from a study of microwave reverberation (mode-stirred) chambers performed at Texas Tech University. Two analytical models of power transfer vs. frequency in a chamber, one for antenna-to-antenna transfer and the other for antenna to D-dot sensor, were experimentally validated in our chamber. Two examples are presented of the measurement and calculation of chamber Q, one for each of the models. Measurements of EM power density validate a theoretical probability distribution on and away from the chamber walls and also yield a distribution with larger standard deviation at frequencies below the range of validity of the theory. Measurements of EM power density at pairs of points which validate a theoretical spatial correlation function on the chamber walls and also yield a correlation function with larger correlation length, R(sub corr), at frequencies below the range of validity of the theory. A numerical simulation, employing a rectangular cavity with a moving wall shows agreement with the measurements. The determination that the lowest frequency at which the theoretical spatial correlation function is valid in our chamber is considerably higher than the lowest frequency recommended by current guidelines for utilizing reverberation chambers in EMC testing. Two suggestions have been made for future studies related to EMC testing.

Algebraic aspects of the driven dynamics in the density operator and correlation functions calculation for multi-level open quantum systems

NASA Astrophysics Data System (ADS)

Bogolubov, Nikolai N.; Soldatov, Andrey V.

2017-12-01

Exact and approximate master equations were derived by the projection operator method for the reduced statistical operator of a multi-level quantum system with finite number N of quantum eigenstates interacting with arbitrary external classical fields and dissipative environment simultaneously. It was shown that the structure of these equations can be simplified significantly if the free Hamiltonian driven dynamics of an arbitrary quantum multi-level system under the influence of the external driving fields as well as its Markovian and non-Markovian evolution, stipulated by the interaction with the environment, are described in terms of the SU(N) algebra representation. As a consequence, efficient numerical methods can be developed and employed to analyze these master equations for real problems in various fields of theoretical and applied physics. It was also shown that literally the same master equations hold not only for the reduced density operator but also for arbitrary nonequilibrium multi-time correlation functions as well under the only assumption that the system and the environment are uncorrelated at some initial moment of time. A calculational scheme was proposed to account for these lost correlations in a regular perturbative way, thus providing additional computable terms to the correspondent master equations for the correlation functions.

Correlates of health-promoting lifestyle behaviors among Vietnamese female immigrants in Taiwan.

PubMed

Hsiao, Chiu-Yueh; Chien, Maio-Ju; Wu, Hua-Shan; Chiao, Chia-Yi

2017-03-01

Immigration is a demanding and challenging life event that may cause married immigrant women to be likely to adopt unhealthy lifestyle behaviors. The aim of the authors of this study was to assess the prevalence of health-promoting lifestyle behaviors and their correlates among Vietnamese female immigrants in Taiwan. A cross-sectional study was conducted with 140 Vietnamese female immigrants from November 2012 to October 2013. Measures included demographic information, the Chinese Health Questionnaire, the General Functioning Scale of the Family Assessment Device, and a short version of the Chinese Health-Promoting Lifestyle Profile. Data analyses included descriptive statistics, Pearson's product-moment correlation coefficients, t-tests, one-way analysis of variance, and a hierarchical multiple regression analysis. Vietnamese female immigrants with better individual health status, higher education from their original country, greater communication ability, better health status of the husband, and adaptive family functioning demonstrated greater participation in health-promoting lifestyle behaviors. Particularly, better husband's health status and family functioning correlated with greater practices of health-promoting lifestyle behaviors after controlling for individual characteristics and experiences, with 38% of the total variance explained. Findings may serve to guide and design culturally specific, family-focused health promotion interventions to assist Vietnamese female immigrants and their families.

The Attenuation of Correlation Coefficients: A Statistical Literacy Issue

ERIC Educational Resources Information Center

Trafimow, David

2016-01-01

Much of the science reported in the media depends on correlation coefficients. But the size of correlation coefficients depends, in part, on the reliability with which the correlated variables are measured. Understanding this is a statistical literacy issue.

Using the bootstrap to establish statistical significance for relative validity comparisons among patient-reported outcome measures

PubMed Central

2013-01-01

Background Relative validity (RV), a ratio of ANOVA F-statistics, is often used to compare the validity of patient-reported outcome (PRO) measures. We used the bootstrap to establish the statistical significance of the RV and to identify key factors affecting its significance. Methods Based on responses from 453 chronic kidney disease (CKD) patients to 16 CKD-specific and generic PRO measures, RVs were computed to determine how well each measure discriminated across clinically-defined groups of patients compared to the most discriminating (reference) measure. Statistical significance of RV was quantified by the 95% bootstrap confidence interval. Simulations examined the effects of sample size, denominator F-statistic, correlation between comparator and reference measures, and number of bootstrap replicates. Results The statistical significance of the RV increased as the magnitude of denominator F-statistic increased or as the correlation between comparator and reference measures increased. A denominator F-statistic of 57 conveyed sufficient power (80%) to detect an RV of 0.6 for two measures correlated at r = 0.7. Larger denominator F-statistics or higher correlations provided greater power. Larger sample size with a fixed denominator F-statistic or more bootstrap replicates (beyond 500) had minimal impact. Conclusions The bootstrap is valuable for establishing the statistical significance of RV estimates. A reasonably large denominator F-statistic (F > 57) is required for adequate power when using the RV to compare the validity of measures with small or moderate correlations (r < 0.7). Substantially greater power can be achieved when comparing measures of a very high correlation (r > 0.9). PMID:23721463

Digital Correlation Microwave Polarimetry: Analysis and Demonstration

NASA Technical Reports Server (NTRS)

Piepmeier, J. R.; Gasiewski, A. J.; Krebs, Carolyn A. (Technical Monitor)

2000-01-01

The design, analysis, and demonstration of a digital-correlation microwave polarimeter for use in earth remote sensing is presented. We begin with an analysis of three-level digital correlation and develop the correlator transfer function and radiometric sensitivity. A fifth-order polynomial regression is derived for inverting the digital correlation coefficient into the analog statistic. In addition, the effects of quantizer threshold asymmetry and hysteresis are discussed. A two-look unpolarized calibration scheme is developed for identifying correlation offsets. The developed theory and calibration method are verified using a 10.7 GHz and a 37.0 GHz polarimeter. The polarimeters are based upon 1-GS/s three-level digital correlators and measure the first three Stokes parameters. Through experiment, the radiometric sensitivity is shown to approach the theoretical as derived earlier in the paper and the two-look unpolarized calibration method is successfully compared with results using a polarimetric scheme. Finally, sample data from an aircraft experiment demonstrates that the polarimeter is highly-useful for ocean wind-vector measurement.

A generalized estimating equations approach for resting-state functional MRI group analysis.

PubMed

D'Angelo, Gina M; Lazar, Nicole A; Eddy, William F; Morris, John C; Sheline, Yvette I

2011-01-01

An Alzheimer's fMRI study has motivated us to evaluate inter-regional correlations between groups. The overall objective is to assess inter-regional correlations at a resting-state with no stimulus or task. We propose using a generalized estimating equation (GEE) transition model and a GEE marginal model to model the within-subject correlation for each region. Residuals calculated from the GEE models are used to correlate brain regions and assess between group differences. The standard pooling approach of group averages of the Fisher-z transformation assuming temporal independence is a typical approach used to compare group correlations. The GEE approaches and standard Fisher-z pooling approach are demonstrated with an Alzheimer's disease (AD) connectivity study in a population of AD subjects and healthy control subjects. We also compare these methods using simulation studies and show that the transition model may have better statistical properties.

Correlations between cerebral glucose metabolism and neuropsychological test performance in nonalcoholic cirrhotics.

PubMed

Lockwood, Alan H; Weissenborn, Karin; Bokemeyer, Martin; Tietge, U; Burchert, Wolfgang

2002-03-01

Many cirrhotics have abnormal neuropsychological test scores. To define the anatomical-physiological basis for encephalopathy in nonalcoholic cirrhotics, we performed resting-state fluorodeoxyglucose positron emission tomographic scans and administered a neuropsychological test battery to 18 patients and 10 controls. Statistical parametric mapping correlated changes in regional glucose metabolism with performance on the individual tests and a composite battery score. In patients without overt encephalopathy, poor performance correlated with reductions in metabolism in the anterior cingulate. In all patients, poor performance on the battery was positively correlated (p < 0.001) with glucose metabolism in bifrontal and biparietal regions of the cerebral cortex and negatively correlated with metabolism in hippocampal, lingual, and fusiform gyri and the posterior putamen. Similar patterns of abnormal metabolism were found when comparing the patients to 10 controls. Metabolic abnormalities in the anterior attention system and association cortices mediating executive and integrative function form the pathophysiological basis for mild hepatic encephalopathy.

Long-term functional, subjective and psychological results after single digit replantation.

PubMed

Chen, Jing; Zhang, Ai Xian; Chen, Qing Zhong; Mu, Shuai; Tan, Jun

2018-03-01

The aim of this study was to analyse the long-term functional, subjective, and psychological results after single-digit replantation. Thirty cases of digital replantation (14 thumbs, 12 index fingers, 2 middle fingers, 1 ring finger, and 1 little finger) in 30 patients (7 females and 23 males) with a mean age of 44.2 years (20-65 years) were evaluated at the end of a mean follow-up time of 36 months (19-50 months). The active range of motion of joints, grip and pinch strength, cutaneous sensibility, upper-extremity functioning, and subjective satisfaction were determined using the Disability of Arm, Shoulder, and Hand (DASH) questionnaire and the Michigan Hand Outcomes questionnaire (MHQ). Psychological sequelae, including depression, anxiety, and posttraumatic stress disorder (PTSD), were assessed. A correlation analysis among variables was also performed. The mean score for the DASH questionnaire was 6.6 (range: 0-39.2). The symptom of cold intolerance occurred in 53% of the patients. Two patients were diagnosed with depression, and only one patient exhibited PTSD. The DASH score had a good statistical correlation with total grip strength, pinch grip strength, and static two-point discrimination (S-2PD) (P < 0.05). Several aspects of the MHQ were also statistically relevant to some or all of the three objective results. Furthermore, the grip strength showed significant correlation with DASH and most aspects of the MHQ in multivariate logistic regression analysis (P < 0.05). Total grip strength is the most important factor positively related to subjective outcomes. The incidence rates of psychological symptoms after digit replantation are very low at long-term follow-up. Level IV, therapeutic study. Copyright © 2017 Turkish Association of Orthopaedics and Traumatology. Production and hosting by Elsevier B.V. All rights reserved.

A method for the estimation of the significance of cross-correlations in unevenly sampled red-noise time series

NASA Astrophysics Data System (ADS)

Max-Moerbeck, W.; Richards, J. L.; Hovatta, T.; Pavlidou, V.; Pearson, T. J.; Readhead, A. C. S.

2014-11-01

We present a practical implementation of a Monte Carlo method to estimate the significance of cross-correlations in unevenly sampled time series of data, whose statistical properties are modelled with a simple power-law power spectral density. This implementation builds on published methods; we introduce a number of improvements in the normalization of the cross-correlation function estimate and a bootstrap method for estimating the significance of the cross-correlations. A closely related matter is the estimation of a model for the light curves, which is critical for the significance estimates. We present a graphical and quantitative demonstration that uses simulations to show how common it is to get high cross-correlations for unrelated light curves with steep power spectral densities. This demonstration highlights the dangers of interpreting them as signs of a physical connection. We show that by using interpolation and the Hanning sampling window function we are able to reduce the effects of red-noise leakage and to recover steep simple power-law power spectral densities. We also introduce the use of a Neyman construction for the estimation of the errors in the power-law index of the power spectral density. This method provides a consistent way to estimate the significance of cross-correlations in unevenly sampled time series of data.

Analysis of Family Functioning and Parent-Child Relationship between Adolescents with Depression and their Parents.

PubMed

Chen, Qing; DU, Wenyong; Gao, Yan; Ma, Changlin; Ban, Chunxia; Meng, Fu

2017-12-25

Drug therapy combined with family therapy is currently the best treatment for adolescent depression. Nevertheless, family therapy requires an exploration of unresolved problems in the family system, which in practice presents certain difficulties. Previous studies have found that the perceptual differences of family function between parents and children reflect the problems in the family system. To explore the characteristics and role of family functioning and parent-child relationship between adolescents with depressive disorder and their parents. The general information and clinical data of the 93 adolescents with depression were collected. The Family Functioning Assessment Scale and Parent-child Relationship Scale were used to assess adolescents with depressive disorder and their parents. a) The dimensions of family functioning in adolescents with depressive disorder were more negative in communication, emotional response, emotional involvement, roles, and overall functioning than their parents. The differences were statistically significant. Parent-child relationship dimensions: the closeness and parent-child total scores were more negative compared with the parents and the differences were statistically significant. b) All dimensions of parent-child relationship and family functioning in adolescents with depression except the time spent together were negatively correlated or significantly negatively correlated. c) The results of multivariate regression analysis showed: the characteristics of family functioning, emotional involvement, emotional response, family structure, and income of the adolescents with depressive disorder mainly affected the parent-child relationship. There were perceptual differences in partial family functioning and parent-child relationship between adolescents with depressive disorder and their parents. Unclear roles between family members, mutual entanglement, too much or too little emotional investment, negligence of inner feelings, parental divorce, and low average monthly family income were the main factors causing adverse parent-child relationship. These perceptual differences have a relatively good predictive effect on family problems, and can be used as an important guide for exploring the family relationship in family therapy.

Analysis of Family Functioning and Parent-Child Relationship between Adolescents with Depression and their Parents

PubMed Central

CHEN, Qing; DU, Wenyong; GAO, Yan; MA, Changlin; BAN, Chunxia; MENG, Fu

2017-01-01

Background Drug therapy combined with family therapy is currently the best treatment for adolescent depression. Nevertheless, family therapy requires an exploration of unresolved problems in the family system, which in practice presents certain difficulties. Previous studies have found that the perceptual differences of family function between parents and children reflect the problems in the family system. Aims To explore the characteristics and role of family functioning and parent-child relationship between adolescents with depressive disorder and their parents. Methods The general information and clinical data of the 93 adolescents with depression were collected. The Family Functioning Assessment Scale and Parent-child Relationship Scale were used to assess adolescents with depressive disorder and their parents. Results a) The dimensions of family functioning in adolescents with depressive disorder were more negative in communication, emotional response, emotional involvement, roles, and overall functioning than their parents. The differences were statistically significant. Parent-child relationship dimensions: the closeness and parent-child total scores were more negative compared with the parents and the differences were statistically significant. b) All dimensions of parent-child relationship and family functioning in adolescents with depression except the time spent together were negatively correlated or significantly negatively correlated. c) The results of multivariate regression analysis showed: the characteristics of family functioning, emotional involvement, emotional response, family structure, and income of the adolescents with depressive disorder mainly affected the parent-child relationship. Conclusions There were perceptual differences in partial family functioning and parent-child relationship between adolescents with depressive disorder and their parents. Unclear roles between family members, mutual entanglement, too much or too little emotional investment, negligence of inner feelings, parental divorce, and low average monthly family income were the main factors causing adverse parent-child relationship. These perceptual differences have a relatively good predictive effect on family problems, and can be used as an important guide for exploring the family relationship in family therapy. PMID:29719348